Improper Gaussian Signaling in Full-Duplex Relay Channels with Residual Self-Interference

TL;DR

This paper explores how improper Gaussian signaling (IGS) can mitigate residual self-interference in full-duplex relay channels, enabling reliable communication even at high interference levels, unlike traditional proper Gaussian signaling.

Contribution

The study derives a tight upper bound for outage probability with IGS in full-duplex relays and demonstrates its effectiveness in managing residual self-interference.

Findings

IGS allows full-duplex relays to operate effectively despite high residual self-interference.

The outage probability with IGS approaches a fixed value, independent of RSI increase.

IGS enables higher relay power budgets compared to proper Gaussian signaling.

Abstract

We study the potential employment of improper Gaussian signaling (IGS) in full-duplex cooperative settings with residual self-interference (RSI). IGS is recently shown to outperform traditional proper Gaussian signaling (PGS) in several interference-limited channel settings. In this work, IGS is employed in an attempt to alleviate the RSI adverse effect in full-duplex relaying (FDR). To this end, we derive a tight upper bound expression for the end-to-end outage probability in terms of the relay signal parameters represented in its power and circularity coefficient. We further show that the derived upper bound is either monotonic or unimodal in the relay's circularity coefficient. This result allows for easily locating the global optimal point using known numerical methods. Based on the analysis, IGS allows FDR systems to operate even with high RSI. It is shown that, while the communication totally fails with PGS as the RSI increases, the IGS outage probability approaches a fixed value that depends on the channel statistics and target rate. The obtained results show that IGS can leverage higher relay power budgets than PGS to improve the performance, meanwhile it relieves its RSI impact via tuning the signal impropriety.