Congestion-aware and hybrid routing protocol for vehicular ad hoc network

In vehicular ad hoc network (VANET), nodes have to cooperate to forward each other´s packets through the networks. Every node, including source and intermediate nodes, has a fair opportunity to transmit a packet. Consequence, the hot spot may incur traffic congestion. The packet loss rate and the transmission delay are increased, but the throughput is decreased. On account of the contention for the shared channel, the throughput of each single node is limited not only by the channel capacity, but also by the transmissions in its neighborhood. Additionally, the network throughput still restrict by the channel capacity. Some other related works using multiple channels simultaneously to transmit packets without interfering each other increases the throughput. But if the traffic load is heavy, these schemes may trigger off more serious packet loss on the contrary because they do not consider the congestion problem especially in VANET environment. In this paper we use cross layer approach to design routing protocol for VANET with aim to restrict the number of packets of every flow passing by congested nodes. Firstly, we estimate congested probability at each node by using MAC overheads, quality of link, and data rate. Subsequently, we use congested probability assessment as route metric. This method enhances link stable and network throughputs. For building routing protocol operation we use hybrid model (inherit good chacters from proactive and reactive routing protocols). It helps restrict route overheads and fast convergence of route discovery process. The simulation results illustrate our prominent proposed routing protocol.