Improving the Estimation of Residual Delay based Forwarding Method in Opportunistic Vehicular Networks

To accommodate the dynamic characteristics in opportunistic networks, "carry-and-forward" technique is utilized. In this paradigm, the next hop forwarding relay node is usually decided by inferring future contact opportunities. A practical method is to predict future encounter time using nodes\´ contact history. But limited by prediction accuracy, this method has only an uncertain effect on improving delay performance. To improve the efficiency of selected relay(s), this paper introduces a new metric used to deicide whether an intermediate node is appropriate to be selected. The metric is based on the estimation of Residual Expected Delay (RED), and combined with a threshold value to guard the fidelity of prediction based relay selection judgement. After then, a single-copy and a multi-copy two-hop forwarding algorithms are proposed. Finally, based on the underlying vehicular opportunistic network extracted from large-scale realistic vehicle trace records, we give an empirical evaluation and analysis of the proposed method. Results show the new metric is efficient in improving delivery ratio with a low delivery cost.