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Ok, sorry, now I understand, we are talking about the Ack Policy in QoS Control field in the QoS Data frames. If it is set to No Ack as 802.11-2007 (sorry I don't have the 2012 edition) 9.11 then Ack is not expected. That's cool but I wonder if someone is using this feature and if someone has tried it and checked if the receiver has really not sent an ACK after receiving such a frame.

I haven't played with this feature, either -- it would be cool to see how much overhead it reduces and how it affects call quality in different environments. In clean air I'm sure it helps a lot, but without L2 retransmissions in a noisy environments I bet call quality actually suffers.

I have tested QOS "No Ack" policy with Ralink Chipset with the Ralink Supplicant in Windows Laptops and the station does not Ack for the DATA frames. sent from the AP's. I think all the other chipsets (Atheros,BRCM etc) should also support this since it's pass criteria for getting WFA certification for 11n. For some chipsets "Ack policy" is in Driver level settings, or in the registry(Windows)

By disabling the STA's Ack policy means that the STA will not Acknowledge to any data frames for that particular access category which implies to AP as "AP need not re-transmit the DATA frame if does not receive an ACK" If the AP's re transmission is disabled or the STA Ack policy is disabled , both should yield the same results. I don't see any difference.

I agree that the net effect would be the same. However, if the AP determines that ACKs are not required, then the amount of time reserved on the medium can be lower, as it won't have to reserve time for the ACK. I have to be honest, I haven't actually tested this.