Chaotic digital code-division multiple access (CDMA) communication systems

In this paper, the structure, principle and framework of chaotic digital code-division multiple access ((CD)(2) MA) communication systems are presented. Unlike the existing CDMA systems, (CD) MA systems use continuous pseudo-random time series to spread the spectrum of message signal and the spread signal is then directly sent through a channel to the receiver. In this sense, the carrier used in (CD)(2) MA is a continuous pseudo-random signal instead of a single tone as used in CDMA. We give the statistical properties of the noise-like carriers. In a (CD)(2) MA system, every mobile station has the same structure and parameters, only different initial conditions are assigned to different mobile stations. Instead of synchronizing two binary pseudo-random sequences as in CDMA systems, we use an impulsive control scheme to synchronize two chaotic systems in (CD)(2) MA. The simulation results show that the channel capacity of (CD)(2) MA is twice as large than that of CDMA.