User device method and user device

Abstract

To provide a method executed by Access and Mobility Management Function (AMF) for handling network slice-specific authentication and authorization procedures.SOLUTION: In one embodiment, a network shall restart a generic UE Configuration Update procedure when encountering radio link failure before completion of the ongoing generic UE configuration update procedure. In another embodiment, the network sends a CONFIGURATION UPDATE COMMAND message containing the Allowed NSSAI when the N1 NAS signaling connection is established after the radio link failure.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates generally to wireless communications, and more particularly, in embodiments, to handling slice authentication and authorization procedures. [Background technology]

[0002] The serving PLMN performs Network Slice-Specific Authentication and Authorization (hereinafter referred to as "NSSAA") for the S-NSSAI of the target HPLMN based on the subscription information, for example, if the REGISTRATION REQUEST message contains a Requested NSSAA including an S-NSSAI that is subject to NSSAA during the registration procedure. The UE indicates whether it supports the NSSAA functionality in the UE 5GMM Core Network Capability in the REGISTRATION REQUEST message. If the UE does not support the NSSAA functionality and the UE requests any of these S-NSSAIs that are subject to NSSAA, the AMF shall not trigger an NSSAA procedure for the UE, and the S-NSSAI of the requested S-NSSAI that is subject to the NSSAA procedure shall be rejected by the PLMN. To perform NSSAA for an S-NSSAI, the AMF invokes an EAP-based NSSAA procedure for the S-NSSAI. When an NSSAA procedure is initiated and ongoing for an S-NSSAI, the AMF stores the NSSAA status of the S-NSSAI as pending, and once the NSSAA procedure is completed, the S-NSSAI becomes either an Allowed NSSAI or a Rejected S-NSSAI, depending on the outcome of the NSSAA procedure. The NSSAA status of each S-NSSAI, if present, is stored and forwarded when the AMF changes. An example of the process involved in the NSSAA procedure is shown in Figure 1. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications". V16.0.0 (2019-06) [Non-patent document 2] 3GPP TS 23.501: "System architecture for the 5G System (5GS)". V16.5.1 (2020-08) [Non-patent document 3] 3GPP TS 23.502: "Procedures for the 5G System (5GS)". V16.5.1 (2020-08) [Non-patent document 4] 3GPP TS 24.501: "Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3". V16.5.1 (2020-07) Summary of the Invention [Problem to be solved by the invention]

[0004] If a radio link failure occurs before the generic UE configuration update procedure is completed, the S-NSSAI status at the UE and the S-NSSAI status at the network side may not match and become out of sync, leading to loss of service for the S-NSSAI for the user. [Means for solving the problem]

[0005] In a first aspect of the present disclosure, there is provided a method for an Access and Mobility Management Function (AMF), the method comprising: transmitting a CONFIGURATION UPDATE COMMAND message, the CONFIGURATION UPDATE COMMAND message including an Allowed Network Slice Selection Assistance Information (NSSAI) or a Rejected NSSAI; starting a timer when the Network Slice Selection Assistance Information (NSSAI) is transmitted; and retransmitting the CONFIGURATION UPDATE COMMAND message upon expiration of the timer if a failure related to a radio link is detected before receiving a CONFIGURATION UPDATE COMPLETE message.

[0006] In a second aspect of the present disclosure, there is provided a method for User Equipment (UE), the method comprising: communicating with an Access and Mobility Management Function (AMF) and initiating a Registration procedure when radio coverage is lost and the UE holds Single Network Slice Selection Assistance Information (NSSAI) in a Pending NSSAI.

[0007] In a third aspect of the present disclosure, an Access and Mobility Management Function (AMF) comprises: means for transmitting a CONFIGURATION UPDATE COMMAND message, the CONFIGURATION UPDATE COMMAND message including an Allowed Network Slice Selection Assistance Information (NSSAI) or a Rejected NSSAI; means for starting a timer when the Network Slice Selection Assistance Information (NSSAI) is transmitted; and means for retransmitting the CONFIGURATION UPDATE COMMAND message upon expiration of the timer if a failure related to a radio link is detected before receiving a CONFIGURATION UPDATE COMPLETE message.

[0008] In a fourth aspect of the present disclosure, a User Equipment (UE) comprises means for communicating with an Access and Mobility Management Function (AMF) and means for initiating a Registration procedure when radio coverage is lost and the UE holds Single Network Slice Selection Assistance Information (NSSAI) in a Pending NSSAI. [Brief explanation of the drawings]

[0009] [Figure 1] Figure 1 shows a general network slice specific authentication and authorization procedure. [Figure 2] FIG. 2 is a signaling diagram illustrating an example of restarting the generic UE configuration update procedure. [Figure 3] FIG. 3 is a signaling diagram illustrating an example of sending a CONFIGURATION UPDATE COMMAND message including an Allowed NSSAI when an N1 NAS signaling connection is established after a radio link failure. [Figure 4] FIG. 4 is a signaling diagram illustrating an example of a PDU session establishment procedure. [Figure 5] FIG. 5 is a signaling diagram illustrating an example of a registration procedure by a UE. [Figure 6] FIG. 6 is a block diagram showing a schematic diagram of a UE. [Figure 7] FIG. 7 is a block diagram showing a schematic diagram of a RAN node. [Figure 8] FIG. 8 is a block diagram showing a schematic diagram of the AMF. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure provides improved systems and methods for handling slice authentication and authorization procedures. More specifically, the present disclosure relates to a method for transmitting an Allowed NSSAI to a UE in weak radio coverage during a network-specific slice authentication and authorization procedure. To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will be made by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. It will be understood that these drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting of scope. The disclosure is illustrated and explained with additional specificity and detail in the figures. Additionally, those skilled in the art will understand that elements in the figures are simplified illustrations and may not necessarily be drawn to scale. Furthermore, with respect to the configuration of a device, one or more components of the device may be represented in the figures by generic symbols, and the figures may show only the specific details pertinent to understanding the embodiments of the present disclosure, so as not to obscure the figures with details that will be readily apparent to one of ordinary skill in the art having the benefit of the description herein.

[0011] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such modifications and further variations in the illustrated systems, and further applications of the principles of the disclosure which would normally occur to one skilled in the art, are to be construed as being within the scope of the present disclosure.

[0012] The terms "comprises," "comprising," or other variations thereof are intended to cover a non-exclusive inclusion, and a process or method comprising a list of steps may not include only those steps, but may also include other steps not expressly listed in or inherent to such process or method. Similarly, the term "comprises" precedes one or more devices, entities, subsystems, elements, structures, or components, and does not, without further constraints, preclude the presence of other devices, subsystems, elements, structures, components, additional devices, additional subsystems, additional elements, additional structures, or additional components. Appearances of the phrases "in one embodiment," "in another embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0013] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The systems, methods, and examples provided herein are illustrative only and are not intended to be limiting.

[0014] In the following specification and claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. As used herein, information is associated with data and knowledge, as data is meaningful information and represents values attributed to parameters. Further knowledge implies understanding of abstract or concrete concepts. Note that this example system has been simplified to facilitate explanation of the disclosed subject matter and is not intended to limit the scope of this disclosure. Other devices, systems, and configurations can be used in addition to, or in place of, the system to implement the embodiments disclosed herein, and all such embodiments are contemplated as being within the scope of this disclosure.

[0015] Problem statement example 1: When the network receives an S-NSSAI that is the subject of NSSAA in the Requested NSSAI during an NAS procedure (e.g., a Registration Procedure), it performs the NSSAA procedure. After performing the NSSAA procedure, the network sends the result of the NSSAA procedure for the S-NSSAI to the UE. If the NSSAA procedure is successful, the network puts the S-NSSAI into the Allowed NSSAI; otherwise, it puts the S-NSSAI into the Rejected NSSAI. The AMF then initiates a generic UE configuration update procedure and sends at least one of the Allowed NSSAI and Rejected NSSAI (either a new Allowed NSSAI or a Rejected NSSAI, or both a new Allowed NSSAI and a Rejected NSSAI) to the UE in a CONFIGURATION UPDATE COMMAND message. If a radio link failure occurs before the generic UE configuration update procedure is completed, the UE may not receive the Allowed NSSAI from the network. Therefore, the status of S-NSSAI in the UE and the status of S-NSSAI on the network side may not match and may not be synchronized with each other, which may lead to loss of service related to S-NSSAI for the user.

[0016] Problem statement example 2: During an NAS procedure (e.g., a registration procedure), if the network receives an S-NSSAI that is the subject of NSSAA in the requested NSSAI, the network performs the NSSAA procedure. After performing the NSSAA procedure, the network sends the result of the NSSAA procedure for the S-NSSAI to the UE. If the NSSAA procedure is successful, the network places the S-NSSAI in the Allowed NSSAI; otherwise, it places the S-NSSAI in the Rejected NSSAI. The network maintains the new Allowed NSSAI and the old Allowed NSSAI, and initiates a generic UE configuration update procedure to send at least one of the new Allowed NSSAI and the Rejected NSSAI (either the new Allowed NSSAI or the Rejected NSSAI, or both the new Allowed NSSAI and the Rejected NSSAI) to the UE in a CONFIGURATION UPDATE COMMAND message. When the network receives a CONFIGURATION UPDATE COMPLETE message from the UE, it deletes the old Allowed NSSAI and maintains the new Allowed NSSAI. The difference between the new Allowed NSSAI and the old Allowed NSSAI is whether it contains an S-NSSAI that is subject to the NSSAA. That is, the new Allowed NSSAI contains at least one S-NSSAI that contains an S-NSSAI that is subject to the NSSAA. The old Allowed NSSAI contains at least one S-NSSAI, but does not contain an S-NSSAI that is subject to the NSSAA.

[0017] If a radio link failure occurs before the Generic UE Configuration Update procedure is completed, the network aborts the Generic UE Configuration Update procedure. In this scenario, if the network does not receive a CONFIGURATION UPDATE COMPLETE message from the UE, the network maintains two Allowed NSSAI lists (i.e., the new Allowed NSSAI and the old Allowed NSSAI). If the network receives a 5G Session Management message (e.g., a PDU session establishment request message) containing an S-NSSAI in the new Allowed NSSAI, the network behavior is unclear: whether the network should perform or reject the PDU Session Establishment procedure.

[0018] This disclosure describes a solution to the problem of S-NSSAI status mismatch between the UE and the network, which may occur due to radio link failure or other reasons.

[0019] All procedures disclosed in each embodiment are applicable to S-NSSAI status management between a UE and a network for 3GPP access and non-3GPP access. All procedures disclosed in each embodiment are applicable to S-NSSAI status management between a UE and a network for PLMN and Stand-alone non-public networks and Public Network Integrated NPN, as described in clauses 5.30.2 and 5.30.3 of 3GPP TS23.501 [2], respectively.

[0020] In some embodiments, it is disclosed that a generic UE configuration update procedure is performed after the AMF detects a radio link failure. For example, steps 8 and 9 of FIG. 3 in embodiment 2. If a registration procedure is performed after the radio link failure, the registration procedure can take over what the generic UE configuration update procedure is about to do. The registration procedure may be an initial registration procedure, a registration procedure due to mobility, or a periodic registration procedure. For example, the Allowed NSSAI sent in the CONFIGURATION UPDATE COMMAND message is sent in the REGISTRATION ACCEPT message. In this case, the following message name substitutions apply to all embodiments: (1) The CONFIGURATION UPDATE COMMAND message is replaced by a REGISTRATION ACCEPT message. (2) The CONFIGURATION UPDATE COMPLETE message is replaced by a REGISTRATION COMPLETE message.

[0021] Embodiment 1 (Solution 1): As shown in Figure 2, if the network encounters a radio link failure before an ongoing Generic UE Configuration Update procedure is completed, the network shall restart the Generic UE Configuration Update procedure.

[0022] The details of this solution are described below.

[0023] 1. The UE sends a REGISTRATION REQUEST message including a Requested NSSAI containing at least one S-NSSAI to the AMF.

[0024] 2. When the AMF receives a REGISTRATION REQUEST message from the UE, it refers to the UE's subscriber data obtained from the UDM using the Nudm_SDM_Get service and determines whether the S-NSSAI included in the Requested NSSAI is subject to NSSAA.

[0025] If the S-NSSAI is subject to an NSSAA procedure, the AMF marks the S-NSSAI as pending.

[0026] 3. The AMF sends a REGISTRATION ACCEPT message to the UE containing the Pending NSSAI, which includes the S-NSSAI.

[0027] 4. The AMF initiates the NSSAA procedure for S-NSSAI as described in section 4.2.9 of 3GPP TS23.502 [3]. This step 4 refers only to the EAP-based Network Slice-Specific Authentication and Authorization for S-NSSAI. The UE Configuration Update procedure that may be performed after the EAP-based Network Slice-Specific Authentication and Authorization is described in step 5 onwards.

[0028] 5. Upon successful completion of the NSSAA procedure for S-NSSAI, the AMF initiates the generic UE configuration update procedure by sending a CONFIGURATION UPDATE COMMAND message containing the Allowed NSSAI including S-NSSAI. The AMF starts a retry timer (e.g., T3555) simultaneously with sending the CONFIGURATION UPDATE COMMAND message or after the AMF sends the CONFIGURATION UPDATE COMMAND message.

[0029] The AMF also starts the retry timer when the NSSAA procedure fails and the AMF sends a CONFIGURATION UPDATE COMMAND message containing a Rejected NSSAI that contains an S-NSSAI. That is, the cause of the retry timer start is the sending of the CONFIGURATION UPDATE COMMAND message. The Allowed NSSAI is a list of at least one S-NSSAI. The Rejected NSSAI is a list of at least one S-NSSAI.

[0030] 6. If the AMF detects that a radio link failure has occurred (for example, if the NG-RAN indicates to the AMF through an NGAP message that the UE radio contact has been lost), the AMF does not interrupt the general UE configuration update procedure, i.e., the AMF continues to run the retry timer.

[0031] 7. When the retry timer expires, the AMF resends the CONFIGURATION UPDATE COMMAND message containing an Allowed NSSAI including S-NSSAI or a Rejected NSSAI including S-NSSAI.

[0032] 8. When the UE receives the CONFIGURATION UPDATE COMMAND message, it updates the status of the S-NSSAI and sends a CONFIGURATION UPDATE COMPLETE message to the AMF.

[0033] 9. When the AMF receives the CONFIGURATION UPDATE COMPLETE message from the UE, if the CONFIGURATION UPDATE COMMAND message in step 7 includes an S-NSSAI in the Allowed NSSAI, it updates the status of the S-NSSAI as valid and updates the status of the S-NSSAI as allowed S-NSSAI. That is, the S-NSSAI becomes part of the Allowed NSSAI. If the CONFIGURATION UPDATE COMMAND message in step 7 includes an S-NSSAI in the Rejected NSSAI, the AMF updates the status of the S-NSSAI as Rejected S-NSSAI. That is, the S-NSSAI becomes part of the Rejected NSSAI. The AMF may retain the associated information to the rejected S-NSSAI because this S-NSSAI failed the NSSAI.

[0034] Variation of Solution 1: In one embodiment, the AMF includes a 5G-GUTI (e.g., a new 5G-GUTI or a current 5G-GUTI) in the CONFIGURATION UPDATE COMMAND message in steps 5 and 7 along with the Allowed NSSAI or Rejected NSSAI. Upon detecting a radio link failure in step 6, the AMF continues to run a retry timer. When the retry timer expires, the AMF resends the CONFIGURATION UPDATE COMMAND message.

[0035] In one embodiment, the above embodiment is also applicable to a scenario where the CONFIGURATION UPDATE COMMAND message includes other information elements of the generic UE CONFIGURATION UPDATE procedure (e.g., Configured NSSAI, allowed CAG information).

[0036] Embodiment 2 (Solution 2): As shown in FIG. 3, the network sends a CONFIGURATION UPDATE COMMAND message containing an Allowed NSSAI when the N1 NAS signaling connection is established after a radio link failure.

[0037] The details of this solution are described below.

[0038] 1. The UE sends a REGISTRATION REQUEST message including a Requested NSSAI containing at least one S-NSSAI to the AMF.

[0039] 2. When the AMF receives a REGISTRATION REQUEST message from the UE, it refers to the UE's subscriber data obtained from the UDM using the Nudm_SDM_Get service to determine whether the S-NSSAI included in the Requested NSSAI is subject to NSSAA. If the S-NSSAI is subject to NSSAA procedures, the AMF marks the S-NSSAI as pending.

[0040] 3. The AMF sends a REGISTRATION ACCEPT message including a Pending NSSAI containing the S-NSSAI to the UE.

[0041] 4. The AMF initiates the NSSAA procedure for S-NSSAI as described in section 4.2.9 of 3GPP TS23.502 [3]. This step 4 refers only to the EAP-based Network Slice-Specific Authentication and Authorization for S-NSSAI. The UE Configuration Update procedure that may be performed after the EAP-based Network Slice-Specific Authentication and Authorization is described in step 5 onwards.

[0042] 5. Upon successful completion of the NSSAA procedure for S-NSSAI, the AMF initiates the generic UE configuration update procedure by sending a CONFIGURATION UPDATE COMMAND message containing the Allowed NSSAI including S-NSSAI. The AMF may start a retry timer (e.g., T3555) simultaneously with sending the CONFIGURATION UPDATE COMMAND message or after the AMF sends the CONFIGURATION UPDATE COMMAND message.

[0043] The AMF may start the retry timer when the NSSAA procedure fails and the AMF sends a CONFIGURATION UPDATE COMMAND message containing a Rejected NSSAI including S-NSSAI, i.e., the retry timer is started due to the transmission of the CONFIGURATION UPDATE COMMAND message.

[0044] 6. If the AMF detects that a radio link failure has occurred (for example, if the NG-RAN indicates to the AMF via an NGAP message that the UE radio contact has been lost), the AMF aborts the general UE configuration update procedure and, if the retry timer is running, the retry timer is stopped.

[0045] The AMF sets the UE status "UCU (UE Configuration Update) needed" in the UE MM context or local memory in the AMF with the message content of the CONFIGURATION UPDATE COMMAND message sent in step 5. The UE status "UCU needed" means that a generic UE configuration update procedure needs to be performed for the UE due to a possible S-NSSAI status mismatch between the UE and the network.

[0046] Alternatively, the AMF sets the S-NSSAI status in the UE MM context or local memory within the AMF to "Unsynchronized". The S-NSSAI status "Unsynchronized" means that the S-NSSAI status between the UE and the network may not match and a generic UE configuration update procedure must be performed for this S-NSSAI. For example, the AMF maintains or stores information indicating at least one of the UE status being "UCU needed" and the S-NSSAI status being "Unsynchronized".

[0047] If an AMF relocation is performed while the AMF maintains at least one of the UE status "UCU needed" and S-NSSAI status "Unsynchronized", at least one of the UE status "UCU needed" and S-NSSAI status "Unsynchronized" must be transferred from the old AMF to the new AMF using the Namf_Communication_UEContextTransfer service as described in clause 5.2.2.2.2 of 3GPP TS23.502 [3].

[0048] 7. A new N1 NAS signaling connection with the UE is established. For example, suppose the UE returns to 3GPP coverage and sends a REGISTRATION REQUEST message to the AMF. The new N1 NAS signaling connection is established by a registration procedure that includes sending a REGISTRATION REQUEST message.

[0049] 8. If the AMF manages (or stores) the UE status as "UCU needed" or the S-NSSAI status as "Unsynchronized", the AMF resends the CONFIGURATION UPDATE COMMAND message containing an Allowed NSSAI containing S-NSSAI or a Rejected NSSAI containing S-NSSAI. When the UE receives the CONFIGURATION UPDATE COMMAND message, it updates the status of the S-NSSAI.

[0050] 9. The UE sends a CONFIGURATION UPDATE COMPLETE message to the AMF.

[0051] 10. When the AMF receives the CONFIGURATION UPDATE COMPLETE message from the UE, if the CONFIGURATION UPDATE COMMAND message in step 8 includes an S-NSSAI in the Allowed NSSAI, it updates the S-NSSAI status as valid and updates the status of the S-NSSAI as allowed S-NSSAI, i.e., the S-NSSAI becomes part of the Allowed NSSAI. If the CONFIGURATION UPDATE COMMAND message in step 8 includes a Rejected NSSAI, the AMF updates the status of the S-NSSAI as Rejected S-NSSAI, i.e., the S-NSSAI becomes part of the Rejected NSSAI. The AMF may maintain related information for the rejected S-NSSAI because this S-NSSAI failed the NSSAI.

[0052] Variation of Solution 2: In one embodiment, if a new N1 NAS signaling connection with the UE is established in step 7 and the AMF maintains the S-NSSAI status as "Unsynchronized", the AMF may initiate an NSSAA procedure for the S-NSSAI. Then, if the NSSAA procedure is completed successfully, the AMF sends the Allowed NSSAI including the S-NSSAI to the UE using the Generic UE Configuration Update procedure. After the NSSAA procedure is completed successfully, the AMF may delete or reset the UE status "UCU needed" or the S-NSSAI status "Unsynchronized".

[0053] In another embodiment, if the AMF receives a REGISTRATION REQUEST message for a new N1 NAS signaling connection in step 7 and the AMF maintains the S-NSSAI status as "Unsynchronized", the AMF may send a REGISTRATION ACCEPT message including an Allowed NSSAI that includes the S-NSSAI to the UE instead of initiating a generic UE configuration update procedure. The AMF shall maintain the new Allowed NSSAI marked as invalid and the old Allowed NSSAI marked as valid, or the AMF shall maintain only the new Allowed NSSAI. When the UE receives the REGISTRATION ACCEPT message with "Allowed NSSAI", it shall send a REGISTRATION COMPLETE message to acknowledge that it has received the latest Allowed NSSAI. When the AMF receives the REGISTRATION COMPLETE message, the AMF shall mark the new allowed NSSAI as valid and mark the old Allowed NSSAI as invalid.

[0054] Embodiment 3 (Solution 3): As shown in Figure 4, the AMF shall allow the PDU session establishment procedure if it receives a request to activate a PDU session including an S-NSSAI in the new Allowed NSSAI.

[0055] The details of this solution are described below.

[0056] 1. The UE sends a REGISTRATION REQUEST message including a Requested NSSAI containing at least one S-NSSAI to the AMF.

[0057] 2. When the AMF receives a REGISTRATION REQUEST message from the UE, it refers to the UE's subscriber data obtained from the UDM using the Nudm_SDM_Get service to determine whether the S-NSSAI included in the Requested NSSAI is subject to NSSAA. If the S-NSSAI is subject to NSSAA procedures, the AMF marks the S-NSSAI as pending.

[0058] 3. The AMF sends a REGISTRATION ACCEPT message including a Pending NSSAI containing the S-NSSAI to the UE.

[0059] 4. The AMF initiates the NSSAA procedure for S-NSSAI as described in section 4.2.9 of 3GPP TS23.502 [3]. This step 4 refers only to the EAP-based Network Slice-Specific Authentication and Authorization for S-NSSAI. The UE Configuration Update procedure that may be performed after the EAP-based Network Slice-Specific Authentication and Authorization is described in steps 5 and onward.

[0060] 5. Upon successful completion of the NSSAA procedure for S-NSSAI, the AMF initiates the generic UE configuration update procedure by sending a CONFIGURATION UPDATE COMMAND message containing a new Allowed NSSAI including the S-NSSAI. The AMF may start a retry timer (e.g., T3555) simultaneously with sending the CONFIGURATION UPDATE COMMAND message or after the AMF sends the CONFIGURATION UPDATE COMMAND message. The AMF maintains (or saves) the new Allowed NSSAI and the old Allowed NSSAI. The old Allowed NSSAI does not include the S-NSSAI that is the subject of the NSSAA procedure in step 4.

[0061] The AMF may start the retry timer when the NSSAA procedure fails and the AMF sends a CONFIGURATION UPDATE COMMAND message containing a Rejected NSSAI including S-NSSAI, i.e., the retry timer is started due to the transmission of the CONFIGURATION UPDATE COMMAND message.

[0062] 6. The UE updates the status of the Allowed NSSAI or Rejected NSSAI based on the contents of the CONFIGURATION UPDATE COMMAND message. If the CONFIGURATION UPDATE COMMAND message contains an S-NSSAI for the Allowed NSSAI, the UE interprets the S-NSSAI as usable.

[0063] 7. The UE sends a CONFIGURATION UPDATE COMPLETE message to the AMF. However, due to a radio link failure, this message cannot reach the AMF.

[0064] 8. If the AMF detects that a radio link failure has occurred (for example, if the NG-RAN indicates to the AMF via an NGAP message that the UE radio contact has been lost), the AMF aborts the general UE configuration update procedure and, if the retry timer is running, the retry timer is stopped.

[0065] 9. The UE sends a UL NAS TRANSPORT message to the AMF to establish a PDU session. The UL NAS TRANSPORT message includes an S-NSSAI and a payload container containing a PDU SESSION ESTABLISHMENT REQUEST message.

[0066] 10. The AMF receives the UL NAS TRANSPORT message. The AMF checks or determines whether the S-NSSAI included in the UL NAS TRANSPORT message is included in the new Allowed NSSAI in the AMF. If the S-NSSAI is included in the new Allowed NSSAI, the AMF allows the establishment of the PDU session and sends a PDU SESSION ESTABLISHMENT REQUEST message to the SMF and continues the PDU SESSION ESTABLISHMENT procedure as described in 4.3.2 of 3GPP TS 23.502 [3].

[0067] The AMF marks (or saves or maintains) the new Allowed NSSAI as valid and deletes the old allowed NSSAI. The AMF may forward the new Allowed NSSAI to NG-RAN in an NGAP message. The AMF may also forward the new Allowed NSSAI to the SMF.

[0068] In one example, in the AMF, if an S-NSSAI exists in the new Allowed NSSAI but does not exist in the old Allowed NSSAI, the AMF understands that the UE has received the last CONFIGURATION UPDATE COMMAND message, validates the new Allowed NSSAI, and deletes the old allowed NSSAI. From this point on, the AMF only maintains the new Allowed NSSAI.

[0069] In one example, the UE determines whether the S-NSSAI is present in either the new Allowed NSSAI or the old NSSAI list or both, and the AMF considers the S-NSSAI to be allowed and sends a PDU SESSION ESTABLISHMENT REQUEST message to the SMF.

[0070] Embodiment 4 (Solution 4): As shown in Figure 5, when the AMF receives a request to activate a PDU session including an S-NSSAI that is not in the old allowed NSSAI list, it rejects the PDU session establishment procedure. The UE then initiates the registration procedure by sending a REGISTRATION REQUEST message including an S-NSSAI in the Requested NSSAI list.

[0071] The details of this solution are described below.

[0072] 1. The UE sends a REGISTRATION REQUEST message including a Requested NSSAI containing at least one S-NSSAI to the AMF.

[0073] 2. When the AMF receives a REGISTRATION REQUEST message from the UE, it refers to the UE's subscriber data obtained from the UDM using the Nudm_SDM_Get service to determine whether the S-NSSAI included in the Requested NSSAI is subject to NSSAA. If the S-NSSAI is subject to NSSAA procedures, the AMF marks the S-NSSAI as pending.

[0074] 3. The AMF sends a REGISTRATION ACCEPT message including a Pending NSSAI containing the S-NSSAI to the UE.

[0075] 4. The AMF initiates the NSSAA procedure for S-NSSAI as described in section 4.2.9 of 3GPP TS23.502 [3]. This step 4 refers only to the EAP-based Network Slice-Specific Authentication and Authorization for S-NSSAI. The UE Configuration Update procedure that may be performed after the EAP-based Network Slice-Specific Authentication and Authorization is described in steps 5 and onward.

[0076] 5. Upon successful completion of the NSSAA procedure for S-NSSAI, the AMF initiates the generic UE configuration update procedure by sending a CONFIGURATION UPDATE COMMAND message containing a new Allowed NSSAI including the S-NSSAI. The AMF may start a retry timer (e.g., T3555) simultaneously with sending the CONFIGURATION UPDATE COMMAND message or after the AMF sends the CONFIGURATION UPDATE COMMAND message. The AMF maintains the new Allowed NSSAI and the old Allowed NSSAI.

[0077] The AMF may also start the retry timer when the NSSAA procedure fails and the AMF sends a CONFIGURATION UPDATE COMMAND message containing a Rejected NSSAI including S-NSSAI, i.e., the cause for starting the retry timer is the transmission of the CONFIGURATION UPDATE COMMAND message.

[0078] 6. The UE updates the status of the Allowed NSSAI or Rejected NSSAI based on the contents of the CONFIGURATION UPDATE COMMAND message. If the CONFIGURATION UPDATE COMMAND message contains an S-NSSAI for the Allowed NSSAI, the UE interprets the S-NSSAI as usable.

[0079] 7. The UE sends a CONFIGURATION UPDATE COMPLETE message to the AMF. However, due to a radio link failure, this message cannot reach the AMF.

[0080] 8. If the AMF detects that a radio link failure has occurred (for example, if the NG-RAN indicates to the AMF via an NGAP message that the UE radio contact has been lost), the AMF aborts the general UE configuration update procedure and, if the retry timer is running, the retry timer is stopped.

[0081] 9. The UE sends a UL NAS TRANSPORT message to the AMF to establish a PDU session. The UL NAS TRANSPORT message contains the S-NSSAI and a Payload container containing the PDU SESSION ESTABLISHMENT REQUEST message.

[0082] 10. If the AMF receives an UPLINK (UL) NAS TRANSPORT message containing an S-NSSAI and the S-NSSAI contained in the UL NAS TRANSPORT message does not exist in the AMF's old Allowed NSSAI, the AMF rejects the UL NAS TRANSPORT message, i.e., the AMF rejects the establishment of the PDU session.

[0083] 11. The AMF sends a DOWNLINK (DL) NAS TRANSPORT message to the UE indicating that the UPLINK (UL) NAS TRANSPORT message of step 10 has been rejected by the AMF. This message may contain a new 5G MM cause of "Unsynchronized S-NSSAI" or "Re-registration required due to Unsynchronized S-NSSAI" or "Network Specific Slice Authentication and Authorization procedure required" or any other cause value indicating to the UE that the S-NSSAI status between the UE and the network may not match and that the registration procedure needs to be performed to synchronize. Upon receiving the DOWNLINK (DL) NAS TRANSPORT message, the UE removes the S-NSSAI from its Allowed NSSAIs.

[0084] 12. The UE may initiate the registration procedure by sending a REGISTRATION REQUEST message containing a Requested NSSAI, which may include an S-NSSAI, based on the information in the DOWNLINK (DL) NAS TRANSPORT message.

[0085] If the AMF determines that the S-NSSAI of the Requested NSSAI is included in the new Allowed NSSAI of the REGISTRATION ACCEPT message, it sends a REGISTRATION ACCEPT message to the UE including a new 5G-GUTI and a new Allowed NSSAI including the S-NSSAI.

[0086] If the S-NSSAI of the Requested NSSAI is the subject of an NSSAA procedure and the AMF decides to perform the NSSAA procedure for the S-NNSAI, the UE and the network perform the NSSAA procedure and the Generic UE Configuration Update procedure for the S-NNSAI. After the NSSAA procedure and the Generic UE Configuration Update procedure are completed, followed by the registration procedure, the status of the Allowed NSSAI is synchronized between the UE and the network, and the AMF activates the new Allowed NSSAI, deactivates the old Allowed NSSAI, and uses the new Allowed NSSAI in subsequent NAS procedures or other procedures.

[0087] The following describes some examples of the details of synchronization of the Allowed NSSAI status between the UE and the network. (1) After receiving a REGISTRATION ACCEPT message including a new Allowed NSSAI including S-NSSAI in response to the REGISTRATION REQUEST message, the UE validates the new Allowed NSSAI and invalidates the old Allowed NSSAI. (2) After the UE sends a REGISTRATION COMPLETE message to the AMF in response to the REGISTRATION ACCEPT message, it validates the new Allowed NSSAI and invalidates the old Allowed NSSAI. (3) After receiving a REGISTRATION COMPLETE message in response to a REGISTRATION ACCEPT message containing a new Allowed NSSAI including S-NSSAI, the AMF validates the new Allowed NSSAI and invalidates the old Allowed NSSAI. (4) After receiving a CONFIGURATION UPDATE COMMAND message containing a new Allowed NSSAI including S-NSSAI, the UE validates the new Allowed NSSAI and invalidates the old Allowed NSSAI. (5) In response to the CONFIGURATION UPDATE COMMAND message, the UE sends a CONFIGURATION UPDATE COMPLETE message to the AMF, then enables the new Allowed NSSAI and disables the old Allowed NSSAI. (6) After receiving a CONFIGURATION UPDATE COMMAND message containing a new Allowed NSSAI including S-NSSAI, the AMF validates the new Allowed NSSAI and invalidates the old Allowed NSSAI.

[0088] In yet another embodiment, when the UE performs a registration procedure after receiving a DL NAS TRANSPORT message from the AMF, the AMF may notify the UE of the S-NSSAI in the Allowed NSSAI instead of putting the S-NSSAI in the Pending NSSAI if the previous NSSAA procedure in step 4 was successful.

[0089] Similar to the above embodiment, when the UE performs the registration procedure after receiving the DL NAS TRANSPORT message from the AMF, the AMF may notify the UE of the S-NSSAI in the Rejected NSSAI instead of putting the S-NSSAI in the Pending NSSAI if the previous NSSAA procedure in step 4 failed authentication and authorization to use the S-NSSAI.

[0090] In the example of step 5, the AMF may include the 5G-GUTI in the CONFIGURATION UPDATE COMMAND. If the network receives the 5G-GUTI sent in the CONFIGURATION UPDATE COMMAND message in an NAS message, such as a SERVICE REQUEST message, the AMF validates the new Allowed NSSAI and deletes the old Allowed NSSAI. The AMF starts using the new Allowed NSSAI in subsequent NAS procedures or other UE-related procedures.

[0091] Variation of Solution 4: If the AMF receives the UL NAS TRANSPORT message in step 9 and finds that there may be a mismatch in the S-NSSAI status between the UE and the network, it may initiate an NSSAA procedure for the S-NSSAI indicated in the UL NAS TRANSPORT message in step 9. Alternatively, the AMF may initiate an NSSAA procedure for all pending S-NSSAIs, or may initiate an NSSAA procedure for all S-NSSAIs in the MM context of the UE within the AMF. After the NSSAA procedure, the UE sends a PDU Session establishment Request message containing the S-NSSAI that has been successfully authenticated and authorized for use.

[0092] Modifications of each embodiment: If the UE transitions to the 5GMM-IDLE state before the NSSAA procedure (step 4) (e.g., the N1 signaling connection is released due to a radio link failure, or the RRC connection is released by NG-RAN, or radio coverage is lost), the UE may initiate a registration procedure or a service request procedure or other NAS procedure to establish the N1 NAS signaling connection during the NSSAA procedure (step 4) and during the UE Configuration Update procedure (steps 5 to 8), so that the AMF can take appropriate actions to complete the NSSAA procedure. The following describes the actions that the AMF takes for each period when the UE transitions to 5GMM-IDLE status. (1) Period 1: The UE receives the Registration Accept message in step 3, but the NSSAA procedure in step 4 has not yet started. (1-1) Actions to be taken by the AMF if an N1 NAS signaling connection is established during Period 1: The AMF initiates NSSAA procedures for all S-NSSAIs of the pending NSSAI. (2) Period 2: During Step 4 of the NSSAA procedure. (2-1) Actions to be performed by the AMF if an N1 NAS signaling connection is established during Period 2: The AMF initiates NSSAA procedures for all S-NSSAIs of the pending NSSAI, or the AMF initiates NSSAA procedures only for S-NSSAIs among the pending NSSAIs that have not yet performed NSSAA procedures. (3) Period 3: After the NSSAA procedure in step 4 is completed, but the generic UE configuration update procedure has not yet been completed. (3-1) Actions to be performed by the AMF if an N1 NAS signaling connection is established during Period 3: The AMF initiates the general UE configuration update procedure.

[0093] If the NSSAA procedure is performed after step 7 of Figure 3 according to a variant of Solution 2, the above process applies to the NSSAA procedure after step 7 of Figure 3.

[0094] The present disclosure may be written as shown in Section 5.4.4.6.

[0095] 5.4.4.6 Network-side abnormality cases The following abnormal cases can be confirmed: a) Expiry of timer T 3555. The network shall retransmit the CONFIGURATION UPDATE COMMAND message upon the first expiry of timer T3555 and reset and start timer T3555. This retransmission shall be repeated four times, i.e. the procedure shall be stopped after five expiry of timer T3555. Furthermore, if the CONFIGURATION UPDATE COMMAND message contains the 5G-GUTI IE, the network shall act as in case b)-1) below. b) Lower layer failure. A lower layer failure is detected before a CONFIGURATION UPDATE COMPLETE message is received, 1) If the CONFIGURATION UPDATE COMMAND message contains a 5G-GUTI IE, the old 5G-GUTI and the new 5G-GUTI are considered valid until the old 5G-GUTI is considered invalid by the AMF. If a new TAI list is provided by the CONFIGURATION UPDATE COMMAND message, the old TAI list and the new TAI list are also considered valid until the old TAI list is considered invalid by the AMF. During this period, the AMF will: i) The AMF shall first use the old 5G-S-TMSI from the old 5G-GUTI to page within the area defined by the old TAI list for an implementation-dependent number of paging attempts for network-initiated transactions. If a new TAI list is provided in the CONFIGURATION UPDATE COMMAND message, the new TAI list may also be used for paging. If there is a response from the UE, the AMF may restart the CONFIGURATION UPDATE COMMAND. If a response is received from a tracking area within the old and new TAI lists, the network restarts the CONFIGURATION UPDATE COMMAND message. If no response to the paging attempt is received, the network may use the new 5G-GS-TMSI from the new 5G-GUTI for paging for an implementation-dependent number of paging attempts. In this case, if a new TAI list was provided with the new 5G-GUTI in the CONFIGURATION UPDATE COMMAND message, the new TAI list shall be used instead of the old one. If there is a response from the UE, the AMF shall consider the new 5G-GUTI valid and the old 5G-GUTI invalid. ii) The AMF shall consider the new 5G-GUTI valid if it is used by the UE and shall additionally consider the new TAI list valid if it is provided together with this 5G-GUTI in a CONFIGURATION UPDATE COMMAND message. iii) The AMF may use the identification procedure if the UE uses the old 5G-GUTI, followed by the new generic UE configuration update procedure. 2) If the CONFIGURATION UPDATE COMMAND message contains the Allowed NSSAI IE, the AMF shall consider the new Allowed NSSAI IE as valid. If the AMF receives a UL NAS TRASPORT message containing an S-NSSAI present in the new Allowed NSSAI, the AMF shall consider the S-NSSAI as allowed and perform the actions specified in clause 5.4.5.3. If the CONFIGURATION UPDATE COMMAND message contains neither the 5G-GUTI IE nor the Allowed NSSAI IE, the network shall abort the procedure. c) Collision between a general UE configuration update and a UE initiated de-registration procedure If the network receives a DEREGISTRATION REQUEST message before an ongoing Generic UE Configuration Update procedure is completed, the network shall abort the Generic UE Configuration Update procedure and proceed with the de-registration procedure. d) Collisions between the general UE configuration update and the registration procedure for mobility and periodic registration update If the network receives a REGISTRATION REQUEST message before the ongoing Generic UE Configuration Update procedure is completed, the network shall abort the Generic UE Configuration Update procedure and proceed with the registration procedures for Mobility and Periodic Registration Update procedure. e) Collision between generic UE configuration update and service request procedure If the network receives a SERVICE REQUEST message before an ongoing Generic UE Configuration Update procedure is completed, both procedures shall proceed.

[0096] Figure 6 is a block diagram illustrating the main components of a UE (600). As shown, the UE (600) includes transceiver circuitry (602) operable to transmit signals to and receive signals from connected nodes via one or more antennas (601). Although not necessarily shown in Figure 6, the UE naturally has all the usual functionality of a conventional mobile device (e.g., a user interface), which may be provided by any one or any combination of hardware, software, and firmware, as appropriate. Software may be pre-installed in memory and / or downloaded, for example, via a telecommunications network or from a removable data storage device (RMD).

[0097] The controller (604) controls the operation of the UE in accordance with software stored in the memory (605). The software includes, among other things, an operating system and a communications control module having at least a transceiver control module. The communications control module (using its transceiver control submodule) is responsible for processing (generating / sending / receiving) signaling and uplink / downlink data packets between the UE and other nodes, such as base stations / (R)AN nodes, MMEs, AMFs (and other core network nodes), etc. Such signaling may include, for example, appropriately formatted signaling messages related to connection establishment and maintenance (e.g., RRC connection establishment and RRC messages), messages related to periodic location updates (e.g., tracking area updates, paging area updates, location area updates), etc. Such signaling may also include, for example, in the receive case, broadcast information (e.g., Master Information and System Information).

[0098] FIG. 7 is a block diagram illustrating the main components of an exemplary (R)AN node (700), e.g., a base station (eNB in LTE, gNB in 5G). As shown, the (R)AN node includes transceiver circuitry (702) operable to transmit signals to and receive signals from connected UEs via one or more antennas (701), and to transmit signals to and receive signals from other network nodes (directly or indirectly) via a network interface (703). A controller (704) controls operation of the (R)AN node in accordance with software stored in memory (705). The software may be pre-installed in the memory and / or downloaded, for example, over a telecommunications network or from a removable data storage device (RMD). The software includes, among other things, an operating system and a communications control module having at least a transceiver control module.

[0099] The communication control module (using its transceiver control sub-module) is responsible for handling (generating / sending / receiving) signaling (e.g., directly or indirectly) between the (R)AN node and other nodes, e.g., UEs, MMEs, AMFs, etc. The signaling may include, for example, appropriately formatted signaling messages related to radio connectivity and location procedures (for a particular UE), in particular connection establishment and maintenance (e.g., RRC connection establishment and other RRC messages), messages related to periodic location updates (e.g., tracking area updates, paging area updates, location area updates), S1 AP messages and NG AP messages (i.e., messages over the N2 reference point), etc. Such signaling may also include, for example, broadcast information (e.g., master information and system information), if sent.

[0100] If implemented, the controller (704) is also configured (by software or hardware) to handle related tasks such as UE mobility estimate and / or moving trajectory estimation.

[0101] FIG. 8 is a block diagram illustrating the main components of an AMF (800). The AMF (800) is included in a 5GC. As shown, the AMF (800) includes a transceiver circuit (801) operable to transmit signals to and receive signals from other nodes (including UEs) via a network interface (804). A controller (802) controls the operation of the AMF (800) in accordance with software stored in memory (803). The software may be pre-installed in the memory (803) and / or may be downloaded, for example, via a telecommunications network or from a removable data storage device (RMD). The software includes, among other things, an operating system and a communications control module having at least a transceiver control module.

[0102] The Communications Control module (using its Transceiver Control sub-module) is responsible for handling (generating / sending / receiving) signaling (directly or indirectly) between the AMF and other nodes, e.g., UEs, base stations / (R)AN nodes (e.g., "gNBs" or "eNBs"), etc. Such signaling may include, e.g., appropriately formatted signaling messages related to the procedures described herein, e.g., NG AP messages (i.e., messages over the N2 reference point) for conveying NAS messages to and from the UE, etc.

[0103] User Equipment (or "UE," "mobile station," "mobile device," or "wireless device") in this disclosure is an entity connected to a network via a radio interface. UE, as used herein, is not limited to dedicated communications devices, but may be any device that has the communications capabilities of a UE as described herein, such as: The terms "User Equipment (UE)" (as used in 3GPP), "mobile station," "mobile device," and "wireless device" are generally intended to be synonymous with each other and may refer to standalone mobile stations such as terminals, mobile phones, smartphones, tablets, cellular IoT terminals, and IoT devices. It should be understood that the terms "UE" and "wireless terminal" also encompass devices that are stationary for extended periods of time.

[0104] The UE may also be, for example, a transportation device (for example, a vehicle, an automobile, a motorcycle, a bicycle, a train, a bus, a cart, a rickshaw, a ship and other watercraft, an airplane, a rocket, a satellite, a drone, a balloon, etc.), or an information and communication device (for example, an electronic computer and related devices, a communication device and related devices, an electronic component, etc.).

[0105] The UE may also be, for example, a refrigerator, refrigerator-applied products and equipment, commercial and service equipment, vending machines, automatic service machines, office machines and equipment, consumer electrical and electronic machinery and appliances (e.g., audio equipment, video equipment, speakers, radios, televisions, oven ranges, rice cookers, coffee makers, dishwashers, washing machines, dryers, fans, ventilation fans and related products, vacuum cleaners, etc.).

[0106] The UE may also be, for example, an electronic application system or device (eg, an x-ray system, a particle accelerator, a radioactive application device, a sonic device, an electromagnetic application device, a power application device, etc.).

[0107] The UE may also be, for example, a personal digital assistant or related device with wireless communication capabilities, such as a wireless card or module designed to be attached to or inserted into other electronic devices (e.g., personal computers, electrical measuring instruments).

[0108] A UE may also be part of a device or system that provides applications, services, or solutions in the "Internet of Things" (IoT), for example, using wired and wireless communication technologies. IoT devices (or things) include appropriate electronics, software, sensors, network connectivity, etc., that enable devices to collect and exchange data with each other and with other communicating devices. IoT devices may also include automated devices that follow software instructions stored in internal memory. IoT devices may also operate without the need for human supervision or attention. IoT devices may also be installed and / or remain inactive for long periods of time. IoT devices may also be implemented as part of (typically) stationary devices. IoT devices may also be embedded in non-stationary devices (e.g., vehicles) or attached to animals or people being monitored / tracked.

[0109] It will be appreciated that IoT technology can be implemented on any communication device that can be connected to a communication network to send and receive data without regard to control by human input or software instructions stored in memory.

[0110] It will be understood that an IoT device may also be referred to as a Machine Type Communication (MTC) device, or a Machine to Machine (M2M) communication device, or a Narrow Band-IoT (NB-IoT) UE. It will also be understood that a UE may support one or more IoT or MTC applications. Some examples of MTC applications are listed below in Table 3 (Source: 3GPP TS 22.368 Annex B, the contents of which are incorporated herein by reference). This list is not exhaustive but rather provides examples of MTC applications.

[0111] Table 1: Some examples of machine-type communication applications [Table 1]

[0112] Examples of applications, services, and solutions include MVNO (Mobile Virtual Network Operator) services, emergency wireless communication systems, PBX (Private Branch eXchange) systems, PHS / digital cordless telephone systems, POS (Point of sale) systems, advertising systems, MBMS (Multimedia Broadcast and Multicast Service), V2X (Vehicle to Everything) systems, train radio systems, location information-related services, disaster / emergency wireless communication services, community services, video distribution services, Femto cell application services, VoLTE (Voice over LTE) services, billing services, radio on-demand services, roaming services, behavior monitoring services, communication carrier / communication network selection services, function restriction services, PoC (Proof of Concept) services, personal information management services, ad hoc networks / DTN (Delay Tolerant Networking) services, and the like.

[0113] It should be understood that the above-mentioned categories of UE are merely examples of applications of the concepts and exemplary embodiments described herein, and that these concepts and embodiments are not limited to the above-mentioned UEs, and that various modifications may be made thereto.

[0114] Other embodiments of this aspect include corresponding computer systems, devices, and computer programs stored on one or more computer storage devices, each configured to perform the operations of the method. One or more computer systems can be configured to perform particular operations or actions by having software, firmware, hardware, or combinations thereof installed on the systems that cause the systems to perform the operations during operation. One or more computer programs can be configured to perform particular operations or actions by including instructions that, when executed by a data processing device, cause the systems to perform the operations.

[0115] Furthermore, a skilled programmer can, for example, write such a computer program or, based on the flowcharts and associated descriptions in the specification, easily identify appropriate hardware circuits for implementing the disclosed invention. Therefore, disclosure of a specific program code instruction set or detailed hardware devices is not considered necessary for a full understanding of how to make and use the invention. The inventive functionality of the claimed computer-implemented process is explained in more detail in the following description, in conjunction with the remaining diagrams illustrating other process flows. Furthermore, certain steps of the processes or process flows described in all the following logical flow diagrams must naturally precede other steps in order for the disclosure to function as described. However, the disclosure is not limited to the order of steps described if such order or sequence does not alter the functionality of the disclosure. That is, it is recognized that some steps can be performed before, after, or in parallel with other steps without departing from the scope of the disclosure.

[0116] Abbreviation For the purposes of this document, 3GPP TR 21.905 [1] and the abbreviations listed below apply. Abbreviations defined in this document take precedence over definitions in 3GPP TR 21.905 [1] if the same abbreviation appears there. 5GC 5G Core Network 5GLAN 5G Local Area Network 5GS 5G System 5G-AN 5G Access Network 5G-AN PDB 5G Access Network Packet Delay Budget 5G-EIR 5G-Equipment Identity Register 5G-GUTI 5G Globally Unique Temporary Identifier 5G-BRG 5G Broadband Residential Gateway 5G-CRG 5G Cable Residential Gateway 5G GM 5G Grand Master 5G-RG 5G Residential Gateway 5G-S-TMSI 5G S-Temporary Mobile Subscription Identifier 5G VN 5G Virtual Network 5QI 5G QoS Identifier AF Application Function AMF Access and Mobility Management Function AS Access Stratum ATSSS Access Traffic Steering, Switching, Splitting ATSSS-LL ATSSS Low-Layer AUSF Authentication Server Function BMCA Best Master Clock Algorithm BSF Binding Support Function CAG Closed Access Group CAPIF Common API Framework for 3GPP northbound APIs CHF Charging Function CN PDB Core Network Packet Delay Budget CP Control Plane DAPS Dual Active Protocol Stacks DL Downlink DN Data Network DNAI DN Access Identifier DNN Data Network Name DRX Discontinuous Reception DS-TT Device-side TSN translator ePDG evolved Packet Data Gateway EBI EPS Bearer Identity EUI Extended Unique Identifier FAR Forwarding Action Rule FN-BRG Fixed Network Broadband RG FN-CRG Fixed Network Cable RG FN-RG Fixed Network RG FQDN Fully Qualified Domain Name GFBR Guaranteed Flow Bit Rate GMLC Gateway Mobile Location Centre GPSI Generic Public Subscription Identifier GUAMI Globally Unique AMF Identifier HR Home Routed (roaming) IAB Integrated access and backhaul IMEI / TAC IMEI Type Allocation Code IPUPS Inter PLMN UP Security I-SMF Intermediate SMF I-UPF Intermediate UPF LADN Local Area Data Network LBO Local Break Out (roaming) LMF Location Management Function LoA Level of Automation LPP LTE Positioning Protocol LRF Location Retrieval Function MCX Mission Critical Service MDBV Maximum Data Burst Volume MFBR Maximum Flow Bit Rate MICO Mobile Initiated Connection Only MPS Multimedia Priority Service MPTCP Multi-Path TCP Protocol N3IWF Non-3GPP InterWorking Function N5CW Non-5G-Capable over WLAN NAI Network Access Identifier NEF Network Exposure Function NF Network Function NGAP Next Generation Application Protocol NID Network identifier NPN Non-Public Network NR New Radio NRF Network Repository Function NSI ID Network Slice Instance Identifier NSSAA Network Slice-Specific Authentication and Authorization NSSAAF Network Slice-Specific Authentication and Authorization Function NSSAI Network Slice Selection Assistance Information NSSF Network Slice Selection Function NSSP Network Slice Selection Policy NW-TT Network-side TSN translator NWDAF Network Data Analytics Function PCF Policy Control Function PDB Packet Delay Budget PDR Packet Detection Rule PDU Protocol Data Unit PEI Permanent Equipment Identifier PER Packet Error Rate PFD Packet Flow Description PNI-NPN Public Network Integrated Non-Public Network PPD Paging Policy Differentiation PPF Paging Proceed Flag PPI Paging Policy Indicator PSA PDU Session Anchor PTP Precision Time Protocol QFI QoS Flow Identifier QoE Quality of Experience RACS Radio Capabilities Signalling optimisation (R)AN (Radio) Access Network RG Residential Gateway RIM Remote Interference Management RQA Reflective QoS Attribute RQI Reflective QoS Indication RSN Redundancy Sequence Number SA NR Standalone New Radio SBA Service Based Architecture SBI Service Based Interface SCP Service Communication Proxy SD Slice Differentiator SEAF Security Anchor Functionality SEPP Security Edge Protection Proxy SMF Session Management Function SMSF Short Message Service Function SN Sequence Number SNPN Stand-alone Non-Public Network S-NSSAI Single Network Slice Selection Assistance Information SSC Session and Service Continuity SSCMSP Session and Service Continuity Mode Selection Policy SST Slice / Service Type SUCI Subscription Concealed Identifier SUPI Subscription Permanent Identifier SV Software Version TNAN Trusted Non-3GPP Access Network TNAP Trusted Non-3GPP Access Point TNGF Trusted Non-3GPP Gateway Function TNL Transport Network Layer TNLA Transport Network Layer Association TSC Time Sensitive Communication TSCAI TSC Assistance Information TSN Time Sensitive Networking TSN GM TSN Grand Master TSP Traffic Steering Policy TT TSN Translator TWIF Trusted WLAN Interworking Function UCMF UE radio Capability Management Function UDM Unified Data Management UDR Unified Data Repository UDSF Unstructured Data Storage Function UL Uplink UL CL Uplink Classifier UPF User Plane Function URLLC Ultra Reliable Low Latency Communication URRP-AMF UE Reachability Request Parameter for AMF URSP UE Route Selection Policy VID VLAN Identifier VLAN Virtual Local Area Network W-5GAN Wireline 5G Access Network W-5GBAN Wireline BBF Access Network W-5GCAN Wireline 5G Cable Access Network W-AGF Wireline Access Gateway Function

[0117] definition For the purposes of this document, the terms and definitions in 3GPP TR21.905[1] and below apply. Terms defined in this document take precedence over definitions in 3GPP TR21.905[1] where the same term appears.

[0118] This application claims the benefit of priority to Indian Patent Application No. 202011042823 filed on October 1, 2020, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0119] 600 UE 601 Antenna 602 Transceiver Circuit 603 User Interface 604 controller 605 memory 700 (R) AN node 701 Antenna 702 Transceiver Circuit 703 Network Interface 704 controller 705 memory 800 AMF 801 Transceiver Circuit 802 Controller 803 Memory 804 network interface

Claims

1. 1. A method for a user device, comprising: Communicates with the Access and Mobility Management Function (AMF), When radio coverage is lost and the user equipment maintains a single NSSAI in the Pending Network Slice Selection Assistance Information (NSSAI), the user equipment initiates a registration procedure when radio coverage returns. method.

2. A user device, a means for communicating with an Access and Mobility Management Function (AMF); means for initiating a registration procedure when radio coverage is lost and the user equipment maintains a Single NSSAI in a Pending Network Slice Selection Assistance Information (NSSAI) and returns to the radio coverage; A user device comprising:

Images