Abstract
This paper introduces a design and implementation of a base station, capable of positioning sensor nodes using an optical scheme. The base station consists of a pulse laser module, optical detectors and beam splitter, which are mounted on a rotation-stage, and a Time to Digital Converter (TDC). The optical pulse signal transmitted to the sensor node with a Corner Cube Retro-reflector (CCR) is reflected to the base station, and the Time of Flight (ToF) data can be obtained from the two detectors. With the angle and flight time data, the position of the sensor node can be calculated. The performance of the system is evaluated by using a commercial CCR. The sensor nodes are placed at different angles from the base station and scanned using the laser. We analyze the node position error caused by the rotation and propose error compensation methods, namely the outlier sample exception and decreasing the confidence factor steadily using the recursive least square (RLS) methods. Based on the commercial CCR results, the MEMS CCR is also tested to demonstrate the compatibility between the base station and the proposed methods. The result shows that the localization performance of the system can be enhanced with the proposed compensation method using the MEMS CCR.
Highlights
Wireless sensor networks consist of devices for monitoring physical world
This paper is dedicated to introducing a 2D position estimation scheme for sensor nodes in an optical sensor network and an implementation of a base station system for MEMS Cube Retro-reflector (CCR)
We evaluated the sensor node localization performance by implementing a base station system
Summary
Wireless sensor networks consist of devices for monitoring physical world. In the sensor network, the field information detected by sensor nodes, for example convoy and routing of an enemy, is delivered to a user through a base station. Topics related to sensor node position estimation in optical wireless sensor networks have not been researched properly yet. This paper is dedicated to introducing a 2D position estimation scheme for sensor nodes in an optical sensor network and an implementation of a base station system for MEMS CCR. By these processes, we provide a system for finding and communicating with MEMS-sized sensor nodes and propose error reduction methods for accurate sensor node localization determined experimentally. The content is organized as follows: Section 2 presents the 2D localization scheme using the Time of Flight (ToF) and Angle of Arrival (AoA) methods for the sensor node in the optical wireless sensor network and covers the actual implementation of the base station.
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