Study Of Resource Allocation Algorithms In OFDM-based Cognitive Radio System

Cognitive Radio technology allows the secondary users to share the spectrumresources with primary users based on the premise that the interference introduced tothe primary users is not serious. Thus the spectrum utilization can be improved. OFDMhas high capability to allocate frequency resources adaptively, so it can be applied toCognitive Radio.In this paper, the research on cognitive radio resource allocation algorithms is basedon OFDM technology which considering the primary users’ interference limitation andthe cognitive users’ transmission limitation. The spectrum utilization can be furtherimproved by optimally allocate the subcarriers and the transmit power of the subcarrier.The thesis firstly introduces the cognitive radio’s principle concept, key technologiesand OFDM-based cognitive radio. Then we mainly research the resource allocationalgorithm based on the fairness among secondary users and the subcarrier matching andpower allocation algorithms in relayed OFDM based cognitive system respectively bothfrom the rate maximization aspect.We consider the problem of the maximization of secondary users’ rate assumptionunder the interference power constraint at primary users, the transmit power constraintof secondary users and the fairness among the secondary users. An optimal resourceallocation algorithm and a suboptimal algorithm that reduces operational complexity aregiven. Simulation results show the correctness and effectiveness of the proposedalgorithms.In this work, we also researched the resource allocation algorithms in decode andforward relayed OFDM based cognitive system. In view of the current algorithmsrequire the cognitive radio transmitter has the instantaneous channel state information,we use a probabilistic model of interference threshold constraint where interference canbe guaranteed in a statistic manner. In this paper, the proposed resource allocationalgorithm requires the knowledge of channel fading statistics instead of instantaneouschannel gain among the secondary users’ transmitter and primary users’ receiver, thuseased restrictions on the requirements of the channel estimation. Meanwhile, a suboptimalalgorithm that reduces the operational complexity is also given in this paper. Simulation resultsshow the correctness and effectiveness of the proposed algorithms.