Opportunistic Wireless Spectrum Access: Protocols, Analysis and Applications

The limited availability of usable wireless spectrum and the ever increasing demands of high bandwidth data transfer raise concerns on whether current spectrum access regimes can match future communication requirements. Moreover, most desirable frequency ranges with good channel characteristics are already licensed, and purchasing new licenses for small operators is often prohibitively expensive. This thesis proposes methods for achiev- ing efficient spectrum access through devising protocols for identifying and sharing unused spectrum, analyzing the theoretical bounds of these protocols, and implementing these so- lutions in practical medical and vehicular environments.;A significant portion of the thesis is focused on opportunistic spectrum access within licensed frequency bands, where cognitive radios transmit on frequencies without inter- fering with the primary users in them. First, a cooperative sensing method based on re- inforcement learning technique is designed to efficiently detect spectrum opportunities. After identifying portions of the available spectrum, a channel allocation technique is de- vised for the cognitive radios with quality of service provisioning. The supporting analyt- ical framework is constructed using Markov process and ensures that radios opportunis- tically using the licensed spectrum meet their latency and throughput requirements. The analytical framework is tested through traces collected in the wireless medical telemetry service (WMTS) band, and reliability enhancements in possible hospital application areas are quantified. A mobile architecture composed of vehicular networks is also investigated, where spectrum databases that provide the spectrum availability information are included in the network design.;Apart from re-use of the licensed spectrum, this thesis investigates full duplex channel access scheme for improving throughput. Full duplex enables simultaneous transmission and reception on the same channel for a single radio, which promises doubling of the throughput. An analytical framework for the performance of CSMA/CA based channel access for full duplex enabled network of nodes is formulated. The closed form expres- sions for the average throughput and packet collision probability in such a network is analytically derived and verified through comprehensive simulations.