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diff --git a/scenarios.tex b/scenarios.tex index 108d5a0..9362551 100644 --- a/scenarios.tex +++ b/scenarios.tex @@ -1,10 +1,97 @@ \section{Usage Scenarios} \subsection{Experimentation} \subsubsection{Creation of Non-Realtime Multiplex} +The creation of a ETI file containing two programmes, one DAB and one \dabplus{} is covered in +section \ref{sec-files}. + \subsubsection{Modulation of ETI for Offline Processing} +The ETI file generated before can then be used with ODR-DabMod to generate a file containing I/Q +samples. Here, we must chose between using the command line or the configuration file. For a very +simple example, using the command line makes sense, but for more advanced features it is preferable +to use a configuration file. For illustration, we will present both. + +To modulate the file \texttt{myfirst.eti} into \texttt{myfirst.iq}, with the default options, the +command is simply + +\begin{lstlisting} +odr-dabmod myfirst.eti -f myfirst.iq +\end{lstlisting} + +This will create a file containing 16-bit interleaved I/Q at $2048000$ samples per second. The +transmission mode is defined by the ETI file. + +The equivalent configuration file would be +\begin{lstlisting} +[input] +transport=file +source=myfirst.eti + +[output] +output=file + +[fileoutput] +filename=myfirst.iq +\end{lstlisting} + +This is a very minimal file that defines only the necessary settings equivalent to the above command +line options. The configuration file however supports more options that the command line, and +becomes easier to manager once the set becomes more complex. It is best to use the example +configuration availble in the \texttt{doc/} folder. \subsection{Interfacing Hardware Devices} \subsubsection{Ettus USRP} +ODR-DabMod integrates support for the UHD library that can interface with all USRP devices from +Ettus. The following configuration file illustrates how to send the \texttt{myfirst.eti} over a USRP +B200 on channel 13C: + +\begin{lstlisting} +[remotecontrol] +telnet=1 +telnetport=2121 + +[input] +transport=file +source=myfirst.eti +loop=1 + +[modulator] +gainmode=2 +digital_gain=0.8 + +[firfilter] +enabled=1 +filtertapsfile=simple_taps.txt + +[output] +output=uhd + +[uhdoutput] +master_clock_rate=32768000 +type=b200 +txgain=40 +channel=13C +\end{lstlisting} + +This example also shows more options that the example for the file output: + +\begin{itemize} + \item \texttt{remotecontrol telnet=1} enables the Telnet server that can be used to set + parameters while the modulator is running. + \item \texttt{loop=1} rewinds the input file when the end is reached. The same ETI file will be + transmitted over and over. + \item \texttt{gainmode=2} sets the GainMode to VAR, which reduces overshoots in the output. + \item \texttt{digital\_gain=0.8} reduces the output sample deviation, to reduce compression in + the USRP. + \item \texttt{firfilter enabled=1} enables an additional FIR filter to improve the spectrum + mask. + \item \texttt{master\_clock\_rate=32768000} sets the USRP internal clock to a multiple of + $2048000$, which is required if we want to use the native DAB sample rate. + \item \texttt{txgain=40} Sets the analog transmit gain of the USRP to 40dB, which is specific to + the B200. +\end{itemize} + +Some of these options are not necessary for the system to work, but they improve the performance. + \subsubsection{Other Hardware} \subsection{Audio sources} |