Application of noise reduction to chaotic communications: A case study

Over the past few years, several methods have been proposed for decontamina ting noisy chaotic signals by exploiting the short-term predictability of c haotic signals. This work evaluates the effectiveness, for a differential c haos shift keying (DCSK) telecommunications system, of a noise reduction ap proach using a deterministic optimization technique. Noise reduction is governed by a cost function which consists of two terms: the first gives the distance between the noisy and enhanced orbits, while the second one checks the dynamics of the cleaned signal. These two terms a re weighted by a scalar Gamma. The effect of this factor on the noise reduc tion performance is also studied. Evaluation of the noise performance of a telecommunication system by comput er simulation requires a very long simulation time. We propose a computatio nally-efficient criterion for quantifying the performance improvement of a DCSK system. We show that the noise reduction technique improves the overal l noise performance only if the energy per bit-to-noise spectral density (E -b/N-0) exceeds a certain threshold. The effect of code length on this thre shold level is also evaluated. Finally, the effect of parameter mismatch, which is present in every practi cal system, is analyzed.