An adaptive multiuser decision-feedback equalizer (DFE) companioned with a Kalman channel estimation algorithm is presented for DS-CDMA systems in multipath fading channels. The Kalman channel estimation algorithm is employed to estimate the multipath fading channels, then the estimates are used to adjust the tap coefficients of the multiuser DFE via a minimum mean-square error design criterion. In this study, we present a novel state-space equation, which is different from the joint multiuser detection/channel estimation method (Wang and Poor, Wireless Networks 4(6) (1998) 453-470), for the multipath fading channel estimation of multiuser DS-CDMA systems. We take not only the estimates of channels but also the statistics of the channel estimation errors into consideration of the multiuser DFE design. We also derive the output signal-to-interference-and-noise ratio and the bit-error-rate for the multiuser detection, in which the influence of multiuser interference, channel estimation errors and channel noise is included. Finally, two fading channel models, i.e., the land-mobile model and the Butterworth model, are simulated to demonstrate our results. The sensitivity of the proposed method to the uncertainties of fading channel parameters is also presented in the simulations. © 2001 Elsevier Science B.V.
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