Buffer-Aided Energy Harvesting Relay Systems under Statistical Energy Underflow Constraint

¹ This paper considers a two-hop communication system with buffer-Aided energy harvesting relay node subject to statistical energy underflow constraint in terms of battery shortage probability. The half-duplex decode-And-forward relay is assumed to be equipped with an infinite size data buffer and a limited size energy harvesting battery. Perfect knowledge of the channel state information (CSI) of the system is assumed to be available at both the source and the relay. Optimal and ON/OFF power control policies with the associated optimal link selection policies under energy underflow constraints are proposed, which are irrespective of the instantaneous battery state. Closed-form characterizations in Rayleigh fading channels are derived. Numerical results are provided as well. It is shown that the proposed schemes can achieve superior performance than the naive power control, where the available energy is exhausted whenever relay transmits.