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Wireless Indoor Positioning Techniques
Rilind BallazhiSupervisor: Prof. Dr. Károly Farkas
Communication Systems SeminarFS 2012
Wireless Indoor Positioning Techniques 1
Agenda
• Introduction
• Positioning Techniques
• Positioning Algorithms
• Measurement Techniques
• Positioning Systems
• Comparison of the Systems
• Summary and Conclusion
• Discussion
Communication Systems Seminar
Wireless Indoor Positioning Techniques 1
Agenda
• Introduction
• Positioning Techniques
• Positioning Algorithms
• Measurement Techniques
• Positioning Systems
• Comparison of the Systems
• Summary and Conclusion
• Discussion
Communication Systems Seminar
Wireless Indoor Positioning Techniques 2
Introduction
• High demand in recent years
• Used in many applications
Objectives:
• Investigate the techniques and systems of wireless indoor positioning
• Compare the different indoor positioning systemsCommunication Systems Seminar
Mobile Terminal
Base Stations
Base Stations
Propagated Signal Location metrics: TOA, AOA...
Positioning Algorithm
Location coordinates
Display System
Reference Point
Reference Point
Received Signal
Wireless Indoor Positioning Techniques 3
Agenda
• Introduction
• Positioning Techniques
• Positioning Algorithms
• Measurement Techniques
• Positioning Systems
• Comparison of the Systems
• Summary and Conclusion
• Discussion
Communication Systems Seminar
Wireless Indoor Positioning Techniques 4
Positioning Techniques
• Positioning Algorithms
• Measurement Techniques
Communication Systems Seminar
Wireless Indoor Positioning Techniques 5
Positioning TechniquesPositioning Algorithms
• Triangulation
• Trilateration
• Scene Analysis
• Proximity
Communication Systems Seminar
Wireless Indoor Positioning Techniques 6
Positioning TechniquesPositioning Algorithms
• Triangulation
• Trilateration
• Scene Analysis
• Proximity
Communication Systems Seminar
• Estimates an object by computing angles relative to multiple reference points
• The object to be located is used as a fixed point of a triangle
• Usually AOA used for angle measurement
Wireless Indoor Positioning Techniques 7
Positioning TechniquesPositioning Algorithms
• Triangulation
• Trilateration
• Scene Analysis
• Proximity
Communication Systems Seminar
• Estimates the position of an object by measuring its distances from multiple reference points
• The distance is computed by multiplying the radio signal velocity and the travel time
• Usually TOA and TDOA used for distance measuring
Wireless Indoor Positioning Techniques 8
Positioning TechniquesPositioning Algorithms
• Triangulation
• Trilateration
• Scene Analysis
• Proximity
Communication Systems Seminar
• Type of algorithms that first collect features of a scene and then estimate the location of an object by matching
• Two stages:• offline• online
• Received Signal Strength is commonly used in Scene Analysis
• RSS could be affected by diffraction, reflection and scattering
• Fingerprinting-based positioning algorithms• probabilistic methods• k-nearest neighbor• neural networks• support vector machine (SVM)• smallest M-vertex polygon (SMP)
Wireless Indoor Positioning Techniques 9
Positioning TechniquesPositioning Algorithms
• Triangulation
• Trilateration
• Scene Analysis
• Proximity
Communication Systems Seminar
• Provides symbolic relative location information
• Relies upon a dense grid of antennas, having a well-known position
• If mobile target detected by a single antenna• mobile target collocated with the single antenna
• If mobile target detected by multiple antennas• collocation with the one with the highest RSS
• RSS is commonly used in proximity
• Simple to be implemented
Wireless Indoor Positioning Techniques 10
Positioning TechniquesMeasurement Techniques
• Angle of Arrival (AOA)
• Time of Arrival (TOA)
• Time Difference of Arrival (TDOA)
• Received Signal Strength (RSS)
Communication Systems Seminar
Wireless Indoor Positioning Techniques 11
Positioning TechniquesMeasurement Techniques
• Angle of Arrival (AOA)
• Time of Arrival (TOA)
• Time Difference of Arrival (TDOA)
• Received Signal Strength (RSS)
Communication Systems Seminar
• Target object can be found by intersection of several pairs of angle direction lines • Commonly referred as direction finding (DF)
• At least two reference Points (A and B) and two angles used, in order to derive the 2D location of the target
• No time synchronization between measuring points
• Requirement of large and complex hardware
Source: H. Liu, H. Darabi, P. Banerjee, J. Liu; “Survey of Wireless Indoor Positioning Techniques and Systems”, IEEE Transactions on Systems, November 2007
Wireless Indoor Positioning Techniques 12
Positioning TechniquesMeasurement Techniques
• Angle of Arrival (AOA)
• Time of Arrival (TOA)
• Time Difference of Arrival (TDOA)
• Received Signal Strength (RSS)
Communication Systems Seminar
• Time taken by the signal to go from the source mobile target to the measuring unit
• The distance from the mobile target to the measuring unit is directly proportional to the propagation time
• All transmitters and receivers in the system have to be precisely synchronized
• For 2D positioning, at least three reference points needed
Source: H. Liu, H. Darabi, P. Banerjee, J. Liu; “Survey of Wireless Indoor Positioning Techniques and Systems”, IEEE Transactions on Systems, November 2007
Wireless Indoor Positioning Techniques 13
Positioning TechniquesMeasurement Techniques
• Angle of Arrival (AOA)
• Time of Arrival (TOA)
• Time Difference of Arrival (TDOA)
• Received Signal Strength (RSS)
Communication Systems Seminar
• Determines the relative position of the mobile transmitter by examining the difference in time at which the signal arrives at multiple measuring units
• The transmitter must lie on a hyperboloid
• The hyperboloid equation is:
• (xi,yi,zi) and (xj,yj,zj) are fixed receivers; (x,y,z) is the coordinate of the target object
• Target location estimated by the intersection of two or more TDOA measurements
Source: H. Liu, H. Darabi, P. Banerjee, J. Liu; “Survey of Wireless Indoor Positioning Techniques and Systems”, IEEE Transactions on Systems, November 2007
Wireless Indoor Positioning Techniques 14
Positioning TechniquesMeasurement Techniques
• Angle of Arrival (AOA)
• Time of Arrival (TOA)
• Time Difference of Arrival (TDOA)
• Received Signal Strength (RSS)
Communication Systems Seminar
• RSS presents the strength of the received signal
• The core idea is to establish a one-to-one relationship between the received signal strength from several reference nodes and the current position of the mobile.
• RSS needs a radio map to be created in the coverage area
• Radio map collects the vectors of signal strengths for each reference node
• Model stored in a central location
Source: H. Liu, H. Darabi, P. Banerjee, J. Liu; “Survey of Wireless Indoor Positioning Techniques and Systems”, IEEE Transactions on Systems, November 2007
Wireless Indoor Positioning Techniques 15
Agenda
• Introduction
• Positioning Techniques
• Positioning Algorithms
• Measurement Techniques
• Positioning Systems
• Comparison of the Systems
• Summary and Conclusion
• Discussion
Communication Systems Seminar
Wireless Indoor Positioning Techniques 16
Positioning Systems
• Fixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
• Pedestrian Indoor Positioning Systems• Beauregard’s System
• FootSLAM
• Fischer’s System
• Bat System
Communication Systems Seminar
Wireless Indoor Positioning Techniques 17
Positioning SystemsFixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Communication Systems Seminar
Wireless Indoor Positioning Techniques 18
Positioning SystemsFixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Communication Systems Seminar
Infrared signals used for signal transmission
• Active Badge system
• Objects tracked by a badge, which emits a unique identifier every 15 sec.
• Each location in the building covered by a network with IR sensors
• Central server for collecting the data from IR sensor• Principle used: Trilateration and TOA
Source: J. Xiao, Z. Liu, Y. Yang, D. Liu, X. Han, “Comparison and Analysis of Indoor Wireless Positioning Techniques”, 2011 International Conference on Computer Science and Service System (CSSS 2011), Nanjing, China, June, 2011
Wireless Indoor Positioning Techniques 19
Positioning SystemsFixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Communication Systems Seminar
Ultrasonic beacons used for signal transmission
• Active Bat system
• Cricket system
Wireless Indoor Positioning Techniques 19
Positioning SystemsFixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Communication Systems Seminar
Ultrasonic beacons used for signal transmission
• Active Bat system
• Cricket system
• Users and objects are tagged with ultrasonic tags identified as “bats”• Signal receivers mounted across the ceiling • A large number of receivers required
Source: J. Xiao, Z. Liu, Y. Yang, D. Liu, X. Han, “Comparison and Analysis of Indoor Wireless Positioning Techniques”, 2011 International Conference on Computer Science and Service System (CSSS 2011), Nanjing, China, June, 2011
Wireless Indoor Positioning Techniques 20
Positioning SystemsFixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Communication Systems Seminar
Ultrasonic beacons used for signal transmission
• Active Bat system
• Cricket systemconsists of Cricket nodes:• beacons: are fixed, attached to the ceiling• listeners: attached to the target objects or people
• Beacons transmit periodically a message to the listener• Listener uses these information to determine its position
Source: Priyantha, N. B; The cricket indoor location system: PhD Thesis, Massachusetts Institute of Technology. 199 p, June 2005
Wireless Indoor Positioning Techniques 21
Positioning SystemsFixed Indoor Positioning Systems
Communication Systems Seminar
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
• Radio Frequency used for signal transmission
• RFID systems consists of RFID readers and RFID tags
RF based systems:
• LANDMARC• RADAR• SpotON
Wireless Indoor Positioning Techniques 21
Positioning SystemsFixed Indoor Positioning Systems
Communication Systems Seminar
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
• Radio Frequency used for signal transmission
• RFID systems consists of RFID readers and RFID tags
RF based systems:
• LANDMARC• RADAR• SpotON
• RFID active tag• RFID reader with 8 power levels, placed in known positions• Extra fixed location reference tags used to help location calibration
Source: Lionel M.NI, Yunhao Liu, Iu Cho Lau, Abhıshek P. Patil; LANDMARC: Indoor Location Sensing Using Active RFID
Wireless Indoor Positioning Techniques 22
Positioning SystemsFixed Indoor Positioning Systems
Communication Systems Seminar
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
• Radio Frequency used for signal transmission
• RFID systems consists of RFID readers and RFID tags
RF based systems:
• LANDMARC• RADAR• SpotON
• Signal strength information collected at multiple receiver location triangulated to find user coordinates
• RSS information is collected during the off-line phase and real-time phase
Wireless Indoor Positioning Techniques 23
Positioning SystemsFixed Indoor Positioning Systems
Communication Systems Seminar
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Source: J. Hightower, R. Want and G. Borriello; SpotON: An indoor 3D location sensing technology based on RF signal strength,UW CSE00-02-02, February 2000
• Radio Frequency used for signal transmission
• RFID systems consists of RFID readers and RFID tags
RF based systems:
• LANDMARC• RADAR• SpotON
• Based on RSS
• Object Tags and Base Stations connected serially
• Server processor maps the RSS values
Wireless Indoor Positioning Techniques 24
Positioning SystemsFixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Communication Systems Seminar
• UWB is based on sending ultrashort pulses• UWB systems transmit a signal over multiple bands of frequencies simultaneously• Signal transmission for a much shorter duration
UWB based systems:
• Ubisense systemconsist of:• Tags: Are carried by persons or targeted objects• Fixed sensor infrastructure: Sensors placed in the building• Location management platform: Processes and distributes
the location information to applications
• Cellular System Architecture
Wireless Indoor Positioning Techniques 25
Positioning SystemsFixed Indoor Positioning Systems
• Infrared Positioning Systems
• Ultrasonic Positioning Systems
• RF Positioning Systems
• Ultra Wideband Systems
• Optical Indoor Positioning Systems
Communication Systems Seminar
• Positioning of objects with a system installed in the building and a mobile sensors (i.e. camera) carried by the user• Used for locating robots within an indoor environment
Proposed system:• CLIPS (Camera and Laser based Indoor Positioning System)
• The laser device is oriented toward the ceiling and laser beams are on the ceiling• The camera device acts as mobile device and tracks the laser beams
Source: Tilch,S.Mautz,R., Current investigations at the ETH Zurich in optical indoor positioning. IEEE Positioning Navigation and Communication (WPNC) conference, 2010
Wireless Indoor Positioning Techniques 26
Positioning SystemsPedestrian Indoor Positioning Systems
• Beauregard’s System
• FootSLAM
• Fischer’s System
• Bat System
Communication Systems Seminar
Wireless Indoor Positioning Techniques 27
Positioning SystemsPedestrian Indoor Positioning Systems
• Beauregard’s System
• FootSLAM
• Fischer’s System
• Bat System
Communication Systems Seminar
• Pedestrian Dead Reckoning (PDR) approach used
• Helmet mounted sensors
• Algorithm used consist of two steps:• step detection and estimation• heading detection and estimation
Source: S. Beauregard, A helmet-mounted pedestrian dead reckoning system, in 4th International Forum on Applied Wearable Computing, 2006
Wireless Indoor Positioning Techniques 28
Positioning SystemsPedestrian Indoor Positioning Systems
• Beauregard’s System
• FootSLAM
• Fischer’s System
• Bat System
Communication Systems Seminar
• System uses foot mounted Inertial Measurement Unit (IMU)
• It builds 2D map of the building, without prior knowledge of the building structure
• The more times places are visited within the building, the better information or map built in regards of the place
• PDR approach used
Source: Robertson, P., Angermann, M, Krach, B., Simultaneous Localization and Mapping for Pedestrians using only Foot-Mounted Inertial Sensors. In Proc. UbiComp 2009, ACM (2009) 93-96
Wireless Indoor Positioning Techniques 29
Positioning SystemsPedestrian Indoor Positioning Systems
• Beauregard’s System
• FootSLAM
• Fischer’s System
• Bat System
Communication Systems Seminar
• Combination of Ultrasound beacons and foot mounted inertial sensors• Two types of errors: heading error and distance error
• Ultrasound beacons for providing better accuracy and less heading error in PDR approach are used
Source: “Ultrasound-aided Pedestrian Dead Reckoning for Indoor Navigation”, http://www2.parc.com/isl/projects/MELT08/ProgramSlides/poster1_3_fischer.ppt.pdf
Wireless Indoor Positioning Techniques 30
Positioning SystemsPedestrian Indoor Positioning Systems
• Beauregard’s System
• FootSLAM
• Fischer’s System
• Bat System
Communication Systems Seminar
• Combination of a foot mounted Inertial Measurement Unit, a detailed building model and a particle filter for providing absolute positioning to reduce complexity
• Initialization of the localization algorithm using WiFi signal strength
• Unknown Initial position and orientation of the user
• Position of the pedestrian at time k is estimated when knowing his position at time k-1
Source: O. Woodman and R. Harle. Pedestrian localisation for indoor environments. In Proc. of the UbiComp 2008, Seoul, South Korea, Sept. 2008
Wireless Indoor Positioning Techniques 31
Agenda
• Introduction
• Positioning Techniques
• Positioning Algorithms
• Measurement Techniques
• Positioning Systems
• Comparison of the Systems
• Summary and Conclusion
• Discussion
Communication Systems Seminar
Wireless Indoor Positioning Techniques 32
Comparisons
Positioning System Accuracy Signal Principle Range Cost Data rate
Active Badge 7cm Infra Red T/TOA 5 m moderate 0.1 Hz
Active Bats 9 cm Ultrasound T/TOA 50 m moderate 75 Hz
Cricket 2 cm Ultrasound T/TOA 10 m low 1 Hz
Dolphin 2 cm Ultrasound T/TOA Room moderate 20 Hz
Radar 2-3 m RF R/RSS Room moderate 4 Hz
Wave LAN 3 m RF R/RSS Room moderate 4 Hz
UWB 10 cm RF T/TOA 15 m moderate 1 Hz
LANDMARC 1-2 m RF R/RSS 50 m moderate 70 Hz
SpotOn 3 m RF R/RSS Room low 2 Hz
CLIPS 0.5 mm Camera images Image process 36 m2 high 30 Hz
Communication Systems Seminar
Comparison of fixed indoor positioning systems
Wireless Indoor Positioning Techniques 33
Comparisons [2]
Positioning System Technique Accuracy 2D/3D Range Robustness
Beauregard’s PDR 10 m 2D Room1. No change in
heading2. No drift caused by
PDR
FootSLAM PDR 1-3 m 3D 2 mImproves with larger number of visits to
locations in the building
Fischer’s US + PDR < 1 m 3D 3 m1. No harsh light
2. Not noisy environment LOS
Bat System Wifi + PDR 0.5 m 3D building Existence of WiFi
Communication Systems Seminar
Comparison of pedestrian indoor positioning systems
Wireless Indoor Positioning Techniques 34
Agenda
• Introduction
• Positioning Techniques
• Positioning Algorithms
• Measurement Techniques
• Positioning Systems
• Comparison of the Systems
• Summary and Conclusion
• Discussion
Communication Systems Seminar
Wireless Indoor Positioning Techniques 35
Summary and Conclusion
Communication Systems Seminar
• Indoor positioning is a huge area, with many applications
• Various indoor positioning techniques
• Many improvements can be carried for different systems
• Fixed indoor positioning systems have a better accuracy compared to the pedestrian positioning systems
Comparisons [3]Thank you for your attention!
Comparisons [3] Questions
Wireless Indoor Positioning Techniques 36
Discussion
• Which of the presented indoor positioning systems you think have more need for improvement? Fixed or pedestrian indoor positioning systems?
• Which of the presented systems you think are most promising systems for the future?
• Do you think that a combination of different techniques can increase the performance of indoor positioning systems?
• Is something you are missing in your daily life, and you would like to have such a system? What kind of systems would match to solve this problem?
Communication Systems Seminar