Ques. I live in 100 sq meter row house my desktop is in ground floor with mtnl triband will be getting mtnl router for wifi whose range is 50 mts (as told by mtnl) I want wifi also on the first floor on other devices . please help
Ans. MTNL router in no way would be sufficient for your needs.
Get a TP link wifi only router or an adsl cum wifi router as per your need with two antennas and turn one antenna in the horizontal direction leaving the other vertical.
The WiFi signal always propagates in the perpendicular direction from a omnidirectional antenna. So keeping in mind the geometry of your first floor you need to adjust the angle of one of your antennas.For reference you can use the images in this query,