Emergency Session Creation in LTE Call Flow

Step | Description |
---|---|
1 |
When an emergency service is required and an emergency PDU session is not already established, the UE initiates the UE-requested PDU session establishment procedure with a request type indicating, "Emergency Request" in LTE. |
2 |
The MME selects an APN or DNN for the emergency PDN creation, and sends a ‘Create Session Request’ to the P-GW via the S-GW. |
3 |
The DNN profile lookup at P-GW is based on the subscriber policy or DNN policy. These policies are associated in the SMF profile. The subscriber policy has higher precedence over DNN policy when both the configurations are present. |
4 |
The DNN policy can have the DNN profile configuration for each of the UE-requested APN or DNN received in the “Create Session Request” from the MME or S-GW. |
5 |
When a new configuration ‘authorization local’ under the selected DNN profile is present:
|
6 |
When the ‘Secondary Authentication Radius’ under the selected DNN profile is not present, the PGW-C rejects the RADIUS-based secondary authentication. |
7 |
When ‘failure handling’ for charging interaction is set as ‘action continue’:
|
8 |
During handover from 4G to 5G using N26, if the emergency PDN gets handed over, the SMF checks the DNN profile and if ‘authentication local’ is present, it skips the UDM interactions for registration and deregistration. |