Roaming questions

[Alexander Ganslandt <alexanga@axis.com>]

Hello,

I'm looking into different roaming solutions and currently evaluating 
iwd, which seems promising so far! My use-case is a device live 
streaming video while moving around large areas, and the goal is to do 
so without hiccups in the live stream. I have a few questions:

Looking at station_roam_failed(), it will schedule a full scan if the 
previous limited scan failed to find a better BSS to roam to. A full 
scan on our chip takes about 7 seconds, which is often enough time for 
the signal to get low enough to deauthenticate the station when you're 
moving. It seems to me that a better approach would be to schedule a 
scan for either the "known frequencies", or all non-DFS frequencies 
(since passive scanning takes extra time) or some other popular group of 
frequencies that won't take long to scan. If we're lucky there is a good 
BSS in that scan, otherwise we schedule a scan for the rest of the 
frequencies. In the worst case, this should be identical to a full scan 
with minor extra overhead. Do you have any thoughts about this from your 
side? Is it something that could be accepted into iwd or could it cause 
issues for other use-cases?

Another question is about the "CriticalRoamThreshold". There seems to be 
a config for this and some functions for lowering and raising the roam 
threshold, but I can't see that they're called from anywhere? It seems 
to me that only "RoamThreshold" is used, or am I missing something? 
There's also a hardcoded delay of 5 seconds from the point where the 
roam threshold is passed before a scan is started, is that just a 
"hysteresis" to not immediately start a scan if the signal temporarily 
drops, or does it have some other function?

Thanks in advance!

Best regards,
Alexander