CREEP: Cognitive relaying enabled efficiency and physical-layer security preserving framework

The object of this work is to improve secrecy capacity of primary user (PU) as well as spectrum utilization. To this end, we present a cognitive relaying enabled efficiency and physical-layer security preserving (CREEP) framework, in which secondary users (SUs) are allowed to perform secondary transmissions. By enabling dual-polarized antenna and leveraging polarization processing at SUs, signals from legitimate users can be separated at the corresponding receivers, while the eavesdropper (EVE) cannot obtain information from PU. We formulate the system model, signaling plan, and key enabling techniques to enhance the spectrum efficiency via allowing SUs´ communications, and to preserve PU´s physical-layer security via SUs´ jamming at EVE. To examine the performance of CREEP, we provide theoretic analysis of a sum capacity maximization under certain rate and power constraints. Numerical results show CREEP not only improves PU´s secrecy capacity but also enhances spectrum utilization.