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Networking Wireless Networking IT

New MU-MIMO Standard Could Allow For Gigabit WiFi Throughput 32

Posted by timothy
from the it-slices-it-dices-it-emits-radiation dept.
MojoKid (1002251) writes "Today, Qualcomm is announcing full support for a new wireless transmission method that could significantly boost performance on crowded networks. The new standard, MU-MIMO (Multiple User — Multiple Input and Multiple Output) has a clunky name — but could make a significant difference to home network speeds and make gigabit WiFi a practical reality. MU-MIMO is part of the 802.11ac Release 2 standard, so this isn't just a custom, Qualcomm-only feature. In SU-MIMO mode, a wireless router creates time slices for every device it detects on the network. Every active device on the network slows down the total system bandwidth — the router has to pay attention to every device, and it can only pay attention to one phone, tablet, or laptop at a time. The difference between single-user and multi-user configurations is that where SU can only serve one client at a time and can therefore only allocate a fraction of total bandwidth to any given device, MU can create groups of devices and communicate with all three simultaneously."
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New MU-MIMO Standard Could Allow For Gigabit WiFi Throughput

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  • I guess I thought this kind of thing was already out there, if not sounds solid to me.
    • Your understanding is reversed.

      TDMA for WiFi is what we have now.

      MU-MIMO is simultaneous comms with each device.

  • by YoopDaDum (1998474) on Thursday April 03, 2014 @09:34AM (#46649087)
    The title could lead some to believe that MU-MIMO is increasing the peak throughput, which is not the case. Spatial multiplexing (SM) MIMO allows to have as many independent concurrent streams as there are antennas on receiver and transceiver (the min of both sides actually). So with 4 antennas on the AP and 3 on the station for example, you can have 3 streams. With SU-MIMO, all three streams are used between the AP and a single station. With MU-MIMO the AP can use its streams with more stations: for example 1 stream to station A, and 2 streams to station B. There is a little bit of degradation of course compared to single use. It's a win when you have for example a 4 antennas AP and only 2 antennas stations, then instead of leaving half the capacity on the floor you can make use of all the streams. But it doesn't increase the peak rate possible with SU-MIMO, it increases the AP capacity when devices do not have as many antennas as the AP, which is the usual case.
    • What a great, informative reply! I learned something. So rare on Slashdot lately. :-/

      So, is 802.11ac a polling MAC layer?

      • Thanks! The MAC layer principles are the same in 802.11ac than in 802.11n. The MU-MIMO feature is really made for the AP to stations direction (downlink). The AP can decide on the combined transmission on its own, based on queued packets: if the AP has packets buffered for several stations that can be sent using MU-MIMO, it can merge them into a single PHY access. There's a gotcha for the ACK part, you don't want the receiving stations to ACK at the same time but for this block ACK is used for all stations
        • by wulfhere (94308)

          I'm a wireless engineer (but not a WiFi engineer), so I might just check out that book. Thanks!

    • Slow down, science boy. Can I haz more lolcats, or what?

    • by George_Ou (849225)
      MU-MIMO does effectively offer higher speeds than SU-MIMO in practice. Since most client devices are single antenna devices and only a few that are dual-antenna, MU-MIMO effectively increases the per-client throughput by improving overall capacity. If four single-antenna clients can be concurrently served by a MU-MIMO access point with 4 antennas, each client can have up to 4 times more throughput than the same 4 clients being served by a 4-antenna SU-MIMO access point. The SU-MIMO 4-antenna AP can't spe
      • Absolutely, and that's why I'm talking about "peak throughput" above and not only throughput. Increasing capacity allows to either offering higher average throughput, or offering the same average throughput to more devices concurrently, or any mix in between. It does matter, and actually changing field a bit capacity in the wireless cellular world is what really matters: stretching things a bit to make a point you could say that in cellular peak throughput is for marketing, capacity improvements are for rea
        • by George_Ou (849225)
          Capacity matters a lot in Wi-Fi as well as cellular data. Very rarely will you see mobile devices be able to leverage 2x MIMO or better because they only have one antenna. Capacity is effective peak performance for most situations. Peak throughput is great for marketing benchmarks and occasionally real life performance when it comes to wireless bridging.
  • ...Token Ring is back?

  • ...what we need more is connectivity and reliability.
  • by Art3x (973401) on Thursday April 03, 2014 @02:17PM (#46652145)

    The new standard, MU-MIMO (Multiple User — Multiple Input and Multiple Output) has a clunky name — but could make a significant difference...

    I thought clunky names were an engineering tradition, like CSMA/CD (Carrier Sense Multiple Access with Collision Detection), which means, Listening Among Others for a Chance to Speak.

  • MU-MIMO is part of wave 2 [google.com.au] of the 802.11ac standard. Right now every shipping product is wave 1.

    If we are lucky the routers will get wave 2 this year, or if not this year definitely next. Apart from allowing more devices to share the same cell MU-MIMO is nice in that it reduces power consumption of devices like phones, as they only see the packets for their stream. Wave 2 also bring doubling of the bandwidth (if the spectrum is available) and other efficiences which translates to 2..3 times the speeds of

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