RFIDPlanner A Coverage Planning Tool for RFID Networks

Transcription

1 RFIDPlanner A Coverage Planning Tool for RFID Networks DDP Thesis Presentation by Nitesh Gupta Under the guidance of Prof. Sridhar Iyer

2 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 2

3 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 3

4 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 4

5 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 5

6 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 6

7 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 7

8 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 8

9 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 9

10 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 10

11 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 11

12 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 12

13 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 13

14 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 14

15 Antenna Range Calculation Range of antenna max distance r where received power is just sufficient to make tag operational r = P RI 10 ( G R ) P f TI G T and G R are gains of tag and reader antennas P TI and P RI are input powers of tag and reader antennas f is transmission frequency 2 G T G R 15

16 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 10 GR GT max = 2 ( PRI ) min f r (P TO ) min = Minimum power output by a just operational tag (P RI ) min = Minimum reflected power input required at reader s antenna for it to detect a tag 16

17 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 17

18 Illustration - Overlay Grid Structure 18

19 RFIDPlanner Architecture 19

20 Reader Emulator Emulates reader s range patterns Two parameters of accuracy for emulating range Number of sections Number of levels of attenuation 20

21 RFIDPlanner Demo 21

22 Emulating Range Calculate start and end coordinates for each attenuation level Consider j th attenuation level of i th section 1. Start coord is same as end coord of (j-1) th level 2. Calculate max attenuation allowed for j th level 3. Calculate corresponding free space distance and find appropriate end coordinate 4. Check for obstacles between start and end coords 5. If no obstacle, calculated end coord is the required value 22

23 Emulating Range (contd.) 6. Else, consider first obstacle from start 7. Calculate total atten at first obstacle including free space atten and obstacle atten 8. If this atten is greater than max atten for j th level, required end coord lies on obstacle 9. Else, shift start coord to coord on obstacle and repeat procedure till max atten for j th level is reached Repeat entire procedure for all attenuation levels in each section, and for all sections 23

24 RFIDPlanner Design 24

25 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 25

26 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 26

27 Heuristic H1 1. Select the first grid that contains an edge of a shelf and place a reader on the middle of this edge 2. Use RFIDPlanner reader emulator to determine which grids are fully and partially covered 3. Add partially covered grids to a FIFO list. These grids are analyzed one by one 4. If grid does not contains shelves no reader added 5. Otherwise place reader such that it covers uncovered portion 6. The new grids partially covered by this reader now added to FIFO list 7. Repeat entire procedure until all shelves are covered 27

28 Illustration Heuristic H1 28

29 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 29

30 Heuristic H2 - Illustration 30

31 Sample Configurations by H1 and H2 Floor Plan FP1 31

32 Sample Configurations by H1 and H2 Floor Plan FP2 32

33 Sample Configurations by H1 and H2 Floor Plan FP3 33

34 Sample Configurations by H1 and H2 Floor Plan FP4 34

35 Sample Configurations by H1 and H2 Floor Plan FP5 35

36 Performance Evaluation 36

37 Algorithmic Complexity H1 for n grids Worst case scenario: O(n 2 ) Best case scenario: O(n) H2 for m shelves of length l O(m(m+l)) if l is variable O(m 2 ) if l is constant 37

38 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 38

39 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 39

40 References S. Iyer, RFID: Technology and Applications, Kanwal Rekhi School of Information Technology, Indian Institute of Technology - Bombay, K. Finkenzeller. RFID Handbook Fundamentals and Applications in Contactless Smart Cards and Identification, Chichester: John Wiley, Leipzig, dritte edition, S. Zvanovec, P. Pechac, M. Klepal, Wireless LAN Networks Design: Site Survey or Propagation Modeling?, Radioengineering, Vol. 12, No.4, December, T. Rappaport, ``Wireless Communications: Principles and Practice'', Prentice Hall, B. Silberberg, Technical State of MHz Radio 40

41 Acknowledgement My sincere thanks to Prof. Sridhar Iyer Swapnil Paranjpe, Rahul Sachdev Nitesh Dixit, Naval Bhandari Persistent Systems Pvt. Ltd. 41

42 Thank You