International Journal of Grid and Distributed Computing Vol. 11, No. 10 (2018), pp.11-28 http://dx.doi.org/10.14257/ijgdc.2018.11.10.02 ISSN: 2005-4262 IJGDC Copyright ⓒ 2018 SERSC Australia Fault Tolerant and optimal Barrier Coverage for Critical Area Monitoring 1 Tariq Benahmed 1* , Khelifa Benahmed 2 and Zeyneb Mokeddem 3 1,3 Department of Computer science, Tahri Mohamed University, ENERGARID Lab, Bechar, Algeria 2 Department of Computer science, Tahri Mohamed University, Bechar, Algeria 1 tarikben3@gmail.com, 2 benahmed_khelifa@yahoo.fr, 3 mokeddem34@gmail.com Abstract Detecting an intruder through the use of barrier coverage is one of the existed applications in wireless sensor networks (WSN). When the intruder is trying to cross the border of the critical area, or move inside it, the deployed WSN should monitor and detect any presence of intruder and generate an alarm to alert the operator to look this specific area. Several solutions have been proposed in the literature like the problem of coverage in wireless sensor networks, which became currently a crucial field of research, especially the barrier coverage for intruder detection. In this paper, we present a new algorithm based on mathematical models, whose objective is to ensure the coverage of our barrier with a minimum possible number of sensors. The idea is to calculate the number of sensors needed to cover a barrier before deployment. We then formulate the problem to minimize the number of sensors to be deployed to properly cover a barrier. Furthermore, we propose a fault-tolerant mechanism, which will be able to detect faulty sensor nodes in the active barrier and activate other sensor nodes in other barriers to ensure a minimum number of sensor nodes needed for a complete coverage barrier. Our simulation results show the validity of our analytical studies and the effectiveness of the proposed algorithms. Keywords: wireless sensor networks, barrier coverage, intruders detection, critical area monitoring, optimal sensor deployment, fault tolerance 1. Introduction The wireless sensor network has emerged as an important means for monitoring the environment. A wireless sensor network is a set of sensors that can detect a specific event, process it and send the information. The sensors can generally deploy in hostile environments in the purpose to monitor and truck some phenomena, we can found this in several kind of applications, such as battlefield surveillance, border surveillance, intruder detection, vehicle tracking, etc., [1, 2, 3]. The sensor nodes are characterized by being limited in resources in the capability of processing, capacity of memorizing, bandwidth of communication and energy. The nodes are usually powered by a battery. Therefore, the associated battery influences directly on the life time of the network. In most cases, they are deployed in a hostile environment where it is very difficult or impossible to replace batteries. the most crucial challenges in wireless sensor networks is how can minimize the energy consumption to prolong the lifetime of the networks [4]. Furthermore, in the field of wireless sensor network, one of the fundamental issues is how to ensure the optimum coverage of the interested area, which allows to recognize the monitoring level of the critical area. The coverage is the concept that introduced due to several viewpoints among Received (May 26, 2018), Review Result (July 17, 2018), Accepted (August 4, 2018) * Corresponding Author