Research On Dynamic Spectrum Allocation For Cognitive Radio Networks

With the development of the wireless communication technologies and the increasing requirement of wireless spectrum resources, cognitive radio networks have gained a lot of attention for their unique characteristics, such as high spectrum utilization and flexible operation, accessing spectrum resources licensed to other primary networks without authorization. Cognitive radio networks have become one of the most important trends of the wireless mobile communication. Special spectrum allocation altorithm are essential to adapt to the time-space varying characteristics of wireless spectrum in cognitive networks. Dynamic spectrum allocaton algorithm with center-based network structure can greatly improve spectrum utilization, reduce system cost of spectrum allocation, and dynamically adjust to meet the communication requirement. Moreover, combined with power control, center-based dynamic spectrum allocation can not only reduce interference to primary users and subcriber users, but also effectively improve spectrum utilization and network performance.Under the support of National Hi-tech Research and Development Program(863) of China, combining with the advantages of center-based dynamic spectrum allocation, the thesis is focused on dynamic spectrum allocation in cognitive radio networks, and Sub-channel Set based Adaptive Dynamic Channel Allocation algorithm is proposed, and with power control, the algorithm greatly improves spectrum utilization and network performance.Firstly, the backgroud, development and advantages of cognitive radio are introduced, and the application environment is illustrated simultaneously. The research status of cognitive radio and dynamic spectrum allocation algorithm are discussed in detail.And then, current research models of cognitive radio and dynamic spectrum allocation are fully studied. The classification, design principle and key technics of spectrum allocation are introduced as the foundation of describling the center-based and distributed models of dynamic spectrum allocation. By establishing mathmatics model and utility function, the design principle is fully analyzed.After that, emphasis is put on center-based dynamic spectrum allocation in cognitive radio networks. According to the mathmatics model of spectrum allocation, several representative dynamic spectrum allocation algorithms are analyzed contrastively. An improved sub-channel set based adaptive dynamic channel allocation algorithm is proposed, on the base of which another algorithm with power control is given. To evaluate performance of the proposed algorithms, the system cost, utilization and fairness are compared and analyzed by matlab simulation results.At last, the united design and implementation of other layers in cognitive networks are described. As the design structures of physical frame, MAC frame are given, through cross-layer design method, the united design of transport layer, MAC layer and physical layer is completed. Moreover, the whole system design is implemented on XScale PXA255 processor and thepractical testing results are given.