Research On Improved Cooperative Spectrum Sensing Algorithm In Cognitive Radio Networks

Cognitive radio technology which based on dynamic spectrum allocation can effectively improve spectrum utilization. Spectrum sensing is the premise of spectrum estimation and spectrum allocation and it’s one of the primary technologies of cognitive radio. This paper mainly focuses on studies of cooperative spectrum sensing technology.The paper presents an algorithm of adaptive cooperative spectrum sensing based on optimal relay with the consideration of sensing performance and energy consumption, which can overcome the problems about fading of sensing channel and huge consumption of relaying. The algorithm obtained reasonable tradeoff between performance and consumption by opportunistic relaying, benefit function based selection of optimal relay and mechanism of system parameters adjustment. And the comparative simulation shows the proposed algorithm can significantly improve system performance with low energy consumption compared with no-relay sensing algorithm and the sensing performance is close to optimal and fixed relay sensing algorithm when the number of sensing user is more. And the sensing process adapts actual needs more by adjusting the system parameters.The paper presents a double threshold cooperative spectrum sensing algorithm which is based on trust and satisfies both reliability and efficiency. The cognitive nodes that satisfy the request of double threshold have the priority to participate in cooperative sensing and that satisfy the requirement of trust parameters can participate in cooperative sensing if only the number of the former is smaller than a preset value. The fusion center stores the sensing records of each cognitive node and set fusion weights according to the partial detect results. Theoretical analysis and simulation show that the bandwidth required for transmitting sensing parameters decreases and detection performance improves caused by the unreliable users reduced. Additionally, the algorithm can be made to adapt to different wireless service by adjusting the parameter.The paper presents a PU state-based sequential cooperative spectrum sensing algorithm which based on the occupation characteristics of authorized channel and sequential spectrum sensing. And the duration of PU’s presence or absence in authorized channel is far greater than sensing period. Cognitive nodes perform different sequential spectrum sensing algorithms according to the sensing result of last time to improve the performance and efficiency of the system. The simulation results show that compared to the hard combination and soft combination cooperative spectrum sensingalgorithm, this algorithm can greatly improves detection performance by smaller transmission bandwidth at the expense of little increasement in time consumption. And this algorithm has the advantages of detection performance and detection expense compared to the non PU state-based sequential algorithm.