Energy efficiency optimization in a parallel relay-assisted UWOC system with simultaneous lightwave information and power transfer

In this paper, we investigate the energy efficiency optimization for a parallel relay-assisted underwater wirelessoptical communication (UWOC) system with simultaneous lightwave information and power transfer (SLIPT)over an aggregate channel. In this system, relay nodes are equipped with energy harvesting devices, getting energyfrom the direct current component of the received signal transmitted by the source node. These nodes utilize theharvested energy to transmit the signal to the destination node with the decoding and forwarding strategy. Theharvested energy for each relay node is derived by the Gauss-Laguerre quadrature formula and the outage prob-ability is deduced by the Meijer-G function. Then, the system's energy efficiency can be calculated and an energyefficiency maximization problem is built up with respect to the bias current. We propose a three-level-iterationalgorithm to solve this problem. In the first level, the Dinkelbach method is used to represent energy efficiency in aparametric subtractive form. In the second level, we use the penalty function method to convert the object functionand constraint. In the third level, the objective function is transformed into a quadratic function by using a succes-sive convex approximate method, thereby solving for the bias current. The effects of system parameters on energyefficiency are also analyzed. Theoretical results and Monte Carlo simulations suggest that employing the solved biascurrent can significantly improve the system's energy efficiency.(c) 2024 Optica Publishing Group