Simple relocation methods in wireless sensor and robot networks

Abstract

The random deployment scheme is easy to implement in Wireless Sensor and Robot Networks (WSRNs). However, with this manner sensors do not ensure full coverage of the Region Of Interest(ROI). So, new problems are emerging in the network such as the existence of uncovered areas (coverage holes) or areas covered by more than one sensor (redundant sensors). Consequently, it is important to pass through a post-deployment phase after a random deployment to improve the area coverage. In this phase, robots are used to carry redundant sensors to fulfill the holes. In this paper, we propose two solutions to deal the problem of sensors relocation. The first one is Simple Relocation Method (SRM) in WSRN. The preliminary phase is a random distribution of the sensors in a bounded and unknown ROI. Once the determination of holes and redundant sensors is completed, the robots move in ROI to relocate nearest (from local information) redundant sensors from their current positions in the nearest hole to increase the coverage. In this proposal, the robots do not explore all area unlike to the most of solutions proposed for relocation. The second solution is the Clustering Relocation Method (CRM) and it is an improvement of the first. In CRM, we added the clustering principle, to minimize the number of messages circulating in the network. Simulation results show the effectiveness of these solutions in terms of relocation time and messages sent.