Evolution of Voice-Oriented Networks

Evolution of Voice-Oriented Networks
Table 2.1 is a brief chronology of the evolution of voice-oriented wireless networks.
The technology for FDMA analog cellular systems was developed at AT&T Bell Laboratories
in the early 1970s. However, the first deployment of these systems took place
in the Nordic countries under the Nordic Mobile Telephone (NMT) initiative about a
year earlier than the deployment of the Advanced Mobile Phone Service (AMPS) in the
United States. In the United States the frequency administration process was slower,
resulting in later deployment. The digital cellular networks were first developed in
Nordic countries with formation of the GSM standardization group. The GSM group
was originally formed to address international roaming, a serious problem for cellular
operation in the European Union (EU) countries, where a number of different analog
systems were being used and were not interoperable. The standardization group soon
decided to standardize on a new digital TDMA technology so as to allow integration of other services, thus expanding the horizon of wireless applications [Hau94]. In the
United States, however, the motivation for migration to digital cellular was that the
growth in analog cellular traffic was predicted to consume the entire capacity of the
analog systems in major metropolitan areas such as New York and Los Angeles, and
there was a need for increasing system capacity within the constraints of the existing
allocated cellular bands. Although Nordic countries, led by Finland, have always had
the world’s highest rate of cellular penetration, in the early days of this industry the U.S.
market was by far the largest. By 1994, there were 41 million subscribers worldwide,
25 million of them in the United States. The need for higher capacity motivated the
study of CDMA, which was originally projected to provide capacity at least an order
of magnitude higher than other proposed approaches, such as analog band splitting or
digital TDMA.
While the debate between proponents of TDMA and CDMA was in progress in
the United States, deployment of the GSM technology began in the EU in the early
1990s. At the same time, developing countries began planning for cellular telephone
networks, and most of them adopted the GSM digital cellular technology over the
legacy analog cellular technology. Soon thereafter, GSM had penetrated into more
than 100 countries. An interesting phenomenon in the evolution of the cellular telephone
industry was the unexpectedly rapid expansion of this industry in developing
countries. In these countries the growth of the infrastructure for wired plain old telephone
service (POTS) was slower than the growth in demand for new subscriptions,
and a subscriber typically experienced a long waiting time before acquiring a telephone
line. As a result, in most of these countries, telephone subscriptions were sold in black
markets at highly inflated prices. Penetration of cellular telephone in these counties
grew rapidly because subscribers were already accustomed to paying high prices for
telephone service. Furthermore, the cellular networks could be built out much more
rapidly than could the legacy wired networks.
In the beginning of the race between TDMA and CDMA, the CDMA technology
was deployed in only a few countries. Also, on-air experiments had shown that the
capacity improvement factor for CDMA was smaller than originally expected. In the
mid-1990s, when the first deployments of CDMA technology began in the United
States, most cellular service companies were subsidizing the cost of mobile terminals
in order to stay in the race with the TDMA and analog alternatives. However,
from the start of deployment, the voice quality experienced with CDMA was superior
to that of TDMA systems installed in the United States. As a result, CDMA
service providers, under such banners as “you cannot believe your ears,” began marketing
this technology in the United States, and it soon become very popular with
users. Meanwhile, given the huge success of digital cellular service, manufacturers
worldwide began working on developments for the next-generation IMT-2000 wireless
networks. Most of these manufacturers adopted wideband cdma2000 as the technology
of choice for IMT-2000, on the premise that CDMA eases integration of services,
provides better voice quality, and supports higher capacity than those of proposed
alternatives.
The local voice-oriented wireless applications began with the introduction into the
market of cordless telephone products in the late 1970s. A cordless telephone provides
a wireless connection to replace the wire between a handset and a telephone
set. The technology for implementation of a cordless telephone was similar to the technology used in walkie-talkies, which had been in use in World War II. As soon as
the cordless telephone was introduced to the market, it became a major commercial
success, selling on the order of tens of millions of phones and generating revenues
exceeding several billion dollars. The success of the cordless telephone encouraged
further developments in this field. The first digital cordless telephone was CT-2, a
standard developed in the UK in the early 1980s. The next generation of cordless
telephones was wireless PBX using the Digital European Cordless Telephone (DECT)
standard. Both CT-2 and DECT required minimal network infrastructures beyond what
was required for the simple cordless telephone, and each covered a larger area and
supported multiple applications. However, despite the huge success of the cordless
telephone, neither CT-2 nor DECT has yet been considered a great commercial success.
These local systems soon evolved into personal communication systems (PCSs),
each a complete system with its own infrastructure, very similar to the cellular mobile
telephone system.
In the technical communities of the early 1990s, PCS systems were differentiated
from cellular systems, as indicated in Fig. 1.1. A PCS service was considered the next
generation of cordless telephone designed for residential areas, providing a variety of
services beyond those supported by the cordless telephone. The first real deployment
of PCS systems was the Personal Handy Phone (PHP), later renamed the Personal
Handy System (PHS), introduced in Japan in 1993. At that time, the technical differentiator
for PCS relative to cellular was perceived to be smaller cell size, better
speech quality, lower tariff, lower power consumption, and lower mobility. However,
from a user’s point of view, the mobile terminals and services for PCS and cellular
looked very similar, and the only significant difference was marketing strategy and
the way that they were introduced to the market. For instance, at around the same
time that PCS was being introduced in the United States, DCS-1800 service was introduced
in the UK as a PCS service. The DCS-1800 systems used GSM technology
at a higher frequency of 1800 MHz but were marketed with a different strategy. The
last PCS standard was PACS in the United States, finalized in 1995. All together,
none of the PCS standards became a major commercial success competing with cellular
services.
In 1995 the FCC in the United States auctioned off the frequency bands around
2 GHz as PCS bands, but PCS-specific standards were not adopted for these frequencies.
Eventually, the name PCS started to appear only as a marketing identity used
by some service providers for digital cellular services, and in some cases the services
offered did not even operate in PCS bands. Whereas the more advanced and complex
PCS services evolving from simple cordless telephone application did not succeed and
merged into the cellular telephone industry, the simple cordless telephone industry
itself remains active. In more recent years the frequency of operation of cordless telephone
products has shifted into unlicensed ISM bands rather than licensed PCS bands.
Cordless telephones operating in the ISM bands can provide a more reliable wireless
connection since they use spread-spectrum technology.