Improvements in and relating to methods for stopping inactivity timer in a user equipment

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The disclosure provides a method for operating at least one slice deregistration inactivity timer, performed by a terminal supporting a network slice usage control, in a wireless communication system. The method comprises transmitting, to an access and mobility management function (AMF), a request message for requesting protocol data unit (PDU) session establishment; receiving, from the AMF, a response message indicating that the requested PDU session establishment is accepted, the response message including a single network slice selection assistance information (S-NSSAI) corresponding to a particular slice associated with the PDU session; and performing an operation for the at least one slice deregistration inactivity timer.

Description

IMPROVEMENTS IN AND RELATING TO METHODS FOR STOPPING INACTIVITY TIMER IN A USER EQUIPMENT

[0001] The present disclosure relates to the field of .wireless communication system. Particularly, the present disclosure relates to methods for stopping an inactivity timer in a User Equipment, UE, the UE being arranged for communication with a telecommunication network.

[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 disclosure relates to a method for ensuring that a UE determines the on-demand S-NSSAI associated with a PDU session based on a defined mechanism, allowing it to stop the appropriate slice deregistration inactivity timer and maintain synchronization with the network.

[0009] One or more shortcomings discussed above are overcome, and additional advantages and features are provided by the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the disclosure.

[0010] In an embodiment, a method for operating at least one slice deregistration inactivity timer, performed by a terminal supporting a network slice usage control, in a wireless communication system, is disclosed. The method comprises: transmitting, to an access and mobility management function (AMF), a request message for requesting protocol data unit (PDU) session establishment; receiving, from the AMF, a response message indicating that the requested PDU session establishment is accepted, the response message including a single network slice selection assistance information (S-NSSAI) corresponding to a particular slice associated with the PDU session; and performing an operation for the at least one slice deregistration inactivity timer.

[0011] In another embodiment, a terminal operating at least one slice deregistration inactivity timer for supporting a network slice usage control, in a wireless communication system, is disclosed. The terminal comprises: transceiver; and at least one processor coupled with the transceiver and configured to: transmit, to an access and mobility management function (AMF) via the transceiver, a request message for requesting protocol data unit (PDU) session establishment; receive, from the AMF via the transceiver, a response message indicating that the requested PDU session establishment is accepted, the response message including a single network slice selection assistance information (S-NSSAI) corresponding to a particular slice associated with the PDU session; and perform an operation for the at least one slice deregistration inactivity timer.

[0012] The foregoing solution is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

[0013] The methods and systems provided by the present disclosure ensure that the UE consistently determines the on-demand S-NSSAI, preventing inconsistent timer behavior and improving network synchronization.

[0014] Figure 1 illustrates a UE in operative communication with a telecommunication network; and

[0015] Figure 2 illustrates a sequence diagram according to an embodiment of the present disclosure.

[0016] Figure 3 illustrates a method according to an embodiment of the present disclosure.

[0017] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

[0018] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0019] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0020] The term "include" or "may include" refers to the existence of a corresponding disclosed function, operation or component which can be used in various embodiments of the present disclosure and does not limit one or more additional functions, operations, or components. The terms such as "include" and / or "have" may be construed to denote a certain characteristic, number, step, operation, constituent element, component or a combination thereof, but may not be construed to exclude the existence of or a possibility of addition of one or more other characteristics, numbers, steps, operations, constituent elements, components or combinations thereof.

[0021] The term "or" used in various embodiments of the present disclosure includes any or all of combinations of listed words. For example, the expression "A or B" may include A, may include B, or may include both A and B.

[0022] Unless defined differently, all terms used herein, which include technical terminologies or scientific terminologies, have the same meaning as that understood by a person skilled in the art to which the present disclosure belongs. Such terms as those defined in a generally used dictionary are to be interpreted to have the meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted to have ideal or excessively formal meanings unless clearly defined in the present disclosure.

[0023] 3GPP has developed several features related to network slicing, one of which uses a slice deregistration inactivity timer where the timer is per slice (S-NSSAI) and per access type (i.e. 3GPP or non-3GPP). The timer guards the inactivity period for the slice in question such that if the timer expires and the UE (or the terminal) has not used the slice, then the slice is deemed to be no longer available for the UE, and the slice is removed from the allowed NSSAI which enforces the lack of the slices availability since only slices in the allowed NSSAI can be used.

[0024] The following is from 3GPP TS 23.501 which describes this concept:

[0025] "The 5GC performs Network Slice 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:

[0026] -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 slice 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 form the Allowed NSSAI. When the slice 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)."

[0027] The following is from section 4.6.2.9 of 3GPP TS 24.501 which describes the start of the timer and the outcome of its expiry (similar to what is shown above):

[0028] "The slice deregistration inactivity timer is:

[0029] 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

[0030] 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."

[0031] The following is from section 6.4.1.3 of 3GPP TS 24.501 which describes that the deregistration inactivity timer is stopped upon the successful establishment of a PDU session, noting that this is associated with explicit session management signaling that is exchanged with the network for the session to be established:

[0032] "If the UE supports network slice usage control and:

[0033] a)a PDU session is successfully established for the on-demand S-NSSAI, the UE shall stop and reset the slice deregistration inactivity timer for the on-demand S-NSSAI over corresponding access type, if running; and

[0034] b)an MA PDU session is successfully established for the on-demand S-NSSAI, the UE shall stop and reset the slice deregistration inactivity timer for the on-demand S-NSSAI over both 3GPP access and non-3GPP access, if running."

[0035] To summarize, the following key points can be observed from the above:

[0036] · A slice is associated with a deregistration inactivity timer, where the timer guards the period of inactivity for the slice. The expiry of the timer means the slice is no longer available for use

[0037] · The timer is per slice and access technology (i.e. 3GPP or non-3GPP)

[0038] · The timer is stopped upon successful establishment of a PDU session, where this requires explicit session management signaling.

[0039] A UE which requests a protocol data unit (PDU) session establishment may not necessarily indicate the actual slice or S-NSSAI for which the request is being sent. This may be due to the User Equipment Route Selection Policy, URSP, rules in the UE such that the default rule may be used which may not have an associated S-NSSAI. The NAS specification in 3GPP TS 24.501 clearly permits the scenario for which the UE can send a PDU session establishment request but without an S-NSSAI. The following is from section 5.4.5.2.3 which describes the network behavior when no S-NSSAI is indicated by the UE, for which the selection is then made by the network:

[0040] "If the S-NSSAI IE is not included, the UE does not have a partially allowed NSSAI, and the allowed NSSAI contains:

[0041] -one S-NSSAI, the AMF shall use the S-NSSAI in the allowed NSSAI as the S-NSSAI. Additionally, for a UE for which the AMF has provided a NS-AoS, the AMF shall use the S-NSSAI in the allowed NSSAI if the UE is inside the NS-AoS with respect to the S-NSSAI;

[0042] -two or more S-NSSAIs and the user's subscription context obtained from UDM contains only one default S-NSSAI that is included in the allowed NSSAI, the AMF shall use the S-NSSAI in the allowed NSSAI that matches the default S-NSSAI as the S-NSSAI; or

[0043] -two or more S-NSSAIs and the user's subscription context obtained from UDM contains two or more default S-NSSAI(s) included in the allowed NSSAI, the AMF shall use an S-NSSAI in the allowed NSSAI selected based on operator policy as the S-NSSAI."

[0044] In other cases, however, the UE may be aware of the S-NSSAI for which the PDU session is requested, and hence the UE will explicitly include the S-NSSAI in the NAS message. Note that only S-NSSAIs from the allowed NSSAI can be requested by the UE.

[0045] Note that the PDU Session Establishment Accept message includes the S-NSSAI for which the PDU session is established, and this information is provided for all cases including the case when the UE did not explicitly indicate the S-NSSAI as part of the PDU session establishment procedure.

[0046] The following key points can be highlighted:

[0047] · A PDU session can be requested with an explicit S-NSSAI which is provided by the UE. The network uses this S-NSSAI for the session establishment;

[0048] · A PDU session can be requested without an explicit S-NSSAI which is indicated by the UE. In this case, the network selects the S-NSSAI for the UE (using the allowed NSSAI). The allowed NSSAI may have more than one entry which the AMF selects from;

[0049] · This S-NSSAI is indicated in the PDU Session Establishment Accept message regardless of whether the S-NSSAI was indicated by the UE, or selected by the network when not provided by the UE.

[0050] As set out above:

[0051] "The slice deregistration inactivity timer is:

[0052] 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

[0053] 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."

[0054] Turning to the slice deregistration inactivity timer, the UE is supposed to stop a timer when a PDU session is established for a particular slice or S-NSSAI. However, this does not provide enough clarity about how the UE identifies the S-NSSAI in question since there are two options for a PDU session and an S-NSSAI as follows:

[0055] · The UE explicitly indicated the S-NSSAI during the PDU session establishment procedure; or

[0056] · The UE did not explicitly indicate the S-NSSAI during the PDU session establishment procedure and so the S-NSSAI was selected by the network.

[0057] Note that in both cases the UE receives the S-NSSAI with which the session is associated in the PDU Session Establishment Accept message.

[0058] A problem therefore becomes the following: it is not clear how the UE identifies the S-NSSAI for which the slice deregistration inactivity timer needs to be stopped after a session is established for an on-demand S-NSSAI. Without an explicit specification or description, different UEs can behave differently as follows:

[0059] One UE implementation may associate the timer to what it explicitly provides. A subsequent problem then becomes related to the UE behavior when nothing is provided. Does it stop the deregistration timer for all slices or randomly picks the slice?

[0060] One UE implementation may associate the timer to what it receives in the Session Establishment Accept message, and so this requires an additional check at the UE which is currently not specified.

[0061] Finally, UEs that behave differently can lead to different results in the system, since at least some UEs may be unsynchronized with the network in terms of having a running deregistration inactivity timer especially when the UE did not indicate a slice in its request for a session.

[0062] It is the aim of embodiments of this invention to clearly specify how the UE identifies an S-NSSAI for which a deregistration inactivity timer should be stopped.

[0063] According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

[0064] In one aspect there is provided a method of operating a slice deregistration inactivity timer in a User Equipment, UE, the UE being in operative communication with a telecommunication network, wherein the slice deregistration inactivity timer is associated with a particular slice, S-NSSAI, and whereby the slice deregistration inactivity is started then the particular slice is not used for a PDU session, wherein: a) the UE determines the particular slice based on the S-NSSAI which is received in a PDU Session Establishment Accept message, and then stops the slice deregistration inactivity timer upon PDU session establishment; or b) the particular slice is the S-NSSAI which the UE explicitly indicated, otherwise it is what the UE receives in a PDU Session Establishment Accept message, and then stops the slice deregistration inactivity timer upon PDU session establishment; or c) if the UE did not indicate an S-NSSAI, then no deregistration inactivity timer is stopped; or d) if the UE did not indicate an S-NSSAI, then all deregistration inactivity timers are stopped upon PDU session establishment.

[0065] In one aspect, the slice deregistration inactivity timer is further associated with an access type. In one aspect, the access type is one of 3GPP and non-3GPP.

[0066] In one aspect, the expiry of the slice deregistration inactivity timer renders the associated slice unavailable.

[0067] In one aspect there is provided an apparatus arranged to perform a method as herein-described.

[0068] The invention focuses on how the UE identifies the on-demand S-NSSAI and hence how it associates the S-NSSAI to a PDU session so that the appropriate / corresponding slice deregistration timer is stopped.

[0069] In one option, the on-demand S-NSSAI associated with the PDU session is determined to be the S-NSSAI which is received in the PDU Session Establishment Accept message. Once the on-demand S-NSSAI is determined, the UE stops and resets the deregistration timer which is associated with this determined on-demand S-NSSAI.

[0070] In one option, if the UE did not indicate an S-NSSAI during PDU session establishment procedure, the the on-demand S-NSSAI associated with the PDU session is determined to be the S-NSSAI which is received in the PDU Session Establishment Accept message. Otherwise if the UE did indicate an S-NSSAI during PDU session establishment procedure, then the UE determines the on-demand S-NSSAI to be that which it provided. Once the on-demand S-NSSAI is deteremined, the UE stops and resets the deregistration timer which is associated with this determined on-demand S-NSSAI.

[0071] In one option, if the UE did not provide an S-NSSAI during PDU session establishment procedure, then the UE does not stop any timer. The UE does not determine any on-demand S-NSSAI, or determines that there is no on-demand S-NSSAI which is associated with the established PDU session, and hence each deregistration timer is kept running

[0072] In one option, if the UE did not provide an S-NSSAI during PDU session establishment procedure, then the UE stops all the deregistration inactivity timer for all on-demand S-NSSAIs that are running on this access technology over which the session is established, or over which the PDU session establishment accept message is received.

[0073] Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0074] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which:

[0075] Figure 1 illustrates a UE in operative communication with a telecommunication network; and

[0076] Figure 1 shows a UE 10, including a slice deregistration inactivity timer 12. The UE 10 is in operative communication with a telecommunication network 20. The UE and network may operate according to one or more telecom standards, such as 5G, 6G etc.

[0077]

[0078] Embodiments of the invention clearly specify how the UE identifies the on-demand S-NSSAI in order to stop the true or correct slice deregistration timer. As indicated earlier, the UE may provide an S-NSSAI during PDU session establishment, but sometimes it does not do so. Hence embodiments ensure that the UE correctly identifies the on-demand S-NSSAI so that the correct timer can be stopped, noting that the prior art does not address this issue.

[0079] For any of the embodiments herein, the stopping of the timer may also mean that the UE first stops the timer and then resets it. As such in all the embodiments below, stopping a timer can also refer to a reset and stop of the timer.

[0080] Note that the PDU session establishment procedure may mean that the UE sends to the network (e.g. access and mobility management function (AMF)) a PDU Session Establishment Request message which is included in the UL NAS TRANSPORT message. The S-NSSAI may or may not be provided in the UL NAS TRANSPORT message.

[0081] The deregistration inactivity timer may be a slice deregistration inactivity timer.

[0082] Embodiments may include one or more of the Options set out below.

[0083] Option 1: the UE determines the S-NSSAI based on the S-NSSAI which is received in the PDU Session Establishment Accept message

[0084] This option provides the most consistent way to identify the on-demand S-NSSAI which is associated with the PDU session.

[0085] In order to stop the correct slice deregistration inactivity timer, the UE considers the on-demand S-NSSAI for the PDU session as that which is received in the PDU Session Establishment Accept message.

[0086] As such, for the purpose of identifying the on-demand S-NSSAI and for stopping the appropriate or correct timer that is associated with the on-demand S-NSSAI, the UE should determine the on-demand S-NSSAI to be the S-NSSAI received in the PDU Session Establishment Accept message and should stop the slice deregistration inactivity timer which is associated with this determined S-NSSAI.

[0087] Optionally the timer is also associated with an access type which may be determined as the access type over which the session is established.

[0088] In another alternative, the access type corresponding to the slice deregistration inactivity timer may be determined to be the access type over which the PDU Session Establishment Accept message is received.

[0089] The UE can behave as described above when:

[0090] · The UE did not provide any S-NSSAI (to the network) during the PDU session establishment procedure

[0091] · The UE indicated or provided an S-NSSAI as part of the PDU session establishment procedure.

[0092] Option 2: the on-demand S-NSSAI is the S-NSSAI which the UE explicitly indicated, otherwise it is what the UE receives in the PDU Session Establishment Accept message

[0093] In this option, the UE uses different methods for determining the on-demand S-NSSAI for which there is a slice deregistration timer that is potentially running.

[0094] In a first method, the on-demand S-NSSAI is determined to be the S-NSSAI which the UE provided in the NAS message during the PDU session establishment procedure, where the NAS message may be an UL NAS TRANSPORT message which can carry the S-NSSAI.

[0095] Therefore, for the purpose of stopping the slice deregistration inactivity timer, if the UE had provided an S-NSSAI during PDU session establishment procedure, the UE determines the on-demand S-NSSAI that is associated with the PDU session as that which the UE provided (during PDU session establishment procedure), and hence the slice deregistration inactivity timer is the timer associated with this determined S-NSSAI. The access type corresponding to the slice deregistration inactivity timer may be determined to be the access type over which the PDU Session Establishment Accept message is received, or the access type over which the session is established.

[0096] In the second method, if the UE did not provide any S-NSSAI during PDU session establishment procedure, then the on-demand S-NSSAI that is associated with the PDU session is determined to be the S-NSSAI that the UE receives in the PDU Session Establishment Accept message. The UE should stop the slice deregistration inactivity timer which is associated with this determined S-NSSAI. The access type corresponding to the slice deregistration inactivity timer may be determined to be the access type over which the PDU Session Establishment Accept message is received, or the access type over which the session is established.

[0097] In this option, the UE operates with both methods described above based on whether the UE had provided an S-NSSAI during PDU session establishment or not.

[0098] In another alternative, for the case when the UE does not provide an S-NSSAI during PDU session establishment procedure, if the UE has only one S-NSSAI in the allowed NSSAI, then the UE determines the on-demand S-NSSAI to be the single S-NSSAI in the allowed NSSAI, and hence the UE stops the deregistration inactivity timer which is associated with this single S-NSSAI (from the allowed NSSAI). The access type corresponding to the slice deregistration inactivity timer may be determined to be the access type over which the PDU Session Establishment Accept message is received, or the access type over which the session is established, or the access type for which there is only one entry in the allowed NSSAI.

[0099] Option 3: no deregistration inactivity timer is stopped if the UE did not indicate an S-NSSAI

[0100] In this option, if the UE did not provide an S-NSSAI during the PDU session establishment procedure, then the UE determines that there is no on-demand S-NSSAI which is associated with the PDU session that was established without any explicit S-NSSAI indication from the UE. As such, the UE does not stop any timer in this case and all the slice deregistration timers are maintained or kept running. In this solution, the stopping of a deregistration timer strictly requires that the UE provides an S-NSSAI during PDU session establishment procedure and hence an on-demand S-NSSAI can only be identified to be associated with a PDU session if the UE provided an S-NSSAI, and that S-NSSAI is determined to be the on-demand S-NSSAI.

[0101] Option 4: all deregistration inactivity timers are stopped if the UE did not indicate an S-NSSAI

[0102] In this option, if the UE did not provide an S-NSSAI during PDU session establishment procedure, then the UE determines that all the on-demand S-NSSAIs which have a timer running should be stopped, where the access type of each timer is determined to be the access type over which the session is established or to be the access type over which the PDU Session Establishment Accept message is received.

[0103] Figure 2 illustrates a method according to an embodiment of the present invention.

[0104] Figure 2 shows a flowchart. At S101 a slice deregistration inactivity timer is started. At S102, a determination is made whether or not to stop the timer or not in response to a PDU establishment activity. At S103, the timer is either stopped, not stopped or all slice deregistration inactivity timers are stopped, depending upon which options is in use.

[0105] Figure 3 illustrates a method according to an embodiment of the present invention.

[0106] At step S301, the terminal transmits, to an access and mobility management function (AMF), a request message for requesting protocol data unit (PDU) session establishment.

[0107] At step S302, the terminal receives, from the AMF, a response message indicating that the requested PDU session establishment is accepted, the response message including a single network slice selection assistance information (S-NSSAI) corresponding to a particular slice associated with the PDU session.

[0108] At step S303, the terminal performs an operation for the at least one slice deregistration inactivity timer. The operation may be performed according to the option 1 to 4 described above.

[0109] An embodiment of the invention may make use of only one or more than one of the options set out herein. In particular, provided there is a consistent use of one or more options, then certainty can be provided, thereby ensuring correct and predictable operation of the UE and network.

[0110] By use of an embodiment of the present invention, the issues in the prior art associated with a lack of certainty can be avoided or at least ameliorated.

[0111] At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as 'component', 'module' or 'unit' used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of others.

[0112] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0113] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0114] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0115] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1.A method for operating at least one slice deregistration inactivity timer, performed by a terminal supporting a network slice usage control, in a wireless communication system, the method comprising:transmitting, to an access and mobility management function (AMF), a request message for requesting protocol data unit (PDU) session establishment;receiving, from the AMF, a response message indicating that the requested PDU session establishment is accepted, the response message including a single network slice selection assistance information (S-NSSAI) corresponding to a particular slice associated with the PDU session; andperforming an operation for the at least one slice deregistration inactivity timer.2.The method of claim 1, wherein, in case that the S-NSSAI is included in the request message, the operation comprising:identifying the particular slice, based on the request message, andstopping a slice deregistration inactivity timer associated with the particular slice.3.The method of claim 1, wherein, in case that the S-NSSAI is not included in the request message, the operation comprises:identifying the particular slice, based on the response message, andstopping a slice deregistration inactivity timer associated with the particular slice.4.The method of claim 1, wherein, in case that the S-NSSAI is not included in the request message, the operation comprises:stopping all of the at least one slice deregistration inactivity timer.5.The method of claim 1, wherein, in case that the S-NSSAI is not included in the request message, the operation comprises:maintaining all of the at least one slice deregistration inactivity timer.6.The method of claim 1, wherein the at least one slice deregistration inactivity timer is further associated with an access type.7.The method of claim 6, wherein the access type is one of 3GPP and non-3GPP.8.The method of claim 1, wherein an expiry of the at least one slice deregistration inactivity timer renders the associated slice unavailable.9.A terminal operating at least one slice deregistration inactivity timer for supporting a network slice usage control, in a wireless communication system, the terminal comprising:transceiver; andat least one processor coupled with the transceiver and configured to:transmit, to an access and mobility management function (AMF) via the transceiver, a request message for requesting protocol data unit (PDU) session establishment;receive, from the AMF via the transceiver, a response message indicating that the requested PDU session establishment is accepted, the response message including a single network slice selection assistance information (S-NSSAI) corresponding to a particular slice associated with the PDU session; andperform an operation for the at least one slice deregistration inactivity timer.10.The terminal of claim 9, wherein, in case that the S-NSSAI is included in the request message, the operation comprising:identifying the particular slice, based on the request message, andstopping a slice deregistration inactivity timer associated with the particular slice.11.The terminal of claim 9, wherein, in case that the S-NSSAI is not included in the request message, the operation comprises:identifying the particular slice, based on the response message, andstopping a slice deregistration inactivity timer associated with the particular slice.12.The terminal of claim 9, wherein, in case that the S-NSSAI is not included in the request message, the operation comprises:stopping all of the at least one slice deregistration inactivity timer.13.The terminal of claim 9, wherein, in case that the S-NSSAI is not included in the request message, the operation comprises:maintaining all of the at least one slice deregistration inactivity timer.14.The terminal of claim 9, wherein the at least one slice deregistration inactivity timer is further associated with an access type.15.The terminal of claim 9, wherein an expiry of the at least one slice deregistration inactivity timer renders the associated slice unavailable.

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