Protocol Details from
3GPP TS 24.229
SDO Emergency Services Coordination Workshop (ESW07)
Jefferson Building of the Library of Congress , Washington DC
April 10-12, 2007
Gary Jones – Director of Standards Policy
T-Mobile USA
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Stage-3 specification ’philosophy’
• 3GPP TS 24.229 specifies the involved IMS
entities
• Reference relevant IETF-RFCs
• Profile RFCs are supported if only partially
• The spec will specify additions and limitations
• Work is ongoing and is planned to be completed
by mid-2007 – But lots of CRs still coming in
2
Involved entities
• UE - in UMTS (3G) mobile telephone systems is the name given to
the User Equipment
– Performs registration to the home IMS network
– The emergency call is handled in the visiting network, thus a
dedicated emergency registration is needed when the terminal
moves out of the home network
– Decides whether CS or IMS domain shall be used for initial
emergency call attempts
– Can perform emergency call without SIM/UICC
• E-CSCF – Emergency Call Session Control Function handles
certain aspects of emergency sessions, e.g. routing of emergency
requests to the correct emergency center or PSAP
– The interface towards the PSAP
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Involved entities
•
P-CSCF – Proxy CSCF is the first point of contact for the IMS terminal. It
can be located either in the visited network (in full IMS networks) or in the
home network (when the visited network isn't IMS compliant yet)
– The initial point for communication with terminals
– Access-agnostic
•
S-CSCF – Serving CSCF is the central node of the signaling plane. It's a
SIP server, but performs session control as well. It's always located in the
home network.
– The central point in the home network handling the subscriber
– Involved for emergency calls due to differences between
normal registrations and emergency registrations
•
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LRF – Location Retrieval Function is a functional entity that handles the
retrieval of location information for the UE
Items of Interest
• IMS aspects to support IMS Emergency sessions is 95%
completed
• WLAN aspects have been completed but the GPRS
aspects remain to be completed
• PS domain aspects to support IMS Emergency Sessions
is 35% completed
• The 3GPP invention "IMS emergency call identifier" has
been removed
• Conversion of location to a PSAP URI is currently
implementation dependent although IETF Ecrit Location to
Service Translation (LoST) Protocol is a possible
candidate
• Clarification of the UE and P-CSCF to support emergency
call redirection to the CS domain only or to the CS or PS
domains
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Outstanding Issues
• Release 7 is functionally frozen at this meeting and functional
modifications may only be made to features with agreed
Exception Sheets
• Release 7 Exceptions
– The interface between LRF and E-CSCF is not defined
– A number of IETF dependencies that are unresolved
– TS 24.008: GPRS access method for registration and
emergency PDP contexts setup for both the UICC and
UICC-less case.
• The protocol between E-CSCF and LRF and between E-CSCF
and an external location server is not included in the this version
of the specification.
– This is to avoid conflict with possible IETF protocol to
retrieve location information and the PSAP address
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Thank you
www.3GPP.org
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