Infinite and Finite Block-Length FD Transmissions With Spatially-Correlated RIS Channels

The reconfigurable intelligent surface (RIS)-assisted wireless communication system is studied in this paper, where two full-duplex (FD) users simultaneously communicate with each other. The reception at each user is facilitated through a dedicated RIS. Owing to the geometry and placements of meta-atoms, the analysis incorporates spatial-correlation among the channels related to RIS. Using moment-matching approach, a new analytical framework is presented for spatially-correlated channels considering the optimal phase-shifts from RIS meta-atoms. The effects of residual self-interference (RSI), self-reflections and interference from the RIS of transmitting user are considered in the analysis. The expressions are derived for the outage probability and ergodic capacity for infinite block-length transmission, and for finite block-length transmission, the expressions are obtained for block-error rate (BLER), ergodic capacity and system goodput. To gain further insights, the expression for the asymptotic outage probability is also derived. The finding of this paper confirms the ability of RIS-assisted communication to counter the detrimental effects of self-interference in FD scenario, even in presence of spatial-correlation. The derived expressions are validated using the Monte-Carlo simulations.