Use of cross-correlation minimization for performance enhancement of chaotic spreading sequence based asynchronous DS-CDMA system

The research is devoted to the reduction of multiple access interference (MAI) in chaos-based asynchronous direct sequence code division multiple access (DS-CDMA) communication systems by use of spreading sequences which are selected from a large set of generated chaotic sequences. For the generation of binary chaotic spreading sequences different 1-dimensional maps are examined. As selection criteria the minimum magnitude of periodic cross correlation among all pairs of selected sequences is used. The impact of the sequence length, the generation method as well as the number of simultaneously used sequences on the selection criteria is studied. For the evaluation and analysis of selection efficiency a baseband MATLAB model of asynchronous DS-CDMA system with an additive white Gaussian noise (AWGN) channel and perfect chip synchronization is employed. Detailed measurements of bit error ratios (BERs) in systems with different numbers of simultaneous users are provided.