Optimal Power Allocation and Secrecy Sum Rate in Two-Way Untrusted Relaying
This work addresses security challenges in wireless communication systems, particularly for scenarios involving untrusted relays, but it is incremental as it builds on existing relaying and jamming techniques.
The paper tackles the problem of maximizing secrecy in two-way untrusted relaying with a friendly jammer by deriving optimal power allocation solutions, resulting in new closed-form expressions for ergodic secrecy sum rate and demonstrating performance gains through numerical examples.
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.