New algorithms for improving the probability of strong barrier coverage using mobile nodes

This thesis treats the problem of the network coverage in randomly deployed wireless sensor networks. Placing the nodes quasi-randomly is often the only way of deploying the network in geographically inaccessible regions. This way of deployment is often present in military applications. In military applications, high quality of the network coverage is usually a primary goal, despite the fact that the nodes cannot be placed manually in the optimal positions where they would all together provide the highest coverage, a certain degree of robustness, and redundancy, by using the minimum number of nodes. Bearing in mind that this kind of installation is usually realized by using artillery or the aircrafts, before approaching the energy, security, and reliability optimization, it is important for the application to meet the basic functionality, i. e., it is important for the values of the basic parameters that provide a certain degree of the network coverage and connectivity for a given area of interest to be assessed. The area of interest can be a region of any shape. In military applications, it is usually the region of size 5-20km2. If the aim is for the whole area to be covered, we deal with the area coverage. Another usual example of the appliance of the wireless sensor networks in military applications is related to the detection of intruders while attempting to cross the line between two regions. In this case, we deal with the barrier coverage. This thesis covers the modeling of the stochastic implementation of the wireless sensor networks, the analysis of the area and the barrier coverage, as well as the methods for improving the barrier coverage by using mobile nodes or robots. Under the initial assumptions and approximations, the conditions for an expected degree of the specific types of coverage are given for those types of coverage whose quality can be expressed in terms of the expected detection probability. But, regarding the strong barrier coverage, instead of assessing the coverage quality, only the information on barrier coverage creation can be derived, i.e., a strong barrier coverage can either be accomplished or not accomplished. According to the theoretical results from literature, it can be concluded that the full barrier coverage can be achieved almost always if the very strict conditions are met. These conditions, however, are hard to be provided. Therefore, in this thesis, two algorithms for creating the full barrier coverage, by filling