Optimal Power Allocation and Secrecy Sum Rate in Two-Way Untrusted Relaying

TL;DR

This paper analyzes the secrecy performance of two-way untrusted relaying with multiple antennas, deriving optimal power allocation and secrecy sum rate expressions, and highlighting the benefits of friendly jamming in enhancing security.

Contribution

It introduces new closed-form solutions for optimal power allocation and ergodic secrecy sum rate in two-way relaying with friendly jamming, considering untrusted relays and multiple antennas.

Findings

Optimal power allocation enhances secrecy sum rate.

Friendly jamming improves security performance.

The impact of FJ's location and antennas is significant.

Abstract

In this paper, we examine the secrecy performance of two-way relaying between a multiple antenna base station (BS) and a single antenna mobile user (MU) in the presence of a multiple antenna friendly jammer (FJ). We consider the untrusted relaying scenario where an amplify-and-forward relay is both a necessary helper and a potential eavesdropper. To maximize the instantaneous secrecy sum rate, we derive new closed-form solutions for the optimal power allocation (OPA) between the BS and MU under the scenario of relaying with friendly jamming (WFJ). Based on the OPA solution, new closed-form expressions are derived for the ergodic secrecy sum rate (ESSR) with Rayleigh fading channel. Furthermore, we explicitly determine the high signal-to-noise ratio slope and power offset of the ESSR to highlight the benefits of friendly jamming. Numerical examples are provided to demonstrate the impact of the FJ's location and number of antennas on the secrecy performance.