Abstract: The multiaccess interference (MAI) and frequency-selective fast-fading of the channels do great harm to credible communication and greatly decrease the capacity of broadband wireless mobile communication systems under the working environment of high-speed vehicle holding.In this paper, a modified partial parallel interference cancellation (PPIC) method is proposed to combat MAI for the uplink of DS CDMA systems, and a new channel model and its corresponding channel tracing method are also proposed for frequency-selective fast-fading channels.An iterative multi-user detection algorithm for the uplink of DS CDMA systems over frequency-selective fast-fading channels is realized through the information exchange between the MPPIC and channel tracking.The simulation results validate the proposed algorithm.

Key words: channel estimation, Kalman filtering, CDMA, PPIC, multiuser detection, recursive least square