A trust framework for peer-to-peer interaction in ad hoc networks

PhDAs a wider public is increasingly adopting mobile devices with diverse applications, the idea of who to trust while on the move becomes a crucial one. The need to find dependable partners to interact is further exacerbated in situations where one finds oneself out of the range of backbone structures such as wireless base stations or cellular networks. One solution is to generate self-started networks, a variant of which is the ad hoc network that promotes peer-to-peer networking. The work in this thesis is aimed at defining a framework for such an ad hoc network that provides ways for participants to distinguish and collaborate with their most trustworthy neighbours. In this framework, entities create the ability to generate trust information by directly observing the behaviour of their peers. Such trust information is also shared in order to assist those entities in situations where prior interactions with their target peers may not have existed. The key novelty points of the framework focus on aggregating the trust evaluation process around the most trustworthy nodes thereby creating a hierarchy of nodes that are distinguished by the class, defined by cluster heads, to which they belong. Furthermore, the impact of such a framework in generating additional overheads for the network is minimised through the use of clusters. By design, the framework also houses a rule-based mechanism to thwart misbehaving behaviour or non-cooperation. Key performance indicators are also defined within this work that allow a framework to be quickly analysed through snapshot data, a concept analogous to those used within financial circles when assessing companies. This is also a novel point that may provide the basis for directly comparing models with different underlying technologies. The end result is a trust framework that fully meets the basic requirements for a sustainable model of trust that can be developed onto an ad hoc network and that provides enhancements in efficiency (using clustering) and trust performance

Ubiquitous Computing

The aim of this book is to give a treatment of the actively developed domain of Ubiquitous computing. Originally proposed by Mark D. Weiser, the concept of Ubiquitous computing enables a real-time global sensing, context-aware informational retrieval, multi-modal interaction with the user and enhanced visualization capabilities. In effect, Ubiquitous computing environments give extremely new and futuristic abilities to look at and interact with our habitat at any time and from anywhere. In that domain, researchers are confronted with many foundational, technological and engineering issues which were not known before. Detailed cross-disciplinary coverage of these issues is really needed today for further progress and widening of application range. This book collects twelve original works of researchers from eleven countries, which are clustered into four sections: Foundations, Security and Privacy, Integration and Middleware, Practical Applications

Discrete Event Simulations

Considered by many authors as a technique for modelling stochastic, dynamic and discretely evolving systems, this technique has gained widespread acceptance among the practitioners who want to represent and improve complex systems. Since DES is a technique applied in incredibly different areas, this book reflects many different points of view about DES, thus, all authors describe how it is understood and applied within their context of work, providing an extensive understanding of what DES is. It can be said that the name of the book itself reflects the plurality that these points of view represent. The book embraces a number of topics covering theory, methods and applications to a wide range of sectors and problem areas that have been categorised into five groups. As well as the previously explained variety of points of view concerning DES, there is one additional thing to remark about this book: its richness when talking about actual data or actual data based analysis. When most academic areas are lacking application cases, roughly the half part of the chapters included in this book deal with actual problems or at least are based on actual data. Thus, the editor firmly believes that this book will be interesting for both beginners and practitioners in the area of DES

Self-organising smart grid architectures for cyber-security

PhD ThesisCurrent conventional power systems consist of large-scale centralised generation and unidirectional power flow from generation to demand. This vision for power system design is being challenged by the need to satisfy the energy trilemma, as the system is required to be sustainable, available and secure. Emerging technologies are restructuring the power system; the addition of distributed generation, energy storage and active participation of customers are changing the roles and requirements of the distribution network. Increased controllability and monitoring requirements combined with an increase in controllable technologies has played a pivotal role in the transition towards smart grids. The smart grid concept features a large amount of sensing and monitoring equipment sharing large volumes of information. This increased reliance on the ICT infrastructure, raises the importance of cyber-security due to the number of vulnerabilities which can be exploited by an adversary. The aim of this research was to address the issue of cyber-security within a smart grid context through the application of self-organising communication architectures. The work examined the relevance and potential for self-organisation when performing voltage control in the presence of a denial of service attack event. The devised self-organising architecture used techniques adapted from a range of research domains including underwater sensor networks, wireless communications and smart-vehicle tracking applications. These components were redesigned for a smart grid application and supported by the development of a fuzzy based decision making engine. A multi-agent system was selected as the source platform for delivering the self-organising architecture The application of self-organisation for cyber-security within a smart grid context is a novel research area and one which presents a wide range of potential benefits for a future power system. The results indicated that the developed self-organising architecture was able to avoid control deterioration during an attack event involving up to 24% of the customer population. Furthermore, the system also reduces the communication load on the agents involved in the architecture and demonstrated wider reaching benefits beyond performing voltage control

Pro-collaborative mobile systems in next generation IP networks

Computing system designs of today take on either the interactive or the proactive form. Motivated by the user’s desire to make his/her computing experience more intelligent and personalised, the progression from interactive (human-centred) to proactive (human-supervised) is evident. It can be observed that current research mainly emphasises the user as the dominant focus of a user-system interaction. Consider a model that we called the opponent-process model. It contains two processes, one representing the user and the other the system, where both processes are capable of dominating each other, though working collaboratively towards a predefined task. We argue the necessity to design computing systems which are balanced in this model, such that the system process, at times, becomes the dominant process. We refer to this as the pro-collaborative design form. We dissect mobility into the notion of a nomadic user and the notion of a nomadic system. The examination into the nomadic user problem space reveals the potential for applying the pro-collaborative approach in optimising handoff management. Significant performance advantages can be obtained with our proposed S-MIP framework, based on the pro-collaborative design, when compared with established handoff latency optimisation schemes. The key differentiator lies in its indicative approach in addressing handoff ambiguity. Instead of passively anticipating through prediction as to when a mobile user might cross network boundaries (user-dominant), the system actively indicates to the user when, where and how to handoff (system-dominant). This eliminates the handoff ambiguity. Regarding the notion of a nomadic system, that is, the ability to move services offered by computing systems to arbitrary points in the Internet, we explore the idea of the dynamic extension of network services to a mobile user on-demand. Based on the pro-collaborative form, we develop the METAMORPHOSE architecture which facilitates such a dynamic service extension. By assuming the proliferation of programmable network switches and computational resources within the Internet, we re-examine how ‘loose’ service agreements between network services providers can be, to achieve such borderless moving-service offerings. The viability of the pro-collaborative form is reflected through our design and implementation of protocols and architectures which address the notion of nomadic user and nomadic system

On uncoordinated wireless ad-hoc networks:data dissemination over WIFI and cross-layer optimization for ultra wide band impulse radio

Emerging pervasive wireless networks, pocket switched networks, Internet of things, vehicular networks and even sensor networks present very challenging communication circumstances. They might involve up to several hundreds of wireless devices with mobility and intermittent connectivity. Centralized coordination in such networks is practically unfeasible. We deal with these challenge using two potential technologies: WIFI and Ultra Wide Band (UWB) Impulse Radio (IR) for medium and short communication range, respectively. Our main goal is to improve the communication performance and to make these networks sustainable in the absence of a centralized coordination. With WIFI, the goal is to design an environment-oblivious data dissemination protocol that holds in highly dynamic unpredictable wireless ad-hoc networks. To this end, we propose a complete design for a scope limited, multi-hop broadcast middleware, which is adapted to the variability of the ad-hoc environment and works in unlimited ad-hoc networks such as a crowd in a city, or car passengers in a busy highway system. We address practical problems posed by: the impossibility of setting the TTL correctly at all times, the poor performance of multiple access protocols in broadcast mode, flow control when there is no acknowledgment and scheduling of multiple concurrent broadcasts. Our design, called "Self Limiting Epidemic Forwarding" (SLEF), automatically adapts its behavior from single hop MAC layer broadcast to epidemic forwarding when the environment changes from being extremely dense to sparse, sporadically connected. A main feature of SLEF is a non-classical manipulation of the TTL field, which combines the usual decrement-when-sending to many very small decrements when receiving. Then, we identify vulnerabilities that are specific to epidemic forwarding. We address broadcast applications over wireless ad-hoc networks. Epidemic forwarding employs several mechanisms such as forwarding factor control and spread control, and each of them can be implemented using alternative methods. Thus, the existence of vulnerabilities is highly dependent on the methods used. We examine the links between them. We classify vulnerabilities into two categories: malicious and rational. We examine the effect of the attacks according to the number of attackers and the different network settings such as density, mobility and congestion. We show that malicious attacks are hard to achieve and their effects are scenario-dependent. In contrast, rational attackers always obtain a significant benefit. The evaluation is carried out using detailed realistic simulations over networks with up to 1000 nodes. We consider static scenarios, as well as vehicular networks. In order to validate our simulation results, we build a solid and widely adaptable experimental testbed for wireless networks. It is composed of 57 mobile wireless nodes equipped with WIFI interface. The adopted platform is OpenWrt, a Linux-like firmware, which makes the testbed robust and easily configurable. With UWB IR, the main problem we deal with is the presence of uncontrolled interference. Indeed, similarly to Code Division Multiple Access (CDMA) systems, signal acquisition with UWB IR signaling requires power control in the presence of interferers, which is very expensive in an uncoordinated system. We solve this problem through a cross-layer optimization: We propose a new signal acquisition method that is independent of the received signal power and we adapt the MAC layer accordingly. Our signal acquisition method is designed to solve the IUI (Inter-User Interference) that occurs in some ad-hoc networks where concurrent transmissions are allowed with heterogeneous power levels. In such scenarios, the conventional detection method, which is based on correlating the received IR signal with a Template Pulse Train (TPT), does not always perform well. The complexity of our proposal is similar to that of the conventional method. We evaluate its performance with the Line Of Sight (LOS) and the Non-LOS (NLOS) office indoor-channel models proposed by the IEEE P802.15.4a study group and find that the improvement is significant. We also investigate the particular case where the concurrent transmissions have the same time-hopping code, and we show that it does not result in collision, such scenarios appear in ad-hoc networks that employ a common code for control or broadcast purposes. At the MAC level, we focus only on one component of a MAC layer, which is the sleeping mode that could be added to any MAC layer proposal adequate to UWB IR. We are motivated by the low power consumption constraint required by the potential applications. We identify the design elements that should be taken into account for an optimal design for a sleeping protocol for UWB-IR such as the possibility of transmitting concurrently without collision and the power consumption model of the hardware behind which is completely different than with the narrow-band signaling. Then, we design two sleeping protocols for centralized and decentralized ad-hoc networks, respectively. We evaluate their performance analytically with the adopted metric being the average life-time of the wireless nodes