Читать книгу Mobile Communications Systems Development - Rajib Taid - Страница 138

In a live network of an operator, once a UE is registered and authenticated by the LTE/EPC as part of the LTE/EPS ATTACH procedure, TS 24.301 [46], a VoLTE‐capable UE is also required to register and authenticate itself with the IMS before it can start using IMS services. For these purposes, SIP signaling messages are exchanged between the UE and the IMS. Example 6.1 below describes and illustrates the flow of signaling messages, starting from registration to call establishment, conversation, and its completion, for a typical VoLTE call between two mobile devices over an IMS.