PDCCH ordered random access channel procedure for reduced capability user equipment
Certain aspects of the present disclosure provide techniques for a physical downlink control channel (PDCCH) ordered random access channel (RACH) procedure. The RACH procedure may be associated with a cell-defining synchronization signal block (SSB) or non-cell-defining SSB. A method for wireless communications by a user equipment (UE) includes transmitting an indication of one or more capabilities of the UE, receiving a PDCCH that orders the UE to perform a RACH procedure on an uplink carrier based on the one or more capabilities of the UE, determining a minimum gap between a last symbol of the PDCCH and a first symbol of a RACH message, wherein the minimum gap includes a half-duplex (HD) switching delay, and performing the RACH procedure on the uplink carrier when a gap between the last symbol of the PDCCH and the first symbol of the RACH message is equal to or larger than the minimum gap.
1. A user equipment, comprising:
one or more memories comprising computer-executable instructions; and
one or more processors configured to execute the computer-executable instructions and cause the user equipment to:
transmit an indication of one or more capabilities of the user equipment;
receive a physical downlink control channel (PDCCH) that orders the user equipment to perform a random access channel (RACH) procedure on an uplink carrier based on the one or more capabilities of the user equipment; and
perform the RACH procedure on the uplink carrier when a gap between a last symbol of the PDCCH and a first symbol of a RACH message is equal to or larger than a minimum gap that is based on a half-duplex switching delay.
2. The user equipment of claim 1 , the one or more processors further cause the user equipment to determine the minimum gap prior to performing the RACH procedure, wherein the minimum gap includes the half-duplex switching delay.
3. The user equipment of claim 1 , wherein the minimum gap is based on at least one of:
a UE processing capability for reference signal received power (RSRP) measurement, the PDCCH, a physical RACH (PRACH), or a physical uplink shared channel (PUSCH);
a minimum subcarrier spacing (SCS) configuration of the PDCCH, the PRACH, or the PUSCH;
a bandwidth part (BWP) switching delay;
a delay extension based on an operating frequency range (FR);
a switching gap between downlink reception and uplink transmission; or a combination thereof.
4. The user equipment of claim 3 , wherein the minimum gap is based on the UE processing capability for RSRP measurement, the PDCCH, the PRACH, or the PUSCH.
5. The user equipment of claim 3 , wherein the minimum gap is based on the minimum SCS configuration of the PDCCH, the PRACH, or the PUSCH.
6. The user equipment of claim 3 , wherein the minimum gap is based on the BWP switching delay.
7. The user equipment of claim 3 , wherein the minimum gap is based on the delay extension based on the operating FR.
8. The user equipment of claim 3 , wherein the minimum gap is based on the switching gap between downlink reception and uplink transmission.
9. The user equipment of claim 3 , wherein:
the BWP switching delay depends on the one or more capabilities of the user equipment; and
the switching gap depends on the one or more capabilities of the user equipment.
10. The user equipment of claim 1 , wherein the PDCCH indicates the uplink carrier, and wherein the uplink carrier is a normal uplink carrier or a supplementary uplink (SUL) carrier within an uplink bandwidth part (BWP) smaller than or equal to a maximum uplink BWP capability of the user equipment.
11. The user equipment of claim 1 , wherein a type of the RACH procedure comprises:
a first type of RACH procedure in which the user equipment transmits a first type of RACH message that includes a physical RACH (PRACH) preamble; or
a second type of RACH procedure in which the user equipment transmits a second type of RACH message that includes a composite of the PRACH preamble and a physical uplink shared channel (PUSCH).
12. The user equipment of claim 11 , wherein:
the RACH procedure is performed with coverage enhancement (CE) based on the one or more capabilities of the user equipment; and
the CE comprises at least one of:
repetition of the PRACH preamble;
repetition of the PUSCH;
frequency hopping for the PRACH preamble;
frequency hopping for the PUSCH; or
demodulation reference signal (DMRS) bundling for the PUSCH.
13. The user equipment of claim 11 , wherein the PDCCH indicates the type of the RACH procedure and a synchronization signal block (SSB) index, wherein an uplink bandwidth part (BWP) for the RACH procedure is associated with a downlink BWP containing the SSB, and wherein the SSB comprises a cell-defining SSB (CD-SSB) or a non-cell-defining SSB (NCD-SSB).
14. The user equipment of claim 12 , wherein the PDCCH indicates the type of the RACH procedure via bits in at least one of:
a frequency domain resource allocation (FDRA) field, a DMRS configuration of the PDCCH;
an index of the PRACH preamble;
an index of a PRACH preamble group; or
an index of a PRACH mask.
15. The user equipment of claim 1 , wherein the minimum gap is based on at least one of:
an uplink switching gap that depends on the one or more capabilities of the user equipment;
an uplink transmission switching option;
a quasi co-location (QCL);
a transmission configuration indicator (TCI) state;
a synchronization signal block (SSB); or
a downlink reference signal configuration of a serving cell.
16. The user equipment of claim 1 , wherein the indication of the one or more capabilities of the user equipment comprises at least one of: an indication that the user equipment is a reduced capability (RedCap) user equipment; or an indication of a capability of the user equipment to support half-duplex.
17. The user equipment of claim 1 , wherein the one or more capabilities of the user equipment comprise at least one of:
a capability of the user equipment to support a type of RACH procedure;
a capability of the user equipment to support coverage enhancement (CE);
a capability of the user equipment to support half-duplex frequency division duplexing (FDD);
a radio frequency (RF) retuning capability of the user equipment; or
a capability of the user equipment for processing the PDCCH, a physical RACH (PRACH), or a physical uplink shared channel (PUSCH).
18. The user equipment of claim 1 , wherein the minimum gap is based on at least one of:
a type of the RACH procedure; or
a coverage enhancement (CE) of the RACH procedure.
19. The user equipment of claim 1 , wherein the PDCCH indicates one or more power control parameters for a physical RACH (PRACH) message based on the one or more capabilities of the user equipment.
20. The user equipment of claim 19 , wherein the one or more power control parameters depend on at least one of:
a type of the RACH procedure;
a power control scheme;
a transmission configuration indicator (TCI) state;
a quasi co-location (QCL) state;
or a contention resolution scheme for the RACH procedure.
21. The user equipment of claim 20 , wherein the one or more power control parameters comprise at least one of:
an indicator of an uplink full power transmission parameter;
a TCI state;
a QCL state;
a transmission power control (TPC) command;
a transmit power ramp-up parameter; or
a transmit power offset between a physical RACH (PRACH) and physical uplink shared channel (PUSCH) transmission.
22. The user equipment of claim 1 , wherein:
the PDCCH comprises a groupcast PDCCH transmitted in a common search space (CSS) set; and
a payload or cyclic redundancy check (CRC) bits of the payload is scrambled by a group radio network temporary identifier (RNTI).
23. The user equipment of claim 1 , wherein the half-duplex switching delay comprises a first delay for the user equipment to switch from uplink transmission to downlink reception or a second delay for the user equipment to switch from downlink reception to uplink transmission.
24. A method of wireless communication by a user equipment, the method comprising:
transmitting an indication of one or more capabilities of the user equipment;
receiving a physical downlink control channel (PDCCH) that orders the user equipment to perform a random access channel (RACH) procedure on an uplink carrier based on the one or more capabilities of the user equipment; and
performing the RACH procedure on the uplink carrier when a gap between a last symbol of the PDCCH and a first symbol of a RACH message is equal to or larger than a minimum gap that is based on a half-duplex switching delay.
25. The method of claim 24 , further comprising determining the minimum gap prior to performing the RACH procedure, wherein the minimum gap includes the half-duplex switching delay.
26. The method of claim 24 , wherein the minimum gap is based on at least one of:
a UE processing capability for reference signal received power (RSRP) measurement, the PDCCH, a physical RACH (PRACH), or a physical uplink shared channel (PUSCH);
a minimum subcarrier spacing (SCS) configuration of the PDCCH, the PRACH, or the PUSCH;
a bandwidth part (BWP) switching delay;
a delay extension based on an operating frequency range (FR);
a switching gap between downlink reception and uplink transmission; or a combination thereof.
27. The method of claim 26 , wherein the minimum gap is based on the UE processing capability for RSRP measurement, the PDCCH, the PRACH, or the PUSCH.
28. The method of claim 26 , wherein the minimum gap is based on the minimum SCS configuration of the PDCCH, the PRACH, or the PUSCH.
29. The method of claim 26 , wherein the minimum gap is based on the BWP switching delay.
30. A network entity, comprising:
one or more memories comprising computer-executable instructions; and
one or more processors configured to execute the computer-executable instructions and cause the network entity to:
obtain an indication of one or more capabilities of a user equipment;
outputting for transmission, to the user equipment, a physical downlink control channel (PDCCH) that orders the user equipment to perform a random access channel (RACH) procedure based on one or more capabilities of the user equipment; and
obtain a RACH message from the user equipment after a minimum gap between a last symbol of the PDCCH and a first symbol of the RACH message, wherein the minimum gap is based on a half-duplex switching delay.