positioning

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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

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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 .

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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.

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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.

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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.

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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

Dept of : Electronics & Telecommunication.,KIT,BBSR

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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.

Dept of : Electronics & Telecommunication.,KIT,BBSR

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Questions ?

“Thank YOU”