Chaos Direct Sequence Spread Spectrum Technology And Its Applications, In The Covert Channel

Spread Spectrum Communication is the principal technology in the military communication.Possessing the strong ability of anti-jamming, anti-fading, anti-interception as well as low spectral density,direct sequence spread spectrum(DSSS) is widely used in the modern military field.The spreading code with good randomicity and correlation have a decisive effect on the performance of communication system.The discovery of chaotic dynamic system broad the way of study of PN sequence.Chaos is a convinced and random kind course that appears in the nonlinear system.It is an unperiod and an irregular course.It is not convergence but dose have a bound,while it is sensitive to its initial value.For all these special performance,chaos has an excellent outlook in the application of telecommunication,especially in the generation of PN sequence.In this paper, we have a deep discuss in DS-SS system, analysis the structure of the system, then we come to PN sequence used in DS-SS system and introduce chaos to the study of PN sequence. Taking Logistic sequence as representation, we analysis its randomicity, correlation and linear complexity,and how to obtain binary sequence. Aiming at the characteristic of DS-SS system, some criteria on optimizing spreading sequences are proposed. The method of choosing is also presented. According to the method, chaotic spreading sequences with better performance are obtained. The FPGA implementation scheme of IF software radio is researched. Based on the scheme, the universal hardware platform of IF software radio is designed and implemented.At the same time, we are trying to seek a method of designing secret channel in DS-SS communication system, and analysis its performance. The original symbol in the secret channel is firstly spread by a short PN code, and then part of the long used in the basic channel. As a result, the secret channel would present excellent anti-interception performance.