Outage Probability and Ergodic Sum Rate Analysis of NOMA‐Based System With Fixed Full‐Duplex Relay Transmission

ABSTRACT Recently, non‐orthogonal multiple access (NOMA) is identified as a promising multiple access technique for 5G/6G networks because of its high spectral efficiency and ability to connect multiple devices. Furthermore, cooperative communication using a relay can improve the performance of wireless networks in terms of coverage, range, capacity, and reliability. Outage probability and ergodic sum rate are the key performance metrics for evaluating the quality of service and measuring the capacity of wireless networks. In this paper, we propose a full‐duplex decode‐and‐forward relay (FD‐DFR)–based cooperative NOMA system with two users, where the FD‐DFR assists the message transmission to the far user. The exact expressions for outage probability and approximate expressions for ergodic sum rate using the Gaussian–Chebyshev quadrature (GCQ) method are derived and analyzed by considering imperfect successive interference cancellation (SIC) and residual self‐interference (RSI). The impact of power allocation coefficients, residual interference level, transmit signal‐to‐noise ratio (SNR), relay SNR, target rates, and channel variances is analyzed. The results obtained from simulations show that the proposed FD‐DFR–based cooperative NOMA system outperforms the half‐duplex decode‐and‐forward relay (HD‐DFR)–based cooperative NOMA system and outage probability of the far user is lower in comparison with the FD‐DFR–based cooperative orthogonal multiple access (OMA) system. We perform the Monte Carlo simulations to verify the analytical results.