SIST EN 17184:2025+A1:2026

SLOVENSKI STANDARD
01-maj-2026
Inteligentni transportni sistemi - e-Varnost - Visokonivojski aplikacijski protokoli
za e-Klic (HLAP) z uporabo IP multimedijskega podsistema (IMS) v paketno
preklopnih omrežjih
Intelligent transport systems - eSafety - eCall High level application protocols (HLAP)
using IP Multimedia Subsystem (IMS) over packet switched networks
Intelligente Verkehrssysteme - eSicherheit - Übergeordnete Anwendungsprotokolle
(HLAP) für eCall unter Verwendung von IPbasierten Multimedia-Subsystemen (IMS)
über paketvermittelte Netzwerke
Systèmes de transport intelligents - eSafety - eCall Protocoles d'application de haut
niveau (HLAP) utilisant les réseaux à commutation de paquets IMS (Internet système
multimédia)
Ta slovenski standard je istoveten z: EN 17184:2024+A1:2026
ICS:
03.220.01 Transport na splošno Transport in general
35.240.60 Uporabniške rešitve IT v IT applications in transport
prometu
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 17184:2024+A1
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2026
EUROPÄISCHE NORM
ICS 35.240.60 Supersedes EN 17184:2024
English Version
Intelligent transport systems - eSafety - eCall High level
application protocols (HLAP) using IP Multimedia
Subsystem (IMS) over packet switched networks
Systèmes de transport intelligents - eSafety - eCall Intelligente Verkehrssysteme - eSicherheit -
Protocoles d'application de haut niveau (HLAP) Übergeordnete Anwendungsprotokolle (HLAP) für
utilisant les réseaux à commutation de paquets IMS eCall unter Verwendung von IPbasierten Multimedia-
(Internet système multimédia) Subsystemen (IMS) über paketvermittelte Netzwerke
This European Standard was approved by CEN on 6 October 2024 and includes Amendment 1 approved by CEN on 29 January
2026.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17184:2024+A1:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 8
4 Symbols and abbreviations . 11
5 Conformance . 13
6 General overview of pan European eCall session via Packet Switched networks . 13
6.1 General principle . 13
6.2 eCall over Packet Switched networks . 14
6.3 eCall using IMS over Packet Switched networks . 14
6.4 The hybrid situation . 19
7 Requirements . 20
7.1 General requirements . 20
7.1.1 General. 20
7.1.2 Enabled IVS . 20
7.1.3 Enabled PSAP . 20
7.1.4 eCall-only IVS . 21
7.1.5 ECL: eCall using IMS support indicator . 21
7.2 Procedures following power-up of the in-vehicle system . 22
7.2.1 Self-test . 22
7.2.2 Standby mode applicable to eCall-only IVS . 22
7.3 Activation . 22
7.3.1 Activation of eCall using IMS over packet switched networks . 22
7.3.2 Activation of a test eCall . 22
7.4 Call set-up . 23
7.4.1 General. 23
7.4.2 eCall in progress . 23
7.4.3 Network selection and registration . 23
7.4.4 Authentication of the subscriber . 24
7.4.5 Establishment of an eCall using IMS over packet switched networks . 25
7.4.6 Caller localization by the network . 25
7.4.7 Manual !cancellation" of eCall by vehicle occupants before trigger confirmation . 25
7.4.8 Call rejection . 25
7.4.9 Call failure . 26
7.4.10 Security . 26
7.5 MSD transfer for eCall using IMS over packet switched networks . 26
7.6 Application layer acknowledgement (AL-ACK) . 27
7.6.1 General. 27
7.6.2 Successful receipt by the PSAP of the initial MSD . 27
7.6.3 Unsuccessful receipt by the PSAP of initial MSD. 28
7.6.4 No receipt of MSD acknowledgement . 28
7.6.5 Other forms of acknowledgement . 28
7.7 PSAP requests a new/updated MSD . 29
7.7.1 General. 29
7.7.2 Before session clear-down . 29
7.7.3 After session clear-down . 30
7.8 MSD transfer using in-band modem (optional) . 30
7.9 Audio link to vehicle occupants . 30
7.10 eCall clear-down. 30
7.11 PSAP call-back . 31
7.12 Rerouting to another PSAP/emergency control centre . 32
7.13 Handling non equipped situations / error cases . 32
7.13.1 Network related issues . 32
7.13.2 MSD related issues . 33
7.13.3 PSAP network/ICT failure . 33
7.13.4 Call related issues . 34
8 Third party services supported eCall (TPS-eCall) . 34
9 Defences against attack (Security provisions) . 35
10 Quality of service requirements . 35
11 Test and conformance requirements . 35
12 Marking, labelling and packaging . 35
13 Declaration of patents and intellectual property . 35
Annex A (normative) Table of timings . 36
Bibliography . 38

European foreword
This document (EN 17184:2024+A1:2026) has been prepared by Technical Committee CEN/TC 278
“Intelligent transport systems”, the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2026, and conflicting national standards shall be
withdrawn at the latest by August 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document includes Amendment 1 approved by CEN on 29 January 2026.
This document supersedes !EN 17184:2024".
The start and finish of text introduced or altered by amendment is indicated in the text by tags !".
The following changes have been introduced in this revision:
— updated parts of 1, 2, 4, 5, 6.3, 6.4, 7.4.3.2, 7.4.5, 7.4.9, 7.6.2, 7.6.3, 7.7.2, 7.8, 7.10, 7.11, 7.13.1.2,
7.13.2.1, 713.4.2 and 11;
— moved parts of 7.4.5 and 7.13.3.3 into the new clause 7.4.8;
— moved parts of 7.13.1.2 into the new clause 7.1.5;
— voided Annex B.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
Introduction
An eCall is an emergency call generated either automatically via activation of in-vehicle sensors or
manually by the vehicle occupants; when activated, to provide notification and relevant location
information to the most appropriate Public Safety Answering Point (PSAP), by means of mobile wireless
communication networks and carries a defined standardized minimum set of data, notifying that there
has been an incident that requires response from the emergency services and establishes an audio
channel between the occupants of the vehicle and the most appropriate PSAP.
EN 15722 specifies a standardized MSD for eCall, and EN 16072 specifies pan-European eCall operating
requirements (for third party systems, EN 16102 specifies third party services supporting eCall operating
requirements; see EC Communication on eCall Implementation 2009 [COM(2009) 434 final] and Official
Journal eCall Recommendation C(2011) 6269 final, for more information) and EN 16062 specifies High
Level Application Protocols for eCall using circuit switched (CS) networks (like GSM/UMTS).
The operating requirements for pan-European eCall are made using Public Land Mobile Networks
(PLMN) (such as GSM and UMTS, and latterly LTE, NR and their successors), as specified in a number of
ETSI standards and technical specifications.
In order to provide the eCall service across a wireless network, high level application protocols are
required as an important essential element to affect this service provision.
NOTE The term PSAP, which is most widely used in the eCall documentation, European Commission
documents, etc., is used throughout this document and equates to the term emergency call response centre used in
the ITS Implementation Directive.
Subsequent to the publication of the suite of eCall standards (EN 16072, EN 16062 and EN 16454) which
support the eCall Regulations, new communications technologies have become available. Over the course
of time, these networks (such as LTE, NR and their successors) are expected to complement and
eventually replace the circuit switched GSM/UMTS networks. These technologies use so called ‘packet
switched’ technologies using Internet protocols (IP). Particularly, 3GPP have evolved a communication
management system called IMS (IP Multimedia Subsystem) which is suitable to operate over a number
of bearer technologies, including LTE, NR and their successors.
In circuit switched networks the eCall is identified as an emergency call and specifically an eCall in the
telecircuit switching (TS) process. No number is dialled as the TS identifiers inform the MNO that the call
is an emergency call/eCall and the MNO has procedures to direct these calls to “the most appropriate”
PSAP. Having established a voice channel, the microphones and speakers are muted and a modem is used
to transfer the Minimum Set of Data (MSD) to the PSAP before opening up the line to enable conversation
between the PSAP operator and the occupants of the vehicle.
In a ‘packet switched’ network, packets of data (including voice) are sent using an internet protocol (IP)
communication system. 3GPP have created the IP Multimedia Subsystem (IMS) which makes use of SIP
(Session Initiation Protocol) for its call management.
This document provides High Level Application Protocols (HLAP) for eCall using IMS. It therefore
provides the IMS packet switched equivalent of EN 16062 for circuit switched networks and should be
suitable for all/any packet switched networks that support IMS and wireless access such as LTE, NR and
their successors.
This document specifies the protocols to put into effect the pan-European eCall operating requirements,
over packet switched networks networks (such as LTE, NR and their successors).
The European Committee for Standardization (CEN) draws attention to the fact that, while no direct
patents are known in express regard to the content of these specifications, the underlying ETSI
communications Standards may involve patents and the reader is directed to the referenced ETSI
standards in these respects.
1 Scope
In respect of pan European eCall (operating requirements defined in EN 16072), this document defines
the high level application protocols, procedures and processes required to provide the eCall service via a
packet switched wireless communications network using IMS (IP Multimedia Subsystem) and wireless
access (such as LTE, NR and their successors).
This document assumes support of eCall using IMS over packet switched networks by an IVS and a PSAP
and further assumes that all PLMNs available to an IVS at the time an eCall or test eCall is initiated are
packet switched networks. Support of eCall where eCall using IMS over packet switched networks is not
supported by an IVS or PSAP or PLMN is out of scope of this document.
At some moment in time packet switched networks will be the only Public Land Mobile Networks (PLMN)
available. However as long as GSM/UMTS PLMNs are available (Teleservice 12/TS12) ETSI TS 122 003
will remain operational. Both the use of such PLMNs and the logic behind choosing the appropriate
network in a hybrid situation (where both packet-switched and circuit-switched networks are available)
are out of scope of this document.
NOTE 1 The objective of implementing the pan-European in-vehicle emergency call system (eCall) is to automate
the notification of a traffic accident, wherever in Europe, with the same technical standards and the same quality of
services objectives by using a PLMN (such as ETSI prime medium) which supports the European harmonized
112/E112 emergency number (TS12 according to ETSI TS 122 003 or IMS equivalent in packet switched networks)
and to provide a means of manually triggering the notification of an emergency incident.
NOTE 2 HLAP requirements for third party services supporting eCall can be found in EN 16102. This document
makes reference to those provisions but does not duplicate them.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 15722:2020, Intelligent transport systems - ESafety - ECall minimum set of data
!EN 16062, Intelligent transport systems - ESafety - eCall high level application requirements (HLAP)
using GSM/UMTS circuit switched networks"
!EN 16072:2025", Intelligent transport systems - ESafety - Pan-European eCall operating
requirements
EN 17905, Intelligent transport systems - eSafety - eCall HLAP in hybrid circuit switched/packet switched
network environments
!ETSI TS 122 003, Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile
Telecommunications System (UMTS); LTE; Circuit Teleservices supported by a Public Land Mobile Network
(PLMN) (3GPP TS 22.003) [Release 14 or later for eCall over 4G; Release 16 or later for eCall over 5G] "
!ETSI TS 122 011, Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile
Telecommunications System (UMTS); LTE; Service accessibility (3GPP TS 22.011) [Release 14 or later for
eCall over 4G; Release 16 or later for eCall over 5G]"
!ETSI TS 122 071, Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile
Telecommunications System (UMTS); LTE; Location Services (LCS); Service description; Stage 1
(3GPP TS 22.071) [Release 14 or later for eCall over 4G; Release 16 or later for eCall over 5G]"
!ETSI TS 122 101, Universal Mobile Telecommunications System (UMTS); LTE; Service aspects; Service
principles (3GPP TS 22.101) [Release 14 or later for eCall over 4G; Release 16 or later for eCall over 5G]"
!ETSI TS 123 122, Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile
Telecommunications System (UMTS); LTE; Non-Access-Stratum (NAS) functions related to Mobile Station
(MS) in idle mode (3GPP TS 23.122) [Release 14 or later for eCall over 4G; Release 16 or later for eCall
over 5G]"
!ETSI TS 123 167, Universal Mobile Telecommunications System (UMTS); LTE; IP Multimedia Subsystem
(IMS) emergency sessions (3GPP TS 23.167) [Release 14 or later for eCall over 4G; Release 16 or later for
eCall over 5G]"
!ETSI TS 123 216, Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile
Telecommunications System (UMTS); LTE; Single Radio Voice Call Continuity (SRVCC); Stage 2
(3GPP TS 23.216) [Release 14 or later for eCall over 4G; Release 16 or later for eCall over 5G]"
!ETSI TS 123 401, LTE; General Packet Radio Service (GPRS) enhancements for Evolved Universal
Terrestrial Radio Access Network (E-UTRAN) access (3GPP TS 23.401) [Release 14 or later]"
ETSI TS 123 501, 5G; System architecture for the 5G System (5GS) (3GPP TS 23.501) [Release 16 or later]
!ETSI TS 124 229, Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile
Telecommunications System (UMTS); LTE; IP multimedia call control protocol based on Session Initiation
Protocol (SIP) and Session Description Protocol (SDP); Stage 3 (3GPP TS 24.229) [Release 14 or later for
eCall over 4G; Release 16 or later for eCall over 5G]"
!ETSI TS 124 301, Universal Mobile Telecommunications System (UMTS); LTE; Non-Access-Stratum
(NAS) protocol for Evolved Packet System (EPS); Stage 3 (3GPP TS 24.301) [Release 14 or later]"
ETSI TS 124 501, 5G; Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 (3GPP TS 24.501)
[Release 16 or later]
!ETSI TS 131 102, Universal Mobile Telecommunications System (UMTS); LTE; Characteristics of the
Universal Subscriber Identity Module (USIM) application (3GPP TS 31.102) [Release 14 or later for eCall
over 4G; Release 16 or later for eCall over 5G]"
!ETSI TS 133 203, Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile
Telecommunications System (UMTS); LTE; 3G security; Access security for IP-based services
(3GPP TS 33.203) [Release 14 or later for eCall over 4G; Release 16 or later for eCall over 5G]"
!ETSI TS 136 331, LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control
(RRC); Protocol specification (3GPP TS 36.331) [Release 14 or later]"
ETSI TS 138 331, 5G; NR; Radio Resource Control (RRC); Protocol specification (3GPP TS 38.331) [Release
16 or later]
IETF RFC 8147, Next-Generation Pan-European eCall
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp/
3.1
single European emergency call number supporting Teleservice 12
Note 1 to entry: See ETSI TS 122 003.
3.2
call clear-down
termination of call and freeing up of line (usually achieved by hanging up the receiver or pressing ‘end
call’ or similar on screen)
3.3
cellular network
wireless communications network consisting of multiple adjacent access points (cells) with the capability
of homogeneous transfer of a communications session instance to an adjacent cell without significant
interruption to the session
3.4
data
representations of static or dynamic objects in a formalized manner suitable for communication,
interpretation, or processing by humans or by machines
Note 1 to entry: In packet switched networks, voice is carried in packets of data.
3.5
data concept
any of a group of data structures (i.e. object class, property, value domain, data elements, message,
interface dialogue, association) referring to abstractions or things in the natural world that can be
identified with explicit boundaries and meaning and whose properties and behaviour all follow the same
rules
3.6
data element
single unit of information of interest (such as a fact, proposition, observation, etc.) about some (entity)
class of interest (e.g. a person, place, process, property, concept, state, event) considered to be indivisible
in a particular context
3.7
eCall
emergency call generated either automatically via activation of in-vehicle sensors or manually by the
vehicle occupants
Note 1 to entry: When activated it provides notification and relevant location information to the most appropriate
Public Safety Answering Point, by means of mobile wireless communications networks, carries a defined standardized
minimum set of data (MSD) notifying that there has been an incident that requires response from the emergency
services, and establishes an audio channel between the occupants of the vehicle and the most appropriate Public
Safety Answering Point.
3.8
eCall generator
occupant of a vehicle or equipment within a vehicle that has cause to trigger an eCall session by automatic
or manual means
3.9
eCall service
end-to-end emergency service to connect occupants of an affected vehicle to the most appropriate PSAP
via an audio link across a PLMN together with the transfer of a minimum set of data to the PSAP
3.10
eCall session
establishment of a mobile wireless communications session across a public wireless communications
network and the transmission of a minimum set of data from a vehicle to a public safety answering point
and the establishment of an audio channel between the vehicle and the PSAP
3.11
Emergency Call Server
ECS
functional entity that consists of a Location Retrieval Function (LRF) and either a routing proxy or a
redirect server
Note 1 to entry: For example an ECS contains a VPC and a Routing Proxy or Redirect Server in NENA I2 architecture.
3.12
emergency control centre
unit which deals with emergency calls and which has the capacity to consider professionally the need for
response, and which has the provision to mobilise the needed resources to deal with the emergency in
question
3.13
emergency call response centre
term used in ITS Implementation Directive to mean Public Safety Answering Point (PSAP)
3.14
identifier
label, symbol or token that names or identifies an entity or a collection of data or the means of designating
or referring to a specific instance of a data concept
3.15
IMS emergency call
IMS based emergency call in packet switched networks, which is the IMS equivalent to Teleservice 12
according to ETSI TS 122 003 in circuit switched networks
3.16
in-vehicle equipment
equipment within the vehicle that provides or has access to in-vehicle data required for the minimum set
of data and any other data that is to be sent as part of or complementary to the minimum set of data to
effect the eCall session via a public mobile wireless communications network providing a link between
the vehicle and a means of enacting the eCall service via a public mobile wireless communications
network
3.17
in-vehicle equipment provider
provider of eCall in-vehicle equipment
Note 1 to entry: The in-vehicle equipment provider can be the vehicle manufacturer or the provider of aftermarket
equipment.
3.18
in-vehicle system
IVS
in-vehicle equipment together with the means to trigger, manage and effect the eCall session
3.19
minimum set of data
MSD
standardised data concept comprising data elements of relevant vehicle generated data essential for the
performance of the eCall service
Note 1 to entry: See EN 15722.
3.20
mobile wireless communications network
wireless communications network with homogeneous handover between network access points
3.21
most appropriate PSAP
destination for eCall defined beforehand by responsible authorities to cover emergency calls from a
certain area or for emergency calls of a certain type
Note 1 to entry: See also PSAP.
Note 2 to entry: A number of different instantiations of PSAP service are supported within this document. A PSAP
can be a Public Authority or a private service provider operating on behalf of the responsible authorities.
3.22
network access device
NAD
device providing communications to a mobile wireless communications network with homogeneous
handover between network access points, also known as mobile wireless communications network device
3.23
network access point
beacon, antenna or similar source of signal propagation and receipt together with equipment to manage
communication sessions with users operating within the operating reach of the network access point and
provide connectivity for the users within the operating reach of the single access point to a wider
communications network
Note 1 to entry: A network access point may, but does not need to, provide homogeneous or heterogeneous
handover to another network access point.
3.24
public mobile wireless communications network
mobile wireless communications network with access to a public telecommunications network
3.25
Public Safety Answering Point
PSAP
physical location working on behalf of the national authorities where emergency calls are first received
under the responsibility of a public authority or a private organization recognized by the national
government
Note 1 to entry: See also most appropriate PSAP.
Note 2 to entry: A number of different instantiations of PSAP service are supported within this document.
3.26
vehicle manufacturer
entity which first assembles the vehicle and provides eCall equipment as part of its specification and
subsequently sells the vehicle directly or via an agent
3.27
vehicle occupant
person inside the vehicle
3.28
wireless communications network
network operating using an air-interface capable of bi-directional transfer of data and or voice
Note 1 to entry: There are different types of wireless communications such as PAN, LAN, cellular network, etc.
4 Symbols and abbreviations
3GPP Third Generation Partnership Project
5G 5th Generation
ACK ACKnowledgement
AL-ACK Application Layer ACKnowledgement
AMF Access and mobility Management Function
CAN Controller-Area Network
CS Circuit Switched
CLI Calling Line Identity
EC European Commission
ECL eCall using IMS over packet switched networks support indicator
ESQK Emergency Service Query Key
ETSI European Telecommunications Standards Institute
GSM Global System for Mobile communications
HPLMN Home Public Land Mobile Network
HSS Home Subscriber Server
IETF Internet Engineering Task Force
IMS IP Multimedia Subsystem
IMSI International Mobile Subscriber Identity
IP-CAN IP- Connectivity Access Network
IVS In-Vehicle System
LAN Local Area Network
LL-ACK Lower Layer ACKnowledgement
LRF Location Retrieval Function
LTE Long Term Evolution
MME Mobility Management Entity
MNO Mobile Network Operator
MSD Minimum Set of Data
NAD Network Access Device
NENA National Emergency Numbering Association
NG-RAN Next Generation Radio Access Network
NR New Radio
PAN Personal Area Network
PLMN Public Land Mobile Network
PS Packet Switched
PSAP Public Safety Answering Point
TEL-URI Telephone Uniform Resource Identifier
SDP Session Description Protocol
SIP Session Initiation Protocol
TPS Third Party Service
TPSP Third Party Service Provider
TS (i) Technical Specification
TS (ii) Teleservice
TS12 Teleservice 12
UE User Equipment
NOTE ETSI/3GPP term which general refers to the IVS in the context of eCall
UMTS Universal Mobile Telecommunication System
USIM Universal Subscriber Identity Module
VoIP Voice over IP
VPC VoIP Positioning Centre
5 Conformance
Conformance to the requirements of this document for eCall using IMS over packet switched networks
are to be found in EN 17240.
This document makes no conformance specifications or requirements in respect of TPS eCall operating
requirements, and conformance requirements in respect of TPS eCall can be found in EN 16454.
This document makes no requirements in respect of eCall HLAP in hybrid circuit switched/packet
switched network environments. Corresponding conformance requirements can be found in EN 18052.
6 General overview of pan European eCall session via Packet Switched networks
6.1 General principle
In the introduction to the document, EN 16072, eCall was described as an emergency call generated either
automatically via activation of in-vehicle sensors or manually by the vehicle occupants (the eCall
generator); when activated, it provides notification and relevant location information to the most
appropriate Public Safety Answering Point, by means of mobile wireless communications networks and
carries a defined standardized minimum set of data, notifying that there has been an incident that requires
response from the emergency services and establishes an audio channel between the occupants of the
vehicle and the most appropriate Public Safety Answering Point.
Figure 1 shows an illustrative view of the pan-European eCall service, as defined in EN 16072.

(SOURCE: European Commission)
Figure 1 — General overview: pan European eCall service using GSM/UMTS
In circuit switched networks the eCall is identified as an emergency call and specifically an eCall in the
telecircuit switching (TS) process. The emergency number (112) is not dialled as the TS identifiers inform
the MNO that the call is an emergency call/eCall and the MNO has procedures to direct these calls to “the
most appropriate” PSAP. Having established a voice channel, the microphones and speakers are muted
and a modem is used to transfer the Minimum Set of Data (MSD) to the PSAP before opening up the line
to enable conversation between the PSAP operator and the occupants of the vehicle.
6.2 eCall over Packet Switched networks
Technology advances and subsequently to the development of the eCall application suite EN 16072,
EN 16062 and EN 16454 standards, packet switched networks have become available. Over the course of
time, these packet switched networks (such as LTE, NR and their successors) are expected to provide
new PLMNs to complement and eventually replace the circuit switched GSM/UMTS networks.
The high level paradigm for eCall remains unchanged, but there are fundamental differences in packet
switched networks: the TS mechanism is not available and the switching paradigm is different, allowing
for a more robust way of data transfer. 3GPP has developed IMS (IP Multimedia Subsystem) which is an
all-IP (Internet Protocol) system designed to assist mobile operators deliver next generation interactive
and interoperable services, cost-effectively, over an architecture providing the flexibility of the Internet.
IMS is designed for packet switched networks and supports IP multimedia applications via IP multimedia
sessions over a multitude of IP Connectivity Access Networks, such as NG-RAN, E-UTRAN, UTRAN,
GERAN, LAN, DOCSIS®, WiMAX™, cdma2000® and DVB-RCS2 access. It is likely that all subsequent
IP based packet switched networks will therefore be able to support IMS, making migration to future, as
yet undeveloped technologies, a simpler and easier to achieve process.
It is therefore appropriate to require the availability of IMS on a packet switched network for eCall to
function, rather than any of the specific wireless technologies, as it provides greater flexibility and
migration potential.
6.3 eCall using IMS over Packet Switched networks
In a packet switched environment where IMS is available, the eCall is established as an internet protocol
based session with the exchange of packets of data (which in this case, are largely packets of voice data),
and the MSD is provided as part of the session establishment. This is completely different from the mode
of operation in circuit switched networks. It is therefore necessary to provide a separate specification for
“High Level Application Protocols” to manage eCall via packet switched networks.
Figure 2 shows the IMS equivalent of Figure 1 and compares it to eCall via circuit switched networks.
Figure 2 — Overview: eCall using IMS over packet switched networks compared to eCall over CS
networks
NOTE 1 Albeit out of scope for this document, IMS has a further advantage in that it can also be used over fixed
lines. This makes the forwarding of eCalls from 1st level PSAP responder to 2nd level PSAP responders and
responding emergency services via fixed lines, an easier and more simple process; and even enabling the call to then
be subsequently diverted to a handset of a responding ambulance, fire truck or police responder.
Session Initiation Protocol (SIP) was selected as the signalling mechanism for IMS (see IETF RFC 3261),
thereby allowing voice, text and multimedia services to traverse all connected networks. And is aligned
with IETF internet protocols to ensure maximum re-usability of internet standards, preventing
fragmentation of IMS standards.
Further information on this system is specified in ETSI:
— ETSI TS 122 228,
— ETSI TS 123 228,
— ETSI TS 123 167,
— ETSI TS 124 229.
(Or their 3GPP equivalent specifications)
IMS carries special and specific provision for emergency communications and these are further provided
in ETSI TS 122 101: “Service principles”, which incorporates the MSD into the SIP INVITE, and provides
priority on the network for emergency communications and IETF RFC 8147, ETSI TS 123 167 and
ETSI TS 124 229 !deleted text".
It is in the nature of the implementation of 3GPP specifications that the provisions that are actually
implemented/supported are left to the implementer. It is not uncommon, especially with PLMN/MNOs,
that not all provisions of a 3GPP release are supported. In order to be compliant with this European
Standard, some provisions relating to eCall from forenamed specifications are not considered mandatory
for PLMN/MNOs, IVS and PSAPs. Where appropriate this is mentioned in the relevant clauses.
NOTE 2 The provisions referenced as optional are so specified because those might not practicably be
supportable by many PSAP organization deployments, and in some of these implementations might cause other
technical issues, and can only be used compliant to the additional provisions elaborated in this European Standard.
With IMS, there is no requirement for eCall for muting and reconnecting loudspeakers and microphones
in the affected vehicle, as the MSD has already been passed on in the SIP INVITE message to initiate the
call setup. A modem is not required at either end of the eCall, although transfer by modem is an optional
requirement. eCall using IMS is therefore simpler, and has higher reliability, and potential for data in
addition to the MSD to be sent, therefore enabling “next generation” capabilities to be added to eCall,
without further changing the basic communications architecture.
Whereas, in circuit switched eCall, there are acknowledgements made at both the lower communications
layer and the upper applications layer (LL-ACK and AL-ACK); using IMS, the lower layer
acknowledgements are provided automatically and invisibly by the IMS system. The MSD is sent as part
of the SIP INVITE requiring only an AL-ACK, which is sent as “MSD ACK” within the SIP 200 OK message
by the receiving party. The AL-ACK confirms that the MSD has not only been received, but has been
successfully decoded.
Figure 3 provides an overview of the process of the eCall using IMS over packet switched networks.
eCall using IMS over packet switched networks will only operate where there is an appropriate PLMN
available supporting packet switched network access with IMS and eCall facilities enabled.
Following the initial resolution of the incident by the PSAP operator, the PSAP operator may clear-down
the call, however, the in-vehicle system (IVS responsible for the eCall system) remains registered on the
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