Re: Conflicting definitions between the radiotap HE PPDU format field and 802.11axD2

On Fri, Jan 26, 2018 at 2:42 AM, Johannes Berg
<[email protected]> wrote:
> Hi Richard,
>
> Sorry, it was too late last night to think clearly about this :-)
>
>> It seems that 802.11ax D2 defines, in Table 28-18, in HE-SIG-A, a
>> 1-bit format fields (B0) that takes the values 0 for HE TB PPDUs and 1
>> for HE SU PPDUs and that is reserved for others but must be set to 1.
>
> Correct. There are four PPDU types:
>  * HE SU PPDU
>  * HE ER SU PPDU
>  * HE TB PPDU
>  * HE MU PPDU
>
> The format bit distinguishes between TB and SU PPDUs. You'll note that
> this bit doesn't even exist in an MU PPDU.
>
> The actual differentiation between the four types is done in another
> way, I'm not entirely sure right now how, you can see it in 28.3.21, in
> particular in Figure 28-59.
>
> Basically what I decided to expose in radiotap is the HE sub-formats as
> per the RXVECTOR (and maybe TXVECTOR, if we use it for TX) parameters.
>
>> However, what seems to be the equivalent radiotap he ppdu format field
>> is 2 bits and uses different values.
>>
>> Have I misunderstood? What is the resolution of this?
>
> Does the above resolve this for you?

I think so. Someone who is involved with the spec also pointed out
that some of those bits are generated based on other criteria.

-- 
Regards,
Richard Sharpe
(何以解憂？唯有杜康。--曹操)