The IMO has recommended on VHF digital communications operation for sailing ships from 2017. In addition, domestic ship of more than 5tons is obliged to digital communications by Fishing Vessels Act and Vessel Safety Act in domestic. Therefore, owner of all vessel is equipped to the automatic position reporting device in accordance with the Notice of the Ministry of Oceans and Fisheries to regulations.
On the one hand, IMO and IALA have undertaken projects that GMDSS modernization and e-Navigation, which is refer to "Future digital communications systems" for a more efficient transmission of voice and data communications in the VHF maritime mobile service.
ITU has also resolved in WRC-07 Resolution 357 to study the use of spectrum efficient technologies in order to provide for the operation of ship and port security and maritime safety systems. IALA and ITU WP5B have established a joint liaison to coordinate the technical developments and the spectrum issues. Since the last WP5B meeting, that had approved the Recommendation ITU-R M.1842. This revision had provided a wideband data service in both 50㎑ and 100㎑ bandwidths in the VHF maritime mobile service.
It shall be ensure to navigations safety and in order to respond quickly in the event of maritime accidents on all vessels. Already, our country has been set up in east sea, which is now underway the annual install plain to the yellow sea and the south sea for VHF digital communications coast stations. But this plan was very difficult that poor of propagation environment for many islands and complex coastline.
This paper has analysed on the propagation environment for VHF digital communications in south sea area. Therefore, it has invested measurement of noise level and communications coverage simulation for selection of location coast stations in south sea, and ship tracking methode for navigation route by RSSI comparison between the VHF coast stations.