A fail safe broadcast protocol for collaborative intelligent vehicles

This paper presents a broadcast protocol that makes cooperative driving applications safer. Collaborative driving is a rapidly evolving trend in intelligent transportation system. Current communication services provided by vehicular ad-hoc network (VANET) cannot guarantee fail-safe operation. We present a fail safe broadcast protocol (FSBP) that resides between the cooperative driving applications and VANET to make the cooperative driving applications work in a safer way. The protocol uses synchronized clocks with the help of GPS to schedule the broadcast transmissions of the participants. Electing not to transmit at a scheduled time is a unique message that cannot be lost because of a noisy or lost communication channel. This message is used to abort a collaborative operation and revert to an autonomous driving mode, similar to the current generation of intelligent vehicles, in which a vehicle protects itself. We describe a particular, simple protocol that uses a token passing mechanism. We specify the protocol as a finite state machine and use probabilistic verification to verify the protocol. This is the first formal verification of a multi-party broadcast protocol.