Research On Channel Allocation And Optimal Cross-Layer Resource Scheduling In Cognitive Systems

The booming of wireless communications is largely furthered by the desire of freely communicating anywhere and anytime. Actually, there is big challenge to the wireless communication technology and structure since the command for system capacity becomes larger and QoS requirement becomes higher. Cognitive Radio (CR) has so big potential to increase spectrum utility that it has been paid close attention to. Researchers take advantage of its spectrum dynamics, and their research works have been far beyond dynamic spectrum access and allocation recently, and they concentrate more on industrial and operational deployment. They apply cognitive technology into practical networks and system, such as Self-Organized Network, Small Cell Network and multi-hop Network, and so on. In the paper, research is done by theory associated with practice and plenty of research results are put forwards.Firstly, two types of channel allocation scheme are proposed after investigation of radio resource allocation methods, that is, Resource Priority Scheme and Demand Priority Scheme. The former one mainly ensures reasonable utility of channel resource and the latter one mainly concentrate on satisfying users’demands. System Performance such as throughput, fairness of users, interruption rate, delay time and spectrum handover frequency is analyzed by theory and simulation. What’s more, the effect to performance caused by number of users, update time of reserved channel list and average available time of channels is investigated, too. Time complexity and storage efficiency are also analyzed to demonstrate the merits and demerits of the two schemes. Numerical results indicate that Resource Priority Scheme is more suitable to channel condition with high dynamic, for it is facilitated with the ability to reply rapid change of channel condition, while in the moderate channel environment, the other scheme with reserved channel list is more appropriate, for its complexity is much lower that the former one, even though there is a little decrease of system performance.Secondly, a kind of practical channel allocation scheme is proposed to solve problems in cognitive systems without spectrum handover ability. The scheme is designed to improve system throughput while ensures the communications of primary users. By the analysis of Markov process and Monte Carlo simulation results, the proposed scheme behaves better than those with spectrum handover ability in service blocking probability while guarantees that interruption rate is not raised largely.Lastly, analysis and cross-layer design is put forward for multiple hops cognitive radio system in Overlay fashion. Through analysis of constraints from physical layer to application layer, cross-layer optimal design is proposed. In the design, optimal object is the maximal router constraint system probable capacity, and the constraints conditions covers resource allocation and scheduling in network access layer, router selection in network layer, connection establishment and flow control in transmission layer and QoS requirement in application layer. Heuristic Algorithm is proposed to solve the complex problem and system performance and algorithm evaluation is put forward to simulate and analyze.