We develop a general three-stage Moving Average Matched Filter (MAMF) receiver system for digital communications in an environment where the noise conditions are unknown a priori and change constantly and significantly with time. The MAMF is a subset of the class of matched filters which are optimal with respect to enhancing the signal energy relative to the noise power in order to improve discrimination between signals at the receiver. In a time-varying noise environment, a fixed signal cannot be designed and used for transmission which will provide optimal performance at the receiver under all noise conditions. Designing a signal for optimality in a particular noise environment will typically lead to a deteriorated performance in another noise environment relative to a signal which is chosen for the new environment. This deterioration in performance can be so severe that the signal-to-noise ratio (SNR) from the input to the output of the filter is degraded. Ideally, to achieve performance which is more nearly optimal under all noise conditions, the transmitted signal should change or adapt in response to variations in the noise environment. For practical reasons, it is desirable to concentrate all adaptivity in the receiver rather than the transmitter. Typically, a MAMF receiver consists of two stages - a filtering stage and a detection stage. We develop the general design expressions for a three-stage MAMF receiver in which the additional stage is a linear pre-filter placed before the filtering and detection stages. Obviously, if the MAMF is optimal for a given noise condition, any operation performed on the received signal plus noise prior to filtering will potentially reduce performance at that given noise condition by some amount. We accept this performance loss in favor of a pre-filtering operation which can effectively manipulate the transmitted signal upon arrival at the receiver and provide more robust performance in the time-varying noise environment. Specifically, we compare a pre-filter consisting of a unity gain with a prefilter that linearly combines k M x 1 partitions of the transmitted signal vector (i.e. transmitted signal vector of length N = k x M). Proper design of the transmitted signals can ensure that the partitions are linearly independent. In this case, we can view the transmitted signal as representing a k-dimensional subspace of the original M-dimensional signal space. By linearly combining these partitions at the receiver we can achieve any vector within this subspace. We show that we can select these partitions such that the resulting signal vector represents an optimum signal subspace for k noise environments. This is contrasted with the fixed 1-dimensional subspace of the original N-dimensional signal subspace when the pre-filter is a constant gain. The two MAMF receivers are compared by measuring the signal-to-noise ratio improvement (SNRI) of the filters. The SNRI is defined as the output signal-to-noise ratio (OSNR) measured at the output of the filtering stage over the input signal-to-noise ratio (ISNR) measured at the input to the pre-filtering stage. We demonstrate through simulation that the signal subspace version can be more robust with respect to deviation from the absolute maximum SNRI achievable by either system. Using maximum likelihood techniques, we derive an optimal detector for an arbitrary bank of L linear pre-filter and MAMF sections. This is shown to outperform a detection scheme that has been derived for use solely in an optimal binary communication scenario. / Master of Science

M.S.

This document explains the design of the microcontroller based Intelligent Communication Controller (ICC) for the Motorola VMEbus. The card transmits and receives serial data on T1 medium at a rate of 1.544 Mbits/sec. This ICC card is a part of the communication system used in a current differential protection scheme for power distribution systems. / Master of Science

In an increasingly digital world, the need for high speed and high fidelity analog-to-digital (A/D) converters is paramount. Performance improvements in electronic A/Ds have not kept pace with demand, hence the need to consider alternative technologies. One such technology is photonics, as it takes advantage of optical sampling, high speed optical switches and low cross-talk interconnects. Optical sampling derives its advantage from the application of ultra low timing jitter (<100fs) mode locked lasers utilised to provide high speed clock pulses. In this thesis the feasibility and simulated performance of three different types of photonic oversampled A/D converters was investigated. The first, and simplest design is that of oversampled pulse-code-modulation (PCM), where a 2-level photonic comparator is used to sample the analog input at a frequency much greater than the Nyquist frequency. Subsequent low pass filtering produces a digital representation of the input. The other two architectures that were investigated are the first-order sigma-delta and error diffusion, which add one level of error correction to the PCM technique. These two architectures require the functional elements of a subtractor, comparator and delay. The photonic comparator and subtractor functionality was provided by Self-Electro-Optic Effect devices (SEED) based upon multiple quantum well (MQW) p-i-n devices. To facilitate calculation of the performance of the different architectures and aid in device design, a simulation of SEED operation based upon experimental data was developed. The simulation’s accuracy was demonstrated by agreement with the results from experimental S-SEED switching and optical subtraction. To emphasize the utility of the model, the simulation was subsequently used to demonstrate tristability of an S-SEED and critical slowing down in a bistable S-SEED. These effects were experimentally verified. To provide enhanced comparator contrast ratio and subtractor dynamic range, resonantly enhanced microcavity multiple quantum well (MQW) p-i-n devices were designed and grown by MOCVD. The operation of the subtractor and comparator was experimentally demonstrated and utilising temperature tuning, optimised performance was achieved with devices from the same wafer. Furthermore, the inclusion of gain was shown to improve the subtractor performance to that demanded by the sigma-delta. The constraints on each architecture imposed by the unipolar nature of the light intensity were derived and the sigma delta architecture was shown to be superior to the error diffusion for a photonic implementation. Using the numerical simulation based upon experimentally derived data, the entire sigma delta architecture was simulated to calculate the expected performance. The signal-to-quantisation-noise ratio (SQNR) was calculated as a function input amplitude and a peak SQNR of 54dB was obtained for an oversampling ratio of 100. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1283979 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2007

<p>In the past half century, numerous improvements have been achieved to make fiber-optic communication systems overweigh other traditional transmission systems such as electrical coaxial systems in many applications. However, the physical features including fiber losses, chromatic dispersion, polarization mode dispersion, laser phase noise, and nonlinear effect still post a huge obstruction in fiber-optic communication system. In the past two decades, along with the evolution of digital signal processing system, digital approach to compensate these effects become a more simple and inexpensive solution.</p> <p>In this thesis, we discuss digital equalization techniques to mitigate the fiber-optic transmission impairments. We explain the methodology in our implementation of this simulation tool. Several major parts of such digital compensation scheme, such as laser phase noise estimator, fixed chromatic dispersion compensator, and adaptive equalizer, are discussed. Two different types of adaptive equalizer algorithm are also compared and discussed. Our results show that the digital compensation scheme using least mean square (LMS) algorithm can perfectly compensate all linear distortion effects, and laser phase noise compensator is optional in this scheme. Our result also shows that the digital compensation scheme using constant modulus algorithm (CMA) has about 3~4db power penalty compare to LMS algorithm. CMA algorithm has its advantage that it is capable of blind detection and self-recovery, but the laser phase noise compensator is not optional in this scheme. A digital compensation scheme which combines CMA and LMS algorithm would be a perfect receiver scheme for future work.</p> / Master of Applied Science (MASc)

This thesis aims to examine the News Usage practices of young Pakistani university students in the networked news media environment. The development of internet and its subsequent technologies have played a significant role in the transition from Mass Media towards Networked Media and this transition has directly influenced news usage practices. In Pakistan, almost 99% of the sample population of this research has mobile phones. The introduction of 3G and 4G mobile technologies in 2014 and recent ICT policy initiatives suggests that there are plans to subsidize smart phones in the country, which will further boost the digital environment. The news users in Pakistan now have more choices to follow news from multiple platforms and via multiple devices. There is a networked media ecosystem around users and it is continuously evolving and consequently transforming the news media institutions and the users’ news usage experience. The practice of using news is changing and transforming the user’s news usage experience but the available theoretical framework did not adequately address this, until the emergence of the ‘Theory of Mediatization’. The four main contributors to mediatization theory have been Lundby (2014) Hepp (2009), Hjarvard, (2008), Couldry (2008) and Krotz (2007) .Building on their contribution, and including the valuable addition by Winfried Schulz (2004), I am applying the framework of mediatization to a cohort of university students in Pakistan to investigate their changing news usage practices in the networked media environment. I have adopted a mixed method approach, following the double sequential loops method.

The Internet of Things is a recent computing paradigm, de- fined by networks of highly connected things – sensors, actuators and smart objects – communicating across networks of homes, buildings, vehicles, and even people. The Internet of Things brings with it a host of new problems, from managing security on constrained devices to processing never before seen amounts of data. While cloud computing might be able to keep up with current data processing and computational demands, it is unclear whether it can be extended to the requirements brought forth by Internet of Things. Fog computing provides an architectural solution to address some of these problems by providing a layer of intermediary nodes within what is called an edge network, separating the local object networks and the Cloud. These edge nodes provide interoperability, real-time interaction, routing, and, if necessary, computational delegation to the Cloud. This paper attempts to evaluate Go, a distributed systems language developed by Google, in the context of requirements set forth by Fog computing. Similar methodologies of previous literature are simulated and benchmarked against in order to assess the viability of Go in the edge nodes of Fog computing architecture.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This dissertation presents measures of efficiency and locality for Internet addressing schemes. Historically speaking, many issues, faced by the Internet, have been solved just in time, to make the Internet just work~\cite{justWork}. Consensus, however, has been reached that today's Internet routing and addressing system is facing serious scaling problems: multi-homing which causes finer granularity of routing policies and finer control to realize various traffic engineering requirements, an increased demand for provider-independent prefix allocations which injects unaggregatable prefixes into the Default Free Zone (DFZ) routing table, and ever-increasing Internet user population and mobile edge devices. As a result, the DFZ routing table is again growing at an exponential rate. Hierarchical, topology-based addressing has long been considered crucial to routing and forwarding scalability. Recently, however, a number of research efforts are considering alternatives to this traditional approach. With the goal of informing such research, we investigated the efficiency of address assignment in the existing (IPv4) Internet. In particular, we ask the question: ``how can we measure the locality of an address scheme given an input AS-level graph?'' To do so, we first define a notion of efficiency or locality based on the average number of bit-hops required to advertize all prefixes in the Internet. In order to quantify how far from ``optimal" the current Internet is, we assign prefixes to ASes ``from scratch" in a manner that preserves observed semantics, using three increasingly strict definitions of equivalence. Next we propose another metric that in some sense quantifies the ``efficiency" of the labeling and is independent of forwarding/routing mechanisms. We validate the effectiveness of the metric by applying it to a series of address schemes with increasing randomness given an input AS-level graph. After that we apply the metric to the current Internet address scheme across years and compare the results with those of compact routing schemes.

Homes are involved in a significant fraction of Internet traffic. However, meaningful and comprehensive information on the structure and use of home networks is still hard to obtain. The two main challenges in collecting such information are the lack of measurement infrastructure in the home network environment and individuals’ concerns about information privacy. To tackle these challenges, the dissertation introduces Home Network Flow Logger (HNFL) to bring lightweight privacy-preserving passive measurement to home networks. The core of HNFL is a Linux kernel module that runs on resource-constrained commodity home routers to collect network traffic data from raw packets. Unlike prior passive measurement tools, HNFL is shown to work without harming either data accuracy or router performance. This dissertation also includes a months-long field study to collect passive measurement data from home network gateways where network traffic is not mixed by NAT (Network Address Translation) in a non-intrusive way. The comprehensive data collected from over fifty households are analyzed to learn the characteristics of home networks such as number and distribution of connected devices, traffic distribution among internal devices, network availability, downlink/uplink bandwidth, data usage patterns, and application traffic distribution.