Description; Overall Concept; Operation - Motorola V2260 Service Manual

Cellular Subscriber Sector

DESCRIPTION

Table 4:
Note
The following description is intended only as a
preliminary general introduction to cellular
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-
telephone
service in the frequency range of 824-894
MHz.
A cellular system provides higher call han-
dling capacity and system availability than
would be possible with conventional radio-
telephone systems that require total system
area coverage on every operating
channel. The cellular system divides the sys-
tem 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 separate RF frequencies or
channels are
used to differentiate subscribers. The codes
©2000 Motorola, Inc.
CDMA 800/AMPS-V2260, T2260
CDMA Dual Mode 800-1900-V2267, T2267
are shared by both the mobile station and
base station and are called "pseudo-random
code sequences". Since CDMA is a spread
CELL B
CELL A CELL C
spectrum technology, all users share a range
of the radio spectrum. CDMA cell coverage
is dependent upon the way the network is
designed. For each system 3 characteristics
must be considered: 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 consistent sound.
- Enhanced privacy.
- Variable rate vocoder.
Figure 1: Hypothetical Cell System

Operation

In Figure 1: "Hypothetical Cell System", the
area bounded by bold lines represents the
total coverage area of a cellular system.
This area is divided into several cells, each
CELL D