Electrical and Electronic Engineering - Theses
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ItemBiological learning mechanisms in spiking neuronal networks(University of Melbourne, 2009)
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ItemDesign and implementation of millimeter-wave transceivers on CMOS(University of Melbourne, 2008)
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ItemMillimeter wave CMOS VCO and PLL design and phase noise mitigation techniques(University of Melbourne, 2008)
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ItemNovel all-optical signal processing schemes and their applications in packet switching in core networks(University of Melbourne, 2007)
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ItemResource allocation for multiuser OFDM systems(University of Melbourne, 2006)
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ItemResource allocation for multiuser OFDM systems(University of Melbourne, 2006)
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ItemTransmission technologies for radio-over-fibre( 2008)The phenomenal growth in global telecommunication networks is continually expanding with the advent of new services and applications. Keys to future generations of mobile communication are multimedia communications capability, wireless access to broadband fixed and mobile networks, and seamless roaming among different systems. Increasing demand for currently used bands at lower frequency spectrum has reduced the ability to allocate the large spectrum bandwidths required for broadband radio applications. Current trend in cellular networks, both in mobile and fixed, are to reduce cell size to accommodate more users and to operate in the microwave and millimetre wave frequency bands to avoid spectral congestion. Moreover, larger radio frequency (RF) propagation losses at mm-wave bands reduce the cell size covered by a single base station (BS) and allow an increased frequency reuse factor to improve spectrum utilization efficiency. These factors demand cellular networks to have a larger number of simple, compact and low-cost BSs connecting to a central office to cover a service area. Furthermore, analog optical link nonlinearity, line-of sight constraint, spectral inefficiency, inefficient remote node (RN) architectures and inefficiency in RF power conversion have become major obstacles in achieving high performance fibre-radio systems for the provision of wireless services. This thesis explores and investigates the design of systems technologies for theimplementation of high-performance, low-cost analog optical links for future fibre-radio systems. For the first time, digitized RF over fibre based on bandpass sampling is proposed. An analytical model is formulated to assess the link’s key design trade-offs and analytical results are experimentally verified. Digitized RF transport over fibre is extended for multiple wireless signal transmission. This thesis also investigates the design and development of new system technologies for the implementation of dense wavelength division multiplexed (DWDM) mm-wave fibre-radio systems. An elegant technique provisioning wavelength-reuse and simultaneous performance enhancement of down and uplink mm-wave channels is proposed and demonstrated. This remote node device is realised by using arrayed waveguide grating (AWG) filter and semiconductor optical amplifier (SOA). A RN optical interface to combat line-of-sight constraint is proposed. The proposed interface is capable of being integrated within existing WDM systems incorporating 100 GHz channel spacing. Furthermore, it has the capacity to simultaneously add 100 GHz channel blocks containing wavelength-interleaved (WI) optical tandem single sideband (OTSSB) mm-wave signals and drop and de-multiplex 100 GHz channel blocks containing WI-OTSSB mm-wave signals. Inclusion of OTSSB in the RN interface greatly simplifies the BS hardware architecture. Access part of the optical network demands greener solutions as it consumes more power than any other segments of the network. This thesis in addition, investigates RF power efficient, low-cost solutions for the delivery of integrated services.
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ItemSignal processing techniques for optical fiber networks( 2007)At present, optical fiber transmissions are dominated by intensity modulation and direct detection, which fundamentally limit the signal processing capabilities in optical fiber networks. On the other hand, manipulation of optical phase enables advanced signal processing techniques for various applications. This thesis includes three parts and makes contributions in three research areas in optical fiber networks, by applying optical and electronic signal processing techniques. In the first part of the thesis, optical signal processing is employed to realize a novel all-optical label swapping (AOLS) technique using synchronous phase modulation. This technique is shown to address the forwarding speed bottleneck in optical packet switched networks (OPSN). By exploiting the unique symmetry of phase-shift keying (PSK), for the first time, label erasure and insertion are performed in a single step by a phase modulator without wavelength conversion. We also propose and demonstrate a polarization insensitive phase modulator to address the polarization sensitivity of AOLS. Furthermore, we emulate multi-hop all-optical label swapping in a re-circulating loop to investigate the power penalties from the accumulated phase errors and the timing mismatch. Based on the experimental and analytical results, we show that this technique can save wavelength converters significantly if compared with conventional AOLS techniques requiring dedicate wavelength converters.
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ItemPerformance of estimation and detection algorithms in wireless networks( 2007)This thesis focuses on techniques for analyzing the performance of estimation and detection algorithms under conditions which could be encountered in wireless networks, with emphasis on wireless sensor networks. These include phenomena such as measurement losses, fading channels, measurement delays and power constraints. We first look at the hidden Markov model (HMM) filter with random measurement losses. The loss process is governed by another Markov chain. In the two-state case we derive analytical expressions to compute the probability of error. In the multi-state case we derive approximations that are valid at high signal-to-noise ratio (SNR). Relationships between the error probability and parameters of the loss process are investigated. We then consider the problem of detecting two-state Markov chains in noise, under the Neyman-Pearson formulation. Our measure of performance here is the error exponent, and we give methods for computing this, firstly when channels are time-invariant, and then for time-varying fading channels. We also characterize the behaviour of the error exponent at high SNR. We will look at the fixed lag Kalman smoother with random measurement losses. We investigate both the notion of estimator stability via expectation of the error covariance, and a probabilistic constraint on the error covariance. A comparison with the Kalman filter where lost measurements are retransmitted is made. Finally we consider the distributed estimation of scalar linear systems using multiple sensors under the analog forwarding scheme. We study the asymptotic behaviour of the steady state error covariance as the number of sensors increases. We formulate optimization problems to minimize the sum power subject to error covariance constraints, and to minimize the error covariance subject to sum power constraints. We compare between the performance of multi-access and orthogonal access schemes, and for fading channels the effects of various levels of channel state information (CSI).
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ItemAnalysis and optimization of MAC protocols for wireless networks( 2007-06)Medium access control (MAC) plays a vital role in satisfying the varied quality of service (QoS) requirements in wireless networks. Many MAC solutions have been proposed for these networks, and performance evaluation, optimization and enhancement of these MAC protocols is needed. In this thesis, we focus on the analysis and optimization of MAC protocols for some recently emerged wireless technologies targeted at low-rate and multimedia applications.