Optimal path planning strategies for monitoring coverage holes in Wireless Sensor Networks

A Wireless Sensor Network (WSN) consists of sensor nodes, which are typically small low-power devices that occasionally have movement capabilities. These nodes monitor their neighbourhood for pertinent environmental changes and any detected events are relayed to a data sink for further analysis. Due to an imperfect initial deployment of sensor nodes, regions may form that are not within the sensing area of the any of the sensor nodes. These areas are referred to as "coverage holes" and may be covered using one or more mobile sensor nodes. Since coverage holes can be dispersed throughout the sensing region, efficient path planning of the mobile node(s) is critical to maximize area coverage in the lowest trip time. In this paper, we propose three Mixed Integer Linear Programming (MILP) formulations to guide a mobile node in an optimal manner. The goal is to route the mobile node in such a way that the required level of coverage can be achieved within a specified time. The first formulation maximizes area coverage, while the second and third minimize the required time. The performance of the MILPs is evaluated through simulations using various network sizes, node sensing and movement capabilities. Comparisons with heuristics and existing approaches in the literature clearly demonstrate that the proposed formulations can achieve superior results in a reasonable time frame. (C) 2019 Elsevier B.V. All rights reserved.