sensor (rfid) - Oklahoma State University

1 downloads 134141 Views 3MB Size Report
quality, integrity, performance monitoring and surveillance. • Simulation based .... Companies like Texas Instruments, Impinj, Philips. Semiconductors, Alien .... 15m or even more. For above mentioned warehouse applications, UHF is the best.
SENSOR (RFID) NETWORKS AND COMPLEX MANUFACTURING SYSTEMS MONITORING (COMMSENS): LABORATORY FOR RFID RESEARCH

Satish Bukkapatnam Associate Professor Oklahoma State University Stillwater OK

REPORT OF WORK CONDUCTED UNDER THE AEGIS OF CELDi STRATEGIC RESEARCH GRANT 2005: “EXPERIMENTAL TEST BED FOR PERFORMANCE EVALUATION OF RFID SYSTEMS”

Contributing Members: Jayjeet M. Govardhan Sharethram Hariharan Vignesh Rajamani Brandon Gardner Andrew Contreras

Oklahoma State University Stillwater OK

TABLE OF CONTENTS EXECUTIVE SUMMARY ....................................................................................................................3 SECTION 1: INTRODUCTION...........................................................................................................5 SECTION 2: GUIDELINES FOR RFID SYSTEM DESIGN AND DEPLOYMENT PART 1: TAG AND READER DESIGN GUIDELINES.................................................................................. 10 SECTION 3: GUIDELINES FOR RFID SYSTEM DESIGN AND DEPLOYMENT PART 2: USE CASE MODEL AND ARCHITECTURE OF SAVANT.......................................................... 28 SECTION 4: SUMMARY OF BEST INDUSTRY PRACTICES & DEVELOPMENTS IN RFID SYSTEMS AND THEIR EXPERIMENTAL INVESTIGATION ................................................... 45 SECTION 5: STATISTICAL ANALYSIS AND DESIGN OF RFID SYSTEMS FOR MONITORING VEHICLE INGRESS/EGRESS IN WAREHOUSE ENVIRONMENTS............ 77

2

Executive Summary In the late fall of 2004, CELDi approved our proposal on developing "Experimental test bed for performance evaluation of RFID systems." This grant has spurred the development of a laboratory for Sensor (RFID) Networks and Complex Systems Monitoring (COMMSENS) research. This lab is spread over 1000 sq. ft. space in the Advanced Technology Research Center (ATRC) of Oklahoma State University. Our initial efforts under this grant were focused on procuring the instrumentation to create an experimental test bay for RFID systems performance assessment. The test bay consisted of AWID and Alien readers and 200 passive tags. Using this test platform, we have successfully validated a systematic approach, based on combining statistical analysis and Electromagnetic principles, for robust design of RFID systems. Publications on the following three topics have emerged as a result of our investigations: 1. Development of Guidelines for Front/Backend Design of an RFID System, 2. Best Industry Practices in RFID System Deployment, and 3. Statistical Analysis and Design of RFID Systems for Monitoring Vehicle Ingress/Egress in Warehouse Environments Furthermore, in order to facilitate a broad dissemination of research undertaken in the COMMSENS on RFID systems and sensor technologies, a new course on RFID applications in manufacturing systems was created in Spring 2005. This course, open to both undergraduates and graduate students at OSU, is one of the first ones offered on RFID applications in production systems. Collaborating with University of Nebraska, we have offered a 6-hour tutorial on RFID fundamentals and Applications at CELDi pre-conference event during Spring 2005. The course content for the next offering of RFID course in the spring of 2005 has been re-designed taking into account an increase in enrollment levels and the need to include the developments that have taken place since the last offering of the course. In fact, many developments have taken place in the recent times that can lead the industries towards efficient adoption of RF and sensor technologies. We strongly feel that more background preparation is necessary in order to bolster the exponential growth of these technologies as well as their adoption in the real world applications.

3

A research is never complete or successful unless it can reach the end users, namely, the industries. Towards this end, we have initiated partnership projects with GM, FAA Logistics Center, and Oklahoma Department of Transportation. This allows us to share our knowledge of RFID systems and sensor technologies with, in some sense, the business world. We have also initiated dialogues with SUN RFID Center, and RFID component vendors, including manufactures like Alien and AWID, RFID consultants, and academic institutions, particularly, the University of Nebraska. We have also been successful in attracting 12 students to participate in our research activities. Their qualification levels range from undergraduate to graduate standing (M.S. to Ph.D. level) with diverse backgrounds such as from mathematics, mechanical and aerospace engineering, industrial engineering, and electrical engineering. Their passion for advancing RFID systems and sensor technologies is a common thread that binds them all. COMMSENS lab research conducted under the aegis of CELDi, thus, has had a positive impact on the students involved as well as on our knowledge and understanding of RFID systems and sensor technologies.

4

Section 1: Introduction 1.1 Background The Sensor Networks (RFID) and Complex Manufacturing Systems Monitoring Research (COMMSENS) lab was established in 2004 at the Advanced Research Center (ATRC) of Oklahoma State University in Stillwater, OK.

The

COMMSENS Lab facilities are spread over 1000 square feet at the ATRC for hosting test-beds for RFID and RF Sensing research. Lab facilities include antennae and readers from Alien and AWID, as well as 200 passive tags of various specifications. The lab also features RF sensing devices like motes from moteiv® (IEEE 802.15.4 compliant) for wireless mesh networking. All RFID information is processed in a Linux server that uses the SUN JAVA RFID software package with an Application Server and Enterprise Manager.

Oracle 10i is used as the database to store

information collected from our experiments. New experimental test bays with the latest Gen 2 specific hardware and software are being set up for the future applications.

1.2 Mission The mission of the lab is to study the principles of monitoring real world complex systems by harnessing information from a network of wired and wireless sensors. Such applications include various complex manufacturing machines, processes, enterprises, consumer products, and infrastructures like bridges, pipelines and railroads. Furthermore, we are attempting to harness large amounts of sensor data to bring substantial improvements to the design and operations, particular in quality and integrity assurance, of these engineering systems, which include many precision manufacturing machines and processes, the Internet, supply networks and infrastructure and lifelines systems. Overall, the objectives of our research are the following: •

Study the origins of complicated patterns in sensor signals from manufacturing machines, processes, and specific infrastructure and lifeline systems 5



Derive theory and methods to capture the dynamics underlying these signals for quality and integrity monitoring

1.3 Accomplishments The following is a list of accomplishments and awards received as a result of COMMSENS research: •

The lab efforts have received support from NSF, CELDi (the nation’s largest Industry-University consortium focused on logistics), General Motors, FAA, and the US Department of Transportation to the tune of $0.9M during 200405



A new course focusing on RFID system applications in manufacturing and engineering systems (one of the firsts of its kind in Industrial Engineering) offered in spring 2005



A systematic statistical approach for experimental design of an RFID system developed. Also the research has yielded new principles for harnessing information on the complex (nonlinear and stochastic) nature of the process underlying signals from RFID and other sensor networks



The research has yielded 25+ journal papers and 20+ publications in refereed conference proceedings apart from being the basis for 3 PhD theses



Currently 16 students including 3 PhD, 5 MS thesis, 2 MS creative component, and 3 undergrad students take part in the lab activities (these include 3 members from underrepresented groups)

1.4 Education Accompanying the research at the COMMSENS lab are several educational components, which include: •

A new course on RFID Applications in Manufacturing Systems offered in Spring 2005



Guest lectures offered by several prominent industry speakers and implementers of RFID to share

ideas and discuss technical issues

surrounding RFID; thus supplementing course material with practical aspects •

Field trip to SUN-RFID Testing Center in Texas was organized where pallet level and item level readability in conveyor environment was demonstrated 6



White papers that describe the quantitative and qualitative aspects of deploying RFID in a given environment have been published ─ papers detailing recent experiments are forthcoming



A 6 hour tutorial on RFID fundamentals and applications offered to industry participants as part of 2005 CELDi pre-conference event

1.5 Capabilities Capabilities and resources of the COMMSENS lab are the following: •

Test bays and a statistical approach for RFID system design and deployment



New design method based on combining statistical and electromagnetism principles to screen parameters affecting an RFID system performance



Framework to undertake customized ROI studies



RFID /RF sensor deployment, instrumentation and integration studies for quality, integrity, performance monitoring and surveillance



Simulation based evaluation of decision enrichment using RFID/RF sensor information



A new simulation approach based on continuous flow dynamics for fast evaluation of system performance



Quality and integrity monitoring of complex machines and processes including precision machining and other manufacturing operations



Sensor-based health monitoring of complex structures for condition-based maintenance and Integrity assurance



Characterization of nonlinear stochastic dynamics underlying in large complex systems including various manufacturing machine operations, smart material and structural systems, large supply and transportation networks, and the Internet. See lab photographs below

7

Reader & Antenna Setup High Tag Density

Foam

Metal

Bubble Wrap

EDS

Linux System

Liquids

Reader & Antenna setup

1.6 People The people involved in COMMSENS research come from a variety of backgrounds such as mathematics, industrial, mechanical, and electrical engineering. The following is a list of the people involved with COMMSENS research at OSU: •

Satish T. S. Bukkapatnam, Ph.D., Associate Professor Topic: Overall Project Supervision



Brandon Gardner, Graduate Student, Dept. IEM Topic: Financial Model of RFID Systems



Sharethram Hariharan, Graduate Student, Dept. IEM Topic: Improved Decision Making in Business Process by the use of Markov Decision Process



Vignesh Rajamani, Graduate Student, Dept. EE Topic: EM Theory Applications in Antennae and RFID Systems Design

8



Jayjeet Govardhan, Graduate Student, Dept. IEM Topic: Technical Aspects of RFID System Design



Alicia Jones, Undergraduate Student, Dept. IEM Topic: RFID Sensor Documentation



Andrew Contreras, Undergraduate Student, Dept. MAE Topic: Gen 2 System Analysis



Amjad Awawdeh, Graduate Student, Graduate Student, Dept. EE Topic: RFID Sensor Applications



Tanay Bapat, Graduate Student, Dept. IEM Topic: Documentation of RFID Coursework



Randy Clark, Undergraduate Student, Dept. of IEM Topic: RFID front-end design



Gerardo Myrin, Undergraduate student, Dept. of IEM Topic: RFID front-end design



Vipul Navale, Graduate student, Dept. of IEM Topic: RFID front-end design



Chetan Yadati, Graduate Student, Dept. of IEM Topic: Implementation of Use Case Analysis in RFID middleware development

1.7 Organization of Report This report is divided in to four main components: I. Guidelines for RFID System Design and Deployment Part 1: Tag and Reader Design Guidelines II. Guidelines for RFID System Design and Deployment Part 2: Use Case Model and Architecture of Savant III. Summary of Best Industry Practices & Developments in RFID systems and their experimental investigation IV. Statistical Analysis and Design of RFID Systems for Monitoring Vehicle Ingress/Egress in Warehouse Environments

9

Section 2: Guidelines for RFID System Design and Deployment Part 1: Tag and Reader Design Guidelines Summary The design and selection of appropriate RFID system components is usually among the first steps in the implementation of an RFID system. Over twenty parameters govern the performance of an RFID system in a given environment. This document is the first of a two part series that guidelines for developing a basic RFID system for a particular application and introduces the relevant RFID fundamentals concepts.

2.1 Introduction to RFID Radio frequency identification (RFID) is a generic term used to describe the technologies that harness radio-frequency waves to transfer data between a reader and a tag to identify, categorize and track objects. RFID is fast, reliable, and does not require physical sight or contact between reader and the tagged object. An RFID system consists of tags (also known as transponders), readers and a computing infrastructure for storing and analyzing the data received from the reader. A transponder is usually a memory device (e.g. Electrically Erasable Programmable Read-only Memory EEPROM) fitted on the object to be identified. It contains information to uniquely identify an object. The reader is capable of generating, receiving, demodulating and deciphering RF signals. As summarized in Figure 1, the reader sends RF signal into the environment. As soon as a tag comes into the reader’s RF electromagnetic field, the tag circuit sends signals back to the reader, thus identifying the object. This identification technology can be used for real time object tracking, goods and/or asset management, etc. The tags can be classified into various types depending on whether they are active or passive, read only and/or writable, etc. The readers too have different specifications like frequency, type of data transmission method, etc. The selection of the tag and reader attributes strongly impact the performance of the RFID system.

10

Figure 1: Components of an RFID System [1]

2.2 RFID Tag Selection Guide The selection of RFID tag plays critical role in the successful deployment of an RFID system. The appropriate tag should conform to the required functionality expected in the given field, application, environmental conditions, and government’s regulations on the frequency use.

2.2.1 Parameters considered in Tag Selection: Following are the seven major parameters [2] considered in the process of tag selection (See Figure 2): 1.

Application Requirements

2.

Read Range

3.

Frequency

4.

Functionality

5.

Environmental Conditions

6.

Form Factor

7.

Standard Compliance EPC/ISO

11

Figure 2: Parameters Affecting Tag Selection

2.2.1.1 Application Requirements RFID system applications include dock door reading, asset management, and transportation, inventory management in warehouses, conveyor reading, and point of sale reading, handheld mobile reading and smart identification card systems. These are the typical examples based on our observation. [The different applications and estimated growth of the global market for RFID systems can be seen in Figure 3].The application determines where and what objects are to be tracked. The applicationimposed constraints, ultimately determine the choice of the read range.

Figure 3: Estimated growth of global market for RFID systems[3]

12

2.2.1.2 Read Range Read Range is the farthest distance between reader and tag at which reader can read the tag. Determinants of read range include frequency of operation, Electromagnetic Interference (EMI) levels, power of the reader (which is usually limited by Federal mandates), tag functionality, size of stored data, read time, relative velocity between the tagged object and the reader, and antenna design. The major factor among these is the frequency of operation based on the read range requirement 2.2.1.3 Frequency Range The frequency ranges are categorized as Low (LF), High (HF), Ultra High (UHF) and Microwave frequency. The choice of frequency range depends upon the application / performance requirements and the regulatory requirements. The actual frequency values vary as per geographical regions. For US and Canada, 13.56 MHz is considered as HF and UHF ranges from 902 MHz-928MHz. This variation in actual frequency range values for geographical regions is a hindrance in developing a unique RFID system that can be deployed worldwide. Refer table for more details [4], [5]

13

Table 1: Geographical Variation in Frequency Ranges

Frequency Zones US and Canada Europe Japan

Low High Frequency(LF) Frequency(HF)

Ultra High Frequency(UHF)

Microwave

125 - 134 KHz

13.56 MHz

902 - 928 MHz

2.4 - 2.48 GHz

125 - 134 KHz 125 - 134 KHz

13.56 MHz 13.56 MHz

868 - 870 MHz 950 - 956 MHz

2.4 - 2.48 GHz 2.4 - 2.48 GHz

2.2.1.4 Functionality Based on functionalities, tags may be classified as passive, active and semipassive. Passive tags are not supported with batteries, but they are powered by the energy supplied by reader field. Passive tags are cost effective and used in supply chain for identifying and tracking objects. Active tags are battery powered. See Figure 4. They can be used for long-range applications. Semi-passive tags are supported with batteries, but they are activated by the reader field. These tags are used for capturing additional details like temperature, humidity, etc.

Figure 4: Tag Functionality

2.2.1.5 Form Factor Form factor determines the size and shape of a tag. Generally, larger tags provide better range performance over tags with smaller form factors. The trade off analysis

14

between the size of the tag and required range performance must be carried out while selecting tag for particular application. See Figure 5.

Figure 5: RFID system classification based on tag functionality

2.2.1.6 Environmental Conditions Environmental conditions and materials near RFID systems can affect RF field parameters like reflectivity/refractivity, absorptive and dielectric properties (detuning). Hence, tag performance is dependant upon materials near the tag and environmental conditions like temperature, humidity, etc. Different frequency ranges experience different degree of effects due to above materials. For example, the attenuation of reflectivity increases with the frequency. The suitable frequency range and tags should be chosen in order to minimize these effects. Table 2: Effect of Materials on RF field

Material Cardboard Conductive liquids Plastics Metals Groups of cans Human body / animals

Effect on RF field Absorption (moisture), Detuning (dielectric) Absorption Detuning (dielectric) Reflection Complex effects (lenses, filters), Reflection Absorption, Detuning (dielectric), Reflection

15

2.2.1.7 RFID Standard Compliance In order to avoid interferences from other RF applications like electric and radio equipments and to achieve interpretability between different tags and readers, RFID system standards are being developed. These standards deal with air-interface protocol, data content, conformance with regulatory requirements, and application. Two major standards available today are Electronic Product Code (EPC) Global and ISO/IEC standards. • EPC Standards EPC has specified standards for tag data content, communication between tag & reader (air-interface protocols), reader protocols, Savant specifications, Physical Mark-up language (PML) specifications, and Object Naming Service (ONS) specifications for HF and UHF ranges. There are two versions of these standards. Version 1 is already in use and version 2(Generation 2) is ratified and going to be adopted in near future. As per this standard, data is stored on the tag, in the format as shown in Figure 6. Version 1 is already in use and version 2(Generation 2) is ratified and going to be adopted in near future. Companies like Texas Instruments, Impinj, Philips Semiconductors, Alien Technology, Symbol Technologies and Intermec Technologies have announced their plans to manufacture Gen 2 tags.

Figure 6:Tag Data Partition

16

Table 3: Tag Classification based on EPC Global Protocol [4]

EPC

Description

Class

Functionality

Remarks Data can be written only once

0

Read Only

Passive tags

during tag manufacturing and read many times

1

Write Once and

2

3

Read only

Read/Write

Read/Write

Data can be written only once Passive tags

by tag manufacturer or user and read many times

Passive tags

Semi-passive tags

User can read/write data many times Can be coupled with on board sensors for capturing parameters like temperatures, pressure, etc. Can be coupled with on board

4

Read/Write

Active tags

sensors and act as radio wave transmitter to communicate with reader

• ISO/IEC 18000 Series ISO & IEC have established Joint Technical Committee to address technology standards. Within JTC -1, Subcommittee 31, Work Group 4 deals with RFID. ISO 15693 and ISO 18000 series provide air interface standards for communication between tag-reader and reader-tag at LF, HF, UHF and microwave frequencies. These standards also specify parameters like data encoding rules, data transmission rates, types of signal modulations and anti-collision protocols [6], [7]. • 18000-1 Part 1 - Generic Parameters for the Air Interface for Globally Accepted Frequencies • 18000-2 Part 2 - Parameters for Air Interface Communications below 135 KHz 18000-3 Part 3 - Parameters for Air Interface Communications at 13.56 MHz 17

• 18000-4 Part 4 - Parameters for Air Interface Communications at 2.45 GHz • 18000-5 Part 5 - Parameters for Air Interface Communications at 5.8 GHz (Withdrawn) • 18000-6 Part 6 - Parameters for Air Interface Communications at 860 to 930 MHz • 18000-7 Part 7 - Parameters for Air Interface Communications at 433 MHz Efforts are initiated to form a unique standard that will avail a common platform for widespread adoption of RFID technology all over the world.

2.3 Market Survey Below is the summary of available tags and tag manufacturers in today’s market. This summary of various tag manufacturers, tag functionalities and their features will help user to select appropriate tag for his application. Table 4: RFID Tag Market Survey

Manufacturer

Model

Frequency

Functionality Standard

Remark General purpose

Alien

ALL-9238,

UHF

ALL-9250,

(902-928

ALL-9254

MHz)

Passive and 64 bit

EPC

item tracking,

Global

suitable in

Class 1

metallic

Technology [8]

environment ALL-9338,

UHF

ALL-9354,

(902-928

ALL-9334

MHz)

UHF Matrics

Dual Dipole

/Symbol

(902-928 MHz)

Passive and 96 bit

Passive 112,128 bits

EPC Global Class1

EPC Global Class 0

Technologies [9]

Single Dipole

UHF (902-928 MHz)

Passive 112,128 bits

EPC Global

General purpose item tracking

General labeling, carton & pallet labeling, and pharmaceutical labeling

Class 0

18

Manufacturer

Model

Frequency

Functionality Standard

Remark

0.4mm x 0.4mm

Hitachi [10]

Mu-chip

13.56 MHz

Passive and 128 bit

EPC

x 0.060 mm size.

Global

Can be used in

Class 1

currency notes for authentication

Used in tire

Tire Tag Insert

tagging. Typical

UHF 869 /915

Passive

Class 1

MHz

[11]

include work in process (WIP),

Intermec Technologies

Applications

quality control Container

UHF

Tag

915 MHz

Passive

Class 1

CIB Meander Free Space Insert

Pallet, carton and container tracking Electronic Article

2.45 GHz

Passive

Class1

Surveillance tags, and inventory management

19

2.4 RFID Reader Selection Guide A reader is critical to a successful deployment of a RFID system. The appropriate reader should fit with required functionality based on the application, environment conditions and country’s frequency norms. This section presents the criteria for reader selection. 2.4.1 RFID Reader Selection Guide Following are major parameters considered in the process of reader selection: 1.

Application Requirement

2.

Frequency Range

3.

Read/Write Range

4.

Functionality of Tag

5.

Standard EPC/ISO Air Interface

Figure 7: Parameters Affecting Reader Selection

20

2.4.1.1 Application Requirement The shape, size and functionality of a reader change according to the application of the RFID system. Some of the common RFID systems are conveyor reading, dock door reading, forklift reading, mobile reading etc. 2.4.1.2 Frequency Range A suitable reader, for a given application, can be selected to match the frequency range chosen (LF, HF, UHF or Microwave). Multi-frequency readers can be chosen if the application requires using both short as well as long read/write ranges. 2.4.1.3 Read/Write Range Read range is based on the frequency chosen, functionality of the tag and power of the reader. Write range is the distance from which a reader can write tags. This range is usually 70% of read range. 2.4.1.4 Functionality of Tag Active and passive tags talk to reader using different air-interface protocols. Hence, reader should support the functionality of tag. A multi-protocol reader which supports different protocols is seen as the best solution and is quiet popular in today’s market. 2.4.1.5 Air Interface Protocol Reader should support the air-interface specifications provided by either EPC or ISO standards. The reader and tag should comply with these standards. Some readers can support EPC as well as ISO standard protocols and these are the most popular ones in the market. 2.4.1.6 Other Factors Other factors like the number of tags read per second, interface to the host and anti-collision (Tag collision and Reader collision) are also important. Based on need of application, suitable parameters can be chosen for the selection of the reader. Anticollision requirement can be the most demanding feature. Reader should recognize

21

uniquely the identity of tags lying in the range of the reader. ISO and EPC protocols define anti-collision implementations.

2.5 Market Survey Below is the summary of readers and their manufacturers in today’s market. Table 5: RFID Reader Market Survey

Manufacturer

Model

Frequency

Type

Standard

Remark Compatible with any LAN

ALR9780

UHF 902-928

Fixed

MHz

EPC Global Class1

network, perfect match for applications where highspeed, highly reliable reads are required. Low-cost, flexible

Alien

industrial reader, The

Technology [8] ALR9640

reader electronics and

UHF 902-928

Fixed

MHz

EPC Global Class1

antenna reside in a single package, eliminating external antenna cables, resulting in a simple and inexpensive installation.

Multiprotocol readerSupports all EPCcompliant passive RFID Matrics/Symbol Tech [9]

UHF AR-400

902-928 MHz

Fixed

EPC Class 0 and Class 1

tags, Allows dynamic data updates for broader application support and provides flexibility in tag usage, EPC Generation 2 Upgradeable

22

Manufacturer

Model

Frequency

Type

Standard

Remark

EPC Class

Samsys Technologies [12]

MP9320 MP9310

UHF 902-928 MHz

Fixed

0, 0+, Class

Flexibility in supporting

1,

multiple tag protocols,

ISO18000-

multi-regional regulatory

6A, 6B, 6B

compliance, and

"fast",

programmability for a

Philips U-

multitude of EPC

code 1.19,

applications environments

1.19 "fast",

Configurable for North

Intermec

America FCC (902-928

Intellitag,

MHz) and European ETSI

EM Marin

(865-869 MHz) regulatory

4022, 4222,

environments

4223

23

2.6 Boilerplate for RFID Component Selection of a Typical Warehouse 2.6.1 Warehouse Operations RFID technology has great potential in streamlining warehouse operations to meet the dynamic market demand. We have developed RFID tag and reader selection guide which can be used to configure the RFID system for particular applications. This section contains a brief discussion of the various warehouse operations and how the RFID tagreader selection guide can be used to configure RFID system for these operations.

2.6.2 Assumptions In preparing the above boilerplate, the following assumptions are made: 1.

The warehouse under consideration is used only for consumer goods.

2.

Case and pallet level tagging are the only ways to deploy RFID tags on the

products. (Item level tagging is not considered).

The key operations in warehouse are: 1.

Receiving

2.

Inspection

3.

Bulk Storage / Cross Docking

4.

Order Picking and Sorting

5.

Shipping

Figure 8: Material Flows in a Warehouse

24

The above operations can be defined briefly, as follows and depicted in Figure 8 and explained below: 1. Receiving Incoming truck is identified and routed to appropriate receiving dock. At receiving dock, products (raw material, semi-finished, or finished) are unloaded. 2. Inspection The quality (mostly visual inspection for damage detection of cartons) and quantity of received products is assured as per requirement. The faulty products are separated. 3. Cross Docking Cross docking is the process of unloading material from one truck or trailer and loading it to outbound truck or trailer without storing it in warehouse. 4. Bulk Storage Received products are identified and routed to appropriate storage location in warehouse. Generally, the products are stored in carousals, racks or on pallets. 5. Order Picking and Sorting Once the order is received, the products are picked in correct quantity. Once order is filled, the products are routed to correct shipping dock. 6. Shipping The shipment of right products to the right customer is ensured.

25

Figure 9: Operations in Warehouse: Receiving, Inspection, Bulk Storage/Cross Docking, Order Picking/Sorting, Shipping

2.6.3 RFID tag and reader selection The various parameters that should be considered for tag and reader selection are application requirement, frequency, read range, functionality of tags, environmental conditions, form factor and standard/compliance. The RFID applications in warehouse include, dock door or portal reading, forklift reading, conveyor reading, stretch wrap reading and overhead reading. Based on these applications, there is a need of RFID system that can track tags placed on individual pallets and cases, at long distances and in large quantities. Low frequency RFID system has read range of few centimeters. For High Frequency systems, range is up to 1m. For Ultra High Frequency (UHF) systems range can be obtained more than 1 m and up to 15m or even more. For above mentioned warehouse applications, UHF is the best suitable frequency due to longer read range and fast and large amount of data transfer. The environmental conditions and the nature of the product also play an important role in selecting RFID frequency range. The presence of metals and liquids near RFID systems can have deleterious effects on RF field like reflection/refraction and absorption. In the

26

case of a consumer goods warehouse, UHF range can yield better results by proper shielding system environment. Passive tags are the best suitable for warehouse operations. The supplier can fix a tag with a unique ID on the cases and pallets. This unique ID can be linked to specific information about individual product ID, product type, product name, date of manufacturing and batch number, etc. Form factor plays an important role the range of any RFID system. In the case leveling tracking, usually a "slap and ship" kind of tag is deployed. In case of pallet level tagging various forms of tags such as plastic coated tags, label tags etc. can be used. These kinds of tags are cost effective for warehouse applications. EPC Global Class 0 tags can be used where the structure of tag information like the number of object classes is fixed and the tag user does not require programming of the tag at it site. When the product range changes are very frequent EPC Global Class 1 tags can be deployed. In this case the tag user has the freedom to program the tag according to its specifications where except the Header partition, all other partitions are programmable. The user can use its own programming techniques for better security.

27

Section 3: Guidelines for RFID System Design and Deployment Part 2: Use Case Model and Architecture of Savant Summary Software products like any other engineered product should be based on solid analysis and realistic modeling. A brilliant solution applied to a wrong problem causes as much, if not more, damage as a bad solution to the problem. Software systems unlike other engineered products are not physically measurable and hence the relevance of analysis and modeling becomes more critical in their development. We attempt to define and describe the middleware of a typical RFID system, called Savants through the use of IBM Rational Unified Process(RUP)® [13].

3.1 Introduction 3.1.1 RFID technology Radio Frequency Identification has recently gained much attention owing to the various mandates by commercial and federal organizations [14], [15]. The concept of using Radio frequencies to store and retrieve information from products has suddenly made many hitherto fantasies very practical. Enterprises are keenly interested in the economics of such a solution. The possibility of tracking every product and being able to store considerable data into each of them has opened up possibilities of unique identification and total automation. As can be expected, however, the technology is still not completely mature in its implementation. There exists a definite lack of benchmarking the performance of various RFID tags has been seen as a major hurdle to be crossed before large-scale adoption can be carried out.

RFID solutions typically contain four main components: Tag readers, the Middleware, the Applications that use the RFID data and the tags themselves. From a systems engineering perspective, the performance of components on deployment makes a very interesting study. Clear guidelines, however, on the specifications of each of these

28

components will go a long way in properly understanding the benefits of an RFID solution. 3.1.2 Savants The middleware components of an RFID solution are collectively called the Savant. They are the most important links that collect raw data and convert it into information that can be understood. Savants are primarily intended to collect, filter and aggregate data that are derived from the readers. Their primary functionalities also include interfacing with other enterprise applications that wish to make use of the information they have collected. The tags read by the tag readers have a unique identification code associated with each of them. Currently there are two standards associated with naming the products - the ISO code[16] and the EPC code [4]. These codes contain information regarding the manufacturer, the current owner, the product type and much more. The savants are expected to collect the tag data and filter out the replications and smoothen out the data set and persists the so collected information. We will examine the functionalities of the savants in more detail in section2. 3.1.3IBM® Rational Unified Process® IBM Rational Unified Process (formerly known as Rational IBM Rational Unified Process) is a software engineering paradigm that specifies a UML [17] based methodology for developing systems. Although the UML is generic and can be applied to the design and development of any system we primarily apply it to the software engineering process in this paper.

RUP is IBM Rational Unified Process, or RUP®, is a configurable software development process platform that delivers proven best practices and a configurable architecture [13].Our primary focus in this paper is to apply RUP in an effort to understand the functionalities of a Savant in clear detail and come up with a generic architecture for the system.

29

3.2 Software Requirements Definition 3.2.1 Goal To develop and deploy a middleware system that enables effective communication between the tag-readers and various other external software applications. 3.2.2 Top level requirements definition 1.

The system should be able to recognize each reader and gather required

data from it and be able to handle exceptional situations like reader breakdown. 2.

The system should be able to perform aggregation activities like counting

the number of items, rate of filling and emptying of aisles/locations of item storage, Positional counts etc. 3.

The System should be able to filter the gathered data so as to help derive

useful information from them. 4.

The system should be able to convert gathered data into proper data

formats (PML). 5.

The system should be able to persist the data gathered into a predefined

repository. The system should also be able to communicate with the repository and perform query response activities. 6.

The system should be able to communicate with other external

applications like ERP systems (may be other savants themselves) to enable decision making activities. 7.

The system should be able to allow a web user to logon and view various

statistics related to the current status of the data gathered. That is, there should be a web interface for viewing the information generated by the savant using the data gathered from the tag reader. 8.

The system should be configurable, i.e. it should be able to recognize and

understand various product code specifications

30

3.3.2 Requirements analysis RUP® suggests that the requirements analysis should be carried out using Use case diagrams. Use case Diagrams are one of the five Diagrams in Unified Modeling Language which forms the basis for the Rational Unified Process. They are central to the modeling of the behavior of the intended system. They aid us in visualizing, specifying and documenting the intended behavior of the system. They adopt a black-box view of the system allowing users to specify just the intended use of the system. This paradigm allows developers to separate the implementation of the system from its interface. 3.3.2.1 Components of a Use case diagram •

Use cases: A use case is a description of a set of sequences of actions,

including variants, that a system performs to yield an observable result of value to an actor [17]. It is graphically represented as an ellipse. Typically use cases are represented as verbs. •

Actors: An Actor represents a coherent set of roles that users play when

interacting with these use cases [1]. They typically represent a human, a hardware device (like tag readers) or even other systems (like other systems). In modeling terms they represent entity being serviced by the use cases. •

Relationships: Use cases can exhibit aggregation, generalization or just

association relationships. Several stereotypes are used to qualify the relationships between use cases and actors. Relationships between use cases are also allowed. •

Notes and Constraints: Notes and any specific constraints can also be

stated in an use case diagram 3.3.2.2 Use Case analysis of Savant We first start with the detection of actors, use cases and then the relationships respectively.

3.3.2.2.1 Actors Actors in practical terms are the stakeholders of the system under consideration. Any change in the system affects the actors alone directly. We expect the following actors for the savant. 31

1. Web User: Although this actor could be modeled as a part of the Applications, we choose to model him separately since, the roles and requirements of this actor are very specific and to an extent different from that of the Applications. This actor is intended to use the savants directly to gather product information. He is expected to view the current status of the product inventory. His set of requirements are as follows: (a)

Login

(b)

Logout

(c)

View the current status of the RFID installation

2. Tag Readers: The relation between the tag holders and the savant is an inverse relation in the sense that the services are expected by the savant than by the tag reader itself. However since the model is for the savant, we try to capture the requirements as if the tag reader requests for it. The following are the requirements of the tag reader: (a)

Identify Tag reader

(b)

Process Tag reader data

(c)

Process Control

3. Applications: These are other software systems which use the data gathered by the savant to perform other activities. Although, the requirements for the Applications are custom defined for each deployment, we assume a least common set of requirements for the current effort. Other requirements could be modeled as extensions of the existing set of requirements and can easily be accommodated. The following are identified as the requirements for the Applications (a)

Identify and recognize applications1

(b)

Process Application queries 2

(c)

Cache queries

(d)

Get PML3

1

This could become a critical requirement when the savant information is transacted between different enterprises automatically, since in such a situation, the savants would have to recognize the message headers from the enterprise applications 2 Applications could be monitoring the reader information in real time. 3 Applications sometimes prefer data to be in particular formats so that they could 32

3.3.2.2.2 Use Cases Use cases capture the behavioral description of the system. They formalize graphically the functional requirements of the system. Although there are no formal set of rules in detecting the use cases, we try to detect the use cases by as king the following questions 1.

What functions does each actor require from the system?

2.

What inputs does the system need?

3.

What outputs does the system provide for each role?

4.

Does the actor need to create, destroy modify or store some kind of

information? 5.

Does the actor require the system to identify/validate access?

Basing on the above questions the following use cases were detected. 1.

login

Assumptions: •

The user is registered

Main flow: •

The user presents his username and password



The System recognizes the user and authenticates him

2.

logout

Main flow: •

The user logs out



The system records the changes if any and stops all transactions initiated

by the user 3.

view

Main flow: •

The user requests the system to show him specific details.



The system creates a view with the requested details and presents it to him

Alternate Flow: •

The user is unauthorized to view the requested details



The systems informs the user about his restrictions and asks him to

understand them. An ideal example would be an XSLT engine which could translate the PML to any other ML 33

reformulate his request 4.

process data

Assumptions: •

The interface of the tag reader is known to the savant

Main flow: •

The savant strips out the headers and converts the data into more a

compact form 5.

process control

Assumptions: •

The interface of the tag reader is known to the savant Main flow:



The savant instructs the tag reader to perform specific activities Alternate Flow:



The savant is not able to communicate with the savant



The savant generates an alert displaying the status

6.

identify reader Main flow:



The system recognizes the location indicators in the message headers



The system recognizes the reader id Alternate Flow:



The message headers carry an unregistered savant id or location id



The system generates an alert displaying the misbehaving reader

particulars 7.

process EPC data Main flow:



The system recognizes EPC headers



It extracts the EPC codes from the tag reader data



It runs preliminary consistency checks to determine if the data obtained is

good Alternate Flow: •

Corrupt data is obtained 34



The savant initiates a re-read

8.

process ISO data

Main flow: •

The system recognizes ISO headers



It extracts the ISO codes from the tag reader data



It runs preliminary consistency checks to determine if the data obtained is

good Alternate Flow: •

Corrupt data is obtained



The savant initiates a re-read

9.

perform maintenance

Main flow: •

The system performs maintenance activities of the readers. This includes,

checking the communication link between the reader and the savant and similar activities 10.

handle interrupts

Assumptions: •

The interrupt handling procedures are well defined

Main flow: •

The savant recognizes the interrupt



It initiates the interrupt handling procedure

11.

initiate reads

Assumptions: •

Either there has been a ’bad read’ or there is a specific instruction by an

authorized application to initiate the reread process Main flow: •

The system identifies the reader to be instructed



It initiates the reread procedure

12.

recognize reader id

Assumptions: •

The reader id is registered 35

Main flow: •

looks up the reader id and checks if it matches any existing entry

13.

recognize reader location

Assumptions: •

Reader id has been recognized

Main flow: •

Obtains the reader location using the reader id

14.

identify application

Assumptions: •

Application interface is known

Main flow: •

Savant associates the application with permissions and restrictions



Savant associates the application with data formats

15.

cache queries

Assumptions: •

Valid queries have been made

Main flow: •

Stores both the query and the result in a local cache for further usage

Alternate Flow: •

The result of a cached query has components which have changed since

last query •

The savant discards the cached information

16.

get PML

Assumptions •

The XSD for the PML is known Main flow:



The system creates a view specific to the PML document



It Converts the view into PML

17.

process queries

Main flow: •

Checks if there is any cached result 36



If there is one then the system displays it



Otherwise, the system initiates a fresh query to the local persistence. Alternate Flow:



There is an invalid query



The system informs the application

18.

filter data

Main flow: •

The system checks the data obtained



It filters out the redundant information from the data and smoothens it out

19.

aggregate/create view Main flow:



Creates a view from existing data

20.

persist Main flow:



Stores the filtered data into predefined data structures

Table 6 : Use Case Nomenclature

Questions Number

Use Case

Software

motivating Requirements the discovery traced to Use of Use case

case

U1

login

Q5

SR7

U2

logout

Q5,Q4

SR7

U3

view

Q1,Q3

SR7

U4

process data

Q1,Q2,Q3

SR1,SR8

U5

process control Q1

SR1

U6

identify reader Q2,Q4,Q5

SR1

U7

process

EPC Q1,Q2,Q3

SR1,SR8

ISO Q1,Q2,Q3

SR1,SR8

data U8

process data

37

Questions Number

Use Case

Software

motivating Requirements the discovery traced to Use of Use case

U9

perform

case

Q1

SR1

Q1

SR1

maintenance U10

handle interrupts

U11

initiate reads

Q1

SR1

U12

recognize

Q2,Q4,Q5

SR1

Q2,Q4,Q5

SR1

Q2,Q5,Q4

SR6

reader id U13

recognize reader location

U14

identify application

U15

cache queries

Q1,Q2,Q3

SR5

U16

get PML

Q1,Q3

SR4

U17

process queries Q1,Q2,Q3

SR5,SR6

U18

filter data

SR3

U19

aggregate/create Q1,Q3

Q1,Q2,Q4

SR2,SR5,SR6

view U20

persist

Q4

SR5

38

Figure 10: Use case diagram

3.4 Architecture Architecture of a system depicts the bridge between the actual design and the requirements model. It tells us meta-relationships between functionalities and structural components of the requirements model. We depict a generic architecture for the design of savants which can be implemented through the use of any set of coherent technologies. In the later section we also present a case study of the Sun Java RFID solution’s savant architecture. 39

Architectural components are hard to find. Some of them naturally classify into many architectural modules. Hitting the right granularity of modules becomes a critical decision during the architecture phase. We as earlier use a question based approach to find architectural components. Our belief is that with this approach the right granularity is easier to attain. Some of typical questions we ask ourselves to detect architectural components are: 1.

Are there functional requirements, which operate with the same

interfaces? 2.

Are there use cases, which have generalization, aggregation relationships?

3.

Are there use cases, which have tightly coupled functionalities?

4.

Are there possibilities that use case implementations could be varied over

time? 5.

Are there use cases related to specific functionalities like security etc?

In answer to these questions and a few more, we detected that there were the following architectural components: 1.

Reader Interface module: This component handles all the reader specific

activities like reader types, physical reader interfaces etc 2.

Event Management module: This component handles all event triggered

activities like parsing the data received, filtering the received data, initiating rereads in case of bad data and such 3.

Information processing module: This module handles the semantics of

the gathered data. It performs aggregation and persistence related activities 4.

Application Interface Module: This component allows for application

level customization where the system is configured to interact with particular application types 5.

Messaging layer: This layer forms the bus for message transactions

between different modules 6.

Data Access and Filtering: This module handles the different code

formats of the data and filtering of received data 7.

Control module: This module handles all physical control activities to be

40

performed by the savant with respect to the tag reader 8.

Persistence manager module: this module handles the local and real time

persistence

Figure 11: General Architecture of a Savant

3.5 Case Study: Sun JAVA ™System RFID Software [18] Sun Microsystems middleware or Savant are geographically distributed servers which are connected to RFID readers at various locations, collect data from them, and also pass on the control signals from the ERP systems. Savants in this system: •

Gathers, stores, and processes EPC data from one or more readers



Smoothes data i.e. filters redundant read values



Corrects duplicate reader or tag entries



Stores and also forwards data up or down the architecture



Monitors for events like low-stock level



Passes up the data to the ERP systems used by the company either

continuously or on a periodic basis Information that is typically collected by a Savant includes: •

EPC of the tag read



EPC of the reader that scanned the tag



Time stamp of the reading i.e. at what instant of time the tag was read by

41

the reader •

Other information such as temperature or geographical position that the

reader is programmed to collect along with the EPC of the tag There are three software modules in the Sun’s version of the auto-id architecture: 1.

Event Management System (EMS)

2.

Real-time in-memory data structure (RIED)

3.

Task Management System (TMS)

3.5.1. Event Management System (EMS) The Event Management system provides event triggered functionality. Its functionalities include: •

A Java TM technology based system



Provide a common interface for various types of readers



Collect data in a standard format



Allow customized filters to smooth and clean data



Provide various mechanisms to log data into a database or remote servers

using standard protocols (HTTP, SOAP, Java Message Service and Java Message Queue) 3.5.2. Real-time in-memory data structure (RIED) The features of the RIED include: •

Stores event information by Edge Savants



Provides the same interface as a database, but offers much better

performance •

Applications can access RIED using JDBCTM technology or a native Java

technology interface •

Also supports SQL operations and can maintain snapshots of the database

at different time stamps 3.5.3. Task Management System (TMS) Task Management system provides an interface to perform administration and maintenance activities. 42



It provides an external interface to schedule tasks



It simplifies the maintenance of distributed Savants because the enterprise

can maintain Savants by merely keeping the tasks on a set of class servers up to date, and appropriately scheduling tasks on the Savants •

In addition to data gathering and transmission the TMS can be used to

request PML and ONS activity and schedule and administer tasks on other Savants

Figure 12: Sun Java System RFID architecture for Savant

The below table captures a trace of the Sun java architecture from our Software requirements:

43

Table 7: Sun Java Architecture

Sun Java System RFID solution component

General Architecture

Use Case

component

Software Requirements

Event Management U4,U7,U8,U13, Event Management System

SR

Module Data filtering Module, Reader

U12,U18,U11

Interface Module Real-Time Inmemory

Data Structure Task Management System

Information processing U14,U15,U16,U17,

SR

module, Persistence manager Control Module

U19,U20

U5,U9,U10,U11

SR

3.6 Conclusion Use case analysis and Architectural modeling of Savants enables better understanding of the system. It provides a basis for further improvements in the design of future versions of the savant. In addition, it provides us with a basis to perform further refinements into the savant specifications.

44

Section

4:

Summary

of

Best

Industry

Practices

&

Developments in RFID Systems and their Experimental Investigation 4.1 Best Industry Practices & Developments in RFID Systems: Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Description

Effect of

The wear of interconnections between

variations in

antenna and chip of a tag affects the

tags

Effect of tag wear

Suggested By

reliability and read distance of the tag. Contacts made by silver epoxy or compression contacts on copper or aluminum degrade over time and are

AVANTE Labs

affected by high temperatures Effect of form factor

There is an almost linear relationship between the size of tag and its readability The read range of a dipole tag increases when the tag becomes parallel to the field and is least when it

Effect of tag

is perpendicular to the field. Tag

K.V.S. Rao

orientation

flipping reduces the tag readability.

(Intermec)

Same is the case with the write range though it is less in all events as compared to the read range.

45

Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Description

Suggested By

Yusuke

Effect of large number of tags

The average tag readability in large

scanned by a

scale events is 96.8%

single reader

Kawakita, and et al ( Keio University Tokyo, Japan)

Usually tags require 7-8db in power for reading at a fixed distance of 1m. The "bad" or weak tags require 25-26 db of power to get activated. Sorting of such "bad" tags from a pool of can increase the tag readability to more than 98% Effect of

Sorting of tags on the basis of energy

Dan Dobkin

"weak" tags

required to respond is a very time

(Enigmatics)

consuming process and if done in the RFID printer itself, requires high degree of calibration when each tag is tested at variable levels of power. If done on a post-application level, it increases the rework by 3-5%. Effect of tag velocity on number of reads Effect of tag velocity on average reading time

The number of reads decrease exponentially with the increase in the tag's velocity

Katariina Penttila, and et al ( Tampere University of

The average reading time decrease exponentially with the increase in the

Technology, Finland)

tag's velocity

46

Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Effect of high tag density

Description

Effect of

Tag identification time increases

number of tags

linearly with the increase in number of

on

tags in close proximity. Multiple tag

identification

identification is successful only up to

time

4m/s of tag velocity

Effect of number of tags on response time

Suggested By

Katariina Penttila, and et al ( Tampere University of Technology, Finland)

The running time in tag response for a set of 60 tags close to each other but well inside the optimized field

Vogt. H.

coverage of the antenna, is more than 6000 milliseconds

Increase in antenna size of both the tag Antenna size

and the reader can increase the read

AVANTE Labs

distance by 25-50% 100% tag readability of UHF tags is Effect of

Relationship

antenna

between antenna diameter and read range

obtained by properly identifying the form factor suitable for a specific read range required for the application. A tag antenna with diameter of 18 mm

Hosaka, R.

can result in 100% readability only within 500 mm distance from the reader

Effect of reader

Low powered handheld readers can Power of

achieve a reader distance of 1/3rd of

reader

the fixed antenna reader i.e. up to 2-3

AVANTE Labs

feet distance

47

Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Description

Suggested By

Forklift mounted RFID readers are the best in warehouse environments. They

Type of reader

provide the flexibility in inventory

John McGinnis

counting procedures.

(AVID

The tags should be placed facing out,

Wireless)

towards the aisle on every asset for this solution to work properly

Effect of Liquids

Effect of proximity to liquids

Attenuation of signals may reduce the read distance by few hundred percents

AVANTE Labs

Metals reduce the read as well as write Effect of Metallic environments

range of tag in their vicinity. For a tag Proximity to

placed on a metal sheet and at a

metals

distance of 1 m from the reader has a

AVANTE Labs

4/5th reduction in read range as that of a tag not in the proximity of metals

Effect of Rain Effect of climate

Read distance can fall even by 100% in rainy or high humidity environments Snow has the same effect as that of

Effect of snow

AVANTE Labs

rain, but here the reduction in read range can be as low as zero

48

Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Description

Suggested By

Hardened plastic, foam and plastic wrap have little effect on tag readability To increase the accuracy and precision Effect of

of tag readability, use of additional tags

plastics

per component, use of higher frequency ranges, use of additional receivers, increase in antenna power, and/or improvement in post processing data must be practiced

Effect of packaging material

Effect of wooden enclosures

Tags covered with wooden blocks from all sides, have zero readability Proximity of metals reduce the tag

Tucker Balch, Adam Feldman and Wesley Wilson

readability by more than 50% as Effect of

compared with non-occluded tags

metallic

Any line of sight occlusions (involving

enclosures

metal) between a tag and any of the receivers results in the occluded receiver not even detecting the tag Tags placed under ceramic moldings

Effect of

have reduced accuracy and less

Ceramics

readability in tag localization as compared to non-occluded tags

Effect of

Effect of PVC

RFID tags enclosed in a PVC container

Hussein Al-

occlusions

pipelines

have less read range though this

Mousawi

49

Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Description

Suggested By

decrease in read range is very less.

(Adger University

Tags up to a distance of 200mm behind

College,

a concrete bar are detectable but

Norway)

Effect of

writing range of such tags is just

Concrete

100mm (though the tag readability also depends on the water and steel content of the concrete block) When tags are enclosed in a plastic

Effect of air

container, a small air gap between the

gap

tag and the container walls increases the readability

Effect of water

Water content in concrete blocks,

content in

decreases the tag readability by up to

concrete

20%

With a WiFi enabled reader, the last

Use of

location of the forklift movement with

performance enhancing

Use of WiFi

technologies

the identifiable RFID tag can be found out which can help in relating the tag movement and its location the

and tools

Michael Oh (TCM RFID Pte Ltd)

warehouse Use of "SAWRFID Technology"

Surface Acoustic Waves (SAW) work better and has a read range of around 300 feet. It works better through metals and tags in the vicinity of metals

John McGinnis (AVID Wireless)

50

Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Description

Suggested By

The tags have very small data storage capacity and work only if we do not need to write anything on the tag and cost a few dollars. Able to scan through all shelves to have an update of stock level with high tag readability. High cost of implementation Use of "Smart

Michael Oh (TCM RFID Pte Ltd)

100% tag readability is possible

Ron Marino

Will not achieve 100% performance

(RAM

above 3 inches off the surface

Engineering &

Close proximity of tags may reduce the

Consulting,

tag readability

Inc.)

Use of non-

Non-metallic conveyor eliminates

Carl Forsythe

metallic slider

electro-magnetic interferences by using

(Globe

bed conveyor

composite polymers that can work at

Composite

temperatures ranging from -40°F to

Solutions, Ltd.)

Shelf"

165°F and the conveyor is virtually transparent to all frequency ranges (HF, UHF and Microwave). Multiple readers can be mounted on the within close proximities. This type of conveyor helps in reducing scattering of RF signals due to metals. Upstream reading and downstream writing or

51

Application

Variables

/ Area of

Affecting Tag

Interest

Readability

Description

Suggested By

verification of tags is possible. FID readers can be mounted, above, below or on either sides of the conveyor thus making it possible to achieve any read angle adjustments Read range as high as 300mm can be obtained while using Mu-chip. The tag is 0.3mm x 0.3mm x 0.06 mm in Use of "Mu-

dimensions and can be fitted easily on

Mitsuo Usami

chip"

electronic circuit boards, miniature

(Hitachi Ltd.)

electronic parts, etc. Very complicated design with high cost of production Active tags work best in metallic environments and have high read range The maximum possible read range

Paul Goodrum

Use of active

achieved by an active tag is not more

and et al

tags

than 9 meters for tags enclosed in

(University of

machine tools.

Kentucky,

The reliable read range is limited to

Lexington)

just above 1.5 meters when used in chilling stations

52

4.2 Experimental Investigation 4.2.1 Standard tests and test setups 4.2.1.1 Options for varying distance: Switched attenuator, fully tested and calibrated, to simulate changes in read distance. An attenuator is a device that attaches to a transmission line (a coaxial cable) and reduces the power of a signal as it travels from the reader to the reader antenna through the cable. Attenuators are usually rated in terms of decibels (dB), a logarithmic measurement of the intensity of emitted energy, and the frequency spectrum they are designed for. They work by dissipating the RF energy into heat.

4.2.1.2 Tags near metal To assess the performance of tags near metal, each tag can be placed at varying distances from a large, flat piece of steel. The tags and metal plate are separated by air. Then use an attenuator to determine the dB attenuation level at which the tag could no longer read. A higher attenuation level, expressed in dB, corresponds to a longer reading distance. At each distance, increase the reader's dB attenuation level until no reads were observed. This will provide an approximate maximum read distance for each tag.

4.2.1.3 Tags near water Placing an aquarium near to the reader or in between the reader and the tag

4.2.1.4 Using a spectrum analyzer A spectrum analyzer can be used to measure ambient RF energy in the room to ensure that there was no electromagnetic interference that would affect the test results.

4.2.1.5 Antenna pattern Separating the reader and the tag by a constant distance and rotating one of them 360º with respect to the other - a 3D plot that shows how much RF is radiated in all

53

directions. The same can be repeated inside an anechoic chamber and a comparison can be provided.

4.2.1.6 Reader placement Increasing the accuracy of read without placing more readers is of great importance when considering minimizing the cost of deployment of RFID systems. This is essentially finding the optimal place for the readers to detect maximum number of tags Varying the reader antenna placement is usually the easiest thing to try first, but is one of the trickiest things to do well. The reader antenna must be placed in a position where powering the tag and receiving data can be optimized for the particular application. In a multiple antenna system, the radiation pattern of all the antennas must be known as well as the location of other nearby readers. It is important to keep in mind that the read range of an RFID system is generally limited by the amount of power that can be captured by the tag. This requirement serves as a simple guide for determining initial antenna placement. Both OATS (Open Air Tests / Free space) measurement and measurements inside the anechoic chamber can be done to determine the antenna pattern of all the antennas that we use in the reader and tags. Once the 3D plot of the antenna pattern is plotted, it will help us largely in the placement of readers [19].

4.2.2 Equipments available for testing •

An anechoic chamber with RF field measurement and analysis instrumentation



Simulation software’s to simulate the cases



Spectrum analyzer to measure EM power levels and the frequency domain measurements of the response of the tags and readers



Oscilloscope to capture the signal response of the tag and the reader



Vector Network Analyzer to measure the antenna parameters of the tag and the readers



Attenuator – to be purchased

54



Antenna tuner for better tuning of the tag and the reader antenna



Signal generator to output certain signals at the desired frequency and power levels



Logistics software’s



Alien and AWID readers/tags



Computers and software’s for specific readers

4.2.3Proposed test beds: Some of the proposed test beds are suggested in Figure 13. The idea was imported from the existing test facility show in Figure 14. For a conveyor belt application, another test bed is proposed as in Figure 15.

Antenna

Figure 13: Test setup 1: For pallet testing and moving a loaded cart

55

Figure 14 : Test setup[20]

Figure 15: Test setup 2: For conveyor belt applications

4.2.4 Challenges It is a challenge because the radio waves that underlie RFID technology can go haywire when placed close to certain items containing liquid or metal. For example, liquids, like soda in a can, tend to absorb the electromagnetic energy needed to power the RFID chip. Meanwhile, the metal of the soda can tends to reflect this energy, bouncing it 56

around in unpredictable ways. In either case, the RFID signal sent by a chip to the reader faces interference, thus dramatically reducing read rates for RFID tags [21].

Could RFID technology be deployed successfully on a factory floor? There are many issues to address:

• Metal: Both the products and the carts used to transport them around the factory floor were made primarily of metal, which blocks radio waves. In addition, directly attaching a tag to metal could create difficulties in reading it. Tags were placed on system components located on an interior surface of the metal chassis, providing further reading difficulties. • Orientation and placement: Tag orientation (with respect to the reader antenna) and placement on the product had an affect on tag-reading ability. • Interference: A factory floor is generally filled with radio waves from other sources, including cellular phones and 802.11 wireless devices. Will these interfere with EPC network tags? • Stray or missed reads: The intend is to prove that the readers could sense all tags that were intended to be read, would not miss any reads, and would not unintentionally pick up stray reads from units that were passing by.

There are some additional goals, such as determining read accuracy and throughput in a production environment; enterprise information systems (EIS) integration capabilities; and gaining hands-on experience. This will be a step toward a larger goal of determining if an EPC network could be implemented throughout a factory, which is expected to eliminate manual key entry and inventory counts while providing item-level tracking and history [22]. The key challenges to using RFID tags are read range and interference from metal objects. The power and size of the reader antenna, the system frequency, and the size of the tag will affect the range. Preliminary research has shown that both inductive and capacitive tags can operate on some products containing metal, such as batteries, but

57

inductive tags need to be specially tuned if they are to be installed on a battery or other metal-containing object in order to maximize the read range. Capacitive tags have been shown to work well on metal products such as steel or aluminum cans, though inductive tags do not. Capacitive tags can also be read through small metal objects, as long as the metal object is not grounded. Both inductive and capacitive tags work well on fluorescent light bulbs, even when placed on a part of the bulb containing metal [23]. 4.2.4.1 Questions related to readability and usage of RFID with respect to change in temperature



How does the tag operate when tags are placed are on the products present inside

a cooler?



When the tags are stored at high temperature (Higher than the room temperature)

how is the readability affected?

4.2.5 Electromagnetic Issues that the lab can address There are many physical interactions taking place in an RFID system. The most important factors are listed below. 4.2.5.1 Absorption and Attenuation As the electromagnetic field propagates through various materials, the dielectric loss and conductive losses in the material attenuate the field of the reader as well as the response signal of the tag. This effect is of particular concern in pallet-level interrogation, where users desire to read multiple tags embedded inside large heterogeneous pallet containers. This can be addressed by simulating multiple tags embedded inside a large pallet using FEMLAB. This will help in better placement of the tags on pallets in a way that the interference between the tags is minimized. 4.2.5.2 Shielding Electromagnetic shielding occurs in materials having high electrical conductivity. In particular, the shielding effect is the result of induced currents by the applied

58

electromagnetic field, which act to cancel the applied field. Understanding this phenomenon is particularly relevant to situations such as reading multiple items inside a pallet containing metal cans or liquids, as well as reading items on a shelf through different shelf materials.

4.2.5.3 Antenna Detuning The conductive and dielectric environment surrounding an RFID label can result in a detuning of the label. This reduces the amount of energy being captured by the tag and also reduces the modulation signal detected by the reader. Although this problem is most well-known for RFID tags operating at 13.56MHz that have a high Q-factor, this is also relevant to some degree for 868-930MHz (ultra-high frequency/UHF) RFID labels as well. In the case of a UHF or microwave backscatter tag, the antenna tuning is primarily a function of the tag geometries and material properties, but it is also susceptible to detuning effects if the tag antenna is made highly resonant.

4.2.5.4 Reflections and Interference The reflected waves from one or more metal surfaces in the environment combine to produce a non-uniform and non-monotonic variation in the field produced by the reader due to the phase differences between the multiple paths. This is the same effect that we experience walking around with a mobile phone inside a building. Depending on the position of the tag, this interference can either enhance read range or it can destroy it, leading to "null spots." For a given RFID frequency, if the geometry of the environment is known, this field variation can be calculated and mapped. Multiple propagation paths can also be created in situations where the reader field is partially blocked or absorbed. Examples of this situation might be a loading dock or warehouse environment where the reader field can be partially blocked by several large objects or perhaps blocked by containers in the pallets themselves. Once again, in this case, if the geometry of the environment is known, the interference effects can be predicted and hopefully avoided.

59

It should also be noted that interference effects (diffraction) can also result from a single aperture alone. This situation may occur if trying to read distant tags from a highfrequency reader through a narrow space, such as layers in a pallet or items stacked on a shelf [24].

4.2.6 RFID security and privacy – can our lab address any of the privacy issues by doing some preliminary tests •

Cover RFID tags with protective mesh or foil



How to kill RFID tags?



Some method of having a encryption thus making the tags not readable with non legitimate readers



Using a blocker tag that can shield the other tags being read from non legitimate readers [25], [26]

4.2.7 Test articles Test articles are used to evaluate the performance of the tags. Here tests are done with products that come in plastic containers and metal containers which have the same shape. The test results will help us in evaluating which tags will be performing better on plastic containers and what will be the effect of bringing a metal into the same tests. The test articles are also chosen in various sizes so that the effect of placing the tags at the right places for large containers can also be determined for increasing the readability. Cylindrical: Large – Folgers coffee cans – Plastic/Metal Medium – Coke cans (Metal) and same size juice bottles (Plastic) Small - Salt shaker (Plastic)

60

4.2.8 Experiments and Results This is a list of all the experiments that have been conducted in the lab in marching towards our goals in the research front. In addition to this a novel method for reading the tags in high metal environment is also under development.

4.2.8.1 No. of tags vs. readability:

Using 20 tags: Free space •

20 tags were stuck to a piece of cardboard sheet at random orientations. The tags are separated from each other i.e., they don’t over lap as shown in Figure 16



The sheet with the tags is held against the reader at distances 20 inches and 50 inches as shown in Figure 17. The plane of testing is parallel plane and as the reader antenna is circularly polarized, the orientation of the tags does not matter



For 20 inches, 18 tags were read successfully and for 50 inches of separation, 14 tags were read successfully

Presence of Metal •

A big sheet of metal was placed right behind the cardboard sheets (Ref: Figure 18) and the same experiment was repeated for a distance of 20 and 50 inches



With the metal present at the back, for a separation of 20 inches 3 tags were read successfully and for 50 inches of separation, only 1 tag was read

Note: In this experiment, the tags and the reader antenna are always in the line of sight.

61

Figure 16: 20 tags placed on a cardboard sheet in random orientations

Figure 17: Reader antenna and tag sheet separated by a distance of 20 inches in free space

62

Figure 18: Tag sheet placed on a big sheet of metal

Using 50 tags stacked: •

50 tags are bunched up together randomly and the reader antenna was held at a distance of 20 inches



20 tags were read successfully. The low read is because of the influence of the tags that are placed one over the other.



When the separation distance was increased from 20 inches to 50 inches, the readability reduced further. This is expected. As the read distance increases, the readability decreases because the power decreases exponentially.



The results for different tests are tabulated in Table 8

Table 8: Experimental results using 20 and 50 tags

Number of

Distance between

No. of

No. of hits when a sheet of metal

Tags

reader and tag

hits

is placed at the back

20

18

3

50

14

1

(inch) 20

63

Number of

Distance between

No. of

No. of hits when a sheet of metal

Tags

reader and tag

hits

is placed at the back

20

20

N/A

50

13

N/A

(inch) 50

4.2.8.2 Tags in books: 4.2.8.2.1 in a book shelf: Using RFID for maintaining a library and getting quick information on the books and their availability is also of interest in the RFID field. So some experiments that will support this theory were done. This experiment is done to get a good idea about tag placement. •

Alien tags are placed inside the books in a book shelf. Ref: Figure 19



The tags are placed in a similar fashion that they are located right below the main cover of the book



There were in total 38 books present and hence 38 tags



The reader antenna is placed perpendicular to the books in the shelf

64

Figure 19: Tags placed inside the books in a book shelf



Number of reads was recorded for varying distance of separation between the tags and the reader



The results are tabulated in Table 9

Table 9: Experimental results using tags on books (Tag orientation - perpendicular)

Number of Tags Distance between reader and tag No. of hits (inch)

38



20

22

35

17

73

8

From the tabulation it can be seen that the readability decreases with increase in the distance of separation

65



Even for small distance of separation, the efficiency of read is low because the tags are in the presence of metal and as seen from the previous experiments, the presence of metal at the back of the tags decreases the read rate



Also the tags are placed in the perpendicular plane with respect to the reader antenna and as known, the read rate in the perpendicular plane is not high



Hence the experiment was repeated by putting the tags in the parallel plane with respect to the reader antenna



The placement of the tags in a parallel plane and on the books can be seen in Figure 20

Figure 20: Tags placed on the sides of the books in a book shelf



When the tags are placed on the sides, they are parallel to the reader so a enhancement in the readability is anticipated



The reader is placed at varying distance from the shelf and the number of hits is determined



The results are tabulated in Table 10

66

Table 10: Experimental results using tags on books (Tag orientation - parallel)

Number of Tags Distance between reader and tag No. of hits (inch)

33



70

11

40

22

20

28-30

As expected the readability has increased when the tags are in parallel in spite of the metal present behind

4.2.8.2.2 Half filled book shelf: This experiment was done to look at the change in readability with the change in tag density. Hence for the same settings the experiment is repeated when the rack in the book shelf is half empty. •

Number of tags is 18. The tags are placed at the same spot as before



The reduced number of tags in books placed in the book shelf can be seen in Figure 21



The reader antenna is held at a distance of 35 inches from the rack and the number of hits is determined and the results are tabulated in Table 11

67

Figure 21: Tags placed inside the books in a half filled book shelf

Table 11: Experimental results using tags on books (Tag density – Half as in the precious stage)

Number of Tags Distance between reader and tag No. of hits (inch)

18

35

16

4.2.8.2.3 Pile of books: •

The tags are placed inside the front cover of the books and the books are piled up on the floor as shown in Figure 22



The reader antenna was placed at a distance of 36 inch from the pile and the number of hits is determined



Note: Now the tags are in a parallel plane with respect to the reader antenna and there is no metal behind the books (While the books were placed in shelves, there was metal present at the back of the books)

68



Also as the books are piled in random orientation, the tags are also in random places

Figure 22: Tags placed inside the books when the books are not in the influence of metal



The number of hits table is given below in Table 12

Table 12 : Experimental results using tags on books (Books are stacked on floor. No influence of metal)

Number of

Distance between reader and tag No. of hits

Tags

(inch)

10

36

10

14

36

14

18

36

16

69

4.2.9 Readability with books considering tag density along with presence of metal After the preliminary set of experiments that was used to determine the readability of tags when present inside books, a more practical and more procedural experiment was carried out to determine how the tag density plays a role in the presence of metal when we are trying to read the tags present in the books. Note: From the results of previous experiments it was noted that the parallel orientation of the tag with respect to the reader is giving maximum readability hence, the same is followed in this set of experiments also. The tag is placed in the side. •

The tags are placed in a similar fashion that they are located parallel to the reader. Ref : Figure 23 and Figure 24







The experiment was carried on for two sets of tags 

Number of tags = 20



Number of tags = 48

Three tag densities are used for the experimentation 

Low – Sparsely placed



Medium – Closely placed



High – Very tightly placed

The experiments were carried on for two varying distances (Distance refers to the distance between the reader and the tag) 

Small – 20 inches



Large – 50 inches



The reader is placed opposite to the tags at the line of sight



The results are tabulated in Table 13 and Table 14

Table 13: Experimental results using tags on books (Influence of metal)

No. of

Distance

Tags

(inch)

Small

20

Tag density

Low

Medium

Presence of

No. of

metal

Hits

Metal

18

No Metal

20

Metal

17

No Metal

20

70

No. of

Distance

Tags

(inch)

Tag density

High

Low Large

Medium

High

Presence of

No. of

metal

Hits

Metal

18

No Metal

20

Metal

15

No Metal

17

Metal

14

No Metal

11

Metal

15

No Metal

17

Table 14: Experimental results using tags on books (Influence of metal)

No. of

Distance

Tags

(inch)

Tag density

Low

Small

Medium

High

48

Low Large

Medium

High •

Presence of metal

No. of Hits

Metal

35

No Metal

38

Metal

31

No Metal

38

Metal

30

No Metal

38

Metal

29

No Metal

32

Metal

21

No Metal

32

Metal

25

No Metal

35

From the table it can be seen that the presence of metal reduces the readability and it gets worse with the increase in distance and tag density

71

Figure 23: Tags placed on the sides of the books in free space

Figure 24: Tags placed on the sides of the books in a book shelf

72

4.2.10 Readability in the presence of water •

Plastic bottles are tagged using the Alien 9354 tag. As the reader antenna is circularly polarized, the orientation of the tag on the plastic bottle is not significant 

This would be significant in using RFID in medicinal applications like in a drug store where it would be easier to find the stock of drugs available



Bottles with the tags placed on them will be placed opposite to the reader as shown in Figure 25 and Figure 26 and the number of successful reads are determined for three varying tag densities



When the tags are placed against water in the bottle, the water will influence the readability of the RFID system so positioning the tag at the right place on the bottle is very important



The effect of having the bottles full of water and half empty with the tags placed near the brim was determined







The experiment was carried on for two sets of bottles 

Number of bottles = 5



Number of bottles = 10

Three tag densities are used for the experimentation 

Low – Sparsely placed



Medium – Closely placed



High – Very tightly placed

The experiments were carried on for two varying distances (Distance refers to the distance between the reader and the tag)





Small – 20 inches



Large – 50 inches

The results are tabulated in Table 15 and Table 16

73

Table 15: Experimental results using 5 tags on bottles

No. of

Distance

Tags

(inch)

Presence of

No. of

Water

Hits

Water

1

Low

Partial

1

(Sparsely placed)

No Water

5

Water

4

Tag density

Small

Medium

Partial

2

(20 inch)

(Closely placed)

No Water

5

Water

3

High

Partial

1

(Tightly placed)

No Water

5

Water

0

Low

Partial

0

(Sparsely placed)

No Water

5

Water

0

Medium

Partial

0

(Closely placed)

No Water

5

Water

0

High

Partial

0

(Tightly placed)

No Water

4

5

Large (50 inch)

74

Table 16: Experimental results using 10 tags on bottles

No. of

Distance

Tags

(inch)

Presence of

No. of

Water

Hits

Water

4

Low

Partial

3

(Sparsely placed)

No Water

10

Water

6

Tag density

Small

Medium

Partial

2

(20 inch)

(Closely placed)

No Water

10

Water

2

High

Partial

2

(Tightly placed)

No Water

10

Water

1

Partial

0

No Water

6

Water

0

Medium

Partial

0

(Closely placed)

No Water

6

Water

0

High

Partial

0

(Tightly placed)

No Water

7

10 Low (Sparsely placed)

Large (50 inch)



From the table it can be seen that the presence of water affects the readability of the RFID system and the variation with respect to distance is also obvious

75

Figure 25: Tags placed on the sides of the bottles with high tag density

Figure 26: Tags placed on the sides of the bottles with low tag density

76

Section 5: Statistical Analysis and Design of RFID Systems for Monitoring Vehicle Ingress/Egress in Warehouse Environments

Summary Many academic and industry research efforts are currently focused on evaluating the potentials of RFID technology for industrial applications. Major applications of RFID technologies are anticipated in warehouse and depot environments. One needs systematic methodologies for effective design and deployment of RFID systems in these environments. The authors present a statistically designed experimentation approach determining the most desirable settings of an RFID system, deployable at vehicle ingress/egress points of a typical warehouse, depot, or a manufacturing plant. The approach yields phenomenological insights into the joint effects of multiple RFID system parameters on the performance of the ingress/egress monitoring system.

77

5.1. Introduction After September 11, the US government as well as the major industries have started placing increasing attention on tracking and monitoring of cargo and vehicles movement [27]. It is becoming imperative for every warehouse, depot, and a manufacturing plant to monitor vehicle ingress and egress through their premises. As a result, many commercial warehouse or storage management systems have begun to include components for vehicle transit monitoring. They are primarily aimed in achieving the following three basic functions: (1) Inventory management, (2) safety of the goods, and (3) security of the warehouse, depot or any manufacturing plant

A typical vehicle transit monitoring system uses checkpoints placed at various locations within a warehouse. The security personnel need to physically examine and identify each container or item, most likely by reading the barcode information. This information is then, transferred to an ERP system to cross-verify the goods being shipped from or arriving into the warehouse. This procedure has some inherent lacunas. For example, the system requires at least one dedicated person to carry out the vehicle ingress/egress monitoring process at each checkpoint, and the system cannot keep a check on the movement of

every vehicle the enters or leaves the premises of a

warehouse. RFID and other such automatic identification technologies offer potential for surmounting these shortcomings.

A typical RFID system consists of tags (also known as transponders), readers (sometimes known as transreceivers) and a computer system for storing and managing the data received from the reader and analyzing it according to the type of software application that uses it. A transponder is usually a memory device (e.g. EEPROM), fitted on the object to be identified [3]. It contains information that uniquely identifies an object. A reader is capable of generating, receiving, demodulating and deciphering RF signals.

78

Tags are classified, into various types depending on whether they are active or passive, readable and/or writable, etc., [2]. Based on the protocol of the tags, they can be differentiated into two main types as EPC and ISO tags. Table 17 represents the classification of EPC based tags. Among these, Class 0 and Class 1 tags are widely accepted by the industry due to their cost effectiveness and easy availability. Tags classified according to the frequency standards in ISO 18000 series [28] are summarized in Table 2 [5]. Whenever a tag comes into a reader’s RF electromagnetic field, it gets powered due to the incident electromagnetic field, and sends signals back to the reader that identifies the tagged object. This identification technology can be used for real time job tracking, goods and/or asset management, etc., [3].

Table 17: Tag Classification of EPC tags

EPC Class

Description

Functionality

Remarks Data can be written only once

0

Read Only

Passive tags

during tag manufacturing and read many times

1

2

3

Write Once and Read only

Read/Write

Read/Write

Data can be written only once Passive tags

by tag manufacturer or user and read many times

Passive tags

Semi-passive tags

User can read/write data many times Can be coupled with on board sensors for capturing parameters like temperatures, pressure, etc. Can be coupled with on board

4

Read/Write

Active tags

sensors and act as radio wave transmitter to communicate with reader

79

The data carrier frequencies recommended by the Federal laws is as shown in Table 18

Table 18: Classification of Frequencies

Low

High

Ultra High

Frequency(LF)

Frequency(HF)

Frequency(UHF)

125 - 134 KHz

13.56 MHz

902 - 928 MHz

Microwave 2.4 - 2.48 GHz

As shown in Figure 27, the information stored in a tag is transmitted to a reader at a carrier frequency. The reader de-modulates the signal and sends the tag information to the RFID middleware. The middleware consists of an event processor and a link to the central database. The event processor uses the central database to retrieve tag-specific data. It then compares the data with that read from the tag. This processed-information is sent to an enterprise application (EA) such as an ERP system [3]. An EA links the database and the user so that a user can extract higher-level information with regard to, vehicle arrival patterns, classification of the vehicle, vehicle authorization, etc.

Figure 27 : RFID Data Flow Diagram[29]

During the last two years, the industry has initiated a few planning studies and pilot deployments of RFID systems. The industry has envisaged potential of RFID systems in improving the practices of supply chain management, logistics, machine health monitoring, warehouse management and customer support. RFID systems are considered in quite a few scenarios to be a better substitute to bar codes due to their ability to identify any part, product or vehicle on item level, and they are considered to be

80

more cost effective compared to many global positioning systems. Many companies are patenting new RFID solutions to an extent that some have started to believe that the bar codes, which are prevalent in many industrial identification applications, will become obsolete in a few years.

However, RFID systems, at present have some inherent

shortcomings. They include: 1. loss of readability in the presence of metals due to signal scattering, 2. a quadratic reduction in readability of tags with an increase in the distance between the tag and the reader, and 3. large dependence of readability on the form factor (i.e. shape, size and orientation), make, standard compliance and reader antennas.

Implementation of RFID system in real world environments therefore requires careful design and selection of key system parameters such as the tag orientation, reader make, vehicle speed, etc., in order to optimize pertinent performance variables including the read rate, robustness to noise, etc. These parameters will henceforth be referred as Key Process Input Variables (KPIVs), and the key output variables will be referred to as Key Process Output Variables (KPOVs).

The objective of the work presented in this paper is to derive a statistical approach towards systematically designing an effective RFID enabled vehicle ingress/egress monitoring system. The following benefits are achieved using such an RFID based monitoring: 1. A current system with barcodes requires a person to manually inspect a vehicle and have the barcode identified by using the barcode reader. An RFID enabled system, obviates the need for such highly repetitive human activity, and thus allows fast and easy information gathering. It will eliminate several non-value added activities and can systematically reduce the paper work and documentation, and excessive reliance on routine manual labor. 2. RFID enables easy bulk identification and verification of vehicles and its contents entering or leaving a warehouse or a manufacturing plant. A

81

RFID system can be coupled with picture identification, thus allowing faster and robust identification of a vehicle from a remote location [30]. 3. The system can be used for monitoring and identification of patterns in vehicle motion states over time. This information can then be used to upgrade the current plant and enterprise practices towards improving overall system performance.

Figure 28 : Schematic of an RFID based vehicle ingress/egress monitoring system

As shown in Figure 28, an RFID based vehicle ingress/egress monitoring system would require modifications to the existing setup/infrastructure in the form of reader antennae placed at the entry and exit checkpoints. One may use multiple (at least two) antennae positioned in tandem to differentiate between ingressing and the egressing vehicles. These modifications will help in tracking the flow of vehicles in the warehouse or plant premises. Each vehicle will be equipped with an RFID tag at an appropriate location (e.g. near the center of windshield). This tag will store information that uniquely identifies the vehicle. Apart from this, all items/containers may be RFID tagged to allow identification of the contents of the vehicle. We note that this paper focuses on determining RFID system elements for vehicle monitoring only. Determination of the

82

locations and other KPIVs of RFID tags on the containers requires a separate statistical and electromagnetic (EM) field analysis, which is beyond the scope of this paper. The presented approach can be applied to design a layer vehicle monitoring system whereby the position of vehicles can be tracked by synchronizing antenna signals at various locations in a warehouse and unauthorized vehicles can be easily tracked and identified.

The remainder part of this paper is organized as follows: A description of our approach to select the KPIVs from among a large number of system parameters is presented in Section 2, our experimentation setup and procedures are described in Section 3, and the results are presented in Section 4.

83

5.2. Determination of KPIVs As summarized in Figure 29 and Table 19, an RFID system is influenced by many factors or Process Input Variables (PIVs). It is important that correct factors be chosen to yield designs for successful implementation of the vehicle monitoring systems. The current EM theoretical models are not tractable for capturing the effects of these factors on the readability in real world environments. Statistical approaches are therefore imperative for effective design of the RFID systems [31]. Further, different factors will have significantly diverse influence on readability Z only a select set of factors have major influence. Therefore, for facilitating tractable statistical analysis, these PIVs need to be filtered to extract a more compact set of KPIVs. Some of them are explained below and detailed further in Appendix A.

Figure 29 : Cause and Effect Diagram

84



The tags used for this application must be durable, cheap and the user must be able to use its conventions to write relevant data on the tag. So, we propose to use two types of tags EPC Class 1 [4] and ISO 18000-6 complaint tags [32]



Orientation of tag is the relative placement of the tag w.r.t. the field of polarization of the reader’s antenna. This may be parallel and perpendicular or oblique to the EM field along various planes of references as shown in Figure 30. The

orientation

is

specified

in

terms

of

angles θx ∈ (0, 90°), θy ∈ (0, 90°) and θz ∈ (0, 180°) .

Y Yθy

Reader

X Tag

Xθx

θz Z Z Figure 30 : Tag Orientation (All angles at zero degrees)



Form Factor refers to the size and shape the tag antenna. It wields a significant influence on the EM field envelope generated in presence of a reader and the tags, which in turn is the main determinant of readability.



Tag Collision is the effect of one or more tags responding to the reader signal at the same time. This confuses the reader and requires complex algorithms such as binary tree method, etc., to distinguish between individual tags

85



Operating environment holds significant influence on readability. For example, metal parts of a vehicle can hinder the free flow of information from the tag to the reader and vice versa, by reflecting the waves in all directions. There are different tags for different purposes. A tag created exclusively for metallic environments such as AWID’s ISO 18000-6 tag [33], works well in such environments than a general-purpose tag. In addition, the presence of other tags and reader antennas may cause an adverse effect on the EM field. Thus, the presence of more than one reader antenna may become a PIV in the experimentation. Table 19: List of PIVs

Controllable(C) /

Sr. No.

PIVs

1

Orientation of tag (θy,(θz)

C

2

Placement of tag (θx)

C

3

Weather

N

4

Vehicle type

N

5

Frequency range

F

6

Speed of vehicle

C

7

Reader placement

C

8

Reader make

C

9

Tag make

C

10

Form factor

F

11

Electronics installed in the

N

Noise(N) / Fixed(F)

vehicle 12

Tag collision

N

13

Metallic environment

N

14

Number of reader antennas

C

15

Frequency used

F

16

Standard compliance

C

17

Tag functionality

C

86

A quality function deployment approach [34] was applied towards selecting the appropriate KPIVs. The selection is done in two phases based on matrix based filtering common to Quality Function Deployment (QFD).

In Phase 1 matrix, PIVs are listed on the top row of the matrix. KPOVs are listed along the first column, and their relative importance (one for least important and four for highly important) is listed in column 2. Among these, tag readability, is defined in terms of the probability that a given tag is read in a specified environment, of particular interest. Tag readability is determined by the fraction of the times a tag is read in a designed experiment. The KPIVs are weighted according to their influence on each of the KPOVs on a 9,3,1,0 scale (9 is the highest and 0 is the lowest influence) [34]. The absolute technical importance is calculated by the following formula, Technical Importance = ∑in=1 influence value × KPOV' s importance

Then the PIVs are ranked in ascending order w.r.t. their technical importance and the PIVs with rank seven of less are chosen from the Phase 1 (see Table 20).

Also, the interrelationship matrix (as shown in Table 22), is built in the following manner. If the relationship between two PIVs is very strong, we say it as a highly positive relationship, which is denoted by the symbol “▲” in the interrelationship chart. A loosely positive relationship is denoted by “+”. If the relationship is weak, it is denoted by “” the case of no relationship is denoted by “▼”.

87

Table 20 : Selection of KPIVs- Phase 1

Number of Antennae

Reader-Tag Distance

EMI

Tag Density

Weather

Vehicle type

Vehicle Speed

9

9

9

9

9

9

9

9

9

3

3

9

2

0

3

3

3

9

3

9

9

9

9

9

9

3

3

3

0

0

9

9

9

0

1

1

1

1

1

1

1

3

1

1

1

3

1

1

1

9

1

9

3

1

Technical Importance

24

43

43

70

84

70

55

58

66

58

42

36

46

Rank

10

7

7

2

1

2

5

4

3

4

8

9

6

Readability

(θy,(θz)

Tag Orientation

3

KPOVs

(θx)

4

Form Factor

Reader Make

ENVIRONMENT

Reader frequency

READER

Tag Protocol

Tag Placement/Position

Importance(Weight)

TAG

(READ) Robust to Noise Compatibility (with most common RFID standards and systems) Cost of study

In Phase 2, we found that certain KPIVs are either fixed or noise, so these are highlighted with “Grey” color and are depicted in Table 21. These KPIVs are eliminated subsequently.

88

Table 21 : Selection of KPIVs - Phase 2

Number of Antennas

Reader-Tag Distance

EMI

Tag Density

Vehicle Speed

4

9

9

9

9

9

9

9

9

9

9

Robust to Noise

2

3

3

3

9

3

9

9

9

9

3

3

0

0

9

9

9

0

1

1

1

1

1

1

1

1

3

1

1

1

9

1

1

Technical Importance

43

43

70

84

70

55

58

66

58

46

Rank

7

7

2

1

2

5

4

3

4

6

C

C

C

F

C

M

C

N

N

C

Compatibility (with most common RFID standards and systems) Cost of study

Controllable [C] - Fixed [F] -Fixed Maximum [M] - Noise [N]

(θy,(θz)

Tag Orientation

Readability (READ)

KPOVs

(θx)

Reader Make

ENVIRONMENT

Reader frequency

READER

Tag Protocol

Tag Placement/Position

Importance(Weight)

TAG

89

Table 22 : Interrelationship Matrix of KPIVs

Highly Positive

▼[37]

▼[35]

+[38]

Reader frequency

▼[35]

▲[35]

Z[38]

▼[37]

Reader Make

▼[35]

▲[36]

+[38]

▲[39]

▼[37]

+[35]

+[38]

Z[35]

▼[40]

Z[35]

▲[37]

▲[35]

+[36]

+[36]

+[35]

▲[4]

▲[37]

▲[37]

EMI

+[3]

▼[3]

+[38]

+[3]

+[35]

+[38]

▲[35]

▼[35]

Tag Density

Z[38]

+[36]

▲[37]

+[41]

Z[35]

▲[37]

+[42]

▼[39]

Z[3]

Weather

Z[36]

▼[35]

Z[38]

▼[35]

+[35]

Z[37]

+[40]

▼[38]

+[35]

▼[37]

Vehicle type

▼[37]

▼[37]

+[37]

▼[37]

▼[37]

▼[37]

Z[37]

Z[37]

Z[37]

Z[37]

▼[37]

Vehicle Speed

Z[40]

+[37]

▲[37]

Z[3]

+[35]

+[37]

▲[37]

▲[37]

Z[37]

▼[37]

▼[37]

Tag Protocol

Number of Antennas Reader-Tag Distance

90

▼[37]

Vehicle Speed

▼[36]

Weather

+[36]

Tag Orientation

Vehicle type

Tag Density

EMI

Reader-Tag Distance

Number of Antennas

▼[35]

Reader Make

Placement/Position

Reader frequency

Tag

Tag Protocol

Form factor

(θy, θz)

Relationship (P)

Tag Orientation

Weak

(θx)

relationship (▼),

Tag Placement/Position

Positive (+), No

Form factor

(▲), Loosely

Hence, we are left with the following variable and controllable factors for our experimentation:

1. Reader make 2. Tag make 3. Distance between tag and reader 4. Tag Placement angle θx 5. Tag Orientation angle θy 6. Tag Orientation angle θz 7. Speed of the vehicle

91

5.3 Experimentation Details Experiments were conducted on an open space at the entry of a parking lot at Oklahoma State University. The objective of these experiments is the following: a) statistically quantify the relative influence of various KPIVs on tag readability, b) propose the optimal combination of KPIVs that will enhance readability, and c) propose a mathematical relationship connecting tag readability to the various combinations of the KPIVs The experimentation setup is summarized in figures 5 and 6. Figure 31 shows an Alien reader held tag a distance of 20 inch from the EPC Class 1 tag, mounted on the vehicle’s windshield.

Alien® Reader EPC Class 1 Tag

Figure 31 : Antenna -tag Setup for experimentation

Figure 32 shows an AWID reader held at a distance of 20 inch from the ISO 18000-6 tag. This setup is one of the various combinations of levels of KPIVs, required for the design of experiments. Figure 33 shows an Alien reader connected to a computer system required to extract the tag information from the reader. The connection from the reader to the backend computer is accomplished through an RS 232 or an Ethernet

92

port.

AWID® Reader

ISO 18000-6 Tag

Figure 32: Antenna -tag Setup for experimentation

Figure 33 : Reader to Computer System Connectivity

93

Some of the KPIVs were either insignificant or their interactions do not comply with their hardware configurations. For example, effect of tag orientation (θx) on readability is insignificant (hence, they were eliminated from the study). The Alien® reader is incompatible with the ISO protocol, and the AWID reader works well, only with the ISO protocol. Lab experiments revealed that, the tag flipping (i.e., changing in θz), had little effect on readability.

A full factorial multi-level experiment was conducted with the following KPIVs: 1. Reader Make 2.

Distance between tag and reader

3. Speed of the vehicle 4. Tag Orientation (θy) With reference to the datasheets of individual readers and lab experiments confirmed the read range distances for each reader. The levels of distance for each reader determined based on prior lab experiments. The details of the various KPIVs and their ranges are summarized in Table 23 and Table 24. It is noteworthy that the reader make ‘R’ is ordinal, in that it is coded as 1 and 2 depending on whether Alien or AWID reader is used. The distance ‘D’ is coded between levels 1- 10, corresponding to the actual distances ranging from 20 inch to 180 inch, as summarized in Table 24. The Speed ‘S’ is coded at three levels for 0, 10 and 20 mph. θy is coded in two levels, for 0° and 90°. The full factorial multi-level design and results with eight replicates for each run are shown in Table in Appendix B.

94

Table 23 : Levels of Distances for each Reader

Alien

AWID

Distance (inch) 50

20

85

45

115

72

145

100

180

125

Table 24 : Coding Scheme of KPIVs

KPIV Reader Make

Distance (inch)

Speed (mph)

Symbol

Type

R

Ordinal

D

S

Continuous

Continuous

Range of Interest Alien®

Level Coding

2

AWID®

2

20

1

45

2

50

3

72

4

85 100

10

(degrees)

θy

Continuous

6

Tape

125

8

145

9

180

10

0

1 3

0 90

Visual

Measuring

7

10

Measured

5

115

20 θy

1

How

2

Vehicle Speedometer

3 2

1 2

Visual

95

5.4. Analysis of the experimental results Analysis of the experimental results is done in two parts. Stepwise regression analysis was performed to identify the main factors. Next, a response surface regression analysis is done to facilitate detailed identification of significant main and interactions effects, and determine optimal settings. The regression model is shown in the following equation READ = 3.04236 − 0.87778 R − 0.16755 D − 0.38125S − 0.45833θy + 0.06869 RD + 0.14375 Sθy .....1 The model captures 78% of variation in readability observed during our experiments (See Table 25). Reader make (R) and the tag orientation (θy) seems to have a strong influence on readability based on examining their relative magnitudes of all KPIVs. Significantly, the joint effects of the reader make (R) and distance (D), as well as that of speed (S) and tag orientation (θy) has a major effect on readability. Table 25 : Response Surface Regression Analysis Results

Term Constant

Coefficient

P

3.04236

0

R

-0.87778

0

D

-0.16755

0

S

-0.38125

0

θy

-0.45833

0

R*D

0.06869

0

S*θy

0.14375

0.001

R-Sq =79.4%

R-Sq(adj) =78.3%

S = 0.1934

96

Alien

AWID

Figure 34 : Interaction Plot for Ybar (Tag Readability)

Figure 34 summarizes the joint effect of reader make R and the distance D on tag readability. The readability of AWID reader to ISO complaint tags sharply drops after 45 inch (around 4 feet). Alien Reader is able to read EPC compliant tags beyond 100 inch. This might be because of the power level of the system. Higher the power radiated, larger will be its read range.

Alien

AWID

Figure 35 : Interaction Plot for Ybar (Tag Readability)

Figure 35 depicts the effect of reader make R and speed S of the vehicle on tag readability. It can be inferred that the tag readability for Alien reader with EPC complaint

97

tags, drops consistently with the increase in speed from 0 mph to 20 mph whereas the tag readability for AWID reader with ISO complaint tags, drops sharply after 0 mph. There is a linear relationship between speed and readability for both the systems.

Alien

AWID

θy Figure 36 : Interaction Plot for Ybar (Tag Readability)

The effect of reader make R and θy over tag readability is shown in Figure 36. Here we see that the tag readability for Alien make reader with EPC complaint tags is higher at θy = 0° than at θy = 90° . The AWID reader with ISO complaint tags has the same effect as above when θy changes from 0° to 90° but in the latter case, the tag readability is considerably lower than in the case of Alien reader. This is because when θy = 0° , the tag is oriented parallel to the reader antenna while at θy = 90° , the tag is oriented perpendicular to the reader antenna. There is a maximum coupling when the tag is oriented in parallel than when it is oriented perpendicular with respect to the reader antenna.

98

θy = 0 °

θy = 90 °

Figure 37 : Interaction Plot for Ybar (Tag Readability)

Figure 37 shows the combined effect of distance D and θy over tag readability. The tag readability decreases consistently with the change in θy from 0° to 90° for each distance level. The readability is inversely proportional to the distance and hence there is a polynomial fall in readability with increase in distance.

0 mph

10 mph 20 mph

θy Figure 38 : Interaction Plot for Ybar (Tag Readability)

Figure 38, shows the effect of Speed S and θy over tag readability. It can be inferred, that the tag readability is highest at 0 mph speed and is lowest at 20 mph speed. 99

It can be also concluded that the tag readability decreases when θy changes from 0°to 90° . There is a relationship between the speed at which the vehicle is moving and θy . This is also reflected in the regression model (Interaction between speed S and θy ). This is because when the vehicle is moving, θy changes i.e. at every position of the vehicle, θy is different.

Figure 39 : Surface Plot of Tag Readability vs. Distance and Speed

The surface plot of tag readability vs. distance D and speed S is depicted in Figure 39. The tag readability decreases consistently with increase in speed and distance. At a speed of 10 mph when the tag is placed at a distance of 0 to 50 inch from the reader, the readability does not vary much with respect to the distance. This region corresponds to a plateau in the surface plot of Figure 39. The optimal value of tag readability can be achieved when the speed is 10 mph and the distance is 100 inch.

100

Conclusions: The study focuses on deriving statistical characterization and models that lead to an optimal design of an RFID system for a specific application of vehicle ingress/egress monitoring system in a warehouse environment. All the PIVs that are known to influence the readability of an RFID system are considered and a method based on quality function deployment (QFD) [34] is used to systematically determine a compact set of KPIVs. From the study, the influence of distance, tag orientation, speed of the vehicle, and reader make has been clearly delineated and rationalized based on electromagnetism. It has been shown that the readability undergoes a polynomial decrement with increase in distance (i.e. read range). In addition, the readability decreases linearly with increase in speed. Maximum read rate is obtained when the tag is placed in parallel with respect to the reader antenna i.e. when θy = 0° . Thus, statistical analysis helps in determining an optimal value of distance, speed, orientation, and other KPIVs for a particular implementation of an RFID system for ingress/egress monitoring.

101

Appendix A A.1 Reader Make Readers used in any applications play an important role in how efficient the system would be. Some of the features of the reader and the types of reader used in our experiments are discussed below. Frequency of operation, ISO or EPC compliant, read distance depending on the manufacturer, isolation of the reader from the influence of other readers are some of the factors that depend on the reader make and that also influence the efficiency of the RFID system. We have used two makes of readers, namely, AWID (MPR 2010AN) and Alien (ALR 9774) reader for the experimentation. •

MPR-2010AN (see Figure 40) is a stationary reader that is able to decode EPC C1, ISO-18000-6 Type B and EM Micro. It is designed to be upgradeable to EPC C1G2 (Class 1 and Generation 2). This reader comes with a near ideal circularpolarized antenna. (A circular polarized antenna radiates energy in both the horizontal and vertical planes and all planes in between) so that tags in random orientations can be captured. The reader is claimed to have a tag dependent range of 12 to 18 feet (3.6 to 5.5 meters).

Figure 40 : Photograph of an AWID (MPR 2010AN) Reader[33]

102



Alien readers support all EPC Gen1 protocols. They allow easy integration with middleware and enterprise software. They are equipped with high capacity memory to store tag history, have circularly polarized antennas and have a tag dependent range of 8-12 feet [8] .

Figure 41 : Photograph of an Alien (ALR 9774) reader [8]

A.2 Communication frequency standards: The selection of appropriate carrier frequency depends on various factors like, the application requirement, environment in which the RFID system is used, desired read range, and the air interface protocol used. The environment for vehicle ingress/egress monitoring usually contain objects like the container, vehicle parts, etc., electronic parts like the vehicle control systems, plastic parts of the vehicle and cardboards enclosing the products transported by the vehicle. The EPC has specified standards for tag data storage and management for frequencies suitable to HF and UHF frequencies. Furthermore, the read range desired for this application is more than three feet. Lower frequency standards such as 13.56 MHz or the HF thus becomes unsuitable for this application [41]. Also, the size of tag and reader antennas are related to the size of the wave, and UHF being a short wave as compared to HF, it requires small size antennas. In addition, UHF frequency is widely used in civil communication like GMRS (General Mobile radio Service). Thus, the most suitable frequency for the application in vehicle ingress/egress monitoring system is 902-928 MHz or UHF.

103

A.3 Tag-make and form factors: The tags used for this application must be durable as well as cheap. We investigate the use of EPC Class 1 tags as well as ISO tags complaint with ISO 18000-6 standards [32]. EPC tags are cheaper and allow user defined conventions to write data into the tag [9]. The tags that are used in the experiment are AWID models, Prox-Linc (MT APL 1216) and Prox-Linc (MT APT 1014) and Alien models 9354 and 9338 tags.

Figure 42 : AWID (MT APL 1216) tags for metallic surfaces

AWID Prox Linc MT APL 1216 tags are designed for mounting directly on metal or other materials. They use a protective plastic to house the circuit and antenna. They allow long read range and are compatible with MPR-2010 readers[33]. AWID Prox-Linc (MT APT 1014) tag circuits are printed on a flexible, clear plastic. They allow a read range of 9 to 11 feet when the tag is attached by self-adhesive to the inside of the vehicle's windshield, as per installation instructions [7].

104

Figure 43 : AWID MT APT 1014 tags[33]

Alien 9354 (M tag) tag (see Figure 44) allow very high gain, and have low environmental dependence.

Figure 44 : Aperture coupled patch antenna used for Alien 9354 tag[8]

The Alien 9338 ("Squiggle T" tag) tag have a small form factor and are very inexpensive.

105

Figure 45 : Folded dipole antenna[8]

The tags used for this application must be durable as well as cheap. We propose to use EPC Class 1 tags for the following reasons: 1. These tags are cheap [4] 2. User can use his conventions to write data on the tag

When using ISO based tags, we propose tags compliant to ISO 18000-6 standards [32].

A.4 Tag Protocol and Standards A protocol is the standard way or a language for communicating across a network. The tags that follow the same class are developed in a way that they achieve interpretability between different tags and readers. The two classes of protocols that are used in the 900 MHz range are ISO- 18000 part 6 and EPC. These standards deal with air-interface protocol, data content, conformance with regulatory requirements, and application. A brief explanation of the two major standards is provided below.

EPC has specified standards for tag data content, communication between a tag and a reader (air- interface protocols), reader protocols, Savant (Savant is a platform used for reading data from different types of readers, data filtering and logging the data or events into various devices) specifications, Physical Mark-up language (PML) specifications, and Object Naming Service (ONS) specifications for HF and UHF ranges. There are two versions of these standards. Version 1 (Generation 1) is already in use and version 2 (Generation 2) is ratified and is being adopted. As per Generation 1 standard, data is stored on the tag, in the format as shown in Figure 46. Companies like Texas Instruments, Impinj, Philips Semiconductors, Alien Technology, Symbol Technologies and Intermec Technologies have announced that they are at various stages in the manufacturing of Generation 2 tags.

106

Figure 46 : Tag Data Partition[37]

ISO 18000-6 Part 6 standards set parameters for Air Interface Communications at 860 to 930 MHz frequency range. These standards also specify parameters like data encoding rules, data transmission rates, types of signal modulations and anti-collision protocols. Efforts are underway to form a unique standard that will avail a common platform for widespread adoption of RFID technology all over the world.

A.5 Read range The operating range is defined as a tag’s maximum distance from the interrogator (reader) in order to satisfy the ASIC’s (Application Specific Integrated Circuit) power consumption. For the tag to operate properly there has to be a minimum voltage induced on the tag to turn on all the electronics in the tag, near the reader antenna. The power received Pr

by a passive tag antenna is calculated given by

Pr =

( Pt ⋅ Gt )G r ⋅ λ2 (4πR ) 2

(1)

Where, Pt is the power transmitted by the reader antenna (transmitter antenna), Gr is the gain of the tag antenna, Gt is the gain of the reader antenna, R is the distance of the tag from reader and λ is the wavelength of the EM RF waves, which for the considered frequency range of 900 MHz is approximately 0.3m. Also ( Pt ⋅ Gt ) is called the Effective Radiated Power (ERP).

As can be seen from the above formula, the power received by the tag is inversely proportional to the square of the distance from the reader antenna. Hence, as the tag moves away from the reader, the performance of the RFID system decreases.

107

A.6 Orientation of the tag Orientation of a tag relative to a reader affects the polarization of the tag antenna with respect to the reader antenna. Polarization is important in wireless communications systems. Polarization, also called wave polarization, is an expression of the orientation of the lines of electric flux in an EM field. Polarization can be constant i.e., remains in a particular orientation at all times, or it can vary with each wave cycle. The physical orientation of a wireless antenna corresponds to the polarization of the radio waves received or transmitted by that antenna. Thus, a vertical antenna receives and emits vertically polarized waves, and a horizontal antenna receives or emits horizontally polarized waves. The best short-range communications is obtained when the transmitting and receiving antennas have the same polarization. The Friis transmission equation that was used in the analysis before can be modified to include the influence of polarization of the antenna [43].

W0 = e t

Pt 4πR 2

Figure 47 : Geometrical orientation of transmitting and receiving antennas for Friis transmission equation (1)

 λ2 Pr = er Dr (θ r , φr )   4π

λ 2 Dt (θt , φt ) Dr (θ r , φr ) Pt  ρˆ t ρˆ r W = e e  t t r 2 π 4 R ( ) 

2

(2)

Where,

108

et and er is the radiation efficiency of the transmitting antenna and receiving antenna respectively Pt is the input power at the transmitter antenna Wt is the isotropic power density at the transmitter

G (θt , φt ) is the gain in the direction (θt , φt ) Dt (θt , φt ) is the directivity of the transmitting antenna in the direction (θt , φt ) Ar is the effective area of the receiving antenna

θ t is tag orientation angle θy t

φ t is the tag orientation angle θz

The power received assumes that the transmitting and receiving antennas are matched to their respective lines or loads (reflection efficiencies are unity) and the polarization of the receiving antenna is matched to the impinging wave (polarization efficiency is unity).

ρˆ t ⋅ ρˆ r

2

is called the polarization loss factor.

From the formula, it can be seen that the polarization loss factor is directly proportional to the power received by the tag antenna. Hence, if there is a polarization mismatch, the efficiency of the RFID system will be decreased. For reflection and polarization matched antennas aligned for maximum directional radiation and reception, the power received reduces to the form in Equation (1).

A.7 Speed An antenna radiates a given amount of power into free space, and ideally, this power propagates without loss in all directions. For the antenna that is used in the reader, the gain is optimized in one direction so the power flow in that direction will be higher than the power flow in any other direction. Considering the tag antenna to be in the vicinity of the reader antenna and moving at a constant rate, if the speed of the tag antenna is less than the propagation delay (it is the time lag between the departure of a signal from the source and the arrival of the signal at the destination) at that particular

109

direction, then the tag will be recognized. The polarization loss factor and directivity of the antenna in that particular direction must also be considered. The Doppler shift that occurs due to the movement of the tag antenna near the reader and how well the receiver clock recovers from that shift has to be explored. The shift in center frequency of the receiver in the reader antenna must be studied also. Further investigation is needed here to justify this fact. To study the propagation delay, some indoor propagation models must be explored in detail.

110

Appendix B Table B1: Full factorial multi-level design and results with eight replicates for each run

Reader Distance Speed Run

θy

Make

(D)

(S)

(R)

(inch)

(mph)

1

Alien

20

0

0

1

1

1

1

1

1

1

1

1

2

Alien

20

0

90

1

1

1

1

1

1

1

1

1

3

Alien

20

10

0

1

1

1

1

1

1

1

1

1

4

Alien

20

10

90

1

1

1

1

1

1

1

1

1

5

Alien

20

20

0

1

1

1

1

1

1

1

1

1

6

Alien

20

20

90

0

1

1

0

0

1

1

1

0.625

7

Alien

45

0

0

1

1

1

1

1

1

1

1

1

8

Alien

45

0

90

1

1

1

1

1

1

1

1

1

9

Alien

45

10

0

1

1

1

1

1

1

1

1

1

10

Alien

45

10

90

1

1

1

0

1

1

1

1

0.875

11

Alien

45

20

0

1

1

1

1

1

1

1

1

1

12

Alien

45

20

90

0

0

1

1

1

1

1

1

0.75

13

Alien

50

0

0

1

1

1

1

1

1

0

1

0.875

14

Alien

50

0

90

1

1

1

1

1

1

1

1

1

15

Alien

50

10

0

1

1

1

1

1

1

1

1

1

16

Alien

50

10

90

1

1

1

1

1

1

1

1

1

17

Alien

50

20

0

0

1

1

1

1

1

1

1

0.875

18

Alien

50

20

90

0

0

0

1

1

1

1

1

0.625

19

Alien

72

0

0

1

1

1

1

1

1

1

1

1

20

Alien

72

0

90

0

0

1

1

1

1

1

1

0.75

21

Alien

72

10

0

0

1

1

1

1

1

1

1

0.875

22

Alien

72

10

90

0

1

0

1

1

1

1

1

0.75

23

Alien

72

20

0

1

1

0

0

1

1

1

1

0.75

24

Alien

72

20

90

0

0

0

0

1

1

1

1

0.5

(degrees)

Y1 Y2 Y3 Y4

Y5

Y6 Y7 Y8 Ybar

111

Reader Distance Speed

θy

Make

(D)

(S)

(R)

(inch)

(mph)

25

Alien

85

0

0

1

1

1

1

1

1

1

1

1

26

Alien

85

0

90

1

0

0

1

1

1

1

1

0.75

27

Alien

85

10

0

1

1

1

1

1

1

1

1

1

28

Alien

85

10

90

0

1

1

1

1

1

1

1

0.875

29

Alien

85

20

0

0

1

1

1

1

1

1

1

0.875

30

Alien

85

20

90

0

0

1

1

1

1

1

1

0.75

31

Alien

100

0

0

1

1

1

1

1

1

1

1

1

32

Alien

100

0

90

0

1

0

0

1

1

1

1

0.625

33

Alien

100

10

0

1

1

0

0

1

0

1

1

0.625

34

Alien

100

10

90

0

0

0

0

0

1

0

0

0.125

35

Alien

100

20

0

0

0

0

0

0

0

0

0

0

36

Alien

100

20

90

0

0

0

0

0

0

0

1

0.125

37

Alien

115

0

0

1

1

1

1

1

1

1

1

1

38

Alien

115

0

90

0

1

0

1

1

0

1

1

0.625

39

Alien

115

10

0

0

1

1

1

0

1

1

1

0.75

40

Alien

115

10

90

0

0

0

1

1

0

0

0

0.25

41

Alien

115

20

0

0

0

0

0

0

0

0

0

0

42

Alien

115

20

90

0

0

0

0

0

0

0

0

0

43

Alien

125

0

0

1

1

1

1

1

1

1

1

1

44

Alien

125

0

90

0

1

0

1

0

1

1

0

0.5

45

Alien

125

10

0

0

1

0

0

0

0

1

1

0.375

46

Alien

125

10

90

0

0

1

0

1

1

1

1

0.625

47

Alien

125

20

0

0

0

0

1

0

0

0

1

0.25

48

Alien

125

20

90

0

0

0

0

0

0

0

0

0

49

Alien

145

0

0

1

1

1

1

0

1

1

1

0.875

50

Alien

145

0

90

0

0

0

0

0

0

0

0

0

51

Alien

145

10

0

0

0

0

0

0

0

0

0

0

Run

(degrees)

Y1 Y2 Y3 Y4

Y5

Y6 Y7 Y8 Ybar

112

Reader Distance Speed

θy

Make

(D)

(S)

(R)

(inch)

(mph)

52

Alien

145

10

90

0

0

0

0

0

0

0

0

0

53

Alien

145

20

0

0

0

0

0

0

0

0

0

0

54

Alien

145

20

90

0

0

0

0

0

0

0

0

0

55

Alien

180

0

0

1

0

1

1

1

1

1

1

0.875

56

Alien

180

0

90

0

0

0

0

0

0

0

0

0

57

Alien

180

10

0

0

0

0

0

0

0

0

0

0

58

Alien

180

10

90

0

0

0

0

0

0

0

0

0

59

Alien

180

20

0

0

0

0

0

0

0

0

0

0

60

Alien

180

20

90

0

0

0

0

0

0

0

0

0

61

AWID

20

0

0

1

1

1

1

1

1

1

1

1

62

AWID

20

0

90

1

0

1

1

1

1

1

1

0.875

63

AWID

20

10

0

1

1

1

1

0

1

0

0

0.625

64

AWID

20

10

90

0

0

0

0

0

0

0

0

0

65

AWID

20

20

0

0

0

0

0

0

0

0

0

0

66

AWID

20

20

90

0

0

0

0

0

0

0

0

0

67

AWID

45

0

0

1

1

1

0

1

1

1

1

0.875

68

AWID

45

0

90

0

0

0

0

0

0

0

0

0

69

AWID

45

10

0

0

0

0

0

0

0

0

0

0

70

AWID

45

10

90

0

0

0

0

0

0

0

0

0

71

AWID

45

20

0

0

0

0

0

0

0

0

0

0

72

AWID

45

20

90

0

0

0

0

0

0

0

0

0

73

AWID

50

0

0

1

1

1

0

1

0

0

1

0.625

74

AWID

50

0

90

0

0

0

0

0

0

0

0

0

75

AWID

50

10

0

0

0

0

0

0

0

0

0

0

76

AWID

50

10

90

0

0

0

0

0

0

0

0

0

77

AWID

50

20

0

0

0

0

0

0

0

0

0

0

78

AWID

50

20

90

0

0

0

0

0

0

0

0

0

Run

(degrees)

Y1 Y2 Y3 Y4

Y5

Y6 Y7 Y8 Ybar

113

Reader Distance Speed

θy

Make

(D)

(S)

(R)

(inch)

(mph)

79

AWID

72

0

0

1

1

1

0

1

0

0

0

0.5

80

AWID

72

0

90

0

0

0

0

0

0

0

0

0

81

AWID

72

10

0

0

0

0

0

0

0

0

0

0

82

AWID

72

10

90

0

0

0

0

0

0

0

0

0

83

AWID

72

20

0

0

0

0

0

0

0

0

0

0

84

AWID

72

20

90

0

0

0

0

0

0

0

0

0

85

AWID

85

0

0

1

1

1

0

0

0

0

0

0.375

86

AWID

85

0

90

0

0

0

0

0

0

0

0

0

87

AWID

85

10

0

0

0

0

0

0

0

0

0

0

88

AWID

85

10

90

0

0

0

0

0

0

0

0

0

89

AWID

85

20

0

0

0

0

0

0

0

0

0

0

90

AWID

85

20

90

0

0

0

0

0

0

0

0

0

91

AWID

100

0

0

1

1

1

0

0

1

0

0

0.5

92

AWID

100

0

90

0

0

0

0

0

0

0

0

0

93

AWID

100

10

0

0

0

0

0

0

0

0

0

0

94

AWID

100

10

90

0

0

0

0

0

0

0

0

0

95

AWID

100

20

0

0

0

0

0

0

0

0

0

0

96

AWID

100

20

90

0

0

0

0

0

0

0

0

0

97

AWID

115

0

0

1

0

1

0

0

0

0

1

0.375

98

AWID

115

0

90

0

0

0

0

0

0

0

0

0

99

AWID

115

10

0

0

0

0

0

0

0

0

0

0

100

AWID

115

10

90

0

0

0

0

0

0

0

0

0

101

AWID

115

20

0

0

0

0

0

0

0

0

0

0

102

AWID

115

20

90

0

0

0

0

0

0

0

0

0

103

AWID

125

0

0

1

1

0

0

0

0

0

0

0.25

104

AWID

125

0

90

0

0

0

0

0

0

0

0

0

105

AWID

125

10

0

0

0

0

0

0

0

0

0

0

Run

(degrees)

Y1 Y2 Y3 Y4

Y5

Y6 Y7 Y8 Ybar

114

Reader Distance Speed

θy

Make

(D)

(S)

(R)

(inch)

(mph)

106

AWID

125

10

90

0

0

0

0

0

0

0

0

0

107

AWID

125

20

0

0

0

0

0

0

0

0

0

0

108

AWID

125

20

90

0

0

0

0

0

0

0

0

0

109

AWID

145

0

0

0

0

0

0

0

0

0

1

0.125

110

AWID

145

0

90

0

0

0

0

0

0

0

0

0

111

AWID

145

10

0

0

0

0

0

0

0

0

0

0

112

AWID

145

10

90

0

0

0

0

0

0

0

0

0

113

AWID

145

20

0

0

0

0

0

0

0

0

0

0

114

AWID

145

20

90

0

0

0

0

0

0

0

0

0

115

AWID

180

0

0

0

0

0

0

0

0

0

0

0

116

AWID

180

0

90

0

0

0

0

0

0

0

0

0

117

AWID

180

10

0

0

0

0

0

0

0

0

0

0

118

AWID

180

10

90

0

0

0

0

0

0

0

0

0

119

AWID

180

20

0

0

0

0

0

0

0

0

0

0

120

AWID

180

20

90

0

0

0

0

0

0

0

0

0

Run

(degrees)

Y1 Y2 Y3 Y4

Y5

Y6 Y7 Y8 Ybar

115

References 1.

Scrawford. [cited March 2005]; Available from: www.scrawford.net/courses/RFID_Basics_qed.ppt. 2. Caen. RFID Standards (http://www.caen.it/rfid/about_rfid3.php). 2005 [cited June 2005]. 3. Finkenzeller, K., RFID Handbook. 2003: Wiley & Sons Ltd. 4. EPCGlobal, Standards & Technology 2005. 5. RFIDJournal. RFIDJournal 2005 [cited June 2005]; Available from: http://rfidjournal.com/article/articleview/1337/1/129/. 6. HighTechAid. [cited Feb 2005]; Available from: www.hightechaid.com/standards/18000.htm 7. AimGlobal. [cited March 2005]; Available from: www.aimglobal.org/standards/rfidstds/sc31.asp 8. Alien, in ALR-9774 Data Sheet. 2005. 9. Symbol. [cited March 2005]; Available from: www.symbol.com/products/rfid/rfid.html 10. Hitachi. [cited Feb 2005]; Available from: www.hitachi.com/New/cnews/030902.html. 11. Intermec. [cited April 2005]; Available from: www.intermec.com/eprise/main/Intermec/content/Products/Products. 12. Samsys. [cited April 2005]; Available from: www.samsys.com/default.php/alpha=products 13. IBM. [cited Feb 2005]; Available from: http://www306.ibm.com/software/awdtools/rup/. 14. Walmart. [cited March 2005]; Available from: www.walmart.com. 15. DoD. [cited March2005]; Available from: www.defenselink.mil. 16. ISO. [cited March 2005]; Available from: http://www.iso.org. 17. Grady Booch, James Rumbaugh, and I. Jacobson, The Unified Modeling Language User Guide. 2000: Addison-Wesley, Pearson Education. 18. SUN. [cited Feb 2005]; Available from: http://java.sun.com. 19. RFIDJournal. 2005 [cited Sept 2005]; Available from: http://www.rfidjournal.com/. 20. Asemec. 2005 [cited Sept 2005]; Available from: http://www.asemec-london.org/presentations/elogistics_d2_3.pdf. 21. COMMSDesign. 2005 [cited Sept. 2005]; Available from: http://www.commsdesign.com/news/tech_beat/showArticle.jhtml?articleID=1707 00571. 22. SUN. SUN RFID Center. 2004 [cited Sept 2005]; Available from: http://www.sun.com/aboutsun/media/presskits/rfid2004/SunSun_RFID_d1b.pdf. 23. Princeton. 2005 [cited Sept 2005]; Available from: http://www.princeton.edu/~jalee/ElecRecy/ElecRecyRFID.htm. 24. RFIDProducts. [cited Sept 2005]; Available from: http://www.rfidproductnews.com. 25. Library Applications. 2004, University of California Berkeley.

116

26.

RSASecurity. [cited Sept 2005]; Available from: http://www.rsasecurity.com/rsalabs/staff/bios/ajuels/publications/pdfs/rfid_survey _28_09_05.pdf. 27. V. Gavrilovich, G.L., S. Kroll et al., Homeland Security, in International Engine and Truck Corp. June 2003. 28. ISO/IEC18000. RFID Air Interface Standards 2004 [cited May 2005]. 29. Progress. RFID Data Concentrator 2005 [cited May 2005]; Available from: http://www.objectstore.com/graphics/rfid_data_concentrator_diag.gif. 30. SUN. SUN RFID Center. 2005 [cited May 2005; Available from: http://www.sun.com/software/products/rfid/index.xml. 31. Scott Seidel, K.T., Theodore Rappaport, Order Statistics For An Indoor Radio Channel Model. IEEE, 1989. 32. ISO/IEC18000-6. Parameters for Air Interface Communications at 860 to 930 MHz. 2004 [cited May 2005]. 33. AWID, MPR-2010AN (915 MHz) Readers Data Sheet. 2005. 34. Forrest, B., Implementing Six Sigma - Smarter Solutions Using Statistical Methods 2nd ed. 2003, New Jersey: John Wiley & Sons Inc. 35. AVANTE. Comment on The Test Data of 13.56 MHz (HF) RFID System and that of 915 MHz (UHF) RFID System. 2004 [cited 2005. 36. Al-Mousawi, H., Performance and reliability of Radio Frequency Identification (RFID), in Agder University College. 2004, Faculty of Engineering and Science p. 107. 37. COMMSEN, COMMSEN White Paper Series -Towards RFID System Design Guidelines. 2005, COMMSEN Lab, Oklahoma State University, Stillwater OK. 38. Vogt, H., Multiple Object Identification with Passive RFID Tags. IEEE International Conference on Systems, 2002. 39. P Wolfe, S.P., J Choi, R. Chatterjee, Evaluation of using RFID passive tags for monitoring product location/ownership. 2005, Arizona State University: Tempe. 40. Tucker Balch, A.F., Wesley Wilson, Assessment of an RFID System for Animal Tracking. smartech.gatech.edu 2004. 41. WANG. RFID Classification 2005 [cited June 2005]; Available from: http://users.bigpond.net.au/WISeAgent/RFID_solutions.htm. 42. Hosaka, R., Feasibility Study of Convenient Automatic Identification System of Medical Articles Using LF-Band RFID in Hospital. Systems and Computers in Japan, 2004. 43. Balanis, C.A., Antenna Theory – Analysis and Design. Third edition ed. 2005: Wiley Interscience.

117