PMTR: Privacy-Enhancing Multilayer Trajectory-Based Routing Protocol for Vehicular Ad Hoc Networks

In this paper we present a trajectory-based routing protocol for vehicular ad hoc networks (VANETs) that routes messages using historical vehicular traffic statistics and coarse privacy-preserving trajectory information provided by vehicles. The protocol is well suited for the initial deployment stage of VANET when the number of VANET-enabled vehicles and roadside units will be very low. Coarse trajectory information preserves privacy of carrier vehicles by allowing vehicles only to report their intended rough travel regions instead of detailed travel paths, and historical vehicular traffic statistics ensure high success rate of message delivery. We have compared the proposed routing protocol with three other routing protocols: a flooding type protocol, a geographical or position-based protocol, where message is greedily forwarded towards destination location using carriers´ destination information (GeoDest), and a geographical or position-based protocol using carriers´ exact trajectory information (GeoTrace). Simulation results have shown that our proposed protocol performs better than GeoDest and equally well or better than GeoTrace (while GeoTrace does not protect carrier vehicles´ privacy). Further, it has far less overheads as compared to Flooding and performs equally well as Flooding in one of the operating modes.