Transmission method and apparatus based on multiple transmitting and receiving points in a communication system

Abstract

A transmission technique based on multiple transmission and reception points in a communication system may be a terminal method, including the steps of: receiving a first SSB (synchronization signal block) included in a first SSB (synchronization signal block) group assigned to a first TRP from a first TRP to generate a first communication link; assigning a first tag to the first communication link; receiving a second SSB included in the second SSB group assigned to the second TRP from a second TRP to generate a second communication link; and assigning a second tag to the second communication link according to a mapping relationship between the second SSB group and the second TRP.

Description

[Technical Field]

[0001] The present disclosure relates to a transmission technology based on multiple transmission / reception points in a communication system, and more particularly, to a transmission technology based on multiple transmission / reception points in a communication system that enables a terminal to transmit signals to multiple transmission / reception points using different transmission times. [Background technology]

[0002] With the development of information and communication technology, various wireless communication technologies are being developed. Representative wireless communication technologies include LTE (long term evolution), NR (new radio), and 6G (6th Generation), which are defined by the 3GPP (3rd Generation Partnership Project) standard. LTE can be one of the wireless communication technologies among 4G (4th Generation) wireless communication technologies, and NR can be one of the wireless communication technologies among 5G (5th Generation) wireless communication technologies.

[0003] To process the rapidly increasing amount of wireless data after the commercialization of 4G communication systems (e.g., communication systems supporting LTE), 5G communication systems (e.g., communication systems supporting NR) that use not only the frequency bands of 4G communication systems (e.g., frequency bands below 6 GHz) but also higher frequency bands than the frequency bands of 4G communication systems (e.g., frequency bands above 6 GHz) can be considered. 5G communication systems can support enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC).

[0004] In a communication system, multiple transmission and reception points (TRPs) and user equipment (UEs) can transmit signals isochronously or sequentially. Multiple TRPs can exist within the same cell and share the same configuration and resources. Alternatively, multiple TRPs can exist in different cells. In this situation, the UE can manage a single timing advance (TA). The propagation delay between the TRP and the UE can be different. Therefore, signals transmitted and received between the TRP and the UE can be subject to inter-symbol interference (ISI) and inter-carrier interference (ICI). Summary of the Invention [Problem to be solved by the invention]

[0005] In order to solve the above problems, an object of the present disclosure is to provide a transmission method and apparatus based on multiple transmission and reception points in a communication system in which a terminal can transmit signals to multiple transmission and reception points using different transmission times. [Means for solving the problem]

[0006] To achieve the above object, a transmission method based on multiple transmission and reception points in a communication system according to a first embodiment of the present disclosure is a method for a terminal, and may include the steps of receiving a first SSB (synchronization signal block) included in a first SSB (synchronization signal block) group assigned to the first TRP from a first TRP; receiving 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 the second TRP; establishing a first communication link between the first TRP and the terminal based on the first SSB; assigning a first tag identifier 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 the second SSB group assigned to the second TRP from a second TRP; establishing a second communication link between the second TRP and the terminal based on the second SSB; and assigning a second tag identifier to the second communication link according to the mapping relationship between the second SSB group and the second TRP.

[0007] Here, the step of establishing a first communication link between the first TRP and the terminal based on the first SSB may include a step of acquiring information on a first random access occasion indicated in a first SIB (system information block) acquired based on the first SSB; a step of conducting a first random access procedure with the first TRP using the acquired first random access occasion; and a step of establishing the first communication link between the first TRP and the terminal according to the first random access procedure.

[0008] Here, the method further includes receiving a measurement request from the first TRP; transmitting a measurement report to the first TRP in response to the measurement request, the measurement report including information on the second SSB and information on a time difference between the reception time of the first SSB and the reception time of the second SSB; and receiving an instruction to establish the second communication link from the first TRP based on the time difference, wherein the second communication link can be established based on the second SSB and the establishment instruction.

[0009] Here, the received establishment instruction instructs link establishment without performing a random access (RA) procedure if the time difference is less than a threshold value, and the second communication link can be established between the second TRP and the terminal without performing the RA procedure.

[0010] Here, the received establishment instruction indicates a RACH-based link establishment if the time difference is greater than or equal to a threshold value, and the step of establishing a second communication link between the second TRP and the terminal based on the second SSB may include the steps of: acquiring information on a second random access occasion indicated in a second SIB acquired based on the second SSB; conducting a second random access procedure with the second TRP using the acquired second random access occasion; and generating the second communication link between the second TRP and the terminal according to the second random access procedure.

[0011] Here, the first TRP may be included in a serving cell, and the second TRP may be included in a non-serving cell.

[0012] Here, if the time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold value, the first tag identifier and the second tag identifier may be identical, and if 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 value, the first tag identifier and the second tag identifier may be different from each other.

[0013] Here, the first SSB group and the second SSB group may be grouped based on an SSB index or a resource interval of a frame.

[0014] Here, the method may include receiving a first downlink TCI (transmission configuration indication) and first downlink scheduling information associated with the first tag identifier from the first TRP; receiving downlink data from the first TRP based on the first downlink TCI and the first downlink scheduling information; receiving a second downlink TCI and second downlink scheduling information associated with the second tag identifier from the second TRP; and receiving downlink data from the second TRP based on the second downlink TCI and the second downlink scheduling information.

[0015] Here, the method may include receiving a first uplink TCI and first uplink scheduling information associated with the first tag identifier from the 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 associated with the second tag identifier from the second TRP; and transmitting uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information.

[0016] Here, 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 value, 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.

[0017] Here, 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 value, 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 can be a transmission method based on multiple transmission and reception points in a communication system according to a first embodiment of the present disclosure to achieve the above object, including the time difference.

[0018] Meanwhile, a transmission method based on multiple transmission and reception points in a communication system according to a second embodiment of the present disclosure to achieve the above object is a method for a terminal, and may include the steps of receiving a first SSB (synchronization signal block) included in a first SSB group assigned to the first TRP from a first transmission and reception point (TRP); receiving a second SSB included in the second SSB group assigned to the second TRP from a second TRP; initiating a first random access procedure with the first TRP based on the first SSB; transmitting information about the second SSB and information about a time difference between the reception time of the first SSB and the reception time of the second SSB to the first TRP in the first random access procedure; establishing a first communication link between the first TRP and the terminal through the first random access procedure; receiving a setup instruction for a second communication link with the second TRP based on the time difference through the first random access procedure from the first TRP; and establishing the second communication link with the second TRP according to the received setup instruction.

[0019] Here, the method may further include assigning a first tag identifier to the first communication link according to a mapping relationship between the first SSB group and the first TRP to distinguish the communication link; and assigning a second tag identifier to the second communication link according to a mapping relationship between the second SSB group and the second TRP.

[0020] Here, the received establishment instruction instructs link establishment without performing a random access (RA) procedure if the time difference is less than a threshold value, and the second communication link can be established between the second TRP and the terminal without performing the RA procedure.

[0021] Here, the received setup instruction instructs the setup of a RACH-based link if the time difference is greater than or equal to a threshold value, and the step of generating the second communication link with the second TRP according to the received setup instruction may include the steps of: acquiring information on a random access occasion indicated in a second SIB acquired based on the second SSB; conducting a second random access procedure with the second TRP using the acquired random access occasion; and establishing the second communication link between the second TRP and the terminal according to the second random access procedure.

[0022] Here, the method includes receiving a first uplink TCI and first uplink scheduling information from the 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 the second TRP; and transmitting uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information, wherein if a time difference between a receiving time of the first SSB and a receiving time of the second SSB is less than a threshold value, a transmission time of transmitting the uplink data to the first TRP and a transmission time of transmitting the uplink data to the second TRP are the same, and if a time difference between a receiving time of the first SSB and a receiving time of the second SSB is equal to or greater than a threshold value, a difference between a transmission time of transmitting the uplink data to the first TRP and a transmission time of transmitting the uplink data to the second TRP may include the time difference.

[0023] Meanwhile, a transmission device based on multiple transmission and reception points in a communication system according to a third embodiment of the present disclosure is a terminal, and includes a processor, and the processor is configured to transmit a first synchronization signal (SSB) assigned to the first TRP from a first transmission and reception point (TRP). receive a first SSB included in a mapping relationship between the first SSB group and the first TRP and a mapping relationship between a second SSB group and the second TRP from the first TRP based on the first SSB; generate a first communication link between the first TRP and the terminal based on the first SSB; assign a first tag identifier to the first communication link for distinguishing the communication link according to the mapping relationship between the first SSB group and the first TRP; receive a second SSB included in the second SSB group assigned to the second TRP from a second TRP; generate a second communication link between the second TRP and the terminal based on the second SSB; and assign a second tag identifier to the second communication link according to the mapping relationship between the second SSB group and the second TRP.

[0024] Here, the processor is operable to cause the terminal to receive a measurement request from the first TRP; transmit a measurement report to the first TRP in response to the measurement request, the measurement report including information on the second SSB and information on the time difference between the reception time of the first SSB and the reception time of the second SSB; and receive a time to prevent establishment of the second communication link from the first TRP based on the time difference.In this case, the processor is operable to cause the terminal to establish the second communication link based on the received establishment instruction in the step of establishing a second communication link between the second TRP and the terminal based on the second SSB.

[0025] Here, the processor may instruct the terminal to establish a RACH-based link if the received establishment instruction indicates that the time difference is greater than or equal to a threshold value, and in establishing the second communication link based on the received establishment instruction, the processor may acquire information on a second random access occasion indicated in a second SIB acquired by the terminal based on the second SSB; perform a second random access procedure with the second TRP using the acquired second random access occasion; and establish the second communication link between the second TRP and the terminal according to the second random access procedure. [Effects of the Invention]

[0026] According to the present disclosure, a terminal can set different transmission times for multiple transmission / reception points. In particular, according to the present disclosure, the terminal can set transmission times for each transmission / reception point by reflecting a propagation delay. Accordingly, according to the present disclosure, signals transmitted and received between the multiple transmission / reception points and the terminal can be less affected by inter-symbol interference (ISI) and inter-carrier interference (ICI). [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a conceptual diagram illustrating a first embodiment of a communication system.

[0028] [Figure 2] 1 is a block diagram illustrating a first embodiment of a communication node that constitutes a communication system.

[0029] [Figure 3a] 1 is a conceptual diagram showing a first embodiment of a communication system having a plurality of transmitting and receiving points.

[0030] [Figure 3b] FIG. 10 is a conceptual diagram showing a second embodiment of a communication system having a plurality of transmitting and receiving points.

[0031] [Figure 4a] FIG. 1 is a conceptual diagram showing a first example of propagation delay in a communication system having multiple transmitting and receiving points.

[0032] [Figure 4b] FIG. 10 is a conceptual diagram showing a second example of propagation delay in a communication system having multiple transmitting and receiving points.

[0033] [Figure 5] 10 is a flowchart illustrating a first embodiment of an initial connection stage.

[0034] [Figure 6] 1 is a flowchart illustrating a first embodiment of a random access setup process.

[0035] [Figure 7] 10 is a flowchart illustrating a second embodiment of a random access setup process.

[0036] [Figure 8] 10 is a flowchart illustrating a third embodiment of a random access setup process.

[0037] [Figure 9] FIG. 1 is a conceptual diagram showing a first embodiment of a method for grouping synchronization signal blocks.

[0038] [Figure 10] FIG. 10 is a conceptual diagram showing a second embodiment of a method for grouping synchronization signal blocks.

[0039] [Figure 11] FIG. 10 is a conceptual diagram showing a third embodiment of a method for grouping synchronization signal blocks.

[0040] [Figure 12] FIG. 10 is a conceptual diagram showing a fourth embodiment of a method for grouping synchronization signal blocks.

[0041] [Figure 13] FIG. 1 is a conceptual diagram showing a first embodiment of a tag ID (identifier) ​​setting method.

[0042] [Figure 14] FIG. 10 is a conceptual diagram showing a second embodiment of a tag ID setting method.

[0043] [Figure 15] 1 is a flowchart illustrating a first embodiment of a method for triggering a transmission configuration indicator.

[0044] [Figure 16] 10 is a flowchart illustrating a first embodiment of a method for recognizing the state of a transmission setting indicator.

[0045] [Figure 17] FIG. 2 is a conceptual diagram illustrating a first embodiment of a terminal-specific transmission setting indicator table.

[0046] [Figure 18] 10 is a flowchart illustrating a second embodiment of a method for recognizing the state of a transmission setting indicator.

[0047] [Figure 19] FIG. 10 is a conceptual diagram showing a second embodiment of a terminal-specific transmission setting indicator table.

[0048] [Figure 20] 1 is a flowchart illustrating a first embodiment of a link configuration method in a multiple transmission and reception point environment.

[0049] [Figure 21] 10 is a flowchart showing a second embodiment of a link configuration method in a multiple transmission and reception point environment.

[0050] [Figure 22] FIG. 10 is a conceptual diagram showing a third embodiment of a tag ID setting method.

[0051] [Figure 23]10 is a flowchart illustrating a third embodiment of a link configuration method in a multiple transmission and reception point environment.

[0052] [Figure 24] 10 is a flowchart showing a fourth embodiment of a link configuration method in a multiple transmission and reception point environment.

[0053] [Figure 25] FIG. 10 is a conceptual diagram showing a fifth embodiment of a method for grouping synchronization signal blocks.

[0054] [Figure 26] FIG. 10 is a conceptual diagram showing a sixth embodiment of a method for grouping synchronization signal blocks.

[0055] [Figure 27] FIG. 10 is a conceptual diagram showing a fourth embodiment of a tag ID setting method.

[0056] [Figure 28] FIG. 10 is a conceptual diagram showing a fifth embodiment of a tag ID setting method.

[0057] [Figure 29] FIG. 10 is a conceptual diagram showing a sixth embodiment of a tag ID setting method.

[0058] [Figure 30] 10 is a flowchart showing a fifth embodiment of a link configuration method in a multiple transmission and reception point environment.

[0059] [Figure 31] FIG. 13 is a conceptual diagram showing a seventh embodiment of a tag ID setting method.

[0060] [Figure 32] FIG. 13 is a conceptual diagram showing an eighth embodiment of a tag ID setting method.

[0061] [Figure 33] 10 is a flowchart showing a sixth embodiment of a link configuration method in a multiple transmission and reception point environment.

[0062] [Figure 34] 10 is a flowchart showing a seventh embodiment of a link configuration method in a multiple transmission and reception point environment.

[0063] [Figure 35] FIG. 13 is a conceptual diagram showing a ninth embodiment of a tag ID setting method.

[0064] [Figure 36] FIG. 19 is a conceptual diagram showing a tenth embodiment of a tag ID setting method.

[0065] [Figure 37] 13 is a flowchart showing an eighth embodiment of a link configuration method in a multiple transmitting and receiving point environment.

[0066] [Figure 38] 13 is a flowchart illustrating a ninth embodiment of a link configuration method in a multiple transmitting and receiving point environment.

[0067] [Figure 39] 1 is a flowchart illustrating a first embodiment of a transmission method in a multiple transmission and reception point environment.

[0068] [Figure 40] 10 is a flowchart illustrating a second embodiment of a transmission method in a multiple transmission and reception point environment.

[0069] [Figure 41] 10 is a flowchart illustrating a third embodiment of a transmission method in a multiple transmission and reception point environment.

[0070] [Figure 42] 10 is a flowchart illustrating a fourth embodiment of a transmission method in a multiple transmission and reception point environment.

[0071] [Figure 43] 10 is a flowchart illustrating a fifth embodiment of a transmission method in a multiple transmission and reception point environment.

[0072] [Figure 44] 10 is a flowchart showing a sixth embodiment of a transmission method in a multiple transmission and reception point environment.

[0073] [Figure 45] 13 is a flowchart showing a seventh embodiment of a transmission method in a multiple transmission and reception point environment.

[0074] [Figure 46] 13 is a flowchart showing an eighth embodiment of a transmission method in a multiple transmission and reception point environment.

[0075] [Figure 47] 1 is a conceptual diagram showing a first embodiment of a downlink time adjustment method for multiple transmitting and receiving points in a communication system.

[0076] [Figure 48] 10 is a conceptual diagram showing a second embodiment of a downlink time adjustment method for multiple transmitting and receiving points in a communication system.

[0077] [Figure 49] 1 is a conceptual diagram showing a first embodiment of an uplink time adjustment method for multiple transmitting and receiving points in a communication system.

[0078] [Figure 50] 10 is a conceptual diagram showing a second embodiment of an uplink time adjustment method for multiple transmitting and receiving points in a communication system.

[0079] [Figure 51] 13 is a flowchart showing a ninth embodiment of a transmission method in a multiple transmission and reception point environment.

[0080] [Figure 52] 16 is a flowchart illustrating a tenth embodiment of a transmission method in a multiple transmission and reception point environment.

[0081] [Figure 53] 11 is a flowchart illustrating an eleventh embodiment of a transmission method in a multiple transmission and reception point environment.

[0082] [Figure 54] 12 is a flowchart illustrating a twelfth embodiment of a transmission method in a multiple transmission and reception point environment.

[0083] [Figure 55] 13 is a flowchart illustrating a thirteenth embodiment of a transmission method in a multiple transmission and reception point environment.

[0084] [Figure 56] 14 is a flowchart showing a fourteenth embodiment of a transmission method in a multiple transmission and reception point environment.

[0085] [Figure 57] 15 is a flowchart illustrating a fifteenth embodiment of a transmission method in a multiple transmission and reception point environment.

[0086] [Figure 58] 16 is a flowchart showing a sixteenth embodiment of a transmission method in a multiple transmission and reception point environment.

[0087] [Figure 59] 17 is a flowchart showing a seventeenth embodiment of a transmission method in a multiple transmission and reception point environment.

[0088] [Figure 60] 18 is a flowchart showing an 18th embodiment of a transmission method in a multiple transmission and reception point environment.

[0089] [Figure 61] 19 is a flowchart illustrating a 19th embodiment of a transmission method in a multiple transmission and reception point environment.

[0090] [Figure 62] 16 is a flowchart illustrating a twentieth embodiment of a transmission method in a multiple transmission and reception point environment. DETAILED DESCRIPTION OF THE INVENTION

[0091] While the present disclosure can be modified in various ways and can have various embodiments, specific embodiments will be illustrated in the drawings and described in detail, but it should be understood that this is not intended to limit the disclosure to the specific embodiments, and that all modifications, equivalents, and alternatives within the spirit and technical scope of the present disclosure are included.

[0092] Terms such as "first," "second," etc. may be used to describe various components, but the components should not be limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be designated a second component, and similarly, a second component may be designated a first component, without departing from the scope of the present disclosure. The term "and / or" includes a combination of multiple related listed items or any of multiple related listed items.

[0093] In the embodiments of the present disclosure, "at least one of A and B" may mean "at least one of A or B" or "at least one of a combination of one or more of A and B." Also, in the embodiments of the present disclosure, "one or more of A and B" may mean "one or more of A or B" or "one or more of a combination of one or more of A and B."

[0094] When a component is said to be "coupled" or "connected" to another component, it should be understood that it may be directly coupled or connected to the other component, but that there may be other components in between. Conversely, when a component is said to be "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0095] The terms used in this disclosure are merely used to describe specific embodiments and are not intended to limit the present disclosure. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this disclosure, terms such as "comprise" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0096] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms as defined in commonly used dictionaries should be interpreted to have a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined in this disclosure.

[0097] Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. In describing the present disclosure, the same reference numerals will be used to refer to the same components in the drawings, and redundant descriptions of the same components will be omitted, in order to facilitate overall understanding.

[0098] FIG. 1 is a conceptual diagram illustrating a first embodiment of a communication system.

[0099] 1, a communication system 100 may include 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. Here, the communication system may be referred to as a "communication network." Each of the multiple communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may support a CDMA (code division multiple access) based communication protocol, a WCDMA (wideband CDMA) based communication protocol, a TDMA (time division multiple access) based communication protocol, an FDMA (frequency division multiple access) based communication protocol, an OFDM (orthogonal frequency division multiplexing) based communication protocol, an OFDMA (orthogonal frequency division multiple access) based communication protocol, an SC (single carrier)-FDMA based communication protocol, a NOMA (non-orthogonal multiple access) based communication protocol, an SDMA (space division multiple access) based communication protocol, etc. Each of the plurality of communication nodes may have the following structure.

[0100] FIG. 2 is a block diagram illustrating a first embodiment of a communication node that constitutes a communication system.

[0101] 2, the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 that is connected to a network and performs communication. The communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, etc. The components included in the communication node 200 are connected to each other via a bus 270 to perform communication. However, the components included in the communication node 200 may be connected to each other via individual interfaces or individual buses centered around the processor 210 rather than via a common bus 270. 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 via a dedicated interface.

[0102] The processor 210 can execute program commands 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 methods according to embodiments of the present invention are performed. The memory 220 and the storage device 260 may each be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be composed of at least one of a read-only memory (ROM) and a random access memory (RAM).

[0103] 1, the communication system 100 may include multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 and multiple user equipments (UEs) 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. The first base station 110-1, the second base station 110-2, and the third base station 110-3 may each form a macro cell. The fourth base station 120-1 and the fifth base station 120-2 may each form a small cell. The fourth base station 120-1, the third UE 130-3, and the fourth UE 130-4 may be within the coverage area of ​​the first base station 110-1. The second UE 130-2, the fourth UE 130-4, and the fifth UE 130-5 may belong within the coverage of the second base station 110-2. The fifth base station 120-2, the fourth UE 130-4, the fifth UE 130-5, and the sixth UE 130-6 may belong within the coverage of the third base station 110-3. The first UE 130-1 may belong within the coverage of the fourth base station 120-1. The sixth UE 130-6 may belong within the coverage of the fifth base station 120-2.

[0104] Here, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be referred to as a Node B, evolved Node B, base transceiver station (BTS), radio base station, radio transceiver, access point, access node, road side unit (RSU), digital unit (DU), cloud digital unit (CDU), radio remote head (RRH), radio unit (RU), transmission point (TP), transmission and reception point (TRP), relay node, etc. Each of the multiple UEs 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may be referred to as a terminal, access terminal, mobile terminal, station, subscriber station, mobile station, mobile subscriber station, node, device, etc.

[0105] Each of the 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 may support cellular communications (e.g., LTE (long term evolution) or LTE-A (advanced) defined in the 3GPP (3rd generation partnership project) standard). Each of the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or the same frequency band. Each of the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other via an ideal backhaul or a non-ideal backhaul, and may exchange information via the ideal backhaul or the non-ideal backhaul. Each of the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network (not shown) via an ideal backhaul or a non-ideal backhaul. Each of the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may transmit signals received from the core network to a corresponding UE 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6, and may transmit signals received from the corresponding UE 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 to the core network.

[0106] Each of the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support OFDMA-based downlink transmission and SC-FDMA-based uplink transmission. Each of the 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 (SU)-MIMO, multi user (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation transmission, unlicensed band transmission, device-to-device (D2D) communication (or ProSe (Proximity Sector)). Each of the plurality of UEs 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 can perform operations corresponding to and supported by base stations 110-1, 110-2, 110-3, 120-1, and 120-2.

[0107] Meanwhile, in a communication system, a plurality of transmission and reception points (TRPs) and user equipment (UEs) (i.e., terminals) can transmit signals isochronously or sequentially.

[0108] FIG. 3a is a conceptual diagram showing a first embodiment of a communication system having multiple transmission and reception points.

[0109] Referring to FIG. 3a, a UE may be present in a serving cell having any physical cell identity (PCI). Two TRPs (TRP1, TRP2) having the same PCI may exist in the serving cell. Such a communication system may be referred to as an intra-cell multi-TRP (M-TRP or MTRP) communication system. Here, the serving cell has two TRPs, but may also contain more TRPs.

[0110] FIG. 3b is a conceptual diagram illustrating a second embodiment of a communication system having multiple transmission and reception points.

[0111] Referring to FIG. 3b, a UE may be present in a serving cell having a given PCI. Within this serving cell, one or more TRPs (TRP1) may exist with the same PCI. Furthermore, a TRP (TRP2) with a PCI different from that of the serving cell may exist in an area adjacent to the serving cell. Such a communication system may be referred to as an inter-cell M-TRP communication system. Here, the serving cell has two TRPs, but may also include more TRPs. Such an intra-cell M-TRP-based or inter-cell M-TRP-based communication system may support downlink and uplink transmission. Here, the downlink may be a link from the TRP to the UE, and the uplink may be a link from the UE to the TRP.

[0112] FIG. 4a is a conceptual diagram showing a first example of propagation delay in a communication system having multiple transmitting and receiving points.

[0113] Referring to FIG. 4a, two TRPs (TRP1, TRP2) may be in the same serving cell and may share the same configuration and resources. In other words, one serving cell may manage one timing advance / adjustment / alignment (TA). Two TRPs in the serving cell may share one TA. As described above, in an intra-cell M-TRP-based communication system, a terminal may perform downlink and uplink transmission by matching the reception synchronization point and transmission synchronization point to one TA managed by the serving cell regardless of the number of TRPs. Here, the reception synchronization point may be the reception time point, and the transmission synchronization point may be the transmission time point.

[0114] In this way, the terminal can manage one TA. In this case, TRP1 and TRP2 located in one serving cell may be far apart. In this situation, a terminal close to TRP1 can perform downlink and uplink transmission by matching the reception synchronization point and transmission synchronization point with the TA of TRP1. The terminal can also perform downlink and uplink transmission to TRP2 by applying the same reception synchronization point and transmission synchronization point according to the TA of TRP1. In this case, the difference between the propagation delay τ1 between TRP1 and the terminal and the propagation delay τ2 between TRP2 and the terminal is the length T of the cyclic prefix (CP). CP αT proportional to CP Therefore, when downlink transmission is performed, the signal received from TRP2 at the terminal may be subject to inter-symbol interference (ISI) and inter-carrier interference (ICI). Conversely, when uplink transmission is performed, the signal received from the terminal at TRP2 may be subject to ISI and ICI.

[0115] FIG. 4b is a conceptual diagram illustrating a second example of propagation delay in a communication system having multiple transmitting and receiving points.

[0116] Referring to FIG. 4b, one TRP (TRP1) can be located in one serving cell. Another TRP (TRP2) can be located in a non-serving cell having a PCI different from the PCI of the serving cell. The UE can manage one TA for the TRP of the serving cell and does not need to manage a TA for the TRP of the non-serving cell. However, the UE can use the TA of the TRP of the serving cell for the TRP of the non-serving cell for downlink and uplink transmission. As described above, in an inter-cell M-TRP-based communication system, the UE can perform downlink and uplink transmission by matching the reception synchronization point and transmission synchronization point to one TA managed by the serving cell, regardless of the number of TRPs.

[0117] In this way, the terminal can manage one TA. TRP1 connected to one serving cell and TRP2 connected to a non-serving cell may be far apart. A terminal close to TRP1 can use the TA of TRP1 for TRP2 of a non-serving cell. In this case, the difference between the propagation delay τ1 between TRP1 and the terminal and the propagation delay τ2 between TRP2 and the terminal is the length T of the cyclic prefix (CP). CP αT proportional to CP Therefore, when downlink transmission is performed, the signal received from TRP2 at the terminal may be subject to ISI and ICI. Conversely, when uplink transmission is performed, the signal received from the terminal at TRP2 may be subject to ISI and ICI.

[0118] Therefore, each of the intracell M-TRP-based communication systems and the intercell M-TRP-based communication systems may require a procedure for mutually recognizing the propagation delay, TA, or related information between any terminal and different TRPs to enable connection and linkage between the terminal and the TRP. Also, each of the intracell M-TRP-based communication systems and the intercell M-TRP-based communication systems may require a downlink transmission method that enables the terminal to simultaneously synchronize and receive signals transmitted from the TRP. Also, each of the intracell M-TRP-based communication systems and the intercell M-TRP-based communication systems may require an uplink transmission method that, conversely, enables the TRP to simultaneously synchronize and receive isochronous or sequential signals transmitted by the terminal.

[0119] In this disclosure, a wireless device may be referred to as a mobile station (MS). A TRP may refer to a device that transmits signals to or receives signals from an MS. A base station (BS) may be a device that manages a TRP. An area managed by a BS may be referred to as a cell. An MS may be referred to as a UE or terminal.

[0120] FIG. 5 is a flow chart showing a first embodiment of the initial connection stage.

[0121] Referring to FIG. 5, a terminal can power on and initially connect to a TRP (S510). To do this, the TRP can transmit beamformed synchronization signal blocks (SSBs) in multiple directions (S511). Accordingly, the terminal can receive the SSBs. The terminal can then perform downlink synchronization from the TRP to the terminal based on one of the received SSBs. Here, the TRP can periodically or aperiodically transmit SSBs for initial synchronization and maintenance of the beamforming-based downlink. After performing this synchronization, the terminal can acquire a master information block (MIB) from the SSB. This MIB can be transmitted to the terminal via a physical broadcast channel (PBCH). This MIB can be the initial system information acquired by the terminal.

[0122] Next, the TRP can transmit SIB1 (system information block 1) to the UE using the time and frequency resources indicated by the MIB (S512). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, the TRP can transmit SIB1 on the PDSCH to the UE. This SIB may be the second system information acquired by the UE. The TRP can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial access phase (S513). In this case, the TRP can transmit control information to the UE informing that SIBs will be transmitted in succession, such as a, after SIB1, on SIB1. Thereafter, the UE and the TRP can proceed with the random access setup procedure (S514).

[0123] Alternatively, the TRP may not transmit multiple SIBs other than SIB1 during the initial connection phase to speed up the connection procedure. In this case, the TRP may send SIB1 carrying control information indicating that multiple SIBs other than SIB1 will not be transmitted. The TRP may then retransmit the beamformed SSB in multiple directions (S520). As a result, the UE can receive the SSB. The TRP then transmits an RRC (radio resource control) configuration message to the UE (S521). The UE can then receive the RRC configuration message from the TRP and configure RRC. The UE may then transmit an RRC configuration complete message to the TRP (S522). As a result, the TRP can receive the RRC configuration complete message from the UE.

[0124] Meanwhile, when the UE has completed RRC setup and is in a system connected state as shown in b, it may transmit a SIB request message to the TRP requesting all or part of SIB1 from the TRP (S523). Then, the TRP may receive the SIB request message from the UE. Then, the TRP may transmit the SIB to the UE (S524). Accordingly, the UE may receive the SIB from the TRP. Alternatively, the UE may request all or part of SIB1 from the TRP during the process of completing RRC setup as shown in b, obtain corresponding information, and complete RRC setup. For convenience of explanation, the TRP may transmit all SIB1 including SIB1 in the initial connection phase as shown in a. However, the present disclosure may not be limited thereto.

[0125] FIG. 6 is a flow chart illustrating a first embodiment of a random access setup process.

[0126] Referring to FIG. 6, after downlink synchronization and system information acquisition, the UE can perform a four-step contention-based random access (CBRA)-based random access setup procedure for uplink synchronization (S610). First, in step 1, the UE can arbitrarily select one preamble from all preambles provided by the TRP. The UE can then transmit the selected preamble to the TRP via the physical random access channel (PRACH) (S611). The TRP can then receive the preamble from the UE via the PRACH. At this time, the beam direction can correspond to the uplink direction, which is complementary to the beam direction when receiving a downlink signal. The resource for transmitting the preamble from the UE to the TRP can be based on previously acquired information on the association between SSB and RACH. The TRP can estimate the propagation delay of the UE using the preamble.

[0127] Next, in step 2, the TRP can determine whether a preamble is present in the signal received through the PRACH. The preamble can be arbitrarily selected and transmitted by the UE. Therefore, the TRP cannot identify which UE transmitted the corresponding preamble based on whether the preamble is detected. Therefore, the TRP cannot determine how many UEs used the detected preamble. Accordingly, the TRP can transmit a random access response (RAR) based on the index of the detected preamble to the UE through the PDSCH (S612). Then, the UE can receive the RAR from the TRP. At this time, the RAR can include a preamble index, a TA value, uplink grant information, and a temporary C-RNTI (cell radio network temporary identifier) ​​value.

[0128] Next, in step 3, the UE may transmit a scheduling request message (or connection request message) and a UE-specific identifier to the TRP via a physical uplink shared channel (PUSCH) by applying a temporary C-RNTI using uplink radio resources indicated by the uplink grant information included in the corresponding RAR (S613). Then, the TRP may receive the connection request message and the UE-specific identifier from the UE. At this time, there may be more than one UE that transmitted the same preamble in step 1. As a result, preamble collision may occur. In this case, all UEs that transmitted the same preamble may refer to the same RAR and transmit messages using the same radio resources. This may result in collision.

[0129] In other words, terminals that transmitted the same preamble in stage 1 may experience resource collisions when transmitting stage 3 messages. Accordingly, each terminal may activate a contention resolution timer during transmission of a stage 3 message as part of a procedure to check whether or not a collision occurs in the transmitted stage 3 message and whether or not it has been successfully decoded.

[0130] Finally, in step 4, the TRP can decode the received step 3 message. Then, the TRP can transmit an acknowledgement message to the UE over the PDSCH for the successfully decoded message (S614). Then, the UE can receive the acknowledgement message from the TRP. The UE can receive the acknowledgement message before the contention resolution timer operated in step 3 expires. In this case, the UE can determine that the voluntary access has been successfully performed and can consider the temporary C-RNTI as its own C-RNTI for continued use in the system connection state. Alternatively, the UE may not receive any acknowledgement message before the contention resolution timer expires. In this case, the UE can determine that decoding failed due to a collision of messages transmitted in step 3. Accordingly, the UE can perform backoff. Thereafter, the UE can attempt the voluntary access procedure again. The TRP can define a maximum number of voluntary access attempts to prevent congestion on the voluntary access channel. Accordingly, the UE may not be able to successfully perform voluntary access within the maximum number of attempts. In such a case, the terminal can abandon the optional connection and start again from downlink synchronization.

[0131] FIG. 7 is a flow chart illustrating a second embodiment of a random access setup process.

[0132] Referring to Figure 7, after completing downlink synchronization and system information acquisition, the UE can perform a two-step CBRA-based random access setup procedure for uplink synchronization (S710). To this end, in step 1, the UE can arbitrarily select one preamble from all preambles. The UE can then transmit the selected preamble to the TRP via the PRACH. At the same time, the UE can transmit a scheduling request (i.e., connection request) message to the TRP via pre-allocated uplink radio resources (i.e., uplink shared channel) (S711). Then, the TRP can receive a message including the preamble and scheduling request from the UE.

[0133] In two steps, the TRP can determine whether the preamble is detected. The TRP can also determine whether the message is successfully decoded. Depending on the result of the determination, the TRP can send a different type of message to the terminal. This may change the subsequent procedure.

[0134] In particular, if the TRP cannot detect the preamble, the TRP may not perform any operation. In other words, the TRP may not check whether a message related to the preamble has been received through the uplink radio resource. As a result, the TRP may not respond if the preamble is not detected. Accordingly, since the terminal has not received any message from the TRP, it may retry the optional connection. This case is referred to as Case 1.

[0135] Alternatively, the TRP may successfully detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, the TRP may transmit a message including the RAR and C-RNTI to the UE via the PDSCH (S712). Accordingly, the UE may receive a message including a successful RAR and C-RNTI from the TRP. This message may serve as an acknowledgement. Accordingly, the UE may successfully terminate the optional access. This case may be referred to as case 2. On the other hand, the TRP may successfully detect the preamble but may not successfully decode the message from the uplink radio resources associated with the preamble. In this case, the TRP may transmit a message including a fallback RAR to the UE via the PDSCH. In this case, the UE receiving the message may retransmit the message it was attempting to send using the uplink radio resources indicated by the uplink grant information included in the fallback RAR.

[0136] FIG. 8 is a flow chart illustrating a third embodiment of a random access setup process.

[0137] Referring to FIG. 8, after completing downlink synchronization and system information acquisition, the UE can perform a two-stage contention-free random access (CFRA)-based random access setup procedure for uplink synchronization (S810). To this end, in step 1, the UE can arbitrarily select one preamble from preambles designated by the TRP. The UE can then transmit the selected preamble to the TRP via the PRACH (S811). The TRP can then receive a message including the preamble from the UE. Thereafter, the TRP can perform TA estimation for the received preamble. The TRP can then determine whether TA has been detected through TA estimation, and generate and transmit an RAR to the UE based on the determination result (S812). The UE can then receive the RAR from the TRP.

[0138] Referring again to FIG. 5, the TRP may transmit an RRC setup message to the UE. Then, the UE may receive the RRC setup message from the TRP and complete the RRC setup. Accordingly, a series of system connections may be completed. Thereafter, the UE is in a system connected state and can communicate with the peer UE through the TRP.

[0139] Hereinafter, a procedure, transmission method, and communication device may be described in which any terminal belonging to one serving cell synchronizes with a TRP present in the cell and transmits and receives signals isochronously or sequentially in downlink and uplink. Alternatively, a procedure, transmission method, and communication device may be described in which any terminal belonging to one serving cell synchronizes with a TRP belonging to the serving cell and a TRP belonging to an adjacent non-serving cell and transmits and receives signals isochronously or sequentially in downlink and uplink. Such a procedure and transmission method may be referred to as an intra-cell / inter-cell M-TRP procedure method. Here, the intra-cell / inter-cell M-TRP procedure method may be a transmission method based on multiple transmission / reception points.

[0140] The description of the present disclosure assumes that up to two TRPs can be connected to one serving cell and one TRP can be connected to an adjacent non-serving cell, as shown in Figures 3a and 3b. However, this is not limited thereto, and the scope of the present disclosure also includes a configuration in which two or more TRPs can be connected to a serving cell and one or more TRPs can be connected to a non-serving cell.

[0141] Referring again to FIG. 5, all TRPs in one serving cell can transmit the same beamformed SSB to the terminal. Then, the terminal can receive the same beamformed SSB from the TRP. At this time, the terminal does not know whether the estimated best SSB and second-best SSB belong to TRP1 or TRP2. As a result, it may be difficult for the terminal to synchronize with each of the two different TRPs and transmit signals isochronously or sequentially. Here, the best SSB may be the SSB with the largest maximum correlation value, and the second-best SSB may have the second largest correlation value. Alternatively, the best SSB may be the SSB with the largest SINR (signal to interference plus noise ratio), and the second-best SSB may have the second largest SINR. The best SSB may be the first best SSB (in other words, the first best SSB). st The second best SSB can be the second best SSB (in other words, the second nd best SSB).

[0142] To solve this problem, the intra-cell / inter-cell M-TRP procedure method can divide available beamformed SSBs into SSB groups. Each SSB group can then be mapped to a TRP. This method can be called the SSB grouping method. Here, the first SSB grouping method can divide SSBs into disjoint SSB groups within the same SSB period, the same number of available beamformed SSBs, or the same half frame. Each SSB group can then be mapped to a TRP.

[0143] FIG. 9 is a conceptual diagram showing a first embodiment of a method for grouping synchronization signal blocks.

[0144] Referring to FIG. 9, SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). In this case, SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. Such SSB group 1 can be mapped to TRP1. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. Such SSB group 2 can be mapped to TRP2. Here, mapping SSB group 1 to TRP1 means that TRP1 is physically mapped to the SSB sweeping. ping), it may mean that beamformed SSBs are transmitted in the corresponding direction using only SSB1, SSB3, SSB5, and SSB7. Similarly, mapping SSB group 2 to TRP2 may mean that beamformed SSBs are transmitted in the corresponding direction using only SSB2, SSB4, SSB6, and SSB8 when TRP2 physically sweeps SSBs. In this case, the number of available SSBs may be 8, but is not limited to this, and may be 4, 16, 64, etc. Here, TRP1 and TRP2 may be included in the serving cell.

[0145] FIG. 10 is a conceptual diagram showing a second embodiment of a method for grouping synchronization signal blocks.

[0146] Referring to FIG. 10, SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. SSB group 1 can be mapped to TRP1 belonging to a serving cell. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. SSB group 2 can be mapped to TRP2 belonging to a non-serving cell. Here, mapping SSB group 1 to TRP1 can mean that when TRP1 physically performs SSB sweeping, it transmits beamformed SSBs in the corresponding direction using only SSB1, SSB3, SSB5, and SSB7. Similarly, mapping SSB group 2 to TRP2 may mean that when TRP2 physically sweeps SSBs, it transmits beamformed SSBs in the corresponding direction using only SSB2, SSB4, SSB6, and SSB8. In this case, the number of available SSBs may be 8, but is not limited to this, and may be 4, 16, 64, etc. Here, TRP1 may be included in the serving cell, and TRP2 may be included in a non-serving cell.

[0147] 9 and 10 are merely some examples, and all methods of dividing SSBs into groups with the same SSB period, the same number of available beamformed SSBs, or the same half frame so that they do not intersect with each other, and mapping each group to a TRP, may be included in the scope of the present disclosure. Meanwhile, the second grouping method may be a method of dividing SSBs into SSB groups with the same SSB period, the same number of available beamformed SSBs, or different half frames so that they do not intersect with each other, and mapping each SSB group to a TRP.

[0148] FIG. 11 is a conceptual diagram showing a third embodiment of a method for grouping synchronization signal blocks.

[0149] Referring to FIG. 11, the SSBs (SSB1 to SSB8) in the first half frame of a frame may be classified as SSB group 1. The SSBs (SSB1 to SSB8) in the remaining half frames of a frame may be classified as SSB group 2. In this way, SSB group 1 may include SSB1 to SSB8 in the first half frame. Such SSB group 1 may be mapped to TRP1. In contrast, SSB group 2 may include SSB1 to SSB8 in the remaining half frames. Such SSB group 2 may be mapped to TRP2. Here, mapping SSB group 1 to TRP1 may mean that, when TRP1 physically performs SSB sweeping, beamformed SSBs are transmitted in the corresponding direction using all of SSB1 to SSB8 in the first half frame. Similarly, mapping SSB group 2 to TRP2 may mean that, when TRP2 physically performs SSB sweeping, beamformed SSBs are transmitted in the corresponding direction using all of SSB1 to SSB8 in the remaining half frames. In this case, the number of available SSBs may be 8, but is not limited to this, and may be 4, 16, 64, etc. Here, TRP1 and TRP2 may be included in the serving cell.

[0150] FIG. 12 is a conceptual diagram showing a fourth embodiment of the method for grouping synchronization signal blocks.

[0151] Referring to FIG. 12, the SSBs (SSB1 to SSB8) in the first half frame of a frame may be classified into SSB group 1. The SSBs (SSB1 to SSB8) in the remaining half frames of a frame may be classified into SSB group 2. In this way, SSB group 1 may include SSB1 to SSB8 in the first half frame. Such SSB group 1 may be mapped to TRP1 belonging to the serving cell. In contrast, SSB group 2 may include SSB1 to SSB8 in the remaining half frames. Such SSB group 2 may be mapped to TRP2 belonging to a non-serving cell. Here, mapping SSB group 1 to TRP1 may mean that when TRP1 physically performs SSB sweeping, beamformed SSBs are transmitted in the corresponding direction using all of SSB1 to SSB8 in the first half frame. Similarly, mapping SSB group 2 to TRP2 may mean that when TRP2 physically sweeps SSBs, beamformed SSBs are transmitted in the corresponding direction using all of SSBs 1 to 8 in the remaining half frame. In this case, the number of available SSBs may be 8, but is not limited to this and may be 4, 16, 64, etc.

[0152] In the second SSB grouping method, Figures 11 and 12 are merely some examples, and the first half of the frame may be expanded to include a first resource, and the remaining half of the frame may be expanded to include a second resource. Each resource may correspond to a different "time resource," "time interval," "frequency resource," or "time and frequency resource." The scope of the present disclosure includes all methods of dividing SSBs transmitted from such resources into disjoint groups and mapping each group to a TRP. The present disclosure also includes a combination of the first and second grouping methods, including all methods of dividing SSBs into disjoint groups with the same SSB period, the same or different numbers of available beamformed SSBs, or the same or different half frames and mapping each group to a TRP. In Figures 9 to 12, SSB group 1 may be associated with a first TA, and SSB group 2 may be associated with a second TA. 9-12, SSB group 1 may be associated with a first tag ID (TAG ID), and SSB group 2 may be associated with a second tag ID. Also, in FIG. 9-12, each SSB in SSB group 1 may be associated with one TAG ID, and each SSB in SSB group 2 may be associated with one TAG ID.

[0153] FIG. 13 is a conceptual diagram showing a first embodiment of a tag ID (identifier) ​​setting method.

[0154] Referring to FIG. 13, for TA adjustment required for uplink synchronization, each SSB group may be mapped to one TRP and associated with one tag ID (e.g., TAG1, TAG2, etc.). For example, SSB group 1 may be associated with TAG1, and SSB group 2 may be associated with TAG2. In this case, TAG1 may be associated with joint transmission configuration indication (TCI) 1, and TAG2 may be associated with joint TCI2. In this way, since TAGs are managed for each SSB group, when a terminal configures one communication link for each of TRP1 and TRP2, it can perform uplink synchronization and communication for each TAG.

[0155] FIG. 14 is a conceptual diagram showing a second embodiment of the tag ID setting method.

[0156] 14, when a terminal configures two communication links within one TRP, it can assign the same TAG to both links to perform uplink synchronization and communication. Here, one communication link may pass through an obstacle.

[0157] Meanwhile, TCI may refer to a transmission configuration indicator that specifies the quasi colocation (QCL) relationship between a downlink or uplink physical channel and a physical signal. Among such TCIs, joint TCI can specify the QCL relationship between downlink and uplink physical channels and a physical signal to reduce control overhead. The TRP may deliver the TCI to the UE via a dynamic control channel, such as a physical downlink control channel (PDCCH), a medium access control element (MAC CE), or a PDSCH containing RRC information. Alternatively, the TRP may deliver the TCI to the UE via an aperiodic control channel, such as a PDCCH, a MAC CE, or a PDSCH containing RRC information. Alternatively, the TRP may deliver the TCI to the UE via a periodic control channel, such as a PDCCH, a MAC CE, or a PDSCH containing RRC information. Alternatively, the TRP may deliver the TCI to the UE via a semi-periodic control channel, such as a PDCCH, a MAC CE, or a PDSCH containing RRC information. In this case, the TRP can apply TCI to match the beam direction and QCL relationship of the antenna port for each communication link, and can transmit the beam direction and QCL relationship of the antenna ports of two communication links in one TCI to the UE.

[0158] FIG. 15 is a flow chart illustrating a first embodiment of a method for triggering a transmission configuration indicator.

[0159] Referring to FIG. 15, the TRP (or NW (network)) may transmit a TCI state table to a UE by carrying it on a PDSCH through higher layer radio resource control (RRC) signaling (S1501). Then, the UE may receive the TCI state table from the TRP. Here, the TCI state table may be referred to as 'tci-StatesToAddModList' defined in the PDSCH configuration (for example, PDSCH-Config). The maximum size of the TCI state table may be, for example, 128. Here, TCI may be defined as follows:

[0160] -TCI can specify the QCL relationship between various physical channels (beams) and antenna ports used in the physical signals (beams). Here, the QCL can specify multiple QCL types in the form of functions such as Doppler shift, Doppler spread, average delay, and spatial Rx parameters. An example QCL type may be as follows:

[0161] -QCL-Type A: Doppler transition, Doppler spread, mean delay, delay spread

[0162] -QCL-type B: Doppler transition, Doppler spread

[0163] -QCL-Type C: Mean delay, Doppler transition

[0164] -QCL-Type D: Spatial transmission parameters

[0165] The 128 downlink TCI configurations defined in RRC may follow the QCL relationship between downlink physical channels (e.g., PDSCH, PDCCH) and downlink physical signals (e.g., SSB, DL CSI-RS (channel state information reference signal) etc.) as follows: The uplink TCI configuration may follow the QCL relationship between uplink physical channels (e.g., PUSCH, PUCCH) and uplink physical signals (e.g., SRS (sounding reference signal), UL CSI-RS etc.).

[0166] -PDCCH / PDSCH QCL (with SSB)

[0167] -PDCCH / PDSCH QCL (with DL CSI-RS)

[0168] -PDCCH / PDSCH QCL (with SSB and DL CSI-RS)

[0169] -DL CSI-RS beam QCL (with SSB beam)

[0170] Next, the TRP (or NW) may transmit the TCI status table to the UE through the MAC CE of the UE-specific PDCCH / PDSCH (S1502). Then, the UE may receive the TCI status table from the TRP.

[0171] FIG. 16 is a flow chart illustrating a first embodiment of a method for recognizing the state of a transmission setting indicator.

[0172] Referring to FIG. 16, the TRP can transmit an SSB based on SSB beam sweeping (S1601). Then, the UE can receive the SSB from the TRP. The UE can then select an SSB to indicate the best beam. The UE can obtain system-related information such as MIB and SIBy from the selected SSB. The UE can perform a random access procedure using information related to random access in the system information to synchronize the uplink (S1602).

[0173] The TRP may transmit an RRC setup message to the UE (S1603). Then, the UE may receive the RRC setup message from the TRP. The UE may configure RRC according to the received RRC setup message and, upon completing the RRC setup, may transmit an RRC setup complete message to the TRP (S1604). Then, the TRP may receive the RRC setup complete message from the UE. Through this process, the UE may be connected to the TRP. Thereafter, the UE may communicate with a counterpart UE through the TRP in a connected state.

[0174] Next, the TRP can transmit a TCI state table called 'tci-StatesToAddModList', for example, with a maximum size of 128, on the PDSCH to the UE (S1605). Then, the UE can receive the TCI state table. Accordingly, the UE can acquire and store a TCI state table associated with the PDCCH, for example, with a maximum size of 64, in 'tci-StatesToAddModList'. Next, the TRP can transmit the corresponding UE-specific TCI state table of FIG. 17 to the UE-specific PDCCH MAC CE on the PDSCH (S1606). Then, the UE can receive, store, and manage the UE-specific TCI state table from the TRP.

[0175] FIG. 17 is a conceptual diagram showing a first embodiment of the terminal-specific transmission setting indicator table.

[0176] 17, in the UE-specific transmission configuration indicator table, octet 1 may be composed of a serving cell ID and a portion of a common control resource set (CORESET) ID for the corresponding PDCCH, and octet 2 may be composed of a portion of the CORESET ID and a TCI state ID indicating one of, for example, 64 states included in the TCI state table.

[0177] Here, two communication links may be configured. Each communication link may be classified into a different TAG to perform reverse synchronization. In this case, a UE-specific PDCCH MAC CE may be sent separately for each link. Alternatively, a UE-specific PDCCH MAC CE may be transmitted separately for one link (for example, the first communication link). Alternatively, a UE-specific PDCCH MAC CE may be integrated and transmitted for one link. When a UE-specific PDCCH MAC CE is transmitted in the form of an integrated MAC CE, a link-specific TCI ID / TAG ID may be assigned to the CE field. Meanwhile, a UE may acquire its own TCI status specified in the TCI status table, decode its own PDCCH, and perform downlink communication.

[0178] FIG. 18 is a flow chart illustrating a second embodiment of a method for recognizing the state of a transmission setting indicator.

[0179] Referring to FIG. 18, the TRP can transmit an SSB based on SSB beam sweeping (S1801). Then, the UE can receive the SSB from the TRP. The UE can then select an SSB to indicate the best beam. The UE can obtain system-related information such as MIB and SIBy from the selected SSB. The UE can perform a random access procedure using information related to random access in the system information to synchronize the uplink (S1802).

[0180] The TRP may transmit an RRC setup message to the UE (S1803). Then, the UE may receive the RRC setup message from the TRP. The UE may configure RRC according to the received RRC setup message and, upon completing the RRC setup, may transmit an RRC setup complete message to the TRP (S1804). Then, the TRP may receive the RRC setup complete message from the UE. Through this process, the UE may be connected to the TRP. Thereafter, the UE may communicate with a counterpart UE through the TRP in a connected state.

[0181] Next, the TRP may transmit a TCI state table, called 'tci-StatesToAddModList', having a maximum size of, for example, 128, on the PDSCH to the UE (S1805). Then, the UE may receive the TCI state table. Accordingly, the UE may acquire and store a TCI state table associated with the PDCCH, having a maximum size of, for example, 64, in 'tci-StatesToAddModList'.

[0182] Next, the TRP can broadcast an RRC configuration parameter called the TCI current state of DCI (for example, tci-PresentInDCI) on the PDSCH through higher layer signaling (S1806). Then, the UE can receive the RRC configuration parameter and acquire the TCI current state information of DCI. The UE can perform the following procedures according to the indication information of the acquired TCI current state information of DCI.

[0183] If the TCI current state of DCI (for example, tci-PresentInDCI) is an omit state, in other words, tci-PresentInDCI may be "tci-PresentInDCI=omit". In this case, the TCI state for PDSCH may be the same as the TCI state for CORESET / PDCCH. In this case, the UE may perform the following procedure.

[0184] First, the TRP can include a UE-specific TCI status table in a UE-specific PDCCH MAC CE and transmit it to the UE over the PDSCH (S1807). The UE can acquire its own TCI status by receiving the specific TCI status table as shown in Figure 17. The UE can acquire its own TCI status specified in the specific TCI status table of Figure 17 and decode its own PDCCH to perform downlink communication.

[0185] If the TCI current state of the DCI is assumed to be an enable state, in other words, if tci-PresentInDCI is 'tci-PresentInDCI=enabled', the following process can be performed. First, the TRP can transmit a UE-specific TCI status table for a UE-specific PDSCH MAC CE as shown in Figure 19 to the UE via the PDSCH. The UE can receive the UE-specific TCI status table as shown in Figure 19 from the TRP.

[0186] FIG. 19 is a conceptual diagram showing a second embodiment of the terminal-specific transmission setting indicator table.

[0187] Referring to FIG. 19, the UE-specific transmission configuration indicator table may be configured with a serving cell ID, a bandwidth part (BWP) ID for the corresponding PDSCH, and one bit for activation (defined as 1) / deactivation (defined as 0) for 128 TCI states. The bottom of FIG. 19 may indicate activation for eight TCI states configured for the UE. Here, two communication links may be configured. Each communication link may be classified into a different TAG to perform reverse synchronization. In this case, the UE-specific PDCCH MAC CE may be sent separately for each link. Alternatively, the UE-specific PDCCH MAC CE may be transmitted separately for one link (for example, the first communication link). Alternatively, the UE-specific PDCCH MAC CE may be integrated and transmitted for one link. In this way, when the UE-specific PDCCH MAC CE is transmitted in the integrated MAC CE format, a link-specific TCI ID / TAG ID may be assigned to the CE field.

[0188] Next, the UE can substitute each of the eight activated TCI states in the codepoint table in ascending order as shown on the right. Meanwhile, the TRP can transmit DL TCI and DCI (for example, DCI 1_1) through a UE-specific PDCCH. The UE can receive DL TCI and DCI from the TRP. Accordingly, the UE can recognize its scheduled codepoint index through the TCI field included in DCI 1_1 and perform downlink communication.

[0189] FIG. 20 is a flowchart showing a first embodiment of a link configuration method in a multiple transmitting and receiving point environment.

[0190] Referring to FIG. 20, a terminal can establish communication links with two TRPs belonging to different SSB groups. At this time, the terminal can establish two communication links from the initial connection. To do this, the terminal can perform SSB beam measurement on beamformed SSBs transmitted by TRP1 and TRP2. At this time, the terminal can select SSB1 from the best SSB (1st best SSB) and SSB2 from the second best SSB (2nd best SSB). The terminal can acquire system information based on the best SSB (S2001). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSBs.

[0191] The UE can recognize SSB1 as the best SSB through the PBCH. It can also recognize the SSB group-TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIB (system information block) y. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. The TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the UE can recognize the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID from the PDSCH containing the system information SIBy.

[0192] Next, TRP1 and the terminal can perform uplink synchronization through a 4-step or 2-step CBRA process according to the random access channel (RACH) occasion (RO) indicated by the SIB obtained from the system information (S2002). Here, RO can be the uplink time / frequency resource location for random access. In this process, the terminal can set TAG1 for the communication link with TRP1. In this way, the terminal can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0193] Next, TRP1 can transmit an RRC setup message to the UE (S2003). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP1 (S2004). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the peer UE through TRP1.

[0194] To this end, TRP1 can transmit downlink-related DCI to the UE (S2009). Then, the UE can receive downlink-related DCI from TRP1. Here, the downlink-related DCI indicates DL / connection TCI1, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and can be transmitted on the PDCCH. Thereafter, TRP1 can transmit downlink data to the UE using the downlink-related DCI (S2010). Then, the UE can receive downlink data from TRP1 based on the downlink-related DCI.

[0195] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S2011). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S2012). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI.

[0196] Meanwhile, the UE may be in an RRC-connected state. TRP1 may request measurement from the UE (S2005). Accordingly, the UE may receive SSB from the neighboring TRP and perform measurement. The UE may then report the SSB-based measurement results for the neighboring TRP to TRP1 via RRC signaling (S2006). At this time, the UE may report SSB2 as the next-best SSB to TRP1. Accordingly, TRP1 may receive a measurement report from the UE. TRP1 may then recognize SSB2 as the next-best SSB through the measurement report. At this time, SSB2 may not be included in the SSB group used by TRP1. Accordingly, TRP1 may recognize TRP2 from the TRP transmitting SSB2 based on the SSB group and TRP relationship.

[0197] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0198] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0199] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as 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 point of the communication link, such as the second SSB index, the third SSB index, etc., does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from TRP1. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index, the third SSB index, etc., exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from TRP1.

[0200] Next, the UE may perform a random access setup process with TRP2 (S2007). In this process, the UE may set up a communication link with TRP2 to TAG2 for uplink synchronization and update of the communication link. This random access setup process for TRP2 may be triggered by TRP1. Alternatively, the random access setup process for TRP2 may be triggered by the UE.

[0201] First, in the TRP1-based triggering method, TRP1 can trigger the random access setup process for TRP2 by instructing the UE to perform CFRA or CBRA random access through higher layer signaling or PDCCH. In contrast, in the UE-based triggering method, the UE can recognize the need to manage other TAGs through the random access process with TRP1. Accordingly, the UE can request random access with SSB2 or TRP2 through higher layer signaling or a physical layer control channel (e.g., PUSCH) to trigger the random access setup process for TRP2.

[0202] Upon receiving this request, TRP1 can instruct the UE to perform CFRA or CBRA random access via higher layer signaling or PDCCH, and proceed with the random access setup procedure for TRP2. In this way, the UE can receive an instruction for the random access setup procedure for TRP2 from TRP1. Accordingly, the UE and TRP2 can perform the random access procedure and complete the random access setup procedure.

[0203] Next, TRP2 and the UE can perform an RRC setup process (S2008). In other words, TRP2 can transmit an RRC setup message to the UE. The UE can receive the RRC setup message from TRP2. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP2. TRP2 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP2. In this connected state, the UE can communicate with the peer UE through TRP1 and TRP2.

[0204] To this end, TRP2 can transmit downlink-related DCI to the UE (S2013). Then, the UE can receive downlink-related DCI from TRP2. Here, the downlink-related DCI indicates DL / connection TCI2, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and can be transmitted on the PDCCH. Then, TRP2 can transmit downlink data to the UE using the downlink-related DCI (S2014). Then, the UE can receive downlink data from TRP2 based on the downlink-related DCI.

[0205] Alternatively, TRP2 may transmit uplink-related DCI to the UE (S2015). Then, the UE may receive uplink-related DCI from TRP2. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates transmission configuration of the UE, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Then, TRP2 may transmit uplink data to the UE using the uplink-related DCI (S2016). Then, TRP2 may receive uplink data from the UE based on the uplink-related DCI. Then, the UE may periodically or aperiodically perform uplink synchronization for TAG1 and TAG2 with TRP1 or TRP2 and update the TA (S2017).

[0206] FIG. 21 is a flowchart showing a second embodiment of a link configuration method in a multiple transmission / reception point environment.

[0207] Referring to Figure 21, a terminal can configure two communication links with one TRP belonging to one SSB group. At this time, the terminal can configure two communication links from the initial connection. To this end, the terminal can perform SSB beam measurement for the beamformed SSB transmitted in TRP1. At this time, the terminal can select SSB1 from the best SSB (1st best SSB) and SSB5 from the second best SSB (2nd best SSB). The terminal can acquire system information based on the best SSB (S2101). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB.

[0208] The UE can recognize SSB1 as the best SSB through the PBCH. It can also recognize the SSB group-TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIBy. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. The TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the UE can recognize the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID from the PDSCH containing SIBy, which is system information.

[0209] Next, TRP1 and the UE can perform uplink synchronization through a 4-step or 2-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S2102). Here, RO can be an uplink time / frequency resource location for random access. In this process, the UE can set TAG1 for the communication link with TRP1. In this way, the UE can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0210] Next, TRP1 can transmit an RRC setup message to the UE (S2103). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP1 (S2104). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the counterpart UE through TRP1.

[0211] To this end, TRP1 may transmit downlink-related DCI to the UE (S2110). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI1, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S2111). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0212] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S2112). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S2113). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI.

[0213] Meanwhile, the UE may be in an RRC-connected state. TRP1 may request measurement from the UE (S2105). Accordingly, the UE may receive SSB from the neighboring TRP and perform measurement. The UE may report the measurement results for the SSB-based neighboring TRP to TRP1 through RRC signaling (S2106). At this time, the UE may report SSB5 as the second-best SSB to TRP1. Accordingly, TRP1 may receive a measurement report from the UE. TRP1 may recognize SSB5 as the second-best SSB through the measurement report. At this time, SSB5 may be included in the SSB group used by TRP1. Accordingly, TRP1 may recognize itself as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Here, although the UE performs the measurement report at the request of TRP1, the UE may also perform the measurement report without such a request.

[0214] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0215] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0216] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP1.

[0217] Meanwhile, the UE can report SSB5 to TRP1 as the next best SSB. In this case, SSB5 may be included in the same SSB group as SSB1. Therefore, the communication link associated with SSB5 is an example of TRP1 and may be a different communication link from the communication link associated with SSB1 that comes in through multipath. Such a communication link associated with SSB5 may be subject to uplink synchronization and update of the communication link based on SSB1 recognized by TAG1. Accordingly, through a RACH-less procedure, TRP1 and the UE can perform beam measurement between the UE and SSB5 as follows.

[0218] To this end, TRP1 can instruct the UE to transmit the uplink beamformed SRS to the TRPs including TRP1 using the scheduling resources determined for the UE (S2107). At this time, TRP1 can instruct the UE to transmit the SRS through RRC signaling including information on the scheduling resources determined for transmitting the uplink beamformed SRS. At this time, TRP1 can inform neighboring TRPs that the uplink beamformed SRS is to be transmitted using the scheduling time / frequency resources determined for the UE for interference suppression. Alternatively, TRP1 may not inform neighboring TRPs that the uplink beamformed SRS is to be transmitted using the scheduling time / frequency resources determined for the UE for resource efficiency.

[0219] Next, the terminal may transmit the beamformed SRS to the TRPs, including TRP1 (S2108). Then, TRP1 may receive the SRS at the terminal. Then, TRP1 may select the most suitable uplink beam based on the received SRS and notify the terminal of the most suitable uplink beam information (in other words, best uplink beam information) (S2109). In other words, TRP1 may notify the terminal of the SRS information with the highest SINR, for example, among the beamformed SRSs received from the terminal. Accordingly, the terminal may receive the best uplink beam information from TRP1. Then, the terminal may determine that the best uplink beam belongs to the terminal. Through this process, the terminal may complete system connection to TRP1 through a communication link related to SSB5. In this connected state, the terminal may communicate with a remote terminal through two communication links of TRP1.

[0220] To this end, TRP1 may transmit downlink-related DCI associated with SSB5 to the UE (S2114). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI1, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S2115). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0221] Alternatively, TRP1 may transmit uplink-related DCI associated with SSB5 to the UE (S2116). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Then, TRP1 may transmit uplink data to the UE via the uplink-related DCI (S2117).

[0222] Then, TRP1 can receive uplink data from the UE based on the DCI associated with the uplink. Thereafter, the UE can periodically or aperiodically perform uplink synchronization for TAG1 with TRP1 and update the TA (S2118). Here, although Figures 20 and 21 describe procedures for configuring two communication links, the method of the present disclosure may not be limited thereto. The TRP and the UE can configure three or more communication links by alternately applying the communication link configuration methods of Figures 20 and 21 to perform downlink and uplink multiplexed TRP communication.

[0223] FIG. 22 is a conceptual diagram showing a third embodiment of the tag ID setting method.

[0224] Referring to FIG. 22, each SSB group may be mapped to one TRP for TA adjustment necessary for uplink synchronization. One tag ID (e.g., TAG1, TAG2, etc.) may be associated with one SSB. For example, SSB1 of SSB group 1 may be associated with TAG1. SSB5 of SSB group 1 may be associated with TAG5. SSB2 of SSB group 2 may be associated with TAG2. In this case, TAG1 may be associated with joint transmission set indicator (TCI) 1. TAG2 and TAG5 may be associated with joint TCI 2. In this way, since TAGs are managed separately for each SSB, when a terminal configures one communication link for each SSB of TRP1 and TRP2, it can perform uplink synchronization and communication for each SSB. In this case, the method of configuring a link in a multi-transmission point communication system may be the same as that shown in FIGS. 23 and 24.

[0225] FIG. 23 is a flowchart showing a third embodiment of a link configuration method in a multiple transmitting / receiving point environment.

[0226] Referring to Figure 23, a terminal can configure two communication links with one TRP belonging to one SSB group. At this time, the terminal can configure two communication links from the initial connection. To do this, the terminal can perform SSB beam measurement for the beamformed SSB transmitted in TRP1. At this time, the terminal can select SSB1 from the best SSB (1st best SSB) and SSB5 from the second best SSB (2nd best SSB). The terminal can acquire system information based on the best SSB (S2301). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB.

[0227] The UE can recognize SSB1 as the best SSB through the PBCH. It can also recognize the SSB group-TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIBy. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. The TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the UE can recognize the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID from the PDSCH containing SIBy, which is system information.

[0228] Next, TRP1 and the UE can perform uplink synchronization through a 4-step or 2-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S2302). Here, RO can be an uplink time / frequency resource location for random access. In this process, the UE can set TAG1 for the communication link with TRP1. In this way, the UE can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0229] Next, TRP1 can transmit an RRC setup message to the UE (S2303). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP1 (S2304). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the peer UE through TRP1.

[0230] To this end, TRP1 may transmit downlink-related DCI to the UE (S2309). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI1, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S2310). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0231] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S2311). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S2312). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI.

[0232] Meanwhile, the UE may be in an RRC-connected state. TRP1 may request measurement from the UE (S2305). Accordingly, the UE may receive SSB from the neighboring TRP and perform measurement. The UE may report the measurement results for the SSB-based neighboring TRP to TRP1 via RRC signaling (S2306). At this time, the UE may report SSB5 as the second-best SSB to TRP1. Accordingly, TRP1 may receive a measurement report from the UE. TRP1 may recognize SSB5 as the second-best SSB through the measurement report. At this time, SSB5 may be included in the SSB group used by TRP1. Accordingly, TRP1 may recognize itself as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Here, although the UE performs the measurement report at the request of TRP1, the UE may also perform the measurement report without such a request.

[0233] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0234] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0235] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP.

[0236] Accordingly, the terminal can perform a random access setup process based on TRP1 and SSB5 (S2307). In this process, the terminal can set up a communication link with TRP1 to TAG5 for uplink synchronization and update of the communication link. This random access setup process based on SSB5 for TRP1 can be triggered by TRP1. Alternatively, the random access setup process based on SSB5 for TRP1 can be triggered by the terminal.

[0237] First, in the TRP1-based triggering method, TRP1 can trigger a random access setup procedure based on SSB5 for TRP1 by instructing the UE to perform CFRA or CBRA random access through higher layer signaling or PDCCH. In contrast, in the UE-based triggering method, the UE can recognize the need to manage other TAGs through the random access procedure with TRP1. Accordingly, the UE can request random access with SSB5 or TRP1 through higher layer signaling or a physical layer control channel (e.g., PUSCH) to trigger a random access setup procedure for TRP1.

[0238] Upon receiving this request, TRP1 instructs the UE to perform CFRA or CBRA random access via higher layer signaling or PDCCH, and can proceed with the random access setup procedure based on SSB5 for TRP1. In this way, the UE can receive an instruction for the random access setup procedure based on SSB5 for TRP1 from TRP1. Accordingly, the UE and TRP1 can perform the random access procedure based on SSB5 to complete the random access setup procedure.

[0239] Next, TRP1 and the terminal can perform an RRC setup process (S2308). In other words, TRP1 can transmit an RRC setup message to the terminal. The terminal can receive the RRC setup message from TRP1. Accordingly, the terminal can set up RRC and transmit an RRC setup complete message to TRP1. TRP1 can receive the RRC setup complete message from the terminal and confirm the RRC setup. Through this process, the terminal can complete a system connection with TRP1 based on SSB5. In this connected state, the terminal can communicate with the counterpart terminal through two communication links of TRP1.

[0240] To this end, TRP1 can transmit downlink-related DCI based on SSB5 to the UE (S2313). Then, the UE can receive downlink-related DCI based on SSB5 from TRP1. Here, the downlink-related DCI indicates DL / connection TCI2, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and can be transmitted on the PDCCH. Then, TRP1 can transmit downlink data to the UE using the downlink-related DCI (S2314). Then, the UE can receive downlink data from TRP1 based on the downlink-related DCI.

[0241] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S2315). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates transmission configuration of the UE, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S2316). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI. Then, the UE may periodically or aperiodically perform uplink synchronization for TAG1 and TAG5 with TRP1 and update the TA (S2317).

[0242] FIG. 24 is a flowchart showing a fourth embodiment of a link configuration method in a multiple transmitting / receiving point environment.

[0243] Referring to Figure 24, a terminal can configure two communication links with one TRP belonging to one SSB group. At this time, the terminal can configure two communication links from the initial connection. To this end, the terminal can perform SSB beam measurement for the beamformed SSB transmitted in TRP1. At this time, the terminal can select SSB1 from the best SSB (1st best SSB) and SSB5 from the second best SSB (2nd best SSB). The terminal can acquire system information based on the best SSB (S2401). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB.

[0244] The UE can recognize SSB1 as the best SSB through the PBCH. It can also recognize the SSB group-TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIBy. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. The TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the UE can recognize the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID from the PDSCH containing SIBy, which is system information.

[0245] Next, TRP1 and the UE can perform uplink synchronization through a 4-step or 2-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S2102). Here, RO can be an uplink time / frequency resource location for random access. In this process, the UE can set TAG1 for the communication link with TRP1. In this way, the UE can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0246] Next, TRP1 may transmit an RRC setup message to the UE (S2403). The UE may receive the RRC setup message from TRP1. Accordingly, the UE may configure RRC and transmit an RRC setup complete message to TRP1 (S2404). TRP1 may receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE may complete a system connection to TRP1. In this connected state, the UE may communicate with the counterpart UE through TRP1.

[0247] To this end, TRP1 may transmit downlink-related DCI to the UE (S2410). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI1, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S2411). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0248] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S2412). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S2413). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI.

[0249] Meanwhile, the UE may be in an RRC-connected state. TRP1 may request measurement from the UE (S2405). Accordingly, the UE may receive SSB from the neighboring TRP and perform measurement. The UE may report the measurement results for the SSB-based neighboring TRP to TRP1 via RRC signaling (S2406). At this time, the UE may report SSB5 as the second-best SSB to TRP1. Accordingly, TRP1 may receive a measurement report from the UE. TRP1 may recognize SSB5 as the second-best SSB through the measurement report. At this time, SSB5 may be included in the SSB group used by TRP1. Accordingly, TRP1 may recognize itself as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Here, the measurement report is performed by the UE at the request of TRP1, but the UE may also perform the measurement report without such a request.

[0250] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0251] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0252] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP.

[0253] Meanwhile, the UE can report SSB5 to TRP1 as the next best SSB. In this case, SSB5 can be included in the same SSB group as SSB1. Therefore, the communication link associated with SSB5 is an example of TRP1 and can be a different communication link from the communication link associated with SSB1 that enters through multipath. In this way, TRP1 can set the communication link associated with SSB5 to TAG5 and perform uplink synchronization and update of the communication link. Accordingly, through a RACH-less procedure, TRP1 and the UE can perform beam measurement between the UE and SSB5 as follows.

[0254] To this end, TRP1 can instruct the UE to transmit the uplink beamformed SRS to the TRP including TPR1 using the scheduling resource determined for the UE (S2407). At this time, TRP1 can instruct the UE to transmit the SRS through RRC signaling including information on the scheduling resource determined for transmitting the uplink beamformed SRS. At this time, TRP1 can inform neighboring TRPs that the UE will transmit the beamformed SRS in the uplink using the scheduling time / frequency resource determined for the UE for interference suppression. Alternatively, TRP1 may not inform neighboring TRPs that the UE will transmit the beamformed SRS in the uplink using the scheduling time / frequency resource determined for the UE for resource efficiency.

[0255] Next, the terminal may transmit the corresponding beamformed SRS to TRPs, including TRP1 (S2408). Then, TRP1 may receive the SRS at the terminal. Then, TRP1 may select the most suitable uplink beam based on the received SRS, estimate the TA, and notify the terminal of the most suitable uplink beam information (in other words, best uplink beam information) and the estimated TA information (S2409). In other words, TRP1 may notify the terminal of the SRS information with the highest SINR, for example, among the beamformed SRSs received from the terminal. Accordingly, the terminal may receive the best uplink beam information and TA information from TRP1. Then, the terminal may determine that the best uplink beam belongs to the terminal. Through this process, the terminal may complete a system connection to TRP1 through a communication link related to SSB5. In this connected state, the terminal may communicate with a remote terminal through two communication links of TRP1.

[0256] To this end, TRP1 may transmit downlink-related DCI associated with SSB5 to the UE (S2414). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI2, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S2415). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0257] Alternatively, TRP1 may transmit uplink-related DCI associated with SSB5 to the UE (S2416). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates transmission configuration of the UE, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Then, TRP1 may transmit uplink data to the UE via the uplink-related DCI (S2417).

[0258] Then, TRP1 can receive uplink data from the UE based on the DCI associated with the uplink. Thereafter, the UE can periodically or aperiodically perform uplink synchronization for TAG1 and TAG5 with TRP1 and update the TA (S2418). Here, although Figures 23 and 24 describe procedures for configuring two communication links, the method of the present disclosure may not be limited thereto. TRP1 and the UE can configure three or more communication links by alternately applying the communication link configuration methods of Figures 23 and 24 to perform downlink and uplink multiple TRP communication.

[0259] FIG. 25 is a conceptual diagram showing a fifth embodiment of a method for grouping synchronization signal blocks.

[0260] Referring to FIG. 25, SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. SSB group 1 can be mapped to TRP1 to TRP A, where A is a positive integer greater than 1. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. SSB group 2 can be mapped to TRP A+1 to TRP B, where B is a positive integer greater than A. Mapping SSB group 1 to TRP1 to TRP A can physically mean that when TRP1 to TRP A perform SSB sweeping, beamformed SSBs are transmitted in the corresponding direction using only SSB1, SSB3, SSB5, and SSB7. Similarly, mapping SSB group 2 to TRP A+1 to TRP B may mean that when TRP A+1 to TRP B physically perform SSB sweeping, they transmit beamformed SSBs in the corresponding direction using only SSB2, SSB4, SSB6, and SSB8. In this case, the number of available SSBs may be 8, but is not limited to this and may be 4, 16, 64, etc. Here, TRP1 to TRP A and TRP A+1 to TRP B may be included in serving cells having the same PCI G.

[0261] FIG. 26 is a conceptual diagram showing a sixth embodiment of a method for grouping synchronization signal blocks.

[0262] Referring to FIG. 26, SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. SSB group 1 can be mapped to TRP1 to TRP A included in the serving cell. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. SSB group 2 can be mapped to TRP A+1 to TRP B included in a non-serving cell. Here, mapping SSB group 1 to TRP1 to TRP A can physically mean that when TRP1 to TRP A perform SSB sweeping, they transmit beamformed SSBs in the corresponding direction using only SSB1, SSB3, SSB5, and SSB7. Similarly, mapping SSB group 2 to TRP A+1 through TRP B may mean that when TRP A+1 through TRP B physically perform SSB sweeping, they transmit beamformed SSBs in the corresponding direction using only SSB2, SSB4, SSB6, and SSB8. In this case, the number of available SSBs may be 8, but is not limited to this and may be 4, 16, 64, etc. Here, TRP1 through TRP A may be included in a serving cell with PCI G. TRP A+1 through TRP B may be included in a non-serving cell with PCI Z. In FIGS. 25 and 26, the two TRP groups, TRP1 through TRP A and TRP A+1 through TRP B, are geographically adjacent and may have similar TA values, enabling multiple TRP transmission for a large number of TRPs.

[0263] FIG. 27 is a conceptual diagram showing a fourth embodiment of the tag ID setting method.

[0264] Referring to FIG. 27, in order to adjust the TA required for uplink synchronization, each SSB group may be mapped to multiple TRPs and associated with one tag ID (for example, TAG1, TAG2, etc.). For example, SSB group 1 may be associated with TAG1, and SSB group 2 may be associated with TAG2. In this case, TAG1 may be associated with joint TCI1, and TAG2 may be associated with joint TCI2. In this way, since TAGs are managed for each SSB group, when a terminal configures one communication link for each of TRP1 and TRP A+1, it can perform uplink synchronization and communication for each TAG.

[0265] FIG. 28 is a conceptual diagram showing a fifth embodiment of the tag ID setting method.

[0266] Referring to FIG. 28, a terminal can configure two communication links within one TRP1. In this case, the terminal can configure one communication link based on TRP1 and SSB1. The terminal can also configure another communication link based on TRP1 and SSB5. The two communication links configured in this manner can have the same TAG1. Based on this TAG1, the terminal can perform uplink synchronization and communication for the two communication links. Here, one communication link can pass through an obstacle. TRP1 and TRP2 can be included in SSB group 1. One link between the terminal and TRP1 can be associated with TAG1 and DL / UL / junction TCI1. And one link between the terminal and TRP1 that passes through an obstacle can be associated with TAG1 and DL / UL / junction TCI2.

[0267] Here, the SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). Here, SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. SSB group 1 can be mapped to TRP1 to TRP A included in the serving cell. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. SSB group 2 can be mapped to TRP A+1 to TRP B included in non-serving cells. Here, TRP1 to TRP A can be included in the serving cell with PCI G. TRP A+1 to TRP B can be included in the non-serving cell with PCI Z.

[0268] FIG. 29 is a conceptual diagram showing a sixth embodiment of the tag ID setting method.

[0269] Referring to FIG. 29, a terminal can configure one communication link based on TRP1 and SSB1. The terminal can also configure another communication link based on TRP2 and SSB5. The two communication links configured in this manner can have the same TAG1. The terminal and the TRP can assign the same TAG1 to the two communication links to perform uplink synchronization and communication. TRP1 and TRP2 can be included in SSB group 1. One link between the terminal and TRP1 can be associated with TAG1 and DL / UL / junction TCI1. And the other link between the terminal and TRP2 can be associated with TAG1 and DL / UL / junction TCI2.

[0270] Here, the SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). Here, SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. SSB group 1 can be mapped to TRP1 to TRP A included in the serving cell. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. SSB group 2 can be mapped to TRP A+1 to TRP B included in non-serving cells. Here, TRP1 to TRP A can be included in the serving cell with PCI G. TRP A+1 to TRP B can be included in the non-serving cell with PCI Z.

[0271] As shown in Figures 25 to 29, each SSB group can be mapped to multiple TRPs to adjust the TA required for uplink synchronization. One tag ID (e.g., TAG1, TAG2, etc.) can be associated with multiple TRPs. For example, TRP1 and TRP2 of SSB group 1 can be associated with TAG1. In this case, TAG1 can be associated with joint TCI1 or joint TCI2. In this way, since TAGs are managed for each SSB group, a terminal can perform uplink synchronization and communication by configuring one communication link for each of TRP1 and TRP2. In the cases of Figures 28 and 29, the link configuration method in a multi-transmission / reception point communication system can be the same as that shown in Figure 30.

[0272] FIG. 30 is a flowchart showing a fifth embodiment of a link configuration method in a multiple transmitting / receiving point environment.

[0273] Referring to FIG. 30, a terminal can configure two communication links with one TRP belonging to one SSB group. Alternatively, the terminal can configure two communication links with two TRPs belonging to one SSB group. In this case, the terminal can configure two communication links from the initial connection. To do this, the terminal can perform SSB beam measurement for the beamformed SSB transmitted in TRP1. In this case, the terminal can select SSB1 from the best SSB (1st best SSB) and SSB5 from the second best SSB (2nd best SSB). The terminal can acquire system information based on the best SSB (S3001). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB.

[0274] The UE can recognize SSB1 as the best SSB through the PBCH. It can also recognize the SSB group-TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIBy. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. The TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the UE can recognize the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID from the PDSCH containing SIBy, which is system information.

[0275] Next, TRP1 and the UE can perform uplink synchronization through a 4-step or 2-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S3002). Here, RO can be an uplink time / frequency resource location for random access. In this process, the UE can set TAG1 for the communication link with TRP1. In this way, the UE can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0276] Next, TRP1 can transmit an RRC setup message to the UE (S3003). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP1 (S3004). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the counterpart UE through TRP1.

[0277] To this end, TRP1 may transmit downlink-related DCI to the UE (S3010). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI1, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S3011). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0278] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S3012). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S3013). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI.

[0279] Meanwhile, the UE may be in an RRC-connected state. TRP1 may request measurement from the UE (S3005). Accordingly, the UE may receive SSBs from neighboring TRPs and perform measurements. The UE may report SSB-based measurement results for neighboring TRPs to TRP1 via RRC signaling (S3006). At this time, the UE may report SSB5 as the next-best SSB to TRP1. Accordingly, TRP1 may receive a measurement report from the UE. TRP1 may recognize SSB5 as the next-best SSB through the measurement report. At this time, SSB5 may be included in the SSB group used by TRP1 and TRP2. Accordingly, TRP1 may recognize itself as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Alternatively, TRP1 may recognize TRP2 as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Here, the measurement report is performed by the terminal upon request from TRP1, but differently, the terminal can perform the measurement report without such a request.

[0280] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0281] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0282] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP.

[0283] Alternatively, the UE can report SSB5 to TRP1 as the next best SSB. In this case, SSB5 can be included in the same SSB group as SSB1. Therefore, the communication link associated with SSB5 is an example of TRP1 and can be a different communication link from the communication link associated with SSB1 that comes in through multipath. Alternatively, the communication link associated with SSB5 can be TRP2. TRP1 can set the communication link associated with SSB5 to TAG1 and perform uplink synchronization and update of the communication link. Accordingly, TRP1 or TRP2 can perform beam measurement between the UE and SSB5 through a RACH-less procedure as follows.

[0284] To this end, TRP1 can instruct the UE to transmit the uplink beamformed SRS to the TRPs using the scheduling resources determined for the UE (S3007). At this time, TRP1 can instruct the UE to transmit the SRS through RRC signaling including information on the scheduling resources determined for transmitting the uplink beamformed SRS. At this time, TRP1 can inform neighboring TRPs that the UE will transmit the beamformed SRS in the uplink using the scheduling time / frequency resources determined for the UE for interference suppression. Alternatively, TRP1 may not inform neighboring TRPs that the UE will transmit the beamformed SRS in the uplink using the scheduling time / frequency resources determined for the UE for resource efficiency.

[0285] Next, the terminal may transmit the beamformed SRS to TRPs including TRP1 and TRP2 (S3008). Then, TRP1 or TRP2 may receive the SRS at the terminal. Then, TRP1 may select the most suitable uplink beam based on the received SRS. Then, TRP1 may notify the terminal of the most suitable uplink beam information (in other words, best uplink beam information) (S3009). In other words, TRP1 may notify the terminal of the SRS information with the highest SINR, for example, among the beamformed SRSs received from the terminal. Then, the terminal may determine that the best uplink beam belongs to itself. Through this process, the terminal may complete system connection to TRP1 through a communication link related to SSB5. Accordingly, the terminal may communicate with a remote terminal through two communication links of TRP1 in this connected state.

[0286] Alternatively, TRP2 can select the most suitable uplink beam based on the received SRS and notify TRP1 of the most suitable uplink beam information (in other words, best uplink beam information). Then, TRP1 can notify the terminal of the most suitable uplink beam information (in other words, best uplink beam information) based on the SRS received by TRP2 (S3009). Accordingly, the terminal can receive the best uplink beam information from TRP1. Then, the terminal knows that the best uplink beam belongs to itself. Through this process, the terminal can complete system connection to TRP2 through a communication link related to SSB5. Accordingly, in this connected state, the terminal can communicate with the other terminal through two communication links, TRP1 and TRP2.

[0287] To this end, TRP1 or TRP2 may transmit downlink-related DCI associated with SSB5 to the UE (S3014). Then, the UE may receive downlink-related DCI from TRP1 or TRP2. Here, the downlink-related DCI indicates DL / connection TCI2, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 or TRP2 may transmit downlink data to the UE using the downlink-related DCI (S3015). Then, the UE may receive downlink data based on the downlink-related DCI from TRP1 or TRP2.

[0288] Alternatively, TRP1 or TRP2 may transmit uplink-related DCI associated with SSB5 to the UE (S3016). Then, the UE may receive uplink-related DCI from TRP1 or TRP2. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates transmission configuration of the UE, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Thereafter, TRP1 or TRP2 may transmit uplink data to the UE via the uplink-related DCI (S3017).

[0289] Then, TRP1 or TRP2 can receive uplink data from the UE based on the DCI associated with the uplink. Thereafter, the UE can periodically or aperiodically perform uplink synchronization for TAG1 with TRP1 or TRP2 and update the TA (S3018). Here, although Figure 30 describes a procedure for configuring two communication links, the method of the present disclosure may not be limited thereto. TRP1 or TRP2 can configure three or more communication links by alternately applying the method for configuring communication links of Figure 30 to perform downlink and uplink multi-TRP communication.

[0290] FIG. 31 is a conceptual diagram showing a seventh embodiment of the tag ID setting method.

[0291] Referring to FIG. 31, when a terminal configures two communication links within one TRP, it can assign different TAGs to the SSBs, perform uplink synchronization, and perform communication. Here, one communication link can pass through an obstacle. In other words, the terminal can configure two communication links within one TRP1. In this case, the terminal can configure one communication link based on TRP1 and SSB1. Then, the terminal can configure another communication link based on TRP1 and SSB5. The communication link based on SSB1 configured in this way can have TAG1, and the communication link based on SSB5 can have TAG5. Based on TAG1, the terminal can perform uplink synchronization for the communication link and perform communication. Also, based on TAG5, the terminal can perform uplink synchronization for the communication link and perform communication. Here, one communication link can pass through an obstacle. TRP1 and TRP2 can be included in SSB group 1. One link between the terminal and TRP1 can be associated with TAG1 and DL / UL / connection TCI1. And one link through the obstacle between the terminal and TRP1 may be associated with TAG5 and may be associated with DL / UL / coupling TCI2.

[0292] Here, the SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). Here, SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. SSB group 1 can be mapped to TRP1 to TRP A included in the serving cell. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. SSB group 2 can be mapped to TRP A+1 to TRP B included in non-serving cells. Here, TRP1 to TRP A can be included in the serving cell with PCI G. TRP A+1 to TRP B can be included in the non-serving cell with PCI Z.

[0293] FIG. 32 is a conceptual diagram showing an eighth embodiment of the tag ID setting method.

[0294] Referring to FIG. 32, when a terminal configures two communication links, TRP1 and TRP2, within one SSB group, the terminal can perform uplink synchronization and communication by assigning different TAGs to the SSBs. In other words, the terminal can configure one communication link based on TRP1 and SSB1. The terminal can also configure another communication link based on TRP2 and SSB5. Of the two communication links configured in this manner, the communication link based on SSB1 can have TAG1, and the communication link based on SSB5 can have TAG5. The terminal and TRP can perform uplink synchronization and communication by assigning different TAG IDs to the two communication links. TRP1 and TRP2 can be included in SSB group 1. One link between the terminal and TRP1 can be associated with TAG1 and DL / UL / junction TCI1. And the other link between the terminal and TRP2 can be associated with TAG5 and DL / UL / junction TCI2.

[0295] Here, the SSBs (SSB1 to SSB8) can be divided into two SSB groups (SSB group 1 and SSB group 2). SSB group 1 can include SSB1, SSB3, SSB5, and SSB7. SSB group 1 can be mapped to TRP1 to TRP A included in the serving cell. In contrast, SSB group 2 can include SSB2, SSB4, SSB6, and SSB8. SSB group 2 can be mapped to TRP A+1 to TRP B included in a non-serving cell. Here, TRP1 to TRP A can be included in the serving cell with PCI G. TRP A+1 to TRP B can be included in a non-serving cell with PCI Z. In the cases of Figures 31 and 32, the link configuration method in a multi-transmission / reception point communication system can be the same as that shown in Figures 33 and 34.

[0296] FIG. 33 is a flowchart showing a sixth embodiment of a link configuration method in a multiple transmitting / receiving point environment.

[0297] Referring to FIG. 33, a terminal can configure two communication links with one TRP belonging to one SSB group. Alternatively, the terminal can configure two communication links with two TRPs belonging to one SSB group. In this case, the terminal can configure two communication links from the initial connection. To this end, the terminal can perform SSB beam measurement for the beamformed SSB transmitted in TRP1. Alternatively, the terminal can perform SSB beam measurement for the beamformed SSB transmitted in TRP2. In this case, the terminal can select SSB1 from the best SSB (1st best SSB) and SSB5 from the second best SSB (2nd best SSB). The terminal can acquire system information based on the best SSB (S3301). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB.

[0298] The UE can recognize SSB1 as the best SSB through the PBCH. It can also recognize the SSB group-TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIBy. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. The TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the UE can recognize the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID from the PDSCH containing SIBy, which is system information.

[0299] Next, TRP1 and the terminal can perform uplink synchronization through a four-step or two-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S3302). Here, RO can be the uplink time / frequency resource location for random access. In this process, the terminal can set TAG1 for the communication link associated with SSB1 with TRP1. In this way, the terminal can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0300] Next, TRP1 can transmit an RRC setup message to the UE (S3303). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP1 (S3304). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the peer UE through TRP1.

[0301] To this end, TRP1 can transmit downlink-related DCI based on SSB1 to the UE (S3309). Then, the UE can receive downlink-related DCI from TRP1. Here, the downlink-related DCI indicates DL / connection TCI1, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and can be transmitted on the PDCCH. Then, TRP1 can transmit downlink data to the UE using the downlink-related DCI (S3310). Then, the UE can receive downlink data from TRP1 based on the downlink-related DCI.

[0302] Alternatively, TRP1 may transmit uplink-related DCI based on SSB1 to the UE (S3311). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S3312). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI.

[0303] Meanwhile, the UE may be in an RRC-connected state. TRP1 may request measurement from the UE (S3305). Accordingly, the UE may receive SSB from the neighboring TRP and perform measurement. The UE may report the measurement results for the SSB-based neighboring TRP to TRP1 via RRC signaling (S3306). At this time, the UE may report SSB5 to TRP1 as the second-best SSB. Accordingly, TRP1 may receive a measurement report from the UE. TRP1 may recognize SSB5 as the second-best SSB through the measurement report. At this time, SSB5 may be included in the SSB group used by TRP1 or TRP2. Accordingly, TRP1 may recognize itself as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Alternatively, TRP1 may recognize TRP2 as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Here, the measurement report is performed by the terminal upon request from TRP1, but differently, the terminal can perform the measurement report without such a request.

[0304] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0305] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0306] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP.

[0307] Meanwhile, the UE may perform a random access setup process based on TRP1 or TRP2 and SSB5 (S3307). In this process, the UE may set up a communication link based on TRP1 or TRP2 and SSB5 to TAG5 for uplink synchronization and update for such a communication link. This random access setup process for TRP1 or TRP2 may be triggered by the TRP. Alternatively, the random access setup process for TRP1 or TRP2 may be triggered by the UE.

[0308] First, in the TRP1-based triggering method, TRP1 can instruct the UE to perform CFRA or CBRA random access through higher layer signaling or PDCCH, thereby triggering the random access setup process based on SSB5 for TRP1 or TRP2. Differently, in the UE-based triggering method, the UE can recognize the need to manage other TAGs through the random access process with TRP1. Accordingly, the UE can request random access with TRP1 or TRP2 based on SSB5 through higher layer signaling or a physical layer control channel (e.g., PUSCH), thereby triggering the random access setup process for TRP1 or TRP2.

[0309] Upon receiving this request, TRP1 instructs the UE to perform CFRA or CBRA random access via higher layer signaling or PDCCH, and can proceed with the random access setup procedure based on SSB5 for TRP1 or TRP2. In this way, the UE can receive an instruction for the random access setup procedure based on SSB5 for TRP1 or TRP2 from TRP1. Accordingly, the UE and TRP1 or TRP2 can perform the random access procedure based on SSB5 to complete the random access setup procedure.

[0310] Next, TRP1 or TRP2 and the terminal can perform an RRC setup process for the communication link created based on SSB5 (S3308). In other words, TRP1 or TRP2 can transmit an RRC setup message to the terminal. The terminal can receive an RRC setup message from TRP1 or TRP2. Accordingly, the terminal can set up RRC and transmit an RRC setup complete message to TRP1 or TRP2. TRP1 or TRP2 can receive the RRC setup complete message from the terminal and confirm the RRC setup. Through this process, the terminal can complete a system connection with TRP1 or TRP2 based on SSB5. In this connected state, the terminal can communicate with the counterpart terminal through two communication links of TRP1. Alternatively, the terminal can communicate with the counterpart terminal through two communication links of TRP1 and TRP2 in this connected state.

[0311] To this end, TRP1 or TRP2 may transmit downlink-related DCI based on SSB5 to the UE (S3313). Then, the UE may receive downlink-related DCI based on SSB5 from TRP1 or TRP2. Here, the downlink-related DCI indicates DL / connection TCI2, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 or TRP2 may transmit downlink data to the UE using the downlink-related DCI (S3314). Then, the UE may receive downlink data from TRP1 or TRP2 based on the downlink-related DCI.

[0312] Alternatively, TRP1 or TRP2 may transmit uplink-related DCI to the UE (S3315). Then, the UE may receive uplink-related DCI from TRP1 or TRP2. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates transmission configuration of the UE, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Then, TRP1 or TRP2 may transmit uplink data to the UE using the uplink-related DCI (S3316). Then, TRP1 or TRP2 may receive uplink data from the UE based on the uplink-related DCI. Then, the UE may periodically or aperiodically perform uplink synchronization for TAG1 and TAG5 with TRP1 or TRP2 and update the TA (S3317).

[0313] FIG. 34 is a flowchart showing a seventh embodiment of a link configuration method in a multiple transmitting / receiving point environment.

[0314] Referring to FIG. 34, a terminal can configure two communication links with one TRP belonging to one SSB group. Alternatively, the terminal can configure two communication links with two TRPs belonging to one SSB group. In this case, the terminal can configure two communication links from the initial connection. To do this, the terminal can perform SSB beam measurement for the beamformed SSB transmitted in TRP1. In this case, the terminal can select SSB1 from the best SSB (1st best SSB) and SSB5 from the second best SSB (2nd best SSB). The terminal can acquire system information based on the best SSB (S3401). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB.

[0315] The UE can recognize SSB1 as the best SSB through the PBCH. It can also recognize the SSB group-TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIBy. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. The TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the UE can recognize the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID from the PDSCH containing SIBy, which is system information.

[0316] Next, TRP1 and the UE can perform uplink synchronization through a 4-step and 2-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S3402). Here, RO can be the uplink time / frequency resource location for random access. In this process, the UE can set TAG1 for the communication link with TRP1. In this way, the UE can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0317] Next, TRP1 may transmit an RRC setup message to the UE (S3403). The UE may receive the RRC setup message from TRP1. Accordingly, the UE may configure RRC and transmit an RRC setup complete message to TRP1 (S3404). TRP1 may receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE may complete a system connection to TRP1. In this connected state, the UE may communicate with the peer UE through TRP1.

[0318] To this end, TRP1 may transmit downlink-related DCI to the UE (S3410). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI1, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S3411). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0319] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S3412). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S3413). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI.

[0320] Meanwhile, the UE may be in an RRC-connected state. TRP1 may request measurement from the UE (S3405). Accordingly, the UE may receive SSB from the neighboring TRP and perform measurement. The UE may report the measurement results for the SSB-based neighboring TRP to TRP1 via RRC signaling (S3406). At this time, the UE may report SSB5 to TRP1 as the second-best SSB. Accordingly, TRP1 may receive a measurement report from the UE. TRP1 may recognize SSB5 as the second-best SSB through the measurement report. At this time, SSB5 may be included in the SSB group used by TRP1 and TRP2. Accordingly, TRP1 may recognize itself as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Alternatively, TRP1 may recognize TRP2 as the TRP transmitting SSB5 based on the relationship between the SSB group and the TRP. Here, the measurement report is performed by the terminal upon request from TRP1, but differently, the terminal can perform the measurement report without such a request.

[0321] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0322] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0323] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP.

[0324] Alternatively, the UE can report SSB5 to TRP1 as the next best SSB. In this case, SSB5 can be included in the same SSB group as SSB1. Therefore, the communication link associated with SSB5 is an example of TRP1 and can be a different communication link from the communication link associated with SSB1 that comes in through multipath. Alternatively, the communication link associated with SSB5 can be TRP2. TRP1 can set the communication link associated with SSB5 to TAG5 and perform uplink synchronization and update of the communication link. Accordingly, TRP1 or TRP2 can perform beam measurement between the UE and SSB5 through a RACH-less procedure as follows.

[0325] To this end, TRP1 can instruct the UE to transmit the uplink beamformed SRS to the TRPs using the scheduling resources determined for the UE (S3407). At this time, TRP1 can instruct the UE to transmit the SRS through RRC signaling including information on the scheduling resources determined for transmitting the uplink beamformed SRS. At this time, TRP1 can inform neighboring TRPs that the UE will transmit the beamformed SRS in the uplink using the scheduling time / frequency resources determined for the UE for interference suppression. Alternatively, TRP1 may not inform neighboring TRPs that the UE will transmit the beamformed SRS in the uplink using the scheduling time / frequency resources determined for the UE for resource efficiency.

[0326] Next, the terminal can transmit the corresponding beamformed SRS to TRPs including TRP1 and TRP2 (S3408). Then, TRP1 or TRP2 can receive the SRS at the terminal. Then, TRP1 can select the most suitable uplink beam based on the received SRS, estimate the TA, and notify the terminal of the most suitable uplink beam information (in other words, the best uplink beam information) and the estimated TA information (S3409). In other words, TRP1 can notify the terminal of the SRS information with the highest SINR, for example, among the beamformed SRSs received from the terminal.

[0327] Alternatively, TRP2 can select the most suitable uplink beam based on the received SRS, estimate the TA, and notify TRP1 of the most suitable uplink beam information (in other words, best uplink beam information) and the estimated TA information. Then, TRP1 can notify the terminal of the most suitable uplink beam information (in other words, best uplink beam information) and the estimated TA information based on the SRS received by TRP2. Accordingly, the terminal can receive the best uplink beam information and TA information from TRP1. Then, the terminal knows that the best uplink beam belongs to itself. Through this process, the terminal can complete system connection to TRP1 or TRP2 through a communication link related to SSB5. In this connection state, the terminal can communicate with a remote terminal through two communication links of TRP1. Alternatively, the terminal can communicate with a remote terminal through two communication links of TRP1 and TRP2 in this connection state.

[0328] To this end, TRP1 or TRP2 may transmit downlink-related DCI associated with SSB5 to the UE (S3414). Then, the UE may receive downlink-related DCI from TRP1 or TRP2. Here, the downlink-related DCI indicates DL / connection TCI2, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and may be transmitted on the PDCCH. Then, TRP1 or TRP2 may transmit downlink data to the UE using the downlink-related DCI (S3415). Then, the UE may receive downlink data from TRP1 or TRP2 based on the downlink-related DCI.

[0329] Alternatively, TRP1 or TRP2 may transmit uplink-related DCI associated with SSB5 to the UE (S3416). Then, the UE may receive uplink-related DCI from TRP1 or TRP2. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates the transmission configuration of the UE, and the scheduling resource location for data transmission, and may be transmitted on the PDCCH. Thereafter, TRP1 or TRP2 may transmit uplink data to the UE via the uplink-related DCI (S3417).

[0330] Then, TRP1 or TRP2 can receive uplink data from the UE based on the DCI associated with the uplink. Thereafter, the UE can periodically or aperiodically perform uplink synchronization for TAG1 and TAG5 with TRP1 or TRP2 and update the TA (S3418). Here, although Figures 33 and 34 describe procedures for configuring two communication links, the method of the present disclosure may not be limited thereto. TRP1 or TRP2 can configure three or more communication links by alternately applying the communication link configuration methods of Figures 33 and 34 to perform downlink and uplink multi-TRP communication.

[0331] FIG. 35 is a conceptual diagram showing a ninth embodiment of the tag ID setting method.

[0332] Referring to FIG. 35, the TRP can share all SSBs for uplink synchronization. In other words, the TRP can use all SSBs redundantly, and can associate TAG IDs with the SSBs according to UE triggering. For example, TRP1 can establish a communication link with the UE using SSB1. TRP2 can also establish a communication link with the UE using SSB1. In this case, the communication link established with the UE by TRP1 using SSB1 can use TAG1. And the communication link established with the UE by TRP2 using SSB1 can use TAG1 or TAG2. Here, TAG1 can be associated with TCI1, and TAG2 can be associated with TCI2.

[0333] FIG. 36 is a conceptual diagram showing a tenth embodiment of the tag ID setting method.

[0334] Referring to FIG. 36, the TRP can share all SSBs for uplink synchronization. In other words, the TRP can use all SSBs redundantly, and can associate TAG IDs with the SSBs according to UE triggering. For example, TRP1 can establish a communication link with the UE using SSB1. TRP2 can also establish a communication link with the UE using SSB5. In this case, the communication link established with the UE by TRP1 using SSB1 can use TAG1. And the communication link established with the UE by TRP2 using SSB5 can use TAG1 or TAG2. Here, TAG1 can be associated with TCI1, and TAG2 can be associated with TCI2.

[0335] Here, SSB5 belongs to TRP2, which is distinct from TRP1, but this is merely an example. SSB5 may also be a multi-path link belonging to TRP1. In the cases of Figures 35 and 36, the link configuration method in the multi-transmission / reception point communication system may be the same as that shown in Figures 37 and 38.

[0336] FIG. 37 is a flowchart showing an eighth embodiment of a link configuration method in a multiple transmitting / receiving point environment.

[0337] Referring to Figure 37, the terminal can configure a communication link based on the same SSB1 of two different TRP1 and TRP2. Alternatively, the terminal can configure a communication link based on different SSB1 and SSB5 of two different TRP1 and TRP2. In this case, the terminal can configure two communication links from the initial connection. To this end, the terminal can perform SSB beam measurement on beamformed SSBs transmitted by TRP1 and TRP2. In this case, the terminal can select SSB1 transmitted from TRP1 as the best SSB, and select SSB1 or SSB5 transmitted from TRP2 as the next best SSB.

[0338] If the terminal can detect the same SSB index through different receiving beams, the terminal can determine that the same SSB index is used through different TRPs. Accordingly, the terminal can recognize the same SSB1 as the best SSB and the second-best SSB. Of course, the terminal may not be able to arbitrarily determine the same SSB1 received through different receiving beams as the best SSB and the second-best SSB. In this case, the TRP1 can report only one SSB1 to the terminal. Alternatively, the TRP1 can report two identical SSB1s by classifying them as the best SSB and the second-best SSB, as described above. In this case, the TRP1 can configure two communication links through the same process as the process for configuring communication links with two different SSBs.

[0339] Meanwhile, the UE can acquire system information based on the best SSB (S3701). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB. The UE can recognize SSB1 as the best SSB through the PBCH. Then, the UE can recognize the SSB group / TRP mapping relationship and the association relationship between TAG IDs and SSB groups from the PDSCH channel(s) containing SIB (system information block) y. The TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID through RRC signaling after the RRC setup process is completed. Also, the TRP does not need to inform the UE of the relationship between the SSB group and TRP and the relationship between the SSB group and TAG ID. Here, the terminal can recognize 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.

[0340] Next, TRP1 and the UE can perform uplink synchronization through a 4-step or 2-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S3702). Here, RO can be an uplink time / frequency resource location for random access. In this process, the UE can set TAG1 for the communication link with TRP1. In this way, the UE can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0341] Next, TRP1 can transmit an RRC setup message to the UE (S3703). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP1 (S3704). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the peer UE through TRP1.

[0342] To this end, TRP1 can transmit downlink-related DCI to the UE (S3009). Then, the UE can receive downlink-related DCI from TRP1. Here, the downlink-related DCI indicates DL / connection TCI1, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and can be transmitted on the PDCCH. Thereafter, TRP1 can transmit downlink data to the UE using the downlink-related DCI (S3710). Then, the UE can receive downlink data from TRP1 based on the downlink-related DCI.

[0343] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S3711). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on a PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S3712). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI. At this time, TRP1 may associate TCI1 with TAG1.

[0344] Meanwhile, the UE may be in an RRC-connected state. Then, TRP1 may request measurement from the UE (S3705). Accordingly, the UE may receive SSB from the neighboring TRP and perform measurement. Then, the UE may report the measurement results for the neighboring TRP based on SSB to TRP1 through RRC signaling (S3706). At this time, the UE may report SSB1 or SSB5 transmitted by TRP2 as the next-best SSB to TRP1. Accordingly, TRP1 may receive a measurement report from the UE. Then, TRP1 may recognize SSB1 or SSB5 transmitted by TRP2 as the next-best SSB through the measurement report.

[0345] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0346] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0347] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP.

[0348] Meanwhile, TRP1 can receive measurement information from the terminal. Alternatively, TRP1 can acquire the terminal's capabilities from the terminal through a terminal-to-terminal communication link via TRP1's SSB1. If TRP1 can trust the terminal in consideration of the terminal's capabilities, it can accept such measurement information or the terminal's request. Of course, if TRP1 cannot trust the terminal in consideration of the terminal's capabilities, it does not have to accept such measurement information or the terminal's request.

[0349] Next, for example, the measurement information may indicate that the time difference between the reception synchronization points of the suboptimal SSB index is greater than or equal to a predetermined threshold. Alternatively, TRP1 may receive a request from the UE to establish a communication link based on the RACH. In this case, TRP1 may trigger random access. The UE may establish a communication link through SSB1 or SSB5 of TRP2 through the random access procedure. Then, the UE may establish TAG2 for the communication link through SSB1 or SSB5 of TRP2 for uplink synchronization and update, and associate UL TCI2 with TAG2. Association information between TAG2 and UL TCI2 (e.g., mapping / association information between TAG ID and UL TCI(s)) may be notified to the UE by RRC signaling or DL / UL MAC CE before, after, or during the establishment of the RACH-based communication link.

[0350] Next, the UE may perform a random access setup process with TRP2 (S3707). In this process, the UE may establish a communication link with TRP2 in TAG2 for uplink synchronization and update of the communication link. This random access setup process for TRP2 may be triggered by TRP1. TRP1 may trigger the random access setup process for TRP2 by instructing the UE to perform CFRA or CBRA random access via higher layer signaling or PDCCH. Optionally, TRP1 may notify neighboring TRPs to estimate and report time / frequency resources related to random access.

[0351] In other words, the terminal receiving the TRP1 instruction can perform a CFRA random access procedure for the second communication link (e.g., the terminal-TRP2 (SSB1 / SSB5) link). At this time, it can transmit a preamble at the time / frequency resource position of the designated RO according to the direction indicated by the second communication link (i.e., according to the transmit beam direction corresponding to the receive beam direction of the second communication link acquired in the SSB sweeping process). At this time, the terminal can transmit the preamble in a downlink synchronized state of the first communication link (i.e., the terminal-TRP1 (SSB1) link). Alternatively, the terminal can know time difference information between the transmission synchronization points between the first communication link and the second-best SSB. Therefore, reflecting this time difference information, the terminal can perform downlink synchronization between the terminal and the second-best SSB (e.g., TRP2 (SSB1 / SSB5)) and transmit a beamformed SRS to TRP2. In the case of a two-phase random access procedure, the host transmitting the RAR may be TRP1 that configured the first communication link, or TRP2 that configured the second communication link.

[0352] Next, TRP2 and the terminal can perform an RRC setup process (S3708). In other words, TRP2 can transmit an RRC setup message to the terminal. The terminal can receive the RRC setup message from TRP2. Accordingly, the terminal can set up RRC and transmit an RRC setup complete message to TRP2. TRP2 can receive the RRC setup complete message from the terminal and confirm the RRC setup. Through this process, the terminal can complete a system connection to TRP2. In this connected state, the terminal can communicate with the counterpart terminal through TRP1 and TRP2. In other words, once the connection with the terminal-TRP2 (SSB1 / SSB5) link is completed, the terminal can communicate with the counterpart terminal through TRP1's SSB1 and TRP2's SSB1 / SSB5-based communication link. In such a TRP2 SSB1 / SSB5-based communication link, the terminal indicates the DL / UL / connection TCI2 that indicates the transmission configuration and the scheduling resource location for data transmission and reception, and can exchange beamformed data in the downlink and uplink according to the DCI transmitted on the PDCCH.

[0353] To this end, TRP2 can transmit downlink-related DCI to the UE (S3713). Then, the UE can receive downlink-related DCI from TRP2. Here, the downlink-related DCI indicates DL / connection TCI2, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and can be transmitted on the PDCCH. Then, TRP2 can transmit downlink data to the UE using the downlink-related DCI (S3714). Then, the UE can receive downlink data from TRP2 based on the downlink-related DCI.

[0354] Alternatively, TRP2 may transmit uplink-related DCI to the UE (S3715). Then, the UE may receive uplink-related DCI from TRP2. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates transmission configuration of the UE, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Then, TRP2 may transmit uplink data to the UE using the uplink-related DCI (S3716). Then, TRP2 may receive uplink data from the UE based on the uplink-related DCI. Then, the UE may periodically or aperiodically perform uplink synchronization for TAG1 and TAG2 with TRP1 or TRP2 and update the TA (S3717).

[0355] FIG. 38 is a flowchart showing a ninth embodiment of a link configuration method in a multiple transmitting / receiving point environment.

[0356] Referring to FIG. 38, a terminal can establish a communication link with the same SSB1 in two different TRPs, TRP1 and TRP2. Alternatively, the terminal can establish a communication link with different SSB1 and SSB5 in two different TRPs, TRP1 and TRP2. In this case, the terminal can select SSB1 in TRP1 as the best SSB and select SSB1 or SSB5 in TRP2 as the second-best SSB. If the terminal can detect the same SSB index in different receiving beams, the terminal can determine that the same SSB index is used in different TRPs. Accordingly, the terminal can recognize the same SSB1 as the best SSB and the second-best SSB. Of course, the terminal may not be able to arbitrarily determine the same SSB1 received through different receiving beams as the best SSB and the second-best SSB. In this case, TRP1 can report only one SSB1 to the terminal. Alternatively, TRP1 can report two identical SSB1s by classifying them as the best SSB and the second-best SSB, as described above. In this case, the TRP1 can establish two communication links through the same process as that for establishing communication links using two different SSBs.

[0357] Meanwhile, the UE can acquire system information based on the best SSB (S3801). This system information is carried on the PBCH and PDSCH channels transmitted on the time / frequency resources determined by the SSB. The UE can recognize SSB1 as the best SSB through the PBCH. Then, it can recognize the SSB group / TRP mapping relationship and the association relationship between the TAG ID and the SSB group from the PDSCH channel(s) containing SIBy. The TRP can inform the UE of the relationship between the SSB group / TRP and the relationship between the SSB group / TAG ID during the RRC setup process after performing the random access procedure. Alternatively, the TRP can inform the UE of the relationship between the SSB group / TRP and the relationship between the SSB group / TAG ID through RRC signaling after the RRC setup process is completed. Also, the TRP does not need to inform the UE of the relationship between the SSB group / TRP and the relationship between the SSB group / TAG ID. Here, the UE can recognize the relationship between the SSB group / TRP and the relationship between the SSB group / TAG ID from the PDSCH containing the system information SIBy.

[0358] Next, TRP1 and the UE can perform uplink synchronization through a 4-step or 2-step CBRA process according to the random access channel occasion (RO) indicated by the SIB acquired based on the system information (S3802). Here, RO can be an uplink time / frequency resource location for random access. In this process, the UE can set TAG1 for the communication link with TRP1. In this way, the UE can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link.

[0359] Next, TRP1 can transmit an RRC setup message to the UE (S3803). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can set up RRC and transmit an RRC setup complete message to TRP1 (S3804). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the peer UE through TRP1.

[0360] To this end, TRP1 may transmit downlink-related DCI to the UE (S3811). Then, the UE may receive downlink-related DCI from TRP1. Here, the downlink-related DCI may indicate DL / connection TCI1, which indicates the reception setting of the UE, and the location of scheduling resources for data reception, and may be transmitted on the PDCCH. Then, TRP1 may transmit downlink data to the UE using the downlink-related DCI (S3812). Then, the UE may receive downlink data from TRP1 based on the downlink-related DCI.

[0361] Alternatively, TRP1 may transmit uplink-related DCI to the UE (S3813). Then, the UE may receive uplink-related DCI from TRP1. Here, the uplink-related DCI indicates UL / connection TCI1, which indicates transmission configuration of the UE, and a scheduling resource location for data transmission, and may be transmitted on the PDCCH. Then, TRP1 may transmit uplink data to the UE using the uplink-related DCI (S3814). Then, TRP1 may receive uplink data from the UE based on the uplink-related DCI. At this time, TRP1 may associate TCI1 with TAG1.

[0362] Meanwhile, the UE may be in an RRC-connected state. Then, TRP1 may request measurement from the UE (S3805). Accordingly, the UE may receive SSB from a neighboring TRP and perform measurement. Then, the UE may report the measurement results for the SSB-based neighboring TRP to TRP1 through RRC signaling (S3806). At this time, the UE may report SSB1 or SSB5 as the next-best SSB to TRP1. Accordingly, TRP1 may receive a measurement report from the UE. Then, TRP1 may recognize SSB1 or SSB5 as the next-best SSB through the measurement report.

[0363] At this time, the measurement report may include the first SSB index (i.e., the best SSB index), the second SSB index (i.e., the next best SSB index), the third SSB index, etc. The measurement report may also include time difference information between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index.

[0364] The terminal can request TRP1 to set the TAG to be the same as the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index does not exceed a predetermined critical value. Alternatively, the terminal can request TRP1 to set the TAG to be different from the current communication link if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of a communication link such as the second SSB index or the third SSB index exceeds a predetermined critical value. When TRP1 sets the TAG to be the same for a communication link different from the current communication link, the load for reverse synchronization and update of the terminal can be reduced.

[0365] In addition, the terminal knows the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index. Therefore, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, does not exceed a predetermined critical value, the terminal can request a second link establishment procedure without a RACH from the TRP. In contrast, if the time difference between the reception synchronization point of the current communication link and the reception synchronization point of the communication link, such as the second SSB index or the third SSB index, exceeds a predetermined critical value, the terminal can request a second link establishment procedure based on a RACH from the TRP.

[0366] Meanwhile, TRP1 can receive measurement information from the terminal. Alternatively, TRP1 can acquire the terminal's capabilities from the terminal through a terminal-to-terminal communication link via TRP1's SSB1. If TRP1 can trust the terminal in consideration of the terminal's capabilities, it can accept such measurement information or the terminal's request. Of course, if TRP1 cannot trust the terminal in consideration of the terminal's capabilities, it does not have to accept such measurement information or the terminal's request.

[0367] Next, for example, the time difference between the reception synchronization points of the next best SSB index in the measurement information may be less than a predetermined critical value. Alternatively, TRP1 may receive a request from the UE to establish a communication link without RACH. Accordingly, TRP2 and the UE can perform beam measurement between the UE and SSB5 through a RACH-less procedure as follows.

[0368] To this end, TRP1 can instruct the UE to transmit the uplink beamforming SRS to the TRPs on the scheduling resources determined for the UE (S3807). At this time, TRP1 can instruct the UE to transmit the SRS through RRC signaling including information on the scheduling resources determined for transmitting the uplink beamforming SRS. At this time, TRP1 can inform neighboring TRPs that the UE will transmit the beamformed SRS on the uplink on the scheduling time / frequency resources determined for the UE for interference suppression. Alternatively, TRP1 may not inform neighboring TRPs that the UE will transmit the beamformed SRS on the uplink on the scheduling time / frequency resources determined for resource efficiency.

[0369] Next, the terminal can transmit the corresponding beamformed SRS to TRPs, including TRP2 (S3808). Then, TRP2 can receive the SRS at the terminal. Then, TRP2 can select the most suitable uplink beam based on the received SRS and estimate the TA. Then, TRP2 can notify TRP1 of the most suitable uplink beam information (i.e., best uplink beam information) and the estimated TA. Then, TRP1 can notify the terminal of the most suitable uplink beam information (i.e., best uplink beam information) received from TRP2 and the estimated TA (S3809). In other words, TRP1 can notify the terminal of the SRS information with the highest SINR, for example, among the beamformed SRSs received from the terminal at TRP2. Accordingly, the terminal can receive the best uplink beam information and TA information from TRP1. Then, the terminal knows that the best uplink beam belongs to itself. Through this process, the terminal can complete system connection to TRP2 through a communication link related to SSB1 or SSB5. During this process, the terminal can set TAG1 for the communication link with TRP2. The terminal can perform uplink synchronization and uplink synchronization update by setting TAG1 for the communication link in this way. In this connected state, the terminal can communicate with the other terminal through two communication links, TRP1 and TRP2.

[0370] To this end, TRP2 can transmit downlink-related DCI associated with SSB1 or SSB5 to the UE (S3814). Then, the UE can receive downlink-related DCI from TRP1. Here, the downlink-related DCI indicates DL / connection TCI2, which indicates the reception setting of the UE, and the scheduling resource location for data reception, and can be transmitted on the PDCCH. Then, TRP2 can transmit downlink data to the UE using the downlink-related DCI (S3815). Then, the UE can receive downlink data from TRP2 based on the downlink-related DCI.

[0371] Alternatively, TRP2 may transmit uplink-related DCI associated with SSB1 or SSB5 to the UE (S3816). The UE may then receive uplink-related DCI from TRP2. Here, the uplink-related DCI indicates UL / connection TCI2, which indicates the UE's transmission configuration, and the location of scheduling resources for data transmission, and may be transmitted on the PDCCH. Then, TRP2 may transmit uplink data to the UE via the uplink-related DCI (S3817).

[0372] Then, TRP2 can receive uplink data from the UE based on the DCI associated with the uplink. Thereafter, the UE can periodically or aperiodically perform uplink synchronization for TAG1 with TRP1 and TRP2 and update the TA (S3818). Here, although Figures 37 and 38 describe procedures for configuring two communication links, the method of the present disclosure may not be limited thereto. The TRP and the UE can configure three or more communication links by alternately applying the communication link configuration methods of Figures 37 and 38 to perform downlink and uplink multiplexed TRP communication.

[0373] Meanwhile, the first intra-cell / inter-cell M-TRP procedure method can be described with reference to Figures 39 to 49. Such a first intra-cell / inter-cell M-TRP method can apply the second SSB grouping method among the SSB grouping methods. Also, the first intra-cell / inter-cell M-TRP method can allow a UE to estimate SSB8 belonging to TRP1 as the best SSB, and SSB1 belonging to TRP2 as the second best SSB.

[0374] In other words, when the terminal is powered on, it can estimate the best and second best SSBs from the beamformed SSBs transmitted by TRP1 and TRP2. At this time, the terminal does not know whether the SSB it estimates belongs to TRP1 or TRP2. Next, the terminal can obtain the SSB index information included in the message in the MIB carried by the PBCH contained in the best SSB to obtain uplink synchronization and C-RNTI with TRP1, which transmitted the best SSB. In this case, the obtained best SSB index may be SSB8, which is transmitted in the first half frame of a frame.

[0375] FIG. 39 is a flowchart showing a first embodiment of a transmission method in a multiple transmission and reception point environment.

[0376] Referring to FIG. 39, the UE may perform an initial access procedure with TRP1 and TRP2 (S3900). Here, TRP1 and TRP2 may be included in the serving cell. To this end, TRP1 may transmit beamformed synchronization signal blocks (SSBs) (e.g., SSB1 to SSB8) in multiple directions using the first half frame of a frame (S3901). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8 transmitted to TRP1. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may transmit SSBs periodically or aperiodically for initial synchronization and maintenance of the beamforming-based downlink. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. Such MIB may be the first system information that the terminal acquires from TRP1.

[0377] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S3902). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB among the received SSBs. In this case, the next-best SSB may be SSB1 transmitted to TRP2. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information the terminal acquires from TRP2.

[0378] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S3903). The UE can acquire SIB1 information located on the time and frequency resources indicated in the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S3904). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will continue to be transmitted. The UE can receive SIBs other than SIB1 from TRP1.

[0379] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S3905). The UE can acquire SIB1 information located on the time and frequency resources indicated in the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE during the initial connection phase (S3906). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0380] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET (common control resource set), CSS (common search space), and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1.The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1.The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0381] In addition, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR2. The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1. The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0382] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a 4-stage CBRA-based random access setup procedure for uplink synchronization with TRP1 (S3910).

[0383] First, in step 1, the UE can arbitrarily select one preamble from all preambles provided by TRP1. Then, the UE can transmit the selected preamble to TRP1 via PRACH (S3911). Then, TRP1 can receive the preamble from the UE via PRACH. At this time, the beam direction can conform to the uplink direction complementary to the beam direction when receiving a downlink signal. The resource for transmitting the preamble to TRP1 from the UE can be based on previously acquired information on the association between SSB and RACH. TRP1 can estimate the propagation delay time of the UE using the preamble.

[0384] Next, in step 2, TRP1 can determine whether a preamble is present in the signal received through the PRACH. The preamble can be arbitrarily selected and transmitted by the UE. Therefore, TRP1 cannot determine which UE transmitted the corresponding preamble based on whether the preamble was detected. Therefore, TRP1 cannot determine how many UEs used the detected preamble. Accordingly, TRP1 can transmit an RAR based on the index of the detected preamble to the UE through the P,DSCH (S3912). Then, the UE can receive the RAR from TRP1. At this time, the RAR can include the preamble index, TA value, uplink grant information, and temporary C-RNTI value.

[0385] Next, in step 3, the UE can transmit a message including a scheduling request (or connection request) and C3 to TRP1 via PUSCH using the uplink radio resources indicated in the uplink grant information included in the corresponding RAR and applying the temporary C-RNTI (S3913). Then, TRP1 can receive the connection request message and C3 message from the UE. At this time, there may be more than one UE that transmitted the same preamble in step 1. As a result, preamble collision may occur. In this case, all UEs that transmitted the same preamble may refer to the same RAR and transmit messages using the same radio resources. This may result in collision.

[0386] Here, the C3 message may include information 3-1 (C3_1) to 3-5 (C3_5). Here, information 3-1 may be information about the second-best SSB. And information 3-2 may be information indicating whether the premise that the PCIs are the same (Same PCI) is true or false. Accordingly, here, the premise that the PCIs are the same (Same PCI=True) may mean that the second-best SSB has the same PCI as the best SSB.

[0387] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0388] In other words, terminals that transmitted the same preamble in phase 1 may experience resource collisions when transmitting phase 3 messages. Accordingly, each terminal can operate a contention resolution timer during phase 3 message transmission as part of a procedure to check whether or not a collision occurs in the transmitted phase 3 message and whether or not it is successfully decoded.

[0389] Finally, in step 4, TRP1 can decode the received step 3 message. Then, TRP1 can transmit the successfully decoded message to the terminal via a PDSCH including an acknowledgement and C4 (S3914). Then, the terminal can receive a message including the acknowledgement and C4 from TRP1. The terminal can receive the message including the acknowledgement and C4 before the contention resolution timer operated in step 3 expires. Here, C4 can include the 4-1 information C4_1 to the 4-5 information C4_5. In this case, the 4-1 information may be information indicating whether TRP2 is true or false. Here, TRP2 being true may mean that the TRP using the next-best SSB transmitted by the terminal is eligible for TRP2.

[0390] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0391] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0392] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0393] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the terminal does not need to perform an additional random access procedure. The terminal can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0394] Meanwhile, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, RA may be true in the 4-2 information, and CBRA may be true in the 4-3 information. The terminal may perform a four-step CBRA-based setup procedure for TRP2 (S3920).

[0395] First, in step 1, the UE can arbitrarily select one preamble from all preambles provided by TRP2. Then, the UE can transmit the selected preamble to TRP2 via PRACH (S3921). TRP2 can then receive the preamble from the UE via PRACH. At this time, the beam direction can conform to the uplink direction complementary to the beam direction when receiving a downlink signal. The resource for transmitting the preamble from the UE to TRP2 can be based on previously acquired information on the association between SSB and RACH. TRP2 can estimate the propagation delay time of the UE using the preamble.

[0396] Next, in step 2, TRP2 can determine whether a preamble is present in the signal received through the PRACH. The preamble can be arbitrarily selected and transmitted by the UE. Therefore, TRP2 cannot identify which UE transmitted the corresponding preamble based on whether the preamble is detected. Therefore, TRP2 cannot determine how many UEs used the detected preamble. Accordingly, TRP2 can transmit an RAR based on the index of the detected preamble to the UE through the PDSCH (S3922). Then, the UE can receive the RAR from TRP2. At this time, the RAR can include the preamble index, TA value, uplink grant information, and temporary C-RNTI value.

[0397] Next, in step 3, the UE can transmit a scheduling request message (or a connection request message) to TRP2 over the PUSCH by applying a temporary C-RNTI using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR (S3923). Then, TRP2 can receive the connection request message from the UE. At this time, there may be more than one UE that transmitted the same preamble in step 1. As a result, preamble collision may occur. In this case, all UEs that transmitted the same preamble may refer to the same RAR and transmit messages using the same radio resources. This may result in collision.

[0398] In other words, terminals that transmitted the same preamble in phase 1 may experience resource collisions when transmitting phase 3 messages. Accordingly, each terminal can operate a contention resolution timer during phase 3 message transmission as part of a procedure to check whether or not a collision occurs in the transmitted phase 3 message and whether or not it is successfully decoded.

[0399] Finally, in step 4, TRP2 can decode the received step 3 message. Then, TRP2 can transmit an acknowledgement message to the terminal over the PDSCH for the successfully decoded message (S3924). Then, the terminal can receive the acknowledgement message from TRP2. The terminal can receive the acknowledgement message before the contention resolution timer operated in step 3 expires. After step 4 is completed in this way, the terminal can proceed to the RRC setup step.

[0400] Next, TRP1 can transmit an RRC setup message to the UE (S3930). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP1 (S3931). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the counterpart UE through TRP1. Also, TRP2 can transmit an RRC setup message to the UE. The UE can receive the RRC setup message from TRP2. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP2. TRP2 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP2. In this connected state, the UE can communicate with the counterpart UE through TRP2.

[0401] FIG. 40 is a flowchart showing a second embodiment of a transmission method in a multiple transmission and reception point environment.

[0402] Referring to FIG. 40, the UE may perform an initial access procedure with TRP1 and TRP2 (S4000). TRP1 and TRP2 may be included in the serving cell. TRP1 may transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the first half frame of a frame (S4001). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may periodically or aperiodically transmit SSBs for initial synchronization and maintenance of the beamforming-based downlink. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. This MIB may be the first system information the UE acquires from TRP1.

[0403] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S4002). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB from the received SSBs. In this case, the next-best SSB may be SSB1. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information that the terminal acquires from TRP2.

[0404] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S4003). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S4004). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will continue to be transmitted. The UE can receive SIBs other than SIB1 from TRP1.

[0405] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S4005). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S4006). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0406] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1. Then, the UE can decode SIB1 according to the instructions in the acquired information to acquire the message in SIB1. In addition, the UE can subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0407] In addition, the UE can acquire information about the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameters indicated in Pdcch-ConfigSIB1, for example, within the MIB acquired in the SSB received from TPR2.The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1.The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.After that, after completing downlink synchronization and system information acquisition, the UE can perform a 4-step CBRA-based random access setup procedure for uplink synchronization with TRP1 (S4010).

[0408] First, in step 1, the UE can arbitrarily select one preamble from all preambles provided by TRP1. Then, the UE can transmit the selected preamble to TRP1 via PRACH (S4011). Then, TRP1 can receive the preamble from the UE via PRACH. At this time, the beam direction can conform to the uplink direction complementary to the beam direction when receiving a downlink signal. The resource for transmitting the preamble from the UE to TRP1 can be based on previously acquired information on the association between SSB and RACH. TRP1 can estimate the propagation delay time of the UE using the preamble.

[0409] Next, in step 2, TRP1 can determine whether a preamble is present in the signal received through the PRACH. A preamble can be arbitrarily selected and transmitted by the UE. Therefore, TRP1 cannot identify which UE transmitted the corresponding preamble based on whether a preamble is detected. Therefore, TRP1 cannot determine how many UEs used the detected preamble. Accordingly, TRP1 can transmit an RAR based on the index of the detected preamble to the UE through the PDSCH (S4012). Then, the UE can receive the RAR from TRP1. At this time, the RAR can include a preamble index, a TA value, uplink grant information, and a temporary C-RNTI value.

[0410] Next, in step 3, the UE can transmit a message including a scheduling request (or connection request) and C3 to TRP1 via PUSCH using the uplink radio resources indicated in the uplink grant information included in the corresponding RAR and applying the temporary C-RNTI (S4013). Then, TRP1 can receive the message including the connection request and C3 from the UE. At this time, there may be more than one UE that transmitted the same preamble in step 1. As a result, preamble collision may occur. In this case, all UEs that transmitted the same preamble may refer to the same RAR and transmit messages using the same radio resources. This may result in collision.

[0411] Here, the C3 message may include information 3-1 (C3_1) to 3-5 (C3_5). Here, information 3-1 may be information about the second-best SSB. And information 3-2 may be information indicating whether the premise that the PCIs are the same (Same PCI) is true or false. Accordingly, here, the premise that the PCIs are the same (Same PCI=True) may mean that the second-best SSB has the same PCI as the best SSB.

[0412] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0413] In other words, terminals that transmitted the same preamble in phase 1 may experience resource collisions when transmitting phase 3 messages. Accordingly, each terminal can operate a contention resolution timer during phase 3 message transmission as part of a procedure to check whether or not a collision occurs in the transmitted phase 3 message and whether or not it is successfully decoded.

[0414] Finally, in step 4, TRP1 can decode the received step 3 message. Then, TRP1 can transmit an acknowledgement message and a C4 message to the terminal over the PDSCH for the successfully decoded message (S4014). Then, the terminal can receive the acknowledgement message and the C4 message from TRP1. The terminal can receive the acknowledgement message and the C4 message before the contention resolution timer operated in step 3 expires. Here, the C4 message can include 4-1 information C4_1 to 4-5 information C4_5. In this case, the 4-1 information may be information indicating whether TRP2 is true or false. Here, TRP2 being true may mean that the TRP using the next best SSB transmitted by the terminal is eligible for TRP2.

[0415] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0416] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0417] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0418] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the terminal does not need to perform an additional random access procedure. The terminal can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0419] Meanwhile, the assumption that the PCIs are identical may be true in the 3-2 information, TRP2 may be true in the 4-1 information, RA may be true in the 4-2 information, and CBRA may be false in the 4-3 information. The terminal may perform a two-stage CFRA-based setup procedure for TRP2 (S4020).

[0420] To this end, in step 1, the UE can arbitrarily select one preamble from the CFRA preambles. Then, the UE can transmit the selected preamble to TRP2 via the PRACH. At the same time, the UE can transmit a scheduling request (i.e., connection request) message to TRP2 via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4021). Then, TRP2 can receive a message including the preamble and the scheduling request from the UE.

[0421] In this case, TRP2 may transmit a message including RAR and C-RNTI to the UE via PDSCH (S4022). Accordingly, the UE may receive a message including successful RAR and C-RNTI from TRP2. This message may serve as an acknowledgement.

[0422] Next, TRP1 can transmit an RRC setup message to the UE (S4030). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP1 (S4031). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with a counterpart UE through TRP1. Also, TRP2 can transmit an RRC setup message to the UE. The UE can receive the RRC setup message from TRP2. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP2. TRP2 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP2. In this connected state, the UE can communicate with a counterpart UE through TRP2.

[0423] FIG. 41 is a flowchart showing a third embodiment of a transmission method in a multiple transmission and reception point environment.

[0424] Referring to FIG. 41, the UE may perform an initial access procedure with TRP1 and TRP2 (S4100). At this time, TRP1 and TRP2 may be included in the serving cell. To this end, TRP1 may transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the first half frame of a frame (S4101). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may periodically or aperiodically transmit SSBs for initial synchronization and maintenance of the beamforming-based downlink. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. This MIB may be the first system information acquired by the UE at TRP1.

[0425] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S4102). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB from the received SSBs. In this case, the next-best SSB may be SSB1. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information that the terminal acquires from TRP2.

[0426] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S4103). The UE can acquire SIB1 information located on the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S3904). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will be transmitted subsequently. The UE can receive SIBs other than SIB1 from TRP1.

[0427] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S4105). The UE can acquire SIB1 information located on the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE at TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE during the initial connection phase (S3906). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0428] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1. Then, the UE can decode SIB1 according to the instructions in the acquired information to acquire the message in SIB1. In addition, the UE can subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0429] In addition, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR2. The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1. The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0430] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a two-stage CBRA-based random access setup procedure for uplink synchronization with TRP1 (S4110).

[0431] To this end, in step 1, the UE may arbitrarily select one preamble from all preambles. Then, the UE may transmit the selected preamble to TRP1 via the PRACH. At the same time, the UE may transmit a message including a scheduling request (i.e., a connection request) and C3 to the TRP via the pre-allocated uplink radio resource (i.e., an uplink shared channel) (S4111). Then, TRP1 may receive the message including the preamble, scheduling request, and C3 from the UE. Here, C3 may include information 3-1 (C3_1) to 3-5 (C3_5). Here, the information 3-1 may be information regarding the second-best SSB. And the information 3-2 may be information indicating whether the assumption that the PCIs are the same (Same PCI) is true or false. Accordingly, if the assumption that the PCIs are the same (Same PCI=True) is true, it may mean that the second-best SSB has the same PCI as the best SSB.

[0432] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0433] In two steps, the TRP can determine whether the preamble is detected. The TRP can also determine whether the message is successfully decoded. Depending on the result of the determination, the TRP can send a different type of message to the terminal. This may change the subsequent procedure.

[0434] In detail, if the TRP cannot detect the preamble, the TRP may not perform any operation. In other words, the TRP may not check whether a message related to the preamble is received through the uplink radio resource. As a result, the TRP may not respond if the preamble is not detected. Accordingly, since the terminal has not received any message from the TRP, it may retry the optional connection. This case is referred to as Case 1.

[0435] In contrast, the TRP can successfully 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, C-RNTI, and C4 to the UE via the PDSCH (S4112). Accordingly, the UE can receive a message including the successful RAR, C-RNTI, and C4 from the TRP. This message can serve as an acknowledgement.

[0436] Here, the C4 message can include 4-1 information C4_1 to 4-5 information C4_5. At this time, the 4-1 information may be information indicating whether TRP2 is true or false. Here, if TRP2 is true, it may mean that the TRP using the next best SSB transmitted by the UE is qualified as TRP2.

[0437] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0438] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0439] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0440] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the terminal does not need to perform an additional random access procedure. The terminal can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0441] Meanwhile, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, RA may be true in the 4-2 information, and CBRA may be true in the 4-3 information. The terminal may perform a two-stage CBRA-based setup procedure for TRP2 (S4120).

[0442] To this end, in step 1, the UE can arbitrarily select one preamble from all preambles. Then, the UE can transmit the selected preamble to TRP2 via the PRACH. At the same time, the UE can transmit a scheduling request (i.e., connection request) message to TRP2 via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4121). Then, TRP2 can receive a message including the preamble and the scheduling request from the UE.

[0443] In two steps, TRP2 can determine whether the preamble is detected. Also, TRP2 can determine whether the message is successfully decoded. Depending on the result of the determination, TRP2 can send a different type of message to the terminal. This may change the subsequent procedure.

[0444] In more detail, if TRP2 cannot detect the preamble, TRP2 may not perform any operation. In other words, TRP2 may not check whether a message related to the preamble has been received through the uplink radio resource. As a result, TRP2 may not respond if the preamble is not detected. Accordingly, the terminal may reattempt optional connection because it did not receive any message from TRP2. This case is referred to as Case 1.

[0445] Alternatively, TRP2 may successfully detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, TRP2 may transmit a message including the RAR and C-RNTI to the UE via the PDSCH (S4112). Accordingly, the UE may receive a message including a successful RAR and C-RNTI from TRP2. This message may serve as an acknowledgement. Accordingly, the UE may successfully terminate the optional access. This case may be referred to as case 2. On the other hand, TRP2 may successfully detect the preamble but may not successfully decode the message from the uplink radio resources associated with the preamble. In this case, TRP2 may transmit a message including a fallback RAR to the UE via the PDSCH. In this case, the UE receiving the message may retransmit the message it was attempting to send using the uplink radio resources indicated by the uplink grant information included in the fallback RAR.

[0446] Next, TRP1 can transmit an RRC setup message to the UE (S4130). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP1 (S4131). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the counterpart UE through TRP1. Also, TRP2 can transmit an RRC setup message to the UE. The UE can receive the RRC setup message from TRP2. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP2. TRP2 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP2. In this connected state, the UE can communicate with the counterpart UE through TRP2.

[0447] FIG. 42 is a flowchart showing a fourth embodiment of a transmission method in a multiple transmission and reception point environment.

[0448] Referring to FIG. 42, the UE may perform an initial access procedure with TRP1 and TRP2 (S4200). Here, TRP1 and TRP2 may be included in the serving cell. To this end, TRP1 may transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the first half frame of a frame (S4201). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may periodically or aperiodically transmit SSBs for initial synchronization and maintenance of the beamforming-based downlink. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. This MIB may be the first system information acquired by the UE via TRP1.

[0449] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S4202). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB from the received SSBs. In this case, the next-best SSB may be SSB1. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information that the terminal acquires from TRP2.

[0450] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S4203). The UE can acquire SIB1 information located on the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S4204). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will continue to be transmitted. The UE can receive SIBs other than SIB1 from TRP1.

[0451] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S4205). The UE can acquire SIB1 information located on the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE at TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE during the initial connection phase (S4206). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0452] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1. Then, the UE can decode SIB1 according to the instructions in the acquired information to acquire the message in SIB1. In addition, the UE can subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0453] In addition, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR2. The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1. The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0454] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a two-stage CBRA-based random access setup procedure for uplink synchronization with TRP1 (S4210).

[0455] To this end, in step 1, the UE can arbitrarily select one preamble from all preambles. Then, the UE can transmit the selected preamble to TRP1 via the PRACH. The UE can simultaneously transmit a scheduling request (i.e., connection request) message and a C3 message to the TRP via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4211). Then, TRP1 can receive the preamble, the message including the scheduling request, and the C3 message from the UE. Here, the C3 message can include information 3-1 (C3_1) to 3-5 (C3_5). Here, the information 3-1 can be information regarding the second-best SSB. And the information 3-2 can be information indicating whether the assumption that the PCIs are the same (Same PCI) is true or false. Accordingly, if the assumption that the PCIs are the same is true (Same PCI=True), it can mean that the second-best SSB has the same PCI as the best SSB.

[0456] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0457] In two steps, the TRP can determine whether the preamble is detected. The TRP can also determine whether the message is successfully decoded. Depending on the result of the determination, the TRP can send a different type of message to the terminal. This may change the subsequent procedure.

[0458] In detail, if the TRP cannot detect the preamble, the TRP may not perform any operation. In other words, the TRP may not check whether a message related to the preamble is received through the uplink radio resource. As a result, the TRP may not respond if the preamble is not detected. Accordingly, since the terminal has not received any message from the TRP, it may retry the optional connection. This case is referred to as Case 1.

[0459] In contrast, the TRP can successfully detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, the TRP1 can transmit a message including the RAR, C-RNTI, and C4 to the UE via the PDSCH (S4112). Accordingly, the UE can receive a message including the successful RAR, C-RNTI, and C4 from the TRP. This message can serve as an acknowledgement.

[0460] Here, the C4 message can include 4-1 information C4_1 to 4-5 information C4_5. At this time, the 4-1 information may be information indicating whether TRP2 is true or false. Here, if TRP2 is true, it may mean that the TRP using the next best SSB transmitted by the UE is qualified as TRP2.

[0461] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0462] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0463] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0464] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the terminal does not need to perform an additional random access procedure. The terminal can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0465] Meanwhile, the assumption that the PCIs are identical may be true in the 3-2 information, TRP2 may be true in the 4-1 information, RA may be true in the 4-2 information, and CBRA may be false in the 4-3 information. The terminal may perform a two-stage CFRA-based setup procedure for TRP2 (S4220).

[0466] To this end, in step 1, the UE can arbitrarily select one preamble from the CFRA preambles. Then, the UE can transmit the selected preamble to TRP2 via the PRACH. At the same time, the UE can transmit a scheduling request (i.e., connection request) message to TRP2 via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4221). Then, TRP2 can receive a message including the preamble and the scheduling request from the UE.

[0467] In this case, TRP2 can transmit a message including RAR and C-RNTI to the UE via PDSCH (S4222). Accordingly, the UE can receive a message including successful RAR and C-RNTI from TRP2. This message can serve as an acknowledgement. At this time, RA can be false in the 4-2 information of the C4 message. In this case, TRP2 can end step 2. Alternatively, RA can be true. In this case, the UE can perform the random access procedure again from step 1. After step 2 is completed, the UE can proceed with the RRC setup step.

[0468] Next, TRP1 can transmit an RRC setup message to the UE (S4230). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP1 (S4231). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the counterpart UE through TRP1. Also, TRP2 can transmit an RRC setup message to the UE. The UE can receive the RRC setup message from TRP2. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP2. TRP2 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP2. In this connected state, the UE can communicate with the counterpart UE through TRP2.

[0469] FIG. 43 is a flowchart showing a fifth embodiment of a transmission method in a multiple transmission and reception point environment.

[0470] Referring to FIG. 43, the UE may perform an initial access procedure with TRP1 and TRP2 (S4300). Here, TRP1 may be included in the serving cell, and TRP2 may be included in a non-serving cell. To this end, TRP1 may transmit beamformed synchronization signal blocks (SSBs) (e.g., SSB1 to SSB8) in multiple directions using the first half frame of a frame (S4301). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may periodically or aperiodically transmit SSBs for initial and maintenance of beamforming-based downlink synchronization. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. Such MIB may be the first system information acquired by the terminal at TRP1.

[0471] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S4302). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB from the received SSBs. In this case, the next-best SSB may be SSB1. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information that the terminal acquires from TRP2.

[0472] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S4303). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S4304). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will be transmitted subsequently. The UE can receive SIBs other than SIB1 from TRP1.

[0473] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S4305). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE at TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE during the initial connection phase (S4306). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0474] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET (common control resource set), CSS (common search space), and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1.The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1.The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0475] In addition, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR2. The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1. The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0476] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a 4-step CBRA-based random access setup procedure for uplink synchronization with TRP1 (S4310).

[0477] First, in step 1, the UE can arbitrarily select one preamble from all preambles provided by TRP1. Then, the UE can transmit the selected preamble to TRP1 via PRACH (S4311). Then, TRP1 can receive the preamble from the UE via PRACH. At this time, the beam direction can conform to the uplink direction complementary to the beam direction when receiving a downlink signal. The resource for transmitting the preamble to TRP1 from the UE can be based on previously acquired information on the association between SSB and RACH. TRP1 can estimate the propagation delay time of the UE using the preamble.

[0478] Next, in step 2, TRP1 can determine whether a preamble is present in the signal received through the PRACH. A preamble can be arbitrarily selected and transmitted by the UE. Therefore, TRP1 cannot identify which UE transmitted the corresponding preamble based on whether a preamble is detected. Therefore, TRP1 cannot determine how many UEs used the detected preamble. Accordingly, TRP1 can transmit an RAR based on the index of the detected preamble to the UE through the PDSCH (S4312). Then, the UE can receive the RAR from TRP1. At this time, the RAR can include a preamble index, a TA value, uplink grant information, and a temporary C-RNTI value.

[0479] Next, in step 3, the UE can transmit a scheduling request message (or connection request message) and a C3 message to TRP1 over the PUSCH by applying a temporary C-RNTI using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR (S4313). Then, TRP1 can receive the connection request message and the C3 message from the UE. At this time, there may be more than one UE that transmitted the same preamble in step 1. As a result, preamble collision may occur. In this case, all UEs that transmitted the same preamble may refer to the same RAR and transmit messages using the same radio resources. This may result in collision.

[0480] Here, the C3 message may include information 3-1 (C3_1) to 3-5 (C3_5). Here, information 3-1 may be information about the second-best SSB. And information 3-2 may be information indicating whether the premise that the PCIs are the same (Same PCI) is true or false. Accordingly, here, the premise that the PCIs are the same (Same PCI=True) may mean that the second-best SSB has the same PCI as the best SSB.

[0481] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0482] In other words, terminals that transmitted the same preamble in phase 1 may experience resource collisions when transmitting phase 3 messages. Accordingly, each terminal can operate a contention resolution timer during phase 3 message transmission as part of a procedure to check whether or not a collision occurs in the transmitted phase 3 message and whether or not it is successfully decoded.

[0483] Finally, in step 4, TRP1 can decode the received step 3 message. Then, TRP1 can transmit an acknowledgement message and a C4 message to the terminal over the PDSCH for the successfully decoded message (S4314). Then, the terminal can receive the acknowledgement message and the C4 message from TRP1. The terminal can receive the acknowledgement message and the C4 message before the contention resolution timer operated in step 3 expires. Here, the C4 message can include 4-1 information C4_1 to 4-5 information C4_5. In this case, the 4-1 information may be information indicating whether TRP2 is true or false. Here, TRP2 being true may mean that the TRP using the next-best SSB transmitted by the terminal is eligible for TRP2.

[0484] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0485] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0486] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0487] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the terminal does not need to perform an additional random access procedure. The terminal can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0488] Meanwhile, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, RA may be true in the 4-2 information, and CBRA may be true in the 4-3 information. The terminal may perform a four-step CBRA-based setup procedure for TRP2 (S4320).

[0489] First, in step 1, the UE can arbitrarily select one preamble from all preambles provided by TRP2. Then, the UE can transmit the selected preamble to TRP2 via PRACH (S4321). Then, TRP2 can receive the preamble from the UE via PRACH. At this time, the beam direction can conform to the uplink direction complementary to the beam direction when receiving a downlink signal. The resource for transmitting the preamble from the UE to TRP2 can be based on previously acquired information on the association between SSB and RACH. TRP2 can estimate the propagation delay time of the UE using the preamble.

[0490] Next, in step 2, TRP2 can determine whether a preamble is present in the signal received through the PRACH. A preamble can be arbitrarily selected and transmitted by the UE. Therefore, TRP2 cannot identify which UE transmitted the corresponding preamble based on whether a preamble is detected. Therefore, TRP2 cannot determine how many UEs used the detected preamble. Accordingly, TRP2 can transmit an RAR based on the index of the detected preamble to the UE through the PDSCH (S4322). Then, the UE can receive the RAR from TRP2. At this time, the RAR can include a preamble index, a TA value, uplink grant information, and a temporary C-RNTI value.

[0491] Next, in step 3, the UE can transmit a scheduling request message (or a connection request message) to TRP2 over the PUSCH by applying a temporary C-RNTI using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR (S4323). Then, TRP2 can receive the connection request message from the UE. At this time, there may be more than one UE that transmitted the same preamble in step 1. As a result, preamble collision may occur. In this case, all UEs that transmitted the same preamble may refer to the same RAR and transmit messages using the same radio resources. This may result in collision.

[0492] In other words, terminals that transmitted the same preamble in phase 1 may experience resource collisions when transmitting phase 3 messages. Accordingly, each terminal can operate a contention resolution timer during phase 3 message transmission as part of a procedure to check whether or not a collision occurs in the transmitted phase 3 message and whether or not it is successfully decoded.

[0493] Finally, in step 4, TRP2 can decode the received step 3 message. Then, TRP2 can transmit an acknowledgement message to the terminal over the PDSCH for the successfully decoded message (S4324). Then, the terminal can receive the acknowledgement message from TRP2. The terminal can receive the acknowledgement message before the contention resolution timer operated in step 3 expires. After step 4 is completed in this way, the terminal can proceed to the RRC setup step.

[0494] Next, TRP1 may transmit an RRC setup message to the UE (S4330). The UE may receive the RRC setup message from TRP1. Accordingly, the UE may establish RRC and transmit an RRC setup complete message to TRP1 (S4331). TRP1 may receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE may complete a system connection to TRP1. In this connected state, the UE may communicate with a counterpart UE through TRP1. Also, TRP2 may transmit an RRC setup message to the UE. The UE may receive an RRC setup message from TRP2. Accordingly, the UE may establish RRC and transmit an RRC setup complete message to TRP2. TRP2 may receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE may complete a system connection to TRP2. In this connected state, the UE may communicate with a counterpart UE through TRP2.

[0495] FIG. 44 is a flowchart showing a sixth embodiment of a transmission method in a multiple transmission and reception point environment.

[0496] Referring to FIG. 44, the UE may perform an initial access procedure with TRP1 and TRP2 (S4400). Here, TRP1 may be included in the serving cell, and TRP2 may be included in a non-serving cell. TRP1 may transmit beamformed synchronization signal blocks (SSBs) (e.g., SSB1 to SSB8) in multiple directions using the first half frame of a frame (S4401). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may periodically or aperiodically transmit SSBs for initial and maintenance of beamforming-based downlink synchronization. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. Such MIB may be the first system information acquired by the terminal at TRP1.

[0497] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S4402). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB from the received SSBs. In this case, the next-best SSB may be SSB1. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information that the terminal acquires from TRP2.

[0498] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S4403). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S4404). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will be transmitted subsequently. The UE can receive SIBs other than SIB1 from TRP1.

[0499] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S4405). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE at TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE during the initial connection phase (S4406). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0500] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET (common control resource set), CSS (common search space), and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1.The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1.The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0501] In addition, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR2. The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1. The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0502] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a 4-step CBRA-based random access setup procedure for uplink synchronization with TRP1 (S4410).

[0503] First, in step 1, the UE can arbitrarily select one preamble from all preambles provided by TRP1. Then, the UE can transmit the selected preamble to TRP1 via PRACH (S4411). Then, TRP1 can receive the preamble from the UE via PRACH. At this time, the beam direction can conform to the uplink direction complementary to the beam direction when receiving a downlink signal. The resource for transmitting the preamble to TRP1 from the UE can be based on previously acquired information on the association between SSB and RACH. TRP1 can estimate the propagation delay time of the UE using the preamble.

[0504] Next, in step 2, TRP1 can determine whether a preamble is present in the signal received through the PRACH. A preamble can be arbitrarily selected and transmitted by the UE. Therefore, TRP1 cannot identify which UE transmitted the corresponding preamble based on whether a preamble is detected. Therefore, TRP1 cannot determine how many UEs used the detected preamble. Accordingly, TRP1 can transmit an RAR based on the index of the detected preamble to the UE through the PDSCH (S4412). Then, the UE can receive the RAR from TRP1. At this time, the RAR can include a preamble index, a TA value, uplink grant information, and a temporary C-RNTI value.

[0505] Next, in step 3, the UE can transmit a scheduling request message (or connection request message) and a C3 message to TRP1 via PUSCH using the uplink radio resources indicated by the uplink grant information included in the corresponding RAR and applying a temporary C-RNTI (S4413). Then, TRP1 can receive the connection request message and the C3 message from the UE. At this time, there may be more than one UE that transmitted the same preamble in step 1. As a result, preamble collision may occur. In this case, all UEs that transmitted the same preamble may refer to the same RAR and transmit messages using the same radio resources. This may result in collision.

[0506] Here, the C3 message may include information 3-1 (C3_1) to 3-5 (C3_5). Here, information 3-1 may be information about the second-best SSB. And information 3-2 may be information indicating whether the premise that the PCIs are the same (Same PCI) is true or false. Accordingly, here, the premise that the PCIs are the same (Same PCI=True) may mean that the second-best SSB has the same PCI as the best SSB.

[0507] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0508] In other words, terminals that transmitted the same preamble in phase 1 may experience resource collisions when transmitting phase 3 messages. Accordingly, each terminal can operate a contention resolution timer during phase 3 message transmission as part of a procedure to check whether or not a collision occurs in the transmitted phase 3 message and whether or not it is successfully decoded.

[0509] Finally, in step 4, TRP1 may decode the received step 3 message. Then, TRP1 may transmit an acknowledgement message and a C4 message to the terminal over the PDSCH for the successfully decoded message (S4414). Then, the terminal may receive the acknowledgement message and the C4 message from TRP1. The terminal may receive the acknowledgement message and the C4 message before the contention resolution timer operated in step 3 expires. Here, the C4 message may include 4-1 information C4_1 to 4-5 information C4_5. In this case, the 4-1 information may be information indicating whether TRP2 is true or false. Here, TRP2 being true may mean that the TRP using the next best SSB transmitted by the terminal is eligible for TRP2.

[0510] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0511] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0512] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0513] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the UE does not need to perform an additional random access procedure. The UE can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0514] Meanwhile, the assumption that the PCIs are identical may be true in the 3-2 information, TRP2 may be true in the 4-1 information, RA may be true in the 4-2 information, and CBRA may be false in the 4-3 information. The UE may perform a two-stage CFRA-based setup procedure for TRP2 (S4420).

[0515] To this end, in step 1, the UE can arbitrarily select one preamble from the CFRA preambles. Then, the UE can transmit the selected preamble to TRP2 via the PRACH. At the same time, the UE can transmit a scheduling request (i.e., connection request) message to TRP2 via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4421). Then, TRP2 can receive a message including the preamble and the scheduling request from the UE.

[0516] In this case, TRP2 can transmit a message including RAR and C-RNTI to the UE via PDSCH (S4422). Accordingly, the UE can receive a message including successful RAR and C-RNTI from TRP2. This message can serve as an acknowledgement. At this time, RA can be false in the 4-2 information of the C4 message. In this case, TRP2 can end step 2. Alternatively, RA can be true. In this case, the UE can perform the random access procedure again from step 1. After step 2 is completed, the UE can proceed with the RRC setup step.

[0517] Next, TRP1 may transmit an RRC setup message to the UE (S4430). The UE may receive the RRC setup message from TRP1. Accordingly, the UE may configure RRC and transmit an RRC setup complete message to TRP1 (S4431). TRP1 may receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE may complete a system connection to TRP1. In this connected state, the UE may communicate with a counterpart UE through TRP1. Also, TRP2 may transmit an RRC setup message to the UE. The UE may receive an RRC setup message from TRP2. Accordingly, the UE may configure RRC and transmit an RRC setup complete message to TRP2. TRP2 may receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE may complete a system connection to TRP2. In this connected state, the UE may communicate with a counterpart UE through TRP2.

[0518] FIG. 45 is a flowchart showing a seventh embodiment of a transmission method in a multiple transmission and reception point environment.

[0519] Referring to FIG. 45, the UE may perform an initial access procedure with TRP1 and TRP2 (S4500). Here, TRP1 may be included in the serving cell, and TRP2 may be included in a non-serving cell. To this end, TRP1 may transmit beamformed synchronization signal blocks (SSBs) (e.g., SSB1 to SSB8) in multiple directions using the first half frame of a frame (S4501). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may periodically or aperiodically transmit SSBs for initial synchronization and maintenance of the beamforming-based downlink. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. Such MIB may be the first system information acquired by the terminal at TRP1.

[0520] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S4502). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB from the received SSBs. In this case, the next-best SSB may be SSB1. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information that the terminal acquires from TRP2.

[0521] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S4503). The UE can acquire SIB1 information located on the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S3904). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will continue to be transmitted. The UE can receive SIBs other than SIB1 from TRP1.

[0522] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S4505). The UE can acquire SIB1 information located in the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE at TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE during the initial connection phase (S3906). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0523] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET (common control resource set), CSS (common search space), and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1.The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1.The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0524] In addition, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR2. The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1. The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0525] After that, the terminal that has completed downlink synchronization and system information acquisition can perform a two-stage CBRA-based random access setup procedure for uplink synchronization with TRP1 (S4510).

[0526] To this end, in step 1, the UE can arbitrarily select one preamble from all preambles. Then, the UE can transmit the selected preamble to TRP1 via the PRACH. The UE can simultaneously transmit a scheduling request (i.e., connection request) message and a C3 message to the TRP via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4511). Then, TRP1 can receive the preamble, the message including the scheduling request, and the C3 message from the UE. Here, the C3 message can include information 3-1 (C3_1) to 3-5 (C3_5). Here, the information 3-1 can be information regarding the second-best SSB. And the information 3-2 can be information indicating whether the assumption that the PCIs are the same (Same PCI) is true or false. Accordingly, if the assumption that the PCIs are the same (Same PCI=True) is true, it can mean that the second-best SSB has the same PCI as the best SSB.

[0527] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0528] In two steps, the TRP can determine whether the preamble is detected and whether the message is successfully decoded. Depending on the result of the determination, the TRP can send a different type of message to the terminal. This may change the subsequent procedure.

[0529] In detail, if the TRP cannot detect the preamble, the TRP may not perform any operation. In other words, the TRP may not check whether a message related to the preamble is received through the uplink radio resource. As a result, the TRP may not respond if the preamble is not detected. Accordingly, since the terminal has not received any message from the TRP, it may retry the optional connection. This case is referred to as Case 1.

[0530] In contrast, the TRP can successfully detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, the TRP1 can transmit a message including the RAR, C-RNTI, and C4 to the UE via the PDSCH (S4512). Accordingly, the UE can receive a message including the successful RAR, C-RNTI, and C4 from the TRP. This message can serve as an acknowledgement.

[0531] Here, the C4 message can include 4-1 information C4_1 to 4-5 information C4_5. At this time, the 4-1 information may be information indicating whether TRP2 is true or false. Here, if TRP2 is true, it may mean that the TRP using the next best SSB transmitted by the UE is qualified as TRP2.

[0532] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0533] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0534] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0535] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the terminal does not need to perform an additional random access procedure. The terminal can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0536] Meanwhile, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, RA may be true in the 4-2 information, and CBRA may be true in the 4-3 information. The terminal may perform a two-stage CBRA-based setup procedure for TRP2 (S4520).

[0537] To this end, in step 1, the UE can arbitrarily select one preamble from all preambles. Then, the UE can transmit the selected preamble to TRP2 via the PRACH. At the same time, the UE can transmit a scheduling request (i.e., connection request) message to TRP2 via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4521). Then, TRP2 can receive a message including the preamble and the scheduling request from the UE.

[0538] In two steps, TRP2 can determine whether the preamble is detected. Also, TRP2 can determine whether the message is successfully decoded. Depending on the result of the determination, TRP2 can send a different type of message to the terminal. This may change the subsequent procedure.

[0539] In more detail, if TRP2 cannot detect the preamble, TRP2 may not perform any operation. In other words, TRP2 may not check whether a message related to the preamble has been received through the uplink radio resource. As a result, TRP2 may not respond if the preamble is not detected. Accordingly, the terminal may reattempt optional connection because it did not receive any message from TRP2. This case is referred to as Case 1.

[0540] Alternatively, TRP2 may successfully detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, TRP2 may transmit a message including the RAR and C-RNTI to the UE via the PDSCH (S4512). Accordingly, the UE may receive a message including a successful RAR and C-RNTI from TRP2. This message may serve as an acknowledgement. Accordingly, the UE may successfully terminate the optional access. This case may be referred to as case 2. On the other hand, TRP2 may successfully detect the preamble but may not successfully decode the message from the uplink radio resources associated with the preamble. In this case, TRP2 may transmit a message including a fallback RAR to the UE via the PDSCH. In this case, the UE receiving the message may retransmit the message it was attempting to send using the uplink radio resources indicated by the uplink grant information included in the fallback RAR.

[0541] Next, TRP1 can transmit an RRC setup message to the UE (S4530). The UE can receive the RRC setup message from TRP1. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP1 (S4531). TRP1 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP1. In this connected state, the UE can communicate with the counterpart UE through TRP1. Also, TRP2 can transmit an RRC setup message to the UE. The UE can receive the RRC setup message from TRP2. Accordingly, the UE can establish RRC and transmit an RRC setup complete message to TRP2. TRP2 can receive the RRC setup complete message from the UE and confirm the RRC setup. Through this process, the UE can complete a system connection to TRP2. In this connected state, the UE can communicate with the counterpart UE through TRP2.

[0542] FIG. 46 is a flowchart showing an eighth embodiment of a transmission method in a multiple transmission and reception point environment.

[0543] Referring to FIG. 46, the UE may perform an initial access procedure with TRP1 and TRP2 (S4600). Here, TRP1 may be included in the serving cell, and TRP2 may be included in a non-serving cell. To this end, TRP1 may transmit beamformed synchronization signal blocks (SSBs) (e.g., SSB1 to SSB8) in multiple directions using the first half frame of a frame (S4601). Accordingly, the UE may receive SSBs from TRP1. The UE may then estimate the best SSB among the received SSBs. In this case, the best SSB may be SSB8. The UE may perform downlink synchronization from TRP1 to the UE using the best SSB. Here, TRP1 may transmit SSBs periodically or aperiodically for initial synchronization and maintenance of the beamforming-based downlink. After performing this synchronization, the UE may acquire MIB information from the best SSB. This MIB may be carried on the PBCH and transmitted to the UE. Such MIB may be the first system information acquired by the terminal at TRP1.

[0544] Meanwhile, TRP2 can transmit beamformed synchronization signal blocks (SSBs) (for example, SSB1 to SSB8) in multiple directions using the second half frame of a frame (S4602). Accordingly, the terminal can receive SSBs from TRP2. The terminal can then estimate the next-best SSB from the received SSBs. In this case, the next-best SSB may be SSB1. The terminal can then perform downlink synchronization from TRP2 to the terminal using the next-best SSB. Here, TRP2 can transmit SSBs periodically or aperiodically for initial and maintenance of beamforming-based downlink synchronization. Such MIBs can be carried on the PBCH and transmitted to the terminal. Such MIBs may be the first system information that the terminal acquires from TRP2.

[0545] Next, TRP1 can transmit SIB1 to the UE using the PDSCH (S4603). The UE can acquire SIB1 information located on the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE from TRP1. TRP1 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE in the initial connection phase (S4604). In this case, TRP1 can transmit control information on SIB1 following SIB1 to indicate that SIBs will be transmitted subsequently. The UE can receive SIBs other than SIB1 from TRP1.

[0546] Meanwhile, TRP2 can transmit SIB1 to the UE using the PDSCH (S4605). The UE can acquire SIB1 information located on the time and frequency resources indicated by the MIB. At this time, SIB1 can be carried on the PDSCH and transmitted to the UE. This SIB can be the second system information acquired by the UE at TRP2. TRP2 can transmit SIBs other than SIB1 (in other words, SIBy, where y is a positive integer greater than or equal to 2) to the UE during the initial connection phase (S4606). In this case, TRP2 can transmit control information on SIB1 to indicate that SIBs will be transmitted following SIB1. The UE can receive SIBs other than SIB1 from TRP2.

[0547] Meanwhile, the UE can acquire the PDCCH / SIB bandwidth, CORESET (common control resource set), CSS (common search space), and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR1.The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1.The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0548] In addition, the UE can acquire the PDCCH / SIB bandwidth, CORESET, CSS, and related PDCCH parameter information indicated in Pdcch-ConfigSIB1 as an example of the MIB acquired in the SSB received from TPR2. The UE can then decode SIB1 as instructed by the acquired information to acquire the message in SIB1. The UE can also subsequently decode SIBy using the instruction information included in the message in SIB1 to acquire the message in SIBy.

[0549] Thereafter, the terminal that has completed downlink synchronization and system information acquisition can perform a two-stage CBRA-based random access setup procedure for uplink synchronization with TRP1 (S4610).

[0550] To this end, in step 1, the UE may arbitrarily select one preamble from all preambles. Then, the UE may transmit the selected preamble to TRP1 via the PRACH. The UE may simultaneously transmit a scheduling request (i.e., connection request) message and a C3 message to the TRP via the pre-allocated uplink radio resource (i.e., uplink shared channel) (S4611). Then, TRP1 may receive the preamble, the message including the scheduling request, and the C3 message from the UE. Here, the C3 message may include information 3-1 (C3_1) to 3-5 (C3_5). Here, the information 3-1 may be information regarding the second-best SSB. And the information 3-2 may be information indicating whether the assumption that the PCIs are the same (Same PCI) is true or false. Accordingly, if the assumption that the PCIs are the same (Same PCI=True) is true, it may mean that the second-best SSB has the same PCI as the best SSB.

[0551] The 3-3 information may be information regarding the time difference between the start point of the best SSB and the start point of the second-best SSB. For example, the 3-3 information may be set to '0' so that if the time difference between the start point of the best SSB and the start point of the second-best SSB is less than a predetermined threshold, it is considered to be no time difference. This allows the UE to reduce the complexity of multiple TRP synchronization updates (e.g., TA updates). Alternatively, the 3-3 information may be set to the time difference value measured by the UE if the time difference value is equal to or greater than a predetermined threshold. The 3-4 information may be information regarding the difference between the maximum correlation value of the timing estimator / other output of the best SSB and the maximum correlation value of the timing estimator / other output of the second-best SSB. The 3-5 information may be other information. The 3-5 information may be any possible information that reduces procedural overhead. The 3-5 information may include time information that can identify the second half-frame in which the second-best SSB was received when the SSB grouping method is the second method.

[0552] In two steps, the TRP can determine whether the preamble is detected and whether the message is successfully decoded. Depending on the result of the determination, the TRP can send a different type of message to the terminal. This may change the subsequent procedure.

[0553] In detail, if the TRP cannot detect the preamble, the TRP may not perform any operation. In other words, the TRP may not check whether a message related to the preamble is received through the uplink radio resource. As a result, the TRP may not respond if the preamble is not detected. Accordingly, since the terminal has not received any message from the TRP, it may retry the optional connection. This case is referred to as Case 1.

[0554] In contrast, the TRP can successfully detect the preamble and successfully decode the message from the uplink radio resources associated with the preamble. In this case, the TRP1 can transmit a message including the RAR, C-RNTI, and C4 to the UE via the PDSCH (S4512). Accordingly, the UE can receive a message including the successful RAR, C-RNTI, and C4 from the TRP. This message can serve as an acknowledgement.

[0555] Here, the C4 message can include 4-1 information C4_1 to 4-5 information C4_5. At this time, the 4-1 information may be information indicating whether TRP2 is true or false. Here, if TRP2 is true, it may mean that the TRP using the next best SSB transmitted by the UE is qualified as TRP2.

[0556] The 4-2 information C4_2 may be information indicating whether RA is true or false. RA being true may mean that random access must be performed to the TRP of the next-best SSB. The 4-3 information C4_3 may be information indicating whether CBRA is true or false. Here, CBRA being true may mean that contention-based random access must be performed. The 4-4 information may also include information regarding a CFRA preamble. The CFRA preamble may mean a preamble used when performing non-contention-based random access. Such a CFRA preamble may be a natural number greater than 1. The 4-5 information may also be other information. Such 4-5 information may be any possible information that reduces procedural overhead.

[0557] In this case, TRP1 can generate the 4-1 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 determines that the second-best SSB included in C3 corresponds to the SSB of TRP2 based on the SSB group-related information. As a result, TRP1 can set the 4-1 information to TRUE. TRP1 can also generate the 4-2 information of C4 based on the information in C3 of the step 3 message. In other words, TRP1 can set the RA of the 4-2 information of C4 to TRUE if the time difference between the start point of the best SSB in the 3-3 information of C3 and the start point of the second-best SSB is equal to or greater than a predetermined threshold value. In addition, TRP1 can arbitrarily determine whether to set the CBRA to TRUE.

[0558] In this situation, the assumption that the PCI is the same in the 3-2 information may be true, and the TRP2 in the 4-1 information may be false. In this case, the UE can ignore other message information, do not need to perform an additional random access procedure, and can proceed with the TRP1 and RRC setup step.

[0559] Alternatively, the assumption that the PCIs are the same may be true in the 3-2 information, TRP2 may be true in the 4-1 information, and RA may be false in the 4-2 information. In this case, the terminal does not need to perform an additional random access procedure. The terminal can then adjust the transmission time of TRP2 using the 3-3 information and the 3-4 information, perform power control, and perform the RRC setup step with TRP2, regarding it as being connected to TRP2 that transmitted the next-best SSB.

[0560] Meanwhile, the assumption that the PCIs are...

Claims

1. 1. A method of a terminal, comprising: receiving, from a first transmission and reception point (TRP), a first synchronization signal block (SSB) included in a first SSB group allocated to 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 SSB group and the first TRP and a mapping relationship between a second SSB group and the second TRP; establishing a first communication link between the first TRP and the terminal based on the first SSB; assigning a first tag identifier to the first communication link for distinguishing the communication link according to a mapping relationship between the first SSB group and the first TRP; receiving a second SSB included in the 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 A method for a terminal, comprising: assigning a second tag identifier to the second communication link according to a mapping relationship between the second SSB group and the second TRP.

2. The step of establishing a first communication link between the first TRP and the terminal based on the first SSB includes: acquiring information on a first random access occasion indicated by a first system information block (SIB) acquired based on the first SSB; performing a first random access procedure with the first TRP in the acquired first random access occasion; and The method of claim 1 , further comprising: establishing the first communication link between the first TRP and the terminal according to the first random access procedure.

3. receiving a measurement request from the first TRP; transmitting a measurement report to the first TRP in response to the measurement request, the measurement report including information on the second SSB and information on a time difference between a receiving time of the first SSB and a receiving time of the second SSB; and receiving an instruction to establish the second communication link from the first TRP based on the time difference; 2. The terminal method of claim 1, wherein the second communication link is established based on the second SSB and the establishment instruction.

4. The received setup instruction instructs link setup without performing a random access (RA) procedure if the time difference is less than a threshold value; The method of claim 3, wherein the second communication link is established between the second TRP and the terminal without performing the RA procedure.

5. The received establishment command instructs RACH-based link establishment if the time difference is equal to or greater than a threshold value, establishing a second communication link between the second TRP and the terminal based on the second SSB; acquiring information on a second random access occasion indicated by a second SIB acquired based on the second SSB; performing a second random access procedure using the second TRP in the acquired second random access occasion; and The method of claim 4, further comprising: generating the second communication link between the second TRP and the terminal according to the second random access procedure.

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

7. 2. The method of claim 1, wherein the first tag identifier and the second tag identifier are identical when a time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold value, and the first tag identifier and the second tag identifier are different from each other when a time difference between the reception time of the first SSB and the reception time of the second SSB is equal to or greater than a threshold value.

8. The method of claim 1, wherein the first SSB group and the second SSB group are grouped based on an SSB index or a resource interval of a frame.

9. receiving a first downlink transmission configuration indication (TCI) and first downlink scheduling information associated with the first tag identifier from the first TRP; receiving downlink data from the first TRP based on the first downlink TCI and the first downlink scheduling information; receiving a second downlink TCI and second downlink scheduling information associated with the second tag identifier from the second TRP; and The method of claim 1, further comprising receiving downlink data from the second TRP based on the second downlink TCI and the second downlink scheduling information.

10. receiving a first uplink TCI and first uplink scheduling information associated with the first tag identifier from the 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 associated with the second tag identifier from the second TRP; and The method of claim 1, further comprising transmitting uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information.

11. The method of claim 10, wherein when a time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold value, a transmission time for transmitting uplink data to the first TRP and a transmission time for transmitting uplink data to the second TRP are the same.

12. The method of claim 10, wherein when a 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 value, a difference between a transmission time for transmitting uplink data to the first TRP and a transmission time for transmitting uplink data to the second TRP includes the time difference.

13. 1. A method of a terminal, comprising: receiving, from a first transmission and reception point (TRP), a first synchronization signal block (SSB) included in a first SSB group allocated to the first TRP; receiving a second SSB included in the second SSB group assigned to the second TRP from the second TRP; initiating a first random access procedure with the first TRP based on the first SSB; transmitting information about the second SSB and information about a time difference between a receiving time point of the first SSB and a receiving time point of the second SSB to the first TRP in the first random access procedure; establishing a first communication link between the first TRP and the terminal through the first random access procedure; receiving, from the first TRP, a setting instruction for a second communication link with the second TRP based on the time difference through the first random access procedure; and A method for a terminal, comprising the step of establishing the second TRP and the second communication link according to the received establishment instruction.

14. assigning a first tag identifier to the first communication link for distinguishing the communication link according to a mapping relationship between the first SSB group and the first TRP; and The method of claim 13, further comprising: assigning a second tag identifier to the second communication link according to a mapping relationship between the second SSB group and the second TRP.

15. The received setup instruction instructs link setup without performing a random access (RA) procedure if the time difference is less than a threshold value; The method of claim 13, wherein the second communication link is established between the second TRP and the terminal without performing the RA procedure.

16. The received establishment instruction instructs establishment of a RACH-based link if the time difference is equal to or greater than a threshold value, generating the second TRP and the second communication link according to the received setting instruction; acquiring information on a random access occasion indicated by a second SIB acquired based on the second SSB; performing a second random access procedure with the second TRP in the acquired random access occasion; and The method of claim 13, further comprising establishing the second communication link between the second TRP and the terminal according to the second random access procedure.

17. receiving a first uplink TCI and a first uplink scheduling information from the 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 the second TRP; and transmitting uplink data to the second TRP based on the second uplink TCI and the second uplink scheduling information; 14. The method of claim 13, wherein when a time difference between the reception time of the first SSB and the reception time of the second SSB is less than a threshold value, the transmission time of transmitting uplink data to the first TRP and the transmission time of transmitting uplink data to the second TRP are the same, and when a 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 value, 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, a processor, The processor is configured to: receiving, from a first TRP (transmission and reception point), a first SSB (synchronization signal block) included in a first SSB group allocated to 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 SSB group and the first TRP and a mapping relationship between the second SSB group and the second TRP; generating a first communication link between the first TRP and the terminal based on the first SSB; assigning a first tag identifier to the first communication link for distinguishing the communication link according to a mapping relationship between the first SSB group and the first TRP; receiving a second SSB included in the second SSB group assigned to the second TRP from the second TRP; generating a second communication link between the second TRP and the terminal based on the second SSB; and A terminal operable to cause the second communication link to be assigned a second tag identifier according to a mapping relationship between the second SSB group and the second TRP.

19. The processor is configured to: receiving a measurement request from the first TRP; transmitting a measurement report to the first TRP in response to the measurement request, the measurement report including information on the second SSB and information on a time difference between a reception time of the first SSB and a reception time of the second SSB; and further operable to cause receiving a time to prevent establishment of the second communication link from the first TRP based on the time difference; In the step of establishing a second communication link between the second TRP and the terminal based on the second SSB, the processor 20. The terminal of claim 18, operative to cause the second communication link to be established based on the received establishment indication.

20. The processor is configured to: The received establishment instruction instructs establishment of a RACH-based link if the time difference is equal to or greater than a threshold value; In the step of establishing the second communication link based on the received establishment instruction, the processor Acquiring information on a second random access occasion indicated by a second SIB acquired based on the second SSB; Conducting a second random access procedure using the second TRP in the acquired second random access occasion; and The terminal of claim 19, further comprising establishing the second communication link between the second TRP and the terminal in accordance with the second random access procedure.

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