CYCLIC DELAY DIVERSITY AND PRECODING FOR WIRELESS COMMUNICATION

• US 20080247364A1
• Filed: 02/05/2008
• Published: 10/09/2008
• Est. Priority Date: 02/06/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Malladi, Durga Prasad, Yoo, Taesang, Kim, Byoung-Hoon, Zhang, Xiaoxia
• Granted Patent: US 8,780,771 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04B 7/0473 taking constraints in layer or codeword to antenna mapping into account
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• CPC Class Codes: H04L 25/03898 codebook-based design selection of codebook or precoding matrix for MIMO diversity systems H04B7/0456
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 5/0023 Time-frequency-space

Abstract

Techniques for sending a MIMO transmission using a combination of cyclic delay diversity and precoding are described. A set of delays (e.g., zero delay, small delay, and large delay) for cyclic delay diversity and a set of precoding matrices may be supported. In one design, a Node B may select a delay specifically for a UE or for a set of UEs served by the Node B. In another design, a UE may evaluate different combinations of precoding matrix and delay, determine the combination with the best performance, and send this combination of precoding matrix and delay to the Node B. The Node B may perform precoding with the precoding matrix and then processing for cyclic delay diversity based on the selected delay. Alternatively, the Node B may perform processing for cyclic delay diversity based on the selected delay and then precoding with the precoding matrix.

Claims

1. An apparatus for wireless communication, comprising:

at least one processor configured to select a delay from among a plurality of delays, to send the selected delay from a first entity to a second entity, and to exchange data with the second entity with cyclic delay diversity based on the selected delay; and

a memory coupled to the at least one processor.

2. The apparatus of claim 1, wherein the first entity is a user equipment (UE) and the second entity is a Node B.

3. The apparatus of claim 2, wherein the at least one processor is configured to evaluate the plurality of delays based on at least one metric, and to select the delay with best at least one metric.

4. The apparatus of claim 2, wherein the at least one processor is configured to evaluate each of the plurality of delays based on a sum-capacity metric, and to select the delay with largest sum-capacity metric.

5. The apparatus of claim 3, wherein the plurality of delays comprise multiple sets of delays for multiple ranks, each set comprising at least one delay usable for a respective rank.

6. The apparatus of claim 2, wherein the at least one processor is configured to evaluate a plurality of precoding matrices in combination with the plurality of delays based on at least one metric, to determine a combination of a precoding matrix and a delay with best at least one metric, and to select the precoding matrix and the delay in the combination.

7. The apparatus of claim 2, wherein the at least one processor is configured to send the selected delay from the UE to the Node B, and to receive a data transmission sent by the Node B with cyclic delay diversity based on the selected delay.

8. The apparatus of claim 7, wherein the at least one processor is configured to derive an effective multiple-input multiple-output (MIMO) channel estimate based on a cyclic delay matrix for the selected delay, and to perform MIMO detection for the received data transmission based on the effective MIMO channel estimate.

9. The apparatus of claim 1, wherein the first entity is a Node B and the second entity is a user equipment (UE).

10. The apparatus of claim 9, wherein the at least one processor is configured to select the delay specifically for the UE, and to send the selected delay to the UE.

11. The apparatus of claim 9, wherein the at least one processor is configured to select the delay for a set of UEs served by the Node B, and to send the selected delay to the set of UEs.

12. The apparatus of claim 9, wherein the at least one processor is configured to perform processing for cyclic delay diversity based on the selected delay, and to perform precoding with a precoding matrix after the processing for cyclic delay diversity.

13. The apparatus of claim 9, wherein the at least one processor is configured to perform precoding with a precoding matrix and to perform processing for cyclic delay diversity based on the selected delay after the preceding.

14. The apparatus of claim 1, wherein the plurality of delays comprise zero delay and a large delay of greater than a cyclic prefix length.

15. The apparatus of claim 14, wherein the large delay corresponds to a cyclic delay of K/L, where K is number of samples in a useful portion of an OFDM symbol and L is number of antennas to apply cyclic delay diversity.

16. The apparatus of claim 14, wherein the plurality of delays further comprise a small delay of less than the cyclic prefix length.

17. The apparatus of claim 1, wherein the at least one processor is configured to select the delay based on data performance, rank, geometry, mobility, channel type, feedback reliability, or a combination thereof.

18. The apparatus of claim 16, wherein the at least one processor is configured to select the zero delay or the small delay for rank 1 and to select the large delay for rank 2.

19. The apparatus of claim 16, wherein the at least one processor is configured to select the zero delay or the small delay for low geometry and to select the large delay high geometry.

20. The apparatus of claim 16, wherein the at least one processor is configured to select the zero delay or the small delay for a data channel and to select the large delay for a control channel.

21. The apparatus of claim 1, wherein the plurality of delays comprise a delay for each of a plurality of ranks, and wherein the at least one processor is configured to select the delay based on rank of transmission.

22. A method for wireless communication, comprising:

selecting a delay from among a plurality of delays;

sending the selected delay from a first entity to a second entity; and

exchanging data with the second entity with cyclic delay diversity based on the selected delay.

23. The method of claim 22, wherein the selecting the delay comprises

evaluating the plurality of delays based on at least one metric, and

selecting the delay with best at least one metric.

24. The method of claim 22, wherein the selecting the delay comprises

evaluating a plurality of precoding matrices in combination with the plurality of delays based on at least one metric,

determining a combination of a precoding matrix and a delay with best at least one metric, and

selecting the precoding matrix and the delay in the combination.

25. The method of claim 22, wherein the exchanging data with the second entity comprises

receiving a data transmission sent by the second entity with cyclic delay diversity based on the selected delay,

deriving an effective multiple-input multiple-output (MIMO) channel estimate based on a cyclic delay matrix for the selected delay, and

performing MIMO detection for the received data transmission based on the effective MIMO channel estimate.

26. The method of claim 22, wherein the exchanging data with the second entity comprises

performing processing for cyclic delay diversity based on the selected delay, and

performing precoding with a precoding matrix after the processing for cyclic delay diversity.

27. The method of claim 22, wherein the exchanging data with the second entity comprises

performing precoding with a precoding matrix, and

performing processing for cyclic delay diversity based on the selected delay after the preceding.

28. An apparatus for wireless communication, comprising:

means for selecting a delay from among a plurality of delays;

means for sending the selected delay from a first entity to a second entity; and

means for exchanging data with the second entity with cyclic delay diversity based on the selected delay.

29. The apparatus of claim 28, wherein the means for selecting the delay comprises

means for evaluating the plurality of delays based on at least one metric, and

means for selecting the delay with best at least one metric.

30. The apparatus of claim 28, wherein the means for selecting the delay comprises

means for evaluating a plurality of precoding matrices in combination with the plurality of delays based on at least one metric,

means for determining a combination of a precoding matrix and a delay with best at least one metric, and

means for selecting the precoding matrix and the delay in the combination.

31. The apparatus of claim 28, wherein the means for exchanging data with the second entity comprises

means for receiving a data transmission sent by the second entity with cyclic delay diversity based on the selected delay,

means for deriving an effective multiple-input multiple-output (MIMO) channel estimate based on a cyclic delay matrix for the selected delay, and

means for performing MIMO detection for the received data transmission based on the effective MIMO channel estimate.

32. The apparatus of claim 28, wherein the means for exchanging data with the second entity comprises

means for performing processing for cyclic delay diversity based on the selected delay, and

means for performing precoding with a precoding matrix after the processing for cyclic delay diversity.

33. The apparatus of claim 28, wherein the means for exchanging data with the second entity comprises

means for performing precoding with a precoding matrix, and

means for performing processing for cyclic delay diversity based on the selected delay after the preceding.

34. A machine-readable medium comprising instructions which, when executed by a machine, cause the machine to perform operations including:

selecting a delay from among a plurality of delays;

sending the selected delay from a first entity to a second entity; and

exchanging data with the second entity with cyclic delay diversity based on the selected delay.