Dynamic Channel Reservation to Enhance Channel Access by Exploiting Structure of Vehicular Networks

VANET protocols need to exploit the special structure of vehicular networks. This structure includes the one-dimensional nature of roads, the structure of lanes, the group mobility of vehicles, and the communication patterns of the envisaged applications. It is therefore of interest to examine how to specifically tailor VANET protocols to exploit all the above properties. In this paper, motivated by the goal of providing significantly better application level QoS, we study the MAC problem, and examine to what extent one can improve the performance of the mechanism employed in the IEEE 802.11p protocol. We design a dynamic channel reservation (DCR) protocol which leverages the special structure of VANET, and provides greater predictability in channel access, simplifying QoS provision. The key idea, in light of the periodic communication pattern of VANET applications, is to transform the per-packet channel contention mechanism of 802.11p into a per-vehicle one in DCR. We implement the protocol on NS-2 for a comparative evaluation against 802.11p under realistic VANET scenarios. DCR demonstrates lower packet loss probability and higher throughput over 802.11p, and the simulation results appear promising enough to develop a complete protocol specifically for vehicular networks.