report_nccr_04.tex~

软件无线电的平台

\documentclass[a4paper,10pt]{report}
\usepackage{graphicx}
\usepackage{geometry}
\geometry{verbose,a4paper,tmargin=2cm,bmargin=3cm,lmargin=2cm,rmargin=2cm}

% Title Page
\title{Project Report}
\author{B.Rimoldi, L.Gasser}


\begin{document}
\maketitle

\section*{Radio-Platform}

 We have implemented a software-radio. We talk about Software Radio when the
two-way map between the row data (in the memory) and the data-carrying antenna
signal is completely specified by the software. Any map that conforms with the
hardware limitations (power, bandwidth, hardware imperfections) may be
implemented by means of an appropriate (software) code.

With this definition in mind, we decided that our software-radio
platform must meet the following characteristics: 1. \emph{Reconfigurability} so
that all parameters can be changed in real-time; 2. \emph{Modularity} based on
schoolbook-definition of a radio transmission; 3. \emph{User Interface} to
interact with the software-radio; 4. \emph{Simulation} in order to help debug
newly written modules 5. \emph{Real Time} for measurements and verification of
the models.

\begin{figure}
\begin{center}
\begin{tabular}{ccc}
\begin{minipage}{70mm}
\includegraphics[width=70mm,keepaspectratio]{capture_sradio}
\caption{\label{cap:fig_gui}Screenshot of Graphical User Interface}
\end{minipage}
\hspace{10mm}
&
\begin{minipage}{80mm}
\includegraphics[bb=0mm -20mm 100mm 60mm,
                 width=80mm,keepaspectratio]{ics-rf}
\caption{\label{cap:fig_ics_rf}From the air to the computer}
\end{minipage}
\end{tabular}
\end{center}
\end{figure}


The figure \ref{cap:fig_software_platform} shows the internal
structure of our platform: 1. \emph{GUI}, the Graphical User
Interface; 2. \emph{Signal Processing} of the received and transmitted
signal; 3. \emph{Antenna} for communication, either over the air or in
simulation.

In figure \ref{cap:fig_gui} you see a screen-shot of
a running session of the software-radio in simulation mode. The modular
structure and the school-book like seperation of the signal processing tasks is
visible. The upper part relates to the transmitter. The lower part to the
receiver. The horizontal thick bar  with thin marks represents the time line
partitioned into slots. Four slots are visible. The figure also indicates that
the transmitter uses the third slot and the receiver the first. Furthermore two
windows are opened that show internal signals. The upper window shows the
synchronisation signal, while the lower window represents the received and
filtered QPSK signal.


\section*{MIMO-hardware}

 The counter-part to the software-framework is the hardware that does the
actual transmission and reception of the samples. In order to keep as much
flexibility as possible, we chose an architecture that is capable of
transmitting and receiving a 2MHz-window anywhere in the range of
2.4~-~2.48~GHz, which corresponds to the free ISM-band.

 We chose an architecture that is composed of two parts, as can be seen in
figure \ref{cap:fig_ics_rf}. The ICS-cards are commercially available
aquisition-cards that offer 4 inputs or 4 outputs, respectively. They are
connected to 4 RF-cards that work at an Intermediat Frequency of 70MHz and
can translate this frequency to \hbox{2.4~-~2.48~GHz}. These RF-cards are
capable of outputting 20dBm and have an input-sensitivity of -80dBm.

\section*{LDPC on MIMO}

 We implemented a working LDPC-algorithm over a MIMO-transmission, using our
full 4x4-antenna setup. Using our software-radio, we could verify the
theoretical behaviour of these algorithms. Furthermore we identified possible
problems due to synchronisation between the antennas.

\section*{Conclusion}

During these three years we managed to set up a working environment for
physical layer measurements and testing of theoretical models. We also
discovered the limits on simple channel models for multiple antenna systems
and are working on a better model.

For the future we plan to use the software-radio in a bigger class of
students and to teach the principles of digital communication using this
tool.

\end{document}