Joint power allocation and subcarrier selection for energy efficiency maximization in OFDM systems under a holistic power model

Energy efficiency (EE) maximization for OFDM transceiver has received much attention in next generation wireless communication systems. Recently, there have been a lot of works on EE maximization by balancing the transmission rate and the holistic power consumption. However, how to maximize EE in OFDM systems by joint power allocation and subcarrier selection under holistic power models has not been extensively investigated yet. In contrast to spectrum efficiency (SE) oriented power allocation and subcarrier selection, which is by a simple waterfilling policy, the EE oriented power allocation and subcarrier selection is a mixed integer programming, which is not trivial to solve. This is simply because an extra circuit power has to be paid as the cost of adding an subcarrier. Fortunately, by delving into the mixed integer programming, we found in this paper that the EE oriented power allocation also has form of waterfilling. Based on these results and approximate methods, explicit decision criterions are proposed for subcarrier selection, which provides insight into how the transmit power and the number of subcarriers balance with the channel states and the circuit power in EE oriented systems. Numerical results show that the proposed strategies achieve near-optimal performance of EE with low complexity.