Rapid growth of wireless communication services in Recent decades has created
a huge demand of radio spectrum. Spectrum scarcity and utilization inefficiency
limit the development of wireless networks. Cognitive radio is a promising tech-
nology that allows secondary users to reuse the underutilized licensed spectrum of
primary users. The major challenge for spectrum sharing is to achieve high spectrum
efficiency while making non-intrusive access to the licensed bands. This requires in-
formation of availability and quality of channel resources at secondary transmitters,
however, is difficult to be obtained perfectly in practice.
Recent decades have shown a tremendous expansion of the Internet. The number of
connected terminals has increased by orders of magnitude, traffic has grown exponen-
tially, coverage has become ubiquitous and worldwide, and today’s sophisticated Web
2.0 applications are increasingly providing services which hitherto have been the realm
of telecommunications, such as Skype and video conferencing. This has even led to the
thought that access to the Internet might one day be a universal right of every citizen.
This evolution will accelerate in the coming decades.
The ever-increasing demand for private and sensitive data transmission over wireless net-
works has made security a crucial concern in the current and future large-scale, dynamic,
and heterogeneous wireless communication systems. To address this challenge, computer
scientists and engineers have tried hard to continuously come up with improved crypto-
graphic algorithms. But typically we do not need to wait too long to find an efficient way
to crack these algorithms. With the rapid progress of computational devices, the current
cryptographic methods are already becoming more unreliable. In Recent years, wireless re-
searchers have sought a new security paradigm termed physical layer security. Unlike the
traditional cryptographic approach which ignores the effect of the wireless medium, physi-
cal layer security exploits the important characteristics of wireless channel, such as fading,
interference, and noise, for improving the communication security against eavesdropping
attacks. This new security paradigm is expected to complement and significantly increase
the overall communication security of future wireless networks.
This book focuses on the study and development of one of the most
advanced topics in broadband wireless communications systems:
power efficiency and power consumption in wireless communications
systems, especially of mobile devices. Hence, the main focus of this
book is on the most Recent techniques for the conservation of power
and increase in power efficiency.
Without doubt, the age of information communications is upon 11s. The rapid
pace of technological advancement in digital data communications can be wit-
nessed in a multitude of applications in our day-to-day existence. In Recent
years, the widespread proliferation of wireless digital cornmunications hass been
readily accepted by the general population worldwide; this is nearly unpa~rallcled
in few other human scientific achievements in terms of scope and speed of devel-
opment.
This book is a result of the Recent rapid advances in two related technologies: com-
munications and computers. Over the past few decades, communication systems
have increased in complexity to the point where system design and performance
analysis can no longer be conducted without a significant level of computer sup-
port. Many of the communication systems of fifty years ago were either power or
noise limited. A significant degrading effect in many of these systems was thermal
noise, which was modeled using the additive Gaussian noise channel.
Quality of Service ( QoS ) has always been in a world of its own, but as the technology
has been refi ned and has evolved in Recent years, QOS usage has increased to the point
where it is now considered a necessary part of network design and operation. As with
most technologies, large - scale deployments have led to the technology becoming more
mature, and QOS is no exception.
We are currently witnessing an increase in telecommunications norms and
standards given the Recent advances in this domain. The increasing number of
normalized standards paves the way for an increase in the range of offers and
services available for each consumer. Moreover, the majority of available radio
frequencies have already been allocated.
The multiple-input multiple-output (MIMO) technique provides higher bit rates
and better reliability in wireless systems. The efficient design of RF transceivers
has a vital impact on the implementation of this technique. This first book is com-
pletely devoted to RF transceiver design for MIMO communications. The book
covers the most Recent research in practical design and applications and can be
an important resource for graduate students, wireless designers, and practical
engineers.
Reliable and accurate positioning and navigation is critical for a diverse set of emerging applications
calling for advanced signal-processing techniques. This book provides an overview of some of the
most Recent research results in the field of signal processing for positioning and navigation, addressing
many challenging open problems.
