Green Communications Based on Physical-layer Security for Amplify-and-forward Relay Networks

In this paper, a green communication scheme based on physical layer security is addressed considering the energy and secrecy constraints. This scheme maximizes the secure Energy Efficiency (EE) of the network by power allocation subject to the maximum power constraint of each node and the target secrecy rate constraint of the network. Furthermore, an iterative algorithm for power allocation is developed based on fractional programming, dual decomposition, and Difference of Convex functions (DC) programming. It is verified by simulations that the proposed algorithm can lead to a significant gain of secure EE yet with some loss of secrecy rate compared with secrecy rate maximization. This is because that there is an inherent tradeoff between EE and secrecy. However, the achievable secrecy rate of the proposed scheme is still superior over that of total transmission power minimization.