Background

UMTS

• Universal Mobile Telecommunications System
• 3rd Generation cell communication
• Based on the GSM system, maintained by 3GPP
• Was in competition with the cdmaOne technology

Main Goal

Clarify Implications of IP-based core network on UMTS

Virtual Home Environment

Standardizing capabilities instead of services.

What is VHE?

• Intended to allow users to access services outside of home network
• Make the user feel "virtually at home"
• Automatic message adaptation depending on what the user is connected to

VHE Terminology

• Service Capability Servers (SCSs) - servers that allow for services to be constructed
• Service Capability Features (SCFs) - classes/services constructed by SCSs
• Their purpose is to raise abstraction of network interfaces in order to simplify app development

VHE SCSs

• UTMS call control servers- manage bearer/call control capabilities, R99 only allows circuit-switched telephony
• Home Location Register (HLR)- database that contains location and subscriber information
• Mobile Execution Environment (MExE)- a JVM or WAP browser, where value-added services are offered
• SIM application toolkit (SAT)- additional SIM features that allow for extra authentication information into terminals
• Customized Application for Mobile Networks Enhanced Logic (CAMEL)- extends traditional intelligent network scope.

R99 UMTS

Voice over IP

Is VoIP better than traditional telephony?

R00 Features

• IP-based multimedia services as extension of packet-switched services
• Circuit-switched transport is replaced by packet-based network transport
• IP transport on the Radio Access Network (RAN/UTRAN)
• Network architecture is independent of transport layer, can be ATM or IP

What it would take for all IP-based core

• Roaming and Handover to 2G support
• Support of 3G circuit-switched terminals (for backwards compatibility)
• Support of new speed, SMS and other services that are all legacy as well as new IP-based versions

R00 All-IP Architecture

New Elements in IP Arch

• MSC- controls calls from circuit-switched terminals to mobile terminated calls, controls VoIP vs non VoIP
• Call state control function(CSCF)- provides/controls multimedia services for packet terminals
• MG at UTRAN side- transforms VoIP packets into UMTS frames
• MG at PTSN side- calls from PTSN converted into VoIP calls for transport in UMTS core network
• Signalling Gateway (SG)- relays all call-related signaling from PTSN/UTRAN on IP bearer and sends data to MGCF
• MGCF- control MGs, and provides translation
• Home Subscriber Server (HSS)- HLR extension with multimedia profile

VoIP in VHE

Two scenarios for providing VoIP in VHE

Scenario 1

SoftSSP Concept INAP/CAP

• The IN Application Part (INAP) triggers Service Control Point (SCP) reliant on Service Switching Point (SSP)
• CAMEL Application Part (CAP) is the same as INAP but in CAMEL
• The "SoftSSP" is to be build on top of the Session Initiation Protocol (SIP) server, to ensure that services can be provided via IN/CAMEL
• Mapping between the SIP call state model and the state model of IN/CAMEL

Scenario 1

VoIP on CSCF

• CSCF-SoftSSP must carry sufficient call data for the SoftSSP to deliver data to the SCP so service logic can function
• It also must allow SCP with the SoftSSP to control VoIP calls, like changing party address, add/remove media components, and to manipulate call information

Scenario 1

Advantages of SoftSSP

• Helps existing operators since UMTS R99 or GSM is already in use
• The newer CAMEL service environment creation methods work on legacy systems
• Mapping between CAP and SIP call control allow for VoIP to act like traditional services

Scenario 1

Disadvantage of SoftSSP

• Third Party Service providers can get access to the operators network via only the SCP
• They cannot get access to the CSCF, which implies no way of access to manage VoIP services

Scenario 2

3rd Party Support via CGI/CPL/SIP

• Two possible gateways for Third Party to allow access and control of network entities
• The Common Gateway Interface (CGI) : a mechanism already used on the internet for dynamic web pages, In the SIP, CGIs are triggered when requests arrive at server
• The the Call Processing Languages (CPL): Scripting language for network servers, allowing for immediate instantiation, and report back to controller CPL

Scenario 2

OSA arch for CGI and CPL

• Standardized representation for creating services in an order to enable multi vendor implementations
• Portability such that abstractions are defined and a high-level and are not SIP-specific, allowing portability between protocols
• Scripts are to be verified to ensure that it can run sucessfully
• Initiated services must be sure they can be terminated
• The integrity of other users must not be effected via the script run

OSA with SCP

vs

OSA with CSCF

Which is better?