MU MIMO questionnaire

[Hussam-Bay]

Hello guys,

I have a couple of questions that are confusing me:

1- Can a 4x4 access point serve four 1x1 clients at the same time or there are other constraints?

2-  When they say the AP is 4x4:4 and it has four streams, what makes an AP physically have four streams and how it can serve four clients at the same time with the same antenna

3- MU-Mimo is only on the 5 GHz band?

Thanks in advance

[BrechtSchamp · Accepted solution]

1. Yes, that's what MU-MIMO is for exactly :). Have a look here:
   https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/802-11ac-solution/q-and-a-c67...
   I thought these images were quite good:
   (SU-)MIMO
   
   MU-MIMO
   
   
2. The AP actually does use multiple antenna's for MIMO. Have a look at this: https://meraki.cisco.com/blog/2011/02/mimo-why-multiple-antennas-matter/ or https://www.ciscolive.com/c/dam/r/ciscolive/emea/docs/2019/pdf/BRKEWN-2017.pdf (slide 38-52)
3. In 802.11ax it works in both bands.

[NolanHerring]

Just keep in mind that the implementation of MU-MIMO with 802.11ac Wave-2 was good on paper but adoption was weak and it didn't really take off. The tech is sound but its almost impossible to 'capture' it in the wild, the only place I've ever seen it function is in a lab.

[Uberseehandel]

The sooner AP vendors concentrate on the 802.11ad standard (60 GHz) the better . . . . 

Lots of small low powered APs, enough bandwidth to allow for separate backhaul, and no competition for spectrum (for now). I hear that developments are going well in Korea. I volunteer to be an alpha tester for Meraki (they have my address)

[NolanHerring]

I've always thought of 802.11ad as a 'long HDMI cable replacement' lol

Gotta be in the same room, so roaming is the killer for that tech =(

[Uberseehandel]

You may need to revise your understanding of what is possible - see this 4 year old paper - https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0167447 

and

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5173383/ 

Korea is even working on 802.11ad-based radar . . . 

[NolanHerring]

I think were talking two different things 😃

60GHz can 100% be used for many things, get tons of good throughput, backhaul, outdoor P2P, same room video streaming, and all that jazz. I'm all for it.  I was actually trying to find a use for it to stream from my desktop to my TV with HDMI-to-802.11ad back to HDMI etc., but it would have cost 400 bucks.  So I just bought a 25 foot HDMI cable for 15 dollars instead  😃

I was just saying that everything I have seen/read for mmWave penetration is that it essentially won't (30GHz - 300GHz).

[Uberseehandel]

Ever since I first started using WiFi, concurrently in NYC, London and Munich I avoided trying to propagate WiFi through walls. Having strong energy conservation proclivities, I had learned the benefits of foil lined wall board, so WiFi was never going to make it. Lots of houses in the US do not provide the same problems as they do in the rest of the world (NYC is only in the US as far as the post codes are concerned 🤣, some of those Manhattan apartment houses are solid). If I need WiFi in another room, I put a wired AP in that space. In the long run this is more reliable.