Two-path successive relaying and jamming for securing the primary system

To guarantee secure communication of the primary system and efficiently utilize the licensed spectrum, in this paper, we propose a two-path successive relaying and jamming based cooperative transmission (TSRJC) scheme. In TSRJC scheme, two secondary users (SU) successively relay the primary message and jam the primary eavesdropper to confirm secure and reliable transmission of the primary system during the first stage. During the second stage, the secondary system will be allowed to access the licensed spectrum for the secondary transmission as a reward. To maximize the secondary transmission, a suboptimal algorithm is proposed to allocate the relaying and jamming power. In addition, the closed-form expressions of both SU's relaying and jamming power and jamming power beamforming vector are derived. Simulation results demonstrate the superior performance of our developed scheme over conventional secure communication scheme in terms of primary users' (PU) secure outage probability and SUs' average transmission rate.