Method and apparatus for information feedback and precoding

• US 9,042,474 B2
• Filed: 04/07/2010
• Issued: 05/26/2015
• Est. Priority Date: 04/07/2010
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Chen, Jinhui, Yang, Hongwei, Lv, Di, Song, Yang
• Primary Examiner(s): FILE, ERIN M
• Application Number:
  US13/639,438
• Publication Number:
  US 20130028344A1
• Time in Patent Office: 1,875 Days
• Field of Search: 375/267
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0421 utilizing implicit feedback, e.g. steered pilot signals
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04B 7/0478 Special codebook structures directed to feedback optimisation
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection

Abstract

Methods and apparatuses for information feedback and precoding have been provided. A method for processing communication data at a user equipment in a wireless communication system may comprise: deriving a spatial correlation matrix R of multiple transmit antennas of a base station based on an obtained downlink channel transmission matrix H; transforming a precoding codebook F according to the spatial correlation matrix R; selecting a precoding matrix F_s based on the transformed precoding codebook; and feeding back information about the spatial correlation matrix R and information about the selected precoding matrix F_s to the base station. A method for data precoding at a base station in a wireless communication system may comprise: obtaining, from a user equipment, information about a spatial correlation matrix R of multiple transmit antennas of the base station and information about a precoding matrix F_s selected by the user equipment; determining a desired precoding matrix F_R,s based on the obtained information and a precoding codebook; and precoding downlink data to be transmitted to the user equipment with the desired precoding matrix F_R,s.

Claims

1. A method for processing communication data at a user equipment in a wireless communication system, comprising:

deriving a spatial correlation matrix R of multiple transmit antennas of a base station based on an obtained downlink channel transmission matrix H;

transforming a precoding codebook F according to the spatial correlation matrix R;

selecting a precoding matrix F_s based on the transformed precoding codebook; and

feeding back information about the spatial correlation matrix R and information about the selected precoding matrix F_s to the base station, wherein the information about the selected precoding matrix F_s includes an index of the selected precoding matrix F_s in the precoding codebook, and the information about the spatial correlation matrix R includes an index of the spatial correlation matrix R in a spatial correlation matrix codebook.

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

averaging the downlink channel transmission matrix H in time and/or frequency to obtain said spatial correlation matrix R.

3. The method of claim 1, wherein the transforming comprises:

quantizing the spatial correlation matrix R; and

transforming the precoding codebook with the quantized spatial correlation matrix.

4. The method of claim 3, wherein at least one codeword F_k in the precoding codebook F is transformed to obtain the transformed precoding matrix F_R,k according to F_R,k=RF_k, where k=1, . . . , K, and K is a position integer.

5. The method of claim 1, wherein the selecting comprises:

performing singular value decomposition on the downlink channel transmission matrix H to obtain H=UΣ

V^H;

taking the first m columns of elements in a right unitary singular matrix V obtained from the singular value decomposition as an ideal precoding matrix V_m, where m is the number of data streams transmitted to the user equipment; and

selecting the precoding matrix F_s from the precoding codebook such that the distance between a precoding matrix F_R transformed via the spatial correlation matrix and the ideal precoding matrix V_m is minimized.

6. The method of claim 5, wherein the distance is

7. A method for data precoding at a base station in a wireless communication system, comprising:

obtaining, from a user equipment, information about a spatial correlation matrix R of multiple transmit antennas of the base station and information about a precoding matrix F_s selected by the user equipment;

determining a desired precoding matrix F_R,s based on the obtained information and a precoding codebook, wherein the determining comprises;

retrieving the selected precoding matrix F_s from the precoding codebook based on the information about the selected precoding matrix F_s, wherein the information about the selected precoding matrix includes an index of the selected precoding matrix in the precoding codebook, and retrieving the spatial correlation matrix R from a spatial correlation matrix codebook based on the information about the spatial correlation matrix R, wherein the information about the spatial correlation matrix R includes an index of the spatial correlation matrix R in the spatial correlation matrix codebook, and transforming the selected precoding matrix F_s with the spatial correlation matrix R to obtain the desired precoding matrix F_R,s; and

precoding downlink data to be transmitted to the user equipment with the desired precoding matrix F_R,s.

8. The method of claim 7, wherein the precoding comprises:

taking the conjugate transpose of the desired precoding matrix F_R,s as an approximate effective channel matrix of the user equipment; and

precoding the downlink data to be transmitted to the user equipment based on the approximate effective channel matrix.

9. The method of claim 7, wherein in a case where there are multiple user equipments, the precoding comprises:

scheduling user equipments of the multiple user equipments whose desired precoding matrices F_R,s are orthogonal to each other.

10. An apparatus for processing communication data at a user equipment in a wireless communication system, comprising:

a deriving module, configured to derive a spatial correlation matrix R of multiple transmit antennas of a base station based on an obtained downlink channel transmission matrix H;

a transforming module, configured to transform a precoding codebook F according to the spatial correlation matrix R;

a selecting module, configured to select a precoding matrix F_s based on the transformed precoding codebook; and

a feedback module, configured to feed back information about the spatial correlation matrix R and information about the selected precoding matrix F_s to the base station, wherein the information about the selected precoding matrix F_s includes an index of the selected precoding matrix F_s in the precoding codebook, and the information about the spatial correlation matrix R includes an index of the spatial correlation matrix R in a spatial correlation matrix codebook.

11. The apparatus of claim 10, wherein the selecting module is configured to:

perform singular value decomposition on the downlink channel transmission matrix H to obtain H=UΣ

V^H;

take the first m columns of elements in the right unitary singular matrix V obtained from the singular value decomposition as an ideal precoding matrix V_m, where m is the number of data streams transmitted to the user equipment; and

select the precoding matrix F_s from the precoding codebook such that the distance between a precoding matrix F_R transformed via the spatial correlation matrix and the ideal precoding matrix V_m is minimized.

12. An apparatus for data precoding at a base station in a wireless communication system, comprising:

an obtaining module, configured to obtain, from a user equipment, information about a spatial correlation matrix R of multiple transmit antennas of the base station and information about a precoding matrix F_s selected by the user equipment;

a determining module, configured to determine a desired precoding matrix F_R,s based on the obtained information and a precoding codebook;

a precoding module, configured to precode downlink data to be transmitted to the user equipment with the desired precoding matrix F_R,s;

a retrieving unit, configured to retrieve the selected precoding matrix F_s from the precoding codebook based on the information about the selected precoding matrix F_s, wherein the information about the selected precoding matrix includes an index of the selected precoding matrix in the precoding codebook, and to retrieve the spatial correlation matrix R from a spatial correlation matrix codebook based on the information about the spatial correlation matrix R, wherein the information about the spatial correlation matrix R includes an index of the spatial correlation matrix R in the spatial correlation matrix codebook; and

a transforming unit, configured to transform the selected precoding matrix F_s with the spatial correlation matrix R to obtain the desired precoding matrix F_R,s.