Abstract
The future of wireless communications looks exciting with the potential new use cases and challenging requirements of future 6th generation (6G) wireless networks. Since the traditional wireless communications, the propagation medium has been perceived as a randomly behaving entity between the transmitter and the receiver, which degrades the quality of the received signal due to the uncontrollable interactions of the transmitted radio waves with the surrounding objects. The recent advent of reconfigurable intelligent surfaces (RIS) in wireless communications enables, on the other hand, network operators to control the radio waves (the scattering, reflection, and refraction characteristics) to eliminate the negative effects of natural wireless propagation. Recent results have revealed that non-orthogonal multiple access (NOMA) benefits from RIS mechanism which can effectively provide effective transmissions. Motivated by the potential of these emerging technologies, we study the impact of hardware impairment in RIS-aided NOMA system in term of performance metrics. We then derive analytical expressions of outage probability and throughput as main performance metrics. Simulations are conducted to validate the analytical expressions. We find that the number of meta-surfaces in RIS, transmit power at the base station, power allocation factors play important role to demonstrate improvement in system performance of RIS relying on NOMA compared with orthogonal multiple access (OMA). Numerical results are presented to validate the effectiveness of the proposed RIS-aided NOMA transmission strategies.
Highlights
As a promising architecture to improve the energy and spectral efficiency, intelligent reflecting surface (IRS) or so-called as reconfigurable intelligent surface (RIS) are introduced to intergrate to emerging wireless networks [1]–[3]
Unlike other published work dealing with the calculation of symbol error probability (SEP) [36], our work provides outage performance evaluation of the RIS-aided non-orthogonal multiple access (NOMA) system in the presence of hardware impairments
In this paper, we have considered a generalized hardware imperfections model in RIS systems at both transmitter and receiver in the context of NOMA, which has been validated in several prior works, in order to assess the impact of hardware impairments on RIS-aided NOMA wireless systems
Summary
As a promising architecture to improve the energy and spectral efficiency, intelligent reflecting surface (IRS) or so-called as reconfigurable intelligent surface (RIS) are introduced to intergrate to emerging wireless networks [1]–[3]. In [30], the authors presented theoretical performance comparison between RIS-assisted downlink communications relying on NOMA and orthogonal multiple access (OMA). They considered the transmit power minimization problems under the discrete unit-modulus reflection constraint on each RIS element. While RIS makes a smart radio environment by using surfaces with capable of manipulating the propagation of incident electromagnetic waves in a programmable manner to actively alter the channel realization By enabling both NOMA and RIS in unique system, wireless channels could be into a controllable system block that can be optimized to enhance overall system performance, especially for system with massive connections. The derivations of asymptotic outage probabilities at high transmit signal to noise ratio (SNR) for two users are provided as an important evaluation to design such the RIS-aided NOMA system in practice.
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