10.6.4 Emergency alerts

23.2833GPPMission Critical Communication Interworking with Land Mobile Radio SystemsRelease 18TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

10.6.4.1 Emergency alert initiated by LMR user

In this procedure, an LMR user is initiating an emergency alert via the IWF. Figure 10.6.4.1-1 shows the procedure for an emergency alert initiated by a user in the LMR system. This subclause is based upon subclause for MCPTT emergency alerts in 3GPP TS 23.379 [7], subclause 10.6.2.6.3.1.

Pre-conditions:

1. The MC service group is previously defined on the group management server with MC service client 1 and MC service client 2 affiliated to that MC service group.

2. The IWF is connected to and is authorized to interwork with the MC system.

3. The MC service group information is available at the IWF, including information that the MC service group is an interworking group (defined in the LMR system or MC the system).

4. The mapping relationship of group and user identities between the MC system and the LMR system has been configured at the IWF.

5. The IWF may or may not have carried out an explicit affiliation procedure with the MC service group.

6. An emergency alert is requested on the LMR system.

NOTE 1: For all signalling messages passing through the IWF between the MC system and the LMR system, the IWF performs identity conversion and protocol translation.

Figure 10.6.4.1-1 MC service emergency alert initiated by LMR user

1. The LMR user initiates an emergency alert.

NOTE 2: How the IWF determines the emergency condition from the LMR system is out of scope of the present document.

2. The IWF sends an IWF emergency alert request to the designated MC service server. If the location of the LMR user is not available to the IWF, the IWF emergency alert request shall contain an indication that location is not available.

3. MC service server checks whether the MC service user ID that represents the LMR user is authorized for initiation of MC service emergency alerts for the indicated MC service group. The MC service server determines the affiliation status of the group members.

4. The MC service server sends an IWF emergency alert response to the IWF to confirm the IWF emergency alert request.

NOTE 3: Sending the IWF emergency alert request without making a request to also start an emergency call does not put the group into an ongoing emergency condition.

5. The MC service server sends an MC service emergency alert request towards the MC service clients of each of those affiliated MC service group members. The MC service emergency alert request message shall contain the following information: Location, MC service ID and MC service group ID (i.e., MC service user’s selected MC service group or dedicated MC service emergency group, as per MC service group configuration) and the MC service user’s mission critical organization name.

6. MC service users are notified of the MC service emergency.

7. The receiving MC service clients send an MC service emergency alert response to the MC service server to acknowledge the MC service emergency alert request.

8. If the group is an interworking group defined in the MC system, the MC service server implicitly affiliates the individual MC service ID of the LMR user to the emergency group if not already affiliated. If the IWF is configured to affiliate on behalf of all of its group members in a single affiliation step, the MC service server affiliates the IWF ID instead of an individual MC service ID.

NOTE 4: Step 8 can be performed any time after step 3 but at the latest immediately after step 7.

NOTE 5: MC service group calls made to this MC service group will be established as emergency calls if this MC service group has an ongoing emergency condition.

NOTE 6: Sending the emergency alert does not put the other UEs in the group into an emergency state.

10.6.4.2 Emergency alert initiated by MC service user

In this procedure, an MC service user is initiating an emergency alert that is delivered to the LMR system via the IWF. Figure 10.6.4.2-1 shows the procedure for an emergency alert initiated by a user in the MC system. This subclause is based upon subclause for MCPTT emergency alerts in 3GPP TS 23.379 [7], subclause 10.6.2.6.3.1.

Pre-conditions:

1. The MC service group is previously defined on the group management server with MC service client 1 and MC service client 2 affiliated to that MC service group.

2. The IWF is connected to and is authorized to interwork with the MC system.

3. The MC service group information is available at the IWF, including information that the MC service group is an interworking group (defined in the LMR system or the MC system).

4. The mapping relationship of group and user identities between the MC system and the LMR system has been configured at the IWF.

NOTE 1: For all signalling messages passing through the IWF between the MC system and the LMR system, the IWF performs identity conversion and protocol translation.

Figure 10.6.4.2-1 MC service emergency alert initiated by MC service user

1. The MC service user 1 initiates an emergency alert.

2. MC service client 1 sends an MC service emergency alert request to the MC service server.

3. The MC service server resolves the group ID, determines the affiliation status of the group members and checks whether the IWF should be informed. In this scenario, the group has affiliated members that are homed on the IWF, thus the IWF shall be involved. MC service server also checks whether the MC service user ID is authorized to initiate MC service emergency alerts for the indicated MC service group.

4. The MC service server sends an MC service emergency alert response to the MC service client 1 to confirm the MC service emergency alert request.

NOTE 2: Sending the emergency alert without making a request to also start an emergency call does not put the group into an ongoing emergency condition.

5. MC service server sends an IWF emergency alert request to the IWF. If the location of the MC service client 1 is not available, the IWF emergency alert request shall contain an indication that location is not available. If the IWF has affiliated to this group on behalf of the group’s LMR users, only one IWF emergency alert request is sent to the IWF. If the IWF has sent individual affiliations for each of its LMR users, the MC service server sends an IWF emergency alert request via the IWF to each affiliated LMR group member.

6. The IWF sends an IWF service emergency alert response to the MC service server to confirm the IWF emergency alert request(s).

7. The MC service server sends an MC service emergency alert request towards the MC service clients of each of those affiliated MC service group members. The MC service emergency alert request message shall contain the following information: Location, MC service ID and MC service group ID (i.e., MC service user’s selected MC service group or dedicated MC service emergency group, as per MC service group configuration) and the MC service user’s mission critical organization name.

8. MC service users are notified of the MC service emergency.

9. The receiving MC service clients send an MC service emergency alert response to the MC service server to acknowledge the MC service emergency alert.

10. The MC service server implicitly affiliates the MC service client 1 to the emergency group if it is not already affiliated.

NOTE 3: Step 10 can be performed any time after step 3. Steps 5 and 7 can be performed in which ever order.

NOTE 4: MC service group calls made to this MC service group will be established as emergency calls if the MC service group has an ongoing emergency condition.

NOTE 5: Sending an emergency alert does not put the other UEs in the group into an emergency state.