Re: Force use of 5GHz band

[James Prestwood <prestwoj@gmail.com>]

Hi Alvin,

On 9/21/23 7:21 AM, Alvin Šipraga wrote:
> On Thu, Sep 14, 2023 at 11:06:18AM -0700, James Prestwood wrote:
>> Hi Jonas,
>>
>> On 9/14/23 10:44 AM, Jonas Große Sundrup wrote:
>>> Hi,
>>>
>>> is there a way to force iwd to use the 5GHz flavor of a specific wifi?
>>> I am aware of BandModifier5GHz, but even with setting this to 1000 I
>>> still end up on the 2.5GHz band. That band specifically, however, is
>>> unfortunately suspect for some stability issues I'm facing and hence I
>>> would like to force iwd onto the 5GHz band to see if the problems still
>>> occur. That proves to be difficult, of course, if iwd is picking the
>>> 2.5GHz band…
>>>
>>> Even though I do see that iwd probably has the better insight into band
>>> stability from a signal-strength point of view, any chance of
>>> overruling iwd's internal mechanisms here? (Or should I just crank up
>>> BandModifier5GHz by a couple of magnitudes?)
>>
>> All we have now is BandModifier5GHz which is multiplied by the computed
>> rank. The stock rank is based mainly on a data rate computation which is
>> theoretical, but uses capabilities and signal strength to estimate.
>>
>> 1000 is pretty high, so essentially your 2.4GHz BSS's would need to have a
>> rank 1000x larger than the 5Ghz ones. So either 5ghz is incredibly low
>> signal, doesn't support HT/VHT, or maybe the IEs are malformed so the data
>> rate isn't being computed correctly e.g. (defaulting to basic rates).
> 
> We had a request at the company to disable 2.4 GHz entirely as well, but I did
> not want to completely disable it as some customers may not even have 5 GHz
> infrastructure. My colleague Pedro drafted a patch which allows for the internal
> BSS ranking to be normalized according to a required bitrate, so that 5 GHz
> networks do not always out-compete 2.4 GHz networks. We found this worked well
> together with the BandModifier option.

Effectively yes this would work, though its not a guarantee to disable 
2.4 (although the option isn't named as such so its not deceiving anyone).

I personally don't take issue to adding such an option, but FWIW I'm 
currently working on a way to explicitly disable a band entirely. This 
is more complicated due to IWD's scanning logic but its better in that 
it prevents IWD from scanning on those bands as well as connecting.

Thanks,
James

> 
> I have asked him to send the patch to the list, so please take a look. Might be
> something of interest for upstream.
> 
> Kind regards,
> Alvin