Optimization of energy efficiency in computationally-aware adaptive OFDM systems

In this paper, the energy efficiency (EE) of an adaptive OFDM (Orthogonal Frequency-Division Multiplexing) system is analyzed taking not just the transmit power, but also the transceiver computation-power consumption into account. Such an energy-efficiency optimization problem belongs to a broader class of problems called convex-concave fractional programs, which in the case of the adaptive modulation and coding techniques is also a mixed-integer nonlinear problem (MINLP). In order to solve it, we propose the joint adaptive power and adaptive modulation and coding (AMC) algorithm with fast convergence based on Dinkelbach method, where the analytical solutions are derived by the numerical method according to the Lagrange multipliers and Karush-Kuhn-Tucker (KKT) conditions. Simulation results show that the adaptive modulation and coding techniques allow for: increased energy efficiency, increased average throughput, reduced required transmit power and reduced total power consumption. Moreover, there exists the optimal point for the transmit power maximizing the energy efficiency.