C O N T E N T S
- Evolution of the Mobile Market
Basics of Cellular Technology and the Use of the Radio
Technologies (FDMA, TDMA, CDMA)
Standards for 1G and 2G
Standards for the Third Generation: ITU's IMT-2000 Family
Acronyms and Terms
Introduction - Evolution
of the Mobile Market
first radiotelephone service was introduced in the US at the
end of the 1940s, and was meant to connect mobile users in
cars to the public fixed network.
In the 1960s, a new system launched by Bell Systems,
called Improved Mobile Telephone Service” (IMTS), brought
many improvements like direct dialing and higher bandwidth.
The first analog cellular systems were based on IMTS
and developed in the late 1960s and early 1970s.
The systems were “cellular” because coverage areas
were split into smaller areas or “cells”, each of which is
served by a low power transmitter and receiver.
first generation (1G)
analog system for mobile communications saw two key
improvements during the 1970s: the invention of the
microprocessor and the digitization of the control link
between the mobilephone and the cell site.
generation (2G) digital cellular systems were first developed at the end of the
These systems digitized not only the control link but
also the voice signal.
The new system provided better quality and higher
capacity at lower cost to consumers.
generation (3G) systems promise faster communications
services, including voice, fax and Internet,
anytime and anywhere with seamless global roaming.
IMT-2000 global standard for 3G has opened the way to
enabling innovative applications and services (e.g. multimedia
entertainment, infotainment and location-based services, among
others). The first 3G network was deployed in
Japan in 2001.
2.5G networks, such as GPRS (Global Packet Radio Service) are
already available in some parts of Europe.
has already begun on the development of fourth
generation (4G) technologies
is to be noted that analog and digital systems, 1G and 2G,
still co-exist in many areas.
Basics of Cellular
Technology and the Use of the Radio Spectrum
operators use radio spectrum to provide their services.
Spectrum is generally considered a scarce resource, and has
been allocated as such. It has traditionally been shared
by a number of industries, including broadcasting, mobile
communications and the military. At the World Radio Conference
(WRC) in 1993, spectrum allocations for 2G mobile were agreed based
on expected demand growth at the time. At WRC
resolutions of the WRC expanded significantly the spectrum
capacity to be used for 3G, by allowing the use of current 2G
spectrum blocks for 3G technology and allocating 3G spectrum
to an upper limit of 3GHz.
the advent of cellular technology, capacity was enhanced
through a division of frequencies, and the resulting addition
of available channels. However, this reduced the total
bandwidth available to each user, affecting the quality of
service. Cellular technology allowed for the division of
geographical areas, rather than frequencies, leading to a more
efficient use of the radio spectrum. This
geographical re-use of radio channels is knows as “frequency
a cellular network, cells are generally organized in groups of
seven to form a cluster. There is a “cell
site” or “ base station” at the centre of each cell,
which houses the transmitter/receiver antennae and switching
equipment. The size of a cell depends on the density of
subscribers in an area: for instance, in a densely populated
area, the capacity of the network can be improved by reducing
the size of a cell or by adding more overlapping cells. This
increases the number of channels available without increasing
the actual number of frequencies being used.
All base stations of each cell are connected to a central
point, called the Mobile Switching Office (MSO), either by
fixed lines or microwave. The MSO is generally connected to
the PSTN (Public Switched Telephone Network):
allows the “ hand-off” of subscribers from one cell to
another as they travel around. This is the key feature which allows the mobility of users.
A computer constantly tracks mobile subscribers of
units within a cell, and when a user reaches the border of a
call, the computer automatically hands-off the call and the
call is assigned a new channel in a different cell.
International roaming arrangements govern the subscriber’s
ability to make and receive calls the home network’s
Access Technologies (FDMA,
Division Multiple Access (FDMA) is the most common analog
system. It is a technique whereby spectrum is divided up
into frequencies and then assigned to users. With FDMA,
only one subscriber at any given time is assigned to a
channel. The channel therefore is closed to other
conversations until the initial call is finished, or until it
is handed-off to a different channel. A
“full-duplex” FDMA transmission requires two
channels, one for transmitting and the other for receiving.
FDMA has been used for first generation analog systems.
Division Multiple Access (TDMA) improves spectrum capacity by
splitting each frequency into time slots. TDMA allows
each user to access the entire radio frequency channel for the
short period of a call. Other users share this same
frequency channel at different time slots. The base
station continually switches from user to user on the channel.
TDMA is the dominant technology for the second generation
mobile cellular networks.
Division Multiple Access is based on “spread” spectrum
technology. Since it is suitable for encrypted
transmissions, it has long been used for military purposes.
CDMA increases spectrum capacity by allowing all users to
occupy all channels at the same time. Transmissions are
spread over the whole radio band, and each voice or data call
are assigned a unique code to differentiate from the other
calls carried over the same spectrum. CDMA allows for a
“ soft hand-off” , which means that terminals can
communicate with several base stations at the same time.
The dominant radio interface for third-generation mobile, or IMT-2000,
be a wideband version of CDMA with three modes (IMT-DS, IMT-MC
for 1G and 2G
Each generation of mobile
communications has been based on a dominant technology, which
has significantly improved spectrum capacity. Until the advent of
IMT-2000, cellular networks
had been developed under a number of proprietary, regional
and national standards, creating a fragmented market.
Advanced Mobile Phone System (AMPS) was first launched in the
US. It is an analog system based on FDMA (Frequency Division
Multiple Access) technology. Today, it is the most
used analog system and the second largest worldwide.
Nordic Mobile Telephone (NMT) was mainly developed in the
Nordic countries. (4.5 million in 1998 in some 40 countries
including Nordic countries, Asia, Russia, and other Eastern
Total Access Communications System (TACS) was first used in
the UK in 1985. It was based on the AMPS technology.
There were also a number
of other proprietary systems, rarely sold outside the home
Global System for Mobile Communications (GSM) was the first
commercially operated digital cellular system. It was
first developed in the 1980s through a pan-European
initiative, involving the Eureopean Commission,
telecommunications operators and equipment manufacturers.
The European Telecommunications Standards Institute was
responsible for GSM standardization. GSM uses TDMA (Time
Division Multiple Access) technology. It is being
used by all European countries, and has been adopeted in other
continents. It is the dominant cellular standard today,
with over (45%) of the world’s subscribers at April 1999.
TDMA IS-136 is the digital enhancement of the analog
AMPS technology. It was called D-AMPS when it was fist
introduced in late 1991 and its main objective was to protect
the substantial investment that service providers had bmade in
AMPS technology. Digital AMPS sevices have been launched
in some 70 countries worldwide (by March 1999, there were
almost 22 million TDMA handsets in circulation, the dominant
markets being the Americas, and parts of Asia)
CDMA IS-95 increases capacity by using the entire radio
band with each using a unique code (CDMA or Code Division
Multiple Access) . It is a family of digital communication
techniques and South Korea is the largest single CDMA IS-95
market in the world.
Personal Digital Cellular (PDC) is the second
largest digital mobile standard although it is exclusively
used in Japan where it was introduced in 1994. Like GSM,
it is based on the TDMA access technology. In November
2001, there were some 66.39 million PDC users in Japan.
Personal Handyphone System (PHS) is a digital
system used in Japan, first launched in 1995 as a cheaper
alternative to cellular systems. It is somewhere in between a
cellular and a cordless technology. It has inferior
coverage area and limited usage in moving vehicles. In
November 2001, Japan had 5.68 million PHS subscribers.
for the Third Generation: The
ITU's IMT-2000 family
is in the mid-1980s that the concept for IMT-2000,
“International Mobile Telecommunications”, was born at the
ITU as the third generation system for mobile communications.
After over ten years of hard work under the leadership
of the ITU, a historic decision was taken in the year 2000 :
unanimous approval of the technical specifications for third
generation systems under the brand IMT-2000. The spectrum between 400 MHz and 3 GHz is technically
suitable for the third generation. The entire
telecommunication industry, including both industry and
national and regional standards-setting bodies gave a
concerted effort to avoiding the fragmentation that had thus
far characterized the mobile market.
This approval meant that for the first time, full
interoperability and interworking of mobile systems could be
achieved. IMT-2000 is
the result of
collaboration of many entities, inside the ITU (ITU-R
and outside the ITU (3GPP,
and so on)
IMT-2000 offers the
capability of providing value-added services and applications
on the basis of a single standard.
The system envisages a platform for distributing
converged fixed, mobile, voice, data, Internet and multimedia
services. One of
its key visions is to provide seamless global roaming,
enabling users to move across borders while using the same
number and handset. IMT-2000
also aims to provide seamless delivery of services, over a
number of media (satellite, fixed, etc…).
It is expected that IMT-2000 will provide higher
transmission rates: a
minimum speed of 2Mbit/s for stationary or walking users, and
348 kbit/s in a moving vehicle.
Second-generation systems only provide speeds ranging
from 9.6 kbit/s to 28.8 kbit/s.
In addition, IMT-2000 has the
following key characteristics:
the large number of mergers and consolidations occurring in
the mobile industry, and the move into foreign markets,
operators wanted to avoid having to support a wide range of
different interfaces and technologies.
This would surely have hindered the growth of 3G
IMT-2000 standard addresses this problem, by providing a
highly flexible system, capable of supporting a wide range of
services and applications. The IMT-2000 standard accommodates
five possible radio interfaces based on three different access
technologies (FDMA, TDMA and CDMA):
services and worldwide applications development on the basis
of one single standard
accommodating five possible radio interfaces based on three
There was agreement among industry that 3G systems had to be
affordable, in order to encourage their adoption by consumers
Compatibility with existing systems
IMT-2000 services have to be compatible with existing systems. 2G systems, such as the GSM standard (prevalent in Europe and
parts of Asia and Africa) will continue to exist for some time
and compatibility with these systems must be assured through
effective and seamless migration paths.
The vision for IMT-2000 systems is that they must be easily
expandable in order to allow for growth in users, coverage
areas, and new services, with minimum initial investment.
Acronyms and Terms
Glossary of Mobile Cellular Terms
Forum : Glossary of Terms
of Telecommunications Terms
Industry Terms from WirelessWeek
Technology Hot Links
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