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@@ -1435,7 +1435,7 @@ channel but in different time slots. Using this technique the voice throughput i
of users can be served at the ``same'' time, i.e. the capacity of parallely speaking GSM users is increased.
TDMA was employed because the voice could be compressed with Linear Predictive Coding (LPC) without the human
noting a difference in the call quality \citep{0824740408}. By taking advantage of LPC, instead of the 64 kbps required for transmission of voice
-it was possible to compress the voice without losing much of the call quality into 6.5 kbps for half rate and 13 kbps for
+it was possible to compress the voice without losing much of the call quality into 8 kbps for half rate and 16 kbps for
full rate\footnote{Human speech has a frequency bandwidth between 0 and 4000 Hz \citep{humanFreq}.
Human voice is by its nature analog and requires to be converted into a digital stream of ones and zeros.
By Nyquist-Shannon sampling theorem the sampling frequency must be at least two times greater
@@ -1461,23 +1461,65 @@ in GSM is known as a burst. Every TDMA frame is assigned a unique integer number
every 3h:28m:53s:760ms, also known as \textit{hyperframe} \citep[Chapter 7]{0890064717}. In the hierarchy pyramid,
a layer lower of the hyperframe is the \textit{superframe}. There are two types of superframes, consisting of two types
of \textit{multiframes}, differing in their length \citep[Chapter 7]{0890064717}. The relations can be seen in figure
-\ref{img:GSMHierarchy} with their duration periods.
+\ref{img:GSMHierarchy} with their duration periods. The multiframe with 26 TDMA frames carries only traffic channels (TCH) and associated
+control channels (CCH). The other multiframe type, with 51 TDMA frames carries solely signaling data. This hierarchy constrain
+was defined due to internal synchronization and cyphering between the MS and the Base Transceiver Station (BTS)
+\citep[Chapter 7]{0890064717}.
\begin{figure}[ht!]
\centering
\includegraphics[scale=0.70]{img/GSMHierarchy.pdf}
- \caption{Hierarchy of the frames in GSM.}
+ \caption{Hierarchy of the GSM frames.}
\label{img:GSMHierarchy}
\end{figure}
+BTS is the first hardware unit the cell phone is communicating with over the air interface
+and provides a ``physical'' connection with the cell phone \citep[Chapter 3]{0890064717}. This physical connection between the
+BTS and the cell phone is the \textit{$U_m$ interface}, as shown in figure \ref{img:GSMBig}. A BTS can serve up
+to seven users on one frequency since one out of eight time slot is used for broadcasting of signaling and system information,
+known as the broadcast control channel (BCCH). By sectorizing BTSs with different frequencies the number of seven mobile users
+can be increas. BTS consists of a RF tranceiver, internal clock and modulator/demodulator. The function of the RF transceiver is
+to enable the reception and transmission on the uplink and downlink channel for the cell frequency where the
+BTS is located\footnote{Cell is the area covered with GSM signal and from which a cell phone can communicate with a BTS.}.
+The main function of the internal clock is to supply the BTS with a frequency such that the internal
+circuits can produce the TDMA frames, with an accuracy of at least $\pm$5 ppm \citep{dennis}.
+Modulator/demodulator main function is the modulation and demodulation of the received and transmitted signals.
+The transmission from the cell phone to the BTS is shifted for 3 time slots compared to the reception
+of the signal from the BTS\footnote{Timing advance factor is added to the three time slots.}
+\citep[Chapter 7]{0890064717} \citep{konrad} \citep{}.
\begin{figure}[ht!]
\centering
\includegraphics[scale=0.50]{img/GSMBig.pdf}
\caption{Basic GSM network block diagram.}
\label{img:GSMBig}
\end{figure}
+
+One or more BTSs are connected to the Base Station Controller (BSC). The main task of the BSC is to control the radio
+resources of the connected BTSs such as assigning radio channels to different BTS, frequency hopping in case of an handover
+and controlling the power levels within channel \citep[Chapter 4]{0470742984} \citep{konrad} \citep[Chapter 3]{0890064717}.
+BSC is connected to the Transcoding Rate and Adaptation Unit (TRAU). This builds the Base Station Subsystem (BSS), as it can
+be seen in figure \ref{img:GSMBig}, on left side inside of the gray dashed line rectangle. Inside of the BSS, TRAU
+is responsibe for compressing and decompressing speech between the cell phone and a speech signal from the other side,
+from 64 kbps to 16 or 8 kbps depending if it is a full or half rate channel.
+
+The next subsystem block is the Network Switching Subsystem (NSS), as it can be seen on figure \ref{img:GSMBig}, on right
+side inside of the gray dashed line rectangle.
+
\section{SDCCH Channel}
+
+
+
+
+
+
+
+
+
+
+
+
+
\chapter{Radio Resource Location Protocol}
This chapter shall focus on the Radio Resource Location Protocol (RRLP) and a description
how it works inside of the GSM network shall be given. RRLP is a protocol from the family of Location Services (LCS)