Energy efficient relaying design for OFDM systems

In this paper, we design energy efficient relay transmission strategy for an orthogonal frequency division multiplexing (OFDM) system, where two source nodes exchange information with each other via an amplify-and-forward relay node. To maximize the energy efficiency (EE), which is defined as the number of transmitted bits per unit of energy, we jointly optimize the bidirectional bit allocation, which leads to a hybrid one- and two-way relay scheme. In particular, we propose a bit allocation algorithm to balance the transmit and circuit power consumptions of the hybrid relay in order to minimize the overall power consumption. Simulation results show that the proposed algorithm achieves much higher EE than the approach that only minimizes the transmit power, and the hybrid relay is more energy efficient than the pure one- and two-way relay.