I had similar problems when my friend connected a Blackberry Z10 to my router, constantly dropping out after about half an hour of connection, so try this:
I found that my at the time SGS2, could only connect in 'g' mode, whereas her BB was connecting in 'n'. I believe this was confusing the crappy B.T. router I have, so I changed the settings of the router to only accept 'g' connections. Problem solved for me.
Worth a try anyway. Especially if the other devices connecting to your router are a bit older and only use a 'g' connection.
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