Daniel W. Engels

Extracting information from tag collisions

In this paper, we develop techniques to extract information from communication collisions involving passive UHF RFID tags. Our goal is to extract information that can enhance the performance of existing anti-collision protocols. Present RFID anti-collision protocols detect a collision at the Medium Access Control (MAC) layer; however, the physical layer signal received during collisions is discarded. This signal contains valuable information, such as the number of tags communicating, that can be used in the anti-collision algorithms. Collecting and utilizing this currently discarded information would provide performance improvements to existing protocols and provide insights that can be used to guide the development of future protocols.We analyzed communication collisions from ISO 18000-6C compliant tags in their response to a Query command. Our techniques enabled us to reliably identify the exact number of tags in the collided slot for up to 4 tags communicating in that slot and the existence of at least 5 tags communicating in a slot with more than 4 tags communicating in that slot.

Localization Systems Using Passive UHF RFID

Since gathering spatial information of objects often provides a large number of extended functions in RFID based applications, many different localization systems have been developed in recent years. Determining and estimating the physical location of tagged objects in an interrogating area is known as localization. In this paper, we study properties of passive UHF RFID systems such as the relationship between distance and RSSI (Received Signal Strength Indictor), performance variations among the same type of passive tags, and readabilities of tags. We propose a received signal strength based Localization Algorithm using passive UHF RFID system. The localization uses the k-nearest neighbor algorithm to estimate the physical position of the target tag. To improve the accuracy of the passive tag attached object location, the properties and characteristics are applied to the localization algorithm. According to the analysis of experimentation, our proposed approach shows over 34% improvement compared with the k-Nearest Neighbor algorithm with the use of single reader and a single antenna, and 13 reference tags.

Active RFID System Augmented With 2D Barcode for Asset Management in a Hospital Setting

We have implemented an active radio frequency identification (RFID) asset management system at a 120 bed acute-care hospital. The RFID system is used to track more than 2500 items within the hospital including infusion pumps, beds, and wheelchairs. The goal of this RFID project is to understand the limitations and benefits of the deployed RFID technology especially with regard to assessment of how the technology could be used to improve patient safety. There were several technical limitations with the deployed RFID technology; 2D barcode technology was implemented to overcome these. This project demonstrates that RFID systems augmented with 2D barcode technology enable the improvement of many processes in the hospital, thereby increasing patient safety and reducing operational costs. In this paper, we examine the RFID technology, including the rational for selecting the specific technology for this project, the installation process, and the benefits and limitations of the technology, as well as the role of a 2D barcode technology to overcome the limitations of the chosen RFID system.

Passive UHF RFID-Based Localization Using Detection of Tag Interference on Smart Shelf

In this paper, we present a novel radio-frequency identification (RFID) smart shelf that accurately locates tagged objects using standard passive UHF RFID tags. This standard-based commercial off-the-shelf approach provides significant advantages over custom HF RFID and other near-field RFID approaches, including reduced tag costs, minimal infrastructure costs, and simple operation. In order to achieve accurate location sensing of objects sitting on the shelf, we utilize a novel localization algorithm that utilizes detected changes in a tags readability to infer the presence of neighboring tags. According to our experimentation results, with a single RFID reader antenna for two wooden shelves of size 91 cm × 152 cm, our smart-shelf system estimates nine box-level object locations with an average error of just 18.48 cm, which is a 71% improvement in accuracy compared with the previously published k nearest neighbor (KNN) algorithm.

Evaluation of RFID Performance for a Pharmaceutical Distribution Chain: HF vs. UHF

In this paper, we investigate and compare the use of passive HF and UHF RFID systems for the item level identification of pharmaceutical products throughout their supply chains. We compare the overall identification performances of both types of RFID systems on individual products and on totes filled with tagged products. Scenarios representative of all aspects of the pharmaceutical distribution chain from the manufacturer to the retailer are considered. We conclude that the tested passive UHF RFID system provides significantly superior identification performance than do passive HF RFID systems.

Environmental and performance analysis of SAW-based RFID systems

This paper describes the environmental effects and performance analysis of 2.45 GHz Surface Acoustic Wave (SAW) based RFID systems. Piezoelectric materials and their underlying principles are reviewed to describe the nature of SAWs. A performance analysis is conducted to measure the readability and read range for individual tags, compared to multiple tags in a field environment. On the other hand, effects of temperature, humidity, altitude and vibration on the readability and operability of the system are described. Finally, a conclusion is drawn with regards to the performance of SAW-based RFID systems.

Routing in Heterogeneous Wireless Ad Hoc Networks

Existing routing protocols for wireless ad hoc networks assume a homogeneous network with either omnidirectional antennas or smart (beamforming) antennas. However it is possible to have a heterogeneous network with each node either using an omnidirectional antenna or a smart antenna. We investigate the routing and MAC layer issues that arise in such heterogeneous networks. We extend the expected number of transmissions (ETX) metric and propose a new power-controlled routing metric applicable for heterogeneous networks. This routing metric also serves the purpose of neighbor discovery, which now additionally involves finding the type of neighbor. We use information from the routing layer to propose changes at the MAC layer. We evaluate the performance of this new routing metric through simulations. We And that using smart antennas along with omnidirectional antennas improve the aggregate the network throughput up to 200 % in a random topology and up to 47 % in a grid topology. We identify issues that need further consideration for improving the performance of heterogeneous networks.

Robust and Dynamic Bin Slotted Anti-Collision Algorithms in RFID System

In this paper, we present the Dynamic Bin Slotted memoryless anti-collision algorithm (DBS) and the Robust Dynamic Bin Slotted memoryless anti-collision algorithm (RDBS) (which is a countermeasure to the strong and weak tag problems). They are based upon a bin slot tree algorithm. Both algorithms combine deterministic and probabilistic approaches to improve performance. We suggest a simple estimator to estimate the number of tags in an interrogation zone that is optimized for bin-slot tree algorithms. Our performance evaluation shows that DBS and RDBS surpass other existing bin slotted algorithms. According to our simulation results, the total identification time of the DBS algorithm for all tags is reduced by 57.28% for 300 tags compared to the conventional Bin Slotted Algorithm (BSA). Moreover, under the strong-weak tag problem, the RDBS algorithm reduces over 29.59% of the total number of PingID commands and 3.51% of the identification time for maximum 300 tags over the Bin-slotted Hybrid Search Algorithm, which is the best reported variation of BSA.

Impacts of RF radiation on the human body in a passive wireless healthcare environment

In this paper, we identify the most significant problems involving the impacts of radio frequency (RF) radiation on the human body. The coming pervasive healthcare environment will rely heavily upon wirelessly communicating devices to provide the information visibility and communication capabilities required to achieve these ambitious systems. The impact of significant and continuous RF radiation exposure must be understood to ensure that we first do no harm with our new environments. The specific absorption rates (SAR) is a dosimetric measure that has been widely adopted as a method for quantifying radiation absorbed by the human body. This tool is both simple and useful. We investigate the factors that affect RF absorption in human tissues to identify the physical and biological factors that impact RF absorption. Similarly, we investigate the factors that influence biological responses to the effects of absorbed and incident RF radiation. We focus specifically on low power and passive communicating systems that will form the vast majority of the wireless devices in a pervasive healthcare environment.

2D localisation using SAW-based RFID systems: a single antenna approach

This paper presents a novel Real-Time Localisation System (RTLS) based upon 2.45 GHz Surface Acoustic Wave (SAW) Radio Frequency Identification (RFID) systems. The system utilises a novel localisation method that combines the angular rotation of the RFID readers antenna system with the inherent Time-of-Flight (TOF) distance measurement capabilities of the SAW RFID system. The system design rests upon the sound physical fundamentals of electromagnetic radiation and SAW operation. The system was implemented and empirically evaluated. It was determined to provide accurate 2-Dimensional (2D) location of the SAW tag that is within 3.17 cm of the actual location for a reader to tag range of up to 10 m.