The future wireless communications systems should be able to offer wide variety of applications, which have vastly different quality of service (QoS) requirements. The time-variable QoS may require the support of variable bit rates on the wireless links to the individual users. Multi-rate DS/CDMA is a promising basis on which to support the variable bit rates on the individual wireless links. Currently, the study on channel estimation and multiuser detection for multi-rate DS/CDMA, which makes full use of the nature of multi-rate signals, is still at its early stage. The thesis deals with the application of subspace-based techniques to blind channel estimation and multiuser detection for multi-rate DS/CDMA, including single-carrier and multicarrier scenarios. For the single-carrier case, space-time blind linear multiuser detection is investigated for synchronous dual-rate systems over the AWGN channel. The performance is evaluated analytically. The multi-rate generalization and the asynchronous extension are discussed. Two-stage space-time dual-rate blind detectors are also presented. Furthermore, blind adaptive channel estimation and detection schemes for asynchronous dual-rate systems over frequency-selective multipath channels are developed. In the context of multicarrier DS/CDMA, based on a finite-length truncation approximation on the band-limited chip waveform, blind timing acquisition and channel estimation scheme is proposed for multi-rate systems. The channel estimation error due to the finite-length chip waveform truncation is analyzed by exploiting a first-order perturbation approximation.

The use of multiple antennas at the transmitter as well as at the receiver can greatly improve the capacity of a wireless link when operating in a rich scattering environment. In such an arrangement all transmitting antennas radiate in the same frequency band so the overall spectral efciency becomes very high. Such a multiple antenna scheme, popularly known as Multiple Input Multiple Output (MIMO) has potential application in wireless local area networks (WLAN) and cellular micro-cells. One reason is that the WLANs and other short range wireless systems often operate in an indoor environment, which offers rich scattering. The other reason is the demand for higher data rates in cellular and WLAN systems to cater for multimedia services. Recently researchers have proposed di erent architectures for materializing the potential of the MIMO scheme. VBLAST (Vertical-Bell Labs Space Time) is a popular architecture that will play an important role in future standardizations. Furthermore, different decoding methods have been proposed for VBLAST. The SVD (Singular Value Decomposition) based system is envisioned as a highly effective MIMO technique in a TDD (Time Division Duplex) framework. Such a system operates by adapting the constellation size across different subchannels. In this work we study the VBLAST and SVD architectures and compare the perfor- mance and computing power requirement of these architectures. Also in this study a new effcient decoding method for the VBLAST architecture is proposed. The original VBLAST decoding method relies on the repetitive computation of the pseudoinverse of the channel matrix. Alternatively, there are methods based on the QR decomposi- tion, the matrix square root etc. Our new decoding method is based on a relatively less known matrix decomposition, the Polar Decomposition. The new method requires less computation and has several other advantages like the possibility of incremental updates, channel rank tracking, etc. We consider three different types of channels: IID random, slow fading and measured channels. The entire work is simulated in the MATLAB environment. The main contribution of this work includes: a comparative study and a head to head comparison of the VBLAST and SVD-based MIMO systems. The application of adaptive modulation in the SVD-based system and the introduction of a new effcient decoding method for the VBLAST system are also included. Simulation results are reported with comments and conclusions.

A prototype optical fibre temperature sensor employing the fluorescence intensity ratio (FIR) technique has been utilised to measure the surface temperature of window glass during a fire. A comparison has been made between the intrinsic optical fibre sensor and thermocouples (the conventional temperature measuring device used in fire research). Neodymium doped fibre was used as the temperature sensing element. Due to the destructive nature of the fire tests on the neodymium doped fibre, a new section of bare doped fibre was spliced for each test. Before each fire test, the (non-glass) coating on the sensing fibre was removed. The detector was calibrated against K-type thermocouples in a stabilised temperature environment. This same bare optical fibre was attached to the window glass pane with an adhesive that was appropriate for the fire test conditions. A preliminary investigation was undertaken to compare the effect of a radiant heat environment on the sensing fibre and thermocouples. The bare fibre showed a significantly lower temperature (about 25C lower) than the average thermocouple temperature. This is consistent with the expectation that the fibre is less subject to the effects of radiation than the thermocouples. Thus it was demonstrated that the thermocouple did not accurately represent the time-dependent temperature behaviour of window glass, and specifically, the temperature within the core of the fibre. Fire tests were conducted in a chamber, which was designed and built to simulate a combustion fire starting in a small room with a window. Both sensor types were used to measure the temperature of the inside surface of the window glass during a fire. The observed temperature difference was smaller than that observed during the preliminary tests where the thermocouples were subject to a radiant heat environment. Reasons for this are discussed within the thesis. The measurement of window glass temperature during a fire has been demonstrated using an optical fibre sensor based on the fluorescence intensity ratio technique. This clearly establishes the existence of a discrepancy between window glass temperature and the temperature measured by thermocouples when they are subjected to a radiant heat environment.

CDMA cellular mobile systems find widespread acceptance particularly in regional centres where there are large geographical areas to cover. However, temporal changes of user density due to formation of congregated population centres (called hot spots) can seriously undermine the system design goals in terms of quality of service (QoS) and system capacity. This investigation deals with the problem of hot spots in a bid to improve system capacity at acceptable quality of service levels. Among the techniques considered is the adaptive ectorisation and its implementation with finite antenna beam switching. The future wireless communications systems are expected to offer a wide variety of services, which have vastly differing QoS requirements. To handle this, the third generation cellular mobile communication systems are designed to carry packet mode traffic. This investigation also deals with the impact of third generation cellular system traffic on system capacity. It examines the system activity in the presence of mixed mode traffic and the capacity and QoS trade-offs possible in Wideband CDMA (WCDMA) cellular systems. Application of adaptive sectorisation to improve capacity in such systems when confronted with hot spots is also investigated. It is found that in all situations the adaptive sectorisation brings an overall improvement to system capacity and this is particularly significant when the user concentration in hot spots is substantially bigger than that of the rest of the cell.

Electrical power systems utilise several voltage levels using power transformers to transfer voltages and connect parts of the power system with different voltage levels. One of these voltage transformations is being performed in the key component of the electrical power system: the distribution power transformer. It connects the Medium Voltage (MV) 11 kV - 33 kV networks and the Low Voltage (LV) 415 V networks, enabling connection of a large number of LV customers as well as (though to a much smaller extent) access of embedded generators to the electrical distribution network. Although the Australian distribution power transformers are considered to be very efficient devices (Minimum Energy Performance Standards - MEPS Fact Sheet, 2004), still roughly 3.2% of distribution transformers’ throughput electricity is lost due to their inefficiencies. The magnitude of these significant losses attributed to distribution transformers is a consequence of: • inefficiencies due to the design, materials and technologies used in distribution transformers; • inadequate type and rating of transformers selected for a particular application. The commitments of various Australian stakeholders (the public, the government agencies, distribution utilities, regulators, electricity industry trade associations, etc.) to limit emissions of greenhouse gases and to actively contribute to the global efforts to protect our environment are closely related to the energy market reform. The recent partial deregulation of the Australian electrical supply industry has introduced competition in retail and generation sectors and also significantly changed the operational environment for the electrical distribution companies. The era of increased competition for capital has commenced. The state based regulators have reduced incentives for over-investments, however, they still request enhancement of quality of supply and improvements of customer services. These, sometimes conflicting requirements have forced the electrical distribution utilities to move focus from improving economic efficiency of electricity supply and abandon long established practices for evaluation of distribution system performances applying multi-level economic analyses and systematic assessment of performances of key system components. It seems that “low initial cost” method (without proper assessment of total life cycle costs) is becoming much more attractive solution for selection of distribution equipment. The expected steady increases in energy demands and the need to undertake effective measures to protect the environment could be partially solved by improving energy efficiency of electrical equipment. The recent focus of the Australian government on the environmental costs associated with use of electrical energy has brought the efficiency of electrical equipment (including distribution transformers) under the spotlight. Highly efficient, yet cost-effective distribution power transformers, which are fully optimised for the expected service conditions (the likely load and the operating environment), are obviously the right solution for reduction of electrical losses. Introduction and use of such equipment would present significant challenge for electrical distribution utilities and private users of distribution transformers as this would have a considerable impact on their competitive position under the new industry structure. This research explores potential design improvements and increase in efficiencies for distribution transformers trough analysis of existing design and manufacturing technologies, relevant international regulatory developments, technological advancements and general trends in the context of the Australian market. It analyses the recently introduced mandatory Minimum Energy Performance Standards (MEPS) for distribution transformer and suggests courses of action for industry, regulatory bodies and the end users, which could help to ensure that those actions are part of the global solution for complex environmental issues. In addition, this research investigates a new two-stage approach for evaluation, assessment and utilisation of distribution power transformers and as such, to some extent, is directed towards a rational risk management and technical methodology to allow Australian electrical utilities and other interested parties to deal cost-effectively with present conventional technologies for distribution transformer used by major Australian manufacturers. The new assessment method for distribution transformers is based on: • development of cost efficiency schedules for selected designs and representative kVA ratings; • thorough financial analysis of distribution transformer losses. This refined methodology highlights importance of design and costing stages in the assessment process. Further, it recommends moving from simple capitalisation of transformer losses by extending evaluation of the total operating costs through introduction of new evaluation factors based on life cycle cost concepts and on expected service and loading conditions. This research is a contribution towards development of new procedures and methodologies, which will provide guidelines and recommendations for improvement of distribution transformer performances and increase compatibility of needs and capabilities of various stakeholders: end users, standards’ setting bodies, regulators, research organisations, equipment manufacturers, designers and consultants.

The zero-forcing algorithm (min-norm algorithm) is one of the proposed methods for downlink beamforming. This algorithm steers the nulls towards interferers and the main beam towards the desired user provided the angles of arrival of these signals are known to the basestation. However, downlink adaptive arrays use additional power when they are required to include null steering in their beam patterns. This excessive transmitted power reduces the effective antenna gain, increases interference in other directions and has implications on the dimensioning of the power amplifiers feeding the antenna elements. In addition, the power distribution among the antenna array elements is no longer equal. The design ratings for the power amplifiers (PAs) on each element can differ by up to 2.9 dB. A distributed amplifier design could solve this problem. This thesis investigates the trade-off of null depth with transmitted power and utility by modifying the zero-forcing algorithm. The performance or utility of the antenna is defined here as the probability that it can accommodate a given angular scenario between the desired user and interfering sources without transmitting excessive power. A -10 dB null increases antenna utility by 6% when steering a single null and 17% when steering 2 nulls if the excessive transmit power is held below 3 dB for a 4-element antenna array. In this work, a modified version of the min-norm algorithm was used to design the antenna weights from angle of arrival information.

Wireless communications has been so far largely based on centralized control, which in effect has limited its deployment, coverage and application scenarios. The paradigm of peer-to-peer wireless communications is fundamentally to remove this bottleneck and to further expand wireless communications into new applications. The technical and design challenges in implementing these networks are however plenty and exist in all the layers of the OSI protocol stack. In this thesis, we only consider the physical layer model of these networks. We identify multiple antenna systems as a vital component of physical layer solutions. We first investigate the case of multiple antenna space-time coding techniques to achieve spatial diversity. We observe that when correlation between the antennas in a local antenna array becomes high due to space constraints in a terminal, current performance achieving strategies do not actually deliver good results. Moreover, most mobile terminals are currently equipped with only one antenna. In view of this limitation, we study the recently proposed user cooperation techniques for exploiting spatial diversity with user power constraints for a simple three terminal network. We find that these systems are beneficial even with relatively simple protocols such as selection relaying. Finally, with simulation results, we demonstrate that the system performance can be improved significantly via near-to optimal selection relaying.

Substation Automation (SA) is a rapidly increasing area of interest in Electrical Engineering these days embracing numerous benefits to utilities. It is clearly the most dynamic and exciting new development in the substation industry with the ultimate goal of efficiently managing operations, maintenance and capital assets with minimal human intervention [1-4]. Intelligent Electronic Devices (IEDs), which are Instrumentation & Control (I&C) devices built using microprocessors, are the most important elements of a SA system. An IED is primarily used as a monitoring, control, protection or data processing device with at least a single serial communication interface. Substation IED networking requires the ability to remotely control, manipulate and monitor newly connected devices through the use of an effective communication system used to link various IEDs in a substation. The existence of a wide variety of vendor specific and hardware-oriented solutions as well as different communication techniques used for the communication between devices had previously stopped utilities from achieving a fully integrated and interoperable SA system. The idea of standardising the language of communication between IEDs has evolved as the key for the advancement of connectivity and interoperability within a SA system. As a consequence, Institute of Electrical and Electronics Engineers (IEEE) and International Electrotechnical Commission (IEC) have been developing SA standards based on Object-Oriented (OO) technologies. IEC 61850, the main topic of discussion in this thesis, is such a standard developed by the IEC Technical Committee (TC) 57. It describes how devices are to communicate in a substation as well as the related system requirements. It features support for all substation functions and their engineering with the use of OO data and service models [5]. However, it has only been abstractly modelled meaning that it focuses on describing what the OO models are indented to provide rather than how they are built. Consequently, the IEC 61850 standard can only be operational when mapped to a specific concrete application layer protocol such as the Manufacturing Message Specification (MMS) or ISO/IEC 8802-3, which are the two communication services put forward by the IEC 61850 standard. The primary objective of this research is the OO implementation of the IEC 61850 standard as a concrete application layer protocol running on a middleware platform designed and implemented in a communication processor environment. In this research, the IEC 61850 implementation is founded on the C/C++ programming language development of the standard’s Abstract Communication Service Interface (ACSI) Object and Service Models (OSMs) as concrete programs based on their published definitions, hence transforming the IEC 61850 standard into a solid protocol. An alternative to the present implementation practice, the mapping process as proposed in the IEC 61850 standard, is recommended where virtual representations of real devices can be modelled and implemented at the application layer of a communication processor making use of the OO implemented OSMs of the standard itself rather than using the equivalent models of another application layer protocol. Middleware is a software layer that resides between the operating system and the applications allowing multiple processes running on different machines to interact over a network. Middleware design is based on architectural issues concerned with the organisation, overall structure and communication patterns dictated by applications as well as the middleware itself [6-7]. This thesis describes the design and implementation of a new middleware architecture aimed at providing diverse communication methods to IEC 61850 related applications. The designed middleware is of the Message-Oriented Middleware (MOM) category and considers the fact that communicating entities may take on different roles such as client/server or peer-to-peer, therefore allowing for different interaction modes such as synchronous invocations and asynchronous message passing. Several simulation studies are also presented in this thesis to demonstrate how IEC 61850 applications can be built at the application layer of a communication processor as well as to test and evaluate the performance of the middleware architecture implemented within the same communication processor environment. Time synchronisation, which involves synchronisation of the date and time of all devices in a network, is another key topic discussed in this thesis. Time synchronisation is crucial in time-sensitive substation applications and its importance has been clearly acknowledged by the IEC 61850 standard as a requirement. The implementation and integration of the Simple Network Time Protocol (SNTP) and its applications into the overall communication processor architecture is another feature proposed in this thesis in order to facilitate the time synchronisation of applications designed in this research. Ultimately, the development of a gateway capability that permits for the testing and evaluation of the designed components over a real network is described. The designed and implemented "Hardware in the Loop" (HITL) capability mainly provides the necessary interface between the real Ethernet network and the simulation environment enabling two or more simulations running on separate computers to be linked together.

This thesis presents investigations aimed at obtaining a system model for the stabilisation of an Active Magnetic Bearing (AMB) System. Furthermore, the study reported here set out to design both conventional and advanced controllers based on the system model. This research report demonstrates that the literature on AMBs shows that AMBs are making their mark in the industry; they are increasingly being used in applications including jet engines, compressors, pumps and flywheel systems. In this study, it has also been observed that the basic design of AMBs is an arrangement of electromagnets placed equidistant in a ring round a rotor. The point of departure for this study is that AMBs are highly nonlinear and inherently unstable. Hence, the need for an automatic control to keep the system stabilized. The first step of the research was to determine the transfer function of the MBC 500 magnetic bearing system both analytically and experimentally. An analytical model has been derived based on principle of physics. As the AMB system under analysis is inherently unstable, it was necessary to identify the model using a closed-loop system identification. Frequency response data has been collected using the two-step closed loop system identification. As there are resonant modes in the MBC 500 magnetic bearing system, the system identification approach has identified the corresponding resonant frequencies. Subsequent to obtaining the model, a conventional controller was designed to stabilise the AMB system. Two notch filters were designed to deal with the magnitude and phase fluctuations around the two dominant resonant frequencies. The designed conventional controller and notch filters have been implemented using MATLAB, SIMULINK and dSPACE DS1102 digital signal processing (DSP) card. Both the step response and robustness tests have demonstrated the effectiveness of the conventional controller and notch filters designed. A significant conclusion has been drawn when designing the conventional controller. It was found that a controller that had a large positive phase angle had a negative effect on the system. This finding was very significant because it restricted the controller specifications and yielded an optimum lead angle for the conventional controller. The advanced PD-like Fuzzy Logic Controller (FLC) has also been designed for AMB system stabilisation. The designed FLC can deal with the magnitude and phase fluctuations around resonant frequencies without using notch filters. The performance of the designed FLC has been evaluated via simulation. Simulation results show that the FLC designed leads to a reliable system performance. Comparison studies of the FLC performances with two different sets of rules, two different inference methods, different membership functions, different t-norm and s-norm operations, and different defuzzification were investigated. To further improve system performance, scaling factors were tuned. Again, simulations showed highly promising results. Comparative studies between the conventional and advanced fuzzy control methods were also carried out. Advantages and disadvantages of both approaches have been summarised. The thesis has also suggested further research work in the control of AMBs.

As power industry enters the new century, powerful driving forces, uncertainties and new functions are compelling electric utilities to make dramatic changes in their information communication infrastructure. Expanding network services such as real time measurement and monitoring are also driving the need for more bandwidth in the communication network and reliable communication infrastructure. These needs will grow further as new remote real-time protection and control applications become more feasible and pervasive. Information embedded power system via wide area network (IEPS-W) is the solution to accommodate the growing demand of wide area monitoring, protection and control. IEPS-W is an extension of traditional power systems with added monitoring, control and telecommunications facilities. Various power system communication protocols are being used within IEPS-W to transmit critical data in real time along with decades old Supervisory Control and Data Acquisition System (SCADA). Most of the protocol in used are not originally developed to use in wide area computer network (WACN) environment. However, protocol developers upgrade their protocols and use it in WACN. This requires experimental investigation of various power system communication protocols before employing it on the power grid. An experimental platform was set up at Victorian Network Switching Centre owned by SP AusNet PTY LTD (an Australian Transmission and Distribution company based in Victoria) in order to experimentally analyse the performance characteristic of Distributed Network Protocol (DNP3) over wide area network (WAN). In this experiment, real time data were sent from Intelligent Electronic Devices to utility control center using WAN. Experimental work reveal that measurement delays associated with DNP3 over WAN is high, as this type of network is much more complex due to the added complexities of routing and switching. This requires further development of DNP3 protocol to be reliably used in IEPS-W. Hence, DNP3 was further developed using Optimized Network Engineering Tools (OPNET). OPNET is the industry‘s leading simulator specialized for network research and development. Finally, a new protocol has been developed based on DNP3 protocol to reliably and securely transmit power system data for IEPS-W.