Enhanced new radio (NR) type II channel state information (CSI) feedback using angle and delay reciprocity

1 . A method performed by a base station, the method comprising:

the base station selecting frequency domain basis vectors; and

the base station transmitting to a user equipment (UE) information identifying the selected frequency domain (FD) basis vectors selected by the base station,

wherein selecting the selected FD basis vectors comprises:

the base station obtaining a measurement of a reference signal (RS) transmitted by the UE; and

the base station selecting the FD basis vectors based on the measurement of the RS transmitted by the UE.

2 . The method of claim 1 , wherein the method further comprises:

the base station, based on a reference signal transmitted by the UE, estimating angles of arrival and associated power delay profiles of the reference signal, wherein the base station selects the FD basis vectors based on the estimated angles of arrival and the associated power delay profiles of the reference signal; and

the base station transmitting a plurality of down link (DL) reference signals based on i) the estimated angles of arrival and/or ii) the associated power delay profiles.

3 . The method of claim 2 , wherein

the method further comprises transmitting at least a first downlink (DL) reference signal and requesting the UE to measure the first DL reference signal and feedback a channel state information (CSI) report based on the first DL reference signal and the selected FD basis vectors, and

the first DL reference signal is associated with one of the estimated angles of arrival.

4 . The method of claim 3 , wherein

the method further comprises, after transmitting to the UE the information identifying the selected FD basis vectors, the base station receiving a CSI report message transmitted by the UE, and

the CSI report message includes at least first coefficient associated with the first DL reference signal and one of the selected FD basis vectors.

5 . The method of claim 1 , wherein the selected FD basis vectors comprise adjacent DFT vectors.

6 . The method of claim 1 , wherein, when the selected FD basis vectors consist of one FD basis vector, the one FD basis vector being a DFT vector associated with zero hertz frequency.

7 . The method of claim 1 , wherein the selected FD basis vectors are commonly used for all transmission layers.

8 . A non-transitory computer readable storage medium storing a computer program comprising instructions for configuring the base station to perform the method of claim 1 .

9 . A base station, the base station comprising:

a transmitter;

memory; and

processing circuitry, wherein the base station is configured to perform a method comprising:

selecting frequency domain basis vectors; and

employing the transmitter to transmit to a user equipment (UE) information identifying the selected frequency domain (FD) basis vectors selected by the base station,

wherein selecting the selected FD basis vectors comprises:

the base station obtaining a measurement of a reference signal (RS) transmitted by the UE; and

the base station selecting the FD basis vectors based on the measurement of the RS transmitted by the UE.

10 . The base station of claim 9 , wherein the method further comprises:

based on a reference signal transmitted by the UE, estimating angles of arrival and associated power delay profiles of the reference signal, wherein the base station selects the FD basis vectors based on the estimated angles of arrival and the associated power delay profiles of the reference signal; and

employing the transmitter to transmit a plurality of down link (DL) reference signals based on i) the estimated angles of arrival and/or ii) the associated power delay profiles.

11 . A method performed by a user equipment (UE), the method comprising:

transmitting a reference signal to a base station;

receiving from the base station information identifying FD basis vectors selected by the base station;

receiving from the base station a plurality of downlink (DL) reference signals (RSs) and a request for channel state information (CSI) feedback based on the plurality of DL RSs and the FD basis vectors selected by the base station;

selecting a subset of the FD basis vectors selected by the base station and estimating CSI based on the plurality of DL RSs and the subset of the FD basis vectors selected by the UE; and

transmitting to the base station a CSI report message including a set of coefficients each associated with one of the plurality of DL RSs and one of the FD basis vectors included in the subset of FD basis vectors selected by the UE.

12 . The method of claim 11 , wherein

the FD basis vectors selected by the base station comprise a first FD basis vector and a second FD basis vector,

the first FD basis vector is included in the subset of FD basis vectors selected by the UE, and

the second FD basis vector is not included in the subset of FD basis vectors selected by the UE.

13 . The method of claim 11 , wherein

the FD basis vectors selected by the base station comprise a first DFT vector and a second DFT vector, and

the first and second DFT vectors are adjacent.

14 . The method of claim 11 , wherein

the FD basis vectors selected by the base station include a set of adjacent DFT vectors, and

the set of adjacent DFT vectors are indicated by i) and index of a first DFT vector in the set of adjacent DFT vectors and the total number of DFT vectors in the set of adjacent DFT vectors.

15 . The method of claim 11 , wherein the FD basis vectors selected by the base station consist of one FD basis vector and the one FD basis vector is a DFT vector associated with zero hertz frequency.

16 . The method of claim 11 , wherein the FD basis vectors selected by the base station are commonly used for all transmission layers.

17 . A non-transitory computer readable storage medium storing a computer program comprising instructions for configuring the UE to perform the method of claim 11 .

18 . A user equipment (UE), the UE comprising:

a receiver;

a transmitter; and

processing circuitry, wherein the UE is configured to perform a method comprising:

transmitting a reference signal to a base station;

receiving from the base station information identifying FD basis vectors selected by the base station;

receiving from the base station a plurality of downlink (DL) reference signals (RSs) and a request for channel state information (CSI) feedback based on the plurality of DL RSs and the FD basis vectors selected by the base station;

selecting a subset of the FD basis vectors selected by the base station and estimating CSI based on the plurality of DL RSs and the subset of the FD basis vectors selected by the UE; and

transmitting to the base station a CSI report message including a set of coefficients each associated with one of the plurality of DL RSs and one of the FD basis vectors included in the subset of FD basis vectors selected by the UE.

19 . The UE of claim 18 , wherein

the subset of the FD basis vectors selected by the base station is the same as the FD basis vectors selected by the base station, and

the FD basis vectors selected by the base station comprise adjacent DFT vectors.