The term ‘wireless’ is often used to describe

all types of devices and technologies that

1
use space as a signal-propagating medium,
and are not connected by a wire or cable.
Wireless communication may be defined
as the transmission of user information
without the use of wires. The user informa-
Evolution
tion could be in the form of human voice,
digital data, e-mail messages, video and
other services. Wireless communication is
of Wireless
revolutionising almost every aspect of our
daily lives. From the ubiquitous mobile
phone to automated inventory counting
in large retail stores to remote wireless sen-
Communication
sors installed in inaccessible locations, wire-
less-communication technology is poised
to continue expanding at a very fast pace.
Systems
Using wireless communications to send and
receive messages, browse the Internet, and
access corporate databases anywhere, any
time across the world has already become
common. A wide array of devices ranging
1.1 BRIEF HISTORY OF WIRELESS
from computers to digital cameras, laser COMMUNICATIONS
printers, and even household appliances To appreciate the current technology and prepare ourselves to
can already communicate without wires.
enhance its development in future, it is always interesting to have
We are moving towards a wireless world
to live in a global village. Starting with a
a quick glance at the history of a technology such as wireless
brief history of wireless communications, communications. There are always several smaller steps that
this chapter provides a quick overview of take place in leading up to the development of a new technology.
comparison and applications of wireless Tracing the development of these earlier discoveries in brief can
communications and systems. Knowing help us better understand how this technology actually functions
about wireless network generations is and contributes towards what could be the next development.
important in studying the evolution to A brief review of the history of wireless communications cover-
next-generation networks. This chapter ing radio, television, radar, satellite, wireless and mobile, cellular
concludes with potential market areas
and other wireless networks are presented here.
and challenges for research in the field of
wireless and mobile communications. 1.1.1 Radio and Television Communications
In 1874, Marconi performed simple experiments to send sig-
nals using electromagnetic waves at short distances of only
about 100 metres. Scientists and other experts at that time
believed that electromagnetic waves could only be transmitted
in a straight line, and the main obstacle to radio transmission
was the curvature of the earth’s surface. Marconi successfully
2 Wireless Communications

experimented to prove that electromagnetic wave transmission was possible between two distant points even
through obstacles in between.
This paved the way for wireless telegraphy, also known as radio communications. The word ‘radio’ comes
from the term ‘radiated energy’. In 1901, Marconi set up a transmitting station in England, and a receiving
station with larger types of antennas suspended from light kites on the other side of the Atlantic Ocean on
the island of Newfoundland. For three hours every day, a signal was transmitted and received at a distance
of about 3,500 kilometres! This was due to the presence of the ionosphere, a layer of the upper atmosphere
between 60 to 500 kilometres above the earth, which was discovered by an English physicist, Edward
Appleton, in 1924. The ionosphere reflects electromagnetic waves which allow a radio signal to travel far
distances and is fundamental to all long-distance wireless radio communications. In 1935, Marconi per-
formed distance-based search experiments that eventually led to the invention of radar.
Marconi also studied microwaves and early television tech-
Facts to Know !
nology. In 1927, Farnsworth gave the first public demonstra-
The word ‘radio’ originated tion of the television system, and developed several of the basic
from the term ‘radiated energy’. concepts of an electronic television system. North America’s
Radio waves were originally
first television station, W3XK in Wheaton, Maryland, was
called Hertzian waves, named
after the German physicist Heinrich Hertz,
started in the 1930s. By 1939, widespread commercial elec-
who discovered radio waves which are a tronic television broadcasting started in the United States.
form of electromagnetic radiation. The National Broadcasting Company (NBC) started regularly
scheduled broadcasts in the New York area to only 400 TV
sets. In 1941, the American Federal Communications Authority set the standards for broadcast television. By
1970, television had become the primary information and entertainment medium in the world. Today, it is esti-
mated that there are more than a billion television sets worldwide. However, the standards for television broad-
casting are not universal. There are 15 different variations of broadcasting standards used around the world.

1.1.2 Radar Communications

Radar has been recognised as one of the greatest scientific developments of the first half of the 20th century.
The development of radar dates back to the discoveries of the 1860s and 1870s, when James Maxwell devel-
oped the equations that outlined the behavior of electromagnetic waves, and Heinrich Hertz discovered radio
waves. The first successful radio range-finding experiment occurred in 1924, when the British scientist Edward
Appleton used radio echoes to determine the height of the ionosphere. The first practical radar system was
produced in 1935 by the British physicist Robert Watson-Watt. By 1939, England had established a chain of
radar stations along its southern and eastern coasts to detect aggressors in the air or on the sea.
Radar is an active remote-sensing system that operates
Facts to Know !
on the principle of echoes. A radar display shows a map-like
Radar was originally called picture of the area being scanned. The centre of the picture
Radio Direction Finder (RDF). corresponds to the radar antenna and the radar echoes are
The term RADAR was coined in shown as bright spots on the screen. Although radar is usu-
1941 as an acronym for RAdio ally associated with detecting airplanes in the sky or ships
Detection And Ranging. The term has since
on the ocean, it is actually used in a variety of different ways
entered the English language as a standard
word, radar, losing the capitalisation. such as to forecast the weather, to scan entire regions for pos-
sible archaeological sites from space satellites and airplanes,
to study potential hidden dangers in highway tunnels, to locate stagnant pools of water in areas of dense
foliage on the earth, and to provide information about the universe. A Doppler radar is being used today by
meteorologists to locate tornados and microbursts, which are downdrafts of air traveling at very high speeds.
Doppler radar is also used by law-enforcement agencies to locate speeding motorists.
 Evolution of Wireless Communication Systems 3

1.1.3 Satellite Communications

A satellite is any object that orbits or revolves around another object. For example, the moon is a satellite
of the earth, and the earth is a satellite of the sun. Man-made satellites provide communication capabili-
ties around the world, transmitting television signals, telephone calls, faxes, computer communications, and
weather information. Satellites can be sent into space through a variety of launch vehicles. The theory of
satellites dates back to 325 years before the first man-made satellite was ever launched. Sir Isaac Newton in
the 1720s was probably the first person to conceive the idea of a satellite. Newton illustrated how an artificial
satellite could be launched from the earth. He pictured the earth as a high mountain and a cannon on top of
the mountain firing shots parallel to the ground. During World War II, the German military made great strides
in the development of rocket technology.
In 1945, Arthur C Clarke, a science-fiction author, envisioned a network of communication satellites.
Three satellites could be placed into space at about 36,000 kilometres above sea level so as to orbit the
planet every 24 hours. These satellites would be able to transmit signals around the world by transmitting
in a line-of-sight direction with other orbiting satellites. In 1957, the Soviet Union launched the Sputnik
1 satellite, followed by Sputnik 2 and its passenger, Laika, a dog who has the distinction of being the first
living creature to enter the earth’s orbit. In 1961, Yuri Gagarin became the first human in orbit. In 1964, an
international organisation known as Intelsat was formed, which launched a series of satellites with the goal
of providing total earth coverage by satellite transmission. This was achieved by 1969.
Today, Intelsat has 19 satellites in orbit that are
open to use by all nations. The Intelsat consortium Facts to Know !
owns the satellites, but each country owns their
Aryabhatta was India’s first satellite, named
earth-receiving stations. The explosive popularity after the great Indian astronomer. It was built
of cellular telephones advanced the idea of always by the Indian Space Research Organisation
being connected everywhere on the earth. Several (ISRO) to conduct experiments related to
companies committed themselves to providing a astronomy. It was launched by the Soviet Union on 19th
solution by using satellites in low earth orbit (LEO) April 1975 using a Cosmos-3M launch vehicle.
at a height of about 650 kilometres. Iridium, spon-
sored by Motorola, planned to launch 66 satellites into the polar orbit to provide communications services to
hand-held phones around the world in 1998.

1.1.4 Wireless and Mobile Communications

Based on the nature of wireless transmission, wireless communication systems may be classified as simplex,
half-duplex or full-duplex. In simplex wireless systems, separate transmitters and receivers operate at the
same frequency and communication is possible in only one direction from the transmitter to the receiver at
any time. For example, paging and messaging systems are simplex wireless communication systems in which
short text or alphanumeric messages are transmitted by fixed paging transmitters and received pagers but the
received messages are not acknowledged. Half-duplex wireless systems allow two-way communication but a
subscriber can only transmit or receive voice information at any given time. The same frequency is used for
both transmission and reception, with a push-to-talk feature for enabling transmission only at a time. Walkie-
talkie wireless communication sets used by police and paramilitary forces are the examples of half-duplex
wireless systems.
ull-duplex wireless communication systems allow simultaneous radio transmission and reception
between the calling and called subscribers of the system, either directly or via a base station. They use
separate frequency channels (frequency division duplex, or FDD) or different time slots on a single radio
channel (time division duplex or TDD) for communication to and from the subscriber. At the base station,
separate transmit and receive antennas are used to accommodate the separate forward and reverse frequency
4 Wireless Communications

channels. However, at the subscriber unit, a single antenna is used for both transmission and reception
simultaneously. A device called a duplexer is used inside the subscriber unit to enable the same antenna to
be used for this purpose. In order to provide sufficient isolation in the duplexer, the transmit and receive
frequencies are generally separated by about 5% of the nominal RF frequency of operation. Full-duplex
mobile communication systems provide many of the capabilities of the standard telephone for voice com-
munication, with the added convenience of communication on the move.
In Time Division Duplexing (TDD), a portion of the time is used to transfer information data from the
base station to the mobile subscriber, and the remaining time is used to transfer information data from the
mobile subscriber to the base station on the same frequency channel. Digital transmission formats and digi-
tal modulation schemes are used in TDD. It is very sensitive to timing accuracies and needs synchronisation
between transmissions and reception of the data at the transmitter and receiver ends respectively. Therefore,
TDD has limited applications such as indoor or small-area wireless applications where the physical cover-
age distances are much smaller than those encountered in conventional cellular telephone systems so as
to keep the radio propagation delay within acceptable limits. In the 1930s and 1940s, two-way full-duplex
vehicle radios were installed and used by police, utility companies, government agencies, and emergency
services.

Facts to Know ! 1.1.5 Cellular Communications

In 1946, AT&T introduced the first American
All wireless communication systems need
commercial mobile radio telephone service to
not be mobile (e.g., TVs, microwaves,
radios, satellites) whereas all mobile com- private customers. It consisted of a central trans-
munication systems (e.g., cellularphones) mitter with one antenna which could serve a wide
use necessarily wireless communications. area. However, this system could not be used with
Generally, wireless communications could be sim- mobiles because of their limited transmitter power.
plex, semi-duplex or full-duplex; whereas mobile To overcome this limitation, smaller receivers with
communication is mostly full-duplex. antennas were placed on top of buildings and on
poles around the city, creating smaller cells. When
a person used his mobile, the conversation that he heard was transmitted on one frequency by the central
transmitter to the moving vehicle. When the user spoke on his mobile, however, that transmission was sent on
a separate frequency that the nearest receiver antenna picked up. The major limitations were availability of
limited spectrum and interference. The concepts of using smaller cells and frequency reuse laid the founda-
tion for cellular telephones. In 1969, the Bell System developed a commercial cellular radio operation using
frequency reuse.
The first modern cellular telephone systems in the early 1980s used 666 channels. Advanced Mobile Phone
Service (AMPS) began setting up analog cellular telephone operations in many parts of the world. Roaming
from one city or state in the United States was easy because the US system was based on an analog cellular
system. In contrast, it was almost impossible to roam in Europe. During the 1980s, a plan was launched to
create a single pan-European digital mobile service with advanced features and easy roaming. This network
started operating in 1991.
Cellular mobile communication systems provide full-duplex communication, in which a pair of sim-
plex RF channels with a fixed and known frequency separation (called duplex spacing) is used to define a
specific radio channel in the system. For example, in the US AMPS standard and European GSM cellular
standard, the forward channel has a frequency that is exactly 45 MHz more than that of the reverse channel.
The channel used to transfer traffic data to the mobile subscriber from a base station is called the forward
channel. The channel used to transfer traffic from the mobile subscriber to the base station is called the
reverse channel.
 Evolution of Wireless Communication Systems 5

1.1.6 Transition from Analog to Digital Systems Facts to Know !

In the 1980s, most mobile cellular systems were based Today cellular telephone deploy-
on analog design. The GSM system can be considered as ment is worldwide, but tech-
the first digital cellular system. The different reasons that nology development remains
explain this transition from analog to digital technology concentrated in Scandinavia, the
are the following: United States, Europe, and Japan.

System Capacity Cellular systems experienced a very

significant growth in the 1980s. Analog systems were not able to cope with this increasing demand. In order
to overcome this problem, new frequency bands were allocated for the development of mobile cellular radio
and new modulation and coding technologies were introduced. The digital radio was, therefore, the best
option to handle the capacity needs in a cost-efficient way.
Quality Aspects The quality of the service can be considerably improved using a digital technology rather
than an analog one. In fact, analog systems carry the physical disturbances in radio transmission such as
fades, multipath reception, spurious signals or interferences to the receiver. These disturbances reduce the
quality of the communication because they produce effects such as fadeouts, crosstalks, hisses, etc.
On the other hand, digital systems avoid these effects, transforming the signal into bits. This transforma-
tion combined with other techniques, such as digital coding, improve the quality of the transmission. The
improvement of digital systems compared to analog systems is more noticeable under difficult reception
conditions than under good reception conditions.
Compatibility with Other Systems such as ISDN The decision Facts to Know !
of adopting a digital technology for GSM was made in the
course of developing the standard. During the development Analog systems do not fully
of GSM, the telecommunications industry converted to dig- utilise the signal between the
ital methods. The ISDN network is an example of this evo- phone and the cellular network
because analog signals cannot
lution. In order to make GSM compatible with the services
be compressed and manipulated as easily
offered by ISDN, it was decided that the digital technology as a true digital signal. This is the reason why
was the best option. Additionally, a digital system allows, many service providers have switched to
easily than an analog one, the implementation of future digital systems.
improvements and the change of its own characteristics.

1.2 ADVANTAGES OF WIRELESS COMMUNICATIONS

There are many advantages of wireless communications, using wireless communications technology and
wireless networking, as compared to wired communications and networks. Some of the major advantages
include mobility, increased reliability, ease of installation, rapid disaster recovery and above all lower cost.
Mobility The primary advantage of wireless communications is to offer the user freedom to move about
while remaining connected with the network within its coverage area. Many business categories, such as the
police department, require its workforce to be mobile instead of fixed at one location. Wireless technology
enables many industries to shift toward an increasingly mobile workforce, whether they are in meetings or
working on a factory floor or conducting research.
Increased Reliability The most common source of network problems is the failure or damage of network cables
due to environment conditions or erosion of metallic conductors. A cable splice that is done incorrectly can cause
unexplainable errors and is very difficult to identify. Using wireless technology not only eliminates these types of
cable failures, but also increases the overall reliability of the network.
6 Wireless Communications

Facts to Know ! Ease of Installation Wireless communications and net-

works make it easier for any office to be modified with
Notebook computers and other
new cubicles or furniture, without worrying about pro-
portable handheld wireless devices
allow team members an added col- viding network connectivity through cables. There is no
laborative convenience of immedi- need to first consider the location of the computer jack in
ate access to the company’s WLAN. the wall when relocating furniture. Instead, the focus can
be on creating the most effective work environment with-
out any delay and hassles. The time required to install
network cabling may take days or even weeks to complete, thereby disrupting the whole work. Using a wire-
less LAN eliminates such disruption.
Rapid Disaster Recovery Accidents may happen due to fires, tornados, and floods at any possible location,
and that too without any prior warning. Any organisation that is not prepared to recover from such natural
disasters will find itself quickly out of business. Since the computer network is a vital part of the daily opera-
tion of a business, the ability to have the network up and immediately working after a disaster is critical.
A documented disaster recovery plan is a must.

Facts to Know ! Lower Cost Of course, eliminating the need to install

cabling and using wireless communications results in
Many businesses are nowadays using significant cost savings. Installing network cabling in
wireless communications and net-
older buildings can be an extremely difficult, slow, and
working, keeping laptop computers
with wireless NICs and access points
costly task. Facilities constructed prior to the mid-1980s
in reserve along with backup network servers. In were built without any thought given to running computer
the event of a disaster, the office can be quickly wiring in each room. In such cases a wireless LAN is the
relocated and made operational, without any need ideal solution. Historical buildings would be preserved,
of finding a new facility with network wiring. harmful asbestos would not be disturbed, and difficult
drilling could be avoided by using a wireless system.

1.3 DISADVANTAGES OF WIRELESS COMMUNICATIONS

Along with the many advantages of wireless communications and technology, there are some disadvantages
and concerns. The most prominent of them are radio signal interference, security issues, and health hazards.

Facts to Know ! Radio Signal Interference Signals from other wireless

External interference from AM or devices can disrupt its radio transmission, or a wireless dev-
FM radio stations, TV broadcast ice may itself be a source of interference for other wireless
stations, or microwave and cel- devices. For example, several commonly used office wire-
lular transmitters does not occur less devices such as cordless telephones, microwave ovens,
because they operate at different frequencies elevator motors, and other heavy electrical manufacturing
and power levels than wireless LANs. machines, transmit radio signals that may interfere with a
wireless LAN operation. These may cause errors to occur
in the transmission between a wireless device and an access point. Similarly, Bluetooth and WLAN devices both
operate in the same radio frequency, potentially resulting in interference between such devices.
Security A wireless communication device transmits radio signals over a wide open area, and hence secu-
rity becomes a major concern. It is possible for an intruder with a notebook computer and wireless NIC to
intercept the signals from a nearby wireless network. Because much of business network traffic may contain
sensitive information, this becomes a serious concern for many users.
 Evolution of Wireless Communication Systems 7

Some wireless technologies can provide added levels of security with authorisation features prior to gaining
access to the network. Network administrators can also limit access for approved wireless devices only. As fur-
ther protection, data transmitted between the wireless device and the access point can also be encrypted in such
a way that only the intended recipient can decode the message.
Health Hazards High power levels of RF energy can pro- Facts to Know !
duce biological damage. However, it is not yet established
accurately as to how much levels of RF can cause adverse Questions exist regarding the
safety of handheld cellular
health effects. But continuous radiations even at lower levels
phones, the kind with a built-
can be harmful to sensitive body organs. Radio transmitters in in antenna that is positioned
wireless communications devices emit radio frequency (RF) very close to the user’s head during normal
energy. Typically, these wireless devices emit low levels of RF conversation.
while being used. Although some research has been done to
address these issues, no clear facts of the biological effects of this type of radiations have emerged to date.
The safety of cordless phones, which have a base unit connected to the telephone wiring in a house and
which operate at far lower power levels and frequencies, has never been questioned. It is always wise to be
aware of the health concerns and to monitor ongoing scientific research, even though the available science
does not conclude either way about the safety of wireless mobile devices.

1.4 WIRELESS NETWORK GENERATIONS

The cellular systems have been classified into three distinct evolution of generations: The first-generation
(1G) analog cellular communication systems are voice-oriented analog cellular systems using frequency
division multiple access technique. The first-generation systems used large cells and omni-directional anten-
nas in the 800-MHz band. The AMPS and ETACS systems use a seven-cell reuse pattern with provisions for
cell-sectoring and cell-splitting to increase capacity when needed. These systems provide satisfactory voice
communication on the move with limited traffic-handling capacity.

1.4.1 First-Generation Analog Cellular Systems

The first-generation cellular systems are based on analog transmission technology. The most popular first-
generation cellular systems are AMPS (widely deployed in most parts of US, South America, Australia,
China), and ETACS (deployed throughout Europe). The systems transmit speech signals employing FM, and
important control information is transmitted in digital form using FSK. The entire service area is divided into
logical cells, and each cell is allocated one specific band in the frequency spectrum. To explore a frequency
reuse pattern, the frequency spectrum is divided among seven cells, improving the voice quality as each sub-
scriber is given a larger bandwidth.
AMPS and ETACS cellular radio systems deploy cell-sites with tall towers that support several receiving
antennas and have transmitting antennas that typically radiate a few hundred watts of effective radiated power.
Each cell-site has one control channel transmitter that broadcasts on the forward control channel, one control
channel receiver that listens on the reverse control channel for any mobile phone to set-up a call, and eight or more
FM duplex voice channels.
Facts to Know !
Table 1.1 shows the worldwide 1G analog cellular systems.
All these systems use two separate frequency bands for for- The channel bandwidth in
ward (from cell-site to mobile) and reverse (from mobile to AMPS is 30 kHz in an 800-MHz
cell-site) links. Such a system is referred to as a frequency spectrum whereas the chan-
nel bandwidth in ETACS is
division duplex ( DD) scheme. The typical allocated overall
30 kHz in a 900-MHz spectrum.
band in each direction, for example, for AMPS, and NMT-900,
8 Wireless Communications

is 25 MHz in each direction. The dominant spectra of operation for these systems are the 800-and 900-MHz
bands. In an ideal situation, all countries should use the same standard and the same frequency bands. However,
in practice, as shown in Table 1.1, a variety of frequencies and standards are adopted all over the world.

Table 1.1 Existing 1G analog cellular systems

Standard orward Reverse Channel Number of Multiple Major region

frequency frequency spacing (kHz) channels access/ of operation
band (MHz) band (MHz) Modulation
technique

AMPS 824–849 869–894 30 832 FDMA/FM US

ETACS 872–905 917–950 25 1240 FDMA/FM UK
NMT 900 890–915 935–960 12.5 1999 FDMA/FM EU
JTACS/ 915–925 860–870 25/12.5 400/800 FDMA/FM Japan
NTACS 898–901 843–846 25/12.5 120/240
918.5–922 863.5–867 12.5 280

AMPS Advanced Mobile Phone System

ETACS Enhanced Total Access Communication System
NMT Nordic Mobile Telephone
JTACS Japanese Total Access Communication System; NTACS: Narrowband JTACS

All the 1G cellular systems use analog frequency modulation (FM) for which the transmission power
requirement depends on the transmission bandwidth. On the other hand, power is also related to the coverage
and size of the cells. Therefore, one can compensate for the reduction in transmission bandwidth per sub-
scriber by reducing the size of a cell in a cellular network. Reduction in size of the cell increases the number
of cells and the cost of installation of the infrastructure. The channel spacing, or bandwidth, allocated to each
subscriber is either 30 kHz or 25 kHz or a fraction of either of them.

1.4.2 Second-Generation Digital Cellular Systems

First-generation analog cellular systems were followed by second-generation digital cellular systems. The second-
generation (2G) cellular systems represent the set of wireless air interface standards that rely on digital modula-
tion and sophisticated digital signal processing in the handset and the base station. Digital cellular technologies
support a much larger number of mobile subscribers within a given frequency allocation, thereby offering higher
user capacity, providing superior security and voice quality, and lay the foundation for value-added services
(including data) that will continue to be developed and enhanced in future. To have efficient use of the frequency
spectrum, time division or code-division multiple access technique is used in 2G digital cellular systems so that
low-rate data along with voice can be processed. Table 1.2 summarises the major 2G digital cellular standards.
There are four major standards in this category: the North American Interim Standard (IS-54) that later on
improved into IS-136; GSM, the pan-European digital cellular; and Personal digital cellular (PDC) — all of
them using TDMA technology; and IS-95 in North America, which uses CDMA technology. Like the 1G analog
cellular systems, the 2G digital cellular systems are all FDD and mostly operate in the 800- and 900-MHz bands.
The carrier spacing of IS-54/136 and PDC is the same as the carrier spacing of 1G analog cellular systems in
their respective regions, but GSM and IS-95 use multiple analog channels to form one digital carrier.
The most popular 2G cellular standards include three TDMA standards and one CDMA standard. Interim
Standard 54 or 136 (IS-54 or IS-136), also known as US Digital Cellular (USDC), which supports three time-
slotted mobile subscribers for each 30-kHz radio channel in both the cellular 800 MHz and PCS 1900 MHz
 Evolution of Wireless Communication Systems 9

Table 1.2 2G digital cellular standards

Standard orward frequency Reverse frequency Multiple access Major region of

band (MHz) band (MHz) technique operation

IS-54/136 869–894 824–849 TDMA/FDD US

GSM 935–960 890–915 TDMA/FDD Europe/Asia
PDC 940–956 810–826 TDMA/FDD Japan
IS-95 869–894 824–849 CDMA/FDD US/Asia

bands. Based on the analog AMPS cellular system, the TDMA system IS-54/136 was developed in the US
that adds digital traffic channels. IS-54/136 uses dual-mode mobile phones and incorporates associated con-
trol channels, authentication procedures using encryption, and mobile assisted handoff. The IS-136 includes
digital control channels which enable to provide several additional services such as identification, voice mail,
SMS, call waiting, group calling, etc. The USDC systems share the same frequency spectrum, frequency
reuse plan, and cell-sites as that of AMPS.
Global System for Mobile (GSM), which Facts to Know !
supports eight time slotted mobile subscribers Three primary benefits of 2G cellular net-
for each 200-kHz radio channel in both the cel- works over their predecessors are that phone
lular and PCS bands; and Pacific Digital Cellular conversations are digitally encrypted, 2G sys-
(PDC), a Japanese TDMA standard that is similar tems are significantly more efficient on the
to IS-136, are the other two most popular TDMA- spectrum allowing for far greater mobile phone penetra-
based digital cellular standards. The popular 2G tion levels; and 2G introduced data services for mobile,
CDMA standard (IS-95), also known as cdmaOne, starting with SMS text messages.
can support up to 64 mobile subscribers that are
orthogonally coded and simultaneously transmitted on each 1.25 MHz channel.
The speech-coding technique of all 2G systems operates at about 10 kbps. It is assumed that large cell
sizes and a large number of subscribers per cell are available, which necessitates lower speech-coding rates.
The peak transmission power of the mobile terminals can be between several hundreds of mW up to 1W, and
on the average they consume about 100 mW. All of these systems employ centralised power control, which
reduces battery power consumption and helps in controlling the interference level. In digital communications,
information is transmitted in packets or frames. The duration of a packet/frame in the air should be short
enough, so that the channel does not change significantly during the transmission, and long enough, so that
the required time interval between packets is much smaller than the length of the packet. A frame length of
around 5 to 40 ms is typically used in 2G cellular networks.
GSM supports eight users in a 200-kHz band; IS-54 and JDC support three users in 30 and 25-kHz
bands, respectively. In other words, GSM uses 25 kHz for each user, IS-54 uses 10 kHz per user, and JDC
uses 8.33 kHz per user. Therefore, GSM supports 2.5 times less number of subscribers in the given band-
width. The number of users for CDMA depends on the acceptable quality of service; therefore, the number
of users in the 1,250 kHz CDMA channels cannot be theoretically fixed. But this number is large enough
to convince the standards organisation to adopt CDMA technology for next-generation 3G systems.

1.4.3 Evolution from 2G to 3G Cellular Networks

There are two steps of 3G evolution paths from present 2G technologies based on GSM and IS-95 CDMA
respectively. An evolution path from second generation digital cellular GSM network to third generation
network is depicted in Fig. 1.1.
10 Wireless Communications

v l i n
M

384 – 2048 kbps

P

384 kbps
P

9.6 – 53.6 kbps

M
M 9.6 – 28.8 kbps P se

9.6 kbps 144 – 384 kbps

r e

Fig. 1.1 An evolution path from GSM to 3G network

GSM is an open, digital cellular technology which supports voice calls and data transfer speeds of up to
9.6 kbps, together with the transmission of SMS (Short Message Service). GSM operates in the 900 MHz and
1.8 GHz bands in Europe and the 850 MHz and 1.9 GHz bands in the US. GSM provides international roam-
ing capability that enables users to access the seamless services
Facts to Know ! when travelling abroad. HSCSD (High Speed Circuit Switched
Data) enables data to be transferred more rapidly than the stan-
The range of GSM and CDMA
dard GSM system by using multiple channels. GPRS is a very
technology is different, and
they also have different rates widely deployed wireless data service, available now with most
and modulation schemes, GSM networks. GPRS offers throughput rates of up to 53.6 kbps,
and that is why handsets are different so that users have a similar access speed to a dial-up modem,
between the two technologies. GSM uses but with the convenience of being able to connect from almost
SIM cards, whereas CDMA based phones anywhere. Further enhancements to GSM networks are provided
do not by Enhanced Data rates for GSM Evolution (EDGE) technology
or EGPRS, which offers up to three times the data capacity of
GPRS. Various mobile data services such as multimedia messaging, high-speed Internet access and e-mail are
possible on the move. EDGE allows it to be overlaid directly onto an existing GSM network with simple soft-
ware-upgrade. WCDMA is the air interface for third-generation mobile communications systems. It enables
the continued support of voice, text and MMS services in addition to richer mobile multimedia services.
UMTS offers data speeds up to 384 kbps on the move and 2.048 Mbps stationary. Chapters 11 and 13 gives
detailed descriptions of GSM based cellular technologies.
Besides GSM, CDMA is the most popular mobile communication standard. The initial evolution of CDMA
started in 1991 as IS-95A cdmaOne 2G digital cellular technology for voice communication as well as data
and multimedia services because it could allow multiple users to communicate within the spectrum, avoid-
ing interference or jamming among users. Code division ensures that each user’s signal remains separate in
the spectrum. An evolution path from second generation digital cellular CDMA networks to third generation
networks is depicted in Fig. 1.2.
 Evolution of Wireless Communication Systems 11

v l i n
M 2000
M 3x

M 2000 14.4 kbps – 2 Mbps

M 1x

14.4 – 307 kbps

5

14.4 – 144 kbps

5

14.4 kbps

r e

Fig.1.2 An evolution path from CDMA to 3G network

IS-95A describes the structure of the wideband 1.25 MHz CDMA channels, power control, call process-
ing, hand-offs, and registration techniques for system operation. In addition to voice services, many IS-95A
operators provide circuit-switched data connections at 14.4 kbps. The IS-95B or cdmaOne, categorised as a
2.5G technology, defines a compatibility standard for 1.8 to 2.0 GHz CDMA PCS systems, offers up to 144
kbps packet-switched data, in addition to voice services. CDMA2000 Multi-Carrier (MC) delivers improved
system capacity and spectrum efficiency over 2G systems and it supports data services at minimum transmis-
sion rates of 144 kbps in mobile (outdoor) and 2 Mbps in fixed (indoor) environments. Chapters 12 and 13
gives the detailed description of CDMA-based cellular technologies.

1.4.4 Third-Generation Digital Cellular Systems

The fundamental purpose of the 3G mobile communications system is to provide a globally integrated wire-
less communication system combining different incompatible network technologies already deployed across
the world. All 2G and 2.5G cellular communications systems and mobile phones will eventually evolve
towards a global standard, which is referred to IMT-2000. While no one common standard for the air interface
has been approved, the number of different standard specifications includes one FDMA standard, one TDMA
standard, and one CDMA standard with three variations. The IMT-2000 system incorporates three variations
of CDMA. The modes differ in how duplexing is accomplished and how many carriers are used. All varia-
tions operate in a 5-MHz channel, as compared to 1.25 MHz for cdmaOne systems. Figure 1.3 illustrates how
these different standards are evolved into one standard IMT-2000.
The need for a capacity increase necessitates a greater spectrum allocation (1885 MHz–2025 MHz and
2110 MHz–2200 MHz) for 3G systems. The key features of the IMT-2000 system defining the ITU’s view of
3G cellular network capabilities are as follows:
(a) High degree of worldwide commonality of design
(b) Compatibility of services with fixed networks and within IMT-2000
(c) More efficient use of the available spectrum
(d) Voice quality comparable to that of PSTN
12 Wireless Communications

13 M dm 2000
M
M M M M
M

M M M M
ime de ire s re d M l i rrier

M M
re en ime in le rrier M 3 m des
M / M M

M 2000

Fig. 1.3 Evolution of IMT-2000 standards

(e) 144–kbps data rate available to users in high-speed vehicles over large areas
(f) 384 kbps available to pedestrians standing or moving slowly over small areas
(g) Support for 2-Mbps data rate for office use
(h) Symmetrical and asymmetrical data-transmission rates
(i) Support for both circuit-switched and packet-switched data services
(j) Support for wide variety of mobile phones for worldwide use including pico, micro, macro, and global
cellular/satellite cells
(k) Worldwide roaming capability
(l) Capability for multimedia applications and a wide range of services
(i) Flexibility to allow the introduction of new services and technologies

The third generation aims to combine telephony,

Internet, and multimedia into a single device. A
ele n
convergence of all these applications in IMT-2000
i e
ide is depicted in Fig. 1.4. This entails an additional
x requirement that it supports the Internet protocols and
M il x be based on a packet-switched network backbone.
n erne
To achieve the convergence of various services,
e s r in IMT-2000 systems have been designed with six broad
m il Convergence classes of service in mind. Cellular service providers
n rm i n IMT-2000
will be able to offer whatever data rates the mobile
M mmer e
users want up to a maximum 2 Mbps or so, and the
M l imedi mobile users will also have flexibility to choose the
elevisi n required data-rate service. Three of the service classes
di are already present on 2G networks to some extent,
n inmen
i n servi es while three more service classes are new and involve
mobile multimedia. In order of increasing data rate
requirements, these services are the following:
(a) Voice 3G systems will offer speech quality at least
Fig. 1.4 Convergence of services in IMT-2000 as good as the fixed telephone network. Voicemail will
 Evolution of Wireless Communication Systems 13

also be eventually integrated fully with email service through computerised voice recognition and synthesis
techniques.
(b) Switched data This includes dial-up access to corporate networks or fax service or the Internet access
that doesn’t support a fully packet-switched network.
(c) Messaging This is an extension of paging, combined with Internet e-mail service. Unlike the text-only
messaging services built into some 2G systems, 3G systems will allow e-mail attachments. It can also be used
for payment and electronic ticketing.
(d) Multimedia Messaging Service (MMS) The MMS is designed to allow rich text, colour, icons and logos,
sound clips, photographs, animated graphics, and video clips. It works over the broadband wireless channels
in 3G networks.
(e) Immediate messaging MMS features push capability that enables the message to be delivered instantly if
the called mobile user is active. It avoids the need for collection from the server. This always-on characteristic
of the mobile users opens up the exciting possibility of multimedia chat in real time.
(f) Medium multimedia This is likely to be the most popular 3G service. Its downstream data rate is ideal for
web surfing, games, location-based maps, and collaborative group working.
(g) High multimedia This can be used for very high-speed Internet access, as well as for high-definition
video and CD-quality audio on demand. Another possible application is online shopping for intangible prod-
ucts that can be delivered over the air such as a software program for a mobile computer.
(h) Interactive high multimediaThis can be used for high-quality videophones, videoconferencing or a com-
bination of videoconferencing and collaborative working.
(i) Sending multimedia postcards A clip of a holiday video could be captured through the integral video cam
of a user’s mobile handset or uploaded via Bluetooth from a standard camcorder, then combined with voice
or text messages and mailed instantly to any other mobile user.

1.4.5 Wireless Networking Technologies

The use of radio signals for data transmission during World War II by the US Army inspired a group of
researchers in 1971 at the University of Hawaii to create the first packet-based radio communications network
called ALOHAnet, the very first wireless local area network (WLAN). It consisted of 7 computers that com-
municated in a bi-directional star topology. The first generation of WLAN technology used an unlicensed
ISM band of 902–928 MHz. To minimise the interference from small appliances and industrial machinery, a
spread spectrum was used which operated at a 500-kbps data rate. In 1990, the IEEE 802 Executive Committee
established the 802.11 Working Group to create the WLAN standard. The standard specified an operating
frequency in the 2.4-GHz ISM band. In 1997, the group approved IEEE 802.11 as the world’s first WLAN
standard with data rates of 1 and 2 Mbps. Like cellphones, wireless-equipped laptops within range of a given
access point have the ability to communicate with the network.
A single access point can communicate with multiple wireless- Facts to Know !
equipped laptops. Many systems allow roaming between access The challenge for future
points. Despite their limited range (up to 100 m) and lower WLANs is to support many
data rates (as compared to 1 Gbps offered by wired Ethernets), users simultaneously with
WLANs have become the preferred Internet access method for extended range for band-
e-mail and Web browsing applications, in many offices, homes, width-intensive applications such as
video.
campus environments, and public places.
14 Wireless Communications

A wireless personal area network (WPAN), such as Bluetooth IEEE 802.15.1, enables wireless com-
munication between devices, ranging from computers and cell phones to keyboards and headphones, and
operates in ISM 2.4 GHz band. WiMAX (WMAN based on the IEEE 802.16 family of standards) will soon
offer wireless broadband Internet access to residences and businesses at relatively low cost.

1.5 COMPARISON OF WIRELESS SYSTEMS

Wireless communication systems primarily comprise of a fixed-base transceiver station and a number of
fixed/mobile subscriber transceiver equipments. The base station as well as the mobile subscriber of vari-
ous types of mobile or portable wireless communication systems can be compared for the types of ser-
vices, functionality (Transmitter Tx only or Receiver Rx only or Transceiver), operating carrier frequency
range, the level of infrastructure needed, configuration complexity, hardware cost, and radio coverage
range. Table 1.3 gives a brief account of the comparison of three most commonly used household wireless
communication systems, that is, paging systems, cordless phone systems, and cellular telephone systems.
The details of all these systems are covered in Chapter 10.

Table 1.3 Comparison of wireless communication systems

Service type unctionality Operating Level of Complexity Hardware cost Range

frequency infrastructure

Paging BS: Tx only < 1 GHz High BS: High BS: High High
system MS: Rx only MS: Low MS: Low
Cordless Transceivers 1–3 GHz Low BS: Low BS: Medium Low
phone system MS: Medium MS: Low
Cellular Transceivers < 2 GHz High High BS: High High
phone system MS: Medium

Virtually, all these wireless communication systems aim to connect a mobile subscriber (vehicle-installed
or handheld or portable) to a fixed wireless base transceiver system having antennas mounted at reasonably
high towers. The user expectations vary widely among the type of services needed. The infrastructure costs
are dependent upon the required coverage area. The radio link between the cordless phone base station and
the portable cordless handset is designed to behave identically to the coiled cord connecting a traditional
wired telephone handset to the telephone base. For example, cordless telephones use fixed base stations so
that they may be plugged into the existing standard telephone line.
Similarly, in case of low power, hand-held cellular phones, a large number of cell sites are required to
ensure that any mobile phone is in close range to a cell site within its service area. If cell sites area is
not within the radio coverage range, a high transmitter
Facts to Know ! power would be required at the mobile phone which is
The cellular systems have been evolved limited by the battery life.
from the first generation of analog Table 1.4 summarises the most common cellular
cellular systems standards through systems standards used in North America, Europe, and
second-generation digital cellular stan- Japan. The details of AMPS, ETACS, USDC-IS 54/136,
dards, followed by more advanced third-generation GSM, PDC, and IS-95 cellular systems are covered in
digital cellular standards providing multiple user Chapters 10–12.
services including voice, high-speed data and mul- The first-generation analog cellular systems use
timedia applications.
frequency modulation scheme for speech transmission.
 Evolution of Wireless Communication Systems 15

Table 1.4 Major cellular communication systems standards

Analog or Cellular systems Frequency band Multiple access Modulation Region

digital standard technique scheme

Analog AMPS 824–894 MHz FDMA FM North America

Analog NMT-900 890–960 MHz FDMA FM Europe
Analog ETACS 900 MHz FDMA FM Europe
Analog JTACS 860–925 MHz FDMA FM Japan
Digital USDC/IS-54 824–894 MHz TDMA π/4-DQPSK North America
or 136
Digital IS-95 824–894 MHz; CDMA QPSK/ North America
1.8–2.0 GHz OQPSK
Digital GSM 890–960 MHz TDMA GMSK Europe
Digital PDC 810–1501 MHz TDMA π/4-DQPSK Japan

Individual calls use different frequencies and share the available spectrum through frequency division
multiple access technique. The world’s earlier cellular systems include North America’s Advanced Mobile
Phone System (AMPS) operating in the 800-MHz band (50 MHz allocated spectrum: 824–849 MHz uplink
and 869–894 MHz downlink), with 832 full-duplex channels, having a one-way channel bandwidth of 30
kHz for a total spectrum occupancy of 60 kHz for each duplex channel. The AMPS system uses a seven-cell
reuse pattern with provisions for three-sectoring per cell and cell splitting to increase capacity when needed.
The analog AMPS system requires that the received signal strength be at least 18 dB above the co-channel
interference to provide acceptable call quality.
In Europe, the earlier cellular systems include the Nordic Mobile Telephone system (NMT 900), devel-
oped for the 900–MHz band. The European Total Access Communications System (ETACS) operates
with a 25-MHz band in the uplink (890–915 MHz), and a 25-MHz band in the downlink (935–960 MHz),
with a total capacity of 1000 full-duplex channels, having a one-way channel bandwidth of 25 kHz for a
total spectrum occupancy of 50 kHz for each duplex channel. The smaller bandwidth channels result in a
slight degradation of signal-to-noise ratio and coverage range.
The United States Digital Cellular (USDC) standards IS-54 Facts to Know !
and then IS-136 allowed cellular operators to replace gracefully
some single-user analog channels with digital channels which North America’s IS-136 digital
support three subscribers in the same 30-kHz bandwidth. In this cellular systems are eventu-
ally being replaced by IS-95
way, US cellular service providers gradually phased out AMPS
based CDMA technology. It
analog mobile phones as more subscribers accepted USDC digital supports a variable number of subscribers
mobile phones. The USDC system uses digital modulation (π/4 in 1.25-MHz wide channels using direct-
differential quadrature phase-shift keying), speech coding, and sequence spread-spectrum modulation
time division multiple access (TDMA) in place of analog FM scheme.
and FDMA as in the case of AMPS. The capacity improvement
offered by USDC is three times that of AMPS.
CDMA systems can operate at much larger interference levels because of their inherent interference resistance
properties. The ability of CDMA to operate with a much smaller signal-to-noise ratio than conventional
narrowband FM techniques allows CDMA systems to use the same set of frequencies in every cell. It provides
a large improvement in the overall system capacity. Unlike other digital cellular systems, the IS-95 system
uses a variable rate vocoder with voice-activity detection that considerably reduces the required data rate and
16 Wireless Communications

Facts to Know ! also the battery drain by the mobile phone. The North American
IS-136 is commonly referred to as digital TDMA cellular systems
The European GSM digital cel-
lular standard is commonly
and the IS-95 standard is called digital CDMA cellular systems.
referred to as digital TDMA The Pan European digital cellular standard GSM (Global
cellular system. In Japan, the System for Mobile) is a 900-MHz band. The GSM standard
Pacific Digital Cellular (PDC) standard has gained worldwide acceptance as the first universal digi-
provides digital cellular coverage using a tal cellular system with modern network features extended to
system similar to North America’s USDC. each mobile subscriber, and is the leading digital air interface
for PCS services above 1800 MHz throughout the world.
The channel bit rate of GSM is 270 kbps whereas that of IS-54 and JDC is 48 kbps and 42 kbps, respectively.
Higher channel bit rates of a digital cellular system allow simple implementation of higher data rates for data
services. By assigning several voice slots to one user in a single carrier, one can easily increase the maximum
supportable data rate for a data service offered by the cellular network. Similarly, the 1228.8 kcps channel chip
rate of IS-95 provides a good ground for integration of higher data rates into IS-95. This fact has been exploited
in IMT-2000 systems to support data rates up to 2 Mbps.

1.6 EVOLUTION OF NEXT-GENERATION NETWORKS

After the successful creation of an environment for second-generation digital mobile cellular communica-
tions systems, demand for further evolution in mobile and wireless systems is now emerging. Users place
emphasis on the integration of mobile communication applications, particularly accommodating multimedia
applications, higher performance, global and seamless coverage of wired and wireless services as well as
greater customisation of services.
At this stage, many uncertainties remain as for the concrete specification of the next-generation wireless
network, but the process of discussion among market drivers and within the standardisation bodies such as
3GPP2, UMTS Forum, and ETSI among others has been launched. There are several areas which have been
identified for a global approach towards regulation, standardisation, frequency allocation, R&D efforts and
international cooperation. The objective is to create a framework which leads to greater choice, improved
quality and lower prices for all users of mobile services, while ensuring full competition within an environ-
ment which fosters the competitiveness that the sector achieved so far.
The recent evolution of the regulatory environment in view of the full liberalisation of telecommunications
has provided a comprehensive framework for both fixed and mobile telecommunications systems. It will be
important to assess the flexibility of that framework against the new demands with the emergence of the concept
of next-generation network (NGN). The same applies for the decision on priorities for standardisation and choices
concerning the most suitable allocation of frequency bands in the spectrum so far reserved for 3G technology.
Recent years have witnessed the rapid evolution of commercially available mobile computing devices and
networks. There are several viable but non-interoperable wireless networking technologies––each targeting a
mobility environment and providing a distinct quality of service.
Figure 1.5 depicts the vision of next-generation networks.
This would also mean enhancement of present 2G/2.5G/3G cellular systems already in operation across
the world. The usage environment would demand high-speed wireless access techniques in hot-spots, that
is, inadequate signal reception areas or indoor multi-structured buildings, and would also require ultra
short-range connectivity in order to access laptop or desktop terminals with a remote wireless digital
device using technology such as Wi-Fi or Bluetooth.
With the advancement in mobile information technologies like ultra high-speed transmission, wireless
Internet protocol IPv6, user-controllable software defined radios, the potential mobile users would be able to
 Evolution of Wireless Communication Systems 17

ell l r M ell l r
2 + M 3

IP based
next
i er ell l r 4
generation
network

P r d s
M /

Fig. 1.5 Vision of next-generation networks

– access the Internet as they do in the office––anywhere, anytime while on move

– use cellphones or laptop computers or any other PDA as mobile communication terminal
– choose freely the services, applications and service-providing networks
– exploit advanced mobile E-commerce applications with higher levels of data security and integrity
during business transactions

1.6.1 Functional Requirements Facts to Know !

Very High-speed and High-quality Transmission Next- The lack of a uniform set of stan-
generation mobile communication systems should be dards, the inconsistency in the qual-
able to handle a large volume of multimedia informa- ity of service, and the diversity in
tion like downloading a full song or sending a com- the networking approaches make it
plete data file or several video clips. This would be difficult for a mobile computing environment to
provide seamless mobility across different wire-
possible by various means like transmitting data at
less networks.
50 Mbps–100 Mbps, having asymmetric data speeds in
up and down links, having continuous coverage over a large geographical area, applying QoS mechanisms
(for example, efficient encoding, error detection and correction techniques, echo cancellers, voice equalisers)
at low, affordable and reasonable operating costs.
Open Platform Next-generation mobile communication systems should be open regarding mobile phone plat-
form, service nodes, and mobile network mechanisms. That would mean that the user can freely select protocols,
applications and networks. Advanced service and content providers can extend their services and contents inde-
pendent of operators. Location and charging information can be shared among networks and applications.
Flexible and Varied Service Functions Next-generation mobile communication networks should be seam-
less with regard to the medium, whether it is wireless or optical fiber or satellite or wireline, with regard to
corresponding hosts or service providers as well as have interconnectivity with other networks like GSM or
CDMA or other telecom networks.
18 Wireless Communications

1.6.2 Seamless Mobility

There is a powerful trend towards seamless mobility in the cellular world, where mobile professionals today
and eventually all users in the future would like to communicate and be able to do their routine business
anytime, anywhere. As a result, there is real demand for ubiquitous connectivity between a wide variety of
mobile devices and access technologies, which include WLANs and WWANs. Roaming and communica-
tions among these technologies are therefore must-haves for seamless mobility to occur.
The next-generation wireless networks intend to provide acces
Facts to Know !
to information anywhere, anytime, with a seamless connection
The future network infra- to a wide range of information and services, and receive a large
structures will consist of a set volume of information, data, images, video, and so on.
of various networks using IP To realise the potential of seamless mobility and ensure contin-
as a common protocol so that
ued profitability, wireless mobile service providers have to focus
users are in control to choose every appli-
cation and environment.
as equally on WLAN implementations as they do on their cellular
WWANs. Wi-Fi and other wireless services are add-ons that can
exist and succeed together and provide users what they want, and when they want it. Users will utilise these
technologies for different reasons and at different times. The 2.5G and 3G technologies such as GPRS, EDGE,
CDMA 1xRTT, and CDMA 1xEV-DO will be used for applications requiring instant access of bursty data like
e-mail, text messaging, and multimedia message service, among others. But WLANs will be used in specific
locations where users need access to their corporate files and Intranets.
One of the most important requirements of the 3G system is that it provides a seamless path of migration
from present-day digital wireless networks that it is capable of inter-working. All major providers of wireless
network systems, services and terminals agree that next-generation networks should evolve from the core
infrastructures contained in today’s digital networks. A comparison of key aspects of all generations of wire-
less and cellular network is depicted in Fig. 1.6.
Seamless mobility is the necessity as a result of extensive primary and secondary research on a variety of
industry participants including cellular service providers, Internet service providers, electronic component
manufacturers, equipment suppliers, and software providers. Technology drivers and obstacles that must be
addressed to achieve growth in the WLAN market such as roaming, security, seamless authentication, hand-
overs, and billing are equally important.
The handoff latency of many new access technologies such as wireless LAN devices is very large, of
the order of hundreds of milliseconds. During this period, mobile nodes cannot receive or transmit packets.

First generation Second generation Third generation Next generation

• n l • i i l • i i l • i i l
r nsmissi n r nsmissi n r nsmissi n r nsmissi n
• M inl s ee • M inl s ee • M inl s ee • M inl s ee
mm ni i n mm ni i n mm ni i n nd vide
mm ni i n
• i e nd • i i ld • n re sin
d di i l d • M inl di i l
• ir i
d
• ir i s i ed • n re sin l
s i ed e s i ed • M inl e
• l lr min
s i ed
• l s s ems • l lr min
• l lr min

Fig. 1.6 Comparison of cellular network generations

 Evolution of Wireless Communication Systems 19

This results in significant performance degradation during hand-off operation. Furthermore, while hand-
ing off across subnets, network layer hand-off can be initiated only after link layer hand-off is complete.
This increases the latency even further. Present cellular systems designed to handle mobility resolve the
latency issue by adding necessary interfaces and intelligence to the network. However, in the IP-based
architectures, the access technologies do not support the level of hand-off coordination that cellular sys-
tems provide. Though packets can be buffered in a local mobility agent and then retransmitted to eliminate
packet losses during hand-offs with some latency.
Based on the developing trends of mobile communication, next-generation wireless networks will have broader
bandwidth, higher data rate, and smoother and quicker hand-off and will focus on ensuring seamless service
across a multitude of wireless systems and networks. Seamless handoffs can be designed for homogeneous net-
works (IEEE 802.11 WLAN and cellular) at the MAC layer and with limited participation of the mobile node in
the decision. For IP to mobile node applications where there is a multiplicity of potential wireless access technolo-
gies, the requirement of functionality in the mobile node and wireless access router to facilitate seamless transfer
(network or mobile node initiated), and the need of Quality of Service (QoS), Authorisation/ Authentication/
Accounting (AAA), as well as the need of security infrastructure changes are to be established.

1.6.3 Wireless Data Communications Technologies

As new wireless communications technologies are introduced, they will become even more integral to our
day-to-day requirements and will continue to change how we live. Wireless data communications technolo-
gies include cellular, wireless LAN, wireless MAN, Bluetooth, RFID, and satellite. Table 1.5 summarises the
key features of various wireless data communications technologies.

Table 1.5 Summary of wireless data communications technologies

S. No. Wireless technology Data speed Radio coverage

1. 2G digital cellular 10 kbps Nationwide through roaming

2. 2.5G digital cellular Up to 384 kbps Nationwide through roaming
3. 3G digital cellular Up to 2 Mbps Nationwide through roaming
4. WLAN 802.11b 11 Mbps Building/campus, 100–120 metres
5. WLAN 802.11g 54 Mbps Building/campus, 90 metres
6. WMAN 802.16 WiMax 75 Mbps Metro city area, 56 kilometres
7. Bluetooth 1 Mbps Room/house, within 10 metres
8. Ultra Wide Band (UWB) 100 Mbps Auditorium, 50 metres
9. RFID Few kbps Small area within a store room, 2.5 cm to 100 m
10. GPS and satellites 250 ms delay Worldwide global

Figure 1.7 illustrates a pictorial view of comparing the capabilities of these wireless data communication
technologies in terms of data speed and range.
Users are constantly demanding more functionality from their computers and laptops, and, as a result,
wireless devices such as cellular phones, personal digital assistants (PDAs), and Smartphones are being com-
bined into a single digital wireless device. Wireless networks play an important role in digital convergence as
users demand to be connected to their voice and data networks at all times at any place. Digital convergence
refers to the power of digital devices such as computers and mobile phones to combine voice, video, and text-
processing capabilities, as well as to be connected to home and business networks and to the Internet. In the
20 Wireless Communications

elli e P

2 /2.5 /3 ell l r ne/d

iM 02.1

02.11

l e

0 100 m e 50 m e s nd ever l
m m s nds
m

Fig. 1.7 Comparative capabilities of wireless data communication technologies

same way, the development of Voice over IP networks use the same protocols and both wired and wireless
media to carry voice conversations as well as data.
The future wireless technologies will see more and more mobile devices, the merging of classical voice and
data-transmission technologies, and the extension of today’s Internet applications onto mobile and wireless
devices. New applications and new wireless mobile networks will bring ubiquitous multimedia computing to
the common user; PDAs, wireless laptops and mobile phones will converge and many different functions will
be available on one device, operating on top of Internet technologies. Figure 1.8 depicts the pictorial view of
a typical fixed wireless network.

Fig. 1.8 A typical fixed wireless network

The next-generation wireless network promises to fulfill the goal of PCC (Personal Computing and
Communication), a vision that affordably provides high data rates seamlessly over a wireless network.
Seamless mobility in wireless networks intends to integrate, from satellite broadband to high-altitude plat-
forms to 3G cellular and 3G systems to WLL and Fixed Wireless Access to WLAN and WPAN, all with IP
 Evolution of Wireless Communication Systems 21

as the integrating mechanism. With this, a range of new services and models will be available. In addition,
next-generation wireless networks will be fully IP-based wireless Internet. Future mobile communication
systems will certainly and surely achieve the concept of a Global Village’. Both, the recent and short-term
future advances in wireless standards and technologies discussed in this book will enable an ever-wider range
of applications for wireless devices.

1.7 APPLICATIONS OF WIRELESS COMMUNICATIONS

Today, more and more people use mobile phones than traditional fixed telephones. These trends create ever-
increasing requirements for well-educated qualified telecom engineers and technocrats who understand the
developments and possibilities of wireless and mobile communications. Cellular communication systems
mainly rely on judicious frequency reuse planning and multiple access techniques to maximise system capac-
ity. Cellular systems have evolved from analog techniques to the more flexible advanced digital techniques
that are currently employed. Future developments are aimed at further enhancing these digital techniques to
integrate voice, messaging, and high-speed data.
Wireless networks can be made available where Facts to Know !
regular wired networks cannot. Wireless applications,
The most widely used wireless com-
the use of wireless communications technologies in munication systems can be broadly
conducting day-to-day business activities, can be found categorised into various distinct
in every industry. Different standards for these systems classes depending on their popu-
have been developed for operation in different regions lar application such as Paging and Messaging
of the world such as North America, Europe, and Japan Systems, Cellular Telephone Systems, Cordless
at the same time. Telephone Systems, Wireless Local Loop, Wireless
The eventual goal of personal communication LAN, Wireless PAN and many others.
systems is to allow each individual user to have one
personal mobile phone and phone number which will take the place of home, office, vehicle, and
portable handheld phones. The third-generation personal cellular systems feature higher maximum
data rates, greater capacity for voice calls, and the ability to work with a wide range of cell sizes and
types. It is more standardised than the second generation. Technologically, the increased capacity is
achieved by using extra spectrum and new modulation techniques such as 8-PSK and spread-spectrum
that squeeze higher data rates from a given spectrum. The 3G standards are backward compatible so
that mobile phones can maintain a connection while moving between cells based on the earlier and the
new technologies. Global roaming will be possible with special multimode mobile phones. A fourth-
generation (4G) or next-generation network, with data rates of 150 Mbps and more, is already under
development.
The main areas of wireless applications can be broadly categorised as follows.
Office and Household Environments Typically, an office space is wired with computer cables for network con-
nections and telephone wires for telephones. With wireless technologies such as WLAN and Bluetooth, that
expensive cabling infrastructure is no longer necessary. This means that an office can be created in a very short
period of time with minimum down time and infrastructure at almost no additional cost. During office renova-
tions or reorganisation, employees can move to another location in the building and can continue working as
usual with immediate access to the wireless network. In addition to the accessibility of networked data, wireless
technologies allow businesses to create an office where the traditional infrastructure doesn’t already exist.
In the construction industry, instant information from the job site including shortage of
Industrial Control
man power or materials, could be relayed back to the main office for rescheduling of workers to other sites
22 Wireless Communications

Facts to Know ! to prevent idle time. Construction equipment such

as bulldozers and earth graders are fitted with wire-
As an example, a hotel conference room
less terminals and GPS which can provide accurate
that may not have the infrastructure to
support a wired network can quickly be
location information on a colour-coded map to guide
turned into a wireless networked office the operator as it digs. Implementing wireless tech-
environment. Wireless-enabled devices have the abil- nology is a key feature for many warehouse opera-
ity to control lights, air conditioners, refrigerators, and tions. By equipping all of the warehouse’s machinery
other household appliances. and personnel with wireless networking devices,
managers can use warehouse management system
Facts to Know ! (WMS) software to manage all of the activities from
receiving through shipping. And since this network
Smart equipment can be connected is connected into the front office computer system,
through wireless transmissions back to managers can have current stock statistics.
the remote office, which tracks engine
Many large suppliers implement RFID in all the
hours and equipment location. Wireless
terminals in the engine’s diagnostic system can send products and some highly sophisticated warehouses
an alert when the oil needs to be changed or other are operating with fully automated pallet machines
maintenance operations are due. and forklifts that can process the storing and retriev-
ing of products completely without human interven-
tion. Because of their huge size and complexity, large manufacturing facilities, such as automotive assembly
plants, are using wireless remote sensors called motes connected to a WLAN, which collect data and transmit it
to a central location. Technicians in a control room can monitor the status of every machine or device and take
corrective measures.
Education Sector Nowadays, most of the university and college campuses are equipped with Wi-Fi technology.
The instructors and students carry their notebooks and laptops with in-built wireless devices. They can access
the campus network wirelessly from almost any location on the campus. This wireless education model makes
computing resources available to students from anywhere (including hostel, cafeteria) and at any time. An instruc-
tor can create a classroom presentation on the notebook computer at his place and then carry it right into the
classroom or lab. Without the need to plug or unplug any cables to connect to the campus computer network, the
notebook automatically gets connected to the classroom network. Teachers can also distribute handouts directly to
students who have brought their own wireless devices to class. Wireless technology translates into cost savings for
university and colleges as well. There is no need to have traditional classrooms or computer labs with expensive
wiring and infrastructure.
Health Services Even telephones are connected to hospital WLANs, employing VoIP technology. Doctors
and nurses no longer have to be paged over the public address system. Doctors can also consult with spe-
cialists (located somewhere else) while they are at a patient’s bedside. Cellular phones cannot be used in
health-care facilities, but handsets that can connect to WLAN and use VoIP are allowed, and these improve
efficiency of health care services in hospitals. Notebook computers on mobile carts or handheld PDAs with
bar code scanners or RFID tags and a wireless connection enable doctors and nurses on duty to document
a patient’s medication administration immediately in the computer as they move from one place to another
place. Nurses first identify themselves to the computer system by scanning their own personal bar-coded ID
badge. The patient’s bar-coded armband is then scanned and all medications that are currently due for that
particular patient are brought up on the screen. The medications to be administered are sealed in bar-coded
pouches. Nurses scan RFID tags before opening the package. An alert immediately appears on the screen if
the wrong medication or incorrect dose is identified. After administration, the nurse indicates through the
wireless network that the medication has been given, essentially electronically signing the distribution form.
 Evolution of Wireless Communication Systems 23

All hospital personnel have real-time access to the latest Facts to Know !
medication and patient status information from their place
Wireless point-of-care computer
of work.
systems installed in medical care
Government and Military Operations Government offices centres and hospitals allow medi-
deploy a broadband wireless network to enable their cal staff to access and update
employees and contractors at remote construction sites to patient records immediately. Select medical
groups provide their physicians with a PDA,
access data stored in a central database. Police officers can
printer, and prescription-writing software. This
both download and upload streaming video to help them technology is intended to reduce errors associ-
tackle road accidents and crime. Wireless technology is ated with illegible handwritten prescriptions.
being used to provide free Internet access to visitors and
business people in public places. Using cellular and satellite communications, military personnel can talk,
access the Internet, and receive full-motion video through their wireless handset. They can also connect with
other wireless devices using the Bluetooth wireless protocol, or to a WLAN for numerous defense applica-
tions in the field.
Event and Travel Management Several large public auditoriums, arenas and sports stadiums are now
equipped with wireless systems to facilitate the process of distribution of valid tickets and overall control
of events. Entry tickets are printed with a unique RFID tag that is scanned at the venue’s point of entry
using a handheld or integrated wireless device connected to a wireless network. The network instantly
validates the ticket and thus prevents the use of counterfeit or stolen tickets. In addition, wireless tech-
nologies are changing the latest information and entertainment experience itself. For example, wireless
transmissions of in-progress game statistics are available to any one in the stadium with a wireless device
such as a notebook computer or PDA. Because wireless technology creates mobility, the travel industry
makes use of its advantages to plan and manage the itinerary. Wireless global positioning systems (GPS)
that tie into emergency roadside assistance services have become standard features. Airport terminals
transmit wireless signals that passengers can pick up on their wireless notebook computers or PDAs while
waiting for their flights. For a nominal fee, they can also surf the Internet or read their e-mail. Even the
airplanes themselves are being equipped with wireless data access, offering wireless Internet capabilities
to passengers on flights.
Home Entertainment FM radio, TV, and satellite radio serves the common man for news and entertainment
services uninterrupted day and night using wireless communications. Several large computer manufacturers
have introduced specialised media PCs that enable audio and movie enthusiasts to download, distribute, and
control all forms of digital entertainment from anywhere. These PCs are equipped with wireless networking
hardware and software to simplify the processing of sound, video, and pictures. One can send music, movies,
or pictures to a stereo receiver, portable device, or PC located anywhere in the building. The files can be
downloaded to digital media portable devices, such as MP3 and video players that can be used while roaming
anywhere.
Facts to Know !
Environmental and Industrial Research Scientists Third-generation (3G) cellular mobile
are now using small, battery- or solar-cell-powered communications systems are critical to
WLAN transmitter-equipped wireless smart sensors the wireless Internet services, offering
in difficult places such as deep caves or on mountain permanent access to the Web, interactive
tops or at the tops of tall trees to monitor the effects video, and voice quality that sounds more like a CD
on dense forests caused by ultraviolet rays due to player than a normal cell phone. 3G systems provide
the holes in the ozone layer. The data recorders can ISDN speeds for everyone, equipped with the nor-
mally used mobile phones anywhere.
be installed in electric power- or generator-operated
24 Wireless Communications

Facts to Know ! nearby locations, and can communicate with the

sensors using wireless technology. This capability
Wireless wide area networks will enable has proven to be a major breakthrough in many dif-
companies of all sizes to interconnect their ferent scientific fields and research. Wireless sen-
offices without the high cost charged by sors are capable of communicating using wireless
telephone carriers for their landline con-
technologies, and are widely used in large manufac-
nections. WLAN applications are found in a wide variety
of industries and organisations turing facilities to monitor equipment and for scien-
tific research.

1.8 POTENTIAL MARKET AREAS

The market for mobile telephones for person-to-person communication has grown rapidly across the globe.
One of the major growth areas for wireless mobile communications is referred to as Machine-to-Machine,
or Man-to-Machine (M2M) communications over cellular radio networks. Wireless communications devices
are integrated within other equipments and are used in many different telemetry applications for making
Short Message Service (SMS) calls or automatically sending data and voice messages to a control centre.
For example, they are being integrated in automobiles, fleet management systems, fire and security alarms,
vending machines, public utility meters and other industrial equipment. Software upgradations have also
been made to allow the seamless transport of data and information. The wireless devices are being built into
host appliances, and controlled through a computerised link.
Wireless communications devices will increasingly be built into a wide variety of equipment, includ-
ing domestic appliances, industrial machinery, metering equipment and all kinds of vehicles, and will soon
be integrated in microchips. Water, electricity and gas meters are already being read digitally and reported
automatically by wireless communication. There are houses, or business premises, where a break-in or fire is
reported to the authorities without human intervention. Vehicles are being developed which not only call for
help automatically after an accident, but which can also identify with pinpoint accuracy where they are, and
even give some information about what type of incident has occurred.
Figure 1.9 depicts the potential usage of a variety of common applications and the related data-rate require-
ment from the wireless technology.
Wireless communications devices will thus automate a wide range of existing functions and will stimulate
the development of many others, which may be beyond imagination as on today. This market is potentially
significantly larger than the person-to-person wireless market. The challenge of marketing M2M technology
is its more-or-less unlimited applications, the only boundary being human imagination. The potential for
wireless device communication could be summed up in the concept of at least one device per house, and one
device per vehicle.
Similarly, a single utility or security company or the builder may provide the first device to the household or
other premises, and automotive manufacturers may supply a single device to a vehicle for a dedicated purpose.
Once this device is in place, it can then be used for a variety of different purposes, and customers will come
to expect more and more communication systems to be channeled through a wireless device. Many domestic
appliances, such as refrigerators, will be routinely equipped with
Facts to Know ! them. These devices will report, probably via a LAN network, to
a central gateway device, which will provide the link between the
In principle, all communication dedicated and the public wireless network.
systems could be channeled
As regards the size of this potential market; a tenfold growth
through the wireless device,
both for home and for vehicle in vehicles is probable worldwide over the next decade, to a total
of 500 million vehicles, with an annual increase of 50 million.
 Evolution of Wireless Communication Systems 25

ex + im e
M mess in M l imedi
ex nl
em e i e

e li in r e ile
r ns er

ireless M l imedi
s rd mess es
M ile
n in mmer e m in
n er ive mes nd
en er inmen
redi rd
veri i i n imi ed r d s
vide

10 kbps 14.4 kbps 44-64 kbps 144 kbps 384 kbps 2 Mbps

Fig. 1.9 Potential market areas versus data-rate requirement

In addition, there are millions of households, vending Facts to Know !

machines, alarms and elevators; each of these has a
potential need for wireless communication. On top The scope for wireless devices is even
greater in the business-to-business world,
of this, there are all types of metering systems, plus
than for these domestic applications, and
many other types of equipment in which the device applications such as fleet management,
has applications. In conjunction with the development remote diagnostics, vending, monitoring of servers,
of this technology, there will be emergence of new etc., and will grow faster and be more significant.
multi-service providers; organisations or businesses
which will act as intermediaries to households in supplying electronic services by wireless communication,
including many forms of entertainment, Internet access, telephone services, security systems and utility
services. There can be mergers between media–entertainment and telecommunications companies and the
emergence of multi-utilities’ companies which provide gas, water and electricity services.
Key Marketing Issues Two developments are key to unleashing the potential of the wireless–device market.
First, decreases in air-time costs on public networks and, second, increases in their bandwidth, to enable a
much broader range of communication services to be delivered via the public wireless channel. There are also
a number of secondary issues concerning standards, reliability, privacy and legal requirements.
Reliability/Signal Quality Several of the potential wireless-device applications will require greater bandwidth
than is currently available via public networks. These bottlenecks will, however, soon be overcome by new
generations of devices and wider bandwidth standards which are currently being developed. The increasing use
of wireless communication for all types of emergency alarm systems will obviously put greater demands on
its reliability as a communications channel. Standards and roaming are also important issues in the automotive
and fleet-management markets.
Privacy/Security The increasing use of wireless communications raises the question of privacy, both
for individuals and for companies. For instance, making the location of people and vehicles traceable by
26 Wireless Communications

unauthorized third parties can clearly be regarded as undesirable. On the other hand, the growing use of digital
signals in itself significantly reduces the possibility of breach in privacy. If the privacy issue is considered
absolutely critical, then encryption is always a possibility. However, information will always be accessible to
the authorised personnel who operate these systems. Ultimately, they have to be trusted not to disclose this
information in illegitimate ways.

1.8.1 Target Business Areas

(a) The Automotive Industry Market The potential for wireless communication in vehicles includes entertain-
ment systems, climate control, mechanical status reports to dealers or vehicle maintenance centres, satellite navi-
gation via GPS (Global Positioning Systems); traffic information including map guidance and advice on traffic
congestion, etc. There are other possibilities such as immediate accident reporting using the triggering of airbags
to signal an alert to the emergency services, to provide an exact location using GPS; seat sensors could provide
the number of passengers, and the details of which airbags have been triggered could provide some information
about the type of accident, for example, whether it was a head-on collision. At present, similar products are being
developed for the high end of the automobile market, and soon they could become standard specification.
(b) The Fleet Management/Vehicle Positioning Market For this application, each vehicle in a fleet will be equipped
with a wireless device capable of checking the vehicle’s position, monitoring and reporting for security including
alarms, and as a backup for the driver’s mobile phone. The device can also be used for vehicle diagnostics.

Facts to Know ! (c) The Utilities MarketIn this market, wireless devices will
be used for remote metering of the consumption of the various
The major market driver in
utilities––gas, electricity and water. Other applications in the
this industry is the increas-
ing introduction of deregu-
utilities business area include infrastructure monitoring, involving
lation, privatisation, and observation and reporting from water-pumping stations, electricity-
opening up to competition. distribution sub-stations, and remote switchgear, as well as service
and maintenance functions. The issue of billing and charging
becomes very important, with the opportunity to change rapidly between suppliers.
(d) The Security Systems Market This market can be categorised in two sectors. The auto alarm sector involves the
retrofitting for alarms, fitted into vehicles after they have been manufactured and sold. The household and building
sector covers building alarms for households, commercial premises of various types, and other buildings. Security
companies are interested in wireless communication because they provide a more secure alarm-reporting system,
given that physical landlines can be cut or damaged and, secondly, it involves much less installation cost.

Facts to Know ! (e) Vending Machines The potential for this market
may include the vending-machine manufacturers,
As an example, if a household has a wire-
the makers of the coin systems for the machines, the
less communication device in it, many
other opportunities are opened up; the
vending operators and the owners of the point of sale.
device can be used for many other appli- Installing a wireless device in a vending machine offers
cations including monitoring the well-being of elderly a large number of benefits, such as it enables enormous
people. This is a step towards the concept of an ‘intel- price flexibility. For example, offers on certain items
ligent house’. can be made automatically and remotely depending on
the local competition for a particular machine. Other
payment options can be introduced, for example, ‘micro-payments’––people could order and pay for goods from a
vending machine via their mobile phone. Such payments could be added to their mobile phone bill.
In addition, the wireless device can provide an enormous database, giving rich and accurate
information on the usage of each machine. This data can be used to optimise the positions of machines,
 Evolution of Wireless Communication Systems 27

the distances between machines and the stock each Facts to Know !
one contains. The manufacturer would need to form
a partnership with an application-service provider Just as the number of different wire-
less devices are on a tremendous
who would manage this specific communication
increase, so is the number of job
service for vending machines. The manufacturer opportunities for professionals, wire-
would then sell or lease the wireless device and other less engineers, wireless network managers, and
equipment, to the machine operators. There is a need wireless technical support personnel to build and
to recruit and coordinate the activities of several other support the ever-growing wireless communica-
players including a telecom operator, access provider, tion technology.
a content and application provider to support the
service, plus an Internet payment provider to manage the financial transactions, leading to a combined
Wireless Application Service Provider (WASP) to be the entrepreneur.

1.9 CHALLENGES FOR RESEARCH

Wireless communications has been one of the major technological areas for research as well as industrial appli-
cations. The world of wireless communications has come of age where true wireless multimedia services can
be offered to highly mobile subscribers seamlessly on a global arena. Future wireless communication networks
are expected to support diverse IP multimedia applications to allow sharing of common resources among
diverse subscribers. Mobility is the most important feature of a cellular wireless communication system. The
potential users of wireless telecommunication systems require establishing voice as well as data communica-
tion with other users while on the move. This results into the deployment of mobile communication systems to
cover large geographic regions. There has been a tremendous growth rate in wireless mobile communication
systems and networks in recent times, mainly due to increasing mobility awareness among people.
While traditional communication paradigms deal with fixed wireline or wireless networks, mobility raises
a new set of wireless communication techniques, complexity, challenges and solutions. Due to the lack of an
appropriate fixed communication infrastructure in many countries, mobile communication is the only viable
alternative.
Cellular communication systems mainly rely on judicious frequency reuse planning and multiple access
techniques to maximise system capacity. Cellular systems have evolved from analog techniques to the more
flexible and advanced digital techniques that are currently employed. Future developments are aimed at
further enhancing these digital techniques to integrate voice, messaging, and high-speed data. The rapid
advancements in the field of VLSI hardware technology as well as embedded software have paved the way
for reliable mobile communication systems.
Building on these current developments, the communications industry is developing a strategic vision of
the next generation of digital mobile systems. Details of future service concepts and of future user require-
ments need to be addressed in order to formulate regulatory, frequency and standardisation responses at the
global level.
The information and communication technologies industries are a critical component of the world econ-
omy in that they are a major and growing part of industrial activity. They are also one of the keys to future
competitiveness of industrial processes, products and services and a platform for the emerging Information
Society. There are two major challenges that need to be addressed—meeting the changing user needs for
mobile services; and further developing the conditions for industrial competitiveness within the mobile com-
munications sector. Achieving these goals will be important not only for the telecommunications sector, but
also for the broader economy.
One of the major issues concerning fair market competition relates to the issue of roaming. At least in the
initial stages of deployment, UMTS systems may have to seek roaming arrangements with GSM networks
28 Wireless Communications

in order to provide a sufficient degree of national and international coverage. Being based on commercial
agreements between operators, the refusal to enter into roaming agreements with UMTS operators would
be a major deterrent to the use of UMTS systems. At a later stage, roaming will take on a new dimension as
different mobile and/or fixed service segments converge. This will require a careful monitoring of roaming
arrangements.
As the basic shape of UMTS or other third-generation systems emerges, ETSI is likely to continue to play
a central role in close cooperation with the UMTS Forum and other interested parties in determining the pre-
cise requirements for standardisation. GSM is a comprehensive and open standard allowing for the evolution
towards different service forms while maintaining the integrity of the GSM platform. To what extent such
an approach can be applied to the UMTS concept is an issue. It needs to be ensured that the development
of UMTS strikes the right balance between formal, open standardisation, and industry-developed de-facto
standards of a more proprietary nature which may often develop more at a pace commensurate with the rapid
life cycle of the information technologies and services which UMTS is likely to offer.

1.10 OUTLINE OF THE BOOK

The objective of this book is to provide a comprehensive technical overview of wireless communications,
with an emphasis on cellular communication principles and systems––one of the fastest growing technologi-
cal application areas in the telecom arena. The knowledge may lead towards convergence of wireless commu-
nication techniques, mobility, networking and information technologies. The various forms of wireless data
communications using cellular communications, wireless LAN, Bluetooth, fixed broadband, and wireless
WAN communications technologies are covered. The book is organised to provide fundamental treatment
about many theoretical and practical aspects that form the basis of wireless and cellular communications,
as well as emerging wireless networking technologies. Technical concepts which are at the core of design,
planning, evaluation, and inventions of cellular communication systems are presented in an order that is
conducive to understanding and grasping general concepts, as well as those specific to current and emerging
cellular systems standards and wireless networks. To accommodate a wide range of previously related techni-
cal knowledge levels, important concepts throughout the text are developed from the basic principles and well
supported with facts and examples.
Chapter 1: Evolution of Wireless Communication Systems An overview of historic evolution of wireless com-
munications, wireless network generations, and a wide range of applications of wireless data communica-
tions is provided. The chapter follows the way the industry is classifying wireless data communications today
and looks at the advantages and disadvantages of wireless data communications.
Chapter 2: Mobile Communication Engineering This chapter presents the fundamental theoretical concepts
of wave propagation in wireless media. The important aspects of mobile communication engineering such as
signal attenuation in wireless media, effects of multipath propagation on radio signals, small-signal fading
phenomenon including simulation of wireless fading channels are introduced.
Chapter 3: The Propagation Models This chapter covers various propagation path loss models under different
operating conditions such as free-space, mobile environment, and the signal attenuation due to foliage. The
impact on received signal strengths at the mobile receiver is well supported with easy-to-follow examples.
Chapter 4: Principles of Cellular CommunicationThis chapter deals with the principles of cellular radio com-
munications such as frequency reuse and cochannel interference, which are at the core of providing wireless
communication service to subscribers on the move using limited radio spectrum while maximising system
capacity. A detailed analysis of hexagonal-geometry based cellular structure including the cluster formation