With the continuous scaling of CMOS technologies, Silicon-on-Insulator (SOI) technologies have become more competitive compared to bulk, due to their lower parasitic capacitances and leakage currents. The shift towards high frequency, low power circuitry, coupled with the increased maturity of SOI process technologies, have made SOI a genuinely costeffective solution for leading edge applications. The original STAG2 model, developed at the University of Southampton, UK, was among the first compact circuit simulation models to specifically model the behaviour of Partially-Depleted (PD) SOI devices. STAG2 was a robust, surface-potential based compact model, employing closed-form equations to minimise simulation times for large circuits. It was able to simulate circuits in DC, small signal, and transient modes, and particular care was taken to ensure that convergence problems were kept to a minimum. In this thesis, the ongoing development of the STAG model, culminating in the release of a new version, STAG3, is described. STAG3 is intended to make the STAG model applicable to process technologies down to 100nm. To this end, a number of major model improvements were undertaken, including: a new core surface potential model, new vertical and lateral field mobility models, quantum mechanical models, the ability to model non-uniform vertical doping profiles, and other miscellaneous effects relevant to deep submicron devices such as polysilicon depletion, velocity overshoot, and the reverse short channel effect. As with the previous versions of STAG, emphasis has been placed on ensuring that model equations are numerically robust, as well as closed-form wherever possible, in order to minimise convergence problems and circuit simulation times. The STAG3 model has been evaluated with devices manufactured in PD-SOI technologies down to 0.25μm, and was found to give good matching to experimental data across a range of device sizes and biases, whilst requiring only a single set of model parameters.

This thesis is aimed at providing detailed transceiver structures employing novel channel coding schemes for enhancing the achievable performance of UltraWideBand (UWB) systems. We commence by a rudimentary introduction to UWB systems, including a brief historical perspective of the field. Chapters 2 to 4 will then provide the designs of channel coded UWB systems with the aid of EXtrinsic Information Transfer (EXIT) charts in order to achieve near-capacity performances. Each chapter constitutes an evolutionary improvement of the previous chapter. Chapter 2 deals with the UWB channel, which is one of the major factors differentiating UWB system from their narrow-band counterparts. This chapter starts with a brief review of the last two decades’ advances in UWB channel estimation. Then the z-domain Discrete Time Transfer Function (DTTF) of UWB channels is derived based on the specifications presented in the preceding sections. This transfer function forms the basis of the proposed memory-efficient implementation of the equalizer advocated. Furthermore, the stability analysis and Mean Convergence Bound (MCB) of the UWB channel transfer function is presented. The UWB channel model is then used by all the following chapters, when developing enhanced UWB systems. Chapter 3 starts with the implications of appropriate diversity order selection. Since it is possible to resolve the closely spaced multipath components of the channel, the system benefits from a high number of independent fading paths, which results in a high multipath diversity gain. Then we propose an EXIT chart aided iteratively detected Direct-Sequence (DS) Code Division Multiple Access (CDMA) system, which uses 2-stage concatenation of an inner and outer encoders, with their corresponding decoders exchanging extrinsic information for the sake of enhancing the attainable system performance. This system model constitutes the foundation for the following chapters, which will be further developed using different coding schemes with the aid of EXIT charts. A DS and a Time-Hopping (TH) Pulse Position Modulated (PPM) UWB systems are studied using EXIT charts and it is demonstrated that classic regular Forward Error Correction (FEC) encoders are unable to arbitrarily approach the system’s capacity. Hence Chapter 4 provides a solution for this problem by replacing the regular FEC codes with more sophisticated irregular FEC codes that are capable of approaching the system’s capacity more closely. More specifically, we have used Irregular Variable Length Codes (IrVLC) in our design of a two-stage concatenated UWB TH Spread-Spectrum (SS) Impulse Radio (IR) system. We then progressed from the two-stage design philosophy to three-stage irregular concatenated UWB systems. Naturally, an improved performance is only achievable at the cost of an increased complexity and interleaver length. Hence, the second half of Chapter 4 addresses the above-mentioned complexity and interleaver delay problem by invoking sophisticated binary Self-Concatenated Convolutional Codes (SeCCC) using different puncturing rates. We commence with a rudimentary introduction of the binary SeCCC design, which is then used for developing a near-capacity TH UWB system. Finally, the achievable performance gains of different puncturing and coding rates are detailed.

Wireless sensor nodes are devices that perform measurements (of parameters such as temperature or vibration) and communicate over a wireless medium. A key benefit is that they can operate autonomously. Nodes are commonly battery-powered so that they can be deployed rapidly without the need to install a wired power supply; however, batteries must be changed when depleted and this can impose a costly maintenance requirement. Energy harvesting is an emerging field, which offers the possibility for nodes to be powered indefinitely from environmental energy (such as light, vibration, or temperature difference). The power generated from environmental energy is often limited and variable, and nodes must be able to adapt their operation to take account of the power available. There have been a number of demonstrations of wireless sensor nodes powered from harvested energy, but existing demonstrators are tailored for specific types of energy resource (constraining their use to applications with suitable energy availability). The existing interfaces between the energy hardware and the nodes' embedded software is bespoke and limited to specific devices, so it is impossible to exchange the energy hardware to adapt to differing energy availability. The work described in this thesis delivers a comprehensive scheme for reconfigurable energy-aware sensor nodes, which overcomes the limitations of the existing systems and allows the energy hardware for sensor nodes to be connected together in a plug-and-play manner. The scheme has been evaluated by way of a prototype which accommodates a range of energy devices. The main contributions of this research are threefold: firstly, the system is enabled by a new hardware interface between the energy devices and sensor node; secondly, an embedded software structure is implemented to interface with the energy hardware; and thirdly, efficient energy-aware modules compliant with the scheme have been produced. The combined result is a novel energy subsystem for wireless sensor nodes that supports a range of energy devices and can deliver energy-aware operation for a range of microcontroller platforms, while imposing a minimal additional resource requirement to deliver this functionality.

Awareness of individual and group activities is critical to successful collaborative authoring. Participants require knowledge of what other contributors are doing and have done, what meaningful changes have been made to a document, and who is editing each section of a document and why. With this information, group dynamics can be improved and members can work more efficiently toward the final product. In this thesis, key problems in collaborative activities are identified through a review of previous research on the subject and from field research of authors engaged in collaborative work. From these initial observations we deduce that many problems in collaborative writing occur due to technology that hinders the proper distribution of information to members of the group. The concept of “awareness”, identified in past research, is discussed, and used as a model to explain the underlying causes behind these common problems. As a specific example of the importance of communication and coordination mechanisms, an analysis is presented of the Wikibooks website, an online collaborative writing site that allows volunteers to work together to develop free textbooks. Statistical analysis of historical data from the site is used to correlate successful books with efficient use of planning, communication and coordination techniques. These results help to further cement the importance of communication and awareness channels. From analysis of these issues, a set of requirements is defined for an effective collaboration tool, specifically the features that such a tool should include in order to support the types of awareness that are necessary for successful collaboration. Existing groupware systems are compared and judged against these requirements, with the discovery that most systems lack support for many different types of awareness. To investigate the subject further, a prototype co-authoring system with features to support awareness (CAWS), developed as part of this research, is described. It is explained how these features attempt to reproduce some of the communications channels implicitly present within an office environment. The results of a usability study using the CAWS system are then presented, with particular reference to the effectiveness of the features of the system. Feedback from participants was gathered with respect to usefulness and ease of gathering information about other users‟ progress and interactions with the workspace with these features present. Finally the observations, findings and the implications of a real world groupware evaluation are presented (undertaken over a period of 17 weeks with 85 students divided into 15 groups). The groupware evaluation gives insight into the effectiveness of awareness mechanisms. This includes the role and effect of planning, the effect of the choice of tool on perceptions of awareness, the relative importance of awareness and how awareness contributes to a successful collaboration. We discuss the outcomes of the research with respect to the research questions and contribution, presenting how the research could be continued in the future.

Exploration of heterogeneous data sources increases the value of information by allowing users to answer questions through exploration across multiple sources; Users can use information that has been posted across the Web to answer questions and learn about new domains. We have conducted research that lowers the interrogation time of faceted data, by combining related information from different sources. The work contributes methodologies in combining heterogenous sources, and how to deliver that data to a user interface scalably, with enough performance to support rapid interrogation of the knowledge by the user. The work also contributes how to combine linked data sources so that users can create faceted browsers that target the information facets of their needs. The work is grounded and proven in a number of experiments and test cases that study the contributions in domain research work.

This thesis reviews the area of e-Research (the use of electronic infrastructure to support research) and considers how the insight gained from the development of social networking sites in the early 21st century might assist researchers in using this infrastructure. In particular it examines the myExperiment project, a website for e-Research that allows users to upload, share and annotate work ows and associated files, using a social networking framework. This Virtual Organisation (VO) supports many of the attributes required to allow a community of users to come together to build an e-Research society. The main focus of the thesis is how the emerging society that is developing out of my-Experiment could use Semantic Web technologies to provide users with a significantly richer representation of their research and research processes to better support reproducible research. One of the initial major contributions was building an ontology for myExperiment. Through this it became possible to build an API for generating and delivering this richer representation and an interface for querying it. Having this richer representation it has been possible to follow Linked Data principles to link up with other projects that have this type of representation. Doing this has allowed additional data to be provided to the user and has begun to set in context the data produced by myExperiment. The way that the myExperiment project has gone about this task and consideration of how changes may affect existing users, is another major contribution of this thesis. Adding a semantic representation to an emergent e-Research society like myExperiment,has given it the potential to provide additional applications. In particular the capability to support Research Objects, an encapsulation of a scientist's research or research process to support reproducibility. The insight gained by adding a semantic representation to myExperiment, has allowed this thesis to contribute towards the design of the architecture for these Research Objects that use similar Semantic Web technologies. The myExperiment ontology has been designed such that it can be aligned with other ontologies. Scientific Discourse, the collaborative argumentation of different claims and hypotheses, with the support of evidence from experiments, to construct, confirm or disprove theories requires the capability to represent experiments carried out in silico. This thesis discusses how, as part of the HCLS Scientific Discourse subtask group, the myExperiment ontology has begun to be aligned with other scientific discourse ontologies to provide this capability. It also compares this alignment of ontologies with the architecture for Research Objects. This thesis has also examines how myExperiment's Linked Data and that of other projects can be used in the design of novel interfaces. As a theoretical exercise, it considers how this Linked Data might be used to support a Question-Answering system, that would allow users to query myExperiment's data in a more efficient and user-friendly way. It concludes by reviewing all the steps undertaken to provide a semantic platform for an emergent e-Research society to facilitate the sharing of research and its processes to support reproducible research. It assesses their contribution to enhancing the features provided by myExperiment, as well as e-Research as a whole. It considers how the contributions provided by this thesis could be extended to produce additional tools that will allow researchers to make greater use of the rich data that is now available, in a way that enhances their research process rather than significantly changing it or adding extra workload.

The area of wireless embedded nodes has attracted significant research interest, primarily with respect to the utilisation of this technology in a number of applications domains. Under this context, the main topic of this thesis pertains to the design of a framework for real-time, range-only target tracking utilizing low power wireless embedded nodes. The proposed tracking system is designed to operate solely on range measurements which are obtained without the need for additional hardware incorporated on the embedded nodes. The core objective of this research was to present a target tracking system that can be applied to real-world applications, incorporating support for effectively tracking manoeuvring targets facilitated by the ability to obtain accurate range readings from low-power embedded nodes and finally the ability to achieve real-time system operation. The contribution of the work presented in this thesis is threefold. The tracking problem is theoretically formulated as a dynamical system with the objective being, the real-time estimation of the target’s kinematic variables based on range observations. To address the need for effective tracking of manoeuvring targets an adaptive multiple-model approach was developed. The resulting system is non-linear, due to the non-linearity between the range observations and the kinematic variables. To solve this system, a novel adaptive multiple-model Particle Filter tracking algorithm is proposed. Secondly, to achieve accurate enough ranging between embedded nodes a Time-of-Flight ranging scheme is adopted as part of the proposed tracking system. The final contribution of this work pertains to the real-time operation of the tracking system. The tracking algorithms were evaluated on a simulation environment under realistic experimental conditions. The ranging method was implemented on embedded nodes and tested in terms of accuracy in various environments. Ultimately, the entire system was implemented on hardware and tested in outdoor experiments. In the experiments carried out one mobile wireless node was used as the target and a set of anchor nodes attempted to infer the target’s kinematic variables. A total of 25 experiments are presented in this thesis. An average accuracy of approximately 2.6m for position and 1.9m/s for velocity was attained in a 15m x 15m square area. Such performance, which is confirmed from the simulation results reveal the potential of the proposed range-only system in application domains where real-time tracking of mobile targets is a demand.

Recognising humans by the way they walk has attracted a significant interest in recent years due to its potential use in a number of applications such as automated visual surveillance. Technologies utilising gait biometrics have the potential to provide safer society and improve quality of life. However, automated gait recognition is a very challenging research problem and some fundamental issues remain unsolved. At the moment, gait recognition performs well only when samples acquired in similar conditions are matched. An operational automated gait recognition system does not yet exist. The primary aim of the research presented in this thesis is to understand the main challenges associated with deployment of gait recognition and to propose novel solutions to some of the most fundamental issues. There has been lack of understanding of the effect of some subject dependentcovariates on gait recognition performance. We have proposed a novel dataset that allows analyses of various covariates in a principled manner. The results of thedatabase evaluation revealed that elapsed time does not affect recognition in the short to medium term, contrary to what other studies have concluded. The analyses show how other factors related to the subject affect recognition performance. Only few gait recognition approaches have been validated in real world conditions. We have collected a new dataset at two realistic locations. Using the database we have shown that there are many environment related factors that can affect performance. The quality of silhouettes has been identified as one of the most important issues for translating gait recognition research to the ‘real-world’. The existing quality algorithms proved insufficient and therefore we extended quality metrics and proposed new ways of improving signature quality and therefore performance. A new fully working automated system has been implemented. Experiments using the system in ‘real-world’ conditions have revealed additional challenges not present when analysing datasets of fixed size. In conclusion, the research has investigated many of the factors that affect current gait recognition algorithms and has presented novel approaches of dealing with some of the most important issues related to translating gait recognition to real-world environments.

Leakage power is a growing concern in modern technology nodes. In some current and emerging applications, speed performance is uncritical but many of these applications rely on untethered power making energy a primary constraint. Leakage power minimisation is therefore key to maximising energy efficiency for these applications. This thesis proposes two new leakage power minimisation techniques to improve the energy efficiency of embedded processors. The first technique, called sub-clock power gating,can be used to reduce leakage power during the active mode. The technique capitalises on the observation that there can be large combinational idle time within the clock period in low performance applications and therefore power gates it. Sub-clock power gating is the first study into the application of power gating within the clock period, and simulation results on post layout netlists using a 90nm technology library show 3.5x, 2x and 1.3x improvement in energy efficiency for three test cases: 16-bit multiplier, ARM Cortex-M0 and Event Processor at a given performance point. To reduce the energy cost associated with moving between the sleep and active mode of operation, a second technique called symmetric virtual rail clamping is proposed. Rather than shutting down completely during sleep mode, the proposed technique uses a pair of NMOS and PMOS transistors at the head and foot of the power gated logic to lower the supply voltage by 2Vth. This reduces the energy needed to recharge the supply rails and eliminates signal glitching energy cost during wake-up. Experimental results from a 65nm test chip shows application of symmetric virtual rail clamping in sub-clock power gating improves energy efficiency, extending its applicable clock frequency range by 400x. The physical layout of power gating requires dedicated techniques and this thesis proposes dRail, a new physical layout technique for power gating. Unlike the traditional voltage area approach, dRail allows both power gated and non-power gated cells to be placed together in the physical layout to reduce area and routing overheads. Results from a post layout netlist of an ARM Cortex-M0 with sub-clock power gating shows standard cell area and signal routing are improved by 3% and 19% respectively. Sub-clock power gating, symmetric virtual rail clamping and dRail are incorporated into power gating design flows and are compatible with commercial EDA tools and gate libraries.

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