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'n Kriptologiese stawingsanalise en getalteoretiese stroomsyfer

  • Authors: Van der Walt, Werner
  • Date: 2014-03-18
  • Subjects: Cryptography , Error-correcting codes (Information theory) , Digital communications
  • Type: Thesis
  • Identifier: uj:4391 , http://hdl.handle.net/10210/9739
  • Description: M.Ing. (Electric and Electrical Engineering) , From the day the first 'apple' was eaten, a species of people existed that wants to misuse other people, This species is normally the first to use new technology to their advantage. It is essential for our own security to restrict the boundaries of their playing-field and to fill the field it self with potholes. This however should be a continuous process, for their dexterity tends to evolveas fast as new techniques are mastered. Firstly this thesis entails the analysis of the boundaries of the playing field of authentication systems without security. The boundaries of authentication systems with security is established with a unique technique. Concluding the first part of the thesis, a new method of code designing for this playing-field is proposed. Reordering the potholes on the playing-field is the subject of the second part of the thesis. Anew public key system is described for this purpose. A novel implementation of insertion/deletion error correcting codes is presented in this new system. To conclude the thesis, a thorough analysis of this public key system is presented.
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Aspekte van die ontwikkeling van 'n herhalermodule vir pulskodemodulasiestelsels

Channel characterisation and coding for the FM SST channel

  • Authors: Albertyn, Eben
  • Date: 2011-11-10
  • Subjects: Signal processing , Digital communications , Radio frequency modulation , FM broadcasting
  • Type: Thesis
  • Identifier: uj:7269 , http://hdl.handle.net/10210/3944
  • Description: M.Ing. , The transmission of digital data at higher data rates and greater reliabilities is becoming increasingly more important in the society of today. The usage of, especially wireless digital data, is increasing at an alarming rate, and the need arises for more bandwidth to be made available for this purpose. Hence, the need arises to optimise and expand the usage of bandwidth currently under use. Existing wireless channels, such as the commercial FM service, need to be re-evaluated and unused bandwidth needs to be developed and used as close to capacity as possible. In this dissertation, a study was launched to develop the FM SST (Supplementary Signal Transmission) commercial analog service as a simplex digital channel that can commercially be used to transmit a myriad of digital data. With the help of a commercial FM radio channel, digital data was transmitted using a number of different modulation schemes to obtain channel measurements for the FM SST channel. The modulation scheme that performed the best, given certain criteria, was GMSK. This raw information was then used to extract first and higher order statistical information from the channel, in order to parameterise discrete channel models, based on a Markov process. The channel models that were used were the Gilbert, GilbertElliott and Fritchman channel models. These channel models were then tested according to their iirst and higher order statistical data to evaluate their effectiveness in modelling the error process on the FM SST channel. It was found that the channel model best approximating the real channels was the Gilbert channel. Once satisfactory results were obtained, these discrete channel models were then used to evaluate various error correction schemes for their ability to correct burst errors on the FM SST channel. From the various schemes evaluated, a (63,39) BCH with an interleaver of index 4 was found to perform the best. The purpose of which is to transmit digital data at the highest data rate possible and at the same time having a bit error rate less than lxl0-6.
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Coding structure and properties for correcting insertion/deletion errors

  • Authors: Clarke, Willem Adriaan
  • Date: 2012-08-08
  • Subjects: Error-correcting codes (Information theory) , Digital communications
  • Type: Thesis
  • Identifier: uj:8945 , http://hdl.handle.net/10210/5418
  • Description: D. Ing. , The digital transmission of information necessitates the compensation for disturbances introduced by the channel. The compensation method usually used in digital communications is error correcting coding. The errors usually encountered are additive in nature, i.e. errors where only symbol values are changed. Understandably, the field of additive error correcting codes has become a mature research field. Remarkable progress has been made during the past 50 years, to such an extent that near Shannon capacity can be reached using suitable coding techniques. Sometimes the channel disturbances may result in the loss and/or gain of symbols and a subsequent loss of word or frame synchronisation. Unless some precautions were made, a synchronisation error may propagate and corrupt large blocks of data. Typical precautions taken against synchronisation errors are: out-of-band clock signals distributed to the transmission equipment in a network; stringent requirements on clock stability and jitter; limits on the number of repeaters and regeneration to curb jitter and delays; line coding to facilitate better clock extraction; and - use of framing methods on the coding level. Most transmission systems in use today will stop data transmission until reliable synchronisation is restored. El multiplexing systems are still the predominantly used technology in fixed telephone line operators and GSM operators, and recovering from a loss of synchronisation (the FAS alarm) typically lasts approximately 10 seconds. Considering that the transmission speed is 2048 KB/s, a large quantity of data is lost in during this process. The purpose of this study is therefore to broaden the understanding of insertion/deletion correcting binary codes. This will be achieved by presenting new properties and coding techniques for multiple insertion/deletion correcting codes. Mostly binary codes will be considered, but in some instances, the results may also hold for non-binary codes. As a secondary purpose, we hope to generate interest in this field of study and enable other researchers to continue to deeper explore the mechanisms of insertion and/or deletion correcting codes.
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Combating impulsive noise and narrowband interference as a mixture in a power line communications channel

Constrained sequences and coding for spectral and error control

  • Authors: Botha, Louis
  • Date: 2014-02-11
  • Subjects: Error-correcting codes (Information theory) , Digital communications
  • Type: Thesis
  • Identifier: uj:3799 , http://hdl.handle.net/10210/9172
  • Description: D.Ing. , When digital information is to be transmitted over a communications channel or stored in a data recording system, it is first mapped onto a code sequence by an encoder. The code sequence has certain properties which makes it suitable for use on the channel, ie the sequence complies to the channel input restrictions. These input restrictions are often described in terms of a required power spectral density of the code sequence. In addition, the code sequence can also be chosen in such a way as to enable the receiver to correct errors which occur in the channel. The set of rules which governs the encoding process is referred to as a line code or a modulation code for the transmission or storage of data, respectively. Before a new line code or modulation code can be developed, the properties that the code sequence should have for compliance to the channel input, restrictions and possession of desired error correction capabilities have to be established. A code' construction algorithm, which is often time consuming and difficult to apply, is then used to obtain the new code. In this dissertation, new classes of sequences which comply to the input restrictions and error correction requirements of practical channels are defined, and new line codes and recording codes are developed for mapping data onto these sequences. Several theorems which show relations between' information theoretical aspects of different classes of code sequences are presented. Algorithms which can be used to transform an existing line code or modulation code into a new code for use on another channel are introduced. These algorithms are systematic and easy to apply, and precludes the necessity of applying a code construction algorithm.
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Design and implementation of an integrated coupling circuit for power line communication

  • Authors: Wright, James Adriaan
  • Date: 2019
  • Subjects: Electronic circuits , Digital integrated circuits , Digital communications
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/481948 , uj:43686
  • Description: Abstract: It is predicted that in 2025 there would be 75 billion devices connected to the Internet of Things. With this immense growth, radio frequency communication will not have the required bandwidth to keep abreast. Power Line Communication allows a communication signal to be transmitted on any electrical infrastructure. The communication signal is connected to the electrical infrastructure using a coupling circuit. This coupling circuit galvanically isolates the communication signal from the power line voltage. By implementing Power Line Communication, the strain on radio frequency communication can be relieved. The purpose of this research is to design and implement an improved coupling circuit. The improved coupling circuit is required to be easily manufactured, be reliable and more cost effective than traditional coupling circuits. Power Line Communication will be used to complement radio frequency communication, thus a considerable number of coupling circuits will be manufactured. A quantitative experimental research method was used. A traditional coupling circuit was characterised with the aim to improve on it. A method to integrate the coupling circuit was proposed and implemented. The performance of the improved coupling circuit was compared to a study in 2008. The traditional coupling circuit operated between 90 kHz to 150 kHz, CENELEC D band. Whereas the improved coupling circuit operates at 1MHz to 100 MHz, G.9960/G.9961. The two Power Line Communication couplers cannot be directly compared to one another; however the frequency response can be juxtaposed. The integrated coupling circuit is compared to a commercial coupling circuit in size and cost. The equations used to design the traditional coupling circuit at a lower frequency holds for coupling circuits designed to operate at a higher frequency. For a coupling circuit to be valid the operating frequency should conform to standard, block the power line voltage and allow the communication signal to pass through the coupling circuit with minimum attenuation. The implementation of an improved coupling circuit was found to be successful. The improved coupling circuit is easily manufactured, reliable and cost effective. Further studies are needed to decrease the size of the improved coupling circuit. , M.Ing.
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Efficient construction of balanced and constant-weight sequences for communication

Impact of modern lighting technology on the power line communications channel

  • Authors: Emleh, Allan Ashraf
  • Date: 2017
  • Subjects: Electric lines , Digital communications , Lighting technology
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/493466 , uj:45105
  • Description: Abstract: In this study, we look at the impact of modern lighting technology on Power Line Communications (PLC). Power Line Communications has become important due to the Smart Grid and Internet of Things (IoT) development. Modern lighting technology has been developed to make efficient use of electric energy. This technology uses power converters to enable the use of different lighting sources. A byproduct of this conversion process is electronic noise. This noise can interfere with the PLC channel. In this study, different lighting technologies are investigated from a noise standpoint and compared to PLC signal levels. Both narrowband and broadband PLC frequency ranges are investigated. This study shows that the influence of noise on the PLC channel depends predominantly on the conversion topology as well as whether filters have been used. The measurement results show that the influence on data communication system can vary in impact from low to severe. Results were obtained for low energy, high energy, indoor and outdoor lighting sources. A common front end topology encounted is the bridge rectifier and high frequency DC-DC converter combination. These topologies are investigated in details. The study presented here shows that lighting technology (causing interference) needs special consideration when designing PLC systems. Of particular importance is the use of filters which ensure compliance with interference standards and limit the noise effects on the PLC signal. , D.Ing. (Electrical and Electronic Engineering Science)
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Implementation issues for M-ARY FSK on narrowband power line communications

  • Authors: Sanya, Timothy Oluwatobi
  • Date: 2012-08-01
  • Subjects: Digital communications , Telecommunication systems , Electric lines - Carrier transmission
  • Type: Thesis
  • Identifier: uj:8921 , http://hdl.handle.net/10210/5391
  • Description: M.Phil. , The advantages offered by power line communications (hereon after called PLC) cannot be over-emphasized neither can the inherent problems affecting its commercial takeover be underestimated. This research work creates a background study for experimental measurement and eventual implementations on power lines. It explains those salient aspects of commercially available communication modules that are rather not straight forward to understand from reading the Comblocks user manual. Especially, addressing those shortcomings of Comblocks that were not indicated in the documentation, we o er solutions to those we could nd our way around. M-ary frequency shift keying was implemented. This implementation tested the ro- bustness of the scheme against noises, attenuation and other power line channel char- acteristics as encountered practically. Based on our results, we nally recommend an optimal set of frequencies; we believe to be good for use in most PLC application pur- poses. Pseudo random bits of information were generated, encoded and modulated; the signals were transmitted over power line channels. The impact of noise sources, impulse noise especially was observed at di erent distances along the channel. Coupling and decoupling circuits used for this research, with associated issues sur- rounding the use of coupling circuitry are also presented. The CENELEC norm for PLC communication was adhered to, hence only frequencies that fall within the CENELEC speci cation for low voltage power distribution network were considered for MFSK use. Signal-to-noise ratio and other factors that a ect signal transmission over PLC was also measured. A complete communication system comprises of the transmitter, the channel and the receiver. This work however did not cover the receiver part of the system. Future work can now be done on this aspect which amongst others can take care of synchronization issues, in which a coding system as well as bit error rates can be determined.
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Impulse noise error modeling over M-QAM-based power line communication channel using software-defined approach

  • Authors: Iyiola, Akintunde Oluremi
  • Date: 2020
  • Subjects: Digital communications , Modulation (Electronics) , Coding theory , Error-correcting codes (Information theory) , Electric lines
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/480143 , uj:43454
  • Description: Abstract: Data transmission through the indoor Power Line Communication (PLC) channel is severely affected by uncoordinated operation of electrical devices connected to the network as well as from external disturbances resulting into high amplitude impulse noise and burst error. In order to address these challenges, recent research efforts have concentrated on developing stable, effective and functional data transmission methods using old methods or developing new methods that can improve the efficiency of transmission as well as the transmission capacity of existing PLC networks... , M.Ing. (Electrical and Electronic Engineering)
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Interfacing power line communications and visible light communications based on phase shift keying and colour shift keying

Modulation performance in the presence of phase noise and impulsive noise in satellite communication

  • Authors: Bondelo, Axel Angioni
  • Date: 2020
  • Subjects: Artificial satellites in telecommunication - Systems engineering , Artificial satellites in telecommunication , Digital communications
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/480148 , uj:43455
  • Description: Abstract: In satellite communication, it is common practice to assume that the transmission channel is Gaussian and does not display impulsive characteristic. Therefore, the link performance computation is conducted assuming that the noise collected at the receiver front-end is Gaussian. The majority of link budget tools employ a simplistic channel model – Additive White Gaussian Noise (AWGN) to predict the performance of the satellite link. In this dissertation, we investigate the performance of modulation schemes employed in satellite communication in the presence of phase noise (PN) considering that the transmission channel is corrupted by both impulsive noise (IN) and AWGN... , M.Phil. (Electrical and Electronic Engineering Science)
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Multilevel sequences and line codes

  • Authors: Botha, Louis
  • Date: 2014-05-13
  • Subjects: Digital communications
  • Type: Thesis
  • Identifier: uj:11051 , http://hdl.handle.net/10210/10623
  • Description: M.Ing. (Electrical Engineering) , As the demand for high-speed data communications over conventional channels such as coaxial cables and twisted pairs grows, it becomes neccesary to optimize every aspect of the communication system at reasonable cost to meet this demand effectively. The choice of a line code is one of the most important aspects in the design of a communications system, as the line code determines the complexity, and thus also the cost, of several circuits in the system. It has become known in recent years that a multilevel line code is preferable to a binary code in cases where high-speed communications are desired. Apart from ternary codes, not many multilevel codes are available. Some of the existing line codes also suffer from serious drawbacks regarding a lack of complying to input restrictions, small values of efficiency, and great code complexity. In this study, Markov models and values of channel capacity are presented for several classes of restricted multilevel sequences which are thought to be of practical importance in view of the channel input restrictions that these codes satisfy. Different coding methods are used to construct low-complexity encoders and decoders for generating and decoding these sequences with high values of efficiency, good error behaviour and favourable power spectral densities
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Multisimbool lynkodes met hoër orde spektrale nulle by gelykstroom

  • Authors: Fouché, Leon
  • Date: 2014-04-16
  • Subjects: Digital communications , Telecommunication systems
  • Type: Thesis
  • Identifier: uj:10746 , http://hdl.handle.net/10210/10255
  • Description: M.Ing. (Electrical and Electronic Engineering) , Since the beginning of telecommunications. more than 100 years ago, systems have been developed through a constant interaction between technical inventions. economic applications and the desire for improved communication facilities to such an extend that there is now a highly efficient communication network whichspans over the entire globe. The still growing demand for data communication. on conventional channels such ascoaxial cables and twisted pairs. made it necessary to develop systems which make use of line codes. In developing countries. like South-Africa. it is not economically feasible to change the existing analog systems to digital systems to enable data communications. In this study. we have done research into the possibility of combining ananalog speech signal with a digital data channel. Ideally the data channel should make use of line codes with low power contents at low frequencies. so that an analog speech channel can be inserted. Different coding methods were used to construct simple encoders and decoders which generate sequences with low power content at low frequencies. The experimental setup used in this thesis. showed that these new line codes exhibit low frequency suppression to such an extend that an analog speech channel can be inserted without the one interfering with the another.
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Spectrum analysis of hybrid power line and visible light communications channels

The database : a digital storage facility for the 22nd century

The effect of coupling circuits in power line communications on impulsive noise

  • Authors: Samakande, Tendai
  • Date: 2019
  • Subjects: Electric lines - Carrier transmission , Directional couplers , Electronic circuits - Noise , Digital communications
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/394351 , uj:32655
  • Description: Abstract : Most researchers in the Power Line Communications field have adopted the practice of using idealized impulse noise models (Middleton class A) directly at the input of the demodulator, as is widely done in simulations. The effect of the coupling circuit on the impulse noise tends to be ignored. However, coupling circuits produce transients. This work focuses on investigating the effect of the coupling circuit on the impulse noise. This was achieved through a series of measurements conducted using different coupling circuits. An experimental set-up was developed which separates the generated impulse noise and the measured impulse noise after the coupling circuit. It was observed that the coupling circuit produces transients which must not be ignored. The transients produced by the coupling circuit introduces ringing to the impulse noise signal affecting its time domain parameters which have the most adverse effects to data transmission on power lines. To further understand the effects of the coupling circuit, an equivalent circuit of the coupling circuit was developed and simulations were conducted. These confirmed the occurrence of resonance in the coupling circuit introducing ringing to the impulsive noise signal. i , M.Ing. (Electrical and Electronic Engineering)
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The strategic use of visual expressions (memes and emojis) in a digital communication strategy : a case study of Discovery

  • Authors: Mkhwanazi, Primrose S'lindile Nokwazi
  • Date: 2021
  • Subjects: Digital communications , Memes , Emojis
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/497108 , uj:45339
  • Description: Abstract: Digital communication continues to accelerate in growth through various digital communication channels. Although brands use visual expressions such as memes and emojis on social media, it is crucial to understand the strategic significance of using these visual elements in a digital communication strategy. In this study the researcher investigated the strategic use of visual expressions in digital communication strategies. The aim was to explore the strategic use of visual expressions on digital communications at Discovery. Semi-structured interviews were conducted with seven digital experts in South Africa and Germany who were purposefully selected to understand people’s experiences with the use of memes and emojis in brand communications. Participants were divided into two groups, general digital experts and digital experts at Discovery. A thematic analysis method was used to analyse data from the interviews. Findings from the research indicate that visual expressions used in brands are key in creating connections with consumers. Furthermore, brands and consumers use memes and emojis to not only start conversations, but they are also used to express emotions and drive online engagements. Brands are advised to be cognisant of potential reputational risks however, and to recognise the need to understand the meaning of visual expressions to avoid using them incorrectly. The results suggest that the use of visual expressions is very impactful in digital communications and that when brands communicate using the language that consumers use when communicating with friends and family members, the brand becomes relatable. It is therefore recommended that brands consider using visual expressions more in order to build long term relationships, connect better with consumers and improve engagement. This approach will not only help to humanise the brand, it will also enhance its relevance. Key terms: memes; emojis; visual expressions; brand engagement; brand interaction; brand communication; relationship building; brand relevance; digital communication. , M.A. (Strategic Communication)
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Undetected error behaviour of linear block codes on channels with memory

  • Authors: Swarts, Francis
  • Date: 2014-03-10
  • Subjects: Digital communications , Information storage and retrieval systems - Engineering , Error-correcting codes (Information theory)
  • Type: Thesis
  • Identifier: uj:4240 , http://hdl.handle.net/10210/9599
  • Description: D.Ing. (Electrical and Electronic) , In this thesis, the problem of undetected errors in digital communication systems employing error detection as the only means of error control, is investigated. In the past, the undetected error probability of linear block codes, was mainly investigated on the binary symmetric channel, which is memoryless. With this thesis, the main aim was to investigate the undetected error probability for linear block codes, on channels with memory. The channel models investigated are the Gilbert-Elliott and Fritchman channel models. Three techniques for calculating the undetected error probability on channels with memory are investigated. These techniques are: (i) Exhaustive codeword generation, (ii) Simulation and (iii) A trellis based technique. The trellis description of a block code based on the states of a syndrome calculating linear feedback shift register, formed the basis of the latter technique. The calculation of the weight spectrum of binary linear block codes, is still largely an unsolved problem. Using the trellis description of a binary linear block code, referred to earlier, we propose a description of binary linear block codes based on graphs, and from this we develop a technique for calculating the weight spectrum of binary linear block codes. The weight spectra of block codes determine the undetected error probability of these codes when used on the binary symmetric channel. Very favourable results were obtained through the application of the techniques developed for undetected error probability calculation as well as weight spectrum calculation.
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