Abstract
One of the key enablers of future wireless communications is constituted by massive users can access the core network in wireless systems simultaneously, which can improve the spectral efficiency. In existing scheme of massive connections, namely non-orthogonal multiple access (NOMA), is investigated in conventional relaying networks. This method results in excessive power consumption and high hardware costs. Recently, reconfigurable intelligent surface (RIS) has been considered as one of the revolutionary technologies to enable energy-efficient and smart wireless communications, which is a two-dimensional structure with a large number of passive elements. This paper examines the RISs used in emerging communications systems based on NOMA scheme. The two-user system model contains the far user and the near user which employing RIS and NOMA is conducted in this study. In particular, we design two links (backscatter and direct links) to target to improve performance of far user. System performance was characterized through closed-form expressions of outage probability, ergodic capacity and throughput, which are beneficial to evaluate performance of two users. In Monte-Carlo simulations, it was revealed that the probability of the two users experiencing system outage was determined by factors related to power allocation, power transmission at the base station, and the number of reflecting elements in the RISs.
Highlights
The commercialization of fifth generation (5G) wireless communication systems faces the crucial challenges in terms of high energy consumption and reduced network deployment cost
As we can see from figure, just slight decrease of ergodic capacity of two users in non-orthogonal multiple access (NOMA) and user in Orthogonal Multiple Access (OMA) mode can be reported in this experiment
In this study, we have adopted NOMA and OMA transmissions to illustrate how these schemes work in reconfigurable intelligent surface (RIS)-aided wireless systems, where the main parameters of the RIS were designed
Summary
The commercialization of fifth generation (5G) wireless communication systems faces the crucial challenges in terms of high energy consumption and reduced network deployment cost. The authors in [30] designed a novel passive beamforming weight at RISs in a multipleinput multiple-output (MIMO) NOMA network for simultaneously serving paired users They derived the closed-form formulas both for the outage probability and for the ergodic rate. In [31], the authors explored RIS assisted wireless communication system with rate splitting multiple access (RSMA) In this network, the authors maximized the energy efficiency performance of the network by controlling the phase shifts of the RIS and beamforming of the base station. To evaluate advantages of RIS, this paper is one of the early attempts to study the performance system metrics such as outage probability, ergodic capacity and throughput for the RIS-aided NOMA systems.
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