The growing interest for high data rate wireless communications over the last few decades
gave rise to the emergence of a number of wideband wireless systems. The resulting scarcity
of frequency spectrum has been forcing wireless system designers to develop methods that
will push the spectral efficiency to its limit.
When joining Siemens in 2001, I also extended my research interest towards radio net-
work planning methodologies. This area of research brought together my personal interest
in mobile communications and in the design of efficient algorithms and data structures.
Between 2001 and 2003, I participated in the EU project Momentum, which was target-
ing the performance evaluation and optimization of UMTS radio networks. I
This book was conceived in such a special way. From our experience, and despite the
increasing interest that we perceived amongst the research community in HAPS,
there was not any book in the market entirely devoted to HAPS. We could only find
some satellite communications books including only fragments related to HAPS,
covering the ‘generalities’. A need for a reference book which could highlight state-
of-the-art HAPS-related topics was therefore envisaged. Moreover, most of the
information related to HAPS could only be found in technical reports, official
recommendations, conference proceedings and journal papers.
An optical fiber amplifier is a key component for enabling efficient transmission of
wavelength-divisionmultiplexed(WDM)signalsoverlongdistances.Eventhough
many alternative technologies were available, erbium-doped fiber amplifiers won
theraceduringtheearly1990sandbecameastandardcomponentforlong-haulopti-
caltelecommunicationssystems.However,owingtotherecentsuccessinproducing
low-cost, high-power, semiconductor lasers operating near 1450 nm, the Raman
amplifiertechnologyhasalsogainedprominenceinthedeploymentofmodernlight-
wavesystems.Moreover,becauseofthepushforintegratedoptoelectroniccircuits,
semiconductor optical amplifiers, rare-earth-doped planar waveguide amplifiers,
and silicon optical amplifiers are also gaining much interest these days.
With this book at your fingertips, you, the reader, and I have something in common. We share
the same interest in mobile radio channels. This area attracted my interest first in autumn 1992
whenImovedfromindustrytoacademiatofindachallengeinmylifeandtopursueascientific
career. Since then, I consider myself as a student of the mobile radio channel who lives for
modelling, analyzing, and simulating them. While the first edition of this book resulted from
my teaching and research activities at the Technical University of Hamburg-Harburg (TUHH),
Germany, the present second edition is entirely an outcome of my work at the University of
Agder, Norway.
Multi-carrier modulation? Orthogonal Frequency Division Multi-
plexing (OFDM) particularly? has been successfully applied to
a wide variety of digital communications applications over the past
several years. Although OFDM has been chosen as the physical layer
standard for a diversity of important systems? the theory? algorithms?
and implementation techniques remain subjects of current interest.
This is clear from the high volume of papers appearing in technical
journals and conferences.
Notwithstanding its infancy, wireless mesh networking (WMN) is a hot and
growing field. Wireless mesh networks began in the military, but have since
become of great interest for commercial use in the last decade, both in local
area networks and metropolitan area networks. The attractiveness of mesh
networks comes from their ability to interconnect either mobile or fixed
devices with radio interfaces, to share information dynamically, or simply to
extend range through multi-hopping.
With the advent of IMT-2000, CDMA has emerged at the focal point of
interest in wireless communications. Now it has become impossible to discuss
wireless communications without knowing the CDMA technologies. There are
a number of books readily published on the CDMA technologies, but they are
mostly dealing with the traditional spread-spectrum technologies and the IS-95
based CDMA systems. As a large number of novel and interesting technologies
have been newly developed throughout the IMT-2000 standardization process
in very recent years, new reference books are now demanding that address the
diverse spectrum of the new CDMA technologies.
Since the first edition of the book was published, the field of modeling and simulation of
communication systems has grown and matured in many ways, and the use of simulation as a
day-to-day tool is now even more common practice. Many new modeling and simulation
approaches have been developed in the recent years, many more commercial simulation
packages are available, and the evolution of powerful general mathematical applications
packages has provided still more options for computer-aided design and analysis. With the
current interest in digital mobile communications, a primary area of application of modeling
and simulation is now to wireless systems of a different flavor than the traditional ones.
Driven by the desire to boost the quality of service of wireless systems closer to that afforded
by wireline systems, space-time processing for multiple-input multiple-output (MIMO)
wireless communications research has drawn remarkable interest in recent years. Excit-
ing theoretical advances, complemented by rapid transition of research results to industry
products and services, have created a vibrant and growing area that is already established
by all counts. This offers a good opportunity to reflect on key developments in the area
during the past decade and also outline emerging trends.
