ICS Protocol over USSD bearer
The present document describes the I1 interface between IMS Centralized Services (ICS) UE and Service Centralization and Continuity (SCC) Application Server (AS).
This specification defines a new application layer protocol over I1 interface, specifies the interaction between the ICS UE and the SCC AS including session control procedures and supplementary services control procedures.
For the current version of the specification the application layer protocol is run over Unstructured Supplementary Service Data (USSD) transport, however the application layer protocol is not restricted to USSD transport.
The overall ICS architecture is specified in 3GPP TS 23.292 [3].
The present document is applicable to User Equipment (UE) and Application Servers (AS) which are intended to support the IMS centralized services.