  Different from conventional reconfigurable intelligent surfaces (RIS), a
recent innovation called simultaneous transmitting and reflecting
reconfigurable intelligent surface (STAR-RIS) has emerged, aimed at achieving
complete 360-degree coverage in communication networks. Additionally,
fullduplex (FD) technology is recognized as a potent approach for enhancing
spectral efficiency by enabling simultaneous transmission and reception within
the same time and frequency resources. In this study, we investigate the
performance of a STAR-RIS-assisted FD communication system. The STAR-RIS is
strategically placed at the cell-edge to facilitate communication for users
located in this challenging region, while cell-center users can communicate
directly with the FD base station (BS). We employ a non-orthogonal multiple
access (NOMA) pairing scheme and account for system impairments, such as
self-interference at the BS and imperfect successive interference cancellation
(SIC). We derive closed-form expressions for the ergodic rates in both the
up-link and down-link communications and extend our analysis to bidirectional
communication between cell-center and cell-edge users. Furthermore, we
formulate an optimization problem aimed at maximizing the ergodic sum-rate.
This optimization involves adjusting the amplitudes and phase-shifts of the
STAR-RIS elements and allocating total transmit power efficiently. To gain
deeper insights into the achievable rates of STAR-RIS-aided FD systems, we
explore the impact of various system parameters through numerical results.
