Robustness of Distributed RTLS for Dense Large-Scale Environments

Abstract

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-ofsight (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.

Integration of Directional Antennas in an RSS Fingerprinting-Based Indoor Localization System

“…Unlike omnidirectional antennas, directional antennas may report better spatial discrimination, because of their higher directivity at some angular directions. Some works have proposed exploiting directional antenna properties in a different way [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ]. In [ 44 ], a review of antennas applied for indoor localization systems can be found.…”

“…An AOA-based technique was presented in [ 45 ], where the angle was estimated from the difference between RSS captured by two directional antennas. Furthermore, [ 46 , 47 , 48 , 49 , 50 , 51 , 52 ] present similar AOA-based techniques employing directional antennas for location estimation in wireless sensor networks (WSN), reducing to two the minimum number of anchor nodes (sensor readers (SRs)) to estimate the tag position by multilateration techniques. In particular, in [ 52 ], the tag position was estimated from TOA and AOA measurements, the last one being estimated from the RSS received by an array of directional antennas.…”

High-Throughput and High-Efficiency Multiple Access Scheme for IEEE802.15.4 Based RFID Sensing

“…Unlike the common used passive tags using centralized clock broadcasted from the reader, each active tag is equipped with a self-clocked micro-controller and distributed in a large area for sensing and monitoring [4], [5]. The active RFID tags provided longer operation distance, greater memory capabilities, and richer additional functions like real-time locating capabilities are hence more desired in wireless sensing networks beyond identifying.…”