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Li-Fi (data via modulated light) Technology Development Difficulties

  1. Oct 28, 2013 #1


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    Greetings PFers
    You’ve probably heard of the new “revolution” called Li-Fi (Light Fidelity) which is a method of data transmission utilizing the modulation of very high frequencies in LED light bulbs. A good demonstration (And probably the first) is here: http://www.ted.com/talks/harald_haas_wireless_data_from_every_light_bulb.html

    I have a basic understanding of networking, Wifi, and electronic components. I’m having a difficult time understanding why it’s been so difficult to develop this technology (and I’m not simply referring to the line-of-sight problem). In my mind, a simple circuit can be developed to receive a binary signal and turn a specific solid state relay (one for each type of LED) on and off at a very high frequency. Modulation enabled = 1 bit, modulation disabled = 0 bit.

    Am I correct when I assume the difficulty is in the software and not so much the hardware?

  2. jcsd
  3. Oct 28, 2013 #2


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    Li-Fi seems to be the "next" method for sending and receiving high density data streams at high speeds. As for technical difficulties, none appeared in a quick search. What specific "difficulty" are you referring to?

    An overview and description of various encoding methods on the Wiki page:

    and this:
    UK researchers say they have achieved data transmission speeds of 10Gbit/s via "li-fi" - wireless internet connectivity using light. The researchers used a micro-LED light bulb to transmit 3.5Gbit/s via each of the three primary colours - red, green, blue - that make up white light.

    As for detectors, see this for example:

    Ultrafast transient responses of optical wireless communication detectors
    The GaAs material response times are investigated experimentally and found to range from approximately 3 ps to 200 fs for 390 nm (violet) to 780 nm (red) photoexcitation.


    “Ultrafast photodetector could lead to increased fiber optical broadband speeds”
    Compared to a normal germanium photodetector, the avalanche design has enhanced the detected signal by a factor of 30. The gain-bandwidth product, which characterizes both the detector enhancement as well as operation speed, is as high as 310 gigahertz.
  4. Oct 29, 2013 #3


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    And that is using "telegraph" technology.
  5. Oct 29, 2013 #4


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    My difficulty is in understanding why this technology hasn't skyrocketed. Homes could be relatively easily retrofitted with adapters in the main breaker or sub breakers in the central breaker panel to modulate standard AC power. Devices equipped with simple recievers to detect even 1 color could transfer data at superior rates. All someone has to do is
    1. design and build an adapter-transciever which integrates into a home's breaker panel and connects to the internet or network source
    2. Find a suitable LED lightbulb capable of being switched on and off from it's main power and integrate a suitable photoelectric sensor. like this one: http://www.thenanoleaf.com/
    3. Design and manufacture a circuit to process the incoming and outgoing data streams over the power lines and directly interface with each light bulb (like these: http://www.newegg.com/Product/Produ...E16833181121&gclid=CKuyv8K-u7oCFaF_QgodnQcAJg)

    4. Develop a plugin for devices and equip them with a optical transciever identical to the one in the light bulb.

    With decent resources and good engineers, I don't expect this to be a monumental challenge. Yet, progress seems stagnant. My difficulty is in understanding why*
  6. Oct 8, 2014 #5
    Hi, can you or someone educate me about how the LED receives & transmits data from/to say a smartphone? Is there a transceiver circuit embedded in a Li-Fi system? If a transceiver is required to enable a communication link then won't the Li-fi become redundant? I am sure that's not the case but I don't understand the basic transmitting & receiving part of function via a LED light. I know that data could be transferred through a very high frequency OOK modulation but am not sure how the LED bulb could receive the signal from say a smartphone or transmit data to a smartphone!

    Please educate me-thanks
  7. Oct 9, 2014 #6


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    well you need a transmitter and a receiver .... so the LED would be the transmitter at each end of the link. And you would need a photo-diode or photo-transistor as the receiver
  8. Oct 9, 2014 #7
  9. Oct 9, 2014 #8


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    well done ;) ... you quoted me but didn't respond ... did you understand what I was getting at ?

  10. Oct 9, 2014 #9
    Thank. Cost & performance wise, how'd you Li-Fi compared against, say Wi-Fi application? I wonder what Li-Fi would offer against Wi-Fi.
  11. Oct 9, 2014 #10
    apology, Dave! Must had hit the wrong button when I did my 'reply' in the car!
  12. Oct 9, 2014 #11


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    the LiFi would be considerably more secure than WiFi as its signal wouldn't penetrate walls to be picked up outside the building
    and if the beamwidth was tight/narrow say from ceiling down into the users work cubical it would have good security even within the building

    The interesting differences would come down to signal to noise ratios of either
    say IR light is going to need lots of good narrow filtering to keep out ambient IR and visible light ... else there's going to be poor SNR
    For 2.4 or 5.8 GHz RF WiFi easy to get excellent SNR

    just some off the cuff general thoughts :)

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