Rank and resource set signaling techniques for multiple transmission-reception point communications
Methods, systems, and devices for wireless communication are described in which a user equipment (UE) may transmit one or more uplink communications to multiple transmission-reception points (TRPs). Transmission parameters for each repetition may be based on parameters (e.g., a number of antenna ports, a spatial domain filter or beam, a rank or number of layers, or any combinations thereof) that are determined from an indication of whether the repetitions are to use different sounding reference signal (SRS) resource sets, and indicated SRS resource of each SRS resource set. The indication may include a same number of bits regardless of whether one SRS resource set is used or multiple SRS resource sets are used, and may be based on a prior configuration of the UE.
1. A method for wireless communication at a user equipment (UE), comprising:
receiving, from a base station via a first control information communication, a control information configuration that indicates how many bits are to-be used for a control information field in a second first control information communication, wherein the control information field indicates, via the set of bits, one of two sounding reference signal resource sets with which a first uplink communication is to be associated;
receiving, from the base station, the second control information communication that includes the control information field and that schedules a first uplink communication for the UE, wherein the control information field indicates one or two sounding reference signal resource sets associated with the first uplink communication;
determining, based at least in part on the second control information communication and the control information configuration, whether one or two sounding reference signal resource sets are associated with the first uplink communication; and
transmitting the first uplink communication to the base station based at least in part on the determining.
2. The method of claim 1 , wherein the control information field further indicates a number of sounding reference signal resources to be associated with the first uplink communication, and wherein the determining further comprises:
determining, based at least in part on the second control information communication and the control information configuration, the number of sounding reference signal resources for each sounding reference signal resource set associated with the first uplink communication.
3. The method of claim 1 , wherein the determining further comprises:
determining, based at least in part on a first bit of the second control information communication, whether one or two sounding reference signal resource sets are associated with the first uplink communication, and wherein the control information field includes a set of bits that indicate a number of sounding reference signal resources for each sounding reference signal resource set associated with the first uplink communication.
4. The method of claim 3 , wherein the first bit is an initial bit of the control information field, or is in a separate field in the second control information communication.
5. The method of claim 3 , wherein the set of bits includes a maximum of a first number of bits or a second number of bits, the first number of bits determined based at least in part on a first maximum rank when one sounding reference signal resource set is associated with the first uplink communication, and the second number of bits determined based at least in part on a second maximum rank when two sounding reference signal resource sets are associated with the first uplink communication.
6. The method of claim 5 , wherein the second maximum rank is less than the first maximum rank.
7. The method of claim 5 , wherein the second maximum rank is a fixed value or a configured value that is provided with the control information configuration.
8. The method of claim 7 , wherein the configured value of the second maximum rank is based at least in part on a capability of the UE that is transmitted to the base station.
9. The method of claim 5 , wherein zero-padding is used in the set of bits when a number of bits necessary to indicate a rank of the one or two sounding reference signal resource sets is less than a total number of bits of the set of bits.
10. The method of claim 5 , wherein the first number of bits is determined based at least in part on a first sounding reference signal resource set having a different number of sounding reference signal resources than a second sounding reference signal resource set.
11. The method of claim 10 , wherein the first number of bits is associated with the first sounding reference signal resource set.
12. The method of claim 10 , wherein the first number of bits is associated with either the first sounding reference signal resource set or the second sounding reference signal resource set, and a separate bit in the control information field provides an indication of which of the first sounding reference signal resource set or the second sounding reference signal resource set is associated with the first uplink communication.
13. The method of claim 5 , wherein the second number of bits is associated with both a first sounding reference signal resource set and a second sounding reference signal resource set, and a first subset of the second number of bits indicates one or more sounding reference signal resources within the first sounding reference signal resource set and a second subset of the second number of bits indicates one or more sounding reference signal resources within the second sounding reference signal resource set.
14. The method of claim 5 , wherein the second number of bits is associated with both a first sounding reference signal resource set and a second sounding reference signal resource set, and provides a joint indication of one or more sounding reference signal resources within each sounding reference signal resource set based on a same number of layers associated with each sounding reference signal resource set.
15. The method of claim 1 , wherein the determining further comprises:
decoding the control information field to identify a set of bits; and identifying, based at least in part on a mapping for the set of bits, a number of sounding reference signal resources for each sounding reference signal resource set associated with the first uplink communication.
16. The method of claim 15 , wherein a first sounding reference signal resource set is ordered ahead of a second sounding reference signal resource set, and a quantity of bits of the set of bits that are included in the control information field is determined as a sum of a first number of possibilities to indicate a first number of sounding reference signal resources associated with the first sounding reference signal resource set when a single sounding reference signal resource set is associated with the first uplink communication, and a second number of possibilities to indicate a second number of sounding reference signal resources associated with both the first and the second sounding reference signal resource set when both the first sounding reference signal resource set and the second sounding reference signal resource set are associated with the first uplink communication.
17. The method of claim 15 , wherein:
a first sounding reference signal resource set or a second sounding reference signal resource set is ordered as an initial sounding reference signal resource set; and
a quantity of bits of the set of bits that are included in the control information field is determined as a sum of a first number of possibilities to indicate a first number of sounding reference signal resources associated with the initial sounding reference signal resource set when a single sounding reference signal resource set is associated with the first uplink communication, and a second number of possibilities to indicate a second number of sounding reference signal resources associated with both the first and the second sounding reference signal resource set when a both the first sounding reference signal resource set and the second sounding reference signal resource set are associated with the first uplink communication.
18. The method of claim 15 , wherein different bit values of the control information field are mapped to different possibilities of the number of sounding reference signal resources that are associated with the first uplink communication.
19. A method for wireless communication at a base station, comprising:
transmitting, to a user equipment (UE) via a first control information communication, a control information configuration that indicates how many bits are to-be used for a control information field in a second control information communication;
determining whether one sounding reference signal resource set or two sounding reference signal resource sets are associated with a first uplink communication;
transmitting, to the UE, the second control information communication that includes the control information field and that schedules the first uplink communication for the UE and indicates whether one sounding reference signal resource set or two sounding reference signal resource sets are associated with the first uplink communication; and
receiving the first uplink communication from the UE based at least in part on the second control information communication.
20. The method of claim 19 , wherein the control information field further indicates a number of sounding reference signal resources to be associated with the first uplink communication.