I have a Sierra Wireless MC7455 installed into a ZBT3526 Router, and am on the Sprint Network, with an unlimited internet plan. I have noticed that sometimes, if streaming videos on YouTube or Amazon Prime, my phone quality takes a hit, with delays in voice transmitted and received. I have flashed LuCI branch (git-17.290.79498-d3f0685) / GoldenOrb_2017-12-15 ( LEDE 17.01.4 r3560-79f57e422d )
I understand that there are some SQM QOS settings that may allow the phone quality to be better. I am not up on the lingo, and am not sure how to set this up.