Cooperative Power Management in Energy Harvesting Communication Systems in Presence of a Helper

We investigate end-to-end throughput maximization problem for an energy harvesting (EH) single user channel in presence of an energy cooperating helper. The EH helper transfers energy to the EH battery-limited transmitter and receiver nodes. These nodes impose energy causality and energy saving constraints on the power consumption. Both of the transmitter and the receiver harvest energy from nature, and also from the helper via energy cooperation links. The EH receiver requires energy for message decoding process which is called the decoding cost. Then, based on status of the batteries at the transmitter and the receiver, five scenarios are investigated. To maximize the achievable throughput, we propose iterative directional waterfilling algorithms based on minimum and maximum constraint violations. Then as a general model, a backward iterative algorithm (based on combination of optimization in feasibility tunnel and directional waterfilling with variable minimum constraints) is presented. Finally, numerical results are presented to highlight the advantages of energy cooperating helper.