Performance Analysis of Double Reconfigurable Intelligent Surfaces Assisted NOMA Networks

TL;DR

This paper analyzes the performance of double cascaded reconfigurable intelligent surfaces (RISs) in NOMA networks, deriving new formulas for outage probability and ergodic data rate, and demonstrating improved performance over traditional methods.

Contribution

It introduces a novel PRIS-ARIS-NOMA network model with closed-form expressions for key performance metrics and compares its advantages over existing RIS-assisted NOMA and OMA systems.

Findings

PRIS-ARIS-NOMA outperforms PRIS-ARIS-OMA in outage behavior

Using more reflecting elements improves outage performance

PRIS-ARIS-NOMA achieves higher ergodic data rate and throughput

Abstract

This paper introduces double cascaded reconfigurable intelligent surfaces (RISs) to non-orthogonal multiple access (NOMA) networks over cascaded Rician fading and Nakagami-$m$ fading channels, where two kinds of passive RIS (PRIS) and active RIS (ARIS) are taken into consideration, called PRIS-ARIS-NOMA networks. Additionally, new closed-form and asymptotic expressions for outage probability and ergodic data rate of two non-orthogonal users are derived with the imperfect/perfect successive interference cancellation schemes. The scenario is modelled around two non-orthogonal users and focuses on analyzing their communication characteristics. Based on the approximate results, the diversity orders and ergodic data rate slopes of two users are obtained in the high signal-to-noise ratios. In addition, the system throughput of PRIS-ARIS-NOMA in delay-limited mode and delay-tolerant mode are discussed according to the outage probability and ergodic data rate. The simulation results verify the correctness of the formulas and yields the following insights: 1) The outage behaviors of PRIS-ARIS-NOMA outperforms than that of PRIS-ARIS assisted orthogonal multiple access (OMA); 2)Use of PRIS-ARIS-NOMA is better than use of PRIS-ARIS-OMA in small transmit power threshold scenarios 3) By increasing the number of reflecting elements of RISs, the PRIS-ARIS-NOMA is able to achieve the enhanced outage performance; and 4) The PRIS-ARIS-NOMA has the higher ergodic data rate and system throughput than double PRISs-NOMA.