Research in the area of CVD diamond thin films has increased significantly during the last decades to the point where single crystal diamond is now commercially available. The remarkable properties of diamond including its extreme hardness, low coefficient of friction, chemical inertness, high thermal conductivity, transparency and semiconducting properties make it attractive for a number of applications, among which electronic devices is one of the key areas. A detailed knowledge of electrical properties of diamond films is therefore critical. This thesis describes (1) a Hall effect study of highly boron-doped (111) diamond films (2) a Hall effect and impedance spectroscopic study of boron δ-doped diamond structures and (3) the synthesis of carbon nanotubes on single crystal diamond. Systematic investigations have been carried out on single crystal, boron-doped (111) diamond films. The influence of ultra pure gases, doping concentration and temperature on carrier transport are discussed in detail. A comprehensive study on boron δ-doped diamond films is also performed; Hall effect and impedance spectroscopy are used to evaluate these films, providing valuable insight into the complex carrier transport mechanisms occurring in these structures. The influence of temperature on carrier mobility and the free carrier density are discussed. This is allied with valuable information gained from impedance spectroscopy, where the presence of multiple semicircular responses (conduction pathways), modelled using a RC parallel circuit, yields data which leads to a greater understanding on the influence of the interface between the boron δ-doped layer and the surrounding intrinsic diamond layers. These semicircular responses are thus attributed to different crystalline regions in these structures, namely the boron δ -doped layer and the interfacial regions surrounding δ-layer. The influence of this interface region on the structures overall conductivity is discussed. Finally the synthesis of carbon nanotubes (CNTs) on single crystal diamond is reported for the first time. Scanning electron microscopy combined with Raman spectroscopy is used to understand the influence of temperature and differing growth gas mixtures on the yield and crystallinity of these as-grown CNTs.

In addition to the prime requirement for ‘always-on’ connectivity, mobile users today are increasingly expecting fixed-mobile convergence (FMC) capabilities, such as session continuity across different access technologies. The challenge for network operators is to provide such capabilities in a cost-effective way for the range of services supported. This thesis addresses this challenge from the perspective of a next-generation network (NGN) operator. The work first determines a set of criteria with which to make a judgment on the desirability of session continuity for each service, which has been applied with a common approach to solutions design focusing on mobility management from the onset. A new type of collaboration-based Session Management for Converged Networks is described, and a catalogue of reusable, fundamental, mobility management components defined. Data measurements are presented from research and development work that substantiates the expected improvements by use of multi-OSI layer solutions, such as the one prototyped by a joint BT and Intel team and the associated architectural feasibility analysis of BT’s Next Generation Network: 21CN. As a result of the better understanding gained of the areas in which performance improvements can make a difference, a Converged Session Management Framework has been developed. It defines a number of procedural steps or phases, along with guidelines to aid the designer embarking on the definition of new applications or services that warrant implementation of mobility management. A new Mobility Management Layer (MML) concept is proposed and detailed with a working example on its use provided. A description on how MML can be used, as a competitive analysis tool is also included. This project has looked at architectural and procedural ways for “solving the mobility-management problem” for heterogeneous networks, rather than the current approach of finding optimised solutions for specific services and access technologies.

Miniaturization of integrated circuits (IC) has allowed very large scale integration (VLSI) of circuits. This has allowed personal communication devices to perform higher levels of data acquisition with faster speed. Due to robustness of digital systems most of the processing in ICs are digital. Therefore, the technology has been optimized for digital circuits. Still a small but very important part of these systems are analogue and it is very difficult to justify the modification of technology for analogue circuits. One of the most important analogue systems in these ICs are analogue to digital converters (ADC) which are implemented by switched capacitor (S/C) circuits. Fundamentally, the power consumption of S/C circuits increase as the power supply is reduced. Thus, reduced supply voltage tends to increase analogue circuit complexity and power consumption. This work focuses on development of digital calibration technique that allows the use of imprecise analogue circuits in order to reduce power consumption. The followings are achieved in the course of this research. An alternative background digital calibration technique that is based on deterministic error measurement. The technique can correct for capacitor mismatch and gain error due to insufficient op-amp DC gain. A system level simulation of the ADC have shown 15 dB signal-to-noise-plus-distortion-ratio (SNDR) and 31 dB spurious-free-dynamic-range (SFDR) improvement over a non-calibrated 12-bit ADC at 20 Ms/s. It also achieved an improvement of 4 LSB in INL and 0.6 LSB in DNL, respectively. A 12-bit 20 Ms/s 3.3 V pipeline ADC with the background digital calibration in 0.35 μm CMOS technology was designed and fabricated. However, primarily due to layout issues and to some extent due to equipment limitations the measured results showed only marginal improvement. A 10-bit 500 ks/s 5 V fully differential successive approximation ADC with a variable input range between 2-5 V in 0.35 μm CMOS technology with 1.5 mW power consumption designed and fabricated. This ADC can be used in moderate performance applications (resolution and speed), such as bio- impedance measurement.

The ultimate goal of future generation wireless communications is to provide ubiquitous seamless connections between mobile terminals such as mobile phones and computers so that users can enjoy high-quality services at anytime anywhere without wires. The feature to provide a wide range of delay constrained applications with diverse quality of service (QoS) requirements, such as delay and data rate requirements, will require QoS-driven wireless resource allocation mechanisms to efficiently allocate wireless resources, such as transmission power, time slots and spectrum, for accommodating heterogeneous mobile data. In addition, multiple-input-multiple-output (MIMO) antenna technique, which uses multiple antennas at the transmitter and receiver, can improve the transmission data rate significantly and is of particular interests for future high speed wireless communications. In the thesis, we develop smart energy efficient scheduling algorithms for delay constrained communications for single user and multi-user single-input-single-output (SISO) and MIMO transmission systems. Specifically, the algorithms are designed to minimize the total transmission power while satisfying individual user’s QoS constraints, such as rate, delay and rate or delay violation. Statistical channel information (SCI) and instantaneous channel state information (CSI) at the transmitter side are considered respectively, and the proposed design can be applied for either uplink or downlink. We propose to jointly deal with scheduling of the users that access to the channel for each frame time (or available spectrum) and how much power is allocated when accessing to the channel. In addition, the algorithms are applied with modifications for uplink scheduling in IEEE 802.16 Worldwide Interoperability for Microwave Access (WiMAX). The success of the proposed research will significantly improve the ways to design wireless resource allocation for delay constrained communications.

This thesis introduces a new dimension in performance scaling of signal processing systems by proposing software frameworks that achieve increased processing throughput when producing approximate results. The first contribution of this work is a new theory for accelerated computation of multimedia processing based on the concept of tight packing (Chapter 2). Usage of this theory accelerates small-dynamic-range linear signal processing tasks (such as convolution and transform decomposition) that map integers to integers, without incurring any accuracy loss. The concept of tight packing is combined with incremental computation that processes inputs in a bitplane-by-bitplane manner (Chapter 3), thereby leading to substantial throughput/distortion scalability within filtering, transform-decomposition and motion-estimation tasks. This framework also provides for region-of-interest computation and has inherent robustness to arbitrary termination of processing, imposed, for example, by a task scheduler. Finally, the concept of packed processing is extended to floating-point (lossy) matrix computations, with particular focus on the generic matrix multiplication (GEMM) routine of BLAS-3 (Chapters 4 and 5). This routine is a fundamental building block for several linear algebra and digital signal processing systems, such as face recognition and neural-network training for metadata-based retrieval systems. In order to compete with the best-performing software designs for GEMM, an implementation using single instruction, multiple data (SIMD) instructions is presented and analyzed. The proposed approach demonstrates substantial performance scaling in practice; specifically, it is shown to achieve up to twice the processing throughput of the best designs for GEMM when producing approximate results (under the same hardware). In summary, the proposed approximate computation of signal processing tasks can be selectively disabled thereby producing conventional full-precision/lower-throughput processing when deemed necessary. Importantly, the proposed software designs run on off-the-shelf computer hardware and provide for on-demand reconfiguration, depending on the input data and the precision specification (from full precision to noisy computation). Thus, the proposed approximate computation framework allows for backward compatibility and can be offered as an add-on service, creating significant competitive advantages for application developers. It can be used in mobile or high-performance computing systems when the precision of computation is not of critical importance (error-tolerant systems), or when the input data is intrinsically noisy.

In this thesis, we focus on the optimization of the two-way relay channel (TWRC), which can double the data rate of communications comparing to the traditional one-way relay channel (OWRC). Because of the broadcasting nature of wireless transmissions, secure transmission is an appealing research topic. We take secrecy rate consideration into the optimization of the TWRC. Overall we provide near-optimal solutions for the secrecy rate maximization problems of the TWRC with imperfect channel state information (ICSI). A much lower complexity optimal SOCP solution is provided for SNR balancing of the TWRC without secrecy consideration. We first look at a flat fading TWRC network model with a multiple-input multiple-output (MIMO) relay where perfect channel state information (CSI) is assumed available. We then formulate an optimization problem, with the objective to minimize the relay’s power usage under the constraints that the signal-to-noise ratio (SNR) of the two transceivers should exceed a preset threshold. A low-complexity optimal beamforming solution is provided to this optimization problem by reformulating it in the form of second-order cone programming (SOCP). Later in the thesis, we consider the presence of an eavesdropper and address the beamforming optimization for minimizing the relay’s power with the constraints of the secrecy rates of the two transceivers. A semi-definite programming (SDP) based searching algorithm is proposed to find a near-optimal solution. For each search of the proposed approach, the previous non-convex optimization problem is transferred into an SDP problem, which can guarantee the optimality of the beamforming matrix. Afterwards, more realistic imperfect CSI (ICSI) situations are considered for the TWRC network models. As ICSI completely changes the structure and the property of the optimization problems, we reformulate the optimization problems into two scenarios. For the first case, we consider that the relay is an untrusted eavesdropper and in this case an SDP solution is provided to maximize the joint-decoding sum-secrecy rate. For the second case, we investigate the robust beamforming problems where the relay is trusted but there is an external eavesdropper, another SDP solution is provided to maximize the sum-secrecy rate.

Over the recent decade, many different concepts of new emerging memories have been proposed. Examples of such include ferroelectric random access memories (FeRAMs), phase-change RAMs (PRAMs), resistive RAMs (RRAMs), magnetic RAMs (MRAMs), nano-crystal floating-gate flash memories, among others. The ultimate goal for any of these memories is to overcome the limitations of dynamic random access memories (DRAM) and flash memories. Non-volatile memories exploiting resistive switching – resistive RAM (RRAM) devices – offer the possibility of low programming energy per bit, rapid switching, and very high levels of integration – potentially in 3D. Resistive switching in a silicon-based material offers a compelling alternative to existing metal oxide-based devices, both in terms of ease of fabrication, but also in enhanced device performance. In this thesis I demonstrate a redox-based resistive switch exploiting the formation of conductive filaments in a bulk silicon-rich silicon oxide. My devices exhibit multi-level switching and analogue modulation of resistance as well as standard two-level switching. I demonstrate different operational modes (bipolar and unipolar switching modes) that make it possible to dynamically adjust device properties, in particular two highly desirable properties: non-linearity and self-rectification. Scanning tunnelling microscopy (STM), atomic force microscopy (AFM), and conductive atomic force microscopy (C-AFM) measurements provide a more detailed insight into both the location and the dimensions of the conductive filaments. I discuss aspects of conduction and switching mechanisms and we propose a physical model of resistive switching. I demonstrate room temperature quantisation of conductance in silicon oxide resistive switches, implying ballistic transport of electrons through a quantum constriction, associated with an individual silicon filament in the SiOx bulk. I develop a stochastic method to simulate microscopic formation and rupture of conductive filaments inside an oxide matrix. I use the model to discuss switching properties – endurance and switching uniformity.

This thesis is concerned with the exposure of electromagnetic fields to school children from Wireless Local Area Networks (WLAN). The research provides insights into how wireless networks are implemented in schools, sets out to develop a systematic methodology to quantify field levels close to WLAN devices and then investigates the extent of exposure thereby assisting the Health Protection Agency (HPA) in providing advice. School children in the UK are being exposed to electromagnetic fields due to the increasing use of Wi-Fi technologies in schools. Many local government authorities and schools are facing difficulties in understanding the health issues associated with the use of WLAN networks and there is increasing pressure from parents to provide reassurance. There is lack of quantitative scientific data, and current methodologies do not provide a realistic measure of the extent of exposure. The results from the exploratory studies and the contribution from existing literature have then been synthesised to develop new methodologies. A set of measurements were made to come to an assessment of the level of radiofrequency fields adjacent to commonly used WLAN equipment. Finally, the way in which children interact with WLAN devices as part of their normal lessons was examined in determine the time averaged exposure. The outcome of this research is a robust measurement methodology and examination of extent of RF exposure to children which represents a significant contribution to the scientific knowledge. The measurement methodology has been demonstrated to be practicable and can be used with a range of wireless devices using pulsed signals and thus is capable of providing valuable information for future studies.

The aim of this project is to investigate the use of high speed digital signal processing (DSP) to improve the performance of low cost, low power wavelength division multiplexed (WDM) optical interconnects. Optical technology offers the multi-Gbit/s transmission capacities that will be required to connect processors in data centres and high performance computers. However, physical effects limit the achievable optical link capacities that can be achieved, one major problem being the crosstalk due to interference between WDM channels which imposes a lower limit on the channel spacing. A method of canceling this crosstalk would have a major impact on the performance of such systems. This thesis begins with an introduction to crosstalk and the theory describing it. Results on crosstalk cancellation previously reported in the literature are analysed. Following this, the DSP-based multiple-input and multiple-output (MIMO) crosstalk cancellation approach proposed in this project is presented, and initial circuit designs and simulation results are presented. The effectiveness of both transmitter- and receiver-based MIMO crosstalk cancellation were assessed for two and three channel WDM systems through simulations. Next a two channel transmitter with crosstalk cancellation, based on Tektronix 12 GS/s arbitrary waveform generators (AWGs) was demonstrated. The DSP for these experiments were carried out offline, using Matlab. A reprogrammable field-programmable gate array (FPGA)-based 10.7 Gb/s optical transmitter incorporating crosstalk cancellation for one and two interfering channels using real-time DSP was then developed and tested through simulations and experiments. Finally, combined transmitter and receiver MIMO processing for crosstalk cancellation was investigated experimentally using off-line DSP, 12 GS/s AWGs and a 50 GS/s real-time oscilloscope.

The main body of this thesis focuses on the fabrication of micro-electro-mechanical (MEM) fluidic flow sensor for integration with large scale integration (LSI) neuron circuit and robot. The proposed MEM sensor consists of a) piezoresistive wheatstone bridge circuits consisting of p-type boron doped regions in n-type single crystalline silicon, integrated with patterned metallization, b) silicon cantilever beams that are integrated with the aforementioned piezoresistive wheatstone bridge/metallization circuits, c) out of plane flaps that are integrated at the free end of the silicon cantilever beams. The p-type piezoresistive wheatstone bridge microfeatures are fabricated by boron implantation in n-type single crystalline silicon, forming p-n junction. Patterned metallizations have been integrated with boron doped microfeatures and the circuits have been characterised by electrical probing. The electrical circuits and microcantilever beams have been fabricated on the device layer of silicon on insulator (SOI) wafers, followed by release of the microstructures by bulk micromachining step, where the silicon handle wafer and buried silicon oxide of the SOI wafer beneath the pre-defined cantilever beams has been removed. However, devices fabricated in the first design iteration did not meet the specifications and therefore could not be integrated with the LSI neuron circuit. In an attempt to address this issue, the MEM device has been redesigned to meet the specifications. For the fabrication of out of plane flaps, the plastic deformation magnetic assembly (PDMA) method has been developed. The final part of this thesis focuses on amorphous silicon carbide thin films and investigation of their suitability for application in SiC membrane based pressure sensors. As amorphous SiC films have been found to not be robust, circular membranes of thermally grown polycrystalline 3C-SiC films for application in absolute pressure sensing devices have been fabricated. Boron doped polycrystalline silicon strain gauges in half active wheatstone bridge arrangement have been integrated with SiC released membranes to transduce pressure induced mechanical deformation of the membranes into electrical signal.