Cognitive multi-relay based on dynamic spectrum leasing

Dynamic spectrum leasing is a new spectrum sharing paradigm to achieve efficient use of the frequency resources for cognitive radio. In this paper, we propose two schemes of selecting secondary nodes as relays. Secondary users act as relays to improve quality of service of primary user, then primary user may lease a fraction of spectrum bands to secondary users. It is shown that these two schemes can improve the performance of primary and secondary network significantly while maintaining a fixed target data rate for the primary user. Moreover, we derive the accurate expression of primary outage probability of using all the secondary nodes as relays. Simulation results are presented to evaluate and compare the performances of the proposed two schemes.