Secure communications of cellular users in device-to-device communication underlaying cellular networks

In this paper, we aim to optimize the secrecy rate of the cellular user (CU) in a single cell where the Device-to-Device (D2D) communication shares the uplink resource with CU. The interference link from CU to the D2D receiver can be considered as the eavesdropping link in the sense that the D2D receiver may try to decode the cellular user's message. The proposed scheme aims to optimize the achievable secrecy data rate of CU when guaranteeing the quality-of-service (QoS) requirement of the D2D link. In particular, for a given D2D pair, we propose an secure region of the CU partner, where the physical layer security of the CU partner can be guaranteed. The D2D link is not allowed to share the spectrum with CU residing outside the secure region. Furthermore, an optimal power allocation algorithm is designed to optimize the secrecy capacity of CU. Numerical results are conducted to evaluate the performance of the proposed scheme and verify the characterization of the secure region.