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

Video communication is an important application in wireless ad hoc network environment. Although current off-the-shelf video communication software would work for ad hoc network operating under stable conditions (e.g., extremely low link and node failures), video communications for ad hoc network operating under extreme conditions remain a challenging problem. This is because traditional video codec, either single steam or layered video, requires at least one relatively stable path between source and destination nodes. Recent advances in multiple description (MD) video coding have opened up new possibilities to offer video communications over ad hoc networks. In this thesis, we perform a systematic study on MD video for ad hoc networks. The theoretical foundation of this research is based on an application-centric approach to formulate a cross-layer multipath routing problem that minimizes the application layer video distortion. The solution procedure to this complex optimization problem is based on the so-called Genetic Algorithm (GA). The theoretical results have been documented in [7] and will be reviewed in Chapter 2. Although the theoretical foundation for MD video over dynamic ad hoc networks has been laid, there remains a lot of skepticisms in the research community on whether such cross-layer optimal routing can be implemented in practice. To fill this gap, this thesis is devoted to the experimental research (or proof-of-concept) for the work in [7]. Our approach is to design and implement an emulation testbed where we can actually implement the ideas and algorithms proposed in [7] in a controlled laboratory setting. The highlights of our experimental research include: 1. A testbed that emulates three properties of a wireless ad hoc network: topology, link success probability, and link bandwidth; 2. A source routing implementation that can easily support comparative study between the proposed GA-based routing with other routing schemes under different network conditions; 3. A modified H.263+ video codec that employs Unequal Error Protection (UEP) approach to generate MD video; 4. Implementation of three experiments that • compared the GA-based routing with existing technologies (NetMeeting video conferencing plus AODV routing); • compared our GA-based routing with network-centric routing schemes (two-disjoint paths routing); • proved that our approach has great potential in supporting video communications in wireless ad hoc networks. 5. Experimental results that show the proposed cross-layer optimization significantly outperforms the current off-the-shelf technologies, and that the proposed cross-layer optimization provides much better performance than network-centric routing schemes in supporting routing of MD video. In summary, the experimental research in this thesis has demonstrated that a cross-layer multipath routing algorithm can be practically implemented in a dynamic ad hoc network to support video communications. / Master of Science

Friginal López, J. (2013). An experimental methodology to evaluate the resilience of ad hoc routing protocols [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18483

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.

Os veículos aéreos não tripulados (VANTs) vêm apresentando destaque crescente no setor aeronáutico mundial, tanto no desenvolvimento dos mesmos quanto nas diferentes aplicações desses veículos, devido ao seu grande potencial de utilização. Em muitas aplicações, a utilização de múltiplos VANTs apresenta várias vantagens sobre um VANT sozinho. No entanto, o agrupamento pode experimentar problemas inerentes à comunicação sem fio, podendo originar novos problemas como inviabilizar a coordenação e a execução cooperativa de uma missão, por exemplo. Em um cenário não colaborativo, VANTs com algum nível de autonomia e que partilhem do mesmo espaço aéreo também deverão ser capazes de trocar informações entre si, principalmente informações sobre posicionamento e rota de voo, e também estarão suscetíveis aos distúrbios da comunicação sem fio. Para balancear as vantagens e as desvantagens, esses robôs precisarão se comunicar cientes das restrições e utilizando a rede de modo otimizado, por meio da aplicação de algoritmos que equilibrem adequadamente técnicas de difusão de informações e técnicas de mitigação de retransmissões. Neste projeto de doutorado foi feita a investigação sobre o método de disseminação de dados, por meio de broadcasting, em uma rede móvel ad hoc entre VANTs, denominada Flying Ad hoc Networks (FANETs). FANETs são um novo paradigma que pode superar as restrições de missões de um único VANT. As FANETs são compostas por vários VANTs que cooperam para realizar alguma missão crítica (por exemplo, uma missão de busca e resgate). Para manter a coordenação, todos os VANTs devem continuamente enviar ou retransmitir mensagens através do canal sem fio para garantir que todos os membros da rede saibam o estado da rede. Geralmente, a troca de dados necessários para manter a sincronização da missão exige o uso de broadcast para que todos os membros da rede possam recebê-los. No entanto, quando essa troca de mensagens é feita arbitrariamente, isso pode causar o problema da tempestade de broadcast (BSP), levando o meio sem fio a um estado inoperante. Apesar de alguns esforços relatados na literatura para o provimento de técnicas gerais de mitigação do problema BSP, o desafio de agregar novas informações ou conhecimento a receptores que estejam voando, ao invés de apenas espalhar os dados na rede, tem recebido menos atenção. Nesta tese, além de demonstrar que o problema BSP intensifica a contenção de rede à medida que o número de VANTs aumenta, também foi criado um método que se prova mais eficiente que os existentes até então. Tal técnica, denominada de Algoritmo Baseado em Vizinhança Dinâmica para o Problema da Tempestade de Broadcast (DNA-BSP), foi desenvolvida e validada com base em experimentos de mundo real e em simulações computacionais. Ele pode mitigar o problema BSP, que é um desafio real nas FANETs, reduzindo a redundância de mensagens em mais de 98% e tornando a entrega de mensagens 99,5% mais rápida do que no cenário de flooding, superando as técnicas gerais de mitigação do BSP quando aplicado em FANETs. Os resultados detalhados neste texto também poderão orientar trabalhos futuros ao fornecer informações úteis para o planejamento e otimização de redes ad hoc móveis para VANTs. / Unmanned aerial vehicles (UAVs) have been showing increasing notoriety in the global aviation scene, both on their development and on the different applications for these vehicles, due to their high potential of use. In many applications, using multiple UAVs has several advantages over a single UAV. However, a cluster of UAVs may experience issues inherent to wireless communication, which may lead to new complications such as making mission coordination and cooperative execution impractible. In a non-collaborative scenario, UAVs with some level of autonomy which share the same airspace should also be able to exchange information among themselves, especially positioning and flight path information, and may also be susceptible to wireless communication disturbances. These robots have to use the network fairly and should communicate under restrictions, appropriately adjusting techniques that disseminate information and that mitigate broadcasts, in order to balance the advantages and disadvantages of being a group. This Ph.D. research investigates how broadcasting is used to disseminate data throughout ad hoc mobile networks between UAVs called Flying Ad hoc Networks (FANETs). FANETs are a new paradigm that can overcome the mission constraints of single UAVs. FANETs are composed of several UAVs that cooperate to accomplish a critical mission (e.g., hazardous area monitoring). Aiming to maintain UAVs coordination, all aircraft must continuously retransmit or relay messages through the wireless channel to assure that every member knows the FANET status. However, when this message exchange is done blindly, it may cause the broadcast storm problem (BSP), leading the wireless medium to a dysfunctional state. Despite some efforts reported in the literature for providing general techniques to mitigate the broadcast storm problem, the challenge of aggregating new information or knowledge to receivers, instead of just spreading the information in the network, has received less attention. In this research, it has been proved that the broadcast storm problem causes network contention as the number of UAVs increases, and the innovative Dynamic Neighborhood-based Algorithm for the Broadcast Storm Problem (DNA-BSP) has been provided as a countermeasure, which was developed and validated based on computer simulations and outdoor experiments. It can mitigate the broadcast storm problem, which is a real challenge in FANETs, reducing message redundancy in more than 98%, and making message delivery 99,5% faster than in flooding scenario, outperforming classical broadcast storm mitigation techniques when applied in FANETs. Our detailed results can also guide future researches and provide useful insights for engineers planning and optimizing mission-critical mobile ad hoc network with support of UAVs.

This work presents the development of the Statistical Location-Assisted Broadcast (SLAB) protocol, a multi-hop wireless broadcast protocol designed for vehicular ad-hoc networking (VANET). Vehicular networking is an important emerging application of wireless communications. Data dissemination applications using VANET promote the ability for vehicles to share information with each other and the wide-area network with the goal of improving navigation, fuel consumption, public safety, and entertainment. A critical component of these data dissemination schemes is the multi-hop wireless broadcast protocol. Multi-hop broadcast protocols for these schemes must reliably deliver broadcast packets to vehicles in a geographically bounded region while consuming as little wireless bandwidth as possible. This work contains substantial research results related to development of multi-hop broadcast protocols for VANET, culminating in the design of SLAB. Many preliminary research and development efforts have been required to arrive at SLAB. First, a high-level wireless broadcast simulation tool called WiBDAT is developed. Next, a manual optimization procedure is proposed to create efficient threshold functions for statistical broadcast protocols. This procedure is then employed to design the Distribution-Adaptive Distance with Channel Quality (DADCQ) broadcast protocol, a preliminary cousin of SLAB. DADCQ is highly adaptive to node density, node spatial distribution pattern, and wireless channel quality in realistic VANET scenarios. However, the manual design process used to create DADCQ has a few deficiencies. In response to these problems, an automated design procedure is created that uses a black-box global optimization algorithm to search for efficient threshold functions that are evaluated using WiBDAT. SLAB is finally designed using this procedure. / Expansive simulation results are presented comparing the performance of SLAB to two well-published VANET broadcast protocols, p -persistence and Advanced Adaptive Gossip (AAG), and to DADCQ. The four protocols are evaluated under varying node density and speed on five different road topologies with varying wireless channel fading conditions. The results demonstrate that unlike p-persistence and AAG, SLAB performs well across a very broad range of environmental conditions. Compared to its cousin protocol DADCQ, SLAB achieves similar reachability while using around 30% less wireless bandwidth, highlighting the improvement in the automated design methodology over the manual design. / by Michael J. Slavik. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 200?. Mode of access: World Wide Web.

A Mobile Ad Hoc Network (MANETs) is a collection of wireless hosts that can be rapidly deployed as a multi hop packet radio network without the aid of any established infrastructure or centralized administration. Such networks can be used to enable next generation of battlefield applications envisioned by the military, including situation awareness systems for maneuvering war fighters, and remotely deployed unmanned microsensor networks. Ad Hoc networks can also provide solutions for civilian applications such as disaster recovery and message exchanges among safety and security personnel involved in rescue missions. Existing solutions for wired network Intrusion Detection Systems (IDSs) do not suit wireless Ad Hoc networks. To utilize either misuse detection or anomaly detection to monitor any possible compromises, the IDS must be able to distinguish normal from anomaly activities. To enable intrusion detection in wireless Ad Hoc networks, the research problems are: • How to efficiently collect normal and anomaly patterns of Ad Hoc networks? The lifetime of the hosts is short and Ad Hoc networks do not have traffic concentration points (router, switch). • How to detect anomalies? The loss could be caused by host movement instead of attacks. Unexpectedly long delay could be caused by unreliable channel instead of malicious discard. In this thesis, we have proposed a novel architecture that uses specification based intrusion detection techniques to detect active attacks against the routing protocols of mobile Ad Hoc networks. Our work analyzes some of the vulnerabilities and discuss the attacks against the AODV protocol. Our approach involves the use of an FSM (Finite State Machine) for specifying the AODV routing behavior and the distributed network monitors for detecting the sequence number attack. Our method can detect most of the bad nodes with low false positive rate and the packet delivery ratio can also be increased with high detection rate. For packet dropping attack, we present a distributed technique to detect this attack in wireless Ad Hoc networks. A bad node can forward packets but in fact it fails to do so. In our technique, every node in the network will check the neighboring nodes to detect if any of them fail to forward the packets. Our technique can detect most of the bad nodes with low false positive rate and the packet delivery ratio can also be increased. The proposed solution can be applied to identify multiple malicious nodes cooperating with each other in MANETs and discover secure routes from source to destination by avoiding malicious nodes acting in cooperation. Our technique will detect the sequence number and Packet Dropping attacks in real time within its radio range with no extra overhead. For resource consumption attack, the proposed scheme incurs no extra overhead, as it makes minimal modifications to the existing data structures and functions related to bad listing a node in the existing version of pure AODV. The proposed scheme is more efficient in terms of the resultant routes established, resource reservations, and computational complexity. If multiple malicious nodes collaborate, they in turn will be restricted and isolated by their neighbors, because they monitor and exercise control over forwarding RREQs by nodes. Hence, the scheme successfully prevents Distributed attacks. The proposed scheme shifts the responsibility of monitoring this parameter to the node's neighbor, ensuring compliance of this restriction. This technique solves all of the problems caused due to unnecessary RREQs from a compromised node. Instead of self-control, the control exercised by a node's neighbor results in preventing this attack. Experiments show that the tool provides effective intrusion detection functionality while using only a limited amount of resources. The loop freedom property has been reduced to an invariant on pairs of nodes. Each node decides & transmits its decision to a control center. Robustness to Threats, Robustness to nodes destruction: Loss of Performance (in terms of ratio) is least for Distributed Option and highest for Centralized Option and Robustness to observations deletion. All the proposed schemes were analyzed and tested under different topologies and conditions with varying number of nodes .The proposed algorithms for improving the robustness of the wireless Ad Hoc networks using AODV protocol against Packet Dropping Attack, Sequence Number attack and resource consumption attack have been simulated for an illustrative network of about 30 nodes. Our experiments have shown that the pattern extracted through simulation can be used to detect attacks effectively. The patterns could also be applied to detect similar attacks on other protocols.

Mobility-Based Routing Overhead Management in Reconfigurable Wireless Ad Hoc Networks Routing Overheads are the non-data message packets whose roles are establishment and maintenance of routes for data packets as well as neighbourhood discovery and maintenance. They have to be broadcasted in the network either through flooding or other techniques that can ensure that a path exists before data packets can be sent to various destinations. They can be sent reactively or periodically to neighbours so as to keep nodes updated on their neighbourhoods. While we cannot do without these overhead packets, they occupy much of the limited wireless bandwidth available in wireless networks. In a reconfigurable wireless ad hoc network scenario, these packets have more negative effects, as links need to be confirmed more frequently than in traditional networks mainly because of the unpredictable behaviour of the ad hoc networks. We therefore need suitable algorithms that will manage these overheads so as to allow data packet to have more access to the wireless medium, save node energy for longer life of the network, increased efficiency, and scalability. Various protocols have been suggested in the research area. They mostly address routing overheads for suitability of particular protocols leading to lack of standardisation and inapplicability to other protocol classes. In this dissertation ways of ensuring that the routing overheads are kept low are investigated. The issue is addressed both at node and network levels with a common goal of improving efficiency and performance of ad hoc networks without dedicating ourselves to a particular class of routing protocol. At node level, a method hereby referred to as "link availability forecast", that minimises routing overheads used for maintenance of neighbourhood, is derived. The targeted packets are packets that are broadcasted periodically (e.g. hello messages). The basic idea in this method is collection of mobility parameters from the neighbours and predictions or forecasts of these parameters in future. Using these parameters in simple calculations helps in identifying link availabilities between nodes participating in maintenance of networks backbone. At the network level, various approaches have been suggested. The first approach is the cone flooding method that broadcasts route request messages through a predetermined cone shaped region. This region is determined through computation using last known mobility parameters of the destination. Another approach is what is hereby referred as "destination search reverse zone method". In this method, a node will keep routes to destinations for a long time and use these routes for tracing the destination. The destination will then initiate route search in a reverse manner, whereby the source selects the best route for next delivery. A modification to this method is for the source node to determine the zone of route search and define the boundaries within which the packet should be broadcasted. The later method has been used for simulation purposes. The protocol used for verification of the improvements offered by the schemes was the AODV. The link availability forecast scheme was implemented on the AODV and labelled AODV_LA while the network level implementation was labelled AODV_RO. A combination of the two schemes was labelled AODV_LARO.

Opportunistic communication techniques have shown to provide significant performance improvements in centralised random access wireless networks. The key mechanism of opportunistic communication is to send back-to-back data packets whenever the channel quality is deemed "good". Recently there have been attempts to introduce opportunistic communication techniques in distributed wireless networks such as wireless ad hoc networks. In line of this research, we propose a new paradigm of medium access control, called Channel MAC based on the channel randomness and opportunistic communication principles. Scheduling in Channel MAC depends on the instance at which the channel quality improves beyond a threshold, while neighbouring nodes are deemed to be silent. Once a node starts transmitting, it will keep transmitting until the channel becomes "bad". We derive an analytical throughput equation of the proposed MAC in a multiple access environment and validate it by simulations. It is observed that Channel MAC outperforms IEEE 802.11 for all probabilities of good channel condition and all numbers of nodes. For higher number of nodes, Channel MAC achieves higher throughput at lower probabilities of good channel condition increasing the operating range. Furthermore, the total throughput of the network grows with increasing number of nodes considering negligible propagation delay in the network. A scalable channel prediction scheme is required to implement the practical Channel MAC protocol in practice. We propose a mean-value based channel prediction scheme, which provides prediction with enough accuracy to be used in the Channel MAC protocol. NS2 simulation result shows that the Channel MAC protocol outperforms the IEEE 802.11 in throughput due to its channel diversity mechanism in spite of the prediction errors and packet collisions. Next, we extend the Channel MAC protocol to support multi-rate communications. At present, two prominent multi-rate mechanisms, Opportunistic Auto Rate (OAR) and Receiver Based Auto Rate (RBAR) are unable to adapt to short term changes in channel conditions during transmission as well as to use optimum power and throughput during packet transmissions. On the other hand, using channel predictions, each source-destinations pair in Channel MAC can fully utilise the non-fade durations. We combine the scheduling of Channel MAC and the rate adaptive transmission based on the channel state information to design the 'Rate Adaptive Channel MAC' protocol. However, to implement the Rate adaptive Channel MAC, we need to use a channel prediction scheme to identify transmission opportunities as well as auto rate adaptation mechanism to select rates and number of packets to transmit during those times. For channel prediction, we apply the scheme proposed for the practical implementation of Channel MAC. We propose a "safety margin" based technique to provide auto rate adaptation. Simulation results show that a significant performance improvement can be achieved by Rate adaptive Channel MAC as compared to existing rate adaptive protocols such as OAR.

Opportunistic communication techniques have shown to provide significant performance improvements in centralised random access wireless networks. The key mechanism of opportunistic communication is to send back-to-back data packets whenever the channel quality is deemed "good". Recently there have been attempts to introduce opportunistic communication techniques in distributed wireless networks such as wireless ad hoc networks. In line of this research, we propose a new paradigm of medium access control, called Channel MAC based on the channel randomness and opportunistic communication principles. Scheduling in Channel MAC depends on the instance at which the channel quality improves beyond a threshold, while neighbouring nodes are deemed to be silent. Once a node starts transmitting, it will keep transmitting until the channel becomes "bad". We derive an analytical throughput equation of the proposed MAC in a multiple access environment and validate it by simulations. It is observed that Channel MAC outperforms IEEE 802.11 for all probabilities of good channel condition and all numbers of nodes. For higher number of nodes, Channel MAC achieves higher throughput at lower probabilities of good channel condition increasing the operating range. Furthermore, the total throughput of the network grows with increasing number of nodes considering negligible propagation delay in the network. A scalable channel prediction scheme is required to implement the practical Channel MAC protocol in practice. We propose a mean-value based channel prediction scheme, which provides prediction with enough accuracy to be used in the Channel MAC protocol. NS2 simulation result shows that the Channel MAC protocol outperforms the IEEE 802.11 in throughput due to its channel diversity mechanism in spite of the prediction errors and packet collisions. Next, we extend the Channel MAC protocol to support multi-rate communications. At present, two prominent multi-rate mechanisms, Opportunistic Auto Rate (OAR) and Receiver Based Auto Rate (RBAR) are unable to adapt to short term changes in channel conditions during transmission as well as to use optimum power and throughput during packet transmissions. On the other hand, using channel predictions, each source-destinations pair in Channel MAC can fully utilise the non-fade durations. We combine the scheduling of Channel MAC and the rate adaptive transmission based on the channel state information to design the 'Rate Adaptive Channel MAC' protocol. However, to implement the Rate adaptive Channel MAC, we need to use a channel prediction scheme to identify transmission opportunities as well as auto rate adaptation mechanism to select rates and number of packets to transmit during those times. For channel prediction, we apply the scheme proposed for the practical implementation of Channel MAC. We propose a "safety margin" based technique to provide auto rate adaptation. Simulation results show that a significant performance improvement can be achieved by Rate adaptive Channel MAC as compared to existing rate adaptive protocols such as OAR.