Performance Analysis of Ergodic Rate and Effective Capacity for RIS-Assisted NOMA Networks Over Nakagami-m Fading Environments

Massive connectivity and green communication will be important problems for the upcoming sixth generation (6G). Reconfigurable intelligent surfaces (RIS) and non-orthogonal multiple access (NOMA) have recently been presented as two major solutions to address the aforementioned issues. The main purpose of this paper is to investigate a downlink RIS-aided NOMA system in which the source intends to communicate with the two NOMA consumers over RIS for solving above problems. Our contributions include studying system performance in terms of ergodic rate and effective capacity, which is an essential assessment measure for delay-sensitive systems. In particular, we obtain analytical formulas for the ergodic rate and the effective capacity of nearby and distant users. In addition, we present orthogonal multiple access (OMA) data for comparison. The followings are the findings of this paper: 1) the ergodic rate and effective capacity of RIS-NOMA networks are superior to those of RIS-assisted OMA networks; 2) the system performance of RIS-NOMA networks can be significantly improved as the number of reflecting elements and Nakafami-m factor increases to improve the ergodic rate and effective capacity of both two users; 3) when compared to OMA, NOMA system has higher ergodic rate and effective capacity due to the short transmission time.