Complex networks are powerful allies of our quest to tackle complexity in all
of science. Many lines can be written about the benefits of using networks to
study complex systems. Nevertheless, if I had to name their single most appealing
property,Iwouldsaysimplicity.Onecanmaptheinteractingelementsofanysystem
to a set of nodes, and connect these nodes with a set of links according to their
interactions.
Radio frequency (RF) power amplifiers are used in everyday life for many applica-
tions including cellular phones, magnetic resonance imaging, semiconductor wafer
processing for chip manufacturing, etc. Therefore, the design and performance of
RF amplifiers carry great importance for the proper functionality of these devices.
Furthermore, several industrial and military applications require low-profile yet
high-powered and efficient power amplifiers.
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.
For nearly a hundred years telecommunications provided mainly voice services and very low speed
data (telegraph and telex). With the advent of the Internet, several data services became mainstream
in telecommunications; to the point that voice is becoming an accessory to IP-centric data networks.
Today, high-speed data services are already part of our daily lives at work and at home (web surfing,
e-mail, virtual private networks, VoIP, virtual meetings, chats...). The demand for high-speed data
services will grow even more with the increasing number of people telecommuting.
Microwave radio network design is a subset of activities that constitute
the overall transmission network design. Transmission networks are
sometimes called transport networks, access networks, or connectivity
networks. For many wireless carriers, microwave is becoming a popu-
lar preference over wireline (leased lines) transport for many reasons,
especially as microwave radio equipment costs decrease and installation
becomes simpler. Low monthly operating costs can undercut those of
typical single (and especially multiple) T1/E1 expenses, proving it to be
more economical over the long term—usually two to four years. Network
operators also like the fact that they can own and control microwave
radio networks instead of relying on other service providers for network
components.
Never have telecommunications operations and network management been so
important. Never has it been more important to move away from practices that date
back to the very beginning of the telecommunications industry. Building and con-
necting systems internally at low cost, on an as - needed basis, and adding software
for supporting new networks and services without an overall architectural design
will not be cost effective for the future. Defi ning operations and network manage-
ment requirements at the 11th hour for new technologies, networks, and services
deployments must also change.
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.
The first gem of wisdom I ever acquired about consulting, obtained many years ago
from a former schoolmate, was to ensure that everything is plugged in: no continuity, no
data. Wires carry voltages and currents from one place to another. Their behavior is
reasonably simple and predictable—at least for sufficiently low data rates and short
lengths—and they can be seen, grabbed, traced, and tugged.
The single-carrier frequency division multiple access (SC-FDMA)
system is a well-known system that has recently become a preferred
choice for mobile uplink channels. This is attributed to its advantages
such as the low peak-to-average power ratio (PAPR) and the use of
frequency domain equalizers. Low PAPR allows the system to relax
the specifications of linearity in the power amplifier of the mobile
terminal, which reduces cost and power consumption.
Ultra-wideband (UWB) technology enables high data-rate short-range communica-
tion, in excess of hundredmegabit-per-secondsand up to multi-gigabit-per-seconds,
over a wide spectrum of frequencies, while keeping power consumption at low lev-
els. This low power operation results in a less-interfering co-existence with other
existed communication technologies (e.g., UNII bands).
In addition to carrying a huge amount of data over a distance of up to 230 feet
at very low power (less than 0.5mW), the UWB signal has the ability to penetrate
through the doors and other obstacles that tend to reflect signals at more limited
bandwidths and higher power densities.
