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Title: Towards Robust and Reliable Communication for Millimeter Wave Networks
Creator: Zarifneshat, Masoud
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The future generations of wireless networks benefit significantly from millimeter wave technology (mmW) with frequencies ranging from about 30 GHz to 300 GHz. Specifically, the fifth generation of wireless networks has already implemented the mmW technology and the capacity requirements defined in 6G will also benefit from the mmW spectrum. Despite the attractions of the mmW technology, the mmW spectrum has some inherent propagation properties that introduce challenges. The first is that free...
Show moreThe future generations of wireless networks benefit significantly from millimeter wave technology (mmW) with frequencies ranging from about 30 GHz to 300 GHz. Specifically, the fifth generation of wireless networks has already implemented the mmW technology and the capacity requirements defined in 6G will also benefit from the mmW spectrum. Despite the attractions of the mmW technology, the mmW spectrum has some inherent propagation properties that introduce challenges. The first is that free space pathloss in mmW is more severe than that in the sub 6 GHz band. To make the mmW signal travel farther, communication systems need to use phased array antennas to concentrate the signal power to a limited direction in space at each given time. Directional communication can incur high overhead on the system because it needs to probe the space for finding signal paths. To have efficient communication in the mmW spectrum, the transmitter and the receiver should align their beams on strong signal paths which is a high overhead task. The second is a low diffraction of the mmW spectrum. The low diffraction causes almost any object including the human body to easily block the mmW signal degrading the mmW link quality. Avoiding and recovering from the blockage in the mmW communications, especially in dynamic environments, is particularly challenging because of the fast changes of the mmW channel. Due to the unique characteristics of the mmW propagation, the traditional user association methods perform poorly in the mmW spectrum. Therefore, we propose user association methods that consider the inherent propagation characteristics of the mmW signal. We first propose a method that collects the history of blockage incidents throughout the network and exploits the historical blockage incidents to associate user equipment to the base station with lower blockage possibility. The simulation results show that our proposed algorithm performs better in terms of improving the quality of the links and blockage rate in the network. User association based only on one objective may deteriorate other objectives. Therefore, we formulate a biobjective optimization problem to consider two objectives of load balance and blockage possibility in the network. We conduct Lagrangian dual analysis to decrease time complexity. The results show that our solution to the biobjective optimization problem has a better outcome compared to optimizing each objective alone. After we investigate the user association problem, we further look into the problem of maintaining a robust link between a transmitter and a receiver. The directional propagation of the mmW signal creates the opportunity to exploit multipath for a robust link. The main reasons for the link quality degradation are blockage and link movement. We devise a learning-based prediction framework to classify link blockage and link movement efficiently and quickly using diffraction values for taking appropriate mitigating actions. The simulations show that the prediction framework can predict blockage with close to 90% accuracy. The prediction framework will eliminate the need for time-consuming methods to discriminate between link movement and link blockage. After detecting the reason for the link degradation, the system needs to do the beam alignment on the updated mmW signal paths. The beam alignment on the signal paths is a high overhead task. We propose using signaling in another frequency band to discover the paths surrounding a receiver working in the mmW spectrum. In this way, the receiver does not have to do an expensive beam scan in the mmW band. Our experiments with off-the-shelf devices show that we can use a non-mmW frequency band's paths to align the beams in mmW frequency. In this dissertation, we provide solutions to the fundamental problems in mmW communication. We propose a user association method that is designed for mmW networks considering challenges of mmW signal. A closed-form solution for a biobjective optimization problem to optimize both blockage and load balance of the network is also provided. Moreover, we show that we can efficiently use the out-of-band signal to exploit multipath created in mmW communication. The future research direction includes investigating the methods proposed in this dissertation to solve some of the classic problems in the wireless networks that exist in the mmW spectrum.
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Title: Toward efficient spectrum use in multicarrier wireless networks
Creator: Huang, Pei
Date: 2014
Collection: Electronic Theses & Dissertations
Description: The last decade has witnessed growing interest in dynamic spectrum access, which is motivated by the observation that a large portion of the radio spectrum has been licensed but remains highly underutilized while a few small unlicensed bands that are open to anyone are getting more crowded due to the explosive expansion of wireless services. To provide more flexible access to radio spectrum, dynamic spectrum access is introduced to enable unlicensed users to opportunistically utilize vacant...
Show moreThe last decade has witnessed growing interest in dynamic spectrum access, which is motivated by the observation that a large portion of the radio spectrum has been licensed but remains highly underutilized while a few small unlicensed bands that are open to anyone are getting more crowded due to the explosive expansion of wireless services. To provide more flexible access to radio spectrum, dynamic spectrum access is introduced to enable unlicensed users to opportunistically utilize vacant spectrum chunks (known as spectrum holes) in licensed frequency bands.In dynamic spectrum access, non-contiguous orthogonal frequency division multiplexing (NC-OFDM) is widely adopted to efficiently utilize fragmented spectrum because it is convenient to keep silent on some spectrum fragments to avoid interference with licensed users. In NC-OFDM, a band of spectrum is divided into many orthogonal subcarriers and data are transmitted on a subset of them simultaneously. The subcarriers that interfere with the licensed users are deactivated. Because each subcarrier can be managed independently, this dissertation introduces a series of techniques that exploit the subcarriers to address problems in dynamic spectrum access.When unlicensed users called secondary users (SUs) are granted the permission to operate in the licensed bands, they must ensure that the interference caused by them to licensed users known as primary users (PUs) is within a limit. Even without such a requirement, SUs should avoid as many collisions as possible. To improve spectrum hole extraction rate and reduce collision rate, we propose a spectrum occupancy prediction model that helps estimate the spectrum availability. It measures a wide band of spectrum with OFDM and groups subcarriers to subchannels based on spectrum use activities. In each subchannel, frequent spectrum occupancy patterns are identified and used to predict future channel states (i.e., busy or idle). With the prediction, SUs are able to make use of spectrum holes more aggressively without introducing undue interference to PUs.In the spectrum holes discovered above, a mechanism is needed to coordinate medium access between devices. Because devices opportunistically utilize spectrum holes, a device may experience severe contentions with devices from various applications. We propose a collision detection and bitwise arbitration (CDBA) mechanism that quickly identifies the winner in a contention using combined information from both the time domain and the frequency domain. It enables collision detection in the frequency domain by selectively deactivating subcarriers at each transmitter.The CDBA assumes that all devices adopt the same channel width, but different radio technologies have different requirements on channel width. When heterogeneous radios coexist in a contention domain, wideband devices can hardly win medium access opportunities in contention with narrowband devices. To address the problem, we propose an adaptive channel bonding protocol in which a wideband device initiates transmission as long as there exist some idle narrow channels and gradually increases channel width during transmission whenever new narrow channels become available. To increase the chance to win some narrow channels, a wideband device contends on subcarriers of each narrow channel with a different priority.After the contention problem is addressed, we study how to increase the transmission speed when a device is granted the permission to transmit. As wireless networks move toward wider channel widths, it is common that different subcarriers experience different fade. To cope with the frequency-selective fading, modulation scheme for each subcarrier should be selected based on the subcarrier channel quality. We exploit the modulation diversity in our modulation scheme coding to improve network throughput.Besides unicast, broadcast is another fundamental mechanism in wireless networks. Because devices utilize spectrum fragments opportunistically, different receivers may have different vacant spectrum fragments at different locations. The broadcast is more challenging in dynamic spectrum access because the transmitter needs to consider the diversity of spectrum availability. We propose a spectrum fragment agile broadcast (SFAB) protocol to support broadcast under nonuniform spectrum availability. It encodes unique sequences on subcarriers of each spectrum fragment to achieve fast spectrum agreement between the transmitter and the receivers.
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Title: Collaboration based spectrum sharing algorithms in cognitive radio networks
Creator: Hyder, Chowdhury Sayeed
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Radio spectrum assignment to wireless providers using traditional fixed allocation policy will no longer be a viable technique to meet the growing spectrum demand of emerging wireless applications. This is because while the available pool of unassigned radio spectrum is low, the spectrum already assigned to existing applications is also often underutilized in time, frequency, and location. With features like transmission flexibility and adaptability cognitive radio (CR) provides a useful...
Show more"Radio spectrum assignment to wireless providers using traditional fixed allocation policy will no longer be a viable technique to meet the growing spectrum demand of emerging wireless applications. This is because while the available pool of unassigned radio spectrum is low, the spectrum already assigned to existing applications is also often underutilized in time, frequency, and location. With features like transmission flexibility and adaptability cognitive radio (CR) provides a useful means of spectrum sharing among growing users as an alternative to the current fixed policy. The cognitive radio network (CRN), based on the functionality of CR, consists of two types of users -- primary users (PU) and secondary users (SU). Primary users are licensed users who have exclusive access rights of a fixed spectrum range. Secondary users are unlicensed users who opportunistically exploit the spectrum holes or negotiate with primary users to earn transmission access rights. The CRN based efficient spectrum sharing algorithms work on different forms of collaboration between the PUs and the SUs (inter-user collaboration) and among the SUs themselves (intra-user collaboration). In the sensing based collaboration model, the SUs sense licensed spectrum and collaboratively decide about its availability based on the sensing results without any involvements from the PUs. In the relay based collaboration model, the SUs coordinate with the PUs directly, relay primary packets in exchange for transmission opportunities, and thus build a win-win cooperative framework to attain mutual benefits. In the auction based collaboration model, the SUs bid for temporary or permanent usage rights of unused licensed spectrum bands that are put into auction for sale by the PUs. Each of these collaboration models faces different sets of challenges towards achieving high spectrum utilization. In this dissertation, we address some of these challenges and present a set of efficient spectrum sharing algorithms based on these collaboration models. The first work in this dissertation addresses the spectrum sensing data falsification (SSDF) attack in IEEE 802.22 wireless regional area network (WRAN) under the sensing based collaboration model. We discuss different strategies of manipulating sensing reports by one or more malicious users and how these manipulation strategies may affect the spectrum utilization. To defend against such malicious attacks, we present an adaptive reputation based clustering algorithm. The algorithm combines the clustering technique with feedback based reputation adjustment to prevent independent and collaborative SSDF attacks and quarantines the attackers from the decision making process. Our next set of work in this dissertation falls under the relay based collaboration model. We investigate the feasibility of this collaboration model in the case of real-time applications. We quantify the impact of packet deadlines and cooperation overhead on the system performance. We discuss the impact of interference that may cause from secondary transmissions. Based on the analysis, we develop an interference aware reliable cooperative framework which improves the packet reception rate of both users with low overhead. We extend our investigation of this relay based collaboration model from single hop to multiple hops in the form of cooperative routing. We formulate the routing problem as an overlapping coalition formation game where each coalition represents a routing path between primary source and destination consisting of multiple SUs as intermediate relays. The proposed model allows SUs to participate in more than one coalitions and creates more transmission opportunities for them while achieving stable routing paths for PUs. Our final set of work in this dissertation deals with the challenges in the auction based collaboration model. We consider an online setting of spectrum auctions where participation and valuation of both bidders and sellers are stochastic. We analyze the behavior of bidders and sellers in such settings and develop truthful auction mechanisms with respect to bid and time, improving spectrum reuse, auction efficiency, and revenue. The findings from our research will help to understand the underlying challenges in future networks, build a better spectrum ecosystem, and encourage new spectrum sharing models in wireless broadband communications."--Pages ii-iv.
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Title: Efficient multicast design for wireless mesh networks
Creator: Zeng, Guokai
Date: 2011
Collection: Electronic Theses & Dissertations
Description: Wireless mesh networks (WMN) have emerged as an efficient means to expand the wireless reach of metro broadband deployments at a variety of locations or scenarios. It provides high quality service to end users as the ?°,,last-mile?°¿ of the Internet. Multicast provides an efficient mechanism for distributing data among a group of nodes, such as online games and video conferences. With the increasing popularity of content distribution and multimedia applications, efficient multicast...
Show moreWireless mesh networks (WMN) have emerged as an efficient means to expand the wireless reach of metro broadband deployments at a variety of locations or scenarios. It provides high quality service to end users as the ?°,,last-mile?°¿ of the Internet. Multicast provides an efficient mechanism for distributing data among a group of nodes, such as online games and video conferences. With the increasing popularity of content distribution and multimedia applications, efficient multicast communication becomes essential for the wide deployment of WMNs. In this dissertation, we discuss several research topics related with multicast communication in WMNs.First, we investigate the problem of routing and channel assignment for multicast communication in link-homogeneous WMNs with the goal of maximizing throughput. In this dissertation, we consider WMNs equipped with multiple channels and multiple interfaces. Previous research work on multicast does not take the multi-channel characteristic into consideration, thus it cannot fully explore the network capacity of WMNs. By exploiting multi-channel and multi-interface, our proposed approach has two major steps: (i) it builds an efficient multicast tree that minimizes the number of relay nodes; and (ii) the dedicated channel assignment strategies are designed to reduce the interference to improve the network capacity. We demonstrate that our proposed protocols not only improve the throughput, but also reduce the delay.Second, we study the multicast problem in link-heterogeneous WMNs. Unlike previous work that focuses on link-homogeneous WMNs only, we consider one important form of link heterogeneity: different link loss ratios. Under this constraint, although minimizing relay nodes helps to decrease interference in the WMN, it is also important to choose high quality links tominimize the number of transmissions. This is because decreasing the number of transmissions helps to increase the throughput. Based on this consideration, we define a new graph theory problem: HW-SCDS to model link-heterogeneity. Maximizing WMN throughput is equivalent to computing a minimum HW-SCDS (MHW-SCDS) in the graph. We prove that computing an MHW-SCDS is NP-hard and devise a greedy algorithm for it. We show that our approach outperforms previous work in terms of throughput and delay.Third, we investigate the problem of opportunistic multicast in WMNs. By exploiting the broadcast nature and spatial diversity of the wireless medium, opportunistic routing has emerged as a new routing paradigm to improve unicast throughput. However, its natural multicast extension does not build any efficient multicast structure, thus the explosion of unnecessary retransmission is unavoidable. To overcome this shortcoming, we propose a new opportunistic multicast protocol to improve throughput in WMNs. The key concept is a tree backbone in this protocol. Our tree backbone protocol represents a tradeoff between traditional structured multicast protocols and unstructured protocols. Therefore, our solution is able to improve throughput by both utilizing spatial diversity and reducing transmissions.
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Title: Energy Conservation in Heterogeneous Smartphone Ad Hoc Networks
Creator: Mariani, James
Date: 2018
Collection: Electronic Theses & Dissertations
Description: In recent years mobile computing has been rapidly expanding to the point that there are now more devices than there are people. While once it was common for every household to have one PC, it is now common for every person to have a mobile device. With the increased use of smartphone devices, there has also been an increase in the need for mobile ad hoc networks, in which phones connect directly to each other without the need for an intermediate router. Most modern smart phones are equipped...
Show moreIn recent years mobile computing has been rapidly expanding to the point that there are now more devices than there are people. While once it was common for every household to have one PC, it is now common for every person to have a mobile device. With the increased use of smartphone devices, there has also been an increase in the need for mobile ad hoc networks, in which phones connect directly to each other without the need for an intermediate router. Most modern smart phones are equipped with both Bluetooth and Wifi Direct, where Wifi Direct has a better transmission range and rate and Bluetooth is more energy efficient. However only one or the other is used in a smartphone ad hoc network. We propose a Heterogeneous Smartphone Ad Hoc Network, HSNet, a framework to enable the automatic switching between Wifi Direct and Bluetooth to emphasize minimizing energy consumption while still maintaining an efficient network. We develop an application to evaluate the HSNet framework which shows significant energy savings when utilizing our switching algorithm to send messages by a less energy intensive technology in situations where energy conservation is desired. We discuss additional features of HSNet such as load balancing to help increase the lifetime of the network by more evenly distributing slave nodes among connected master nodes. Finally, we show that the throughput of our system is not affected due to technology switching for most scenarios. Future work of this project includes exploring energy efficient routing as well as simulation/scale testing for larger and more diverse smartphone ad hoc networks.
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Title: Improving spectrum efficiency in heterogeneous wireless networks
Creator: Liu, Chin-Jung
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Over the past decades, the bandwidth-intensive applications that are previously confined to wired networks are now migrating to wireless networks. This trend has brought unprecedented high demand for wireless bandwidth. The wireless traffic is destined to dominate the Internet traffic in the future, but many of the popular wireless spectrum bands, especially the cellular and ISM bands, are already congested. On the other hand, some other wireless technologies, such as TV bands, often do not...
Show moreOver the past decades, the bandwidth-intensive applications that are previously confined to wired networks are now migrating to wireless networks. This trend has brought unprecedented high demand for wireless bandwidth. The wireless traffic is destined to dominate the Internet traffic in the future, but many of the popular wireless spectrum bands, especially the cellular and ISM bands, are already congested. On the other hand, some other wireless technologies, such as TV bands, often do not fully utilize their spectrum. However, the spectrum allocation is tightly regulated by the authority and adjusting the allocation is extremely difficult. The uneven utilization and the rigid regulation have led to the proposal of heterogeneous wireless networks, including cognitive radio networks (CRN) and heterogeneous cellular networks (HetNet). The CRNs that usually operate on different technologies from the spectrum owner attempt to reuse the idle spectrum (i.e., white space) from the owner, while HetNets attempt to improve spectrum utilization by smallcells. This dissertation addresses some of the challenging problems in these heterogeneous wireless networks.In CRNs, the secondary users (SU) are allowed to access the white spaces opportunistically as long as the SUs do not interfere with the primary users (PU, i.e., the spectrum owner). The CRN provides a promising means to improve spectral efficiency, which also introduces a set of new research challenges. We identify and discuss two problems in CRNs, namely non-contiguous control channel establishment and k-protected routing protocol design. The first problem deals with the need from SUs for a channel to transfer control information. Most existing approaches are channel-hopping (CH) based, which is inapplicable to NC-OFDM. We propose an efficient method for guaranteed NC-OFDM-based control channel establishment by utilizing short pulses on OFDM subcarriers. The results show that the time needed for establishing control channel is lower than that of CH-based approaches. The second problem deals with the interruption to a routing path in a CRN when a PU becomes active again. Existing reactive approaches that try to seek for an alternative route after PU returns suffer from potential long delay and possible interruption if an alternative cannot be found. We propose a k-protected routing protocol that builds routing paths with preassigned backups that are guaranteed to sustain from k returning PUs without being interrupted. Our result shows that the k-protected routing paths are never interrupted even when k PUs return, and have significantly shorter backup activation delays.HetNets formed by smallcells with different sizes of coverage and macrocells have been proposed to satisfy increased bandwidth demand with the limited and crowded wireless spectrum. Since the smallcells and macrocells operate on the same frequency, interference becomes a critical issue. Detecting and mitigating interference are two of the challenges introduced by HetNets. We first study the interference identification problem. Existing interference identification approaches often regard more cells as interferers than necessary. We propose to identify interference by analyzing the received patterns observed by the mobile stations. The result shows that our approach identifies all true interferers and excludes most non-interfering cells. The second research problem in HetNets is to provide effective solutions to mitigate the interference. The interference mitigation approaches in the literature mainly try to avoid interference, such as resource isolation that leads to significantly fewer resources, or power control that sacrifices signal quality and coverage. Instead of conservatively avoiding interference, we propose to mitigate the interference by precanceling the interfering signals from known interferers. With precancellation, the same set of resources can be shared between cells and thus throughput is improved.This dissertation addresses several challenges in heterogeneous wireless networks, including CRNs and HetNets. The proposed non-contiguous control channel protocol and k-protected routing protocol for CRNs can significantly improve the feasibility of CRNs in future wireless network applications. The proposed interference identification and interference precancellation approaches can effectively mitigate the interference and improve the throughput and spectrum utilization in HetNets. This dissertation aims at breaking the barriers for supporting heterogeneous wireless networks to improve the utilization of the precious and limited wireless spectrum.
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Title: Flexible spectrum use in channel bonding wireless networks
Creator: Yang, Xi (Software engineer)
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Channel bonding, which assembles multiple narrow channels into one logical channel, can speed up data transmission and achieve better bandwidth utilization in wireless networks. Since introduced in 802.11n, channel bonding has been extended continually to support wider channels, making low-lag high-speed wireless communication possible. However, different radio technologies have different requirements on channel width. Devices that use different channel widths coexist in a contention domain...
Show moreChannel bonding, which assembles multiple narrow channels into one logical channel, can speed up data transmission and achieve better bandwidth utilization in wireless networks. Since introduced in 802.11n, channel bonding has been extended continually to support wider channels, making low-lag high-speed wireless communication possible. However, different radio technologies have different requirements on channel width. Devices that use different channel widths coexist in a contention domain may cause inefficiency and unfairness issues. For example, narrowband devices are easier to obtain medium access opportunities because they do not need to wait for the entire wide band to be idle. Therefore, although wideband devices can provide higher transmission speed, they are at an unfavorable position in contentions with narrowband devices.To this end, we propose a flexible spectrum use channel bonding (FSUB) protocol in which a node is allowed to start a transmission whenever there are some idle narrow channels and gradually increases the channel width during transmission. Because a node dynamically adjusts the channel width in a communication, we use a convolution method to achieve fast spectrum agreement between the transmitter and the receiver. To address contentions between devices in a wide band of spectrum, we introduce a compound preamble to make the collisions detectable in the frequency domain and use a parallel bitwise arbitration mechanism to quickly determine the winner. We implement and evaluate the proposed protocol through both the GNU Radio/USRP platform and ns-2 simulations. The results show that the proposed protocol well addresses the inefficiency and unfairness issues caused by heterogeneous radio coexistence. Channel bonding devices usingFSUB have more medium access opportunities and can aggregate wider channels than using other channel bonding protocols in presence of narrowband interference. The FSUB enables a device to always benefit from channel bonding without concerns about narrowband interference level.
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Title: Implementation of a high throughput low power MAC protocol in wireless sensor networks
Creator: Liu, Chin-Jung
Date: 2011
Collection: Electronic Theses & Dissertations
Description: This thesis presents the design, implementation, and evaluation of TATD-MAC, a TDMA-based low duty cycle synchronous MAC protocol that improves throughput by increasing channel uti- lization with a traffic-adaptive time slot scheduling method. Conventional time division multiple access (TDMA) introduces significant end-to-end packet delivery delay and its throughput is lim- ited. TATD-MAC achieves higher throughput by improving TDMA with a novel traffic-adaptive mechanism that assigns time...
Show moreThis thesis presents the design, implementation, and evaluation of TATD-MAC, a TDMA-based low duty cycle synchronous MAC protocol that improves throughput by increasing channel uti- lization with a traffic-adaptive time slot scheduling method. Conventional time division multiple access (TDMA) introduces significant end-to-end packet delivery delay and its throughput is lim- ited. TATD-MAC achieves higher throughput by improving TDMA with a novel traffic-adaptive mechanism that assigns time slots only to nodes that are expecting traffic. Our traffic-adaptive mechanism is a two-phase design, which decomposes the DATA period into traffic notification part and data transmission scheduling part. The two-phase design enables TATD-MAC to optimize the control packets and improve their energy efficiencies according to the characteristics of each phase. The source nodes inform all nodes on the routing path that these sources have outgoing traffic by transmitting traffic notification packets in a "pulse" fashion. With traffic notification packets, ev- ery node on the routing path claims time slots in data transmission part. Therefore, TATD-MAC is able to forward a packet over multiple hops in a single cycle and thus reduce the end-to-end delay. The data transmission scheduling mechanism only assigns time slots to nodes with traf- fic through an ordered schedule negotiation scheme. This innovative traffic-adaptive scheduling mechanism assigns time slots based on traffic and totally eliminates the idle listening slots on nodes with no traffic. Moreover, if any other nodes need more time slots, they are able to claim them, which further improves channel utilization and achievable throughput. We implemented a TATD-MAC prototype on Tmote-Sky running TinyOS 2.1.0. Performance evaluation shows that TATD-MAC significantly improves throughput compared to conventional TDMA and achieves the same throughput as TDMA with slot stealing while having 70% less power consumption.
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Title: Security and privacy in resource constrained wireless networks
Creator: Pongaliur, Kanthakumar Mylsamy
Date: 2012
Collection: Electronic Theses & Dissertations
Description: Wireless networks use radio waves as a communication medium which allows for faster and cheaper deployment. The networks being wireless, are out in the open, which makes them vulnerable to malicious users that can hinder their performance. Of the several types of wireless networks, we focus on security and privacy in wireless sensor networks (WSN) and cognitive radio mobile ad-hoc networks (CR-MANET). The devices in these networks are limited in resources such as energy, low power radio, etc....
Show moreWireless networks use radio waves as a communication medium which allows for faster and cheaper deployment. The networks being wireless, are out in the open, which makes them vulnerable to malicious users that can hinder their performance. Of the several types of wireless networks, we focus on security and privacy in wireless sensor networks (WSN) and cognitive radio mobile ad-hoc networks (CR-MANET). The devices in these networks are limited in resources such as energy, low power radio, etc. CR-MANET devices are mobile, requiring them to run on limited amount of energy supplied by batteries, and conserve energy by reducing communication cost using low power radios. In addition, sensor devices have limited storage and a slower CPU. The purpose of a WSN is to sense and report event occurrences, whereas a CR-MANET provides improved spectrum utilization.We studied three kinds of attacks on WSN. The first type of attack is on the source privacy of sensor nodes. This attack happens because an important characteristic of events detected by sensor devices is bound to the location of event occurrence that can be revealed by compromise of detecting sensor device's source privacy. Thus, protecting privacy of event detecting sensor device is of paramount importance for which we present an encryption based solution to protect source privacy under eavesdropping and node compromise attacks. The second type of attack by the malicious entity can be invasive in nature, which could possibly cause damage to the device, or can be passive as in side channel attacks. A comprehensive study of side channel attacks on WSN is presented, along with a process obfuscation technique. The third type of attack is on the propagation of data packet generated by the sensor device. The detected event data is sent to the base station. If a malicious entity is able to prevent such event reporting packets from reaching the base station and segregate the attack zone, it will be able to carry out its malicious activity without getting caught. To cover such scenarios, a proactive dynamic camouflage event generation solution is presented.CR-MANET devices sense for vacant licensed spectrum and improve its utilization in an opportunistic manner. Accurate licensed spectrum occupancy detection by a CR-MANET device is hampered by signal fading, hidden terminal problems, etc. Spectrum occupancy decision can be improved by cooperative spectrum sensing (CSS). However, CSS is made difficult by the presence of malicious users. The malicious users can have two goals: one is to disrupt the network, another is to manipulate the network for its own personal gains. The malicious users can create havoc in a CR-MANET by falsifying spectrum sensing information leading to interference with the primary user. The devices in a CR-MANET are mobile, which gives an opportunity for the malicious entity to hide behind the changing neighborhood. We present three solutions to overcome the spectrum sensing data falsification attack and incorrect reporting of signal measurement due to byzantine failures. The first is a multi-fusion based distributed spectrum sensing (MFDSS) using reputation propagation. In the second solution, a continuously evolving virtual neighbor cluster of past neighbor devices aid in validating the input gathered from the current neighboring devices (ReNVaS). Third, a recursive partitioning around medoids based clustering is performed to identify a tightly bound set of valid inputs for decision making (TMC). A unified and non-unified decision making strategy is presented using ReNVaS and TMC. MFDSS performs better in a fast changing network while performance of unified fusion is better in a slow mobility network with respect to primary user spectrum occupancy detection accuracy.
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