Published Article / Radio-frequency Identification (RFID) technology promises to revolutionize business processes. While RFID technology is improving rapidly, a reliable deployment of this technology is still a significant challenge impeding its widespread adoption. In this paper we provide a brief overview of some common fundamental characteristics of RFID data and devices, which pose significant challenges in the design of RFID middleware systems. In addition, the development of a multi-agent RFID middleware solution to address the RFID data and device management challenges is discussed.

Zugl.: Münster (Westfalen), Univ., Diss., 2008

The reliability of RFID systems depends on a number of factors including: RF interference, deployment environment, configuration of the readers, and placement of readers and tags. While RFID technology is improving rapidly, a reliable deployment of this technology is still a significant challenge impeding wide-spread adoption. This research investigates system software solutions for achieving a highly reliable deployment that mitigates inherent unreliability in RFID technology. We have considered two different problem domains for large scale RFID deployment. One is item tracking and the other is guidance-monitoring. Item tracking considers applications that have statically placed RFID readers to observe the RFID tagged objects in motion. An airport scenario to observe the tagged baggage or warehouse scenarios to track the tagged goods are examples of item tracking applications. A self guided tour, search and rescue scenario or a visually impaired person looking for direction and guidance in a tagged environment are examples of item location applications. It is observed that there is a notion of path that follows the direction and flow of the mobile items in the item tracking applications and a path gets created along the direction and flow of the mobile object in item location applications. A system level knowledge of the data flow can benefit the system in different aspects such as improved reliability, resource management and real time response. We have designed and implemented an RFID middleware for item tracking: RF²ID (Reliable Framework for Radio Frequency Identification) to organize and support queries over data streams in an efficient manner. We have developed (1) a virtual reader abstraction to improve the potentially error-prone nature of reader generated data (2) a novel path abstraction to capture the logical flow of information among virtual readers. Prototype implementation using both RFID readers and simulated readers using an empirical model of RFID readers show that RF²ID is able to provide high reliability, support path-based object detection and use efficient resource management techniques. We propose a middleware solution that takes into account the data flow information for item location application that requires real time response. The guidance-monitoring scenario considers mobile RFID readers that traverse in a tagged environment. We consider the scenario of an Assisted Living Center for elderly residents as a motivating guidance-monitoring application. The solution for guidance-monitoring system is called GuardianAngel. The application scenario considers a tagged indoor environment with residents having their own RFID readers to provide them with adequate information about the surroundings. The guidance and monitoring requirement can be conflicting. The guidance information requires very fine grain information about the environment to make proper decisions. On the other hand, the monitoring system must not have a fine grain knowledge which can introduce concerns such as privacy concerns. We consider this aspect during the design and implementation. The system is a two layered infrastructure that has the upper layer which is the monitoring layer. This layer is in charge of monitoring of the actors in the environment. The monitoring layer is physically a set of distributed virtual stations that have the knowledge about the environment. The environment itself is equipped with RFID tags. The residents of the environment have the mobile object that has a sensing element and a computing element (e.g., handhold device with a portable RFID reader) - the guidance server runs on this mobile object. The guidance server is in charge of making local decisions to the users. It is resource limited and asks for new information from the virtual stations as needed. The guidance server also provides the monitoring server with the information regarding the status of the mobile object. But the status information is not fine grain information - the guidance server wraps up the information over a period of time and over a larger region to hide the detailed information of the users.The system uses the logical path based abstraction to guide the users. We have implemented the real testbed using grid structured RFID devices along with scalability study using emulated RFID readers. The basic contribution of our work is based on providing novel middleware solution that is able to serve the application taking into account the inherent unreliability of RFID technology. Our path abstraction that uses the physical flow of data as an ally to generate a logical system level flow enhances the performance in many ways.

On assiste de nos jours à une utilisation croissante des systèmes RFID (Radio Frequency IDentification systems) dans diversdomaines d’application (logistique, systèmes de production, inventaires, traçabilité, etc.). Certaines de ces applicationsprésentent un caractère critique à l’image du respect de la chaîne de froid lors de l’acheminement de denrées alimentaires oudans le cas de systèmes de manutention de bagages dans les aéroports. Or, la sensibilité des systèmes RFID vis-à-vis de leurenvironnement, notamment des perturbations électromagnétiques ou de la présence d’obstacles, les rend vulnérables. Demême, de par le nombre important d’éléments (étiquettes, lecteurs) mis en oeuvre dans de tels systèmes, des comportementserronés peuvent survenir en raison de fautes dans les divers éléments constituant le système. D’où l’importance et la nécessitéde traiter le problème de la sûreté de fonctionnement et de la tolérance aux fautes dans le but de rendre ces systèmes plusrobustes.L’objectif de cette thèse concerne la proposition d’approches logicielles de test et de diagnostic en ligne adaptées aux systèmesRFID en vue d’améliorer leur robustesse. Depuis quelques années, une exploitation efficace des systèmes RFID a vu ledéveloppement d’intergiciels ou de middlewares RFID, dont le rôle est de proposer des services permettant la gestion desquantités de données importantes en provenance des lecteurs RFID. L’utilisation de tels intergiciels est d’un grand intérêt pourla sûreté de fonctionnement des systèmes RFID en raison de la nature distribuée de ces systèmes ; en particulier, grâce àl’intégration des mécanismes de sûreté de fonctionnement, plus précisément le test et le diagnostic en ligne, au niveau dumiddleware. Dans cette thématique, nous avons proposé plusieurs solutions pour couvrir les deux couches centrales du systèmeà savoir la couche middleware et son interface de communication avec les sources de données, le protocole LLRP (Low LevelReader Protocol). Nous avons proposé une solution middleware compatible avec le standard de communication des systèmesRFID, et utilisée comme un réceptacle pour une solution algorithmique de diagnostic probabiliste qui permet de détecter lesdéfaillances potentielles des composants du système sur la base d’un modèle probabiliste qui tient compte de l’environnementd’exécution. Ensuite, nous avons proposé un mécanisme d’analyse des fichiers log de l’interface de communication LLRP,complémentaire à l’algorithme probabiliste et qui permet d’approfondir le diagnostic en recherchant les causes de la défaillancedétectée sur la base de différentes signatures de défaillances déjà établies. Enfin, nous avons proposé une extension dustandard de communication LLRP qui tient compte de plusieurs comportements défaillants dans le but de rendre ce dernier plusfiable. / We are witnessing today a growing use of RFID (Radio Frequency IDentification) systems in various application areas (logistics,production systems, product traceability, etc.). Some of these applications are critical such as food-related cold chain logistics orbaggage handling systems in airports. Nevertheless, RFID are very sensitive to their environment, including electromagneticdisturbances or presence of obstacles, making them error-prone. Also, because of the large number of elements (tags, readers,and sensors) constituting current RFID systems, erroneous behaviors are more frequent. Hence, it is important to address all theproblems related to RFID system dependability and deal with them in order to make these systems more robust.The goal of this thesis is the development of software test and online diagnosis facilities for RFID systems to improve theirrobustness. In recent years, the effective use of RFID systems has seen the development of RFID middleware solutions, whoserole is to provide services for the management of large amounts of raw data of the various RFID sources. Due to the distributednature of current RFID systems, the use of such solutions is of great interest regarding the improvement of RFID systemdependability. In particular, thanks to the integration of dependability mechanisms, specifically the online test and diagnosisapproaches in the RFID middleware solution. In addition, because of the middleware is considered as the backbone of an RFIDsystem, whereby the whole RFID dataflow passes; all the needed information will be availabe to our proposed approaches toperform a correct diagnosis. We proposed several solutions to cover the two main layers of RFID systems; namely, themiddleware layer and the communication layer between the middleware and the data sources, the Low Level Reader Protocol(LLRP). We have proposed a LLRP compliant middleware solution, used to accommodate a probabilistic diagnosis algorithm todetect potential failures of the RFID system components on the basis of a probabilistic model that takes into account theexecution conditions. Then, we proposed a complementary mechanism to the previous algorithm for analyzing the log files ofthe LLRP communication interface allowing further analysis by looking for the causes of the detected failures on the basis of an already defined set of failure signatures. Finally, we proposed an extension of the LLRP standard to make it more reliable bytaking into account several RFID failures.