Atheros Driver, changing ACK timeout?

Is there a way to change the ACK timeout for the atheros driver? 

I want to do some long distance links ( eg, 30km + ) and the default ACK 
timeout is not long enough for the RF to get there and back. As a result, 
DUP packets occur when pinging, and in general performance is horrid. 

Ive looked thru the ath driver stuff, and I could not see anything relating 
to changing the ACK timeout.. perhaps it is in the HAL? 

Any ideas? I dont want to use staros or such like ( which can alter the ACK 
timeout ) 

Thanks 

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