Embracing Collisions to Increase Fidelity of Sensing Systems with COTS Tags

RFID techniques have been extensively used in sensing systems due to their low cost. However, limited by the structural simplicity, collision is one key issue which is inevitable in RFID systems, thus limiting the accuracy and scalability of such sensing systems. Existing anti-collision techniques try to enable parallel decoding without sensing based applications in mind, which can not operate on COTS RFID systems. To address the issue, we propose COFFEE, which enables parallel channel estimation of COTS passive tags by harnessing the collision. We revisit the physical layer design of current standard. By exploiting the characteristics of low sampling rate and channel diversity of RFID tags, we separate the collided data and extract the channels of the collided tags. We also propose a tag identification algorithm which explores history channel information and identify the tags without decoding. COFFEE is compatible with current COTS RFID standards which can be applied to all RFID-based sensing systems without any modification on tag side. To evaluate the real world performance of our system, we build a prototype and conduct extensive experiments. The experimental results show that we can achieve up to 7.33x median time resolution gain for the best case and 3.42x median gain on average.

Modelling and Evaluation of the Absorption of the 866 MHz Electromagnetic Field in Humans Exposed near to Fixed I-RFID Readers Used in Medical RTLS or to Monitor PPE

The aim of this study was to model and evaluate the Specific Energy Absorption Rate (SAR) values in humans in proximity to fixed multi-antenna I-RFID readers of passive tags under various scenarios mimicking exposure when they are incorporated in Real-Time Location Systems (RTLS), or used to monitor Personal Protective Equipment (PPE). The sources of the electromagnetic field (EMF) in the modelled readers were rectangular microstrip antennas at a resonance frequency in free space of 866 MHz from the ultra-high frequency (UHF) RFID frequency range of 865–868 MHz. The obtained results of numerical modelling showed that the SAR values in the body 5 cm away from the UHF RFID readers need consideration with respect to exposure limits set by international guidelines to prevent adverse thermal effects of exposure to EMF: when the effective radiated power exceeds 5.5 W with respect to the general public/unrestricted environments exposure limits, and with respect to occupational/restricted environments exposure limits, when the effective radiated power exceeds 27.5 W.

Privacy-Preserving RFID-Based Search System

The employment of mobile readers (or mobile phone collaborated with a Radio frequency identification (RFID) reader) opens a novel application for RFID technology. In particular, an RFID tag search system has been designed to find a particular tag in a group of tags using a mobile reader. Unfortunately, privacy infringement and availability issues in the search system have not been adequately addressed to date. In this paper, we propose a novel RFID tag search protocol that will enhance mobile reader user privacy while being able to operate under conditions of unstable connection to a central server. First, the proposed protocol preserves the privacy of mobile reader users. The privacy of the mobile reader user is at risk because the signal strength emitted from a mobile reader is much stronger than that from the tag, exposing the location of the mobile reader user and thus compromising the user’s privacy. Thus far, such privacy issues have been overlooked. The second issue is presented because of wireless connections that are either unreliable or too remote, causing a mobile reader to disconnect from the central server. The proposed protocol enables serverless RFID tag searches with passive tags, which obtain operating power from the mobile reader. In unstable environments, the protocol can successfully locate specific tags without any server.

Evaluation of SAR in Human Body Models Exposed to EMF at 865 MHz Emitted from UHF RFID Fixed Readers Working in the Internet of Things (IoT) System

The aim of this ongoing study was to evaluate the specific energy absorption rate (SAR) values in the body of a person present near-fixed readers of ultra-high frequency (UHF) radio frequency identification (RFID) passive tags incorporated in real-time locating systems (RTLS), operating at a frequency range of 865–868 MHz, considering various exposure scenarios. The modelled electromagnetic field (EMF) source was a rectangular microstrip antenna designed at resonance frequency in free space at 865 MHz. The SAR values in the body exposed to EMF 5 cm away from the UHF RFID readers need consideration with respect to general public exposure limits, when the radiated power exceeds 8 W.

New Capacitive Thermal Age Tag for Predicting Remaining Thermal Life of Multiple Products

This paper proposes use of a new capacitive thermal age sensor that inherently integrates time and temperature without batteries or electronic memory to predict the remaining thermal life of a wide range of monitored products. The sensor is a tiny capacitor comprising a polymeric dielectric between two conductive plates. Capacitance of the sensor increases during thermal aging due to shrinkage of the polymer. Additives such as catalysts adjust the activation energy (Ea) of capacitance change with thermal age.A thermal age tag, incorporating two capacitive sensors of different activation energy, can be used to determine the effective temperature (Teff) of a complex thermal environment at wide range of product degradation activation energies. Correlation of the thermal age of the tag at the monitored product’s degradation activation energy to product thermal aging data provides estimated remaining thermal life of the product. The thermal age tag requires no batteries or electronic memory required in data-logging approaches resulting in reduced size, weight and cost. These passive tags are potentially maintenance free for the life of the product.This paper describes the development of a universal thermal age (UTA) tag incorporating capacitive thermal age sensors and preliminary co-aging trials with a variety of selected polymeric products to demonstrate feasibility of this approach.

Statistical Analysis on Readability of RFID Gen2 Passive Tags Using Bayesian Information Criterion and 2-Level Factorial Design

RFID holds a large potential for changing how a process is manipulated and controlled. RFID is a valuable improvement in many organizations, whether it is used for monitoring logistics and supply chains, securing access within the facility to locate and validate inventory. Most of the time, the main technical concern with RFID is whether the tags can be read in the environment they are being incorporated in. This paper examines the effect of different factors such as distance from an antenna, tag size, the surface on which tag is placed, tag location & velocity/speed on the readability of the RFID tag. In this paper, we developed an effective model analysis of the factors that affect the readability of the RFID tag using the Bayesian Information Criterion (BIC) & Design of Experiment (DOE) technique. Experiments were conducted and readings were taken to consider the effect of different factors and identify the critical factors that affect the readability, and a redundant regression model was developed using BIC. Design of Experiments (DOE) was used, specifically 2k factorial design and 2(k-1) fractional factorial design to perform statistical analysis and understand the source of variation in the model. The two designs were compared and the best out of the two was chosen to develop a model. Statistical analysis was performed using Minitab software to validate. The developed model intends to read the intensity of the tag with 97% accuracy.