How to configure two wireless routers (Separated by distance) with the same network?

Hello,

I have two wireless routers configured properly following my Inteet Service Povider instructions.

Our house is composed of two floors and in each floor there is an ADSL socket, to which is coected each of my two routers (using ADSL filters).

My problem is that i can't get the two routers to work at the same time. In order for one of them to work properly and coect me to the inteet , the other one should be shut down.

So, is there any kind of configuration that could be made in order to get the two routers to work properly at the same time?

N.B: The two routers are separated by distance and caot be linked to each other (LAN-to-LAN or Lan-to-WAN).

Thanks in advance