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Non-orthogonal multiple access techniques for 6G and beyond radio access networks
No full textRadio Access Networks (RANs) have experienced an enormous development in a relatively short time. Since their appearance at the beginning of the 1980s, they have become a key tool in human beings' progress. They have completely shifted the way humankind communicates and performs daily activities in a relatively short period of time. This huge success also brings important challenges when designing future access networks. Everyday, there are more devices requiring to be connected to mobile networks, and the services they request have become extremely demanding in terms of data rate, latency and reliability.
RANs use multi-user techniques to allow several users to be connected simultaneously. Traditionally, these techniques have been developed utilising orthogonality as an important design factor. It has facilitated the process to keep users' data easily separable and without interfering other users' data. Orthogonal Multiple Access (OMA) techniques have been prosperous in matching the service requirements during the first generations of wireless cellular technology. Some well-know examples are: Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiple Access (OFDMA). These techniques utilise time, frequency, code, or a combination of some of them, to create orthogonal resources that are allocated to users. It is precisely the available amount of this resources which set the capacity limit on any of these multiple-access techniques. Nevertheless, this never-ending quest for improvement, has obligated multi-user techniques to look beyond the orthogonality threshold they have held for more than 40 years. Non-orthogonal Multiple Access (NOMA) techniques appear as an efficient way to take advantage of the limited electromagnetic spectrum resource, making it possible to handle modern service needs. Therefore, NOMA is able to accommodate more users than OMA utilizing the same radio resources, making a more efficient use of them. This is crucial when dealing with massive amounts of devices, which is precisely the scenario envisioned by the Internet of Things (IoT) and Massive Machine-Type Communications (mMTC). Additionally, it improves the scheduling process, reducing the time that users need to wait to access the service. It also opens the door to achieve higher data rates, which will be required by new applications and rich multi-media content applications. In the present research work, we contribute with the complex task of enhancing NOMA techniques by conducting performance analysis, and through the development of suitable new schemes and algorithms. We also studied the application of NOMA in other important telecommunication technologies.
In the first part of our work, we investigate the fairness behaviour of NOMA and delve into NOMA configurable properties and inherent design features that rule it. For this purpose we design a framework to specifically understand fairness in NOMA, both at system and at pair level. This framework includes various reference levels to make it versatile and applicable to diverse scenarios. We propose a power allocation scheme based on fairness, and a pairing scheme prioritizing fairness at individual and pair level. We validated our schemes through simulations and demonstrate the high adaptability that NOMA is able to provide under specific fairness requirements.
In the second part of our research, we explore the application of NOMA in Cognitive Radio (CR). By conducting a theoretical study of successive interference cancellation (SIC) hybrid algorithms, we developed closed-form expressions for the probability of success of the primary and secondary users. We analysed the differences between two different SIC hybrid algorithms and highlight the advantages that NOMA is able to deliver to CR. We verify our theoretical analysis utilizing Monte Carlo simulations.
In the third part of this research, we study the Physical Layer Security (PLS) performance of NOMA, which is a transcendent point to consider in any emerging technology. Specifically, we analyse the Secrecy Performance of the system under a coordinate eavesdropping scenario, to explain and propose methods to enhance security when designing NOMA. We show how SIC decoding order has an important impact on the system secrecy rate. Two solutions are proposed to the SIC decoding order selection. The first one based on interference, and a second one utilizing deep-learning to enhance the selection process. Both solutions are compared with the optimal one, and they are demonstrated to reach high performance at lower computational complexity level.
In the final part of this work, we have a look at satellite communications, where we believe NOMA can be applied to address current challenges. We analyse the effects of intra-beam and inter-beam interference in a NOMA multi-beam satellite system. An optimisation problem to enhance system capacity is proposed considering interference. We also consider secrecy capacity maximisation as an alternative to enhance the system bit rate and improve security at the same time. The solutions to the aforementioned problems are given in terms of NOMA power allocation, which were verified using numerical simulations.
In this way, this research work contributes towards the development and enhancement of NOMA, and its application in other modern communication technologies, for Next-Generation Radio Access Network
Caring in and through our practices towards shared and reflexive communities of curatorial care
No full textFor post-representational curatorial practice, to explore and respond to the many globally implicated and radically situated crises occurring at this moment is a weighted undertaking. Post-representational curatorial practice is not about staging or producing exhibitions, but a lively practice of actively and deliberately bringing people together through social and transdisciplinary approaches to knowledge production, translation and transmission. It is a practice that shares its origins with the dematerialisation of the art as object, new institutionalism, and the educational turn, and has expanded across cultural and civic spaces—for collectively thinking about and making sense of how human and more-than-human worlds are shifting. This is a practice where different kinds of stories and imaginaries, experiences and capabilities can become meaningful ways to gather, to contemplate and think through converging crises—from climate collapse to global pandemics—and learn to live well with uncertain and possible futures.
This creative practice-led research project demonstrates that to care within relational and differently affected worlds also activates a range of tensions about our practices, which we as curatorial practitioners increasingly find ourselves grappling with. These are tensions that prompt us to reconsider how neoliberal capitalism, systems and structures inextricably linked to colonialism, shape the (temporal, hierarchical, extractive, inequitable) organising logics of the organisations in which our practices occur. In turn, they rub against the choices we make in deciding for whom do we care, what for, why and how, in and through our practices. In a pandemic-impacted world, in which a crisis of care has highlighted the very real need for redressing caring imbalances, including within the arts sector, where do we as curators—whose discipline shares an etymological link with the Latin word curare, meaning to take care of—begin?
Thinking with a host of intersectional, decolonial, antiracist and multispecies feminist thinkers, voices whose scholarship on care recognise that care is situated, care is an ethical obligation and a practical labour, care is complex and relational, care is speculative, this research project argues that it is precisely at the intersection of these tensions of practice that we, as practitioners, begin. Underpinned by feminist care ethics, this creative research-led project arrives at this understanding informed by a series of interviews and workshops with practitioners whose practices traverse post-representational curatorial practice. A qualitative analysis of these relational, affective and generative research components identified the need and want for prefiguring a community of care, and the conditions and tools for engaging with shared reflexivity, between and among practitioners, within and across institutional affiliations. Informed by these findings, and a practice fifteen years in the making, accompanying this dissertation is the creative work, caring in and through our practices.
The creative work is an online resource and pedagogical tool, presented as a website, which I have developed (as a proof of concept) for practitioners to engage with through a series of scaffolded questions organised around four interrelated themes—Grounding Practice, Doing Practice, Troubling Practice and Extending Practice. Caring in and through our practices is not a templated manual on how to do practice. Rather, it is designed to prompt and facilitate shared practitioner reflexivity. In doing so, as care (ethics) does not prescribe how to care, caring in and through our practices is a pedagogical invocation for us as practitioners to:
• make space and time to navigate, together, the potentialities and possibilities, limitations and accountabilities of post-representational curatorial practice;
• become attuned conceptually, methodologically and practically to what needs to be transformed, what is transforming, and how we might be able to do so at different scales;
• collectively manifest the kinds of curatorial practices, and responsive and equitable organisations, our complex futures demand; and to
• take turns, as practitioners, in caring with, for, and about each other’s practices.
This research project argues that creating space, collectively, for this kind of practitioner reflexivity, by sitting with questions that do not always have clear answers, is ultimately an act of shared intent: for maintaining, repairing, and, where necessary and possible, transmogrifying elements of our curatorial practices and organisational systems and structures that no longer serve
Deep learning-based building envelope information extraction for BIPV application
No full textExtracting building façade information from a building is a challenging task that is crucial in many building-related studies, especially in the development of building-integrated photovoltaics (BIPV) application studies. Many studies regarding BIPV application in urban environments had been conducted and by examining these studies. It is discovered that reduction factors such as reduction coefficients and window-to-wall ratio (WWR) have been applied to total surface areas on building envelopes to estimate areas that are BIPV compatible. These values used for reduction factors vary differently based on studies which can result in varying BIPV surface area estimation results. Therefore, this can affect the accuracy of the BIPV energy potential estimation when conducting solar energy potential analysis.
Artificial intelligence, particularly deep learning framework has been applied in many computer vision problems to recognise objects. Deep learning frameworks have been applied to recognise building element objects such as windows, balconies, and roofs in built environments. Many deep learning application studies for built environments have shown promising results for being able to identify these building elements. Although deep learning has been applied successfully in these studies, not many studies have attempted to utilise deep learning to recognise BIPV applicable surface areas on building facades and roofs for the purpose of BIPV energy potential analysis. There are many research gaps surrounding the issue of extracting BIPV surface areas from building images using deep learning frameworks and performing BIPV solar energy analysis on the extracted surfaces.
This research aims to address these research gaps. Through the literature reviews, six popular building elements were identified for the purpose of BIPV applications which can be broken into two macro categories such as facades and roofs. BIPV application studies were reviewed to identify the commonly used reduction factors so that it can serve as a baseline comparison for this study. Deep learning applications in built environments were also reviewed to select the most suitable deep learning model for this task. The Mask Region-Based Convolutional Neural Network (Mask R-CNN) model was identified as the model of choice for this study as it has been proven effective and easy to use. Although many deep learning studies utilised street view images to generate the necessary training data for the model, this study utilised photomesh data due to its advantages of providing a 360-degree view of the selected building.
Mask R-CNN framework was deployed for building façade extraction (windows and glazing facades) from image input. This study utilised transfer learning to train the proposed methodology using Common Objects in Context (COCO) dataset with building façade images collected from public photomesh data of Melbourne Central Business District (CBD). The trained model was used to perform segmentation tasks and produce prediction masks on identified building surfaces which were later used for surface area estimation.
Model evaluation results show that the trained model achieved a mean average precision of 76.9% at 0.5 Intersection over union (IoU) threshold. The process of the surface area calculation was done using a grid-based system which allowed shading height to be applied to identify unshaded regions on the building façade. The same process was also applied to building roofs to identify BIPV compatible roof areas. Four buildings in Melbourne were selected to test the model prediction. The prediction results were validated against ground truth data, and it achieved 75.8% overall accuracy for predicting building elements on the ground truth correctly.
Solar energy and shading analysis were conducted for the selected buildings using Quantum Geographic Information System (QGIS) to provide a detailed breakdown of suitable surface area for BIPV installation. Solar energy potential on unshaded surface areas of the building can be estimated accurately using the model’s prediction data. BIPV simulations were conducted for two buildings to compare the accuracy of this methodology against conventional BIPV area estimation. The results confirm that the proposed methodology provides BIPV energy potential estimation which is closer to the ground truth data
Vernacular security and the spiritual landscape in Timor-Leste
No full textAfter nearly 500 years of Portuguese colonial rule and a 24-year resistance struggle against Indonesian occupation, the population of Timor-Leste voted overwhelmingly for independence in the 1999 Popular Consultation Vote. After three years of UN transitional administration (UNTAET), the nation formally gained independence in May 2002. Since then, Timor-Leste has been host to on-going international efforts to reform, develop and capacity-build the security sector with significant time and resources allocated towards supporting the formation of new state institutions. The majority of academic and policy documentation available gives the impression that the security, stability and development of the nation rests, by and large, on the success or failure of such statebuilding.
In contrast to the common assumption that posits the state as the primary location in terms of the production of security, communities across the territory continue to demonstrate high levels of resilience in dealing with sources of (in)security in ways that go beyond the utilisation of and reliance on what might be seen as the conventional architecture of the state. In Timor-Leste, many people live their lives with a powerful sense of the presence and influence of ancestral and nature spirits. As part of this, the land itself is understood as enlivened by spiritual forces, where everything in nature has a spirit and where God is the source and creator of life. This worldview of the spiritual landscape has ramifications for many different aspects of people’s lives including agriculture and natural resource management, fertility, politics and national identity, and—as I will demonstrate in this thesis—the production of security.
In its simplest form, this thesis argues that the spiritual landscape is often critical to how people experience and produce security in their daily lives in Timor-Leste. This overarching argument consists of three subsidiary claims: firstly, that the spiritual landscape is typically comprised relationally of humans, nature spirits, ancestors and an entity that takes the form of a Catholic God; secondly, that people’s security is most often reproduced at the local and everyday level, outside the machinations of the state; and thirdly, that there are four dimensions of social life—community, regulation, exchange and production—which are particularly relevant in highlighting the link between the spiritual landscape and security production.
This thesis and its arguments are situated within the growing critical discourse problematising conventional approaches to security studies, particularly its Western and Euro-centric origins and subsequent blindness to what is often categorised as ‘the other’. Such an argument involves reorienting social inquiry onto that which falls outside the ‘status quo’ of referent objects and agents in terms of whose ideas and needs are taken into consideration and prioritised, and what lived experiences are considered relevant to discussions of security. To draw from the lexicon of human security, this entails focusing on the ‘end-user’. While terms such as fear, threat, risk, harm, danger and safety are ‘existential features’ of the human condition (Giddens 1991), how people experience and deal with such conditions are socially and culturally constituted, rooted in situated knowledge and worldviews.
As such, this thesis builds on this growing body of alternative social inquiry, applying a vernacular lens in the context of Timor-Leste with the purpose of demonstrating the plurality of security. I do this by way of a particular focus on non-secular, non-anthropocentric beliefs and practices which are often dismissed as illogical or irrational, but which have very real impacts on people’s lives and experiences. This is not to say that security in Timor-Leste is constituted entirely by the spiritual landscape, but rather that to ignore the centrality of the spiritual landscape is to overlook a key dimension of security in Timor-Leste
A cognitive human-machine system for low-altitude airspace management
No full textThe emergence of the Low Altitude Airspace Management (LAAM) framework, which includes UAS Traffic Management (UTM), Urban Air Mobility (UAM), and Advanced Air Mobility (AAM), has led to the potential for designating new systems and airspace structures that are suitable for low altitude airspace, particularly in denser urban and suburban areas. A high level of automation support has increasingly been adopted in traditional Air Traffic Management (ATM) and is expected to further increase in the LAAM system, with the aim of supporting human supervision and decision-making in the presence of dense and less predictable UAS traffic. Effective human-machine collaboration at a high level of automation is necessary to account for the scale and varying capabilities of the emerging unmanned aircraft population. Therefore, a Human-Machine System (HMS) featuring adaptive automation, which varies the level of autonomy in real-time to promote the interaction and collaboration of human and machine, is essential and is brought forward by the Cognitive Human-Machine Interfaces and Interactions (CHMI2) system. The CHMI2 system implements advanced cognitive processing and machine learning techniques to achieve trusted autonomy in the next generation of aerospace systems.
This research project addresses the development of the core CHMI2 cognitive state processing and the key Human-Machine Interfaces (HMI) functionalities in the LAAM HMS. The foundation of any HMI functions is laid upon the distinct human-machine responsibilities and coordination; hence, the human operator's task analysis and human-machine decision-making workflow in LAAM are utilised. Development and test activities focused on verifying the operability of CHMI2 sensing and inference modules are followed by Human-in-the-Loop (HITL) testing, adopting ATM test scenarios. The correlations between eye activities and cardiorespiratory parameters and mental workload are modelled. The HMI formats and functions tailored explicitly for the LAAM framework are designed and prototyped. The challenges posed by high traffic complexity, in terms of significant variation in Communication, Navigation and Surveillance (CNS) performance and mission profiles, are subject to the human operator’s interpretability of the situation and the machine’s capability to calculate and compute solutions. This suggests that the optimal approach is to capitalise on performance-based approaches in airspace modelling and traffic clustering to enhance traffic safety, efficiency, and human-machine teaming. The developed human role in LAAM and the HMI functionalities support the future development of more complex and fully integrated HMS in LAAM
Assessment of train passengers’ pre- and post-boarding behaviors and insights into platform and carriage design, preference, and satisfaction
No full textRail transportation is widely acknowledged as an efficient and sustainable mode of transport. As train travel continues to grow in popularity, it has become increasingly important to understand how passengers interact with platform and carriage design features. Despite the many efforts to improve public transportation services in modern cities, there is still a lack of understanding of how design features affect passenger behaviours, perceptions and preferences. Conversely, how passengers respond and interact with different design features is not fully understood. This lack of understanding can lead to less effective design solutions that do not fully meet the needs and expectations of train passengers.
The study begins with a thorough review of the literature, highlighting the factors influencing passenger behaviours, perceptions and design preferences. It reveals a lack of understanding about the factors influencing passengers’ decisions before and after boarding. In addition, there is a lack of frameworks that systematically evaluate passenger behaviours, perceptions and preferences. Efforts have primarily focused on monitoring passenger flow and assessing satisfaction levels based on service quality, which is insufficient to provide a comprehensive evaluation. Therefore, a new framework is designed and tested with the survey data.
This study proposes six research questions that aim to investigate various aspects of passenger behaviours, perceptions and preferences, as well as their relationship with train and platform design. A systematic approach is proposed for assessing passenger behaviours, perceptions and preferences to address the research gap. The conceptual framework comprises four domains, which help break down the overall assessment into manageable components. The first domain gathers information about traveller and trip characteristics, including demographics and trip frequency, to identify factors influencing passenger experiences. The second domain examines general behaviours and perceptions before and after boarding, providing insights into passengers’ overall travel experience. The third domain evaluates passengers’ responses to different design features on trains and platforms, helping identify crucial design elements that affect passengers’ travel experiences. The fourth domain explores passengers’ perceptions of service quality and overall satisfaction, using these insights to improve the overall passenger experience.
Collecting information from all four domains is vital to achieve a complete understanding of passenger experiences and inform strategies for optimising rail operations and enhancing customer satisfaction. This study developed an original passenger survey tailored to gather data on various aspects of train passengers’ experiences. The survey was conducted online in March 2021 targeting Melbourne Metro train users. The survey serves multiple purposes, including understanding passengers’ characteristics and trip details, capturing passengers’ behaviours on the platform and in the carriage, identifying preferences for interior and platform design features, collecting opinions on existing services and uncovering the reasons behind passengers’ riding decisions. By utilising the questionnaire survey, the research can collect data from a significant sample size of train users in a cost-effective and efficient manner.
The methodology employed in this study involves integrating various statistical techniques to conduct a comprehensive analysis of the survey data. Descriptive statistics provide initial insights into the data, enabling a better understanding of train users’ characteristics, trip characteristics and opinions. T-tests and Analysis of Variance (ANOVA) are employed to examine variations in the perceptions and preferences between different subgroups. Correlation analysis helps identify potential factors that may influence passengers’ behaviours and perceptions as well as overall satisfaction. These analytical methods allow patterns within the data to be identified, enabling a deeper understanding of the research questions. The insights gained from the analysis will contribute to answering the research questions and provide valuable information for proposing strategies and interventions aimed at enhancing the user experience.
The assessment of pre-boarding behaviours reveals some general behaviour patterns and the correlations between passenger characteristics and behaviours. For instance, senior passengers experience fewer delays and confusion about boarding lines, while passengers with larger items are more likely to choose alternative paths. These insights aid in designing facilities and services that cater to diverse passenger needs. Furthermore, the assessment of post-boarding behaviours highlights the importance of balanced passenger distribution among carriages and strategies to encourage passengers to move further into the train. Preferences for standing/sitting are influenced by factors such as travel frequency, group travel and carrying large items. Designing onboard areas with stable surfaces for standing passengers and improving carriage connections can enhance passenger comfort and satisfaction.
The study also explores passenger perceptions and preferences for train and platform design. Findings indicate a preference for a 2 + 2 seating arrangement and vertical pole handholds. Additionally, passengers prioritise clear signage, real-time occupancy data and wider aisles. Demographic factors such as gender and age group influence preferences for seat removal and platform gap perceptions. Understanding these variations is crucial for rail operators and train manufacturers to tailor their offerings to different passenger segments.
Finally, the study evaluates the relationship between passenger satisfaction and various travel experience attributes. Regression models confirm a linear relationship between overall satisfaction and traveller, trip, service and other attributes. Service attributes are the most significant predictors of overall satisfaction, followed by other attributes, traveller attributes and trip attributes. Recognising the importance of these attributes can help improve service quality and enhance the overall passenger experience.
In conclusion, this research provides a comprehensive overview of passenger behaviours, perceptions and preferences related to train and platform design. The findings contribute to the understanding of key factors influencing passenger experiences, informing the development of strategies and interventions to optimise transportation systems and improve customer satisfaction.
This research offers a theoretical contribution by proposing a systematic approach to evaluating passenger behaviour and provides several practical implications. By understanding what passengers want and need from their train journeys, operators can develop new services, features and amenities that enhance the passenger experience and make train travel a more attractive option. Ultimately, by systematically assessing passenger behaviour, service providers can create more customer-centred services that meet their passengers’ needs, improve satisfaction levels and increase ridership
Radical transparency, WikiLeaks, and the global (dis)order: correcting geopolitical historiography
No full textThis thesis aims to evaluate the contribution of radical transparency, as articulated by WikiLeaks, to understanding information geopolitics, using the practice of US public diplomacy in the Middle East (2006) as a case study. The research assesses to what extent radical transparency activism represents a corrective to conventional diplomatic secrecy and how it contributes to a geopolitical historiographic understanding of the recent past.
The thesis makes an innovative contribution by framing the study of radical transparency activism within the information geopolitics discipline, providing a historiographic review of the Second Lebanon War using, for the first time, private information published by WikiLeaks Cablegate, and contributing to studying the correlation between public information management strategies and conflict resolution within the United Nations Security Council framework. Framed within the information geopolitics and transparency studies inter-disciplinary families, the study understands the US public diplomacy-based military supremacy strategy in the Middle East to have been affected by the 2010 WikiLeaks’ Cablegate non-state radical transparency action – the release of 251,287 US diplomatic cables.
Cablegate’s impact on the academic field was significant but uneven – media and communications scholars seemed unsurprised by the arrival of radical transparency activism. International relations academics debated the action’s legal and ethical ambiguity, sometimes dismissing it as irrelevant in contributing to a better understanding of diplomacy and geopolitics. Nonetheless, most scholars have neglected to mention that we can use radical transparency to review the historiography of recent past events.
Conducted in two phases, the thesis uses historical, content, and discourse analysis on primary and secondary data, including US diplomatic cables released by Cablegate. First, to assess to what extent radical transparency activism represents a corrective to conventional diplomatic secrecy, the researcher delivers a macro analysis aiming to identify the relevance of WikiLeaks’ attempt at disrupting contemporary information environments. The corrective capacity of radical transparency refers to its contribution to enabling the general public to critically examine state actors and their motivations, potentially reducing their susceptibility to the prevailing public diplomacy discourse. Second, the study evaluates the specific historiographic relevance of such disruption to contribute to a better academic understanding of the past, researching at the micro-level what the information provided by Cablegate tells us about US public diplomacy strategies in recent Middle East crises like the 2006 Second Lebanon War and how they affected the UN Security Council capacity to resolve conflict crises. This thesis follows the premise that, even in our information age, the fight for infosphere supremacy is not so much about innovative communication technology as it is about communication content. It is a war of words to persuade public opinion. In the context of information geopolitics, the WikiLeaks Cablegate was a content-based information power action against US public diplomacy (Lonsdale 1999). Instead of directly engaging in countering the US government’s public diplomacy and strategic narrative, WikiLeaks’ strategy consisted of expanding the civilian information environment, allowing access to information traditionally kept away from it by employing conventional diplomatic secrecy.
Nevertheless, for WikiLeaks, Cablegate was not only about the content but about discussing what areas of information should be available for public scrutiny. |I argue that their activism includes a dual strategy – making content available for an investigative journalistic approach to countering superpowers’ public diplomacy and arguing that the secrecy that protected that content before its illegal publication was not legitimate nor justified. Therefore, the purpose of this PhD research must also be dual, focusing both on the significance of WikiLeaks’ actions in contemporary information environments and the impact-by-historiographic-relevance of the content released. This PhD research assessed how valuable this contribution was – how impactful the use of radical transparency in applying information geopolitics, arguing that it acts as a corrective to conventional diplomatic secrecy and, in particular, that WikiLeaks’ Cablegate is relevant in the historiographic review of the US public diplomacy during the Second Lebanon War.
The findings demonstrate that radical transparency represents a valuable geopolitical historiography method to better understand international relations and security.
The material revealed by Cablegate suggests a strong alignment of US and Israel agendas during the Second Lebanon War beyond what US public diplomacy acknowledged. While the alignment of US and Israel security interests has been acknowledged, the WikiLeaks cables add a contemporary confirmation to this fact. This circumstance contributed to unnecessary delays in the UN Security Council’s capacity to produce a definitive ceasefire, leading to avoidable loss of life and the further deterioration of international security.
These revelations contradict the US public diplomacy strategy during the Second Lebanon War, applied with the purpose of managing the conflict for the benefit of national interests instead of resolving it. Accordingly, the study concludes that Cablegate’s radical transparency represents a severe corrective to the US and others’ information supremacy strategies based on conventional diplomatic secrecy in the Middle East and internationally. Transparency contributes to increased legitimacy in the international public opinion arena
A programmatic multistate-BGP manager for multi-domain software defined networking
No full textBorder Gateway Protocol version-4 (BGP-4) is the glue that holds the Internet together by routing Internet traffic around the world. BGP-4 is used between Autonomous Systems (AS) to enable and exchange reachability and routing information. The AS represents separately managed networks that have been allocated public Internet Protocol (IP) number ranges. AS are identified by a unique global IP v4 identifier known as the Autonomous System Number (ASN) in the range of 1-65535 that is allocated by the Internet Assigned Numbers Authority (IANA). An AS network consists of routers, switches and other network devices that are managed and controlled by a single administrative domain. The ASN, utilized in BGP-4 routing, represents the grouping of IP routing prefixes allotted to a single administrative domain. Classless Interdomain-Routing (CIDR) supports hierarchical routing in the Internet backbone. As the Internet has grown, BGP has been updated to tackle challenges, including the growing routing tables, improved load-balancing, BGP-hijacking and security, and AS transit times. One of the major challenges remaining is the BGP convergence delay, which is the time taken for a set of routers to agree on the network topology. Convergence delay has become an issue for large networks due to changing network topologies causing route updates and path failures that cause instability in the network. A network’s instability might cause packet loss or delay, loss of connectivity, and a delay in message transmission.
A novel technique named" MultiState-BGP Manager" is proposed in this research that controls and manages multi-domain SDN networks and decreases the BGP convergence delay. It incorporates Software Defined Networking (SDN) and the BGP-4 protocol. The proposed Manager is an extension of the proposed approach "INDOPRONOS" [3], which covers the previous work limitations regarding the high BGP convergence delay and packet loss. The proposed Manager can provide a flexible and programmatic mechanism to enhance the BGP-4 operation. It can also improve End-To-End service performance, enhance routing efficiency, and Avoid BGP-4 instability, which causes unstable networks. In MultiState-BGP Manager, the SDN ONOS controller has been used to implement automated communication between different domains, reducing the time taken to update network devices. The information exchange used for MultiState-BGP communication was achieved using the BGP-4 community attribute to exchange a Path Priority Number between the two domains (customer and ISP). The ONOS controller's BGP-4 module (SDN-IP application modules) has been modified, and the INDOPRONOS module was used and improved. The Path Priority Number is used to send specific agreed information to trigger a provisioning action in the remote domain. The communication between domains can occur manually or automatically without intervention from the remote domain administrator. The evaluation results of the proposed Manager show an improvement in minimizing the BGP convergence delay by 18 seconds and the packet loss by 3.24% compared to the base approach
Mitigating voltage deviations in a residential distribution grid using predictive control of community battery storage system
No full textThe increasing adoption of Distributed Energy Resources (DERs), including solar photovoltaic (PV) systems and behind-the-meter battery Systems (BTM batteries), has introduced new challenges for Distribution Network Service Providers (DNSPs) in maintaining power reliability. Low voltage (LV) distribution grids with a mix of PV, BTM batteries, and EVs are constantly experiencing power quality issues due to the intermittent nature of renewable energy sources such as rooftop PV. However, managing these power quality issues, such as voltage fluctuations, remains a critical challenge.
This research focuses on real-time control of a community Battery Energy Storage System (BESS) to mitigate voltage deviations resulting from rooftop solar PV's intermittency and generation surplus. A Model Predictive Control (MPC) system is proposed to control the community BESS intelligently.
This thesis addresses two research questions; How does the MPC strategy regulate the community BESS's charging and discharging rates to mitigate voltage fluctuations in the network? And What is the minimum size of the community BESS needed for adequate control? The ideal placement of the BESS along the feeder will also be determined. Furthermore, the identified research gaps indicate the need for further investigations into optimal battery sizing and using complex weather conditions for simulations which is out of the scope of this research.
Here, the simulations are conducted on an LV residential radial network with fourteen households to evaluate the performance of the MPC-controlled BESS located at the beginning or end of the feeder. The simulation results demonstrate that the proposed MPC controller effectively reduces voltage deviations in the LV residential grid compared to a fixed charging schedule. Notably, the MPC-controlled BESS placed at the end of the distribution feeder exhibits the lowest cumulative voltage error (the best performance). Conversely, applying a fixed charging schedule to a BESS placed at the end of the feeder results in the highest cumulative voltage error (the worst performance).
Additionally, the research proposes a minimum size for the community BESS required to implement the MPC. Extensive simulations reveal that the minimum battery size depends on the desired level of voltage deviation that grid operators are willing to accept. In the case of the studied LV residential grid, the minimum battery size that can be used to mitigate the voltage fluctuations while adhering to all the constraints is 43 kWh, with a maximum charging/discharging rate of 10 kW, allowing for a voltage deviation of only 240 ± 6.7 V. These results suggest DNSPs choose the size of the battery based on their desired level of voltage deviation.</p
Optimized resection planning and novel tool development for bone tumour surgery
No full textCorrect surgical treatment of a bone tumour requires that all the diseased tissue be removed from the patient, in one piece, along with a cuff of healthy tissue surrounding the diseased mass to ensure no cancerous cells remains in the surgical site. To achieve this, a surgeon will make cuts in the bone around the tumour. The position and alignment of these cuts are specified in a pre-operative planning stage, where medical images can be used by a clinician to decide where each cutting plane should pass through the bone, its distance from the tumour, and whether it is possible to preserve any nearby critical healthy tissue. This resection plan can also be used for the development of a reconstructive solution for the affected region, which returns function and structure to the compromised anatomy, and improves the post-operative quality of life to the patient.
Preparing these resection plans can be a technically demanding and time-consuming process, with only limited assistance available to clinicians through software and virtual tools. Positive treatment outcomes are heavily dependent on good quality resection plan, which itself relies on a clinician's experience with similar cases, the availability of medical imaging software capable of planning a bone tumour resection, as well as the user's familiarity with that software. Measurements can be performed on a resected mass post-operatively to check whether the disease has been completely removed from the surgical site, and the consistency between a resection plan to how it was performed. However there are no quantifiable measures of a resection plan itself, and the quality of a resection plan is largely a subjective assessment made by the surgeon, based primarily on whether the approach will result in removal of all diseased tissue.
The absence of a standardized measure of quality for a resection plan, the aggressive nature of malignant bone tumours, and the importance of timely treatment limits a clinician's opportunity to consider multiple resection plans for a single patient. Additionally, proposing elaborate resection plans to preserve critical anatomy is a risky proposition, as novel surgical approaches may result in some unforseen complications, meaning resection plans similar to others with a history of success are deemed less likely to fail, and are therefore the typical treatment approach.
Recent technological advances of additively manufactured patient-specific implants and robot-assisted orthopaedic surgery are on the cusp of being integrated into the bone tumour surgical treatment workflow, and may provide both intraoperative and post-operative improvements. However, in order to maximize the capabilities of these technologies, the planning stage must be standardized such that the selected surgical approach can be quantified, and the plan specifying the intraoperative execution and reconstructive solution is one which provides an optimal post-operative treatment outcome. Furthermore, proposing any novel surgical approach would require the development of specialized tooling to facilitate the optimal treatment.
This thesis reports the research performed in quantifying bone tumours and their resection plans; a method for automatically generating planar and elaborate resection plans optimized for minimum healthy bone loss; and novel tool designs to assist in performing the proposed optimized resections.
A selection of 20 anonymized osteosarcoma and chondrosarcoma within the femur and tibia are used to develop consistent and comparable measurements of bone tumours, whereby a tumour's size is measured volumetrically, and its infiltration and shape are measured as a percentage of that volume. In collaboration with an experienced surgeon, a resection plan is manually prepared for each tumour case, using software tailored for bone tumour resections. A measurement is proposed for the manually-prepared resection plans, independent of the tumour size, serving as a measure of the resection plan efficiency.
Using the bone waste value from the manually-prepared resection plans as a baseline for each case, two general methods of optimizing resection plans are developed, the first for planar cuts, the second for more elaborate, non-planar geometries. A stochastic optimization approach (particle swarm) configures the position and alignment of a resection plan defined by the tumour geometry data, by minimizing healthy bone collaterally removed with the tumour (bone waste). For planar resections, a validation check on the alignment of the cutting planes ensures all resection plans can be extracted from the bone. Both methods are found to improve upon the bone waste of the manually-prepared resection plans. More generally, it is found that the more a resection plan conforms to the curvature of the tumour, the lower the bone waste, and that using more than five cutting planes results in diminishing returns to bone waste.
To assist with the treatment workflow, a system of selecting the optimal surgical approach is described where each resection plan is scored by its intraoperative complexity and the benefit provided to the patient. Factors of each resection plan such as the number of cutting planes, the accessibility of each cut, and the ease of implanting the reconstructive solution contributed to a two value score, allowing for an objective comparison of multiple resection plans for a single tumour.
Finally, two novel tool designs are investigated to facilitate curved and planar cuts underneath a tumour. First, a tool is presented with a 2 degree-of-freedom kinematic structure in which the cutting tip of a robotic linkage is bound to the surface of a parametrically-defined torus. Second, an investigation into cutting behaviour of wire saws is conducted, and a prototype tool for performing a reciprocating sawing action underneath a volume of material is proposed.
The future direction of this work will focus on optimizing resection plan generation, development of novel resection geometries, application to tumours in different anatomy, integration with surgical robotics and additive manufacturing, and clinical evaluation of the optimized resection plans