Content for TS 23.379 Word version: 19.4.0

1… 7… 10… 10.5… 10.6… 10.6.2.3… 10.6.2.4… 10.6.2.5… 10.6.2.6… 10.6.2.9… 10.6.3… 10.7… 10.7.3… 10.7.5… 10.7.6… 10.9… 10.9.1.3.3… 10.9.1.4… 10.9.2… 10.10… 10.12… 10.19… 10.19.3… 10.19.3.1.4… 10.19.3.2… 10.19.3.2.4… 10.19.3.2.6… A…

3.1 Definitions 3.2 Symbols 3.3 Abbreviations 5.1 Media routing requirements 5.2 Requirements for user identity management 5.3 MCPTT group affiliation and MCPTT group de-affiliation 5.4 MCPTT call requirements 5.5 GCS AS requirements for the MCPTT service 5.6 Group selection 5.7 Bearer management 5.8 MCPTT system interconnect requirements
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1 Scope p. 13

This document specifies the functional architecture, procedures and information flows needed to support the mission critical push to talk (MCPTT) service. The MCPTT service utilizes the common functional architecture to support MC services over LTE including the common services core defined in TS 23.280.Support for both MCPTT group calls and MCPTT private calls operating in on-network and off-network modes of operation is specified.

The corresponding service requirements are defined in TS 22.179 and TS 22.280.

The present document is applicable primarily to MCPTT voice service using E-UTRAN access based on the EPC architecture defined in TS 23.401. Certain application functions of the MCPTT service such as dispatch and administrative functions could also be supported via non-3GPP access networks but no additional functionality is specified to support non-3GPP access.

The MCPTT service requires preferential handling compared to normal telecommunication services e.g. in support of police or fire brigade including the handling of prioritised MCPTT calls for emergency and imminent threats.

The MCPTT service can be used for public safety applications and also for general commercial applications e.g. utility companies and railways.

In the present document, MCPTT calls between MCPTT users on different MCPTT systems are considered.

2 References p. 13

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]

TR 21.905: "Vocabulary for 3GPP Specifications".

[2]

TS 22.179: "Mission Critical Push to Talk (MCPTT)"; Stage 1.

[3]

TS 23.002: "Network Architecture".

[4]

TS 23.203: "Policy and charging control architecture".

[5]

TS 23.228: "IP Multimedia Subsystem (IMS); Stage 2".

[6]

TS 23.237: "IP Multimedia Subsystem (IMS) Service Continuity; Stage 2".

[7]

TS 23.303: "Proximity-based services (ProSe); Stage 2".

[8]

TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".

[9]

TS 23.468: "Group Communication System Enablers for LTE (GCSE_LTE); Stage 2".

[10]

TS 29.468: "Group Communication System Enablers for LTE (GCSE_LTE); MB2 Reference Point; Stage 3".

[11] Void

[12]

TS 36.331: "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification".

[13]

RFC 5245 (April 2010): "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols".

[14] Void

[15] Void

[16]

TS 23.280: "Common functional architecture to support mission critical services".

[17]

TS 22.280: "Mission Critical Common Requirements (MCCoRe); Stage 1".

[18]

TS 29.283: "Diameter data management applications".

[19]

TS 33.180: "Security of the mission critical service".

[20]

TS 23.283: "Mission Critical Communication Interworking with Land Mobile Radio Systems; Stage 2".

3 Definitions, symbols and abbreviations p. 14

3.1 Definitions p. 14

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

Automatic commencement mode:

A mode in which the initiation of the private call does not require any action on the part of the receiving MCPTT user.

First-to-answer call:

A call that is started when the first MCPTT user among multiple potential target recipients' answers. This call requires the answering MCPTT user to answer manually; automatic answer is not allowed

Group call:

A mechanism by which an MCPTT user can make a one-to-many MCPTT transmission to other users that are members of MCPTT group(s).

Group home MCPTT system:

The MCPTT system where the MCPTT group is defined.

Group host MCPTT server:

The MCPTT server within an MCPTT system that provides centralised support for MCPTT services of an MCPTT group defined in a group home MCPTT system.

Manual commencement mode:

A mode in which the initiation of the private call requires the receiving MCPTT user to perform some action to accept or reject the call setup.

MCPTT client:

An instance of an MC service client that provides the client application function for the MCPTT service.

MCPTT group:

An MC service group configured for MCPTT service.

MCPTT group affiliation:

An MC service group affiliation for MCPTT.

MCPTT group de-affiliation:

An MC service group de-affiliation for MCPTT.

MCPTT ID:

An instance of an MC service ID within the MCPTT service.

MCPTT server:

An instance of an MC service server that provides the server application function for the MCPTT service.

On-network MCPTT service:

The collection of functions and capabilities required to provide MCPTT via EPS bearers using E-UTRAN to provide the last hop radio bearers.

Preconfigured MCPTT group:

an MCPTT group used only for regrouping that has been configured in advance of a group or user regrouping operation to serve as the source of regroup group configuration.

Pre-selected MCPTT user profile:

An instance of the pre-selected MC service user profile for MCPTT.

UE-to-network relay MCPTT service:

The collection of functions and capabilities required to provide MCPTT via a ProSe UE-to-network relay using ProSe direct communication paths to provide the last hop radio bearer(s).

For the purposes of the present document, the following terms and definitions given in TS 22.179 apply:

Dispatcher

Floor control

Group-broadcast group

MCPTT administrator

MCPTT service

MCPTT system

MCPTT UE

MCPTT user

MCPTT User Profile

Mission Critical Organization

Mission Critical Push To Talk

Off-network MCPTT service

Partner MCPTT system

Primary MCPTT system

Private call

Multi-talker control

User-broadcast group

For the purposes of the present document, the following terms and definitions given in RFC 5245 apply:

Candidate

Candidate pair

For the purposes of the present document, the following terms and definitions given in TS 23.280 apply:

Ad hoc Group Communication

Active MC service user profile

Chat group

MC service client

MC service group

MC service group affiliation

MC service group de-affiliation

MC service ID

MC service server

Pre-arranged group

Pre-selected MC service user profile

For the purposes of the present document, the following terms and definitions given in TS 22.280 apply:

Functional alias

3.2 Symbols p. 15

For the purposes of the present document, the following symbols given in TS 22.179 apply:

N10

N11

3.3 Abbreviations p. 16

For the purposes of the present document, the abbreviations given in TR 21.905 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.

APN

Access Point Name

ARP

Allocation and Retention Priority

BM‑SC

Broadcast Multicast Service Centre

CHAP

Challenge-Handshake Authentication Protocol

CSCF

Call Server Control Function

Downlink

DPF

Direct Provisioning Function

E-UTRAN

Evolved Universal Terrestrial Radio Access Network

E2EE

End to End Encryption

ECGI

E-UTRAN Cell Global Identifier

EPC

Evolved Packet Core

EPS

Evolved Packet System

GBR

Guaranteed Bit Rate

GCS AS

Group Communication Service Application Server

GCSE_LTE

Group Communication Service Enabler over LTE

GRUU

Globally Routable User agent URI

HLR

Home Location Register

HSS

Home Subscriber Server

HTTP

Hyper Text Transfer Protocol

I-CSCF

Interrogating CSCF

ICE

Interactive Connectivity Establishment

IM CN

IP Multimedia Core Network

IMPI

IP Multimedia Private Identity

IMPU

IP Multimedia PUblic identity

IMS

IP Multimedia Subsystem

ITSI

Individual TETRA Subscriber Identity

LMR

Land Mobile Radio

MBMS

Multimedia Broadcast and Multicast Service

MBSFN

Multimedia Broadcast multicast service Single Frequency Network

Mission Critical

MC ID

Mission Critical user identity

MCPTT

Mission Critical Push To Talk

MCPTT AS

MCPTT Application Server

MCPTT group ID

MCPTT group identity

MCPTT ID

MCPTT user identity

NAT

Network Address Translation

PAP

Password Authentication Protocol

P-CSCF

Proxy CSCF

PCC

Policy and Charging Control

PCRF

Policy and Charging Rules Function

PLMN

Public Land Mobile Network

ProSe

Proximity-based Services

PSI

Public Service Identity

PTT

Push To Talk

QCI

QoS Class Identifier

QoS

Quality of Service

RAN

Radio Access Network

Radio Frequency

RSI

Radio Set Identity

S-CSCF

Serving CSCF

SAI

Service Area Identifier

SDF

Service Data Flow

SIP

Session Initiated Protocol

SSL

Secure Sockets Layer

TLS

Transport Layer Security

TMGI

Temporary Mobile Group Identity

Unacknowledged Mode

URI

Uniform Resource Identifier

USB

Universal Serial Bus

WLAN

Wireless Local Area Network

4 Introduction p. 17

The MCPTT service supports communication between several users (i.e. group call), where each user has the ability to gain access to the permission to talk in an arbitrated manner. The MCPTT service also supports private calls between two users.

The MCPTT architecture utilises the common functional architecture to support mission critical services over LTE defined in TS 23.280 and aspects of the IMS architecture defined in TS 23.228, the Proximity-based Services (ProSe) architecture defined in TS 23.303, the Group Communication System Enablers for LTE (GCSE_LTE) architecture defined in TS 23.468 and the PS-PS access transfer procedures defined in TS 23.237 to enable support of the MCPTT service.

The MCPTT UE primarily obtains access to the MCPTT service via E-UTRAN, using the EPS architecture defined in TS 23.401. Certain application functions of MCPTT service such as dispatch and administrative functions can be supported using either MCPTT UEs in E-UTRAN or using MCPTT UEs via non-3GPP access networks.

MCPTT UEs that use non-3GPP access can only support a subset of the functionality specified in this specification that is supported by the non-3GPP access network.

The MCPTT system provides the function to support interworking with LMR systems defined in TS 23.283.

5 Architectural requirements p. 17

5.1 Media routing requirements p. 17

The voice media flow for a private call shall be routed according to one of the following two options:

Option 1:
1. Through the primary MCPTT system if both users in the call belong to the same organisation; or
2. Through the primary MCPTT system of both users, if the users in the call do not belong to the same organisation.
Option 2: The voice media flow may be routed locally, under the control of the primary MCPTT system, through an entity allowing the duplication of the media flow to the primary MCPTT system of each user.

The voice media flow for a group call shall be routed to the group home MCPTT system.

The routing of media flow shall be end-to-end from transmitter to receiver(s), except for the MCPTT control function.

5.2 Requirements for user identity management p. 17

To allow for confidentiality of user identities in various cases of business relationship as defined in clause 6, the MCPTT application may provide public user identities to the MCPTT UE, to be used by MCPTT UE for MCPTT services.

5.3 MCPTT group affiliation and MCPTT group de-affiliation p. 18

MCPTT group affiliation shall be as specified in clause 5.2.5 of TS 23.280. In addition, the following requirements shall be fulfilled by the MCPTT service for MCPTT users affiliated to MCPTT groups:

MCPTT users receive notifications for MCPTT group call setup and invitations for their affiliated MCPTT group(s).
MCPTT users receive media and events from their affiliated MCPTT group(s).

5.4 MCPTT call requirements p. 18

5.4.1 General p. 18

The on-network MCPTT service shall support the use of pre-established sessions.

5.4.2 Group call requirements p. 18

The MCPTT service shall support the chat group (restricted) call model for MCPTT group call.

The MCPTT service shall support the pre-arranged group call model for MCPTT group call.

5.5 GCS AS requirements for the MCPTT service p. 18

The GCS AS architecture requirements for MC services are specified in TS 23.280.

5.6 Group selection p. 18

The following functionalities shall be supported by the MCPTT service.

The MCPTT user shall select an affiliated group to initiate a new group call or transmit media in an existing group call.
An authorized MCPTT user (e.g., dispatcher) may remotely force or request to change other on-network MCPTT users' selected MCPTT group to a particular affiliated group.

5.7 Bearer management p. 18

5.7.1 General p. 18

The MCPTT UE shall use the APNs as defined in subclause 5.2.7.0 of TS 23.280.

5.7.2 EPS bearer considerations p. 18

The EPS bearer considerations specified in subclause 5.2.7.2 of TS 23.280 shall apply.

5.7.2.1 Void

5.7.2.2 Void

5.7.3 EPS unicast bearer considerations for MCPTT p. 18

For an MCPTT call session request, resources shall be requested utilising interaction with dynamic PCC. The MCPTT system shall request resources over Rx to a PCRF. The dedicated bearer for voice shall utilise the QCI value of 65 (as specified in TS 23.203) and the bearer for MCPTT-4 reference point messaging shall utilise the QCI value of 65 or the QCI value of 69 (as specified in TS 23.203). The request of resources over Rx shall include an application identifier for MCPTT in order for the PCRF to evaluate the correct QCI.

The UE is required to support at minimum one UM bearer which is used for MCPTT voice (see Annex A in TS 36.331).

Depending on operator policy:

the MCPTT system may be able to request modification of the priority (ARP) of an existing bearer without the need to initiate a new dedicated GBR bearer; or
the EPS bearers for MCPTT call may enable pre-emption of lower priority EPS bearers if the maximum number of UM bearers has been reached in favour of MCPTT initiated EPS bearer, if the EPS bearer used for MCPTT call has higher priority level (ARP) than the UM bearer(s) used for other application(s) and if the bearers for non MCPTT application are pre-emptable. In this case, the EPS bearer for MCPTT call pre-empts one of the existing EPS bearers when the maximum number of bearers is established for other applications.

The EPS bearer for MCPTT emergency call shall have highest priority level among MCPTT call types. The EPS bearer for MCPTT imminent peril call shall have higher priority level than one for MCPTT call.

To ensure that the MCPTT service always has access to a dedicated bearer for MCPTT media, a pre-established session may be setup that includes a request for resources at the first MCPTT group affiliation.

This means that the PCC may multiplex MCPTT media streams from multiple concurrent MCPTT calls into one EPS bearer on one shared network priority regardless of MCPTT call priority.

5.7.4 MBMS bearer management p. 19

The MBMS bearer management for MC services is specified in subclause 5.2.7.1 of TS 23.280.

5.8 MCPTT system interconnect requirements p. 19

The architecture for interconnect between MCPTT systems is specified, allowing the affiliation of MCPTT users from an MCPTT system with MCPTT groups defined in another MCPTT system. When both MCPTT systems are served by different networks, interconnect of signalling and media is achieved using the interfaces defined for interconnect between PLMNs.

6 Involved business relationships p. 19

The description of the involved business relationships for the MCPTT service is contained in clause 6 of TS 23.280.