ZF710: MU-MIMO and BeamFlex

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Is there a white paper or other reference explaining how MU-MIMO works in conjunction with BeamFlex?
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Jason Hintersteiner

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Posted 2 years ago

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Munish Dhiman, Employee

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Eizens Putnins

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There was actually good whitepaper before release ov R710, where this was dicussed.

I think it was named "using all tools we got" or something similar.

Interesting that  Beamflex+ is in fact the only  technology on market which can work together with MU MIMO. So it becomes only more important with wave 2...

Most important modification made in latest realisation of Beamflex+  in comparison with Wave 1 is that every Beamflex antenna (set of multiple elements) can be optimised separately in the same time for different clients when  MU MIMO is used.

All other trechnologies (including Cisco Client Link and 802.11ac standard beamforming) use pair of antennas to get max theoretical 3 db gain, which decreases number of spacial streams or MU MIMO clients 2 times. 3db signal gain may provide  10% additional bandwidth, but loosing second spacial stream cuts performance 2 times. So probably 802.11ac standard beamforming and Cisco Clientlink will be never used (as they are not used in practice now), because even if they work, they benefits are heavily outweighted by 2x performance loss.

By the way, it makes sense to remind, that currently you can realise benefits of Wave2 in R710, as there is no clients supporting Wave 2 and even standard itself isn't yet officially complited. But as R710 is software defined, and all hardware dependencies are there already, it is a brilliant investment in future proof network -- any possible last-minute changes of standard will be implemented as firmware upgrade, but when new clients will come to network, performance will grow without any additional investments.

So if you thought about buying  R700 - go for R710 without any reservations. For what it is providing, it is actually cheap.

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John D, AlphaDog

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MU-MIMO and Wave 2 aside, note that the R710 has a specced receive sensitivity of -104dBm, which is a substantial improvement over the previous Ruckus AP's, and further widens Ruckus's already substantial competitive advantage.

Mobile devices tend to have low transmit power, so having a greater receive sensitivity is crucial to getting good range and upload performance on such clients.
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Primož Marinšek, AlphaDog

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I don't think that having a low Rx sensitivity is not a competitive advantige. Lower sesnsitivity means more backoff in environments with more than one AP due to CCI.
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Eizens Putnins

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http://www.theruckusroom.net/2014/05/beamforming-bull.html
link to document about beamforming I mentioned.
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Eizens Putnins

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Sensitivity is one thing, backoff threshold is something completely different. More sensitive AP means that it actually hears weak signals and can make competent decision backoff or not. If sensitivity is not so good, AP just can't hear this signals and takes no actions. It also means that level of own noise is reduced, so for normal and low signal levels SNR is a bit improved.
I don't know how exactly backoff policy is optimized, but it is obviously that it is done in Ruckus (and probably all other enterprise vendors do it too).
I have seen multiple installations near busy wi-fi networks (mostly hotels), where level from neighbor hotel network was about -75 - 80 db, no other interference, and SOHO equipment just didn't work (Linksys, Ubiquity, Mikrotik) even when client is nearby (5 m).
We observed 100% signal level, packet loss  about 20% and ping times 50 - 1000 ms. So nothing worked. I suppose reason is that AP hears hotel network traffic all the time, and as a result has almost no airtime, because hotel network is heavily loaded and ignores AP frames (or doesn't hear them at all).
Just replacing AP by Ruckus resolved this problems.
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John D, AlphaDog

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I've observed the same thing as Eizens — even though my Ruckus AP's are capable of seeing other AP's much better than my consumer equipment before it, it seems to be able to make just as good if not better decisions about whether or not to wait or talk, as well as being able to hear mobile device transmissions from a further range.

Of course, only Ruckus knows what their magic sauce is here (whether or not the periodic noise floor calibrations set the threshold for wait or transmit on top of noise, or if on the decode side ML is used to decode the smartphone transmission superimposed on other weak noise), but it seems like sensitivity works in its favor, not against it.

The R700 being a couple dB more sensitive on 5GHz than the R600 yields similar range benefits in my experience.
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Primož Marinšek, AlphaDog

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I think you might be mixing a few things here. In my experience Ruckus solves many problems also, however an AP receives ALL RF signals present in the air and there's A LOT more to it than a high sensitivity threshold. That's all I'm saying.