Re: IWD 1.27 with brcmfmac not working for roaming

[Denis Kenzior <denkenz@gmail.com>]

Hi Arend,

>>
>> One may question why -67 AP was preferred over -29 one?  We'd need logs to 
>> answer that question.  It could be the -29 one was simply not seen in the scan 
>> results at the time of the initial scan / connection.
> 
> The roaming algorithm is not that intuitive. Roaming and rate selection are not 
> based on signal strength alone. They may look at PER (packet error ratio) to 
> decide. -29 dBm might actually be too strong. I always try to get between -40 
> and -60 dBm.

I was mostly thinking of the initial BSS selection which iwd can influence at 
initial CMD_CONNECT.  iwd sorts APs according to highest expected throughput, 
but that generally means that if 2 APs are identical, the one with better RSSI 
wins.  Still, without logs there's no way of knowing why the lower rssi one was 
picked.

I'm curious: what are the downsides to using RSSI above -40 dBm?

> 
> The nl80211 API actually offer the possibility to affect the BSS selection. The 
> NL80211_CMD_CONNECT command can have the attribute NL80211_ATTR_BSS_SELECT for 
> that [2]. When not provided the firmware will obviously use its default behavior 
> whatever that is. Not sure if IWD or wpa_supplicant support this, but I am 
> fairly sure brcmfmac supports it. However I do not know if it also applies to 
> roaming.

iwd does not.  Doesn't look like wpa_s does either.

Regards,
-Denis