The Key Technology Researching Of Underwater Measurement And Control Link

The physical layer of the underwater measurement and control link is basic to realize the transmission of the measurement and control instruction, message and data in underwater measurement and control networks. And its main role is to solve the establishment of the inter-node communication channel and the modulation and demodulation of the communication message, and meanwhile it supplies the upper applications such as time synchronization and positioning navigation with steady and reliable sending and capture mechanism. Due to the complicated variety of the underwater acoustic channel, its model would vary on the environmental parameters, and many of its properties such as multi-path effect, Doppler frequency shift, transmission loss and marine noise would also have a huge impact on the transmission of acoustic signals. As a result, we need to adopt perfect modulation and demodulation algorithm and steady signal sending and capture mechanism to reduce the impact of the underwater acoustic channel to insure the inter-node communication quality of the link.This paper sets about the properties of the underwater acoustic channel, and researches on the modulation and demodulation techniques of the underwater acoustic signals, devising time synchronization signals for the upper precise time synchronization application, and also, it has put forward high-precision time synchronization signals capture method on condition of multi-path and taken verification tests at the node of homemade underwater measurement and control. The main work of this paper includes the following aspects:(1)This paper analyzes and summarizes the properties of the underwater acoustic channel, including multi-path effect, Doppler frequency shift, transmission loss, marine noise and so on. Based on this, this paper proposes a simplified underwater acoustic channel model based on the practical situation, which made up of Transducer signal transmission model, Input signal model and Simplify the underwater acoustic channel decline model. This paper has also made a model simulation in MATLAB and compared it with send -receive signals of actual acoustic channel.(2)On accounts of the complicated variety of the underwater channel, in order to insure the In order to ensure the effective transmission of the underwater acoustic signals, this paper has studied on three modulation and demodulation methods of the underwater acoustic signals, and it has also simulated the modulation and demodulation algorithm of these signals and drawn some useful conclusions.(3)In order to realize high-precision time synchronization in the underwater measurement and control link and overcome the multi-path effect and the Doppler frequency shift influence on time synchronization signal, this paper has analyzed the properties of several common sonar signals and devises the high-precision underwater time synchronization signal. Based on this, it compares the properties of underwater time synchronization signal under ideal circumstance with the one under multi-path, and it proposes the capture and error correction method on condition of multi path.(4)The paper designs general underwater measurement and control node test platform, and in the platform, it has taken a series of key technology experiments related with the physical layer of the underwater measurement and control link, and has achieved good results.