On Aug 09, 2010, at 05:10 AM, Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org> wrote:
I've put a modified proposal here:
http://www.radiotap.org/suggested-fields/MCS-proposal2

I also added some a-MPDU status bits. They might not quite belong to
HT/MCS only, but they will typically be used with that and everything
else can indeed be masked out if really necessary

Thoughts?
 
I think the proposal2 looks great. The info mask is great for both tx specification and rx capture.

Adding single-bit fields has the advantage that they can be left out of
the header when, eg., you just know the MCS, but you don't know whether
it was 20 or 40 MHz (which, incidentally, is quite useless).
 
I think the mask for 20/40 is useful when using radiotap headers to do packet transmit. Some test setups only need the raw 802.11 format and possibly some HT modulation information, but may not care about 20/40. For instance, some test script may inject a packet for a STA to send to its associated AP and specify MCS 0 (for robustness) but leave the 20/40 info out so that the driver just sends at whatever the association has set up. Likewise, the test script may leave the shortGI/LDCP info unspecified.

-Bill