The Emergency APN (Em‑APN) is an APN used to derive a PDN GW selected for IMS Emergency call support. The
exact encoding of the Em‑APN is the responsibility of each PLMN operator as it is only valid within a given PLMN.
The ePDG Fully Qualified Domain Name (ePDG FQDN) contains an Operator Identifier that shall uniquely identify the
PLMN where the ePDG is located. The ePDG FQDN is composed of seven labels. The last three labels shall be
"pub.3gppnetwork.org". The third and fourth labels together shall uniquely identify the PLMN. The first two labels
shall be "epdg.epc". The result of the ePDG FQDN will be:
In the roaming case, the UE may utilise the services of the VPLMN. In this case, the ePDG FQDN Operator Identifier
shall be constructed as described above, but using the MNC and MCC of the VPLMN.
HNB Unique Identity uniquely identifies a Home NodeB or Home eNodeB.
The HNB unique identity shall be defined as either a 48‑bit or 64‑bit extended unique identifier (EUI‑48 or EUI‑64).
For use in HNB certificates, the HNB Unique Identity shall be transformed into a FQDN in the form:
<EUI48/64> is the first label which shall be the EUI‑48 or EUI‑64, represented as a string of 12 or 16 hexadecimal
digits including any leading zeros. <REALM> denotes the realm which may consist of 3 labels, e.g. hnb.femtocellvendor.com.