Abysmal RT-AC56U performance

[krlkv]

I recently upgraded to a ThinkPad X1 Carbon with AC8265 (2x2 ac) and decided to upgrade my n WiFi router to ac.

I have an RT-N66U which worked fine for 5+ years providing an average downlink of 15MBps on 5GHz WiFi n 3m away from the router.

I bought a cheap RT-AC56U, thinking it would provide a moderate speedup. To my surprise not only it didn't improve download speed, it actually made it 2x worse, down to 7-8 MBps in exact same location.

Using merlin on both routers.

AFAIK, this is not normal at all, but I have no idea what's wrong.

Any suggestions?

 

[Grisu]

2x2 wont make anything faster if not used in MuMimo.
Set bandwith to 40 or 80MHz and it will get faster.

 

[krlkv]

2x2 wont make anything faster if not used in MuMimo.
Set bandwith to 40 or 80MHz and it will get faster.

Bandwidth is set to 80MHz.

 

[ColinTaylor]

2x2 wont make anything faster if not used in MuMimo.

It's got nothing to do with MU-MIMO. With his old router he could have got a link speed of 300Mbps @ 40MHz. With his new router that could increase to 400Mbps @ 40MHZ or 867Mbps @ 80MHz.

@krlkv Check what link speed you are getting, both on the router's System Log - Wireless Log page and the client's network adaptor. Also, try changing the bandwidth to 20/40/80. Try different channels.

 

[krlkv]

@krlkv Check what link speed you are getting, both on the router's System Log - Wireless Log page and the client's network adaptor. Also, try changing the bandwidth to 20/40/80. Try different channels.

Wow, it seems to be fixed now. First time in 2 hours I finally see 25-30Mbps (twice what I got on N66U).

What did I do? Nothing really. First I switched channel bandwidth from 80MHz to 20MHz to verify that my speed dropped to roughly 4MBps (half of 8MBps that I was getting before with 80MHz, but my laptop card is 2x2). Then I switched back to 80MHz and suddenly it went up to 25Mbps.

Some strange ASUS / Merlin bug? Don't know.

 

[ColinTaylor]

Where were you copying the files to and from? Maybe it's nothing to do with the wireless connection. 25.4MBps (203Mbps) looks like its being limited by the write speed of the destination drive. You could try using a wired Ethernet connection (to the source and destination) instead to check what the maximum possible write speed is.

 

[krlkv]

Where were you copying the files to and from? Maybe it's nothing to do with the wireless connection. 25.4MBps (203Mbps) looks like its being limited by the write speed of the destination drive. You could try using a wired Ethernet connection (to the source and destination) instead to check what the maximum possible write speed is.

From Synology NAS (RAID 1) connected to the AC56U using 1Gbps Ethernet to my X1 Carbon laptop with NVMe SSD. This is what I always did to test WiFi speed. Both with N66U and today with AC56U. So no, I don't think read / write speeds were a bottleneck.

To give you an idea of write performance, if I simply copy file to another folder I get almost 1GBps write speed.

 

[ColinTaylor]

It might be helpful to verify what speed you do get over a wired connection just to eliminate it from any troubleshooting. You can easily spend weeks trying to diagnose WiFi problems, so it's not something you want to do if the problem lies elsewhere.

 

[krlkv]

It might be helpful to verify what speed you do get over a wired connection just to eliminate it from any troubleshooting. You can easily spend weeks trying to diagnose WiFi problems, so it's not something you want to do if the problem lies elsewhere.

Yes. But the thing is I have only Carbons in my household and they don't have Ethernet port.

 

[ColinTaylor]

Yes. But the thing is I have only Carbons in my household and they don't have Ethernet port.

Ah, OK. I didn't realise that.

 

[sfx2000]

Yes. But the thing is I have only Carbons in my household and they don't have Ethernet port.

USB3 to ethernet adapter - not very expensive, and handy to have...

Trendnet has a decent one that is supported by Win/Mac/Linux - plug and play