# A 40 Mb/s VLC System Reusing an Existing Large LED Panel in an Indoor Office Environment
## 1 Introduction  
Visible light communication (VLC) has attracted continued research interest [1, 2, 3], while solid-state lighting has dominated the mass market over the last two decades [4]. The use of solid-state semiconductor devices, such as light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs) [5, 6, 7], and laser diodes (LDs) [8, 9], in the visible range enables intensity modulation of the optical power for communication simultaneously with illumination. Therefore, the VLC technology has the potential to reuse the existing lighting infrastructure to deliver add-on functionality in a cost-effective manner that can be adopted in future smart indoor and outdoor environments. The outdoor lighting infrastructure covers a variety of LED-based luminaries that range from street lights, traffic lights, tocar lights, which have inspired the use of VLC in infrastructure-to-vehicular (I2V) and vehicular-to-vehicular (V2V) communications [10; 11]. Experiments using existing traffic lights and car lights as transmitters have been reported to demonstrate the feasibility of VLC in the outdoor I2V/V2V communications [12; 13]. When compared with the outdoor environment, the indoor scenarios often find large LED luminaries installed in the ceiling or relatively small LED desk lamps placed directly above the table to provide a guaranteed light level for illuminance. This benefits the indoor VLC applications greatly since those LED luminaries' high output optical power can ensure a decent signal-to-noise (SNR) profile within rooms/offices if their intensity is efficiently modulated. In this work, we hereafter limit the scope to VLC deployment in the indoor environment because of its advantages and popularity. Being motivated by the potential of VLC, standardisation has been carried out by several organisations [14; 15; 16]. Recent standardisation activities are mainly conducted within the Institute of Electrical and Electronics Engineers (IEEE) and the International Telecommunication Union Telecommunication Standardisation Sector (ITU-T) [16]. In March 2017, the IEEE 802.15.13 task group was established with the goal of defining an optical wireless communication (OWC) standard that supports data rates of up to 10 Gb/s using wavelength that ranged from 190 to 10,000 nm. The first draft was finished in 2019 with a letter ballot held in 2020. The standard is expected to be completed in 2021. In parallel with 802.15.13, the IEEE 802.11 bb task group was formed in May 2017 to develop a global OWC standard targeted at the mass market within the well-known IEEE 802.11 wireless local area networks (WLAN, which is often linked and used interchangeably with WiFi, i.e., wireless fidelity) standard family. Because the latest standards typically define communications operating in the band beyond the visible light spectrum, the concept of light fidelity (LiFi), which covers both visible and infrared bands, has been introduced [17]. The ambition of 802.11 bb is to operate as closely as possible to the base 802.11 standards to allow for integration with WLAN chipset vendors. Consequently, the physical (PHY) layer of 802.11a with a bandwidth of 20 MHz has been adopted as the common PHY mode in 802.11 bb. The draft is still under discussion and expected to be completed in 2021. As another influential standardisation body, ITU-T published a new VLC/LiFi standard G.991 (also known as G.vlc) [18] in 2019, which is highly based on the ITU-T's high-speed power-line communication standard G.9960 (also known as G.hn) [19; 20]. In the PHY layer, G.9991 defines two PHY modes that employ the orthogonal frequency division multiplex (OFDM) modulation with three band plans. The total bandwidth in the three band plans is 50, 100, and 200 MHz, respectively. A maximum data rate of 2 Gb/s is supported. Since the release of G.9991, several chipset implementations have been available from the G.hn semiconductor vendors, helping to accelerate VLC/LiFi applications in the real world [16].