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TECHNICAL REPORT
Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS);
LTE;
Service aspects and requirements for network sharing
(3GPP TR 22.951 version 15.0.0 Release 15)
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3GPP TR 22.951 version 15.0.0 Release 15 1 ETSI TR 122 951 V15.0.0 (2018-07)
Reference
RTR/TSGS-0122951vf00
Keywords
GSM,LTE,UMTS
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3GPP TR 22.951 version 15.0.0 Release 15 2 ETSI TR 122 951 V15.0.0 (2018-07)
Intellectual Property Rights
Essential patents
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Foreword
This Technical Report (TR) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
.
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
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Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 4
Introduction . 4
1 Scope . 5
2 References . 5
3 Definitions, symbols and abbreviations . 5
3.1 Definitions . 5
3.2 Symbols . 5
3.3 Abbreviations . 6
4 General Aspects . 6
5 Network Sharing Scenarios . 6
5.1 Scenario1: Multiple core networks sharing common radio access network in R99 . 6
5.1.1 Limitations . 7
5.2 Scenario 2: Geographically split networks sharing . 7
5.3 Scenario 3: Common Network Sharing . 8
5.4 Scenario 4: Common spectrum network sharing . 8
5.5 Scenario 5: Multiple radio access networks sharing common core network . 9
6 Network Identities and User Classification . 10
7 User Requirements . 10
7.1 Network selection . 10
7.2 Network name display . 10
7.3 UE requirements . 10
8 Network requirements . 10
9 Mobility Requirements . 11
9.1 Service continuity . 11
9.2 Handover . 11
9.3 Roaming . 11
10 Security Requirements . 11
11 Charging Requirements . 11
12 Conclusions . 12
12.1 Impacts on 3GPP Specifications . 12
Annex A (informative): Examples of network sharing realisations . 13
A.1 Advanced Geographical split with seamless national roaming . 13
A.1.1 Functionalities needed . 14
A.2 Common shared spectrum scenario . 14
A.2.1 Functionalities needed . 15
Annex B (informative): Change history . 19
History . 20
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Foreword
rd
This Technical Report has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG 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.
Introduction
Network sharing is becoming more and more popular as a means to provide coverage quickly and in a cost efficient
way. The high price paid for the license in some countries as well as mergers, acquisitions have raised recently high
interest in this topic. For these reasons 3GPP has decided to investigate what shortcomings currently in the technical
specifications may prevent a standardized approach to the deployment of shared networks. This TR is aimed to describe
a wide variety of possible network sharing and highlight the expected user experience for each of the scenarios.
Charging aspects, terminal aspects and security are also investigated.
The purpose of this technical report is to collate in a single document the requirements, considerations and deployment
scenarios that operators as well as users need to see fulfilled for a successful use of a shared network. Particular
attention has been given in making possible the avoidance of proprietary solutions particularly for what concerns the
terminals.
Furthermore, the concepts discussed in this report may be applied to sharing a GERAN and UTRAN infrastructure, in
this sense the interest in network sharing tools extends to the vast majority of the existing GSM operators who intend to
deploy a UMTS Terrestrial Radio Access Network layer to complement the existing GSM/GPRS coverage.
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1 Scope
In the current dynamic market place, as a result of partnerships, acquisitions, creative agreements among operators and
so on, the need for tools that enable various degrees of network sharing is becoming more and more important.
When GSM and then UMTS were specified, the possibility of sharing part or all of the network by two or more
separated commercial entities was not considered and as a result the standards lack some functionalities that enable the
realisation of such commercial agreements.
GSM was designed under the principle "one operator, one radio access network". The GSM network has some
possibilities of infrastructure sharing, but it does not support true radio access network sharing. The initial design of
3GPP system has followed the same principle.
This technical report is aimed to capture the service and user requirements that must be fulfilled by the 3GPP system in
order to enable network sharing in a standardised way. Section 5 describes various Network sharing includes various
scenarios e.g. spanning from common radio access network connected to multiple core networks toor multiple radio
access networks sharing one core network. Section 6 contains a summary of the user classification and network
identities. In section 7 the user requirements are described, while section 8 deals with the network operator
requirements. Section 9 describes the mobility requirements in a shared network. The rest of the document is covering
security (section 10) and charging (section 11). Some conclusions can be found in section 12 and an annex with
examples of practical realisation of network sharing is provided.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications ".
3 Definitions, symbols and abbreviations
3.1 Definitions
Core Network Operator: Operator that offers core network services.
Iu-flex: Routing functionality for intra domain connection of RAN nodes to multiple CN nodes.
Radio Access Network Operator: Operator that offers radio access to one or more core network operators.
RAN sharing: Two or more CN operators share the same RAN, i.e. a RAN node (RNC or BSC) is connected to
multiple CN nodes (SGSNs and MSC/VLRs) belonging to different CN operators.
Roaming: The ability for a user to function in a serving network different from the home network. The serving network
could be a shared network operated by two or more network operator.
Shared Network: When two or more network operator sharing network elements.
3.2 Symbols
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3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
4 General Aspects
5 Network Sharing Scenarios
Sharing networks and network infrastructure has become a very important part of 3GPP systems. There are many
network-sharing scenarios possible depending on different operator strategies but also on rules and legislation in
different countries. 3GPP systems are originally not fully designed for network sharing between different operators
however some limited support exists in the 3GPP Release 99.The equivalent PLMN feature in Release 99 allows
operators to share a common UTRAN, with certain parts of the core networks also shared between the operators, see
Figure 1.
Operator A
Core Network 1
Common
UTRAN Core Network 1 + 2
Operator B
Core Network 2
Figure 1: Two operators sharing the same UTRAN. To make this work, parts of the core network need
to shared as well.
Important to note here is that this network-sharing scenario allows operators without a UMTS license to share the
network and supply its customers with 3G services. For example, a 2G operator may supply its subscribers with 3G
services using another operator’s allocated spectrum. A geographically split network, i.e. a scenario in which
cooperating operators cover different parts of a country, is also possible in Release 99. One operator’s core network
may also be connected to several UTRANs, see Figure 1.
Different kinds of evolution paths are essential for shared networks. For example, it is not only the sharing solution at a
certain time that is important, but also how it is possible for the sharing partners to evolve either to a more dedicated
network or to a more joint network. That is, the set of infrastructure sharing solutions and scenarios that is discussed in
the industry cover alternatives that together include:
- solution alternatives targeting at dedicated networks in the near future,
- solutions for infrastructure sharing not targeting at immediate exit, but at exit when for example the network
capacity demand so requires,
- infrastracture sharing targeting at long term sharing, which for example is the case when one of the operators
lacks a frequency license.
Although these network-sharing scenarios are possible in Release 99 of 3GPP systems, the solutions are far from
optimised. Identifying, changing, and adding appropriate functionality in the network will definitely lead to a better
shared-network operation.
5.1 Scenario1: Multiple core networks sharing common radio
access network in R99
For operators that have multiple frequency allocations it is possible to share the RAN elements, but not to share the
radio frequencies. In this case the operators connect directly to their own dedicated carrier layer in the shared RNC in
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the shared RAN. This solution is possible with 3GPP Release 99 and is illustrated below in Figure 2 for the case when
two operators have one license each.
Shared RNC
Shared Node B
Operator one
MNC
Frequency one
Frequency one
Operator two
one
Frequency two MNC
Frequency two
two
Figure 2: The figure illustrates how it is possible to within the 3GPP Release 99 framework have
dedicated carrier layers in the RAN for multiple operator. The operators transmit their own mobile
network code (MNC) on their dedicated carrier
5.1.1 Limitations
FFS
5.2 Scenario 2: Geographically split networks sharing
In this scenario, two (or more) operators with individual 3G licenses will with their respective radio access networks
cover different parts of a country but together provide coverage of the entire country.
This scenario can be divided into following cases:
1) When two (or more operators) employ national roaming for the users, which implies that only one core network
will be associated with each radio access network. Care is obviously needed when coverage regions overlap,
which makes this a valid shared-networks scenario. This case is shown in Figure 3.
2) The operators can have their individual core networks connected to both radio access networks throughout the
entire coverage area, but utilizing the different operator’s allocated spectrum in different parts of the coverage
area. There will thus be multiple core network operators in each of the shared radio access networks. The
connection of the core networks to the radio access networks can either be done by connecting the radio network
controllers to both operators' core network elements or by sharing parts of the core network, e.g. SGSNs and/or
MSCs. The work on shared networks in Rel-6 should not make any of these possibilities mandatory and it should
be the choice of the operator which one is implemented. Additionally it should, be possible to introduce Iu-flex
functionality between the common core network parts and the radio access network for purely load-sharing
purposes.
Core Network Core Network
A B
Radio Access Radio Access
Network Network
A B
Figure 3: Geographically split network using national
roaming between operators.
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Core Network Core Network
A B
Core Network Core Network
A B Common core
A+B
Radio Access Radio Access Radio Access Radio Access
Network Network Network Network
A B A B
Figure 4: Geographically split shared radio networks scenarios
with dedicated or common core networks
The national roaming scenario and the common core network scenario in Figure 4 can be deployed already today using
R99 functionality and are therefore important in the future work of 3GPP. The scenario with dedicated core networks in
Figure 4 is not supported by Rel-5 specifications.
In areas where more than one of the operators provide coverage, it should be possible to restrict the access rights so that
the users are only allowed to use the radio access network provided by their home operator.
5.3 Scenario 3: Common Network Sharing
In this scenario, one operator will deploy coverage in a specific geographical area, and other operators will be allowed
to use this coverage for their subscribers. Outside this geographical area, coverage is provided by each of the operators.
For example, in the case of two operators, a third-party could provide UTRAN coverage to operators A and B’
subscribers in areas with high population density. In less dense areas, GERAN coverage is provided by operator A and
operator B and in these areas the subscribers should connect to the access network of their operator.
5.4 Scenario 4: Common spectrum network sharing
Common spectrum network sharing is applicable when
- one operator has a 3G license and shares the allocated spectrum with other operators.
- a number of operators decide to pool their allocated spectrums and share the total spectrum (operators without
allocated spectrum may also share this pooled spectrum).
The scenario can be realized as follows.
1. Connecting each operator’s core networks and to the shared radio access network(s), see case 1 in Figure 5
below (only 1 radio network controller for simplicity). In this case it should be possible that one or more of the
core network operators use Iu Flex between their core network and the shared radio access network. The
technical realisation of this scenario may reuse some of the mechanisms already specified in REL-5 Iu Flex.
Described in the figure below are three network operators, A, B and C. Operators A and C are not using multiple
core network nodes (CN) and therefore may not need to use Iu-Flex. Operator B is using multiple CNs and has
decided to use Ie-Flex to enable the intra-domain sharing of CNs
2. The core network entities connected to radio access network can be shared, see case 2 in Figure 5 below.
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Operator B's CN nodes
No Iu Flex using Iu Flex No Iu Flex
Operator A Op. B's Op. B's Op. B's Operator C
CN node CN node CN node CN node CN node
Iu Flex
Iu interface
Radio Network Controller
Operator X
Core Network Core Network
A B
Common Core
A+B
Radio Access
Network
A
Figure 5: Two different cases of common spectrum network sharing
The work on shared networks in Rel-6 should not make any of these possibilities mandatory and it should be the choice
of the operator which one is implemented.
5.5 Scenario 5: Multiple radio access networks sharing
common core network
In this scenario multiple radio access networks share a common network. The multiple RANs can belong to different
PLMNs and network operators. Due to operators’ deployment different nodes or part of the common core network i.e.
HSS/HLR, SGSN etc can be shared.
The scenario is depicted in the figure below:
Common Core Network
A + B + C
Radio Access Radio Access Radio Access
Network Network Network
A B C
Figure 6: Multiple RANs sharing a common CN
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6 Network Identities and User Classification
To fully support for example handover, service differentiation and access rights in shared networks it is occasionally
necessary to identify to which operator that a user belongs to and possibly group the users according to this information.
To avoid complicated operation and maintenance procedures, such user classification should be general for all the
functions in the shared network that needs information about the user identity.
7 User Requirements
Network sharing is an agreement between network operators and is transparent to the user.
7.1 Network selection
When network sharing exists between different operators and a user roams into the shared network it should be possible
for that user to register with a core network operator (among the network sharing partners) that either
(i) the user has a subscription with, or
(ii) the user’s home operator has a roaming agreement with,
even if the operator is not offering radio coverage.
This requirement implies that it is possible to discriminate between core network operators connected to a shared radio
access network. The selection of a core network operator among those connected to the shared radio access network can
either be manual (i.e. performed by the user after receiving a list of available core network operators) or automatic (i.e.
performed by the UE according to user and operator preferred settings).
7.2 Network name display
The terminal always displays the name of the core network operator the user has registered with. It should be noted that
for pre-Rel-6 UEs the network name display for roaming users in Scenarios 2 and 4 are not supported.
7.3 UE requirements
A Rel-6 network sharing solution should support legacy (pre-Rel-6) UEs. This requirement is important since a Rel-6
network sharing solution may imply changes in the UEs.
Without changes to pre-Rel 6 specifications, pre-Rel-6 UEs may in certain cases not be able to support the full set of
Rel-6 enhancements. The following two cases have currently been identified:
- Manual network selection for roaming users in Scenario 2 and Scenario 4.
- Network name display for roaming users in Scenario 2 and Scenario 4.
8 Network requirements
The service capabilities and requirements should not be restricted by network sharing scenarios.
It should be possible for a network operator to differentiate its service offering from other network operators within
shared network.
The services and service capabilities offered should not be restricted by the existence of network sharing.
It should be possible for a network operator to differentiate its service offering from other network operators within
shared network.
The provision of services and service capabilities that is possible to offer in a network should not be restricted by the
existence of the network sharing It should be possible for a core network operator to differentiate its service offering
from other core network operators within the shared network.
It should be possible to control the access to service capabilities offered by a shared network according to the core
network operator the user is subscribed to.
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9 Mobility Requirements
9.1 Service continuity
The mobility in a shared network, both when controlled by the UE and when controlled by the network should not cause
any undue interruption of service.
It should be possible for a subscriber to roa
...