Wifi appears to be slow after moving from Lede 17.04.x to OpenWrt 18.06.1

Hi everyone, I have upgraded my TL-WRT3500 from the latest LEDE release to the new openwrt release.

I found the WIFI to be much slower. Is that a problem that has been reported before? How can I debug such issues?

Thanks!

You mean TL-WDR3500 v1?

How much slower? Can you please provide numbers for 17.01.x and 18.06.1?

Yes, sorry, that's the one I was talking about. Sorry for the confusion

So, I am drawing a very subjective conclusion: it just felt much slower on both my phone and my notebook. What would be a good way to measure wifi speed?

Thanks in advance!