On the Accuracy improvement Issues in GSM

On the Accuracy improvement Issues in GSM - On the Accuracy...

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On the Accuracy improvement Issues in GSM Location Fingerprinting C. M. Takenga, Student Member IEEE 1 , Quan Wen 1 , K. Kyamakya 2 1 IKT, University of Hannover, Hannover, Germany, takenga@ant.uni-hannover.de 2 Alpen Adria University Klagenfurt, Chair of Transportation Informatics, Klagenfurt Austria, kyamakya@isys.uni-klu.ac.at Abstract – Determining the position of mobile users in GSM networks has become more and more important. Such services as emergency calls and other location dependent services have been of great importance in the last years. A key factor for the success of any localization technology is its accuracy. This work is focused on localization in a dense urban scenario or in any other area where the GPS signal is not available or its error is very big due to some obstruction of the satellites. Different methods such as those based on neural network localization, database correlation, dead reckoning and a tracking algorithm in case of user mobility have been examined in this work in order to find the optimal in terms of accuracy. The pre-processing of the received signal strengths (rss) is performed to reduce the positioning error due to the rss- stochastic behaviour. Results show that, a tracking algorithm using NN positioning results and an extended Kalman filter (EKF) supplies better results in case of mobility of the user. Index Terms – Dead reckoning, Fingerprint localization, Neural networks, Noise cancellation, Tracking. I. INTRODUCTION. There are three main approaches to positioning, namely satellite based, terrestrial based and stand alone. The first two methods can be called radio-location methods because they rely on the property of radio signal. The most accurate positioning today is achieved using the satellite-based and its combinations. However, GPS is usable only in case of clear sky, which makes it hardly usable in urban areas, mountainous terrain, closed and covered space. An example of a terrestrial based positioning is the localization within a gsm network. In such positioning systems many methods have been developed: cell ID (CI), which just returns the weighted center of the serving cell as a position estimate. Cell ID plus Timing advance (CI+TA) based methods which take into account an estimate of the distance to the base transceiver station. Angle of arrival (AOA), time of arrival (TOA), time difference of arrival (TDOA) and pattern matching or fingerprint methods. With the TOA, TDOA and AOA methods, location of the mobile system (MS) is calculated under assumption of the line of sight propagation between the base station (BS) and MS. This assumption is not valid in city centers where high buildings often obstruct the line of sight. Moreover, severe multipath propagation characteristic to these environments makes it difficult to detect the angle or time of arrival of the direct component. Consequently, these methods are not suited for dense cellular
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On the Accuracy improvement Issues in GSM - On the Accuracy...

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