An RFID-Based Object Localization Framework and System

Abstract

Locating objects is a key requirement in several of the emerging computing paradigms. The problem of locating objects has been extensively studied from a variety of technological and technique-oriented perspectives. Recently, Radio Frequency Identification (RFID), a wireless automated identification technology, has come forth as a viable platform for locating objects, particularly in indoor environments. While rapid advances in RFID-based object localization are evident, current approaches lack adaptability, reliability, and scalability. This thesis addresses these issues and presents an RFID-based object localization framework and system to help locate stationary and mobile objects with high accuracy. Our RFID-based object localization framework and system is resilient in select environmental conditions, accommodates numerous use-case scenarios, and is tag orientation and vendor hardware-agnostic. We demonstrate that radio signal strength, a technique used in our location system and traditionally considered unreliable, can be used as a reliable metric for locating objects in selective cases. Additionally, we show that tag sensitivity caused by manufacturing variation influences object localization performance and we present tag selection and binning techniques. This ensure range and cost-optimized uniformly sensitive tags, leading to a reliable and high-performance object localization. We further improve the object localization characteristics of our system by matching tags to readers and demonstrating that reference tags could be made optional without significant loss in performance. Rigorous experimental evidence suggests that our RFID-based object location system can simultaneously locate several stationary and mobile objects in realistic noisy indoor environments with localization accuracy in the range of 0.15-0.84 meters. We have also developed several visualization applications focusing on a variety of computing platforms to help visualize the targeted object's location. i Approval Sheet This dissertation is submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Computer Science) Kirti Chawla This dissertation has been read and approved by the Examining Committee:

An accurate real-time RFID-based location system

“…The RFID-based object localisation research landscape consists of numerous approaches that utilise techniques such as signal Angle of Arrival (AoA), signal Time of Arrival (ToA), signal Time Difference of Arrival (TDoA), signal phase, and signal strength (Azzouzi et al, 2011;Arumugam and Engels, 2009;Brchan et al, 2012;Chawla et al, 2010a;Chawla et al, 2010b;Chawla and Robins, 2011a;Chawla and Robins, 2011b;Chawla et al, 2013;Chawla and Robins, 2013b;Chawla and Robins, 2013c;Chawla et al, 2014a;Chawla et al, 2014b;Chawla et al, 2014c;Chawla, 2014;Chawla and Robins, 2015;Hekimian-Williams et al, 2010;Ni et al, 2003). In this paper, we focus primarily on signal strength-based indoor localisation approaches.…”

“…However, these have tended to provide poor localisation performance and limited applicability (Bechteler and Yenigun, 2003;Bekkali et al, 2007;Wang et al, 2007;Zhang et al, 2007;Zhao et al, 2007). Furthermore, few approaches have addressed the key challenges that preclude high performance, robustness, and scalability, while maintaining reasonable solution cost (Chawla et al, 2010a;Chawla et al, 2010b;Chawla and Robins, 2011a;Chawla and Robins, 2011b;Chawla and Robins, 2012;Chawla et al, 2013;Chawla and Robins, 2013b;Chawla and Robins, 2013c;Chawla, 2014;Chawla and Robins, 2015). Given the current state of the art, there remains significant research work to be done in the utilisation of RFID technology for object localisation.…”

“…We show that in addition to such sources of environmental interference, further localisation performance degradation is caused by the highly variable radio sensitivity of tags due to manufacturing inconsistencies. Few RFID-based object localisation approaches currently account for tag sensitivity variation and thus either suffer from low localisation performance, high cost or both (Chawla et al, 2010a;Chawla et al, 2010b;Chawla and Robins, 2011a;Chawla and Robins, 2011b;Chawla et al, 2013;Chawla and Robins, 2013b;Chawla and Robins, 2013c;Chawla, 2014;Chawla and Robins, 2015;. To mitigate the variability in tags' radio sensitivity, we propose the technique of sorting tags based on detection sensitivity and only using uniformly sensitive tags for localisation.…”

“…We propose to locate tags attached to stationary and mobile objects by establishing power-distance relationships correlating the tags' RSS behaviour with tag-reader distance. However, given that radio frequency signal behaviour can vary considerably in a given environment, theoretical power-distance relationships cannot directly be used to reliably locate tags (Chawla et al, 2010a;Chawla et al, 2010b;Chawla and Robins, 2011a;Chawla and Robins, 2011b;Chawla et al, 2013;Chawla and Robins, 2013b;Chawla and Robins, 2013c;Chawla, 2014;Chawla and Robins, 2015;Finkenzeller, 2003). We assume that the average environment-specific impact on a tag's RSS is statistically invariant due to our focus on well-characterised applications.…”

RFID-Based Smart Shelving Storage Systems

“…depends on number of reference tags; by using few of them, the accuracy can be notably reduced; on the contrary, a better localization accuracy can be achieved if using many reference tags, despite of less available readings for each target tag and higher computational cost. Obviously a bound exists after which by increasing the number of reference tags the computational cost increased without improving the localization accuracy [39]. It is noteworthy that, as alternative to reference tags and multiple readers deployment, the RSSI could be employed to determine an accurate empirical path loss model as in classical indoor scenario [40]- [41], but the Friis equation cannot be used to describe a power-distance model in scenario of the same order of the wavelength, as in smart shelves at the UHF band, and a more-complicated accurate path loss model should be derived.…”