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From: Adrian Chadd <adrian@freebsd.org>
To: Viet-Ha Pham <hapvbk@yahoo.co.uk>
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Cc: freebsd-net@freebsd.org, Bernhard Schmidt <bschmidt@freebsd.org>
Subject: Re: Wifi throughput test issue (FreeBSD 8.2)
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Hi,

Hm. Selecting a static rate would mean that you'd end up populating
the rate control statistics with more "wins" for that particular TX
rate, so when you go back to "any", it will choose 54mbit more often.

I suggest looking at the code in
sys/dev/ath/ath_rate/sample/sample.[ch] and see what's going on.  You
can investigate the current statistics by "sysctl
dev.ath.X.sample_stats=1" and then check dmesg.

It sounds like your noise is causing some tx failures to occur at
higher rates, which makes sample back off very quickly. It may not
then sample the higher rates often enough if it sees failures early
on.


Adrian