The radio spectrum is one of the most precious resources which must be managed
to ensure efficient access for the wireless communication services which use it. The
allocation and management of spectrum are administered by the regulatory
authorities. Traditionally, spectrum allocation is carried out exclusively of its use in
large geographic areas and assigning frequency bands to specific USERS or service
providers is proved to be inefficient. Recently, substantial knowledge about
dynamic spectrum access scheme has been accumulated to enable efficient spectrum
sharing.
Radio frequency spectrum is a scarce and critical natural resource that is utilized for
many services including surveillance, navigation, communication, and broadcast-
ing. Recent years have seen tremendous growth in the use of spectrum especially by
commercial cellular operators. Ubiquitous use of smartphones and tablets is one
of the reasons behind an all-time high utilization of spectrum. As a result, cellular
operators are experiencing a shortage of radio spectrum to meet bandwidth
demands of USERS. On the other hand, spectrum measurements have shown that
much spectrum not held by cellular operators is underutilized even in dense urban
areas. This has motivated shared access to spectrum by secondary systems with no
or minimal impact on incumbent systems. Spectrum sharing is a promising
approach to solve the problem of spectrum congestion as it allows cellular operators
access to more spectrum in order to satisfy the ever-growing bandwidth demands of
commercial USERS.
A wireless communication network can be viewed as a collection of nodes, located in some domain, which
can in turn be transmitters or receivers (depending on the network considered, nodes may be mobile USERS,
base stations in a cellular network, access points of a WiFi mesh etc.). At a given time, several nodes
transmit simultaneously, each toward its own receiver. Each transmitter–receiver pair requires its own
wireless link. The signal received from the link transmitter may be jammed by the signals received from
the other transmitters. Even in the simplest model where the signal power radiated from a point decays in
an isotropic way with Euclidean distance, the geometry of the locations of the nodes plays a key role since
it determines the signal to interference and noise ratio (SINR) at each receiver and hence the possibility of
establishing simultaneously this collection of links at a given bit rate. The interference seen by a receiver is
the sum of the signal powers received from all transmitters, except its own transmitter.
The use of mobile devices now surpasses that of traditional computers: wireless
USERS will hence soon be demanding the same rich multimedia services on their
mobile devices that they have on their desktop personal computers. In addition,
new services will be added, especially related with their mobile needs, such as
location-based information services.
When 3GPP started standardizing the IMS a few years ago, most analysts expected the
number of IMS deploymentsto grow dramatically as soon the initial IMS specifications were
ready (3GPP Release 5 was functionallyfrozenin the first half of 2002and completedshortly
after that). While those predictions have proven to be too aggressive owing to a number of
upheavals hitting the ICT (Information and Communications Technologies) sector, we are
now seeing more and more commercial IMS-based service offerings in the market. At the
time of writing (May 2008), there are over 30 commercial IMS networks running live traffic,
addingup to over10million IMS USERS aroundthe world; the IMS is beingdeployedglobally.
In addition, there are plenty of ongoing market activities; it is estimated that over 130 IMS
contracts have been awarded to all IMS manufacturers. The number of IMS USERS will grow
substantially as these awarded contracts are launched commercially. At the same time, the
number of IMS USERS in presently deployed networks is steadily increasing as new services
are introduced and operators running these networks migrate their non-IMS USERS to their
IMS networks.
When thinking about mobile radio engineers there is a tendency to
assume that the engineering function relates solely to the technical
aspects of the network, such as the equipment design or the network
design. That is certainly a key part of the role of a mobile radio engineer.
However,increasinglyengineersarerequiredtointeractwithprofession-
als from other divisions. The “complete wireless professional” should
know about mobile networks; fixed networks; other types of mobile
systems; regulatory and government policy; the requirements of the
USERS; and financial, legal, and marketing issues.
Changes in telecommunications are impacting all types of user
group, which include business USERS, traveling USERS, small and
home offices, and residential USERS. The acceptance rate of telecom-
munications and information services is accelerating significantly.
Voice services needed approximately 50 years to reach a very high
teledensity; television needed just 15 years to change the culture
and lives of many families; the Internet and its related services have
been penetrating and changing business practices and private com-
munications over the last 2 to 3 years.
Recent advances in wireless communication technologies have had a transforma-
tive impact on society and have directly contributed to several economic and social
aspects of daily life. Increasingly, the untethered exchange of information between
devices is becoming a prime requirement for further progress, which is placing an
ever greater demand on wireless bandwidth. The ultra wideband (UWB) system
marks a major milestone in this progress. Since 2002, when the FCC allowed the
unlicensed use of low-power, UWB radio signals in the 3.1–10.6GHz frequency
band, there has been significant synergistic advance in this technology at the cir-
cuits, architectural and communication systems levels. This technology allows for
devices to communicate wirelessly, while coexisting with other USERS by ensuring
that its power density is sufficiently low so that it is perceived as noise to other
USERS.
Once upon a time, cellular wireless networks provided two basic services: voice
telephony and low-rate text messaging. USERS in the network were separated
by orthogonal multiple access schemes, and cells by generous frequency reuse
patterns [1]. Since then, the proliferation of wireless services, fierce competition,
andthe emergenceof new service classes such as wireless data and multimediahave
resulted in an ever increasing pressure on network operators to use resources in a
moreefficient manner.In the contextof wireless networks,two of the most common
resources are power and spectrum—and, due to regulations, these resources are
typically scarce. Hence, in contrast to wired networks, overprovisioning is not
feasible in wireless networks.
Today wireless is becoming the leader in communication choices among
USERS. It is not anymore a backup solution for nomadic travellers but really a
newmoodnaturallyusedeverywhereevenwhenthewiredcommunicationsare
possible. Many technologies evolve then continuously, changing the telecom-
munication world. We talk about wireless local area networks (WLANs), wire-
less personal area networks (WPANs), wireless metropolitan area networks
(WMANs), wireless wide area networks (WWANs), mobile ad hoc networks
(MANETs), wireless sensor networks (WSNs) and mesh networks. Since we
can find today a multitude of wireless technologies we decided to group a
numberofcomplementarytechnologiesintoonedocumenttomakeiteasierfor
areadertounderstandsomeofthetechnicaldetailsofeachmedia.
