summaryrefslogtreecommitdiffstats
path: root/vorlagen/thesis/src/kapitel_x.tex
blob: 223e7856072646fae95f90636afad4e64223b2e6 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
\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}
\section{GPS Principles}
\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.50]{img/GPS-Principle.pdf}
  \caption[]{nanoBTS with its plastic cover. Image courtesy of ip.access ltd}
\label{img:gpsprinciple}
\end{figure}

\section{GPS signal modulation}
\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.50]{img/GPS-Modulation.pdf}
  \caption[]{Modulation of the GPS signal L1}
\label{img:gpsmod}
\end{figure}

\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.50]{img/NAV-Message.pdf}
  \caption[]{One frame of 1500 bits on L1 frequency carrier}
\label{img:gpsframe}
\end{figure}



\section{GPS signal demodulation}
The GPS satellites\footnote{Satellites are named as space vehicles 
and the abrevation SV is used in the equation notations
to denote a parameter related to the satellite itself.}
orbiting our planet, at a distance of approximately 20,200 km,
are equiped with precise atomic clocks \citep[Chapter 2.7]{diggelen2009a-gps}.
These atomic clocks are calibrated and maintained on
a daily basis by the U.S. Air Force, \citep{GPS-Pentagon}. 
The time the clock generates is called \textit{GPS
system time}, denoted as $t_{SV}$,
and it is generated as a time stamp at the moment
of the frame broadcast \citep{GPS-Interface-Specification}.
Each satellite signs the frame with its exact
broadcast time. The broadcast time is encapsulated in the
subframe 1 of the 1500 bit long frame. In addition to the
broadcast time, subframe 1 contains parameters to account
for the deterministic clock errors embedded in the
broadcasted GPS system time stamp. These errors can be
characterized as bias, drift and aging errors
\citep{GPS-Interface-Specification}. The correct broadcast
time, denoted as $t$, can be estimated using the model equation given in
\eqref{eq:timecorrection1} \citep{GPS-Interface-Specification}. 
In equation \eqref{eq:timecorrection2}, where the GPS
receiver is required to calculate the satellite clock
offset, denoted as $\Delta t_{SV}$, a number of unknown terms can be
seen. These terms are encapsulated in the subframe 1 or they
can be estimated using predefined equations. The polynomial
coefficients: $a_{f0}$ - \textit{clock offset}, $a_{f1}$ - 
\textit{fractional frequency offset}, $a_{f2}$ - \textit{
fractional frequency drift}; and
$t_{0c}$ - \textit{reference epoch} are encapsulated inside
of subframe 1. Finally, the only unknown term left in equation 
\eqref{eq:timecorrection2} is the \textit{relativistic correction
term}, denoted as $\Delta t_{r}$. $\Delta t_{r}$ can be evaluated
by applying the equation given in \eqref{eq:timecorrection3}.
$F$ is a constant calculated from the given parameters
in \eqref{eq:paramconst1} and \eqref{eq:paramconst2},
whereas $e$, $\sqrt{A}$ and $E_{k}$ are \textit{orbit
parameters} encapsulated in subframe 2 and 3
\citep{GPS-Interface-Specification}. 

\begin{equation}
\label{eq:timecorrection1}
\centering
t=t_{SV}-\Delta t_{SV} 
\end{equation}

\begin{alignat}{4}
 & \Delta t_{SV} &= \;& a_{f0} + a_{f1}(t_{SV}-t_{oc}) + a_{f2}(t_{SV}-t_{oc})^{2} + \Delta t_{r} \label{eq:timecorrection2} \\
 & \Delta t_{r}  &= \; & Fe\sqrt{A}\sin{E_{k}} \label{eq:timecorrection3} \\
 & F &= \;& \frac{-2\sqrt{\mu_{e}}} {c^{2}} = -4.442807633 \cdot 10^{-10} \frac{s}{\sqrt{m}} \label{eq:timecorrection4} 
\end{alignat}

However, the broadcast satellite time
information is not sufficient to estimate the precise
time at the moment of the signal arival. Even though the signal
arives in approximately 77 ms, the precision of the atomic clock
is in the range of 10 ns \citep[Chapter 2]{diggelen2009a-gps}. 
Undoubtedly the signal propagation (travel)
time, denoted as $t_{prop}$, has to be taken into account.
Then the exact time at the moment of arival, denoted as
$t_{exact}$, is given in equation \eqref{eq:exactTime}.
The signal propagation time must be known to
estimate the distance from the satellite
as well as to estimate the position of the GPS receiver. 
\begin{equation}
\label{eq:exactTime}
t_{exact} = t_{prop}+t
\end{equation}
In order to calculate the signal propagation time between
the satellite and the receiver, the internal clock 
wave of the of the receiver crystal needs to be
synchronized with the carrier clock wave
of the satellite \citep{4560215}. In other words,
the identical carrier wave replica has to be generated
on the receiver as on the satellite. 
Due to the nature of wave propagation and various
errors the signal arives phase disordered at the
receiver \citep{4560215}. 
The observed phase at the receiver antenna, 
denoted as $\varphi_{o}$, can be described using
the equation given in \eqref{eq:phaseShift}, 
where $\varphi_{GPS}$ represents the known satellite
carrier wave phase, $\delta \varphi_{SV}$ the clock
instabilities on the GPS satellite,
$\varphi_{a}$ the phase shift error
caused by propagation delays in the ionosphere
and troposphere respectively and $\delta \varphi_{w}$
is the wideband noise. 
\begin{equation}
\label{eq:phaseShift}
\varphi_{o} = \varphi_{GPS}+ \delta\varphi_{SV} + \varphi_{a} + \delta \varphi_{w}
\end{equation}
The task of the syncrhonization process is to 
generate a replica carrier wave with the matching
phase shift. In the ideal case, the observed phase
on the antenna and the generated phase on the
receiver, denoted as $\varphi_{r}$, cancel each other
out, in other words, equation \eqref{eq:phaseIdealCaset}
equals to zero.
\begin{equation}
\label{eq:phaseIdealCaset}
\Delta \varphi = \varphi_{o} - \varphi_{r}
\end{equation}
\begin{figure}[ht!]
  \centering
  \includegraphics[scale=1.0]{img/Phase-Diff.pdf}
  \caption[]{Two equivalent carrier waves with phase shift}
\label{img:phaseShift}
\end{figure}
If this property is not satisfied, it is not possible
to demudalte the C/A code from the received signal. 





More importantly, $t_{exact}$ is used to synchronize various system dependent.


\begin{alignat}{4}
 & A & = & \; (\sqrt{A})^2 \nonumber \\
 & n_{0} & = &\; \sqrt{\frac{\mu}{A^3}} \nonumber \\
 & t_{k} & = &\; t-t_{oe} \nonumber \\
 & n & = &\; n_{0} + \Delta n \nonumber \\
 & M_{k} & = &\; M_{0} + nt_{k} \nonumber \\
 & M_{k} & = &\; E_{k} - e\sin E_{k} \nonumber \\
 & v_{k} & = & \tan ^{-1} \left( \frac{\sin v_{k}}{\cos v_{k}} \right) = \tan ^{-1} \left( \frac{\frac{\sqrt{1-e^2} \sin E_{k}}{1-e \cos E_{k}}}{\frac{\cos E_{k}-e}{1-e\cos E_{k}}} \right) \nonumber \\
 & v_{k} & = & \tan ^{-1} \left( \frac{\sin v_{k}}{\cos v_{k}} \right) = \tan ^{-1} \left( \frac{\sqrt{1-e^2} \sin E_{k}/(1-e \cos E_{k})}{(\cos E_{k}-e)/(1-e\cos E_{k})} \right) = \tan ^{-1} \left( \frac{\sqrt{1-e^2} \sin E_{k}}{\cos E_{k} - e} \right) \nonumber \\
 & E_{k} & = & \cos ^{-1} \left( \frac{e+\cos v_{k}}{1+e \cos v_{k}} \right) \nonumber \\
 & \Phi_{k} & = &\; v_{k} + \omega \nonumber \\
 & \delta u_{k} & = &\;  c_{us} \sin{2\Phi_{k}} + C_{us} \cos{2\Phi_{k}}  \\
 & \delta r_{k} & = &\;  c_{rc} \cos{2\Phi_{k}} + C_{rs} \sin{2\Phi_{k}} \nonumber \\
 & \delta i_{k} & = &\;  c_{ic} \cos{2\Phi_{k}} + C_{is} \sin{2\Phi_{k}} \nonumber \\
 & u_{k} & = &\;  \Phi_{k} + \delta u_{k} \nonumber \\
 & r_{k} & = &\; A(1-e\cos{E_{k}})+\delta r_{k} \nonumber \\
 & i_{k} & = &\; i_{0} + \delta i_{k} + (IDOT)t_{k} \nonumber \\
 & x_{k}^{'} & = &\; r_{k} \cos{u_{k}} \nonumber \\
 & y_{k}^{'} & = &\; r_{k} \sin{u_{k}} \nonumber \\
 & \Omega_{k} & = &\; \Omega_{0} + (\Omega - \Omega_{e})t_{k} - \Omega_{e}t_{oe} \nonumber \\
 & x & = &\; x_{k}^{'} \cos{\Omega_{k}}-y_{k}^{'}\cos{i_{k}}\sin{\Omega_{k}} \nonumber \\
 & y & = &\; x_{k}^{'} \sin{\Omega_{k}}-y_{k}^{'}\cos{i_{k}}\cos{\Omega_{k}} \nonumber \\
 & z & = &\; y_{k}^{'} \sin{i_{k}} \nonumber
\end{alignat}

The received signal after the RF frontend is given
in equation \eqref{eq:GPSSignalReceived} \citep{1656803}.
\begin{equation}
\label{eq:GPSSignalReceived}
S(t) = \sqrt{\frac{P}{2}}D(t)C(t)cos(2\pi f_{c}+\varphi_{SV}) + n(t)
\end{equation}
Each tracked GPS satellite signal is demodulated seperately 
using the same PRN code, code chipping rate and carrier frequency
phase for the given satellite \citep[Chapter 4]{understandGPS}. 
The PRN codes for each GPS satellite are well defined and
known by the GPS receiver. The receiver has to generate the
same PRN code with matching code chipping rate (phase)
of the C/A code,
this is depicted in figure \ref{img:prnCodeCompare} 
\citep[Chapter 5]{understandGPS}.
\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.50]{img/PRN-ChipRate.pdf}
  \caption[]{Comparison of original C/A code generated on the
  GPS satellite with two synthesized PRN codes with phase shift on the receiver}
\label{img:prnCodeCompare}
\end{figure}
For the particular example, the matching phase shift was achieved with
the second replica PRN code, with a phase shift of $\tau=0$ but
there could be a case with any other value of $\tau$, $\tau\in[0,1023]$.
The PRN code synthesizer implementation depends on the GPS receiver
manufacturer but it is usually implemented as a linear feedback shift
registers (LFSR) that produces an output according to a predefined function $f(\tau)$. 
This function generates an PRN code, that is
delayed in phase by $\tau$, where $\tau$ is a multiple of the chipping period
$T_{c}=977.5 ns$. The chipping period $T_{c}$
can be derived from equation \eqref{eq:chipPeriod}.
The time required to find a matching PRN code shift ($\tau$)
is proportional to the amount of LFSR on the system
\citep[Chapter 3]{bensky2008wireless}. Particularly with more LFSRs
the required time for finding the matching phase shift increases.
\begin{equation}
\label{eq:chipPeriod}
T_{c} = \frac{1}{f_{PRN}} = \frac{1}{1.023\cdot 10^6}
\end{equation}

To determine whether the synthesized PRN code,
matches the incoming C/A code from the satellite,
known correlation properties of PRN codes are used. 
Since the signal is modeled as a sequence of +1's and
-1's, the autocorrelation of
a signal is at its maximum if it is in phase, i.e. 
summing up the sequence products yields the absolute
maximum value. As an illustration of the idea, an example is
given in figure \ref{img:correlatingSignals}. The cross-correlation
of the incoming C/A code with the first synthesized PRN produces a 
result of $-3=(+1)\cdot(-1)+(-1)\cdot(+1)+(+1)\cdot(-1)+(+1)\cdot(+1)+(-1)\cdot(+1)$,
whereas the cross-correlation of the incoming C/A code
and the second synthesized PRN code yields a result of 
$+5=(+1)\cdot(+1)+(-1)\cdot(-1)+(+1)\cdot(+1)+(+1)\cdot(+1)+(-1)\cdot(-1)$.
\begin{figure}[ht!]
  \centering
  \includegraphics[scale=0.50]{img/Correlation.pdf}
  \caption[]{Cross-correlation on three different signals}
\label{img:correlatingSignals}
\end{figure}
The same principle applies to the sent C/A and 
PRN code sequences in the GPS receiver and thus can be modeled using
the equation given in \eqref{eq:autocorrelationProperty}, 
where, $G_{i}(t)$ is the C/A code Gold code sequence as a
function of time, $t$, for the GPS satellite $i$; $T_{C/A}$ is the
C/A chipping period of $977.5 ns$ and $\tau$ is the phase shift 
in the auto-correlation function \citep[Chapter 4]{understandGPS}.
\begin{equation}
\label{eq:autocorrelationProperty}
R_{i}(t) = \frac{1}{1023\cdot T_{C/A}} \int_{t=0}^{1023} G_{i}(t)G_{i}(t+\tau)d\tau
\end{equation}
Another correlation property of the PRN codes comes in useful,
the fact that in the ideal case the cross-correlation of two
different PRN codes yields a result of zero. The ideal case 
can be modeled as in equation \eqref{eq:prnIdealCaseZero},
\begin{equation}
\label{eq:prnIdealCaseZero}
R_{ij}(\tau) = \int_{-\infty}^{+\infty} PRN_{i}(t)PRN_{j}(t+\tau)d\tau = 0
\end{equation}
where $PRN_{i}$ is the PRN code waveform for GPS satellite $i$ and 
$PRN_{j}$ is the PRN code waveform for every other GPS satellite other
than $i$, $i\neq j$ \citep[Chapter 4]{understandGPS}. Equation
\eqref{eq:prnIdealCaseZero} ``states that the PRN waveforms of satellite
$i$ does not correlate with PRN waveform of any other satellite for
any phase shift $\tau$'' \citep[Chapter 4]{understandGPS}.
Without this
property, the GPS receiver would not be able to smoothly 
differentiate between best phase shifts.

\section{Distance and position estimation}

\chapter{Radio Resource Location Protocol}

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

\chapter{System}
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.\todo{Referenz für lorem ipsum}
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}