Allowing station to over-ride default VHT-oper element?

Allowing station to over-ride default VHT-oper element?

[Ben Greear]

I'm trying to figure out how to make a VHT station with hardware capable
of 80Mhz width instead force itself to advertise/use just 40Mhz width,
but still support VHT.

Similar to how the VHT-capabilities overrides works, but for
VHT-operation.

First, is this even a valid thing to do, or does VHT imply
that stations are always available to do 80Mhz?

And second, if it is a valid thing to do, any hints on a
proper way to go about this.  I'm getting a bit tangled in
the code trying to figure out where to apply any overloads
properly.

Possibly in ieee80211_determine_chantype?

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Allowing station to over-ride default VHT-oper element?

[Johannes Berg]

On Wed, 2015-06-10 at 12:29 -0700, Ben Greear wrote:

> First, is this even a valid thing to do, or does VHT imply
> that stations are always available to do 80Mhz?

According to the spec, a VHT STA must support 80 MHz:

802.11ac-2013, 22.1.1:

	A VHT STA shall support the following features:
		[...]
		- 20 MHz, 40 MHz, and 80 MHz channel widths

Consequently, there's no bit indicating whether or not 80 MHz bandwidth
is supported (like there is, for VHT, indicating 40 MHz is supported or
not.)

Also it is invalid to advertise a VHT capabilities IE and an HT
capabilities IE without 40 MHz.

johannes

Re: Allowing station to over-ride default VHT-oper element?

[Ben Greear]

On 06/10/2015 12:55 PM, Johannes Berg wrote:
> On Wed, 2015-06-10 at 12:29 -0700, Ben Greear wrote:
> 
>> First, is this even a valid thing to do, or does VHT imply
>> that stations are always available to do 80Mhz?
> 
> According to the spec, a VHT STA must support 80 MHz:
> 
> 802.11ac-2013, 22.1.1:
> 
> 	A VHT STA shall support the following features:
> 		[...]
> 		- 20 MHz, 40 MHz, and 80 MHz channel widths
> 
> Consequently, there's no bit indicating whether or not 80 MHz bandwidth
> is supported (like there is, for VHT, indicating 40 MHz is supported or
> not.)
> 
> Also it is invalid to advertise a VHT capabilities IE and an HT
> capabilities IE without 40 MHz.

Ok, thanks for that..one less piece of work for me to do :)

>From what I can tell, it *IS* ok to have an AP do VHT on 40Mhz though?

Thanks,
Ben



-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: Allowing station to over-ride default VHT-oper element?

[Johannes Berg]

On Wed, 2015-06-10 at 12:58 -0700, Ben Greear wrote:

> Ok, thanks for that..one less piece of work for me to do :)
> 
> From what I can tell, it *IS* ok to have an AP do VHT on 40Mhz though?

It may even be compelled to do so by the spec, since there could be
overlapping networks (see 10.39.2.)

johannes