Think over next scenario: You are caught in a area where a festival is held and a massive flux of people come. You are lost in space, your smartphone doesn’t reach the tower communication because it’s overloaded by all people that are desperate of communicate. They leave the internet connection switched on all the time in the desire to be up to date with all apps.
A simple&effective trick
A good trick that I learned by myself is switching your cell phone network connection on GSM (2.5g) instead of using dual band UMTS (3g). In that way your cell phone reaches a less busy communication tower. On I-phone you just toggle of 3g connection. This tip should also help your phones battery life. Even when you would have a good 3G coverage, turning the connection to GSM only will help battery life immensely.