Study Of The Key Technique Of Building VHF DSC Wireless Communication Network And Realization Of The System

The transportation on the sea has been playing an important role in our life. In recent years, because of the increasement of the traffic of vessels and of the tonnage of transport and of the speed of vessels, the condition of maritime traffic has become more and more crowded and dangerous. The safety of vessels has become the most important problem to be resolved.VHP DSC (Very High Frequency Digital Selective Call), as a main means of alarm, is very important for the vessels to navigate safely. However, at present the number of digital shore-stations of VHP DSC is limited. And its spread characteristic of visibility range has decided the coverage range of VHP only to be a round area of 25 n miles from the shore-station. Additionally, it tends to be influenced by the conditions and terrain of the ocean, which will certainly bring the blind area and cannot realize the seamless coverage. So the VHP has some difficulty to communicate efficiently with ships in distress to deal with their alarms. The safety information of vessels cannot be reported credibly to the shore station in time, which makes the so call assistance SAR difficult to be realized. Accordingly this paper brings such a design as building VHP DSC area network, to realize the seamless coverage of the safety information of the vessels in the offing and within the port area and to ensure the safety of navigation. This paper firstly brought out the design project of the system. And then discussed the modulations of the baseband signal relative to the network, including two level FSK and GMSK, and it also introduced the data format of DSC.The emphasis of this paper is how to realize the system designed. On the basis of the experiments, and by advanced computer technique it has has improved the VHP DSC device and successfully built the communication platform of software and hardware. And it transferred the VHP DSC network. In this system any alarm data from a ship or many ships within its area network should be sent rapidly to the local control center, and it can communicate with the designate base station in VHP CH16. The control center should monitor the no-man base station.Finally, by testing of the system it proved that the data format and the system flow were satisfied with the requirement of the VHP DSC 's function, and the data information can be ensured to transmit credibly and efficiently. The research, according to the requirement of VHP DSC of many countries, based on the actuality of VHP DSC in our country, response to the national "tenth-five" project, has overcome the limitation of VHP DSC and developed its coverage range and ensured the safety of communication between vessels.