This paper develops a teletraffic-based energy-efficiency analysis of QoS-constrained NOMA using an order-statistics framework for underlay secondary-access operation. Throughput is derived from the ordered SIR distribution for an orthogonal reference and for NOMA under minimum-rate requirements. A linear base-station power model is then incorporated to define energy efficiency, including both transmit power and SIC-related processing. For the multiuser case, the analysis shows that QoS constraints impose a structural feasibility limit on the supported number of users, which is also approximated in closed form through the Lambert W function. By coupling this feasibility result with a birth–death teletraffic model, the average energy efficiency is obtained as a function of the offered load. The results show that stricter QoS requirements reduce energy efficiency, while NOMA preserves a wider feasible region than the orthogonal reference in the setting considered. From a symmetry/asymmetry perspective, the orthogonal reference provides a more symmetric access structure, whereas NOMA introduces asymmetry through user ordering, unequal power allocation, and SIC. The resulting framework links ordered-user operation, QoS feasibility, SIC-aware power consumption, and traffic dynamics in the energy-efficiency characterization of underlay secondary access.
Perez-Salgado et al. (2026) studied this question.