Hybrid Full-/Half-Duplex Relaying in Cognitive Networks

摘要

In cognitive radio full-duplex (FD) relay networks, self-interference (SI) generated from the relay and harmful interference from secondary user (SU) on primary user (PU) would jointly deteriorate the system performance. In this paper, we analyze the physical layer security issue of a cognitive relay network. Specially, a SU source transmits message to a SU receiver through multi-antenna relay under the interference constraints on PU. In practical, FD and half-duplex (HD) model have its own advantages. Thus, we employ the hybrid protocols that switch adaptively between FD and HD relaying models. The motivation for hybrid adaptive protocols selection comes from trade-off of spectral efficiency and SI suppression: The HD model avoids inherently the SI at the cost of halving the data rate while FD model is spectral efficiency that achieve full data rate, but it suffers from severe SI. We propose a combination of hybrid protocols selection and secure on-off transmission to enhance the system performance. Simulation results demonstrate that our hybrid strategy with secure on-off transmission outperforms the system design that utilizes either relay mode.