[wireless-regdb] wireless-regdb: update CA rules for 5600 - 5650 mHz

[Zefir Kurtisi]

On 07/07/2015 10:11 PM, Seth Forshee wrote:
> On Mon, Jul 06, 2015 at 04:40:56PM +0200, Zefir Kurtisi wrote:
>> On 07/06/2015 03:27 PM, Seth Forshee wrote:
>>> On Fri, Jul 03, 2015 at 05:01:20PM +0200, Zefir Kurtisi wrote:
>>>> On 07/03/2015 04:20 PM, Wei Zhong wrote:
>>>> [...]
>>>> From your other post:
>>>>>>     >
>>>>>>     >  -       (5490 - 5730 @ 160), (24), DFS
>>>>>>     >  +       (5490 - 5590 @ 80), (24), DFS
>>>>>>
>>>>>>     I agree. 5590 is more strict than 5600.
>>>>>>
>>>>>>  
>>>>>> On a second thought,  5590 implies channel 116 can't have 40MHz. I think that is
>>>>>> still allowed per regulation.
>>>>>>
>>>>>>
>>>>
>>>> No, channel 116 is not usable for HT40 if weather radar channels are disabled,
>>>> since it can only be combined with channel 120 and that one partially falls into
>>>> the restricted range.
>>>
>>> It's not necessary to restrict the band down to 5590 or break out the
>>> rule for channel 116 separately, the software is smart enough to work
>>> out what's allowed based on the original rule Wei supplied for 5490-5600
>>> MHz. In fact that rule exactly matches what we used to have in db.txt
>>> for the US prior to the TDWR restrictions being lifted.
>>>
>>
>> Yes, the SW is smart and sane enough to extract the limitations even if they are
>> defined less restrictive than required. Which raises the general question of what
>> needs to be defined as rule and what can be relied on to be handled correctly by
>> the SW.
>>
>> Example: why do we need to bother about the max-bw parameter for a rule at all? We
>> know there is no 160MHz channel within 5490 and 5600, as does the SW. If we wrote
>> (5490 - 5600 @ 160) instead of (5490 - 5600 @ 80), nothing would change.
>>
>> To me it sounds not fully consistent to explicitly limit max-bw while relying on
>> SW to sanitize frequency ranges. Not that it really matters in practice, but it
>> has a potential to simplify the rules (i.e. provide max-bw parameter only if the
>> according country defines restrictions and leave SW to handle it otherwise).
> 
> The database is just about capturing the rules of the various regulatory
> bodies. I don't know off the top of my head if there are any cases today
> where the maximum allowed badwidth in a given range is less than the
> maximum possible bandwidth in that range, but it certainly doesn't seem
> impossible. So I wouldn't call it inconsistent.
> 
> We aren't expecting the kernel to "sanitize" the frequency ranges
> either. It doesn't rely on the regdb to tell it which frequencies are
> legitimate.
> 
> Seth
> 
Sure and understood. Still I see room for ambiguity.

My claim is that in its current state the regdb does not exactly formalize the
limitations given by regulatory for a simple reason: it uses channel semantics
where it should only handle frequency ranges. Take the discussed rules for CA at
hand: while the linked document considers frequencies from 5150 to 5350, the
according rule for CA is defined as (5170 - 5250 @ 80). Why 5170 instead of 5150?
Because we know there is no channel defined below 5170 - but why do we need to
embed this information as a rule when it is already handled by SW?

In the current regdb, both semantics are used, e.g. UA (5150-5350) vs. CA
(5170-5250) or ES (5470-5725) vs. FI (5490-5710)).

This might sound like an irrelevant difference, but here is why it matters: the
above mentioned rules for ES and FI would give the same channel lists - as long as
we think in HT20 and HT40. But only ES gives access to 10 and 5MHz operation on
channel 144.


My bottom line is: regulatory rules must not contain channel semantics - this is
done by the SW. Rules must be a literal formalization of the country's regulatory,
which always uses frequency ranges within defined band edges.


Sorry for this going off-topic. It has nothing to do with the changes proposed by
Wei, but is more about something to keep in mind when considering upcoming support
for narrow band channels at band edges.



Thanks,
Zefir