Deco M9 select source signal
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I've just purchased two more M9's to go with the two i currently have and the one in my office is choosing to connect to the main device which is further awy than one in the middle it subsequently tells me i have a poor wifi connection.
I thought the whole point was it optimsed hte system and could tell me where to locate i don't see this happening at all.
After few experiments with satellite M5 Deco, I suspect I know where the issue might be. First, my network layout: M9 Plus Main Deco in the middle of the first floor, M9 Plus Satellite Deco in the middle of the second floor between bedrooms, both connect nicely with each other through wireless backhaul.
I have got new M5 that I plan to place in the basement, but not in a hurry so used it as a test unit.
I found the place on the second floor in the bedroom where the 5Ghz signal from Main Deco is the weakest, used WiFi analyzer on smartphone at that same place and this is what I've got:
Placed M5 there and turned it on, made it join the mesh, and it connected to Main Deco M9 - successfully. Logically, it should have connected to Satellite Deco M9, but it did not.
Connection didn't stay good for long: LED started to go Red, Yellow, Red - all symptoms of unhealthy situation. The M5 device is not defective - after tests I took it to the basement where it will belong, wired with Ethernet and it runs fine.
So, I am assuming the logic with which new (or restarted) Deco joins existent Deco mesh is:
IF Signal to Main Deco is good (above threshold)
THEN Always Connect to Main Deco
ELSE look for other Decos to connect to
Same goes for backhaul connectivity
IF Signal to Main Deco is good (above threshold)
THEN keep LED Green
ELSE switch LED to Red and do something (reboot, restart?)
This works fine with single band, and is solid logic, because with good signal you really want Satellite Decos hook to Main Deco only. I suspect the logic was copied from when WiFi networking did only run on 2.4GHz, or used just single band for backhaul.
The problem: there are two WiFi bands M5 and M9 work with, and one (5Ghz) could often be way weaker than another, especially in houses with walls and ceilings between devices.
So, if Satellite Deco device decision to connect to only considers 2.4GHz band, it'll choose Main Deco in very many cases, because Decos provide really good 2.4GHz coverage.
Meanwhile, if backhaul needs both 2.4GHz and 5GHz bands to operate, that will keep randomly failing because 5 GHz will be weak, or backhaul will be slow because it'll stick with 2.4GHz.
Problem manifestation conditions:
Must have more than 2 Decos in mesh.
Out of all Decos, more than one satellite Deco must be not ethernet cable wired. I.e., two or more satellite Decos use WiFi backhaul.
Main Deco is not located in between other Decos.
Which means, not every Deco mesh user will experience that issue. For example, I used to have 2-Deco layout, no problem for me. Now I have 3-Deco layout, but one device is wired so I won't see that problem.
Potential Solutions:
1. Allowing user select default Deco to which Satellite Deco will connect is great configuration option, but this must be buried in Advanced settings, because it could easy create a bigger mess with more support requests. This also might need longer time to implement, because it requires change in UI and in code logic in multiple places
2. TP-Link Support, would you please pass request to developers to review how selection by new (or restarted) dual-band Deco to which Deco to connect in existent Deco mesh is performed. For Decos operating on dual band, signal strength of both bands must be good (above their thresholds) to use Main Deco. This might be an easy code modification, if flagged as bugfix it might be implemented and deployed sooner than option for manual Deco selection.
Request for more info:
TP-Link Support, you keep saying "the signal strength the satellite Deco obtained from the main Deco is good enough, or it does not reach the threshold value" . Please ask your developers what the threshold is for each of two bands, and share the value(s) with us. There is enough technologically smart people in these forums to check if Decos follow that threshold trigger and, perhaps, people can find better spot for their Decos if they know what the threshold is and for which band.
I also do suspect that threshold will be just for 2.4GHz, because -82 dBm on 5GHz seem to be quite weak to consider it acceptable, yet my M5 selects Main Deco to connect to.
