Beamspace-time coding based on channel quality feedback

• US 8,670,504 B2
• Filed: 03/09/2007
• Issued: 03/11/2014
• Est. Priority Date: 12/19/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Naguib, Ayman Fawzy
• Primary Examiner(s): Ahn, Sam K
• Assistant Examiner(s): Haider, Syed
• Application Number:
  US11/684,321
• Publication Number:
  US 20080144737A1
• Time in Patent Office: 2,559 Days
• Field of Search: 375/146, 375/219, 375/259, 375/267, 375/299, 375/347, 455/69, 455/73, 455/101, 455/272, 455/446, 455/561, 370/210, 370/328, 370/334, 370/335, 370/336
• 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 encoded signals from a transmit signal, wherein each space-time encoded signal is associated with a distinct space-time antenna group that comprises multiple antennas;

receiving a channel quality indication from a first device, wherein receiving the channel quality indication comprises receiving a signal based on a sum of magnitude square of respective channel estimates;

generating at least one weight vector at a second device based on the channel quality indication, wherein generating the at least one weight vector comprises adjusting a phase of a weight in a weight vector without adjusting an amplitude of the weight until the phase is optimized, and wherein generating the at least one weight vector further comprises selecting weights for a weight vector from a predetermined constellation of weights, wherein the constellation of weights comprises a first plurality of weights positioned substantially uniformly about a first circle having a first radius and a second plurality of weights positioned substantially uniformly about a second circle having a second radius, wherein the second radius is larger than the first radius; and

beamforming, at the second device, by using the channel quality indication from the first device, the plurality of space-time encoded signals, wherein beamforming a particular space-time encoded signal comprises dividing that space-time encoded signal into multiple duplicate signal streams, separately weighting the multiple duplicate signal streams and providing the weighted signal streams to different antennas in the associated antenna group.

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 indicating a change in signal quality at a receiver of a beamformed space-time encoded signal.

6. 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.

7. 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.

8. 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.

18. The method of claim 1, wherein generating the at least one weight vector further comprises adjusting the amplitude of the weight without adjusting the phase of the weight until the amplitude of the weight is optimized.

9. 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, wherein each transmit diversity/space-time encoded stream is associated with a distinct antenna group that comprises multiple antennas;

a weight matrix generator configured to receive a channel quality indication from a first device, wherein the channel quality indication is representative of a sum of magnitude square of respective channel estimates, and generate, at a second device, at least one weight vector from a set of weight vectors based on the channel quality indication, wherein generating the at least one weight vector comprises varying a phase of a weight without varying an amplitude of the weight until the phase is optimized, and wherein generating the at least one weight vector further comprises selecting weights for a weight vector from a predetermined constellation of weights, wherein the constellation of weights comprises a first plurality of weights positioned substantially uniformly about a first circle having a first radius and a second plurality of weights positioned substantially uniformly about a second circle having a second radius, wherein the second radius is larger than the first radius; 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, at the second device, based on the received channel quality indication from the first device, the plurality of transmit diversity/space-time encoded transmit streams by providing the weighted substreams to different antennas in the associated antenna group.

10. The apparatus of claim 9, 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.

11. The apparatus of claim 9, wherein the channel quality indication is representative of a channel estimate.

12. The apparatus of claim 9, wherein the channel quality indication is representative of a change in channel estimates.

13. The apparatus of claim 9, wherein the weight matrix generator is configured to select weights from a predetermined set of weights.

14. The apparatus of claim 9, wherein the weight matrix generator is configured to vary a phase of at least one weight based on the channel quality indication.

15. The apparatus of claim 9, wherein the weight matrix generator is configured to vary an amplitude of at least one weight based on the channel quality indication.

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

means for generating a plurality of space-time encoded signals from a transmit signal, wherein each space-time encoded signal is associated with a distinct space-time antenna group that comprises multiple antennas;

means for receiving a channel quality indication from a first device, wherein the means for receiving a channel quality indication comprises a means for receiving a signal based on a sum of magnitude square of respective channel estimates;

means for generating at least one weight vector at a second device based on the channel quality indication, wherein the means for generating the at least one weight vector comprises means for adjusting a phase of a weight in a weight vector without adjusting an amplitude of the weight until the phase is optimized, and wherein the means for generating the at least one weight vector comprises means for selecting weights for a weight vector from a predetermined constellation of weights, wherein the constellation of weights comprises a first plurality of weights positioned substantially uniformly about a first circle having a first radius and a second plurality of weights positioned substantially uniformly about a second circle having a second radius, wherein the second radius is larger than the first radius; and

means for beamforming, at the second device, by using the channel quality indication from the first device, the plurality of space-time encoded signals, wherein the means for beamforming a particular space-time encoded signal comprises means for dividing that space-time encoded signal into multiple duplicate signal streams, means for separately weighting the multiple duplicate signal streams and means for providing the weighted signal streams to different antennas in the associated antenna group.

17. A non-transitory 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 encoded signals from a transmit signal, wherein each space-time encoded signal is associated with a distinct space-time antenna group that comprises multiple antennas;

instructions for receiving a channel quality indication from a first device, wherein the instructions for receiving a channel quality indication comprises instructions for receiving a signal based on a sum of magnitude square of respective channel estimates;

instructions for generating at least one weight vector at a second device based on the channel quality indication, wherein the instructions for generating the at least one weight vector comprise instructions for adjusting a phase of a weight in a weight vector without adjusting an amplitude of the weight until the phase is optimized, wherein the instructions for generating the at least one weight vector comprise instructions for selecting weights for a weight vector from a predetermined constellation of weights, wherein the constellation of weights comprises a first plurality of weights positioned substantially uniformly about a first circle having a first radius and a second plurality of weights positioned substantially uniformly about a second circle having a second radius, wherein the second radius is larger than the first radius; and

instructions for beamforming, at the second device, by using the channel quality indication from the first device, the plurality of space-time encoded signals, wherein the instructions for beamforming a particular space-time encoded signal comprise instructions for dividing that space-time encoded signal into multiple duplicate signal.