[HN Gopher] 100x Faster Than Wi-Fi: Light-Based Networking Stand...
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100x Faster Than Wi-Fi: Light-Based Networking Standard Released
Author : rbanffy
Score : 236 points
Date : 2023-07-13 11:53 UTC (11 hours ago)
(HTM) web link (www.tomshardware.com)
(TXT) w3m dump (www.tomshardware.com)
| Mistletoe wrote:
| https://en.wikipedia.org/wiki/Li-Fi
|
| For those like me confused about how this would even work.
| trollied wrote:
| Clicked into the comments hoping such a comment would be here.
|
| Of note is that the first commercially available Li-Fi system
| has been available since 2014, and it hasn't gained any
| traction?
| meragrin_ wrote:
| > Of note is that the first commercially available Li-Fi
| system has been available since 2014, and it hasn't gained
| any traction?
|
| Probably for the normal early reasons, too big, fiddly, and
| pricey. Someone must have finally shrunk and/or cheapened it
| enough for a large segment of enthusiast or business for it
| to gain more attention again.
| stOneskull wrote:
| reading that, it seems to be about consumption/receiving data
| rather than the sending of data. or do you have light shining
| out of your laptop back at it?
|
| there is an example of a school using it, and the students have
| a usb device in their laptop to read the light, but is it slow
| upload or are they also connected to wi-fi?
| imhoguy wrote:
| > Light's line-of-sight propagation enhances security
|
| I am not convinced here, especially that picture that data
| doesn't leave the place. Eavesdropping thru windows is a thing.
| supertrope wrote:
| In high security environments windowless room are specified.
| Like a SCIF.
| NegativeK wrote:
| An enhancement doesn't imply perfection. For instance, this
| would make wardriving far more difficult.
| bytephilosopher wrote:
| [dead]
| themerone wrote:
| The best application for this would be to implement high
| bandwidth NFC.
| downrightmike wrote:
| "In the Fraunhofer HHI video above you can see a Li-Fi system re-
| using a building's lighting infrastructure for data. "
|
| Oh cool, so if you want to hack a network, you just have to tap
| into their power line by climbing a pole or opening their service
| box. Kind of just like how people would climb telephone poles to
| make long distance calls.
| IshKebab wrote:
| Presumably it will be encrypted.
| HPsquared wrote:
| Reminds me of the trend in the mid-2000s of laptops having IrDA
| ports. A little bit annoying to use for portable devices.
|
| Definitely has a niche application in areas where RFI is to be
| minimized.
| appplication wrote:
| Also to a more trivial extent, perhaps the same idea behind the
| IR ports on Gameboy Colors. Which is a really interesting and
| probably underutilized feature to think back on now. And even
| more interesting in that this preceded the first mass consumer
| devices offering WiFi, which Wikipedia tells me only really
| took off with Apple's iBooks in 1999.
| darkwater wrote:
| Well I remember syncing my Palm Pilot via IrDA (but it was
| connected to the serial port, I just had a tower PC)
| gcr wrote:
| Lego Mindstorms bricks could be programmed over an IR
| connection like this. The earliest ones shipped with an IR
| transmitter that had a 9-pin serial socket on the back.
| EvanAnderson wrote:
| I immediately thought of https://en.wikipedia.org/wiki/RONJA
| Cthulhu_ wrote:
| IR was great, you could do things like transfer contacts and
| data between palmtops.
|
| I mean I got a palmtop (a Palm V iirc) for cheap well after
| they were commonly used and I never used it for anything
| important, but still, it was a cool device. I think I have it
| somewhere still, wonder if it still works. I mainly used it to
| play Sudoku on though.
| JohnClark1337 wrote:
| [dead]
| aeonik wrote:
| I've researched LiFi before, but everytime I research it I find
| expensive commercial equipment, or hobbyists playing with very
| low data rates on Arduino.
|
| I have many questions, especially how a LiFi receiver works.
| wouldn't this essentially need to be a high speed camera with
| very few pixels?
|
| Does anyone have recommendations of a dev kit, or transceivers to
| play with this? Also, ones that don't cost several thousand
| dollars?
| Eisenstein wrote:
| > wouldn't this essentially need to be a high speed camera with
| very few pixels?
|
| A camera sensor 'pixel' is just a device which conducts
| proportional to the amount of photons that hit it. A typical
| digital color camera uses CMOS chips to do this, with a filter
| on top of them to isolate red, green, and blue. It is pretty
| basic; the real trick is getting millions of them on a 1/4"
| sensor and having them relay the data properly with a
| reasonable amount of noise.
|
| So, yes.
| NoZebra120vClip wrote:
| We have other devices that are "just a device which conducts
| proportional to the amount of photons that hit it" but we do
| not call all of them "cameras".
|
| A camera is a device which receives light signals and
| translates those into an image of some format.
|
| A photovoltaic cell in a solar panel is a device which
| generates electricity proportional to the number of photons
| that hit it.
|
| A photoresistor is a device which resists current in
| proportion to the number of photons which hit it.
|
| See now, such a LiFi transceiver would not necessarily be
| termed a "camera" any more than the infrared sensor in
| urinals is a camera. I believe that's the way we want it to
| be, right? LiFi has no use for producing images, only
| translating light back into network and signaling data.
| That's not called a "camera" by any means.
| Eisenstein wrote:
| > We have other devices that are "just a device which
| conducts proportional to the amount of photons that hit it"
| but we do not call all of them "cameras".
|
| But if you took those devices and made an array of them you
| can make a camera sensor. Ergo, if you take one element of
| a camera sensor you have a light detector element.
| NoZebra120vClip wrote:
| You want to call it a "camera sensor" but I personally
| would not attach the moniker "camera" unless they are in
| the business of translating light into images of some
| kind. Here, let's ask Wikipedia:
|
| "A camera is an optical instrument used to capture and
| store images or videos, either digitally via an
| electronic image sensor, or chemically via a light-
| sensitive material such as photographic film."
|
| See now, a camera is the whole instrument, not merely its
| image sensor. But a camera uses an "image sensor". What
| is an image sensor?
|
| "An image sensor or imager is a sensor that detects and
| conveys information used to form an image. It does so by
| converting the variable attenuation of light waves (as
| they pass through or reflect off objects) into signals,
| small bursts of current that convey the information."
|
| So there is no way we've described what's going on in
| LiFi. For example, you walk up to a urinal and the
| infrared sensor detects you. Does it paint an image of
| your privates on a website? No. There is no camera in the
| urinal, hopefully. The urinal is only interested in
| whether you are standing right there or if you've left.
| The urinal does not employ an "image sensor", it uses
| something dumber.
|
| Likewise, do your solar panels use cameras? They conduct
| based on exposure to light, don't they? But what is a
| solar panel concerned about? It generates electricity,
| not images. A photovoltaic cell is not an image sensor
| because it has nothing to do with images.
|
| What would your camera be if I disabled the viewfinder
| display and eliminated its ability to save files on
| sdcard? Would it still be a camera if its sensors
| produced electricity but it couldn't provide me an image
| based on that conduction?
|
| LiFi is not using something dumber, but LiFi is likewise
| unconcerned about creating images. Since a camera is, by
| definition, concerned with images, LiFi does not use
| cameras.
| numpad0 wrote:
| > but LiFi is likewise unconcerned about creating images.
|
| Off topic, but I sense great pun potential here.
| Eisenstein wrote:
| It isn't a 'camera' but what is 'essentially a camera
| with very few pixels' but a small array of light sensor
| elements?
|
| I think you should take a step back and look at this
| logically and stop trying to be right.
| NoZebra120vClip wrote:
| > stop trying to be right.
|
| I think you would benefit from this advice as well; and I
| did attempt to apply logic, but you're ignoring the
| quoted Wikipedia definitions, and essentially we're just
| talking past each other, and I have no idea what sort of
| terminology you're trying to throw around now because it
| doesn't evidently have anything to do with LiFi tooling
| as it is.
| Eisenstein wrote:
| I answered a simple question: 'is this essentially a
| camera with few pixels', and I defined what a camera
| pixel is and agreed that it is 'essentially a camera with
| few pixels'. It obviously isn't a camera, just like a
| bicycle is not a motorcycle, but it is 'essentially a
| motorcycle with a person as an engine'.
|
| If you still think that is wrong, then that's fine I
| guess; it's your opinion and you are welcome to it.
| Remnant44 wrote:
| I think the words being look for here are analogy rather
| than essential.
|
| The essence of a bicycle is not a motorcycle with a human
| motor. However, that is a very good analogy for what a
| bicycle is.
| NoZebra120vClip wrote:
| I appreciate the agreeable answer, but it's also worth
| noting that the bicycle came first in its simplicity, and
| so the correct framing is that a motorcycle is a bicycle
| with an internal combustion human.
|
| So how did cameras start? Well, the word is literally
| Latin for "room" because a man would go into a small,
| darkened room with only a pinhole opening at one end, and
| he could observe an image projected on the far wall.
|
| So the original "camera obscura" had no lens or sensors
| at all! It was essentially a refractive element and a
| screen. The observer could then paint or draw according
| to the projected image he perceived with the image
| sensors in his eyes.
| numpad0 wrote:
| Basically, the only new principle involved is that instead of
| de-serialized and subcarrier modulated data modulated onto
| 2.4GHz sinewave and emitted from antennae as electrical field
| changes, it is now sent as changes in light level on subcarrier
| frequency.
|
| Or more simply, maybe it could be done in YouTuber style by a
| light-emitting diode on Tx antenna port and a photo-sensitive
| diode on Rx antenna port? Switching speed of Tx side LED could
| become the limiting factor in that case.
| Night_Thastus wrote:
| >Basically, the only new principle involved...
|
| But you forgot the most important aspect: Is side-fumbling
| effectively prevented?
| bloggie wrote:
| The technology is mostly in those two camps because it's new,
| expensive, and niche, like WiFi was 20 years ago. As production
| increases (starts?), components will drop in cost and become
| standardized and more ubiquitious. At the moment there is a lot
| of practical research you can read about from conferences like
| OFC [1] and SPIE PW at the free-space laser or telecom tracks
| [2]. At the moment transmitters and receivers are made up of
| highly specified components for their use case and are very
| parametrized, for example there are hundreds of different DFB
| lasers that can be used as sources.
|
| I'm a little surprised that IEEE has already standardized,
| especially given the wavelength they chose but I imagine their
| members were forced to adopt a prolific technology as without a
| standard they risk the technology moving ahead without them.
|
| [1] https://www.ofcconference.org/en-us/home/about/archive/ [2]
| https://spie.org/Publications/Proceedings/Volume/12413?&orig...
| red-iron-pine wrote:
| > Uses IR
|
| > can disrupt my wife's livestream by pointing the TV remote and
| it and jamming random buttons
| RyanAdamas wrote:
| Sounds like the best use case for this tech is to control a whole
| host of robots in a building from a central processing unit that
| means you could have very small robots receiving their commands
| from a new wave mainframe orchestrating the entire activity of
| say... a manufacturing facility.
| theandrewbailey wrote:
| > 100x Faster Than Wi-Fi: Light-Based Networking Standard
| Released
|
| My first thought on reading that headline: isn't that
| single/multimode fiber?
| throw0101c wrote:
| > _My first thought on reading that headline: isn 't that
| single/multimode fiber?_
|
| Kind of how radio being a wireless telegram system:
|
| > _You see, wire telegraph is a kind of a very, very long cat.
| You pull his tail in New York and his head is meowing in Los
| Angeles. Do you understand this? And radio operates exactly the
| same way: you send signals here, they receive them there. The
| only difference is that there is no cat._
|
| * https://quoteinvestigator.com/2012/02/24/telegraph-cat/
|
| This time the tail is fibre and not copper, but without the cat
| tail.
| Aaronstotle wrote:
| I recall seeing a LiFi demonstration video around 2012-2013 and
| was wondering what ever happened to it. (source:
| https://lifi.co/lifi-videos/harald-haas-ted-talk-2011/)
| dheera wrote:
| > This is exactly the approach we detail below and in our paper:
| we modify libjpeg to output DCT coefficients directly to
| TensorFlow
|
| Why not just implement 2D DCT in TensorFlow or PyTorch or
| whatever you use, and keep the entire pipeline in GPU memory?
|
| A quick glance at the TensorFlow reference shows that it already
| has tf.signal.fft2d. I suppose you could just implement
| tf.signal.dct2d similarly.
|
| (Disclaimer: I haven't used TensorFlow in a while, I've been
| doing everything in PyTorch of late.)
| jassyr wrote:
| What is the use case today for 224 GB/s wifi? 8k+ video?
| Genuinely curious.
| numpad0 wrote:
| 10x 22.4GB/s download from CDN or 1x 112GB/s Li-Fi to Li-Fi
| local transfer before inevitable massive derating
| 7373737373 wrote:
| high fidelity AR/VR without cabling
| hamilyon2 wrote:
| Wireless hdmi, 4k webcams would be nice.
| ErneX wrote:
| You can do 4K with way less that a hundred megabits, some PoE
| cameras don't even put a gigabit port anymore since it
| doesn't need it.
| lostlogin wrote:
| 4K can mean a lot of things but some of the low bitrate
| iterations look fairly average.
| ErneX wrote:
| Yeah but OP mentioned "webcams"
| crote wrote:
| Only with compression. Uncompressed 4k60 is 12.54 Gbit/s,
| so high data rates are definitely useful for wireless HDMI.
| post_break wrote:
| iPhones that still have USB 2.0 ports /s
| nocsi wrote:
| Synchronizing LLMs, streaming AR textures, downloading Linux
| ISOs. If you give someone bandwidth, they will fill it.
| tyingq wrote:
| "LiFi" does seem pretty niche. Anywhere you're okay with a
| 10-15m range, have full line-of-sight, somehow can't run a wire
| or fiber run, and don't want regular WiFi for whatever reason.
| wincy wrote:
| Only thing I can think of is full fat uncompressed VR
| streaming to a wireless headset.
| Eisenstein wrote:
| Could be useful for modular autonomous robotic devices that
| act as a single organism, like ants or cells. They would
| each do their own thing but communicate using this (or
| something else fast, short-range, and error-resilient) so
| as to work towards a unified goal without a lot of
| redundancy.
| slashdev wrote:
| Niche also means it will be expensive.
| anyfactor wrote:
| That is like saying, "handing a 2tb hard drive to someone is
| 1500x times the download speed of wifi".
| Kon-Peki wrote:
| "Never underestimate the bandwidth of a station wagon full
| of tapes hurtling down the highway."
|
| https://archive.org/details/computernetworks02tane/page/56/
| m...
| amluto wrote:
| I can think of two uses:
|
| Open floor plan offices. (Sigh.)
|
| Datacenters or server rooms. This could give quite nice data
| rates within a rack.
| dsr_ wrote:
| Any place you have this in a point-to-point rig, you could
| have fiber cables guiding the light and creating a private
| collision domain, improving overall bandwidth, reliability
| and security.
|
| The cost of datacenters is not currently constrained by
| fiber.
| amluto wrote:
| Fiber is not free to run. In an open floor plan office
| with 20 workstations on an overgrown table, you could run
| 20 fiber pairs (or cat5e cables or cat6a cables), and you
| could terminate them and connect them, or you could set
| up one LiFi access point and 20 client devices. The
| latter is a lot less cable bundle and a lot less labor.
| dsr_ wrote:
| This can be done now with wifi. The question I answered
| was about datacenters.
|
| There is wifi in datacenters -- usually for the benefit
| of visiting techs. Not for inside a rack.
|
| Incidentally, if asked to set up 20 workstations on an
| overgrown table, and it's not a very temporary thing
| while the office is in turmoil, I recommend finding a
| different employer.
| lostlogin wrote:
| Maybe this is the solution to my niche issue.
|
| Better network speeds in a room surrounded by Faraday cages
| with MR scanners in them.
|
| Optical is an option but a right pita to run without holing
| the cage or circumnavigating it.
| todotask wrote:
| The use case can be found here: https://lifi.co/lifi-
| applications/
|
| I can only think of useful for conference where everywhere
| there's light.
| dspillett wrote:
| For you home network, they're are likely few or no use card to
| warrant a new tech like this.
|
| But for offices, schools, conference halls, and other place
| with many people together it could be useful as a very fast
| zero-wire solution. Even then it'll be niche: most office
| workers or conference attendees don't need 100Mbit let alone
| more than 1Gbit. But some will: maybe said office is full of
| video editors and such.
|
| Remember that the bandwidth is a shared resource like WiFi:
| that isn't "up to 224Gbit/s for every device in the room" it is
| "up to 224Gbit/s for every device in total". And that "up to"
| value is for ideal circumstances: there will be some
| environmental interference (though LOS limitations will work in
| this techs favour there) and, more significantly, the more
| devices you have in a given collision domain the more they will
| interfere slightly with each other too because they can't share
| the group resource with complete efficiency (and this
| difficulty grows exponentially after a certain threshold). Get
| a couple of machines transferring arbitrary data as far as they
| can via WiFi, take the total of transfer speeds they are
| getting and now add more machines doing the same. The total
| might scale well for an irritation or two of this test, but
| there will be a pint when it significantly won't and the total
| bandwidth will actually fall (and latency will shoot up).
|
| The main push for 5G mobile networks wasn't better max
| bandwidth per device, but better performance (latency and
| throughout) for every device when you have a lot of them
| sharing the same collision domain. The headline figure of 224G
| bit is (while not at all dishonest) just that: a figure to gain
| interest via headlines. Those who actually have a need or want
| for such tech will be looking much deeper into it than that.
| drjasonharrison wrote:
| home networks in high density condo towers where WiFi network
| channels are often already occupied by neighbors on the same
| and adjacent floors. The 5GHz band might have a "limited
| distance" but it's still enough to interfere between
| neighbors.
| api wrote:
| Niche: video editing, interacting with AI/ML training clusters,
| ...?
| [deleted]
| exabrial wrote:
| Back in the day, I had a laptop with Infrared Serial Port.
| Considering WiFi cards weren't not a thing at the time, it was
| pretty handy to "Air Drop" files to other students.
| dirtyid wrote:
| Will lifi work with a lot reflective surfaces?
|
| e: over post limit
|
| I assumed it would need LOS. I'm wondering if light bounces off
| reflective surfaces like mirrors would meaningfully degrade the
| signal.
| pyrolistical wrote:
| Are you asking if direct line of sight is needed? I'm wondering
| as well
| collsni wrote:
| Guess we're not turning the lights off
| sesuximo wrote:
| Why does any end user machine need more than a GB/sec?
| dspillett wrote:
| It probably doesn't, except for a few cases like a video
| editing station not working with entirely local resources.
|
| But when you have a lot of devices in the same collision domain
| (like WiFi, and hubbed rather than switched networks of old)
| this is a shared network leg: get a 50+ devices in the same
| room pushing data back & forth at various rates and I doubt
| you'd see anything like the theoretical total bandwidth of
| 224Gbit/sec for that network leg (and latency will shoot up).
| Maybe you'll still reliably get 1Gbit/device which you wouldn't
| with other tech, but you won't see anything like 224/50+Gbit
| per device. Try doing anything much on shared WiFi at a large
| conference, or on your phone's non-wifi data capabilities in a
| large public venue with hundreds of other phones even just idly
| interacting with the network, and you'll see what I mean.
|
| The speed figure is just a headline figure, and attention
| grabber, not actually misleading but not at all as meaningful
| as the headline writers might think. The more important details
| are how well the tech works when congested, how much how many
| devices can do before the effective available bandwidth falls
| through the floor and/or latency figures reach for the moon.
| That 224Git figure is the upper limit for the whole collision
| domain (the room, as this is an LoS constrained technology),
| much like 56Mbit was the upper limit on 802.11g and 11Mbit was
| the upper limit on 802.11b (how often did you see those rates
| even on aggregate with more than a couple of devices active at
| a time?).
| crote wrote:
| The same reason end users want more than 640k of memory.
| haswell wrote:
| I'm curious to see what VR/AR applications this might have.
|
| Imagine peripheral devices capable of much more than they are
| today merely because of more bandwidth.
|
| Imagine how useful it would be to have a wireless NAS capable
| of acting as an iSCSI target without having to worry about
| running cables.
|
| And as "spatial" computing use cases increase along with
| extremely high res formats like ProRes, we'll quickly find ways
| to use the extra bandwidth.
| wakamoleguy wrote:
| Newb question: since they are both electromagnetic radiation, how
| does Li-Fi get up to 100x faster than Wi-Fi? Are the light
| transmitters and sensors that much faster? Or perhaps is it able
| to use a wider band of frequencies?
|
| I'm also so curious how this ends up working in practice. Even
| using infrared, would it interfere with things like baby monitors
| in night mode? The Wikipedia article says it can be tuned to be
| less intense than humans can perceive, but I'm curious if that's
| true in practice. (Granted, babies don't typically need Internet
| access while they are sleeping, but maybe the monitor itself
| does.)
| bmacho wrote:
| > Newb question: since they are both electromagnetic radiation,
| how does Li-Fi get up to 100x faster than Wi-Fi?
|
| They specified that they wanted to be 100x faster, and they
| added parallel channels, until they reached that goal. No,
| really, this is the _real_ reason.
|
| It is entirely nonsensical to ask for a physical reason,
| because different channels are just different.
| cowl wrote:
| well the physical reason is that the band available at the
| visible light spectrum allows you to add that much channels
| in parallel. You can't do that at 2.4GHz
| jbperry wrote:
| My understanding is they went with 800 to 1000 nm (infrared),
| or ~ 375 to 300 THz. I'm not sure as to the total combined
| bandwidth of all of WiFi 6 or 7, but 75,000 GHz band gives them
| a lot to play with.
| embwbam wrote:
| You can encode a lot more information in higher frequencies.
|
| But each frequency has different things that are opaque to it,
| and travel different distances before dropping off.
|
| Wi-Fi is already "really low frequency, really low intensity
| infrared light", so I suspect the article is correct when it
| says we won't notice it.
| cdumler wrote:
| Correct. The reason why microwaves can cook food isn't the
| fact that it is a microwave frequency. Microwaves ovens cook
| by flipping the polarity back and forth. The frequency
| emitted is the same resonant frequency as water molecules, so
| the water molecules attempt to align constantly to the ever
| changing polarity. Movement is heat; thus, the water heats
| the food.
| oehtXRwMkIs wrote:
| I've heard the resonance with water explanation is a common
| misconception:
| https://physics.stackexchange.com/questions/150128/how-do-
| mi...
| rolph wrote:
| more of an oversimplification. polar bonds interact with
| EM field of microwave oven.
|
| water is one of many thousands of compounds having polar
| bonds
| pfedak wrote:
| To set the record straight for the above comment -
|
| - it's true that there isn't a precise frequency needed for
| microwave ovens to heat food
|
| - however, "polarity flipping" is just a description of
| electromagnetic radiation itself, and shooting enough EM
| radiation at food in a frequency range it absorbs will heat
| it up via dielectric heating
|
| - microwaves have no relationship to any specific resonant
| frequency of water - the vibration frequencies are orders
| of magnitude higher https://en.wikipedia.org/wiki/Electroma
| gnetic_absorption_by_... while rotation response inherently
| does not have a peak
|
| - otherwise, yes, the motion of (polar) molecules induced
| by an electric field is indeed the mechanism of dielectric
| heating
| NotYourLawyer wrote:
| > Wi-Fi is already "really low frequency, really low
| intensity infrared light"
|
| No, infrared by definition starts around 300 GHz and goes up
| from there.
| admax88qqq wrote:
| I don't know anything about LiFi, but for EM radiation in
| general, the higher the frequency, the higher the theoretical
| maximum bandwidth.
|
| https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theore...
|
| Wifi is 2.6 Ghz or 5Ghz, visible red light is 430 terahertz.
|
| Or it sounds like LiFi is just pulsing the lights on an off, in
| which case the Nyquist Rate that was invented for telegrams is
| a better analogy
|
| https://en.wikipedia.org/wiki/Nyquist_rate
| rbanffy wrote:
| Just imagine what we'll be able to do with Gamma data
| transmissions ;-)
|
| I like to explain to my kids that it's all colors - we are
| transparent to some (such as X-rays) the same way some fish
| are mostly transparent to the light we can see and walls are
| transparent to the radios we use in Wi-Fi, and also that both
| snakes and bees can see light in colors we can't (snakes see
| IR, bees see UV).
| noobface wrote:
| Face melting speed.
| sinak wrote:
| I think you're misreading Shannon's Law. It's not that the
| higher the frequency the greater the max bandwidth. It's the
| higher the bandwidth the more data you can put through.
| OnACoffeeBreak wrote:
| I am agreeing with you and providing more info:
|
| https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theor
| e...
|
| Maximum channel capacity depends on signal bandwidth and
| SNR.
| makeworld wrote:
| > the higher the frequency, the higher the theoretical
| maximum bandwidth.
|
| This is not true and is unrelated to Shannon's theorem.
|
| Shannon's theorem shows us that wider bandwidths allow for
| larger bit rates. At higher frequencies our bandwidths _can_
| be bigger. For example a band from 1 to 2 terahertz is 1
| terahertz wide, which is 1000 times larger than a band from 1
| to 2 gigahertz (1 gigahertz wide).
|
| The total bandwidth available (including multiple channels)
| for 2.4 GHz Wi-Fi is about 100 MHz. The total space available
| for this new standard is 800 to 1000 nm [0], which is 450
| THz. That's 4.5 million times wider than Wi-Fi. _That_ is why
| you get higher bit rates with this new standard, AKA more
| throughput, or more "bandwidth", when the term is used to
| mean data rate.
|
| [0]: https://standards.ieee.org/ieee/802.11bb/10823/
| deely3 wrote:
| Can I ask a noob question?
|
| Suppose we have 1Hz signal, what stopping us from
| sending/receiving 10 or 100 bits of info every second by
| modulationg amplitude of signal?
| [deleted]
| pclmulqdq wrote:
| You can use FM, AM, QAM, or other multi-bit modulation
| schemes to send that information, but you need to have
| the signal-to-noise ratio to demodulate it. WiFi actually
| goes up to QAM-1024 (10 bits per symbol) in the more
| recent specs. However, the SNR you need to decode that is
| perfectly is something like 35 DB, while recovering a
| signal that sends 1 bit at a time needs ~3 DB. A 35 DB
| SNR is very hard to reach unless the RF environment is
| quiet (basically impossible in an apartment building, for
| example), but 3 DB is easy.
|
| Shannon's limit tells you about the total information
| capacity of a channel given its bandwidth and SNR. This
| is usually achieved by using deeper modulation than
| theoretical, and using error-correcting codes to recover
| the lost data.
| p_j_w wrote:
| When you modulate that 1 Hz signal you're generating
| power at frequencies other than your 1 Hz carrier.
|
| See https://en.wikipedia.org/wiki/Amplitude_modulation#Sp
| ectrum
| thfuran wrote:
| The only signal that contains only 1 Hz and no other
| frequencies is a perfect 1 Hz sine wave. As soon as you
| start modulating the amplitudes away from that sine wave,
| you're introducing content at higher frequencies. You can
| use that higher frequency content to transmit information
| at more than 1 bit per second, but you're not exactly
| using the 1 Hz signal to transmit information.
| megous wrote:
| https://en.wikipedia.org/wiki/Single-sideband_modulation
|
| No need for higher frequency content. But SNR will have
| to be good enough.
| cycomanic wrote:
| > > the higher the frequency, the higher the theoretical
| maximum bandwidth.
|
| > This is not true and is unrelated to Shannon's theorem.
|
| You are correct that it is unrelated to Shannon, but it is
| still true. The higher your carrier frequency the higher
| your theoretical maximum bandwidth (in the correct meaning,
| i.e occupied spectrum), you can never have negative
| frequencies, so modulation the maximum bandwidth you can
| modulate a 1Hz to is 2 Hz (modulation bandwidth extends to
| positive and negative frequencies). A 10 Hz carrier can be
| modulated to 20 Hz...
|
| > Shannon's theorem shows us that wider bandwidths allow
| for larger bit rates. At higher frequencies our bandwidths
| _can_ be bigger. For example a band from 1 to 2 terahertz
| is 1 terahertz wide, which is 1000 times larger than a band
| from 1 to 2 gigahertz (1 gigahertz wide).
|
| So you are contradicting yourself? Not sure why you said
| the earlier statement is not treu?
| metacritic12 wrote:
| I mean it sort of is true. If you're at 100THz, you can get
| a bandwidth of 1THz. If you're at 100KHz, you are not going
| to get a bandwidth of 1THz.
| Isamu wrote:
| True, The "band" is a range of frequencies, from lower
| bound to upper bound. You can have a single frequency
| carrier that you modulate, in which case your bandwidth
| has more to do with your modulation scheme, and the rates
| implied by that
| bloggie wrote:
| I think Li-Fi is more comparable to Ethernet instead of Wi-Fi,
| not because the fundamentals are very different but because of
| the link budgets available. If you think of an ethernet line as
| a pipe carrying data, then a collimated laser can be thought of
| in a similar way - most of the energy that you transmit is
| going to make it to the destination, and that is not the case
| with Wi-Fi, even with very high gain antennas. This allows for
| different modulation schemes and thus higher throughput. Copper
| ethernet is now capable of 1.6 Tbps [1] and Li-Fi doesn't seem
| so very fast compared to that; however keep in mind this is
| comparing only physical layers. Demonstrations of optical laser
| links of hundreds of Gbps over hundreds of kilometers have
| taken place [2] using COTS optical ethernet transceivers and
| special output stages providing precise collimation and
| pointing.
|
| [1]
| https://en.wikipedia.org/wiki/Ethernet_physical_layer#1.6_Tb...
|
| [2]
| https://ntrs.nasa.gov/api/citations/20210026855/downloads/sp...
|
| For your second question, I'm not sure how baby monitors work
| but the proposed wavelengths are unlicenced and there are
| little if any rules for how to deal with interference. There
| are rules for eye safety of laser which limits the maximum
| energy that can be delivered to the output. Generally as Li-Fi
| gets more common we will have to learn to deal with
| interference as it arrives. For example, Lidar systems (older,
| noncoherent ones) interfere with one another and are even
| susceptible to interferece from IR motion detectors and such,
| but these aspects have to be considered during design.
| Tade0 wrote:
| > Even using infrared, would it interfere with things like baby
| monitors in night mode?
|
| If you're referring to the infrared LEDs that illuminate the
| baby, their light is not polarized, while light used for
| communication is, so a polarizing filter in the receiver can
| filter out such noise.
| Shadowmist wrote:
| Baby monitors with night vision usually have a small set of
| tiny infrared lights so that they can see. Adding additional
| infrared to the room will help the monitor to see better.
| DropInIn wrote:
| Given how they are calibrated I don't think so.... More
| likely the image would be getting constantly washed out,
| right?
| anyoneamous wrote:
| Depending on how fast the extra IR light is pulsing, it
| might end up looking like your baby is sleeping through a
| rave - which would be entertaining enough to be passed
| off as a feature rather than a bug.
| DropInIn wrote:
| "Between 3-30 hertz (flashes per second) are the common
| rates to trigger seizures but this varies from person to
| person. While some people are sensitive at frequencies up
| to 60 hertz, sensitivity under 3 hertz is not common"
|
| https://epilepsysociety.org.uk/about-epilepsy/epileptic-
| seiz...
|
| This came immediately to mind which when comorbid with
| infrared sensitivity is likely to trigger people without
| any apparent cause to third party observers....
|
| People forget that the average human barely see jack sht
| compared to the remarkable exceptions of our species, let
| alone that such exceptions often have disabling/uncommon
| conditions comorbid with thier remarkable capabilities.
| appplication wrote:
| On one hand, I see where this could be helpful in certain
| scenarios like an office, where there is a consistent and planned
| layout specifically for the purpose of productivity. Or for
| military applications, where EMSEC is taken very seriously (to
| the point where Wi-Fi is generally not used at all in most
| classified facilities). Though I am also not convinced this would
| change the calculus much there in reality.
|
| On the other hand, I don't see the draws outweighing what seem to
| be clear setbacks. E.g. if I put my LiFi enabled phone in my
| pocket mid download, it will completely cease to work.
|
| What is interesting is the idea of a much more comprehensively
| connected future. E.g. imagine a building either both Wi-Fi and
| LiFi enabled, with automatic switching between the two based on
| which is less congested and provides the best speeds. As our
| daily bandwidth footprint grows, I can see the benefit in having
| multiple spectra for information transmission.
| TOMDM wrote:
| This is mentioned in the article
|
| > Of course, Li-Fi isn't going to sweep away Wi-Fi and 5G
| alternatives (nor wired networks). Radio waves still have a
| distinct advantage with regard to transmission through the
| atmosphere at great distance, and though opaque objects.
| Instead, work must concentrate on using horses for courses -
| with Li-Fi advantages being harvested where possible.
| noodlesUK wrote:
| I'm not sure that this provides any benefit from an EMSEC
| perspective, as you'd basically be going from a position where
| you're avoiding radios and even cables and similar things that
| aren't TEMPEST shielded for fear of emissions leaking sensitive
| data, to a position where you're broadcasting your sensitive
| data over the air, and a listening device simply needs to look
| at your lights somehow. I will agree that it's easier to block
| light than radio, but I think that's where the advantages end.
| kaibee wrote:
| I think you have this backwards. You'd still encrypt your
| transmissions same as if you were using WiFi, so its a wash
| in terms of security. But it should be much harder to jam
| your receiver/transmitter, because its point-to-point.
| [deleted]
| Cthulhu_ wrote:
| > E.g. if I put my LiFi enabled phone in my pocket mid
| download, it will completely cease to work.
|
| The light part, sure, but the regular radio wifi part will be
| fine; it'll be slower, but it won't go away. Ideally there's
| seamless transition between the networks, LiFi if you have your
| phone out and there's a sender in the receiver's signal, WiFi
| in other cases.
| dietr1ch wrote:
| I think it'll work as well as moving from ethernet to wifi,
| or from wifi to cellular, which is, it doesn't really work
| seamlessly and it's quirky :(
| Kon-Peki wrote:
| Your mobile phone needs to move between cellular towers
| quite frequently when you are moving around. You don't
| notice this handoff because it is important to the
| functioning of the network.
|
| If we decide that moving from Li-Fi to Wi-Fi is important,
| we can make it seamless.
| dietr1ch wrote:
| Right, but I think it's not pretty in our carrier's side.
| Maybe some more abstraction over where exactly is the
| data flowing through is needed similar to what Wireguard
| does.
| awestroke wrote:
| Moving between wifi access points is already completely
| seamless in a modern mesh wifi network.
| mrtesthah wrote:
| >* if I put my LiFi enabled phone in my pocket mid download, it
| will completely cease to work.*
|
| As per your EMSEC use-case, this is also a privacy benefit, as
| your pocket becomes a defacto faraday cage guaranteeing that
| your devices can only transmit information when you want them
| to.
| gcanyon wrote:
| In your pocket, or just turn around so your body is in between
| the source and your device? Maybe reflections get the job done,
| but that _has_ to harm data rates, right? I am not an optical
| expert.
| Dwedit wrote:
| Whatever happened to 802.11ad? (or even 802.11ay for that matter)
| That's also practically line-of-sight.
| fsniper wrote:
| Isn't this require a "clear line of sight?" Wi-fi works across
| walls, around corners and so on. Is this possible with this li-
| fi?
| [deleted]
| meragrin_ wrote:
| > Isn't this require a "clear line of sight?"
|
| It's a very nice feature. Imagine not having to share bandwidth
| with your neighbors.
|
| > Wi-fi works across walls, around corners and so on. Is this
| possible with this li-fi?
|
| Think of this as a wireless ethernet cable. Instead of having a
| jack in the wall, you have a light fixture in the room.
| profmonocle wrote:
| > Imagine not having to share bandwidth with your neighbors.
|
| 6 GHz Wi-Fi ("Wi-Fi 6E") is going to be a big help with this.
| Many more channels than 5 GHz, and the higher frequency means
| it doesn't travel as far. As someone who lives in a high-rise
| where 5 GHz is already pretty crowded, I'm looking forward to
| more devices supporting it.
|
| I'll be honest, I don't see Li-Fi taking off for normal
| consumer use. Few users are going to be interested in
| arranging their home to have direct line of site between
| their access and point and game consoles, TV, etc. And there
| would need to be some _very_ fast and reliable mechanism to
| handover between Li-Fi and Wi-Fi, so that you don 't cut out
| when you, for example, move your head slightly during a VoIP
| call.
| tinco wrote:
| The line of sight does not need to be direct, light can bounce
| and still retain enough brightness to communicate. Which is
| also how 5ghz wifi works because 5ghz wifi also has trouble
| with going through objects like walls.
| reflectiv wrote:
| The 'light-based' network thing kinda threw me for a
| second...wifi IS technically light, its just a frequency (RF)
| at which we can't see it and that can (somewhat) penetrate
| walls.
| DrThunder wrote:
| Not sure about direct line of sight but the article mentions
| that it'll never fully replace wifi for the reason you've
| stated. Radio waves can go much further distances and penetrate
| walls/buildings etc. Light can't do that.
| [deleted]
| yieldcrv wrote:
| > 802.11bb
|
| Chiral ghost Internet?
| jl6 wrote:
| > speeds as fast as 224 GB/s
|
| How do you build devices capable of producing or consuming data
| at that rate? I looked up the data transfer rates of RAM[0], and
| this is twice as fast as the fastest species of dual-channel
| DDR5.
|
| [0] https://www.softwareok.eu/?seite=faq-This-and-That-or-
| Other&...
| senttoschool wrote:
| I think the applications would have to be in data centers where
| environments are controlled and certain hardware can easily
| eclipse 224GB/s such as GPU memory.
|
| But I'd assume that if you're in a datacenter, you can use
| physical wires since you control everything.
| jbotz wrote:
| Even if your devices can't produce or consume data nearly that
| fast, it's still good to have all that bandwidth at the link
| level because you'll probably be sharing it with multiple
| devices.
| lostlogin wrote:
| Doesn't that leave the same problem - the thing linked with
| multiple devices can't take that data rate?
|
| Or are you saying that A > B might use half that data rate
| while X > Y uses the other half?
| jakewins wrote:
| Maybe this would be in some sort of specialised network
| appliance, bridging the link into a wired network of some kind,
| not a general-purpose machine buffering the network data in
| regular RAM?
| justinclift wrote:
| From rough memory, network switches often have total switch
| bandwidth figures measured in terabits per second.
|
| So "where several other devices intersect" seems like
| reasonable first thought for where large speeds are needed.
| ooterness wrote:
| Modern GPUs routinely exceed 5 Tbps in memory bandwidth.
| (GDDR6X at 20 Gbps per pin, times 256-bit bus width is 5120
| Gbps.)
|
| The original article unfortunately quotes incorrect units: 224
| Gbps (gigabits per second) is NOT the same as 224 GBps
| (gigabytes per second).
| orev wrote:
| This was tried with WiGig, and that didn't solve any problems
| significant enough that it caught on. People tried to use WiGig
| for things like wireless docking stations, and I suspect it just
| wasn't needed because at such short ranges, most people would
| want/need to have a power cable connected (which naturally leads
| to the USBC docking stations we have today, where both power and
| data go over the same cable).
| Avamander wrote:
| WiGig just came too early, the underlying tech was also barely
| able to support it. Windows 7 and Vista era, expensive and the
| software really wasn't there either.
|
| It might be different now with VR and the rise of docks.
| ooterness wrote:
| The wireless adapter for the HTC Vive headset was based on
| WiGig. The range is limited to a few meters, but that's more
| than enough for room-scale VR. The need for massive bandwidth
| and low latency make it a perfect use case for WiGig.
| nnevod wrote:
| Wigig wasn't fast enough to be useful for wireless HDMI,
| especially given 4k displays arrived right at that moment, and
| 2nd gen WiGig it's probably way to expensive.
|
| The question is whether it's possible to create a full-rate 224
| gbps transciever that is cheap enough to appear in mid range
| phones, notebooks and TVs and whether it would work without
| line of sight, but in the same room, with reflected light.
| tomxor wrote:
| > by preventing wall penetration, reducing jamming
|
| This is the main selling point I think, but not intentional
| jamming... regardless of the inherent lower latency, lower jitter
| and higher throughput, unlike wifi none of these aspects are
| hampered by proximity to adjacent signals from other networks and
| other EM sources.
|
| Even if people don't want to kit out their entire house a la PoE,
| it would be a nice benefit to have this work side by side with
| wifi... bad signal? just walk into the room with the router, auto
| switch to lifi and it's effectively as good as wired. Also more
| devices automatically using lifi when wifi is not necessary will
| alleviate interference for everything and everybody else where
| it's actually necessary. It's a win win technology.
|
| It's also interesting to see something move (relatively) quickly
| from experiment to standards proposal. I suppose that's due to
| the practicality of this tech.
| drjasonharrison wrote:
| In high density living (condo towers, downtown etc), it is
| common to have interference from neighbor's wifi network on the
| same floor or adjacent floors.
|
| Having a network that expands using a non-interfering frequency
| would be a godsend. Especially given the limited number of
| channels for existing WiFi standard.
| DropInIn wrote:
| This is stupid....
|
| Just because the _average_ human can 't see it doesn't mean it
| won't affect any humans or animals
|
| Tons of animals see infrared and this Will have negative impacts
| on environs it's used in as a result.
|
| Theres even some humans who actually can see partly into
| Infrared/UV and this is just evil to do to them.
|
| I call this a moronic suggestion.
| Per_Bothner wrote:
| I believe we're talking about the equivalent of a small LED,
| like half your devices already have one or more of, but
| infrared and probably lower intensity. I.e. a teeny invisible
| glow. Even for animals that can see the glow, it would low
| enough intensity to be barely noticable.
| nashashmi wrote:
| If it is used as a light bulb, I am sure someone will be able
| to see it. Some light bulbs flicker. And it causes headache.
| [deleted]
| mkoubaa wrote:
| I wonder what effect this light will have on nonhuman animals,
| especially bees and mosquitos. If there was a specific frequency
| of light that repelled mosquitos, I want _that_ to be used by
| wifi
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