CIF: Small: Cognitive Spectrum Access: Fundamental Limits, Protocols, and Performance Analysis

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Wireless access through unlicensed spectrum is a major component for future broadband initiatives. Unfortunately, unlicensed frequency bands are congested, and existing technologies do not provide quality assurance for users with different access priorities and needs. The lack of quality of service guarantee is a key roadblock to providing multimedia content and facilitating broadband communications. There is a cogent need for technologies that provide distributed hierarchical access of unlicensed spectrum through dynamic spectrum sensing, learning, and cognitive sharing of spectrum opportunities. This research develops mathematical theory and practical methodologies for the cognitive access of wireless spectrum shared by multiple classes of users. The technical approaches of this research are based on the structural optimality of certain carrier sensing policies. The optimality and simplicity of these policies result in new practical yet optimal solutions to cognitive spectrum sharing among users from different priority classes. The overall objective is twofold. First, it aims at gaining a foundational understanding of the limits of cognitive spectrum access in hierarchical networks. In particular, it characterizes the maximum throughput and effective bandwidth regions for users for different priority classes by exploiting structures of optimal policies for cognitive sensing and access. Second, this research develops engineering practical solutions for decentralized cognitive access of shared spectrum. In particular, new multiuser sensing and access protocols are developed and tested for practical applications. Effects of fading, interference and other implementation issues are also examined. This research includes a significant education component aimed at integrating frontier research with undergraduate and graduate curricula.