Sounding reference signal (SRS) guided downlink channel state information-reference signal (CSI-RS) scan
Certain aspects of the present disclosure generally relate to methods and apparatus for sounding reference signal (SRS) guided downlink channel state information-reference signal (CSI-RS) scan. One example method for wireless communication generally includes determining whether to perform channel measurement and reporting operations for a user-equipment (UE) using a reciprocity-based scheme or a channel state information-reference signal (CSI-RS) based scheme based on a criteria of a cell, and performing the channel measurement and reporting operations based on the determination.
1. A method for wireless communication, comprising:
receiving sounding reference signals (SRSs) from a user-equipment (UE);
selecting multiple sets of beams based on the SRSs received from the UE;
transmitting first channel state information-reference signals (CSI-RSs) to the UE via the multiple sets of beams;
receiving first channel measurement feedback information from the UE indicating a set of beams of the multiple sets of beams received at the UE with a best quality;
transmitting a second CSI-RS based on the first channel measurement feedback information from the UE;
receiving second channel measurement feedback information from the UE based on the second CSI-RS; and
communicating data with the UE based on the second channel measurement feedback information.
2. The method of claim 1 , wherein the first CSI-RSs are transmitted using up to 64 CSI-RS ports.
3. The method of claim 1 , wherein each of the multiple sets of beams comprises up to eight beams.
4. The method of claim 1 , wherein the first CSI-RSs are transmitted via a resource set having a plurality of resources, each of the plurality of resources corresponding to one set of the multiple sets of beams.
5. The method of claim 4 , wherein the first channel measurement feedback information from the UE comprises a wideband CSI-RS resource indicator (CRI) indicating one of the plurality of resources received with the best quality at the UE.
6. The method of claim 4 , wherein the first channel measurement feedback information from the UE comprises multiple subband CRIs indicating one of the plurality of resources received with the best quality for each subband at the UE.
7. A method for wireless communication by a user-equipment (UE), comprising:
transmitting sounding reference signals (SRSs) to a base station;
receiving first channel state information-reference signals (CSI-RSs) from the base station via multiple sets of beams;
selecting a set of beams of the multiple sets of beams corresponding to one of the first CSI-RSs received at the UE with a best quality;
transmitting first channel measurement feedback information indicating the set of beams of the multiple sets of beams;
receiving a second CSI-RS from the base station based on the first channel measurement feedback information;
transmitting second channel measurement feedback information based on the second CSI-RS; and
communicating data based on the second channel measurement feedback information.
8. The method of claim 7 , wherein the first CSI-RSs are transmitted using up to 64 CSI-RS ports by the base station.
9. The method of claim 7 , wherein each of the multiple sets of beams comprises four beams.
10. The method of claim 7 , wherein the first CSI-RSs are transmitted by the base station via a resource set having a plurality of resources, each of the plurality of resources corresponding to one set of the multiple sets of beams.
11. The method of claim 10 , wherein the plurality of resources comprises up to eight resources.
12. The method of claim 10 , wherein the first channel measurement feedback information comprises a wideband CSI-RS resource indicator (CRI) indicating one of the plurality of resources received with the best quality at the UE.
13. The method of claim 10 , wherein the first channel measurement feedback information comprises multiple subband CRIs indicating one of the plurality of resources received with the best quality for each subband at the UE.
14. The method of claim 10 , wherein each of the plurality of resources comprises four orthogonal CSI-RS ports for each of two polarizations.
15. A network node for wireless communication, the network node comprising:
a memory storing instructions; and
at least one processor coupled to the memory, the at least one processor configured to cause the network node to:
receive sounding reference signals (SRSs) from a user-equipment (UE);
select multiple sets of beams based on the SRSs received from the UE;
transmit first channel state information-reference signals (CSI-RSs) to the UE via the multiple sets of beams;
receive first channel measurement feedback information from the UE indicating a set of beams of the multiple sets of beams received at the UE with a best quality;
transmit a second CSI-RS based on the first channel measurement feedback information from the UE;
receive second channel measurement feedback information from the UE based on the second CSI-RS; and
communicate data with the UE based on the second channel measurement feedback information.
16. The network node of claim 15 , wherein the first CSI-RSs are transmitted using up to 64 CSI-RS ports.
17. The network node of claim 15 , wherein each of the multiple sets of beams comprises up to eight beams.
18. The network node of claim 15 , wherein the first CSI-RSs are transmitted via a resource set having a plurality of resources, each of the plurality of resources corresponding to one set of the multiple sets of beams.
19. The network node of claim 18 , wherein the first channel measurement feedback information from the UE comprises a wideband CSI-RS resource indicator (CRI) indicating one of the plurality of resources received with the best quality at the UE.
20. The network node of claim 18 , wherein the first channel measurement feedback information from the UE comprises multiple subband CRIs indicating one of the plurality of resources received with the best quality for each subband at the UE.
21. A user-equipment (UE), the UE comprising:
a memory storing instructions; and
at least one processor coupled to the memory, the at least one processor configured to cause the UE to:
transmit sounding reference signals (SRSs) to a base station;
receive first channel state information-reference signals (CSI-RSs) from the base station via multiple sets of beams;
select a set of beams of the multiple sets of beams corresponding to one of the first CSI-RSs received at the UE with a best quality;
transmit first channel measurement feedback information indicating the set of beams of the multiple sets of beams;
receive a second CSI-RS from the base station based on the first channel measurement feedback information;
transmit second channel measurement feedback information based on the second CSI-RS; and
communicate data based on the second channel measurement feedback information.
22. The UE of claim 21 , wherein the first CSI-RSs are transmitted using up to 64 CSI-RS ports by the base station.
23. The UE of claim 21 , wherein each of the multiple sets of beams comprises four beams.
24. The UE of claim 21 , wherein the first CSI-RSs are transmitted by the base station via a resource set having a plurality of resources, each of the plurality of resources corresponding to one set of the multiple sets of beams.
25. The UE of claim 24 , wherein the plurality of resources comprises up to eight resources.
26. The UE of claim 24 , wherein the first channel measurement feedback information comprises a wideband CSI-RS resource indicator (CRI) indicating one of the plurality of resources received with the best quality at the UE.
27. The UE of claim 24 , wherein the first channel measurement feedback information comprises multiple subband CRIs indicating one of the plurality of resources received with the best quality for each subband at the UE.
28. The UE of claim 24 , wherein each of the plurality of resources comprises four orthogonal CSI-RS ports for each of two polarizations.