Stability analysis for energy harvesting sources over time varying wireless channels with relays

In this paper, we propose and analyze transmission strategies for a source node with energy harvesting capability. The source node is able to either transmit directly to the destination or transmit with the help of a relay node through a network-level cooperation protocol. The relay node also has energy harvesting capability. The channels between different nodes are time varying. The packets arrival to the source and the energy arrival to the source and the relay are modeled by discrete-time stochastic processes. We derive the maximum stable throughput rate of the source for different transmission strategies in closed-form. The proposed strategies exploit the channel state information (CSI). We derive the stability conditions also in the case of imperfect channel measurements. Finally, we propose and analyze a modified relaying strategy which enhances the performance when the relay has a low energy arrival rate.