In 1989, the cellular industry began the task of migrating cellular
from an analog technology to one of several digital technologies,
primarily to increase capacity in several cities that
were in danger of running out of voice capacity (as in New York
and Los Angeles). Data was not the overriding concern for the
standard bodies, and unfortunately, not every region adopted
the same migration path. This created a challenge to the network
designers working to maintain uniformity of operation.
The European community chose collectively to migrate
their existing networks to Global System for Mobile
Communications (GSM) for their first-generation digital networks.
Meanwhile North America chose to develop a digital
standard in two parts. The first was referred to as Interim
Standard-54 (IS-54) or North American Digital Cellular. This
standard, based on a version of Time Division Multiple Access
(TDMA), is similar to GSM but incompatible. IS-54 was
developed during the early 1990s and was soon followed with
IS-136. The difference between the two was that IS-54 continued
to use analog control channels and used both analog
and digital traffic channels. IS-136 contained both digital and
analog channels for control and traffic. IS-54 was not widely
popular because it lacked clear advantages to the user. The
promise of greater battery life with IS-136 alone was inducement
enough to win customers over even had it lacked other
advantages.
Having two different network architectures wasn’t too bad
but wait—there’s a new show in town. Here comes a company
out of San Diego that no one has ever heard of before, and
they claim to have a better solution to digital cellular. The
company was Qualcomm and the solution proposed was Code
Division Multiple Access (CDMA). Today, Europe still has
GSM and North America has TDMA, CDMA, and a little
GSM for variety. By 2001, GSM occupied about 65 percent of
the worldwide cellular market and CDMA held about 17 percent
market share.
As far as wireless data is concerned, we have only three
choices: CDPD on an analog channel, Short Message Service
(SMS) if it is available, or an internal modem in the phone or
device. Each choice has its pros and cons. Short Message
Service is just that—short—so speed is very important to the
user. The rate for CDPD is 19.2 Kbps, which is fine for certain
text applications, and because it is packet-based, valuable spectrum
is not wasted. The third option is a built-in modem in the
phone that connects to a laptop computer by either cable or
infrared. Speeds with an internal modem range from 8 Kbps to
9.6 Kbps. The data simply replaces the voice traffic transmitted
by the phone; the connection is circuit-switched, so spectrum
is wasted. None of these options is satisfactory for
real-time access to the Internet or streaming video. 43