BEAMSPACE-TIME CODING BASED ON CHANNEL QUALITY FEEDBACK

• US 20080144737A1
• Filed: 03/09/2007
• Published: 06/19/2008
• Est. Priority Date: 12/19/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Naguib, Ayman Fawzy
• Granted Patent: US 8,670,504 B2
• Time in Patent Office: Days
• US Class Current: 375/299
• CPC Class Codes: H04B 7/063 Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0625 Transmitter arrangements

Abstract

Methods and apparatus for increasing diversity gain at a receiver by applying beamforming to transmit diversity space-time coded signals. A transmit signal is space-time coded over a plurality of space-time antenna groups, with each space-time antenna group associated with a specific space-time code. The signal at each space-time antenna group is beamformed over the plurality of antenna in the space-time antenna group. Each of the plurality of antenna in a space-time antenna group is weighted with a distinct weight, relative to the other antenna in the space-time group. The beamforming weights can vary based on a channel quality feedback indication from a receiver. The amplitude, phase, or a combination of amplitude and phase of each weight or of a vector of multiple weights can vary as a function of the channel quality indication in order to improve the quality of the received signal.

Claims

1. A method for providing transmit diversity, the method comprising:

generating a plurality of space-time encode signals from a transmit signal;

receiving a channel quality indication;

generating at least one weight vector based on the channel quality indication; and

beamforming at least one of the plurality of space-time encoded signals using a corresponding weight vector from the at least one weight vector.

2. The method of claim 1, wherein generating the plurality of space-time encoded signals comprises:

separating a transmit signal stream into duplicate transmit signal streams; and

providing one of a delay, rotation, conjugation, or combination thereof to one of the duplicate transmit signal streams.

3. The method of claim 1, wherein receiving the channel quality indication comprises receiving a feedback message from a receiver of a beamformed space-time encoded signal.

4. The method of claim 1, wherein receiving the channel quality indication comprises receiving a signal representative of a channel estimate from a receiver of a beamformed space-time encoded signal.

5. The method of claim 1, wherein receiving the channel quality indication comprises receiving a signal representative of a combination of channel estimates from a receiver of a beamformed space-time encoded signal.

6. The method of claim 1, wherein receiving the channel quality indication comprises receiving a signal indicating a change in signal quality at a receiver of a beamformed space-time encoded signal.

7. The method of claim 1, wherein generating at least one weight vector comprises adjusting a phase of a weight in a weight vector based on the channel quality indication.

8. The method of claim 1, wherein generating at least one weight vector comprises adjusting an amplitude of a weight in a weight vector based on the channel quality indication.

9. The method of claim 1, wherein generating at least one weight vector comprises selecting weights for a weight vector from a predetermined constellation of weights.

10. The method of claim 1, further comprising:

receiving a downlink interference estimate; and

wherein generating at least one weight vector comprises generating at least one weight vector based on the channel quality indication and the downlink interference estimate.

11. A method for providing transmit diversity, the method comprising:

generating a plurality of space-time encode signals from a transmit signal;

receiving a channel quality indication; and

beamforming each of the space-time encode signals using a corresponding weight vector, wherein at least one weight vector is determined, in part, based on the channel quality indication.

12. A method of optimizing transmit diversity, the method comprising:

receiving a plurality of signals, each of the plurality of signals received in a corresponding signal beam;

determining a channel estimate for each signal beam;

determining a channel quality indication based on the channel estimates; and

transmitting the channel quality indication as feedback information to a transmit source of the signal beams.

13. The method of claim 12, wherein determining the channel estimate comprises determining a channel estimate based on a pilot signal in the signal beam.

14. The method of claim 12, wherein determining the channel quality indication comprises determining a channel quality value representative of each channel estimate.

15. The method of claim 12, wherein determining the channel quality indication comprises determining the channel quality indication based on a combination of channel estimates.

16. The method of claim 12, wherein determining the channel quality indication comprises determining the channel quality indication based on a change in channel estimates.

17. An apparatus for providing transmit diversity, the apparatus comprising:

a transmitter configured to generate a transmit signal stream;

a transmit diversity encoder configured to receive the transmit signal stream and configured to generate a plurality, G, of transmit diversity/space-time encoded transmit streams from the transmit signal stream;

a weight matrix generator configured to receive a channel quality indication and generate at least one weight vector from a set of weight vectors based on the channel quality indication; and

a plurality of beamforming encoders, each of the plurality of beamforming encoders configured to receive one of the plurality of transmit diversity/space-time encoded transmit streams and generate a plurality, K, of weighted substreams based on a weight vector from the set of weight vectors to beamform the one of the plurality of transmit diversity/space-time encoded transmit streams.

18. The apparatus of claim 17, further comprising:

a receiver configured to receive the channel quality indication in at least one feedback message; and

a processor configured to extract the channel quality indication from the at least one feedback message and communicate the channel quality indication to the weight matrix generator.

19. The apparatus of claim 17, wherein the channel quality indication is representative of a channel estimate.

20. The apparatus of claim 17, wherein the channel quality indication is representative of a combination of channel estimates.

21. The apparatus of claim 17, wherein the channel quality indication is representative of a change in channel estimates.

22. The apparatus of claim 17, wherein the weight matrix generator is configured to select weights from a predetermined set of weights.

23. The apparatus of claim 17, wherein the weight matrix generator is configured to vary a phase of at least one weight based on the channel quality indication.

24. The apparatus of claim 17, wherein the weight matrix generator is configured to vary an amplitude of at least one weight based on the channel quality indication.

25. An apparatus for optimizing transmit diversity, the apparatus comprising:

a receiver configured to receive a plurality of space-time encoded transmit signals in a plurality of beams, wherein each space-time encoded transmit signal is carried within a distinct beam;

a pilot extraction module coupled to the receiver and configured to extract at least one pilot signal from each beam;

a channel estimation module coupled to the pilot extraction module and configured to determine a channel estimate for each of the plurality of beams based on the at least one pilot signal;

a channel quality indication generator configured to determine a channel quality indication based on the channel estimates;

a transmitter configured to generate a feedback message including the channel quality indication and transmit the feedback message to a source of the space-time encoded transmit signals.

26. The apparatus of claim 25, further comprising a transform module configured to transform time domain samples of the space-time encoded transmit signals to a frequency domain representation and wherein the pilot extraction module is configured to extract the at least one pilot signal from the frequency domain representation.

27. The apparatus of claim 25, wherein the channel quality indication generator is configured to generate a distinct channel quality indication based on each channel estimate.

28. The apparatus of claim 25, wherein the channel quality indication generator is configured to generate the channel quality indication based on a combination of channel estimates.

29. An apparatus for providing transmit diversity, the apparatus comprising:

means for generating a plurality of space-time encode signals from a transmit signal;

means for receiving a channel quality indication;

means for generating at least one weight vector based on the channel quality indication; and

means for beamforming at least one of the plurality of space-time encoded signals using a corresponding weight vector from the at least one weight vector.

30. An apparatus for optimizing transmit diversity, the apparatus comprising:

means for receiving a plurality of signals, each of the plurality of signals received in a corresponding signal beam;

means for determining a channel estimate for each signal beam;

means for determining a channel quality indication based on the channel estimates; and

means for transmitting the channel quality indication as feedback information to a transmit source of the signal beams.

31. A computer readable media including instructions thereon configured to cause a transmitter to provide transmit diversity, the instructions comprising:

instructions for generating a plurality of space-time encode signals from a transmit signal;

instructions for receiving a channel quality indication;

instructions for generating at least one weight vector based on the channel quality indication; and

instructions for beamforming at least one of the plurality of space-time encoded signals using a corresponding weight vector from the at least one weight vector.

32. A computer readable media including instructions thereon configured to cause a device to optimize transmit diversity, the instructions comprising:

instructions for receiving a plurality of signals, each of the plurality of signals received in a corresponding signal beam;

instructions for determining a channel estimate for each signal beam;

instructions for determining a channel quality indication based on the channel estimates; and

instructions for transmitting the channel quality indication as feedback information to a transmit source of the signal beams.