Hao Ji , Lei Xie , Yafeng Yin, Sanglu Lu State Key Laboratory for Novel Software Technology,

1. GLOBECOM 2013 An Efficient Indoor Navigation Scheme Using RFID-based Delay Tolerant Network HaoJi, Lei Xie, Yafeng Yin, SangluLu State Key Laboratory for Novel Software Technology, Nanjing University, Nanjing, China Presenter: Dr. Lei Xie, Associate Professor

2. Outline 1 2 3 4 5 Evaluation and Conclusion Motivation Related Works Problem Description Our Solutions

3. Mobile Indoor Navigation Is Necessary How to locate and navigate to a mobile target Although now people have several ways to communicate with each other, finding a mobile target (e.g., children, puppies) in a public place, such as in a supermarket, theme park, or shopping mall, can be difficult. Motivation Related Works Problem Description Our Solutions Evaluation 1

4. Indoor localization Technology Wireless/Radio Signal Design and Evaluation of a Wireless Magnetic-based Proximity Detection Platform for Indoor Applications ACM/IEEE IPSN 2012, MSRA Magnetic Mining Frequent Trajectory Patterns for Activity Monitoring Using Radio Frequency Tag Arrays IEEE Transactions on Parallel and Distributed Systems (TPDS), 2012. (RFID) RFID Wifilocalization and navigation for autonomous indoor mobile robots International Conference on Robotics and Automation (ICRA), pp. 4379--4384, 2010. Wi-Fi Providing location based information/advertising for existing mobile phone users Personal and Ubiquitous Computing, pp. 3–10, 2008. Bluetooth The cricket location-support system MobiCom, pp. 32–43, 2000. Precise Positioning Ultrasonic The active badge location system ACM Transactions on Information System, pp. 91–102, 1992. Infrared Smartphone Did you see Bob?: human localization using mobile phones. ACM MobiCom 2010，Duke University. Proximity Detection Computer Vision (CV) Motivation Related Works Problem Description Our Solutions Evaluation 2

5. Challenges for Indoor Localization Infrared Ultrasonic Magnetic RFID Wi-Fi Bluetooth Accuracy of positioning Transmission Capability Identification Capability Accuracy & Transmission & Identification Motivation Related Works Problem Description Our Solutions Evaluation 3

6. Design and Evaluation of a Wireless Magnetic-based Proximity Detection Platform for Indoor Applications ACM/IEEE IPSN 2012, MSRA Wireless Proximity Detection based on Magnetic Induction Deploying inside a large food court to offer context-aware and personalized advertisements and diet suggestions at a per-counter granularity. Motivation Related Works Problem Description Our Solutions Evaluation 4

7. Did you see Bob?: human localization using mobile phones. ACM MobiCom 2010，Duke University. Using mobile phone sensors and opportunisticuser-intersections to develop an indoor navigation system. B(t) B(t) T_BC C(t) T_AC C(t) Motivation Related Works Problem Description Our Solutions Evaluation 5

8. Compare With Actual Situation Traditional Indoor Navigation System • Centralized System Architecture • There is centralized server in the system. • The Position of the Target Is Stationery • Position of the target is stationery on the map. • Direct Communication Ability with the Centralized Server • Each client directly reports its location info to server whenever possible. Actual Situation • Distributed System Architecture • The Position of the Mobile Target Is Continuously Changing. • No Direct Communication among Clients. • Sufficiently Reduce the Cost of Deployment and Hardware. Motivation Related Works Problem Description Our Solutions Evaluation 6

9. Deploying RFID TAGs as a Delay Tolerant Network Noncontact Identification Storage Capacity Low Cost MassivelyDeployed RFID tags are deployed on key locations Entrancesof building Doorof office room, meeting room and washing room Cornersof corridor, elevators etc Motivation Related Works Problem Description Our Solutions Evaluation 7

10. Problem Description Navigation To A Moving Target User In Indoor Environment. • Client need not to have long distance communication ability. • There is no centralized server in the system. • Whenever client pass by a location sensing device, the location info can be recorded locally. Motivation Related Works Problem Description Our Solutions Evaluation 8

11. Location Info——Event Message Two components in the system: • Location sensing devices(like RFID tags)----stationary • Users----mobile When a user passes by a RFID tag, an event message will be left on the tag. A location1 Event <A, location1,time1> was written to this tag. Which means “user A pass by location1 at time1” Motivation Related Works Problem Description Our Solutions Evaluation 9

12. Spread of Event Message Location Info(Event) can be spread by other users. B <B,loc1’,t1> <B,loc2’,t2> A <A,loc1,t1> <A,loc2,t2> <A,loc3,t3> <A,loc4,t4> <B,loc3’,t3> <B,loc4’,t4> <A,loc2,t2> <B,loc5’,t5> <A,loc2,t2> User B carried user A’s location info <A,loc2,t2> to loc4’ and loc5’ Motivation Related Works Problem Description Our Solutions Evaluation 10

13. Request Info——Request Message When a user A wants to find user B. A Request R<A, B, time1> was written to this tag. Which means “please help user Ato find user B” Motivation Related Works Problem Description Our Solutions Evaluation 11

14. Spread of Request Message User A wants to find user B, if another user Cis also in the system. B C A R<A,B,t1> R<A,B,t2> R<A,B,t3> R<A,B,t4> <A,B,t2> <A,B,t2> User C brought user A’s request R<A,B,t2> more places Motivation Related Works Problem Description Our Solutions Evaluation 12

15. Two Kinds of Messages Event Message: -----------“I was once here” Request Message: -----------“Please help me to find T” Motivation Related Works Problem Description Our Solutions Evaluation 13

16. H User S want to find user T <S,loc1’ ,t1’> <S,loc2’,t2’> <S,loc3’,t3’> T <T,loc1,t1> <T,loc2,t2> <T,loc3,t3> <T,loc4,t4> <T,loc5,t5> <T,loc9,t9> <T,loc8,t8> <T,loc7,t7> <T,loc6,t6> <S,loc4’,t4’> <S,loc5’,t5’> <T,loc5,t5> <S’,loc6’,t6> <T,loc5,t5> <T,loc5,t5> S Req<T> <S,loc7’,t7’> Req<T> Req<T> Req<T> Req<T> Req<T> <S’,loc1’’,t1’> <S,loc2’’,t2’’> <S,loc3’’,t3’’> <S,loc4’’,t4’’> <S,loc5’’,t5’’> User H carried user T’s location info <T,loc5,t5> to user S

17. Navigation Scheme • Normal Mode: • Transmit his own “check-in” to surrounding location sensing devices. • Collect other users’ “check-in” from surrounding location sensing devices. • Collect surrounding “request”. • Process collected requests. • Searcher Mode: • Transmit “request” to surrounding location sensing devices. • Transmit his own “check-in” to surrounding location sensing devices. • Collect other users’ “check-in” from surrounding location sensing devices. • Collect surrounding “request”. • Process collected requests. • Use collected targets’ “check-in” info to make path decision. Crowdsourcing Motivation Related Works Problem Description Our Solutions Evaluation 14

18. Management of Storage Resource The memory size of RFID tag is limited, So we should make full use of these storage resources. Under the navigation framework, post operation will write messages to tags. Therefore, a reasonable writing and replacing strategy should be used. Motivation Related Works Problem Description Our Solutions Evaluation 15

19. Each Tag maintains at most λ event messages of each user Hi. when new event message arrive <A,loc,t4>, <A,loc1,t1>will be removed. FIFO • Each Tag maintains at most one request message of searcher S and target T. • When a helper passes by a vertex, he will post messages to the vertex with a posting probability p. Example 1 2 3 Memory space of Tag posting probability p = 1/3

20. Navigation Algorithm When searcher S has collected more than one event messages of the target T, how to use these event message to calculate the current position of target T? Motivation Related Works Problem Description Our Solutions Evaluation 16

21. Target region A simple way to do this is selecting the neighbor vertex which is nearest to the latest appearance location of the target. We use a target region rather than a single point. Three reasons: • The location with latest timestamp may be far away. There should be a tradeoff between the timestamp of the trace and distance. • The target is a moving object whose motion is a continuous process. • The movement behavior of the target has locality in the real world. Motivation Related Works Problem Description Our Solutions Evaluation 17

22. Navigation Algorithm Pre-calculate the distance matrix Calculate the distance weight Calculate distance cost function

23. Example <T,loc4,t4> 1. We select the top 3 timestamp event message location as the target region. <T,loc1,t1> <T,loc3,t3> <T,loc2,t2> 2. Calculate the weighted distance according to event message’s timestamp. S 3. Select the minimum cost neighbor.

24. Evaluation Experiment Settings • 30 X 30 grid-graph • Length of each edge is 4m • Movement speed of the searcher is 2m/s, other user’s are 1m/s • For all figures presented, we run the simulation 1,000 times to get average values. Evaluation Motivation Related Works Problem Description Our Solutions 18

25. Evaluation To Simulate The Mobility of Human Beings • Random Walk Mobility Model(RW) • Random Way-Point Mobility Model(RWP) the radius of the circle obeys a normal distribution the stay time of each user obeys a truncated power-law distribution Motivation Related Works Problem Description Our Solutions Evaluation 19

26. Evaluation More users means more helpers for the searcher Smaller average searching time Motivation Related Works Problem Description Our Solutions Evaluation 20

27. Evaluation Too small request TTL means fewer helper will “see” it. The larger time to live of request message is, the smaller average searching time is. Motivation Related Works Problem Description Our Solutions Evaluation 21

28. Evaluation Average searching time and expectation of movement region radius does not satisfy the monotonic relation. Motivation Related Works Problem Description Our Solutions Evaluation 22

29. Evaluation The Number of Request message reduce with the increment of time. Motivation Related Works Problem Description Our Solutions Evaluation 23

30. Conclusion • We propose a framework leveraging RFID-based delay tolerant network for localization and navigation. Store-and-forward of the DTN Crowdsourcing • We propose a time-efficient scheme to locate and navigate to a mobile target who is continuously moving. The most possible region of the target Motivation Related Works Problem Description Our Solutions Conclusion 24

31. GLOBECOM 2013 Questions ? Thank you !