Shashika Biyanwila Research Engineer 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 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 Cellular Positioning

1. Geometrical Approach Based on distance measurements Two Steps: - Distance calculation - Location Estimation Cellular Positioning

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 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.. 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.. 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 Probability Cellular Positioning

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

How to collect fingerprints? By measurements DCM contd… How to collect fingerprints? By measurements Using a Network planning tool High sampling resolution is needed. Measurement Fingerprint Test route Cellular Positioning

Compare the input measurement with reference fingerprints DCM contd… Location estimation Input Measurement DCM Algorithm Database Estimated Location Compare the input measurement with reference fingerprints - Using Cost Functions Location of the best matching reference fingerprint Estimated Location Cellular Positioning

Implementation Interfacing Program Database RSS Measurement Unit RSSI + GPS Reading Commands Interfacing Program Database Location Estimation Algorithm Display Program Software environment Location ? Hardware Environment Cellular Positioning

Trial & Results Urban - Wellawaththa to Kolpetty Suburban - Katubedda to Piliyandala Rural - Ibbagamuwa Cellular Positioning

Urban area….. Cellular Positioning

Suburban area ………. Cellular Positioning

Rural area …….. Cellular Positioning

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

Implementation of a positioning engine and associated services Get your own location Track others – web-based location on a map GSM Network Estimated Location Received Signal Fingerprint Location Estimation using Received Signal Fingerprint & database System Information Calibration Fingerprints Digital Maps Positioning Engine Cellular Positioning

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