Monitoring Quality Optimization in Wireless Sensor Networks with a Mobile Sink

The exploitation of sink mobility has been proven to improve various network performance significantly, including network lifetime, data delivery latency, network connectivity, and so on. In this paper we consider a novel network model consisting of sensors, gateways, and a mobile sink, which can be applied to many realistic applications such as city traffic monitoring, patients monitoring, and forest fire surveillance. We assume that there is a roadmap in the monitoring region for the mobile sink to access, and gateways are located on roads. The mobile sink moves at a constant speed along a closed tour of roads to collect data from gateways. The travelling distance of the mobile sink per tour is bounded by a given value. Due to the limited communication time between the sink and each gateway, sometimes it is not possible for the mobile sink to collect the data generated from all sensors, consequently causing monitoring quality loss. In this paper, we study the problem by formulating it to find a closed tour for the mobile sink, such that the monitoring quality loss is minimized, subject to the tour length constraint. Since the problem is NP-hard, we propose a heuristic for it. Also, we design an energy-efficient routing protocol for data collection that balances the energy consumption among sensors. We finally conduct extensive experiments by simulation to evaluate the performance of the proposed schemes. The experiment results show the effectiveness of the proposed heuristic to optimize the network performance.