| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 89 === 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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