The Mobile Telephone Network - Ericsson EF738 Service Manual

System Introduction

The Mobile Telephone Network

A cellular mobile telephone system (CMS) controlled by one single exchange is
illustrated in fig. 1. The basic units of such a system are:
• the mobile services switching centre (MSC)
• the base stations (BS)
• the mobile telephones (MT)
The MSC is the interface between the radio system and the public switching tele-
phone network (PSTN). Calls to and from the mobile subscriber are switched by the
MSC, which also provides all signalling functions needed to establish the calls.
In order to obtain radio coverage of a given geographical area, a certain number of
base stations is required. The number of base stations may range from one up to a
hundred or more. Such a geographical area is called an MSC service area.
The number of MSCs varies from one country to another, depending on traffic den-
sity, the number of base stations, and so on. Each MSC handles calls from one serv-
ice area which, in turn, is divided into radio zones. A service area consists of a
number of radio zones (or cells), each of which is serviced by a base station.
Figure 1: Basic Units in the Mobile Telephone System
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