Patent Description:
Non-public networks (NPN) are intended for the sole use of a private entity such as an enterprise, and may be deployed in a variety of configurations, utilizing both virtual and physical elements. Specifically, they may be deployed as completely standalone networks, they may be hosted by a public land mobile network (PLMN), or they may be offered as a slice of a PLMN.

In any of these deployment options, it is expected that unauthorized user equipments (UEs), those that are not associated with the enterprise, will not attempt to access the non-public network, which could result in resources being used to reject that UE and thereby not be available for the UEs of the enterprise. It is also expected that UEs of the enterprise will not attempt to access a network they are not authorized to access. For example, some enterprise UEs may be restricted to only access the non-public network of the enterprise, even if PLMN coverage is available in the same geographic area. Other enterprise UEs may be able to access both a non-public network and a PLMN where specifically allowed.

<CIT> discloses a method for indicating local area data network (LADN) data network names (DNNs). A UE provides a list of configured LADN DNNs in a registration request message during a registration procedure. An Access and Mobility Management Function (AMF) determines LADN information for the UE by looking into configured LADN DNNs in the AMF and/or retrieved LADN authorization/subscription information. The LADN information includes a list of LADN DNNs and corresponding LADN service area(s) that the UE can use, including LADN DNNs that the UE can use in a current registration area. The AMF sends the LADN information to the UE in a registration accept message.

In situations where a UE connects to a Standalone NPN (SNPN) using credentials belonging to an entity separate from the SNPN, there is a need to support service continuity if that UE moves.

In another aspect, which is not specifically claimed herein, a method performed by a User Equipment (UE) operating in a wireless communication system is provided. The method comprises moving from a source network to a target network and transmitting a registration request message of a second registration procedure to an Access and mobility Management Function (AMF) of the target network. The registration request message includes i) a Registration Type set to Mobility Registration Update, ii) a <NUM> Globally Unique Temporary Identifier (<NUM>-GUTI) of the UE assigned by the source network; and iii) an indicator indicating that the UE has moved from another network.

The present disclosure may have various advantageous effects.

For example, during the registration procedure with the target network, the source network may delay and/or withhold deleting the context for an existing established HR PDU session. Thus, service continuity can be supported through an existing HR PDU session without requiring additional procedures to establish a new PDU session.

For example, the source network can inform the UE in advance whether it supports the N14 interface during the registration procedure. Thus, the UE can directly perform the initial registration procedure with the target network based on the network configuration and reduce the registration-related signaling between the UE and the AMF of the target network.

Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

Evolution of 3GPP LTE includes LTE-A (advanced), LTE-A Pro, and/or <NUM> new radio (NR).

Also, parentheses used in the present disclosure may mean "for example". In detail, when it is shown as "control information (PDCCH)", "PDCCH" may be proposed as an example of "control information". In other words, "control information" in the present disclosure is not limited to "PDCCH", and "PDCCH" may be proposed as an example of "control information". In addition, even when shown as "control information (i.e., PDCCH)", "PDCCH" may be proposed as an example of "control information".

AI refers to the field of studying artificial intelligence or the methodology that can create it, and machine learning refers to the field of defining various problems addressed in the field of AI and the field of methodology to solve them. Machine learning is also defined as an algorithm that increases the performance of a task through steady experience on a task.

Robot means a machine that automatically processes or operates a given task by its own ability. In particular, robots with the ability to recognize the environment and make self-determination to perform actions can be called intelligent robots. Robots can be classified as industrial, medical, home, military, etc., depending on the purpose or area of use. The robot can perform a variety of physical operations, such as moving the robot joints with actuators or motors. The movable robot also includes wheels, brakes, propellers, etc., on the drive, allowing it to drive on the ground or fly in the air.

Autonomous driving means a technology that drives on its own, and autonomous vehicles mean vehicles that drive without user's control or with minimal user's control. For example, autonomous driving may include maintaining lanes in motion, automatically adjusting speed such as adaptive cruise control, automatic driving along a set route, and automatically setting a route when a destination is set. The vehicle covers vehicles equipped with internal combustion engines, hybrid vehicles equipped with internal combustion engines and electric motors, and electric vehicles equipped with electric motors, and may include trains, motorcycles, etc., as well as cars. Autonomous vehicles can be seen as robots with autonomous driving functions.

Extended reality is collectively referred to as VR, AR, and MR. VR technology provides objects and backgrounds of real world only through computer graphic (CG) images. AR technology provides a virtual CG image on top of a real object image. MR technology is a CG technology that combines and combines virtual objects into the real world. MR technology is similar to AR technology in that they show real and virtual objects together. However, there is a difference in that in AR technology, virtual objects are used as complementary forms to real objects, while in MR technology, virtual objects and real objects are used as equal personalities.

NR supports multiples numerologies (and/or multiple subcarrier spacings (SCS)) to support various <NUM> services. For example, if SCS is <NUM>, wide area can be supported in traditional cellular bands, and if SCS is <NUM>/<NUM>, dense-urban, lower latency, and wider carrier bandwidth can be supported. If SCS is <NUM> or higher, bandwidths greater than <NUM> can be supported to overcome phase noise.

Referring to <FIG>, a first wireless device <NUM> and a second wireless device <NUM> may transmit/receive radio signals to/from an external device through a variety of RATs (e.g., LTE and NR).

In <FIG>, {the first wireless device <NUM> and the second wireless device <NUM>} may correspond to at least one of {the wireless device 100a to 100f and the BS <NUM>}, {the wireless device 100a to 100f and the wireless device 100a to 100f} and/or {the BS <NUM> and the BS <NUM>} of <FIG>.

The first wireless device <NUM> may include at least one transceiver, such as a transceiver <NUM>, at least one processing chip, such as a processing chip <NUM>, and/or one or more antennas <NUM>.

The processing chip <NUM> may include at least one processor, such a processor <NUM>, and at least one memory, such as a memory <NUM>. It is exemplarily shown in <FIG> that the memory <NUM> is included in the processing chip <NUM>. Additional and/or alternatively, the memory <NUM> may be placed outside of the processing chip <NUM>.

The processor <NUM> may control the memory <NUM> and/or the transceiver <NUM> and may be adapted to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. For example, the processor <NUM> may process information within the memory <NUM> to generate first information/signals and then transmit radio signals including the first information/signals through the transceiver <NUM>. The processor <NUM> may receive radio signals including second information/signals through the transceiver <NUM> and then store information obtained by processing the second information/signals in the memory <NUM>.

The memory <NUM> may be operably connectable to the processor <NUM>. The memory <NUM> may store various types of information and/or instructions. The memory <NUM> may store a software code <NUM> which implements instructions that, when executed by the processor <NUM>, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code <NUM> may implement instructions that, when executed by the processor <NUM>, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code <NUM> may control the processor <NUM> to perform one or more protocols. For example, the software code <NUM> may control the processor <NUM> to perform one or more layers of the radio interface protocol.

Herein, the processor <NUM> and the memory <NUM> may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver <NUM> may be connected to the processor <NUM> and transmit and/or receive radio signals through one or more antennas <NUM>. Each of the transceiver <NUM> may include a transmitter and/or a receiver. The transceiver <NUM> may be interchangeably used with radio frequency (RF) unit(s). In the present disclosure, the first wireless device <NUM> may represent a communication modem/circuit/chip.

The second wireless device <NUM> may include at least one transceiver, such as a transceiver <NUM>, at least one processing chip, such as a processing chip <NUM>, and/or one or more antennas <NUM>.

The processor <NUM> may control the memory <NUM> and/or the transceiver <NUM> and may be adapted to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. For example, the processor <NUM> may process information within the memory <NUM> to generate third information/signals and then transmit radio signals including the third information/signals through the transceiver <NUM>. The processor <NUM> may receive radio signals including fourth information/signals through the transceiver <NUM> and then store information obtained by processing the fourth information/signals in the memory <NUM>.

Herein, the processor <NUM> and the memory <NUM> may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver <NUM> may be connected to the processor <NUM> and transmit and/or receive radio signals through one or more antennas <NUM>. Each of the transceiver <NUM> may include a transmitter and/or a receiver. The transceiver <NUM> may be interchangeably used with RF unit. In the present disclosure, the second wireless device <NUM> may represent a communication modem/circuit/chip.

As an example, one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in the one or more processors <NUM> and <NUM>. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software and the firmware or software may be adapted to include the modules, procedures, or functions. Firmware or software adapted to perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be included in the one or more processors <NUM> and <NUM> or stored in the one or more memories <NUM> and <NUM> so as to be driven by the one or more processors <NUM> and <NUM>. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software in the form of code, commands, and/or a set of commands.

The one or more transceivers <NUM> and <NUM> may be connected to the one or more antennas <NUM> and <NUM> and the one or more transceivers <NUM> and <NUM> may be adapted to transmit and receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, through the one or more antennas <NUM> and <NUM>. In the present disclosure, the one or more antennas <NUM> and <NUM> may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).

The one or more transceivers <NUM> and <NUM> may convert received user data, control information, radio signals/channels, etc., from RF band signals into baseband signals in order to process received user data, control information, radio signals/channels, etc., using the one or more processors <NUM> and <NUM>. The one or more transceivers <NUM> and <NUM> may convert the user data, control information, radio signals/channels, etc., processed using the one or more processors <NUM> and <NUM> from the base band signals into the RF band signals. For example, the one or more transceivers <NUM> and <NUM> can up-convert OFDM baseband signals to OFDM signals by their (analog) oscillators and/or filters under the control of the one or more processors <NUM> and <NUM> and transmit the up-converted OFDM signals at the carrier frequency. The one or more transceivers <NUM> and <NUM> may receive OFDM signals at a carrier frequency and down-convert the OFDM signals into OFDM baseband signals by their (analog) oscillators and/or filters under the control of the one or more processors <NUM> and <NUM>.

In the implementations of the present disclosure, a UE may operate as a transmitting device in uplink (UL) and as a receiving device in downlink (DL). In the implementations of the present disclosure, a BS may operate as a receiving device in UL and as a transmitting device in DL. Hereinafter, for convenience of description, it is mainly assumed that the first wireless device <NUM> acts as the UE, and the second wireless device <NUM> acts as the BS. For example, the processor(s) <NUM> connected to, mounted on or launched in the first wireless device <NUM> may be adapted to perform the UE behavior according to an implementation of the present disclosure or control the transceiver(s) <NUM> to perform the UE behavior according to an implementation of the present disclosure. The processor(s) <NUM> connected to, mounted on or launched in the second wireless device <NUM> may be adapted to perform the BS behavior according to an implementation of the present disclosure or control the transceiver(s) <NUM> to perform the BS behavior according to an implementation of the present disclosure.

The communication unit <NUM> may include a communication circuit <NUM> and transceiver(s) <NUM>. For example, the communication circuit <NUM> may include the one or more processors <NUM> and <NUM> of <FIG> and/or the one or more memories <NUM> and <NUM> of <FIG>. For example, the transceiver(s) <NUM> may include the one or more transceivers <NUM> and <NUM> of <FIG> and/or the one or more antennas <NUM> and <NUM> of <FIG>. The control unit <NUM> is electrically connected to the communication unit <NUM>, the memory unit <NUM>, and the additional components <NUM> and controls overall operation of each of the wireless devices <NUM> and <NUM>. For example, the control unit <NUM> may control an electric/mechanical operation of each of the wireless devices <NUM> and <NUM> based on programs/code/commands/information stored in the memory unit <NUM>.

As an example, the control unit <NUM> may be configured by a set of a communication control processor, an application processor (AP), an electronic control unit (ECU), a graphical processing unit, and a memory control processor. As another example, the memory unit <NUM> may be configured by a RAM, a DRAM, a ROM, a flash memory, a volatile memory, a non-volatile memory, and/or a combination thereof.

Referring to <FIG>, a UE <NUM> may correspond to the first wireless device <NUM> of <FIG> and/or the wireless device <NUM> or <NUM> of <FIG>.

The processor <NUM> may be adapted to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The processor <NUM> may be adapted to control one or more other components of the UE <NUM> to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. Layers of the radio interface protocol may be implemented in the processor <NUM>. The processor <NUM> may include ASIC, other chipset, logic circuit and/or data processing device. The processor <NUM> may be an application processor. The processor <NUM> may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). An example of the processor <NUM> may be found in SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™ series of processors made by Samsung®, A series of processors made by Apple®, HELIO™ series of processors made by MediaTek®, ATOM™ series of processors made by Intel® or a corresponding next generation processor.

<FIG> shows an example of <NUM> system architecture to which implementations of the present disclosure is applied.

The <NUM> system (5GS) architecture consists of the following network functions (NF).

Furthermore, the following network functions may be considered.

<FIG> depicts the <NUM> system architecture in the non-roaming case, using the reference point representation showing how various network functions interact with each other.

In <FIG>, for the sake of clarity of the point-to-point diagrams, the UDSF, NEF and NRF have not been depicted. However, all depicted Network Functions can interact with the UDSF, UDR, NEF and NRF as necessary.

For clarity, the UDR and its connections with other NFs, e.g., PCF, are not depicted in <FIG>. For clarity, the NWDAF and its connections with other NFs, e.g., PCF, are not depicted in <FIG>.

The <NUM> system architecture contains the following reference points:.

The following reference points show the interactions that exist between the NF services in the NFs.

In some cases, a couple of NFs may need to be associated with each other to serve a UE.

A registration procedure is described. Section <NUM>. <NUM> of 3GPP TS <NUM> V16. <NUM> (<NUM>-<NUM>) can be referred.

<FIG> and <FIG> show an example of a registration procedure to which implementations of the present disclosure is applied.

A UE needs to register with the network to get authorized to receive services, to enable mobility tracking and to enable reachability. The UE initiates the registration procedure using one of the following registration types:.

The general registration procedure in <FIG> and <FIG> applies on all these registration procedures, but the periodic registration update need not include all parameters that are used in other registration cases.

The general registration procedure in <FIG> and <FIG> is also used for the case of registration in 3GPP access when the UE is already registered in a non-3GPP access, and vice versa. Registration in 3GPP access when the UE is already registered in a non-3GPP access scenario may require an AMF change.

First, procedures of <FIG> are described.

The Registration Request message may include AN parameters. In the case of NG-RAN, the AN parameters include, e.g., <NUM> SAE temporary mobile subscriber identity (<NUM>-S-TMSI) or globally unique AMF ID (GUAMI), the selected public land mobile network (PLMN) ID (or PLMN ID and network identifier (NID)) and Requested network slice selection assistance information (NSSAI). The AN parameters also include establishment cause. The establishment cause provides the reason for requesting the establishment of an RRC connection. Whether and how the UE includes the Requested NSSAI as part of the AN parameters is dependent on the value of the access stratum connection establishment NSSAI inclusion mode parameter.

The Registration Request message may include a registration type. The registration type indicates if the UE wants to perform an initial registration (i.e., the UE is in RM-DEREGISTERED state), a mobility registration update (i.e., the UE is in RM-REGISTERED state and initiates a registration procedure due to mobility or due to the UE needs to update its capabilities or protocol parameters, or to request a change of the set of network slices it is allowed to use), a periodic registration update (i.e., the UE is in RM-REGISTERED state and initiates a registration procedure due to the periodic registration update timer expiry) or an emergency registration (i.e., the UE is in limited service state).

When the UE is performing an initial registration, the UE shall indicate its UE identity in the Registration Request message as follows, listed in decreasing order of preference:.

When the UE performing an initial registration has both a valid EPS GUTI and a native <NUM>-GUTI, the UE shall also indicate the native <NUM>-GUTI as additional GUTI. If more than one native <NUM>-GUTIs are available, the UE shall select the <NUM>-GUTI in decreasing order of preference among items (ii)-(iv) in the list above.

When the UE is performing an initial registration with a native <NUM>-GUTI, then the UE shall indicate the related GUAMI information in the AN parameters. When the UE is performing an initial registration with its SUCI, the UE shall not indicate any GUAMI information in the AN parameters.

For an emergency registration, the SUCI shall be included if the UE does not have a valid <NUM>-GUTI available; the permanent equipment identifier (PEI) shall be included when the UE has no subscriber permanent identifier (SUPI) and no valid <NUM>-GUTI. In other cases, the <NUM>-GUTI is included and it indicates the last serving AMF.

The Registration Request message may also include security parameters, PDU Session Status, etc. The security parameters are used for authentication and integrity protection. The PDU Session Status indicates the previously established PDU sessions in the UE. When the UE is connected to the two AMFs belonging to different PLMN via 3GPP access and non-3GPP access then the PDU Session status indicates the established PDU Session of the current PLMN in the UE.

(<NUM>) Step <NUM>: The (R)AN selects an AMF.

If a <NUM>-S-TMSI or GUAMI is not included or the <NUM>-S-TMSI or GUAMI does not indicate a valid AMF, the (R)AN, based on (R)AT and requested NSSAI, if available, selects an AMF.

If UE is in CM-CONNECTED state, the (R)AN can forward the Registration Request message to the AMF based on the N2 connection of the UE.

If the (R)AN cannot select an appropriate AMF, it forwards the Registration Request message to an AMF which has been configured, in the (R)AN, to perform AMF selection.

(<NUM>) Step <NUM>: The (R)AN transmits a Registration Request message to the new AMF. The Registration Request message corresponds to N2 message.

The Registration Request message may include whole information and/or a part of information included in the Registration Request message received from the UE which is described in step <NUM>.

The Registration Request message may include N2 parameters. When NG-RAN is used, the N2 parameters include the selected PLMN ID (or PLMN ID and NID), location information and cell identity related to the cell in which the UE is camping, UE context request which indicates that a UE context including security information needs to be setup at the NG-RAN. When NG-RAN is used, the N2 parameters shall also include the establishment cause.

If the Registration type indicated by the UE is Periodic Registration Update, then steps <NUM> to <NUM> may be omitted.

(<NUM>) Step <NUM>: If the UE's <NUM>-GUTI was included in the Registration Request message and the serving AMF has changed since last registration procedure, the new AMF may invoke the Namf_Communication_UEContextTransfer service operation on the old AMF including the complete registration request non-access stratum (NAS) message to request the UE's SUPI and UE context.

(<NUM>) Step <NUM>: The Old AMF may respond to the new AMF for the Namf_Communication_UEContextTransfer invocation by including the UE's SUPI and UE context.

(<NUM>) Step <NUM>: If the SUCI is not provided by the UE nor retrieved from the old AMF, the identity request procedure may be initiated by the new AMF sending the Identity Request message to the UE requesting the SUCI.

(<NUM>) Step <NUM>: The UE may respond with an Identity Response message including the SUCI. The UE derives the SUCI by using the provisioned public key of the home PLMN (HPLMN).

(<NUM>) Step <NUM>: The new AMF may decide to initiate UE authentication by invoking an AUSF. In that case, the new AMF selects an AUSF based on SUPI or SUCI.

(<NUM>) Step <NUM>: Authentication/security may be established by the UE, new AMF, AUSF and/or UDM.

(<NUM>) Step <NUM>: If the AMF has changed, the new AMF may notify the old AMF that the registration of the UE in the new AMF is completed by invoking the Namf_Communication_RegistrationCompleteNotify service operation. If the authentication/security procedure fails, then the registration shall be rejected, and the new AMF may invoke the Namf_Communication_RegistrationCompleteNotify service operation with a reject indication reason code towards the old AMF. The old AMF may continue as if the UE context transfer service operation was never received.

(<NUM>) Step <NUM>: If the PEI was not provided by the UE nor retrieved from the old AMF, the Identity Request procedure may be initiated by the new AMF sending an Identity Request message to the UE to retrieve the PEI. The PEI shall be transferred encrypted unless the UE performs emergency registration and cannot be authenticated.

(<NUM>) Step <NUM>: Optionally, the new AMF may initiate ME identity check by invoking the N5g-eir _EquipmentIdentityCheck_Get service operation.

Now, procedures of <FIG>, which follow the procedures of <FIG>, are described.

(<NUM>) Step <NUM>: If step <NUM> below is to be performed, the new AMF, based on the SUPI, may select a UDM, then UDM may select a UDR instance.

(<NUM>) Step <NUM>: The new AMF may register with the UDM.

(<NUM>) Step <NUM>: The new AMF may select a PCF.

(<NUM>) Step <NUM>: The new AMF may optionally perform an AM Policy Association Establishment/Modification.

(<NUM>) Step <NUM>: The new AMF may transmit Update/Release SM Context message (e.g., Nsmf_PDUSession_UpdateSMContext and/or Nsmf_PDUSession_ReleaseSMContext) to the SMF.

(<NUM>) Step <NUM>: If the new AMF and the old AMF are in the same PLMN, the new AMF may send a UE Context Modification Request to the N3IWF/TNGF/W-AGF.

(<NUM>) Step <NUM>: The N3IWF/TNGF/W-AGF may send a UE Context Modification Response to the new AMF.

(<NUM>) Step <NUM>: After the new AMF receives the response message from the N3IWF/TNGF/W-AGF in step <NUM>, the new AMF may register with the UDM.

(<NUM>) Step <NUM>: The new AMF transmits a Registration Accept message to the UE.

The new AMF sends a Registration Accept message to the UE indicating that the Registration Request has been accepted. <NUM>-GUTI is included if the new AMF allocates a new <NUM>-GUTI. If the UE is already in RM-REGISTERED state via another access in the same PLMN, the UE shall use the <NUM>-GUTI received in the Registration Accept message for both registrations. If no <NUM>-GUTI is included in the Registration Accept message, then the UE uses the <NUM>-GUTI assigned for the existing registration also for the new registration. If the new AMF allocates a new registration area, it shall send the registration area to the UE via Registration Accept message. If there is no registration area included in the Registration Accept message, the UE shall consider the old registration area as valid. Mobility Restrictions is included in case mobility restrictions applies for the UE and registration type is not emergency registration. The new AMF indicates the established PDU sessions to the UE in the PDU Session status. The UE removes locally any internal resources related to PDU sessions that are not marked as established in the received PDU Session status. When the UE is connected to the two AMFs belonging to different PLMN via 3GPP access and non-3GPP access then the UE removes locally any internal resources related to the PDU session of the current PLMN that are not marked as established in received PDU Session status. If the PDU Session status information was in the Registration Request message, the new AMF shall indicate the PDU Session status to the UE.

The Allowed NSSAI provided in the Registration Accept message is valid in the registration area and it applies for all the PLMNs which have their tracking areas included in the registration area. The Mapping Of Allowed NSSAI is the mapping of each S-NSSAI of the Allowed NSSAI to the HPLMN S-NSSAIs. The Mapping Of Configured NSSAI is the mapping of each S-NSSAI of the Configured NSSAI for the serving PLMN to the HPLMN S-NSSAIs.

Furthermore, optionally the new AMF performs a UE Policy Association Establishment.

(<NUM>) Step <NUM>: The UE may send a Registration Complete message to the new AMF when it has successfully updated itself.

The UE may send a Registration Complete message to the new AMF to acknowledge if a new <NUM>-GUTI was assigned.

(<NUM>) Step <NUM>: For registration over 3GPP Access, if the new AMF does not release the signaling connection, the new AMF may send the RRC Inactive Assistance Information to the NG-RAN. For registration over non-3GPP Access, if the UE is also in CM-CONNECTED state on 3GPP access, the new AMF may send the RRC Inactive Assistance Information to the NG-RAN.

(<NUM>) Step <NUM>: The new AMF may perform information update towards the UDM.

(<NUM>) Step <NUM>: The UE may execute Network Slice-Specific Authentication and Authorization procedure.

Support of non-3GPP access is described. Section <NUM>. <NUM> of 3GPP TS <NUM> V16. <NUM> (<NUM>-<NUM>) can be referred.

<FIG> shows an example of non-roaming architecture for 5GC with untrusted non-3GPP access to which implementations of the present disclosure is applied.

The <NUM> Core Network supports connectivity of UEs via non-3GPP access networks, e.g., wireless local area network (WLAN) access networks.

The <NUM> Core Network supports both untrusted non-3GPP access networks and trusted non-3GPP access networks (TNANs).

An untrusted non-3GPP access network shall be connected to the <NUM> Core Network via a N3IWF, whereas a trusted non-3GPP access network shall be connected to the <NUM> Core Network via a TNGF. Both the N3IWF and the TNGF interface with the <NUM> Core Network CP and UP functions via the N2 and N3 interfaces, respectively.

A non-3GPP access network may advertise the PLMNs for which it supports trusted connectivity and the type of supported trusted connectivity (e.g., "<NUM> connectivity"). Therefore, the UEs can discover the non-3GPP access networks that can provide trusted connectivity to one or more PLMNs.

When the UE decides to use untrusted non-3GPP access to connect to a <NUM> Core Network in a PLMN:.

When the UE decides to use trusted non-3GPP access to connect to a <NUM> Core Network in a PLMN:.

A UE that accesses the <NUM> Core Network over a standalone non-3GPP access shall, after UE registration, support NAS signaling with <NUM> Core Network control-plane functions using the N1 reference point.

When a UE is connected via a NG-RAN and via a standalone non-3GPP access, multiple N1 instances shall exist for the UE, i.e., there shall be one N1 instance over NG-RAN and one N1 instance over non-3GPP access.

A UE simultaneously connected to the same <NUM> Core Network of a PLMN over a 3GPP access and a non-3GPP access shall be served by a single AMF in this <NUM> Core Network.

When a UE is connected to a 3GPP access of a PLMN, if the UE selects a N3IWF and the N3IWF is located in a PLMN different from the PLMN of the 3GPP access, e.g., in a different VPLMN or in the HPLMN, the UE is served separately by the two PLMNs. The UE is registered with two separate AMFs. PDU sessions over the 3GPP access are served by V-SMFs different from the V-SMF serving the PDU Sessions over the non-3GPP access. The same can be true when the UE uses trusted non-3GPP access, i.e., the UE may select one PLMN for 3GPP access and a different PLMN for trusted non-3GPP access.

The PLMN selection for the 3GPP access does not depend on the PLMN that is used for non-3GPP access. In other words, if a UE is registered with a PLMN over a non-3GPP access, the UE performs PLMN selection for the 3GPP access independently of this PLMN.

A UE shall establish an IPsec tunnel with the N3IWF or with the TNGF in order to register with the <NUM> Core Network over non-3GPP access.

It shall be possible to maintain the UE NAS signaling connection with the AMF over the non-3GPP access after all the PDU sessions for the UE over that access have been released or handed over to 3GPP access.

N1 NAS signaling over standalone non-3GPP accesses shall be protected with the same security mechanism applied for N1 over a 3GPP access.

Stand-alone non-public network (SNPN) is described. Section <NUM>. <NUM> of 3GPP TS <NUM> V16. <NUM> (<NUM>-<NUM>) can be referred.

An SNPN is operated by an NPN operator and not relying on network functions provided by a PLMN. On the other hand, a public network integrated (PNI) NPN is a non-public network deployed with the support of a PLMN.

SNPN 5GS deployments are based on the architecture depicted above in <FIG>, the architecture for 5GC with untrusted non-3GPP access, described above in <FIG>, for access to SNPN services via a PLMN (and vice versa) and the additional functionality described below.

Interworking with EPS is not supported for SNPN.

The combination of a PLMN ID and network identifier (NID) identifies an SNPN.

The NID shall support two assignment models:.

An optional human-readable network name helps to identify an SNPN during manual SNPN selection.

When a UE is set to operate in SNPN access mode, the UE does not perform normal PLMN selection procedures.

UEs operating in SNPN access mode read the available PLMN IDs and list of available NIDs from the broadcast system information and take them into account during network selection.

For automatic network selection, the UE selects and attempts to register with the available SNPN identified by a PLMN ID and NID for which the UE has SUPI and credentials.

For manual network selection, UEs operating in SNPN access mode provide to the user the list of NIDs and related human-readable names (if available) of the available SNPNs the UE has respective SUPI and credentials for.

When a UE performs initial registration to an SNPN, the UE shall indicate the selected NID and the corresponding PLMN ID to NG-RAN. NG-RAN shall inform the AMF of the selected PLMN ID and NID.

To access PLMN services, a UE in SNPN access mode that has successfully registered with an SNPN may perform another registration via the SNPN user plane with a PLMN (using the credentials of that PLMN) following the same architectural principles as specified above for the non-3GPP access and the SNPN taking the role of "Untrusted non-3GPP access" in <FIG>.

To access SNPN services, a UE that has successfully registered with a PLMN may perform another registration via the PLMN user plane with an SNPN (using the credentials of that SNPN) following the same architectural principles as specified above for the non-3GPP access and the PLMN taking the role of "Untrusted non-3GPP access" in <FIG>.

One of the objectives for enhancements of NPN in 3GPP Rel-<NUM> is to support service continuity for UE mobility in situations where the UE has accessed the SNPN using credentials owned by an entity separate from the SNPN. For example, a scenario may be considered where a UE accesses to SNPN #<NUM> using credentials owned by a separate entity, and the UE moves from SNPN #<NUM> to SNPN #<NUM>. As another example, a scenario may be considered where a UE accesses SNPN #<NUM> using credentials owned by a PLMN, and the UE moves from SNPN #<NUM> to that PLMN.

To support service continuity for the UE mobility, two solutions may be considered as follows.

In solution <NUM>, the following definitions may be used.

Visited-SNPN (V-SNPN): An SNPN for which the UE does not have a subscription associated with the SNPN's identity (PLMN ID and NID combination) and which supports access using credentials (Home SP credentials) owned by an entity separate from the SNPN.

Home Service Provider (Home SP): An entity separate from the SNPN that supports that its subscription is used to access a (different) SNPN. Also referred simply as "Service Provider".

The following are the main principles of the solution <NUM>.

The UE is configured with the following.

If the Rel-<NUM> UE does not need to be prevented from attempting to register with a Rel-<NUM> SNPN completely, the Rel-<NUM> UE may attempt to connect to a Rel-<NUM> SNPN (e.g., because the serving SNPN ID is configured in the UE configured lists). In this case, the SNPN rejects the registration attempt with an appropriate rejection cause (e.g., #<NUM> (Temporarily not authorized for this SNPN) or #<NUM> (Permanently not authorized for this SNPN). This will prevent the Rel-<NUM> UEs (either temporarily or permanently) from future registration attempts with this SNPN.

If the Rel-<NUM> UE needs to be prevented from attempting to register with a Rel-<NUM> SNPN completely, then it is proposed to use a new SIB indication (with the meaning "access using Home SP credentials is supported") so that Rel-<NUM> UEs can only attempt to connect to an SNPN using Home SP credentials when this indication is advertised.

The principles for SNPN discovery and selection with support for SPs is as given below.

If the UE is in coverage of the SP's SNPN (i.e., the information broadcasted on the radio interface includes the PLMN ID + NID tuple of the SNPN), the UE selects this SNPN.

Key idea of solution <NUM> is that a V-SNPN broadcasts information that enables a UE to determine whether the UE can access the V-SNPN using any of the Home SP credentials that the UE is configured with.

In particular, a V-SNPN may broadcast IDs of Home SPs that the V-SNPN has an agreement with, i.e., which supports access to the V-SNPN using the credentials of those Home SPs.

A V-SNPN may also broadcast the IDs of Home SP Groups that the V-SNPN has an agreement with for access to the V-SNPN using the credentials of any of the Home SPs that are part of the Home SP Group. The UE is assumed to be configured by the Home SP with one or more Home SP Groups that the Home SP is part of so that the UE can select a V-SNPN that supports one of the Home SP Groups the UE is configured with. One benefit of the Home SP Group is that the V-SNPN does not need to broadcast the IDs of all the Home SPs that are part of the Home SP Group but only needs to broadcast the Home SP Group ID instead.

Home SP Group examples include the followings.

NG-RAN nodes which support access using Home SP credentials broadcast the following information per SNPN:.

A UE is configured with a Home SP subscription and the corresponding Home SP ID.

For SNPN subscription, a Home SP subscription issued by an SNPN may optionally contain the following additional information.

The above information (except the user-controlled list) can be updated by the Home SP using the UE Configuration Update procedure.

For SNPN subscription, the UE operates in SNPN access mode.

For PLMN subscription, a Home SP subscription issued by a PLMN may optionally contain the following additional information.

For PLMN subscription, the UE does not operate in SNPN access mode.

The procedures for using an SNPN subscription are described.

In automatic network selection and registration procedure, if the UE's Home SP network is not available, then the UE discovers and selects an SNPN as follows.

Once the UE has selected an SNPN according to the procedure above, the UE performs the registration procedure. The UE provides the SUCI of the Home SP subscription. The UE is authenticated by the Home SP.

In manual network selection and registration procedure, the UE presents available SNPNs that broadcast the indication that access using Home SP credentials is supported for selection.

Once the user has selected an SNPN from the available networks, the UE performs the registration procedure. The UE provides the SUCI of the Home SP subscription. The UE is authenticated by the Home SP.

Procedures using a PLMN subscription are described.

In automatic network selection and registration procedure, if the UE's RPLMN (Registered PLMN) or (E)HPLMN is not available, then the UE discovers and selects an SNPN or PLMN as follows.

Once the UE has selected an SNPN or PLMN according to the procedure above, the UE performs the registration procedure. The UE provides the SUCI of the Home SP subscription. The UE is authenticated by the Home SP.

In manual network selection and registration procedure, the UE presents the following networks for selection.

Once the user has selected an SNPN or PLMN from the available networks, the UE performs the registration procedure. The UE provides the SUCI of the Home SP subscription. The UE is authenticated by the Home SP.

Session continuity support is described.

If a UE is registered with a V-SNPN using a Home SP subscription moves to a different V-SNPN that supports access using Home SP credentials for the same Home SP but no N14 interface between source V-SNPN and target V-SNPN, then the UE attempts to transfer PDU sessions to the target V-SNPN using the PDU Session Establishment procedure with Existing PDU Session indication.

If a UE is registered with a V-SNPN using a Home SP subscription (where Home SP = PLMN) moves to a PLMN which does not support the N14 interface between V-SNPN and PLMN, then the UE attempts to transfer PDU sessions to the PLMN using the PDU Session Establishment procedure with Existing PDU Session indication.

If a UE is registered with a PLMN and moves to a V-SNPN that supports access using Home SP credentials for the UE's HPLMN but does not support the N14 interface between V-SNPN and PLMN, then the UE attempts to transfer PDU sessions to the target V-SNPN using the PDU Session Establishment procedure with Existing PDU Session indication.

Session continuity is only supported for PDU sessions anchored in the Home SP network.

As described in solution <NUM> and/or solution <NUM> above, in a scenario where a UE accesses to a source network using credentials owned by a separate entity and moves to a target network (e.g., another SNPN and/or PLMN) where no N14 interface exists between the source network and the target network, a PDU session establishment procedure including "Existing PDU session" indication may be performed for handover of a Home-Routed (HR) PDU session. However, before the PDU session establishment procedure for the PDU session to be handed over is finalized in the target network, the AMF of the source network may release the context for the HR PDU session. In this case, the service cannot continue to be provided because the UE has to establish a new HR PDU session in place of the HR PDU session already in use.

Hereinafter, a method for ensuring service continuity between networks that do not have an N14 interface according to the present disclosure will be described.

According to implementations of the present disclosure, a UE may inform the target network that it has moved from the source network during the registration procedure. Upon receiving this, the AMF of the target network may inform the UDM of the home SP of that fact, together with an indication that no N14 interface exists between the target network and the source network. Upon receiving this, the UDM of the home SP may announce the de-registration to the source network, along with an indication that no N14 interface exists between the target network and the source network. Upon receiving this, the AMF of the source network may defer deleting the context for the HR PDU session.

In the following description, new service operations other than conventional service operations may be defined and used for service operations between NFs. Also, in the following description, new N2 messages other than conventional N2 messages may be defined and used for N2 messages exchanged between the AMF and the NG-RAN. Furthermore, in the following description, a new RRC message other than a conventional RRC message may be defined and used for RRC messages exchanged between the NG-RAN and the UE.

In the following description, some of the steps may be performed simultaneously and/or in parallel, or may be performed in an alternating order.

In the following description, the designations of indications and/or parameter information are by way of example only. The designations of such indications and/or parameter information may be substituted with other designations for the procedures/purposes/methods described herein.

The following drawings are created to explain specific embodiments of the present disclosure. The names of the specific devices or the names of the specific signals/messages/fields shown in the drawings are provided by way of example, and thus the technical features of the present disclosure are not limited to the specific names used in the following drawings.

<FIG> shows an example of a method performed by an AMF of a source network to which implementations of the present disclosure is applied.

In step S900, the method comprises receiving a deregistration notification message from a UDM of a Home SP. The deregistration notification message informs that i) a UE has moved from the source network to a target network, and ii) there is no N14 interface between the source network and the target network.

In some implementations, the deregistration notification message may be received based on the target network failing to retrieve the UE context via the N14 interface from the source network. In some implementations, the deregistration notification message may be received based on the UDM of the home SP receiving information from an AMF of the target network informing that the UE has moved to the target network which does not have the N14 interface with the source network. That is, if the target network fails to retrieve the UE context via the N14 interface from the source network, the UDM of the home SP receives information from an AMF of the target network informing that the UE has moved to the target network which does not have the N14 interface with the source network, and accordingly, the deregistration notification message may be received.

In step S910, the method comprises, after receiving the deregistration notification message, starting a timer.

In some implementations, the context status notification message may be received based on the SMF of the source network receiving information from the SMF of the home SP informing that the PDU session associated with the UE has been handed over from the source network to the target network. That is, if the SMF of the source network receives information from the SMF of the home SP informing that the PDU session associated with the UE has been handed over from the source network to the target network, the context status notification message may be received accordingly.

In some implementations, the PDU session may be a HR PDU session that is anchored to the home SP.

In some implementations, a value of the timer may be set such that handover of the PDU session can be completed before the timer completes.

In step S920, the method comprises, while the timer is running, delaying deletion of a UE context of the UE within the source network.

In step S930, the method comprises receiving a context status notification message from a SMF of the source network. The context status notification message may inform that a PDU session associated with the UE has been handed over from the source network to the target network.

In step S940, the method comprises, based on expiry of the timer, deleting the UE context of the UE within the source network.

In some implementations, the home SP may have credentials that are used for the UE to access the source network.

In some implementations, the home SP may be a SNPN and/or a PLMN.

In some implementations, the home SP may have an SLA with the source network and/or the target network.

In some implementations, the source network and/or the target network may be a SNPN and/or a PLMN.

<FIG> shows an example of a method performed by a UE to which implementations of the present disclosure is applied.

In step S1000, the method comprises performing a first registration procedure with a source network.

In step S1010, the method comprises performing a PDU session establishment procedure with the source network.

In step S1020, the method comprises moving from the source network to a target network and transmitting a registration request message of a second registration procedure to an AMF of the target network. The registration request message includes i) a Registration Type set to Mobility Registration Update, ii) a <NUM>-GUTI of the UE assigned by the source network; and iii) an indicator indicating that the UE has moved from another network.

In step S1030, the method comprises, based on absence of an N14 interface between the source network and the target network, transmitting a SUCI of the UE to the AMF of the target network.

In step S1040, the method comprises completing the second registration procedure with the target network.

In some implementations, a PDU session established by the PDU session establishment procedure may be a HR PDU session that is anchored to a Home SP, and the HR PDU session may be handed over from the source network to the target network.

In some implementations, the method may further comprise, after completing the second registration procedure, transmitting to the AMF of the target network a PDU session establishment request message including an "Existing PDU session" indication for the HR PDU session.

In some implementations, the UE may be in communication with at least one of a mobile device, a network, and/or autonomous vehicles other than the UE.

Furthermore, the method in perspective of the UE described above in <FIG> may be performed by the first wireless device <NUM> shown in <FIG>, the wireless device <NUM> shown in <FIG>, and/or the UE <NUM> shown in <FIG>.

More specifically, the UE comprises at least one transceiver, at least one processor, and at least one memory operably connectable to the at least one processor. The at least one memory stores instructions to cause the at least one processor to perform operations below.

The UE performs a first registration procedure with a source network.

The UE performs a PDU session establishment procedure with the source network.

The UE moves from the source network to a target network and transmits, via the at least one transceiver, a registration request message of a second registration procedure to an AMF of the target network. The registration request message includes i) a Registration Type set to Mobility Registration Update, ii) a <NUM>-GUTI of the UE assigned by the source network; and iii) an indicator indicating that the UE has moved from another network.

based on absence of an N14 interface between the source network and the target network, The UE transmits, via the at least one transceiver, a SUCI of the UE to the AMF of the target network.

The UE completes the second registration procedure with the target network.

Furthermore, the method in perspective of the UE described above in <FIG> may be performed by control of the processor <NUM> included in the first wireless device <NUM> shown in <FIG>, by control of the communication unit <NUM> and/or the control unit <NUM> included in the wireless device <NUM> shown in <FIG>, and/or by control of the processor <NUM> included in the UE <NUM> shown in <FIG>.

More specifically, a processing apparatus operating in a wireless communication system comprises at least one processor, and at least one memory operably connectable to the at least one processor. The at least one processor is adapted to perform operations comprising: performing a first registration procedure with a source network; performing a PDU session establishment procedure with the source network; moving from the source network to a target network and generating a registration request message of a second registration procedure with the target network, wherein the registration request message includes i) a Registration Type set to Mobility Registration Update, ii) a <NUM>-GUTI of the UE assigned by the source network; and iii) an indicator indicating that the UE has moved from another network; based on absence of an N14 interface between the source network and the target network, generating a SUCI; and completing the second registration procedure with the target network.

Furthermore, the method in perspective of the UE described above in <FIG> may be performed by a software code <NUM> stored in the memory <NUM> included in the first wireless device <NUM> shown in <FIG>.

The technical features of the present disclosure may be embodied directly in hardware, in a software executed by a processor, or in a combination of the two. For example, a method performed by a wireless device in a wireless communication may be implemented in hardware, software, firmware, or any combination thereof. For example, a software may reside in RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disk, a removable disk, a CD-ROM, or any other storage medium.

Some example of storage medium may be coupled to the processor such that the processor can read information from the storage medium. For other example, the processor and the storage medium may reside as discrete components.

The computer-readable medium may include a tangible and non-transitory computer-readable storage medium.

For example, non-transitory computer-readable media may include RAM such as synchronous dynamic random access memory (SDRAM), ROM, non-volatile random access memory (NVRAM), EEPROM, flash memory, magnetic or optical data storage media, or any other medium that can be used to store instructions or data structures. Non-transitory computer-readable media may also include combinations of the above.

In addition, the method described herein may be realized at least in part by a computer-readable communication medium that carries or communicates code in the form of instructions or data structures and that can be accessed, read, and/or executed by a computer.

According to some implementations of the present disclosure, a non-transitory computer-readable medium (CRM) has stored thereon a plurality of instructions.

More specifically, CRM stores instructions to cause at least one processor to perform operations. The operations comprise: performing a first registration procedure with a source network; performing a PDU session establishment procedure with the source network; moving from the source network to a target network and generating a registration request message of a second registration procedure with the target network, wherein the registration request message includes i) a Registration Type set to Mobility Registration Update, ii) a <NUM>-GUTI of the UE assigned by the source network; and iii) an indicator indicating that the UE has moved from another network; based on absence of an N14 interface between the source network and the target network, generating a SUCI; and completing the second registration procedure with the target network.

Various implementations of the present disclosure are described below.

<FIG> show an example of procedure to support service continuity for HR PDU session in absence of N14 interface between a source network and a target network, to which the first implementation of the present disclosure is applied.

In the first implementation of the present disclosure described in the procedures of <FIG>, the home SP may be an SNPN or a PLMN. The source network and/or the target network may also be SNPNs or PLMNs.

The procedures of <FIG> assume that the source network, home SP, and target network are all different. However, the procedures of <FIG> are also applicable when the source network and home SP are the same and/or the target network and home SP are the same. It is assumed that there is no N14 interface between the source network and the target network. It is also assumed that both the source network and the target network have an SLA with the home SP, and therefore have interfaces N8, N16, N9, etc..

First, <FIG> is described. <FIG> describes steps <NUM> to <NUM> of the procedure.

Step <NUM>: The UE is registered in the source network according to the registration procedure described in <FIG>.

Step <NUM>: The UE performs a PDU session establishment procedure to receive services from the source network. The PDU session may be an HR PDU session anchored to the home SP.

In some implementations, the PDU session establishment procedure may be performed for non-roaming and Local BreakOut (LBO) PDU sessions if the source network and home SP are the same.

Step <NUM>: The UE moves from the source network to the target network.

Step <NUM>: When the UE moves out of the tracking area established by the source network and enters a new network area, the UE does not know if there is an N14 interface between the source network and the target network. Therefore, the UE transmits a registration request message with the registration type set to mobility registration update to the AMF of the target network via the NG-RAN of the target network. The registration request message may include the <NUM>-GUTI assigned by the source network. In addition, to inform the AMF of the target network that the UE has moved from another network, the UE may include a "Mobility from other network" indication in the registration request message.

In some implementations, the UE may select a new SNPN and/or PLMN and perform initial registration with the selected target network because it has moved out of the source network (e.g., SNPN) it is currently being served. In this case, it may go directly to step <NUM>, which will be discussed later. In this case, to inform the AMF of the target network that the UE has moved from another network, the UE may still include a "Mobility from other network" indication in the registration request message.

In some implementations, a new registration type may be set and transmitted to the AMF of the target network instead of the "Mobility from other network" indication. Alternatively, the source network's 5GMM status, i.e., 5GMM-REGISTERED, may be indicated to indicate that it has moved from another network.

Step <NUM>: The AMF of the target network finds the AMF of the source network and attempts to retrieve the UE context using the <NUM>-GUTI received from the UE in step <NUM>. However, since there is no N14 interface between the AMF of the target network and the AMF of the source network, the AMF of the target network fails to retrieve the UE context.

Step <NUM>: The AMF of the target network uses the ID request/response procedure to obtain the SUCI of the UE.

Step <NUM>: The AMF of the target network uses the SUCI obtained in step <NUM> to select a UDM within the home SP.

Step <NUM>: The AMF of the target network registers with the UDM of the home SP using the Nudm_UECM_Registration procedure. In this case, based on the information obtained in steps <NUM> and <NUM> and the information configured in the AMF of the target network (e.g., presence of N14 interface, SLA), the AMF of the target network may know that the UE has moved from the source network to the target network and that there is no N14 interface between the two networks, and may inform the UDM of the home SP through the "Mobility in absence of N14 interface" indication.

<FIG> is now described. <FIG> describes steps <NUM> to <NUM> of the procedure.

Step <NUM>: The AMF of the target network obtains the subscription data for the UE from the UDM using the Nudm_SDM_Get procedure. Then, it performs Nudm_SDM_Subscribe.

Step <NUM>: The UDM located in the home SP notifies the AMF of the source network that it has been deregistered using the Nudm_UECM_DeregistrationNotification procedure. In this case, the UDM of the home SP may add a "Mobility in absence of N14 interface" indication in the deregistration notification message to indicate that the UE has now moved from the source network to the target network and that there is no N14 interface between the two networks.

In some implementations, the indication in the deregistration notification message transmitted by the UDM of the home SP to the AMF of the source network may indicate to delete UE's context after a period of time rather than immediately.

In some implementations, the UDM of the home SP may not transmit a deregistration notification message to the AMF of the source network immediately after receiving a registration request from the AMF of the target network, but may notify the deregistration to the AMF of the source network after a period of time. In this case, the UDM of the home SP may indicate that it is an initial registration, so that the AMF of the source network can immediately clean up the session associated with the UE and delete the UE context.

Step <NUM>: The AMF of the source network performs the Nudm_SDM_Unsubscribe procedure on the UDM, provided that it does not have any additional UE context for non-3GPP access.

Step <NUM>: The AMF of the source network starts a timer, based on the receipt of the "Mobility in absence of N14 interface" indication in step <NUM>. Until the timer ends, the AMF of the source network does not initiate a procedure to delete the UE context within the source network.

Step <NUM>: Steps <NUM> to <NUM> of the registration procedure described in <FIG> and <FIG> are performed.

Step <NUM>: If required for service continuity, the UE attempts to perform a handover to the target network for the HR PDU session anchored to the home SP, i.e., the UE performs a PDU session establishment procedure to the target network, by including the PDU session ID for which it wants to perform a handover and the indication "Existing PDU session". The corresponding PDU session may be an HR PDU session anchored to the home SP.

In some implementations, if the target network and the home SP are the same, the PDU session establishment procedure may be performed for non-roaming and LBO PDU sessions.

In some implementations, the UE may not be able to distinguish whether a PDU session is an LBO PDU session or an HR PDU session. Therefore, the UE may perform the handover for all PDU sessions. If the handover is not possible because the PDU session is an LBO PDU session, the target network may reject the handover. To avoid such unnecessary attempts, when establishing the PDU session in step <NUM> of <FIG>, the SMF of the source network may include information about whether the PDU session is an LBO PDU session or an HR PDU session in the PDU session establishment accept message. Alternatively, in step <NUM>, when the UE performs registration with the target network, the AMF of the target network may inform the UE in the registration accept message about the PDU sessions available for handover based on the subscription information obtained from the UDM. Based on the obtained information, the UE may perform handover only for HR PDU sessions.

Step <NUM>: After the handover of the PDU session is completed through the procedure in step <NUM>, the SMF located in the home SP requests the release of the corresponding PDU session from the SMF of the source network (V-SMF). The SMF of the home SP may include the "Mobility in absence of N14 interface" indication and/or the release cause in the Nsmf_PDUSession_Update request message in order to inform the SMF of the source network exactly about the release cause.

In addition, the SMF of the home SP requests the SMF of the source network not to inform the UE of the release of the corresponding PDU session. This may be done based on the "Mobility in absence of N14 interface" indication and/or release cause transmitted by the SMF of the home SP.

Step <NUM>: The SMF of the source network releases the UP resources associated with the corresponding PDU session existing within the UPF of the source network through the N4 session release procedure.

Step <NUM>: If user plane resources are allocated in the NG-RAN, the SMF of the source network forwards a release request to the AMF of the source network using the Namf_Communication_N1N2MessageTransfer procedure, in order to to delete the context and user plane resources associated with the corresponding PDU session in the NG-RAN of the source network.

Step <NUM>: The AMF of the source network uses the NG PDU session resource release command message to request the NG-RAN of the source network to release the context and user plane resources for the PDU session.

After releasing the context and user plane resources associated with the corresponding PDU session, the NG-RAN of the source network responds to the AMF of the source network with an NG PDU session resource release response message.

Step <NUM>: The AMF of the source network informs the SMF of the source network that the NG-RAN has released the PDU session resource using the Nsmf_PDUSession_UpdateSMContext procedure.

Step <NUM>: The SMF of the source network transmits an Nsmf_PDUSession_Update response message to indicate that the release of the PDU session requested by the SMF of the home SP in step <NUM> has been successfully processed.

Step <NUM>: The SMF of the home SP transmits an Nsmf_PDUSession_StatusNotify message with the "Mobility in absence of N14 interface" indication and/or the release cause to the SMF of the source network, informing that the corresponding PDU session has been handed over from the source network to the target network and requesting to release all contexts associated with the corresponding PDU session.

Step <NUM>: The SMF of the source network transmits an Nsmf_PDUSession_SMContexStatusNotify message with the "Mobility in absence of N14 interface" indication and/or the release cause to the AMF of the source network, informing that the corresponding PDU session has been handed over from the source network to the target network and requesting to release all contexts associated with the corresponding PDU session.

In some implementations, if there are multiple HR PDU sessions anchored to the home SP via the source network, the UE may repeat steps <NUM> to <NUM> to handover the required PDU sessions to the target network.

Step <NUM>: The timer operated in step <NUM> of <FIG> is terminated.

In some implementations, it may be assumed that the timer is set to a value sufficient to move all HR PDU sessions already established in the source network for the UE to the target network before the timer ends.

Step <NUM>: The AMF of the source network initiates a procedure to delete all contexts associated with the UE within the source network. In this case, any LBO PDU sessions established for the UE are also released.

According to the first implementation of the present disclosure, in the registration procedure to the target network, the deletion of contexts for previously established HR PDU sessions by the source network can be delayed and/or withheld. Thus, service continuity can be supported through an existing HR PDU session without the need for additional procedures to establish a new PDU session.

<FIG> shows an example of procedure to support service continuity for HR PDU session in absence of N14 interface between a source network and a target network, to which the second implementation of the present disclosure is applied.

In the second implementation of the present disclosure described in the procedures of <FIG>, the home SP may be an SNPN or a PLMN. The source network and/or the target network may also be SNPNs or PLMNs.

Step <NUM>: To register with the source network, the UE transmits a registration request message to the AMF of the source network via the NG-RAN of the source network.

In some implementations, the registration request message may include a Preferred Network List. The Preferred Network List may include network IDs (e.g., PLMN ID and/or combination of PLMN ID and NID) and priority information for other networks with which the UE is currently can register. If there are multiple networks with which the UE can register, serving continuity to the network with the highest priority may be considered first.

In some implementations, the network IDs and priority information for the PLMN and SNPN with which the UE has established an SLA may be pre-configured in the UE. That is, when the UE wishes to register with a PLMN, the UE may include in the Preferred Network List the ID of the SNPN that has established an SLA with that PLMN (e.g., a combination of the PLMN ID and NID) and the priority information therefor. If the UE wishes to register with a SNPN, the UE may include in the Preferred Network List the ID of the PLMN that has established an SLA with that SNPN and priority information therefor. If the UE does not know if it has established an SLA, it may only provide information about the networks that the UE can register with, regardless of the SLA. In this case, the handover to the network with which it has established an SLA among the available networks may be prioritized.

In some implementations, the network ID and priority information for PLMNs and SNPNs with which the UE has established an SLA may be updated via the UE configuration update procedure.

Step <NUM>: If the UE's registration request is acceptable, the AMF of the source network determines the Supported Network List available to the UE based on the Preferred Network List obtained from the UE, subscriber information obtained from the UDM, presence of N14 interface, SLA, etc. The network IDs included in the Supported Network List are determined within the Preferred Network List transmitted by the UE.

To notify the UE of the registration accept and to create a UE context in the NG-RAN of the source network, the AMF of the source network forwards a NGAP INITIAL CONTEXT SETUP REQUEST message to the NG-RAN containing the Supported Network List and the registration accept message. The NG-RAN of the source network forwards the registration accept message received from the AMF of the source network to the UE. The registration accept message includes the Supported Network List.

In some implementations, depending on the subsequent mobility situation of the UE, the NG-RAN of the source network may trigger an Xn-based or NG-based handover using the N14 interface for networks included in the Supported Network List. To do so, the NG-RAN of the source network may pre-command the UE to take measurements for connected mode mobility using RRC messages.

In some implementations, a DOWNLINK NAS TRANSPORT message may be utilized instead of the NGAP INITIAL CONTEXT SETUP REQUEST message.

Step <NUM>: The UE performs the PDU session establishment procedure to receive services from the source network. The PDU session may be an HR PDU session anchored to the home SP.

In some implementations, the PDU session establishment procedure may be performed for non-roaming and LBO PDU sessions if the source network and home SP are the same.

In some implementations, the NG-RAN of the source network may know in advance that an N14 interface exists between the source network and the target network based on the Supported Network List received in step <NUM>, and may initiate an Xn-based or NG-based handover procedure to provide service continuity to the UE.

Step <NUM>: Since the UE already knows that no N14 interface exists between the source network and the target network based on the Supported Network List received in step <NUM>, the UE transmits a registration request message with registration type set to Initial Registration to the AMF of the target network via the NG-RAN of the target network. In addition, the registration request message may include the SUCI of the UE so that the AMF of the target network can find the UDM located in the home SP.

Further, to inform the AMF of the target network that the UE has moved from another network, the UE may include a "Mobility from other network" indication in the registration request message.

Step <NUM>: The AMF of the target network registers with the UDM in the home SP using the Nudm_UECM_ Registration procedure. In this case, based on the information obtained in step <NUM> and the information configured in the AMF of the target network (e.g., presence of N14 interface, SLA, etc.), the AMF of the target network may know that the UE has moved from the source network to the target network and that there is no N14 interface between the two networks, and may notify the UDM of the home SP through the "Mobility in absence of N14 interface" indication.

The operations described in <FIG> and <FIG> may then be performed. A detailed description thereof will be omitted.

According to the second implementation of the present disclosure, in the registration procedure to the target network, the deletion of contexts for previously established HR PDU sessions by the source network can be delayed and/or withheld. Thus, service continuity can be supported through an existing HR PDU session without the need for additional procedures to establish a new PDU session.

According to the second implementation of the present disclosure, the source network can proactively inform the UE whether it supports the N14 interface in the registration procedure. Thus, the UE can directly perform the initial registration procedure with the target network based on the network configuration and reduce the registration-related signaling between the UE and the AMF of the target network.

Claim 1:
A method performed by an Access and mobility Management Function, AMF, of a source network configured to operate in a wireless communication system, the method being characterized by:
receiving (S900) a deregistration notification message from a United Data Management, UDM, of a Home Service Provider, Home SP, wherein the deregistration notification message informs that i) a User Equipment, UE, has moved from the source network to a target network, and ii) there is no N14 interface between the source network and the target network;
after receiving the deregistration notification message, starting (S910) a timer;
while the timer is running, delaying (S920) deletion of a UE context of the UE within the source network;
receiving (S930) a context status notification message from a Session Management Function, SMF, of the source network, wherein the context status notification message informs that a Protocol Data Unit, PDU, session associated with the UE has been handed over from the source network to the target network; and
based on expiry of the timer, deleting (S940) the UE context of the UE within the source network.