Abstract
The present invention is related to a method and apparatus for blindly equalizing received signals in the time domain based on independent component analysis (ICA). Received signals are demodulated and oversampled by a rate at least twice the symbol rate to populate a mixing matrix. The received signal samples are cast into the form of a signal separation problem as represented by the multiplication of the mixing matrix with the transmitted symbols such that the unknowns can be solved by ICA. Applying ICA to the received signal samples provides a demixing matrix which can be multiplied by the received signal samples to estimate the transmitted symbol sequence. The proposed ICAbased equalization method simultaneously corrects other transmission imperfections, such as DCoffset, carrier phase offset and inphase and quadrature imbalance, all in the time domain. As an alternative to oversampling, multiple copies of the received signals are received via a plurality of antennas.
Claims

A method for equalizing a received signal that includes a plurality of symbols having a predetermined symbol rate, the method comprising:
demodulating the received signal to generate an inphase (I) signal and a quadrature (Q) signal;
sampling the I signal and the Q signal at a sampling rate that is at least twice the predetermined symbol rate to generate a plurality of I signal samples and a corresponding plurality of Q signal samples per symbol;
generating a demixing matrix by applying independent component analysis (ICA) in a time domain to the generated I and Q signal samples; and
generating an estimate of a symbol in the plurality of symbols by multiplying the demixing matrix with the generated I and Q signal samples.
 The method of claim 1 wherein the generating of the demixing matrix includes applying the ICA to matrix columns of the generated I and Q signal samples such that the demixing matrix is an approximation of an inverse of a mixing matrix where each column matrix is equivalent to the mixing matrix multiplied by respective transmitted I symbol and Q symbol plus an offset.
 The method of claim 1 wherein the sampling includes oversampling at the sampling rate that is a multiple of the predetermined symbol rate where the multiple is equal to the number of the I signal samples generated per symbol.
 The method of claim 1 wherein the demodulating includes generating an I signal and a Q signal for each of a plurality of signals received by a plurality of antennas, and the sampling comprises sampling each of the I and Q signals.
 The method of claim 4 wherein the sampling comprises oversampling such that the sampling rate is a multiple of the predetermined symbol rate.
 The method of claim 1 further comprising storing the I and Q signal samples.
 The method of claim 6 wherein the generating of the demixing matrix is performed using a FastICA algorithm applied to the stored I and Q signal samples.

A receiver for equalizing a received signal including a plurality of symbols having a predetermined symbol rate comprising:
a demodulator configured to demodulate the received signal to generate an inphase (I) signal and a quadrature (Q) signal;
a sampler configured to sample the I signal and the Q signal at a sampling rate that is at least twice the predetermined symbol rate to generate a plurality of I signal samples and a corresponding plurality of Q signal samples per symbol; and
a processor configured to generate a demixing matrix by applying independent component analysis (ICA) in a time domain to the generated I and Q signal samples, and to generate an estimate of a symbol in the plurality of symbols by multiplying the demixing matrix with the generated I and Q signal samples.
 The receiver of claim 8 wherein the processor configured to generate the demixing matrix by applying the ICA to matrix columns of the generated I and Q signal samples such that the demixing matrix is an approximation of an inverse of a mixing matrix where each column matrix is equivalent to the mixing matrix multiplied by respective transmitted I symbol and Q symbol plus an offset.
 The receiver of claim 8 wherein the sampler configured to oversample such that the sampling rate is a multiple of the predetermined symbol rate where the multiple is equal to the number of the I signal samples generated per symbol.

The receiver of claim 8 further comprising:
a plurality of antennas configured to receive a plurality of signals wherein the demodulator is configured to generate the I signals and the Q signals for each of the plurality of signals and the sampler is configured to sample each of the I and Q signals.
 The receiver of claim 8 wherein the sampler is configured to oversample at the sampling rate that is a multiple of the predetermined symbol rate.
 The receiver of claim 8 further comprising a memory configured to store the I and Q signal samples.
 The receiver of claim 13 wherein the processor configured to use a FastICA algorithm applied to the stored I and Q signal samples to generate the demixing matrix.
 A wireless transmit/receive unit (WTRU) comprising the receiver of claim 8.
 A base station comprising the receiver of claim 8.
Owners (US)

Interdigital Technology Corporation
(Mar 06 2007)
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Applicants

Interdigital Technolgy Corp
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Inventors

Haghighat Afshin
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CPC Classifications
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 Publication: Aug 3, 2010

Application:
Dec 29, 2006
US 61801206 A

Priority:
Dec 29, 2006
US 61801206 A

Priority:
Feb 10, 2006
US 77247906 P