Multi-RIS-aided Wireless Systems: Statistical Characterization and Performance Analysis

Abstract

In this paper, we study the statistical characterization and modeling of distributed multi-reconfigurable intelligent surface (RIS)-aided wireless systems. Specifically, we consider a practical system model where the RISs with different geometric sizes are distributively deployed, and wireless channels associated to different RISs are assumed to be independent but not identically distributed (i.n.i.d.). We propose two purposeoriented multi-RIS-aided schemes, namely, the exhaustive RISaided (ERA) and opportunistic RIS-aided (ORA) schemes. In the ERA scheme, all RISs participate in assisting the communication of a pair of transceivers, whereas in the ORA scheme, only the most appropriate RIS participates and the remaining RISs are utilized for other purposes. A mathematical framework, which relies on the method of moments, is proposed to statistically characterize the end-to-end (e2e) channels of these schemes. It is shown that either a Gamma distribution or a LogNormal distribution can be used to approximate the distribution of the magnitude of the e2e channel coefficients in both schemes. With these findings, we evaluate the performance of the two schemes in terms of outage probability (OP) and ergodic capacity (EC), where tight approximate closed-form expressions for the OP and EC are derived. Representative results show that the ERA scheme outperforms the ORA scheme in terms of OP and EC. Nevertheless, the ORA scheme gives a better energy efficiency (EE) in a specific range of the target spectral efficiency (SE). In addition, under i.n.i.d. fading channels, the reflecting element setting and location setting of RISs have a significant impact on the overall system performance of both the ERA or ORA schemes. A centralized large-RIS-aided scheme might achieve higher EC than the distributed ERA scheme when the large-RIS is located near a transmitter or a receiver, and vise-versa.

Perspective method for reconfigurable intelligent surface design for NOMA transmission: Theoretical study

“…4 MIMO-RIS-NOMA evaluation based on Kennedy (1969) For the evaluation of RIS-NOMA-MIMO paradigm characteristics, it might be reasonable to accept the approach for evaluation of the (upper and lower) boundaries for certain "global" characteristics of the information transmission, as exact analytical solutions might be cumbersome (Abrardo et al, 2021;Do et al, 2021). For evaluation of the boundaries, it might be adequate to take the fundamental information-theoretic approach, based on the results of Shannon, Fano, etc., first applied in (Kennedy, 1969).…”

RIS-aided Cooperative FD-SWIPT-NOMA Performance over Nakagami-m Channels

“…We consider that the RIS is programmed by a dedicated controller connected to the S via a high-speed back-haul [39], whose main aim is to update systematically the RIS phases shift at each coherence-time since the phase-shift variables are directly related to the CSI, which is assumed to be perfectly known at the S.…”

Stochastic Geometry Analysis of IRS-Assisted Downlink Cellular Networks

“…Another series of research works considered multiple IRSs, single source, and single destination [14]- [16]. In [14], the authors derived the outage probability considering Rayleigh fading with the direct transmission blocked.…”

“…Similarly, in [16], the authors derived the outage probability by approximating the end-to-end IRS-assisted channel with the log-normal and gamma distribution.…”