The Study Of Chaotic Spread Spectrum Sequence And Its Application In Spread Spectrum Communication

Today, with the fast fierce development of personal communication technology, people havea higher request upon communication. The CDMA system based on spread spectrum technologywill be attached more importance for its advantage of anti-jam and anti multi-access. For aspread spectrum communication, the performance of system will be directly decided by thespread spectrum code of the generator. Thus for the signal source, how to improve theperformance of spread spectrum code become an important issue for a spread spectrumcommunication system.New idea was proposed for spread spectrum sequence research by the discovery on chaoticdynamics. Chaotic phenomenon is a determinate and random process in non-linear dynamicsystem, which is non-periodic, non-convergent, but limitary, depending on initial valuesensitively. This particular characteristic of chaos makes it fit for communication especially inapplications of generating the spread spectrum codes. The research on spread spectrumcommunication was firstly conducted in this article, secondly the theorem of communication wasanalyzed, and the usual code in spread spectrum system was also studied. Then finally the basiccharacteristic of chaos was introduced. It was substituted in the spread spectrum communicationaccording to the correlation and variance of spread spectrum sequence.Based on the logistic-map, an optimized method of generating the spread-spectrumsequences was proposed. In this method, an initial value was given and iterated in the logisticmap, then L bit qualification was done to every point, in this way, new spread spectrum sequencewould be achieved by shorten. It was compared with conventional chaotic code and GOLD codeand finally simulated in the DS-CDMA systems. Another classic chaotic map (Tent map) wasdone by the same way; a satisfied answer was got too. By this method, the advantage was asfollows: the iterative times were reduced and the calculating speed was improved. Thespread-spectrum sequences could be reshaped with any length. The address number of thesesequences was larger than gold sequence in being and The BER (bit error ratio) was reduced. Atlast the best quantification order was got by many experiment. These results had some referencevalues to the research on spread spectrum code in spread spectrum communication.