Date of Award

Fall 2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical and Computer Engineering

Committee Director

Dimitrie Popescu

Committee Member

Oscar R. Gonzalez

Committee Member

Linda Vahala

Call Number for Print

Special Collections LD4331.E55 A56 2015

Abstract

Wireless communication is an essential part of modern society. The convenience of wireless technology is utilized daily around the world. Users have the ability to access data through mobile devices to access online content. As the need for wireless access increases, the burden on the wireless spectrum will continue to increase as a result. The need for acquiring licensed bands in the wireless spectrum is high. Therefore, this need has created a challenging task to acquire licensed bands in the wireless spectrum.

The cognitive radio is a technology that can be used to solve the under-utilization problem of the wireless spectrum. A cognitive radio is a smart radio that is aware of the wireless services that are available and can obtain these services. Consequently, the main attractive attribute of the cognitive radio is the ability to exploit unused licensed bands. Cognitive radios accomplish this by allowing unlicensed secondary users the capability of temporarily accessing the unused licensed band without degradation/interference to the licensed primary user. In the licensed band, there exists one legitimate primary user per band. However, secondary users may share this band when the primary user is not present. Due to the nature of this concept, there exist potential for malicious secondary users to present themselves as primary users. This is called primary user emulation (PUE).

The addition of secondary users in a wireless network adds to the complexity of the network. The cognitive radio network must be secure for both the primary and secondary users. For a cognitive radio network to function properly, secondary users must be able to accurately determine whether the transmitted signal is safe to use. This is accomplished by localization techniques. Knowledge of the location of the source signaI is crucial in avoiding PUE attacks. An estimated location of the primary user can be used to compare to the known location of the primary user. The comparison of the estimated location with the known location can indicate whether the source is trustworthy. If the estimated location is not consistent with the known transmitter location, it is most likely an illegitimate source. In this thesis, two localization methods are employed to illustrate how a secondary user can determine the legitimacy of the source signal and prevent primary user emulation attacks from malicious nodes. The two localization methods provide estimates of the location of the primary user. The first method obtains the location estimates through received signal strength. The second method achieves the estimates through time difference of arrival of the received signal. Since the primary transmitter is assumed to be known a priori, the estimates determined by each scheme is compared to the known location of the primary transmitter.

For the localization schemes to aid in preventing PUE attacks, the localization schemes must provide reliable data. The accuracy of the localization methods can be investigated by performing simulations. With the simulated results, the known error can be taken into account when utilizing the particular method. The intent of this study is to investigate locational awareness of the primary user in order to prevent primary user emulation attacks in a cognitive radio network. By providing an accurate location of the primary users, this simulation based study has the potential to provide improvements on physical layer security through localization.

Rights

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DOI

10.25777/80a3-yj79

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