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Turbocodes and their application in telecommunication systems
Trčka, Tomáš ; Křivánek, Vítězslav (referee) ; Němec, Karel (advisor)
This Diploma thesis deals with Turbo code problems. The Turbo codes belong to the group of error correction codes, sometimes referred to as forward error correcting (FEC) codes or channel codes. This thesis can be thematically divided into two basic parts. The first part describes turbo code encoder and decoder block diagram with the illustration of two most frequently used iterative decoding algorithms (SOVA and MAP). The end of this part contains best known turbo codes, which are used in present communication systems. The second part pursues simulation results for the turbo codes using Binary Phase Shift Keying (BPSK) over Additive White Gaussian Noise (AWGN) channels. These simulations were created in the MATLAB/SIMULINK computer program. It will be shown here, that there exist many different parameters, greatly affecting turbo codes performance. Some of these parameters are: number of decoding iterations used, the input data frame length, generating polynoms and RSC encoders constraint lengths, properly designed interleaving block, decoding algorithm used, etc.
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Systems Design of Correction Coding
Křivánek, Vítězslav ; Němec, Karel (advisor)
Due to growing transmission speed burst-forming errors tend to occur still more frequently not exclusively in data transmission. The presented paper concentrates on the search for alternative burst error correction solutions complementing the existing methods in use. Its objective is an elaboration of a detailed analysis of the issue of convolution codes for error burst correction which can be used in individual anti-error systems and thus an achievement of better results than those attained by mass application of the existing solutions. First the methods implemented to remove or suppress burst errors are briefly characterized. This part is followed by a detailed description of the individual systematic convolution codes by means of mathematical tools which extend the set of possible evaluative criteria of anti-error systems which can be applied while assessing proposals for individual solutions. The acquired code properties are compared with convolution codes as well as with other versions of proposals for message protection against an error burst. The processed convolution codes are subject to testing by means of Matlab mathematical programme simulation in order to validate the correctness of the derived mathematical tools. This is because simulation represents the principal method applied to verify and present an already proposed security process and enables the acquisition of a better overview of the issue at hand. The feasibility of the individual anti-error systems is then confirmed by way of creating a circuit behaviour description in the VHDL language. Its high portability presents a big advantage when drafting individual systems of the actual implementation.
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Effect of Light Polarization on Optical Fibre Links
Obručník, Ondřej ; Křivánek, Vítězslav (referee) ; Kyselák, Martin (advisor)
The bachelor thesis deals with the emergence of polarization mode dispersion, its mathematical expression and also the influence, which polarization mode dispersion has on the optical communication channel. First, the chapters birefringence in fibers and polarization debate its emergence and basic characteristics, then are introduced two possibilities of mathematical expression polarization mode dispersion namely in Stokes and Jones space, whence is more closely examine Jones space. End work adverts about dependencies wavelength and birefringence on differential group delay, also about using fibre Bragg gratings in optical fibres and fall of characteristics grating on differential group delay.
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VoIP and QoS
Kolmačka, Jan ; Křivánek, Vítězslav (referee) ; Kovář, Petr (advisor)
The bachelor’s thesis gives the basic information about the solution of a problem with Quality of Service in sequence with the VoIP telephony. In a few last years the VoIP technologies and basically the other multimedia applications have unbelievable grow. It is caused by a big demand internet user’s for the new interactive applications offering voice transfers and streaming video. These new habits bring quite big requests on networks from the side of QoS. That is why, it was necessary to develop new methods, which reach requested parameters of QoS in single categories. The first part discuss theoretically about protocols used in the VoIP telephony. The second part presents QoS, parameters of QoS and two basic methods for guarantee QoS. In the last part of the bachelor’s thesis is theoretically described the QoS support in Wi-Fi with the main aim on new technologies QoS reservation defined in the 802.11e. The following simulations and the results of the different settings parameters QoS are made by the powerful simulating software Opnet Modeler.
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Methods Decoding Convolucional Code
Vlček, Peter ; Zezula, Radek (referee) ; Křivánek, Vítězslav (advisor)
Convolutional codes belongs to among linear tree codes. There are codes used for channel coding. At build - up project, then comparison separate algorithms were gateway into the account Viterbiho algorithm, Stack algorithm, Stack- bucket algorithm, Fano algorithm and Feedback decoding. Was built-up suggestion convolutional encoder and decoder, which at his activities make use of Viterbiho algorithm and Stack algorithm, what serves for contrast of both methods. It turned out, that the Viterbiho algorithm get past in the main for codes with smaller compulsory longitude, because has stand-by cost quantity calculated effect. At Stack algorithms is quantity calculated effect dependent on longitude received sequence, what may result in much smaller number calculated effect, however at very noisy channel is able to state, that the calculated effect will much more as with Viterbiho algorithm. Nothing less is Stack algorithm or his variation Stack- bucket algorithm used primarily on codes with bigger compulsory longitude. Feedback decoding is gainst for simple construction decoder acceptable alternative toward decoding most likely and to sequential decoding.
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Design of Graphic Interface for Calculation of Differential Group Delay
Vohralík, Jan ; Křivánek, Vítězslav (referee) ; Kyselák, Martin (advisor)
The Bachelor's thesis is aimed to the problems regarding Polarization mode dispersion in optical fibre. Polarization mode disperzion limits the bandwidth of high speed comunication system. It cases a differential group delay between different polarizatins. If the delay is too high than the bits overlap and a bit error rate is increased. The work include description of polarization in Jones space and Stokem space. For description of Polarization mode disperzion is used PMD vector. I demonstrate influence of differential group delay in optical fibre at special grafic program develop in C# language.
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Design of Multiplex Optical Fibre Link
Krejča, Libor ; Křivánek, Vítězslav (referee) ; Kyselák, Martin (advisor)
In this thesis I consider problems of optical multiplexers, optical amplifiers and designing optical networks with this components. CWDM and DWDM are the most common used multiplexers today. I describe principles of realization multiplexers from basic level to realization in WDM networks. EDFA is also common used amplifier today and I describe his internal structure and how it works. Today, we can observe many realization of optical netwoks with Raman amplifiers, especially in long haul networks. Raman amplifier is characterized in brief. In next chapter I describe the design of optical communication systems and the main designing equations are explained. Then I used the equations for example of designing optical communication system with multiplexers, EDFAs and other components, which are needed for function of the system. In last chapter I explain mathematical model of signal propagation in optical fiber called nonlinear Schrodinger equation, which includes main optical effects in fiber like chromatic dispersion or Kerr effect. The simulation model and his numeric solution was designed including PMD effect, the simulation model is programmed in MATLAB.
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Error protection of data transmission using BCH Codes
Kašpar, Jaroslav ; Křivánek, Vítězslav (referee) ; Němec, Karel (advisor)
The thesis Data transmission error-protection with BCH codes deals with a large class of random-error correcting cyclic codes which are able to protect binary data and can be used for example in data storages, high speed modems. Bose, Chaudhuri and Hocquenghem (BCH) codes operate over algebraic structures called Galois fields. The BCH encoding is the same as cyclic encoding and can be done with linear feedback shift register but decoding is more complex and can be done with different algorithms - in this thesis there are two algorithms for decoding Peterson and Berlekam-Massey mentioned. The aim of this thesis is to find BCH code which is able to correct t = 6 independent errors in up to data sequence n = 150 bits, then peruse possible realizations of the codecs and set criteria for the best realization, then design and test this realization. This thesis is split into three main parts. In the first part there are encoding and decoding methods of the BCH code generally described. The second part deals with selecting of the right code and realization. There was chosen BCH (63,30) code and realization with FPGA chip. In the last part is described design of BCH encoder and decoder and compilation in the Altera design software.
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Turbocodes and their application in telecommunication systems
Trčka, Tomáš ; Křivánek, Vítězslav (referee) ; Němec, Karel (advisor)
This Diploma thesis deals with Turbo code problems. The Turbo codes belong to the group of error correction codes, sometimes referred to as forward error correcting (FEC) codes or channel codes. This thesis can be thematically divided into two basic parts. The first part describes turbo code encoder and decoder block diagram with the illustration of two most frequently used iterative decoding algorithms (SOVA and MAP). The end of this part contains best known turbo codes, which are used in present communication systems. The second part pursues simulation results for the turbo codes using Binary Phase Shift Keying (BPSK) over Additive White Gaussian Noise (AWGN) channels. These simulations were created in the MATLAB/SIMULINK computer program. It will be shown here, that there exist many different parameters, greatly affecting turbo codes performance. Some of these parameters are: number of decoding iterations used, the input data frame length, generating polynoms and RSC encoders constraint lengths, properly designed interleaving block, decoding algorithm used, etc.
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