Method for controlling terminal connection in a communication system

Abstract

This invention provides a method for controlling connections in a communication system according to the operating status of a terminal. [Solution] The terminal operation method includes the steps of receiving configuration information for a two-stage random access (RA) procedure from a base station, transmitting an RA MSG-A including an RA preamble and an RA payload to the base station based on the configuration information, and receiving an RA MSG-B, which is a response to the RA MSG-A, from the base station, wherein the RA-RNTI for the two-stage random access procedure is configured differently from the RA-RNTI for the four-stage random access procedure.

Description

[Technical Field]

[0001] The present invention relates to terminal connection technology in a communication system, and more particularly to connection control technology for competitive and non-competitive bases in a communication system using a high frequency band. [Background technology]

[0002] With the advancement of information and communication technology, a variety of wireless communication technologies have been developed. Representative wireless communication technologies include LTE (Long Term Evolution) and NR (New Radio), which are defined by the 3GPP (Registered Trademark) (3rd Generation Partnership Project) standards. LTE can be one of the wireless communication technologies within 4G (4th Generation) wireless communication technologies, and NR can be one of the wireless communication technologies within 5G (5th Generation) wireless communication technologies.

[0003] To handle the surge in wireless data following the commercialization of 4G communication systems (e.g., systems supporting LTE), 5G communication systems (e.g., systems supporting NR) that utilize not only the frequency bands of 4G communication systems (e.g., frequency bands below 6 GHz) but also higher frequency bands (e.g., frequency bands above 6 GHz) are being considered. 5G communication systems can support eMBB (enhanced Mobile Broadband), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication).

[0004] On the other hand, millimeter frequency bands (e.g., 6-90 GHz frequency bands) may be used to process rapidly increasing data. Small base stations may be used in higher frequency bands (e.g., millimeter frequency bands) due to degradation of received signal performance caused by path attenuation and reflection of radio waves. In communication systems supporting millimeter frequency bands, instead of a small base station supporting all functions of the radio protocol, "multiple remote radio transmit / receive blocks (e.g., RRHs (remote radio heads)) and one centralized baseband processing function block" may be used.

[0005] In other words, all functions of a wireless protocol can be distributed and supported by a functional split method, using a remote wireless transmit / receive block and a baseband processing function block. When the functional split technique is used, a communication system can be composed of multiple transmission and reception points (TRPs). Multiple transmission and reception points can communicate using methods such as carrier aggregation, dual connectivity, and duplication transmission. A method is needed to efficiently perform terminal connection procedures (e.g., random access procedures) in communication systems that support functional split, carrier aggregation, dual connectivity, bi-casting, and duplication transmission. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The objective of the present invention, in order to solve the aforementioned problems, is to provide a method and apparatus for controlling connections in a communication system according to the operating state of a terminal. [Means for solving the problem]

[0007] A terminal operation method according to a first embodiment of the present invention for achieving the above objective includes the steps of: receiving configuration information for a two-stage random access procedure from a base station; transmitting an RA MSG-A including an RA preamble and an RA payload to the base station based on the configuration information; and receiving an RA MSG-B from the base station which is a response to the RA MSG-A, wherein the RA MSG-B includes one or more MAC sub-PDUs, each of the one or more MAC sub-PDUs includes a MAC sub-header, and the MAC sub-header includes a first indicator and / or a second indicator indicating the type of MAC sub-PDU.

[0008] This may further include receiving system information from the base station, which includes information indicating an MCS level for the RA payload, and the RA payload may be transmitted based on the MCS level indicated by the system information.

[0009] Here, the first indicator can indicate that the MAC sub-PDU is a first type-MAC sub-PDU including a BI, a second type-MAC sub-PDU including a fallback RAR, or a third type-MAC sub-PDU including a successful RAR.

[0010] Here, the size of the first indicator may be 2 bits, the first bit of which can indicate the first type-MAC sub-PDU or the second type-MAC sub-PDU, and the second bit of which can indicate the third type-MAC sub-PDU.

[0011] Here, the operation method of the terminal may further include the step of performing the two-step random access procedure or the four-step random access procedure based on the BI included in the RA MSG-B when the first indicator included in the RA MSG-B indicates the first type-MAC sub-PDU.

[0012] Here, when the first indicator included in the RA MSG-B indicates the second type-MAC sub-PDU, the method of operating the terminal may further include transmitting RA MSG3 to the base station by a four-step random access procedure.

[0013] Here, the RA MSG3 may be transmitted using the resources indicated by the UL grant included in the fallback RAR.

[0014] Here, the RA MSG-B including the fallback RAR may be generated based on the format of RA MSG2 of the four-step random access procedure.

[0015] Here, when the first indicator indicates the third type-MAC sub-PDU, the two-step random access procedure may be terminated.

[0016] Here, the size of the second indicator may be 1 bit, and the second indicator may indicate whether there is a fourth type-MAC sub-PDU including a MAC SDU (for example, data or control information).

[0017] Here, when the RA MSG-B is received within the RAR window from the time when the transmission of the RA preamble ends, it may be determined that the contention has been resolved in the two-step random access procedure.

[0018] Here, the MAC sub-header may further include a third indicator indicating whether there are other MAC sub-PDUs.

[0019] The method for operating a base station according to the second embodiment of the present invention for achieving the above object includes a step of transmitting two-step setting information for a two-step random access procedure to a terminal, a step of transmitting four-step setting information for a four-step random access procedure to the terminal, a step of receiving Message 1 from the terminal by performing a monitoring operation using the two-step setting information and the four-step setting information, and a step of transmitting RA MSG-B including one or more MAC sub-PDUs to the terminal when the Message 1 is RA MSG-A of the two-step random access procedure. Each of the one or more MAC sub-PDUs includes a MAC sub-header, and the MAC sub-header includes a first indicator indicating the type of the MAC sub-PDU.

[0020] Here, the method for operating the base station may further include a step of transmitting system information including information indicating an MCS level for the RA payload included in the RA MSG-A to the terminal.

[0021] Here, the first indicator may indicate that the MAC sub-PDU is a first type-MAC sub-PDU including a BI, a second type-MAC sub-PDU including a fallback RAR, or a third type-MAC sub-PDU including a successful RAR.

[0022] Here, when the first indicator included in the RA MSG-B indicates the second type-MAC sub-PDU, the method for operating the base station may further include a step of receiving RA MSG3 by the four-step random access procedure from the terminal through the resource indicated by the UL grant included in the fallback RAR.

[0023] Here, the RA MSG-B including the fallback RAR may be generated based on the format of RA MSG2 of the four-step random access procedure.

[0024] Here, if the RA MSG-B is received by the terminal within the RAR window from the end of transmission of the RA preamble, and the first indicator contained in the RA MSG-B indicates the third type-MAC sub-PDU, the two-stage random access procedure may be terminated.

[0025] Here, one of the one or more MAC sub-PDUs may include a MAC SDU containing control information or data, and the RNTI for the one MAC sub-PDU containing the MAC SDU may be set independently of the RNTI for the other MAC sub-PDUs containing the BI, the fallback RAR, or the successful RAR.

[0026] Here, the MAC subheader may further include a third indicator that indicates whether other MAC subPDUs are present.

[0027] A terminal operation method according to a third embodiment of the present invention for achieving the above objective includes the steps of: receiving configuration information for a two-stage random access procedure from a base station; transmitting an RA MSG-A including an RA preamble and an RA payload to the base station based on the configuration information; determining an RA-RNTI using the information of the transmitted radio resource and a pre-set offset in the RA preamble; receiving a DCI including resource allocation information for an RA MSG-B from the base station by performing a PDCCH monitoring operation using the RN-RNTI; and receiving the RA MSG-B from the base station through the resource indicated by the resource allocation information included in the DCI.

[0028] Here, the RA-RNTI for the two-stage random access procedure may be set differently from the RA-RNTI for the four-stage random access procedure.

[0029] Here, the RA-RNTI can be determined by applying the preset offset to the RA-RNTI for a four-step random access procedure.

[0030] Here, the pre-set offset can be received from the base station.

[0031] Here, the PDCCH monitoring operation can be performed within the RAR window.

[0032] In this case, if the two-stage random access procedure is performed using the CFRA method, the configuration information may include transmission resource information of the RA MSG-A allocated exclusively for the terminal.

[0033] A base station operation method according to a fourth embodiment of the present invention for achieving the above objective includes the steps of: transmitting configuration information for a two-stage random access procedure to a terminal; receiving an RA MSG-A including an RA preamble and an RA payload from the terminal by performing a monitoring operation using the configuration information; determining an RA-RNTI for transmitting and receiving an RA MSG-B using the radio resource information and a pre-set offset of the RA preamble; performing a scrambling operation on a DCI including resource allocation information for the RA MSG-B using the RN-RNTI; transmitting the scrambled DCI to the terminal; and transmitting the RA MSG-B to the terminal using the resources indicated by the resource allocation information included in the DCI.

[0034] Here, the RA-RNTI for RA MSG-B transmission and reception can be determined by applying the preset offset to the RA-RNTI for the four-stage random access procedure.

[0035] Here, the operation method of the base station may further include the step of transmitting the pre-set offset to the terminal.

[0036] Here, the scrambled DCI can be transmitted to the terminal within the RAR window.

[0037] In this case, if the two-stage random access procedure is performed using the CFRA method, the configuration information may include transmission resource information of the RA MSG-A allocated exclusively for the terminal. [Effects of the Invention]

[0038] According to the present invention, the communication system can support both two-stage random access procedures and four-stage random access procedures. A terminal can perform a two-stage random access procedure if it satisfies the first execution condition, and can perform a four-stage random access procedure if it satisfies the second execution condition. The RA (random access) MSG-A of the two-stage random access procedure and the RA MSG1 of the four-stage random access procedure can be distinguished based on the RA preamble index or the transmission resource.

[0039] The RA-RNTI (radio network temporary identifier) ​​used for sending and receiving RA MSG-B in a two-stage random access procedure may be configured differently from the RA-RNTI used for sending and receiving RA MSG2 in a four-stage random access procedure. A terminal can use the RA-RNTI to receive RA MSG-B or RA MSG2 from a base station. The MAC (medium access control) subheader of the RA MSG-B may include an indicator that identifies the type of RA MSG-B. The terminal can determine the type of RA MSG-B based on this indicator. Therefore, random access procedures can be performed more efficiently, and the performance of the communication system can be improved. [Brief explanation of the drawing]

[0040] [Figure 1] Conceptual diagram illustrating the first embodiment of the communication system. [Figure 2] Block diagram illustrating the first embodiment of a communication node constituting a communication system. [Figure 3]Conceptual diagram illustrating a second embodiment of the communication system. [Figure 4] Conceptual diagram illustrating the first embodiment of an integrated communication system. [Figure 5] Conceptual diagram illustrating a second embodiment of the integrated communication system. [Figure 6] A conceptual diagram illustrating the first embodiment of a communication method for a beamforming substrate in a communication system. [Figure 7] A conceptual diagram illustrating the first embodiment of a method for setting the bandwidth portion (BWP) in a communication system. [Figure 8] Conceptual diagram illustrating the first embodiment of the terminal's operating state in a communication system. [Figure 9] A flowchart illustrating the first embodiment of a random access procedure in a communication system. [Figure 10] A flowchart illustrating a second embodiment of random access procedures in a communication system. [Figure 11] A conceptual diagram illustrating the first embodiment of a method for transmitting RA MSG-A in a communication system. [Figure 12a] Conceptual diagram illustrating the first embodiment of the MAC subheader in a random access procedure. [Figure 12b] Conceptual diagram illustrating a second embodiment of the MAC subheader in a random access procedure. [Figure 12c] Conceptual diagram illustrating the first embodiment of RA MSG-B using a random access procedure. [Figure 12d] Conceptual diagram illustrating the second embodiment of RA MSG-B using a random access procedure. [Figure 12e] Conceptual diagram illustrating the third embodiment of RA MSG-B using a random access procedure. [Figure 12f] Conceptual diagram illustrating the fourth embodiment of RA MSG-B using a random access procedure. [Figure 13a] Conceptual diagram illustrating the fifth embodiment of RA MSG-B using a random access procedure. [Figure 13b] Conceptual diagram illustrating the sixth embodiment of RA MSG-B using a random access procedure. [Figure 13c]Conceptual diagram illustrating the seventh embodiment of RA MSG-B using a random access procedure. [Figure 14a] Conceptual diagram illustrating the eighth embodiment of RA MSG-B using a random access procedure. [Figure 14b] Conceptual diagram illustrating the ninth embodiment of RA MSG-B using a random access procedure. [Figure 14c] Conceptual diagram illustrating the 10th embodiment of RA MSG-B using a random access procedure. [Figure 15] Timing diagram illustrating a third embodiment of random access procedures in a communication system. [Figure 16a] Conceptual diagram illustrating a third embodiment of the MAC subheader in a random access procedure. [Figure 16b] Conceptual diagram illustrating the fourth embodiment of the MAC subheader in a random access procedure. [Figure 16c] Conceptual diagram illustrating the 11th embodiment of RA MSG-B using a random access procedure. [Figure 16d] Conceptual diagram illustrating the 12th embodiment of RA MSG-B using a random access procedure. [Figure 16e] Conceptual diagram illustrating the 13th embodiment of RA MSG-B using a random access procedure. [Figure 16f] Conceptual diagram illustrating the 14th embodiment of RA MSG-B using a random access procedure. [Figure 16g] Conceptual diagram illustrating the 15th embodiment of RA MSG-B using a random access procedure. [Figure 17a] Conceptual diagram illustrating the fifth embodiment of the MAC subheader in a random access procedure. [Figure 17b] Conceptual diagram illustrating the sixth embodiment of the MAC subheader in a random access procedure. [Figure 17c] Conceptual diagram illustrating the seventh embodiment of the MAC subheader in a random access procedure. [Figure 17d] Conceptual diagram illustrating the eighth example of a MAC subheader in a random access procedure. [Figure 17e]Conceptual diagram illustrating the ninth example of a MAC subheader in a random access procedure. [Figure 17f] Conceptual diagram illustrating the 16th embodiment of RA MSG-B using a random access procedure. [Figure 17g] Conceptual diagram illustrating the 17th embodiment of RA MSG-B using a random access procedure. [Figure 18] A flowchart illustrating a third embodiment of a random access procedure in a communication system. [Modes for carrying out the invention]

[0041] While the present invention can be modified in various ways and has a variety of embodiments, specific embodiments will be illustrated and described in detail with reference to the drawings. However, this should not be understood as limiting the present invention to specific embodiments, but rather as including all modifications, equivalents, or substitutes that fall within the spirit and technical scope of the present invention.

[0042] The terms "first," "second," etc., may be used to describe a variety of components, but the components should not be limited by these terms. The terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The terms "and / or" include a combination of multiple related described items or any of the multiple related described items.

[0043] When it is mentioned that one component is "linked" or "connected" to another component, it should be understood that it may be directly linked or connected to the other component, or that other components may exist in between. Conversely, when it is mentioned that one component is "directly linked" or "directly connected" to another component, it should be understood that there are no other components in between.

[0044] The terminology used in this application is used solely to describe specific embodiments and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “includes” or “having” are intended to specify the existence of features, figures, stages, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preemptively exclude the possibility of the existence or addition of one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0045] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not as ideal or overly formal unless expressly defined herein.

[0046] Preferred embodiments of the present invention will be described in more detail below with reference to the attached drawings. In this description of the present invention, the same reference numerals are used for the same components in the drawings to aid overall understanding, and redundant descriptions of the same components are omitted.

[0047] A communication system to which an embodiment of the present invention is applied is described below. The communication system to which an embodiment of the present invention is applied is not limited to the one described below, and the embodiment of the present invention can be applied to a variety of communication systems. Here, "communication system" may be used interchangeably with "communication network."

[0048] Figure 1 is a conceptual diagram illustrating a first embodiment of the communication system.

[0049] Referring to Figure 1, the communication system 100 can 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. Multiple communication nodes can support 4G communication (e.g., LTE (Long Term Evolution), LTE-A (Advanced)), 5G communication (e.g., NR (New Radio)), etc., as defined by 3GPP (3rd Generation Partnership Project) standards. 4G communication can be performed in frequency bands below 6 GHz, while 5G communication can be performed not only in frequency bands below 6 GHz but also in frequency bands above 6 GHz.

[0050] For example, for 4G and 5G communication, multiple communication nodes use communication protocols based on CDMA (code division multiple access), WCDMA (wideband CDMA), TDMA (time division multiple access), FDMA (frequency division multiple access), OFDM (orthogonal frequency division multiplexing), Filtered OFDM, CP (cyclic prefix)-OFDM, DFT-s-OFDM (discrete Fourier transform-spread-OFDM), OFDMA (orthogonal frequency division multiple access), SC (single carrier)-FDMA, NOMA (Non-orthogonal Multiple Access), GFDM (generalized frequency division multiplexing), FBMC (filter bank multi-carrier), and UFMC (universal filtered It can support multi-carrier-based communication protocols, SDMA (Space Division Multiple Access)-based communication protocols, and more.

[0051] Furthermore, the communication system 100 may also include a core network. If the communication system 100 supports 4G communication, the core network may include an S-GW (serving gateway), a P-GW (packet data network gateway), an MME (mobility management entity), etc. If the communication system 100 supports 5G communication, the core network may include a UPF (user plane function), an SMF (session management function), an AMF (access and mobility management function), etc.

[0052] On the other hand, each of the multiple communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 that constitute the communication system 100 can have the following structure.

[0053] Figure 2 is a block diagram illustrating a first embodiment of a communication node constituting a communication system.

[0054] Referring to Figure 2, the communication node 200 may include at least one processor 210, memory 220, and a transceiver 230 connected to the network to perform communication. The communication node 200 may also further include an input interface device 240, an output interface device 250, a storage device 260, etc. Each component included in the communication node 200 is connected by a bus 270 to communicate with one another.

[0055] However, each component included in the communication node 200 may be connected via individual interfaces or individual buses centered around the processor 210, rather than via the common bus 270. For example, the processor 210 may be connected via a dedicated interface to at least one of the following: memory 220, transceiver 230, input interface device 240, output interface device 250, and storage device 260.

[0056] 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 mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which the method according to an embodiment of the present invention is performed. The memory 220 and the storage device 260 may each consist of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may consist of at least one of a read-only memory (ROM) and a random access memory (RAM).

[0057] Referring again to Figure 1, the communication system 100 may include multiple base stations 110-1, 110-2, 110-3, 120-1, 120-2, and multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6. The communication system 100, including the base stations 110-1, 110-2, 110-3, 120-1, 120-2, and terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6, may be referred to as an "access network". The first base station 110-1, the second base station 110-2, and the third base station 110-3 can each form a macro cell. The fourth base station 120-1 and the fifth base station 120-2 can each form a small cell. The cell coverage of the first base station 110-1 may include the fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4. The cell coverage of the second base station 110-2 may include the second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5. The cell coverage of the third base station 110-3 may include the fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6. The cell coverage of the fourth base station 120-1 may include the first terminal 130-1. The cell coverage of the fifth base station 120-2 may include the sixth terminal 130-6.

[0058] Here, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can be referred to as Node B, evolved Node B, BTS (base transceiver station), radio base station, radio transceiver, access point, access node, RSU (roadside unit), RRH (radio remote head), TP (transmission point), TRP (transmission and reception unit), eNB, gNB, etc.

[0059] Each of the multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 can be referred to as UE (user equipment), terminal, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, IoT (Internet of Things) device, mounted module / device / terminal or onboard device / terminal, etc.

[0060] On the other hand, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can operate in different frequency bands or in the same frequency band. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can be connected via an ideal backhaul link or a non-ideal backhaul link, and can exchange information via the ideal backhaul link or the non-ideal backhaul link. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can be connected to the core network via an ideal backhaul link or the non-ideal backhaul link. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can transmit signals received from the core network to the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6, and can transmit signals received from the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 to the core network.

[0061] Furthermore, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support MIMO transmission (e.g., SU (single user)-MIMO, MU (multi-user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, CA (carrier aggregation) transmission, transmission in unlicensed band, direct device-to-device communication (D2D) (or ProSe (proximity services)), etc. Here, each of the multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 can perform operations corresponding to base stations 110-1, 110-2, 110-3, 120-1, and 120-2, as well as operations supported by base stations 110-1, 110-2, 110-3, 120-1, and 120-2. For example, the second base station 110-2 can transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method, and the fourth terminal 130-4 can receive a signal from the second base station 110-2 using the SU-MIMO method. Alternatively, the second base station 110-2 can transmit signals to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, and the fourth terminal 130-4 and the fifth terminal 130-5 can each receive signals from the second base station 110-2 using the MU-MIMO scheme.

[0062] Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 can transmit signals to the fourth terminal 130-4 based on the CoMP method, and the fourth terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 based on the CoMP method. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can send and receive signals with terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 belonging to their own cell coverage based on the CA method. The first base station 110-1, the second base station 110-2, and the third base station 110-3 can each control D2D between the fourth terminal 130-4 and the fifth terminal 130-5, and the fourth terminal 130-4 and the fifth terminal 130-5 can each perform D2D under the control of the second base station 110-2 and the third base station 110-3, respectively.

[0063] Next, the method for configuring and managing the wireless interface in the communication system is described. Within the communication nodes, if a method performed by a first communication node (e.g., signal transmission or reception) is described, the corresponding second communication node can perform a method corresponding to that performed by the first communication node (e.g., signal reception or transmission). That is, if the operation of a terminal is described, the corresponding base station can perform an operation corresponding to that of the terminal. Conversely, if the operation of a base station is described, the corresponding terminal can perform an operation corresponding to that of the base station.

[0064] On the other hand, in a communication system, a base station can perform all functions of the communication protocol (e.g., remote radio transmission and reception function, baseband processing function). Alternatively, the remote radio transmission and reception function among all functions of the communication protocol may be performed by a TRP (transmission reception point) (e.g., f(flexible)-TRP), and the baseband processing function among all functions of the communication protocol may be performed by a BBU (baseband unit) block. A TRP may be an RRH (remote radio head), RU (radio unit), TP (transmission point), etc. A BBU block may contain at least one BBU or at least one DU (digital unit). A BBU block may be referred to as a "BBU pool," "centralized BBU," etc. A TRP may be connected to a BBU block via a wired fronthaul link or a wireless fronthaul link. A communication system consisting of backhaul links and fronthaul links may be as follows: When the function split technique of the communication protocol is applied, the TRP can selectively perform some of the functions of the BBU or some of the functions of MAC (medium access control) / RLC (radio link control).

[0065] Figure 3 is a conceptual diagram illustrating a second embodiment of the communication system.

[0066] Referring to Figure 3, the communication system can include a core network and an access network. The core network supporting 4G communication can include MME, S-GW, P-GW, etc. The core network supporting 5G communication can include AMF310-1, UPF310-2, PDN-GW310-3, etc. The access network can include macro base stations 320, small base stations 330, TRP350-1, 350-2, terminals 360-1, 360-2, 360-3, 360-4, 360-5, etc. The macro base station 320 or small base station 330 can be connected to the termination nodes of the core network via wired backhaul. TRP350-1 and 350-2 can support remote radio transmission and reception functions among all functions of the communication protocol, and the baseband processing function for TRP350-1 and 350-2 can be performed in the BBU block 340. The BBU block 340 can belong to either the access network or the core network. Communication nodes belonging to the communication system (e.g., MME, S-GW, P-GW, AMF, UPF, PDN-GW, macro base station, small base station, TRP, terminal, BBU block) may be identical or similarly configured to the communication node 200 shown in Figure 2.

[0067] The macro base station 320 can be connected to the core network (e.g., AMF310-1, UPF310-2, MME, S-GW) using a wired or wireless backhaul link and can provide communication services to terminals 360-3 and 360-4 based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol). The small base station 330 can be connected to the core network (e.g., AMF310-1, UPF310-2, MME, S-GW) using a wired or wireless backhaul link and can provide communication services to a fifth terminal 360-5 based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol).

[0068] The BBU block 340 can be located on the AMF310-1, UPF310-2, MME, S-GW, or macro base station 320. Alternatively, the BBU block 340 can be located independently of each of the AMF310-1, UPF310-2, MME, S-GW, and macro base station 320. For example, the BBU block 340 may consist of a logical function block between the macro base station 320 and the AMF310-1 (or UPF310-2). The BBU block 340 can support multiple TRP350-1, 350-2 units and can be connected to each of the multiple TRP350-1, 350-2 units using wired or wireless fronthaul links. That is, the links between the BBU block 340 and the TRP350-1, 350-2 units may be referred to as "fronthaul links".

[0069] The first TRP 350-1 may be connected to the BBU block 340 via a wired or wireless fronthaul link and can provide communication services to the first terminal 360-1 based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol). The second TRP 350-2 may be connected to the BBU block 340 via a wired or wireless fronthaul link and can provide communication services to the second terminal 360-2 based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol).

[0070] In the embodiments described below, a communication system including an access network, an xHaul network, and a core network may be referred to as an "integration communication system." Communication nodes belonging to the integrated communication system (e.g., MME, S-GW, P-GW, AMF, UPF, BBU block, DU (distributed unit), CU (central unit), base station, TRP, terminal, etc.) may be identical or similarly configured to communication node 200 shown in Figure 2. Communication nodes belonging to the xHaul network may be connected using xHaul links, which may be backhaul links or fronthaul links.

[0071] Furthermore, in an integrated communication system, the UPF (or S-GW) may refer to a terminal communication node of the core network that exchanges packets (e.g., control information, data) with base stations, and the AMF (or MME) of an integrated communication system may refer to a communication node of the core network that performs control functions in the radio connection section (or interface) of a terminal. Here, backhaul link, fronthaul link, xHaul link, DU, CU, BBU block, S-GW, MME, AMF, and UPF may each be referred to by different terms depending on the function of the communication protocol by RAT (radio access technology) (e.g., the function of the xHaul network, the function of the core network).

[0072] Figure 4 is a conceptual diagram illustrating the first embodiment of the integrated communication system.

[0073] Referring to Figure 4, the integrated communication system can include an access network, an xHaul network, and a core network. The xHaul network can be located between the access network and the core network and can support communication between the access network and the core network. Communication nodes belonging to the integrated communication system can be identical or similar to communication node 200 shown in Figure 2. The access network can include TRP430, terminal 440, etc. The xHaul network can include multiple communication nodes 420-1, 420-2, 420-3. Communication nodes constituting the xHaul network can be referred to as "DU" or "CU". In the xHaul network, DU420-1, 420-2 and CU420-3 can be connected using a wireless xHaul link and can be connected based on a multi-hop scheme. The core network can include UPF / AMF410-1 (or S-GW / MME), PDN-GW410-2, etc. UPF / AMF410-1 may refer to a communication node including UPF and AMF, and S-GW / MME may refer to a communication node including S-GW and MME. BBU block 450 may be located in UPF / AMF410-1 and may be connected to CU420-3 via a wired link.

[0074] The first DU420-1 in the xHaul network may be connected to the TRP430 using a wired link, or the first DU420-1 may be configured to be integrated into the TRP430. The second DU420-2 may be connected to the first DU420-1 and CU420-3 respectively using a wireless link (e.g., a wireless xHaul link), and the CU420-3 may be connected to the core network's terminal communication node (e.g., UPF / AMF410-1) using a wired link. The CU420-3 connected to the core network's terminal communication node in the xHaul network may be referred to as an "aggregator". The aggregator's function may be performed by the UPF / AMF410-1.

[0075] Communication between DU420-1, 420-2 and CU420-3 can be carried out using access protocols (for example, communication protocols used for communication between terminal 440 and TRP430 (or macro base stations, small base stations)) and other communication protocols for xHaul links (hereinafter referred to as "xHaul protocols"). Packets to which the xHaul protocol is applied can be transmitted through the xHaul link to the core network and the access network, respectively. Here, packets can indicate control information, data, etc.

[0076] The TRP430 can provide communication services to the terminal 440 using an access protocol (e.g., 4G communication protocol, 5G communication protocol) and can be connected to the first DU420-1 via a wired link. The TRP430 can support the remote radio transmission and reception function among all the functions of the communication protocol, and the baseband processing function for the TRP430 can be performed by the BBU block 450. The link between the TRP430 performing the remote radio transmission and reception function and the BBU block 450 performing the baseband processing function (e.g., the link "TRP430-first DU420-1-second DU420-2-CU420-3-BBU block 450 (or UPF / AMF410-1)") may be referred to as the "fronthaul link". For example, the fronthaul link may be configured differently depending on the location of the BBU block 450 performing the baseband processing function.

[0077] Figure 5 is a conceptual diagram illustrating a second embodiment of the integrated communication system.

[0078] Referring to Figure 5, the integrated communication system can include an access network, an xHaul network, and a core network. The xHaul network can be located between the access network and the core network and can support communication between the access network and the core network. Communication nodes belonging to the integrated communication system can be identical or similar to communication node 200 shown in Figure 2. The access network can include macro base stations 530, small base stations 540, TRP 550, terminals 560-1, 560-2, 560-3, etc. The xHaul network can include multiple communication nodes 520-1, 520-2, 520-3, 520-4, 520-5, 520-6. Communication nodes constituting the xHaul network can be referred to as "DU" or "CU". In the xHaul network, DU 520-1, 520-2, 520-3, 520-4, 520-5 and CU 520-6 can be connected using a wireless xHaul link and can be connected based on a multi-hop scheme. BBU block 570 can be located in one of CU / DU520-1, 520-2, 520-3, 520-4, 520-5, or 520-6. For example, BBU block 570 can be located in DU520-5. The core network may include UPF / AMF510-1 (or S-GW / MME), PDN-GW510-2, etc. UPF / AMF510-1 may refer to a communication node including UPF and AMF, and S-GW / MME may refer to a communication node including S-GW and MME.

[0079] The first DU520-1 of the xHaul network may be connected to or configured to be integrated with the macro base station 530 using a wired link. The second DU520-2 of the xHaul network may be connected to or configured to be integrated with the small base station 540 using a wired link. The fourth DU520-4 of the xHaul network may be connected to or configured to be integrated with the TRP550 using a wired link.

[0080] CU520-6 in an xHaul network can be connected to a core network termination communication node (e.g., UPF / AMF510-1) using a wired link. CU520-6 connected to a core network termination communication node may be referred to as an "aggregator". Communication between CU / DU520-1, 520-2, 520-3, 520-4, 520-5, and 520-6 can be performed using the xHaul protocol. Packets to which the xHaul protocol is applied (e.g., data, control information) can be transmitted to the core network and access network, respectively, via the xHaul link.

[0081] Macro base station 530 can provide communication services to first terminal 560-1 using an access protocol (e.g., 4G communication protocol, 5G communication protocol) and can be connected to first DU 520-1 using a wired link. Macro base station 530 can be connected to the core network via the xHaul network, and the link "macro base station 530 - first DU 520-1 - CU 520-6 - UPF / AMF 510-1" may be referred to as a "backhaul link". Small base station 540 can provide communication services to second terminal 560-2 using an access protocol (e.g., 4G communication protocol, 5G communication protocol) and can be connected to second DU 520-2 using a wired link. Small base station 540 can be connected to the core network via the xHaul network, and the link "small base station 540 - second DU 520-2 - third DU 520-3 - CU 520-6 - UPF / AMF 510-1" may be referred to as a "backhaul link".

[0082] The TRP550 can provide communication services to a third terminal 560-3 using an access protocol (e.g., 4G communication protocol, 5G communication protocol) and can be connected to a fourth DU520-4 using a wired link. The TRP550 can support remote radio transmission and reception functions among all the functions of the communication protocol, and the baseband processing function for the TRP550 can be performed by the BBU block 570. The link between the TRP550 performing the remote radio transmission and reception function and the BBU block 570 performing the baseband processing function (e.g., the link "TRP550-fourth DU520-4-BBU block 570 (or fifth DU520-5)") may be referred to as the "fronthaul link", and the link between the BBU block 570 and the UPF / AMF510-1 (e.g., the link "BBU block 570 (or fifth DU520-5)-CU520-6-UPF / AMF510-1") may be referred to as the "backhaul link". For example, the front haul link may be configured differently depending on the location of the BBU block 570, which performs the baseband processing function.

[0083] On the other hand, referring to Figures 4 and 5, when the functional separation technique is applied, CU420-3, 520-6 and DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, 520-5 can perform different functions from each other. CU420-3 and 520-6 may be gNB-CUs in an NR communication system, while DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, 520-5 may be gNB-DUs in an NR communication system. CU420-3 and 520-6 can control the operation of one or more DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, and 520-5, and may be logical nodes that perform RRC (radio resource control), SDAP (service data adaptation protocol), and / or PDCP (packet data convergence protocol) functions. DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, and 520-5 may be logical nodes that perform RLC (radio link control), MAC (medium access control), and / or PHY (physical) functions (e.g., some PHY functions).

[0084] A single DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, or 520-5 can support one or more cells, and a single cell can support one DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, or 520-5. The operation of DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, or 520-5 (for example, some operations) can be controlled by CU420-3 or 520-6, and communication between DU420-1, 420-2, 520-1, 520-2, 520-3, 520-4, or 520-5 and CU420-3 or 520-6 can be performed through the F1 interface.

[0085] Depending on the node configuration, role, and / or attributes for functional isolation, DU420-2, 520-3, and 520-5 may be present in the connection section between DU420-1, 520-1, 520-2, and 520-4 and CU420-3, 520-6 for relay purposes. In this case, relay links may be formed between DU420-1, 520-1, 520-2, and 520-4 and DU420-2, 520-3, and 520-5. DU420-1 and 520-4 may be connected wirelessly or wired to TRP430 and 550. DU520-1 and 520-2 may be configured in conjunction with base stations 530 and 540.

[0086] Figure 6 is a conceptual diagram illustrating a first embodiment of a beamforming-based communication method in a communication system.

[0087] Referring to Figure 6, the communication system may include base stations 611, 612, 613, terminals 621, 622, etc., and communication nodes belonging to the communication system (e.g., base stations, terminals) can perform communication using beamforming. For example, base stations 611, 612, and 613 can perform communication using multiple beams (e.g., beams #1 to #4), and terminals 621 and 622 can perform communication using multiple beams (e.g., beams #1 to #4).

[0088] The operating state of the first terminal 621 may be one in which connection settings with the first base station 611 have been completed. For example, the operating state of the first terminal 621 may be either an RRC (radio resource control) connected state or an RRC inactive state. Alternatively, the first terminal 621 can operate in an RRC idle state within the service area of ​​the first base station 611. The operating state of the second terminal 622 may be one in which connection settings with the second base station 612 or the third base station 613 have been completed. For example, the operating state of the second terminal 622 may be either an RRC connected state or an RRC inactive state. Alternatively, the second terminal 622 can operate in an RRC idle state within the service area of ​​the second base station 612 or the third base station 613.

[0089] Base stations 611, 612, and 613 can support mobility functions, thereby ensuring the mobility of terminals 621 and 622 between base stations 611, 612, and 613. Signals received from terminals 621 and 622 may be used to select the optimal beam within base stations 611, 612, and 613.

[0090] A beam pair (e.g., transmit beam (beam #3) - receive beam (beam #2)) may be established between the first base station 611 and the first terminal 621, and communication services may be provided using the beam pair. Here, the receive beam may be the receiving direction of the first terminal 621. The beam pair may be reconfigured due to changes in the quality of the radio channel between the first base station 611 and the first terminal 621. For example, the transmit beam of the first base station 611 may be changed from beam #3 to beam #2 or beam #4, and the receive beam (e.g., the receiving direction) of the first terminal 621 may be changed from beam #2 to beam #1, beam #3, or beam #4.

[0091] Furthermore, a beam pair may be established between the second base station 612 and the second terminal 622, and communication services may be provided using the beam pair. Due to changes in the quality of the radio channel between the second base station 612 and the second terminal 622 and / or the movement of the second terminal 622, the second terminal 622 may be connected to the third base station 613 by performing a handover procedure, and a beam pair may be established between the third base station 613 and the second terminal 622. That is, in order to change the beam pair, the mobility support function and radio resource management function of the handover procedure infrastructure may be performed.

[0092] To perform mobility support and radio resource management functions, base stations can transmit synchronization signals (e.g., SS / PBCH (synchronization signal / physical broadcast channel) blocks) and / or reference signals. To support multiple numerologies, frame formats that support symbols of different lengths may be configured. In this case, terminals can perform monitoring operations for synchronization signals and / or reference signals in frames with initial numerology, default numerology, or default symbol lengths. Initial numerology and default numerology may be applied to frame formats applied to radio resources where a UE (common search space) is configured, to frame formats applied to radio resources where CORESET (control resource set) #0 of the NR communication system is configured, and / or to frame formats applied to radio resources where a synchronization symbol burst that can identify a cell in the NR communication system is transmitted.

[0093] The frame format may represent a radio frame (or subframe) containing information about the subcarrier spacing, control channel (e.g., CORESET), symbol, slot, and / or configuration parameters for a reference signal (e.g., configuration parameter values, offset, index, identifier, range, period, interval, duration). The base station may notify the terminal of the frame format using system information and / or control messages (e.g., dedicated control messages).

[0094] A terminal connected to a base station can transmit a reference signal (e.g., an uplink-only reference signal) to the base station using resources configured by the base station. For example, an uplink-only reference signal may include an SRS (sounding reference signal). A terminal connected to a base station can also receive a reference signal (e.g., a downlink-only reference signal) from the base station using resources configured by the base station. A downlink-only reference signal may be a CSI-RS (channel state information-reference signal), PT-RS (phase tracking-reference signal), DM-RS (demodulation-reference signal), etc. Both the base station and the terminal can perform beam management operations through monitoring of the configured beam or active beam based on the reference signal.

[0095] For example, the first base station 611 can transmit synchronization signals and / or reference signals so that the first terminal 621 located within the communication service area can find itself and perform downlink synchronization maintenance, beam setting, or link monitoring operations. The first terminal 621 connected to the first base station 611 (e.g., a service base station) can receive physical-level radio resource configuration information from the first base station 611 for connection configuration and radio resource management. The physical-level radio resource configuration information may be configuration parameters included in RRC control messages in LTE and / or NR communication systems. For example, wireless resource configuration information may include PhysicalConfigDedicated, PhysicalCellGroupConfig, PDCCH-Config(Common), PDSCH-Config(Common), PDCCH-ConfigSIB1, ConfigCommon, PUCCH-Config(Common), PUSCH-Config(Common), BWP-DownlinkCommon, BWP-UplinkCommon, ControlResourceSet, RACH-ConfigCommon, RACH-ConfigDedicated, RadioResourceConfigCommon, RadioResourceConfigDedicated, ServingCellConfig, ServingCellConfigCommon, etc.

[0096] Radio resource configuration information can include parameter values ​​such as the configuration period (or allocation period) of signals (or radio resources) in the frame format of the base station (or transmission frequency), time resource allocation information for transmission, frequency resource allocation information for transmission, and transmission timing (or allocation timing). To support multiplexing numerology, the frame format of the base station (or transmission frequency) may mean a frame format in which multiple subcarrier intervals within a single radio frame result in different symbol lengths. For example, within a single radio frame (e.g., a frame with a length of 10 ms), the number of symbols constituting each minislot, slot, and subframe may differ from one another.

[0097] [Base station transmission frequency and frame format settings information] Transmission frequency setting information: All transmission carriers of the base station (e.g., cell-level transmission frequencies), bandwidth part (BWP), and transmission reference time or time difference information between base station transmission frequencies (e.g., transmission period or offset parameter indicating the transmission reference time (or time difference) of the synchronization signal), etc. Frame format configuration information: Configuration parameters for minislots, slots, and subframes, where the symbol lengths differ from each other due to the subcarrier interval.

[0098] [Setting information for downlink reference signals (e.g., CSI-RS, common RS, etc.)] Common RS configuration information includes setting parameters such as the transmission period, transmission location, code sequence, and masking sequence (or scrambling sequence) of the reference signal that are commonly applied to the coverage of base stations (or beams).

[0099] [Uplink control signal settings information] SRS, reference signals for uplink beam sweeping (or beam monitoring), radio resources (or preambles) for uplink grant-free operation, etc.

[0100] [Setting information for the downlink control channel (e.g., PDCCH (physical downlink control channel))] Reference signals for PDCCH demodulation, beam common reference signals (e.g., reference signals that can be received by all terminals in the beam coverage), reference signals for beam sweeping (or beam monitoring), reference signals for channel estimation, etc.

[0101] [Configuration information for the uplink control channel (e.g., PUCCH (physical uplink control channel))]

[0102] [Setting information for scheduling request signals]

[0103] [Configuration information for transmission resources used in feedback (e.g., ACK (acknowledgement) or NACK (negative ACK)) via HARQ (hybrid automatic repeat request) procedures]

[0104] [Number of antenna ports, information on antenna arrangement, beam configuration and / or beam index mapping information for beamforming application]

[0105] [Configuration information for downlink and / or uplink signals (or uplink access channel resources) for beam sweeping (or beam monitoring)]

[0106] [Setting information such as beam setting operation, beam recovery operation, beam reconfiguration operation, radio link re-establishment operation, beam change operation at the same base station, beam reception signal that triggers the handover procedure to another base station, and control timers for the aforementioned operations.]

[0107] In a wireless frame format that supports different symbol lengths to support multiple numerology, the setting period (or allocation period), time resource allocation information, frequency resource allocation information, transmission timing, and / or allocation timing of the parameters constituting the aforementioned information may be information set according to the corresponding symbol length (or subcarrier interval).

[0108] In the following embodiment, “Resource-Config information” may be a control message containing one or more parameters of the radio resource configuration information at the physical layer. “Resource-Config information” may also refer to the attributes and / or settings (or ranges) of the information element (or parameter) transmitted by the control message. The information element (or parameter) transmitted by the control message may be radio resource configuration information that applies commonly across the entire base station (or beam) coverage, or radio resource configuration information that is dedicated to a specific terminal (or group of terminals).

[0109] The configuration information contained in "Resource-Config information" may be transmitted through a single control message or through different control messages based on the attributes of the configuration information. Beam index information may not be expressed in a way that clearly distinguishes between the transmit beam index and the receive beam index. For example, beam index information may be expressed using the corresponding beam index and an associated reference signal or an index (or identifier) ​​of the TCI (transmission configuration indicator) state for beam management.

[0110] Therefore, a first terminal 621 operating in an RRC-coupled state can receive communication services through a beam (e.g., a beam pair) configured between the first terminal 621 and the first base station 611. For example, if communication services are provided using beam #3 of the first base station 611 and beam #2 of the first terminal 621, the first terminal 621 can perform radio channel discovery or monitoring operations using synchronization signals and / or reference signals transmitted through beam #3 of the first base station 611. Here, "communication services being provided through a beam" may mean "packets being sent and received through an activated beam among one or more configured beams." In an NR communication system, "a beam being activated" may mean "a configured TCI state being activated."

[0111] Terminal 621 can operate in RRC paused or RRC inactive state. In this case, terminal 621 can perform downlink channel discovery operations (e.g., monitoring operations) using parameters obtained from system information or common Resource-Config information. Alternatively, terminal 621 operating in RRC paused or RRC inactive state can attempt to establish a connection using an uplink channel (e.g., a random access channel or a physical hierarchical uplink control channel). Or, terminal 621 can transmit control information using an uplink channel.

[0112] Terminal 621 can sense or detect a radio link problem by performing RLM (radio link monitoring) operations. Here, "detection of a radio link problem" may mean "an abnormality in the synchronization setting or maintenance of the physical layer for the radio link." For example, "detection of a radio link problem" may mean "detection that the physical layer synchronization between base station 611 and terminal 621 has not been synchronized for a predetermined period of time." If a radio link problem is detected, the terminal can perform radio link recovery operations. If the radio link cannot be recovered, the terminal can declare RLF (radio link failure) and perform radio link re-establishment procedures.

[0113] Procedures for detecting physical layer problems in a wireless link, recovering a wireless link, detecting (or declaring) a wireless link failure, and re-establishing a wireless link by RLM operations can be performed by the functions of layer 1 (e.g., physical layer), layer 2 (e.g., MAC layer, RLC layer, PDCP layer, etc.), and / or layer 3 (e.g., RRC layer) of the wireless protocol that constitutes the wireless link.

[0114] The physical layer of a terminal can monitor the radio link by receiving downlink synchronization signals (e.g., PSS (primary synchronization signal), SSS (secondary synchronization signal), SS / PBCH block) and / or reference signals. In this case, the reference signal may be a common base station reference signal, a beam common reference signal, or a terminal (or terminal group) specific reference signal (e.g., a dedicated reference signal assigned to a terminal (or terminal group)). Here, the common reference signal may be used for channel estimation operations for all terminals located within the coverage (or service area) of the base station or beam in question. The dedicated reference signal may be used for channel estimation operations for a specific terminal or a specific group of terminals within the coverage of the base station or beam.

[0115] Therefore, if the base station or beam (e.g., the configured beam between the base station and the terminal) is changed, the dedicated reference signal for beam management may be changed. The beam may be changed based on the configured parameters between the base station and the terminal. A procedure for changing the configured beam may be required. "A beam being changed in an NR communication system" may mean "the index (or identifier) ​​of a TCI state being changed to the index of another TCI state," "a new TCI state being configured," or "a TCI state being changed to an activated state." The base station may transmit system information, including configuration information for the common reference signal, to the terminal. The terminal may obtain the common reference signal based on the system information. In a handover procedure, a synchronous reconfiguration procedure, or a concatenation reconfiguration procedure, the base station may transmit a dedicated control message, including configuration information for the common reference signal, to the terminal.

[0116] To provide service continuity between base stations and terminals, methods can be considered in which a base station allocates multiple beams to a single terminal to provide service. For example, in the embodiment illustrated in Figure 6, base stations 611, 612, and 613 can allocate multiple beams to terminals 621 and 622. Base station 611 can allocate beams #2 to #4 to terminal 621. Base station 612 can allocate beams #3 and #4 to terminal 622. The procedure for allocating multiple beams can be carried out taking into account the terminal's speed, direction of movement, location information, radio channel quality, and / or beam interference. For example, if terminal 621 is moving slowly, base station 611 can allocate consecutive beams #2 and #3 to terminal 621. If terminal 621 is moving fast, base station 611 can allocate non-consecutive beams #2 and #4 to terminal 621.

[0117] Base station 612 can allocate beams #3 and #4 to terminal 622 and provide service to terminal 622 using beams #3 and #4. In this case, terminal 622 can move from base station 612's coverage to base station 613's coverage. If base station 612's cell (or sector) is different from base station 613's cell (or sector), terminal 622 can perform a handover procedure. In the handover procedure, base station 612 can transmit a handover (or mobility) control message to terminal 622 that includes base station 613's beam configuration information (e.g., configuration information for beams #1 and #2). Terminal 622 can receive base station 613's beam configuration information from base station 612.

[0118] Beam configuration information may include the indices of the transmit and / or receive beams set by the results of beam monitoring or beam measurement operations, configuration information for each beam (e.g., transmit power, beamwidth, vertical angle, horizontal angle, etc.), transmit and / or receive timing information for each beam (e.g., subframe index, slot index, mini-slot index, symbol index, offset), and configuration information for the reference signal of each beam (e.g., sequence, index). To allocate multiple beams, control messages containing configuration information for multiple beams, terminal movement status information (e.g., movement speed, direction of movement, position information, etc.), and beam monitoring (or measurement) results may be sent and received between base stations 612, 613 and terminal 622. Here, the control message may be a control signaling message for performing a handover.

[0119] Base station 612 can allocate beams #3 and #4 to terminal 622 and provide services to terminal 622 using beams #3 and #4. In this case, terminal 622 can move from base station 612's coverage to base station 613's coverage. If the cell (or sector) of base station 612 is the same as the cell (or sector) of base station 613, a transmission node change procedure can be performed intra-cell. In this case, base stations 612 and 613 may be transmission nodes with functional isolation applied (e.g., RRH, TRP). For example, base stations 612 and 613 may support the functions of some layers within the physical layer (i.e., PHY layer), MAC layer, RLC layer, PDCP layer, adaptation layer, and RRC layer, where the adaptation layer may be a higher layer than the PDCP layer. The adaptive layer can perform mapping functions between QoS flows and data radio bearers (DRBs) and / or marking functions for QoS flow identifiers on downlink (or uplink) packets.

[0120] If base stations 612 and 613, which belong to the same cell, support the functions of some layers of the radio protocol layer excluding the RRC layer, terminal 622 can perform the change procedure from base station 612 to base station 613 by exchanging MAC layer control messages (e.g., MAC CE (control element) or control PDU (protocol data unit)) without exchanging RRC layer control messages.

[0121] The layer responsible for generating, transmitting, and receiving control messages for base station changes may be determined by the layers included in base stations 612 and 613. For example, if base stations 612 and 613 include "from the physical layer to the MAC layer" or "from the physical layer to the RLC layer," then control messages for base station changes may be generated, transmitted, and received by layers higher than the MAC layer (or RLC layer). The MAC function (or MAC function and RLC function) of base stations 612 and 613 and terminal 622 may be reset and then newly configured.

[0122] If base stations 612 and 613 support only some functions of the MAC layer, or if base stations 612 and 613 support only functions of the physical layer, control messages for base station changes may be generated / transmitted / received by the MAC layer. The base station change procedure can be performed without resetting the MAC functions of base stations 612 and 613 and terminal 622.

[0123] In the base station change procedure, information for classifying base stations can be transmitted to terminal 622 using RRC hierarchical control messages, MAC hierarchical control messages, or physical hierarchical control channels, depending on the hierarchical level included in base stations 612 and 613. In this embodiment, RRC hierarchical control messages may be referred to as "RRC control messages" or "RRC messages," MAC hierarchical control messages may be referred to as "MAC control messages" or "MAC messages," and physical hierarchical control channels may be referred to as "PHY control channels," "PHY control messages," or "PHY messages."

[0124] Here, the information for distinguishing base stations may include one or more of the following: base station identifier, reference signal information, reference symbol information, configured beam information, and configured TCI status information. The reference signal information (or reference symbol information) may include configuration information for reference signals assigned to each base station (e.g., radio resources, sequence, index) and / or configuration information for dedicated reference signals assigned to terminals (e.g., radio resources, sequence, index).

[0125] Here, the radio resource information of the reference signal may include time-domain resource information (e.g., frame index, subframe index, slot index, symbol index) and frequency-domain resource information (e.g., parameters indicating the relative or absolute position of subcarriers). Parameters indicating the radio resources of the reference signal may include the RE (resource element) index, resource set index, RB (resource block) index, subcarrier index, etc. The RB index may be the PRB (physical resource block) index or the CRB (common resource block) index.

[0126] In the following embodiment, the reference signal information may include the transmission period information, sequence information (e.g., code sequence), masking information (e.g., scrambling information), radio resource information, and / or index information of the reference signal. The reference signal identifier may mean a parameter (e.g., resource ID, resource set ID) used to distinguish each of multiple reference signal information. The reference signal information may mean the configuration information of the reference signal.

[0127] The configured beam information may include one or more of the following: configured beam index (or identifier), configured TCI status index (or identifier), configured information for each beam (e.g., transmit power, beam width, vertical angle, horizontal angle), transmit and / or receive timing information for each beam (e.g., subframe index, slot index, minislot index, symbol index, offset), reference signal information corresponding to each beam, and reference signal identifier.

[0128] In the embodiment, the base station may be an airborne base station. For example, the base station may be installed on an unmanned aerial vehicle (e.g., a drone), a manned aerial vehicle, or a satellite.

[0129] The terminal can receive base station configuration information (e.g., base station identification information) from the base station through one or more of the following: RRC messages, MAC messages, and PHY messages. Based on this configuration information, the terminal can identify the base station that will perform beam monitoring operations, radio access operations, and / or control (or data) packet transmission and reception operations.

[0130] When multiple beams are configured, communication between the base station and the terminal can be carried out using multiple beams. In this case, the number of downlink beams may be the same as the number of uplink beams, or the number of downlink beams may be different from the number of uplink beams. For example, there may be two or more downlink beams and one uplink beam.

[0131] When multiple beams are configured, communication between the base station and the terminal may be carried out using some of the beams, with the remaining beams being configured as reserve or candidate beams. For example, control information and data may not be transmitted through the reserve and / or candidate beams. Multiple beams can be classified as primary beams, secondary beams, and reserve (or candidate) beams. In an NR communication system, "configuring multiple beams" may mean "dividing and configuring the configured TCI status IDs into primary TCI status IDs, secondary TCI status IDs, and reserve TCI status IDs."

[0132] For example, a primary beam (e.g., a beam relating to a primary TCI status ID) may mean a beam capable of transmitting and receiving data and control information. A secondary beam (e.g., a beam relating to a secondary TCI status ID or a beam relating to a deactivated TCI status ID) may mean a beam capable of transmitting and receiving data excluding control information. "Exclusion of control information" may mean "control signaling is restricted by the physical layer, layer 2 (e.g., MAC layer, RLC layer, PDCP layer), and / or layer 3 (e.g., RRC layer) on a layer-by-layer basis," "control signaling is partially restricted by the functionality of the physical layer, layer 2, and / or layer 3," or "control signaling is restricted by the type of control message."

[0133] Control messages (e.g., RRC messages, MAC messages, PHY messages) may be used for discontinuous transmission / reception operations (e.g., DRX (discontinue reception) operations, DTX (discontinue transmission) operations), retransmission operations, coupling / setting / management operations, measurement / reporting operations, paging operations, and / or connection operations.

[0134] The reserve (or candidate) beam (e.g., the beam for the reserve TCI state ID or the beam for the deactivated TCI state ID) does not have to be used for sending and receiving data and / or control information. The reserve (or candidate) beam may be used for beam monitoring and measurement / reporting operations for beam matching (or configuration) at the base station and / or terminal.

[0135] Therefore, measurement results for a backup (or candidate) beam may be reported through the primary or secondary beam. Measurement / reporting operations for a backup (or candidate) beam may be performed based on pre-set parameters, or they may be performed based on terminal decisions or event conditions. Measurement / reporting operations for a backup (or candidate) beam may be performed periodically or aperiodicly.

[0136] The results of measurement operations on a backup (or candidate) beam (e.g., beam monitoring operations) may be reported via a physical hierarchical control channel (e.g., PUCCH) and / or MAC messages (e.g., MAC CE, control PDU). Here, the results of a beam monitoring operation may be measurement results for one or more beams (or beam groups). For example, the results of a beam monitoring operation may be measurement results for a beam (or beam group) due to a base station's beam sweeping operation.

[0137] The base station can obtain the results of beam measurement or beam monitoring operations from the terminal and modify the beam attributes or TCI state attributes based on the results of the beam measurement or beam monitoring operations. Beams can be classified by attribute into primary beam, secondary beam, reserve (or candidate) beam, active beam, and inactive beam. TCI states can be classified by attribute into primary TCI state, secondary TCI state, reserve (or candidate) TCI state, serving TCI state, configured TCI state, active TCI state, and inactive TCI state. Primary TCI states and secondary TCI states can be assumed to be active TCI states and serving TCI states, respectively. Reserve (or candidate) TCI states can be assumed to be inactive TCI states or configured TCI states.

[0138] The procedure for changing beam (or TCI status) attributes may be controlled by the RRC hierarchy and / or MAC hierarchy. When the procedure for changing beam (or TCI status) attributes is controlled by the MAC hierarchy, the MAC hierarchy can notify higher hierarchies of information regarding the change in beam (or TCI status) attributes. Information regarding the change in beam (or TCI status) attributes may be transmitted to the terminal via MAC messages and / or physical hierarchical control channels (e.g., PDCCH). Information regarding the change in beam (or TCI status) attributes may be included in DCI (downlink control information) or UCI (uplink control information). Information regarding the change in beam (or TCI status) attributes may be expressed in separate indicators or fields.

[0139] A terminal can request a change in the TCI status attribute based on the results of a beam measurement or beam monitoring operation. The terminal can transmit control information (or feedback information) requesting a change in the TCI status attribute to the base station using one or more of the PHY message, MAC message, and RRC message. The control information (or feedback information, control message, control channel) requesting a change in the TCI status attribute may be composed of one or more of the aforementioned configured beam information.

[0140] A change in beam (or TCI state) attribute can mean "change from active beam to inactive beam," "change from inactive beam to active beam," "change from primary beam to secondary beam," "change from secondary beam to primary beam," "change from primary beam to reserve (or candidate) beam," or "change from reserve (or candidate) beam to primary beam." The beam (or TCI state) attribute change procedure may be controlled by the RRC hierarchy and / or MAC hierarchy. The beam (or TCI state) attribute change procedure may be carried out through partial cooperation between the RRC hierarchy and the MAC hierarchy.

[0141] If multiple beams are allocated, one or more of these beams may be configured to transmit a physical hierarchical control channel. For example, the primary beam and / or secondary beam may be used for sending and receiving physical hierarchical control channels (e.g., PHY messages), where the physical hierarchical control channel may be a PDCCH or a PUCCH. The physical hierarchical control channel may be used for transmitting one or more of the following: scheduling information (e.g., radio resource allocation information, MCS (modulation and coding scheme) information), feedback information (e.g., CQI (channel quality indication), PMI (precoding matrix indicator), HARQ ACK, HARQ NACK), resource request information (e.g., SR (scheduling request)), results of beam monitoring operations to support beamforming functionality, TCI status ID, and measurement information for active (or inactive) beams.

[0142] A physical hierarchical control channel may be configured to transmit to the downlink primary beam. In this case, feedback information may be transmitted and received through the primary beam, and data scheduled by the control information may be transmitted and received through the secondary beam. A physical hierarchical control channel may be configured to transmit to the uplink primary beam. In this case, resource request information (e.g., SR) and / or feedback information may be transmitted and received through the primary beam.

[0143] In a procedure for allocating multiple beams (or setting the TCI state), information indicating the allocated (or set) beam index, the spacing between beams, and / or whether consecutive beams are allocated may be transmitted and received through a signaling procedure between the base station and the terminal. The signaling procedure for beam allocation information may be performed differently depending on the terminal's status information (e.g., speed, direction of movement, location information) and / or the quality of the radio channel. The base station may obtain the terminal's status information from the terminal, or the base station may obtain the terminal's status information through other means.

[0144] Radio resource information may include parameters that indicate frequency domain resources (e.g., center frequency, system bandwidth, PRB index, number of PBRs, CRB index, number of CRBs, subcarrier index, frequency offset) and time domain resources (e.g., radio frame index, subframe index, TTI (transmission time interval), slot index, minislot index, symbol index, time offset, transmission (or reception) period, length, window). Furthermore, radio resource information may include information for the hopping pattern of radio resources, beamforming (e.g., beam shaping) operation (e.g., beam configuration information, beam index), and resource information occupied by the characteristics of the code sequence (or bit sequence, signal sequence).

[0145] The names of physical hierarchical channels and / or transport channels may vary depending on the type (or attributes) of data, the type (or attributes) of control information, the transmission direction (e.g., uplink, downlink, sidelink), etc.

[0146] Reference signals for beam (or TCI status) or radio link management may include synchronization signals (e.g., PSS, SSS, SS / PBCH block), CSI-RS, PT-RS, SRS, DM-RS, etc. Reference parameters for the received quality of the reference signals for beam (or TCI status) or radio link management may include measurement time units, measurement time intervals, reference values ​​indicating the degree of improvement in received quality, reference values ​​indicating the degree of deterioration in received quality, etc. Each measurement time unit and measurement time interval may be set in absolute time (e.g., millisecond, second), TTI, symbol, slot, frame, subframe, scheduling period, base station operating period, or terminal operating period units.

[0147] Reference values ​​indicating the degree of change in reception quality can be set as absolute values ​​(dBm) or relative values ​​(dB). Furthermore, the reception quality of a reference signal for beam (or TCI status) or radio link management can be expressed using metrics such as RSRP (reference signal received power), RSRQ (reference signal received quality), RSSI (received signal strength indicator), SNR (signal-to-noise ratio), and SIR (signal-to-interference ratio).

[0148] On the other hand, in NR communication systems using millimeter frequency bands, flexibility in the operation of channel bandwidth for packet transmission can be ensured based on the BWP (bandwidth part) concept. A base station can configure up to four BWPs with different bandwidths at a terminal. BWPs can be configured independently for downlink and uplink. That is, downlink BWPs can be distinguished from uplink BWPs. Each BWP can have not only different bandwidths but also different subcarrier spacings. For example, BWPs can be configured as follows:

[0149] Figure 7 is a conceptual diagram illustrating a first embodiment of a method for setting the bandwidth portion (BWP) in a communication system.

[0150] Referring to Figure 7, multiple bandwidth segments (BWP#1-4) can be configured within the base station's system bandwidth. BWP#1-4 can be configured so as not to exceed the base station's system bandwidth. The bandwidths of BWP#1-4 can differ from each other, and different subcarrier spacings can be applied to BWP#1-4. For example, BWP#1 may have a bandwidth of 10 MHz and a subcarrier spacing of 15 kHz. BWP#2 may have a bandwidth of 40 MHz and a subcarrier spacing of 15 kHz. BWP#3 may have a bandwidth of 10 MHz and a subcarrier spacing of 30 kHz. BWP#4 may have a bandwidth of 20 MHz and a subcarrier spacing of 60 kHz.

[0151] BWPs can be classified into initial BWPs (e.g., first BWP), active BWPs (e.g., active BWP), and default BWPs. A terminal can perform initial connection procedures (e.g., access procedures) with a base station using the initial BWP. One or more BWPs may be configured by an RRC coupling configuration message, and one of these BWPs may be configured as the active BWP. Both the terminal and the base station can send and receive packets using the active BWP among the configured BWPs. Therefore, a terminal can perform monitoring operations on the control channel for packet transmission and reception using the active BWP.

[0152] A terminal can change its operating BWP from the initial BWP to the active BWP or the default BWP. Alternatively, a terminal can change its operating BWP from the active BWP to the initial BWP or the default BWP. The BWP change operation may be performed based on instructions from the base station or a timer. The base station may transmit information instructing a BWP change to the terminal using one or more of the following: RRC messages, MAC messages (e.g., MAC CE (control element)), and PHY messages (e.g., DCI). The terminal can receive information instructing a BWP change from the base station and change its operating BWP to the BWP instructed by the received information.

[0153] In an NR communication system, if no random access (RA) resource is configured in the active uplink (UL) BWP, the terminal can change its operational BWP from the active UL BWP to the initial UL BWP in order to perform random access procedures. The operational BWP may be the BWP on which the terminal performs communication (e.g., sending and receiving signals and / or channels).

[0154] Measurement operations (e.g., monitoring operations) for beam (or TCI status) or radio link management can be performed at the base station and / or terminal. The base station and / or terminal can perform measurement operations (e.g., monitoring operations) using parameters set for the measurement operations. The terminal can report measurement results using setting parameters for measurement reporting.

[0155] If the measured quality of the reference signal meets a preset threshold and / or preset timer conditions, the base station can decide whether to perform a beam (or radio link) management operation, a beam switching operation, or a beam deactivation operation (or beam activation operation) due to beam blockage conditions. If it is determined that a particular operation should be performed, the base station can transmit a message to the terminal that triggers the performance of that operation. For example, the base station can transmit a control message to the terminal instructing the performance of a particular operation. The control message may include configuration information for the particular operation.

[0156] If the reception quality of the reference signal based on the measurement results conforms to a preset reference value and / or preset timer conditions, the terminal can report the measurement results to the base station. Alternatively, the terminal can transmit a control message to the base station that triggers beam (or radio link) management operations, beam switching operations (or TCI status ID change operations, attribute change operations), or beam deactivation operations (or beam activation operations) based on beam blocking conditions. The control message may request the performance of a specific operation.

[0157] Basic procedures for beam (or TCI status) management through wireless link monitoring may include beam failure detection (BFD) procedures and beam recovery (BR) request procedures for the wireless link. Each of the following can be performed: "an action to determine whether to perform the beam failure detection procedure and / or beam recovery request procedure," "an action to trigger the performance of the beam failure detection procedure and / or beam recovery request procedure," and "a control signaling action for the beam failure detection procedure and / or beam recovery request procedure." These actions can be performed by one or more of the PHY hierarchy, MAC hierarchy, and RRC hierarchy.

[0158] The procedure by which a terminal connects to a base station (e.g., a random access procedure) can be classified into initial connection procedures and non-initial connection procedures. A terminal operating in the RRC dormant state can perform an initial connection procedure. Alternatively, if there is no context information managed by the base station, a terminal operating in the RRC connected state can perform an initial connection procedure. Context information may include RRC context information, AS (access stratum) configuration information (e.g., AR context information), etc. Context information may include one or more of the following: RRC configuration information for the terminal, encryption (security) configuration information, PDCP information including ROHC (robust header compression) status, identifiers (e.g., C-RNTI (cell-radio resource temporary identifier)), and identifiers of base stations with which connection configuration with the terminal has been completed.

[0159] Non-initial connection procedures may refer to connection procedures performed by the terminal in addition to the initial connection procedures. For example, non-initial connection procedures may be performed by the terminal for data arrival, resume, resource allocation requests, user (UE) requests for infrastructure information transmission, link reset requests after radio link failure (RLF), mobility function (e.g., handover function) support, addition / modification of secondary cells, addition / modification of active beams, or connection requests for physical layer synchronization settings.

[0160] Random access procedures can be performed based on either an initial connection procedure or a non-initial connection procedure, depending on the operating state of the terminal.

[0161] Figure 8 is a conceptual diagram illustrating the first embodiment of the operating state of a terminal in a communication system.

[0162] Referring to Figure 8, the operating states of a terminal can be classified into RRC connected state, RRC inactive state, and RRC dormant state. When a terminal is operating in the RRC connected state or RRC inactive state, the RAN (radio access network) (e.g., the RAN control function block) and the base station can store / manage the RRC connected setting information and / or context information (e.g., RRC context information, AS context information) of the terminal.

[0163] A terminal operating in RRC-connected mode can receive configuration information for the physical hierarchical control channel and / or reference signal necessary for maintaining the connection setting and transmitting / receiving data from the base station. The reference signal may be a reference signal for demodulating data, or it may be a reference signal for channel quality measurement or beamforming. Therefore, a terminal operating in RRC-connected mode can transmit and receive data without delay.

[0164] When a terminal operates in an RRC inactive state, mobility management functions / operations identical or similar to those supported in an RRC dormant state may be supported for that terminal. That is, when a terminal operates in an RRC inactive state, a data bearer for sending and receiving data does not need to be configured, and MAC hierarchy functions may be deactivated. Therefore, a terminal operating in an RRC inactive state can transition its operating state from an RRC inactive state to an RRC connected state by performing a non-initial connection procedure to transmit data. Alternatively, a terminal operating in an RRC inactive state can transmit data of limited size, data with limited quality of service, and / or data related to limited services.

[0165] When a terminal operates in RRC dormant state, a connection setting between the terminal and the base station is not required, and the terminal's RRC connection setting information and / or context information (e.g., RRC context information, AS context information) does not need to be stored in the RAN (e.g., the RAN's control function block) and the base station. To transition the terminal's operating state from RRC dormant state to RRC connected state, the terminal can perform an initial connection procedure. Alternatively, if the initial connection procedure is performed, the terminal's operating state may transition from RRC dormant state to RRC inactive state at the base station's discretion.

[0166] A terminal can transition from the RRC paused state to the RRC inactive state by performing an initial connection procedure or a separate connection procedure defined for the RRC inactive state. If a terminal is provided with restricted services, the terminal's operational state can transition from the RRC paused state to the RRC inactive state. Alternatively, the terminal's operational state can transition from the RRC paused state to the RRC inactive state due to its capabilities.

[0167] The base station and / or RAN control function block can set conditions for transitioning to the RRC inactive state, taking into account one or more of the terminal type, capabilities, and services (e.g., services currently provided, services to be provided), and can control the transition operation to the RRC inactive state based on the set conditions. If the base station allows the transition operation to the RRC inactive state or if it is configured to be transitionable to the RRC inactive state, the terminal's operating state may transition from the RRC connected state or RRC idle state to the RRC inactive state.

[0168] Figure 9 is a flowchart illustrating the first embodiment of a random access procedure in a communication system.

[0169] Referring to Figure 9, the communication system may include base stations, terminals, etc. The base stations may be base stations 110-1, 110-2, 110-3, 120-1, and 120-2 as shown in Figure 1, and the terminals may be terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 as shown in Figure 1. The base stations and terminals may be identical or similarly configured to the communication nodes shown in Figure 2. The random access procedure may be performed in four stages.

[0170] A base station can transmit system information and / or control messages to a terminal, including configuration information for radio resources (e.g., uplink radio resources) for random access procedures (S901). The terminal can obtain the configuration information for radio resources for random access procedures by receiving the system information and / or control messages from the base station. The system information may be common system information used by multiple base stations or base station-specific system information (e.g., cell-specific system information). The control messages may be dedicated control messages.

[0171] System information may be configured per base station, per beam group, or per beam. System information may include allocation information for radio resources (e.g., uplink radio resources) for random access procedures. Configuration information for radio resources for random access procedures may include one or more of the following: physical layer transmission frequency information, system bandwidth information (or BWP configuration information), subcarrier spacing information, beam configuration information by beamforming techniques (e.g., beamwidth, beam index), variable configuration information for radio resources in the frequency and / or time domains (e.g., reference value, offset of radio resources), and inactive (or unused) radio resource area / section information.

[0172] A terminal can transmit RA MSG1, which includes an RA preamble, to the base station using radio resources configured by the base station (for example, PRACH (physical random access channel) (S902). In a four-step random access procedure, message 1, which includes an RA preamble, may be referred to as "RA MSG1," and in a four-step random access procedure, the RA preamble may be referred to as "four-step RA preamble."

[0173] A terminal can randomly select a defined code sequence (e.g., RA preamble, signature) for a random access procedure and transmit an RA MSG1 containing the selected code sequence. In contention-based random access (CBRA) procedures, a terminal can randomly select an RA preamble. In contention-free random access (CFRA) procedures, a base station can pre-assign an RA preamble to a terminal. "Pre-assignment of an RA preamble" may mean "the index, masking information, etc. of the RA preamble for RA MSG1 are allocated exclusively for the terminal." In this case, the terminal can perform a random access procedure (e.g., a CFRA procedure) without competition with other terminals.

[0174] The base station can receive RA MSG1 from the terminal. The base station can generate RA MSG2 as a response to RA MSG1 and transmit RA MSG2 to the terminal (S903). In a four-step random access procedure, RA MSG2 can mean message 2, RAR (random access response), or RA response message. In step S902, the base station can determine the information required by the terminal based on the received RA MSG1 or the radio resource from which RA MSG1 was received. In this case, the base station can transmit the required information to the terminal in step S903.

[0175] "Confirming the necessary information at the terminal" may mean confirming, based on the information received in step S901 (e.g., preamble index, specific signal sequence for uplink resource request (e.g., sequence, signature), specific field value of the uplink control channel), that it is a "terminal request (on-demand) for the transmission of system information," a "terminal firmware or required software update for the transmission of downlink data," or an "uplink resource allocation request."

[0176] In this case, uplink radio resource allocation information may be transmitted in step S903. Alternatively, RA MSG2 may be transmitted via PDCCH or PDSCH (physical downlink shared channel).

[0177] In step S903, the base station may transmit only the PDCCH (e.g., DCI) without the RA response message (e.g., RA MSG2) transmitted through the PDSCH. In this case, the DCI may include one or more of the following: uplink resource allocation information (e.g., scheduling information), transmission timing adjustment information (e.g., TA (timing advance) value, TA command), transmission power adjustment information, backoff information, beam setting information, TCI status information, CS (Configured scheduled) status information, state transition information, PUCCH setting information, the index of RA MSG1 received in step S902 (e.g., the index of the RA preamble), and uplink resource allocation information for the transmission of RA MSG3 in step S904.

[0178] Here, beam setting information may be information that instructs the activation or deactivation of a specific beam. TCI status information may be information that instructs the activation or deactivation of a specific TCI state. CS status information may be information that instructs the activation or deactivation of radio resources allocated by the CS method. State transition information may be information that instructs the transition of the operating state of the terminal shown in Figure 8. State transition information can instruct a transition from a specific operating state to an RRC pause state, an RRC connected state, or an RRC inactive state. Alternatively, state transition information can instruct to maintain the current operating state. PUCCH setting information may be allocation information for SR (scheduling request) resources. Alternatively, PUCCH setting information may be information that instructs the activation or deactivation of SR resources.

[0179] If the base station transmits only a PDCCH (e.g., DCI) without an RA MSG2 in stage S903, the terminal can recognize that there is no RA MSG2 to be transmitted via the PDSCH by using the control information contained in the PDCCH, the DCI format contained in the PDCCH, and / or the scheduling identifier used for the transmission of the PDCCH. The base station can transmit the scheduling information of the RA MSG2 to the terminal using RA (random access)-RNTI. For example, the CRC (cyclic redundancy check) of a DCI containing the scheduling information of the RA MSG2 may be scrambled by RA-RNTI, and the DCI may be transmitted via the PDCCH. Alternatively, the base station can transmit the RA MSG2 using C (cell)-RNTI. The base station can transmit the RA MSG2 via the PDSCH indicated by the scheduling information addressed by the scheduling identifier (e.g., RA-RNTI, C-RNTI). The terminal can receive the RA MSG2 from the base station. The terminal can transmit an RA MSG3 (i.e., message 3) containing its own information to the base station (S904). The terminal information may include one or more of the following: terminal identifier, capability, attributes, mobile status, location information, reason for wireless connection, uplink data size information (e.g., BSR (buffer status report)), connection setting request information, and uplink data. Also in step S904, the terminal can transmit information to the base station requesting information that it needs.

[0180] Furthermore, the terminal can transmit one or more of the following information using RA MSG3: beam failure recovery request information, BWP change request information, BWP deactivation / activation request information, measurement result information to the base station (or cell) in a CA (carrier aggregation) environment, and CA activation / deactivation request information. Here, the beam failure recovery request information can request the execution of a beam recovery procedure based on beam measurement results when a random access procedure for beam recovery is performed after detection of a beam failure. In this case, the terminal can transmit beam-specific measurement result information and / or TCI status information for a new beam setting to the base station.

[0181] Each "BWP change request information" or "BWP deactivation / activation request information" may include one or more of the following: "active BWP change request information based on measurement results for the BWP," "measurement result information for the inactive BWP," and "active BWP information preferred by the terminal." Additionally, the RA MSG3 may include one or more of the following: BWP identifier, base station (or cell) identifier, and configured beam information (e.g., TCI status, CSI-RS index, SS / PBCH index that can identify the beam). The RA MSG3 may be transmitted in the form of a MAC CE or RRC message.

[0182] If RA MSG2 is received in step S903 based on PDCCH (or DCI), the terminal can perform actions based on the information elements contained in PDCCH (or DCI). The information elements contained in PDCCH (or DCI) may include one or more of the following: "information requesting a transition in the terminal's operating state," "information requesting the maintenance of the terminal's operating state," "information instructing the activation or deactivation of the beam," "information instructing the activation or deactivation of the TCI state," and "information instructing the activation or deactivation of the CS state." In this case, the random access procedure may be terminated without performing step S904.

[0183] If RA MSG2 is received in step S903 based on PDCCH (or DCI) and no uplink radio resources have been allocated for RA MSG3, the terminal may wait until it receives information about the allocation of uplink radio resources for RA MSG3. If the allocation information for uplink radio resources for RA MSG3 is received before the pre-set timer expires, the terminal can use the uplink radio resources to transmit RA MSG3 to the base station. Conversely, if the allocation information for uplink radio resources for RA MSG3 is not received by the time the pre-set timer expires, the terminal can perform the random access procedure again. That is, the terminal can start again from step S902.

[0184] In step S905, the base station can transmit downlink information requested by the terminal. Alternatively, the base station can transmit downlink data or control messages to the terminal. In step S905, the base station can transmit the terminal identifier received from the terminal (for example, the terminal identifier received in step S904) to the terminal. The message 4 transmitted by the base station in step S905 may be referred to as "RA MSG4".

[0185] A base station can transmit resource allocation information (e.g., scheduling information) for the transmission of RA MSG3 to a terminal using RA MSG2. The scheduling information may include one or more of the following: an identifier for the base station transmitting the scheduling information, a beam index, a segment numerator for segmenting the scheduling information, radio resource allocation information, MCS information, and resource allocation information for transmitting feedback information (e.g., ACK, NACK) indicating whether the scheduling information has been received. The radio resource allocation information may include frequency domain resource allocation information (e.g., transmission bandwidth information, subcarrier allocation information) and / or time domain resource allocation information (e.g., frame index, subframe index, slot index, symbol index, transmission interval, transmission timing).

[0186] In the random access procedure illustrated in Figure 9, RA MSG3 may contain one or more of the following information elements.

[0187] - Terminal identifier (ID) - Device capabilities, attributes, mobility state, and location information - Reasons for attempting a connection procedure (e.g., a random access procedure) - Uplink data and / or size information of the uplink data (e.g., LI (length indicator)) - Uplink buffer size information (e.g., BSR) - Control message for linking setting request - Wireless channel measurement results - Uplink resource allocation information - Handover request information or measurement result information - Request information for transition (or change) of the terminal's operating state - Wireless channel restart (resume) information - Wireless channel re-establishment information - Information regarding beam sweeping, beam reconfiguration, or beam modification for beamforming. - Information regarding physical channel synchronization acquisition - Location information update - Movement status or buffer status report

[0188] The reasons for attempting a connection procedure may be "a request for transmission of system information at the terminal's request," "a request for downlink data transmission due to an update of terminal firmware or required software," or "a request for allocation of uplink resources." Information indicating the reason for attempting a connection procedure may be information that distinguishes the reason for performing the connection procedure.

[0189] If the RA MSG3 contains the aforementioned information elements, the control fields indicating whether the information elements are included, the attributes of the data (or control information), and the length may consist of a MAC header, a logical channel identifier (e.g., LCID (logical channel identifier)), or MAC CE format.

[0190] Figure 10 is a flowchart illustrating a second embodiment of a random access procedure in a communication system.

[0191] Referring to Figure 10, the communication system may include base stations, terminals, etc. The base stations may be base stations 110-1, 110-2, 110-3, 120-1, and 120-2 shown in Figure 1, and the terminals may be terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 shown in Figure 1. The base stations and terminals may be identical or similarly configured to the communication nodes shown in Figure 2. The random access procedure may be performed in two stages.

[0192] The base station can transmit system information and / or control messages to a terminal, including configuration information for radio resources (e.g., uplink resources) for random access procedures (S1001). The terminal can obtain the configuration information for radio resources for random access procedures by receiving the system information and / or control messages from the base station. Here, the control messages may be dedicated control messages. The system information and / or dedicated control messages may be identical or similar to the system information and / or dedicated control messages in step S901 shown in Figure 9.

[0193] The terminal can transmit RA MSG-A to the base station using radio resources configured by the base station (S1002). RA MSG-A may include an RA preamble and a terminal identifier (e.g., UE ID, C-RNTI). RA MSG-A may also further include uplink data and / or control information. In a two-step random access procedure, message 1 may be referred to as "RA MSG-A," and RA MSG-A may be distinguished from RA MSG1 in a four-step random access procedure.

[0194] An RA MSG-A can contain an RA preamble and an RA payload. In a two-step random access procedure, the RA preamble may be referred to as a "two-step RA preamble," and the RA payload may be referred to as a "two-step RA payload." The RA preamble of an RA MSG-A may be selected by the terminal's MAC hierarchy. The RA payload of an RA-MSG-A may be generated by the MAC hierarchy or the RRC hierarchy. The RA preamble selected from the terminal's MAC hierarchy and the RA payload generated by the terminal's MAC hierarchy or RRC hierarchy may be transmitted to the physical hierarchy. The RA payload of an RA MSG-A may contain one or more of the following: terminal identifier (e.g., UE ID, C-RNTI), uplink data, and control information.

[0195] The control information may include one or more of the following: BSR, measurement result information (e.g., quality information), BFR request information, RLF report information, RRC connection setup request information, RRC connection re-establishment request information, resume request information, terminal location information (e.g., GPS signal, positioning measurement method, or location estimated by built-in sensors, etc.), and system information transmission request information. If a CBRA procedure or CFRA procedure is performed, the RA payload may include a terminal identifier. Uplink radio resources for the transmission of the RA preamble may be configured independently of the uplink radio resources for the transmission of the RA payload.

[0196] For example, radio resources configured (or allocated) for a radio connection procedure may be discontinuous in the time domain or frequency domain. If the radio resources of the RA preamble contained in the RA MSG-A and the radio resources of the RA payload contained in the RA MSG-A are discontinuous, a time domain offset may be set between the radio resources configured (or allocated) for the RA preamble and the RA payload. Alternatively, radio resources configured (or allocated) for a radio connection procedure may be continuous in the time domain or frequency domain. Radio resources for a radio connection procedure may be radio resources configured (or allocated) in a different manner. Alternatively, radio resources for a radio connection procedure may be radio resources defined by other physical hierarchical channels.

[0197] "Different radio resources for wireless connection procedures" can mean "one or more of the following are set differently in the time domain or frequency domain: location of the radio resource, index of the radio resource, index of the RA preamble, transmission timing, and offset." The RA preamble or RA payload may be transmitted using different radio resources. For example, the RA preamble may be transmitted via PRACH, and the RA payload may be transmitted via PUSCH (physical uplink shared channel).

[0198] To configure the transmission resources for the RA preamble of RA MSG-A differently from those for the RA payload of RA MSG-A, the uplink radio resources for the transmission of the RA payload of RA MSG-A (e.g., PUSCH configured for RA payload transmission of RA MSG-A) may be configured to correspond to the RA preamble of MSG-A. That is, a mapping relationship may be established between the uplink radio resources for the transmission of the RA preamble of MSG-A and the uplink radio resources for the transmission of the RA payload of RA MSG-A.

[0199] For example, the transmission resources of the RA preamble can be mapped one-to-one with the transmission resources of the RA payload. In this case, one PRACH can be mapped to one PUSCH. Alternatively, multiple transmission resources of the RA preamble can be mapped to one transmission resource of the RA payload. In this case, multiple PRACHs can be mapped to one PUSCH. Alternatively, one transmission resource of the RA preamble can be mapped to multiple transmission resources of the RA payload. In this case, one PRACH can be mapped to multiple PUSCHs. To improve the reception quality of the RA payload, the RA payload may be transmitted repeatedly. Uplink radio resources may be configured for repeated transmission of the RA payload, and such uplink radio resources may be mapped to the transmission resources of the RA preamble. That is, one or more uplink radio resources may be configured for repeated transmission of the RA payload or for other reasons. If one or more radio resources for RA payload transmission are configured, the RA payload configuration information may include information indicating the time interval for the transmission of multiple RA payloads, the number of RA payload transmission radio resources within the time interval, the symbol interval between radio resources, and the number of symbols that make up each radio resource (or the start symbol, end symbol, and / or length of the radio resource).

[0200] For example, if "the transmission resources for RA MSG-A are pre-configured" or "the RA preamble for RA MSG-A is transmitted through a pre-configured area (or group)", the base station can configure uplink radio resources for repeated transmission of the RA payload of RA-MSG-A. Therefore, if "the coverage extension is applied" or "pre-configured criteria are met", the terminal can select an RA preamble resource or RA preamble index for repeated transmission of the RA payload and repeatedly transmit the RA payload based on the selected resource or index. The terminal can repeatedly transmit the RA payload using the uplink radio resources mapped to the RA preamble index. Uplink radio resources for RA payload transmission (e.g., overlapping radio resources) may be configured within a pre-configured interval in the frequency domain or time domain. Mapping relationship information for uplink radio resources for RA MSG-A transmission may be transmitted to the terminal through system information and / or RRC messages.

[0201] If a two-stage random access procedure is performed in a non-competitive manner, the transmission resources of the RA preamble and / or RA payload of the RA MSG-A may be allocated exclusively for the terminal. Resource information for the RA preamble set as terminal-exclusive in the CFRA procedure may include the SS / PBCH resource list, CSI-RS resource list, SS / PBCH index, CSI-RS index, RA preamble index, etc. The transmission resources for the RA payload of the RA MSG-A may be determined based on the mapping relationship (e.g., one-to-one mapping relationship) between the transmission resources of the RA preamble and the transmission resources of the RA payload. Resource information for the RA payload set as terminal-exclusive in the CFRA procedure may include allocation information for uplink radio resources for RA payload transmission, beam setting information, MCS information, etc.

[0202] In a two-stage random access procedure, the transmission resources of the RA preamble may be contiguous with the transmission resources of the RA payload in the time domain. The transmission resources of the RA payload may be allocated within a time window. A terminal performing a two-stage random access procedure can transmit the RA payload using radio resources contiguous with the RA preamble. Alternatively, the terminal can transmit the RA payload using radio resources not contiguous with the radio resources of the RA preamble (for example, radio resources within a time window after a time domain offset from the radio resources of the RA preamble).

[0203] Furthermore, parameters for allocating transmission resources in the RA preamble and the RA payload may include frequency offsets and / or time offsets. Thus, a terminal can transmit an RA payload using the radio resources for the RA payload mapped to the RA preamble. Alternatively, the terminal can randomly select one of several radio resources mapped to the RA preamble configured for RA payload transmission and transmit the RA payload using the selected radio resource.

[0204] The RA payload of RA MSG-A transmitted in step 1002 may be identical or similar to RA MSG3 transmitted in step S904 as shown in Figure 9. For example, the RA payload of RA MSG-A may include one or more of the following: terminal identifier, capabilities, attributes, mobile status, location information, reason for attempting connection procedure, beam failure recovery request information, measurement results for the base station (or cell) in the CA environment, CA activation / deactivation request information, BWP change request information, BWP deactivation / activation request information, uplink data, uplink data size, uplink buffer size information (e.g., BSR), control message for coupling setup request, and radio channel measurement results.

[0205] Here, beam failure recovery request information may mean information requested by a terminal that has detected a beam failure, based on beam measurement results via a random access procedure, to recover the beam. In this case, the terminal can transmit beam-specific measurement results and / or TCI status information for a new beam configuration to the base station. BWP change request information and BWP deactivation / activation request information can each include one or more of the following: an active BWP change request based on measurement results for a configured BWP, measurement results for a deactivated BWP, and active BWP information preferred by the terminal. Beam failure recovery request information, measurement results for a base station (or cell) in a CA environment, CA activation / deactivation request information, BWP change request information, and BWP deactivation / activation request information can each include one or more of the following: measurement results, BWP identifier, base station (or cell) identifier, and configured beam information (e.g., TCI status, CSI-RS index, SS / PBCH index that can identify the beam). Beam failure recovery request information, measurement results for base stations (or cells) in a CA environment, CA activation / deactivation request information, BWP change request information, and BWP deactivation / activation request information may be transmitted via MAC messages and / or RRC messages.

[0206] When the RA payload is transmitted with the RA preamble in step 1002, the RA payload may include one or more of the following: terminal identifier, uplink data, and control information. The attributes of the uplink data, the length of the uplink data, the attributes of the control information, the length of the control information, and information indicating whether control information is included may be indicated by the MAC header, logical channel identifier (e.g., LCID), or MAC CE. For transmission timing adjustment (e.g., adjustment of TA value) or transmission power control, the terminal may insert a preamble, pilot symbol, or reference signal into the first symbol or some symbols in the RA payload of the RA MSG-A.

[0207] The base station can receive RA MSG-A from the terminal and obtain the RA preamble and RA payload contained in RA MSG-A. The base station can also obtain one or more of the following from the RA payload: terminal identifier, uplink data, and control information. The base station can generate RA MSG-B (e.g., message 2, RAR) as a response to RA MSG-A and transmit RA MSG-B to the terminal (S1003). The terminal can receive RA MSG-B from the base station and verify the information elements contained in RA MSG-B.

[0208] RA MSG-B may include one or more of the following: BI (backoff indicator), uplink radio resource allocation information, RA preamble of RA MSG-A (e.g., RA preamble index), transmission timing adjustment information (e.g., TA value, TA instruction), scheduling identifier (e.g., C-RNTI, TC (temporary cell)-RNTI, etc.), and terminal identifier for contention resolution (e.g., UE contention resolution ID).

[0209] An RA MSG-B (e.g., a MAC PDU) can contain one or more MAC subPDUs. Each of the one or more MAC subPDUs contained in the RA MSG-B may be configured based on one of the following configuration schemes. Information indicating the configuration scheme of a MAC subPDU may be included in the MAC subheader of the MAC subPDU in question. MAC subPDU can mean "MAC subPDU".

[0210] -Configuration Method #1: MAC subheader including BI (backoff indicator) -Configuration method #2: MAC subheader and fallback RAR -Configuration method #3: MAC subheader and successful RAR -Configuration method #4: MAC subheader and MAC SDU (service data unit) (e.g., data or control information) -Configuration method #5: MAC subheader and padding

[0211] If "RA MSG-B is scheduled by the C-RNTI assigned to the terminal" or "RA MSG-B contains a terminal identifier (e.g., UE decommissioning ID) included in RA MSG-A", the terminal can be determined to be decommissioned. In other words, the terminal can be determined to have completed the two-step random access procedure.

[0212] If the DCI's CRC, which contains scheduling information for the PDSCH on which RA MSG-B (e.g., RAR for RA MSG-A) is transmitted, is scrambled by C-RNTI, and RA MSG-B containing TA information and / or UL grants is received within the RAR window (or before the timer ends), the terminal can determine that the competition for the two-step random access procedure has been resolved. Here, TA information may be a TA value or a TA instruction.

[0213] A specific field (or bit) within the PDCCH (e.g., DCI or UCI) can indicate that the RA MSG-B scheduled by the PDCCH is the RA MSG-B scheduled by the C-RNTI. Alternatively, a field in the MAC subheader or the Logical Channel Identifier (LCID) for MAC CE transmission for the RA MSG-B can indicate that the RA MSG-B scheduled by the PDCCH is the RA MSG-B scheduled by the C-RNTI.

[0214] In a four-stage random access procedure, the RAR window can begin at the end of transmission of RA MSG1. In a two-stage random access procedure, the RAR window can begin at the end of transmission of the RA payload of RA MSG-A. If RA MSG-B containing TA information and / or UL grants (e.g., RA MSG-B scheduled by C-RNTI) is not received within the RAR window (or before the timer ends), the terminal can determine that the competition for the two-stage random access procedure has not been resolved.

[0215] When an RA MSG-B scheduled by C-RNTI is transmitted in response to an RA MSG-A in a two-step random access procedure, the PDCCH (e.g., DCI or UCI) may include TA information, an indicator indicating that the PDCCH contains scheduling information for the response to RA MSG-A, etc. The RA MSG-B can be transmitted in the form of a MAC message (e.g., MAC CE) or an RRC message. When the RA MSG-B is transmitted in the form of a MAC message, the RRC layer of the base station that has obtained information from RA MSG-A can transmit the parameters contained in the RA MSG-B to the base station's MAC layer, and the base station's MAC layer can generate an RA MSG-B in MAC CE form. The RA MSG-B may include a terminal identifier obtained through the RA payload of RA MSG-A.

[0216] If the RA preamble of RA MSG-A is assigned exclusively to a terminal, or if the radio resources of the RA preamble of RA MSG-A are mapped one-to-one with the radio resources of the RA payload of RA MSG-A, then RA MSG-B does not need to include the index of the RA preamble received from the terminal.

[0217] If the RA preamble of RA MSG-A is assigned exclusively to a terminal, or if the RA payload of RA MSG-A contains a scheduling identifier assigned to the terminal (e.g., C-RNTI), the base station can transmit a DCI containing scheduling information for the transmission resource of RA MSG-B to the terminal using the scheduling identifier assigned to the terminal. That is, the CRC of the DCI can be scrambled by the scheduling identifier assigned to the terminal. The terminal can receive the DCI using the scheduling identifier assigned to the terminal, obtain the scheduling information for the transmission resource of RA MSG-B contained in the DCI, and receive RA MSG-B on the transmission resource indicated by the scheduling information.

[0218] In step S1003, the base station can transmit a PDCCH for scheduling uplink radio resources, a PDCCH for RAR (e.g., DCI) for RAR (e.g., RA MSG-B), or RA MSG-B. RA MSG-B can be transmitted via a PDSCH. If only a PDCCH is transmitted in step S1003, the PDCCH may contain one or more of the following: uplink radio resource allocation information for the terminal (e.g., scheduling information), transmission timing adjustment information (e.g., TA information), transmission power adjustment information, backoff information, beam setting information, TCI status information, CS status information, state transition information, PUCCH setting information, the index of the RA preamble contained in RA MSG-A, and radio resource allocation information for transmitting the RA payload of RA MSG-A. Also, if only a PDCCH is transmitted in step S1003, the terminal can recognize that there is no RA MSG2 transmitted via the PDSCH based on the DCI format in the PDCCH and / or the aforementioned PDCCH configuration information.

[0219] Beam setting information may indicate the activation or deactivation of a specific beam. TCI status information may indicate the activation or deactivation of a specific TCI state. CS status information may indicate the activation or deactivation of radio resources allocated in the CS scheme. State transition information may indicate the transition of operating states as illustrated in Figure 8. State transition information can indicate a transition from the current operating state to the RRC pause state, RRC inactive state, or RRC connected state. Alternatively, state transition information can indicate maintaining the current operating state. PUCCH setting information may indicate the allocation of SR transmission resources. Alternatively, PUCCH setting information may indicate the activation or deactivation of SR transmission resources.

[0220] The base station can transmit the control information described above in step S1003 via the PDSCH by transmitting only the PDCCH. The control message transmitted via the PDSCH may include one or more of the following: uplink radio resource allocation information (e.g., scheduling information), transmission timing adjustment information (e.g., TA information), transmission power adjustment information, backoff information, beam setting information, TCI status information, CS (Configured scheduled) status information, status transition information, PUCCH setting information, the index of the RA preamble included in the RA MSG-A, and uplink radio resource allocation information for the transmission of uplink data and / or control messages in step 1004.

[0221] In the RA MSG-B generation / transmission procedure, the base station can transmit a DCI containing scheduling information for the transmission of the RA MSG-B using the RA-RNTI or a scheduling identifier assigned to the terminal (e.g., C-RNTI). That is, the CRC of the DCI can be scrambled by the RA-RNTI or C-RNTI. The base station can transmit the RA MSG-B to the terminal using the PDSCH indicated by the DCI.

[0222] If the terminal successfully receives RA-MSG-B from the base station, the two-stage random access procedure may be terminated. The terminal that received RA-MSG-B can use the uplink scheduling information (e.g., scheduling information contained in RA-MSG-B) to transmit uplink data and / or control messages to the base station (S1004).

[0223] "Information indicating whether a base station (or cell) allows the execution of a two-step random access procedure" and / or "conditions for the execution of a two-step random access procedure" may be transmitted to the terminal via broadcast system information, multicast control messages, or dedicated control messages. "Information indicating whether a base station (or cell) allows the execution of a two-step random access procedure" may be "information indicating whether a base station allows terminals located within its service area to attempt to connect via a two-step random access procedure," "information indicating whether a base station restricts terminals located within its service area to attempt to connect via a two-step random access procedure," or "information indicating whether a base station partially restricts terminals located within its service area to attempt to connect via a two-step random access procedure."

[0224] If attempts to connect via the two-step random access procedure are restricted, the base station may notify the terminal of the restrictions on the two-step random access procedure. If attempts to connect via the two-step random access procedure are partially restricted, the base station may notify the terminal of the partial restrictions on the two-step random access procedure. The terminal may also be unable to attempt the two-step random access procedure if "the base station does not allow the two-step random access procedure" or if "the restrictions or partial restrictions on the two-step random access procedure are met."

[0225] A terminal can perform a two-stage random access procedure if the conditions for performing the procedure (e.g., tolerance conditions) are met. For example, if the quality of the radio channel measured by the terminal is greater than or equal to a critical value (e.g., reference value) set by the base station, the terminal can perform a two-stage random access procedure. If the quality of the radio channel measured by the terminal is less than the critical value set by the base station, the terminal can perform a four-stage random access procedure. For example, the quality of the radio channel may be RSSI (received signal strength indicator), RSCP (received signal code power), RSRP (reference signal received power), or RSRQ (reference signal received quality). Alternatively, the quality of the radio channel may be other parameters (e.g., reference parameters that measure the quality of the radio section between the base station (or cell, TRP) and the terminal).

[0226] In a four-step random access procedure, the RA preamble (e.g., signature) of RA MSG1 can be constructed identically to the RA preamble (e.g., signature) of RA MSG-A in a two-step random access procedure. In the RA preamble generation procedures for RA MSG1 and RA MSG-A, the code sequence can be generated using the same code generation formula.

[0227] In a four-step random access procedure, the transmission resources of the RA preamble for RA MSG1 may be the same as or different from the transmission resources of the RA preamble for RA MSG-A in a two-step random access procedure.

[0228] If the transmission resources for the RA preamble of RA MSG1 and the RA preamble of RA MSG-A are the same, the index of the RA preamble of RA MSG1 and the index of the RA preamble of RA MSG-A may be set differently. That is, within the same RA preamble transmission resources, the index range for the RA preamble of RA MSG1 and the index range for the RA preamble of RA MSG-A may be set differently.

[0229] If the transmission resources of the RA preamble of RA MSG1 and the RA preamble of RA MSG-A are different, the transmission resources of the RA preamble of RA MSG1 may be configured to be distinct from the transmission resources of the RA preamble of RA MSG-A in the time and / or frequency domains. In the frequency domain, the transmission resources of the RA preamble may include one or more of the following: frequency band information, PRB information, CRB information, subcarrier information, and beam information from beamforming techniques. In the time domain, the transmission resources of the RA preamble may be configured / indicated in units of radio frames, subframes, TTI, slots, minislots, symbols, or specific time intervals. The base station can determine whether a four-step random access procedure or a two-step random access procedure is performed based on the RA preamble received from the terminal or the radio resources from which the RA preamble was received.

[0230] The size of the RA payload of RA MSG-A and / or the MCS level for the RA payload of RA MSG-A may be determined as follows: The base station may set the size of the RA payload of RA MSG-A to a fixed value from among several candidate values, and may set the MCS level for the transmission of the RA payload of RA MSG-A to a fixed level from among several candidate levels. The base station may notify the terminal of the size of the RA payload and / or the MCS level set by the base station. The base station may configure the terminal to select the RA preamble of RA MSG-A based on the size of the RA payload and / or the MCS level of RA MSG-A. For example, the terminal may select the RA preamble of RA MSG-A based on one or more of the downlink channel radio quality information received from the base station (e.g., path loss information), the size of the RA payload of RA MSG-A, and the MCS level for the transmission of the RA payload of RA MSG-A. The terminal may transmit the selected RA preamble of RA MSG-A to the base station.

[0231] Therefore, based on the RA preamble of the RA MSG-A received from the terminal, the base station can estimate one or more of the MCS level, size, and radio quality of the downlink channel for the RA payload of the RA MSG-A. The available RA preambles for the RA MSG-A may vary depending on the radio quality of the downlink channel, the size of the RA payload of the RA MSG-A, and / or the MCS level. The base station can transmit system information and / or control messages (e.g., dedicated control messages) to the terminal, which may include the available RA preamble information depending on the radio quality of the downlink channel, the size of the RA payload of the RA MSG-A, and / or the MCS level.

[0232] Furthermore, system information and / or control messages (e.g., dedicated control messages) may include configuration parameters for selecting an available RA preamble for RA MSG-A based on the downlink channel radio quality, the size of the RA payload for RA MSG-A, and / or the MCS level. The configuration parameters may include one or more of the following: downlink channel radio quality information, the size of the RA payload for RA MSG-A, reference values ​​for the MCS level, etc., information about the RA preamble for RA MSG-A corresponding to the reference value (e.g., index, index range), and transmission resource information for the RA preamble for RA MSG-A corresponding to the reference value.

[0233] Alternatively, the MCS level for RA payload transmission of RA MSG-A can be fixed. The base station can set the MCS level for RA payload transmission of RA MSG-A to a single fixed level. The base station can transmit system information and / or control messages (e.g., dedicated control messages) including the MCS level for RA payload transmission of RA MSG-A to the terminal. The terminal can confirm the MCS level for RA payload transmission of RA MSG-A (e.g., a fixed MCS level) set by the base station by receiving the system information and / or control messages (e.g., dedicated control messages) from the base station. The terminal can then transmit the RA payload of RA MSG-A using the fixed MCS level.

[0234] Furthermore, the RA payload of RA MSG-A may include the MCS level applicable to that RA payload. For example, a terminal can determine the MCS level for the RA payload of RA MSG-A and transmit the RA payload of RA MSG-A, including the determined MCS level, to the base station. The RA payload of RA MSG-A may include other information elements in addition to the MCS level. The base station can set the MCS level range for the RA payload of RA MSG-A and transmit system information and / or control messages (e.g., dedicated control messages) including the MCS level range to the terminal.

[0235] In this case, the terminal can select an MCS level within the MCS level range set by the base station and transmit the RA payload of the RA MSG-A to the base station using the selected MCS level. Here, the RA payload of the RA MSG-A may include the MCS level selected by the terminal. The base station can receive the RA payload of the RA MSG-A from the terminal and can determine the MCS level applied to the RA payload by examining a specific part of the RA payload (e.g., UCI). Based on the determined MCS level, the base station can perform demodulation and decoding operations on the RA payload of the RA MSG-A.

[0236] Alternatively, the RA preamble of RA MSG-A may be selected through a combination of the methods described above. Similarly, the size and / or MCS level of the RA payload of RA MSG-A may be selected through a combination of the methods described above. For example, the RA preamble of RA MSG-A may be selected based on the radio quality of the downlink channel and / or the size of the RA payload of RA MSG-A. The MCS level of the RA payload of RA MSG-A may be fixed at a specific level. A specific portion within the RA payload of RA MSG-A (e.g., UCI) may indicate the MCS level applied to that RA payload.

[0237] The index (e.g., RA preamble index), masking information, and / or offset of RA MSG1 may be set differently depending on the downlink path loss and / or the magnitude of RA MSG3. If the base station supports both four-stage and two-stage random access procedures, the conditions (or criteria) for a terminal to select the RA preamble of RA MSG-A in the two-stage random access procedure may be set to be the same as the conditions (or criteria) for a terminal to select RA MSG1 (e.g., the RA preamble) in the four-stage random access procedure.

[0238] The base station can transmit to the terminal, using system information and / or control messages (e.g., dedicated control messages), one or more of the following: information indicating whether to support a four-stage random access procedure; information indicating whether to support a two-stage random access procedure; selection criteria (e.g., selection standards) for RA MSG1 (e.g., RA preamble) in a four-stage random access procedure; and selection criteria (e.g., selection standards) for the RA preamble of RA MSG-A in a two-stage random access procedure.

[0239] The terminal can obtain resource configuration information for the two-stage random access procedure from the base station through system information and / or control messages, based on the purpose of performing the two-stage random access procedure (e.g., BFR procedure, restart request, linking setup request, system information request), the size of the RA payload transmitted by the terminal, the radio quality of the downlink channel, etc. The resource configuration information for the two-stage random access procedure may include transmission resource information and / or MCS levels for the RA MSG-A (e.g., RA preamble, RA payload). The terminal can select resources that meet the aforementioned selection conditions (e.g., selection criteria) and perform the two-stage random access procedure by transmitting the RA MSG-A (e.g., RA preamble, RA payload) using the selected resources.

[0240] The terminal can determine the MCS level for the RA payload based on the selection method for radio resources for RA payload transmission of the RA MSG-A. For example, the base station can configure the radio resources for transmission of the RA payload based on the size and / or MCS level of the RA payload in the RA MSG-A, and can transmit the resource configuration information for the RA payload to the terminal using system information and / or control messages (e.g., dedicated control messages). The radio resources for transmission of the RA payload may be configured differently depending on the size and / or MCS level of the RA payload.

[0241] The terminal can receive resource configuration information for the RA MSG-A RA payload from the base station and select a radio resource corresponding to the size and / or MCS level of the RA payload based on the resource configuration information. The terminal can transmit an RA preamble for the RA MSG-A corresponding to the selected radio resource (e.g., mapped) to the base station and transmit the RA payload for the RA MSG-A to the base station using the selected radio resource. The base station can receive the RA preamble for the RA MSG-A from the terminal and verify the size and / or MCS level of the RA payload corresponding to the radio resource from which the RA preamble was received (e.g., mapped). The base station can receive the RA payload for the RA MSG-A based on the verified size and / or MCS level of the RA payload.

[0242] In a two-step random access procedure, a scheduling identifier for RA MSG-B transmission (e.g., RA-RNTI) can be distinguished from an RA-RNTI for message 2 (e.g., RA MSG2) transmission in a four-step random access procedure. In a two-step random access procedure, RA-RNTI may be a separately configured RA-RNTI for RA MSG-B transmission (e.g., MSG-B RA-RNTI). MSG-B RA-RNTI can be mapped to the transmission resource (e.g., radio resource) of the RA preamble for RA MSG-A. If the terminal selects the transmission resource of the RA preamble for RA MSG-A, an MSG-B RA-RNTI for receiving RA MSG-B can be determined in a two-step random access procedure.

[0243] In a two-step random access procedure, the format of an RA MSG-B may vary depending on the parameters contained in the RA MSG-B. To support diverse RA MSG-B formats, a separate MAC subheader or a separate field within the MAC CE may be defined for the RA MSG-B. A "MsgB-type" field indicating the format of the RA MSG-B may be set within the separate MAC subheader or MAC CE for the RA MSG-B. For example, the "MsgB-type" field may be set in the first octet of the separate MAC subheader or MAC CE for the RA MSG-B. If the size of the "MsgB-type" field is 2 bits, the format of the RA MSG-B may be defined as follows. The parameters contained in the RA MSG-B may vary depending on the format of the RA MSG-B.

[0244] 00: TA information, UL grant, TC-RNTI, UE ID (e.g., terminal identifier included in RA MSG-A) 01: UL Grant, TC-RNTI, UE ID 10: TA information, UL grant, beam setting information, TCI status information 11: UL Grant, Beam Setting Information, TCI Status Information

[0245] TA information (e.g., TA value, TA command) may be used to adjust uplink transmission timing. UL grant may be uplink scheduling information. TC-RNTI may be a scheduling identifier assigned to a terminal (e.g., Temporary C-RNTI).

[0246] The size of the "MsgB-type" field may be 1 bit or more. The "MsgB-type" field can indicate the parameters included in the RA MSG-B. The parameters included in the RA MSG-B may be one or more of the following: TA information, UL grant, TC-RNTI, UE ID, beam setting information, TCI status information, other control information, and downlink data.

[0247] If the resources for the RA preamble of RA MSG-A and the resources for RA MSG1 (e.g., the RA preamble) are configured in the same manner, the scheduling identifier for sending and receiving RA MSG-B may not be distinguished from the scheduling identifier for sending and receiving RA MSG2. Here, the scheduling identifier may be RA-RNTI.

[0248] The transmission resources of the RA preamble of RA MSG-A may be the same as those of RA MSG1, and the index of the RA preamble of RA MSG-A may be different from the index of RA MSG1 (e.g., the index of the RA preamble). The scheduling identifier for sending and receiving RA MSG-B may be determined by the transmission resources and / or index of the RA preamble of RA MSG-A. The scheduling identifier for sending and receiving RA MSG2 may be determined by the transmission resources and / or index of RA MSG1 (e.g., the RA preamble). If the transmission resources of the RA preamble of RA MSG-A are the same as those of RA MSG1, and the index of the RA preamble of RA MSG-A is different from the index of RA MSG1 (e.g., the index of the RA preamble), then the scheduling identifier for sending and receiving RA MSG-B may be the same as the scheduling identifier for sending and receiving RA MSG2.

[0249] Even when the scheduling identifier for sending and receiving RA MSG-B and the scheduling identifier for sending and receiving RA MSG2 are set in the same manner, the RA-RNTI for RA MSG-B (e.g., MSG-B RA-RNTI) may be set differently from the RA-RNTI for RA MSG2. The RA-RNTI for RA MSG-B may be determined by adding a predetermined offset value to the RA-RNTI for RA MSG2. That is, the RA-RNTI for RA MSG-B may be determined by adding a certain constant value to the RA-RNTI for RA MSG2.

[0250] The base station can transmit information indicating whether the resources for the RA preamble of RA MSG-A are set in the same manner as the resources for RA MSG1 to the terminal using system information and / or control messages (e.g., dedicated control messages). The same RA-RNTI determined in the same way can be used in the two-step random access procedure and the four-step random access procedure. In this case, the terminal can distinguish whether the corresponding RAR is RA MSG-B of the two-step random access procedure or RA MSG2 of the four-step random access procedure based on a specific field in the MAC header (or MAC sub-header) included in the RAR received based on the RA-RNTI.

[0251] For example, the spare bits in the MAC sub-header included in the RAR (e.g., RA MSG-B) can indicate whether the corresponding RAR is RA MSG-B or RA-MSG2. The spare bits set to "00" can indicate that the corresponding RAR is RA MSG2. The spare bits set to "01, 10, or 11" can indicate that the corresponding RAR is RA MSG-B.

[0252] When RA MSG-B and RA MSG2 are transmitted through one radio resource region, RA MSG-B can be transmitted before RA MSG2 within one radio resource region. For this operation, the MAC sub-header of RA MSG-B can be located before the MAC sub-header of RA MSG2. Or RA MSG-B can be transmitted after RA MSG2 within one radio resource region. For this operation, the MAC sub-header of RA MSG-B can be located after the MAC sub-header of RA MSG2.

[0253] If the MAC subheader of RA MSG-B is located after the MAC subheader of RA MSG2, then in a downlink message for the transmission of RA MSG-B and / or RA MSG2, all MAC subheaders for one or more RA MSG2s may be located before the MAC subheader for RA MSG-B. If there are no RA MSG2s to be transmitted by the base station, the downlink message may only contain the MAC subheader for RA MSG-B.

[0254] Conversely, if the MAC subheader of RA MSG-B is located before the MAC subheader of RA MSG2, then in the downlink message for the transmission of RA MSG-B and / or RA MSG2, all MAC subheaders for one or more RA MSG-Bs may be located before the MAC subheader for RA MSG2.

[0255] RA MSG-B may include the aforementioned parameters and RRC messages (e.g., RRC control information). When an RA MSG-A containing RRC messages (e.g., a link request message, a resumption request message) is received (e.g., the RA payload of RA MSG-A), the base station can generate a MAC PDU for each terminal-specific RA MSG-B and transmit the MAC PDU for each terminal.

[0256] In a two-stage random access procedure, the MAC PDU of RA MSG-B can include the aforementioned parameters (e.g., TA information, UL grant, TC-RNTI, UE ID, beam configuration information, etc.) without RRC control information. A MAC PDU of RA MSG-B containing the aforementioned parameters without RRC control information may be referred to as "MSG-B with UEsMux". Alternatively, the MAC PDU of RA MSG-B can include the aforementioned parameters together with RRC control information. A MAC PDU of MSG-B containing the aforementioned parameters together with RRC control information may be referred to as "MSG-B with SRB". MSG-B with UEsMux can include RA MSG-B for multiple terminals, and MSG-B with SRB can include RA MSG-B for a single terminal. RA MSG-B for multiple terminals can be multiplexed with MSG-B with UEsMux, which consists of a single MAC PDU.

[0257] A scheduling identifier that addresses a PDCCH (e.g., DCI) containing scheduling information for the PDSCH on which MSG-B with SRB is transmitted may be assigned separately. The RA-RNTI for sending and receiving MSG-B with UEsMux may be set independently of the RA-RNTI for sending and receiving MSG-B with SRB. The RA-RNTI that addresses the scheduling information for the PDSCH on which MSG-B with SRB is transmitted may be set differently from the RA-RNTI that addresses the scheduling information for the PDSCH on which MSG-B with UEsMux is transmitted. A terminal that has transmitted RA MSG-A using a two-step random access procedure can perform PDCCH monitoring operations using both the RA-RNTI for MSG-B with SRB and the RA-RNTI for MSG-B with UEsMux. For example, the RA-RNTI for MSG-B with SRB may be an RA-RNTI to which a pre-configured offset has been applied to the RA-RNTI for MSG-B with UEsMux.

[0258] Alternatively, the RA-RNTI for MSG-B with SRB may be the RA-RNTI of RA MSG2 to which a pre-configured first offset has been applied, and the RA-RNTI for MSG-B with UEsMux may be the RA-RNTI of RA MSG2 to which a pre-configured second offset has been applied. The first offset may differ from the second offset. In the embodiments described above, the base station can notify the terminal of the pre-configured offsets (e.g., the first offset, the second offset). The terminal can use the pre-configured offsets obtained from the base station to verify the RA-RNTI for MSG-B with SRB and the RA-RNTI for MSG-B with UEsMux. If scheduling identifiers (e.g., RA-RNTI) are set differently in a two-stage random access procedure and / or a four-stage random access procedure, the terminal can use the scheduling identifier to distinguish between RA response messages (e.g., RA MSG2, RA MSG-B, MSG-B with SRB, or MSG-B with UEsMux) in the two-stage random access procedure and / or the four-stage random access procedure. The RA response message in a two-stage random access procedure may represent a successful RAR (e.g., MSG-B with SRB MAC PDU, MSG-B with UEsMux MAC PDU) or a fallback RAR as described below. Therefore, RA MSG-B in a two-stage random access procedure may consist of the aforementioned BI (Backoff Indicator), contention resolution information using the terminal identifier (e.g., a successful RAR), or a fallback RAR. If the scheduling identifier for transmitting RA response messages in a two-stage random access procedure is set to MSG-B RA-RNTI, the terminal can distinguish and receive RA MSG2 for a four-stage random access procedure and RA MSG-B for a two-stage random access procedure using the scheduling identifier RA-RNTI and MSG-B RA-RNTI.

[0259] When reporting uplink measurement results using the RA payload of RA MSG-A in a two-step random access procedure, when reporting uplink measurement results using the message of step S1004 shown in Figure 10, or when reporting uplink measurement results using RA MSG3 in a four-step random access procedure, the uplink measurement results may include information for distinguishing downlink beams (e.g., TCI status setting information, SS / PBCH index, CSI-RS index) and / or BWP identifiers. When uplink measurement results are transmitted by the beam order in a beam setting list included in a control message for setting multiple beams, the uplink measurement results do not need to include information for distinguishing downlink beam identifiers (e.g., downlink beam identifiers). When uplink measurement results are transmitted by the BWP order in a BWP setting list included in a control message for setting multiple BWPs, the uplink measurement results do not need to include BWP identifiers.

[0260] In a four-step random access procedure, RA MSG3 and in a two-step random access procedure, RA MSG-A (e.g., RA payload) may be configured using the same format. Alternatively, RA MSG3 and RA MSG-A (e.g., RA payload) may be configured using different formats. Here, format can mean the form that constitutes the MAC message or RRC message. "Using the same format" can mean "the parameters, fields, and / or information elements contained in the MAC message or RRC message are the same."

[0261] Regardless of whether the format of RA MSG3 and RA MSG-A (e.g., RA payload) are identical, fields and / or logical channel identifiers (e.g., LCID) may be set in the MAC header (or MAC subheader) to distinguish RA MSG3 from RA MSG-A (e.g., RA payload).

[0262] The fields in the MAC header (or MAC subheader) indicating RA MSG3 may be set differently from the fields in the MAC header (or MAC subheader) indicating RA MSG-A (e.g., RA payload). The field in the MAC header (or MAC subheader) used to distinguish between RA MSG3 and RA MSG-A (e.g., RA payload) may be referred to as the "RA-M3" field. The "RA-M3" field set to "1" can indicate that the message is an RA MSG3. The "RA-M3" field set to "0" can indicate that the message is an RA MSG-A (e.g., RA payload).

[0263] The LCID indicating RA MSG3 may be set differently from the LCID indicating RA MSG-A (e.g., RA payload). Therefore, a base station can distinguish between RA MSG3 and RA MSG-A (e.g., RA payload) based on the LCID included in the MAC header (or MAC subheader, MAC message).

[0264] The terminal can perform the aforementioned four-stage random access procedure and two-stage random access procedure, respectively, based on the CBRA method or the CFRA method. If the terminal transmits message 1 (e.g., RA MSG-A (e.g., RA preamble, RA payload), RA MSG1) more than a predetermined number of times in the CFRA procedure, or if the terminal fails to receive a RAR for message 1 within the time corresponding to a predetermined timer in the CFRA procedure, the terminal can switch from the CFRA procedure to the CBRA procedure. In other words, the terminal can perform the two-stage random access procedure or the four-stage random access procedure using the CBRA method.

[0265] If a dedicated radio resource is set up for a two-stage random access procedure or a four-stage random access procedure in a CFRA procedure, and the criteria for transmitting the RA preamble (e.g., radio channel quality) are not met, a CBRA procedure may be performed instead of the CFRA procedure. For example, if the radio channel quality is above the criteria, the terminal can perform the CFRA procedure using the dedicated radio resource allocated for the CFRA procedure. If the radio channel quality is below the criteria, the terminal can perform the CBRA procedure instead of the CFRA procedure.

[0266] When the two-stage random access procedure illustrated in Figure 10 is performed, in stage S1002 the base station may receive the RA preamble or RA payload contained in RA MSG-A. That is, the base station may not receive both the RA preamble and the RA payload. In this case, the base station may not transmit RA MSG-B, which is the response to RA MSG-A, to the terminal. If RA MSG-B is not received from the base station within the RAR window, the terminal may perform a retransmission operation of RA MSG-A for a predetermined time interval (or a predetermined number of times).

[0267] Alternatively, if the base station receives an RA preamble or RA payload in step S1002, the base station and / or terminal may operate as follows: In a two-step random access procedure, the RAR window (or timer) for receiving RA MSG-B can start from the time of transmission of the RA payload of RA MSG-A. If the RA payload of RA MSG-A is transmitted repeatedly, the RAR window can start from the time of transmission of the last RA payload. The time of transmission of the RA payload of RA MSG-A can be the start or end of transmission of the RA payload. The time of transmission of the RA payload of RA MSG-A can be expressed in subframes, slots, minislots, or symbols.

[0268] In a two-stage random access procedure, the RAR window for receiving RA MSG-B may be set to be the same as the RAR window for receiving RA MSG2. The RAR window for receiving RA MSG-B may be set based on parameters relating to the RAR window for receiving RA MSG2. If the base station (or cell) is configured using a radio protocol function split scheme, the base station may transmit one or more of the configuration information for the RAR window for receiving RA MSG-B (e.g., parameters) and the configuration information for the RAR window for receiving RA MSG2 (e.g., parameters) to the terminal using system information and / or control messages (e.g., RRC messages).

[0269] If only the RA preamble of RA MSG-A is received at the base station, the retransmission procedure for the RA payload of RA MSG-A may be performed. The retransmission procedure for the RA payload of RA MSG-A may be performed as follows:

[0270] The two-stage random access procedure can be performed using the CFRA method. In stage S1002, the base station can receive the RA preamble of RA MSG-A from the terminal. "If the decoding operation of the RA payload of RA MSG-A fails" or "if the RA payload of RA MSG-A is set to a pre-configured timer (hereinafter referred to as "T") 2-stepRA If not received before the end of the RA MSG-A, the base station can identify the terminal that initiated the two-stage random access procedure based on the RA preamble of the RA MSG-A.

[0271] T 2-stepRA This can be initiated at the base station when it receives the RA preamble (e.g., at the start of reception, at the end of reception). The base station is T 2-stepRA This can be notified to the terminal using system information and / or control messages (e.g., dedicated control messages). The terminal is T 2-stepRABefore the end of , the RA payload must be transmitted to the base station. If the RA preamble of RA MSG-A is mapped to the RA payload of RA MSG-A, T 2-stepRA can be a timer according to the time relation corresponding to the mapping relationship between the RA preamble and the RA payload.

[0272] From the time point of receiving the RA preamble (for example, the start time point of reception, the end time point of reception), if the RA payload is not received from the terminal before the end time point of T 2-stepRA , the base station can transmit DCI including scheduling information for the PDSCH on which RA MSG-B is transmitted using the following scheduling identifiers. The DCI can be transmitted through the PDCCH.

[0273] - Scheduling identifier set for the terminal - Scheduling identifier for RA MSG-B transmission (for example, MSG-B RA-RNTI) - Scheduling identifier for RA MSG-B transmission requesting retransmission of the RA payload of RA MSG-A

[0274] In step S1003, the base station may transmit a DCI containing uplink radio resource allocation information (e.g., scheduling information) through the PDCCH. Alternatively, in step S1003, the base station may transmit an RA MSG-B through the PDSCH. An RA MSG-B requesting the retransmission of the RA payload of RA MSG-A may be transmitted through the PDSCH (e.g., a PDSCH scheduled by the DCI). An RA MSG-B requesting the retransmission of the RA payload may include some information elements. For example, an RA MSG-B may include one or more of the following: uplink radio resource allocation information (e.g., scheduling information), transmission timing adjustment information, transmission power adjustment information, beam setting information, retransmission request information for the RA payload of RA MSG-A (e.g., retransmission instruction information), radio resource allocation information for the (re)transmission of the RA payload of RA MSG-A, and the MCS level. Each of the multiple information elements included in the RA MSG-B may be configured in MAC CE form. Alternatively, the multiple information elements included in the RA MSG-B may be configured in a single MAC CE form. In this case, a different MAC header format may be used.

[0275] If a base station that has received only the RA preamble of RA MSG-A transmits RA MSG-B requesting the retransmission of the RA payload of RA MSG-A, the terminal can receive RA MSG-B from the base station and verify the information elements contained in RA MSG-B. The information elements contained in RA MSG-B may include radio resource allocation information for (re)transmission of the RA payload, MCS level, TA information, transmission power adjustment information, and / or set beam information. Based on the information elements contained in RA MSG-B, the terminal can retransmit the RA payload of RA MSG-A. If the retransmitted RA payload is received from the terminal, the base station can transmit RA MSG-B to the terminal. The terminal can receive RA MSG-B from the base station. If RA MSG-B is received from the base station, the terminal can determine that the RA payload of RA MSG-A was successfully received at the base station.

[0276] On the one hand, when only the RA preamble of RA MSG-A is received at the base station, the two-step random access procedure can be converted into a four-step random access procedure. The two-step random access procedure can be performed by the CFRA method. At stage S1002, the base station can receive the RA preamble of RA MSG-A from the terminal. "When the decoding operation of the RA payload of RA MSG-A fails" or "when the RA payload of RA MSG-A is not received before the expiration of a preset timer (hereinafter referred to as "T" 2-stepMsgA "), the base station can identify the terminal that started the two-step random access procedure based on the RA preamble of RA MSG-A. That is, when the two-step random access procedure by the CFRA method is performed, the base station can identify the corresponding terminal based on the radio resource or index of the RA preamble of RA MSG-A by the CFRA method received from the terminal. T 2-stepMsgA can start at the time when the RA preamble is received at the base station (for example, the start time of reception, the end time of reception). The base station can notify T 2-stepMsgA to the terminal using system information and / or control messages (for example, dedicated control messages). The terminal must transmit the RA payload to the base station before the expiration of T 2-stepMsgA . If the RA payload is received from the terminal before the expiration of T 2-stepMsgA , the base station can transmit RA MSG-B to the terminal. T 2-stepMsgA can be larger than T 2-stepRA .

[0277] From the time of receiving the RA preamble of the two-step random access procedure by the CFRA method to T 2-stepMsgAIf the RA payload is not received from the terminal before the end of the transmission, the base station can identify the terminal based on the RA preamble of the RA MSG-A received from the terminal using the CFRA method. Therefore, the base station can transmit a DCI containing scheduling information for the PDSCH on which the RA MSG-B is transmitted to the terminal using a scheduling identifier specifically assigned to the terminal (e.g., C-RNTI) or a scheduling identifier for RAR transmission (e.g., RA-RNTI or RNTI for RA MSG-B transmission / reception). The DCI can be transmitted through the PDCCH. Therefore, the terminal can receive the DCI by performing a PDCCH monitoring operation using the scheduling identifier for RAR reception or the scheduling identifier assigned to it. By receiving the DCI from the base station, the terminal can obtain one or more of the scheduling information for the PDSCH on which the RA MSG-B is transmitted, downlink scheduling information, and uplink scheduling information.

[0278] In step S1003, the base station may transmit a DCI containing uplink radio resource allocation information (e.g., scheduling information) through the PDCCH. Alternatively, in step S1003, the base station may transmit an RA MSG-B through the PDSCH. The RA MSG-B may be transmitted through the PDSCH (e.g., a PDSCH scheduled by the DCI). The RA MSG-B may contain some information elements. For example, the RA MSG-B may contain one or more of the following: uplink radio resource allocation information (e.g., scheduling information), transmission timing adjustment information, transmission power adjustment information, beam setting information, retransmission request information for the RA payload of the RA MSG-A (e.g., retransmission instruction information), radio resource allocation information for the (re)transmission of the RA payload of the RA MSG-A, and the MCS level. Each of the multiple information elements contained in the RA MSG-B may be configured in MAC CE format. Alternatively, the multiple information elements contained in the RA MSG-B may be configured in a single MAC CE format. In this case, a separate MAC header format may be used. The transmission operation of RA MSG-B based on RA-RNTI may be the transmission operation of message 2 at stage S903, as shown in Figure 9.

[0279] The DCI transmitted in response to RA MSG-A may contain one or more information elements from the information elements included in the aforementioned RA MSG-B. The terminal can receive the DCI from the base station in response to RA MSG-A. In this case, the terminal can retransmit the RA payload of RA MSG-A using the radio resources indicated by the scheduling information included in the DCI. Alternatively, the terminal can transmit the uplink data and / or control information of step S1004 shown in Figure 10 to the base station using the radio resources indicated by the scheduling information included in the DCI.

[0280] In stage S1002 of the CBRA method, the base station can receive the RA preamble of RA MSG-A from the terminal. "If the decoding operation of the RA payload of RA MSG-A fails" or "if the RA payload of RA MSG-A is set to a pre-configured timer (e.g., T 2-stepRA or T 2-stepMsgA If it is not received before the end of step S903, the base station may not be able to identify the terminal that initiated the two-stage random access procedure based on the RA preamble of RA MSG-A. In this case, if the pre-set timer has finished, the base station can transmit RA MSG2 of step S903 shown in Figure 9, or RA MSG-B configured identically to RA MSG2 (e.g., fallback RAR) to the terminal. In other words, the two-stage random access procedure can be converted into a four-stage random access procedure. Therefore, a terminal that transmitted RA MSG-A in step S1002 using the CBRA method can perform both the PDCCH monitoring operation for receiving RA MSG-B of step S1003 shown in Figure 10 (e.g., PDCCH monitoring operation in USS (UE specific search space)) and the PDCCH monitoring operation for receiving RA MSG2 of step S903 shown in Figure 9 (e.g., PDCCH monitoring operation in CSS (common search space)).

[0281] If RA MSG-B (e.g., fallback RAR) or RA MSG2 is received from the base station after step S1002, the terminal can transmit RA MSG3 of step S904, as shown in Figure 9, to the base station. That is, if RA MSG-B (e.g., fallback RAR) or RA MSG2 is received from the base station, the terminal can determine that the two-step random access procedure has transitioned to a four-step random access procedure, and can transmit RA MSG3 of the four-step random access procedure to the base station. The base station can receive RA MSG3 from the terminal and transmit RA MSG4 to the terminal.

[0282] On the other hand, if the base station receives only the RA payload of the RA MSG-A, the following actions may be performed. The terminal can transmit the RA MSG-A, which includes the RA preamble and RA payload, to the base station in step S1002 of the CFRA method. The base station can receive only the RA payload of the RA MSG-A. That is, the base station may not receive the RA preamble of the RA MSG-A. In this case, the base station can identify the terminal identifier based on the information elements contained in the RA payload of the RA MSG-A. Alternatively, the base station can obtain information to identify the terminal that transmitted the RA payload based on the resource allocation rules of the CFRA method. For example, if "the transmission resource for the RA payload is allocated exclusively to the terminal" or "the transmission resource for the RA payload is allocated exclusively to the terminal and the transmission resource for the RA preamble is mapped to the transmission resource for the RA payload", the terminal can identify the terminal that initiated the random access procedure based on the resource from which the RA payload was received, according to the resource allocation rules of the CFRA method.

[0283] If only the RA payload of RA MSG-A is received and the terminal that initiated the corresponding random access procedure based on the RA payload is identified, the base station can transmit RA MSG-B at stage S1003, as shown in Figure 10, to the terminal.

[0284] Upon receiving the RA preamble, the base station can transmit a DCI containing scheduling information for the PDSCH on which the RA MSG-B is transmitted to the terminal using a terminal-specific scheduling identifier or a scheduling identifier for RAR transmission (e.g., MSG-B RA-RNTI). The DCI can be transmitted through the PDCCH. Here, the base station can transmit uplink resource allocation information to the terminal through the PDCCH. The base station can transmit the RA MSG-B to the terminal through the PDSCH indicated by the scheduling information contained in the DCI. The aforementioned information elements of the RA MSG-B may be included. The transmission operation of the RA MSG-B based on RA-RNTI may be identical or similar to the transmission operation of the RA MSG2 in step S903 shown in Figure 9.

[0285] The DCI transmitted in response to message 1 (e.g., RA MSG-A, RA preamble) may include one or more of the following: uplink resource allocation information (e.g., scheduling information), transmission timing adjustment information, transmission power adjustment information, and resource allocation information for the transmission of the RA payload of the RA MSG-A. If only the DCI is received in response to the RA MSG-A, the terminal can retransmit the RA MSG-A (e.g., RA payload) in step S1002 as shown in Figure 10 using the radio resources indicated by the scheduling information contained in the DCI. Alternatively, the terminal can transmit the uplink data and / or control message in step S1004 as shown in Figure 10 using the radio resources indicated by the scheduling information contained in the DCI.

[0286] In stage S1002 of the CBRA method, the base station can receive the RA preamble of RA MSG-A from the terminal. "If the decoding operation of the RA payload of RA MSG-A fails" or "if the RA payload of RA MSG-A is set to a pre-configured timer (e.g., T 2-stepRA or T 2-stepMsgAIf it is not received before the end of step S1002, the base station may not be able to identify the terminal that initiated the two-stage random access procedure based on the RA preamble of RA MSG-A. In this case, once the pre-set timer has finished, the base station can transmit RA MSG2 of step S903, as shown in Figure 9, to the terminal. That is, the two-stage random access procedure can be converted into a four-stage random access procedure. Therefore, a terminal that transmitted RA MSG-A in step S1002 using the CBRA method can perform both the PDCCH monitoring operation for receiving RA MSG-B of step S1003, as shown in Figure 10 (e.g., PDCCH monitoring operation with USS) and the PDCCH monitoring operation for receiving message 2 of step S903, as shown in Figure 9 (e.g., RA MSG2, fallback RAR) (e.g., PDCCH monitoring operation with CSS).

[0287] The RA-RNTI for MSG-B with SRB may be configured differently from the RA-RNTI for MSG-B with UEsMux. In this case, the terminal can perform PDCCH monitoring operations based on the RA-RNTI for MSG-B with SRB and PDCCH monitoring operations based on the RA-RNTI for MSG-B with UEsMux.

[0288] If, after step S1002, RA MSG2 of a four-step random access procedure is received instead of RA MSG-B of a two-step random access procedure, the terminal can transmit RA MSG3 of step S904, as shown in Figure 9, to the base station. In this case, RA MSG3 may be constructed based on the RA payload of RA MSG-A. RA MSG3 may include information elements that constitute the RA payload of RA MSG-A. If the configuration of RA MSG3 differs from the configuration of the RA payload of RA MSG-A, RA MSG3 and the RA payload of RA MSG-A can be distinguished using fields and / or LCID in the MAC header (or MAC subheader). If RA MSG3 of step S904, as shown in Figure 9, is received from the terminal, the base station can transmit RA MSG4 of step S905 to the terminal.

[0289] When a two-step random access procedure is converted to a four-step random access procedure, the terminal can determine whether the RAR received from the base station is the RA MSG-B for the two-step random access procedure (e.g., fallback RAR) or the RA MSG2 for the four-step random access procedure. For this operation, the base station can indicate whether the RAR is the RA MSG-B for the two-step random access procedure (e.g., fallback RAR) or the RA MSG2 for the four-step random access procedure based on the following method.

[0290] -Method #1: The scheduling identifier for the transmission of RA MSG-B (e.g., fallback RAR) is set differently from the scheduling identifier for the transmission of RA MSG2.

[0291] -Method #2: The CORESET, search interval, and PDCCH for the scheduling information of RA MSG-B (e.g., fallback RAR) are set differently from the CORESET, search interval, and PDCCH for the scheduling information of RS MSG2.

[0292] -Method #3; The DCI (e.g., a specific field within the DCI) contains information indicating that the scheduling information contained in the DCI is scheduling information for RA MSG-B (e.g., fallback RAR) or RA MSG2.

[0293] -Method #4: The RAR contains information indicating that the RAR is RA MSG-B (e.g., a fallback RAR) or RA MSG2.

[0294] RA MSG-B for a two-step random access procedure can be distinguished from RA MSG2 for a four-step random access procedure by the RAR scheduling identifier (e.g., RA-RNTI). In this case, RA MSG-B may be transmitted based on scheduling information addressed to RA-RNTI configured for RA MSG-B, and RA MSG2 may be transmitted based on scheduling information addressed to RA-RNTI configured for RA MSG2.

[0295] Alternatively, if a two-step random access procedure is converted to a four-step random access procedure, a separate RA-RNTI (e.g., a fallback RA-RNTI) may be assigned for message 2. The terminal that initiated the two-step random access procedure can transmit the RA MSG2 of the four-step random access procedure. In this case, the RA MSG2 may be transmitted based on scheduling information addressed by the fallback RA-RNTI.

[0296] Scheduling information for transmission resources of RA MSG-B can be transmitted and received using RA-RNTI configured for RA MSG-B. Scheduling information for transmission resources of fallback RAR can be transmitted and received using RA-RNTI configured for 4-stage random access procedures or for fallback RAR. Therefore, RA-RNTI for RA MSG2, RA-RNTI for RA MSG-B (e.g., successful RAR), and RA-RNTI for fallback RAR can be configured differently from each other, and the configured RA-RNTI can be signaled from the base station to the terminal. RA MSG-B can be classified into successful RAR and fallback RAR. A successful RAR may be an RA MSG-B transmitted from a base station that has received all of the RA preamble and RA payload of RA MSG-A. A fallback RAR may be an RA MSG-B transmitted from a base station that has received only the RA preamble of RA MSG-A.

[0297] The CORESET, search interval, and / or PDCCH may be configured differently from each other for RA MSG2, successful RAR, and / or fallback RAR. The base station can configure different CORESET, search interval, and / or PDCCH resources for each message (e.g., RA MSG2, successful RAR, fallback RAR), and can transmit configuration information for the CORESET, search interval, and / or PDCCH resources to the terminal using system information and / or control messages (e.g., dedicated control messages).

[0298] Alternatively, a DCI containing resource allocation information (e.g., scheduling information) of the PDSCH on which message 2 is transmitted may further include a field indicating whether message 2 scheduled by the DCI is an RA MSG2, a successful RAR, or a fallback RAR. In this case, a terminal can receive the DCI containing the scheduling information using an RA-RNTI and determine whether message 2 scheduled by the DCI is an RA MSG2, a successful RAR, or a fallback RAR based on the fields included in the DCI.

[0299] Alternatively, a separate MAC subheader or an "MsgB-type" field may be set to indicate the format of the RA MSG-B for the transmission of message 2. The MAC subheader or "MsgB-type" field can indicate whether message 2 is an RA MSG2, a successful RAR, or a fallback RAR. The base station can transmit a MAC subheader or "MsgB-type" field indicating whether message 2 is an RA MSG2, a successful RAR, or a fallback RAR. The terminal can receive the MAC subheader or "MsgB-type" field from the base station and can determine whether message 2 is an RA MSG2, a successful RAR, or a fallback RAR based on the MAC subheader or "MsgB-type" field.

[0300] When carrier aggregation (CA) functionality is supported, multiple cells (or base stations) can provide communication services to a terminal. The primary cell (PCell), which controls the CA operation, can activate or deactivate secondary cells (SCell) that support the CA function. Furthermore, the terminal can perform CFRA or CBRA procedures with the PCell and SCell respectively for beam recovery with multiple cells. If radio resources for CFRA procedures are allocated exclusively to a terminal, the terminal can perform a CBRA procedure instead of a CFRA procedure for beam recovery if the quality of those radio resources does not meet existing conditions.

[0301] CFRA or CBRA procedures may be performed to restore the beams of PCell and SCell, respectively. In this case, the terminal can transmit one or more of the following to the base station using the RA payload of RA MSG3 or RA MSG-A: terminal identifier, configured beam information (e.g., TCI status that can identify the beam, CSI-RS index, SS / PBCH index), beam measurement result information, and cell measurement result information. The terminal can also transmit information about preferred beams to the base station.

[0302] When a random access procedure is performed to support terminal mobility, the terminal can transmit information requesting the deactivation of a base station (or cell) using the RA payload of RA MSG3 or RA MSG-A. For example, in a handover procedure where a source base station and a target base station simultaneously provide communication services to a terminal, the terminal can transmit information requesting the deactivation of the source or target base station (e.g., information that triggers deactivation) using the RA payload of RA MSG3 or RA MSG-A. In this case, the terminal can transmit the identifier of the base station to be deactivated along with the information requesting deactivation.

[0303] Beam failure or RLF may occur during the handover procedure. In this case, the base station and terminal will use a pre-set timer (e.g., T RRC_CONT Context information (e.g., RRC context information, AS context information) can be saved / maintained until the end of the procedure. If a beam failure or RLF occurs during the handover procedure, the RRC connection re-establishment procedure may be performed. In this case, the RRC connection re-establishment procedure may be performed using a pre-set timer (T RRC_CONT If completed before the end of the process, the base station and terminal can reuse the stored context information (e.g., RRC context information, AS context information).

[0304] In this case, during the CBRA or CFRA procedure performed in the RRC connection re-establishment procedure, some parameters may be reset based on the aforementioned measurement results. During the RRC connection re-establishment procedure, some parameters may be updated (e.g., changed) in the context information between the base station and the terminal, while the remaining parameters in the context information may be reused. For example, beam setting parameters or BWP setting parameters may be newly set in the context information, while the remaining parameters in the context information may be maintained. For this operation, the base station T RRC_CONT You can set T RRC_CONT This information can be transmitted to the terminal using system information and / or control messages (e.g., dedicated control messages).

[0305] Each of the RA MSG1 in a four-stage random access procedure and the RA MSG-A in a two-stage random access procedure can be transmitted one or more times within a single random access opportunity (e.g., RO). Before receiving message 2 from the base station, the terminal can repeatedly transmit RA MSG1 or RA MSG-A using radio resources that differ from each other in time and / or frequency domains. In such a repeated transmission procedure, the terminal can randomly select RA (random access) resources based on mapping relationships to the SS / PBCH index or CSI-RS index (e.g., CSI-RS resource index). Alternatively, in such a repeated transmission procedure, the terminal can select radio resources associated with the mapping relationships of the initially selected RA resources (e.g., transmission resources for RA MSG1, transmission resources for RA MSG-A (e.g., RA preamble, RA payload)).

[0306] For BFR or handover procedures, a base station can allocate multiple RA resources to a terminal as dedicated (e.g., CFRA scheme). For example, the base station can transmit information to the terminal about multiple RA resources mapped to multiple beams. Alternatively, the base station can transmit information to the terminal about multiple RA resources configured in time and / or frequency domains, independently of beams. The terminal can receive information about multiple RA resources allocated to it as dedicated from the base station and repeatedly transmit RA MSG1 or RA MSG-A using multiple RA resources.

[0307] In an OFDMA-based communication system, if synchronization of the uplink physical layer between multiple terminals is maintained, interference between multiple terminals can be reduced. The base station can transmit transmission timing adjustment information (e.g., TA information) to the terminals. Based on the transmission timing adjustment information received from the base station, the terminals can synchronize their uplink physical layer with the base station. Therefore, signals received by the base station from multiple terminals can be aligned within a specific time interval, and in this case, interference between multiple terminals can be reduced.

[0308] A two-stage random access procedure allows a terminal to transmit the RA payload of RA MSG-A to the base station without transmission timing adjustment information. If uplink synchronization between the terminal and the base station is not maintained, the RA payload of RA MSG-A may cause interference between terminals, and the reception performance of the RA payload of RA MSG-A may be degraded. To solve this problem, a transmission gap may be set in the forward region of the uplink radio resource (e.g., PUSCH) through which the RA payload of RA MSG-A is transmitted.

[0309] Figure 11 is a conceptual diagram illustrating a first embodiment of the RA MSG-A transmission method in a communication system.

[0310] Referring to Figure 11, the PUSCH resources for the first terminal may be aligned to a subframe. For example, the start time of the PUSCH resources for the first terminal in the time domain may be aligned to the start time of subframe #2, and the end time of the PUSCH resources for the first terminal in the time domain may be aligned to the end time of subframe #2. The transmission resources for the RA payload of RA MSG-A may be allocated within subframe #2. A transmission gap may be set before the transmission resources for the RA payload of RA MSG-A within subframe #2. The RA payload of RA MSG-A may be transmitted using the transmission resources after the transmission gap. The embodiment illustrated in Figure 11 may also apply when the transmission resources for PUSCH and RA payload are set in slots or minislots instead of subframes.

[0311] The subframe in which the transmission resources for the RA payload of RA MSG-A are located may be the same as the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) are located, rather than the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) are located, rather than the subframe in which the transmission resources for the RA payload of RA MSG-A are located, rather than the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) the RA payload of RA MSG-A are located, rather than the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) are located, rather than the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) are located, rather than the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) are located, rather than the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) are located, rather than the subframe in which the transmission resources for other uplink transmission procedures (e.g., the PUSCH of the first terminal) are located

[0312] For example, subframe #1 may be configured with radio resources for a random access procedure (e.g., RA resources), while other subframes (e.g., subframes #2-#3) may be configured with radio resources for a general uplink transmission procedure that is not a random access procedure. The transmission gap may be configured in symbol units or absolute time units. The base station may transmit information indicating whether a transmission gap exists and the length of the transmission gap to a terminal (e.g., a second terminal) using system information and / or control messages (e.g., a dedicated control message).

[0313] The second terminal can determine whether a transmission gap exists and its length by receiving system information and / or control messages (e.g., dedicated control messages) from the base station before performing the two-step random access procedure. If a transmission gap exists, the second terminal can transmit the RA payload of RA MSG-A to the base station using radio resources after the transmission gap. If no transmission gap exists, the second terminal can transmit the RA payload of RA MSG-A to the base station based on the estimated subframe synchronization. In this case, the RA payload of RA MSG-A may be transmitted from the beginning of the subframe. For example, the transmission resources for the RA payload of RA MSG-A may be set as PUSCH in subframe #2.

[0314] A transmission gap may be used for the transmission of a reference signal or preamble signal for a two-step random access procedure (e.g., RA MSG-A). The reference signal (or preamble signal) may be a signal designed to compensate for base station delay spread or transmission delay in the radio section. The reference signal (or preamble signal) may be designed considering the cyclic prefix (CP) of OFDMA symbols. The reference signal (or preamble signal) may be transmitted in the transmission gap, or it may be transmitted through radio resources after the transmission gap. The RA payload of RA MSG-A may be transmitted after the transmission of the reference signal (or preamble signal). For example, in the time domain, the transmission resources for the reference signal (or preamble signal) may be located after the transmission gap, and the transmission resources for the RA payload of RA MSG-A may be located after the transmission resources for the reference signal (or preamble signal).

[0315] Figure 12a is a conceptual diagram illustrating the first embodiment of the MAC subheader using a random access procedure, Figure 12b is a conceptual diagram illustrating the second embodiment of the MAC subheader using a random access procedure, Figure 12c is a conceptual diagram illustrating the first embodiment of the RA MSG-B using a random access procedure, Figure 12d is a conceptual diagram illustrating the second embodiment of the RA MSG-B using a random access procedure, Figure 12e is a conceptual diagram illustrating the third embodiment of the RA MSG-B using a random access procedure, and Figure 12f is a conceptual diagram illustrating the fourth embodiment of the RA MSG-B using a random access procedure.

[0316] Referring to Figures 12a to 12f, RA MSG-B can be classified as a successful RAR and a fallback RAR. RA MSG-B may include a MAC header (e.g., MAC subheader) and / or a MAC payload (e.g., MAC RAR or MAC subPDU). Alternatively, if RA MSG-B contains only a MAC payload (e.g., MAC RAR), the MAC header (e.g., MAC subheader) may be configured separately from the MAC RAR (or MAC subPDU). The embodiments illustrated in Figures 12c to 12f may represent a MAC payload (e.g., MAC RAR).

[0317] The MAC subheader included in the RA MSG-B may be a BI (backoff indicator) subheader or a RAPID (random access preamble identifier or random access preamble index) subheader. The BI subheader and the RAPID subheader can be distinguished using the T field of the MAC subheader. As shown in Figure 12a, a MAC subheader with a T field set to 0 may be a BI subheader, and as shown in Figure 12b, a MAC subheader with a T field set to 1 may be a RAPID subheader. When a terminal performs a random access procedure to request the transmission of system information, the RA MSG-B may include a RAPID subheader in that random access procedure.

[0318] RA MSG-B can be transmitted based on scheduling information addressed by a scheduling identifier for a two-step random access procedure (e.g., MSG-B RA-RNTI). The RAPID subheader illustrated in Figure 12b can be generated based on the RA preamble of RA MSG-A. The RAPID in the RAPID subheader can indicate the RA preamble index of RA MSG-A. The T fields contained in the BI subheader and the RAPID subheader, respectively, can be used to identify different RA MSG-Bs (e.g., MAC RAR).

[0319] As illustrated in the embodiment shown in Figure 12c, if a C-RNTI is assigned to a terminal and an RA MSG-A is received from that terminal, the T field may be set to 0. The RA MSG-B may include transmission timing adjustment information (e.g., TA instruction), uplink resource allocation information (e.g., UL grant), and the C-RNTI assigned to the terminal. As illustrated in the embodiment shown in Figure 12d, if a C-RNTI is not assigned to a terminal and an RA MSG-A is received from that terminal, the T field may be set to 1. The RA MSG-B may include transmission timing adjustment information (e.g., TA instruction), uplink resource allocation information (e.g., UL grant), a TC-RNTI, and a UE de-competition ID for de-competition. The UE de-competition ID may be a terminal identifier (e.g., UE ID) included in the RA payload of the RA MSG-A. If the size of the UE de-competition ID is 6 bytes (i.e., 48 bits), then in Figure 12d, octet N may be octet 13.

[0320] In the RA MSG-B shown in Figure 12d, the UE decommissioning ID may be omitted. In this case, the UE decommissioning ID may be transmitted in the form of a MAC CE. For example, the RA MSG-B may consist of a MAC CE containing the information elements shown in Figure 12d and a separate MAC CE containing the UE decommissioning ID. If the RA MSG-B contains two MAC CEs, the two MAC CEs may be transmitted in the same radio resource area, or the two MAC CEs may be transmitted through different radio resource areas. Alternatively, the RA MSG-B may include "MAC CE + RRC control information" or "MAC CE + downlink data". The RRC control information or downlink data may be transmitted in the transmission resource for the second MAC CE of the RA MSG-B.

[0321] The MAC RAR format for RA MSG-B may be the same as the MAC RAR format for RA MSG2. In this case, the scheduling identifier for the transmission of message 2 (e.g., RA-RNTI, MSG-B RA-RNTI) may be shared between the two-step random access procedure and the four-step random access procedure.

[0322] The embodiment illustrated in Figure 12e may be a MAC RAR for RA MSG2. If C-RNTI is not assigned to a terminal and RA MSG-A is received from the terminal, the base station may transmit RA MSG-B to the terminal, which includes transmission timing adjustment information (e.g., TA information), uplink resource allocation information (e.g., UL grant), and scheduling identifier (e.g., TC-RNTI). The UE de-competition ID may be transmitted through the MAC header (or MAC subheader), and the LCID may be transmitted in a separate MAC CE. RA MSG-B, which includes the UE de-competition ID, may be configured as in the embodiment illustrated in Figure 12d. In this case, the T field in octet 1 may be replaced with the R field.

[0323] In the embodiment shown in Figure 12f, when C-RNTI is assigned to a terminal and RA MSG-A is received from that terminal, the base station can transmit RA MSG-B to the terminal, which includes transmission timing adjustment information (e.g., TA information), uplink resource allocation information (e.g., UL grant), and the scheduling identifier assigned to the terminal (e.g., C-RNTI).

[0324] Figure 13a is a conceptual diagram illustrating the fifth embodiment of RA MSG-B using a random access procedure, Figure 13b is a conceptual diagram illustrating the sixth embodiment of RA MSG-B using a random access procedure, and Figure 13c is a conceptual diagram illustrating the seventh embodiment of RA MSG-B using a random access procedure.

[0325] Referring to Figures 13a and 13c, the RA MSG-B may be transmitted based on scheduling information addressed by the RA-RNTI or C-RNTI. The RA MSG-B may selectively include a BI subheader (e.g., the BI subheader shown in Figure 12a). If the terminal performs a random access procedure to obtain system information, the RA MSG-B may include only a RAPID subheader (e.g., the RAPID subheader shown in Figure 12b).

[0326] In the embodiment illustrated in Figures 13b and 13c, if a scheduling identifier (e.g., C-RNTI) is not assigned to a terminal and the terminal performs a two-step random access procedure, the base station can transmit RA MSG-B based on MSG-B RA-RNTI. The RA preamble of RA MSG-A transmitted by the terminal may include the RAPID subheader shown in Figure 12b. The base station can receive RA MSG-A from the terminal and transmit RA MSG-B to the terminal as a response to RA MSG-A. The T field may indicate whether RA MSG-B contains a TA instruction.

[0327] An RA MSG-B containing a T field set to "1" (for example, the RA MSG-B shown in Figure 12d) may contain the following information elements.

[0328] - Transmission timing adjustment information (e.g., TA instruction) - Uplink resource allocation information (e.g., UL grants) - Scheduling identifier (e.g., TC-RNTI) -UE decompression ID

[0329] An RA MSG-B containing a T field set to "0" (for example, the RA MSG-B shown in Figure 13a) may contain the following information elements.

[0330] - Uplink resource allocation information (e.g., UL grants) - Scheduling identifier (e.g., TC-RNTI) -UE decompression ID

[0331] The E fields in the BI subheader shown in Figure 12a and the RAPID subheader shown in Figure 12b may indicate whether or not there is an extension. An E field set to "1" can indicate that other MAC subheaders are consecutively following that MAC subheader. An E field set to "0" can indicate that that MAC subheader is the last MAC subheader. In other words, there may be no other MAC subheaders following a MAC subheader containing an E field set to "0".

[0332] In the embodiment described above, the scheduling identifier for the scheduling information of message 2 (e.g., MSG-B RA-RNTI, RA-RNTI, C-RNTI) may vary depending on whether C-RNTI is assigned to the terminal attempting the two-step random access procedure. Alternatively, the base station can transmit the scheduling information of message 2 to the terminal using the scheduling identifier regardless of whether C-RNTI is assigned, and can then transmit message 2 (e.g., RA MSG2, RA MSG-B) to the terminal based on the scheduling information.

[0333] For example, if a base station receives an RA MSG-A containing a C-RNTI considering downlink radio resources or a RAR window, or if a base station is aware of the C-RNTI of a terminal that has initiated a two-step random access procedure using the CFRA scheme, the base station can transmit a DCI containing scheduling information to the terminal using MSG-B RA-RNTI or RA-RNTI, and then transmit message 2 (e.g., RA MSG-B) to the terminal using the resources indicated by the scheduling information. The base station can transmit message 2, which has the same format, to the terminal regardless of whether a C-RNTI has been assigned. Therefore, a terminal that has transmitted an RA MSG-A can perform a PDCCH monitoring operation using all of MSG-B RA-RNTI (or RA-RNTI) and C-RNTI to receive an RA MSG-B. If the MSG-B RA-RNTI for MSG-B with SRB is configured differently from the MSG-B RA-RNTI for MSG-B with UEsMux, the terminal can use both the MSG-B RA-RNTI for MSG-B with SRB and the MSG-B RA-RNTI for MSG-B with UEsMux to perform PDCCH monitoring operations.

[0334] On the other hand, a terminal can receive MSG-B with UEsMux that does not contain RRC control information. In this case, the terminal can perform PDCCH monitoring operations using the TC-RNTI included in MSG-B with UEsMux to receive RRC messages or DRB packets. The PDSCH on which MSG-B with UEsMux is transmitted in a two-step random access procedure may be configured differently from the PDSCH on which RRC messages or DRB packets are transmitted. A base station can transmit MSG-B with UEsMux on one PDSCH and DRB packets on another PDSCH. In this case, the terminal can perform PDCCH monitoring operations using the MSG-B RA-RNTI for MSG-B with UEsMux and all the TC-RNTI included in MSG-B with UEsMux to receive scheduling information for MSG-B with UEsMux and RRC messages (or DRB packets).

[0335] When RA MSG-B is transmitted via a two-stage random access procedure based on scheduling information addressed by MSG-B RA-RNTI, the base station can transmit message 2 (e.g., RA MSG-B) to one or more terminals via the PDSCH in the embodiments illustrated in Figures 12 and 13. A separate MAC subheader or a “MsgB-type” field indicating the format type of RA MSG-B can indicate the information elements contained in RA MSG-B. RA MSG-B may include one or more of the following: TA information, UL grant, TC-RNTI, UE ID, beam configuration information, and TCI status information.

[0336] Furthermore, the MAC subheader can indicate whether message 2 is an RA MSG2, a successful RAR, or a fallback RAR. For example, a terminal can transmit an RA MSG-A to a base station and receive message 2 from the base station. Based on the MAC subheader included in message 2, the terminal can determine whether message 2 is an RA MSG2, a successful RAR, or a fallback RAR.

[0337] The MAC RAR formats for successful RARs and fallback RARs may be the same as the MAC RAR formats of the embodiments illustrated in Figures 12, 13, 14, 16, and 17. RA MSG-Bs (e.g., successful RAR, fallback RAR) may include one or more of the following: TA information, UL grant, TC-RNTI, UE ID, beam configuration information, and TCI status information. RA MSG-Bs may be generated without the RAPID subheader shown in Figure 12b. That is, RA MSG-Bs may be generated by the embodiments shown in Figures 14, 16, and 17. To transmit RA MSG-Bs for one or more terminals, a MAC subheader may be generated to identify the RA MSG-B for each terminal. The MAC subheader may be located in the forward region of the MAC RAR within the MSG-B MAC PDU. That is, it may be configured as a separate MAC subheader, as shown in the embodiment illustrated in Figure 12. The terminal can determine the number of MAC RARs contained in the MSG-B MAC PDU based on the MAC subheader contained within the MSG-B MAC PDU.

[0338] In a two-step random access procedure, a terminal can distinguish between successful RARs and fallback RARs based on the MAC subheader within the MSG-B MAC PDU. The terminal can determine if message 2 is for it by comparing its own UE ID (e.g., the UE ID included in RA MSG-A) with the UE ID included in message 2. A successful RAR may mean "RA MSG-B transmitted by a base station that successfully received RA MSG-A (e.g., RA preamble, RA payload)." A base station can generate a single MAC PDU containing RA MSG-B for one or more terminals and transmit a single MAC PDU over a downlink channel (e.g., PDSCH).

[0339] If the transmission resources for the RA preamble of a two-stage random access procedure are the same as those for the RA preamble of a four-stage random access procedure, and the RA preamble index of the two-stage random access procedure is different from the RA preamble index of the four-stage random access procedure, then RA MSG2 and the fallback RAR can be multiplexed in a single MAC PDU. A single MAC PDU containing RA MSG2 and the fallback RAR can be transmitted over a downlink channel (e.g., PDSCH). This operation can be performed if the scheduling identifier for the two-stage random access procedure (e.g., RA-RNTI) is the same as the scheduling identifier for the four-stage random access procedure. Since RA MSG2 contains the index of the RA preamble contained in RA MSG1 transmitted by the terminal, and RA MSG-B contains the index of the RA preamble contained in RA MSG-A transmitted by the terminal, the terminal can distinguish between RA MSG2 and RA MSG-B based on the index of the RA preamble it transmitted.

[0340] Figure 14a is a conceptual diagram illustrating the eighth embodiment of RA MSG-B using a random access procedure, Figure 14b is a conceptual diagram illustrating the ninth embodiment of RA MSG-B using a random access procedure, and Figure 14c is a conceptual diagram illustrating the tenth embodiment of RA MSG-B using a random access procedure.

[0341] The embodiments shown in Figures 14a and 14b may be RA MSG-B generated based on the RAPID subheader, while the embodiment shown in Figure 14c may be RA MSG-B generated without the RAPID subheader. The E field can indicate whether other MAC RARs exist after the MAC RAR in question (i.e., the MAC RAR containing the E field). An E field set to "1" indicates that other MAC RARs exist after the MAC RAR in question. An E field set to "0" indicates that no other MAC RARs exist after the MAC RAR in question. That is, a MAC RAR containing an E field set to "0" may be the last MAC RAR.

[0342] The T field can indicate whether the MAC RAR is a successful RAR or a fallback RAR. A T field set to "1" indicates that the MAC RAR (i.e., the MAC RAR containing the T field) is a successful RAR (e.g., RA MSG-B as shown in Figure 14a). A T field set to "0" indicates that the MAC RAR is a fallback RAR (e.g., RA MSG-B as shown in Figure 14b). If RA MSG-B is generated without a RAPID subheader, the fallback RAR may include RAPID as in the embodiment shown in Figure 14c.

[0343] If the length of the UE IDs (e.g., UE decommissioning IDs) in a MAC RAR is fixed to two values, the ID field can indicate whether the UE IDs in the MAC RAR are long or short. An ID field set to "1" indicates that the MAC RAR (i.e., the MAC RAR containing the ID field) contains long UE IDs. An ID field set to "0" indicates that the MAC RAR contains short UE IDs. Because the length of the UE IDs in a MAC RAR is fixed to two values, the terminal can determine the number of octets representing the UE ID based on the ID field. In other words, the terminal can determine N as shown in Figure 14 based on the ID field.

[0344] The G field can indicate whether the second message contains a UL grant. A G field set to "1" indicates that the second message in question (i.e., the second message containing the G field) contains a UL grant. If a G field in a successful RAR is set to "1", that G field can also indicate that the successful RAR contains a UL grant. A G field set to "0" indicates that the second message in question does not contain a UL grant. When a G field is set to "1", the successful RAR (e.g., RA MSG-B shown in Figure 14b) can also contain a UL grant if the T field in the successful RAR is set to "1". A UL grant can contain one or more of the following: uplink resource allocation information (e.g., resource allocation information in the time and frequency domains), MCS level, BWP index, information indicating whether there is a retransmission (or repeat transmission), the number of retransmissions (or repeat transmissions), and time intervals for retransmissions (or repeat transmissions).

[0345] The embodiments illustrated in Figures 12 to 14 may be RA MSG-B. The arrangement order of fields included in RA MSG-B may differ from the arrangement order of fields in the embodiments illustrated in Figures 12 to 14. RA MSG-B may include some of the fields shown in Figures 12 to 14. The MAC subheader for RA MSG-B may be the BI subheader described above. The MAC subheader for a successful RAR or fallback RAR may be the RAPID subheader.

[0346] A MAC subheader for RA MSG-B may further include information indicating the time when RA MSG-A was received. This information may be represented by the SFN (system frame number), subframe index, slot index, symbol index, and / or offset. When a RAPID subheader is used for RA MSG-B, the RA MSG-B in question (e.g., an associated or corresponding RA MSG-B to the RAPID subheader) may be distinguished from other MAC RARs (e.g., RA MSG-B associated with a BI subheader, a successful RAR, or a fallback RAR). If the BI subheader is transmitted before a successful RAR or a fallback RAR, the BI subheader may be the first MAC subheader in a sequence. If the RAPID subheader is transmitted before the BI subheader, the BI subheader may be the last MAC subheader in a sequence.

[0347] The MAC subheaders for a successful RAR (e.g., the RAPID subheader) and the MAC subheaders for a fallback RAR (e.g., the RAPID subheader) may not be transmitted alternately. The RAPID subheader for the fallback RAR may be placed first, and the RAPID subheader for a successful RAR may be placed after the last RAPID subheader for the fallback RAR. Or, the RAPID subheader for a successful RAR may be placed first, and the RAPID subheader for a fallback RAR may be placed after the last RAPID subheader for a successful RAR. If the RAPID subheader for a successful RAR is placed before the RAPID subheader for a fallback RAR, the fallback RAR may be transmitted after the successful RAR. Or, if the RAPID subheader for a fallback RAR is placed before the RAPID subheader for a successful RAR, the successful RAR may be transmitted after the fallback RAR.

[0348] When an RA MSG-B is generated based on the RAPID subheader shown in Figure 12b, successful RARs and fallback RARs can be distinguished based on the control fields shown in Figure 14. For example, successful RARs and fallback RARs can be distinguished based on the T field. The MAC subheader for an RA MSG-B may be 2 bytes in size. A MAC subheader with a size of 2 bytes can include the aforementioned E field, T field (e.g., a T field with a size of 2 bits), and RAPID. A T field set to "00" can indicate that a BI is being transmitted. A T field set to "10" can indicate that the message 2 in question (e.g., message 2 associated with the MAC subheader containing the T field) is a successful RAR. A T field set to "01" can indicate that the message 2 in question is a fallback RAR. A T field set to "11" can indicate that the message 2 in question is an RA MSG-B (e.g., MSG-B with SRB) containing RRC control information. If the T field is set to "11", the MAC subheader and / or RAR may include an LCID for RRC messages (e.g., RRC control information).

[0349] The RAPID subheader may be included in the fallback RAR. If both the successful RAR and the fallback RAR are transmitted, the RAPID subheader may be associated with the fallback RAR. The fallback RAR may be placed / transmitted according to the placement order of the RAPID subheader. The successful RAR may be placed after the fallback RAR. That is, the successful RAR may be transmitted after the fallback RAR. An E field may be located in the region preceding the successful RAR, and the E field may indicate whether there are other RARs after the successful RAR in question. The successful RAR may contain the UE de-competition ID, TC-RNTI, TA instruction, etc. In this case, the placement order of the information elements included in the successful RAR may be as follows:

[0350] -Placement Order #1: E-field → UE de-competition ID → TC-RNTI → TA instruction -Placement Order #2: E-field → UE de-competition ID → TA instruction → TC-RNTI -Placement Order #3: UE Dispute ID → E Field → TC-RNTI → TA Instruction -Placement Order #4: UE Dispute ID → E Field → TA Instruction → TC-RNTI -Placement Order #5: E Field → TC-RNTI → TA Instruction → UE De-competition ID -Placement Order #6: E-field → TA instruction → TC-RNTI → UE de-competition ID -Placement Order #7: UE de-competition ID → TC-RNTI → TA instruction → E field -Placement Order #8: UE Dispute ID → TA Instruction → TC-RNTI → E Field -Placement order #9: TC-RNTI → TA instruction → UE de-competition ID → E field -Placement Order #10: TA Instruction → TC-RNTI → UE De-competition ID → E Field

[0351] The MSG-B MAC PDU or successful RAR may further include a BWP index to which an RRC message or uplink message is transmitted after the successful RAR. The terminal can obtain the BWP index from the RA MSG-B received from the base station and obtain scheduling information by performing a PDCCH monitoring operation within the BWP corresponding to the BWP index.

[0352] The following embodiments may be considered for the two-stage random access procedure and the four-stage random access procedure described above. The transmission resources for the RA preamble for the two-stage random access procedure and the four-stage random access procedure, respectively, may be configured based on "PRACH configuration method #1" or "PRACH configuration method #2" described below.

[0353] -PRACH configuration method #1: PRACH resources for two-step random access procedures are configured differently from PRACH resources for four-step random access procedures.

[0354] -PRACH configuration method #2: PRACH resources are shared between two-stage random access procedures and four-stage random access procedures. The same PRACH resources are used by both two-stage random access procedures and four-stage random access procedures.

[0355] A PRACH resource may be referred to as "RO (RACH occasion)". When PRACH configuration method #1 or PRACH configuration method #2 is used, the following may be considered. RA MSG-B in a two-step random access procedure may be distinguished from RA MSG2 in a four-step random access procedure. The terminal can determine whether message 2 (e.g., RA MSG-B) in a two-step random access procedure is a successful RAR, a fallback RAR, or a RAR containing BI. RAR transmission scenarios may be defined as shown in Table 1 below.

[0356] [Table 1]

[0357] When PRACH setting method #1 in Table 1 is used in a communication system, the successful RAR, fallback RAR, BI (e.g., RAR containing BI), and RA MSG2 may be identified by case #1 or case #2. In case #1, the RA-RNTI for RA MSG-B may be set differently from the RA-RNTI for RA MSG2. If the RO of a two-step random access procedure is distinguished from the RO of a four-step random access procedure, the RA-RNTI for a two-step random access procedure may be set differently from the RA-RNTI for a four-step random access procedure.

[0358] The ROs in a two-stage random access procedure and the ROs in a four-stage random access procedure can be distinguished based on the mapping relationship (e.g., association relationship) between PRACH and RO. Here, PRACH may be the resource to which message 1 (e.g., RA MSG1, RA MSG-A) was actually transmitted, and RO may be candidate resources to which message 1 can be transmitted. The terminal can distinguish between RA MSG-B and RA MSG2 using RA-RNTI associated with ROs in a two-stage random access procedure and RA-RNTI associated with ROs in a four-stage random access procedure, which are configured to be distinct from each other. The terminal can distinguish between successful RARs, fallback RARs, and BIs (e.g., RARs containing BIs) based on information obtained by PHY signaling and / or MAC signaling.

[0359] In Case #2, one RA-RNTI associated with the RO of a two-step random access procedure may be used for the transmission of a successful RAR, and another RA-RNTI associated with the RO of the two-step random access procedure may be used for the transmission of a fallback RAR. The RA-RNTI may be determined by the association scheme for the RO of a four-step random access procedure. A new association scheme may set a new RA-RNTI (e.g., MSG-B RA-RNTI) associated with the RO of a two-step random access procedure, and this new RA-RNTI may be used for the transmission of a fallback RAR. An offset may be applied to the association scheme for the RO of a four-step random access procedure in order to set the new RA-RNTI (e.g., MSG-B RA-RNTI).

[0360] The scheduling identifier for the transmission of a BI (e.g., a RAR containing a BI) may be a new RA-RNTI (e.g., MSG-B RA-RNTI). Alternatively, the scheduling identifier for the transmission of a BI (e.g., a RAR containing a BI) may be a scheduling identifier for a successful RAR or a fallback RAR. The terminal can distinguish between a BI (e.g., a RAR containing a BI), a successful RAR, and a fallback RAR based on information obtained through PHY signaling and / or MAC signaling.

[0361] When PRACH configuration method #2 in Table 1 is used in a communication system, the successful RAR, fallback RAR, BI (e.g., RAR containing BI), and RA MSG2 may be identified by case #3, case #4, or case #5. In PRACH configuration method #2, the RO for a two-step random access procedure may be the same as the RO for a four-step random access procedure, or the same RO may be shared between two-step and four-step random access procedures. The RA-RNTI associated with the RO for a four-step random access procedure may be the same as the RA-RNTI associated with the RO for a two-step random access procedure.

[0362] In Case #3, a new MSG-B RA-RNTI may be introduced, allowing the terminal to distinguish between successful RARs, fallback RARs, and BIs (e.g., RARs containing BIs) based on information obtained through PHY signaling and / or MAC signaling. The new MSG-B RA-RNTI may be set by applying an offset to the relevant scheme for ROs for a four-stage random access procedure.

[0363] In case #4, a new MSG-B RA-RNTI may be introduced for successful RARs and another new MSG-B RA-RNTI for fallback RARs. The new MSG-B RA-RNTI may be set by applying an offset to the associated scheme for ROs for four-stage random access procedures. An additional MSG-B RA-RNTI may be assigned for BI transmissions (e.g., RARs containing BIs). Alternatively, the scheduling identifier for BI transmissions (e.g., RARs containing BIs) may be a scheduling identifier for successful RAR or fallback RAR transmissions.

[0364] In case #5, a new MSG-B RA-RNTI may be introduced for successful RAR transmission. The RA-RNTI for fallback RAR may be the same as the RA-RNTI for RA MSG2. The base station can multiplex fallback RAR and RA MSG2 in a single MAC PDU, and the single MAC PDU can be transmitted through the PDSCH. Also, BI (e.g., RAR containing BI) can be multiplexed together with fallback RAR and RA MSG2 in a single MAC PDU. The terminal can distinguish between fallback RAR, BI (e.g., RAR containing BI), and RA MSG2 based on information obtained through PHY signaling and / or MAC signaling.

[0365] The base station can transmit to the terminal, through system information and / or control messages (e.g., dedicated control messages), the parameters for PRACH configuration method #1, the parameters for PRACH configuration method #2, and the offsets applied to the relevant scheme for configuring the new MSG-B RA-RNTI. Information elements transmitted through MAC signaling may be those indicated by the fields shown in Figures 12 to 14. Information elements transmitted through PHY signaling may be those indicated by the fields included in DCI.

[0366] If the MSG-B RA-RNTI for a successful RAR is configured differently from the MSG-B RA-RNTI for a fallback RAR, PHY signaling and / or MAC signaling for transmitting information to distinguish between successful and fallback RARs may not be necessary. If multiple RA MSG-A (e.g., RA preamble) are received from multiple terminals in a two-stage random access procedure, the base station can multiplex multiple successful RARs (or multiple fallback RARs) which are responses to multiple RA MSG-A in a single MAC PDU, and transmit the single MAC PDU through the PDSCH. To distinguish between successful and fallback RARs, informational elements contained in the MAC header, MAC subheader, and / or MAC message may be used.

[0367] For example, a base station can multiplex one or more successful RARs in a single MAC PDU based on one or more RAPID subheaders as shown in Figure 12b, and transmit one MAC PDU through a PDSCH. Alternatively, a base station can multiplex one or more fallback RARs in a single MAC PDU based on one or more RAPID subheaders as shown in Figure 12b, and transmit one MAC PDU through a PDSCH. A terminal can receive a RAPID subheader from the base station and receive a successful RAR or fallback RAR where the index of the RA preamble indicated by the RAPID subheader maps to the same case as the index of the RA preamble transmitted by the terminal. A BI can be transmitted along with the successful RAR or fallback RAR. The BI can be useful if a random access procedure fails; therefore, the BI can be transmitted along with the fallback RAR. Alternatively, the BI can be transmitted independently of the successful RAR and fallback RAR, respectively.

[0368] If the MSG-B RA-RNTI for successful RAR is configured differently from the MSG-B RA-RNTI for fallback RAR, the terminal can verify RA MSG-B using the MSG-B RA-RNTI for successful RAR. If RA MSG-B cannot be verified based on the MSG-B RA-RNTI for successful RAR, the terminal can verify RA MSG-B using the MSG-B RA-RNTI for fallback RAR. If RA MSG-B cannot be verified based on the MSG-B RA-RNTI for fallback RAR, the terminal can perform a backoff procedure based on BI and then perform a two-stage random access procedure or a four-stage random access procedure under pre-configured conditions.

[0369] Figure 15 is a timing diagram illustrating a third embodiment of a random access procedure in a communication system.

[0370] Referring to Figure 15, the communication system may include a base station, a first terminal, and a second terminal. The first terminal may be a terminal that performs a four-step random access procedure. The second terminal may be a terminal that performs a two-step random access procedure.

[0371] The first terminal can transmit RA MSG1 to the base station via PRACH. The base station can receive RA MSG1 from the first terminal and transmit RA MSG2 to the first terminal as a response to RA MSG1. The first terminal can receive RA MSG2 from the base station within the RAR window based on the results of its monitoring operation on the downlink channel (e.g., PDCCH). The RAR window can start from the end of the transmission of RA MSG1. Alternatively, the RAR window can start from the first symbol of the earliest CORESET (e.g., the CORESET on which PDCCH is located) after the transmission of RA MSG1. The RAR offset can indicate the difference between the end of the transmission of RA MSG1 (e.g., the last symbol of PRACH) and the first symbol of the CORESET.

[0372] The first terminal can transmit RA MSG3 to the base station using resources indicated by the scheduling information (e.g., UL grant) contained in RA MSG2. The base station can receive RA MSG3 from the first terminal and transmit RA MSG4 to the first terminal. The first terminal can receive RA MSG4 from the base station. If RA MSG4 is successfully received by the first terminal, the four-step random access procedure may be terminated.

[0373] On the other hand, in a two-stage random access procedure, the second terminal can transmit RA MSG-A to the base station. RA MSG-A may include an RA preamble and an RA payload. The RA preamble may be transmitted via PRACH, and the RA payload may be transmitted via PUSCH. The transmission interval D between the RA preamble and the RA payload may vary depending on the resources configured for the two-stage random access procedure (e.g., resource mapping relationships). The base station can transmit resource configuration information for the two-stage random access procedure (e.g., resource mapping relationship information) to the terminal (e.g., the second terminal) via system information and / or control messages.

[0374] The base station can receive RA MSG-A (e.g., RA preamble, RA payload) from the second terminal. If both the RA preamble and RA payload are successfully received, the base station can transmit RA MSG-B (e.g., successful RAR) to the second terminal as a response to RA MSG-A. If only the RA preamble is received, the base station can transmit a fallback RAR to the second terminal as a response to RA MSG-A. The terminal can perform PDCCH monitoring operations within the RAR window to receive RA MSG-B. The RAR window can start from the end of transmission of RA MSG-A (e.g., RA payload). Alternatively, the RAR window can start from the first symbol of the earliest CORESET (e.g., the CORESET on which the PDCCH is located) after the transmission of RA MSG-A (e.g., RA payload). The RAR offset can indicate the difference between the end of transmission of RA MSG-A (e.g., RA payload) (e.g., the last symbol of the PDCCH) and the first symbol of the CORESET.

[0375] The second terminal can receive RA MSG-B (e.g., successful RAR, fallback RAR) from the base station within the RAR window. If a successful RAR is received within the RAR window, the two-stage random access procedure may be terminated. If a fallback RAR is received within the RAR window, the second terminal can transmit the RA payload of RA MSG-A to the base station using the resources indicated by the scheduling information (e.g., UL grant) contained in the fallback RAR. That is, if a fallback RAR is received from the base station, the second terminal can determine that the base station received the RA preamble for RA MSG-A but not the RA payload for RA MSG-A. The base station can receive the RA payload of RA MSG-A from the second terminal and transmit RA MSG4 or the same information as RA MSG4 (e.g., identifier information for the second terminal for de-competition) to the second terminal as a response to the RA payload of RA MSG-A. If RA MSG4 is successfully received by the second terminal, the two-stage random access procedure (e.g., fallback random access procedure) may be terminated.

[0376] The RAR window for a four-stage random access procedure (hereinafter referred to as the "four-stage RAR window") may overlap with the RAR window for a two-stage random access procedure (hereinafter referred to as the "two-stage RAR window") due to the RAR offset and / or transmission interval D. Alternatively, the four-stage RAR window may not overlap with the two-stage RAR window due to the RAR offset and / or transmission interval D. If the four-stage RAR window overlaps with the two-stage RAR window, a method is needed to distinguish whether message 2 (e.g., RAR) received in the overlapping section between the four-stage RAR window and the two-stage RAR window is RA MSG2 or RA MSG-B (e.g., successful RAR, fallback RAR). If the aforementioned PRACH setting method #2 is used, an additional method is needed to distinguish whether message 2 received in the overlapping section between the four-stage RAR window and the two-stage RAR window is RA MSG2 or RA MSG-B. Based on the aforementioned cases #3 to #5, RA MSG2, successful RAR, fallback RAR, and BI (e.g., RAR with BI) can be distinguished.

[0377] If the 4-stage RAR window does not overlap with the 2-stage RAR window, the transmission resources of RA MSG2 may differ from those of RA MSG-B in the time domain. Since the interval in which the first terminal (e.g., the terminal that initiated the 4-stage random access procedure) performs PDCCH monitoring operations within the RAR window is different from the interval in which the second terminal (e.g., the terminal that initiated the 2-stage random access procedure) performs PDCCH monitoring operations within the RAR window, it is not necessary to use different scheduling identifiers for the first and second terminals. Furthermore, MAC messages may not be used to distinguish between the 4-stage random access procedure and the 2-stage random access procedure.

[0378] Even when PRACH setting method #2 is used, the PRACH for a two-stage random access procedure does not need to be set differently from the PRACH for a four-stage random access procedure. The base station can transmit information indicating whether there is an overlap between the four-stage RAR window and the two-stage RAR window, and information on setting PRACH and RO due to the overlap between the four-stage RAR window and the two-stage RAR window, to the terminal using system information and / or control messages (e.g., dedicated control messages). If information indicating whether there is an overlap between the four-stage RAR window and the two-stage RAR window is not received from the base station, the terminal (e.g., first terminal, second terminal) can determine whether there is an overlap between the two-stage RAR window and the four-stage RAR window using the RAR offset, transmission interval D, four-stage RAR window setting information, and / or two-stage RAR window setting information.

[0379] The base station can transmit to the terminal, using system information and / or control messages (e.g., dedicated control messages), parameters for a two-step random access procedure, information indicating whether or not to apply the parameters in the two-step random access procedure, parameters for a four-step random access procedure, and information indicating whether or not to apply the parameters in the four-step random access procedure.

[0380] Figure 16a is a conceptual diagram illustrating the third embodiment of the MAC subheader using a random access procedure, Figure 16b is a conceptual diagram illustrating the fourth embodiment of the MAC subheader using a random access procedure, Figure 16c is a conceptual diagram illustrating the eleventh embodiment of the RA MSG-B using a random access procedure, Figure 16d is a conceptual diagram illustrating the twelfth embodiment of the RA MSG-B using a random access procedure, Figure 16e is a conceptual diagram illustrating the thirteenth embodiment of the RA MSG-B using a random access procedure, Figure 16f is a conceptual diagram illustrating the fourteenth embodiment of the RA MSG-B using a random access procedure, and Figure 16g is a conceptual diagram illustrating the fifteenth embodiment of the RA MSG-B using a random access procedure.

[0381] The MAC subheader shown in Figure 16a may be subheader #1 for successful RARs, and the MAC subheader shown in Figure 16b may be subheader #2 for successful RARs (e.g., UE CRID (UE contention resolution ID) subheader). In the embodiments shown in Figures 16a and 16b, the T field may be set to "0" and the S field may be set to "1". An S field set to "0" can indicate that the MAC subheader in question (e.g., the MAC subheader containing the S field) contains a BI. An S field set to "1" can indicate that the MAC subheader in question is a subheader for successful RARs. Subheader #1 for successful RARs shown in Figure 16a may further include a NOSR (number of success RAR) field, which can indicate the number of successful RARs contained in the MSG-B MAC PDU. Alternatively, the NOSR field can indicate whether a successful RAR exists in the MSG-B MAC PDU. In this case, the size of the NOSR field may be 1 bit. For example, setting the NOSR field to "1" indicates that RA MSG-B contains a successful RAR. Setting the NOSR field to "0" indicates that RA MSG-B does not contain a successful RAR.

[0382] The RA MSG-B shown in Figure 16c may be a fallback RAR, and the RA MSG-B shown in Figure 16d may be a successful RAR. In the embodiments shown in Figures 16c and 16d, a T field set to "0" can indicate that the RA MSG-B (e.g., the MAC RAR containing the T field) is a fallback RAR, and a T field set to "1" can indicate that the RA MSG-B is a successful RAR. The order of the fields included in a successful RAR can be set in various ways. For example, the UE de-competition ID may be located after the T field in a successful RAR.

[0383] When the RAPID subheader indicates a fallback RAR, a subheader for a successful RAR may be used in the embodiments shown in Figures 12e, 16e, 16f, and 16g. The RAPID subheader may correspond to a fallback RAR. The subheader for a successful RAR can indicate whether the MSG-B MAC PDU contains a successful RAR, or it can indicate the number of successful RARs contained in the MSG-B MAC PDU. The RA MSG-B shown in Figure 12e may be a fallback RAR. The RA MSG-B shown in Figures 16e to 16g may be a successful RAR.

[0384] If the index of the RA preamble indicated by the RAPID subheader is the same as the index of the RA preamble in the RA MSG-A transmitted from the terminal, the terminal can obtain a fallback RAR from the base station corresponding to the RAPID subheader. If there is no RAPID subheader indicating the same RA preamble as the RA preamble in the RA MSG-A transmitted from the terminal, the terminal can check the information elements contained in the subheader for a successful RAR. If a successful RAR is found to exist, the terminal can obtain the successful RAR from the base station and compare the UE decommissioning ID contained in the successful RAR with the UE decommissioning ID contained in the RA MSG-A transmitted from the terminal. The UE decommissioning ID comparison operation may be performed until a successful RAR with an E field set to "0" (e.g., the last successful RAR) is obtained. If the UE decommissioning ID contained in the successful RAR is the same as the UE decommissioning ID contained in the RA MSG-A transmitted from the terminal, the terminal can determine that the two-step random access procedure is complete.

[0385] Alternatively, subheader #2 for successful RAR, as illustrated in Figure 16b, can indicate whether RA MSG-B contains a successful RAR. Subheader #2 for successful RAR may include an S field set to "1", a UE de-competition ID, etc. If both the T field and S field in subheader #2 for successful RAR are set to "0", the terminal can determine that the corresponding MAC subheader (e.g., subheader #2 for successful RAR) contains a BI.

[0386] If the T field is set to "0" and the S field is set to "1" in subheader #2 for successful RAR, the terminal can determine that the MAC subheader in question (e.g., subheader #2 for successful RAR) contains the UE de-competition ID. If the UE de-competition ID contained in subheader #2 for successful RAR is the same as the UE de-competition ID contained in the RA MSG-A transmitted from the terminal, the terminal can obtain a successful RAR associated with subheader #2 for successful RAR. In this case, the successful RARs illustrated in Figures 16e to 16g do not need to contain the UE de-competition ID. Also, the successful RAR does not need to contain the E field.

[0387] Figure 17a is a conceptual diagram illustrating the fifth embodiment of the MAC subheader using a random access procedure, Figure 17b is a conceptual diagram illustrating the sixth embodiment of the MAC subheader using a random access procedure, Figure 17c is a conceptual diagram illustrating the seventh embodiment of the MAC subheader using a random access procedure, Figure 17d is a conceptual diagram illustrating the eighth embodiment of the MAC subheader using a random access procedure, Figure 17e is a conceptual diagram illustrating the ninth embodiment of the MAC subheader using a random access procedure, Figure 17f is a conceptual diagram illustrating the sixteenth embodiment of RA MSG-B using a random access procedure, and Figure 17g is a conceptual diagram illustrating the seventeenth embodiment of RA MSG-B using a random access procedure.

[0388] The MAC subheaders shown in Figures 17a to 17e may be MAC subheaders for RA MSG-B. A MAC subheader may contain a T field, the size of which may be 2 bits. In the embodiment shown in Figure 17a, a T field set to "00" may indicate that the MAC subheader contains BI. In the embodiment shown in Figure 17b, a T field set to "01" may mean that the MAC subheader indicates a fallback RAR. In the embodiment shown in Figure 17c, a T field set to "10" may mean that the MAC subheader indicates a successful RAR.

[0389] In the embodiment illustrated in Figure 17d, the T field set to "11" can indicate that the MAC subheader is the last MAC subheader among multiple MAC subheaders. In the MAC subheader illustrated in Figure 17d, all bits after the T field can be set to "0" or "1". The size of a MAC subheader indicating that it is the last MAC subheader among multiple MAC subheaders can be one octet, and all bits constituting the octet can be set to the same value (e.g., 0 or 1). If a MAC subheader that does not indicate a successful RAR and / or fallback RAR (e.g., the MAC subheader illustrated in Figure 17a) is transmitted, the MAC subheader illustrated in Figure 17d may be transmitted after that MAC subheader.

[0390] Padding bits or bytes may be added to the MAC PDU containing the RA MSG-B. In this case, the spare bits (R) of the MAC subheader, as shown in Figure 17d, can indicate the number of padding bits or bytes included in the MSG-B MAC PDU. If a MAC subheader containing a T field set to "11" is detected, or if a MAC subheader containing one octet set to the same value (e.g., 0 or 1) is detected, the terminal can determine that the MAC subheader for the RA MSG-B is complete. In this case, the terminal can abort the MAC subheader search operation (e.g., confirmation operation) and perform the RA MSG-B reception operation (e.g., BI, successful RAR, fallback RAR) based on the MAC subheader search result (e.g., confirmation result).

[0391] If the RAPID contained in the MAC subheader is the same as the index in the RA preamble of the RA MSG-A transmitted from the terminal, the terminal can perform a successful RAR or fallback RAR reception operation. If a MAC subheader containing the T field set to "10", RAPID, and UE de-competition ID (for example, the MAC subheader shown in Figure 17e) is received, and the UE de-competition ID contained in the MAC subheader is the same as the UE de-competition ID contained in the RA MSG-A transmitted from the terminal, the terminal can perform a successful RAR reception operation. Here, the fallback RAR may be the fallback RAR shown in Figure 12e.

[0392] If the MAC subheader shown in Figure 17c is received, the successful RAR may consist of the remaining fields from the RA MSG-B shown in Figures 16e to 16g, excluding the E field. If the MAC subheader shown in Figure 17e is received, the successful RAR may be the RA MSG-B shown in Figures 17f and 17g.

[0393] When a two-step random access procedure requires the transmission of radio bearer (e.g., SRB (signaling radio bearer) or DRB (data radio bearer)) packets, the MAC message used for transmitting the radio bearer packets may include a successful RAR and other MAC subPDUs (or MAC PDUs). The radio bearer packets may be contained within other MAC subPDUs or other MAC PDUs. The spare bits (R) included in the MAC subheader or MAC RAR that constitute the aforementioned RA MSG-B can indicate whether a MAC subPDU or MAC PDU containing the radio bearer packets exists.

[0394] MAC control information for wireless bearer packets may include one or more of the following: an indicator indicating the presence or absence of a MAC subPDU or MAC PDU for the transmission of wireless bearer packets (e.g., whether or not transmission occurs); a time offset from the time of reception of the RA MSG-B (e.g., start and end of reception) to the time of reception of the MAC subPDU or MAC PDU for the transmission of wireless bearer packets (e.g., start and end of reception); the LCID of the wireless bearer; beam setting information (or TCI state, active TCI index information) for the MAC subPDU or MAC PDU for the transmission of wireless bearer packets; and BWP information on which the MAC subPDU or MAC PDU for the transmission of wireless bearer packets is transmitted (e.g., BWP setting parameters, BWP index, or BWP activation indicator information).

[0395] The order of the fields included in the aforementioned RA MSG-B can vary. The RA MSG-B may contain one or more of the fields mentioned above. The MAC subheader, the MAC subPDU (or MAC PDU) containing the fallback RAR, and the MAC subPDU (or MAC PDU) containing the successful RAR may each be aligned byte by byte. If the MAC subheader, the MAC subPDU (or MAC PDU) containing the fallback RAR, and the MAC subPDU (or MAC PDU) containing the successful RAR are not aligned byte by byte, spare bits may be omitted. If the successful RAR is located after the fallback RAR, a specific bit pattern (e.g., one octet set to the same value) may be inserted after the fallback RAR to demarcate the boundary between the fallback RAR and the successful RAR. A specific bit pattern (e.g., one octet set to the same value) may be inserted after the fallback RAR and / or successful RAR to indicate that a valid RA MSG-B or MAC RAR has ended.

[0396] Figure 18 is a flowchart illustrating a third embodiment of a random access procedure in a communication system.

[0397] Referring to Figure 18, the communication system may include base stations and terminals. The base stations may be base stations 110-1, 110-2, 110-3, 120-1, and 120-2 as shown in Figure 1, and the terminals may be terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 as shown in Figure 1. The base stations and terminals may be identical or similarly configured to the communication node 200 shown in Figure 2.

[0398] The base station can transmit configuration information for a four-stage random access procedure (hereinafter referred to as "four-stage configuration information") to the terminal (S1801). The base station can also transmit configuration information for a two-stage random access procedure (hereinafter referred to as "two-stage configuration information") to the terminal (S1802). The four-stage configuration information and the two-stage configuration information may be transmitted through different messages, or the four-stage configuration information and the two-stage configuration information may be transmitted through a single message. Here, the message may be an RRC message or a MAC message.

[0399] Each of the four-stage and two-stage configuration information may include PRACH occasion configuration information, RA preamble sequence information, channel quality critical values ​​(e.g., RSRP critical values), etc. When the CFRA method is used, each of the four-stage and two-stage configuration information may include PRACH occasion configuration information and RA preamble sequence information allocated specifically for the terminal. The PRACH occasion configuration information may include PRACH occasion period information, time-domain resource information, and frequency-domain resource information. The two-stage configuration information for the CFRA method may further include RA payload configuration information for RA MSG-A. Here, the RA payload configuration information may be determined based on the mapping relationship (e.g., one-to-one mapping relationship) between the transmission resources of the RA preamble and the transmission resources of the RA payload. The two-stage configuration information for the CFRA method may include one or more of the information elements #1 to #6 described below. The four-stage or two-stage configuration information for the CFRA method may be transmitted to the terminal using a dedicated control message.

[0400] A PRACH occasion for a four-stage random access procedure may be the same as a PRACH occasion for a two-stage random access procedure. Alternatively, a PRACH occasion for a four-stage random access procedure may be different from a PRACH occasion for a two-stage random access procedure. In this case, the base station can determine that message 1 received in a PRACH occasion for a four-stage random access procedure is RA MSG1, and that message 1 received in a PRACH occasion for a two-stage random access procedure is RA MSG-A.

[0401] The sequence (or index) group to which an RA preamble sequence (or index) used in a four-step random access procedure belongs (hereinafter referred to as the "four-step sequence group") may be defined differently from the sequence group to which an RA preamble sequence used in a two-step random access procedure belongs (hereinafter referred to as the "two-step sequence group"). The four-step sequence group may be referred to as the four-step sequence set, and the two-step sequence group may be referred to as the two-step sequence set. In the following embodiment, an RA preamble sequence may mean an RA preamble index, a four-step sequence group may mean a four-step index group or a four-step index set, and a two-step sequence group may mean a two-step index group or a two-step index set.

[0402] RA preamble sequences belonging to a 4-stage sequence group may differ from those belonging to a 2-stage sequence group. In this case, if the PRACH occasion for a 4-stage random access procedure is the same as the PRACH occasion for a 2-stage random access procedure, the base station can determine, based on the RA preamble sequence, that message 1 received in the PRACH occasion is either RA MSG1 or RA MSG-A. 4-stage configuration information may include information for a 4-stage sequence group, and 2-stage configuration information may include information for a 2-stage sequence group.

[0403] A channel quality critical value (e.g., RSRP critical value) can be used to determine the type of random access procedure performed by the terminal. If the channel quality between the terminal and the base station is equal to or greater than the RSRP critical value, the terminal can perform a two-step random access procedure. If the channel quality between the terminal and the base station is less than the RSRP critical value, the terminal can perform a four-step random access procedure. The channel quality critical value may be included in system information instead of four-step and two-step configuration information. That is, the base station can transmit system information to the terminal that includes the RSRP critical value (e.g., channel quality critical value) used to determine the type of random access procedure.

[0404] Furthermore, the two-stage configuration information may include one or more of the following information elements.

[0405] -Information Element #1: Time-domain offset between the resource (e.g., PRACH) to which the RA preamble contained in RA MSG-A is transmitted and the resource (e.g., PUSCH) to which the RA payload contained in RA MSG-A is transmitted. -Information Element #2: Frequency domain offset between the resource to which the RA preamble contained in the RA MSG-A is transmitted (e.g., PRACH) and the resource to which the RA payload contained in the RA MSG-A is transmitted (e.g., PUSCH). - Information Element #3: Mapping relationship information between the resource to which the RA preamble contained in the RA MSG-A is transmitted (e.g., PRACH) and the resource to which the RA payload contained in the RA MSG-A is transmitted (e.g., PUSCH). - Information element #4: Information that indicates the start timing of the resource to which the RA payload contained in RA-MSG-A is transmitted (e.g., the start symbol index of PUSCH) - Information Element #5: Information contained in RA-MSG-A that indicates the length of the resource being transmitted by the RA payload (e.g., duration of PUSCH, interval between PUSCHs, number of PUSCHs, number of symbols constituting a PUSCH (or start symbol, end symbol, and / or length of PUSCH)) -Information Element #6: Information indicating the MCS level used for transmitting the RA payload contained in RA MSG-A.

[0406] Two-stage configuration information includes a time domain offset which can be either "the interval between the end of PRACH and the start of PUSCH" or "the interval between the start of PRACH and the start of PUSCH". Two-stage configuration information includes a frequency domain offset which can be "the interval between the start RB of PRACH and the start RB of PUSCH", "the interval between the end RB of PRACH and the start RB of PUSCH", or "the interval between a reference RB (e.g., the start RB of the system bandwidth or BWP (bandwidth part)) and the start RB of PUSCH". Here, RB can be PRB or CRB. The start RB may be the RB with the lowest frequency resources among the RBs occupied by the channel in question (e.g., bandwidth), and the end RB may be the RB with the highest frequency resources among the RBs occupied by the channel in question.

[0407] Two-stage configuration information may include information indicating the MCS level. The RA payload contained in RA MSG-A may be transmitted based on the MCS level indicated by the two-stage configuration information. Alternatively, information indicating the MCS level for the RA payload contained in RA MSG-A may be included in the system information instead of the two-stage configuration information. That is, the base station may transmit system information containing information indicating the MCS level to the terminal. The terminal may receive one or more of the system information, four-stage configuration information, and two-stage configuration information from the base station. If four-stage configuration information is received and two-stage configuration information is not received, the terminal may perform a four-stage random access procedure based on the four-stage configuration information. If two-stage configuration information is received and four-stage configuration information is not received, the terminal may perform a two-stage random access procedure based on the two-stage configuration information. If both four-stage and two-stage configuration information are received, the type of random access procedure performed by the terminal may be determined based on the channel quality between the terminal and the base station (S1803). For example, a terminal can receive a reference signal and / or SS / PBCH block from a base station and measure the quality of the received signal (e.g., RSRP). If the RSRP measured by the terminal is greater than or equal to the RSRP critical value set by the base station, the terminal can perform a two-step random access procedure based on the two-step configuration information. If the RSRP measured by the terminal is less than the RSRP critical value set by the base station, the terminal can perform a four-step random access procedure based on the four-step configuration information.

[0408] If it is determined that a two-stage random access procedure will be performed, the terminal can generate an RA MSG-A containing an RA preamble and an RA payload, and transmit the RA MSG-A to the base station (S1804). The terminal can select an RA preamble sequence within a two-stage sequence group and transmit the selected RA preamble sequence (i.e., the RA preamble). The RA preamble may be transmitted through a PRACH occasion indicated by the two-stage configuration information.

[0409] Furthermore, when switching to a two-stage random access procedure using the CBRA method while CFRA is configured, the terminal can determine the group of RA preamble sequences based on the size of the RA payload in RA MSG-A or RA MSG3 in the four-stage random access procedure, select an RA preamble within the determined group, and transmit the selected RA preamble. When switching from a two-stage random access procedure to a four-stage random access procedure, the terminal can select the group of RA preamble sequences and the RA preamble in the same way and transmit the selected RA preamble.

[0410] The RA payload can be transmitted via a PUSCH confirmed by one or more of the following in the two-step configuration information: time domain offset, frequency domain offset, PUSCH start symbol index, PUSCH duration, and mapping relationship information. The RA payload can be transmitted based on the MCS level set by the base station. The RA payload can include one or more of the following: terminal identifier, data, and control information. Here, the control information can include one or more of the following: BSR, measurement result information (e.g., radio channel quality information), BFR request information, RLF report information, RRC connection setup request information, RRC connection re-establishment request information, resume request information, terminal location information (e.g., location estimated by GPS signal, positioning measurement method, or built-in sensor, etc.), and system information transmission request information. The RA payload can include the information contained in RA MSG3 via a four-step random access procedure. The terminal can calculate RA-RNTI based on the radio resource information of the PRACH (e.g., PRACH occasion) to which the RA preamble was transmitted. The RA-RNTI used for receiving RA MSG-B in a two-step random access procedure may be referred to as "MSG-B RA-RNTI" or "MSGB-RNTI". For example, MSGB-RNTI may be calculated based on Equation 1 below.

[0411]

number

[0412] s id t can be the index of the first symbol in the PRACH occasion. id f could be the index of the first slot of the PRACH occasion in a system frame (e.g., a radio frame). id This can be an index of PRACH occasions in the frequency domain. UL carrier_idThis can specify the UL carrier used for RA preamble transmission. When a NUL (normal uplink) carrier is used, UL carrier_id It can be 0. When a SUL (supplementary uplink) carrier is used, UL carrier_id It can be 1. The offset can be signaled from the base station to the terminal. For example, the base station can transmit an RRC message, MAC message, or DCI containing the offset to the terminal. The offset used for generating the MSG-RNTI can be included in system information or two-stage configuration information. A time-domain offset or frequency-domain offset included in the two-stage configuration information can be used as the offset for generating the MSG-RNTI. Alternatively, the offset can be predefined in the technical standard.

[0413] The RA-RNTI used for receiving RA MSG 2 in a four-stage random access procedure can be calculated based on Equation 2 below. That is, the offset in Equation 1 may not apply to Equation 2. Therefore, even if the radio resources of the PRACH occasion in which the RA preamble was transmitted in a two-stage random access procedure are the same as the radio resources of the PRACH occasion in which the RA preamble was transmitted in a four-stage random access procedure, the MSGB-RNTI may be set differently from the RA-RNTI in the four-stage random access procedure.

[0414]

number

[0415] On the other hand, a base station can receive RA MSG-A or RA MSG1 by performing monitoring operations on PRACH occasions indicated by two-stage configuration information and / or four-stage configuration information. If "Message 1 is received on a PRACH occasion indicated by two-stage configuration information" or "the RA preamble sequence of Message 1 belongs to a two-stage sequence group", the base station can determine that Message 1 is an RA MSG-A of a two-stage random access procedure. Conversely, if "Message 1 is received on a PRACH occasion indicated by four-stage configuration information" or "the RA preamble sequence of Message 1 belongs to a four-stage sequence group", the base station can determine that Message 1 is an RA MSG1 of a four-stage random access procedure.

[0416] When RA MSG-A is received, the base station can verify the information contained in the RA payload of RA MSG-A. The base station can also calculate MSGB-RNTI based on Equation 1. When RA MSG1 is received, the base station can calculate RA-RNTI based on Equation 2. Here, we assume that the base station received RA MSG-A from the terminal.

[0417] The base station can generate RA MSG-B in response to RA MSG-A (S1805). RA MSG-B may be a MAC PDU. RA MSG-B may contain one or more MAC sub-PDUs. Each of the one or more MAC sub-PDUs may be generated by one of the following configurations. MAC sub-PDUs may be configured by the embodiments illustrated in Figures 12, 14, 16, and / or 17 described above.

[0418] -Configuration method #1: MAC subheader including BI -Configuration method #2: MAC subheader and fallback RAR -Configuration Method #3: MAC Subheader and Successful RAR -Configuration method #4: MAC subheader and MAC SDU (e.g., data or control information) -Configuration Method #5: MAC Subheader and Padding

[0419] A MAC subheader may include a first indicator that indicates the type of MAC subPDU containing the MAC subheader (e.g., the type of information contained in the MAC subPUD). The first indicator can indicate that the MAC subPDU is a first-type MAC subPDU containing BI (e.g., a MAC subPDU by configuration scheme #1), a second-type MAC subPDU containing fallback RAR (e.g., a MAC subPDU by configuration scheme #2), or a third-type MAC subPDU containing successful RAR (e.g., a MAC PDU by configuration scheme #3). The size of the first indicator may be 2 bits, the first bit of which can indicate a first-type MAC subPDU or a second-type MAC subPDU, and the second bit of which can indicate a third-type MAC subPDU.

[0420] Alternatively, the first indicator can indicate that the MAC sub-PDU is a first-type MAC sub-PDU containing a BI (e.g., a MAC sub-PDU by configuration scheme #1), a second-type MAC sub-PDU containing a fallback RAR (e.g., a MAC sub-PDU by configuration scheme #2), a third-type MAC sub-PDU containing a successful RAR (e.g., a MAC PDU by configuration scheme #3), or a fourth-type MAC sub-PDU containing a MAC SDU (e.g., a MAC PDU by configuration scheme #4). The size of the first indicator can be 2 bits, the first bit of which can indicate a first-type MAC sub-PDU or a second-type MAC sub-PDU, and the second bit of which can indicate a third-type MAC sub-PDU or a fourth-type MAC sub-PDU.

[0421] The MAC subheader may also include a second indicator that indicates the presence or absence of a fourth type-MAC sub-PDU. The size of the second indicator can be 1 bit. A second indicator set to "0" indicates that a fourth type-MAC sub-PDU does not exist. A second indicator set to "1" indicates that a fourth type-MAC sub-PDU exists.

[0422] Furthermore, a MAC subheader may include a third indicator that indicates whether or not other MAC sub-PDUs exist after the MAC sub-PDU containing the MAC subheader. The size of the third indicator can be 1 bit. A third indicator set to "0" indicates that no other MAC sub-PDUs exist after the MAC sub-PDU in question. A third indicator set to "1" indicates that other MAC sub-PDUs exist after the MAC sub-PDU in question.

[0423] Furthermore, the first type-MAC sub-PDU may contain information indicating a conversion to a four-stage random access procedure. Information indicating a conversion from a two-stage random access procedure to a four-stage random access procedure may be set by separate bits, which may be included in the first type-MAC sub-PDU together with the BI. Alternatively, information indicating a conversion from a two-stage random access procedure to a four-stage random access procedure may be set by a specific pattern of the bit sequence that constitutes the BI.

[0424] The base station can generate a DCI containing resource allocation information for RA MSG-B, perform scrambling operations on the DCI (e.g., the CRC of the DCI) using MSGB-RNTI, and transmit the DCI (e.g., the scrambled DCI) to the terminal (S1806).

[0425] DCI can be transmitted within a RAR window. A RAR window can begin at the start of PRACH, the end of PRACH, the start of PUSCH, the end of PUSCH, the start of the RA preamble, the end of the RA preamble, the start of the RA payload, or the end of the RA payload. Here, PRACH may be the radio resource on which the RA preamble of RA MSG-A is transmitted, and PUSCH may be the radio resource on which the RA payload of RA MSG-A is transmitted. The base station can notify the terminal of the duration of the RAR window (or the end of the RA window, the timer of the RAR window). Information indicating the duration of the RAR window (or the end of the RA window, the timer of the RAR window) may be included in system information and / or two-stage configuration information.

[0426] The terminal can perform PDCCH monitoring operations using MSGB-RNTI. PDCCH monitoring operations can be performed within a RAR window. For example, the terminal can perform descrambling operations on DCI received from the base station using MSGB-RNTI. If the DCI is successfully received from the base station, the terminal can obtain resource allocation information for RA MSG-B contained in the DCI. The terminal can perform monitoring operations for receiving RA MSG-B on the radio resources indicated by the resource allocation information for RA MSG-B.

[0427] The base station can transmit the RA MSG-B to the terminal using the DCI described in step S1806 (S1807). The RA MSG-B can be transmitted through radio resources indicated by resource allocation information included in the DCI scrambled by MSGB-RNTI. The terminal can receive the RA MSG-B from the base station. The terminal can determine the type of the MAC sub-PDU by checking the first indicator of the MAC sub-header included in the MAC sub-PDU identified through the RA MSG-B. For example, the terminal can determine whether the MAC sub-PDU is a first-type MAC sub-PDU, a second-type MAC sub-PDU, or a third-type MAC sub-PDU based on the first indicator included in the MAC sub-header. The terminal can also determine if a fourth-type MAC sub-PDU exists by checking the second indicator included in the MAC sub-header.

[0428] Furthermore, the terminal can check if other MAC sub-PDUs exist after the relevant MAC sub-PDU by examining the third indicator in the MAC sub-header. If other MAC sub-PDUs exist, the terminal can examine the first, second, and / or third indicators contained in those other MAC sub-PDUs and perform actions based on the results of the examination.

[0429] If the RA MSG-B received from the base station includes a MAC subheader containing a BI, the terminal can perform a two-step random access procedure after a backoff operation due to the received BI. Alternatively, the terminal can perform a four-step random access procedure again without a backoff operation. Furthermore, if information is received from the base station instructing a transition to a four-step random access procedure, the terminal can perform a four-step random access procedure again without a backoff operation.

[0430] If the RA MSG-B received from the base station includes a MAC subheader and a fallback RAR, the terminal can transmit RA MSG3 to the base station using a four-step random access procedure. That is, a two-step random access procedure can be converted to a four-step random access procedure. RA MSG3 can be transmitted through radio resources indicated by the UL grant included in the fallback RAR. RA MSG-B, including the MAC subheader and fallback RAR, can be generated based on the format of RA MSG2 in a four-step random access procedure. For example, RA MSG-B may contain the information included in RA MSG2. The base station can receive RA MSG3 from the terminal and transmit RA MSG4 to the terminal. The terminal can receive RA MSG4 from the base station. In this case, the random access procedure can be terminated; that is, competition between terminals can be eliminated.

[0431] If the RA MSG-B received from the base station contains a MAC subheader and a successful RAR, the terminal can determine that the two-step random access procedure has been completed. If the RA MSG-B containing the MAC subheader and a successful RAR is received within the RAR window, the terminal can determine that the two-step random access procedure has been completed. In other words, competition between terminals can be resolved.

[0432] When the CFRA two-stage random access procedure is performed in steps S1804 to S1807, the base station may only receive the RA preamble of RA MSG-A in CFRA format from the terminal, and may not receive the RA payload of RA MSG-A. In this case, the base station can identify the terminal through the radio resource or index information of the RA preamble of RA MSG-A in CFRA format received from the terminal. Therefore, the base station can transmit a DCI containing scheduling information for the PDSCH on which RA MSG-B is transmitted to the terminal using a scheduling identifier (e.g., C-RNTI) or MSGB-RNTI specifically assigned to the terminal. Therefore, the terminal can receive the DCI by performing a PDCCH monitoring operation using MSGB-RNTI or the scheduling identifier assigned to it. Through the DCI received from the base station, the terminal can obtain one or more of the scheduling information for the PDSCH on which RA MSG-B is transmitted, downlink scheduling information, and uplink scheduling information.

[0433] Furthermore, if the aforementioned two-stage configuration information (e.g., information element #1 to information element #6) does not include configuration information for the radio resources for the RA payload, the terminal can transmit only the RA preamble in stage S1804 when transmitting the RA MSG-A. In other words, if the two-stage configuration information does not include related information (e.g., mapping relationship information) between the RA preamble and the RA payload contained in the RA MSG-A, the terminal can transmit only the RA preamble of the RA MSG-A, and may not be able to transmit the RA payload of the RA MSG-A. In this case, if the terminal transmits only the RA preamble of the RA MSG-A for the two-stage random access procedure, the base station and the terminal can perform an operation equivalent to a four-stage random access procedure.

[0434] In other words, the base station can recognize that it will receive only an RA preamble from the terminal based on two-stage configuration information. Therefore, when an RA preamble is received from the terminal, the base station can transmit a random access response message to the terminal using the aforementioned two-stage random access procedure or four-stage random access procedure. A base station following the two-stage random access procedure can transmit an RA MSG-B, which consists of a fallback RAR, to the terminal using the MSG-B RNTI. A base station following the four-stage random access procedure can transmit a response message, which consists of an RA MSG2 format, to the terminal using the RA-RNTI.

[0435] Furthermore, the terminal can monitor the DCI for receiving a random access response message after transmitting only the MSG-A RA preamble. In this case, the RAR window can start from the point when the terminal transmits PRACH (for example, at the start or end of PRACH transmission). The terminal can then monitor the PDCCH using both the RA-RNTI and MSG-B RNTI. Through PDCCH monitoring, the terminal can receive a response message composed in RA MSG2 format using the RA-RNTI. Alternatively, through PDCCH monitoring, the terminal can receive an RA MSG-B composed of a fallback RAR using the MSG-B RNTI.

[0436] In this invention, the quality of a wireless channel may be CSI (channel status indicator), RSSI (received signal strength indicator), RSRP (reference signal received power), RSRQ (reference signal received quality), or SINR (signal to interference and noise ratio). In relation to the operation of a timer as defined or described in this invention, operations such as starting, stopping, resetting, restarting, and expiring of a timer may mean the operation of the timer or the operation of a counter for the timer.

[0437] In this invention, a base station (or cell) may be a NodeB, an evolved NodeB, a BTS (base transceiver station), a radio base station, a radio transceiver, an access point, an access node, an RSU (roadside unit), an RRH (radio remote head), a TP (transmission point), a TRP (transmission & reception point), or a gNB. Furthermore, a base station (or cell) may be a CU node or DU node to which functional isolation is applied.

[0438] In this invention, a terminal may be a UE, terminal, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, IoT (Internet of Things) device, or mounted module / device / terminal or onboard device / terminal.

[0439] The method according to the present invention can be embodied in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the computer-readable medium may be specifically designed and configured for the present invention or may be available that are publicly known to those skilled in the computer software art.

[0440] Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The aforementioned hardware devices may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

[0441] As described above with reference to examples, those skilled in the art will understand that the present invention can be modified and altered in various ways without departing from the spirit and scope of the invention as described in the following claims.

Claims

1. A method of operation for a terminal in a communication system, The stage in which configuration information for the two-stage random access procedure is received from the base station; A step of transmitting an RA (random access) preamble and an RA payload, including an RA (random access) message-A, to the base station based on the aforementioned configuration information; The RA preamble determines the RA-RNTI (random access-radio network temporary identifier) ​​using the transmitted radio resource information and a pre-set offset; The step of receiving DCI (downlink control information) containing resource allocation information for RA MSG-B from the base station by performing PDCCH (physical downlink control channel) monitoring operation using the RA-RNTI; The step of receiving the RA MSG-B, including a fallback RAR (random access response), from the base station through the resource indicated by the resource allocation information included in the DCI; If the RA MSG-B includes a fallback RAR, the step of transmitting the RA MSG3, which includes the RA payload contained in the RA MSG-A, to the base station; and The step includes receiving an RA MSG4 from the base station as a response to the RA MSG3 which includes the RA payload, The RA-RNTI for the two-stage random access procedure is set differently from the RA-RNTI for the four-stage random access procedure. How the device works.

2. The terminal operation method according to claim 1, wherein the RA-RNTI is determined by applying the preset offset to the RA-RNTI for the four-stage random access procedure.

3. The terminal operation method according to claim 1, wherein the aforementioned pre-set offset is received from the base station.

4. The terminal operation method according to claim 1, wherein the PDCCH monitoring operation is performed within the RAR window.

5. The terminal operation method according to claim 1, wherein when the two-stage random access procedure is performed in the CFRA (containment-free random access) manner, the configuration information includes the transmission resource information of the RA MSG-A allocated exclusively for the terminal.

6. A method for operating a base station in a communication system, The stage in which configuration information for a two-step random access procedure is transmitted to the terminal; The step of receiving an RA message-A, including an RA (random access) preamble and RA payload, from the terminal by performing a monitoring operation using the aforementioned configuration information; The RA preamble determines the RA-RNTI (random access-radio network temporary identifier) ​​using the received radio resource information and a pre-set offset; The step involves performing a scrambling operation on the DCI (downlink control information) containing resource allocation information of RA MSG-B using the aforementioned RA-RNTI; The step of transmitting the scrambled DCI to the terminal; and The step of transmitting the RA MSG-B, including a fallback RAR (random access response), to the terminal using the resources indicated by the resource allocation information included in the DCI; If the RA MSG-B containing a fallback RAR is transmitted, the terminal receives an RA MSG3 containing the RA payload included in the RA MSG-A; and The step includes transmitting RA MSG4 to the terminal as a response to RA MSG3 which includes the RA payload, The RA-RNTI for the two-stage random access procedure is set differently from the RA-RNTI for the four-stage random access procedure. How the base station operates.

7. The method for operating a base station according to claim 6, wherein the RA-RNTI is determined by applying the preset offset to the RA-RNTI for the four-stage random access procedure.

8. The operation method of the base station is as follows: The method for operating a base station according to claim 6, further comprising the step of transmitting the pre-set offset to the terminal.

9. The method of operating a base station according to claim 6, wherein the scrambled DCI is transmitted to the terminal within the RAR window.

10. The method for operating a base station according to claim 6, wherein, when the two-stage random access procedure is performed in the CFRA (containment-free random access) manner, the configuration information includes transmission resource information of the RA MSG-A allocated exclusively for the terminal.

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