Blind adaptive estimation and diversity combining of a fast varying, correlated multipath channel for DS/SS systems

The maximum ratio combining (MRC) of a fast varying, correlated multipath fading channel is investigated. A practical solution to the problem of simultaneously estimating the channel state and the channel parameters is proposed. Based on the expectation maximization (EM) algorithm, the procedure of iterating batches of data is simplified to an adaptive algorithm with only forward time recursions, which helps remove the required training sequences, and significantly reduces the memory requirement. Through computer simulations, we have found a near ideal MRC BER performance and demonstrated the efficacy of the new algorithm when applied to channels with changing Doppler spreads.