uni/year4/semester2/CT420/notes/CT420.tex

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\author{Andrew Hayes}

\begin{document}
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        \Huge \textsc{ct420}
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       Real-Time Systems
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                Name: & Andrew Hayes \\
                Student ID: & 21321503 \\
                E-mail: & \href{mailto://a.hayes18@universityofgalway.ie}{a.hayes18@universityofgalway.ie} \\
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\section{Introduction}
\subsection{Lecturer Contact Information}
\begin{itemize}
    \item   Name: Dr. Michael Schukat.
    \item   E-mail: \href{mailto://michael.schukat@universityofgalway.ie}{michael.schukat@universityofgalway.ie}.
    \item   Office: CSB-3002.
\end{itemize}

\begin{itemize}
    \item   Name: Dr. Jawad Manzoor.
    \item   E-mail: \href{jawad.manzoor@universityofgalway.ie}{jawad.manzoor@universityofgalway.ie}.
    \item   Office: CSB-3012.
\end{itemize}

\subsection{Assessment}
\begin{itemize}
    \item   2 hours of face-to-face \& virtual labs per week from Week 03.
    \item   30\% Continuous Assessment:
            \begin{itemize}
                \item   2 assignments, 10\% each.
                \item   2 in-class quizzes between Week 07 \& Week 12, worth 5\%.
            \end{itemize}
\end{itemize}

\subsection{Introduction to Real-Time Systems}
A system is said to be \textbf{real-time} if the total correctness of an operation depends not only upon its logical correctness but also upon the time in which it is performed.
Contrast functional requirements (logical correctness) versus non-functional requirements (time constraints).
There are two main categorisation factors:
\begin{itemize}
    \item   \textbf{Criticality:}
            \begin{itemize}
                \item   \textbf{Hard RTS:} deadlines (responsiveness) is critical.
                        Failure to meet these have severe to catastrophic consequences (e.g., injury, damage, death).
                \item   \textbf{Soft RTS:} deadlines are less critical, in many cases significant tolerance can be permitted.
            \end{itemize}

    \item   \textbf{Speed}
            \begin{itemize}
                \item   \textbf{Fast RTS:} responses in microseconds to hundreds of microseconds.
                \item   \textbf{Slow RTS:} responses in the range of seconds to days.
            \end{itemize}
\end{itemize}

A \textbf{safety-critical system (SCS)} or life-critical system is a system whose failure or malfunction may result in death or serious injury to people, loss of equipment / property or severe damage, \& environmental harm.

\section{The Essence of Time: From Measurement to Navigation \& Beyond}
\textbf{Time} is the continued sequence of existence \& events that occurs in an apparently irreversible succession from past, through the present, into the future.
Methods of temporal measurement, or chronometry, take two distinct forms:
\begin{itemize}
    \item   The \textbf{calendar}, a mathematical tool for organising intervals of term;
    \item   The \textbf{clock}, a physical mechanism that counts the passage of time.
\end{itemize}

Global (maritime) exploration requires exact maritime navigation, i.e., longitude \& latitude calculation.
\textbf{Latitude} (north-south) orientation is straightforward; \textbf{longitude} (east-west orientation) requires a robust (maritime) clock.
\\\\
\textbf{Ground-based navigation systems} like LORAN (LOng RAnge Navigation) were developed in the 1940s and were in use until recently, and required fixed terrestrial longwave radio transmitters, and receivers on-board of ships \& planes.
They are also referred to as hyperbolic navigation or multilateration.
The principles of ground-based navigation systems is as follows:
\begin{enumerate}
    \item   A \textbf{master} with a known location broadcasts a radio pulse.
    \item   Multiple \textbf{slave} stations with a known distance from the master send their own pulse, upon receiving the master pulse.
    \item   A \textbf{receiver} receives master \& slave pulses and measures the delay between them.
    \item   This allows the receiver to deduce the distance to each of the stations, providing a fix.
\end{enumerate}






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