Carrier-dependent random access channel (RACH) response search space
Certain aspects of the present disclosure relate to communication systems, and more particularly, to random access channel (RACH) procedures in deployments where a RACH transmission may be sent on different UL carriers, which may include supplemental UL (SUL) carriers.
1. A method for wireless communications by a user equipment (UE), comprising:
transmitting a random access channel (RACH) transmission on an uplink carrier selected from at least two available uplink carriers;
determining, based on the uplink carrier on which the RACH transmission was transmitted, a search space to monitor for a random access channel response (RAR) transmitted on a downlink carrier, wherein determining the search space comprises:
determining, based on the uplink carrier on which the RACH transmission was transmitted, a control resource set (CORESET) that includes time and frequency resources configured for conveying control information; and
selecting, based on the uplink carrier on which the RACH transmission was transmitted, the search space from multiple search spaces within the determined CORESET;
determining a random access radio network temporary identifier (RA-RNTI) based on an identifier of the selected uplink carrier; and
monitoring for the RAR in the selected search space using the determined RA-RNTI.
2. The method of claim 1 , wherein:
the at least two available uplink carriers have different numerologies; and
the RA-RNTI is determined also based on the numerology of the uplink carrier on which the RACH transmission was transmitted.
3. A method for wireless communications by a network entity, comprising:
receiving a random access channel (RACH) transmission on an uplink carrier from at least two available uplink carriers;
determining, based on the uplink carrier on which the RACH transmission was transmitted, a search space to use for transmitting a random access channel response (RAR) on a downlink carrier, wherein determining the search space comprises:
determining, based on the uplink carrier on which the RACH transmission was transmitted, a control resource set (CORESET) that includes time and frequency resources configured for conveying control information; and
selecting, based on the uplink carrier on which the RACH transmission was transmitted, the search space from multiple search spaces within the determined CORESET;
determining a random access radio network temporary identifier (RA-RNTI) based on an identifier of the uplink carrier; and
transmitting the RAR in the selected search space using the determined RA-RNTI.
4. The method of claim 3 , wherein:
the at least two available uplink carriers have different numerologies; and
the RA-RNTI is determined also based on the numerology of the uplink carrier on which the RACH transmission was transmitted.
5. An apparatus for wireless communications by a user equipment (UE), comprising:
means for transmitting a random access channel (RACH) transmission on an uplink carrier selected from at least two available uplink carriers;
means for determining, based on the uplink carrier on which the RACH transmission was transmitted, a search space to monitor for a random access channel response (RAR) transmitted on a downlink carrier, wherein the means for determining the search space comprises:
means for determining, based on the uplink carrier on which the RACH transmission was transmitted, a control resource set (CORESET) that includes time and frequency resources configured for conveying control information; and
means for selecting, based on the uplink carrier on which the RACH transmission was transmitted, the search space from multiple search spaces within the determined CORESET;
means for determining a random access radio network temporary identifier (RA-RNTI) based on an identifier of the selected uplink carrier; and
means for monitoring for the RAR in the selected search space using the determined RA-RNTI.
6. The apparatus of claim 5 , wherein:
the at least two available uplink carriers have different numerologies; and
the RA-RNTI is determined also based on the numerology of the uplink carrier on which the RACH transmission was transmitted.
7. An apparatus for wireless communications by a network entity, comprising:
means for receiving a random access channel (RACH) transmission on an uplink carrier from at least two available uplink carriers;
means for determining, based on the uplink carrier on which the RACH transmission was transmitted, a search space to use for transmitting a random access channel response (RAR) on a downlink carrier, wherein the means for determining the search space comprises:
means for determining, based on the uplink carrier on which the RACH transmission was transmitted, a control resource set (CORESET) that includes time and frequency resources configured for conveying control information; and
means for selecting, based on the uplink carrier on which the RACH transmission was transmitted, the search space from multiple search spaces within the determined CORESET;
means for determining a random access radio network temporary identifier (RA-RNTI) based on an identifier of the uplink carrier; and
means for transmitting the RAR in the determined search space using the determined RA-RNTI.
8. The apparatus of claim 7 , wherein:
the at least two available uplink carriers have different numerologies; and
the RA-RNTI is determined also based on the numerology of the uplink carrier on which the RACH transmission was transmitted.
9. An apparatus for wireless communications by a user equipment (UE), comprising:
a transmitter configured to transmit a random access channel (RACH) transmission on an uplink carrier selected from at least two available uplink carriers;
at least one processor configured to:
determine, based on the uplink carrier on which the RACH transmission was transmitted, a search space to monitor for a random access channel response (RAR) transmitted on a downlink carrier, wherein the at least one processor is configured to determine the search space comprises:
determining, based on the uplink carrier on which the RACH transmission was transmitted, a control resource set (CORESET) that includes time and frequency resources configured for conveying control information; and
selecting, based on the uplink carrier on which the RACH transmission was transmitted, the search space from multiple search spaces within the determined CORESET; and
determine a random access radio network temporary identifier (RA-RNTI) based on an identifier of the selected uplink carrier; and
a receiver configured to monitor for the RAR in the selected search space using the determined RA-RNTI.
10. An apparatus for wireless communications by a network entity, comprising:
a receiver configured to receive a random access channel (RACH) transmission on an uplink carrier from at least two available uplink carriers;
at least one processor configured to:
determine, based on the uplink carrier on which the RACH transmission was transmitted, a search space to use for transmitting a random access channel response (RAR) on a downlink carrier, wherein the at least one processor is configured to determine the search space by:
determining, based on the uplink carrier on which the RACH transmission was transmitted, a control resource set (CORESET) that includes time and frequency resources configured for conveying control information; and
selecting, based on the uplink carrier on which the RACH transmission was transmitted, the search space from multiple search spaces within the determined CORESET; and
determine a random access radio network temporary identifier (RA-RNTI) based on an identifier of the uplink carrier; and
a transmitter configured to transmit the RAR in the selected search space using the determined RA-RNTI.