New applications such as video conferencing, video on demand, multi-
media transcoders, Voice-over-IP (VoIP), intrusion detection, distributed
collaboration, and intranet security require advanced functionality from
networks beyond simple forwarding congestion control techniques.
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).
Employing multiple transmit and receive antennas, namely using multi-input multi-output
(MIMO) systems, has proven to be a major breakthrough in providing reliable wireless
communication links. Since their invention in the mid-1990s, transmit diversity, achieved
through space-time coding, and spatial multiplexing schemes have been the focus of much
research in the area of wireless communications.
Today’s wireless services have come a long way since the roll out of the
conventional voice-centric cellular systems. The demand for wireless access
in voice and high rate data multi-media applications has been increasing.
New generation wireless communication systems are aimed at accommodating
this demand through better resource management and improved transmission
technologies.
This introduction takes a visionary look at ideal cognitive radios (CRs) that inte-
grate advanced software-defined radios (SDR) with CR techniques to arrive at
radios that learn to help their user using computer vision, high-performance
speech understanding, global positioning system (GPS) navigation, sophisticated
adaptive networking, adaptive physical layer radio waveforms, and a wide range
of machine learning processes.
Mobile communication has gained significant importance in today’s society. As
of 2010, the number of mobile phone subscribers has surpassed 5 billion [ABI10],
and the global annual mobile revenue is soon expected to top $1 trillion [Inf10].
While these numbers appear promising for mobile operators at first sight, the
major game-changer that has come up recently is the fact that the market is
more and more driven by the demand for mobile data traffic [Cis10].
It is commonly accepted today that optical fiber communications have revolutionized
telecommunications. Indeed, dramatic changes have been induced in the way we interact
with our relatives, friends, and colleagues: we retrieve information, we entertain and
educate ourselves, we buy and sell, we organize our activities, and so on, in a long list
of activities. Optical fiber systems initially allowed for a significant curb in the cost of
transmission and later on they sparked the process of a major rethinking regarding some,
generation-old, telecommunication concepts like the (OSI)-layer definition, the lack of
cross-layer dependency, the oversegmentation and overfragmentation of telecommunica-
tions networks, and so on.