Channel covariance feedback for enhanced FD-MIMO

Patent metadata

Field	Value
Publication number	US-11632208-B2
Application number	US-201716078434-A
Country	US
Kind code	B2
Filing date	Feb 17, 2017
Priority date	Mar 31, 2016
Publication date	Apr 18, 2023
Grant date	Apr 18, 2023

Abstract

Channel covariance feedback is disclosed for enhanced full-dimension multiple input, multiple output (eFD-MIMO) systems. Channel state information (CSI) reference signal (CSI-RS) feedback operations are implemented using spatial covariance feedback of a covariance estimate. After obtaining a set of orthogonal basis vectors, a user equipment (UE) measures the CSI-RS from a base station and determines the spatial covariance matrix from the signal. The UE may then compress the spatial covariance matrix into a lower-dimension covariance estimate matrix using the orthogonal basis vectors. The lower-dimension matrix along with element-wise quantization allows for feedback of spatial covariance for eFD-MIMO systems without excessive feedback overhead.

First claim

What is claimed is:

1. A method of wireless communication, comprising:
measuring a non-precoded channel state information (CSI) reference signal (CSI-RS) received from a base station;
obtaining a set of orthogonal basis vectors;
determining a spatial covariance matrix of the non-precoded CSI-RS;
compressing the spatial covariance matrix into a spatial covariance estimate matrix by projecting one or more eigenvectors of the spatial covariance matrix on the set of orthogonal basis vectors;
transmitting the spatial covariance estimate matrix and a beam index of each of the vectors in the set of orthogonal basis vectors to the base station;
measuring a beamformed CSI-RS received from the base station;
generating a CSI report based on measurement of the beamformed CSI-RS; and
transmitting the CSI report to the base station.

2. The method of claim 1 , wherein the obtaining the set of orthogonal basis vectors includes:
receiving the set of orthogonal basis vectors from the base station, wherein the set of orthogonal basis vectors is based on an estimate of an uplink received signal.

3. The method of claim 1 , wherein the obtaining the set of orthogonal basis vectors includes:
calculating a first set of discrete Fourier transform (DFT) vectors based on measurement of the non-precoded CSI-RS;
identifying a dominant DFT vector having a value that is largest of the first set of DFT vectors;
determining a second set of DFT vectors orthogonal to the dominant DFT vector; and
generating the set of orthogonal basis vectors by removing a plurality of DFT vectors from the second set of DFT vectors with values below a threshold.

4. The method of claim 3 , further including: transmitting an index of the dominant DFT vector to the base station.

5. The method of claim 1 , further including: performing an element-wise quantization of the spatial covariance estimate matrix prior to the transmitting.

6. The method of claim 5 , wherein the element-wise quantization includes:
a first multibit uniform quantization for real entries of the spatial covariance estimate matrix;
a second multibit uniform quantization for phase in [0, 2π] for complex entries of the spatial covariance estimate matrix; and
a third multibit bit uniform quantization of an amplitude.

7. The method of claim 6 , wherein the first, second, and third multibit uniform quantizations are 4-bit uniform quantizations.

8. The method of claim 1 , wherein the transmitting the spatial covariance estimate matrix and the beam index of each of the vectors in the set of orthogonal basis vectors occurs according to a defined period and includes:
transmitting a first report including a rank corresponding to a number of vectors in the set of orthogonal basis vectors, wherein the first report is transmitted according to a first period configured by higher layer signaling; and
transmitting a second report including the set of orthogonal basis vectors and the beam index of each of the vectors in the set of orthogonal basis vectors, wherein the second report is transmitted according to a second period based in part on the first report.

9. The method of claim 8 , wherein the beam index of each of the vectors in the spatial covariance estimate matrix are reported cyclically from the beam index for a first vector in the spatial covariance estimate matrix having a highest value to a last vector in the spatial covariance estimate matrix having a lowest value.

10. The method of claim 1 , further including: receiving a trigger signal for reporting the spatial covariance estimate matrix to the base station, wherein the transmitting the spatial covariance estimate matrix and the beam index of each of the vectors in the set of orthogonal basis vectors is based on the trigger signal and includes:
separately transmitting a number of vectors in the set of orthogonal basis vectors, the beam index of each of the vectors in the set of orthogonal basis vectors, and an element-wise quantization of one or more matrix coefficients of the spatial covariance estimate matrix.

11. The method of claim 1 , further including:
receiving a trigger signal for reporting the spatial covariance estimate matrix to the base station, wherein the transmitting the spatial covariance estimate matrix and the beam index of each of the vectors in the set of orthogonal basis vectors is based on the trigger signal and includes:
jointly transmitting, in a same subframe, a number of vectors in the set of orthogonal basis vectors, the beam index of each of the vectors in the set of orthogonal basis vectors, and an element-wise quantization of one or more matrix coefficients of the spatial covariance estimate matrix.

12. The method of claim 1 , wherein the beamformed CSI-RS is precoded at the base station based on a set of DFT vectors in the set of orthogonal basis vectors.

13. An apparatus configured for wireless communication, comprising:
means for measuring a non-precoded channel state information (CSI) reference signal (CSI-RS) received from a base station;
means for obtaining a set of orthogonal basis vectors;
means for determining a spatial covariance matrix of the non-precoded CSI-RS;
means for compressing the spatial covariance matrix into a spatial covariance estimate matrix by projecting one or more eigenvectors of the spatial covariance matrix on the set of orthogonal basis vectors;
means for transmitting the spatial covariance estimate matrix and a beam index of each of the vectors in the set of orthogonal basis vectors to the base station;
means for measuring a beamformed CSI-RS received from the base station;
means for generating a CSI report based on measurement of the beamformed CSI-RS; and
means for transmitting the CSI report to the base station.

14. The apparatus of claim 13 , wherein the means for obtaining the set of orthogonal basis vectors includes:
means for receiving the set of orthogonal basis vectors from the base station, wherein the set of orthogonal basis vectors is based on an estimate of an uplink received signal.

15. The apparatus of claim 13 , wherein the means for obtaining the set of orthogonal basis vectors includes:
means for calculating a first set of discrete Fourier transform (DFT) vectors based on measurement of the non-precoded CSI-RS;
means for identifying a dominant DFT vector having a value that is largest of the first set of DFT vectors;
means for determining a second set of DFT vectors orthogonal to the dominant DFT vector; and
means for generating the set of orthogonal basis vectors by removing a plurality of DFT vectors from the second set of DFT vectors with values below a threshold.

16. The apparatus of claim 15 , further including:
means for transmitting an index of the dominant DFT vector to the base station.

17. The apparatus of claim 13 , further including:
means for performing an element-wise quantization of the spatial covariance estimate matrix prior to executing the means for transmitting.

18. The apparatus of claim 17 , wherein the element-wise quantization includes:
a first multibit uniform quantization for real entries of the spatial covariance estimate matrix;
a second multibit uniform quantization for phase in [0, 2π] for complex entries of the spatial covariance estimate matrix; and
a third multibit bit uniform quantization of an amplitude, wherein the first, second, and third multibit uniform quantizations are 4-bit uniform quantizations.

19. The apparatus of claim 13 , wherein transmission of the spatial covariance estimate matrix and

Assignees

• Qualcomm Inc

Inventors

• Chen Bo
• Wei Chao
• Wu Liangming
• Wang Neng

Classifications

• H04B7/0417 Primary

  Feedback systems · CPC title

• H04B7/0413

  MIMO systems · CPC title

• H04B7/063

  Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection · CPC title

• H04W24/10

  Scheduling measurement reports {; Arrangements for measurement reports} · CPC title

• H04B7/0626

  Channel coefficients, e.g. channel state information [CSI] · CPC title