Author Topic: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap  (Read 6995 times)

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Offline ataradov

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #1 on: February 26, 2018, 08:14:15 am »
That thing has been around for a while, but I don't think any has ever seen an independent review of a practical implementation.

It surfaces every trade show cycle, gets press resales published in sketchy places, like engadged, and then slowly gets quiet, until the next trade show.
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Offline NiHaoMike

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #2 on: March 02, 2018, 06:05:40 am »
I see it as more of a supplement than a replacement for Wifi, and there apparently are still a bunch of challenges to overcome.

BTW, before Wifi, some hobbyists have figured out how to send Ethernet over laser pointers.
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Offline David Hess

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #3 on: March 02, 2018, 12:45:16 pm »
I would be satisfied with an updated IRDA standard for portable devices like cameras to exchange information with desktops.  It would be more secure and could be more reliable than WiFi, Bluetooth, and similar radio standards.  I live in perpetual fear of breaking the micro USB connector on my camera or wearing out the SD card slot and WiFi for cameras just sucks.
 

Offline Marco

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #4 on: March 02, 2018, 12:57:51 pm »
Li-Fi can't replace WiFi, but it might make mm wave superfluous for communication in consumer applications. They both compete in the same space, but light has some advantages.

The concept developed by University of Eindhoven is interesting. Central optical emitter, bunch of cheap fibre through the house with passive access points (download only, wifi for upload).
 

Offline Cyberdragon

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #5 on: March 02, 2018, 04:13:40 pm »
The concept developed by University of Eindhoven is interesting. Central optical emitter, bunch of cheap fibre through the house with passive access points (download only, wifi for upload).

Most communications are two way. With no upload, the clients can't make any requests so they can't initiate any sort of transfer! The only thing you could do might be imaging drives or something, but it would be in UDP with no corrections. So if a fly goes across your emitter, everything gets corrupted!

You could use it with wifi to have two-way, but then again...why? You would be limited to the infrared range anyway.

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Offline Marco

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #6 on: March 02, 2018, 05:13:27 pm »
It's for asymmetrical bandwidth applications. Mbps upload through wifi, Gbps download through lifi.
 

Offline Cyberdragon

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #7 on: March 02, 2018, 05:27:43 pm »
It's for asymmetrical bandwidth applications. Mbps upload through wifi, Gbps download through lifi.

If you need infrared for whatever reason, then why not use a regular two-way infrared connection?
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Offline Marco

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #8 on: March 02, 2018, 06:38:20 pm »
Because you can passively turn a coherent collimated beam from a fibre into a wide beam to cover the room, but you can't passively turn light from a device in the room into a coherent collimated beam to send through the fibre in the other direction.
 

Offline Cyberdragon

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #9 on: March 02, 2018, 06:54:04 pm »
Because you can passively turn a coherent collimated beam from a fibre into a wide beam to cover the room, but you can't passively turn light from a device in the room into a coherent collimated beam to send through the fibre in the other direction.

Which is exactly why their system is pointless!
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Offline Marco

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #10 on: March 02, 2018, 07:15:28 pm »
It's an elegant and potentially low cost way to provide 10+ Gbps downstream bandwidth wirelessly throughout a home.
 

Offline Cyberdragon

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #11 on: March 02, 2018, 08:13:54 pm »
It's an elegant and potentially low cost way to provide 10+ Gbps downstream bandwidth wirelessly throughout a home.

:-DD

You sound like a shill at this point. Time to crush your bubble with a hydraulic press.

802.11ac has been invented as gigabit wifi. Without the need to run fiber optics everywhere, and is two way by default. 8)

https://en.wikipedia.org/wiki/IEEE_802.11ac

Plus, no home would ever need a 10Gb connection, let alone a single device! That's the speed of a main fiber for a small building!
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Offline Brumby

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #12 on: March 03, 2018, 02:22:30 am »
Plus, no home would ever need a 10Gb connection, let alone a single device! That's the speed of a main fiber for a small building!

How long before this statement falls down?

2 years ...?  5 years ...?
 
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Offline NiHaoMike

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #13 on: March 03, 2018, 03:01:03 am »
Plus, no home would ever need a 10Gb connection, let alone a single device! That's the speed of a main fiber for a small building!

How long before this statement falls down?

2 years ...?  5 years ...?
Right now if you count wireless VR. That's obviously LAN rather than WAN but the wireless solution doesn't care.
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Offline Brumby

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #14 on: March 03, 2018, 03:14:49 am »
I was thinking about two words in particular: "home", but especially "need".

Capability is a different thing.
 

Offline Cyberdragon

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #15 on: March 03, 2018, 03:27:15 am »
Plus, no home would ever need a 10Gb connection, let alone a single device! That's the speed of a main fiber for a small building!

How long before this statement falls down?

2 years ...?  5 years ...?

Right, I forgot about all the IOT loving hipsters hogging bandwidth with their privacy destroying advertisement machines. ::) Or if you're a mad scientist with a Watson supercomputer in your house. But those VR systems have their own interlinks, they don't use the wifi (because they eat bandwidth).

But the point is that a one way LOS infrared system is still useless, when you have to have wifi anyway just to make it work! :palm:
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Offline Brumby

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #16 on: March 03, 2018, 03:44:11 am »
I was thinking more along the lines of multiple 8K (or higher) video streaming ... and perhaps more bandwidth hungry websites and other such things .... but, yeah, I suppose the IOT realm will be a part of it.



I don't know why - but I just had a random thought that led me to look up "id": "The id acts according to the "pleasure principle"—the psychic force that motivates the tendency to seek immediate gratification of any impulse"

Then the "Internet Of Things" fell in place after that - and the resultant word just struck a chord.
 

Offline Marco

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #17 on: March 03, 2018, 04:44:17 am »
You sound like a shill at this point.
I wouldn't have been so repetitive if you hadn't been so obtuse. There was a method to what you consider madness, as we have now established.
Quote
802.11ac has been invented as gigabit wifi.
5GHz still has reach and thus contention issues in urban environments, and they are an order of magnitude apart in potential bandwidth ... not a 1:1 replacement.
Quote
Without the need to run fiber optics everywhere
Still need to put routers everywhere and run wire between them, not like there's anything left of that gigabit potential after a single wall.
Quote
Plus, no home would ever need a 10Gb connection, let alone a single device! That's the speed of a main fiber for a small building!
That's the meat of the issue, it's certainly the rock mm wave ran ashore on ... but maybe VR takes off, never know, humans are fickle.

LiFi has advantages over mm wave, no multipath fading, low cost to put multiple emitters in a room, etc.
 

Offline Cyberdragon

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #18 on: March 03, 2018, 05:57:44 am »
You can't talk about reach with an infrared LOS system, unless it uses a direct laser beam. But even then you would have to contend with walls, coffee cups, paper airplains, wandering pets, and anything else that could inadvertantly block the sensor.

Quote
Without the need to run fiber optics everywhere
Still need to put routers everywhere and run wire between them, not like there's anything left of that gigabit potential after a single wall.

You just said yourself you need to run wifi to make this work anyway since it's send only. So  you would need to run TWO systems of wiring for ONE interlink. :palm: Gig wifi is not "blocked by a single wall", it's been in use since 2011 and has had no such problems. Plus, an optical system would be blocked by a fly landing on the sensor! And you would only need one access point per room for wifi since it's not LOS, and is two way.

VR would only be a local interlink, between two devices (the computer/console and the headset) not throughout a house. But even then, it's VR, so you'd be moving, the detriment of any LOS system.
« Last Edit: March 03, 2018, 06:00:28 am by Cyberdragon »
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Offline Marco

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #19 on: March 03, 2018, 07:07:19 am »
But even then you would have to contend with walls, coffee cups, paper airplains, wandering pets, and anything else that could inadvertantly block the sensor.
Whether it's purely LOS or detectable after some bounce/refraction/diffusion depends on noise margins, much like mm wave.
Quote
So  you would need to run TWO systems of wiring for ONE interlink.
You need high density access points to get near the throughput potential of 802.11ac, but lifi wouldn't need to get near that potential, because upload requirements are almost always far lower.

It's like you're unaware that there is quite a large industry out there trying to push mm wave systems ... doesn't necessarily need to succeed, but it does allow me to appeal to authority.
« Last Edit: March 03, 2018, 07:13:05 am by Marco »
 

Offline BrianHG

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #20 on: March 04, 2018, 08:14:02 pm »
This will be the future of WiFi : http://www.newelectronics.co.uk/electronics-news/full-duplex-radio-ics-transmit-and-receive-at-the-same-frequency/75059/

The document underestimates the speed increases.  A whole lot of handshaking & overhead will be lost once you sync 2 radios on the same frequency where both sides transmits continuously simultaneously, not to mention looking for clean alternate open channels.
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Offline Cyberdragon

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #21 on: March 04, 2018, 09:09:23 pm »
But even then you would have to contend with walls, coffee cups, paper airplains, wandering pets, and anything else that could inadvertantly block the sensor.
Whether it's purely LOS or detectable after some bounce/refraction/diffusion depends on noise margins, much like mm wave.
Quote
So  you would need to run TWO systems of wiring for ONE interlink.
You need high density access points to get near the throughput potential of 802.11ac, but lifi wouldn't need to get near that potential, because upload requirements are almost always far lower.

It's like you're unaware that there is quite a large industry out there trying to push mm wave systems ... doesn't necessarily need to succeed, but it does allow me to appeal to authority.

You only need two points to get at least 1 gig speed for 802.11ac. And again, that's one system, not entirely two different and seperate systems that have to work together.

I never said infrared was entirely useless, it has specialized applications. I just think it's a stupid idea for residential or office use.
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Offline helius

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #22 on: March 04, 2018, 09:22:31 pm »
Infrared was originally part of the 802.11 standard in 1997. Along with FHSS, it was dropped from the next revision of the standard in 1999.
 

Offline NiHaoMike

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #23 on: March 04, 2018, 10:24:02 pm »
This will be the future of WiFi : http://www.newelectronics.co.uk/electronics-news/full-duplex-radio-ics-transmit-and-receive-at-the-same-frequency/75059/

The document underestimates the speed increases.  A whole lot of handshaking & overhead will be lost once you sync 2 radios on the same frequency where both sides transmits continuously simultaneously, not to mention looking for clean alternate open channels.
I'm not sure why they didn't think of it the day dual band Wifi became commonplace. Negotiate with the device to transmit on one band while receiving with the other, full duplex.
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Offline Marco

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Re: Li-Fi to replace Wi-Fi? Sounds like Sci-Fi or bullcrap
« Reply #24 on: March 04, 2018, 11:27:17 pm »
How do they distinguish a signal from a weak reflection? Only way I see to do full duplex on the "same" frequency is using part of the constellations for transmit and the rest for receive, but that doesn't double the bandwidth.

PS. oh, it learns the multipath response during the preamble .... that's smart. The hand shaking is kind of an essential part of what makes it work, CSMA isn't going away either.
« Last Edit: March 05, 2018, 01:12:29 am by Marco »
 


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