Initially, the development of LBSs progressed with the success of cellular networks, which achieved their high user penetration during the 1990s. At this time, operators were looking for new sophisticated services, which could provide a considerable added value to mobile subscribers in order to generate new revenues. As cellular networks track subscribers on a permanent basis for location management, offering services making use of a subscriber’s “network location” was obvious. Recall from Chapter 2 that this kind of location refers to the topology of a (cellular) network, that is, to the subnetwork and base station the subscriber is currently attached to. The idea was to transfer a network location into a spatial or descriptive location using spatial databases and GIS and to exploit the resulting location information for LBSs.

However, very soon it turned out that network locations often do not meet the accuracy demands of many LBSs, and especially not those required for enhanced emergency services such as E-911 in the United States. This gave rise to the development of more accurate positioning methods and their integration into cellular networks. Nevertheless, location management is still of relevance in the field of LBSs, because it provides basic functions that these advanced positioning methods rely on. Also, there are some similarities between location management and location services with regard to the dissemination and maintenance of location information, which requires some knowledge about the architectures, topology, and limitations of cellular networks.

This chapter gives a general introduction to cellular networks and location management. Starting with an overview of different cellular systems, it focuses on the network architectures of GSM, GPRS, and UMTS. Subsequently, it identifies the common mechanisms of location management and illustrates their realization in these systems.

Contents

• Overview of Cellular Systems
• Principles of Cellular Networks
  • GSM Architecture
  • GPRS Architecture
  • UMTS Architecture
• Mobility Management
• Common Concepts of Location Management
  • Location Update and Paging
  • Database Concepts
• Location Management in CS Networks
  • Identifiers and Addresses
  • Localization and Routing
  • Location Updates
• Location Management in PS Networks
  • Localization and Routing
  • Characteristics of CS and PS Traffic
  • Location Updates
• Conclusion