Chaotic Sequence And Its Applied Research In Communication System

As a random-like phenomenon in non-linear deterministic dynamical system, Chaos widely exists in the real world. Because chaos is extremely sensitive to initial conditions of the chaotic system, and a large number of non-periodic, continuous broadband frequency spectrum, noise-like, yet deterministic and reproducible signals can be generated, it has natural concealment. What's more, chaotic signals can't be forecast for a long term, and it is very complicated, and easily realized, the application of chaos theory has been one of important issues and forefront project. Based on applications of chaotic technology in contemporary secure communication, some deeper researches has been performed, the following innovative results are given:1. The PN sequence of CDMA communication system is focused in the thesis, mainly including generation and performance analysis of chaos direct spread sequences. Firstly, an improved chaos map (varying-parameter Tent chaos map) is put forward. Owing to the bifurcation parameter varied in a limited range, and chaos is sensitive to initial condition, the security of communication system is greatly enhanced. And a kind of new chaotic spread-spectrum sequence is presented, the performance of PN code is calculated and simulated. Results show the chaotic spread-spectrum sequence has good properties. Then, both varying-parameter Tent chaotic sequence and Tent chaotic sequence are applied to the model of direct spread CDMA system and the error rate of system is demonstrated, the simulation results further indicate that the multiple-access interferences (MAI) from other users and the multiple-path interference (MPI) using the presented chaotic sequence are very small, they can be used as spread-spectrum sequence because of their excellent properties.2. Application of hyperchaos signals to encryption of active images is studied, a new method for encryption of active images utilizing...