Multi-User Detection Research On Multi-Carrier CDMA

Traditional CDMA have advantages of large system capacity and good security performance, but its data transfer rate is relatively low, can not meet the needs of high-speed data communications. Multi-carrier CDMA is a combination of CDMA and OFDM, not only retains the advantages of CDMA, but also inherits the advantages of high transfer rate and strong anti multi-path interference ability from OFDM, and its bandwidth efficiency is higher than them. In multi-carrier CDMA, the multi-users share the same frequency band, identifying different users only depend on their spreading codes. In practice, for various reasons, it is difficult to maintain the orthogonal among of spreading sequences, thus inevitably produce multiple access interference, and it not only make the system sensitive to the near-far effect, but also restrict the system capacity.The traditional single-user detection deals with multiple access interference as Gaussian white noise, unable to get good detection performance, and the Multi-user detection gets good effect in resisting multiple access interference through making use of the users' spreading codes structural information.This paper analyzes the difference of three schemes of multi-carrier CDMA, then make MC-CDMA as the research object, analysis and the establishment its mathematical model, and on the simulation platform of this model, conduct simulation experiment for EGC and MRC in single-user detection, and analysis the simulation results and conclude that single-user detection problems, leads to the concept of multi-user detection, then conduct simulation experiments for several typical types of multi-user detection, and analyze and compare the result. Finally introduction partial parallel interference cancellation and two kinds of algorithm of solving optimal interference cancellation factor:the algorithm based on solving the minimum mean square error of the expectations and judgments output, and the algorithm based on solving the minimum residual interference variance, then conduct simulation experiment for partial parallel interference cancellation and this two kinds of algorithm, find out several factors of affecting optimal interference cancellation factor, and the results of the comparison of two algorithms.