Multiuser Detection Techniques In DS-CDMA Communication Systems

Multiuser detection(MIJD) is one of the key techniques for CDMA systems.Through joint detection and interference canceling,multiuser detection can reduce multiple access interference(MAI) and intersymbol interference(ISI) dramatically,relax "nearfar" effect,improve the system performance and increase the capacity of CDN4A svstems.MUD techniques in DS-CDMA systems are studied in this dissertatiomand the computer simulation results prove to be favorable.The main works of the dissertation can be summarized as follows:oBy exploring the model of DS-CDMA systems.we study the matrix expression of received signal in asyncL-onous DS-CDMA,simplifv it reasonably and present a dehiasin~ decorrelating multi-user detector applied to as'vnchronous transmittiing channel. The complexity of the detector is lower than that of the ordinary decorre]atinc detector and it precedes conventional detector in eliminating the MAT and "near-far~ resistance.oA blind adaptive decorrelating RAKE receiver based on the Kalman filter is i~roposed. The salient features of the receiver are that it doesnt require training sequences and estimate the fading parameters in advance.The receiver can suppress the MAT and solve the problem of the "near-far" effect effectively.And it can converge rapidly.oBy exploring the model of CDMA systems and good approximation properties of wavelet.we propose two wavelet networks multiuser detectors based on matehe~ filter and space-time filter respectively.Two detectors avoid computing the inverse of correlation matrix involved in the decorrelating detector and have good detection performance,but they need training sequences.oCombining space-time processing and the MUDwe propose a novel blind space-time multiuser detector based on the Kalman filten The detector only requires the signature waveform and multipath delay of the interesting user,while it does not need estimating maltipath gain and the DOA of maltipath signal.The detector precedes the conventional space-time 2-dimensional RAKE receiver in eliminating the MAT and "near-far" resistance. And it can converge rapidly.This paper is supported by National Natural Science Foundation of China and "863" High-Tech Program.