Cooperative Spectrum Sharing based on Amplify and Forward Relaying in Cognitive Radio Networks

摘要

In this paper, we consider a cognitive radio system in non-ideal fading wireless channels and propose a geometric approach based on cooperative amplify and forward relaying for the secondary users, which serves as an alternative way to ensure the primary user’s transmission and realize spectrum sharing. The whole system consists of a pair of primary transmitter and receiver and a pair of secondary transmitter (ST) and receiver. The key feature of the proposed approach is that ST acts as a half-relaying for the primary system by linearly combining the primary signal with the secondary signal and allocating fractions λ and 1 ? λ of the transmit power to the primary and secondary signals separately. We show that for a fixed λ, we can find a critical region for ST restricted in two-dimension where outage probability of the primary system is kept or lower than the case without spectrum sharing. The outage performance achieved by the secondary system is also derived. We get the optimal λ and location for the secondary system when the secondary parameters are changeable. Finally, the bit error rate for both primary and secondary systems are derived in closed-form expressions. Simulation results illustrate that the proposed scheme can significantly realize spectrum sharing.