Chapter 8. Cellular Positioning
In recent years, GPS is gaining more and more momentum for LBSs. This tendency is certainly fostered by advances achieved in GPS receiver technology during the recent years, which have made it possible to build low-cost GPS receivers that need only low power consumption and to increasingly integrate them into more and more consumer products like cellular phones and PDAs.
However, positioning methods were also developed for cellular networks, for which an important driving force was the E-911 mandate in the United States. The introduction of E-911 was scheduled in two phases, one that obliged operators to provide location data obtained on the basis of radio cells not later than April 1998, and the other that prescribed to enable positioning under much stronger accuracy demands not later than December 2005. This second phase resulted in the development of advanced positioning methods and their installation in cellular networks. Examples are E-OTD, U-TDoA, and A-FLT. An important alternative to these pure cellular methods is the integration of GPS so that the cellular network provides terminals with assistance and correction data of the satellites and thus helps to significantly increase position accuracy and decrease the TTFF. This method is known as A-GPS.
This chapter deals with these cellular positioning methods with a special focus on GSM and UMTS networks. At first, the air interfaces of both systems are explained, as this is required for understanding ...
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