Light Fidelity (Li-Fi)

Dr. Harald Haas
Dr. Harald Haas

Very recently, I was browsing stuff on YouTube, when I stumbled upon Li-Fi. It was a presentation by Dr. Harald Haas and his theory of Li-Fi or light fidelity. No – I haven’t misspelt it it’s indeed Li-Fi and not Wi-Fi.


Light Fidelity (Li-Fi) is a bi-directional, high-speed and fully networked wireless communication technology similar to Wi-Fi.

Now to simplify – the term Light Fidelity (Li-Fi) was coined by Harald Haas, German Professor of Mobile Communications at the University of Edinburgh, during a TED Talk in 2011. Li-Fi uses common household LED (light emitting diodes) light bulbs to enable data transfer, boasting speeds of up to 224 gigabits per second (GB/s). The technology uses Visible Light Communication (VLC), a medium that uses visible light between 400 and 800 terahertz (THz).

Click here to watch the video by ColdFusion.

It works almost like a highly-advanced form of Morse code – just like flicking a LED on and off at extreme speeds can be used to write and transmit things in binary code. We’re talking LEDs that can be switched on and off at speeds imperceptible to the naked eye.

How does it work?

  • Li-Fi, just like Wi-Fi, transmits data electromagnetically. While Wi-Fi uses radio waves, Li-Fi runs on visible light.
  • As mentioned earlier, Li-Fi is a Visible Light Communications (VLC) system. This means that it accommodates a photo-detector to receive light signals and a signal processing element to convert the data into ‘stream-able’ content.
  • A LED light bulb is a semiconductor light source meaning that the constant current of electricity supplied to an LED light bulb can be dipped and dimmed, up and down at extremely high speeds, without being visible to the human eye. e.g. data is fed into a LED light bulb (with signal processing technology).
  • It then sends data (embedded in its beam) at rapid speeds to the photo detector (photo diode).
  • The tiny changes in the rapid dimming of LED bulbs are then converted by the ‘receiver’ into an electrical signal.
  • The signal is then converted back into a binary data stream that we would recognize as web, video and audio applications that run on the internet enables devices.

So, can Li-Fi beat Wi-Fi hollow? Not so fast… here are some pros and cons of Li-Fi that we must consider before we come to a conclusion:

Pros Cons
It’s said to be about 100 times faster than some Wi-Fi implementations, reaching speeds of 224 GB/s.
Deployment possibly limited to the LAN technology only – and not on WAN technology because of the limited range. It could be overcome with time and newer innovations, but the beginning is only likely to have scope for LAN technologies. Another limitation is said to be that it cannot be used outside in daylight, as the direct sunlight would then impede with the LED signals.
Li-Fi signals cannot pass through walls – it does make the data stream more secure, as the data cannot be intercepted without the clear line of sight. Also, the technology eliminates neighbouring network interference.
Issues with the line of sight. Unlike Wi-Fi, Li-Fi signals cannot pass through walls. Li-Fi technology uses visible light communication or infra-red spectrum – which only travels in straight lines.
Every one of us who have used a remote control, know that if any object comes between us and the TV, the line- of-sight transmission won’t work.
Greater accessibility of Internet is inherent and could arguably be the most welcomed outcome of the Li-Fi roll-out. The Internet could be accessed in the areas where Optical Fiber isn’t the best or viable option – and also in public areas where there is light already, like bus stops, public parks, street-walkways, etc.
In the hindsight to the Li-Fi ultimately eliminating a big pool of network equipment, the use of Li-Fi would require uninterruptedly powered on LED Lights – regardless of whether its day or night, and both indoor & outdoor. This leads to unnecessary energy consumption and will only amplify with every roll-out.
One glint of good news with this is that Li-Fi is said to work even if the lights are dimmed to near darkness.
After (and during the process of) the eventual mass- adoption of Li-Fi, the decommissioning of all the Edge Network Equipment will bring about an unprecedented reduction in power consumption.
There are over 46.6 Million Wi-Fi Hotspots alone in the world, i.e., 1 Wi-Fi Hotspots for every 150 People. Imagine all of those being taken down – slowly, but eventually. It could turn out to be a very eco-friendly innovation in the communications sector.
The vast majority of the Core and Edge Equipment that is pre-existent across the wider network of today’s network architecture, are not built to support the bandwidths offered by Li-Fi. This leads to either ruling out the adoption into the WAN world altogether or an enormous investment in the Equipment. With the sheer volume of equipment & device replacement prospect, the latter is certainly not an imminent possibility.
Information-sensitive places like Hospitals, Government, and Military – Li-Fi adoption will bring about a great sense of relief, and Peace of Mind with the vastly reduced data interception possibility, compared to traditional Wi-Fi
Health consequences. Any form of radiation, including visible light, or radio waves, could potentially be dangerous if greatly concentrated into a tight & compact beam of high power. Albeit we are engrossed in infrared radiation in our everyday lives, considerably generous doses of IR waves are understood to cause cancer, leukemia, and other disorders, including damages to Eyes and Skin.

That being said, Li-Fi is very likely to change the way Internet is accessed all over the planet! And it’ll be interesting to see the early stage uptake by the Industry as a whole.

Is it for real or just a theory? Right and Wrong – both. It’s not just a theory – however, it’s not as commonplace as the above description would have it. It definitely has cool applications in addition to the mundane ‘web browsing’… here’s what it can do.

Applications of Li-Fi

The dramatic growth in the use of LEDs (Light Emitting Diodes) for lighting provides the opportunity to incorporate Li-Fi technology into a plethora of LED environments.

Li-Fi is particularly suitable for many popular internet “content consumption” applications such as video and audio downloads, live streaming, etc. These applications place heavy demands on the down link bandwidth but require minimal up link capacity. In this way, the majority of the internet traffic is off-loaded from existing RF channels, thus also extending cellular and Wi-Fi capacities.

There are many applications for Li-Fi. These include:

  • RF Spectrum Relief: Excess capacity demands of cellular networks can be off-loaded to Li-Fi networks where available. This is especially effective on the downlink where bottlenecks tend to occur.
  • Smart Lighting: Any private or public lighting including street lamps can be used to provide Li-Fi hotspots and the same communications and sensor infrastructure can be used to monitor and control lighting and data.
  • Mobile Connectivity: Laptops, smartphones, tablets and other mobile devices can interconnect directly using Li-Fi. Short range links give very high data rates and also provides security.
  • Hazardous Environments: Li-Fi provides a safe alternative to electromagnetic interference from radio frequency communications in environments such as mines and petrochemical plants.
  • Hospital & Health care: Li-Fi emits no electromagnetic interference and so does not interfere with medical instruments, nor is it interfered with by MRI scanners.
  • Aviation: Li-Fi can be used to reduce weight and cabling and add flexibility to seating layouts in aircraft passenger cabins where LED lights are already deployed. In-flight entertainment (IFE) systems can also be supported and integrated with passengers’ own mobile devices.
  • Underwater Communications: Due to strong signal absorption in water, RF use is impractical. Acoustic waves have the extremely low bandwidth and disturb marine life. Li-Fi provides a solution for short-range communications.
  • Vehicles & Transportation: LED headlights and tail-lights are being introduced. Street lamps, signage, and traffic signals are also moving to LED. This can be used for vehicle-to-vehicle and vehicle-to-roadside communications. This can be applied for road safety and traffic management.
  • RF Avoidance: Some people claim they are hypersensitive to radio frequencies and are looking for an alternative. Li-Fi is a good solution to this problem.
  • Location Based Services (LBS): Highly accurate location-specific information services such as advertising and navigation that enable the recipient to receive appropriate, pertinent information in a timely manner and location.
  • Toys: Many toys incorporate LED lights and these can be used to enable extremely low-cost communication between interactive toys.

The way I look at it, it’s here to stay. But we (at least in India) need to wait for a long time before we can really call it commonplace. Considering the onslaught of emerging technologies that have been served to us on a platter by our ISPs – I’m sure someday we’ll be browsing the internet at super fast speeds on Li-Fi.

Till then, happy Wi-Fi browsing, folks!!!

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