Cellular Overview; Overall Concept - Motorola T720 Service Manual

Personal Communications Sector

Cellular Overview

Table 4:
Note
The following description is intended only as a
preliminary general introduction
systems. This description is greatly simplified and
does not illustrate the full operating capabilities,
techniques, or technology involved in cellular
systems.

Overall Concept

Cellular systems are used to provide radio-tele-
phone service in the frequency range of 824-894
MHz.
A cellular system provides higher call handling
capacity and system availability than would be
possible with conventional
systems that require total system area coverage
on every operating channel. The cellular system
divides the system coverage area into several
adjoining sub-areas, or cells.
Each cell contains a base station (cell site) which
provides transmitting and receiving facilities.
CDMA is a "spread spectrum" technology,
which means that it spreads the information
contained in a particular signal of interest over a
greater bandwidth than the original signal. With
CDMA, unique digital codes, rather than sepa-
rate RF frequencies or channels are used to
differentiate subscribers.
The codes are shared by both the mobile station
and base station and are called "pseudo-random
code sequences". Since CDMA is a spread spec-
to cellular
trum technology, all users share a range of the
radio spectrum. CDMA cell coverage is depen-
dent upon the way the network is designed. For
each system 3 characteristics must be consid-
radiotelephone
ered: coverage, quality, and capacity. These 3
must be balanced for desired lever of perfor-
mance.
Some of the CDMA benefits are:
• Improved call quality with better and more
• Enhanced privacy.
• Variable rate vocoder.
• Soft hand off.
16
Cellular Overview
CELL B
CELL A CELL C
consistent sound.
T720
CELL D
©2002 Motorola, Inc.