On EE-SE Trade-Off for Downlink Full Duplex MISO Systems with Self-Energy Recycling

Energy efficiency (EE) and spectral efficiency (SE) are among the key performance metrics for any wireless standards. In this work, we study the trade-off between EE-SE for supporting the downlink data rate as well as opportunistically harvesting the ambient radio frequency (RF) energy. The goal is to maximize EE while maintaining the requisite data rate for the downlink. We consider a case of downlink full duplex multi-input single-output (MISO) system where the transmitter having multiple antennas is transmitting to a user equipped with single antenna. At the transmitter, few antennas are reserved for selfenergy recycling (S-ER) while the remaining antennas are utilized for information transmission. S-ER enhances the EE of the system at the expense of SE due to loss in the array gain. In order to improve the SE, we incorporate the adaptive S-ER scheme which utilizes selection of antennas corresponding to higher gains for information transmission. This compensates the loss in the SE along with the increase in EE of the system. Both linear and nonlinear transmitter cases have been considered for analyzing the trade-off and the simulation results are shown by obtaining the outage probability.