ANALYSIS OF SPATIAL CORRELATION PROPERTIES AND RECEIVED SIGNAL CHARACTERISTICS OF LARGE DIMENSIONAL RIS-ASSISTED COMMUNICATION IN NEXT GENERATION RADIO NETWORKS

The reconfigurable intelligent surface (RIS) is envisioned to be a key serving technology in 6G wireless systems and it is also known as smart repeater or holographic radio. RIS is fully capable of controlling the EM waves in terms of reflections, refractions, scattering, amplitudes, phases, and polarization. Its response is adaptive over time as well as network conditions. It enhances the performance of a radio system in terms of capacity, energy efficiency, security, power consumption, and coverage. In this paper, a physically realizable RIS-assisted channel model is presented which uses the spatial correlation properties of the channel. The main objective of this work is to derive the fading distribution for RIS-assisted channels, characterize their spatial channel correlation, and minimize the channel training overhead. The proposed channel estimation model minimizes the number of required pilot signals for channel estimation. The channel properties are analyzed in terms of spatial correlation matrices rank, RIS physical geometry, and channel hardening. Monte Carlo simulations have verified the analytical results. The results proved that eigenvalue distribution and rank of spatial correlated matrix are favorable for lower dimensions of RIS reflecting elements.