1G Systems

Numerous mobile wireless systems have been deployed throughout the
world. Each of the various 1G wireless systems has its own unique advantage
and disadvantages, depending on the spectrum available and the services
envisioned for delivery.

1G mobility systems are defined as analog systems and are typically
referred to as an AMPS or TACS system. It is important to note that analog
systems utilize digital signaling in many aspects of their network, including the air interface. However, the analog reference applies to the
method that the information content is transported over; that is, no CODEC
is involved.

Table 2-1 represents the popular 1G wireless mobility service offerings
that have been deployed. As mentioned previously, the two most prolific 1G
systems deployed in the world are AMPS and TACS.
All of the 1G systems shown in the table utilize a Frequency Division
Multiple Access (FDMA) scheme for radio system access. However, the specific
channel bandwidth that each use is slightly different, as is the typical
spectrum allocations for each of the services. The channel bandwidths are
as follows:
■ AMPS is the cellular standard that was developed for use in North
America. This type of system operates in the 800-MHz frequency band.
AMPS systems have also been deployed in South America, Asia, and
Russia.
■ Narrow Band AMPS (NAMPS) is a product that is used in part of the
United States, Latin America, and other parts of the world. NAMPS is
a cellular standard that was developed as an interim platform between
1G and 2G systems and was developed by Motorola. Specifically, NAMPS is an analog radio system that is very similar to AMPS, with
the exception that it utilized 10-kHz-wide voice channels instead of the
standard 30-kHz channels. The obvious advantage with this technology
is the capability to deliver, under ideal conditions, three times more
capacity of a system over that of regular AMPS.

NAMPS is able to achieve this smaller bandwidth through changing
the format and methodology for Supervisory Audio Tone (SAT) and
control communications from the cell site to the subscriber unit. In
particular in NAMPS, they use a subcarrier method and use a digital
color code in place of SAT. These two methods make it possible to use
less spectrum while communicating the same amount of, or even more,
information all at the same time and increasing the capacity of the
system with the same spectrum.

However, this advantage in capacity, of course, requires a separate
transmitter, either a Power Amplifier (PA) or transceiver, for each
NAMPS channel deployed. However, the control channel that is used
for the cell site is the standard control channel, 30 kHz, which is used
by AMPS and other technology platforms used for cellular communication.
Additionally, the Carrier-to-Interferer (C/I) requirements due to
the narrower bandwidth channels are different than that of a regular
AMPS system, which has a direct impact on the capacity of the system.

■ TACS is a cellular band that was derived from the AMPS technology.
TACS systems operate in both the 800-MHz band and the 900-MHz
band. The first system of this kind was implemented in England. Later
these systems were installed in Europe, Hong Kong, Singapore, and the
Middle East. A variation of this standard was implemented in Japan,
JTACS.

■ Nordic Mobile Telephone (NMT) is the cellular standard that was
developed by the Nordic countries of Sweden, Denmark, Finland, and
Norway in 1981. This type of system was designed to operate in the
450-MHz and in the 900-MHz frequency bands. These are noted as
NMT 450 and NMT 900. NMT systems have also be deployed
throughout Europe, Asia, and Australia.
The basic service offering for 1G systems is and was voice communication.
These systems have been extremely successful and many of them are
still in service offering 1G services only.

1G systems, however, suffer from a number of difficulties. Some of those
difficulties were addressed by additional technology added to the network and some of the difficulties have required the implementation of 2G technology.
The biggest problem that led to the introduction of 2G technology
was the fact that the 1G systems had limited system capacity. This became
a serious issue as the popularity of mobile communications grew to a level
that far exceeded anyone’s expectations. Other problems included the fact
that the technologies in question addressed only the air interface, and other
interfaces in the network were not specified (at least not initially), which
meant limited roaming, particularly between networks that were supplied
by different vendors. The technologies did not initially include security
mechanisms, which allowed for fraud. Finally, some limitation in the technologies
led to the problem of “lost mobiles,” where a subscriber is located at
one MSC and the network thinks that the subscriber is elsewhere.
Nevertheless, it is worth emphasizing the popularity of these technologies
and the fact that, in some cases, they have been the foundation upon
which 2G and 3G technologies have been built.