  Well-designed simultaneously transmitting and reflecting RIS (STAR-RIS),
which extends the half-space coverage to full-space coverage, incurs wireless
communication environments to be smart and reconfigurable. In this paper, we
survey how STAR-RIS affects the performance of full-duplex communication
systems with the presence of full-duplex users, wherein the base station (BS)
and the uplink users are subject to maximum transmission power constraints.
Firstly, the weighted sum-rate (WSR) is derived as a system performance metric.
Then, we formulate the resource allocation design into an equivalent weighted
minimum mean-square-error form and then transform it into several convex
sub-problems to maximize the WSR as an optimization problem which jointly
optimizes the beamforming and the combining vectors at the BS, the transmit
powers of the uplink users, and phase shifts of STAR-RIS. Although the WSR
optimization is non-convex, an efficient iterative alternating procedure is
proposed to achieve a sub-optimal solution for the optimization problem.
Secondly, the STAR-RIS's phase shifts are optimized via the successive convex
approximation technique. Finally, numerical results are provided to explain how
STAR-RIS improves the performance metric with the presence of full-duplex
users.
