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6
Future Trends: Fourth
Generation (4G) Systems and
Beyond
6.1 Introduction
By looking back to the history of wireless systems, one can reach the conclusion that the
industry follows a ten-year cycle. First generation systems were introduced in 1981 followed
by the deployment of second generation systems in 1991, ten years later. Moreover, third
generation systems are due for deployment in 2001–2002. From the point of view of services,
1G systems offered only voice services, 2G systems also offered support for a primitive type
of low-speed data services and 3G systems will enable a vast number of advanced voice and
high-speed data services. The trend is towards support for even advanced data services.
3G networks, although having the advantage of support for IP and enhanced mobility, will
suffer from a divergence between several standards. This divergence will limit easy roaming
between 3G networks based on different standards, thus limiting user mobility. Furthermore,
3G networks will have, in the best case, an upper capacity limit of 2 Mbps. Although more
than enough for the application demands of the years to come, 3G networks will most likely
need to evolve in order to meet the mobile application demands of the next decades. As in all
areas of technology, the quest for better and more efficient systems never ends and as soon as
the time for deployment of a system comes, research on the next generation is usually under
way. Consequently, the imminent deployment of 3G systems is accompanied by initiation of
research on the next generation of systems. If the ten-year cycle continues, it is logical to
expect that the next generation of wireless systems, known as Fourth Generation (4G), will
reach deployment stage somewhere around 2010.
As seen later in the chapter, the vision for 4G and future systems is towards unification of
various mobile and wireless networks. However, there is a fundamental difference between
wireless cellular and wireless data networks, such as WLANs. The difference is that cellular
systems are commonly circuit-switched, meaning that for a certain call, a connection estab-
lishment has to take place prior to the call. On the contrary, wireless data networks are packet-
switched. It is expected that the evolution of wireless networks towards an integrated system
will produce a common packet-switched (possibly IP-based) platform for wireless systems,

Wireless Networks. P. Nicopolitidis, M. S. Obaidat, G. I. Papadimitriou and A. S. Pomportsis
Copyright
¶ 2003 John Wiley & Sons, Ltd.
ISBN: 0-470-84529-5
thus enabling the ‘wireless Internet’. However, in order for such an integration to take place
research is needed in order to provide interoperability between wireless cellular networks and
wireless data networks. The envisioned unified platform for the next generations of wireless
networks will provide transparent integration with the wired networks and enable users to
seamlessly access multimedia contents such as voice, data and video, irrespective of the
access methods of the various wireless networks involved.
The next generations of wireless networks target the market of 2010 and beyond, aiming to
offer increased data rates with reports mentioning from 50 Mbps to 155 Mbps. In the course of
their development many different types of issues (technical, economical, etc.) must be studied
and resolved. Some of them, such as the development of even more efficient modulation
techniques, identification of new spectrum, and developments in battery technology/power
consumption, are quite straightforward and have been identified during 2G and 3G research
and development stages. Other issues are not so clear and are heavily dependent on the
evolution of the telecommunications market and society in general. These issues need to
be identified and resolved at the earliest possible stage in order to unsure market success for
4G and beyond wireless systems.
6.1.2 Scope of the Chapter
This chapter provides a vision of some of the characteristics of 4G and future systems.
Section 6.2 describes the design goals and corresponding research issues for 4G systems.
Section 6.3 presents a preliminary set of possible 4G service classes. Section 6.4 identifies the
challenge of predicting the future of wireless communications and provides three possible
scenarios for the future. Finally, the chapter ends with a brief summary in Section 6.5.
6.2 Design Goals for 4G and Beyond and Related Research Issues
Since 4G systems target the market of 2010 and beyond, there is time for 4G research and
standards development. So far, no 4G standard has been defined and only speculations have
been made regarding the structure and operation of 4G systems. The question to ask here is

what will be the desired advantages and new features of 4G systems over their predecessors.
Due to the fact that related research is under way, 4G is still an acronym without a generally
accepted meaning. However, research efforts [1–3] agree more or less on the following
targets:
† System interoperability. 4G and future systems should bring something that is missing
from their predecessors: flexible interoperability of the various kinds of existing wireless
networks, such as satellite, cellular wireless, WLAN, PAN and systems for wireless access
to the fixed network. Alternatively, this can be thought of as an ability to roam between
multiple wireless and mobile standards (e.g. moving from a cellular network to a WLAN
while maintaining connections). If the target of system interoperability is met, the whole
worldwide communications infrastructure will be turned into a transparent network allow-
ing users to use it independent of a specific access method. Due to the requirement for
interoperability of different mobile and wireless networks, a big challenge will be how to
access several different mobile and wireless networks through the same terminal. We can
identify the three possible configurations described below [3]:
Wireless Networks190
– Multimode terminals. This option provides for further development of older generation
systems and has also been applied in the past (e.g. dual AMPS-CDMA cellular phones).
It calls for a single terminal which is capable of accessing several different wireless
networks. This is obviously achieved by incorporating multiple interfaces to the term-
inal, one for the access method of every different kind of wireless network. The ability
to use many access methods will enable users to use a single device to access the 4G
network irrespective of the particular access method used. The option of multimode
terminals will offer increased coverage and reliable wireless access in the case of failure
of one or more networks in an area. Furthermore, the multimode terminal option lowers
the complexity of the fixed part of the network due to the fact that the additional
complexity is incorporated into the device [3].
– Overlay network. In this architecture users will access the 4G network through the
Access Points (APs) of an overlay network. Upon connection with a terminal, an AP
will select the wireless network to which the terminal will be connected. This choice

will be made based on user-defined choices, resource availability, QoS requirements,
etc. The AP will perform protocol translation and QoS negotiation for the connections.
Since APs can monitor the resources used by a user, this architecture supports single
billing and subscription.
– Common access protocol. This choice calls for use of one or two standard access
protocols by the wireless networks. A possible option is for the wireless networks to
use either ATM cells with additional headers or WATM cells.
† Terminal bandwidth and battery life. Terminals of next generation networks will be
characterized by a wide range of supported bandwidths, ranging from several kbps to
about 100 Mbps or beyond. The battery life of these devices is expected to be around one
week. This advance will be accompanied by reduction in the weight and volume of
batteries.
† Packet-switched fixed network. According to studies, the 4G architecture will use a
connectionless packet switching (possibly IP-based) fixed network to interconnect the
several different mobile and wireless networks.
† Varying quality of bandwidth for wireless access. The mixing and internetworking of
different networks on a common platform will provide a set of, possibly overlapping,
layers with different access technologies complementing each other. Depending on their
geographical location, users will be served by different layers and enjoy different qualities
of wireless access in terms of bandwidth. Possible layers will be [1]:
– Distribution layer. This will support digital video and broadcasting services at moder-
ate speeds over relatively large cells. This layer will support full coverage and mobility
and will cover sparsely populated rural areas.
– Cellular layer. This layer will comprise 2G and 3G systems. It will provide high
capacities in terms of users and data rates inside densely populated areas such as cities.
This layer will offer support for rates up to 2 Mbps. The cell size will obviously be
smaller than that used in the distribution layer. This layer will also support full coverage
and mobility.
– Hot-spot layer. This layer will support high-rate services over short ranges, like offices
or buildings. It will comprise WLAN systems, such as IEEE 802.11 and HIPERLAN.

Future Trends: Fourth Generation (4G) Systems and Beyond 191
This layer is not expected to provide full coverage, due to its short range, however,
roaming should be provided.
– Personal network layer. This layer will comprise very short-range wireless connec-
tions, such as Bluetooth. Due to the very short range, mobility will be limited, however,
roaming should also be provided in this layer.
– Fixed layer. This will comprise the fixed access systems, which will also be part of the
4G network of the future.
† Advanced base stations. Base stations of future generation networks will utilize smart
antennas to increase system capacity. Furthermore, base stations will employ self-config-
uring functionality in an effort to reduce operating costs. Finally, these devices will
obviously support a multitude of air interfaces in order to accommodate a wide range
of terminals.
† Higher data rates. 3G systems will have, in the best case, an upper capacity limit of 2
Mbps. Although more than enough for the application demands of the years to come, 3G
systems will most likely need to evolve in order to meet the mobile application demands of
the next decades. 4G systems aim to provide support for such applications. Although there
exists some vagueness regarding the maximum number for data rates of 4G systems, with
reports mentioning from 50 Mbps [3,4] to 155 Mbps [2], 4G systems will surely offer
significantly higher speeds than 3G systems.
In order to support the higher data rates new air interfaces will obviously be introduced. An
ideal air interface should be spectrum efficient and provide the flexibility to offer different bit
rates. Furthermore, such an interface should be resistant to frequency-selective fading and
require little equalization; Orthogonal Frequency Division Multiplexing (OFDM) is an air
interface that can meet such requirements and is expected to be greatly used in the wireless
systems of tomorrow. It is described in the next subsection.
6.2.1 Orthogonal Frequency Division Multiplexing (OFDM)
Orthogonal Frequency Division Multiplexing (OFDM) is a form of multicarrier modulation,
which splits the message to be transmitted into a number of parts. The available spectrum is
also split into a large number of low-rate carriers and the parts of the message are simulta-

neously transmitted over a large number of low-rate frequency channels. By recalling that (a)
the phenomenon that dominates the error behavior of wireless channels is fading; (b) fading is
frequency-selective; and (c) delay spread must be very long to cause significant interference
to a carrier, one can realize the inherent robustness of OFDM to fading. Thus, by splitting a
message into parts and slowly sending (due to low-carrier bandwidths) these parts in parallel
over a number of low-rate carriers, signal reflections due to multipath propagation will
probably be late at the receiver only by a small amount of a bit time. This, together with
the fact that overall message transmission is made over a large number of low-rate carriers in
the same time, results in a high-capacity, multipath-resistant link.
OFDM resembles FDMA in that they both split the available bandwidth into a number of
carriers. The obvious difference of course is that FDMA is a multiple access technique
whereas OFDM is a form of multicarrier transmission. Another difference concerns effi-
ciency: FDMA is inefficient in terms of spectrum utilization, since it wastes a significant
amount of bandwidth as guard interval between neighboring channels in order to ensure that
Wireless Networks192
they do not interfere with one another. This bandwidth overhead allows signals from neigh-
boring channels to be filtered out correctly at the receiver. TDMA systems which allow a
single user to utilize the entire channel capacity for a specific time period are also subject to a
bandwidth overhead since TDMA systems need to be synchronized. As a result, guard time
periods occur at the beginning of each user’s slot in order to compensate for synchronization
problems between stations. Thus, TDMA systems also waste some bandwidth to ensure their
proper operation.
Such bandwidth overheads are not desirable in future generations of wireless systems. This
is because spectrum is expected to be a scarce resource, and given a certain amount of
spectrum this will need to be utilized to the highest extent possible in order to accommodate
as many users as possible. OFDM tries to solve this problem by significantly reducing the
amount of wasted spectrum by dividing the message to be transmitted into a number of
frequency carriers and spacing these carriers very close to each other. In order to ensure
that OFDM carriers do not interfere, they are made orthogonal to one another. Orthogonality
ensures that although carriers are very close in frequency and their spectra overlap, messages

in different carriers do not interfere with one another since detection for one carrier is made at
the point where all other carriers are null.
In an OFDM system, detection is performed in the frequency domain. The actual signal
transmission, however, occurs in the time domain. To better understand this, Figure 6.1
illustrates the operation of a simple OFDM system. As can be seen, OFDM transmission/
reception comprises the following states:
† Transmitter: serial to parallel conversion. The data stream to be transmitted takes the
form of the word size required for transmission. For instance, if QPSK is used, the stream
is split into data words of two bits each. Then each data word is assigned to a different
carrier.
† Transmitter: modulation of each carrier. The data word that forms the input of each carrier
is modulated.
† Transmitter: Inverse Fourier Transform (IFT). After the actual contents of the various
frequency carriers have been defined, the contents of these carriers form the input to an
IFT in order to obtain a representation of the OFDM signal in the time domain. The IFT
can be performed using the Fast Fourier Transform (FFT), which nowadays can be imple-
mented at low cost.
† Transmitter: Digital to Analog Conversion (DAC). The output of the IFT is converted into
an analog form suitable for radio transmission.
† Receiver. In order to receive the message, the receiver performs the reverse operation to
Future Trends: Fourth Generation (4G) Systems and Beyond 193
Figure 6.1 A simple OFDM system
the transmitter. It digitizes the received signal (the ADC box in Figure 6.1) and performs
an FFT on the received signal in order to obtain its representation in the frequency domain.
The output of this is the actual content of the carriers, which are then demodulated in order
to obtain the data words transmitted in each carrier. The data words are then combined to
produce the original message.
One can realize from the above discussion that before OFDM modulation the data on each
carrier is considered to be in the frequency domain. Figure 6.2 shows the various carriers of
an OFDM transmission. The spectrum of each OFDM carrier has a sin(x)/x form and is

modulated at a certain symbol rate. For the purposes of this discussion we assume l ¼ 1
kHz symbol rate. Assuming that the main lobe of the signal on the first carrier is at k kHz, this
signal will have the first null at k 1 l,with subsequent nulls occurring every lkHz. If we
modulate the second carrier at a frequency exactly l kHz (the symbol rate) higher than the
first using the same symbol rate, the mail lobe of the second carrier occurs at a null of the first
one. Using this approach, the main lobe of each carrier occurs at nulls of the other carriers.
Thus, at the point of detection there is no interference from any other carriers.
In an effort to increase the robustness of each carrier to inter-symbol interference (ISI)
caused by multipath propagation, the transmitted symbols can be prolonged by adding a
guard interval between successive symbol transmissions. The existence of a guard interval
allows for delayed components of a symbol’s transmission to reach the receiver before the
energy of the next symbol is received. The actual content of the guard interval is produced by
repeating the ‘tail’ of the symbol and placing that tail before the actual symbol transmission.
Provided that delayed echoes of a signal carrying a symbol k are within the guard interval,
multipath propagation does not affect detection of the next symbol, k 1 1. However, by
preceding the useful part of the symbol’s transmission time by the guard interval, we lose
some bandwidth that cannot be used for transmitting information. Figure 6.3 illustrates the
transmission of OFDM symbols in the time domain with use of guard intervals. The arrows in
cases ‘a’ to ‘c’ represent the energy of symbol 2 at the receiver, in the time domain. In case
‘a’, there is obviously no intersymbol interference, thus decoding of symbol 3 produces the
correct symbol. Decoding is also successful in case ‘b’, where delayed echoes of symbol 2
Wireless Networks194
Figure 6.2 Detection of OFDM symbols
overlap with the guard interval of symbol 3. However, in case ‘c’, decoding of symbol 3 will
be affected by intersymbol interference since echoes of symbol 2 overlap in time with symbol
3.
Variants of OFDM also exist. COFDM stands for Coded OFDM. COFDM enables further
resistance to errors due to fading. This is due to the fact that a carrier suffering one or more bit
errors can be corrected by the error-correcting code which is transmitted on a different carrier,
which may be error-free since fading is frequency selective. However, since coding for error

correction is used in most of today’s OFDM systems, the ‘C’ is redundant. Wideband OFDM
(WOFDM) is a variant of OFDM where the spacing between carriers is wider in an effort to
alleviate the problem of frequency errors between a transmitter and a receiver. The larger
spacing ensures that such an error falls in the spacing and thus have a negligible effect on the
performance of the system. Thus, an offset occurring at a transmitter will be perceived by the
receiver only as a sampling error, which can be tolerated.
6.3 4G Services and Applications
The applications and service classes that will dominate the 4G-market are not yet known,
however, some trends are emerging from ongoing research [5–8]. A nonexhaustive but
indicative list of service classes is as follows:
† Tele-presence. This class will support applications that use full stimulation of all senses to
provide users with the illusion of actually being in a specific place. These will be real-time
virtual reality services and will offer virtual meetings, an evolution of today’s teleconfer-
encing applications. The conference attendants, although in different places, will have the
illusion of participating in a conference in the very same room. Such applications, coupled
with efficient compression techniques, will require capacities in the order of 100 Mbps.
Furthermore, extremely strict delays and QoS levels will be demanded due to the real-time
nature of these applications. The concept of a virtual meeting will be one of the major
applications foreseen in 4G and future systems.
† Information access. This class will call for the ability of instantaneous access to large
volumes of data such as large video and audio files. Compared to tele-presence, such
Future Trends: Fourth Generation (4G) Systems and Beyond 195
Figure 6.3 Adding a guard interval to transmitted symbols
applications will be less delay sensitive, since real-time delivery of data is not needed here.
As far as data rates are concerned, this class will demand the highest rates possible.
However, the traffic pattern will probably be asymmetrical, with 50/1 ratios or more
characterizing the downlink/uplink data rate ratio.
† Inter-machine communication. This service class will offer devices the ability to commu-
nicate with one another either for maintenance or for intelligence purposes. An example
application of this type is car engine equipment that contains wireless interfaces enabling

parts to contact the respective vendors when malfunctions occur.
† Intelligent shopping. This will offer users access to information regarding prices and
products offered by shops they visit. Upon entering a shop, the user terminals will auto-
matically tune to the shop’s service providers and display information regarding the
products sold by the shop.
† Security. Secure services will be an indispensable feature of the future generations of
networks. Integrity of data is bound to be a crucial factor that will enable the proliferation
of banking and electronic payment applications. Furthermore, security services will
protect the privacy of users’ personal information.
† Location-based services. It is envisioned that 4G and future systems will have the ability to
determine the location of users with a high level of accuracy. This cannot be made true
with today’s systems which can only report the cell servicing the user, thus being accurate
to within a few city blocks at best. Emergency applications will greatly benefit from
location-based services. For example, if a person with a health problem calls an ambulance
from his handset but is unable to report his location to the operator, his position can be
determined with high accuracy by querying the user’s handset for its location.
6.4 Challenges: Predicting the Future of Wireless Systems
In the course of research on 4G and future systems many issues of different types (technical,
economical, etc.) must be studied and resolved. Some, such as the development of even more
efficient modulation techniques, identification of new spectrum, and developments in battery
technology/power consumption, are quite straightforward and have been identified during 2G
and 3G research and development stages. Other issues are not so clear and are dependent on
the evolution of the telecommunications market and society in general. Although the aim of
4G research will obviously be towards better performance, certain aspects of the telecom-
munications market and society’s perception of communications may significantly influence
the market penetration of products for the next generation of mobile and wireless networks.
As already mentioned, 4G and future systems target the market of 2010 and beyond. Since
we cannot reliably foresee the state of telecommunications and society after such a time
period, it is practical to study possible evolution scenarios in order to identify issues that may
impact the future market for such systems and thus affect the related research. Three such

scenarios have been identified [5–8]. In the remainder of this section, we provide a short
overview of the concepts of these scenarios, how these three scenarios were created and
finally present the three scenarios.
Wireless Networks196
6.4.1 Scenarios: Visions of the Future
The concept of scenarios as tools for prediction future situations was first used after World
War II to evaluate the significance of development in various technological areas. In order to
keep up with the increasing pace of development, the two superpowers needed to set certain
priorities. The problem was which priorities to set. A possible solution was to spy on the other
side, understand its priorities and act accordingly. The other option was to act independently
by predicting the developments and set priorities according to the predictions. Since a single
prediction is not accurate, more than one possible prediction for the future was preferable in
order to prepare for more than one different alternative situation. Each of these different
predictions is called a scenario.
Scenarios are basically stories that express assumptions about the future. These assump-
tions are the result of different individuals’ and groups’ beliefs about the future. Scenarios are
usually produced by posing specific questionnaires to, possibly, specialized groups of people.
The individual opinions combine to produce a set of trends for the future. By identifying the
trends that are sure to play an important role in the future and varying the relative impact of
other trends, several scenarios are produced.
Scenarios are useful in cases where limited knowledge on a future situation exists,
however, a decision regarding the situation has to be made. There are, of course, inherent
vulnerabilities of the scenario-based approach: one cannot predict what will really happen,
but only speculate based on present situations. Furthermore, in the process of identifying the
trends that make up the scenarios, several factors that influence the situation might be over-
looked or misinterpreted. Furthermore, as we approach the time of the situation under study,
visions on the situation may change and thus some trends may vanish and new ones may
appear.
6.4.2 Trends for Next-generation Wireless Networks
In the process of the research mentioned in Ref. [8], several trends regarding next generation

wireless networks (2010 and beyond) were identified. These are briefly summarized below:
† Globalization of products, services and companies. Globalization has affected peoples’
lives ever since the time ancient civilizations started to come in contact with each other.
However, globalization show a surge with the invention of television, Internet and tele-
communications in general. According to the survey, the impact of globalization will
continue to exist and will surely affect the telecommunications scene of the future.
† Communicating appliances. This trend states that future consumer devices, such as TV
sets, videos and stereos, will employ ‘intelligence’. Although this is also true for the
present, future consumer devices are expected to make certain kinds of decisions on
their own and have the necessary equipment to communicate with other devices.
† Services become more independent of the underlying infrastructure. This trend states that
future services are expected to be more separated from the infrastructure they use. This
will enable many different devices to use the same network infrastructure.
† Information trading/overflow. Communications in the society of the future will be an
integral part of peoples’ lives. Computers will be the primary means for accessing infor-
mation, thus diminishing the importance of printed versions of mass communications like
newspapers. This trend also identifies the possibility of individuals receiving large
Future Trends: Fourth Generation (4G) Systems and Beyond 197
amounts of information, much more than they can handle. This trend identifies the need for
refining and controlling information exchanges.
† Standardization diversification. This trend identifies the possibility of companies taking
over control of the market and forcing their own de facto standards. This could be either
due to political issues inside standards development organizations or market success
giving power to some companies.
The following sections provide three scenarios for the future of telecommunications that were
identified by research. Figure 6.4 shows the way social issues and standardization affect the
generation of those scenarios.
6.4.3 Scenario 1: Anything Goes
This scenario has the following characteristics:
† High development rate for telecommunications.

† Transparent access to the network.
† Manufacturing companies have a strong market power.
† Large number of de facto standards.
† Generic hardware equipment will run software enabling specialized services.
† Self-configuring systems.
In this scenario, telecommunications technology is envisioned to achieve a deep market
penetration and become an essential part of peoples’ everyday life. This will lead to fierce
industrial competition and decreased cost of product manufacturing and service offering. The
reduced cost of products and services will enable almost everyone to have the ability to
Wireless Networks198
Figure 6.4 The three scenarios’ dependence on standardization and social issues.
seamlessly access the services of the next generations of networks regardless of what access
system is used. The increased acceptance of 4G and future systems will raise research to
extreme levels with crucial aims being the identification of techniques offering efficient
management of the scarce spectrum (possibly altering regulation processes) and efficient
handling of the high number of subscribers. Furthermore, since telecommunications will
become an integral part of peoples’ lives, a high degree of mobility is expected to appear.
This will require research for flexible and fully automated dynamic resource allocation and
flexible roaming schemes.
The increased popularity of telecommunication systems will make companies manufactur-
ing such products a dominant player in the telecommunications world. This will possibly
change the way standardization work is conducted in the future. Companies that enjoy a big
market share will probably establish their own de facto standards bypassing standards devel-
opments organizations. This means that the significance of such organizations will diminish.
The deep penetration of telecommunications in peoples’ lives will serve a very diverse
range of needs. Users will demand availability of ready-to-use systems, tailored for their
needs. Thus, it would be desirable to research towards intelligent ad hoc systems, able to
either automatically deploy and configure themselves or demand little such knowledge and
intervention by users. Furthermore, personal adaptation of services based on user preferences
would also be desirable. This will lead to individual applications adapted to specific users.

Such intelligent systems will use a generic set of hardware and employ all the necessary
functionality to support different networks and services in software.
6.4.4 Scenario 2: Big Brother
This scenario has the following characteristics:
† Privacy is the first priority.
† Governmental organizations ensure privacy.
† Limited telecommunications market.
† Low development rate of telecommunications.
† Very few operators.
This scenario foresees a limited telecommunications development speed. This is due to the
fact that the rapid development of telecommunications in the earlier decade has led to a point
where it will be easy to find almost any information about a person or a company, by directly
eavesdropping on data exchanges, through the WWW, or by buying it from information
thieves and traders. This, of course, is illegal, but the inherent freedom of the WWW provides
the means to post and trade such information. Society will be very reluctant to use telecom-
munications services unless a high level of security is guaranteed.
To solve security problems, governments will form agencies responsible for certifying
operators to be trusted and secure. These agencies will eventually come up with a mandatory
security standard and act as Orwell’s Big Brother, by making sure that all companies either
follow this standard or are shut down. Every company that either manufactures telecommu-
nication products or offers services will be tested to ensure compliance with the security
standard. This will possibly lower the number of legal operators and product manufacturers
since a number of companies may not pass certification and go out of business. The decreased
number of companies and the reluctance of users to embrace telecommunications due to fears
Future Trends: Fourth Generation (4G) Systems and Beyond 199
related to security problems will obviously limit the telecommunications market. The smaller
market will make operating companies offer less money for research, thus lowering the speed
of telecommunications development.
In such a scenario, the most important research issues will concern security and privacy.
Since a lot of bandwidth will be consumed for security purposes, a ‘security overhead’ will

characterize the performance of all telecommunication systems. Thus, development of effi-
cient techniques offering high channel capacities over the same amount of spectrum will need
to be addressed.
6.4.5 Scenario 3: Pocket Computing
This scenario has the following characteristics:
† Social and political differences.
† Existence of highly differentiated service and pricing categories.
† Service providers offering specialized services also provide equipment for specialized
purposes.
This scenario envisions a world in which technological development is fast, however, the
customer base is divided into two parts due to economical and sociological factors. The first
part will comprise those customers who possess the financial ability to keep up with technol-
ogy developments while the second part will comprise those who do not. The customers in the
latter category will be ordinary people who prefer to pay for reduced services at minimum
price. These people will use evolved versions of legacy 2G/3G systems. Evolved variants of
GSM will still possess a significant market share due its low pricing, however, it will remain
inappropriate for supporting multimedia needs due to lack of bandwidth. DECT, IS-95 and
other legacy systems will also continue to exist. The second part of the customer base will
comprise those users who will be able to afford the increased cost of advanced services. Such
services will use the different wireless networks in combination and will be relatively expen-
sive. Consequently apart from other research issues, the issue of smooth integration and
interoperability of 4G and future systems and 2G/3G legacy systems will have to be effi-
ciently solved. Furthermore, despite the fact that the customer base will be divided, tele-
communications is bound to become an integral part of peoples’ lives. Thus, as in the case of
the ‘anything goes’ scenario, a high degree of mobility is expected to appear. This will require
research for flexible and fully automated dynamic resource allocation and flexible roaming
schemes.
To support such a divided customer base, the service providers are likely to offer a wide
range of different services, addressing the needs of various user groups. Furthermore, equip-
ment developers will need to provide specialized terminals for each user group. Finally,

spectrum regulation issues will need to be resolved, as new spectrum will be needed for
the advanced services.
6.5 Summary
This chapter provides a vision of 4G and future mobile and wireless systems. Such systems
target the market of 2010 and beyond, aiming to offer support to mobile applications demand-
ing data rates of 50 Mbps and beyond. Due to the large time window to their deployment, both
Wireless Networks200
the telecommunications scene and the services offered by 4G and future systems are not
known yet and as a result aims for these systems may change over time. However, as 3G
systems move from the research to the implementation stage, 4G and future systems will take
their place as an extremely interesting field of research on future generation wireless systems.
This chapter has covered a number of issues:
† 4G design goals and related research issues. 4G and future systems aim to provide a
common IP-based platform for the multiple mobile and wireless systems and possibly
offer higher data rates. The desired properties of 4G systems are identified. OFDM, a
promising technology for providing high data rates, is presented.
† 4G services and applications. Although the applications and service classes that will
dominate the 4G market are not yet known, research has identified some possibilities.
Tele-presence, information access services, inter-machine communication and intelligent
shopping will be enabled by 4G and future systems.
† The challenge of predicting the future of wireless systems. The exact state of 4G and future
systems cannot be reliably foreseen, due to the large time window until their deployment.
Many issues of these systems are not so clear and are dependent on the evolution of the
telecommunications market and society in general. Scenarios are tools for predicting
future situations and setting research priorities. Three different scenarios for the future
generations of wireless networks are presented, along with possible research issues for
each scenario.
WWW Resources
† this is the home page of the Personal Computing and
Communication research group of the Swedish Royal Institute of Technology. The

group’s effort is towards development of a 4G system.
† : this is the home page of the industry-initiated OFDM Forum.
The Forum is open to anyone interested in OFDM and its aim is to achieve market
acceptance of OFDM through the establishment of a single high-speed OFDM standard.
References
[1] Mohr W. Development of Mobile Communications Systems Beyond Third Generation, Wireless Personal
Communications, Kluwer, June 2001, pp. 191-207.
[2] Lilleberg J and Prasad R. Research Challenges for 3G and Paving the Way for Emerging New Generations,
Wireless Personal Communications, Kluwer, June 2001, pp. 355-362.
[3] Varshney U and Jain R. Issues in Emerging 4G Wireless Networks, IEEE Computer, June 2001, pp. 94-96.
[4] Wideband Orthogonal Frequency division Multiplexing (W-OFDM), Wi-LAN Inc., version 1.0, 2000.
[5] Flament M, Gessler F, Lagergren F, Queseth O, Stridh R, Unbehaun M, Wu J and Zander J. Key Research Issues
in 4
th
Generation Wireless Infrastructures, In Proc. of the PCC Workshop, Stockholm, Sweden, 1998.
[6] Flament M, Gessler F, Lagergren F, Queseth O, Stridh R, Unbehaun M, Wu J and Zander J. Telecom scenarios
for the 4
th
Generation Wireless Infrastructures, In Proc. of the PCC Workshop, Stockholm, Sweden, 1998.
[7] Flament M, Gessler F, Lagergren F, Queseth O, Stridh R, Unbehaun M, Wu J and Zander J. An Approach to 4
th
Generation Wireless Infrastructures-Scenarios and Key Research Issues, In Proc. of IEEE VTC 1999.
[8] M. Flament, F. Lagergren, R. Stridh, O. Queseth, M. Unbehaun, J. Wu, J. Zander, Telecom Scenarios : a wireless
infrastructure perspective, PCC Group report (2010) 1998.
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