###### Abstract  
Indoor smart-farming based on artificial grow lights has gained attention in the past few years. In modern agricultural technology, the growth status is generally monitored and controlled by radio-frequency communication networks. However, it is reported that the radio frequency (RF) could negatively impact the growth rate and the health condition of the vegetables. This work proposes an energy-efficient solution replacing or augmenting the current RF system by utilizing light-emitting diodes (LEDs) as the grow lights and adopting visible light communications and optical camera communication for the smart-farming systems. In particular, in the proposed system, communication data is modulated via a 24% additional green grow LED light that is also known to be beneficial for the growth of the vegetables. Optical cameras capture the modulated green light reflected from the vegetables for the uplink connection. A combination of white ceiling LEDs and photodetectors provides the downlink, enabling an RF-free communication network as a whole. In the proposed architecture, the smart-farming units are modularized, leading to flexible mobility. Following theoretical analysis and simulations, a proof-of-concept demonstration presents the feasibility of the proposed architecture by successfully demonstrating the maximum data rates of 840 b/s (uplink) and 20 Mb/s (downlink). Li-Fi; smart farm; optical camera communication; optical wireless communications; visible light communications; OWC; VLC +
Footnote †: journal: _Sensors_  
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was also deployed in agricultural projects. In reference [7], plowing, cup-cutting, pesticide-spraying, and seeding applications were done by a robot via Bluetooth. Some other agricultural management systems currently are in the market, where sensors transmit data through a 920 MHz wireless channel for the uplink, and 3G/LTE channel is adopted for the downlink [8]. These up-to-date smart management systems in the agriculture field rely on the radio-frequency (RF) spectrum as a medium for data transmission. However, some experiments showed the impact of RF radiation from Wi-Fi routers on the germination of the seeds, and the growth of the vegetables could be detrimental [9; 10]. It was reported that seeds exposed for a longer time to the RF radiation took a much longer time to germinate or failed to grow. In addition, the vegetables exposed to the radiation showed lesser and brighter leaves and were shorter in size than those not exposed to the radiation. The work showed that conventional Wi-Fi routers could affect the life cycle of vegetables, causing a decrease in their fruit quality and the photosynthesis process. With these possible side-effects from RF-based indoor smart-farming systems, visible light communication (VLC) has been gaining attention as a promising candidate for replacing or augmenting the current RF-based systems [11]. VLC typically uses light-emitting diodes (LEDs) as light sources and data transmitters, providing the simultaneous functions of illumination and communication [12]. Reference [13] presented that LEDs can provide the required energy for photosynthesis which is the primary process for the growth of vegetables. The work also reported that the LEDs showed maximum energy efficiency and reduced cost compared to other artificial grow lights. In addition, reference [14] investigated the energy consumption of VLC compared to RF technologies and showed VLC's superiority in energy efficiency. Another study proved that VLC is a safer, faster, greener, and cheaper technology [15]. Therefore, VLC can be an attractive solution by generating lights for growing vegetables and constructing a communication network for smart-farming. In this work, we propose a new smart-farming architecture guaranteeing an RF-free growing environment for plants to increment crop production and ensure the best quality of products.