Half-Duplex or Full-Duplex Communications: Degrees of Freedom Analysis under Self-Interference

TL;DR

This paper compares half-duplex and full-duplex wireless communication systems in terms of degrees of freedom, considering realistic self-interference models, and identifies conditions where FD outperforms HD.

Contribution

It provides a comprehensive DoF analysis of HD and FD systems across various scenarios, incorporating practical residual self-interference models.

Findings

AC FD under imperfect SI performs below HD for two-way channels.

RC FD can outperform HD when SI cancellation is sufficient.

FD benefits in two-hop channels with many antennas and good SI suppression.

Abstract

In-band full-duplex (FD) communication provides a promising alternative to half-duplex (HD) for wireless systems, due to increased spectral efficiency and capacity. In this paper, HD and FD radio implementations of two way, two hop and two way two hop communication are compared in terms of degrees of freedom (DoF) under a realistic residual self-interference (SI) model. DoF analysis is carried out for each communication scenario for HD, antenna conserved (AC) and RF chain conserved (RC) FD radio implementations. The DoF analysis indicates that for the two way channel, the achievable AC FD with imperfect SI cancellation performs strictly below HD, and RC FD DoF trade-off is superior when the SI can be sufficiently cancelled. For the two hop channel, FD is better when the relay has large number of antennas and enough SI cancellation. For the two way two hop channel, when both nodes require similar throughput, the achievable DoF pairs for FD do not outperform HD. FD still can achieve better DoF pairs than HD, provided the relay has sufficient number of antennas and SI suppression.