T-Mobile has formally announced that it has rolled out VoLTE service in its home market of Seattle, Washington. What makes T-Mobile’s roll out different from the AT&T and long-planned VoLTE rollout by Verizon is the fact that it is based on the newer LTE-Advanced implementation in Enhanced Single Radio Voice Call Continuity (eSRVCC), which will allow for proper call handoffs from LTE to HSPA+/GSM/EDGE without interruption and initial voice call setup on the LTE data channel. The VoLTE implementation will also rely on the same AMR-WB voice codec implementation currently used for its HD Voice service while also allowing for simultaneous voice and data access and much faster call setup as a result.
Currently, T-Mobile will be offering support for the service on three smartphones, with the LG G Flex, Galaxy Note 3 and Galaxy Light having software updates being pushed out beginning tomorrow in order to support the rollout, with further expansion throughout the year.
I have a Light and the update has yet to come on for it.