Recursive Geometric Water-filling for wireless links with hybrid energy systems

As a preferred choice for supporting green communication, energy harvest makes use of energy from the environment. However, since harvesting energy depends on natural conditions, it is not a stable energy source. As a result, the energy from power grid is often included to serve as a supplementary source to regulate the overall energy supply of the system. The conventional way to solve the optimal power allocation problem is to solve the KKT conditions, and then find the water level(s) and the power allocation solutions. In this paper, we developed a Recursive Geometric Water-Filling algorithm for this Hybrid problem of throughput maximization, so the algorithm is abbreviated as RGWFH. The proposed algorithm avoided complexity of solving the KKT conditions of the problems with multiple variables. For the target problem, the proposed algorithm showed that the harvested energy and the grid power can be optimally allocated by separate steps. Therefore, the proposed algorithm is more efficient and accurate. A numerical example is provided to illustrate the steps of the proposed algorithm.