@Elbetosan 

"There is no setting where you can determine a fixed band for a device… it should have, though… it would solve my problem."

Depending on type of device, it could be possible to force device use specific band. If it is Windows desktop or laptop or latest model Surface Pro tablet, its WiFi device driver may have the setting to force WiFi on 5GHz or on 2.4GHz only.

Also, it is possible to split 5GHz and 2.4GHz bands in Deco, by utilizing both Main and Guest networks. See screenshot below from my home Deco configuration. Devices I want to always stay on 5GHz I connect to Main Network, devices I need to use 2.4GHz I connect to Guest network.

Alexandre. wrote

@Elbetosan 

 

Depending on type of device, it could be possible to force device use specific band. If it is Windows desktop or laptop or latest model Surface Pro tablet, its WiFi device driver may have the setting to force WiFi on 5GHz or on 2.4GHz only.

 

Also, it is possible to split 5GHz and 2.4GHz bands in Deco, by utilizing both Main and Guest networks. See screenshot below from my home Deco configuration. Devices I want to always stay on 5GHz I connect to Main Network, devices I need to use 2.4GHz I connect to Guest network.

 

 

-------------- 

My son's computer is an old Windows desktop with a D-Link AC dual-band nano USB adapter. It's plug-and-play but even so I downloaded the D-Link application to see if there would be a way to keep it fixed at 5GHz, but there wasn't. That's why I bought another Deco.

I appreciate your solution but now that I have spent a good amount of money on the M9 Plus (they're expensive where I live), I kinda have to get it to work...

Cheers.

@Elbetosan 

I run Deco mesh which is a mix of M9 and M5, I think I may have useful suggestion for you to make your mesh work, if you decided to keep M9.

The mistake you made is to place new Satellite M5 (old Main Deco) in your son's room. I am assuming that Satellite M5 is connected to Main M9 by WiFi. Turn M5 in your son's room off for now (you may be able to reuse it later). If you need longer explanation why it is not the right place, just ask. I don't want to expand this my post, but can answer separately. This post is to offer steps "to make it work." 

Keep M9 as Main Deco, it is definitely better hardware and stronger WiFi signal. Keep M9 as Main especially if your son's computer connected to it - and it should, now that you turned off M5 in his room.

Another mistake you may be making is assumption that you need 5GHz for your son's online classes. In fact, 2.4GHz could be enough, even if classes stream in 4K (which I doubt), and because Deco M5 and especially M9 broadcast strong 2.4GHz signal, that could help to avoid interruptions vs. weaker and less reliable but faster 5GHz. 

I recommend to enable Guest Network on Deco, password protect it and configure it as 2.4GHz only, make your son's desktop Forget (in WiFi settings) Main Network and connect desktop to Guest network.

If all other devices are doing OK on Main Network, you won't even need to change Main Network to 5GHz only, keep it dual band.

Additionally, not very many dual band USB WiFi adapters truly do well with band steering. By connecting desktop to single band Guest Network you'll eliminate USB WiFi adapter possible quirks. 

Then, if desktop works fine with Guest Network on 2.4GHz, if you wish you could test if it can do well on 5GHz. Again, M9 delivers stronger WiFi signal than M5, proven in tests in my house, so it might do well with 5GHz in yours. To test, disable 2.4GHz on Guest Network and enable 5GHz on it. Once again, your Guest Network will be single band, now 5GHz, and desktop connected to it.

Perhaps, that will work, and if not - you can go back to running Guest Network on 2.4GHz.

@Alexandre. If you could explain why turning the M5 off would improve my network overall I'd appreciate it. I'd like to learn more about this. 

Elbetosan wrote

@Alexandre. If you could explain why turning the M5 off would improve my network overall I'd appreciate it. I'd like to learn more about this. 

@Elbetosan 

Turning off Satellite M5 in your son's room should improve his desktop network connectivity. 

Satellite Deco behaves like WiFi range extender. You can google "what is the best location for WiFi range extender" for very many articles on that topic, but this is quick summary:

----------Summary start

Satellite Deco must have good WiFi signal to Main Deco to work properly. If you place it in a room where signal from Main is already weak, Satellite Deco will not improve it. Yes, it'll broadcast strong signal to WiFi devices such as desktop in the same room, and desktop will report perfect WiFi connection. Yet, data will travel to Satellite M5 and, then, over weak unreliable WiFi link to Main Deco at very low speeds and with possible interruptions. Not the desired end result.

----------Summary end

The proper place for that Satellite M5 of yours is not in your son's room, but if you draw an imaginary line between Main Deco and desktop in his room - in the middle of that line. As close to that middle as possible. 

Objects that create interference must be considered, such as ceiling. For example, if your Main Deco is on the first floor, and his room is on opposite side of the house on the second floor, a good place for Satellite M5 could be under his room on first floor. Depends.

Finding good spot for a Satellite Deco could be challenge, that is why I suggested as a first step to establish a good baseline with configuration settings I suggested and M5 in his room turned off. After that, you can start moving M5 around to see at which place his desktop connectivity improves even further - or you might found you don't have to, and can reuse that M5 somewhere else in your house.

@Alexandre. 

I've turned down the node in my son's room but the overall performance hasn't improved. Pings are still slower and videos are still taking a little longer to start on apps like YouTube and Netflix. The speed does not come close to what the M5 provided. It is really weird.

I’ve set the mesh technology off of all my stationary devices, such as TVs and desktop computers, but it didn’t affect the results.

I have optimized the channels, but that hasn’t changed the outcome.

The firewall is on and I do have parent control set for some devices, but they where all there with the M5…

Firmware is up to date on all Decos.

I did set fast roaming on... I'll try turning it off later today...

Should I recreate the network? That’s the only thing I haven’t done. I’ve added the M9+ as a satellite and then set it as main Deco…

Or maybe there’s something wrong with the M9 Plus… it should at least have a range improvement when it replaced the M5, since it has twice the antennas, but it wasn’t...

Cheers.

@Elbetosan 

Yes, it is dissapointing. I have Deco M9/M5 mesh with M9 as Main node and M5 as one of satellites, I am quite pleased with their performance. The only thing different is I initially had 2-pack M9s and added M5 as Satellite later. 

Not sure if redoing network could help, with setting M9 first, making it Main and adding M5s to it, but if you are out of options, you won't lose anything by trying.

Now that you turned off M5 in your son's room, have you placed that M5 in the middle of imaginary line between his room and M9? Place M5 in the middle of that line, that might improve WiFi signal.

Have you tried connecting your son's computer to 2.4GHz WiFi only? That might improve quality of WiFi signal, even if could slow down speed somewhat.

Consider switching Deco mesh to Access Point mode for troubleshooting purpose, just to see that it is not misconfigured in router mode. You will lose Parental Controls and Antivirus, so if you need them you can change back Deco to its default Router mode after checking how Deco behaves in AP mode.

Finally, and that just came on a different conversation I had in this forum. It is possible that large contributing factor to issues with your son's computer is its USB WiFi adapter. To check this, bring "his" M5 back to his room, power it on, unplug USB WiFi adapter from your son's PC and connect computer to M5 by Ethernet cable. Yes, I know it is an opposite of what I suggested before, but let's cover all possibilities.

Also, I should have asked you this before, what signal strength is reported under Signal Source by M5 when it is on in your son's room? This is what mine reports, as an example: