ERICSSON EF738 SystIntro

System Introduction

Ericsson Mobile Phone EF738

System Introduction

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System Introduction

Contents

The Mobile Telephone Network _______________________ 5

Base Station and Cell ______________________________________ 6 Radio Channels ___________________________________________ 6 Radio Coverage ___________________________________________ 7 Transmission Control and Communication ____________________ 8 Quality Control ___________________________________________ 9 Data Transmission________________________________________ 10

Frequency Tables ___________________________________11

Table 1: Channels 1329 - 2047 ______________________________ 12

Channels 1329 - 1478 ___________________________________ 12 Channels 1479 - 1628 ___________________________________ 13 Channels 1629 - 1778 ___________________________________ 14 Channels 1779 - 1928 ___________________________________ 15 Channels 1929 - 2047 ___________________________________ 16

Table 2: Channels 0 - 600 __________________________________ 17

Channels 0 - 149 _______________________________________ 17 Channels 150 - 299 _____________________________________ 18 Channels 300 - 449 _____________________________________ 19 Channels 450 - 600 _____________________________________ 20

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System Introduction

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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 telephone 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 density, the number of base stations, and so on. Each MSC handles calls from one service 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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System Introduction

Base Station and Cell

A base station is able to communicate with any mobile telephone within a certain area close to it. This area is called a cell.

The base station contains channel units. Each channel unit is equipped with a radio transmitter, a radio receiver, and a control unit. The control unit is used for data communication with the MSC and for data signalling with the mobile telephones on the radio path. A channel uses two separate radio frequencies, one for transmission by the mobile telephone and one for transmission by the base station. Such a channel is called a duplex channel. The distance between these two frequencies, the duplex distance, is always the same and is 45 MHz.

Figure 2: Channel Unit

All base stations within a service area are connected to the MSC via dedicated lines in the public telephone network.

Radio Channels

Two different types of radio channels exist in a base station:

•voice channels (VC)

•control channels (CC)

The majority of channel units are voice channel units. Such a voice channel unit is engaged in carrying one telephone call at a time. Depending on how many simultaneous calls a base station is required to handle, the number of

voice-channel units in some base stations may be only a few, while in others up to a hundred or more.

There is normally only one control channel in each cell. A mobile telephone being within a cell, and not in the conversation state, is always tuned to the control channel of this cell. The telephone supervises the continuous data stream.

The total number of channels available in a mobile telephone system is limited. As the radio waves only reach so far from the base station, however, identical channel frequencies can be used by several base stations, provided the distance between them is sufficient to prevent interference. This method is used to increase the capacity of the system.

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