iOS 9 update utilizes mobile Data when the Wi-Fi network to which you are connected is poor
As a solution to all the Wi-Fi connectivity miseries faced by the iPhone users, the iOS 9 update has come up with the Wi-Fi Assist. This software update intelligently switches on your mobile Data during sessions of poor Wi-Fi connectivity. With this feature your iPhone is allowed to access cellular data when Wi-Fi is poor. It seems like a simple toggle which you can enable just once and thereafter it will automatically do the swap for you.
Even though the feature is dubbed as 'Wi-Fi Assist' the option can be spotted under the 'Cellular' menu in the iOS settings app. When you turn this on the device will be forced to get itself connected to a 3G or 4G network connection if the Wi-Fi data transmission falls short of an unspecified signal strength.
The date of the release of this update with this amazing feature has not yet been announced by speculations suggests that we can expect this new version of the OS by September.