Delay diversity and spatial rotation systems and methods

1. A transmitter usable for wireless communication, comprising:

a plurality of transmit antennas, wherein each transmit antenna transmits a respective transmit signal;

means for introducing respective time shifts to each of a plurality of spatial stream signals to produce a plurality of time-shifted spatial stream signals, wherein each of the plurality of spatial stream signals is based at least in part on a data stream;

means for operating on each of the plurality of time-shifted spatial stream signals with a spatial rotation vector matrix to apply respective spatial rotation to each of the plurality of time-shifted spatial stream signals, to thereby map the plurality of time-shifted spatial stream signals respectively to the respective transmit signals that are respective time-shifted spatially-rotated spatial stream signals of a plurality of time-shifted spatially-rotated spatial stream signals, to reduce nulls, including deep nulls, associated with the data stream, in a received channel, wherein the spatial rotation vector matrix is a Walsh matrix; and

means for transforming each of a plurality of spatial stream signals using an Inverse Fast Fourier Transform (IFFT), wherein the means for transforming is applied to the plurality of spatial stream signals before the means for introducing respective time shifts is applied to each of the plurality of spatial stream signals and before the means for operating on each of the plurality of time-shifted spatial stream signals with a spatial rotation vector matrix.

2. The transmitter of claim 1 , wherein the means for introducing time shifts to each of a plurality of spatial stream signals comprises means for introducing cyclic shifts.

3. The transmitter of claim 2 , wherein the means for introducing cyclic shifts to each of a plurality of spatial stream signals comprises means for introducing cyclic delays to at least one of the plurality of spatial streams.

4. The transmitter of claim 2 , wherein the means for introducing cyclic shifts to each of a plurality of spatial stream signals comprises means for introducing cyclic advances to at least one of the plurality of spatial streams.

5. The transmitter of claim 2 , wherein the means for introducing cyclic shifts to each of a plurality of spatial stream signals comprises means for introducing cyclic shifts in the time domain.

6. The transmitter of claim 2 , wherein the means for introducing cyclic shifts to each of a plurality of spatial stream signals comprises means for introducing cyclic shifts in the frequency domain.

7. The transmitter of claim 1 , wherein the means for introducing time shifts to each of a plurality of spatial stream signals comprises means for introducing linear time shifts to each of a plurality of spatial stream signals.

8. A method of communicating in a wireless network, comprising:

receiving a number (Nss) of input signals;

transforming at least a portion of the Nss input signals using an Inverse Fast Fourier Transform (IFFT);

producing a number (Ntx) of output signals that are respectively time shifted copies of the Nss input signals, wherein Ntx is greater than or equal to Nss;

operating on the Ntx output signals using a Ntx-by-Ntx unitary spatial rotation matrix to provide respective spatial rotation to all of the Ntx output signals, wherein the Ntx-by-Ntx unitary spatial rotation matrix comprises a Walsh matrix, wherein the transforming of the at least a portion of the Nss input signals is performed before the producing of the number of Ntx output signals that are respectively time shifted copies of the Nss input signals and before the operating on the Ntx output signals using the Ntx-by-Ntx unitary spatial rotation vector matrix; and

broadcasting the Ntx output signals, which are respectively time shifted and respectively spatially rotated, to reduce nulls, including deep nulls, associated with the Nss input signals, in a received channel that is one of a certain number of highly correlated channels.

9. The method of claim 8 , wherein producing Ntx output signals that are time shifted copies of the Nss input signals comprises producing Ntx output signals that are cyclically shifted copies of the Nss input signals.

10. The method of claim 9 , wherein producing Ntx output signals that are cyclically shifted copies of the Nss input signals comprises producing Ntx output signals wherein at least one of the Ntx output signals comprises a cyclically delayed signal.

11. The method of claim 9 , wherein producing Ntx output signals that are cyclically shifted copies of the Nss input signals comprises producing Ntx output signals wherein at least one of the Ntx output signals comprises a cyclically advanced signal.

12. The method of claim 9 , wherein producing Ntx output signals that are cyclically shifted copies of the Nss input signals comprises producing Ntx output signals that are cyclically shifted in the time domain.

13. The method of claim 9 , wherein producing Ntx output signals that are cyclically shifted copies of the Nss input signals comprises producing Ntx output signals that are cyclically shifted in the frequency domain.

14. The method of claim 8 , wherein producing Ntx output signals that are time shifted copies of the Nss input signals comprises producing Ntx output signals that are linearly shifted copies of the Nss input signals.

15. A wireless transmitter for transmitting a plurality of transmit stream signals, the transmitter comprising:

an Inverse Fast Fourier Transform (IFFT) module that transforms one or more of a plurality of spatial stream signals using an Inverse Fast Fourier Transform (IFFT);

a time shift module adapted to introduce time shifts to the one or more of the plurality of spatial stream signals to produce a plurality of time-shifted spatial stream signals, wherein the spatial stream signals are generated based at least in part on a data stream; and

a spatial rotation module communicatively coupled with the time shift module and adapted to receive the plurality of time-shifted spatial stream signals from the time shift module and to operate on each of the time-shifted spatial stream signals with a spatial rotation vector matrix to apply respective spatial rotation to each of the plurality of time-shifted spatial stream signals, to thereby map each of the plurality of time-shifted spatial stream signals correspondingly to a respective one of the transmit stream signals that are respective time-shifted spatially-rotated spatial stream signals of a plurality of time-shifted spatially-rotated spatial stream signals, to reduce nulls, including deep nulls, associated with the data stream, in a received channel that is one of a certain number of highly correlated channels, wherein the spatial rotation vector matrix comprises a Walsh matrix, wherein the transformation of the one or more of the plurality of spatial stream signals using the Inverse Fast Fourier Transform (IFFT) is performed prior to the introduction of time shifts to the one or more of the plurality of spatial stream signals and prior to the operation on each of the time-shifted spatial stream signals with the spatial rotation vector matrix.

16. The transmitter of claim 15 , wherein the time shift module is adapted to introduce cyclic shifts to one or more of the plurality of spatial stream signals.

17. The transmitter of claim 16 , wherein the time shift module is adapted to introduce a cyclic delay to at least one of the plurality of spatial stream signals.

18. The transmitter of claim 16 , wherein the time shift module is adapted to introduce a cyclic advance to at least one of the plurality of spatial stream signals.

19. The transmitter of claim 16 , wherein the time shift module is adapted to introduce cyclic shifts in the time domain.

20. The transmitter of claim 16 , wherein the time shift module is adapted to introduce cyclic delays in the frequency domain.

21. The transmitter of claim 15 , wherein the time shift module is adapted to introduce linear time shifts to one or more of the plurality of spatial stream signals.

22. The transmitter of claim 15 , wherein the spatial rotation vector matrix comprises the Walsh matrix having dimensions based at least in part on a number of spatial stream signals in the plurality of spatial stream signals and a number of transmit stream signals in the plurality of transmit stream signals.

23. A non-transitory computer-readable medium having stored thereon computer-executable instructions executed by a processor to perform the acts comprising:

introducing respective time shifts to each of a plurality of spatial stream signals to produce a plurality of time-shifted spatial stream signals, wherein each of the plurality of spatial stream signals is based at least in part on a data stream;

operating on each of the plurality of time-shifted spatial stream signals with a spatial rotation vector matrix to apply respective spatial rotation to each of the plurality of time-shifted spatial stream signals, to thereby map the plurality of time-shifted spatial stream signals respectively to transmit signals that are respective time-shifted spatially- rotated spatial stream signals of a plurality of time-shifted spatially-rotated spatial stream signals, to reduce nulls, including deep nulls, associated with the data stream, in a received channel, wherein the spatial rotation vector matrix is a Walsh matrix; and

transforming each of a plurality of spatial stream signals using an Inverse Fast Fourier Transform (IFFT), wherein the transforming of each of a plurality of spatial stream signals using an Inverse Fast Fourier Transform (IFFT) is applied to the plurality of spatial stream signals before the introducing of respective time shifts is applied to each of the plurality of spatial stream signals and before the operating on each of the plurality of time-shifted spatial stream signals with a spatial rotation vector matrix.

24. The non-transitory computer-readable medium of claim 23 , wherein the computer- executable instructions for introducing time shifts to each of the plurality of spatial stream signals further comprises computer-executable instructions for introducing cyclic shifts to each of the plurality of spatial stream signals.

25. The non-transitory computer-readable medium of claim 24 , wherein the computer- executable instructions for introducing cyclic shifts to each of the plurality of spatial stream signals further comprises computer-executable instructions for introducing at least one of cyclic delays or cyclic advances to at least one of the plurality of spatial streams.

26. The non-transitory computer-readable medium of claim 24 , wherein the computer- executable instructions for introducing cyclic shifts to each of the plurality of spatial stream signals further comprises computer-executable instructions for introducing cyclic shifts in at least one of a time domain or a frequency domain.

27. The non-transitory computer-readable medium of claim 23 , wherein the computer- executable instructions for introducing time shifts to each of the plurality of spatial stream signals further comprises computer-executable instructions for introducing linear time shifts to each of the plurality of spatial stream signals.