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Cellular Positioning. Shashika Biyanwila Research Engineer. Outline. What is Cellular Positioning Positioning Parameters Feasible Approaches Identified Implementation Some Trial Results Future Approach of the Research. What is cellular positioning ?.

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cellular positioning

Cellular Positioning

Shashika BiyanwilaResearch Engineer

  • What is Cellular Positioning
  • Positioning Parameters
  • Feasible Approaches Identified
  • Implementation
  • Some Trial Results
  • Future Approach of the Research

Cellular Positioning

what is cellular positioning
What is cellular positioning ?
  • Determining the position of a Mobile Station (MS), using location sensitive parameters
  • Why ????
    • To provide Location Based Services…

Cellular Positioning


Applications of cellular positioning

  • Operator services
  • Billing
  • Network management
  • Location based services
  • Wireless Gaming
  • Assistance
  • Roadside assistance
  • Personal or vehicle emergency
  • Alarm management
  • Driving Directions
  • Tracking
  • Tracking criminals
  • Tracking external resources containers etc
  • Monitoring
  • Monitoring delivery process
  • Fleet & freight tracking
  • Personal Child Security
  • Mobile Worker management
  • Information
  • Traffic
  • Nearest service
  • news
  • navigation help
  • advertising
  • Information Directory

Cellular Positioning


Positioning Parameters

  • Cell-ID
  • Received Signal Strength Intensity (RSSI)
  • Timing Advance (TA)
  • Uplink Time (Difference) Of Arrival (TDOA)
  • Downlink Observed Time Differences (E-OTD)
  • Angle of Arrival (AOA)

Cellular Positioning

feasible approaches identified
Feasible Approaches Identified

Cellular Positioning

1 geometrical approach
1. Geometrical Approach
  • Based on distance measurements
  • Two Steps:

- Distance calculation

- Location Estimation

Cellular Positioning

geometrical approach contd
Geometrical approach contd..
  • Distance Calculation

- Measure the RSSI from neighboring cells

- Apply Propagation models to calculate the distance

  • Propagation Models

- Hata Model

- Extended Hata Model

- Lee’s Model

- CCIR Model

- Walfisch-Ikegami Model (for micro cells)

Cellular Positioning

2 statistical approach
2. Statistical Approach
  • Construct a statistical propagation model for the RSSI
    • Find RSSI at distance d from the transmitter
    • Offsite calibration is necessary to estimate the propagation parameters
  • Define a probability distribution for the RSSI
  • Location estimation problem is solved as an inverse or, rather, inference problem

Cellular Positioning

statistical approach contd
Statistical Approach contd..
  • Log-loss or Log-distance model
  • Gaussian Probability Distribution
  • Propagation Parameter Estimation

- Maximum Likelihood estimation

  • Location Estimation

- Maximum A posteriori Probability

Cellular Positioning

statistical approach cntd
Statistical Approach cntd..
  • Area being considered is divided into several squares
  • A posterior probability of the location be within a square, is calculated for each square

Square with

Maximum A posterior


Cellular Positioning

3 database correlation method dcm
3. Database correlation Method (DCM)
  • Involves a database of reference fingerprints for the whole area of interest.
  • Fingerprint – a recorded measurement sample from a certain location in the area

GPS coordinates of a location

RSSI (from available cells) in that location

Cellular Positioning

dcm contd




Test route

DCM contd…
  • How to collect fingerprints?
    • By measurements
    • Using a Network planning tool
  • High sampling resolution is needed.

Cellular Positioning

dcm contd1



DCM Algorithm




DCM contd…
  • Location estimation
  • Compare the input measurement with reference fingerprints
  • - Using Cost Functions
  • Location of the best matching reference fingerprint
  • Estimated Location

Cellular Positioning



RSSI + GPS Reading

Location ?

Measurement Unit


  • Interfacing Program
  • Database
  • Location Estimation Algorithm
  • Display Program
  • Software environment

Hardware Environment

Cellular Positioning

trial results

- Wellawaththa to Kolpetty


- Katubedda to Piliyandala


- Ibbagamuwa

Trial & Results

Cellular Positioning

Urban area…..

Cellular Positioning

Suburban area ……….

Cellular Positioning

rural area
Rural area ……..

Cellular Positioning

future approach of the research
Future Approach of the Research
  • Improvements to the current DCM approach
    • Drawbacks

- Few instances of poor estimations

- Creating, updating & maintenance of the database

    • How To Overcome

- Refined estimation techniques

- Use of a Network planning tool to create fingerprints

Cellular Positioning


GSM Network

Received Signal Fingerprint

Estimated Location

  • System Information
  • Calibration Fingerprints
  • Digital Maps

Location Estimation using Received Signal Fingerprint & database

Positioning Engine

  • Implementation of a positioning engine and associated services


      • Get your own location
      • Track others – web-based location on a map

Cellular Positioning