forcing fixed client tx rate

Is this possible to force CLIENT TX RATE to fixed value eg. 2 of 5.5Mbps form AP side (MT 2.9.34 on RB112 + Senao nmp-8602+). Client cards TX rate option is set to "Auto’.
This would be very important feature because output power of client cards is very weak in higher tx rates so by putting it to low values I can force theme to use more power


Thanks
Marek

Marek, you need to set ‘rate-set=configured’ for the wireless interface, and modify the following settings,
http://www.mikrotik.com/testdocs/ros/2.9/interface/wireless.php?permalink=0.12793517950904876

Thank you sergejs for your answer but I know how to change AP TX Rate but I don’t know how to set remotly CLIENT TX RATE (transmiting speed of client card to the AP). I can set it by selecting right option in client card driver, but every one in my network has this options set to ‘Auto’ and I don’t want to go to every user to change this…
I hope I made myself clear…

Now I noticed that setting fixed Tx rate in client card driver seems resulting with no effect! It worked with my old one AP (Linksys WRT54GS with OpenWrt software).
Moreover the client signal levels seen by AP was stronger with old one!! what is going on??? Linksys has rather medium quality radio module (Broadcom 2050) but worked better than MT with top grade Atheros module (senao nmp-8602+ 400mW - Atheros 5006X).
Is this possible that there is some incompatibility with DC shorted antenna which I use? (horizontal polarity)