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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Performance comparison of two implementations of TCM for QAM

Peh, Lin Kiat 12 1900 (has links)
Approved for public release; distribution is unlimited. / Trellis-Coded Modulation (TCM) is employed with quadrature amplitude modulation (QAM) to provide error correction coding with no expense in bandwidth. There are two common implementations of TCM, namely pragmatic TCM and Ungerboeck TCM. Both schemes employ Viterbi algorithms for decoding but have different code construction. This thesis investigates and compares the performance of pragmatic TCM and Ungerboeck TCM by implementing the Viterbi decoding algorithm for both schemes with 16-QAM and 64-QAM. Both pragmatic and Ungerboeck TCM with six memory elements are considered. Simulations were carried out for both pragmatic and Ungerboeck TCM to evaluate their respective performance. The simulations were done using Matlab software, and an additive white Gaussian noise channel was assumed. The objective was to ascertain that pragmatic TCM, with its reduced-complexity decoding, is more suitable to adaptive modulation than Ungerboeck TCM. / Civilian
132

Contamination des composants électroniques par des éléments radioactifs / Contamination of electronic devices by radiaoctive isotopes

Gedion, Michael 06 September 2012 (has links)
Cette thèse a pour objet l'étude des éléments radioactifs qui peuvent altérer le bon fonctionnement des composants électroniques au niveau terrestre. Ces éléments radioactifs sont appelés émetteurs alpha. Intrinsèques aux composants électroniques, ils se désintègrent et émettent des particules alpha qui ionisent la matière du dispositif électronique et déclenchent des SEU (Single Event Upset). Ces travaux visent à évaluer la fiabilité des circuits digitaux due à cette contrainte radiative interne aux composants électroniques. Dans ce but, tous les émetteurs alpha naturelles ou artificielles susceptibles de contaminer les matériaux des circuits digitaux ont été identifiés et classés en deux catégories : les impuretés naturelles et les radionucléides introduits. Les impuretés naturelles proviennent d'une contamination naturelle ou involontaire des matériaux utilisés. Afin d'évaluer leurs effets sur la fiabilité, le SER (Soft Error Rate) a été déterminé par simulations Monte-Carlo pour différents nœuds technologiques dans le cas de l'équilibre séculaire. Par ailleurs, avec la miniaturisation des circuits digitaux, de nouveaux éléments chimiques ont été suggérés ou employés dans la nanoélectronique. Les radionucléides introduits regroupent ce type d'élément naturellement constitué d'émetteurs alpha. Des études basées sur des simulations Monte-Carlo et des applications analytiques ont été effectués pour évaluer la fiabilité des dispositifs électroniques. Par la suite, des recommandations ont été proposées sur l'emploi de nouveaux éléments chimiques dans la nanotechnologie. / This work studies radioactive elements that can affect the proper functioning of electronic components at ground level. These radioactive elements are called alpha emitters. Intrinsic to electronic components, they decay and emit alpha particles which ionize the material of the electronic device and trigger SEU (Single Event Upset).This thesis aims to assess the reliability of digital circuits due to this internal radiative constraint of electronic components. For that, all alpha-emitting natural or artificial isotopes that can contaminate digital circuits have been identified and classified into two categories: natural impurities and introduced radionuclides.Natural impurities result from a natural or accidental contamination of materials used in nanotechnology. To assess their effects on reliability, the SER (Soft Error Rate) was determined by Monte Carlo simulations for different technology nodes in the case of secular equilibrium. Besides, a new analytical approach was developed to determine the consequences of secular disequilibrium on the reliability of digital circuits.Moreover, with the miniaturization of digital circuits, new chemical elements have been suggested or used in nanoelectronics. The introduced radionuclides include this type of element consisting of natural alpha emitters. Studies based on Monte Carlo simulations and analytical approches have been conducted to evaluate the reliability of electronic devices. Subsequently, recommendations were proposed on the use of new chemical elements in nanotechnology.
133

Zabezpečení přenosu dat proti dlouhým shlukům chyb / Protection of data transmission against long error bursts

Malach, Roman January 2008 (has links)
This Master´s thesis discuses the protection of data transmission against long error bursts. The data is transmited throught the channel with defined error rate. Parameters of the channel are error-free interval 2000 bits and length of burst error 250 bits. One of the aims of this work is to make a set of possible methods for the realization of a system for data correction. The basic selection is made from most known codes. These codes are divided into several categories and then the best one is chosen for higher selection. Of course interleaving is used too. Only one code from each category can pass on to the higher level of the best code selection. At the end the codes are compared and the best three are simulated using the Matlab program to check correct function. From these three options, one is chosen as optimal regarding practical realization. Two options exist, hardware or software realization. The second one would seem more useful. The real codec is created in validator language C. Nowadays, considering language C and from a computer architecture point of view the 8 bits size of element unit is convenient. That´s why the code RS(255, 191), which works with 8 bits symbols, is optimal. In the next step the codec of this code is created containing the coder and decoder of the code above. The simulation of error channel is ensured by last program. Finally the results are presented using several examples.
134

Simulace přenosu DVB-T v prostředí MATLAB / Simulation of DVB-T transmission chain in the MATLAB environment

Obruča, Martin January 2009 (has links)
This thesis deals with Matlab application developed for simulation of the DVB-T channel coder and decoder. The first part of this thesis includes description of terrestrial digital video broadcasting system and comparison with analogue television. Channel coding and OFDM modulation, used in the DVB-T standard, is described in detail. Application developed in the Matlab environment is described in the second part. The application simulates data transfer of the DVB-T system. Results of the simulated transmission, using developed application are presented in the last part. Namely dependence of the BER on the S/N ratio, using various coder settings, was examined. Maximal possible data rate was determined for these various setting. All obtained values are graphically represented.
135

Modelování PLC komunikačního systému pro zajištění spolehlivosti komunikace / Modelling of PLC system to ensure the reliability of communication

Procházka, Vít January 2010 (has links)
The master´s thesis is focussed on principles and characteristics of Powerline Communications (PLC), practical usage possibilities and advantages and disadvantage of it. There are described mudulations and a channel encoding which are in PLC used. The main part of the thesis deals with a design of a channel as transfer function through the use of two methods, an echo model and the ABCD matrix. After finishing of the design of transfer function the model of communication was created in the Matlab-Simulink program. There were used the narrowband modulations in the model and analyzed the bit error rate of the tranfer data. In the end all results were treated graphically and evaluated.
136

Parametry silnoproudých vedení / Power line parameters

Kavan, Pavel January 2011 (has links)
At the beginning is diploma thesis focused on a distribute power line parameters measurement and examination changes of this parameters depending on using of various power line cables. On the basis of measurements is made a transmission channel in Matlab & Simulink, where are executed simulations with power transmission line. The simulated power line is based on measured distribute parameters or physical proportions of cabels. By changing different parts of simulated communication channel is a symbol error rate expressed on the lenght of transmission line.
137

Model distribuční energetické sítě / Power distribution network model

Bradáč, Lubomír January 2012 (has links)
The thesis is focused on PLC technology issues and thus the data transmission over a power-line. This work describes characteristics of the PLC technology, its usage, functional principles and used modulation techniques. The main part of the work describes individual kinds of interferences in the network. The method of necessary steps against these interferences by using the right modulation and relevant coding is also described in the thesis. On the basis of theoretical knowledge, the models of interferences are realized in Matlab/Simulink. The simulative model of power-lines with random parameters is designed and realized for each elected techniques of modulation (BPSK, QPSK, ASK, FSK). The method of PLC channels modeling is chose as a multipath signal spreading for topology with one and two branching and the dependence of their transmission functions are inquired too. The analysis of interference influence on the data transmission is performed via the created models. All acquired results are compared and evaluated in the conclusion of this thesis.
138

Filtering of Clinical NGS Data to Improve Low Allele Frequency Variant Calling

Cumlin, Tomas January 2022 (has links)
Massive parallel sequencing (NGS) is useful in detecting and later classifying somatic driver mutations in cancer tumours. False-positive variants occur in the NGS workflow and they may be mistaken for low frequency somatic cancer mutations in a patient sample. This pushes the need for decreasing the noise rate in the NGS workflow since it may improve the detection of rare allele frequency variants, in particular cancer mutations. In this project, the aim was to reduce the level of false-positive variants in an NGS workflow. The scope was limited to looking at substitution errors and their neighbouring nucleotides. Alongside this, it was also a way to understand how different types of substitution errors are distributed in the data, if their frequencies are affected by neighbouring nucleotides and how data processing may affect these substitution rates. A bioinformatic pipeline was set up where a commercially available genomic DNA sample with known variants was subjected to different trimming and filtering settings. The goal was to reduce the substitution error rate as much as possible, without removing any true variants from the data. The optimised settings were trimming the sequencing reads with 5 bp from the tail and filtering sequencing reads that contained 5 or more substitutions. Three additional samples, whereof two were clinical and the third commercial, were tested with these settings. The results showed that in all samples, C:G>T:A substitutions were of a higher frequency compared to the rest of the substitution types. For all samples, A:T>C:G substitutions, where the neighbouring nucleotide was a C or a G on each side, had a higher frequency compared to A:T>C:G substitutions with other neighbouring nucleotides on both sides. Those substitution types were especially targeted by the trimming. For the two commercial samples, substitutions that resulted in the nucleotide combinations >XAA or >XTT were of a higher frequency compared to the same substitution types that did not result in those nucleotide combinations. Filtering reads with 5 or more substitutions particularly targeted these substitution types. Consequently, filtering had a greater effect on the commercial samples, compared to the clinical samples. Overall, trimming and filtering helped reduce transversions more than the transitions, increasing the transition/transversion ratio after processing the data. The results suggest that trimming and filtering can be a useful method to computationally reduce the transversion errors introduced in an NGS workflow, but transition errors to a lesser extent, in particular A:T>G:C transitions. To confirm these findings, more samples should be tested using this methodology. To better understand the effect of trimming and filtering on variant calling, the scope could in the future be expanded to also look at small insertions and deletions.
139

Application of NOMA for Mobile High Definition Images

Danda, Aishwarya Reddy, Chama, Naga Manikanta January 2021 (has links)
The telecommunications technology has been developed tremendously as there has been an ever-increasing demand for more speed and reliability. The enormous increase in the number of smart phones and other data consuming devices, combined with the development of enhanced multimedia applications has resulted in a dramatic increase in the volume of mobile data traffic. In order to accommodate the growing needs, it is required to utilise the spectrum efficiently. The design of radio access technology plays an important role in the aspect of system performance. These radio access technologies are typically characterised by the multiple-access techniques used. Non-Orthogonal Multiple Access (NOMA) is a multiple access scheme proposed for 5G and it utilises the power domain which was not sufficiently utilised in the previous systems.        This thesis work is mainly focused on the performance analysis of the NOMA technique in mobile media (images). This analysis is achieved by transmitting a high definition image at various power levels to two users who are located at two different distances from the base station. The images are transmitted through suitable noise channels. An analysis is done on how NOMA copes with the users having poor channel conditions. The performance is analysed by comparing the output images at both the receivers based on the structural similarity index and bit error rate parameters.
140

Impacts des non-linéarités dans les systèmes multi-porteuses de type FBMC-OQAM / OFDM-FBMC performance in presence of non-linear high power amplifier

Bouhadda, Hanen 22 March 2016 (has links)
Dans cette thèse une étude des performances des systèmes OFDM et FBMC/OQAM en présence d'amplificateur de puissance sans mémoire en terme de TEB est présentée. Ensuite, nous avons proposé une technique de linéarisation d'AP par pré-distorsion adaptative neuronale. Aussi, nous avons proposé deux techniques de correction des non-linéarités au niveau du récepteur. / In our work, we have studied the impact of in-band non linear distortions caused by PA on both OFDM and FBMC/OQAM systems. A theoretical approach was proposed to evaluate the BER performance for the two systems. This approach is based on modeling the in-band non-linear distortion with a complex gain and an uncorrelated additive white Gaussian noise, given by the Bussgang theorem. Then, we have proposed different techniques to compensate this NLD either on the transmitter or the receiver sides.

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