EM-based joint data detection and channel estimation in asynchronous multi-rate DS/CDMA

In this paper, we present an efficient iterative receiver architecture of tractable complexity for joint multiuser detection and channel estimation (JDE) in DS/CDMA based on the EM algorithm. The EM algorithm provides a set of free parameters called weight coefficients which can be selected to optimize its performance. Two optimality criteria are defined and analytical expressions for the corresponding optimized weight coefficients are given. Monte Carlo simulations of an asynchronous multi-rate system operating in flat Rayleigh fading channel show that the proposed receiver is near-far resistant and robust against errors in estimation of the channel parameters.