6 ms·

How could LiFi be truly wireless if anything can obstruct the path of light? How’s my phone in my pocket going to get connection?

dmm 5y ago
Why restrict yourself to visible light? There are frequencies of em waves that would easily penetrate your jeans: https://en.wikipedia.org/wiki/Gamma_ray https://en.wikipedia.org/wiki/Gamma_ray
- Denvercoder9 5y ago
  Usually we go to the lower-energy, longer-wavelength part of the spectrum for applications like this, since gamma rays and the high-energy, short-wavelength part of the spectrum is very hard to control and gives you cancer.
- causality0 5y ago
  Keeping a multi-watt transmitter of ionizing radiation in your pocket is a very bad idea.
  - ben_w 5y ago
    Or indeed a single-milliwatt transmitter, if it’s in your pocket for more than an hour or so per lifetime.
    - causality0 5y ago
      I see this "cell phones will use x-rays and gamma rays in the future" claim often enough that I wish an expert in the field would write an article on just how bad the effects would be.
- croes 5y ago
  Isn't the use of visible light the whole point LiFi?
- deleted 5y ago
  [deleted]
14 5y ago
there are many use cases that don’t require you to be connected 24/7. You could while driving under a street light download a movie in seconds. Then go on your way loading your cars infotainment with maps and several movies for your kids in the back or whatever. I haven’t looked into the tech in years but the promised of faster downloads and a city wide array of street lights made it seem like the future.
- zbrozek 5y ago
  Aperture fouling (dirt / grime) seems like it would make such a service flaky. Aside from needlessly low data caps, the cell network is pretty great for road trip connectivity. High bandwidth intermittent connectivity would be nice for self-driving car sensor log offload. Inside my home it would be cool to have 10 gbps to my laptop, but I don't have a real use case where that's meaningfully better than the 500-800 mbps that I already get with WiFi.
  - bogwog 5y ago
    > pretty great for road trip connectivity Until people start getting seizures while driving from all the flashing lights
    - 14 5y ago
      The flashing happens so fast it is invisible to human eye. LED lights already do with with pulse width modulation to make them as efficient as they are and it is not an issue.
      - zbrozek 5y ago
        Correct, though I was actually referring to the existing cell network as great for road trips.
      - dekhn 5y ago
        I can see LEDs flashing out of the corner of my eye when it's moving quickly, it's really obnoxious.
up6w6 5y ago
It seems that light reflected off walls can achieve up to 70 Mbit/s in a controlled environment. But yeah, it's still hard to think about direct applications in our lives. https://en.wikipedia.org/wiki/Li-Fi https://en.wikipedia.org/wiki/Li-Fi https://www.abc.net.au/radionational/programs/scienceshow/the-internet-on-beams-of-led-light/5134888 https://www.abc.net.au/radionational/programs/scienceshow/th...
croes 5y ago
If you don't need a cable it's wireless notwithstanding any other disadvantages

dmm 5y ago

Why restrict yourself to visible light? There are frequencies of em waves that would easily penetrate your jeans: https://en.wikipedia.org/wiki/Gamma_ray https://en.wikipedia.org/wiki/Gamma_ray

Denvercoder9 5y ago
Usually we go to the lower-energy, longer-wavelength part of the spectrum for applications like this, since gamma rays and the high-energy, short-wavelength part of the spectrum is very hard to control and gives you cancer.
causality0 5y ago
Keeping a multi-watt transmitter of ionizing radiation in your pocket is a very bad idea.
- ben_w 5y ago
  Or indeed a single-milliwatt transmitter, if it’s in your pocket for more than an hour or so per lifetime.
  - causality0 5y ago
    I see this "cell phones will use x-rays and gamma rays in the future" claim often enough that I wish an expert in the field would write an article on just how bad the effects would be.
croes 5y ago
Isn't the use of visible light the whole point LiFi?
deleted 5y ago
[deleted]

14 5y ago

there are many use cases that don’t require you to be connected 24/7. You could while driving under a street light download a movie in seconds. Then go on your way loading your cars infotainment with maps and several movies for your kids in the back or whatever. I haven’t looked into the tech in years but the promised of faster downloads and a city wide array of street lights made it seem like the future.

zbrozek 5y ago
Aperture fouling (dirt / grime) seems like it would make such a service flaky. Aside from needlessly low data caps, the cell network is pretty great for road trip connectivity. High bandwidth intermittent connectivity would be nice for self-driving car sensor log offload. Inside my home it would be cool to have 10 gbps to my laptop, but I don't have a real use case where that's meaningfully better than the 500-800 mbps that I already get with WiFi.
- bogwog 5y ago
  > pretty great for road trip connectivity Until people start getting seizures while driving from all the flashing lights
  - 14 5y ago
    The flashing happens so fast it is invisible to human eye. LED lights already do with with pulse width modulation to make them as efficient as they are and it is not an issue.
    - zbrozek 5y ago
      Correct, though I was actually referring to the existing cell network as great for road trips.
    - dekhn 5y ago
      I can see LEDs flashing out of the corner of my eye when it's moving quickly, it's really obnoxious.

up6w6 5y ago

It seems that light reflected off walls can achieve up to 70 Mbit/s in a controlled environment. But yeah, it's still hard to think about direct applications in our lives. https://en.wikipedia.org/wiki/Li-Fi https://en.wikipedia.org/wiki/Li-Fi https://www.abc.net.au/radionational/programs/scienceshow/the-internet-on-beams-of-led-light/5134888 https://www.abc.net.au/radionational/programs/scienceshow/th...

croes 5y ago

If you don't need a cable it's wireless notwithstanding any other disadvantages