Li-Fi: IoT at the Speed of Light

Smart Communication

Li-Fi: IoT at the Speed of Light

The future demand for wireless communication networks within buildings and outside will further increase. The optical light communication called Light Fidelity (Li-Fi), using LED-based light sources as data transmitters, offers an alternative to existing technologies such as Wi-Fi and LTE.

by Gerhard Kafka

Communication by light, in the form of beacons, has already been used since 800 BC, reaching its climax in 280 BC with the legendary Alexandria lighthouse. Around 400 BC Greeks used polished shields, so-called heliographs, to transmit signals during armed conflicts. Over 2,000 years later, in 1880, Alexander Graham Bell and Charles Sumner Tainter developed the Photophone, a telephone that used light to transmit speech. In 2005, research into optical wireless communication (OWC) began at the University of Paris-Saclay and is reaching market readiness today.

Li-Fi - Line of Sight - Heliographs

Line of Sight: Heliographs (from the Greek helios for “sun” and graphein for “write”) is a wireless telegraph that signals by flashes of sunlight reflected on a mirror. Invented in the early 19th century, they were still in use by the British and Australian armies as late as the 1960s.

The annual growth of the Light Fidelity (Li-Fi) market is estimated to be 80 percent up to 2023 and the sales volume, worth $0.5bn in 2016, could explode to $75bn in 2023. The term Li-Fi was coined by Professor Harald Haas, a German researcher at the universities of Bremen and Edinburgh, during a presentation at the 2011 TED Global Talk conference and stands for visible light communication (VLC). Li-Fi can deliver speeds up to 200 times faster than Wi-Fi – theoretically more than 200 Gbps. The advantages can be summarized as follows:

  • Faster than traditional network access
  • No electromagnetic interference
  • Very precise GPS capabilities
  • Eco-friendly
  • Improved indoor connectivity (medical, aeronautical, defense)
  • Increased security
  • No health risks
  • Very economical (no license)
  • Works well in places where radio frequencies are not permitted or may cause interference with other machines (schools, hospitals, aircraft, industrial plants)
Li-fi networks can deliver speeds 200 times faster than Wi-fi.
Professor Harald Haas, University of Bremen, who coined the term 'Li-Fi'


EU Consortium ELIoT

In July 2019, the start of a three-year project called Enhancing Lighting for the Internet of Things (ELIoT) was announced. The aim of the project is the development of mass market IoT applications based on LiFi. As a project partner, Fraunhofer Fokus will ensure the integration of Li-Fi into 5G networks. ELIoT originates from the EU innovation program Horizon 2020 and receives €6m in funding from the public– private partnership Photonics21. In addition to Fraunhofer Fokus, its Heinrich Hertz Institute (HHI) plus Signify (formerly Philips Lighting), Nokia, MaxLinear, Deutsche Telekom, KPN, Weidmüller, LightBee, the University of Oxford, and Eindhoven University of Technology are also participating in ELIoT. The main objectives of the project are to provide an open reference architecture for the support of the Internet of Things and to contribute to the standardization of applications based on communication by light.

Lighting systems could be able to provide wireless connectivity in every room.
Professor Jean-Paul Linnartz, Signify


For this purpose, Li-Fi must meet the ever-increasing demands on existing communication networks in terms of data rates, stability, and latency. “With ELIoT, we have established a powerful consortium of companies and organizations from the European lighting and communications industries. ELIoT forms a closed value chain with partners representing the components, chipsets, systems, and applications sectors and research institutes, working together on the commercialization of Li-Fi for the future IoT,” says Volker Jungnickel, head of the Metro, Access, and In-house Systems Group at Fraunhofer HHI, who serves as project coordinator for ELIoT. Professor Jean-Paul Linnartz, co-initiator of ELIoT and also leader of Signify’s research in Li-Fi, confirms the potential of ELIoT: “Li-Fi can deliver high-speed communication, interference-free with high reliability. The available spectrum can be fully reused in every room. The lighting infrastructure is in an excellent position to provide wireless connectivity for the rapidly increasing number of wireless devices in every room.”

Li-Fi in Aircraft

Li-Fi addresses a large variety of applications in the fields of live streaming, hospitals, workplaces, manufacturing facilities, schools, retail, and many more. If, for example, it is employed in aerospace, Li-Fi has the potential to transform both the overall passenger experience and enhance in-flight connectivity. Transmitting data through illumination is attracting the interest of a number of airline companies.

Li-Fi - Airspace-Cabin - photo ©: Airbus

No Interference: Internet by light can help avoid disturbing electromagnetic signals in airplanes and other sensitive areas.

Faster and less expensive than WiFi, it could transform the whole passenger experience. At the June 2019 International Paris Air Show in Le Bourget, Air France, Latécoère Group, and Ubisoft demonstrated Li-Fi technology in an in-flight video game tournament showcasing this technology. According to experts, the use of LiFi on board would save the equivalent of ten to 20 people in weight per aircraft. “Optical fibers are a thousand times lighter than copper,” said Serge Berenger, senior VP of innovation at Latécoère. “LiFi will allow airline companies to do away with data communication boxes beneath seats, each of which weigh a kilogram.” Li-Fi connection speeds are more than 200 times faster than those of Wi-Fi and could mean quicker bank transactions on board planes. “At the moment, airlines have to wait until a plane lands before in-flight transactions can be approved,” explains Micheline Perrufel, an engineer with mobile telecoms company Orange, “but, in the future, flight attendants will be able to approve in-flight payments immediately thanks to the installation of Li-Fi in the cabin.” As well as offering new applications for passengers, Li-Fi will also bring benefits for pilots because it is safer than Wi-Fi and does not pose any risk of electromagnetic interference.

Li-Fi - Infographic Airbus - Li-Fi - Infographic Airbus

The Way to Go: Transmitting data and voice through illumination systems offers potential benefits for both passengers and crew.

Airbus is considering the possibility of installing Li-Fi in its airplane cockpits with a view to connecting the pilot’s controls and equipment in a way that is simpler and safer. Li-Fi has the potential to give the future passenger experience a boost. Introducing Li-Fi to the cockpit reduces the number of cables and removes a great deal of deadweight. While Wi-Fi could solve this problem, it cannot be implemented without careful consideration of its vulnerability to external interference and hacking. Li-Fi, on the other hand, is safer as it cannot be transmitted through hulls and windows like Wi-Fi and is therefore impossible to tap from outside. This would make it much easier to prevent data streams in the cockpit from being hacked from inside the passenger cabin than if Wi-Fi was used. Today, we are surfing wirelessly but tomorrow we may all share a brighter future using light.

VLC (visible light communication) is well on its way to becoming a world standard. With the IEEE and ITU-T standards bodies. The first standard, IEEE 802.15.7, was approved in November 2011 and the Li-Fi activities have been continued in the IEEE 802.15.13 Multi-Gigabit/s Optical Wireless Communications Task Group. The standard is capable of delivering data rates up to 10 Gbps at distances up to 200 meters’ unrestricted line of sight. It is designed for point-to-point and point-to-multipoint communications in both non-coordinated and coordinated topologies.
IEEE is also working on a corresponding change to the IEEE 802.11 (Wi-Fi) standard. The main objective is to amend the IEEE 802.11bb standard serving mass-market requirements for light communication relating to low-cost and low-energy consumption.
The new ITU G.9991 standard is the first to enable very-high-speed VLC. “This market-making ITU standard is already considered a de facto standard,” says Marcos Martinez, system engineer at MaxLinear, and associate rapporteur for ITU’s “broadband in-premises networking” standardization. “We are seeing vendors of proprietary VLC solutions moving toward this ITU standard – it is already being implemented before final approval.” The standard details the system architecture, physical layer, and data-link layer specification for high-speed indoor VLC transceivers, the VLC access points within lightbulbs. “VLC is a valuable complement to Wi-Fi,” says Martinez. “VLC and Wi-Fi have different strengths and VLC’s strengths provide a strong complement where Wi-Fi faces challenges.”

Li-Fi Security Infobox - photo ©: Signify

Li-Fi Provides Highly Secure Communications because signals stay within a room and cannot leak out through the walls.

In addition, VLC, modulated with ITU’s Gigabit Home Networking ( technology, is set to be the next major innovation in realizing the full potential of both the smart home and the smart city, according to industry alliance group HomeGrid Forum. This approach continues to demonstrate the tremendous flexibility of technology to run over any medium as wireless joins the ranks of powerline, co-ax, twisted pair, and polymer optical fiber (POF) as a medium. “VLC has great potential for IoT and smart homes with high-density connectivity needs, especially where sensitive data is transmitted between connected devices in one room. The light spectrum provides low latency and avoids the usual interruption of radio-frequency spectrum during congestion time,” says Livia Rosu, marketing chair of HomeGrid Forum.

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