WiFi keeps dropping to TV/Roku

Our Xfi Router is in the 2nd floor right hand side of the house.  We have no problem getting WiFi signal all the way down to the basement on that side of the house.  However, on the other side of the house, middle floor, the Wifi (internet connection) is constantly dropping the ROKU and any other app on that TV.  

When I do a speed test it varies but it is always above 35 mbps (and sometimes above 100).  Why does the connection drop?  Would the xfi pods fix this?  If so, could I try them but return them if they don't work?