Search space configurations for random access messaging
Methods, systems, and devices for wireless communications are described. In some systems, a user equipment (UE) may perform a random access (RACH) procedure based on a selected synchronization signal block (SSB). During this RACH procedure, a base station may transmit physical downlink control channel (PDCCH) messages for UE RACH message handling. To receive PDCCH signaling for RACH Messages 2, 3, or 4 (Msg 2/3/4), the UE may identify a set of time resources used by the base station for transmitting SSBs that are not quasi-co-located (QCL) with the selected SSB. The UE may identify a Msg 2/3/4 search space that does not overlap with this identified set of resources, and may monitor this identified search space. The search space may correspond to a modified remaining minimum system information (RMSI) search space indicated by the base station, or a valid RMSI search space not indicated by the base station.
1. A user equipment (UE), comprising:
one or more memories storing processor-executable code; and
one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the UE to:
receive a synchronization signal block (SSB) via a receive beam of the UE;
transmit a random access (RACH) message based at least in part on the SSB received via the receive beam of the UE; and
monitor one or more monitoring occasions of a Type0 physical downlink control channel (Type0-PDCCH) common search space over two consecutive slots for a physical downlink control channel (PDCCH) message in a search space, the Type0-PDCCH common search space corresponding to the SSB and configured via a physical broadcast channel (PBCH) configuration, wherein a start of the search space is based at least in part on the RACH message and an end of the search space is based at least in part on a response timer.
2. The UE of claim 1 , wherein the PDCCH message comprises a PDCCH grant for a RACH message 2 (Msg2) transmission, a PDCCH grant for a RACH message 3 (Msg3) transmission, a PDCCH grant for a RACH message 4 (Msg4) transmission, or a combination thereof.
3. The UE of claim 1 , wherein the one or more processors are individually or collectively operable to execute the code to further cause the UE to:
receive one or more other SSBs via one or more second receive beams that are different from the receive beam.
4. The UE of claim 1 , wherein
the PBCH configuration indicates a remaining minimum system information (RMSI) search space corresponding to the SSB.
5. The UE of claim 4 , wherein
one or more time resources are removed from the RMSI search space that overlap with a set of time resources associated with one or more other SSBs, wherein the search space comprises remaining time resources of the RMSI search space based on the one or more time resources being removed.
6. The UE of claim 5 , wherein
the search space comprises same symbol index locations as the RMSI search space but with an altered slot-level periodicity different from a slot-level periodicity of the RMSI search space.
7. The UE of claim 4 , wherein the one or more processors are individually or collectively operable to execute the code to further cause the UE to:
receive an RMSI transmission associated with a default search space, wherein
monitoring for the PDCCH message is further based at least in part on one or more second monitoring occasions of the RMSI search space.
8. The UE of claim 1 , wherein
the search space comprises a remaining minimum system information (RMSI) search space with time resources non-overlapping with a set of time resources associated with one or more other SSBs.
9. The UE of claim 1 , wherein the one or more processors are individually or collectively operable to execute the code to further cause the UE to:
receive an indication of a first set of time resources for the search space, wherein
one or more time resources of a second set of time resources associated with one or more other SSBs are removed from the first set of time resources for the search space, wherein the search space comprises remaining time resources of the first set of time resources for the search space based on the one or more time resources of the second set of time resources being removed.
10. The UE of claim 9 , wherein:
the indication of the first set of time resources for the search space comprises a time window for the search space; and
a subset of slots of the time window comprise the search space.
11. The UE of claim 10 , wherein the subset of slots comprises each slot of the time window.
12. The UE of claim 1 , wherein the response timer comprises a random access response (RAR) window, a contention resolution timer, or a combination thereof.
13. The UE of claim 1 ,
wherein the RACH message is transmitted in a RACH occasion corresponding to the SSB.
14. The UE of claim 1 ,
wherein the search space is monitored using the receive beam during time resources that are different from a set of time resources associated with one or more other SSBs, and wherein
at least one SSB of the one or more other SSBs is received via a second receive beam different from the receive beam during the set of time resources.
15. The UE of claim 14 , wherein the one or more processors are individually or collectively operable to execute the code to further cause the UE to:
receive the at least one SSB of the one or more other SSBs based at least in part on the time resources for the search space not overlapping with the set of time resources associated with the one or more other SSBs.
16. The UE of claim 1 , wherein the one or more processors are individually or collectively operable to execute the code to further cause the UE to:
receive the PDCCH message in one or more control channel elements (CCEs) of the search space based at least in part on the monitoring.
17. The UE of claim 1 , wherein one or more other SSBs associated with a set of time resources comprise one or more SSBs actually transmitted by a network entity.
18. The UE of claim 17 , wherein the one or more processors are individually or collectively operable to execute the code to further cause the UE to:
receive an indication of the one or more SSBs actually transmitted by the network entity via remaining minimum system information (RMSI), other system information (OSI), a radio resource control (RRC) message, a medium access control (MAC) control element (CE), a handover message, or a combination thereof.
19. A method for wireless communications at a user equipment (UE), comprising:
receiving a synchronization signal block (SSB) via a receive beam of the UE;
transmitting a random access (RACH) message based at least in part on the SSB received via the receive beam of the UE; and
monitoring one or more monitoring occasions of a Type0 physical downlink control channel (Type0-PDCCH) common search space over two consecutive slots for a physical downlink control channel (PDCCH) message in a search space, the Type0-PDCCH common search space corresponding to the SSB and configured via a physical broadcast channel (PBCH) configuration, wherein a start of the search space is based at least in part on the RACH message and an end of the search space is based at least in part on a response timer.
20. An apparatus for wireless communications at a network entity, comprising:
one or more memories; and
one or more processors coupled to the one or more memories and configured to:
transmit a synchronization signal block (SSB) associated with a receive beam of a user equipment (UE);
receive a random access (RACH) message based at least in part on the SSB associated with the receive beam of the UE; and
transmit, based on one or more monitoring occasions of a Type0 physical downlink control channel (Type0-PDCCH) common search space over two consecutive slots, a physical downlink control channel (PDCCH) message associated with a search space, the Type0-PDCCH common search space corresponding to the SSB and configured via a physical broadcast channel (PBCH) configuration, wherein a start of the search space is based at least in part on the RACH message and an end of the search space is based at least in part on a response timer.