Geographic Routing Enhancement for Urban VANETs Using Link Dynamic Behavior: A Cross Layer Approach

Geographic routing protocols are suitable for VANETs because of their scalability and low overhead. However, the optimal selection of next-hop forwarding nodes is challenged by the dynamic topology of VANETs, in addition to the variable quality of wireless links and the temporal changes in available bandwidth. In this paper, we introduce a scheme to select the next-hop forwarder based on its mobility relative to the destination and the dynamic behavior of its link with the current forwarder. We present a cross-layer model of link dynamic behavior (LDB), which takes into account the loss ratio, physical interference, and medium access control (MAC) overhead, including queuing and retransmission delays experienced on a wireless link. Based on LDB, we propose an enhancement of geographic routing, called Geo-CAP, for urban VANETs. By selecting more reliable links and timely reacting to varying nodes load and network conditions, the proposed protocol can offer considerable performance gains by reducing packet loss and delay. This performance is demonstrated using extensive simulation experiments in NS-3.