METHOD AND APPARATUS FOR INFORMATION FEEDBACK AND PRECODING

• US 20130028344A1
• Filed: 04/07/2010
• Published: 01/31/2013
• 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
• Granted Patent: US 9,042,474 B2
• Time in Patent Office: Days
• 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.

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 each 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. The method of claim 1, wherein in the feeding back,

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.

8. 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; and

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

9. The method of claim 8, 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.

10. The method of claim 8, 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.

11. The method of claim 8, 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.

12. 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.

16. The apparatus of claim 12, 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.

13-15. -15. (canceled)

17-18. -18. (canceled)

19. 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; and

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

20. The apparatus of claim 19, wherein the determining module further comprises:

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.

21-22. -22. (canceled)