How to change rate control algorithm in MadWifi SVN

Hi,

How do I enable different rate control algorithms in MadWifi. Im 
noticing a lot of

  kernel: ath_rate_sample: ath_rate_ctl_reset 00:00:00:00:00:00 no rates 
(fixed 4294967295)

messages in the kernel logs. Does anyone know what this could be caused 
due to and if changing the rate control algorithm will help. Im using a 
modified version of  MadWifi from SVN.

Thanks
regards,
Aditya Bhave

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