近年來，直接序列分碼多工存取系統(direct-sequence code-division multiple access, DS-CDMA )廣泛地使用在個人通訊，行動通訊，無線通訊等應用上。然而傳統的通道估測器無法對多用戶偵測器提供精準的通道資訊，尤其是通道中存在脈衝雜訊(impulse noise)、高速的都卜勒位移(Doppler shift)、及大量的多用戶干擾(multiuser access interference, MAI)。本篇所提出的強健線性趨勢追蹤技巧不需要事先知道通道參數，且透過本篇提出的強健通道估測器可以同時估測出多用戶的時變通道資訊。 在通道估測完成之後，本篇論文提出了以卡曼濾波器(Kalman filter)結合決策回授等化器(decision feedback equalization, DFE)為基礎的強健多用戶偵測演算法。 最後，我們結合本篇提出的強健通道估測、強健多用戶偵測演算法提出了通訊接收端的解決方案。透過接收端內建的非線性限制功能，本篇提出的接收器可以有效地在多路徑雷萊衰退(Rayleigh fading)通道中克服通道估測錯誤、資料錯誤、及脈衝雜訊所造成的問題。 論文最末，我們提供了各種情形下的模擬結果，驗證了本篇提出的接收器的確可以有效地改善直接序列分碼多工存取系統(DS-CDMA)的性能表現。

Recently, direct sequence code-division multiple access (DS/CDMA) systems are extensively used for cellular, personal, and mobile radio communication systems. However, the conventional channel estimators can not provide accurate channel information for multiuser detection in the presence of impulse noise, fast fading (large Doppler Spread) and large multiuser access interference (MAI). The proposed robust linear-trend tracking method does not need to identify the parameters of channel model. The multiuser time-varying channels can be estimated simultaneously by the proposed robust channel estimator using the state dynamic via robust Kalman filter technique. Following channel estimation, a robust multiuser detection algorithm is developed via a Kalman-based decision feedback equalization (DFE). Finally, a mixed channel estimation/ multiuser detection receiver embedded with a nonlinear limitation function is presented to mitigate the effects of channel estimation error, data missing and impulse noise to prevent the severe error propagation under frequency selective Rayleigh fading channel. The performance analysis considering the effect of channel estimation error is derived. Simulation results conclude that the performance of DS/CDMA system is much improved by using proposed receiver.

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