Channel state information overhead reduction for multi-transmission reception point/panel and cell free multiple input, multiple output
Techniques of performing CSI reporting include identifying a cluster of TRPs sharing common information in their CSI and transmitting a complete CSI report to a selected TRP of the cluster while transmitting partial CSIs reports to other TRPs of the cluster. Along these lines, in an example implementation, a UE receives a CSI-RS from a network, with the CSI-RS carrying a plurality of reference symbols from a plurality of TRPs. Based on the plurality of symbols, the UE generates TRP data representing CSI feedback for each of the TRPs. From the CSI feedback, the UE identifies, as a cluster, a subset of the TRPs that share common information within the CSI feedback. The UE then sends first identification data identifying the subset of the TRPs that make up the cluster to the network.
1. A method comprising:
generating, by a user equipment (UE), transmission and reception point (TRP) data representing respective channel state information (CSI) feedback for a plurality of TRPs connected to a network;
performing an identification operation on the TRP data to identify a subset of TRPs of the plurality of TRPs, each TRP of the identified subset of TRPs having a common portion within their respective CSI feedback; and
transmitting, to the network, identification data representing the identified subset of TRPs,
wherein the CSI feedback for the plurality of TRPs is frequency domain CSI feedback including a respective frequency domain compression matrix W f ,
wherein the frequency domain compression matrix W f for a first TRP of the subset of TRPs includes a shifted version of the frequency domain compression matrix W f for a second TRP of the subset of TRPs,
and wherein the method further comprises transmitting, to a primary TRP, an entire CSI feedback for the primary TRP, the CSI feedback for other TRPs of the subset of TRPs being deduced from the CSI feedback for the primary TRP.
2. The method as in claim 1 , wherein generating the TRP data includes:
receiving a reference signal, the reference signal including a plurality of reference symbols from each of the plurality of TRPs; and
generating the CSI feedback based on the plurality of reference symbols, and wherein the reference signal is a CSI reference signal (CSI-RS).
3. The method as in claim 2 , wherein the identification data is first identification data,
and wherein the method further comprises:
receiving second identification data from the network representing a revised subset of TRPs, the second identification data being based on a quality of backhaul connections between the subset of TRPs.
4. The method as in claim 1 , wherein the identification data includes a primary TRP identifier identifying the primary TRP, the other TRPs of the subset of TRPs being secondary TRPs, and wherein the method further comprises:
transmitting a portion of the respective CSI feedback that is not common to the subset of TRPs to each of the other TRPs of the subset of TRPs.
5. The method as in claim 1 , wherein the primary TRP is a TRP configured to receive physical uplink control channel (PUCCH) and/or physical uplink shared channel (PUSCH) transmission.
6. The method as in claim 1 , wherein the common portion of the CSI feedback for the subset of TRPs includes at least one column of the frequency domain compression matrix W f for the primary TRP of the subset of TRPs.
7. The method as in claim 1 , wherein the CSI feedback for the plurality of TRPs is frequency domain CSI feedback further including a respective grid of beams (GoB) matrix W 1 , and a respective matrix of linear combining coefficients {tilde over (W)} 2 .
8. The method as in claim 7 , wherein the common portion of the CSI feedback for the subset of TRPs includes at least one column of the GoB matrix W 1 for the primary TRP.
9. The method as in claim 7 , wherein the GoB matrix W 1 for the first TRP of the subset of TRPs includes a shifted version of the GoB matrix W 1 for the second TRP of the subset of TRPs.
10. The method as in claim 7 , wherein the common portion of the CSI feedback for the subset of TRPs includes data representing a reduced set of orthogonal beams selected from an oversampled GoB.
11. The method as in claim 7 , wherein a portion of the CSI feedback not common to the subset of the TRPs includes elements of the matrix of linear combining coefficients {tilde over (W)} 2 .
12. The method as in claim 1 , wherein the CSI feedback for the plurality of TRPs is time domain explicit CSI feedback including a channel support vector s.
13. The method as in claim 12 , wherein the common portion of the CSI feedback for the subset of TRPs includes at least one element of the channel support vector s.
14. The method as in claim 12 , wherein the channel support vector s for the first TRP of the subset of TRPs includes a shifted version of the channel support vector s for the second TRP of the subset of TRPs.
15. An apparatus comprising:
at least one processor; and
at least one memory including computer program code,
the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:
generate transmission and reception point (TRP) data representing respective channel state information (CSI) feedback for a plurality of TRPs connected to a network;
perform an identification operation on the TRP data to identify a subset of TRPs of the plurality of TRPs, each TRP of the identified subset of TRPs having a common portion within their respective CSI feedback; and
transmit, to the network, identification data representing the identified subset of TRPs,
wherein the CSI feedback for the plurality of TRPs is frequency domain CSI feedback including a respective frequency domain compression matrix W f ,
wherein the frequency domain compression matrix W f for a first TRP of the subset of TRPs includes a shifted version of the frequency domain compression matrix W f for a second TRP of the subset of TRPs,
and wherein the least one memory and the computer program code are further configured to, with the at least one processor, further cause the apparatus at least to:
transmit, to a primary TRP, an entire CSI feedback for the primary TRP, the CSI feedback for other TRPs of the subset of TRPs being deduced from the CSI feedback for the primary TRP.
16. The apparatus as in claim 15 , wherein the at least one memory and the computer program code configured to generate the TRP data, with the at least one processor, further cause the apparatus at least to:
receive a reference signal, the reference signal including a plurality of reference symbols from each of the plurality of TRPs; and
generate the CSI feedback based on the plurality of reference symbols, and wherein the reference signal is a CSI reference signal (CSI-RS).
17. The apparatus as in claim 15 , wherein the identification data is first identification data,
and wherein the least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to:
receive second identification data from the network representing a revised subset of TRPs, the second identification data being based on an indicated quality of backhaul connections between the subset of TRPs.
18. The apparatus as in claim 15 , wherein the identification data includes a primary TRP identifier identifying the primary TRP, the other TRPs of the subset of TRPs being secondary TRPs,
and wherein the least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to:
transmit a portion of the respective CSI feedback that is not common to the subset of TRPs to each of the other TRPs of the subset of TRPs.
19. The apparatus as in claim 15 , wherein the primary TRP is a TRP configured to receive physical uplink control channel (PUCCH) and/or physical uplink shared channel (PUSCH) transmission.
20. The apparatus as in claim 15 , wherein the common portion of the CSI feedback for the subset of TRPs includes at least one column of the frequency domain compression matrix W f for the primary TRP of the subset of TRPs.
21. The apparatus as in claim 15 , wherein the CSI feedback for the plurality of TRPs is frequency domain CSI feedback further including a respective grid of beams (GoB) matrix W 1 , and a respective matrix of linear combining coefficients {tilde over (W)} 2 .
22. The apparatus as in claim 21 , wherein the common portion of the CSI feedback for the subset of TRPs includes at least one column of the GoB matrix W 1 for the primary TRP.
23. The apparatus as in claim 21 , wherein the GoB matrix W 1 for the first TRP of the subset of TRPs includes a shifted version of the GoB matrix W 1 for the second TRP of the subset of TRPs.
24. The apparatus as in claim 21 , wherein the common portion of the CSI feedback for the subset of TRPs includes data representing a reduced set of orthogonal beams selected from an oversampled GoB.
25. The apparatus as in claim 21 , wherein a portion of the CSI feedback not common to the subset of the TRPs includes elements of the matrix of linear combining coefficients {tilde over (W)} 2 .
26. The apparatus as in claim 21 , wherein the CSI feedback for the plurality of TRPs is time domain explicit CSI feedback including a channel support vector s.
27. The apparatus as in claim 26 , wherein the common portion of the CSI feedback for the subset of TRPs includes at least one element of the channel support vector s.
28. The apparatus as in claim 26 , wherein the channel support vector s for the first TRP of the subset of TRPs includes a shifted version of the channel support vector s for the second TRP of the subset of TRPs.