Motorola Timeport P8190, Service Manual

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© 2000 Motorola, Inc.
TDMA Timeport™ P8190 Cellular 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