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twist radio beams to send data: Transmissions reach speeds of 32 gigibits per second

  • 19-09-2014 11:17pm
    #1
    Rucking_Fetard
    Closed Accounts Posts: 1,260 ✭✭✭


    Researchers twist four radio beams together to achieve high data transmission speeds. The researchers reached data transmission rates of 32 gigabits per second across 2.5 meters of free space in a basement lab. For reference, 32 gigabits per second is fast enough to transmit more than 10 hour-and-a-half-long HD movies in one second and is 30 times faster than LTE wireless.
    Future research will focus on attempting to extend the transmission's range and capabilities.
    http://www.sciencedaily.com/releases/2014/09/140916132515.htm


    Any addition Watty?


Comments

  • #2
    AlmightyCushion
    Moderators, Education Moderators, Technology & Internet Moderators Posts: 35,125 Mod ✭✭✭✭AlmightyCushion


    How does it perform at distances greater than 2.5m? That's what will make this a game changer or not.


  • #3
    watty
    Registered Users, Registered Users 2 Posts: 32,417 ✭✭✭✭watty


    It's of almost zero terrestrial value. It might be useful between two spaceships.

    They don't say how much spectrum they are using. So it's some kind of Polarisation diversity, Right and Left Circular polarisation is used today. Assume it's perfect (it won't be) then per beam is 8Gbps.

    They don't say what QAM is used either. But more than 4bits isn't very robust except short range or in a cable (a cable can't use polarisation diversity at all). So let us say a 2Gbps symbol rate. That would need carrier frequencies at 10GHz band or higher. Basically point to point Microwave links.
    If they used 256 QAM per beam the signal is very susceptible to noise and cross talk between the beams. That would be 8 bits per symbol. It would also need 16 times better Signal to Noise (assuming perfect) or 16 times less crosstalk between beams. Still need LOS microwave.

    I can't see how this can ever relate to Mobile, WiFi or Rural Fixed Wireless. The technique is only doubling or tripling existing possibilities for LOS microwave links and might not ever give good enough SNR / low enough crosstalk for the real world.

    The references to DNA and comparisons to LTE are spurious and incorrect. It's 300 x faster than most LTE and almost 1000x faster than what average LTE user speeds are. Since it's four signals rather than one, then for similar scenario you need 75x to 250x times the 20MHz channel of LTE, ie. 1,500 MHz wide channels minimum! That's really 47GHz 200GHz carrier territory.


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