ETSI TR 103 459 V1.2.1 (2020-08)

Rail Telecommunications (RT); Future Rail Mobile Communication System (FRMCS); Study on system architecture

RTR/RT-0052

General Information

• Status: Not Published
• Technical Committee: RT - Railway telecommunications
• Current Stage: 12 - Completion
• Due Date: 17-Aug-2020
• Completion Date: 19-Aug-2020

Standards Content (Sample)

TECHNICAL REPORT
Rail Telecommunications (RT);
Future Rail Mobile Communication System (FRMCS);
Study on system architecture
2 ETSI TR 103 459 V1.2.1 (2020-08)

Reference
RTR/RT-0052
Keywords
architecture, FRMCS, railways
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3 ETSI TR 103 459 V1.2.1 (2020-08)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 6
Executive summary . 7
Introduction . 7
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 10
3.1 Terms . 10
3.2 Symbols . 11
3.3 Abbreviations . 11
3.4 Notion of logical architecture, technical realization and physical implementation . 13
4 High level description . 14
5 Analysis of architectural implications of key aspects to be covered by FRMCS . 15
5.1 General . 15
5.2 Analysis of architectural requirements from UIC TOBA . 15
5.3 Analysis of architectural requirements from 3GPP TR 22.889 . 16
5.4 Identification and addressing . 20
5.4.1 General . 20
5.4.2 Design assumptions . 21
5.4.3 Identification and addressing schemes . 21
5.4.3.1 General . 21
5.4.3.2 Identification and addressing in the application stratum . 22
5.4.3.3 Identification and addressing in the service stratum . 22
5.4.3.3.1 Introduction and definitions . 22
5.4.3.3.2 Relationship between identities in the IMS . 23
5.4.3.3.3 Basic MC service identities . 24
5.4.3.3.4 Alternative MC service identities . 24
5.4.3.3.5 Relationship identities . 25
5.4.3.4 Identification and addressing in the transport stratum. 25
5.4.4 Implications on the FRMCS system architecture. 25
5.5 System Security . 26
5.5.1 Introduction and requirements . 26
5.5.2 Expected security layers in the FRMCS system . 27
5.5.3 Required security functions . 28
5.5.4 Required interfacing with external systems . 29
5.5.5 Implications on the FRMCS system architecture. 30
5.6 Positioning . 30
5.6.1 Definitions . 30
5.6.2 General . 31
5.6.3 Position processing categories . 32
5.6.4 For further study . 32
5.7 Migration from GSM-R to FRMCS . 33
5.7.1 Introduction. 33
5.7.2 Onboard migration . 33
5.7.3 ETCS transport modes . 33
5.7.4 GSM-R/FRMCS communication service migration at deployment boundaries . 34
5.7.5 Implications on the FRMCS system architecture. 35
6 FRMCS logical architecture . 35
6.1 System boundaries and high-level logical architecture . 35
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4 ETSI TR 103 459 V1.2.1 (2020-08)
6.2 Description of main logical entities . 36
6.2.1 FRMCS Mobile Application Client and FRMCS Service Client . 36
6.2.1.1 Introduction . 36
6.2.1.2 FRMCS Mobile Application Client . 37
6.2.1.3 FRMCS Service Client . 38
6.2.2 FRMCS Mobile Gateway . 38
6.2.3 Mobile Radio . 38
6.2.4 Trackside Transport . 39
6.2.5 FRMCS Service Server . 39
6.3 Key reference points to be specified. 39
6.3.1 OB . 39
APP
6.3.2 OB . 40
RAD
6.3.3 TS . 40
FS
7 FRMCS deployment and border crossing scenarios . 40
7.1 General . 40
7.2 Scenario 1a: Multiple trackside access domains with a common core network . 41
7.3 Scenario 1b: Multiple trackside access domains under a common core network (infrastructure sharing) . 41
7.4 Scenario 2: Interconnected Trackside Transport domains with separate core networks . 42
7.5 Scenario 3: Isolated transport and service domains . 43
7.6 Scenario 4: Border-crossing scenarios . 44
7.6.1 General . 44
7.6.2 Scenario 4a: Border-crossing scenario (isolated application domains) . 45
7.6.3 Scenario 4b: Border-crossing scenario (shared application domain) . 47
7.6.4 Scenario 4c: Border-crossing scenario (shared application and service domain) . 49
8 Possible technical realization of the FRMCS system . 49
8.1 General . 49
8.2 Potential 3GPP building blocks and reference points mapped to FRMCS logical architecture . 49
8.3 Potential solutions for the support of multiple Mobile Radios and/or multiple Trackside Transport
domains . 52
8.3.1 Introduction. 52
8.3.2 Service-level solution based on the MC framework . 52
8.3.3 Transport-level solutions: Core-centric integration using ATSSS . 54
8.3.4 Transport-level solutions: Above-the-core using MAMS . 55
8.3.5 Transport-level solutions: Above-the-core using ATSSS-Emulated solution . 56
8.3.6 Comparison of the possible solutions . 57
8.3.7 Preliminary conclusion . 61
8.4 Potential physical implementation of onboard system . 61
8.5 Potential physical implementation of trackside system . 62
8.6 Potential technical realization of a handheld device . 62
9 Gap analysis . 63
9.1 Mapping of functional service requirements to standardized 3GPP functions . 63
9.2 Identified risks . 65
10 Topics for further study . 65
Annex A: Supportive Material on MC, 4G and 5G Support for Rail Communication . 66
A.1 Mission Critical service support for Rail Communication . 66
A.1.1 General . 66
A.1.2 Arguments for loose coupling of data centric Railway Applications . 66
A.1.3 Integration of data centric Railway Applications . 66
A.1.4 Conclusion . 67
A.2 FRMCS/4G support for Railway Applications . 67
A.2.1 General . 67
A.2.2 QoS Management in LTE . 68
A.3 FRMCS/5G support for Railway Applications . 68
A.3.1 General . 68
A.3.2 QoS Management in 5G/NR . 69
A.3.3 Comparison and Suitability of QoS Management Options for Rail Operations . 70
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5 ETSI TR 103 459 V1.2.1 (2020-08)
A.4 Possibility to realize FRMCS System with 4G core network . 70
Annex B: Change History . 72
History . 73

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6 ETSI TR 103 459 V1.2.1 (2020-08)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is 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 Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, 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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Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Railway Telecommunications (RT).
The contents of the present document are subject to continuing work within TC RT and may change following formal
TC RT approval. Should RT modify the contents of the present document, it will be re-released by the TC RT with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
0 presented to TC RT for information;
1 presented to TC RT for approval; or
2 greater indicates TC RT approved document under change control;
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.;
z the third digit is incremented when editorial only changes have been incorporated in the document.
Modal verbs terminology
In the present document "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.
ETSI
7 ETSI TR 103 459 V1.2.1 (2020-08)
Executive summary
Since the first studies on the successor to GSM-R have been launched by UIC in 2012, the railway community has been
considering how to meet railway requirements with a future proof and flexible radio communication system.
The rail needs are defined in the User Requirements Specification (URS) [i.1] and the Telecom Onboard Architecture
(TOBA) Requirements [i.2] delivered by the UIC Project Future Railway Mobile Communications System (FRMCS).
From the UIC requirements, requirements relevant to 3GPP have been captured in 3GPP TR 22.889 [i.3]. Altogether,
the stated requirements are the basis for the development of the GSM-R successor.
The present document is a study on FRMCS system architecture, which initially describes a potential logical FRMCS
architecture that is suitable to meet the rail requirements according to the requirement documents cited before, and the
key reference points that are to be specified. As one input to the design, it provides an analysis of specific challenges
such as security, migration, positioning, etc., and derives their implications on the FRMCS architecture. The present
document also describes several deployment scenarios (for instance related to setups with multiple transport networks
operated by different entities), which are also relevant to the design of the FRMCS system architecture, as this should
support all deployment scenarios that are currently envisioned. Beyond the description of the logical FRMCS
architecture, the present document then elaborates on possible technical realizations of the FRMCS architecture through
building blocks from 3GPP and from other standards bodies. Special emphasis is here put on consideration for the
support of multiple onboard/handheld radios and/or multiple trackside transport domains, and the support of border-
crossing scenarios. Finally, the present document provides a functional gap analysis and identifies risks, before listing
topics for further study.
Introduction
The Technical Committee Rail Telecommunications (TC RT) is the "home" for those telecommunication aspects of rail
transportation which are not part of the specification of the current mobile communication technologies themselves. TC
RT is in particular responsible for the development and maintenance of GSM-R standards.
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 new User Requirements Specifications (URS) [i.1] focusing
mainly on rail communication needs - as a basis for the development of the GSM-R successor.
The present document is a study on the FRMCS system architecture, which defines a logical FRMCS architecture and
likely deployment scenarios, and which elaborates in detail on possible technical realizations of the FRMCS system.
The result of this study is expected to provide the basis for the subsequently following normative work on FRMCS in
ETSI.
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8 ETSI TR 103 459 V1.2.1 (2020-08)
1 Scope
The present document is a technical report, in line with the scope and field of application of its related Work Item. In
particular, it covers:
• Definition of key terms and a high-level description of the FRMCS architecture, as agreed among UIC and ETSI
(see clauses 3 and 4, respectively).
• An analysis of the architectural implications of various requirements on the FRMCS system captured in UIC
TOBA and 3GPP TR 22.889 [i.3], and of aspects such as identification and addressing, security, positioning and
migration (see clause 5).
• A description of the logical architecture of the FRMCS system, including a description of the main logical
entities and key reference points among these (see clause 6).
• A derivation of key deployment and border-crossing scenarios that the FRMCS architecture should support (see
clause 7).
• An investigation of possible technical realizations of the FRMCS system, based on the usage of building blocks
from 3GPP and other standards bodies (see clause 8).
• A gap analysis and identification of risks related to the FRMCS standardization, for instance due to its
dependency on timelines of different standards bodies (see clause 9).
Finally, the present document identifies the next steps to ensure the complete definition of the FRMCS system.
2 References
2.1 Normative references
Normative references are not applicable in the present document.
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 are not necessary for the application of the present document, but they assist the
user with regard to a particular subject area.
[i.1] UIC FRMCS URS v5.0: "User Requirements Specification".
[i.2] UIC FRMCS TOBA-7510 (V1.0.0) (April 2020): "FRMCS Telecom On-Board System -
Functional Requirements Specification".
[i.3] 3GPP TR 22.889 (V17.2.0) (January 2020): "Study on Future Railway Mobile Communication
System (FRMCS)".
[i.4] 3GPP TS 21.905 (V16.0.0) (June 2019): "Vocabulary for 3GPP Specifications".
[i.5] 3GPP TS 23.501 (V16.4.0) (March 2020): "System architecture for the 5G System (5GS)
(Release 16)".
[i.6] 3GPP TS 24.501 (V16.4.1) (April 2020): "Non-Access-Stratum (NAS) protocol for 5G System
(5GS); Stage 3 (Release 16)".
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9 ETSI TR 103 459 V1.2.1 (2020-08)
[i.7] 3GPP TS 22.280 (V17.2.0) (December 2019): "Mission Critical Services Common Requirements
(MCCoRe); Stage 1".
[i.8] 3GPP TR 28.801 (V15.1.0) (January 2018): "Telecommunication management; Study on
management and orchestration of network slicing for next generation network".
[i.9] 3GPP TS 23.228 (V16.4.0) (March 2020): "IP Multimedia Subsystem (IMS); Stage 2".
[i.10] 3GPP TS 23.003 (V16.2.0) (March 2020): "Numbering, addressing and identification".
[i.11] 3GPP TS 23.280 (V17.2.0) (March 2020): "Common functional architecture to support mission
critical services; Stage 2".
[i.12] UIC FRMCS TOBA-7540 (V1.0.0) (April 2020): "FRMCS Telecom On-Board System -
Architecture Migration Scenarios".
[i.13] 3GPP TR 23.796 (V16.0.0) (March 2019): "Study on application architecture for the Future
Railway Mobile Communication System (FRMCS) Phase 2".
[i.14] 3GPP TS 27.007 (V16.4.0) (March 2020): "AT command set for User Equipment (UE)".
[i.15] ETSI TS 123 002 (V15.0.0): "Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS); LTE; Network architecture (3GPP
TS 23.002 version 15.0.0 Release 15)".
[i.16] 3GPP TS 24.193 (V1.2.0) (May 2020): "5G System; Access Traffic Steering, Switching and
Splitting (ATSSS); Stage 3".
[i.17] IETF RFC 8743 (March 2020): "Multi-Access Management Services (MAMS)".
[i.18] 3GPP TR 23.783 (V0.10.0) (June 2020): "Study on Mission Critical (MC) services support over
the 5G System (5GS)".
[i.19] IETF RFC 7542 (May 2015): "The Network Access Identifier".
[i.20] IETF RFC 1035 (November 1987): "Doman names - implementation and specification".
[i.21] IETF RFC 1123 (October 1989): "Requirements for Internet Hosts -- Application and Support".
[i.22] IETF RFC 3966 (December 2004): "The tel URI for Telephone Numbers".
[i.23] IETF RFC 3261 (June 2002): "SIP: Session Initiation Protocol".
TM
[i.24] IEEE 802.11 : "IEEE Standard for Information technology--Telecommunications and
information exchange between systems Local and metropolitan area networks--Specific
requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications".
[i.25] ETSI TS 123 271: "Digital cellular telecommunications system (Phase 2+) (GSM); Universal
Mobile Telecommunications System (UMTS); LTE; Functional stage 2 description of Location
Services (LCS) (3GPP TS 23.271)".
[i.26] ETSI TS 123 282: "LTE; Functional architecture and information flows to support Mission
Critical Data (MCData); Stage 2 (3GPP TS 23.282)".
[i.27] TIA-603-D: "Land Mobile FM or PM Communications Equipment Measurement and Performance
Standards".
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10 ETSI TR 103 459 V1.2.1 (2020-08)
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
communication services: services enabling the exchange of information between two or more service users
complementary services: ancillary services, e.g. providing and/or utilizing the location of the service user, supporting
communication services and the railway application stratum
FRMCS Mobile Application Client: client that enables authorization of an application to the FRMCS Mobile
Gateway
FRMCS Mobile Gateway: gateway that provides access to the FRMCS Transport Stratum for FRMCS Users through
FRMCS Service Client(s)
FRMCS Service Client: client that enables the use of the Communication Services and/or Complementary Services for
the railway applications
FRMCS System: telecommunication system conforming to FRMCS specifications, consisting of Transport Stratum
and Service Stratum
FRMCS User: human or machine making use of Communication Services and/or Complementary Services
FRMCS User Identity: unique identity associated with a single or multiple FRMCS User and can be complemented by
alternative addressing schemes
legacy conversion: function that provides conversion towards legacy interfaces (e.g. V.24 serial interface)
NOTE: The Legacy Conversion provides encapsulation/de-capsulation for control and user plane data as well as
the necessary conversion of the physical interfaces between legacy GSM-R UE and FRMCS.
mobile radio: 3GPP User Equipment or non-3GPP equivalent, which supports selected 3GPP and/or non-3GPP access
(e.g. 4G, 5G, Wi-Fi, satellite)
on-board transport system: system that provides on-train only transport services and enables the interaction with the
FRMCS Gateway and the FRMCS Service Stratum where applicable
proxy: person or entity that is acting or being used in the place of someone or something else
railway application stratum: railway-specific functionalities using services offered by the service stratum
reference point: conceptual point applicable for interaction between functional services that enables authorized
functions, e.g. in the network, to access their services
service domain: implementation of (parts of) the Service Stratum which belongs to and/or is operated by a unique
organization
service stratum: communication services and complementary services
train communication network: sub-system of the on-board transport system that aggregates various train backbones
transport domain: implementation of (parts of) the transport stratum which belongs to and/or is operated by a unique
organization
transport stratum: set of access and corresponding core functions applicable for the FRMCS system
User Equipment (UE): equipment according to 3GPP terminology (see 3GPP TS 21.905 [i.4]) that allows access to
3GPP transport services
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11 ETSI TR 103 459 V1.2.1 (2020-08)
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
rd
3GPP 3 Generation Partnership Project
4G Fourth Generation Mobile Networks
5G Fifth Generation Mobile Networks
5GS 5G System
AF Application Function
AKA Authentication and Key Agreement
AMF Access and Mobility Management Function
APN Access Point Name
ARP Allocation and Retention Priority
AS Access Stratum
ATO Automatic Train Operation
ATSSS Access Traffic Steering, Switching & Splitting
ATSSS-LL Access Traffic Steering, Switching & Splitting - Low Layer
CAPIF Common API Framework
CCM Client Connection Manager
C-MADP Client Multi-Path Data Proxy
CP Control Plane
CS Circuit-switched
CT Call Type
CTCS Chinese Train Control System
EAP Extensible Authentication Procedure
eDECOR enhancements of DEdicated CORe networks
eNB evolved NodeB
EPC Enhanced Packet Core
EPS Enhanced Packet System
ETCS European Train Control System
EUG ERTMS Users' Group
E-UTRA(N) Evolved Universal Terrestrial Radio Access (Network)
E-UTRAN Enhanced UMTS Terrestrial Radio Access Network
FC Functional Code
FFS For Future Study
FRMCS Future Rail Mobile Communications System
FSSI FRMCS Service Session Interface
FTS Fixed Terminal Subsystem
GNSS Global Navigation Satellite System
GRUU Globally Routable User-agent URI
GSM-R Global System for Mobile communication for Railways applications
GW Gateway
HW Hardware
IC International Code
IEEE Institute of Electrical and Electronics Engineers
IMEI International Mobile Equipment Identity
IMPI IP Multimedia Private Identity
IMPU IP Multimedia Public identity
IMS Internet Multimedia Subsystem
IMSI International Mobile Subscriber Identity
IN Intelligent Network
IoT Internet of Things
IP Internet Protocol
ISDN Integrated Services Digital Network
IWF InterWorking Function
KASME Key Access Security Management Entries
LAA Licensed-Assisted Access
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12 ETSI TR 103 459 V1.2.1 (2020-08)
LAN Local Area Network
LBS Location Based Service
LDS Location Dependent Service
LTE Long Term Evolution
LTE-U Long Term Evolution-Unlicensed
LWA LTE-WLAN Aggregation
MAC Media Access Control
MAMS Multi Access Management Services
MC Mission Critical
MCData Mission Critical Data
MCPTT Mission Critical Push To Talk
MCVideo Mission Critical Video
MCX Mission Critical Services
MOCN Multi Operator Core Network
MPTCP Multi-Path Transmission Control Protocol
MSISDN Mobile Subscriber ISDN Number
NAI Network Access Identifier
NAS Non-Access Stratum
NCM Network Connection Manager
N-MADP Network Multi Access Data Proxy
NR New Radio
OB Onboard Application Interface
APP
OB Onboard Radio Interface
RAD
OSI Open Systems Interconnection
PCF Policy Control Function
PDU Packet Data Unit
PLMN Public Land Mobile Network
PLMN-ID Public Land Mobile Network Identification
PS Packet-Switched
PSTN Public Switch Telephone Network
QCI QoS Class Identifier
QoS Quality of Service
RAN Radio Access Network
RAT Radio Access Technology
RBC Radio Block Centre
RFC Request For Comments
RG Residential Gateway
RRC Radio Resource Control
RTT Round-Trip Time
SBA Service Based Architecture
SDAP Service Data Adaptation Protocol
SDF Service Data Flow
SDS Short Data Service
SEPP Security Edge Protection Proxy
SIEM Security Information and Event Management
SIM Subscriber Identity Module
SIP Session Initiation Protocol
SMF Session Management Function
SRS System Requirement Specification
SS7 Signalling System No 7
SST Slice/Service Type
SW Software
TCP Transmission Control Protocol
TCRT Technical Committee Rail Telecommunications
TETRA Terrestrial Trunked Radio
TS Trackside FRMCS Service Interface
FS
UE User Equipment
UIC Union Internationale des Chemins de fer (English: International Rail Union)
UIN User Identification Number
UN User Number
UP User Plane
UPF User Plane Function
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13 ETSI TR 103 459 V1.2.1 (2020-08)
URI Uniform Resource Identifier
URLLC Ultra-Reliable Low-Latency Communications
URS User Requirements Specification
URSP User Equipment Route Selection Policy
W-AGF Wireline Access Gateway Function
TM
WiFi Wireless Fidelity
WLAN Wireless Local Area Network
3.4 Notion of logical architecture, technical realization and
physical implementation
In the remainder of the present document, the FRMCS architecture is described in different forms, with a general
differentiation between:
• Logical architecture: Describes the FRMCS system in the form of logical function blocks and reference
points in between. The logical architecture is purposely kept solution-agnostic. Clauses 6 and 7 in the present
document describe the FRMCS system from a logical architecture perspective.
• Technical realization: Describes one or multiple possibilities to realize the FRMCS system by using building
blocks from 3GPP or other bodies. In the present document, clause 8 delves into technical realization options
for the FRMCS system, with the aim to identify any possible technology gaps and ensure that the reference
points in the logical architecture are defined in a meaningful way.
• Physical implementation: Describes how (parts of) the FRMCS system could be mapped to physical entities
or products from a vendor. Since physical implementations are not relevant for standardization, they are only
used for illustration purposes in the present document, for instance in clause 8.4 in the context of onboard
architecture.
These forms of architecture description are also illustrated in figure 3-1.

Figure 3-1: Notion of logical architecture, technical realization and physical implementation
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14 ETSI TR 103 459 V1.2.1 (2020-08)
4 High level description
One key objective behind the design of FRMCS is a clear separation between the so-called Railway Application
Stratum, Service Stratum, and Transport Stratum, as illustrated in figure 4-1. The following definition applies:
• The Railway Application Stratum provides railway-specific functionalities using services offered by the
Service Stratum.
• The Service Stratum comprises Communication services and Complementary Services:
- Communication Services are services enabling the exchange of information between two or more
service users.
- Complementary Services are ancillary services, e.g. providing and/or utilizing the location of the
service user, supporting Communication Services and the Railway Application Stratum.
• The Transport Stratum comprises the set of access and corresponding core functions applicable for the
FRMCS system.
Figure 4-1: High-level FRMCS architecture overview
It is commonly assumed that:
• Applications in the Railway Application Stratum should use Communication Services to guarantee
interoperable service behaviour and the deterministic and controlled use of the Transport Stratum. Once a
service user, e.g. an application, has been authenticated and authorized itself to the Communication Service
instances, the application should be able to obtain control about the services, and the system should allow a
direct user plane connection for this application between Application Stratum and Transport Stratum if
possible.
• Communication Services may use Complementary Services (and vice versa). In the Service Stratum, the
control plane may contain user plane information content, e.g. MCData service SDS, embedded in the
signalling content.
Which functions of the Service Stratum are covered by the Communication Services and Complementary Services is
further elaborated in clause 6.2.
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15 ETSI TR 103 459 V1.2.1 (2020-08)
5 Analysis of architectural implications of key aspects
to be covered by FRMCS
5.1 General
Before introducing the FRMCS logical architecture, clause 5 elaborates on requirements from UIC TOBA-7510 [i.2]
and 3GPP TR 22.889 [i.3] which have explicit implications on the FRMCS architecture. In dedicated clauses, further
elaboration on the functional and architectural implications of aspects such as addressing, migration, security, etc., is
provided.
5.2 Analysis of architectural requirements from UIC TOBA
Table 5-1 lists requirements from UIC TOBA-7510 [i.2] with implications on the FRMCS architecture. Note that the
listed requirements are a snapshot from [i.2] and may change over time. They are only listed here for the
purpose of a preliminary analysis.
Table 5-1: Requirements from UIC TOBA-7510 [i.2] with FRMCS architecture impact
Number in UIC Quoted requirement Comment
FRMCS TOBA-
7510 [i.2]
R1 "The FRMCS On-Board System shall have the Solutions for the support of multiple
(clause 7.2.2.1) capability to simultaneously control multiple FRMCS UEs/Mobile Radios are compared in
Radio Modules." clause 8.3 and assessed w.r.t. this
requirement.
R2 "The FRMCS On-Board System shall have the Solutions for the support of multiple
(clause 7.4.2.1) capability to share FRMCS Radio Modules among UEs/Mobile Radios are compared in
different communication services (e.g. multiple clause 8.3 and assessed w.r.t. this
applications using the same FRMCS Radio Module)." requirement.
R3 "The FRMCS On-Board System shall detect the This translates into:
(clause 7.2.2.2) non-availability/availability of transport capabilities • requirements on the FRMCS Mobile
provided by the FRMCS Radio Modules."
Gateway, see clause 6.2;
• requirements on reference point
OB , see clause 6.3.
RAD
R4 "The FRMCS On-Board System shall provide a Solutions for the support of multiple
(clause 7.3.2.5) mechanism to allow reestablishment of transport UEs/Mobile Radios are compared in
services using a different FRMCS Radio Module in clause 8.3 and assessed w.r.t. this
case of a failure of the FRMCS Radio Module in use requirement.
or upon detection of a persistent service outage of
the FRMCS Radio Module in use."
R5 "The FRMCS onboard system shall provide transport This translates into requirements on both
(clause 7.5.2.1) and communication service exposure, such as reference points OB and OB , see
APP RAD
providing information about the network (e.g. PLMN
clause 6.3.
ID) to which the FRMCS Radio Modules are
registered."
R6 "The FRMCS On-Board System shall request a This translates into requiremen
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