It will depand upon where you keep your router.Normally it is suggested that it be kept in a central location of the house. However if it is not possible then try and keep it such that there is as less obstruction as possible, in the way. If the room is directly above your router then the signal wll be very less or nil because of the concrete cieling is in the way. You may need a range extender(repeater).
I have a situation very similar to yours. My router is located with the PC in a room in one corner of the house. Moving my laptop out of that room, the signal becomes weak. I am also considering options to increase the range....... Placing the router away from the PC, which is connected with ethernet cable to the router, will pose a problem of wiring externally from PC to router and back, which is not a great option..
Do give me your feedback on how you sort your problem..
Regards