Research And Design On Chaotic Spread Spectrum Sequence Base On Cascade

In recent years, the technology of CDMA has been more widely used, which isbased on spread spectrum communications technology. With the development of thetimes, the traditional spreading code increasingly prominent defect in performance.We need a new sequence which has ideal relevance, balance and sufficient quantity tobe spreading code in spread spectrum communication system to satisfy the growingneeds of users in contemporary communications.The application of chaos theory in the field of communications provides a newidea to solve this problem. Chaos is a deterministic stochastic phenomena generatedby the nonlinear system. Because of its non-cyclical, not bounded convergence,highly sensitive to the initial value and other characteristics, in this paper this idea todesign a new type of chaotic spreading sequence has been introduced. The majornonlinear systems to produce chaotic spreading sequence are Logistic map andChebyshev map. Their initial sensitivity, auto-correlation, cross correlation andbalance has been analyzed. The affect for the performance on the sequence of theselection of their parameter, the initial value and the truncated length has beenresearched.Single-stage chaos mapping method has some inadequacies, for example, theinitial value of the sequence number generation caused by limited accuracy is limited,the mapping system complexity does not lead to information easily intercepted high,there may be a sequence generated periodic windows, etc. So in this paper animproved cascade chaotic spreading sequence which is based on cascade method hasbeen present, and excellent performance of the improved cascade chaotic spreadingsequence has been vivificated through simulation. Finally, one optimization method ofsequence has been designed. And it has been comparative analyzed with theperformance of traditional single-stage mapping chaotic spreading sequence to verifyits superiority.The improved cascade chaotic spreading sequence which is designed in thispaper has excellent chaos, initial sensitivity, auto-correlation, cross correlation,balance. And it also has quite adequate number of available sequences. It can makethe system has a good anti-jamming, anti-attack, anti-interception and carrier leakagesuppression capabilities. It also can provide very adequate user capacity in a CDMAsystem. With further research in the future, the improved cascade chaotic sequencewill have good value and development prospects.