The Research On Amphibious Acoustic-electric Joint Communications Network Technology

Along with the people to further study and utilization of marine resources, underwater acoustic communication has been paid more and more attention. Most existing studies focus on how to improve the underwater acoustic channel bandwidth utilization ratio and reduce the error rate, less concern for real time. In fact, in marine seismic monitoring, marine and military application, underwater acoustic communication system on real-time requirements are very high. Therefore, how to reduce the communication time delay, improve the real-time performance of underwater acoustic communication should also become the focus of research in the field of underwater acoustic communication.At present, the land wireless communication technology to be applied directly to the underwater acoustic channel is put in a lot of problem, such as: underwater acoustic transducer energy restriction, the narrow bandwidth of underwater acoustic channel, severe multipath effect and intersymbol interference. What's more,for real-time systems, the long transmission delay of underwater acoustic communication is a factor that cannot be ignored.: average transmission rate of ultrasonic in water transmission is 1500m / s, but the electromagnetic wave in the air transmission speed is 3×108m / S, which means that the time cost caused by signal transmission cannot be ignored. Therefore, the land wireless communication protocol is not completely suitable for underwater acoustic communication. So,the most important problem is how to find the available channels and effectively guarantee the real-time communication. Therefore, for the specific application which requests high real-time performance, based on underwater acoustic channel characteristic, this paper presents a surface acoustic electric combined communication networking method. According to the characteristics of underwater acoustic delay,it uses spectrum prediction technique to find the available channel,and then uses those channels for multi channel parallel transmission. The main work and innovation are as follows:1. The environment of underwater acoustic channel is so special that lots of factors are needed to be considered for underwater acoustic channel modeling , such as the channel bandwidth, transmission delay, multipath effect, Doppler effect, fluctuation effects and transmission attenuation.This paper analyzes several classical acoustic channel model.2.Analyses the cognitive radio spectrum detection and spectral prediction algorithm,and mainly focuses on three classical predition modles:Markov chain model,ON/OFF model POMDP model. As the Marcov chain prediction model has a lower prediction error rate,this paper improves the spectrum prediction algorithm that based on Markov chain model and makes it suitable for underwater acoustic channel.The MATLAB simulation results show that the prediction error rate of Marcov chain model is lower than ON-OFF model.3. Propose a amphibious acoustic-electric joint communications method of communication, sending data in parallel using multi-channel mix, and joints communications buoys to achieve underwater acoustic communication. Then describes in detail the basis of relevant theories, procedures and work flow of this communication method. Also,this paper uses MATLAB software to do a simulation of its performance. The results show that the new method can greatly reduce the collision back-off delay, improve the communication of real-time.