Cooperative spectrum sharing protocol based on transform domain processing with joint secondary selection and power allocation

In order to reduce interference to the primary system and further improve the spectrum efficiency, the Fractional Fourier Transform is introduced as a tool to solve the spectrum sharing problem and a new spectrum sharing protocol is proposed in this paper where sinusoidal signals and chirp signals are utilized for primary users and cognitive users, respectively. In our spectrum sharing protocol, secondary users take the initiative to access the spectrum or act as a DF relay to assist the primary system adaptively according to the channel conditions of the direct transmission link. Moreover, the joint optimization of power allocation and user selection of distributed secondary users is studied to achieve the maximum achievable data rate for the secondary system while guaranteeing the target data rate of primary user. Simulation results show that compared with previous protocols, the outage probability of both primary and secondary systems can be improved, and with an increase in the number of secondary users, a higher achievable data rate can be obtained for the secondary system.