Method and apparatus for transmission based on multiple transmission and reception points in communication system

Abstract

A method of a terminal may include: establishing a first communication link by receiving, from a first TRP, a first SSB included in a first SSB group allocated to the first TRP; allocating a first label to the first communication link; establishing a second communication link by receiving, from the second TRP, a second SSB included in a second SSB group allocated to the second TRP; and allocating a second label to the second communication link according to the mapping relationship between the second SSB group and the second TRP.

Description

Technical Field

[0001] The present disclosure relates to a transmission technique based on multiple transmit and receive points in a communication system, and more particularly, to a transmission technique based on multiple transmit and receive points in a communication system that allows a terminal to transmit signals to multiple transmit and receive points using different transmission times. Background Art

[0002] With the development of information and communication technologies, various wireless communication technologies have emerged. Typical wireless communication technologies include Long Term Evolution (LTE) and New Radio (NR), both of which are defined in the Third Generation Partnership Project (3GPP) standards. LTE can be one of the fourth generation (4G) wireless communication technologies, and NR can be one of the fifth generation (5G) wireless communication technologies.

[0003] To handle the rapidly growing wireless data after the commercialization of fourth generation (4G) communication systems (such as Long Term Evolution (LTE) communication systems or Long Term Evolution - Advanced (LTE - A) communication systems), fifth generation (5G) communication systems (such as New Radio (NR) communication systems) are being considered. This system uses frequency bands higher than those of 4G communication systems (such as 6 GHz or above) as well as frequency bands of 4G communication systems (such as 6 GHz or below). 5G communication systems can support enhanced mobile broadband (eMBB), ultra - reliable low - latency communication (URLLC), and massive machine - type communication (mMTC).

[0004] In addition, in a communication system, multiple transmit and receive points (TRPs) and user equipment (UE) can transmit and receive signals simultaneously or sequentially. In this case, multiple TRPs can be located within the same cell and share the same configuration and resources. Alternatively, multiple TRPs can be located in different cells. In this case, the UE can manage a single timing advance (TA). At this time, the propagation delay between the TRP and the UE can vary. Therefore, the signals transmitted and received between the TRP and the UE may suffer from inter - symbol interference (ISI) and inter - carrier interference (ICI). Summary of the Invention

[0005]

Technical Problem

[0006] To solve the above problems, the present disclosure aims to provide a transmission method and device based on multiple TRPs that allow a terminal to transmit signals to multiple TRPs using different transmission times.

[0007]

Technical Solution

[0008] According to a first exemplary embodiment of the present disclosure, to achieve the above object, a transmission method based on multiple TRPs in a communication system may include: receiving a first SSB included in a first set of synchronization signal blocks (SSBs) allocated to a first transmission and reception point (TRP) from the first TRP; receiving system information from the first TRP based on the first SSB, the system information including a mapping relationship between the first set of SSBs and the first TRP and a mapping relationship between a second set of SSBs and a second TRP; establishing a first communication link between the first TRP and a terminal based on the first SSB; allocating a first label identifier for communication link identification to the first communication link according to the mapping relationship between the first set of SSBs and the first TRP; receiving a second SSB included in a second set of SSBs allocated to the second TRP from the second TRP; establishing a second communication link between the second TRP and the terminal based on the second SSB; and allocating a second label identifier to the second communication link according to the mapping relationship between the second set of SSBs and the second TRP.

[0009] Establishing a first communication link between the first TRP and the terminal based on the first SSB may include: obtaining information about a first random access opportunity indicated by a first system information block (SIB) obtained based on the first SSB; performing a first random access procedure with the first TRP in the first random access opportunity; and establishing a first communication link between the first TRP and the terminal according to the first random access procedure.

[0010] The method may further include: receiving a measurement request from the first TRP; in response to the measurement request, transmitting a measurement report to the first TRP, the measurement report including information about the second SSB and information about a time difference between a reception time of the first SSB and a reception time of the second SSB; and receiving a link establishment instruction for the second communication link from the first TRP based on the time difference, wherein the second communication link is established based on the second SSB and the establishment instruction.

[0011] When the time difference is less than a threshold, the received establishment instruction may indicate link establishment without performing a random access (RA) procedure, and the second communication link is established between the second TRP and the terminal without performing the RA procedure.

[0012] When the time difference is greater than or equal to the threshold, the received establishment instruction may indicate link establishment based on a random access channel (RACH), and establishing a second communication link between the second TRP and the terminal based on the second SSB may include: obtaining information about a second random access opportunity indicated by a second SIB obtained based on the second SSB; performing a second random access procedure with the second TRP in the second random access opportunity; and establishing a second communication link between the second TRP and the terminal according to the second random access procedure.

[0013] The first TRP may be included in the serving cell, and the second TRP may be included in the non-serving cell.

[0014] When the time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold, the first label identifier and the second label identifier may be the same, and when the time difference between the reception time of the first SSB and the reception time of the second SSB is equal to or greater than the threshold, the first label identifier may be different from the second label identifier.

[0015] The first SSB group and the second SSB group may be grouped based on the SSB index or the resource period of the frame.

[0016] The method may further include: receiving, from the first TRP, a first downlink transmission configuration indication (TCI) associated with the first label identifier and first downlink scheduling information; receiving downlink data from the first TRP based on the first downlink TCI and the first downlink scheduling information; receiving, from the second TRP, a second downlink TCI associated with the second label identifier and second downlink scheduling information; and receiving downlink data from the second TRP based on the second downlink TCI and the second downlink scheduling information.

[0017] The method may further include: receiving, from the first TRP, a first uplink TCI associated with the first label identifier and first uplink scheduling information; transmitting uplink data to the first TRP based on the first uplink TCI and the first uplink scheduling information; receiving, from the second TRP, a second uplink TCI associated with the second label identifier and second uplink scheduling information; and transmitting uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information.

[0018] When the time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold, the transmission time of transmitting uplink data to the first TRP and the transmission time of transmitting uplink data to the second TRP may be the same.

[0019] When the time difference between the reception time of the first SSB and the reception time of the second SSB is greater than or equal to a threshold, the difference between the transmission time of transmitting uplink data to the first TRP and the transmission time of transmitting uplink data to the second TRP may include the time difference.

[0020] According to a second exemplary embodiment of the present disclosure, to achieve the above object, a transmission method based on multiple TRPs in a communication system may include: receiving a first synchronization signal block (SSB) included in a first SSB group allocated to a first transmission and reception point (TRP) from the first TRP; receiving a second SSB included in a second SSB group allocated to a second TRP from the second TRP; initiating a first random access procedure with the first TRP based on the first SSB; during the first random access procedure, transmitting information about the second SSB and information about the time difference between the reception time of the first SSB and the reception time of the second SSB to the first TRP; establishing a first communication link between the first TRP and the terminal through the first random access procedure; receiving, through the first random access procedure, an establishment instruction for establishing a second communication link with the second TRP based on the time difference; and establishing a second communication link with the second TRP according to the received establishment instruction.

[0021] The method may further include: allocating a first label identifier for communication link identification to the first communication link according to the mapping relationship between the first SSB group and the first TRP; and allocating a second label identifier to the second communication link according to the mapping relationship between the second SSB group and the second TRP.

[0022] When the time difference is less than a threshold, the received establishment instruction may indicate link establishment without performing a random access (RA) procedure, and the second communication link is established between the second TRP and the terminal without performing the RA procedure.

[0023] When the time difference is greater than or equal to the threshold, the received establishment instruction may indicate link establishment based on a random access channel (RACH), and establishing the second communication link with the second terminal TRP according to the received establishment instruction may include: obtaining information about a second random access opportunity indicated by a second system information block (SIB) obtained based on the second SSB; performing a second random access procedure with the second TRP at the second random access opportunity; and establishing a second communication link between the second TRP and the terminal according to the second random access procedure.

[0024] The method may further include: receiving a first uplink TCI and first uplink scheduling information from a first TRP; transmitting uplink data to the first TRP based on the first uplink TCI and the first uplink scheduling information; receiving a second uplink TCI and second uplink scheduling information from a second TRP; and transmitting uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information, wherein when the time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold, the transmission time of transmitting the uplink data to the first TRP is the same as the transmission time of transmitting the uplink data to the second TRP, and when the time difference between the reception time of the first SSB and the reception time of the second SSB is greater than or equal to the threshold, the difference between the transmission time of transmitting the uplink data to the first TRP and the transmission time of transmitting the uplink data to the second TRP includes the time difference.

[0025] According to a third exemplary embodiment of the present disclosure, to achieve the above object, a transmitting device in a communication system based on multiple TRPs, as a terminal, may include a processor, and the processor may cause the terminal to perform: receiving a first synchronization signal block (SSB) included in a first SSB group assigned to a first TRP from the first transmit and receive point (TRP); receiving system information from the first TRP based on the first SSB, the system information including the mapping relationship between the first SSB group and the first TRP and the mapping relationship between a second SSB group and a second TRP; establishing a first communication link between the first TRP and the terminal based on the first SSB; allocating a first label identifier for communication link identification to the first communication link according to the mapping relationship between the first SSB group and the first TRP; receiving a second SSB included in a second SSB group assigned to the second TRP from the second TRP; establishing a second communication link between the second TRP and the terminal based on the second SSB; and allocating a second label identifier to the second communication link according to the mapping relationship between the second SSB group and the second TRP.

[0026] The processor may further cause the terminal to perform: receiving a measurement request from the first TRP; in response to the measurement request, transmitting a measurement report to the first TRP, the measurement report including information about the second SSB and information about the time difference between the reception time of the first SSB and the reception time of the second SSB; and receiving an establishment instruction for the second communication link from the first TRP based on the time difference, wherein when establishing the second communication link between the second TRP and the terminal based on the second SSB, the processor may further cause the terminal to perform: establishing the second communication link based on the establishment instruction.

[0027] When the time difference is greater than or equal to a threshold, the received establishment instruction may indicate link establishment based on a random access channel (RACH), and when establishing a second communication link based on the received establishment instruction, the processor may also cause the terminal to perform: obtaining information about a second random access opportunity indicated by a second SIB obtained based on a second SSB; performing a second random access procedure with a second TRP in the second random access opportunity; and establishing a second communication link between the second TRP and the terminal according to the second random access procedure.

[0028]

Technical Effects

[0029] According to the present disclosure, a terminal may configure different transmission times for a plurality of transmission and reception points. Specifically, according to the present disclosure, a terminal may configure the transmission time by reflecting the propagation delay of each transmission and reception point. Therefore, according to the present disclosure, signals transmitted and received between the terminal and a plurality of transmission and reception points may be less affected by inter-symbol interference (ISI) and inter-carrier interference (ICI). Description of the Drawings

[0030] Figure 1 is a conceptual diagram showing a first exemplary embodiment of a communication system.

[0031] Figure 2 is a block diagram showing a first exemplary embodiment of a communication node constituting a communication system.

[0032] Figure 3a is a conceptual diagram showing a first exemplary embodiment of a communication system having a plurality of transmission and reception points.

[0033] Figure 3b is a conceptual diagram showing a second exemplary embodiment of a communication system having a plurality of transmission and reception points.

[0034] Figure 4a is a conceptual diagram showing a first exemplary embodiment of propagation delay in a communication system having a plurality of transmission and reception points.

[0035] Figure 4b is a conceptual diagram showing a second exemplary embodiment of propagation delay in a communication system having a plurality of transmission and reception points.

[0036] Figure 5 is a sequence diagram showing a first exemplary embodiment of an initial access phase.

[0037] Figure 6 is a sequence diagram showing a first exemplary embodiment of a random access establishment process.

[0038] Figure 7It is a sequence diagram showing a second exemplary embodiment of the random access establishment process.

[0039] Figure 8 It is a sequence diagram showing a third exemplary embodiment of the random access establishment process.

[0040] Figure 9 It is a conceptual diagram showing a first exemplary embodiment of a method for grouping synchronization signal blocks.

[0041] Figure 10 It is a conceptual diagram showing a second exemplary embodiment of a method for grouping synchronization signal blocks.

[0042] Figure 11 It is a conceptual diagram showing a third exemplary embodiment of a method for grouping synchronization signal blocks.

[0043] Figure 12 It is a conceptual diagram showing a fourth exemplary embodiment of a method for grouping synchronization signal blocks.

[0044] Figure 13 It is a conceptual diagram showing a first exemplary embodiment of a tag ID configuration method.

[0045] Figure 14 It is a conceptual diagram showing a second exemplary embodiment of a tag ID configuration method.

[0046] Figure 15 It is a sequence diagram showing a first exemplary embodiment of a TCI triggering method.

[0047] Figure 16 It is a sequence diagram showing a first exemplary embodiment of a method for identifying TCI states.

[0048] Figure 17 It is a conceptual diagram showing a first exemplary embodiment of a UE-specific TCI state table.

[0049] Figure 18 It is a sequence diagram showing a second exemplary embodiment of a method for identifying TCI states.

[0050] Figure 19 It is a conceptual diagram showing a second exemplary embodiment of a UE-specific TCI state table.

[0051] Figure 20 It is a sequence diagram showing a first exemplary embodiment of a link configuration method in a multi-TRP environment.

[0052] Figure 21 It is a sequence diagram showing a second exemplary embodiment of a link configuration method in a multi-TRP environment.

[0053] Figure 22 It is a conceptual diagram showing a third exemplary embodiment of a label ID configuration method.

[0054] Figure 23 It is a sequence diagram showing a third exemplary embodiment of a link configuration method in a multi-TRP environment.

[0055] Figure 24 It is a sequence diagram showing a fourth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0056] Figure 25 It is a conceptual diagram showing a fifth exemplary embodiment of a method for grouping synchronization signal blocks.

[0057] Figure 26 It is a conceptual diagram showing a sixth exemplary embodiment of a method for grouping synchronization signal blocks.

[0058] Figure 27 It is a conceptual diagram showing a fourth exemplary embodiment of a label ID configuration method.

[0059] Figure 28 It is a conceptual diagram showing a fifth exemplary embodiment of a label ID configuration method.

[0060] Figure 29 It is a conceptual diagram showing a sixth exemplary embodiment of a label ID configuration method.

[0061] Figure 30 It is a sequence diagram showing a fifth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0062] Figure 31 It is a conceptual diagram showing a seventh exemplary embodiment of a label ID configuration method.

[0063] Figure 32 It is a conceptual diagram showing an eighth exemplary embodiment of a label ID configuration method.

[0064] Figure 33 It is a sequence diagram showing a sixth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0065] Figure 34 It is a sequence diagram showing a seventh exemplary embodiment of a link configuration method in a multi-TRP environment.

[0066] Figure 35 It is a conceptual diagram showing a ninth exemplary embodiment of a label ID configuration method.

[0067] Figure 36 It is a conceptual diagram showing a tenth exemplary embodiment of a label ID configuration method.

[0068] Figure 37 It is a sequence diagram showing an eighth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0069] Figure 38 It is a sequence diagram showing a ninth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0070] Figure 39 It is a sequence diagram showing a first exemplary embodiment of a transmission method in a multi-TRP environment.

[0071] Figure 40 It is a sequence diagram showing a second exemplary embodiment of a transmission method in a multi-TRP environment.

[0072] Figure 41 It is a sequence diagram showing a third exemplary embodiment of a transmission method in a multi-TRP environment.

[0073] Figure 42 It is a sequence diagram showing a fourth exemplary embodiment of a transmission method in a multi-TRP environment.

[0074] Figure 43 It is a sequence diagram showing a fifth exemplary embodiment of a transmission method in a multi-TRP environment.

[0075] Figure 44 It is a sequence diagram showing a sixth exemplary embodiment of a transmission method in a multi-TRP environment.

[0076] Figure 45 It is a sequence diagram showing a seventh exemplary embodiment of a transmission method in a multi-TRP environment.

[0077] Figure 46 It is a sequence diagram showing an eighth exemplary embodiment of a transmission method in a multi-TRP environment.

[0078] Figure 47 It is a conceptual diagram showing a first exemplary embodiment of a method for controlling the downlink timing of multiple transmit and receive points in a communication system.

[0079] Figure 48 It is a conceptual diagram showing a second exemplary embodiment of a method for controlling the downlink timing of multiple transmit and receive points in a communication system.

[0080] Figure 49 It is a conceptual diagram showing a first exemplary embodiment of a method for controlling the uplink timing of multiple transmit and receive points in a communication system.

[0081] Figure 50It is a conceptual diagram showing a second exemplary embodiment of a method for controlling uplink timing of multiple transmit and receive points in a communication system.

[0082] Figure 51 It is a sequence diagram showing a ninth exemplary embodiment of a transmission method in a multi-TRP environment.

[0083] Figure 52 It is a sequence diagram showing a tenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0084] Figure 53 It is a sequence diagram showing an eleventh exemplary embodiment of a transmission method in a multi-TRP environment.

[0085] Figure 54 It is a sequence diagram showing a twelfth exemplary embodiment of a transmission method in a multi-TRP environment.

[0086] Figure 55 It is a sequence diagram showing a thirteenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0087] Figure 56 It is a sequence diagram showing a fourteenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0088] Figure 57 It is a sequence diagram showing a fifteenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0089] Figure 58 It is a sequence diagram showing a sixteenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0090] Figure 59 It is a sequence diagram showing a seventeenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0091] Figure 60 It is a sequence diagram showing an eighteenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0092] Figure 61 It is a sequence diagram showing an eighteenth exemplary embodiment of a transmission method in a multi-TRP environment.

[0093] Figure 62 It is a sequence diagram showing a twentieth exemplary embodiment of a transmission method in a multi-TRP environment. Detailed Embodiments

[0094] Since the present disclosure can be modified in various ways and has various forms, specific exemplary embodiments will be shown in the drawings and will be described in detail in the specific embodiments. However, it should be understood that the present disclosure is not intended to be limited to the specific exemplary embodiments. On the contrary, the present disclosure is intended to cover all modifications and alternatives falling within the spirit and scope of the present disclosure.

[0095] Relative terms such as first and second can be used to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first component can be named a second component, and similarly, a second component can be named a first component without departing from the scope of the present disclosure. The term "and / or" means any one or a combination of multiple related and described items.

[0096] In the exemplary embodiments of the present disclosure, "at least one of A and B" can refer to "at least one of A or B" or "at least one of a combination of one or more of A and B". In addition, "one or more of A and B" can refer to "one or more of A or B" or "one or more of a combination of one or more of A and B".

[0097] When referring to a certain component being "coupled" or "connected" to another component, it should be understood that the component is directly "coupled" or "connected" to the other component, or other components can be provided therebetween. On the contrary, when referring to a certain component being "directly coupled" or "directly connected" to another component, it should be understood that no other components are provided therebetween.

[0098] The terms used in the present disclosure are only used to describe specific exemplary embodiments and are not intended to limit the present disclosure. Unless otherwise clearly specified in the context, the singular form also includes the plural form. In the present disclosure, terms such as "including" or "having" are intended to indicate the existence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but it should be understood that these terms do not exclude the existence or addition of one or more features, numbers, steps, operations, components, parts, or combinations thereof.

[0099] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure pertains. Terms that are commonly used and are included in a dictionary should be understood to have a meaning consistent with the context of the art. In this specification, unless clearly defined, terms are not necessarily understood to have a formal meaning.

[0100] The following will describe the forms of the present disclosure in detail with reference to the accompanying drawings. When describing the present disclosure, for the sake of a comprehensive understanding of the present disclosure, throughout the description of the accompanying drawings, the same numerals denote the same elements, and their repeated descriptions are omitted.

[0101] Figure 1 is a conceptual diagram showing a first exemplary embodiment of a communication system.

[0102] Referring to Figure 1 , the communication system 100 may include a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Here, the communication system may be referred to as a "communication network". Each of the plurality of communication nodes may support a communication protocol based on code division multiple access (CDMA), a communication protocol based on wideband CDMA (WCDMA), a communication protocol based on time division multiple access (TDMA), a communication protocol based on frequency division multiple access (FDMA), a communication protocol based on orthogonal frequency division multiplexing (OFDM), a communication protocol based on filtered OFDM, a communication protocol based on orthogonal frequency division multiple access (OFDMA), a communication protocol based on single carrier FDMA (SC-FDMA), a communication protocol based on non-orthogonal multiple access (NOMA), or a communication protocol based on space division multiple access (SDMA), etc. Each of the plurality of communication nodes may have the following structure.

[0103] Figure 2 is a block diagram showing a first exemplary embodiment of a communication node constituting a communication system.

[0104] Referring to Figure 2 , the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, and a storage device 260, etc. The corresponding components included in the communication node 200 may be connected by a bus 270 and communicate with each other. However, the corresponding components included in the communication node 200 may also not be connected to the common bus 270, but be connected to the processor 210 through an individual interface or an individual bus. For example, the processor 210 may be connected to at least one of the memory 220, the transceiver 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface.

[0105] The processor 210 may execute a program stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the method of the embodiments of the present disclosure is executed. Both the memory 220 and the storage device 260 may be constituted by at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may include at least one of a read-only memory (ROM) and a random access memory (RAM).

[0106] Referring again to FIG. 1, the communication system 100 may include a plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2, and a plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell, and each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage area of the first base station 110-1. In addition, the second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage area of the second base station 110-2. In addition, the fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the cell coverage area of the third base station 110-3. In addition, the first terminal 130-1 may belong to the cell coverage area of the fourth base station 120-1, and the sixth terminal 130-6 may belong to the cell coverage area of the fifth base station 120-2.

[0107] Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be referred to as a Node B (NB), an evolved Node B (eNB), a base transceiver station (BTS), a radio base station, a radio transceiver, an access point (AP), an access node, a roadside unit (RSU), a digital unit (DU), a cloud digital unit (CDU), a radio remote head (RRH), a radio unit (RU), a transmission point (TP), a transmission and reception point (TRP), or a relay node, etc. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may be referred to as a terminal, an access terminal, a mobile terminal, a station, a user station, a mobile station, a portable user station, a node, or a device, etc.

[0108] Each of the multiple communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 can support cellular communication (e.g., LTE, LTE-Advanced (LTE-A), etc.). Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can operate in the same frequency band or different frequency bands. The multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can be connected to each other via ideal backhaul links or non-ideal backhaul links and exchange information with each other via ideal or non-ideal backhaul links. In addition, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can be connected to the core network via an ideal backhaul link or a non-ideal backhaul link. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can transmit the signals received from the core network to the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6, and transmit the signals received from the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 to the core network.

[0109] Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support OFDMA-based downlink (DL) transmission and SC-FDMA-based uplink (UL) transmission. In addition, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support multiple-input multiple-output (MIMO) transmission (e.g., single-user MIMO (SU-MIMO), multi-user MIMO (MU-MIMO), or massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, unlicensed band transmission, device-to-device (D2D) communication (or proximity service (ProSe)), Internet of Things (IoT) communication, or dual connectivity (DC), etc. Here, each of the multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 can perform operations corresponding to the operations of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 (i.e., the operations supported by the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2).

[0110] In addition, in a communication system, a user equipment (UE) (i.e., a terminal) and multiple transmit and receive points (TRP) can transmit and receive signals simultaneously or sequentially.

[0111] Figure 3a It is a conceptual diagram showing a first exemplary embodiment of a communication system having multiple transmission and reception points.

[0112] Referring to Figure 3a , a terminal can exist within the coverage area of a serving cell having a physical cell identifier (PCI). Two TRPs (i.e., TRP 1 and TRP 2) having the same PCI can exist within the serving cell. This communication system can be referred to as an in-cell multi-TRP (or M-TRP or MTRP) communication system. Here, the serving cell is equipped with two TRPs, but it can also include more TRPs.

[0113] Figure 3b It is a conceptual diagram of a second exemplary embodiment of a communication system having multiple transmission and reception points.

[0114] Referring to Figure 3b , a terminal can exist within the coverage area of a serving cell having a PCI. More than one TRP (i.e., TRP 1) having the same PCI can exist within the serving cell. In addition, a TRP (i.e., TRP 2) having a PCI different from that of the serving cell can exist in an adjacent area of the serving cell. This communication system can be referred to as an inter-cell M-TRP communication system. Here, the serving cell is equipped with two TRPs, but it can also include more TRPs. Such a communication system based on in-cell M-TRP or inter-cell M-TRP can support downlink and uplink transmissions. Here, the "downlink" can be a link from the TRP to the terminal, and the "uplink" can be a link from the terminal to the TRP.

[0115] Figure 4a It is a conceptual diagram showing a first exemplary embodiment of propagation delay in a communication system having multiple transmission and reception points.

[0116] Referring to Figure 4a , two TRPs (i.e., TRP 1 and TRP 2) can be located within the same serving cell and share the same configuration and resources. In other words, a serving cell can manage one timing advance (Timing Advance / Adjustment / Alignment, TA). The two TRPs within the serving cell can share one TA. In the above in-cell M-TRP-based communication system, the terminal can perform downlink and uplink transmissions by adjusting the reception synchronization point and the transmission synchronization point according to one TA managed by the serving cell, regardless of the number of TRPs. Here, the reception synchronization point can refer to the reception time point, and the transmission synchronization point can refer to the transmission time point.

[0117] As described above, the terminal can manage one TA. In this case, TRP 1 and TRP 2 located within a serving cell can be separated by a relatively large distance. In this case, the terminal close to TRP 1 can perform downlink and uplink transmissions by adjusting the receive synchronization point and the transmit synchronization point according to the TA of TRP 1. In addition, the terminal can perform downlink and uplink transmissions for TRP 2 by equally applying the receive synchronization point and the transmit synchronization point according to the TA of TRP 1. In this case, the difference between the propagation delay τ1 between TRP 1 and the terminal and the propagation delay τ2 between TRP 2 and the terminal can be greater than αT CP , αT CP is proportional to the cyclic prefix (CP) length T CP Therefore, when performing downlink transmission, the signal received by the terminal from TRP 2 may suffer from inter-symbol interference (ISI) and inter-carrier interference (ICI). Conversely, when performing uplink transmission, the signal received by TRP 2 from the terminal may suffer from ISI and ICI.

[0118] Figure 4b is a conceptual diagram showing a second exemplary embodiment of the propagation delay in a communication system having multiple transmission and reception points.

[0119] Referring to Figure 4b , one TRP (i.e., TRP 1) can be located within a serving cell. In addition, another TRP (i.e., TRP 2) can be located within a non-serving cell having a different PCI from the serving cell. The terminal can manage one TA of the TRP in the serving cell without managing the TA of the TRP in the non-serving cell. However, the terminal can use the TA of the TRP in the serving cell as the TA of the TRP in the non-serving cell to perform downlink and uplink transmissions. As described above, in a communication system based on inter-cell M-TRP, the terminal can perform downlink and uplink transmissions by adjusting the receive synchronization point and the transmit synchronization point according to one TA managed by the serving cell, regardless of the number of TRPs.

[0120] As described above, the terminal can manage one TA. TRP 1 connected to the serving cell and TRP 2 connected to the non-serving cell can be separated by a relatively large distance. The terminal close to TRP 1 can use the TA of TRP 1 for communication with TRP 2 in the non-serving cell. In this case, the difference between the propagation delay τ1 between TRP 1 and the terminal and the propagation delay τ2 between TRP 2 and the terminal may be greater than αT CP , αT CP is proportional to the CP length T CPIs directly proportional. Therefore, when performing downlink transmission, the signal received by the terminal from TRP 2 may suffer from ISI and ICI. Conversely, when performing uplink transmission, the signal received by TRP 2 from the terminal may suffer from ISI and ICI.

[0121] Therefore, each of the communication system based on in-cell M-TRP and the communication system based on inter-cell M-TRP may require a process to identify the propagation delay, TA, or related information between the terminal and different TRPs, so as to achieve access and connection establishment between the terminal and the TRP. In addition, each of the communication system based on in-cell M-TRP and the communication system based on inter-cell M-TRP may require a downlink transmission method that allows the terminal to synchronously receive signals transmitted from the TRP. In addition, each of the communication system based on in-cell M-TRP and the communication system based on inter-cell M-TRP may require an uplink transmission method that allows the TRP to synchronously receive synchronous or continuous signals from the terminal.

[0122] In the present disclosure, the wireless device may refer to a mobile station (MS). The TRP may refer to a device that transmits signals to the MS or receives signals from the MS. The base station (BS) may refer to a device that manages the TRP. The area managed by the base station (BS) may refer to a cell. The MS may refer to a UE or a terminal.

[0123] Figure 5 Is the sequence diagram of the first embodiment in the initial access phase.

[0124] Referring to Figure 5 , the terminal may power on and initially access the TRP (S510). To this end, the TRP may transmit beamformed synchronization signal blocks (SSBs) in multiple directions (S511). Therefore, the terminal may receive the SSBs. In addition, the terminal may perform downlink synchronization from the TRP to the terminal based on one of the received SSBs. Here, the TRP may transmit the SSBs periodically or aperiodically for initial synchronization and maintenance of the beamformed downlink. After performing such synchronization, the terminal may obtain the master information block (MIB) from the SSB. The MIB may be transmitted to the terminal on the physical broadcast channel (PBCH). The MIB may be the first system information obtained by the terminal.

[0125] Then, the TRP can use the time resources and frequency resources indicated by the MIB to transmit the System Information Block 1 (SIB1) (S512) to the terminal. The terminal can obtain the SIB 1 located in the time resources and frequency resources indicated by the MIB. In this case, the TRP can transmit the SIB 1 to the terminal on the PDSCH. The SIB 1 can be the second system information obtained by the terminal. The TRP can transmit other SIBs (i.e., SIBy, where y is a positive integer greater than or equal to 2) except for SIB 1 to the terminal during the initial access phase (S513). In this case, the TRP can transmit control information to the terminal through the SIB 1, informing that the SIBs after SIB 1 will be transmitted in sequence as shown in "a". After that, the terminal and the TRP can continue with the random access establishment process (S514).

[0126] On the other hand, to speed up the access process, the TRP may not transmit multiple SIBs other than SIB 1 during the initial access phase. In this case, the TRP can transmit control information through the SIB 1, informing the TRP not to transmit multiple SIBs other than SIB 1. Then, the TRP can retransmit the beamformed SSB in multiple directions (S520). Thus, the terminal can receive the SSB. Then, the TRP can transmit a Radio Resource Control (RRC) setup message to the terminal (S521). Then, the terminal can establish an RRC connection by receiving the RRC setup message from the TRP. Thereafter, the terminal can transmit an RRC setup complete message to the TRP (S522). Thus, the TRP can receive the RRC setup complete message from the terminal.

[0127] In addition, when the terminal completes the RRC establishment and is in the system connected state, the terminal can transmit an SIB request message to the TRP, requesting all or part of the SIBy (S523), as shown in "b". Then, the TRP can receive the SIB request message from the terminal. The TRP can transmit the SIB to the terminal (S524). Accordingly, the terminal can receive the SIB from the TRP. Alternatively, the terminal can complete the RRC establishment by requesting all or part of the SIBy from the TRP during the process of completing the RRC establishment to obtain the requested SIB, as shown in "b". For ease of description, it can be assumed that the TRP transmits all SIBs including SIB 1 during the initial access phase, as shown in "a". However, the present disclosure is not limited thereto.

[0128] Figure 6 It is a sequence diagram showing the first exemplary embodiment of the random access establishment process.

[0129] Refer to Figure 6, after completing downlink synchronization and system information acquisition, the terminal can perform a four-step random access establishment procedure based on contention-based random access (CBRA) for uplink synchronization (S610). First, in the first step, the terminal can randomly select a preamble from all the preambles provided by the TRP. Then, the terminal can transmit the selected preamble to the TRP via the physical random access channel (PRACH) (S611). Then, the TRP can receive the preamble from the terminal on the PRACH. In this case, the beam direction can follow the uplink direction, which is opposite to the beam direction when receiving the downlink signal. The resource for transmitting the preamble from the terminal to the TRP can be based on the pre-acquired information about the association between the SSB and the RACH occasion. The TRP can estimate the propagation delay of the terminal based on the preamble.

[0130] Then, in the second step, the TRP can determine whether there is a preamble in the signal received via the PRACH. The preamble can be randomly selected and transmitted by the terminal. Therefore, the TRP cannot specify which terminal transmitted the preamble based on whether the preamble is detected. Therefore, the TRP cannot determine how many terminals used the detected preamble. Therefore, the TRP can transmit a random access response (RAR) to the terminal on the PDSCH based on the index of the detected preamble (S612). Then, the terminal can receive the RAR from the TRP. In this case, the RAR can include the preamble index, TA value, uplink grant information, and a temporary cell radio network temporary identifier (C-RNTI).

[0131] Then, in the third step, the terminal can transmit a scheduling request message (or connection request message) and a terminal-specific identifier to the TRP on the physical uplink shared channel (PUSCH) by applying the temporary C-RNTI and using the uplink radio resources indicated by the uplink grant information included in the RAR (S613). Then, the TRP can receive the connection request message and the terminal-specific ID from the terminal. Here, there may be more than one terminal that transmitted the same preamble in step S611. Therefore, preamble collisions may occur. In this case, all the terminals that transmitted the same preamble can refer to the same RAR and transmit messages using the same radio resources. This may lead to conflicts.

[0132] In other words, the terminals that transmitted the same preamble in the first step may eventually encounter resource conflicts when transmitting the messages in the third step. Therefore, each terminal can start a contention resolution timer when transmitting the messages in the third step as part of the process of checking whether the transmitted messages in the third step conflict and whether the message decoding is successful.

[0133] Finally, in the fourth step, the TRP can decode the received message from the third step. Then, the TRP can transmit an acknowledgement message for the successfully decoded message to the terminal on the PDSCH (S614). Then, the terminal can receive the acknowledgement message from the TRP. The terminal can receive the acknowledgement message before the expiration of the contention resolution timer initiated in the third step. In this case, the terminal can consider the random access to have been successfully executed and can regard the temporary C-RNTI as its own C-RNTI for continued use in the system connected state. On the other hand, the terminal may not receive any acknowledgement message before the expiration of the contention resolution timer. In this case, the terminal can determine that the decoding has failed due to a collision in the message transmitted in the third step. Therefore, the terminal can perform a backoff process. Thereafter, the terminal can reattempt the random access process. The TRP can define the maximum number of random access attempts to prevent random access channel congestion. Therefore, the terminal may not successfully perform random access within the maximum number of attempts. In this case, the terminal can abandon the random access and re-perform downlink synchronization.

[0134] Figure 7 is a sequence diagram showing a second exemplary embodiment of the random access establishment process.

[0135] Referring to Figure 7 , a terminal that has completed downlink synchronization and system information acquisition can perform a two-step random access establishment process based on CBRA for uplink synchronization (S710). To this end, in the first step, the terminal can randomly select a preamble from all the preambles. Then, the terminal can transmit a selected preamble to the TRP on the PRACH. In addition, simultaneously, the terminal can transmit a scheduling request (i.e., a connection request) to the TRP via a pre-allocated uplink radio resource (i.e., an uplink shared channel) (S711). Then, the TRP can receive a message including the preamble and the scheduling request from the terminal.

[0136] Then, in the second step, the TRP can determine whether a preamble has been detected. In addition, the TRP can determine whether the message has been successfully decoded. The TRP can transmit different types of messages to the terminal according to the determination result. This can lead to different subsequent processes.

[0137] More specifically, if the TRP does not detect a preamble, the TRP can perform no operation. In other words, the TRP does not even check whether a message has been received via the uplink radio resource associated with the preamble. Therefore, in the case where no preamble is detected, the TRP can make no response. Therefore, the terminal can reattempt the random access because it has not received any message from the TRP. This case can be referred to as "Case 1".

[0138] On the other hand, the TRP can normally detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, the TRP can transmit a message including the RAR (i.e., the successful RAR) and the C-RNTI to the terminal on the PDSCH (S712). Therefore, the terminal can receive a message including the successful RAR and the C-RNTI from the TRP. This message can be used as an acknowledgement. Therefore, the terminal can successfully terminate the random access. This case can be referred to as "Case 2". Additionally, although the TRP normally detects the preamble, the TRP may not be able to successfully decode the message from the uplink radio resources associated with the preamble. In this case, the TRP can transmit a message including a fallback RAR to the terminal on the PDSCH. In this case, the terminal that receives this message can use the uplink radio resources indicated by the uplink authorization information included in the fallback RAR to retransmit the message that the terminal wishes to transmit.

[0139] Figure 8 is a sequence diagram showing a third exemplary embodiment of the random access establishment process.

[0140] Referring to Figure 8 , a terminal that has completed downlink synchronization and system information acquisition can perform a two-step random access establishment process based on contention-free random access (CFRA) for uplink synchronization (S810). To this end, in the first step, the terminal can randomly select a preamble from the preambles specified by the TRP. Then, the terminal can transmit a selected preamble to the TRP on the PRACH (S811). The TRP can receive a message including the preamble from the terminal. Then, the TRP can perform TA estimation on the received preamble. In addition, the TRP can determine whether the TA is detected based on the determination result, generate an RAR according to the determination result, and transmit the RAR to the terminal (S812). Then, the terminal can receive the RAR from the TRP.

[0141] Referring again to Figure 5 , the TRP can transmit an RRC establishment message to the terminal. Then, the terminal can complete the RRC establishment by receiving the RRC establishment message from the TRP. Thus, a series of system connection operations are completed. After that, the terminal can enter the system connection state and communicate with other terminals through the TRP.

[0142] The following will describe the process, transmission method, and communication device for a terminal belonging to a serving cell to synchronously or sequentially transmit and receive signals in the downlink and uplink in synchronization with an existing TRP in the cell. In addition, the process, transmission method, and communication device for a terminal belonging to a serving cell to synchronously or sequentially transmit and receive signals in the downlink and uplink in synchronization with a TRP belonging to the serving cell and a TRP belonging to an adjacent non-serving cell will also be described. These processes and transmission methods may be referred to as intra-cell / inter-cell M-TRP processes / methods. Here, the intra-cell / inter-cell M-TRP processes / methods may be transmission processes / methods based on multiple TRPs.

[0143] The description of the present disclosure assumes that at most two TRPs can be connected to a serving cell, and one TRP can be connected to an adjacent non-serving cell, as Figure 3a and 3b shown. However, the present disclosure is not limited thereto, and the case where two or more TRPs can be connected to a serving cell and one or more TRPs can be connected to a non-serving cell is also included within the scope of the present disclosure.

[0144] Referring again to Figure 5 , all TRPs within a serving cell can transmit the same beamformed SSB to the terminal. Then, the terminal can receive the same beamformed SSB from the TRPs. In this case, the terminal may not be able to know whether the estimated optimal SSB and the estimated sub-optimal SSB belong to TRP 1 or TRP 2. Therefore, it may be difficult for the terminal to synchronously or sequentially transmit signals by synchronizing with each of the two different TRPs. Here, the optimal SSB may be the SSB with the maximum correlation value, and the sub-optimal SSB may have the second largest correlation value. Alternatively, the optimal SSB may be the SSB with the maximum signal-to-interference-plus-noise ratio (SINR), and the sub-optimal SSB may have the second largest SINR. The optimal SSB may be the first optimal SSB (i.e., the 1st optimal SSB), and the sub-optimal SSB may be the second optimal SSB (i.e., the 2nd optimal SSB).

[0145] To solve the above problems, the intra-cell / inter-cell M-TRP method may divide the available beamformed SSBs into SSB groups. Each SSB group can be mapped to a TRP. This method may be referred to as the "SSB grouping method". Here, as a first SSB grouping method, the SSBs can be divided into non-overlapping SSB groups within the same SSB period and the same half-frame while maintaining the same number of available beamformed SSBs. Then, each SSB group can be mapped to a TRP.

[0146] Figure 9 is a conceptual diagram showing a first exemplary embodiment of a method for grouping synchronization signal blocks.

[0147] Referring to Figure 9 , the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (i.e., SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, SSB 5, and SSB 7. SSB group 1 can be mapped to TRP 1. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8. SSB group 2 can be mapped to TRP 2. Here, mapping SSB group 1 to TRP 1 can mean that TRP 1 only uses SSB 1, SSB 3, SSB 5, and SSB 7 to transmit beamformed SSBs in the corresponding direction during SSB scanning. Similarly, mapping SSB group 2 to TRP 2 can mean that TRP 2 only uses SSB 2, SSB 4, SSB 6, and SSB 8 to transmit beamformed SSBs in the corresponding direction during SSB scanning. In this case, the number of available SSBs can be 8, but is not limited thereto, and can be 4, 16, or 64, etc. Here, TRP 1 and TRP 2 can belong to the serving cell.

[0148] Figure 10 is a conceptual diagram showing a second exemplary embodiment of a method for grouping synchronization signal blocks.

[0149] Referring to Figure 10 , the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (i.e., SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, SSB 5, and SSB 7. SSB group 1 can be mapped to TRP 1 belonging to the serving cell. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8. SSB group 2 can be mapped to TRP 2 belonging to a non-serving cell. Here, mapping SSB group 1 to TRP 1 can mean that TRP 1 only uses SSB1, SSB 3, SSB 5, and SSB 7 to transmit beamformed SSBs in the corresponding direction during SSB scanning. Similarly, mapping SSB group 2 to TRP 2 can mean that TRP 2 only uses SSB 2, SSB 4, SSB 6, and SSB 8 to transmit beamformed SSBs in the corresponding direction during SSB scanning. In this case, the number of available SSBs can be 8, but is not limited thereto, and can be 4, 16, or 64, etc. Here, TRP 1 can belong to the serving cell, while TRP 2 can belong to a non-serving cell.

[0150] Figure 9 and Figure 10The first SSB grouping method described is only an exemplary embodiment. All methods of dividing SSBs into non-overlapping SSB groups within the same SSB period and the same half-frame while maintaining the same number of available beamforming SSBs, and mapping each SSB group to a TRP are included within the scope of the present disclosure. On the other hand, the second grouping method may be a method of dividing SSBs into non-overlapping SSB groups within the same SSB period but spanning different half-frames while maintaining the same number of available beamforming SSBs, and mapping each SSB group to a TRP.

[0151] Figure 11 is a conceptual diagram showing a third exemplary embodiment of a method for grouping synchronization signal blocks.

[0152] Referring to Figure 11 , the SSBs (SSB 1 to SSB 8) in the first half-frame within a frame can be classified as SSB group 1. In addition, the SSBs (SSB 1 to SSB 8) in the second half-frame within a frame can be classified as SSB group 2. SSB group 1 may include SSB1 to SSB 8 in the first half-frame. SSB group 1 can be mapped to TRP 1. On the other hand, SSB group 2 may include SSB 1 to SSB 8 in the second half-frame. SSB group 2 can be mapped to TRP 2. Here, mapping SSB group 1 to TRP 1 may mean that TRP 1 uses all of the SSBs 1 to SSB 8 in the first half-frame to transmit beamformed SSBs in the corresponding direction during SSB scanning. Similarly, mapping SSB group 2 to TRP 2 may mean that TRP 2 uses all of the SSBs 1 to SSB 8 in the second half-frame to transmit beamformed SSBs in the corresponding direction during SSB scanning. In this case, the number of available SSBs can be 8, but is not limited thereto, and can be 4, 16, or 64, etc. Here, TRP 1 and TRP 2 may belong to the serving cell.

[0153] Figure 12 is a conceptual diagram showing a fourth exemplary embodiment of a method for grouping synchronization signal blocks.

[0154] Referring to Figure 12, the SSBs (SSB 1 to SSB 8) of the first half-frame within a frame can be classified into SSB group 1. In addition, the SSBs (SSB 1 to SSB 8) of the second half-frame within a frame can be classified into SSB group 2. SSB group 1 can include SSB1 to SSB 8 of the first half-frame. SSB group 1 can be mapped to TRP 1 belonging to the serving cell. On the other hand, SSB group 2 can include SSB 1 to SSB 8 of the second half-frame. SSB group 2 can be mapped to TRP 2 belonging to the non-serving cell. Here, mapping SSB group 1 to TRP 1 can mean that TRP 1 uses all SSB 1 to SSB 8 of the first half-frame to transmit beamformed SSBs in the corresponding direction during SSB scanning. Similarly, mapping SSB group 2 to TRP 2 can mean that TRP 2 uses all SSB 1 to SSB 8 of the second half-frame to transmit beamformed SSBs in the corresponding direction during SSB scanning. In this case, the number of available SSBs can be 8, but is not limited thereto, and can be 4, 16, or 64, etc.

[0155] Figure 11 and Figure 12 The second SSB grouping method described in is only an exemplary embodiment, and the first half-frame is generally referred to as the first resource, while the second half-frame is generally referred to as the second resource. Each resource can correspond to different time resources, time periods, frequency resources, or time / frequency resources. The scope of the present disclosure can include all methods of dividing the SSBs transmitted from these resources into disjoint groups and mapping each group to a TRP. In addition, the scope of the present disclosure can also include all grouping methods that combine the first SSB grouping method and the second SSB grouping method. These grouping methods can include dividing the SSBs into non-overlapping groups within the same SSB period, across the same or different half-frames, using the same number or different numbers of available beamformed SSBs. Then, each group can be mapped to one or more TRPs. In Figures 9 to 12 SSB group 1 can be associated with the first TA, and SSB group 2 can be associated with the second TA. In Figures 9 to 12 SSB group 1 can be associated with the first tag identifier (i.e., timing advance group (TAG) ID), and SSB group 2 can be associated with the second tag ID. In Figures 9 to 12 Each SSB of SSB group 1 can be associated with a tag ID, and each SSB of SSB group 2 can also be associated with a tag ID.

[0156] Figure 13 is a conceptual diagram showing a first exemplary embodiment of the tag ID configuration method.

[0157] Referring to Figure 13, To adjust the TA required for uplink synchronization, each SSB group can be mapped to a TRP and can be associated with a tag ID (e.g., TAG 1, TAG 2, etc.). As an example, SSB group 1 can be associated with TAG 1, while SSB group 2 can be associated with TAG 2. In this case, TAG 1 can be associated with joint transmission configuration indication (TCI) 1, while TAG 2 can be associated with joint TCI 2. As described above, since the TAG is managed for each SSB group, when the terminal establishes a communication link for each of TRP 1 and TRP 2, uplink synchronization and communication can be performed for each TAG.

[0158] Figure 14 is a conceptual diagram showing a second exemplary embodiment of a tag ID configuration method.

[0159] Referring to Figure 14 , when establishing two communication links using one TRP, the terminal can perform uplink synchronization and communication by assigning the same TAG to the two links. Here, one communication link can pass through an obstacle.

[0160] In addition, TCI can refer to a transmission configuration indication that defines the quasi - co - location (QCL) relationship of downlink or uplink physical channels and physical signals. Joint TCI can define the QCL relationship of downlink and uplink physical channels and physical signals to reduce control overhead. The TRP can dynamically deliver TCI to the terminal through the physical downlink shared channel (PDSCH) or the physical downlink control channel (PDCCH, i.e., the control channel) including medium access control (MAC) control element (CE) or RRC information. Alternatively, the TRP can deliver TCI to the terminal aperiodically through the PDSCH or PDCCH including MAC CE or RRC information. Alternatively, the TRP can deliver TCI to the terminal periodically through the PDSCH or PDCCH including MAC CE or RRC information. Alternatively, the TRP can deliver TCI to the terminal semi - persistently through the PDSCH or PDCCH including MAC CE or RRC information. In this case, the TRP can apply TCI according to the beam direction and QCL relationship of the antenna ports of each communication link. In addition, the TRP can also use one TCI to deliver the beam direction and QCL relationship of the antenna ports of two communication links through one communication link.

[0161] Figure 15 is a sequence diagram showing a first exemplary embodiment of a TCI triggering method.

[0162] Referring to Figure 15, the TRP (or Network (NW)) can use high-layer RRC signaling to transmit the TCI state table (S1501) to the terminal on the PDSCH. Then, the terminal can receive the TCI state table from the TRP. Here, the TCI state table can be configured through the tci-StatesToAddModList defined in the PDSCH configuration (such as PDSCH-Config). The maximum size of the TCI state table can be 128, for example. Here, TCI can be defined as follows:

[0163] - TCI can define the QCL relationships for each antenna port used in various physical channels (beams) and physical signals (beams). Here, various QCL types can be defined in the form of functions such as Doppler frequency shift, Doppler spread, average delay, and / or spatial reception parameters. For example, the QCL types can be as follows.

[0164] - QCL-Type A: Doppler frequency shift, Doppler spread, average delay, delay spread

[0165] - QCL-Type B: Doppler frequency shift, Doppler spread

[0166] - QCL-Type C: average delay, Doppler frequency shift

[0167] - QCL-Type D: spatial transmission parameters

[0168] - The 128 downlink TCI configurations defined by RRC signaling can depend on the QCL relationships of the following downlink physical channels (such as PDSCH, PDCCH, etc.) and downlink physical signals (such as SSB, downlink channel state information reference signal (CSI-RS), etc.). The uplink TCI configuration can depend on the QCL relationships of the uplink physical channels (such as PUSCH, PUCCH, etc.) and uplink physical signals (such as sounding reference signal (SRS), uplink CSI-RS, etc.).

[0169] - PDCCH / PDSCH QCL (with SSB)

[0170] - PDCCH / PDSCH QCL (with DL CSI-RS)

[0171] - PDCCH / PDSCH QCL (with SSB and DL CSI-RS)

[0172] - DL CSI-RS beam QCL (with SSB beam)

[0173] Then, the TRP (or NW) can transmit the TCI state table to the terminal via the UE-specific PDCCH or the UE-specific MAC CE of the PDSCH (S1502). Then, the terminal can receive the TCI state table from the TRP.

[0174] Figure 16 is a sequence diagram showing a first exemplary embodiment of a method for identifying TCI states.

[0175] Referring to Figure 16 , the TRP can transmit the SSB based on the SSB beam sweep (S1601). Then, the terminal can receive the SSB from the TRP and can select the SSB that indicates the optimal beam. The terminal can obtain system information such as the MIB and SIBy from the selected SSB. The terminal can achieve uplink synchronization by performing a random access procedure using the information related to random access in the system information (S1602).

[0176] The TRP can transmit an RRC setup message to the terminal (S1603). Then, the terminal can receive the RRC setup message from the TRP. When the terminal completes the RRC setup according to the received RRC setup message, the terminal can transmit an RRC setup complete message to the TRP (S1604). Then, the TRP can receive the RRC setup complete message from the terminal. Through this process, the terminal can be connected to the TRP. Thereafter, the terminal can communicate with other terminals via the TRP in the connected state.

[0177] For example, the TRP can transmit a TCI state table with a maximum size of 128 configured by tci-StatesToAddModList to the terminal on the PDSCH (S1605). Then, the terminal can receive the TCI state table. Thus, the terminal can obtain and store the TCI state table related to the PDCCH with a maximum size of 64 as an example configured by tci-StatesToAddModList. The TRP can use the UE-specific PDCCH MAC CE on the PDSCH to Figure 17 the UE-specific TCI state table to the terminal (S1606). The terminal can receive the UE-specific TCI state table from the TRP and store and manage the UE-specific TCI state table.

[0178] Figure 17 is a conceptual diagram showing a first exemplary embodiment of the UE-specific TCI state table.

[0179] Referring to Figure 17, octet 1 in the UE-specific TCI state table can be composed of the serving cell ID and a part of the common control resource set (CORESET) ID of the corresponding PDCCH. Octet 2 can be composed of the remaining part of the CORESET ID and the TCI state ID indicating one of the 64 TCI states in the TCI state table.

[0180] Here, two communication links can be established. In addition, each communication link can correspond to a different TAG, and uplink synchronization can be performed based on the TAG. In this case, the UE-specific PDCCH MAC CE can be transmitted separately for each link. Alternatively, the UE-specific PDCCH MAC CE can be transmitted separately on one link (e.g., the first communication link). Alternatively, the UE-specific PDCCH MAC CE can be transmitted integrated on one link. When the UE-specific PDCCH MAC CE is transmitted in the form of an integrated MAC CE, the TCI ID / TAG ID of each link can be assigned to a certain field of the MAC CE. In addition, the terminal can obtain the TCI state specified in the TCI state table, decode its PDCCH, and perform downlink communication.

[0181] Figure 18 is a sequence diagram showing a second exemplary embodiment of a method for identifying TCI states.

[0182] Referring to Figure 18 , the TRP can transmit the SSB based on SSB beam scanning (S1801). Then, the terminal can receive the SSB from the TRP and can select the SSB indicating the optimal beam. The terminal can obtain system information such as the MIB and SIBy from the selected SSB. The terminal can perform a random access procedure using the information related to random access in the system information, thereby achieving uplink synchronization (S1802).

[0183] The TRP can transmit an RRC establishment message to the terminal (S1803). Then, the terminal can receive the RRC establishment message from the TRP. When the terminal completes RRC establishment according to the received RRC establishment message, the terminal can transmit an RRC establishment complete message to the TRP (S1804). Then, the TRP can receive the RRC establishment complete message from the terminal. Through this process, the terminal can be connected to the TRP. After that, the terminal can communicate with other terminals through the TRP in the connected state.

[0184] For example, the TRP may transmit a TCI state table with a maximum size of 128 configured by tci-StatesToAddModList to the terminal on the PDSCH (S1805). Then, the terminal may receive the TCI state table. Accordingly, the terminal may obtain and store a TCI state table related to the PDCCH with a maximum size of 64 as an example configured by tci-StatesToAddModList.

[0185] Then, the TRP may broadcast RRC configuration parameters (such as tci-PresentInDCI) on the PDSCH through higher layer signaling, and the RRC configuration parameters indicate whether there is a TCI state in the DCI (S1806). Then, the terminal may receive the RRC configuration parameters and identify whether there is a TCI state in the DCI. The terminal may perform the following processing according to the information on whether there is a TCI state obtained in the DCI.

[0186] A parameter indicating whether there is a TCI state in the DCI (such as tci-PresentInDCI) may be set to the "omit" state. In other words, tci-PresentInDCI may be set to "tci-PresentInDCI = omit". In this case, the TCI state of the PDSCH may be the same as the TCI state of the corresponding CORESET / PDCCH. Then, the terminal may perform the following processing.

[0187] First, the TRP may transmit it to the terminal by including the UE-specific TCI state in the UE-specific PDCCH MAC CE on the PDSCH (S1807). The terminal may obtain its TCI state by receiving the UE-specific TCI state table as Figure 17 shown. The terminal may obtain the TCI state specified in the UE-specific TCI state table obtained Figure 17 and perform downlink communication by decoding its PDCCH according to the TCI state.

[0188] The parameter tci-PresentInDCI may be set to the "enabled" state. In other words, when the parameter tci-PresentInDCI is set to "tci-PresentInDCI = enabled", the terminal may perform the following processing. First, the TRP may transmit the UE-specific TCI state table as Figure 19 shown for the UE-specific PDSCH MAC CE to the terminal on the PDSCH. The terminal may receive the UE-specific TCI state table as Figure 19 shown from the TRP.

[0189] Figure 19It is a conceptual diagram showing a second exemplary embodiment of a UE-specific TCI state table.

[0190] Referring to Figure 19 , the UE-specific TCI state table may include a serving cell ID, a bandwidth part (BWP) ID of the corresponding PDSCH, and 128-bit bits respectively indicating activation (defined as 1) or deactivation (defined as 0) of 128 TCI states. At the Figure 19 bottom. The case where 8 TCI states configured for the terminal are activated is shown. At this time, two communication links can be established. In addition, each communication link can correspond to a different TAG, and uplink synchronization can be performed based on the TAG. In this case, UE-specific PDCCH MAC CE can be transmitted separately for each link. Alternatively, UE-specific PDCCH MAC CE can be integrated and transmitted on one link. When UE-specific PDCCH MAC CE is transmitted in the form of integrated MAC CE, the TCI ID / TAG ID of each link can be assigned to a certain field of the MAC CE. In addition, the terminal can obtain the TCI state specified in the TCI state table, decode its PDCCH, and perform downlink communication.

[0191] Then, the terminal can map 8 activated TCI states to the code point table in ascending order, as shown on the right. In addition, the TRP can transmit downlink TCI and downlink DCI (such as DCI1_1) through UE-specific PDCCH. The terminal can receive downlink TCI and DCI from the TRP. Therefore, the terminal can identify the scheduled code point index through the TCI field included in the DCI (such as DCI1_1), so as to perform downlink communication.

[0192] Figure 20 It is a sequence diagram showing a first exemplary embodiment of a link configuration method in a multi-TRP environment.

[0193] Referring to Figure 20 , the terminal can establish communication links with two TRPs belonging to different SSB groups respectively. In this case, the terminal can establish two communication links starting from the initial access phase. For this purpose, the terminal can perform SSB beam measurement on the beamforming SSBs transmitted from each of TRP 1 and TRP 2. In this case, the terminal can select SSB 1 as the optimal SSB (i.e., the first optimal SSB), and select SSB 2 as the sub-optimal SSB (i.e., the second optimal SSB). The terminal can obtain system information based on the optimal SSB (S2001). The system information can be carried on the PBCH and PDSCH channels transmitted in the time / frequency resources determined according to the SSB.

[0194] The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAG ID and the SSB group from the PDSCH channel including SIBy (i.e., System Information Block y). The TRP can allow the terminal to identify the mapping relationship between the SSB group and the TRP and the association relationship between the SSB group and the TAG ID during the RRC establishment process after the random access procedure. Alternatively, the TRP can allow the terminal to identify the mapping relationship between the SSB group and the TRP and the association relationship between the SSB group and the TAG ID through RRC signaling after the RRC establishment process is completed. In addition, the TRP can not inform the terminal of the mapping relationship between the SSB group and the TRP and the association relationship between the SSB group and the TAG ID. At this time, the terminal can identify the mapping relationship between the SSB group and the TRP and the association relationship between the SSB group and the TAG ID from the PDSCH including SIBy (which is system information).

[0195] Then, TRP 1 and the terminal can perform uplink synchronization (S2002) according to the SIB indication obtained from the system information and according to the random access channel (RACH) opportunity (RO) in accordance with a four-step or two-step CBRA process. Here, the RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 to the communication link with TRP 1. The terminal can perform uplink synchronization and update of uplink synchronization according to the configuration of TAG 1 for this communication link.

[0196] Then, TRP 1 can transmit an RRC establishment message to the terminal (S2003). The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S2004). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0197] For this purpose, TRP 1 can transmit DCI related to the downlink to the terminal (S2009). Then, the terminal can receive the DCI related to the downlink from TRP1. Here, the DCI related to the downlink can indicate DL / Combined TCI 1 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal according to the DCI related to the downlink (S2010). Then, the terminal can receive the downlink data from TRP 1 according to the DCI related to the downlink.

[0198] On the other hand, TRP 1 may transmit DCI related to the uplink to the terminal (S2011). Then, the terminal may receive the DCI related to the uplink from TRP 1. Here, the DCI related to the uplink may indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and may be transmitted on the PDCCH. Thereafter, the terminal may transmit uplink data to TRP 1 according to the DCI related to the uplink (S2012). Then, TRP 1 may receive the uplink data from the terminal based on the DCI related to the uplink.

[0199] In addition, the terminal may be in the RRC connected state. TRP 1 may request the terminal to perform measurements (S2005). Therefore, the terminal may perform measurements by receiving SSBs from neighboring TRPs. In addition, the terminal may report the SSB-based measurement results for the neighboring TRPs to TRP 1 through RRC signaling (S2006). In this case, the terminal may report SSB 2 to TRP 1 as the sub-optimal SSB. Therefore, TRP 1 may receive the measurement report from the terminal. TRP 1 may identify SSB 2 as the sub-optimal SSB through the measurement report. In this case, SSB 2 may not be included in the SSB group used by TRP 1. Therefore, TRP 1 may identify TRP 2 as the TRP transmitting SSB 2 according to the relationship between the SSB group and the TRP.

[0200] In this case, the measurement report may include a first SSB index (i.e., the optimal SSB index), a second SSB index (i.e., the sub-optimal SSB index), a third SSB index, etc. In addition, the measurement report may include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index and the third SSB index.

[0201] If the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal may request TRP 1 to configure the same TAG as the current communication link thereby. Alternatively, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index and the third SSB index exceeds a predetermined threshold, the terminal may request TRP 1 to configure a different TAG from the current communication link thereby. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of terminal reverse synchronization and its update may be reduced.

[0202] In addition, the terminal can obtain the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index and the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal can request the TRP 1 to perform a second link establishment process without RACH. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal can request the TRP 1 to perform a second link establishment process based on RACH.

[0203] Then, the terminal can perform a random access establishment process (S2007) with the TRP 2. In this process, the terminal can allocate TAG 2 for the communication link corresponding to the TRP 2 for uplink synchronization and its update. The random access establishment process for the TRP 2 can be triggered by the TRP 1. Alternatively, the random access establishment process for the TRP 2 can also be triggered by the terminal.

[0204] First, in the triggering method of the TRP 1, the TRP 1 can indicate to the terminal to perform CFRA or CBRA random access through high-layer signaling or PDCCH, thereby triggering the random access establishment process for the TRP 2. On the other hand, in the triggering method of the terminal, the terminal can identify the need to manage another TAG through the random access process with the TRP 1. Therefore, the terminal can request to use SSB 2 or the TRP 2 for random access through high-layer signaling or a physical layer control channel (such as PUSCH, etc.) to trigger the random access establishment process for the TRP 2.

[0205] The received TRP 1 can indicate to the terminal to perform CFRA or CBRA random access through high-layer signaling or PDCCH to continue the random access establishment process for the TRP 2. In this way, the terminal can receive an indication from the TRP 1 regarding the random access establishment process for the TRP 2. Therefore, the terminal and the TRP 2 can complete the random access establishment process by performing the random access process.

[0206] Then, TRP 2 and the terminal can perform the RRC establishment procedure (S2008). In other words, TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 2. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 2. TRP 2 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 2. In the connected state, the terminal can communicate with other terminals through TRP 1 and TRP 2.

[0207] For this purpose, TRP 2 can transmit DCI related to the downlink to the terminal (S2013). Then, the terminal can receive the DCI related to the downlink from TRP2. Here, the DCI related to the downlink can indicate DL / Combined TCI 2 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. After that, TRP 2 can transmit downlink data to the terminal according to this DCI related to the downlink (S2014). Then, the terminal can receive the downlink data from TRP 2 according to this DCI related to the downlink.

[0208] On the other hand, TRP 2 can transmit DCI related to the uplink to the terminal (S2015). Then, the terminal can receive the DCI related to the uplink from TRP 2. Here, the DCI related to the uplink can indicate UL / Combined TCI 2 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 2 according to the DCI related to the uplink (S2016). Then, TRP 2 can receive the uplink data from the terminal based on the DCI related to the uplink. Then, the terminal can update the TA by performing uplink synchronization for TAG 1 and TAG 2 with TRP 1 or TRP 2 periodically or aperiodically (S2017).

[0209] Figure 21 It is a sequence diagram showing a second exemplary embodiment of a link configuration method in a multi-TRP environment.

[0210] Refer to Figure 21, the terminal can establish two communication links with the TRP belonging to the same SSB group. In this case, the terminal can establish two communication links starting from the initial access phase. To this end, the terminal performs SSB beam measurement on the beamformed SSB transmitted from TRP 1. In this case, the terminal can select SSB 1 as the optimal SSB (i.e., the first optimal SSB), and select SSB 5 as the sub-optimal SSB (i.e., the second optimal SSB). The terminal can obtain system information based on the optimal SSB (S2101). This system information can be carried on the PBCH and PDSCH transmitted in the time / frequency resources determined according to the SSB.

[0211] The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can also identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAG ID and the SSB group based on the PDSCH including SIBy. The TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID during the RRC establishment process after the random access process is executed. Alternatively, the TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID through RRC signaling after the RRC establishment process is completed. In addition, the TRP can not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID from the PDSCH including the system information SIBy.

[0212] Then, TRP 1 and the terminal can perform uplink synchronization according to the SIB indication obtained based on the system information, according to the RO, in accordance with a four-step or two-step CBRA process (S2102). Here, the RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization and update of uplink synchronization according to the configuration of TAG 1 for the communication link.

[0213] Then, TRP 1 can transmit an RRC establishment message to the terminal (S2103). The terminal can receive the RRC establishment message from TRP 1. Accordingly, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S2104). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0214] To this end, TRP 1 may transmit DCI related to the downlink (S2110) to the terminal. Then, the terminal may receive the DCI related to the downlink from TRP1. Here, the DCI related to the downlink may indicate DL / Combined TCI 1 (which indicates the receiving configuration of the terminal and the scheduling resource location for data reception of the terminal), and may be transmitted on the PDCCH. After that, TRP 1 may transmit downlink data to the terminal according to the DCI related to the downlink (S2111). Then, the terminal may receive the downlink data from TRP 1 according to the DCI related to the downlink.

[0215] On the other hand, TRP 1 may transmit DCI related to the uplink (S2112) to the terminal. Then, the terminal may receive the DCI related to the uplink from TRP 1. Here, the DCI related to the uplink may indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and may be transmitted on the PDCCH. Thereafter, the terminal may transmit uplink data to TRP 1 according to the DCI related to the uplink (S2113). Then, TRP 1 may receive the uplink data from the terminal based on the DCI related to the uplink.

[0216] In addition, the terminal may be in the RRC connected state. TRP 1 may request the terminal to perform measurements (S2105). Therefore, the terminal may perform measurements by receiving SSBs from neighboring TRPs. In addition, the terminal may report the SSB-based measurement results for neighboring TRPs to TRP 1 through RRC signaling (S2106). In this case, the terminal may report SSB 5 to TRP 1 as a sub-optimal SSB. Therefore, TRP 1 may receive the measurement report from the terminal. TRP 1 may identify that SSB5 is a sub-optimal SSB through the measurement report. In this case, SSB 5 may be included in the SSB group used by TRP 1. Therefore, TRP 1 may identify itself as the TRP that transmits SSB 5 according to the relationship between the SSB group and the TRP. Here, the measurement report is described as being performed by the terminal according to the request of TRP 1. However, differently, even without such a request, the terminal may perform the measurement report.

[0217] In this case, the measurement report may include the first SSB index (i.e., the optimal SSB index), the second SSB index (i.e., the sub-optimal SSB index), the third SSB index, etc. In addition, the measurement report may also include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index.

[0218] If the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal may request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of terminal reverse synchronization and reverse synchronization update can be reduced.

[0219] In addition, the terminal can obtain the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal may request TRP 1 for a second link establishment process without RACH. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request TRP 1 for a second link establishment process based on RACH.

[0220] In addition, the terminal may report SSB 5 to TRP 1 as a sub-optimal SSB. In this case, SSB 5 may be included in the same SSB group as SSB 1. Thus, for example, the communication link associated with SSB 5 may be a different communication link from the communication link associated with SSB 1, which is from the multi-path transmission of TRP 1. The communication link associated with this SSB 5 may follow the uplink synchronization and the update of uplink synchronization of the communication link based on SSB 1 identified by TAG 1. Accordingly, through the RACH-less process, TRP 1 and the terminal may perform the following beam measurements between the terminal and SSB 5.

[0221] For this purpose, TRP 1 may instruct the terminal to transmit an uplink beamformed SRS (S2107) to the TRP including TRP 1 using the specified scheduling resources. In this case, TRP 1 may instruct the terminal to transmit the SRS through RRC signaling, and the RRC signaling includes information about the specified scheduling resources for transmitting the uplink beamformed SRS. In this case, TRP 1 may inform neighboring TRPs that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS to suppress interference. Alternatively, to improve resource efficiency, TRP 1 may not inform neighboring TRPs that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS.

[0222] Then, the terminal can transmit the beamformed SRS to the TRP including TRP 1 (S2108). TRP 1 can receive the SRS from the terminal. In addition, TRP 1 can select the most suitable uplink beam based on the received SRS, and inform the terminal of the information about the most suitable uplink beam (i.e., the optimal uplink beam) (S2109). In other words, for example, TRP 1 can inform the terminal of the information about the SRS with the highest SINR among the beamformed SRS received from the terminal. Accordingly, the terminal can receive the information about the optimal uplink beam from TRP 1. The terminal can confirm that the optimal uplink beam belongs to itself. Through this process, the terminal can complete the system connection with TRP 1 through the communication link associated with SSB 5. In the connected state, the terminal can communicate with other terminals through two communication links of TRP 1.

[0223] For this purpose, TRP 1 can transmit the DCI related to the downlink associated with SSB 5 to the terminal (S2114). Then, the terminal can receive the DCI related to the downlink from TRP 1. Here, the DCI related to the downlink can indicate DL / Combined TCI 1 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Subsequently, TRP 1 can transmit downlink data to the terminal according to the DCI related to the downlink (S2115). Then, the terminal can receive the downlink data from TRP 1 according to the DCI related to the downlink.

[0224] On the other hand, TRP 1 can transmit the DCI related to the uplink associated with SSB 5 to the terminal (S2116). Then, the terminal can receive the DCI related to the uplink from TRP 1. Here, the DCI related to the uplink can indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Subsequently, the terminal can transmit uplink data to TRP 1 according to the DCI related to the uplink (S2117).

[0225] Then, TRP 1 can receive the uplink data from the terminal based on the DCI related to the uplink. Thereafter, the terminal can update the TA by performing uplink synchronization with TRP 1 periodically or aperiodically for TAG 1 (S2118). Although Figure 20 and 21 the process of establishing two communication links is described, the method of the present disclosure is not limited thereto. The TRP and the terminal can establish more or less than two communication links by applying Figure 20 and 21The method of establishing a communication link as shown establishes three or more communication links and performs multi-TRP communication in the downlink and uplink.

[0226] Figure 22 It is a conceptual diagram showing a third exemplary embodiment of a tag ID configuration method.

[0227] Referring to Figure 22 , each SSB group can be mapped to one TRP to adjust the TA required for uplink synchronization. One tag ID (such as TAG 1, or TAG 2, etc.) can be associated with one SSB. For example, SSB 1 in SSB group 1 can be associated with TAG 1, and SSB 5 in SSB group 1 can be associated with TAG 5. In addition, SSB 2 in SSB group 2 can be associated with TAG 2. In this case, TAG 1 can be associated with joint transmission configuration indication (TCI) 1. TAG 2 and TAG 5 can be associated with joint TCI2. Since, as described above, the TAG is managed for each SSB, when establishing a communication link for each SSB of TRP 1 and TRP 2, the terminal can perform uplink synchronization for each SSB and perform communication for each SSB. In this case, the method of establishing a link in a multi-TRP communication system can be as Figure 23 and 24 shown.

[0228] Figure 23 It is a sequence diagram showing a third exemplary embodiment of a link configuration method in a multi-TRP environment.

[0229] Referring to Figure 23 , the terminal can establish two communication links with one TRP belonging to one SSB group. The terminal can establish two communication links starting from the initial access phase. To this end, the terminal can perform SSB beam measurement on the beamforming SSB transmitted from TRP 1. In this case, the terminal can select SSB 1 as the optimal SSB (i.e., the 1st optimal SSB), and select SSB 5 as the sub-optimal SSB (i.e., the 2nd optimal SSB). The terminal can obtain system information based on the optimal SSB (S2301). This system information can be carried by PBCH and PDSCH, and PDSCH can be transmitted in the time / frequency resources determined according to the SSB.

[0230] The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can also identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAG ID and the SSB group based on the PDSCH including SIBy. The TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID during the RRC establishment process after the random access process is executed. Alternatively, the TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID through RRC signaling after the RRC establishment process is completed. In addition, the TRP can not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID from the PDSCH including the system information SIBy.

[0231] Then, TRP 1 and the terminal can perform uplink synchronization (S2302) according to the SIB indication obtained based on the system information and according to the RO in a four-step or two-step CBRA process. Here, the RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization according to the configuration of TAG 1 for the communication link and update the uplink synchronization.

[0232] Then, TRP 1 can transmit an RRC establishment message to the terminal (S2303). The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S2304). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0233] For this purpose, TRP 1 can transmit downlink-related DCI to the terminal (S2309). Then, the terminal can receive the downlink-related DCI from TRP 1. Here, the downlink-related DCI can indicate DL / Combined TCI 1 (which indicates the receiving configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal according to the downlink-related DCI (S2310). Then, the terminal can receive the downlink data from TRP 1 based on the downlink-related DCI.

[0234] On the other hand, TRP 1 can transmit uplink-related DCI (S2311) to the terminal. Then, the terminal can receive the uplink-related DCI from TRP 1. Here, the uplink-related DCI can indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 1 according to the uplink-related DCI (S2312). Then, TRP 1 can receive the uplink data from the terminal based on the uplink-related DCI.

[0235] In addition, the terminal can be in the RRC connected state. TRP 1 can request the terminal to perform measurements (S2305). Therefore, the terminal can perform measurements by receiving SSBs from neighboring TRPs. In addition, the terminal can report the SSB-based measurement results for neighboring TRPs to TRP 1 via RRC signaling (S2306). In this case, the terminal can report SSB 5 to TRP 1 as a sub-optimal SSB. Therefore, TRP 1 can receive the measurement report from the terminal. TRP 1 can identify that SSB 5 is a sub-optimal SSB through the measurement report. In this case, SSB 5 can be included in the SSB group used by TRP 1. Therefore, TRP 1 can identify itself as the TRP that transmits SSB 5 according to the relationship between the SSB group and the TRP. Here, the measurement report is described as being performed by the terminal according to the request of TRP 1. However, differently, even without such a request, the terminal can perform the measurement report.

[0236] In this case, the measurement report can include the first SSB index (i.e., the optimal SSB index), the second SSB index (i.e., the sub-optimal SSB index), the third SSB index, etc. In addition, the measurement report can include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc.

[0237] If the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc. does not exceed a predetermined threshold, the terminal can request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc. exceeds the predetermined threshold, the terminal can request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of terminal reverse synchronization and reverse synchronization update can be reduced.

[0238] In addition, the terminal can obtain the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal can request the TRP for a second link establishment process without RACH. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal can request the TRP for a second link establishment process based on RACH.

[0239] Therefore, the terminal can perform a random access establishment process (S2307) based on SSB 5 and TRP 1. In this process, the terminal can configure TAG 5 for uplink synchronization for the communication link with TRP 1 and update the uplink synchronization for the communication link with TRP 1. The random access establishment process based on SSB 5 with TRP 1 can be triggered by TRP 1. Alternatively, the random access establishment process based on SSB 5 with TRP 1 can be triggered by the terminal.

[0240] First, in the triggering method of TRP 1, TRP 1 can indicate to the terminal to perform CFRA or CBRA random access through high-layer signaling or PDCCH, so as to trigger a random access establishment process based on SSB 5 for TRP 1. On the other hand, in the terminal triggering method, the terminal can identify the need to manage another TAG through the random access process with TRP 1. Therefore, the terminal can request random access based on SSB 5 for TRP 1 through high-layer signaling or a physical layer control channel (such as PUSCH, etc.) to trigger a random access establishment process for TRP 1.

[0241] The receiving TRP 1 can indicate to the terminal to perform a CFRA or CBRA random access process through high-layer signaling or PDCCH, so as to continue the random access establishment process based on SSB 5 for TRP 1. The terminal can receive an indication of the random access establishment process based on SSB 5 for TRP 1 from TRP 1. Therefore, the terminal and TRP 1 can complete the random access establishment process by performing the random access process based on SSB5.

[0242] Then, TRP 1 and the terminal can perform the RRC establishment procedure (S2308). In other words, TRP 1 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to TRP 1. TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 1 based on SSB 5. In the connected state, the terminal can communicate with other terminals through two communication links of TRP 1.

[0243] For this purpose, TRP 1 can transmit DCI related to the downlink associated with SSB 5 to the terminal (S2313). Then, the terminal can receive the DCI related to the downlink associated with SSB 5 from TRP 1. Here, the DCI related to the downlink can indicate DL / Combined TCI 2 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal according to the DCI related to the downlink (S2314). Then, the terminal can receive the downlink data from TRP 1 according to the DCI related to the downlink.

[0244] On the other hand, TRP 1 can transmit DCI related to the uplink to the terminal (S2315). Then, the terminal can receive the DCI related to the uplink from TRP 1. Here, the DCI related to the uplink can indicate UL / Combined TCI 2 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 1 according to the DCI related to the uplink (S2316). TRP 1 can receive the uplink data from the terminal based on the DCI related to the uplink. Thereafter, the terminal can update the TA by performing uplink synchronization with TRP 1 periodically or aperiodically for TAG 1 and TAG 5 (S2317).

[0245] Figure 24 It is a sequence diagram showing a fourth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0246] Refer to Figure 24, the terminal can establish two communication links with a TRP belonging to an SSB group. In this case, the terminal can establish two communication links starting from the initial access phase. To this end, the terminal can perform SSB beam measurements on the beamformed SSBs transmitted from TRP 1. In this case, the terminal can select SSB 1 as the optimal SSB (i.e., the first optimal SSB), and select SSB 5 as the sub-optimal SSB (i.e., the second optimal SSB). The terminal can obtain system information based on the optimal SSB (S2401). This system information can be carried on the PBCH and PDSCH transmitted in the time / frequency resources determined according to the SSB.

[0247] The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAGID and the SSB group based on the PDSCH including SIBy. During the RRC establishment process after performing the random access procedure, the TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID. Alternatively, the TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID through RRC signaling after the RRC establishment process is completed. In addition, the TRP may not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID from the PDSCH including the system information SIBy.

[0248] Then, TRP 1 and the terminal can perform uplink synchronization according to the SIB indication obtained based on the system information and according to the RO in a four-step or two-step CBRA process (S2102). Here, the RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization and update of uplink synchronization according to the configuration of TAG 1 for this communication link.

[0249] Then, TRP 1 can transmit an RRC establishment message to the terminal (S2403). The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S2404). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0250] To this end, TRP 1 may transmit downlink-related DCI (S2410) to the terminal. Then, the terminal may receive the downlink-related DCI from TRP 1. Here, the downlink-related DCI may indicate DL / Combined TCI 1 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and may be transmitted on the PDCCH. Thereafter, TRP 1 may transmit downlink data to the terminal according to the downlink-related DCI (S2411). Then, the terminal may receive the downlink data from TRP 1 based on the downlink-related DCI.

[0251] On the other hand, TRP 1 may transmit uplink-related DCI (S2412) to the terminal. Then, the terminal may receive the uplink-related DCI from TRP 1. Here, the uplink-related DCI may indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and may be transmitted on the PDCCH. Thereafter, the terminal may transmit uplink data to TRP 1 according to the uplink-related DCI (S2413). Then, TRP 1 may receive the uplink data from the terminal based on the uplink-related DCI.

[0252] In addition, the terminal may be in the RRC connected state. TRP 1 may request the terminal to perform measurements (S2405). Therefore, the terminal may perform measurements by receiving SSBs from neighboring TRPs. The terminal may report the SSB-based measurement results for the neighboring TRPs to TRP 1 through RRC signaling (S2406). In this case, the terminal may report SSB 5 as the sub-optimal SSB to TRP 1. Therefore, TRP 1 may receive the measurement report from the terminal. TRP 1 may identify SSB 5 as the sub-optimal SSB through the measurement report. In this case, SSB 5 may be included in the SSB group used by TRP 1. Therefore, TRP 1 may identify itself as the TRP transmitting SSB 5 according to the relationship between the SSB group and the TRP. Here, the measurement report is described as being performed by the terminal at the request of TRP 1, but differently, even without such a request, the terminal may perform the measurement report.

[0253] In this case, the measurement report may include the first SSB index (i.e., the optimal SSB index), the second SSB index (i.e., the sub-optimal SSB index), the third SSB index, etc. In addition, the measurement report may further include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc.

[0254] If the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal may request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of terminal reverse synchronization and reverse synchronization update can be reduced.

[0255] In addition, the terminal can obtain the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index. Therefore, if the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal may request a second link establishment procedure without RACH from the TRP. On the other hand, if the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request a second link establishment procedure based on RACH from the TRP.

[0256] In addition, the terminal may report SSB 5 to TRP 1 as a sub-optimal SSB. In this case, SSB 5 may be included in the same SSB group as SSB1. Therefore, for example, the communication link associated with SSB 5 may be a different communication link from the communication link associated with SSB 1, which is from the multipath of TRP 1. TRP 1 may configure TAG 5 for the communication link associated with SSB 5 to perform uplink synchronization and update the uplink synchronization of this communication link. Accordingly, through the RACH-less procedure, TRP 1 and the terminal may perform the following beam measurements between the terminal and SSB 5.

[0257] For this purpose, TRP 1 may instruct the terminal to transmit an uplink beamformed SRS (S2107) to the TRP including TRP 1 using the specified scheduling resources. In this case, TRP 1 may instruct the terminal to transmit the SRS through RRC signaling, and the RRC signaling includes information about the specified scheduling resources for transmitting the uplink beamformed SRS. In this case, TRP 1 may inform neighboring TRPs that the terminal transmits an uplink beamformed SRS using the determined scheduling time / frequency resources to suppress interference. Alternatively, to improve resource efficiency, TRP 1 may not inform neighboring TRPs that the terminal transmits an uplink beamformed SRS using the determined scheduling time / frequency resources.

[0258] Then, the terminal can transmit the beamformed SRS to the TRP including TRP 1 (S2408). TRP 1 can receive the SRS from the terminal. In addition, TRP 1 can select the most suitable uplink beam based on the received SRS and estimate the TA, and inform the terminal of the information about the most suitable uplink beam (i.e., the optimal uplink beam) and the information about the estimated TA (S2409). In other words, TRP 1 can inform the terminal of the information about the SRS with the highest SINR among the beamformed SRS received from the terminal. Accordingly, the terminal can receive the information about the optimal uplink beam and the information about the TA from TRP 1. The terminal can confirm that the optimal uplink beam belongs to itself. Through this process, the terminal can complete the system connection with TRP 1 through the communication link associated with SSB 5. In the connected state, the terminal can communicate with other terminals through two communication links of TRP 1.

[0259] For this purpose, TRP 1 can transmit the DCI related to the downlink associated with SSB 5 to the terminal (S2414). Then, the terminal can receive the DCI related to the downlink from TRP 1. Here, the DCI related to the downlink can indicate DL / Combined TCI 2 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal based on the DCI related to the downlink (S2415). Then, the terminal can receive the downlink data from TRP 1 based on the DCI related to the downlink.

[0260] On the other hand, TRP 1 can transmit the DCI related to the uplink associated with SSB 5 to the terminal (S2416). Then, the terminal can receive the DCI related to the uplink from TRP 1. Here, the DCI related to the uplink can indicate UL / Combined TCI 2 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 1 based on the DCI related to the uplink (S2417).

[0261] Then, TRP 1 can receive the uplink data from the terminal based on the DCI related to the uplink. Thereafter, the terminal can update the TA by performing uplink synchronization with TRP 1 periodically or aperiodically for TAG 1 and TAG 5 (S2418). Although Figure 23 and Figure 24 the process of establishing two communication links is described, the method of the present disclosure is not limited thereto. TRP1 and the terminal can apply Figure 23 and Figure 24Establish three or more communication links by the method of establishing a communication link as shown, and perform multi-TRP communication in the downlink and uplink.

[0262] Figure 25 It is a conceptual diagram showing a fifth exemplary embodiment of a method for grouping synchronization signal blocks.

[0263] Referring to Figure 25 , the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, and SSB 5, and SSB group 1 can be mapped to TRP 1 to TRP A. Here, A can be a positive integer greater than 1. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8, and SSB group 2 can be mapped to TRP A + 1 to TRP B. Mapping SSB group 1 to TRP 1 to TRP A can mean that when TRP 1 to TRP A perform SSB scanning, only SSB 1, SSB 3, SSB 5, and SSB 7 are used to transmit beamformed SSBs in the corresponding directions. Similarly, mapping SSB group 2 to TRP A + 1 to TRP B can mean that when TRP A + 1 to TRP B perform SSB scanning, only SSB 2, SSB 4, SSB 6, and SSB 8 are used to transmit beamformed SSBs in the corresponding directions. In this case, the number of available SSBs can be 8, but it is not limited thereto, and it can also be 4, 16, or 64, etc. Here, TRP 1 to TRP A and TRP A + 1 to TRP B can be included in a serving cell having the same PCIG.

[0264] Figure 26 It is a conceptual diagram showing a sixth exemplary embodiment of a method for grouping synchronization signal blocks.

[0265] Referring to Figure 26, the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, SSB 5, and SSB 7, and SSB group 1 can be mapped to TRP 1 to TRP A belonging to the serving cell. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8. SSB group 2 can be mapped to TRP A+1 to TRP B belonging to the non-serving cell. Here, mapping SSB group 1 to TRP 1 to TRP A can mean that when TRP 1 to TRP A perform SSB scanning, only SSB 1, SSB 3, SSB 5, and SSB 7 are used to transmit beamformed SSBs in the corresponding directions. Similarly, mapping SSB group 2 to TRP A+1 to TRP B can mean that when TRP A+1 to TRP B perform SSB scanning, only SSB 2, SSB 4, SSB 6, and SSB 8 are used to transmit beamformed SSBs in the corresponding directions. In this case, the number of available SSBs can be 8, but is not limited thereto, and can also be 4, 16, or 64, etc. Here, TRP 1 to TRP A can belong to the serving cell with PCI G. TRP A+1 to TRP B can belong to the non-serving cell with PCI Z. In Figure 25 and Figure 26 , for each TRP in each of the two TRP groups, TRP 1 to TRP A and TRP A+1 to TRP B, are geographically adjacent and can have similar TA values, so that multiple TRP transmissions can be achieved for a large number of TRPs.

[0266] Figure 27 is a conceptual diagram showing a fourth exemplary embodiment of the tag ID configuration method.

[0267] Referring to Figure 27 , each SSB group can be mapped to multiple TRPs to adjust the TA required for uplink synchronization and can be associated with one tag ID (such as TAG 1, TAG 2, etc.). For example, SSB group 1 can be associated with TAG 1, while SSB group 2 can be associated with TAG 2. In this case, TAG 1 can be associated with joint TCI 1. TAG 2 can be associated with joint TCI2. Since the TAG is managed for each SSB group, the terminal can perform uplink synchronization for each TAG and communicate when establishing a communication link for TRP 1 and TRP A+1 respectively.

[0268] Figure 28 is a conceptual diagram showing a fifth exemplary embodiment of the tag ID configuration method.

[0269] Reference Figure 28 The terminal can establish two communication links with a TRP 1. In this case, the terminal can establish a communication link with the TRP 1 based on SSB 1. In addition, the terminal can establish another communication link with the TRP 1 based on SSB 5. The two communication links established as described above can have the same TAG 1. Based on TAG 1, the terminal can perform uplink synchronization and communication on these two communication links. Here, one communication link can pass through an obstacle. TRP 1 and TRP2 can be included in SSB group 1. One link between the terminal and TRP 1 can be associated with TAG 1, and can be associated with DL / UL / Combined TCI 1. The other link between the terminal and TRP 1 passing through the obstacle can be associated with TAG 1, and can be associated with DL / UL / Combined TCI 2.

[0270] Here, the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, SSB 5, and SSB 7, and SSB group 1 can be mapped to TRP1 to TRP A belonging to the serving cell. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8. SSB group 2 can be mapped to TRP A+1 to TRP B belonging to the non-serving cell. Here, TRP 1 to TRP A can belong to the serving cell with PCIG. TRP A+1 to TRP B can belong to the non-serving cell with PCIZ.

[0271] Figure 29 It is a conceptual diagram showing a sixth exemplary embodiment of the label ID configuration method.

[0272] Reference Figure 29 The terminal can establish a communication link with a TRP 1 based on SSB 1. In addition, the terminal can establish another communication link with a TRP 2 based on SSB 5. The two communication links established as described above can have the same TAG 1. The terminal and the TRP can perform uplink synchronization and communication by assigning the same TAG 1 to these two communication links. TRP1 and TRP 2 can belong to SSB group 1. One link between the terminal and TRP 1 can be associated with TAG 1, and can be associated with DL / UL / Combined TCI 1. The other link between the terminal and TRP 2 can be associated with TAG 1, and can be associated with DL / UL / Combined TCI 2.

[0273] Here, the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, SSB 5, and SSB 7, and SSB group 1 can be mapped to TRP1 to TRP A belonging to the serving cell. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8. SSB group 2 can be mapped to TRP A+1 to TRP B belonging to the non-serving cell. Here, TRP 1 to TRP A can belong to the serving cell with PCIG. TRP A+1 to TRP B can belong to the non-serving cell with PCIZ.

[0274] As described above Figures 25 to 29 shown, each SSB group can be mapped to multiple TRPs to adjust the TA required for uplink synchronization. One tag ID (such as TAG 1, TAG 2, etc.) can be associated with multiple TRPs. For example, TRP 1 and TRP2 of SSB group 1 can be associated with TAG 1. In this case, TAG 1 can be associated with joint TCI 1 or joint TCI 2. Since the TAG is managed for each SSB group, when establishing a communication link for TRP 1 and TRP 2 respectively, the terminal can perform uplink synchronization and communication. In Figure 28 and 29 cases, the link configuration method in a multi-TRP communication system can be as follows Figure 30 shown.

[0275] Figure 30 is a sequence diagram showing a fifth exemplary embodiment of the link configuration method in a multi-TRP environment.

[0276] Referring to Figure 30 , the terminal can establish two communication links with one TRP belonging to one SSB group. Alternatively, the terminal can establish two communication links with two TRPs belonging to one SSB group. The terminal can establish two communication links from the initial access phase. To this end, the terminal can perform SSB beam measurement on the beamformed SSB transmitted from TRP 1. In this case, the terminal can select SSB 1 as the optimal SSB (i.e., the 1st optimal SSB), and select SSB 5 as the sub-optimal SSB (i.e., the 2nd optimal SSB). The terminal can obtain system information based on the optimal SSB (S3001). This system information can be carried on the PBCH and PDSCH transmitted in the time / frequency resources determined according to the SSB.

[0277] The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can also identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAG ID and the SSB group based on the PDSCH including SIBy. The TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID during the RRC establishment process after the random access process is executed. Alternatively, the TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID through RRC signaling after the RRC establishment process is completed. In addition, the TRP may not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID from the PDSCH including the system information SIBy.

[0278] Then, TRP 1 and the terminal can perform uplink synchronization (S3002) according to the SIB indication obtained based on the system information and according to the RO in a four-step or two-step CBRA process. At this time, the RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization and the update of uplink synchronization according to the configuration of TAG 1 for this communication link.

[0279] Then, TRP 1 can transmit an RRC establishment message to the terminal (S3003). The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S3004). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0280] For this purpose, TRP 1 can transmit downlink-related DCI to the terminal (S3010). Then, the terminal can receive the downlink-related DCI from TRP 1. Here, the downlink-related DCI can indicate DL / Combined TCI 1 (which indicates the receiving configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal according to the downlink-related DCI (S3011). Then, the terminal can receive the downlink data from TRP 1 based on this downlink-related DCI.

[0281] On the other hand, the TRP 1 may transmit uplink-related DCI to the terminal (S3012). Then, the terminal may receive the uplink-related DCI from the TRP 1. Here, the uplink-related DCI may indicate the UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and may be transmitted on the PDCCH. Thereafter, the terminal may transmit uplink data to the TRP 1 according to the uplink-related DCI (S3013). Then, the TRP 1 may receive the uplink data from the terminal based on the uplink-related DCI.

[0282] In addition, the terminal may be in the RRC connected state. The TRP 1 may request the terminal to perform measurements (S3005). Therefore, the terminal may perform measurements by receiving SSBs from neighboring TRPs. In addition, the terminal may report the SSB-based measurement results for the neighboring TRPs to the TRP 1 through RRC signaling (S3006). In this case, the terminal may report the SSB 5 as the sub-optimal SSB to the TRP 1. Therefore, the TRP 1 may receive the measurement report from the terminal. The TRP 1 may identify the SSB 5 as the sub-optimal SSB through the measurement report. In this case, the SSB 5 may be included in the SSB group used by the TRP 1 and the TRP 2. Therefore, the TRP1 may identify itself as the TRP transmitting the SSB 5 according to the relationship between the SSB group and the TRP. Alternatively, the TRP 1 may identify the TRP 2 as the TRP transmitting the SSB 5 according to the relationship between the SSB group and the TRP. Here, the measurement report is described as being performed by the terminal according to the request of the TRP 1, but differently, even without such a request, the terminal may perform the measurement report.

[0283] In this case, the measurement report may include the first SSB index (i.e., the optimal SSB index), the second SSB index (i.e., the sub-optimal SSB index), the third SSB index, etc. In addition, the measurement report may further include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links of the second SSB index, the third SSB index, etc.

[0284] If the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal may request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of terminal reverse synchronization and reverse synchronization update can be reduced.

[0285] In addition, the terminal can obtain the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index. Therefore, if the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index does not exceed the predetermined threshold, the terminal may request the TRP for a second link establishment process without RACH. On the other hand, if the time difference between the receive synchronization point of the current communication link and the receive synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request the TRP for a second link establishment process based on RACH.

[0286] In addition, the terminal can report SSB 5 to TRP 1 as a sub-optimal SSB. In this case, SSB 5 can be included in the same SSB group as SSB1. Thus, for example, the communication link associated with SSB 5 can be a communication link different from the communication link associated with SSB 1, which is transmitted via multipath from TRP 1. Alternatively, the communication link associated with SSB 5 can be a communication link from TRP 2. TRP 1 can configure TAG 1 to the communication link associated with SSB 5 to perform uplink synchronization and update the uplink synchronization of this communication link. Accordingly, through the RACH-less process, TRP 1 or TRP 2 and the terminal can perform beam measurement between the terminal and SSB 5 as follows.

[0287] For this purpose, TRP 1 may instruct the terminal to transmit an uplink beamformed SRS to the TRP using the specified scheduling resources (S3007). In this case, TRP 1 may instruct the terminal to transmit the SRS through RRC signaling, and the RRC signaling includes information on the specified and scheduling resources for transmitting the uplink beamformed SRS. In this case, TRP 1 may inform neighboring TRPs that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS to suppress interference. Alternatively, to improve resource efficiency, TRP 1 may not inform neighboring TRPs that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS.

[0288] Then, the terminal may transmit the beamformed SRS to the TRPs including TRP 1 and TRP 2 (S3008). TRP 1 and TRP 2 may receive the SRS from the terminal. In addition, TRP 1 may select the most suitable uplink beam based on the received SRS, and inform the terminal of the information on the most suitable uplink beam (i.e., the optimal uplink beam) (S3009). In other words, TRP 1 may inform the terminal of the information on the SRS with the highest SINR among the beamformed SRSs received from the terminal. Therefore, the terminal may confirm that the optimal uplink beam belongs to itself. Through this process, the terminal may complete the system connection with TRP 1 through the communication link associated with SSB 5. In the connected state, the terminal may communicate with other terminals through two communication links of TRP 1.

[0289] Alternatively, TRP 2 may select the most suitable uplink beam based on the received SRS, and inform TRP 1 of the information on the most suitable uplink beam (i.e., the optimal uplink beam). Then, TRP 1 may, based on the SRS received from TRP 2, inform the terminal of the information on the most suitable uplink (i.e., the optimal uplink beam) (S3009). Therefore, the terminal may receive the information on the optimal uplink beam from TRP 1. The terminal may confirm that the optimal uplink beam belongs to itself. Through this process, the terminal may complete the system connection with TRP 2 through the communication link associated with SSB 5. In the connected state, the terminal may communicate with other terminals through two communication links of TRP 1 and TRP 2.

[0290] To this end, TRP 1 or TRP 2 may transmit DCI related to the downlink associated with SSB 5 to the terminal (S3014). Then, the terminal may receive the DCI related to the downlink from TRP 1 or TRP 2. Here, the DCI related to the downlink may indicate DL / Combined TCI 2 (indicating the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and may be transmitted on the PDCCH. Thereafter, TRP 1 or TRP 2 may transmit downlink data to the terminal according to the DCI related to the downlink (S3015). Then, the terminal may receive the downlink data from TRP 1 or TRP 2 according to the DCI related to the downlink.

[0291] On the other hand, TRP 1 or TRP 2 may transmit DCI related to the uplink associated with SSB 5 to the terminal (S3016). Then, the terminal may receive the DCI related to the uplink from TRP 1 or TRP 2. Here, the DCI related to the uplink may indicate UL / Combined TCI 2 (indicating the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and may be transmitted on the PDCCH. Thereafter, the terminal may transmit uplink data to TRP 1 or TRP 2 according to the DCI related to the uplink (S3017).

[0292] Then, TRP 1 or TRP 2 may receive the uplink data from the terminal based on the DCI related to the uplink. Thereafter, the terminal may update the TA by performing uplink synchronization with TRP 1 or TRP 2 for TAG 1 periodically or aperiodically (S3018). Although Figure 30 the process of establishing two communication links is described, the method of the present disclosure is not limited thereto. TRP1 or TRP 2 and the terminal may establish three or more communication links by applying Figure 30 the shown communication link establishment method, and perform multi-TRP communication in the downlink and uplink.

[0293] Figure 31 Conceptual diagram of the seventh exemplary embodiment of the label ID configuration method.

[0294] Referring to Figure 31, when establishing two communication links with a TRP, the terminal can perform uplink synchronization and communication by assigning different TAGs to each SSB. Here, one communication link can pass through an obstacle. In other words, the terminal can establish two communication links with a TRP 1. In this case, the terminal can establish one communication link with TRP 1 based on SSB 1. In addition, the terminal can configure another communication link with TRP 2 based on SSB 5. As described above, the communication link established based on SSB 1 can have TAG 1, while the communication link established based on SSB 5 can have TAG 5. The terminal can perform uplink synchronization and communication on the communication link based on TAG 1. In addition, the terminal can perform uplink synchronization and communication on the communication link based on TAG 5. Here, one communication link can pass through an obstacle. TRP 1 and TRP 2 can be included in SSB group 1. One link between the terminal and TRP 1 can be associated with TAG 1, and can be associated with DL / UL / Combined TCI 1. In addition, another link passing through the obstacle between the terminal and TRP 1 can be associated with TAG 5, and can be associated with DL / UL / Combined TCI 2.

[0295] Here, the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, SSB 5, and SSB 7, and SSB group 1 can be mapped to TRP1 to TRP A belonging to the serving cell. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8. SSB group 2 can be mapped to TRP A+1 to TRP B belonging to the non-serving cell. Here, TRP 1 to TRP A can belong to the serving cell with PCIG. TRP A+1 to TRP B can belong to the non-serving cell with PCIZ.

[0296] Figure 32 is a conceptual diagram showing an eighth exemplary embodiment of the tag ID configuration method.

[0297] Refer to Figure 32, when establishing two communication links for TRP 1 and TRP 2 within the same SSB group, the terminal can achieve uplink synchronization and communication by assigning different TAGs to each SSB. In other words, the terminal can establish a link with TRP 1 based on SSB 1. Additionally, the terminal can configure another communication link with TRP 2 based on SSB 5. In the two communication links established above, the communication link based on SSB 1 can have TAG 1, while the communication link based on SSB 5 can have TAG 5. The terminal and the TRP can achieve uplink synchronization and communication for this communication link by assigning different TAGIDs to the two communication links. TRP 1 and TRP 2 can be included in SSB group 1. One link between the terminal and TRP 1 can be associated with TAG 1, and can also be associated with DL / UL / Combined TCI 1. Additionally, the other link between the terminal and TRP 2 can be associated with TAG 5, and can also be associated with DL / UL / Combined TCI 2.

[0298] Here, the SSBs (SSB 1 to SSB 8) can be divided into two SSB groups (SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB 1, SSB 3, SSB 5, and SSB 7, and SSB group 1 can be mapped to TRP1 to TRP A belonging to the serving cell. On the other hand, SSB group 2 can include SSB 2, SSB 4, SSB 6, and SSB 8. SSB group 2 can be mapped to TRP A + 1 to TRP B belonging to the non-serving cell. Here, TRP 1 to TRP A can belong to the serving cell with PCIG. TRP A + 1 to TRP B can belong to the non-serving cell with PCIZ. In Figure 31 and 32 this case, the link configuration method in the multi-TRP communication system can be as follows Figure 33 and 34 shown.

[0299] Figure 33 is a sequence diagram showing a sixth exemplary embodiment of the link configuration method in a multi-TRP environment.

[0300] Refer to Figure 33, the terminal can establish two communication links with one TRP belonging to an SSB group. Alternatively, the terminal can establish two communication links with two TRPs belonging to an SSB group. In this case, the terminal can establish two communication links starting from the initial access phase. To this end, the terminal can perform SSB beam measurements on the beamformed SSBs transmitted from TRP 1. Alternatively, the terminal can perform SSB beam measurements on the beamformed SSBs transmitted from TRP 2. In this case, the terminal can select SSB 1 as the optimal SSB (i.e., the first optimal SSB), and select SSB 5 as the sub-optimal SSB (i.e., the second optimal SSB). The terminal can obtain system information based on the optimal SSB (S3301). This system information can be carried on the PBCH and PDSCH transmitted in the time / frequency resources determined according to the SSB.

[0301] The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAG ID and the SSB group based on the PDSCH including SIBy. The TRP allows the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID during the RRC establishment process after performing the random access procedure. Alternatively, the TRP allows the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID through RRC signaling after the RRC establishment process is completed. In addition, the TRP may not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID based on the PDSCH including SIBy (i.e., system information).

[0302] Then, TRP 1 and the terminal can perform uplink synchronization according to the SIB indication obtained based on the system information, according to the RO, in a four-step or two-step CBRA process (S3302). Here, RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization and update uplink synchronization according to the configuration of TAG 1 for the communication link.

[0303] Then, TRP 1 can transmit an RRC establishment message (S3303) to the terminal. The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete RRC establishment and transmit an RRC establishment complete message to TRP 1 (S3304). TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0304] For this purpose, TRP 1 can transmit DCI related to the downlink associated with SSB 1 to the terminal (S3309). Then, the terminal can receive the DCI related to the downlink from TRP 1. Here, the DCI related to the downlink can indicate DL / Combined TCI 1 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal according to the DCI related to the downlink (S3310). Then, the terminal can receive the downlink data from TRP 1 based on the DCI related to the downlink.

[0305] On the other hand, TRP 1 can transmit DCI related to the uplink associated with SSB 1 to the terminal (S3311). Then, the terminal can receive the DCI related to the uplink from TRP 1. Here, the DCI related to the uplink can indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 1 according to the DCI related to the uplink (S3312). Then, TRP 1 can receive the uplink data from the terminal based on the DCI related to the uplink.

[0306] In addition, the terminal is in the RRC connected state. TRP 1 can request the terminal to perform measurements (S3305). Therefore, the terminal can perform measurements by receiving SSBs from neighboring TRPs. In addition, the terminal can report the SSB-based measurement results for neighboring TRPs to TRP 1 via RRC signaling (S3306). In this case, the terminal can report SSB 5 to TRP 1 as a sub-optimal SSB. Therefore, TRP 1 can receive the measurement report from the terminal. TRP 1 can identify that SSB 5 is a sub-optimal SSB through the measurement report. In this case, SSB 5 can be included in the SSB set used by TRP 1 or TRP 2. Therefore, TRP 1 can identify itself as the TRP transmitting SSB 5 according to the relationship between the SSB set and the TRP. Alternatively, TRP 1 can identify TRP 2 as the TRP transmitting SSB 5 according to the relationship between the SSB set and the TRP. Here, the measurement report is described as being performed by the terminal upon the request of TRP 1. However, differently, even without such a request, the terminal can perform the measurement report.

[0307] In this case, the measurement report may include a first SSB index (i.e., the optimal SSB index), a second SSB index (i.e., the sub-optimal SSB index), a third SSB index, etc. In addition, the measurement report may further include information on the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links of the second SSB index, the third SSB index, etc.

[0308] If the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links of the second SSB index, the third SSB index, etc. does not exceed a predetermined threshold, the terminal can request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links of the second SSB index, the third SSB index, etc. exceeds the predetermined threshold, the terminal can request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of terminal reverse synchronization and reverse synchronization update can be reduced.

[0309] In addition, the terminal can obtain the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal can request the TRP for a second link establishment process without RACH. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal can request the TRP for a second link establishment process based on RACH.

[0310] In addition, the terminal can perform a random access establishment process (S3307) based on SSB 5 and TRP 1 or TRP 2. In this process, the terminal can configure TAG 5 for the communication link of TRP 1 or TRP 2 based on SSB 5 to perform uplink synchronization and update the uplink synchronization of the communication link. The random access establishment process for TRP 1 or for TRP 2 can be triggered by the TRP. Alternatively, the random access establishment process for TRP 1 or for TRP 2 can also be triggered by the terminal.

[0311] First, in the TRP 1 triggering method, TRP 1 can indicate to the terminal to perform a CFRA or CBRA random access process through high-layer signaling or PDCCH, thereby triggering the random access establishment process for TRP 1 or for TRP 2 based on SSB 5. On the other hand, in the terminal triggering method, the terminal can identify the need to manage another TAG through the random access process with TRP 1. Therefore, the terminal can request random access to TRP 1 or TRP 2 based on SSB 5 through high-layer signaling or a physical layer control channel (such as PUSCH, etc.) to trigger the random access establishment process for TRP 1 or for TRP 2.

[0312] The receiving TRP 1 can indicate to the terminal to perform a CFRA or CBRA random access process through high-layer signaling or PDCCH, thereby continuing the random access establishment process for TRP 1 or for TRP 2 based on SSB 5. In this way, the terminal can receive an indication of the random access establishment process for TRP 1 or for TRP 2 based on SSB 5 from TRP 1. Therefore, the terminal and TRP 1 or TRP 2 can complete the random access establishment process by performing the random access process.

[0313] Then, TRP 1 or TRP 2 and the terminal can perform an RRC establishment procedure (S3308) for the communication link established based on SSB 5. In other words, TRP 1 or TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 1 or TRP 2. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 or TRP 2. TRP 1 or TRP 2 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1 or TRP 2 based on SSB 5. In the connected state, the terminal can communicate with other terminals through two communication links of TRP 1. Alternatively, in the connected state, the terminal can communicate with other terminals through two communication links of TRP 1 and TRP 2.

[0314] For this purpose, TRP 1 or TRP 2 can transmit DCI related to the downlink associated with SSB 5 to the terminal (S3313). Then, the terminal can receive the DCI related to the downlink associated with SSB 5 from TRP 1 or TRP 2. Here, the DCI related to the downlink can indicate DL / Combined TCI 2 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 or TRP 2 can transmit downlink data to the terminal according to the DCI related to the downlink (S3314). Then, the terminal can receive the downlink data from TRP 1 or TRP 2 based on the DCI related to the downlink.

[0315] On the other hand, TRP 1 or TRP 2 can transmit DCI related to the uplink to the terminal (S3315). Then, the terminal can receive the DCI related to the uplink from TRP 1 or TRP 2. Here, the DCI related to the uplink can indicate UL / Combined TCI 2 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 1 or TRP 2 according to the DCI related to the uplink (S3316). Then, TRP 1 or TRP 2 can receive the uplink data from the terminal based on the DCI related to the uplink. Then, the terminal can update the TA by performing uplink synchronization with TRP 1 or TRP 2 periodically or aperiodically for TAG 1 and TAG 5 (S3317).

[0316] Figure 34 It is a sequence diagram showing a seventh exemplary embodiment of a link configuration method in a multi-TRP environment.

[0317] Refer toFigure 34 The terminal can establish two communication links with one TRP belonging to an SSB group. Alternatively, the terminal can establish two communication links with two TRPs belonging to the same SSB group. In this case, the terminal can establish two communication links starting from the initial access phase. To this end, the terminal can perform SSB beam measurements on the beamformed SSB transmitted from TRP 1. In this case, the terminal can select SSB 1 as the optimal SSB (i.e., the first optimal SSB), and select SSB 5 as the sub-optimal SSB (i.e., the second optimal SSB). The terminal can obtain system information (S3401) based on the optimal SSB. This system information can be carried on the PBCH and PDSCH transmitted in the time / frequency resources determined according to the SSB.

[0318] The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can also identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAG ID and the SSB group based on the PDSCH including SIBy. The TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID during the RRC establishment process after performing the random access procedure. Alternatively, the TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID through RRC signaling after the RRC establishment process is completed. In addition, the TRP may not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID from the PDSCH including the system information SIBy.

[0319] Then, TRP 1 and the terminal can perform uplink synchronization (S3402) according to the SIB indication obtained based on the system information and according to the RO in a four-step or two-step CBRA process. At this time, the RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization and update of uplink synchronization according to the configuration of TAG 1 for the communication link.

[0320] Then, TRP 1 can transmit an RRC establishment message (S3403) to the terminal. The terminal can receive the RRC establishment message from TRP 1. Accordingly, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to TRP 1 (S3404). TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0321] For this purpose, TRP 1 can transmit DCI related to the downlink to the terminal (S3410). Then, the terminal can receive the DCI related to the downlink from TRP 1. Here, the DCI related to the downlink can indicate DL / Combined TCI 1 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal according to the DCI related to the downlink (S3411). Then, the terminal can receive the downlink data from TRP 1 based on the DCI related to the downlink.

[0322] On the other hand, TRP 1 can transmit DCI related to the uplink to the terminal (S3412). Then, the terminal can receive the DCI related to the uplink from TRP 1. Here, the DCI related to the uplink can indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 1 according to the DCI related to the uplink (S3413). Then, TRP 1 can receive the uplink data from the terminal based on the DCI related to the uplink.

[0323] In addition, the terminal may be in the RRC connected state. TRP 1 may request the terminal to perform measurements (S3405). Therefore, the terminal may perform measurements by receiving SSBs from neighboring TRPs. In addition, the terminal may report the SSB-based measurement results for the neighboring TRPs to TRP 1 via RRC signaling (S3406). In this case, the terminal may report SSB 5 to TRP 1 as a sub-optimal SSB. Therefore, TRP 1 may receive the measurement report from the terminal. TRP 1 may identify SSB 5 as a sub-optimal SSB via the measurement report. In this case, SSB 5 may be included in the SSB group used by TRP 1 and TRP 2. Therefore, TRP1 may identify itself as the TRP transmitting SSB 5 based on the relationship between the SSB group and the TRP. Alternatively, TRP 1 may identify TRP 2 as the TRP transmitting SSB 5 based on the relationship between the SSB group and the TRP. Here, the measurement report is described as being performed by the terminal upon the request of TRP 1. However, differently, even without such a request, the terminal may perform the measurement report.

[0324] In this case, the measurement report may include a first SSB index (i.e., the optimal SSB index), a second SSB index (i.e., the sub-optimal SSB index), a third SSB index, etc. In addition, the measurement report may further include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc.

[0325] If the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc. does not exceed a predetermined threshold, the terminal may request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc. exceeds the predetermined threshold, the terminal may request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of reverse synchronization and reverse synchronization update at the terminal may be reduced.

[0326] In addition, the terminal can obtain the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal can request the TRP to perform a second link establishment process without RACH. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal can request the TRP to perform a second link establishment process based on RACH.

[0327] In addition, the terminal can report SSB 5 to TRP 1 as a sub-optimal SSB. In this case, SSB 5 can be included in the same SSB group as SSB1. Therefore, for example, the communication link associated with SSB 5 can be a different communication link from the communication link associated with SSB 1, which is transmitted through multipath from TRP 1. Alternatively, the communication associated with SSB 5 can be a communication link from TRP 2. TRP 1 can configure TAG 5 for the communication associated with SSB 5 to perform uplink synchronization and update the uplink synchronization of this communication link. Therefore, through the RACH-less process, TRP 1 or TRP 2 and the terminal can perform beam measurement between the terminal and SSB 5 as follows.

[0328] To this end, TRP 1 can instruct the terminal to transmit an uplink beamformed SRS (S3407) to the TRP using the specified scheduling resources. In this case, TRP 1 can instruct the terminal to transmit the SRS through RRC signaling, which includes the specified scheduling resource information for transmitting the uplink beamformed SRS. In this case, TRP 1 can inform neighboring TRPs that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS to suppress interference. Alternatively, to improve resource efficiency, TRP 1 can not inform neighboring TRPs that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS.

[0329] Then, the terminal can transmit the beamformed SRS to the TRP (S3408) including TRP 1 and TRP 2. TRP1 or TRP 2 can receive the SRS from the terminal. In addition, TRP 1 can select the most suitable uplink beam and the estimated TA based on the received SRS, and inform the terminal of the information about the most suitable uplink beam (i.e., the optimal uplink beam) and the information about the estimated TA (S3409). In other words, TRP 1 can inform the terminal of the information about the SRS with the highest SINR among the beamformed SRSs received from the terminal.

[0330] Alternatively, TRP 2 may select the most suitable uplink beam according to the received SRS, estimate the TA, and inform TRP 1 of the information on the most suitable uplink beam (i.e., the optimal uplink beam) and the estimated TA. Then, TRP 1 may inform the terminal of the information on the most suitable uplink beam (i.e., the optimal uplink beam) and the estimated TA according to the SRS information received from TRP 2. Therefore, the terminal may receive the optimal uplink beam information and TA information from TRP 1. The terminal may confirm that the optimal uplink beam belongs to itself. Through this process, the terminal may complete the system connection with TRP 1 and TRP 2 through the communication link associated with SSB 5. In the connected state, the terminal may communicate with other terminals through two communication links of TRP 1. Alternatively, in the connected state, the terminal may communicate with other terminals through two communication links of TRP 1 and TRP 2.

[0331] For this purpose, TRP 1 or TRP 2 may transmit DCI related to the downlink associated with SSB 5 to the terminal (S3414). Then, the terminal may receive the DCI related to the downlink from TRP 1 or TRP 2. Here, the DCI related to the downlink may indicate DL / Combined TCI 2 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and may be transmitted on the PDCCH. Thereafter, TRP 1 or TRP 2 may transmit downlink data to the terminal according to the DCI related to the downlink (S3415). Then, the terminal may receive the downlink data from TRP 1 or TRP 2 based on the DCI related to the downlink.

[0332] On the other hand, TRP 1 or TRP 2 may transmit DCI related to the uplink associated with SSB 5 to the terminal (S3416). Then, the terminal may receive the DCI related to the uplink from TRP 1 or TRP 2. Here, the DCI related to the uplink may indicate UL / Combined TCI 2 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and may be transmitted on the PDCCH. Thereafter, the terminal may transmit uplink data to TRP 1 or TRP 2 according to the DCI related to the uplink (S3417).

[0333] Then, TRP 1 or TRP 2 may receive the uplink data from the terminal based on the DCI related to the uplink. Thereafter, the terminal may update the TA by performing uplink synchronization with TRP 1 or TRP 2 periodically or aperiodically for TAG 1 and TAG 5 (S3418). Although Figure 33 and Figure 34The process of establishing two communication links is described, but the method of the present disclosure is not limited thereto. TRP 1 or TRP 2 and the terminal can establish three or more communication links by applying the Figure 33 and Figure 34 shown method of establishing a communication link, and perform multi-TRP communication in the downlink and uplink.

[0334] Figure 35 is a conceptual diagram showing a ninth exemplary embodiment of a tag ID configuration method.

[0335] Referring to Figure 35 , the TRP can share all SSBs for uplink synchronization. In other words, the TRP can reuse all SSBs, and the tag ID can be associated with the SSB by triggering from the terminal. For example, TRP 1 can use SSB 1 to establish a communication link with the terminal. In addition, TRP 2 can also use SSB 1 to establish a communication link with the terminal. In this case, the communication link established between TRP 1 and the terminal using SSB 1 can use TAG 1. The communication link established between TRP 2 and the terminal using SSB 1 can use TAG 1 or TAG 2. Here, TAG 1 can be associated with TCI 1, and TAG 2 can be associated with TCI 2.

[0336] Figure 36 is a conceptual diagram showing a tenth exemplary embodiment of a tag ID configuration method.

[0337] Referring to Figure 36 , the TRP can share all SSBs for uplink synchronization. In other words, the TRP can reuse all SSBs, and the TAGID can be associated with the SSB by triggering from the terminal. For example, TRP 1 can use SSB 1 to establish a communication link with the terminal. In addition, TRP 2 can also use SSB 5 to establish a communication link with the terminal. In this case, the communication link established between TRP 1 and the terminal using SSB 1 can use TAG 1. The communication link established between TRP 2 and the terminal using SSB 5 can use TAG 1 or TAG 2. Here, TAG 1 can be associated with TCI 1, and TAG 2 can be associated with TCI 2.

[0338] Although SSB 5 has been described as belonging to TRP 2, which is different from TRP 1, this is only an example. SSB 5 can correspond to a multipath link belonging to TRP 1. In Figure 35 and 36 cases, the link establishment method in the multi-TRP communication system can be as follows Figure 37 and 38 shown.

[0339] Figure 37 It is a sequence diagram showing an eighth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0340] Referring to Figure 37 , the terminal can establish communication links with TRP 1 and TRP 2 respectively based on the same SSB 1 of two different TRPs 1 and 2. Alternatively, the terminal can establish communication links with TRP 1 and TRP 2 respectively based on different SSB 1 and SSB 5 of two different TRPs 1 and 2. In this case, the terminal can establish two communication links from the initial access phase. To this end, the terminal can perform SSB beam measurement on the beamformed SSBs transmitted by each of TRP 1 and TRP 2. In this case, the terminal can select SSB 1 transmitted from TRP 1 as the optimal SSB, and select SSB 1 or SSB 5 transmitted from TRP 2 as the sub-optimal SSB.

[0341] The terminal can detect the same SSB index from different received beams. In this case, the terminal can learn that the same SSB index is used in different TRPs. Therefore, the terminal can identify the same SSB 1 as the optimal SSB and the sub-optimal SSB. Alternatively, the terminal cannot arbitrarily determine the same SSB 1 received through different received beams as the optimal SSB and the sub-optimal SSB. In this case, TRP 1 can allow the terminal to report only one SSB 1. Alternatively, TRP 1 can allow the terminal to report two instances of SSB 1 and distinguish them as the optimal SSB and the sub-optimal SSB, as described above. In this case, TRP 1 can establish two communication links by the same process as establishing communication links with two different SSBs.

[0342] In addition, the terminal can obtain system information based on the optimal SSB (S3701). The system information can be carried on the PBCH and PDSCH transmitted in the time / frequency resources determined according to the SSB. The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAG ID and the SSB group according to the PDSCH including SIBy. The TRP allows the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID during the RRC establishment process after the random access process. Alternatively, the TRP allows the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID through RRC signaling after the RRC establishment process is completed. In addition, the TRP may not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAG ID according to the PDSCH including SIBy (i.e., system information).

[0343] Then, TRP 1 and the terminal can perform uplink synchronization according to the SIB indication obtained based on the system information and according to the RO in a four-step or two-step CBRA process (S3702). Here, the RO can refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization according to the configuration of TAG 1 for the communication link and update the uplink synchronization.

[0344] Then, TRP 1 can transmit an RRC establishment message to the terminal (S3703). The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S3704). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0345] To this end, TRP 1 may transmit downlink-related DCI (S3709) to the terminal. Then, the terminal may receive the downlink-related DCI from TRP 1. Here, the downlink-related DCI may indicate DL / Combined TCI 1 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and may be transmitted on the PDCCH. Thereafter, TRP 1 may transmit downlink data (S3710) to the terminal according to the downlink-related DCI. Then, the terminal may receive the downlink data from TRP 1 based on the downlink-related DCI.

[0346] On the other hand, TRP 1 may transmit uplink-related DCI (S3711) to the terminal. Then, the terminal may receive the uplink-related DCI from TRP 1. Here, the uplink-related DCI may indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and may be transmitted on the PDCCH. Thereafter, the terminal may transmit uplink data (S3712) to TRP 1 according to the uplink-related DCI. Then, TRP 1 may receive the uplink data from the terminal based on the uplink-related DCI. In this case, TRP 1 may associate TCI1 with TAG 1.

[0347] In addition, the terminal may be in the RRC connected state. TRP 1 may request measurement from the terminal (S3705). Therefore, the terminal may perform measurement by receiving the SSB from the neighboring TRP. In addition, the terminal may report the SSB-based measurement result for the neighboring TRP to TRP 1 through RRC signaling (S3706). In this case, the terminal may report SSB 1 or SSB 5 transmitted by TRP 2 as the sub-optimal SSB. Therefore, TRP 1 may receive the measurement report from the terminal. TRP 1 may identify SSB 1 or SSB 5 transmitted by TRP 2 as the sub-optimal SSB through the measurement report.

[0348] In this case, the measurement report may include the first SSB index (i.e., the optimal SSB index), the second SSB index (i.e., the sub-optimal SSB index), the third SSB index, etc. In addition, the measurement report may further include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of the communication links corresponding to the second SSB index, the third SSB index, etc.

[0349] If the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index does not exceed a predetermined threshold, the terminal may request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of reverse synchronization and reverse synchronization update of the terminal can be reduced.

[0350] In addition, the terminal can obtain the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index does not exceed the predetermined threshold, the terminal may request TRP for a second link establishment process without RACH. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links such as the second SSB index and the third SSB index exceeds the predetermined threshold, the terminal may request TRP for a second link establishment process based on RACH.

[0351] In addition, TRP 1 can receive measurement information from the terminal. Alternatively, TRP 1 can obtain the capability information of the terminal through the communication link based on SSB 1 between the terminal and TRP 1. Moreover, if TRP 1 can trust the terminal considering the capability of the terminal, it can accept the measurement information or request from the terminal. If TRP 1 cannot trust the terminal considering the capability of the terminal, it can not accept the measurement information or request from the terminal.

[0352] Then, as an example, the time difference between the reception synchronization points of the sub-optimal SSB indexes in the measurement information may be greater than the predetermined threshold. Alternatively, TRP 1 can receive a request from the terminal to establish a communication link based on RACH. In this case, TRP 1 can trigger random access. The terminal can establish a communication link through SSB 1 or SSB 5 of TRP 2 through the random access process. Then, the terminal can configure TAG 2 for the communication link established through SSB 1 or SSB 5 of TRP 2 for uplink synchronization and update of uplink synchronization, and associate UL TCI 2 with TAG 2. The association information between TAG 2 and UL TCI 2 (e.g., the mapping / association information between TAGID and UL TCI) can be notified to the terminal by TRP 1 before, after, or during the establishment of the communication link based on RACH.

[0353] Then, the terminal can perform a random access establishment procedure (S3707) with TRP 2. In this process, the terminal can configure TAG 2 to the communication link with TRP 2 for uplink synchronization and update the uplink synchronization of the communication link with TRP 2. The random access establishment procedure for TRP 2 can be triggered by TRP 1. TRP 1 can instruct the terminal to perform a CFRA or CBRA random access procedure through high-layer signaling or PDCCH, thereby triggering the random access establishment procedure for TRP 2. Optionally, TRP 1 can instruct neighboring TRPs to perform time / frequency resource estimation and reporting related to random access.

[0354] In other words, the terminal that receives the indication from TRP 1 can perform a CFRA random access procedure on the second communication link (e.g., the link between the terminal and TRP 2 (i.e., SSB 1 / SSB 5)). In this case, based on the direction pointed to by the second communication link (i.e., based on the transmit beam direction corresponding to the receive beam direction of the second communication link obtained in the SSB scanning process), the terminal can transmit a preamble at the time / frequency resource position of the indicated RO. In this case, the terminal can transmit a preamble in the downlink synchronization state of the first communication link (i.e., the link between the terminal and TRP 1 (SSB 1)). Alternatively, the terminal can obtain information on the time difference of the receive synchronization point between the first communication link and the sub-optimal SSB. Therefore, by reflecting the information on the time difference, the terminal can perform downlink synchronization between the terminal and the sub-optimal SSB (e.g., TRP 2 (SSB 1 / SSB 5)) and transmit beamformed SRS to TRP 2. In the two-step random access procedure, the entity that transmits the RAR can be TRP 1 that establishes the first communication link. Alternatively, in the case of the two-step random access procedure, the entity that transmits the RAR can be TRP 2 that establishes the second communication link.

[0355] Then, TRP 2 and the terminal can perform the RRC establishment procedure (S3708). In other words, TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 2. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to TRP 2. TRP 2 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 2. In the connected state, the terminal can communicate with other terminals through TRP1 and TRP 2. In other words, once the link connection between the terminal and TRP 2 (SSB 1 / SSB 5) is established, the terminal can communicate with other terminals through the communication link based on SSB 1 of TRP 1 and SSB 1 / SSB 5 of TRP 2. On the communication link of TRP 2 based on SSB 1 / SSB 5, the terminal can transmit and receive data according to DCI beamforming, where the DCI indicates DL / UL / Combined TCI 2 (which indicates the transmission configuration and scheduling resource location for data transmission and reception) and is transmitted on the PDCCH.

[0356] For this purpose, TRP 2 can transmit downlink-related DCI to the terminal (S3713). Then, the terminal can receive the downlink-related DCI from TRP 2. Here, the downlink-related DCI can indicate DL / Combined TCI 2 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal) and can be transmitted on the PDCCH. Thereafter, TRP2 can transmit downlink data to the terminal according to the downlink-related DCI (S3714). Then, the terminal can receive the downlink data from TRP 2 according to the downlink-related DCI.

[0357] On the other hand, TRP 2 can transmit uplink-related DCI to the terminal (S3715). Then, the terminal can receive the uplink-related DCI from TRP 2. Here, the uplink-related DCI can indicate UL / Combined TCI 2 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal) and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 2 according to the uplink-related DCI (S3716). Then, TRP 2 can receive the uplink data from the terminal based on the uplink-related DCI. After that, the terminal can update the TA by performing uplink synchronization with TRP 1 or TRP 2 periodically or aperiodically for TAG 1 and TAG 2 (S3717).

[0358] Figure 38 It is a sequence diagram showing a ninth exemplary embodiment of a link configuration method in a multi-TRP environment.

[0359] Referring to Figure 38 , the terminal can establish communication links with TRP 1 and TRP 2 respectively based on the same SSB 1 of two different TRPs 1 and 2. Alternatively, the terminal can establish communication links with TRP 1 and TRP 2 respectively based on different SSB 1 and SSB 5 of two different TRPs 1 and 2. In this case, the terminal can select the SSB 1 transmitted by TRP 1 as the optimal SSB, and select the SSB 1 or SSB 5 transmitted by TRP 2 as the sub-optimal SSB. The terminal can detect the same SSB index from different received beams. In this case, the terminal can learn that different TRPs use the same SSB index. Therefore, the terminal can identify the same SSB 1 as the optimal SSB and the sub-optimal SSB. Alternatively, the terminal cannot arbitrarily determine the same SSB 1 received through different received beams as the optimal SSB and the sub-optimal SSB. In this case, TRP 1 can allow the terminal to report only one SSB 1. Alternatively, TRP 1 can allow the terminal to report two instances of SSB 1 and distinguish them as the optimal SSB and the sub-optimal SSB, as described above. In this case, TRP 1 can establish two communication links through the same process as establishing communication links with two different SSBs.

[0360] In addition, the terminal can obtain system information based on the optimal SSB (S3801). This system information can be carried on the PBCH and PDSCH transmitted in the time / frequency resources determined according to the SSB. The terminal can identify SSB 1 as the optimal SSB through the PBCH. In addition, the terminal can identify the mapping relationship between the SSB group and the TRP and the association relationship between the TAGID and the SSB group based on the PDSCH including SIBy. The TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID during the RRC establishment process after performing the random access process. Alternatively, the TRP can allow the terminal to identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID through RRC signaling after the RRC establishment process is completed. In addition, the TRP may not inform the terminal of the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID. At this time, the terminal can identify the relationship between the SSB group and the TRP and the relationship between the SSB group and the TAGID from the PDSCH including the system information SIBy.

[0361] Then, TRP 1 and the terminal can perform uplink synchronization (S3802) according to the SIB indication obtained based on the system information, using the RO, in accordance with a four-step or two-step CBRA process. Here, the RO may refer to the uplink time / frequency resource location for random access. In this process, the terminal can configure TAG 1 for the communication link with TRP 1. In this way, the terminal can perform uplink synchronization according to the configuration of TAG 1 for the communication link and update the uplink synchronization.

[0362] Then, TRP 1 can transmit an RRC establishment message to the terminal (S3803). The terminal can receive the RRC establishment message from TRP 1. Accordingly, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to TRP 1 (S3804). TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1.

[0363] For this purpose, TRP 1 can transmit downlink-related DCI to the terminal (S3811). Then, the terminal can receive the downlink-related DCI from TRP 1. Here, the downlink-related DCI can indicate DL / Combined TCI 1 (which indicates the reception configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 1 can transmit downlink data to the terminal according to the downlink-related DCI (S3812). Then, the terminal can receive the downlink data from TRP 1 based on the downlink-related DCI.

[0364] On the other hand, TRP 1 can transmit uplink-related DCI to the terminal (S3813). Then, the terminal can receive the uplink-related DCI from TRP 1. Here, the uplink-related DCI can indicate UL / Combined TCI 1 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 1 according to the uplink-related DCI (S3814). Then, TRP 1 can receive the uplink data from the terminal based on the uplink-related DCI. In this case, TRP 1 can associate TCI 1 with TAG1.

[0365] In addition, the terminal can be in the RRC connected state. TRP 1 can request the terminal to perform measurements (S3805). Therefore, the terminal can perform measurements by receiving SSBs from neighboring TRPs. In addition, the terminal can report the SSB-based measurement results for neighboring TRPs to TRP 1 via RRC signaling (S3806). In this case, the terminal can report SSB 1 or SSB 5 to TRP 1 as the sub-optimal SSB. Accordingly, TRP 1 can receive the measurement report from the terminal. TRP 1 can identify SSB 1 or SSB 5 as the sub-optimal SSB via the measurement report.

[0366] In this case, the measurement report can include a first SSB index (i.e., the optimal SSB index), a second SSB index (i.e., the sub-optimal SSB index), a third SSB index, etc. In addition, the measurement report can also include information about the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links with the second SSB index, the third SSB index, etc.

[0367] If the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links with the second SSB index, the third SSB index, etc. does not exceed a predetermined threshold, the terminal can request TRP 1 to configure the same TAG as the current communication link accordingly. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links with the second SSB index, the third SSB index, etc. exceeds the predetermined threshold, the terminal can request TRP 1 to configure a different TAG from the current communication link accordingly. If TRP 1 configures the same TAG for the current communication link and other communication links, the burden of terminal reverse synchronization and reverse synchronization update can be reduced.

[0368] In addition, the terminal can know the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links with the second SSB index, the third SSB index, etc. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links with the second SSB index, the third SSB index, etc. does not exceed a predetermined threshold, the terminal can request the TRP for a second link establishment process without RACH. On the other hand, if the time difference between the reception synchronization point of the current communication link and the reception synchronization points of communication links with the second SSB index, the third SSB index, etc. exceeds the predetermined threshold, the terminal can request the TRP for a second link establishment process based on RACH.

[0369] In addition, the TRP 1 can receive measurement information from the terminal. Alternatively, the TRP 1 can obtain the capability information of the terminal through the communication link based on the SSB 1 between the terminal and the TRP 1. Furthermore, if the TRP 1 can trust the terminal considering the capabilities of the terminal, the TRP 1 can accept the measurement information or requests from the terminal. If the TRP 1 cannot trust the terminal considering the capabilities of the terminal, the TRP 1 can reject the measurement information or requests from the terminal.

[0370] As an example, the time difference between the reception synchronization points of the sub-optimal SSB indices in the measurement information can be less than a predetermined threshold. Alternatively, the TRP 1 can receive a request from the terminal to establish a RACH-less communication link. Accordingly, through the RACH-less procedure, the TRP 2 and the terminal can perform beam measurements between the terminal and the SSB 5 as follows.

[0371] To this end, the TRP 1 can instruct the terminal to transmit the uplink beamformed SRS (S3807) to the TRP using the specified scheduling resources. In this case, the TRP 1 can instruct the terminal to transmit the SRS through RRC signaling, which includes the specified scheduling resource information for transmitting the uplink beamformed SRS. In this case, the TRP 1 can inform the neighboring TRP that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS to suppress interference. Alternatively, to improve resource efficiency, the TRP 1 can refrain from informing the neighboring TRP that the terminal uses the determined scheduling time / frequency resources to transmit the uplink beamformed SRS.

[0372] Then, the terminal can transmit the beamformed SRS to the TRP including TRP 2 (S3808). Then, TRP 2 can receive the SRS from the terminal. TRP 2 can select the most suitable uplink beam and estimate the TA based on the received SRS. After that, TRP 2 can inform TRP 1 of the information about the most suitable uplink beam (i.e., the optimal uplink beam) and the estimated TA information. Then, TRP 1 can inform the terminal of the information about the most suitable uplink beam (i.e., the optimal uplink beam) received from TRP 2 and the estimated TA (S3809). In other words, TRP 1 can inform the terminal of the information about the SRS with the highest SINR in the beamformed SRS received by TRP 2 from the terminal. Therefore, the terminal can receive the information about the optimal uplink beam and the information about the TA from TRP 1. The terminal can confirm that the optimal uplink beam belongs to itself. Through this process, the terminal can complete the system connection with TRP 2 through the communication link associated with SSB 1 or SSB 5. In this process, the terminal can configure TAG 1 on the communication link with TRP 2. In this way, the terminal can perform uplink synchronization and update uplink synchronization according to the configuration of TAG 1 for the communication link. In the connected state, the terminal can communicate with other terminals through two communication links with TRP 1 and TRP 2.

[0373] For this purpose, TRP 2 can transmit the DCI related to the downlink associated with SSB 1 or SSB 5 to the terminal (S3814). Then, the terminal can receive the DCI related to the downlink from TRP 1. Here, the DCI related to the downlink can indicate DL / Combined TCI 2 (which indicates the receiving configuration of the terminal and the scheduling resource location for data reception of the terminal), and can be transmitted on the PDCCH. Thereafter, TRP 2 can transmit downlink data to the terminal according to the DCI related to the downlink (S3815). Then, the terminal can receive the downlink data from TRP 2 based on the DCI related to the downlink.

[0374] On the other hand, TRP 2 can transmit the DCI related to the uplink associated with SSB 1 or SSB 5 to the terminal (S3816). Then, the terminal can receive the DCI related to the uplink from TRP 2. Here, the DCI related to the uplink can indicate UL / Combined TCI 2 (which indicates the transmission configuration of the terminal and the scheduling resource location for data transmission of the terminal), and can be transmitted on the PDCCH. Thereafter, the terminal can transmit uplink data to TRP 2 according to the DCI related to the uplink (S3817).

[0375] Then, TRP 2 can receive uplink data from the terminal based on uplink-related DCI. After that, the terminal can update TA by performing uplink synchronization with TRP 1 and TRP 2 periodically or aperiodically for TAG 1 (S3818). Although Figure 37 and Figure 38 describe the process of establishing two communication links, the method of the present disclosure is not limited thereto. The TRP and the terminal can establish three or more communication links by applying the communication link establishment methods shown in Figure 37 and Figure 38 and perform multi-TRP communication in the downlink and uplink.

[0376] In addition, a first intra-cell / inter-cell M-TRP method will be described with reference to Figures 39 to 49 The first intra-cell / inter-cell M-TRP method can apply the second SSB grouping method in the SSB grouping method. In addition, in the first intra-cell / inter-cell M-TRP method, the terminal can estimate SSB 8 belonging to TRP 1 as the optimal SSB and SSB1 belonging to TRP 2 as the sub-optimal SSB.

[0377] In other words, when the terminal powers on, the terminal can estimate the optimal SSB and the sub-optimal SSB from the beamformed SSBs transmitted by TRP 1 and TRP 2. In this case, the terminal may not know whether the SSB it estimates belongs to TRP 1 or TRP 2. Then, in order to obtain uplink synchronization with TRP 1 that transmits the optimal SSB and obtain C-RNTI from TRP 1, the terminal can obtain information about the SSB index included in the message in the MIB transmitted through the PBCH existing in the optimal SSB. In this case, the obtained optimal SSB index can indicate SSB 8, which is transmitted in the first half-frame of a frame.

[0378] Figure 39 is a sequence diagram showing a first exemplary embodiment of a transmission method in a multi-TRP environment.

[0379] Refer to Figure 39, the terminal can continue the initial access procedure for TRP 1 and TRP 2 (S3900). Here, TRP 1 and TRP 2 can belong to the serving cell. To this end, TRP 1 can use the first half-frame of a frame to transmit beamformed SSBs (such as SSB 1 to SSB 8) in multiple directions (S3901). Thus, the terminal can receive the SSBs from TRP 1, and the terminal can estimate the optimal SSB among the received SSBs. In this case, the optimal SSB can be SSB 8 transmitted by TRP 1. The terminal can use the optimal SSB to perform downlink synchronization from TRP 1 towards the terminal direction. Here, TRP 1 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. After performing such synchronization, the terminal can obtain the MIB from the optimal SSB. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 1.

[0380] On the other hand, TRP 2 can use the second half-frame of a frame to transmit beamformed SSBs (such as SSB 1 to SSB 8) in multiple directions (S3902). Thus, the terminal can receive the SSBs from TRP 2, and can estimate the sub-optimal SSB among the received SSBs. In this case, the sub-optimal SSB can be SSB 1 transmitted from TRP 2. The terminal can use the sub-optimal SSB to perform downlink synchronization from TRP 2 towards the terminal direction. Here, TRP 2 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 2.

[0381] Then, TRP 1 can use the PDSCH to transmit SIB 1 to the terminal (S3903). The terminal can obtain SIB 1 from the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. This SIB can be the second system information obtained by the terminal from TRP 1. TRP 1 can transmit other SIBs (i.e., SIBy, where y is a positive integer greater than or equal to 2) other than SIB1 to the terminal during the initial access phase (S3904). In this case, TRP 1 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs other than SIB 1 from TRP 1.

[0382] On the other hand, TRP 2 can transmit SIB 1 (S3905) to the terminal using the PDSCH. The terminal can obtain SIB 1 located in the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal via the PDSCH. This SIB can be the second system information obtained by the terminal from TRP 2. TRP 2 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) other than SIB 1 to the terminal during the initial access phase (S3906). In this case, TRP 2 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs other than SIB 1 from TRP 2.

[0383] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, common control resource set (CORSET), common search space (CSS), and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 1. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0384] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 2. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0385] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a four-step random access establishment process based on CBRA with TRP 1 for uplink synchronization (S3910).

[0386] First, in the first step, the terminal can randomly select a preamble from all the preambles provided by TRP 1. The terminal can transmit the selected preamble to TRP 1 on the PRACH (S3911). Then, TRP 1 can receive the preamble from the terminal through the PRACH. In this case, the beam direction can follow the uplink direction opposite to the beam direction used when receiving the downlink signal. The resource for the terminal to transmit the preamble to TRP 1 can be based on the pre-acquired information about the association between the SSB and the RACH. TRP 1 can use this preamble to estimate the propagation delay of the terminal.

[0387] After that, in the second step, TRP 1 can determine whether there is a preamble in the signal received through the PRACH. This preamble can be randomly selected and transmitted by the terminal. Therefore, TRP 1 cannot specify which terminal transmitted the preamble by whether the preamble is detected. Therefore, TRP 1 cannot determine how many terminals used the detected preamble. Therefore, TRP 1 can transmit a RAR based on the detected preamble index to the terminal on the PDSCH (S3912). Then, the terminal can receive the RAR from TRP 1. In this case, the RAR can include the preamble index, TA value, uplink grant information, and temporary C-RNTI.

[0388] After that, in the third step, the terminal can transmit a message including a scheduling request (or connection request message) and a C3 message to TRP 1 through the PUSCH by applying the temporary C-RNTI and using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR (S3913). TRP 1 can receive the connection request message and the C3 message from the terminal. In this case, multiple terminals may have transmitted the same preamble in the first step. Therefore, preamble collisions may occur. In this case, all the terminals that transmitted the same preamble may use the same radio resources indicated by the RAR to transmit messages, thus possibly causing collisions.

[0389] Here, the C3 message can include C3_1 to C3_5 information. Here, the C3_1 information can be information about the sub-optimal SSB. The C3_2 information can be information indicating whether the premise that the PCI is the same (i.e., "same PCI") is true or false. Therefore, the premise that the PCI is the same (i.e., "same PCI" = true) can mean that the sub-optimal SSB has the same PCI as the optimal SSB.

[0390] The C3_3 information may be information about the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB. In this case, for example, the C3_3 information may be set to 0, such that when the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB is less than a predetermined threshold, it is regarded as having no time difference. Thus, the terminal can reduce the complexity caused by the synchronous update of multiple TRPs (such as TA update, etc.). On the other hand, if the time difference is equal to or greater than the predetermined threshold, the C3_3 information may be set to the time difference measured by the terminal. In addition, the C3_4 information may be information about the difference between the maximum correlation value output by the timing estimator of the optimal SSB, etc., and the maximum correlation value output by the timing estimator of the sub-optimal SSB, etc. The C3_5 information may be other information. The C3_5 information may be any information that can reduce the process overhead. When using the second SSB grouping method, the C3_5 information may include information about time, which may specify the second half-frame for receiving the sub-optimal SSB.

[0391] In other words, terminals that transmit the same preamble in the first step may eventually encounter resource conflicts when transmitting the third-step message. Therefore, each terminal may start a contention resolution timer when transmitting the third-step message as a process of checking whether the transmitted third-step message conflicts and whether it is successfully decoded.

[0392] Finally, in the fourth step, TRP 1 may decode the received third-step message. TRP 1 may transmit a PDSCH including an acknowledgment and a C4 message to the terminal on the PDSCH (S3914) in response to the successfully decoded message. Then, the terminal may receive a message including an acknowledgment and a C4 message from TRP1. The terminal may receive the message including the acknowledgment and the C4 message before the contention resolution timer started in the third step expires. Here, the C4 message may include C4_1 information to C4_5 information. In this case, the C4_1 information may be information indicating whether "TRP 2" is true or false. Here, setting "TRP 2" to true may mean that the TRP using the sub-optimal SSB informed by the terminal is eligible to be TRP 2.

[0393] The C4_2 information may be information indicating whether "RA" is true or false. Here, setting "RA" to true may mean that random access needs to be performed on the TRP of the sub-optimal SSB. In addition, the C4_3 information may be information indicating whether "CBRA" is true or false. Here, setting "CBRA" to true may mean that contention-based random access needs to be performed. In addition, the C4_4 information may include information about the CFRA preamble. The CFRA preamble may refer to the preamble to be used when performing non-contention-based random access. The CFRA preamble may be represented by a natural number greater than 1. In addition, the C4_5 information may be other information. The C4_5 information may be any information that can reduce the process overhead.

[0394] TRP 1 can generate the C4_1 information of the C4 message based on the information in the C3 message of the third-step message. In other words, TRP 1 can identify that the sub-optimal SSB included in the C3 message corresponds to the SSB of TRP 2 based on the SSB group-related information. Then, TRP 1 can set the C4_1 information to true. In addition, TRP 1 can generate the C4_2 information of the C4 message based on the information in the C3 message of the third-step message. In other words, when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB in the C3_3 information of the C3 message is equal to or greater than a predetermined threshold, TRP 1 can set the "RA" of the C4_2 information of the C4 message to true. In addition, TRP 1 can arbitrarily decide whether to set "CBRA" to true.

[0395] In this case, the premise that the PCI is the same in the C3_2 information can be true, and the "TRP 2" in the C4_1 information can be false. At this time, the terminal can ignore other message information, not perform an additional random access procedure, and can perform an RRC establishment procedure with TRP 1.

[0396] On the contrary, the premise that the PCI is the same in the C3_2 information can be true, the "TRP 2" in the C4_1 information can be true, and the "RA" in the C4_2 information can be false. At this time, the terminal does not perform an additional random access procedure. In addition, the terminal can use the C3_3 information and the C3_4 information to adjust the transmission timing of TRP 2, and perform an RRC establishment procedure with TRP 2 by performing power control and assuming that the terminal has accessed TRP 2 that transmits the sub-optimal SSB.

[0397] In addition, the premise that the PCI is the same in the C3_2 information can be true, the "TRP 2" in the C4_1 information can be true, the "RA" in the C4_2 information can be true, and the "CBRA" in the C4_3 information can be true. The terminal can perform a four-step establishment procedure (S3920) based on CBRA for TRP 2.

[0398] First, in the first step, the terminal can randomly select a preamble from all the preambles provided by TRP 2. The terminal can transmit the selected preamble to TRP 2 on the PRACH (S3921). Then, TRP 2 can receive the preamble from the terminal through the PRACH. In this case, the beam direction can follow the uplink direction opposite to the beam direction used when receiving the downlink signal. The resource for the terminal to transmit the preamble to TRP 2 can be based on the pre-acquired information about the association between the SSB and the RACH. TRP 2 can use the preamble to estimate the propagation delay of the terminal.

[0399] After that, in the second step, TRP 2 can determine whether there is a preamble in the signal received through the PRACH. The preamble can be randomly selected and transmitted by the terminal. Therefore, TRP 2 cannot specify the terminal that transmitted the preamble by whether the preamble is detected. Therefore, TRP 2 cannot determine how many terminals used the detected preamble. Therefore, TRP 2 can transmit a RAR (S3922) based on the detected preamble index to the terminal on the PDSCH. Then, the terminal can receive the RAR from TRP 2. In this case, the RAR can include the preamble index, TA value, uplink grant information, and temporary C-RNTI.

[0400] Subsequently, in the third step, the terminal can transmit a message (S3923) including a scheduling request message (or connection request message) to TRP 2 through the PUSCH by applying the temporary C-RNTI and using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR. TRP 2 can receive the connection request message from the terminal. In this case, multiple terminals may have transmitted the same preamble in the first step. Therefore, a preamble collision may occur. In this case, all terminals that transmitted the same preamble may transmit messages using the same radio resources indicated by the RAR. This may cause a collision.

[0401] In other words, terminals that transmitted the same preamble in the first step may ultimately encounter a resource collision when transmitting the third-step message. Therefore, each terminal can start a contention resolution timer when transmitting the third-step message as a process of checking whether the transmitted third-step message has collided and whether it has been successfully decoded.

[0402] Finally, in the fourth step, TRP 2 can decode the received third-step message. TRP 2 can transmit an acknowledgment message to the terminal on the PDSCH in response to the successfully decoded message (S3924). Then, the terminal can receive the acknowledgment message from TRP 2. The terminal can receive the acknowledgment message before the contention resolution timer started in the third step expires. As described above, once the fourth step is completed, the terminal can continue the RRC establishment process.

[0403] Then, TRP 1 can transmit an RRC establishment message (S3930) to the terminal. The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment complete message (S3931) to TRP 1. TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1. In addition, TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 2. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to TRP 2. TRP 2 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 2. In the connected state, the terminal can communicate with other terminals through TRP 2.

[0404] Figure 40 It is a sequence diagram showing a second exemplary embodiment of a transmission method in a multi-TRP environment.

[0405] Referring to Figure 40 , the terminal can continue the initial access process of TRP 1 and TRP 2 (S4000). TRP 1 and TRP 2 can belong to the serving cell. TRP 1 can transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions using the first half-frame of a frame (S4001). Therefore, the terminal can receive the SSBs from TRP 1 and can estimate the optimal SSB among the received SSBs. In this case, the optimal SSB can be SSB 8. The terminal can perform downlink synchronization from TRP 1 towards the terminal direction using the optimal SSB. Here, TRP 1 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. After performing such synchronization, the terminal can obtain the MIB from the optimal SSB. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 1.

[0406] On the other hand, TRP 2 can transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions using the second half-frame of a frame (S4002). Thus, the terminal can receive SSBs from TRP 2 and can estimate sub-optimal SSBs in the received SSBs. In this case, the sub-optimal SSB can be SSB 1. The terminal can use the sub-optimal SSB to perform downlink synchronization from TRP 2 towards the terminal direction. Here, TRP 2 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information that the terminal obtains from TRP 2.

[0407] Then, TRP 1 can transmit SIB 1 to the terminal using the PDSCH (S4003). The terminal can obtain SIB 1 from the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. The SIB can be the second system information that the terminal obtains from TRP 1. TRP 1 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) to the terminal in the initial access phase (S4004). In this case, TRP 1 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs from TRP 1 except SIB 1.

[0408] On the other hand, TRP 2 can transmit SIB 1 to the terminal using the PDSCH (S4005). The terminal can obtain SIB 1 from the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. The SIB can be the second system information that the terminal obtains from TRP 2. TRP 2 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) to the terminal in the initial access phase (S4006). In this case, TRP 2 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive SIBs other than SIB 1 from TRP2.

[0409] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 1. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0410] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 2. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message. After that, the terminal that has completed downlink synchronization and system information acquisition can perform a four-step random access establishment procedure based on CBRA with TRP 1 for uplink synchronization (S4010).

[0411] First, in the first step, the terminal can randomly select a preamble from all the preambles provided by TRP 1. Then, the terminal can transmit the selected preamble to TRP 1 on the PRACH (S4011). Then, TRP 1 can receive the preamble from the terminal on the PRACH. In this case, the beam direction can follow the uplink direction opposite to the beam direction used when receiving the downlink signal. The resource for the terminal to transmit the preamble to TRP 1 can be based on the pre-obtained information about the association between the SSB and the RACH. TRP 1 can estimate the propagation delay of the terminal using the preamble.

[0412] Subsequently, in the second step, TRP 1 can determine whether there is a preamble in the signal received on the PRACH. The preamble can be randomly selected and transmitted by the terminal. Therefore, TRP 1 cannot specify the terminal that transmitted the preamble by whether the preamble is detected. Therefore, TRP 1 cannot determine how many terminals used the detected preamble. Therefore, TRP 1 can transmit a RAR based on the detected preamble index to the terminal on the PDSCH (S4012). Then, the terminal can receive the RAR from TRP 1. In this case, the RAR can include the preamble index, TA value, uplink authorization information, and temporary C-RNTI.

[0413] Subsequently, in the third step, the terminal can transmit a message (S4013) including a scheduling request (or connection request) and a C3 message to TRP 1 via PUSCH by applying a temporary C-RNTI and using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR. TRP 1 can receive the connection request message and the C3 message from the terminal. In this case, multiple terminals may have transmitted the same preamble in the first step. Therefore, preamble collisions may occur. In this case, all terminals that transmitted the same preamble may transmit messages using the same radio resources indicated by the RAR. This may lead to collisions.

[0414] Here, the C3 message can include C3_1 to C3_5 information. Here, the C3_1 information can be information about the sub-optimal SSB. The C3_2 information can be information indicating whether the premise that the PCI is the same (i.e., "same PCI") is true or false. Therefore, the premise that the PCI is the same (i.e., "same PCI" = true) can mean that the sub-optimal SSB has the same PCI as the optimal SSB.

[0415] The C3_3 information can be information about the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB. In this case, for example, the C3_3 information can be set to 0 so that when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB is less than a predetermined threshold, it is regarded as having no time difference. Therefore, the terminal can reduce the complexity caused by the synchronous update (such as TA update, etc.) of multiple TRPs. On the other hand, if the time difference is equal to or greater than the predetermined threshold, the C3_3 information can be set to the time difference value measured by the terminal. In addition, the C3_4 information can be information about the difference between the maximum correlation value output by the timing estimator of the optimal SSB and the maximum correlation value output by the timing estimator of the sub-optimal SSB. The C3_5 information can be other information. The C3_5 information can be any information that can reduce the process overhead. When using the second SSB grouping method, the C3_5 information can include information about time, which can specify the second half-frame for receiving the sub-optimal SSB.

[0416] In other words, terminals that transmitted the same preamble in the first step may ultimately encounter resource collisions when transmitting the third-step message. Therefore, each terminal can start a contention resolution timer when transmitting the third-step message as a process of checking whether the transmitted third-step message has collided and whether it has been successfully decoded.

[0417] Finally, in the fourth step, TRP 1 can decode the received message of the third step. TRP 1 can transmit a PDSCH including an acknowledgment and a C4 message to the terminal on the PDSCH in response to the successfully decoded message (S4014). Then, the terminal can receive a message including an acknowledgment and a C4 message from TRP1. The terminal can receive the message including the acknowledgment and the C4 message before the expiration of the contention resolution timer started in the third step. Here, the C4 message can include C4_1 information to C4_5 information. In this case, the C4_1 information can be information indicating whether "TRP 2" is true or false. Setting "TRP 2" to true here can mean that the TRP using the sub-optimal SSB informed by the terminal is eligible as TRP 2.

[0418] The C4_2 information can be information indicating whether "RA" is true or false. Setting "RA" to true here can mean that random access needs to be performed on the TRP of the sub-optimal SSB. In addition, the C4_3 information can be information indicating whether "CBRA" is true or false. Setting "CBRA" to true here can mean that contention-based random access needs to be performed. In addition, the C4_4 information can include information about the CFRA preamble. The CFRA preamble can refer to the preamble to be used when performing non-contention-based random access. The CFRA preamble can be represented by a natural number greater than 1. In addition, the C4_5 information can be other information. The C4_5 information can be any information that can reduce processing overhead.

[0419] TRP 1 can generate the C4_1 information of the C4 message based on the information in the C3 message of the third-step message. In other words, TRP 1 can identify that the sub-optimal SSB included in the C3 message corresponds to the SSB of TRP 2 based on the SSB group-related information. Then, TRP 1 can set the C4_1 information to true. In addition, TRP 1 can generate the C4_2 information of the C4 message according to the information in the C3 message of the third-step message. In other words, when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB in the C3_3 information of the C3 message is equal to or greater than a predetermined threshold, TRP 1 can set "RA" of the C4_2 information of the C4 message to true. In addition, TRP 1 can arbitrarily decide whether to set "CBRA" to true.

[0420] In this case, the premise that the PCI is the same in the C3_2 information can be true, and "TRP 2" in the C4_1 information can be false. At this time, the terminal can ignore other message information, not perform an additional random access process, and can perform an RRC establishment process with TRP 1.

[0421] Conversely, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, and "RA" in the C4_2 information can be false. At this time, the terminal does not perform an additional random access procedure. In addition, the terminal can use the C3_3 information and the C3_4 information to adjust the transmission timing of TRP 2, and perform the RRC establishment procedure with TRP 2 by performing power control and assuming that the terminal has accessed TRP 2 that transmits a suboptimal SSB.

[0422] In addition, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, "RA" in the C4_2 information can be true, and "CBRA" in the C4_3 information can be false. The terminal can continue the two-step CFRA-based establishment procedure for TRP 2 (S4020).

[0423] For this purpose, in the first step, the terminal can randomly select a preamble from the CFRA preambles. Then, the terminal can transmit the selected preamble to TRP 2 via PRACH. In addition, simultaneously, the terminal can transmit a scheduling request (i.e., a connection request) message to TRP 2 via pre-allocated uplink radio resources (i.e., the uplink shared channel) (S4021). Then, TRP 2 can receive a message including the preamble and the scheduling request from the terminal.

[0424] In this case, TRP 2 can transmit a message including the RAR and the C-RNTI to the terminal on the PDSCH (S4022). Accordingly, the terminal can receive a message including a successful RAR and the C-RNTI from TRP 2. This message can be used as an acknowledgment.

[0425] Then, TRP 1 can transmit an RRC establishment message to the terminal (S4030). The terminal can receive the RRC establishment message from TRP 1. Accordingly, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S4031). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP1. In the connected state, the terminal can communicate with other terminals via TRP 1. In addition, TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 2. Accordingly, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 2. TRP 2 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 2. In the connected state, the terminal can communicate with other terminals via TRP 2.

[0426] Figure 41 This is a sequence diagram of the third exemplary embodiment of the transmission method in a multi-TRP environment.

[0427] Referring to Figure 41 , the terminal can continue the initial access process of TRP 1 and TRP 2 (S4100). TRP 1 and TRP 2 can belong to the serving cell. TRP 1 can transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions using the first half-frame of a frame (S4101). Thus, the terminal can receive the SSBs from TRP 1 and can estimate the optimal SSB among the received SSBs. In this case, the optimal SSB can be SSB 8. The terminal can perform downlink synchronization from TRP 1 towards the terminal direction using the optimal SSB. Here, TRP 1 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. After performing such synchronization, the terminal can obtain the MIB from the optimal SSB. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 1.

[0428] On the other hand, TRP 2 can transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions using the second half-frame of a frame (S4102). Thus, the terminal can receive the SSBs from TRP 2 and can estimate the sub-optimal SSB among the received SSBs. In this case, the sub-optimal SSB can be SSB 1. The terminal can perform downlink synchronization from TRP 2 towards the terminal direction using the sub-optimal SSB. Here, TRP 2 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 2.

[0429] Then, TRP 1 can transmit SIB 1 to the terminal using the PDSCH (S4103). The terminal can obtain SIB 1 located in the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. The SIB can be the second system information obtained by the terminal from TRP 1. TRP 1 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) to the terminal in the initial access stage (S4104). In this case, TRP 1 can transmit control information to inform that the SIBs will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs from TRP1 except SIB 1.

[0430] On the other hand, TRP 2 can use the PDSCH to transmit SIB 1 (S4105) to the terminal. The terminal can obtain SIB 1 located in the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. This SIB can be the second system information obtained by the terminal from TRP 2. TRP 2 can transmit other SIBs (i.e., SIBy, where y is a positive integer greater than or equal to 2) other than SIB 1 to the terminal during the initial access phase (S4106). In this case, TRP 2 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs other than SIB 1 from TRP 2.

[0431] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 1. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0432] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 2. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0433] Thereafter, the terminal that has completed downlink synchronization and system information acquisition can perform a two-step random access establishment process based on CBRA with TRP 1 for uplink synchronization (S4110).

[0434] To this end, in the first step, the terminal can randomly select a preamble from all the preambles. Then, the terminal can transmit the selected preamble to TRP 1 via the PRACH. In addition, simultaneously, the terminal can transmit a message (S4111) including a scheduling request (i.e., a connection request) and a C3 message to TRP 1 via pre-allocated uplink radio resources (i.e., the uplink shared channel). Then, TRP 1 can receive the preamble and the message including the scheduling request and the C3 message from the terminal. Here, the C3 message can include C3_1 to C3_5 information. Here, the C3_1 information can be information about the sub-optimal SSB. The C3_2 information can be information indicating whether the premise that the PCIs are the same (i.e., "same PCI") is true or false. Therefore, the premise that the PCIs are the same (i.e., "same PCI" = true) can mean that the sub-optimal SSB has the same PCI as the optimal SSB.

[0435] The C3_3 information can be information about the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB. In this case, for example, the C3_3 information can be set to 0 so that when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB is less than a predetermined threshold, it is regarded as having no time difference. Therefore, the terminal can reduce the complexity caused by the synchronization update (e.g., TA update, etc.) of multiple TRPs. On the other hand, if the time difference is equal to or greater than the predetermined threshold, the C3_3 information can be set to the time difference measured by the terminal. In addition, the C3_4 information can be information about the difference between the maximum correlation value output by the timing estimator of the optimal SSB and the maximum correlation value output by the timing estimator of the sub-optimal SSB. The C3_5 information can be other information. The C3_5 information can be any information that can reduce the process overhead. When using the second SSB grouping method, the C3_5 information can include information about time, which can specify the second half-frame for receiving the sub-optimal SSB.

[0436] In the second step, the TRP can determine whether a preamble is detected. In addition, the TRP can determine whether the message is successfully decoded. The TRP can transmit different types of messages to the terminal according to the determination result. This can lead to differences in subsequent processes.

[0437] More specifically, if the TRP does not detect a preamble, the TRP can not perform any operation. In other words, the TRP can not check whether a message is received via the uplink radio resources associated with the preamble. Therefore, when a preamble is not detected, the TRP can not make any response. Therefore, the terminal can re-attempt random access because it does not receive any message from the TRP. This situation can be called "Case 1".

[0438] On the other hand, the TRP can normally detect the preamble and successfully decode the message from the uplink radio resource associated with the preamble. In this case, TRP 1 can transmit a message including the RAR, C-RNTI, and C4 message to the terminal on the PDSCH (S4112). Therefore, the terminal can receive a message including the successful RAR, C-RNTI, and C4 message from the TRP. This message can be used as an acknowledgment.

[0439] Here, the C4 message can include C4_1 to C4_5 information. In this case, the C4_1 information can be information indicating whether "TRP2" is true or false. Here, setting "TRP 2" to true can mean that the TRP using the sub-optimal SSB informed by the terminal is eligible as TRP 2.

[0440] The C4_2 information can be information indicating whether "RA" is true or false. Here, setting "RA" to true can mean that random access needs to be performed on the TRP of the sub-optimal SSB. In addition, the C4_3 information can be information indicating whether "CBRA" is true or false. Here, setting "CBRA" to true can mean that contention-based random access needs to be performed. In addition, the C4_4 information can include information about the CFRA preamble. The CFRA preamble refers to the preamble used when performing non-competition-based random access. The CFRA preamble can be represented by a natural number greater than 1. In addition, the C4_5 information can be other information. The C4_5 information can be any information that can reduce the process overhead.

[0441] In this case, TRP 1 can generate the C4_1 information of the C4 message according to the information in the C3 message of the third-step message. In other words, TRP 1 can identify that the sub-optimal SSB included in the C3 message corresponds to the SSB of TRP2 according to the SSB group-related information. Then, TRP 1 can set the C4_1 information to true. In addition, TRP 1 can generate the C4_2 information of the C4 message according to the information in the C3 message of the third-step message. In other words, when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB in the C3_3 information of the C3 message is equal to or greater than a predetermined threshold, TRP 1 can set "RA" of the C4_2 information of the C4 message to true. In addition, TRP 1 can arbitrarily decide whether to set "CBRA" to true.

[0442] In this case, the premise that the PCI is the same in the C3_2 information can be true, and "TRP 2" in the C4_1 information can be false. Then, the terminal can ignore other message information, not perform an additional random access process, and can perform an RRC establishment process with TRP 1.

[0443] Conversely, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, and "RA" in the C4_2 information can be false. Then, the terminal may not perform an additional random access procedure. In addition, the terminal can use the C3_3 information and the C3_4 information to adjust the transmission timing of TRP 2, and perform the RRC establishment procedure with TRP 2 by performing power control and assuming that the terminal has accessed TRP 2 that transmits the sub-optimal SSB.

[0444] In addition, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, "RA" in the C4_2 information can be true, and "CBRA" in the C4_3 information can be true. The terminal can perform a two-step establishment process (S4120) based on CBRA for TRP 2.

[0445] To this end, in the first step, the terminal can randomly select a preamble from all preambles. Then, the terminal can transmit the selected preamble to TRP 2 on the PRACH. In addition, simultaneously, the terminal can transmit a scheduling request (i.e., a connection request) message to TRP 2 through pre-allocated uplink radio resources (i.e., the uplink shared channel) (S4121). Then, TRP 2 can receive the preamble and the message including the scheduling request from the terminal.

[0446] In the second step, TRP 2 can determine whether a preamble is detected. In addition, TRP 2 can also determine whether the message is successfully decoded. TRP 2 can transmit different types of messages to the terminal according to the determination result. This can lead to differences in subsequent processes.

[0447] More specifically, if TRP 2 does not detect a preamble, then TRP 2 may not perform any operation. In other words, TRP 2 may not check whether a message is received through the uplink radio resources associated with the preamble. Therefore, when a preamble is not detected, TRP 2 may not make any response. Therefore, the terminal can re-attempt random access because it has not received any message from TRP 2. This situation can be called "Case 1".

[0448] On the other hand, TRP 2 can normally detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, TRP 2 can transmit a message including the RAR and C-RNTI to the terminal on the PDSCH (S4122). Therefore, the terminal can receive a message including the successful RAR and C-RNTI from TRP 2. This message can be used as an acknowledgement. Therefore, the terminal can successfully complete random access. This case can be referred to as "Case 2". Additionally, TRP 2 can normally detect the preamble, but may not successfully decode the message from the uplink radio resources associated with the preamble. In this case, TRP 2 can transmit a message including a fallback RAR to the terminal on the PDSCH. In this case, the terminal that receives this message can use the uplink radio resources indicated by the uplink authorization information included in the fallback RAR to retransmit the message it wants to transmit.

[0449] Then, TRP 1 can transmit an RRC establishment message to the terminal (S4130). The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete RRC establishment and transmit an RRC establishment complete message to TRP 1 (S4131). TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals through TRP 1. Additionally, TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 2. Therefore, the terminal can complete RRC establishment and transmit an RRC establishment complete message to TRP 2. TRP 2 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 2. In the connected state, the terminal can communicate with other terminals through TRP 2.

[0450] Figure 42 is a sequence diagram showing a fourth exemplary embodiment of a transmission method in a multi-TRP environment.

[0451] Refer to Figure 42, the terminal can continue the initial access procedure for TRP 1 and TRP 2 (S4200). TRP 1 and TRP 2 can belong to the serving cell. TRP 1 can transmit beamformed SSBs (such as SSB 1 to SSB 8) in multiple directions using the first half-frame of a frame (S4201). Thus, the terminal can receive the SSBs from TRP 1 and can estimate the optimal SSB among the received SSBs. In this case, the optimal SSB can be SSB 8. The terminal can perform downlink synchronization from TRP 1 towards the terminal direction using the optimal SSB. At this time, TRP 1 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. After performing such synchronization, the terminal can obtain the MIB from the optimal SSB. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 1.

[0452] On the other hand, TRP 2 can transmit beamformed SSBs (such as SSB 1 to SSB 8) in multiple directions using the second half-frame of a frame (S4202). Thus, the terminal can receive the SSBs from TRP 2 and can estimate the sub-optimal SSB among the received SSBs. In this case, the sub-optimal SSB can be SSB 1. The terminal can perform downlink synchronization from TRP 2 towards the terminal direction using the sub-optimal SSB. Here, TRP 2 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 2.

[0453] Then, TRP 1 can transmit SIB 1 to the terminal using the PDSCH (S4203). The terminal can obtain SIB 1 from the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. The SIB can be the second system information obtained by the terminal from TRP 1. TRP 1 can transmit other SIBs (i.e., SIBy, where y is a positive integer greater than or equal to 2) other than SIB1 to the terminal during the initial access phase (S4204). In this case, TRP 1 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs other than SIB 1 from TRP 1.

[0454] On the other hand, TRP 2 can use the PDSCH to transmit SIB 1 (S4205) to the terminal. The terminal can obtain SIB 1 located in the time and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. This SIB can be the second system information obtained by the terminal from TRP 2. TRP 2 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) other than SIB 1 to the terminal during the initial access phase (S4206). In this case, TRP 2 can transmit control information to inform that the SIB will be continuously transmitted after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs other than SIB 1 from TRP2.

[0455] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 1. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0456] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 2. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0457] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a two-step random access establishment process based on CBRA with TRP 1 for uplink synchronization (S4210).

[0458] To this end, in the first step, the terminal can randomly select a preamble from all the preambles. Then, the terminal can transmit the selected preamble to TRP 1 via the PRACH. In addition, simultaneously, the terminal can transmit a scheduling request (i.e., a connection request) message and a C3 message (S4211) to TRP 1 via pre-allocated uplink radio resources (i.e., the uplink shared channel). Then, TRP 1 can receive the preamble and the message including the scheduling request and the C3 message from the terminal. Here, the C3 message can include C3_1 to C3_5 information. Here, the C3_1 information can be information about the sub-optimal SSB. The C3_2 information can be information indicating whether the premise of the same PCI (i.e., "Same PCI") is true. Therefore, the premise of the same PCI (i.e., SamePCI = true) can mean that the sub-optimal SSB has the same PCI as the optimal SSB.

[0459] The C3_3 information can be information about the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB. In this case, for example, the C3_3 information can be set to 0 so that when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB is less than a predetermined threshold, it is regarded as having no time difference. Therefore, the terminal can reduce the complexity caused by the synchronization update (such as TA update, etc.) of multiple TRPs. On the other hand, if the time difference is equal to or greater than the predetermined threshold, the C3_3 information can be set to the time difference measured by the terminal. In addition, the C3_4 information can be information about the difference between the maximum correlation value output by the timing estimator of the optimal SSB and the maximum correlation value output by the timing estimator of the sub-optimal SSB. The C3_5 information can be other information. The C3_5 information can be any information that can reduce the process overhead. When using the second SSB grouping method, the C3_5 information can include information about time, which can specify the second half-frame for receiving the sub-optimal SSB.

[0460] In the second step, the TRP can determine whether a preamble is detected. In addition, the TRP can also determine whether the message has been successfully decoded. The TRP can transmit different types of messages to the terminal according to the determined result. This can lead to differences in subsequent processes.

[0461] More specifically, if the TRP does not detect a preamble, the TRP can not perform any operation. In other words, the TRP can not check whether a message is received via the uplink radio resources associated with the preamble. Therefore, when a preamble is not detected, the TRP can not make any response. Therefore, since the terminal does not receive any message from the TRP, the terminal can re-attempt random access. This situation can be called "Case 1".

[0462] On the other hand, the TRP can normally detect the preamble and successfully decode the message from the uplink radio resource associated with the preamble. In this case, TRP 1 can transmit a message including the RAR, C-RNTI, and C4 message to the terminal on the PDSCH (S4212). Therefore, the terminal can receive a message including the successful RAR, C-RNTI, and C4 message from the TRP. This message can be used as an acknowledgement.

[0463] Here, the C4 message can include C4_1 information to C4_5 information. In this case, the C4_1 information can be information indicating whether "TRP 2" is true or false. Here, setting "TRP 2" to true can mean that the TRP using the sub-optimal SSB informed by the terminal is eligible to be TRP 2.

[0464] The C4_2 information can be information indicating whether "RA" is true or false. Here, setting "RA" to true can mean that random access needs to be performed on the TRP of the sub-optimal SSB. In addition, the C4_3 information can be information indicating whether "CBRA" is true or false. Here, setting "CBRA" to true can mean that contention-based random access needs to be performed. In addition, the C4_4 information can include information about the CFRA preamble. The CFRA preamble refers to the preamble used when performing non-competition-based random access. The CFRA preamble can be represented by a natural number greater than 1. In addition, the C4_5 information can be other information. The C4_5 information can be any information that can reduce the process overhead.

[0465] In this case, TRP 1 can generate the C4_1 information of the C4 message according to the information in the C3 message of the third-step message. In other words, TRP 1 can identify that the sub-optimal SSB included in the C3 message corresponds to the SSB of TRP2 according to the SSB group-related information. Then, TRP 1 can set the C4_1 information to true. In addition, TRP 1 can generate the C4_2 information of the C4 message according to the information in the C3 message of the third-step message. In other words, when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB in the C3_3 information of the C3 message is equal to or greater than a predetermined threshold, TRP 1 can set "RA" of the C4_2 information of the C4 message to true. In addition, TRP 1 can arbitrarily decide whether to set "CBRA" to true.

[0466] In this case, the premise that the PCI is the same in the C3_2 information can be true, and "TRP 2" in the C4_1 information can be false. At this time, the terminal can ignore other message information, not perform an additional random access process, and can perform an RRC establishment process with TRP 1.

[0467] Conversely, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, and "RA" in the C4_2 information can be false. At this time, the terminal does not perform an additional random access procedure. In addition, the terminal can use the C3_3 information and the C3_4 information to adjust the transmission timing of TRP 2, and perform the RRC establishment procedure with TRP 2 by performing power control and assuming that the terminal has accessed TRP 2 that transmits the suboptimal SSB.

[0468] In addition, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, "RA" in the C4_2 information can be true, and "CBRA" in the C4_3 information can be false. The terminal can perform a two-step CFRA-based establishment procedure for TRP 2 (S4220).

[0469] For this purpose, in the first step, the terminal can randomly select a preamble from the CFRA preambles. Then, the terminal can transmit the selected preamble to TRP 2 via PRACH. In addition, at the same time, the terminal can transmit a scheduling request (i.e., a connection request) message to TRP 2 via pre-allocated uplink radio resources (i.e., the uplink shared channel) (S4221). Then, TRP 2 can receive the preamble and the message including the scheduling request from the terminal.

[0470] In this case, TRP 2 can transmit a message including a RAR and a C-RNTI to the terminal on the PDSCH (S4222). Accordingly, the terminal can receive a message including a successful RAR and a C-RNTI from TRP 2. This message can be used as an acknowledgement. In this case, "RA" in the C4_2 information of the C4 message can be false. Then, TRP 2 can complete the second step. Alternatively, "RA" can be true. Then, the terminal can re-perform the random access procedure from the first step. After the second step is completed, the terminal can continue the RRC establishment procedure.

[0471] Then, the TRP 1 can transmit an RRC establishment message (S4230) to the terminal. The terminal can receive the RRC establishment message from the TRP 1. Accordingly, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to the TRP 1 (S4231). The TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with the TRP 1. In the connected state, the terminal can communicate with other terminals through the TRP 1. In addition, the TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from the TRP 2. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to the TRP 2. The TRP 2 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with the TRP 2. In the connected state, the terminal can communicate with other terminals through the TRP 2.

[0472] Figure 43 is a sequence diagram showing a fifth exemplary embodiment of a transmission method in a multi-TRP environment.

[0473] Referring to Figure 43 , the terminal can continue the initial access process of the TRP 1 and the TRP 2 (S4300). Here, the TRP 1 can belong to the serving cell, and the TRP 2 can belong to the non-serving cell. For this purpose, the TRP 1 can use the first half-frame of a frame to transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions (S4301). Therefore, the terminal can receive the SSBs from the TRP 1, and the terminal can estimate the optimal SSB among the received SSBs. In this case, the optimal SSB can be SSB 8. The terminal can perform downlink synchronization from the TRP 1 towards the terminal direction using the optimal SSB. Here, the TRP 1 can transmit the SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. After performing such synchronization, the terminal can obtain the MIB from the optimal SSB. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from the TRP 1.

[0474] On the other hand, TRP 2 can transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions using the second half-frame of a frame (S4302). Therefore, the terminal can receive SSBs from TRP 2 and can estimate sub-optimal SSBs among the received SSBs. In this case, the sub-optimal SSB can be SSB 1. The terminal can use the sub-optimal SSB to perform downlink synchronization from TRP 2 towards the terminal direction. At this time, TRP 2 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information that the terminal obtains from TRP 2.

[0475] Then, TRP 1 can transmit SIB 1 to the terminal using the PDSCH (S4303). The terminal can obtain SIB 1 located in the time resource and frequency resource indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal via the PDSCH. This SIB can be the second system information that the terminal obtains from TRP 1. TRP 1 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) to the terminal during the initial access phase (S4304). In this case, TRP 1 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs from TRP1 except SIB 1.

[0476] On the other hand, TRP 2 can transmit SIB 1 to the terminal using the PDSCH (S4305). The terminal can obtain SIB 1 located in the time resource and frequency resource indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. This SIB can be the second system information that the terminal obtains from TRP 2. TRP 2 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) to the terminal during the initial access phase (S4306). In this case, TRP 2 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs from TRP 2 except SIB 1.

[0477] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 1. Then, the terminal can decode SIB 1 as indicated by the obtained information to obtain the message in SIB 1. In addition, the terminal can sequentially decode SIBy by using the indication information included in the SIB 1 message to obtain the message in SIBy.

[0478] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 2. Then, the terminal can decode SIB 1 as indicated by the obtained information to obtain the message in SIB 1. In addition, the terminal can sequentially decode SIBy by using the indication information included in the SIB 1 message to obtain the message in SIBy.

[0479] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a four-step random access establishment procedure based on CBRA with TRP 1 for uplink synchronization (S4310).

[0480] First, in the first step, the terminal can randomly select a preamble from all the preambles provided by TRP 1. The terminal can transmit the selected preamble to TRP 1 on the PRACH (S4311). Then, TRP 1 can receive the preamble from the terminal through the PRACH. In this case, the beam direction can follow the uplink direction opposite to the beam direction used when receiving the downlink signal. The resource for the terminal to transmit the preamble to TRP 1 can be based on the pre-acquired information about the association between the SSB and the RACH. TRP 1 can use the preamble to estimate the propagation delay of the terminal.

[0481] After that, in the second step, TRP 1 can determine whether there is a preamble in the signal received through the PRACH. The preamble can be randomly selected and transmitted by the terminal. Therefore, TRP 1 cannot specify which terminal transmitted the preamble by whether the preamble is detected. Therefore, TRP 1 cannot determine how many terminals used the detected preamble. Therefore, TRP 1 can transmit a RAR based on the detected preamble index to the terminal on the PDSCH (S4312). Then, the terminal can receive the RAR from TRP 1. In this case, the RAR can include the preamble index, TA value, uplink grant information, and temporary C-RNTI.

[0482] After that, in the third step, the terminal can transmit a message (S4313) including a scheduling request message (or a connection request message) and a C3 message to TRP 1 via PUSCH by applying the temporary C-RNTI and using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR. TRP 1 can receive the connection request message and the C3 message from the terminal. In this case, multiple terminals may have transmitted the same preamble in the first step. Therefore, preamble collisions may occur. In this case, all terminals that transmitted the same preamble may transmit messages using the same radio resources indicated by the RAR. This may lead to collisions.

[0483] Here, the C3 message can include C3_1 to C3_5 information. Here, the C3_1 information can be information about the sub-optimal SSB. The C3_2 information can be information indicating whether the premise that the PCI is the same (i.e., "same PCI") is true or false. Therefore, the premise that the PCI is the same (i.e., "same PCI" = true) can mean that the sub-optimal SSB has the same PCI as the optimal SSB.

[0484] The C3_3 information can be information about the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB. In this case, for example, the C3_3 information can be set to 0 so that when the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB is less than a predetermined threshold, it is regarded as having no time difference. Therefore, the terminal can reduce the complexity caused by the synchronization update (such as TA update, etc.) of multiple TRPs. On the other hand, if the time difference is equal to or greater than the predetermined threshold, the C3_3 information can be set to the time difference measured by the terminal. In addition, the C3_4 information can be information about the difference between the maximum correlation value output by the timing estimator of the optimal SSB and the maximum correlation value output by the timing estimator of the sub-optimal SSB. The C3_5 information can be other information. The C3_5 information can be any information that can reduce the process overhead. When using the second SSB grouping method, the C3_5 information can include information about time, which can specify the second half-frame in which the sub-optimal SSB is received.

[0485] In other words, the terminals that transmitted the same preamble in the first step may eventually encounter resource conflicts when transmitting the third-step message. Therefore, each terminal can start a contention resolution timer when transmitting the third-step message as a process of checking whether the transmitted third-step message has collided and whether it has been successfully decoded.

[0486] Finally, in the fourth step, TRP 1 can decode the received message of the third step. TRP 1 can transmit an acknowledgment message and a C4 message on the PDSCH to the terminal in response to the successfully decoded message (S4314). Then, the terminal can receive the acknowledgment message and the C4 message from TRP 1. The terminal can receive the acknowledgment message and the C4 message before the expiration of the contention resolution timer started in the third step. Here, the C4 message can include C4_1 to C4_5 information. In this case, the C4_1 information can be information indicating whether "TRP 2" is true or false. Here, setting "TRP 2" to true can mean that the TRP using the sub-optimal SSB informed by the terminal is eligible to be TRP 2.

[0487] The C4_2 information can be information indicating whether "RA" is true or false. Here, setting "RA" to true can mean that random access needs to be performed on the TRP of the sub-optimal SSB. In addition, the C4_3 information can be information indicating whether "CBRA" is true or false. Here, setting "CBRA" to true can mean that contention-based random access needs to be performed. In addition, the C4_4 information can include information about the CFRA preamble. The CFRA preamble can refer to the preamble to be used when performing contention-free random access. The CFRA preamble can be represented by a natural number greater than 1. In addition, the C4_5 information can be other information. The C4_5 information can be any information that can reduce the process overhead.

[0488] In this case, TRP 1 can generate the C4_1 information of the C4 message according to the information in the C3 message of the third-step message. In other words, TRP 1 can identify that the sub-optimal SSB included in the C3 message corresponds to the SSB of TRP2 based on the SSB group-related information. Then, TRP 1 can set the C4_1 information to true. In addition, TRP 1 can generate the C4_2 information of the C4 message according to the information in the C3 message of the third-step message. In other words, when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB in the C3_3 information of the C3 message is equal to or greater than a predetermined threshold, TRP 1 can set "RA" of the C4_2 information of the C4 message to true. In addition, TRP 1 can arbitrarily decide whether to set "CBRA" to true.

[0489] In this case, the premise that the PCI is the same in the C3_2 information can be true, and "TRP 2" in the C4_1 information can be false. At this time, the terminal can ignore other message information, not perform an additional random access process, and can perform an RRC establishment process with TRP 1.

[0490] Conversely, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, and "RA" in the C4_2 information can be false. At this time, the terminal does not perform an additional random access procedure. In addition, the terminal can use the C3_3 information and the C3_4 information to adjust the transmission timing of TRP 2, and perform the RRC establishment procedure with TRP 2 by performing power control and assuming that the terminal has accessed TRP 2 that transmits the suboptimal SSB.

[0491] In addition, the premise that the PCI is the same in the C3_2 information can be true, "TRP 2" in the C4_1 information can be true, "RA" in the C4_2 information can be true, and "CBRA" in the C4_3 information can be true. The terminal can continue with the four-step CBRA-based establishment procedure (S4320) for TRP 2.

[0492] First, in the first step, the terminal can randomly select a preamble from all the preambles provided by TRP 2. The terminal can transmit the selected preamble to TRP 2 on the PRACH (S4321). Then, TRP 2 can receive the preamble from the terminal on the PRACH. In this case, the beam direction can follow the uplink direction opposite to the beam direction used when receiving the downlink signal. The resource for the terminal to transmit the preamble to TRP 2 can be based on the pre-acquired information about the association between the SSB and the RACH. TRP 2 can use the preamble to estimate the propagation delay of the terminal.

[0493] After that, in the second step, TRP 2 can determine whether there is a preamble in the signal received through the PRACH. The preamble can be randomly selected and transmitted by the terminal. Therefore, TRP 2 cannot specify which terminal transmitted the preamble based on whether the preamble is detected. Therefore, TRP 2 cannot determine how many terminals used the detected preamble. Therefore, TRP 2 can transmit a RAR based on the detected preamble index to the terminal on the PDSCH (S4322). Then, the terminal can receive the RAR from TRP 2. In this case, the RAR can include the preamble index, TA value, uplink grant information, and temporary C-RNTI.

[0494] After that, in the third step, the terminal can transmit a scheduling request message (or connection request message) to TRP 2 via PUSCH by applying the temporary C-RNTI and using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR (S4323). TRP 2 can receive the connection request message from the terminal. In this case, multiple terminals may have transmitted the same preamble in the first step. Therefore, preamble collisions may occur. In this case, all terminals that transmitted the same preamble may transmit messages using the same radio resources indicated by the RAR. This may lead to collisions.

[0495] In other words, the terminals that transmitted the same preamble in the first step may eventually encounter resource collisions when transmitting the third-step message. Therefore, each terminal can start a contention resolution timer when transmitting the third-step message as a process of checking whether the transmitted third-step message collides and whether it is successfully decoded.

[0496] Finally, in the fourth step, TRP 2 can decode the received third-step message. TRP 2 can transmit an acknowledgment message and a C4 message to the terminal on the PDSCH in response to the successfully decoded message (S4324). Then, the terminal can receive the acknowledgment message from TRP 2. The terminal can receive the acknowledgment message before the contention resolution timer started in the third step expires. As described above, after the fourth step is completed, the terminal can continue the RRC establishment process.

[0497] Then, TRP 1 can transmit an RRC establishment message to the terminal (S4330). The terminal can receive the RRC establishment message from TRP 1. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 1 (S4331). TRP 1 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 1. In the connected state, the terminal can communicate with other terminals via TRP 1. In addition, TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 2. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment completion message to TRP 2. TRP 2 can confirm the RRC establishment by receiving the RRC establishment completion message from the terminal. Through this process, the terminal can complete the system connection with TRP 2. In the connected state, the terminal can communicate with other terminals via TRP 2.

[0498] Figure 44 is a sequence diagram showing a sixth exemplary embodiment of a transmission method in a multi-TRP environment.

[0499] Refer to Figure 44, the terminal can perform the initial access procedure (S4400) for TRP 1 and TRP 2. Here, TRP 1 can belong to the serving cell, while TRP 2 can belong to the non-serving cell. For this purpose, TRP 1 can use the first half-frame of a frame to transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions (S4401). Thus, the terminal can receive the SSBs from TRP1 and can estimate the optimal SSB among the received SSBs. In this case, the optimal SSB can be SSB 8. The terminal can use the optimal SSB to perform downlink synchronization from TRP 1 towards the terminal direction. Here, TRP 1 can transmit SSBs periodically or aperiodically for the initial synchronization and maintenance of synchronization of the beamformed downlink. After performing such synchronization, the terminal can obtain the MIB from the optimal SSB. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 1.

[0500] On the other hand, TRP 2 can use the second half-frame of a frame to transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions (S4402). Thus, the terminal can receive the SSBs from TRP 2 and can estimate the sub-optimal SSB among the received SSBs. In this case, the sub-optimal SSB can be SSB 1. The terminal can use the sub-optimal SSB to perform downlink synchronization from TRP 2 towards the terminal direction. At this time, TRP 2 can transmit SSBs periodically or aperiodically for the initial synchronization and maintenance of synchronization of the beamformed downlink. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 2.

[0501] Then, TRP 1 can transmit SIB 1 to the terminal on the PDSCH (S4403). The terminal can obtain SIB 1 from the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. The SIB can be the second system information obtained by the terminal from TRP 1. TRP 1 can transmit other SIBS (i.e., SIBy, where y is a positive integer greater than or equal to 2) other than SIB 1 to the terminal during the initial access phase (S4404). In this case, TRP 1 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBS other than SIB 1 from TRP 1.

[0502] On the other hand, TRP 2 can use the PDSCH to transmit SIB 1 (S4405) to the terminal. The terminal can obtain SIB 1 from the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. This SIB can be the second system information obtained by the terminal from TRP 2. TRP 2 can transmit other SIBs (i.e., SIBy, where y is a positive integer greater than or equal to 2) other than SIB 1 to the terminal during the initial access phase (S4406). In this case, TRP 2 can transmit control information to inform that the SIB will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs other than SIB 1 from TRP2.

[0503] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 1. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0504] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 2. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 as indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0505] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a four-step random access establishment process based on CBRA with TRP 1 for uplink synchronization (S4410).

[0506] First, in the first step, the terminal can randomly select a preamble from all the preambles provided by TRP 1. The terminal can transmit the selected preamble to TRP 1 on the PRACH (S4411). Then, TRP 1 can receive the preamble from the terminal through the PRACH. In this case, the beam direction can follow the uplink direction opposite to the beam direction used when receiving the downlink signal. The resource for the terminal to transmit the preamble to TRP 1 can be based on the pre-acquired information about the association between the SSB and the RACH. TRP 1 can use this preamble to estimate the propagation delay of the terminal.

[0507] After that, in the second step, TRP 1 can determine whether there is a preamble in the signal received through the PRACH. The preamble can be randomly selected and transmitted by the terminal. Therefore, TRP 1 cannot specify which terminal transmitted the preamble by whether the preamble is detected. Therefore, TRP 1 cannot determine how many terminals used the detected preamble. Therefore, TRP 1 can transmit a RAR (S4412) based on the detected preamble index to the terminal on the PDSCH. Then, the terminal can receive the RAR from TRP 1. In this case, the RAR can include the preamble index, TA value, uplink grant information, and temporary C-RNTI.

[0508] After that, in the third step, the terminal can transmit a scheduling request message (or connection request message) and a C3 message (S4413) to TRP 1 through the PUSCH by applying the temporary C-RNTI and using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR. TRP 1 can receive the connection request message and the C3 message from the terminal. In this case, multiple terminals may have transmitted the same preamble in the first step. Therefore, preamble collisions may occur. In this case, all terminals that transmitted the same preamble may transmit messages using the same radio resources indicated by the RAR. This may lead to collisions.

[0509] Here, the C3 message can include C3_1 to C3_5 information. Here, the C3_1 information can be information about the sub-optimal SSB. The C3_2 information can be information indicating whether the premise that the PCI is the same (i.e., "same PCI") is true or false. Therefore, the premise that the PCI is the same (i.e., "same PCI" = true) can mean that the sub-optimal SSB has the same PCI as the optimal SSB.

[0510] The C3_3 information may be information about the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB. In this case, for example, the C3_3 information may be set to 0, such that when the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB is less than a predetermined threshold, it is regarded as having no time difference. Thus, the terminal can reduce the complexity caused by the synchronous updates of multiple TRPs (such as TA updates, etc.). On the other hand, if the time difference is equal to or greater than the predetermined threshold, the C3_3 information may be set to the time difference measured by the terminal. In addition, the C3_4 information may be information about the difference between the maximum correlation value output by the timing estimator of the optimal SSB, etc., and the maximum correlation value output by the timing estimator of the sub-optimal SSB, etc. The C3_5 information may be other information. The C3_5 information may be any information that can reduce the process overhead. When using the second SSB grouping method, the C3_5 information may include information about time, which may specify the second half-frame for receiving the sub-optimal SSB.

[0511] In other words, terminals that transmit the same preamble in the first step may eventually encounter resource conflicts when transmitting the third-step message. Therefore, each terminal may start a contention resolution timer when transmitting the third-step message as a process of checking whether the transmitted third-step message has a conflict and whether it is successfully decoded.

[0512] Finally, in the fourth step, TRP 1 may decode the received third-step message. TRP 1 may transmit an acknowledgment message and a C4 message on the PDSCH to the terminal in response to the successfully decoded message (S4414). Then, the terminal may receive the acknowledgment message and the C4 message from TRP 1. The terminal may receive the acknowledgment message and the C4 message before the contention resolution timer started in the third step expires. Here, the C4 message may include C4_1 information to C4_5 information. In this case, the C4_1 information may be information indicating whether "TRP2" is true or false. Here, setting "TRP 2" to true may mean that the TRP using the sub-optimal SSB informed by the terminal is eligible to be TRP 2.

[0513] The C4_2 information may be information indicating whether "RA" is true or false. Here, setting "RA" to true may mean that random access needs to be performed on the TRP of the sub-optimal SSB. In addition, the C4_3 information may be information indicating whether "CBRA" is true or false. Here, setting "CBRA" to true may mean that contention-based random access needs to be performed. In addition, the C4_4 information may include information about the CFRA preamble. The CFRA preamble may refer to the preamble to be used when performing non-contention-based random access. The CFRA preamble may be represented by a natural number greater than 1. In addition, the C4_5 information may be other information. The C4_5 information may be any information that can reduce the process overhead.

[0514] In this case, TRP 1 can generate the C4_1 information of the C4 message based on the information in the C3 message of the third-step message. In other words, TRP 1 can identify that the sub-optimal SSB included in the C3 message corresponds to the SSB of TRP2 based on the SSB group-related information. Then, TRP 1 can set the C4_1 information to true. In addition, TRP 1 can generate the C4_2 information of the C4 message based on the information in the C3 message of the third-step message. In other words, when the time difference between the start point of the optimal SSB and the start point of the sub-optimal SSB in the C3_3 information of the C3 message is equal to or greater than a predetermined threshold, TRP 1 can set the "RA" of the C4_2 information of the C4 message to true. In addition, TRP 1 can arbitrarily decide whether to set "CBRA" to true.

[0515] In this case, the premise that the PCI is the same in the C3_2 information can be true, and the "TRP 2" in the C4_1 information can be false. Then, the terminal can ignore other message information, not perform an additional random access procedure, and can perform an RRC establishment procedure with TRP 1.

[0516] On the contrary, the premise that the PCI is the same in the C3_2 information can be true, the "TRP 2" in the C4_1 information can be true, and the "RA" in the C4_2 information can be false. Then, the terminal can not perform an additional random access procedure. In addition, the terminal can adjust the transmission timing of TRP 2 using the C3_3 information and the C3_4 information, and perform an RRC establishment procedure with TRP 2 by performing power control and assuming that the terminal has accessed TRP 2 that transmits the sub-optimal SSB.

[0517] In addition, the premise that the PCI is the same in the C3_2 information can be true, the "TRP 2" in the C4_1 information can be true, the "RA" in the C4_2 information can be true, and the "CBRA" in the C4_3 information can be false. The terminal can perform a two-step CFRA-based establishment procedure for TRP 2 (S4420).

[0518] For this purpose, in the first step, the terminal can randomly select a preamble from the CFRA preambles. Then, the terminal can transmit a selected preamble to the TRP through the PRACH. In addition, at the same time, the terminal can transmit a scheduling request (i.e., a connection request) message to TRP 2 through pre-allocated uplink radio resources (i.e., the uplink shared channel) (S4421). Then, TRP 2 can receive the preamble and the message including the scheduling request from the terminal.

[0519] In this case, TRP 2 can transmit a message including a RAR and a C-RNTI to the terminal on the PDSCH (S4422). Accordingly, the terminal can receive a message including a successful RAR and a C-RNTI from TRP 2. This message can be used as an acknowledgement. In this case, "RA" in the C4_2 information of the C4 message can be false. Then, TRP 2 can complete the second step. Alternatively, "RA" can be true. Then, the terminal can re-execute the random access procedure from the first step. After the second step is completed, the terminal can continue with the RRC establishment procedure.

[0520] Then, TRP 1 can transmit an RRC establishment message to the terminal (S4430). The terminal can receive the RRC establishment message from TRP 1. Accordingly, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to TRP 1 (S4431). TRP 1 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP1. In the connected state, the terminal can communicate with other terminals through TRP 1. In addition, TRP 2 can transmit an RRC establishment message to the terminal. The terminal can receive the RRC establishment message from TRP 2. Therefore, the terminal can complete the RRC establishment and transmit an RRC establishment complete message to TRP 2. TRP 2 can confirm the RRC establishment by receiving the RRC establishment complete message from the terminal. Through this process, the terminal can complete the system connection with TRP 2. In the connected state, the terminal can communicate with other terminals through TRP2.

[0521] Figure 45 It is a sequence diagram showing a seventh exemplary embodiment of a transmission method in a multi-TRP environment.

[0522] Refer to Figure 45, the terminal can continue the initial access procedure for TRP 1 and TRP 2 (S4500). Here, TRP 1 can belong to the serving cell, while TRP 2 can belong to a non-serving cell. For this purpose, TRP 1 can use the first half-frame of a frame to transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions (S4501). Thus, the terminal can receive the SSBs from TRP 1, and the terminal can estimate the optimal SSB among the received SSBs. In this case, the optimal SSB can be SSB 8. The terminal can use the optimal SSB to perform downlink synchronization from TRP 1 towards the terminal direction. Here, TRP 1 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. After performing such synchronization, the terminal can obtain the MIB from the optimal SSB. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 1.

[0523] On the other hand, TRP 2 can use the second half-frame of a frame to transmit beamformed SSBs (e.g., SSB 1 to SSB 8) in multiple directions (S4502). Thus, the terminal can receive the SSBs from TRP 2, and can estimate the sub-optimal SSB among the received SSBs. In this case, the sub-optimal SSB can be SSB 1. The terminal can use the sub-optimal SSB to perform downlink synchronization from TRP 2 towards the terminal direction. Here, TRP 2 can transmit SSBs periodically or aperiodically for initial synchronization and maintenance of synchronization for beamformed downlink. The MIB can be transmitted to the terminal on the PBCH. The MIB can be the first system information obtained by the terminal from TRP 2.

[0524] Then, TRP 1 can transmit SIB 1 to the terminal using the PDSCH (S4503). The terminal can obtain SIB 1 located in the time resources and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal via the PDSCH. This SIB can be the second system information obtained by the terminal from TRP 1. TRP 1 can transmit other SIBs (i.e., SIBy, where y is a positive integer greater than or equal to 2) other than SIB 1 to the terminal during the initial access phase (S4504). In this case, TRP 1 can transmit control information to inform that the SIBs will be transmitted continuously after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs other than SIB 1 from TRP1.

[0525] On the other hand, TRP 2 can transmit SIB 1 (S4505) to the terminal using the PDSCH. The terminal can obtain SIB 1 from the time and frequency resources indicated by the MIB. In this case, SIB 1 can be transmitted to the terminal on the PDSCH. This SIB can be the second system information obtained by the terminal from TRP 2. TRP 2 can transmit other SIBs (i.e., SIBy, where y is a positive integer of 2 or greater) (S4506) to the terminal in the initial access phase except for SIB 1. In this case, TRP 2 can transmit control information to inform that the SIB will be continuously transmitted after SIB 1 by including the control information in SIB 1. The terminal can receive other SIBs except for SIB 1 from TRP 2.

[0526] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 1. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0527] In addition, the terminal can obtain information about the PDCCH / SIB bandwidth, CORSET, CSS, and related PDCCH parameters, as informed by Pdcch-ConfigSIB1, from the MIB obtained from the SSB received from TRP 2. Then, the terminal can obtain the message in SIB 1 by decoding SIB 1 indicated by the obtained information. In addition, the terminal can obtain the message in SIBy by sequentially decoding SIBy using the indication information included in the SIB 1 message.

[0528] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a two-step random access establishment process based on CBRA with TRP 1 for uplink synchronization (S4510).

[0529] To this end, in the first step, the terminal can randomly select a preamble from all the preambles. Then, the terminal can transmit a selected preamble to TRP 1 via the PRACH. In addition, simultaneously, the terminal can transmit a scheduling request (i.e., connection request) message and a C3 message (S4511) to the TRP via pre-allocated uplink radio resources (i.e., the uplink shared channel). Then, TRP 1 can receive the preamble, the scheduling request message, and the C3 message from the terminal. Here, the C3 message can include C3_1 information to C3_5 information. Here, the C3_1 information can be information about the sub-optimal SSB. The C3_2 information can be information indicating whether the premise that the PCI is the same (i.e., "same PCI") is true or false. Therefore, the premise that the PCI is the same (i.e., "same PCI" = true) can mean that the sub-optimal SSB has the same PCI as the optimal SSB.

[0530] The C3_3 information can be information about the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB. In this case, for example, the C3_3 information can be set to 0 so that when the time difference between the starting point of the optimal SSB and the starting point of the sub-optimal SSB is less than a predetermined threshold, it is regarded as having no time difference. Therefore, the terminal can reduce the complexity caused by the synchronous update of multiple TRPs (such as TA update, etc.). On the other hand, if the time difference is equal to or greater than the predetermined threshold, the C3_3 information can be set to the time difference measured by the terminal. In addition, the C3_4 information can be information about the difference between the maximum correlation value output by the timing estimator of the optimal SSB and the maximum correlation value output by the timing estimator of the sub-optimal SSB. The C3_5 information can be other information. The C3_5 information can be any information that can reduce the process ...

Claims

1. A method for a terminal, comprising: Receive a first synchronization signal block (SSB) from a first transmission and reception point (TRP), the first SSB being included in a first SSB group assigned to the first TRP; Receive system information from the first TRP based on the first SSB, the system information including a mapping relationship between the first SSB group and the first TRP and a mapping relationship between a second SSB group and a second TRP; Establish a first communication link between the first TRP and the terminal based on the first SSB; According to the mapping relationship between the first SSB group and the first TRP, assign a first tag identifier for communication link identification to the first communication link; Receive a second SSB from the second TRP, the second SSB being included in the second SSB group assigned to the second TRP; Establish a second communication link between the second TRP and the terminal based on the second SSB; And According to the mapping relationship between the second SSB group and the second TRP, assign a second tag identifier to the second communication link.

2. The method according to claim 1, wherein, Establishing the first communication link between the first TRP and the terminal based on the first SSB includes: Obtain information about a first random access opportunity indicated by a first system information block (SIB), the first SIB being obtained based on the first SSB; Perform a first random access procedure with the first TRP in the first random access opportunity; and Establish a first communication link between the first TRP and the terminal according to the first random access procedure.

3. The method according to claim 1, further comprising: Receive a measurement request from the first TRP; In response to the measurement request, transmit a measurement report to the first TRP, the measurement report including information about the second SSB and information about the time difference between the reception time of the first SSB and the reception time of the second SSB; And Based on the time difference, receive a setup instruction for the second communication link from the first TRP, wherein the second communication link is established based on the second SSB and the setup instruction.

4. The method according to claim 3, wherein, When the time difference is less than a threshold, the received setup instruction indicates link establishment without performing a random access (RA) procedure, and the second communication link is established between the second TRP and the terminal without performing an RA procedure.

5. The method according to claim 4, wherein, When the time difference is greater than or equal to the threshold, the received setup instruction indicates link establishment based on the random access channel (RACH), and establishing the second communication link between the second TRP and the terminal based on the second SSB includes: Obtain information about a second random access opportunity indicated by a second SIB, the second SIB being obtained based on the second SSB; Perform a second random access procedure with the second TRP in the second random access opportunity; and Establish the second communication link between the second TRP and the terminal according to the second random access procedure.

6. The method according to claim 1, wherein, The first TRP is included in a serving cell, and the second TRP is included in a non-serving cell.

7. The method according to claim 1, wherein, When the time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold, the first label identifier is the same as the second label identifier, and when the time difference between the reception time of the first SSB and the reception time of the second SSB is equal to or greater than the threshold, the first label identifier is different from the second label identifier.

8. The method according to claim 1, wherein, The first SSB group and the second SSB group are grouped based on the SSB index or the resource period of the frame.

9. The method according to claim 1, further comprising: Receive a first downlink transmission configuration indication (TCI) associated with the first label identifier and first downlink scheduling information from the first TRP; Receive downlink data from the first TRP based on the first downlink TCI and the first downlink scheduling information; Receive a second downlink TCI associated with the second label identifier and second downlink scheduling information from the second TRP; And Receive downlink data from the second TRP based on the second downlink TCI and the second downlink scheduling information.

10. The method according to claim 1, further comprising: Receive a first uplink TCI associated with the first label identifier and first uplink scheduling information from the first TRP; Transmit uplink data to the first TRP based on the first uplink TCI and the first uplink scheduling information; Receive a second uplink TCI associated with the second label identifier and second uplink scheduling information from the second TRP; And Transmit uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information.

11. According to the method of claim 10, wherein, When the time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold, the transmission time of transmitting uplink data to the first TRP is the same as the transmission time of transmitting uplink data to the second TRP.

12. According to the method of claim 10, wherein, When the time difference between the reception time of the first SSB and the reception time of the second SSB is greater than or equal to a threshold, the difference between the transmission time of transmitting uplink data to the first TRP and the transmission time of transmitting uplink data to the second TRP includes the time difference.

13. A method for a terminal, comprising: Receive a first synchronization signal block (SSB) from a first transmission and reception point (TRP), and the first SSB is included in a first SSB group assigned to the first TRP; Receive a second SSB from a second TRP, and the second SSB is included in a second SSB group assigned to the second TRP; Initiate a first random access procedure with the first TRP based on the first SSB; During the first random access procedure, transmit information about the second SSB and information about the time difference between the reception time of the first SSB and the reception time of the second SSB to the first TRP; Establish a first communication link between the first TRP and the terminal through the first random access procedure; Through the first random access procedure, receive an establishment instruction for a second communication link with the second TRP from the first TRP based on the time difference; And Establish the second communication link with the second TRP according to the received establishment instruction.

14. According to the method of claim 13, further comprising: Allocate a first label identifier for communication link identification to the first communication link according to the mapping relationship between the first SSB group and the first TRP; And Allocate a second label identifier to the second communication link according to the mapping relationship between the second SSB group and the second TRP.

15. According to the method of claim 13, wherein, When the time difference is less than the threshold, the received establishment instruction indicates link establishment without performing a random access (RA) procedure, and the second communication link is established between the second TRP and the terminal without performing the RA procedure.

16. According to the method of claim 13, wherein, When the time difference is greater than or equal to the threshold, the received establishment instruction indicates link establishment based on the random access channel (RACH), and establishing the second communication link with the second TRP according to the received establishment instruction includes: Obtain information about a second random access opportunity indicated by a second system information block (SIB), where the second SIB is obtained based on the second SSB; Perform a second random access procedure with the second TRP during the second random access opportunity; and Establish the second communication link between the second TRP and the terminal according to the second random access procedure.

17. According to the method of claim 13, further comprising: Receive a first uplink TCI and first uplink scheduling information from the first TRP; Transmit uplink data to the first TRP based on the first uplink TCI and the first uplink scheduling information; Receive a second uplink TCI and second uplink scheduling information from the second TRP; And Transmit uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information, where when the time difference between the reception time of the first SSB and the reception time of the second SSB is less than the threshold, the transmission time of transmitting uplink data to the first TRP is the same as the transmission time of transmitting uplink data to the second TRP, and when the time difference between the reception time of the first SSB and the reception time of the second SSB is greater than or equal to the threshold, the difference between the transmission time of transmitting uplink data to the first TRP and the transmission time of transmitting uplink data to the second TRP includes the time difference.

18. A terminal, comprising a processor, wherein, The processor causes the terminal to execute: Receive a first synchronization signal block (SSB) from a first transmission and reception point (TRP), where the first SSB is included in a first SSB group allocated to the first TRP; Receive system information from the first TRP based on the first SSB, where the system information includes the mapping relationship between the first SSB group and the first TRP and the mapping relationship between the second SSB group and the second TRP; Establish a first communication link between the first TRP and the terminal based on the first SSB; Allocate a first label identifier for communication link identification to the first communication link according to the mapping relationship between the first SSB group and the first TRP; Receive a second SSB from the second TRP, where the second SSB is included in the second SSB group allocated to the second TRP; Establish a second communication link between the second TRP and the terminal based on the second SSB; And Allocate a second tag identifier to the second communication link according to the mapping relationship between the second SSB group and the second TRP.

19. The terminal according to claim 18, wherein, The processor further causes the terminal to execute: Receive a measurement request from the first TRP; In response to the measurement request, transmit a measurement report to the first TRP, where the measurement report includes information about the second SSB and information about the time difference between the reception time of the first SSB and the reception time of the second SSB; And Based on the time difference, receive an establishment instruction for the second communication link from the first TRP, wherein, in establishing the second communication link between the second TRP and the terminal based on the second SSB, the processor further causes the terminal to execute: establish the second communication link based on the establishment instruction.

20. The terminal according to claim 19, wherein, When the time difference is greater than or equal to a threshold, the received establishment instruction indicates link establishment based on a random access channel (RACH), and in establishing the second communication link based on the received establishment instruction, the processor further causes the terminal to execute: Obtain information about a second random access opportunity indicated by a second SIB, which is obtained based on the second SSB; Execute a second random access procedure with the second TRP during the second random access opportunity; And Establish the second communication link between the second TRP and the terminal according to the second random access procedure.

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