5.1 Introduction

Chapter 4 introduces the concept of modulating the information (voice, data, video, etc.) onto a variety of transmission systems. We now need to consider how these systems are used in telecommunication networks. As discussed in Chapter 1, all telecommunication networks, and indeed most other sorts of networks, comprise an access portion which connects the population of users to a serving network node, and a core portion which interconnects the set of serving network nodes. These portions are transmission networks in their own right, containing links and nodes, and are usually known as the Access Network and the Core Transmission Network (or similar), respectively. (Of course, the core portion also contains switches or exchanges, data routers, control nodes, etc., which are contained in separate core switching, data routeing, control networks, etc.) The Access Network may be provided over fixed transmission links (using wires, optical fibre cable or radio systems) or over mobile radio links (using a mobile handset), while the core is always provided over a fixed link. This chapter describes the structure and characteristics of the fixed Access and Core Transmission Networks; Chapter 9 covers the mobile access.

5.2 Access Networks