Thesis (Ph. D.)--University of Michigan, 1928. / "Reprinted from Physical Review ... vol. 34, no. 8, October 15, 1929.

Inaug.-diss.--Breslau. / Lebenslauf.

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Inaug.-diss.--Rostock.

Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-104). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

The rapid growth of data hungry wireless applications has boosted the demand for wireless communication systems with improved reliability, wider coverage, and higher throughput. The main challenges facing the design of such systems are the limited resources, such as bandwidth, restricted transmission power, etc., and the impairments of the wireless channels, including fading effects, interference, and noise. Multiple-input multiple-output (MIMO) communication has been shown to be one of the most promising emerging wireless technologies that can efficiently enhance link reliability, improve system coverage, and boost the data transmission rate. Consequently, MIMO is now extensively adopted by many mainstream wireless industry standards, including 3GPP WCDMA/HSDPA, LTE, EVDO, WiFi, and WiMAX. By deploying multiple antennas at both transmitter and receiver sides, MIMO techniques license a new dimension (spatial dimension) that can be applied in various ways for combating the impairments of wireless networks. Furthermore, this new dimension has introduced a new concept known as Interference Alignment that can efficiently deal with the interference presentin the wireless communication networks. In particular, IA is highly attractive in terms of providing more degrees of freedom compared to techniques such as TDMA/FDMA. With this in mind, this thesis will focus on studying and developing advanced techniques and algorithms for reducing interference in cellular communication networks. The contributions of the thesis are as follows. Initially, a review is provided to reiterate some basic concepts of wireless communications and discuss the challenges faced by the techniques that deal with interference mitigation. Next, Chapter 3 presents a novel IA based cancellation scheme that is proposed for combating the interfering signals present in the compounded MIMO broadcast channels, where the users experience a multi-source transmission from several base stations. After defining the interference channel (IC) interference and X-channel interference, the partial transmit beamforming matrices of the closed-form downlink scheme alleviate the corresponding types of interference. Applying the proposed scheme allows one to treat the multi-cell network as a set of single-cell MIMO network, which leads to the simultaneous BER performance enhancement and data rate increase. Moreover, a generalization scheme is given to assign the appropriate antenna configuration for achieving maximum DoF. Furthermore, Chapter 4 demonstrates a comprehensive analysis on the number of DoF achievable by exploiting the transmit beamforming technique. Additionally, the proposed scheme is able to provide the maximum data rate under a certain antenna setting or compute a transmitter-receiver configuration in order to meet the required number of DoF. Chapter 5 considers a modified IA scheme for the compounded MIMO network when different classes of users communicate in the overlapped area. Due to various antenna settings of each receiver, the effect of spatial correlation on the achievable data rate is investigated. Moreover, an algorithm is derived for calculating the antenna configuration for different users classes. Then, the proposed scheme is extended for the case of Large-scale MIMO, which in turn provides sufficient insights into the impact of the deployment of a large number of antennas. Finally, Chapter 6 presents an alternative design of the IA scheme with no symbol extension for the cellular MIMO network. Subsequently, a modified eigenvalue-based scheme is proposed to enhance the overall system performance. Finally, the achievable data rate is calculated under different CSI acquisition scenarios. Chapter 7 concludes the thesis and provides a list of potential future work directions for further investigation.

M.Ing. / Open-wire telecommunications were developed in the 19th and early 20th centuries without any consideration of the deleterious effects of power lines; compatibility problems were later caused by the proximity of power lines and telephone lines. The coexistence of such systems requires careful planning in terms of energy coupled to the telephone lines; this induction can cause interference, as well as dangerous overvoltages in telephone circuits, and requires detailed studies of the effects of coupling between high voltage lines and telephone systems to be done. In terms of inductive co-ordination in South Africa, the minimum separation distances between high voltage power lines and communication systems are calculated only for power frequency and lower order harmonics (up to the 13th). The aim of the study was to explore the agreement between theory and measurement for frequencies from 50 Hz to the high order harmonic range of 4 kHz; this makes it possible to extend existing methods for predicting compatible separations to cases where high order harmonics (up to the 73rd) are present (balanced and unbalanced) on a 132 kV power line feeding a large aluminium smelter plant.

M.Ing. (Electrical and Electronic Engineering) / Recent world events such as the fall of Communism. attempts at the unification of Europe and the reaching of the most extensive international trade agreement yet (GATT ::: General Agreement on Trade and Tariffs). have all contributed to the expansion of world markets as well as a marked intensification in the competition in those markets. Rivalry in the market for power electronic equipment is as relentless as in any other. Strict regulations with regard to Electromagnetic Interference (EMf) and Electromagnetic Compatibility (EMC) apply in Europe and compliance with these standards is legally enforced. In South Africa, compliance with such standards is merely recommended, hence local manufacturers have not yet considered these phenomena seriously enough to pose a threat to their European opposition. The two main causes of EMI are switching action, which is such an integral part of power electronics, and the excitation of parasitic circuit elements. This thesis describes the investigation carried out to determine the effect of certain layout and construction parameters on the generation of EMf. Parasitic loop inductances, self-capacitances of coils and the ground connection of heat sinks were examined in the process. A test convener containing a full-bridge converter perfonning DC·DC conversion, was built. These converters are important building blocks for equipment such as uninterruptible power supplies. One configuration of this converter was designated as the reference configuration. For every modification of a layout or construction parameter its effect on the interference spectrum was determined through a comparison with the measured interference spectrum of the reference configuration. The use of snubbers and the minimisation of the self-capacitances of inductors in an output filter effected a marked decrease in the measured interference spectrum (approximately 10 dB or a third less). Certain loop inductances have to be minimised in the design stages through proper layout of conveners, and heat sinks should preferably be grounded through high resistances. Paying due attention to these aspects in the design of power electronic converters can aid in decreasing the size and cost of bulky, expensive EMf filters required to meet the standards. It could give local manufacturers a considerable advantage over their overseas competitors.

The use of periodic structures to reduce interference from large reflecting surfaces is proposed. Instrument landing system (ILS) interference from large hangars and terminal buildings is cited as a typical problem. An analytical and numerical investigation of an infinite fin-corrugated surface composed of infinitely thin fins of spacing λ/2<a<λ under TM polarized plane wave illumination is described. Specular reflection from this surface can be completely converted to back-scatter in a direction opposite to the incident wave when the angle of incidence from the normal to the surface and the fin height are properly chosen. Experiments were performed at 35 and 37 GHz. using finite size fin-corrugated surfaces with fins of finite thickness under non-plane wave illumination and the results indicate that these surfaces behave essentially as predicted. In addition, the experimental surfaces remain completely effective for small oblique angles of incidence and have sufficient bandwidth for ILS applications. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate