IMS Emergency Call in LTE Network

                                   

    LTE : IMS Emergency Call in LTE Network

 

Emergency service is provided to the Lte enabled UE in the following situations:

1. User calls an emergency number.
2. UE is in the state where network is not available to serve the UE.
3. User can make IMS emergency call even if does not have a SIM card.
4. UE is in limited service state i.e limited service state where UE is not allowed to call or roam.

-         To make an IMS Emergency call, UE sends Attach type as Emergency attach and request type as Emergency in Attach Request.

-         MME(Lte Network) should be configured with the Emergency support enabled otherwise MME rejects the emergency call.

-         Following are the various configurations in MME according to which MME proceeds the Emergency call.

 

Emergency Type      

             · IMSI Authentication mandatory: Emergency call is successful only when

               IMSI comes in Attach Request and Authentication from HSS

               should be successfully done for this IMSI.

             · IMSI Mandatory Authentication optional: Emergency call is successful

                only when IMSI comes in Attach Request and Authentication from HSS

                needs not to be successfully done.In case authentication fails, network keeps
                tracking of that IMSI's that are unauthenticated.

             · IMSI Optional IMEI mandatory: In this case UE is identified in the network

               by its IMEI only.UE may or may not send IMSI in Attach Request. If UE sends IMSI
               it is not neccassary be authenticated. 

             · Emergency not supported.

Emergency APN

         That is needed to identify the PGW for emergency call.

Emergency QoS

               That is required by the MME only when the UE authentication is optional.

               Otherwise HSS sends it in Subscription Data.

 

 

For Emergency call secrets Click on  Emergency_Secrets