Radio waves

LiFi communicates with photons instead of radio waves – and it’s very useful for the Internet of Things

Photonics is a promising technology in almost every industry, today and tomorrow. Many scientists are exploring the possibilities of this light technology. But how useful is it for businesses in different industries? How will they apply photonics? This is the whole purpose of Photonic Applications Week. A week full of workshops, congresses, exhibitions, conferences and debates to show professionals from different disciplines what photonics can bring to their sector.

the Photonic Applications Week will begin on September 30. Innovation Origins prepares you for it in a short series. Today we have a conversation with Jean-Paul Linnartz, who leads the project ELIoT on behalf of Signify and TU Eindhoven. What light – instead of radio waves – can do for the Internet of Things is to be invented in this European project, which revolves around a technology developed by Signify that uses LiFi, a wireless communication network generation that sends information via light beams instead via radio waves, as is the case with WiFi.

Jean-Paul Linnartz is a full-time professor in the Signal Processing Systems group at TU Eindhoven. He focuses on algorithms for smart lighting systems and wireless communication networks. Linnartz has over 60 patents granted to his name. His publications on electronic watermarking, anonymous biometrics, radio communication and wireless optical communication have been cited over 10,000 times. His research ideas are used in three successful companies. At Signify (Philips Lighting), he leads research for the LiFi-Venture.

“We want ELIoT to connect Internet things,” says Linnartz. “And we prefer to do it via light because we believe it’s better and safer than the usual methods that use radio waves. In other words, LiFi instead of WiFi. One of the exciting aspects is safety, Linnartz immediately states. “I’m hesitant to guarantee LiFi is ‘secure’ just because it stays in one room. Even if you read stories that LiFi is secure as soon as you close the door behind you, you can’t trust it. By the time you are going to release this system, you just need to do your crypto at least as well as on other systems, but it surely helps that you still have a layer of security on top of that. The light remains well inside the walls of a room, also because our windows today are very insulating against infrared light. And that’s how you get that extra layer of security.

Industry 4.0

It’s not for nothing that Linnartz places so much emphasis on the importance of safety. “Look at companies such as BMW, Audi, Airbus or other representatives of ‘industry 4.0”, where conveyor belt systems and autonomous robots operate, and soon also drones for parts supply. If someone walks past such a factory and starts disturbing the WiFi system, the whole installation will be down for at least 48 hours. It’s a huge cost. What Linnartz means: This could well translate into a security requirement that plays hugely in favor of LiFi.

Subscribe to IO on Telegram!

Want to be inspired 365 days a year? Here is the opportunity. We offer you one “origin of innovation” per day in a compact Telegram message. Seven days a week, delivered around 8:00 p.m. CET. Live from our newsroom. Sign up here, it’s free!


Signify is very well positioned for the future communication system, says Linnartz. “Users will want higher and higher speeds. The only way to achieve this is to create very small cells: using your radio signal to cover exactly the part that reaches the end user. If you sit indoors, you prefer to do so by the ceiling, outdoor floor lamps are fine. This can be done via light, but in principle also via 5G. In either direction, you can create beams that bring out all the energy in the right place.


To explain why our focus today is more on density than on the widest possible coverage, Linnartz takes us to 1904. “That’s how I always explain it to my students. Guglielmo Marconi, the inventor of the wireless telegraph, was proud to have succeeded in sending radio signals 5,000 kilometers across the Atlantic Ocean. Years later, we had the medium wave. Radio Luxembourg and Radio Moscow reached all of Europe, hundreds of kilometers away. With FM it became much more targeted, regional radio programs also became possible. These distances have therefore been reduced from 5,000 kilometers to 500 kilometers to 50 kilometers. The breakthrough of the 80s for the use of car radios was the decision to no longer place the antennas on the highest mountain, but rather in the valley, because that is exactly where your users are. So you go from coverage to density. Cells have become smaller, in the 90s for the first time as WiFi, with which you can cover your own house, about 30 meters in other words. And Bluetooth travels from my pocket to my ear, so it’s an even shorter distance. And if you want to get even closer, making the bundle more focused is exactly the step you need. Then you see it becomes easier to aim with light beams than to use radio waves to create a phased network“.

One of the reasons for this is also power consumption. “Radio wave antennas consume a lot of energy. Yes, 5G is much more economical, at least if you look at the energy radiated per bit that reaches the user. But you are burning a tremendous amount of energy in your signal processing, so even before you create a radio signal. A small photonic node on the ceiling or in a lamp post can, on the contrary, be very simple, it does not need all these processors, and is therefore much more energy efficient.

Li-Fi © Signify


Can light signals also work in the dark? Linnartz laughs at the question. Then, seriously: “Yes, we think that infrared works even better, for example because it consumes even less energy. All communication electronics work best with infrared. We still believe that the ceiling and the lamp have the best location for LiFi. Outdoors, the floor lamp is ideal, but there the sunlight causes some noise; it shoots a lot of photons around, you have to find a very weak signal between those huge rays of light, so there too you can work much better with infrared.

Already in the 1990s, an attempt was made to bring infrared communication to the market, but it was foiled by WiFi, observes Linnartz. “Why would it work now, one might rightly ask. Well, for this we can quote Johan Cruijff, with his ‘every disadvantage has its advantage‘. At the time, we mainly wanted coverage. With a single wifi box, we could cover an entire building, which was an advantage. But at a certain point, when there are more and more people, it becomes an advantage not to let the signal pass through the walls. Then you can create the connection you have in one room, in the next one as well. In fact, it’s better to reuse your features. It used to be bits per second, but now it’s bits per second per square meter. Outside of the urban environment however, traditional radio signals are still preferred. “That’s not where the density problem lies. Radio technology is therefore always a better option in these places.

Higher throughput

More density will remain the objective in the years to come. “Our desire to further increase throughput will be our guide in the next steps. The key to achieving this is aggregation: the closer your signal gets to the user, the better. One of the biggest challenges with a ceiling LiFi source is that you spread your photons throughout the room, so you need to emit a reasonable amount of photons per bit. If you can focus the beam better, it will be easier to increase throughputs. This brings you closer to photonic integration, laser beams, but then you need to have the technology to place the laser beams in exactly the right place. For a region like Brainport, which claims to be at the heart of photonics, this can be a great opportunity. We have already taken steps with a LiFi fixture which, with a much more focused beam, currently offers a 250 Mbps connection – the world’s fastest commercially available LiFi connection.

[learn_more caption=”ELIoT during the Photonics Application Week”] During Photonics Application Week, several partners within ELIoT will be present. For Jean-Paul Linnartz, this is another excellent opportunity to strengthen the ties between them. “Through international discussions, you hear a lot of things, you trigger yourself. The link with German industry is important, but for Signify it is also an additional way to connect with the universities of Eindhoven and Oxford. You always want to look a little further than technology from your own background. These are the times when this is possible. If you’re only driven by what you want to bring to market as products next year, you might be missing a beat.[/learn_more]