Robustness of Distributed RTLS for Dense Large-Scale Environments

RTLS (Real Time Locating Systems) are used to track the location of an object or person in real time. However, if there are many tags and readers, the conventional centralized RTLS server with a single location engine may fail to estimate the location of the tags. Furthermore, if the server does not receive a tag's signal due to pass loss or none line-of-sight (NLOS) from more than three readers, the server fails to estimate the location of the tag. In this paper, we propose a special reader that incorporates an RTLS location engine for distributed RTLS. Furthermore, we use a multidirectional antenna array, alleviating the multipath effect and allowing estimation of a tag's location using only two readers. To assess the performance of the system, we implement an entire RTLS system based on IEEE 802.15.4a. The experiment results show that the distributed RTLS enhances the location response time and reduces network confusion. Moreover, we can obtain the tag's location with only two readers using directional information.