Subject: [NEXTEL-1] NEXT STEP IN DIGITAL CELLULAR (DATED)

From: [email-masked]
Date: Tue, 14 Oct 2003 12:55:42 -0400

NEXT STEP IN DIGITAL CELLULAR (Dated)
Personal communications services systems usher in the next generation of cellular
telephony.

BY BRIAN C. FENTON

Telephony went through a major revolution in the early 1980s when cellular
technology broke on the scene. Later on, in the early '90s, cellular telephony had
its own revolution with the introduction of digital technology. And now, you can
get ready for yet another digital cellular revolution-new personal communications
services (PCS) systems are coming online.

The PCS systems springing up around the United States are offering all kinds of
new phone capabilities, thanks to their all-digital nature. The threat of stiff
competition has also spurred the traditional cellular providers to upgrade their
systems and provide more services so they can compete with PCS. In fact, some PCS
providers are building dual-band networks that consist of both traditional
800-megahertz (MHz) systems and new 1900-MHz systems.

The analog cellular system that has been in place since 1983 is known as AMPS, the
advanced mobile phone service. Most of the almost 45 million cellular users in the
United States still have analog AMPS phones, which transmit voice signals much
like FM walkie-talkies.

Demand for cellular service grew at such an unexpected clip that the cellular
industry was hard pressed to find a way to increase capacity. Motorola developed
N-AMPS, or narrowband AMPS, which reduced the bandwidth of the FM signals and
could boost the capacity of a system by a factor of three.  Unfortunately,
although it allowed some digital features to be added, it was still an analog
system.

The rest of the cellular industry started to look for digital solutions, which
began to hit the market in the early 1990s. Today, traditional cellular providers
offer AMPS and either N-AMPS or one of two digital technologies: time-division
multiple-access (TDMA) or code-division multiple-access (CDMA).
In Europe, things happened quite differently. The European cellular market
developed in a fractured way, with each nation choosing its own technology, thus
limiting the roaming possibilities available to subscribers.

With the North American AMPS market serving as an instructive example, the
European telecommunications industry recognized that a single standard was
required to reduce hardware costs and spur market growth by providing better value
to consumers. So in 1982, Europe started to look for digital solutions not because
growth was causing capacity problems, but because incompatible national cellular
systems were stifling growth.

The transition to digital began with the formation of Groupe Speciale Mobile, or
GSM. Today, GSM stands for "global system for mobile communications." The first
commercial GSM systems went into operation in 1991. Now, more than 90 countries
conform to the GSM standards, which are based on TDMA digital technology.

This year, it's time for the U.S. market to be fractured. New companies,
partnerships and established telecommunications companies took part in the FCC
auctions for PCS frequencies. But they didn't all choose to follow the same course
by using the same technologies.

Those differences make a concise definition of PCS difficult, but in general, PCS
is an all-digital phone service operating at 1900 MHz. It allows providers to
offer such features as voice-mail, caller identification, short e-mail messaging
and paging.

Most PCS providers are not requiring that consumers sign long-term contracts.
Instead,
customers buy phones and services separately.

Most consumers won't really care whether their
phones use TDMA or CDMA technology, or whether
their particular flavor of TDMA is GSM (known in the
United States as PCS-1900) or D-AMPS 1900
(digital AMPS 1900). After all, a PCS-1900 user can
place a call to a D-AMPS user as easily as he can
to his wife on a wired phone at home, or to a CDMA
user. And advertisements promoting the various
services are unlikely to confuse potential new users
- who by definition are not early adopters - with details of communications
protocols.

The buildout of new infrastructure for digital cellular telephony is at such an
early stage that it's impossible to predict what the performance of some of the
systems will be. New players building their systems are finding out that the
process isn't an exact science. A city can't be modeled adequately to determine
how the signals from a cellular base station will suffer when reflected or
absorbed by buildings, or how things will differ on a clear day (when more of the
energy of the transmitted microwaves is radiated into space) compared to a cloudy
one.

Choosing the right technology, of course, is essential for companies risking so
much capital on their success. The various companies paid more than $21 billion
just to secure PCS licenses at the FCC's auction. Add in the bills for building
the infrastructure and advertising to potential customers, and the costs are
staggering. Not surprisingly, the technology choices seem to have been made with
an even ratio of technical to business concerns.

Some existing cellular operators - AT&T Wireless and Southwestern Bell Mobile
Systems, for example - bid for PCS licenses where they did not already have a
market presence so that they could offer nationwide service.

Those existing providers also wanted to protect their investments in their
existing infrastructure and make sure that their current analog customers were
still served. To increase the area where their service was available, they also
wanted the new digital phones to fall back to analog service where digital service
wasn't available.

When they roll out their new PCS systems, they'll be based on D-AMPS 1900. It
maintains complete compatibility with the D-AMPS used in their digital cellular
systems, but operates at the higher frequency of 1900 MHz. The phones that will be
available - called either "tri-mode" or "dual-mode dual-frequency" - will operate
on 800-MHz analog, 800-MHz digital and 1900-MHz digital. Switching between modes
will be automatic. If you're in an area that offers only analog service, you'll
still be able to use your phone, though you'll lose the nice digital touches of
e-mail messaging, paging and enhanced security.

CDMA is yet another rival digital communications protocol that was chosen by some
providers, including PCS PrimeCo and Sprint PCS.

PCS PrimeCo, the 4-way partnership of AirTouch Communications, Bell Atlantic,
NYNEX and US West, won 11 licenses to provide PCS. The licenses were chosen to
fill in the holes in the existing coverage of the four owners, which use CDMA
technology in their existing digital cellular systems.

PCS PrimeCo plans to create a nationwide wireless network by combining the
existing cellular properties of the four partners with a PCS network. Although
PCS-only phones will be available, users will also be able to buy phones that can
operate on analog, 800-MHz digital and 1900-MHz digital for maximum flexibility.

Sprint PCS, a partnership of Sprint, TCI, Cox and ComCast, was the biggest winner
in the FCC auctions. It is building a nationwide digital PCS phone network. This
one-of-a-kind network would allow users to make calls virtually anywhere in the
country without incurring roaming charges, and without worrying whether calls were
being made using analog or digital technology.
Other PCS providers - those with no existing cellular infrastructure - have chosen
to go with the competing digital technology GSM, or PCS-1900. Leading the way - by
earning a pioneer's preference award from the FCC, which allowed it to obtain a
PCS license to serve the New York market for the bargain price of $350 million -
is Omnipoint Corp. Additional license purchases have made Omnipoint the fourth
largest PCS provider by population coverage.

Omnipoint began its system rollout late last year,
and so far, it has built out its system in the New
York City area. The system, like other GSM
systems worldwide, features a subscriber
information module (SIM) smart card, which holds all of a subscriber's personal
information (including his phone number) and phone settings. The card can be
switched from phone to phone, making the new phone receive all calls to the
subscriber's number.  The SIM card makes it possible to roam around the world
where other GSM networks are operating. As long as a roaming agreement exists, you
can just rent a phone, insert your SIM card and make and receive calls just as if
you were home.
Those old analog systems are far from dead. One of the signs of new life is
cellular digital packet data (CDPD) technology, which transmits digital data
during the natural silences of conversations.
(Roughly 30% of a typical conversation is silence.)

The packet technology does away with the need for a modem - and therefore
eliminates the problems modem users encountered when traveling between cells. Your
phone can have its own IP address, and can receive data from the Internet or
dedicated service providers.

http://popularmechanics.com/technology/telecom/1997/6/Next_Step_Digital_Cellular/print.phtml

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