A Distributed Token Passing Protocol for Time Constrained Data Gathering in VANETs

This paper proposes a novel approach for time constrained information gathering in a typical Vehicular Ad Hoc Network (VANET), based on a token passing scheme, adapted to wireless communications by creating a virtual ring where nodes are connected to a predecessor and a successornode. To address the typical fast topology changes of VANETs, we proposed a specific approach called Tom Thumb, that is a distributed protocol that node-by-node circulates a special packet, called token, which collects the information stored in each vehicle until returning to the first unit within a specified time constraint. The protocol has been properly designed in terms of (i) the more effective hop-by-hop and distributed heuristic implementing the objective function ii) the token packet format, i.e., the syntax and semantics of its fields. Finally, the performance of the proposed approach is validated for different time constraints and numbers of vehicles, always pointing out a remarkable gain, especially in the presence of severe constraints, i.e., in terms of time deadline, collected information amount and success probability.