Hard disk drives function perfectly satisfactorily when used in a stable environment, but in certain applications they are subjected to shock and vibration. During the work reported in this thesis it has been found that when typical hard disk drives are subjected lo vibration, data transfer failure is found to be significant at frequencies between 440Hz and 700Hz, at an extreme, failing at only Ig of sinusoidal vibration. These failures can largely be attributed to two key components: the suspension arm and the hard disk. At non-critical frequencies of vibration the typical hard disk drive can reliably transfer data whilst subjected to as much as 45g. When transferring data to the drive controller, the drive's operations are controlled and monitored using BIOS commands. Examining the embedded error signals proved that the drive predominantly failed due lo tracking errors. Novel piezo-electric sensors have been developed to measure unobtrusively suspension arm and disk motion, the results from which show the disk to be the most significant failure mechanism, with its First mode of resonance at around 440Hz. The suspension arm movement has been found to be greatest at IkHz. Extensive modelling of the flexure of the disk, clamped and unclamped, has been undertaken using finite element analysis. The theoretical modelling strongly reinforces the empirical results presented in this thesis. If suspension arm movement is not directly coupled with disk movement then a flying height variation is created. This, together with tracking variations, leads to data transfer corruption. This has been found to occur at IkHz and 2kHz. An optical system has been developed and characterised for a novel and inexpensive flying height measurement system using compact disc player technology.

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With the increasing number of Vehicular Autonomous Network (VANET) architectures and applications, user privacy must be addressed and protected. Internet of Things (IoT) and their applications take care of everyday mundane task in order to increase user convenience and productivity. However, studies have shown that IoT architectures can be a weak spot in network security, including data being sent plain text. In this thesis, a VANET architecture is proposed that is capable of securing anonymous data collection from a distributed set of autonomous vehicles. The proposed architecture features a hybrid combination of centralized and decentralized routing concepts. Unlike other VANET implementations, our proposed architecture provides anonymity to users in the network. Lower latency can be achieved by merging data from live short-range ad-hoc routing methods with the data collected from a pseudo-live long range centralized routing methods. The proposed architecture guarantees user anonymity within the VANET framework. Most VANET models assume users do not value the privacy of their identity. We assume that each vehicle is equipped with a VANET computer capable of storing data, performing calculations, and both sending and receiving data wirelessly. Therefore vehicles can communicate directly with each other and exchange data within short distances as well as communicate with long-range wireless infrastructure. Simulation results show the implementation is equipped to handle diverse traffic scenarios as well as deter adversaries to the network from maliciously trying to manipulate collected data.

The iOS 7 Core Bluetooth Framework (CB) is finally at a level where it can be used in projects to create valuable iOS applications. Due to its maximum broadcast radius of 30ft it lends itself to nearby communication. This thesis explores the Bluetooth space generally before delving into location-based data transfer using Bluetooth. The CB provided by Apple is powerful, but somewhat cumbersome. It forces the developer to deal with details related to device discovery and connections which can be tangential to the goal of the developer: sending data between devices. I built the Lightweight Bluetooth Framework (LBF) which makes the features of the CB more accessible by abstracting away from the implementation details of CB. LBF supports any number of data types being transferred as well as any number of total pieces of data regardless of data type. The system accomplishes this by assigning specific Characteristics to a particular data type and having pieces of data be uniquely identified with an ID when they are broadcasted. This unique ID is then used to associated the proper object with the received data. This will enable developers to focus on the implementation of their App without getting hung up on the details of the CB. Additionally, benchmark tests are done on the Lightweight Bluetooth Framework to determine what data transfer speed the framework supports. These tests reveal that transfer speed depends on hardware, but independent of hardware are too slow to transfer images, video, or sound.

South Africa is a developing country with great potential to be leaders in technology and research, especially in the medical field. Rural areas in many countries do not have access to basic healthcare services due to the distance and inaccessibility of these services. Currently people living in the rural areas in South Africa are required to rely on the people within the area, who may not be trained; on doctors who make house calls, who may not be able to access the patient in time or on finding transport to the nearest hospital, which may be hundreds of kilometres away. This leads to many rural residents not seeking aid for aliments thereby often lowering life expectancy. South Africa has many world-renowned medical practitioners who would be able to assist the residents in these areas if there were methods for observation and recording of health statuses without the need for either party to travel. This dissertation studied and developed a method to assist not only the residents in rural areas, but also urban residents to record their vital signs without the assistance of a licenced medical practitioner, to upload the data to a database and to then allow the data to be viewable by the medical practitioner who may be situated elsewhere in South Africa or the world. This system allows for the elimination of human error when recording vital sign data as recording is not done through human intervention. Through the use of communications technologies such as Bluetooth, NFC and Wi-Fi a system was designed which ensures that a patient can record medical data without the presence of a medical practitioner, the patient can access previous health records and readings and the patient can give a new medical practitioner a full medical history. The patient's data has been secured using AES and RSA encryption as well as verification through hash values at all points of transfer and access is granted to the patients' medical data only through the patient or a licenced medical practitioner. The data recording and transfer has been completed taking into consideration all the medical legislation and laws in South Africa. This system allows the South African medical health sector to service all South Africa residents, including the residents in rural areas. / Dissertation (MEng)--University of Pretoria, 2016. / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

Graphics Processing Units (GPUs) are workhorses of modern performance due to their ability to achieve massive speedups on parallel applications. The massive number of threads that can be run concurrently on these systems allow applications which have data-parallel computations to achieve better performance when compared to traditional CPU systems. However, the GPU is not perfect for all types of computation. The massively parallel SIMT architecture of the GPU can still be constraining in terms of achievable performance. GPU-based systems will typically only be able to achieve between 40%-60% of their peak performance. One of the major problems affecting this effeciency is the GPU memory system, which is tailored to the needs of graphics workloads instead of general-purpose computation. This thesis intends to show the importance of memory optimizations for GPU systems. In particular, this work addresses problems of data transfer and global atomic memory contention. Using the novel AMD Fusion architecture, we gain overall performance improvements over discrete GPU systems for data-intensive applications. The fused architecture systems offer an interesting trade off by increasing data transfer rates at the cost of some raw computational power. We characterize the performance of different memory paths that are possible because of the shared memory space present on the fused architecture. In addition, we provide a theoretical model which can be used to correctly predict the comparative performance of memory movement techniques for a given data-intensive application and system. In terms of global atomic memory contention, we show improvements in scalability and performance for global synchronization primitives by avoiding contentious global atomic memory accesses. In general, this work shows the importance of understanding the memory system of the GPU architecture to achieve better application performance. / Master of Science

Low Earth Orbit (LEO) satellite networks have revolutionized space internet access, offering better network performance than previous alternatives. While being the best option for space internet access, it does not yet compete with terrestrial networks in latency and bandwidth. The QUIC transport protocol was developed for Hypertext Transfer Protocol (HTTP) to reduce page load times and work better in low-bandwidth and high-loss networks than the Transmission Control Protocol (TCP). Studies have shown that QUIC performs well for small file sizes, which can be achieved by using compression. This thesis investigates whether combining QUIC as a general data transfer protocol with lossless compression enhances encrypted data transmission in a LEO satellite network. To test this, a program consisting of a client and server deployed on a LEO satellite network emulator is developed, where files with increasing sizes are compressed and sent using both QUIC and TCP in various network conditions. Results indicate that QUIC should be paired with lossless compression for file sizes up to 1MB. It should not be implemented for file sizes above 1MB in low-loss and high-bandwidth conditions, while it can be implemented in medium to poor conditions.

There is a growing interest in the development of broadband services and networks for commercial use in both local area and wide area networks. The primary reasons for this is a pressing need to meet the demand for increased bandwidth for remote sites interconnection, and in high speed data transfer of bulk data such as images etc. There has also been a significant change in the characteristics of network traffic. It is increasingly taking the form of bursty traffic characterized by an unpredictable demand for bandwidth of several megabytes. A new generation of networking technologies have emerged to meet the demand of growing and uncertain bandwidth requirements. One such technology is called Asynchronous Transfer Mode (ATM) for use on broadband networks under the banner of broadband ISDN. ATM enables interconnection at high speeds in the range of Mbit/s or Gbit/s over wide areas, which effectively moves the bottleneck from networks to end systems. Furthermore, the user is able to access bandwidth on demand and the user is only charged for the bandwidth actually used. As more and more information (audio, image and data) is transferred over ATM networks, security issues are becoming increasingly critical. The rapidly growing use of the Internet to transfer confidential and sensitive information only enhances the importance of security services. One may even argue that the success of ATM will be determined not by its cost effectiveness but also to the level of trust that can be placed on its performance, security and availability. The objective of this dissertation is to address the issues involved in the design of security services for ATM networks. / Master of Science (Hons)

Novel techniques for high-performance wireless power transmission and data interfacing with implantable medical devices (IMDs) were proposed. Several system- and circuit-level techniques were developed towards the design of a novel wireless data and power transmission link for a multi-channel inductively-powered wireless implantable neural-recording and stimulation system. Such wireless data and power transmission techniques have promising prospects for use in IMDs such as biosensors and neural recording/stimulation devices, neural interfacing experiments in enriched environments, radio-frequency identification (RFID), smartcards, near-field communication (NFC), wireless sensors, and charging mobile devices and electric vehicles. The contributions in wireless power transfer are the development of an RFID-based closed-loop power transmission system, a high-performance 3-coil link with optimal design procedure, circuit-based theoretical foundation for magnetic-resonance-based power transmission using multiple coils, a figure-of-merit for designing high-performance inductive links, a low-power and adaptive power management and data transceiver ASIC to be used as a general-purpose power module for wireless electrophysiology experiments, and a Q-modulated inductive link for automatic load matching. In wireless data transfer, the contributions are the development of a new modulation technique called pulse-delay modulation for low-power and wideband near-field data communication and a pulse-width-modulation impulse-radio ultra-wideband transceiver for low-power and wideband far-field data transmission.