iBUST: An intelligent behavioural trust model for securing industrial cyber-physical systems

To meet the demand of the world's largest population, smart manufacturing has accelerated the adoption of smart factories—where autonomous and cooperative instruments across all levels of production and logistics networks are integrated through a Cyber-Physical Production System (CPPS). However, these networks are comprised of various heterogeneous devices with varying computational power and memory capabilities. As a result, many secure communication protocols – that demand considerably high computational power and memory – can not be verbatim employed on these networks, and thereby, leaving them more vulnerable to security threats and attacks over conventional networks. These threats can largely be tackled by employing a Trust Management Model (TMM) by exploiting the behavioural patterns of nodes to identify their trust class. In this context, ML-based models are best suited due to their ability to capture hidden patterns in data, learning and improving the pattern detection accuracy over time to counteract and tackle threats of a dynamic nature, which is absent in most of the conventional models. However, among the existing ML-based solutions in detecting attack patterns, many of them are computationally expensive, require a long training time, and a considerably large amount of training data—which are seldom available. An aid to this is the association rule learning (ARL) paradigm, whose models are computationally inexpensive and do not require a long training time. Therefore, this paper proposes an ARL-based intelligent Behavioural Trust Model (iBUST) for securing the CPPS. For this intelligent TMM, a variant of Frequency Pattern Growth (FP-Growth), called enhanced FP-Growth (EFP-Growth) algorithm is developed by altering the internal data structures for faster execution and by developing a modified exponential decay function (MEDF) to automatically calculate minimum supports for adapting trust evolution characteristics. In addition, a new optimisation model for finding optimum parameter values in the MEDF and an algorithm for transmuting a 1D quantitative feature into a respective categorical feature are developed to facilitate the model. Afterwards, the trust class of an object is identified employing the Naïve Bayes classifier. This proposed model is evaluated on a trust evolution-supported experimental environment along with other compared models taking a benchmark dataset into consideration, where it outperforms its counterparts

Resource Allocation in Next Generation Mobile Networks

The increasing heterogeneity of the mobile network infrastructure together with the explosively growing demand for bandwidth-hungry services with diverse quality of service (QoS) requirements leads to a degradation in the performance of traditional networks. To address this issue in next-generation mobile networks (NGMN), various technologies such as software-defined networking (SDN), network function virtualization (NFV), mobile edge/cloud computing (MEC/MCC), non-terrestrial networks (NTN), and edge ML are essential. Towards this direction, an optimal allocation and management of heterogeneous network resources to achieve the required low latency, energy efficiency, high reliability, enhanced coverage and connectivity, etc. is a key challenge to be solved urgently. In this dissertation, we address four critical and challenging resource allocation problems in NGMN and propose efficient solutions to tackle them. In the first part, we address the network slice resource provisioning problem in NGMN for delivering a wide range of services promised by 5G systems and beyond, including enhanced mobile broadband (eMBB), ultra-reliable and low latency (URLLC), and massive machine-type communication (mMTC). Network slicing is one of the major solutions needed to meet the differentiated service requirements of NGMN, under one common network infrastructure. Towards robust mobile network slicing, we propose a novel approach for the end-to-end (E2E) resource allocation in a realistic scenario with uncertainty in slices' demands using stochastic programming. The effectiveness of our proposed methodology is validated through simulations. Despite the significant benefits that network slicing has demonstrated to bring to the management and performance of NGMN, the real-time response required by many emerging delay-sensitive applications, such as autonomous driving, remote health, and smart manufacturing, necessitates the integration of multi-access edge computing (MEC) into network sliding for 5G networks and beyond. To this end, we discuss a novel collaborative cloud-edge-local computation offloading scheme in the next two parts of this dissertation. The first part studies the problem from the perspective of the infrastructure provider and shows the effectiveness of the proposed approach in addressing the rising number of latency-sensitive services and improving energy efficiency which has become a primary concern in NGMN. Moreover, taking into account the perspective of application (higher layer), we propose a novel framework for the optimal reservation of resources by applications, resulting in significant resource savings and reduced cost. The proposed method utilizes application-specific resource coupling relationships modeled using linear regression analysis. We further improve this approach by using Reinforcement Learning to automatically derive resource coupling functions in dynamic environments. Enhanced connectivity and coverage are other key objectives of NGMN. In this regard, unmanned aerial vehicles (UAVs) have been extensively utilized to provide wireless connectivity in rural and under-developed areas, enhance network capacity, and provide support for peaks or unexpected surges in user demand. The popularity of UAVs in such scenarios is mainly owing to their fast deployment, cost-efficiency, and superior communication performance resulting from line-of-sight (LoS)-dominated wireless channels. In the fifth part of this dissertation, we formulate the problem of aerial platform resource allocation and traffic routing in multi-UAV relaying systems wherein UAVs are deployed as flying base stations. Our proposed solution is shown to improve the supported traffic with minimum deployment cost. Moreover, the new breed of intelligent devices and applications such as UAVs, AR/VR, remote health, autonomous vehicles, etc. requires a novel paradigm shift from traditional cloud-based learning to a distributed, low-latency, and reliable ML at the network edge. To this end, Federated Learning (FL) has been proposed as a new learning scheme that enables devices to collaboratively learn a shared model while keeping the training data locally. However, the performance of FL is significantly affected by various security threats such as data and model poisoning attacks. Towards reliable edge learning, in the last part of this dissertation, we propose trust as a metric to measure the trustworthiness of the FL agents and thereby enhance the reliability of FL