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

[Dave Taht <dave.taht@gmail.com>]

On Wed, May 11, 2016 at 6:45 AM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> Luca Muscariello <luca.muscariello@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.

http://web.archive.org/web/20150911055537/http://nms.csail.mit.edu/projects/apware/


>> 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
> 802.11g.
>
>> 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! ;)
>
> -Toke
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-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org