Data and channel aided symbol timing estimation for cooperative communications

A data and channel aided maximum likelihood (DCA-ML) symbol timing estimator for cooperative communications operating in flat fading channels is presented. The performance of the estimator is evaluated in terms of bit-errorrate (BER) and estimator variance. The BER performance is evaluated in various fading conditions and compared to a non-data-aided near maximum likelihood (NDA-NML) timing estimator and a correlation based data-aided maximum likelihood (DA-ML) timing estimator. For more severe fading the DCA-ML estimator performs better than the NDA-NML estimator and the DA-ML estimator. Three node cooperative communications, detect-and-forward relaying and various combining techniques are considered. The performance gains of the DCA-ML estimator over that of the DA-ML estimator become more significant in cooperative transmissions than single-link node-to-node transmission when operating in Weibull fading and Lognormal fading conditions.