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theses

In the last decade, there have been several technological trends that have occurred together and have caused a shift in how wireless systems will be deployed. The significant increase in the capabilities of mobile devices, combined with the proliferation of Internet enabled services, and the improvement in the communication support provided by new waveforms for wireless communications, have initiated a shift from the traditional, macrocell-based cellular network to new forms of radio access technologies (RATs) involving multiple, smaller cells deployed in vicinity of each other. These small cells will often support diverse wireless technologies and be operated by different providers. The resulting heterogeneity, unfortunately, can lead to serious internetwork interference that can negate the improvement in overall system performance that was the original motivation for employing many small cells in close proximity. In this thesis, we examine different technologies that are needed for flexible spectrum management to support the coordination that is needed for coexistence between many small cell wireless networks. Motivated by the need for internetwork architectures that support spectrum coordination, we (1) conduct performance evaluation associated with the joint deployment of mobile and fixed hotspot networks, (2) develop spectrum models that characterize interference among different wireless entities, (3) provide new methods for efficient hardware emulation of wireless channels, (4) devise algorithms that estimate radio spectrum usage, and (5) provide algorithms for coordination between different wireless systems to improve the overall system performance and spectrum efficiency. The first part of the thesis investigates spectrum coexistence in wireless networks by exploring the underlying performance challenges that exist when mobile hotspots are deployed in an environment of densely deployed, static wireless access networks. Next part of thesis investigates design of hardware emulator of radio channels to accurately capture the effect of real-world wireless channels upon communications waveforms while minimizing computational complexity. Next, we explore a fundamental building block of spectrum management for supporting better utilization of radio spectrum which involves predicting the impact that an emitter will have at different geographic locations. We then examine various challenges associated with coordinating spectrum access between different wireless technologies by exploring the specific case of Wi-Fi and LTE coexistence in emerging unlicensed frequency bands. Finally, recognizing the broad challenges associated with addressing spectrum coexistence in emerging wireless systems, we identify several directions for future investigation and suggest different approaches for tackling these challenges.

ETD_7267

Ph.D.

Includes bibliographical references

by Shweta S. Sagari

doi:10.7282/T30G3NBD

ETD doctoral

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