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关键词： Protocols   Indexes   RFID tags   Servers   Mobile computing   Temperature sensors   Search problems   Double index   double polling   information collection   RFID  

摘要： The significance of RFID-based information collection is becoming increasingly visible as more and more sensor-augmented RFID systems are deployed. Tag information collection aims at efficiently and accurately collecting valuable information from target objects attached with RFID tags. Polling-based information collection can effectively avoid response collisions between RFID tags, and it is widely adopted to accurately inventory tags. However, in the traditional polling mode, a polling vector can only be used to query a tag at a time, which is inefficient. In this paper, we design a double polling mode to improve the utilization of polling vectors, which can simultaneously interrogate a pair of tags. Afterwards, several techniques are developed to reduce the polling vector length. First, the Basic Double Polling-based protocol (BDP) employs double indexes to collect information, which greatly reduces the number of polling vectors. Second, the Segmented Double Polling-based protocol (SDP) divides the double indexes into several segments to cut the polling vector length down. Third, the Partial Double Polling-based protocol (PDP) replaces the double index with the size of the empty segment between two adjacent non-zero indexes to further reduce the average polling vector length. Finally, the Differential Double Polling-based protocol (DDP) utilizes the size of the empty segment between two double indexes to improve the utilization of polling vectors. After that, extensive theoretical analyses and simulations are conducted, which demonstrate the feasibility and effectiveness of the proposed protocols.

关键词： Array signal processing   Backscatter   Radio frequency   Antenna arrays   RF signals   Transmitting antennas   System recovery   Beamforming   RFID  

摘要： Although billions of battery-free backscatter devices (e.g., RFID tags) are intensively deployed nowadays, they are still unsatisfying in the two major performance limitations (i.e., short reading range and high miss reading rate) resulting from the current harvesting inefficiency. The classic beamforming technique is regarded as the most promising solution to address the issue. However, applying it to backscatter systems meets the deadlock start problem, i.e., without enough power, the backscatter cannot wake up to provide channel parameters;but, without channel parameters, the system cannot form beams to provide power. In this work, we propose a new paradigm called transfer beamforming (${\sf TBF}$TBF), namely, the beamforming strategies can be transferred from reference tags with known positions to power up other unknown neighbor tags of interest. In short, transfer beamforming (is accomplished) via (launching) beamforming (to reference tags first) for (the purpose of) transfer. To do so, we adopt the semi-active tags as the reference tags, which can be powered up with a normal reader in a wide range. Then the beamforming is initiated and transferred to power up the low-sensitive but cost-effective passive tags surrounded by reference tags. A prototype evaluation of ${\sf TBF}$TBF with 8 transmitting antennas presents a 99.9% inventory coverage rate in a crowded warehouse with 2,160 RFID tags. Our comprehensive evaluation reveals that ${\sf TBF}$TBF can improve the power transmission by 6.9 dB and boost the inventory speed by 2x compared with state-of-art methods.

关键词： crop pollination   honeybee behaviour   hybrid carrot   RFID   vegetable seed  

摘要： Hybrid vegetable varieties have become essential for global agricultural production, offering key advantages for yield, quality and disease resistance. The production of hybrid seeds is however limited by pollination challenges, with these systems commonly associated with unattractive and low-quality floral resources, isolated growing environments and frequent insecticide ***, we utilise commercial carrot seed crops to investigate the impact of hybrid pollination on the behaviour of the honey bee (Apis mellifera).Six full-strength bee colonies were equipped with solar powered radio frequency identification systems and over 900 tagged bees per season. These colonies were deployed to commercial hybrid seed crops over two consecutive seasons. The colonies were allocated to either an on-crop or off-crop group. Individual bees were autonomously monitored for the pollination period to assess key parameters such as survival, age at foraging and the number and duration of orientation and foraging *** carrots were found to have a significant impact on bee foraging behaviour. Bees situated on the carrot crop undertook less frequent yet longer foraging trips, resulting in less total time outside of the colony compared to off-crop bees. However, bees placed in carrot fields survived to an older age, orientated successfully, became foragers later and collected more pollen by weight, despite only 2% originating from carrot. We hope that the improved behavioural understanding can be utilised to enhance both pollinator health and hybrid seed production globally.

关键词： Faces   RF signals   Feature extraction   Authentication   Facial features   Three-dimensional displays   Privacy   RFID   wireless sensing   Internet of Things   facial authentication  

摘要： Current facial authentication (FA) systems are mostly based on the images of human faces, thus suffering from privacy leakage and spoofing attacks. Mainstream systems utilize facial geometry features for spoofing mitigation, but they are still vulnerable to feature manipulation, e.g., 3D-printed human faces. In this article, we propose a novel privacy-preserving anti-spoofing FA system, named RFace, which extracts both the 3D geometry and inner biomaterial features of faces using a COTS RFID tag array. These features are difficult to obtain and forge, hence are resistant to spoofing attacks. Unlike images, RF signals are not perceptible to human eyes, so RFace protects user's privacy. We build a theoretical model to rigorously prove the feasibility of feature acquisition and the correlation between facial features and RF signals. To enhance the security of RFace, we specify the tag reading order for each authentication to defend against the signal replay attack. For practicality, we design an effective algorithm to mitigate the impact of unstable distance and angle deflection from the face to the array. Extensive experiments with 30 participants and three types of spoofing attacks show that RFace achieves an average authentication success rate of over 95.7% and an EER of 4.4%. More importantly, no replay attack or spoofing attack succeeds in deceiving RFace in the experiments.

关键词： Artificial magnetic conductor   Backscattering   Chipless RFID   Read range  

摘要： The paper proposes a low-profile chipless RFID tag with an enhanced read range. To improve the read range, an artificial magnetic conductor (AMC) is used as the backplane of the resonator. The proposed technique is presented at the operating frequency of 5.07 GHz, which could further be shifted to other frequencies in the UWB band by optimizing the geometric parameters of the design. The octagonal-shaped resonator of the tag and the AMC backplane is designed on a 0.15-mm and 1.6-mm-thick FR-4 substrate, respectively. The AMC as backplane leads to seven times enhancement of the read range. The simulated results of the tag are experimentally validated using the bistatic measurement method. The overall dimension of the proposed tag is 28 x 28 mm(2) and is suitable for tracking and identification of small-sized objects. The proposed technique of read range enhancement could further be matured for multi-resonance chipless RFID tags.

关键词： Modulation   Channel capacity   Backscatter   Wireless communication   Integrated circuit modeling   Voltage measurement   Radiofrequency identification   Backscatter communication   load modulation   channel capacity   ambient backscatter   RFID  

摘要： In backscatter communication (BC), a passive tag transmits information by just affecting an external electromagnetic field through load modulation. Thereby, the feed current of the excited tag antenna is modulated by adapting the passive termination load. This paper studies the achievable information rates with a freely adaptable passive load. As a prerequisite, we unify monostatic, bistatic, and ambient BC with circuit-based system modeling. We present the crucial insight that channel capacity is described by existing results on peak-power-limited quadrature Gaussian channels, because the steady-state tag current phasor lies on a disk. Consequently, we derive the channel capacity for the case of an unmodulated external field, for general passive, purely reactive, or purely resistive tag loads. We find that modulating both resistance and reactance is important for very high rates. We discuss the capacity-achieving load statistics, rate asymptotics, technical conclusions, and rate losses from value-range-constrained loads (which are found to be small for moderate constraints). We then demonstrate that near-capacity rates can be attained by more practical schemes: 1) amplitude-and-phase-shift keying on the reflection coefficient and 2) simple load circuits of a few switched resistors and capacitors. Finally, we draw conclusions for the ambient BC channel capacity in important special cases.

关键词： Writing   Radiofrequency identification   Standards   Encoding   Servers   Optimization   Multicast algorithms   Batch writing   throughput optimization   COTS RFID systems  

摘要： We study the batch writing problem in RFID systems, where the reader seeks the most time-efficient way to write information into a given subset of tags. The problem is analogous to the multicast problem in classical networks, but one-to-many transmission is not supported in COTS RFID systems. Driven by the technical challenge, this paper addresses the problem of designing batch writing algorithms for COTS RFID systems. We make three contributions. First, we establish the minimal execution time for any batch writing algorithm, thus setting the theoretical performance limit. Second, we quantitatively compare and gauge the existing propositions applicable to our problem. Third, we develop a novel batch writing algorithm with minimal 25% performance gain over the best state-of-the-art solution. Our key technicalities are designing an encoding scheme allowing the reader to efficiently perform batch writing and optimizing the batch writing sequence to minimize the overall execution time. We also perform extensive experiments to demonstrate the effectiveness of our algorithm.

关键词： Artificial magnetic conductor (AMC)   epidermal antenna   healthcare   RFID antenna  

摘要： This article presents a compact AMC structure used as a shielding element for a generic wearable RFID tag at UHF frequencies for on-body applications, with an overall footprint limited to an area of only lambda(2)(0) (41.4 x 82.8 mm). Thanks to the isolation provided by the AMC planar structure, the tag antenna gain and reading range are increased by about one order of magnitude in comparison with the case of a conventional tag attached to the human body. The designed antenna is platform tolerant, with very good robustness and isolation with respect to the human body, exhibiting a high reliability. The AMC structure is implemented on a thin, flexible, and biocompatible high permittivity silicon-doped dielectric substrate, with apertures both in the substrate and in the ground plane to allow skin transpiration. Therefore, the presented device can be effectively used also as an epidermal antenna, allowing the "on-skin" sampling of the most typical health parameters. The presented configuration has been designed using CST Studio Suite. A prototype has been fabricated and fully characterized, and measured results are in very good agreement with simulations.

关键词： chipless RFID   humidity sensing   smart packaging   microwave sensor   threshold sensor  

摘要： Packaging solutions have recently evolved to become smart and intelligent thanks to technologies such as RFID tracking and communication systems, but the integration of sensing functionality in these systems is still under active development. In this paper, chipless RFID humidity sensors suitable for smart packaging are proposed together with a novel strategy to tune their performances and their operating range. The sensors are flexible, fast, low-cost and easy to fabricate and can be read wirelessly. The sensitivity and the humidity range where they can be used are adjustable by changing one of the sensor's structural parameters. Moreover, these sensors are proposed as double parameter sensors, using both the frequency shift and the intensity variation of the resonance peak for the measure of the relative humidity. The results show that the sensitivity can vary remarkably among the sensors proposed, together with the operative range. The sensor suitability in two specific smart packaging applications is discussed. In the first case, a threshold sensor in the low-humidity range for package integrity verification is analyzed, and in the second case, a more complex measurement of humidity in non-hermetic packages is investigated. The discussion shows that the sensor configuration can easily be adapted to the different application needs.

关键词： Fault detection  

摘要： Apart from the widespread acceptance of the digital library as a major research response among university lecturers and students, little is known about the reliability of its RFID software (RFIDS), the challenges posed during software flaws, and the improvement strategies that can be used to maintain the RFID software reliability. The various NHPP software reliability growth models (SRGMs) to investigate the reliabilities of software products of this kind in real-world software development has not always been achieved because those studies were primarily concerned with modeling fault detection processes (FDP) and ignoring the fault correction processes (FCP). Here, we propose a reliability model of RFID software while keeping in mind the interdependence between fault quantities of the dual procedures of fault detection and fault correction. In evaluating the software reliability, fault introduction and testing coverage rates were eventually included to the parameters making our proposed model to be highly effective in estimating and forecasting the dependability of the software when compared with existing NHPP software reliability growth models (SRGMs).