Many wireless communications channels consist of multiple signal paths from the
transmitter to receiver. This multiplicity of paths leads to a phenomenon known
as multipath fading. The multiple paths are caused by the presence of objects in the
physical environment that, through the mechanisms of propagation, alter the path of
radiated energy. These objects are referred to as scatterers. In the past, researchers
often looked at ways to mitigate multipath scattering, such as in diversity systems.
Multiple-input, multiple-output (MIMO) systems, on the other hand, use multipath
diversity to their advantage; a MIMO system has the ability to translate increased
spatial diversity into increased channel capacity.
標簽：
Multiple-Output
Multiple-Input
Channel
Models
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2020-05-31
上傳用戶：shancjb
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.
標簽：
Communications
Physical
Security
Wireless
Layer
in
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2020-05-31
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n the first part of this book, we give an introduction to the basic applications of wireless com-
munications, as well as the technical problems inherent in this communication paradigm. After a
brief history of wireless, Chapter 1 describes the different types of wireless services, and works
out their fundamental differences. The subsequent Section 1.3 looks at the same problem from
a different angle: what data rates, ranges, etc., occur in practical systems, and especially, what
combination of performance measures are demanded (e.g., what data rates need to be transmitted
over short distances; what data rates are required over long distances?) Chapter 2 then describes
the technical challenges of communicating without wires, putting special emphasis on fading and
co-channel interference. Chapter 3 describes the most elementary problem of designing a wireless
system, namely to set up a link budget in either a noise-limited or an interference-limited system.
After studying this part of the book, the reader should have an overview of different types of
wireless services, and understand the technical challenges involved in each of them. The solutions
to those challenges are described in the later parts of this book.
標簽：
Communications
Wireless
Edition
2nd
上傳時間：
2020-06-01
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