Performance analysis for multiple access CSK and DCSK communication systems

Chaotic signals, by virtue of their wideband characteristics, can be used to spread narrowband information over a wider frequency spectrum, as in conventional spread-spectrum communication. However, like other forms of spread-spectrum communication systems, chaos-based systems must allow multiple access in order to make efficient use of the available bandwidth. In this paper, multiple access techniques for use with chaos-shift-keying and differential chaos-shiftkeying under a noisy condition are analyzed using a discretetime approach. A mixed analysis-simulation technique is developed to calculate the bit error rates. When certain assumptions are made, closed-form analytical expressions of the bit error rates are found. The factors governing the performance of the system are then studied. Illustrative examples are given, and computer simulations are performed for the cases where each user employs a distinct or the same chaotic map. Furthermore, for the case where one particular map is used by all users, performance is evaluated for different choices of the chaotic map. It is found that the bit error rates obtained from both the mixed-analytical method and the analytical approach are consistent with those found from simulations. The methods presented in this paper are applicable to other multiple access schemes.