WiFi is too easy to interfere with so there's that. But the usual solutions are powerline networks with powerline WiFi Access points for ease of setup. You can add more WiFi WiFi Access points where needed.
There are dozens of things that do this or you can use a powerline bridge and a WAP (or a router configured as a WAP.)
http://www.netgear.com/home/products/networking/powerline/XWNB5201.aspx#tab-idealuses for example.
Bob
Hi,
I am considering a wi-fi connection for my duplex house. I want something that would give me a fast and stable connection, and is accessible through devices in both the floors. However, the connection should be supported in all mobile devices for greater convenience. Cost is not a major issue. Can somebody give me an effective solution?
Regards
Chaim Citronenbaum

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