5 13meeting佑任
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5 13meeting佑任 5 13meeting佑任 Presentation Transcript

  • Time and Power Based Positioning Scheme for Indoor Location Aware Services 學生 : 佑任 老師 : 劉宏煥
  • Reference A. El Moutia , Kia Makki , ” Time and Power Based Positioning Scheme for Indoor Location Aware Services,” CCNC 2008. 5th IEEE , 10-12 Jan. 2008 , page(s) : 868 - 872
  • Outline
    • Indoor location schemes and range estimation techniques
    • Network model
    • Time-and-power based positioning scheme
    • Step1:range detection
    • Step2:location computer
    • Performance evalution
  • Indoor positioning scheme
    • Ultrasound:
      • Calculates location using some triangulation from short pulses of ultrasound emitted from a transmitter worn on the body to beacons installed in the roof
    • Radio Frequency:
      • Use wireless network infrastructure to determine location
      • Low setup cost,long range
  • Range estimation techniques
    • RSS:computes distance based on the transmitted and received power lavels
    Apha=path loss coeffient C=const (antenna gain,height)
    • TDoA using RF and Ultrasound:
      • sends a radio and an ultrasound simultaneously
      • When RF arrivaled ,start measuring the time until ultrasound transmission arrivaled
    Vs is the speed of sound in air at 21 ℃
  • Network model
    • The system models augments the existing IEEE 802.11 access protocol
    • The overlay network is composed of three types of sensor nodes
      • Manager node:attached to the access point,it initializes the sensor relays by conveying information about the associated access point
      • 45it serves as the data aggregation server where reassociation requests from mobile nodes are gathered, and reassociation responses are sent back
      • The relays are fixed sensors uniformly placed throughout the coverage area of an access point
      • the relays are used to route messages between the manager and the sensor agents. They are also responsible for sensing the frequency bands
      • The agents are sensors attached to the mobile nodes. They communicate with the relay sensors upon entering the transmission area
  • Time-and-Power based Positioning Scheme
    • TPPS is based on time difference of arrival TDoA and RSS using RF and US signals to detect range difference from wireless mobile terminal to three sensors nodes
  • Step 1: Range Detection
    • Now, let the received power at the master sensor be:
    C = const (consider carrier frequency and transmitted power) α = attenuation exponent rA = the distance between the mobile terminal and master sensor A sensor A estimates the received power levels and stores this information to perform averaging with a deep of I samples to increase the accuracy
  • The distance at time instant i can be estimated from the average received power using equation like:
    • Consider channel fading
      • Multiplied Factor (accounting for the fading amplitude)
      • Rayleigh pdf
  • Step 2: Location Computation
    • Based on trilateration and Pythagorean Theorem
    Subtracting second and third from first
  • minimizes the mean square error by That is
  • PERFORMANCE EVALUATION
    • 12 sensor nodes uniformly distributed in the coverage area of 100mx100m and 20 mobile terminals
    • each MT picks a random destination and a speed, ranging from 0 to 10 m/s
    • After a MT arrives at the destination, it pauses for a period of time ranging from 0s to 500s
  •  
  • The effect of the number of sensor nodes
  •