Supporting cross-TAG scheduling and 2-step RACH payload transmission for a PDCCH-ordered contention-free random access procedure
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive, via a first cell, downlink control information for physical downlink control channel ordered contention-free random access, wherein the downlink control information indicates a timing advance group of a second cell and one or more parameters associated with a random access message to be transmitted by the UE via the second cell, wherein the first cell and the second cell belong to different timing advance groups. The UE may transmit the random access message via the second cell according to the one or more parameters and a timing advance value determined based at least in part on the timing advance group of the second cell. Numerous other aspects are provided.
1. A method of wireless communication performed by a user equipment (UE), comprising:
receiving, via a first cell, downlink control information for physical downlink control channel ordered contention-free random access, wherein the downlink control information indicates a timing advance group of a second cell and one or more parameters associated with a random access message to be transmitted by the UE via the second cell, wherein the first cell and the second cell belong to different timing advance groups,
wherein the downlink control information includes one or more bits indicating whether the random access message is to be transmitted as part of a two-step random access procedure or a four-step random access procedure; and
transmitting, based on receiving the downlink control information, the random access message via the second cell according to the one or more parameters and a timing advance value determined based at least in part on the timing advance group of the second cell.
2. The method of claim 1 , wherein the random access message includes at least one of a random access preamble, a random access payload, or a combination thereof.
3. The method of claim 1 , wherein the timing advance group of the second cell is not configured with a scheduling secondary cell and all other timing advance groups associated with the UE are configured with a scheduling cell.
4. The method of claim 1 , wherein the downlink control information indicates the timing advance group of the second cell in a field that includes a timing advance group identifier or a carrier indicator that identifies an index of an uplink carrier in the timing advance group.
5. The method of claim 4 , wherein a bit width of the field is indicated in a radio resource control message.
6. The method of claim 1 , wherein the one or more parameters indicate a frequency domain resource allocation for the random access message.
7. The method of claim 1 , wherein the one or more parameters indicate a time domain resource allocation for the random access message.
8. The method of claim 1 , wherein the one or more parameters indicate at least one of a payload size, a modulation and coding scheme, a rate matching scheme, or a redundancy version associated with the random access message.
9. The method of claim 1 , wherein the one or more parameters indicate a demodulation reference signal resource configuration for the random access message.
10. The method of claim 1 , wherein the downlink control information includes a field to indicate a random access preamble index, a field to indicate a synchronization signal block index, a field to indicate a physical random access channel mask index, and a set of reserved bits that includes the one or more bits, the set of reserved bits to indicate at least one of:
whether the random access message is to be transmitted as part of the two-step random access procedure or the four-step random access procedure,
the timing advance group of the second cell,
a frequency domain resource allocation for the random access message,
a time domain resource allocation for the random access message,
a payload size associated with the random access message,
a modulation and coding scheme for the random access message,
a rate matching scheme for the random access message,
a redundancy version for the random access message,
a demodulation reference signal resource configuration for the random access message, or
a combination thereof.
11. The method of claim 1 , wherein cyclic redundancy check bits of the downlink control information are scrambled using at least one of:
a cell radio network temporary identifier, or
a UE identifier that is a function of the cell radio network temporary identifier and a timing advance group index.
12. The method of claim 1 , wherein the timing advance group of the second cell is not configured with a scheduling secondary cell and at least one other timing advance group associated with the UE is not configured with a scheduling cell.
13. The method of claim 1 , further comprising:
receiving, via the first cell, second downlink control information for physical downlink control channel ordered contention-free random access, wherein the second downlink control information indicates a second timing advance group of a third cell and one or more second parameters associated with a second random access message to be transmitted by the UE via the third cell, wherein the third cell belongs to a different timing advance group than the first cell and the second cell; and
transmitting the second random access message via the third cell according to the one or more second parameters and a second timing advance value determined based at least in part on the second timing advance group of the third cell.
14. The method of claim 13 , wherein first cyclic redundancy check bits of the downlink control information are scrambled using a first identifier and second cyclic redundancy check bits of the second downlink control information are scrambled using a second identifier.
15. The method of claim 13 , wherein joint cyclic redundancy check bits of the downlink control information and the second downlink control information are scrambled using an identifier.
16. A method of wireless communication performed by a user equipment (UE), comprising:
receiving downlink control information for physical downlink control channel ordered contention-free random access, wherein the downlink control information indicates one or more parameters associated with a random access message to be transmitted by the UE as part of a two-step random access procedure,
wherein the downlink control information includes one or more bits indicating that the random access message is to be transmitted as part of the two-step random access procedure; and
transmitting, based on receiving the downlink control information, the random access message for the two-step random access procedure according to the one or more parameters.
17. The method of claim 16 , wherein the random access message includes at least one of a random access preamble, a random access payload, or a combination thereof.
18. The method of claim 16 , wherein the one or more parameters indicate at least one of:
whether the random access message is to be transmitted as part of the two-step random access procedure or a four-step random access procedure,
a frequency domain resource allocation for the random access message,
a time domain resource allocation for the random access message,
a payload size of the random access message,
a modulation and coding scheme for the random access message,
a rate matching scheme for the random access message,
a redundancy version for the random access message,
a demodulation reference signal resource configuration for the random access message, or
a combination thereof.
19. The method of claim 16 , wherein the downlink control information includes a field to indicate a random access preamble index, a field to indicate a synchronization signal block index, a field to indicate a physical random access channel mask index, and a set of reserved bits, including the one or more bits, to indicate the one or more parameters.
20. The method of claim 16 , further comprising receiving an indication that a timing advance group associated with transmission of the random access message is the same as a timing advance group associated with a cell via which the downlink control information is received.
21. The method of claim 20 , wherein the indication is included in at least one of a radio resource control message or a field in the downlink control information.
22. The method of claim 20 , wherein the indication is based at least in part on at least one of a preamble indicated in the downlink control information, a demodulation reference signal configuration indicated in the downlink control information, a cyclic redundancy check mask applied to the downlink control information, an identifier used for scrambling cyclic redundancy check bits of the downlink control information, or a combination thereof.
23. A user equipment (UE) for wireless communication, comprising:
a memory; and
one or more processors coupled to the memory, the one or more processors configured to:
receive, via a first cell, downlink control information for physical downlink control channel ordered contention-free random access, wherein the downlink control information indicates a timing advance group of a second cell and one or more parameters associated with a random access message to be transmitted by the UE via the second cell, wherein the first cell and the second cell belong to different timing advance groups,
wherein the downlink control information includes one or more bits indicating whether the random access message is to be transmitted as part of a two-step random access procedure or a four-step random access procedure; and
transmit, based on receiving the downlink control information via the first cell, the random access message via the second cell according to the one or more parameters and a timing advance value determined based at least in part on the timing advance group of the second cell.
24. The UE of claim 23 , wherein the timing advance group of the second cell is not configured with a scheduling secondary cell and all other timing advance groups associated with the UE are configured with a scheduling cell.
25. The UE of claim 23 , wherein the one or more bits comprise a set of reserved bits.
26. The UE of claim 23 , wherein the downlink control information indicates the timing advance group of the second cell in a field that includes a timing advance group identifier or a carrier indicator that identifies an index of an uplink carrier in the timing advance group.
27. The UE of claim 23 , wherein the timing advance group of the second cell is not configured with a scheduling secondary cell and at least one other timing advance group associated with the UE is not configured with a scheduling cell.
28. The UE of claim 23 , wherein the one or more processors are further configured to:
receive, via the first cell, second downlink control information for physical downlink control channel ordered contention-free random access, wherein the second downlink control information indicates a second timing advance group of a third cell and one or more second parameters associated with a second random access message to be transmitted by the UE via the third cell, wherein the third cell belongs to a different timing advance group than the first cell and the second cell; and
transmit the second random access message via the third cell according to the one or more second parameters and a second timing advance value determined based at least in part on the second timing advance group of the third cell.
29. A user equipment (UE) for wireless communication, comprising:
a memory; and
one or more processors coupled to the memory, the one or more processors configured to:
receive downlink control information for physical downlink control channel ordered contention-free random access, wherein the downlink control information indicates one or more parameters associated with a random access message to be transmitted by the UE as part of a two-step random access procedure,
wherein the downlink control information includes one or more bits indicating that the random access message is to be transmitted as part of the two-step random access procedure; and
transmit, based on receiving the downlink control information, the random access message for the two-step random access procedure according to the one or more parameters.
30. The UE of claim 29 , wherein the downlink control information includes a field to indicate a random access preamble index, a field to indicate a synchronization signal block index, a field to indicate a physical random access channel mask index, and a set of reserved bits to indicate the one or more parameters.