Performance Analysis And Simulation Of The New Chaotic Spreading Sequence

The CDMA (Code Division Multiple Access)communication system which is basedon spread spectrum technology has the advantages of becoming the mainstreamtechnology in the third generation mobile communication standards.The performance ofspreading cords which play the role of spread spectrum in a direct sequence spreadspectrum have a direct impact on system,so the PN sequence selected is crux of theDS-SS system.In the spread spectrum communication system，The limited sequence length andnumber of m sequences and Gold sequences which are generated by maximum lengthlinear shift register will restrict the system capacity.The discovery of chaotic dynamicsprovides a new idea for the spreading sequences. Chaotic sequence generation, as a newspreading spectrum technique, has been extensively investigated in its application area ofwireless spreading spectrum communication systems for some years. Currently the studyof advantages of chaotic spreading spectrum (CSS) over conventional direct spreading(DS) technique has become a key topic.First in-depth discussion of the spread spectrum communication system,the model isgiven and the focus of analysis architecture principles based on Direct Sequence SpreadSpectrum system.Followed by a brief introduction of chaos theory and chaotic dynamicsto the study of the spreading sequence,giving the characteristics of the definition,themean and the correlation function of the four classical chaos map.Then have a brief introduction of the m sequence,Gold sequence and propose a newchaotic sequence based on the series sequence.Giving a specific construct and analyzethe pseudo-random features of the new sequence,compared with the conventional chaoticsequence and the m sequence Gold sequence. Finally,build a simulation model of the DSsystem in the Simulink platform,observe the error number of the chaotic sequence spreadspectrum code system and compare the system BER with different sepreading code.Simulation results and theory analysis shows that the characteristics of the chaoticsequence meet the requirements of pseudo-random sequence and avoid the appearance of periodic windows effectively.The improved sequence maintained the characteristics ofthe chaotic sequence and the method is simple, easy-to-copy,so it is suitable forDS/CDMA spread spectrum communication system.