Time-varying least-mean-fourth-based channel equalization method and system
AssigneeKing Fahd University of Petroleum and Minerals
InventorsAZZEDINE ZERGUINE, LAHOUARI CHEDED, MUSA U. OTARU
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Abstract
The time-varying least-mean-fourth-based channel equalization method is an automated procedure that provides an adaptive equalizer in a CDMA receiver. Equalizer filter coefficients are estimated using a least-mean-fourth (LMF) error calculation based on a training set of symbols sent by the transmitter. When the LMF error calculation is combined with a power-of-two quantization (PTQ) process, superior receiver performance is achieved in a time-varying CDMA channel operating in non-Gaussian noise environments.
Claims12
A time-varying least-mean-fourth-based channel equalization system, comprising:
- means for digitally receiving CDMA encoded symbols transmitted over at least one time-varying channel;
- an equalizer including an adaptive filter having weighted coefficients, the equalizer accepting the at least one time-varying channel as input and providing an equalized, noise cancelled output of the at least one time-varying channel, the equalizer having:
- means for calculating a least-mean-fourth error associated with a comparison of the adaptive filter equalizer's output versus a transmitted training set of the CDMA encoded symbols;
- a power-of-two quantizer;
- means for combining the power-of-two quantizer with the means for calculating the least-mean-fourth error;
- and
- means for recursively updating the adaptive filter weighted coefficients based on an output of the means for combining the power-of-two quantizer with the means for calculating the least-mean-fourth error;
- and
- a threshold detector accepting the adaptive filter equalizer output and providing a threshold detector output including the transmitted CDMA encoded symbols detected by the equalizer.
A computer-implemented time-varying least-mean-fourth-based channel equalization method, comprising the steps of:
- digitally receiving CDMA encoded symbols transmitted over at least one time-varying channel;
- equalizing the at least one time-varying channel as input and providing an equalized, noise-cancelled output of the at least one time-varying channel, the equalizing step including synthesis of an adaptive filter having weighted filter coefficients;
- calculating a least-mean-fourth error associated with a comparison of an output of the equalization step versus a transmitted training set of the CDMA encoded symbols;
- power-of-two quantizing the at least one time-varying channel;
- combining the power-of-two quantization with the least-mean-fourth error calculation;
- recursively updating the adaptive filter weighted coefficients based on an output of the step of combining the power-of-two quantization with the least-mean-fourth error calculation;
- and
- threshold detecting the noise-cancelled output of the at least one time-varying channel, thereby providing the transmitted CDMA encoded symbols detected by the equalizer.
A computer software product, comprising a medium readable by a processor, the medium having stored thereon a set of instructions for performing a time-varying least-mean-fourth-based channel equalization method, the set of instructions including:
- (a) a first sequence of instructions which, when executed by the processor, causes said processor to digitally receive CDMA encoded symbols transmitted over at least one time-varying channel;
- (b) a second sequence of instructions which, when executed by the processor, causes said processor to equalize said at least one time-varying channel as input and provide an equalized, noise-cancelled output of the at least one time-varying channel, the equalization including the synthesis of an adaptive filter having weighted filter coefficients;
- (c) a third sequence of instructions which, when executed by the processor, causes said processor to calculate a least-mean-fourth error associated with a comparison of an output of the equalization versus a transmitted training set of the CDMA encoded symbols;
- (d) a fourth sequence of instructions which, when executed by the processor, causes said processor to perform a power-of-two quantization of the at least one time-varying channel;
- (e) a fifth sequence of instructions which, when executed by the processor, causes said processor to combine the power-of-two quantization with the least-mean-fourth error calculation;
- (f) a sixth sequence of instructions which, when executed by the processor, causes said processor to recursively update the adaptive filter weighted coefficients based on an output of combining the power-of-two-quantization with the least-mean-fourth error calculation;
- and
- (g) a seventh sequence of instructions which, when executed by the processor, causes said processor to threshold detect the noise-cancelled output of the at least one time-varying channel, thereby providing the transmitted CDMA symbols detected.
Dependencies are inferred from the claim text.