Delay-constrained Gaussian relay channel with energy harvesting nodes

This paper considers the use of energy harvesters, instead of conventional time-invariant energy sources, in wireless cooperative communication. For the purpose of exposition, we study the classic three-node Gaussian relay channel with decode-and-forward (DF) relaying, in which the source and relay nodes transmit with power drawn from energy-harvesting sources. Assuming a deterministic energy-harvesting model under which the energy arrival time and the harvested energy amount are known prior to transmission, the throughput maximization problem over a finite horizon of N transmission blocks is investigated for the delay-constrained (DC) case (for which only one-block decoding delay is allowed at the destination). By exploiting the structures of the optimal source and relay power profiles, we show that the joint source and relay power allocation over time is necessary to achieve the maximum throughput, and propose an efficient forward two-dimensional search algorithm to compute the optimal power profiles.