Combined Application Of Turbo Codes And Multi - User Detection

Based on the thorough analysis of coding and decoding theory of Turbo code and multiuser detection, this paper introduces the idea of Turbo into multiuser detection, and proposes a scheme of joint detection of Turbo code and multiuser detection in DS/CDMA mobile communication system. In the scheme, Turbo code is used as channel coding, and at the receiver, K single Turbo decoders follow multiuser and function as channel decoders, these decoder have the ability of soft input and soft output(SISO), the output of these decoder are not information sequence but their a posteriori probability. They were feedback to the multiuser detector as a priori probability for next iterative detection. When the iterative detection terminate, the decoder make a hard decision and output the estimate value of information sequence.This paper simulate this scheme in a environment of added white gauss noise(AWGN) and various of signal noise ratios and different number of user with MATLAB software, the simulation result show that the bit error ratio(BER) of this scheme is reduced obviously when compared with the conventional receiver and the multiuser detector with no such iterative scheme. When the user number is 5, and the signal noise ratio is between 2 to 4 dB, the performance of this scheme approach that of the single user system.