Slotted ALOHA Techniques In Spectrum Sharing Wireless Systems

As a smart spectrum sharing technology under limited spectrum resources, cognitive radio (CR) can significantly improve the spectrum utilization of authorized users. In this thesis, random access techniques in media access layer of cognitive radio are considered and the performance of the slotted ALOHA access protocol and its related protocol is mainly studied. Chapter1discusses the technical backgrounds and status of CR, research meaning of CR and our work. Chapter2discusses conventional multi-access techniques and the CR media access protocols et al. In chapter3, ALOHA and CSMA is discussed briefly, and then comparison of throughput performance is performed by computer simulation.Chapter4studies a type of hybrid slotted ALOHA protocols for the special CR scenario where the secondary users can utilized slotted ALOHA access, non-slotted CSMA access respectively, in condition of primary user by means of slotted ALOHA access. Throughput of the primary user and the secondary users are theoretical derived and verified, and then comparison of throughput performance in two access modes of secondary users is performed.Chapter5studies a type of hybrid CSMA protocols for the special CR scenario where the secondary users can utilize slotted CSMA access slotted ALOHA access respectively, in condition of the primary user by means of slotted CSMA access. Throughput of the primary user and the secondary users are theoretical derived and verified, and then Comparison of throughput performance in two access modes of secondary users is performed.Chapter6summarizes the full thesis and outlined areas for further research directions.