CHAOS BASED DIGITAL MODULATION TECHNIQUES IN COMMUNICATION SYSTEMS

Abstract

This dissertation investigates various chaos-based digital modulation techniques, with the aim of studying their performance in various environments and identifying scopes for their application in various fields. Chaos in dictionary meaning may be tunnoil, but from physics point of view is really order, in the guise of apparent disorderliness. Chaos in nonlinear deterministic systems is guided by the steady state behaviour of the system and extremely sensitive towards initial conditions. This property leads to noise-like correlation values, which makes chaos signals well-suited for secure communication, without requiring additional hardware and power for signal encryption, and thus reducing system cost. The main focus of our work is on chaos-based digital modulation techniques. Over past few decades many modulation techniques have been proposed, but in terms of BER performance only a few schemes have been widely investigated. Our goal is to properly investigate the important techniques and their performance in various transmission environments. A new, exthanced technique for modulation has also been proposed, which can yield relatively better performance at reasonable SNR levels than most other techniques. Also, the possibility of application of noncoherent chaotic communication techniques in Ultra-Wideband impulse radio communication systems has been explored. In UWB-IR noncoherent communication, mainly the low data-rate UWB multipath fading channel indoor environments have been considered. The scope and performance of our scheme in UWB environment also has been evaluated. Overall, it can be concluded that application of chaos-based modulations in UWB radio systerns is feasible and it can provide relatively secure spread spectrum communication in UWB environment at much lesser cost than the conventional communication systems