Ensuring Connectivity in Wireless Sensor Network with a Robot-Assisted Sensor Relocation

Wireless sensor networks (WSN) are used to survey a given Region Of Interest (ROI) especially the WSNs are used to survey hazardous and unreacheable zones like military zone or frontiers, the survey of this kind of areas is very important and can prevent from terorrist events. Ensuring connectivity between all deployed sensors of the (ROI) is a challenging issue. Random technique of node deployment such as stochastic node dropping result in hole creating in some areas of the network and redundant nodes may appear in other areas. In this paper, we propose two assisted-robot algorithms in which we use redundant sensors and relocate them in order to cover holes. We exploit here the redundancy of sensors to connect the formed partitions of sensors. We propose two strategies for the robot functioning and sensor relocation, the first strategy is a grid based one, in this solution the controlled area is divided into a virtual grid and the robot movement is based on this grid, we called this strategy “Grid-Based Walk with Memorization” (GBWM). The second strategy is an island based strategy, the network is composed of a set of disconnected island and the task of the robot is to connect the formed islands, we called this strategy “Island-Based Walk with Memorization”, noted (IBWM). Through extensive simulations we show the importance of these algorithms.