MIMO communication system and method for beamforming using polar-cap codebooks

1. A method performed by a transmitting station for transmitting two or more data streams through a channel, the method comprising:

receiving a codeword of a full-manifold codebook, the codeword generated based on an initial channel matrix;

subsequently receiving a codeword of a polar-cap codebook, the codeword of the polar-cap codebook representing deviations in the channel since receiving the codeword of the full-manifold codebook; and

performing beamforming to transmit packets to a receiving station by applying beamforming coefficients derived from a codeword of the full-manifold codebook to an initial data transmission and by applying beamforming coefficients derived from a codeword of the polar-cap codebook to a subsequent data transmission,

wherein the polar-cap codebook comprises a differential codebook that is smaller in size than the full-manifold codebook.

2. The method of claim 1 wherein the codeword of the full-manifold codebook corresponds to an initial beamforming matrix for application by a beamformer of the transmitting station, and

wherein the codeword of the polar-cap codebook corresponds to a differential beamforming matrix for use in deriving a second beamforming matrix by the transmitting station using the differential beamforming matrix and the initial beamforming matrix.

3. The method of claim 2 wherein the full-manifold codebook comprises codewords corresponding to vectors that populate a surface of a manifold, and

wherein codewords of the polar-cap codebook are within a polar ring on the surface of the manifold.

4. The method of claim 2 wherein the receiving station generates the initial channel matrix based on measured channel conditions and calculates the initial beamforming matrix by performing a decomposition of the initial channel matrix, and

wherein the receiving station generates a second channel matrix based on subsequently measured channel conditions and calculates the differential beamforming matrix associated with the codeword of the polar-cap codebook.

5. The method of claim 4 wherein the receiving station derives the differential beamforming matrix from the equation V′ 2 =V 2 H *V 1 in which V′ 2 represents the differential beamforming matrix, V 1 represents the initial beamforming matrix, and V 2 H represents a Hermitian transpose of the second beamforming matrix, and

wherein the second beamforming matrix V 2 comprises a decomposition matrix of the second channel matrix.

6. A method performed by a transmitting station for transmitting two or more data streams through a channel, the method comprising:

receiving a codeword of a full-manifold codebook, the codeword generated based on an initial channel matrix;

subsequently receiving a codeword of a polar-cap codebook, the codeword of the polar-cap codebook representing deviations in the channel since receiving the codeword of the full-manifold codebook;

performing beamforming to transmit packets to a receiving station using the codeword;

after receiving the codeword of the full-manifold codebook, applying beamforming coefficients derived from the codeword of the full-manifold codebook to a first data transmission; and

after receipt of the codeword of the polar-cap codebook, applying beamforming coefficients derived from the codeword of the polar-cap codebook for a subsequent data transmission,

wherein the polar-cap codebook comprises a differential codebook that is smaller in size than the full-manifold codebook,

wherein the codeword of the full-manifold codebook corresponds to an initial beamforming matrix for application by a beamformer of the transmitting station,

wherein the codeword of the polar-cap codebook corresponds to a differential beamforming matrix for use in deriving a second beamforming matrix by the transmitting station using the differential beamforming matrix and the initial beamforming matrix,

wherein the codewords of the polar-cap codebook and the full-manifold codebook correspond to beamforming matrices for use by the beamformer of the transmitting station.

7. The method of claim 1 wherein a coherency time of the channel is greater than a time between receiving the codeword of the full-manifold codebook and receiving the codeword of the polar-cap codebook allowing the transmitting station to react in a time less than the coherency time.

8. A method performed by a transmitting station for transmitting two or more data streams through a channel, the method comprising:

receiving a codeword of a full-manifold codebook, the codeword generated based on an initial channel matrix;

subsequently receiving a codeword of a polar-cap codebook, the codeword of the polar-cap codebook representing deviations in the channel since receiving the codeword of the full-manifold codebook; and

performing beamforming to transmit packets to a receiving station using the codeword,

wherein the polar-cap codebook comprises a differential codebook that is smaller in size than the full-manifold codebook,

wherein the channel comprises an orthogonal frequency division multiplexed (OFDM) comprising a plurality of tones,

wherein a cluster of tones has a bandwidth that is less than a coherence bandwidth of the channel,

wherein feedback comprising codewords of the full-manifold codebook is provided for some of the clusters,

wherein feedback comprising codewords of the polar-cap codebook is provided for at least some other of the clusters for which the codewords of the full-manifold codebook were not provided, and

wherein the codewords are generated by time-domain sampling groups of received OFDM symbols over time.

9. The method of claim 8 wherein the feedback comprising the codewords of the full-manifold codebook and the feedback comprising the codewords of the polar-cap codebook are shifted over time to different clusters.

10. The method of claim 8 further comprising refraining from providing feedback comprising either the codewords of the full-manifold codebook or the codewords of the polar-cap codebook for some clusters.

11. The method of claim 1 wherein the codeword of the full-manifold codebook and the codeword of the polar-cap codebook are received as part of separately transmitted packets transmitted by the receiving station,

wherein the codeword of the full-manifold codebook is quantized to a first predetermined number of bits and the codeword of the polar-cap codebook is quantized to a second predetermined number of bits, the second predetermined number being less than the first predetermined number, and

wherein the codeword of the full-manifold codebook and the codeword of the polar-cap codebook are transmitted by the receiving station as part of separate channel-quality-indicator (CQI) packets.

12. A method for beamforming performed by a transmitting station, the method comprising:

initially receiving a codeword of a polar-cap codebook; and

subsequently receiving additional codewords of the polar-cap codebook, the subsequently received codewords of the polar-cap codebook representing deviations in a channel since receiving a prior codeword of the polar-cap codebook;

performing beamforming to transmit packets to a receiving station by applying beamforming coefficients derived from a codeword of a full-manifold codebook to an initial data transmission and by applying beamforming coefficients derived from a codeword of the polar-cap codebook to a subsequent data transmission,

wherein the polar-cap codebook is a differential codebook comprising codewords within a polar ring on a surface of a manifold of the full-manifold codebook, and

wherein the full-manifold codebook comprises a full set of codewords for use in encoding a beamforming matrix.

13. The method of claim 12 wherein the codewords of the polar-cap codebook are received at the transmitting station and are determined by the receiving station based on decomposition of a current channel matrix and decomposition of a prior channel matrix.

14. The method of claim 13 further comprising:

generating beamforming coefficients from the codewords of the polar-cap codebook received from the receiving station; and

applying the beamforming coefficients to frequency-domain signals of two or more data streams prior to transmission.

15. A transmitting station for transmitting two or more data streams through a channel, the transmitter comprising:

a matrix generator to generate an initial beamforming matrix from a received codeword of a full-manifold codebook, the codeword generated based on an initial channel matrix, the matrix generator to further generate a second beamforming matrix from a subsequently received codeword of a polar-cap codebook, the codeword of the polar-cap codebook representing deviations in the channel since the generation of the codeword of the full-manifold codebook; and

a beamformer to apply the beamforming matrices to frequency-domain signals prior to transmission by two or more antennas,

wherein the beamformer is to apply beamforming coefficients derived from a codeword of the full-manifold codebook to an initial data transmission and is to apply beamforming coefficients derived from a codeword of the polar-cap codebook to a subsequent data transmission, and

wherein the polar-cap codebook comprises a differential codebook that is smaller in size than the full-manifold codebook.

16. The transmitting station of claim 15 wherein the codeword of the full-manifold codebook corresponds to an initial beamforming matrix for application by the beamformer,

wherein the codeword of the polar-cap codebook corresponds to a differential beamforming matrix for use in deriving the second beamforming matrix by the transmitting station using the differential beamforming matrix and the initial beamforming matrix,

wherein the full-manifold codebook comprises codewords corresponding to vectors that populate a surface of a manifold, and

wherein codewords of the polar-cap codebook are within a polar ring on the surface of the manifold.

17. The transmitting station of claim 16 wherein the channel comprises an orthogonal frequency division multiplexed (OFDM) comprising a plurality of tones,

wherein a cluster of tones has a bandwidth that is less than a coherence bandwidth of the channel,

wherein feedback comprising codewords of the full-manifold codebook is provided for some of the clusters,

wherein feedback comprising codewords of the polar-cap codebook is provided for at least some other of the clusters for which the codewords of the full-manifold codebook were not provided, and

wherein the codewords are generated by time-domain sampling groups of received OFDM symbols over time.

18. A multiple-input multiple-output (MIMO) system comprising:

a receiving station to generate a codeword of a full-manifold codebook based on an initial channel matrix, and to subsequently generate a codeword of a polar-cap codebook, the codeword of the polar-cap codebook representing deviations in the channel since receiving the codeword of the full-manifold codebook; and

a transmitting station to generate an initial beamforming matrix from the codeword of the full-manifold codebook to perform beamforming for an initial data transmission, and to further generate a second beamforming matrix from a subsequently received codeword of the polar-cap codebook to perform beamforming for a subsequent data transmission, the codeword of the polar-cap codebook representing deviations in the channel since the generation of the codeword of the full-manifold codebook,

wherein the polar-cap codebook comprises a differential codebook that is smaller in size than the full-manifold codebook.

19. The MIMO system of claim 18 wherein the codeword of the full-manifold codebook corresponds to the initial beamforming matrix for application by a beamformer,

wherein the codeword of the polar-cap codebook corresponds to a differential beamforming matrix for use in deriving the second beamforming matrix by the transmitting station using the differential beamforming matrix and the initial beamforming matrix,

wherein the full-manifold codebook comprises codewords corresponding to vectors that populate a surface of a manifold, and

wherein codewords of the polar-cap codebook are within a polar ring on the surface of the manifold.

20. The MIMO system of claim 19 wherein the transmitting station comprises a matrix generator to generate the beamforming matrices, and a beamformer to apply the beamforming matrices to two or more data streams for transmission through the channel using two or more transmit antennas.