Spectrum Sharing Opportunities of Full-Duplex Systems using Improper Gaussian Signaling

TL;DR

This paper explores how improper Gaussian signaling can enhance secondary user performance in full-duplex spectrum sharing scenarios by optimizing signal parameters to meet primary user quality-of-service constraints.

Contribution

It introduces a simplified algorithm for optimizing secondary user signal parameters using improper Gaussian signaling in full-duplex spectrum sharing.

Findings

IGS outperforms PGS in weak PU channels

Optimized parameters improve SU achievable rate

Algorithm effectively balances SU performance and PU QoS

Abstract

Sharing the licensed spectrum of full-duplex (FD) primary users (PU) brings strict limitations on the underlay cognitive radio operation. Particularly, the self interference may overwhelm the PU receiver and limit the opportunity of secondary users (SU) to access the spectrum. Improper Gaussian signaling (IGS) has demonstrated its superiority in improving the performance of interference channel systems. Throughout this paper, we assume a FD PU pair that uses proper Gaussian signaling (PGS), and a half-duplex SU pair that uses IGS. The objective is to maximize the SU instantaneous achievable rate while meeting the PU quality-of-service. To this end, we propose a simplified algorithm that optimizes the SU signal parameters, i.e, the transmit power and the circularity coefficient, which is a measure of the degree of impropriety of the SU signal, to achieve the design objective. Numerical results show the merits of adopting IGS compared with PGS for the SU especially with the existence of week PU direct channels and/or strong SU interference channels.