Approximate analysis of a multiple geocast routing among geographical regions in VANET applications

We consider VANET applications which divide urban areas into geographical regions among which aggregated information by area should be disseminated. In each region, a circular area called emitter and receiver center (ERC) is used for sending and receiving messages. Vehicles within each ERC send and receive messages to and from vehicles inside the other ERCs, defining a multiple geocast routing problem. Each vehicle to cross an ERC sends a message to the multiple destinations using the minimum spanning tree (MST) whose vertices are the ERCs, with a root node in the sender. Messages are routed between the neighboring ERCs using a point-to-point position-based protocol. The messages that arrive at an ERC are disseminated within the region using flooding. Multicast QoS parameters are mainly based on end-to-end delay measures. In VANETs, the communication link delays are random variables because they depend on the underlying vehicle flows. This paper develops an approximate model for end-to-end delay distribution based on phase-type (PH) distributions, and also examines a new QoS multicast parameter adequate to cooperative information gathering and sharing applications. The results are validated by simulation.