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% SPDX-License-Identifier: CC-BY-SA-4.0
%
% Copyright (c) 2020 Philipp Le
%
% Except where otherwise noted, this work is licensed under a
% Creative Commons Attribution-ShareAlike 4.0 License.
%
% Please find the full copy of the licence at:
% https://creativecommons.org/licenses/by-sa/4.0/legalcode
\chapter{Spread Spectrum and Multiple Access}
\begin{refsection}
\section{Spread Spectrum}
\begin{figure}[H]
\centering
\begin{tikzpicture}
\begin{axis}[
height={0.15\textheight},
width=0.8\linewidth,
scale only axis,
xlabel={$\omega$},
ylabel={$|\mathrm{S}_{XX}|$},
%grid style={line width=.6pt, color=lightgray},
%grid=both,
grid=none,
legend pos=north east,
axis y line=middle,
axis x line=middle,
every axis x label/.style={
at={(ticklabel* cs:1.05)},
anchor=north,
},
every axis y label/.style={
at={(ticklabel* cs:1.05)},
anchor=east,
},
xmin=0,
xmax=10.5,
ymin=0,
ymax=1.2,
xtick={0},
xticklabels={0},
ytick={0},
axis x discontinuity=parallel,
]
\addplot[blue, smooth] coordinates {(4.6,0) (4.7,0.02) (4.8,0.2) (4.9,0.71) (5,1) (5.1,0.71) (5.2,0.2) (5.3,0.02) (5.4,0)};
\addlegendentry{Narrow-band signal};
\addplot[red, smooth] coordinates {(2,0) (2.5,0.01) (3,0.05) (5,0.05) (7,0.05) (7.5,0.01) (8,0)};
\addlegendentry{Spread spectrum signal};
\end{axis}
\end{tikzpicture}
\caption[PSD of a narrow-band and spread spectrum signal]{\acs{PSD} of a narrow-band and spread spectrum signal. Both signals carry the same information and have the equal power. The narrow-band signal concentrates the whole signal power in a narrow frequency band. In contrast, the spread spectrum signal distributes the signal power over a wide frequency band.}
\end{figure}
\todo{Purpose: Noise immunity}
\todo{Noise like}
\todo{Purpose: Immunity against narrowband disturbances}
\todo{Purpose: Coexistence with other services, multiple access}
\todo{Purpose: Plausible deniability}
\todo{Purpose: Encryption, confidentiality}
\subsection{Direct-Sequence Spread Spectrum}
\todo{pseudorandom number}
\todo{Processing Gain}
\subsection{Frequency-Hopping Spread Spectrum}
\subsection{Time-Hopping Spread Spectrum}
\section{Multi-carrier Modulation}
\todo{OFDM}
\section{Multiple Access}
\todo{Multiplexing}
\todo{Sharing Resources}
\subsection{Space-Division Multiple Access}
\subsection{Time-Division Multiple Access}
\subsection{Frequency-Division Multiple Access}
\subsection{Code-Division Multiple Access}
\subsection{Orthogonal Frequency-Division Multiple Access}
\section{Orthogonal Codes}
\nocite{ipatov2005}
\phantomsection
\addcontentsline{toc}{section}{References}
\printbibliography[heading=subbibliography]
\end{refsection}
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