  In this paper, a two-hop communication system with energy harvesting nodes is
considered. Unlike battery powered wireless nodes, both the source and the
relay are able to harvest energy from environment during communication,
therefore, both data and energy causality over the two hops need to be
considered. Assuming both nodes know the harvested energies in advance,
properties of optimal transmission policies to maximize the delivered data by a
given deadline are identified. Using these properties, optimal power allocation
and transmission schedule for the case in which both nodes harvest two energy
packets is developed.
