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Content for  TS 33.127  Word version:  19.4.0

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7.6 PTC service  7.6.1 General  7.6.2 Target identities  7.6.3 IRI events  7.6.4 Common IRI parameters  7.6.5 Specific IRI parameters  7.6.6 Common CC parameters  7.6.7 Specific CC parameters  7.6.8 Network topologies 
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7.6  PTC service  p. 113

7.6.1  General  p. 113

7.6.1.1  Background  p. 113

In clause 7.6 "PTC" will be used to reference events or services that occur in either of two different architectures unless specified otherwise, e.g., Mission Critical Push To Talk (MCPTT) or Push to talk over Cellular (PoC).
The following servers support PTC architecture:
The PTC server will be used to represent the MCPTT server or PoC server for group communication services.
If two or more different parties involved in a PTC communication are each a target of interception, each interception shall operate independently of the others and the results of each intercept shall be delivered to the respective LEMF in accordance with the applicable warrant.
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7.6.1.2  LI architecture for PTC  p. 113

Figure 7.6.1.2-1 provides a reference point representation of the LI architecture for PTC with PTC Server providing the IRI-POI and CC-POI functions. Any interactions needed between the IRI-POI and CC-POI (e.g. to use the same Correlation Identifier) is implementation specific.
Copy of original 3GPP image for 3GPP TS 33.127, Fig. 7.6.1.2-1: LI architecture for PTC
Figure 7.6.1.2-1: LI architecture for PTC
(⇒ copy of original 3GPP image)
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The PTC Server is an IMS-based application server and therefore all the SIP signalling messages and media pass to and from the target UE pass through the IMS domain.
The PTC Server shown in Figure 7.6.1.2-1 includes the functionalities of a Presence Server as well.
The IRI-POI present in the PTC Server detects the PTC related events, generates and delivers the related xIRI to the MDF2 over LI_X2. The MDF2 delivers the IRI messages to the LEMF over LI_HI2.
When interception of communication contents is required, the CC-POI present in the PTC Server generates the xCC from PTC media and delivers the xCC (that includes the correlation number and the target identity) to the MDF3. The MDF3 delivers the CC to the LEMF over LI_HI3.
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7.6.2  Target identities  p. 114

A provisioned target identity can be the following:
  • MCPTT ID.
  • Instance Identifier URN.
  • IMPU.
  • IMPI.
  • PTC Chat GroupID.
The interception performed on the above identities are mutually independent, even though, an xIRI may contain the information about the other identities when available.

7.6.3  IRI events  p. 115

The IRI-POI present in the PTC Server shall generate xIRI when it detects the following specific events or information:
  • PTC service registration.
  • PTC session initiation.
  • PTC session abandon.
  • PTC session start.
  • PTC session end.
  • PTC start of interception.
  • PTC pre-established Session.
  • PTC instant personal alert.
  • PTC party join.
  • PTC party drop.
  • PTC party hold.
  • PTC media modification.
  • PTC group advertisement.
  • PTC floor control.
  • PTC target presence.
  • PTC associate presence.
  • PTC list management.
  • PTC access policy.
The events above trigger the transmission of information from the IRI-POI to the MDF2.
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7.6.4  Common IRI parameters  p. 115

Each xIRI shall include at the minimum the following information:
  • Target identity.
  • Time stamp.
  • Correlation information.
  • PTC related information (e.g., PTC group ID, PTC party).
When location is available and authorized to be reported it shall be part of the xIRI as well. Details are provided in clause 7.5.2 of TS 33.128.
In case the CC-POI within the PTC server cannot deliver the unencrypted xCC, the xIRI shall also contain encryption parameters including any additional information required for decryption.
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7.6.5  Specific IRI parameters  p. 116

The parameters in each xIRI are defined in TS 33.128.

7.6.6  Common CC parameters  p. 116

In addition to the intercepted content of communications, the following information needs to be transferred from the CC-POI to the MDF3 in order to allow the MDF3 to perform its functionality:
  • Target identity.
  • Correlation information.
  • Time stamp.
  • Identity of source of media.

7.6.7  Specific CC parameters  p. 116

The parameters in xCC are defined in TS 33.128.

7.6.8  Network topologies  p. 116

The PTC server resides in the home network. The PTC Server shall provide IRI-POI and CC-POI functionality as illustrated in Figure 7.6.1.2-1. The concept of target non-local ID does not apply to PTC.

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