Data delivery scheme for intermittently connected mobile sensor networks
In mobile sensor networks, connectivity between nodes is intermittent due to blockage of radio and nodal mobility. Consequently, the efficient delivery of packets requires nodes communicate while connectivity is reliable and delay during other times. In such cases, the challenging issue is setting delay duration at each node. In this paper, we aim to provide a reliable data delivery scheme for mobile sensor networks with an enhanced delaying technique. In the proposed scheme, nodes estimate connectivity and expect inter-encounter time with sink nodes. Connectivity is estimated based on ratio of past and present connections. When the connectivity is unreliable, nodes delay the transmission for the remaining inter-encounter duration or per-hop lifetime. Since packets are forwarded if the connectivity reaches a reliable threshold before delay time expires, delivery latency is significantly reduced. Our scheme adopts receiver-based opportunistic forwarding to reduce delivery cost. To this end, we analyze the connectivity estimation and optimal delaying technique via theory and simulation. The proposed protocol deals well with network partitioning and indefinite link disconnection, which often arises in mobile sensor networks, and satisfies the requirement for delivery latency. Simulation results show that the proposed protocol outperforms other protocols in terms of packet delivery and per packet delivery cost.