Hybrid resource mapping for RAR

A method of wireless communication performed by a base station (BS), the method comprising:

• receiving, from a user equipment (UE), a first random access channel (RACH) message as part of a RACH procedure;
• determining, in response to successfully decoding at least a portion of the first RACH message, a PDSCH channel from among a plurality of PDSCH channels and downlink modulation reference signal (DMRS) resource configuration for the UE;
• including a plurality of DMRS resource configurations including the DMRS resource configuration for the UE in downlink control information (DCI) in a physical downlink control channel (PDCCH), each DMRS resource configuration corresponding to a different PDSCH channel from among the plurality of PDSCH channels;
• configuring each consecutive bit in a configuration field of the DCI as a distinct flag for a different DMRS resource;
• including a random access response (RAR) message for the UE in the determined PDSCH channel;
• and
• transmitting, to the UE, a second RACH message as part of the RACH procedure, the second RACH message comprising the PDCCH and the determined PDSCH channel scheduled by the PDCCH.

A user equipment, comprising:

• a memory;
• a transceiver;
• and
• at least one processor coupled to the memory and the transceiver, wherein the user equipment is configured to:
• receive, from a base station (BS), a random access channel (RACH) response message as part of a RACH procedure;
• decode a physical downlink control channel (PDCCH) in the RACH response message transmitted in a common search space to obtain downlink control information (DCI) from the PDCCH;
• determine a scheduled physical downlink shared channel (PDSCH) from among a plurality of PDSCH channels in the DCI and a downlink modulation reference signal (DMRS) resource configuration for the user equipment from among a plurality of DMRS resource configurations in a configuration field of the DCI, each DMRS resource configuration corresponding to a different PDSCH channel from among the plurality of PDSCH channels;
• demodulate the scheduled PDSCH based on the DMRS resource configuration identified by the DCI;
• and
• decode, based on the determining, each scheduled PDSCH with a corresponding distinct flag asserted in the configuration field of the DCI until decoding the scheduled PDSCH for the UE to obtain a random access response (RAR) message from the BS.

A base station, comprising:

• a memory;
• a transceiver;
• and
• at least one processor coupled to the memory and the transceiver, wherein the base station is configured to:
• receive, from a user equipment (UE), a first random access channel (RACH) message as part of a RACH procedure;
• determine, in response to successfully decoding at least a portion of the first RACH message, a PDSCH channel from among a plurality of PDSCH channels and downlink modulation reference signal (DMRS) resource configuration for the UE;
• include a plurality of DMRS resource configurations including the DMRS resource configuration for the UE in downlink control information (DCI) in a physical downlink control channel (PDCCH), each DMRS resource configuration corresponding to a different PDSCH channel from among the plurality of PDSCH channels;
• configure each consecutive bit in a configuration field of the DCI as a distinct flag for a different DMRS resource;
• include a random access response (RAR) message for the UE in the determined PDSCH channel;
• and
• transmit, to the UE, a second RACH message as part of the RACH procedure, the second RACH message comprising the PDCCH and the determined PDSCH channel scheduled by the PDCCH.