Design and Implementation of AIS Link Layer Using SDL-RT

AIS (automatic identification system) is an advanced maritime navigation system mainly used to improve safety on the sea. It exchanges navigation data with other vessels and with coastal monitoring stations on VHF maritime mobile band. It is based on a self-organized medium access network and relies on the use of a GPS receiver to compute and transmit boat positions. To bring about such a network and ensure its reliability, the nodes must be designed with stringent requirements in mind. In this paper we propose to design and implement the link layer, and therefore the medium access process, of the AIS system. Specification and description language real time (SDL-RT) which is a real time extension of SDL is used to design the system. SDL-RT offers a hierarchical graphical tool which facilities system complexity management, functional testing capabilities and optimized code generation. The generated code is implemented and tested on a digital signal processor (DSP).