NOMA Performance in α-μ and Mixed Fadings: Exact Formulations and Accurate Approximations

Bit error rate (BER) is a critical performance metric for any communication system, including wireless ones, especially for the latter in emerging technologies like non-orthogonal multiple access (NOMA). While NOMA’s performance has been extensively studied under standard fading models, research on more general ones like α-μ, known to better characterize ample fading scenarios like terahertz communications, remains limited. Existing studies on α-μ fading primarily focus on metrics like outage probability and ergodic capacity, with BER analysis receiving comparatively little attention. This paper addresses such gap by deriving an unprecedented exact analytical expression for the BER of a NOMA system operating over α-μ fading channels, explicitly incorporating the impact of imperfect successive interference cancellation. Our exact formulations are computationally efficient, enabling practical evaluation using standard mathematical tools. Importantly, the proposed analyses can also accommodate an arbitrary number of users, offering broad applicability for optimizing NOMA-based systems in complex propagation environments. The approach is versatile and applicable to yield highly accurate BER approximate analysis in mixed fading environments, showcasing its relevance to more complex and realistic propagation conditions.