Talk:Li-Fi

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first testkits available

with up to 10 GBit/s: https://www.ipms.fraunhofer.de/de/research-development/wireless-microsystems/LiFi/lifi-gigadock.html

underwater Li-Fi

I think light very fast fade underwater versus longwawes radio... And it's unuseful underwater. — Preceding unsigned comment added by Mogwaika (talk • contribs) 18:24, 13 December 2016 (UTC)

Early comment

Is it like you can access the internet in visible light, not in the darkness? Or is it like the infrared or like invisible spectrum also can be used ?

 Yes but it works in the darkness too, as long as the led is not completely switched off, the data will transmit, and an LED can be dimmed so far, the human eye perceives it as off though it is just very dim.

The idea is that your computer would have a sensor that can detect the flickering of an LED lightbulb. The data would be encoded in the flickering light instead of going through radio waves as it does in wifi. I'm not sure how your computer is supposed to talk back to the lamp, though.

It uses the same technology as there is a sensor elsewhere to receive outgoing data

The introduction paragraph needs cleaning and elaboration. It says "Li-Fi should not be confused with the more general term visible light communications (VLC), which is the use of the visible light portion of the electromagnetic spectrum to transmit information," but it fails to explain what it is. If it is not similar to infra-red or fiber optics, what is it? What portion of the light spectrum is used? How does it overcome the line-of-sight issue? — Preceding unsigned comment added by 24.223.156.13 (talk) 14:29, 19 October 2013 (UTC)

I guess it could use either visible or non-visible light. It doesn't matter. They would both work as well.

To talk back, the computer can have it's own LED. It's not as if the LED *must* be a light bulb on the ceiling.

The line-of-sight issue is handled by it being able to use scattered light. Eg. If you switch on a light bulb you can see the light is blocked by objects and creates shadows, but the shadows aren't completely black. There is still some light in the shaded area coming from reflections of the wall and ceiling etc. , and switching the bulb on and off will still have an visible effect in the shadow. The light signal is of course much weaker (maybe 10 or 100 times) and this will slow the data rate but not reduce it to zero.

Line of sight is more of a problem outdoors when there are no objects nearby to reflect the signal or where the distance between the stations is so great that the reflections are not strong enough. The OFDM technology also helps to make the scattered signals readable. (used by WiFi, 4G wireless and DVB-T and DAB digital TV and Radio broadcasting. — Preceding unsigned comment added by 220.244.92.239 (talk) 07:03, 21 October 2013 (UTC)

Advertisment Alert

The article has great relevance in this moment, since LiFi can become a significant technology, but the article at this moment sounds like an advert for pureVLC, so we need to change this to reflect the fact that a consortium is being formed and this technology is being pushed as forward.

Just like 3Com for Ethernet, pureVLC could be the company that makes it real, but we need other examples for it to become relevant as a encyclopedic entry, which would mean other players and an interoperable standard chiefly if they get IEEE standards body certification. — Preceding unsigned comment added by 187.163.127.19 (talk) 00:17, 20 October 2013 (UTC)

Indeed, although someone tried to blank out most of the article without any edit summary. That is not a good approach, even if done in good faith, since it was just reverted. I have a few minutes now to cut down the promotion and let us see if that makes it more stable. W Nowicki (talk) 15:57, 22 October 2013 (UTC)

It is not about advertising a single company, rather it is about establishing the true meaning behind Li-Fi. The IEEE 802.15.7 standard and many of the others are not true Li-Fi systems. There are no high data rate system that are implemented with this technology. pureVLC/pureLiFi are the only ones that are working toward a real solution. The goal is to clarify why the standard is not as good as it could be and clearly distinguish between Li-Fi and VLC. — Preceding unsigned comment added by Nikola.serafimovski (talk • contribs) 19:46, 18 December 2013 (UTC)

IrDA 2.0 ? Fiberless-Optic Networking

In evaluating whether there is a need for this concept, it would be interesting to analyse why IrDA has all but died out, and what the difference is.

OK : IrDA was slow, one-to-one and one-metre line-of-sight - what has changed now ? Why didn't IrDA just evolve ? Why is it being re-launched ? Call me skeptical, but I think this will not take off, because WiFi worked whereas IrDA didn't ... Yes 2.4GHz is congested (also used for Bluetooth, CCTV, keyboards, mice, radio microphones, microwave ovens etc), but isn't 5GHz Dual-Band WiFi underused and taking off ? (In Europe ...)

--195.137.93.171 (talk) 12:46, 11 November 2013 (UTC)

Come to that, why not just let the light from fiber-optic networking out of the fibers ?

Answer : Range, speed and reliability will suffer !

--195.137.93.171 (talk) 13:26, 11 November 2013 (UTC)

IrDA died because of a number of reasons. These include the fact that you could not effectively receive anything because it was only line of sight and you couldn't really see where the optimal location was. In addition, the power constraints for an IR system are not applicable in this context because light can be as bright as you like. Furthermore, the IrDA was using outdated technology. This is the key differentiator between pureLiFi and other potential Li-Fi competitors. — Preceding unsigned comment added by Nikola.serafimovski (talk • contribs) 19:49, 18 December 2013 (UTC)

With regard to the 5 GHz for Wi-Fi, it does not matter how much more bandwidth is allocated. The demand for mobile data is growing exponentially and the supply is finite. The FCC (from the US), OFCOM (from the UK) and many other regulatory bodies have clearly pointed to this trend and warn that something must be done now. The largest growth in data rates over the last few decades has come from increased spatial bandwidth reuse, ie., smaller cell sizes, not from gains in the spectral efficiency (the bits/s/Hz of a system). Li-Fi is merely the logical progression of this trend. ([User talk: Nikola.serafimovski]) — Preceding unsigned comment added by Nikola.serafimovski (talk • contribs) 19:53, 18 December 2013 (UTC)

RONJA

I'm not sure about the timmings, but using light to carry data isn't new, so some background research is appropriate. https://en.wikipedia.org/wiki/RONJA 10 Mbps full duplex over 1.4 km with BER 10^-9 RONJA was released as a DIY openssource guide in 2001 http://ronja.twibright.com/ https://www.prnewswire.com/news-releases/visible-light-communication-vlcli-fi-technology--free-space-optics-fso-market-2013-2018---by-component-led-image-sensor-opto-couplers-application-indoor-networking-underwater-communication-location-based-service--187265961.html http://ronja.twibright.com/tetrapolis/spec.php — Preceding unsigned comment added by 27.109.113.242 (talk) 22:38, 8 December 2020 (UTC)

My initial thoughts, however there's a difference between what I played with 45 years ago and today - there now is a standard - 802.11bb. Having a communications standard is the difference between some crude kludge and an actual functioning technology.Wzrd1 (talk) 16:01, 11 June 2024 (UTC)

Couple things

Why are these words in bold:
networked, mobile, high-speed communication
I don't believe they should be in bold.

Because it is critical that people distinguish Li-Fi from VLC. Li-Fi means networked, mobile and high-speed along multiple users. VLC is even low-rate, one direction/broadcast only applications. The readers should be educated to understand the difference.

Next thing:
This part of a sentence is so complicated:
Although Li-Fi can be used to off-load data from existing Wi-Fi networks, implementations may be used chiefly to provide capacity for the greater downlink demand
Can we make this easier to read?

I have rephrased this sentence. --Wyn.junior (talk) 15:53, 18 December 2013 (UTC)

Complicated sentence improved

This sentence is now improved, though still very complicated:
Li-Fi can be used to off-load data from existing Wi-Fi networks to provide capacity for the greater downlink demand as complementary to the existing wireless or wired network infrastructure.
What does "downlink" mean?
--Wyn.junior (talk) 20:47, 18 December 2013 (UTC)

All data flows in two directions. One from the server to the user, which is called downlink. The other is from the user to the servers, this is called uplink. It is fairly well known wording for anyone in communications. — Preceding unsigned comment added by Nikola.serafimovski (talk • contribs) 20:57, 18 December 2013 (UTC)

I don't believe I have heard "downlink", though I have commonly used the word "download" for that purpose.
Does the sentence mentioned above mean that Li-Fi provides greater capacity for downloading data only and not for uploading?
--Wyn.junior (talk) 22:16, 18 December 2013 (UTC)

Another issue of understanding could be because we probably live in different countries (I live in USA). Same English language, though different terms and sentences of expression are used.--Wyn.junior (talk) 22:20, 18 December 2013 (UTC)

"Downloading" is the act of copying data from a server to a client. The "downlink" is the part of the comm channel that supports data moving in that direction. A downlink can be established and functional even if you're not actually downloading anything (or very little).

The term "downlink" is actually used a lot more with regard to satellite communications than it is with connections to your ISP.

The sentence in question above refers to the idea that comms between machines in the same room could ride over Li-Fi, leaving the WiFi bandwidth for communication with one's ISP. It does not imply anything about asymmetric bandwidth in Li-Fi. Jeh (talk) 06:54, 28 February 2014 (UTC)

Li-Fi faster than Wi-Fi. Why? How?

Because everything in the electromagnetic spectrum travels at the speed of light, shouldn't all internet be the same speed?--Wyn.junior (talk) 03:38, 28 February 2014 (UTC)

Speed of light is the ultimate limit on how fast information can get from one place to another (the latency). But how much information (how many bits) is getting there per unit time is another question.

When someone says "Li-Fi is faster than Wi-Fi", what they mean is that it can move more bits per second. This has little directly to do with the speed of light.

Analogy: Suppose I have two fuel tanker trucks. They are both governor-limited to 100 kph. But one has a capacity of only 1000 liters, while the other is 10,000 liters. The latter can obviously move more fuel over a given distance in the same amount of time, even though they're both traveling at the same velocity.

In data communication via electromagnetic phenomena, your maximum bit rate is limited by your bandwidth, not the speed of light. Bandwidth is in turn limited by how much of the EM spectrum you're using, your actual and tolerable SNR, and your modulation methods. Dr. Claude Shannon did some terrific work in this area.

If you want to really be surprised, look up how slow is "electron drift velocity" in a wire. Jeh (talk) 04:14, 28 February 2014 (UTC)

I guess bandwidth is a major factor of internet speed. Thanks.--Wyn.junior (talk) 05:10, 28 February 2014 (UTC)

For another example, consider old-fashioned dial-up modems. In the early days these were limited to 300 bits/sec. Eventually they worked up to 56 kbits/sec! Although 28k was far more commonly achieved. This was using the same telephone wires as the old Bell 103 standard modems, so the analog bandwidth of the medium was the same, and certainly the speed of signal transmission over the phone wires was the same. What changed (radically) was the modulation method, along with the addition of error correction protocols, line "training," etc. Jeh (talk) 06:57, 28 February 2014 (UTC)

You know what'd be even FASTER? GAMMA RAYS! ROFLCOPTER but for real, Li-fi is a pretty good idea Shiggity (talk) 07:57, 28 November 2015 (UTC)

Possible paragraph

User:Jeh deleted this paragraph, saying "this makes no sense. Cable and DSL providers have nothing to do with control of the radio spectrum"

Here is the paragraph:
"Unlike radio waves, of which 96% of the country's broadband access is controlled by DSL and Cable providers, visible light waves are not regulated, owned or controlled by any person, private company or government organization."

If User:Jeh is correct, then only part of this paragraph should have been deleted. It could read like this:
"Unlike radio waves, visible light waves are not regulated and are free to use."

I am not sure that User:Jeh is totally correct though. The part about cable and DSL providers is referenced. Here is an exerpt from the source (http://www.theregister.co.uk/2007/08/01/fcc_opens_up_us_wireless_spectrum/):
"Google and its coalition of public advocates are working to provide consumers with more online choices, arguing that big name telecoms like AT&T and Verizon have too much control over the wireless spectrum as well as the broadband internet market. DSL and cable providers, they argue, control 96 per cent of the country's broadband access, and if the U.S. radio spectrum is opened up, it could give consumers a viable third option."

--Wyn.junior (talk) 04:52, 5 March 2014 (UTC)

First, you're misunderstanding your source. The claim that "DSL and cable providers control 96 percent of the country's broadband access" may or may not be true, but whatever the percentage is, that control is not because they have the RF spectrum tied up. You see, cable and DSL do not use licensed RF spectrum at all. Licenses to use the RF spectrum only apply to, and are only necessary for, EM waves that are transmitted through the "airwaves". Cable operators do not have to get an FCC license to run 54 MHz through 1000 MHz through their systems! (They do have to make darn sure that their systems are sealed against signal egress. This is why the cable guy uses a small wrench to tighten down the nuts on the "F" connectors. You should use one too.)

Similarly with DSL. A telco does not have to get a license to use a part of the broadcast spectrum to set up your DSL because DSL is not broadcast over the airwaves. What part of this is not clear?

They have the degree of control they have (whatever the percentage is) because they are an approved duopoly. In most areas there is one cable provider and one DSL provider, and nobody else can get permission from the municipality to string either cable TV coax or phone lines.

It is true that opening up some of the RF spectrum for use by internet broadband providers could give consumers a third option.

But that has nothing to do with Li-Fi. Li-Fi will not give consumers another option for broadband internet access, even though it would be unlicensed, because you can't use Li-Fi the way you would use RF. It doesn't go far enough, nor through enough obstacles. If they put a Li-Fi emitter on the cell tower down the street the only way it would help you access the internet from inside your house is if a) you kept enough of your window shades open so the light could get in; and b) if your "Li-Fi modem" or whatever it was called had a bright enough Li-Fi emitter on it to send back to the tower. That is not what anybody is talking about in connection with Li-Fi (and not, I think, anything you would want to be in the same room with).

The Li-Fi proponents are talking about using it within a room, maybe down the hall. But absolutely not as a way to connect your equipment to an internet broadband provider. Jeh (talk) 06:17, 5 March 2014 (UTC)

I think you are right. Visible light communication is free and unregulated, although it still has to travel through the same broadband cables. Its not over the air. (No need for quick insults on Wikipedia please. Go to the forums for that stuff.)--Wyn.junior (talk) 14:32, 5 March 2014 (UTC)

Huh? Visible light communication does not travel over cables at all, broadband or otherwise. And it is over the air. It's just a different part of the spectrum. Radio waves are photons and vice versa. Jeh (talk) 18:14, 5 March 2014 (UTC)

You say that DSL and cable providers don't need a license for the RF they use. Is that for the RF running through cables or are you referring to the RF wi-fi modems?--Wyn.junior (talk) 15:31, 5 March 2014 (UTC)

It's both. What's running through their cables doesn't need to be licensed, regardless of frequency, because it isn't radiated. WiFi devices aren't licensed either (although the manufacturer does need to get "type approval"), even though WiFi is radiated, because they operate in a part of the spectrum that's been set aside for unlicensed, low-power use. This works out ok because it's very short range. Jeh (talk) 18:14, 5 March 2014 (UTC)

You're saying that optical fiber cables use radio waves?--Wyn.junior (talk) 23:39, 5 March 2014 (UTC)

It's not the typical terminology, but yes. Very very very short-wavelength radio waves. And AM radio uses photons: very very very long-wavelength photons. The only difference between light and the AM broadcast band is wavelength. The propagation medium is of course different for optical fiber (glass or plastic vs. air or vacuum). Jeh (talk) 03:22, 6 March 2014 (UTC)

You saying that fiber optics use radio waves isn't supported anywhere that I have read. Read that Fiber-optic communication article. Everything I have read says that either light or lasers are used, not radio waves (hense the term optical).--Wyn.junior (talk) 03:45, 6 March 2014 (UTC)

("Either light or lasers are used" is a strange statement, since lasers produce light.) What I am saying is that there is no fundamental difference between light waves and radio waves except their wavelength. A flashlight emits electromagnetic waves, and a radio transmitter's antenna emits photons. It's all part of the same Electromagnetic spectrum. If it were technically possible (it isn't) to build a "radio transmitter" with a tuning dial that went up high enough, you would find that as you tuned up to around 400 petahertz (400x10¹⁵ Hz), your "antenna" would be emitting a deep red light. Keep going and the radiated light would run through the spectrum through violet, then disappear as you went into UV. By convention the term "radio" is not used at such high frequencies/short wavelengths, and "light" is not used for frequencies that don't stimulate our retina, but really, it's all EM waves. Why do you think light and radio waves both propagate through vacuum at the same speed (300,000 km/sec)? They're the same phenomena. Just different wavelengths. Jeh (talk) 05:29, 6 March 2014 (UTC)

Laser is a type of light. Light and lasers are the terms used that I have read about. Light is part of the electromagnetic spectrum, yes. But it isn't a radio waves. Everything in the electromagnetic spectrum travels at the speed of light (roughly 186,000 miles per second). End of conversation. Thank you.--Wyn.junior (talk) 15:20, 6 March 2014 (UTC)

By convention, we refer to some long-wavelength EM waves as "radio", and some short-wavelength EM waves as "light." My point is that they're all EM waves, just of different wavelengths—all part of the same spectrum. What we commonly call "light" is no different from what we commonly call "radio", just of very very very much shorter wavelengths. And vice versa. If you don't get this, you're failing to understand the most basic point about the Electromagnetic spectrum. Walk away if you like, but please take a basic physics course before opining further. Jeh (talk) 17:57, 6 March 2014 (UTC)

Your switching the terms radio frequency with radio waves, big difference.--Wyn.junior (talk) 19:34, 6 March 2014 (UTC)

The term "radio frequency" did not appear here until you just used it, so I obviously did not "switch" it with anything. And, anyway, there isn't a difference. That's what I'm trying to get across. Light waves and radio waves, both EM waves, both photons... same thing except for frequency/wavelength. Jeh (talk) 19:43, 6 March 2014 (UTC)

I meant you're switching the ideas of electromagnetic spectrum with the idea of radio frequency. No more discussion.--Wyn.junior (talk) 19:52, 6 March 2014 (UTC)

Again, I haven't "switched" anything. What we commonly call "radio frequencies" are part of the EM spectrum, as are the frequencies that produce light, and the boundaries for both designations are fairly arbitrary. Light is the same thing as radio waves, just of vastly shorter wavelength, and vice versa. (Verb. Sap.: When you say "no more discussion", that is not binding on anyone but you. If you don't want to discuss further, simply don't reply. If you do reply, don't be surprised when I reply again.) Jeh (talk) 20:37, 6 March 2014 (UTC)

You keep saying "we". Who is "we"?--Wyn.junior (talk) 00:00, 7 March 2014 (UTC)

People who work with this stuff. Jeh (talk) 04:37, 7 March 2014 (UTC)

Another question. The RF spectrum is going to fill with time. Cabled signals don't count against that space do they? Because cabled signals are that, inside the cables.--Wyn.junior (talk) 00:00, 7 March 2014 (UTC)

One might say that the easy parts of the RF spectrum are already somewhat full, but inefficiently so. By "easy" I mean the parts of the spectrum for which we can already build transmission and reception hardware that solves some communications problems at a reasonable cost; this means microwaves and longer freqs. By "inefficiently" I mean there are often better ways to use various parts of the spectrum, and better ways to do things, than were first employed. For example: Until recently there was, in many cities, a shortage of channels for police and other public service voice comms. Now, "trunking" systems allow the job to be done while using far fewer frequencies and simultaneously providing better functionality and easier use. Another example: We're still tying up hundreds of MHz for UHF TV channels (from 470 to 700 MHz) and we can't even use them all in any one market because TV receivers don't have good enough selectivity to deal with stations on adjacent channels. You may have heard of the concept of "whitespace devices", which will attempt to find those parts of the TV spectrum not in use locally and use it for other things.

As a general rule, RF is regulated. Is parts of it don't require a license, then that's part of the regulations. From what I understand, VLC isn't regulated.--Wyn.junior (talk) 00:04, 7 March 2014 (UTC)

Correct. Hm, well... setting up bright lights where they will get into your neighbors' windows, or where they might interfere with drivers' vision at night, or etc., may be unlawful, depending. But not due to spectrum use regulations. Jeh (talk) 04:37, 7 March 2014 (UTC)

Incidently, the reason the 2.4 GHz band used by WiFi, Bluetooth, microwave ovens, etc., was set aside for low-power but unlicensed operation is the same reason that it works well for microwave ovens: microwaves at this frequency are very readily absorbed by water. You've probably heard that microwave ovens work by heating the water that's in the food. Oh, they heat other stuff too, but mostly they heat the water. Well, water vapor in the air does the same thing: It absorbs 2.4 GHz microwaves. So it would take a lot more power to communicate over any given distance at 2.4 GHz than at, say, 2 or 3 GHz; at 2.4 GHz most of your transmit power just ends up heating the water vapor in the air. But, it does work well enough for mostly-indoor, short-range stuff like WiFi and Bluetooth. Jeh (talk) 06:35, 7 March 2014 (UTC)

References

Reference question

Can this be used as a reference?--Wyn.junior (talk) 01:55, 29 March 2014 (UTC)

For what? Jeh (talk) 01:06, 30 March 2014 (UTC)

For information on some of these articles. I guess I should have asked: Is this an authoritative reference?--Wyn.junior (talk) 01:30, 30 March 2014 (UTC)

It looks like a pie-in-the-sky proposal. I can't see the relevance to Li-Fi or to LEDs. When I asked "for what?" I meant "For what specific statement or claim were you thinking of using this as a reference?" Jeh (talk) 06:17, 30 March 2014 (UTC)

News release?

About the News release template at the article. In February 2014 user:Jeh added the tempĺate... I agree, that version of the article reads like a news release.

Then many edits later, by many other users (the mine are little but other have some effort)... It is better (!). Not perfect, but better... So, suggestion: to remove the template. --Krauss (talk) 21:59, 18 June 2014 (UTC)

PS: I have splitted the text with new sections where we can see that the problem is not an "advertising style"... ṕerhaps needs only good english and some didactic approach.

It reads less like a press release now, but there is still some of that aspect, and it needs some significant re-org. Jeh (talk) 23:00, 18 June 2014 (UTC)

Ok, I can help and colaborate... Please show what you think, what is "still some of that aspect", and what it needs about "some significant re-org". --Krauss (talk) 22:16, 19 June 2014 (UTC)

tone of article and historical context

I don't really like the tone of this article, it makes it sound like the professor invented the concept of using light for communications. When all that he has really done is to add some specific protocols to an already well known technique, and figured out a way to market his package as if it were something new. For example, back in the 1980's in Byte Magazine, Steve Circia's (sp?) Circuit Cellar column published a How To project for linking computers together over a distance of several miles using infrared light emitting diodes. The technology itself was already well known even then. I recall in the mid 1990's looking at a commercial product that used a laser beam. It was designed as a solution to the massive expense of putting cables under the street in order to connect the networks of two buildings together. As long as you could get line of sight from either a window or the rooftop, you could use their laser beam communication system to send IP packets between the buildings. There is nothing new under the sun, and I resent that this guy appears to be claiming to have invented something that is in fact quite old (or at least this article conveys that impression). He may have created a cutesy name for it and defined a protocol to ensure device inter-operation, but the actual technology has been around for many decades. Also it has been known for an equally long time that light can be bounced off of walls. Anyone who has ever aimed their tv remote at the wall behind them has already experienced this in action. As far as IrDA goes, it suffered from two major problems. Transmission speeds were typically quite low and most setups were for one way communication. This lead to a lack of enthusiasm and resulted in a lack of software and hardware support. As I recall, at one point a number of laptops added an IrDA as a feature. I recall being excited about it at the time, when I bought a computer that had this. But they provided no software to run it, you had to write our own. On top of that it was (typically) not hooked up to a UART thus the software had to do a lot of bit banging, which is complicated and inefficient. Nobody ever found a killer app for IrDA, IMHO the closest they came was to use it for wireless printing, but it never reached critical mass and the protocols weren't standardized. Once WiFi got established it made far more sense to use the existing infrastructure of WiFi for communication to devices like printers. One of the reasons for the WiFi crisis is the on-coming Internet of Things. You just can't have billions of devices all transmitting on the limited WiFi spectrum. LiFi would make a lot of sense for that application. I just feel that the article should make it clear that LiFi does not create any new technologies, all it does is define a Trademark for a group of Inter-operable protocols, which are implemented using well known (and quite old) technologies. codeslinger@compsalot (too lazy to login).

Define "Medium" for this article

I have a problem with the use of the word "medium" in the 1st sentence in the "Technology details" section:

This OWC technology uses light from light-emitting diodes (LEDs) as a medium to deliver networked, mobile, high-speed communication in a similar manner to Wi-Fi.[3]

It is the light itself that is the "medium" and not the LED's. I also do not like the use of the word "bulbs" two sentences later:

Visible light communications (VLC) works by switching bulbs on and off within nanoseconds,[5]

LEDs are not bulbs, nor are they the medium and both of these statements are both technically wrong, as well as wrong in the sence that they will not do anything but confuse the layperson.

In the first point, there is no problem. The sentence does not say the LEDs are a medium. It says the light is the medium. The light happens to come from LEDs. The second point is a trivial fix. Jeh (talk) 18:32, 1 December 2015 (UTC)

Somebody explain how it works at night you know when lights are off

the on/off switch of the light bulbs are so fast and the off time will be so long that you can't see it.

or you can use infrared which you can't see at all.

"Light fidelity"

Is there any citation for li-fi being a contraction of "light-fidelity"? "Light-fidelity" doesn't mean anything. — Preceding unsigned comment added by Apepper (talk • contribs) 14:26, 19 January 2016 (UTC)

agreed. This should be removed as it is incorrect. I now reading a PhD dissertation where the author used the name "Light Fidelity". Probably sourced from this page... JHBonarius (talk) 11:37, 10 April 2018 (UTC)

"Li-Fi" was chosen for the similarity to "Wi-Fi"; "Wi-Fi" is a combination of "Wireless" and "Hi-Fi", not "Fidelity". Matthias Alexander Jude Shapiro (talk) 14:23, 24 July 2016 (UTC)

AFAIK your statement is incorrect. See https://boingboing.net/2005/11/08/wifi-isnt-short-for.html JHBonarius (talk) 11:37, 10 April 2018 (UTC)

Your source appears to support what Matthias Alexander Jude Shapiro said. In case it wasn't clear enough:

"Hi-Fi" or "HiFi" DOES stand for "High Fidelity". (The nickname came into being when the only "fidelity" possible was analog audio fidelity).

"Sci-Fi" or "SciFi" DOES stand for "Science Fiction". (Many people prefer "SF").

"Wi-Fi" or "WIFi" DOESN'T stand for anything, but was chosen to be similar to Hi-Fi. In particular "Wireless Fidelity" makes no sense and was not part of the decision to coin the phrase "Wi-Fi".

"Li-Fi" or "LiFi" DOESN'T stand for anything, but was chosen to be similar to Wi-Fi. In particular "Light Fidelity" makes no sense and was not part of the decision to coin the phrase "Li-Fi".

Alas, it looks like people will be using Wi-Fi and "Li-Fi" long after "Hi-Fi" is no longer in common usage.

Next up: why most computers have icons showing a dial telephone and a floppy disk when many users have never seen either of those, why keyboards have the QWERTY layout, any why letters have serifs (the serifs are there to make it easier for the ancient Romans to chisel inscriptions into stone...). --Guy Macon (talk) 14:50, 10 April 2018 (UTC)

Many inappropriate edits made

Many spammers are making edits to this post which is seriously affecting the quality of the post. — Preceding unsigned comment added by RyanAfrish7 (talk • contribs) 03:44, 24 August 2016 (UTC)

Lifi Technology

Imagine a world where every one of the billions of lightbulbs in use today is a wireless hotspot delivering connectivity at speeds that can only be dreamed of with Wi-Fi. That's the goal of the man who invented such a technology, and this week Li-Fi took a step out of the domain of science fiction and into the realm of the real when it was shown to deliver speeds 100 times faster than current Wi-Fi technology in actual tests.

An Estonian startup called Velmenni used a Li-Fi-enabled lightbulb to transmit data at speeds as fast as 1 gigabit per second (Gbps), which is about 100 times faster than current Wi-Fi technology, meaning a high-definition film could be downloaded within seconds. The real-world test is the first to be carried out, but laboratory tests have shown theoretical speeds of 224 Gbps.

So, just what is Li-Fi, how does it work, and will it really revolutionize the way we connect to the Internet?

Li-Fi refers to visible light communications (VLC) technology, which delivers high-speed, bidirectional, networked mobile communications in a manner similar to Wi-Fi. It promises huge speed advantages, as well as more-secure communications and reduced device interference. — Preceding unsigned comment added by Harshalkamble1996 (talk • contribs) 08:44, 20 October 2016 (UTC)

How Does Li-Fi Work?

This is how pureLiFi describes the operation of its technology:

When a constant current is applied to an LED [light-emitting-diode] lightbulb, a constant stream of photons are emitted from the bulb which is observed as visible light. If the current is varied slowly, the output intensity of the light dims up and down. Because LED bulbs are semiconductor devices, the current, and hence the optical output, can be modulated at extremely high speeds which can be detected by a photodetector device and converted back to electrical current. The intensity modulation is imperceptible to the human eye, and thus communication is just as seamless as RF [radio frequency technology]. Using this technique, high-speed information can be transmitted from an LED lightbulb. — Preceding unsigned comment added by Harshalkamble1996 (talk • contribs) 08:49, 20 October 2016 (UTC)

Pronunciation of Lifi

According to the IPA in the article the pronunciation of Lifi is /liː-faɪ/ - the first i is pronunced as the two e's in "seed". Shouldn't it be /ˈlaɪfaɪ/ as pronunced in the TED video of Prof. Harald Haas and with the same vowel as light (/laɪt/)?

That seems to be correct. That was just me who put it in there with my next to none IPA know-how :) I was hoping it would encourage someone to correct me. Thank you and most appreciated -MayureshK 08:39, 22 January 2018 (UTC)

Bigger edits

Made some bigger changes on the page, especially regarding promotional info, by removing a lot of mentions/references to individual companies and their achievements when not mentioned in the History context. I think it's a lot less promotional in tone, but will wait a bit before removing the advertisement warning. Abraxxass12 (talk) 12:41, 15 June 2022 (UTC)

W J VOlfi 11monthsago

123456 124.106.197.105 (talk) 06:19, 9 June 2023 (UTC)