VoLTE calls will be carried over IP on our LTE network instead of a circuit-switched path on our 4G HSPA+ network. This is advantageous because your phone stays on our wicked fast LTE network to make a call. The tricky bit in all this is the smooth mobility between our various radio layers. Enhanced Single Radio Voice Call Continuity (eSRVCC) is a new LTE Advanced function and we’re excited to be the first to deploy it in the U.S. All of this basically helps ensure that your capable phone won’t drop a call if you leave an LTE area and it switches to 4G HSPA+ or 2G coverage.
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