Secure Transmission in Wiretap Channels Using Full-Duplex Relay-Aided D2D Communications With Outdated CSI

This letter examines the physical layer security of a cellular network with inband underlay relay-aided Device-to-Device (D2D) communication, considering the scenario where the channel state information is outdated. The relay node, which operates in a full-duplex mode, can concurrently serve as a friendly jammer to enhance the cellular network secrecy performance while increasing the D2D communication data transmission. A passive eavesdropper utilizes combining approaches to combine the eavesdropping signals. Closed-form expressions for the D2D outage probability and the secrecy outage probability are derived. Furthermore, the asymptotic results are also provided.