Online power control for cooperative relaying with energy harvesting

We consider a two-hop amplify and forward relay network with energy harvesting source and relay nodes. With finite battery storage, we design a power control strategy for both the source and the relay aiming at maximizing the long-term time-averaged data rate. Using Lyapunov optimization technique, we develop an online algorithm to determine transmit powers at the source and the relay based on the current energy level of the battery and channel fade conditions. Our power control algorithm does not rely on any knowledge of the statistics of energy arrivals and fading channels. The solution is provided in closed-form. We further bound the performance of the proposed algorithm to that of the optimal solution.