ETSI TS 103 147 V1.1.1 (2013-06)

Railway Telecommunications (RT); GSM-R Core Network Redundancy

DTS/RT-0026

General Information

• Status: Published
• Publication Date: 26-Jun-2013
• Technical Committee: RT - Railway telecommunications
• Current Stage: 12 - Completion
• Due Date: 08-Jul-2013
• Completion Date: 27-Jun-2013

Standards Content (Sample)

Technical Specification
Railway Telecommunications (RT);
GSM-R Core Network Redundancy
2 ETSI TS 103 147 V1.1.1 (2013-06)

Reference
DTS/RT-0026
Keywords
GSM-R, railways
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3 ETSI TS 103 147 V1.1.1 (2013-06)
Contents
Intellectual Property Rights . 4
Foreword . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definitions and abbreviations . 6
3.1 Definitions . 6
3.2 Abbreviations . 6
4 General description. 7
4.1 Basic concept . 7
4.2 Technical Requirements . 7
4.3 System Architecture . 8
5 Components of GSM-R Core Network Redundancy . 8
5.1 Intra-domain connection of RAN nodes to multiple CN nodes (RANflex) . 8
5.1.1 Main concept . 8
5.1.2 References specifying RANflex . 9
5.2 Coexistence of VGCS/VBS and RANflex . 9
5.2.1 Main concept . 9
5.2.2 References specifying "Coexistence of VGCS/VBS and RANflex" . 10
5.3 GCSMSC and GCR Redundancy for VGCS/VBS . 12
5.3.1 Main concept . 12
5.3.2 References specifying "GCSMSC and GCR Redundancy for VGCS/VBS" . 13
Annex A (informative): Bibliography . 16
History . 17

ETSI
4 ETSI TS 103 147 V1.1.1 (2013-06)
Intellectual Property Rights
IPRs essential or potentially essential to the present document 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 (http://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.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Railway Telecommunications
(RT).
Introduction
GSM-R is a safety related and "Quality of Service" critical operation; therefore, redundancy in the Core Network is a
solution to cope with MSC single outages.
In 3GPP/ETSI Technical Specifications a number of features have been defined which in combination are providing the
means to fulfil the requirements for a redundant Core Network used for railway operation.
The present document collects the references required for the GSM-R Core Network Redundancy solution, in particular
those needed for the redundancy of the network entities required for VGCS/VBS, the Group Call Serving MSC
(GCSMSC) and its associated GCR.
ETSI
5 ETSI TS 103 147 V1.1.1 (2013-06)
1 Scope
The present document describes the GSM-R Core Network Redundancy which is based on several features described in
ETSI/3GPP Technical Specifications. In particular these features are:
- Intra-domain connection of RAN nodes to multiple CN nodes (RANflex).
- Coexistence of VGCS/VBS and RANflex.
- GCSMSC and GCR Redundancy for VGCS/VBS.
The present document is focussing on the relevant references needed for the GSM-R Core Network Redundancy. It
does not describe the detailed requirements for the feature GSM-R Core Network Redundancy or the above listed sub-
features respectively as these are available in TS 143 068 [i.4], TS 143 069 [i.5], TS 129 002 [i.3] and TS 123 236 [i.6].
The minimum requirements on ETSI/3GPP for the use of GSM for application on railway networks are based on the
Release 99 version of the Technical Specifications as described in EN 301 515 [i.1] plus a set of Change Requests as
described in TS 102 281 [i.2]. The features forming the basis for GSM-R Core Network redundancy are described in
releases later than Release 99. So the present document is referring to specifications versions later than Release 99 but
is not mandating any other functionality than covered by the applicable 3GPP Work Items and referenced in the
applicable paragraphs as listed in clauses 5.1.2, 5.2.2 and 5.3.2.
2 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
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
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] ETSI EN 301 515 (V2.3.0): "Global System for Mobile communication (GSM); Requirements for
GSM operation on railways".
[i.2] ETSI TS 102 281: "Railways Telecommunications (RT); Global System for Mobile
communications (GSM); Detailed requirements for GSM operation on Railways".
[i.3] ETSI TS 129 002: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Mobile Application Part (MAP) specification
(3GPP TS 29.002 version 11.6.0 Release 11)".
[i.4] ETSI TS 143 068: "Digital cellular telecommunications system (Phase 2+); Voice Group Call
Service (VGCS); Stage 2 (3GPP TS 43.068)".
ETSI
6 ETSI TS 103 147 V1.1.1 (2013-06)
[i.5] ETSI TS 143 069: "Digital cellular telecommunications system (Phase 2+); Voice Broadcast
service (VBS); Stage 2 (3GPP TS 43.069)".
[i.6] ETSI TS 123 236: "Digital cellular telecommunications system (Phase 2+); 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)".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
Mobile-service Switching Center (MSC): CN node which might be a single Mobile-switching Center entity or the
couple MSC-Server + Media Gateway
RANflex: feature "Intra-domain connection of RAN nodes to multiple CN nodes" which has been added to the 3GPP
standard in Rel-5 (see TS 123 236 [i.6]) and which allows providing a redundant MSC configuration ("MSC pool") for
the support of point-to-point communication services and which does not group call redundancy
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
BSC Base Station Controller
CN Core Network
CS Circuit Switched
EIRENE European Integrated Radio Enhanced Network
GCR Group Call Register
GCSMSC Group Call Serving MSC
GSM-R Global System for Mobile communication for Railways applications
IMSI International Mobile Station Identifier
LAC Location Area Code
MAP Mobile Application Part
MSC Mobile-service Switching Center
NRI Network Resource Identifier
PLMN Public Land Mobile Network
PS Packet Switched
QoS Quality of Service
RANflex Radio Network flexibility
RNC Radio Network Controller
SGSN Serving GPRS Support Node
TMSI Temporary Mobile Station Identity
UMTS Universal Mobile Telecommunications System
UTRAN UMTS Terrestrial Radio Access Network
VBS Voice Broadcast Service
VGCS Voice Group Call Service
VLR Visitor Location Register
VMSC Visited MSC
ETSI
7 ETSI TS 103 147 V1.1.1 (2013-06)
4 General description
4.1 Basic concept
Railway traffic management is a safety and quality of service critical related operation; therefore, redundancy in the
core network is required in order to cope with MSC single outages. This redundancy functionality is required in case of
unplanned external events (as e.g. earthquakes, fire, terrorist attacks) as well as in case of planned events (as e.g.
maintenance activities) which may cause downtimes of MSC or core network.
GSM-R Core Network Redundancy is based on several features described in 3GPP/ETSI Technical Specifications. In
particular these features are:
- Intra-domain connection of RAN nodes to multiple CN nodes (RANflex)
This feature has been added to the 3GPP standard in Rel-5 (see TS 123 236 [i.6]) and allows providing a
redundant MSC configuration ("MSC pool") for the support of point-to-point communication services by
enabling connection of a BSC to multiple MSC servers.
- Coexistence of VGCS/VBS and RANflex
In railway operation the point-to-multipoint communication services Voice Group Call Service and Voice
Broadcast Service (TS 143 068 [i.4] and TS 143 069 [i.5]) are frequently used. For the coexistence of
VGCS/VBS and RANflex within the same network special enhancements for voice group calls and voice
broadcast calls are required. These enhancements have been added to 3GPP Rel-7 (TS 143 068 [i.4],
TS 143 069 [i.5], TS 129 002 [i.3] and TS 123 236 [i.6]) and guarantee e.g. that also in a network using
RANflex a setup request for a voice group call or voice broadcast call is routed to the appropriate serving
Anchor MSC.
- GCSMSC and GCR Redundancy for VGCS/VBS
As the coexistence of VGCS/VBS and RANflex does not support redundancy of the network entities required
for VGCS/VBS, the Group Call Serving MSC (GCSMSC) and its associated GCR, further enhancements are
necessary to offer the possibility of routing the signaling to a backup GCSMSC when the original target is out
of service. These enhancements have been added to 3GPP Rel-11 (TS 143 068 [i.4], TS 143 069 [i.5] and
TS 129 002 [i.3]).
4.2 Technical Requirements
This list provides a (non-exhaustive) set of technical requirements:
- The basic requirement of the GSM-R Core Network Redundancy is the ability to reach more than one MSC
from the same geographical location.
- GSM-R Core Network Redundancy is required for point to point calls and for voice group calls and voice
broadcast calls. The point to point calls may be voice communication or circuit switched data communication.
- For the voice group calls and voice broadcast calls the backup MSC shall have the same information as the
failed one when the original target fails. Therefore a redundancy of the group call register is required. This is
including both operational and maintenance aspects. The backup functionality is required on a per group call
reference level.
- The redundancy concept shall ensure that all requests for one specific group call reference are handled by the
same MSC in a MSC pool for the entire duration of this specific group call or broadcast call.
- Inter PLMN voice group calls (international common group call areas) shall be supported.
- The GSM-R Core Network Redundancy shall provide redundancy without the need of physical intervention in
case of disaster recovery, i.e. automatic switchover, no manual switchover.
- At installation of the redundancy functionality in the network a manual impact (configuration) on neighbour
networks is valid.
- It is not required to maintain ongoing calls in case of MSC outages.
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8 ETSI TS 103 147 V1.1.1 (2013-06)
4.3 System Architecture
In principle the GSM-R Core Network Redundancy as described in the present document is architecture neutral, i.e. it is
applicable to either Rel-99 CN architecture or Rel-4 CN architecture. However in order to reach the high QoS
requirements of GSM-R networks the GSM-R Core Network Redundancy is assumed to be implemented in a Rel-4 CN
architecture.
3GPP TS does not restrict the number of MSCs within the core networks or RANflex pools. As the majority of the
railway networks using Rel-4 CN architecture will consist of only 2 MSCs at a maximum, the GSM-R Core Network
Redundancy is mainly focused on 'basic' 1+1 configuration. Nevertheless the present document also covers the 1+N
configuration.
5 Components of GSM-R Core Network Redundancy
As explained in clause 4.1, the GSM-R Core Network Redundancy is a combination of several features described in
3GPP/ETSI Technical Specifications. This clause contains one clause for each of these features containing a high level
description for the sake of reminder and a list of the references describing the feature in detail.
5.1 Intra-domain connection of RAN nodes to multiple CN
nodes (RANflex)
5.1.1 Main concept
RANflex is answering the need for a flexible network structure as the former requirements to have a BSC controlled by
a single MSC server or SGSN lead to certain limitations. Allowing the BSCs to connect to a number of MSC servers
increases the networks performance in terms of scalability, distributing the network load amongst the serving entities,
and reducing the required signalling as the user roams.
The Intra Domain Connection of RAN Nodes to Multiple CN Nodes overcomes the strict hierarchy, which restricts the
connection of a RAN node to just one CN node. This restriction results from routing mechanisms in the RAN nodes
which differentiate only between information to be sent to the PS or to the CS domain CN nodes and which do not
differentiate between multiple CN nodes in each domain. The Intra Domain Connection of RAN Nodes to Multiple CN
Nodes introduces a routing mechanism (and other related functionality), which enables the RAN nodes to route
information to different CN nodes within the CS or PS domain, respectively.
NOTE 1: PS domain communications are outside the scope of the present document.
The Intra Domain Connection of RAN Nodes to Multiple CN Nodes introduces further the concept of "pool-areas"
which is enabled by the routing mechanism in the RAN nodes. A pool-area is comparable to an MSC or SGSN service
area as a collection of one or more RAN node service areas. In difference to an MSC or SGSN service area a pool-area
is served by multiple CN nodes (MSCs or SGSNs) in parallel which share the traffic of this area between each other.
Furthermore, pool-areas may overlap which is not possible for MSC or SGSN service areas.
RANflex is applicable for RAN nodes in general, i.e. for BSC and RNC. However, as UTRAN is not applicable for
railway operation the GSM-R Core Network Redundancy is relying on BSC as RAN node only.
NOTE 2: The usage of RANflex in the core network requires the support of the functionality in the radio network
as well.
Primarily RANflex is providing the ability for loadsharing but due to the MSC pool concept it allows providing a
redundant MSC configuration for the s
...