Abstract
Abstract Direct sequence-code division multiple access (DS-CDMA) has been extensively investigated in the cellular mobile telephone system. In this thesis, we discuss non-Gaussian noise effect to the DS-CDMA system. Because the signal is influenced by the impulse noise in the course of transmitting, the signal cannot return to original signal at receiver. The impulse noise is usually due to the human-made electromagnetic interference and a large number of natural noise as well. It is known through experiment measurements to be a non-Gaussian distribution. And then we can exploit a Gaussian mixture model in [4], it is composed of two kinds of Gaussian distribution which have different variance. So we can use the mixture model to attain the impulse noise which affects the transmitted signal. We will use some methods to estimate the original signal in the receiver. There are some estimators that use iteration to suppress the impulse noise, least square and minimax decorrelating detector, etc. In statistics, there are also some estimators, for instance, least median of square (LMedS), reweighted least square (RLS), consecutive mean excision (CME) and forward consecutive mean excision (FCME). Those methods let the signals be an outlier and cancel them when they are interfered seriously. All of those methods want to solve the impulse noise problem in the system and we will use simulation program to compare the performance of all estimators. We will also simplify the complexity operation of different methods to obtain the new method here. Such as, our proposed methods improve the overly complicated problem in LMedS and RLS. The performance upper bound of CME and FCME are found by our proposed method. Using the method of M-estimator [4], we analyze all methods and compare the performance of different methods analytically. In the end, we compute the complexity operation of all estimators. So we can find a low complexity and high performance method.