Multiple antenna multicarrier transmitter and method for adaptive beamforming with transmit-power normalization

• US 20060120469A1
• Filed: 12/03/2004
• Published: 06/08/2006
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Maltsev, Alexander A., Davydov, Alexei V., Li, Qinghua
• Granted Patent: US 7,822,128 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2637 with direct modulation of individual subcarriers
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

In a multi-antenna, multicarrier transmitter, a multicarrier communication signal is generated by normalizing beamforming matrices based on an average subcarrier power loading for each of the transmit antennas. One or more spatial streams may be transmitted by two or more antennas.

Claims

1. A method of generating a multicarrier communication signal comprising normalizing beamforming matrices based on an average subcarrier power loading for each of a plurality of transmit antennas.

2. The method of claim 1 further comprising applying elements of the normalized beamforming matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams.

3. The method of claim 1 wherein normalizing comprises:

determining the average subcarrier power loading for each of the transmit antennas by averaging a sum of squares of elements of the beamforming matrices associated with one of the transmit antennas;

generating a normalization factor for each of the transmit antennas by dividing an average signal power associated with the transmit antennas by the average subcarrier power loading for an associated one of the transmit antennas; and

applying the normalization factors to the beamformer matrices to generate normalized beamformer matrices.

4. The method of claim 1 wherein the multicarrier communication signal comprises a plurality of substantially orthogonal subcarriers,

wherein each of the beamforming matrices is associated with one of the subcarriers, and

wherein normalizing comprises normalizing each of the beamforming matrices to generate a normalized beamformer matrix for each subcarrier.

5. The method of claim 4 further comprising applying, for each subcarrier, elements of one of the normalized beamformer matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams to generate symbol-modulated subcarriers for each transmit antenna,

wherein a number of the transmit antennas is greater than or equal to a number of the spatial streams.

6. The method of claim 1 further comprising generating multicarrier signals for transmission by the transmit antennas after applying elements of the normalized beamforming matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams.

7. The method of claim 6 wherein each of the transmit antennas transmits an orthogonal frequency division multiplexed symbol using the same subcarrier frequencies as the other transmit antennas, and

wherein the orthogonal frequency division multiplexed symbols transmitted together by the transmit antennas represent the one or more spatial streams, each of the transmit antennas being associated with an antenna stream.

8. The method of claim 7 wherein one or more spatial streams are transmitted by at least two transmit antennas.

9. The method of claim 6 further comprising performing a singular value decomposition on a channel matrix to generate the beamforming matrices for each subcarrier of the multicarrier communication signal,

wherein each element of the beamforming matrices is associated with one of the spatial streams and one of the transmit antennas.

10. The method of claim 9 further comprising transmitting the multicarrier signal to a multicarrier receiving station,

wherein the multicarrier receiving station is to apply a linear processing algorithm to detect the one or more spatial streams received through a multicarrier communication channel having characteristics of the channel matrix.

11. The method of claim 10 wherein the linear processing algorithm comprises one of either a zero-forcing or a minimum mean-squared-error processing algorithm.

12. The method of claim 9 further comprising transmitting the multicarrier signal to a multicarrier receiving station,

wherein the multicarrier receiving station is to apply a non-linear multiple-input, multiple-output equalization technique to separate two or more spatial streams.

13. The method of claim 9 further comprising receiving the channel matrix from a multicarrier receiving station.

14. A multicarrier transmitter comprising:

a normalizer to normalize beamforming matrices based on an average subcarrier power loading for each of a plurality of transmit antennas; and

beamformers to apply elements of normalized beamforming matrices to frequency-domain symbol-modulated subcarriers of a multicarrier communication signal.

15. The multicarrier transmitter of claim 14 wherein the beamformers are to apply elements of the normalized beamforming matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams.

16. The multicarrier transmitter of claim 14 wherein the normalizer is to determine the average subcarrier power loading for each of the transmit antennas by averaging a sum of squares of elements of the beamforming matrices associated with one of the transmit antennas,

wherein the normalizer is further to generate a normalization factor for each of the transmit antennas by dividing an average signal power associated with the transmit antennas by the average subcarrier power loading for an associated one of the transmit antennas, and

wherein the normalizer is further to apply the normalization factors to the beamformer matrices to generate the normalized beamformer matrices.

17. The multicarrier transmitter of claim 14 wherein the multicarrier communication signal comprises a plurality of substantially orthogonal subcarriers,

wherein each of the beamforming matrices is associated with one of the subcarriers, and

wherein the normalizer is to normalize the beamforming matrices to generate a normalized beamformer matrix for each subcarrier.

18. The multicarrier transmitter of claim 17 wherein the beamformers are to apply, for each subcarrier, elements of one of the normalized beamformer matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams to generate symbol-modulated subcarriers for each transmit antenna, and

wherein the symbol-modulated subcarriers are associated with a number of transmit antennas which is greater than or equal to a number of the spatial streams.

19. The multicarrier transmitter of claim 14 further comprising:

inverse Fourier transformation circuitry and digital-to-analog conversion circuitry to generate multicarrier signals for transmission by the transmit antennas after the beamformers apply elements of the normalized beamforming matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams.

20. The multicarrier transmitter of claim 19 wherein each transmit antenna transmits an orthogonal frequency division multiplexed symbol comprising a plurality of subcarriers using the same subcarrier frequencies as the other transmit antennas,

wherein the orthogonal frequency division multiplexed symbols transmitted together by the transmit antennas represent the one or more spatial streams, and

wherein each of the transmit antennas is associated with an antenna stream.

21. The multicarrier transmitter of claim 20 wherein one or more spatial streams are transmitted by at least two transmit antennas.

22. The multicarrier transmitter of claim 19 further comprising singular value decomposition circuitry to perform a singular value decomposition on a channel matrix to generate the beamforming matrices for each subcarrier of the multicarrier communication signal,

wherein each element of the beamforming matrices is associated with one of the spatial streams and one of the transmit antennas.

23. The multicarrier transmitter of claim 22 wherein the transmit antennas are to further transmit the multicarrier signal to a multicarrier receiving station,

wherein the multicarrier receiving station is to apply a linear processing algorithm to detect the one or more spatial streams through a channel having characteristics of the channel matrix.

24. The multicarrier transmitter of claim 23 wherein the linear processing algorithm comprises one of either a zero-forcing or a minimum mean-squared-error processing algorithm.

25. The multicarrier transmitter of claim 22 wherein the transmit antennas are to further transmit the multicarrier signal to a multicarrier receiving station,

wherein the multicarrier receiving station is to apply a non-linear multiple-input, multiple-output equalization technique to separate two or more spatial streams.

26. The multicarrier transmitter of claim 22 further comprising circuitry to receive the channel matrix from a multicarrier receiving station.

27. A multicarrier communication system comprising:

a multicarrier transmitting station having a normalizer to normalize beamforming matrices based on an average subcarrier power loading for each of a plurality of transmit antennas, and beamformers to apply elements of normalized beamforming matrices to frequency-domain symbol-modulated subcarriers of a multicarrier communication signal; and

a multicarrier receiving station to receive the multicarrier communication signal through a channel from the transmitting station, the channel having characteristics of a channel matrix associated with the beamforming matrices, wherein the multicarrier receiving station applies a processing algorithm to detect one or more spatial streams.

28. The system of claim 27 wherein the beamformers are to apply elements of the normalized beamforming matrices to frequency-domain symbol-modulated subcarriers associated with the one or more spatial streams.

29. The system of claim 28 wherein the normalizer is to determine the average subcarrier power loading for each of the transmit antennas by averaging a sum of squares of elements of the beamforming matrices associated with one of the transmit antennas,

wherein the normalizer is further to generate a normalization factor for each of the transmit antennas by dividing an average signal power associated with the transmit antennas by the average subcarrier power loading for an associated one of the transmit antennas, and

wherein the normalizer is further to apply the normalization factors to the beamformer matrices to generate the normalized beamformer matrices.

30. A system comprising:

two or more substantially omnidirectional antennas for transmitting a multicarrier communication signal; and

a multicarrier transmitter comprising a normalizer and beamformers, wherein the normalizer normalizes beamforming matrices based on an average subcarrier power loading for each of the transmit antennas,

wherein the beamformers apply elements of normalized beamforming matrices to frequency-domain symbol-modulated subcarriers of the multicarrier communication signal.

31. The system of claim 30 wherein the beamformers are to apply elements of the normalized beamforming matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams.

32. The system of claim 30 wherein the normalizer is to determine the average subcarrier power loading for each of the transmit antennas by averaging a sum of squares of elements of the beamforming matrices associated with one of the transmit antennas,

wherein the normalizer is further to generate a normalization factor for each of the transmit antennas by dividing an average signal power associated with the transmit antennas by the average subcarrier power loading for an associated one of the transmit antennas, and

wherein the normalizer is further to apply the normalization factors to the beamformer matrices to generate the normalized beamformer matrices.

33. A machine-accessible medium that provides instructions, which when accessed, cause a machine to generate a multicarrier communication signal by normalizing beamforming matrices based on an average subcarrier power loading for each of a plurality of transmit antennas.

34. The machine-accessible medium of claim 33 wherein the instructions, when further accessed, cause the machine to perform operations further comprising applying elements of the normalized beamforming matrices to frequency-domain symbol-modulated subcarriers associated with one or more spatial streams.

35. The machine-accessible medium of claim 34 wherein the instructions, when further accessed, cause the machine to perform operations further comprising:

determining the average subcarrier power loading for each of the transmit antennas by averaging a sum of squares of elements of the beamforming matrices associated with one of the transmit antennas;

generating a normalization factor for each of the transmit antennas by dividing an average signal power associated with the transmit antennas by the average subcarrier power loading for an associated one of the transmit antennas; and

applying the normalization factors to the beamformer matrices to generate the normalized beamformer matrices.