ETSI TS 103 792 V1.0.0 (2025-07)
Rail Telecommunications (RT); Future Railway Mobile Communication System (FRMCS); Interworking with GSM-R
Rail Telecommunications (RT); Future Railway Mobile Communication System (FRMCS); Interworking with GSM-R
DTS/RT-0088
Železniške telekomunikacije (RT) - Prihodnji sistem radijskih komunikacij za železnice (FRMCS) - Sodelovanje z GSM-R
General Information
Standards Content (Sample)
Draft ETSI TS 103 792 V1.0.0 (2025-07)
TECHNICAL SPECIFICATION
Rail Telecommunications (RT);
Future Railway Mobile Communication System (FRMCS);
Interworking with GSM-R
2 Draft ETSI TS 103 792 V1.0.0 (2025-07)
Reference
DTS/RT-0088
Keywords
FRMCS, GSM-R, interworking, railways
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ETSI
3 Draft ETSI TS 103 792 V1.0.0 (2025-07)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 6
Introduction . 6
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 9
3 Definition of terms, symbols and abbreviations . 10
3.1 Terms . 10
3.2 Symbols . 11
3.3 Abbreviations . 11
4 Services . 12
4.1 General . 12
4.2 Group call . 12
4.3 Emergency group call . 13
4.4 Point-to-point call . 13
4.5 Text messaging service . 13
5 Functional model . 13
5.1 Functional model description . 13
5.2 Reference points . 14
5.2.0 General . 14
5.2.1 Reference point IWF-1 (between the IWF and the MCPTT server) . 15
5.2.2 Reference point IWF-2 (between the IWF and the MCData server) . 15
5.2.3 Reference point IWF-3 (between the IWF and the group management server) . 15
5.2.4 Reference point IWF-g1 (between the IWF and the MSC server/MGCF) . 15
5.2.5 Reference point IWF-g2 (between the IWF and MGW). 15
5.2.6 Reference point IWF-g5 (between the IWF and IP-SM-GW) . 16
6 Identities and addressing . 16
6.0 General . 16
6.1 Identity definitions . 16
6.2 Representation in interworking systems . 17
6.3 Identity mapping and addressing . 18
6.3.0 General . 18
6.3.1 Management policies for identity mapping and routing . 18
6.3.1.1 General . 18
6.3.1.2 Examples for the changing of the domain in SIP URIs . 19
6.3.2 SIP routing services . 20
6.3.2.1 GSM-R to FRMCS out-of-dialog SIP requests . 20
6.3.2.2 FRMCS to GSM-R out-of-dialog SIP requests . 20
6.3.3 Identity mapping services . 21
6.3.3.0 General . 21
6.3.3.1 Generic procedures for identity mapping . 21
6.3.3.1.0 General . 21
6.3.3.1.1 Generic identity mapping for GSM-R to FRMCS SIP messages . 21
6.3.3.1.2 Generic identity mapping for FRMCS to GSM-R SIP messages . 22
6.3.3.2 Mapping of basic address parameters for MCPTT private calls . 22
6.3.3.2.0 General . 22
6.3.3.2.1 Basic address parameters for GSM-R to FRMCS private calls . 23
6.3.3.2.2 Basic address parameters for FRMCS to GSM-R private calls . 23
6.3.3.3 Identity mapping for MCData SDS . 24
6.3.3.3.0 General . 24
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4 Draft ETSI TS 103 792 V1.0.0 (2025-07)
6.3.3.3.1 Address parameters for GSM-R to FRMCS text messages . 24
6.3.3.3.2 Address parameters for FRMCS to GSM-R text messages . 25
6.3.3.4 Identity mapping for supplementary services. 25
6.3.3.4.0 General . 25
6.3.3.4.1 Presentation of Functional Number - User To User Information . 26
6.3.3.4.2 Call Diversion - Call History Address List . 26
6.3.3.4.3 Explicit Call Transfer - Connected Address . 27
6.3.3.5 Mapping of Identities, Criteria and Domains for MCPTT group calls . 27
6.3.3.5.0 General . 27
6.3.3.5.1 Mapping of basic address parameters for MCPTT group calls . 28
6.3.3.5.2 Mapping of FRMCS criteria and EIRENE CT5 FN . 28
7 Group calls . 29
7.1 Interworking procedures . 29
7.1.0 General . 29
7.1.1 Information flows . 30
7.1.1.1 Stage 2 information flows . 30
7.1.1.1.1 General . 30
7.1.1.1.2 IWF GSM-R IWF ad-hoc group call request. 31
7.1.1.1.3 IWF GSM-R IWF ad-hoc group call response . 31
7.1.1.2 Stage 3 Information flows . 31
7.2 Group call principles . 32
7.2.1 Group call initiated by a GSM-R user . 32
7.2.1.1 Group call initiated by a GSM-R user interacting with MCPTT group call . 32
7.2.1.1.1 Stage 2 procedure . 32
7.2.1.1.2 Stage 3 procedure . 33
7.2.2 Group call initiated by an MCPTT user . 35
7.2.2.1 Group call setup initiated by MCPTT user interacting with the GSM-R system . 35
7.2.2.1.1 Stage 2 procedure . 35
7.2.2.1.2 Stage 3 procedure . 37
7.2.3 Late entry . 39
7.2.3.1 Late entry of an MCPTT user . 39
7.2.3.1.1 Stage 2 procedure . 39
7.2.3.1.2 Stage 3 procedure . 41
7.2.3.2 Late entry of a GSM-R user . 41
7.2.3.2.1 Stage 2 procedure . 41
7.2.3.2.2 Stage 3 procedure . 42
7.2.4 Group call release . 42
7.2.4.1 General . 42
7.2.4.2 Group call release initiated from the GSM-R side . 42
7.2.4.2.1 Procedure . 42
7.2.4.3 Group call release initiated from the MCPTT side . 43
7.2.4.3.1 Procedure . 43
7.2.5 Talker control . 44
7.2.5.1 General . 44
7.2.5.2 Talker control operation initiated from the GSM-R side . 44
7.2.5.2.1 Procedure . 44
7.2.5.3 Talker control operation initiated from the MCPTT side . 45
7.2.5.3.1 Procedure . 45
7.2.6 Handling of mute and unmute in GSM-R . 47
7.2.6.1 General . 47
7.2.6.2 Procedure . 47
7.2.7 Media encryption . 49
7.2.8 Codec negotiation . 49
7.2.8.1 Codec negotiation for calls initiated by MCPTT user . 49
7.2.8.2 Codec negotiation for calls initiated by GSM-R user . 49
7.2.9 Codec transcoding . 50
8 Point-to-point call . 50
8.1 General . 50
8.2 Point-to-point call from GSM-R user to user on MCPTT system . 51
8.2.1 Point-to-point call . 51
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5 Draft ETSI TS 103 792 V1.0.0 (2025-07)
8.2.1.1 Stage 2 procedure . 51
8.2.1.2 Stage 3 procedure . 51
8.2.2 Point-to-point call rejected by MCPTT system . 53
8.2.2.1 Stage 2 procedure . 53
8.2.2.2 Stage 3 procedure . 53
8.3 Point-to-point call initiated by an MCPTT user . 54
8.3.1 Point-to-point call . 54
8.3.1.1 Stage 2 procedure . 54
8.3.1.2 Stage 3 procedure . 54
8.3.2 Point-to-point call rejected by GSM-R system . 55
8.3.2.1 Stage 2 procedure . 55
8.3.2.2 Stage 3 procedure . 55
8.4 Point-to-point call release . 56
8.4.1 Individual call release by GSM-R user . 56
8.4.1.1 Stage 2 procedure . 56
8.4.1.2 Stage 3 procedure . 56
8.4.2 Individual call release by FRMCS user . 57
8.4.2.1 Stage 2 procedure . 57
8.4.2.2 Stage 3 procedure . 57
9 Text messaging service . 58
9.1 General . 58
9.2 One-to-one text messaging procedures . 58
9.2.1 One-to-one SDS to Instant Messaging interworking principles . 58
9.3 One-to-One text messaging protocols IWF to/from the MCData server . 61
Annex A (informative): Voice transcoding to and from AMR-WB when AMR-WB is not
supported by a GSM-R system . 63
A.1 Introduction . 63
A.2 Transcoding in a GSM-R system . 63
A.3 Implementation of transcoding in the FRMCS Domain . 63
History . 64
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6 Draft ETSI TS 103 792 V1.0.0 (2025-07)
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Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Railway Telecommunications (RT)
and is now submitted for the combined Public Enquiry and Vote phase of the ETSI Standardisation Request deliverable
Approval Procedure (SRdAP).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
GSM-R has been a great success not only in Europe, where more than 100 000 km of railway tracks are daily operated
through GSM-R, but also worldwide, and this number will double within the next years due to the on-going installations
of this technology all over the world.
As the needs of the railways are constantly evolving, in particular in the context of the digitalisation of rail operation
that is pursued in many countries and considering the upcoming obsolescence of GSM-R technology, UIC launched in
2012 the first studies for a successor to GSM-R, pertinently named Future Railway Mobile Communication System
(FRMCS). The UIC project then concretely delivered the FRMCS Functional Requirements Specifications (FRS) [1]
and FRMCS System Requirement Specifications (SRS) [2] focusing mainly on rail communication needs - as a basis
for the development of the GSM-R successor.
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7 Draft ETSI TS 103 792 V1.0.0 (2025-07)
The present document has been written to satisfy the identified need for interworking between GSM-R and the FRMCS
Mission Critical applications specified by 3GPP, to enable communications between users and groups operating on the
two system technologies. It provides solutions to the considerations documented in ETSI TR 103 768 [i.1], which
studied the issues for interworking between the two technologies.
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8 Draft ETSI TS 103 792 V1.0.0 (2025-07)
1 Scope
The present document defines the functional model including reference points as well as the protocol and procedure for
interworking between GSM-R R4 and FRMCS and covers the following services:
• Group call.
• Emergency group call.
• Point-to-point call.
• Text messaging Service.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found in the
ETSI docbox.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long-term validity.
The following referenced documents are necessary for the application of the present document.
[1] UIC FU-7120: "Future Railway Mobile Communication System - Functional Requirements
th
Specification", Version 2.0.0 December 13 , 2024.
[2] UIC FW-AT 7800: "Future Railway Mobile Communication System - System Requirements
th
Specification", Version 2.0.0 December 13 , 2024.
[3] UIC FIS-7970: "Future Railway Mobile Communication System - Functional Interface
th
Specification", Version 2.0.0 December 13 , 2024.
[4] ETSI TS 103 765-2: "Rail Telecommunications (RT); Future Railway Mobile Communication
System (FRMCS); Building blocks and functions; Part 2: Service Stratum".
[5] IETF RFC 8101: "IANA Registration of New Session Initiation Protocol (SIP) Resource-Priority
Namespace for Mission Critical Push To Talk Service".
[6] ETSI TS 103 389 (V3.4.1): "Rail Telecommunications (RT); Global System for Mobile
communications (GSM); Usage of Session Initiation Protocol (SIP) on the Network Switching
Subsystem (NSS) to Fixed Terminal Subsystem (FTS) interface for GSM Operation on Railways".
[7] ETSI TS 123 228 (V18.9.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; IP Multimedia Subsystem
(IMS); Stage 2 (3GPP TS 23.228 version 18.9.0 Release 18)".
[8] ETSI TS 129 379 (V18.0.0): "LTE; 5G; Mission Critical Push To Talk (MCPTT) call control
interworking with Land Mobile Radio (LMR) systems; Stage-3 (3GPP TS 29.379 version 18.0.0
Release 18)".
[9] ETSI TS 124 282 (V18.10.0): "LTE; Mission Critical Data (MCData) signalling control; Protocol
specification (3GPP TS 24.282 version 18.10.0 Release 18)".
[10] ETSI TS 124 379 (V18.10.0): "LTE; Mission Critical Push To Talk (MCPTT) call control;
Protocol specification (3GPP TS 24.379 version 18.10.0 Release 18)".
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9 Draft ETSI TS 103 792 V1.0.0 (2025-07)
[11] ETSI TS 123 283 (V18.3.0): "LTE; Mission Critical Communication Interworking with Land
Mobile Radio Systems (3GPP TS 23.283 version 18.3.0 Release 18)".
[12] ETSI TS 129 163 (V18.1.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; Interworking between the IP
Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networks (3GPP
TS 29.163 version 18.1.0 Release 18)".
[13] ETSI TS 133 180 (V18.1.0): "LTE; Security of the Mission Critical (MC) service (3GPP
TS 33.180 version 18.1.0 Release 18)".
[14] IETF RFC 3428: "Session Initiation Protocol (SIP) Extension for Instant Messaging".
[15] IETF RFC 5373: "Requesting Answering Modes for the Session Initiation Protocol (SIP)".
[16] IETF RFC 3261: "SIP: Session Initiation Protocol".
[17] IETF RFC 3841: "Caller Preferences for the Session Initiation Protocol (SIP)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents may be useful in implementing an ETSI deliverable or add to the reader's
understanding, but are not required for conformance to the present document.
[i.1] ETSI TR 103 768: "Rail Telecommunications (RT); Future Rail Mobile Communication System
(FRMCS); Interworking study with legacy systems".
[i.2] EIRENE System Requirements Specification, Version 16.1.0, February 2023.
[i.3] ETSI TS 123 280 (V18.12.0): "LTE; Common functional architecture to support mission critical
services; Stage 2".
[i.4] ETSI TS 123 040 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; Technical realization of the
Short Message Service (SMS) (3GPP TS 23.040 version 18.0.0 Release 18)".
[i.5] ETSI TS 123 002 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; Network architecture (3GPP
TS 23.002 version 18.0.0 Release 18)".
[i.6] ETSI TS 123 379 (V18.12.0): "LTE; Functional architecture and information flows to support
Mission Critical Push To Talk (MCPTT); Stage 2 (3GPP TS 23.379 version 18.12.0 Release 18)".
[i.7] ETSI TS 123 282 (V18.10.0): "LTE; Functional architecture and information flows to support
Mission Critical Data (MCData); Stage 2 (3GPP TS 23.282 version 18.10.0 Release 18)".
[i.8] ETSI TS 143 068 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Voice Group Call Service (VGCS); Stage 2 (3GPP TS 43.068 version 18.0.0 Release 18)".
[i.9] ETSI TS 123 236 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; Intra-domain connection of Radio
Access Network (RAN) nodes to multiple Core Network (CN) nodes (3GPP TS 23.236
version 18.0.0 Release 18)".
[i.10] ETSI TS 129 311 (V18.0.0): "Universal Mobile Telecommunications System (UMTS); LTE;
Service Level Interworking (SLI) for messaging services (3GPP TS 29.311 version 18.0.0
Release 18)".
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10 Draft ETSI TS 103 792 V1.0.0 (2025-07)
[i.11] ETSI TS 124 229 (V18.7.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; IP multimedia call control
protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP);
Stage 3 (3GPP TS 24.229 version 18.7.0 Release 18)".
[i.12] ETSI TR 103 791: "Rail Telecommunications (RT); Future Railway Mobile Communication
System (FRMCS); Terminology for FRMCS specifications".
[i.13] ETSI TS 123 283 (V18.2.0): "LTE; Mission Critical Communication Interworking with Land
Mobile Radio Systems (3GPP TS 23.283 version 18.2.0 Release 18)".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in ETSI TR 103 791 [i.12] and the following apply:
E.164 SIP-R URI: SIP-R URI which describes an international E.164 address
EIRENE SIP-R URI: SIP-R URI which describes an international EIRENE address
FA(164): Functional Alias (FA) which takes the form of an E.164 SIP-R URI and is transmitted in MCX related
messages, according to the transmission of FAs
NOTE: As specified in ETSI TS 124 379 [10] and ETSI TS 124 282 [9].
FA(EIRENE): Functional Alias (FA) which takes the form of an EIRENE SIP-R URI and is transmitted in MCX
related messages, according to the transmission of FAs
NOTE: As specified in ETSI TS 124 379 [10] and ETSI TS 124 282 [9].
FRMCS Entity: entity which is either:
a) a user of the MCX system;
b) a user of a partner MC system of the MCX system;
c) a group of users of the MCX system;
d) a group of users of a partner MC system of the MCX system;
e) a railway function that is registered or activated as FA at the MCX system; or
f) a railway function that is registered or activated as FA at a partner MC system of the MCX system.
GSM-R Entity: entity which is either GSM-R user, a GSM-R service or a railway function that is not an FRMCS entity
identity and criteria mapping: local service of the IWF for mapping between identities and criteria achieved without
requests from the IWF to external data bases or other remote storage (i.e. it is achieved by local address lookup or by
rule-based rephrasing)
local address lookup: local lookup of identity mappings within the IWF, e.g. by tables that have been setup during
provisioning time
rephrasing: rule-based mapping of EIRENE addresses to FRMCS FAs and vice versa
NOTE: This rule-based rephrasing is based on FRMCS FRS [1].
subscribers: user identified by E.164 addresses.
NOTE: This can mean:
a) GSM-R subscribers;
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11 Draft ETSI TS 103 792 V1.0.0 (2025-07)
b) Users of the MCX system;
c) Groups of users of the MCX system.
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
rd
3GPP 3 Generation Partnership Project
AMR-WB Adaptative MultiRate-Wide Band
CdA Called Address
CgA Calling Address
CHPC Confirmation of High Priority Call
CSC Coding Scheme Code
CT Call Type
CT5 Call Type 5
ECT Explicit Call Transfer
EIR Equipment Identity Register
EIRENE European Integrated Railway Radio Enhanced Network
ETSI European Telecommunications Standards Institute
EVS-SWB Enhanced Voice Service - Super Wide Band
FA Functional Alias
FIS Functional Interface Specification
FN Functional Number
FRMCS Future Railway Mobile Communication System
FRS Functional Requirement Specification
FTS Fixed Terminal Subsystem
GCR Group Call Register
GCref Group Call Reference
GID Group call Identity
GPS Global Positioning System
GSM Global System for Mobile communications
GSM-R Global System for Mobile communications - Railways
GW GateWay
HLR Home Location Register
IC International Code
IE Information Element
IETF Internet Engineering Task Force
IM Intstant Messaging
IMS IP Multimedia Subsystem
IMSI International Mobile Subscriber Identity
IP Internet Protocol
IP-SM-GW IP Short Message Gateway
ISC IP multimedia subsystem Service Control interface
IWF InterWorking Function
IW-GW InterWorking-GateWay
MAP Mobile Application Part
MC Mission-Critical
MCData Mission-Critical Data
MCPPT Mission Critical Push To Talk
MCPTT Mission-Critical Push-To-Talk
MCX Mission Critical communications
MDF Media Distribution Frame
MGCF Media Gateway Control Function
MGW Media GateWay
MIME Multipurpose Internet Mail Extensions
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12 Draft ETSI TS 103 792 V1.0.0 (2025-07)
MS Mobile Station
MSC Mobile Switching Centre
MSS Mobile Switching Subsystem
OIP Originating Identification Presentation
OMA-TS Open Mobile Alliance-Technical Specification
OTDI Originator To Dispatcher Information
PABX Private Automatic Branch eXchange
PAI P-Asserted Identity
PFN Presentation Functional Number
PTT Push-To-Talk
REC Railway Emergency Call
RFC Request For Comments
RTCP Real time Ta
S-CSCF Serving-Call Session Control Function
SDP Session Description Protocol
SDS Short Data Service
SIM Subscriber Identity Module
SIP Session Initiation Protocol
SIP-R Session Initiation Protocol for Railways
SLI Service Level Interworking
SM Short Message
SMPP Short Message Peer-to-Peer protocol
SMS Short Message Service
SMSC Short Message Service Center
SRS System Requirement Specification
TIP Terminating Identification Presentation
TR Technical Report
TS Technical Specification
UE User Equipment
URI Uniform Resource Identifier
URN Uniform Resource Number
VBS Voice Broadcast Service
VGCS Voice Group Call Service
XML eXtensible Markup Language
4 Services
4.1 General
This clause describes the services for interworking between GSM-R and FRMCS 3GPP MC systems supported in the
present document.
4.2 Group call
This clause describes group call services that are supported for groups defined on the MC system and groups defined on
the GSM-R system.
The following group call procedures are supported:
• Initiation of a group call by a FRMCS user.
• Initiation of a group call by a GSM-R user.
• Late entry.
• Termination of a group call.
• Interworking of floor control on MCPTT with uplink control and dispatcher mute/unmute in GSM-R.
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13 Draft ETSI TS 103 792 V1.0.0 (2025-07)
• Interworking of the media codecs and encryption between GSM-R and MCPTT.
4.3 Emergency group call
Emergency group calls, i.e. group calls with pre-emptive priority, are supported for the same cases as described in
clause 4.2.
4.4 Point-to-point call
The following point-to-point call procedures are supported:
• Initiating a point-to-point call from a user on the GSM-R system to a user on the MC system.
• Initiating a point-to-point call from a user on the FRMCS system to a user on the GSM-R system.
• Interworking of the media codecs and encryption between GSM-R and MCPTT.
• Termination of a point-to-point call.
NOTE: Point-to-point calls for interworking are without floor control.
4.5 Text messaging service
The GSM-R system includes Mobile Stations (MS) capable of performing various types of calls, such as voice and data
calls, and also supports text messaging by enabling the transmission of Short Messages (SMs) between mobile stations.
EIRENE System Requirements Specification [i.2] specifies that, whenever text messaging is implemented in the
GSM-R network, the Short Message Service (SMS) - is to be used (see clause 12.2.1 of EIRENE System Requirements
Specification [i.2]).
The Short Message Service and Short Messages are defined in ETSI TS 123 040 [i.4].
The present document specifies Short Data Service (SDS) interworking between GSM-R users and MCData clients
using one-to-one standalone SDS messages. The IWF behaves as a peer MCData server to other MCData servers for the
FRMCS side and it implements the ISC interface as an S-CSCF, as the IP-SM-GW (SMS application server) is
considered a part of the GSM-R side.
When a GSM-R user attempts to send a GSM-R message to the MCData service, the IWF converts the Instant Message
from the IP-SM Gateway into a request to send an MCData SDS message. When an MCData user sends an SDS
message to the GSM-R system, the IWF converts the message to an Instant Message and converts the destination and
originating address using the same mapping techniques as in point-to-point voice calls. The IWF then forwards the
Instant Message via the IP-SM-GW to the GSM-R SMSC.
NOTE: MCDATA SDS is limited to MCDATA SDS Text Messaging.
5 Functional model
5.1 Functional model description
The present document defines the reference points between the IWF and the FRMCS servers as well as the reference
points between the IWF and the GSM-R nodes. Additionally, it defines the functionality of the IWF, which acts as an
MC service server connected with the FRMCS MC service server utilizing the IWF-1
...
SLOVENSKI STANDARD
01-september-2025
Železniške telekomunikacije (RT) - Prihodnji sistem radijskih komunikacij za
železnice (FRMCS) - Sodelovanje z GSM-R
Rail Telecommunications (RT) - Future Railway Mobile Communication System
(FRMCS) - Interworking with GSM-R
Ta slovenski standard je istoveten z: ETSI TS 103 792 V1.0.0 (2025-07)
ICS:
33.060.01 Radijske komunikacije na Radiocommunications in
splošno general
45.020 Železniška tehnika na Railway engineering in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
Draft ETSI TS 103 792 V1.0.0 (2025-07)
TECHNICAL SPECIFICATION
Rail Telecommunications (RT);
Future Railway Mobile Communication System (FRMCS);
Interworking with GSM-R
2 Draft ETSI TS 103 792 V1.0.0 (2025-07)
Reference
DTS/RT-0088
Keywords
FRMCS, GSM-R, interworking, railways
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ETSI
3 Draft ETSI TS 103 792 V1.0.0 (2025-07)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 6
Introduction . 6
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 9
3 Definition of terms, symbols and abbreviations . 10
3.1 Terms . 10
3.2 Symbols . 11
3.3 Abbreviations . 11
4 Services . 12
4.1 General . 12
4.2 Group call . 12
4.3 Emergency group call . 13
4.4 Point-to-point call . 13
4.5 Text messaging service . 13
5 Functional model . 13
5.1 Functional model description . 13
5.2 Reference points . 14
5.2.0 General . 14
5.2.1 Reference point IWF-1 (between the IWF and the MCPTT server) . 15
5.2.2 Reference point IWF-2 (between the IWF and the MCData server) . 15
5.2.3 Reference point IWF-3 (between the IWF and the group management server) . 15
5.2.4 Reference point IWF-g1 (between the IWF and the MSC server/MGCF) . 15
5.2.5 Reference point IWF-g2 (between the IWF and MGW). 15
5.2.6 Reference point IWF-g5 (between the IWF and IP-SM-GW) . 16
6 Identities and addressing . 16
6.0 General . 16
6.1 Identity definitions . 16
6.2 Representation in interworking systems . 17
6.3 Identity mapping and addressing . 18
6.3.0 General . 18
6.3.1 Management policies for identity mapping and routing . 18
6.3.1.1 General . 18
6.3.1.2 Examples for the changing of the domain in SIP URIs . 19
6.3.2 SIP routing services . 20
6.3.2.1 GSM-R to FRMCS out-of-dialog SIP requests . 20
6.3.2.2 FRMCS to GSM-R out-of-dialog SIP requests . 20
6.3.3 Identity mapping services . 21
6.3.3.0 General . 21
6.3.3.1 Generic procedures for identity mapping . 21
6.3.3.1.0 General . 21
6.3.3.1.1 Generic identity mapping for GSM-R to FRMCS SIP messages . 21
6.3.3.1.2 Generic identity mapping for FRMCS to GSM-R SIP messages . 22
6.3.3.2 Mapping of basic address parameters for MCPTT private calls . 22
6.3.3.2.0 General . 22
6.3.3.2.1 Basic address parameters for GSM-R to FRMCS private calls . 23
6.3.3.2.2 Basic address parameters for FRMCS to GSM-R private calls . 23
6.3.3.3 Identity mapping for MCData SDS . 24
6.3.3.3.0 General . 24
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4 Draft ETSI TS 103 792 V1.0.0 (2025-07)
6.3.3.3.1 Address parameters for GSM-R to FRMCS text messages . 24
6.3.3.3.2 Address parameters for FRMCS to GSM-R text messages . 25
6.3.3.4 Identity mapping for supplementary services. 25
6.3.3.4.0 General . 25
6.3.3.4.1 Presentation of Functional Number - User To User Information . 26
6.3.3.4.2 Call Diversion - Call History Address List . 26
6.3.3.4.3 Explicit Call Transfer - Connected Address . 27
6.3.3.5 Mapping of Identities, Criteria and Domains for MCPTT group calls . 27
6.3.3.5.0 General . 27
6.3.3.5.1 Mapping of basic address parameters for MCPTT group calls . 28
6.3.3.5.2 Mapping of FRMCS criteria and EIRENE CT5 FN . 28
7 Group calls . 29
7.1 Interworking procedures . 29
7.1.0 General . 29
7.1.1 Information flows . 30
7.1.1.1 Stage 2 information flows . 30
7.1.1.1.1 General . 30
7.1.1.1.2 IWF GSM-R IWF ad-hoc group call request. 31
7.1.1.1.3 IWF GSM-R IWF ad-hoc group call response . 31
7.1.1.2 Stage 3 Information flows . 31
7.2 Group call principles . 32
7.2.1 Group call initiated by a GSM-R user . 32
7.2.1.1 Group call initiated by a GSM-R user interacting with MCPTT group call . 32
7.2.1.1.1 Stage 2 procedure . 32
7.2.1.1.2 Stage 3 procedure . 33
7.2.2 Group call initiated by an MCPTT user . 35
7.2.2.1 Group call setup initiated by MCPTT user interacting with the GSM-R system . 35
7.2.2.1.1 Stage 2 procedure . 35
7.2.2.1.2 Stage 3 procedure . 37
7.2.3 Late entry . 39
7.2.3.1 Late entry of an MCPTT user . 39
7.2.3.1.1 Stage 2 procedure . 39
7.2.3.1.2 Stage 3 procedure . 41
7.2.3.2 Late entry of a GSM-R user . 41
7.2.3.2.1 Stage 2 procedure . 41
7.2.3.2.2 Stage 3 procedure . 42
7.2.4 Group call release . 42
7.2.4.1 General . 42
7.2.4.2 Group call release initiated from the GSM-R side . 42
7.2.4.2.1 Procedure . 42
7.2.4.3 Group call release initiated from the MCPTT side . 43
7.2.4.3.1 Procedure . 43
7.2.5 Talker control . 44
7.2.5.1 General . 44
7.2.5.2 Talker control operation initiated from the GSM-R side . 44
7.2.5.2.1 Procedure . 44
7.2.5.3 Talker control operation initiated from the MCPTT side . 45
7.2.5.3.1 Procedure . 45
7.2.6 Handling of mute and unmute in GSM-R . 47
7.2.6.1 General . 47
7.2.6.2 Procedure . 47
7.2.7 Media encryption . 49
7.2.8 Codec negotiation . 49
7.2.8.1 Codec negotiation for calls initiated by MCPTT user . 49
7.2.8.2 Codec negotiation for calls initiated by GSM-R user . 49
7.2.9 Codec transcoding . 50
8 Point-to-point call . 50
8.1 General . 50
8.2 Point-to-point call from GSM-R user to user on MCPTT system . 51
8.2.1 Point-to-point call . 51
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5 Draft ETSI TS 103 792 V1.0.0 (2025-07)
8.2.1.1 Stage 2 procedure . 51
8.2.1.2 Stage 3 procedure . 51
8.2.2 Point-to-point call rejected by MCPTT system . 53
8.2.2.1 Stage 2 procedure . 53
8.2.2.2 Stage 3 procedure . 53
8.3 Point-to-point call initiated by an MCPTT user . 54
8.3.1 Point-to-point call . 54
8.3.1.1 Stage 2 procedure . 54
8.3.1.2 Stage 3 procedure . 54
8.3.2 Point-to-point call rejected by GSM-R system . 55
8.3.2.1 Stage 2 procedure . 55
8.3.2.2 Stage 3 procedure . 55
8.4 Point-to-point call release . 56
8.4.1 Individual call release by GSM-R user . 56
8.4.1.1 Stage 2 procedure . 56
8.4.1.2 Stage 3 procedure . 56
8.4.2 Individual call release by FRMCS user . 57
8.4.2.1 Stage 2 procedure . 57
8.4.2.2 Stage 3 procedure . 57
9 Text messaging service . 58
9.1 General . 58
9.2 One-to-one text messaging procedures . 58
9.2.1 One-to-one SDS to Instant Messaging interworking principles . 58
9.3 One-to-One text messaging protocols IWF to/from the MCData server . 61
Annex A (informative): Voice transcoding to and from AMR-WB when AMR-WB is not
supported by a GSM-R system . 63
A.1 Introduction . 63
A.2 Transcoding in a GSM-R system . 63
A.3 Implementation of transcoding in the FRMCS Domain . 63
History . 64
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6 Draft ETSI TS 103 792 V1.0.0 (2025-07)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI IPR online database.
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
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not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its
Members. 3GPP™, LTE™ and 5G™ logo are trademarks of ETSI registered for the benefit of its Members and of the
3GPP Organizational Partners. oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and of ®
the oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Railway Telecommunications (RT)
and is now submitted for the combined Public Enquiry and Vote phase of the ETSI Standardisation Request deliverable
Approval Procedure (SRdAP).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
GSM-R has been a great success not only in Europe, where more than 100 000 km of railway tracks are daily operated
through GSM-R, but also worldwide, and this number will double within the next years due to the on-going installations
of this technology all over the world.
As the needs of the railways are constantly evolving, in particular in the context of the digitalisation of rail operation
that is pursued in many countries and considering the upcoming obsolescence of GSM-R technology, UIC launched in
2012 the first studies for a successor to GSM-R, pertinently named Future Railway Mobile Communication System
(FRMCS). The UIC project then concretely delivered the FRMCS Functional Requirements Specifications (FRS) [1]
and FRMCS System Requirement Specifications (SRS) [2] focusing mainly on rail communication needs - as a basis
for the development of the GSM-R successor.
ETSI
7 Draft ETSI TS 103 792 V1.0.0 (2025-07)
The present document has been written to satisfy the identified need for interworking between GSM-R and the FRMCS
Mission Critical applications specified by 3GPP, to enable communications between users and groups operating on the
two system technologies. It provides solutions to the considerations documented in ETSI TR 103 768 [i.1], which
studied the issues for interworking between the two technologies.
ETSI
8 Draft ETSI TS 103 792 V1.0.0 (2025-07)
1 Scope
The present document defines the functional model including reference points as well as the protocol and procedure for
interworking between GSM-R R4 and FRMCS and covers the following services:
• Group call.
• Emergency group call.
• Point-to-point call.
• Text messaging Service.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found in the
ETSI docbox.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long-term validity.
The following referenced documents are necessary for the application of the present document.
[1] UIC FU-7120: "Future Railway Mobile Communication System - Functional Requirements
th
Specification", Version 2.0.0 December 13 , 2024.
[2] UIC FW-AT 7800: "Future Railway Mobile Communication System - System Requirements
th
Specification", Version 2.0.0 December 13 , 2024.
[3] UIC FIS-7970: "Future Railway Mobile Communication System - Functional Interface
th
Specification", Version 2.0.0 December 13 , 2024.
[4] ETSI TS 103 765-2: "Rail Telecommunications (RT); Future Railway Mobile Communication
System (FRMCS); Building blocks and functions; Part 2: Service Stratum".
[5] IETF RFC 8101: "IANA Registration of New Session Initiation Protocol (SIP) Resource-Priority
Namespace for Mission Critical Push To Talk Service".
[6] ETSI TS 103 389 (V3.4.1): "Rail Telecommunications (RT); Global System for Mobile
communications (GSM); Usage of Session Initiation Protocol (SIP) on the Network Switching
Subsystem (NSS) to Fixed Terminal Subsystem (FTS) interface for GSM Operation on Railways".
[7] ETSI TS 123 228 (V18.9.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; IP Multimedia Subsystem
(IMS); Stage 2 (3GPP TS 23.228 version 18.9.0 Release 18)".
[8] ETSI TS 129 379 (V18.0.0): "LTE; 5G; Mission Critical Push To Talk (MCPTT) call control
interworking with Land Mobile Radio (LMR) systems; Stage-3 (3GPP TS 29.379 version 18.0.0
Release 18)".
[9] ETSI TS 124 282 (V18.10.0): "LTE; Mission Critical Data (MCData) signalling control; Protocol
specification (3GPP TS 24.282 version 18.10.0 Release 18)".
[10] ETSI TS 124 379 (V18.10.0): "LTE; Mission Critical Push To Talk (MCPTT) call control;
Protocol specification (3GPP TS 24.379 version 18.10.0 Release 18)".
ETSI
9 Draft ETSI TS 103 792 V1.0.0 (2025-07)
[11] ETSI TS 123 283 (V18.3.0): "LTE; Mission Critical Communication Interworking with Land
Mobile Radio Systems (3GPP TS 23.283 version 18.3.0 Release 18)".
[12] ETSI TS 129 163 (V18.1.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; Interworking between the IP
Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networks (3GPP
TS 29.163 version 18.1.0 Release 18)".
[13] ETSI TS 133 180 (V18.1.0): "LTE; Security of the Mission Critical (MC) service (3GPP
TS 33.180 version 18.1.0 Release 18)".
[14] IETF RFC 3428: "Session Initiation Protocol (SIP) Extension for Instant Messaging".
[15] IETF RFC 5373: "Requesting Answering Modes for the Session Initiation Protocol (SIP)".
[16] IETF RFC 3261: "SIP: Session Initiation Protocol".
[17] IETF RFC 3841: "Caller Preferences for the Session Initiation Protocol (SIP)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents may be useful in implementing an ETSI deliverable or add to the reader's
understanding, but are not required for conformance to the present document.
[i.1] ETSI TR 103 768: "Rail Telecommunications (RT); Future Rail Mobile Communication System
(FRMCS); Interworking study with legacy systems".
[i.2] EIRENE System Requirements Specification, Version 16.1.0, February 2023.
[i.3] ETSI TS 123 280 (V18.12.0): "LTE; Common functional architecture to support mission critical
services; Stage 2".
[i.4] ETSI TS 123 040 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; Technical realization of the
Short Message Service (SMS) (3GPP TS 23.040 version 18.0.0 Release 18)".
[i.5] ETSI TS 123 002 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; Network architecture (3GPP
TS 23.002 version 18.0.0 Release 18)".
[i.6] ETSI TS 123 379 (V18.12.0): "LTE; Functional architecture and information flows to support
Mission Critical Push To Talk (MCPTT); Stage 2 (3GPP TS 23.379 version 18.12.0 Release 18)".
[i.7] ETSI TS 123 282 (V18.10.0): "LTE; Functional architecture and information flows to support
Mission Critical Data (MCData); Stage 2 (3GPP TS 23.282 version 18.10.0 Release 18)".
[i.8] ETSI TS 143 068 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Voice Group Call Service (VGCS); Stage 2 (3GPP TS 43.068 version 18.0.0 Release 18)".
[i.9] ETSI TS 123 236 (V18.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; Intra-domain connection of Radio
Access Network (RAN) nodes to multiple Core Network (CN) nodes (3GPP TS 23.236
version 18.0.0 Release 18)".
[i.10] ETSI TS 129 311 (V18.0.0): "Universal Mobile Telecommunications System (UMTS); LTE;
Service Level Interworking (SLI) for messaging services (3GPP TS 29.311 version 18.0.0
Release 18)".
ETSI
10 Draft ETSI TS 103 792 V1.0.0 (2025-07)
[i.11] ETSI TS 124 229 (V18.7.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; 5G; IP multimedia call control
protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP);
Stage 3 (3GPP TS 24.229 version 18.7.0 Release 18)".
[i.12] ETSI TR 103 791: "Rail Telecommunications (RT); Future Railway Mobile Communication
System (FRMCS); Terminology for FRMCS specifications".
[i.13] ETSI TS 123 283 (V18.2.0): "LTE; Mission Critical Communication Interworking with Land
Mobile Radio Systems (3GPP TS 23.283 version 18.2.0 Release 18)".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in ETSI TR 103 791 [i.12] and the following apply:
E.164 SIP-R URI: SIP-R URI which describes an international E.164 address
EIRENE SIP-R URI: SIP-R URI which describes an international EIRENE address
FA(164): Functional Alias (FA) which takes the form of an E.164 SIP-R URI and is transmitted in MCX related
messages, according to the transmission of FAs
NOTE: As specified in ETSI TS 124 379 [10] and ETSI TS 124 282 [9].
FA(EIRENE): Functional Alias (FA) which takes the form of an EIRENE SIP-R URI and is transmitted in MCX
related messages, according to the transmission of FAs
NOTE: As specified in ETSI TS 124 379 [10] and ETSI TS 124 282 [9].
FRMCS Entity: entity which is either:
a) a user of the MCX system;
b) a user of a partner MC system of the MCX system;
c) a group of users of the MCX system;
d) a group of users of a partner MC system of the MCX system;
e) a railway function that is registered or activated as FA at the MCX system; or
f) a railway function that is registered or activated as FA at a partner MC system of the MCX system.
GSM-R Entity: entity which is either GSM-R user, a GSM-R service or a railway function that is not an FRMCS entity
identity and criteria mapping: local service of the IWF for mapping between identities and criteria achieved without
requests from the IWF to external data bases or other remote storage (i.e. it is achieved by local address lookup or by
rule-based rephrasing)
local address lookup: local lookup of identity mappings within the IWF, e.g. by tables that have been setup during
provisioning time
rephrasing: rule-based mapping of EIRENE addresses to FRMCS FAs and vice versa
NOTE: This rule-based rephrasing is based on FRMCS FRS [1].
subscribers: user identified by E.164 addresses.
NOTE: This can mean:
a) GSM-R subscribers;
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11 Draft ETSI TS 103 792 V1.0.0 (2025-07)
b) Users of the MCX system;
c) Groups of users of the MCX system.
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
rd
3GPP 3 Generation Partnership Project
AMR-WB Adaptative MultiRate-Wide Band
CdA Called Address
CgA Calling Address
CHPC Confirmation of High Priority Call
CSC Coding Scheme Code
CT Call Type
CT5 Call Type 5
ECT Explicit Call Transfer
EIR Equipment Identity Register
EIRENE European Integrated Railway Radio Enhanced Network
ETSI European Telecommunications Standards Institute
EVS-SWB Enhanced Voice Service - Super Wide Band
FA Functional Alias
FIS Functional Interface Specification
FN Functional Number
FRMCS Future Railway Mobile Communication System
FRS Functional Requirement Specification
FTS Fixed Terminal Subsystem
GCR Group Call Register
GCref Group Call Reference
GID Group call Identity
GPS Global Positioning System
GSM Global System for Mobile communications
GSM-R Global System for Mobile communications - Railways
GW GateWay
HLR Home Location Register
IC International Code
IE Information Element
IETF Internet Engineering Task Force
IM Intstant Messaging
IMS IP Multimedia Subsystem
IMSI International Mobile Subscriber Identity
IP Internet Protocol
IP-SM-GW IP Short Message Gateway
ISC IP multimedia subsystem Service Control interface
IWF InterWorking Function
IW-GW InterWorking-GateWay
MAP Mobile Application Part
MC Mission-Critical
MCData Mission-Critical Data
MCPPT Mission Critical Push To Talk
MCPTT Mission-Critical Push-To-Talk
MCX Mission Critical communications
MDF Media Distribution Frame
MGCF Media Gateway Control Function
MGW Media GateWay
MIME Multipurpose Internet Mail Extensions
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12 Draft ETSI TS 103 792 V1.0.0 (2025-07)
MS Mobile Station
MSC Mobile Switching Centre
MSS Mobile Switching Subsystem
OIP Originating Identification Presentation
OMA-TS Open Mobile Alliance-Technical Specification
OTDI Originator To Dispatcher Information
PABX Private Automatic Branch eXchange
PAI P-Asserted Identity
PFN Presentation Functional Number
PTT Push-To-Talk
REC Railway Emergency Call
RFC Request For Comments
RTCP Real time Ta
S-CSCF Serving-Call Session Control Function
SDP Session Description Protocol
SDS Short Data Service
SIM Subscriber Identity Module
SIP Session Initiation Protocol
SIP-R Session Initiation Protocol for Railways
SLI Service Level Interworking
SM Short Message
SMPP Short Message Peer-to-Peer protocol
SMS Short Message Service
SMSC Short Message Service Center
SRS System Requirement Specification
TIP Terminating Identification Presentation
TR Technical Report
TS Technical Specification
UE User Equipment
URI Uniform Resource Identifier
URN Uniform Resource Number
VBS Voice Broadcast Service
VGCS Voice Group Call Service
XML eXtensible Markup Language
4 Services
4.1 General
This clause describes the services for interworking between GSM-R and FRMCS 3GPP MC systems supported in the
present document.
4.2 Group call
This clause describes group call services that are supported for groups defined on the MC system and groups defined on
the GSM-R system.
The following group call procedures are supported:
• Initiation of a group call by a FRMCS user.
• Initiation of a group call by a GSM-R user.
• Late entry.
• Termination of a group call.
• Interworking of floor control on MCPTT with uplink control and dispatcher mute/unmute in GSM-R.
ETSI
13 Draft ETSI TS 103 792 V1.0.0 (2025-07)
• Interworking of the media codecs and encryption between GSM-R and MCPTT.
4.3 Emergency group call
Emergency group calls, i.e. group calls with pre-emptive priority, are supported for the same cases as described in
clause 4.2.
4.4 Point-to-point call
The following point-to-point call procedures are supported:
• Initiating a point-to-point call from a user on the GSM-R system to a user on the MC system.
• Initiating a point-to-point call from a user on the FRMCS system to a user on the GSM-R system.
• Interworking of the media codecs and encryption between GSM-R and MCPTT.
• Termination of a point-to-point call.
NOTE: Point-to-point calls for interworking are without floor control.
4.5 Text messaging service
The GSM-R system includes Mobile Stations (MS) capable of performing various types of calls, such as voice and data
calls, and also supports text messaging by enabling the transmission of Short Messages (SMs) between mobile stations.
EIRENE System Requirements Specification [i.2] specifies that, whenever text messaging is implemented in the
GSM-R network, the Short Message Service (SMS) - is to be used (see clause 12.2.1 of EIRENE System Requirements
Specification [i.2]).
The Short Me
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