If the whole house is wired RJ-45 from the basement, there should be a switch there. If this is the case, you can also connect your ISP's router to this switch and then use one of your RJ-45 sockets (preferably centrally located on the whole living area) to connect a network cable via the wan port of your ASUS router. This should give you good reception on all floors. In a three-storey house, place the ASUS router centrally on the middle floor for best coverage.

I am aware that I have worked with many assumptions here. However, the tip applies to all wifi routers, even if the house is not wired RJ-45. (otherwise you would have to be a little more specific about your living situation).
Another thing to consider is metals of all kinds (in walls, e.g. power cables). In the floor, e.g. concrete reinforcement or floor heating) attenuate the signal strength of a radio signal to a certain degree.

I hope I was able to be helpful with this contribution.
LG Rahuna

You can certainly use it as a repeater.
But your question is too vague.
I think you have the modem in the basement and want to connect it with a network cable on the ground floor ... but as a repeater? More like a router? LG Swizzy