A directional wireless sensor network (DWSN) consists of a number of directional sensors. Many types of directional sensors have been widely used in constructing a wireless sensor network for IoT applications. These types of sensors include infrared sensors, microwave sensors, ultrasonic sensors, cameras, and radar. Compared with an omni-directional sensor, a directional sensor can achieve better performance because it can additionally report the direction of an intruder. Unfortunately, most existing barrier-coverage mechanisms adopt omni-directional sensor networks. They cannot be efficiently applied to DWSNs because the sensing area of each directional sensor is fan-shaped. This paper investigates the surveillance service problem which supports the surveillance quality of k-barrier coverage in DWSNs. Three algorithms, called BA, BTA and BRA, are proposed which aim at finding a maximal number of different defense barriers, each of which supports k-coverage. Using these algorithms, at least k directional sensors can detect intruders intending to cross the monitoring area. Performance analyses of the proposed algorithms are conducted in Section 5 to verify the performance improvement from a theoretical point of view. In the performance study, the proposed algorithms are compared with other existing algorithms. The experimental study shows that the proposed k-barrier coverage algorithm achieves similar performance with the optimal solution but has fewer control packets. Furthermore, the proposed BRA achieves better performance in terms of the numbers of control packets and constructed defense barriers, as compared with existing algorithms.
