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

Toke Høiland-Jørgensen toke at toke.dk
Wed May 11 09:45:14 EDT 2016

Luca Muscariello <luca.muscariello at gmail.com> writes:

> Toke,
> I'd suggest to add this in you list of references:
> Godfrey Tan and John Guttag, Time-based fairness improves performance in multi-rate WLANs. In Proc of USENIX 2004
> https://www.usenix.org/legacy/publications/library/proceedings/usenix04/tech/general/full_papers/tan/tan.pdf

Awesome, was not aware of that. Thanks!

> It's worth having a look to the APware project for freeBSD and Godfrey Tan PhD thesis at MIT.
> http://nms.csail.mit.edu/projects/apware/

Hmm, that link is not working for me right now; will try again later.

> this work predates 802.11n and aggregation.

Yeah, I'm aware that there is a lot of stuff that predates 802.11n. In
fact the article I linked (Kim et al) is the only one I've found that
talks about 802.11n. We also had some people at my uni doing stuff with

> Ten years ago I played with SFQ and madwifi for 802.11g to get max-min
> time fairness (and so proportional rate fairness) with excellent
> results. The hacking I made was based on using time quanta instead of
> bytes. Which required me to get the current PHY rates (AP to all
> STAtions) and dynamically compute/update SFQ time quanta.

Do you happen to recall what precision you achieved or how much the
precision was really important? Several papers seem to assume that very
high precision is not terribly important since it all evens out in the
end, and I can see how that could be true; but would like to have it
confirmed :)

> It's surprising that 802.11 standard never considered time fairness in
> the EDCF. A reason might be the time fairness might be enforced using
> the PCF.

Might be. Might also be that no one thought to measure for that? A lot
of vendors seem to only test single-station raw throughput...

Are you aware of any open source 802.11 stuff that uses PCF at all?

> IMO, It's a very good topic.
> Thanks for bringing this up.

You're very welcome! ;)


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