Robust adaptive MMSE/DFE multiuser detection in multipath fading channel with impulse noise

The direct-sequence code-division multiple-access (DS/CDMA) technique is extensively used for cellular, personal, and mobile radio communication systems. However, the conventional channel estimators cannot provide accurate channel information for multiuser detection in the presence of impulsive noise and Doppler spread, especially in the time-varying fading channel. We propose a linear-trend tracking method for estimating the impulse response of the time-varying channel via a robust Kalman filtering with a scheme that can automatically adjust the variance of the driving noise. The proposed method need not identify the parameters of the channel model and is insensitive to the speed of channel variation. Following channel estimation, a robust multiuser detection algorithm is developed via a Kalman-based decision feedback equalization (DFE). A nonlinear limitation function is incorporated to mitigate the effects of channel estimation error and impulsive noise and to prevent severe error propagation. Simulation results conclude that the performance of the DS/CDMA system is improved by using the proposed receiver.