Masters Degrees (Electronic Engineering)

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https://hdl.handle.net/10413/6868

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Design and performance analysis of class-B power amplifier with double-gate MOSFET.
(2023) Mbonane, Sandile Handsum.; Srivastava, Viranjay Mohan.
This work presents the design of a class-B power amplifier with the use of Double-Gate (DG) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). It analyzes the indices of system performance indices for class-B power amplifiers using DG MOSFET. It presents a comparative analysis of three power amplifiers using different switching devices, i.e., BJT, traditional single-gate MOSFET, and designed amplifier using DG MOSFET. It was realized that the class-B power amplifier with the use of DG MOSFET reduces the crossover distortion which is a major issue faced by class-B power amplifiers. The hardware design is also presented and tested with advanced electronic components such as oscilloscope, function generator, and DC power supply, it was observed that the crossover distortions are not exist in the output waveforms of the hardware circuit design. The class-B power amplifier is commonly used for power amplification due to its performance, such as high input signal fidelity at the output and high-power efficiency. These power amplifiers are being designed and simulated to test the switching speed to receive the output signal when an input signal is applied. The comparison of these three power amplifier circuits is taken to conclude which power amplifier circuit performs better regarding its switching speed. The basics switching speed is the time the power takes to amplify the signal, which is the same as the time to amplify the signal to a specific gain. In addition, the settling time for these three types of power amplifiers also have been tested and presented to justify the performance of these three types of power amplifiers. Losses of the class-B power amplifier using DG MOSFET are presented and compared to the design of class-B power amplifier using traditional single-gate MOSFET. This thesis describes the design of a power amplifier having DG MOSFET, which is a device used to amplify any input signal; it can be an audio signal or any signal. The thesis provides information on the problem identification/description, design objectives/requirements, and the design specifications, both functional and non-functional, together with design constraints and simulation circuits. Various solutions to the problem are discussed and the preferred solution is proposed, together with analysis.
Combining local descriptors and classification methods for human emotion recognition.
(2023) Badi Mame, Antoine.; Tapamo, Jules-Raymond.
Human Emotion Recognition occupies a very important place in artificial intelligence and has several applications, such as emotionally intelligent robots, driver fatigue monitoring, mood prediction, and many others. Facial Expression Recognition (FER) systems can recognize human emotions by extracting face image features and classifying them as one of several prototypic emotions. Local descriptors are good at encoding micro-patterns and capturing their distribution in a sub-region of an image. Moreover, dividing the face into sub-regions introduces information about micro-pattern locations, essential for developing robust facial expression features. Hence, local descriptors’ efficiencies depend heavily on parameters such as the sub-region size and histogram length. However, the extraction parameters are seldom optimized in existing approaches. This dissertation reviews several local descriptors and classifiers, and experiments are conducted to improve the robustness and accuracy of existing FER methods. A study of the Histogram of Oriented Gradients (HOG) descriptor inspires this research to propose a new face registration algorithm. The approach uses contrast-limited histogram equalization to enhance the image, followed by binary thresholding and blob detection operations to rotate the face upright. Additionally, this research proposes a new method for optimized FER. The main idea behind the approach is to optimize the calculation of feature vectors by varying the extraction parameter values, producing several feature sets. The best extraction parameter values are selected by evaluating the classification performances of each feature set. The proposed approach is also implemented using different combinations of local descriptors and classification methods under the same experimental conditions. The results reveal that the proposed methods produced a better performance than what was reported in previous studies. Furthermore, the results showed an improvement of up to 2% compared with the performance achieved in previous works. The results showed that HOG was the most effective local descriptor, while Support Vector Machines (SVM) and Multi-Layer Perceptron (MLP) were the best classifiers. Hence, the best combinations were HOG+SVM and HOG+MLP.
Rain Attenuation Modelling and Prediction for Optical Wireless Communication Systems in Durban, South Africa.
(2021) Buthelezi, Sabelo Qiniso.; Afullo, Thomas Joachim Odhiambo.; Mosalaosi, Modisa.
The continuous demand for more reliable wireless communication systems with extremely high data rates has accelerated various aspects of research topics to be able to meet future needs. One of the most crucial topics in the field of communication is free-space optics (also known as optical wireless communication). It is well-known that the performance of any optical wireless communication system is strongly influenced by the atmospheric conditions in a given environment. In foggy, rainy, and clear weather conditions, optical signals are known to be attenuated due to scattering. The received signal is diminished in the presence of snow, rain, or even haze. Rain and clear weather conditions will be the focus of this research as there is hardly snow or haze in South Africa, especially Durban since it is a subtropical region. In this research work, rain attenuation modelling and prediction will be done using an empirical method based on the relationship between the observed attenuation distribution and the related observed rain intensity distribution at a 30 second integration period. A disdrometer is used to obtain the rain intensity, and a power meter is used to log the received signal power level every 30 seconds to evaluate the influence of rain on the signal transmitted. The International Telecommunication Union (ITU-R) recommends targeting for 99.99 % system availability; as a result, the rainfall rate (R0.01) in the research region must be estimated for 0.01 percent of the time. The rain intensity and raindrop size distribution (DSD) modelling is then performed from the empirical method, obtaining R0.01 for Durban for all months throughout the experiment period. Using the disdrometer diameter ranges, the spherical droplet assumption is used to estimate the scattering parameters for frequencies between 2 GHz and 1000 GHz. The relationship between the received signal level and the intensity of rain for a particular weather condition at a specific time is then obtained. Transceivers with a fixed length of 7 meters between them, due to shortage of material such as the fiber cables to link the transceivers to the computer for data monitoring and logging, and for accurate alignment, were used to conduct these experiments. This relationship is compared against the French model at a wavelength of 850 nm. The main results obtained from this work reveal that there are extremely high attenuation values compared to the French model, which thus calls for further investigation to provide the optimum model that can accurately predict these effects for reliable optical wireless communications in Durban, South Africa.
Characterization and modelling of the channel and noise for broadband indoor powerline communication (plc.) networks.
(2016) Mosalaosi, Modisa.; Afullo, Thomas Joachim Odhiambo.
Power Line Communication (PLC) is an interesting approach in establishing last mile broad band access especially in rural areas. PLC provides an already existing medium for broad band internet connectivity as well as monitoring and control functions for both industrial and indoor usage. PLC network is the most ubiquitous network in the world reaching every home. However, it presents a channel that is inherently hostile in nature when used for communication purposes. This hostility is due to the many problematic characteristics of the PLC from a data communications’ perspective. They include multipath propagation due to multiple reflections resulting from impedance mismatches and cable joints, as well as the various types of noise inherent in the channel. Apart from wireless technologies, current high data rate services such as high speed internet are provided through optical fibre links, Ethernet, and VDSL (very-high-bit-rate digital subscriber line) technology. The deployment of a wired network is costly and demands physical effort. The transmission of high frequency signals over power lines, known as power line communications (PLC), plays an important role in contributing towards global goals for broadband services inside the home and office. In this thesis we aim to contribute to this ideal by presenting a powerline channel modeling approach which describes a powerline network as a lattice structure. In a lattice structure, a signal propagates from one end into a network of boundaries (branches) through numerous paths characterized by different reflection/transmission properties. Due to theoretically infi nite number of reflections likely to be experienced by a propagating wave, we determine the optimum number of paths required for meaningful contribution towards the overall signal level at the receiver. The propagation parameters are obtained through measurements and other model parameters are derived from deterministic power system. It is observed that the notch positions in the transfer characteristics are associated with the branch lengths in the network. Short branches will result in fewer notches in a fixed bandwidth as compared to longer branches. Generally, the channel attenuation increase with network size in terms of number of branches. The proposed model compares well with experimental data. This work presents another alternative approach to model the transfer characteristics of power lines for broadband power line communication. The model is developed by considering the power line to be a two-wire transmission line and the theory of transverse electromagnetic (TEM) wave propagation. The characteristic impedance and attenuation constant of the power line v are determined through measurements. These parameters are used in model simplification and determination of other model parameters for typical indoor multi-tapped transmission line system. The transfer function of the PLC channel is determined by considering the branching sections as parallel resonant circuits (PRC) attached to the main line. The model is evaluated through comparison with measured transfer characteristics of known topologies and it is in good agreement with measurements. Apart from the harsh topology of power line networks, the presence of electrical appliances further aggravates the channel conditions by injecting various types of noises into the system. This thesis also discusses the process of estimating powerline communication (PLC) asynchronous impulsive noise volatility by studying the conditional variance of the noise time series residuals. In our approach, we use the Generalized Autoregressive Conditional Heteroskedastic (GARCH) models on the basis that in our observations, the noise time series residuals indicate heteroskedasticity. By per forming an ordinary least squares (OLS) regression of the noise data, the empirical results show that the conditional variance process is highly persistent in the residuals. The variance of the error terms are not uniform, in fact, the error terms are larger at some portions of the data than at other time instances. Thus, PLC impulsive noise often exhibit volatility clustering where the noise time series is comprised of periods of high volatility followed by periods of high volatility and periods of low volatility followed by periods of low volatility. The burstiness of PLC impulsive noise is therefore not spread randomly across the time period, but instead has a degree of autocorrelation. This provides evidence of time-varying conditional second order moment of the noise time series. Based on these properties, the noise time series data is said to suffer from heteroskedasticity. GARCH models addresses the deficiencies of common regression models such as Autoregressive Moving Average (ARMA) which models the conditional expectation of a process given the past, but regards the past conditional variances to be constant. In our approach, we predict the time-varying volatility by using past time-varying variances in the error terms of the noise data series. Subsequent variances are predicted as a weighted average of past squared residuals with declining weights that never completely diminish. The parameter estimates of the model indicates a high de gree of persistence in conditional volatility of impulsive noise which is a strong evidence of explosive volatility. Parameter estimation of linear regression models usually employs least squares (LS) and maximum likelihood (ML) estimators. While maximum likelihood remains one of the best estimators within the classical statistics paradigm to date, it is highly reliant vi on the assumption about the joint probability distribution of the data for optimal results. In our work, we use the Generalized Method of Moments (GMM) to address the deficien cies of LS/ML in order to estimate the underlying data generating process (DGP). We use GMM as a statistical technique that incorporate observed noise data with the information in population moment conditions to determine estimates of unknown parameters of the under lying model. Periodic impulsive noise (short-term) has been measured, deseasonalized and modeled using GMM. The numerical results show that the model captures the noise process accurately. Usually, the impulsive signals originates from connected loads in an electrical power network can often be characterized as cyclostationary processes. A cyclostationary process is described as a non-stationary process whose statistics exhibit periodic time varia tion, and therefore can be described by virtue of its periodic order. The focus of this chapter centres on the utilization of cyclic spectral analysis technique for identification and analysis of the second-order periodicity (SOP) of time sequences like those which are generated by electrical loads connected in the vicinity of a power line communications receiver. Analysis of cyclic spectrum generally incorporates determining the random features besides the pe riodicity of impulsive noise, through the determination of the spectral correlation density (SCD). Its effectiveness on identifying and analysing cyclostationary noise is substantiated in this work by processing data collected at indoor low voltage sites.
Production of graphene for the frabrication of graphene fibres.
(2016) Ojageer, Sarisha.; Jarvis, Alan Lawrence Leigh.; Swanson, Andrew Graham.
Graphene consists of a single atomic layer of carbon atoms arranged in a hexagonal lattice and exhibits two-dimensional properties. This material is of particular interest as it is a highly efficient conductor of heat and electricity and possesses an exceptionally high strength-to-weight ratio. The uses of graphene extend to a variety of industries, including the fields of life sciences; electronics; and chemistry. The properties of graphene are largely determined by the method of fabrication thereof. These methods include chemical vapour deposition as well as mechanical and chemical exfoliation. In this study, research has been conducted to investigate these various fabrication routes so as to determine a reliable method of producing graphene of a high quality for the production and study of graphene fibres. Specifically, graphene produced via the chemical oxidation of graphite was investigated due to its cost-effectiveness, viability and scalable nature. This process resulted in the production of an intermediate product, graphene oxide, which was then reduced to form graphene. Thermal and chemical reduction methods of graphene were also investigated. The produced graphene exhibits high correlation with graphene reported in the literature. The quality of the synthesised material was analysed using various diagnostic tools, including Scanning and Transmission Electron Microscopy, Energy-Dispersive X-Ray Spectroscopy and X-Ray Diffraction. The graphene was used for the fabrication of graphene fibres with the addition of the polymer materials, polyvinyl alcohol and polystyrene. A microscopic fibre fabrication route was explored and the outcome of this research was the production of graphene nanofibres which may be used in various applications, including strengthening fillers in composite materials.
Index modulation for next generation radio communications.
(2021) Oso, Oluwabukunmi Williams.; Pillay, Narushan.; Xu, Hongjun.
Man’s insatiable desire for swift and more efficient internet service, a wide range of connectivity and increased data rate of transmission necessitated the need for further research to improve the efficiency of the existing systems. The development and evolution of the next-generation communication systems can be ascribed to the multiple-input multiple-output (MIMO) techniques implemented. The fundamental founding block of the MIMO systems is the spatial modulation (SM) which interestingly was able to attain high spectral efficiency as the receiver maintained significantly lower complexity. However, even with the feat achieved by the SM scheme, there was still a need improve on the performance of the SM scheme which meant an increase in the spectral efficiency was required, this prompted further research and a new scheme was introduced. The quadrature SM (QSM) scheme was introduced to better the performance of the conventional SM. QSM retains all the good benefits the SM scheme offers, while still enhancing the spectral efficiency and improving overall throughput. However, the demand for increased reliability, i.e., improving the QSM scheme’s error performance led to a new scheme being introduced. Space-time QSM (ST-QSM) improves the QSM scheme’s error performance by achieving second-order diversity gain for QSM. This scheme combines both the spatial dimension and diversity to the QSM scheme, bringing about a new and improved scheme. In this dissertation, a scheme was introduced to fix the high computational complexity (CC) that affects MIMO systems transmitting at high data rates. Signal orthogonal projection (OP) was employed to decrease the CC of the space-time block coded spatial modulation (STBC-SM). The proposed scheme is called STBC-SM-OP and its results were investigated by comparing it with the STBC-SM with maximum likelihood detection (STBC-SM-ML). The proposed STBC-SM-OP scheme’s error performance matched that of STBC-SM-ML tightly down to low BER whilst maintaining a low CC.
Metasurface based MIMO microstrip antenna with reduced mutual coupling.
(2022) Dubazane, Sthembile Promise.; Kumar, Pradeep.; Afullo, Thomas Joachim Odhiambo.
In this thesis, a negative permeability (μ) metasurface is used to reduce the mutual coupling of a 2-port Multiple-Input Multiple-Output (MIMO) rectangular inset fed microstrip antenna. That was designed using the transmission model of analysis, simulated and optimized using CST microwave studio. The microstrip antenna that operates at the (5.9-6.1) GHz band is designed for 5G applications, at the extended 6 GHz band (5.925-7.125) GHz. The extended band was chosen because of its new additional spectrum, which results in less noise interference. Three metasurface wall based antenna designs and two metasurface superstrate based antenna designs are conducted. The metasurface wall based antenna designs are formulated by placing a metasurface wall vertically between the two radiating antenna elements. The metasurface superstrate based antenna designs are formulated by suspending a metasurface superstrate above the 2-port microstrip antenna. Both the metasurface wall and superstrate are made up metasurface unit cells, which are formulated by periodic split ring resonators printed on a FR-4 dielectric substrate. The metasurface cells are responsible for introducing a negative permeability medium, which converts the electromagnetic propagating waves into evanescent hence rejecting mutual coupling. In the first metasurface based antenna design, a single metasurface wall is vertically placed between the two microstrip antenna elements. A slight increase of 0.5 dB in mutual coupling is observed. In the second design, a double metasurface wall is vertically placed between the two antenna elements. A mutual coupling reduction of 11 dB is achieved. In the third design a triple metasurface wall is also placed between the two antenna elements, a mutual coupling reduction of 25 dB and up to 17 % bandwidth enhancement is achieved. In the fourth design a single metasurface superstrate is suspended above the 2-port microstrip antenna. A mutual coupling reduction of 32 dB is achieved. Lastly, in the fifth design a metasurface superstrate is also suspended above the 2-port microstrip antenna. A mutual coupling reduction of 22 dB, a 38% bandwidth enhancement and a 2.09 dB gain enhancement is achieved.
High gain wideband microstrip patch antennas with defected ground structure for Sub-6 GHz 5G communications.
(2021) Olawoye, Taiwo Oluwafemi.; Kumar, Pradeep.
5G communication utilizes the two frequency ranges i.e. frequency range 1 (FR1) and frequency range 2 (FR2). The FR1 is the low frequency band with the frequency range from 450 MHz to 6 GHz. As FR1 contains the frequency range upto 6 GHz, it is also known as sub-6 GHz frequency band. The FR2, known as mm-wave frequency range, uses the frequencies above 24 GHz. The lower frequency including electromagnetic (EM) waves can travel farther as these are less a ected by the weather such as rain, snow etc. The low frequency EM waves can penetrate the solid objects like buildings etc. The sub-6 GHz 5G radio band will handle the wider bandwidth needed for high speed 5G communication devices. This research work presents the design of 5 GHz microstrip patch antennas for use in sub-6 GHz 5G communication. Antennas designed for 5G network must have high gain and necessary wideband capabilities to handle the large data requirements at high speed. This research proposes the design of a high gain rectangular microstrip patch antenna (HGRMPA) for use in sub-6 GHz 5G communication. A HGRMPA, that utilizes the patch with T-shaped slot, is designed. The defected ground structure (DGS) technology is used to improve the performance of the HGRMPA. The DGS of the proposed HGRMPA consists a C-shaped slot. The C-shaped slot along with cuts at its upper and lower parts is incorporated in the ground plane to further improve the performance of the HGRMPA. A re ective plate is placed at the back of the proposed HGRMPA to reduce the side lobes and back lobes produced by the antenna. This will improve the main lobe of the radiated signal and the gain of the HGRMPA. The proposed HGRMPA is fed using inset feeding technique and the antenna is mounted on the FR-4 epoxy substrate. The size of the proposed HGRMPA is 28:03 23:45 5:35 mm3 and it provides the maximum gain and maximum directivity of 5.49 dB and 7.12 dB, respectively. The bandwidth of the proposed HGRMPA is from 4:775 GHz to 5:049 GHz, which covers the 4:8 GHz􀀀5 GHz sub-6 GHz 5G communication band. Further, a high gain wideband microstrip patch antenna (HGWBMPA), using partial ground plane with triangular strip, is also presented. The proposed HGWBMPA operates in the sub-6 GHz 5G wireless networking band. The HGWBMPA utilizes the re ective plate to reduce the development of the back lobes and increasing the gain. The inset feed technique is used to feed the antenna and the antenna is mounted on the FR-4 epoxy substrate. The proposed design is simulated and optimized with commercially available EM software i.e. CST studio suite. The size of the proposed HGWBMPA is compact with the patch dimension of 18:43 13:85 mm2. The maximum gain, maximum directivity ande ciency of the HGWBMPA are 6:21 dB, 7:56 dB and 78%, respectively. The proposed HGWBMPA works from 4:921 GHz to 5:784 GHz, which covers the 4:9 GHz - 5:8 GHz sub-6 GHz 5G communications range.
Efficient method of estimating Direction of Arrival (DOA) in communications systems.
(2021) Nxumalo, Bongani Prudence.; Walingo, Tom Mmbasu.
In wireless communications systems, estimation of Direction of Arrival (DOA) has been used both for military and commercial purposes. The signal whose DOA is being estimated, could be a signal that has been reflected from a moving or stationary object, or a signal that has been generated from unwanted or illegal transmitter. When combined with estimating time of arrival, it is also possible to pinpoint the location of a target in space. Localization in space can also be achieved by estimating DOA using two receiving nodes with capability of estimating DOA. The beamforming pattern in smart antenna system is adjusted to emphasize the desired signal and to minimize the interference signal. Therefore, DOA estimation algorithms are critical for estimating the Angle of Arrival (AOA) and beamforming in smart antennas. This dissertation investigates the performance, angular accuracy and resolution of the Minimum Variance Distortionless Response (MVDR), Multiple Signal Classification (MUSIC) and our proposed method Advanced Multiple Signal Classification (A-MUSIC) as DOA algorithms on both Non-Uniform Array (NLA) and Uniform Linear Array (ULA). DOA is critical in antenna design for emphasizing the desired signal and minimizing interference. The scarcity of radio spectrum has fuelled the migration of communication networks to higher frequencies. This has resulted into radio propagation challenges due to the adverse environmental elements otherwise unexperienced at lower frequencies. In rainfall-impacted environments, DOA estimation is greatly affected by signal attenuation and scattering at the higher frequencies. Therefore, new DOA algorithms cognisant of these factors need to be developed and the performance of the existing algorithms quantified. This work investigates the performance of the Conventional Minimum Variance Distortion-less Look (MVDL), Subspace DOA Estimation Methods of Multiple Signal Classification (MUSIC) and the developed hybrid DOA algorithm on a weather impacted wireless channel. The performance of the proposed Advanced-MUSIC (A-MUSIC) algorithm is compared to the conventional DOA estimation algorithms of Minimum Variance Distortionless Response (MVDR) and the Multiple Signal Classification (MUSIC) algorithms for both NLA and ULA antenna arrays. The developed simulation results show that A-MUSIC shows superior performance compared to the two other algorithms in terms of Signal Noise Ratio (SNR) and the number of antenna elements. The results show performance degradation in a rainfall impacted communication network with the developed algorithm showing better performance degradation.
Thermocouple signal conditioning using artificial neural networks.
(2022) Maseko, Moses Linda.; Agee, John Terhile.
Thermocouples are probably the most widely used temperature sensing devices in industrial applications. This is due to their relatively high accuracy. Thermocouples sense temperature using thermoelectric voltages arising due to temperature differences between the hot and cold junctions of the thermocouple. The generated thermoelectric voltage is nonlinear in form. Linear approximations in the conversion of thermoelectric voltages into temperature readings compromise the accuracy of the derived temperature values: requiring further processing of the thermocouple voltage for improved temperature measurements. Moreover, undetected variations in the cold junction temperature could further worsen the accuracy of the temperature sensor. The current study researched the enhancement of the accuracy of thermocouple temperature measurement subjected to both random variations in the reference junction temperature and nonlinearities, with a validation of the design process using T, R, E, and J, thermocouples. To this end, the ITS-90 thermocouple tables based on a fixed 0°C reference junction temperature were not adequate for use in the study, so the thermocouple polynomial equations for the T, R, E, and J thermocouples were simulated in MATLAB, with randomly generated cold-junction temperature values, to produce augmented ITS-90 tables for the four thermocouples studied. Results show that the augmented thermocouple tables accurately compared with the ITS-90 tables when the reference junction temperature was set to 0°C. Data samples were generated from each of the augmented thermocouple tables for neural network studies. Half of the data samples for each of the thermocouples was used to train ‘table-lookup’ Multilayer Perceptron (MLP) neural networks in MATLAB. Each neural network used the cold-junction temperatures and thermoelectric voltages as inputs, while the corresponding hot-junction temperatures were used as the target outputs. The validation process for the augmented ITS-90 thermocouple tables showed that the E, T, R, and J thermocouples could all reproduce the hot junction temperature within 0.01% of the results found on the ITS-90 tables. The performance results for the neural networks showed that the E-type thermocouple neural network has a worst-case error within 0.2% in reproducing the hot junction temperature. The J-type thermocouple neural network showed a worst-case error within 0.1%, while the T and R-type thermocouple neural network produced worst error case within 0.04% of the results generated by the augmented ITS-90 tables. For the practical validation of the development presented in this thesis, the structure of each of the trained MLP neural networks was coded as a subroutine within an Arduino Uno microprocessor. The hot junction of the thermocouple was placed in a TTM-004 controller or oven. The cold junction of the thermocouple was located in the ambient of the used laboratory and monitored by an LM 35 temperature sensor connected to one of the inputs of the microcontroller. The experimental results showed that temperature of the TTM-004 controller or oven was evaluated to within 2%, 4% and 3% by the signal conditioning unit using T-type, J-type and E-type thermocouple respectively.
Application of real-world modulation schemes to advanced spatial modulation systems.
(2022) Khalid, Ahmad Bin.; Quazi, Tahmid Al-Mumit.; Xu, Hongjun.
Abstract available in PDF.
Power allocation in a QoS-aware cellular-based vehicular communication system.
(2021) Mankge, Sello Leonard.; Ghayoor, Najafabadi Farzad.
The task of a driver assistance system is to monitor the surrounding environment of a vehicle and provide an appropriate response in the case of detecting any hazardous condition. Such operation requires real-time processing of a large amount of information, which is gathered by a variety of sensors. Vehicular communication in future vehicles can pave the way for designing highly efficient and cost-effective driver assistance systems based on collaborative and remote processing solutions. The main transmission links of vehicular communication systems are vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I). In this research, a cellular-based vehicular communication system is proposed where Device-to-device (D2D) communication links are considered for establishing V2V links, and cellular communication links are employed for V2I links. D2D communication is one of the enablers of the next generation of cellular networks for improving spectrum and power utilization. D2D communication allows direct communication between user equipments within a cellular system. Nevertheless, implementing D2D communication should not defect nearby ongoing communication services. As a result, interference management is a significant aspect of designing D2D communication systems. Communication links in a cellular network are supposed to support a required level of data rates. The capacity of a communication channel is directly proportional to the energy of a transmitted signal, and in fact, achieving the desired level of Quality of Service (QoS) requires careful control of transmission power for all the radio sources within a system. Among different methods that are recommended for D2D communications, in-band D2D can offer better control over power transmission sources. In an underlay in-band D2D communication system, D2D user equipments (DUEs) usually reuse the cellular uplink (UL) spectrum. In such a system, the level of interference can effectively be managed by controlling the level of power that is transmitted by user equipments. To effectively perform the interference management, knowledge of the channel state information is required. However, as a result of the distributed nature of DUEs, such information is not fully attainable in a practical D2D system. Therefore, statistical methods are employed to find boundaries on the allocated transmission powers for achieving sufficient spectral efficiencies in V2I and V2V links without considering any prior knowledge on vehicles’ locations or the channel state information. Furthermore, the concepts of massive multiple-input multiple-output and underlay D2D communication sharing the uplink spectrum of a cellular system are used to minimize the interference effect.
Artificial intelligence based design optimization for improving diversity in wireless links.
(2021) Solwa, Shaheen.; Naidoo, Bashan.; Quazi, Tahmid Al-Mumit.
Abstract available in PDF.
Contributions to optical coherence tomography fingerprint images.
(2021) Mgaga, Sboniso Sifiso.; Tapamo, Jules-Raymond.; Khanyile, Nontokozo Portia.
Abstract available in PDF.
Design and analysis of MOSFET based absorber for 5G massive MIMO base station.
(2021) Omoru, Elliot Osahon.; Srivastava, Viranjay Mohan.
The Fifth Generation (5G) technology suffers from a series of drawbacks ranging from the high cost of infrastructure development, replacement of old devices that may not be compatible with 5G, and losses within the 5G base station construct. During transmission, these losses have a negative effect on the overall performance and efficiency of transmission systems. The 5G massive-Multiple Input Multiple Output (MIMO) base station structure suffers from these losses. In addition, a loss experienced in the 5G technology is due to the reflection of signals from the receiver (Rx) branch connected to the circulators in the 5G massive-MIMO base station. Operators often specify that the worst-case reflections (return loss) over the system's operating frequency range must be 18 dB lower than the signal transmitted into the system. As feed systems become shorter and antenna systems are required to operate over broader frequency ranges, achieving an 18 dB return loss may not be practical, most especially at a 5G frequency regime. This reflection loss experienced in the 5G massive-MIMO base station results from the Rx branch's unmatched load impedance with the source impedance of the Transceiver (TX) branch. However, this problem can be solved by designing a matched circuit between the TX and RX branch of the base station. But Engineers are often faced with the challenge of designing a matching network for impedance mismatch, most especially at high frequency. For this reason, an N-channel Metal Oxide Field Effect Transistor (MOSFET) connected to a circulator has been proposed as an alternative solution to the performance and efficiency reducing effects of reflected radio frequency signal. The proposed model has been presented by connecting the Tx branch, antenna, Rx branch, and the MOSFET to each of the assumed four-port circulator ports. Two comparisons have been made between the source current and drain current of the MOSFET whenever there is a reflection from the base station's Rx branch, In this research, four case of reflection from the RX branch of the base station have been examined at 28 Ghz to analyse the model's performance. Various performance parameters (Insertion loss, Reflection coefficient, Total Power Absorbed by MOSFET (TPAM), Total Power Lost to Rectifier (TPLR), S-parameter, efficiency, etc.) have been analyzed for the validity, stability, and reliability of the proposed model. At worst case reflection from port-3 of the circulator, TPAM, TPLR and reflection coefficient have been observed to be 0.64 mW, 2.95 mW, and 0.0001179. Comparisons have been made with existing RF absorber models using efficiency, insertion loss, frequency, RF power absorption level, and ease of implementation as a standard. The model has been observed to have an efficiency greater than 90 %, an insertion loss more significant than 38 dBm at a frequency of 28 GHz.
Design and analysis of low voltage smart feeder protection using PhotoMOS and proficient monitoring model of real-time IOT applications.
(2021) Kumar, Akshay.; Srivastava, Viranjay Mohan.
Abstract available in PDF.
Scale coding a bag of words for real-time video-based action recognition.
(2021) Govender, Divina.; Tapamo, Jules-Raymond.
Abstract available in PDF.
Towards automatic face recognition using discrete cosine transforms and neural networks.
(1998) Debipersad, Sanjeev Chundurduth.; Broadhurst, Anthony D.
Abstract available in PDF.
Performance analysis of biological resource allocation algorithms for next generation networks.
(2020) Sefako, Thabelang Victor.; Walingo, Tom Mmbasu.
Abstract available in PDF.
Design and development of a low-cost high-performance vehicle mounted UHF RFID system for tracking goods and inventory.
(2020) Naidoo, Sheridan Joash.; Bhero, Ernest.; Hoffman, Alwyn.
This research work investigates how to design and implement a low-cost high-performance vehicle mounted ultra-high frequency (UHF) radio frequency identification (RFID) system to keep track of cargo whilst in transit. The vehicle mounting include – inside or on cargo vehicle enclosures, the shipping containers, and so forth. In order to achieve a low-cost system, a low cost circularly polarized microstrip patch antenna, which also had a low axial ratio (AR) was designed. Since multiple antennas will be used, the cost factor will be reduced substantially if the cost of each antenna was reduced as compared to reducing the cost of a single RFID reader. The proposed antenna design, measuring 200mm x 200mm x 6.4mm, utilized the corner truncated technology with a thicker substrate and larger ground plane. Two independent simulations were done as well as empirical work. One of the simulations used Computer Simulation Technology (CST) studio suite software and the other used gpr Max simulation software. The investigations aimed at determining how different materials (steel, plastic, and wood) worsen the performance of the UHF RFID system inside a steel container as well as in free space. The investigation involved placing these materials onto the RFID tag and then varying the thickness of the material. The simulation results showed that the proposed antenna has a reflection coefficient of less than -10dB from 886.23 MHz to 924.96 MHz with a bandwidth of 38.73 MHz. The antenna provides the AR less than 3 dB for the frequency range from 915 MHz to 919 MHz. The designed and fabricated antenna has a bandwidth of 57.527 MHz and achieves a minimum reflection coefficient of -27.97 dB at 914.045 MHz. These results were then compared to other similar antenna designs. The antenna designed in this research achieved a lower axial ratio while still offering a respectable amount of gain, directivity and bandwidth. Previous papers showed that there was always a notably trade-off between having a low axial ratio and a high gain, directivity or bandwidth. The results for the simulation tests indicated that wood performs the best, followed by plastic and then steel. Wood and plastic were still detected by the RFID reader’s antenna at their maximum thickness of 20cm and 5cm respectively. It was further found out that the RFID system performs better inside a steel container than in free space. In conclusion the design of a low-cost high-performance circularly polarized microstrip patch antenna allows the cost of the overall UHF RFID system to be reduced, making it a more cost-effective solution for tracking containerized cargo. The antenna also achieved circular polarization which is beneficial to the performance of the UHF RFID system. A circularly polarized antenna allows the UHF RFID reader to detect RFID tags in almost any orientation. The simulation results emulate the data obtained when a horizontally orientated paper RFID tag was used. The results obtained showed the use of steel performed optimally when it is placed directly in line with the receiver. When using plastics, placing them directly in line with the receiver at a distance of 2.36 m, does not offer the best performance. If the plastic material is placed 3 m to the side of the receiver, it is best to use thicker material. The power increased by 3.73 dBm when the thickness of the plastic, increased from 5 mm to 50mm. The system’s performance increased with wood when the RFID tag is in line with the receiver at a distance of 2.36 m, and as the thickness was increased from 20 mm to 200 mm. When the RFID tag was placed 3 m to the side of the receiver, the system’s performance decreased as the thickness was increased from 20 mm to 200 mm.

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