RIS-assisted User Pairing NOMA System for THz Communications

Abstract

The main characteristic of the next-generation wire-less communications are seamless connectivity, large bandwidth, and high spectral and energy efficiencies. To acheive these objectives, reconfigurable intelligent surface (RIS), terahertz (THz) communication, and user pairing nonorthogonal multiple access (NOMA) have been recognized as key enabling technologies. In this paper, we propose a RIS-assisted user pairing THz-NOMA system, which is referred to as RTHz-NOMA. The user pairing is performed based on the distance between users and power allocation between the users. We show through simulations that, under the molecular absorption, sum-rate performance of the proposed RTHz-NOMA system is better than the orthogonal multiple access (OMA). In addition to sum-rate, the proposed user-pairing approach can significantly enhance the bit error rate (BER) also, as compared to conventional THz NOMA and OMA without RIS. Further, impact of user pairing distance and number of reflecting elements is studied for the proposed system. The proposed user pairing scheme is applicable for the entire THz frequency range. © 2023 IEEE.