Handling slice deregistration inactivity timer of on-demand single network slice selection assistance information

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments herein provide a method and system for handling a slice deregistration inactivity timer of an on-demand S-NSSAI. The method includes detecting the slice inactivity deregistration timer configured for an alternative S-NSSAI by a network apparatus (302). Further, the method includes establishing a PDU session with a first S-NSSAI and the alternative S-NSSAI. Further, the method includes detecting whether the alternative S-NSSAI is the on-demand S-NSSAI and the slice inactivity deregistration timer is running. The detection is performed after the PDU session is established with the first S-NSSAI and the alternative S-NSSAI or when an existing PDU session of the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. Further, the method includes stopping the slice deregistration inactivity timer associated with the alternate S-NSSAI, when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

Description

HANDLING SLICE DEREGISTRATION INACTIVITY TIMER OF ON-DEMAND SINGLE NETWORK SLICE SELECTION ASSISTANCE INFORMATION

[0001] The present disclosure is related to the field of satellite and wireless communication. More particularly, the present disclosure is related to handling a slice deregistration inactivity timer of an on-demand single network slice selection assistance information (S-NSSAI).

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] The present invention has been made to address at least the above problems and / or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention provides a method and apparatus for method and apparatus for handling a slice deregistration inactivity timer of on-demand single nework slice selection assistance information.

[0009] In accordance with an aspect of the disclosure, a method performed by a user equipment (UE) in a communication system is provided. The method comprising: establishing a PDU session over first single - network slice selection assistance information (S-NSSAI); stopping a first slice deregistration inactivity timer associated with the first S-NSSAI; establishing the PDU session with the first S-NSSAI and an alternative S-NSSAI; and stopping a second slice deregistration inactivity timer associated with the alternative S-NSSAI.

[0010] In accordance with an aspect of the disclosure, a method performed by a first entity performing a session managmenet function (SMF), in a communication system. The method comprising: receiving, from a user equipment (UE), a first protocol data unit (PDU) session establishment request message for a first single - network slice selection assistance information (S-NSSAI); as a response to the first PDU session establishment request message for the first S-NSSAI, transmitting, to the UE, a first PDU session establishment accept message; transmitting, to the UE, a PDU session modification message for the alternative S-NSSAI; receiving, from the UE, a second PDU session establishment request message for the first S-NSSAI and the alternative S-NSSAI; and receiving, from the first entity performing the SMF, a second PDU session establishment accept message for the first S-NSSAI and the alternative S-NSSAI, wherein a first slice deregistration inactivity timer associated with the first S-NSSAI is stopped after a PDU session over the first S-NSSAI is established, and wherein a second slice deregistration inactivity timer associated with the alternative S-NSSAI is stopped after the PDU session over the first S-NSSAI and the alternative S-NSSAI is established.

[0011] In accordance with an aspect of the disclosure, a user equipment (UE) in a communication system is provided. The UE comprising: a transceiver; and a controller coupled with the transceiver, and configured to: establish a PDU session over first single - network slice selection assistance information (S-NSSAI), stop a first slice deregistration inactivity timer associated with the first S-NSSAI, establish the PDU session with the first S-NSSAI and an alternative S-NSSAI, and stop a second slice deregistration inactivity timer associated with the alternative S-NSSAI.

[0012] In accordance with an aspect of the disclosure, a first entity perfomring a session management function (SMF) in a communication system is provided. The first entity performing the SMF is comprising: a transceiver; and a controller coupled with the transceiver, and configured to: receive, from a user equipment (UE), a first protocol data unit (PDU) session establishment request message for a first single - network slice selection assistance information (S-NSSAI), as a response to the first PDU session establishment request message for the first S-NSSAI, transmit, to the UE, a first PDU session establishment accept message, transmit, to the UE, a PDU session modification message for the alternative S-NSSAI, receive, from the UE, a second PDU session establishment request message for the first S-NSSAI and the alternative S-NSSAI, and receive, from the first entity performing the SMF, a second PDU session establishment accept message for the first S-NSSAI and the alternative S-NSSAI, wherein a first slice deregistration inactivity timer associated with the first S-NSSAI is stopped after a PDU session over the first S-NSSAI is established, and wherein a second slice deregistration inactivity timer associated with the alternative S-NSSAI is stopped after the PDU session over the first S-NSSAI and the alternative S-NSSAI is established.

[0013] Advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. For more enhanced communication system, there is a need for method and apparatus for handling a slice deregistration inactivity timer of on-demand single nework slice selection assistance information.

[0014] These and other features, aspects, and advantages of the present embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0015] Fig. 1 is a sequence diagram that illustrates the slice deregistration inactivity timer on alternative S-NSSAI according to prior art.

[0016] Fig. 2 is a block diagram that illustrates a schematic of a UE implemented to carry out the disclosed subject matter according to an embodiment as disclosed herein.

[0017] Fig. 3 is a block diagram that illustrates a schematic of a network apparatus implemented to carry out the disclosed subject matter according to an embodiment as disclosed herein.

[0018] Fig. 4 is a sequence diagram that illustrates stopping the slice deregistration inactivity timer on the alternative S-NSSAI according to an embodiment as disclosed herein.

[0019] Fig. 5 is a sequence diagram that illustrates starting the slice deregistration inactivity timer on the alternative S-NSSAI according to an embodiment as disclosed herein.

[0020] Fig. 6 is a sequence diagram that illustrates a scenario where the UE and the AMF do not remove the alternative S-NSSAI immediately according to an embodiment as disclosed herein.

[0021] Fig. 7 is a sequence diagram that illustrates a scenario where a SMF indicates the UE with the alternative S-NSSAI by keeping the PDU session according to an embodiment as disclosed herein.

[0022] Fig. 8 is a sequence diagram that illustrates a scenario when the alternative S-NSSAI is indicated and removed from the PDU session according to an embodiment as disclosed herein.

[0023] Fig. 9 is a flow diagram that illustrate a method for handling a slice deregistration inactivity timer of on-demand S-NSSAI by the UE according to an embodiment as disclosed herein.

[0024] Fig. 10 is a flow diagram that illustrate a method for handling a slice deregistration inactivity timer of on-demand S-NSSAI by the network apparatus according to an embodiment as disclosed herein.

[0025] These and other aspects of the example embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating example embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the example embodiments herein without departing from the spirit thereof, and the example embodiments herein include all such modifications.

[0026] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0027] For the purposes of interpreting this specification, the definitions (as defined herein) will apply and whenever appropriate the terms used in singular will also include the plural and vice versa. It is to be understood that the terminology used herein is for the purposes of describing particular embodiments only and is not intended to be limiting. The terms "comprising", "having" and "including" are to be construed as open-ended terms unless otherwise noted.

[0028] The words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.," , "i.e.," are merely used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein using the words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.," , "i.e.," is not necessarily to be construed as preferred or advantageous over other embodiments.

[0029] Embodiments herein may be described and illustrated in terms of blocks which carry out a described function or functions.　These blocks, which may be referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by a firmware. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block.　Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure.　Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the disclosure.

[0030] It should be noted that elements in the drawings are illustrated for the purposes of this description and ease of understanding and may not have necessarily been drawn to scale. For example, the flowcharts / sequence diagrams illustrate the method in terms of the steps required for understanding of aspects of the embodiments as disclosed herein. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Furthermore, in terms of the system, one or more components / modules which comprise the system may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0031] The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any modifications, equivalents, and substitutes in addition to those which are particularly set out in the accompanying drawings and the corresponding description. Usage of words such as first, second, third etc., to describe components / elements / steps is for the purposes of this description and should not be construed as sequential ordering / placement / occurrence unless specified otherwise.

[0032] A slice deregistration inactivity timer is a feature used in 5G to manage network resources efficiently. The slice deregistration inactivity timer is associated with network slicing. Network slicing is a technology that allows operators to divide a physical network into multiple virtual slices, where each virtual slice is tailored for specific use cases or services. Each network slice is identified by the identifier S-NSSAI (single-network slice selection assistance information) The slice deregistration inactivity timer tracks the inactivity of specific S-NSSAIs associated with a user equipment (UE). If the UE does not use the services of the S-NSSAI through establishment of PDU session for a certain period, the associated of the S-NSSAI is then deregistered i.e removed from the allowed NSSAI list.

[0033] Scenario 1: A UE and a network supports slice network replacement feature and network slice usage control. The UE has two S-NSSAIs i.e. S-NSSAI-1 and S-NSSAI-2 where both of these S-NSSAIs are configured as on-demand S-NSSAI with slice deregistration inactivity timer T1 and T2. The UE is registered with S-NSSAI-1 and S-NSSAI-2 (i.e S-NSSAI-1 and S-NSSAI-2 in the allowed NSSAI). The UE has the S-NSSAI-2 as an alternative NSSAI of S-NSSAI-1. As there is no PDU session on S-NSSAI-1 and S-NSSAI-2, as per the current specification, the slice deregistration inactivity timer T1 and T2 will start. The UE establishes the PDU session on S-NSSAI-1 with additional parameter S-NSSAI-2 as alternative S-NSSAI. This will cause the slice deregistration inactivity timer associated with S-NSSAI-1 to be stopped. T1 is stopped, but T2 will be running. After T2 timer expiry, UE and the AMF will remove the S-NSSAI-2 from the allowed NSSAI and this cause PDU session released.

[0034] Scenario 2: A UE and a network supports slice network replacement feature and network slice usage control. The UE has two S-NSSAIs i.e. S-NSSAI-1 and S-NSSAI-2 where both of these S-NSSAIs are configured as on-demand S-NSSAI with slice deregistration inactivity timer T1 and T2. The UE is registered with S-NSSAI-1 and S-NSSAI-2 (i.e S-NSSAI-1 and S-NSSAI-2 in the allowed NSSAI).. As there is no PDU session on S-NSSAI-1 and S-NSSAI-2, as per the current specification, the slice deregistration inactivity timer T1 and T2 will start. The UE establishes the PDU session on S-NSSAI-1. This will cause the slice deregistration inactivity timer associated with S-NSSAI-1 to be stopped. T1 is stopped, but T2 will be running Now, S-NSSAI-1 becomes congested. Thus, an AMF will need to initiate a PDU session modification procedure to move the UE to the alternative-S-NSSAI-2. After T2 timer expiry, UE and the AMF will remove the S-NSSAI-2 from the allowed NSSAI and this cause PDU session released.

[0035] Scenario 3: The UE is registered with S-NSSAI-1 and S-NSSAI-2. UE has established PDU session with S-NSSAI-1 and associated alternative S-NSSAI S-NSSAI-2 due to S-NSSAI-1 is congested and S-NSSAI-2 is configured by the network as alternative S-NSSAI for the S-NSSAI-1. Now The S-NSSAI-1 become available and the PDU session is moved back to S-NSSAI-1 (e.g through the PDU session modification procedure). Currently, it is not specified how to handle such a slice inactivity deregistration timer for the S-NSSAI-2.

[0036] Scenario 4: The UE is registered with S-NSSAI-1 and S-NSSAI-2. UE has established PDU session with S-NSSAI-1 and associated alternative S-NSSAI S-NSSAI-2 due to S-NSSAI-1 is congested and S-NSSAI-2 is configured by the network as alternative S-NSSAI for the S-NSSAI-1. Now PDU session is released. Currently, it is not specified how to handle such a slice inactivity deregistration timer for the S-NSSAI-2

[0037] Scenario 5: The UE is registered with S-NSSAI-1 and S-NSSAI-2 and S-NSSAI-3. UE has established PDU session with S-NSSAI-1 and associated alternative S-NSSAI S-NSSAI-2 due to S-NSSAI-1 is congested and S-NSSAI-2 is configured by the network as alternative S-NSSAI for the S-NSSAI-1 Now, S-NSSAI-2 become congested and network move the PDU session to the S-NSSAI-3 through PDU session modification procedure. Currently, it is not specified how to handle such a slice inactivity deregistration timer for the S-NSSAI-2 and S-NSSAI-3 considering S-NSSAI-3 is configured as on-demand S-NSSAI.

[0038] Hence, is desirable to address the above mentioned problems and disadvantages or at least provide a useful alternative.

[0039] The principal object of the embodiments herein is to provide a system and method for handling a slice deregistration inactivity timer of an on-demand S-NSSAI.

[0040] Another object of the embodiments herein is to stop the slice inactivity deregistration timer associated with the alternative S-NSSAI (S-NSSAI-2) when the PDU session is established on the alternative S-NSSAI.

[0041] Yet another object of the embodiments herein is to re-start slice inactivity deregistration timer associated with the alternative S-NSSAI when the PDU session is moved back to S-NSSAI-1 or a first S-NSSAI-1.

[0042] In an aspect, the objectives are achieved by providing a method for handling a slice deregistration inactivity timer of an on-demand S-NSSAI. The method includes detecting the slice inactivity deregistration timer configured for an alternative S-NSSAI by a network apparatus (e.g. AMF-access and mobility function). Further, the method includes establishing a PDU session with a first S-NSSAI and the alternative S-NSSAI. Further, the method includes detecting whether the alternative S-NSSAI is the on-demand S-NSSAI and the slice inactivity deregistration timer is running. The detection is performed after the PDU session is established with the first S-NSSAI and the alternative S-NSSAI or when an existing PDU session of the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. Further, the method includes stopping the slice deregistration inactivity timer associated with the alternate S-NSSAI, when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0043] In another aspect, the objectives are achieved by providing a method for handling a slice deregistration inactivity timer of on-demand S-NSSAI. The method includes configuring the slice inactivity deregistration timer at a UE for an alternative S-NSSAI. Further, the method includes detecting that the UE has established a PDU session with a first S-NSSAI and the alternative S-NSSAI. Further, the method includes determining whether the alternative S-NSSAI is an on-demand S-NSSAI and the slice inactivity deregistration timer is running after establishing the PDU session with the alternative S-NSSAI or an existing PDU session with first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. Further, the method includes stopping the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0044] In another aspect, the objectives are achieved by providing a UE for handling a slice deregistration inactivity timer of on-demand S-NSSAI. The UE includes a first memory including the slice inactivity deregistration timer configured by a network apparatus, a first processor, and UE slice deregistration inactivity timer controller coupled to the first memory and the first processor. The UE slice deregistration inactivity timer controller detects the slice inactivity deregistration timer configured for an alternative S-NSSAI by a network apparatus. Further, the UE slice deregistration inactivity timer controller establishes a PDU session with a first S-NSSAI and the alternative S-NSSAI. Further, the UE slice deregistration inactivity timer controller detects whether the alternative S-NSSAI is the on-demand S-NSSAI and the slice inactivity deregistration timer is running after establishing the PDU session with the first S-NSSAI and the alternative S-NSSAI or an existing PDU session when the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. Further, the UE slice deregistration inactivity timer controller stops the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0045] In another aspect, the objectives are achieved by providing a network apparatus for handling a slice deregistration inactivity timer of on-demand S-NSSAI. The network apparatus includes a second memory including the slice inactivity deregistration timer, a second processor, and a network slice deregistration inactivity timer controller coupled to the second memory and the second processor. The network slice deregistration inactivity timer controller configures the slice inactivity deregistration timer at a UE for an alternative S-NSSAI. Further, the network slice deregistration inactivity timer controller detects that the established PDU session with a first S-NSSAI and the alternative S-NSSAI. Further, the network slice deregistration inactivity timer controller determines whether the alternative S-NSSAI is an on-demand S-NSSAI and the slice inactivity deregistration timer is running after establishing the PDU session with the alternative S-NSSAI or an existing PDU session with first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. Further, the network slice deregistration inactivity timer controller stops the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0046] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications be made within the scope of the embodiments herein.

[0047] 1) 5GMM-NULL

[0048] 2) 5GMM-DEREGISTERED

[0049] a) 5GMM-DEREGISTERED.NORMAL-SERVICE

[0050] b) 5GMM-DEREGISTERED.LIMITED-SERVICE

[0051] c) 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION

[0052] d) 5GMM-DEREGISTERED.PLMN-SEARCH

[0053] e) 5GMM-DEREGISTERED.NO-SUPI

[0054] f) 5GMM-DEREGISTERED.NO-CELL-AVAILABLE

[0055] g) 5GMM-DEREGISTERED.eCALL-INACTIVE

[0056] h) 5GMM-DEREGISTERED.INITIAL-REGISTRATION- NEEDED

[0057] 3) 5GMM-REGISTERED-INITIATED

[0058] 4) 5GMM-REGISTERED

[0059] a) 5GMM-REGISTERED.NORMAL-SERVICE

[0060] b) 5GMM-REGISTERED.NON-ALLOWED-SERVICE

[0061] c) 5GMM-REGISTERED.ATTEMPTING-REGISTRATION- UPDATE

[0062] d) 5GMM-REGISTERED.LIMITED-SERVICE

[0063] e) 5GMM-REGISTERED.PLMN-SEARCH

[0064] f) 5GMM-REGISTERED.NO-CELL-AVAILABLE

[0065] g) 5GMM-REGISTERED.UPDATE-NEEDED

[0066] 5) 5GMM-DEREGISTERED-INITIATED

[0067] 6) 5GMM-SERVICE-REQUEST-INITIATED

[0068] 5GMM-IDLE mode: In the present disclosure, if the term is used standalone, a UE in 5GMM-IDLE mode means the UE can be either in 5GMM-IDLE mode over 3GPP access or in 5GMM-IDLE mode over non-3GPP access.

[0069] 5GMM-CONNECTED mode: In the present disclosure, if the term is used standalone, a UE in 5GMM-CONNECTED mode means the UE can be either in 5GMM-CONNECTED mode over 3GPP access or in 5GMM-CONNECTED mode over non-3GPP access.

[0070] 5GMM-IDLE mode over 3GPP access: A UE is in 5GMM-IDLE mode over 3GPP access when no N1 NAS signaling connection between the UE and network over 3GPP access exists. The term 5GMM-IDLE mode over 3GPP access used in the present document corresponds to the term CM-IDLE state for 3GPP access used in 3GPP TS 23.501.

[0071] 5GMM-CONNECTED mode over 3GPP access: A UE is in 5GMM-CONNECTED mode over 3GPP access when an N1 NAS signalling connection between the UE and network over 3GPP access exists. The term 5GMM-CONNECTED mode over 3GPP access used in the present document corresponds to the term CM-CONNECTED state for 3GPP access used in 3GPP TS 23.501

[0072] Support of network slice usage control:

[0073] The UE during the Registration procedure may indicate in UE MM Core Network Capability that it supports UE configuration of network-controlled Slice Usage Policy. If so, the AMF determines Slice Usage Policy for a network slice for the UE and may configure the UE with this information together with Configured NSSAI to control the usage of this network slice. The AMF may be locally configured with network Slice Usage Policy or receive the policy from the (AM-) PCF.

[0074] The network-controlled Slice Usage Policy is provided to the UE in the Registration Accept or the UE Configuration Update Command and may include an indication, for one or more of S-NSSAI(s) of the HPLMN in the Configured NSSAI, whether the UE needs to register the network slice with the network when applications in the UE require data transmission in the network slice (i.e. the UE needs to register the network slice only on demand).

[0075] NOTE: All Other network slices in the Configured NSSAI are handled by the UE using UE specific policies (e.g. they can be registered irrespective of applications need).

[0076] For all on demand S-NSSAI(s) of the HPLMN in the Configured NSSAI, a deregistration inactivity timer that causes the UE to deregister the network slice after the last PDU Session associated with the S-NSSAI is released.

[0077] This deregistration inactivity timer is started at the UE and AMF per access type when the last PDU Session associated with the S-NSSAI is released, or the network slice is included in the Allowed NSSAI and no PDU session is established.

[0078] The deregistration inactivity timer is stopped and reset when the first PDU session is established or the S-NSSAI is removed from the Allowed NSSAI. The AMF and UE may locally remove the S-NSSAI from the Allowed NSSAI when the timer expires. The AMF may also send a UE Configuration Update Command to remove the slice from the Allowed NSSAI.

[0079] The 5GC performs usage monitoring to be able to enforce the release of inactive PDU Sessions, and deregistering of UEs from network slices with no PDU Sessions on them according to its own policies. In order to support usage monitoring for a network slice:

[0080] The AMF runs a slice deregistration inactivity timer per S- NSSAI and access type to deregister the network slice which is started when the network slice is not used by any PDU Session over the corresponding access type. The deregistration inactivity timer is stopped and reset when at least a PDU Session associated with the network slice is successfully established or the network slice is removed from the Allowed NSSAI. When the deregistration inactivity timer for a network slice over an access type expires, the AMF removes the network slice from the Allowed NSSAI over the access type by sending the UE Configuration Update Command to impacted UE(s).

[0081] The SMFs provide to UPFs that handle the PDU sessions in the network slice a PDU Session inactivity timer. The PDU Session inactivity timer is started after no data packet is transmitted or received and runs until the next data packet is transmitted or received which restarts the timer again. If the PDU Session inactivity timer expires before any packet is received or transmitted, the UPF reports this PDU Session inactivity event to the SMF to cause the SMF to release the PDU Session. When the AMF receives the notification of PDU Session release and it includes the indication of network slice removal and if the network slice of the released PDU Session is not used by other PDU Sessions (i.e. the last PDU Session using the network slice is released) over the corresponding access type, the AMF may trigger the UE Configuration Update procedure to remove the network slice from the Allowed NSSAI over that corresponding access type. The deregistration inactivity and PDU Session inactivity timers are either pre-configured in the AMF / SMF or received from the PCF / UDM.

[0082] Mobility management based network slice usage control:

[0083] If the UE and the network support network slice usage control, the AMF monitors network slice usage by running a slice deregistration inactivity timer per S-NSSAI and access type. The AMF may also provide on-demand NSSAI to the UE in the REGISTRATION ACCEPT message or in the CONFIGURATION UPDATE COMMAND message. The on-demand NSSAI consists of one or more on-demand S- NSSAIs and, optionally, the slice deregistration inactivity timer per on-demand S-NSSAI. The slice deregistration inactivity timer is:

[0084] a) started when there is no established PDU session, including any MA PDU session, associated with the S-NSSAI over the corresponding access type; and

[0085] b) stopped and reset when at least a PDU session, including any MA PDU session, associated with the S-NSSAI is successfully established over the corresponding access type(s) or the S-NSSAI is removed from the allowed NSSAI.

[0086] If the slice deregistration inactivity timer value is updated, the AMF updates the stored timer value and may provide the updated timer value to the UE in the REGISTRATION ACCEPT message or the CONFIGURATION UPDATE COMMAND message. When the UE receives an updated slice deregistration inactivity timer value in the REGISTRATION ACCEPT message or the CONFIGURATION UPDATE COMMAND message from the AMF, the UE updates the stored timer value.

[0087] Upon expiry of the slice deregistration inactivity timer, the AMF locally removes the S-NSSAI from the allowed NSSAI over the access type. In addition, the AMF may send the CONFIGURATION UPDATE COMMAND message to the UEs with the new allowed NSSAI.

[0088] The UE includes the on-demand S-NSSAI which the UE requests in the requested NSSAI during the registration procedure. Upon expiry of the slice deregistration inactivity timer, the UE locally removes the S-NSSAI from the allowed NSSAI over the access type. If the UE supports network slice usage control, the AMF provides on-demand NSSAI in the Configured NSSAI to the UE in the REGISTRATION ACCEPT message or in the UE Configuration Update Command message. The on- demand NSSAI consists of one or more configured S-NSSAIs.

[0089] The on-demand S-NSSAI(s) is deleted by the UE from the stored on-demand NSSAI, when the associated configured S-NSSAI(s) is deleted by the UE from the stored configured NSSAI. Note: The network slice usage control feature is not supported in roaming scenarios.

[0090] Mobility management based network slice replacement:

[0091] The support for network slice replacement by a UE or network is optional. If the UE and network support network slice replacement, and the AMF determines that an S-NSSAI included in the allowed NSSAI needs to be replaced with an alternative S-NSSAI, the AMF provides:

[0092] a) the alternative S-NSSAI in the allowed NSSAI, if not included yet;

[0093] b) the alternative S-NSSAI in the configured NSSAI, if not included yet;

[0094] c) the alternative S-NSSAI in the NSAG information, if not included yet and the UE supports NSAG; and

[0095] d) the mapping information between the S-NSSAI to be replaced and the alternative S-NSSAI, to the UE during the UE configuration update procedure or during the registration procedure as follows:

[0096] e) For non-roaming UE, the AMF provides the mapping information between the S-NSSAI included in the allowed NSSAI and the alternative S-NSSAI to the UE; and

[0097] NOTE 1: In non-roaming scenarios, the alternative S-NSSAI does not have to be part of the subscribed S-NSSAI(s) in the UE subscription.

[0098] a) for roaming UE:

[0099] 1) if the S-NSSAI included in the allowed NSSAI needs to be replaced (i.e. the S-NSSAI to be replaced is part of the VPLMN S- NSSAIs), the AMF provides the mapping information between the S-NSSAI included in the allowed NSSAI and the alternative S- NSSAI to the UE; and

[0100] 2) if the S-NSSAI included in the mapped S-NSSAI(s) for the allowed NSSAI needs to be replaced (i.e. the S-NSSAI to be replaced is part of the HPLMN S-NSSAIs), the AMF provides the mapping information between the S-NSSAI and the alternative S- NSSAI to the UE.

[0101] NOTE 1A: In roaming scenarios, the alternative S-NSSAI part of the HPLMN S-NSSAIs does not have to be part of the subscribed S-NSSAI(s) in the UE subscription.

[0102] NOTE 2: It is up to AMF local policy to determine when to provide the mapping information between the S-NSSAI to be replaced and the alternative S-NSSAI to the UE, e.g. when the alternative S-NSSAI is available and there is no PDU session associated with the S- NSSAI to be replaced, or wait until the UE establishes the first PDU session associated with the S-NSSAI to be replaced.

[0103] If the AMF determines that the S-NSSAI which has been replaced is available, the AMF provides the updated alternative NSSAI excluding the S-NSSAI which has been replaced and the corresponding alternative S-NSSAI to the UE during the UE configuration update procedure or during the registration procedure.

[0104] If all the S-NSSAI(s) that were replaced in alternative NSSAI are available, the AMF provides the alternative NSSAI with Length of Alternative NSSAI contents set to 0 in the UE configuration update procedure or registration procedure. The AMF also provides the updated allowed NSSAI and configured NSSAI to the UE.

[0105] TS 24.501 specifies for session management with network slice replacement:

[0106] If:

[0107] a) the UE and network support network slice replacement;

[0108] b) the UE is provided with the mapping information between the S- NSSAI to be replaced and the alternative S-NSSAI; and

[0109] c) the UE decides to establish a new PDU session with the S-NSSAI to be replaced, the UE provides both the S-NSSAI to be replaced and the alternative S- NSSAI during PDU session establishment procedure. If the timer T3584 or timer T3585 is running for the S-NSSAI to be replaced, the UE should not stop the timer during PDU session establishment procedure. If the SMF receives both the S-NSSAI to be replaced and the alternative S-NSSAI during PDU session establishment procedure, the SMF proceeds with the PDU session establishment procedure with the alternative S-NSSAI. If the PDU session establishment request is accepted, the SMF includes the alternative S-NSSAI in the PDU session establishment accept message.

[0110] If the UE is provided with the mapping of the VPLMN S- NSSAI to a VPLMN alternative S-NSSAI, the UE provides both the VPLMN alternative S-NSSAI and the VPLMN S-NSSAI in the PDU SESSION ESTABLISHMENT REQUEST message. If the UE is provided with the mapping of the HPLMN S-NSSAI to a HPLMN Alternative S- NSSAI, the UE provides both the HPLMN alternative S-NSSAI and the HPLMN S-NSSAI in the PDU SESSION ESTABLISHMENT REQUEST message. The AMF sends both HPLMN alternative S-NSSAI and HPLMN S-NSSAI to the SMF.

[0111] If the SMF receives from the AMF an alternative S-NSSAI for existing PDU session and:

[0112] a) if the SMF decides to retain the existing PDU session (i.e. the SMF can serve both the alternative S-NSSAI and the S-NSSAI to be replaced with), the SMF sends the alternative S-NSSAI to the UE during network- requested PDU session modification procedure; or

[0113] b) if the SMF decides to re-activate the existing PDU session and:

[0114] 1) if the SSC mode of the PDU session is SSC mode 3, the SMF initiates PDU session modification procedure to trigger PDU Session reactivation by the UE; or

[0115] 2) If the SSC mode of the PDU session is SSC mode 1 or SSC mode 2, the SMF initiates PDU session release procedure to trigger PDU session reactivation by the UE.

[0116] If the timer T3584 or timer T3585 is running for the S-NSSAI that was replaced and the S-NSSAI that was replaced in alternative NSSAI is available and the AMF provides the updated allowed NSSAI and configured NSSAI to the UE, the UE should stop the timer.

[0117] Suppose, S-NSSAI-1 and S-NSSAI-2, S-NSSAI-3 are in configured NSSAI. AMF configured S-NSSAI-1 and S-NSSAI-3 as on-demand S-NSSAI and provided slice deregistration inactivity timer as:

[0118] On-Demand NSSAISSAISlice Deregistration inactivity timerS-NSSAI-1T1S-NSSAI-3T3

[0119] Case 1: Network indicate the slice deregistration inactivity timer to the UE

[0120] Scenario 1:

[0121] - UE initiated PDU session with S-NSSAI-1, T1 would stop.

[0122] - Network (e.g. AMF) sees the congestion on S-NSSAI-1 and indicate UE to move to S-NSSAI-3 as an alternative S-NSSAI-3.

[0123] The network can indicate to the UE to move to alternative S-NSSAI through following procedure

[0124] 1) PDU session modification command (with 5GSM cause #39 "reactivation requested"and including alternative S-NSSAI. In this case, UE release PDU session and initiate PDU session establishment procedure including alternative S-SNSSAI)

[0125] 2) PDU session modification command (without 5GSM cause #39 "reactivation requested"and including alternative S-NSSAI. In this case existing PDU session continued). This happens when SMF can handle both S-NSSAI to be replaced and alternative S-NSSAI

[0126] 3) PDU session release command with 5GSM cause #39 "reactivation requested". And including alterative S-NSSAI IE (information element). In this case, UE initiate PDU session establishment procedure with S-NSSAI to be replaced and alternative S-NSSAI.

[0127] As per the current state of Art, when PDU session is established then slice de-registration timer is stopped. Here, UE is still establishing PDU session with S-NSSAI to be replaced (S-NSSAI-1) and additionally including alternative S-NSSAI (S-NSSAI-3) so UE and AMF will only stop timer for S- NSSAI-1 and not the T3 which is related to S-NSSAI-3. Upon T3 timer expiry, UE and AMF will remove the S-NSSAI-3 from allowed NSSAI locally.

[0128] Scenario 2:UE is indicated with alternative S-NSSAI in the registration accept or UE configuration update command. UE starts slice deregistration inactivity timer T1 and T3 as PDU session is not yet established.

[0129] UE initiates the PDU session on S-NSSAI-1 with alternative S-NSSAI-3. In the current state of the art, the UE and AMF will only stop T1. As the T3 is running so after timer expiry, UE and network (e.g. AMF) will remove the S-NSSAI-3 from the allowed S-NSSAI locally.

[0130] Issue:to continue PDU session with alternative S-NSSAI, both S-NSSAI-1 and S-NSSAI-3 has to be in the allowed S-NSSAI. This problem will be more severe when SMF wants to retain the PDU session (procedure 2) and only indicate the alternative S-NSSAI to the UE in the network initiated PDU session modification procedure.

[0131] Case 2:Network doesn't indicated the slice deregistration inactivity timer to the UE

[0132] Scenario 1:

[0133] UE initiated PDU session with S-NSSAI-1, T1 would stop.

[0134] Network (e.g. AMF) sees the congestion on S-NSSAI-1 and indicate UE to move to S-NSSAI-3 as an alternative S-NSSAI-3.

[0135] The network can indicate to the UE to move to alternative S-NSSAI through below procedure.

[0136] 1) PDU session modification command (with 5GSM cause #39 "reactivation requested "and including alternative S-NSSAI. In this case, UE release PDU session and initiate PDU session establishment procedure including alternative S-SNSSAI)

[0137] 2) PDU session modification command (without 5GSM cause #39 "reactivation requested "and including alternative S-NSSAI. In this case existing PDU session continued). This happens when SMF can handle both S-NSSAI to be replaced and alternative S-NSSAI

[0138] 3) PDU session release command with 5GSM cause #39 "reactivation requested". And including alterative S-NSSAI IE (information element). In this case, UE initiate PDU session establishment procedure with S-NSSAI to be replaced and alternative S-NSSAI.

[0139] As per the current state of Art, when PDU session is established then slice deregistration inactivity timer is stopped. Here, UE is still establishing PDU session with S-NSSAI to be replaced (i.e. S-NSSAI- 1) and additionally including alternative S-NSSAI-3 so AMF will only stop timer T1 for S-NSSAI-1 and not the T3 which is related to S-NSSAI-3. Upon T3 timer expiry, AMF will remove the S-NSSAI-3 from allowed NSSAI and update UE with new allowed NSSAI through configuration update procedure (in this case, AMF will remove S-NSSAI-3 from the allowed NSSAI).

[0140] Scenario 2:UE is indicated with alternative S-NSSAI in the registration accept or UE configuration update command. UE starts slice deregistration inactivity timer T1 and T3 as PDU session is not yet established.

[0141] UE initiated PDU session on S-NSSAI-1 with alternative S- NSSAI-3. As current state of Art, AMF will only stop T1. As the T3 is running so after timer expiry, the network (e.g. AMF) will remove the S-NSSAI-3 from the allowed S-NSSA and update UE with new allowed NSSAI through configuration update procedure (in this case, AMF will remove S-NSSAI-3 from the allowed NSSAI).

[0142] Issue:to continue PDU session, S-NSSAI-1 and S-NSSAI-3 has to be in the allowed S-NSSAI. This problem will be more severe when SMF wants to retain the PDU session (procedure 2) and only indicate the alternative S-NSSAI to the UE in the network initiated PDU session modification procedure.

[0143] The network can configure slice-specific polices; more specifically, it is proposed to use PCF or local AMF configuration / policy for handling network policies related to S-NSSAIs subject to network control during the registration procedure. These policies can include one or more of the following components:

[0144] Whether the registration needs to be performed based on demand / usage or configuration. This indication can be configured by HPLMN and / or VPLMN (if authorized by HPLMN, based on e.g. UDM indication) and can be provided via existing UE configuration procedures e.g. together with the Configured NSSAI.

[0145] The slice deregistration inactivity timer after a slice is implicitly deregistered if no PDU sessions are present. This applies only for slices (S-NSSAIs) that are configured as on-demand S-NSSAI. The timer runs at the UE (if configured) and the AMF. The timer is provided by the HPLMN or the VPLMN (AMF policy) during the Registration procedure for the Configured NSSAI in the on-demand NSSAI. The timer can be per S-NSSAI and associated with access.

[0146] The AMF determines to deregister the network slice if no PDU session is using the slice for a determined network slice deregistration time which runs only at the AMF. The SMF determines to release the PDU session if no user data is sent over the PDU session for a determined PDU session inactivity timer which runs only at the UPF. The AMF may also removes the S-NSSAI from the Allowed NSSAI based on indication from the SMF after completion other PDU session for the same slice over related access type.

[0147] The PDU session inactivity timer, which cause the release of a PDU session if no data was transmitted or received for the duration of the inactivity timers, or Network slice Deregistration timer which cause the removal of a given S-NSSAI from an Allowed NSSAI after the last PDU session in the network slice was released, may be set by authorized AF (if PLMN allows and for slices solely dedicated for the AF and not shared with others) and stored in the network (e.g. UDM or PCF per S-NSSAI / DNN. The timer from network can be obtained by an AMF and SMF respectively at the time of UE registration and PDU session establishment. For EPS case, the PDN connections have similar handling to PDU sessions in 5GS.

[0148] Fig. 1 is a sequence diagram that illustrates the slice deregistration inactivity timer on alternative S-NSSAI according to prior art. As shown in the sequence diagram, a UE (102), an AMF (104), and a SMF (106) are in communication with each other.

[0149] At step 1, pre-condition: the UE (102) is registered over 3GPP access (3GPPA) types via the AMF (104) and S-NSSAI-1 and S-NSSAI-3 is configured as on-demand on 3GPPA with slice deregistration inactivity timer T1 and T3 for the S-NSSAI-1 and S-NSSAI-2. At step 2, the UE (102) establishes a PDU session over an on-demand S-NSSAI (e.g.: S-NSSAI 1) over an access type such as 3GPPA. At step 3, the UE (102) receives a PDU session establishment accept. At step 4, the slice deregistration inactivity timer associated with S-NSSAI-1 on 3GPPA or the AMF (104) is stopped.

[0150] At step 5, the UE (102) receives the below downlink NAS message.

[0151] Case 1: PDU Session modification request with 5GSM cause #39 and alternative S-NSSAI.

[0152] Case 2: PDU session modification command with alternative S-NSSAI-3.

[0153] Case 3: PDU session release command with 5GSM cause #39 with alternative S-NSSAI-3.

[0154] At step 6, the UE (102) initiates a PDU session establishment request with S-NSSAI-1 and alternative S-NSSAI-3 for the case 1 and case 3 in step-5. For the case 2 in step-5: The UE (102) and the AMF (104) keep the mapping of S- NSSAI-1 and its alternative S-NSSAI-3.

[0155] At step 7, the UE (102) receives a PDU session establishment accept (for the case 1 and 3).

[0156] At step 8, Issue: The AMF (104) and / or the UE (102) continue to run the slice deregistration inactivity timer T3 and after expiry:

[0157] Case 1: If the UE (102) and slice deregistration inactivity timer is configured in the UE (102), the UE (102) and the AMF (104) remove S-NSSAI-3 from allowed NSSAI locally after T3 expiry.

[0158] Case 2: If the UE (102) is not configured with the slice deregistration inactivity timer, then the AMF (104) removes the S-NSSAI-3 from the allowed NSSAI and updates the UE (102) with the new allowed NSSAI with removing S-NSSAI-3.

[0159] For the PDU session using alternative S-NSSAI, both S- NSSAI-1 and S-NSSAI-3 shall be in the allowed NSSAI. But here, the UE (102) and the AMF (104) will remove S-NSSAI from the allowed NSSAI may cause the AMF (104) or UE (102) to release PDU session with alternative S-NSSAI.

[0160] Fig. 2 is a block diagram that illustrates a schematic of the UE (102) implemented to carry out the disclosed subject matter according to an embodiment as disclosed herein. Examples of the UE (102) can include, but are not limited to, Consumer Electronics (such as Mobile Phones and Smartphones), Tablets, Wearable Devices, Computing Devices (such as Laptops, Notebooks, Desktops, Workstations, etc.), IoT Devices, Automotive Systems (such as connected cars, Autonomous Vehicles, Vehicle-to-Everything (V2X) communication devices, etc.), Enterprise Devices such as robotics, Specialized Equipment (such as Medical Devices, Public Safety Devices, etc.), Media Devices (such as Gaming Consoles, Streaming Devices, etc.).

[0161] In an embodiment, in Fig. 2, the UE (102) includes a first processor (108), a first memory (110), a first I / O interface (112), and a UE slice deregistration inactivity timer controller (114) coupled to the first processor (108) and the first memory (110). The components are explained in further detail below.

[0162] The first processor (108) communicates with the first memory (110), the first I / O interface (112), and the UE slice deregistration inactivity timer controller (114). The first processor (108) is configured to execute instructions stored in the first memory (110) and to perform various processes. The first processor (108) includes one or a plurality of processors, is a general-purpose processor such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial Intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0163] The first memory (110) includes storage locations to be addressable through the first processor (108). The first memory (110) is not limited to a volatile memory and / or a non-volatile memory. Further, the first memory (110) includes a plurality of computer-readable storage media. The first memory (110) includes non-volatile storage elements. For example, non-volatile storage elements includes magnetic hard disks, optical disks, floppy disks, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

[0164] The first I / O interface (112) transmits the information between the first memory (110) and external peripheral devices. The peripheral devices are the input-output devices associated with the UE (102). Further, the UE slice deregistration inactivity timer controller (114) communicates with the first I / O interface (112) and the first memory (110). The UE slice deregistration inactivity timer controller (114) is coupled to the first memory (110) and the first processor (108). The UE slice deregistration inactivity timer controller (114) is innovative hardware that are realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

[0165] In an embodiment, the UE slice deregistration inactivity timer controller (114) detects the slice inactivity deregistration timer configured for an alternative S-NSSAI by a network apparatus. The alternative S-NSSAI refers to additional S-NSSAIs provided by a network to offer flexibility in network slice selection. The alternative S-NSSAI servers as a substitute for the first S-NSSAI when the first S-NSSAI is unavailable or congested.

[0166] In an embodiment, the UE slice deregistration inactivity timer controller (114) establishes a PDU session with a first S-NSSAI and the alternative S-NSSAI. Upon establishment of the PDU session, the UE (102) can send and receive data over the 5GC network. The PDU session established can support different data types of protocols, such as IPv4, IPv6, IPv4v6, Ethernet, and the like.

[0167] In an embodiment, the UE slice deregistration inactivity timer controller (114) detects whether the alternative S-NSSAI is the on-demand S-NSSAI and the slice inactivity deregistration timer is running. This detection is performed after the PDU session is established with the first S-NSSAI and the alternative S-NSSAI or an existing PDU session is established with the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI through e,g PDU session modification procedure. The on-demand S-NSSAI refers to an S-NSSAI that is not pre-configured or readily available, but can be dynamically initiated upon request from the UE (102). The UE slice deregistration inactivity controller (114) then stops the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0168] In an embodiment, the UE slice deregistration inactivity timer controller (114) determines whether that the PDU session established with the first S-NSSAI and the alternate S-NSSAI is moved back to the first S-NSSAI (e.g through PDU session modification procedure) or whether the PDU session associated with the first S-NSSAI and the alternative S-NSSAI is released. The UE slice deregistration inactivity timer controller (114) then restarts or starts the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternate S-NSSAI is moved back to the first S-NSSAI or the PDU session associated with the alternative S-NSSAI is released.

[0169] Fig. 3 is a block diagram that illustrates a schematic of the network apparatus (302) implemented to carry out the disclosed subject matter according to an embodiment as disclosed herein. As shown, the network apparatus (302) includes a second processor (304), a second memory (306), a second I / O interface (308), and a network slice differentiated service controller (310).

[0170] The network apparatus (302) includes various hardware and software components that facilitate communication between user equipment and network infrastructure. Examples of the network apparatus (302) can include, but is not limited to Base Stations (such as macro cells, small cells, femtocells, picocells, etc.) for wireless communication, Antennas and RF Units (e.g., MIMO, beamforming) to enhance signal coverage and data throughput, Core Network Equipment (e.g., MMEs, S-GWs, P-GWs in 4G; AMFs, SMFs, UPFs in 5G) for data routing, mobility, and session control, Network Function Virtualization (NFV) and Software-Defined Networking (SDN) for dynamic resource allocation and scalability, Edge Computing Nodes (e.g., MEC servers) for low-latency processing, Backhaul and Transport Equipment (e.g., fiber-optic links, microwave relays, Ethernet switches) to connect base stations to the core network, Network Management Systems (NMS) and Operation Support Systems (OSS) for network configuration, fault management, and optimization, Radio Network Controllers (RNCs) in 3G, Distributed Units (DUs), and Centralized Units (CUs) in 5G, Network Slicing Components for virtualized resource allocation, Security elements (e.g., Firewalls, IDS, AAA Servers) for secure communication.

[0171] The network slice differentiated service controller (310) is coupled to the second memory (306) and the second processor (304). The network slice differentiated service controller (310) is innovative hardware that are realized through the physical implementation of both analog and digital circuits, including logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, as well as optical components.

[0172] In an embodiment, the network slice differentiated service controller (310) configures the slice inactivity deregistration timer at the UE (102) for an alternative S-NSSAI. When a first S-NSSAI or a requested S-NSSAI is unavailable, then the alternative S-NSSAI is assigned for fulfilling similar network requirements than the first S-NSSAI. The slice inactivity deregistration timer monitors an activity on the alternative S-NSSAI.

[0173] In an embodiment, the network slice differentiated service controller (310) detects that the UE (102) has established a PDU session with a first S-NSSAI and the alternative S-NSSAI. The UE (102) initiates the PDU session by including its desired S-NSSAI. If the desired slice is available, then the first S-NSSAI is assigned to the PDU session. Else, the alternate S-NSSAI that can fulfill the service requirements of the PDU session is assigned if the desired slice is unavailable.

[0174] In an embodiment, the network slice differentiated service controller (310) determines whether the alternative S-NSSAI is the on-demand S-NSSAI and the slice inactivity deregistration timer is running. This determination is performed after the PDU session is established with the alternative S-NSSAI or an existing PDU session is established when the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. The network slice differentiated service controller (310) then stops the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0175] In an embodiment, the second differentiated service controller (310) detects whether the PDU session established with the first S-NSSAI and the alternate S-NSSAI is moved back to the first S-NSSAI or whether the PDU session associated with the alternative S-NSSAI is released by the UE (102) or by the network apparatus (302). The network slice differentiated service controller (310) then starts or restarts the slice deregistration inactivity timer associated with the alternative S-NSSAI when PDU session with alternative S-NSSAI is moved back to the first S-NSSAI or when the PDU session with alternative S-NSSAI is released by the UE (102) or by the the network (by the AMF(104) or SMF(106)).

[0176] Fig. 4 is a sequence diagram that illustrates stopping the slice deregistration inactivity timer on the alternative S-NSSAI according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102), the AMF (104), and the SMF (106) are in communication with each other.

[0177] At step 1, the pre-condition: The UE (102) is registered over 3GPP access (3GPPA) types via the AMF (104) and S-NSSAI-1 and S-NSSAI-3 is configured as on- demand on 3GPPA with slice deregistration inactivity timer T1 and T3 for the S-NSSAI-1 and S-NSSAI-2. At step 2, the UE (102) establishes a PDU session over an on-demand S-NSSAI (eg: S-NSSAI 1) over an access type such as 3GPPA. At step 3, the UE (102) receives a PDU session establishment accept.

[0178] At step 4, slice deregistration inactivity timer associated with S-NSSAI-1 on the 3GPPA / AMF (104) and / or UE (102) is stopped .

[0179] At step 5, the UE (102) receive one of the below downlink NAS message

[0180] Case 1: PDU Session modification request with 5GSM cause #39 and alternative S-NSSAI. Case 2: PDU session modification command with alternative S-NSSAI-3. Case 3: PDU session release command with 5GSM cause #39 with alternative S-NSSAI-3.

[0181] At step 6, the UE (102) initiates a PDU session establishment request with S-NSSAI-1 and alternative S-NSSAI-3 for the case 1 and case 3. For the case 2: The UE (102) and the AMF (104) keep the mapping of S- NSSAI-1 and its alternative S-NSSAI-3. At step 7, the UE (102) receives a PDU session establishment accept (for the case 1 and 3). At step 8, for the case where the UE (102) establishes the PDU session with S-NSSAI-1 (called slice to be replaced) and the alternative S-NSSAI (in this case S-NSSAI-3), the UE (102) and the AMF (104) shall stop the slice deregistration inactivity timer associated with the alternative S-NSSAI if running. In this case, slice deregistration inactivity timer (T3) associated with S-NSSAI-3is stopped.

[0182] In an embodiment, the solution may be applicable for the 3GPP access and non-3GPP access. The slice deregistration inactivity timer and alternative NSSAI is access specific.

[0183] In an embodiment, when the UE (102) establishes the PDU session with S-NSSAI to be replaced (S-NSSAI-1) and alternative S-NSSAI (S-NSSAI- 3), the UE (102) considers that the PDU session is associated with the S-NSSAI to be replaced and alternative S-NSSAI. The UE (102) and the AMF (104) stop the running the slice de- registration inactivity timer for S-NSSAI associated with the PDU session. In this case S-NSSAI-1 and S-NSSAI-3 are associated with the PDU session so timer T1 and T3 will be stopped, if running.

[0184] In an embodiment, slice deregistration inactivity timer on alternative S-NSSAI (T3) is stopped at the time of PDU session establishment request is sent with slice to be replaced and alternative S-NSSAI or after PDU session establishment accept is received with alternative S-NSSAI or when PDU session modification command is received with alternative S-NSSAI optionally with 5GSM cause#39 "reactivation requested"or PDU session release is received with alternative S-NSSAI and 5GSM cause#39"reactivation requested."

[0185] In an embodiment, when the UE (102) receives the PDU session modification command with the alternative S-NSSAI without 5GSM, a cause 39"reactivation is requested". The AMF (104) and / or the UE (102) shall stop the running slice deregistration inactivity timer on alternative S-NSSAI, if any.

[0186] In an embodiment, if the S-NSSAI or the mapped S-NSSAI of the PDU session needs to be replaced and the SMF (106) determines that the PDU session needs to be retained, the SMF (106) shall include the Alternative S-NSSAI IE in the PDU SESSION MODIFICATION COMMAND message. The UE (102) and the AMF (104) shall stop the slice de-registration inactivity timer if running for the alternative S-NSSAI included in the Alternative S-NSSAI IE

[0187] In an embodiment, If the selected SSC mode of the PDU session is "SSC mode 3", the S-NSSAI or the mapped S-NSSAI associated with the PDU session needs to be replaced and the SMF (106) determines that the PDU session needs to be re-established on the alternative S-NSSAI, the SMF (106) shall include the Alternative S-NSSAI IE and 5GSM cause #39　"reactivation requested" in the PDU SESSION MODIFICATION COMMAND message. The UE (102) and the AMF (104) shall stop the slice de-registration inactivity timer if running for the alternative S-NSSAI included in the Alternative S-NSSAI IE.

[0188] In an embodiment, If the selected SSC mode of the PDU session is "SSC mode 2" or "SSC mode 1", the S-NSSAI or the mapped S-NSSAI of the PDU session needs to be replaced, the SMF (106) shall include the Alternative S-NSSAI IE and 5GSM cause #39　"reactivation requested" in the PDU SESSION RELEASE COMMAND message. The UE (102) and the AMF (104) shall stop the slice de-registration inactivity timer if running for the alternative S-NSSAI included in the Alternative S-NSSAI IE.

[0189] In an embodiment, If the PDU SESSION ESTABLISHMENT Request include alternative S-NSSAI associated with the S-NSSAI to be replaced, if an alternative S-NSSAI for the S-NSSAI or the mapped S-NSSAI exists then The UE (102) and the AMF (104) shall stop the slice de-registration inactivity timer if running for the alternative S-NSSAI. If the PDU session establishment accept include the alternative S-NSSAI, then the UE (102) and the AMF (104) shall stop the slice de-registration inactivity timer if running for the alternative S-NSSAI.

[0190] Fig. 5 is a sequence diagram that illustrates starting the slice deregistration inactivity timer on the alternative S-NSSAI according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102), the AMF (104), and the SMF (106) are in communication with each other.

[0191] At step 1, the pre-condition: The UE (102) is registered over 3GPP access (3GPPA) types via the AMF (104) and S-NSSAI-1 and S-NSSAI-3 is configured as on-demand on 3GPPA with slice deregistration inactivity timer T1 and T3 for the S-NSSAI-1 and S-NSSAI-2. At step 2, the UE (102) establishes a PDU session over an on-demand S-NSSAI (for example, S-NSSAI 1) over an access type such as 3GPPA. At step 3, the UE (102) receives a PDU session establishment accept. At step 4, slice deregistration inactivity timer associated with S-NSSAI-1 on 3GPPA is stopped.

[0192] At step 5, the UE (102) receives a one of the below downlink NAS message

[0193] Case 1: PDU Session modification request with 5GSM cause #39 and alternative S-NSSAI.

[0194] Case 2: PDU session modification command with alternative S-NSSAI-3.

[0195] Case 3: PDU session release command with 5GSM cause #39 with alternative S-NSSAI-3.

[0196] At step 6, the UE (102) initiates a PDU session establishment request with S-NSSAI-1 and alternative S-NSSAI-3 for the case 1 and case 3. For the case 2: the UE (102) and the AMF (104) keep the mapping of S-NSSAI-1 and its alternative S-NSSAI-3. At step 7, the UE (102) receives a PDU session establishment accept (for the case 1 and 3). At step 8, for the case where the UE (102) establishes the PDU session with the S-NSSAI-1 (called slice to be replaced) and alternative S-NSSAI (in this case S-NSSAI-3), the UE (102) and the AMF (104) shall stop the slice deregistration inactivity timer associated with the alternative S-NSSAI if running. In this case, S-NSSAI-3 slice deregistration inactivity timer is stopped (T3). At step 9, the PDU session modification commend / PDU session release request is initiated.

[0197] Solution: at step 10

[0198] Case 1: PDU Session modification request with 5GSM cause #39 S-NSSAI-1.

[0199] Case 2: PDU session modification command with S-NSSAI-1.

[0200] Case 3: PDU session release command with 5GSM cause #39 with S-NSSAI-1.

[0201] For case 1 and case 3:The AMF (104) and / or the UE (102) shall start the slice deregistration inactivity alternative S-NSSAI-3(T3) if there is no other PDU session associated with the alternative S-NSSAI (S-NSSAI-3)on the corresponding access. The AMF (104) and / or the UE (102) shall start the slice deregistration inactivity timer for the S-NSSAI-1 (T1) if there is no other PDU session associated with S-NSSA-1.

[0202] For the case 2: AMF (104) and / or the UE (102) shall start the slice deregistration inactivity alternative S-NSSAI-3(T3) if there is no other PDU session associated with the alternative S-NSSAI (S-NSSAI-3) on the corresponding access. The AMF (104) and / or the UE (102) shall not start the slice deregistration timer for the S-NSSAI-1 (T1).

[0203] In an embodiment, starting and stopping of the slice deregistration inactivity timer is associated with the access (i.e 3GPP access, non-3GPP access).In an embodiment, PDU session release command may come to replace the alternative S-NSSAI-3 with other S-NSSAI-x (i.e change S-NSSAI to be replaced S-NSSAI-1 with alternative S-NSSAI-3 to S-NSSAI-1 to be replaced S-NSSAI-1 with alternative S-NSSAI-x). So, the AMF (104) and / or the UE (102) can either start running timer T1 and T3 (if any) or then stop T1 once the PDU session establishment procedure is started or doesn't start T1. The UE (102) starts T3 if it is configured in on-demand S-NSSAI for the S-NSSAI-3 and there is no other PDU session with the S-NSSAI-3. Additionally UE (102) shall stop the slice deregistration timer associated with the S-NSSAI-x.

[0204] In an embodiment, if the replaced S-NSSAI is available and the SMF (106) determines that the PDU session (associated with slice to be replaced (S-NSSAI-1) and alternative S-NSSAI (S-NSSAI-S3)) needs to be retained, the SMF (106) include replaced S-NSSAI (S-NSSAI-1) in the PDU SESSION MODIFICATION COMMAND message. The AMF (104) and / or the UE (102) shall start the slice deregistration inactivity timer for alternative S-NSSAI-3(T3) if there is no other PDU session associated with the alternative S-NSSAI (S-NSSAI-3)on the corresponding access

[0205] In an embodiment, if the selected SSC mode of the PDU session is "SSC mode 3", the replaced S-NSSAI (S-NSSAI-1) is available and the SMF (106) determines that the PDU session needs to be re-established on the replaced S-NSSAI (S-NSSAI-1), the SMF (106) shall include and 5GSM cause #39　"reactivation requested" and include the replaced S-NSSAI (S-NSSAI-1) in the PDU SESSION MODIFICATION COMMAND message. The AMF (104) and / or the UE (102) shall start the slice deregistration inactivity timer for alternative S-NSSAI-3(T3) if there is no other PDU session associated with the alternative S-NSSAI (S-NSSAI-3) on the corresponding access.

[0206] in an embodiment, If the selected SSC mode of the PDU session is "SSC mode 2" or "SSC mode 1", replaced S-NSSAI(S-NSSAI-1) is available and the SMF(106) determines that the PDU session needs to be re-established on the replaced S-NSSAI (S-NSSA-1), the SMF(106) shall include 5GSM cause #39　"reactivation requested" and the replaced S-NSSAI(S-NSSAI-1) in the PDU SESSION RELEASE COMMAND message. The AMF (104) and / or the UE (102) shall start the slice deregistration inactivity timer for alternative S-NSSAI-3(T3) if there is no other PDU session associated with the alternative S-NSSAI (S-NSSAI-3)on the corresponding access.

[0207] In an embodiment, no other PDU session associated S-NSSAI (e.g S-NSSAI-x) means there is no other PDU session including MA PDU session established with S-NSSAI (S-NSSAI-x) and there is no PDU session including MA PDU session established with S-NSSAI-x as alternative S-NSSAI. If the AMF (104) determines that the S-NSSAI, which has been replaced is available, the AMF (104) provides the updated alternative NSSAI excluding the S-NSSAI which has been replaced and the corresponding alternative S-NSSAI to the UE (102) during the UE configuration update procedure or during the registration procedure. If all the S-NSSAI(s) that were replaced in the alternative NSSAI are available, the AMF (104) provides the alternative NSSAI with length of alternative NSSAI contents set to 0 in the UE configuration update procedure or registration procedure. The AMF (104) also provides the updated allowed NSSAI and configured NSSAI to the UE (102). Then the AMF (104) and / or the UE (102) shall start the slice deregistration inactivity timer associated with the alternative S-NSSAI (if configured as on-demand) if there is no PDU session associated with alternative S-NSSAI is established or being established. In this case, the AMF (104) and / or the UE (102) will start the slice deregistration inactivity timer T3 if there is no PDU session associated with S-NSSAI-3 on the access.

[0208] In an embodiment, the AMF (104) doesn't configure on-demand S- NSSAI for the alternative S-NSSAI.

[0209] In an embodiment, when the AMF (104) sees that S-NSSAI-3 is configured as on-demand S-NSSAI, then it doesn't indicate S-NSSAI-3 as the alternative S-NSSAI to the UE (102) / SMF (106).

[0210] In an embodiment, when the AMF (104) sees that S-NSSAI-3 is configured as on-demand S-NSSAI and it need to be alternative S-NSSAI, the AMF (104) updates the UE (102) with new on-demand NSSAI IE removing S-NSSAI-3. Optionally when the S-NSSAI is removed from alternative S-NSSAI, the AMF (104) may update the UE (102) with updated on-demand NSSAI including S-NSSAI-3 in the on-demand NSSAI IE The on-demand NSSAI IE can be included in the registration accept or UE configuration update command.

[0211] In an embodiment, the AMF (104) doesn't consider S-NSSAI in the on-demand NSSAI for the slice replacement. If it wants to do the slice replacement of the on-demand S-NSSAI, then the AMF (104) makes it non on-demand (remove S-NSSAI-3 from on-demand NSSAI).

[0212] Fig. 6 is a sequence diagram that illustrates a scenario where the UE (102) and the AMF (104) do not remove the alternative S-NSSAI immediately according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102), the AMF (104), and the SMF (106) are in communication with each other.

[0213] At step 1, the pre-condition: The UE (102) is registered over a 3GPP access (3GPPA) types via the AMF (104) and S-NSSAI-1 and S-NSSAI-3 is configured as on- demand on 3GPPA with slice deregistration inactivity timer T1 and T3 for the S-NSSAI-1 and S-NSSAI-2. At step 2, the UE (102) establishes a PDU session over an on-demand S-NSSAI (eg: S-NSSAI 1) over an access type such as 3GPPA. At step 3, the UE (102) receives a PDU session establishment accept. At step 4, the slice deregistration inactivity timer associated with S-NSSAI-1 on 3GPPA is stopped.

[0214] At step 5, the UE (102) receives a downlink NAS message

[0215] Case 1: PDU Session modification request with 5GSM cause #39 and alternative S-NSSAI. Case 2: PDU session modification command with alternative S-NSSAI-3. Case 3: PDU session release command with 5GSM cause #39 with alternative S-NSSAI-3.

[0216] At step 6, the UE (102) initiate a PDU session establishment request with S-NSSAI-1 and alternative S-NSSAI-3 for the case 1 and case 3. For the case 2: the UE (102) will not send PDU session establishment request. At step 7, the UE (102) receives a PDU session establishment accept.

[0217] Solution: at step 8, T3 running.

[0218] The AMF (104) and / or UE-Timer T3 expiry. The UE (102) and the AMF (104) doesn't remove the S-NSSAI-3 from the allowed NSSAI if PDU there is PDU session associated with alternative S-NSSAI-3. The AMF (104) and / or the UE (102) remove S-NSSAI-3 once the PDU session associated with S-NSSAI-3 or alternative S-NSSAI-3 is released.

[0219] The below embodiment applies if the UE (102) supports network slice usage control. The alternative S-NSSAI is treated as the same way as S-NSSAI to be replaced. I.e. if slice deregistration inactivity timer is configured with alternative S-NSSAI. The UE (102) stops the timer when the PDU session is established. The UE (102) starts the slice deregistration inactivity timer associated with alternative S-NSSAI if there is no other PDU session on the alternative S-NSSAI and the S-NSSAI is no longer alternative S-NSSAI (alternative S-NSSAI is removed) or PDU session associated with alternative S-NSSAI is released.

[0220] In an embodiment, a PDU session is successfully established for the on-demand alternative S-NSSAI, the AMF (104) and / or UE (102) shall stop and reset the slice deregistration inactivity timer for the on- demand alternative S-NSSAI over corresponding access type, if running.

[0221] In an embodiment, the PDU session is successfully established associated with alternative S-NSSAI (on-demand alternative S- NSSAI), the AMF (104) and / or the UE (102) shall stop and reset the slice deregistration inactivity timer for the on-demand alternative S-NSSAI over corresponding access type, if running.

[0222] In an embodiment, If the UE (102) supports network slice usage control:

[0223] a) all PDU session associated with an on-demand S-NSSAI are released and there is no MA PDU session associated with this on-demand S-NSSAI or there is no PDU session associated with alternative S-NSSAI (e.g S-NSSAI-1) on this on-demand S-NSSAI (S-NSSAI-1), the UE (102) shall start the slice deregistration inactivity timer for this on-demand S-NSSAI (S-NSSAI-1) over the corresponding access type;

[0224] b) all MA PDU session associated with an on-demand S-NSSAI are

[0225] released ,there is no PDU session associated with this on-demand S-NSSAI or there is no PDU session associated with alternative S-NSSAI (e.g S- NSSAI-1) on this on-demand S-NSSAI (S-NSSAI-1), the UE (102) shall start the slice deregistration inactivity timer for this on-demand S-NSSAI over both 3GPP access and non-3GPP access; or

[0226] c) all PDU session and all MA PDU session associated with an on- demand S-NSSAI are released and there is no PDU session associated with alternative S-NSSAI (e.g S-NSSAI-1) on this on-demand S- NSSAI (S-NSSAI-1), the UE (102) shall start the slice deregistration inactivity timer for this on-demand S-NSSAI over both 3GPP access and non-3GPP access.

[0227] In an embodiment, the slice deregistration inactivity timer is:

[0228] a) started when there is no established PDU session, including any MA PDU session, associated with the S-NSSAI or alternative S-NSSAI over the corresponding access type; and

[0229] b) stopped and reset when at least a PDU session, including any MA PDU session, associated with the S-NSSAI or alternative S-NSSAI is successfully established over the corresponding access type(s) or the S- NSSAI is removed from the allowed NSSAI.

[0230] In an embodiment, suppose S-NSSAI-x is configured as on-demand S-NSSAI (with slice deregistration inactivity timer T)

[0231] The slice deregistration inactivity timer is:

[0232] a) started for (T started) when there is no established PDU session, including any MA PDU session, associated with the S-NSSAI (S-NSSAI-x) or alternative S-NSSAI (S-NSSAI-x) over the corresponding access type (i.e if S-NSSAI-x is on-demand and the UE (102) has not established PDU session with S-NSSAI-X or alternative S-NSSAI-x, then the AMF (104) and / or the UE (102) starts the slice deregistration inactivity timer for the S-NSSAI-x); and

[0233] b) stopped and reset (Timer T) when at least a PDU session, including any MA PDU session, associated with the S-NSSAI (S-NSSAI-x) or alternative S-NSSAI (S-NSSAI-x) is successfully established over the corresponding access type(s) or the S-NSSAI is removed from the allowed NSSAI.

[0234] In an embodiment, if the UE (102) supports network slice usage control and: a PDU session is successfully established with S-NSSAI (S- NSSAI to be replaced) and alternative S-NSSAI.

[0235] - If the S-NSSAI / S-NSSAI to be replaced is on-demand S-NSSAI, AMF (104) and / or the UE (102) stop / reset slice deregistration inactivity timer if running.

[0236] - If the alternative S-NSSAI is on-demand S-NSSAI, the AMF (104) and / or the UE (102) shall stop / reset slice deregistration inactivity timer associated with alternative S-NSSAI, if running

[0237] In an embodiment, the UE (102) sent S-NSSAI in PDU session establishment request (along with Uplink NAS transport) and also called S-NSSAI to be replaced if alternative S-NSSAI is available for the S-NSSAI.

[0238] In an embodiment, if the S-NSSAI or the mapped S- NSSAI of the PDU session needs to be replaced and the SMF (106) determines that the PDU session needs to be retained, the SMF (106) shall include the alternative S-NSSAI IE in the PDU SESSION MODIFICATION COMMAND message. If the Alternative S-NSSAI is on-demand NSSAI, then the AMF (104) and or shall stop slice deregistration inactivity timer for the alternative S-NSSAI.

[0239] Fig. 7 is a sequence diagram that illustrates a scenario where the SMF (106) indicates the UE (102) with the alternative S-NSSAI by keeping the PDU session according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102), the AMF (104), and the SMF (106) are in communication with each other.

[0240] At step 5, if the S-NSSAI or the mapped S-NSSAI of the PDU session needs to be replaced and the SMF (106) determines that the PDU session needs to be retained, the SMF (106) shall include the Alternative S- NSSAI IE in the PDU SESSION MODIFICATION COMMAND message. As per the prior art, AMF (104) and / or the UE (102) will not stop slice deregistration inactivity timer for the alternative S-NSSAI (consider alternative S-NSSAI is on-demand S-NSSAI)

[0241] At step 6, if the SMF (106) have some other trigger for the PDU session modification, it sends the alternative S-NSSAI or not is not in the prior art. If the SMF (106) doesn't send the alternative S-NSSAI, the UE (102) may assume that the alternative S-NSSAI is no more required and the UE (102) is on the S-NSSAI-1 alone. At step 7-8, the AMF (104) sends to the UE (102) that S-NSSAI-1 is no longer congested in the configuration update command with updated Alternative NSSAI (with removing alternative S-NSSAI S-NSSAI-1 to S-NSSAI-2 mapping) or sending length of alternative NSSAI to zero. It is not specified, whether this indication is treated as the UE (102) move back to the S- NSSAI-1 or UE (102) will wait for the PDU session modification command. This is not specified in prior art.

[0242] Fig. 8 is a sequence diagram that illustrates a scenario when the alternative S-NSSAI is indicated and removed from the PDU session according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (102), the AMF (104), and the SMF (106) are in communication with each other.

[0243] At step 5, if the S-NSSAI or the mapped S-NSSAI of the PDU session needs to be replaced and the SMF (106) determines that the PDU session needs to be retained, the SMF (106) shall include the Alternative S- NSSAI IE in the PDU SESSION MODIFICATION COMMAND message. The AMF (104) and / or the UE (102) will shall stop the slice deregistration inactivity timer for the alternative S-NSSAI (consider alternative S-NSSAI is on-demand S-NSSAI). The UE (102) can stop slice deregistration inactivity timer for the S-NSSAI-2 in step 4 as well when the UE (102) receives S-NSSAI-2 as alternative S-NSSAI to S-NSSAI-1 where PDU session is already established.

[0244] At step 6, unless, congestion is removed on S-NSSAI-1, the SMF (106) shall send alternative S-NSSAI in every PDU session modification command. At step 7, solution a) the AMF (104) sends to the UE (102) that S-NSSAI-1 is no longer congested in the configuration update command with updated Alternative NSSAI (with removing alternative S-NSSAI S-NSSAI-1 to S-NSSAI-2 mapping). The UE (102) deems that alternative S-NSSAI-2 is no longer associated with PDU session (specifically when the UE (102) receives PDU session modification with alternative S-NSSAI without 5GSM cause 39 previously to indicate alternative S-NSSAI associated with PDU session). The AMF (104) / UE (102) starts slice deregistration inactivity timer associated with the alternative S-NSSAI-2 if no other PDU session is established on S-NSSAI- 2.

[0245] At step 8, solution b) The UE (102) receive PDU session modification command with alternative S-NSSAI set to dummy value or Length of S-NSSAI contents set to 0. When the UE (102) receive PDU session modification command with alternative S-NSSAI set to dummy value or Length of S-NSSAI contents set to 0. The AMF (104) / UE (102) starts the slice deregistration inactivity timer associated with alternative S-NSSAI-2 if no other PDU session is established on S-NSSAI-2.

[0246] In an embodiment, suppose alternative S-NSSAI-Y and / or S-NSSAI is to be replaced S-NSSAI-X are on-demand S-NSSAI. The PDU session is established with alternative S-NSSAI (i.e S-NSSAI-X (slice to be replaced) and S-NSSAI-Y (Alternative S-NSSAI)), the AMF (104) and / or the UE (102) shall start the slice inactivity de-registration timer associated with S-NSSAI-X if there is no other PDU session is established on S-NSSI-x. The AMF (104) and / or the UE (102) shall start slice inactivity de-registration timer associated with S-NSSAI-Y (alternative S-NSSAI) if there is no PDU session is established on S-NSSAI-Y including MA PDU session.

[0247] In an embodiment, the UE (102) with PDU session is established with S-NSSAI-X and Alternative S-NSSAI-Y and the PDU session is moved to other S-NSSAI-Z, then the AMF (104) / UE (102) shall start slice deregistration inactivity timer associated with S-NSSAI-Y if there is no other PDU session on S-NSSAI-Y including MA PDU session on S-NSSAI-Y and stop the slice deregistration inactivity timer associated with S-NSSAI-z if running.

[0248] In an embodiment, the AMF (104) can indicated to the UE (102) that alternative S-NSSAI is deleted (i.e PDU session is established or to be established with S-NSSAI-X). In this case, the UE (102) shall start slice deregistration inactivity timer associated with S-NSSAI-Y if there is no other PDU session on S-NSSAI-Y including MA PDU session.

[0249] In an embodiment, the UE (102) can be indicate about the alternative S-NSSAI / indication that Alternative S-NSSAI is removed, in the UE configuration update command or PDU session release command or PDU session modification command. The UE (102) can consider any command NAS message to decide about the alternate S-NSSAI inclusion with the PDU session, removal / deletion of alternative S-NSSAI from the PDU session. In this embodiment, stopping the slice deregistration inactivity timer means stop and reset the ongoing timer.

[0250] In an embodiment, removing alternative S-NSSAI (e.g. S-NSSAI-1) associated with PDU session established with S-NSSAI (e.g. S-NSSAI-1. S-NSSAI-1 is also referred as S-NSSAI / slice to be replaced) can happens when the AMF (104) sees congestion is removed on alternative S-NSSAI (S-NSSAI-1) or the AMF (104) finds other alternative S-NSSAI (S-NSSAI-2) for the S-NSSAI-1 and indicates to the UE (102) (through NAS message e.g. PDU session modification procedure or PDU session release procedure and / or UE configuration update command).

[0251] In an embodiment, starting and stopping slice inactivity timer is associated with access (3GPP and non-3GPP) for normal. In case of MA PDU session, the slice deregistration inactivity timer can be stopped on both the access when the PDU session is established on S-NSSAI / alternative S- NSSAI and the slice deregistration inactivity timer can be started on both the access when MA PDU session associated with S-NSSAI / alternative S-NSSAI is released and there is no other PDU session associated with the S- NSSAI / alternative S-NSSAI is established.

[0252] In an embodiment, the slice deregistration inactivity timer for the S-NSSAI is applicable in the UE (102) when S-NSSAI is on-demand S-NSSAI and slice deregistration inactivity timer associated with S-NSSAI is indicated to the UE (102) in on-demand NSSAI IE and the slice deregistration inactivity timer for the S-NSSAI is applicable in the AMF (104) when S-NSSAI is on-demand S-NSSAI.

[0253] In an embodiment, if S1,S2,S3 are on-demand S-NSSAI and the slice inactivity deregistration timer for the S1,S2 and S3 are T1,T2,T3 is handled on the associated access as follows (optionally, if currently there is no other PDU session exist for the S1,S2 and S3 on the access including MA PDU session).

[0254] Case 1: Network (e.g. the AMF (104) has not indicated slice inactivity deregistration timer associated with the on-demand S-NSSAI S1, S2, and S3) S1, S2, S3 are allowed S-NSSAI.

[0255] a) The UE (102) established PDU session on S1. The AMF (104) stops the timer T1.

[0256] b) Network indicated S2 as alternative S-NSSAI for the S1. The AMF (104) shall stop T2

[0257] c) The SMF (106) / AMF (104) indicates that S3 is alternative S-NSSAI for the S1. The AMF (104) shall stop T3 and start T2.

[0258] d) The SMF (106) / AMF (104) indicate that S3 is not alternative S-NSSAI for the S1 (S3 is removed from alternative S-NSSAI). The AMF (104) shall start T3.

[0259] e) The Network indicated S2 as alternative S-NSSAI for the S1. The AMF (104) shall stop T2

[0260] f) The PDU session associated with S1 and alternative S-NSSAI S2 are released. The AMF (104) starts, T1 and T2.

[0261] If any slice deregistration inactivity timer is expired, the AMF (104) indicate to the UE (102) the new allowed NSSAI removing the associated S- NSSAI whose timer expired (e.g if T1 is expired, the AMF (104) indicates the new allowed NSSAI to the UE (102) without S1).

[0262] Case 2: The Network (e.g. the AMF (104) has indicated slice inactivity deregistration timer associated with the on-demand S-NSSAI S1, S2 and S3) S1, S2, S3 are allowed S-NSSAI.

[0263] g) The UE (102) established the PDU session on S1. The AMF (104) stop the timer T1.

[0264] h) The Network indicated S2 as alternative S-NSSAI for the S1. The AMF (104) shall stop T2

[0265] i) The SMF (106) / AMF (104) indicates that S3 is alternative S-NSSAI for the S1. The UE (102) and the AMF (104) shall stop T3 and start T2.

[0266] j) The SMF (106) / AMF (104) indicate that S3 is not alternative S-NSSAI for the S1 (S3 is removed from alternative S-NSSAI). The UE (102) and AMF (104) shall start T3.

[0267] k) The Network indicated S2 as alternative S-NSSAI for the S1. The UE (102) and the AMF (104) shall stop T2.

[0268] l) The PDU session associated with S1 and alternative S-NSSAI S2 are released. The UE (102) and the AMF (104) starts, T1 and T2.

[0269] If any slice deregistration inactivity timer is expired, the AMF (104) and the UE (102) remove the corresponding S-NSSAI from allowed SNSSAI locally (e.g. if T1 is expired then the UE (102) and the AMF (104) will remove S1 from allowed SNSSAI locally).

[0270] Fig. 9 is a flow diagram that illustrate a method for handling a slice deregistration inactivity timer of on-demand S-NSSAI by the UE (102) according to an embodiment as disclosed herein. The method includes steps (902-912). Each step is explained in further detail below.

[0271] At step (902), the UE (102) detects the slice inactivity deregistration timer configured for an alternative S-NSSAI by the network apparatus (302). The alternative S-NSSAI denotes additional S-NSSAIs provided by the network apparatus (302) to enhance flexibility in the selection of network slices. The alternative S-NSSAI acts as a replacement when the primary S-NSSAI is not accessible.

[0272] At step (904), the UE (102) establishes a PDU session with a first S-NSSAI and the alternative S-NSSAI. Upon establishment of the PDU session, the UE (102) can send and receive data over the 5GC network. The PDU session established can support different data types of protocols, such as IPv4, IPv6, IPv4v6, Ethernet, and the like.

[0273] At step (906), the UE (102) detects whether the alternative S-NSSAI is the on-demand S-NSSAI and the slice inactivity deregistration timer is running. This detection is carried out after the PDU session is established with the first S-NSSAI and the alternative S-NSSAI or an existing PDU session is established when the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. The on-demand S-NSSAI refers to an S-NSSAI that is not pre-configured or readily available, but can be dynamically initiated upon request from the UE (102). At step (908), the UE (102) then stops the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0274] At step (910), the UE (102) determines whether that the PDU session established with the first S-NSSAI and the alternate S-NSSAI is moved back to the first S-NSSAI or whether the PDU session associated with the first S-NSSAI and the alternative S-NSSAI is released.. At step (912), the UE (102) then restarts or starts the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternate S-NSSAI is moved back to the first S-NSSAI or the PDU session associated with the alternative S-NSSAI is released.

[0275] Fig. 10 is a flow diagram that illustrate a method for handling a slice deregistration inactivity timer of on-demand S-NSSAI by the network apparatus (302) according to an embodiment as disclosed herein. The method includes steps (1002-1012). Each step is explained in further detail below.

[0276] At step (1002), the network apparatus (302) configures the slice inactivity deregistration timer at the UE (102) for an alternative S-NSSAI. When a first S-NSSAI or a requested S-NSSAI is unavailable, then the alternative S-NSSAI is assigned for fulfilling similar network requirements than the first S-NSSAI. The slice inactivity deregistration timer monitors an activity on the alternative S-NSSAI.

[0277] At step (1004), the network apparatus (302) detects that the UE (102) has established a PDU session with a first S-NSSAI and the alternative S-NSSAI. The UE (102) begins the PDU session by specifying its preferred S-NSSAI. If the requested slice is accessible, the first S-NSSAI is allocated to the PDU session. If the preferred slice is not available, an alternative S-NSSAI that meets the service requirements of the PDU session will be assigned.

[0278] At step (1006), the network apparatus (302) determines whether the alternative S-NSSAI is the on-demand S-NSSAI and the slice inactivity deregistration timer is running. This determination is performed after the PDU session is established with the alternative S-NSSAI or an existing PDU session is established when the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI. At step (1008), the network apparatus (302) then stops the slice deregistration inactivity timer associated with the alternate S-NSSAI when the alternative S-NSSAI is the on-demand S-NSSAI and the slice deregistration inactivity timer is running.

[0279] At step (1010), the network apparatus (302) detects whether the PDU session established with the first S-NSSAI and the alternate S-NSSAI is moved back to the first S-NSSAI or whether the PDU session associated with the alternative S-NSSAI is released by the UE (102) or by the network apparatus (302). At step (1012), the network apparatus (302) then starts or restarts the slice deregistration inactivity timer associated with the alternate S-NSSAI when alternate S-NSSAI is moved back to the first S-NSSAI or when the alternative S-NSSAI is released by the UE (102).

[0280] In this embodiment, existing PDU session with the first S-NSSAI is moved to the first S-NSSAI and the alternative S-NSSAI by the below procedure:

[0281] If the SMF (106) receives from the AMF (104) an alternative S-NSSAI for the existing PDU session and:

[0282] a) if the SMF (106) decides to retain the existing PDU session (i.e. the SMF can serve both the alternative S-NSSAI and the first S-NSSAI-referred as slice to be replaced), the SMF (106) sends the alternative S-NSSAI to the UE (102) during network-requested PDU session modification procedure; or

[0283] b) if the SMF (106) decides to re-activate the existing PDU session and:

[0284] 1) if the SSC mode of the PDU session is SSC mode 3, the SMF (106) initiates PDU session modification procedure to trigger PDU session reactivation by the UE (102); or

[0285] 2) if the SSC mode of the PDU session is SSC mode 1 or SSC mode 2, the SMF (106) initiates PDU session release procedure to trigger PDU session reactivation by the UE (102), and the UE (102) provides both the S-NSSAI to be replaced (first S-NSSAI) and the alternative S-NSSAI during PDU session establishment procedure.

[0286] in this embodiment, PDU session established with the first S-NSSAI and the alternate S-NSSAI is moved back to the first S-NSSAI using below procedure:

[0287] a) if the SMF (106) decides to retain the existing PDU session (i.e. the SMF (106) can serve the first S-NSSAI- referred as slice to be replaced), the SMF (106) sends the first S-NSSAI (i.e replaced S-NSSAI) to the UE (102) during network-requested PDU session modification procedure; or

[0288] b) if the SMF (106) decides to re-activate the existing PDU session and:

[0289] 1) if the SSC mode of PDU session is SSC mode 3, the SMF (106) sends the first S-NSSAI(i.e replaced S-NSSAI) to the UE (102) during PDU session modification procedure to trigger PDU session reactivation by the UE (102); or

[0290] 2) if the SSC mode of the PDU session is SSC mode 1 or SSC mode 2, the SMF (106) sends the first S-NSSAI (i.e replaced S-NSSAI) to the UE (102) during PDU session release procedure to trigger PDU session reactivation by the UE (102); and the UE (102) provides the first S-NSSAI (i.e replaced S-NSSAI) during PDU establishment procedure.

[0291] In this embodiment, the slice deregistration inactivity timer stop means stop and reset the timer.

[0292] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

1.A method performed by a user equipment (UE) in a communication system, the method comprising:establishing a PDU session over first single - network slice selection assistance information (S-NSSAI);stopping a first slice deregistration inactivity timer associated with the first S-NSSAI;establishing the PDU session with the first S-NSSAI and an alternative S-NSSAI; andstopping a second slice deregistration inactivity timer associated with the alternative S-NSSAI.2.The method of claim 1, further comprising:transmitting, to a first entity performing a session management function (SMF), a first protocol data unit (PDU) session establishment request message for the first S-NSSAI; andas a response to the first PDU session establishment request message for the first S-NSSAI, receiving, from the first entity performing the SMF, a first PDU session establishment accept message.3.The method of claim 1, further comprising:receiving, from the first entity performing the SMF, a PDU session modification message for the alternative S-NSSAI;transmitting, to the first entity performing the SMF, a second PDU session establishment request message for the first S-NSSAI and the alternative S-NSSAI; andreceiving, from the first entity performing the SMF, a second PDU session establishment accept message for the first S-NSSAI and the alternative S-NSSAI.4.The method of claim 1,wherein the UE is registered over a 3rdgeneration partnership project (3GPP) access types via a second entity performing an access and mobility management function (AMF).5.The method of claim 1,wherein the first S-NSSAI and the alternative S-NSSAI are configured as an on-demand.6.A method performed by a first entity performing a session management function (SMF), in a communication system, the method comprising:receiving, from a user equipment (UE), a first protocol data unit (PDU) session establishment request message for a first single - network slice selection assistance information (S-NSSAI);as a response to the first PDU session establishment request message for the first S-NSSAI, transmitting, to the UE, a first PDU session establishment accept message;transmitting, to the UE, a PDU session modification message for the alternative S-NSSAI;receiving, from the UE, a second PDU session establishment request message for the first S-NSSAI and the alternative S-NSSAI; andreceiving, from the first entity performing the SMF, a second PDU session establishment accept message for the first S-NSSAI and the alternative S-NSSAI,wherein a first slice deregistration inactivity timer associated with the first S-NSSAI is stopped after a PDU session over the first S-NSSAI is established, andwherein a second slice deregistration inactivity timer associated with the alternative S-NSSAI is stopped after the PDU session over the first S-NSSAI and the alternative S-NSSAI is established.7.The method of claim 6,wherein the UE is registered over a 3rdgeneration partnership project (3GPP) access types via a second entity performing an access and mobility management function (AMF).8.The method of claim 6,wherein the first S-NSSAI and the alternative S-NSSAI are configured as an on-demand.9.A a user equipment (UE) in a communication system, the UE comprising:a transceiver; anda controller coupled with the transceiver, and configured to:establish a PDU session over first single - network slice selection assistance information (S-NSSAI),stop a first slice deregistration inactivity timer associated with the first S-NSSAI,establish the PDU session with the first S-NSSAI and an alternative S-NSSAI, andstop a second slice deregistration inactivity timer associated with the alternative S-NSSAI.10.The UE of claim 9, wherein the controller is further configured to:transmit, to a first entity performing a session management function (SMF), a first protocol data unit (PDU) session establishment request message for the first S-NSSAI, andas a response to the first PDU session establishment request message for the first S-NSSAI, receive, from the first entity performing the SMF, a first PDU session establishment accept message.11.The UE of claim 9, wherein the controller is further configured to:receive, from the first entity performing the SMF, a PDU session modification message for the alternative S-NSSAI,transmit, to the first entity performing the SMF, a second PDU session establishment request message for the first S-NSSAI and the alternative S-NSSAI, andreceive, from the first entity performing the SMF, a second PDU session establishment accept message for the first S-NSSAI and the alternative S-NSSAI.12.The UE of claim 9,wherein the UE is registered over a 3rdgeneration partnership project (3GPP) access types via a second entity performing an access and mobility management function (AMF).13.The UE of claim 9,wherein the first S-NSSAI and the alternative S-NSSAI are configured as an on-demand.14.A first entity performing a session management function (SMF), in a communication system, the first entity comprising:a transceiver; anda controller coupled with the transceiver, and configured to:receive, from a user equipment (UE), a first protocol data unit (PDU) session establishment request message for a first single - network slice selection assistance information (S-NSSAI),as a response to the first PDU session establishment request message for the first S-NSSAI, transmit, to the UE, a first PDU session establishment accept message,transmit, to the UE, a PDU session modification message for the alternative S-NSSAI,receive, from the UE, a second PDU session establishment request message for the first S-NSSAI and the alternative S-NSSAI, andreceive, from the first entity performing the SMF, a second PDU session establishment accept message for the first S-NSSAI and the alternative S-NSSAI,wherein a first slice deregistration inactivity timer associated with the first S-NSSAI is stopped after a PDU session over the first S-NSSAI is established, andwherein a second slice deregistration inactivity timer associated with the alternative S-NSSAI is stopped after the PDU session over the first S-NSSAI and the alternative S-NSSAI is established.15.The base station of claim 14,wherein the UE is registered over a 3rdgeneration partnership project (3GPP) access types via a second entity performing an access and mobility management function (AMF), andwherein the first S-NSSAI and the alternative S-NSSAI are configured as an on-demand.

Images