EFFICIENT SIGNALING FOR CLOSED-LOOP TRANSMIT DIVERSITY

• US 20110085537A1
• Filed: 10/08/2009
• Published: 04/14/2011
• Est. Priority Date: 10/08/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wu, Ann Tsuey Jiuan, Cai, Hailiang, Tsai, Ming-Chang
• Granted Patent: US 8,902,873 B2
• Time in Patent Office: Days
• US Class Current: 370/342
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0636 Feedback format

Abstract

Techniques for encoding a phase adjustment for a feedback signal in a closed-loop transmit diversity system. In an aspect, codewords for the phase adjustments are chosen according to a variable-length prefix code. The prefix code aspect allows the codewords to be transmitted in sequence on the feedback channel without being separated by “commas” or demarcation symbols. The variable-length aspect provides a variety of coarse and fine phase adjustment quantization step sizes to accommodate multiple different channel scenarios. In an aspect, the length of the codewords may be further optimized according to the Huffman encoding algorithm.

Claims

1. An apparatus for transmitting information on a feedback channel, the apparatus comprising:

a receiver configured to receive a signal on a primary channel;

an update calculation module configured to determine an adjustment to be applied on the primary channel based on the received signal;

an encode module configured to encode the adjustment to be applied using a variable-length prefix code; and

a transmitter configured to transmit the encoded adjustment on the feedback channel.

2. The apparatus of claim 1, the receiver configured to receive a composite signal on a wireless channel from two antennas, the update calculation module comprising a phase update calculation module configured to compute a phase adjustment to be applied between the two antennas to optimize the quality of the composite signal, the encode module comprising a phase encode module configured to encode the phase adjustment, and the transmitter configured to transmit the encoded phase adjustment.

3. The apparatus of claim 1, the receiver configured to receive a composite signal on a wireless channel from two antennas, the update calculation module comprising a differential phase adjustment to be applied to a previously applied phase difference between the two antennas to optimize the quality of the composite signal, the encode module comprising a phase encode module configured to encode the differential phase adjustment, and the transmitter configured to transmit the encoded differential phase adjustment.

4. The apparatus of claim 2, the phase encode module configured to assign a codeword of the variable-length prefix code to a phase adjustment, the codewords non-uniformly quantizing a 360°

range of possible phase adjustments.

5. The apparatus of claim 2, a first codeword of the variable-length prefix code encoding a first phase adjustment, a second codeword of the variable-length prefix encoding a second phase adjustment, the absolute value of the first phase adjustment being larger than the absolute value of the second phase adjustment, the length of the first codeword being not longer than the length of the second codeword.

6. The apparatus of claim 2, the transmitter configured to transmit codewords of the variable-length prefix code sequentially on the feedback channel.

7. The apparatus of claim 2, the feedback channel comprising successive slots of a frame, the transmitter configured to transmit two bits of a codeword of the variable-length prefix code in each slot.

8. The apparatus of claim 7, the frame being an up-link frame as defined according to the W-CDMA standard.

9. The apparatus of claim 1, the apparatus comprising a mobile station for a wireless communications system.

10. The apparatus of claim 2, the encode module further configured to encode, using the variable-length prefix code, a mode parameter signaling a quantization step size of the phase adjustment, and to transmit the encoded mode parameter on the feedback channel.

11. The apparatus of claim 1, the encode module further configured to transmit on the feedback channel an indication to change a codebook of the variable-length prefix code, and encoding the adjustment to be applied using the changed codebook.

12. The apparatus of claim 1, the receiver further configured to receive on the primary channel an indication to change a codebook of the variable-length prefix code, the encode module configured to encode the adjustment to be applied using the changed codebook.

26. The method of claim 2, the feedback channel comprising successive slots of a frame, the transmitting comprising transmitting two bits of a codeword of the variable-length prefix code in each slot.

27. The method of claim 26, the frame being an up-link frame as defined according to the W-CDMA standard.

13. An apparatus for receiving information on a feedback channel, the apparatus comprising:

a transmitter configured to transmit first and second signals using first and second antennas, respectively, on a primary channel, the first and second signals having a relative phase difference;

a receiver configured to receive an encoded phase adjustment signal on a feedback channel;

a phase decode module configured to decode the encoded phase adjustment signal using a variable-length prefix code; and

a phase control module configured to adjust the relative phase difference based on the decoded phase adjustment signal.

14. The apparatus of claim 13, codewords of the variable-length prefix code non-uniformly quantizing a 360°

range of possible phase adjustments.

15. The apparatus of claim 13, the receiver configured to receive codewords of the variable-length prefix code sequentially on the feedback channel.

16. The apparatus of claim 13, the feedback channel comprising successive slots of a frame, the receiver configured to receive two bits of a codeword of the variable-length prefix code in each slot.

17. The apparatus of claim 13, the frame being an up-link frame as defined according to the W-CDMA standard.

18. The apparatus of claim 13, the apparatus comprising a base station for a wireless communications system.

19. The apparatus of claim 13, the apparatus comprising a mobile station for a wireless communications system.

20. A method for transmitting information on a feedback channel, the method comprising:

receiving a signal on a primary channel;

determining an adjustment to be applied on the primary channel based on the received signal;

encoding the adjustment to be applied using a variable-length prefix code; and

transmitting the encoded adjustment on the feedback channel.

21. The method of claim 20, the receiving the signal on the primary channel comprising receiving a composite signal on a wireless channel from two antennas, the determining the adjustment comprising computing a phase adjustment to be applied between the two antennas to optimize the quality of the composite signal, the encoding the adjustment comprising encoding the phase adjustment, and the transmitting the encoded signal comprising transmitting the encoded phase adjustment.

22. The method of claim 20, the receiving the signal on the primary channel comprising receiving a composite signal on a wireless channel from two antennas, the determining the adjustment comprising computing a differential phase adjustment to be applied to a previously applied phase difference between the two antennas to optimize the quality of the composite signal, the encoding the adjustment comprising encoding the differential phase adjustment, and the transmitting the encoded signal comprising transmitting the encoded differential phase adjustment.

23. The method of claim 21, the encoding the phase adjustment comprising assigning a codeword of the variable-length prefix code to a phase adjustment, the codewords non-uniformly quantizing a 360°

range of possible phase adjustments.

24. The method of claim 21, a first codeword of the variable-length prefix code encoding a first phase adjustment, a second codeword of the variable-length prefix encoding a second phase adjustment, the absolute value of the first phase adjustment being larger than the absolute value of the second phase adjustment, the length of the first codeword being not longer than the length of the second codeword.

25. The method of claim 21, the transmitting the encoded adjustment comprising transmitting codewords of the variable-length prefix code sequentially on the feedback channel.

28. A method for receiving information on a feedback channel, the method comprising:

transmitting first and second signals using first and second antennas, respectively, on a primary channel, the first and second signals having a relative phase difference;

receiving an encoded phase adjustment signal on a feedback channel;

decoding the encoded phase adjustment signal using a variable-length prefix code; and

adjusting the relative phase difference based on the decoded phase adjustment signal.

29. The method of claim 28, the frame being an up-link frame as defined according to the W-CDMA standard.

30. The method of claim 28, the transmitting and receiving being performed by a base station for a wireless communications system.

31. The method of claim 28, the transmitting and receiving being performed by a mobile station for a wireless communications system.

32. An apparatus for transmitting information on a feedback channel, the apparatus comprising:

means for receiving a signal on a primary channel;

means for determining an adjustment to be applied on the primary channel based on the received signal;

means for encoding the adjustment to be applied; and

means for transmitting the encoded adjustment on the feedback channel.

33. The apparatus of claim 32, the means for encoding the adjustment to be applied comprising means for encoding the adjustment using a variable-length prefix code.

34. A computer program product for transmitting information on a feedback channel, the product comprising:

computer-readable medium comprising;

code for causing a computer to receive a signal on a primary channel;

code for causing a computer to determine an adjustment to be applied on the primary channel based on the received signal;

code for causing a computer to encode the adjustment to be applied using a variable-length prefix code; and

code for causing a computer to transmit the encoded adjustment on the feedback channel.