Paper presented @Tyrrhenian Workshop on the Internet of Things 2009 ZigBee is probably the most popular IEEE 802.15.4 implementation used for Wireless Sensor Networks (WSN). The radio communication can also be used for localization purposes using fixed network devices as reference points. In this paper, the authors describe a procedure for automatically configuring a ZigBee-based localization appli-cation with environment-optimized parameters.

1. U. BiaderCeipidor, L. D’Ascenzo, C. M. Medaglia, M. Dibitonto Localization Issues in a ZigBee Based IoT Scenario

3. Departmentof Electronic EngineeringFacultyofEngineering, Univ. ofRome “Sapienza”

4. DepartmentofInformaticEngineeringFacultyofEngineering, Univ. ofRome “Sapienza”

5. DepartmentofLogisticsFacultyofCommerce, Univ. ofRome “Sapienza”

6. CentreforTransports and Logistics(CTL), FacultyofEngineering, Univ. ofRome “Sapienza”

7. Departmentof Computer ScienceFacultyof Computer Science, Univ. ofRome “Sapienza”

8. DepartmentofCommunicationsSciencesFacultyof Mass Communication, Univ. ofRome “Sapienza”

9. DepartmentofComputer Science, Systems and Production (DISP), FacultyofEngineering, Università di Roma “Tor Vergata”

10. DepartmentofEnterpriseEngineering(DII), FacultyofEngineering, Università di Roma “Tor Vergata”

11. Institutefor the Protection and Security of the CitizenJRC Joint Research Centre UE04/09/2009 2 Tyrrhenian Workshop - Pula

12. Cattid Labs 04/09/2009 3 Tyrrhenian Workshop - Pula

13. Internet of Things “A global network infrastructure, linking physical and virtual objects through the exploitation of data capture and communication capabilities” “It will offer specific object-identification, sensor and connection capability as the basis for the development of independent federated services and applications.” “These will be characterised by a high degree of autonomous data capture, transfer event network connectivity and interoperability“ 04/09/2009 4 Tyrrhenian Workshop - Pula CASAGRAS (Coordination And Support Action for Global RFID-related Activities and Standardisation )

14. Internet ofThings The atomic elements of this vision are the so called “smart objects”, device able to autonomously collect and process information and interact with other devices. Those devices could be: 04/09/2009 5 Tyrrhenian Workshop - Pula

15. Internet of Services Smart objects could provide and access services that can be queried through Gateway and Information Management System. Passive tags Information Management System Sensors Gateway Internet Actuators Information Management System …. Gateway …. 04/09/2009 6 Tyrrhenian Workshop - Pula

16. ContextAwareness Objects acquire information on the surrounding environment, processing, managing and sharing collected data. The capability to determine with a certain accuracy the position of an object, especially when it’s a moving object, gives an important information that contextualizes all other data collected. 04/09/2009 7 Tyrrhenian Workshop - Pula ContextAwareness

17. 04/09/2009 Tyrrhenian Workshop - Pula 8 Indoor Localization From Macro to Micro From “location-based services” to “sensor-based services”

19. Different accuracy for different applications

20. Some provide good accuracy even for indoor applicationsACTIVE RFID ZigBee GPS 10 m Wi-Fi accuracy 1 m Passive RFID UWB 10 cm 1cm Outdoor Semiurban Urban Building Room Objects 1cm

21. ZigBee WSN ZigBee is a protocol for wireless communications, based on IEEE 802.15.4 infrastructure . 04/09/2009 10 Tyrrhenian Workshop - Pula It can be classified as a low bitrate WPAN (250 kbps). It provides a reliable, robust and energy efficient exchange of information between devices equipped with any kind of sensors.

23. Searchesforavailablenetworks

24. Transfers data fromitsapplicationasnecessary

25. Determineswhether data ispending

26. Requests data from the network coordinator

27. Can sleep for extended periods04/09/2009 11 Tyrrhenian Workshop - Pula

28. Localization Through ZigBee Network infrastructures created by a ZigBee WSN can be also used to determine the position of nodes. Tests have been conducted using the kit CC2431DK of Texas Instruments that implements a RSSI based trilateration algorithm in its Location Engine RSSI = - ( 10 · n ·log10d + A ) A is the absolute value of average power in dBm received at a reference distance of 1 meter . n describes the decrease of the power varying with the distance d between transmitter node and receiver node. 04/09/2009 12 Tyrrhenian Workshop - Pula

30. Study Room : that room can be a model for an office in which metal objects and computers create multiple paths and destructive interference.04/09/2009 13 Tyrrhenian Workshop - Pula

31. Field Test Campaign The Location Engine requires at least 3 references to estimate the position, but tests were initially performed by placing 4 Reference Nodes along the perimeter of the rooms, 2 meters above the floor, trying to create a regular area and placing the Blind Node in a central position in the so created area. = RN = BN 04/09/2009 14 Tyrrhenian Workshop - Pula

32. Field Test Campaign The first test was performed varying the parameter n over all the 32 possible values. The coordinates estimated were compared with the known position of the Blind Node. Results obtained show that, for low values of the n parameter, the error is so high that the node is located outside the area of interest . The error tends to decrease in the neighborhood of n=19, and then rise again for higher values. 04/09/2009 15 Tyrrhenian Workshop - Pula

33. Field Test Campaign The test was then repeated by increasing progressively from 4 to 6 the number of references, in order to estimate the importance of the number of inputs to the Location Engine. Results showed that increasing the number of Reference Nodes does not improve so much localization accuracy. 04/09/2009 16 Tyrrhenian Workshop - Pula

34. Algorithm optimization After the test campaign, the focus of research turned to find an automatic procedure for identifying the value that optimizes precision. The existing routines have been integrated with an automatic procedure to estimate the value of the exponent that describes the decay of power with distance . Setting the coordinates for each Reference Node; Division of the references in groups; Estimation of the parameter n via a Blind Test. 04/09/2009 17 Tyrrhenian Workshop - Pula

35. Algorithm optimization Step 1 Setting up ReferenceNodes: nodeswereplacedaround the perimeterof the room and were set withtheircoordinates. xr2, yr2 xr1, yr1 xr4, yr4 xr3, yr3 04/09/2009 18 Tyrrhenian Workshop - Pula

36. Algorithm optimization Step 2 Grouping Nodes : the test results showed that, in the same environment, adjacent rooms had different values for the n parameter. This behavior led us to organize reference nodes into groups that match a room area and that share the same n parameter. 04/09/2009 19 Tyrrhenian Workshop - Pula

37. Algorithm optimization Step 3 Blind Node Test: a Blind Node is placed inside the room, receives its own coordinates, and repeatedly performs the location procedure, iterating on all possible values of the n parameter, and calculates the position error respect to the coordinates given above. The value of the n parameter that brings better accuracy is sent to the closest reference that transmits it to all nodes that are part of the group. The whole procedure takes about 10 seconds. ni n = ni xbn2 , ybn2 xbn1 , ybn1 04/09/2009 20 Tyrrhenian Workshop - Pula

38. Second Field Test Campaign A second field test campaign was performed to evaluate performances of the optimized algorithm. The n parameter calculated was in 80% of cases corresponding to the one that showed the best performances with an accuracy of 1 meter. 04/09/2009 21 Tyrrhenian Workshop - Pula nfor RFID Labroom nforstudyroom

40. using localization as service for domotic application.ni xbn2 , ybn2 xbn1 , ybn1 04/09/2009 22 Tyrrhenian Workshop - Pula

41. Field Test Campaign Thank you!! Q&(hopefully)A 04/09/2009 23 Tyrrhenian Workshop - Pula

42. ZigBee WSN vs UWB UWB was conceived for short range, high data rate applications. Low Rate WPANs have tighter power consumption requirements and thus are better suited for creating an autonomous and reliable network infrastructure L. Jin-Shyan, S. Yu-Wei, and S. Chung-Chou, "A Comparative Study of Wireless Protocols: Bluetooth, UWB, ZigBee, and Wi-Fi," in Industrial Electronics Society, 2007. IECON 2007. 33rd Annual Conference of the IEEE, 2007, pp. 46-51 04/09/2009 24 Tyrrhenian Workshop - Pula