A testbed for distributed target tracking with directional sensors

Target tracking is an important application of Wireless Sensor Networks (WSN). This paper presents the design of a WSN testbed that used a custom-built wireless sensor node, specifically designed for target tracking. The sensor node consists of a Digi Xbee device, a Passive Infrared (PIR) and MaxSonar ultrasonic ranging sensors. Appropriate multi-channel MAC protocols were designed and implemented. The experiments were conducted with up to 20 sensor nodes in indoor and outdoor environments, with a human target moving at pedestrian speeds. We found that directional sensing, inter-sensor interference, sensing and processing delays are significant in determining the target location. This work highlights some of the practical difficulties in realizing such systems in practice. The experiments show that the ultra-sonic ranging sensor does indeed provide improved target tracking information when compared to the PIR sensor.