From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Barber Subject: Re: [RFC] VHT fields Date: Mon, 18 Jun 2012 11:32:06 -0700 Message-ID: <4FDF7426.2050202@superduper.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Sender: radiotap-owner-sUITvd46vNxg9hUCZPvPmw@public.gmane.org To: Alwin Beukers Cc: "radiotap-sUITvd46vNxg9hUCZPvPmw@public.gmane.org" List-Id: radiotap@radiotap.org I'm not very familar with 11ac - but does this information together=20 with the packet data give you enough to calculate precisely the=20 packet's duration in time? Are there any duration fields, as there are=20 in 11n that might be useful? Simon On Fri 15 Jun 2012 01:15:26 AM PDT, Alwin Beukers wrote: >> On Tue, 2012-06-12 at 15:05 +0000, Alwin Beukers wrote: >>> Hi everyone, >>> >>> This is a proposal for adding support for 802.11ac. Four fields were >> added to the suggested-fields section: >>> >>> http://www.radiotap.org/suggested-fields/SU_VHT >>> http://www.radiotap.org/suggested-fields/MU_VHT >>> http://www.radiotap.org/suggested-fields/GROUP_ID >>> http://www.radiotap.org/suggested-fields/PARTIAL_AID >>> >>> A Wireshark patch for parsing SU_VHT, GROUP_ID and PARTIAL_AID is >> attached. >> >> What's the reason for splitting it up? > > Johannes, > > The reason for splitting it up is to avoid extra overhead related to MU= -MIMO > when describing VHT SU PPDUs. The separation is based on the different = PLCP > header formats (VHT-SIG-A1/A2/B) for SU and MU PPDUs: > > SU PPDUs: > - Only one NSTS, MCS and Coding field. > - Partial AID identifies recipient > - Group ID is always 0 (addressed to AP/mesh STA) or 63 (addressed to S= TA) > > MU PPDUs: > - NSTS, MCS and Coding fields for up to four users > - Partial AID is not applicable > - Group ID is 1..62 > > All fields common to both SU and MU are in the SU_VHT field. The MU_VHT= field > contains additional information for MU PPDUs. The GROUP_ID and PARTIAL_= AID > fields have varying value or applicability. > > So for SU PPDUs you would likely have SU_VHT and PARTIAL_AID fields, an= d maybe > a GROUP_ID field (for SU the GROUP_ID field only provides direction inf= o that > could also be determined from PARTIAL_AID and/or MAC header). > For MU PPDUs you would have SU_VHT (for the common fields as well as > NSTS/MCS/Coding for the first user), MU_VHT (for NSTS/MCS/Coding for > additional users), and GROUP_ID. > > By combining fields we can reduce complexity at the expense of some inc= reased > overhead, what are your thoughts on his? Also, I was wondering if we ne= ed all > of the 'known' flags in SU_VHT. The MCS field (after which SU_VHT was m= odeled) > also has these, but I don=E2=80=99t know the rationale behind them. Can= one assume a > driver has full access to the PLCP header and thus can fill in most of = fields > in the SU_VHT field? > > Thanks, > Alwin > >> johannes >> > >