D2D Communications with Enhanced Physical Layer Security in Cellular Networks

In this paper, we consider secure device-to-device (D2D) direct communication in cellular networks for wiretap channel. We assume that D2D transmitter sends its data to desired D2D receiver by reusing frequency resources originally allocated to the cellular link transmission between a base station (BS) and a cellular user. When there is a single eavesdropper (ED) in wiretap channel, we propose a physical layer security enhancement scheme by applying a precoding vector at D2D transmitter. In the proposed scheme, the precoding vector is designed to maximize the secrecy capacity that is defined as the difference from the sum capacity of BS and D2D receiver to the ED capacity. Through computer simulation, we show that the secrecy capacity can be improved by applying an appropriate precoding vector at D2D transmitter.