Spectrum Sensing And Access Control Algorithm In Cognitive Radio Networks

With the development of mobile Internet and the coming of big data, there has been more and more demand for network resources. Cognitive radio technology provides a new solution for solving the problem which lacks of spectrum resource in the present environment. To realize spectrum sharing, the first step needs rapid and accurate spectrum sensing; which second step is how to allocate the spectrum hole to the cognitive users so as to maximize the spectrum utilization.To improve the spectrum sensing performance over doubly-selective fading channels, this thesis proposed a spectrum sensing method for channel modeling based on the modified complex exponential basis expansion model. This model could reflect the facticity of the doubly-selective fading channels; meanwhile, the affected induced by time-selected fading is compensated effectively by basal adaptive mobile speed. Under the conditions of constant false alarm rate, the spectrum sensing of authorized user is taking advantage of the cyclostationary of received signal. Simulation results show that the proposed method is robustness and will get better sensing performance in the low SNR and the dynamic moving speed environment for CR users.Traversing search algorithm which based on branching processes is proposed to maximize the throughput of spectrum resource allocation. To find effective allocation schemes, assign an natural number from 1 to MN to each spectrum allocations as the address, then build a tree according the value of the address from small to large, branching all processed allocation schemes under the condition which can guarantee the minimum-rate and normal communication of every cognitive users; Then gradually pruning by eliminating some allocation schemes which are not match condition to get optimal solution which means the optimal resource allocation. Simulation results demonstrate that effective allocation schemes are enhanced by the proposed scheme; it also increases throughput of system and utilization of spectral efficiency.