Reference coordinates for two-step RACH resource configuration
A random access configuration information based on a reference SCS may allow for a unified coordinate system used by the base station and UEs that describes the time-frequency resource configuration for a two-step RACH procedure. The apparatus receives, from a base station, random access configuration information for the base station. The apparatus determines a first time duration for a preamble of a first random access message based on the random access configuration information received from the base station and a reference SCS associated with an uplink BWP configured for the first random access message. The apparatus determines a second time duration for a payload of the first random access message based on the random access configuration information received from the base station and the reference SCS. The apparatus transmits the first message to the base station to initiate a random access procedure.
1. An apparatus for wireless communication at a user equipment (UE), comprising:
a memory; and
at least one processor coupled to the memory and, based at least in part on information stored in the memory, the at least one processor is configured to:
receive, from a base station, a bandwidth part (BWP) configuration and a random access configuration information for the UE within the BWP configuration;
measure a downlink reference signal associated with the random access configuration information;
select a resource for a first random access message based on UE capabilities and measurements of the downlink reference signal;
determine, based at least on a reference subcarrier spacing (SCS) associated with the random access configuration information, a first time duration for a preamble portion of the first random access message, a second time duration for a payload portion of the first random access message, and a gap time duration between the preamble portion and the payload portion of the first random access message; and
transmit the preamble portion and the payload portion of the first random access message within the BWP configuration.
2. The apparatus of claim 1 , further comprising a transceiver coupled to the at least one processor.
3. The apparatus of claim 1 , wherein random access resources for the first random access message comprises time and frequency resources for one or more random access occasions and at least one physical uplink shared channel (PUSCH) occasion, wherein the at least one PUSCH occasion is associated with a demodulation reference signal (DMRS), and the reference SCS for the random access resources are associated with a SCS configured for a BWP for the UE.
4. The apparatus of claim 3 , wherein a configuration for the DMRS is comprised within the random access configuration information comprised within system information or dedicated radio resource control (RRC) signaling.
5. The apparatus of claim 1 , wherein the downlink reference signal associated with the random access configuration information comprises a reference slot index that is mapped at least once to one or more random access channel (RACH) occasions and physical uplink shared channel (PUSCH) occasions with associated demodulated reference signal (DMRS) resources within the first time duration and the second time duration.
6. The apparatus of claim 1 , wherein the at least one processor is configured to:
determine a configuration for the BWP and random access resources associated with a two-step random access channel (RACH) procedure based on UE capabilities.
7. A method of wireless communication at a User Equipment (UE), comprising:
receiving, from a base station, a bandwidth part (BWP) configuration and a random access configuration information for the UE within the BWP configuration;
measuring a downlink reference signal associated with the random access configuration information;
selecting a resource for a first random access message based on UE capabilities and measurements of the downlink reference signal;
determining, based at least on a reference subcarrier spacing (SCS) associated with the random access configuration information, a first time duration for a preamble portion of the first random access message, a second time duration for a payload portion of the first random access message, and a gap time duration between the preamble portion and the payload portion of the first random access message; and
transmitting the preamble portion and the payload portion of the first random access message within the BWP configuration.
8. The method of claim 7 , wherein random access resources for the first random access message comprises time and frequency resources for one or more random access occasions and at least one physical uplink shared channel (PUSCH) occasion, wherein the at least one PUSCH occasion is associated with a demodulation reference signal (DMRS), and the reference SCS for the random access resources are associated with a SCS configured for a BWP for the UE.
9. The method of claim 8 , wherein a configuration for the DMRS is comprised within the random access configuration information comprised within system information or dedicated radio resource control (RRC) signaling.
10. The method of claim 7 , wherein the downlink reference signal associated with the random access configuration information comprises a reference slot index that is mapped at least once to one or more random access channel (RACH) occasions and physical uplink shared channel (PUSCH) occasions with associated demodulated reference signal (DMRS) resources within the first time duration and the second time duration.
11. The method of claim 7 , further comprising:
determining a configuration for the BWP and random access resources associated with a two-step random access channel (RACH) procedure based on UE capabilities.