  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.
