Sotdma Ais Applied Research

Nowadays, the communication between vessels mainly depends on the VHP on board. Because of the various kinds of languages and low efficiency of the communication, it is very easy to cause the time delay and mutual misunderstanding of the others' maneuvering intention and leads to the occurrence of the marine accidents. Among the existing navigation aids, the information provided by the radar and ARPA are very limited. It cannot identify the other vessel and conduct the communication between vessels as well. Its limitations are morn serious in the areas with the heavy traffics and seas. Meanwhile, the modern international shipping industry is developed with the larger size, high speed and full automation of the vessels for saving the cost of operation. To ensure the safety navigation of vessels and protect the natural environment of seas, it needs a new navigation aid and communication system, which is reliable for the communication between ship to ship and ship to shore. Base on this necessity and the development of new and high technology, the ship's automatic identification system (A1S) has been developed and applied.AIS is a system specially applied for the ship's collision avoidance and vessel traffic service (VTS). It can provide the identified information and real time data of the vessel's movement (position, heading, course and speed to the ground, etc.). Comparing with the radar, it can provide more real time and high quality data and information. It can be a supporting device or substitution for the radar and ARPA. AIS can also support the application of more automation technology on board vessels and it will change essentially the existing methods for collision avoidance and the models of VTS. In fact, it will bring a new revolution to the monitoring of vessels at sea.The foreign researchers have done a lot for the development of AIS, the specification and standard have been revised and updated. The devices of AIS have been put into practical use. The national research work for AIS has been developed in recent years, some institutes have stated to develop and manufacture the devices of AIS. Due to lack of the latest technical information and deep research of some core technology, such as the technology of the self-organized time division multiple access(SOTDMA), and there will still be a lot to do for the national development of AIS. For getting more study and research about the AIS, the author of this dissertation has done the following work:a. Introducing and summarizing the components, application and development of AIS according to the technical information, papers both issued at home and abroad, and the specification and standards of International Maritime Organization.,b. Studying and analyzing the core technologies, such as HDLC> OMSK, SOTDMA, mainly analyzing about the conduction of the methods for the systematic synchronism and the modulation and decode of OMSK.c. Systematically analyzing the data link of SOTDMA , communication procedure and slot selection, looking out the working flow of AIS and having some initial experimental work for the data link of SOTDMA.There will be the practical significance for the self-development of the AIS core technology through the research and analysis of the above items in this dissertation...