Optimization of a Two-HoP Network with Energy Conferencing Relays

This paper considers a two-hop network consisting of a source, two parallel half-duplex relay nodes, and two destinations. While the destinations have an adequate power supply, the source and relay nodes rely on harvested energy for data transmission. Different from all existing works, the two relay nodes can also transfer their harvested energy to each other. For such a system, an optimization problem is formulated with the objective of maximizing the total data rate and conserving the source and relays transmission energy, where any extra energy saved in the current transmission cycle can be used in the next cycle. It turns out that the optimal solutions for this problem can be either found in a closed form or through one-dimensional searches, depending on the scenario. Simulation results based on both the average data rate and the outage probability show that energy cooperation between the two relays consistently improves the system performance.