[Make-wifi-fast] Thoughts on tackling airtime fairness

[Dave Taht]

On Wed, May 11, 2016 at 9:41 AM, Dave Taht <dave.taht at gmail.com> wrote:
> On Wed, May 11, 2016 at 9:09 AM, Luca Muscariello
> <luca.muscariello at gmail.com> wrote:
>> Correct, but in between that time and now a lot has been done in different
>> areas but not much on this point.
>> The fact that some part of the industry is looking at LTE-U is also because
>> 802.11 standard is not good enough.
>
> What do you think of LTE-LAA?
>
> I do think very strongly that actual usage of 802.11 can be made
> vastly more efficient, that we can use up a great deal of the mac
> currently being left unused, and schedule txops way more efficiently -
> and that I'd love to test with michal's patch set against the LTE-U
> tests cablelabs, etc which did
>
> 100 stations before (stock):
>
> http://blog.cerowrt.org/flent/drr/10tothe5.svg
>
> after
>
> http://blog.cerowrt.org/flent/drr/newcode.svg

Seeing "only" 250ms worth of delay for 100 stations here was what
kicked off a prior thread, my understanding of a theoretical base
number here would be about 70ms. (?)

...

Adding in mu-mimo to the picture makes my head hurt. My understanding
of how mu-mimo is supposed to work is you have to have accumulated
2-3ms worth of packets for the number of stations you are going to
schedule before it's worthwhile at all.

The stations are going to typically be limited to 1 antenna (most
laptops have 2), I think. So a 4 antenna system *could* send to 4
stations if all have traffic pending... at a cost of a (proposed, I
don't agree with it) 500 usec sounding phase every 10ms. My take on
that is you should only sound when you actually have some potential to
share that many flows to that many stations, sounding being more of an
aspect of rate control, also.

Having only 2 stations that you can mu-mimo to seems like a lose generally.

Based on normal traffic behaviors the stations that could be sent to
varies, and gang scheduling with lots of stations would require even
more soundings...

...

I don't have a lot of hope for mu-mimo, although what I kind of expect
is the work done here will end up marketed as due to that feature in
the wave2 stuff...