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  • 5 13meeting2

    1. 1. Time and Power Based Positioning Scheme for Indoor Location Aware Services 學生 : 佑任 老師 : 劉宏煥
    2. 2. 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
    3. 3. Outline <ul><li>Range estimation techniques </li></ul><ul><li>Network model </li></ul><ul><li>Time-and-power based positioning scheme </li></ul><ul><li>Step1:range detection </li></ul><ul><li>Step2:location computer </li></ul><ul><li>Performance evalution </li></ul>
    4. 4. Range estimation techniques <ul><li>RSS : computes distance based on the transmitted and received power lavels </li></ul>α =path loss coeffient C=const (antenna gain,height) path loss model:
    5. 5. <ul><li>TDoA using RF and Ultrasound: </li></ul><ul><ul><li>sends a radio and an ultrasound simultaneously </li></ul></ul><ul><ul><li>When RF arrivaled ,start measuring the time until ultrasound transmission arrivaled </li></ul></ul>Vs is the speed of sound in air at 21 ℃
    6. 6. Network model <ul><li>The system models augments the existing IEEE 802.11 access protocol </li></ul>
    7. 7. The overlay network is composed of three types of sensor nodes <ul><ul><li>Manager node: </li></ul></ul><ul><ul><ul><li>it initializes the sensor relays by conveying information about the associated access point </li></ul></ul></ul><ul><ul><ul><li>it serves as the data aggregation server </li></ul></ul></ul><ul><ul><li>The relays : </li></ul></ul><ul><ul><ul><li>uniformly placed throughout the coverage area of an AP </li></ul></ul></ul><ul><ul><ul><li>used to route messages </li></ul></ul></ul><ul><ul><ul><li>sensing the frequency bands and estimate location </li></ul></ul></ul><ul><ul><li>The agents : </li></ul></ul><ul><ul><ul><li>They communicate with the relay sensors upon entering the transmission area </li></ul></ul></ul>
    8. 8. Time-and-Power based Positioning Scheme <ul><li>TPPS is based on TDoA and RSS using RF and US signals to detect range difference from wireless mobile terminal to three sensors nodes </li></ul>
    9. 9. Step 1: Range Detection
    10. 10. <ul><li>Now, let the received power at the master sensor be: </li></ul>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
    11. 11. <ul><li>Consider channel fading </li></ul><ul><ul><li>Multiplied Factor (accounting for the fading amplitude) </li></ul></ul><ul><ul><li>Rayleigh pdf </li></ul></ul><ul><li>The distance at time instant i can be estimated from the </li></ul><ul><li>average received power using equation like: </li></ul>
    12. 12. Step 2: Location Computation <ul><li>Based on trilateration and Pythagorean Theorem </li></ul>Subtracting second and third from first
    13. 13. minimizes the mean square error by That is
    14. 14. PERFORMANCE EVALUATION <ul><li>12 sensor nodes uniformly distributed in the coverage area of 100mx100m and 20 mobile terminals </li></ul><ul><li>each MT picks a random destination and a speed, ranging from 0 to 10 m/s </li></ul><ul><li>After a MT arrives at the destination, it pauses for a period of time ranging from 0s to 500s </li></ul>
    15. 16. The effect of the number of sensor nodes