  This paper established a novel multi-input multi-output (MIMO) communication
network, in the presence of full-duplex (FD) transmitters and receivers with
the assistance of dual-side intelligent omni surface. Compared with the
traditional IOS, the dual-side IOS allows signals from both sides to reflect
and refract simultaneously, which further exploits the potential of
metasurfaces to avoid frequency dependence, and size, weight, and power (SWaP)
limitations. By considering both the downlink and uplink transmissions, we aim
to maximize the weighted sum rate, subject to the transmit power constraints of
the transmitter and the users and the dual-side reflecting and refracting phase
shifts constraints. However, the formulated sum rate maximization problem is
not convex, hence we exploit the weighted minimum mean square error (WMMSE)
approach, and tackle the original problem iteratively by solving two
sub-problems. For the beamforming matrices optimizations of the downlink and
uplink, we resort to the Lagrangian dual method combined with a bisection
search to obtain the results. Furthermore, we resort to the quadratically
constrained quadratic programming (QCQP) method to optimize the reflecting and
refracting phase shifts of both sides of the IOS. In addition, we introduce the
case without a dual-side IOS for comparison. Simulation results validate the
efficacy of the proposed algorithm and demonstrate the superiority of the
dual-side IOS.
