Joint optimization of power allocation and load balancing for hybrid VLC/RF networks

In this paper, we propose and study a new jointloadbalancing(LB)andpowerallocation(PA)scheme for a hybrid visible light communication (VLC) and radio frequency (RF) system consisting of one RF access point (AP) and multiple VLC APs. An iterative algorithm is proposed to distribute users on APs and distribute the powers of the APs on their users. In the PA subproblem, an optimization problem is formulated to allocate the power of each AP to the connected users for total achievable data rate maximization. In this subproblem, we propose a new efficient algorithm that finds optimal dual variables after formulating them in terms of each other. This new algorithm provides faster convergence and better performance than thetraditionalsubgradientmethod.Inaddition,itdoesnot dependonthestepsizeortheinitialvaluesofthevariables, which we look for, as the subgradient does. Then, we start withtheuseroftheminimumdatarateseekinganotherAP thatoffersahigherdatarateforthatuser.Userswithlower dataratescontinuereconnectingfromoneAPtoanotherto balancetheloadonlyifthistravelincreasesthesummation of the achievable data rates and enhances the system fairness. Two approachesareproposedtohavethejointPAand LB performed: a main approach that considers the exact interference information for all users, and a suboptimal approach that aims to decrease the complexity of the first approach by considering only the approximate interference information of users. The numerical results demonstrate that the proposed algorithms improve the system capacity and system fairness with fast convergence.