Meanwhile in a separate segment of communications, another
revolution was taking place—cellular telephones. In the late
1970s AT&T Bell Laboratories began working with several leading
United States and Japanese companies to create a cellular
telephone system based on dividing coverage areas into small
cells and reusing frequencies. Previous mobile telephone technologies
operated on limited numbers of channels, thus limiting
the number of users in any given coverage area to a very small
number. The result was low user use and costly service and
equipment. A core group was created to develop a standard
called the Advanced Mobile Phone Service (AMPS). In
December 1983, AMPS was launched in Chicago, Illinois with
great fanfare. It proved immensely popular. Now before someone
says, “Hey, wait a minute, AMPS wasn’t the first cellular
system!,” let’s give that credit to the Nordic Mobile Telephone
(NMT) system. NMT was launched in 1981 in Scandinavia, but
in terms of market size, AMPS potential market in the United
States was vastly larger. AMPS quickly spread to other countries
in North and South America, Korea, and Australia. A similar
standard, Total Access Communications System (TACS), was
developed in the United Kingdom as well.
Today, there are many competing standards in mobile telephones
worldwide. In fact the word “mobile” means something
entirely different today than it did in 1983. The majority of cellular
telephones sold today are hand-held, not permanently
installed in vehicles. Each competing standard is incompatible
with others on the basic technology used, but to the end user,
all cellular telephones should perform the basic functions
expected. (Even though many new carriers would like to distinguish
themselves from “cellular” companies by calling themselves
“PCS” companies, we consider both as cellular
applications in this book. This is not to say that companies with
PCS spectrum in the 1900 MHz band may or may not have
some advantages over carriers with traditional spectrum allocations
in the 800 MHz band. But because many carriers own
spectrum in both bands this is a moot point.)
Cellular radio got its name from the physical layout of a system
in a pattern resembling a honeycomb figuratively. In
Figure 1-2, a vehicle traveling from point A to C, will initially
be communicating through cellsite 1. As it moves to position B,
communications is handed off to cell site 2 and similarly for
position C. Each cell site will operate on a different frequency
so that neighboring cells do not interfere with one another.
However, frequencies can be re-used if they are separate by
sufficient distance. This is referred to as the re-use pattern.