Before delving into the details of orthogonal frequency division multiplexing (OFDM), relevant
background material must be presented first. The purpose of this chapter is to provide the necessary
building blocks for the development of OFDM principles. Included in this chapter are reviews of stochastic
and random process, discrete-time signals and systems, and the Discrete Fourier Transform (DFT). Tooled
with the necessary mathematical foundation, we proceed with an overview of digital communication
systems and OFDM communication systems. We conclude the chapter with summaries of the OFDM
wireless LAN standards currently in existence and a high-level comparison of single carrier systems versus
OFDM.
Emerging technologies such as WiFi and WiMAX are profoundly changing the
landscape of wireless broadband. As we evolve into future generation wireless
networks, a primary challenge is the support of high data rate, integrated multi-
media type traffic over a unified platform. Due to its inherent advantages in
high-speed communication, orthogonal frequency division multiplexing (OFDM)
has become the modem of choice for a number of high profile wireless systems
(e.g., DVB-T, WiFi, WiMAX, Ultra-wideband).
Orthogonal frequency division multiplexing (OFDM) has been shown to be
an effective technique to combat multipath fading in wireless channels. It
has been and is going to be used in various wireless communication systems.
This book gives a comprehensive introduction on the theory and practice of
OFDM for wireless communications.
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.
Visible light communications (VLC) is the name given to an optical wireless
communication system that carries information by modulating light in the visible spectrum
(400–700 nm) that is principally used for illumination [1–3]. The communications signal
is encoded on top of the illumination light. Interest in VLC has grown rapidly with the
growth of high power light emitting diodes (LEDs) in the visible spectrum. The
motivation to use the illumination light for communication is to save energy by exploiting
the illumination to carry information and, at the same time, to use technology that is
“green” in comparison to radio frequency (RF) technology, while using the existing
infrastructure of the lighting system.
The advent of modern wireless devices, such as smart phones and MID 1 terminals,
has revolutionized the way people think of personal connectivity. Such devices
encompass multiple applications ranging from voice and video to high-speed data
transfer via wireless networks. The voracious appetite of twenty-first century users
for supporting more wireless applications on a single device is ever increasing.
These devices employ multiple radios and modems that cover multiple frequency
bands and multiple standards with a manifold of wireless applications often running
simultaneously.
The first edition as well as its forerunner of Kuffel and Abdullah published in
1970 and their translations into Japanese and Chinese languages have enjoyed
wide international acceptance as basic textbooks in teaching senior under-
graduate and postgraduate courses in High-Voltage Engineering. Both texts
have also been extensively used by practising engineers engaged in the design
and operation of high-voltage equipment. Over the years the authors have
received numerous comments from the text’s users with helpful suggestions
for improvements. These have been incorporated in the present edition. Major
revisions and expansion of several chapters have been made to update the
continued progress and developments in high-voltage engineering over the
past two decades.
There is an unprecedented enthusiasm for radio frequency
identification (RFID) technologies today. RFID is based on the
exchange of information carried by electromagnetic waves between a
label, or tag, and a reader. This technology is currently in full
economic expansion, which has manifested itself in widely backed
research activities, some of which will be examined in this book.
Radio frequency identification (RFID) is a type of automatic identification systems
which has gained popularity in recent years for being fast and reliable in keeping
track of the individual objects. In RFID systems, contactless object identification
is achieved using radio signals without the need for physical contact as the case
with other existing identification technologies such as barcodes. Therefore, a huge
number of items can be identified in a short amount of time with high reliability
and low cost which makes the RFID technology very attractive for a wide range of
applications such as supply chain management, e-health, monitoring humans, pets,
animals, and many other objects, toll control, and electrical tagging. Furthermore,
RFID technology eliminates the human error and reduces the total cost of the
products.
