Efficient rank and precoding matrix feedback for MIMO systems

1. A receiver, comprising:

a receive unit configured to receive transmissions from multiple antennas;

a rank feedback unit configured to provide a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme; and

a precoding feedback unit configured to provide a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme and wherein the precoding matrix selection is restricted to a subset of available precoding matrices that is transmission-configured or receiver-determined.

2. A receiver, comprising:

a receive unit configured to receive transmissions from multiple antennas;

a rank feedback unit configured to provide transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme; and

a precoding feedback unit configured to provide a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme and wherein the precoding matrix selection corresponds to a subset of precoding matrices that relates to a reference precoding matrix.

3. The receiver as recited in claim 2 wherein the reference precoding matrix is the last precoding matrix selection.

4. The receiver as recited in claim 2 wherein the reference precoding matrix is a wideband precoding matrix selected for at least a portion of the system bandwidth.

5. The receiver as recited in claim 2 wherein the subset contains precoding matrices that are closest to the reference precoding matrix according to a distance measure.

6. The receiver as recited in claim 5 wherein the distance measure is selected from the group consisting of:

a Chordal distance norm; and

a Frobenius distance norm.

7. A receiver, comprising:

a receive unit configured to receive transmissions from multiple antennas;

a rank feedback unit configured to provide a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme; and

a precoding feedback unit configured to provide a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme and wherein the precoding matrix selection is a differential precoding matrix that corresponds to a difference between a current precoding matrix and a reference precoding matrix.

8. A method of operating a receiver, comprising:

receiving transmissions from multiple antennas;

feeding back a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme; and

feeding back a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme and wherein the precoding matrix selection is restricted to a subset of available precoding matrices that is transmission-configured or receiver-determined.

9. A method of operating a receiver, comprising:

receiving transmissions from multiple antennas;

feeding back a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme; and

feeding back a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme and wherein the precoding matrix selection corresponds to a subset of precoding matrices that relates to a reference precoding matrix.

10. The method as recited in claim 9 wherein the reference precoding matrix is the last precoding matrix selection.

11. The method as recited in claim 9 wherein the reference precoding matrix is a wideband precoding matrix selected for at least a portion of the system bandwidth.

12. The method as recited in claim 9 wherein the subset contains precoding matrices that are closest to the reference precoding matrix according to a distance measure.

13. The method as recited in claim 12 wherein the distance measure is selected from the group consisting of:

a Chordal distance norm; and

a Frobenius distance norm.

14. A method of operating a receiver, comprising:

receiving transmissions from multiple antennas;

feeding back a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme; and

feeding back a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme and wherein the precoding matrix selection is a differential precoding matrix that corresponds to a difference between a current precoding matrix and a reference precoding matrix.

15. A transmitter comprising:

a rank decoding unit configured to extract a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme;

a precoding decoding unit configured to extract a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme, wherein the precoding matrix selection is restricted to a subset of available precoding matrices that is transmitter-configured or receiver-determined; and

a transmit unit that is coupled to multiple antennas and configured to apply the transmission rank and precoding matrix selections to data to be transmitted.

16. A transmitter comprising:

a rank decoding unit configured to extract a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme;

a precoding decoding unit configured to extract a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme, wherein the precoding matrix selection corresponds to a subset of precoding matrices that relates to a reference precoding matrix; and

a transmit unit that is coupled to multiple antennas and configured to apply the transmission rank and precoding matrix selections to data to be transmitted.

17. The transmitter as recited in claim 16 wherein the reference precoding matrix is the last precoding matrix selection.

18. The transmitter as recited in claim 16 wherein the reference precoding matrix is a wideband precoding matrix selected for at least a portion of the system bandwidth.

19. The transmitter as recited in claim 16 wherein the subset contains precoding matrices that are closest to the reference precoding matrix according to a distance measure.

20. The transmitter as recited in claim 19 wherein the distance measure is selected from the group consisting of:

a Chordal distance norm; and

a Frobenius distance norm.

21. A transmitter comprising:

a rank decoding unit configured to extract a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme;

a precoding decoding unit configured to extract a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme, wherein the precoding matrix selection is a differential precoding matrix that corresponds to a difference between a current precoding matrix and a reference precoding matrix; and

a transmit unit that is coupled to multiple antennas and configured to apply the transmission rank and precoding matrix selections to data to be transmitted.

22. A method of operating a transmitter comprising:

extracting a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme;

extracting a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme, wherein the precoding matrix selection is restricted to a subset of available precoding matrices that is transmitter-configured or receiver-determined; and

applying the transmission rank and precoding matrix selections to data to be transmitted.

23. A method of operating a transmitter comprising:

extracting a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme;

extracting a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme, wherein the precoding matrix selection corresponds to a subset of precoding matrices that relates to a reference precoding matrix; and

applying the transmission rank and precoding matrix selections to data to be transmitted.

24. The method as recited in claim 23 wherein the reference precoding matrix is the last precoding matrix selection.

25. The method as recited in claim 23 wherein the reference precoding matrix is a wideband precoding matrix selected for at least a portion of the system bandwidth.

26. The method as recited in claim 23 wherein the subset contains precoding matrices that are closest to the reference precoding matrix according to a distance measure.

27. The method as recited in claim 26 wherein the distance measure is selected from the group consisting of:

a Chordal distance norm; and

a Frobenius distance norm.

28. A method of operating a transmitter comprising:

extracting a transmission rank selection, wherein the transmission rank selection corresponds to a transmission rank feedback reduction scheme;

extracting a precoding matrix selection, wherein the precoding matrix selection corresponds to a precoding matrix feedback reduction scheme, wherein the precoding matrix selection is a differential precoding matrix that corresponds to a difference between a current precoding matrix and a reference precoding matrix; and

applying the transmission rank and precoding matrix selections to data to be transmitted.