Sensitivity Study of Sensors´ Coverage within Wireless Sensor Networks

The coverage problem in wireless sensor networks is to place sensor devices in a service area so that the entire service area is covered/sensed. We have modeled the coverage problem as two sub-problems: floorplan and placement. The floorplan problem is to partition the service area into well-defined geometric cells, whereas the placement problem is to assign the sensor devices into a set of cells. The cardinality of the set of cells is considered as all possible candidate locations to place the sensors; therefore, we transformed the search space from continuous to discrete. Thus, we have reduced the complexity of the coverage problem, but we have merged the two sub-problems (floorplan and placement) into a single optimization problem to achieve good solutions. The objective function is to maximize the coverage of the service area while not exceeding a given budget. The merged optimization problem has been coded into the evolutionary approach. We have conducted five studies, where three studies compare the behavior of coverage ratio, cost, and radius of coverage of all allocated sensors with the number of generations separately. The fourth study examines the cell size versus coverage ratio. The fifth study looks at the average number of neighbors covered by a sensor with respect to the generations. Our experimental results present interesting findings in all five studies and our computerized evolutionary methodology generates solutions under 5 minutes.