This paper focuses on the multiple-input-multiple-output (MIMO) two-way relay system with
an untrusted relay and investigates its secure and energy-efficient precoding design issue
based on the physical layer security technology. We first provide theoretical modeling for the
index of secrecy energy efficiency (SEE) and formulate the optimal precoding design for
SEE maximization (SEEM) as a high-dimensional non-convex programming problem. By
exploring the techniques like fractional programming, alternate optimization and semi …

In this paper, we investigate energy-efficient secure communications in an untrusted two-
way relay network, where two source nodes exchange messages via an untrusted relay.
Considering both security threats and energy limitation, the performance metric secure
energy efficiency is defined as the ratio of the secrecy sum rate to the total power
consumption. Our objective is to maximize the secure energy efficiency by jointly designing
the source and relay beamformers. We first derive the expression of secure energy efficiency …