Study Of Spread Spectrum Communcation Based On Chaos Sequence For Power Line Communication

Power line carrier communication (PLC) is a kind of special communicationtechnology taking power line as the media conveying information, and transportinganalog or digital signal through the carrier way at high speed. Considering the powerline is the biggest line resource in world, PLC benefits from low investment, shortconstruction period, simple equipment, good safety in communications, and is good atreal-time character. However, due to the presence of unexpected high noise, multipatheffect and channel decay, PLC requires special communication mode, this thesischooses the spread spectrum system which benefits from anti-interference abilitySpread spectrum code is the key factor influencing the performance of spreadspectrum system, and the current widespread use of spread spectrum codes is msequence and gold sequence with excellent performance. But they can’t meet the needsof the secret for limited and fixed length. An effective alternative is chaos sequences,which is produced by the chaos phenomenon. They meet the performance requirementsof spread spectrum system since they are hard to predict with no cycle.Aiming to solve these problems, this dissertation does research on power linecommunication and chaotic sequence By the analysis of chaotic code generationprinciple, we discuss the application of chaotic spread spectrum system in the powerline communication. The main content of this thesis is as follows:1. Power line channel model is established by considering the channel attenuationand all kinds of noise. The spread spectrum technology is chosen for PLC afterdiscussing the advantages and disadvantages of many communication technologies.2. Through extensive analysis of chaotic sequence generation method and thestatistical characteristic, a method of establishing compound sequence is found out byanalyzing of the generation method and the statistical characteristic of chaotic sequence.The presented algorithm generates the spread spectrum sequence by quantifying themultiplication result of two independent chaos sequences.Under four chaos mapping, the performance of the composite sequence is testedand compared with single sequence, such as proportionality, autocorrelation function and power spectrum. The simulation result shows that composite sequence has betterbalance power and power spectrum, the autocorrelation function of which is more acute.3. Based on the power line channel environment, chaotic sequence is applied inspread spectrum system. The error rate is compared between the composite sequence SSsystem and the single sequence SS system during various modulation modes. At thesame time, PSK exerts stronger anti-interference ability than ASK and FSK, thus it issuitable for power line environment4. With PSK modulation, the spread spectrum system based on the optimalsequence is simulated by Simulink under the condition of the power linecommunication.According to the simulation result, spread spectrum system using new sequencewith the excellent property has exerted a better effect than using chaotic sequence inPLC. The new sequence is verified to have a great value in practice.