RFID Systems

Research Trends and Challenges

Miodrag Bolic, David Simplot-Ryl, Ivan Stojmenovic, Miodrag Bolic, David Simplot-Ryl, Ivan Stojmenovic

• Publisher: Wiley
• Year: 2010
• Print ISBN: 9780470746028
• eBook ISBN: 9780470975664
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria elettronica e telecomunicazioni

This book provides an insight into the 'hot' field of Radio Frequency Identification (RFID) Systems

In this book, the authors provide an insight into the field of RFID systems with an emphasis on networking aspects and research challenges related to passive Ultra High Frequency (UHF) RFID systems. The book reviews various algorithms, protocols and design solutions that have been developed within the area, including most recent advances. In addition, authors cover a wide range of recognized problems in RFID industry, striking a balance between theoretical and practical coverage. Limitations of the technology and state-of-the-art solutions are identified and new research opportunities are addressed. Finally, the book is authored by experts and respected researchers in the field and every chapter is peer reviewed.

Key Features:

• Provides the most comprehensive analysis of networking aspects of RFID systems, including tag identification protocols and reader anti-collision algorithms
• Covers in detail major research problems of passive UHF systems such as improving reading accuracy, reading range and throughput
• Analyzes other "hot topics" including localization of passive RFID tags, energy harvesting, simulator and emulator design, security and privacy
• Discusses design of tag antennas, tag and reader circuits for passive UHF RFID systems
• Presents EPCGlobal architecture framework, middleware and protocols
• Includes an accompanying website with PowerPoint slides and solutions to the problems http://www.site.uottawa.ca/~mbolic/RFIDBook/

This book will be an invaluable guide for researchers and graduate students in electrical engineering and computer science, and researchers and developers in telecommunication industry.

Part One

Components of RFID Systems and Performance Metrics

Chapter 1

Performance of Passive UHF RFID Systems in Practice

Components of RFID Systems and Performance Metrics

Miodrag Boli

1

Akshay Athalye2

Tzu Hao Li1

1School of Information Technology and Engineering, University of Ottawa, Canada

2Astraion LLC, NY, US

1.1 Introduction

1.1.1 Overview

Radio Frequency Identification (RFID) is a technology that has risen to prominence over the past decade. The clear advantages of this technology over traditional identification methods, along with mandates from supply chain giants like Wal Mart and the Department of Defense, led to a large number of research and commercialization efforts in the early 2000s. However, almost a decade on, the early promise of widespread, ubiquitous adoption of RFID is yet to materialize. This is due to a combination of several technical and commercial factors. The technical imperfections and shortcomings existing in present day RFID systems pose a very significant obstacle to the widespread adoption of RFID. Overcoming some of these challenges would amount to a very significant step forward towards realizing the tremendous potential of RFID technology. This book describes the ongoing efforts of some of the leading researchers in the field towards tackling the most challenging issues in today's RFID systems. With this in mind, the aim of this chapter is to clearly demonstrate, through experimentation, some of these technical challenges faced by RFID systems in practice. This chapter will enable the reader to better recognize the shortcomings of today's RFID systems and will allow for a better understanding and appreciation of the research efforts described in the rest of the book.

In this chapter, we focus on passive RFID systems operating in the Ultra High Frequency (UHF) band and adhering to the popular EPC Global Class 1 Generation 2 (Gen 2) standard (1). We begin with the characterization of a hypothetical “ideal” RFID system. We then proceed to examine the performance of practical RFID systems through simple experiments and point out the non idealities and problems that arise in practical systems. We begin this examination by considering a simple system involving a single stationary reader and a single stationary tag in free space. We then examine systems with increasing degrees of complexity with multiple (possibly mobile) readers and tags in more challenging deployment environments. As complexity of RFID systems increase, more problems (non idealities) are observed in the performance while problems identified with simpler systems remain. We believe that the approach of analyzing RFID systems with an increasing degree of complexity and identifying challenges as they appear will give the reader a sound understanding of the challenges facing real world RFID systems.

Please note that this book chapter represents our viewpoint on imperfections of RFID systems. We have tried to point out some of the major issues in existing UHF RFID systems. This is not meant to be an exhaustive listing of all the possible challenges in practical UHF RFID systems, and there may be some problems and issues that have not been addressed here.

1.1.2 Background

RFID is a wireless technology that allows for automated remote identification of objects (2). The major components of an RFID system are tags or transponders that are affixed to objects of interest and readers or interrogators that communicate remotely with the tags to enable identification. RFID systems exist in various flavors that can be classified based on the frequency of operation, power source of the tag and the method of communication between the reader and the tags. A detailed classification of the commercial RFID systems based on the above criteria is presented in Chapter 2. In addition, the overview of RFID technology is presented in a number of publications including (3, 4). In this introductory chapter, we focus on passive RFID systems operating in the 860–960 MHz band. Passive RFID tags draw the power required for operation from the radio wave transmitted to them by the reader and communicate with the reader by controlled reflection of a portion of this incident wave. This technique of communication by controlled reflection is referred to as backscatter modulation. Although this technique was used as early as World War II, RFID transponders were expensive, large devices that remained confined to military applications. However, the tremendous progress in VLSI technology along with the establishment of standards in the early 2000s, enabled RFID tags to be manufactured in high volumes resulting in a price point that initiated numerous commercial applications. The main goal of commercial RFID systems is to automate and enhance asset management by providing global asset visibility. This ability of RFID systems finds various applications in diverse fields such as supply chain management, indoor asset and personnel tracking, access control, robotics and many more.

The immense commercial potential of RFID is mainly due to the numerous advantages that the technology possesses over traditional identification mechanisms such as barcodes. Some of these advantages are: (i) passive RFID tags can be read at much greater distances than barcodes; (ii) there is no need for a line of sight between the reader and tag; (iii) multiple tags can be read at much higher rates than barcodes; (iv) RFID tags have much larger memory than barcodes which allows storage of a lot more information than just the ID; and (v) the information contained in the RFID tag can be modified dynamically using the interrogator.

As mentioned earlier, in order to harness the advantages of RFID technology to build viable commercial solutions, a number of technical challenges needs to be overcome. Some of these challenges are common to other wireless technologies while others are unique to the RFID system to hand. Each RFID technology, including passive, semi passive and active RFID systems operating at different frequencies, poses a unique set of challenges to obtain the desired performance. In addition, design requirements, performance specifications and protocols for active, passive and semi passive systems are also very different. Therefore, in this chapter, we will limit our discussion to long range passive backscatter based UHF RFID systems operating in the 860–960 MHz band. In our opinion, this type of RFID has the most potential for significant commercial impact. As a result, it has seen the most research and standardization activity in recent years, more than other types of RFID systems. Today commercial systems of this type adhere to the EPC Global Class 1 Generation 2 (Gen 2) standard that has been in effect since 2005 (1). Gen 2 compliant readers and tags are readily available in today's market from several vendors all over the world including Alien Technology, Impinj Inc., Motorola and others.

There have been several approaches in characterizing RFID systems. They are mainly based on (1) experimental characterization; and (2) mathematical modeling and simulation based analysis. Experimentation is either performed in a controlled environment such as anechoic chamber, in the laboratory environment (5), (6), (7), (8) or in the application specific setups such as conveyer applications (8). An example of modeling and simulation based analysis is performed in (9) where tag characteristics, propagation environment, and RFID reader parameters have been modeled and simulated. In this chapter, RFID systems are characterized through experimentation in an anechoic chamber and laboratory environment.

1.2 Ideal RFID System

We begin our analysis of practical RFID systems by presenting the characteristics of a hypothetical ideal RFID system. Of course, like most other ideal systems, this RFID system would be unrealizable in practice. However, formulating such a system will give us a better understanding of the problems faced by real world RFID systems. Once again, we point out that this ideal system is formulated in the context of UHF passive RFID systems.

Since passive tags do not have a battery, they need to receive enough energy to turn on the tags' integrated circuit. Therefore, in order for a passive RFID system to operate, the tag needs to receive enough power to wake up, and its backscattered response needs to be correctly received and decoded by the reader. In addition to this basic functionality, an RFID system has several other requirements for efficient operation that will be described later as desired features. The characteristics of an ideal RFID system, that mainly correspond to the basic functionality, can be summarized as follows:

1. There exists a well defined, controllable read zone for each reader. For every tag within its read zone, each reader has a 100% read rate or read accuracy and for tags outside its read zone, each reader has a 0% read rate.1

2. Performance is insensitive to the physical orientation of tags.

3. Performance is insensitive to the nature of the object on which the tag is placed.

4. Performance is insensitive to the environment in which the syst...

Table of contents

• Cover
• Title Page
• Copyright
• Dedication
• About the Editors
• Preface
• Acknowledgements
• Part One: Components of RFID Systems and Performance Metrics
• Part Two: Tag Identification Protocols
• Part Three: Reader Infrastructure Networking
• Part Four: Addressing other Challenges in RFID Systems
• Index