How does Li Fi work in detail

Sending internet data via light beams? Sounds like a cool gadget in a sci-fi story. In fact, it is a very real technology that companies and researchers are actively promoting. Do not doubt yourself if you haven't heard anything about the so-called LiFi. Because although the tech bubble is discussing the topic as a potential “next big thing”, the curtain is only gradually rising. Philips Hue manufacturer Signify (formerly Philips Lighting) is one of the first companies to have a LiFi system ready for the market. The manufacturer recently demonstrated them to journalists at the company's headquarters in Hamburg. Always interested in innovation topics, we were happy to take a look at Signify's solution.

This is behind internet technology

LiFi is a technology for wireless data transmission at speeds on an extremely fast broadband level. It is thus similar to WLAN, but with one important difference. Because instead of surfing on radio waves, the data at LiFi surf on light beams. Depending on the system, both visible and invisible light in the infrared range are used.

The light-emitting diodes of modern LED lamps, as they are found in practically all lamps today, serve as transmitters. Each luminaire is equipped with its own modem. This in turn is connected to the Internet router via the wall wiring. The lights receive their signals, for example, via network cables, which can also serve as power cables (Power over Ethernet).

All devices that now also connect to the Internet are intended as wireless receivers for LiFi signals. Because there is no corresponding reception technology in any laptop or smartphone, a LiFi dongle on the USB port is currently used as a bridge solution.

Based on the brand name of WLAN, WiFi, the German computer scientist Harald Haas introduced the name LiFi in 2011. Other research groups and companies adopted the term and have since been working on getting the technology to fly. This also includes Signify, one of the major players in the lighting industry.

Why do we need LiFi instead of WiFi?

"The use of LiFi comes into question wherever WLAN is interfered with by other radio signals or can interfere with them itself - in airplanes and hospitals, for example," explains Martin Kapralek, IT system architect at Signify in Hamburg. The young internet technology also scores in terms of security. Because unlike WLAN radio waves, light does not penetrate the solid walls of the office space.

Data is only transmitted when there is direct visual contact or via light reflected from surfaces. Hackers would have to be physically on site to access data. They cannot break in there remotely. "This makes LiFi potentially interesting for the financial sector, government agencies and all other office environments in which sensitive data is exchanged," emphasizes Martin Kapralek. There, knowledge workers who are still attached to the LAN cable with their computers for security reasons could finally use the advantages of mobile computers.

In practice: YouTube streaming by light

At the company headquarters in Hamburg, Martin Kapralek from Signify demonstrated how to imagine such a setup. The components: an insert lamp measuring about one meter square for the office ceiling, a standard Windows laptop and a USB receiver, about the size of a cigarette packet. Martin Kapralek streamed a YouTube video in full HD resolution on the laptop. The LiFi signal from the office light served as the only connection. The laptop was verifiably in flight mode, so it had no WiFi access. The office luminaire itself was connected to the in-house network via the PoE ceiling cabling and thus surfed the YouTube server. The demo ran smoothly, and the YouTube video was transmitted smoothly with no dropouts in picture and sound. Conducting video conferences via LiFi connection is therefore a conceivable application.

If it was up to Signify, we could have watched various other web videos on other devices at the same time. Signify's system has so far enabled a downstream of up to 30 Mbit / s. Compared to what DSL lines can provide, there is not much, but according to Martin Kapralek, more than is necessary for normal office tasks. 8 Mbit / s would be sufficient for this. But technically, LiFi is capable of significantly higher speeds. Under ideal test conditions, other researchers have even achieved insane LiFi top speeds of 240 Gbit / s. For the time being, however, this is neither a realistic nor a required value for commercial use.

The "dark sides"

At Signify's LiFi demonstration, however, the, pardon, downsides, i.e. the compromises of this technology, became tangible. The LiFi technology can only be used sensibly over short distances, even if not only in such a small space as the compact demo station suggested during our visit to Signify. Martin Kapralek explained that the luminaire and receiver should not be more than 150 to 400 centimeters apart. That sets limits. “Several LiFi-capable lights are required to cover an entire room. When users cross the room with their laptops, for example, they simply contact the nearest LiFi access point, ”explains the IT system architect.

But that multiplies the already high acquisition costs of a LiFi setup. A compatible recessed luminaire from the Signify series Philips PowerBalance gen2 and Philips LuxSpace Downlight starts at 1,500 euros. There is also the USB receiver for 250 euros each. Since these are pioneering products, LiFi-compatible lights are correspondingly expensive and can currently only be justified for larger corporate customers.

After all, LiFi does not increase energy costs very much. Because the Signify lights do not have to shine as brightly as possible to transmit data. For a stable transfer it is sufficient if they are dimmed down to 20 to 30 percent. And if you still use conventional light bulbs in the office, you can save a lot of electricity by upgrading to LED.

LiFi still has a long way to go into the limelight

It is clearly a fascinating Internet technology with great potential for use in many areas. The advantages over WLAN are obvious. Internet via light does not interfere and is safer. And the beginning has been made. Finally, after years of preparation, in addition to Signify, the much smaller specialists Oledcomm and PureLiFi have brought products for a WiFi alternative to market maturity.

But in addition to the high installation costs, there is also a very banal disadvantage that slows the breakthrough of LiFi. The USB dongles that were still required up to now are simply too impractical for long-term everyday use. The lack of laptops and smartphones with integrated light internet is currently the biggest bottleneck. At large manufacturers such as Apple and Samsung, the topic has been on the development agenda for a while, but it is more in the “future music” category.

“We assume that integrated LiFi connections will be available in popular consumer devices in five years,” predicts Martin Kapralek of Signify. Maybe we will see the first prototypes during the upcoming Mobile World Congress. PureLiFi in particular has always been good for a surprise at its MWC stand in recent years. In 2018, the pioneer presented a smartphone case with an integrated LiFi module for a Samsung Galaxy S5. Not exactly at the speed of light, but with triple steps LiFi is getting closer and closer to its breakthrough.

Office lighting at Amazon (Provisonslink)

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Images by zinaidasopina112 / Adobe Stock; Berti Kolbow-Lehradt

Berti Kolbow-Lehradt

is a freelance technology journalist. For the Netzpiloten, he deals with many aspects of the digital world. This includes the smart home, photography, smartphones, the Apple world and other areas of consumer electronics and IT. Member of the Netzpiloten Blogger Network.


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Keywords: broadband Internet, Internet of Things, LiFi, Philips Lighting, Signify, smart lighting, Wifi, wlan