ts and to change cells during a session (handover); - signaling of the IMS network, allowing the mobile to register, to establish a session and to negotiate the media; - DIAMETER signaling exchanged between, firstly, the EPS or IMS networks, and, secondly, the environment of these networks. Chapter 3 presents the different basic procedures: - the attachment and the detachment of the mobile with the EPS network and the establishment of the default bearer to transport SIP flows; - the registration and the deregistration of the mobile with the IMS network; - the establishment and the release of VoLTE and ViLTE session. Chapter 4 presents the characteristics of the radio interface, for which the following features are described: data structure, transmission chain of the physical layer, frequency time and space multiplexing. Preface The same chapter also illustrates two procedures of the radio interface: access control of the mobile to network and data transfer. Chapter 5 presents the supplementary telephone and videophone services offered by a particular entity of the IMS network, the telephony application server (TAS). These services include call forwarding, identity presentation, message waiting indication, call hold, conference call, call waiting and call barring. It also presents the characteristics of audio and video streams. Chapter 6 presents the interconnection to the public switched telephone network (PSTN) or to the public land mobile network (PLMN) (Figure 2). IP packet IP packet Figure 2. Interconnection to the PSTN and PLMN network Chapter 6 also presents the interconnection of the IMS network with IMS third-party networks. Chapter 7 presents the mechanisms of intra-system and PS-PS inter- system handover. The intra-system handover is performed when the mobile changes cell but does not change the 4G network concerned. The PS-PS inter-system handover is performed when the mobile changes cell and network but holds the PS mode. This type of handover is applied to VoLTE or ViLTE services if the same function