Performance of multiuser detection with adaptive channel estimation

An adaptive decorrelating multiuser detector is considered for application in Rayleigh fading multipath channels with significant fading rate (Doppler spread). A suboptimal receiver structure, in which decorrelation is decoupled from multipath recombining, allows efficient implementation of adaptive channel estimation, e.g. via LMS algorithm. The channel estimates are used to perform maximum ratio combining. Bit error rate is evaluated analytically as a function of fading statistics and receiver tracking parameters. Results demonstrate performance sensitivity to the choice of the LMS step size when the channel is modeled as a second-order AR process. Performance degradation increases with fading rate, leading to the saturation of the error probability at a level determined by the fading rate of the channel and the deviation of the step size from the optimal value. The receiver is near-far resistant regardless of the fading rate of the channel.