Research And Implementation Of AIS Protocols

In recent years, with the development of marine technology and business transportation, the number and speed of vessels continually improved, so that the increase in maritime traffic density put forwards new demands for collision avoidance, traffic control and navigation and port safety .In this situation, radar and VHF radiotelephone cannot meet the marine safety requirements, so AIS comes into being.By time synchronization, AIS stations obtain slot information .When in the initialization stage AIS stations obtain slot status by monitoring the channel, and then AIS stations select Nominal Transmission Slot in the light of four kinds of information transmission protocols and transfer messages after packaging. When receiving messages receiving stations should decoding data in accordance with corresponding format, and identify slot's status for the future choice of stations'transmission slot.Based on the study of AIS transmission protocols, by using VC++, the design realize transmission protocols and AIS main functions according above. The achievement of the design is showed as flows:1. The design realizes AIS protocols of RATDMA, SOTDMA and ITDMA and information packaging by using C language, easier for transplanting to the hardware platform.2. The design using client program as shipboard AIS device ,by using multi-threading technology and network communication technology and the timing thread achieving slot synchronization ,achieves messages'transport to each other.3. The paper achieves AIS continuous operation of stages of initialization, network logon, first frame, continuous operation and change the reporting rate.