TACS/ETACS
The original analog version of this wireless system was
brought to commercial deployment by AT&T in 1983, prior
to divestiture, based on the concept that higher capacity
could be achieved by small (i.e. low power) cells, allowing
frequencies to be reused. Other advantages, not known
at the time, included the possibility of handheld phones
and low terminal prices due to advances in electronics technology
and the economies of scale of the mass market. Consequently,
an industry that was estimated by optimists when the first
systems in Chicago and Washington/Baltimore came online in
1983 as likely to serve 1 million subscribers in the US by
the year 2000, actually was serving well over 50 million
subscribers by 1998!
AMPS originally operated as an analog system in the 800
MHz frequency band. However, it has since expanded
to TDMA and CDMA digital operation and, more recently into
the 1800 MHz - 2200 MHz PCS frequency band. The best
known AMPS systems are in the US and Canada, but AMPS is
also a de facto standard throughout Mexico, Central and South
America, very common in the Pacific Rim and also found in
Africa and the remains of the USSR. In summary, AMPS
is on every continent except Europe and Antarctica. AMPS
is defined not by a single standard, but by many standards. All
the standards are developed by the TR-45 committee within
the TIA (Telecommunications Industry Association). Even
the radio interfaces are defined by several families of standards,
one for each technology (Analog, NAMPS, TDMA and CDMA). Automatic
roaming with a cellular phone is made possible by the TIA/EIA-41
standard that provides intersystem handoff, call delivery,
remote feature control, short message delivery, validation
and authentication through an intersystem messaging protocol. TIA/EIA-41,
developed by the TIA TR-45.2 subcommittee, is often discussed
in Cellular Networking Perspectives. There are other
forms of cellular and PCS in the world:
The European 900 MHz digital cellular system, which has
also expanded to many parts of the world and into the PCS
band (where it is known as DCS1800 or PCS1900). GSM
provides intersystem operations through its own MAP (Mobile
Application Part) protocol, making its operation relatively
incompatible with the AMPS family that shares the common
TIA/EIA-41 intersystem operations protocol. GSM is
the biggest challenger to the AMPS family of technologies.
A Scandinavian 450/900 MHz analog cellular system, the closest
thing in Europe to a standard prior to GSM. NMT systems
have been installed in many countries outside Europe. Most
NMT systems will eventually be displaced by GSM.
AMPS with a few minor changes, operating in the 900 MHz
frequency band. The largest TACS networks are in the
UK, but it has also been installed in many other countries
around the world.
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