Communication with Chaos over Band-Limited Channels

Methods of communications using chaotic signals use an ability of a chaos generator (encoder) and matched response system (decoder) to behave identically despite the instability of chaotic oscillations. Chaotic oscillations cover a wide spectral domain and can efficiently mask an information signal scrambled by the chaotic encoder. At the same time the wide spectrum poses intrinsic difficulties in the chaotic decoding if the chaotic signal is transmitted over real communication channels with limited bandwidth. We address this problem both numerically and experimentally. Two alternative ways to improve communication with chaos over band-limited channels are investigated. The first method employs a matching filter in the decoder which compensates channel distortions of the transmitted signal. This modification does not change the individual dynamics of chaotic systems in the synchronous state however the information signal injected into the driving system, breaks the symmetry between encoder and decoder and therefore exact recovery is impossible. We show that this approach has limited ability for synchronization of chaotic encoder. The second approach does not use adaptive compensation but relies on the design of chaotic oscillators which produce narrow-band chaotic waveforms.