Research On Cooperative Spectrum Sensing Technologies Of Cognitive Radio

Cognitive radio (CR), an innovative technology to mitigate the spectrum scarcity problem, is being paid on increasingly attention as a key technology in the next-generation wireless network. And spectrum sensing, one of the most important issues in CR networks, has become a hot research topic in recent years. Cooperative spectrum sensing can improve the inference accuracy and sensitivity by using diversity of CR users. This thesis summarizes existing cooperative spectrum sensing schemes, and then focuses on the following two issues:First, and then cooperative spectrum sensing using double threshold energy detection is investigated. A fusion rule called'β-ratio'rule is analyzed for improving the accuracy of sensing. The performance parameters of the sensing system whose sensing channel is AWGN channel or Rayleigh fading channel, and reporting channel is perfect or imperfect are derived and then simulated, which are compared with those of a system based on'and'fusion rule or'or'fusion rule. The conclusion is that'β-ratio'rule has quite obvious superiority both on improving sensing accuracy and reducing transmission overheads.Second, a cooperative spectrum sensing model is proposed based on asynchronous distributed fusion. An optimal fusion rule is derived, and a suboptimal scheme, maximum posteriori probability (MAP) estimate-K-rank fusion scheme is analyzed, which does not require prior knowledge of primary user. The probabilities of system by using these two schemes are theoretically analyzed and then simulated respectively. Simulation results show that both of them could improve spectrum sensing reliability effectively.