• GPS Phone Positioning And Tracking


     Applications requiring positioning in mobile networks have gained importance in recent years. Examples include not only LBSs, but also enhanced emergency call services such as the North American E911 and the newly defined Emergency Call (eCall), which is planned to become a European standard as part of the eSafety initiative of the European commission. Mobile network providers already offer LBSs along with positioning, although the accuracy and reliability of the present techniques do not yet meet the requirements of such services in all cases. One of the most popular positioning systems in navigation is the personal tracking device , which is satellite based, widely available and quite accurate, as long as the receiver to be localized and the satellites have an LOS connection. Since most common mobile phones do not support the GPS, network providers evaluate the position of the network’s base stations (BSs) which have connections to the mobile stations (MASs) to be located. The accuracy of the present position estimation techniques can be increased by evaluating additional protocol data from the cellular network, for example in the case of GSM. Some additional information which can be evaluated is measured by the mobile station and available only there. This leads to the approach of mobile-assisted position estimation techniques.

    Nowadays, known stars and constellations have been replaced by the satellites of Global Navigation Satellite Systems (GNSSs). For positioning, it is sufficient to receive the radio signals of at least four satellites whose positions are known. The first GNSS and the predecessor of the well-known GPS was originally called the Navy Navigation Satellite System (NNSS), later called Transit. Starting in 1958, Transit was developed by the US Navy to provide accurate location information to ballistic missiles and submarines. From 1967 it was also used for civil applications. Its accuracy was between 500 and 15 m. Transit was shut down in 1996. GLONASS is a satellite navigation system developed by the Russian Space Forces. It was deployed during the Cold War as a competitor to the GPS, starting in 1976. The Chinese Beidou navigation system is a project for the development of an independent satellite navigation system. It is named after the Big Dipper constellation, which is called Beidou in Chinese. It is an experimental system of only four satellites, but the final GNSS with global coverage will include 35 satellites and be called Compass.
    One simple network-based GPS-free positioning method is based on the cell coverage, by means of evaluating the cell identification. This scheme is commonly deployed by mobile network operators. The position of a mobile connected to a particular BTS, which is identified by its cell ID, is determined by the location of the base station itself. A more advanced network-based GPS-free positioning method using the cell coverage determines the location of a mobile connected to a multiantenna BTS by evaluating the center of gravity of the sector that the mobile belongs to, thus using that location as the estimated position of the mobile. Several cellular positioning techniques have already been commercially deployed for emergency call location and for mobile tracking services from mobile network operators, which allow a mobile to be localized using a Web interface, for instance. The Google Maps Mobile Application also provides tracking devices for people for navigation purposes. 

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