Motorola M3097 Service Manual download pdf (Page 14)

©1999 Motorola, Inc.

Cellular OverviewService Manual

3

naling required to establish a telephone call.

Control channels are used to send and receive

only digital data between the base station

and the cellular telephone. Voice channels

are used for both audio and signaling once a

call is established. The 21 control channels

in each band may be dedicated according to

two different applications: access and pag-

ing channels.

The data on the forward control channel gen-

erally provides some basic information about

the particular cellular system, such as the

system ID and the range of channels to scan

to find the access and paging channels. Ac-

cess channels are used to respond to a page

or originate a call. The system and the cel-

lular telephone will use access channels

where two-way data transfer occurs to deter-

mine the initial voice channel. Paging chan-

nels, if used, are the normal holding place

for the idle cellular telephone. When a call

is received at the central controller for a cel-

lular telephone, the paging signaling will

occur on a paging channel. In many systems

both control channel functions will be served

by the same control (access) channel for a par-

ticular cell. Only in very high density areas

will multiple control (paging) channels be re-

quired.

Primary control channels are used by all

types of telephones. Secondary control chan-

nels are only used by TDMA telephones, pro-

viding them with an improved probability of

locking onto a TDMA control channel.

Voice Channels

Voice channels are primarily used for con-

versation, with signaling being employed as

necessary to handle cell-to-cell hand-offs,

output power control of the cellular radio-

telephone, and special local control features.

Data from the cell site (known as FORWARD

DATA) and data from the mobile or portable

(known as REVERSE DATA) is sent using

frequency shift keying. In AMPS signaling,

various control and response tones are used

for a variety of applications to be described

later. However, in NAMPS signaling, the sig-

naling data and tones have been replaced by

sub-audible digital equivalents that con-

stantly ride underneath the audio. And, of

course, in digital cellular, all signaling is digi-

tal.

Signaling Protocol

In 1983, when the Federal Communications

Commission (the FCC) licensed cellular te-

lephony, the signaling protocol used was

AMPS. AMPS (Advanced Mobile Phone Ser-

vice) was the invention of Bell Labs, the sig-

naling protocol that was ultimately adopted

by all the governments of the entire Western

Hemisphere and, eventually, several other

governments throughout the world.

Today, with the implementation of Narrow

AMPS and TDMA, and the imminence of

CDMA, it may seem that AMPS is out of date.

The truth is that AMPS is very much alive,

at the very core of all these traffic expanding

alternatives to the original signaling proto-

col developed for conventional cellular tele-

phony.

Under the original AMPS protocol there were

21 control channels assigned to each of two

possible carriers in any metropolitan area,

with a total of 333 channels assigned to each

carrier. Prior to 1987 the FCC had allocated

312 channels to voice (voice, DTMF, or data)

Introduction

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