Evaluation of a continuous valued chaotic spreader used in a chaotic digital code-division multiple access ((CD)²MA) system

This paper presents a possible realization of a (CD)²MA multiuser communication system. The state variables of two synchronized chaotic Chua's circuits are thereby used to generate identical continuous valued spreader sequences in the transmitter and the receiver. To create a higher degree of randomness in the signatures, the state variables are processed by a k-shift cypher. The performance to be expected for such a system as opposed to designs using binary spreaders can be estimated theoretically. For verification, extensive simulations were run that allow for a direct comparison of the chaotic spreader with a traditional binary Gold sequence or a sequence of continuous random numbers, respectively, in terms of the achievable bit error ratio for a given data rate and number of simultaneous users per channel. A brief description of the system and channel models implemented in the simulation program is provided. The simulation results are presented and discussed.