Electrical and Electronic Engineering - Theses

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    Biological learning mechanisms in spiking neuronal networks
    Gilson, Matthieu. (University of Melbourne, 2009)
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    Design and implementation of millimeter-wave transceivers on CMOS
    Ta, Chien Minh. (University of Melbourne, 2008)
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    Novel all-optical signal processing schemes and their applications in packet switching in core networks
    Gopalakrishna Pillai, Bipin Sankar. (University of Melbourne, 2007)
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    Resource allocation for multiuser OFDM systems
    Chen, Liang. (University of Melbourne, 2006)
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    Resource allocation for multiuser OFDM systems
    Chen, Liang. (University of Melbourne, 2006)
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    A Bayesian signal processing framework for dual polarized weather radar
    Samarasekera, Senaka ( 2015)
    Current Weather radar algorithms for rain micro-physical parameter estimation do not make optimal use of the micro-physical models that govern the rain drop states. This leads to an increased uncertainty at higher radar resolutions, and the underline assumptions of these models can be inconsistent. In this thesis, I design and implement a non-linear filter that estimates the static micro-physical parameters of rain using dual polarised radar returns.I model the radar returns as electromagnetic backscattering from random anisotropic medium, and introduce a likelihood function that enables joint estimation of the rain micro-physical parameters. I then look at identifiability constraints of this model and well-condition it using the Bayesian framework. The filter takes the form of a Rao-Blackwellized sequential Monte -Carlo sampler. The filter convergence is achieved with the use of independent Metropolis-Hasting move kernels and progressive correction. Application of the filter on rain-storm data suggests it can give higher resolution estimates at increased precision.
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    Modeling fetal cardiac valve intervals and fetal-maternal interactions
    Marzbanrad, Faezeh ( 2015)
    Despite the advances in fetal healthcare, in Australia around 9-10 out of 1000 babies die in perinatal period, which is defined as starting from 22 weeks of pregnancy and extending to the first week after birth. This mortality rate is three to four times higher in some developing countries. Furthermore, false alarms produced by the current fetal surveillance technology impose unnecessary interventions, which involve additional costs and potential maternal and fetal risks. Therefore there is a critical need for more accurate fetal assessment methods for reliable identification of fetal risks. Fetal heart assessment is one of the main concerns in fetal healthcare and provides significant information about the fetal development and well-being. The aim of this research is to develop automated and accurate fetal heart assessment methods using noninvasive and less specialized techniques. In this research, automated methods were developed for estimation of the fetal cardiac valve intervals which are fundamental and clinically significant part of the fetal heart physiology. For this purpose simultaneous recordings of one dimensional Doppler Ultrasound (1-D DUS) signal and noninvasive fetal Electrocardiography (fECG) were used. New methods were developed for decomposition of the DUS signal into the component manifesting the valves' motion. Opening and closing of the valves were then identified automatically based on the features of the DUS component, their temporal order and duration from the R-peak of fECG. Result of evaluating the cardiac intervals over healthy gestational ages and in heart anomaly cases, showed evidences of their effectiveness in assessing fetal development and well-being. Fetal heart activity is influenced by not only the fetal conditions and maturation, but also the maternal psychological and physiological conditions. Therefore this research also focused on the relationship between maternal and fetal heart rates. To this aim, a model-free method based on Transfer Entropy (TE) was used to quantify directed interactions between maternal and fetal heart rates at various time delays and gestational ages. The changes of the coupling throughout gestation provided detailed information on the fetal-maternal relationship, which can provide novel clinical markers of healthy versus pathological fetal development.
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    Energy efficient wireless system design
    Kudavithana, Dinuka ( 2015)
    The demand for telecommunication networks is increasing rapidly. Wireless access is a major contributor to this trend. On the other hand, wireless is considered as a least energy efficient transmission medium mainly due to its unguided nature. The general focus of increasing wireless system energy efficiency is on reduction of the transmit power. However, this strategy may not save energy in short distance communication systems as the processing energy in hardware becomes more significant compared to the transmit radio energy. This thesis focuses on looking at the energy consumption of wireless systems by modeling the energy consumption as a function of several parameters such as receiver SNR, RF bandwidth, information rate, modulation scheme and code rate. We propose energy models for synchronization systems and other digital signal processing modules by considering the computational complexity of the algorithm and the required circuitry. Initially we focus on the synchronization aspects of wireless receivers. We study various algorithms on symbol timing recovery, carrier frequency recovery and carrier phase recovery and compare the performance in order to identify the suitable algorithms to operate at different SNR regions. We then develop energy models for those synchronization sub-systems by analyzing the computational complexity of circuitries based on a number of arithmetic, logic and memory operations. We define a new metric - energy consumption to achieve a given performance as a function of SNR - in order to compare the energy efficiency of different estimation algorithms. Next, we investigate the energy-efficiency trade-offs of a point-to-point wireless system by developing energy models of both the transmitter and receiver that include practical aspects such as error control coding, synchronization and channel equalization. In our system, a multipath Rayleigh-fading channel model and a low-density parity check (LDPC) coding scheme are chosen. We then develop a closed-form approximation for the total energy consumption as a function of receiver SNR and use it to find a minimum-energy transmission configuration. The results reveal that low SNR operation (i.e. low transmit power) is not always the most energy efficient strategy, especially in short distance communication. We present an optimal-SNR concept which can save a significant amount of energy mainly in short-range transmission systems. We then focus on cooperative relay systems. We investigate the energy efficiency trade-offs of single--relay networks by developing energy models for two relay strategies: amplify-and-forward (AF) and detect-and-forward (DF). We then optimize the location and power allocation of the relay to minimize the total energy consumption. The optimum location is found in two-dimensional space for constrained and unconstrained scenarios. We then optimize the total energy consumption over the spectral efficiency and derive expressions for the optimal spectral efficiency values. We use numerical simulations to verify our results. Finally, we focus on energy efficiency of multi-relay systems by considering a dual-relay cooperative system using DF protocol with full diversity. We propose a location-and-power-optimization approach for the relays to minimize the transmit radio energy. We then minimize the total system energy from spectral efficiency perspective for two scenarios: throughput-constrained and bandwidth-constrained configurations. Our proposed approach reduces the transmit energy consumption compared to an equal-power allocated and equidistant-located relay system. Finally, we present an optimal transmission scheme as a function of distance by considering single-hop and multi-hop schemes. The overall results imply that more relays are required as the transmission distance increases in order to maintain a higher energy efficiency.