Henry Chen (Committee Member), Yong Pei (Committee Member), Ryan Thomas (Committee Member), Zhiqiang Wu (Advisor), Yan Zhuang (Committee Member)
Doctor of Philosophy (PhD)
With the emergence of increasing number of wireless devices and demands for higher data rates, spectrum crowding and congestion increases. Spectrum congestion problem has been challenging wireless communication engineers for a few decades. However, recent studies indicate that most of the time wide ranges of the radio spectrum are rarely utilized. Hence, the spectrum congestion is mainly due to the inefficient spectrum usage rather than the spectrum scarcity. To exploit under used spectrum and utilize the spectrum efficiently in dynamically changing environments, a new technology is needed. Cognitive Radio (CR) arises to be a possible solution to spectral crowding problem by introducing the opportunistic usage of frequency bands that are not heavily occupied by licensed users.
In this dissertation, we implement and demonstrate an autonomous cognitive radio system in mobile environment via SDR. We first design and implement an intelligent spectrum sensing engine which can detect the existence of the primary user (PU) signal and accurately estimate its radio frequency (RF) parameters. Second, with the aid of the spectrum sensing engine, a spectrum mask is provided. Meanwhile, a multi-carrier waveform is generated based on spectrally modulated spectrally encoded (SMSE) framework. With the dynamic multi-carrier non-contiguous waveform, an intelligent interference avoidance SMSE-based cognitive radio is implemented and demonstrated using universal software radio peripheral(USRP) and GNU software defined radio (SDR) platform. Third, we propose a novel total intercarrier interference (ICI) cancellation scheme to eliminate the ICI in mobile environment, apply the algorithm to the SMSE base cognitive radio, employ GNU SDR platform and USRP, implement and demonstrate an SMSE based cognitive radio in high mobility environment. Combined with the spectrum sensing engine, the cognitive radio is capable of detecting the availability of each and every subcarrier in the operational bandwidth. By turning off those subcarriers occupied by the primary users, the cognitive radio implements a non-contiguous SMSE transmission waveform. Integrated with total ICI cancellation algorithm, the cognitive radio has the ability to eliminate the ICI due to the frequency offset caused by mobility.
There are a few unique features of our cognitive radio implementation: (1) we have demonstrated real-time seamless video transmission without interference to primary users, and without interference from primary users; (2) our cognitive radio is capable of taking advantage of multiple spectrum holes and operating over multiple non-contiguous spectrum bands (our demonstration is the first in the world to stitch multiple non-contiguous spectrum holes together); (3) the cognitive radio dynamically adjusts which subcarriers to turn off according to the primary users'transmission; (4) the cognitive radio can also adjust other parameters such as the total number of subcarriers, center frequency, and bandwidth of each subcarrier; (5) the cognitive radio maintains all the features even in high mobility environment, making it a flexible, agile, and robust cognitive radio node in mobile communication system.
Department or Program
Ph.D. in Engineering
Year Degree Awarded
Copyright 2012, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.