The combination of CS and IMS services (CSI) is the parallel operation of a CS service and an IMS session between the same two users. It does not require a specific subscription and a specific charging correlation.
This TS provides architectural details to combine CS services and IMS services for using them in parallel between the same two users in a peer-to-peer context. The document provides a detailed description of how capabilities and identities are exchanged to enable the combination of CS and IMS services between the same two UEs.
