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A snaphost on an IMS-based PSTN/ISDN Emulation subsystem 3GPP – ETSI TISPAN Workshop 22 – 23 June 2004. B.Chatras. IMS and PSTN/ISDN Emulation. A lot of similarities Two session-based control subsystems: For supporting multimedia services and PSTN/ISDN services simulation (IMS)
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A snaphost on an IMS-based PSTN/ISDN Emulation subsystem3GPP – ETSI TISPAN Workshop 22 – 23 June 2004 B.Chatras
IMS and PSTN/ISDN Emulation • A lot of similarities • Two session-based control subsystems: • For supporting multimedia services and PSTN/ISDN services simulation (IMS) • For supporting PSTN/ISDN services emulation • Above a managed IP network • Supporting operators’ requirements • Quality of service, Security, Charging capabilities, Regulatory constraints.... • Clear Benefits • Enables the deployment of common control planes/platforms • Towards a unique infrastructure for supporting multimedia services and TDM- switches replacement • Enables service convergence • new voice services available to all types of subscribers • Enables the scope of nomadism to be extended to legacy access lines
Technical context • Requirements • All PSTN/ISDN services shall remain available and identical (i.e. with the same ergonomics); such that end users are unaware that they are not connected to a TDM-based PSTN/ISDN. • End to End ISDN feature transparency shall be ensured for call transiting through the PSTN/ISDN Emulation subsystem. • Impact on IMS • Requires new entities (residential/access gateways, access gateway controller) with H.248 interfaces. • Requires SIP with encapsulated ISUP. • Most IMS entities re-used unchanged (transparent to the ISUP bodies) or with minor changes (e.g. removal of ISUP body, based on destination). • ISDN/PSTN service logic / call model shifted to application servers.
A candidate IMS-like functional architecture ? PSTN/ISDN Specificlogic/data Reference points Dxx : DIAMETER Sxx : SIP or SIP-I Hxx : H.248 Ixx : TISPAN specific
Flexible deployment options Enables various degrees of convergence and a wide range of implementation options
Options for physical scenarios • A unique infrastructure • Identical or similar functional entities from both functional planes are merged in the physical plane into a single plateform. • Two distinct infrastructures • Various physical configurations (incuding a basic softswitch-like approach) can be envisioned for the PSTN/ISDN emulation subsystem, based on different strategies for grouping functional entities into physical platforms. • Hybrid scenarios • E.g. Platforms implementing MRFC/MRFP and/or MGC/IM-MGW are shared by both subsystems. Other platforms are implemented separatly.
Changes to IMS interfaces/entities • MRFC, MRFP, SLF: Unchanged. • S/I-CSCF, BGCF: Minor impact due to SIP-I relay. • MGCF: Interworking procedures impacted by SIP-I. • HSS: Impacted by the presence of PSTN/ISDN profile information • Specific entities : AGCF (i.e. RGW/AGW control) and Application Servers hosting « class 5 » service logic.
Emulation vs Simulation • PSTN/ISDN Simulation • The provision of PSTN/ISDN-like services to advanced terminals such as IP-phones. There is no strict requirement to make all PSTN/ ISDN services available or identical, although end users expect to have access to the most popular ones, possibly with different ergonomics. • PSTN/ISDN Emulation • Mimicing a PSTN/ISDN network from the point of view of a legacy terminal by an IP network, through a gateway. All PSTN/ISDN services remain available and identical (i.e. with the same ergonomics); such that end users are unaware that they are not connected to a TDM-based PSTN/ISDN.
