Patent Description:
To meet the demand for ever-increasing wireless data traffic after commercialization of the 4th generation (<NUM>) communication system, there have been efforts to develop an advanced 5th generation (<NUM>) or pre-<NUM> communication system. For this reason, the <NUM> or pre-<NUM> communication system is also called a beyond 4th-generation (<NUM>) network communication system or post long term evolution (LTE) system.

Implementation of the <NUM> communication system using ultra-frequency (mmWave: millimeter wave) bands, e.g., <NUM> giga-Hertz (GHz) bands is considered to achieve higher data rates. To reduce propagation loss of radio waves and increase a transmission range of radio waves in the ultra-frequency bands, beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large-scale antenna techniques are under discussion.

To improve system networks, technologies for advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device to device (D2D) communication, wireless backhaul, moving networks, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like are also being developed in the <NUM> communication system. In addition, in the <NUM> system, an advanced coding modulation (ACM), e.g., hybrid FSK and QAM modulation (FQAM), sliding window superposition coding (SWSC), and an advanced access technology, e.g., filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) are being developed.

With the development of various information technologies (ITs), virtualization techniques are applied to network equipments, enabling the network equipments to evolve to virtualized network functions (NFs). As the virtualized NFs are free from physical constraints and implemented in software, they may be installed/operated in various types of clouds or data centers (DCs). In particular, the NF may be freely scaled, initiated, or terminated depending on service requirements, system capacity, or network load. The NFs need to be driven basically in a physical entity, e.g., a certain equipment even though implemented in software, so it is noted that physical entities in relation to the NFs are not left out of consideration. Alternatively, the NFs may be implemented in a simple physical configuration, i.e., in hardware.

A network slicing technology has been introduced to support various services in such various network architectures. Network slicing is a technology that logically configures a network into a set of NFs to support a certain service, and separate one slice from another slice. A terminal may access two or more slices to receive various services.

According to <CIT>, a method for a user equipment to update a policy in a wireless communication system may include transmitting a first registration request message to an access and mobility management function (AMF), wherein the first registration request message includes requested network slice selection assistance information (NSSAI) including single (S)-NSSAI corresponding to a network slice with which the user equipment wants to register; receiving a first registration accept message as a response to the first registration request message from the AMF, wherein the first registration accept message includes an allowed NSSAI including at least one S-NSSAI allowed by the AMF; and requesting the update of a network slice selection policy (NSSP) associated with new S-NSSAI from the AMF when the new S-NSSAI not included in the requested NSSAI is included in the allowed NSSAI and the NSSP associated with the new S-NSSAI is not present.

In a discussion paper to <NPL>, in Reno, Nevada, USA, it was discussed why slice based AMF overload control at NG-RAN is needed and useful for 3GPP operators.

In another discussion paper to <NPL>, a new key issue to study what enhancements in the 5G5 would be needed to support the enforcement of the "Quota on a Network Slice granularity" was proposed.

Embodiments of the disclosure will be described in detail with reference to accompanying drawings. Technological content well-known in the art or not directly related to the disclosure is omitted in the following description. Through the omission of content that might otherwise obscure the subject matter of the disclosure, the subject matter will be understood more clearly. For the same reason, some parts in the accompanying drawings are exaggerated, omitted or schematically illustrated. The size of the respective elements may not fully reflect their actual size. Like numbers refer to like elements throughout the drawings.

Advantages and features of the disclosure, and methods for achieving them will be understood more clearly when the following embodiments are read with reference to the accompanying drawings. The embodiments of the disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments of the disclosure are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments of the disclosure to those of ordinary skill in the art. Like numbers refer to like elements throughout the specification.

It may be understood that respective blocks and combinations of the blocks in processing flowcharts will be performed by computer program instructions. The computer program instructions may be loaded on a processor of a universal computer, a special-purpose computer, or other programmable data processing equipment, and thus they generate means for performing functions described in the block(s) of the flowcharts when executed by the processor of the computer or other programmable data processing equipment. The computer program instructions may also be stored in computer-usable or computer-readable memories oriented for computers or other programmable data processing equipment, so it is possible to manufacture a product that contains instruction means for performing functions described in the block(s) of the flowchart. The computer program instructions may also be loaded on computers or programmable data processing equipment, so it is possible for the instructions to generate a process executed by the computer or the other programmable data processing equipment to provide steps for performing functions described in the block(s) of the flowchart.

Furthermore, each block may represent a part of a module, segment, or code including one or more executable instructions to perform particular logic function(s). It is noted that the functions described in the blocks may occur out of order in some alternate embodiments of the disclosure. For example, two successive blocks may be performed substantially at the same time or in reverse order.

Furthermore, the term 'unit' or 'module' as herein used refers to a software or hardware component, such as field programmable gate array (FPGA) or application specific integrated circuit (ASIC) which plays a certain role. However, the module is not limited to software or hardware. The module may be configured to be stored in an addressable storage medium, or to execute one or more processors. For example, the modules may include components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program codes, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, and variables. Functions served by components and modules may be combined into a smaller number of components and modules, or further divided into a larger number of components and modules. Moreover, the components and modules may be implemented to execute one or more central processing units (CPUs) in a device or security multimedia card. In embodiments, the module may include one or more processors.

Herein, the terms to identify access nodes, the terms to refer to network entities, the terms to refer to messages, the terms to refer to interfaces among network entities, the terms to refer to various types of identification information, etc., are examples for convenience of explanation. Accordingly, the disclosure is not limited to the terms as herein used, and may use different terms to refer to the items having the same meaning in a technological sense.

A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing a communication function.

In the disclosure, a layer (or a layer apparatus) may also be referred to as an entity.

Throughout the specification, terms and definitions defined by standards for fifth generation (<NUM>), new radio (NR), and long term evolution (LTE) systems will be used for convenience of explanation. The disclosure is not, however, limited to the terms and definitions, and may equally apply to any systems that conform to other standards.

Although embodiments of the disclosure will be primarily focused on communication standards defined by the third generation partnership project (3GPP), the subject matter of the disclosure may also be applicable to other communication systems with a similar technical background with minor changes without significantly departing from the scope of the disclosure, which may be possible under the determination of those of ordinary skill in the art to which the disclosure pertains.

Furthermore embodiments of the disclosure will be primarily focused on a vehicle communication service, but the subject matter of the disclosure may also be applicable to other services provided in <NUM> networks with minor changes without significantly departing from the scope of the disclosure, which may be possible under the determination of those of ordinary skill in the art to which the disclosure pertains. In the disclosure, for example, a proximity service (ProSe) layer may refer to an overall layer that performs control operations for device to device (D2D) or ProSe communication services. The ProSe layer exists over an Access Stratum (AS) layer and refers to a layer that exchanges signaling with the AS layer for D2D communication connection.

The <NUM> system is considering support for various services in contrast to the existing <NUM> system. For example, the most representative services may include an enhanced mobile broad band (eMBB) communication service, an ultra-reliable and low latency communication (URLLC) service, a massive machine type communication (mMTC) service, an evolved multimedia broadcast/multicast service (eMBMS), etc. A system for providing the URLLC service may be referred to as a URLLC system, and a system for providing the eMBB communication service may be referred to as an eMBB system. The terms 'service' and 'system' may be interchangeably used.

Embodiments of the disclosure provide a method and apparatus for supporting various services in a wireless communication system. Specifically, a technology to support various services by supporting mobility of the UE in a wireless communication system will be described in the disclosure.

Herein, terms to identify access nodes, terms to refer to network entities or network functions (NFs), terms to refer to messages, terms to refer to interfaces between network entities, terms to refer to various types of identification information, etc., are examples for convenience of explanation. Accordingly, the disclosure is not limited to the terms as herein used, and may use different terms to refer to the items having the same meaning in a technological sense.

For convenience of explanation, the disclosure will hereinafter use terms and definitions defined by the 3GPP LTE and <NUM> standards. The disclosure is not, however, limited to the terms and definitions, and may equally apply to any systems that conform to other standards.

Entities that exchange information for access control and status management will now be collectively called 'NFs' for convenience of explanation. For example, the NF may be at least one of an access and mobility management function (AMF) device, a session management function (SMF) device, or a network slice selection function (NSSF) device. Embodiments of the disclosure may, however, be equally applied to an occasion when the NF is implemented as an instance, e.g., an AMF instance, an SMF instance, an NSSF instance, etc..

In an embodiment of the disclosure, delivering information or policies about a radio access technology (RAT) has the same meaning as delivering information that may be used for selecting a certain RAT, i.e., information about an access type or a policy.

<FIG> illustrates a wireless communication system, according to an embodiment of the disclosure.

Referring to <FIG>, a radio access node (RAN) <NUM> and a UE <NUM> are shown as part of nodes that use a radio channel in a wireless communication system. Although there is one RAN <NUM> and one UE <NUM> shown in <FIG>, another RAN, which is identical or similar to the RAN <NUM>, may be further included. Furthermore <FIG> is focused on an occasion when the single UE <NUM> performs communication in the single RAN <NUM>. It is, however, obvious that there may be a plurality of UEs communicating in the single RAN <NUM>.

The RAN <NUM> is a network infrastructure that provides wireless access for the UE <NUM>. The RAN <NUM> has coverage defined to be a certain geographical area based on a range within which a signal may be transmitted from the RAN <NUM> (not shown in <FIG>). The RAN <NUM> may also be referred to as a base station (BS), an access point (AP), an eNodeB (eNB), a <NUM> node, a wireless point, a transmission/reception point (TRP), or other terms having equal technical meaning.

The UE <NUM> is a device used by a user, which performs communication with the RAN <NUM> through a radio channel. In some cases, the UE <NUM> may be operated without intervention of the user. For example, the UE <NUM> is a device for performing machine type communication (MTC), which may not be carried by the user. The UE <NUM> shown in <FIG> may include at least one user portable device, which may include at least one MTC. The UE <NUM> may also be referred to as a terminal, an MS, a subscriber station, a remote terminal, a wireless terminal, a user device, or other terms having equal technical meaning.

An AMF device <NUM> may be a network entity that manages mobility of the UE <NUM>. An SMF device <NUM> may be a network entity that manages connection of a packet data network for providing packing data to the UE <NUM>. Connection between the UE <NUM> and the SMF <NUM> may be a packet data unit (PDU) session.

A user plane function (UPF) device <NUM> may be a gateway that delivers packets transmitted or received by the UE <NUM> or a network entity that serves as the gateway. The UPF device <NUM> may be connected to a data network (DN) <NUM> via the Internet to provide a path between the UE <NUM> and the DN <NUM> for data transmission or reception. Accordingly, the UPF device <NUM> may route data to be delivered to the Internet from among the packets transmitted by the UE <NUM> to an Internet data network.

An NSSF device <NUM> may be a network entity that performs a network selection operation, e.g., an operation of selecting a network slice, as will be described in the disclosure. Operations of the NSSF device <NUM> will be described in detail later in connection with the drawings.

An authentication server function (AUSF) device <NUM> may be a network entity that provides a subscriber authentication service.

A network exposure function (NEF) device <NUM> may be a network entity that is able to access information for managing the UE <NUM> in the <NUM> network, subscribe to a mobility management event of the UE <NUM>, subscribe to a session management event of the UE <NUM>, request session-related information, set charging information of the UE <NUM>, request a change in PDU session policy for the UE <NUM>, and transmit a small amount of data for the UE <NUM>.

A network repository function (NRF) device <NUM> may be an NF or network entity that stores an NF profile containing information about details of each NF or status information of the NF or NF instance, and may deliver the NF profile or the status information stored therein when requested by another NF.

A policy and charging function (PCF) device <NUM> may be a network entity that applies a mobile communication operator's service policy, charging policy, and PDU session policy for the UE <NUM>.

A unified data management (UDM) device <NUM> may be a network entity that stores information about a subscriber and/or the UE <NUM>.

An application function (AF) device <NUM> may be a service application server or network entity which work with a network to provide a service.

The aforementioned AMF device <NUM>, the SMF device <NUM>, the UPF device <NUM>, the NSSF device <NUM>, the AUSF device <NUM>, the NEF device <NUM>, the NRF device <NUM>, the PCF device <NUM>, the UDM device <NUM>, the AF device <NUM>, and the SCP <NUM> device may have the form of software or firmware to be driven in at least one of devices and/or systems. Alternatively, the devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be implemented in hardware when required. In the following description, these terms will be simply expressed without the word 'device'. For example, the AMF device <NUM> will be called AMF <NUM>, and the SMF device <NUM> will be called SMF <NUM>.

In the meantime, symbols by lines connecting between each network entity, the UE <NUM>, and the RAN <NUM> may denote interfaces for the respective entities. For example, interface N1 may be used between the UE <NUM> and the AMF <NUM>, interface N2 may be used between the RAN <NUM> and the AMF <NUM>, and interface N3 may be used between the RAN <NUM> and the UPF <NUM>. Likewise, interface N4 may be used between the SMF <NUM> and the UPF <NUM>, interface N9 may be used between UPFs <NUM> or within the UPF <NUM>, and interface N6 may be used between the UPF <NUM> and the DN <NUM>.

<NUM> shows a configuration of a wireless communication system, according to various embodiments of the disclosure.

Referring to <FIG>, a mobile communication system (e.g., a <NUM> or <NUM> operator network) may include a wireless base station, e.g., the RAN <NUM>, and one or more core network slices. In <FIG>, there are N core network slices <NUM>, <NUM>,. , 21N shown. The RAN <NUM> may perform data transmission or reception between a UE, e.g., the UE <NUM> of <FIG>, and the DN <NUM> through at least one core network slice. Depending on the operator network configuration, a core network may be configured in the form of slices or without slices, or may coexist between them. A core network slice may basically include one or more core network NFs. NFs corresponding to a core network may include the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>. In another embodiment of the disclosure, the NFs may include at least one of the AMF <NUM>, the SMF <NUM>, or the UPF <NUM>. In still another embodiment of the disclosure, the NFs may further include other network function device in addition to the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>. In yet another embodiment of the disclosure, the NFs may include at least one of the AMF <NUM>, the SMF <NUM>, or the UPF <NUM>, and further include at least one other device than the aforementioned devices.

In an embodiment of the disclosure, the network slices <NUM>, <NUM>,. , and 21N may respectively provide services suited to their characteristics, and capacities that may be simultaneously provided by the respective network slices <NUM>, <NUM>,. , and 21N may be different. The capacities of the network slices <NUM>, <NUM>,. , and 21N may each correspond to e.g., the maximum number of UEs (subscribers) and the number of sessions. Each of the network slices <NUM>, <NUM>,. , and 21N may control access to a network based on its capacity.

Referring to <FIG>, for example, the first network slice <NUM> may be accessed by <NUM>,<NUM> UEs and accommodate <NUM>,<NUM> sessions. The second network slice <NUM> may be accessed by <NUM>,<NUM> UEs and accommodate <NUM>,<NUM> sessions. The N-th network slice 21N may be accessed by <NUM>,<NUM> UEs and accommodate <NUM>,<NUM> sessions.

As shown in <FIG>, capacities of the respective network slices <NUM>, <NUM>,. , and 21N may be differently set according to the mobile communication operator's settings. When a certain single slice is leased or sold to a separate service provider, capacities for the respective slices may be differently set according to a service level agreement (SLA).

In an embodiment of the disclosure, a capacity or quota of a network slice may be represented by at least one of the following parameters:.

In an embodiment of the disclosure, the capacity of a single network slice may be set based on the number of UEs that may simultaneously access the network slice (parameter <NUM>) and the maximum number of sessions that may be simultaneously supported by the network slice (parameter <NUM>). Furthermore, the capacity of a single network slice may be set using at least one, or two or more of the aforementioned parameters.

The parameters related to sessions and flows (e.g., parameters <NUM> to <NUM> among the aforementioned parameters) may be represented by a certain value for each slice (e.g., support <NUM>,<NUM> sessions per network slice), or by a certain value for each UE that accesses the network slice (e.g., support up to <NUM> sessions at a time for each UE that accesses the network slice).

In an embodiment of the disclosure, with capacity control for each network slice, an operator's mobile communication network may be protected from being overloaded, resources of the network may be effectively used, and accurate charging between the mobile communication operator and the network slice user may be performed.

In an embodiment of the disclosure, when quota-based access control for each network slice is performed, it may happen to reach a limit of the quota actually set for the network slice. In the case that the quota for the network slice is set as the maximum number of concurrent access users (or UEs), when an access request beyond the quota occurs, a technology to deal with this is required.

In an embodiment of the disclosure, a method of dealing with an access request occurring when the maximum number of concurrent access users has reached a quota limit may be proposed as follows:.

<FIG> illustrates a flowchart illustrating a procedure for performing access control for each network slice, according to an embodiment of the disclosure.

Referring to <FIG>, the NSSF <NUM> may provide information of a network slice. Instead of the NSSF <NUM>, however, the NRF <NUM>, the SCP <NUM>, or the PCF <NUM> may also provide the information of the network slice.

In operation S310, the UE <NUM> may select a network slice that the UE <NUM> intends to access, and transmit a connection request (e.g., radio resource control (RRC) connection (network slice selection assistance information (NSSAI)) message to the NG-RAN <NUM>. In <FIG>, the NG-RAN <NUM> is an example of a base station, without being limited thereto. That is, any type of base station may be used for the NG-RAN <NUM>.

In operation S311, the NG-RAN <NUM> may select the AMF <NUM> by using a network slice identifier specified by the UE <NUM>, and forward an initial UE message including a registration request (e.g., Registration Req (Requested NSSAI)) to the AMF <NUM> based on the connection request message, e.g., N1 (NAS) message (e.g., the registration request message) transmitted by the UE <NUM>.

The AMF <NUM> may perform an operation to process the registration request message transmitted by the UE <NUM> through the NG-RAN <NUM>. When the AMF <NUM> needs to receive subscription data of the UE <NUM>, the AMF <NUM> may receive the subscription data from the UDM <NUM>, in which case access and mobility related subscription data may include information of a slice, to which the UE <NUM> is subscribed (one or more pieces of subscribed S-NSSAI), in operation S312.

In operation S313, when a new network slice needs to be selected for the UE <NUM>, or the network slice in question needs to be changed, or a new AMF that belongs to the network slice needs to be selected, the AMF <NUM> may transmit a network slice selection request (NSSelection Req) message to the NSSF <NUM>. The network slice selection request (NSSelection Req) message may be used through Nnssf_NSSelection service's GET operation provided by the NSSF <NUM>. In this case, information for slice selection may be requested not only from the NSSF <NUM> but from the NRF <NUM>, the SCP <NUM>, or the PCF <NUM>. For this, service operation for each NF may be used, or information stored in the AMF <NUM> may be used. When the AMF <NUM> transmits the network slice selection request (NSSelection Req) message, the AMF may include network slice identifiers requested by the UE <NUM> (requested NSSAI) and network slice identifiers included in the subscription data (subscribed NSSI) in the network slice selection request (NSSelection Req) message. Furthermore, when the AMF <NUM> transmits the network slice selection request (NSSelection Req) message, the AMF <NUM> may inform that targets to be selected are all NFs included in the network slice or designate a particular NF type to be selected in the network slice. In operation S314, the NSSF <NUM> may perform an operation to select a network slice at the request of the AMF <NUM>. In this case, information for each slice (e.g., maximum capacity or current load (quantity used) for the slice) received from an NF or operations, administration and management (OAM) or stored may be taken into account. When the request of the AMF <NUM> is about the whole network slice, the network slice and candidate NFs included in the network slice may be selected, taking into account the whole status of the network slice. For example, when the network slice includes the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>, the AMF <NUM>, the SMF <NUM>, and the UPF <NUM> may all be included in the candidate NFs. When the request of the AMF <NUM> designates a particular NF that belongs to the network slice, candidate NFs having the corresponding NF type may be selected. When the network slice is made up with instances, a network slice instance may be selected. When there are several NFs or instances to be selected, the NFs or instances may be selected such that the load is distributed in consideration of a maximum capacity received and a current load state.

In operation S315, in response to the network slice selection request (NSSelection Req) message from the AMF <NUM>, the NSSF <NUM> may deliver a network slice selection response that includes network slice information to the AMF <NUM>. In this case, the network slice selection response may be implemented in the form of Nnssf_NSSelection Service, and may include authorized network slice information (AuthorizedNetworkSliceInfo) that includes information of the previously selected network slice. For example, when the request of the AMF <NUM> is about the whole network slice, the network slice and candidate NFs included in the network slice may be included in the AuthorizedNetworkSliceInfo, taking into account the whole status of the network slice. When the network slice includes the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>, information of candidates of the AMF <NUM>, the SMF <NUM>, and the UPF <NUM> may be included. When the request of the AMF <NUM> designates a particular NF that belongs to the network slice, candidate NFs having the corresponding NF type may be included. When the network slice is made up with instances, a slice instance may be included. The information including the network slice may be made up in the form of a name or identifier to identify the selected network slice candidate or the selected instance. When selection of a network slice or an NF that is able to deal with the request has failed, e.g., when the network slice exceeds its allowable quota, the NSSF <NUM> may transmit a result and/or cause of the failure in the network slice selection response message. By doing this, the NSSF <NUM> may inform the AMF <NUM> of the cause of the NF selection failure. In the embodiment of the disclosure, in allowable quota based control for a slice, a detailed cause (e.g., of the quota, which one-the number of UEs/subscribers, the number of sessions, or the like- has reached the highest value) may be informed.

In operation S316, access control for a situation where of the slice's quota, the maximum number of users (or UEs) of the slice is about to be exceeded or the maximum number of sessions belonging to the particular slice is about to be exceeded is considered. The AMF <NUM> may know based on the slice information received in operation S315 that the corresponding condition has occurred to one or more slices requested by the UE <NUM> for access.

In operation S317, the AMF <NUM> transmits a response message to the registration request to the UE <NUM> that has transmitted the registration request. When the slice requested by the UE <NUM> is allowed to be accessed based on the subscription data but actual access to the slice is restricted due to the quota limit, or when one or more of the slices requested by the UE <NUM> may be accessed, the response message may be an accept (e.g., registration accept) message. When access to the slice is restricted due to the quota limit, the response message may include rejected slice information which may indicate that the quota (the number of users that access the slice, the number of slice sessions, etc.) limit is a cause of the rejection, i.e., a cause of why the access is pending. In this process, the AMF <NUM> is required to have stored information about the requested slice and the slice, access to which is pending due to the quota limit, in a UE context for the UE <NUM>.

In operation S318, upon reception of the registration response from the AMF <NUM>, the UE <NUM> performs the rest of the registration process. When the received response message includes information indicating that access to a particular slice or slices is rejected due to the quota limit and the access to the slice is pending, an operation (traffic transmission to the slice and PDU session creation process for the traffic transmission) using the slice is suspended and may not be proceeded until separate accept information is received from the network. Optionally, the UE <NUM> may notify an upper layer that access to the particular slice or slices is rejected due to the quota limit for the slice and the access is pending, so that a service application may operate by taking this into account or perform an operation such as transmitting an alarm to the user.

In operation S319, in the aforementioned processes, when a certain slice among the slices, access to which is pending due to the slice quota limit, becomes accessible (i.e., the slice shifts into a state of having less accesses than the quota of the slice), the AMF <NUM> may find whether there is a UE whose access is pending and start an operation to notify the UE that the slice becomes accessible, based on the UE context stored.

In operation S320, the AMF <NUM> may transmit information indicating that a slice becomes accessible to the UE <NUM> whose access to the slice was pending due to the quota limit of the slice but is allowed now. In this case, the AMF <NUM> may give the information using a UE configuration update procedure. Specifically, a corresponding NAS message may indicate that identifiers of the slices (s-nassai), access to which was originally rejected and pending, are included in allowed slices (Allowed nassai), and an indicator indicating that the slices, access to which was pending due to the quota limit, become available. When a change of the AMF <NUM> is required or a separate registration process is required due to update of an allowed slice (e.g., when a service/mobility allowable region is required to be changed), indication that a registration procedure of the UE <NUM> is required may be included.

In operation S321, the UE <NUM> may know from the message received from the AMF <NUM> that the slice(s), access to which was originally pending, is now accessible. Accordingly, the UE <NUM> may perform an additional procedure required, e.g., a procedure of session creation for traffic transmission through the slice, and when the message received includes information indicating that a separate registration process is required, the UE <NUM> may perform the registration procedure.

Referring to <FIG>, an occasion when the NSSF <NUM> provides information of a network slice is shown. In this regard, however, the NSSF <NUM> may be replaced by the NRF <NUM>, the SCP <NUM>, or the PCF <NUM>.

In operation S410, the UE <NUM> may select a network slice that the UE <NUM> intends to access, and transmit a connection request (e.g., RRC connection (NSSAI)) message to the NG-RAN <NUM>. In <FIG>, the NG-RAN <NUM> is an example of a base station, without being limited thereto. That is, any type of base station may be used for the NG-RAN <NUM>.

In operation S420, the NG-RAN <NUM> may select the AMF <NUM> by using a network slice identifier specified by the UE <NUM>, and forward an initial UE message including a registration request (e.g., Registration Req (Requested NSSAI)) to the AMF <NUM> based on the connection request message, e.g., N1 (NAS) message (e.g., the registration request message as described above) transmitted by the UE <NUM>.

In operation S430, the AMF <NUM> may perform an operation to process the registration request message transmitted by the UE <NUM> through the NG-RAN <NUM>. When the AMF <NUM> needs to receive subscription data of the UE <NUM>, the AMF <NUM> may receive the subscription data from the UDM <NUM>, in which case access and mobility related subscription data may include information of a slice to which the UE subscribes (one or more pieces of subscribed S-NSSAI) and information of a default available slice (one or more pieces of Default S-NSSAI). When it is hard for the UE <NUM> to access the slice the UE <NUM> has requested or the slice exceeds its access capacity or quota, the subscription data may include whether fallback to another slice is allowed. In operation S440, when a new network slice needs to be selected for the UE <NUM>, or the network slice in question needs to be changed, or a new AMF that belongs to the network slice needs to be selected, the AMF <NUM> may transmit a network slice selection request (NSSelection Req) message to the NSSF <NUM>. The network slice selection request (NSSelection Req) message may be used through Nnssf_NSSelection service's GET operation provided by the NSSF <NUM>. In this case, information for slice selection may be requested not only from the NSSF <NUM> but from the NRF <NUM>, the SCP <NUM>, or the PCF <NUM>. For this, service operation for each NF may be used, or information stored in the AMF <NUM> may be used. When the AMF <NUM> transmits the network slice selection request (NSSelection Req) message, the AMF <NUM> may insert network slice identifiers requested by the UE <NUM> (requested NSSAI) and network slice identifiers included into the subscription data (subscribed NSSI) in the network slice selection request (NSSelection Req) message. Furthermore, when the AMF <NUM> transmits the network slice selection request (NSSelection Req) message, the AMF <NUM> may inform that targets to be selected are all NFs included in the network slice or designate a particular NF type to be selected in the network slice. In operation S450, the NSSF <NUM> may perform an operation to select a network slice at the request of the AMF <NUM>. In this case, information for each slice (e.g., maximum capacity for each slice or current load (quantity used)) received from an NF or OAM or stored may be taken into account. When the request of the AMF <NUM> is about the whole network slice, the network slice and candidate NFs included in the network slice may be selected, taking into account the whole status of the network slice. For example, when the network slice includes the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>, the AMF <NUM>, the SMF <NUM>, and the UPF <NUM> may all be included in the candidate NFs. When the request of the AMF <NUM> designates a particular NF that belongs to the network slice, candidate NFs having the corresponding NF type may be selected. When the network slice is made up with instances, a network slice instance may be selected. When there are several NFs or instances to be selected, the NFs or instances may be selected such that the load is distributed in consideration of a maximum capacity or quota and a current load state.

In operation S460, in response to the network slice selection request (NSSelection Req) message from the AMF <NUM>, the NSSF <NUM> may deliver a network slice selection response that includes network slice information to the AMF <NUM>. In this case, the network slice selection response may be implemented in the form of Nnssf_NSSelection Service, and may include authorized network slice information (AuthorizedNetworkSliceInfo) that includes information of the previously selected network slice. For example, when the request of the AMF <NUM> is not limited to the AMF but about the whole network slice, the network slice and an identifier of the network slice instance or candidate NFs included in the network slice may be selected in AuthorizedNetworkSliceInfo, taking into account the whole status of the network slice. When the network slice includes the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>, information of candidates of the AMF <NUM>, the SMF <NUM>, and the UPF <NUM> may be included. When the request of the AMF <NUM> designates a particular NF that belongs to the network slice, candidate NFs having the corresponding NF type may be included. When the network slice is made up with instances, a slice instance may be included. The information including the network slice may be made up in the form of a name or identifier to identify the selected candidate or the selected instance. When selection of a network slice or an NF that is able to deal with the request has failed, e.g., when the network slice exceeds its allowable quota, the NSSF <NUM> may transmit a result and/or cause of the failure in the network slice selection response message. By doing this, the NSSF <NUM> may inform the AMF <NUM> of the cause of the NF selection failure. In the embodiment of the disclosure, in allowable quota based control for a slice, a detailed cause (e.g., of the quota, which one-the number of UEs/subscribers, the number of sessions, or the like- has reached the highest value) may be informed.

In operation S470, access control for a situation where of the slice's quota, the maximum number of users (or UEs) of the slice is exceeded or the maximum number of sessions belonging to a particular slice is exceeded is considered. The AMF <NUM> may know based on the slice information received in operation S460 that a corresponding condition has occurred to one or more slices requested to be accessed by the UE <NUM>. In this case, the AMF <NUM> may allow the UE <NUM> to change and have access to a default slice, thereby enabling a default service to be provided for the UE <NUM> through the default slice yet having difficulty in providing services through the slice requested by the UE <NUM>.

In operation S480, the AMF <NUM> transmits a response message to the registration request to the UE <NUM>. When the slice requested by the UE <NUM> is allowed to be accessed based on the subscription data but actual access to the slice is restricted due to the quota limit, or when one or more of the slices requested by the UE <NUM> may be accessed, the response message may be an accept (e.g., registration accept) message. In the case that access to the slice is restricted due to the quota limit and that the UE <NUM> is guided to change and have access to another default slice, an allowed slice (allowed nssai) may include an identifier of the allowed slice and a rejected slice (rejected nssai) may include an identifier of the rejected slice in the response message. This information may indicate that the quota (e.g., the number of users accessing the slice, the number of sessions of the slice, etc.) limit is a cause of the rejection and access to the slice is pending. The message may further include an indication that the UE <NUM> is allowed to change and have access to another slice because the slice originally requested by the UE <NUM> is hardly accessed. Furthermore, the message may include information of an allowed DNN indicating that a DNN mapped to the slice originally requested is available for the default slice. Moreover, the message may include a timer value used when whether to try re-access to the slice, access to which is pending due to the limit of quota, i.e., the maximum number of accesses, is determined. In this process, the AMF <NUM> is required to have stored information about the requested slice and the slice, access to which is pending due to the quota limit, in a UE context for the UE <NUM>.

In operation S490, upon reception of the registration response from the AMF <NUM>, the UE <NUM> performs the rest of the registration process. When the received response message includes information indicating that access to a particular slice or slices is rejected due to the quota limit and the access to the slice is pending, an operation (traffic transmission to the slice and PDU session creation process for the traffic transmission) using the slice is suspended and the UE <NUM> may not re-try the access until the UE <NUM> receives separate accept information from the network or until the timer is expired when the timer for retry has been received. When the accept message includes information indicating that services through the default slice are available, the UE <NUM> may receive the service through the default slice. Furthermore, the UE <NUM> may optionally notify an upper layer that access to the particular slice or slices is rejected due to the quota limit for each slice and the access to the slice is pending, so that a service application may operate by taking this into account or transmit an alarm to the user.

As described above in connection with <FIG>, when the slice becomes accessible, the AMF <NUM> may notify the UE <NUM> of this, i.e., operations S319 to S321 may be equally applied in <FIG>.

<FIG> illustrates a flowchart illustrating a procedure of shifting a UE into another radio access type to provide a service, according to an embodiment of the disclosure.

Referring to <FIG>, the NSSF <NUM> may provide information of a network slice. In this regard, however, the NSSF <NUM> may be replaced by the NRF <NUM>, the SCP <NUM>, or the PCF <NUM>.

In operation S510, the UE <NUM> may select an access type and a network slice that the UE <NUM> intends to access, and transmit a connection request (e.g., RRC connection (NSSAI)) message to the NG-RAN <NUM>. In <FIG>, it is noted that the NG-RAN <NUM> is an example of a base station, without being limited thereto. That is, any type of base station may be used for the NG-RAN <NUM>.

In operation S520, the NG-RAN <NUM> may select the AMF <NUM> by using a network slice identifier specified by the UE <NUM>, and forward an initial UE message including a registration request (e.g., Registration Req (Requested NSSAI)) to the AMF <NUM> based on the connection request message, e.g., N1 (NAS) message (e.g., the registration request message as described above) transmitted by the UE <NUM>.

In operation S530, the AMF <NUM> may perform an operation to process the registration request message transmitted by the UE <NUM> through the NG-RAN <NUM>. When the AMF <NUM> needs to receive subscription data of the UE <NUM>, the AMF <NUM> may receive the subscription data from the UDM <NUM>, in which case access and mobility related subscription data may include information of a slice to which the UE subscribes (one or more pieces of subscribed S-NSSAI), information of a default available slice (one or more pieces of Default S-NSSAI), and information of an allowed wireless network (access type), and the subscription data may additionally include whether fallback of the UE <NUM> to a particular access type is allowed when it is hard for the UE <NUM> to access the slice the UE <NUM> has requested or the slice exceeds its access capacity or quota.

In operation S540, when a new network slice needs to be selected for the UE <NUM>, or the network slice in question needs to be changed, or a new AMF that belongs to the network slice needs to be selected, the AMF <NUM> may transmit a network slice selection request (NSSelection Req) message to the NSSF <NUM>. The network slice selection request (NSSelection Req) message may be used through Nnssf_NSSelection service's GET operation provided by the NSSF <NUM>. In this case, information for slice selection may be requested not only from the NSSF <NUM> but from the NRF <NUM>, the SCP <NUM>, or the PCF <NUM>. For this, service operation for each NF may be used, or information stored in the AMF <NUM> may be used. To transmit the network slice selection request (NSSelection Req) message, the AMF <NUM> may insert network slice identifiers requested by the UE <NUM> (requested NSSAI) and network slice identifiers included in the subscription data (subscribed NSSI) into the network slice selection request (NSSelection Req) message. Furthermore, when transmitting the network slice selection request (NSSelection Req) message, the AMF <NUM> may inform that targets to be selected are all NFs included in the network slice or designate a particular NF type to be selected in the network slice.

In operation S550, the NSSF <NUM> may perform an operation to select a network slice at the request of the AMF <NUM>. In this case, information for each slice (e.g., maximum capacity for each slice or current load (quantity used)) received from an NF or OAM or stored may be taken into account. When the request of the AMF <NUM> is about the whole network slice, the network slice and candidate NFs included in the network slice may be selected, taking into account the whole status of the network slice. For example, when the network slice includes the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>, the AMF <NUM>, the SMF <NUM>, and the UPF <NUM> may all be included in the candidate NFs. When the request of the AMF <NUM> designates a particular NF that belongs to the network slice, candidate NFs having the corresponding NF type may be selected. When the network slice is made up with instances, a network slice instance may be selected. When there are several NFs or instances to be selected, the NFs or instances may be selected such that the load is distributed in consideration of a maximum capacity or quota received and a current load state.

In operation S560, in response to the network slice selection request (NSSelection Req) message from the AMF <NUM>, the NSSF <NUM> may deliver a network slice selection response that includes network slice information to the AMF <NUM>. In this case, the network slice selection response may be implemented in the form of Nnssf_NSSelection Service, and may include authorized network slice information (AuthorizedNetworkSliceInfo) that includes previously selected network slice information. For example, when the request of the AMF <NUM> is about the whole network slice, the network slice and candidate NFs included in the network slice may be selected in the AuthorizedNetworkSliceInfo, taking into account the whole status of the network slice. When the network slice includes the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>, the AMF <NUM>, the SMF <NUM>, and the UPF <NUM> may include information of candidates of them. When the request of the AMF <NUM> designates a particular NF that belongs to the network slice, slice information included in a response message may include candidate NFs that correspond to the corresponding NF type. When the network slice is made up with instances, an instance may include a slice instance. The information including the network slice may be made up in the form of a name or identifier to identify the selected candidate or the selected instance. When selection of a network slice or an NF that is able to deal with the request has failed, e.g., when the network slice exceeds its allowable quota, the NSSF <NUM> may transmit a result and/or cause of the failure in the network slice selection response message. By doing this, the NSSF <NUM> may inform the AMF <NUM> of the cause of the NF selection failure. In the allowable quota based control for a slice in particular, the NSSF <NUM> may give information about a detailed cause (e.g., of the quota, which one-the number of UEs/subscribers, the number of sessions, or the like- has reached the highest value). In operation S570, access control for a situation where of the slice's quota, the maximum number of users (or UEs) of the slice is exceeded or the maximum number of sessions belonging to the particular slice is exceeded is considered. The AMF <NUM> may know based on the slice information received in operation S560 that a corresponding condition has occurred to one or more slices requested by the UE <NUM> for access. In this case, the AMF <NUM> may allow the UE <NUM> to have access to another RAT so that the UE <NUM> may receive a default service from the other RAT although hardly receiving a service through a slice requested by a RAT currently requested by the UE <NUM> for access.

In operation S580, the AMF <NUM> transmits a response message to the registration request to the UE <NUM> that has transmitted the registration request. When access to all the slices requested by the UE <NUM> is restricted due to the quota limits, the response message may be a UE registration reject message. When access to the slice is restricted due to the quota limit, rejected slice information (rejected nssai) may include an identifier of the rejected slice and may indicate that quota (the number of users accessing the slice, the number of sessions of the slice, etc.) limit is a cause of the rejection of the access. The response message may also include an indication to guide access through a particular RAT. Moreover, the response message may include a timer value used when whether to try re-access to the current RAT and slice, access to which has been rejected due to the limit of quota, i.e., the maximum number of accesses, is determined. In this process, the AMF <NUM> is required to have stored information about the requested slice and the slice, access to which is pending due to the quota limit, in a UE context for the UE <NUM>.

In the meantime, guiding the UE <NUM> to access the particular RAT may be informed by the AMF <NUM> directly to the UE <NUM> in an NAS response as described above. Furthermore in another embodiment of the disclosure, the AMF <NUM> may insert information (RFSP Index or SPID) guiding the UE <NUM> to increase priority of access to the particular RAT (in the embodiment of the disclosure, another RAT to be accessible when the slice exceeds its capacity) into a message transmitted to the NG-RAN <NUM>, and the NG-RAN <NUM>, upon receiving the message, may change a radio access configuration of the UE <NUM> to increase priority of access to the particular RAT.

In operation S590, the UE <NUM> that has received a registration response from the AMF <NUM> may shift to a particular RAT to perform an operation for receiving a service when the response message includes information to access the particular RAT and operate accordingly. When a retry timer is included in the message received from the AMF <NUM>, the UE <NUM> may not retry the registration request for the rejected slice in the original RAT until the timer is expired. When the timer is expired, the UE <NUM> may change the RAT again and try registration request for the corresponding slice. Furthermore the UE <NUM> may optionally notify an upper layer that access to the particular slice or slices is rejected due to the quota limit for each slice and a change in RAT is to be made, so that a service application may operate by taking this into account or may be guided to an operation e.g., transmitting an alarm to the user.

Even in the embodiment of the disclosure, as described above in connection with <FIG>, when the slice becomes accessible, the AMF <NUM> may notify the UE <NUM> of this, i.e., operations S319 to S321 may be equally applied in the embodiment of the disclosure. In a case that a system accessed by the UE <NUM> is to be changed to <NUM> rather than <NUM> according to the aforementioned operations, a mobility management entity (MME) (not shown) may receive information indicating that a particular slice has become available from a <NUM> NF such as the AMF <NUM> or the UDM <NUM>, and the message may be forwarded to the UE <NUM> from the MME instead of the AMF <NUM>. Furthermore, the UE <NUM> may additionally perform an operation to change the RAT before performing a registration procedure.

<FIG> illustrates a block diagram illustrating a configuration <NUM> of a UE, according to an embodiment of the disclosure.

Referring to <FIG>, the UE in the disclosure may include a transceiver <NUM>, a memory <NUM>, and a processor <NUM>. The transceiver <NUM>, the memory <NUM>, and the processor <NUM> of the UE may operate according to the aforementioned communication method of the UE. Components of the UE are not, however, limited thereto. For example, the UE may include more or fewer elements than described above. In addition, the transceiver <NUM>, the memory <NUM>, and the processor <NUM> may be implemented in a single chip.

The transceiver <NUM> is a collective term of a UE transmitter and a UE receiver, and may transmit or receive a signal to or from a base station. The signals to be transmitted to or received from the BS may include control information and data. For this, the transceiver <NUM> may include an RF transmitter for up-converting the frequency of a signal to be transmitted and amplifying the signal and an RF receiver for low-noise amplifying a received signal and down-converting the frequency of the received signal. Transceiver <NUM> is merely an example, and the elements of the transceiver <NUM> are not limited to the RF transmitter and RF receiver.

In addition, the transceiver <NUM> may receive a signal on a wireless channel and output the signal to the processor <NUM>, or transmit a signal output from the processor <NUM> on a wireless channel. The memory <NUM> may store a program and data required for operation of the BS. Furthermore, the memory <NUM> may store control information or data included in a signal obtained by the UE. The memory <NUM> may include a storage medium such as a read only memory (ROM), a random access memory (RAM), a hard disk, a compact disc ROM (CD-ROM), and a digital versatile disc (DVD), or a combination of storage mediums.

The processor <NUM> may control a series of processes for the UE to be operated according to the embodiments of the disclosure. The processor <NUM> may include at least one processor. For example, the processor <NUM> may include a communication processor (CP) for controlling communication and an application processor (AP) for controlling an upper layer such as an application program.

<FIG> illustrates a block diagram illustrating a configuration of a network entity, according to an embodiment of the disclosure.

Referring to <FIG>, a network entity in the disclosure may include a transceiver <NUM>, a memory <NUM>, and a processor <NUM>. The transceiver <NUM>, the memory <NUM>, and the processor <NUM> of the network entity may operate according to the aforementioned communication method of the network entity. Components of the network entity are not, however, limited thereto. For example, the network entity may include more or fewer elements than described above. In addition, the transceiver <NUM>, the memory <NUM>, and the processor <NUM> may be implemented in a single chip. The network entity may include NFs such as an AMF, an SMF, a PCF, a NEF, a UDM, a UPF, etc., as described above. Furthermore, the network entity may include a base station.

The transceiver <NUM> is a collective term of a network entity transmitter and a network entity receiver, and may transmit or receive a signal to or from a UE or another network entity. The signal to be transmitted to or received may include control information and data. For this, the transceiver <NUM> may include an RF transmitter for up-converting the frequency of a signal to be transmitted and amplifying the signal and an RF receiver for low-noise amplifying a received signal and down-converting the frequency of the received signal. Transceiver <NUM> is merely an example, and the elements of the transceiver <NUM> are not limited to the RF transmitter and RF receiver. The transceiver <NUM> may include a wired/wireless transceiver, including various components for signal transmission and reception.

In addition, the transceiver <NUM> may receive a signal on a communication channel (e.g., a wireless channel) and output the signal to the processor <NUM>, or transmit a signal output from the processor <NUM> on the communication channel.

The memory <NUM> may store a program and data required for an operation of the network entity. Furthermore, the memory <NUM> may store control information or data included in a signal obtained by the network entity. The memory <NUM> may include a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage mediums.

The processor <NUM> may control a series of processes for the network entity to be operated according to the embodiments of the disclosure. The processor <NUM> may include at least one processor.

<FIG> illustrates another block diagram illustrating a configuration of a network entity, according to an embodiment of the disclosure.

The network entity of <FIG> may be configured to correspond to the configuration of the network entity as described above in connection with <FIG>. In <FIG>, the network entity may include NFs, which may include the AMF <NUM>, the SMF <NUM>, and the UPF <NUM>, as described above. In addition, the NFs may include the NSSF <NUM>, the NFR <NUM>, and the SCP <NUM>. In another example, the NFs may be implemented as separate network entities.

Referring to <FIG>, a network interface <NUM> may communicate with another network entity in a core network. For example, when the NF is the AMF <NUM>, the NF may communicate with the SMF <NUM>, the UPF <NUM>, the NSSF <NUM>, the NRF <NUM>, and/or the SCP <NUM>. In another example, when the NF is the SMF <NUM>, the NF may communicate with the AMF <NUM>, the UPF <NUM>, the NSSF <NUM>, the NRF <NUM>, and/or the SCP <NUM>. In still another example, when the NF is the NSSF <NUM>, the NF may communicate with the AMF <NUM>, the UPF <NUM>, the SMF <NUM>, the NRF <NUM>, and/or the SCP <NUM>. Likewise, when the NF is a certain network entity, the NF may communicate with other entities in the core network.

A controller <NUM> may be implemented with at least one processor and/or program for performing an operation of the NF. For example, when the NF is the AMF <NUM>, the controller <NUM> may perform the aforementioned operation of the AMF <NUM>. In another example, when the NF is the NSSF <NUM>, the controller may perform the aforementioned operation of the NSSF <NUM>. Even for another network entity, the controller <NUM> may control the aforementioned operation of the network entity.

A memory <NUM> may store a program and various kinds of control information required by the controller <NUM>, and the respective information as described above. For example, when the NF is the AMF <NUM>, the memory <NUM> may store the aforementioned information received from the AMF <NUM> or an external entity. In another example, when the NF is the NSSF <NUM>, the memory <NUM> may store control information required by the NSSF <NUM> and/or information received. Even for another network entity, the memory <NUM> may store information required for the aforementioned operation of the network entity.

<FIG> illustrates a flowchart illustrating operations between a UE and a network, according to an embodiment of the disclosure.

In operation <NUM>, a UE transmits a registration request message requesting to use a certain slice to an AMF. The message may include a set of identifiers (S-NSSAI) of target slices that the UE requests permission to use, i.e., Requested NSSAI. The message may include information indicating whether to support a function for quota management for each slice (cause reception, back-off timer use, rejected/pending NSSAI handling, etc.) or whether to support a generic network slice template (gst) based slice control function, which may be included as part of <NUM> mobility management (5GMM) capability in the registration request.

In operation <NUM>, when there is a slice among slices in the network, whose quota (limitation of the maximum number of concurrent access UEs/subscribers) is to be managed, the AMF may identify current status of the slice (status of the number of currently concurrent access UEs/subscribers for the slice, whether a new UE/subscriber is additionally accepted or not, etc.). The identification may be performed by exchanging information between an NF that manages the quota of the slice in the network (counts the number of access UEs/subscribers of the slice) and the AMF. Specifically, the NF that manages the quota (e.g., an NF that manages the slice quota, or a counting NF) may collects the number of UEs currently registered for each slice from other NFs (e.g., AMF) in the network, and considering this comprehensively, determine whether the number of UEs has reached the maximum number of concurrent access UEs set for the slice. The slice quota management NF may determine and deliver to the AMF information of the slice (at least one of a total number of access UEs for the current slice, the maximum allowable number of concurrent UEs of the slice, or whether a new UE is allowed to access the current slice or whether the quota limit of the slice has been reached), and parameters (e.g., a cause value and preferred back-off timer) to be used when access to the slice is restricted. The operations <NUM> and <NUM> may be performed separately or in a reverse order.

In operation <NUM>, the AMF may process the registration request of the UE. When the UE determines that there is a slice whose quota (a limit of the maximum number of concurrent access UEs/subscribers) is to be managed, among slices identified by S-NSSAIs included in Requested NSSAI requested by the UE, the UE may determine, based on the information received in operation <NUM>, whether the UE is allowed to register for the slice according the current status of the slice. Parameters set by the AMF to control the UE may be applied in this and following operations when the AMF is informed in the operation <NUM> that the UE supports a quota based slice control function or a GST based slice control function.

In operation <NUM>, when the slice quota reaches an upper limit or access to the slice needs to be restricted, the AMF may include information relating to access restriction based on quota management for each slice in a registration response (e.g., registration accept or registration reject) message to be transmitted to the UE. When access to a slice corresponding to at least one of S-NSSIs included in the UE requested NSSI is restricted, the AMF may operate by selecting one of the following three options:.

The AMF may store the information (the rejected or pending NSSAI and associated cause, or the back-off timer value) in a context of the UE.

In operation <NUM>, the UE may store the information received from the AMF in the registration response message in operation <NUM>. When the message received by the UE includes a cause indicating that access to a slice is restricted due to the quota limit of the slice, and a back-off timer vale, the UE may start a back-off timer and may not transmit a registration request for an associated S-NSSAI in the corresponding PLMN until the back-off timer is expired. The UE is unable to expire or cancel the timer even while in cell change, RAT change, PLMN change, or access type change. The UE may operate differently according to the options of the operation <NUM>. Operations of the UE according to options <NUM> to <NUM> will now be described.

Option <NUM>: in a case that the UE receives a rejected NSSAI having a cause of the quota limit of the slice, and the rejected NSSAI is applied to the overall PLMN, the registration request of the UE for an S-NSSAI included in the NSSAI in the entire PLMN is not accepted. Furthermore, when the rejected NSSAI is applied to the registration area RA, the registration request may not be accepted in the registration area RA but accepted in other registration areas RAs. When the UE receives the rejected NSSAI having a cause of the quota limit of the slice, the UE may delete a corresponding S-NSSAI from the rejected NSSAI when a back-off timer associated with the S-NSSAI is expired. Subsequently, the UE may start requesting registration for permission for use of the corresponding slice S-NSSAI.

Option <NUM>: in a case that the UE receives a pending NSSAI having a cause of quota limit of the slice, and the NSSAI is applied to the overall PLMN, the registration request of the UE for an S-NSSAI included in the NSSAI in the entire PLMN is not accepted. Furthermore, when the NSSAI is applied to the registration area RA, the registration request may not be accepted in the registration area RA but accepted in other registration areas RAs. When the UE receives the pending NSSAI having a cause of the quota limit of the slice, the UE may delete a corresponding S-NSSAI from the pending NSSAI when a back-off timer associated with the S-NSSAI is expired. Subsequently, the UE may start requesting registration for permission for use of the corresponding slice S-NSSAI.

Option <NUM>: when the UE receives a back-off timer value associated with an S-NSSAI having a cause of the quota limit of a slice, the UE is not able to request registration related to the S-NSSAI while the timer is running, and may start requesting registration for permission for use of the slice S-NSSAI after the timer is expired.

Operation <NUM> and the subsequent operations may be performed optionally after the previous operation. For example, the operation <NUM> and the subsequent operations may not be performed.

In operation <NUM>, the AMF may determine whether at least one of the slices that have not accepted new access thereto due to the quota limit becomes newly accessible. This may be performed by receiving the status information of the slice as in the operation <NUM>.

In operation <NUM>, for the slice that becomes accessible, the AMF may deliver information indicating that the slice becomes available to the UE that transmitted an access request for the slice but access of which is pending. When the slice is included in the pending NSSAI for a particular UE, the AMF may change the slice into available state by inserting the slice into the allowed NSSAI. In another method, the AMF may transmit a cause or indicator indicating that the slice is in a state of allowing an access request for the slice while maintaining the pending NSSAI status for the UE. Alternatively, the AMF may set the back-off timer of the slice to '<NUM>' and transmit the value to the UE. In operation <NUM>, when the UE transmitted a registration request, the registration response message may be used, and otherwise, a UE configuration update message may be used. In operation <NUM>, the UE may update the status of the slice based on the message received from the AMF. When some slices that have been included in the pending NSSAI are included in the allowed NSSAI in the operation <NUM>, the UE may determine that use of the slice is permitted. When the cause or indicator indicates that the slice included in the pending NSSAI is allowed to be requested for access, the UE may expire the back-off timer for the slice and transmit the registration request for the slice. When the UE receives '<NUM>' of the back-off timer for a slice, the UE may set a timer value to '<NUM>' or expire the timer and transmit a registration request for the slice.

Methods according to the claims of the disclosure or the embodiments of the disclosure described in the specification may be implemented in hardware, software, or a combination of hardware and software.

When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors in an electronic device. The one or more programs may include instructions that cause the electronic device to perform the methods in accordance with the claims of the disclosure or the embodiments described in the specification.

The programs (software modules, software) may be stored in a RAM, a non-volatile memory including a flash memory, a ROM, an electrically erasable programmable ROM (EEPROM), a magnetic disc storage device, a CD-ROM, a DVD or other types of optical storage device, and/or a magnetic cassette. Alternatively, the programs may be stored in a memory including a combination of some or all of them. There may be a plurality of memories.

The program may also be stored in an attachable storage device that may be accessed over a communication network including the Internet, an intranet, a local area network (LAN), a wide LAN (WLAN), or a storage area network (SAN), or a combination thereof. The storage device may be connected to an apparatus performing the embodiments of the disclosure through an external port. In addition, a separate storage device in the communication network may be connected to the apparatus performing the embodiments of the disclosure.

In an embodiment of the disclosure, services may be provided more effectively.

In the embodiments of the disclosure, a component is represented in a singular or plural form. It should be understood, however, that the singular or plural representations are selected appropriately according to the situations presented for convenience of explanation, and the disclosure is not limited to the singular or plural form of the component. Further, the component expressed in the plural form may also imply the singular form, and vice versa.

Several embodiments of the disclosure have thus been described, but it will be understood that various modifications can be made without departing the scope of the disclosure. Thus, it will be apparent to those ordinary skilled in the art that the disclosure is not limited to the embodiments described, but can encompass not only the appended claims but the equivalents.

Claim 1:
A method performed by a user equipment, UE, (<NUM>) in a wireless communication system, the method comprising:
transmitting, to an access and mobility management function, AMF, entity (<NUM>), a registration request message including a requested network slice selection assistance information, NSSAI, and information related to support of a rejected NSSAI, wherein the requested NSSAI contains at least one single NSSAI, S-NSSAI;
receiving, from the AMF entity, a registration response message including a rejected NSSAI including a rejected S-NSSAI with a reject cause, based on the registration request message;
identifying whether the rejected S-NSSAI is associated with the reject cause indicating a maximum number of UEs per network slice being reached;
in case that the rejected S-NSSAI is associated with the reject cause indicating the maximum number of UEs per network slice being reached, starting a back-off timer for the rejected S-NSSAI; and
removing the rejected S-NSSAI from the rejected NSSAI in case that the back-off timer is expired.