Research On Cooperative Communication Technology In Cognitive Radio Networks

Cognitive radio is an intelligent spectrum sharing technology[1-2]. By sensing communicationenvironment to dynamically detect idle spectrum, secondary users adaptively change the systemoperating parameters based on the learning and decision-making algorithm. So spectrum sharingand dynamic spectrum allocation can be achieved to effectively improve the spectrum utilization.Collaborative communication technology is used to get space diversity gain for improving thesystem capacity. In multi-user environment, users of collaborative communication construct"virtual multi-antenna array" by sharing antenna for making channel transmission effect which issimilar to multi-input multi-output system on coping channel fading.Under the background of cognitive wireless network, the article makes an in-depth study ofcooperative transmission strategy and system performance in cognitive radio. The main content ofthe article is as follows:Firstly, the article makes a detailed introduction to the working principle of cognitive radio andcooperative communication and has a classified discussion on spectrum sensing program ofcognitive radio and relay cooperative strategy of collaborative communication. At the same time,the article conducts a study on the combination mode of cognitive radio and cooperativecommunication.Secondly, because of the simultaneous existence of primary users and secondary users incognitive radio network, the communication of secondary users is carried out under condition ofthe secondary users don’t cause interference to the communication of primary users. However,secondary users also have communication performance requirement. In order to ensure thecommunication quality of secondary users, the article proposes a new type of cooperativetransmission strategy in cognitive wireless network and defines the concept of conflict-freetransmission time of secondary users. And then it make a detailed theoretical analysis onconflict-free transmission time of secondary users in new cooperative transmission strategy. Forcomparison the article also make a theoretical analysis on conflict-free transmission time ofsecondary users in single relay cooperative strategy. Simulation experiment is carried out toverify the new cooperative transmission strategy proposed significantly improves system capacityperformance than single relay cooperative strategy. Then, the article has analysis on error performance of the new type cooperative transmissionstrategy and provides the analytical expression of bit error rate of single relay cooperativetransmission mode and new type cooperative transmission mode. And then Monte Carlosimulation experiment is carried out to verify the new type cooperative transmission strategysignificantly improves error performance of the secondary user network than single relaycooperative transmission strategy.Finally, the article has study on collaborative technology between primary users and secondaryusers in cognitive wireless network environment. Secondary users cooperate with primary userswhich are in busy state while single-relay cooperation is carried out between secondary users. Thecollaboration for primary users can improve the data transfer rate of primary users, so thatsecondary users can strive for more transmission time. And article carry out a detailedtheoretical analysis and simulation verification on conflict-free transmission time of secondaryusers. The results show that the collaboration strategy between primary users and secondary userswe proposed further enhance system capacity performance than single relay cooperative strategy.