Securing Full-Duplex Amplify-and-Forward Relay-Aided Transmissions Through Processing-Time Optimization

TL;DR

This paper explores how optimizing processing delay at a full-duplex relay can enhance physical-layer security by converting the channel into flat-fading sub-channels and injecting artificial noise to thwart eavesdroppers.

Contribution

It introduces a novel approach of using relay processing time to improve security in FD AF relay channels by leveraging ISI channel modeling and artificial noise injection.

Findings

Processing time affects artificial noise effectiveness.

DFT-based modulation converts ISI channel to flat-fading.

Optimized delay improves security against eavesdroppers.

Abstract

We investigate physical-layer security of the full-duplex (FD) amplify-and-forward (AF) relay channel. We provide a new perspective on the problem and show that the processing time (delay) at the relay can be exploited to improve the system's security. We show that the FD AF relay channel can be seen as an intersymbol-interference (ISI) channel, hence, the discrete-Fourier transform (DFT) can be used for data modulation and demodulation to convert the frequency-selective channel into flat-fading channel per sub-channel/sub-carrier. By exploiting the fact that the channel memory needs to be cleared by inserting the cyclic-prefix, Alice injects an artificial-noise (AN) signal that hurts the eavesdropping nodes only. The strength of this AN signal and its interference rank are controlled by the relay's processing time.