Weighted RLS channel estimators for DS/CDMA signals in multipath

Channel estimation and equalization is explored in the context of Direct-Sequence/Code-Division Multiple-Access signals transmitted through multipath channels. The focus is on adaptive and recursive methods which exploit pilot symbols or pilot signals, resulting in algorithms which are alternatively appropriate for the uplink or the downlink. Moderate complexity, linear estimators and receivers are investigated which optimize the minimum-mean squared error or a weighted least-squares criterion, respectively. Different weight estimators are thus investigated. The proposed algorithms are explored via Monte Carlo simulations and are shown to be robust and offer near-optimal performance in certain scenarios. Fast convergence is also achieved. In addition, the channel estimation algorithms do not require coordination amongst the active users in terms of the transmission of pilots. Finally, the effects of mismatch in synchronization data are explored and methods to compensate for such errors are examined.