I have TP-Link TL-MR3020 with OpenWrt  15.051 installed.  I have tested the phone tethering on my PC and it does not randomly shutoff tethering, it has worked for days.  But when connected to the TP-Link the phone will shutdown the tether in less than 20 minutes .

I have searched for answers on the web and also went through most of the settings on the phone and on OpenWrt configuration web pages, and no help.

Any one have any ideas what the issue is or how to resolve it.