Finite-Blocklength RIS-Aided Transmit Beamforming

Abstract

This paper considers the downlink of an ultrareliable low-latency communication (URLLC) system in which a base station (BS) serves multiple single-antenna users in the short (finite) blocklength (FBL) regime with the assistance of a reconfigurable intelligent surface (RIS). In the FBL regime, the users' achievable rates are complex functions of the beamforming vectors and of the RIS's programmable reflecting elements (PREs). We propose the joint design of the transmit beamformers and PREs, the problem of maximizing the geometric mean (GM) of these rates (GM-rate) and show that this aforementioned results are providing fair rate distribution and thus reliable links to all users. A novel computational algorithm is developed, which is based on closed forms to generate improved feasible points, using its execution. The simulations show the merit of our solution.

Rate Splitting in MIMO RIS-Assisted Systems With Hardware Impairments and Improper Signaling

“…where [ij] ̸ = [lk] includes all possible i, j pairs, except for the case where i = l and simultaneously j = k. Substituting the concave lower bound in (28) and the convex upper bound in (30) into the FBL rate expression proves the lemma.…”

Spectral and Energy Efficiency Maximization of MISO STAR-RIS-Assisted URLLC Systems

“…The use of RIS in FBL regimes has been investigated in [19]- [29]. For instance, [22], [29], [31] showed that RIS can improve the performance of SISO/MISO BCs with treating interference as noise (TIN) in URLLC systems.…”

“…The use of RIS in FBL regimes has been investigated in [19]- [29]. For instance, [22], [29], [31] showed that RIS can improve the performance of SISO/MISO BCs with treating interference as noise (TIN) in URLLC systems. Moreover, [28] showed that RIS can increase the sum rate of a multi-cell MISO orthogonal frequency division multiplexing (OFDM) BC.…”