Improper Gaussian signaling in full-duplex relay channels with residual self-interference

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.

Overlay Spectrum Sharing using Improper Gaussian Signaling

“…Consider the optimization problem in (8) and simplify it by rewriting the first constraint in terms of α using the the monotonic increasing characteristic of the logarithmic function in the objective function obtaining equivalent optimization problem…”

“…On the other hand, IGS scheme achieves superior rate improvements for systems not supported with interference cancellation techniques and deal with interference as noise. IGS scheme is employed in different interference scenarios such as two user single input single output interference channel [6], k-user multiple input single output interference channel [7], full duplex relaying [8], alternate relaying [9] and underlay cognitive radio [10]- [16].…”

Information-Theoretic Analysis of a Family of Improper Discrete Constellations

“…Similar DoF results were derived for the four-user interference channel in [14]. After that, a number of new works has emerged, and the payoffs of improper signaling have been revealed for different multiuser scenarios such as the interference channel [3][4][5]15], Z-interference channel [6,[16][17][18], broadcast channels with linear precoding [19,20], underlay and overlay cognitive radio networks [7,8,21] and relay channels [22,23]. More recently, in [24], the authors showed the advantages of improper signaling in a multiuser scenario where a point-to-point link coexists with a multiple access channel.…”

Improper Gaussian Signaling for Multiple-Access Channels in Underlay Cognitive Radio

“…They found that, while PGS provided 1 DoF, 1.2 DoF were achievable by IGS. A great deal of works has followed these lines showing the payoffs of IGS for different interference-limited networks, such as the IC [6]- [8] (also with discrete modulation schemes in [9]), the Z-IC [10]- [13], broadcast channel treating interference as noise [14], [15], underlay and overlay CR [16]- [20], relay channels [21], [22], etc.…”