tp link is just a notch above ISP routers, they're not that great. Although not as advanced as the W9980B, I have a W8960N and the range is very poor.
I tried everything, upgraded antannaes, tried every channel with every signal strength selection. But could not get wifi access to every room on a 3 floor house [ground included].
I had to run a patch45 lead from the openreach modem to the 1st floor (middle floor) to the W8960N so it was in the middle of the hose so top floor could get reception.
Meanwhile on my devices my nextdoor neighbours router gets stronger coverage, even a mifi device has a stronger signal than the W8960N.