TABLE OF CONTENTS The purpose of this chapter is to describe the milestones in the evolution of cellular mobile systems. Particular attention is paid to the third generation (3G) systems to which the UMTS belong.
The performance of mobile cellular systems is often discussed with respect to the radio access technology they support, thus neglecting other important aspects. However, a cellular mobile communication system is much more than a simple radio access method, as illustrated in Figure 1.1. The mobile terminal is the vector enabling a user to access the mobile services he subscribed to throughout the radio channel. The core network is in charge of handling mobile-terminated and mobile-originated calls within the mobile network and enables communication with external networks, both fixed and mobile. Billing and roaming functions are also located in the core network. The transfer of users' data from the terminal to the core network is the role of the radio access network. Implementing appropriate functions gives to the core network and to the terminal the impression of communicating in a wired link. One or several radio access technologies are implemented in both the radio access network and the mobile terminal to enable wireless radio communication.
Surveying the different multiple-access techniques is equivalent to describing the key milestones in the evolution of modern mobile communication systems. In the past, not all users of the radio spectrum recognized the need for the efficient use...
