Demonstration of 575-Mb/s downlink and 225-Mb/s uplink bi-directional SCM-WDM visible light communication using RGB LED and phosphor-based LED

TLDR

The authors propose and experimentally demonstrate a full‑duplex bi‑directional subcarrier‑multiplexing wavelength‑division‑multiplexing visible light communication system using commercially available RGB LEDs and a phosphor‑based LED, achieving 575 Mb/s downstream and 225 Mb/s upstream data rates. The system assigns red and green wavelengths to carry data on the downlink while keeping blue for illumination, uses a low‑cost phosphor‑based LED for the uplink, and applies pre‑ and post‑equalization to compensate the LEDs’ severe frequency response within a QAM‑OFDM SCM‑WDM framework. The demonstration supports four‑user downlink and one‑user uplink transmission with BERs below the 3.8 × 10⁻³ pre‑FEC threshold over 66 cm free‑space, and can scale to more users by adjusting sub‑channel bandwidth, indicating strong practical potential for VLC.

Abstract

We propose and experimentally demonstrate a novel full-duplex bi-directional subcarrier multiplexing (SCM)-wavelength division multiplexing (WDM) visible light communication (VLC) system based on commercially available red-green-blue (RGB) light emitting diode (LED) and phosphor-based LED (P-LED) with 575-Mb/s downstream and 225-Mb/s upstream transmission, employing various modulation orders of quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM). For the downlink, red and green colors/wavelengths are assigned to carry useful information, while blue chip is just kept lighting to maintain the white color illumination, and for the uplink, the low-cost P-LED is implemented. In this demonstration, pre-equalization and post-equalization are also adopted to compensate the severe frequency response of LEDs. Using this scheme, 4-user downlink and 1-user uplink transmission can be achieved. Furthermore, it can support more users by adjusting the bandwidth of each sub-channel. Bit error rates (BERs) of all links are below pre-forward-error-correction (pre-FEC) threshold of 3.8x 10(-3) after 66-cm free-space delivery. The results show that this scheme has great potential in the practical VLC system.