\setchapterpreamble[u]{%
  \dictum[Stobaeus] {What use is knowledge if there is no understanding?}
}
\chapter{Introduction to GSM and GPS}
\section{Motivation}
\section{Goals of the thesis}
The goal of the following thesis is to:
- implement the Radio Resource Location Protocol inside of OpenBSC, to the extent of 
delivering correct GPS assistance data to cell phone subscribers
inside the GSM network
- test the protocol on 5-10 different smart phones
- describe and analyze the background processes taking place inside of the cell phone
\chapter{Assisted GPS}

\chapter{Radio Resource Location Protocol}

\chapter {Working}
\section{Zitieren..}
citep: \citep{kopka1997latex} \\
citet: \citet{kopka1997latex}

\chapter{System}
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Test test
\chapter{Software}

Author's test system operated on the ARFCN 877 channel. ARFCN (Absolute Radio
Frequency Channel Number) defines the uplink and downlink channel frequency insdide 
the GSM network \citep{Richard2011Master}. ARFCN 877 corresponds to the uplink frequency
of 1,783.2 MHz and a downlink frequency of 1,878.2 MHz, where the uplink direction
represents the direction from the nanoBTS to the mobile stations and downlink the
opposite direction. The decision to use the ARFCN 877 channel was derived from
the fact that the channel was free, measurements were carried out with a
spectrum analyzer built on the USRP hardware. 

\chapter{Hardware}
In the following chapter the author will introduce the reader to the hardware
components used in the thesis. The hardware components will be presented
according to their importance of building an operational and
functional GSM network with GPS localization capabilities. Firstly the nanoBTS
will be introduced since it is the main hardware component used for building a
basic GSM network infrastructure. Then a short insight into the used
GPS receiver will be given. Additionally the mobile stations used for
testing of the system will be reviewed. Finally, a hardware connection diagram
will be given.
 
\section{GSM BTS - nanoBTS}
In recent years, there has been an increasing interest in deployment of
private cellular networks in remote areas or for research which lead to
the devolopment of diverse ``low-cost'' GSM hardware solutions. According to 
ip.access\footnote{http://www.ipaccess.com}, the manufacturer of nanoBTS,
their hardware product is deployed for coverage of ``hard-to-reach places;
in-buildings; remote areas; marine and aviation; and public spaces''.
A nanoBTS with its plastic cover can be seen in Figure \ref{img:nanoBTSPlastic}. 
Our University GSM network consists of three nanoBTS stations. The deployed
nanoBTS in author's thesis works in the 1800 MHz frequency range,
for which the University of Freiburg had obtained a licence from the
Federal Network Agency (German: $Bundesnetzagentur$). The transmission frequencies
range between 1805-1880 MHz, with 200 KHz channel spacing and maximal output power
of +13 dBm ($\approx$20 mW)\todo{Check the output powere 20 dBm}, whereas the receiving frequencies
lie in the range between 1710-1785 MHz and same channel spacing as for transmission
of 200 KHz \citep{nanoGSM2007brochure}. \todo{Add the Abis over IP protocol}

\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.50]{img/nanoBTS.jpg}
  \caption[]{nanoBTS with its plastic cover. Image courtesy of ip.access ltd}
\label{img:nanoBTSPlastic}
\end{figure}

The nanoBTS is equiped with an internal 0 dBi (nominal) omni-directional antenna. However, 
two external antennas sized 30x36 mm, one for transmission (TX) and the other one for
reception (RX) of radio waves were used to extend the coverage area. These
antennas are connected via the SMA connectors. By using an RF amplifier
and larger antennas, for these frequency ranges, the covered area with the GSM signal
reception can be increased. For the gain estimation and radiation angle of the used antennas
the measurement equipment was missing and therefore was not conducted and described
in this work.\todo{Check for what NWL is}

At the bottom of the nanoBTS there are 5 ports, as seen in Figure \ref{img:nanoBTSPorts}.
The ports from left to right are: voltage supply, ethernet cable with power supply, USB
port, TIB-IN and TIB-OUT. In the next paragraph a brief overview of each port will be given. 

\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.15]{img/nanoBTSPorts.jpg}
  \caption[]{nanoBTS with two external antennas and five connection ports}
\label{img:nanoBTSPorts}
\end{figure}

The left most port is the power supply port used for supplying the nanoBTS with 48 V DC
and is optionally used depending on the cable configuration. In author's hardware
configuration the power supply port is not used. The following port is for the ethernet
connection with 48 V DC power supply. This port is connected to a power supply
that is supplied with the nanoBTS. It extends the ethernet connection with 48 V DC 
for the normal operation mode of the nanoBTS which is in the range between 38-50 V DC.
The power consumtion of the nanoBTS is 13 W. More details on how to interconnect the cables
will be given in section \ref{sec:hardwareConfig}. In the middle of the five port region,
the mini USB port can be found. It is used by the manufacturer to write the firmware software
to the nanoBTS. The last two ports are the TIB-IN and TIB-OUT port\footnote{TIB stands
for Timing Interface Bus}. These two ports are used if the GSM network operator requires more
than 11 channels to increase the overall capacity of the network. 
``Up to 4 nanoBTS can be combined into a multiple TRX cell, increasing the number of 
supported users per TRX by up to 200\%. The TIB-OUT from the Master TRX must be connected to
the TIB-IN of the slave TRX. This in turn has its TIB-OUT connected to the next TRX in the chain''
\citep{multipleTRX}. The multiple TRX cell configuration will not be further discussed in this work
since the purpose of the work was not to boost the capacity of a GSM network but implementation 
and testing of the RRLP protocol.

To determine the working state of the nanoBTS, an indicator status LED is located on the
left side of the five ports region. After the nanoBTS is connected to the power suplly
with the ethernet cable, it will change its color and blink speed according to the state
it is in. The states can be seen in the Table given in \ref{tbl:LEDStatus} \citep{installnanoBTS}.

One of the key limitations of gathering more technical data and the critical aspect of this
description lies in the fact, that nanoBTS is not an open source hardware platform and ip.access does not 
offer more details on their product. The lack of systematic hardware analysis can be seen as 
a major drawback of working with the nanoBTS hardware. However, the given technical data 
are sufficient for reproducing and conducting the RRLP tests described in this thesis. 


\begin{table}[h!t!p!]
\begin{center}
\caption{Indicator LED status on the nanoBTS}

\begin{tabular}{|c||p{3cm}|p{5cm}|c|c|}
\hline
% \T and \B would not work if it is placed here (needs to go inside cell)
 State&Color \& Pattern&When&Precedence \\ \hline\hline
 Self-test failure&Red - Steady&In boot or application code when a power on self-test fails&1 (High) \\ \hline
 Unspecified failure&Red - Steady &On software fatal errors&2 \\ \hline
 No ethernet&Orange - Slow flash &Ethernet disconnected&3 \\ \hline
 Factory reset&Red - Fast blink &Dongle detected at start up and the factory defaults have been applied&4 \\ \hline
 Not configured&Alternating Red/Green - Fast flash &The unit has not been configured&5 \\ \hline
 Downloading code&Orange - Fast flash &Code download procedure is in progress&6 \\ \hline
 Establishing XML&Orange - Slow blink &A management link has not yet been established but is needed for the TRX to become operational. Specifically: for a master a Primary OML or Secondary OML is not yet established; for a slave an IML to its master or a Secondary OML is not yet established.&7 \\ \hline
 Self-test &Orange - Steady & From power on until end of backhaul powe on self-test&8 \\ \hline
 NWL-test &Green - Fast flash & OML established, NWL test in progress&9 \\ \hline
 OCXO Calibration &Alternating Green/Orange - Slow blink & The unit is in the fast calibrating state [SYNC]&10 \\ \hline
 Not transmitting &Green - Slow flash & The radio carrier is not being transmitted &11 \\ \hline
 Operational &Green - Steady & Default condition if none of the above apply&12 (Low) \\ \hline
 
\end{tabular}
\end{center}
\label{tbl:LEDStatus} 
\end{table}


\newpage
\section{GPS Receiver - NL-402U}
\label{sec:gpsDevice}
In the next paragraphs the used GPS device will be described. 
In contrast to the earlier described hardware, nanoBTS, which the University of Freiburg
already owned, the budget for the GPS receiver was limited and the Navilock NL-402U
was bought considering only the single criterion, the price. The Navilock NL-402U
GPS receiver is based on the u-blox UBX-G5000 single chipset and is a one 
chip solution \citep{ubxDatasheet}. It can be seen on Figure \ref{img:gpsNavilock}
with its passive ceramic patch antenna. 1575,42 MHz is the operating frequency of
the receiver which corresponds to the L1 civil frequencies and Coarse/Acquisition (C/A) code.
The GPS chipset consists of 50 channels,
each channel tracks the transmission from a single satellite \citep{understandGPS}.
It is important to note, the number of channels inside a GPS receiver interrelates 
with the amount of time required to get the first fix. Receiver tracking sensitivity is 
-160 dBm ($10^{-16}$ mW). 
The GPS receiver communicates with the computer ovet the USB port.
Although the GPS receiver uses an USB interface, on the computer it emulates 2 UART ports, 
which are serial communication interfaces.


\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.12]{img/gpsNavlock.jpg}
  \caption[]{Navilock NL-402U, opened up with the antenna and USB cable}
\label{img:gpsNavilock}
\end{figure}

\section{Cable configuration}
\label{sec:hardwareConfig}
In the next section, the author will focus on properly connecting the hardware. 
At least 4 ethernet cables with RJ45 connectors, on both sides, were required
and one switch or hub connected to the internet. One should
take notice of the cabling between the nanoBTS and the ethernet switch or hub,
since wrong cabling with the power supply unit (PSU) could damage one of
the devices. In Figure \ref{img:connectionDiagram}, the junction points are
label according to the used configuration setting. The ethernet cables
between the switch/hub, PSU and nanoBTS should not be longer
than 100 m \citep{installnanoBTS}.

\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.5]{img/hardwareConnection}
  \caption[]{Cable connections, showing interconnection diagram}
\label{img:connectionDiagram}
\end{figure}

\chapter{Implementation}

\chapter{Future work}

\chapter{Summary}

\chapter*{Dictionary of acronyms}
\begin{itemize}
\item \emph{ARFCN} - Absolute Radio Frequency Channel Number - The channel number specifies the physical frequency channel used for transmission and reception of radio waves inside of an BTS covered area.
\item \emph{BTS} - Base Transceiver Station - 
\item \emph{DC} - Direct Current
\item \emph{GNSS} - Global Navigation Satellite System - A satellite navigation system that allows a specialized receive to determine its location on Earth.
\item \emph{LED} - Light Emitting Diode - A diode that emitts light.
\item \emph{IP Address} - \todo{Write what an IP address is}.
\item \emph{PCB} - Printed Circuit Board - The board where electronic components are soldered onto and wired through conductive tracks.
\item \emph{RRLP} - Radio Resource Location Protocol - The employed protocol in GSM, UMTS and other wireless networks for providing and exchange of geolocation information. 
\item \emph{SMA} - SubMiniature version A - SMA is a connector used for interconnecting coaxial cables or PCB electronics that work in the frequency range between 0-18 GHz.
\item \emph{TIB} - Time Interface Bus - The TIB is used to provide the synchronization of the clock, frequency and frame number between the nanoBTS when operating in a single 2-4 BTS configuration.
\item \emph{TRX} - 
\item \emph{UART} - Universal Asynchronous Receiver Transmitter - A serial communication interface used by computers or other peripheral devices to communicate.
\item \emph{UMTS} - Universal Mobile Telecommunications System - Third generation mobile network based on the GSM standards. 
\end{itemize}