The design and implementation of a wideband digital radio receiver

Historically radio has been implemented using largely analogue circuitry. Improvements in mixed signal and digital signal processing technology are rapidly leading towards a largely digital approach, with down-conversion and filtering moving to the digital signal processing domain. Advantages of this technology include increased performance and functionality, as well as reduced cost. Wideband receivers place the heaviest demands on both mixed signal and digital signal processing technology, requiring high spurious free dynamic range (SFDR) and signal processing bandwidths. This dissertation investigates the extent to which current digital technology is able to meet these demands and compete with the proven architectures of analogue receivers. A scalable generalised digital radio receiver capable of operating in the HF and VHF bands was designed, implemented and tested, yielding instantaneous bandwidths in excess of 10 MHz with a spurious-free dynamic range exceeding 80 decibels below carrier (dBc). The results achieved reflect favourably on the digital receiver architecture. While the necessity for minimal analogue circuitry will possibly always exist, digital radio architectures are currently able to compete with analogue counterparts. The digital receiver is simple to manufacture, based on the use of largely commercial off-the-shelf (COTS) components, and exhibits extreme flexibility and high performance when compared with comparably priced analogue receivers

Macrocriminology and Freedom

How can power over others be transformed to 'power with'? It is possible to transform many institutions to build societies with less predation and more freedom. These stretch from families and institutions of gender to the United Nations. Some societies, times and places have crime rates a hundred times higher than others. Some police forces kill at a hundred times the rate of others. Some criminal corporations kill thousands more than others. Micro variables fail to explain these patterns. Prevention principles for that challenge are macrocriminological. Freedom is conceived in a republican way as non-domination. Tempering domination prevents crime; crime prevention reduces domination. Many believe a high crime rate is a price of freedom. Not Braithwaite. His principles of crime control are to build freedom, temper power, lift people from poverty and reduce all forms of domination. Freedom requires a more just normative order. It requires cascading of peace by social movements for non-violence and non-domination. Periods of war, domination and anomie cascade with long lags to elevated crime, violence, inter-generational self-violence and ecocide. Cybercrime today poses risks of anomic nuclear wars. Braithwaite’s proposals refine some of criminology’s central theories and sharpen their relevance to all varieties of freedom. They can be reduced to one sentence. Strengthen freedom to prevent crime, prevent crime to strengthen freedom

Macrocriminology and Freedom

How can power over others be transformed to 'power with'? It is possible to transform many institutions to build societies with less predation and more freedom. These stretch from families and institutions of gender to the United Nations. Some societies, times and places have crime rates a hundred times higher than others. Some police forces kill at a hundred times the rate of others. Some criminal corporations kill thousands more than others. Micro variables fail to explain these patterns. Prevention principles for that challenge are macrocriminological. Freedom is conceived in a republican way as non-domination. Tempering domination prevents crime; crime prevention reduces domination. Many believe a high crime rate is a price of freedom. Not Braithwaite. His principles of crime control are to build freedom, temper power, lift people from poverty and reduce all forms of domination. Freedom requires a more just normative order. It requires cascading of peace by social movements for non-violence and non-domination. Periods of war, domination and anomie cascade with long lags to elevated crime, violence, inter-generational self-violence and ecocide. Cybercrime today poses risks of anomic nuclear wars. Braithwaite’s proposals refine some of criminology’s central theories and sharpen their relevance to all varieties of freedom. They can be reduced to one sentence. Strengthen freedom to prevent crime, prevent crime to strengthen freedom

Dynamics analysis and integrated design of real-time control systems

Real-time control systems are widely deployed in many applications. Theory and practice for the design and deployment of real-time control systems have evolved significantly. From the design perspective, control strategy development has been the focus of the research in the control community. In order to develop good control strategies, process modelling and analysis have been investigated for decades, and stability analysis and model-based control have been heavily studied in the literature. From the implementation perspective, real-time control systems require timeliness and predictable timing behaviour in addition to logical correctness, and a real-time control system may behave very differently with different software implementations of the control strategies on a digital controller, which typically has limited computing resources. Most current research activities on software implementations concentrate on various scheduling methodologies to ensure the schedulability of multiple control tasks in constrained environments. Recently, more and more real-time control systems are implemented over data networks, leading to increasing interest worldwide in the design and implementation of networked control systems (NCS). Major research activities in NCS include control-oriented and scheduling-oriented investigations. In spite of significant progress in the research and development of real-time control systems, major difficulties exist in the state of the art. A key issue is the lack of integrated design for control development and its software implementation. For control design, the model-based control technique, the current focus of control research, does not work when a good process model is not available or is too complicated for control design. For control implementation on digital controllers running multiple tasks, the system schedulability is essential but is not enough; the ultimate objective of satisfactory quality-of-control (QoC) performance has not been addressed directly. For networked control, the majority of the control-oriented investigations are based on two unrealistic assumptions about the network induced delay. The scheduling-oriented research focuses on schedulability and does not directly link to the overall QoC of the system. General solutions with direct QoC consideration from the network perspective to the challenging problems of network delay and packet dropout in NCS have not been found in the literature. This thesis addresses the design and implementation of real-time control systems with regard to dynamics analysis and integrated design. Three related areas have been investigated, namely control development for controllers, control implementation and scheduling on controllers, and real-time control in networked environments. Seven research problems are identified from these areas for investigation in this thesis, and accordingly seven major contributions have been claimed. Timing behaviour, quality of control, and integrated design for real-time control systems are highlighted throughout this thesis. In control design, a model-free control technique, pattern predictive control, is developed for complex reactive distillation processes. Alleviating the requirement of accurate process models, the developed control technique integrates pattern recognition, fuzzy logic, non-linear transformation, and predictive control into a unified framework to solve complex problems. Characterising the QoC indirectly with control latency and jitter, scheduling strategies for multiple control tasks are proposed to minimise the latency and/or jitter. Also, a hierarchical, QoC driven, and event-triggering feedback scheduling architecture is developed with plug-ins of either the earliest-deadline-first or fixed priority scheduling. Linking to the QoC directly, the architecture minimises the use of computing resources without sacrifice of the system QoC. It considers the control requirements, but does not rely on the control design. For real-time NCS, the dynamics of the network delay are analysed first, and the nonuniform distribution and multi-fractal nature of the delay are revealed. These results do not support two fundamental assumptions used in existing NCS literature. Then, considering the control requirements, solutions are provided to the challenging NCS problems from the network perspective. To compensate for the network delay, a real-time queuing protocol is developed to smooth out the time-varying delay and thus to achieve more predictable behaviour of packet transmissions. For control packet dropout, simple yet effective compensators are proposed. Finally, combining the queuing protocol, the packet loss compensation, the configuration of the worst-case communication delay, and the control design, an integrated design framework is developed for real-time NCS. With this framework, the network delay is limited to within a single control period, leading to simplified system analysis and improved QoC

Compromising Anonymous Communication Systems Using Blind Source Separation

We propose a class of anonymity attacks to both wired and wireless anonymity networks. These attacks are based on the blind source separation algorithms widely used to recover individual signals from mixtures of signals in statistical signal processing. Since the philosophy behind the design of current anonymity networks is to mix traffic or to hide in crowds, the proposed anonymity attacks are very effective. The flow separation attack proposed for wired anonymity networks can separate the traffic in a mix network. Our experiments show that this attack is effective and scalable. By combining the flow separation method with frequency spectrum matching, a passive attacker can derive the traffic map of the mix network. We use a nontrivial network to show that the combined attack works. The proposed anonymity attacks for wireless networks can identify nodes in fully anonymized wireless networks using collections of very simple sensors. Based on a time series of counts of anonymous packets provided by the sensors, we estimate the number of nodes with the use of principal component analysis. We then proceed to separate the collected packet data into traffic flows that, with help of the spatial diversity in the available sensors, can be used to estimate the location of the wireless nodes. Our simulation experiments indicate that the estimators show high accuracy and high confidence for anonymized TCP traffic. Additional experiments indicate that the estimators perform very well in anonymous wireless networks that use traffic padding

Cascades of Violence

War and crime are cascade phenomena. War cascades across space and time to more war; crime to more crime; crime cascades to war; and war to crime. As a result, war and crime become complex phenomena. That does not mean we cannot understand how to prevent crime and war simultaneously. This book shows, for example, how a cascade analysis leads to an understanding of how refugee camps are nodes of both targeted attack and targeted recruitment into violence. Hence, humanitarian prevention also must target such nodes of risk. This book shows how nonviolence and nondomination can also be made to cascade, shunting cascades of violence into reverse. Complexity theory implies a conclusion that the pursuit of strategies for preventing crime and war is less important than understanding meta strategies. These are meta strategies for how to sequence and escalate many redundant prevention strategies. These themes were explored across seven South Asian societies during eight years of fieldwork