Optimal Energy Sharing for Cooperative Relaying in a Random Access Network With Energy Harvesting Nodes

In this article, we consider an energy harvesting cooperative network comprised of two data sources and one relay. All nodes transmit based on a predefined slotted Aloha protocol in a random access environment. The main challenge we study is to find how the relay node must share its energy between two sources to optimize their QoS metrics, i.e., throughput and average transmission delay (ATD), separately. Thus, according to our multi-source scenario, we encounter a multi-objective optimization problem (MOOP). Since the relay does not prioritize between two sources, in order to solve the MOOP, we optimize equal-weight linear aggregation of the QoS metrics of two sources. Interestingly, we show that our problem can be modeled as an exact potential game in which the Nash equilibrium strategy is an optimal and stable solution of the related MOOP. The cooperative relaying strategy proposed in this article assures that the throughput and ATD of each source is better than the corresponding metrics without relay. Finally, we present numerical results to show how much the derived cooperative relaying strategies improve the QoS of each source.