Mode Selection and Spectrum Partition for D2D Inband Communications: A Physical Layer Security Perspective

This paper investigates the fundamental issues of mode selection and spectrum partition in cellular networks with in-band device-to-device (D2D) communication from the physical-layer security (PLS) perspective. We consider a mode selection scheme allowing each D2D pair to probabilistically switch between the underlay and overlay modes, and also a spectrum partition scheme where the system spectrum is orthogonally partitioned between cellular and overlay D2D communications. We first develop a general theoretical framework to model the secrecy outage and secrecy capacity performance of cellular users as well as the outage and capacity performance of D2D pairs. Optimization problems are also solved to identify the optimal mode selection and spectrum partition for secrecy capacity maximization and secrecy outage probability minimization. A case study is then provided to demonstrate the application of our theoretical framework for performance modeling and optimization, and also to illustrate the impacts of mode selection and spectrum partition on the PLS performances of in-band D2D communications.