ETSI TS 123 085 V17.0.0 (2022-04)

Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); Closed User Group (CUG) supplementary service; Stage 2 (3GPP TS 23.085 version 17.0.0 Release 17)

RTS/TSGC-0423085vh00

General Information

• Status: Not Published
• Technical Committee: 3GPP CT 4 - MAP/CAMEL/GTP/BCH/SS/TrFO/IMS/GUP/WLAN (formely CN4)
• Current Stage: 12 - Completion
• Completion Date: 12-Apr-2022

Standards Content (Sample)

ETSI TS 123 085 V17.0.0 (2022-04)






TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS);
Closed User Group (CUG) supplementary service;
Stage 2
(3GPP TS 23.085 version 17.0.0 Release 17)

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3GPP TS 23.085 version 17.0.0 Release 17 1 ETSI TS 123 085 V17.0.0 (2022-04)

Reference
RTS/TSGC-0423085vh00
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ETSI

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3GPP TS 23.085 version 17.0.0 Release 17 2 ETSI TS 123 085 V17.0.0 (2022-04)
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ETSI

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3GPP TS 23.085 version 17.0.0 Release 17 3 ETSI TS 123 085 V17.0.0 (2022-04)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 4
0 Scope . 5
0.1 References . 5
0.2 Definitions . 5
0.3 Abbreviations . 6
1 Closed user group (CUG) . 6
1.1 Handling of Closed User Group . 6
1.1.1 Mobile Originated (MO) CUG call handling . 6
1.1.1.1 MO CUG call handling at the MSC . 7
1.1.1.2 MO CUG call handling at the VLR . 7
1.1.2 Mobile Terminated (MT) CUG call handling . 7
1.1.2.1 MT CUG handling at the GMSC . 7
1.1.2.2 MT CUG handling functions at the HLR . 7
1.1.2.3 MT CUG handling functions at the MSC . 8
1.1.2.4 MT CUG handling functions at the VLR . 8
1.1.3 CUG subscriber roaming requirements. 8
1.1.4 CUG interworking requirements . 9
1.1.4.1 Non-CUG GSM PLMNs . 9
1.1.4.2 Interworking to Non-CUG networks . 9
1.1.5 Supplementary service interactions . 9
1.1.5.1 Interaction with Call Forwarding . 9
1.1.5.2 Interaction with call waiting . 9
1.1.5.3 Interaction with Anonymous Call Rejection . 10
1.2 Functions and information flows . 10
1.2.1 Functions . 10
1.2.2 Information flows . 12
1.3 Information stored in the HLR . 18
1.4 Information stored in the VLR . 19
1.5 Handover . 19
1.6 Cross phase compatibility . 20
1.6.1 MSC, VLR only support phase 1 . 20
1.6.2 GMSC only supports phase 1 . 20
Annex A (informative): Change history . 21
History . 22

ETSI

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3GPP TS 23.085 version 17.0.0 Release 17 4 ETSI TS 123 085 V17.0.0 (2022-04)
Foreword
rd
This Technical Specification 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.
ETSI

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3GPP TS 23.085 version 17.0.0 Release 17 5 ETSI TS 123 085 V17.0.0 (2022-04)
0 Scope
The present document gives the stage 2 description of the closed user group supplementary service.
The community of interest supplementary service defined is:
- closed user group (CUG) (see clause 1).
0.1 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 ".
[2] 3GPP TS 22.085: "Closed User Group (CUG) Supplementary Services; Stage 1".
[3] 3GPP TS 23.088: "Call Barring (CB) Supplementary Service; Stage 2".
0.2 Definitions
CUG terminology defined in 3GPP TS 22. 085 [2] is applicable to the present document. In addition, the following
definitions apply.
CUG Authorisation Functions: Checks performed by the network to ensure that the integrity of a CUG related call is
guarantied. CUG calls are rejected if they do not meet the criteria of these checks.
CUG call: CUG call, in signalling terms, is a call where CUG information is passed from the originating switching
entity to the destination entity.
CUG Index: Code used to select a CUG for an outgoing call, or to indicate an incoming CUG call. Indices are passed
between the user and the network and have significance only within the context of a users subscription.
CUG Interlock Code: Code which uniquely identifies a CUG within a network. The Interlock code is passed from the
point of origin to the destination in a CUG call to identify the CUG which has been invoked.
CUG Related Call Barring: CUG related call barring is call barring applied to a CUG subscriber by the home network
when roaming in a non-CUG network. The user is unable to remove CUG related call barring.
Explicit CUG Invocation: Explicit CUG invocation is where a calling user attempts to invoke a CUG by passing CUG
information to the network in a call request.
Implicit CUG Invocation: Implicit CUG invocation is where the user invokes some default characteristic of a CUG
without providing any CUG information in the call request.
Normal Call: Normal call in the context of this CUG TS is a call established from a CUG subscriber where no CUG
information is passed from the originating switching entity to the destination entity.
Outgoing Access Indicator: Indication passed from the point of origin to the destination in a CUG call to indicate that
the calling user has subscribed to the Outgoing Access inter-CUG accessibility subscription option.
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3GPP TS 23.085 version 17.0.0 Release 17 6 ETSI TS 123 085 V17.0.0 (2022-04)
0.3 Abbreviations
In addition to those listed below abbreviations used in the present document are listed in 3GPP TR 21.905 [1].
For the purposes of the present document, the following abbreviations apply:
BS Basic Service
CI CUG Index
CUG Closed User Group
IA Incoming Access
IC Interlock Code
IC(pref) Interlock code of the preferential CUG
IC+OA Interlock Code and Outgoing Access indicator.
ICB Incoming Calls Barred within the CUG
OA Outgoing Access
OCB Outgoing Calls Barred within the CUG
Pref CUG Preferential CUG
SOA Suppress OA
SPC Suppress Preferential CUG
1 Closed user group (CUG)
The responsibilities of GSM network nodes with respect to CUG are described in the CUG handling clause. The
Functions clause 1.2.1 describes the CUG service logic and how CUG information is used. The flow of CUG
information in various call cases is shown in the Information Flows clause 1.2.2.
1.1 Handling of Closed User Group
A GSM PLMN supporting the CUG supplementary service must guarantee the integrity of any CUG which it handles.
It is not however mandatory for a PLMN to support the CUG supplementary service.
A CUG is uniquely identified within a network by a CUG Interlock Code. The Interlock Code is transferred between
terrestrial network entities to indicate a CUG call.
A user identifies a CUG by a CUG Index. A CUG Index is used to select or indicate the use of a specific CUG in
relation to a call. The index is locally transferred between the mobile station and serving VLR and only has significance
within the context of an individual subscription.
1.1.1 Mobile Originated (MO) CUG call handling
A CUG subscriber may invoke a CUG by providing the network with a CUG Index at call establishment. This is termed
Explicit CUG invocation. Alternatively, if the subscription allows, some default characteristic of a CUG may be
invoked automatically if no CUG information is provided. This is termed Implicit CUG invocation. The network may
optionally indicate the use of an implicitly invoked CUG to the calling user.
A CUG subscriber may suppress certain CUG attributes by providing suppression indicators during call set-up. The
provision of such suppression indicators results in explicit CUG invocation.
Any non-CUG related Call Barring supplementary service requirements shall be discharged before CUG authorisation
occurs.
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3GPP TS 23.085 version 17.0.0 Release 17 7 ETSI TS 123 085 V17.0.0 (2022-04)
1.1.1.1 MO CUG call handling at the MSC
The MSC shall pass any user provided CUG information to the VLR at call establishment.
If an Interlock Code, or Interlock code with Outgoing Access indicator, is received from the VLR the MSC shall
establish a CUG call with the destination network using this information. If a CUG Index is received from the VLR the
MSC shall pass this to the calling MS.
If the CUG call authorisation is unsuccessful the MSC shall pass an indication to the mobile station.
1.1.1.2 MO CUG call handling at the VLR
Authorisation of a MO CUG call is performed by the serving VLR. Authorisation is determined by the information
provided by the user, the subscription information stored in the VLR and the MO CUG call authorisation function, see
Functions clause.
Successful authorisation may result in a normal MO call (call without CUG information transferred to the called party)
or a MO CUG call (call with CUG information transferred to the called party).
When a CUG call is to be made the VLR passes CUG information to the MSC to be used in the call establishment.
Note, the VLR may optionally pass a CUG Index to the MSC (to be passed to the calling user) to indicate that a CUG
has been implicitly invoked. This parameter is not passed to the call destination.
In the case of a normal call, no CUG information is passed to the MSC and the call is established normally.
On authorisation failure the VLR shall reject the call providing a suitable indication to the serving MSC which is passed
to the calling party.
1.1.2 Mobile Terminated (MT) CUG call handling
The terminating network is responsible for enforcing the integrity of a CUG related call. The terminating network must
therefore ensure that the calling party attributes and the called party subscription meet CUG restrictions. The
terminating network provides the called user with an indication of an incoming CUG call.
Non-CUG related Call Barring supplementary service requirements are discharged before CUG authorisations. Call
forwarding requirements are discharged after CUG authorisations.
1.1.2.1 MT CUG handling at the GMSC
The GMSC shall pass any CUG information contained in an incoming call establishment message to the HLR in the
routing enquiry.
The GMSC shall continue the call establishment using the CUG information received from the HLR rather than that
which was initially received. Note, in rare circumstances the HLR may discard CUG parameters, see the Call
Forwarding interaction.
If a CUG call fails the GMSC shall return an indication to the originating network.
1.1.2.2 MT CUG handling functions at the HLR
Authorisation of a MT CUG call is performed at the called parties HLR. Authorisation is determined by the information
received in the call establishment signalling, the called party subscription information stored in the HLR, and the MT
CUG call authorisation function, see Functions clause.
On successful authorisation, the HLR supplies the GMSC with CUG information for the continuation of the call
establishment. On unsuccessful authorisations the HLR rejects the call supplying an indication of the reason for failure.
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3GPP TS 23.085 version 17.0.0 Release 17 8 ETSI TS 123 085 V17.0.0 (2022-04)
1.1.2.3 MT CUG handling functions at the MSC
The MSC shall pass any CUG related information received in incoming call establishment signalling to the VLR.
If the VLR returns CUG information to the serving MSC in response, the MSC shall pass the information to the called
party in the call set-up signalling.
If the CUG call is rejected by the VLR (due to the call forwarding interaction) the MSC shall return an indication to the
originating network.
1.1.2.4 MT CUG handling functions at the VLR
When the VLR receives an incoming call enquiry for a CUG subscriber, it shall attempt to provide a CUG call
indication to the called party. The indication is sent depending on the attributes of the incoming call and the called
parties subscription, as shown in table 1.1. The indication is achieved by sending the CUG Index, associated with the
Interlock Code of the invoked CUG, to the called user.
Table 1.1: CUG Index provision at terminating VLR
┌──────────┬─────────╥───────────────────────────────────────┐
│     │     ║    Called party subscription   │
│ Calling │     ╟────────────────────────────┬──────────┤
│  Party │Interlock║    CUG subscriber    │     │
│  CUG  │ check ╟────────────┬───────────────┤ Normal │
│ Infor- │     ║  No IA  │   IA    │subscriber│
│ mation │     ╟──────┬─────┼──────┬────────┤     │
│     │     ║No ICB│ ICB │No ICB│ ICB  │     │
╞══════════╪═════════╬══════╪═════╪══════╪════════╪══════════╡
│     │ Match ║Index │ - │Index │  -  │     │
│Interlock ├─────────╫──────┴─────┼──────┴────────┤  -   │
│     │ No Match║   -   │   -    │     │
├──────────┼─────────╫──────┬─────┼──────┬────────┼──────────┤
│Interlock │ Match ║Index │ - │Index │No Index│     │
│+ Outgoing├─────────╫──────┴─────┼──────┴────────┤ No Index │
│ Access │ No Match║   -   │  No Index  │     │
├──────────┼─────────╫────────────┼───────────────┼──────────┤
│ No CUG │  -  ║   -   │  No Index  │ No Index │
│  Info. │     ║      │        │     │
└──────────┴─────────╨────────────┴───────────────┴──────────┘
NOTE: "-" = Not Applicable, this check is not performed since such calls are rejected by the called parties HLR.
1.1.3 CUG subscriber roaming requirements
Normal CUG restrictions apply to CUG subscribers when roaming in CUG supporting GSM PLMNs. Extra restrictions
(specified in GSM 02.85) are applied to CUG subscribers roaming in non-CUG GSM VPLMNs to preserve the integrity
of CUG.
These restrictions are applied by the application of call barring programmes which are not under user control. Such
restrictions only apply to a subscribers ability to make outgoing calls using CUG related basic services. Extra
restrictions are not applicable in the MT call case since the requirements are met by the HLR MT CUG authorisation
function and by CUG interworking restrictions.
When a CUG subscriber first roams into a network not supporting CUG, the HLR will pass to the VLR subscription
data indicating that normal Outgoing Call Barring is active for each basic service which is affected by CUG and for
which the user has no CUG Outgoing Access.
The HLR shall store the status of the CUG related barring separately from the previous user controlled status and CUG
related barring shall take precedence over the user controlled status.
The user may still perform SS operations on the user controlled Outgoing Call Barring services. The status of the
barring service as a result of these operations will be stored in the HLR in the normal way, however the HLR will
ensure that the VLR in the non-CUG network continues to have the CUG related call barring programs active as
described above.
When entering a CUG supporting network the CUG related barring activations shall be removed and the user controlled
barring status restored.
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3GPP TS 23.085 version 17.0.0 Release 17 9 ETSI TS 123 085 V17.0.0 (2022-04)
1.1.4 CUG interworking requirements
1.1.4.1 Non-CUG GSM PLMNs
If a GSM switching entity receives a CUG Interlock code in a call establishment message but does not support the CUG
service, it shall abort the call, reason for rejection: Incompatible Destination. However if an Interlock and Outgoing
Access indicator are received the call shall continue to be established as a normal call with no CUG information.
1.1.4.2 Interworking to Non-CUG networks
If a GSM switching entity is unable to interwork with a destination switching entity for a CUG call , it shall abort the
call, reason for rejection: Incompatible Destination. However if the call was a CUG call indicating outgoing access the
GSM switching entity shall attempt to establish the call as a normal call (no CUG information).
1.1.5 Supplementary service interactions
1.1.5.1 Interaction with Call Forwarding
The interaction between CUG and Call Forwarding services is specified in GSM 02.85. The interaction is applied after
the calling and called party CUG call has been successfully authorised, and Call Forwarding has been invoked. The
interaction is the same for all types of call forwarding.
In the case of Call Forward Unconditional and Call Forwarding on Mobile Subscriber Not Reachable (invoked at HLR),
the interaction is applied at the forwarding parties HLR.
In the case of CFB, CFNRy, CFNRc (invoked at the serving VLR) the interaction is applied at the forwarding parties
serving VLR.
Table 1.2 indicates the requirements on the forwarding node when CUG and call forwarding interact. In each case the
resultant information sent to the relevant MSC (either gateway or serving MSC) is given. This information should be
used by the MSC for the forwarding or rejection. Note that the CUG information for the forwarding part of the call may
be different from that initially used. The interlock code used for forwarding is always that of the calling party.
Table 1.2: CUG-Call Forwarding interaction
┌─────────┬─────────╥─────────────────────────────────────────┐
│     │     ║ Forwarding party subscription for BS  │
│Forwarded│     ╟──────────────────────────────┬──────────┤
│ Party │Interlock║    CUG subscriber     │     │
│  CUG  │ check ╟──────────────┬───────────────┤ Normal  │
│ Infor- │     ║  No OA   │   OA    │subscriber│
│ mation │     ╟───────┬──────┼───────┬───────┤     │
│     │     ║No OCB │ OCB │No OCB │ OCB │     │
╞═════════╪═════════╬═══════╪══════╪═══════╪═══════╪══════════╡
│Interlock│ Match ║ IC  │Reject│ IC  │Reject │   -  │
├─────────┼─────────╫───────┼──────┼───────┼───────┼──────────┤
│Interlock│ Match ║ IC  │Reject│ IC+OA │ Normal│Interlock │
│+Outgoing├─────────╫───────┴──────┼───────┴───────┤+ Outgoing│
│ Access │No Match ║  Reject  │ Interlock+OA │ Access │
├─────────┼─────────╫──────────────┼───────────────┼──────────┤
│ No CUG │  -  ║  Reject  │   Normal  │ Normal │
│ Info. │     ║       │   call   │  call  │
└─────────┴─────────╨──────────────┴───────────────┴──────────┘
NOTE: "-" = Not applicable.
Reason for rejection in all cases:
Called party supplementary service interaction violation.
1.1.5.2 Interaction with call waiting
There is no interaction with call waiting, however a
...