The Key Technology Researching Of The VHF-VoIP Gateway

As the center of maritime traffic command and control,Vessel Traffic Service(VTS)aims at increasing maritime transportation efficiency and reducing maritime accident etc.VHF communication subsystem is an important part of VTS,which provides guarantee for voice communication function of transportation between VTS center and ships.But traditional VHF communication system use the special shore-based VHF communication equipment,which has defects such as high engineering cost and poor extensibility.VoIP technology is gradually used for VTS,and still has many problems due to using the exist voice technology of commercial version and makes no adjustment and improvement for VHF communication.Therefore,VHF communication system has the problem of asynchronous communication between voice and control signals,as well as the incomplete and poor quality in the voice transmission.This thesis mainly studies a set of VHF communication subsystem based on VoIP technology and marine VHF equipment.Firstly,aiming at VHF equipment,the overall design scheme of VHF communication system is proposed based on VoIP technology,and the key modules of each part of VHF-VoIP gateway are designed and analyzed.Secondly,in order to overcome the shortcomings of asynchronization between voice and control signals in VHF communication subsystem,two VTS network packet models are proposed.The voice and control signals are packaged through the networking protocol,which can solve the problems of incomplete and poor quality of voice transmission effectively.Contrastive analysis for compression codec algorithm of LPC,DPCM,ADPCM and CS-ACELP.Using CS-ACELP speech codec algorithm,the improved VAD pre-coding algorithm with simple structure is proposed.Under circumstance of high compression ratio,algorithmic complexity is simplified and real-time and flexibility for VHF communication is improved.This topic result shows that VHF-VoIP gateway not only implement the real-time call between VHF terminal and VHF transceiver,but also realize the remote control and state of receipt between VHF terminal and base station VHF transceiver in VTS.Meanwhile,the digital transmission and digital control management of voice communication in the VHF information system have been optimized.This topic also solves the existing problems in the VHF communication subsystem implemented by VoIP technology of VTS system.Through using VHF-VoIP gateway,the application of VHF in the VTS system can be realized.