Systems and methods for UE coordination based CSI feedback

1. A method for a first user equipment (UE) to perform channel state information (CSI) feedback in coordination with one or more second UE, the method comprising:

processing configuration information from a wireless network to configure the first UE for CSI measurement and reporting;

measuring, based on the configuration information, CSI reference signal (CSI-RS) resources to determine first CSI;

in response to a CSI report trigger for a coordination group comprising the first UE and the one or more second UE, transmitting a first CSI report to the wireless network for the coordination group, the first CSI report comprising at least the first CSI; and

coordinating with the one or more second UE to receive a second CSI from the one or more second UE in the coordination group, wherein the first CSI report comprises the first CSI for the first UE and the second CSI for the one or more second UE.

2. The method of claim 1 , further comprising sending a message to the wireless network indicating a supported mode for UE coordination based CSI feedback, wherein in a first mode both the first UE and the one or more second UE perform CSI measurements to be reported by the first UE, and wherein in a second mode only the first UE performs the CSI measurements to be reported by the first UE.

3. The method of claim 1 , wherein the CSI report trigger corresponds to one or more CSI report configuration information element (CSI-reportConfig IE) associated with at least one of the first UE and the one or more second UE.

4. The method of claim 3 , wherein control signaling from the wireless network for the CSI report trigger comprises a UE identifier (ID) and a CSI-reportConfig ID for each of the one or more CSI-reportConfig IE to be reported.

5. The method of claim 4 , further comprising multiplexing the first CSI and the second CSI in the first CSI report based on the UE ID and the CSI-reportConfig ID.

6. The method of claim 3 , wherein each of the one or more CSI-reportConfig IE comprises a UE identifier (ID), and wherein control signaling from the wireless network for the CSI report trigger comprises a CSI-reportConfig ID for each of the one or more CSI-reportConfig IE to be reported.

7. The method of claim 1 , wherein the CSI report trigger comprises a radio resource control (RRC) signal, a media access control (MAC) control element (CE), or downlink control information (DCI) transmitted to the first UE, transmitted separately to the first UE and the one or more second UE, or transmitted to the first UE and the one or more second UE in a group based manner.

8. The method of claim 1 , wherein the first UE comprises a maximum number of receive (Rx) antennas for the coordination group.

9. The method of claim 8 , wherein the configuration information comprises a CSI report configuration information element (CSI-reportConfig IE) comprising UE identifiers (IDs) for each of the first UE and the one or more second UE, wherein a rank restriction is configured per UE, wherein the first CSI is based on measuring the CSI-RS resources by the first UE using the maximum number of Rx antennas, and wherein the first CSI report comprises the first CSI for the first UE and any of the one or more second UE comprising the maximum number of Rx antennas.

10. The method of claim 9 , further comprising:

determining, by the first UE, a third CSI based on measuring the CSI-RS resources using a subset of Rx antennas that is less than the maximum number of Rx antennas; and

transmitting a second CSI report to the wireless network comprising the third CSI for at least one of the one or more second UE comprising a number of Rx antennas corresponding to the subset of Rx antennas.

11. The method of claim 10 , wherein the subset of Rx antennas comprises a predetermined subset of Rx antennas of the first UE, a selected subset of Rx antennas of the first UE determined by the first UE, or an indicated subset of Rx antennas determined by the wireless network.

12. The method of claim 10 , wherein the subset of Rx antennas comprises a best subset of Rx antennas or a worst subset of Rx antennas as measured by the first UE.

13. The method of claim 8 , wherein the configuration information comprises a CSI report configuration information element (CSI-reportConfig IE) indicating one or more maximum number of downlink (DL) layers for reporting, wherein the maximum number of DL layers implies a number of Rx antennas per UE, and wherein a rank restriction is configured per the maximum number of DL layers.

14. The method of claim 13 , further comprising reporting the first CSI for a first maximum number of DL layers and a third CSI for a second maximum number of DL layers.

15. The method of claim 14 , wherein the second maximum number of DL layers corresponds to a predetermined subset of Rx antennas of the first UE, a selected subset of Rx antennas of the first UE determined by the first UE, or an indicated subset of Rx antennas of the first UE determined by the wireless network.

16. The method of claim 14 , wherein the second maximum number of DL layers corresponds to a best subset of Rx antennas or a worst subset of Rx antennas as measured by the first UE.

17. The method of claim 8 , wherein the configuration information comprises a CSI report configuration information element (CSI-reportConfig IE) configured for a single UE or for multiple UEs in the coordination group, wherein a rank restriction is configured per a maximum number of DL layers.

18. The method of claim 17 , further comprising reporting the first CSI for a first maximum number of DL layers and a third CSI for a second maximum number of DL layers.

19. The method of claim 18 , wherein the second maximum number of DL layers corresponds to a predetermined subset of Rx antennas of the first UE, a selected subset of Rx antennas of the first UE determined by the first UE, or an indicated subset of Rx antennas of the first UE determined by the wireless network.