Joint spatial-temporal spectrum sensing and cooperative relaying for cognitive radio networks




Do, Tuan T

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The number of wireless systems and services has grown tremendously over the last two decades. As a result, the availability of wireless spectrum has become extremely limited. Cognitive radio is a new technique to overcome the issue of spectrum scarcity. In cognitive radio networks, the licensed users of the spectrum are called primary users. Secondary users equipped with cognitive radios can opportunistically transmit via so-called “spectrum holes” which can be categorized as spatial or temporal spectrum holes. In this dissertation, we propose a joint spatial-temporal spectrum sensing scheme for cognitive radios. We show that our joint spatial-temporal spectrum sensing scheme outperforms pure temporal sensing schemes. In addition, joint spatial-temporal sensing increases the point-to-point transmission capacity of cognitive radio link compared to pure temporal or spatial sensing. We also propose a temporal spectrum sensing scheme that exploits multiuser diversity in wireless networks. In wireless networks with fading, multiuser diversity exists because different users experience peak channel quality at different times. By exploiting multiuser diversity, our spectrum sensing method can outperform the spectrum sensing schemes that do not exploit multiuser diversity. We develop and analyze a joint spatial-temporal sensing scheme that incorporates cooperative relaying to further increase the capacity of a cognitive radio network. We consider both amplify-and-forward and decode-and-forward cooperative transmission strategies. Finally, we study joint spatialtemporal spectrum sensing in a multichannel cognitive radio scenario and present randomized and maximized signal-to-noise ratio algorithms that improve performance in term of symbol error probability.



Cognitive Radio, Spectrum Sensing, Cooperative Diversity, Turbo Code, Multiuser Diversity, Multichannel Cognitive Radio