Energy-Efficient Link Adaptation for Secure D2D Underlaid Cellular Networks

We study energy-efficient secure link adaptation for large-scale device-to-device (D2D) underlaid cellular networks, where base stations (BSs), D2D transmitters, and eavesdroppers (Eve nodes) are distributed as independent homogeneous Poisson point processes. First, we analyze the impact of the underlaid D2D network on the secrecy performance, i.e., secrecy spectral efficiency (SE) and secrecy energy efficiency (EE) of the existing cellular network. We show that when the ratio of the Eve node density to the BS density is above a certain threshold, the secrecy performance of the cellular network first increases and then decreases with the D2D power. Otherwise, it decreases with the D2D power. Next, based on the results, we develop a link-adaptation scheme that controls the D2D power, the confidential message rate, and the redundancy rate to strike a balance between the D2D network's secrecy EE and secrecy SE while guaranteeing a required secrecy performance of the existing cellular network. Simulation results show that the proposed link-adaptation scheme can achieve all the points on the Pareto boundary.