Research Of The Spread Spectrum Communication System Based On The Chaotic Sequence

For good security and anti-interference ability spread spectrum communication isthe key technology of the code division multiple access (CDMA) technology. Basedon the traditional pseudo random code (PN code) spread spectrum system’s practicaluse is restricted because of less available PN code block sequence number, lowsequence complexity, shortcomings of the confidentiality. So the chaotic spreadspectrum communication technology arises at the historic moment. Chaotic spreadspectrum communication system provides a new train of thought for the developmentof spread spectrum sequence study, chaotic spread spectrum sequence which isaperiodic, initial value sensitivity and of a large number became a research hot spot ofthe modern communication technology.Based on fully research of spread spectrum theory, chaos theory,MATLAB/SIMULINK simulation principle and the foundation which previousresearch on chaotic spread spectrum sequence, this paper has put forward the directspread spectrum communication system of a kind of new digital chaotic spreadspectrum sequence generation method. Firstly, the text analyses the chaotic properties,including Feigenbaum iterative trajectory and maximum Lyapunov index; Then as qspread spectrum code,the article analysis and simulate the new chaotic sequence’sproperties such as the timing diagram, initial value sensitivity, balance, the autorelevance, mutual relevance, power spectrum characteristic; Lastly, builds the chaoticDS-CDMA spread spectrum system SIMULINK model by myself, which includesNewLogistic sequence produce module, send subsystem, receiving system, the errorrate calculation module, and the parameters of the modules can change according tothe actual simulation conditions, different environment.Through the programminganalysis the new chaotic sequence’s signal transceiver waveform、spread and despreadspectrum、he system ber and other performance on the constructed chaotic direct spread spectrum communication system.The simulation results show when compared with the original logistic、Kent、Chebyshev chaotic mapping PN sequence acting on the direct spread spectrumcommunication system，the random permutation composite logistic PN’s sending andreceiving data waveform consistently; after expanding signal is submerged in noise,after demodulation receiving and send signal spectrum consistently.The simulationresults also show that in less than13db signal-to-noise ratio, four BER curve roughlycoincidence, but in more than18db,the random permutation composite logisticsequence of DS-CDMA system error rate was significantly lower than the others. Sothe random permutation composite logistic chaotic sequence’s performance is betterthan the original chaotic spread spectrum sequenceas a spread spectrum. The newmethod on creating a random permutation composite logistc sequence not onlyimproves the simulation efficiency but further improve the spread spectrumcommunication security.