This Recommendation describes the principles, service and network capabilities, and architectures for IP multimedia subsystem (IMS) based fixed-mobile convergence (FMC).

This Recommendation describes a network architecture that uses IMS to provide the same set of services to user terminals, regardless of whether they use fixed or mobile access network technologies, and ensures service continuity when the point of attachment of the terminal changes between different access network technologies.

The architecture employs the functional entities groupings defined in [ITU-T Y.2021] for IMS related entities, and [ITU-T Y.2012] for non-IMS related entities functionality. This Recommendation details IMS FMC specific architectural entities requirements which are generically defined in [ITU-T Y.2012] and [ITU-T Y.2021].

Although this Recommendation is focused on future IMS-based networks, some legacy fixed network requirements are also addressed.