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- Title
- Stochastic modeling of routing protocols for cognitive radio networks
- Creator
- Soltani, Soroor
- Date
- 2013
- Collection
- Electronic Theses & Dissertations
- Description
-
Cognitive radios are expected torevolutionize wireless networking because of their ability tosense, manage and share the mobile available spectrum.Efficient utilization of the available spectrum could be significantly improved by incorporating different cognitive radio based networks. Challenges are involved in utilizing the cognitive radios in a network, most of which rise from the dynamic nature of available spectrum that is not present in traditional wireless networks. The set of available...
Show moreCognitive radios are expected torevolutionize wireless networking because of their ability tosense, manage and share the mobile available spectrum.Efficient utilization of the available spectrum could be significantly improved by incorporating different cognitive radio based networks. Challenges are involved in utilizing the cognitive radios in a network, most of which rise from the dynamic nature of available spectrum that is not present in traditional wireless networks. The set of available spectrum blocks(channels) changes randomly with the arrival and departure of the users licensed to a specific spectrum band. These users are known as primary users. If a band is used by aprimary user, the cognitive radio alters its transmission power level ormodulation scheme to change its transmission range and switches to another channel.In traditional wireless networks, a link is stable if it is less prone to interference. In cognitive radio networks, however, a link that is interference free might break due to the arrival of its primary user. Therefore, links' stability forms a stochastic process with OFF and ON states; ON, if the primary user is absent. Evidently, traditional network protocols fail in this environment. New sets of protocols are needed in each layer to cope with the stochastic dynamics of cognitive radio networks.In this dissertation we present a comprehensive stochastic framework and a decision theory based model for the problem of routing packets from a source to a destination in a cognitive radio network. We begin by introducing two probability distributions called ArgMax and ArgMin for probabilistic channel selection mechanisms, routing, and MAC protocols. The ArgMax probability distribution locates the most stable link from a set of available links. Conversely, ArgMin identifies the least stable link. ArgMax and ArgMin together provide valuable information on the diversity of the stability of available links in a spectrum band. Next, considering the stochastic arrival of primary users, we model the transition of packets from one hop to the other by a Semi-Markov process and develop a Primary Spread Aware Routing Protocol (PSARP) that learns the dynamics of the environment and adapts its routing decision accordingly. Further, we use a decision theory framework. A utility function is designed to capture the effect of spectrum measurement, fluctuation of bandwidth availability and path quality. A node cognitively decides its best candidate among its neighbors by utilizing a decision tree. Each branch of the tree is quantified by the utility function and a posterior probability distribution, constructed using ArgMax probability distribution, which predicts the suitability of available neighbors. In DTCR (Decision Tree Cognitive Routing), nodes learn their operational environment and adapt their decision making accordingly. We extend the Decision tree modeling to translate video routing in a dynamic cognitive radio network into a decision theory problem. Then terminal analysis backward induction is used to produce our routing scheme that improves the peak signal-to-noise ratio of the received video.We show through this dissertation that by acknowledging the stochastic property of the cognitive radio networks' environment and constructing strategies using the statistical and mathematical tools that deal with such uncertainties, the utilization of these networks will greatly improve.
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- Title
- Cost-aware routing protocols for location-privacy and efficiency in wireless sensor networks
- Creator
- Lightfoot, Leron J.
- Date
- 2015
- Collection
- Electronic Theses & Dissertations
- Description
-
Wireless sensor networks (WSNs) can provide the world with a technology for real-time event monitoring for both military and civilian applications. One of the primary concerns that hinders the successful deployment of wireless sensor networks is how to provide adequate source and destination nodes location privacy. The privacy of the location is vital and highly jeopardized by the usage of wireless communications. While message content privacy can be ensured through message encryption, it is...
Show moreWireless sensor networks (WSNs) can provide the world with a technology for real-time event monitoring for both military and civilian applications. One of the primary concerns that hinders the successful deployment of wireless sensor networks is how to provide adequate source and destination nodes location privacy. The privacy of the location is vital and highly jeopardized by the usage of wireless communications. While message content privacy can be ensured through message encryption, it is much more difficult to adequately address the location privacy issue. For WSNs, location privacy service is further complicated by the fact that sensors consist of low-cost and energy efficient radio devices. Therefore, using computationally intensive cryptographic algorithms (such as public-key cryptosystems) and large scale broadcasting-based protocols are not suitable for WSNs.Many protocols have been proposed to provide location privacy but most of them are based on public-key cryptosystems, while others are either energy inefficient or have certain security flaws. After analyzing the security weaknesses of the existing schemes, we propose several creative and secure energy-aware routing protocols that can address the location privacy issue in WSNs. For source-location privacy, we propose 3 schemes. The first scheme routes each message to a randomly selected intermediate node (RSIN) before it is transmitted to the SINK node. However, this scheme can only provide local source-location privacy. In the second scheme, a network mixing ring (NMR) is proposed to provide network-level source-location privacy. The third scheme achieves network-level source-location privacy through a technique we call the Sink Toroidal Region (STaR) routing. For destination-location privacy, we propose the Bubble routing protocol and a series of R-STaR routing protocols. For each of these routing schemes, both security analysis using quantitative measurements and simulation results show that the proposed protocols are secure and energy-efficient.While providing location privacy is vital, prolonging the lifetime of the network can be a very essential component as well. In this dissertation, we propose a cluster-based energy-aware routing scheme, called Quad-Region Cluster-Head Selection (Q-ReCHS), which will prolong the network lifetime by evenly distributing the energy load among all the nodes. Our extensive simulation results on cluster-based routing demonstrates that our proposed Q-ReCHS scheme can out perform many of the existing schemes.
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