High-accuracy and low-cost localisation scheme for wireless sensor networks

Recently, wireless sensor networks have been used in many promising applications including military surveillance, wildlife tracking, habitat monitoring and so on. They are an indispensable requirement for a sensor node to be able to find its own location. Many range-free estimate approaches eliminate the need of high-cost specialised hardware, at the cost of a less accurate localisation. In addition, the radio propagation characteristics vary over time and are environment dependent, thus imposing high calibration costs for the range-free localisation schemes. In order to reconcile the need for the high accuracy in location estimation, we describe, design, implement and evaluate a novel localisation scheme called laser beam scan localisation (BLS) by combining grid and light (laser) with mobile localisation policy for wireless sensor networks. The scheme utilises a moving location assistant (LA) with a laser beam, through which the deployed area is scanned and Zigbee platform is adopted for experiments in this article. The LA sends IDs to unknown nodes to obtain the locations of sensor nodes. High localisation accuracy can be achieved without the aid of expensive hardware on the sensor nodes, as required by other localisation systems. The scheme yields significant benefits compared with other localisation methods. First, BLS is a distributed and localised scheme, and the LA broadcasts IDs while unknown nodes listen passively. No interactive intersensor communications are involved in this process; thus, sensor energy is saved. Second, BLS reaches a sub-metre localisation error. Third, because the equation is simple, computational cost is low. Finally, BLS is a low-cost scheme because it does not require any infrastructure or additional hardware for sensor nodes.