Steering diversity for an OFDM-based multi-antenna communication system

• US 20050249174A1
• Filed: 02/24/2005
• Published: 11/10/2005
• Est. Priority Date: 05/07/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Walton, Jay Rodney, Howard, Steven J., Lundby, Stein A.
• Granted Patent: US 8,285,226 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04L 27/2602 Signal structure

Abstract

A transmitting entity uses different steering vectors for different subbands to achieve steering diversity. Each steering vector defines or forms a beam for an associated subband. Any steering vector may be used for steering diversity. The steering vectors may be defined such that the beams vary in a continuous instead of abrupt manner across the subbands. This may be achieved by applying continuously changing phase shifts across the subbands for each transmit antenna. As an example, the phase shifts may change in a linear manner across the subbands for each transmit antenna, and each antenna may be associated with a different phase slope. The application of linearly changing phase shifts to modulation symbols in the frequency domain may be achieved by either delaying or circularly shifting the corresponding time-domain samples.

Claims

1. A method of transmitting data in a wireless communication system, comprising:

obtaining input symbols to be transmitted on a plurality of frequency subbands of a plurality of antennas;

modifying an input symbol for each frequency subband of each antenna with a phase shift selected for the frequency subband and the antenna to generate a phase-shifted symbol for the frequency subband and the antenna; and

processing phase-shifted symbols for the plurality of frequency subbands of each antenna to obtain a sequence of samples for the antenna.

2. The method of claim 1, further comprising:

applying linearly varying phase shifts across the plurality of frequency subbands for each antenna.

3. The method of claim 1, further comprising:

applying a different phase slope across the plurality of frequency subbands for each antenna.

4. The method of claim 1, further comprising:

applying continuously varying phase shifts across the plurality of frequency subbands for each antenna.

5. The method of claim 4, further comprising:

determining the continuously varying phase shifts across the frequency subbands for each antenna based on a function selected for the antenna.

6. The method of claim 1, wherein the processing the phase-shifted symbols comprises

performing orthogonal frequency division multiplexing (OFDM) modulation on the phase-shifted symbols for the plurality of frequency subbands of each antenna to obtain the sequence of samples for the antenna.

7. An apparatus in a wireless communication system, comprising:

a spatial processor to obtain input symbols to be transmitted on a plurality of frequency subbands of a plurality of antennas and to modify an input symbol for each frequency subband of each antenna with a phase shift selected for the frequency subband and the antenna to generate a phase-shifted symbol for the frequency subband and the antenna; and

a modulator to process phase-shifted symbols for the plurality of frequency subbands of each antenna to obtain a sequence of samples for the antenna.

8. The apparatus of claim 7, wherein the spatial processor applies linearly varying phase shifts across the plurality of frequency subbands for each antenna.

9. The apparatus of claim 7, wherein the spatial processor applies a different phase slope across the plurality of frequency subbands for each antenna.

10. The apparatus of claim 7, wherein the spatial processor applies continuously varying phase shifts across the plurality of frequency subbands for each antenna.

11. An apparatus in a wireless communication system, comprising:

means for obtaining input symbols to be transmitted on a plurality of frequency subbands of a plurality of antennas;

means for modifying an input symbol for each frequency subband of each antenna with a phase shift selected for the frequency subband and the antenna to generate a phase-shifted symbol for the frequency subband and the antenna; and

means for processing phase-shifted symbols for the plurality of frequency subbands of each antenna to obtain a sequence of samples for the antenna.

12. The apparatus of claim 11, further comprising:

means for applying linearly varying phase shifts across the plurality of frequency subbands for each antenna.

13. The apparatus of claim 11, further comprising:

means for applying a different phase slope across the plurality of frequency subbands for each antenna.

14. The apparatus of claim 11, further comprising:

means for applying continuously varying phase shifts across the plurality of frequency subbands for each antenna.

15. A method of transmitting data in a wireless communication system, comprising:

processing data to obtain an input sequence of time-domain samples;

generating a plurality of output sequences of time-domain samples for a plurality of antennas by temporally modifying the input sequence of time-domain samples; and

transmitting the plurality of output sequences from the plurality of antennas.

16. The method of claim 15, wherein the processing the data comprises

performing an inverse discrete Fourier transform on a plurality of input symbols for a plurality of frequency subbands to obtain a plurality of time-domain samples, and

repeating a portion of the plurality of time-domain samples to obtain the input sequence of time-domain samples.

17. The method of claim 16, wherein the generating the plurality of output sequences of time-domain samples comprises

delaying the input sequence by different amounts to generate the plurality of output sequences.

18. The method of claim 16, wherein the generating the plurality of output sequences of time-domain samples comprises

delaying the input sequence by different integer numbers of sample periods to generate the plurality of output sequences.

19. The method of claim 16, wherein the generating the plurality of output sequences of time-domain samples comprises

delaying the input sequence by different fractional amounts of a sample period to generate the plurality of output sequences.

20. The method of claim 16, wherein the transmitting the plurality of output sequences comprises

transmitting the plurality of output sequences from the plurality of antennas starting at different times.

21. The method of claim 15, wherein the processing the data comprises

performing an inverse discrete Fourier transform on a plurality of input symbols for a plurality of frequency subbands to obtain the input sequence of time-domain samples.

22. The method of claim 21, wherein the generating the plurality of output sequences of time-domain samples comprises

circularly shifting the input sequence of time-domain samples by different amounts to obtain a plurality of intermediate sequences of time-domain samples, and

repeating a portion of each intermediate sequence of time-domain samples to obtain a respective output sequence of time-domain samples.

23. The method of claim 22, wherein the circularly shifting the input sequence comprises

circularly shifting the input sequence by different integer numbers of samples to obtain the plurality of intermediate sequences.

24. The method of claim 21, wherein the transmitting the plurality of output sequences comprises

transmitting the plurality of output sequences from the plurality of antennas starting at same time.

25. An apparatus in a wireless communication system, comprising:

a modulator to process data to obtain an input sequence of time-domain samples;

a processor to generate a plurality of output sequences of time-domain samples for a plurality of antennas by temporally modifying the input sequence of time-domain samples; and

a plurality of transmitter units to transmit the plurality of output sequences from the plurality of antennas.

26. The apparatus of claim 25, wherein the modulator performs an inverse discrete Fourier transform on a plurality of input symbols for a plurality of frequency subbands to obtain a plurality of time-domain samples and further repeats a portion of the plurality of time-domain samples to obtain the input sequence of time-domain samples.

27. The apparatus of claim 26, wherein the processor delays the input sequence by different amounts to generate the plurality of output sequences.

28. The apparatus of claim 26, wherein the processor comprises

a plurality of delay unit to delay the input sequence by different fractional amounts of a sample period to generate the plurality of output sequences.

29. The apparatus of claim 25, wherein the plurality of transmitter units transmit the plurality of output sequences from the plurality of antennas starting at different times.

30. The apparatus of claim 25, wherein the processor circularly shifts the input sequence of time-domain samples by different amounts to obtain a plurality of intermediate sequences of time-domain samples and repeats a portion of each intermediate sequence of time-domain samples to obtain a respective output sequence of time-domain samples.

31. The apparatus of claim 25, wherein the plurality of transmitter units transmit the plurality of output sequences from the plurality of antennas starting at same time.

32. An apparatus in a wireless communication system, comprising:

means for processing data to obtain an input sequence of time-domain samples;

means for generating a plurality of output sequences of time-domain samples for a plurality of antennas by temporally modifying the input sequence of time-domain samples; and

means for transmitting the plurality of output sequences from the plurality of antennas.

33. The apparatus of claim 32, wherein the means for processing the data comprises

means for performing an inverse discrete Fourier transform on a plurality of input symbols for a plurality of frequency subbands to obtain a plurality of time-domain samples, and

means for repeating a portion of the plurality of time-domain samples to obtain the input sequence of time-domain samples.

34. The apparatus of claim 33, wherein the means for generating the plurality of output sequences of time-domain samples comprises

means for delaying the input sequence by different amounts to generate the plurality of output sequences.

35. The apparatus of claim 32, wherein the means for transmitting the plurality of output sequences comprises

means for transmitting the plurality of output sequences from the plurality of antennas starting at different times.

36. The apparatus of claim 32, wherein the means for generating the plurality of output sequences of time-domain samples comprises

means for circularly shifting the input sequence of time-domain samples by different amounts to obtain a plurality of intermediate sequences of time-domain samples, and

means for repeating a portion of each intermediate sequence of time-domain samples to obtain a respective output sequence of time-domain samples.

37. The apparatus of claim 32, wherein the means for transmitting the plurality of output sequences comprises

means for transmitting the plurality of output sequences from the plurality of antennas starting at same time.