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Global
System for Mobile Communications (GSM) 1900
GSM 1900, also known as PCS-1900
or DCS-1900, is one of the three PCS technologies in North
America. Like IS-136 TDMA, GSM's air interface is based
on narrowband TDMA technology, where available frequency
bands are divided into time slots, with each user having
access to one time slot at regular intervals. Narrow
band TDMA allows eight simultaneous communications on a
single radio multiplexer and is designed to support 16 half-rate
channels.
GSM is currently the only one
of the three technologies that provides data services
(the capability to do email, fax, Internet browsing, and
intranet/LAN access wirelessly).
GSM is also
the only one that permits
roaming between
North America and European countries.
This works by removing the user-specific SIM card
from inside the American network's phone and placing it
into a European network's phone, or vice-versa.
Major carriers of GSM 1900
include Omnipoint, Pacific Bell, BellSouth, Sprint Spectrum,
Microcell, Western Wireless, Powertel, and Aerial. GSM service
is now available in most, but not all, metropolitan areas.
A note about GSM:
In Europe, a different political landscape led
to the almost uniform adoption of GSM as the cellular standard.
Now there are roughly 215 operators in over 100 countries.
A user with a European GSM phone can roam almost anywhere
in that continent, as well as parts of Asia, and their phone
will work. Click here for
more information about the development of GSM.
The European version of GSM
operates at the 900 MHz frequency (and now at the newer
1800 MHz frequency). Since the North American version of
GSM operates at the 1900 MHz frequency, the phones are not
interoperable, but the SIMs are. Dual-band 900 -1800 and
900 -1900 phones are already released and in production.
Tri-band 900 -1800 -1900 GSM phone are expected to be manufactured
in the next few years, which will allow interoperability
between Europe and North America. If your interest is in
European GSM 900 or 1800, visit our
sister site, the GSM Data Knowledge Site.
To learn more about GSM 1900
technology in North America, visit the following sites:
For an in-depth technical overview
of the GSM network architecture, radio link and network
aspects, see Overview
of the Global System for Mobile Communications.
Code
Division Multiple Access (CDMA) Technology
The CDMA technology used in
North America is based on the IS-95 protocol standard first
developed by QUALCOMM. CDMA differs from the other two technologies
by its use of spread spectrum techniques for transmitting
voice or data over the air. Rather than dividing RF spectrum
into separate user channels by frequency slices or time
slots, spread spectrum technology separates users by assigning
them digital codes within the same broad spectrum. Advantages
of CDMA technology include high user capacity and immunity
from interference by other signals. Like TDMA IS-136, CDMA
operates in the 1900-MHz band as well as the 800 band.
The major US carriers using
CDMA are AirTouch, Bell Atlantic/Nynex, GTE, Primeco (PCS
consortium of AirTouch, Bell Atlantic/Nynex and USWest),
and Sprint PCS (consortium of Sprint, Comcast, Cox and TCI).
To learn more about CDMA technology,
visit the following sites:
Time
Division Multiple Access (TDMA) IS-136
Technology
TDMA is so named because frequency
bands available to the network are divided into time slots,
with each user having access to one time slot at regular
intervals. TDMA thereby makes more efficient use of available
bandwidth than the previous generation analog technology.
Like CDMA, TDMA IS-136 exists in North America at both the
800MHz and 1900MHz bands.
IS-136 TDMA normally co-exists
with analog channels on the same network. One advantage
of this dual-mode technology is that users can benefit from
the broad coverage of established analog networks while
IS-136 TDMA coverage grows within, and at the same time
take advantage of the more advanced technology of IS-136
TDMA where it exists.
Major US carriers using TDMA
are AT&T Wireless Services, BellSouth and Southwestern
Bell.
To learn more about IS-136
TDMA and IS-136 TDMA technologies, visit the following sites:
A word
about analog cellular
By definition, analog cellular
technology is not included as a PCS technology because PCS
only refers to digital technologies, which were designed
specifically to provide improvements over analog. Analog
cellular is inherently less optimal than digital for transmitting
data.
However, analog cellular can
be used for data computing, albeit less successfully, and
should be considered as a backup solution to PCS technologies.
The analog cellular system has the widest coverage of any
system, with service available in almost any city or town,
and on most major highways in the US. For this reason, analog
cellular will remain the only wireless data option in rural
areas for some time to come.
Here's more information about
analog cellular data computing.
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