Design And Implementation Of Underwater Acoustic Communication System

As a key technology in marine research,marine environmental monitoring has great significance for marine resources exploration and development,disaster early warning,military defense.Composed of the underwater sensor nodes through the acoustic link,the underwater acoustic sensor network is an effective way to realize the marine environment monitoring in the future,having the characteristic of situ monitoring,wide coverage,high spatial and temporal resolution.However,having the characteristics of high propagation delay,high ambient noise,multi-path effects,Doppler Effect,space and temporal variation random,the acoustic channel brings great challenge to the underwater information network transmission.In this paper,an underwater communication system is designed to realize the function of underwater communication and networking according to the needs of the 863 project and the channel characteristics.In this paper,we first study the characteristics of underwater acoustic channel and its influence on communication and networking,and propose the countermeasures of multipath interference and Doppler jamming.Aiming at the design requirements of underwater acoustic communication system,the communication system is designed and system function are implemented.The system uses ARM as the main control module,through the FPGA for digital signal processing,multi-threaded and parallel processing mode to ensure the efficient operation of the system.In order to meet the low power consumption and long-distance communication needs,the system sending and receiving module is designed and implemented,and the system lifetime is extended while reaching the distance index requirement.The communication coding,modulation/demodulation and synchronization module are designed and implemented,which solves the problem of low bit error rate information transmission,weak signal detection under low SNR and synchronization reference offset.Aiming at the problem of noise and multi-path interference in the underwater acoustic channel,combine with the architecture of the single-input multi-out acoustic communication system,a decision feedback receiver based on diversity combining is proposed,which can effectively improve the received signal-to-noise ratio and anti-multipath interference capability.In order to realize the network self-organization of underwater multi-node,the network protocol system suitable for underwater acoustic channel is designed to ensure the self-organization of the network and the reliable transmission of data,including the media access control protocol of the underwater acoustic link,the routing protocol and the transmission protocol.Finally,to verify the reliability of the communication and networking function of the underwater acoustic communication system,the experiment on the lake is carried out.The experiment results show that the error rate of the system at 3.3km below 10-4 and multi-node organizing network is achieved,indicating that the system can be used in underwater sensor networks.