Patent Publication Number: US-2022225419-A1

Title: Method and apparatus for transmitting/receiving wireless signal in wireless communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of KR Application No. 10-2021-0004487 filed on Jan. 13, 2021 which is hereby incorporated by reference as if fully set forth herein. 
     TECHNICAL FIELD 
     The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting/receiving a wireless signal. 
     BACKGROUND 
     Generally, a wireless communication system is developing to diversely cover a wide range to provide such a communication service as an audio communication service, a data communication service and the like. The wireless communication is a sort of a multiple access system capable of supporting communications with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). For example, the multiple access system may be any of a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, and a single carrier frequency division multiple access (SC-FDMA) system. 
     SUMMARY 
     An object of the present disclosure is to provide a method of efficiently performing wireless signal transmission/reception procedures and an apparatus therefor. 
     It will be appreciated by persons skilled in the art that the objects and advantages that could be achieved with the present disclosure are not limited to what has been particularly described hereinabove and the above and other objects and advantages that the present disclosure could achieve will be more clearly understood from the following detailed description. 
     According to an embodiment of the present disclosure, a method of receiving a signal by a user equipment (UE) in a wireless communication system may include configuring a first transmission and reception point (TRP) using resources of a first cell and a second TRP using resources of a second cell, receiving random access channel (RACH) configuration information including resource allocation information for the first cell, based on an RACH being triggered for the first cell, transmitting an RACH-related message based on the RACH configuration information, receiving a response to the RACH-related message, and transmitting uplink scheduling information on a physical uplink shared channel (PUSCH) based on the response. 
     Alternatively, the first cell may be a cooperating cell, and the second cell may be a serving cell. 
     Alternatively, the RACH may be triggered for the first cell by timing advance (TA) timer expiry or beam failure detection for the first cell. 
     Alternatively, different RACH backoff values may be configured for the first TRP and the second TRP. 
     Alternatively, the PUSCH may include at least one of uplink control information (UCI) or a medium access control (MAC) protocol data unit (PDU) including a specific MAC control element (CE). 
     Alternatively, the UCI or the specific MAC CE may include at least one of a UE identifier (ID) allocated by the second cell, a UE ID for the first cell, an indicator indicating an RACH transmission for the first cell, or a cell index or TRP ID identifying the first TRP for the first cell. 
     Alternatively, the method may further include receiving MSG4 based on the RACH being a contention-based RACH. 
     Alternatively, the RACH-related message may be transmitted to the first TRP, and the response to the RACH-related message may be received from the second TRP. 
     Alternatively, the method may further include receiving an MSG4 MAC CE or an MSGB MAC CE from the second TRP, based on a MAC entity of a base station (BS) to which the second TRP of the second cell belongs generating the MSG4 MAC CE or the MSGB MAC CE. 
     According to another embodiment of the present disclosure, a non-transitory computer-readable medium recording a program code for performing the method is disclosed. 
     According to another embodiment of the present disclosure, a UE for receiving a signal in a wireless communication system may include a transceiver and at least one processor coupled to the transceiver. The at least one processor may be configured to configure a first TRP using resources of a first cell and a second TRP using resources of a second cell, receive RACH configuration information including resource allocation information for the first cell, based on an RACH being triggered for the first cell, transmit an RACH-related message based on the RACH configuration information, receive a response to the RACH-related message, and transmit uplink scheduling information on a PUSCH based on the response. 
     According to other aspect of the present invention, a non-transitory computer readable medium recorded thereon program codes for performing the aforementioned method is presented. 
     According to another aspect of the present invention, the UE configured to perform the aforementioned method is presented. 
     According to another aspect of the present invention, a device configured to control the UE to perform the aforementioned method is presented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates physical channels used in a 3rd generation partnership project (3GPP) system, which is an example of wireless communication systems, and a general signal transmission method using the same; 
         FIG. 2  illustrates a radio frame structure; 
         FIG. 3  illustrates a resource grid of a slot; 
         FIG. 4  illustrates exemplary mapping of physical channels in a slot; 
         FIG. 5  is a diagram illustrating a signal flow for a physical downlink control channel (PDCCH) transmission and reception process; 
         FIG. 6  illustrates exemplary multi-beam transmission of an SSB; 
         FIG. 7  illustrates an exemplary method of indicating an actually transmitted SSB; 
         FIG. 8  illustrates an example of PRACH transmission in the NR system; 
         FIG. 9  illustrates an example of a RACH occasion defined in one RACH slot in the NR system; 
         FIGS. 10A to 10E  illustrate various embodiments of the configurations of medium access control (MAC)/hybrid automatic repeat request (HARQ) entities of a user equipment (UE) and a next generation Node B (gNB), for inter-cell multiple transmission and reception point (MTRP) applicable to the present disclosure; 
         FIG. 11  illustrates an exemplary physical random access channel (PRACH) resource allocation method for inter-cell MTRP according to the present disclosure; 
         FIG. 12  illustrates an exemplary UE identification method based on MSG3/A UCI for inter-cell MTRP according to the present disclosure; 
         FIG. 13  illustrates an exemplary random access channel (RACH) method based on Option 1 or Option 2, for inter-cell MTRP according to the present disclosure; 
         FIG. 14  illustrates an exemplary RACH method based on Option 3 for inter-cell MTRP according to the present disclosure; 
         FIG. 15  illustrates an exemplary contention-free RACH method for a cooperating cell TRP operation according to the present disclosure; 
         FIG. 16  illustrates a method of receiving a signal by a UE in an embodiment of the present disclosure; 
         FIG. 17  to  FIG. 20  illustrate a communication system 1 and wireless devices applied to the present disclosure; and 
         FIG. 21  illustrates an exemplary discontinuous reception (DRX) operation applied to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are applicable to a variety of wireless access technologies such as code division multiple access (CDMA), frequency division multiple access (1-DMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access (SC-FDMA). CDMA can be implemented as a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented as a radio technology such as Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA can be implemented as a radio technology such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwide interoperability for Microwave Access (WiMAX)), IEEE 802.20, and Evolved UTRA (E-UTRA). UTRA is a part of Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of Evolved UMTS (E-UMTS) using E-UTRA, and LTE-Advanced (A) is an evolved version of 3GPP LTE. 3GPP NR (New Radio or New Radio Access Technology) is an evolved version of 3GPP LTE/LTE-A. 
     As more and more communication devices require a larger communication capacity, there is a need for mobile broadband communication enhanced over conventional radio access technology (RAT). In addition, massive Machine Type Communications (MTC) capable of providing a variety of services anywhere and anytime by connecting multiple devices and objects is another important issue to be considered for next generation communications. Communication system design considering services/UEs sensitive to reliability and latency is also under discussion. As such, introduction of new radio access technology considering enhanced mobile broadband communication (eMBB), massive MTC, and Ultra-Reliable and Low Latency Communication (URLLC) is being discussed. In the present disclosure, for simplicity, this technology will be referred to as NR (New Radio or New RAT). 
     For the sake of clarity, 3GPP NR is mainly described, but the technical idea of the present disclosure is not limited thereto. 
     Details of the background, terminology, abbreviations, etc. used herein may be found in 3GPP standard documents published before the present disclosure. 
     Following documents are incorporated by reference: 
     3GPP LTE
         TS 36.211: Physical channels and modulation   TS 36.212: Multiplexing and channel coding   TS 36.213: Physical layer procedures   TS 36.300: Overall description   TS 36.321: Medium Access Control (MAC)   TS 36.331: Radio Resource Control (RRC)       

     3GPP NR
         TS 38.211: Physical channels and modulation   TS 38.212: Multiplexing and channel coding   TS 38.213: Physical layer procedures for control   TS 38.214: Physical layer procedures for data   TS 38.300: NR and NG-RAN Overall Description   TS 38.321: Medium Access Control (MAC)   TS 38.331: Radio Resource Control (RRC) protocol specification       

     Abbreviations and Terms
         PDCCH: Physical Downlink Control CHannel   PDSCH: Physical Downlink Shared CHannel   PUSCH: Physical Uplink Shared CHannel   CSI: Channel state information   RRM: Radio resource management   RLM: Radio link monitoring   DCI: Downlink Control Information   CAP: Channel Access Procedure   Ucell: Unlicensed cell   PCell: Primary Cell   PSCell: Primary SCG Cell   TBS: Transport Block Size   SLIV: Starting and Length Indicator Value   BWP: BandWidth Part   CORESET: COntrol REsourse SET   REG: Resource element group   SFI: Slot Format Indicator   COT: Channel occupancy time   SPS: Semi-persistent scheduling   PLMN ID: Public Land Mobile Network identifier   RACH: Random Access Channel   RAR: Random Access Response   Msg3: Message transmitted on UL-SCH containing a C-RNTI MAC CE or CCCH SDU, submitted from upper layer and associated with the UE Contention Resolution Identity, as part of a Random Access procedure.   Special Cell: For Dual Connectivity operation the term Special Cell refers to the PCell of the MCG or the PSCell of the SCG depending on if the MAC entity is associated to the MCG or the SCG, respectively. Otherwise the term Special Cell refers to the PCell. A Special Cell supports PUCCH transmission and contention-based Random Access, and is always activated.   Serving Cell: A PCell, a PSCell, or an SCell       

     In a wireless communication system, a user equipment (UE) receives information through downlink (DL) from a base station (BS) and transmit information to the BS through uplink (UL). The information transmitted and received by the BS and the UE includes data and various control information and includes various physical channels according to type/usage of the information transmitted and received by the UE and the BS. 
       FIG. 1  illustrates physical channels used in a 3GPP NR system and a general signal transmission method using the same. 
     When a UE is powered on again from a power-off state or enters a new cell, the UE performs an initial cell search procedure, such as establishment of synchronization with a BS, in step S 101 . To this end, the UE receives a synchronization signal block (SSB) from the BS. The SSB includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast channel (PBCH). The UE establishes synchronization with the BS based on the PSS/SSS and acquires information such as a cell identity (ID). The UE may acquire broadcast information in a cell based on the PBCH. The UE may receive a DL reference signal (RS) in an initial cell search procedure to monitor a DL channel status. 
     After initial cell search, the UE may acquire more specific system information by receiving a physical downlink control channel (PDCCH) and receiving a physical downlink shared channel (PDSCH) based on information of the PDCCH in step S 102 . 
     The UE may perform a random access procedure to access the BS in steps S 103  to S 106 . For random access, the UE may transmit a preamble to the BS on a physical random access channel (PRACH) (S 103 ) and receive a response message for preamble on a PDCCH and a PDSCH corresponding to the PDCCH (S 104 ). In the case of contention-based random access, the UE may perform a contention resolution procedure by further transmitting the PRACH (S 105 ) and receiving a PDCCH and a PDSCH corresponding to the PDCCH (S 106 ). 
     After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S 107 ) and transmit a physical uplink shared channel (PUSCH)/physical uplink control channel (PUCCH) (S 108 ), as a general downlink/uplink signal transmission procedure. Control information transmitted from the UE to the BS is referred to as uplink control information (UCI). The UCI includes hybrid automatic repeat and request acknowledgement/negative-acknowledgement (HARQ-ACK/NACK), scheduling request (SR), channel state information (CSI), etc. The CSI includes a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), etc. While the UCI is transmitted on a PUCCH in general, the UCI may be transmitted on a PUSCH when control information and traffic data need to be simultaneously transmitted. In addition, the UCI may be aperiodically transmitted through a PUSCH according to request/command of a network. 
       FIG. 2  illustrates a radio frame structure. In NR, uplink and downlink transmissions are configured with frames. Each radio frame has a length of 10 ms and is divided into two 5-ms half-frames (HF). Each half-frame is divided into five 1-ms subframes (SFs). A subframe is divided into one or more slots, and the number of slots in a subframe depends on subcarrier spacing (SCS). Each slot includes 12 or 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols according to a cyclic prefix (CP). When a normal CP is used, each slot includes 14 OFDM symbols. When an extended CP is used, each slot includes 12 OFDM symbols. 
     Table 1 exemplarily shows that the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary according to the SCS when the normal CP is used. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 SCS (15*2 u ) 
                 N slot   symb   
                 N frame, u   slot   
                 N subframe, u   slot   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 15 KHz (u = 0) 
                 14 
                 10 
                 1 
               
               
                   
                 30 KHz (u = 1) 
                 14 
                 20 
                 2 
               
               
                   
                 60 KHz (u = 2) 
                 14 
                 40 
                 4 
               
               
                   
                 120 KHz (u = 3)  
                 14 
                 80 
                 8 
               
               
                   
                 240 KHz (u = 4)  
                 14 
                 160 
                 16 
               
               
                   
                   
               
               
                   
                 * N slot   symb : Number of symbols in a slot 
               
               
                   
                 * N frame, u   slot : Number of slots in a frame 
               
               
                   
                 * N subframe, u   slot : Number of slots in a subframe 
               
            
           
         
       
     
     Table 2 illustrates that the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary according to the SCS when the extended CP is used. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 SCS (15*2 u ) 
                 N slot   symb   
                 N frame, u   slot   
                 N subrame, u   slot   
               
               
                   
                   
               
             
            
               
                   
                 60 KHz (u = 2) 
                 12 
                 40 
                 4 
               
               
                   
                   
               
            
           
         
       
     
     The structure of the frame is merely an example. The number of subframes, the number of slots, and the number of symbols in a frame may vary. 
     In the NR system, OFDM numerology (e.g., SCS) may be configured differently for a plurality of cells aggregated for one UE. Accordingly, the (absolute time) duration of a time resource (e.g., an SF, a slot or a TTI) (for simplicity, referred to as a time unit (TU)) consisting of the same number of symbols may be configured differently among the aggregated cells. Here, the symbols may include an OFDM symbol (or a CP-OFDM symbol) and an SC-FDMA symbol (or a discrete Fourier transform-spread-OFDM (DFT-s-OFDM) symbol). 
       FIG. 3  illustrates a resource grid of a slot. A slot includes a plurality of symbols in the time domain. For example, when the normal CP is used, the slot includes 14 symbols. However, when the extended CP is used, the slot includes 12 symbols. A carrier includes a plurality of subcarriers in the frequency domain. A resource block (RB) is defined as a plurality of consecutive subcarriers (e.g., 12 consecutive subcarriers) in the frequency domain. A bandwidth part (BWP) may be defined to be a plurality of consecutive physical RBs (PRBs) in the frequency domain and correspond to a single numerology (e.g., SCS, CP length, etc.). The carrier may include up to N (e.g., 5) BWPs. Data communication may be performed through an activated BWP, and only one BWP may be activated for one UE. In the resource grid, each element is referred to as a resource element (RE), and one complex symbol may be mapped to each RE. 
       FIG. 4  illustrates exemplary mapping of physical channels in a slot. In the NR system, a DL control channel, DL or UL data, and a UL control channel may be included in one slot. For example, the first N symbols (hereinafter, referred to as a DL control region) of a slot may be used to transmit a DL control channel (e.g., PDCCH), and the last M symbols (hereinafter, referred to as a UL control region) of the slot may be used to transmit a UL control channel (e.g., PUCCH). Each of N and M is an integer equal to or larger than 0. A resource region (hereinafter, referred to as a data region) between the DL control region and the UL control region may be used to transmit DL data (e.g., PDSCH) or UL data (e.g., PUSCH). A guard period (GP) provides a time gap for transmission mode-to-reception mode switching or reception mode-to-transmission mode switching at a BS and a UE. Some symbol at the time of DL-to-UL switching in a subframe may be configured as a GP. 
     The PDCCH delivers DCI. For example, the PDCCH (i.e., DCI) may carry information about a transport format and resource allocation of a DL shared channel (DL-SCH), resource allocation information of an uplink shared channel (UL-SCH), paging information on a paging channel (PCH), system information on the DL-SCH, information on resource allocation of a higher-layer control message such as an RAR transmitted on a PDSCH, a transmit power control command, information about activation/release of configured scheduling, and so on. The DCI includes a cyclic redundancy check (CRC). The CRC is masked with various identifiers (IDs) (e.g. a radio network temporary identifier (RNTI)) according to an owner or usage of the PDCCH. For example, if the PDCCH is for a specific UE, the CRC is masked by a UE ID (e.g., cell-RNTI (C-RNTI)). If the PDCCH is for a paging message, the CRC is masked by a paging-RNTI (P-RNTI). If the PDCCH is for system information (e.g., a system information block (SIB)), the CRC is masked by a system information RNTI (SI-RNTI). When the PDCCH is for an RAR, the CRC is masked by a random access-RNTI (RA-RNTI). 
       FIG. 5  is a diagram illustrating a signal flow for a PDCCH transmission and reception process. 
     Referring to  FIG. 5 , a BS may transmit a control resource set (CORESET) configuration to a UE (S 502 ). A CORSET is defined as a resource element group (REG) set having a given numerology (e.g., an SCS, a CP length, and so on). An REG is defined as one OFDM symbol by one (P)RB. A plurality of CORESETs for one UE may overlap with each other in the time/frequency domain. A CORSET may be configured by system information (e.g., a master information block (MIB)) or higher-layer signaling (e.g., radio resource control (RRC) signaling). For example, configuration information about a specific common CORSET (e.g., CORESET #0) may be transmitted in an MIB. For example, a PDSCH carrying system information block 1 (SIB1) may be scheduled by a specific PDCCH, and CORSET #0 may be used to carry the specific PDCCH. Configuration information about CORESET #N (e.g., N&gt;0) may be transmitted by RRC signaling (e.g., cell-common RRC signaling or UE-specific RRC signaling). For example, the UE-specific RRC signaling carrying the CORSET configuration information may include various types of signaling such as an RRC setup message, an RRC reconfiguration message, and/or BWP configuration information. Specifically, a CORSET configuration may include the following information/fields.
         controlResourceSetId: indicates the ID of a CORESET.   frequencyDomainResources: indicates the frequency resources of the CORESET. The frequency resources of the CORESET are indicated by a bitmap in which each bit corresponds to an RBG (e.g., six (consecutive) RBs). For example, the most significant bit (MSB) of the bitmap corresponds to a first RBG. RBGs corresponding to bits set to 1 are allocated as the frequency resources of the CORESET.   duration: indicates the time resources of the CORESET. Duration indicates the number of consecutive OFDM symbols included in the CORESET. Duration has a value of 1 to 3.   cce-REG-MappingType: indicates a control channel element (CCE)-REG mapping type. Interleaved and non-interleaved types are supported.   interleaverSize: indicates an interleaver size.   pdcch-DMRS-ScramblingID: indicates a value used for PDCCH DMRS initialization. When pdcch-DMRS-ScramblingID is not included, the physical cell ID of a serving cell is used.   precoderGranularity: indicates a precoder granularity in the frequency domain.   reg-BundleSize: indicates an REG bundle size.   tci-PresentInDCI: indicates whether a transmission configuration index (TCI) field is included in DL-related DCI.   tci-StatesPDCCH-ToAddList: indicates a subset of TCI states configured in pdcch-Config, used for providing quasi-co-location (QCL) relationships between DL RS(s) in an RS set (TCI-State) and PDCCH DMRS ports.       

     Further, the BS may transmit a PDCCH search space (SS) configuration to the UE (S 504 ). The PDCCH SS configuration may be transmitted by higher-layer signaling (e.g., RRC signaling). For example, the RRC signaling may include, but not limited to, various types of signaling such as an RRC setup message, an RRC reconfiguration message, and/or BWP configuration information. While a CORESET configuration and a PDCCH SS configuration are shown in  FIG. 5  as separately signaled, for convenience of description, the present disclosure is not limited thereto. For example, the CORESET configuration and the PDCCH SS configuration may be transmitted in one message (e.g., by one RRC signaling) or separately in different messages. 
     The PDCCH SS configuration may include information about the configuration of a PDCCH SS set. The PDCCH SS set may be defined as a set of PDCCH candidates monitored (e.g., blind-detected) by the UE. One or more SS sets may be configured for the UE. Each SS set may be a USS set or a CSS set. For convenience, PDCCH SS set may be referred to as “SS” or “PDCCH SS”. 
     A PDCCH SS set includes PDCCH candidates. A PDCCH candidate is CCE(s) that the UE monitors to receive/detect a PDCCH. The monitoring includes blind decoding (BD) of PDCCH candidates. One PDCCH (candidate) includes 1, 2, 4, 8, or 16 CCEs according to an aggregation level (AL). One CCE includes 6 REGs. Each CORESET configuration is associated with one or more SSs, and each SS is associated with one CORESET configuration. One SS is defined based on one SS configuration, and the SS configuration may include the following information/fields.
         searchSpaceId: indicates the ID of an SS.   controlResourceSetId: indicates a CORESET associated with the SS.   monitoringSlotPeriodicityAndOffset: indicates a periodicity (in slots) and offset (in slots) for PDCCH monitoring.   monitoringSymbolsWithinSlot: indicates the first OFDM symbol(s) for PDCCH monitoring in a slot configured with PDCCH monitoring. The first OFDM symbol(s) for PDCCH monitoring is indicated by a bitmap with each bit corresponding to an OFDM symbol in the slot. The MSB of the bitmap corresponds to the first OFDM symbol of the slot. OFDM symbol(s) corresponding to bit(s) set to 1 corresponds to the first symbol(s) of a CORESET in the slot.   nrofCandidates: indicates the number of PDCCH candidates (one of values 0, 1, 2, 3, 4, 5, 6, and 8) for each AL where AL={1, 2, 4, 8, 16}.   searchSpaceType: indicates common search space (CSS) or UE-specific search space (USS) as well as a DCI format used in the corresponding SS type.       

     Subsequently, the BS may generate a PDCCH and transmit the PDCCH to the UE (S 506 ), and the UE may monitor PDCCH candidates in one or more SSs to receive/detect the PDCCH (S 508 ). An occasion (e.g., time/frequency resources) in which the UE is to monitor PDCCH candidates is defined as a PDCCH (monitoring) occasion. One or more PDCCH (monitoring) occasions may be configured in a slot. 
     Table 3 shows the characteristics of each SS. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Type 
                 Search Space 
                 RNTI 
                 Use Case 
               
               
                   
               
             
            
               
                 Type0-PDCCH 
                 Common 
                 SI-RNTI on a primary cell 
                 SIB Decoding 
               
               
                 Type0A-PDCCH 
                 Common 
                 SI-RNTI on a primary cell 
                 SIB Decoding 
               
               
                 Type1-PDCCH 
                 Common 
                 RA-RNTI or TC-RNTI on a primary cell 
                 Msg2, Msg4 
               
               
                   
                   
                   
                 decoding in 
               
               
                   
                   
                   
                 RACH 
               
               
                 Type2-PDCCH 
                 Common 
                 P-RNTI on a primary cell 
                 Paging 
               
               
                   
                   
                   
                 Decoding 
               
               
                 Type3-PDCCH 
                 Common 
                 INT-RNTI, SFI-RNTI, TPC-PUSCH-RNTI, 
               
               
                   
                   
                 TPC-PUCCH-RNTI, TPC-SRS-RNTI, C-RNTI, 
               
               
                   
                   
                 MCS-C-RNTI, or CS-RNTI(s) 
               
               
                   
                 UE 
                 C-RNTI, or MCS-C-RNTI, or CS-RNTI(s) 
                 User specific 
               
               
                   
                 Specific 
                   
                 PDSCH 
               
               
                   
                   
                   
                 decoding 
               
               
                   
               
            
           
         
       
     
     Table 4 shows DCI formats transmitted on the PDCCH. 
     
       
         
           
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 DCI format 
                 Usage 
               
               
                   
               
             
            
               
                 0_0 
                 Scheduling of PUSCH in one cell 
               
               
                 0_1 
                 Scheduling of PUSCH in one cell 
               
               
                 1_0 
                 Scheduling of PDSCH in one cell 
               
               
                 1_1 
                 Scheduling of PDSCH in one cell 
               
               
                 2_0 
                 Notifying a group of UEs of the slot format 
               
               
                 2_1 
                 Notifying a group of UEs of the PRB(s) and OFDM 
               
               
                   
                 symbol(s) where UE may assume no transmission is 
               
               
                   
                 intended for the UE 
               
               
                 2_2 
                 Transmission of TPC commands for PUCCH and PUSCH 
               
               
                 2_3 
                 Transmission of a group of TPC commands for SRS 
               
               
                   
                 transmissions by one or more UEs 
               
               
                   
               
            
           
         
       
     
     DCI format 0_0 may be used to schedule a TB-based (or TB-level) PUSCH, and DCI format 0_1 may be used to schedule a TB-based (or TB-level) PUSCH or a code block group (CBG)-based (or CBG-level) PUSCH. DCI format 1_0 may be used to schedule a TB-based (or TB-level) PDSCH, and DCI format 1_1 may be used to schedule a TB-based (or TB-level) PDSCH or a CBG-based (or CBG-level) PDSCH (DL grant DCI). DCI format 0_0/0_1 may be referred to as UL grant DCI or UL scheduling information, and DCI format 1_0/1_1 may be referred to as DL grant DCI or DL scheduling information. DCI format 2_0 is used to deliver dynamic slot format information (e.g., a dynamic slot format indicator (SFI)) to a UE, and DCI format 2_1 is used to deliver DL pre-emption information to a UE. DCI format 2_0 and/or DCI format 2_1 may be delivered to a corresponding group of UEs on a group common PDCCH which is a PDCCH directed to a group of UEs. 
     DCI format 0_0 and DCI format 1_0 may be referred to as fallback DCI formats, whereas DCI format 0_1 and DCI format 1_1 may be referred to as non-fallback DCI formats. In the fallback DCI formats, a DCI size/field configuration is maintained to be the same irrespective of a UE configuration. In contrast, the DCI size/field configuration varies depending on a UE configuration in the non-fallback DCI formats. 
     A CCE-to-REG mapping type is set to one of an interleaved type and a non-interleaved type.
         Non-interleaved CCE-to-REG mapping (or localized CCE-to-REG mapping): 6 REGs for a given CCE are grouped into one REG bundle, and all of the REGs for the given CCE are contiguous. One REG bundle corresponds to one CCE.   Interleaved CCE-to-REG mapping (or distributed CCE-to-REG mapping): 2, 3 or 6 REGs for a given CCE are grouped into one REG bundle, and the REG bundle is interleaved within a CORESET. In a CORESET including one or two OFDM symbols, an REG bundle includes 2 or 6 REGs, and in a CORESET including three OFDM symbols, an REG bundle includes 3 or 6 REGs. An REG bundle size is configured on a CORESET basis.       

     System Information Acquisition 
     A UE may acquire AS-/NAS-information in the SI acquisition process. The SI acquisition process may be applied to UEs in RRC_IDLE state, RRC_INACTIVE state, and RRC_CONNECTED state. 
     SI is divided into a master information block (MIB) and a plurality of system information blocks (SIBs). The SI except for the MIB may be referred to as remaining minimum 
     system information (RMS) and other system information (OSI). RMSI corresponds to SIB1, and OSI refers to SIBs of SIB2 or higher other than SIB1. For details, reference may be made to the followings.
         The MIB includes information/parameters related to reception of systemInformaitonBlockType1 (SIB1) and is transmitted on a PBCH of an SSB. MIB information may include the following fields.   pdcch-ConfigSIB1: Determines a common ControlResourceSet (CORESET), a common search space and necessary PDCCH parameters. If the field ssb-SubcarrierOffset indicates that SIB1 is absent, the field pdcch-ConfigSIB1 indicates the frequency positions where the UE may find SS/PBCH block with SIB1 or the frequency range where the network does not provide SS/PBCH block with SIB 1.   ssb-SubcarrierOffset: Corresponds to kSSB which is the frequency domain offset between SSB and the overall resource block grid in number of subcarriers. The value range of this field may be extended by an additional most significant bit encoded within PBCH. This field may indicate that this cell does not provide SIB1 and that there is hence no CORESET#0 configured in MIB. In this case, the field pdcch-ConfigSIB1 may indicate the frequency positions where the UE may (not) find a SS/PBCH with a control resource set and search space for SIB1.   subCarrierSpacingCommon: Subcarrier spacing for SIB1, Msg.2/4 for initial access, paging and broadcast SI-messages. If the UE acquires this MIB on an FR1 carrier frequency, the value scs15or60 corresponds to 15 kHz and the value scs30or120 corresponds to 30 kHz. If the UE acquires this MIB on an FR2 carrier frequency, the value scs15or60 corresponds to 60 kHz and the value scs30or120 corresponds to 120 kHz.       

     In initial cell selection, the UE may determine whether there is a control resource set (CORESET) for a Type0-PDCCH common search space based on the MIB. The Type0-PDCCH common search space is a kind of a PDCCH search space, and is used to transmit a PDCCH scheduling an SI message. In the presence of a Type0-PDCCH common search space, the UE may determine (i) a plurality of consecutive RBs and one or more consecutive symbols in a CORESET and (ii) PDCCH occasions (i.e., time-domain positions for PDCCH reception), based on information (e.g., pdcch-ConfigSIB1) in the MIB. Specifically, pdcch-ConfigSIB1 is 8-bit information, (i) is determined based on the most significant bits (MSB) of 4 bits, and (ii) is determined based on the least significant bits (LSB) of 4 bits. 
     In the absence of any Type0-PDCCH common search space, pdcch-ConfigSIB1 provides information about the frequency position of an SSB/SIB1 and a frequency range free of an SSB/SIB1. 
     For initial cell selection, a UE may assume that half frames with SS/PBCH blocks occur with a periodicity of 2 frames. Upon detection of a SS/PBCH block, the UE determines that a control resource set for Type0-PDCCH common search space is present if k SSB ≤23 for FR1 (Frequency Range 1; Sub-6 GHz; 450 to 6000 MHz) and if k ssB ≤11 for FR2 (Frequency Range 2; mm-Wave; 24250 to 52600 MHz). The UE determines that a control resource set for Type0-PDCCH common search space is not present if k ssB &gt;23 for FR1 and if k ssB &gt;11 for FR2. k ssB  represents a frequency/subcarrier offset between subcarrier 0 of SS/PBCH block to subcarrier 0 of common resource block for SSB. For FR2 only values up to 11 are applicable. k ssB  may be signaled through the MIB.
         SIB1 includes information related to the availability and scheduling (e.g., a transmission periodicity and an SI-window size) of the other SIBs (hereinafter, referred to as SIBx where x is an integer equal to or larger than 2). For example, SIB1 may indicate whether SIBx is broadcast periodically or provided by an UE request in an on-demand manner When SIBx is provided in the on-demand manner, SIB1 may include information required for the UE to transmit an SI request. SIB1 is transmitted on a PDSCH, and a PDCCH scheduling SIB1 is transmitted in a Type0-PDCCH common search space. SIB1 is transmitted on a PDSCH indicated by the PDCCH.   SIBx is included in an SI message and transmitted on a PDSCH. Each SI message is transmitted within a time window (i.e., an SI-window) which takes place periodically.       

       FIG. 6  illustrates exemplary multi-beam transmission of an SSB. Beam sweeping refers to changing the beam (direction) of a wireless signal over time at a transmission reception point (TRP) (e.g., a BS/cell) (hereinbelow, the terms beam and beam direction are interchangeably used). An SSB may be transmitted periodically by beam sweeping. In this case, SSB indexes are implicitly linked to SSB beams. An SSB beam may be changed on an SSB (index) basis. The maximum transmission number L of an SSB in an SSB burst set is 4, 8 or 64 according to the frequency band of a carrier. Accordingly, the maximum number of SSB beams in the SSB burst set may be given according to the frequency band of a carrier as follows.
         For frequency range up to 3 GHz, Max number of beams=4   For frequency range from 3GHz to 6 GHz, Max number of beams=8   For frequency range from 6 GHz to 52.6 GHz, Max number of beams=64   * Without multi-beam transmission, the number of SS/PBCH block beams is 1.       

     When a UE attempts initial access to a BS, the UE may perform beam alignment with the BS based on an SS/PBCH block. For example, after SS/PBCH block detection, the UE identifies a best SS/PBCH block. Subsequently, the UE may transmit an RACH preamble to the BS in PRACH resources linked/corresponding to the index (i.e., beam) of the best SS/PBCH block. The SS/PBCH block may also be used in beam alignment between the BS and the UE after the initial access. 
       FIG. 7  illustrates an exemplary method of indicating an actually transmitted SSB (SSB_tx). Up to L SS/PBCH blocks may be transmitted in an SS/PBCH block burst set, and the number/positions of actually transmitted SS/PBCH blocks may be different for each BS/cell. The number/positions of actually transmitted SS/PBCH blocks are used for rate-matching and measurement, and information about actually transmitted SS/PBCH blocks is indicated as follows.
         If the information is related to rate-matching: the information may be indicated by UE-specific RRC signaling or remaining minimum system information (RMSI). The UE-specific RRC signaling includes a full bitmap (e.g., of length L) for frequency ranges below and above 6 GHz. The RMSI includes a full bitmap for a frequency range below 6 GHz and a compressed bitmap for a frequency range above 6 GHz, as illustrated. Specifically, the information about actually transmitted SS/PBCH blocks may be indicated by a group-bitmap (8 bits)+an in-group bitmap (8 bits). Resources (e.g., REs) indicated by the UE-specific RRC signaling or the RMSI may be reserved for SS/PBCH block transmission, and a PDSCH/PUSCH may be rate-matched in consideration of the SS/PBCH block resources.   If the information is related to measurement: the network (e.g., BS) may indicate an SS/PBCH block set to be measured within a measurement period, when the UE is in RRC connected mode. The SS/PBCH block set may be indicated for each frequency layer. Without an indication of an SS/PBCH block set, a default SS/PBCH block set is used. The default SS/PBCH block set includes all SS/PBCH blocks within the measurement period. An SS/PBCH block set may be indicated by a full bitmap (e.g., of length L) in RRC signaling. When the UE is in RRC idle mode, the default SS/PBCH block set is used.       

     Random Access Operation and Related Operation 
     When there is no PUSCH transmission resource (i.e., uplink grant) allocated by the BS, the UE may perform a random access operation. Random access of the NR system can occur 1) when the UE requests or resumes the RRC connection, 2) when the UE performs handover or secondary cell group addition (SCG addition) to a neighboring cell, 3) when a scheduling request is made to the BS, 4) when the BS indicates random access of the UE in PDCCH order, or 5) when a beam failure or RRC connection failure is detected. 
     The RACH procedure of LTE and NR consists of 4 steps of Msg1 (PRACH preamble) transmission from the UE, Msg2 (RAR, random access response) transmission from the BS, Msg3 (PUSCH) transmission from the UE, and Msg4 (PDSCH) transmission from the BS. That is, the UE transmits a physical random access channel (PRACH) preamble and receives an RAR as a response thereto. When the preamble is a UE-dedicated resource, that is, in the case of contention free random access (CFRA), the random access operation is terminated by receiving the RAR corresponding to the UE itself. If the preamble is a common resource, that is, in the case of contention based random access (CBRA), after the RAR including an uplink PUSCH resource and a RACH preamble ID (RAPID) selected by the UE is received, Msg3 is transmitted through a corresponding resource on the PUSCH. And after a contention resolution message is received on the PDSCH, the random access operation is terminated. In this case, a time and frequency resources to/on which the PRACH preamble signal is mapped/transmitted is defined as RACH occasion (RO), and a time and frequency resource to/on which the Msg3 PUSCH signal is mapped/transmitted is defined as PUSCH occasion (PO). 
     In Rel. 16 In NR and NR-U, a 2-step RACH procedure has been introduced, which is a reduced procedure for the 4-step RACH procedure. The 2-step RACH procedure is composed of MsgA (PRACH preamble+Msg3 PUSCH) transmission from the UE and MsgB (RAR+Msg4 PDSCH) transmission from the gNB. 
     The PRACH format for transmitting the PRACH preamble in the NR system consists of a format composed of a length 839 sequence (named as a long RACH format for simplicity) and a format composed of a length 139 sequence (named as a short RACH format for simplicity). For example, in frequency range 1 (FR1), the sub-carrier spacing (SCS) of the short RACH format is defined as 15 or 30 kHz. Also, as shown in  FIG. 8 , RACH can be transmitted on 139 tones among 12 RBs (144 REs). In  FIG. 8 , 2 null tones are assumed for the lower RE index and 3 null tones are assumed for the upper RE index, but the positions may be changed. 
     The above-mentioned short PRACH format comprises values defined in Table 5. Here, μ is defined as one of {0, 1, 2, 3} according to the value of subcarrier spacing. For example, in the case of 15 kHz subcarrier spacing, μ is 0. In the case of 30 kHz subcarrier spacing, μ is 1. Table 5 shows Preamble formats for L RA =139 and Δf RA =15×2 μ  kHz, where μ ∈{0,1,2,3}, κ= T   s /T c =64. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Format 
                 L RA   
                 Δf RA   
                 N u   
                 N CP   RA   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 A1 
                 139 
                 15 × 2 μ  kHz 
                 2 × 2048κ × 2 −μ   
                 288κ × 2 −μ   
               
               
                 A2 
                 139 
                 15 × 2 μ  kHz 
                 4 × 2048κ × 2 −μ   
                 576κ × 2 −μ   
               
               
                 A3 
                 139 
                 15 × 2 μ  kHz 
                 6 × 2048κ × 2 −μ   
                 864κ × 2 −μ   
               
               
                 B1 
                 139 
                 15 × 2 μ  kHz 
                 2 × 2048κ × 2 −μ   
                 216κ × 2 −μ   
               
               
                 B2 
                 139 
                 15 × 2 μ  kHz 
                 4 × 2048κ × 2 −μ   
                 360κ × 2 −μ   
               
               
                 B3 
                 139 
                 15 × 2 μ  kHz 
                 6 × 2048κ × 2 −μ   
                 504κ × 2 −μ   
               
               
                 B4 
                 139 
                 15 × 2 μ  kHz 
                 12 × 2048κ × 2 −μ   
                 936κ × 2 −μ   
               
               
                 C0 
                 139 
                 15 × 2 μ  kHz 
                 2048κ × 2 −μ   
                 1240κ × 2 −μ   
               
               
                 C2 
                 139 
                 15 × 2 μ  kHz 
                 4 × 2048κ × 2 −μ   
                 2048κ × 2 −μ   
               
               
                   
               
            
           
         
       
     
     The BS can announce which PRACH format can be transmitted as much as a specific duration at a specific timing through higher layer signaling (RRC signaling or MAC CE or DCI, etc.) and how many ROs (RACH occasions or PRACH occasions) are in the slot. Table 6 shows a part of PRACH configuration indexes that can use A1, A2, A3, B1, B2, B3. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 6 
               
             
            
               
                   
                   
               
               
                   
                   
                 N t   RA, slot , 
                   
               
               
                   
                   
                 number of 
               
               
                   
                 Number of 
                 time-domain 
               
               
                   
                 PRACH 
                 PRACH 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 PRACH 
                   
                 n SFN mod 
                   
                   
                 slots 
                 occasions 
                 N dur   RA , 
               
               
                 Configuration 
                 Preamble 
                 x = y 
                 Subframe 
                 Starting 
                 within a 
                 within a 
                 PRACH 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Index 
                 format 
                 x 
                 y 
                 number 
                 symbol 
                 subframe 
                 PRACH slot 
                 duration 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 81 
                 A1 
                 1 
                 0 
                 4.9 
                 0 
                 1 
                 6 
                 2 
               
               
                 82 
                 A1 
                 1 
                 0 
                 7.9 
                 7 
                 1 
                 3 
                 2 
               
               
                 100 
                 A2 
                 1 
                 0 
                 9 
                 9 
                 1 
                 1 
                 4 
               
               
                 101 
                 A2 
                 1 
                 0 
                 9 
                 0 
                 1 
                 3 
                 4 
               
               
                 127 
                 A3 
                 1 
                 0 
                 4.9 
                 0 
                 1 
                 2 
                 6 
               
               
                 128 
                 A3 
                 1 
                 0 
                 7.9 
                 7 
                 1 
                 1 
                 6 
               
               
                 142 
                 B1 
                 1 
                 0 
                 4.9 
                 2 
                 1 
                 6 
                 2 
               
               
                 143 
                 B1 
                 1 
                 0 
                 7.9 
                 8 
                 1 
                 3 
                 2 
               
               
                 221 
                 A1/B1 
                 1 
                 0 
                 4.9 
                 2 
                 1 
                 6 
                 2 
               
               
                 222 
                 A1/B1 
                 1 
                 0 
                 7.9 
                 8 
                 1 
                 3 
                 2 
               
               
                 235 
                 A2/B2 
                 1 
                 0 
                 4.9 
                 0 
                 1 
                 3 
                 4 
               
               
                 236 
                 A2/B2 
                 1 
                 0 
                 7.9 
                 6 
                 1 
                 2 
                 4 
               
               
                 251 
                 A3/B3 
                 1 
                 0 
                 4.9 
                 0 
                 1 
                 2 
                 6 
               
               
                 252 
                 A3/B3 
                 1 
                 0 
                 7.9 
                 2 
                 1 
                 2 
                 6 
               
               
                   
               
            
           
         
       
     
     Referring to Table 6, information about the number of ROs defined in a RACH slot for each preamble format (i.e., N t   RA, slot : number of time-domain PRACH occasions within a PRACH slot), and the number of OFDM symbols occupied by each PRACH preamble for the preamble format (i.e., N dur   RA , PRACH duration) can be known. In addition, by indicating the starting symbol of the first RO, information about the time at which the RO starts in the RACH slot can also be provided.  FIG. 9  shows the configuration of the ROs in the RACH slot according to the PRACH configuration index values shown in Table 6. 
     Cooperative Transmission from Multiple TRPs/Panels/Beams 
     Coordinated multi-point (CoMP) is a technique in which a plurality of BSs cooperatively transmit signals to a UE by exchanging feedback channel information (e.g., an RI/CQI/PMI/LI) received from the UE with each other (e.g., via an X2 interface) or using the feedback channel information to effectively control interference. CoMP schemes may be divided into joint transmission (JT), coordinated scheduling (CS), coordinated beamforming (CB), dynamic point selection (DPS), and dynamic point blacking (DPB) according to their use mechanisms. 
     CoMP transmission was introduced to the LTE system, and partially introduced to NR Rel-15. For CoMP transmission, there are various schemes including a same layer joint transmission scheme in which a plurality of transmission and reception points (TRP) transmit the same signal or information, a point selection scheme in which a plurality of TRPs share information to be transmitted to a UE, and a specific TRP transmits the information to the UE at a specific time in consideration of radio channel quality or traffic load, and an independent layer joint transmission scheme in which a plurality of TRPs transmit different signals or information in spatial dimension multiplexing (SDM) from spatial layers. In a main point selection scheme called dynamic point selection (DPS), a TRP participating in transmission may be changed each time a PDSCH is transmitted. A term defined to indicate a TRP that transmits a PDSCH is quasi-co-location (QCL). The BS may indicate/configure to/or for the UE whether to assume that different antenna ports are identical in terms of a specific property (e.g., Doppler shift, Doppler spread, average delay, delay spread, or spatial reception (RX) parameter), by QCL. When TRP #1 transmits a PDSCH, the BS indicates a specific RS (e.g., CSI-RS resource #1) transmitted from TRP #1 and QCL between corresponding PDSCH DMRS antenna ports, and when TRP #2 transmits a PDSCH, the BS indicates a specific RS (e.g., CSI-RS resource #2) transmitted from TRP #2 and QCL between corresponding PDSCH DMRS antenna ports. To indicate instantaneous QCL information by DCI, a PDSCH quasi-co-location information (PQI) field is defined in LTE, and a transmission configuration information (TCI) field is defined in NR. The QCL indication/configuration method defined in the standards may generally be used for cooperative transmission between a plurality of TRPs, cooperative transmission between a plurality of panels (antenna groups) in the same TRP, and cooperative transmissions between a plurality of beams in the same TRP. This is because the use of different transmission panels or beams may lead to different Doppler delays or different reception beams (spatial Rx parameters) that signals transmitted by the panels or beams experience, despite the transmissions from the same TRP. 
     In NR Rel-16, standardization of a method of transmitting different layer groups to a UE by a plurality of TRPs/panels/beams, called independent layer joint transmission (ILJT) or non-coherent joint transmission (NCJT) is under discussion. 
     Multi-Transmission/Reception Point (Multi-TRP)-related Operations 
     Multi-TRP (MTRP) transmission schemes in which M TRPs transmit data to a single UE may be divided into eMBB MTRP transmission for increasing a transmission rate significantly and URLLC MTRP transmission for increasing a reception success rate and reducing latency. 
     From the perspective of DCI transmission, MTRP transmission schemes may include i) a multiple DCI (M-DCI)-based MTRP transmission scheme in which each TRP transmits different DCI, and ii) a single DCI (S-DCI)-based MTRP transmission scheme in which a single TRP transmits DCI. For example, all scheduling information about data transmitted by multiple TRPs should be delivered by one piece of DCI in the S-DCI-based M-TRP transmission scheme. Accordingly, this scheme may be used in an ideal backhaul (BH) environment in which two TRPs may cooperate with each other dynamically. 
     Scheme 3/4 is being standardized in TDM-based URLLC. Specifically, scheme 4 refers to a scheme in which one TRP transmits a transport block (TB) in one slot. Scheme 4 achieves the effect that a data reception probability may be increased through the same TB received over multiple slots from multiple TRPs. In contrast, scheme 3 refers to a scheme in which one TRP transmits a TB over a few consecutive 01-DM symbols (i.e., a symbol group). In scheme 3, multiple TRPs may be configured to transmit the same TB in different symbol groups within one slot. 
     Further, the UE may recognize PUSCHs (or PUCCHs) scheduled by DCI received in different CORESETs (or CORESETs of different CORESET groups) as PUSCHs (or PUCCHs) transmitted to different TRPs or PUSCHs (or PUCCHs) for different TRPs. Further, UL transmissions (e.g., PUSCHs/PUCCHs) directed to different TRPs may be performed in the same manner as UL transmissions (e.g., PUSCHs/PUCCHs) directed to different panels within the same TRP. 
     Further, MTRP-URLLC may refer to transmitting the same TB in different layers/times/frequencies from multiple TRPs. A UE configured with an MTRP-URLLC transmission scheme may be notified of TCI state(s) by DCI and assume that data received using a QCL RS of each TCI state is the same TB. MTRP-eMBB may refer to transmitting different TBs in different layers/times/frequencies from multiple TRPs. A UE configured with an MTRP-eMBB transmission scheme may be notified of TCI state(s) by DCI and assume that data received using a QCL RS of each TCI state is a different TB. In this regard, the UE may identify/determine whether a corresponding MTRP transmission is a URLLC transmission or an eMBB transmission by separately using an RNTI configured for MTRP-URLLC and an RNTI configured for MTRP-eMBB. That is, when DCI received by the UE has been CRC-masked by the RNTI for MTRP-URLLC, this may correspond to an URLLC transmission. When DCI received by the UE has been CRC-masked by the RNTI for MTRP-eMBB, this may correspond to an eMBB transmission. 
     The term CORESET group ID as described/mentioned in the present disclosure may mean an index/identification information (e.g., ID) identifying CORESETs of a TRP/panel. A CORESET group may be a group/union of CORESETs identified by an index/identification information (e.g., IDs)/a CORESET group ID for CORESETs of a TRP/panel. For example, a CORESET group ID may be specific index information defined by a CORESET configuration. For example, a CORESET group may be configured/indicated/defined by an index defined in the CORESET configuration of each CORESET. And/or a CORESET group ID may mean an index/identification information/indicator for distinguishing/identifying CORESETs configured for/associated with a TRP/panel. A CORESET group ID described/mentioned in the present disclosure may be replaced with a specific index/specific identification information/a specific indicator for distinguishing/identifying CORESETs configured for/associated with a TRP/panel. The CORESET group ID, that is, the specific index/specific identification information/specific indicator for distinguishing/identifying the CORESETs configured for/associated with the TRP/panel may be configured/indicated by higher-layer signaling (e.g., RRC signaling)/L2 signaling (e.g., a MAC control element (MAC-CE))/L1 signaling (e.g., DCI)). For example, it may be configured/indicated that a PDCCH from each TRP/panel is detected on a CORESET group basis, and/or it may be configured/indicated that UCI (e.g., CSI, HARQ-A/N, and SR) and/or UL physical channel resources (e.g., PUCCH/PRACH/SRS resources) for each TRP/panel are separately managed/controlled on a CORESET group basis, and/or an HARQ A/N (process/retransmission) for a PDSCH/PUSCH scheduled by each TRP/panel may be managed on a corresponding CORESET group basis. 
     For example, a higher-layer parameter, ControlResourceSet information element (IE) is used to configure a time/frequency CORESET. For example, the CORESET may be related to detection and reception of DCI. The ControlResourceSet IE may include the ID of a CORESET (e.g., controlResourceSetID)/the index of a CORESET pool of the CORESET (e.g., CORESETPoolIndex)/a time/frequency resource configuration for the CORESET/TCI information related to the CORESET. For example, the index of the CORESET pool (e.g., CORESETPoolIndex) may be set to 0 or 1. In the above description, a CORESET group may correspond to a CORESET pool, and a CORESET group ID may correspond to a CORESET pool index (e.g., CORESETPoolIndex). 
     Random Access for Multiple TX/RX Points of Multiple Cells 
     When a single UE is configured with MTRP transmission and reception, one of multiple TRPs may use serving cell resources of the UE, and another TRP may use non-serving cell resources of the UE. In the present disclosure, the former TRP is referred to as a serving cell TRP, and the latter TRP is referred to as a cooperating cell TRP. 
     In this inter-cell MTRP environment, when an RACH is triggered for UL synchronization, an SR, or a BFR, and the UE performs an RACH procedure in PRACH resources of a cooperating cell TRP, a gNB controlling a cooperating cell (e.g., a gNB-DU) may not recognize the UE. Therefore, an operation for UL synchronization, an SR, or a BFR may not be supported in the inter-cell MTRP environment. 
     The UE configures one or more serving cells and one or more cooperating cells for multiple TRPs. The gNB configures a serving cell and a cooperating cell for the UE and interconnects the cells by hackhaul. The cooperating cell is a non-serving cell or a serving cell of another type. 
     In the present disclosure, UL resources for a specific cell/TRP may be interpreted as UL resources having specific DL RS(s) (DL RS set(s)) as beams (e.g., spatial filters and spatial relations) and/or pathloss reference RSs or as UL resources for a specific UE panel (ID). 
     Operation between Transmitter and Receiver 
     A serving cell and a cooperating cell belong to different gNB-DUs or the same gNB-DU of the same gNB. A serving cell and a cooperating cell for a specific UE may or may not be connected by carrier aggregation (CA) or dual connectivity (DC). For the perspective of the UE, both the serving cell and the cooperating cell may be PCells, PSCells, or SCells, or only one of the serving cell and the cooperating cell may be a PCell, a PSCell, or an SCell. Alternatively, when the UE is performing handover, the serving cell may be a target cell, and the cooperating cell may be a source cell. 
       FIGS. 10A to 10E  illustrate various embodiments of the configurations of MAC/HARQ entities in a UE and a gNB, for inter-cell MTRP applicable to the present disclosure. 
     Referring to  FIGS. 10A to 10E , a gNB is divided into a gNB-centralized unit (gNB-CU) and a gNB-distributed unit (gNB-DU). A serving cell TRP, a cooperating cell TRP, MTRP, and a UE are illustrated. There may be one or more gNB-DUs, and each of a gNB and the UE includes a MAC entity and an HARQ entity. 
     Specifically,  FIG. 10A  illustrates the configuration of serving cell MAC/HARQ entities, when a serving cell and a cooperating cell have different gNB-DUs.  FIG. 10B  illustrates the configuration of serving cell MAC/HARQ entities, when a serving cell and a cooperating cell have the same gNB-DU.  FIG. 10C  illustrates the configuration of serving cell MAC/HARQ entities and cooperating cell HARQ entities, when a serving cell and a cooperating cell have the same gNB-DU.  FIG. 10D  illustrates the configuration of serving cell MAC/HARQ entities and cooperating cell HARQ entities, when a serving cell and a cooperating cell have different gNB-DUs.  FIG. 10E  illustrates the configuration of serving cell MAC/HARQ entities and cooperating cell MAC/HARQ entities, when a serving cell and a cooperating cell have different gNB-DUs. 
     Inter-Cell MTRP RACH Method 
     A serving cell and a cooperating cell may be managed in different time advance groups (TAGs). For example, a serving cell TRP and a cooperating cell TRP may be managed in different TAGs. In this case, different RACH procedures need to be performed for different TRPs, for UL synchronization. For example, a TAG dedicated to a cooperating cell may be required. 
     Accordingly, the following methods are proposed for a UE performing an MTRP operation in RACH resources. The gNB may perform an RACH procedure in one or more of the following methods to distinguish a case in which a UE performs an RACH procedure in RACH resources of a specific cell configured as a serving cell for the UE from a case in which a UE recognizing the specific cell as a cooperating cell performs an RACH procedure in RACH resources of the specific cell, for an MTRP operation. For example, Method 1 may be applied for a contention-free RACH, and Method 2 or Method 3 may be applied for a contention-based RACH. Alternatively, an RACH procedure may be performed in a combination of Method 1 and Method 2 or a combination of Method 1 and Method 3. 
     In DL transmissions of MSG2, MSG4, and MSGB in an RACH procedure through MTRPs of a serving cell and a cooperating cell, one or more MAC entities located in one or more gNB-DUs configure a random access response MAC CE or a contention resolution MAC CE, for a serving cell TRP and a cooperating cell TRP. Preferably, the plurality of gNB-DUs are connected to the same gNB-CU, and different MAC entities for one UE are located in the same or different gNB-DUs. 
     In UL transmissions of MGS1, MSG3, and MSGA in an RACH procedure through MTRPs of a serving cell and a cooperating cell, one or more MAC entities located in the UE select preambles for the serving cell TRP and the cooperating cell TRP, and configure a TB for MSG3 or MSGA. 
     Method 1: Separate PRACH Resource Allocation for Inter-Cell MTRP 
     When an RACH directed to a cooperating cell TRP is triggered for a TAG or a BFR, a UE which configures a specific cell as a cooperating cell for MTRP transmits RACH MSG1 or RACH MSGA in specific PRACH resources. For example, a gNB may allocate specific preamble indexes, specific ROs, or specific PRACH time/frequency resources as the specific PRACH resources. This specific PRACH resource allocation information may be configured for each BWP of a specific cell, and the gNB transmits the PRACH resource allocation information to the UE by a UE-specific message or system information. When the UE transmits MSG1 or MSGA in the specific PRACH resources, the gNB considers that the UE is performing an RACH procedure with the cooperating cell TRP. 
       FIG. 11  illustrates an exemplary PRACH resource allocation method for inter-cell MTRP according to the present disclosure. 
     Referring to  FIG. 11 , the UE may trigger a contention-based RACH for the cooperating cell TRP due to TA timer expiry or beam failure detection for the cooperating cell TRP. In this case, the UE transmits MSG1 or MSGA using a specific preamble index, specific RO, or specific PRACH time/frequency resources configured for the cooperating TRP by the gNB. A gNB MAC entity (a serving cell or cooperating cell MAC entity) to which the cooperating cell TRP belongs may perform an RACH procedure through the cooperating TRP. 
     Method 2: MSG3/A UCI-Based UE Identification for Inter-Cell MTRP 
       FIG. 12  illustrates an exemplary MSG3/A UCI-based UE identification method for inter-cell MTRP according to the present disclosure. 
     Referring to  FIG. 12 , when an RACH directed to a cooperating cell TRP is triggered, a UE which has configured a specific cell as a cooperating cell for MTRP may transmit UCI together with MSG3 or MSGA payload. The UCI may include all or part of the following information:
         UE ID allocated by serving cell   UE ID for cooperating cell   Indicator indicating RACH transmission to cooperating cell   Cell index or TRP ID for identifying cooperating cell TRP       

     The gNB may identify the UE transmitting the RACH to the cooperating cell based on the above UCI. The gNB may separately configure a UE ID, cell index, or TRP ID for the UE, for this operation. Alternatively, the UE ID may be a UE-specific RNTI (C-RNTI or the like) allocated by an old serving cell or another ID corresponding to the UE-specific RNTI. For example, the UE ID may be a full 16-bit C-RNTI or an N-bit UE ID (N&lt;16) generated based on the 16-bit C-RNTI. Although the cell index may be a corresponding full cell ID, a short serving cell ID for the UE may be allocated. 
     Method 3: MSG3/A MAC CE-Based UE Identification for Inter-Cell MTRP 
     When an RACH directed to a cooperating cell TRP is triggered for a TAG or a BFR, an MSG3 or MSGA MAC PDU transmitted from a UE which has configured a specific cell as a cooperating cell for MTRP may include a specific MAC CE. The MAC CE may include all or part of the following information:
         UE ID allocated by serving cell   UE ID for cooperating cell   Indicator indicating RACH transmission to cooperating cell   Cell index or TRP ID for identifying cooperating cell TRP       

     The gNB may separately configure a UE ID, cell index, or TRP ID for the UE, for this operation. Alternatively, the UE ID may be a UE-specific RNTI (C-RNTI or the like) allocated by an old serving cell or another ID corresponding to the UE-specific RNTI. For example, the UE ID may be a full 16-bit C-RNTI or an N-bit UE ID (N&lt;16) generated based on the 16-bit C-RNTI. Although the cell index may be a corresponding full cell ID, a short serving cell ID for the UE may be allocated. 
     When an RACH procedure is performed with the cooperating cell TRP in the above methods, the cooperating cell receives MSG3 or MSGA payload from the UE, and transmits the received MSG3 or MSGA payload to a gNB-DU that controls the cooperating cell or a gNB-DU that controls a serving cell connected to the cooperating cell. 
     When the RACH directed to the cooperating cell TRP is a contention-based RACH, the UE receives an MSG4 MAC CE or MSGB MAC CE. For this purpose, the gNB may transmit the MSG4 MAC CE or MSGB MAC CE as follows. In the following options, a gNB-DU to which the cooperating cell TRP may be identical to or different from a gNB-DU to which the serving cell TRP belongs.
         Option 1: A MAC entity of the gNB -DU to which the cooperating cell TRP belongs generates the MSG4 MAC CE or MSGB MAC CE and transmits MSG4/MSGB to the cooperating cell TRP.
           The MAC entity of the gNB-DU to which the cooperating cell TRP belongs generates the MSG4 MAC CE or MSGB MAC CE and transmits a PDCCH/PDSCH for the MAC CE to the UE through the cooperating cell TRP. The UE receives the PDCCH/PDSCH through the cooperating cell TRP.   In this method, the UE transmits MSG1 and MSG3 in UL resources for the cooperating cell TRP, and receives MSG2 and MSG4 in DL resources of the cooperating cell TRP. When a 2-step RACH procedure is used, the UE transmits MSGA in the UL resources for the cooperating cell TRP, and receives MSGB in the DL resources of the cooperating cell TRP.   
           Option 2: A MAC entity of the gNB-DU to which the serving cell TRP belongs generates the MSG4 MAC CE or MSGB MAC CE and transmits MSG4/MSGB to the cooperating cell TRP.
           The MAC entity of the gNB-DU to which the serving cell TRP belongs generates the MSG4 MAC CE or MSGB MAC CE and transmits the PDCCH/PDSCH for the MAC CE to the UE through the cooperating cell TRP. The UE receives the PDCCH/PDSCH through the cooperating cell TRP.   In this method, the UE transmits MSG1 and MSG3 in the UL resources for the cooperating cell TRP, and receives MSG2 and MSG4 in the DL resources of the cooperating cell TRP. When the 2-step RACH procedure is used, the UE transmits MSGA in the UL resources for the cooperating cell TRP, and receives MSGB in the DL resources of the cooperating cell TRP.   
           Option 3: The MAC entity of the gNB-DU to which the serving cell TRP belongs generates the MSG4 MAC CE or MSGB MAC CE and transmits MSG4/MSGB to the serving cell TRP.
           The MAC entity of the gNB-DU to which the serving cell TRP belongs generates the MSG4 MAC CE or MSGB MAC CE and transmits the PDCCH/PDSCH for the MAC CE to the UE through the serving cell TRP. The UE receives the PDCCH/PDSCH through the serving cell TRP.   In this method, the UE transmits MSG1 in the UL resources for the cooperating cell TRP, and receives MSG2 in DL resources of the cooperating cell TRP or the serving cell TRP. Further, the UE transmits MSG3 in UL resources for the cooperating cell TRP or the serving cell TRP, and receives MSG4 in UL resources for the serving cell TRP. When the 2-step RACH procedure is used, the UE transmits MSGA in the UL resources for the cooperating cell TRP, and receives MSGB in the DL resources of the serving cell TRP.   
               

       FIG. 13  illustrates an exemplary Option 1-based or Option 2-based RACH method for inter-cell MTRP according to the present disclosure, and  FIG. 14  illustrates an exemplary Option 3-based RACH method for inter-cell MTRP according to the present disclosure. 
     Method 4: Contention-Free RACH Method for Cooperating Cell TRP Operation 
       FIG. 15  illustrates an exemplary contention-free RACH method for a cooperating cell TRP operation according to the present disclosure. 
     A gNB may trigger an RACH directed to a cooperating cell TRP by transmitting DCI that allocates a UE-specific preamble through a serving cell TRP or a cooperating cell TRP. In this case, the DCI may indicate the cooperating cell TRP by indicating the index of a UE-specific random access preamble and a cell index or a TRP ID. The UE receives a serving RACH configuration and a cooperating cell RACH configuration separately. The UE which has received the DCI from the serving cell TRP triggers the RACH by using the RACH configuration (an RACH RO, PO, or the like) of the cooperating cell TRP. 
     In the above multiple methods, the gNB may indicate MSG3 retransmission resources by DCI during an RACH procedure in PRACH resources of the cooperating cell TRP. The DCI is transmitted in DCI format0_0, and the CRC of the DCI is scrambled with a temporary C-RNTI. The UE may receive the DCI in a search space/CORESET of the cooperating cell TRP (or a search space/CORESET of the serving cell TRP), and receive HARQ retransmission resources for MSG3. The DCI may allocate TRP1 PUSCH resources or TRP2 PUSCH resources. The UE may perform an N th  MSG3 transmission on a TRP1 PUSCH and an (N+1) th  MSG3 transmission on a TRP2 PUSCH. In this case, the gNB (e.g., the HARQ entity of the serving cell) may soft-combine the N th  MSG3 transmission with the (N+1) th  MSG3 transmission. 
     Further, the UE may set different RACH backoff values for the cooperating cell TRP and the serving cell TRP. For example, in the case where MSG2 received from the gNB configures different backoff values for the cooperating cell TRP and the serving cell TRP, when the UE performs an RACH procedure in PRACH resources of the cooperating cell TRP, the UE performs backoff using the backoff value for the cooperating cell TRP, and when the UE performs an RACH procedure in PRACH resources of the serving cell TRP, the UE performs backoff using the backoff value for the serving cell TRP. The gNB may configure different backoff values for the cooperating cell TRP and the serving cell TRP by one MSG2 RAR, or cooperating cell MSG2 and serving cell MSG2 may separately configure backoff values for the respective TRPs, or a backoff value indicated by MSG2 may be applied only to one cell TRP (e.g., the serving cell TRP), while a scaled value of the received backoff value may be applied to the other cell TRP (e.g., the cooperating cell TRP). 
     Upon occurrence of RACH failure during the RACH procedure in PRACH resources of the cooperating cell TRP, the UE may indicate the RACH failure of the cooperating cell TRP by using UL resources of the serving cell TRP. On the contrary, upon occurrence of RACH failure during the RACH procedure in PRACH resources of the serving cell TRP, the UE may indicate the RACH failure of the serving cell TRP by using UL resources of the cooperating cell TRP. 
       FIG. 16  illustrates a method of receiving a signal by a UE according to an embodiment of the present disclosure. 
     When an RACH directed to a cooperating cell TRP is triggered due to a TAG or a BFR ( 1601 ), a UE which has configured a specific cell as a cooperating cell for MTRP transmits RACH MSG1 or RACH MSGA in specific PRACH resources ( 1603 ). 
     According to another embodiment, when an RACH directed to a cooperating cell TRP is triggered due to a TAG or a BFR ( 1601 ), a UE which has configured a specific cell as a cooperating cell for MTRP may transmit UCI together with MSG3 or MSGA payload, or an MSG3 or MSGA MAC PDU transmitted by the UE may include a specific MAC CE. 
     Specifically, the UE may trigger a contention-based RACH for the cooperating cell TRP in view of TA timer expiry or beam failure detection for the cooperating cell TRP. 
     The UE receives an RA response (MSG2 or MSGB) on a PDSCH ( 1605 ). 
     When an RACH procedure is performed with the cooperating cell TRP, the cooperating cell receives MSG3 or MSGA payload from the UE ( 1607 ), and transmits received MSG or MSGA payload to a gNB-DU that controls the cooperating cell or a gNB-DU that controls a serving cell connected to the cooperating cell. 
     When the RACH for the cooperating cell TRP is a contention-based RACH, the UE receives an MSG4 MAC CE or an MSGB MAC CE ( 1609 ). For this purpose, the gNB may transmit the MSG4 MAC CE or the MSGB MAC CE. In this case, the gNB-DU to which the cooperating cell TRP belongs may be identical to or different from the gNB-DU to which the serving cell TRP belongs. 
     Effects of the Present Disclosure 
     As a UE configured with inter-cell MTRP triggers an RACH for a serving cell TRP or an RACH for a cooperating cell TRP, and the RACH for the serving cell TRP and the RACH for the cooperating cell TRP are distinguished from each other by PRACH resources or transmission of an MSG3 PUSCH or MSGA PUSCH, an RACH procedure for UL synchronization, an SR, or a BFR may be performed in an inter-cell MTRP environment. 
       FIG. 17  illustrates a communication system  1  applied to the present disclosure. 
     Referring to  FIG. 17 , a communication system  1  applied to the present disclosure includes wireless devices, Base Stations (BSs), and a network. Herein, the wireless devices represent devices performing communication using Radio Access Technology (RAT) (e.g., 5G New RAT (NR)) or Long-Term Evolution (LTE)) and may be referred to as communication/radio/5G devices. The wireless devices may include, without being limited to, a robot  100   a , vehicles  100   b - 1  and  100   b - 2 , an eXtended Reality (XR) device  100   c , a hand-held device  100   d , a home appliance  100   e , an Internet of Things (IoT) device  100   f , and an Artificial Intelligence (AI) device/server  400 . For example, the vehicles may include a vehicle having a wireless communication function, an autonomous driving vehicle, and a vehicle capable of performing communication between vehicles. Herein, the vehicles may include an Unmanned Aerial Vehicle (UAV) (e.g., a drone). The XR device may include an Augmented Reality (AR)/Virtual Reality (VR)/Mixed Reality (MR) device and may be implemented in the form of a Head-Mounted Device (HMD), a Head-Up Display (HUD) mounted in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, etc. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), and a computer (e.g., a notebook). The home appliance may include a TV, a refrigerator, and a washing machine. The IoT device may include a sensor and a smartmeter. For example, the BSs and the network may be implemented as wireless devices and a specific wireless device  200   a  may operate as a BS/network node with respect to other wireless devices. 
     The wireless devices  100   a  to  100   f  may be connected to the network  300  via the BSs  200 . An AI technology may be applied to the wireless devices  100   a  to  100   f  and the wireless devices  100   a  to  100   f  may be connected to the AI server  400  via the network  300 . The network  300  may be configured using a 3G network, a 4G (e.g., LTE) network, or a 5G (e.g., NR) network. Although the wireless devices  100   a  to  100   f  may communicate with each other through the BSs  200 /network  300 , the wireless devices  100   a  to  100   f  may perform direct communication (e.g., sidelink communication) with each other without passing through the BSs/network. For example, the vehicles  100   b - 1  and  100   b - 2  may perform direct communication (e.g. Vehicle-to-Vehicle (V2V)/Vehicle-to-everything (V2X) communication). The IoT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices  100   a  to  100   f.    
     Wireless communication/connections  150   a,    150   b,  or  150   c  may be established between the wireless devices  100   a  to  100   f /BS  200 , or BS  200 /BS  200 . Herein, the wireless communication/connections may be established through various RATs (e.g., 5G NR) such as uplink/downlink communication  150   a,  sidelink communication  150   b  (or, D2D communication), or inter BS communication (e.g. relay, Integrated Access Backhaul (IAB)). The wireless devices and the BSs/the wireless devices may transmit/receive radio signals to/from each other through the wireless communication/connections  150   a  and  150   b.  For example, the wireless communication/connections  150   a  and  150   b  may transmit/receive signals through various physical channels. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, and resource mapping/demapping), and resource allocating processes, for transmitting/receiving radio signals, may be performed based on the various proposals of the present disclosure. 
       FIG. 18  illustrates wireless devices applicable to the present disclosure. 
     Referring to  FIG. 18 , a first wireless device  100  and a second wireless device  200  may transmit radio signals through a variety of RATs (e.g., LTE and NR). Herein, {the first wireless device  100  and the second wireless device  200 } may correspond to {the wireless device  100   x  and the BS  200 } and/or {the wireless device  100   x  and the wireless device  100   s } of  FIG. 17 . 
     The first wireless device  100  may include one or more processors  102  and one or more memories  104  and additionally further include one or more transceivers  106  and/or one or more antennas  108 . The processor(s)  102  may control the memory(s)  104  and/or the transceiver(s)  106  and may be configured to implement the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. For example, the processor(s)  102  may process information within the memory(s)  104  to generate first information/signals and then transmit radio signals including the first information/signals through the transceiver(s)  106 . The processor(s)  102  may receive radio signals including second information/signals through the transceiver  106  and then store information obtained by processing the second information/signals in the memory(s)  104 . The memory(s)  104  may be connected to the processor(s)  102  and may store a variety of information related to operations of the processor(s)  102 . For example, the memory(s)  104  may store software code including commands for performing a part or the entirety of processes controlled by the processor(s)  102  or for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. Herein, the processor(s)  102  and the memory(s)  104  may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver(s)  106  may be connected to the processor(s)  102  and transmit and/or receive radio signals through one or more antennas  108 . Each of the transceiver(s)  106  may include a transmitter and/or a receiver. The transceiver(s)  106  may be interchangeably used with Radio Frequency (RF) unit(s). In the present disclosure, the wireless device may represent a communication modem/circuit/chip. 
     The second wireless device  200  may include one or more processors  202  and one or more memories  204  and additionally further include one or more transceivers  206  and/or one or more antennas  208 . The processor(s)  202  may control the memory(s)  204  and/or the transceiver(s)  206  and may be configured to implement the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. For example, the processor(s)  202  may process information within the memory(s)  204  to generate third information/signals and then transmit radio signals including the third information/signals through the transceiver(s)  206 . The processor(s)  202  may receive radio signals including fourth information/signals through the transceiver(s)  106  and then store information obtained by processing the fourth information/signals in the memory(s)  204 . The memory(s)  204  may be connected to the processor(s)  202  and may store a variety of information related to operations of the processor(s)  202 . For example, the memory(s)  204  may store software code including commands for performing a part or the entirety of processes controlled by the processor(s)  202  or for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. Herein, the processor(s)  202  and the memory(s)  204  may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver(s)  206  may be connected to the processor(s)  202  and transmit and/or receive radio signals through one or more antennas  208 . Each of the transceiver(s)  206  may include a transmitter and/or a receiver. The transceiver(s)  206  may be interchangeably used with RF unit(s). In the present disclosure, the wireless device may represent a communication modem/circuit/chip. 
     Hereinafter, hardware elements of the wireless devices  100  and  200  will be described more specifically. One or more protocol layers may be implemented by, without being limited to, one or more processors  102  and  202 . For example, the one or more processors  102  and  202  may implement one or more layers (e.g., functional layers such as PHY, MAC, RLC, PDCP, RRC, and SDAP). The one or more processors  102  and  202  may generate one or more Protocol Data Units (PDUs) and/or one or more Service Data Unit (SDUs) according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. The one or more processors  102  and  202  may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. The one or more processors  102  and  202  may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document and provide the generated signals to the one or more transceivers  106  and  206 . The one or more processors  102  and  202  may receive the signals (e.g., baseband signals) from the one or more transceivers  106  and  206  and acquire the PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. 
     The one or more processors  102  and  202  may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The one or more processors  102  and  202  may be implemented by hardware, firmware, software, or a combination thereof. As an example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in the one or more processors  102  and  202 . The descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document may be implemented using firmware or software and the firmware or software may be configured to include the modules, procedures, or functions. Firmware or software configured to perform the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document may be included in the one or more processors  102  and  202  or stored in the one or more memories  104  and  204  so as to be driven by the one or more processors  102  and  202 . The descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document may be implemented using firmware or software in the form of code, commands, and/or a set of commands. 
     The one or more memories  104  and  204  may be connected to the one or more processors  102  and  202  and store various types of data, signals, messages, information, programs, code, instructions, and/or commands. The one or more memories  104  and  204  may be configured by Read-Only Memories (ROMs), Random Access Memories (RAMs), Electrically Erasable Programmable Read-Only Memories (EPROMs), flash memories, hard drives, registers, cash memories, computer-readable storage media, and/or combinations thereof. The one or more memories  104  and  204  may be located at the interior and/or exterior of the one or more processors  102  and  202 . The one or more memories  104  and  204  may be connected to the one or more processors  102  and  202  through various technologies such as wired or wireless connection. 
     The one or more transceivers  106  and  206  may transmit user data, control information, and/or radio signals/channels, mentioned in the methods and/or operational flowcharts of this document, to one or more other devices. The one or more transceivers  106  and  206  may receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document, from one or more other devices. For example, the one or more transceivers  106  and  206  may be connected to the one or more processors  102  and  202  and transmit and receive radio signals. For example, the one or more processors  102  and  202  may perform control so that the one or more transceivers  106  and  206  may transmit user data, control information, or radio signals to one or more other devices. The one or more processors  102  and  202  may perform control so that the one or more transceivers  106  and  206  may receive user data, control information, or radio signals from one or more other devices. The one or more transceivers  106  and  206  may be connected to the one or more antennas  108  and  208  and the one or more transceivers  106  and  206  may be configured to transmit and receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document, through the one or more antennas  108  and  208 . In this document, the one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports). The one or more transceivers  106  and  206  may convert received radio signals/channels etc. from RF band signals into baseband signals in order to process received user data, control information, radio signals/channels, etc. using the one or more processors  102  and  202 . The one or more transceivers  106  and  206  may convert the user data, control information, radio signals/channels, etc. processed using the one or more processors  102  and  202  from the base band signals into the RF band signals. To this end, the one or more transceivers  106  and  206  may include (analog) oscillators and/or filters. 
       FIG. 19  illustrates another example of a wireless device applied to the present disclosure. The wireless device may be implemented in various forms according to a use-case/service (refer to  FIG. 19 ). 
     Referring to  FIG. 19 , wireless devices  100  and  200  may correspond to the wireless devices  100  and  200  of  FIG. 18  and may be configured by various elements, components, units/portions, and/or modules. For example, each of the wireless devices  100  and  200  may include a communication unit  110 , a control unit  120 , a memory unit  130 , and additional components  140 . The communication unit may include a communication circuit  112  and transceiver(s)  114 . For example, the communication circuit  112  may include the one or more processors  102  and  202  and/or the one or more memories  104  and  204  of  FIG. 18 . For example, the transceiver(s)  114  may include the one or more transceivers  106  and  206  and/or the one or more antennas  108  and  208  of  FIG. 18 . The control unit  120  is electrically connected to the communication unit  110 , the memory  130 , and the additional components  140  and controls overall operation of the wireless devices. For example, the control unit  120  may control an electric/mechanical operation of the wireless device based on programs/code/commands/information stored in the memory unit  130 . The control unit  120  may transmit the information stored in the memory unit  130  to the exterior (e.g., other communication devices) via the communication unit  110  through a wireless/wired interface or store, in the memory unit  130 , information received through the wireless/wired interface from the exterior (e.g., other communication devices) via the communication unit  110 . 
     The additional components  140  may be variously configured according to types of wireless devices. For example, the additional components  140  may include at least one of a power unit/battery, input/output (I/O) unit, a driving unit, and a computing unit. The wireless device may be implemented in the form of, without being limited to, the robot ( 100   a  of  FIG. 17 ), the vehicles ( 100   b - 1  and  100   b - 2  of  FIG. 17 ), the XR device ( 100   c  of  FIG. 17 ), the hand-held device ( 100   d  of  FIG. 17 ), the home appliance ( 100   e  of  FIG. 17 ), the IoT device ( 100   f  of  FIG. 17 ), a digital broadcast terminal, a hologram device, a public safety device, an MTC device, a medicine device, a fintech device (or a finance device), a security device, a climate/environment device, the AI server/device ( 400  of  FIG. 17 ), the BSs ( 200  of  FIG. 17 ), a network node, etc. The wireless device may be used in a mobile or fixed place according to a use-example/service. 
     In  FIG. 19 , the entirety of the various elements, components, units/portions, and/or modules in the wireless devices  100  and  200  may be connected to each other through a wired interface or at least a part thereof may be wirelessly connected through the communication unit  110 . For example, in each of the wireless devices  100  and  200 , the control unit  120  and the communication unit  110  may be connected by wire and the control unit  120  and first units (e.g.,  130  and  140 ) may be wirelessly connected through the communication unit  110 . Each element, component, unit/portion, and/or module within the wireless devices  100  and  200  may further include one or more elements. For example, the control unit  120  may be configured by a set of one or more processors. As an example, the control unit  120  may be configured by a set of a communication control processor, an application processor, an Electronic Control Unit (ECU), a graphical processing unit, and a memory control processor. As another example, the memory  130  may be configured by a Random Access Memory (RAM), a Dynamic RAM (DRAM), a Read Only Memory (ROM)), a flash memory, a volatile memory, a non-volatile memory, and/or a combination thereof. 
       FIG. 20  illustrates a vehicle or an autonomous driving vehicle applied to the present disclosure. The vehicle or autonomous driving vehicle may be implemented by a mobile robot, a car, a train, a manned/unmanned Aerial Vehicle (AV), a ship, etc. 
     Referring to  FIG. 20 , a vehicle or autonomous driving vehicle  100  may include an antenna unit  108 , a communication unit  110 , a control unit  120 , a driving unit  140   a,  a power supply unit  140   b,  a sensor unit  140   c,  and an autonomous driving unit  140   d.  The antenna unit  108  may be configured as a part of the communication unit  110 . The blocks  110 / 130 / 140   a  to  140   d  correspond to the blocks  110 / 130 / 140  of  FIG. 19 , respectively. 
     The communication unit  110  may transmit and receive signals (e.g., data and control signals) to and from external devices such as other vehicles, BSs (e.g., gNBs and road side units), and servers. The control unit  120  may perform various operations by controlling elements of the vehicle or the autonomous driving vehicle  100 . The control unit  120  may include an Electronic Control Unit (ECU). The driving unit  140   a  may cause the vehicle or the autonomous driving vehicle  100  to drive on a road. The driving unit  140   a  may include an engine, a motor, a powertrain, a wheel, a brake, a steering device, etc. The power supply unit  140   b  may supply power to the vehicle or the autonomous driving vehicle  100  and include a wired/wireless charging circuit, a battery, etc. The sensor unit  140   c  may acquire a vehicle state, ambient environment information, user information, etc. The sensor unit  140   c  may include an Inertial Measurement Unit (IMU) sensor, a collision sensor, a wheel sensor, a speed sensor, a slope sensor, a weight sensor, a heading sensor, a position module, a vehicle forward/backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illumination sensor, a pedal position sensor, etc. The autonomous driving unit  140   d  may implement technology for maintaining a lane on which a vehicle is driving, technology for automatically adjusting speed, such as adaptive cruise control, technology for autonomously driving along a determined path, technology for driving by automatically setting a path if a destination is set, and the like. 
     For example, the communication unit  110  may receive map data, traffic information data, etc. from an external server. The autonomous driving unit  140   d  may generate an autonomous driving path and a driving plan from the obtained data. The control unit  120  may control the driving unit  140   a  such that the vehicle or the autonomous driving vehicle  100  may move along the autonomous driving path according to the driving plan (e.g., speed/direction control). In the middle of autonomous driving, the communication unit  110  may aperiodically/periodically acquire recent traffic information data from the external server and acquire surrounding traffic information data from neighboring vehicles. In the middle of autonomous driving, the sensor unit  140   c  may obtain a vehicle state and/or surrounding environment information. The autonomous driving unit  140   d  may update the autonomous driving path and the driving plan based on the newly obtained data/information. The communication unit  110  may transfer information about a vehicle position, the autonomous driving path, and/or the driving plan to the external server. The external server may predict traffic information data using AI technology, etc., based on the information collected from vehicles or autonomous driving vehicles and provide the predicted traffic information data to the vehicles or the autonomous driving vehicles. 
       FIG. 21  is a diagram illustrating a DRX operation of a UE according to an embodiment of the present disclosure. 
     The UE may perform a DRX operation in the afore-described/proposed procedures and/or methods. A UE configured with DRX may reduce power consumption by receiving a DL signal discontinuously. DRX may be performed in an RRC_IDLE state, an RRC_INACTIVE state, and an RRC_CONNECTED state. The UE performs DRX to receive a paging signal discontinuously in the RRC_IDLE state and the RRC_INACTIVE state. DRX in the RRC_CONNECTED state (RRC_CONNECTED DRX) will be described below. 
     Referring to  FIG. 21 , a DRX cycle includes an On Duration and an Opportunity for DRX. The DRX cycle defines a time interval between periodic repetitions of the On Duration. The On Duration is a time period during which the UE monitors a PDCCH. When the UE is configured with DRX, the UE performs PDCCH monitoring during the On Duration. When the UE successfully detects a PDCCH during the PDCCH monitoring, the UE starts an inactivity timer and is kept awake. On the contrary, when the UE fails in detecting any PDCCH during the PDCCH monitoring, the UE transitions to a sleep state after the On Duration. Accordingly, when DRX is configured, PDCCH monitoring/reception may be performed discontinuously in the time domain in the afore-described/proposed procedures and/or methods. For example, when DRX is configured, PDCCH reception occasions (e.g., slots with PDCCH SSs) may be configured discontinuously according to a DRX configuration in the present disclosure. On the contrary, when DRX is not configured, PDCCH monitoring/reception may be performed continuously in the time domain. For example, when DRX is not configured, PDCCH reception occasions (e.g., slots with PDCCH SSs) may be configured continuously in the present disclosure. Irrespective of whether DRX is configured, PDCCH monitoring may be restricted during a time period configured as a measurement gap. 
     Table 7 describes a DRX operation of a UE (in the RRC_CONNECTED state). Referring to Table 7, DRX configuration information is received by higher-layer signaling (e.g., RRC signaling), and DRX ON/OFF is controlled by a DRX command from the MAC layer. Once DRX is configured, the UE may perform PDCCH monitoring discontinuously in performing the afore-described/proposed procedures and/or methods, as illustrated in  FIG. 5 . 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                 Type of signals 
                 UE procedure 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 1 st  step 
                 RRC signalling(MAC- 
                 Receive DRX configuration 
               
               
                   
                 CellGroupConfig) 
                 information 
               
               
                 2 nd  Step 
                 MAC CE((Long) DRX 
                 Receive DRX command 
               
               
                   
                 command MAC CE) 
               
               
                 3 rd  Step 
                 — 
                 Monitor a PDCCH during an 
               
               
                   
                   
                 on-duration of a DRX cycle 
               
               
                   
               
            
           
         
       
     
     MAC-CellGroupConfig includes configuration information required to configure MAC parameters for a cell group. MAC-CellGroupConfig may also include DRX configuration information. For example, MAC-CellGroupConfig may include the following information in defining DRX.
         Value of drx-OnDurationTimer: defines the duration of the starting period of the DRX cycle.   Value of drx-InactivityTimer: defines the duration of a time period during which the UE is awake after a PDCCH occasion in which a PDCCH indicating initial UL or DL data has been detected   Value of drx-HARQ-RTT-TimerDL: defines the duration of a maximum time period until a DL retransmission is received after reception of a DL initial transmission.   Value of drx-HARQ-RTT-TimerDL: defines the duration of a maximum time period until a grant for a UL retransmission is received after reception of a grant for a UL initial transmission.   drx-LongCycleStartOffset: defines the duration and starting time of a DRX cycle.   drx-ShortCycle (optional): defines the duration of a short DRX cycle.       

     When any of drx-OnDurationTimer, drx-InactivityTimer, drx-HARQ-RTT-TimerDL, and drx-HARQ-RTT-TimerDL is running, the UE performs PDCCH monitoring in each PDCCH occasion, staying in the awake state.