Pre-decorrelation in Turbo-coded DS-CDMA system using Space-Time Coding over fading channels

In this paper, we deal with the Multiple Access Interference (MAI) suppression problem in Turbo coded Space-Time Block Coded (STBC) Direct Sequence Code-Division Multiple-Access (DS-CDMA) systems. In the proposed system, we preprocess (decorrelate) the coded bits in the transmitter side instead of using a decorrelating detector in the receiver. Using this method, the base station can perform decorrelation before transmission, and the mobile unit uses the conventional receiver achieving approximately the performance of the decorrelating detector. Performance comparison is made between this method and existing decorrelating detector in fading channels. This paper also investigates the performance improvement due to channel coding. Performance comparison between turbo coded STBC DS-CDMA systems employing different interleaver sizes and Soft-Decision Convolutional Codes (SD-CC) is also provided.