On the optimal transmission policy in hybrid energy supply wireless communication systems

This paper addresses the optimal transmission scheduling problem in hybrid energy supply systems with the save-then-transmit protocol, where the energy supply of the transmitter comes from both the primary battery and the energy harvester. We first consider minimizing the outage probability for a given amount of battery energy by optimizing the saving factor. It is demonstrated that harvesting external energy is unnecessary for a large spectral efficiency requirement. Then, we consider joint packet scheduling and saving factor optimization to the battery energy consumption minimization (BECM) problem in both single packet arrival and burst packet arrival scenarios. Both optimal and suboptimal offline policies with full information on the traffic profile, the harvesting power, and the channel state are developed. We also propose an optimal online policy in the case that only causal information is available. Numerical results are presented that validate the effectiveness of the proposed algorithms.