Relay assisted spectrum sharing in cognitive radio networks

In this paper, we propose a relay assisted spectrum sharing (RASS) scheme based on the mixed sharing strategy in cognitive radio networks. Mixed sharing is a more general sharing strategy which provides a higher spectrum utilization efficiency than underlay sharing and interweave sharing. Compared to conventional mixed sharing, the proposed approach enhances the throughput of secondary users while not causing harmful interference to the primary receiver. The optimal time allocation which maximizes the achievable capacity of the secondary system is derived. At the same time, the existence of the optimal sensing time is proved and the optimal sharing time allocation between the two-hop relay links is presented. Numerical results show that there exists global optimal time allocation for sensing and sharing in the proposed RASS scheme.