Section: 10.2.1.2 UE in RM-DEREGISTERED state requests a PDU Session for IMS Emergency services
Content: The UE shall first initiate a normal initial registration procedure to register with the 5G network. Upon successful normal registration, the UE initiates the UE requested PDU session establishment procedure to establish a PDU Session to receive emergency services as specified in TS 23.502[ Procedures for the 5G System (5GS) ]  [8]. At the time of registration, the security mode control procedure shall be applied to authenticate the UE and setup NAS and AS security. Thus, integrity protection (and optionally ciphering) shall be applied to the emergency bearers as for normal bearers. If authentication fails for any reason, it shall be treated the same way as any registration. Once the IMS Emergency Session is in progress with NAS and AS integrity protection (and optionally ciphering) applied, failure of integrity checking or ciphering (for both NAS and AS) is an unusual circumstance and shall be treated as in the case of a normal bearer.