In this paper, we consider an indoor hybrid visible light communication (VLC) and radio frequency (RF) communication scenario with two-hop downlink transmission. The LED carries both data and energy in the first phase, VLC, to an energy harvester relay node, which then uses the harvested energy to re-transmit the decoded information to the RF user in the second phase, RF communication. The direct current (DC) bias and the assigned time duration for VLC transmission are taken into account as design parameters. The optimization problem is formulated to maximize the data rate with the assumption of decode-and-forward relaying for fixed receiver orientation. The non-convex optimization is split into two sub-problems and solved cyclically. It optimizes the data rate by solving two sub-problems: fixing time duration for VLC link to solve DC bias and fixing DC bias to solve time duration. The effect of random receiver orientation on the data rate is also studied, and closed-form expressions for both VLC and RF data rates are derived. The optimization is solved through an exhaustive search, and the results show that a higher data rate can be achieved by solving the joint problem of DC bias and time duration compared to solely optimizing the DC bias.

翻译：本文研究了一种室内混合可见光通信（VLC）与射频（RF）通信场景，采用两跳下行传输模式。在第一阶段VLC中，发光二极管（LED）同时传输数据和能量至能量采集中继节点，该节点利用采集的能量在第二阶段RF通信中将解码后的信息重新传输至RF用户。我们将直流偏置（DC bias）和VLC传输的分配时长作为设计参数。在固定接收器方向的解码转发中继假设下，建立了最大化数据速率的优化问题。该非凸优化被分解为两个子问题并循环求解：通过固定VLC链路时长求解直流偏置，以及固定直流偏置求解时长，从而优化数据速率。同时研究了随机接收器方向对数据速率的影响，推导了VLC与RF数据速率的闭式表达式。通过穷举搜索实现优化求解，结果表明，联合优化直流偏置与时长的方案相比仅优化直流偏置可获得更高的数据速率。