History
- IMS was originally defined by an industry forum called 3G.IP, formed
in 1999. 3G.IP developed the initial IMS architecture, which was
brought to the 3rd Generation Partnership Project (3GPP), as part of their standardization work for 3G mobile phone systems in UMTS networks. It first appeared in Release 5 (evolution from 2G to 3G networks), when SIP-based multimedia was added. Support for the older GSM and GPRS networks was also provided.[3]
- 3GPP2 (a different organization from 3GPP) based their CDMA2000 Multimedia Domain (MMD) on 3GPP IMS, adding support for CDMA2000.
- 3GPP release 6 added interworking with WLAN,
inter-operability between IMS using different IP-connectivity networks,
routing group identities, multiple registration and forking, presence,
speech recognition and speech-enabled services (Push to talk).
- 3GPP release 7 added support for fixed networks by working together with TISPAN
release R1.1, the function of AGCF (access gateway control function)
and PES (PSTN emulation service) are introduced to the wire-line network
for the sake of inheritance of services which can be provided in PSTN
network. AGCF works as a bridge interconnecting the IMS networks and the
Megaco/H.248 networks. Megaco/H.248 networks offers the possibility to
connect terminals of the old legacy networks to the new generation of
networks based on IP networks. AGCF acts a SIP User agent towards the
IMS and performs the role of P-CSCF. SIP User Agent functionality is
included in the AGCF, and not on the customer device but in the network
itself.
Also added voice call continuity between circuit switching and packet switching domain (
VCC), fixed broadband connection to the IMS, interworking with non-IMS networks, policy and charging control (
PCC), emergency sessions.
- 3GPP release 8 added support for LTE / SAE, multimedia session continuity, enhanced emergency sessions and IMS centralized services.
- 3GPP release 9 added support for IMS emergency calls over GPRS and EPS, enhancements to multimedia telephony, IMS media plane security, enhancements to services centralization and continuity.
- 3GPP release 10 added support for inter device transfer,
enhancements to the single radio voice call continuity (SRVCC),
enhancements to IMS emergency sessions.
- 3GPP release 11 added USSD simulation service, network-provided location information for IMS, SMS submit and delivery without MSISDN in IMS.
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