Method and apparatus for determining power allocation in a MIMO communication system

• US 7,502,420 B2
• Filed: 08/03/2005
• Issued: 03/10/2009
• Est. Priority Date: 10/15/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ketchum, John W.
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US11/197,497
• Publication Number:
  US 20050265281A1
• Time in Patent Office: 1,315 Days
• Field of Search: 375/260, 375/267, 375/299, 375/340, 375/347
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0443 utilizing "waterfilling" technique
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0025 Spatial division following the spatial signature of the channel
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04W 52/34 TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading

Abstract

In a MIMO communication system (100) with limited power for each antenna, a method, apparatus and a processor (420) provide for determining bin energy level allocation to each OFDM frequency bin at each transmit antenna. An estimate of a solution vector including elements of the allocation bin energy level to each OFDM frequency bin at each antenna is determined. An error function based on the determined solution vector is also determined. An error magnitude is determined based on the determined error function. The error magnitude is compared to an error threshold. The processor (420) accepts the estimate of the solution vector with the elements of the allocation bin energy level when the error magnitude is less than the error threshold.

Claims

1. A method of allocating transmit power in a communication system, comprising:

determining a signal-to-noise ratio (SNR) for each of a plurality of frequency bins of each of a plurality of transmit antennas; and

determining transmit power for each frequency bin of each transmit antenna based on SNRs for the plurality of frequency bins of the transmit antenna and total transmit power for the transmit antenna, the transmit power for each frequency bin of each transmit antenna being inversely related to the SNR for the frequency bin of the transmit antenna and being zero or greater, and a sum of transmit powers for the plurality of frequency bins of each transmit antenna being less than or equal to the total transmit power for the transmit antenna.

2. The method of claim 1, wherein the determining the transmit power for each frequency bin of each transmit antenna comprises

determining a water-pouring parameter for each transmit antenna based on the SNRs for the plurality of frequency bins of the transmit antenna, and

determining the transmit power for each frequency bin of each transmit antenna based further on the water-pouring parameter for the transmit antenna.

3. The method of claim 1, wherein the determining the transmit power for each frequency bin of each transmit antenna comprises

initially allocating predetermined transmit powers to the plurality of frequency bins of each transmit antenna based on the total transmit power for the transmit antenna, and

iteratively adjusting the transmit powers for the plurality of frequency bins of the plurality of transmit antennas until a termination condition is satisfied.

4. The method of claim 3, wherein the iteratively adjusting the transmit powers for the plurality of frequency bins of the plurality of transmit antennas comprises

forming an error vector based on the transmit powers for the plurality of frequency bins of the plurality of transmit antennas and a plurality of water-pouring parameters for the plurality of transmit antennas,

determining an error function based on the error vector and the SNRs for the plurality of frequency bins of the plurality of transmit antennas, and

updating the error vector based on the error function.

5. The method of claim 4, wherein the updating the error vector based on the error function comprises

deriving partial derivatives of the error vector with respect to the transmit powers for the plurality of frequency bins of the plurality of transmit antennas and with respect to the plurality of water-pouring parameters,

determining a correction vector based on the partial derivatives, and

updating the error vector based on the correction vector.

6. The method of claim 4, wherein the iteratively adjusting the transmit powers for the plurality of frequency bins of the plurality of transmit antennas further comprises

updating the error function based on the updated error vector,

computing an error value based on the updated error function,

repeating the determining the error function and the updating the error vector if the error value exceeds a predetermined threshold, and

determining the transmit powers for the plurality of frequency bins of the plurality of transmit antennas based on the updated error vector if the error value is below the predetermined threshold.

7. The method of claim 1, wherein the determining the SNR for each of the plurality of frequency bins of each of the plurality of transmit antennas comprises

determining the SNR for each frequency bin of each transmit antenna based on a channel response vector for the frequency bin of the transmit antenna.

8. The method of claim 7, wherein the determining the SNR for each of the plurality of frequency bins of each of the plurality of transmit antennas further comprises

determining the SNR for each frequency bin of each transmit antenna based further on a receiver processing technique used to recover data streams transmitted from the plurality of transmit antennas.

9. The method of claim 1, further comprising:

scaling data for each frequency bin of each transmit antenna based on the transmit power for the frequency bin of the transmit antenna.

10. An apparatus comprising:

means for determining a signal-to-noise ratio (SNR) for each of a plurality of frequency bins of each of a plurality of transmit antennas; and

means for determining transmit power for each frequency bin of each transmit antenna based on SNRs for the plurality of frequency bins of the transmit antenna and total transmit power for the transmit antenna, the transmit power for each frequency bin of each transmit antenna being inversely related to the SNR for the frequency bin of the transmit antenna and being zero or greater, and a sum of transmit powers for the plurality of frequency bins of each transmit antenna being less than or equal to the total transmit power for the transmit antenna.

11. The apparatus of claim 10, wherein the means for determining the transmit power for each frequency bin of each transmit antenna comprises

means for determining a water-pouring parameter for each transmit antenna based on the SNRs for the plurality of frequency bins of the transmit antenna, and

means for determining the transmit power for each frequency bin of each transmit antenna based further on the water-pouring parameter for the transmit antenna.

12. The apparatus of claim 10, wherein the means for determining the transmit power for each frequency bin of each transmit antenna comprises

means for initially allocating predetermined transmit powers to the plurality of frequency bins of each transmit antenna based on the total transmit power for the transmit antenna, and

means for iteratively adjusting the transmit powers for the plurality of frequency bins of the plurality of transmit antennas until a termination condition is satisfied.

13. The apparatus of claim 12, wherein the means for iteratively adjusting the transmit powers for the plurality of frequency bins of the plurality of transmit antennas comprises

means for forming an error vector based on the transmit powers for the plurality of frequency bins of the plurality of transmit antennas and a plurality of water-pouring parameters for the plurality of transmit antennas,

means for determining an error function based on the error vector and the SNRs for the plurality of frequency bins of the plurality of transmit antennas, and

means for updating the error vector based on the error function.

14. The apparatus of claim 13, wherein the means for updating the error vector based on the error function comprises

means for deriving partial derivatives of the error vector with respect to the transmit powers for the plurality of frequency bins of the plurality of transmit antennas and with respect to the plurality of water-pouring parameters,

means for determining a correction vector based on the partial derivatives, and

means for updating the error vector based on the correction vector.

15. The apparatus of claim 13, wherein the means for iteratively adjusting the transmit powers for the plurality of frequency bins of the plurality of transmit antennas further comprises

means for updating the error function based on the updated error vector,

means for computing an error value based on the updated error function,

means for repeating determining the error function and updating the error vector if the error value exceeds a predetermined threshold, and

means for determining the transmit powers for the plurality of frequency bins of the plurality of transmit antennas based on the updated error vector if the error value is below the predetermined threshold.

16. An apparatus comprising:

at least one processor configured to determine a signal-to-noise ratio (SNR) for each of a plurality of frequency bins of each of a plurality of transmit antennas, and to determine transmit power for each frequency bin of each transmit antenna based on SNRs for the plurality of frequency bins of the transmit antenna and total transmit power for the transmit antenna, the transmit power for each frequency bin of each transmit antenna being inversely related to the SNR for the frequency bin of the transmit antenna and being zero or greater, and a sum of transmit powers for the plurality of frequency bins of each transmit antenna being less than or equal to the total transmit power for the transmit antenna.

17. The apparatus of claim 16, wherein the at least one processor is configured to determine a water-pouring parameter for each transmit antenna based on the SNRs for the plurality of frequency bins of the transmit antenna, and to determine the transmit power for each frequency bin of each transmit antenna based further on the water-pouring parameter for the transmit antenna.

18. The apparatus of claim 16, wherein the at least one processor is configured to initially allocate predetermined transmit powers to the plurality of frequency bins of each transmit antenna based on the total transmit power for the transmit antenna, and to iteratively adjust the transmit powers for the plurality of frequency bins of the plurality of transmit antennas until a termination condition is satisfied.

19. The apparatus of claim 18, wherein the at least one processor is configured to form an error vector based on the transmit powers for the plurality of frequency bins of the plurality of transmit antennas and a plurality of water-pouring parameters for the plurality of transmit antennas, to determine an error function based on the error vector and the SNRs for the plurality of frequency bins of the plurality of transmit antennas, and to update the error vector based on the error function.

20. The apparatus of claim 19, wherein the at least one processor is configured to derive partial derivatives of the error vector with respect to the transmit powers for the plurality of frequency bins of the plurality of transmit antennas and with respect to the plurality of water-pouring parameters, to determine a correction vector based on the partial derivatives, and to update the error vector based on the correction vector.

21. The apparatus of claim 19, wherein the at least one processor is configured to update the error function based on the updated error vector, to compute an error value based on the updated error function, to repeat determining the error function and updating the error vector if the error value exceeds a predetermined threshold, and to determine the transmit powers for the plurality of frequency bins of the plurality of transmit antennas based on the updated error vector if the error value is below the predetermined threshold.

22. A method of allocating transmit power in a communication system, comprising:

determining a signal-to-noise ratio (SNR) for each of a plurality of data streams; and

determining transmit power for each data stream based on SNRs for the plurality of data streams and total transmit power for each of the plurality of transmit antennas, the transmit power for each data stream being inversely related to the SNR for the data stream and being zero or greater, and a sum of transmit powers for the plurality of data streams for each transmit antenna being less than or equal to the total transmit power for the transmit antenna.

23. The method of claim 22, wherein the determining the transmit power for each data stream comprises

determining a water-pouring parameter based on the SNRs for the plurality of data streams, and

determining the transmit power for each data stream based further on the water-pouring parameter.

24. The method of claim 22, wherein the determining the transmit power for each data stream comprises

initially allocating predetermined transmit powers to the plurality of data streams based on total transmit powers for the plurality of transmit antennas, and

iteratively adjusting the transmit powers for the plurality of data streams until a termination condition is satisfied.

25. The method of claim 22, further comprising:

selecting a modulation and coding scheme for each data stream based on the transmit power for the data stream; and

processing each data stream based on the modulation and coding scheme selected for the data stream.

26. The method of claim 22, further comprising:

scaling each data stream based on the transmit power for the data stream.

27. The method of claim 22, further comprising:

transmitting each data stream on a respective one of a plurality of spatial subchannels in a multiple-input multiple-output (MIMO) channel formed with the plurality of transmit antennas.

28. The method of claim 22, wherein the determining the SNR for each of the plurality of data streams comprises

receiving a set of rates for the plurality of data streams, and

determining the SNRs for the plurality of data streams based on the set of rates.

29. An apparatus comprising:

means for determining a signal-to-noise ratio (SNR) for each of a plurality of data streams; and

means for determining transmit power for each data stream based on SNRs for the plurality of data streams and total transmit power for each of the plurality of transmit antennas, the transmit power for each data stream being inversely related to the SNR for the data stream and being zero or greater, and a sum of transmit powers for the plurality of data streams for each transmit antenna being less than or equal to the total transmit power for the transmit antenna.

30. The apparatus of claim 29, wherein the means for determining the transmit power for each data stream comprises

means for determining a water-pouring parameter based on the SNRs for the plurality of data streams, and

means for determining the transmit power for each data stream based further on the water-pouring parameter.

31. The apparatus of claim 29, wherein the means for determining the transmit power for each data stream comprises

means for initially allocating predetermined transmit powers to the plurality of data streams based on total transmit powers for the plurality of transmit antennas, and

means for iteratively adjusting the transmit powers for the plurality of data streams until a termination condition is satisfied.

32. The apparatus of claim 29, further comprising:

means for selecting a modulation and coding scheme for each data stream based on the transmit power for the data stream; and

means for processing each data stream based on the modulation and coding scheme selected for the data stream.

33. An apparatus comprising:

at least one processor configured to determine a signal-to-noise ratio (SNR) for each of a plurality of data streams, and to determine transmit power for each data stream based on SNRs for the plurality of data streams and total transmit power for each of the plurality of transmit antennas, the transmit power for each data stream being inversely related to the SNR for the data stream and being zero or greater, and a sum of transmit powers for the plurality of data streams for each transmit antenna being less than or equal to the total transmit power for the transmit antenna.

34. The apparatus of claim 33, wherein the at least one processor is configured to determine a water-pouring parameter based on the SNRs for the plurality of data streams, and to determine the transmit power for each data stream based further on the water-pouring parameter.

35. The apparatus of claim 33, wherein the at least one processor is configured to initially allocate predetermined transmit powers to the plurality of data streams based on total transmit powers for the plurality of transmit antennas, and to iteratively adjust the transmit powers for the plurality of data streams until a termination condition is satisfied.

36. The apparatus of claim 33, wherein the at least one processor is configured to select a modulation and coding scheme for each data stream based on the transmit power for the data stream, and to process each data stream based on the modulation and coding scheme selected for the data stream.