configuration of power safe mode in ah-hoc networks

[silvia lafuente]

Hi,
I am studying the power safe mode (PSM) in ad-hoc networks. I've read in 
several articles and books that there is a paremeter called ATIM window 
that you need to set, so the stations wait that window of time (before 
going to an inactive state) to see if some other station has pendant 
packets for him (this information comes in a ATIM frame).
If I do "iwlist wlan0 scan", in the results, sometimes comes an extra 
field called "atim", but is only for reading.
I am using both hostap and madwifi drivers (I have two different chipset 
cards), and I thought it might be one of the parameters that you can 
modify through iwpriv, but there isn't any with a name that can resemble 
atim window in any of the drivers.
I have been asking in both drivers mailing lists  and nobody has 
answered me yet, so I am writing to this list to see if anybody using 
wireless has used this features of the standard.
How can I set the atim window? Or in another words, is it possible to 
set it, or is something that the driver calculates from the beacon 
interval when power management is on?
Besides setting this parameter, I understand that I have to set the 
listen interval as in the infraestructure case (ie. iwconfig wlan0 power 
period n). Is it like this, or on the contrary the stations have to get 
active every beacon interval?
Thanks for your help.
Silvia