Operation method due to slice deregistration inactivity timer expiry

A user equipment (UE) comprising:

• a transceiver;
• and
• a processor configured to control the transceiver thereby performing operations including:
• transmitting information indicating a support of a network slice replacement during a registration procedure;
• receiving a registration accept message including a slice usage policy;
• storing the slice usage policy with a configured network slice selection assistance information (NSSAI) for a serving public land mobile network (PLMN),
• wherein the slice usage policy is kept stored for as long as a configured NSSAI remains stored for the PLMN, and
• wherein when the configured NSSAI is updated, the UE receives a new slice usage policy;
• starting a slice deregistration inactivity timer;
• locally removing a Single Network Slice Selection Assistance Information (S-NSSAI) from an Allowed NSSAI if the slice deregistration inactivity timer expires;
• and
• de-mapping a replaced S-NSSAI and an alternative S-NSSAI in an access type when the replaced S-NSSAI or the alternative S-NSSAI is removed from the allowed NSSAI due to the slice deregistration inactivity timer expiry over a corresponding access type,
• wherein during a handover procedure, if the S-NSSAI has to be replaced with the alternative S-NSSAI, the handover procedure including any protocol data unit (PDU) session associated with the S-NSSAI to be replaced continues unaffected by the network slice replacement,
• wherein the network slice replacement is used to temporarily replace the S-NSSAI with the alternative S-NSSAI when the S-NSSAI becomes unavailable or congested,
• wherein during the handover procedure, any network slice replacement for the S-NSSAI does not take place,
• wherein for the replaced S-NSSAI or the Alternative S-NSSAI, a network slice admission control (NSAC) for maximum number of PDU sessions is configured,
• wherein the replaced S-NSSAI is subject to area restrictions,
• wherein the slice deregistration inactivity timer is started if the Network Slice is added to the Allowed NSSAI and there are no PDU Sessions associated with the Network Slice over a corresponding access type,
• wherein when the S-NSSAI is replaced by the alternative S-NSSAI, the UE associates both of the replaced S-NSSAI and the Alternative S-NSSAI with a PDU session, and
• wherein an association to the PDU session based on a UE route selection policy (URSP) and establishment of the PDU session is based on the replaced S-NSSAI, but not based on alternative S-NSSAI.

A semiconductor chipset equipped into a user equipment (UE), comprising:

• at least one processor;
• and
• at least one memory capable of storing instructions and being connected electrically to the at least one processor operably,
• wherein operations, performed when the instructions are executed by the at least one processor, include:
• transmitting information indicating a support of a network slice replacement during a registration procedure;
• receiving a registration accept message including a slice usage policy;
• storing the slice usage policy with a configured network slice selection assistance information (NSSAI) for a serving public land mobile network (PLMN),
• wherein the slice usage policy is kept stored for as long as a configured NSSAI remains stored for the PLMN, and
• wherein when the configured NSSAI is updated, the UE receives a new slice usage policy;
• starting a slice deregistration inactivity timer;
• locally removing a Single Network Slice Selection Assistance Information (S-NSSAI) from an Allowed NSSAI if the slice deregistration inactivity timer expires;
• and
• de-mapping a replaced S-NSSAI and an alternative S-NSSAI in an access type when the replaced S-NSSAI or the alternative S-NSSAI is removed from the allowed NSSAI due to the slice deregistration inactivity timer expiry over a corresponding access type,
• wherein during a handover procedure, if the S-NSSAI has to be replaced with the alternative S-NSSAI, the handover procedure including any protocol data unit (PDU) session associated with the S-NSSAI to be replaced continues unaffected by the network slice replacement,
• wherein the network slice replacement is used to temporarily replace the S-NSSAI with the alternative S-NSSAI when the S-NSSAI becomes unavailable or congested,
• wherein during the handover procedure, any network slice replacement for the S-NSSAI does not take place,
• wherein for the replaced S-NSSAI or the Alternative S-NSSAI, a network slice admission control (NSAC) for maximum number of PDU sessions is configured,
• wherein the replaced S-NSSAI is subject to area restrictions, and
• wherein the slice deregistration inactivity timer is started if the Network Slice is added to the Allowed NSSAI and there are no PDU Sessions associated with the Network Slice over a corresponding access type,
• wherein when the S-NSSAI is replaced by the alternative S-NSSAI, the UE associates both of the replaced S-NSSAI and the Alternative S-NSSAI with a PDU session, and
• wherein an association to the PDU session based on a UE route selection policy (URSP) and establishment of the PDU session is based on the replaced S-NSSAI, but not based on alternative S-NSSAI.