Added supplementary slides for choice of gamma, mu and rho
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@ -76,7 +76,7 @@
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@mastersthesis{yanxia_lu_thesis,
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author = {Lu, Yanxia},
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title = {Realization of Channel Decoding Using Optimization Techniques},
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year = {2023},
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year = {2022},
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type = {Bachelor's Thesis},
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institution = {KIT},
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}
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@ -87,7 +87,7 @@ return $\boldsymbol{s}$
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+ \underbrace{\sum\nolimits_{j\in\mathcal{J}} g_j\left( \boldsymbol{T}_j\tilde{\boldsymbol{c}} \right) }
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_{\text{Constraints}} \\
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\text{subject to}\hspace{5mm} &
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\tilde{\boldsymbol{c}} \in \mathbb{R}^n
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\tilde{\boldsymbol{c}} \in \left[ 0, 1 \right]^n
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\end{align*}
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\begin{genericAlgorithm}[caption={}, label={},
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@ -21,7 +21,7 @@ For example:%
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%
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\begin{align*}
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x \in \left\{ -1, 1 \right\} &\to \tilde{x} \in \mathbb{R}\\
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c \in \mathbb{F}_2 &\to \tilde{c} \in \left[ 0, 1 \right]
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c \in \mathbb{F}_2 &\to \tilde{c} \in \left[ 0, 1 \right] \subseteq \mathbb{R}
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.\end{align*}
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%
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Additionally, a shorthand notation will be used to denote series of indices and series
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@ -29,9 +29,10 @@ of indexed variables:%
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%
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\begin{align*}
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\left[ m:n \right] &:= \left\{ m, m+1, \ldots, n-1, n \right\},
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\hspace{5mm} m,n\in\mathbb{Z}\\
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\hspace{5mm} m < n, \hspace{2mm} m,n\in\mathbb{Z}\\
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x_{\left[ m:n \right] } &:= \left\{ x_m, x_{m+1}, \ldots, x_{n-1}, x_n \right\}
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.\end{align*}
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\todo{Not really slicing. How should it be denoted?}
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%
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In order to designate elemen-twise operations, in particular the \textit{Hadamard product}
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and the \textit{Hadamard power}, the operator $\circ$ will be used:%
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@ -50,16 +51,17 @@ and the \textit{Hadamard power}, the operator $\circ$ will be used:%
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\section{Preliminaries: Channel Model and Modulation}
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\label{sec:theo:Preliminaries: Channel Model and Modulation}
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In order to transmit a bit-word $\boldsymbol{c}$ of length $n$ over a channel,
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it has to be mapped onto a symbol $\boldsymbol{x}$ that can be physically
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transmitted.
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In order to transmit a bit-word $\boldsymbol{c} \in \mathbb{F}_2^n$ of length
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$n$ over a channel, it has to be mapped onto a symbol
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$\boldsymbol{x} \in \mathbb{R}^n$ that can be physically transmitted.
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This is known as modulation. The modulation scheme chosen here is \ac{BPSK}:%
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%
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\begin{align*}
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\boldsymbol{x} = \left( -1 \right)^{\boldsymbol{c}}
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\boldsymbol{x} = 1 - 2\boldsymbol{c}
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.\end{align*}
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%
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The symbol that reaches the receiver, $\boldsymbol{y}$, is distorted by the channel.
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The transmitted symbol is distorted by the channel and denoted by
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$\boldsymbol{y} \in \mathbb{R}^n$.
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This distortion is described by the channel model, which in the context of
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this thesis is chosen to be \ac{AWGN}:%
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%
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@ -87,7 +89,7 @@ of the channel \cite[Sec. II.B.]{mackay_rediscovery} while having a structure
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that allows for very efficient decoding.
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The lengths of the data words and codewords are denoted by $k\in\mathbb{N}$
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and $n\in\mathbb{N}$, respectively.
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and $n\in\mathbb{N}$, respectively, with $k \le n$.
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The set of codewords $\mathcal{C} \subset \mathbb{F}_2^n$ of a binary
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linear code can be represented using the \textit{parity-check matrix}
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$\boldsymbol{H} \in \mathbb{F}_2^{m\times n}$, where $m$ represents
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@ -103,14 +105,14 @@ $\boldsymbol{c} \in \mathbb{F}_2^n$ using the \textit{generator matrix}
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$\boldsymbol{G} \in \mathbb{F}_2^{k\times n}$:%
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%
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\begin{align*}
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\boldsymbol{c} = \boldsymbol{u}^\text{T}\boldsymbol{G}
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\boldsymbol{c} = \boldsymbol{u}\boldsymbol{G}
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.\end{align*}
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%
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After obtaining a codeword from a data word, it is transmitted over a channel
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as described in section \ref{sec:theo:Preliminaries: Channel Model and Modulation}.
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The received signal $\boldsymbol{y}$ is then decoded to obtain
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an estimate of the transmitted codeword, $\hat{\boldsymbol{c}}$.
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an estimate of the transmitted codeword, denoted as $\hat{\boldsymbol{c}}$.
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Finally, the encoding procedure is reversed and an estimate of the originally
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sent data word, $\hat{\boldsymbol{u}}$, is produced.
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The methods examined in this work are all based on \textit{soft-decision} decoding,
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@ -170,7 +172,17 @@ criterion:%
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\right)
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.\end{align*}%
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%
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The \ac{MAP}- and \ac{ML}-criteria are closely connected through
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\textit{Bayes' theorem}:%
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%
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\begin{align*}
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\argmax_{c\in\mathcal{C}} p_{\boldsymbol{C} \mid \boldsymbol{Y}}
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\left( \boldsymbol{c} \mid \boldsymbol{y} \right)
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= TODO
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.\end{align*}
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%
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This has the consequence that if the probability \ldots, the two criteria are
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equivalent.
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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@ -472,8 +484,8 @@ and minimizing $g$ using the proximal operator
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\cite[Sec. 4.2]{proximal_algorithms}:%
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%
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\begin{align*}
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\boldsymbol{x} \leftarrow \boldsymbol{x} - \lambda \nabla f\left( \boldsymbol{x} \right) \\
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\boldsymbol{x} \leftarrow \textbf{prox}_{\lambda g} \left( \boldsymbol{x} \right)
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\boldsymbol{x} &\leftarrow \boldsymbol{x} - \lambda \nabla f\left( \boldsymbol{x} \right) \\
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\boldsymbol{x} &\leftarrow \textbf{prox}_{\lambda g} \left( \boldsymbol{x} \right)
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,\end{align*}
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%
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Since $g$ is minimized with the proximal operator and is thus not required
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