After reading some old discussions on this list, it's still not clear to me at which rate are beacons and ACK frames sent.

Some say that Beacons are sent at lowest rate, some others that beacons are sent at the highest "basic rate"  (24Mbps for 11a and 11g). As for ACKs or CTSs, some say they are sent at the highest rate in
 the basic rate set *or* the highest rate that is less than or equal to the rate of the frame that causes them to be sent, while other state that they are sent at the exact same rate of the preceding frame.

Can anyone give a final answer to that?

Thank you!