Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); Mobile radio interface layer 3 specification@ core network protocols; Stage 2 (V12.0.0; 3GPP TS 23.108 version 12.0.0 Release 12)
"The present document specifies the procedures used at the radio interface (Reference Point Um@ see 3GPP TS 24.002 [15]) for Call Control (CC)@ Mobility Management (MM)@ and Session Management (SM). When the notations for ""further study"" or ""FS"" or ""FFS"" are present in the present document they mean that the indicated text is not a normative portion of this standard. These procedures are defined in terms of messages exchanged over the control channels of the radio interface. The control channels are described in 3GPP TS 44.003 [16]. The structured functions and procedures of this protocol and the relationship with other layers and entities are described in general terms in 3GPP TS 24.007 [20]."