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| -rw-r--r-- | doc/thesis/Fading.tex | 4 | ||||
| -rw-r--r-- | doc/thesis/chapters/conclusions.tex | 7 | ||||
| -rw-r--r-- | doc/thesis/chapters/implementation.tex | 17 | ||||
| -rw-r--r-- | doc/thesis/chapters/introduction.tex | 6 | ||||
| -rw-r--r-- | doc/thesis/chapters/theory.tex | 2 |
5 files changed, 22 insertions, 14 deletions
diff --git a/doc/thesis/Fading.tex b/doc/thesis/Fading.tex index 3a9eaca..c20ddc5 100644 --- a/doc/thesis/Fading.tex +++ b/doc/thesis/Fading.tex @@ -104,8 +104,8 @@ \begin{abstract} - In wireless communication today, it is important to know how signals change on their way to the receiver. There are many different ways how this can happen, in this paper will be focuses on the study of the \emph{multipath fading effect}. The aim is to easily illustrate the change of the signal evoked through this effect. - First of all some basical fundamentals are discussed, followed by the implementation in as simulation of those different models, including the transmitter and reviser chain, later with the help of two SDRs. + In today's wireless communication, it is important to know how signals change on their way to the receiver. There are many different ways how this can happen. This paper will be focused on the study of the \emph{multipath fading effect}. The aim is to easily illustrate the change of the signal evoked through this effect. + First some basic fundamentals are discussed, followed by the implementation in as simulation of those different models, including the transmitter and receiver chain. Later implemented with the help of two SDRs. The effect is finally shown with the help of a GUI. diff --git a/doc/thesis/chapters/conclusions.tex b/doc/thesis/chapters/conclusions.tex index d7b8e8c..8cb3a5d 100644 --- a/doc/thesis/chapters/conclusions.tex +++ b/doc/thesis/chapters/conclusions.tex @@ -32,3 +32,10 @@ In addition to fixing the aforementioned issue, a very important missing feature \section{Closing words} \section{Acknowledgements} + + +We would like to thank everyone who took the time to help us. Specially Michel Nyffenegger, Nicola Ramagnano for his explanations, with the GNU Radio tool, +Marcel Kluser, who has provided the equipment, Prof. Dr. Heinz Mathis for the opportunity and to our fiends whose supported us in different ways. + + + diff --git a/doc/thesis/chapters/implementation.tex b/doc/thesis/chapters/implementation.tex index 77be697..1ecfd9d 100644 --- a/doc/thesis/chapters/implementation.tex +++ b/doc/thesis/chapters/implementation.tex @@ -55,7 +55,7 @@ class myblock(gr.sync_block): To construct a graphical interface for a demonstration platform the Dear IMGUI (immediate mode graphical user interface) library was chosen, mainly for its ease of use, wide range of techincal capabilites and high refresh rate. Dear PyGUI (DPG) are the Python bindings for the Dear IMGUI library. -The DPG GUI communicates with the GR flow graphs using the IP/UDP protocol. This decision to separate the project into two parts that communicate over the IP network was made because it is not very easy to extend the graphical interface of GRC without interfering with the sophisticated multi-threaded architecture of GR. Furthermore, this allows to have multiple correctly configure flow graph on disk and to choose which one to run and display on the graphical interface, instead of having a single flow graph whose parameters need to be changed each time. As a side effect, in theory this setup allows to have one computer running the graphical interface, and another remote machine running just the flow graph. +The DPG GUI communicates with the GR flow graphs using the IP/UDP protocol. This decision to separate the project into two parts that communicate over the IP network was made because it is not easy to extend the graphical interface of GRC without interfering with the sophisticated multi-threaded architecture of GR. Furthermore, this allows to have multiple correctly configure flow graph on disk and to choose which one to run and display on the graphical interface, instead of having a single flow graph whose parameters need to be changed each time. As a side effect, in theory this setup allows to have one computer running the graphical interface, and another remote machine running just the flow graph. \section{Hardware} @@ -295,24 +295,25 @@ Thus, they will be distributed among the other whole numbers. A window function \subsection{Fading with statistical model} -In order to represent the effect of the multipaht fading not only statically, a second model was created using the Frequency Selective Fading Model from Gnu Radio, according to \ref{sec:statistical-model},which was implemented after the algorithm from the paper \cite{Alimohammad2009}, with the help of the sum-of sinusoid principal (SOS). The algorithm in this block is implemented with the aim that only a small number of sinusoids are needed. +In order to represent the effect of the multipath fading not only statically, a second model was created using the Frequency Selective Fading Model from GR, according to \ref{sec:statistical-model},which was implemented after the algorithm from the paper \cite{Alimohammad2009}, with the help of the sum-of sinusoid principal (SOS). The algorithm in this block is implemented with the aim that only a small number of sinusoids are needed. This number represent the sinusoids which are simulated for each ray, for the foaling simulations shown the value 8 has been chosen. -It can also be chosen whish statical model should be taken for the simulation Rayleigh or Rician. When the Rician model is taken also a realistic value for the factor \(K\) need to be given. Whish is something between zero and ten. As mentioned earlier, when \(K=0\) the distribution is the same as with the Rayleight model. For a faktor \(K = 5.1\) the probability function is gaussien distributed. +It can also be chosen whish statical model should be taken for the simulation Rayleigh or Rician. When the Rician model is taken, a realistic value for the factor \(K\) needs to be given. Which is between zero and ten. As mentioned earlier, when \(K=0\) the distribution is the same as with the Rayleight model. For a factor \(K = 5.1\) the probability function is gaussian distributed. +%TODO : Sätze anpassen -The power delay profile which specify the delay in time for each impulse need to be in sample. For this delayed vector some realistic values are for the first delay \cite{Mathworks}, when theirs non line of side zero. The second delayed path depend on the environment of measurement. In an indoor environment it is usually between \(1\cdot10^{-9}\) to \(1\cdot10^{-7}\) and in an outdoor environment between \(1\cdot10^{-7}\) to \(1\cdot10^{-5}\). The rest depends on the bandwidth. +The power delay profile which specifies the delay in time uses sample as unit. For this delay vector some realistic values are for the first delay \cite{Mathworks}. If there is non line of sight it should be zero. The second delayed path depends on the environment of the measurement. In an indoor environment it is usually between \(1\cdot10^{-9}\) to \(1\cdot10^{-7}\) and in an outdoor environment between \(1\cdot10^{-7}\) to \(1\cdot10^{-5}\). The rest depends on the bandwidth. -The magnitudes of the pulses are given with the linear value. In practices the avarage path gain of a fading path is in the range of \([ -20 \text{dB} , 0\text{dB}]\). +The magnitudes of the pulses are given with the linear value. In practices the average path gain of a fading path is in the range of \([ -20 \text{dB} , 0\text{dB}]\). -To add some movement, like a movable transmitter some Doppler shift can be initialized after the formula \eqref{Doppler-shift}. But it need to be normalized with the sampling rate. +To add some movement, some Doppler shift can be introduced according to the formula \eqref{Doppler-shift}. But it needs to be normalized with the sampling rate. An example of such a simulation plot is shown in \figref{fig:qpsk-simulations-dynamic}. -When nothing mentioned the number of how many FIR- filter taps are used is eight. +When nothing else is mentioned, the number of FIR-filter taps used is eight. %TODO: Should this be mentoned \subsubsection{Issues} -Some difficulty was how to check the correction of the statistical models, if there is noise in the channel, from the fading effect, especially when the doppler frequency is included. This was difficult to recreate, when the parameter haven't the special case in which the the amplitude and the phase shift can be seen exactly. +A difficulty was to check the correctness of the statistical models, if there is noise in the channel from the fading effect. Especially when the Doppler frequency is included. This was difficult to recreate, when the amplitude and phase parameter in which the amplitude and the phase shift can be seen exactly. To have some indication to verified the plot, mainly whether the movement could be correct a little Matlab model was used with the same values for the different distributions. %TODO: Other Plots? diff --git a/doc/thesis/chapters/introduction.tex b/doc/thesis/chapters/introduction.tex index 9e406b8..8e9e0fe 100644 --- a/doc/thesis/chapters/introduction.tex +++ b/doc/thesis/chapters/introduction.tex @@ -6,9 +6,9 @@ It is undeniable that in the last two decades wireless devices have become extremely ubiquitous, and are no longer employed under carefully chosen conditions. -Nowadays smart phones, internet of things (IoT) devices and many other wireless devices omnipresent have to work in environments that are very far from ideal. Furthermore in addition to the already large class of networked appliances, next generation wireless devices in urban environments will include the new category of vehicles \cite{AntonescuTB17}, where reliability of intra-vehicular communication directly translates into safety. While at the same time in rural regions, developing countries as well as in other low-user density areas, wireless transmission links using mesh networks have become a practical alternative to wired broadband \cite{Macmillan2019tidal,Subramanian2006rethinking,Flickenger2007wireless}. +Nowadays, smart phones, internet of things (IoT) devices and many other wireless applications are omnipresent and have to work in environments that are very far from ideal. Furthermore, in addition to the already large class of networked appliances, next generation wireless devices in urban environments will include the new category of vehicles \cite{AntonescuTB17}, where reliability of inter-vehicular communication directly translates into safety. While at the same time in rural regions, developing countries as well as in other low-user density areas, wireless transmission links using mesh networks have become a practical alternative to wired broadband \cite{Macmillan2019tidal,Subramanian2006rethinking,Flickenger2007wireless}. -Thus today the study of problems concerning wireless devices is very relevant topic. In particular, a common issue observed in the previously mentioned use cases is the so called \emph{multipath fading effect}, that degrades the reliability of a wireless transmission links \cite{Mathis, Gallager}. The problem of fading was actually foreseen \cite{Frederiksen2002overview,Maddocks1993introduction} and today most modern transmission schemes implement measures to reduce the effects fading \cite{Mathis,Hsu}. +Thus today the study of problems concerning wireless devices is a very relevant topic. In particular, a common issue observed in the previously mentioned use cases is the so called \emph{multipath fading effect}, that degrades the reliability of a wireless transmission links \cite{Mathis, Gallager}. The problem of fading was actually foreseen \cite{Frederiksen2002overview,Maddocks1993introduction} and today most modern transmission schemes implement measures to reduce the effects fading \cite{Mathis,Hsu}. This work studies the multipath fading effect, and how it affects modern digital transmission systems that use quadrature amplitude (QAM) and phase shift keying (PSK) modulation. @@ -22,4 +22,4 @@ The entire task description is found in the appendix. \section{Overview} -In chapter \ref{chp:theory} the theoretical formulation and mathematical basis for the modulation schemes and channel models that have been used in this project are presented. Specifically \(M\)-ary QAM, \(M\)-PSK modulation, and three models for multipath fading are explained (continuous time, discrete time and statistical). Chapter \ref{chp:implementation} describes in detail our implementation. The transmitter and receiver chains are explained and simulations as well as measurements under different multipath fading conditions are presented. Finally some problems of the current implementation project are addressed. Chapter \ref{chp:conclusions} discusses the results of the project, and suggests how the device could be improved in the future. +In chapter \ref{chp:theory}, the theoretical formulation and mathematical basis for the modulation schemes and channel models that have been used in this project are presented. Specifically \(M\)-ary QAM, \(M\)-PSK modulation, and three models for multipath fading are explained (continuous time, discrete time and statistical). Chapter \ref{chp:implementation} describes in detail our implementation. The transmitter and receiver chains are explained and simulations as well as measurements under different multipath fading conditions are presented. Finally some problems of the current implementation project are addressed. Chapter \ref{chp:conclusions} discusses the results of the project, and suggests how the device could be improved in the future. diff --git a/doc/thesis/chapters/theory.tex b/doc/thesis/chapters/theory.tex index 9e1b563..bb948a8 100644 --- a/doc/thesis/chapters/theory.tex +++ b/doc/thesis/chapters/theory.tex @@ -15,7 +15,7 @@ \section{Overview} -The following two sections will briefly introduce mathematical formulations of the modulation schemes and of the channel models used in this project. The notation used is summarised in \figref{fig:notation}. For conciseness encoding schemes and (digital) signal processing calculations are left out and discussed later. Section \ref{sec:multipath-fading} presents an established mathematical model to understand multipath fading, as well as a brief description of a discrete-time model and the intricacies caused by the sampling process. Finally the concept of stochastic models is mentioned, as they are often used to simulate multipath channels \cite{Messier,Mathis}. +The following two sections will briefly introduce mathematical formulations of the modulation schemes and of the channel models used in this project. The notation used is summarised in \figref{fig:notation}. For conciseness, encoding schemes and (digital) signal processing calculations are left out and discussed later. Section \ref{sec:multipath-fading} presents an established mathematical model to understand multipath fading, as well as a brief description of a discrete-time model and the intricacies caused by the sampling process. Finally, the concept of stochastic models is mentioned, as they are often used to simulate multipath channels \cite{Messier,Mathis}. %% TODO: A section on maths? % \section{Signal space and linear operators} |