System and method for distributed input distributed output wireless communications

• US 7,599,420 B2
• Filed: 08/20/2007
• Issued: 10/06/2009
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: Rearden, LLC
• Original Assignee: Rearden, LLC
• Inventors: Forenza, Antonio, Perlman, Stephen G., van der Laan, Roger, Heath, Robert W. Jr., Speck, John
• Primary Examiner(s): Ha; Dac V
• Application Number:
  US11/894,394
• Publication Number:
  US 20080130790A1
• Time in Patent Office: 778 Days
• Field of Search: 375/141, 375/146, 375/219, 375/220, 375/222, 375/260, 375/267, 375/285, 375/296, 375/298, 375/299, 370/278, 370/282, 370/286, 370/464, 370/465, 455/501, 455/67.13, 455/69, 455/561, 455/103, 455/114.2, 455/114.3, 455/126
• US Class Current: 375/141
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04B 7/0684 using different training sequences per antenna
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04J 11/0033 by pre-cancellation of known interference, e.g. using a matched filter, dirty paper coder or Thomlinson-Harashima precoder correlative coding in synchronous or start-stop systems H04L25/497
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 2025/0377 during the reception of training signals
• CPC Class Codes: H04L 2025/03802 Signalling on the reverse channel
• CPC Class Codes: H04L 2027/002 using feedback from a remote receiver
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• 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 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols

Abstract

A system and method are described for compensating for frequency and phase offsets in a multiple antenna system (MAS) with multi-user (MU) transmissions (“MU-MAS”). For example, a method according to one embodiment of the invention comprises: transmitting a training signal from each antenna of a base station to one or each of a plurality of wireless client devices, one or each of the client devices analyzing each training signal to generate frequency offset compensation data, and receiving the frequency offset compensation data at the base station; computing MU-MAS precoder weights based on the frequency offset compensation data to pre-cancel the frequency offset at the transmitter; precoding training signal using the MU-MAS precoder weights to generate precoded training signals for each antenna of the base station; transmitting the precoded training signal from each antenna of a base station to each of a plurality of wireless client devices, each of the client devices analyzing each training signal to generate channel characterization data, and receiving the channel characterization data at the base station; computing a plurality of MU-MAS precoder weights based on the channel characterization data, the MU-MAS precoder weights calculated to pre-cancel frequency and phase offset and/or inter-user interference; precoding data using the MU-MAS precoder weights to generate precoded data signals for each antenna of the base station; and transmitting the precoded data signals through each antenna of the base station to each respective client device.

Claims

1. A method for compensating for frequency and phase offsets in a multiple antenna system (MAS) with multi-user (MU) transmissions (“

MU-MAS”

) comprising;

transmitting a training signal from each antenna of a base station to one or each of a plurality of wireless client devices, one or each of the client devices analyzing each training signal to generate frequency offset compensation data, and receiving the frequency offset compensation data at the base station;

computing MU-MAS precoder weights based on the frequency offset compensation data to pre-cancel the frequency offset at the transmitter;

precoding training signal using the MU-MAS precoder weights to generate

precoded training signals for each antenna of the base station;

transmitting the precoded training signal from each antenna of a base station to each of a plurality of wireless client devices, each of the client devices analyzing each training signal to generate channel characterization data, and receiving the channel characterization data at the base station;

computing a plurality of MU-MAS precoder weights based on the channel characterization data, the MU-MAS precoder weights calculated to pre-cancel frequency and phase offset and/or inter-user interference;

precoding data using the MU-MAS precoder weights to generate precoded data signals for each antenna of the base station; and

transmitting the precoded data signals through each antenna of the base station to each respective client device.

2. The method as in claim 1 wherein the base station is an access point coupling the wireless client devices to a wide area network.

3. The method as in claim 1 wherein one centralized transmitter unit estimates the frequency offset between all the transmit units and pre-compensates for that offset or the Distributed-Input-Distributed-Output (“

DIDO”

) transmit antennas share a frequency reference through a wired, optical, or wireless network (without need of precoded training and users'"'"' feedback during the frequency offset estimation step).

4. The method as in claim 1 wherein training precoding is performed by one or plurality of users on a long-term basis to reduce feedback overhead.

5. The method as in claim 1 wherein the transmitter or receiver estimates the rate of change of the frequency offset and decides the rate of update of the training precoder.

6. The method as in claim 1 wherein data precoding is performed using block diagonalization (BD) techniques.

7. The method of claim 1 wherein the MU-MAS system is a distributed-input distributed output (DIDO) communication system and wherein the MU-MAS precoder weights are DIDO precoder weights.

8. A wireless client device for use in a system for compensating for frequency and phase offsets for a multiple antenna system (MAS) with multi-user (MU) transmissions (MU-MAS) communication comprising:

one or more RF units to receive signals transmitted from one or more MU-MAS transmitter units, and downconvert the signals to baseband;

one or more analog to digital (A/D) conversion units to receive the downconverted signals and to convert the signals from analog signals to digital signals;

a frequency/phase offset estimation/compensation unit that estimates the frequency and/or phase offset and feedbacks this information to the transmitter for pre-compensation;

one or more orthogonal frequency division multiplexing (“

OFDM”

) units to remove cyclic prefix and perform a fast Fourier transform (FFT) on the digital signals to report the signals in the frequency domain;

a channel estimate unit which receives a signal output from the one or more OFDM units during a training period and responsively calculates channel estimate data; and

a feedback generator unit to transmit the channel estimate data to a base station for use in precoding signals prior to transmission to the wireless client device;

wherein the feedback generator unit further comprises logic for quantizing the frequency offset and channel estimates prior to transmission to the base station.

9. The system as in claim 8 where the channel estimates are computed in the time domain by using the input to the OFDM units.

10. The wireless client device as in claim 8 further comprising:

a receiver unit which receives outputs from the OFDM units and responsively computes the receiver and demodulates/decodes the signal to obtain the estimate of the transmitted data.

11. The wireless client device as in claim 10 wherein the receiver unit is a minimum mean square error (MMSE) receiver, zero-forcing (ZF) receiver, a maximum likelihood (ML) or a decision-feedback maximum a posteriori (“

MAP”

) receiver.

12. The system as in claim 8 wherein the MU-MAS communication comprises Distributed-Input-Distributed-Output (“

DIDO”

) communication and wherein the one or more RF units receive signals transmitted from one or more DIDO transmitter units, and downconvert the signals to baseband.

13. The system as in claim 8 wherein the frequency/phase offset estimation/compensation unit carries out means for coarse frame synchronization, means for fractional frequency offset correction, means for integer frequency offset correction and/or means for integer frequency offset correction.

14. A wireless client device for use in a system for compensating for frequency and phase offsets for a multiple antenna system (MAS) with multi-user (MU) transmissions (MU-MAS) communication comprising:

one or more RF units to receive signals transmitted from one or more MU-MAS transmitter units, and downconvert the signals to baseband;

one or more analog to digital (A/D) conversion units to receive the downconverted signals and to convert the signals from analog signals to digital signals;

a frequency/phase offset estimation/compensation unit that estimates the frequency and/or phase offset and feedbacks this information to the transmitter for pre-compensation;

one or more orthogonal frequency division multiplexing (“

OFDM”

) units to remove cyclic prefix and perform a fast Fourier transform (FFT) on the digital signals to report the signals in the frequency domain;

a channel estimate unit which receives a signal output from the one or more OFDM units during a training period and responsively calculates channel estimate data; and

a feedback generator unit to transmit the channel estimate data to a base station for use in precoding signals prior to transmission to the wireless client device;

wherein the frequency/phase offset estimation/compensation unit carries out means for coarse frame synchronization, means for fractional frequency offset correction, means for integer frequency offset correction and/or means for integer frequency offset correction.