Random access response mapping for two-step random access channel procedure
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a base station (BS) may group and selectively multiplex a plurality of random access channel responses (RARs) and radio resource control (RRC) messages in a message B (msgB) communication, together with supplementary scheduling information for other RARs to be mapped to a different msgB communication. The BS may transmit the msgB communication to one or more user equipments. Numerous other aspects are provided.
1. A base station (BS) for wireless communication, comprising:
one or more memories; and
one or more processors, coupled to the one or more memories, configured to cause the BS to:
transmit, to a plurality of user equipment (UEs), a first message B (msgB) communication, the first msgB communication including:
an indication that a plurality of random access channel responses (RARs) directed to the plurality of UEs are included in a second msgB communication, and
supplementary scheduling information for other RARs;
group and selectively multiplex the plurality of RARs in the second msgB communication; and
transmit the second msgB communication to the plurality of UEs, the second msgB communication being transmitted after the first msgB communication.
2. The BS of claim 1 , wherein the one or more processors, to cause the BS to group and selectively multiplex the plurality of RARs in the second msgB communication, are configured to cause the BS to:
group the plurality of RARs into a plurality of sets of RARs; and
map different sets of RARs, of the plurality of sets of RARs to different time occasions within an RAR time window associated with a plurality of msgB communications, the second msgB communication being included in the plurality of msgB communications.
3. The BS of claim 2 , wherein a first set of RARs, of the plurality of sets of RARs, is transmitted during an earlier portion of the RAR time window relative to a portion of the RAR time window in which a second set of RARs is transmitted, and
wherein transmitting the first set of RARs during the earlier portion of the RAR time window triggers a prioritized retransmission of a message A (msgA) communication associated with the first set of RARs.
4. The BS of claim 2 , wherein the one or more processors are further configured to cause the BS to:
scramble the plurality of msgB communications using a same msgB radio network temporary identifier or using a same set of msgB radio network temporary identifiers mapped to a same random access occasion (RO).
5. The BS of claim 1 , wherein the second msgB communication is transmitted during a first portion of an RAR time window, and
wherein transmitting the second msgB communication during the first portion of the RAR time window triggers a prioritized retransmission of a message A (msgA) communication.
6. The BS of claim 1 , wherein the one or more processors are further configured to cause the BS to:
transmit, to the plurality of UEs, an indication of a transmission timing for the second msgB communication in the supplementary scheduling information for other RARs to be mapped to a different msgB communication.
7. The BS of claim 1 , wherein the plurality of RARs comprise at least one of:
one or more fallback RARs,
one or more success RARs with an associated radio resource control (RRC) message, or
one or more success RARs without an RRC message.
8. The BS of claim 1 , wherein the plurality of RARs 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.
9. The BS of claim 1 , wherein the one or more processors, to cause the BS to group and selectively multiplexing the plurality of RARs in the second msgB communication, are configured to cause the BS to:
multiplex the plurality of RARs in the second 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 plurality of 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.
10. The BS of claim 1 , wherein the second msgB communication identifies one or more physical uplink control channel (PUCCH) parameters for hybrid automatic repeat request (HARQ) feedback associated with the msgB communication,
wherein the one or more PUCCH parameters comprise at least one of:
one or more common PUCCH parameters, or
one or more UE-specific PUCCH parameters.
11. The BS of claim 10 , wherein the one or more PUCCH parameters comprise at least one of:
a PUCCH power control parameter,
a physical downlink shared channel (PDSCH)-to-HARQ feedback timing indicator,
a PUCCH resource allocation, or
a HARQ feedback timing indicator.
12. The BS of claim 10 , wherein the one or more common PUCCH parameters are included in at least one of:
downlink control information included in a physical downlink control channel portion of the second msgB communication,
a common medium access control (MAC) sub-header included in a physical downlink shared channel (PDSCH) portion of the second msgB communication, or
a common MAC sub-protocol data unit (PDU) included in the PDSCH portion of the second msgB communication; and
wherein the one or more PUCCH parameters include the one or more UE-specific PUCCH parameters and the one or more UE-specific PUCCH parameters are included in at least one of:
a UE-specific MAC sub-header included in the PDSCH portion of the second msgB communication,
a UE-specific MAC sub-PDU included in the PDSCH portion of the second msgB communication, or
an implicit indication based on an ordering of UE-specific MAC sub-header or UE-specific MAC sub-PDU, a preamble sequence index, a demodulation reference signal (DMRS) resource index, or a physical uplink shared channel (PUSCH) resource unit index used in a two-step random access procedure.
13. A method of wireless communication performed by a base station (BS), comprising:
transmitting, to a plurality of user equipment (UEs), a first message B (msgB) communication, the first msgB communication including:
an indication that a plurality of random access channel responses (RARs) directed to the plurality of UEs are included in a second msgB communication, and
supplementary scheduling information for other RARs;
grouping and selectively multiplexing the plurality of RARs in the second msgB communication; and
transmitting the second msgB communication to the plurality of UEs, the second msgB communication being transmitted after the first msgB communication.
14. The method of claim 13 , wherein grouping and selectively multiplexing the plurality of RARs in the second msgB communication comprises:
grouping the plurality of RARs into a plurality of sets of RARs; and
mapping different sets of RARs, of the plurality of sets of RARs to different time occasions within an RAR time window associated with a plurality of msgB communications, the second msgB communication being included in the plurality of msgB communications.
15. The method of claim 14 , wherein a first set of RARs, of the plurality of sets of RARs, is transmitted during an earlier portion of the RAR time window relative to a portion of the RAR time window in which a second set of RARs is transmitted, and
wherein transmitting the first set of RARs during the earlier portion of the RAR time window triggers a prioritized retransmission of a message A (msgA) communication associated with the first set of RARs.
16. The method of claim 14 , further comprising:
scrambling the plurality of msgB communications using a same msgB radio network temporary identifier or using a same set of msgB radio network temporary identifiers mapped to a same random access occasion (RO).
17. The method of claim 13 , wherein the second msgB communication is transmitted during a first portion of an RAR time window, and
wherein transmitting the second msgB communication during the first portion of the RAR time window triggers a prioritized retransmission of a message A (msgA) communication.
18. The method of claim 13 , further comprising:
transmitting, to the plurality of UEs, an indication of a transmission timing for the second msgB communication in the supplementary scheduling information for other RARs to be mapped to a different msgB communication.
19. The method of claim 13 , wherein the plurality of RARs comprise at least one of:
one or more fallback RARs,
one or more success RARs with an associated radio resource control (RRC) message, or
one or more success RARs without an RRC message.
20. The method of claim 13 , wherein the plurality of RARs 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.
21. The method of claim 13 , wherein grouping and selectively multiplexing the plurality of RARs in the second msgB communication comprises:
multiplexing the plurality of RARs in the second 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 plurality of 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.
22. The method of claim 13 , wherein the second msgB communication identifies one or more physical uplink control channel (PUCCH) parameters for hybrid automatic repeat request (HARQ) feedback associated with the msgB communication,
wherein the one or more PUCCH parameters comprise at least one of:
one or more common PUCCH parameters, or
one or more UE-specific PUCCH parameters.
23. The method of claim 22 , wherein the one or more PUCCH parameters comprise at least one of:
a PUCCH power control parameter,
a physical downlink shared channel (PDSCH)-to-HARQ feedback timing indicator,
a PUCCH resource allocation, or
a HARQ feedback timing indicator.
24. The method of claim 22 , wherein the one or more common PUCCH parameters are included in at least one of:
downlink control information included in a physical downlink control channel portion of the second msgB communication,
a common medium access control (MAC) sub-header included in a physical downlink shared channel (PDSCH) portion of the second msgB communication, or
a common MAC sub-protocol data unit (PDU) included in the PDSCH portion of the second msgB communication; and
wherein the one or more PUCCH parameters include the one or more UE-specific PUCCH parameters and the one or more UE-specific PUCCH parameters are included in at least one of:
a UE-specific MAC sub-header included in the PDSCH portion of the second msgB communication,
a UE-specific MAC sub-PDU included in the PDSCH portion of the second msgB communication, or
an implicit indication based on an ordering of UE-specific MAC sub-header or UE-specific MAC sub-PDU, a preamble sequence index, a demodulation reference signal (DMRS) resource index, or a physical uplink shared channel (PUSCH) resource unit index used in a two-step random access procedure.
25. A non-transitory computer-readable medium storing a set of instructions for wireless communication, the set of instructions comprising:
one or more instructions that, when executed by one or more processors of a base station (BS), cause the BS to:
transmit, to a plurality of user equipment (UEs), a first message B (msgB) communication, the first msgB communication including:
an indication that a plurality of random access channel responses (RARs) directed to the plurality of UEs are included in a second msgB communication, and
supplementary scheduling information for other RARs;
group and selectively multiplex the plurality of RARs in the second msgB communication; and
transmit the second msgB communication to the plurality of UEs, the second msgB communication being transmitted after the first msgB communication.
26. The non-transitory computer-readable medium of claim 25 , wherein the one or more instructions, that cause the BS to group and selectively multiplex the plurality of RARs in the second msgB communication, cause the BS to:
group the plurality of RARs into a plurality of sets of RARs; and
map different sets of RARs, of the plurality of sets of RARs to different time occasions within an RAR time window associated with a plurality of msgB communications, the second msgB communication being included in the plurality of msgB communications.
27. The non-transitory computer-readable medium of claim 26 , wherein a first set of RARs, of the plurality of sets of RARs, is transmitted during an earlier portion of an RAR time window relative to a portion of the RAR time window in which a second set of RARs is transmitted, and
wherein transmitting the first set of RARs during the earlier portion of the RAR time window triggers a prioritized retransmission of a message A (msgA) communication associated with the first set of RARs.
28. The non-transitory computer-readable medium of claim 26 , wherein the one or more instructions further cause the BS to:
scramble the plurality of msgB communications using a same msgB radio network temporary identifier or using a same set of msgB radio network temporary identifiers mapped to a same random access occasion (RO).
29. The non-transitory computer-readable medium of claim 25 , wherein the second msgB communication is transmitted during a first portion of an RAR time window, and
wherein transmitting the second msgB communication during the first portion of the RAR time window triggers a prioritized retransmission of a message A (msgA) communication.
30. An apparatus for wireless communication, comprising:
means for transmitting, to a plurality of user equipment (UEs), a first message B (msgB) communication, the first msgB communication including:
an indication that a plurality of random access channel responses (RARs) directed to the plurality of UEs are included in a second msgB communication, and
supplementary scheduling information for other RARs;
means for grouping and selectively multiplexing the plurality of RARs in the second msgB communication; and
means for transmitting the second msgB communication to the plurality of UEs, the second msgB communication being transmitted after the first msgB communication.