Antonis G. Dimitriou

Improving Backscatter Radio Tag Efficiency

This paper studies tag properties for optimized tag-to-reader backscatter communication. The latter is exploited in RF identification (RFID) systems and utilizes binary reflection coefficient change of the tag antenna-load circuit. It is shown that amplitude maximization of complex reflection coefficient difference between the two states is not sufficient for optimized tag-to-reader backscatter communication, contrary to what is commonly believed in the field. We provide a general tag load selection methodology that applies to any tag antenna, including minimum scattering antennas as a special case. The method is based on tag antenna structural mode closed-form calculation (given three values of tag radar cross section), employs simple antenna/communication theory, and applies to both passive, as well as semipassive RFID tags.

Single-Antenna Coherent Detection of Collided FM0 RFID Signals

This work derives and evaluates single-antenna detection schemes for collided radio frequency identification (RFID) signals, i.e. simultaneous transmission of two RFID tags, following FM0 (biphase-space) encoding. In sharp contrast to prior art, the proposed detection algorithms take explicitly into account the FM0 encoding characteristics, including its inherent memory. The detection algorithms are derived when error at either or only one out of two tags is considered. It is shown that careful design of one-bit-memory two-tag detection can improve bit-error-rate (BER) performance by 3dB, compared to its memoryless counterpart, on par with existing art for single-tag detection. Furthermore, this work calculates the total tag population inventory delay, i.e. how much time is saved when two-tag detection is utilized, as opposed to conventional, single-tag methods. It is found that two-tag detection could lead to significant inventory time reduction (in some cases on the order of 40%) for basic framed-Aloha access schemes. Analytic calculation of inventory time is confirmed by simulation. This work could augment detection software of existing commercial RFID readers, including single-antenna portable versions, without major modification of their RF front ends.

A novel technique for the approximation of 3-D antenna radiation patterns

In this paper, a novel technique for the approximation of three-dimensional (3-D) antenna radiation patterns is presented. The proposed method combines the two principal cuts in order to acquire an adequate estimate of the 3-D antenna radiation solid. The absolute error from the theoretical solution is analyzed along with other statistical measures for various types of antenna structures, namely omni-directional and directive arrays. The performance of the method is compared against other existing extrapolation algorithms. The proposed technique exhibits low approximation errors and is easily integrated into 3-D radio propagation planning tools (such as ray-tracing algorithms).

On the Design, Installation, and Evaluation of a Radio-Frequency Identification System for Healthcare Applications [Wireless Corner]

In this paper, we present the design, implementation, and testing of a radio-frequency identification (RFID) system for healthcare applications. The constantly growing passive RFID technology at ultra-high frequencies (UHF), in conjunction with current state-of-the-art information and communication technologies (ICTs), was used for the system design. The end product was installed at an oncology hospital in Cyprus, where it was thoroughly evaluated by medical staff and hospital administrators. This pilot project had three main objectives: a) automatic and error-free patient identification of in-hospital patients using RFID-enabled cards or wristbands; b) Real-time location service (RTLS) for locating and tracking medical assets and high-value equipment in the hospital ward; c) quick and hassle-free drug inventory management through the use of inexpensive smart labels and cost-effective stationary readers. Here, we present a detailed description of the three major subsystems of the pilot project, emphasizing the main features and capabilities of the system, important design and implementation issues, as well as system evaluation and testing. During the design stage of the project, special emphasis was placed on user friendliness, system capabilities, adequate coverage and tag readability, privacy and security of sensitive patient data, system reliability, and the daily practices of medical personnel and hospital administrators.

Room-Coverage Improvements in UHF RFID with Commodity Hardware [Wireless Corner]

This work studies the three-dimensional (3D) identification performance of UHF RFID systems with commodity hardware. Detailed three-dimensional propagation modeling is developed, with ray-tracing that allows examination of tag- as well as reader-antenna diversity. It is shown that multipath can enhance identification performance compared to free-space conditions. Furthermore, it is found that tag diversity can enhance identification performance on the order of 10%. Reader-antenna diversity becomes beneficial only when special attention is given to controlling the destructive summation of the transmitted fields and simple, general antenna-installation rules are provided. Performance can be further enhanced with the introduction of a phase shifter or appropriate transmission scheduling, and various examples are discussed. Measurements inside a room with a dense three-dimensional grid of passive RFID tags confirmed the results. Finally, a method to perform power-measurements with commodity RFID hardware that exploits the sensitivity-during-read threshold of each tag is put forth.

A Site-Specific Stochastic Propagation Model for Passive UHF RFID

This letter proposes a computationally inexpensive, site-specific propagation model, useful in coverage evaluation of radio frequency identification (RFID) networks with passive tags. The parameters of a Rice distribution for each point in the volume of interest are computed using site-specific approximations that address overall space geometry, materials, and polarization. The probability of successful identification of passive RFID tags is calculated. Coverage statistics and performance evaluation of complex RFID networks can be quickly conducted. Experimental results at the UHF regime corroborate the accuracy of the model.

Europe and the Future for WPT: European Contributions to Wireless Power Transfer Technology

This article presents European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to high-power electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301. WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions. The article discusses the latest developments in research by some of the members of this group.This article presents recent European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to highpower electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301 (Table 1). WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions.

Design and Implementation of a Radio Frequency IDentification (RFID) System for Healthcare Applications

This paper presents the use of RFID technology in the healthcare sector. A highly sophisticated RFID system, which also incorporates advanced Information and Communication Technologies (ICTs), was carefully designed in order to be implemented as a pilot project at the premises of the Bank of Cyprus Oncology Center (BOCOC) in Cyprus. The RFID system will be used for automatic and error-free patient identification through the use of RFID wristbands and/or tagequipped plastic cards, for Real Time Location Service (RTLS) in order to locate medical equipment (e.g., infusion pumps, walkers, wheelchairs, etc.) in the premises of the hospital, and inventory control for the pharmacy. The RFID technology that is used in this pilot project is based on the UHF-band EPC C1 Generation 2 data exchange protocol. A Graphical User Interface for a medical tablet PC was developed which interfaces the RFID hardware (e.g., stationary and handheld readers, RFID printers, etc.) with the everyday routine tasks of the hospital’s medical personnel. The application platform developed by the research team is extremely easy-to-use by doctors and nurses, powerful, effective, and superior to traditional paper-bound processes.

Automated RFID network planning with site-specific stochastic modeling and particle Swarm Optimization

In this paper, a solution for automated passive RFID network planning is proposed. The proposed scheme comprises two parts; i) a fast site specific stochastic propagation model that extracts the probabilities of successful identification for any possible reader-antenna configuration, ii) a particle swarm optimization (PSO) algorithm that selects a subset of the antenna-configurations to be installed so that a given cost function is satisfied. In contrast to prior art, the combinatorial performance of all reader antennas is evaluated at each tag location; this revealed that good identification-performance is recorded at overlapping regions, where no single reader-antenna would operate adequately. As a result, the final solution includes less equipment, reducing the cost of the network. Results presented herein demonstrate that nearly half the number of antennas are needed for the same problem, compared to prior art.

Site-specific stochastic propagation model for automated RFID network planning

In this paper, we propose a model to calculate the probability of successful identification of passive UHF RFID tags in a given environment. The validity of the proposed model is verified by comparison with analytical ray-tracing results and measurements. The model can be included in automated RFID network planning algorithms to evaluate the identification performance of different configurations.