Performance and security are two critical functions of wireless ad-hoc networks (WANETs). Network security ensures the integrity, availability, and performance of WANETs. It helps to prevent critical service interruptions and increases economic productivity by keeping networks functioning properly. Since there is no centralized network management in WANETs, these networks are susceptible to packet drop attacks. In selective drop attack, the neighboring nodes are not loyal in forwarding the messages to the next node. It is critical to identify the illegitimate node, which overloads the host node and isolating them from the network is also a complicated task. In this paper, we present a resistive to selective drop attack (RSDA) scheme to provide effective security against selective drop attack. A lightweight RSDA protocol is proposed for detecting malicious nodes in the network under a particular drop attack. The RSDA protocol can be integrated with the many existing routing protocols for WANETs such as AODV and DSR. It accomplishes reliability in routing by disabling the link with the highest weight and authenticate the nodes using the elliptic curve digital signature algorithm. In the proposed methodology, the packet drop rate, jitter, and routing overhead at a different pause time are reduced to 9%, 0.11%, and 45%, respectively. The packet drop rate at varying mobility speed in the presence of one gray hole and two gray hole nodes are obtained as 13% and 14% in RSDA scheme.

No / Trust management in mobile ad hoc networks (MANETs) has become a significant issue in securing routing protocols to choose reliable and trusted paths. Trust is used to cope with defection problems of nodes and stimulate them to cooperate. However, trust is a highly complex concept because of the subjective nature of trustworthiness, and has several social properties, due to its social origins. In this paper, a friendship-based trust model is proposed for MANETs to secure routing protocol from source to destination, in which multiple social degrees of friendships are introduced to represent the degree of nodes' trustworthiness. The model considers the behaviour of nodes as a human pattern to reflect the complexity of trust subjectivity and different views. More importantly, the model considers the dynamic differentiation of friendship degree over time, and utilises both direct and indirect friendship-based trust information. The model overcomes the limitation of neglecting the social behaviours of nodes when evaluating trustworthiness. The empirical analysis shows the greater robustness and accuracy of the trust model in a dynamic MANET environment.

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<p>A cognitive radio network is a multi-user system, in which different radio units compete for limited resources in an opportunistic manner, interacting with each other for access to the available resources. The fact that both users and spectrum holes (i.e., under-utilized spectrum sub-bands) can come and go in a stochastic manner, makes a cognitive radio network a highly non- stationary, dynamic and challenging wireless environment. Finding robust decentralized resource-allocation algorithms, which are capable of achieving reasonably good solutions fast enough in order to guarantee an acceptable level of performance, is crucial in such an environment. In this thesis, a novel dynamic spectrum management (DSM) scheme for cognitive radio networks, termed the self-organizing dynamic spectrum management (SO-DSM), is described and its practical validity is demonstrated using computer simulations. In this scheme, CRs try to exploit the primary networks’ unused bands and establish link with neighbouring CRs using those bands. Inspired by human brain, the CRs extract and memorize primary network’s and other CRs’ activity patterns and create temporal channel assignments on sub-bands with no recent primary user activities using self-organizing maps (SOM) technique. The proposed scheme is decentralized and employs a simple learning rule with low complexity and minimal memory requirements. A software testbed was developed to simulate and study the proposed scheme. This testbed is capable of simulating CR network alongside of a cellular legacy network. In addition to SO-DSM, two other DSM schemes, namely centralized DSM and no-learning decentralized DSM, can be used for CR networks in this software testbed. The software testbed was deployed on parallel high capacity computing clusters from Sharcnet to perform large scale simulations of CR network. The simulation results show, comparing to centralized DSM and minority game DSM (MG-DSM), the SO-DSM decreases the probability of collision with primary users and also probability of CR link interruption significantly with a moderate decrease in CR network spectrum utilization.</p> / Doctor of Philosophy (PhD)

Despite recent advances in wireless local area network (WLAN) technologies, today's WLANs still cannot offer the same data rates as their wired counterparts. The throughput problem is further aggravated in multi-hop wireless environments due to collisions and interference caused by multi-hop routing. Because all current IEEE 802.11 physical (PHY) standards divide the available frequency into several orthogonal channels, which can be used simultaneously within a neighborhood, increasing capacity by exploiting multiple channels becomes particularly appealing. To improve the capacity of wireless ad hoc networks by exploiting multiple available channels, I propose three principles that facilitate the design of efficient distributed channel assignment protocols. Distributed channel assignment problems have been proven to be <i>NP</i>-complete and, thus, computationally intractable. Though being a subject of many years of research, distributed channel assignment remains a challenging problem. There exist only a few heuristic solutions, none of which is efficient, especially for the mobile ad hoc environment. However, protocols that implement the proposed design principles are shown to require fewer channels and exhibit significantly lower communication, computation, and storage complexity, compared with existing approaches. As examples, I present two such protocols that build on standard reactive and proactive routing protocols. In addition, I prove the correctness of the algorithms and derive an upper bound on the number of channels required to both resolve collisions and mitigate interference. A new multi-channel medium access control (MC-MAC) protocol is also proposed for multi-hop wireless ad hoc networks. MC-MAC is compatible with the IEEE 802.11 medium access control (MAC) standard and imposes the minimum system requirements among all existing multi-channel MAC protocols. In addition, simulation results show that even with only a single half-duplex transceiver, MC-MAC, by exploiting multiple channels, can offer up to a factor of four improvement in throughput over the IEEE 802.11 MAC protocol. The reduction in delay is even more significant. Therefore, the MC-MAC protocol and the accompanying distributed channel assignment protocols constitute an effective solution to the aforementioned performance problem in a multi-hop wireless network. Finally, I generalize the cross-layer design principle to more general networking functions and present a network architecture to motivate and facilitate cross-layer designs in wireless networks. A literature survey is provided to validate the proposed cross-layer design architecture. Current cross-layer design research can be categorized into two classes: joint-layer design using optimization techniques, and adaptive techniques based on system-profile and/or QoS requirements. Joint-layer design based on optimization techniques can achieve optimal performance, but at the expense of complexity. Adaptive schemes may achieve relatively good performance with less complexity. Nevertheless, without careful design and a holistic view of the network architecture, adaptive schemes may actually cause more damage than benefit. / Ph. D.

An important aspect of wireless networks is their dynamic behavior. The conventional protocol stack is inflexible as various protocol layers communicate in a strict manner. In such a case the layers are designed to operate under the worst conditions as opposed to adapting to changing conditions. This leads to inefficient use of spectrum and energy. Adaptation represents the ability of network protocols and applications to observe and respond to channel conditions. Traditional simulation methodologies independently model the physical and higher layers. When multiple layer simulations are required, an abstraction of one layer is inserted into the other to provide the multiple layer simulation. However, recent advances in wireless communication technologies, such as adaptive modulation and adaptive antenna algorithms, demand a cross layer perspective to this problem in order to provide a sufficient level of fidelity. However, a full simulation of both layers often results in excessively burdensome simulation run-times. The benefits and possible parametric characterization issues arising due to the cross-layer integration of lower physical and higher network layers are investigated in this thesis. The primary objective of investigating cross-layer simulation techniques is to increase the fidelity of cross-layer network simulations while minimizing the simulation runtime penalties. As a study of cross-layer system design a medium access control (MAC) scheme is studied for a MANET wherein the nodes are equipped with smart antennas. Traditional MAC protocols assume the use of omnidirectional antennas. Nodes with directional antennas are capable of transmitting in certain directions only and significantly reduce the chances of collision and increase the effective network capacity. MANETs using omni-directional antennas severely limit system performance as the entire space around a node up to its radio range is seen as a single logical channel. In this research a MAC protocol is studied that exploits space division multiple access at the physical layer. This is a strong example where physical and MAC design must be carried out simultaneously for adequate system performance. Power control is a very important in the design of cellular CDMA systems which suffer from the near-far problem. Finally, the interaction between successive interference cancellation (SIC) receivers at the physical layer and power control, which is a layer 2 radio resource management issue, is studied. Traffic for future wireless networks is expected to be a mix of real-time traffic such as voice, multimedia teleconferencing, and games and data traffic such as web browsing, messaging, etc. All these applications will require very diverse quality of service guarantees. A power control algorithm is studied, which drives the average received powers to those required, based on the QoS requirements of the individual users for a cellular CDMA system using SIC receivers. / Master of Science

<p dir="ltr">VANET is formed by vehicles, road units, infrastructure components, and various con- nected objects.It aims mainly to ensure public safety and traffic control. New emerging applications include value-added and user-oriented services. While this technological ad- vancement promises ubiquitous deployment of the VANET, security and privacy challenges must be addressed. Thence, vehicle authentication is a vital process to detect malicious users and prevent them from harming legitimate communications. Hover, the authentication pro- cess uses sensitive information to check the vehicle’s identity. Sharing this information will harm vehicle privacy. In this thesis, we aim to deal with this issues:</p><ul><li>How can we ensure vehicle authentication and avoid sensitive and identity information leaks simultaneously?</li><li>When nodes are asked to provide identity proof, how can we ensure that the shared information is only used by an authorized entity?</li><li>Can we define an effective scheme to distinguish between legitimate and malicious network nodes?This dissertation aims to address the preservation of vehicle private information used within the authentication mechanism in VANET communications.The VANET characteristics are thoroughly presented and analyzed. Security require- ments and challenges are identified. Additionally, we review the proposed authentication techniques and the most well-known security attacks while focusing on the privacy preser- vation need and its challenges.To fulfill, the privacy preservation requirements, we proposed a new solution called Active Bundle AUthentication Solution based on SDN for Vehicular Networks (ABAUS). We intro- duce the Software Defined Networks (SDN) as an authentication infrastructure to guarantee the authenticity of each participant. Furthermore, we enhance the preservation of sensitive data by the use of an active data Bundle (ADB) as a self-protecting security mechanism. It ensures data protection throughout the whole data life cycle. ABAUS defines a dedicated registration protocol to verify and validate the different members of the network.</li></ul><p dir="ltr">first solution focused on legitimate vehicle identification and sensitive data pro- tection. A second scheme is designed to recognize and eliminate malicious users called BEhaviour-based REPutation scheme for privacy preservation in VANET using blockchain technology (BEREP). Dedicated public blockchains are used by a central trust authority to register vehicles and store their behavior evaluation and a trust scoring system allows nodes to evaluate the behavior of their communicators and detect malicious infiltrated users.</p><p dir="ltr">By enhancing sensitive data preservation during the authentication process and detect- ing malicious attempts, our proposed work helps to tackle serious challenges in VANET communications.</p>

As developments in wireless ad hoc networks continue, there is an increasing expectation with regard to supporting content-rich multimedia communications (e.g., video) in such networks, in addition to simple data communications. The recent advances in multiple description (MD) video coding have made it highly suitable for multimedia applications in such networks. In this thesis, we study three important problems regarding multiple description video communications in wireless ad hoc networks. They are multipath routing for MD video, MD video multicast, and joint routing and server selection for MD video in wireless ad hoc networks. In multipath routing for MD video problem, we follow an applicationcentric cross-layer approach and formulate an optimal routing problem that minimizes the application layer video distortion. We show that the optimization problem has a highly complex objective function and an exact analytic solution is not obtainable. However, we find that a metaheuristic approach such as Genetic Algorithms (GAs) is eminently effective in addressing this type of complex cross-layer optimization problems. We provide a detailed solution procedure for the GA-based approach, as well as a tight lower bound for video distortion. We use numerical results to compare this approach to several other approaches and demonstrate its superior performance. In MD video multicast problem, we take the similar application-centric, cross-layer approach as in the multipath routing problem. We propose an MD video multicast scheme where multiple source trees are used. Furthermore, each video description is coded into multiple layers in order to cope with diversity in wireless link bandwidths. Based on this multicast model, we formulate the multicast routing as a combinatorial optimization problem and apply Genetic Algorithm (GA)-based metaheuristic procedure to solove this problem. Performance comparisons with existing approaches show significant gains for a wide range of network operating conditions. In the last problem, we study the important problem of joint routing and server selection for MD video in ad hoc networks. We formulate the task as a combinatorial optimization problem and present tight lower and upper bounds for the achievable distortion. The upper bound also provides a feasible solution to the formulated problem. Our extensive numerical results show that the bounds are very close to each other for all the cases studied, indicating the near-global optimality of the derived upper bounding solution. Moreover, we observe significant gains in video quality achieved by the proposed approach over existing server selection schemes. This justifies the importance of jointly considering routing and server selection for optimal MD video streaming in wireless ad hoc networks. / Master of Science

Popularity of mobile devices along with the presence of ad hoc networks requiring no infrastructure has contributed to recent advances in the field of mobile computing in ad hoc networks. Mobile ad hoc networks have been mostly utilized in military environments. The recent advances in ad hoc network technology now introduce a new class of applications. In this thesis, we design, implement and analyze a multi-hop ad hoc messenger application using Pocket PCs and Microsoft .Net Compact Framework. Pocket PCs communicate wirelessly with each other using the IEEE 802.11b technology without the use of an infrastructure. The main protocol implemented in this application is based on Dynamic Source Routing (DSR), which consists of two important mechanisms, Route Discovery and Route Maintenance. We adopt DSR since DSR operates solely based on source routing and "on-demand" process, so each packet does not have to transmit any periodic advertisement packets or routing information. These characteristics are desirable for the ad hoc messenger application for which a conversation is source-initiated on-demand. To test our application easily, we have developed a testing strategy by which a mobility configuration file is pre-generated describing the mobility pattern of each node generated based on the random waypoint mobility model. A mobility configuration file thus defines topology changes at runtime and is used by all nodes to know whether they can communicate with others in a single-hop or multi-hops during an experimental run. We use five standard metrics to test the performance of the wireless ad hoc messenger application implemented based on DSR, namely, (1) average latency to find a new route, (2) average latency to deliver a data packet, (3) delivery ratio of data packets, (4) normalized control overhead, and (5) throughput. These metrics test the correctness and efficiency of the wireless ad hoc messenger application using the DSR protocol in an 802.11 ad hoc network that imposes limitations on bandwidth and resources of each mobile device. We test the effectiveness of certain design alternatives for implementing the ad hoc messenger application with these five metrics under various topology change conditions by manipulating the speed and pause-time parameters in the random waypoint model. The design alternatives evaluated include (1) Sliding Window Size (SWS) for end-to-end reliable communication control; (2) the use of per-hop acknowledgement packets (called receipt packets) deigned for rapid detection of route errors by intermediate nodes; and (3) the use of cache for path look-up during route discovery and maintenance. Our analysis results indicate that as the node speed increases, the system performance deteriorates because a higher node speed causes the network topology to change more frequently under the random waypoint mobility model, causing routes to be broken. On the other hand, as the pause time increases, the system performance improves due to a more stable network topology. For the design alternatives evaluated in our wireless ad hoc messenger, we discover that as SWS increases, the system performance also increases until it reaches an optimal SWS value that maximizes the performance due to a balance of a higher level of data parallelism introduced and a higher level of medium contention in 802.11 because of more packets being transmitted simultaneously as SWS increases. Beyond the optimal SWS, the system performance deteriorates as SWS increases because the heavy medium contention effect outweighs the benefit due to data parallelism. We also discover that the use of receipt packets is helpful in a rapidly changing network but is not beneficial in a stable network. There is a break-even point in the frequency of topology changes beyond which the use of receipt packets helps quickly detect route errors in a dynamic network and would improve the system performance. Lastly, the use of cache is rather harmful in a frequently changing network because stale information stored in the cache of a source node may adversely cause more route errors and generate a higher delay for the route discovery process. There exists a break-even point beyond which the use of cache is not beneficial. Our wireless ad hoc messenger application can be used in a real chatting setting allowing Pocket PC users to chat instantly in 802.11 environments. The design and development of the dynamic topology simulation tool to model movements of nodes and the automatic testing and data collection tool to facilitate input data selection and output data analysis using XML are also a major contribution. The experimental results obtained indicate that there exists an optimal operational setting in the use of SWS, receipt packets and cache, suggesting that the wireless ad hoc messenger should be implemented in an adaptive manner to fine-tune these design parameters based on the current network condition and performance data monitored to maximize the system performance. / Master of Science