HARQ in Full-Duplex Relay-Assisted Transmissions for URLLC

TL;DR

This paper explores full-duplex relay-assisted HARQ mechanisms to enhance ultra-reliable low-latency communication (URLLC) in 6G, proposing new relay strategies and analyzing their performance through simulations.

Contribution

It introduces a hybrid FD relay system with two HARQ procedures designed to reduce latency and improve reliability for URLLC, supported by an analytical framework.

Findings

Enhanced HARQ procedures outperform conventional methods in latency and reliability.

Relay-assisted HARQ systems show significant improvements over direct source-to-destination communication.

Monte-Carlo simulations validate the theoretical performance gains.

Abstract

The Release 16 completion unlocks the road to an exciting phase pertain to the sixth generation (6G) era. Meanwhile, to sustain far-reaching applications with unprecedented challenges in terms of latency and reliability, much interest is already getting intensified toward physical layer specifications of 6G. In support of this vision, this work exhibits the forward-looking perception of full-duplex (FD) cooperative relaying in support of upcoming generations and adopts as a mean concern the critical contribution of hybrid automatic repeat request (HARQ) mechanism to ultra-reliable and low-latency communication (URLLC). Indeed, the HARQ roundtrip time (RTT) is known to include basic physical delays that may cause the HARQ abandonment for the 1 ms latency use case of URLLC. Taking up these challenges, this article proposes a hybrid FD amplify-and-forward (AF)-selective decode-and-forward (SDF) relay-based system for URLLC. Over this build system, two HARQ procedures within which the HARQ RTT is shortened, are suggested to face latency and reliability issues, namely, the conventional and the enhanced HARQ procedures. We develop then an analytical framework of this relay based HARQ system within its different procedures. Finally, using Monte-Carlo simulations, we confirm the theoretical results and compare the proposed relay-assisted HARQ procedures to the source-to-destination (S2D) HARQ-based system where no relay assists the communication between the source and the destination.