Maximizing Lifetime of Sensor Surveillance Systems with Directional Sensors

In this paper, we address the maximal lifetime scheduling problem in sensor surveillance systems with directional sensors. The sensors are directional in sensing objects (or watching targets) and their sensing orientations can be adjusted dynamically. Given a set of sensors and a set of targets in a plane, each target needs to be watched all the time and a sensor can watch all the targets within its sensing range. The problem of our concern is to schedule the sensors to watch all the targets and transmit the sensed data to the base station, such that the lifetime of this surveillance system is maximized. The lifetime is the duration up to the time when there exists a target that cannot be watched by any sensor or the sensed data cannot be transmitted to the base station due to the depletion of energy of some sensors. This problem is NP-hard. We propose a heuristic method that divides the system lifetime into sessions and the sensors are scheduled to work in turn in these sessions. The heuristic method consists of two steps: (1) selecting sensors to work for each session, (2) scheduling the length of each session such that the total working time for all sessions is maximized. Extensive simulations have been conducted to demonstrate that our proposed method can significantly improve the lifetime of the system.