Energy Efficient Power Allocation for Multi-carrier Non-orthogonal Multiple Access (NOMA) Systems with Proportional Rate Constraints

Non-orthogonal multiple access (NOMA) is an essential component of the 5G wireless communications. Since NOMA adopts power domain for multiple access, the power allocation plays a crucial role in NOMA systems. In this paper, we study the energy efficient power allocation for a multi-carrier NOMA systems. Different from existing works, proportional rate constraints are taken into consideration in order to guarantee fairness among users. We demonstrate the existence of a unique globally maximum energy efficiency and propose an optimal power allocation algorithm to achieve the optimal solution. Numerical results verify the optimality of our algorithm and show that our algorithm can significantly improve the energy efficiency compared with spectral efficient algorithms and conventional orthogonal multiple access (OMA) schemes.