Comparative Performance Analysis of Different Hybrid NOMA Schemes

Hybrid non-orthogonal multiple access (H-NOMA), which combines the advantages of pure NOMA and conventional OMA organically, has emerged as a highly promising multiple access technology for future wireless networks. Recent studies have proposed various H-NOMA systems by employing different successive interference cancellation (SIC) methods for the NOMA transmission phase. However, existing analyses typically assume a fixed channel gain order between paired users, despite the fact that channel coefficients follow random distribution, leading to their magnitude relationships inherently stochastic and time varying. This paper analyzes the performance of three H-NOMA schemes under stochastic channel gain ordering: a) fixed order SIC (FSIC) aided H-NOMA scheme; b) hybrid SIC with non-power adaptation (HSIC-NPA) aided H-NOMA scheme; c) hybrid SIC with power adaptation (HSIC-PA) aided H-NOMA scheme. Theoretical analysis derives closed-form expressions for the probability that H-NOMA schemes underperform conventional OMA. Asymptotic results in the high signal-to-noise ratio (SNR) regime are also developed. Simulation results validate our analysis and demonstrate the performance of H-NOMA schemes across different SNR scenarios, providing a theoretical foundation for the deployment of H-NOMA in next-generation wireless systems.