I am convinced from all that I've read from various sources that this is an Apple engineering problem. It apparently is caused by some kind of temperature sensor in the iPhone triggered by an iPhone iOS update. Unfortunately this has never been resolved by subsequent iOS updates. I'm up to version 9.3.2 and Apple still has not addressed the problem with an update to iOS.
The best permanent solution I've heard of is to replace the WiFI antenna component BUT this is too much work.
Instead I chose a simpler (possibly less temporary) solution to just cool down my iPhone to trigger the temperature sensor logic in the iPhone.
Do not heat up your phone as some people have suggested. "Thermal Cycling" is bad for your phone. I've been able to reset the temperature sensor in my iPhone 4S by putting it in the freezer (in a zip lock bag) for about 15 minutes. It may not be a permanent solution but will re-enable the WiFI until the temperature sensor triggers the WiFi to shutdown again.
Однажды Они, Вы смогут просмотреть график вашего рейтинга, накопленного за всё время.
Репутация еще не заработана.