Energy Efficiency and Spectral Efficiency Tradeoff for Multicarrier NOMA Systems with User Fairness

We propose a novel low-complexity resource allocation scheme to provide a tradeoff between energy efficiency (EE) and spectral efficiency (SE) for multicarrier non-orthogonal multiple access (NOMA) systems with the constraint of user fairness. The proposed optimization approach provides high degree of freedom, as the tradeoff of EE and SE can be optimal by assigning their corresponding weights. Also, a closed-form expression is derived for subchannel power allocation with user fairness, requiring no high-complexity search. A suboptimal power allocation approach is proposed on each subchannel for NOMA user pairing. Numerical results show that the proposed NOMA system provides higher EE and SE than the state-of-art methods, while requiring low complexity.