Comparison of chaotic sequences in a chaos-based DS-CDMA system

This paper provides a performance analysis of a direct-sequence code division multiple access (DS- CDMA) system when chaotic sequences are used instead of conventional pseudo-noise (PN) spreading codes. Dif- ferent chaotic maps are compared by observing their statis- tical properties and calculating bit error rate (BER) in the single user case quence given by the Chebyshev map in terms of SNR im- provement. The proposed work deals with the analysis of statistical properties of several chaotic maps. First, the probability distribution functions of the chaotic times series are pro- vided. It is then shown how these distribution functions affect the performance when these series are used as direct spreading sequences for the DS-CDMA. The paper is organized as follows. In section 2 we pre- sent the different chaotic maps for spreading spectrum. Then, in third section, the transmission system is illus- trated. In this section also the performance of CSS, and the lower and upper bound of the BER are presented. Sec- tion 4 shows simulation results. Finally, section 5 reports some conclusive remarks. 2. Chaotic generator For this study, two kinds of one-dimensional map are chosen. The first one is the Chebyshev polynomial func- tion of order 2 (CPF) and the second is a one-dimensional noninvertible piecewise linear map (PWL).