Motorola M3097 Service Manual download pdf (Page 15)

©1999 Motorola, Inc.

TDMA M3090/M3097Cellular Overview

4

applications for each carrier. In 1987 the

FCC expanded the cellular spectrum (Ex-

panded Spectrum) from a total of 666 chan-

nels to 832 channels, allowing for an increase

of 83 voice channels for each carrier. But the

number of control channels remained con-

stant, 21 control channels for each carrier.

In 1991, responding to the demand for even

more voice channels, Motorola introduced

NAMPS (Narrow AMPS), expanding the

voice channels by a factor of 3, assuming all

subscribers are using NAMPS telephones.

But one thing remained constant, there were

21 control channels for each carrier.

In 1992, when Motorola tested its TDMA digi-

tal product, digitizing three communication

links on each of 395 voice channels, one thing

remained constant: there were still 21 con-

trol channels for each carrier.

Leaving the control channels more or less un-

touched is the key to allowing telephones that

are not capable of NAMPS or digital opera-

tion to have access to the system using the

conventional AMPS scheme. In virtually

every scheme (AMPS, NAMPS, or digital),

each control channel has a bandwidth of 30

kHz and uses the signaling protocol, with

minor variations for NAMPS and digital,

developed for conventional AMPS

The primary difference between NAMPS and

AMPS is that a NAMPS voice channel has a

bandwidth of only 10 kHz, whereas an AMPS

voice channel has a bandwidth of 30 kHz. In

addition, NAMPS does not make use of cer-

tain control and response tones on voice chan-

nels as does AMPS, but uses digital equiva-

lents instead.

As the name implies, the primary difference

between digital cellular and AMPS is that

all signals are digitized, including voice.

At a basic level, cellular telephony has two

divisions: analog cellular and digital cellu-

lar. In the following section, analog cellular

(AMPS and NAMPS) will be discussed. In

the succeeding section, digital cellular will

be treated.

Introduction

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