Research On Cognitive Radio Technologies Based On Cooperative Relay

With the rapid requirement of communication capacity, the wireless communicationresources (expecially wireless spectrum resources) which can be exploited become less andless. Consequently, efficient wireless communication technologies become the highlight ofcommunication field to resolve the problem. Cognitive Raido (CR) which can improveutilization ratio of spectrum resources and realize the communication between the authorizedusers and non authorized users is a protencial technology to solove the problem, CR is alsothe highlight of recent researches.Meanwhile, in wireless communication field cooperative relay technology can enlargethe communication distance between the transmitter and the receiver and improve spatialdiversity of the receiver. Cooperative cognitive relay network (CCRN) can improve spetrumdiversity of cognitive radio network (CRN) and accuracy of spectrum sensing.Consequently, CCRN is the research object of the paper, the problems researched are asfollows:(1) An adaptive power allocation algorithm is proposed and outage propobability isanalized based on proposed CCRN.(2) An adaptive power allocation algorighm is proposed. Combination of secondaryuser’s transmission power constraint and primary user’s interference constraint is consideredto establish mathematical optimal model in AF (amplify-and-forward) and DF(decode-and-forward) relay schemes. By non-convex and convex optimization methods,optimal power solutions can be derived.(3) Outage probability of CCRN is analized. When the peak transmit power of cognitiveuser is limited, outage probability of CCRN is analized under primary user’s peak and averageinterference constraints separately. Under primary’s peak interference constraint, the outageprobability of cognitive relay system with single relay node can be analyzed by outageprobability definition. However, under primary’s average interference constraint, a powerallocation algorithm is proposed and the outage probability can be analyzed based on thepower allocation algorithm. Meanwhile based on the cognitive relay system with single node, the outage probability of cognitive relay system with multiple relay nodes can be analyzed. Atlast theoretical results are compared with simulation results to testify the accuracy of thetheoretical results.