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TECHNICAL SPECIFICATION
Universal Mobile Telecommunications System (UMTS);
LTE;
Network sharing;
Architecture and functional description
(3GPP TS 23.251 version 15.1.0 Release 15)
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3GPP TS 23.251 version 15.1.0 Release 15 1 ETSI TS 123 251 V15.1.0 (2018-09)
Reference
RTS/TSGS-0223251vf10
Keywords
LTE,UMTS
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3GPP TS 23.251 version 15.1.0 Release 15 2 ETSI TS 123 251 V15.1.0 (2018-09)
Intellectual Property Rights
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Foreword
This Technical Specification (TS) 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 "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.
ETSI
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3GPP TS 23.251 version 15.1.0 Release 15 3 ETSI TS 123 251 V15.1.0 (2018-09)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 5
Introduction . 5
1 Scope . 6
2 References . 6
3 Definitions and abbreviations . 7
3.1 Definitions . 7
3.2 Void . 8
3.3 Abbreviations . 8
4 General Description . 8
4.1 Overview . 8
4.2 Core Network Operator and Network Selection . 9
4.2.1 Core network operator identity . 9
4.2.2 Broadcast system information for network sharing . 10
4.2.3 Network selection in a shared network . 10
4.2.3.1 Behaviour of supporting UEs (GERAN, UTRAN and E-UTRAN) . 10
4.2.3.2 Behaviour of non-supporting UEs (GERAN, UTRAN) . 10
4.2.4 Assignment of core network operator and core network node . 10
4.2.5 PS and CS domain registration coordination in UTRAN and GERAN . 11
4.2.5a PS and CS domain registration coordination in E-UTRAN . 11
4.2.5.1 Void. 12
4.2.5.2 Void. 12
4.2.5.3 CS/PS domain coordination and operator selection in GERAN and UTRAN . 12
4.2.6 Attach/detach handling . 13
4.3 Network Name Display for Supporting UEs . 13
4.4 HPLMN Support . 13
4.5 Support of Cell Broadcast Services and Warning System . 14
4.6 Support of Extended Access Barring. 14
4.7 Support of service identification for improved radio utilization for GERAN . 14
5 Functional description . 14
5.1 UE functions . 14
5.2 RNC functions . 14
5.2a eNodeB functions . 15
5.2b BSC functions . 15
5.3 MSC functions . 17
5.4 SGSN functions . 17
5.5 MME functions . 18
6 Charging and accounting aspects . 20
7 Example signalling flows . 20
7.1 Network selection . 20
7.1.2 Non-supporting UEs in a GWCN configuration . 20
7.1.3 Supporting UEs in a GWCN configuration . 21
7.1.4 Non-supporting UEs in a MOCN configuration . 22
7.1.4.1 UTRAN based MOCN configuration. 22
7.1.4.2 GERAN based MOCN configuration. 25
7.1.4.3 CS registration after PS Handover . 28
7.1.5 Supporting UEs in a MOCN configuration . 30
7.1.5.1 UTRAN based MOCN configuration. 30
7.1.5.2 GERAN based MOCN configuration. 31
7.1.6 Query to opposite domain . 32
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3GPP TS 23.251 version 15.1.0 Release 15 4 ETSI TS 123 251 V15.1.0 (2018-09)
Annex A (informative): Network Resource Indicator (NRI) allocation examples. 33
A.1 NRI in shared UTRAN/GERAN networks . 33
A.2 Alternatives for NRI split in UTRAN and GERAN . 34
A.3 NRI and CS/PS coordination in GWCN . . 35
A.4 CSPS Coordination . 35
Annex B (normative): Interaction with other network capabilities . 38
B.1 General . 38
B.2 Support for RAN sharing for CSG and hybrid cells . 38
Annex C (informative): Change History . 39
History . 40
ETSI
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3GPP TS 23.251 version 15.1.0 Release 15 5 ETSI TS 123 251 V15.1.0 (2018-09)
Foreword
This Technical Specification has been produced by the 3rd 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 a way for operators to share the heavy deployment costs for mobile networks, especially in the roll-
out phase. In the current mobile telephony marketplace, functionality that enables various forms of network sharing is
becoming more and more important. These aspects have not really been addressed before Release 6 in 3GPP UTRAN
based access networks, before Release 8 in 3GPP E-UTRAN based access networks and before Release 10 in 3GPP
GERAN based access networks, although there has been functionality that supports a very basic type of network
sharing since the Release 5 versions of the 3GPP specifications.
To cope with 3GPP pre-Release 6 UTRAN UEs and with non supporting 3GPP GERAN UEs, this specification
describes extra functionality for MSCs, SGSNs, BSCs and RNCs in order to provide network sharing functionality to
"non-supporting UEs".
In this Release of the specifications, all UTRAN and E-UTRAN capable UEs are required to support the UTRAN and
E-UTRAN network sharing requirements. Hence the E-UTRAN and MMEs (which were introduced in 3GPP
Release 8) do not need functionality to handle "non-supporting UEs".
Scenarios and user requirements are described in TR 22.951 [1], while the current document presents the stage 2 details
and descriptions of how these requirements are supported in a 3GPP GERAN, UTRAN and/or E-UTRAN based
network.
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3GPP TS 23.251 version 15.1.0 Release 15 6 ETSI TS 123 251 V15.1.0 (2018-09)
1 Scope
The present document covers the details of Network Sharing for GERAN, UTRAN and E-UTRAN. It shows how
several core network operators can share one radio access network and details the impacts on the network architecture.
All UEs shall comply with existing requirements, among them PLMN selection and system information reception. The
present document also defines requirements for network-sharing supporting UEs.
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 22.951: "Service Aspects and Requirements for Network Sharing".
[2] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[3] 3GPP TS 25.331: "RRC Protocol Specification".
[4] 3GPP TS 23.122: "NAS Functions related to Mobile Station (MS) in idle mode".
[5] 3GPP TS 32.250: "Telecommunication management; Charging management; Circuit Switched
(CS) domain charging".
[6] 3GPP TS 32.251: "Telecommunication management; Charging management; Packet Switched
(PS) domain charging".
[7] 3GPP TS 24.008: "Mobile radio interface Layer 3 specification; Core network protocols; Stage 3".
[8] 3GPP TS 23.236: "Intra-domain connection of Radio Access Network (RAN) nodes to multiple
Core Network (CN) nodes".
[9] 3GPP TS 23.401: "Technical Specification Group Services and System Aspects; GPRS
enhancements for E-UTRAN access".
[10] 3GPP TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal
Terrestrial Radio Access (E-UTRAN); Overall description; Stage 2".
[11] 3GPP TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource
Control (RRC); Protocol specification".
[12] 3GPP TS 24.301: "Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS);
Stage 3".
[13] 3GPP TS 25.413: "UTRAN Iu interface, Radio Access Network Application Part (RANAP)
signalling".
[14] 3GPP TS 36.413: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1
Application Protocol (S1AP)".
[15] 3GPP TS 23.272: "Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2".
[16] 3GPP TS 44.018: "Radio Resource Control RRC Protocol Specification".
[17] 3GPP TS 25.467: "UTRAN architecture for 3G Home Node B (HNB); Stage 2".
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3GPP TS 23.251 version 15.1.0 Release 15 7 ETSI TS 123 251 V15.1.0 (2018-09)
[18] 3GPP TS 22.042: "Network Identity and Time Zone (NITZ); Service description; Stage 1".
[19] 3GPP TS 44.064: "General Packet Radio Service (GPRS); Mobile Station - Serving GPRS Support
Node (MS SGSN) Logical Link Control (LLC) layer specification".
[20] 3GPP TS 23.041: "Technical realization of Cell Broadcast Service (CBS)".
[21] 3GPP TS 29.280: "3GPP Sv interface (MME to MSC, and SGSN to MSC) for SRVCC".
[22] 3GPP TS 23.060: "General Packet Radio Service (GPRS); Service description; Stage 2".
[23] 3GPP TS 22.011: "Service Accessibility".
[24] 3GPP TS 48.018: "General Packet Radio Service (GPRS); Base Station System (BSS) - Serving
GPRS Support Node (SGSN); BSS GPRS Protocol (BSSGP)".
[25] 3GPP TS 48.008: "Mobile-services Switching Centre Base Station System (MSC BSS) interface;
Layer 3 specification".
[26] 3GPP TS 29.018: "General Packet Radio Service (GPRS); Serving GPRS Support Node (SGSN)
Visitors Location Register (VLR); Gs interface layer 3 specification".
[27] 3GPP TS 29.118: "Mobility Management Entity (MME) - Visitor Location Register (VLR) SGs
interface specification".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definition below apply. Terms and definitions not
defined below can be found in TR 21.905 [2].
Conventional network: A PLMN consisting of radio access network and core network, by which only one serving
operator provides services to its subscriber. Subscribers of other operators may receive services by national or
international roaming.
Common PLMN: The PLMN-id indicated in the system broadcast information as defined for conventional networks,
which non-supporting UEs understand as the serving operator.
Core network operator: An operator that provides services to subscribers as one of multiple serving operators that
share at least a radio access network. Each core network operator may provide services to subscriber of other operators
by national or international roaming.
Gateway Core Network: A network sharing configuration in which parts of the core network (MSCs/SGSNs/MMEs)
are also shared.
Multi-Operator Core Network: A network-sharing configuration in which only the RAN is shared.
Non-supporting UE: A UE that does not support network sharing in the sense that it ignores the additional broadcast
system information that is specific for network sharing for 3GPP UTRAN and GERAN. In other specifications, the term
"network sharing non-supporting UE" may be used.
Supporting UE: A UE that supports network sharing in the sense that it is able to select a core network operator as the
serving operator within a shared network. In other specifications, the term "network sharing supporting UE" may be
used.
Anchor PLMN: With regard to SRVCC from CS to PS, this Anchor PLMN points to the PS domain operator in which
the voice media is anchored in Access Transfer Gateway as part of the SRVCC procedure.
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3GPP TS 23.251 version 15.1.0 Release 15 8 ETSI TS 123 251 V15.1.0 (2018-09)
3.2 Void
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in TR 21.905 [2] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [2].
BSC Base Station Controller
CN Core Network
E-UTRAN Evolved Universal Terrestrial Radio Access Network
eNodeB E-UTRAN NodeB
gsmSCF GSM Service Control Function
GERAN GSM/EDGE Radio Access Network
GUTI Globally Unique Temporary Identity
GWCN Gateway Core Network
HLR Home Location Register
HSS Home Subscriber Server
MCC Mobile Country Code
MME Mobility Management Entity
MNC Mobile Network Code
MOCN Multi-Operator Core Network
MSC Mobile Switching Centre
NITZ Network Identity and Time Zone
PLMN Public Land Mobile Network
RNC Radio Network Controller
SGSN Serving GPRS Support Node
TMSI Temporary Mobile Subscriber Identity
UE User Equipment
UTRAN Universal Terrestrial Radio Access Network
VLR Visitor Location Register
4 General Description
4.1 Overview
A network sharing architecture shall allow different core network operators to connect to a shared radio access network.
The operators do not only share the radio network elements, but may also share the radio resources themselves. In
addition to this shared radio access network the operators may or may not have additional dedicated radio access
networks, like for example, 2G radio access networks. There are two identified architectures to be supported by network
sharing. They are shown in the figures below.
In both architectures, the radio access network is shared. Figure 1 below shows reference architecture for network
sharing in which also MSCs and SGSNs are shared. This configuration will be referred to as a Gateway Core Network
(GWCN) configuration.
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3GPP TS 23.251 version 15.1.0 Release 15 9 ETSI TS 123 251 V15.1.0 (2018-09)
CN CN CN
......... .........
Operator A Operator B Operator C
Shared Shared Shared
MSC/SGSN MSC/SGSN MSC/SGSN
Iu
RNC RNC RNC
Radio Access Network
Operator X
Figure 1: A Gateway Core Network (GWCN) configuration for network sharing.
Besides shared radio access network nodes, the core network operators also
share core network nodes
Figure 2 below shows the reference architecture for network sharing in which only the radio access network is shared,
the Multi-Operator Core Network (MOCN) configuration.
CN CN CN
......... .........
Operator A Operator B Operator C
Iu
RNC
Radio Access Network
Operator X
Figure 2: A Multi-Operator Core Network (MOCN) in which multiple CN nodes are
connected to the same RNC and the CN nodes are operated by different operators
The UE behaviour in both of these configurations shall be the same. No information concerning the configuration of a
shared network shall be indicated to the UE.
For the Evolved Packet System, only the PS domain of the above figures is relevant. For E-UTRAN access Figures 1
and 2 both apply but with the MME replacing the SGSN, the eNodeB replacing the RNC, and the S1 reference point
replacing the Iu interface.
For GERAN access, both GWCN and MOCN are applicable but with the BSC replacing the RNC and the A/Gb-
Interfaces replacing the Iu interface.
4.2 Core Network Operator and Network Selection
Network sharing is an agreement between operators and shall be transparent to the user. This implies that a supporting
UE needs to be able to discriminate between core network operators available in a shared radio access network and that
these operators can be handled in the same way as operators in non-shared networks.
4.2.1 Core network operator identity
A core network operator is identified by a PLMN-id (MCC+MNC).
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3GPP TS 23.251 version 15.1.0 Release 15 10 ETSI TS 123 251 V15.1.0 (2018-09)
4.2.2 Broadcast system information for network sharing
If a shared RAN is configured to indicate available core network operators for selection by UEs, each cell in shared
radio access network shall in the broadcast system information include information concerning available core network
operators in the shared network.
The available core network operators shall be the same for all cells of a Location Area in a shared UTRAN or GERAN
network.
For E-UTRAN, the Broadcast System Information broadcasts a basic set of PLMN IDs and optionally one or more
additional set of PLMN IDs. All E-UTRAN UEs support reception of the basic set, only Release 14 and later E-
UTRAN UEs are required to receive the additional set (see TS 36.331 [11]).
The available core network operators shall be the same for all cells of a Tracking Area in a shared E-UTRAN network.
The basic and the additional sets allow different (sets of) PLMNs to have different cell ID and TAC.
A supporting UE decodes the broadcast system information and takes the information concerning available core
network operators into account in network and cell (re-)selection procedures. Broadcast system information is specified
in TS 44.018 [16] for GERAN, TS 25.331 [3] for UTRAN and TS 36.331 [11] for E-UTRAN.
4.2.3 Network selection in a shared network
4.2.3.1 Behaviour of supporting UEs (GERAN, UTRAN and E-UTRAN)
In some sharing scenarios, the sharing operators require the UTRAN/GERAN to broadcast, to non-supporting UEs, a
PLMN ID that does not identify any of the sharing core network operators. In this case, it is necessary that a supporting
UE does not select this "common PLMN ID".
In other sharing scenarios, the sharing operators may want the PLMN broadcast to non-supporting UEs to be selectable
by supporting UEs.
A supporting UE decodes the broadcast system information to determine available core network operators in the shared
network. The UE regards both the core network operators indicated in the broadcast system information and
conventional networks as individual networks. The core network operators together with all conventional networks are
candidate PLMNs for the PLMN selection procedure that shall be performed by the UE as specified in TS 23.122 [4].
In GERAN and UTRAN, non-supporting UEs use the broadcast "common PLMN-id" in their PLMN (re)selection
processes.
In UTRAN, supporting UEs shall use the PLMN-ids that are broadcast in the Multiple PLMN ID List information
element in their PLMN (re)selection processes. UTRAN AS signalling permits the Multiple PLMN ID List to indicate
to supporting UEs whether to include or exclude the MCC+MNC of the "common PLMN-id" in their network
(re)selection processes.
For supporting UEs, GERAN provides equivalent functionality to UTRAN.
For E-UTRAN, the UE uses all of the received broadcast PLMN-ids in its PLMN (re)selection processes.
4.2.3.2 Behaviour of non-supporting UEs (GERAN, UTRAN)
Non-supporting UEs ignore the broadcast system infor
...