ACAR: Adaptive Connectivity Aware Routing Protocol for Vehicular Ad Hoc Networks

Developing routing protocol for vehicular ad hoc networks (VANET) is a challenging task due to potentially large network sizes, rapidly changing topology and frequent network disconnections, which can cause failure or inefficiency in traditional ad hoc routing protocols. We propose an adaptive connectivity aware routing (ACAR) protocol that addresses these problems by adaptively selecting an optimal route with the best network transmission quality based on the statistical and realtime density data that are gathered through an on-the-fly density collection process. The protocol consists of two parts: (1) select an optimal route, consisting of road segments, with the best estimated transmission quality (2) in each road segment in the selected route, select the most efficient multi-hop path that will improve delivery ratio and throughput. The optimal route can be selected using our new connectivity model that takes into account vehicles densities and traffic light periods to estimate transmission quality at road segments, which considers the probability of connectivity and data delivery ratio for transmitting packets. In each road segment along the optimal path, each hop is selected to minimize the packet error rate of the entire path. Our simulation results show that the proposed ACAR protocol outperforms existing VANET routing protocols in terms of data delivery ratio, throughput and data packet delay. In addition, ACAR works very well even if accurate statistical data is not available.