Research On Chaos Based Signal Processing And Secure Communications

Chaotic signal processing, especially its technical aspects have beeninvestigated increasingly and intensively during last decades in various applicationsdue to its attractive properties, such as strong sensitivity to initial conditions andparameters, non-periodicity, uncorrelativity, long-term unpredictability and its broadpower spectra similar to random noise, which coincide with requirements for signalsapplied to communication systems, particularly for spread-spectrum communications,multi-user communications and secure communications (cryptography). In thisdissertation, we focus the research on chaos control and synchronization, chaoticsignal processing, chaos research in underwater acoustic engineering and chaoticpseudo random generator which can be applied to chaotic communication andcryptography. The main research work and new ideas are as follows:1,A brief review on the development, current status and existing problems ofchaos-based communication is presented. Emphases are put on the securityperformance and hardware implementation in chaos-based communication system.2,Based on summary of various methods for chaos control and synchronization,two novel means of chaos control and synchronization are presented, one for theunified chaotic system and the other for chaotic systems with different order. In themean time, adaptive and observer-based chaos control and synchronization methodare studied.3,A practical method for determining the embedding dimension of underwateracoustic signals is proposed, which can effectively lessen the computational costcompared with conventional methods.4,Two optimization methods are proposed, chaos-based Differential Evolutionalgorithm(CDE) and chaos-based particle swarm optimization algorithm (CPSO),which could greatly increase optimization speed, convergence and searchingcapability. These methods are feasible, efficient and robust, and can be applied tovarious optimization aspects.5,A brief survey on chaos-based research in underwater acoustic engineering isgiven, focus is put on the feasibility of applying chaos-based techniques tounderwater communications, which would pave the way for practical applications inthe near future. 6,A new method to construct chaotic pseudo random sequences which has goodstatistical properties is proposed. Applications include conventional cryptology, suchas image encryption, and chaos-based communication, such as spread-spectrumcommunications.7,A new method to construct chaotic hopping sequence with large hop gaps isgiven, which could provide the theoretical guidelines for engineering applications,and can be applied to chaos-based frequency hopping communication, such as lowrate long-range underwater information transmission.Finally, perspective of chaos-based communication is addressed in this thesis andfew questions are raised towards possible future research work in this area.