Stochastic channel modelling of cooperative STAR-RIS-assisted wireless channels

Insight into a wireless channel using a geometry-based three-dimensional (3D) channel model and its stochastic characterization is given in this paper. It is considered that the outdoor wireless channel is equipped with cooperative double (CODE), simultaneously transmitting and reflecting a reconfigurable intelligent surface (STAR-RIS). Other system elements include multiple-input multiple-output (MIMO) system realized using a transmitter (Tx), two distributed STAR-RISs and two users, [Formula: see text] and [Formula: see text]. To use the advantage of [Formula: see text] coverage area of STAR-RIS, users are positioned on transmit-side ([Formula: see text]) and reflect-side ([Formula: see text]) of STAR-RIS. It is presumed that STAR-RIS operates with the energy splitting (ES) protocol as the underlying mechanism. Space-time cross-correlation function (ST-CCF) is an important time-domain performance measure to characterize a wireless channel. ST-CCF is estimated for parametric variations in the normalized antenna spacing of Tx, [Formula: see text]/ [Formula: see text], position of STAR-RIS, array size of the STAR-RIS and its orientation with respect to the azimuth plane. Simulation results are analyzed in terms of leverage from cooperative STAR-RIS deployment and its practical inferences.