Low complexity delay-optimal power control for energy harvesting wireless system with finite energy storage

In this paper, we consider delay-optimal power control for an energy harvesting wireless system with finite energy storage. The system is powered solely by a renewable energy source with bursty data arrivals, and is characterized by data and energy queues. We consider delay-optimal power control and formulate an infinite horizon average cost Markov Decision Process (MDP). To deal with the curse of dimensionality, we introduce a virtual continuous time system and derive closed-form approximate priority functions for the MDP at various operating regimes. Based on the approximation, we obtain a low complexity online power control solution which is adaptive to the channel state information as well as the data and energy queue state information. The derived power control solution has a multilevel water-filling structure, where the water level is determined jointly by the data and energy queue lengths.