The Research And Implementation Of Transmission Content Of NAVDAT Security Information

NAVDAT is a new kind of marine wireless digital communication system.It broadcast maritime security information and related imformation from shore to ship at 495kHz~505kHz,and the center frequency is 500 kHz.It is brought into e-navigation by IALA as the important component.In 2012,it was added into IALA Maritime Radio Communications Plan,as the important part of modernization of GMDSS.It can be used as a supplementary system to the current NAVTEX.NAVDAT is similar to NAVTEX in its coverage,but the transmission rate is more than 200 times of the latter.NAVDAT system can transmit the information by text message,file message(data or picture)and so on.In addition,NAVDAT system has three ways to broadcast information to satisfy its professional requirements,which are general broadcast,selective broadcast and point-to-point broadcast.NAVDAT system has been in the stage of practice.The main works of this paper are to study the system's information transmission content and information broadcast technology on the basis of current achievement in NAVDAT system.On basis of current maritime safety information service,combining NAVDAT system data transmission characteristics and investigation and analysis of current status of maritime security service system,and many other factors,eventually determine the content of information transmission system.Explore the information broadcast technology through the forma,pattern,structure,priorities and time-sharing schedule of information.It can provide some help and references for actual use and business operations of NAVDAT in the future.The study begins with tracking dynamic information about NAVDAT in order to master the current situation and its prospects.It firstly starts from the architecture and transmission characteristics and working principle of NAVDAT system in order to provide the theory basis for broadcast technology research.Through the research on NAVDAT transmission types and diagnoses on Maritime Safety Information and service requirements,it preliminary design the content of NAVDAT information as an operation work of the system.Learning information transmission protocol and coordination work procedures from the current NAVTEX system,it carries out the research in the aspects of information broadcast mode,setting of radio stations,structure of safety information,format of sending and receiving information,time-sharing working as well as the information transmission priority setting,etc.,and form a complete output.