Secrecy capacity and energy efficiency in D2D-enabled cellular networks

Device-to-device (D2D) communication is introduced in cellular networks to allow devices in close proximity to communicate directly with each other, freeing up spectral and other system resources. We propose a scheme that promotes the coexistence of cellular users (CUs) and D2D users (DUs). DUs are allowed to access the CU channel for D2D communications, enhancing the spectral efficiency. On the other hand, DU is expected to protect the secrecy of CU's data by transmitting artificial noise to jam any potential eavesdroppers near the CU link, which may include other DUs. This enhances the cellular secrecy capacity at the expense of DU's energy, which motivates us to assess the CU's secrecy capacity and DU's energy efficiency of this scheme. We have identified the causes and conditions of increased energy efficiency under certain secrecy capacity requirement, e.g. an optimal DU's sensing duration that results in maximal energy efficiency. Such information is important for the planning of an efficient access control and scheduling scheme for the DU links in cellular networks.