Study of Sensing Issues in Dynamic Spectrum Access
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Dynamic Spectrum Access (DSA) is now a commonly used spectrum sharing paradigm to mitigate the spectrum shortage problem. DSA technology allows unlicensed secondary users to access the unused frequency bands without interfering with the incumbent users. The key technical challenges in DSA systems lie in spectrum allocation problems and spectrum user's security issues. This thesis mainly focuses on spectrum monitoring technology in spectrum allocation and incumbent users' (IU) privacy issue. Spectrum monitoring is a powerful tool in DSA to help commercial users to access the unused bands. We proposed a crowdsourcing-based unknown IU pattern monitoring scheme that leverages the power of masses of portable mobile devices to reduce the cost of the spectrum monitoring and demonstrate the ability of our system to capture not only the existing spectrum access patterns but also the unknown patterns where no historical spectrum information exist. Due to the energy limit of the battery-based system, we then leverage solar energy harvesting and develop an energy management scheme to support our spectrum monitoring system. We also provide best privacy-protection strategies for both static and mobile IUs in terms of hiding their true location under the detection of Environmental Sensing Capabilities system. In this thesis, the heuristic approach for our mathematical formulations and simulation results are described in detail. The simulation results show our spectrum monitoring system can obtain a high spectrum monitoring coverage and low energy consumption. Our IU privacy scheme provides great protection for IU's location privacy.
General Audience Abstract
Spectrum relates to the radio frequencies allocated to the federal users and commercial users for communication over the airwaves. It is a sovereign asset that is overseen by the government in each country to manage the radio spectrum and issue spectrum licenses. In addition, spectrum bands are utilized for various purposes because different bands have different characteristics. However, the overly crowded US frequency allocation chart shows the scarcity of usable radio frequencies. The actual spectrum usage measurements reflect that multiple prized spectrum bands lay idle at most time and location, which indicates that the spectrum shortage is caused by the spectrum management policies rather than the physical scarcity of available frequencies. Dynamic spectrum access (DSA) was proposed as a new paradigm of spectrum sharing that allows commercial users to access the abundant white spaces in the licensed spectrum bands to mitigate the spectrum shortage problem and increase spectrum utilization. In DSA, two of the key technical challenges lie in how to dynamically allocate the spectrum and how to protect spectrum users’ security. This thesis focuses on the development of two types of mechanisms for addressing the above two challenges: (1) developing efficient spectrum monitoring schemes to help secondary users (SU) to accurately and dynamically access the white space in spectrum allocation and (2) developing privacy preservation schemes for incumbent users (IU) to protect their location privacy. Specifically, we proposed an unknown IU pattern monitoring scheme that leverages the power of masses of portable mobile devices to reduce the cost of common spectrum monitoring systems. We demonstrate that our system can track not only the existing IU spectrum access patterns but also the unknown patterns where no historical spectrum information exists. We then leverage the solar energy harvesting and design energy management scheme to support our spectrum monitoring system. Finally, we provide a strategy for both static and mobile IUs to hide their true location under the monitoring of Environmental Sensing Capabilities systems.
- Masters Theses