Re: MCS field - STBC and Ness

[Wojciech Dubowik <Wojciech.Dubowik-ASv44eHyqLVBDgjK7y7TUQ@public.gmane.org>]

Hello,
   Atheros families 9002 and 9003 support only one STBC stream. I think 
I have seen a Ralink chipset
which supports 2 stream at least on receive. I am not sure about transmiter.
On Atheros you get STBC flag and two bits Ness field for received 
packets but In the patch there is is only flag reading but you could add 
Ness yourself it's only two bits left from the flag.

Myself I have tested only one stream but I did it only by looking 
whether other party is setting rx descriptor bit. I don't know how it 
looks "in the air". I trust manufacturer;o)

It's true that only one bit was allocated in wireshark extension. Should 
have been two but it's a bit waste. My proposal wasn't accepted but in 
the end I think it's ok becasue I have managed to get all info in vendor 
namesapes where I can do what I want.

Br,
Wojtek

>
> I am writing a Wireshark extension to visualise 802.11 frames on a 
> timeline. In order to do this I need to be able to calculate the 
> duration from start of TX to end of TX for each frame.
>
> For 802.11n I need to know the number of HT-DLTF and HT-ELTF training 
> symbols that are sent in the header - I have everything else needed to 
> calculate the duration. Given the MCS and the STBC and the Ness 
> (Number of extension spatial streams) I can calculate the number of 
> training symbols.
>
> Both STBC and Ness are encoded in the HT-SIG transmitted at the start 
> of each HT frame.
>
> The current proposal (or has it not yet been accepted?) for STBC 
> allocates just 1 bit - but the STBC field can have values or 0, 1 or 2.
>
> Ness can be 0-3, so the remaining 2 bits could be allocated to Ness, 
> but this does not solve the problem of how to encode the modes with 2 
> spatial streams and 2 additional streams for STBC.
>
> Does anyone know what current hardware supports - STBC values or 
> 0,1,2? Ness values of 0-3?
>
> Any suggestions for how to convey these
>
> Simon