1 Indoor Location Sensing Using Active RFID Lionel M. Ni, HKUST Yunhao Liu, HKUST Yiu Cho Lau, IBM Abhishek P. Patil, MSU Indoor Location Sensing Using Active RFID Lionel M. Ni, HKUST Yunhao Liu, HKUST Yiu Cho Lau, IBM Abhishek P. Patil, MSU

2 Motivation Overview of RFID Performance Evaluation LANDMARC Approach LANDMARC Approach Conclusion

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4 Location-aware Computing The location is an important context that changes whenever the object moves Location-aware services allow to offer value-added service to the user, depending on their current geographic position and will be a key feature of many future mobile applications Sensing the location: explicit and implicit cooperation; outdoor or indoor

5 Location Sensing Techniques Triangulation: use geometric properties of triangle to compute object locations –Signal strength: signal attenuation is a function of distance to the signal source Scene analysis: use features of a scene observed from a certain reference point Proximity: determine if an object is near a known location

6 Sensing Technologies Infrared Ultrasonic Radio Frequency –RFID – –Bluetooth Others

7 Existing Technologies and Systems Infrared Example: Active Badge Location System Low power requirements Low circuitry costs: $2-$5 for the entire coding/decoding circuitry Simple circuitry Higher security Portable High noise immunity Line-of-sight Coarse resolution Short range Blocked by common materials Light, weather sensitive Pollution can affect transmission

8 IEEE Example: RADAR It is using a standard network adapter to measure signal strengths at multiple base stations positioned to provide overlapping coverage in a given area

9 Strength –Easy to set up –Requires few base stations –Uses the same infrastructure that provides general wireless networking in the building Weakness –Poor overall accuracy: scene-analysis: within 3 meters with 50 percent probability signal strength: 4.3 meters at the same probability –Support Wave LAN NIC Microsoft RADAR

10 Ultrasonic Active Bat (AT&T) –ultrasound time- of-flight measurement –can locate Bats to within 9cm of their true position for 95 percent of the measurements

11 Cricket Location Support System (M.I.T) Ultrasonic time-of- flight and a radio frequency control signal Lateration and proximity techniques Decentralized scalability 4x4 square-foot regions

12 RFID: SpotON Objects are located by homogenous sensor nodes without central control SpotOn tags use received radio signal strength information as a sensor measurement for estimating inter-tag distance No complete system yet

13 LANDMARC Prototype Selection criteria –Use commodity products or off-the-shelf components –Low cost –Resolution: no more than 2-3 meters Decision: RFID technology

14 What is RFID (Radio Frequency Identification) ? RFID is a means of storing and retrieving data through electromagnetic transmission to a RF compatible integrated circuit 3 basic components

15 Passive RFID

16 Active RFID RF Reader –Range up to 150 feet –Identify 500 tags in 7.5 seconds with the collision avoidance –Support 8 power levels (function of distance) Active Tag system –Emit signal, which consists of a unique 7-character ID, every 7.5 seconds for identification by the readers –Button-cell battery (2-5 years life) –Operate at the frequency of MHz

17 Active RFID Advantages Non-line-of-sight nature RF tags can be read despite the extreme environmental factors : snow, fog, ice, paint … be read in less than 100 milliseconds promising transmission range cost-effectiveness

18 Using RFID: First Attempt How many readers are needed? –Build an array of readers: too expensive How reliable is the tag detection? –Not very reliable due to signal attenuation Placement of RF readers Cannot measure distance directly

19 the received signal power at distance is given by free space loss is given by

20 Difficulties

21 LANDMARC Approach The LANDMARC system mainly consists of two physical components, the RF readers and RF tags

22 The Concept of Reference Tags

23 Distance estimation Placement of reference tags Selection of k neighboring reference tags Weight of each selected reference tags Known Reference Tags

24 the placement of the reference tags Three Key Issues the value of k in this algorithm the formula of the weight

25 Distance Estimation: Signal Strength Signal Strength Vector of an unknown tag Signal Strength Vector of a reference tag Euclidian distance

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28 Effect of the Value k Cumulative Percentile Of Error Distance When K Value Is 2, 3, 4, 5

29 Influence of The Environmental Factors Cumulative Percentile Of Error Distance in Daytime & Night

30 Influence of The Environmental Factors (cont ’ d) Change The Placements Of Tracking Tags

31 Influence of The Environmental Factors (cont ’ d) Cumulative Percentile Of Error Distance When Changing The Placement Of Tracking Tags

32 Effect of The Number of Readers Cumulative Percentile Of Error Distance With 3 or 4 Readers Data

33 The Effect of Placement of Reference Tags Without Partition

34 Effect of Placement of Reference Tags (cont ’ d) With Partition

35 Effect of Placement of Reference Tags (cont ’ d) With Partition

36 Placement of Reference Tags Replacements of the Reference Tags with a Higher Density

37 Effect of Higher Density Reference Tags Cumulative Percentile Of Error Distance With Higher Reference Tag Density

38 Lower Density of Reference Tags Replacements of the Reference Tags with a Lower Density

39 Effect of Lower Density Reference Tags Cumulative Percentile Of Error Distance With lower Reference Tag Density

40 Using 4 RF readers in the lab, with one reference tag per square meter, accurately locate the objects within error distance such that the largest error is 2 meters and the average is about 1 meter.

41 Conclusions RFID can be a good candidate for building location-sensing systems Able to handle dynamic environments Suffer some problems –Difference of Tags’ Behavior –RFID does not provide the signal strength of tags directly –Unable to adjust emitting interval –Standardization

42 Questions?

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44 Desk Refrigerator Desk Sofa Refrigerator 2. Tracking movement 3. Notify where you are (Location sensing) 4. Notify your eating schedule 7. Time sensing 8. immobility sensing 11. Proximity sensing 16. Notify “ ok to eat ” 1.walk 5.Stop eating 6.Back to desk 10. Walk around 9. Notify to move 12. Walk away from sofa 13. Distance& Time sensing 14. Notify to stop 15. Go back to desk 17. Go to kitchen 18. Refer Healthy food 19. Eat matched food

45 Triangulation –Lateration Direct Time-of-flight Attenuation –Angulation

46 (2)Scene Analysis use features of a scene observed from a certain reference point (3)Proximity determine if an object is near a known location

47 Project Motivation GPS ’ s inability for accurate indoor location sensing Develop a cost-effective indoor location sensing infrastructure Enables location-based Web services for mobile-commerce (m-commerce) environment Plenty of other application scenarios, depending on your imagination and creativity

48 Passive RFID vs. Active RFID Active tag System

49 A Triangulation Approach

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51 Active RFID RF Reader –Range up to 150 feet –Identify 500 tags in 7.5 seconds with the collision avoidance –Support 8 power levels (function of distance) Active Tag system –Emit signal, which consists of a unique 7- character ID, every 7.5 seconds for identification by the readers –Button-cell battery (2-5 years life) –Operate at the frequency of MHz