A Study For Maritime VHF Communication System Based On Ad Hoc Network

With the rapid development of economy,the number of ships on the sea is increasing and the maritime traffic is becoming busier.As the resource of wireless channel is limited,the situation of maritime mobile communication becomes more congested.For this circumstance,this paper provides the application of Ad Hoc network in the existing maritime VHF communication system.Ad Hoc network is a communication system which does not rely on any fixed facilities.It is a temporary,multi-hop and self-organized wireless network which is composed by a group of mobile nodes.These nodes cooperate with each other.The integration of Ad Hoc network and the maritime VHF communication system can make a larger self-organized communication scope and relieve the channel congestion.The purpose of this paper is to design a speech codecs which is used in the maritime VHF system based on Ad Hoc network.This paper introduces a speech coding technology MELP(Mixed Excitation Linear Prediction) vocoder to use on maritime VHF communication.It can decrease the transmission rate to 2.4kbps and ensure a good quality of voice at the same time.It is possible that maritime VHF communication facility can transmit digital voice signal.In this paper,it gives a brief analysis of the concept and features about Ad Hoc network.It gives emphasis on the principle of MELP encoder and decoder.The key technology of MELP vocoder is discussed,too.This paper uses the software of matlab to simulate the MELP algorithm.The implementation of MELP vocoder is achieved with TMS320VC5416 DSK as the hardware development platform and C language as the software.At last,it gives an analysis of the application of MELP vocoder.This paper introduces an advanced speech-processing technology to maritime VHF communication system and it resolves some problems in the system.It is an important part of all-digital maritime VHF communication system and it has some practical value.