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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/3645

Title: Reconfigurable antennas for wireless network security
Authors: Mookiah, Prathaban
Keywords: Electric engineering;Wireless security;Reconfigurable antenna
Issue Date: 29-Nov-2011
Abstract: Large scale proliferation of wireless technology coupled with the increasingly hostile information security landscape is of serious concern as organizations continue to widely adopt wireless networks to access and distribute critical and con dential information. Private users also face more risks than ever as they exchange more and more sensitive information over home and public networks through their ubiquitous wireless-enabled laptops and hand held devices. The fundamental broadcast nature of wireless data transmission aggravates the situation, since unlike wired networks, it introduces multiple avenues for attack and penetration into a network. Though several traditional mechanisms do exist to protect wireless networks against threats, such schemes are a carryover from the traditional wire based systems. Hence vulnerabilities continue to exist, and have been repeatedly demonstrated to be susceptible to failure under di erent circumstances. The resulting uncertainties have led to a signi cant paradigm shift in the design and implementation of wireless security in recent times, among which wireless channel based security schemes have shown the most promise. Channel based security schemes are rooted on the simple fact that a legitimate user and an adversary cannot be physically co-located and hence the underlying multi-path structure corresponding to the two links cannot be the same. However most wireless systems are constrained in terms of bandwidth, power and number of transceivers, which seriously limit the performance of such channel based security implementations. To overcome these limitations, this thesis proposes a new dimension to the channel based security approach by introducing the capabilities of recon gurable antennas. The main objective of this work is to demonstrate that the ability of recon gurable antennas to generate di erent channel realizations that are uncorrelated between di erent modes will lead to signi cant improvements in intrusion detection rates. To this end, two di erent schemes that make use of channels generated by a recon gurable antenna are proposed and evaluated through measurements. The rst scheme is based on associating a channel based ngerprint to the legitimate user to prevent intrusion. The three main components of this scheme are i ) a ngerprint derived from the di erent modes of the antenna, ii ) a metric to compare two ngerprints and iii ) a hypothesis test based on the proposed metric to classify intruders and legitimate transmitters. The second scheme relies on monitoring the statistics of the channels for the legitimate transmitters' links since any intrusion will result in an observable change in the channel's statistics. The problem is posed as a generalized likelihood ratio test (GLRT) which responds to any change in the channel statistics by a large spike in the likelihood ratio's value. The detector's performance is studied as a function of pattern correlation coe cient for both schemes to provide insights on designing appropriate antenna modes for better performance. Moreover this thesis takes a holistic approach to studying the antenna based security schemes. A novel channel modeling approach which combines the cluster channel model and site speci c ray tracer results is proposed and validated to facilitate the analysis of such schemes through simulations without resorting to comprehensive channel measurements. This approach is motivated by the lack of an intuitive and simple channel model to study systems that use recon gurable antennas for any application. Finally the design of a metamaterial based substrate that can help miniaturize antenna arrays and recon gurable antennas is presented. The magnetic permeability enhanced metamaterial's capability to miniaturize an antenna's size while maintaining an acceptable level of isolation between elements in an array is experimentally demonstrated. The bene ts gained in a wireless communication system that uses a patch antenna arrray built on this substrate is quanti ed in terms of mean e ective gain, correlation between the antennas and channel capacity through channel measurements. Despite their capability to signi cantly improve spectral e ciency, the widespread adoption of recon gurable antennas in wireless devices has been hampered by their complexity, cost and size. The work presented in this thesis is therefore intended to serve as a catalyst to the widespread adoption of recon gurable antenna technology by i ) adding value to such antennas by utilizing them for enhancing system security and ii ) providing a mechanism to miniaturize them to facilitate their integration into modern space constrained wireless devices.
URI: http://hdl.handle.net/1860/3645
Appears in Collections:Drexel Theses and Dissertations

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