On the Energy Efficiency Optimality of OFDMA for SISO-OFDM Downlink System

This letter considers energy-efficient resource allocation for a general SISO-OFDM downlink system. A fundamental result is proven that OFDMA is optimal for achieving the maximum energy efficiency measured by bits per joule. Using the OFDMA solution structure, we turn the nonconvex energy-efficient power allocation problem into a quasi-convex optimization problem and propose an efficient power allocation algorithm which requires solving at most two simple subproblems. The achieved energy efficiency performance of the proposed power allocation algorithm is verified via simulations.