Efficient branch and node testing

Software testing evaluates the correctness of a program’s implementation through a test suite. The quality of a test case or suite is assessed with a coverage metric indicating what percentage of a program’s structure was exercised (covered) during execution. Coverage of every execution path is impossible due to infeasible paths and loops that result in an exponential or infinite number of paths. Instead, metrics such as the number of statements (nodes) or control-flow branches covered are used. Node and branch coverage require instrumentation probes to be present during program runtime. Traditionally, probes were statically inserted during compilation. These static probes remain even after coverage is recorded, incurring unnecessary overhead, reducing the number of tests that can be run, or requiring large amounts of memory In this dissertation, I present three novel techniques for improving branch and node coverage performance for the Java runtime. First, Demand-driven Structural Testing (DDST) uses dynamic insertion and removal of probes so they can be removed after recording coverage, avoiding the unnecessary overhead of static instrumentation. DDST is built on a new framework for developing and researching coverage techniques, Jazz. DDST for node coverage averages 19.7% faster than statically-inserted instrumentation on an industry-standard benchmark suite, SPECjvm98. Due to DDST’s higher-cost probes, no single branch coverage technique performs best on all programs or methods. To address this, I developed Hybrid Structural Testing (HST). HST combines different test techniques, including static and DDST, into one run. HST uses a cost model for analysis, reducing the cost of branch coverage testing an average of 48% versus Static and 56% versus DDST on SPECjvm98. HST never chooses certain techniques due to expensive analysis. I developed a third technique, Test Plan Caching (TPC), that exploits the inherent repetition in testing over a suite. TPC saves analysis results to avoid recomputation. Combined with HST, TPC produces a mix of techniques that record coverage quickly and efficiently. My three techniques reduce the average cost of branch coverage by 51.6–90.8% over previous approaches on SPECjvm98, allowing twice as many test cases in a given time budget

Digital CMOS ISFET architectures and algorithmic methods for point-of-care diagnostics

Over the past decade, the surge of infectious diseases outbreaks across the globe is redefining how healthcare is provided and delivered to patients, with a clear trend towards distributed diagnosis at the Point-of-Care (PoC). In this context, Ion-Sensitive Field Effect Transistors (ISFETs) fabricated on standard CMOS technology have emerged as a promising solution to achieve a precise, deliverable and inexpensive platform that could be deployed worldwide to provide a rapid diagnosis of infectious diseases. This thesis presents advancements for the future of ISFET-based PoC diagnostic platforms, proposing and implementing a set of hardware and software methodologies to overcome its main challenges and enhance its sensing capabilities. The first part of this thesis focuses on novel hardware architectures that enable direct integration with computational capabilities while providing pixel programmability and adaptability required to overcome pressing challenges on ISFET-based PoC platforms. This section explores oscillator-based ISFET architectures, a set of sensing front-ends that encodes the chemical information on the duty cycle of a PWM signal. Two initial architectures are proposed and fabricated in AMS 0.35um, confirming multiple degrees of programmability and potential for multi-sensing. One of these architectures is optimised to create a dual-sensing pixel capable of sensing both temperature and chemical information on the same spatial point while modulating this information simultaneously on a single waveform. This dual-sensing capability, verified in silico using TSMC 0.18um process, is vital for DNA-based diagnosis where protocols such as LAMP or PCR require precise thermal control. The COVID-19 pandemic highlighted the need for a deliverable diagnosis that perform nucleic acid amplification tests at the PoC, requiring minimal footprint by integrating sensing and computational capabilities. In response to this challenge, a paradigm shift is proposed, advocating for integrating all elements of the portable diagnostic platform under a single piece of silicon, realising a ``Diagnosis-on-a-Chip". This approach is enabled by a novel Digital ISFET Pixel that integrates both ADC and memory with sensing elements on each pixel, enhancing its parallelism. Furthermore, this architecture removes the need for external instrumentation or memories and facilitates its integration with computational capabilities on-chip, such as the proposed ARM Cortex M3 system. These computational capabilities need to be complemented with software methods that enable sensing enhancement and new applications using ISFET arrays. The second part of this thesis is devoted to these methods. Leveraging the programmability capabilities available on oscillator-based architectures, various digital signal processing algorithms are implemented to overcome the most urgent ISFET non-idealities, such as trapped charge, drift and chemical noise. These methods enable fast trapped charge cancellation and enhanced dynamic range through real-time drift compensation, achieving over 36 hours of continuous monitoring without pixel saturation. Furthermore, the recent development of data-driven models and software methods open a wide range of opportunities for ISFET sensing and beyond. In the last section of this thesis, two examples of these opportunities are explored: the optimisation of image compression algorithms on chemical images generated by an ultra-high frame-rate ISFET array; and a proposed paradigm shift on surface Electromyography (sEMG) signals, moving from data-harvesting to information-focused sensing. These examples represent an initial step forward on a journey towards a new generation of miniaturised, precise and efficient sensors for PoC diagnostics.Open Acces

Evolutionary Approach to Efficient Provisioning and Self-organization in Wireless Sensor Networks (WSN)

Advances in low-power digital integration and microelectro-mechanical systems (MEMS) have paved the way for micro-sensors. These sensors are equipped with data processing capabilities along with sensory circuits. Sensor data are processed on these individual sensors and transmitted to the target (sink). Lowcost integration and small sizes of these sensors have generated special interest in the area of disposable-sensors and large scale platform management. Queries to these sensors are addressed to nodes which have data satisfying the same condition. However, these sensors may be constrained in energy, bandwidth, storage, and processing capabilities. Large number of such sensors along with these constraints creates a sensor-management problem. At the network layer it amounts to setting up the efficient route that transmits the non-redundant data from source to the sink in order to maximize one or more sensor objectives (e.g. battery (and sensor's) life, Sensor-Data yield). This is done while adapting to changing connectivity due to failure of some nodes and new nodes powering up. First part of the thesis propose a reduced-complexity genetic algorithm (GA) for optimization of multi-hop battery-constrained sensor networks. The goal of the system is to generate optimal number of sensor-clusters with cluster-heads. It results in minimization of the power consumption of the sensor system while maximizing the sensor objectives (coverage and exposure). The genetic algorithm is used to adaptively create various components such as cluster-members, cluster-heads, and next-cluster. These components are then used to evaluate the average fitness of the system based on the sequence of communication links towards the sink. We then enhance the genetic algorithm (GA) approach for secure deployment of resource constrained multi-hop sensor networks. The goal in this case is to achieve secure coverage and improve battery life by dynamically optimizing security attributes (Like authentication and encryption). Further, we augment the GA approach for intrusion detection of resource constrained multi-hop sensor networks. Traditional intrusion detection mechanisms have limited applicability to the sensor networks due to scarce battery and processing resources. Therefore, we propose an effective scheme that would offer a power efficient and lightweight approach to identify malicious attacks. We evaluate sensor node attributes by measuring the perceived threat and its suitability to host local monitoring node (LMN) that acts as trusted proxy agent for the sink and capable of securely monitoring its neighbors. Security attributes in conjunction with genetic algorithm jointly optimizes the selection of monitoring nodes (i.e., LMN) by dynamically evaluating node fitness by profiling workloads patterns, packet statistics, utilization data, battery status, and quality-of-service compliance. Second part of the thesis delves into application of Information Technology (and Industrial) Systems and devices where the use of sensor networks can deliver non-intrusive and effective telemetry for group-based server management. These systems (Like Data Centers or Shipment tracking) face major challenges in seamless integration of telemetry and control data that is essential to various autonomic management functions related to power, thermal, reliability, predictability, survivability, locality and adaptability. Such systems that are supported by a dense network of sense-points operating in noisy environment (Metals, Cables) are required to deliver reliable trends, measurements and analysis in a timely fashion. The traditional approaches to provide distributed observability and control using wired solutions are static, expensive, and nonscalable. We apply the proposed GA approach for this unique environment that replaces static wired sensors with dynamically reconfigurable battery-powered wireless sensors. The proposed technique employs machine learning approach to optimize sensor node function assignment, clustering decisions, route establishment and data collection trees for improved throughput that results in effective controls

Reconfigurable Antenna Systems: Platform implementation and low-power matters

Antennas are a necessary and often critical component of all wireless systems, of which they share the ever-increasing complexity and the challenges of present and emerging trends. 5G, massive low-orbit satellite architectures (e.g. OneWeb), industry 4.0, Internet of Things (IoT), satcom on-the-move, Advanced Driver Assistance Systems (ADAS) and Autonomous Vehicles, all call for highly flexible systems, and antenna reconfigurability is an enabling part of these advances. The terminal segment is particularly crucial in this sense, encompassing both very compact antennas or low-profile antennas, all with various adaptability/reconfigurability requirements. This thesis work has dealt with hardware implementation issues of Radio Frequency (RF) antenna reconfigurability, and in particular with low-power General Purpose Platforms (GPP); the work has encompassed Software Defined Radio (SDR) implementation, as well as embedded low-power platforms (in particular on STM32 Nucleo family of micro-controller). The hardware-software platform work has been complemented with design and fabrication of reconfigurable antennas in standard technology, and the resulting systems tested. The selected antenna technology was antenna array with continuously steerable beam, controlled by voltage-driven phase shifting circuits. Applications included notably Wireless Sensor Network (WSN) deployed in the Italian scientific mission in Antarctica, in a traffic-monitoring case study (EU H2020 project), and into an innovative Global Navigation Satellite Systems (GNSS) antenna concept (patent application submitted). The SDR implementation focused on a low-cost and low-power Software-defined radio open-source platform with IEEE 802.11 a/g/p wireless communication capability. In a second embodiment, the flexibility of the SDR paradigm has been traded off to avoid the power consumption associated to the relevant operating system. Application field of reconfigurable antenna is, however, not limited to a better management of the energy consumption. The analysis has also been extended to satellites positioning application. A novel beamforming method has presented demonstrating improvements in the quality of signals received from satellites. Regarding those who deal with positioning algorithms, this advancement help improving precision on the estimated position

Securing emerging IoT systems through systematic analysis and design

The Internet of Things (IoT) is growing very rapidly. A variety of IoT systems have been developed and employed in many domains such as smart home, smart city and industrial control, providing great benefits to our everyday lives. However, as IoT becomes increasingly prevalent and complicated, it is also introducing new attack surfaces and security challenges. We are seeing numerous IoT attacks exploiting the vulnerabilities in IoT systems everyday. Security vulnerabilities may manifest at different layers of the IoT stack. There is no single security solution that can work for the whole ecosystem. In this dissertation, we explore the limitations of emerging IoT systems at different layers and develop techniques and systems to make them more secure. More specifically, we focus on three of the most important layers: the user rule layer, the application layer and the device layer. First, on the user rule layer, we characterize the potential vulnerabilities introduced by the interaction of user-defined automation rules. We introduce iRuler, a static analysis system that uses model checking to detect inter-rule vulnerabilities that exist within trigger-action platforms such as IFTTT in an IoT deployment. Second, on the application layer, we design and build ProvThings, a system that instruments IoT apps to generate data provenance that provides a holistic explanation of system activities, including malicious behaviors. Lastly, on the device layer, we develop ProvDetector and SplitBrain to detect malicious processes using kernel-level provenance tracking and analysis. ProvDetector is a centralized approach that collects all the audit data from the clients and performs detection on the server. SplitBrain extends ProvDetector with collaborative learning, where the clients collaboratively build the detection model and performs detection on the client device

Design of an embedded system and cloud backend for remote monitoring of smart traps

The convergence of low cost cloud services, widespread Internet deployment and low cost SOCs gives rise to systems placing the Internet’s vast compute power at the service of simple, everyday devices. Assisted by ubiquitous Wi-Fi deployment and smartphone ownership, a default infrastructure is emerging that supports rapid development of easy to use, low cost, Internet enabled devices. This nascent extension of the Internet into common, everyday devices has been termed the Internet of Things (IoT) and is attracting considerable commercial and academic interest. This paper evaluates the selection and application of IoT technologies to the operations of an existing industry that would benefit from a low cost, remote monitoring system by reducing the cost of delivering their services to their customers. The US pest control industry was selected for analysis as it has a healthy, growing revenue base ($7B in 2013) with a service delivery model that requires expensive manual monitoring (~$45 per inspection) of deployed traps and cages. A prototype system was built entailing a Wi-Fi connected smart rat trap, a cloud based monitoring system and a smartphone app for associating the trap with a Wi-Fi access point.Electrical and Computer Engineerin