Techniques for user equipment (UE) procedures for random access channel (RACH) type selection and random access response (RAR) monitoring in a wireless communication system

1. A method of communications at a user equipment (UE) for coverage enhancement, comprising:

receiving an allocation of a physical uplink shared channel (PUSCH) resource unit (PRU) resource set including multiple PRUs from a network entity;

receiving a set of criteria for a random access channel (RACH) type selection and a reference signal received power (RSRP) measurement object for at least one of a two-step RACH procedure or a four-step RACH procedure;

receiving an index of a RACH occasion (RO) having at least one unutilized PRU resource for each physical RACH (PRACH) slot within an synchronization signal block (SSB)-to-RO association pattern period or a channel state indication reference signal (CSI-RS)-to-RO association pattern period;

determining whether to perform the two-step RACH procedure or a four-step RACH procedure;

selecting the two-step RACH procedure based at least on a UE capability type, an RSRP measurement or a target for coverage enhancement;

ignoring the at least one unutilized PRU resource based on determining to perform the two-step RACH procedure;

determining a mapping ratio for a message A preamble and the PRU resource set, wherein the multiple PRUs are associated with a number of PUSCH occasions (POs) for the message A transmission;

validating the POs according to at least one of: joint validation of the POs associated with the PRU resource set or separate validation of the POs; and

performing a message A transmission as part of the two-step RACH procedure based at least on the determined mapping ratio.

2. The method of claim 1 , wherein the allocation of the PRU resource set is for a message A initial transmission or a message A retransmission for a single transmit block.

3. The method of claim 1 , wherein the multiple PRUs are aggregated PUSCH slots with Type A mapping or Type B mapping for a single transmit block.

4. The method of claim 1 , wherein the PRU resource set spans multiple slots in a time domain.

5. The method of claim 1 , wherein the PRU resource set is configured with inter-slot frequency hopping or intra-slot frequency hopping.

6. The method of claim 1 , wherein determining the mapping ratio for the message A preamble and the PRU resource set includes:

receiving one of a system information message or a radio resource control (RRC) message including the mapping ratio for a defined message A configuration; and

decoding the system information message or the RRC message to obtain the mapping ratio.

7. The method of claim 1 , wherein determining the mapping ratio for the message A preamble and the PRU resource set includes:

deriving the mapping ratio based on a function of a number of valid physical RACH (PRACH) resources, a number of valid PRU resource sets, and a number of PRUs per PRU resource set.

8. The method of claim 1 , further comprising:

determining that mapping information for the two-step RACH procedure can be decoded; and

based on having a valid RACH occasion (RO) for the two-step RACH procedure and not having a valid PRU resource set for the two-step RACH procedure:

transmitting message 1 of the four-step RACH procedure; and

monitoring message 2 only within a random access response (RAR) window starting after a message 1 transmission, or

monitoring both message 2 and message B within an extended RAR window after the message 1 transmission.

9. The method of claim 8 , wherein a cyclic redundancy check (CRC) of a downlink control information (DCI) for the message 2 is masked by a cell radio network identifier (C-RNTI), a temporary cell RNTI (TC-RNTI) or a random access RNTI (RA-RNTI).

10. The method of claim 8 , wherein a cyclic redundancy check (CRC) of a downlink control information (DCI) for a message B is masked by a cell radio network identifier (C-RNTI) or a message B-RNTI, and wherein a length of the extended RAR window is upper bounded by a sum of a message 2 RAR window length and a message B RAR window length.

11. An apparatus for coverage enhancement, comprising:

a transceiver;

a memory configured to store instructions; and

at least one processor communicatively coupled with the transceiver and the memory, wherein the at least one processor is configured to:

receive an allocation of a physical uplink shared channel (PUSCH) resource unit (PRU) resource set including multiple PRUs from a network entity;

receive a set of criteria for a random access channel (RACH) type selection and a reference signal received power (RSRP) measurement object for at least one of a two-step RACH procedure or a four-step RACH procedure;

receive an index of a RACH occasion (RO) having at least one unutilized PRU resource for each physical RACH (PRACH) slot within an synchronization signal block (SSB)-to-RO association pattern period or a channel state indication reference signal (CSI-RS)-to-RO association pattern period;

determine whether to perform the two-step RACH procedure or a four-step RACH procedure;

select the two-step RACH procedure based at least on a UE capability type, an RSRP measurement or a target for coverage enhancement;

ignore the at least one unutilized PRU resource based on determining to perform the two-step RACH procedure;

determine a mapping ratio for a message A preamble and the PRU resource set, wherein the multiple PRUs are associated with a number of PUSCH occasions (POs) for the message A transmission;

validate the POs according to at least one of: joint validation of the POs associated with the PRU resource set, or separate validation of the POs; and

perform a message A transmission as part of the two-step RACH procedure based at least on the determined mapping ratio.

12. The apparatus of claim 11 , wherein the allocation of the PRU resource set is for a message A initial transmission or a message A retransmission for a single transmit block.

13. The apparatus of claim 11 , wherein the multiple PRUs are aggregated PUSCH slots with Type A mapping or Type B mapping for a single transmit block.

14. The apparatus of claim 11 , wherein the PRU resource set spans multiple slots in a time domain.

15. The apparatus of claim 11 , wherein the PRU resource set is configured with inter-slot frequency hopping or intra-slot frequency hopping.

16. The apparatus of claim 11 , wherein to determine the mapping ratio for the message A preamble and the PRU resource set, the at least one processor is further configured to:

receive one of a system information message or a radio resource control (RRC) message including the mapping ratio for a defined message A configuration; and

decode the system information message or the RRC message to obtain the mapping ratio.

17. The apparatus of claim 11 , wherein to determine the mapping ratio for the message A preamble and the PRU resource set, the at least one processor is further configured to:

derive the mapping ratio based on a function of a number of valid physical RACH (PRACH) resources, a number of valid PRU resource sets, and a number of PRUs per PRU resource set.

18. The apparatus of claim 11 , wherein the at least one processor is further configured to:

determine that mapping information for the two-step RACH procedure can be decoded; and

based on having a valid RACH occasion (RO) for the two-step RACH procedure and not having a valid PRU resource set for the two-step RACH procedure:

transmit message 1 of the four-step RACH procedure; and

monitor message 2 only within a random access response (RAR) window starting after a message 1 transmission, or

monitor both message 2 and message B within an extended RAR window after the message 1 transmission.

19. The apparatus of claim 18 , wherein a cyclic redundancy check (CRC) of a downlink control information (DCI) for the message 2 is masked by a cell radio network identifier (C-RNTI), a temporary cell RNTI (TC-RNTI) or a random access RNTI (RA-RNTI).

20. The apparatus of claim 18 , wherein a cyclic redundancy check (CRC) of a downlink control information (DCI) for a message B is masked by a cell radio network identifier (C-RNTI) or a message B-RNTI, and wherein a length of the extended RAR window is upper bounded by a sum of a message 2 RAR window length and a message B RAR window length.

21. An apparatus for coverage enhancement, comprising:

means for receiving an allocation of a physical uplink shared channel (PUSCH) resource unit (PRU) resource set including multiple PRUs from a network entity;

means for receiving a set of criteria for a random access channel (RACH) type selection and a reference signal received power (RSRP) measurement object for at least one of a two-step RACH procedure or a four-step RACH procedure;

means for receiving an index of a RACH occasion (RO) having at least one unutilized PRU resource for each physical RACH (PRACH) slot within an synchronization signal block (SSB)-to-RO association pattern period or a channel state indication reference signal (CSI-RS)-to-RO association pattern period;

means for determining whether to perform the two-step RACH procedure or a four-step RACH procedure;

means for selecting the two-step RACH procedure based at least on a UE capability type, an RSRP measurement or a target for coverage enhancement;

means for ignoring the at least one unutilized PRU resource based on determining to perform the two-step RACH procedure;

means for determining a mapping ratio for a message A preamble and the PRU resource set, wherein the multiple PRUs are associated with a number of PUSCH occasions (POs) for the message A transmission;

means for validating the POs according to at least one of: joint validation of the POs associated with the PRU resource set, or separate validation of the POs; and

means for performing a message A transmission as part of RACH procedure based at least on the determined mapping ratio.

22. The apparatus of claim 21 , wherein the multiple PRUs are aggregated PUSCH slots with Type A mapping or Type B mapping for a single transmit block.

23. The apparatus of claim 21 , wherein the PRU resource set spans multiple slots in a time domain, and wherein the PRU resource set is configured with inter-slot frequency hopping or intra-slot frequency hopping.

24. A non-transitory computer-readable medium including stored instructions for coverage enhancement, executable by a processor to:

receive an allocation of a physical uplink shared channel (PUSCH) resource unit (PRU) resource set including multiple PRUs from a network entity;

receive a set of criteria for a random access channel (RACH) type selection and a reference signal received power (RSRP) measurement object for at least one of a two-step RACH procedure or a four-step RACH procedure;

receive an index of a RACH occasion (RO) having at least one unutilized PRU resource for each physical RACH (PRACH) slot within an synchronization signal block (SSB)-to-RO association pattern period or a channel state indication reference signal (CSI-RS)-to-RO association pattern period;

determine whether to perform the two-step RACH procedure or a four-step RACH procedure;

select the two-step RACH procedure based at least on a UE capability type, an RSRP measurement or a target for coverage enhancement;

ignore the at least one unutilized PRU resource based on determining to perform the two-step RACH procedure;

determine a mapping ratio for a message A preamble and the PRU resource set, wherein the multiple PRUs are associated with a number of PUSCH occasions (POs) for the message A transmission;

validate the POs according to at least one of: joint validation of the POs associated with the PRU resource set, or separate validation of the POs; and

perform a message A transmission as part of the two-step random access channel (RACH) RACH procedure based at least on the determined mapping ratio.

25. The non-transitory computer-readable medium of claim 24 , wherein the multiple PRUs are aggregated PUSCH slots with Type A mapping or Type B mapping for a single transmit block.

26. The non-transitory computer-readable medium of claim 24 , wherein the PRU resource set spans multiple slots in a time domain, and wherein the PRU resource set is configured with inter-slot frequency hopping or intra-slot frequency hopping.