RFID Localisation For Internet Of Things Smart Homes: A Survey

The Internet of Things (IoT) enables numerous business opportunities in fields as diverse as e-health, smart cities, smart homes, among many others. The IoT incorporates multiple long-range, short-range, and personal area wireless networks and technologies into the designs of IoT applications. Localisation in indoor positioning systems plays an important role in the IoT. Location Based IoT applications range from tracking objects and people in real-time, assets management, agriculture, assisted monitoring technologies for healthcare, and smart homes, to name a few. Radio Frequency based systems for indoor positioning such as Radio Frequency Identification (RFID) is a key enabler technology for the IoT due to its costeffective, high readability rates, automatic identification and, importantly, its energy efficiency characteristic. This paper reviews the state-of-the-art RFID technologies in IoT Smart Homes applications. It presents several comparable studies of RFID based projects in smart homes and discusses the applications, techniques, algorithms, and challenges of adopting RFID technologies in IoT smart home systems.Comment: 18 pages, 2 figures, 3 table

RePos : relative position estimation of UHF-RFID tags for item-level localization

Radio frequency identification (RFID) technology brings tremendous applications in location-based services. Specifically, ultra-high frequency (UHF) RFID tag positioning based on phase (difference) of arrival (PoA/PDoA) has won great attention, due to its better positioning accuracy than signal strength-based methods. In most cases, such as logistics, retailing, and smart inventory management, the relative orders of the objects are much more attractive than absolute positions with centimetre-level accuracy. In this paper, a relative positioning (RePos) approach based on inter-tag distance and direction estimation is proposed. In the RePos positioning system, the measured phases are reconstructed based on unwrapping method. Then the distances from antenna to the tags are calculated using the distance differences of pairs of antenna's positions via a least-squares method. The relative relationships of the tags, including relative distances and angles, are obtained based on the geometry information extracted from PDoA. The experimental results show that the RePos RFID positioning system can realize about 0.28-meter ranging accuracy, and distinguish the levels and columns without ambiguity

Digital Beamforming Techniques for Passive UHF RFID Tag Localization

Radio-frequency identification (RFID) technology is on the way to substitute traditional bar codes in many fields of application. Especially the availability of passive ultra-high frequency (UHF) RFID transponders (or tags) in the frequency band between 860 MHz and 960 MHz has fostered the global application in supply chain management. However, the full potential of these systems will only be exploited if the identification of objects is complemented by accurate and robust localization. Passive UHF RFID tags are cost-effective, very small, extremely lightweight, maintenancefree, rugged and can be produced as adhesive labels that can be attached to almost any object. Worldwide standards and frequency regulations have been established and a wide infrastructure of identification systems is operated today. However, the passive nature of the technology requires a simple communication protocol which results in two major limitations with respect to its use for localization purposes: the small signal bandwidth and the small allocated frequency bandwidth. In the presence of multipath reflections, these limitations reduce the achievable localization accuracy and reliability. Thus, new methods have to be found to realize passive UHF RFID localization systems which provide sufficient performance in typical multipath situations. In this thesis, an enhanced transmission channel model for passive UHF RFID localization systems has been proposed which allows an accurate estimation of the channel behaviour to multipath. It has been used to design a novel simulation environment and to identify three solutions to minimize multipath interference: a) by varying the channel interface parameters, b) by applying diversity techniques, c) by installation of UHF absorbers. Based on the enhanced channel model, a new method for tag readability prediction with high reliability has been introduced. Furthermore, a novel way to rate the magnitude of multipath interference has been proposed. A digital receiver beamforming localization method has been presented which uses the Root MUSIC algorithm for angulation of a target tag and multipath reducing techniques for an optimum localization performance. A new multiangulation algorithm has been proposed to enable the application of diversity techniques. A novel transmitter beamforming localization approach has been presented which exploits the precisely defined response threshold of passive tags in order to achieve high robustness against multipath. The basic technique has been improved significantly with respect to angular accuracy and processing times. Novel experimental testbeds for receiver and transmitter beamforming have been designed, built and used for verification of the localization performance in real-world measurements. All the improvements achieved contribute to an enhancement of the accuracy and especially the robustness of passive UHF RFID localization systems in multipath environments which is the main focus of this researc

A review of RFID based solutions for indoor localization and location-based classification of tags

Wireless communication systems are very used for indoor localization of items. In particular, two main application field can be identified. The former relates to detection or localization of static items. The latter relates to real-time tracking of moving objects, whose movements can be reconstructed over identified timespans. Among the adopted technologies, Radio-Frequency IDentification (RFID), especially if based on cheap passive RFID tags, stands out for its affordability and reasonable efficiency. This aspect makes RFID suitable for both the above-mentioned applications, especially when a large number of objects need to be tagged. The reason lies in a suitable trade-off between low cost for implementing the position sensing system, and its precision and accuracy. However, RFID-based solutions suffer for limited reading range and lower accuracy. Solutions have been proposed by academia and industry. However, a structured analysis of developed solutions, useful for further implementations, is missing. The purpose of this paper is to highlight and review the recently proposed solutions for indoor localization making use of RFID passive tags. The paper focuses on both precise and qualitative location of objects. The form relates to (i) the correct position of tags, namely mapping their right position in a 2D or 3D environment. The latter relates to the classification of tags, namely the identification of the area where the tag is regardless its specific position

Location estimation in smart homes setting with RFID systems

Indoor localisation technologies are a core component of Smart Homes. Many applications within Smart Homes benefit from localisation technologies to determine the locations of things, objects and people. The tremendous characteristics of the Radio Frequency Identification (RFID) systems have become one of the enabler technologies in the Internet of Things (IOT) that connect objects and things wirelessly. RFID is a promising technology in indoor positioning that not only uniquely identifies entities but also locates affixed RFID tags on objects or subjects in stationary and real-time. The rapid advancement in RFID-based systems has sparked the interest of researchers in Smart Homes to employ RFID technologies and potentials to assist with optimising (non-) pervasive healthcare systems in automated homes. In this research localisation techniques and enabled positioning sensors are investigated. Passive RFID sensors are used to localise passive tags that are affixed to Smart Home objects and track the movement of individuals in stationary and real-time settings. In this study, we develop an affordable passive localisation platform using inexpensive passive RFID sensors. To fillful this aim, a passive localisation framework using minimum tracking resources (RFID sensors) has been designed. A localisation prototype and localisation application that examined the affixed RFID tag on objects to evaluate our proposed locaisation framework was then developed. Localising algorithms were utilised to achieve enhanced accuracy of localising one particular passive tag which that affixed to target objects. This thesis uses a general enough approach so that it could be applied more widely to other applications in addition to Health Smart Homes. A passive RFID localising framework is designed and developed through systematic procedures. A localising platform is built to test the proposed framework, along with developing a RFID tracking application using Java programming language and further data analysis in MATLAB. This project applies localisation procedures and evaluates them experimentally. The experimental study positively confirms that our proposed localisation framework is capable of enhancing the accuracy of the location of the tracked individual. The low-cost design uses only one passive RFID target tag, one RFID reader and three to four antennas

ReLoc: Hybrid RSSI- and phase-based relative UHF-RFID tag localization with COTS devices

Radio frequency identification (RFID) technology brings tremendous advancements in the Industrial Internet of Things (IIoT), especially for smart inventory management, as it provides a fast and low-cost way of counting or positioning items in the warehouse. In the last decade, many novel solutions, including absolute and relative positioning methods, have been proposed for this application. However, the available methods are quite sensitive to the minor changes in the deployment scenario, including the orientation of the tag and antenna, the materials contained inside the carton, tag distortion, and multipath propagation. To this end, we propose a hybrid relative passive RFID localization method (ReLoc) based on both the received signal strength indicator (RSSI) and measured phases, which orders the RFID tags horizontally and vertically. In this article, the phase-based variant maximum likelihood estimation is proposed for lateral positioning, and the RSSI profiles of two tilted antennas are compared with each other for level distinguishing. We implement the proposed positioning system ReLoc with commercial off-the-shelf RFID devices. The experiment in a warehouse shows that ReLoc is a powerful solution for practical item-level inventory management. The experimental results show that ReLoc achieves an average lateral and level ordering accuracy of 94.6% and 94.3%, respectively. Notably, when considering liquid or metal materials inside the carton or tag distortion, ReLoc still performs excellently with more than 93% ordering accuracy both horizontally and vertically, indicating the robustness of the proposed method

Diseño y aplicaciones de sistemas de antenas inteligentes para redes inalámbricas en el contexto de la internet de las cosas

[SPA] Esta tesis doctoral se presenta bajo la modalidad de compendio de publicaciones. Las antenas de onda de fuga (LWA) consisten en una estructura de guía de onda que permite la fuga de parte de la potencia a lo largo de la estructura. Por esta razón, la radiación de la antena se produce por la fuga de energía. Para producir una radiación coherente, es necesario controlar esta tasa de radiación a lo largo de la estructura radiante. Así, ajustando con precisión la tasa de radiación, se controla la forma del diagrama de radiación. Las LWAs han sido ampliamente estudiadas por la comunidad científica debido a sus ventajas, tales como, red de alimentación simple, alta directividad y escaneo en frecuencia pasivo. Sin embargo, presentan ciertas desventajas entre las cuales, la más importante a destacar es el efecto de beam-squinting. Éste se produce por la propiedad dispersiva inherente a este tipo de antenas. Además, presentan dificultades a la hora de generar radiación coherente en las direcciones broadside y endfire, aumentando la complejidad del diseńo para la radiación en dichas direcciones. Las LWA han sido relativamente poco utilizadas en aplicaciones prácticas hasta la fecha, a pesar de sus ventajas. Las pocas aplicaciones en las que se han utilizado son los radares de onda continua modulada en frecuencia y los sistemas de enfoque controlado en frecuencia de campo cercano. Esta tesis propone el uso de las LWAs en aplicaciones prácticas aprovechando las ventajas mencionadas anteriormente y teniendo en cuenta los inconvenientes de este tipo de antenas para que su uso no sea limitado. Recientemente, las LWAs han sido propuestas para aplicaciones de localización de bajo coste, ya que permiten el diseńo de estructuras planas con haces directivos. Además, debido al aumento exponencial del uso de la tecnología, es necesario encontrar nuevas tecnologías para una transmisión de datos mayor, más rápida y más eficiente, manteniendo bajos costes de fabricación. Por lo tanto las LWAs pueden ser una solución crucial al mezclar bajos costes de fabricación, alta integrabilidad en diferentes sistemas debido a su tecnología impresa planar y alta directividad al mismo tiempo que se aprovecha su característica dispersiva que proporciona un escaneo pasivo en frecuencia. En este contexto, la principal aportación de esta Tesis consiste en el estudio, análisis, diseńo e integración de LWAs en aplicaciones reales y prácticas. Esta Tesis presenta las siguientes tres contribuciones principales, definidas en los tres bloques principales de este documento: • Estudio y análisis de LWAs para su uso en sistemas de estimación de dirección de llegada basados en técnicas de amplitud de monopulso. Comparar las características y prestaciones de las LWAs junto con las antenas comerciales más utilizadas. Para ello, diseńar y fabricar las HWM-LWAs con el fin de comparar sus prestaciones con las antenas de panel adquiridas comercialmente. Dado que cada aplicación requiere el diseńo de una HWM-LWA nueva y diferente, estudiar y proponer una técnica eficiente de análisis y diseńo de antenas para obtener fácilmente diagramas de radiación monopulso escaneados en frecuencia. • Una vez analizado que las HWM-LWA son una solución factible para su uso en aplicaciones reales de localización debido a sus diversas ventajas. Integrar las HWM-LWAs diseńadas en sistemas digitales para estimación del ángulo de llegada en interiores. Por lo tanto, diseńar, desarrollar, configurar e integrar las LWAs en diferentes sistemas basados en las bandas de frecuencia Wi-Fi ISM de 2,4 GHz y 5 GHz. Finalmente, comparar los resultados de estimación obtenidos con otras soluciones propuestas para corroborar que los LWAs pueden ser utilizados en aplicaciones reales. • Asimismo, debido a su bajo coste de fabricación y a su principal propiedad de escaneo en frecuencia. Ampliar el uso de las LWAs para la localización angular en redes de sensores inalámbricas (WSN) utilizando la banda de frecuencias UHF de 900 MHz. Utilizando así etiquetas RFID pasivas. También estudiar su aplicabilidad en WSNs utilizando etiquetas LoRa activas. Este documento se presenta como una Tesis por compendio, por lo que se presentarán y explicarán brevemente los 4 artículos de revistas que se han publicado durante el programa de doctorado. Además, también se presentarán algunos artículos de conferencias y otros trabajos en revisión para exponer algunas de las investigaciones que no han sido publicadas en revistas hasta la fecha de depósito de tesis. El documento está organizado como se indica a continuación: En la Introducción, se presenta una contextualización del estado del arte y una explicación rigurosa sobre las LWAs y las aplicaciones anteriormente mencionadas. Las dos partes siguientes se vi dedican a presentar y explicar brevemente los trabajos publicados que contribuyen a esta Tesis. En la parte II, se presentan los cuatro artículos que conforman el compendio. Esto es, el análisis de las LWAs para la estimación de la dirección del ángulo de llegada y la integración de las LWAs en sistemas de localización digital usando el protocolo Wi-Fi en el Capítulo 1, la banda de frecuencias ISM UHF 900 MHz se utiliza junto con los HWM-LWAs en el Capítulo 2, luego se implementa en un sistema en tiempo real para la estimación de la dirección de llegada de múltiples tags pasivos en el Capítulo 3 y la integración de LoRa en el Capítulo 4. Finalmente, en la Parte III, se discuten las conclusiones generales y las futuras líneas de investigación. [ENG] This doctoral dissertation has been presented in the form of thesis by publication. Leaky-Wave Antennas (LWA) consist on a waveguide structure which allows the leakage of part of the power along the structure. For this reason, the radiation of the antenna is produced by the leakage of power. In order to produce coherent radiation, it is necessary to control this leakage rate along the radiating structure. Thus, precisely adjusting the leakage rate, the shape of the radiation pattern is controlled. LWAs have been widely studied by the scientific community due to their advantages, such as, simple feeding network, high directivity and passive frequency-scanning performance. However, they present certain disadvantages among which, the most important to highlight is the beam-squinting effect. TThis is due to the inherent dispersion property of this type of antenna. In addition, LWAs present difficulties when generating coherent radiation in broadside and endfire directions, increasing the complexity of the design for radiation in these directions. LWAs have been relatively unused in practical applications to date, despite of their benefits. The few applications in which they have been used are frequency modulated continuous wave radars and near-field frequency controlled focusing systems.This thesis proposes the use of LWAs in practical applications by exploiting the advantages mentioned above while taking into account the drawbacks of this type of antennas so that their use is not limited. Recently, LWAs have been proposed for low-cost localization applications, as they allow the design of planar structures with directive beams. In addition, due to the exponential increase in the use of technology, it is necessary to find new technologies for higher, faster and more efficient data transmission while maintaining low manufacturing costs. Therefore, LWAs can be a crucial solution mixing low manufacturing costs, high integrability in different systems due to their planar printed technology and high directivity while taking advantage of their dispersive characteristic that provides passive frequency scanning. In this context, the main contribution of this Thesis consist of the study, analysis, design and integration of LWAs in real and practical applications. This Thesis presents the following three main contributions, defined in the three main blocks of this document: • Study and analysis of LWAs for its use in direction of arrival estimation systems based on monopulse amplitude techniques. Compare the characteristics and performance of LWAs along with widely used commercial antennas. For this purpose, design and manufacture the HWM-LWAs in order to compare their performance with commercially acquired panel antennas. Since each application requires the design of a new and different HWM-LWA, a main objective of this block is to study and propose an efficient antenna analysis and design technique to facilitate obtaining frequency-scanned monopulse patterns. • Once analyzed that LWAs are a feasible solution for its use in real localization applications due to their several advantages, integrate the designed half-width microstrip (HWM-LWAs) in digital indoor angle-of-arrival estimation systems. Therefore, design, develop, configure and integrate LWAs in different systems based on the Wi-Fi ISM 2.4 GHz and 5 GHz frequency bands. Finally, compare the obtained estimation results with other proposed solutions to corroborate that LWAs can be used in real applications. • Extending the use of antennas for angular localization in sensor networks using the 900 MHz UHF frequency band: the main properties of low manufacturing cost and passive frequency beam scanning can be used in other applications. Thus, the localization estimation of passive RFID tags is studied, as well as their application in Wireless Sensor Networks (WSNs) using active tags with LORA technology. This document is presented as a Thesis by compilation, so the 4 journal articles that have been published during the Ph.D program will be presented and briefly explained. Besides, some conference articles and other work under review will be also presented to expose some of the research that has not been published in journals. The document is organized as outlined hereafter: In Part I, a state-of-the-art contextualization, a rigorous explanation about LWAs and the previous applications mentioned above is presented. The next two parts are dedicated to present and briefly explain the published works included in this Thesis and their main contributions. In Part II the explanation of the four papers which compose the compendium are presented. This is, LWAs analysis for direction of arrival estimation and the integration of LWAs in digital Wi-Fi localization systems in chapter 1, the UHF 900 MHz ISM frequency band is used in conjunction with HWM-LWAs in chapter 2, then, it is implemented in a real time system for direction of arrival estimation of multi RFID tags in chapter 3 and LoRa integration in chapter 4. Finally, in Part III, the overall conclusions and the future research lines are discussed.Esta tesis doctoral se presenta bajo la modalidad de compendio de publicaciones. Está formada por un total de cuatro artículos. Article 1.-: A. Gil-Martinez, M. Poveda-Garcia, J. A. Lopez-Pastor, J. C. Sanchez-Aarnoutse and J. L. Gomez-Tornero, Wi-Fi Direction Finding with Frequency-Scanned Antenna and Channel Hopping Scheme IEEE sensors Journal, , vol. 22, no. 6, pp. 5210-5222, 2022. DOI: 10.1109/JSEN.2021.3122232. Article 2.-: A. Gil-Martinez, M. Poveda-Garcia, D. Cañete-Rebenaque, and J. L. Gomez-Tornero, Frequency-Scanned Monopulse Antenna for RSSI-based Direction Finding of UHF RFID tags IEEE Antennas and Wireless Propagation Letters,, vol. 21, no. 1, pp. 158-162, 2022. DOI: 10.1109/LAWP.2021.3122232. Article 3.-: A. Gil-Martinez, M. Poveda-Garcia, J. Garcia-Fernandez, M. Campo-Valera, D. Cañete-Rebenaque, and J. L. Gomez-Tornero, Direction Finding of RFID tags in UHF Band Using a Passive Beam-Scanning Leaky-Wave Antenna IEEE Journal of Radio Frequency Identi cation, doi: 10.1109/JRFID.2021.3122233. Article 4.-: J. L. Gomez-Tornero, A. Gil-Martinez, M. Poveda-Garcia and D. Cañete-Rebenaque, ARIEL: Passive Beam-Scanning Antenna TeRminal for Iridiscent and E cient LEO Satellite Connectivity in IEEE Antennas and Wireless Propagation Letters, doi: 10.1109/LAWP.2022.3193040.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma Doctorado en Tecnologías de la Información y las Comunicacione

Sensors and Systems for Indoor Positioning

This reprint is a reprint of the articles that appeared in Sensors' (MDPI) Special Issue on “Sensors and Systems for Indoor Positioning". The published original contributions focused on systems and technologies to enable indoor applications