BER PERFORMANCE EVALUATION FOR ASYNCHRONOUS DS-CDMA SYSTEM USING OPTIMAL CHAOTIC SPREADING SEQUENCES

摘要

The use of chaotic spreading sequences is a new approach for spread-spectrum systems. Some chaotic spreading sequences show better correlation properties than conventional binary sequences, which are crucial for the BER (Bit Error Rate) performances. This paper is presenting a design method for optimal sets of chaotic sequences for the A-DS-CDMA (Asynchronous Direct-Sequence Code-Division Multiple Access) system. The discrete aperiodic autocorrelation function of the optimal spreading sequences for the A-DS-CDMA system are derived by minimizing the average BER expression under the SGA (Standard Gaussian Approximation) condition. Using some results from the ergodic theory, a practical implementation of the optimal spreading sequences by using chaotic dynamical systems is considered, and the BER performances for the A-DS-CDMA system using these sequences is analyzed.