Study On The Key Technologies In Underwater Acoustic Communication System

Acoustic communication is a very challenging and complex reserch topic in the field of water technology. With the characteristics of high ambient noise level,very narrow bandwidth,low carrier frequency,enormous propagation latency and time-space-frequency variant multipath effect(MPE),the stochastic ocean channel is very complex and difficult to achieve reliable UWA communications. It is still very difficult to achieve low bit error rate and high data rate in uderwater acoustic communication system.So acoustic communication becomes one of the most complex technologies in nowadays.In this paper, the acoustic communication system is designed for a unmanned underwater vehicle which is used in a real-time monitoring system of depth for the port channel. When the submersible dives to a certain depth, this acoustic communication system can provide underwater communication instead of VHF to ensure real-time communications between the remote control platform and the submersible verhicle.First of all,we analysised the marine water channel's transmission characteristics and it's impact to the acoustic communication.Then we introduced several modulation techniques which are commonly used in the current acoustic communication and the corresponding demodulation principle and methods.Furthermore,we conducted a more in-depth analysis of the techniques,such as balance, diversity, error control technology to ensure the communication performance.Next we studied the performance, the working principle and use methods of Model LinkQuest's modem UWM10000. We also test its performance parameters to provide a more adequate parameter information to complete the formation of acoustic communication system.And then we complete a applicable acoustic communication system at the core of this modem including the designs of the hardware system and the control software.This acoustic communication system mainly composed of the host computer hardware remote control systems, shore-based transfer control systems, acoustic modem UWM10000, stepper motor and the underwater control system. PC software is composed of 4 parts : remote control interface, shore-based information transfer, underwater messaging and motor rotation control.After sea experiments we proved that this underwater communication system can achieve acoustic communication and we also verified the reliability under different conditions.The system is valueable in project and it can be applied to the measurement of underwater vehicle system which can complete the underwater communications.