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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 Shashika BiyanwilaResearch 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
Fingerprint Measurement Fingerprint Test route DCM contd… • How to collect fingerprints? • By measurements • Using a Network planning tool • High sampling resolution is needed. Cellular Positioning
Input Measurement DCM Algorithm Estimated Location Database 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
RSS RSSI + GPS Reading Location ? Measurement Unit Commands • Interfacing Program • Database • Location Estimation Algorithm • Display Program • Software environment Implementation Hardware Environment Cellular Positioning
Urban - Wellawaththa to Kolpetty Suburban - Katubedda to Piliyandala Rural - Ibbagamuwa Trial & Results 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
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 Services • Get your own location • Track others – web-based location on a map Cellular Positioning