BEAM SPACE TIME CODING AND TRANSMIT DIVERSITY

• US 20080144738A1
• 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 9,106,296 B2
• Time in Patent Office: Days
• US Class Current: 375/299
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0667 of delayed versions of same signal using space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• 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. Transmit diversity can be provided at a signal source by space-time coding the signal. 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. Each weight can have a distinct amplitude, phase, or combination of amplitude and phase. The weights can be static or dynamic. The dynamic weights can vary amplitude, phase, or a combination of amplitude and phase of each weight over time.

Claims

1. A transmitter comprising:

a generator 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; 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 to beamform the one of the plurality of transmit diversity/space-time encoded transmit streams.

2. The transmitter of claim 1, wherein the transmitter is coupled to a plurality of groups of antennas coupled to the plurality of beamforming encoders, each of the plurality of groups of antennas having K antennas and configured to broadcast a beamformed encoded transmit stream from the plurality of transmit diversity/space-time encoded transmit streams.

3. The transmitter of claim 2, wherein the plurality of groups of antennas comprises N=G×

K antennas.

4. The transmitter of claim 1, further comprising a weight matrix generator configured to generate a plurality of weight vectors, and wherein each of the plurality of beamforming encoders generates the plurality of weighted substreams by weighting the one of the plurality of transmit diversity/space-time encoded transmit streams by a corresponding weight vector.

5. The transmitter of claim 4, wherein the weight matrix generator is configured to generate at least one varying weight vector.

6. The transmitter of claim 5, wherein the at least one varying weight vector comprises a time varying weight vector.

7. The transmitter of claim 5, wherein the at least one varying weight vector comprises a weight vector determined based on a transmitter event.

8. The transmitter of claim 4, wherein the weight matrix generator is configured to generate at least one complex weight vector.

9. The transmitter of claim 4, wherein the weight matrix generator is configured to generate a distinct complex weight vector for each of a plurality of access terminals.

10. The transmitter of claim 1, wherein at least one of the plurality of beamforming encoders is configured to split a received encoded transmit stream into K substreams and weight at least one of the K substreams by an element from a complex weight vector.

11. The transmitter of claim 1, wherein the transmit stream comprises Orthogonal Frequency Division Multiplex (OFDM) symbols frequency converted to an operating frequency.

12. The transmitter of claim 1, wherein the transmit diversity encoder is configured to delay a version of the transmit stream as at least part of the process of generating a transmit diversity/space-time encoded transmit stream.

13. The transmitter of claim 1, wherein the transmit diversity encoder is configured to conjugate a version of the transmit stream as at least part of the process of generating a transmit diversity/space-time encoded transmit stream.

14. The transmitter of claim 1, wherein the transmit diversity encoder is configured to rotate a version of the transmit stream as at least part of the process of generating a transmit diversity/space-time encoded transmit stream.

15. A method of introducing transmit diversity, the method comprising:

generating a transmit stream;

dividing the transmit stream into a plurality of G signal streams;

transmit diversity/space-time encoding the G signal streams;

beamforming each of the G signal streams over K antennas; and

transmitting the G beamformed signals.

16. The method of claim 15, wherein transmit diversity/space-time encoding the G signal streams comprises time delaying at least one of the G signal streams relative to a first of the G signal streams.

17. The method of claim 15, wherein transmit diversity/space-time encoding the G signal streams comprises conjugating at least one of the G signal streams relative to a first of the G signal streams.

18. The method of claim 15, wherein transmit diversity/space-time encoding the G signal streams comprises rotating at least one of the G signal streams relative to a first of the G signal streams.

19. The method of claim 15, wherein beamforming each of the G signal streams over K antennas comprises weighting at least one of the G signal streams with a varying beamforming vector.

20. The method of claim 19, wherein the varying beamforming vector comprises a predetermined time varying beamforming vector.

21. The method of claim 15, wherein beamforming each of the G signal streams over K antennas comprises:

separating each of the G signal streams to K substreams;

weighting each of the K substreams by an element from a corresponding weight vector.

22. The method of claim 21, wherein weighting each of the K substreams comprises multiplying a substream by a complex weight from the corresponding weight vector.

23. The method of claim 21, wherein weighting each of the K substreams comprises weighting at least one substream with a varying weight.

24. A transmitter, the system comprising:

means for generating a transmit stream;

means for transmit diversity/space-time encoding the transmit stream to generate G encoded transmit streams;

means for beamforming each of the G encoded transmit streams to generate G beamformed groups; and

a plurality of antennas for transmitting the G beamformed groups.

25. The transmitter of claim 24, wherein the means for transmit diversity/space-time encoding the transmit stream comprises an element configured to generate at least one of a delayed, conjugated, rotated, or negated signal stream from the transmit stream.

26. The transmitter of claim 24, further comprising means for generating a weight matrix having at least one varying weight vector and wherein the means for beamforming each of the G encoded transmit streams comprises means for multiplying at least one of the G encoded transmit streams by a first of the at least one varying weight vector.

27. The transmitter of claim 26, further comprising a means for timing and synchronization configured to generate a timing reference used by the means for generating the weight matrix to vary the at least one varying weight vector.

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

instructions for transmitting G signal streams;

instructions for transmit diversity/space-time encoding the G signal streams; and

instructions for weighting each of the G signal streams with a corresponding complex weight vector to beamform each of the G signal streams.

29. The computer-readable media of claim 28, further comprising instructions for generating at least one varying weight vector.