Cellular Positioning 30.11.20 12 1 Pabitra kumar chhatai Reg no- xxxxxxxxx GUIDED BY: Ast.prof Dillip kumar bhadra Dept. of : Electronics & Telecommunication Koustuv institute of Technology , BBSR
Jan 15, 2015
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Cellular Positioning
30.11.2012
Pabitra kumar chhatai Reg no- xxxxxxxxx
GUIDED BY: Ast.prof Dillip kumar bhadra
Dept. of : Electronics & Telecommunication Koustuv institute of Technology , BBSR
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Outline
Dept of : Electronics & Telecommunication.,KIT,BBSR
Introduction. Positioning Systems. Global positioning system(GPS). Differential global positioning system (DGPS). Wide Area Augmentation Signal(WAAS).
Method of Measurement. Time of Arrival(TOA). Time Differential of Arrival(TDOA). Signal Strength(SS). Angle of Arrival(AOA).
Comparison Of 4 methods Conclusion
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What is cellular positioning ?
Determining the position of a Mobile Station (MS),using
location sensitive parameters .
GNNS(Global Navigation Satellite System) A network of satellites that used for positioning
and navigation around the globe. US- Global Positioning System(GPS) Russian- GLObal NAvigation Satellite
System(GLONASS) European-GALILEO System
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Why we need cellular positioning ?
To provide location based services like... Tracking criminals. Providing emergency services . Military - defence system . Map-making. Navigation-car navigation system . Mountain climbing .
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Types of positioning systems.
Mobile centric systems. Positioning technology inserted inside the
cell. Currently there 200 millions of cell phones
with out GPS receiver. Network centric systems. Positioning technology resides in the
network. This type of systems are compatible with
the phones currently in use.
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Positioning of a mobile.
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What is GPS ?
Global positioning system(GPS). A network of satellites that continuously transmit coded information, which makes it
possible to precisely identify locations on earth by measuring distance from satellite.
Developed in 1980s by U.S Department of defence.
24 satellites approximately 20200 km above the earth
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Differential GPS(DGPS)
By placing additional GPS receiver(called reference station)
A technique where a data receiver at a known location is used to correct the data at an unknown location.
DGPS corrected solution is significantly more accurate , typical DGPS accuracy is 1-5 meters.
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DGPS
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Wide Area Augmentation Signal.
Wide Area Augmentation Signal. A satellite navigation system designed by
the U.S Federal Aviation Administration(FAA) to boost the accuracy of GPS satellite navigation .
Wide Area refers to a network of 25 ground reference stations cover the U.S and some of Canada and Mexico.
Each station connected to a master station.
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WAAS
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Accuracy of positioning system
Range
Positioning System
100 m
GPSWith SA
15 m GPSWithout SA
3-5 m DGPS
< 3 m WASS
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Methods of measurement
Time Of Arrival(TOA) Estimated by distance between
transmitter and receiver. Transmitted by the MS and received at
multiple BSs. Requirement: -Position of satellite -Timestamp
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TOA
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Location probability figures
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TOA
Specific positioning AlgorithmsMeasurements Estimated position d1,d2,d3 X m , Y m Where distance between MS and BS =
Propagation time * Propagation velocity. Al least 3 BSs are required to find the
exact position of MS.
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Time Different Of Arrival(TDOA)
Hyperbolic system. Converted to a constant distance
difference to two base stations. Intersection of two hyperbolas. Requirement: -Geographical coordinates. -Precisely synchronized clocks.
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TDOA
Specific positioning AlgorithmsMeasurements Estimated position d32,d31 X m , Y m
Al least 3 BSs are required to find the exact position of MS from a couple of TDOAs.
When the TOT of MS is unavailable.
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TDOA
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Signal Strength
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Distributed Receiving System(monitoring post).
Distributed Transmission System(Sing post.)
Similar to TOA. Measures signal attenuation. Path-loss ∆P(dB)=10α.log(f/c)-10βlog(4πd). Okumura-Hata model (OH). Long distance model.
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Signal Strength at diff. distance
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Angle Of Arrival(AOA)
Measuring the direction angles. Least two antenna array systems The position of the cell phone is
determined by the intersection of the two bearings of the cell sites.
Require: -Two dimensional positioning -Antennas installation -Interconnection of antennas
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AOA
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Comparison OF 4 methods
Measurement Type Advantages Disadvantages
Time of Arrival (TOA) • time measurement required forTDMA/CDMA network operation• simple computations
• synchronized network requiredreceiver must know time oftransmission• expensive measurement
Time Difference ofArrival (TDOA)
•time measurement required forTDMA/CDMA network operation• receiver does not need time oftransmission
• synchronized network requiredexpensive measurement• complex calculations
Signal Strength • low cost measurements •low accuracy in large cells• simple computations
•low accuracy in large cells
Angle of Arrival (AOA) •simple computations • specialized antennae• low accuracy in large cells
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Conclusion
We have described about accuratepositioning of mobile telephones, which
can beused for several applications. The important considerations to be
undertaken while selecting a location based technology are location accuracy , implementation cost, reliability, increasing functionality.
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Questions ?
“Thank YOU”