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Localization Issues in a ZigBee based Internet of Things scenario
 

Localization Issues in a ZigBee based Internet of Things scenario

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Paper presented @Tyrrhenian Workshop on the Internet of Things 2009...

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.

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  • First of all, I’d like to introduce you the RFID Lab of the University of Rome “Sapienza”. The lab has been working on RFID and other wireless technologies since three years, putting together different skills in order to have a complete vision of the process, from the application design, to its implementation, until its usability. In order to do that, we work with people that come from different faculties and different departments. There are persons coming from the Faculty of Engineering, from the Department of Computer Science, but also people coming from the Faculty of Mass Communication of “Sapienza” University.
  • Moreover, the RFID Labis just oneof the labs inside CATTID, whichiscomposedalsoby the e-learning lab, the Usability and AccessibilityLab, and the Multimedia lab. Activities:RFID and wireless for cultural heritageRFID forinclusionWireless Sensor NetworkRealTime Location SystemMobile / NFCFoodtraceabilitySupplychain managementDissemination
  • Among the various techniques for estimating the position of a node, measuring the power of the signal received (RSSI) is one of the most suitable, thanks to its implementation simplicity and to the limited hardware resources required
  • In the original Location Engine algorithm there are no given rules to set the n parameter.The test has shown the importance of the n parameter to achieve better localization results
  • Through the functionality provided by the ZigBee protocol is possible to group a variable number of network addresses in a single 16-bit address: Using this feature to represent a room, you can ensure that the Reference Nodes can provide to the Blind Node the best n parameter value for that environment.Multicast

Localization Issues in a ZigBee based Internet of Things scenario Localization Issues in a ZigBee based Internet of Things scenario Presentation Transcript

  • U. BiaderCeipidor, L. D’Ascenzo, C. M. Medaglia, M. Dibitonto
    Localization Issues in a ZigBee Based IoT Scenario
  • RFID Lab Academic Partners
    Director: Prof. Gianni Orlandi, Full Professor of Telecommunication
    Coordinator: Prof. Carlo Maria Medaglia, Associate Professor of HCI
    • Centrefor the ApplicationsofTelevision and DistanceLearningTechniques(CATTID), UniversityofRome “Sapienza”
    • Departmentof Electronic EngineeringFacultyofEngineering, Univ. ofRome “Sapienza”
    • DepartmentofInformaticEngineeringFacultyofEngineering, Univ. ofRome “Sapienza”
    • DepartmentofLogisticsFacultyofCommerce, Univ. ofRome “Sapienza”
    • CentreforTransports and Logistics(CTL), FacultyofEngineering, Univ. ofRome “Sapienza”
    • Departmentof Computer ScienceFacultyof Computer Science, Univ. ofRome “Sapienza”
    • DepartmentofCommunicationsSciencesFacultyof Mass Communication, Univ. ofRome “Sapienza”
    • DepartmentofComputer Science, Systems and Production (DISP), FacultyofEngineering, Università di Roma “Tor Vergata”
    • DepartmentofEnterpriseEngineering(DII), FacultyofEngineering, Università di Roma “Tor Vergata”
    • Institutefor the Protection and Security of the CitizenJRC Joint Research Centre UE
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  • Cattid Labs
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  • 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“
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    CASAGRAS (Coordination And Support Action for Global RFID-related Activities and Standardisation )
  • 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:
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  • 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
    ….
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  • 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.
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    ContextAwareness
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    Indoor Localization
    From Macro to Micro
    From “location-based services” to “sensor-based services”
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    Wireless Localization
    • Possible with a wide range of technologies
    • Different accuracy for different applications
    • Some provide good accuracy even for indoor applications
    ACTIVE RFID
    ZigBee
    GPS
    10 m
    Wi-Fi
    accuracy
    1 m
    Passive
    RFID
    UWB
    10 cm
    1cm
    Outdoor
    Semiurban
    Urban
    Building
    Room
    Objects
    1cm
  • ZigBee WSN
    ZigBee is a protocol for wireless communications, based on IEEE 802.15.4 infrastructure .
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    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.
  • ZigBee WSN
    Coordinator
    Sets up a network
    Transmits network beacons
    Manages network nodes
    Stores network node information
    Router
    Routesmessagesbetweenpairednodes
    Typically operates in the receive State
    Node
    • Designed for battery powered/high energysavings
    • Searchesforavailablenetworks
    • Transfers data fromitsapplicationasnecessary
    • Determineswhether data ispending
    • Requests data from the network coordinator
    • Can sleep for extended periods
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  • 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.
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  • Field Test Campaign
    A field test campaign was performed with the objective of verifying the performance or the original Texas Instruments’ localization algorithm.
    Test were performed in two different environment:
    • RFID Lab : considered as the worst-case scenario because of the presence of several wireless 802.11 networks, infrastructures for localization through the same router, some RFID readers and NFC devices. Interference on the same band used by the nodes is active at all times and with varying intensity.
    • Study Room : that room can be a model for an office in which metal objects and computers create multiple paths and destructive interference.
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  • 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
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  • 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.
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  • 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.
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  • 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.
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  • Algorithm optimization
    Step 1
    Setting up ReferenceNodes: nodeswereplacedaround the perimeterof the room and were set withtheircoordinates.
    xr2, yr2
    xr1, yr1
    xr4, yr4
    xr3, yr3
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  • 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.
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  • 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
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  • 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.
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    nfor RFID Labroom
    nforstudyroom
  • Future Works
    Future works will focus on avoiding obsolescence of the n parameter (due to changes in the environment ) and on the integration with other application :
    • using other sensors as triggers to activate the auto configuration procedure.
    • using localization as service for domotic application.
    ni
    xbn2 , ybn2
    xbn1 , ybn1
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  • Field Test Campaign
    Thank you!!
    Q&(hopefully)A
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  • 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
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