Hi there,

I had faced a similar problem with my new router 940N (450Mbps N-Router) when using with my BSNL-FTTH 50Mbps Fiber connection.

From the LAN on the router i could get >50Mbps but over Wi-Fi it was simply limited to a slower speed of 20Mbps for some reason.

I tried with multiple devices and they all showed the same slow speed of 20~25Mbps downloads/uploads.

I had contacted the TPLink Tech-support but could not get this solved over remote/Tele-call.

The next day after a few trials of my own I finally found the root-cause and solved it and its been working great since then.

The Solution that worked for me:

Since this is an N-Router, at the Wireless security settings, TP-Link Setup wizard itself recommends not to set TKIP Encryption but my BSNL technician did set TKIP wrongly during installation.

On finding this info from the Wireless Security settings page itself, I tried changing it back to the alternate option of AES. 

Now here is the strange and funny part.

For some reason the Router though it showed the settings saved as AES, it seems it never was actually applied it. The speed was still slow at <20Mbps.

Now even after a hard-reset and fresh re-configuration of the Router with AES encryption settings, it did not work.

Then I tried disabling the "Security" itself first, on which I got >55Mbps speed and then next I set it to AES.

This time it seemed to have applied the settings correctly and the high speed was retained and i have never had the slow-speed  issue again.

To confirm this fix i reproduced the steps of going with TKIP and Hard Reset etc and finally back to AES and it has proved to be correct.

Not sure if its a bug in the Router.

Anyway, for anybody facing this issue, please do try these steps. I was almost on the verge of returning my router via Amazon but managed to avoid doing it.

Best Regards,

Thomas