Experimental Evaluation of an Angle Based Indoor Localization System

In this paper, we present an experimental prototype of an indoor localization system that uses angle estimation and decentralized computations. The system uses three rotating optical beacon signal generators that are built using commonly available off-the-shelf components. Wireless sensor nodes equipped with photo sensors determine their locations from the estimated angular separations between the optical sources. No additional hardware is required at the sensor nodes. The system also does not involve any centralized server or off-line measurements, which are key requirements of RF-based localization systems. We present the design principles, possible sources of error, and the lessons learnt from building the experimental localization system. Performance results obtained from laboratory experiments are presented. The proposed system provides location estimates that are accurate within a few inches in indoor applications. In addition, the idea may be extended to large scale outdoor sensor systems where it may not be economically or physically viable to use additional localization hardware such as GPS.