Fixing the Tx rate

[Yariv Bash]

Hi guys,

I'm trying to fix (as in fixate or choose only one) the Tx rate of a TP
LINK TL-WN722N device, containing the Atheros AR9271 chip.
Specifically I want it fixed on a low rate - I want to play with the
1,2,5.5 and 6 MBPS rates.
Yes, 6 belongs to 802.11g, I know :)

I've tried variations of the:
sudo iw dev wlan0 set bitrates legacy-2.4 6
Command, while the device is down, up, configured and what not, and
unfortunately, this does not work too well - The device still falls to
1MBit when the connection becomes unstable, and almost never returns to a
higher rate (or takes a lot of time)

I'm working with a raspberry pi, already compiled the ath9k_htc driver (FW
Version 1.4), and I already have 2 raspberry pi's talking directly - one as
the host of course (hostapd 2.3) each with its own WN722N device.
Oh, and I'm working with the Minstrel rate algorithm, but could of course
change to PID if it helps.

One thing I thought about was that 1MBit is a default fallback with
minstrel, so it might be hardwired. But again, even when the link shows
really good reception (-40-50dBm), the link stays at 1MBPS after it falls
there on a bad connection.

I'm considering tweaking the firmware code to just one rate, not sure if
this is the best option, but would love any directions as to where in the
code that can be done, or what am I doing wrong...

Many thanks in advance,
Yariv.