Modem-based communications using synchronized chaos

This paper considers the use of chaotic dynamics to enhance or add value to telecommunications systems. An application in the form of secure communications, with particular emphasis on mobile radio systems is investigated. Standard continuous time descriptions of the Lorenz and Chua chaotic attractors are transformed into the discrete time domain and used in the design of a secure chaotic modem which includes the digital modulation schemes: quadrature phase shift keying (QPSK) and pi /4-QPSK with square-root raised cosine pulse shaping filters. The results of analytical computer simulations show that the performance of both modem systems over limited bandwidth additive white Gaussian noise (AWGN), and Rayleigh and Rician fading channels induces no degradation in the bit error probability. Finally, in order to demonstrate that the chaotic modem offers a degree of robustness to eavesdropping, a reconstruction model is derived and applied tea the communication scheme. It is shown that, due to inaccurate information surrounding the state of the system, a reconstruction of the system was not possible. Copyright (C) 2001 John Wiley & Sons, Ltd.