[HN Gopher] Electric light transmits data faster than Wi-Fi
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Electric light transmits data faster than Wi-Fi
Author : danboarder
Score : 28 points
Date : 2023-12-30 17:15 UTC (5 hours ago)
(HTM) web link (techxplore.com)
(TXT) w3m dump (techxplore.com)
| transpute wrote:
| https://spectrum.ieee.org/lifi-standards
|
| _> The new standard for Li-Fi, IEEE 802.11bb, is designed to
| provide a global framework to deploy light-based devices that are
| compatible with each other. It was ratified in June [2023] ...
| Li-Fi simply appears as if it was another band of Wi-Fi ... It
| can achieve data rates of 1 Gbps or more from a range of 20
| centimeters to 3 meters._
| FergusArgyll wrote:
| > Notably, Li-fi ensures robust security by exclusively
| transmitting data to areas illuminated by light.
|
| Can someone explain how this ensures security?
|
| Because hackers always work in the dark? /s
| transpute wrote:
| _> security_
|
| Wi-Fi passes through walls, can be used to remotely infer
| keystrokes, human biometrics, position and activity.
|
| _> dark_
|
| Li-Fi can use infrared light, does not pass through walls.
| ReactiveJelly wrote:
| It might enable security but I wouldn't say it _ensures_ it.
|
| It just means that visible or IR light (What are they using?)
| won't leak through walls the way Wi-Fi does. Depending on how
| wide the beam is and exactly how it all works, it _might_ still
| leak out of windows and under doors. But it's not like someone
| casually wardriving outside your house will get as much as they
| would from Wi-Fi, I would think.
| Turing_Machine wrote:
| Yeah, you'd want blackout curtains (or better, paint) on your
| windows. Still cheaper and easier than making your office
| into a Faraday cage.
| bb88 wrote:
| That assumes that Li-Fi doesn't leak RF still.
| jfoutz wrote:
| Working graveyard and renting, I learned aluminum foil is
| perfect. cheap, trivial to install and remove. and
| perfectly opaque.
| swayvil wrote:
| What did you use to attach the foil?
| jfoutz wrote:
| my windows had little bits of molding and surfaces for
| the foil to crumple up against and conform to. I didn't
| need anything else. I suppose tape would work.
| smallnix wrote:
| How can visible light pass from a core of a star or planet to
| the outside, but some routers light not? I guess it's just
| super duper faint?
| colechristensen wrote:
| Visible light does not pass from the core of a star to the
| outside.
|
| The sun has a radius of about 700,000 km. Only a few
| hundred km is transparent enough for light to pass through
| and has a density of about 300 mg per cubic meter. Roughly
| the density of air at the altitude where airliners cruise.
|
| The photons you see originate from a layer that's just 0.5%
| of the radius of the sun. That layer is heated with other
| photons from inside. The core temp is 15 million K while
| the photosphere is around 5800 K. The spectrum of the core
| were the rest of the sun transparent would be much
| different and ... unsafe. (Not that this really makes
| sense, if the rest of the star was transparent it would go
| nova)
| Modified3019 wrote:
| Using light to heat up the walls of a home enough to start
| emitting significant black body radiation poses some
| additional engineering challenges.
| Turing_Machine wrote:
| Poor wording. I think what they're getting at is that, unlike
| wifi, light doesn't pass through walls, floors, ceilings, etc.
| Anything that isn't directly illuminated by the light beam will
| have effectively no signal, making it less likely to be picked
| up from (say) five offices away.
| Dylan16807 wrote:
| Though if there's a window around that light might go further
| than 60GHz, which is presumably the best competitor for same-
| room high-bandwidth links.
| thrill wrote:
| Caution, do not look at ElFi router with remaining eye.
| neilv wrote:
| Now we know why three-leet haxorz wear hoodies up, and
| sunglasses indoors.
| cornholio wrote:
| I cannot but feel that some part of the spectrum that is
| invisible, so it can work when the light is turned off, and is
| capable of penetrating the walls so as to not require an
| expensive wired repeater in every room, would still remain the
| best choice for providing local connectivity in general.
|
| I can see applications for LiFi, but it will not replace WiFi any
| time soon.
| Syonyk wrote:
| > _...so as to not require an expensive wired repeater in every
| room..._
|
| Why do you speak of the feature as though it's a bug?
|
| It's great for wiring contractors, great for LiFi vendors,
| what's the problem?
|
| _sigh_
| osigurdson wrote:
| What you are looking for is a spectrum of light known as
| subter-subter-infra-red which is around 2.4GHz.
| mlyle wrote:
| I don't think this is a candidate to replace wifi. But if it's
| cheap and becomes ubiquitous (unlikely) it would make wifi a
| lot better.
|
| The advantage of the visible light approach is that it _doesn
| 't_ reach through walls.
|
| It's inherently very dense, and can provide users in its
| footprint nearly unlimited bandwidth. If it reaches only 50% of
| users in a classroom or office building, then those 50% of
| users will have very fast connectivity, and wifi will be twice
| as fast for everyone else.
| ianburrell wrote:
| One place where it would work well is offices. Office
| buildings have drop ceilings that make it easier to mount
| devices on the ceiling. Then have one Lifi in each office or
| pretty dense in open plan offices.
|
| This could solve the problem of getting reliable speeds to
| devices without Ethernet, that are either hard to wire or
| don't want to plug in.
| cornholio wrote:
| The speeds would be completely reliable until somebody
| starts walking around the office, disrupting the line of
| sight to the lightspot in the ceiling.
| XorNot wrote:
| The benefit of LiFi would be the exact opposite: in a congested
| signal space, that it's actually _easy_ to mostly shield an
| area from it - i.e. you and your neighbor can have LiFi APs
| screaming out signal and a simple plasterboard wall would
| almost completely shield the interference.
|
| It strikes me that 400nm UV LEDs would be a good choice for
| this application: we can't perceive 400nm, it doesn't penetrate
| cells (FYI: this is why all "LED" sterilizers are snake-oil),
| and most importantly the UV spectrum is almost entirely blocked
| by regular glass-windows so the sun wouldn't interfere and the
| signal would attenuate to nothing at the bounds of a building.
| mlyle wrote:
| 400nm UV is still probably bad for your eyes.
|
| > (FYI: this is why all "LED" sterilizers are snake-oil)
|
| Most are snake oil, but there are definitely UV-C LEDs out
| there.
|
| IMO, we should just use ordinary white LED lighting for this.
| Easy to ensure that no matter what the data, the lights are
| at 80% DC brightness, and you can still get an absurd amount
| of data throughput per light fixture.
| ammut wrote:
| While cool I am skeptical on this tech given the light
| propagation. How many LiFi APs would I need to buy for a full
| office compared to existing WiFi?
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