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To configure the emergency calls for the roaming users in the S8HR model, the home and visited network for the UE must be configured.

Configuring Home Network

Configuring SBC as P-CSCF

For detailed information, refer to Configuring SBC as P-CSCF.

Configuring HPLMN and VPLMN Profiles

Execute the following command to configure the HPLMN profile:

% set profiles services hplmnProfile IND_PLMN_PROF hplmnId 40471

Execute the following command to configure the VPLMN profile:

% set profiles services vplmnProfile US_PLMN_PROF vplmnId 310010 emergencyPrefix 911

Execute the following command to attach the hplmnProfile and vplmnProfile to the TG:

% set addressContext default zone defaultSigZone sipTrunkGroup TG1 services hplmnProfile IND_PLMN_PROF
% set addressContext default zone defaultSigZone sipTrunkGroup TG1 services vplmnProfile US_PLMN_PROF

Configuring the S8HR Support Flag

Execute the following command to support the emergency call in S8HR model:

% set addressContext default zone defaultSigZone sipTrunkGroup TG1 signaling s8hrSupport enabled

When S8HR processing flag is enabled, the SBC triggers PCRF based VPLMN ID retrieval procedures. The SBC subscribes for the PLMN changes at the time of registration of the UE and supports subscribing IP CAN, RAT and PLMN-ID types to the PCRF registrations.

  • If the S8HR flag is enabled and signalingPathflag is disabled, the P-CSCF subscribes only for the PLMN ID change notification.
  • If signalingPath flag is enabled along with S8HRflag, the P-CSCF subscribes for the PLMN-ID, RAT, and IP-CAN type in the same AAR.

The SBC indicates that the PLMN info is supported to the PCRF by setting the "PLMNInfo" (bit 19) of the "Feature-List" AVP in the Supported-Features-AVP in the AAR message. The SBC stores the VPLMN ID in the RCB when it receives the AAA or RAR with Specific-Action-AVP set to PLMN_CHANGE in case of PCRF based VPLMN ID information. The PLMN ID is fetched from the 3GPP-SGSN-MCC-MNC AVP. The SBC checks the MCC and MNC values received from the PCRF with the list of configured HPLMN and VPLMN values.

  • If the value matches with the HPLMN, the UE is a home, or RAVEL, or S8HR inbound user.   
  • If the value matches with the VPLMN, the UE is an S8HR outbound user.

Configuring PSX Query with Domain Name and PLMN ID

In case of Home/RAVEL/S8HR inbound roamers, the roaming status is decided by the PSX based on the domain name of the UE's home network. In case of S8HR outbound roamers, the SBC decides it and sends the query to the PSX with the PLMN information. The PSX matches the PLMN ID with the list of VPLMNs and sends emergency call treatment mechanism to the SBC.

Figure 1: PLMN Profile



NULL Encryption Support

When the flag Do not create security association is enabled in the PSX, the SBC does not create any security association and the SBC implements NULL encryption towards UE and use only RTP for media. Irrespective of the encryption preference configured and SRTP enabled on the SBC, the SBC must implement NULL encryption forS8HR outbound user and use only RTP for media.

Configuring Visited Network

Configuring SBC as P-CSCF

For detailed information, refer to Configuring SBC as P-CSCF.

Configuring GIBA Support for Inbound User

Execute the following command to configure GIBA support for inbound user:

% set addressContext default zone defaultSigZone sipTrunkGroup TG1 signaling gibaSupportForS8hrInboundUser enabled

Configuring Roaming Type in External PSX

To differentiate between RAVEL and S8HR inbound user, the option Roaming Type is added to the Carrier Domain.

Figure 2: Roaming Type


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