Exploiting the available diversity from various sources in wireless networks is an easy way to improve performance at the expense of additional hardware, space, complexity and/or bandwidth. Signal space diversity (SSD) and cooperative communication are two promising techniques that exploit the available signal space and space diversity respectively. This study first presents symbol error rate (SER) analysis of an SSD system containing a single transmit antenna and N receive antennas with maximal-ratio combining (MRC) reception; thereafter it presents a simplified maximum-likelihood (ML) detection scheme for SSD systems, and finally presents the incorporation of SSD into a distributed switch and stay combining with partial relay selection (DSSC-PRS) system. Performance analysis of an SSD system containing a single transmit antenna and multiple receive antennas with MRC reception has been presented previously in the literature using the nearest neighbour (NN) approximation to the union bound, however results were not presented in closed form. Hence, closed form expressions are presented in this work. A new lower bound for the SER of an SSD system is also presented which is simpler to evaluate than the union bound/NN approximation and also simpler to use with other systems. The new lower bound is based on the minimum Euclidean distance of a rotated constellation and is termed the minimum distance lower bound (MDLB); it is also presented here in closed form. The presented bounds have been validated with simulation and found to be tight under certain conditions. The SSD scheme offers error performance and diversity benefits with the only penalty being an increase in detector complexity. Detection is performed in the ML sense and conventionally, all points in an M-ary quadrature amplitude modulation (M-QAM) constellation are searched to find the transmitted symbol. Hence, a simplified detection scheme is proposed that only searches m symbols from M after performing initial signal conditioning. The simplified detection scheme is able to provide SER performance close to that of optimal ML detection in systems with multiple receive antennas. Cooperative communication systems can benefit from the error performance and diversity gains of the spectrally efficient SSD scheme since it requires no additional hardware, bandwidth or transmit power. Integrating SSD into a DSSC-PRS system has shown an improvement of approximately 5dB at an SER of 10-4 with a slight decrease in spectral efficiency at low SNR. Analysis has been performed using the newly derived MDLB and confirmed with simulation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

Piracy is still a significant threat to ships in a maritime environment. Areas such as the coast of Somalia and the Strait of Malacca are still plagued by pirates, and the total international cost of piracy numbers in the billions of dollars. The first line of defence against these threats is early detection and thus maritime surveillance has become an increasingly important task over the years. While surveillance has traditionally been a manual task using crew members in lookout positions on parts of the ship, much work is being done to automate this task using digital cameras equipped with computer vision software. While these systems are beneficial in that they do not grow tired like their human counterparts, the maritime environment is a challenging task for computer vision systems. This dissertation aims to address some of these challenges by presenting a system that is able to use prior knowledge of an object’s shape to aid in detection and tracking of the object. Additionally, it aims to test this system under various environmental conditions (such as weather). The system is based around the segmentation technique known as the level set method, which uses a contour in the image that is evolved to separate regions of interest. The system is split into two parts, comprising of an object detection stage that initially finds objects in a scene, and an object tracking stage that tracks detected objects for the rest of the sequence. The object detection stage uses a kernel density estimation-based background subtraction and a binary image level set filter, while the object tracker makes use of a tracking level set algorithm for its functionality. The object detector was tested using a group of 4 sequences, of which it was able to find a prior-known object in 3. The object tracker was tested on a group of 10 sequences for 300 frames a sequence. In 6 of these sequences the object tracker was able to successfully track the object in every single frame. It is shown that the developed video tracking system outperforms level set–based systems that don’t use prior shape knowledge, working well even where these systems fail. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

High capacity wireless and xed-line broadband services have a relatively small footprint over South Africa's vast expanse. This results in many rural areas, as well as military communication when deployed, relying on low-bandwidth communication networks instead, making live video communication over these links impractical. Traditional and advanced data compression methods cannot produce the payload reduction required for video use over these bandwidths. Instead, a model-based vision system is used to address this problem. This is not video compression but rather image understanding and representation in the context of prior models of the observed object. Markerless human tracking and pose recovery are the specific interests of this research. Markerless human pose tracking is a relatively new and growing field of image processing. It has many potential areas of application apart from low-bandwidth video communication, including the medical field, sporting arena, security and surveillance and human-machine interaction. As multimedia technologies continue to grow and improve, pose tracking systems have the potential to be used more and more. While a few markerless tracking devices are beginning to emerge, many currently available commercial motion capture systems require the use of a special suit and markers or sensors. This makes them very impractical for easy everyday, anywhere use. Current research in computer vision and image processing incorporates a significant focus on the development of markerless approaches to human motion capture. This dissertation looks at a complete markerless human pose tracking system which can be split into four distinct but interlinking stages: the image capture, image processing, body model and optimisation stages. After video data from multiple camera views is captured, the processing stage extracts image cues such as silhouettes, 2-D edges and 3-D colour volumetric reconstruction. Following the basic principle of a model-based approach, a 24 degree-of-freedom superellipsoid body model is fitted to the observed image cue data. An objective function is used to measure the closeness of this match. A number of different optimisation approaches are examined for use in refining and finding the best fitting body pose for each image frame. These approaches are all based around Stochastic Meta Descent (SMD) optimisation with SMD by itself, SMD in a hierarchical approach, SMD with pose prediction and Smart Particle Filtering, SMD inside a particle filter framework, all explored. The performance of the system with the various optimisation approaches is tested using the HumanEvaII datasets. These datasets contain a number of different subjects performing a variety of actions while wearing ordinary clothes. They contain markerbased ground-truth data obtained using a ViconPeak motion capture system. This allows a relative error measurement of the predicted poses to be calculated. With its robustness to clutter and occlusion, the Smart Particle Filter approach is shown to give the best results. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

There is need to improve prediction results in rain attenuation in order to achieve reliable wireless communication systems. Existing models require improvements or we need fresh approaches. This dissertation presents a model of rain attenuation prediction for terrestrial and satellite radio links based on a novel approach. This approach postulates that the difference in rain attenuation for various locations is attributed to the dissimilar rain drop sizes and rain cell diameter sizes and that cell sizes derived from local measurements would depict the true nature of rain cells better than the cells derived from long term rain data gathered from different climates. Therefore all other link parameters used in the attenuation equation are presented by the use of mathematical analysis; but the rain cell size is derived from local rain rate measurements. The physical link aspects considered in the mathematical attenuation model are: the Fresnel ellipsoid of the link path, the effect of elevation angle, the rain cell diameter size and the shape of growth of rain rates in the cell. The effect of the elevation angle of the link on the scale of attenuation is accounted for through the proposed coefficient of elevation equation. The coefficient of elevation is considered to modify the size of the rain cell diameter in proportion to the elevation angle of the link and the rain rate growth is taken to be of the truncated-Gaussian form. On the other hand, the rain cell diameter is derived from rain rate measurements as a power law model and substituted in the attenuation expression. The rain cell size model evaluated in this dissertation is based on point rain rate measurement data from the disdrometer located at the University of KwaZulu-Natal, South Africa. The “Synthetic Storm” technique is applied to develop the rain cell diameter distributions and the rain cell diameter model. In addition, the impact of the rain cell diameter size model in site diversity and cellular network-area planning for the region is discussed. To validate the model for terrestrial links, attenuation data collected from Durban, South Africa is used while that for satellite links, attenuation data from 15 links which are located in tropical climatic zones are used. In each case, the new model is tested against some well-known global rain attenuation prediction models including the standard ITU-R models. The performance of the proposed models for the sampled radio links based on error estimations shows that improvements have been achieved and may be regarded as a universal tropical model especially for satellite links. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

An introduction to the fundamental concepts of X-ray physics and X-ray tube design is given. This discussion also includes a brief description of various X-ray tube types available commercially for a number of different industrial applications. The design of a high-energy MgO cold cathode X-ray tube, which is to be used in an X-ray fluorescence (XRF) spectrometer, is described in detail with emphasis placed on the electron beam focusing mechanism and the theory of operation as well as the construction of the X-ray tube MgO cold cathode, which functioned as the electron emitter of the device. A detailed account is also given of the output characteristics of the X-ray tube power supply, which has a direct effect on the design requirements and consequently the performance of the X-ray tube. An investigation into the manufacture of the vacuum envelope with particular attention focused on the production of reliable metal-to-ceramic seals was performed. A number of tests were conducted especially with regard to the maximum temperature that such seals may withstand without becoming permanently damaged. These tests were essential, since high temperature gradients tend to develop in an X-ray tube during operation, which the metal-to-cerarnic seals of the tube must be capable of withstanding if damage to the device is to be avoided. The set-up of the XRF spectrometer in which the completed X-ray tube was tested is discussed, in which the X-ray current and voltage measuring techniques are described. Furthermore a detailed account of the operation of the X-ray detector system and the multichannel analyser is given, which was used to detect and record spectra of the sample elements excited by the primary radiation of the X-ray tube. Finally the measured X-ray tube performance characteristics are discussed and compared to the predicted results. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.

Digital image steganography has been made relevant by the rapid increase in media sharing over the Internet and has thus experienced a renaissance. This dissertation starts with a discussion of the role of modern digital image steganography and cell-based digital image stego-systems which are the focus of this work. Of particular interest is the fact that cell-based stego-systems have good security properties but relatively poor embedding capacity. The main research problem is stated as the development of an approach to improve embedding capacity in cell-based systems. The dissertation then tracks the development of digital image stego-systems from spatial and naïve to transform-based and complex, providing the context within which cell-based systems have emerged and re-states the research problem more specifically as the development of an approach to determine more efficient data embedding and error coding schemes in cell-based stego-systems to improve embedding capacity while maintaining security. The dissertation goes on to describe the traditional application of data handling procedures particularly relating to the likely eventuality of JPEG compression of the image containing the hidden information (i.e. stego-image) and proposes a new approach. The approach involves defining a different channel model, empirically determining channel characteristics and using them in conjunction with error coding systems and security selection criteria to find data handling parameters that optimise embedding capacity in each channel. Using these techniques and some reasoning regarding likely cover image size and content, image-global error coding is also determined in order to keep the image error rate below 1% while maximising embedding capacity. The performance of these new data handling schemes is tested within cell-based systems. Security of these systems is shown to be maintained with an up to 7 times improvement in embedding capacity. Additionally, up to 10% of embedding capacity can be achieved versus simple LSB embedding. The 1% image error rate is also confirmed to be upheld. The dissertation ends with a summary of the major points in each chapter and some suggestions of future work stemming from this research. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

Power Line Communications (PLC) is a recent and rapidly evolving technology, aiming at the utilization of the electricity power lines for the transmission of data. PLC technology opens up new opportunities for the mass provision of local, last-mile access at a reasonable cost. PLC can furthermore provide a multitude of new Information Society services - both in the energy and telecom domains - to residential and commercial users that are difficult or costly to implement through other technologies. PLC technology has a number of important strengths: it offers a permanent on-line connection as well as symmetric, two-way communication; it has good performance, very good geographical coverage, and is relatively cheap because most of the infrastructure is already in place. Currently, the main weaknesses of PLC technology are that it is still in the developmental stage. It is likely not to be the only one: rather, it will be part of a range of complementary technologies, because each technology yields a different compromise between bandwidth, reach, noise immunity, and cost. This report starts by looking at access technologies and describing the power line as a communication medium and then frequency response and noise characteristics. A transmission technique (OFDM) that avoids power line noise and uses the common modulation formats is also explained. The results of this work shows that the power line technology can be used as a communication channel for urban areas and fast developing rural areas. This is because of the bandwidth is uses. A proposed future research for slow developing rural areas is found in the conclusion. / Thesis (M.Sc.Eng.)- University of KwaZulu-Natal, 2005.

Since the ascendance of CDMA (Code Division Multiple Access) as the generally accepted multiple access technology of choice for next generation networks, the rate of development of the wireless cellular communication industry has been phenomenal. Next generation wireless cellular networks offer a myriad of voice, video, data and text based information services for the future multimedia and information society. This mixed service scenario implies that the same [mite resource i.e. the air interface must be shared amongst different classes of user, each with a specific quality of service. With multiple services competing for the same resource and with the inherent soft capacity nature of CDMA, call admission control becomes a formidable task. The problem is further compounded by the introduction of priorities between classes. Call admission control is an essential component of these next generation networks and the open nature of the current standards, such as UMTS (Universal Mobile Telecommunication System) allow for vendor implementation of different call admission control policies. The main area of focus in this dissertation is on a proposed downlink, load-based, mixed service call admission policy. In a CDMA environment with symmetrical service and equal bandwidths in each direction, the uplink is commonly considered to be the bottleneck. Based on the asymmetric nature of the expected traffic in next generation networks the downlink is envisaged as the future bottleneck. Some of the more common choices for downlink call admission control include number based as well as power based call admission policies. A load-based call admission policy has been chosen as the maximum load threshold that can be supported varies with the state of the system and thus effectively models the behaviour of a soft capacity CDMA network. This dissertation presents a teletraffic performance analysis model of a load-based call admission control policy for downlink mixed service CDMA cellular networks. The performance analysis yields customer oriented grade-of-service parameters such as call blocking probability which is essential for network planning. In our analysis we incorporate a Birth-Death Markov queuing model. This mathematical model is verified though computer simulation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007.

Reviews of possible telecommunication services that can be deployed in the rural areas are highlighted. These services range from narrowband to broadband. The aim of these services is to target rural Kwazulu-Natal areas that are without or with limited telecommunications infrastructure. Policies that govern telecommunications in South Africa are also reviewed with emphasis on Universal Service Obligation. The importance of telecommunications infrastructure in rural areas is also reviewed to the benefit of Kwazulu-Natal. FDMA, TDMA, CDMA, VSAT, MMDS and MVDS are compared for a possible use in rural areas. Cost comparison of GSM and CDMA is conducted with emphasis on fade margin, path loss and penetration rate. CDMA system design and coverage areas are discussed for rural KwaZulu-Natal. Lastly bit error rate graphs and power control algorithms are presented for Kwazulu-Natal scenario. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.

The thesis presents an implementation of a multiple input single output orthogonal frequency division multiplex (MISO OFDM) communication system testbed. The project was developed in order to evaluate whether the channel estimation algorithms developed by Dr Oyerinde [1] could be implemented in a real time communication system that uses today’s technology. This implementation based validation would help determine the practicality of algorithms and methods that promise better performance for communication systems from a simulation point of view. The benefits of using multiple orthogonal carriers are discussed as well as how an OFDM system works. The benefits of using multiple antennas at the transmitter, as opposed to using just one, are also discussed. The Alamouti scheme which allows space diversity to be achieved without the cost of having a lower data rate is presented. Modules common to all communication systems, such as those dedicated to synchronization, channel estimation, symbol detection and channel coding, are discussed. The different methods of synchronization for OFDM communication systems are presented and compared. The channel estimation algorithm developed by Dr Oyerinde is presented and is adopted for an indoor channel. Most of the system blocks and parameters used in the testbed are the same as those used in [1] in order to easily compare the results obtained by simulation and those obtained by implementation. The system bandwidth required for the project was too high for the processor chosen for the testbed. A qualitative evaluation of the practicality of Dr Oyerinde’s channel estimation algorithms was performed instead. From this evaluation it was derived that Dr Oyerinde’s non-iterative decision directed channel estimation algorithm was more suitable for real time non-iterative decision directed channel estimation communication systems than for iterative versions. Apart from processing demands that couldn’t be met, the other aspects of the project were implemented successfully. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.