Network Coding-Based Flooding with a Mobile Sink in Low-Duty-Cycle Wireless Sensor Networks

Network coding and schedule-based flooding trees have been widely deployed to improve the performance of a flooding process in low-duty-cycle wireless sensor networks (WSNs). However, the conventional schemes induce too long flooding delay because there is only one static sink node as a single source. In this paper, we use a mobile sink to travel around the monitoring area. When the mobile sink travels to a position, it serves as a new source. Since multiple sources can simultaneously forward data packets, flooding speed can be accelerated. We investigate the new problems when both a mobile sink and network coding are integrated with a schedule-tree-based flooding scheme. We model the process to deliver multiple encoded packets from the source to a node as a Markov process, and we theoretically investigate how to minimize the total expected flooding delay with a mobile sink by considering all the possible traveling orders of the branches. We propose a heuristic algorithm to obtain an appropriate trajectory by accounting for the effect of traveling delay of the mobile sink. Simulation results show that our proposed flooding scheme with a mobile sink can significantly reduce the flooding delay.