Research On Multi-Dimensional Spectrum Sensing In Cognitive Radio

With the development of wireless communication technology,the existing spectrum resources are unable to meet the increasing demands for the wireless services.Cognitive radio technology can provide fundamental solutions to address the contradiction between the fixed spectrum allocation policy and the need to improve efficiency in spectrum utilization.As one of the most essential and key technologies in cognitive radio,spectrum sensing has long been a hot topic,in which multi-dimensional spectrum sensing has been seen as a significant developing trend.Based on the literature review of spectrum sensing,this thesis explicitly introduces the key methods of transmitter sensing,including energy detection,matched filter detection and cyclostationary detection.Joint spatial-temporal spectrum sensing has been researched in this thesis in detail.The main research results in this thesis are as follows.(1)First and foremost,the properties of conventional spectrum sensing methods including energy detection,matched filter detection and cyclostationary detection have been analyzed and simulated.Particularly,a threshold optimization approach adopting linear integral approximation in average false alarm probability for energy detection with noise uncertainty is proposed.Tradeoff has been made between false alarm probability and detection probability in the novel algorithm.The proposed optimization approach can realize robust sensing and improve the detection performance of cognitive users.(2)For multi-dimensional spectrum sensing,the thesis mainly analyzes the model of joint spatial-temporal spectrum sensing and the communication strategies of cognitive users in heterogeneous network.According to spatial opportunity,this thesis proposes a robust sensing model and provides the definitions of the three regions,primary user distributed region,protection region as well as sensing region based on robust sensing and primary user interception constrains.The methodical formulas in closed-form have also been derived.Both numerical and simulation results show that the proposed model can satisfy sensing and interception constrains,exhibit flexibility as well as improve usable spatial resources.(3)The thesis further proposes directional antenna strategy for cognitive user in replace of the traditional omnidirectional antenna policy.For the proposed opportunistic Overlay and opportunistic Silence modes in the transition region,the sensing model has been improved and the properties of the improved model have been derived and analyzed.To better depict spatial-temporal sensing opportunity,throughput criteria have been given.Simulation results view that the proposed directional antenna strategy can achieve higher throughput as well as reduce interference to primary users.Research results in this thesis have good reference values in cognitive radio spectrum sensing and its applications.