Multiple input multiple output multicarrier communication system and methods with quantized beamforming feedback

• US 20050287978A1
• Filed: 06/25/2004
• Published: 12/29/2005
• Est. Priority Date: 06/25/2004
• Status: Active Grant

• Current Assignee: Tahoe Research Limited (f/k/a Learndale Limited) (Vector Capital Corporation)
• Original Assignee: Intel Corporation
• Inventors: Maltsev, Alexander A., Tiraspolsky, Sergey, Davydov, Alexei V., Sadri, Ali S., Flaksman, Alexander
• Granted Patent: US 7,570,696 B2
• Time in Patent Office: Days
• US Class Current: 455/403
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0641 Differential feedback
• CPC Class Codes: H04B 7/066 Combined feedback for a number of channels, e.g. over several subcarriers like in orthogonal frequency division multiplexing [OFDM]
• CPC Class Codes: H04B 7/0842 Weighted combining
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03783 Details of reference signals
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

Abstract

A multicarrier receiver generates a quantized transmit beamformer matrix ({tilde over (V)}) for each subcarrier of a multicarrier communication channel for use by a multicarrier transmitting station. The multicarrier receiver applies a corrected receiver beamformer matrix (Ũ^H) to received subcarriers signals generated by signals received from the transmitting station.

Claims

1. A multicarrier transmitter comprising:

transmit subcarrier beamformers to apply quantized transmit beamforming coefficients to a plurality of symbol-modulated subcarriers in a signal path before an inverse Fourier transform (IFFT) is performed on the symbol-modulated subcarriers,

wherein the quantized transmit beamforming coefficients comprise predetermined numbers of bits for the subcarriers indicating amounts to weight an amplitude and shift a phase of an associated one or more subcarriers.

2. The transmitter of claim 1 wherein each one of the transmit subcarrier beamformers is associated with one subcarrier of a multicarrier communication channel.

3. The transmitter of claim 2 further comprising a plurality of transmit antennas for transmitting a plurality of spatial streams on a corresponding plurality of spatial channels over a multicarrier communication channel,

wherein a number of the spatial streams is less than or equal to a number of the transmit antennas, and

wherein the quantized transmit beamforming coefficients for each subcarrier correspond to a quantized transmit beamforming matrix ({tilde over (V)}) for each subcarrier, the matrix being a unitary matrix having a number of rows equaling the number of the transmit antennas, and a number of columns equaling the number of the spatial streams,

wherein elements of the quantized transmit beamforming matrix ({tilde over (V)}) comprise an amplitude subfield and a phase subfield, each subfield having a predetermined number of bits.

4. The transmitter of claim 2 wherein the transmitter is part of a transmitting station and receives channel feedback information comprising a quantized transmit beamforming matrix ({tilde over (V)}) for each subcarrier from a receiving station, and

wherein the receiving station measures signals received from the transmitting station to estimate a channel transfer matrix (H) for each subcarrier of the multicarrier communication channel, and generates the quantized beamforming matrix ({tilde over (V)}) for each subcarrier for transmission to the transmitting station in a response packet.

5. The transmitter of claim 4 wherein the receiving station measures a preamble of a packet received from the transmitting station to estimate the channel transfer matrix (H) for each subcarrier of the multicarrier communication channel.

6. The transmitter of claim 4 wherein the receiving station performs a singular value decomposition (SVD) on the channel transfer matrix (H) to generate the quantized beamforming matrix ({tilde over (V)}) for each subcarrier.

7. The transmitter of claim 3 wherein the predetermined numbers of bits comprising the amplitude subfield and the phase subfield is lower during initial portions of a packet exchange between the transmitting station and a receiving station and is greater during subsequent portions of the packet exchange.

8. The transmitter of claim 7 wherein during the initial portions of the packet exchange, the transmitting station and the receiving station operate in a coarse quantization mode wherein the predetermined number of bits comprising the amplitude subfield ranges from zero bits to two bits and the predetermined number of bits comprising phase subfield ranges from one-bit to three bits, and

wherein during the subsequent portions the packet exchange, the transmitting station and the receiving station operate in a fine quantization mode wherein the predetermined number of bits comprises the amplitude subfield ranges from two bits to four bits and the predetermined number of bits comprising phase subfield ranges from three bits to five bits.

9. The transmitter of claim 3 wherein elements of the quantized beamforming matrix ({tilde over (V)}) represent differences from previously received beamforming coefficients, and

wherein the channel feedback information comprises an indicator to indicate whether the elements of the quantized beamforming matrices (V) represent a difference from the previously generated elements or represent absolute beamformer coefficients.

10. The transmitter of claim 1 wherein the plurality of transmit subcarrier beamformers apply the quantized beamformer coefficients to groups of subcarriers.

11. The transmitter of claim 1 further comprising:

processing circuitry to provide the quantized beamforming coefficients from a quantized beamforming matrix ({tilde over (V)}) received from a receiving station as part of channel feed back information;

symbol mapping circuitry to generate the symbol-modulated subcarriers from spatial channel multiplexed bit streams for the transmit subcarrier beamformers; and

inverse fast Fourier transform circuitry (IFFT) circuitry for each transmit antenna to perform a FFT on the symbol-modulated subcarriers after application of the quantized transmit beamforming coefficients by the transmit subcarrier beamformers.

12. The transmitter of claim 1 wherein the transmitter is part of a first communication station and wherein the quantized transmit beamforming coefficients are used for transmitting a data packet to a second communication station,

wherein the second communication station comprises a channel estimator to estimate a channel transfer matrix (H) for each subcarrier from a current packet sent by the first communication station and beamformer matrix calculation circuitry to generate the quantized transmit beamformer matrices ({tilde over (V)}) for use by the first communication station.

13. The transmitter of claim 12 wherein the second communication station combines input subcarrier signals generated from receipt of the data packet in accordance with a receiver beamformer matrix (Ũ

^H) for each subcarrier to separate constellation signals from each spatial channel,

wherein the beamformer matrix calculation circuitry calculates the receiver beamformer matrices (Ũ

^H) from the channel transfer matrix (H) and the quantized transmit beamformer matrix ({tilde over (V)}).

14. The transmitter of claim 1 wherein the transmitter is part of a multicarrier communication station which further comprises a multicarrier receiver, the multicarrier receiver comprising:

a channel estimator to estimate a channel transfer matrix (H) for each subcarrier from a current packet sent by another multicarrier communication station;

beamformer matrix calculation circuitry to generate quantized transmit beamformer matrix ({tilde over (V)}) for each subcarrier for use by the other communication station; and

a plurality of receiver beamformers to combine in the frequency domain, subcarrier signals generated from receipt of a data packet from the other communication station in accordance with a receiver beamformer matrix (Ũ

^H) for each subcarrier to separate constellation signals from each spatial channel,

wherein beamformer matrix calculation circuitry further calculates the receiver beamformer matrices (Ũ

^H) from the channel transfer matrix (H) and the quantized transmit beamformer matrix ({tilde over (V)}).

15. A multicarrier receiver comprising:

a channel estimator to estimate a channel transfer matrix (H) for one or more subcarriers of a multicarrier communication channel;

beamformer matrix calculation circuitry to generate a quantized transmit beamformer matrix ({tilde over (V)}) for each of the subcarriers from an associated one of the channel transfer matrices (H); and

a plurality of receiver beamformers to combine input subcarrier signals in accordance with a receiver beamformer matrix (Ũ

^H) for each subcarrier to separate constellation signals from each spatial channel,

wherein the calculation circuitry calculates the receiver beamformer matrices (Ũ

^H) from the channel transfer matrix (H) and the quantized transmit beamformer matrix ({tilde over (V)}) for an associated one of the subcarriers.

16. The receiver of claim 15 wherein the quantized transmit beamforming matrix ({tilde over (V)}) for each subcarrier comprises quantized transmit beamforming coefficients having predetermined numbers of bits indicating amounts for transmit subcarrier beamformers to weight an amplitude and shift a phase of an associated subcarrier,

wherein the channel estimator estimates the channel transfer matrix (H) for each subcarrier of the multicarrier communication channel based on channel measurements from a preamble of a current packet.

17. The receiver of claim 15 wherein the calculation circuitry performs, for each subcarrier, a singular value decomposition (SVD) on the channel transfer matrix (H) to generate an initial transmit beamforming matrix (V),

wherein the calculation circuitry performs a quantization on the initial transmit beamforming matrix (V) for each subcarrier to generate the quantized transmit beamforming matrix (V) for each subcarrier, and

wherein the calculation circuitry generates an equivalent channel transfer matrix ({tilde over (H)}) based on the quantized transmit beamforming matrix ({tilde over (V)}) and

wherein the calculation circuitry generates receiver beamformer matrices (Ũ

^H) based on the equivalent channel transfer matrix ({tilde over (H)}) for an associated subcarrier.

18. The receiver of claim 15 wherein each one of the receiver subcarrier beamformers is associated with one subcarrier of the multicarrier communication channel.

19. The receiver of claim 18 further comprising a plurality of receiver antennas for receiving a plurality of spatial streams on a corresponding plurality of spatial channels over a multicarrier communication channel,

wherein a number of the spatial streams is less than or equal to a number of the receiver antennas, and

wherein the receiver beamforming matrix (Ũ

^H) for each subcarrier comprises a unitary matrix having a number of columns equaling the number of receive antennas used in receiving the spatial streams, and a number of rows equaling the number of the spatial streams,

wherein elements of the quantized transmit beamforming matrix ({tilde over (V)}) comprise an amplitude subfield and a phase subfield, each subfield having a predetermined numbers of bits.

20. The receiver of claim 19 wherein the predetermined numbers of bits comprising the amplitude subfield and the phase subfield is lower during initial portions of a packet exchange between a transmitting station and a receiving station and is greater during subsequent portions of the packet exchange.

22. The receiver of claim 19 wherein elements of the quantized transmit beamforming matrix ({tilde over (V)}) represent differences from previously generated beamforming coefficients, and

wherein the receiver sends channel feedback information to a transmitting station comprising an indicator to indicate whether the elements of the quantized transmit beamforming matrix ({tilde over (V)}) represent a difference from the previously generated elements or represent absolute beamformer coefficients.

23. The receiver of claim 15 wherein the plurality of receiver subcarrier beamformers apply coefficients from the receiver beamformer matrix (Ũ

^H) to groups of adjacent subcarriers.

21. The receiver of claim 21 wherein during the initial portions of the packet exchange, the transmitting station and the receiving station operate in a coarse quantization mode wherein the predetermined number of bits comprising the amplitude subfield ranges from zero bits to two bits and the predetermined number of bits comprising phase subfield ranges from one-bit to three bits, and

wherein during the subsequent portions the packet exchange, the transmitting station and the receiving station operate in a fine quantization mode wherein the predetermined number of bits comprises the amplitude subfield ranges from two bits to four bits and the predetermined number of bits comprising phase subfield ranges from three bits to five bits.

24. A method for communicating signals over a multicarrier communication channel comprising:

applying quantized transmit beamforming coefficients to a plurality of symbol-modulated subcarriers; and

performing an inverse fast Fourier transform to the symbol-modulated subcarriers after applying the quantized transmit beamforming coefficients,

wherein the quantized transmit beamforming coefficients comprise predetermined numbers of bits for each subcarrier of a multicarrier communication channel indicating amounts to weight an amplitude and shift a phase of an associated subcarrier.

25. The method of claim 24 further comprising receiving a quantized transmit beamformer matrix ({tilde over (V)}) for each subcarrier from a receiving station, wherein the receiving station measures signals received from a transmitting station to estimate a channel transfer matrix (H) for each subcarrier and generates the quantized beamforming matrix ({tilde over (V)}) for each subcarrier for transmission to the transmitting station, wherein the receiving station performs a singular value decomposition (SVD) on the channel transfer matrix (H) to generate the quantized beamforming matrix ({tilde over (V)}) for each subcarrier.

26. The method of claim 25 wherein the predetermined numbers of bits comprising the quantized transmit beamforming matrices is lower during initial portions of a packet exchange between the transmitting station and the receiving station and is greater during subsequent portions of the packet exchange.

27. A method for communicating multicarrier communication signals over a multicarrier communication channel comprising:

estimating a channel transfer matrix (H) for each subcarrier of the multicarrier communication channel;

generating a quantized transmit beamformer matrix (V) for each subcarrier from an associated one of the channel transfer matrices (H); and

combining input subcarrier signals in accordance with a receiver beamformer matrix (Ũ

^H) for each subcarrier to separate constellation signals from each spatial channel,

wherein the receiver beamformer matrix (Ũ

^H) for a subcarrier is calculated from the channel transfer matrix (H) and the quantized transmit beamformer matrix ({tilde over (V)}) for the associated subcarrier, and

wherein the input subcarrier signals were transmitted a transmitting station using the quantized transmit beamformer matrix ({tilde over (V)}).

28. The method of claim 27 further comprising:

performing, for each subcarrier, a singular value decomposition (SVD) on the channel transfer matrix (H) to generate an initial transmit beamforming matrix (V),

performing a quantization on the initial transmit beamforming matrix (V) for each subcarrier to generate the quantized transmit beamforming matrix ({tilde over (V)}) for each subcarrier.

29. The method of claim 28 further comprising:

generating an equivalent channel transfer matrix ({tilde over (H)}) based on the quantized transmit beamforming matrix ({tilde over (V)}); and

generating corrected receiver beamformer matrices (Ũ

^H) based on the equivalent channel transfer matrix ({tilde over (H)}).

30. A system comprising:

one or more substantially omnidirectional antennas to receive signals through a multicarrier communication channel;

a channel estimator to estimate a channel transfer matrix (H) for one or more subcarriers of the multicarrier communication channel;

beamformer matrix calculation circuitry to generate a quantized transmit beamformer matrix ({tilde over (V)}) for each of the subcarriers from an associated one of the channel transfer matrices (H); and

a plurality of receiver beamformers to combine input subcarrier signals in accordance with a receiver beamformer matrix (Ũ

^H) for each subcarrier to separate constellation signals from each spatial channel,

wherein the calculation circuitry calculates the receiver beamformer matrices (Ũ

^H) from the channel transfer matrix (H) and the quantized transmit beamformer matrix ({tilde over (V)}) for an associated one of the subcarriers.

31. The system of claim 30 wherein the quantized transmit beamforming matrix ({tilde over (V)}) for each subcarrier comprises quantized transmit beamforming coefficients having predetermined numbers of bits indicating amounts for transmit subcarrier beamformers to weight an amplitude and shift a phase of an associated subcarrier,

wherein the channel estimator estimates the channel transfer matrix (H) for each subcarrier of the multicarrier communication channel based on channel measurements from a preamble of a current packet.

32. The system of claim 31 wherein the calculation circuitry performs, for each subcarrier, a singular value decomposition (SVD) on the channel transfer matrix (H) to generate an initial transmit beamforming matrix (V),

wherein the calculation circuitry performs a quantization on the initial transmit beamforming matrix (V) for each subcarrier to generate the quantized transmit beamforming matrix ({tilde over (V)}) for each subcarrier, and

wherein the calculation circuitry generates an equivalent channel transfer matrix ({tilde over (H)}) based on the quantized transmit beamforming matrix ({tilde over (V)}) and

wherein the calculation circuitry generates receiver beamformer matrices (Ũ

^H) based on the equivalent channel transfer matrix ({tilde over (H)}) for an associated subcarrier.

33. A machine-readable medium that provides instructions, which when executed by one or more processors, cause the processors to perform operations comprising:

estimating a channel transfer matrix (H) for each subcarrier of a multicarrier communication channel;

generating a quantized transmit beamformer matrix ({tilde over (V)}) for each subcarrier from an associated one of the channel transfer matrices (H); and

combining input subcarrier signals in accordance with a receiver beamformer matrix (Ũ

^H) for each subcarrier to separate constellation signals from each spatial channel,

wherein the receiver beamformer matrix (Ũ

^H) for a subcarrier is calculated from the channel transfer matrix (H) and the quantized transmit beamformer matrix ({tilde over (V)}) for the associated subcarrier, and

wherein the input subcarrier signals were transmitted a transmitting station using the quantized transmit beamformer matrix ({tilde over (V)}).

34. The machine-readable medium of claim 33 wherein the instructions, when further executed by one or more of the processors cause the processors to perform operations further comprising:

performing, for each subcarrier, a singular value decomposition (SVD) on the channel transfer matrix (H) to generate an initial transmit beamforming matrix (V),

performing a quantization on the initial transmit beamforming matrix (V) for each subcarrier to generate the quantized transmit beamforming matrix ({tilde over (V)}) for each subcarrier.

35. The machine-readable medium of claim 34 wherein the instructions, when further executed by one or more of the processors cause the processors to perform operations further comprising:

generating an equivalent channel transfer matrix ({tilde over (H)}) based on the quantized transmit beamforming matrix ({tilde over (V)}); and

generating corrected receiver beamformer matrices (Ũ

^H) based on the equivalent channel transfer matrix ({tilde over (H)}).