Random access response enhancement for user equipments with reduced capabilities

1. A method of wireless communication for a user equipment (UE), comprising:

transmitting a message to a serving base station, the message including a request for timeline relaxation for transmission of a subsequent message, the message and the subsequent message being associated with a random access procedure;

receiving a response message from the serving base station, the response message being associated with the random access procedure and indicating one or more timing offsets corresponding to the timeline relaxation, wherein the one or more timing offsets includes at least one slot offset based on at least one lookup table (LUT); and

transmitting the subsequent message to the serving base station based on the one or more timing offsets indicated by the serving base station, wherein the subsequent message acknowledges the response message.

2. The method of claim 1 , wherein the one or more timing offsets includes a first timing offset comprising a first slot offset and a second slot offset, wherein a value of the first slot offset is obtained from a first set of lookup tables (LUTs) based on at least the request for the timeline relaxation, a physical uplink shared channel (PUSCH) mapping type or a PUSCH numerology in an active uplink (UL) bandwidth part (BWP), and wherein a value of the second slot offset is obtained from a second set of lookup tables (LUTs) based on at least the request for the timeline relaxation or the PUSCH numerology in the active uplink (UL) bandwidth part (BWP).

3. The method of claim 2 , wherein the PUSCH mapping type is a type of predetermined standard-based mapping, and wherein the PUSCH numerology is based on a subcarrier spacing (SCS) value, a normal cyclic prefix, or an extended cyclic prefix.

4. The method of claim 1 , wherein the one or more timing offsets includes a first timing offset and a second timing offset, wherein the first timing offset comprises a first slot offset and a second slot offset, and wherein the second timing offset comprises a third slot offset.

5. The method of claim 4 , wherein the UE receives the response message using a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH), and wherein the response message indicates a value of the third slot offset in at least one of a lookup table preconfigured by a network for the UE, in a downlink control information (DCI) received on the physical downlink control channel (PDCCH) as part of the random access procedure, or in a media access control (MAC) header, a MAC subheader, or a MAC sub protocol data unit (subPDU) received on the physical downlink shared channel (PDSCH) as part of the random access procedure.

6. A method of wireless communication for a user equipment (UE), comprising:

transmitting a first message or a third message of a random access procedure to a serving base station, the first message or the third message including a request for timeline relaxation for transmission of an acknowledgment message in the random access procedure;

receiving a second message or a fourth message of the random access procedure from the serving base station, the second message or the fourth message indicating a timing offset corresponding to the timeline relaxation, wherein the timing offset is indicated as a number of slots using one or more bits of a downlink control information (DCI) format and a plurality of bits allocated to a physical downlink shared channel (PDSCH) to hybrid automatic repeat request (HARQ) feedback (FB) timing indicator in the DCI format; and

transmitting the acknowledgement message on a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH) in response to the second message or fourth message of the random access procedure based on the timing offset.

7. The method of claim 6 , wherein the one or more bits of the DCI format and the plurality of bits allocated to the PDSCH to HARQ FB timing indicator in the DCI format form a 5-bit value.

8. The method of claim 7 , wherein the 5-bit value indicates a value for the timeline relaxation that is within a range of one to 32 slots.

9. The method of claim 6 , wherein:

the timing offset is indicated by a group-specific slot offset and a UE-specific slot offset, wherein the group-specific slot offset is indicated as a number of slots using one or more UE group-specific bits carried by downlink control information (DCI) of a physical downlink control channel (PDCCH) or by a common media access control (MAC) header of the PDSCH, and

the UE-specific slot offset is indicated as one or more UE-specific bits carried by downlink control information (DCI) of the PDCCH, or by a MAC subheader or a MAC sub protocol data unit (subPDU) of the PDSCH, and

wherein the PDCCH and the PDSCH are mapped to the response message.

10. The method of claim 6 , wherein the second message or the fourth message carries a success random access response (SuccessRAR) with respect to the first message or the third message of the random access procedure.

11. An apparatus for wireless communication, comprising:

at least one processor;

a transceiver communicatively coupled to the at least one processor; and

a memory communicatively coupled to the at least one processor,

wherein the at least one processor is configured to:

transmit a message to a serving base station, the message including a request for timeline relaxation for transmission of a subsequent message, the message and the subsequent message being associated with a random access procedure;

receive a response message from the serving base station, the response message being associated with the random access procedure and indicating one or more timing offsets corresponding to the timeline relaxation, wherein the one or more timing offsets includes at least one slot offset based on at least one lookup table (LUT); and

transmit the subsequent message to the serving base station based on the one or more timing offsets indicated by the serving base station, wherein the subsequent message acknowledges the response message.

12. The apparatus of claim 11 , wherein the one or more timing offsets includes a first timing offset comprising a first slot offset and a second slot offset, wherein a value of the first slot offset is obtained from a first set of lookup tables (LUTs) based on at least the request for the timeline relaxation, a physical uplink shared channel (PUSCH) mapping type or a PUSCH numerology in an active uplink (UL) bandwidth part (BWP), and wherein a value of the second slot offset is obtained from a second set of lookup tables (LUTs) based on at least the request for the timeline relaxation or the PUSCH numerology in the active uplink (UL) bandwidth part (BWP).

13. The apparatus of claim 12 , wherein the PUSCH mapping type is a type of predetermined standard-based mapping, and wherein the PUSCH numerology is based on a subcarrier spacing (SCS) value, a normal cyclic prefix, or an extended cyclic prefix.

14. The apparatus of claim 11 , wherein the one or more timing offsets includes a first timing offset and a second timing offset, wherein the first timing offset comprises a first slot offset and a second slot offset, and wherein the second timing offset comprises a third slot offset.

15. The apparatus of claim 14 , wherein the apparatus receives the response message using a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH), and wherein the response message indicates a value of the third slot offset in at least one of a lookup table preconfigured by a network for the apparatus, in a downlink control information (DCI) received on the physical downlink control channel (PDCCH) as part of the random access procedure, or in a media access control (MAC) header, a MAC subheader, or a MAC sub protocol data unit (subPDU) received on the physical downlink shared channel (PDSCH) as part of the random access procedure.