Research On The Technology Of Spectrum Sensing And Spectrum Aggregation Of Cognitive Radio

Cognitive radio can dynamically use radio resources which are temporarily idle in time and space, provide working band for new wireless applications. Therefore it is considered to be one of the key technologies to dynamic spectrum access and solve wireless spectrum scarcity in the future.The primary task of cognitive radio is sensing the spectrum environment; this embodies the characteristics of the most significant cognitive. The multipath fading channel, shadowing effect and the hidden primary user problem, which increase in a single cognitive user uncertainty of the results of primary users. To overcome this series of problem, cooperative sensing has become a hotspot worthy of research.This paper studies the spectrum sensing technology in the cooperative sensing technology, proposed fusion decision algorithm based on centralized framework for Cooperative Sensing. This algorithm is soft-decision algorithm of weight channel impulse response. This paper analyzed the principle of the algorithm model, derived the formula of false alarm probability, detection probability and decision threshold, compared with the algorithms using the "and-rule" and "or-rule". The simulation results show that the algorithm can effectively reduce the decision threshold, while maintaining a low false alarm probability in the case to achieve a higher detection probability, effectively increasing the perceived performance. Cognitive radio must have a noncontinuous spectrum aggregation ability which can aggregate the perceived discrete bands with different width, so it can use "empty holes" for the large bandwidth data transmission. However, current commercial systems using the carrier binding mechanism lack flexibility, and can not adapt to the changing conditions of the dynamic discrete spectrum well.In this thesis, spectrum sensing adopts OFDM-based multi-carrier sensing mechanism, and a physical layer solution is proposed based on the OFDM sub-carrier aggregation, with greater flexibility to adapt dynamic discrete spectrum conditions. An instance calculates the spectrum utilization rate and the spectrum efficiency of using OFDM sub-carrier aggregation, in which the result shows that the targets can meet the demand for high data rate services very well.In this paper, new solutions of spectrum sensing and spectrum aggregation with key technologies are proposed, which make a bases of improving the sensing performance and data transfer rate in cognitive radio networks.