diff --git a/latex/thesis/chapters/introduction.tex b/latex/thesis/chapters/introduction.tex index 6ab5b8e..f741acc 100644 --- a/latex/thesis/chapters/introduction.tex +++ b/latex/thesis/chapters/introduction.tex @@ -6,26 +6,38 @@ of data by detecting and correcting any errors that may occur during its transmission or storage. One class of binary linear codes, \ac{LDPC} codes, has become especially popular due to being able to reach arbitrarily small probabilities of error -at code rates up to the capacity of the channel, while retaining a structure -that allows for very efficient decoding. +at code rates up to the capacity of the channel \cite[Sec. II.B.]{mackay_rediscovery}, +while retaining a structure that allows for very efficient decoding. While the established decoders for \ac{LDPC} codes, such as \ac{BP} and the \textit{min-sum algorithm}, offer reasonable decoding performance, they are suboptimal in most cases and exhibit an \textit{error floor} for high \acp{SNR}, -making them unsuitable for applications with extreme reliability requiremnts. +making them unsuitable for applications with extreme reliability requirements. Optimization based decoding algorithms are an entirely different way of approaching -the decoding problem, in some cases coming with stronger theoretical guarantees -and promising to alleviate the error floor issue \cite[Sec. I]{original_admm}. +the decoding problem. +The initial introduction of optimization techniques as a way of decoding binary +linear codes was conducted in Feldman's 2003 Ph.D. thesis and subsequent paper, +establishing the field of \ac{LP} decoding \cite{feldman_thesis}, \cite{feldman_paper}. +There, the \ac{ML} decoding problem is approximated by a \textit{linear program}, +a linear, convex optimization problem, which can subsequently be solved using +a number of different algorithms \cite{alp}, \cite{interior_point}, +\cite{original_admm}, \cite{pdd}. +More recently, novel approaches such as \textit{proximal decoding} have been +introduced. Proximal decoding is based on a non-convex optimization formulation +of the \ac{MAP} decoding problem \cite{proximal_paper}. + +The motivation behind applying optimization methods to channel decoding is to +utilize existing techniques in the broad field of optimization theory, as well +as find new decoding methods not suffering from the same disadvantages or exhibiting +other desirable properties. +\Ac{LP} decoding, for example, comes with strong theoretical guarantees +allowing it to be used as a way of closely approximating \ac{ML} decoding, +and proximal decoding is applicable to non-trivial channel models such +as \ac{LDPC}-coded massive \ac{MIMO} channels. This thesis aims to further the analysis of optimization based decoding -algorithms as well as verify and generalize the considerations present in -the existing literature by considering a variety of different codes. -Specifically, the \textit{proximal decoding} \cite{proximal_paper} -algorithm and \ac{LP} decoding using the \ac{ADMM} \cite{original_admm} are explored. -The two algorithms are analyzed based on their theoretical structure -and based on the results of the simulations conducted in the scope of this work. -Approaches to determine the optimal value of each parameter are derived -and the computational and decoding performance of the algorithms is examined. -An improvement on proximal decoding is suggested, achieving up to $\SI{1}{dB}$ -of gain, depending on the parameters chosen and the -code considered. +algorithms as well as verify and complement the considerations present in +the existing literature. +Specifically, the proximal decoding algorithm and \ac{LP} decoding using +the \ac{ADMM} \cite{original_admm} are explored within the context of +\ac{BPSK} modulated \ac{AWGN} channels. diff --git a/latex/thesis/thesis.tex b/latex/thesis/thesis.tex index 791ed2a..439fc64 100644 --- a/latex/thesis/thesis.tex +++ b/latex/thesis/thesis.tex @@ -6,7 +6,7 @@ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -\thesisTitle{Application of Optimization Algorithms for Channel Decoding} +\thesisTitle{Application o Optimization Algorithms for Channel Decoding} \thesisType{Bachelor's Thesis} \thesisAuthor{Andreas Tsouchlos} \thesisAdvisor{Prof. Dr.-Ing. Laurent Schmalen} @@ -14,7 +14,7 @@ \thesisSupervisor{Dr.-Ing. Holger Jäkel} \thesisStartDate{24.10.2022} \thesisEndDate{24.04.2023} -\thesisSignatureDate{Signature date} % TODO: Signature date +\thesisSignatureDate{24.04.2023} % TODO: Signature date \thesisLanguage{english} \setlanguage @@ -35,7 +35,7 @@ \usetikzlibrary{spy} \usetikzlibrary{shapes.geometric} \usetikzlibrary{arrows.meta,arrows} -\tikzset{>=latex} +\tikzset{>=stealth} \pgfplotsset{compat=newest} \usepgfplotslibrary{colorbrewer}