Method and apparatus for codebook based feedback in a closed loop wireless communication system

1. A method for providing feedback for closed-loop transmitting with a plurality of transmit antenna elements and a plurality of receive antenna elements, the method comprising:

providing a codebook containing sets of weightings for the plurality of transmit antenna elements with each set of weightings identified by an index and the codebook known to a transmitter and a receiver;

pre-coding pilot signals using a precoding matrix to produce pre-coded pilot signals;

transmitting the pre-coded pilot signals to the receiver via the plurality of transmit antenna elements; and

in response to transmitting the pre-coded pilot signals, receiving at the transmitter an index to a set of weightings in the codebook for use in a subsequent transmission of a data stream wherein the set of weightings are based on a determined effective channel for a subset of rank 1 codebook weightings that produce ‘S’ effective channels and for each remaining codebook weightings as a low complexity function of the ‘S’ effective channels.

2. The method of claim 1 , wherein pre-coding pilot signals comprises pre-coding pilot signals using a unitary matrix.

3. The method of claim 2 , wherein the receiver is not informed, by the transmitter, of the unitary matrix used to pre-code the pilot pattern.

4. The method of claim 1 , further comprising:

receiving the pre-coded pilot signals;

estimating a composite channel between the plurality of transmit antenna elements and the plurality of receive antenna elements based on the received pre-coded pilot signals;

selecting a set of weightings based on the composite channel estimates; and

feeding back an index of the set of weightings to a transmitter associated with the plurality of transmit antenna elements for use in a subsequent transmission of a data stream.

5. The method of claim 1 , wherein the codebook weights are restricted to a finite alphabet.

6. The method of claim 1 , wherein the same codebook is used for all ranks.

7. A base station capable of operating in a multiple input, multiple output communication system, the base station comprising:

an antenna array comprising plurality of antenna elements;

a codebook containing sets of weightings for the plurality of transmit antenna elements with each set of weightings identified by an index known to the base station and a mobile station serviced by the base station;

an antenna array signal processor that pre-codes pilot signals using a matrix to produce pre-coded pilot signals that is transmitted via the plurality of transmit antenna elements; and

a receiver that receives an index to a set of weightings in the codebook for use in a subsequent transmission of a data stream, wherein the set of weightings are based on a determined effective channel for a subset of rank 1 codebook weightings that produce ‘S’ effective channels and for each remaining codebook weightings as a low complexity function of the ‘S’ effective channels.

8. The base station of claim 7 , wherein the antenna array signal processor pre-codes the pilot signals using a unitary matrix.

9. The base station of claim 8 , wherein the mobile station is not informed, by the base station, of the unitary matrix used to pre-code the pilot pattern.

10. The base station of claim 7 , wherein the codebook weights are restricted to a finite alphabet.

11. The base station of claim 7 , wherein the same codebook is used for all ranks.

12. A system comprising the base station of claim 7 and further comprising a mobile station having a plurality of antenna elements and that is configured to receive the pre-coded pilot signal, estimate a composite channel between the plurality of transmit antenna elements and the plurality of receive antenna elements based on the received pre-coded pilot signal, selecting a set of weightings for each data stream based on the composite channel estimate, and feed back an index of the set of weightings to a transmitter associated with the plurality of transmit antenna elements for use in subsequent transmissions of a data stream, wherein the set of weightings are based on a determined effective channel for a subset of rank 1 codebook weightings that produce ‘S’ effective channels and for each remaining codebook weightings as a low complexity function of the ‘S’ effective channels.

13. A method for providing feedback for closed-loop transmitting with a plurality of transmit antenna elements and a plurality of receive antenna elements, the method comprising:

providing a codebook containing sets of weightings for the plurality of transmit antenna elements with each set of weightings identified by an index and the codebook known to a transmitter and a receiver;

pre-coding pilot signals using a precoding matrix to produce pre-coded pilot signals;

transmitting the pre-coded pilot signals to the receiver via the plurality of transmit antenna elements; and

in response to transmitting the pre-coded pilot signals, receiving at the transmitter an index to a set of weightings in the codebook for use in a subsequent transmission of a data stream, wherein the receiver is not informed of the precoding matrix used to pre-code the pilot signals.

14. A base station capable of operating in a multiple input, multiple output communication system, the base station comprising:

an antenna array comprising plurality of antenna elements;

a codebook containing sets of weightings for the plurality of transmit antenna elements with each set of weightings identified by an index known to the base station and a mobile station serviced by the base station;

an antenna array signal processor that pre-codes pilot signals using a matrix to produce pre-coded pilot signals that is transmitted via the plurality of transmit antenna elements; and

a receiver that receives an index to a set of weightings in the codebook for use in a subsequent transmission of a data stream, wherein the receiver is not informed of the precoding matrix used to pre-code the pilot signals.