Random access message transmission for reduced capability user equipment

Abstract

A base station and a user equipment (UE) may exchange messages to perform a random access channel (RACH) procedure. The UE performs measurements on a plurality of signal synchronization blocks (SSBs); selects M physical random access channel (PRACH) groups based on one or more of the measured SSBs satisfying a predetermined threshold; provides the measurements for the M PRACH groups to the base station in an initial access transmission for the RACH procedure; and monitors a random access response (RAR) message based on a repetition number of the RAR message indicated by the base station.

Description

Technical Field

[0001] The present application relates generally to wireless communications, and more particularly to random access message transmission for reduced capability user equipment. Background Art

[0002] Reduced Capability (Redcap) devices such as industrial wireless sensors, video surveillance, and wearable devices typically have reduced battery life and may be configured with various capabilities that require a smaller amount of power relative to devices supporting normal capabilities. Some Redcap devices may have a reduced number of receive / transmit (Rx / Tx) antennas and reduced bandwidth, such as 20 MHz instead of 100 MHz (as with normal-capable devices), which may result in significant coverage reduction and smaller transport block sizes for downlink transmissions including unicast PDSCH and broadcast messages such as random access response (RAR) (Msg2) transmissions. Summary of the invention

[0003] Some exemplary embodiments relate to a processor configured to perform operations including: performing measurements on a plurality of signal synchronization blocks (SSBs); selecting M physical random access channel (PRACH) groups based on one or more of the measured SSBs satisfying a predetermined threshold; providing measurements for the M PRACH groups to a base station in an initial access transmission for a RACH procedure; and monitoring a random access response (RAR) message based on a number of repetitions of the RAR message indicated by the base station.

[0004] Other exemplary embodiments relate to a processor configured to perform operations including: receiving, in an initial access transmission for a RACH procedure, measurements of a plurality of signal synchronization blocks (SSBs) for M physical random access channel (PRACH) groups, the M PRACH groups being selected by a user equipment (UE) based on one or more of the measured SSBs satisfying a predetermined threshold; indicating a repetition number of a random access response (RAR) message to the UE, wherein the UE monitors the RAR message based on the repetition number; and transmitting the RAR message with the repetition number. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 Exemplary network arrangements are shown according to various exemplary embodiments.

[0006] Figure 2 An exemplary UE according to various exemplary embodiments is shown.

[0007] Figure 3 Exemplary network cells are shown according to various exemplary embodiments.

[0008] Figure 4 An exemplary multiplexing configuration for two PRACH groups is shown according to various exemplary embodiments.

[0009] Figure 5 An exemplary reuse of reserved bits in DCI format 1_0 according to various exemplary embodiments is shown.

[0010] Figure 6 A table for indicating a repetition number using one of two different scrambling sequences according to various exemplary embodiments is shown.

[0011] Figure 7 An exemplary frequency domain resource allocation (FDRA) for Msg2 repetition is shown according to various exemplary embodiments.

[0012] Figure 8 A signaling diagram for multi-beam / multi-TRP repetition for MsgB repetition in an exemplary two-step RACH process according to various exemplary embodiments is shown.

[0013] Figure 9a An interleaving pattern for FDRA resource mapping according to various exemplary embodiments is shown.

[0014] Figure 9b A non-interleaved mode for FDRA resource mapping according to various exemplary embodiments is shown.

[0015] Fig.10 An exemplary PDCCH MO splitting operation between different QCL hypotheses associated with two SSBs reported by a UE is shown according to various exemplary embodiments.

[0016] Fig.11 An exemplary MsgB repeat partitioning operation is shown according to various exemplary embodiments.

[0017] Fig.12 Examples of different alternatives for Msg2 / MsgB transmission according to various exemplary embodiments are shown.

[0018] Fig.13 A table showing redundancy version determination for Msg2 repetition according to various exemplary embodiments is shown. DETAILED DESCRIPTION

[0019] The exemplary embodiments may be further understood with reference to the following description and associated drawings, wherein similar elements have the same reference numerals. The exemplary embodiments describe operations for determining a repetition number of a random access (RACH) procedure transmission from a base station, such as a random access response (RAR) message (Msg2 / MsgB). The repetition number may be signaled to a user equipment (UE) for use in determining a monitoring opportunity (MO) for RACH transmissions, and may be based on a signal synchronization block (SSB) measurement performed by the UE and reported to the base station. Specific embodiments relate to either or both of a two-step or four-step RACH procedure.

[0020] network / equipment

[0021] Figure 1 An exemplary network arrangement 100 according to various exemplary embodiments is shown. The exemplary network arrangement 100 includes a plurality of UEs 110, 112. Those skilled in the art will appreciate that a UE may be any type of electronic component configured to communicate via a network, such as a component of a connected car, a mobile phone, a tablet computer, a smart phone, a tablet phone, an embedded device, a wearable device, an Internet of Things (IoT) device, etc. It should also be appreciated that an actual network arrangement may include any number of UEs used by any number of users. Therefore, an example with two UEs 110, 112 is provided for illustrative purposes only. In some exemplary embodiments described below, a UE group may be employed to perform corresponding channel measurements.

[0022] UE 110, 112 can communicate directly with one or more networks. In the example of network configuration 100, the networks with which UE 110, 112 can wirelessly communicate are 5G NR radio access network (5G NR-RAN) 120, LTE radio access network (LTE-RAN) 122, and wireless local area network (WLAN) 124. Therefore, UE 110, 112 may include a 5G NR chipset that communicates with 5G NR-RAN 120, an LTE chipset that communicates with LTE-RAN 122, and an ISM chipset that communicates with WLAN 124. However, UE 110, 112 may also communicate with other types of networks (e.g., traditional cellular networks), and UE 110 may also communicate with the network via a wired connection. Referring to the exemplary embodiment, UE 110, 112 may establish a connection with 5G NR-RAN 120 and / or LTE-RAN 122.

[0023] 5G NR-RAN 120 and LTE-RAN 122 may be parts of cellular networks that may be deployed by cellular providers (e.g., Verizon, AT&T, T-Mobile, etc.). These networks 120, 122 may include, for example, cells or base stations (NodeB, eNodeB, HeNB, eNBS, gNB, gNodeB, macrocell base stations, microcell base stations, small cell base stations, femtocell base stations, etc.) configured to send and receive traffic from UEs equipped with appropriate cellular chipsets. WLAN 124 may include any type of wireless local area network (WiFi, hotspot, IEEE 802.11x network, etc.).

[0024] UE 110, 112 may be connected to 5G NR-RAN 120 via at least one of next generation Node B (gNB) 120A and / or gNB 120B. Reference to two gNBs 120A, 120B is for illustrative purposes only. Exemplary embodiments may be applied to any appropriate number of gNBs. For example, UE 110, 112 may be connected to multiple gNBs simultaneously in a multi-cell CA configuration and exchange data. UE 110, 112 may also be connected to LTE-RAN 122 via either or both of eNBs 122A, 122B, or to any other type of RAN, as described above. In network arrangement 100, UE 110 is shown as having a connection to gNB 120A, while UE 112 is shown as having a connection to gNB 120B. According to certain exemplary embodiments, the connection of UE 110 to gNB 120A may be at a frequency greater than 52.6 GHz.

[0025] In addition to networks 120, 122, and 124, network arrangement 100 also includes a cellular core network 130, the Internet 140, an IP multimedia subsystem (IMS) 150, and a network service backbone 160. Cellular core network 130 (e.g., 5GC of NR) can be considered as an interconnected collection of components that manage the operation and traffic of a cellular network. Cellular core network 130 also manages traffic flowing between the cellular network and the Internet 140.

[0026] The IMS 150 may be generally described as an architecture for delivering multimedia services to the UE 110 using the IP protocol. The IMS 150 may communicate with the cellular core network 130 and the Internet 140 to provide multimedia services to the UE 110. The network service backbone 160 communicates directly or indirectly with the Internet 140 and the cellular core network 130. The network service backbone 160 may be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a set of services that may be used to extend the functionality of the UE 110 to communicate with various networks.

[0027] Figure 2 An exemplary UE 110 is shown according to various exemplary embodiments. Figure 1 100 is used to describe the UE 110. The UE 110 may represent any electronic device and may include a processor 205, a memory arrangement 210, a display device 215, an input / output (I / O) device 220, a transceiver 225, and other components 230. The other components 230 may include, for example, an audio input device, an audio output device, a battery providing a limited power source, a data acquisition device, a port for electrically connecting the UE 110 to other electronic devices, a sensor for detecting the status of the UE 110, and the like. Figure 2 The UE 110 shown may also represent UE 112.

[0028] The processor 205 may be configured to execute a plurality of engines of the UE 110. For example, the engines may include a random access (RACH) procedure monitoring engine 235 for performing operations including selecting a PRACH group for a RACH procedure and monitoring a random access response (RAR) message based on a repetition number indicated by a base station, which will be described in detail below.

[0029] The above-described engine as an application (e.g., program) executed by the processor 205 is merely exemplary. The functions associated with the engine may also be represented as an independently integrated component of the UE 110, or may be a modular component coupled to the UE 110, such as an integrated circuit with or without firmware. For example, an integrated circuit may include an input circuit system for receiving a signal and a processing circuit system for processing signals and other information. The engine may also be embodied as an application or multiple separate applications. In addition, in some UEs, the functionality described for the processor 205 is shared between two or more processors such as a baseband processor and an application processor. The exemplary embodiments may be implemented in any of these or other configurations of the UE.

[0030] The memory 210 may be a hardware component configured to store data related to operations performed by the UE 110. The display device 215 may be a hardware component configured to display data to a user, and the I / O device 220 may be a hardware component that enables a user to perform input. The display device 215 and the I / O device 220 may be separate components or may be integrated together (such as a touch screen). The transceiver 225 may be a hardware component configured to establish a connection with the 5G-NR RAN 120, the LTE RAN 122, etc. Thus, the transceiver 225 may operate on a variety of different frequencies or channels (e.g., a continuous frequency group). For example, when, for example, NR-U is configured, the transceiver 225 may operate on an unlicensed spectrum.

[0031] Figure 3 An exemplary network cell, in this case a gNB 120A, is shown according to various exemplary embodiments. As described above with reference to UE 110, gNB 120A may represent a cell that provides service as a PCell or SCell or is configured independently from UE 110. gNB 120A may represent any access node of a 5G NR network through which UEs 110, 112 may establish connections and manage network operations. Figure 3 The gNB 120A shown may also represent gNB 120B.

[0032] The gNB 120A may include a processor 305, a memory arrangement 310, an input / output (I / O) device 320, a transceiver 325, and other components 330. The other components 330 may include, for example, an audio input device, an audio output device, a battery, a data acquisition device, a port for electrically connecting the gNB 120A to other electronic devices, and the like.

[0033] The processor 305 may be configured to execute a plurality of engines of the gNB 120A. For example, the engines may include a random access (RACH) process engine 335 for performing operations including receiving an initial access message from a user equipment and transmitting a random access response (RAR) message with a given repetition number based on PRACH channel conditions, which will be described in detail below.

[0034] The engines described above are each represented as an application (e.g., a program) executed by the processor 305 and are exemplary only. The functionality associated with the engines may also be represented as independently integrated components of the gNB 120A, or may be modular components coupled to the gNB 120A, such as integrated circuits with or without firmware. For example, an integrated circuit may include input circuitry for receiving signals and processing circuitry for processing signals and other information. In addition, in some gNBs, the functionality described for the processor 305 is split between multiple processors (e.g., a baseband processor, an application processor, etc.). The exemplary embodiments may be implemented in any of these or other configurations of the gNB.

[0035] The memory 310 may be a hardware component configured to store data related to operations performed by the UE 110, 112. The I / O device 320 may be a hardware component or port that enables a user to interact with the gNB 120A. The transceiver 325 may be a hardware component configured to exchange data with the UE 110, 112 and any other UE in the system 100. The transceiver 325 may operate on a variety of different frequencies or channels (e.g., a set of continuous frequencies). For example, when the NR-U function is configured, the transceiver 325 may operate on an unlicensed bandwidth. Thus, the transceiver 325 may include one or more components (e.g., a radio component) to enable data exchange with various networks and UEs.

[0036] Random access procedure for reduced capability user equipment

[0037] In the RAN 86 meeting, the work item "Supporting Reduced Capability NR Devices" was approved to study a list of user equipment (UE) features and parameters for devices with lower end capabilities relative to Release 16 enhanced mobile broadband (eMBB) and ultra-reliable low latency communications (URLLC) new radio (NR) devices to serve use cases including industrial wireless sensors, video surveillance, and wearable devices with eMBB and / or URLLC capabilities. More specifically, a list of potential UE reduction features was identified for further study, including UE receive / transmit (Rx / Tx) antenna number reduction, UE bandwidth reduction, half-duplex frequency division duplex (FDD), UE processing time relaxation, and UE processing capability relaxation.

[0038] Reducing the number and bandwidth of Rx antennas (e.g., reducing the bandwidth from 100MHz to 20MHz) results in reduced coverage and smaller transport block sizes not only for unicast physical downlink shared channel (PDSCH) transmissions but also for broadcast messages (e.g., Msg2 random access response (RAR) transmissions in the random access channel (RACH) process). When the number of Rx antennas is reduced to 1, the Msg2 / Msg4 coverage is significantly affected. Therefore, it is necessary to develop solutions for recovering coverage loss to facilitate operator's cell planning and achieve comparable coverage performance of Redcap UEs with conventional eMBB UEs.

[0039] The UE sends the PRACH preamble as the first message from the UE to the base station when establishing initial access. In the contention-based random access (CBRA) procedure, the UE transmits a PRACH preamble (e.g., Msg1) with a preamble signature randomly selected by the UE from a preamble pool shared with other UEs in the cell. In the contention-free RA (CFRA) procedure, the UE uses a dedicated preamble provided specifically for the UE by the network via, for example, radio resource control (RRC) signaling or downlink control information (DCI) on the physical downlink control channel (PDCCH). In either procedure, the network responds to the detected RACH preamble (i.e., Msg1) with a random access response (RAR) (e.g., Msg2) on the physical downlink shared channel (PDSCH), which is scheduled by the PDCCH and includes a resource allocation (e.g., Msg3) for the UE's subsequent physical uplink shared channel (PUSCH) transmission. In CBRA, the network performs a contention resolution procedure and transmits Msg4 based on the detected UE identifier in the Msg3 PUSCH. The base station may use the repetition technique for Msg2 and Msg4 for coverage enhancement (CE).

[0040] According to certain aspects of the present disclosure, before initiating a random access (RACH) procedure with a serving cell, a Redcap UE may have information about an available set of physical RACH (PRACH) resources that may be used for transmission of a RACH preamble (Msg1). According to some embodiments, the set of PRACH resources available for Redcap UE transmissions may be divided into one or more groups. Different PRACH groups may be multiplexed in the same physical resource block (PRB) by using different cyclic shifts between PRACH groups in a code division multiplexing (CDM) manner. Alternatively, different PRACH groups may be frequency division multiplexed (FDM) or time division multiplexed (TDM).

[0041] Figure 4 An exemplary multiplexing configuration 400 for two PRACH groups according to various exemplary embodiments is shown. As shown in 405, a first PRACH group and a second PRACH group may be multiplexed using CDM with different cyclic shift (CS) values. As shown in 410 and 415, the first PRACH group and the second PRACH group may be multiplexed using FDM or TDM. In each of the three scenarios, a PRACH group may be selected based on the measured RSRP of a system synchronization block (SSB), which will be explained in further detail below.

[0042] A PRACH resource group may be mapped to a coverage recovery level (e.g., a maximum number of repetitions) for associated Msg2 and / or Msg4 transmissions. The PRACH resource group mapping may be determined as follows. For example, multiple reference signal received power (RSRP) thresholds may be defined in the parameter rsrp-ThresholdsSSBInfoList. These RSRP thresholds may be transmitted to the UE in a system information block (SIB) (e.g., SIB1) before the RACH process begins. In some embodiments, the RSRP thresholds may be defined by a standard (e.g., a 3GPP standard). The UE may also receive a criterion for selecting a corresponding PRACH group index based on RSRP measurement results, which may also be included in the parameter rsrp-ThresholdsSSBInfoList, for example. The UE may select a corresponding PRACH group based on the measured RSRP value of a synchronization signal block (SSB) that meets the threshold to help the gNB determine the number of repetitions for Msg2 and Msg4 transmissions in the RACH process. The following configurations may also be provided in the SIB for different PRACH groups to support different values: RA response (RAR) (eg, Msg2) window size and maximum number of repetitions of Msg2 / Msg4 transmissions.

[0043] According to some exemplary embodiments, multiple methods may be considered to indicate the number of repetitions of Msg2 transmission. In a first option, the number of repetitions may be fixed to a maximum value signaled in the SIB message as described above.

[0044] In a second option, the X bits in the scheduling DCI format 1_0 can be used to dynamically indicate the number of repetitions, where the cyclic redundancy check (CRC) is scrambled by the random access (RA) radio network temporary identifier (RNTI) (RA-RNTI) or MsgB-RNTI. For the second option, in some embodiments, the reserved bits of the X bits in the DCI format 1_0 (16 bits for RA-RNTI and 14 bits for MsgB-RNTI) can be reused to indicate the actual number of repetitions of Msg2 and / or Msg4 transmissions. The number of bits can be defined by X=[log2(I)], where I represents the total number of repetitions, which can be defined by a standard (e.g., a 3GPP standard) or signaled in SIB1 on a per-serving cell basis. For example, when I=4, the bits can represent the number of repetitions as {1, 2, 4, reserved}.

[0045] Figure 5An exemplary reuse of reserved bits 500 in DCI format 1_0 according to various exemplary embodiments is shown. DCI format 1_0 has 14 or 16 reserved bits, depending on whether the scrambling sequence is RA-RNTI or MsgB-RNTI. A repetition number field 505 is introduced, which includes X bits, depending on the value of I, such as I=4, as described above.

[0046] For the second option, in other embodiments, the number of repetitions can be determined by the scrambling sequence [w0, w1, ..., w 23 ] carries the cyclic redundancy check (CRC) bits of DCI format 1_0 to be scrambled. Figure 6 A table 600 is shown for indicating a repetition number using one of two different scrambling sequences. Column 605 shows the repetition number, such as R1, R2, R3, or R4. Column 610 shows the first scrambling sequence corresponding to the repetition number, and column 615 shows the second scrambling sequence corresponding to the repetition number.

[0047] Different approaches to improving Msg2 performance with a given "K" number of repetitions may be considered. According to some exemplary embodiments, resource determination that depends on the number of repetitions may be used in the frequency domain. When the "VRB to PRB mapping" information element (IE) in DCI format 1_0 is set to "1" (indicating staggered VRB to PRB) mapping, the virtual resource block (VRB) bundle j∈{0,1,...,N bundle -1} Based on the equation j = f(i,j) = rC + c + Δ i is mapped to a physical resource block (PRB) bundle, where i∈{0,...,K-1} represents the retransmission index. In this embodiment, Δ i =(C*i) / K. Parameter j = cR+r, where r = 0, 1, ..., R-1, and C = [N bundle / R. In some embodiments, Where L is the bundle size of RBs used for VRBs.

[0048] Figure 7 An exemplary frequency domain resource allocation (FDRA) 700 for Msg2 repetition according to various exemplary embodiments is shown. In the exemplary FDRA 700, it is assumed that L=2,N bundle =25 and K=4. According to the above equation, Δ i =(C*i) / K∈[0,3,6,9], and

[0049] The resources in the frequency domain are shifted across different repetitions. Figure 7 , each bundle includes 25 PRBs (e.g., N bundle=25), as marked by the VRB bundle index on the left (0-24). There are 4 bundle repetitions (e.g., K=4), as marked by the repetition index at the bottom (0-3). Then, consider that for repetition K=0, blocks 2, 4, 6 indexed by VRBs are mapped to PRBs 1, 2, 3, respectively. For repetition K=1, blocks 2, 4, 6 indexed by VRBs are mapped to PRBs 4, 5, 6, respectively. Therefore, for repetition K=1, Δ1=3. For repetition K=2, blocks 2, 4, 6 indexed by VRBs are mapped to PRBs 7, 8, 9, respectively. Therefore, for repetition K=2, Δ2=6. For repetition K=3, blocks 2, 4, 6 indexed by VRBs are mapped to PRBs 10, 11, 12, respectively. Therefore, for repetition K=3, Δ3=9. Therefore, this example shows how resources in the frequency domain can be shifted across different repetitions.

[0050] According to other exemplary embodiments, multi-beam / multi-TRP (transmit and receive point) repetition may be used for Msg2 / MsgB transmission.The first scenario involves MsgB repetition in a Type 2 Random Access (RACH) procedure.

[0051] Figure 8 A signaling diagram 800 for multi-beam / multi-TRP repetition for MsgB repetition in an exemplary two-step RACH process according to various exemplary embodiments is shown. Prior to the signaling shown in 800, the UE may be provided by a SIB (e.g., SIB1) whether to enable multi-beam / multi-TRP based retransmission for Msg2 or MsgB repetition. In 805, the UE receives an SSB transmission from a serving cell. Those skilled in the art will appreciate that each SSB may correspond to a beam. The UE will measure the RSRP of each SSB and select the "M" best RSRP measurements. Typically, best usually means the highest measured RSRP value. However, it should be understood that the RSRP values ​​may be evaluated in different ways to determine the M best values.

[0052] In 810, after transmitting the selected MsgA PRACH, the UE may provide the M best RSRP values ​​including the SS / PBCH block index to the gNB in ​​MsgA PUSCH. In this example, it may be considered that M=2.

[0053] In response to the PRACH transmission, the gNB transmits MsgB PDCCH / PDSCH in 815, and the UE attempts to detect DCI format 1_0 with a CRC scrambled by the corresponding RA-RNTI during a random access response (RAR) window, assuming a different spatial relationship. The detection of DCI format 1_0 may be performed in various ways.

[0054] In some exemplary embodiments, the UE may detect DCI format 1_0 by evenly dividing the monitoring opportunities (MO) and MsgB repetitions within the RAR window in the time domain for different spatial relationships. To continue the above example of M=2, the UE may use quasi-co-location (QCL) to divide the MO within the RAR window and MsgB repetitions with the SSB having the best RSRP value and the SSB having the second best RSRP value.

[0055] In other exemplary embodiments, the UE may detect DCI format 1_0 by unevenly partitioning PDCCH MO and MsgB repetition for different beams / TRPs with different SSB indices. In some exemplary embodiments, a set of uneven partitioning patterns for PDCCH MO and / or MsgB repetition may be defined in a standard (e.g., a 3GPP standard) or configured in SIB information. One or more of these partitioning patterns may be used in the scheduling DCI format 1_0 in the same manner as described above in the Figure 4 A similar approach as shown in is used to dynamically signal by reusing reserved bits.

[0056] For example, a partitioning factor α∈{1 / 4, 1 / 2, 3 / 4, 1} can be introduced in the SIB and signaled to determine the PDCCH MO and Msg B repetitions, as shown in Equation M ssb,0 =α*M total ;M sssb,1 =(1-α)*M total As shown in ssb,0 represents the MO quasi-co-located (QCLed) with the best / strongest SSB within the SSB reported by the UE in 810 of the above method 800, and M ssb,1 represents the MOs quasi-co-located by the suboptimal SSBs within these SSBs.

[0057] In addition, different mapping patterns can be defined to determine the precise time domain position of each MO with different spatial QCL relationships, thereby balancing random access delay and resource efficiency and taking into account UL beam switching delay. Figure 9a An interleaving pattern for FDRA resource mapping according to various exemplary embodiments is shown. Figure 9b A non-interleaved mode for FDRA resource mapping according to various exemplary embodiments is shown. Examples of interleaved mode and non-interleaved mode will be described below.

[0058] Fig.10 An exemplary PDCCH MO partitioning operation 1000 between different QCL hypotheses associated with two SSBs reported by a UE is shown according to various exemplary embodiments. In the exemplary operation 1000, it may be considered that α=3 / 4, M total=4, and multi-TRP repetition is enabled, as signaled in the SIB. Based on the exemplary two-step RACH procedure discussed above, the UE reports the best M=2 beams in MsgA PUSCH. The UE then monitors PDCCH MO with different spatial relationships according to the staggered or non-staggered mode discussed above. Fig.10 As shown, when the staggered mode is used, the UE monitors the first SSB at MO indexes 0, 2, and 3 within the RAR window and monitors the second SSB at MO index 1. When the non-staggered mode is used, the UE monitors the first SSB at MO indexes 0, 1, and 2 within the RAR window and monitors the second SSB at MO index 3.

[0059] In similar operation, the split factor based approach may be extended for MsgB RAR transmission over PDSCH. In some exemplary embodiments, a common split factor may be used for both MsgB PDCCH MO and MsgB PDSCH repetition. In other designs, separate split factors may be configured for MsgB PDCCH MO (e.g., in SIB1) and MsgB PDSCH repetition, such as α1 in SIB1 and α2 in DCI format 1_0.

[0060] Fig.11 An exemplary MsgB repetition partitioning operation 1100 according to various exemplary embodiments is shown. In the exemplary operation 1100, a common factor may be considered to indicate that α=3 / 4, I=4. Fig.11 In the example of , it can be seen that the staggered case has a smaller number of gaps for beam switching. However, this is just an example, and there may be scenarios where the non-staggered case has fewer switching gaps for MsgB repetition. Therefore, different exemplary embodiments may be used for different scenarios.

[0061] According to other exemplary embodiments, Msg2 may be sent in multiple repetitions in the time domain. In a first option, for Msg2 repetitions, if consecutive slots are associated with the same spatial relationship, the same symbol allocation (regardless of type A or type B RA) may be applied across consecutive slots. In a second option, the time domain position may be determined based on the start and length indicator value (SLIV) indicated by the scheduling DCI format 1_0, as described in detail below. The time slot at which the repetition starts is determined by n0+[(S+k* is given by, and the start symbol relative to the start of each consecutive time slot is given by modS+i*L, where This equation ensures that a single repetition does not cross slot boundaries to reduce RS overhead. The slot at which the repetition ends is given by 1. The end symbol relative to the start of the slot is given by Given.

[0062] Fig.12 Examples of different alternatives for using row 6 in the existing default TDRA table 5.1.2.1.1-2 for Msg2 / MsgB transmission in Rel-15 / Rel-16 are shown, assuming K=4 repetitions according to the equation discussed above.

[0063] For Msg2 repetition, the redundancy version (RV) used for repetition can be determined as follows. Fig.13 As shown in Table 1 / 2 of , the redundancy version (k∈0,...,K-1) to be applied on the kth repetition with the same spatial relationship is determined based on the RV field signaling by scheduling DCI format 1_0. In other designs, the RV sequence can be hard-coded in the specification, for example using the sequence <0,3,1,2>. It should be noted that if it is assumed that the RV sequences are quasi-co-located with different spatial relationships, the RV sequence should be restarted for retransmission. Table 2 is motivated by the following design: repetitions can be triggered by independent DCI formats, in which the remaining repetitions and associated RV sequences are indicated.

[0064] According to certain aspects of the present disclosure, an unused state "11" in DCI format 1_0 with a CRC scrambled by RA-RNTI or MsgB-RNTI can be used to introduce and indicate a smaller scaling factor, and thus an increased number of PRBs can be used to transmit Msg2 or MsgB with a lower code rate without repeating in the time domain. In some examples, S=0.125.

[0065] Those skilled in the art will appreciate that the exemplary embodiments described above may be implemented with any suitable software configuration or hardware configuration or combination thereof. Exemplary hardware platforms for implementing the exemplary embodiments may include, for example, Intel x86-based platforms with compatible operating systems, Windows OS, Mac platforms and MAC OS, mobile devices with operating systems such as iOS, Android, etc. In other examples, the exemplary embodiments of the above methods may be embodied as a program including lines of code stored on a non-transitory computer-readable storage medium, which, when compiled, may be executed on a processor or microprocessor.

[0066] Although this patent application describes various combinations of various aspects, each with different features, those skilled in the art will understand that any feature of one aspect may be combined with features of other aspects or features that are not functionally or logically inconsistent with the operation or function of the device of the aspects disclosed in the present invention in any manner not publicly denied.

[0067] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0068] It will be apparent to those skilled in the art that various modifications may be made to the present disclosure without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to cover modifications and variations of the present disclosure, provided that these modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. A method performed by one or more processors, the method comprising: An indication of whether receiving multi-beam or multi-transmit and receive points, i.e., multi-TRP retransmission, is enabled; Performing measurements on a plurality of signal synchronization blocks SSB; Selecting M physical random access channel (PRACH) groups based on one or more of the measured SSBs satisfying a predetermined threshold; providing said measurements for said M PRACH groups to a base station in an initial access transmission for a RACH procedure; monitoring the random access response (RAR) message based on a repetition number of the RAR message indicated by the base station; as well as The monitoring occasions MO for the RAR message are divided across the M PRACH groups.

2. The method of claim 1 , wherein the measurement comprises a Reference Signal Received Power (RSRP) measurement, and the predetermined threshold for the RSRP measurement is hard-coded in the specification or signaled in a System Information Block (SIB) and is based on the selected PRACH group.

3. The method according to claim 2, wherein a maximum number of repetitions of the RAR message or a RAR message window size is provided in the SIB. 4 . The method according to claim 3 , wherein the repetition number for the RAR message is fixed to the maximum repetition number or is dynamically indicated in scheduling downlink control information DCI format 1_0. 5 . The method according to claim 4 , wherein the DCI format 1_0 includes X reserved bits, the X reserved bits are reused to indicate the repetition number, and the value of X is based on a radio network temporary identifier (RNTI). 6 . The method according to claim 4 , wherein the repetition number is carried by a scrambling sequence to scramble cyclic redundancy check (CRC) bits in the DCI format 1_0.

7. The method of claim 1, wherein a frequency domain resource allocation (FDRA) for the RAR message comprises frequency resources shifted across different repetitions of the RAR message.

8. The method of claim 1, wherein the MO for the RAR message is evenly divided across the PRACH groups in the time domain for different spatial relationships.

9. The method of claim 1, wherein the MO for the RAR message is unevenly divided across the PRACH groups in the time domain based on a division pattern, The partitioning mode is either hard-coded in the specification or dynamically signaled in the scheduling DCI format 1_0.

10. The method of claim 9, wherein the partitioning mode comprises an interleaved mode or a non-interleaved mode.

11. The method according to claim 1, wherein: For the time domain, if consecutive time slots are associated with the same spatial relationship, the same symbol allocation applies across the time slots.

12. The method of claim 1, wherein the RV for the RAR message is applied based on a redundancy version RV field signaled in a scheduling DCI format 1_0.

13. The method according to claim 1, wherein the RACH procedure is any one of a two-step RACH or a four-step RACH.

14. A method performed by one or more processors, the method comprising: receiving, in an initial access transmission for a RACH procedure, measurements of a plurality of signal synchronization blocks (SSBs) for M physical random access channel (PRACH) groups, the M PRACH groups being selected by a user equipment (UE) based on one or more of the measured SSBs satisfying a predetermined threshold; Indicating whether multi-beam or multi-transmission and reception point, i.e., multi-TRP retransmission is enabled, wherein the UE divides the monitoring occasions MO for the RAR message across the M PRACH groups based on the indication; indicating a repetition number of a random access response (RAR) message to the UE, wherein the UE monitors the RAR message based on the repetition number; and The RAR message is transmitted with the repetition number.

15. The method of claim 14, wherein the measurement comprises a Reference Signal Received Power (RSRP) measurement, and the predetermined threshold for the RSRP measurement is hard-coded in a UE specification or signaled to the UE in a System Information Block (SIB) and is based on the selected PRACH group.

16. The method according to claim 15, wherein a maximum number of repetitions of the RAR message or a RAR message window size is provided in the SIB.

17. The method of claim 16, wherein the repetition number for the RAR message is fixed to the maximum repetition number or is dynamically indicated in scheduling downlink control information DCI format 1_0.

18. The method of claim 17, wherein the DCI format 1_0 includes X reserved bits, the X reserved bits are reused to indicate the repetition number, and a value of X is based on a Radio Network Temporary Identifier (RNTI).

19. The method according to claim 17, wherein the repetition number is carried by a scrambling sequence to scramble cyclic redundancy check (CRC) bits in the DCI format 1_0.

20. The method of claim 14, wherein a frequency domain resource allocation (FDRA) for the RAR message comprises frequency resources shifted across different repetitions of the RAR message.

21. The method of claim 14, wherein the MO for the RAR message is evenly divided across the PRACH groups in the time domain for different spatial relationships.

22. The method of claim 14, wherein the MO for the RAR message is unevenly divided across the PRACH groups in the time domain based on a division pattern, The partitioning mode is either hard-coded in the UE specification or dynamically signaled in the scheduling DCI format 1_0. The method according to claim 22 , wherein the partitioning mode comprises an interleaved mode or a non-interleaved mode.

24. The method according to claim 14, wherein: For the time domain, if consecutive time slots are associated with the same spatial relationship, the same symbol allocation applies across the time slots.

25. The method of claim 14, wherein the RV for the RAR message is applied based on a redundancy version RV field signaled in a scheduling DCI format 1_0.

26. The method of claim 14, wherein the RACH procedure is any one of a two-step RACH or a four-step RACH.

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