The world's first public GSM call was made on 1 July 1991 in a city park in Helsinki, Finland. This event is now hailed as the birthday of second-generation mobile telephony. GSM has been an overwhelming success, which was difficult to predict at that early stage. In the past 10 years GSM has become a truly global system for mobile communications. We now have cellular phone penetration rates exceeding 70% in many countries and approaching 90% in the Nordic countries, while, globally, the number of mobile phones has already passed the number of fixed phones, exceeding an expected figure of 1.5 billion in the near future. A decade later GSM has brought us to the early stages of the third-generation mobile communications system-the Universal Mobile Telecommunications System (UMTS). The first networks have begun operations and a new generation of fancy mobile phones has appeared. By the end of October 2004 some 50 UMTS commercial networks were open for business around the world. UMTS networks are introducing a completely new, high bit-rate radio technology-Wideband Code Division Multiple Access (WCDMA)- for wide area use. Nevertheless, the core network part of the UMTS system is firmly founded on the successful GSM network, which has evolved from the circuit-switched voice network into a global platform for mobile packet data services like short messaging, mobile Web browsing and mobile email access. The latest estimates show that packet-switching traffic in mobile core networks will exceed circuit-switching traffic in the near future. This transition is enabled by the UMTS system, which makes it possible for network operators to provide equally robust circuit-switched and packet-switched domains to meet data speed and capacity demands. Most voice and time-critical data services may still use circuitswitching, while less time-sensitive data pass through the UMTS mobile packet core network. One of the key advantages of UMTS mobile computing and communications devices is the ability to deliver information to users at almost anytime and anywhere. In the UMTS the mobile phone is becoming regarded as a personal trusted device, a life management tool for work and leisure. Among the new possibilities for communication, entertainment and business are new kinds of rich call and multimedia data services, fuelled by the mobility and personalisation of users and their terminals. This is a book about the way in which UMTS networks can be used as a thirdgeneration platform for mobility and services. It aims to provide a comprehensive overview of the system architecture and its evolution and to serve as a guidebook to those who need to study specifications from the Third Generation Partnership Project (3GPP). The content of the book is divided into three parts. The first part consists of Chapters 1 and 2, which serve as an executive summary of the UMTS system. Chapter 1 introduces the UMTS technical and service architecture and key system concepts. Chapter 2 is an illustrated history of mobile network evolution from second-generation GSM to the first UMTS multi-access release and beyond to full IP mobility networks. The second part consists of Chapters 3-9, which examine the radio technology aspects, radio access and core network as well as, to a certain extent, the terminal in more detail. It also explains the functions and services provided to end users. Chapter 3 on the key architecture design challenges of cellular networks provides an overview of the fundamental challenges facing cellular networks and the way they have been resolved, particularly in the UMTS network. Chapter 4 presents an overview of UMTS access technologies, including the latest enhancements in WCDMA technology within the scope of 3GPP Release 5. In addition, it addresses the other access technologies, like GSM/EDGE and WLAN, as complementary components of the UMTS multi-access network. Chapters 5 and 6 describe the functional split between controlling functions distributed among the UMTS network elements in the radio access and core network parts. Chapter 7 provides an overview of UMTS user equipment, focusing on those aspects that are most visible to the rest of the UMTS network. In Chapter 8 the UMTS network is examined as a network for services. It addresses service realisation by describing Quality of Service (QoS) and giving some examples of services that can be brought about by UMTS. The advanced security solutions of the UMTS network are then discussed in Chapter 9. The remaining chapters (Chapters 10 and 11) form the third part of the book. In these chapters we take a protocol-oriented view to describe the system-wide interworking between the different architectural elements. Chapter 10 first elaborates on the basic UMTS protocol architecture and then introduces the individual system protocols one by one. Chapter 11 returns to the network-wide view of earlier chapters by showing selected examples of the system procedures that describe how transactions are carried out across UMTS network interfaces under the coordination of system protocols. At such an early stage of third-generation mobile communications the success of UMTS will be further enhanced by the thousands of leading system and software engineers, content providers, application developers, system integrators and network operators. We hope this book will help all of them reach their targets and let them enjoy and benefit from the UMTS networking environment. This book represents the views and opinions of the authors and, therefore, does not necessarily represent the views of their employers.
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