Finite-block length transmissions for RIS-assisted communication system with spatial correlation

This paper investigates reconfigurable intelligent surface (RIS)-based multiple-destination downlink communication system under ultra-reliable low-latency communications (URLLC) constraints. A source communicates with multiple destinations with the aid of RIS and direct path transmissions. We consider the effect of spatial correlation arising due to the RIS geometry. Assuming that the source can communicate with only one destination in the given time-slot, we examine several scheduling schemes, such as random (RND), absolute (ABS) channel power based (CPB) and normalized (NRM) CPB. The expressions for the block-error rate (BLER) are derived for all the scheduling schemes and verified using the Monte-Carlo simulations. Effects of various parameters such as, channel uses, number of destinations, number of information bits, correlation are analyzed and the performance for the considered scheduling schemes is compared.