Research On System Of Wireless Chaos DS-SS Communication Based On Automatic Hydrologic Telemetering System

Wireless communication plays a key role in the Automatic Hydrologic Telemetering System(AHTS) because of the system's feature about geographic distribution. Nowadays the major communicating mode of the AHTS in China is the VHF Relay Channel(VHF-RC). The multipath interference, resulted from interfering between the signals of the Line of Sight (LOS) and the line of ground reflection in VHF-RC, makes Bit Error Rate of data transmission increased and system reliability attenuated. Besides, traditional modes, such as AM and FM without spread spectrum, cannot meet requirements of hydrologic data transmission in the adverse circumstances during the high-water or tide season, since those modes are easily interfered and have high Bit Error Rate. Based on the analysis of VHF-RC, the method of applying Chaos Direct Sequence Spread Spectrum Communication (CDS-SSC) to AHTS has been studied and discussed in this thesis.In this method, CDS-SSC, which combines Chaos Sequences(CS) of high rand quality with DS-SS excelling in resisting interferences, is used to realize the transmission of hydrologic data. The finite precision effect brought by the digital realization of CS and the deterioration of the Sequence's properties caused by interception have been studied. Moreover, after analyzing the effect of the existing ways to improve the performance of CS, especially the perturbation, the effectness of a kind of Chaos Sequence Generator by means of Software High-Precision Computation (SHPC) has been disscussed. Finally, with the optimized chaos sequences, the results of software simulation on VHF-RC indicates that DS-SS outbalances the BPSK system without spread spectrum due to BER and the DS-SS with Kent sequence is better than the one with Golden sequence in some extend.