iPhone 4S losing Wi-Fi when locked

Hey guys!

i know it's a known issue, but i haven't being able to find a solution. My iPhone 4s sometimes loses connection with WiFi while in the lock screen, connecting again when unlocked. Anybody else having this issue?

Also, my battery life has been terrible after iOS7, about 4 hours of usages. The iPhone is relatively new, less than a year.

Thanks in advance!