Optimal resource allocation for multiple access channels with a shared renewable energy source

This paper investigates the optimal resource allocation for a Gaussian multiple access channel (MAC) with two transmitters powered by a shared energy harvester. A deterministic energy-harvesting (EH) model is adopted, which assumes that the energy arrival amounts and timing are non-causally known before transmissions. Besides, packets for both transmitters are assumed always ready before transmissions. We first formulate the resource allocation problem to characterize the maximum departure region over a finite time horizon as a convex optimization problem. The structural properties of the sum power profile is then studied by exploiting the convexity of the sum power function, which simplifies the optimization problem. Finally, the optimal resource allocation between the two transmitters, in which there exists a cut-off rate at the stronger transmitter, is obtained. We also demonstrate that under the same energy arrival profile, MAC with shared energy harvester achieves the same maximum departure region as its dual broadcast channel (BC).