From: Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
To: radiotap-S783fYmB3Ccdnm+yROfE0A@public.gmane.org
Subject: Re: [RFC] VHT MU-MIMO correction
Date: Fri, 04 Dec 2015 11:48:40 +0100 [thread overview]
Message-ID: <1449226120.2574.0.camel@sipsolutions.net> (raw)
In-Reply-To: <1445418906.4558.7.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
I guess this has passed a three-week minimum review time - bump, I'll
make those changes unless I hear objections within ~a week?
johannes
On Wed, 2015-10-21 at 11:15 +0200, Johannes Berg wrote:
> Hi,
>
> As we're looking into MU-MIMO again, we found some issue with the way
> the VHT radiotap field is defined. The issue is the following: the VHT
> SIG-A field defines the NSTS (NSS) for each user, and it would be good
> to have that shown. However, radiotap ties the validity of the MCS to
> the existence of the NSS, which is incorrect.
>
> Therefore, I suggest to make the following edit:
>
> Change this language:
>
> If the NSS field for a user is zero, the user is not present and
> the MCS and coding (in the coding field) associated with that user
> are not valid. For SU PPDUs, only the first user will have a
> nonzero NSS field.
>
> To read:
>
> If the NSS field for a user is zero, the user is not present and
> the MCS and coding (in the coding field) associated with that user
> are not valid. If the NSS field for a user is non-zero, but the MCS
> is not known (for example due to receiving only data for a single
> user), the MCS shall be set to 15.
> For SU PPDUs, only the first user will have a nonzero NSS field.
>
>
> The coding should be known for all, since it's also part of VHT-SIG-A,
> so I'm not suggesting to add validity flags for that. Does anyone think
> that is necessary?
>
> A wireshark patch won't really be necessary since it will already
> display the MCS as "15 (invalid)" in this case, which seems reasonable
> though it could be changed to just "not known" instead.
>
> johannes
>
next prev parent reply other threads:[~2015-12-04 10:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-21 9:15 [RFC] VHT MU-MIMO correction Johannes Berg
[not found] ` <1445418906.4558.7.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
2015-12-04 10:48 ` Johannes Berg [this message]
[not found] ` <1449226120.2574.0.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
2016-01-20 12:44 ` Johannes Berg
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