Secure Power Allocation of Two-Way Relaying with an Untrusted Denoise-and-Forward Relay

This paper proposes an secure transmit power allocation (STPA) scheme for a two-way denoise-and-forward (DNF) relaying network with the aim of maximizing the secrecy sum rate of the network. Here, the DNF relay could act not only as a forwarder but also a potential eavesdropper, i.e., an untrusted relay. First, the secure-rate-region of the two sources that their messages can be strictly kept secret is derived from an information theory point of view. On this basis, an optimal power allocation problem subject to an individual peak-power limit is studied, giving closed-form expressions of the individual transmit powers than can maximize the network secrecy sum rate. Computer simulation results show that compared with the conventional equal-power allocation scheme, the proposed STPA scheme is capable of enhancing the secrecy sum rate and reducing the intercept probability simultaneously.