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 the principles behind the different positioning methods. Subsequently, the chapter introduces the positioning network components and explains the control and coordination of the different methods. The chapter concludes with an overview of positioning in AMPS, CdmaOne, and Cdma2000 and with a discussion and comparison of the presented positioning methods taking into consideration different criteria.

Contents

• Positioning in GSM Networks
  • GSM Air Interface
  • GSM Positioning Components
  • Cell-Id Combined with Timing Advance
  • E-OTD
  • U-TDoA
• Positioning in UMTS Networks
  • UMTS Air Interfaces
  • UMTS Positioning Components
  • Cell-based Methods
  • OTDoA-IPDL
  • RIT Measurements in UMTS
• Assisted GPS in GSM and UMTS
• Positioning in other Cellular Systems
• Conclusion