RFIDPlanner – A Coverage Planning Tool for RFID Networks

DDP Thesis Presentation byNitesh Gupta

Under the guidance ofProf. Sridhar Iyer

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Radio Frequency Identification or RFID Technology� Uses radio frequency to identify objects � RFID Tags

� Microchip coupled with small antenna� Tagged to object to be identified and stores

information about the object� Reflects its information with radio waves

� RFID Readers� Radio frequency module for two way

communication with tags

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RFID Technology - Applications� Data intensive business processes such as

� Supply chain management (SCM)� Warehouse management systems (WMS)� Enterprise resource planning (ERP)

� Equipment and livestock tracking� Security

� Automobile theft prevention

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Problem Definition� RFID networks involve large number of readers� To remain cost effective, deploy minimum number

of readers to cover given area� Determining optimal configuration of reader layout

involve� Manual site surveys� Testing different reader positions� Significant time and monetary costs

� Deploying RFID readers in a fast and cost effective way is a difficult problem

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Related Work: Coverage Planning in Indoor WLANs� Coverage planning in RFID networks can be

thought of as similar to coverage planning in indoor WLANs

� In WLANs� Minimum number of access points � Ensure complete coverage� Take into consideration effect of obstacles

� Several Simulation tools available� WISE � SpectraGuard Planner

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Wireless Systems Engineering (WISE)� Developed at AT&T Bell Labs� Uses 3-D ray tracing techniques to model

radio waves and determine received signal strength

� Uses computational geometry and optimization algorithms to place access points

� Provides a GUI for 3-D visualization and interaction

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SpectraGuard Planner� Developed by AirTight

Networks� Uses 3-D ray tracing

techniques� Provides a GUI for 2-D

visualization and interaction

� Provides security coverage and risk level management

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Indoor WLANs vs. RFID Systems� Not easy to adapt WLAN coverage tools for RFID

networks� In WLANs

� Wireless devices such as laptops and PDAs � Inbuilt power supply � Superior processing capabilities� Tolerance to communication errors

� Larger ranges of access points

� In RFID Systems� Passive tags used to remain cost effective� Limited range of RFID readers

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RFIDCover� Coverage planning tool to provides complete

coverage within specified period � Uses a combination of fixed and mobile RFID

readers� Generates optimum placement and movement

patterns for readers � Cost of deployment – number of readers� Tag reading time – total time to read all tags

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RFIDCover - Limitations� Neglects the effect of obstacles in RFID

reader’s range, assuming circular range� Provides periodic coverage and not

continuous� Relies on mobile readers, which might not be

feasible always� No flexibility of covering only portions

containing tags - covers entire area

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Solution Outline - RFIDPlanner� Develop RFIDPlanner - a coverage planning tool

� Given� Details of area� Properties of obstacles� Reader and tag specifications

� RFIDPlanner� Emulates reader’s range attenuation patterns� Allows interactive visualization and modification of

different reader layout configurations� Eliminates site surveys to bring down cost and time taken

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RFIDPlanner - Assumptions� RFID readers being used are of same type� RFID tags being used are passive and of same

type� Antennas are isotropic having circular ranges� Obstacles are rectangular� Obstacles are aligned either along x-axis or y-

axis

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RFIDPlanner – Objectives� Places readers statically to cover given area� Simulate range attenuation patterns in

presence of different obstacles� Provide visualization tool to display reader

layout configurations� Allow modification during run-time

� Adding new readers� Moving and deleting existing readers

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Propagation Modeling� Deterministic

� Based on electromagnetic wave propagation theory using ray tracing techniques

� Input requirements can be complicated and difficult to obtain

� Empirical – used in RFIDPlanner� Statistically processed representative measurements –

effects of reflection, diffraction and scattering are taken care of

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Antenna Range Calculation� Range of antenna – max distance r where

received power is just sufficient to make tag operational

� GT and GR are gains of tag and reader antennas� PTI and PRI are input powers of tag and reader

antennas� f is transmission frequency

2

76.14)10( 1010fP

GGPrTI

RT

GRI

R

×××××

=

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Maximum Antenna Read Range� Maximum range of antenna – the maximum distance

at which power reflected by just operational tag is just sufficient for reader’s antenna to detect the tag

� (PTO) min = Minimum power output by a just operational tag

� (PRI) min = Minimum reflected power input required at reader’s antenna for it to detect a tag

14.76min

max 2min

( ) 10( )

TO R T

RI

P G GrP f× × ×

=×

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RFIDPlanner Architecture� Based on overlay grid structure

� Given area divided uniformly into grids� Diagonal of grid equal to the maximum reader

range � Each grid has details of obstacles lying in it and

readers covering it� Makes mathematical modeling of obstacles and

reader range easier

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Illustration - Overlay Grid Structure

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RFIDPlanner Architecture

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Reader Emulator� Emulates reader’s range patterns� Two parameters of accuracy for emulating

range� Number of sections� Number of levels of

attenuation

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RFIDPlanner

Demo

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Emulating Range� Calculate start and end coordinates for each

attenuation level� Consider jth attenuation level of ith section

1. Start coord is same as end coord of (j-1)th level 2. Calculate max attenuation allowed for jth level 3. Calculate corresponding free space distance and

find appropriate end coordinate4. Check for obstacles between start and end coords5. If no obstacle, calculated end coord is the

required value

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Emulating Range (contd.)6. Else, consider first obstacle from start7. Calculate total atten at first obstacle including

free space atten and obstacle atten8. If this atten is greater than max atten for jth level,

required end coord lies on obstacle9. Else, shift start coord to coord on obstacle and

repeat procedure till max atten for jth level is reached

� Repeat entire procedure for all attenuation levels in each section, and for all sections

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RFIDPlanner Design

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Sample configuration� 85 readers covering a

20m x 30m hall with shelves and obstacles

� Took less than 30 minutes to arrange the readers online, while an actual site survey would have taken lot more time

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RFIDPlanner Evaluation – Shopping Mall Scenario� Huge hall with wooden partitions for different

items. Each partition has steel or glass shelves on which tagged items are placed

� Need to cover only the shelves� Two heuristics have been designed, to ensure

complete coverage of desired area

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Heuristic H11. Select the first grid that contains an edge of a shelf and place

a reader on the middle of this edge2. Use RFIDPlanner reader emulator to determine which grids

are fully and partially covered3. Add partially covered grids to a FIFO list. These grids are

analyzed one by one4. If grid does not contains shelves no reader added5. Otherwise place reader such that it covers uncovered portion6. The new grids partially covered by this reader now added to

FIFO list7. Repeat entire procedure until all shelves are covered

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Illustration – Heuristic H1

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Heuristic H2� Attempt to capture logic used while placing

readers manually� Readers are placed on obstacles so that no

need for additional infrastructure� In case there are adjacent shelves, place

reader such that it covers both shelves � All shelves are analyzed one by one

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Heuristic H2 - Illustration

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Sample Configurations by H1 and H2 – Floor Plan FP1

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Sample Configurations by H1 and H2 – Floor Plan FP2

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Sample Configurations by H1 and H2 – Floor Plan FP3

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Sample Configurations by H1 and H2 – Floor Plan FP4

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Sample Configurations by H1 and H2 – Floor Plan FP5

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Performance Evaluation

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Algorithmic Complexity� H1 – for n grids

� Worst case scenario: O(n2) � Best case scenario: O(n)

� H2 – for m shelves of length l� O(m(m+l)) if l is variable� O(m2) if l is constant

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PINES™ � RFID middleware developed by Persistent Systems

Pvt. Ltd.� Layout and device management� Data aggregation and filtering� Query processing and event based notification

� Currently user provides reader layout� RFIDPlanner can be easily integrated with PINES™

layout management engine � Provide additional functionality during initial phase of

RFID network configuration� Make PINES™ more user friendly

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Conclusions� RFID domain specific coverage tools are necessary

for fast and efficient deployment of RFID networks� RFIDPlanner architecture provides

� Basic framework for a RFID coverage planning tool, including reader range emulation algorithm

� High flexibility to allow further enhancement, such as support for slant obstacles, new heuristics and direct support for different tags and readers

� High level of integrability with RFID middleware to provide a single platform for deploying, monitoring and operating RFID networks

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References� S. Iyer, “RFID: Technology and Applications”, Kanwal

Rekhi School of Information Technology, Indian Institute of Technology - Bombay, 2004. http://www.it.iitb.ac.in/~sri/talks/RFID-05.ppt

� K. Finkenzeller. “RFID Handbook – Fundamentals and Applications in Contactless Smart Cards and Identification”, Chichester: John Wiley, Leipzig, dritte edition, 2003.

� S. Zvanovec, P. Pechac, M. Klepal, “Wireless LAN Networks Design: Site Survey or Propagation Modeling?”, Radioengineering, Vol. 12, No.4, December, 2003.

� T. Rappaport, ``Wireless Communications: Principles and Practice'', Prentice Hall, 1996.

� B. Silberberg, “Technical State of 868-870 MHz Radio

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AcknowledgementMy sincere thanks to

Prof. Sridhar IyerSwapnil Paranjpe, Rahul Sachdev

Nitesh Dixit, Naval BhandariPersistent Systems Pvt. Ltd.

Thank You