Differential feedback scheme for closed-loop MIMO beamforming
View Patent ↗A first N×M codebook of a first rank M may be used to generate a second N×(N−M) codebook of a second rank (N−M). This second codebook is both orthogonal and complementary to the first codebook. In practice, this may reduce storage requirements in closed-loop MIMO beamforming, because the second codebook may be dynamically generated as needed by a base station and/or a mobile station. In some cases, a higher rank beamforming matrix or precoding matrix may be formed from a lower rank (e.g., one or two) beamforming matrix or precoding matrix. Also, a novel way to generate the rotation matrix Q v(t-1) is disclosed.
1. A method of performing codebook-based precoding comprising:
obtaining at least part of a first differential codebook having a first rank;
generating at least part of a second differential codebook having a second rank from the first differential codebook;
receiving an index into the second differential codebook from a remote station via at least one of a plurality of antennas; and
precoding data for transmission via the plurality of antennas using a codeword chosen from the second differential codebook based on the index.
2. The method of claim 1 , wherein the obtaining includes reading the first differential codebook from a memory.
3. The method of claim 1 , wherein the first rank is one or two or greater, and
wherein the second rank is a difference between a number of the plurality of antennas and the first rank.
4. The method of claim 1 , wherein the second rank is greater than the first rank.
5. The method of claim 1 , further comprising:
storing the second differential codebook in a memory.
6. The method of claim 1 , wherein the generating includes:
performing a complementary expansion on the first differential codebook to generate an intermediate codebook having the second rank; and
rotating the intermediate codebook to generate the second differential codebook.
7. A non-transitory processor-readable storage media containing processor-executable instructions for execution by a processor for carrying out the method of claim 1 .
8. A method of performing codebook-based, closed-loop transmission via N antennas, where N is an integer two or greater, comprising:
providing an N×M differential codebook, where M is an integer number of data streams that is less than N;
generating an N×(N−M) differential codebook from the N×M differential codebook, including:
performing a complementary expansion of the N×M differential codebook; and
precoding (N−M) streams of data for transmission via the N antennas using a codeword chosen from the N×(N−M) differential codebook.
9. The method of claim 8 , wherein the providing includes reading the N×M differential codebook from a memory.
10. The method of claim 8 , wherein M is one or two or greater.
11. The method of claim 8 , wherein N is two, three, four, or eight.
12. The method of claim 8 , further comprising:
storing the N×(N−M) differential codebook in a memory.
13. The method of claim 8 , wherein the generating includes:
rotating an intermediate matrix produced by the complementary expansion of the N×M differential codebook.
14. A non-transitory processor-readable storage media containing processor-executable instructions for execution by a processor for carrying out the method of claim 8 .