Re: MCS field - STBC and Ness

[Simon Barber <simon-vp0mx6+5gkqFX2APIN6yfw@public.gmane.org>]

Hi Johannes & Wojciech,

My work has been on hold, but has recently come off hold. I'm getting 
the patches together. As I rebase my work onto the current wireshark 
trunk I've found a simpler implementation of STBC has been applied by 
Wojciech. My proposal extends the STBC from his implemented 1 bit to 
the full 2 bits allowed in the 11n specification, and also includes 2 
bits of Ness. I've posted an ieee80211 patch, and an intel driver patch 
(both attached to the proposed radiotap extension page). l'll post a 
wireshark patch shortly to start the comment period.

Simon


On Thu 05 Jul 2012 02:12:30 AM PDT, Johannes Berg wrote:
> On Fri, 2012-05-11 at 21:27 -0700, Simon Barber wrote:
>> Another slight tweak - I think STBC is more commonly used than Ness (as
>> witnessed by Wojciech's interest), so give STBC the simpler encoding. I
>> believe Ness is used for beamforming soundings.
>>
>> Spec would look like this:
>>
>> known    definition
>> 0x01    bandwidth
>> 0x02    MCS index known (in mcs part of the field)
>> 0x04    guard interval
>> 0x08    HT format
>> 0x10    FEC type
>> 0x20    STBC
>> 0x40    Ness - Number of extension spatial streams is known
>> 0x80    Ness2 - bit 1 (MSB) of Number of extension spatial streams.
>>
>> The flags field is any combination of the following:
>>
>> flag    definition
>> 0x03    bandwidth - 0: 20, 1: 40, 2: 20L, 3: 20U
>> 0x04    guard interval - 0: long GI, 1: short GI
>> 0x08    HT format - 0: mixed, 1: greenfield
>> 0x10    FEC type - 0: BCC, 1: LDPC
>> 0x60    STBC - 0, 1 or 2: number of STBC streams
>> 0x80    Ness - bit 0 (LSB) of Number of extension spatial streams.
>>
>> What should I do to advance this as an approved radiotap extension?
>
> I suppose you already have patches for wireshark for this? I can help
> you out with a patch for the Linux kernel as an example producer of
> this, and then I think just repost it to the list again to leave some
> more discussion time.
>
> johannes
>