Wireless Transmission And Communication System Of Sea Buoy Based On Spread Spectrum

With the development of marine exploration,more and more new types of buoys and sensors for marine information monitoring and collection have been invented.On the one hand,the information transmitted has gradually changed from low-speed sensor data to high-speed data such as image and video.Hence people are looking for better quality and higher speed of maritime communication.On the other hand,there are still many factors restricting the development of maritime communication system,such as poor maritime channel,limited power consumption,less spectrum resources and so on.However,the existing maritime communication systems has the problems of lower speed and higher cost.Therefore,it is of great theoretical significance and application value to develop a multi-buoy maritime wireless communication system,which can resist the severe channel and has higher transmission rate.Firstly,the research status of maritime wireless transmission system at home and abroad is studied.by studying the characteristics of maritime channel,the difficulties of maritime wireless transmission are analyzed,and the maritime channel model is constructed.Aiming at the problems of strong interference and large attenuation,the basic transmitter and receiver model of the multi-buoy wireless transmission system based on spread spectrum is proposed.Meanwhile,the basic framework and signal frame format of the system are designed.Secondly,the time-frequency synchronization algorithm of the receiver is studied.Combined with the characteristics of spread spectrum system,a time-frequency synchronization algorithm based on spread spectrum is proposed.On the one hand,using the characteristics of signal frame format and the design of symbol timing synchronization algorithm,the mode and buoy access algorithms are proposed,which achieve the expected results under the strong interference of marine channel.On the other hand,in view of the poor accuracy and high complexity of the carrier frequency synchronization,the calculation of the algorithm related window is improved,which significantly improves the estimation accuracy without increasing the complexity.The performance of the algorithm is verified by MATLAB simulation.Thirdly,the signal dispreading and demodulation algorithms are studied.In order to reduce the influence of multipath effect on the received signal,the multipath component in the marine channel is estimated.Moreover,the decision strategy of signal dispreading algorithm is designed to effectively combat the problems of extremely low SNR and sampling bias.By combing the signals and demodulating the signal based on soft decision output,the SNR gain of the system is further improved.The receiving performance of the proposed system is verified by simulation.Finally,an implementation scheme of the buoy wireless transmission system based on FPGA is proposed.According to the above theory and algorithm,the implementation scheme of the system and the circuit design scheme of the main modules of transmitter and receiver are designed,and the port list of each modules is given.The feasibility of the scheme is verified by simulation in MATLAB.