Patent Description:
A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipments (UEs).

The <NPL>, makes the following observations: Observation <NUM>: It will be necessary to enable configurations of the MsgB windows which are longer than the maximum allowable RAR window in legacy NR. Observation <NUM>: RA-RNTI can only be used unambiguously during the RAR window. Observation <NUM>: SFN, msgB length, indication of RRC and E bit would be useful to have in a new msgB/RAR subheader. Observation <NUM>: The legacy E/T/R/R/BI subheader can be coded to prevent legacy Ues to parse beyond the subheader. Moreover, the authors make the following proposals: Proposal <NUM>: msgB should include the LSBs of SFN. Proposal <NUM>: Adopt the coding of the E/T/R/R/BI subheader to prevent legacy Ues to parse beyond the subheader and use it as identifier of NR-U RAR or msgB. Proposal <NUM>: Adopt the subheader for NR-U RAR as shown in <FIG> of said draft. Proposal <NUM>: Adopt the subheader for msgB as shown in <FIG>. Proposal <NUM>: Adopt the subheader for msgB with RRC as shown in <FIG> of said draft. Proposal <NUM>: Adopt the msgB for <NUM>-step back off as shown in Figure <NUM> of said draft. Proposal <NUM>: Adopt the subheader for fallback as shown in Figure <NUM> of said draft. Proposal <NUM>: A UE specific RNTI based on the CR identity may be used additionally to the RA-RNTI/msgB-RNTI.

In some aspects, a method of wireless communication, performed by a base station (BS), is described, as defined in claim <NUM>.

In some aspects, a method of wireless communication, performed by a UE, is described, as defined in claim <NUM>.

In some aspects, a UE for wireless communication is described, as defined in claim <NUM>.

In some aspects, a computer program is described, as defined in claim <NUM>.

In some aspects, a base station for wireless communication is described, as defined in claim <NUM>.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with random access response (RAR) mapping for two-step random access channel (RACH) procedures, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG>, process <NUM> of <FIG>, and/or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively. In some aspects, memory <NUM> and/or memory <NUM> may comprise a non-transitory computer-readable medium storing one or more instructions for wireless communication. For example, the one or more instructions, when executed by one or more processors of the base station <NUM> and/or the UE <NUM>, may perform or direct operations of, for example, process <NUM> of <FIG>, process <NUM> of <FIG>, and/or other processes as described herein.

In some aspects, UE <NUM> may include means for receiving, from a BS <NUM>, a message B (msgB) communication associated with a two-step RACH procedure between the UE <NUM> and the BS <NUM>, means for identifying an RAR, associated with the UE <NUM>, among a plurality of RARs multiplexed in the msgB communication and supplementary scheduling information for other RARs, and/or the like. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>, such as controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, and/or the like.

In some aspects, base station <NUM> may include means for grouping and selectively multiplexing a plurality of RARs in a msgB communication, means for transmitting the msgB communication to one or more UEs <NUM>, and/or the like. In some aspects, such means may include one or more components of base station <NUM> described in connection with <FIG>, such as antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, and/or the like.

A UE may access a wireless network by negotiating a connection with a BS included in the wireless network. During connection establishment, the UE and the BS may synchronize the connection in the downlink direction (that is, from BS to UE) and in the uplink direction (that is, from UE to BS).

To synchronize the connection in the downlink direction, the UE may read a synchronization signal block (SSB) that includes various synchronization signals transmitted from the BS. The synchronization signals may include a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a primary broadcast channel (PBCH), and/or the like. The UE may use the PSS to determine symbol timing in the downlink direction, may use the SSS to determine a physical cell identifier associated with the BS, and may use the PBCH to determine the frame timing.

To synchronize the connection in the uplink direction, the UE and the BS may perform a RACH procedure. In some aspects, the UE and the BS may perform a four-step RACH procedure. In a four-step RACH procedure, the UE and the BS may exchange four primary RACH communications. The UE may transmit a Message <NUM> (msg1) communication to the BS (e.g., as defined in a 3GPP four-step RACH procedure). The msg1 communication may be a RACH preamble communication that is transmitted in a RACH occasion (e.g., a particular set of time-frequency resources), the combination of which may be referred to as a RACH signature. The BS may respond to the msg1 communication with a Message <NUM> (msg2) communication (e.g., as defined in a 3GPP four-step RACH procedure), which may be a random access response (RAR) communication. The UE may respond to the msg2 communication with a Message <NUM> (msg3) communication (e.g., as defined in a 3GPP four-step RACH procedure), which may be a radio resource control (RRC) connection request communication. The BS may respond to the msg3 communication with a Message <NUM> (msg4) communication (e.g., as defined in a 3GPP four-step RACH procedure), which may be a medium access control (MAC) control element (MAC-CE) contention resolution identifier communication and may include an RRCSetup command, and/or the like.

In some cases, the four-step RACH procedure may not meet the low latency requirements of <NUM>/NR wireless systems. Accordingly, the UE and the BS may use a two-step RACH procedure to reduce latency in synchronizing the connection in the uplink direction. In a two-step RACH procedure, the UE may combine the msg1 communication and the msg3 communication into a communication referred to as a message A (msgA) communication (e.g., as defined in a 3GPP two-step RACH procedure). The msg1 portion of the msgA communication may be referred to as the preamble portion of the msgA communication. The msg3 portion of the msgA communication may be referred to as the payload portion of the msgA communication. The UE may transmit the msg <NUM> portion and the msg3 portion sequentially and prior to receiving the msg2 communication and the msg4 communication.

The BS may receive the msgA communication and may transmit a msgB communication (e.g., as defined in a 3GPP four-step RACH procedure), which may include the msg2 communication and the msg4 communication. The msgB communication may include a physical downlink control channel (PDCCH) portion and a physical downlink shared channel (PDSCH) portion. The PDSCH portion may carry the payload of the msgB communication, which may include an RAR directed to the UE.

The RAR may be a fallback RAR, a success RAR (with or without an associated radio resource control (RRC) message), a backoff indicator, and/or the like. A fallback RAR may be transmitted if the preamble portion of the msgA communication is detected and decoded but not the payload portion. A fallback RAR may indicate to the UE to fall back to a four-step RACH procedure, and may include a random access preamble identifier (RAPID) for the UE, an RAR grant, a timing advance command, and a temporary cell radio network temporary identifier (TC-RNTI) for retransmitting the msg3 or payload portion of the msgA communication.

A success RAR may be transmitted if the preamble portion and the payload portion are detected and decoded. A success RAR may indicate to the UE to proceed with the two-step RACH procedure, and may identify a contention resolution identifier, a timing advance command, and a cell radio network temporary identifier (C-RNTI).

A UE may monitor for a msgB communication during an RAR reception window. The starting point of the RAR reception window may be aligned with the first PDCCH symbol of the earliest search space for the msgB communication. If the UE does not receive a success RAR or fallback RAR by the expiration of the RAR reception window, the UE may retransmit the msgA communication.

In some cases, a BS may transmit a respective RAR to each of a plurality of UEs, where each RAR is included in a separate msgB communication. This may cause increased power consumption at the plurality of UEs because each UE may have to monitor for and decode a plurality of msgB communications during an associated RAR reception window to receive the RAR directed to the UE. Moreover, the BS may also transmit RAR retransmissions during the RAR reception window in separate msgB communications, which further increases the quantity of msgB communications that each UE may have to monitor for and decode during an associated RAR reception window.

Some aspects described herein provide techniques and apparatuses for RAR mapping for two-step RACH procedures. In some aspects, a BS may multiplex a plurality of RARs into a single msgB communication, and may transmit the msgB communication to one or more UEs. This permits the BS to reduce the quantity of msgB communications transmitted to the UEs relative to transmitting the plurality of RARs in individual and/or separate msgB communications. The reduced quantity of msgB communications in turn decreases processing, memory, and power resource consumption at the UEs because the UEs may monitor for and decode fewer msgB communications during associated RAR reception windows to receive RARs.

To further decrease processing, memory, and power resource consumption at the UEs, the BS may multiplex the same type of RARs and/or different types of RARs in the same msgB communication, which permits success RARs, fallback RARs, initial RAR transmissions, and/or RAR retransmissions to be included in the same msgB communication. The BS may also provide an early indication of which msgB communication will carry an RAR directed to a particular UE or group of UEs, which further decreases processing, memory, and power resource consumption at the UEs.

<FIG> are diagrams illustrating one or more examples <NUM> of RAR mapping for two-step RACH procedures, in accordance with various aspects of the present disclosure. As shown in <FIG>, example(s) <NUM> may include communication between a BS (e.g., BS <NUM>) and a plurality of UEs (e.g., UE <NUM>), such as UE1-UEn, and/or the like. The BS and the plurality of UEs may be included in a wireless network, such as wireless network <NUM> and/or the like.

In some aspects, each of the plurality of UEs may perform a RACH procedure with the BS to establish a wireless connection with the BS. The RACH procedure may include, for example, a two-step RACH procedure, a four-step RACH procedure, and/or the like. In some aspects, a UE of the plurality of UEs may initiate a two-step RACH procedure by transmitting a msgA communication to the BS. In this case, the UE may transmit a preamble portion of the msgA communication in a preamble occasion (e.g., one or more time-frequency resources configured for RACH preamble transmission), and may transmit a payload portion of the msgA communication in a physical uplink shared channel (PUSCH) occasion (e.g., one or more time-frequency resources configured for msgA payload transmission).

As shown in <FIG>, and by reference number <NUM>, the BS may multiplex RARs directed to the plurality of UEs in a msgB communication. In some aspects, the BS may multiplex the RARs directed to the plurality of UEs in the same msgB communication. In some aspects, the BS may time division multiplex RARs in the msgB communication, may frequency division multiplex RARs in the msgB communication, may spatially multiplex RARs in the msgB communication, or a combination thereof. In some aspects, the BS may multiplex subsets of the RARs directed to the plurality of UEs in different msgB communications. In this case, the BS may scramble the msgB communications with the same RNTI (e.g., same msgB-RNTI and/or another type of RNTI). In some aspects, if the RAR window if long (e.g., >=<NUM>), the value of the msgB RNTI may change over time. For example, msgB_RNTI (K)=msgB_RNTI(K-<NUM>)+delta(K-<NUM>), wherein delta(K-<NUM>) captures the time variation of msgB_RNTI from radio frame (K-<NUM>) to radio frame (K). This, in some cases, the BS may scramble the msgB communications using the same set of msgB radio network temporary identifiers mapped to the same random access occasion.

In some aspects, the BS may multiplex the same type of RARs in a msgB communication, may multiplex different types of RARs in the msgB communication, or a combination thereof. For example, the BS may multiplex one or more success RARs (with or without an associated RRC message) in a msgB communication, may multiplex one or more fallback RARs in the msgB communication, and/or the like. As another example, the BS may multiplex initial or first transmissions of one or more RARs in a msgB communication (e.g., one or more initial or first transmissions of a success RAR, a fallback RAR, and/or the like), may multiplex retransmissions of one or more RARs in the msgB communication (e.g., one or more retransmissions of a success RAR, a fallback RAR, and/or the like), and/or the like.

<FIG> and <FIG> illustrate various examples of RARs multiplexed in one or more msgB communications. As shown in an example illustrated in <FIG>, the BS may multiplex different subsets of RARs directed to five UEs (e.g., RAR <NUM> through RAR <NUM>) in respective msgB communications. In particular, the BS may multiplex the initial transmissions of RAR <NUM>, RAR <NUM>, and RAR <NUM> (e.g., directed to a UE1, a UE2, and a UE3, respectively) in msgB <NUM>, may multiplex the initial transmissions of RAR <NUM> and RAR <NUM> (e.g., directed to UE4 and UE5, respectively) in msgB <NUM>, and may multiplex retransmissions of RAR <NUM>, RAR <NUM>, and RAR <NUM> (e.g., directed to a UE1, a UE2, and a UE3, respectively) in msgB <NUM>.

As further shown in the example illustrated in <FIG>, different types of RARs may be multiplexed in the same msgB communication. For example, msgB <NUM> may include a success RAR without an associated RRC message (e.g., RAR <NUM>), a success RAR with an associated RRC message (e.g., RAR <NUM>), and a fallback RAR (e.g., RAR <NUM>). As another example, msgB <NUM> may include a fallback RAR (e.g., RAR <NUM>) and a success RAR with an associated RRC message (e.g., RAR <NUM>). As another example, msgB <NUM> may include a success RAR without an associated RRC message (e.g., RAR <NUM>), a success RAR with an associated RRC message (e.g., RAR <NUM>), and a fallback RAR (e.g., RAR <NUM>).

As shown in an example illustrated in <FIG>, the BS may multiplex different subsets of RARs directed to five UEs (e.g., RAR <NUM> through RAR <NUM>) in respective msgB communications. In particular, the BS may multiplex the initial transmissions of RAR <NUM>, RAR <NUM>, and RAR <NUM> (e.g., directed to a UE1, a UE2, and a UE3, respectively) in msgB <NUM>, may multiplex a retransmission of RAR <NUM> with the initial transmissions of RAR <NUM> (e.g., directed to UE4) in msgB <NUM>, and may include the initial transmission of RAR <NUM> (e.g., directed to a UE5) in msgB <NUM>.

As further shown in the example illustrated in <FIG>, different types of RARs may be multiplexed in the same msgB communication. For example, msgB <NUM> may include a success RAR without an associated RRC message (e.g., RAR <NUM>), a success RAR with an associated RRC message (e.g., RAR <NUM>), and a fallback RAR (e.g., RAR <NUM>). As another example, msgB <NUM> may include an initial transmission of a fallback RAR (e.g., RAR <NUM>) and a retransmission of a success RAR without an associated RRC message (e.g., RAR <NUM>).

The BS may use various techniques to identify RARs that are to be multiplexed in the same msgB communication. In some aspects, the BS may multiplex RARs in the same msgB communication based at least in part on respective priorities associated with each of the RARs. For example, the BS may multiplex RARs of a high priority in the same msgB communication and may transmit the msgB communication earlier in time relative to a msgB communication carrying multiplexed RARs of a relatively lower priority.

In some aspects, the BS may multiplex RARs in the same msgB communication based at least in part on respective payload sizes associated with the RARs to efficiently use the available space in the msgB communication. For example, the BS may be permitted to include a particular quantity of bits or bytes in the payload portion of a msgB communication, and the BS may multiplex RARs in the msgB communication such that the RARs utilize the most amount of the available space in the msgB communication.

In some aspects, the BS may group RARs, directed to UEs that transmitted preambles in the same preamble occasion, into one or more sets of RARs. The BS may multiplex each set of RARs into a respective msgB communication such that the transmissions of the sets of RARs are ordered in time. The order of the sets of RARs may be based at least in part on starting symbols of respective RAR reception windows associated with each of the UEs. For example, the BS may multiplex RARs directed to a first group or set of UEs having an associated RAR reception window starting on the same symbol into a first msgB communication, may multiplex RARs directed to a second group or set of UEs having an associated RAR reception window starting on the same symbol into a second msgB communication, and so on.

<FIG> and <FIG> illustrate various examples of grouping RARs into sets based at least in part on a starting symbol of a respective RAR reception window associated with one or more UEs. In an example illustrated in <FIG>, a plurality of UEs may transmit RACH preambles (e.g., preamble portions of a msgA communication in a two-step RACH procedure) in the same preamble occasion X. A first subset of the UEs may transmit a msgA payload portion in a PUSCH occasion Y, and a second subset of the UEs may transmit a msgA payload portion in a PUSCH occasion Z that occurs after PUSCH occasion Y. In this example, the starting symbol of a first RAR reception window associated with preamble occasion/PUSCH occasion combination (X,Y) may be a different symbol than the starting symbol of a second RAR reception window associated with preamble occasion/PUSCH occasion combination (X,Z). Accordingly, the BS may multiplex RARs directed to the first subset of UEs into a first msgB communication (X,Y) and may transmit the first msgB communication in the first RAR reception window. Moreover, the BS may multiplex RARs directed to the second subset of UEs into a second msgB communication (X,Z) and may transmit the second msgB communication in the second RAR reception window.

In an example illustrated in <FIG>, a plurality of UEs may transmit RACH preambles (e.g., preamble portions of a msgA communication in a two-step RACH procedure) in the same preamble occasion X. A first subset of the UEs may transmit a msgA payload portion in a PUSCH occasion Y, and a second subset of the UEs may transmit a msgA payload portion in a PUSCH occasion Z. In this example, the starting symbol of a first RAR reception window associated with preamble occasion/PUSCH occasion combination (X,Y) may be the same symbol as the starting symbol of a second RAR reception window associated with preamble occasion/PUSCH occasion combination (X,Z). Accordingly, the BS may multiplex RARs directed to the first subset of UEs and the second subset of UEs into the same msgB communication (X,Y) & (X,Z), and may transmit the msgB communication in the RAR reception window.

As shown in <FIG>, and by reference number <NUM>, the BS may transmit a msgB communication to the plurality of UEs. The msgB communication may include a multiplexed plurality of RARs directed to the plurality of UEs. In some aspects, if the BS multiplexes subsets of the plurality of RARs in different msgB communications, the BS may transmit the msgB communications to the plurality of UEs. The BS may transmit the msgB communication(s) during RAR reception windows associated with each of the plurality of UEs.

As indicated above, a UE may monitor for and decode msgB communications during an associated RAR reception window. A UE may need to decode a plurality of msgB communications before identifying the RAR directed to the UE, which increases processing, memory, and/or power consumption at the UE. To decrease the quantity of msgB communications that are to be decoded by the UE during the RAR reception window, the BS may include an early indicator, in one or more msgB communications transmitted during the RAR reception window, of a transmission timing for the msgB communication carrying the RAR directed to the UE. In this way, the UE may decode a msgB communication, may identify the early indicator in the msgB communication (e.g., which may identify a subsequent msgB communication that will carry the RAR directed to the UE), and may refrain from monitoring for and decoding any intervening msgB communications prior to the msgB communication carrying the RAR directed to the UE.

<FIG> illustrates an example of an early indicator of an RAR directed to a UE (or a set or group of UEs). As shown in <FIG>, the BS may transmit a plurality of msgB communications during an RAR reception window associated with one or more UEs. The RAR(s) directed to the UE(s) may be included in msgB <NUM>, which may be transmitted after msgB <NUM> and msgB <NUM> in the RAR reception window. In this example, the BS may include the early indicator, that the RAR(s) will be included in msgB <NUM>, in msgB <NUM> and msgB <NUM>. Accordingly, a UE may receive and decode msgB <NUM>, identify the early indicator, and refrain from receiving and decoding msgB <NUM> based at least in part on the early indicator. If the UE misses or is unable to decode msgB <NUM>, the UE may receive and decode msgB <NUM>, may identify the early indicator, and may monitor for and receive msgB <NUM> based at least in part on the early indicator.

In some aspects, the BS may include an early indicator of a transmission timing for a msgB communication carrying an RAR in a PDCCH portion of another msgB communication, in a PDSCH portion of another msgB communication, and/or the like. For example, an early indicator may be included in downlink control information (DCI) in the PDCCH portion of another msgB communication, may be included in a medium access control (MAC) sub-header in the PDCCH portion or PDSCH portion, may be included in a MAC sub-protocol data unit (PDU) in the PDCCH portion or PDSCH portion, and/or the like.

In some aspects, an early indicator of a transmission timing for a msgB communication carrying an RAR may include a compressed UE identifier associated with the UE (or UEs) to which the RAR is directed. The UE may determine that the early indicator is for the UE based at least in part on the compressed UE identifier indicated in the msgB communication carrying the early indicator. The compressed UE identifier may include a RAPID associated with the UE, a most significant bit (MSB) of a C-RNTI associated with the UE, a least significant bit (LSB) of the C-RNTI associated with the UE, an MSB of an idle or inactive radio network temporary identifier (I-RNTI) associated with the UE, an LSB of the I-RNTI associated with the UE, and/or another type of compressed UE identifier.

In some aspects, the early indicator may include a timing offset between the msgB communication carrying the early indicator and the msgB communication carrying the RAR directed to the UE, and the timing offset may include a slot-level offset, a symbol-level offset, a back off indication, or a combination thereof. The timing offset may be specified for a control resource set (CORESET) or search space associated with the msgB communication carrying the RAR directed to the UE, and may be indicated relative to the msgB communication carrying the early indicator. In some aspects, the early indicator may include an index of the search space associated with the msgB communication carrying the RAR directed to the UE. Accordingly, the UE may identify the msgB communication carrying the RAR directed to the UE based at least in part on the timing offset and/or the index of the search space.

As shown in <FIG>, and by reference number <NUM>, UE1 may receive a msgB communication from the BS and may identify an RAR, associated with UE1, included in the msgB communication. In some aspects, UE1 may identify the RAR among a plurality of RARs multiplexed in the msgB communication. In some aspects, UE1 may identify the RAR based at least in part on the RAR being scrambled using an RNTI associated with the UE and/or another type of UE identifier associated with the UE. In some aspects, the other UEs in the plurality of UEs may receive msgB communications from the BS and may identify associated RARs using similar techniques.

In some aspects, a UE (e.g., UE1 and/or another UE of the plurality of UEs) may transmit hybrid automatic repeat request (HARQ) feedback to the BS based at least in part on a msgB communication. The HARQ feedback may include an acknowledgement (ACK) if the UE is able to decode the msgB communication, or a negative ACK (NACK) if the UE is unable to decode the msgB communication or did not receive the msgB communication. In some aspects, the UE may transmit the HARQ feedback in a physical uplink control channel (PUCCH) communication to the BS (e.g., during a two-step RACH procedure, after the two-step RACH procedure, and/or the like).

In some aspects, the BS may include one or more PUCCH parameters for the HARQ feedback in the associated msgB communication, in another msgB communication that is transmitted prior to the associated msgB communication (e.g., along with an early indicator), and/or the like. The one or more PUCCH parameters may be included in a PDCCH portion of a msgB communication, in a PDSCH portion of a msgB communication, and/or the like. In some aspects, a UE may transmit HARQ feedback associated with a msgB communication based at least in part on the one or more PUCCH parameters.

To reduce signaling overhead of transmitting an indication of the one or more PUCCH parameters, the BS may configure the one or more PUCCH parameters to include one or more common PUCCH parameters that are shared by a plurality of UEs, and one or more UE-specific PUCCH parameters that are specific to a particular UE. The one or more common PUCCH parameters may include a common PUCCH power control parameter (e.g., an indication of a transmit power for the PUCCH communication carrying the HARQ feedback), a PUCCH resource allocation (e.g., an indication of a common set of time-frequency resources for transmitting the PUCCH communication carrying the HARQ feedback), a HARQ feedback timing indicator (e.g., an indication of a timing for transmitting the HARQ feedback), and/or the like. The one or more UE-specific PUCCH parameters may include a UE-specific PUCCH power control parameter, a PDSCH-to-HARQ feedback timing indicator, a UE-specific PUCCH resource allocation, a UE-specific HARQ feedback timing indicator, and/or other UE-specific parameters.

In some aspects, the one or more common PUCCH parameters may be included in DCI of a PDCCH portion of a msgB communication, in a MAC sub-header of a PDSCH portion of the msgB communication, in a MAC sub-PDU of the PDSCH portion of the msgB communication, and/or the like. In some aspects, the one or more UE-specific PUCCH parameters may be included in a MAC sub-header of a PDSCH portion of the msgB communication, in a MAC sub-PDU of the PDSCH portion of the msgB communication, or be derived implicitly from the ordering of UE specific MAC sub-header, the ordering of UE specific MAC sub-PDU, the preamble sequence index, the demodulation reference signal (DMRS) resource index, the PUSCH resource unit index, and/or the like.

In this way, the BS may multiplex a plurality of RARs into a single msgB communication, and may transmit the msgB communication to one or more of the plurality of UEs. This permits the BS to reduce the quantity of msgB communications transmitted to the UEs relative to transmitting the plurality of RARs in individual and/or separate msgB communications. The reduced quantity of msgB communications in turn decreases processing, memory, and power resource consumption at the UEs because the UEs may monitor for and decode fewer msgB communications during associated RAR reception windows to receive RARs. Moreover, the BS may further decrease processing, memory, and power resource consumption at the UEs by multiplexing the same type of RARs and/or different types of RARs in the same msgB communication, which may permit success RARs, fallback RARs, initial RAR transmissions, and/or RAR retransmissions to be included in the same msgB communication. The BS may also provide an early indication of which msgB communication will carry an RAR directed to a particular UE or group of UEs, which further decreases processing, memory, and power resource consumption at the UEs.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a BS, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where the BS (e.g., BS <NUM>) performs operations associated with RAR mapping for two-step RACH procedures.

As shown in <FIG>, in some aspects, process <NUM> may include grouping and selectively multiplexing a plurality of RARs in a msgB communication (block <NUM>). For example, the BS (e.g., using transmit processor <NUM>, receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may grouping and selectively multiplex a plurality of RARs in a msgB communication, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include transmitting the msgB communication to one or more UEs (block <NUM>). For example, the BS (e.g., using transmit processor <NUM>, receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may transmit the msgB communication to one or more UEs, as described above.

Grouping and selectively multiplexing the plurality of RARs in the msgB communication may comprise multiplexing the plurality of RARs and supplementary scheduling information for other RARs in a plurality of msgB communications, the msgB communication being included in the plurality of msgB communications, wherein the plurality of msgB communications are time division multiplexed. Process <NUM> may include scrambling the plurality of msgB communications using a same msgB radio network temporary identifier or a same set of msgB radio network temporary identifiers mapped to the same random access occasion (RO). The plurality of RARs may comprise at least one of one or more fallback RARs, one or more success RARs with an associated RRC message, or one or more success RARs without an RRC message.

The plurality of RARs may comprise at least one of an initial transmission of one or more RARs of the plurality of RARs or a retransmission of one or more RARs of the plurality of RARs. Multiplexing the plurality of RARs in the msgB communication may comprise multiplexing the plurality of RARs in the msgB communication based at least in part on at least one of a starting symbol of a respective RAR reception window associated with each of the one or more UEs sharing a same random access occasion, a respective priority associated with each of the plurality of RARs, a respective quality of service (QoS) class associated with each of the plurality of RARs, or a respective payload size of each of the plurality of RARs.

Process <NUM> may include transmitting, to the one or more UEs, an indication of a transmission timing for the msgB communication. The indication of the transmission timing for the msgB communication may be included in another msgB communication, and transmitting the indication of the transmission timing for the msgB communication may comprise transmitting the other msgB communication prior to transmitting the msgB communication.

The indication of the transmission timing for the msgB communication may be included in at least one of DCI of the other msgB communication, a MAC sub-header of the other msgB communication, or a MAC sub-protocol data unit of the other msgB communication. The indication of the transmission timing for the msgB communication may comprise at least one of a respective compressed UE identifier associated with each of the one or more UEs, a timing offset, relative to the other msgB communication, of a control resource set or search space associated with the msgB communication, or an index of the search space associated with the msgB communication.

The respective compressed UE identifier associated with each of the one or more UEs may comprise a random access preamble identifier, an MSB of a C-RNTI, an LSB of the C-RNTI, an MSB of an I-RNTI, or an LSB of the I-RNTI. The msgB communication may identify one or more PUCCH parameters for HARQ feedback associated with the msgB communication, wherein the one or more PUCCH parameters may comprise at least one of one or more common PUCCH parameters or one or more UE-specific PUCCH parameters.

The one or more common PUCCH parameters may comprise at least one of a PUCCH power control parameter, a PUCCH resource allocation, a PDSCH-to-HARQ feedback timing indicator, or a HARQ feedback timing indicator. The one or more common PUCCH parameters may be included in at least one of DCI included in a PDCCH portion of the msgB communication, a common MAC sub-header included in a PDSCH portion of the msgB communication, or a common MAC sub-PDU included in the PDSCH portion of the msgB communication, and the one or more UE-specific PUCCH parameters may be included in at least one of a UE-specific MAC sub-header included in the PDSCH portion of the msgB communication or a UE-specific MAC sub-PDU included in the PDSCH portion of the msgB communication. The UE-specific PUCCH parameters can also be derived from an implicit indication based on the ordering of UE-specific MAC sub-header, the ordering of UE-specific MAC sub-PDU, the preamble sequence index, the DMRS resource index or the PUSCH resource unit index used by the UE in the two-step random access procedure.

Process <NUM> may further comprise transmitting, to the one or more UEs, an indication of a transmission timing for the msgB communication in the supplementary scheduling information for other RARs to be mapped to a different msgB communication.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where the UE (e.g., UE <NUM>) performs operations associated with RAR mapping for two-step RACH procedures.

As shown in <FIG>, in some aspects, process <NUM> may include receiving, from a BS, a msgB communication associated with a two-step RACH procedure between the UE and the BS (block <NUM>). For example, the UE (e.g., using receive processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may receive, from a BS, a msgB communication associated with a two-step RACH procedure between the UE and the BS, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include identifying an RAR, associated with the UE, among a plurality of RARs multiplexed in the msgB communication and supplementary scheduling information for other RARs (block <NUM>). For example, the UE (e.g., using receive processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may identify an RAR, associated with the UE, among a plurality of RARs multiplexed in the msgB communication and supplementary scheduling information for other RARs, as described above.

The plurality of RARs may comprise at least one of one or more fallback RARs, one or more success RARs with an associated RRC message, or one or more success RARs without an RRC message. The plurality of RARs may comprise at least one of an initial transmission of one or more RARs of the plurality of RARs or a retransmission of one or more RARs of the plurality of RARs. Process <NUM> may include receiving, from the BS, an indication of a transmission timing for the msgB communication; and identifying the msgB communication based at least in part on the indication of the transmission timing for the msgB communication in the supplementary scheduling information multiplexed with RARs.

Process <NUM> may include receiving the indication of the transmission timing for the msgB communication in another msgB communication that is transmitted prior to the msgB communication. Process <NUM> may include identifying the indication of the transmission timing for the msgB communication in at least one of DCI of the other msgB communication, a MAC sub-header of the other msgB communication, or a MAC sub-protocol data unit of the other msgB communication.

The indication of the transmission timing for the msgB communication may comprise at least one of a respective compressed UE identifier associated with each of the one or more UEs, a timing offset, relative to the other msgB communication, of a control resource set or search space associated with the msgB communication, or an index of the search space associated with the msgB communication.

The respective compressed UE identifier associated with each of the one or more UEs may comprise a random access preamble identifier, an MSB of a C-RNTI, an LSB of the C-RNTI, an MSB of an I-RNTI, or an LSB of the I-RNTI, and wherein the timing offset may comprise at least one of a slot level offset, a symbol level offset, or a back off indicator. Process <NUM> may include identifying one or more PUCCH parameters for HARQ feedback and transmitting, to the BS, HARQ feedback associated with the msgB communication based at least in part on the one or more PUCCH parameters.

The one or more PUCCH parameters may comprise at least one of one or more common PUCCH parameters or one or more UE-specific PUCCH parameters.

The one or more PUCCH parameters may comprise at least one of a PUCCH power control parameter, a PUCCH resource allocation, a PDSCH-to-HARQ feedback timing indicator, or a HARQ feedback timing indicator. The one or more common PUCCH parameters may be included in at least one of DCI included in a PDCCH portion of the msgB communication, a common MAC sub-header included in a PDSCH portion of the msgB communication, or a common MAC sub-PDU included in the PDSCH portion of the msgB communication, and the one or more UE-specific PUCCH parameters may be included in at least one of a UE-specific MAC sub-header included in the PDSCH portion of the msgB communication or a UE-specific MAC sub-PDU included in the PDSCH portion of the msgB communication. The UE specific PUCCH parameters can also be derived from an implicit indication based on the ordering of MAC sub-header, the ordering of MAC sub-PDU, the preamble sequence index, the DMRS resource index, and the PUSCH resource unit index used by the UE in the two-step random access procedure.

Claim 1:
A method of wireless communication performed by a base station (<NUM>), BS, comprising:
grouping and selectively multiplexing (<NUM>) a plurality of random access channel responses, RARs, in a message B, msgB, communication; and
transmitting (<NUM>) the msgB communication to one or more user equipments (<NUM>), UEs;
wherein multiplexing the plurality of RARs in the msgB communication comprises:
multiplexing the plurality of RARs in the msgB communication based at least in part on at least one of:
a starting symbol of a respective RAR reception window associated with each of the one or more UEs (<NUM>) sharing a same random access occasion,
a respective priority associated with each of the plurality of RARs,
a respective quality of service, QoS, class associated with each of the plurality of RARs, or
a respective payload size of each of the plurality of RARs.