Last days I finally realized that the wi-fi always reconnects and is ready to use after unlock the device. The cases when it was disconnected was when I had walked out of the wireless coverage, and when I got back, the iphone5 just took a while (like 10-20 sec) to reconnect again. That was only it! So, I indeed discovered that when I stay under wi-fi coverage, iphone5 always is readily connected after unlock the screen. I've tested/checked it many times ever since ; )
Sorry , in a previous post I put a solution that finally did not worked.
But now I think I found the solution, as you'll seee below.
At work, my phone (iphone5 with ios7) was keeping wifi on when lock screen. At home the opposite. So the conclusion was, logically, that I had a problem with my router (Dlink 605L). After 2 days of googling, I fonud this post:
So I changed my router's name from "dlink" to other name (no matter which kynd of name) and the problem is solved now!!
Hello there.. i had the same problem and i thought my iphone was broken. once i googled, i found out that many iphone users are facing the same prob. i tried everything posted here but none of them worked. However, I found a way.. and it worked on my iphone 5. maybe you could try this.
Go to setting --> Wi-Fi --> Choose your network
once u r connected to your selected wifi network, there will be an symbol next to it.. click on that symbol. under HTTP proxy, click Auto.
hope this helps.