CEA-Leti Researchers Set Throughput Record for Li-Fi Communications

CEA-Leti has set a new world record for throughput in light communications (VLC). The researchers used a single 10-μm GaN blue micro-LED to achieve a data transmission rate of 7.7 Gb/s, compared to the previous record of 5.1 Gb/s. The transmission rate marks another step toward commercialization and use of VLC.

VLC, commonly called Li-Fi (short for “light fidelity”), offers an alternative or a complementary technology to radio frequency systems such as Wi-Fi and 5G. It shows significant promise in security applications, as light can be confined to a room with no information leakage, as opposed to Wi-Fi communication, which penetrates walls.

CEA-Leti testbed for single GaN blue micro-LED that achieved throughput of 7.7 Gb/s. Courtesy of CEA-Leti.

“This technology has exciting potential for mass-market applications,” CEA-Leti research scientist Benoit Miscopein said. “Multi-LED systems could replace Wi-Fi, but wide-scale adoption will require a standardization process to ensure the systems’ interoperability between different manufacturers.”

The Light Communications Alliance was created in 2019 to encourage the industry to implement this standardization, he said. In addition to a stand-alone Wi-Fi-like standard, the possibility to include the new technology as a component carrier in the downlink of 5G-NR, a radio-access technology for 5G mobile considerations, is also under investigation to bring a large additional license-free bandwidth.

“This may be feasible because CEA-Leti’s Li-Fi physical layer relies on the same concepts as Wi-Fi and 5G technologies,” Miscopein said. “Matrices of thousands of micro-LEDs could also open the way to mid- to long-range applications, such as indoor wireless multiple access.”

Preserving the bandwidth of each micro-LED within a matrix requires that each signal is generated as close as possible to the micro-optical source.

“To meet this challenge, we expect to hybridize the micro-LED matrix onto another matrix of CMOS drivers: One simple CMOS driver will pilot one micro-LED,” Miscopein said. “This will also enable the additional feature of piloting each micro-LED pixel independently, and that allows new types of digital-to-optical waveforms that could eliminate the need for digital-to-analog converters commonly used in the conventional ‘analogue’ implementations of Li-Fi.”

CEA-Leti will continue its research in order to foster a better understanding of the electrical behavior of single LEDs in high-frequency regimes and the link between bandwidth and electromigration patterns, and techniques to improve the range and/or increase the data rate using multi-LED emissive devices. This requires adapting the waveform generation as well as a CMOS interposer to drive the matrix on a pixel basis.