User equipment shift randomization for uplink control channel transmission
Methods, systems, and devices for wireless communications are described. In some cases, randomized shifts of a base sequence may be used for transmitting uplink control information. For example, a user equipment (UE) may identify a base sequence of an uplink control message. The UE may also receive signaling that indicates a UE-specific initial shift that may be applied to the base sequence. In some examples, the signaling that indicates the randomized shift may be explicit, implicit, or a combination thereof. After determining one or more shifted sequences based on the UE-specific initial shift, a payload of the uplink control message, and the base sequence, the UE may select a shifted sequence to be transmitted, where the selection is based on a payload of the uplink control message. For example, different shifted sequences may be selected for respective transmissions of scheduling requests, 1-bit acknowledgments (ACKs), 2-bit ACKs, and the like.
1. A method for wireless communication at a user equipment (UE) comprising:
identifying a base sequence for transmission of an uplink control message;
receiving signaling that indicates a UE-specific initial shift to be used with the base sequence, the signaling comprising:
an indication of a subset of resources for the uplink control message included within acknowledgment (ACK) resource indicator (ARI) bits of a downlink control information (DCI) message; and
a downlink grant control message having a control channel element (CCE) index;
deriving a resource block (RB) index and a shift index for the UE-specific initial shift based at least in part on the CCE index as applied to the subset of resources;
determining uplink control information (UCI) for the uplink control message;
determining a shifted sequence of the base sequence based at least in part on the UE-specific initial shift and the UCI; and
transmitting the UCI in the uplink control message based at least in part on the shifted sequence.
2. The method of claim 1 , wherein the downlink grant control message comprises the DCI message.
3. The method of claim 2 , wherein the UE receives the downlink grant control message on a physical downlink control channel (PDCCH).
4. The method of claim 1 , wherein the uplink control message is formatted as a short physical uplink control channel message, and wherein a payload of the uplink control information comprises a one-bit ACK or a two-bit ACK.
5. The method of claim 1 , wherein a number of the ARI bits X) is defined such that two raised to the number of the ARI bits (2 X ) is less than a number of resources (Y) configured for the uplink control message (2 X <Y).
6. The method of claim 1 , further comprising:
identifying that a payload of the uplink control information is one of a one-bit ACK or a two-bit ACK; and
determining the shifted sequence based at least in part on the identified payload.
7. The method of claim 1 , wherein determining the shifted sequence of the base sequence further comprises:
determining a plurality of shifted sequences of the base sequence based at least in part on the UE-specific initial shift and the UCI; and
selecting the shifted sequence from the plurality of shifted sequences.
8. 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:
identify a base sequence for transmission of an uplink control message;
receive signaling that indicates a UE-specific initial shift to be used with the base sequence, the signaling comprising:
an indication of a subset of resources for the uplink control message include within acknowledgement (ACK) resource indicator (ARI) bits of a downlink control information (DCI) message; and
a downlink grant control message have a control channel element (CCE) index;
derive a resource block (RB) index and a shift index for the UE-specific initial shift based at least in part on the CCE index as applied to the subset of resources;
determine uplink control information (UCI) for the uplink control message;
determine a shifted sequence of the base sequence based at least in part on the UE-specific initial shift and the UCI; and
transmit the UCI in the uplink control message based at least in part on the shifted sequence.
9. The UE of claim 8 , wherein the downlink grant control message comprises the DCI message.
10. The UE of claim 9 , wherein the UE receives the downlink grant control message on a physical downlink control channel (PDCCH).
11. The UE of claim 8 , wherein a payload of the uplink control message includes a 1-bit ACK, or a 2-bit ACK.
12. The UE of claim 8 , wherein the uplink control message is formatted as a short physical uplink control channel message and comprises one or two bits corresponding to the UCI.
13. The UE of claim 8 , wherein a number of the ARI bits (X) is defined such that two raised to the number of the ARI bits (2 X ) is less than a number of resources (Y) configured for the uplink control message (2 X <Y).
14. The UE of claim 8 , wherein the one or more processors individually or collectively are further operable to execute the code to cause the UE to:
identify that a payload of the uplink control information is one of a one-bit ACK or a two-bit ACK; and
determine the shifted sequence based at least in part on the identified payload.
15. The UE of claim 8 , wherein, to determine the shifted sequence of the base sequence, the one or more processors are individually or collectively further operable to execute the code to cause the UE to:
determine a plurality of shifted sequences of the base sequence based at least in part on the UE-specific initial shift and the UCI; and
select the shifted sequence from the plurality of shifted sequences.
16. An apparatus for wireless communication, comprising:
means for identifying a base sequence for transmission of an uplink control message;
means for receiving signaling that indicates a UE-specific initial shift to be used with the base sequence, the signaling comprising:
means for an indication of a subset of resources for the uplink control message included within acknowledgment (ACK) resource indicator (ARI) bits of a downlink control information (DCI) message; and
means for a downlink grant control message having a control channel element (CCE) index;
means for deriving a resource block (RB) index and a shift index for the UE-specific initial shift based at least in part on the CCE index as applied to the subset of resources;
means for determining uplink control information (UCI) for the uplink control message;
means for determining a shifted sequence of the base sequence based at least in part on the UE-specific initial shift and the UCI; and
means for transmitting the UCI in the uplink control message based at least in part on the shifted sequence.
17. The apparatus of claim 16 , wherein the downlink grant control message comprises the DCI message.
18. The apparatus of claim 17 , wherein the apparatus receives the downlink grant control message on a physical downlink control channel (PDCCH).
19. The apparatus of claim 16 , wherein a payload of the uplink control message includes a 1-bit ACK or a 2-bit ACK.
20. The apparatus of claim 16 , wherein the uplink control message is formatted as a short physical uplink control channel message and comprises one or two bits corresponding to the UCI.
21. The apparatus of claim 16 , wherein a number of the ARI bits (X) is defined such that two raised to the number of the ARI bits (2 X ) is less than a number of resources (Y) configured for the uplink control message (2 X <Y).
22. The apparatus of claim 16 , further comprising:
means for identifying that a payload of the uplink control information is one of a one-bit ACK or a two-bit ACK; and
means for determining the shifted sequence based at least in part on the identified payload.
23. The apparatus of claim 16 , wherein the means for determining the shifted sequence of the base sequence further comprise:
means for determining a plurality of shifted sequences of the base sequence based at least in part on the UE-specific initial shift and the UCI; and
means for selecting the shifted sequence from the plurality of shifted sequences based at least in part on a payload of the UCI.
24. A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by one or more processors to:
identify a base sequence for transmission of an uplink control message;
receive signaling that indicates a UE-specific initial shift to be used with the base sequence, the signaling comprising:
an indication of a subset of resources for the uplink control message include within acknowledgement (ACK) resource indicator (ARI) bits of a downlink control information (DCI) message; and
a downlink grant control message have a control channel element (CCE) index;
derive a resource block (RB) index and a shift index for the UE-specific initial shift based at least in part on the CCE index as applied to the subset of resources;
determine uplink control information (UCI) for the uplink control message;
determine a shifted sequence of the base sequence based at least in part on the UE-specific initial shift and the UCI; and
transmit the UCI in the uplink control message based at least in part on the shifted sequence.
25. The non-transitory computer-readable medium of claim 24 , wherein the downlink grant control message comprises the DCI message.
26. The non-transitory computer-readable medium of claim 25 , wherein the downlink grant control message is received on a physical downlink control channel (PDCCH).
27. The non-transitory computer-readable medium of claim 24 , wherein the uplink control message is formatted as a short physical uplink control channel message, and wherein a payload of the uplink control information comprises a one-bit ACK or a two-bit ACK.