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Yes / The reliability of delivering packets through multi-hop intermediate nodes is a significant issue in the mobile ad hoc networks (MANETs). The distributed mobile nodes establish connections to form the MANET, which may include selfish and misbehaving nodes. Recommendation based trust management has been proposed in the literature as a mechanism to filter out the misbehaving nodes while searching for a packet delivery route. However, building a trust model that relies on the recommendations from other nodes in the network is vulnerable to the possible dishonest behaviour, such as bad-mouthing, ballot-stuffing, and collusion, of the recommending nodes. . This paper investigates the problems of attacks posed by misbehaving nodes while propagating recommendations in the existing trust models. We propose a recommendation based trust model with a defence scheme that utilises clustering technique to dynamically filter attacks related to dishonest recommendations within certain time based on number of interactions, compatibility of information and node closeness. The model is empirically tested in several mobile and disconnected topologies in which nodes experience changes in their neighbourhoods and consequently face frequent route changes. The empirical analysis demonstrates robustness and accuracy of the trust model in a dynamic MANET environment.

A mobile ad hoc network (MANET) is a wireless network that uses multi-hop peer-to-peer routing instead of static network infrastructure to provide network connectivity. MANETs have applications in rapidly deployed and dynamic military and civilian systems. The network topology in a MANET usually changes with time. Therefore, there are new challenges for routing protocols in MANETs since traditional routing protocols may not be suitable for MANETs. For example, some assumptions used by these protocols are not valid in MANETs or some protocols cannot efficiently handle topology changes. Researchers are designing new MANET routing protocols and comparing and improving existing MANET routing protocols before any routing protocols are standardized using simulations. However, the simulation results from different research groups are not consistent with each other. This is because of a lack of consistency in MANET routing protocol models and application environments, including networking and user traffic profiles. Therefore, the simulation scenarios are not equitable for all protocols and conclusions cannot be generalized. Furthermore, it is difficult for one to choose a proper routing protocol for a given MANET application. According to the aforementioned issues, my Ph.D. research focuses on MANET routing protocols. Specifically, my contributions include the characterization of differ- ent routing protocols using a novel systematic relay node set (RNS) framework, design of a new routing protocol for MANETs, a study of node mobility, including a quantitative study of link lifetime in a MANET and an adaptive interval scheme based on a novel neighbor stability criterion, improvements of a widely-used network simulator and corresponding protocol implementations, design and development of a novel emulation test bed, evaluation of MANET routing protocols through simulations, verification of our routing protocol using emulation, and development of guidelines for one to choose proper MANET routing protocols for particular MANET applications. Our study shows that reactive protocols do not always have low control overhead, as people tend to think. The control overhead for reactive protocols is more sensitive to the traffic load, in terms of the number of traffic flows, and mobility, in terms of link connectivity change rates, than other protocols. Therefore, reactive protocols may only be suitable for MANETs with small number of traffic loads and small link connectivity change rates. We also demonstrated that it is feasible to maintain full network topology in a MANET with low control overhead. This dissertation summarizes all the aforementioned methodologies and corresponding applications we developed concerning MANET routing protocols. / Ph. D.

With the proliferation of fairly powerful mobile devices and ubiquitous wireless technology, traditional mobile ad hoc networks (MANETs) now migrate into a new era of service-oriented MANETs wherein a node can provide and receive service from other nodes it encounters and interacts with. This dissertation research concerns trust management and its applications for service-oriented MANETs to answer the challenges of MANET environments, including no centralized authority, dynamically changing topology, limited bandwidth and battery power, limited observations, unreliable communication, and the presence of malicious nodes who act to break the system functionality as well as selfish nodes who act to maximize their own gain. We propose a context-aware trust management model called CATrust for service-oriented ad hoc networks. The novelty of our design lies in the use of logit regression to dynamically estimate trustworthiness of a service provider based on its service behavior patterns in a context environment, treating channel conditions, node status, service payoff, and social disposition as 'context' information. We develop a recommendation filtering mechanism to effectively screen out false recommendations even in extremely hostile environments in which the majority recommenders are malicious. We demonstrate desirable convergence, accuracy, and resiliency properties of CATrust. We also demonstrate that CATrust outperforms contemporary peer-to-peer and Internet of Things trust models in terms of service trust prediction accuracy against collusion recommendation attacks. We validate the design of trust-based service management based on CATrust with a node-to-service composition and binding MANET application and a node-to-task assignment MANET application with multi-objective optimization (MOO) requirements. For either application, we propose a trust-based algorithm to effectively filter out malicious nodes exhibiting various attack behaviors by penalizing them with trust loss, which ultimately leads to high user satisfaction. Our trust-based algorithm is efficient with polynomial runtime complexity while achieving a close-to-optimal solution. We demonstrate that our trust-based algorithm built on CATrust outperforms a non-trust-based counterpart using blacklisting techniques and trust-based counterparts built on contemporary peer-to-peer trust protocols. We also develop a dynamic table-lookup method to apply the best trust model parameter settings upon detection of rapid MANET environment changes to maximize MOO performance. / Ph. D.

Policy based network management is a promising approach for provisioning and management of quality of service in mobile ad hoc networks. In this thesis, we focus on performance evaluation of this approach in context of the amount of service received by certain nodes called policy execution points (PEPs) or policy clients from certain specialized nodes called the policy decision points (PDPs) or policy servers. We develop analytical models for the study of the system behavior under two scenarios; a simple Markovian scenario where we assume that the random variables associated with system processes follow an exponential distribution and a more complex non-Markovian scenario where we model the system processes according to general distribution functions as observed through simulation. We illustrate that the simplified Markovian model provides a reasonable indication of the trend of the service availability seen by policy clients and highlight the need for an exact analysis of the system without relying on Poisson assumptions for system processes. In the case of the more exact non-Markovian analysis, we show that our model gives a close approximation to the values obtained via empirical methods. Stochastic Petri Nets are used as performance evaluation tools in development and analysis of these system models. / Master of Science

The wireless technology of today provides combat systems with the potential to communicate mission critical data to every asset involved in the operation. In such a dynamic environment, the network must be able maintain communication by adapting to subsystems moving relative to each other. A theoretical and experimental foundation is developed that allows an autonomous ground vehicle to serve as an adaptive communication node in a larger network. The vehicle may perform other functions, but its primary role is to constantly reposition itself to maintain optimal link quality for network communication. Experimentation with existing wireless network hardware and software led to the development, implementation, and analysis of two main concepts that provided a signal optimization solution. The first attracts the communication ground vehicle to the network subsystems with weaker links using a vector summation of the signal-to-noise ratio and network subsystem position. This concept continuously generates a desired waypoint for repositioning the ground vehicle. The second concept uses a-priori GIS data to evaluate the desired vehicle waypoint determined by the vector sum. The GIS data is used primarily for evaluating the viewshed, or line-of-sight, between two network subsystems using elevation data. However, infrastructure and ground cover data are also considered in navigation planning. Both concepts prove to be powerful tools for effective autonomous repositioning for maximizing the communication link quality. / Master of Science

Controles de segurança, também chamados de mecanismos de proteção, voltados para previsão e detecção de eventos indesejados são cada vez mais empregados em ambientes de Tecnologia da Informação (TI). O pouco entendimento sobre as características dos eventos indesejados que agem nos sistemas e a baixa compatibilidade existente entre os diversos mecanismos de proteção são problemas que se destacam neste tipo de cenário. Diferentes configurações dificultam a combinação dos resultados destes mecanismos e raramente dois ou mais controles de segurança se complementam. Por esse motivo, o agrupamento entre mecanismos de detecção e de previsão não é trivialmente resolvido. Neste trabalho é proposta uma arquitetura, denominada de Arquitetura Estratégica de Agrupamento - Strategic Grouping Architecture (SGA) - para agrupamento de controles de segurança voltados para detecção e/ou previsão, que tem como base a busca de um equilíbrio entre as configurações e os resultados individuais de cada mecanismo de proteção envolvido. Para alcançar este equilíbrio a arquitetura proposta divide a análise dos eventos (legítimos e maliciosos) que passam pelos controles de segurança em dois níveis de abstração: o técnico, onde são coletadas as configurações e os resultados dos controles de segurança; e o estratégico, onde os dados obtidos no nível técnico são analisados por meio de barganhas cooperativas irrestritas - Unrestricted Cooperative Bargains (UCB), conceito proveniente da Teoria dos Jogos, que busca a otimização e equilíbrio entre resultados. Justamente por ser realizada em um nível de abstração diferente, a análise gerada pelo SGA identifica a influência que cada configuração exerce nos resultados agrupados. Para explorar a capacidade da arquitetura proposta, dois experimentos, bastante diferentes, que envolvem a ação de eventos indesejados em ambientes de TI são conduzidos. Os resultados obtidos mostram a viabilidade do agrupamento de controles de segurança de detecção e previsão e a possibilidade do uso do SGA em outros ambientes, que não estejam necessariamente ligados à segurança de TI. Baseada na literatura científica a validação do SGA consiste de uma transformação prévia na categoria dos jogos estratégicos usados - cooperativos para não-cooperativos - e na busca de situações como o Equilíbrio de Nash (EN) e o ótimo de Pareto, que indicam os melhores resultados de um jogo. / Security controls, also called protection mechanisms, focused on forecasting and detection of unwanted events are increasingly employed in Information Technology (IT) environments. The little understanding about the characteristics of unwanted events which act on the systems and the low rate of compatibility among several protection mechanisms are both problems that arise in that scenario. Different settings make difficult combining the results of these mechanisms and two or more controls rarely complement each other. Due to that, grouping mechanisms of detection and forecasting is not a trivial matter. In this work a framework called Strategic Grouping Architecture (SGA) is proposed to grouping security controls focused on detection and/or forecasting. SGA is based on the search for equilibrium between the settings and the individual results of each protection mechanism involved. In order to reach this equilibrium the proposed framework divide the analysis of events (legitimates and malicious) which go through the security controls in two abstract levels: the technical level, where the settings and the results of security controls are collected; and the strategic level, where the data obtained in the technical level are analyzed through Unrestricted Cooperative Bargains (UCB), concept from Game Theory that seeks to optimize and balance the results. Precisely because it is performed on a different level of abstraction, the analysis generated by the SGA identifies the influence that each setting has on the clustered results. In order to exploit the capability of the proposed architecture, two experiments, quite different, involving the action of unwanted events in IT environments, are conducted. The obtained findings show the feasibility of grouping detection and forecasting security controls and the possibility of using the SGA in other environments that are not necessarily related to IT security. Based on scientific literature SGA validation consists of a previous transformation in the category of strategy games used - cooperative to non-cooperative - and the search for situations such as the Nash Equilibrium (NE) and the Pareto optimal, indicating the best results a game.

Controles de segurança, também chamados de mecanismos de proteção, voltados para previsão e detecção de eventos indesejados são cada vez mais empregados em ambientes de Tecnologia da Informação (TI). O pouco entendimento sobre as características dos eventos indesejados que agem nos sistemas e a baixa compatibilidade existente entre os diversos mecanismos de proteção são problemas que se destacam neste tipo de cenário. Diferentes configurações dificultam a combinação dos resultados destes mecanismos e raramente dois ou mais controles de segurança se complementam. Por esse motivo, o agrupamento entre mecanismos de detecção e de previsão não é trivialmente resolvido. Neste trabalho é proposta uma arquitetura, denominada de Arquitetura Estratégica de Agrupamento - Strategic Grouping Architecture (SGA) - para agrupamento de controles de segurança voltados para detecção e/ou previsão, que tem como base a busca de um equilíbrio entre as configurações e os resultados individuais de cada mecanismo de proteção envolvido. Para alcançar este equilíbrio a arquitetura proposta divide a análise dos eventos (legítimos e maliciosos) que passam pelos controles de segurança em dois níveis de abstração: o técnico, onde são coletadas as configurações e os resultados dos controles de segurança; e o estratégico, onde os dados obtidos no nível técnico são analisados por meio de barganhas cooperativas irrestritas - Unrestricted Cooperative Bargains (UCB), conceito proveniente da Teoria dos Jogos, que busca a otimização e equilíbrio entre resultados. Justamente por ser realizada em um nível de abstração diferente, a análise gerada pelo SGA identifica a influência que cada configuração exerce nos resultados agrupados. Para explorar a capacidade da arquitetura proposta, dois experimentos, bastante diferentes, que envolvem a ação de eventos indesejados em ambientes de TI são conduzidos. Os resultados obtidos mostram a viabilidade do agrupamento de controles de segurança de detecção e previsão e a possibilidade do uso do SGA em outros ambientes, que não estejam necessariamente ligados à segurança de TI. Baseada na literatura científica a validação do SGA consiste de uma transformação prévia na categoria dos jogos estratégicos usados - cooperativos para não-cooperativos - e na busca de situações como o Equilíbrio de Nash (EN) e o ótimo de Pareto, que indicam os melhores resultados de um jogo. / Security controls, also called protection mechanisms, focused on forecasting and detection of unwanted events are increasingly employed in Information Technology (IT) environments. The little understanding about the characteristics of unwanted events which act on the systems and the low rate of compatibility among several protection mechanisms are both problems that arise in that scenario. Different settings make difficult combining the results of these mechanisms and two or more controls rarely complement each other. Due to that, grouping mechanisms of detection and forecasting is not a trivial matter. In this work a framework called Strategic Grouping Architecture (SGA) is proposed to grouping security controls focused on detection and/or forecasting. SGA is based on the search for equilibrium between the settings and the individual results of each protection mechanism involved. In order to reach this equilibrium the proposed framework divide the analysis of events (legitimates and malicious) which go through the security controls in two abstract levels: the technical level, where the settings and the results of security controls are collected; and the strategic level, where the data obtained in the technical level are analyzed through Unrestricted Cooperative Bargains (UCB), concept from Game Theory that seeks to optimize and balance the results. Precisely because it is performed on a different level of abstraction, the analysis generated by the SGA identifies the influence that each setting has on the clustered results. In order to exploit the capability of the proposed architecture, two experiments, quite different, involving the action of unwanted events in IT environments, are conducted. The obtained findings show the feasibility of grouping detection and forecasting security controls and the possibility of using the SGA in other environments that are not necessarily related to IT security. Based on scientific literature SGA validation consists of a previous transformation in the category of strategy games used - cooperative to non-cooperative - and the search for situations such as the Nash Equilibrium (NE) and the Pareto optimal, indicating the best results a game.

In urban search and rescue (USAR) operations, there is a considerable amount of danger faced by rescuers. The use of mobile robots can alleviate this issue. Coordinating the search effort is made more difficult by the communication issues typically faced in these environments, such that communication is often restricted. With small numbers of robots, it is necessary to break communication links in order to explore the entire environment. The robots can be viewed as a broken ad hoc network, relying on opportunistic contact in order to share data. In order to minimise overheads when exchanging data, a novel algorithm for data exchange has been created which maintains the propagation speed of flooding while reducing overheads. Since the rescue workers outside of the structure need to know the location of any victims, the task of finding their locations is two parted: 1) to locate the victims (Search Time), and 2) to get this data outside the structure (Delay Time). Communication with the outside is assumed to be performed by a static robot designated as the Command Station. Since it is unlikely that there will be sufficient robots to provide full communications coverage of the area, robots that discover victims are faced with the difficult decision of whether they should continue searching or return with the victim data. We investigate a variety of search techniques and see how the application of biological foraging models can help to streamline the search process, while we have also implemented an opportunistic network to ensure that data are shared whenever robots come within line of sight of each other or the Command Station. We examine this trade-off between performing a search and communicating the results.