Towards Two Hops Opportunistic Relaying with the Estimation of Residual Expected Delay
Jia Jianbin, Chen Yingwen, Xu Ming, Yu Gu, Xie Bo and Xiao Xiaoqiang
Opportunistic forwarding leverages the intermittent connectivity to delivery data in opportunistic networks using a “Carry-and-forward” way. In this technique, to determine the next hop relaying node is important for delivery performance. A traditional method is to predict the future encounter time using nodes’ contact history. But limited by prediction accuracy, this method has only an uncertain effect on improving forwarding performance. To improve opportunistic relaying efficiency, this paper introduces a new metric used to decide whether an intermediate node is appropriate to be chosen as a relay. The metric is based on the estimation of Residual Expected Delay (RED), and combined with a threshold value to guard the fidelity of relay judgement. Based on these, we devise a single-copy and a multi-copy two-hop forwarding algorithms. Finally, using the opportunistic network extracted from realistic vehicle trace records, we make simulations to evaluate our proposals. Results show the new metric and threshold based method is efficient in improving delivery ratio with a low delivery cost.
Keywords: Opportunistic networks; relay selection metric; residual expected delay