I. Introduction
Wireless sensor networks (WSNs) have emerged as an attractive technology which can gather information by the collective effort of numerous sensor nodes [1]. Due to many attractive characteristics of sensor nodes such as small size and low cost, WSNs were adopted by extensive applications. One of the important applications is target tracking, such as vehicle tracking, and migration behaviour of animals tracking. In such application scenarios, the sensor nodes collectively monitor the roaming path of moving targets in the area of deployment. Since the sensor nodes are always deployed in an unattended environment, it is very difficult to replace their battery after the deployment. As a result, tracking the moving target and gathering the sensed information from the sensor nodes surrounding the target in an energy-efficient way is a critical design issue for target tracking WSNs.