[Commotion-dev] Throughput advantage to 802.11s support

[Ben West]

Hi All,

I'm happy to read that the Hackday just past went well!  The roadmap wiki
page<https://code.commotionwireless.net/projects/commotion/wiki/Hackday-Roadmap-Notes>looks
pretty dense, although unfortunately my suggestion would be to
increase its density by adding *802.11s support*.  My recent work to
extract Robin/Cloudtrax dashboard stuff into a standalone package was part
of a larger effort to get a modern replacement for a Robin nodes.  And,
this is what is now prompting my recommendation for 802.11s support.

Since I have the expectation of remotely re-flashing all the Robin nodes in
the field sometime soon, I did throughput tests for old vs new to make sure
I wouldn't be deploying a regression.  And, looks like 802.11g adhoc
meshing, even under Attitude Adjustment with the latest atheros drivers, is
*15% to 20% slower* than the ahdemo meshing done by Kamikaze+madwifi based
Robin firmware!  This performance penalty appears to come from the fact
adhoc mode require beacons, while ah-demo does not, hence it not being
supported by the 802.11 standard.  Furthermore, the mac80211 /
compat-wireless radio drivers currently packaged into OpenWRT appear to
enforce a maximum 1000ms interval for such beacons.

For 5.8GHz adhoc, a potential work-around is to use short slot-times as
implemented in this patch:

https://patchwork.kernel.org/patch/1835531/

2.8GHz adhoc, however, must still use long slot times to remain
standards-compliant.  The work-around is that 802.11s meshing can use short
slot times, which this patch implements:

https://patchwork.kernel.org/patch/2050741/

While I do admit that doing speed tests on near-obsolete platforms like
ath5k would normally yield diminishing returns, these slot-time
enhancements should apply just as well to ath9k, too.


-- 
Ben West
http://gowasabi.net
ben at gowasabi.net
314-246-9434
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