ETSI TS 142 056 V15.0.0 (2018-07)

Digital cellular telecommunications system (Phase 2+) (GSM); GSM Cordless Telephony System (CTS), Phase 1; Service description; Stage 1 (3GPP TS 42.056 version 15.0.0 Release 15)

RTS/TSGS-0142056vf00

General Information

• Status: Published
• Publication Date: 12-Jul-2018
• Technical Committee: 3GPP SA 1 - Services
• Current Stage: 12 - Completion
• Completion Date: 13-Jul-2018

Standards Content (Sample)

TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
GSM Cordless Telephony System (CTS), Phase 1;
Service description;
Stage 1
(3GPP TS 42.056 version 15.0.0 Release 15)

R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
3GPP TS 42.056 version 15.0.0 Release 15 1 ETSI TS 142 056 V15.0.0 (2018-07)

Reference
RTS/TSGS-0142056vf00
Keywords
GSM
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3GPP TS 42.056 version 15.0.0 Release 15 2 ETSI TS 142 056 V15.0.0 (2018-07)
Intellectual Property Rights
Essential patents
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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
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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.
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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
http://webapp.etsi.org/key/queryform.asp.
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
3GPP TS 42.056 version 15.0.0 Release 15 3 ETSI TS 142 056 V15.0.0 (2018-07)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 5
Introduction . 6
1 Scope . 7
2 References . 7
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 8
4 Description . 9
4.1 System overview . 9
4.2 Service aspects . 10
4.2.1 General . 10
4.2.2 User aspects . 10
4.2.3 Subscriptions. 11
4.2.3.1 CTS-roaming aspects . 11
4.2.3.2 Withdrawal of CTS subscription . 11
4.2.4 GSM coverage . 11
4.2.5 Mobility . 12
4.2.5.1 Mode selection between CTS and PLMN . 12
4.2.5.2 Attachment of the same CTS-MS with multiple CTS-FPs. 12
4.2.5.3 Attachment of multiple CTS-MSs with the same CTS-FP. 12
4.2.5.4 Attachment status of a CTS-MS . 13
4.2.6 CTS applications . 13
4.2.6.1 Tele-services . 13
4.2.6.2 Supplementary services . 13
4.2.6.3 Additional support for fixed network supplementary services . 13
4.2.6.4 Man Machine Interface (MMI) . 13
4.2.6.5 CTS internal calls . 14
4.2.6.6 CTS internal call transfer . 14
4.2.6.7 CTS internal call hold . 14
4.2.6.8 Mobile hunting . 14
4.2.6.9 SMS-MT . 14
4.2.6.10 SMS-MO . 14
4.2.6.11 Other services . 14
4.3 Radio interface and GSM co-existence aspects . 14
4.3.1 General principles . 14
4.3.2 Broadcast channel functionality . 15
4.4 Security requirements . 15
4.4.1 General . 15
4.4.2 Enrolment . 15
4.4.3 Attachment . 15
4.4.4 Protection of communications . 15
4.4.5 Security Parameter Storage Requirements . 15
4.4.6 De-activation. 16
5 Normal Procedures . 16
5.1 Enrolment of CTS-FP . 16
5.1.1 CTS operator procedure for enrolment of CTS-FP . 16
5.1.2 User procedure for enrolment of CTS-FP . 16
5.2 Enrolment of CTS-MSs . 17
5.3 De-enrolment of a CTS-MS . 17
5.4 Attachment of CTS-MS . 18
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5.5 Call procedures . 18
5.5.1 CTS-MS originated calls . 18
5.5.1.1 Number compatibility between GSM formats and fixed network formats . 18
5.5.2 CTS-MS terminated calls . 18
5.5.3 CTS internal calls (optional) . 19
5.5.4 CTS internal call transfer (optional) . 19
5.6 Maintenance . 19
6 CTS de-activation . 20
6.1 CTS-FP de-activation by the CTS operator . 20
6.2 CTS-FP de-activation by the user . 20
6.3 CTS-FP de-activation by self controlling features . 20
6.4 CTS-MS de-activation by the CTS operator . 20
7 Exceptional procedures . 20
8 Charging aspects . 20
9 Cross Phase Compatibility . 20
Annex A (informative): Later phases of CTS . 21
Annex B (informative): Change History . 22
History . 24

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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
3GPP TS 42.056 version 15.0.0 Release 15 6 ETSI TS 142 056 V15.0.0 (2018-07)
Introduction
Today, there exists a clear distinction between the public mobile telephone systems for wide area coverage on the one
hand, and private cordless telephone systems for local area coverage on the other hand. Recently, attempts have been
made to integrate the wide area cellular and the local area cordless function into one and the same Mobile Equipment
(ME). However, because of the incompatibility between the existing cellular and cordless standards, this results in ME
implementations with rather low cost-efficiency.
The intention of the GSM Cordless Telephony System (CTS) is therefore to provide cordless functionality to a standard
GSM Mobile Station (MS) with minimum impact on the MS. The impact would ideally be limited to an upgrade of the
ME and SIM software. This can only be accomplished if the radio interface of the cordless system is identical, or very
similar, to the standard GSM radio interface.
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1 Scope
The scope of the present document is to describe the Service aspects of a GSM Cordless Telephony System (CTS),
which provides the possibility for users of GSM terminals to have cordless access to a fixed network, such as
PSTN/ISDN or a radio network such as GSM.
Due to the time constraints to have a first specification ready for market needs, a phased approach is necessary. The first
phase aims primarily at an application supporting the speech teleservice (including DTMF support) in a residential
single cell environment. The focus is on the requirements necessary to elaborate the radio interface and the security
aspects for such an application.
To not prevent or impede the evolution of CTS to additional services and functions, later phases may have to be
considered when now defining the means to fulfil the above mentioned requirements for the first phase of CTS.
Therefore, additional support on the CTS radio interface for later phase services (e.g. SMS, subscriber authentication
and GSM supplementary services), is included already in CTS Phase 1, provided that such services are clearly defined.
Other expected services and functions in later phases are included in annex A.
The standardisation of the physical layers of the GSM-CTS fixed network interface is not in the scope of the present
document. However, consideration may need to be given to communication of application data between CTS and
PLMN via the fixed network.
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".
[2] 3GPP TS 22.101: "UMTS Service Principles".
[3] 3GPP TS 42.009: "Security aspects".
[4] 3GPP TS 22.081: "Line identification Supplementary Services - Stage 1".
[5] 3GPP TS 22.096: "Name identification Supplementary Services - Stage 1".
[6] 3GPP TS 23.040: "Short Message Service (SMS)".
[7] ETSI ETS 300 111 (1992): "Integrated Services Digital Network (ISDN); Telephony 3,1 kHz
teleservice, service description".
[8] ETSI ETS 300 109 (1992): "Integrated Services Digital Network (ISDN); Circuit-mode 64 kbit/s 8
kHz structured bearer service category usable for speech information transfer, service description".
[9] ETSI ETS 300 110 (1992): "Integrated Services Digital Network (ISDN); Circuit-mode 64 kbit/s 8
kHz structured bearer service category usable for 3,1 kHz audio information transfer, service
description".
[10] ETSI EN 301 144-1 (V1.1): "The Signalling application for the mobility management service on
the alpha interface; Part 1: Protocol specification".
[11] 3GPP TS 22.030: "Man Machine Interface (MMI) of the Mobile Station (MS)".
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3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
FP Enrolment: procedure where a CTS-FP is loaded with data necessary to obtain CTS operation. After this procedure
CTS operation may commence.
MS Enrolment: procedure where a CTS-MS is associated for the first time with a CTS-FP. After this procedure CTS-
MS has access to this CTS-FP.
Attachment: procedure where an MS attaches to a certain CTS-FP. When attached, it is possible to make and receive
calls via the CTS-FP. The CTS-MS must have been initialised correctly to the CTS-FP before attachment can take part.
Generic Frequency List (GFL): Generic Frequency List (GFL) contains all absolute radio frequency channel numbers
(ARFCN), as defined in GSM 05.05, on which the CTS-FP is allowed to operate. The CTS-FP will never use
frequencies which are not listed in the GFL.
CTS Mobile Station: GSM MS with CTS capability.
CTS Fixed Part: CTS-FP is a device which offers a personnal cordless coverage and acts as a link between the CTS-
MS and the fixed network or the GSM network.
GSM Operator: GSM operator is the operator who provides GSM cellular service to the MS.
CTS licence exempt frequencies: frequency band that may be allocated by national regulator to CTS usage outside of
a GSM licence allocated to a GSM operator.
CTS operator: CTS operator is the operator who provides the GFL to the CTS-FP. The CTS operator may be the same
than the GSM operator.
FP-SIM: FP-SIM is the SIM card inserted in the CTS-FP, which materialised the CTS subscription. The FP- SIM
belongs to the CTS operator.
CTS subscription: when a GSM licensed band is used, the right to use a CTS operator's frequency spectrum for
communication between a CTS-FP and CTS-MS(s).
CTS-FP owner: person who has the CTS-FP control and may authorise MS Enrolment.
CTS user: person who has a CTS-MS which is allowed to do CTS operations.
CTS-MS local number: number in the range of 0-99 optionally assigned to the CTS-MS at enrolment. This number is
used for CTS internal calls.
CTS-Roaming: right for an additional CTS-MS to be enrolled to a CTS-FP which is initialised to an operator other
than the HPLMN operator of the additional CTS-MS.
3.2 Abbreviations
In addition to those below, abbreviations used in the present document are listed in GSM 01.04.
CTS Cordless Telephony System
CTS-FP Cordless Telephony System - Fixed Part
CTS-MS Cordless Telephony System - Mobile Station
FP – SIM Fixed Part – Subscriber Identity Module
GFL Generic Frequency List
IFPEI International Fixed Part Equipment Identity
ISDN Integrated Services Digital Network
MS Mobile Station
PSTN Public Switched Telephone Network
SMS - MO Short Message Service - Mobile Originated
SMS - MT Short Message Service - Mobile Terminated
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4 Description
4.1 System overview
The GSM Cordless Telephone System (GSM-CTS) described in the present document is a radio communications
system based on a GSM-compatible cellular interface between a private radio base station called CTS Fixed Part (CTS-
FP) and a CTS mobile station (CTS-MS). The CTS-FP is connected either via a wireline to the PSTN/ISDN network or
via a radio connection to a GSM network.
When connected to the fixed network, the CTS-FP will be compliant with the existing fixed network standards
(e.g. support the telephony 3,1 kHz teleservice (see [7]), the speech bearer service (see [8]) and the 3,1 kHz audio bearer
service (see [9] in case of an ISDN CTS-FP and the relevant national standards in case of PSTN CTS-FP). There is no
direct radio communication between different CTS-FPs. However, this does not preclude indirect communication,
e.g. via the fixed network or via the MS.
When connected to a GSM network, the CTS-FP is compliant with the existing ETSI standards applicable to a GSM
mobile. From the GSM network point of view, the CTS-FP is seen as a standard GSM mobile including a standard
GSM SIM card. (i.e. the CTS-FP may include 2 SIM cards: one for the GSM subscription and one for the CTS
subscription).
An illustration of the CTS concept is shown in figure 1. Due to the low transmit power of the CTS-FP, the coverage
area is restricted and limited. When the CTS-MS comes in range of the CTS-FP, it may attach to the CTS. When
connected to the fixed network, from then on, the user can make and accept calls directly via the PSTN without the
intervention of the public cellular network. When attached, the MS checks whether it is still in range of the CTS and
whether it is paged. As an option, the MS may simultaneously work in both the cellular and the cordless mode, in a so
called parallel mode, i.e. be attached both in the GSM PLMN and the CTS. When the MS comes out of range of the
CTS it may switch to the GSM mode. This switch shall be indicated to the user. When the CTS-MS is in either CTS
mode or GSM mode and is searching for a potential channel to attach with in the other mode, it shall be able to respond
to paging messages from the mode in which it is currently attached.
The radio interface between the CTS-FP and the CTS-MS is a modified GSM interface. The carrier frequencies used are
the same as assigned for cellular service. These carrier frequencies can be part of a licence exempt band or a licensed
band.
When CTS-FP operates in a licenced band:
- these frequencies can be reserved by the operator for GSM-CTS usage, or can be shared with the cellular system.
In every case, however, the GSM operator controls, on an area and time basis, on which frequencies the CTS is
allowed to operate. In case of co-existence in the same operating area, a procedure shall be deployed to minimise
interference between GSM PLMN and CTS users.
NOTE: The frequencies used for CTS could be in any frequency band defined for GSM, i.e. GSM900, DCS1800
or PCS1900. This applies both to the CTS-FP and the CTS-MS.
The quality of service (e.g. service accessibility, call set-up time, bit rate for data services) of the 'GSM only'
subscribers shall remain unaffected by the introduction of CTS. Means to guarantee that the quality of service of GSM
subscribers does not degrade due to CTS introduction have to be defined.
Since the MS uses the same frequency spectrum both for the cellular mode and the cordless mode, the ME hardware can
be reused. The intention is that hardware modifications in the radio transceiver of a standard GSM ME should not be
necessary. It is also a requirement that the introduction of CTS shall not destabilise any existing GSM mobile
equipment or degrade the mobile equipment's dedicated (e.g. in call) or idle mode performance.
When a licensed band is used:
- the CTS operator can administer all CTS-FPs and the corresponding CTS. When the CTS is initialised, the
required operation parameters are downloaded into the CTS. This can either be done via the fixed network or via
the GSM radio interface.
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GSM PLMN
GSM CTS
GSM BTS
CTS Fixed
Part
Figure 1: Concept for the GSM CTS functionality when connected to the PSTN
4.2 Service aspects
4.2.1 General
In the first phase of CTS an application for residential environment serving one cell is intended. The services and
features to be supported relate to this assumption.
4.2.2 User aspects
The user of the CTS shall be required to perform a simple installation process in order to initialise the CTS operation.
This process shall include:
• connection of the CTS-FP to the power supply and to either the fixed network or the GSM network interface;
• enrolment of the CTS-FP (CTS-FP enrolment).
As the CTS-FP shall not be GSM operator specific, it has to be enrolled with operation specific data, e.g. a list of
allowed frequencies (Generic Frequency List GFL);
• enrolment of one or several CTS-MSs with the CTS-FP (CTS-MS enrolment).
Once initialised, CTS operation shall not require any specific action of the user to maintain the operation as long as the
CTS-FP is not de-activated (see clause 6).
To have service granted by the CTS-FP, a CTS-MS shall attach at the CTS-FP. In order to attach, a CTS-MS has to be
enrolled with the CTS-FP, the user has to bring the CTS-MS in range of the CTS-FP and the appropriate operation
mode has to be selected (see subclause 4.2.5.1).
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4.2.3 Subscriptions
The CTS-FP owner shall have a valid CTS subscription from a CTS operator. This subscription is materialised by an
FP-SIM. It gives the right to the CTS-FP owner to initialise the CTS-FP and enroll CTS-MSs under conditions defined
by the CTS operator. In exchange of a subscription to a CTS operator, the CTS-FP owner will receive a CTS-GFL in
the CTS-FP.
The user of the GSM CTS service shall have a subscription with a GSM operator, which allows CTS service. This CTS
authorisation may be given to all the CTS-MSs of a PLMN or may be linked to a specific service subscription given by
the GSM operator. By default the CTS-MS are not allowed to do CTS operations. The use of a GSM subscription for
'CTS only' service is not precluded. Corresponding information may be stored in the SIM.
In order to be able to use the CTS service on the fixed network, a subscription to the fixed network is also required.
When connected to the GSM network, the fixed network subscription is replaced by a GSM subscription and the CTS-
FP shall include a GSM SIM card corresponding to this GSM subscription.
The fixed network, GSM and CTS subscriptions may be independent of each other. However at CTS-FP enrolment
(see subclause 5.1) the CTS-FP may obtain operation data specific to the CTS operator, the user of the CTS service has
subscribed to, thus the CTS-FP operation may be tied to a specific GSM operator.
The CTS-FP is normally not subscribed to, it is the users' property. After the CTS service subscription to one operator is
cancelled, it shall be possible to use the same CTS-FP for a CTS service subscription to another operator.
4.2.3.1 CTS-roaming aspects
A CTS-FP owner may only have one CTS subscription to a single CTS operator. This operator defines which CTS-MSs
are allowed to enroll onto a particular CTS-FP. Several control levels are offered by the CTS:
- uncontrolled roaming: all CTS-MS from any GSM operator are allowed to enrol on the CTS-FP without CTS-
operator control;
- no roaming: the CTS-operator and the GSM operator are the same and only the CTS-MSs from the CTS
operator are allowed to attach on the CTS-FP;
- control roaming: on a case by case basis, the CTS-operator controls CTS-MS enrolment using CTS-MS IMSI.
In any cases, the CTS-FP owner authorisation is mandatory for CTS-MS enrolment.
NOTE: CTS-roaming has no impact on CTS-FP operational mode defined by the CTS-operator (e.g. frequency
management).
4.2.3.2 Withdrawal of CTS subscription
When used within a licensed band:
- if the CTS subscription is withdrawn, the user looses the right to use a CTS- operator's frequency spectrum for
CTS usage and CTS operation shall stop.
As the CTS service is not obtained directly from the GSM network like other GSM services (e.g. SMS), means of
subscription control have to be defined.
4.2.4 GSM coverage
The concept should allow CTS operation during all GSM coverage scenarios, e.g. the following:
• area with no GSM coverage;
• area with GSM coverage of the HPLMN operator;
• area with no HPLMN coverage, but coverage of other PLMN operator(s).
Depending on the enrolment concept being used (see subclause 5.1), a limitation may be that the MS need to be in
HPLMN (or at least PLMN) coverage once, before the CTS-FP can be correctly initialised (if the GSM radio interface
is used for enrolment data download).
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In the case of a CTS-FP connected to a PLMN, a GSM coverage is necessary for CTS operations.
4.2.5 Mobility
4.2.5.1 Mode selection between CTS and PLMN
The CTS-MS may operate in one of six different operation modes. It is not required that the CTS-MS support all the
modes. It shall be possible for the user to select between the supported modes at any time, except during an active call.
a) Manual mode: GSM only, i.e. the normal GSM operation.
b) Manual mode: CTS only, i.e. calls can only be originated or received via the CTS-FP. The MS is not attached to
the GSM PLMN.
c) Automatic mode with CTS preferred: The MS attaches to CTS, when in range, and then automatically tries to
attach with GSM PLMN, when out of CTS range. An MS attached with a GSM PLMN and coming in range of
the CTS shall not attach to CTS if a connection in the GSM PLMN is active. In that case the MS shall wait until
the connection is finished.
d) Automatic mode with GSM preferred: the MS attaches to GSM PLMN, when in range, and then automatically
tries to attach with CTS, when out of GSM PLMN range. A MS attached with CTS and coming in range of a
GSM PLMN shall not attach to the GSM PLMN, if a connection in the CTS is active. In that case the MS shall
wait until the connection is finished.
e) Parallel mode - single active mode: the MS tries to attach with both GSM PLMN and CTS. If a CTS-MS is
attached to both CTS-FP and GSM, it shall offer double service in idle mode (i.e. full service on both systems in
idle mode), and at least single service in active mode (i.e. when involved in an active call on one system, no
service is required on the other system). Techniques shall avoid excessive signalling load on the GSM PLMN.
f) Parallel mode - double active mode: the MS tries to attach with both GSM PLMN and CTS. If a CTS-MS is
attached to both CTS-FP and GSM, it shall offer full service on both types of networks, e.g. the CTS-MS shall
be able to successfully handle all applicable terminating calls that are addressed to its MSISDN and to the CTS-
FP number.
When switched on, the CTS-MS enters the last selected operation mode.
NOTE: The user may, optionally, define a default mode setting, in which case the default mode is always entered
when the CTS-MS is switched on.
The selected mode and the current coverage (CTS and/or GSM) shall be indicated to the user.
The user of the CTS-MS might have subscribed to the CTS service only. Access of the CTS-MS to the GSM network
may however be required in order to establish a signalling link, e.g. to exchange operation control data.
4.2.5.2 Attachment of the same CTS-MS with multiple CTS-FPs
A CTS-MS shall be able to attach to all CTS-FPs it is initialised with however it may only be attached with only one
CTS-FP at a time.
A list of all CTS-FPs, the CTS-MS is enrolled to, shall be stored in the CTS-MS, preferably on the MS-SIM. This list
shall for each CTS-FP/CTS-MS pair contain all data which defines their association.
This list may also define the preference of attachment in the case that the CTS-MS is in range of several CTS-FPs when
entering the CTS mode of operation. The user may be able to change the preference order of CTS-FPs in the list.
A manual attachment mode may be implemented which enables the user to scan for CTS-FPs the CTS-MS is enrolled to
in order to select a specific CTS-FP, of those in range, for attachment.
4.2.5.3 Attachment of multiple CTS-MSs with the same CTS-FP
Enrolment and parallel attachment of multiple MS on a single CTS-FP shall be possible. The CTS-FP control however
what MSs are allowed to be enrolled and attached.
A minimum number of 8 CTS-MSs shall be possible to attach with the same CTS-FP.
ETSI
3GPP TS 42.056 version 15.0.0 Release 15 13 ETSI TS 142 056 V15.0.0 (2018-07)
4.2.5.4 Attachment status of a CTS-MS
A mechanism to provide information about the attachment status of a CTS-MS shall be supported by the CTS-FP. This
mechanism can be used for network information or routing purposes. This mechanism shall provide a notification in the
following situations:
a) when attaching with the CTS;
b) when de-attaching with the CTS.
This mechanism shall be transparent to the user.
In addition, when the mobile is leaving the GSM network for CTS attachment (i.e. not in the parallel mode), it shall
behave towards the GSM network as if it was being switched off.
4.2.6 CTS applications
4.2.6.1 Tele-services
The first phase of CTS shall support the speech teleservice on the CTS radio interface.
Emergency calls shall be supported for attached MSs only. The call origination of an emergency call shall be according
to the selected mode. The quality of the speech teleservice shall be at least equal to existing GSM speech qualities. The
existing GSM phase 2 requirements on voice codecs according to ref. [xx] shall be applicable to CTS.
If the user attempts to set up calls other than speech or emergency calls, this request shall be sent to the CTS-FP. The
CTS-FP may issue a rejection cause.
4.2.6.2 Supplementary services
Supplementary services invoked from the CTS-MS are directed towards the CTS-FP or the GSM network, depending
on the current mode and coverage. In parallel mode it should be possible for the user to choose the preferential network
and regardless of the preferential origination, to select on a per transaction basis the used network.
As an option (both in the CTS-MS and CTS-FP) the user with CTS should be capable of supporting all the standardized
supplementary services that are provided in the GSM. From the point of view of the CTS-MS and the radio interface,
the operation of the services shall be the same in GSM and in cordless mode. The CTS radio interface protocol shall
therefore support the GSM supplementary services and correspond to the GSM radio interface with respect to the
supplementary services. Additional optional procedures may be provided in the CTS-FP, i.e. an interworking function
between the CTS radio interface protocol and the fixed network access protocol for the support of supplementary
services. Services not supported in the CTS-FP shall be rejected in the same way as in the GSM.
The CTS-MS shall indicate to the user if the CTS-FP cannot be used to handle the requested service, e.g. due to that the
line is busy or the CTS-FP do not support the above-mentioned interworking.
4.2.6.3 Additional support for fixed network supplementary services
In order to enable support of supplementary services in the fixed network, DTMF handling on the CTS Radio Interface,
during CTS calls, shall be handled in the same way as in GSM. The CTS-FP shall generate the corresponding tones and
messages for the fixed network.
Since some fixed networks make use of hook-flash signalling, it shall be possible for the user to send a hook-flash
request to the CTS-FP, which shall then perform the hook-flash signalling on the line interface.
4.2.6.4 Man Machine Interface (MMI)
If the CTS mode is selected as the preferential mode for mobile originated activities (see subclauses 4.2.6.2 and 5.5.1
for supplementary service operations and call set-up, respectively), the handset should not change its behaviour
regarding input MMI string. Normal rules according to GSM 02.30 should be used by the MS and the CTS-FP, which
would then perform the proper interworking towards the fixed network or the GSM network on which the CTS-FP is
connected.
ETSI
3GPP TS 42.056 version 15.0.0 Release 15 14 ETSI TS 142 056 V15.0.0 (2018-07)
4.2.6.5 CTS internal calls
In the case when more than one CTS-MS are attached to a CTS-FP, internal calls (without billing) between the MSs at
this CTS-FP should be possible, as an option (both in the CTS-MS and CTS-FP).
4.2.6.6 CTS internal call transfer
As an option (both in the CTS-MS and CTS-FP) the user should be able to internally transfer an external network call
from one CTS-MS to another if both CTS-MSs are attached to the same CTS-FP.
4.2.6.7 CTS internal call hold
As an option (both in the CTS-MS and CTS-FP) the user should be able to put a external network call on internal hold,
i.e. to release the call on the CTS Radio Interface but keep it active on the external network interface. If this option is
supported, it shall also be possible to retrieve the call.
4.2.6.8 Mobile hunting
As an option, it should be possible to trigger a general procedure which makes all the attached MSs ring on a special
way and therefore allows the user to locate them. The procedure should be triggered by the CTS-FP or CTS-MS.
4.2.6.9 SMS-MT
As an option the user should be able to have a Mobile Terminated Short Message presented, provided this message is
made available to the CTS-FP. The support of SMS-MT on the CTS radio interface is mandatory for the CTS-MS.
4.2.6.10 SMS-MO
As an option the user should be able to generate a Mobile Originated Short Message and send it towards the CTS-FP.
The CTS-FP may issue a rejection cause, if the feature is not supported.
4.2.6.11 Other services
Other services are not required for the first phase.
4.3 Radio interface and GSM co-existence aspects
4.3.1 General principles
It should be possible to use the GSM-Cordless Telephony System (CTS) on the same carrier frequencies as assigned for
the cellular service. These carrier frequencies can be part of a licence exempt band or a licensed band. In the second
case these frequencies can be reserved for GSM-CTS usage, or can be shared with the cellular system. In any case a set
of frequencies (Generic Frequency List) needs to be defined by a CTS operator or a regulator to enable CTS operations.
The CTS licence exempt mode is only applicable in countries where the national regulator allocates a suitable band.
A mechanism shall be employed to insure that the CTS-FP will only operate in Licence exempt mode in an area or
country where it is authorized to do so.
When used within a licensed band:
- it is necessary for the CTS operator to have complete control, on an area and time basis, over the frequencies the
CTS can use. These frequencies shall be part of the frequency set under its responsibility.
Interference to the cellular system or other CTS systems shall be minimised.
The requirements in respect to the receiver and transmitter characteristics of the CTS FP shall allow communication
with a GSM MS.
The CTS-FP shall also have a self-controlling feature to minimise interference in the case where no attached MS is in
range of the CTS-FP.
In the case of the CTS-Fixed Part connected to PLMN, means should be implemented in the CTS-FP in order
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