Generating Chaotic Spread Spectrum Sequences And Its Applications In Spread Spectrum Communication

Spread spectrum communication uses much larger bandwidth than required by spreading original information using pseudo noise (PN) sequences. A spread spectrum receiver then uses the synchronized replica of the pseudo noise sequences to recover the original information. Due to this pseudo noise property of the spreading sequences, spread spectrum communication can work at low power spectral density and has many good characters such as anti-noise, anti-interference, anti-multipath effect, multiple access, efficient frequency usage. It has been applied widely in civil mobile communication and military communication. It is well-known that the spreading sequences generation is first step for achieving spread spectrum communication, and the auto-correlation property and cross-correlation property of the spreading sequences are very importance for spread spectrum communication. Research has showed that conventional PN has low complication and low security, et al. In addition, PN sequences with good correlation property are not many enough. Chaos is produced by deterministic nonlinear systems, its phenomena is pseudo random. Because chaotic systems exhibit sensitivity to initiaI conditions, they can generate many enough PNsequences with good correlation propertyIn this article, the methods of generating cbaotic spreadspectrum sequences by using chua's circuit, logistics-map, andcoupled map Iattice are studied. The characters of these 8equencesare also anaIyzed such as auto-correlation property andcross-correIation property We find a fact that chaotic spreadspectrum sequences have well enough auto-correlation propertyand cross-correIation property chaotic sequences can repIaceconventional PN sequences in spread spectrum communication andimprove communication system property such as capacity In orderto exam the feasibiIity of chaotic sequences applying for real spreadspectrum teIecommunications, we anaIyze the EBR in AWGNchannel in theoretics and give BER formula. The feasibiIity ofchaotic sequences are able to be used in spread spectrumcommunication systems is proved by theoretic calculation andMonte CarIo method simulation. In the last chapter of tbe article,BER that chaotic spread spectrum sequences apply in mobilesatellite spread spectrum communication system is studied.