@WouterP 

 

>T-Mobile blames the TP-Link network, instead of looking in their modem or anything

 

I have to agree with T-Mobile on that one. Changing ISP should not change quality of Deco mesh network. If you have had different speed test results in Deco for different ISP, that could have been a coincidence. 

 

First things first, a couple of recommendations:

 

1. It appears you run T-Mobile modem/router in router mode. I would suggest switching Deco mesh to AP mode and keeping it in AP mode, as long as you don't need Deco router freatures such as parental controls and antivirus.

2. I would suggest turning off WiFi on T-Mobile modem/router, if you haven't done it yet, leaving only Deco WiFi covering your house.

3. For speed tests, turn off 2.4 GHz WiFi on Deco Main Network. Does not make difference if you run all speed tests from computer wired to Satellite Deco, but could make difference if you try speed test on device wirelessly connected to Deco.

 

Deco M9 Plus is quite good WiFi mesh hardware, I have two M9 units and I like them. I can compare what I have with what you've got, and I run mine in AP mode. My ISP provides gigabit connection.

 

>Only the download speed via the internal speedtest changes. When it's a router I get the highest possible download (865 mbit), but when it's an access point it only gets 500 mbit through the speedtest

 

This is Deco internal speedtest reporting bug. Just ignore that. You are still getting almost gigabit. You can verify that by connecting PC by Ethernet to second port of Main Deco running in AP mode, and run speedtest from PC.

 

>My main unit on the ground floor, is connected with a 5e utp cable to the modem, and gets 800-900 mbit download and upload speed through a wired connection.

Wifi gives about 500-600 mbit.

 

Same as mine.

 

>My 2nd unit on the 1st floor in our bedroom is about 5 metres away from the first unit, only with a ceiling between them. WiFi already dropped to 200 mbit. 

 

Mine is similarly located above Main Deco. Top WiFi speed I ever got was 490Mbps, but it were after many, many tries, with finding best position for smartphone I run speedtest on, and is the best result. Random speed tests from device connected by WiFi to my 2nd Deco give 250-350Mbps. 

 

Perhaps, your ceiling is better than mine. Mine is made from almost cardboard, American style. Excellent for WiFi penetration, not so good for anything else. What is your ceiling made of: solid wood, concrete?

 

>On the attic where the 3rd unit is located I only get 144 mbit download, wired to my computer

 

I would suggest you check to which unit your 3rd unit is connected to - to 2nd unit or to Main Deco? You can find that in Deco app. While you are at it, also check quality of backhaul between 3rd unit and whatever unit it is connected to. 

Example:

 

 

In this example, my 2nd unit reports an excellent connection to Main Deco which is named Living Room.

 

If your 3rd unit connects to Main Deco and backhaul signal is weak, that may explain a lot. 

@Alexandre. 
 

sorry for replying to you late, I was out on a holiday and was not around the tp link.

I've put the deco in AP mode as you suggested.

My ceiling is made of concrete, so it's pretty thick, but so was it with a different ISP.

 

I also checked to what deco unit my attic is connected to, and it's connected with the one on the first floor (bedroom). It has a signal strength of 2 out of 3, so it's not a perfect connection, but so is the bedroom to the living room.

 

But as I see in your reply it's quite normal that it drops significantly with a wifi backhaul?

@WouterP 

 

It is normal for WiFi speed to drop significantly with WiFi backhaul, especially if there is signal obstacle such as concrete floor between WiFi mesh units.

 

WiFi mesh units communicate with each other using standard WiFi protocols, and that is true for any WiFi mesh, not just Deco. If signal must penetrate WiFi unfriendly material, speed and signal will degrade. 

Also, other types of interference could impact WiFi speed: if you placed WiFi unit near cordless phone, for example, or could be even when microwave is running. 

 

If you are not happy with speeds you've got, you could try to move attic and bedroom Deco units as close to each other as possible, it might help to improve WiFi speed. You can wall mount or ceiling mount Deco M9, google for "Wall Mount Holder for TP-Link Deco M9 Plus." There are two types of holders: one to plug into electric outlet, another to mount anywhere on wall or ceiling, with screws.

 

Deco M9 is top of the line TP-Link mesh hardware for WiFi5. You can't get better than that from TP-Link. If you expect better, try WiFi mesh from different brand, but make sure it comes with good and easy return policy. There are no miracles with WiFi mesh systems, they all work based on same underlying principles.

 

Finally, do you by any chance have TV cable terminating in the bedroom on the first floor, where your bedroom Satellite Deco is? Because, if you do, you may consider connecting bedroom Satellite Deco to the home network using MoCa adapters (Ethernet over TV cable). If you do that, it'll make you bedroom Satellite Deco WiFi speed as fast as Main Deco, and also could improve WiFi speed from attic Deco.

 

 

 

@Alexandre. Thanks for your replies, it really make things clear!

But can you explain one thing?

 

How is it, that when I was with Ziggo (IPS in the Netherlands) with a 300 mbit band, I received with the same setup, 200-250 "wired" on the attic unit on my pc, and when I have 1000 mbit, I only get 100-140 mbit. It's even less and there hasn't been changed anything in the setup. Same concrete walls, same spots where the units are located.

 

But a mechanic of T-mobile drops by tomorrow (finally), because I had one of there WI-FI repeaters and it was even worse than my tp links, so I hope he can sort some things out.

@WouterP 

 

When you changed ISP, something else must have happened in your house that is coincided with it. Moving to different ISP can only impact link between Main Deco and ISP modem/router. Because your Main Deco is as fast as mine, and at about max of its realistic WiFi speed, there is nothing wrong with your ISP. Yet, if it were, you'll see it with Main Deco.

 

My point is, even if you go back to Ziggo, but change nothing else at your home, you won't get old WiFi speeds in attic. 

 

Have you, maybe, bought new Smart TV about same time, replaced microwave, changed cordless phone system? If nothing like that had happened, perhaps one of your neighbors got new powerful WiFi router or military surplus WiFi signal booster and that creates new interference in your house.

 

I am assuming T-Mobile technician will come tomorrow to try to find optimal places for their repeaters. If it is so, when he leaves saying "it is the best they can do," power them off and put Satellite Decos in their places. These will be places where Decos will do the best they can. Check how they do and choose what brand is better. As I said, there are no miracles in WiFi mesh systems, they all work based on same principles and protocols. 

Except, M9s are top of the line from TP-Link, and T-Mobile repeaters might not be as good, just average.

 

Also, if T-Mobile technician willing to troubleshoot Decos, explain to him (in case he is not familiar with Deco) that Main Deco plays role of WiFi router in Deco mesh and Satellite Decos are WiFi range extenders, like T-Mobile repeaters. Perhaps, he could point at more optimal places for Satellite Decos.

 

Also, one last thought: ask him if MoCa is possibility between your bedroom and other location of your home network. If you have TV cable terminating in your bedroom where Satellite Deco is, this is really worth to check.

When you run Deco in AP mode, you can connect other side of TV cable, through MoCa adapter, to any link (switch, Ethernet port) of your wired home network.