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I think it doesn't make sense for it not to be. It seems like a very good way to transfer data with almost no drawback given a decent setup. I don't understand

I think it doesn't make sense for it not to be. It seems like a very good way to transfer data with almost no drawback given a decent setup. I don't understand why that isn't used more often.

xnzakg 11y ago
> almost no drawback 1. You need to purchase a Li-Fi "router" for each room (if not several) instead of purchasing a single router 2. Connecting the "routers" to internet: you would either need a lot of cables... or Wi-Fi. 3. Only works in line-of-sight, while Wi-Fi works through walls... and pockets. Li-Fi probably wouldn't be useful for smartphones. Enough drawbacks?
- smileysteve 11y ago
  I'm glad you mentioned pockets. That's what hit me first. Also, everybody holds their smartphone differently, including at the top (where LED notification lights are), especially in landscape mode.
- dogma1138 11y ago
  You don't need separated routers each LED light bulb can be used as an access point, there are already LED bulbs with WiFi because people will buy anything that looks like an Apple product. You need WiFi still because the LiFi channel is only one way. It can still sorta work through some pockets but rule of thumb is that if your mobile device is in your pocket you don't need the fastest speed possible and you can fallback to WiFi. But yeah the tech is kinda silly in general.
  - xnzakg 11y ago
    > You don't need separated routers each LED light bulb can be used as an access point But you need to buy one that supports LiFi, and LiFi bulbs will probably be more expensive than normal lightbulbs (if they become a thing) And if you still need WiFi, what's the point of buying LiFi bulbs and setting them up when you can just keep using WiFi? It just doesn't seem to be worth it unless you're in a place with hundreds of WiFi devices (and it still probably won't help a lot).
    - dogma1138 11y ago
      You would have to buy special light bulbs anyhow, you won't be able to use a commercial of the shelf bulb for this no matter what the BBC thinks. The LED's need to be able to turn on and off in nano-seconds so you can't just twitch the AC power because the voltage regulator will not respond fast enough (there is enough juice in the capacitors to drive the LED's for a few seconds usually this is why cheap LED light bulbs don't turn off straight away, the more expensive ones have usually have a current shunt that will clear the capacitors to ground when you hit the light switch) and most likely simply die after a few minutes. So you need to do in-circuit modulation which means a dedicated light bulb. Well in theory you start building light bulbs that can be effectively turned on and off about about a billion times a second which is not going to happen and even then you'll still need some device that will modulate the light so instead of a dedicated light bulb you'll have a dedicated lamp. Considering the engineering limitations and the cost involved having normal light bulbs that can connect to your network via either WiFi or well via basically "DSL" via sending a phase modulated signal over the AC wiring in your house similar to how those power plug Ethernet / WiFi extenders work. https://en.wikipedia.org/wiki/Power-line_communication https://en.wikipedia.org/wiki/Power-line_communication Again this is a very kickstarter / TED talk worthy idea that sounds brilliant but it will probably go the way of the GyroJet because it's just so dumb on so many levels.
dogma1138 11y ago
too many issues, shadows refraction and most importantly power and LED stability if you take a slow motion capture of all current LED lights you see that the flicker quite a bit usually at much higher frequencies and more erratically than the solid 50/60hz incandescence bulbs do. And you still need to use Wi-Fi as your upload channel, communication protocols which require 2 separated mediums tend not to work very well. Pretty much for Li-Fi to work reliably you need to build and power LED's that will produce a similar illumination stability to current laser diodes which are used in fiber optics, build light sensors on equipment and still maintain a Wireless network for your up channel, so I really don't understand why this is trying to become a thing at all.
Mithaldu 11y ago
Three drawbacks i can think of right away: 1. You need to maintain line-of-sight with the receiver on your receiving device, and the transmitter. No, you can't turn around with your cellphone in your hand. 2. Interference potential is high due to environmental other lights, reflective surfaces, etc. 3. The camera in the receive won't be particularly cheap.
- wyldfire 11y ago
  Algorithms and economics can mitigate 2 and 3. Requiring LOS absolutely kills this for replacing WiFi, though. Maybe could find its way into applications where we need high throughput and we can easily get stable LOS.
  - msandford 11y ago
    I don't believe that strict LOS is a requirement. If the room is getting ever so slightly brighter and dimmer, that's enough of a signal. Current wifi works down to -80dBm (or lower) which is a crazy small signal. -100dBm is a tenth of a picowatt of received signal strength. I'm not saying that non-LOS is guaranteed by any means. But LOS isn't strictly required for this scheme to work. If only one light bulb out of 100 in a room is Li-Fi enabled it's going to be tough. If all three light bulbs in a room are Li-Fi enabled there's definitely hope. The proportion of non-Li-Fi lightings to Li-Fi lighting is probably going to determine your SNR and thus your feasibility. Trying to make Li-Fi work with a 100 lumen bulb in direct sunlight is going to be a bad time since the sensor only has so much dynamic range. But if you increase the power of your light to be within an order of magnitude or two of the sunlight, you've got a fighting chance.

I think it doesn't make sense for it not to be. It seems like a very good way to transfer data with almost no drawback given a decent setup. I don't understand why that isn't used more often.

xnzakg 11y ago

> almost no drawback 1. You need to purchase a Li-Fi "router" for each room (if not several) instead of purchasing a single router 2. Connecting the "routers" to internet: you would either need a lot of cables... or Wi-Fi. 3. Only works in line-of-sight, while Wi-Fi works through walls... and pockets. Li-Fi probably wouldn't be useful for smartphones. Enough drawbacks?

smileysteve 11y ago
I'm glad you mentioned pockets. That's what hit me first. Also, everybody holds their smartphone differently, including at the top (where LED notification lights are), especially in landscape mode.
dogma1138 11y ago
You don't need separated routers each LED light bulb can be used as an access point, there are already LED bulbs with WiFi because people will buy anything that looks like an Apple product. You need WiFi still because the LiFi channel is only one way. It can still sorta work through some pockets but rule of thumb is that if your mobile device is in your pocket you don't need the fastest speed possible and you can fallback to WiFi. But yeah the tech is kinda silly in general.
- xnzakg 11y ago
  > You don't need separated routers each LED light bulb can be used as an access point But you need to buy one that supports LiFi, and LiFi bulbs will probably be more expensive than normal lightbulbs (if they become a thing) And if you still need WiFi, what's the point of buying LiFi bulbs and setting them up when you can just keep using WiFi? It just doesn't seem to be worth it unless you're in a place with hundreds of WiFi devices (and it still probably won't help a lot).
  - dogma1138 11y ago
    You would have to buy special light bulbs anyhow, you won't be able to use a commercial of the shelf bulb for this no matter what the BBC thinks. The LED's need to be able to turn on and off in nano-seconds so you can't just twitch the AC power because the voltage regulator will not respond fast enough (there is enough juice in the capacitors to drive the LED's for a few seconds usually this is why cheap LED light bulbs don't turn off straight away, the more expensive ones have usually have a current shunt that will clear the capacitors to ground when you hit the light switch) and most likely simply die after a few minutes. So you need to do in-circuit modulation which means a dedicated light bulb. Well in theory you start building light bulbs that can be effectively turned on and off about about a billion times a second which is not going to happen and even then you'll still need some device that will modulate the light so instead of a dedicated light bulb you'll have a dedicated lamp. Considering the engineering limitations and the cost involved having normal light bulbs that can connect to your network via either WiFi or well via basically "DSL" via sending a phase modulated signal over the AC wiring in your house similar to how those power plug Ethernet / WiFi extenders work. https://en.wikipedia.org/wiki/Power-line_communication https://en.wikipedia.org/wiki/Power-line_communication Again this is a very kickstarter / TED talk worthy idea that sounds brilliant but it will probably go the way of the GyroJet because it's just so dumb on so many levels.

dogma1138 11y ago

too many issues, shadows refraction and most importantly power and LED stability if you take a slow motion capture of all current LED lights you see that the flicker quite a bit usually at much higher frequencies and more erratically than the solid 50/60hz incandescence bulbs do. And you still need to use Wi-Fi as your upload channel, communication protocols which require 2 separated mediums tend not to work very well. Pretty much for Li-Fi to work reliably you need to build and power LED's that will produce a similar illumination stability to current laser diodes which are used in fiber optics, build light sensors on equipment and still maintain a Wireless network for your up channel, so I really don't understand why this is trying to become a thing at all.

Mithaldu 11y ago

Three drawbacks i can think of right away: 1. You need to maintain line-of-sight with the receiver on your receiving device, and the transmitter. No, you can't turn around with your cellphone in your hand. 2. Interference potential is high due to environmental other lights, reflective surfaces, etc. 3. The camera in the receive won't be particularly cheap.

wyldfire 11y ago
Algorithms and economics can mitigate 2 and 3. Requiring LOS absolutely kills this for replacing WiFi, though. Maybe could find its way into applications where we need high throughput and we can easily get stable LOS.
- msandford 11y ago
  I don't believe that strict LOS is a requirement. If the room is getting ever so slightly brighter and dimmer, that's enough of a signal. Current wifi works down to -80dBm (or lower) which is a crazy small signal. -100dBm is a tenth of a picowatt of received signal strength. I'm not saying that non-LOS is guaranteed by any means. But LOS isn't strictly required for this scheme to work. If only one light bulb out of 100 in a room is Li-Fi enabled it's going to be tough. If all three light bulbs in a room are Li-Fi enabled there's definitely hope. The proportion of non-Li-Fi lightings to Li-Fi lighting is probably going to determine your SNR and thus your feasibility. Trying to make Li-Fi work with a 100 lumen bulb in direct sunlight is going to be a bad time since the sensor only has so much dynamic range. But if you increase the power of your light to be within an order of magnitude or two of the sunlight, you've got a fighting chance.