Method, apparatus and communication unit

1. An apparatus comprising:

means for determining a rank for a set of sub-bands;

means for outputting first feedback information regarding the rank;

means for selecting a sub-band precoding matrix for a sub-band that is selected from the set of sub-bands;

means for outputting a sub-band precoding matrix index (“PMI”) regarding the sub-band precoding matrix based on the rank that is determined for the set of the sub-bands; and

means for receiving a data stream transmitted based on the sub-band precoding matrix.

2. The apparatus of claim 1 , wherein the sub-band precoding matrix is selected according to 3GPP-LTE standard.

3. The apparatus of claim 1 , wherein the means for selecting the sub-band precoding matrix selects the sub-band precoding matrix from a precoding codebook for the selected sub-band.

4. The apparatus of claim 1 , wherein the rank is constant over the set of the sub-bands.

5. The apparatus of claim 1 , wherein means for selecting the sub-band precoding matrix comprises selecting the sub-band precoding matrix to maximize a data rate of the data stream.

6. The apparatus of claim 1 , further comprising:

means for selecting a wideband precoding matrix for the set of sub-bands from a precoding codebook for the set of sub-bands.

7. The apparatus of claim 6 , wherein the means for selecting the wideband precoding matrix is to select the wideband precoding matrix based on a maximum likelihood estimate of a transmit correlation matrix.

8. The apparatus of claim 6 , further comprising:

means for outputting a wideband precoding matrix index of the selected wideband precoding matrix.

9. The apparatus of claim 6 , wherein the wideband precoding matrix is constant over the set of sub-bands.

10. An apparatus, comprising:

means for outputting a feedback for a rank over a set of sub-bands;

means for outputting a wideband precoding matrix index for a wideband precoding matrix from a codebook for the set of sub-bands based on the rank of the set of sub-bands;

means for outputting a sub-band precoding matrix index for a sub-band precoding matrix from the codebook for a sub-band from the set of the sub-bands, and wherein the sub-band precoding matrix index is generated based on the rank of the set of sub-bands; and

means for receiving a data stream to be transmitted based on the sub-band precoding matrix.

11. The apparatus of claim 10 , wherein the wideband precoding matrix is constant over the set of sub-bands.

12. The apparatus of claim 10 , wherein the apparatus is in a baseband chip of a mobile phone, a handheld device, or a base station.

13. The apparatus of claim 10 , further comprising: means for selecting the wideband precoding matrix to maximize a data rate in transmission.

14. An apparatus comprising:

means for providing a rank corresponding to a set of sub-bands and a feedback on the rank;

means for providing a wideband precoding matrix index of a wideband precoding matrix corresponding to the set of sub-bands and the rank of the set of sub-bands, wherein the wideband precoding matrix is based on a maximum likelihood estimate of a transmit correlation matrix; and

means for providing a sub-band precoding matrix index of a sub-band precoding matrix for a sub-band from the set of the sub-bands, and wherein the sub-band precoding matrix is generated corresponding to the rank of the set of sub-bands.

15. The apparatus of claim 14 , wherein the sub-band precoding matrix is used to precode a transmission signal.

16. The apparatus of claim 15 , further comprising:

means for receiving the transmission signal precoded by the sub-band precoding matrix.

17. An apparatus comprising:

means for selecting a wideband precoding matrix over a set of sub-bands;

means for determining a rank of the wideband precoding matrix;

means for generating a rank feedback for the rank, wherein the rank feedback corresponds to the set of sub-bands;

means for selecting a sub-band precoding matrix for a sub-band that is selected from the set of the sub-bands; and

means for generating a sub-band precoding matrix index (“PMI”) of the sub-band precoding matrix, wherein the sub-band precoding matrix is generated based on the rank of the wideband precoding matrix.

18. An apparatus comprising:

means for selecting a wideband precoding matrix for a set of sub-bands;

means for generating first feedback information to provide an indication of the wideband precoding matrix, the first feedback information to be fed back to a second device;

means for selecting a sub-band precoding matrix for a sub-band of the set of sub-bands;

means for generating second feedback information to provide an indication of the sub-band precoding matrix, the second feedback information to be fed back to the second device; and

means for receiving a modulated data stream transmitted by the second device, wherein the modulated data stream is transmitted based on the wideband precoding matrix or the sub-band precoding matrix.

19. The apparatus of claim 18 , further comprising:

means for selecting a rank for the set of sub-bands; and

means for generating third feedback information to provide an indication of the selected rank.

20. The apparatus of claim 19 , wherein the means for selecting the sub-band pre-coding matrix is to select the sub-band pre-coding matrix for the rank.

21. The apparatus of claim 18 , wherein the sub-band pre-coding matrix is a first sub-band pre-coding matrix, the sub-band is a first sub-band, and the apparatus further comprises:

means for selecting a second sub-band pre-coding matrix for a second sub-band of the set of sub-bands; and

means for generating third feedback information to provide an indication of the second sub-band pre-coding matrix.

22. The apparatus of claim 18 , wherein the sub-band precoding matrix is selected according to 3GPP-LTE standard.

23. The apparatus of claim 18 , wherein means for selecting the sub-band precoding matrix are to select the sub-band precoding matrix from a precoding codebook for the sub-band.

24. The apparatus of claim 18 , wherein the means for selecting the wideband precoding matrix are to select the wideband precoding matrix based on a maximum likelihood estimate of a transmit correlation matrix.

25. The apparatus of claim 18 , wherein the first feedback information includes an indication of a first pre-coding matrix index that corresponds to the wideband pre-coding matrix and the second feedback information includes an indication of a second pre-coding matrix index that corresponds to the sub-band pre-coding matrix.