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Dissertations / Theses on the topic 'Propagation channel modelling'
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1
Laurensen, David Irvine. "Indoor radio channel propagation modelling by ray tracing techniques." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/12397.
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In response to the requirement for a more detailed channel model based on the physical characteristics of the environment within which indoor radio communications operate, this thesis presents a channel model based on ray tracing techniques. The mathematical basis for the model is presented in terms of the electromagnetic properties of simple objects. The resulting model is coded into a simulation system which takes a description of a building in terms of the structure of internal walls, floors and ceilings. Through repeated application of the reflection process, a description of the channel impulse response is created for a given transmitter and receiver position from the multipath components generated. This model is applied, in progressing degrees of complexity, to two buildings for which narrowband physical measurements are available. Comparison is made between the measured results and the narrowband simulation results which leads to an analysis of the various propagation mechanisms involved in in-building communications. It is found that the model, while not accurately predicting the measured results, does produce a model that, considering the unknown parameters of the environment and experimental procedure, relates well to the channel experienced by a communication system. Wideband channel characteristics are determined from the simulation model, and found to give access to more detailed information on the channel than is obtainable through physical measurement. The results of the wideband simulations are compared with published material containing measurement results, and the relationship to the narrowband results already presented is shown.
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Morrison, Gerald Dale. "Measurement, characterization, and modelling of the indoor radio propagation channel." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq64829.pdf.
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Ghazal, Ammar. "Propagation channel characterisation and modelling for high-speed train communication systems." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/3079.
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High-mobility scenarios, e.g., High-Speed Train (HST) scenarios, are expected to be typical scenarios for the Fifth Generation (5G) communication systems. With the rapid development of HSTs, an increasing volume of wireless communication data is required to be transferred to train passengers. HST users demand high network capacity and reliable communication services regardless of their locations or speeds, which are beyond the capability of current HST communication systems. The features of HST channels are significantly different from those of low-mobility cellular communication systems. For a proper design and evaluation of future HST wireless communication systems, we need accurate channel models that can mimic the underlying channel characteristics, especially the non-stationarity for different HST scenarios. Inspired by the lack of such accurate HST channel models in the literature, this PhD project is devoted to the modelling and simulation of non-stationary Multiple-Input Multiple-Output (MIMO) channels for HST communication systems. In this thesis, we first give a comprehensive review of the measurement campaigns conducted in different HST scenarios and address the recent advances in HST channel models. We also highlight the key challenges of HST channel measurements and models. Then, we study the characterisation of non-stationary channels and propose a theoretical framework for deriving the statistical properties of these channels. HST wireless communication systems encounter different channel conditions due to the difference of surrounding geographical environments or scenarios. HST channel models in the literature have either considered large-scale parameters only and/or neglected the non-stationarity of HST channels and/or only consider one of the HST scenarios. Therefore, we propose a novel generic non-stationary Geometry-Based Stochastic Model (GBSM) for wideband MIMO HST channels in different HST scenarios, i.e., open space, viaduct, and cutting. The corresponding simulation model is then developed with angular parameters calculated by the Modified Method of Equal Area (MMEA). The system functions and statistical properties of the proposed channel models are thoroughly studied. The proposed generic non-stationary HST channel models are verified by measurements in terms of stationary time for the open space scenario and the Autocorrelation Function (ACF), Level Crossing Rate (LCR), and stationary distance for the viaduct and cutting scenarios. Transmission techniques which are capable of utilising Three-Dimensional (3D) spatial dimensions are significant for the development of future communication systems. Consequently, 3D MIMO channel models are critical for the development and evaluation of these techniques. Therefore, we propose a novel 3D generic non-stationary GBSM for wideband MIMO HST channels in the most common HST scenarios. The corresponding simulation model is then developed with angular parameters calculated by the Method of Equal Volume (MEV). The proposed models considers several timevarying channel parameters, such as the angular parameters, the number of taps, the Ricean K-factor, and the actual distance between the Transmitter (Tx) and Receiver (Rx). Based on the proposed generic models, we investigate the impact of the elevation angle on some of the channel statistical properties. The proposed 3D generic models are verified using relevant measurement data. Most standard channel models in the literature, like Universal Mobile Telecommunications System (UMTS), COST 2100, and IMT-2000 failed to introduce any of the HST scenarios. Even for the standard channel models which introduced a HST scenario, like IMT-Advanced (IMT-A) and WINNER II channel models, they offer stationary intervals that are noticeably longer than those in measured HST channels. This has inspired us to propose a non-stationary IMT-A channel model with time-varying parameters including the number of clusters, powers, delays of the clusters, and angular parameters. Based on the proposed non-stationary IMT-A channel model, important statistical properties, i.e., the time-variant spatial Cross-correlation Function (CCF) and time-variant ACF, are derived and analysed. Simulation results demonstrate that the stationary interval of the developed non-stationary IMT-A channel model can match that of relevant HST measurement data. In summary, the proposed theoretical and simulation models are indispensable for the design, testing, and performance evaluation of 5G high-mobility wireless communication systems in general and HST ones in specific.
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King, P. R. "Modelling and management of the land mobile satellite MIMO radio propagation channel." Thesis, University of Surrey, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441874.
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Fang, Cheng. "The characterisation and modelling of the wireless propagation channel in small cells scenarios." Thesis, University of Bedfordshire, 2015. http://hdl.handle.net/10547/595693.
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The rapid growth in wireless data traffic in recent years has placed a great strain on the wireless spectrum and the capacity of current wireless networks. In addition, the makeup of the typical wireless propagation environment is rapidly changing as a greater percentage of data traffic moves indoors, where the coverage of radio signals is poor. This dual fronted assault on coverage and capacity has meant that the tradition cellular model is no longer sustainable, as the gains from constructing new macrocells falls short of the increasing cost. The key emerging concept that can solve the aforementioned challenges is smaller base stations such as micro-, pico- and femto-cells collectively known as small cells. However with this solution come new challenges: while small cells are efficient at improving the indoor coverage and capacity; they compound the lack of spectrum even more and cause high levels of interference. Current channel models are not suited to characterise this interference as the small cells propagation environment is vast different. The result is that overall efficiency of the networks suffers. This thesis presents an investigation into the characteristics of the wireless propagation channel in small cell environments, including measurement, analysis, modelling, validation and extraction of channel data. Two comprehensive data collection campaigns were carried out, one of them employed a RUSK channel sounder and featured dual-polarised MIMO antennas. From the first dataset an empirical path loss model, adapted to typical indoor and outdoor scenarios found in small cell environments, was constructed using regression analysis and was validated using the second dataset. The model shows good accuracy for small cell environments and can be implemented in system level simulations quickly without much requirements.
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Pal, Arindam. "Modelling the impact of antenna radiation patterns and propagation conditions on MIMO channel capacity." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435739.
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Goulianos, A. A. "Empirical-statistical modelling and simulation of the ultra wideband body-centric radio propagation channel." Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/842846/.
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Ultra Wide-Band (UWB) communications is an emerging technology which can provide numerous advantages compared to conventional wireless systems. UWB technology aims to incorporate low-power, noise-like signal transmissions, making them ideal for use in Wireless Body Area Network (WBAN) communication systems. Towards this end, the work presented in this thesis is oriented to the statistical characterization and modelling of UWB-WB AN channels. The most important aspects of the work undertaken in this thesis are reviewed below. The first contribution of this thesis is an enhancement upon the existing UWB on-body channels. More specifically, an advanced Markov-chain technique has been employed in order to predict the path arrival sequence on channels of this sort. Results suggest that this methodology can accurately represent the experimental data, and provide more reliable results when compared to the classic Poisson approach. The second contribution of the thesis introduces a novel two-dimensional signal strength prediction model, applicable to the UWB off-body propagation channel, This model is based on real-body measurements, carried out in controlled environments. The parameters that characterize this specific propagation environment have been evaluated and validated by means of comparison with the empirical data. The third contribution of this thesis incorporates a generalization of the UWB off-body total power gain model for different types of indoor environments. More specifically, the effect of the indoor scattering in the received signal strength is thoroughly examined with respect to both the distance and body orientation. Furthermore, the small-scale fading, the temporal correlation and the time dispersion characteristics of the received signal are investigated. Finally, bringing all pieces together, a statistical Power Delay Profile (PDP) model for the evaluation and design of UWB off-body systems has been developed. Due to the dependence of the radio propagation channel on the body orientation, separate stochastic tapped-delay-line models are developed for each body region. It is shown that die proposed modeling technique can adequately capture the key channel metrics of the UWB off-body propagation channel.
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Blanc, Grégory, Alexandre Skrzypczak, and Jean-Guy Pierozak. "BLIND EQUALIZATION WITH LDPC CODE: TO QUASIERROR FREE TRANSMISSIONS IN TELEMETRY." International Foundation for Telemetering, 2016. http://hdl.handle.net/10150/624248.
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In a telemetry system, it has been frequently proved that multipath channels and transmission
noise are the most critical sources of distortion. While equalization allows a strong limitation of
the multipath effects, the noise impact can be efficiently reduced if forward error correction is
used. This paper proves that the combination of blind equalization and a powerful FEC like
LDPC strongly improves bit error rates for the SOQPSK modulation. We also prove that a LDPC
code is able to fully correct the residual errors that may persist at the equalizer output. In other
terms, the combination of equalization and LDPC code enables quasi-error free transmissions in
various channel scenarios that represent the various phases of a telemetry mission.
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Adegoke, Elijah. "Radio frequency channel characterization for energy harvesting in factory environments." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/33412.
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This thesis presents ambient energy data obtained from a measurement campaign carried out at an automobile plant. At the automobile plant, ambient light, ambient temperature and ambient radio frequency were measured during the day time over two days. The measurement results showed that ambient light generated the highest DC power. For plant and operation managers at the automobile plant, the measurement data can be used in system design considerations for future energy harvesting wireless sensor nodes at the plant. In addition, wideband measurements obtained from a machine workshop are presented in this thesis. The power delay profile of the wireless channel was obtained by using a frequency domain channel sounding technique. The measurements were compared with an equivalent ray tracing model in order to validate the suitability of the commercial propagation software used in this work. Furthermore, a novel technique for mathematically recreating the time dispersion created by factory inventory in a radio frequency channel is discussed. As a wireless receiver design parameter, delay spread characterizes the amplitude and phase response of the radio channel. In wireless sensor devices, this becomes paramount, as it determines the complexity of the receiver. In reality, it is sometimes difficult to obtain full detail floor plans of factories for deterministic modelling or carry out spot measurements during building construction. As a result, radio provision may be suboptimal. The method presented in this thesis is based on 3-D fractal geometry. By employing the fractal overlaying algorithm presented, metallic objects can be placed on a floor plan so as to obtain similar radio frequency channel effects. The environment created using the fractal approach was used to estimate the amount of energy a harvesting device can accumulate in a University machine workshop space.
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Herbert, Steven John. "Wireless communication in vehicles." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/280675.
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There is an increasing interest in the deployment of wireless communication systems in vehicles. The motivation for this work is to provide a fundamental characterisation of the in-vehicle Electromagnetic (EM) wave propagation environment, and to demonstrate how this can be used to aid the deployment of wireless communication systems in vehicles. The fundamental characterisation of the in-vehicle EM wave propagation environment presented in this dissertation yields a number of useful outcomes. The instantaneous impulse response of the in-vehicle channel is characterised, which is presented in the form of a statistical model for arriving rays. Noticing that it is impractical to undertake a full statistical characterisation of the time-varying impulse response, the time variation of the in-vehicle channel is instead characterised as a Doppler spread. This approach provides parameters which are sufficient to perform an information theoretic analysis to lower bound the capacity of the in-vehicle channel. For typical operating conditions, it is found that the channel capacity is approximately equal to that of the same channel with perfect channel state information available at the receiver. Having established the fundamental EM wave propagation characteristics for a single in-vehicle wireless channel, the EM properties of the cavity itself are characterised. This is achieved through a thorough investigation into the analogy between vehicle cavities and reverberation chambers, specifically considering the quality factor (and hence time constant), EM isolation, and electric field uniformity of typical vehicle cavities. This approach yields the important insight that the root mean square delay spread is approximately the same for all wireless links in a typical vehicle cavity. Also, that the angular spread of energy received at any given location (away from the cavity boundaries) is approximately uniform, and that over short distances the coherence distance is well defined, and hence Multiple Input Multiple Output antenna arrays should work well in vehicles. To what extent a typical wireless system can exploit this characterisation depends on how well the parameters can be estimated by a typical wireless communication system. This is also addressed, specifically investigating the estimation of the cavity time constant, and channel time variation. It is found that both of these can be estimated well using a typical wireless sensor network system.
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Křivka, Petr. "Počítačové modelování datového přenosu po silnoproudých vedeních." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219335.
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The master‘s thesis is focused on data transfer over power lines. The influence of connected devices on data signal is studied. In this thesis, you can find the descriptions of PLC technology characteristics, sources of signal interruption and, mainly, the method of modelling the PLC channels as a multipath signal propagation environment is thoroughly discussed. There are models of PLC channels using this method projected in Simulink. The analysis of the influence of connected devices to bit error rate of a signal is processed. The devices are modelled by connected impedance.
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Lau, W. H. "Investigation of techniques for modelling telecommunication channels subject to multipath phenomena." Thesis, University of Portsmouth, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235295.
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Li, Fang. "Modelling of premixed laminar flame propagating in channels." Thesis, University of Central Lancashire, 2004. http://clok.uclan.ac.uk/21904/.
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The dynamics of the intrinsically unstable premixed flames propagating in channels is studied by means of numerical modelling in this work. Critical conditions of extinction and the influence of the thermal-diffusive effect on the dynamics of flame propagating in planar channels with cold sidewalls under gravity is investigated. For the horizontally propagating flames, the appearance of inversion influences the effect of thermal-diffusion on the asymmetry of flame fronts. For upwards propagating flames, the convex shape of the flame imposed by the mode of ignition combined with buoyancy can suppress the thermal-diffusive effects; in contrast, the buoyancy alone cannot damp the thermal diffusive effects even for quite large Froud numbers in regard to the appearance of inversion. The variation of Lewis number has no essential effect on the planar flame shape formation when flame propagates downward. Lowering Lewis number can significantly decrease the critical conditions of extinction. However, if Lewis number is smaller than some limit, its further effect on the critical extinction conditions is unsignificant. In the two-step consecutive reaction, the effects of the ratio of Damkohler numbers, heat release rates, activation energy and Lewis number on the separation and fragmentation of flames are considered. The inversion is more pronounced in combustion with separated flame fronts than for single-step reactions. However, the inversion is obvious only when the two flame fronts are close enough to each other. Thus, the details of combusiiition chemistry may have a strong effect on the stability of the flame front. The thermal diffusive effect of the first flame is, in certain way, dominant and has influence on the second flame. The presence of the first reaction suppresses the thermal-diffusive effect of the second reaction in regard to the appearance of inversion. The propagation of flames at a variety of Reynolds number ranging from 70 to 1000 are explored. For longer channels or a flat initial flame front, the inversion of the flame is apparent for Reynolds number higher than 200. For large &, the computational grids should be very fine because of the small thickness of preheat zone. The Generalized Curvilinear Coordinate Gridding method is introduced and an elliptic grid generator based on the variational approach is employed to construct the solution-adaptive grids. However, we found out that the global structure of the algorithm required by the adaptive grid approach might be not as efficient as simplified non-adaptive grids for prospective use of massively parallel computers.
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Unar, Manzoor Hussain. "Wideband mobile propagation channels : modelling, measurements and characterisation for microcellular environments." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436766.
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Hamraz, Bahram. "Engineering change modelling using a function-behaviour-structure scheme." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/245074.
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Engineering changes are unavoidable and occur throughout the lifecycle of products. Due to the high interconnectivity of engineering products, a single change to one component usually has knock-on effects on other components causing further changes. This change propagation significantly affects the success of a product in the market by increasing development cost and time-to-market. As such engineering change management is essential to companies, but it is a complex task for managers and researchers alike. To address this challenge, the thesis at hand investigates the state-of-the-art of research in engineering change management and develops a method to support engineering change propagation analysis, termed FBS Linkage. This method integrates functional reasoning with change prediction. A product is modelled as a network of its functional, behavioural, and structural attributes. Change propagation is then described as spread between the elements along the links of this network. The FBS Linkage concept is designed based on a comprehensive set of requirements derived from both the literature and industry practices as well as a comparative assessment of existing change methods and functional reasoning schemes. A step-by-step technique of building and using an FBS Linkage model is demonstrated. The method’s potential benefits are discussed. Finally, the application of the method to two industrial case studies involving a diesel engine and a scanning electron microscope is presented. The method evaluation indicates that the benefits of the method outweigh its application effort and pinpoints areas for further refinement.
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Lemmens, Yves Claude Jean. "Modelling and analysis of engineering changes in complex systems." Thesis, Cranfield University, 2007. http://dspace.lib.cranfield.ac.uk/handle/1826/5071.
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Complex products are comprised of a large number of tightly integrated components, assemblies and systems resulting in extensive logical and physical interdependences between the constituent parts. Thus a change to one item of a system is highly likely to lead to a change to another item, which in turn can propagate further. The aim of this research therefore is to investigate dependency models that can be used to identify the impact and trace thepropagation of changes in different information domains, such as requirements, physical product architecture or organisation. Cont/d.
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Saleem, Rashid. "Towards an end-to-end multiband OFDM system analysis." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/towards-an-endtoend-multiband-ofdm-system-analysis(e711f32f-1ac6-4b48-8f4e-58309c0482d3).html.
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Ultra Wideband (UWB) communication has recently drawn considerable attention from academia and industry. This is mainly owing to the ultra high speeds and cognitive features it could offer. The employability of UWB in numerous areas including but not limited to Wireless Personal Area Networks, WPAN's, Body Area Networks, BAN's, radar and medical imaging etc. has opened several avenues of research and development. However, still there is a disagreement on the standardization of UWB. Two contesting radios for UWB are Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) and DS-UWB (Direct Sequence Ultra Wideband). As nearly all of the reported research on UWB hasbeen about a very narrow/specific area of the communication system, this thesis looks at the end-to-end performance of an MB-OFDM approach. The overall aim of this project has been to first focus on three different aspects i.e. interference, antenna and propagation aspects of an MB-OFDM system individually and then present a holistic or an end-to-end system analysis finally. In the first phase of the project the author investigated the performance of MB-OFDM system under the effect of his proposed generic or technology non-specific interference. Avoiding the conventional Gaussian approximation, the author has employed an advanced stochastic method. A total of two approaches have been presented in this phase of the project. The first approach is an indirect one which involves the Moment Generating Functions (MGF's) of the Signal-to-Interference-plus-Noise-Ratio (SINR) and the Probability Density Function (pdf) of the SINR to calculate the Average Probabilities of Error of an MB-OFDM system under the influence of proposed generic interference. This approach assumed a specific two-dimensional Poisson spatial/geometric placement of interferers around the victim MB-OFDM receiver. The second approach is a direct approach and extends the first approach by employing a wider class of generic interference. In the second phase of the work the author designed, simulated, prototyped and tested novel compact monopole planar antennas for UWB application. In this phase of the research, compact antennas for the UWB application are presented. These designs employ low-loss Rogers duroid substrates and are fed by Copla-nar Waveguides. The antennas have a proposed feed-line to the main radiating element transition region. This transition region is formed by a special step-generating function-set called the "Inverse Parabolic Step Sequence" or IPSS. These IPSS-based antennas are simulated, prototyped and then tested in the ane-choic chamber. An empirical approach, aimed to further miniaturize IPSS-based antennas, was also derived in this phase of the project. The empirical approach has been applied to derive the design of a further miniaturized antenna. More-over, an electrical miniaturization limit has been concluded for the IPSS-based antennas. The third phase of the project has investigated the effect of the indoor furnishing on the distribution of the elevation Angle-of-Arrival (AOA) of the rays at the receiver. Previously, constant distributions for the AOA of the rays in the elevation direction had been reported. This phase of the research has proposed that the AOA distribution is not fixed. It is established by the author that the indoor elevation AOA distributions depend on the discrete levels of furnishing. A joint time-angle-furnishing channel model is presented in this research phase. In addition, this phase of the thesis proposes two vectorial or any direction AOA distributions for the UWB indoor environments. Finally, the last phase of this thesis is presented. As stated earlier, the overall aim of the project has been to look at three individual aspects of an MB-OFDM system, initially, and then look at the holistic system, finally. Therefore, this final phase of the research presents an end-to-end MB-OFDM system analysis. The interference analysis of the first phase of the project is revisited to re-calculate the probability of bit error with realistic/measured path loss exponents which have been reported in the existing literature. In this method, Gaussian Quadrature Rule based approximations are computed for the average probability of bit error. Last but not the least, an end-to-end or comprehensive system equation/impulse response is presented. The proposed system equation covers more aspects of an indoor UWB system than reported in the existing literature.
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Svensson, Elin. "Physical modelling of acoustic shallow-water communication channels." Doctoral thesis, Stockholm : Farkost och flyg, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4572.
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Kafaru, Olutumininu Olufolabomi. "An environment-dependent approach to wideband modelling and computer simulation of UHF mobile radio propagation in built-up areas." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253411.
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Jorge, Flávio Miguel da Silva. "High-order Earth-satellite propagation channel measurement and modelling at Ka and Q/V-bands." Doctoral thesis, 2020. http://hdl.handle.net/10773/28937.
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This work focuses on high-capacity spectral-efficient Earth-space microwave
communication links, supporting the access to wider and less congested
bandwidths and providing the required technological advances on radiowave
propagation for the design and operation of system-technologies improving the
spectral efficiency, proposing the operation of frequency-reuse schemes and
polarization diversity techniques at Ka- and Q/V-bands.
Because the suitable planning, successful deployment and effective, spectralefficient
and interference-free, operation of all space-borne systems and services
is necessarily related and directly dependent, although not exclusively, on the
propagation channel conditions, this work provides a comprehensive and
systematic approach intending the relevant propagation phenomena
characterization and understanding, modelling and mitigation.
It is proved that there is a bigger operational margin for the operation of the
abovementioned system-technologies than what may be believed by considering
the international recommended models. Major challenges are envisaged,
specially in what concerns the ice-induced depolarization that is more persistent
and takes longer than the corresponding rain-induced effects. Nevertheless, their
mitigation is possible for which the depolarization shall be the controlling variable.
The time lag of 15 minutes is identified as the best trade-off between affordable
time and achievable gain in the framework of a time diversity scheme.Este trabalho foca-se em links de comunicação Terra-espaço em microondas espectralmente eficientes e de elevada capacidade, suportando o acesso a larguras de banda maiores e menos congestionadas e ofereçendo os avanços tecnológicos necessários em termos de propagação de ondas de rádio para o projeto e operação de tecnologias de sistema que visam o uso otimizado do espectro, propondo a operação de esquemas de reuso de frequência e de técnicas de diversidade de polarização nas bandas Ka e Q/V. Porque o adequado planeamento, a implementação bem sucedida, bem como a efetiva operação, espectralmente eficiente e livre de interferências, de todos os sistemas e serviços espaciais está necessariamente relacionada e diretamente dependente, ainda que não exclusivamente, das condições do canal de propagação, este trabalho oferece uma abordagem completa e sistemática pretendendo a caracterização, compreensão, modelação e mitigação dos fenómenos de propagação relevantes. É provado existir uma maior margem operacional para a operação das tecnologias acima mencionadas do que aquela que se acredita existir considerando os modelos internacionais recomendados. São previstos maiores desafios, especialmente no que concerne à despolarização causada por gelo que é mais persistente e que dura mais tempo do que os correspondentes efeitos causados por chuva. De qualquer forma, a sua mitigação é possível e para a qual a despolarização deverá ser a variável de controlo. O intervalo de tempo de 15 minutos é identificado como o melhor compromisso entre tempo acessível e ganho alcançável no contexto de um esquema de diversidade temporal.
Programa Doutoral em Engenharia Eletrotécnica
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Hussain, Intikhab. "Channel modelling and analysis of Wits mock-mine with different antenna parameters." Thesis, 2017. http://hdl.handle.net/10539/23519.
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A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2017In the mining industry, communications systems are important for ensuring personnel safety and optimizing the mining processes underground. Achieving robust and reliable through-the-air (TTA) communication systems has always been a challenge in the underground mining environment due to harsh and dynamic conditions. TTA requires radio channel characterization for efficient designing and deploying of the communications systems. The literature covers the statistical radio propagation of a room and pillar coal mine, a longwall coal mine, CANMET Gold mine, Camborne School of Mines hard rock mine tunnel, MUZ Coal mine, an iron-ore mine and a lead-zinc mine with linearly polarized antennas at different frequencies. [Abbreviated Abstract. Open document to view full version]
MT 2017
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Lambrechts, Johannes Wynand. "Modelling of transceiver propagation characteristics through an analogue SiGe BiCMOS integrated circuit." Thesis, 2013. http://hdl.handle.net/2263/32461.
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Vlok, Jacobus David. "Sparse graph codes on a multi-dimensional WCDMA platform." Diss., 2007. http://upetd.up.ac.za/thesis/available/etd-07042007-155428.
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Liu, Wentao. "Three Dimensional Hydrodynamic Modelling of Lake Erie: Kelvin Wave Propagation and Potential Effects of Climate Change on Thermal Structure and Dissolved Oxygen." Thesis, 2013. http://hdl.handle.net/10012/7659.
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This thesis investigates physical processes in Lake Erie, a large, shallow mid-latitude lake, from two perspectives: climate change impacts on the thermal structure and dissolved oxygen concentration and small-scale eddy dynamics generated by internal Kelvin wave propagation. A three-dimensional hydrodynamic and aquatic ecological coupled model ELCOM-CAEDYM, validated by the field data collected in 2008, is first used to investigate the responses of the thermal structure and dissolved oxygen concentration in Lake Erie to potential changes in air temperature and wind speed. A new method is presented to define spatially and temporally varying regions for the epilimnion, thermocline, and hypolimnion. Four metrics are selected to quantify the characteristics of the thermal structure: mean epilimnion temperature, mean hypolimnion temperature, onset and breakdown of stratification, and thermocline depth. Exploiting the power of the three dimensional model to provide a more authentic characterization of thermal structure in such large lakes, it is shown that patterns inferred from simple isotherm dynamics, as typically done with one dimensional models, are not always accurate. In the dissolved oxygen studies similar analyses are presented. Three factors related to lake hydrodynamics have strong influences on hypolimnetic hypoxia: water temperature, stratification duration, and hypolimnion thickness. The present results show the potential for complicated and interactive effects of climate forcing on important biogeochemical processes in Lake Erie as well as other large mid-latitude lakes. Taking advantage of high performance computing, the generation of eddies when a baroclinic Kelvin wave propagates past a peninsula is studied using the MITgcm. The grid resolution can be refined from 2 km to 200 m in the parallel computing environment. With the finer resolution small-scale processes which cannot be resolved in the coarse resolution applied previously are able to be explored. The eddy dynamics are studied in detail in both an idealized lake and in Lake Erie. This work presents a first attempt at simulating small-scale hydrodynamic processes in large lakes and contributes to our understanding of how energy is moved from large scales (the scale of the basins in Lake Erie) to smaller scales (the scale of the peninsula or Point Pelee).