MU-MIMO vs. Smart antenna

[kfarley]

Hi all,
I was curious as to if someone could provide a quick explanation as to why the “smart antenna” feature disables MU-MIMO and why this is a recommended choice from extreme vs. enabling MU-MIMO.

i understand what MU-MIMO is but i guess the better question is, why is Smart antenna better than MU-MIMO and why does enabling smart antenna, Disable MU-MIMO?

thanks!

[Tomasz]

Hi,

I’m curious to better understand Smart Antenna feature on those APs myself, but what I’d say for sure, don’t consider MU-MIMO if you have more than very few devices per radio. MU-MIMO can work nice in stationary environment where devices are sparsely distributed over the place (like house with a TV, set top box and something else, or in building-to-building connection). There’s at least one reason for that not being suitable in dense mobile environments, the sounding mechanism that introduces roughly 1ms of an overhead per each connected MU, and it runs every 40ms. With 30 MUs on a radio you get 30/40 = 75% channel utilization, which is saturation. At 50% CU video is likely disrupted, at 20% CU voice is likely disrupted. More on this:http://divdyn.com/moo-mimo/

Hope that helps,

Tomasz