Method and apparatus for performing random access procedure

Abstract

The present disclosure provides a method for receiving a physical downlink shared channel (PDSCH) by a terminal in a wireless communication system. Specifically, the method may include: transmitting a physical random access channel (PRACH); monitoring a downlink control channel (DCI) for scheduling a PDSCH related to the PRACH; and based on detecting the DCI according to a radio network temporary identifier (RNTI), receiving the PDSCH based on the DCI.

Description

Technical Field

[0001] The present disclosure relates to a method and apparatus for performing a random access procedure, and more particularly, to a method and apparatus for performing a 2-step random access procedure (Type 2 random access procedure) by a user equipment (UE). Background Art

[0002] As more and more communication devices require greater communication services and the current trend, the next generation fifth generation (5G) system is needed to provide enhanced wireless broadband communication compared to the traditional LTE system. In the next generation 5G system, communication scenarios are divided into enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC), massive machine type communication (mMTC), etc.

[0003] In this article, eMBB is a next-generation mobile communication scenario characterized by high spectral efficiency, high user experience data rate and high peak data rate, URLLC is a next-generation mobile communication scenario characterized by ultra-high reliability, ultra-low latency and ultra-high availability (e.g., vehicle-to-everything (V2X), emergency services and remote control), and mMTC is a next-generation mobile communication scenario characterized by low cost, low energy, short packets and large-scale connections (e.g., the Internet of Things (IoT)). Summary of the invention

[0004] Technical issues

[0005] An object of the present disclosure is to provide a method and device for performing a random access procedure.

[0006] Those skilled in the art will recognize that the objectives that can be achieved by the present disclosure are not limited to what has been specifically described above, and the above and other objectives that can be achieved by the present disclosure will be more clearly understood from the following detailed description.

[0007] Technical Solution

[0008] In one aspect of the present disclosure, a method for receiving a physical downlink shared channel (PDSCH) in a wireless communication system by a user equipment (UE) is provided. The method may include: transmitting a physical random access channel (PRACH); monitoring downlink control information (DCI) for scheduling a PDSCH related to the PRACH; and based on detecting the DCI according to a radio network temporary identifier (RNTI), receiving the PDSCH based on the DCI.

[0009] In this case, regardless of whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH, the PDSCH is received.

[0010] Additionally, based on the UE being unable to check whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH, the PDSCH is received based on the DCI.

[0011] Additionally, based on the UE being able to check whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH and the UE confirming that the two bits of the first SFN are not identical to the two bits of the second SFN, the PDSCH is not received.

[0012] Additionally, based on the UE being able to check whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH and the UE confirming that the two bits of the first SFN are identical to the two bits of the second SFN, the PDSCH is received based on the DCI.

[0013] Additionally, the length of the monitoring window for DCI may exceed 10 ms.

[0014] Additionally, the RNTI is MsgB-RNTI.

[0015] In another aspect of the present disclosure, a UE configured to receive a PDSCH in a wireless communication system is provided. The UE may include: at least one transceiver; at least one processor; at least one memory, which is operatively connected to the at least one processor and configured to store instructions, which, when executed, cause the at least one processor to perform operations. The operations may include: transmitting a physical random access channel (PRACH) through at least one transceiver; monitoring downlink control information (DCI) for scheduling a PDSCH related to the PRACH; and based on detecting the DCI according to a radio network temporary identifier (RNTI), receiving the PDSCH through at least one transceiver based on the DCI.

[0016] In this case, regardless of whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH, the PDSCH is received.

[0017] Additionally, based on the UE being unable to check whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH, the PDSCH is received based on the DCI.

[0018] Additionally, based on the UE being able to check whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH and the UE confirming that the two bits of the first SFN are not identical to the two bits of the second SFN, the PDSCH is not received.

[0019] Additionally, based on the UE being able to check whether two bits of a first system frame number (SFN) included in the DCI are identical to two bits of a second SFN transmitting the PRACH and the UE confirming that the two bits of the first SFN are identical to the two bits of the second SFN, the PDSCH is received based on the DCI.

[0020] Additionally, the length of the monitoring window for DCI may exceed 10 ms.

[0021] Additionally, the RNTI is MsgB-RNTI.

[0022] In another aspect of the present disclosure, a device configured to receive a PDSCH in a wireless communication system is provided. The device may include: at least one processor; at least one memory operatively connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations. The operations may include: transmitting a physical random access channel (PRACH); monitoring downlink control information (DCI) for scheduling a PDSCH associated with the PRACH; and based on detecting the DCI according to a radio network temporary identifier (RNTI), receiving the PDSCH based on the DCI.

[0023] Technical Effects

[0024] According to the present disclosure, when a user equipment (UE) does not know the index of a system frame number (SFN) used to transmit a physical random access channel (PRACH) or does not interpret the index of the SFN included in received downlink control information (DCI) to reduce the delay caused by decoding of the DCI, the UE can efficiently perform a 2-step random access procedure (type 2 random access procedure).

[0025] Those skilled in the art will recognize that the effects that can be achieved by the present disclosure are not limited to what has been specifically described above, and other advantages of the present disclosure will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a diagram illustrating physical channels in a 3GPP system and a general signal transmission method using the physical channels.

[0027] Figure 2 , Figure 3 and Figure 4 is a diagram illustrating the structure of a radio frame and a time slot used in a New RAT (NR) system.

[0028] Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9 and Fig.10 is a diagram illustrating the composition of a synchronization signal / physical broadcast channel (SS / PBCH) block and a method of transmitting the SS / PBCH block.

[0029] Fig.11 is a diagram illustrating an exemplary 4-step Random Access Channel (RACH) procedure.

[0030] Fig.12 is a diagram illustrating an exemplary two-step RACH procedure.

[0031] Fig.13 is a diagram illustrating an exemplary contention-free RACH procedure.

[0032] Fig.14 is a diagram illustrating synchronization signal (SS) block transmission and physical random access channel (PRACH) resources linked to the SS block.

[0033] Fig.15 is a diagram illustrating SS block transmission and PRACH resources linked to the SS blocks.

[0034] Fig.16 is a diagram illustrating an exemplary RACH opportunity configuration.

[0035] Figures 17 to 19 Detailed Description of the Invention It is a diagram for explaining operations of a user equipment (UE) and a base station (BS) according to an embodiment of the present disclosure.

[0036] Figure 20 to Figure 22 is a diagram for explaining a method of monitoring downlink control information (DCI) for message B (MsgB) transmission according to an embodiment of the present disclosure.

[0037] Fig.23 An example of a communication system to which an embodiment of the present disclosure is applied is illustrated.

[0038] Figure 24 to Figure 27 Examples of various wireless devices to which the embodiments of the present disclosure are applied are illustrated. DETAILED DESCRIPTION

[0039] With the embodiments of the present disclosure described with reference to the accompanying drawings, the configuration, operation and other features of the present disclosure will be easily understood.The embodiments of the present disclosure set forth herein are examples in which the technical features of the present disclosure are applied to a 3rd Generation Partnership Project (3GPP) system.

[0040] Although the embodiments of the present disclosure are described in the context of a Long Term Evolution (LTE) system and an Advanced LTE (LTE-A) system, they are purely exemplary. Therefore, the embodiments of the present disclosure are applicable to any other communication system as long as the above definition is valid for the communication system.

[0041] The term base station (BS) may be used to encompass the meaning of terms including remote radio head (RRH), evolved Node B (eNB or eNode B), transmission point (TP), reception point (RP), relay, etc.

[0042] The 3GPP communication standard defines a downlink (DL) physical channel corresponding to a resource element (RE) carrying information from a higher layer, and a DL physical signal used in the physical layer and corresponding to an RE that does not carry information from a higher layer. For example, a physical downlink shared channel (PDSCH), a physical broadcast channel (PBCH), a physical multicast channel (PMCH), a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), and a physical hybrid ARQ indicator channel (PHICH) are defined as DL physical channels, and a reference signal (RS) and a synchronization signal (SS) are defined as DL physical signals. RS (also called a pilot signal) is a signal with a predefined special waveform known to both a gNode B (gNB) and a user equipment (UE). For example, a cell-specific RS, a UE-specific RS (UE-RS), a positioning RS (PRS), and a channel state information RS (CSI-RS) are defined as DL RS. The 3GPP LTE / LTE-A standard defines an uplink (UL) physical channel corresponding to an RE carrying information from a higher layer, and a UL physical signal used in the physical layer and corresponding to an RE not carrying information from a higher layer. For example, a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH) are defined as UL physical channels, and a demodulation reference signal (DM RS) for UL control / data signals and a sounding reference signal (SRS) for UL channel measurement are defined as UL physical signals.

[0043] In the present disclosure, PDCCH / PCFICH / PHICH / PDSCH refers to a set of time-frequency resources or a set of REs that carry downlink control information (DCI) / control format indicator (CFI) / DL acknowledgement / negative acknowledgement (ACK / NACK) / DL data. In addition, PUCCH / PUSCH / PRACH refers to a set of time-frequency resources or a set of REs that carry UL control information (UCI) / UL data / random access signals. In the present disclosure, specifically, time-frequency resources or REs allocated to or belonging to PDCCH / PCFICH / PHICH / PDSCH / PUCCH / PUSCH / PRACH are referred to as PDCCH RE / PCFICH RE / PHICH RE / PDSCH RE / PUCCH RE / PUSCH RE / PRACH RE or PDCCH resources / PCFICH resources / PHICH resources / PDSCH resources / PUCCH resources / PUSCH resources / PRACH resources. Hereinafter, if it is said that the UE sends PUCCH / PUSCH / PRACH, this means that UCI / UL data / random access signal is sent on or through PUCCH / PUSCH / PRACH. In addition, if it is said that the gNB sends PDCCH / PCFICH / PHICH / PDSCH, this means that DCI / control information is sent on or through PDCCH / PCFICH / PHICH / PDSCH.

[0044] In the following, an orthogonal frequency division multiplexing (OFDM) symbol / carrier / subcarrier / RE allocated with CRS / DMRS / CSI-RS / SRS / UE-RS or configured for CRS / DMRS / CSI-RS / SRS / UE-RS is referred to as a CRS / DMRS / CSI-RS / SRS / UE-RS symbol / carrier / subcarrier / RE. An OFDM symbol allocated with a tracking RS (TRS) or configured for TRS is referred to as a TRS symbol, a subcarrier allocated with TRS or configured for TRS is referred to as a TRS subcarrier, and an RE allocated with TRS or configured for TRS is referred to as a TRS RE. In addition, a subframe configured to send TRS is referred to as a TRS subframe. In addition, a subframe carrying a broadcast signal is referred to as a broadcast subframe or a PBCH subframe, and a subframe carrying a synchronization signal (SS) (e.g., a primary synchronization signal (PSS) and / or a secondary synchronization signal (SSS)) is referred to as an SS subframe or a PSS / SSS subframe. The OFDM symbol / subcarrier / RE to which the PSS / SSS is allocated and for which the PSS / SSS is configured is referred to as a PSS / SSS symbol / subcarrier / RE.

[0045] In the present disclosure, a CRS port, a UE-RS port, a CSI-RS port, and a TRS port refer to an antenna port configured to send a CRS, an antenna port configured to send a UE-RS, an antenna port configured to send a CSI-RS, and an antenna port configured to send a TRS, respectively. Antenna ports configured to send a CRS can be distinguished from each other by the position of REs occupied by the CRS according to the CRS port, antenna ports configured to send a UE-RS can be distinguished from each other by the position of REs occupied by the UE-RS according to the UE-RS port, and antenna ports configured to send a CSI-RS can be distinguished from each other by the position of REs occupied by the CSI-RS according to the CSI-RS port. Therefore, the term CRS / UE-RS / CSI-RS / TRS is also used to refer to the pattern of REs occupied by CRS / UE-RS / CSI-RS / TRS in a predetermined resource area.

[0046] Figure 1 Physical channels in a 3GPP system and a general method for transmitting signals on the physical channels are illustrated.

[0047] Reference Figure 1 , when the UE is powered on or enters a new cell, the UE performs an initial cell search (S201). The initial cell search involves the acquisition of synchronization with the eNB. Specifically, the UE synchronizes its timing with the eNB and acquires the cell identifier (ID) and other information by receiving the primary synchronization channel (P-SCH) and the secondary synchronization channel (S-SCH) from the eNB. The UE can then acquire information broadcast in the cell by receiving the physical broadcast channel (PBCH) from the eNB. During the initial cell search, the UE can monitor the DL channel status by receiving the downlink reference signal (DL RS).

[0048] After the initial cell search, the UE may acquire detailed system information by receiving a physical downlink control channel (PDCCH) and receiving a physical downlink shared channel (PDSCH) based on information included in the PDCCH (S202).

[0049] If the UE initially accesses the eNB or has no radio resources for signal transmission to the eNB, the UE may perform a random access procedure with the eNB (S203 to S206). In the random access procedure, the UE may send a predetermined sequence as a preamble on a physical random access channel (PRACH) (S203 and S205), and may receive a response message to the preamble on a PDCCH and a PDSCH associated with the PDCCH (S204 and S206). In the case of a contention-based RACH, the UE may additionally perform a contention resolution procedure.

[0050] After the above process, the UE can receive PDCCH and / or PDSCH from the eNB (S207), and send a physical uplink shared channel (PUSCH) and / or a physical uplink control channel (PUCCH) to the eNB (S208), which is a general DL and UL signal transmission process. Specifically, the UE receives downlink control information (DCI) on the PDCCH. Here, the DCI includes control information such as resource allocation information for the UE. Different DCI formats are defined according to different uses of the DCI.

[0051] The control information sent by the UE to the eNB on the UL or received by the UE from the eNB on the DL includes a DL / UL Acknowledgement / Negative Acknowledgement (ACK / NACK) signal, a Channel Quality Indicator (CQI), a Precoding Matrix Index (PMI), a Rank Indicator (RI), etc. In the 3GPP LTE system, the UE may send control information such as CQI, PMI, RI, etc. on the PUSCH and / or PUCCH.

[0052] In the NR system, the use of ultra-high frequency bands (i.e., millimeter frequency bands of 6 GHz or above) is being considered to transmit data using a wide frequency band for multiple users while maintaining a high transmission rate. 3GPP calls this system NR. In this disclosure, this system will be referred to as the NR system hereinafter.

[0053] The NR system adopts an OFDM transmission scheme or a similar transmission scheme. Specifically, the NR system can use OFDM parameters different from those in LTE. In addition, the NR system can follow the legacy LTE / LTE-A parameter set, but with a larger system bandwidth (e.g., 100MHz). In addition, in the NR system, a cell can support multiple parameter sets. That is, UEs operating with different parameter sets can coexist in one cell.

[0054] Figure 2 The structure of a radio frame used in NR is illustrated.

[0055] In NR, UL transmission and DL transmission are configured into frames. The length of the radio frame is 10ms and is defined as two 5ms half frames (HF). A half frame is defined as five 1ms subframes (SF). A subframe is divided into one or more time slots, and the number of time slots in a subframe depends on the subcarrier spacing (SCS). Each time slot includes 12 or 14 OFDM (A) symbols depending on the cyclic prefix (CP). When a normal CP is used, each time slot includes 14 symbols. When an extended CP is used, each time slot includes 12 symbols. Here, the symbol may include an OFDM symbol (or CP-OFDM symbol) and a SC-FDMA symbol (or DFT-s-OFDM symbol).

[0056] Table 1 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 a normal CP is used.

[0057] [Table 1]

[0058] SCS(15*2^u) <![CDATA[N slot symb ]]> <![CDATA[N frame,u slot ]]> <![CDATA[N subframe,u slot ]]> 15kHz(u=0) 14 10 1 30KHz(u=1) 14 20 2 60KHz(u=2) 14 40 4 120KHz(u=3) 14 80 8 240KHz(u=4) 14 160 16

[0059] *N slot symb : Number of symbols in a time slot * N frame,u slot : Number of time slots in a frame

[0060] *N subframe,u slot : Number of time slots in a subframe

[0061] 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.

[0062] [Table 2]

[0063] SCS(15*2^u) <![CDATA[N slot symb ]]> <![CDATA[N frame,u slot ]]> <![CDATA[N subframe,u slot ]]> 60KHz(u=2) 12 40 4

[0064] In the NR system, OFDM (A) parameter sets (e.g., SCS, CP length, etc.) can be configured differently between multiple cells merged for one UE. Therefore, the (absolute time) duration of a time resource (e.g., SF, time slot, or TTI) (abbreviated as time unit (TU)) consisting of the same number of symbols can be set differently between the merged cells.

[0065] Figure 3 The time slot structure of the NR frame is illustrated. A time slot includes multiple symbols in the time domain. For example, in the case of a normal CP, a time slot includes seven symbols. On the other hand, in the case of an extended CP, a time slot includes six symbols. A carrier includes multiple 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) is defined as a plurality of consecutive (P) RBs in the frequency domain and may correspond to a parameter set (e.g., SCS, CP length, etc.). A carrier may include up to N (e.g., five) BWPs. Data communication is performed through an activated BWP, and only one BWP may be activated for a UE. In a resource grid, each element is referred to as a resource element (RE) and a complex symbol may be mapped therein.

[0066] Figure 4The structure of a self-contained time slot is illustrated. In the NR system, the frame has a self-contained structure in which DL control channels, DL or UL data, UL control channels, etc. can all be contained in one time slot. For example, the first N symbols in the time slot (hereinafter, the DL control region) can be used to transmit the DL control channel, and the last M symbols in the time slot (hereinafter, the UL control region) can be used to transmit the UL control channel. N and M are integers greater than or equal to 0. The resource area (hereinafter, the data area) between the DL control region and the UL control region can be used for DL ​​data transmission or UL data transmission. For example, the following configuration can be considered. The various parts are listed in chronological order.

[0067] 1. DL configuration only

[0068] 2. UL configuration only

[0069] 3. Hybrid UL-DL configuration

[0070] -DL area + protection period (GP) + UL control area

[0071] -DL control area + GP + UL area

[0072] *DL area: (i) DL data area, (ii) DL control area + DL data area

[0073] *UL area: (i) UL data area, (ii) UL data area + UL control area

[0074] The PDCCH may be sent in the DL control region, and the PDSCH may be sent in the DL data region. The PUCCH may be sent in the UL control region, and the PUSCH may be sent in the UL data region. Downlink control information (DCI), such as DL data scheduling information, UL data scheduling information, etc., may be sent on the PDCCH. Uplink control information (UCI), such as ACK / NACK information about DL data, channel state information (CSI), and scheduling request (SR), may be sent on the PUCCH. The GP provides a time interval during the process of the UE switching from a transmit mode to a receive mode or from a receive mode to a transmit mode. Some symbols when switching from DL to UL within a subframe may be configured as GP.

[0075] Figure 5 The synchronization signal block (SSB) structure is illustrated. The UE can perform cell search, system information acquisition, beam alignment for initial access, DL measurement, etc. based on the SSB. The SSB and synchronization signal / physical broadcast channel (SS / PBCH) blocks can be used interchangeably.

[0076] Reference Figure 5, SSB includes PSS, SSS and PBCH. SSB is configured on four consecutive OFDM symbols, and PSS, PBCH, SSS / PBCH and PBCH are sent on corresponding OFDM symbols. PSS and SSS can each include 1 OFDM symbol and 127 subcarriers, and PBCH can include 3 OFDM symbols and 576 subcarriers. Polarization coding and quadrature phase shift keying (QPSK) are applied to PBCH. For each OFDM symbol, PBCH can have data RE and demodulation reference signal (DMRS) RE. Each RB can have three DMRS REs, and there can be three data REs between DMRS REs.

[0077] Community Search

[0078] Cell search refers to the process by which the UE acquires time / frequency synchronization of a cell and detects the cell ID (e.g., physical layer cell ID (PCID)) of the cell. PSS can be used to detect a cell ID within a cell ID group, and SSS can be used to detect a cell ID group. PBCH can be used to detect SSB (time) index and half frame.

[0079] The cell search procedure of the UE can be summarized as shown in Table 3 below.

[0080] [Table 3]

[0081]

[0082] Figure 6 SSB transmission is illustrated.

[0083] Reference Figure 6 , SSB is sent periodically according to the SSB periodicity. The basic SSB period assumed by the UE in the initial cell search is defined as 20ms. After cell access, the SSB period can be set to one of {5ms, 10ms, 20ms, 40ms, 80ms, 160ms} by the network (e.g., BS). An SSB burst set can be configured at the beginning of the SSB period. The SSB burst set can be configured with a 5ms time window (i.e., half a frame), and the SSB can be repeatedly sent up to L times within the SS burst set. The maximum number of transmissions L of the SSB can be given according to the frequency band of the carrier as follows. One time slot includes a maximum of two SSBs.

[0084] - For the frequency range up to 3 GHz, L = 4

[0085] - For the frequency range from 3 GHz to 6 GHz, L = 8

[0086] - For the frequency range from 6 GHz to 52.6 GHz, L = 64

[0087] The temporal position of the SSB candidate in the SS burst set may be defined according to the SCS as follows: The temporal position of the SSB candidate is assigned an index (SSB index) from 0 to L-1 in temporal order within the SSB burst set (ie, half-frame).

[0088] - Case A - 15kHz SCS: The index of the starting symbol of the candidate SSB is given as {2, 8} + 14 × n. When the carrier frequency is lower than or equal to 3 GHz, n = 0, 1. When the carrier frequency is 3 GHz to 6 GHz, n = 0, 1, 2, 3.

[0089] - Case B - 30kHz SCS: The index of the starting symbol of the candidate SSB is given as {4, 8, 16, 20} + 28 × n. When the carrier frequency is lower than or equal to 3 GHz, n = 0. When the carrier frequency is 3 GHz to 6 GHz, n = 0, 1.

[0090] - Case C - 30kHz SCS: The index of the starting symbol of the candidate SSB is given as {2, 8} + 14 x n. When the carrier frequency is lower than or equal to 3 GHz, n = 0. When the carrier frequency is 3 GHz to 6 GHz, n = 0, 1, 2, 3.

[0091] - Case D - 120kHz SCS: The index of the starting symbol of the candidate SSB is given as {4,8,16,20}+28×n. When the carrier frequency is higher than 6GHz, n=0,1,2,3,5,6,7,8,10,11,12,13,15,16,17,18.

[0092] - Case E - 240kHz SCS: The indices of the starting symbols of the candidate SSBs are given as {8, 12, 16, 20, 32, 36, 40, 44} + 56 x n. When the carrier frequency is above 6 GHz, n = 0, 1, 2, 3, 5, 6, 7, 8.

[0093] Figure 7 An exemplary acquisition of information about DL time synchronization at a UE is illustrated.

[0094] Reference Figure 7 , the UE can acquire DL synchronization by detecting the SSB. The UE can identify the structure of the SSB burst set based on the index of the detected SSB and thus detect the symbol / time slot / half-frame boundary. The number of the frame / half-frame to which the detected SSB belongs can be identified by the SFN information and the half-frame indication information.

[0095] Specifically, the UE may acquire 10-bit SFN information s0 to s9 from the PBCH. 6 bits of the 10-bit SFN information are acquired from a master information block (MIB), and the remaining 4 bits are acquired from a PBCH transport block (TB).

[0096] Subsequently, the UE can obtain 1-bit half-frame indication information c0. When the carrier frequency is 3 GHz or below, the half-frame indication information can be implicitly signaled through the PBCH DMRS. The PBCH DMRS uses one of the 8 PBCH DMRS sequences to indicate 3 bits of information. Therefore, if L=4, the remaining one bit of the 3-bit information indicated by the 8 PBCH DMRS sequences, except for the two bits indicating the SSB index, can be used as a half-frame indication.

[0097] Ultimately, the UE can obtain the SSB index based on the DMRS sequence and the PBCH payload. In the SSB burst set (i.e., half-frame), the SSB candidates are indexed from 0 to L-1 in chronological order. If L=8 or L=64, the three least significant bits (LSBs) b0 to b2 of the SSB index can be indicated by 8 different PBCH DMRS sequences. If L=64, the three most significant bits (MSBs) b3 to b5 of the SSB index are indicated by PBCH. If L=2, the two LSBs b0 and b1 of the SSB index can be indicated by 4 different PBCH DMRS sequences. If L=4, the remaining one bit b2 of the 3-bit information indicated by the 8 PBCH DMRS sequences, except for the two bits indicating the SSB index, can be used as a half-frame indication.

[0098] System information acquisition

[0099] Figure 8 The system information (SI) acquisition process is illustrated. The UE can obtain access stratum (AS) information / non-access stratum (NAS) information in the SI acquisition process. The SI acquisition process can be applied to UEs in RRC_CIDLE, RRC_INACTIVE and RRC_CONNECTED states.

[0100] SI is divided into MIB and multiple system information blocks (SIBs). MIB and multiple SIBs are further divided into minimum SI and other SI. Minimum SI may include MIB and systemInformationBlock1 (SIB1), which carries basic information required for initial access and information required to obtain other SI. SIB1 can also be called remaining minimum system information (RMSI). For details, refer to the following content.

[0101] -MIB includes information / parameters related to the reception of SIB1 and is sent on the PBCH of the SSB. The UE assumes that the half frame including the SSB is repeated every 20ms during the initial cell selection. The UE can determine from the MIB whether there is any control resource set (CORESET) for the Type0-PDCCH common search space. The Type0-PDCCH common search space is a PDCCH search space and is used to send a PDCCH that schedules SI messages. In the presence of a Type0-PDCCH common search space, the UE can determine (i) one or more consecutive symbols and multiple consecutive RBs included in the CORESET, and (ii) the PDCCH timing (e.g., the time domain position at which the PDCCH will be received) based on the information included in the MIB (e.g., pdcch-ConfigSIB1). In the absence of a Type0-PDCCH common search space, pdcch-ConfigSIB1 provides information about the frequency position where the SSB / SIB1 exists and information about the frequency range without any SSB / SIB1.

[0102] -SIB1 includes information related to the availability and scheduling of the remaining SIBs (hereinafter referred to as SIBx, where x is an integer equal to or greater than 2) (e.g., transmission period and SI window size). For example, SIB1 may indicate whether SIBx is broadcast periodically or on-demand at the request of the UE. If SIBx is provided on-demand, SIB1 may include information required for the UE to send an SI request. The PDCCH that schedules SIB1 is sent in the Type0-PDCCH common search space, and SIB1 is sent on the PDSCH indicated by the PDCCH.

[0103] -SIBx is included in the SI message and sent on the PDSCH. Each SI message is sent within a periodic time window (ie, SI window).

[0104] Beam Alignment

[0105] Fig. 9 An exemplary multi-beam transmission of SSB is illustrated.

[0106] Beam scanning refers to changing the beam (direction) of a wireless signal at a transmit receive point (TRP) (eg, BS / cell) over time (hereinafter, the terms beam and beam direction are used interchangeably). Fig. 9, the SSB can be sent periodically by beam scanning. In this case, the SSB index is implicitly linked to the SSB beam. The SSB beam can be changed based on the SSB (index) or based on the SS (index) group. In the latter, the same SSB beam remains in the SSB (index) group. That is, the transmission beam direction of the SSB is repeated for multiple consecutive SSBs. Depending on the frequency band of the carrier, the maximum allowed transmission number L of SSBs in the SSB burst set is 4, 8 or 64. Therefore, the maximum number of SSB beams in the SSB burst set can be given as follows according to the frequency band of the carrier.

[0107] - For frequency range up to 3 GHz, maximum number of beams = 4

[0108] - For the frequency range of 3 GHz to 6 GHz, the maximum number of beams = 8

[0109] - For the frequency range of 6 GHz to 52.6 GHz, the maximum number of beams = 64

[0110] *When there is no multi-beam transmission, the number of SSB beams is 1.

[0111] When a UE attempts initial access to a BS, the UE may align the beam with the BS based on the SSB. For example, the UE performs SSB detection and then identifies the best SSB. Subsequently, the UE may send a RACH preamble in a PRACH resource linked / corresponding to the index (i.e., beam) of the best SSB. Even after initial access, the SSB may be used for beam alignment between the BS and the UE.

[0112] Channel Measurement and Rate Matching

[0113] Fig.10 An exemplary method of indicating the actually transmitted SSB, SSB_tx, is illustrated.

[0114] Up to L SSBs may be transmitted in an SSB burst set, and the number and position of the SSBs actually transmitted may be different for each BS or cell. The number and position of the SSBs actually transmitted are used for rate matching and measurement, and information about the SSBs actually transmitted is indicated as follows.

[0115] –If the information is about rate matching, the information may be indicated by UE-specific RRC signaling or RMSI. UE-specific RRC signaling includes a complete bitmap (e.g., length L) for frequency ranges below and above 6 GHz. As shown in the figure, RMSI includes a complete bitmap for frequency ranges below 6 GHz and a compressed bitmap for frequency ranges above 6 GHz. Specifically, information about the SSB actually transmitted may be indicated by a group bitmap (8 bits) + an intra-group bitmap (8 bits). Resources (e.g., REs) indicated by UE-specific RRC signaling or RMSI may be reserved for SSB transmission, and SSB resources may be considered for rate matching of PDSCH / PUSCH.

[0116] – If the information is related to measurement, the network (e.g., BS) may indicate the SSB set to be measured during the measurement period when the UE is in RRC connected mode. The SSB set may be indicated for each frequency layer. In the absence of an indication of an SSB set, a default SSB set is used. The default SSB set includes all SSBs during the measurement period. The SSB set may be indicated by a complete bitmap (e.g., of length L) in RRC signaling. When the UE is in RRC idle mode, the default SSB set is used.

[0117] In the NR system, a massive multiple-input multiple-output (MIMO) environment in which the number of transmit / receive (Tx / Rx) antennas is significantly increased can be considered. That is, when considering a massive MIMO environment, the number of Tx / Rx antennas can be increased to tens or hundreds. The NR system supports communications in frequency bands above 6 GHz (i.e., millimeter bands). However, the millimeter band is characterized by the following frequency characteristics: due to the use of too high a frequency band, the signal decays very quickly according to the distance. Therefore, in an NR system operating at 6 GHz or above, beamforming (BF) is considered, in which a signal is sent in a specific direction (rather than omnidirectionally) with concentrated energy to compensate for the rapid propagation attenuation. Therefore, a hybrid BF combining analog BF and digital BF is required according to the position of the application BF weight vector / precoding vector for the purpose of ease of frequency direction beam control, flexible resource allocation, and increased performance in a massive MIMO environment.

[0118] Random Access (RACH) Procedure

[0119] When the UE initially accesses the BS or has no radio resources for signal transmission, the UE may perform a random access procedure with the BS.

[0120] The random access procedure is used for various purposes. For example, the random access procedure can be used for initial network access in the RRC_IDLE state, RRC connection re-establishment procedure, handover, UE-triggered UL data transmission, transition in the RRC_INACTIVE state, time alignment establishment in SCell addition, OSI request, and beam failure recovery. The UE can acquire UL synchronization and UL transmission resources during the random access procedure.

[0121] The random access procedure can be classified into a contention-based random access procedure and a contention-free random access procedure. The contention-based random access procedure is further divided into a 4-step random access (4-step RACH) procedure and a 2-step random access (2-step RACH) procedure.

[0122] (1) 4-step RACH: Type 1 random access procedure

[0123] Fig.11 is a diagram illustrating an exemplary 4-step RACH procedure to which various embodiments of the present disclosure are applicable.

[0124] When the (contention-based) random access procedure is performed in four steps (4-step RACH procedure), the UE can send a message (message 1 (Msg1)) including a preamble code related to a specific sequence on the PRACH (1101) and receive a response message (RAR message) for the preamble code on the PDCCH and the PDSCH corresponding to the PDCCH (message 2 (Msg2)) (1103). The UE sends a message (message 3 (Msg3)) including a PUSCH based on the scheduling information included in the RAR (1105) and performs a contention resolution procedure involving receiving a PDCCH signal and a PDSCH signal corresponding to the PDCCH signal. The UE can receive a message (message 4 (Msg4)) (1107) including contention resolution information for the contention resolution procedure from the BS.

[0125] The 4-step RACH procedure of the UE can be summarized in Table 4 below.

[0126] [Table 4]

[0127]

[0128] In the random access procedure, the UE may first send a RACH preamble as Msg1 on the PRACH.

[0129] Two different lengths of random access preamble sequences are supported. The longer sequence length 839 is applied to SCSs of 1.25kHz and 5kHz, while the shorter sequence length 139 is applied to SCSs of 15kHz, 30Hz, 60kHz, and 120kHz.

[0130] Multiple preamble formats are defined by one or more RACH OFDM symbols and different CPs (and / or guard times). The RACH configuration of a cell is provided to the UE in the system information of the cell. The RACH configuration includes information about the PRACH SCS, available preambles, and preamble formats. The RACH configuration includes information about the association between SSBs and RACH (time-frequency) resources. The UE sends a random access preamble in the RACH time-frequency resources associated with the detected or selected SSB.

[0131] The SSB threshold for RACH resource association may be configured by the network, and the RACH preamble is transmitted or retransmitted based on the SSB having a reference signal received power (RSRP) measurement that satisfies the threshold. For example, the UE may select one of the SSBs that satisfies the threshold, and transmit or retransmit the RACH preamble based on the RACH resource associated with the selected SSB. For example, when retransmitting the RACH preamble, the UE may reselect one of the SSBs and retransmit the RACH preamble in the RACH resource associated with the reselected SSB. That is, the RACH resource used for the retransmission of the RACH preamble may be the same as or different from the RACH resource used for the transmission of the RACH preamble.

[0132] Upon receiving the RACH preamble from the UE, the BS sends a RAR message (Msg2) to the UE. The PDCCH that schedules the PDSCH carrying the RAR is masked with a cyclic redundancy check (CRC) by a random access radio network temporary identifier (RA-RNTI) and sent. Upon detecting the PDCCH masked by the RA-RNTI, the UE can receive the RAR on the PDSCH scheduled by the DCI carried on the PDCCH. The UE determines whether the RAR includes RAR information for the preamble (that is, Msg1) sent to it. The UE can make a determination by checking the presence or absence of the RACH preamble ID of the preamble it sends in the RAR. In the absence of a response to Msg1, the UE can resend the RACH preamble a predetermined number of times or less while performing a power ramp. The UE calculates the PRACH transmission power for preamble retransmission based on the latest path loss and power ramp counter.

[0133] The RAR information may include a preamble sequence sent by the UE, a temporary cell RNTI (TC-RNTI) that the BS has assigned to the UE attempting random access, UL transmit time alignment information, UL transmit power adjustment information, and UL radio resource allocation information. Upon receiving its RAR information on the PDSCH, the UE may obtain the initial UL grant, TC-RNTI, and timing advance information for UL synchronization. The timing advance information is used to control the UL signal transmission timing. For better alignment between the UE's PUSCH / PUCCH transmission and the subframe timing on the network side, the network (e.g., BS) may measure the time difference between PUSCH / PUCCH / SRS reception and the subframe, and send timing advance information based on the time difference. The UE may send an UL signal on the UL-SCH as Msg3 for the random access procedure based on the RAR information. Msg3 may include an RRC connection request and a UE ID. The network may send Msg4 in response to Msg3. Msg4 may be regarded as a contention resolution message on the DL. When the UE receives Msg4, the UE may enter the RRC_CONNECTED state.

[0134] As mentioned above, the UL grant included in the RAR schedules the PUSCH transmission to the BS. The PUSCH carrying the initial UL transmission based on the RAR UL grant is called Msg3 PUSCH. The content of the RAR UL grant starts from the most significant bit (MSB) and ends in the least significant bit (LSB), as shown in Table 5.

[0135] [Table 5]

[0136] RAR UL authorization field Number of bits Frequency Hopping Flag 1 Msg3 PUSCH frequency resource allocation 12 Msg3 PUSCH time resource allocation 4 Modulation and Coding Scheme (MCS) 4 Msg3 PUSCH Transmit Power Control (TPC) 3 CSI Request 1

[0137] The transmit power control (TPC) command is used to determine the transmission power of Msg3 PUSCH. For example, the TPC command is interpreted according to Table 6.

[0138] [Table 6]

[0139] TPC Command Value [dB] 0 -6 1 -4 2 -2 3 0 4 2 5 4 6 6 7 8

[0140] (2) 2-step RACH: Type 2 random access procedure

[0141] Fig.12 is a diagram illustrating an exemplary 2-step RACH procedure to which various embodiments of the present disclosure are applicable.

[0142] A (contention-based) RACH procedure performed in two steps (ie, a 2-step RACH procedure) has been proposed to simplify the RACH procedure, thus achieving low signaling overhead and low latency.

[0143] In the 2-step RACH process, the operation of sending Msg1 and the operation of sending Msg3 in the 4-step RACH process can be combined into the operation of the UE sending one message (message A (MsgA) including PRACH and PUSCH). The operation of sending Msg2 by the BS and the operation of sending Msg4 by the BS in the 4-step RACH process can be combined into the operation of sending one message (message B (MsgB) including RAR and contention resolution information).

[0144] That is, in the 2-step RACH procedure, the UE may combine Msg1 and Msg3 of the 4-step RACH procedure into one message (eg, MsgA) and send the message to the BS (1201).

[0145] In addition, in the 2-step RACH procedure, the BS may combine Msg2 and Msg4 of the 4-step RACH procedure into one message (eg, MsgB) and send the message to the UE (1203).

[0146] Based on the combination of these messages, the 2-step RACH procedure can become a low-latency RACH procedure.

[0147] More specifically, in the 2-step RACH procedure, MsgA may carry the PRACH preamble included in Msg1 and the data included in Msg3. In the 2-step RACH procedure, MsgB may carry the RAR included in Msg2 and the contention resolution information included in Msg4.

[0148] (3) Non-contention RACH

[0149] Fig.13 is a diagram illustrating an exemplary contention-free RACH procedure to which various embodiments of the present disclosure are applicable.

[0150] The contention-free RACH process can be used for the UE to switch to another cell or BS, or can be performed at the request of the BS command. The contention-free RACH process is basically similar to the contention-based RACH process. However, compared with the contention-based RACH process in which the preamble to be used is randomly selected from multiple RACH preambles, the BS assigns the UE the preamble to be used by the UE (called a dedicated RACH preamble) (1301) in the contention-free RACH process. Information about the dedicated RACH preamble may be included in an RRC message (e.g., a handover command) or provided to the UE via a PDCCH command. When the RACH process starts, the UE sends a dedicated RACH preamble to the BS (1303). When the UE receives a RAR from the BS, the RACH process is completed (1305).

[0151] In the contention-free RACH procedure, the CSI request field in the RAR UL grant indicates whether the UE is to include aperiodic CSI reporting in the corresponding PUSCH transmission. The SCS for Msg3 PUSCH transmission is provided by the RRC parameters. The UE can send PRACH and Msg3 PUSCH in the same UL carrier of the same serving cell. The UL BWP for Msg3 PUSCH transmission is indicated by SIB1.

[0152] (4) Mapping between SSB blocks and PRACH resources (timings)

[0153] Fig.14 and Fig.15 is a diagram showing an example of transmission of an SS block and a PRACH resource linked to the SS block according to various embodiments of the present disclosure.

[0154] In order for a BS to communicate with a UE, it is necessary to find the optimal beam direction between the BS and the UE, and as the UE moves, the optimal beam direction may change, and therefore it is necessary to continuously track the optimal beam direction. The process of finding the optimal beam direction between the BS and the UE may be referred to as a beam acquisition process, and the process of continuously tracking the optimal beam direction may be referred to as a beam tracking process. This process may be required for a state in which the optimal beam is lost and communication with the BS cannot be maintained in an optimal communication state or enters a state in which communication is impossible (i.e., for beam recovery to recover beam failure during 1) initial access when the UE attempts to access the BS for the first time, 2) switching from one BS to another BS, and 3) beam tracking to find the optimal beam between the UE and the BS).

[0155] In the case of an NR system, a multi-step beam acquisition process for beam acquisition in an environment using multiple beams is discussed. In the multi-step beam acquisition process, the BS and the UE can use a wide beam to perform connection establishment in the initial access phase, and after the connection establishment is completed, the BS and the UE can use a narrow beam to perform communication with optimal quality. An example of a beam acquisition process in an NR system of various embodiments of the present disclosure will be described below.

[0156] -1) The BS may send a synchronization block for each wide beam so that the UE can find the BS in the initial access phase (that is, perform cell search or cell acquisition), measure the quality of the channel of each beam of the wide beam, and find the optimal wide beam to be used in the main phase of beam acquisition.

[0157] -2) The UE can perform a cell search on a synchronization block for each beam and can perform DL beam acquisition using the detection result for each beam.

[0158] -3) The UE may perform a RACH procedure in order to notify the UE of its intention to access a BS discovered by the UE.

[0159] -4) In order for the UE to inform the BS of the DL beam acquisition result (e.g., beam index) at the wide beam level simultaneously with the RACH process, the BS may connect or associate the synchronization block transmitted for each beam and the PRACH resource to be used for PRACH transmission. When the UE performs the RACH process using the PRACH resource connected to the optimal beam direction discovered by the UE, the BS may acquire information about the DL beam suitable for the UE during the process of receiving the PRACH preamble.

[0160] In a multi-beam environment, it may be important for the UE and / or the transmit and receive point (TRP) to accurately determine the Tx beam and / or Rx beam direction between the UE and the TRP. In a multi-beam environment, beam scanning for repeatedly transmitting or receiving signals according to the TX / RX reciprocal capability of the TRP (e.g., BS) or the UE may be considered. The TX / RX reciprocal capability may be referred to as the TX / RX beam correspondence in the TRP and the UE. In a multi-beam environment, when the TX / RX reciprocal capability in the TRP and the UE is not maintained, the UE may not be able to send a UL signal in the beam direction in which the UE receives a DL signal. This is because the optimal path for the UL and the optimal path for the DL are different. When the TRP determines the TRP RX beam for corresponding UL reception based on the DL measurement of one or more TX beams of the UE relative to the TRP and / or the TRP determines the TRP TX beam for corresponding DL transmission based on the UL measurement of one or more RX beams of the TRP' relative to the TRP, the TX / RX beam correspondence in the TRP can be maintained. The TX / RX beam correspondence in the UE may be maintained when the UE determines a UE RX beam for corresponding UL transmission based on DL measurements of one or more RX beams of the UE relative to the UE and / or the UE determines a UE RX beam for corresponding DL reception based on an indication of a TRP based on UL measurements of one or more TX beams of the UE relative to the UE.

[0161] (5) PRACH preamble structure

[0162] In the NR system, a RACH signal used for initial access to a BS (that is, initial access to the BS through a cell used by the BS) may be configured using the following factors.

[0163] - Cyclic Prefix (CP): This can prevent the interface from the previous / previous (OFDM) symbol and can bundle the PRACH preamble signals arriving at the BS with various time delays in the same time zone. That is, when the CP is set to be suitable for the maximum cell radius, the PRACH preamble sent by the UE in the cell in the same resource can enter the PRACH reception window corresponding to the length of the PRACH preamble set by the BS for PRACH reception. The length of the CP can generally be set to be equal to or greater than the maximum round trip delay. The CP can have a length of T CP .

[0164] - Preamble (sequence): A sequence used by a BS to detect the transmission of a signal may be defined, and the preamble may carry the sequence. The preamble sequence may have a length of T SEQ .

[0165] - Guard Time (GT): This may be a duration defined to prevent a PRACH signal from interfering with a signal arriving at the BS after the PRACH symbol duration, the PRACH signal is transmitted from a location farthest from the BS in the PRACH coverage and arrives at the BS with a delay, and the UE does not transmit a signal during this duration, so the GT may not be defined based on the PRACH signal. The GT may have a length of T GP .

[0166] (6) Physical resources mapped to the physical random access channel

[0167] The random access preamble may be sent only within a time resource acquired based on a RACH configuration table preconfigured for RACH configuration, FR1, FR2, and a preconfigured spectrum type.

[0168] The PRACH configuration index in the RACH configuration table may be given as follows.

[0169] -For the RACH configuration table for random access configuration for FR1 and unpaired spectrum, the PRACH configuration index in the RACH configuration table can be given from the higher layer parameter prach-ConfigurationIndexNew (if configured). Otherwise, the PRACH configuration index in the RACH configuration table can be given from prach-ConfigurationIndex, msgA-prach-ConfigurationIndex, msgA-prach-ConfigurationIndexNew (if configured), etc.

[0170] -For the RACH configuration table for random access configuration regarding FR1 and paired spectrum / supplementary uplink and for the RACH configuration table for random access configuration regarding FR2 and unpaired spectrum, the PRACH configuration index in the RACH configuration table may be given from higher layer parameters prach-ConfigurationIndex, msgA-prach-ConfigurationIndexNew (if configured), etc.

[0171] The RACH configuration table may be about PRACH configuration index, preamble format, n SFN A table of relationships between one or more of mod x=y, a subframe number, a starting symbol, a number of PRACH slots, a number of time-domain PRACH opportunities within a PRACH slot, and in some cases a PRACH duration.

[0172] These situations are described below.

[0173] -(1) Random access configuration for FR1 and paired spectrum / supplementary uplink

[0174] -(2) Random access configuration for FR1 and unpaired spectrum

[0175] -(3) Random access configuration for FR2 and unpaired spectrum

[0176] Table 7 below shows a portion of an example of a RACH configuration index for (2) random access configuration of FR1 and unpaired spectrum.

[0177] [Table 7]

[0178]

[0179] The RACH configuration table indicates specific values ​​of parameters required for configuring RACH opportunities (e.g., preamble format, period, SFN offset, RACH subframe / time slot index, starting OFDM symbol, number of RACH time slots, number of opportunities, OFDM symbols used for RACH format, etc.). When a RACH configuration index is indicated, a specific value associated with the indicated index may be used.

[0180] For example, when the start OFDM symbol parameter is n, one or more consecutive (time domain) RACH opportunities may be configured from the OFDM symbol with index #n.

[0181] For example, the number of one or more RACH opportunities may be indicated by the following parameter: the number of time-domain PRACH opportunities within a RACH slot.

[0182] For example, a RACH slot may include one or more RACH opportunities.

[0183] For example, the number of RACH slots (in a subframe and / or slot with a particular SCS) may be indicated by the following parameter: Number of RACH slots.

[0184] For example, the system frame number (SFN) including the RACH opportunity can be obtained by n SFN mod x=y is determined, where mod is a modular operation (modular arithmetic or modular operation), which is an operation for obtaining a remainder r obtained by dividing a dividend q by a divisor d (r=q mod(d)).

[0185] For example, the subframe / timeslot (index) including the RACH opportunity in the system frame may be indicated by the following parameter: RACH subframe / timeslot index.

[0186] For example, the preamble format used for RACH transmission / reception may be indicated by the following parameters: Preamble Format.

[0187] Reference Fig.16 (a), for example, when the starting OFDM symbol is indicated as 0, one or more consecutive (time domain) RACH opportunities can be configured from OFDM symbol #0. For example, the number of one or more RACH opportunities can depend on the value indicated by the following parameter: the number of time domain RACH opportunities within the RACH slot. For example, the preamble format can be indicated by the following parameter: preamble format. For example, the preamble formats A1, A2, A3, B4, C0, C2, etc. can be indicated. For example, one of the last two OFDM symbols can be used as a GT, and the other can be used for transmission of other UL signals such as PUCCH, sounding reference signal (SRS), etc.

[0188] Reference Fig.16 (b), for example, when the starting OFDM symbol is indicated as 2, one or more consecutive (time domain) RACH opportunities may be configured from OFDM symbol #2. For example, 12 OFDM symbols may be used for RACH opportunities, and GT may not be configured in the last OFDM symbol. For example, the number of one or more RACH opportunities may depend on a value indicated by the following parameter: the number of time domain RACH opportunities within a RACH slot. For example, the preamble format may be indicated by the following parameter: preamble format. For example, preamble formats A1 / B1, B1, A2 / B2, A3 / B3, B4, C0, C2, etc. may be indicated.

[0189] Reference Fig.16(c), for example, when the starting OFDM symbol is indicated as 7, one or more consecutive (time domain) RACH opportunities can be configured from OFDM symbol #7. For example, 6 OFDM symbols can be used for RACH opportunities, and the last OFDM symbol (OFDM symbol #13) can be used for transmission of other UL signals such as PUCCH, SRS, etc. For example, the number of one or more RACH opportunities can depend on the value indicated by the following parameter: the number of time domain RACH opportunities within the RACH slot. For example, the preamble format can be indicated by the following parameter: preamble format. For example, the preamble formats A1, B1, A2, A3, B3, B4, C0, C2, etc. can be indicated.

[0190] For example, the parameters included in the RACH configuration table may satisfy a predetermined correspondence relationship identified / determined by the RACH configuration table and the RACH configuration index. For example, a predetermined correspondence relationship between the following parameters may be satisfied: PRACH configuration index, RACH format, period (x)=8, SFN offset (y), subframe number, start symbol (index), number of PRACH slots within a subframe, number of PRACH opportunities within a PRACH slot, PRACH duration / OFDM symbol for RACH format, etc. The correspondence relationship may be identified by the RACH configuration index and the RACH configuration table.

[0191] Hereinafter, a method for performing a RACH procedure according to an embodiment of the present disclosure will be described.

[0192] Reference Figures 17 to 19 , the overall operation process of the UE and the BS according to the embodiment of the present disclosure will be described.

[0193] Fig.17 The overall operation process of the UE according to the embodiment of the present disclosure is illustrated.

[0194] Reference Fig.17 , the UE may send MsgA to the BS (S1701). In this case, the MsgA may include only the PRACH or may include the PUSCH and the PRACH. When the MsgA includes both the PRACH and the PUSCH, the UE may send the PUSCH after sending the PRACH.

[0195] In this case, the UE may transmit the PRACH while knowing the SFN used to transmit the PRACH. Alternatively, the UE may transmit the PRACH without knowing the SFN used to transmit the PRACH. The details will be described in the following embodiments.

[0196] The UE may monitor and receive the DCI scheduling MsgB (S1703). The UE may descramble the CRC from the DCI based on the MsgB-RNTI. If the UE confirms the CRC, the UE may decode the information bits included in the DCI.

[0197] The UE may decode the lower two bits of the index of the SFN in the DCI, and then compare the lower two bits with the lower two bits of the index of the SFN used to transmit the PRACH.

[0198] However, if the UE sends PRACH without knowing the SFN used to send PRACH, the UE may not be able to compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to send PRACH. For example, in general, when the UE performs a handover, the UE may need to perform a PBCH decoding process to obtain the SFN of the target cell to be switched to. However, the RACH process can be performed without PBCH decoding to reduce the time delay caused by PBCH decoding and the burden on the UE due to PBCH decoding. In this case, when the UE intends to send PRACH to the target cell, the UE can send PRACH without knowing the SFN used for PRACH transmission.

[0199] This will be described in detail in the following embodiments.

[0200] The UE may receive the PDSCH for RAR based on the DCI (S1705). In this case, the UE may receive the PDSCH according to the result of comparing the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH. On the other hand, the UE may receive the PDSCH regardless of the result of comparing the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH.

[0201] In addition, depending on whether the UE can compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH and / or according to the comparison result, the UE can receive the PDSCH or perform other operations instead of receiving the PDSCH.

[0202] Depending on whether the UE is able to compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH and / or the UE operation according to the comparison result may be based on the following embodiments.

[0203] The UE may send a UL signal based on the PDSCH (S1707). In this case, the UL signal sent by the UE may vary depending on the RAR of the PDSCH and whether the PDSCH is received. For example, if the RAR is a fallback RAR, the UE may send a PRACH for a type 1 RACH procedure. As another example, if the RAR is a successful RAR, the UE may send a PUCCH by including HARQ-ACK information corresponding to the ACK in the PUCCH.

[0204] If the UE does not receive the PDSCH, the UE may send the PRACH according to a type-1 RACH procedure or send (or retransmit) the PRACH and the PUSCH according to a type-2 RACH procedure.

[0205] The above UE operations according to S1701 to S1707 may be based on one or more of the following embodiments. That is, the UE operations according to S1701 to S1707 may be performed based on any one of the following embodiments or any combination of two or more of the following embodiments.

[0206] Fig.18 is a diagram for explaining an overall operation process of a BS according to an embodiment of the present disclosure.

[0207] Reference Fig.18 , the BS may receive MsgA from the UE (S1801). In this case, the MsgA may include only the PRACH or may include the PUSCH and the PRACH. When the MsgA includes both the PRACH and the PUSCH, the BS may receive the PUSCH after receiving the PRACH.

[0208] The BS may decode MsgA and transmit DCI having CRC scrambled by MsgB-RNTI to the UE based on the decoding result (S1803).

[0209] The BS may send a PDSCH for RAR based on the DCI (S1805). If the BS detects both PRACH and PUSCH in S1801, the RAR may be a successful RAR. If the BS detects only PRACH but not PUSCH in S1801, the RAR may be a fallback RAR. If the BS does not detect both PRACH and PUSCH in S1801, the BS may not send both DCI and PDSCH. That is, in this case, S1803 and S1805 may be omitted.

[0210] If the BS transmits the PDSCH, the BS may receive a UL signal based on the PDSCH (S1807). In this case, the UL signal may vary depending on the RAR of the PDSCH and whether the UE receives the PDSCH. For example, if the RAR is a fallback RAR, the BS may receive a PRACH for a type 1 RACH procedure. As another example, if the RAR is a successful RAR, the BS may receive a PUCCH including HARQ-ACK information corresponding to the ACK.

[0211] If the UE does not receive the PDSCH, the BS may receive the PRACH according to the type-1 RACH procedure or receive (or re-receive) the PRACH and the PUSCH according to the type-2 RACH procedure.

[0212] The above BS operation according to S1801 to S1807 may be based on one or more of the following embodiments. That is, the BS operation according to S1801 to S1807 may be performed based on any one of the following embodiments or any combination of two or more of the following embodiments.

[0213] Fig.19 It is a diagram for explaining the overall operation process of a network according to an embodiment of the present disclosure.

[0214] Reference Fig.19 , the UE may send MsgA to the BS (S1901). In this case, the MsgA may include only the PRACH or may include the PUSCH and the PRACH. When the MsgA includes both the PRACH and the PUSCH, the UE may send the PUSCH after sending the PRACH.

[0215] In this case, the UE may transmit the PRACH while knowing the SFN used to transmit the PRACH. Alternatively, the UE may transmit the PRACH without knowing the SFN used to transmit the PRACH. The details will be described in the following embodiments.

[0216] The BS may decode the received MsgA (S1903), and transmit DCI having CRC scrambled by MsgB-RNTI to the UE based on the decoding result (S1905).

[0217] The UE may monitor and receive the DCI scheduling MsgB (S1703). The UE may descramble the CRC from the DCI based on the MsgB-RNTI. If the UE confirms the CRC, the UE may decode the information bits included in the DCI.

[0218] The UE may decode the lower two bits of the index of the SFN in the DCI, and then compare the lower two bits with the lower two bits of the index of the SFN used to transmit the PRACH.

[0219] However, if the UE sends PRACH without knowing the SFN used to send PRACH, the UE may not be able to compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to send PRACH. For example, in general, when the UE performs a handover, the UE may need to perform a PBCH decoding process to obtain the SFN of the target cell to be switched to. However, the RACH process can be performed without PBCH decoding to reduce the time delay caused by PBCH decoding and the burden on the UE due to PBCH decoding. In this case, when the UE intends to send PRACH to the target cell, the UE can send PRACH without knowing the SFN used for PRACH transmission.

[0220] This will be described in detail in the following embodiments.

[0221] The BS may send a PDSCH for RAR based on the DCI (S1907). If the BS detects both PRACH and PUSCH in S1903, the RAR may be a successful RAR. If the BS detects only PRACH but not PUSCH in S1903, the RAR may be a fallback RAR. If the BS does not detect both PRACH and PUSCH in S1903, the BS may not send DCI and PDSCH. That is, in this case, S1905 and S1907 may be omitted. In this case, the UE may send (or retransmit) MsgA to the BS.

[0222] The UE may receive the PDSCH based on the result of comparing the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH. On the other hand, the UE may receive the PDSCH regardless of the result of comparing the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH.

[0223] In addition, depending on whether the UE can compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH and / or according to the comparison result, the UE can receive the PDSCH or perform other operations without receiving the PDSCH.

[0224] Depending on whether the UE is able to compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH and / or the UE operation according to the comparison result may be based on the following embodiments.

[0225] The UE may send a UL signal based on the PDSCH (S1909). In this case, the UL signal sent by the UE may vary depending on the RAR of the PDSCH and whether the PDSCH is received. For example, if the RAR is a fallback RAR, the UE may send a PRACH for a type 1 RACH procedure. As another example, if the RAR is a successful RAR, the UE may send a PUCCH by including HARQ-ACK information corresponding to the ACK in the PUCCH.

[0226] If the UE does not receive the PDSCH, the UE may send the PRACH according to a type-1 RACH procedure or send (or retransmit) the PRACH and the PUSCH according to a type-2 RACH procedure.

[0227] The above UE operations according to S1901 to S1909 may be based on one or more of the following embodiments. That is, the UE operations according to S1901 to S1909 may be performed based on any one of the following embodiments or any combination of two or more of the following embodiments.

[0228] In the following, we will base on Figures 17 to 19 Specific embodiments of the present disclosure are described.

[0229] 1. Implementation Method 1

[0230] In the 2-step RACH procedure, the following three cases may be considered for network operation depending on whether the BS successfully receives MsgA.

[0231] - Case 1: When the BS successfully detects both the PRACH preamble and the PUSCH, the BS may send MsgB to the UE.

[0232] - Case 2: When the BS detects only the PRACH preamble but fails to detect the PUSCH, the BS may send a fallback RAR which instructs the UE to perform a 4-step RACH procedure.

[0233] The BS may include a message indicating the transmission of Msg3 of the 4-step RACH process in MsgB to send the message to the UE. The UE may monitor the PDCCH for MsgB and receive the PDCCH related to MsgB. In addition, the UE may decode the PDSCH related to the PDCCH and then obtain an indicator for UE operation.

[0234] For example, when the UE receives Msg3 of the 4-step RACH procedure, the UE may send a PUSCH after a predetermined time.

[0235] - Case 3: When the BS fails to detect the PRACH preamble, the BS may not send RAR or MsgB to the UE. If the UE fails to receive RAR or MsgB within a predetermined time period (e.g., a monitoring window for MsgB reception), the UE may send (or retransmit) MsgA. On the other hand, when the BS fails to detect the PRACH preamble, the BS may attempt to detect PUSCH. However, the BS may not attempt to detect PUSCH.

[0236] In addition, in case 1 and / or case 2, RNTI (e.g., TC-RNTI) may be required to monitor the PDCCH for MsgB. However, it may be difficult to allocate TC-RNTI to the UE that intends to perform PDCCH monitoring. Therefore, it is necessary to study whether PDCCH monitoring based on TC-RNTI is required. If necessary, a method for allocating TC-RNTI needs to be studied. In addition, it is also necessary to study whether TC-RNTI is used in common for a group of UEs or allocated to each UE.

[0237] To this end, an RNTI used by the UE to monitor the PDCCH for MsgB can be defined. Such an RNTI can be provided in the RAR. When the UE sends a PRACH preamble and the BS detects the PRACH preamble, the BS can send a response (e.g., RAR) to the random access procedure identifier (RAPID) associated with the detected PRACH preamble to the UE. In this case, the BS can include information about the RNTI associated with the RAPID in the RAR to send the information about the RNTI to the UE. If the UE detects the RAPID sent by the UE from the RAR and also detects the RNTI associated with the RAPID, the UE can send UL data such as PUSCH based on the TC-RNTI, or can monitor the PDCCH for MsgB or the PDCCH for other DL data (e.g., PDSCH). In addition, the UE can use the corresponding RNTI as the initialization seed value of the scrambling sequence of the UL data.

[0238] In order to generate an RNTI for monitoring the PDCCH for MsgB, Equation 1 may be used, which is used to generate an RA-RNTI associated with a specific RACH opportunity (RO).

[0239] [Formula 1]

[0240] RA_RNTI=1+s_id+14*t_id+14*80*f_id+14*80*8*ul_carrier_id

[0241] In Equation 1, s_id represents the first OFDM symbol index of the transmitted PRACH and has a value of 0≤s_id<14.

[0242] In Equation 1, t_id represents the first slot index in the system frame of the transmitted PRACH and has a value of 0≤t_id<80.

[0243] In Formula 1, f_id represents an index of a PRACH in the frequency domain and has a value of 0≤f_id<8.

[0244] In Formula 1, ul_carrier_id represents an indicator of a UL carrier. Specifically, if the UL carrier is a normal carrier, the value of ul_carrier_id is "0", and if the UL carrier is a supplementary uplink (SUL) carrier, the value of ul_carrier_id is "1".

[0245] According to an embodiment of the present disclosure, when a 2-step PRACH preamble is sent on an RO, a TC-RNTI or a new RNTI associated with the corresponding RO may be defined. As a parameter for this, the RNTI may be generated by applying a predetermined offset to a parameter associated with the time resource to which the RO is mapped. For example, among the indexes of the s_id and / or t_id of Formula 1, there are actually unused indexes and used indexes. Therefore, an index other than the index for mapping the s_id and / or t_id of the corresponding RO may be used.

[0246] For example, if the RA-RNTI of the 4-step RACH process is generated based on the time slot index and the OFDM symbol starting position (or the starting OFDM symbol index) included in the RACH configuration table, the RNTI of the 2-step RACH process can be generated by applying a predetermined offset to the time slot index and the OFDM symbol starting position (or the starting OFDM symbol index) included in the RACH configuration table.

[0247] For example, a short sequence-based PRACH preamble may consist of at least two OFDM symbols. For PRACH preamble format A1, OFDM symbol index 0, 2, 4, 6, 8, or 10 may be used for RA-RNTI for a 4-step RACH procedure, and OFDM symbol index 1, 3, 5, 7, 9, or 11 may not be used. Therefore, OFDM symbol index 1, 3, 5, 7, 9, or 11 may be used to generate an RNTI for a 2-step RACH procedure.

[0248] In addition, the slot index may be used to generate the RNTI for the 2-step RACH procedure. Even though the RACH configuration duration is 10 ms for both the 2-step RACH and 4-step RACH procedures, for the RA-RNTI for the 4-step RACH procedure, only slot indexes 0, 2, 4, 6, or 8 are used at intervals of 2 ms based on 15 kHz slots. Therefore, slot indexes 1, 3, 5, 7, or 9 may be used for the RNTI for the 2-step RACH procedure.

[0249] That is, the RNTI for the 2-step RACH procedure can be generated by selecting a value that is not used to generate the RNTI for the 4-step RACH procedure from at least one of s_id and t_id. In this case, at least 8 different RNTIs can be generated in consideration of f_id.

[0250] As another example, if the transmission time of the 2-step PRACH preamble and the 4-step PRACH preamble is divided in units of subframes, more RNTIs can be generated for the 2-step RACH process. For example, if a duration of 20 ms is used for the RACH configuration, the first half of 10 ms can be used for the 4-step RACH process (or the 2-step RACH process), and the second half of 10 ms can be used for the 2-step RACH process (or the 4-step RACH process).

[0251] On the other hand, when the 2-step RACH process and the 4-step RACH process share the same RO, the RA-RNTI of the 4-step RACH process may be generated using the timeslot index indicated by the RACH configuration, and a specific offset may be applied to the timeslot index indicated by the RACH configuration to generate the 2-step RACH RNTI.

[0252] For example, assuming that slot indices 0 to 79 are supported for RACH generation, if the SCS in FR1 is 15 kHz or 30 kHz, slot indices 0 to 39 can be used for the 4-step RACH procedure, and slot indices 40 to 79 can be used for the 2-step RACH procedure.

[0253] If the RACH slot index indicated for the 4-step RACH procedure is 0, 2, 4, 6, or 8, then the slot index 1, 3, 5, 7, or 9 may be used to generate the RNTI for the 2-step RACH procedure.

[0254] In addition, slot indexes 0 to 9 may be used for RACH slots with an SCS of 15 kHz, and slot indexes 0 to 39 may be used for RACH slots with an SCS of 60 kHz. In this case, if an SCS of 30 / 120 kHz is indicated, only one of the two slots included in the 15 / 60 kHz SCS slot may be used to generate an RA-RNTI for a 4-step RACH procedure. In this case, the remaining one slot index may be used to generate an RNTI for a 2-step RACH procedure.

[0255] As another example, the 2-step RNTI and the 4-step RA-RNTI may be generated with different values ​​as follows: the slot index and / or OFDM symbol index used to generate the RA-RNTI for the 4-step RACH procedure may be maintained for a specific duration, and a different slot index and / or OFDM symbol index may be used for the RA-RNTI for the 2-step RACH procedure. Here, the duration for generating the 2-step RNTI procedure may be after the duration for generating the RA-RNTI for the 4-step RACH procedure.

[0256] On the other hand, if the maximum length of the RAR window is 10 ms, the contention resolution timer for receiving Msg4 can be configured to operate for a duration longer than 10 ms. Fig. 20 , when the length of the RAR window is 10ms, the contention resolution timer may have a length of 20ms, which includes two RAR windows. In this case, if a TC-RNTI or a new RNTI associated with a RO is created, the TC-RNTI or the new RNTI may overlap every 10ms. To solve this problem, the time offset value applied to the RO may change every 10ms.

[0257] As another example, the UE may generate a RA-RNTI based on the RO when sending a PRACH preamble. Thereafter, the UE may monitor the PDCCH based on the corresponding RA-RNTI. In this case, the PDCCH to be monitored may be for RAR or MsgB.

[0258] As another example, the UE may recalculate the RA-RNTI for monitoring the PDCCH associated with the RO after a predetermined time (e.g., 10 ms) has elapsed from the time when the UE monitors the PDCCH. In order to generate a RA-RNTI different from the previous RA-RNTI, the above-mentioned method of using a time slot index or an OFDM symbol index may be considered.

[0259] On the other hand, the above method is not limited to being applied to PDCCH monitoring of a 2-step RACH procedure. That is, the method can be applied even when the duration (e.g., monitoring window) of PDCCH monitoring for a 4-step RACH procedure becomes longer than a predetermined level. For example, considering that PDCCH transmission may be delayed due to listen-before-talk (LBT) in an unlicensed band, the above method can be considered when the RAR monitoring window of a 4-step RACH procedure is increased to 10 ms or more.

[0260] As another example, the UE may initially generate a RA-RNTI by replacing a slot index on the RO with a slot index in a duration of 20 ms or longer. For example, for a 15 kHz SCS, the UE may replace the slots included in two frames with slot indexes 0 to 19, and generate a RA-RNTI using the slot indexes. To this end, the UE needs to accurately know the start and end points of the duration of 20 ms or longer. However, when the UE performs a handover in an asynchronous network, the UE needs to obtain SFN information about the target cell in order to ensure that the duration is longer than the boundary of the 10 ms duration of the target cell. Since the corresponding information is included in the PBCH, the UE needs to decode the PBCH to obtain the SFN information about the target cell. Therefore, in order to implement this embodiment, it is also necessary to consider the possibility that a delay may occur due to PBDH decoding during the handover.

[0261] The 2-step RACH process and the 4-step RACH process can share the same RO. In this case, the UE performing the 2-step RACH process and the UE performing the 4-step RACH process can each monitor the RAR. The RA-RNTI used for RAR monitoring can be determined based on the RO. In addition, the UE performing the 2-step RACH process needs to monitor MsgB. However, the RNTI used to monitor MsgB needs to be different from the RNTI used for RAR. For the RNTI used for MsgB monitoring, the existing RA-RNTI generation formula can be reused. For example, the RNTI for MsgB can be generated by the above-mentioned implementation including the implementation based on formula 1.

[0262] Next, the RNTI generation method described in the example of implementation mode 1 and examples to which the RNTI generation method can be applied will be summarized.

[0263] (1) Usage 1: The RNTI generation method can be used to distinguish the RA-RNTI of the 2-step RACH process and the RA-RNTI of the 4-step RACH process.

[0264] (2) Usage 2: In the 2-step RACH process, both RAR and MsgB need to be monitored. Therefore, Embodiment 1 can be used to distinguish the RA-RNTI used for RAR monitoring and the RNTI used for MsgB monitoring.

[0265] (3) Usage 3: When the length of the PDCCH monitoring window exceeds 10ms, the RNTI generation method can be used to distinguish the RA-RNTI used for RAR monitoring on the RO at a specific time point and the RA-RNTI used for RAR monitoring on the RO having the same OFDM symbol, time slot and frequency position as the RO at the specific time point but with an offset of 10ms.

[0266] Usage 3 can be applied to the following scenarios.

[0267] 1) For transmission in the unlicensed band, due to LBT, it may be difficult to obtain the opportunity to send PDCCH, so the length of the PDCCH monitoring window can be configured to be longer than 10ms. For example, the length of the PDCCH monitoring window can be set to 20ms, 30ms or 40ms.

[0268] 2) The size of the MsgB monitoring window of the 2-step RACH process may exceed 10ms.

[0269] 3) If the RA-RNTI used for MsgB monitoring in the 2-step RACH process is generated in a PUSCH opportunity group to which a specific RO is mapped (e.g., UL time and frequency resources for MsgA PUSCH transmission), the RNTI generation method can be used to distinguish the RA-RNTI associated with the specific PUSCH opportunity group from the RA-RNTI associated with another PUSCH opportunity group.

[0270] 4) When the RA-RNTI for MsgB monitoring in the 2-step RACH procedure is generated based on the associated RO, the MsgB monitoring window can overlap with another MsgB monitoring window associated with the RO with a 10ms offset, even if the size of the MsgB monitoring window is 10ms, because the starting point of the MsgB monitoring window is after the time when the MsgA PUSCH is sent, such as Fig.21 As shown. Therefore, the RNTI generation method can be used to distinguish the RNTI associated with the overlapping MsgB monitoring window. In addition, the MsgA PUSCH can be sent after the MsgA PRACH preamble. Therefore, the time position of the PUSCH resource associated with the MsgA PRACH preamble can change for each MsgA PRACH preamble.

[0271] Furthermore, Usage 3 can be applied to scenarios other than the above four scenarios.

[0272] 2. Implementation Method 2

[0273] Hereinafter, a method of distinguishing a 4-step RACH procedure from a 2-step RACH procedure based on a PDCCH while using an existing RA-RNTI and a method of identifying which PDCCH monitoring window is used for a PDCCH when there are overlapping PDCCH monitoring windows will be described.

[0274] (1) Implementation 2-1: Method using PDCCH scrambling sequence

[0275] The RNTI may consist of 16 bits, and the CRC scrambled to 16 bits may consist of 24 bits. Therefore, when mapping the 16-bit RNTI, 8 bits remain. Among these 8 bits, at least one bit may be used to scramble the CRC. For example, in addition to the commonly used RNTI, bits that can additionally specify the corresponding PDCCH may be used for CRC scrambling.

[0276] By doing so, the RAR can be distinguished from the MsgB of the 2-step RACH procedure. In addition, if the length of the monitoring window exceeds 10 ms, embodiment 2-1 can be used to distinguish which monitoring window the PDCCH received in the overlapping monitoring windows is related to.

[0277] (2) Implementation 2-2: Method using DMRS sequence

[0278] To generate a DMRS sequence, RNTI and N id In this case, a common RNTI may be used as a seed value, and different RNTIs for specifying a PDCCH may be used. id The value is used to distinguish the corresponding PDCCH.

[0279] (3) Implementation 2-3: Method using PDCCH content

[0280] Some bits included in the DCI may be used to indicate that the PDCCH is used for other purposes but uses the same RA-RNTI. Here, the PDCCH for other purposes may refer to different PDCCHs for distinguishing between RAR and MsgB, different PDCCHs for distinguishing between RAR of a 2-step RACH process and RAR of a 4-step RACH process, or different PDCCHs for distinguishing between RAR (or MsgB) received within a predetermined time (e.g., 10 ms) from the start of the monitoring window and RAR (or MsgB) received after the predetermined time.

[0281] On the other hand, the corresponding indicator may be included in the RAR message or MsgB instead of the PDCCH content.

[0282] 3. Implementation Method 3

[0283] Hereinafter, specific examples will be described with reference to Embodiments 1 and 2.

[0284] (1) Embodiment 3-1: Distinguishing PDCCH for RAR in 2-step RACH procedure and RAR in 4-step RACH procedure PDCCH method

[0285] The RO may be shared for both the 2-step RACH procedure and the 4-step RACH procedure. In this case, a different PRACH preamble may be allocated for each of the 2-step RACH procedure and the 4-step RACH procedure. However, if the RA-RNTI is generated based on the RO, a UE that wishes to receive different responses depending on the RACH procedure may have difficulty distinguishing which RACH procedure the received response is associated with.

[0286] In the 4-step RACH procedure, the UE can monitor the PDCCH for Msg2 from the time slot after the PRACH preamble is transmitted. Specifically, the UE can monitor the PDCCH based on the RA-RNTI within a monitoring window up to 10ms included in the RAR search space for PDCCH monitoring indicated by the BS.

[0287] On the other hand, in the 2-step RACH procedure, the UE may monitor the PDCCH for RAR for the 2-step RACH procedure in a time slot configured as DL or flexible after a predetermined time has elapsed from when the UE transmits the MsgA PRACH preamble and the MsgAPUSCH (e.g., after PUSCH transmission or at the end of a PUSCH group).

[0288] In this case, the UE may monitor the PDCCH within the search space configured for the 2-step RAR. On the other hand, the search space configured for the 2-step RAR may be the same as the search space configured for the 4-step RACH procedure. Alternatively, the search space configured for the 2-step RAR may be specified separately for the 2-step RACH procedure.

[0289] When the UE monitors the PDCCH for 2-step RAR, the UE may use different RNTIs based on the state of the UE. For example, when the UE is in the RRC CONNECTED state, the UE may use the C-RNTI to receive a successful RAR, and at the same time, the UE may use the RA-RNTI to receive a fallback RAR. Alternatively, when the UE is in the RRC CONNECTED state, the UE may use only the RA-RNTI to receive both a successful RAR and a fallback RAR.

[0290] On the other hand, when the UE is in the RRC IDLE / INACTIVE state, the UE may use the RA-RNTI to receive the 2-step RAR. For example, the 2-step RA-RNTI may be different from the 4-step RA-RNTI. As another example, the 4-step RA-RNTI and the 2-step RA-RNTI may be the same, and in this case, the specific bit string used for the 2-step RACH process may be masked to the N bits remaining after CRC mapping. For example, if the CRC is 24 bits and the RA-RNTI is 16 bits, 8 bits remain. Therefore, the specific bit string is masked to the remaining 8 bits, and the 2-step RAR and the 4-step RAR can be distinguished based on the masked specific bit string.

[0291] Even if the PDCCH for 2-step RAR and the PDCCH for 4-step RAR are identified by the above method, there may be a conflict between the 2-step RA-RNTIs due to the following reasons: The monitoring of the PDCCH for 2-step RAR starts when the PUSCH opportunity (PO) is sent after the RO, the monitoring duration may exceed 10ms, and the existing RA-RNTI is repeated every 10ms.

[0292] To solve this problem, information indicating whether the RA-RNTI is used for RO or PO can be indicated by a control signal (e.g., DCI) or a RAR message for a 2-step RACH RAR. For example, the lower N bits of the SFN can be included in the control signal or the RAR message. For example, N can be one of 1, 2, and 3, and the value of N can be determined based on the RAR monitoring window and the PDCCH search start time. In addition, information about the relative time elapsed from RO can be included in the control signal or the RAR message. For example, information about N*10ms from RO can be included, in which case N can have a value of 1, 2, 3, 4, 5, 6, 7, or 8.

[0293] Implementation 3-2: When there is a 2-step PRACH preamble code in the mapping of RO and PO that is not mapped to PUSCH resources Method for monitoring PDCCH for RAR when PRACH preamble of source unit (PRU)

[0294] In the 2-step RACH process, the UE can map the PRACH preamble of a specific RO to the PRU of a specific PO to configure MsgA.

[0295] However, when the number of ROs is greater than the number of POs, some ROs may not be mapped to a PO. Alternatively, some PRACH preambles may not be mapped to a PRU. When the UE performs a two-step RACH procedure, the UE may send MsgA by selecting, from among the two-step PRACH preambles, a PRACH preamble that is not mapped to a PRU at a specific time. In this case, the time at which the UE monitors the PDCCH for the RAR for the two-step RACH procedure may be after the PO of the expected PUSCH transmission (although no PUSCH is actually transmitted). However, if the PRACH preamble that does not perform the PRACH preamble to PRU mapping or the RO associated with the unmapped PRACH preamble is known to the BS and the UE, PDCCH monitoring may be performed from the time slot after transmitting the two-step PRACH preamble, as in the existing four-step RACH procedure, where monitoring is performed from the time slot after transmitting the PRACH preamble. That is, the time slot after transmitting the two-step PRACH preamble may be the start time for monitoring the PDCCH for the two-step RAR. Additionally, in this case, since no PUSCH is actually transmitted, the BS may not detect the PUSCH, and thus the UE may expect to receive a fallback RAR.

[0296] (3) Implementation 3-3: Including time information in DCI or RAR message when the PDCCH monitoring window exceeds 10 ms method.

[0297] Referring to Fig. 22 , when the PDCCH is transmitted in a time slot within 10 ms with respect to the RACH time slot including the RO, the time information included in the DCI or RAR message may be set to "000". When the receiver (e.g., the UE) obtains the time information "000" in the DCI or RAR message, the receiver may recognize that the corresponding RAR is a response to the RACH transmitted from the RO within 10 ms. When the PDCCH is transmitted in a time slot within 10 ms to 2*10 ms, the time information included in the DCI or RAR message may be set to "001". The time information may be configured for other time ranges in a similar manner as described above. Additionally, the bit size of the time information is not limited. For example, if the time information consists of 3 bits as described above, the duration from 0 to X ms (40 ms < X ≤ 80 ms) may be divided into Y durations (4 < Y ≤ 8) in units of 10 ms, and it may be recognized in which of the 8 divided durations the PDCCH is transmitted. Further, if the time information consists of 5 bits, the duration from 0 to X ms (160 ms < X ≤ 320 ms) may be divided into Y durations (16 < Y ≤ 32) in units of 10 ms, and it may be recognized in which of the 32 divided durations the PDCCH is transmitted.

[0298] When the PDCCH is transmitted in a time slot within 10 ms with respect to the time slot used to monitor the Msg2 RAR, the time information may be set to "000". When the receiver (e.g., UE) obtains the time information "000", the receiver can identify that the corresponding Msg2 RAR is a response to the RACH transmitted from the RO within 10 ms. When the PDCCH is transmitted in a time slot within 10 ms to 2*10 ms with respect to the time slot used to monitor the Msg2 RAR, the time information may be set to "001". The time information can be configured for other time ranges in a similar manner as described above. In addition, the bit size of the time information is not limited. For example, if the time information consists of 3 bits as described above, the duration from 0 to X ms (40 ms < X ≤ 80 ms) can be divided into Y durations (4 < Y ≤ 8) in units of 10 ms, and it can be identified in which of the 8 divided durations the PDCCH is transmitted. Additionally, if the time information consists of 5 bits, the duration from 0 to X ms (160 ms < X ≤ 320 ms) can be divided into Y durations (16 < Y ≤ 32) in units of 10 ms, and it can be identified in which of the 32 divided durations the PDCCH is transmitted.

[0299] The time information can be configured in a similar manner as the above method, but the reference time slot can be the time slot used to monitor the MsgB RAR.

[0300] The time information can be the information indicating the relative difference between the number of the frame including the RO and the number of the frame at the time of receiving the PDCCH.

[0301] (4) Implementation 3-4: When both MsgB and Msg2 use the same RNTI, CRC scrambling is used to distinguish Method for DCI for MsgB and DCI for Msg2

[0302] The following is extracted from Section 7.3.2 CRC attachment of 3GPP TS 38.212.

[0303] - Error detection for DCI transmission can be performed by CRC. The entire payload of the CRC can be used to calculate the CRC parity bits. The payload bits can be defined as a0, a1, a2, a3,..., a A-1 , and the parity bits can be defined as p0, p1, p2, p3,..., p L-1 , where A is the payload size and L is the number of parity bits. The parity bits are calculated based on the input bit sequence of a’0, a’1, a’2, a’3,..., a’ A+L-1 , and according to Section 5.1 of 3GPP TS 38.212. In this case, L can be 24 bits and is attached based on the generating polynomial.

[0304] - If K = A + L, then b0, b1, b2, b3, ..., b K-1 The output bits can be defined as:

[0305] When k = 0, 1, 2, ..., A-1, b k =a k ; and when k = A, A+1, A+2, ..., A+L-1, b k =p k-A .

[0306] -After attaching, c0, c1, c2, c3, ..., c4, c5, c6, c7, c8, c9, c10, c1 ...8, c9, c10, c11, c2 K-1 The CRC parity bits are scrambled in the form of a bit sequence of k and b k The relationship between is given by when k = 0, 1, 2, ..., A + 7 k =b k And when k = A+8, A+9, A+10, ..., A+23, c k =(b k +x rnti,k-A-8 )mod 2 definition.

[0307] As described above, referring to the contents of Section 7.3.2 of 3GPP TS 38.212, when 16 bits of RNTI are scrambled to 24 bits of CRC and additional scrambling is performed on the remaining bits, the CRC bits may be configured in the same manner as in the following Equation 2.

[0308] [Formula 2]

[0309] For k = 0, ..., A-1, c k =b k

[0310] For k=A, ..., A+7, c k =(b k +X mask,k-A )mod 2

[0311] For k = A+8, ..., A+23, c k =(b k +x rnti,k-A-8 )mod 2

[0312] Here, the previously used {0, 0, 0, 0, 0, 0, 0} can be used as Xmask. If an additional mask is required, a bit string with at least one different bit can be used, such as {0, 1, 0, 1, 0, 1, 0, 1}, {0, 0, 0, 0, 0, 0, 0, 1}, etc.

[0313] Embodiments 3-4 can be applied even when RNTI is increased to 24 bits. In this case, for a conventional RNTI having 16 bits and an RNTI using extended bits (eg, 24 bits), the number of scrambled bits can be determined based on the above value range.

[0314] 4. Implementation Method 4

[0315] In Embodiment 4, the time synchronization assumption between BSs including gNB, mobile BS, satellite, vehicle, etc. in a network supporting a 2-step RACH procedure will be described.

[0316] Specifically, a time synchronization assumption used by the UE to perform handover will be described. That is, Embodiment 4 is not limited to a system including a UE and a gNB, and Embodiment 4 can be applied to various types of BSs and UEs including a repeater such as an access and backhaul integration (IAB) and a relay and an artificial satellite such as a non-terrestrial network (NTN). Embodiment 4 can also be applied to communication between various UEs, such as communication between vehicles or communication between flying objects.

[0317] In the 2-step RACH procedure, the UE may send a MsgA PRACH preamble and a MsgA PUSCH. Upon receiving the MsgAPRACH preamble and the MsgA PUSCH, the BS may attempt to detect the MsgA PRACH preamble and then attempt to obtain information about the UE from the MsgA PUSCH. If the BS successfully obtains the UE information based on the MsgA PRACH preamble detection and the MsgA PUSCH decoding, the BS may send a success RAR to the UE. On the other hand, when the BS detects the MsgA PRACH preamble but fails to decode the MsgAPUSCH, the BS may send a fallback RAR to the UE to instruct the UE to fall back to the 4-step RACH procedure associated with the successfully detected PRACH preamble.

[0318] If the BS fails in both MsgA PRACH preamble detection and MsgA PUSCH decoding, the BS may not send any RAR to the UE.

[0319] To receive the successful RAR or fallback RAR sent by the BS, the UE may monitor the PDCCH for MsgB based on the MsgB-RNTI. When detecting the DCI associated with the corresponding MsgB-RNTI, the UE may obtain the message of the successful RAR or fallback RAR from the PDSCH scheduled by the DCI.

[0320] However, when the length of the monitoring window for the UE to monitor the PDCCH for MsgB based on the MsgB-RNTI is 10ms or more, if different UEs select the MsgA PRACH preamble on different ROs but use the same MsgB-RNTI, the monitoring windows for PDCCH monitoring may overlap. In this case, there is a problem that the UE cannot accurately know which RO the detected PDCCH for the MsgA PRACH preamble is related to.

[0321] To solve this problem, a method can be introduced to allow UEs using the same MsgB-RNTI to distinguish RARs associated with detected DCI by sending information about the index of the frame in which the corresponding RO is selected in DCI. The details of this method have been described in Embodiments 1 to 3.

[0322] In LTE and NR systems, the frame index can be sent by a parameter called SFN, and SFN is included in the PBCH. In other words, SFN can be obtained by decoding the PBCH.

[0323] For example, when the UE selects a specific cell in the initial access phase, the UE can detect the physical cell ID (PCID) from the primary synchronization signal / secondary synchronization signal (PSS / SSS) and obtain various time information including SFN (for example, SSB index, half-frame index, etc.) and information required to receive system information block type 1 (SIB1) (for example, RMSICORESET, search space, SCS, resource block alignment, etc.) by decoding the PBCH.

[0324] When the UE obtains RACH related information from SIB1, if the network indicates a 2-step RACH procedure, the UE can send MsgA and then use the SFN information obtained from PBCH decoding while monitoring MsgB.

[0325] When the primary cell (Spcell) of the primary cell group or the secondary cell group is added to the UE with dual connectivity, the UE can receive the RACH configuration for the RACH performed by the Spcell from the Pcell. The UE can then perform the RACH procedure according to the corresponding RACH configuration. In addition, when a handover is indicated, the UE can receive the RACH configuration of the target cell through a handover command. The UE can then perform the RACH procedure for the target cell based on the corresponding RACH configuration.

[0326] If each of the RACH period and the RO to SSB association pattern period is 10ms or longer when the UE performs dual connectivity or handover, the UE may need to know the SFN of the target cell to perform the RACH process. If the UE needs to complete the RACH process and time / frequency tracking within the interruption time as in handover, decoding the PBCH of the target cell to obtain the SFN may be a significant burden on the UE. When the UE needs to complete the RACH process within the interruption time as in handover in LTE and NR systems due to the above-mentioned problems, the UE may be allowed to perform the RACH process without PBCH decoding to reduce the time delay caused by PBCH decoding and reduce the burden on the UE caused by PBCH decoding. That is, UE operations requiring PBCH decoding may not be adopted.

[0327] In addition, if the size of the MsgB monitoring window is 10 ms or larger, similar problems may occur in the 2-step RACH procedure.

[0328] To solve these problems, a method of identifying multiple ROs using the same MsgB-RNTI by configuring a specific time to identify UEs using the same MsgB-RNTI and sending information about the duration from the specific time to the time when DCI is received to the UE has been proposed in embodiment 3.

[0329] According to the method proposed in Embodiment 3, the UE needs to obtain SFN information from PBCH decoding. However, when the UE needs to complete the RACH process within the interruption time as in handover as described above, a method is required that enables the UE to obtain or assume the SFN associated with the selected RO without PBCH decoding. Therefore, a method is proposed that allows the UE to assume or obtain the SFN without PBCH decoding.

[0330] (1) Implementation method 4-1:

[0331] 1) If the 2-step RACH procedure is configured during the handover process, the UE can assume that the synchronization between the current cell and the target cell is aligned.

[0332] 2) If the 2-step RACH procedure is configured during the handover process and the MsgB monitoring window size exceeds 10ms, the UE can assume that the synchronization between the current cell and the target cell is aligned.

[0333] 3) If during the handover process, at least one of the MsgB monitoring window for 2-step RACH contention-free random access (CFRA) and the MsgB monitoring window for 2-step RACH contention-based random access (CBRA) exceeds 10ms, the UE can assume that the synchronization between the current cell and the target cell is aligned.

[0334] Hereinafter, the operation of the UE assuming synchronization alignment between the current cell and the target cell in implementation mode 4-1 will be described in detail.

[0335] When a 2-step RACH procedure is configured during handover to a target cell, the UE may assume that the absolute time difference between radio frame i of the current cell and radio frame i of the target cell is N. In this case, N may be, for example, 153600Ts (5ms) or 76800Ts (2.5ms), where Ts may be 1 / 2048 / 15000 seconds.

[0336] Specifically, when the target cell has Lmax=4 and uses paired or unpaired spectrum, N=153600Ts may be applied. In addition, when the target cell has Lmax=8 and uses unpaired spectrum and when the source cell uses paired or unpaired spectrum, N=76800Ts may be applied.

[0337] In other words, for frequency division duplex (FDD) in FR1 below 3 GHz, it can be assumed that the frame index of the target cell is equal to the frame index of the current cell within a time error range of + / -5 ms. In addition, for time division duplex (TDD) in frequency bands below 2.8 GHz, it can be assumed that the frame index of the target cell is equal to the frame index of the current cell within a time error range of + / -5 ms. In addition, for TDD in frequency bands above 2.8 GHz in FR1, it can be assumed that the frame index of the target cell is equal to the frame index of the current cell within a time error range of + / -2.5 ms.

[0338] (2) Implementation method 4-2:

[0339] If the MsgB monitoring window size for 2-step RACH CFRA is less than 10ms and the MsgB monitoring window size for 2-step RACH CBRA is greater than 10ms, the UE may perform 2-step RACH CFRA based on the handover command. Alternatively, the UE may perform CBRA by selecting 4-step RACH CBRA instead of 2-step RACH CBRA.

[0340] (3) Implementation method 4-3:

[0341] When the UE performs handover, the network can inform the UE whether the network is synchronous or asynchronous through the synchronization assumption indicator. If the corresponding indicator indicates that the network is synchronous and a 2-step RACH procedure is configured, the UE can perform the 2-step RACH procedure. On the other hand, if the corresponding indicator indicates that the network is asynchronous, the UE can perform a 4-step RACH procedure instead of the 2-step RACH procedure. However, even in this case, if the UE completes the handover and acquires the SFN, the UE can perform the 2-step RACH procedure. In some cases, the UE can perform the 4-step RACH procedure.

[0342] (4) Implementation method 4-4:

[0343] The network may provide the UE with information about the SFN of the target cell through a handover command. For example, the network may provide the UE with the relative difference between the SFN of the current cell and the SFN of the target cell through a handover command.

[0344] 5. Implementation Method 5

[0345] If the BS successfully decodes the MsgA PUSCH, the BS can send a successful RAR to the UE based on the C-RNTI. The UE does not need to obtain the SFN because the UE receives the DCI based on the C-RNTI. In addition, in this case, the length of the monitoring window can be relatively increased.

[0346] However, if the BS fails to decode the MsgA PUSCH, the BS may send a fallback RAR based on the MsgB-RNTI. In this case, if the UE receives the DCI based on the MsgB-RNTI, the UE needs to obtain information about the SFN of the target cell to decode the SFN-related information included in the DCI.

[0347] For example, when the UE receives DCI based on MsgB-RNTI, the UE may compare the SFN related information included in the DCI with the SFN of the MsgA PRACH preamble sent by the UE. If it is determined that the SFN included in the DCI matches or corresponds to the SFN of the MsgA PRACH preamble sent, the UE may perform a subsequent RACH procedure.

[0348] Here, the subsequent RACH process may mean that when the BS successfully decodes the PUSCH and sends a successful RAR, the UE sends a PUCCH including HARQ-ACK information with an ACK value indicating that the UE has successfully received Msg B. In addition, the subsequent RACH process may also mean that when the BS sends a fallback RAR due to a PUSCH decoding failure, the UE performs a process of falling back to the 4-step RACH process.

[0349] However, as described in Embodiment 4, when the UE performs handover, if the UE performs a RACH procedure without decoding the PBCH of the target cell, it may be difficult for the UE to obtain the SFN of the target cell.

[0350] In embodiment 5, an operation method of allowing the UE to terminate the RACH process when the UE fails to acquire the SFN of the target cell will be described. For example, if the UE does not decode the PBCH during the handover process in order to reduce the time delay and processing load of the UE caused by PBCH decoding, the UE can perform the RACH process in a state where the UE does not know the information about the SFN that transmits the MsgA PRACH preamble.

[0351] That is, in Embodiment 5, it will be described how the UE works when the UE fails to acquire the SFN of the target cell.

[0352] When the UE does not acquire the SFN of the target cell, the UE may send MsgA. In addition, when monitoring MsgB, the UE may assume that the monitoring window is shorter than the monitoring window configured by the network. In addition, when the UE receives DCI based on MsgB-RNTI, the UE may decode the PDSCH scheduled by the corresponding DCI without checking the validity of the SFN indicator (e.g., SFN-related information) included in the DCI.

[0353] Here, the operation that the UE does not check the validity of the SFN-related information included in the DCI may mean that the UE does not check whether the SFN of the transmitted MsgA PRACH preamble matches and / or corresponds to the SFN-related information included in the DCI. In addition, the operation may mean that the UE decodes the PDSCH scheduled by the DCI and checks the RAR without checking whether the SFN of the transmitted MsgA PRACH preamble matches and / or corresponds to the SFN-related information included in the DCI.

[0354] Hereinafter, a specific method in which the UE decodes the PDSCH without checking the validity of the SFN-related information included in the DCI will be described.

[0355] (1) Implementation Method 5-1

[0356] When the UE monitors DCI based on the C-RNTI, the UE may use the value of the monitoring window (eg, window length) configured for the C-RNTI as it is.

[0357] On the other hand, when the UE monitors DCI based on MsgB-RNTI, the length of the monitoring window may be limited to 10 ms. When receiving DCI based on MsgB-RNTI, the UE may perform PDSCH decoding regardless of SFN-related information included in the DCI.

[0358] When the UE does not receive a successful RAR within the C-RNTI-based monitoring window, the UE may retransmit MsgA or send Msg1 to fall back to the 4-step RACH procedure.

[0359] When the UE receives the fallback RAR based on the MsgB-RNTI, if the BS sends the fallback RAR within 10ms of the monitoring window, there may be no problem due to the contention of the fallback RAR. In addition, in this case, the UE's PBCH decoding may have no problem.

[0360] (2) Implementation Method 5-2

[0361] The UE may use the length of the monitoring window configured based on the MsgB-RNTI as is. In this case, the monitoring window may be the MsgB monitoring window and / or the RA monitoring window. For example, if the monitoring window length based on the MsgB-RNTI exceeds 10ms, the UE may monitor the DCI associated with the MsgB-RNTI by assuming that the monitoring window is longer than 10ms. In this case, the UE may ignore the SFN-related information included in the received DCI. That is, the UE may decode the PDSCH on the PDSCH resource indicated by the DCI regardless of the value of the SFN-related information.

[0362] Here, the operation of the UE ignoring the SFN-related information may mean that the UE does not decode the SFN-related bits included in the DCI, or even if the UE decodes the SFN-related bits included in the DCI to obtain information about the SFN, the UE discards the decoded bits.

[0363] For example, if the UE sends MsgA to the target cell during the handover process but fails to acquire information about the SFN that sends the MsgAPRACH preamble and detects DCI based on MsgB-RNTI, the UE can decode the PDSCH on the PDSCH resources indicated by the DCI regardless of the SFN-related information included in the DCI.

[0364] For example, if the UE does not decode the PBCH during the handover process in order to reduce the UE's processing load and time delay caused by PBCH decoding, the UE can send MsgA to the target cell without knowing the SFN of the MsgA PRACH preamble. In this case, the UE can decode the PDSCH on the PDSCH resources indicated by the DCI regardless of the SFN related information included in the DCI.

[0365] In addition, when the RAR obtained from PDSCH decoding is a successful RAR, the UE sends HARQ-ACK information with an ACK value to the BS through the PUCCH. When the obtained RAR is a fallback RAR, the UE can perform a 4-step RACH process.

[0366] (3) Implementation Method 5-3

[0367] In order to perform handover to the target cell in an asynchronous network, the UE may monitor the DCI within a monitoring window (e.g., a 40 ms monitoring window) after sending MsgA. When the UE receives DCI for MsgB, in which RAPID and RNTI related parameters other than the two SFN related bits match within the corresponding monitoring window, the UE may perform subsequent procedures until contention resolution succeeds or fails without verifying the validity of the two SFN related bits used to receive MsgB.

[0368] However, if the UE can confirm that the SFN-related two bits included in the DCI for MsgB do not match the least significant two bits of the SFN of the frame in which the UE transmits MsgA, the UE may not perform a subsequent RACH procedure by determining that MsgB is invalid.

[0369] In other words, according to embodiment 5-3, if the UE detects DCI for MsgB based on MsgB-RNTI, the UE can decode the PDSCH on the PDSCH resources indicated by the DCI regardless of the SFN-related information included in the DCI (or by ignoring the SFN-related information), as described in embodiment 5-2.

[0370] However, if the UE knows the SFN of the transmitted MsgA for some reason, and if the UE obtains and decodes the SFN-related information included in the DCI, the UE can compare the SFN of the transmitted MsgA with the SFN-related information included in the DCI. If the UE knows that the SFN of the transmitted MsgA does not match or correspond to the SFN-related information included in the DCI, the UE can determine that the PDSCH received on the PDSCH resource indicated by the DCI is invalid, and therefore transmits the PRACH for the 4-step RACH process or retransmits the MsgA for the 2-step RACH process.

[0371] That is, if the UE decodes the PBCH of the target cell for some reason or identifies the SFN that sends MsgA to the target cell without performing PBCH decoding, the UE may be able to accurately perform the RACH procedure by checking the validity of the SFN-related information included in the DCI. This is because in this case, the UE may neither need to ignore the SFN-related information included in the DCI nor need to perform the validity check procedure.

[0372] (4) Implementation Method 5-4

[0373] When the length of the RAR monitoring window is set to be greater than 10 ms, if the UE switches from an asynchronous network to a target cell, the UE may assume that the length of the corresponding monitoring window is up to 10 ms.

[0374] (5) Implementation Method 5-5

[0375] The handover (HO) interruption time may be redefined for the 2-step RACH procedure. For example, the HO interruption time for the 2-step RACH procedure may be set to be less than or equal to the existing interruption time.

[0376] (6) Implementation Method 5-6

[0377] If the UE performs more than one PBCH decoding within the HO interruption time, the UE may perform a RACH procedure. The network may determine whether the PBCH decoding within the HO interruption time may be more than one, and notify the UE of the determination by sending a parameter including a predetermined threshold to the UE. If the predetermined threshold in the corresponding parameter satisfies a specific measurement, the UE may determine that the UE is capable of performing more than one PBCH decoding within the HO interruption time, and then perform PBCH decoding.

[0378] (7) Implementation Method 5-7

[0379] When the UE is capable of low-latency PBCH decoding in an asynchronous network, the UE may perform PBCH decoding if a signal-to-noise ratio (SNR) range capable of detecting PBCH once (i.e., single PBCH) is configured, or if the corresponding SNR range is met.

[0380] For example, the UE may perform the 2-step RACH procedure only when the PBCH detection success rate exceeds a predetermined level (eg, 99.9%) after several attempts (eg, one attempt).

[0381] However, for synchronous networks, the UE can perform a 2-step RACH procedure without any conditions. If the network provides a RACH of 20ms or longer, it is assumed that the network is synchronous. Therefore, RAN4 needs to include a condition that the RACH is successful only within 20ms. For example, a second HO minimum performance can be included. That is, a UE that meets this new condition or a UE that can obtain the necessary information before HO by decoding the PBCH of a neighboring cell can perform a 2-step RACH procedure.

[0382] The details of the above UE capabilities, HO conditions, new conditions, monitoring windows, SFN-related information, etc. are applicable to wireless communication systems operating in unlicensed frequency bands, and specifically, these details can be applied to a 4-step RACH procedure and a 2-step RACH procedure.

[0383] Each sub-embodiment of Embodiment Mode 5 can be implemented independently, but the sub-embodiments can be combined. In addition, the sub-embodiments described in Embodiment Mode 1 to Embodiment Mode 4 or Embodiment Mode 6 to Embodiment Mode 9 can also be implemented in combination with the sub-embodiment of Embodiment Mode 5.

[0384] 6. Implementation Method 6

[0385] In CFRA for 2-step RACH procedure, the UE may send MsgA. Upon receiving MsgA, the BS may detect the PRACH preamble and decode the PUSCH associated with the detected PRACH preamble. If the BS successfully detects the PUSCH, the BS may send a response thereto to the UE. In this case, the CRC may be masked with the C-RNTI of the DCI. The UE may detect the DCI based on the C-RNTI and obtain information sent by the BS through the PDSCH.

[0386] Hereinafter, a method of configuring MsgA of CFRA for a 2-step RACH procedure will be described.

[0387] In CFRA, the UE may be allowed to send only the MsgA PRACH preamble without mapping to PUSCH resources. Therefore, MsgA may include only the PRACH preamble.

[0388] When the UE selects 2-step RACH, if the channel quality (e.g., RSRP) of SSB / CSI-RS is higher than a specific value, the UE may perform 2-step RACH CFRA in which the UE transmits only the PRACH preamble. If the channel quality becomes less than or equal to a specific value, the UE may perform 2-step RACH CBRA in which the UE transmits both the PRACH preamble and the PUSCH.

[0389] Specifically, in the conventional 4-step RACH procedure, CFRA may be performed in two phases. When CFRA is performed in two phases, the UE may start monitoring the RAR after transmitting the PRACH preamble, and then receive the RAR as a response to the PRACH preamble.

[0390] However, in the 2-step RACH procedure, if MsgA includes MsgA PUSCH as well as MsgA PRACH preamble, the UE may perform RA monitoring after transmitting the MsgA PUSCH. Therefore, if the 2-step RACH CFRA is configured with the MsgA PRACH preamble and the MsgA PUSCH, the 2-step RACH CFRA may require not only the time for MsgA transmission but also the time for the BS to receive and process MsgA and the time for the UE to monitor random access. As a result, the total time required for the RACH procedure may increase. However, when the interruption time needs to be considered as in HO, the increase in the total time required for the RACH procedure may not be desirable.

[0391] If there is a greater benefit in transmitting the information required for PUSCH during the RACH procedure even if the RACH time is increased, then sending the PRACH preamble and PUSCH may be considered. Otherwise, increasing the RACH time is not desirable.

[0392] If the parameters configured for CFRA do not indicate PUSCH related information, MsgA in CFRA may include only PRACH preamble. If PUSCH related information is indicated, MsgA may consist of MsgA PRACH preamble and MsgA PUSCH, and MsgA may be sent by UE to BS.

[0393] The BS may configure multiple POs to the UE. In this case, the multiple POs may have a one-to-one relationship with the PRACH preamble code used for the RO. When there is a mask index and an SSB / CSI-RS index for indicating the RO, the SSB / CSI-RS index applied to the RACH may be applied to the PO. The RACH slot may be mapped to a PO included in a PUSCH slot having a predetermined duration.

[0394] If the number of ROs indicated by the RACH mask index is greater than the number of POs, only the PRACH preamble can be sent on a specific RO, while both MsgA PRACH and MsgA PUSCH can be sent on the remaining ROs. In this case, the specific RO may be an RO that is not mapped to a PO, and the remaining ROs may be ROs mapped to a PO.

[0395] If the number of ROs is smaller than the number of POs, only some POs may be used for MsgA transmission, and the remaining POs may not be used. In this case, the POs used for MsgA transmission may be POs mapped to the ROs.

[0396] 7. Implementation Method 7

[0397] In Embodiment 7, a method of configuring a monitoring window for MsgA including only a PRACH preamble will be described. Specifically, Embodiment 7 may be applied to CBRA.

[0398] The UE may send only the PRACH preamble on a valid PRACH opportunity in the following two cases:

[0399] - When the PO associated with the DMRS resource is not mapped to a PRACH preamble in a valid PRACH opportunity; and

[0400] - When a PRACH opportunity is mapped to a valid PO but PUSCH transmission is dropped due to LBT failure in the shared spectrum.

[0401] (1) Implementation 7-1: When PO is not mapped to a PRACH preamble in a valid PRACH opportunity

[0402] MsgA can be configured by combining MsgA PRACH preamble and MsgA PUSCH. However, if the number M of available PRACH preambles included in a specific duration is different from the number N of PUSCH resources (or DMRS resources), some PRACH preambles may not be mapped to PUSCH resources. For example, if M=K*N is satisfied, M / K PRACH preambles can be mapped to one PUSCH resource. Therefore, all PRACH preambles can be mapped to PUSCH resources.

[0403] On the other hand, if M>K*N is satisfied, K=ceiling(M / L) PRACH preambles can be mapped to one PUSCH resource. Therefore, some PRACH preambles can be mapped to all N PUSCH resources, but MK*N PRACH preambles are reserved. In this case, MsgA can be considered to include only the remaining PRACH preambles.

[0404] After sending MsgA, the starting point of the monitoring window for MsgB needs to be determined.

[0405] When MsgA consists of a PRACH preamble and a PUSCH, the MsgB monitoring window can be configured for the PO for the transmission of the MsgA PUSCH associated with the MsgA PRACH preamble. However, when MsgA includes only the PRACH preamble, there may be no MsgA PUSCH mapped to the PRACH preamble, and thus it may be difficult to configure the MsgB monitoring window for the PO.

[0406] To solve this problem, the following two methods can be considered.

[0407] Method 1) The MsgB monitoring window can be configured for the PO associated with the transmission of a specific PUSCH, although there is no mapping relationship between the PUSCH and the PRACH preamble code.

[0408] For example, the MsgB monitoring window may be configured for the PO of a PUSCH resource mapped to a specific PRACH preamble in the RO including the MsgA PRACH preamble.

[0409] In other words, the MsgB monitoring window may start at the first symbol of the earliest CORESET after the last symbol of the PO associated with the PUSCH transmission corresponding to the PRACH preamble in the valid PRACH opportunity.

[0410] As another example, the MsgB monitoring window may be configured for a specific PO (eg, the first or last PO among valid POs) among POs included in a PUSCH slot designated based on a RACH slot including a MsgA PRACH preamble.

[0411] Method 2) The MsgB monitoring window may be configured for the RO associated with the PRACH preamble transmission.

[0412] In other words, the MsgB monitoring window may start at the first symbol of the earliest CORESET after the last symbol of the PRACH opportunity associated with the PRACH transmission.

[0413] (2) Implementation 7-2: When PUSCH transmission is discarded due to LBT failure,

[0414] The MsgB monitoring window may be configured for POs attempting PUSCH transmissions associated with a PRACH preamble.

[0415] In other words, the MsgB monitoring window may start at the first symbol of the earliest CORESET after the last symbol of the PO attempting a PUSCH transmission.

[0416] 8. Implementation Method 8

[0417] In implementation 8, a case where the network detects the PRACH preamble without decoding the PUSCH will be described. In this case, the network operation can be considered equivalent to the reception of Msg1, so that the network can provide the UE with the necessary information in the RAR. If the UE supports the 2-step RACH process, the UE can continuously attempt to decode the PDCCH for MsgB until MsgB is detected. Providing information in the RAR may not be a burden for the UE. That is, considering the relationship with MsgB, the RAR can be reused for PUSCH decoding failure or fallback mechanism.

[0418] (1) Implementation 8-1: Indication of Successful PRACH Preamble Detection and Failed PUSCH Decoding in RAR

[0419] Upon receiving MsgA (PRACH preamble + PUSCH) transmitted by the UE in the 2-step RACH procedure, the BS may perform PRACH preamble detection and PUSCH decoding. When the BS successfully detects the PRACH preamble, the BS may decode the PUSCH associated with the PRACH preamble.

[0420] In addition, when the BS determines through CRC check that the BS successfully receives the information bits or when the BS fails to recover the information bits, the BS may send information about the PRACH preamble code that the BS has successfully detected to the UE in RAR. The BS may send the RAPID of the detected PRACH preamble code to the UE.

[0421] When the BS fails to decode the PUSCH, the BS may send a UL grant related to the corresponding RAPID, a timing advance (TA) command, a TC-RNTI, etc. On the other hand, when the BS successfully decodes the PUSCH, the BS may notify the UE of the success or failure of PUSCH decoding by using some bits and / or some code points included in the RAR message. For example, the BS may notify the UE of the success or failure of PUSCH decoding by using some of the various states indicated by the bits of the UL grant.

[0422] The UE can monitor the PDCCH based on the RA-RNTI and receive the RAR message based on the PDCCH. In addition, the UE can check the RAPID of the PRACH preamble sent by the UE from the RAR message, and can also check whether the RAPID detection is successful and whether the PUSCH decoding is successful. If the UE confirms that the RAPID detection is successful and the PUSCH decoding is successful, the UE can obtain the TA command and TC-RNTI and use them to monitor the MsgB PDCCH sent later. The obtained TA command can be used for UL transmission.

[0423] On the other hand, if the UE confirms that RAPID detection is successful but PUSCH decoding fails, the UE can obtain the TA command, TC-RNTI and / or UL authorization, etc., and then send Msg3.

[0424] If the UE confirms that the PRACH preamble detection is unsuccessful, the UE may retransmit MsgA of the 2-step RACH procedure or send Msg1 (ie, the PRACH preamble) by falling back to the 4-step RACH procedure.

[0425] If the UE does not receive the RAR within the RAR monitoring window, the UE may retransmit MsgA of the 2-step RACH procedure after the RAR monitoring window ends. Alternatively, the UE may fall back to the 4-step RACH procedure and send Msg1 (ie, PRACH preamble).

[0426] (2) Implementation 8-2: Indication of Successful PRACH Preamble Detection in RAR and Fallback to 4-Step RACH in MsgB Instructions for the process Msg3

[0427] In the 2-step RACH procedure, the UE may send the MsgA PRACH preamble and the MsgA PUSCH. After sending the MsgAPRACH preamble, the UE may receive the PDCCH for RAR in the RAR monitoring window. In addition, after sending the MsgA PUSCH, the UE may receive the PDCCH for MsgB in the monitoring window for MsgB.

[0428] In this case, the starting point of the RAR monitoring window may be earlier than the monitoring window for MsgB. In addition, the length of the RAR monitoring window may be different from the length of the monitoring window for MsgB. In addition, the RAR monitoring window and the monitoring window for MsgB may partially overlap.

[0429] Upon receiving the MsgA PRACH preamble and MsgA PUSCH sent by the UE, the BS may perform PRACH preamble detection and PUSCH decoding. If the BS successfully detects the PRACH preamble, the BS may inform the UE in the RAR whether the PRACH preamble is successfully detected. The RAR content may include RAPID, TA, UL grant, and / or TC-RNTI. In the 2-step RACH process, an indicator indicating whether the PRACH preamble detection is successful may be sent together with the RAPID.

[0430] For example, the BS may send information about the success or failure of PRACH preamble detection to the UE by using some bits or some code points of the RAR message. Specifically, the BS may send information about the success or failure of PRACH preamble detection to the UE by using some of the various states indicated by the UL authorized bit. In addition, the BS may also send TA and / or TC-RNTI to the UE. If the BS sends TA, TC-RNTI, etc. in MsgB instead of RAR, the bits used for TA and TC-RNTI may be reserved or used for other purposes.

[0431] When the UE obtains the RAR based on the RAR monitoring, the UE may check the RAPID. If the UE confirms that the PRACH preamble detection is successful, the UE may continue to monitor the PDCCH for MsgB until the monitoring window for MsgB ends even after the RAR monitoring window ends.

[0432] If the UE does not receive a message related to RAPID within the RAR monitoring window, the UE may retransmit MsgA or fall back to the 4-step RACH procedure to perform RACH again. Alternatively, the UE may attempt to access a new cell by discovering another cell ID.

[0433] When the BS receives the MsgA PUSCH transmitted by the UE and successfully detects the PUSCH, the BS may transmit a message for performing a contention resolution procedure to the UE in MsgB.

[0434] If the BS fails to decode the PUSCH, the BS may send a UL grant for Msg3 transmission to the UE in MsgB. If TA, TC-RNTI, etc. are sent to the UE in the RAR message, TA, TC-RNTI, etc. may not be sent in MsgB. Conversely, if TA, TC-RNTI, etc. are not sent in the RAR message, TA, TC-RNTI, etc. may be sent to the UE in MsgB. For example, if MsgB is sent before RAR, if only MsgB is sent, or if TA, TC-RNTI, etc. are not included in the 2-step RACH RAR, TA, TC-RNTI, etc. may be sent to the UE in MsgB.

[0435] After detecting the PRACH preamble from the RAR confirmation, the UE may continuously perform monitoring for MsgB. Upon receiving MsgB, the UE may perform a contention resolution procedure or may send Msg3 to the BS.

[0436] 9. Implementation Method 9

[0437] If the UE does not receive MsgB within the monitoring window for MsgB, the UE may retransmit MsgA. The above process is similar to retransmitting Msg1 when the UE cannot receive RAR in LTE.

[0438] In this case, it is necessary to discuss how to configure the monitoring window and its timer for MsgB. According to implementation mode 9, since the PRACH preamble and PUSCH are sent in MsgA, the starting point of the monitoring window for MsgB can be later than the starting point of the RAR monitoring window, such as Fig.21 shown.

[0439] It is obvious that each example of the proposed method may also be included as an implementation method, and therefore each example may be considered as a proposed method. Although the above-mentioned embodiments may be implemented independently, some embodiments may be combined and implemented. In addition, it may be provided that information on whether an implementation is applied (or information on rules related to an implementation) is sent from the BS to the UE via a predefined signal (e.g., a physical layer signal, a high layer signal, etc.).

[0440] The various details, functions, processes, proposals, methods and / or operational flowcharts described above in this document can be applied to various fields requiring wireless communication / connection between devices (e.g., 5G).

[0441] Hereinafter, a description will be given in detail with reference to the accompanying drawings. In the following drawings / descriptions, unless otherwise described, the same reference numerals may represent the same or corresponding hardware blocks, software blocks or functional blocks.

[0442] Fig.23 A communication system 1 applied to the present disclosure is illustrated.

[0443] Reference Fig.23 , the communication system 1 applied to the present disclosure includes a wireless device, a BS and a network. The wireless device is a device that performs communication using a radio access technology (RAT) (e.g., 5G NR (or new RAT) or LTE), also referred to as a communication / radio / 5G device. The wireless device may include, but is not limited to, a robot 100a, a vehicle 100b-1 and 100b-2, an extended reality (XR) device 100c, a handheld device 100d, a home appliance 100e, an IoT device 100f, and an artificial intelligence (AI) device / server 400. For example, a vehicle may include a vehicle with a wireless communication function, an autonomous driving vehicle, and a vehicle capable of vehicle-to-vehicle (V2V) communication. In this article, a vehicle 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) installed in a vehicle, a television (TV), a smart phone, a computer, a wearable device, a home appliance, a digital signage, a vehicle, a robot, etc. Handheld devices may include smart phones, smart tablets, wearable devices (e.g., smart watches or smart glasses), and computers (e.g., laptop computers). Home appliances may include TVs, refrigerators, washing machines, etc. IoT devices may include sensors, smart meters, etc. For example, BSs and networks may be implemented as wireless devices, and a specific wireless device 200a may operate as a BS / network node for other wireless devices.

[0444] The wireless devices 100a to 100f may be connected to the network 300 via the BS 200. AI technology may be applied to the wireless devices 100a to 100f, and the wireless devices 100a to 100f 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 100a to 100f may communicate with each other via the BS 200 / network 300, the wireless devices 100a to 100f may perform direct communication (e.g., side link communication) with each other without the intervention of the BS / network. For example, the vehicles 100-1 and 100-2 may perform direct communication (e.g., V2V / vehicle-to-everything (V2X) communication). An IoT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., a sensor) or other wireless devices 100a to 100f.

[0445] Wireless communication / connection 150a, 150b and 150c can be established between wireless devices 100a to 100f / BS200 and between BS 200. In this article, wireless communication / connection can be established through various RATs (e.g., 5G NR) such as UL / DL communication 150a, side link communication 150b (or D2D communication) or inter-BS communication (e.g., relay or integrated access backhaul (IAB)). Wireless signals can be sent and received between wireless devices, between wireless devices and BSs, and between BSs through wireless communication / connection 150a, 150b and 150c. For example, signals can be sent and received on various physical channels through wireless communication / connection 150a, 150b and 150c. To this end, various configuration information configuration processes for sending / receiving wireless signals, various signal processing processes (e.g., channel coding / decoding, modulation / demodulation and resource mapping / demapping) and at least a part of the resource allocation process can be performed based on various proposals of the present disclosure.

[0446] Fig.24 A wireless device suitable for use with the present disclosure is illustrated.

[0447] Reference Fig.24 , the first wireless device 100 and the second wireless device 200 may transmit wireless signals through various RATs (e.g., LTE and NR). {The first wireless device 100 and the second wireless device 200} may correspond to Fig.23 {wireless device 100x and BS 200} and / or {wireless device 100x and wireless device 100x}.

[0448] The first wireless device 100 may include one or more processors 102 and one or more memories 104, and also include one or more transceivers 106 and / or one or more antennas 108. The processor 102 may control the memory 104 and / or the transceiver 106, and may be configured to implement the descriptions, functions, processes, proposals, methods, and / or operational flowcharts disclosed in this document. For example, the processor 102 may process the information in the memory 104 to generate first information / signals, and then transmit a wireless signal including the first information / signals through the transceiver 106. The processor 102 may receive a wireless signal including second information / signals through the transceiver 106, and then store information obtained by processing the second information / signals in the memory 104. The memory 104 may be connected to the processor 102 and may store various pieces of information related to the operation of the processor 102. For example, the memory 104 may store software codes including instructions for executing all or part of a process controlled by the processor 102 or for executing the descriptions, functions, processes, proposals, methods, and / or operational flowcharts disclosed in this document. The processor 102 and the memory 104 may be part of a communication modem / circuit / chip designed to implement a RAT (e.g., LTE or NR). The transceiver 106 may be connected to the processor 102 and transmit and / or receive wireless signals through one or more antennas 108. Each of the transceivers 106 may include a transmitter and / or a receiver. The transceiver 106 may be used interchangeably with a radio frequency (RF) unit. In the present disclosure, the wireless device may be a communication modem / circuit / chip.

[0449] Hereinafter, a description will be given of instructions and / or operations controlled by the processor 102 and stored in the memory 104 of the first wireless device 100 according to an embodiment of the present disclosure.

[0450] Although the following operations are described from the perspective of the processor 102 in the context of controlling operations of the processor 102 , software codes for performing the operations may be stored in the memory 104 .

[0451] Specifically, the processor 102 may control to send MsgA to the BS. In this case, MsgA may include only PRACH or may include PUSCH and PRACH. When MsgA includes both PRACH and PUSCH, the processor 102 may send PUSCH after sending PRACH.

[0452] In this case, the processor 102 may transmit the PRACH while knowing the SFN used to transmit the PRACH, or may transmit the PRACH without knowing the SFN used to transmit the PRACH. The details thereof may be found in the above-mentioned embodiments.

[0453] The processor 102 may control to monitor and receive the DCI scheduling MsgB. The processor 102 may descramble the CRC from the DCI based on the MsgB-RNTI. Upon confirming the CRC, the processor 102 may decode the information bits included in the DCI.

[0454] The processor 102 may decode the lower two bits of the index of the SFN in the DCI, and then compare the lower two bits with the lower two bits of the index of the SFN used to transmit the PRACH.

[0455] However, if the processor 102 controls to transmit the PRACH without knowing the SFN used to transmit the PRACH, the processor 102 may not compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH.

[0456] The details can be found in the above-mentioned embodiments.

[0457] The processor 102 may control to receive the PDSCH for RAR based on the DCI. In this case, the processor 102 may receive the PDSCH according to the result of comparing the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH. On the other hand, the processor 102 may control to receive the PDSCH regardless of the result of comparing the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH.

[0458] In addition, depending on whether the processor 102 can compare the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH and / or according to the comparison result, the processor 102 can control to receive the PDSCH or perform other operations instead of receiving the PDSCH.

[0459] Depending on whether the processor 102 is capable of comparing the lower two bits of the SFN included in the DCI with the lower two bits of the SFN used to transmit the PRACH and / or the operation of the processor 102 according to the comparison result may be based on the above-mentioned embodiments.

[0460] The processor 102 may control to transmit a UL signal based on the PDSCH. In this case, the UL signal transmitted by the processor 102 may vary depending on the RAR of the PDSCH and whether the PDSCH is received. For example, if the RAR is a fallback RAR, the processor 102 may control to transmit a PRACH for a type 1 RACH procedure. As another example, if the RAR is a successful RAR, the processor 102 may control to transmit the PUCCH by including HARQ-ACK information corresponding to the ACK in the PUCCH.

[0461] If the processor 102 does not receive the PDSCH, the processor 102 may control to transmit the PRACH according to the Type 1 RACH procedure or to transmit (or retransmit) the PRACH and the PUSCH according to the Type 2 RACH.

[0462] The operation of the processor 102 may be based on one or more of the above embodiments. That is, the operation of the processor 102 may be performed based on any one of the above embodiments or any combination of two or more of the above embodiments.

[0463] Hereinafter, a description will be given of instructions and / or operations controlled by the processor 202 and stored in the memory 204 of the second wireless device 200 according to an embodiment of the present disclosure.

[0464] Although the following operations are described from the perspective of the processor 202 in the context of controlling operations of the processor 202 , software codes for performing the operations may be stored in the memory 204 .

[0465] The processor 202 may control receiving MsgA from the UE. In this case, MsgA may include only PRACH or may include PUSCH and PRACH. When MsgA includes both PRACH and PUSCH, the processor 202 may control receiving PUSCH after receiving PRACH.

[0466] The processor 202 may control to decode MsgA and transmit DCI having CRC scrambled by MsgB-RNTI to the UE based on the decoding result.

[0467] The processor 202 may control to transmit the PDSCH for the RAR based on the DCI. If the processor 202 detects both the PRACH and the PUSCH, the RAR may be a successful RAR. If the processor 202 detects only the PRACH but not the PUSCH, the RAR may be a fallback RAR. If the processor 202 does not detect the PRACH and the PUSCH, the processor 202 may control not to transmit the DCI and the PDSCH.

[0468] If the processor 202 transmits the PDSCH, the processor 202 may control to receive a UL signal based on the PDSCH. In this case, the UL signal may vary depending on the RAR of the PDSCH and whether the UE receives the PDSCH. For example, if the RAR is a fallback RAR, the processor 202 may control to receive a PRACH for a type 1 RACH procedure. As another example, if the RAR is a successful RAR, the processor 202 may control to receive a PUCCH including HARQ-ACK information corresponding to an ACK.

[0469] If the UE does not receive the PDSCH, the processor 202 may control to receive the PRACH according to the Type 1 RACH procedure or to receive (or re-receive) the PRACH and the PUSCH according to the Type 2 RACH procedure.

[0470] The above operations of the processor 202 may be based on one or more of the above embodiments. That is, the operations of the processor 202 may be performed based on any one of the above embodiments or any combination of two or more of the above embodiments.

[0471] The hardware elements of the wireless devices 100 and 200 will now be described in more detail. One or more protocol layers may be implemented by, but not limited to, one or more processors 102 and 202. For example, one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as physical (PHY), medium access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), RRC, and service data adaptation protocol (SDAP)). According to the description, functions, processes, proposals, methods, and / or operational flowcharts disclosed in this document, one or more processors 102 and 202 may generate one or more protocol data units (PDUs) and / or one or more service data units (SDUs). One or more processors 102 and 202 may generate messages, control information, data, or information according to the description, functions, processes, proposals, methods, and / or operational flowcharts disclosed in this document, and provide the messages, control information, data, or information to one or more transceivers 106 and 206. One or more processors 102 and 202 may generate a signal (e.g., a baseband signal) including a PDU, SDU, message, control information, data, or information according to the description, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this document, and provide the generated signal to one or more transceivers 106 and 206. One or more processors 102 and 202 may receive a signal (e.g., a baseband signal) from one or more transceivers 106 and 206, and obtain the PDU, SDU, message, control information, data, or information according to the description, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this document.

[0472] One or more processors 102 and 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. One or more processors 102 and 202 may be implemented by hardware, firmware, software, or a combination thereof. For 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 one or more processors 102 and 202. The descriptions, functions, processes, proposals, methods, and / or operational flow charts disclosed in this document may be implemented using firmware or software, and the firmware or software may be configured to include modules, processes, or functions. Firmware or software configured to execute the descriptions, functions, processes, proposals, methods, and / or operational flow charts disclosed in this document may be included in one or more processors 102 and 202, or may be stored in one or more memories 104 and 204 and executed by one or more processors 102 and 202. The descriptions, functions, processes, proposals, methods and / or operational flow charts disclosed in this document may be implemented using firmware or software in the form of codes, instructions and / or instruction sets.

[0473] One or more memories 104 and 204 may be connected to one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, codes, instructions, and / or commands. One or more memories 104 and 204 may be configured to include read-only memory (ROM), random access memory (RAM), electrically erasable programmable read-only memory (EPROM), flash memory, hard drive, register, cache memory, computer-readable storage medium, and / or combinations thereof. One or more memories 104 and 204 may be located inside and / or outside of one or more processors 102 and 202. One or more memories 104 and 204 may be connected to one or more processors 102 and 202 via various technologies such as wired or wireless connections.

[0474] One or more transceivers 106 and 206 can send user data, control information and / or wireless signals / channels mentioned in the method and / or operation flow chart of this document to one or more other devices. One or more transceivers 106 and 206 can receive user data, control information and / or wireless signals / channels mentioned in the description, function, process, proposal, method and / or operation flow chart disclosed in this document from one or more other devices. For example, one or more transceivers 106 and 206 can be connected to one or more processors 102 and 202 and send and receive wireless signals. For example, one or more processors 102 and 202 can perform control so that one or more transceivers 106 and 206 can send user data, control information or wireless signals to one or more other devices. One or more processors 102 and 202 can perform control so that one or more transceivers 106 and 206 can receive user data, control information or wireless signals from one or more other devices. One or more transceivers 106 and 206 may be connected to one or more antennas 108 and 208, and one or more transceivers 106 and 206 may be configured to send and receive user data, control information, and / or wireless signals / channels mentioned in the description, functions, processes, proposals, methods, and / or operation flow charts disclosed in this document through one or more antennas 108 and 208. In this document, one or more antennas may be multiple physical antennas or more logical antennas (e.g., antenna ports). One or more transceivers 106 and 206 may convert the received wireless signals / channels from RF band signals to baseband signals so as to process the received user data, control information, and wireless signals / channels using one or more processors 102 and 202. One or more transceivers 106 and 206 may convert the user data, control information, and wireless signals / channels processed using one or more processors 102 and 202 from baseband signals to RF band signals. To this end, one or more of the transceivers 106 and 206 may include (analog) oscillators and / or filters.

[0475] Fig.25 Another example of a wireless device applied to the present disclosure is illustrated. The wireless device may be implemented in various forms according to use cases / services (see Fig.23 ).

[0476] Reference Fig.25 , the wireless devices 100 and 200 may correspond to Fig.24The wireless devices 100 and 200 may be configured to include various elements, components, units / parts 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 an additional component 140. The communication unit 110 may include a communication circuit 112 and a transceiver 114. For example, the communication circuit 112 may include Fig.24 The one or more processors 102 and 202 and / or the one or more memories 104 and 204 of the present invention. For example, the transceiver 114 may include Fig.24 The control unit 120 is electrically connected to the communication unit 110, the memory 130, and the additional components 140, and provides overall control of the wireless device. For example, the control unit 120 may control the electrical / mechanical operation of the wireless device based on the program / code / instruction / information stored in the memory unit 130. The control unit 120 may send information stored in the memory unit 130 to the outside (e.g., other communication devices) through a wireless / wired interface via the communication unit 110, or store information received from the outside (e.g., other communication devices) through a wireless / wired interface in the memory unit 130 via the communication unit 110.

[0477] The additional component 140 may be configured in various ways depending on the type of the wireless device. For example, the additional component 140 may include at least one of a power unit / battery, an input / output (I / O) unit, a drive unit, and a computing unit. The wireless device may be, but is not limited to, a robot ( Fig.23 100a), vehicles ( Fig.23 100b-1 and 100b-2), XR devices ( Fig.23 100c), handheld device ( Fig.23 100d), household appliances ( Fig.23 100e), IoT devices ( Fig.23 100f), digital broadcast terminal, hologram device, public safety device, MTC device, medical device, Fintech device (or financial device), security device, climate / environmental device, AI server / device ( Fig.23 400), BS( Fig.23 200), network node, etc. Depending on the use case / service, the wireless device can be mobile or fixed.

[0478] exist Fig.25In the wireless devices 100 and 200, all the various elements, components, units / parts 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 connected wirelessly 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 the first unit (e.g., 130 and 140) may be connected wirelessly through the communication unit 110. Each element, component, unit / part and / or module in the wireless devices 100 and 200 may also include one or more elements. For example, the control unit 120 may be configured with a set of one or more processors. For example, the control unit 120 may be configured with a group of communication control processors, application processors, electronic control units (ECUs), graphics processing units, and memory control processors. In another example, the memory 130 may be configured with RAM, dynamic RAM (DRAM), ROM, flash memory, volatile memory, non-volatile memory, and / or a combination thereof.

[0479] The following will describe with reference to the accompanying drawings Fig.25 An implementation example of .

[0480] Fig.26 1 is a block diagram illustrating a handheld device 100 to which another embodiment of the present disclosure may be applied. The handheld device may include a smartphone, a tablet (also referred to as a smart tablet), a wearable device (e.g., a smart watch or smart glasses), and a portable computer (e.g., a laptop computer). The handheld device 100 may be referred to as a mobile station (MS), a user terminal (UT), a mobile subscriber station (MS), a subscriber station (SS), an advanced mobile station (AMS), or a wireless terminal (WT).

[0481] Reference Fig.26 , the handheld device 100 may include an antenna unit 108, a communication unit 110, a control unit 120, a memory unit 130, a power supply unit 140a, an interface unit 140b, and an input / output (I / O) unit 140c. The antenna unit 108 may be configured as a part of the communication unit 110. Blocks 110 to 130 / 140a to 140c correspond to Fig.25 Blocks 110 to 130 / 140.

[0482] The communication unit 110 may send and receive signals (e.g., data and control signals) to and from another wireless device and a BS. The control unit 120 may perform various operations by controlling the elements of the handheld device 100. The control unit 120 may include an application processor (AP). The memory unit 130 may store data / parameters / programs / codes / commands required for the operation of the handheld device 100. In addition, the memory unit 130 may store input / output data / information. The power supply unit 140a may supply power to the handheld device 100 and include a wired / wireless charging circuit and a battery. The interface unit 140b may support the connection between the handheld device and other external devices. The interface unit 140b may include various ports (e.g., audio I / O ports and video I / O ports) for connecting to external devices. The I / O unit 140c may receive or output video information / signals, audio information / signals, data and / or user input information. The I / O unit 140c may include a camera, a microphone, a user input unit, a display 140d, a speaker and / or a tactile module.

[0483] For example, for data communication, the I / O unit 140c can acquire information / signals (e.g., touch, text, voice, image, and video) received from the user, and store the acquired information / signals in the memory unit 130. The communication unit 110 can convert the information / signals into radio signals and directly transmit the radio signals to another device or BS. In addition, the communication unit 110 can receive radio signals from another device or BS, and then restore the received radio signals to the original information / signals. The restored information / signals can be stored in the memory unit 130 and output in various forms (e.g., text, voice, image, video, and tactile effects) through the I / O unit 140c.

[0484] Fig. 27 The vehicle or autonomous driving vehicle applied to the present disclosure is illustrated. The vehicle or autonomous driving vehicle can be implemented as a mobile robot, a car, a train, a manned / unmanned aerial vehicle (AV), a ship, etc.

[0485] Reference Fig. 27 , the vehicle or autonomous driving vehicle 100 may include an antenna unit 108, a communication unit 110, a control unit 120, a drive unit 140a, a power supply unit 140b, a sensor unit 140c, and an autonomous driving unit 140d. The antenna unit 108 may be configured as a part of the communication unit 110. Blocks 110 / 130 / 140a to 140d correspond to Fig.24 Block 110 / 130 / 140.

[0486] The communication unit 110 may send and receive signals (e.g., data and control signals) to and from external devices such as other vehicles, BSs (e.g., gNBs and roadside units), and servers. The control unit 120 may perform various operations by controlling elements of the vehicle or autonomous driving vehicle 100. The control unit 120 may include an ECU. The drive unit 140a may enable the vehicle or autonomous driving vehicle 100 to travel on a road. The drive unit 140a may include an engine, a motor, a powertrain, wheels, brakes, a steering device, etc. The power supply unit 140b may supply power to the vehicle or autonomous driving vehicle 100, and include a wired / wireless charging circuit, a battery, etc. The sensor unit 140c may acquire information about the vehicle status, surrounding environment information, user information, etc. The sensor unit 140c 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 location 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, a lighting sensor, a pedal position sensor, etc. The autonomous driving unit 140d may implement a technology for maintaining a lane in which the vehicle is driving, a technology for automatically adjusting a speed (such as adaptive cruise control), a technology for autonomous driving along a determined path, a technology for driving by automatically setting a route with a destination set, and the like.

[0487] For example, the communication unit 110 may receive map data, traffic information data, etc. from an external server. The autonomous driving unit 140d may generate an autonomous driving route and a driving plan from the obtained data. The control unit 120 may control the drive unit 140a so that the vehicle or the autonomous driving vehicle 100 may move along the autonomous driving route according to the driving plan (e.g., speed / direction control). During autonomous driving, the communication unit 110 may obtain the latest traffic information data from the external server irregularly / periodically, and obtain surrounding traffic information data from adjacent vehicles. During autonomous driving, the sensor unit 140c may obtain information about the vehicle state and / or surrounding environment information. The autonomous driving unit 140d may update the autonomous driving route and driving plan based on the newly obtained data / information. The communication unit 110 may transmit information about the vehicle position, autonomous driving route, and / or driving plan to an external server. The external server may use AI technology to predict traffic information data based on information collected from the vehicle or autonomous driving vehicle, and provide the predicted traffic information data to the vehicle or autonomous driving vehicle.

[0488] The embodiments of the present disclosure described below herein are combinations of elements and features of the present disclosure. Unless otherwise mentioned, elements or features may be considered to be selective. Each element or feature may be practiced without being combined with other elements or features. In addition, the embodiments of the present disclosure may be constructed by combining the parts of elements and / or features. The order of operations described in the embodiments of the present disclosure may be rearranged. Some constructions of any one embodiment may be included in another embodiment and may be replaced by the corresponding construction of another embodiment. It will be apparent to those skilled in the art that claims that are not explicitly cited in the attached claims may be presented in combination as embodiments of the present disclosure, or may be included as new claims by subsequent amendments after the application is submitted.

[0489] In the embodiments of the present disclosure, the data transmission and reception relationship between the BS, the relay and the MS is described. In some cases, a specific operation described as being performed by the BS may be performed by an upper node of the BS. That is, it is obvious that in a network consisting of a plurality of network nodes including the BS, various operations performed for communication with the MS may be performed by the BS or a network node other than the BS. The term "BS" may be replaced by the term "fixed station", "Node B", "enhanced Node B (eNode B or eNB)", "access point", etc.

[0490] Those skilled in the art will recognize that the present disclosure may be performed in other specific ways different from those set forth herein without departing from the spirit and essential features of the present disclosure. Therefore, the above embodiments should be interpreted as illustrative and not restrictive in all respects. The scope of the present disclosure should be determined by the appended claims and their legal equivalents, rather than by the above description, and all changes falling within the meaning and equivalent scope of the appended claims are intended to be included therein.

[0491] Industrial Applicability

[0492] A method and apparatus for performing a random access channel (RACH) procedure have been described based on a fifth generation (5G) new radio access technology (New RAT) system, but the method and apparatus are applicable to various wireless communication systems including a 5G NR system.

Claims

1. A method for transmitting an uplink signal by a user equipment UE in a wireless communication system, the method comprising the following steps: Sending a physical random access channel PRACH; monitoring downlink control information DCI in response to the PRACH; Receiving a physical downlink shared channel (PDSCH) based on the DCI; and Based on the UE being unable to check whether two bits of a first system frame number SFN included in the DCI are the same as two bits of a second SFN for transmitting the PRACH, regardless of whether the two bits of the first SFN are the same as the two bits of the second SFN, transmitting the uplink signal based on the PDSCH, The uplink signal is sent based on the UE being able to check whether the two bits of the first SFN are the same as the two bits of the second SFN and based on the UE confirming that the two bits of the first SFN are the same as the two bits of the second SFN.

2. The method according to claim 1, wherein: Based on the UE being able to check whether the two bits of the first SFN are identical to the two bits of the second SFN, and based on the UE confirming that the two bits of the first SFN are not identical to the two bits of the second SFN, the uplink signal is not transmitted.

3. The method according to claim 1, wherein: The length of the monitoring window of the DCI exceeds 10 ms.

4. The method according to claim 1, wherein: The DCI is scrambled by MsgB - Radio Network Temporary Identifier RNTI.

5. A user equipment UE configured to send an uplink signal in a wireless communication system, the UE comprising: at least one transceiver; at least one processor; as well as at least one memory operatively connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations comprising: Sending a physical random access channel PRACH by the at least one transceiver; monitoring downlink control information DCI in response to the PRACH; Receiving, by the at least one transceiver, a physical downlink shared channel (PDSCH) based on the DCI; and Based on the UE being unable to check whether two bits of a first system frame number SFN included in the DCI are the same as two bits of a second SFN for transmitting the PRACH, regardless of whether the two bits of the first SFN are the same as the two bits of the second SFN, transmitting the uplink signal based on the PDSCH, The uplink signal is sent based on the UE being able to check whether the two bits of the first SFN are the same as the two bits of the second SFN and based on the UE confirming that the two bits of the first SFN are the same as the two bits of the second SFN.

6. The UE according to claim 5, wherein: Based on the UE being able to check whether the two bits of the first SFN are identical to the two bits of the second SFN, and based on the UE confirming that the two bits of the first SFN are not identical to the two bits of the second SFN, the uplink signal is not transmitted.

7. The UE according to claim 5, wherein: The length of the monitoring window of the DCI exceeds 10 ms.

8. The UE according to claim 5, wherein: The DCI is scrambled by MsgB - Radio Network Temporary Identifier RNTI.

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