No description available.

RFID technology has attracted much attention due to its wide range of applications, such as inventory control and object tracking. Passive RFID tags are battery-less, mobile and lack intercommunication. Hence, they require a central node (the reader) to power them up, organize their replies, and read their data. In the last decade, several proposals have targeted the channel efficiency in RFID systems to improve time and power efficiencies. While such proposals achieve significant performance improvements, they are limited by the backscattering half-duplex channel in which the reader has to wait for the tag to finish its reply (even if the reply is corrupt or redundant). In this thesis, the Modulation Silencing Mechanism (MSM) is proposed as a novel full-duplex-like communication over half-duplex RFID links. With a simple additional circuit at the tag and upgraded software algorithms at the reader, the reader is capable of terminating the tag's non-useful transmissions. Consequently, we propose three schemes that utilize MSM in key application domains where the tag-reader transaction contains a considerable amount of non-useful transmissions. MSM is utilized to enhance tag identification, tag count estimation and tag authentication. First, we propose a Modulation Silencing Anti-collision (MSA) scheme that targets collision time reduction in time slotted anti-collision protocols. In MSA, the time requirements of state of the art identification protocols are significantly reduced. Moreover, we establish a backward compatibility procedure for proper identification of legacy and MSM-enabled tags. Secondly, a Variance- Modulation Silencing Estimation (VMSE) scheme is proposed to increase tag estimation accuracy and to minimize overall estimation time. Variance-to-mean ratio estimator is proposed to determine the most accurate tag count estimate. VMSE combines both, the accuracy of the variance-to-mean ratio estimator and the time efficiency of MSM and delivers rapid, accurate, and anonymous tag estimation that outperform recent estimation schemes for small and large scale tag deployment. Finally, we propose Unique Hash Sequence Authentication (UHSA) scheme for efficient tag authentication. The UHSA is based on hashed key prefetching algorithm at the reader augmented by the MSM circuitry at the tag. UHSA scheme provides higher time efficiency and robustness against tracking and compromising attacks. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-04-30 12:38:44.0

No description available.

A Identificação por radiofrequência (Radio Frequency Identification - RFID) tem revolucionado a forma de identificar objetos, sendo usada desde aplicações de controle de estoques até o processo automatizado de pagamentos. Sua ampla aceitação e aplicabilidade tem estimulado pesquisadores a criar cada vez mais aplicações. Um problema chave da RFID são as colisões que ocorrem na identificação por meio dos protocolos de acesso múltiplo. Como, na prática, um leitor precisa identificar várias etiquetas em sua área de cobertura, algumas etiquetas podem responder ao mesmo tempo o que gera colisões e desperdício de recursos. Por este motivo, torna-se de grande valor um estudo abrangente sobre como melhorar a identificação das etiquetas de modo a reduzir o número de colisões. Além disso, aspectos como consumo de energia e tempo necessário para identificação também devem ser levados em consideração, uma vez que a utilização cada vez maior de dispositivos alimentados à bateria tem sido observada na prática. Esta tese investiga a categoria de protocolos anticolisão denominada Frame Slotted Aloha - FSA, pois é a categoria que possui maior potencial de utilização prática em sistemas RFID. Além disso, as diferentes métricas de análise de desempenho são também analisadas e categorizadas, uma vez que identificou-se que um conjunto de métricas devem ser observadas com o intuito de realizarem-se comparações justas com as propostas da literatura. Descobriu-se que a maioria das propostas não levam em consideração os aspectos chave de tempo e energia, assim como a característica de ser fácil de implementar e baixa complexidade. Esta tese propõe quatro algoritmos que visam diminuir o consumo de energia e o tempo do processo de identificação das etiquetas mantendo-se as características de baixa complexidade e similaridade com o padrão atual EpcGlobal Classe 1 Geração 2 (C1G2). O primeiro mecanismo visa diminuir a quantidade de respostas desnecessárias em cenários de localização e rastreamento. Os demais consistem em três propostas de algoritmos anticolisão para sistemas RFID. Os dois primeiros diferem na forma como o tamanho inicial de quadro é definido e como as colisões são tratadas, representando evoluções progressivas em direção a um melhor desempenho. O terceiro considera a ocorrência do efeito captura, o que traz a necessidade de mudanças no funcionamento do algoritmo anterior. Resultados de simulação mostram que os quatro mecanismos podem melhorar propostas existentes sem aumento de complexidade, resultando consequentemente em diminuição de recursos desperdiçados. Além disso também foram desenvolvidos dois softwares de apoio aos mecanismos propostos: nsRFIDsim e jRFIDsim. O primeiro trata-se de um módulo para o simulador ns-2 que simula um sistema RFID passivo. O segundo implementa uma proposta de benchmark para avaliação de desempenho de algoritmos anticolisão para RFID, visando fornecer para a comunidade científica uma forma padronizada de avaliar este tipo de algoritmo. / The Radio Frequency Identification - RFID has revolutionized the way objects are identified, being used in several areas, from inventory control applications to automated payment process. Its wide acceptance and applicability has stimulated researchers to create more and more new applications. One RFID key problem is the collisions on identification by means of multiple access protocols. Since generally, a reader needs to identify multiple tags in its coverage area, some tags tend to reply at the same time which can cause collision and waste of resources. For this reason a comprehensive study on how to improve the identification of tags in order to reduce the number of collisions becomes important. Additionally, issues such as energy consumption and time required for identification must also be taken into consideration, since an increasing use of battery-powered devices has been observed in practice. This thesis investigates the category of anti-collision protocols called Frame Slotted Aloha - FSA, as it is the category that has the greatest potential for practical use in RFID systems. Further analysis of the different performance metrics are also analyzed and categorized, since it was identified that a set of metrics must be observed in order to carry out up fair comparisons with the proposals found on the literature. It was found that most of the proposals do not consider the key aspects of time and energy as well as the characteristic of being easy to implement and having low complexity. This thesis proposes four algorithms aimed at reducing the consumption of energy and the time to identify the tags while maintaining the characteristics of low complexity and similarity to the current standard EPCglobal Class 1 Generation 2 (C1G2). The first mechanism aims to decrease the unnecessary answers in locating and tracking scenarios. The other ones consist of three proposals for anti-collision algorithms for RFID systems. They differ in how the initial size is defined and how collisions are resolved, representing progressive evolutions toward a better performance. The third one considers the occurrence of the capture effect, which brings the need for changes in the previous algorithm operation. Simulation results show that the four mechanisms can improve existing proposals without increasing complexity, resulting in consequent energy savings. In addition we have also developed two softwares to evaluate the proposed mechanisms: nsRFIDsim and jRFIDsim. The former is a module for the ns-2 simulator that simulates a passive RFID system. The second one implements a proposal for benchmark performance evaluation of anti-collision algorithms for RFID in order to provide to the scientific community a standardized way to assess this type of algorithm.

In passive RFID systems, how to reduce the collision among tags is an important issue at the medium access control layer. The Framed Slotted ALOHA and its variations are well-known anti-collision algorithms for RFID systems. However, when the Framed Slotted ALOHA is used, the system efficiency and the average time delay deteriorate rapidly when the total number of tags increases. On the other hand, the total number of slots in a frame can¡¦t be infinity. In this thesis, we first compare existing anti-collision protocols and then propose a novel algorithm based on the Enhanced Dynamic Framed Slotted ALOHA (EDFSA) and the Progressing Scanning (PS) algorithm. The proposed algorithm is called Dynamic Grouping (DG). The DG algorithm partitions the RFID tags according to the distances from tags to the reader in order to avoid using too many slots in a frame. Inparticular, the DG algorithm estimates the spatial distribution of tags based on previous scanning results and then adjusts the partition accordingly. Unlike PS algorithm, the DG algorithm is applicable when the RFID tags are uniformly distributed or normally distributed.

Radio Frequency IDentification (RFID) is growing prominence as an automated identification technology able to turn everyday objects into an ad-hoc network of mobile nodes; which can track, trigger events and perform actions. Energy scavenging and backscattering techniques are the foundation of low-cost identification solutions for RFIDs. The performance of these two techniques, being wireless, significantly depends on the underlying communication architecture and affect the overall operation of RFID systems. Current RFID systems are based on a centralized master-slave architecture hindering the overall performance, scalability and usability. Several proposals have aimed at improving performance at the physical, medium access, and application layers. Although such proposals achieve significant performance gains in terms of reading range and reading rates, they require significant changes in both software and hardware architectures while bounded by inherited performance bottlenecks, i.e., master-slave architecture. Performance constraints need to be addressed in order to further facilitate RFID adoption; especially for ultra large scale applications such as Internet of Things. A natural approach is re-thinking the distributed communication architecture of RFID systems; wherein control and data tasks are decoupled from a central authority and dispersed amongst spatially distributed low-power wireless devices. The distributed architecture, by adjusting the tag's reflectivity coefficient creates micro interrogation zones which are interrogated in parallel. We investigate this promising direction in order to significantly increase the reading rates and reading range of RFID tags, and also to enhance overall system scalability. We address the problems of energy-efficient tag singulations, optimal power control schemes and load aware reader placement algorithms for RFID systems. We modify the conventional set cover approximation algorithm to determine the minimal number of RFID readers with minimal overlapping and balanced number of tags amongst them. We show, via extensive simulation analysis, that our approach has the potential to increase the performance of RFID technology and hence, to enable RFID systems for ultra large scale applications. / Thesis (Ph.D, Computing) -- Queen's University, 2011-08-30 23:41:02.937

In a passive radio-frequency identification (RFID) system the reader communicates with the tags using the EPC Global UHF Class 1 Generation 2 (EPC Gen-2) protocol with dynamic framed slotted ALOHA. Due to the unique challenges presented by a low-power, random link, the channel efficiency of even the most modern passive RFID system is less than 40%. Hence, a variety of methods have been proposed to estimate the number of tags in the environment and set the optimal frame size. Some of the algorithms in the literature even claim system efficiency beyond 90%. However, these algorithms require fundamental changes to the underlying protocol framework which makes them ineligible to be used with the current hardware running on the EPC Gen-2 platform and this infrastructure change of the existing industry will cost billions of dollars. Though numerous types of tag estimation algorithms have been proposed in the literature, none had their performance analyzed thoroughly when incorporated with the industry standard EPC Gen-2. In this study, we focus on some of the algorithms which can be utilized on today’s current hardware with minimal modifications. EPC Gen-2 already provides a dynamic platform in adjusting frame sizes based on subsequent knowledge of collision slots in a given frame. We choose some of the popular probabilistic tag estimation algorithms in the literature such as Dynamic Frame Slotted ALOHA (DFSA) – I, and DFSA – II, and rule based algorithms such as two conditional tag estimation (2CTE) method and incorporate them with EPC Gen-2 using different strategies to see if they can significantly improve channel efficiency and dynamicity. The results from each algorithm are also evaluated and compared with the performance of pure EPC Gen-2. It is important to note that while integrating these algorithms with EPC Gen-2 to modify the frame size, the protocol is not altered in any substantial way. We also kept the maximum system efficiency for any MAC layer protocol using DFSA as the upper bound to have an impartial comparison between the algorithms. Finally, we present a novel and comprehensive analysis of the probabilistic tag estimation algorithms (DFSA-I & DFSA-II) in terms of their statistically significant correlations between channel efficiency, algorithm estimation accuracy and algorithm utilization rate as the existing literature only look at channel efficiency with no auxiliary analysis. In this study, we use a scalable and flexible simulation framework and created a light-weight, verifiable Gen-2 simulation tool to measure these performance parameters as it is very difficult, if not impossible, to calculate system performance analytically. This framework can easily be used to test and compare more algorithms in the literature with Gen-2 and other DFSA based approaches.

A Identificação por radiofrequência (Radio Frequency Identification - RFID) tem revolucionado a forma de identificar objetos, sendo usada desde aplicações de controle de estoques até o processo automatizado de pagamentos. Sua ampla aceitação e aplicabilidade tem estimulado pesquisadores a criar cada vez mais aplicações. Um problema chave da RFID são as colisões que ocorrem na identificação por meio dos protocolos de acesso múltiplo. Como, na prática, um leitor precisa identificar várias etiquetas em sua área de cobertura, algumas etiquetas podem responder ao mesmo tempo o que gera colisões e desperdício de recursos. Por este motivo, torna-se de grande valor um estudo abrangente sobre como melhorar a identificação das etiquetas de modo a reduzir o número de colisões. Além disso, aspectos como consumo de energia e tempo necessário para identificação também devem ser levados em consideração, uma vez que a utilização cada vez maior de dispositivos alimentados à bateria tem sido observada na prática. Esta tese investiga a categoria de protocolos anticolisão denominada Frame Slotted Aloha - FSA, pois é a categoria que possui maior potencial de utilização prática em sistemas RFID. Além disso, as diferentes métricas de análise de desempenho são também analisadas e categorizadas, uma vez que identificou-se que um conjunto de métricas devem ser observadas com o intuito de realizarem-se comparações justas com as propostas da literatura. Descobriu-se que a maioria das propostas não levam em consideração os aspectos chave de tempo e energia, assim como a característica de ser fácil de implementar e baixa complexidade. Esta tese propõe quatro algoritmos que visam diminuir o consumo de energia e o tempo do processo de identificação das etiquetas mantendo-se as características de baixa complexidade e similaridade com o padrão atual EpcGlobal Classe 1 Geração 2 (C1G2). O primeiro mecanismo visa diminuir a quantidade de respostas desnecessárias em cenários de localização e rastreamento. Os demais consistem em três propostas de algoritmos anticolisão para sistemas RFID. Os dois primeiros diferem na forma como o tamanho inicial de quadro é definido e como as colisões são tratadas, representando evoluções progressivas em direção a um melhor desempenho. O terceiro considera a ocorrência do efeito captura, o que traz a necessidade de mudanças no funcionamento do algoritmo anterior. Resultados de simulação mostram que os quatro mecanismos podem melhorar propostas existentes sem aumento de complexidade, resultando consequentemente em diminuição de recursos desperdiçados. Além disso também foram desenvolvidos dois softwares de apoio aos mecanismos propostos: nsRFIDsim e jRFIDsim. O primeiro trata-se de um módulo para o simulador ns-2 que simula um sistema RFID passivo. O segundo implementa uma proposta de benchmark para avaliação de desempenho de algoritmos anticolisão para RFID, visando fornecer para a comunidade científica uma forma padronizada de avaliar este tipo de algoritmo. / The Radio Frequency Identification - RFID has revolutionized the way objects are identified, being used in several areas, from inventory control applications to automated payment process. Its wide acceptance and applicability has stimulated researchers to create more and more new applications. One RFID key problem is the collisions on identification by means of multiple access protocols. Since generally, a reader needs to identify multiple tags in its coverage area, some tags tend to reply at the same time which can cause collision and waste of resources. For this reason a comprehensive study on how to improve the identification of tags in order to reduce the number of collisions becomes important. Additionally, issues such as energy consumption and time required for identification must also be taken into consideration, since an increasing use of battery-powered devices has been observed in practice. This thesis investigates the category of anti-collision protocols called Frame Slotted Aloha - FSA, as it is the category that has the greatest potential for practical use in RFID systems. Further analysis of the different performance metrics are also analyzed and categorized, since it was identified that a set of metrics must be observed in order to carry out up fair comparisons with the proposals found on the literature. It was found that most of the proposals do not consider the key aspects of time and energy as well as the characteristic of being easy to implement and having low complexity. This thesis proposes four algorithms aimed at reducing the consumption of energy and the time to identify the tags while maintaining the characteristics of low complexity and similarity to the current standard EPCglobal Class 1 Generation 2 (C1G2). The first mechanism aims to decrease the unnecessary answers in locating and tracking scenarios. The other ones consist of three proposals for anti-collision algorithms for RFID systems. They differ in how the initial size is defined and how collisions are resolved, representing progressive evolutions toward a better performance. The third one considers the occurrence of the capture effect, which brings the need for changes in the previous algorithm operation. Simulation results show that the four mechanisms can improve existing proposals without increasing complexity, resulting in consequent energy savings. In addition we have also developed two softwares to evaluate the proposed mechanisms: nsRFIDsim and jRFIDsim. The former is a module for the ns-2 simulator that simulates a passive RFID system. The second one implements a proposal for benchmark performance evaluation of anti-collision algorithms for RFID in order to provide to the scientific community a standardized way to assess this type of algorithm.

Made available in DSpace on 2015-05-14T12:36:49Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3512497 bytes, checksum: 22606000aee179c4fa5e12daeebccb2c (MD5) Previous issue date: 2014-02-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The development of algorithms oriented to robotic systems, in simulation environments, supports the identification and prediction of many problems before their tests in real environments. However, there is still not a process to ensure that an algorithm evaluated in a simulation platform will similarly work when migrated to real robots. The interference of several factors, such as engine and sensors properties, as well as the lack of a methodology that supports the interaction simulation/reality is considered as one of the main problems in this transition, so that there is a large conceptual development gap between real and simulated environments. This work aims to contribute with the formalization of a conceptual model to assist in the transition process, in which it is possible to highlight the peculiarities that require further attention from developers.. For that end, as a case study, it was developed an anti-collision algorithm, which involves several characteristics of a robotic system. Its implementation was carried out in both Unity3D simulator and real robots developed in the Arduino platform. The results were obtained and compared by a quantitative analysis of graphs using MATLAB. All necessary changes were classified and evaluated, raising up an initial idea of the transition model, which formalizes the main particulars of the project / O desenvolvimento de algoritmos voltados para sistemas robóticos, em ambientes de simulação, auxilia na identificação e antecipação de muitos problemas antes mesmo de serem testados em ambientes reais. Porém, nada garante que um algoritmo avaliado em uma plataforma de simulação funcione quando migrado para robôs reais. A interferência de diversos fatores, como propriedades dos motores e sensores, bem como a falta de uma metodologia necessária para interação simulação/realidade, se caracteriza como um dos principais problemas desta transição, de modo que, existe um grande gap conceitual entre o desenvolvimento para ambientes reais e simulados. Este trabalho tem o objetivo de contribuir com a formalização de um modelo conceitual que auxilie no processo de transição, no qual é possível destacar as peculiaridades que carecem de uma maior atenção por parte dos desenvolvedores. Para isso, como estudo de casos, foi desenvolvido um algoritmo de anticolisão, que engloba diversas características de um sistema robótico, sendo realizada sua implementação tanto no simulador Unity3D, quanto em robôs reais desenvolvidos na plataforma Arduino. Os resultados foram obtidos e comparados através de uma análise quantitativa de gráficos originados pelo MATLAB. Todas as alterações necessárias foram classificadas e avaliadas, de forma que possamos ter uma ideia do modelo de transição inicial, o qual formalize as principais particularidades do projeto

This thesis describes design of Simulator FM-CW range finders. It is choosing the optimal method of realization and inform about basic properties of continuous working radar. The work includes an analysis of errors in real rangefinder and a numerical estimate of the maximum error in real devices. Contains detailed block diagram of simulator FM-CW range-finder and computer simulation of function generator frequency modulated signal, demodulator. Further work includes the complete construction documents for the preparation and implementation of basic functional verification