IMPROVEMENT FOR 5G NAS SECURITY CONTEXT HANDLING WHEN UE SUPPORTS BOTH 3GPP AND NON-3GPP ACCESSES

A method of handling of 5G NAS security context for UEs supporting multiple registrations to different PLMNs over both 3GPP and non-3GPP access types is proposed. The UE should handle the NAS security contexts of the same PLMN similarly, and should handle the NAS security contexts of different PLMNs for different access types independently. If the UE registers to a PLMN over 3GPP or non-3GPP then the security contexts of the PLMN for both 3GPP and non-3GPP are set invalid. If the UE has been registered in a PLMN over 3GPP or non-3GPP and has stored security context for the PLMN and is now deregistered from the PLMN over 3GPP or non-3GPP, the security context of the PLMN becomes valid for both access types.