Re: [RFC] VHT fields

[Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>]

On Fri, 2012-07-27 at 14:41 +0000, Alwin Beukers wrote:
> > One question on this:
> > 
> > "Note: for receive capture, the total bandwidth of the transmitter is
> > not generally known, so the bandwidth will only be recorded as 20, 40,
> > 80, or 160, with the Channel field indicating the transmission center
> > frequency."
> > 
> > I'm not sure that's generally true, though it points out something that
> > we may need to define in more detail: we have (in Linux at least) always
> > had the Channel field indicate the control channel, not the transmission
> > center frequency.
> 
> I think indicating the control channel wouldn't work very well in this case, 
> especially for >40MHz bandwidths.
> 
> How do you feel about extending [X]Channel with a flag that indicates 
> we're specifying transmission center frequency?

I don't think that'd be a good idea, it wouldn't be backward compatible.
We're just discussing for Linux how to specify the channel parameters
and we need to consider 80+80 as well. Maybe these discussions should
cross-pollinate.

I see two basic options:
 * continue what we do now, and specify the control channel & type
   around it (40+/40+,...)
   + this is how linux works now
   - many many channel types (4 for 80 MHz, 8 for 160 MHz)
   - doesn't handle 80+80
 * specify the center frequency, width & control channel offset
   + more aligned with the spec (?)
   - requires backward compat handling
   - doesn't handle 80+80

johannes