Voice call continuity allows users to move voice calls between the Circuit-Switched (CS) domain and the Multimedia Domain (MMD), connected through different Internet Protocol -Connectivity Access Networks (IPCANs) (e.g., WLAN, HRPD). This document defines an inter-technology Domain Transfer (DT) call model which supports procedures that allow a
mobile subscriber to DT from an HRPD or WLAN multimedia session with a voice component to a 1x CS voice session and from a 1x CS voice session to a WLAN VoIP session.
It is the goal of this specification to allow the core network to know as precisely as possible
the current accessibility of the User Equipment (UE) and to deliver services efficiently across
the appropriate access network while minimizing the impact on the legacy systems.
The UEs in this specification include two kinds - one is HRPD/1x dual mode handset, and the
other is WLAN/1x dual mode handset. HRPD/1x handsets are assumed to be incapable of
simultaneous full-duplex radio communications with both an HRPD radio access network and
a 1x radio access network, while WLAN /1x handsets are capable of being in simultaneous
full-duplex communication with both a WLAN access network and a 1x radio access network.
Supplementary services and supplementary services continuity are not addressed in this
specification (e.g., Call Waiting, Call Transfer, 3WC, Call Hold). These topics will be further
addressed in the subsequent versions of the document.
The Stage 2 of this document specifies the interactions and signaling flows between a new
functional entity in the MMD network called the VCC Application Server (VCC AS) and the:
? Serving-Call/Session Control Function (S-CSCF)
? Home Location Register (HLR)
? Home Subscriber Server (HSS)
? High Rate Packet Data Access Terminal (HRPD AT)
? Wireless Local Area Network (WLAN) Station (STA)
? Mobile Switching Center (MSC)
? Media Gateway Control Function (MGCF)
The Stage 3 specification in this document provides the protocol details for voice call
continuity between the MMD based on the Session Initiation Protocol (SIP) and the Session
Description Protocol (SDP) and the the 3GPP2CS domain which uses MAP and ISUP.
This document makes no VCC specific enhancements to SIP, SIP events or SDP, beyond those specified in [MMD Part-4].
This document is applicable to UEs, AS and MGCF providing voice call continuity capabilities.