Architecture and protocol design for a car-to-infrastructure packet radio network

The authors define the structure of a packet radio network which must operate in an environment characterized by the presence of mobile stations and a ground network with fixed access points. Each of these points represents a ground station with a certain coverage area which must exchange data in packet form with the mobiles over a common radio channel. Mobiles flowing along the road within the coverage area of a ground station must coordinate their access to the common channel. The design and analysis of the multiaccess protocol and the procedure for the passage from one ground station coverage area to the next along the direction of flow are considered. The resulting strategy is based on a mixture of centralized and decentralized information and actions and combines the features of ISA (an access protocol for the maximization of one-step throughput that has proved very effective) with a controlled ALOHA scheme, which is used to accept new stations within an area, either from the previous one or from outside the system. The integration of this MAC (media access control) layer protocol with existing packet radio software that also covers higher layer features (e.g., TCP/IP) is also discussed