Abstract
Infrastructure-to-vehicle (I2V) group message delivery is a common operation required by a wide variety of vehicular ad hoc network (VANET) applications. However, due to the highly dynamic mobility in VANETs, I2V group message delivery remains a difficult problem to deliver messages to a group of moving vehicles scattering over the whole network. The purpose and contribution of this paper is to propose the first trajectory-based I2V group message delivery protocol, TGMD, that exploits vehicle trajectories to improve the group-message delivery performance. TGMD contains two phases. The first phase determines a small set of rendezvous points from which the member vehicles can receive the message. Then the second phase transmits the group message over multiple hops to these selected rendezvous points using a multicast-like forwarding scheme to avoid redundant packet transmissions over the overlapped road segments. The message is kept at the rendezvous points for later last-hop delivery when the member vehicles pass through. TGMD aims to minimize the required number of network-layer packet transmissions under a relatively loose delay constraint. Our extensive simulation results indicate that in comparison with the trajectory-based single-destination I2V message delivery scheme (through N-unicasting), TGMD significantly reduces the required number of packet transmissions (and thus bandwidth consumption) while achieving a high delivery ratio around 90\%.