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ITU Standard Could Make Fast Home VLC Visible Light Networks a Reality

Tuesday, January 22nd, 2019 (9:21 am) - Score 1,670

The International Telecommunication Union is close to giving its final approval to a new standard (G.9991 / G.vlc), which could finally help to turn secure high-speed indoor Visible Light Communication (VLC / LiFi) networks into something that you can buy instead of WiFi.

At the root of this all is a simple idea that has taken years to develop, which involves turning a Light-Emitting Diode (LED) based home or office light bulb into a sophisticated wireless data network (like infrared). This is achieved by turning the bulb(s) on and off many times a second and by altering the length of these “flickers“, as well as other properties of the light, you can introduce digital communications (e.g. Morse Code with a torch but way more sophisticated).

The process itself happens so fast that it is imperceivable to a normal human eye, which means that the bulb will appear to work just like a regular one. The obvious difference being that with VLC (or Light Fidelity [Li-Fi] as it’s sometimes known) you’re now transmitting data using room lighting, or possibly other devices that emit light using LEDs (computer screens, desk lamps etc.).

Marcos Martinez, ITU Associate Rapporteur, said:

“Security, no interference and spectrum saving are very attractive features of VLC. VLC and WiFi have different strengths, and VLC’s strengths provide a strong complement where WiFi faces challenges. Crowded spectrum is creating real problems in the deployment of WiFi and VLC can alleviate some of [that].”

At the experimental level we’ve previously seen data rates reach as high as 224Gbps (Gigabits per second) under lab conditions, albeit usually over very short distances (a handful of metres) and across a limited field of view. Since then various proprietary VLC solutions have been developed, but these are expensive and you’re more likely to get speeds of around 40Mbps to 250Mbps (depending upon the setup and number of bulbs etc.).

The problem with proprietary standards is that you don’t encourage a proper ecosystem to develop and grow, which is why today you can search Amazon for VLC and LiFi adapters until your eyes melt but you’ll still come up empty. Even those that do sell such kit tend to aim it more toward bespoke office installations than the mainstream market. Thankfully the ITU may be about to change all that.

Marcos Martinez added:

“Standards are really the only way for these different worlds to speak to one another and collaborate successfully in stimulating the growth of the VLC market. We have seen a variety of proprietary VLC solutions, but without standards it has been impossible to create an ecosystem.”

In response the ITU’s Study Group 15 has developed G.9991 (ex G.vlc), which specifies the system architecture, physical (PHY) layer and data link layer (DLL) for a high-speed indoor optical wireless communication transceiver using visible light. This is now in the final stages of approval (it secured first-stage approval (“consent“) last year and is practically complete).

As a result Martinez says that G.9991 is “already considered” a de facto standard, with key vendors of proprietary VLC solutions now moving toward its adoption even before final approval. “New VLC products compliant with this ITU standard will enter the market very fast, at much the same time as the standard is approved,” says Martinez.

Of course VLC, as alluded above, has its pros and cons. The main advantages stem from an ability to easily setup a discreet indoor Local Area Network (LAN) that is likely to be much more secure (doesn’t go through walls) than WiFi and one that resolves the problems with capacity (limited radio spectrum frequency) and thus the interference that tends to plague WiFi, particularly in dense urban environments.

On the other hand you’re probably going to need a fair few bulbs and relays in order to stretch the signal around a typical home, which adds to the cost of deployment. It also remains to be seen whether it’s more energy efficient to run a WiFi vs VLC network (WiFi has had many years to refine but VLC is still in its early life).

We’d also disagree with the “no interference” remark above. Light bounces off surfaces and therefore VLC is not strictly a line-of-sight technology, which also means that interference is still an issue but the typical room-by-room setup of such a network should mitigate that.

Nevertheless we continue to reserve judgement on VLC until such time as we actually see vendors selling a selection of competing products to ordinary consumers. It’s definitely something we’d be willing to try, albeit perhaps more out of curiosity than a genuine need. Much will no doubt depend upon its affordability, ease of setup and performance.

Leave a Comment
19 Responses
  1. Joe says:

    Photosensitive epilepsy is going to be interesting with this!

    1. Mark Jackson says:

      I was thinking the same, although the flicker is so rapid with this technology that it may be far less likely than say.. computer/TV displays or even normal LED lights to trigger it. Still I don’t know enough about the trigger point for an attack to make a judgement.

    2. Joe says:

      Although back in the day most people could see the difference of 60hz -v- 72hz in the old CRTs and some got eye strain with the 1st

    3. Mark Jackson says:

      Worth noting that CRT and LED/LCD refresh rates are perceived differently due to the technologies working in very different ways. A 60 refresh on CRT would give an ugly flicker in all content but 60Hz on an LCD is not something your eye will spot and is fairly normal (the backlight is key with LCD and that usually operates several times above 60Hz).

    4. Joe says:

      fwiw I get sore eyes with prolonged use @ 60hz on LCD but not 72 so even if I can’t see the flicker as on crt I can feel the difference.

    5. Mark Jackson says:

      Wasn’t this more about epilepsy? You’ll get sore eyes from using screens for all sorts of reasons.

    6. Joe says:

      Yes it was but my point was that I can obviously feel the difference in small refresh rates. So someone with far greater sensitivity would doubtless feel it more …

    7. Karen says:

      LCD screens thereself do NOT flicker. Any perceived flickering effect on an LCD screen is either down to
      1). The actual flicker of pixels updating (positive and then negative voltages being applied to produced the pixel)
      2). The LCD backlight itself, more noticeable if it is an older Fluorescent light design.

      In both cases the screen itself does not flicker. LCD screens do NOT update like CRT screens did. In basic terms CRT screen drew lines rapidly, LCD tech turns pixels on, off, or dims/brightens them.

      Also most flat screens nowadays are LED lit and LEDs do not flicker unlike the older lighting from Fluorescent. Any perceived flicker from them and the LED light is normally down the the LEDs dimming or turning on and off completely to help produce more realistic black and white levels.

      Eye strain and Epilepsy with regards to modern screens today is more down to the light being emitted from them and motion of that light. Low refresh/frame rate in a screen and fast motion makes motion look stuttery. Prolonged viewing of it in some people actually makes them experience similar feelings to sea sickness and of course that can trigger Epilepsy also.

      Eye strain is normally down to either…
      1. Resolution (higher is not always better for your eyes) lower resolution many make everything look bigger and blockier but if you are near sighted and sit close to a screen 24inches or smaller a lower resolution may actually be better for you. Near sighted-ness likes things bigger rather than smaller (4k resolution on a 22inch screen well thats some small icons and text which = eye strain for some).

      2. Brightness and contrast… Turn brightness down, especially at night, all the way down as far as you can until white actually at first glance does not look like white anymore. On a decent modern (within the last 5 years) display you should not, if your monitors brightness setting is 1-100 ever need it above 30, not even if you are sitting right near a sunny window. At night you should be able to reduce that to around 20, possibly less. Do almost the same thing for contrast only kinda in reverse start at 100 and go as low as you can to retain black level.

      Number 2 is the most common issue wrong brightness normally makes your eyes feel dry, wrong contrast normally makes it feel like you have trouble focusing your eyes on something small or stuff at distance after using the monitor. The worst thing you can do with a computer screen is use one in a dim room, modern screens are much brighter than CRT tech was and unlike them which constatly updated by drawing lines LCD and LED screens do not so you are basically sitting in front of a GOOD AS always on bright light. If you go start at a light bulb only 3ft or so away for several hours thats going to F&^K up your eyes also, a modern screen is not that different.

      Best tips
      1) Take a 5 minute break from the screen every 30 mins
      2) if you use a screen which is in a room where the room light is normally lower than the screen light (especially a dark room) is buy a cheap bendy desk lamp and sit that by the side of the monitor pointing the light behind or upwards/away from the screen or better sit the lamp behind the monitor, your eyes will feel more relaxed as they are looking at a varying and gradual levels of light rather than just one searing your eyes like the sun. Thus reducing glare effect from the screen.

      If that does not help try different resolutions, but as far as flicker in an LCD i doubt that is the the main cause of your eye strain.

      PS… If you wear glasses do NOT bother being sold on the scam of lens which block blue light. Blue light is everywhere, its not just that damaging your eyes. Its the actual starring at a screen for hours, your eyes would become dry, sore, itchy etc if you stare at anything the same for hours.

      The amount of peoples eyes i see in a day that use computer screens and have helped their eyes just taking breaks, lowering screen brightness and adjusting room light is far greater than any witch craft magic lenses, new fangled screen tech and other lets sell you something, which wont solve anything fluff.

  2. wireless pacman says:

    Just need to remember to close the curtains when you use it, to stop the spooks eavesdropping! 🙂

    1. NE555 says:

      Exactly what I was going to say. It might be secure through walls, but it could propagate for miles through windows.

    2. Mark Jackson says:

      Interestingly there is a study on this, which found that you could intercept the signal (albeit at a lower bandwidth) when pointing, from outside, directly at an internal emitter (bulb etc.):


      Mind you an attacker would need some quite large and specialised receivers to pull this off and that’s likely to be more obvious than somebody just sitting on a bench snooping the WiFi.

      Some ways around this would be to ensure that those outside cannot get an angle on the bulb(s), such as by changing the angle of blinds, using a polarised window filter or moving the lights themselves to angle differently so they can’t be locked from outside.

    3. TheFacts says:

      Encryption? And mirrors to improve coverage…

  3. Optimist says:

    How do devices communicate back to the hub in the other direction?

  4. MrZipf says:

    This seems like niche technology, but kudos for the proponents.

    Being otherwise naive, this was a quick and helpful backgrounder – https://purelifi.com/technology/ . Diagram shows using PLC as the next hop (or PoE wiring to the socket). The latter being for new builds only.

  5. Phil says:

    So this will mean our energy saving LED light bulbs will need to be on in daylight as well as when it is dark! Also interference is surely just as much a problem in a bright room during daytime? Infra-red has the advantage you can easily filter out visible light, but how does that work here with visible light from other sources and data to receive from LED bulbs using visible light? What about if you want to dim the lights to watch a streaming service but your streaming box or laptop is using LiFi?

    It seems infra-red is used to send data back up to the bulb, why not just use infra-red in both directions, which is capable of fast speeds as well?

    Seems like someone has a patent they are desperate to monetise, rather than this being anything practical or worthwhile.

    1. Joe says:

      I doubt light is an issue here…plenty of tech ways to work out signal from noise…just as back in the day with modems.

    2. Phil says:


      “I doubt light is an issue here…plenty of tech ways to work out signal from noise…just as back in the day with modems.”

      On their FAQ they do answer the question about using LiFi in daylight where they have stated they have tested it in 77,000 lux of sunlight, however a quick Google shows typical bright sunlight conditions are over a 100,000 lux, so make of that what you will. However indoors unless the device is sat in the sunshine on a windowsill it will hopefully be less than 77,000 lux. They don’t say if the data-rate suffers in bright conditions.

      You can dim the bulb down to around 10% to achieve an almost dark room, and for complete blackness they say other technology like infra-red could be used. Surely infra-red would be better to use for download and upload from the start…. but…..

      Doing a search for LiFi patents reveals there are many related to using visible light for data communication, hence using Infrared would be someone else’s patents and royalties paid elsewhere perhaps!

      You still need a special LED light, and that light needs to connect back to a network somehow, you need to override any switches to stop people just turning the lights off and breaking all communications! I fail to see any advantages over Wi-Fi, and given the improvements with new Wi-Fi Version 6, it just seems Li-Fi will be one of those things that will never take off because it doesn’t solve any problems.

      “Sorry, can you move and get of my light as iPlayer has stopped working”

    3. Joe says:

      ” I fail to see any advantages over Wi-Fi, and given the improvements with new Wi-Fi Version 6, it just seems Li-Fi will be one of those things that will never take off because it doesn’t solve any problems.”

      Congestion – pretty common in flats apartments. Not saying this is the solution but it might be.

  6. J.B. Groves III says:

    Been giving presentations at educational conferences (including the NSF HITEC Conference) for over a year about how “LiFi will Change Our Lives”.

    There has been a lot of great work being done in the Africa using LiFi.

    Take a look:


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