Method for PDU session management in wireless communication system and apparatus therefor

Abstract

A method performed by a terminal in a wireless communication system according to the present disclosure may comprise the steps of: transmitting, to a network, a registration request message including information indicating that the terminal supports an operation according to a store-and-forward (S&F) mode of a satellite; receiving, from the network, a registration accept message including information indicating that the operation according to the S&F mode is supported or provided; transmitting, to the network, a request message for a request related to an always-on protocol data unit (PDU) session; and receiving, from the network, a rejection message for rejecting the request related to the always-on PDU session, wherein the rejection message includes a cause value indicating that the always-on PDU session is not supported as the operation according to the S&F mode is supported or provided.

Description

Method for PDU session management in a wireless communication system and apparatus for the same

[0001] The present disclosure relates to a wireless communication system, and more specifically, to a method for managing PDU sessions in a wireless communication system and an apparatus for the same.

[0002]

[0003] Mobile communication systems were developed to provide voice services while ensuring user mobility. However, mobile communication systems have expanded their scope to include data services as well as voice. Currently, due to the explosive increase in traffic leading to resource shortages and users demanding higher-speed services, more advanced mobile communication systems are required.

[0004] The requirements for next-generation mobile communication systems largely include the ability to accommodate explosive data traffic, a dramatic increase in transmission rates per user, a significantly increased number of connected devices, very low end-to-end latency, and high energy efficiency. To achieve this, various technologies are being researched, such as dual connectivity, massive multiple input multiple output (MMIMO), in-band full duplex, non-orthogonal multiple access (NOMA), super wideband support, and device networking.

[0005]

[0006] The present disclosure aims to provide a method for PDU session management in a wireless communication system and an apparatus for the same.

[0007] The problems to be solved by the present disclosure are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0008]

[0009] A method performed by a terminal in a wireless communication system according to the present disclosure comprises: transmitting a Registration Request message to a network that includes information indicating that the terminal supports operation according to the S&F (Store and Forward) mode of a satellite; receiving a Registration Accept message from the network that includes information indicating that operation according to the S&F mode is supported or provided; transmitting a request message to the network for a request related to an Always-on (protocol data unit Session) session; and receiving a rejection message from the network for rejecting a request related to an Always-on PDU session, wherein the rejection message may include a reason value indicating that the Always-on PDU session is not supported as operation according to the S&F mode is supported or provided.

[0010] Additionally, a method performed by a network in a wireless communication system according to the present disclosure comprises: receiving a Registration Request message from a terminal containing information indicating that the terminal supports operation according to the S&F (Store and Forward) mode of a satellite; transmitting a Registration Accept message to the terminal containing information indicating that operation according to the S&F mode is supported or provided; receiving a request message from the terminal for a request related to an Always-on (protocol data unit Session) session; and transmitting a rejection message to the terminal for rejecting a request related to an Always-on PDU session, wherein the rejection message may include a reason value indicating that the Always-on PDU session is not supported as operation according to the S&F mode is supported / provided.

[0011] Additionally, a terminal of a wireless communication system according to the present disclosure comprises a transceiver and a controller connected to the transceiver, wherein the controller is configured to transmit a Registration Request message to a network containing information indicating that the terminal supports operation according to the S&F (Store and Forward) mode of a satellite, receive a Registration Accept message from the network containing information indicating that operation according to the S&F mode is supported or provided, transmit a request message to the network for a request related to an Always-on Protocol Data Unit Session, and receive a rejection message from the network for rejecting a request related to an Always-on Protocol Data Unit Session, wherein the rejection message may include a reason value indicating that the Always-on Protocol Data Unit Session is not supported as operation according to the S&F mode is supported or provided.

[0012] Additionally, a method performed by a terminal in a wireless communication system according to the present disclosure may include the steps of: transmitting a Registration Request message to a network that includes information indicating that the terminal supports operation according to the S&F (Store and Forward) mode of a satellite; receiving a Registration Accept message from the network that includes information indicating that operation according to the S&F mode is supported or provided; transmitting and receiving data to and from the network in the S&F mode; and, if there is a request related to an Always-on Protocol Data Unit Session, searching for a second network different from the network that supports the request related to the Always-on Protocol Data Unit Session.

[0013] Additionally, a terminal of a wireless communication system according to the present disclosure includes a transceiver and a controller connected to the transceiver, and the controller transmits a Registration Request message to a network containing information indicating that the terminal supports operation according to the S&F (Store and Forward) mode of a satellite, receives a Registration Accept message from the network containing information indicating that operation according to the S&F mode is supported or provided, transmits and receives data with the network in the S&F mode, and when there is a request related to an Always-on Protocol Data Unit Session, can search for a second network different from the network that supports the request related to the Always-on Protocol Data Unit Session.

[0014]

[0015] The method proposed in this specification can provide an effective method for PDU session management in a wireless communication system.

[0016] The effects obtained by the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0017]

[0018] Figure 1 is a diagram illustrating the structure of a next-generation mobile communication system.

[0019] Figures 2 and 3 illustrate an example of a non-terrestrial network for communication based on a repeater satellite.

[0020] Figures 4 and 5 illustrate an example of a non-terrestrial network for communication based on a regenerative satellite.

[0021] Figure 6 is a diagram illustrating an example of signaling to enable S&F mode between a terminal and a network.

[0022] FIGS. 7 to 10 illustrate a method for processing an always-on PDU session setup / modification request between a terminal and a network while S&F mode is in operation.

[0023] FIG. 11 is a flowchart illustrating an example of a method performed by a terminal in a wireless communication system according to one embodiment of the present disclosure.

[0024] FIG. 12 is a flowchart illustrating an example of a method performed by a network in a wireless communication system according to one embodiment of the present disclosure.

[0025] FIG. 13 is a drawing illustrating the structure of a terminal in a wireless communication system according to one embodiment of the present disclosure.

[0026] FIG. 14 is a drawing illustrating the structure of a base station in a wireless communication system according to one embodiment of the present disclosure.

[0027] FIG. 15 is a drawing illustrating the structure of a network in a wireless communication system according to one embodiment of the present disclosure.

[0028]

[0029] Embodiments of the present disclosure will be described in detail below with reference to the drawings. However, detailed descriptions of known functions or configurations that may obscure the gist of the present disclosure in the following description and the attached drawings are omitted. Additionally, throughout the present disclosure, the term "comprising" any component means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0030] Additionally, terms such as first, second, etc. may be used to describe various components, but said components should not be limited by said terms. Such terms may be used for the purpose of distinguishing one component from another. For example, without departing from the scope of the rights of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component.

[0031] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as “comprising” or “comprising” are intended to specify the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0032] Unless specifically defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this disclosure pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure.

[0033] Figure 1 is a diagram illustrating the structure of a next-generation mobile communication system.

[0034] Referring to FIG. 1, as illustrated, the wireless access network of a next-generation mobile communication system (New Radio, NR) consists of a next-generation base station (New Radio Node B, hereinafter gNB) (110) and an AMF (105, New Radio Core Network). A user terminal (New Radio User Equipment, hereinafter NR UE or terminal) (115) connects to an external network through the gNB (110) and the AMF (105).

[0035] In FIG. 1, the gNB corresponds to the eNB (Evolved Node B) of the existing LTE system. The gNB is connected to the user terminal via a wireless channel (120) and can provide superior service compared to the existing Node B (or eNB). In the next-generation mobile communication system, since all user traffic is serviced through a shared channel, a device is required to collect status information such as the buffer status, available transmission power status, and channel status of user terminals and perform scheduling, and this is handled by the gNB (110). The gNB (110) typically controls multiple cells. To achieve ultra-high-speed data transmission compared to existing LTE, it can support a bandwidth greater than the existing maximum bandwidth, and additionally, beamforming technology can be incorporated by using Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) as the wireless access technology. In addition, an Adaptive Modulation & Coding (hereinafter referred to as AMC) method is applied to determine the modulation scheme and channel coding rate according to the channel conditions of the terminal.

[0036] The AMF (105) performs functions such as mobility support, bearer configuration, and QoS configuration. The AMF is a device responsible for various control functions as well as mobility management functions for the terminal, and is connected to multiple base stations. Additionally, the next-generation mobile communication system can be interconnected with the existing LTE system, and the AMF (access and mobility management function) (105) is connected to the MME (mobility management entity) (125) via a network interface. The MME (125) is connected to the existing base station, eNB (130). A terminal supporting LTE-NR Dual Connectivity can transmit and receive data while maintaining a connection to both the gNB and the eNB.

[0037] Non-Terrestrial Network (NTN)

[0038] 3GPP paved the way for the commercial application of 5G by finalizing the first global 5G New Radio (NR) standard in Release 15. In addition, NR-based Non-Terrain Networks (NTN) are being considered as one of the evolutionary stages of NR to enable 5G activation and expand the ecosystem. Due to their extensive service coverage capabilities and reduced vulnerability to physical attacks and natural disasters on space / aviation platforms, NTNs can provide 5G services in a cost-effective manner in areas not served by terrestrial 5G networks (isolated or remote areas, onboard aircraft or ships) and in areas with weak service (suburban or rural areas). Furthermore, they enable service continuity for M2M and IoT devices or passengers on mobile platforms (aircraft, ships, high-speed trains, buses, etc.), and support highly reliable, omni-accessible 5G services for key communications such as future railway, maritime, and aviation communications. Along with this, they can support the availability of 5G networks by providing efficient multicast / broadcast resources for data delivery to the network edge or user terminals. These benefits can be provided through standalone NTNs or integrated terrestrial and non-terrestrial networks, and are expected to have an impact in sectors such as transportation, public safety, media and entertainment, eHealth, energy, agriculture, finance, and automotive.

[0039] Such cellular-based satellite communication refers to a satellite communication system that has a communication and functional structure based on mobile communication standards. According to the 3GPP TR 38.821 report, satellite types in non-terrestrial networks (NTN) are broadly classified into two types. One is a transparent satellite type that simply amplifies communication signals and retransmits them by changing only the frequency, and the other is a regenerative satellite type that is equipped with a receiver, processing unit, transmitter, etc. on the satellite itself to digitally process and regenerate signals.

[0040] Figures 2 and 3 illustrate an example of a non-terrestrial network for communication based on a repeater satellite.

[0041] Referring to FIG. 2, in a non-terrestrial network for communication based on a repeater satellite, all signals between a terrestrial network including a terrestrial terminal and a terrestrial gateway are relayed in bypass mode. Referring to FIG. 2 and FIG. 3, a 5G NR (New Radio) based wireless interface is used for both the service link between the terminal and the satellite and the feeder link between the satellite and the ground station, and base station and core functions are provided through the terrestrial network.

[0042] Figures 4 and 5 illustrate an example of a non-terrestrial network for communication based on a regenerative satellite.

[0043] Referring to FIG. 4, the satellite is equipped with some or all functions of a mobile communication base station and is connected to a terminal or terrestrial network via multi-hop communication using an Inter-Satellite Link (ISL). Referring to FIG. 5, the service link between the terminal and the satellite uses a 5G NR-based radio interface, whereas the PD link with the ground station uses a mobile communication protocol based on the existing Satellite Radio Interface (SRI). Additionally, depending on the functions of the satellite, some functions or core functions of the base station are provided through the terrestrial network.

[0044] The following is a partial overview of the ongoing Rel-19 FS_5GSAT_Ph3 through the contents of 3GPP TR 22.865. In SA1, cases are being identified and requirements are being analyzed for providing communication services between terminals via satellite only under satellite coverage, and for providing latency-insensitive services via satellite where the connection with the terrestrial network may be interrupted for a period of time.

[0045] To provide latency-insensitive services, the Store and Forward (S&F) method is used. This applies to non-geostationary satellites, and depending on the satellite's movement, situations may arise where the satellite is connected only via a service link with the terminal, or only via a feeder link with the terrestrial network. In the former case, the satellite exchanges and stores signaling and data through the service link with the terminal; in the latter case, it transmits the previously stored signaling and data to the terrestrial network via the feeder link. It is also possible for the order of the former and the latter to be reversed. Examples of providing communication services between terminals solely via satellite under satellite coverage include cases where vessels in the open sea communicate via the same satellite without a connection to a terrestrial network, or cases where communication is provided between vessels via satellite-to-satellite connections without a connection to a terrestrial network, even when some vessels enter and connect to a different satellite's coverage area.

[0046] The following defines the terms used in the present disclosure.

[0047] Store and Forward Satellite operation: An operation mode that provides communication services to a terminal when the service satellite is discontinuously connected to a ground network and the connection to the ground network is unavailable when the satellite interacts with the terminal.

[0048] S&F (Store and Forward) mode: Refers to a mode in which user terminals, RAN (radio access network) and core network entities perform store and forward satellite operations.

[0049] The following briefly describes the standard-related content associated with this specification. For a detailed description, refer to 3GPP TS 23.501 V18.8.0 (3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; System architecture for the 5G System (5GS); Stage 2 (Release 18)).

[0050] - Always-on protocol data unit session: A PDU session that must be activated whenever a user plane resource transitions from CM-IDLE mode to CM-CONNECTED state.

[0051] Under the direction of the upper layer, the user terminal may request to set the PDU session as an always-on PDU session. The session management function (SMF) determines whether the PDU session can be set as an always-on PDU session. In the case of home routed roaming, the V-SMF participates according to the local policy to determine whether the PDU session can be set as an always-on PDU session.

[0052] When a user terminal requests the 5GC (5G core network) to modify a PDU session set in EPS into an always-on PDU session after the first inter-system change from EPS to 5GS, the SMF determines whether the PDU session can be set into an always-on PDU session in accordance with the procedure described in 3GPP TS 23.501 V18.8.0.

[0053] The user terminal must request user plane resource activation for the PDU session that is always on, even if there is no uplink data waiting for this PDU session or a service request is triggered.

[0054] If a user terminal has one or more established PDU sessions that are not allowed as always-on PDU sessions on the network, and there is no uplink user data waiting to be transmitted for said PDU session, the user terminal should not request user plane resource activation for said PDU session.

[0055] - Satellite backhaul support

[0056] -general details

[0057] Satellites can be used as part of the backhaul between (R)AN and 5GC. 5G systems support the reporting of satellite backhaul usage as described below.

[0058] In some deployments, a user plane function (UPF) may be deployed on a satellite. In such cases, edge computing or local switching via the satellite-deployed UPF may be performed as described in Sections 5.43.2 and 5.43.3 of 3GPP TS 23.501 V18.8.0. Deployments with satellite backhaul and edge computing with a ground-based UPF are supported as described in Section 5.13, that is, without satellite backhaul requirements.

[0059] - Edge computing via UPF deployed on satellites

[0060] The description provided herein applies only when edge computing is deployed with User Plane Functions (UPFs) and edge computing services onboard the satellite. The UPF deployed on the satellite can operate as a UL CL / BP / local PSA UPF (PDU Session Anchor User Plane Function) or as a PSA UPF.

[0061] To select a UPF deployed on a satellite as a PSA, the following improvements are applied:

[0062] - When a UE is connecting to a gNB via satellite backhaul and the AMF is aware of the satellite backhaul category, the AMF transmits the satellite backhaul category to the policy control function (PCF). When the GEO satellite backhaul category is indicated, the PCF takes this into account and creates or updates a user route selection policy (URSP) rule defined in Section 6.1.2.2 of 3GPP TS 23.503 V18.8.0 (3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Policy and charging control framework for the 5G System (5GS); Stage 2 (Release 18)) to include an appropriate route selection descriptor for the service deployed on the GEO satellite, thereby enabling the establishment of a PDU session via the PSA UPF on the satellite.

[0063] Based on the GEO satellite ID provided by the AMF, the SMF enables the selection (including, if possible) of a UPF distributed from the GEO satellite by performing PSA UPF selection or UL CL / BP / local PSA selection and insertion during the PDU session setup procedure described in Section 4.3.2 of 3GPP TS 23.502 V18.8.0 (3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Procedures for the 5G System (5GS); Stage 2 (Release 18)) or the PDU session modification procedure described in Section 4.3.3 of 3GPP TS 23.502 V18.8.0.

[0064] - The AMF can determine the GEO satellite ID providing service to the user terminal based on the configuration and transmit it to the SMF. For example, if the GEO satellite ID changes due to reasons such as the user terminal handing over to a gNB using a different GEO satellite as part of the backhaul, the AMF can update the SMF with the latest GEO satellite ID.

[0065] - The SMF determines the DNAI based on the local configuration, DNN, S-NSSAI, or both, and the GEO satellite ID received from the AMF. The operator may assign one or more DNAI values ​​to each GEO satellite ID, and the SMF locally configures the mapping relationship between the DNAI and the GEO satellite ID.

[0066] - If the user terminal is allowed access to the service according to the EAS deployment information described in Section 6.2.3.4 of 3GPP TS 23.548 V18.8.0 (3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; 5G System Enhancements for Edge Computing; Stage 2 (Release 18)), the SMF selects the PSA UPF or UL CL / BP / local PSA based on the DNAI corresponding to the GEO satellite ID and other factors described in Section 6.2.3.2 of 3GPP TS 23.548 V18.8.0.

[0067] - Local switch for communication between user terminals via UPF deployed on GEO satellites

[0068] - general details

[0069] Traffic between user terminals can be locally routed to target user terminals through a local switch by a UPF deployed on the satellite, without passing through a satellite gateway on the ground.

[0070] Here, local switching via UPF deployed on the satellite applies only to GEO satellite backhaul, and for 5G VN, only DNN and slicing are considered.

[0071] An N19 tunnel can be established between two UPFs deployed on different satellites for traffic between user terminals. Additionally, an N6 tunnel can be used to transmit traffic between UPFs distributed on different satellites.

[0072] Only a single SMF is supported for local switching and N19 forwarding. That is, both user terminals receive service from the same SMF.

[0073] In this case, the latency optimization achievable through inter-satellite links between UPFs deployed on different GEO satellites can vary significantly depending on the number of deployed satellites and the distance between them.

[0074] Section 5.43.3.2 of 3GPP TS 23.501 V18.8.0 describes the case of a PSA UPF deployed on a satellite, and Section 5.43.3.3 describes the case of a UL CL / BP and local PSA deployed on a satellite. In this case, the PSA UPF is located on the ground. The selection of the PSA UPF or UL CL / BP / local PSA on the satellite is described in Section 6.3.3 of 3GPP TS 23.501 V18.8.0, and the DNAI decision for selecting the UPF deployed on the relevant GEO satellite reuses the mechanism described in Section 5.43.2 of 3GPP TS 23.501 V18.8.0.

[0075] For communication between users where a backhaul with UPF applied is deployed on GEO satellites, the operator assigns a DNN / S-NSSAI combination, and URSP is described in 3GPP TS 23.503 V18.8.0; furthermore, the configuration for enabling Selective PSA UPF on GEO satellites reuses the mechanism described in Section 5.43.2 of 3GPP TS 23.503 V18.8.0. This is briefly explained below.

[0076] - Local switch with PSA UPF deployed on the satellite

[0077] When an SMF selects a UPF deployed on a satellite as the PSA of a user terminal's PDU session, the SMF configures the user terminal's N4 session to forward / receive packets on the internal interface as specified in Section 5.8.2.13.1 (Support for Unicast Traffic Forwarding in 5G VN) of 3GPP TS 23.501 V18.8.0 for the configuration of the N4 session of a 5G VN group member.

[0078] SMF can configure group-level N4 session rules for each N19 tunnel by reusing the mechanism described in Section 5.8.2.13.1 of 3GPP TS 23.501 V18.8.0.

[0079] When establishing an N19 tunnel between PSA UPFs mounted on the satellite, the PSA UPF is controlled by the same SMF.

[0080] To process packets between the user terminal and the server residing in the DN, the SMF configures rules to route traffic through N6 as described in Section 5.8.2.13.1.

[0081] Group-level N4 sessions are DNN and S-NSSAI units. SMF can create, update, or delete group-level N4 sessions (e.g., adding or deleting N4 rules, allocating or releasing N19 tunnel resources based on operator deployment) (e.g., based on the planned obsolescence of GEO satellites or the setup of new GEO satellites).

[0082] N6 can be used to transmit traffic between PSA UPFs deployed on different satellites. When using N6, the SMF configures the corresponding N4 rule for traffic processing with N6.

[0083] - Local switching using local PSA UPF and UL CL / BP deployed on the satellite

[0084] If a user terminal using a GEO satellite backhaul is serviced by the same SMF and a UPF is deployed on the GEO satellite providing service to said user terminal, the SMF may decide to enable local switching and N19 forwarding for the user terminal according to the following:

[0085] 1) An AF request including a user terminal identifier requiring communication between user terminals as described in Section 5.29.2 of 3GPP TS 23.501 V18.8.0; and / or

[0086] 2) Destination IP address(s) reported by the ground PSA UPF according to the current reporting mechanism of Section 5.8.5.7 of 3GPP TS 23.501 V18.8.0. To enable destination IP address reporting, the SMF configures the ground PSA UPF to detect uplink packets with destination IP addresses belonging to the current UPF address pool.

[0087] If the SMF determines that user terminals corresponding to the AF request of 1) and / or the destination IP address reported in 2) belong to the same GEO satellite (or multiple connectable GEO satellites) based on the GEO satellite ID reported by the AMF, and that the user terminals are allowed to access the DNAI corresponding to the GEO satellite ID, the SMF may, for each user terminal communicating with a target user terminal within the communication group, select and insert the UPF distributed to the GEO satellite according to the DNAI as the UL CL / BP and L-PSA, and configure the UL CL / BP with the following rules:

[0088] Data traffic received from the user terminal and destined for the IP address of the target user terminal is routed to the L-PSA.

[0089] Other data traffic received from the user terminal is routed to the PSA UPF of the user terminal's PDU session.

[0090] SMF determines whether GEO satellites can be connected based on the configuration.

[0091] The SMF configures local PSAs with local forwarding rules to deliver data traffic directly to target user terminals. If different L-PSAs are selected for user terminals within the communication group, an N19 tunnel is established between the L-PSAs. If an N19 tunnel is established between UPFs on the satellite, the UPFs are controlled by the same SMF. If the user terminals are members of the same 5G VN group, the SMF may configure local data forwarding rules for the L-PSAs using the 5G VN user plane forwarding mechanism of Section 5.8.2.13.1 (Support for Unicast Traffic Forwarding in 5G VN) of 3GPP TS 23.501 V18.8.0.

[0092] The selected UPF deployed on the satellite can be inserted into the UL CL / BP / L-PSA by reusing the existing UL CL / BP insertion procedure defined in 3GPP TS 23.502 or 3GPP TS 23.548 V18.8.0.

[0093] N6 can be used to transmit traffic between L-PSA UPFs deployed on different satellites. When using N6, the SMF configures the corresponding N4 rule for traffic processing with N6.

[0094] - Satellite Backhaul Report on SMF

[0095] If the AMF becomes aware that satellite backhaul is being used for a 5G AN, the AMF may report this to the SMF as part of the PDU session setup procedure as described in Section 4.3.2 of 3GPP TS 23.502 V18.8.0. If the AMF becomes aware that the satellite backhaul category has changed (e.g., at handover), the AMF reports the current satellite backhaul category to the SMF. The SMF reports this to the PCF if the “Satellite Backhaul Category Change” PCRT is equipped as specified in 3GPP TS 23.503 V18.8.0, or notifies other NFs upon request as described in Section 5.2.8.3 of 3GPP TS 23.502 V18.8.0. If the backhaul network changes from a satellite type to a terrestrial network, the AMF reports that the non-satellite backhaul network is being used with the satellite backhaul category.

[0096] The satellite backhaul category is a term referring to the types of satellites used for backhaul (e.g., GEO, MEO, LEO, or OTHERSAT, DYNAMIC_GEO, DYNAMIC_MEO, DYNAMIC_LEO, and DYNAMIC_OTHERSAT) as specified in Section 5.4.3.39 of 3GPP TS 29.571 V18.8.0 (3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; 5G System; Common Data Types for Service Based Interfaces; Stage 3 (Release 18)). The dynamic satellite backhaul category (e.g., DYNAMIC_GEO, DYNAMIC_MEO, DYNAMIC_LEO, and DYNAMIC_OTHERSAT) means that the functionality of the satellite backhaul (latency and / or bandwidth) changes over time due to the use of various inter-satellite links as part of the backhaul. Only one backhaul category may be indicated.

[0097] It is assumed that AMF can determine the satellite backhaul category for notification to SMF based on the local configuration (e.g., global RAN node ID associated with the satellite backhaul).

[0098] - QoS monitoring when using dynamic satellite backhaul

[0099] When dynamic satellite backhaul is used, QoS monitoring can be used to measure packet delay as specified in Section 5.45.2 of 3GPP TS 23.501 V18.8.0.

[0100] If the satellite backhaul category received from the SMF indicates that dynamic satellite backhaul is being used, the PCF may request QoS monitoring for packet delay between the user terminal and the PSA UPF as specified in Section 5.45.2 of 3GPP TS 23.501 V18.8.0, depending on the PCF local policy or configuration. The AF may initiate QoS monitoring by requesting a QoS monitoring report from the PCF, as in the case of receiving the dynamic satellite backhaul category.

[0101] When operations supporting S&F mode (S&F mode: a mode in which user terminals, RANs, and core network entities perform store and forward satellite operations) are performed between a user terminal and a network, if Session Establishment / Modification request procedures related to Always-on PDU Sessions are executed for connections to ultra-low latency, time-sensitive, and real-time communication services, inefficient operations may lead to issues with ultra-low latency service connections, signaling overhead, and resource waste. Therefore, when operations supporting S&F mode are performed between a user terminal and a network, an efficient and clear solution is absolutely necessary for the problems arising from the execution of Session Establishment / Modification request procedures related to Always-on PDU Sessions for connections to ultra-low latency, time-sensitive, and real-time communication services.

[0102] According to the present disclosure, a processing method can be implemented to efficiently set up an always-on PDU session when an operation supporting S&F mode is performed between a terminal and a network, thereby reducing unnecessary signaling overhead, minimizing waste of battery and resources of the user terminal and network, and continuously providing ultra-low latency services.

[0103] If a user terminal performing an operation that supports S&F mode and a network perform a PDU session setup / modification request procedure related to an always-on PDU session, and the network allows the user terminal to perform the PDU session setup / modification request procedure, the S&F mode operation suitable for data transmission related to delay-tolerant services and the operation based on an always-on PDU session suitable for data transmission related to real-time or time-sensitive communication services will conflict with each other, and as a result, it becomes difficult to guarantee QoS related to delay-tolerant services or real-time or time-sensitive communication services, and therefore communication between the user terminal and the network becomes inefficient and may lead to resource waste.

[0104] Therefore, an efficient control function is required to resolve issues that may arise when a terminal performing an operation supporting S&F mode and a network performs a procedure for requesting the establishment or modification of a PDU session related to a PDU session that is always on. However, current 3GPP technical specifications do not describe, and are unclear, any operation that can be applied when a terminal performing an operation supporting S&F mode and a network performs a procedure for requesting the establishment or modification of a PDU session related to a PDU session that is always on.

[0105] Accordingly, the present disclosure proposes an always-on PDU session management operation method that can be efficiently applied in an operating terminal and network environment supporting S&F mode.

[0106] First, we will explain an example of signaling to enable S&F mode between the terminal and the network.

[0107] Figure 6 is a diagram illustrating an example of signaling to enable S&F mode between a terminal and a network.

[0108] In a 3GPP network, the terminal and the network may or may not support S&F (Store and Forward) mode.

[0109] In the present disclosure, the network may mean a satellite (Geosynchronous Earth Orbit (GEO), Low Earth Orbit (LEO), or general satellite), an MME of the EPC, or an AMF or SMF of the 5GC.

[0110] S&F mode refers to a satellite Store and Forward (S&F) method for providing services that are not sensitive to latency, such as general data transmission. A terminal may have its S&F mode support capability pre-configured. That is, S&F mode support capabilities may be configured or provided to the user terminal through pre-configuration, or the network may configure or provide S&F mode support capabilities to the user terminal according to operator policies or URSP rules. The network may configure or provide S&F mode support capabilities to the user terminal by transmitting configuration information via a Registration Accept message or a Configuration Update Command message. In this case, the user terminal may request configuration information via a Registration Request message or respond that the configuration is complete via a Configuration Update Complete message.

[0111] Referring to FIG. 6, if the terminal has an S&F mode support function configured and supports S&F mode, the terminal transmits a Registration Request message (210) to the network containing S&F mode support information / indication. If the network does not support S&F mode or cannot provide S&F mode to the terminal, the network rejects the Registration Request message requested by the terminal. At this time, the network may provide the terminal with a Registration Accept message or a Registration Reject message (220) containing a cause value for S&F mode not supported or S&F mode not available and / or a back-off (or wait) timer value.

[0112] At this time, the terminal may recognize that the network does not support or provide S&F mode based on the cause value of "S&F mode not available" included in the registration rejection message or registration acceptance message. In this case, the terminal does not resend a registration request message containing S&F mode support information to the network. Additionally, if the terminal receives a back-off / wait timer value from the network via the registration rejection message or registration acceptance message, when the back-off / wait timer value expires (240), the terminal may resend a registration request message containing S&F support information to the network (250).

[0113] Meanwhile, if the network can accept / provide the S&F mode support requested by the terminal to the terminal, the network transmits a registration acceptance message (230) to the terminal in response to a registration request message containing the terminal's S&F support information. At this time, the registration acceptance message includes information indicating that the S&F mode is supported or that the S&F mode is available. The network may provide the terminal with information regarding the estimated data delivery time for the downlink or uplink.

[0114] As a first embodiment for always-on PDU session management that can be performed between a terminal operating in S&F mode and a network by signaling according to FIG. 6, a method of rejecting always-on PDU session settings when operating in S&F mode in the network may be considered.

[0115] Below, we describe the specific operation of a method for rejecting PDU session settings that are always on when the network is operating in S&F mode.

[0116] FIGS. 7 to 10 illustrate a method for processing an always-on PDU session setup / modification request between a terminal and a network while S&F mode is in operation.

[0117] Referring to FIGS. 7 to 10, depending on the configuration of the terminal and the network, the method of processing the always-on PDU session setup / modification request between the terminal and the network may differ.

[0118] Referring to FIGS. 7 to 10, a terminal and a network supporting S&F mode have mutually confirmed that they can support S&F mode through the registration procedure shown in FIG. 6, and based on this, they are performing an operation (310) that supports S&F mode.

[0119] At this time, the terminal may want to establish an always-on PDU session for connection to ultra-low latency, time-sensitive, real-time communication services, etc. To establish an always-on PDU session, the application layer of the terminal transmits an always-on PDU session establishment request to the NAS layer of the terminal. To perform the always-on PDU session establishment, the NAS of the terminal transmits a PDU session establishment request message or a PDU session modification request message containing information on the always-on PDU session request to the network (320).

[0120] If the network receives a PDU session setup / modification request message containing information about an always-on PDU session from a terminal while an operation supporting S&F mode is being performed (310), the network may reject the always-on PDU session setup and modification requested by the terminal. This is because, during an operation supporting S&F mode, it is difficult to support or provide time-sensitive services or real-time services as data transmission delays are allowed.

[0121] Subsequently, the network responds to the terminal by transmitting a PDU session establishment reject message or a PDU session modification reject message (330) containing a cause value #xy "Always-on PDU session not supported due to S&F mode activated" (reject cause value). At this time, the network may additionally include a back-off timer Tabcd along with the cause value in the PDU session establishment reject message or the PDU session modification reject message.

[0122] The NAS of a terminal that receives a PDU session formation rejection message or a PDU session modification rejection message from the network containing cause value #xy "Always-on PDU session not supported due to S&F mode activated" informs the application layer of the terminal that the always-on PDU session setup has failed. The NAS of the terminal that receives that the always-on PDU session setup has failed due to S&F mode being activated can perform various actions depending on the configuration.

[0123] Referring to FIG. 7, during Configuration 1, the terminal does not retry the always-on PDU session setup. Accordingly, the terminal does not resend to the network a PDU session formation request message or a PDU session modification request message containing always-on PDU session request information. However, if the PDU session formation rejection message or PDU session modification rejection message received from the network contains a back-off timer Tabcd, the terminal can activate the back-off timer Tabcd, and when the back-off timer Tabcd expires (340), it can resend to the network a PDU session formation request message or a PDU session modification request message containing always-on PDU session request information. That is, the terminal can retry the always-on PDU session setup for a connection such as an ultra-low latency, time-sensitive, or real-time communication service. At this time, the back-off timer Tabcd can be activated at the same time based on the same value at the terminal and the network, respectively, and can expire at the same time.

[0124] In the case of the second to fifth settings, the NAS of the terminal may perform a selection of a Public Land Mobile Network (PLMN), a Radio Access Technology (RAT), or a combination of PLMN and RAT (360) to find another network that can set up a PDU session that is always turned on. In each setting, the time interval for finding another network may be different.

[0125] Here, the other network selected according to the PLMN selection, RAT selection, or combination of PLMN+RAT selection may be a network provided by a different operator than the one providing the network currently connected to the terminal, where the same RAT as the one used in the network currently connected to the terminal is used, or a network provided by a different operator than the one providing the network currently connected to the terminal is used, where a different type of RAT than the one used in the network currently connected to the terminal is used.

[0126] Afterward, the terminal may attempt to re-establish an always-on PDU session on the newly selected PLMN, RAT, or PLMN+RAT network. The terminal's NAS may transmit (370) a PDU session formation request message or a PDU session modification request message containing information on the always-on PDU session request to the newly selected PLMN, RAT, or PLMN+RAT network.

[0127] Referring to FIG. 7, during Configuration 2, the terminal may perform a PLMN selection, a RAT selection, or a combination of PLMN+RAT selection to search for another network only if the back-off timer Tabcd is not included in the PDU session formation rejection message or PDU session modification rejection message received from the network. In this case, the terminal may perform a PLMN selection, a RAT selection, or a combination of PLMN+RAT selection (360) to search for another network immediately after receiving the PDU session formation rejection message or PDU session modification rejection message from the network.

[0128] In the second setting, if the PDU session formation rejection message or PDU session modification rejection message received from the network includes a back-off timer Tabcd, the terminal can activate the back-off timer Tabcd in the same way as in the first setting, and when the back-off timer Tabcd expires (340), it can send back to the network a PDU session formation request message or a PDU session modification request message containing PDU session request information that is always turned on.

[0129] Referring to FIG. 8, during Configuration 3, the terminal can perform PLMN selection, RAT selection, or a combination of PLMN+RAT selection (360) to search for another network only when the back-off timer Tabcd is included in the PDU session formation rejection message or PDU session modification rejection message received from the network and the back-off timer Tabcd has expired (340).

[0130] In the third configuration, if the PDU session formation rejection message or PDU session modification rejection message received from the network does not include a back-off timer Tabcd, similar to the second configuration, a PLMN selection, a RAT selection, or a combination of PLMN+RAT can be performed to immediately search for another network.

[0131] Referring to FIG. 9, during Configuration 4, if the terminal receives a PDU session formation rejection message or a PDU session modification rejection message from the network that includes a back-off timer Tabcd, the terminal may perform a PLMN selection, a RAT selection, or a combination selection of PLMN+RAT to search for another network during the time the back-off timer Tabcd is running. In this case, the terminal may immediately perform a PLMN selection, a RAT selection, or a combination selection of PLMN+RAT to search for another network (360) immediately after receiving a PDU session formation rejection message or a PDU session modification rejection message containing a back-off timer Tabcd from the network. At this time, if the terminal finds a new network before the back-off timer Tabcd expires (340), and a new network capable of setting up an always-on PDU session is found, the terminal may transmit a PDU session formation request message or a PDU session modification request message containing information on a PDU session that is always-on to the new network (370). On the other hand, if the terminal does not find a new network until the back-off timer Tabcd expires (340), the terminal may send back to the network a PDU session formation request message or a PDU session modification request message containing PDU session request information that is always turned on to the existing connected network.

[0132] Referring to FIG. 5, during Configuration 5, a Search Timer may be included in the PDU session formation rejection message or PDU session modification rejection message separately from the back-off timer Tabcd to set a time interval for performing PLMN selection, RAT selection, or a combination selection of PLMN+RAT to search for another network. In this case, the terminal may perform PLMN selection, RAT selection, or a combination selection of PLMN+RAT only while the Search Timer is running. At this time, the Search Timer may be set to expire before the back-off timer Tabcd. Accordingly, when the back-off timer Tabcd is running and the Search Timer is running, the terminal may perform PLMN selection, RAT selection, or a combination selection of PLMN+RAT to search for a new network. Among these, if a new network capable of setting an always-on PDU session is discovered, a PDU session formation request message or a PDU session modification request message containing always-on PDU session request information may be transmitted to the new network (370).

[0133] When the search timer expires (380), the terminal can terminate the selection of a PLMN, a RAT, or a combination of PLMN+RAT to search for a new network. And when the back-off timer Tabcd expires (340), it can send a PDU session formation request message or a PDU session modification request message (350) containing PDU session request information that is always on again to the currently connected network.

[0134] Next, as a second embodiment for always-on PDU session management that can be performed between a terminal and a network while performing an operation supporting S&F mode by signaling according to FIG. 6, a method may be considered in which the always-on PDU session setting is set / defined so that it is impossible to set when the S&F mode is operated at the user terminal.

[0135] Below, we describe the specific operation of a method in which a PDU session setting that is always on is disabled when the terminal operates in S&F mode.

[0136] Referring to FIG. 7, the terminal and network supporting S&F mode have mutually confirmed that they can support S&F mode through the registration procedure shown in FIG. 6, and based on this, they are performing an operation (310) that supports S&F mode.

[0137] In this case, the terminal may want to establish an always-on PDU session to connect to ultra-low latency, time-sensitive, or real-time communication services. To establish an always-on PDU session, the terminal application layer transmits a request to form an always-on PDU session to the terminal NAS layer.

[0138] The terminal NAS can recognize that it should not perform an always-on PDU session setup because an operation supporting S&F mode is currently being performed. Additionally, the terminal NAS can recognize that it cannot transmit a PDU session formation request message or a PDU session modification request message to the network. Therefore, unlike operation 320 shown in FIG. 7, the terminal NAS does not transmit a PDU session formation request message or a PDU session modification request message to the network.

[0139] Through the above operation, the terminal's NAS can reject the request for an always-on PDU session setup received from the terminal's application layer. In response to the request for an always-on PDU session setup received from the terminal's application layer, the terminal's NAS informs the application layer that the transmission of the PDU session setup request message or the PDU session modification request message has failed.

[0140] Subsequently, a request from the application layer of the terminal or the NAS layer of the terminal may perform general PDU session setup or modification, rather than PDU session setup or modification that is always on.

[0141] Additionally, depending on other settings, the terminal's NAS can select PLMN, RAT, or a combination of PLMN and RAT to find another network capable of establishing an always-on PDU session.

[0142] Here, the other network selected according to the PLMN selection, RAT selection, or combination of PLMN+RAT selection may be a network provided by a different operator than the one providing the network currently connected to the terminal, where the same RAT as the one used in the network currently connected to the terminal is used, or a network provided by a different operator than the one providing the network currently connected to the terminal is used, where a different type of RAT than the one used in the network currently connected to the terminal is used.

[0143] Afterward, the terminal may attempt to re-establish an always-on PDU session on the newly selected PLMN, RAT, or PLMN+RAT network. The terminal's NAS may transmit (370) a PDU session formation request message or a PDU session modification request message containing information on the always-on PDU session request to the newly selected PLMN, RAT, or PLMN+RAT network. It may transmit (370) to the PLMN, or, RAT, or PLMN+RAT network.

[0144] Additionally, the method of the network rejecting the always-on PDU session setting during S&F mode operation according to the first embodiment and the method of setting / defining so that the terminal cannot request the always-on PDU session setting according to the second embodiment may be operated in combination.

[0145] When an operation supporting S&F mode between a terminal and a network is performed, and a procedure for requesting the formation of a PDU session or the modification of a PDU session related to an always-on PDU session for connecting ultra-low latency, time-sensitive, or real-time communication services is executed, problems with ultra-low latency service connection, signaling overhead, and resource waste are caused by inefficient operation. According to the present disclosure, there is an effect of providing an efficient and clear solution for such problems.

[0146] According to the present disclosure, when an always-on PDU session is configured or modified while the S&F mode is supported, an efficient processing method is performed, thereby reducing unnecessary signaling overhead, minimizing waste of battery and network resources, and enabling the continuous provision of ultra-low latency services.

[0147] FIG. 11 is a flowchart illustrating an example of a method performed by a terminal in a wireless communication system according to one embodiment of the present disclosure.

[0148] Referring to FIG. 11, the terminal can transmit a Registration Request message to the network containing information indicating that the terminal supports operation according to the satellite's S&F (Store and Forward) mode (610).

[0149] Next, the terminal can receive a Registration Accept message from the network containing information indicating that operation according to S&F mode is supported / available (620).

[0150] Next, the terminal can send a request message for a request related to a PDU session that is always turned on to the network (630).

[0151] Subsequently, the terminal may receive a rejection message from the network to reject a request related to an always-on PDU session based on the operation according to the S&F mode being supported / provided (640). At this time, the rejection message may include a reason value indicating that an always-on PDU session is not supported based on the operation according to the S&F mode being supported / provided.

[0152] FIG. 12 is a flowchart illustrating an example of a method performed by a network in a wireless communication system according to one embodiment of the present disclosure.

[0153] Referring to FIG. 12, the network may receive a registration request message from a terminal containing information indicating that the terminal supports operation according to the satellite's S&F (Store and Forward) mode (710).

[0154] Next, the network can send a registration acceptance message to the terminal containing information indicating that operation according to S&F mode is supported / available (720).

[0155] Next, the network can receive a request message for a request related to a PDU session that is always on from the terminal (730).

[0156] Subsequently, the network may send a rejection message to the terminal to reject a request related to an always-on PDU session based on the support / provision of operation according to S&F mode (740). At this time, the rejection message may include a reason value indicating that an always-on PDU session is not supported as the support / provision of operation according to S&F mode is provided.

[0157] FIG. 13 is a drawing illustrating the structure of a terminal in a wireless communication system according to one embodiment of the present disclosure.

[0158] Referring to FIG. 13, the terminal may include a transceiver comprising a terminal receiver (800) and a terminal transmitter (810), a memory (not shown), and a terminal processing unit (805, or a terminal control unit or processor). Depending on the communication method of the terminal described above, the transceiver (800, 810), memory, and terminal processing unit (805) of the terminal may operate. However, the components of the terminal are not limited to the examples described above. For example, the terminal may include more components or fewer components than the components described above. Furthermore, the transceiver, memory, and processor may be implemented in the form of a single chip.

[0159] The transceiver (800, 810) can transmit and receive signals with a base station. Here, the signal may include control information and data. To this end, the transceiver may be composed of an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies a received signal and down-converts the frequency. However, this is merely one embodiment of the transceiver, and the components of the transceiver are not limited to an RF transmitter and an RF receiver.

[0160] Additionally, the transceiver (800, 810) can receive a signal through a wireless channel and output it to a processor (805), and transmit the signal output from the processor (805) through a wireless channel.

[0161] Memory can store programs and data necessary for the operation of the terminal. Additionally, memory can store control information or data included in signals transmitted and received by the terminal. Memory may be composed of storage media or combinations of storage media such as ROM, RAM, hard disk, CD-ROM, and DVD. Additionally, there may be multiple memories.

[0162] Additionally, the processor (805) can control a series of processes to enable the terminal to operate according to the above-described embodiment. For example, the processor (805) can control the components of the terminal to receive a DCI composed of two layers and receive multiple PDSCHs simultaneously. There may be multiple processors (805), and the processor (805) can perform the control operation of the terminal components by executing a program stored in memory.

[0163] FIG. 14 is a drawing illustrating the structure of a base station in a wireless communication system according to one embodiment of the present disclosure.

[0164] Referring to FIG. 14, the base station may include a transceiver unit, which refers to a base station receiver (930) and a base station transmitter (910), a memory (not shown), and a base station processing unit (905, or a base station control unit or processor). Depending on the communication method of the base station described above, the transceiver unit (900, 910), memory, and base station processing unit (905) of the base station may operate. However, the components of the base station are not limited to the examples described above. For example, the base station may include more components or fewer components than the components described above. In addition, the transceiver unit, memory, and processor may be implemented in the form of a single chip.

[0165] The transceiver (900, 910) can transmit and receive signals with a terminal. Here, the signal may include control information and data. To this end, the transceiver (900, 910) may be composed of an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies a received signal and down-converts the frequency. However, this is merely one embodiment of the transceiver, and the components of the transceiver are not limited to an RF transmitter and an RF receiver.

[0166] Additionally, the transceiver (900, 910) can receive a signal through a wireless channel and output it to a processor (905), and transmit the signal output from the processor (905) through a wireless channel.

[0167] Memory can store programs and data necessary for the operation of the base station. Additionally, memory can store control information or data included in signals transmitted and received by the base station. Memory can be composed of storage media or combinations of storage media such as ROM, RAM, hard disk, CD-ROM, and DVD. Additionally, there may be multiple memories.

[0168] The processor (905) can control a series of processes to enable the base station to operate according to the embodiments of the present disclosure described above. For example, the processor (905) can control each component of the base station to configure two layers of DCIs containing allocation information for a plurality of PDSCHs and to transmit them. There may be multiple processors (905), and the processor (905) can perform the control operation of the base station components by executing a program stored in memory.

[0169] FIG. 15 is a drawing illustrating the structure of a network in a wireless communication system according to one embodiment of the present disclosure.

[0170] In the previous description and FIG. 15, the network refers to a device equipped in a 5G core network (5GC) or an EPC (Evolved Packet Core network), and may be an AMF or an MME.

[0171] Referring to FIG. 15, the network may include a transceiver (referring to a network receiver (1000) and a network transmitter (1010)), a memory (not shown), and a network processing unit (1005, or a network control unit or processor). Depending on the communication method of the network described above, the transceiver (1000, 1010), memory, and network processing unit (1005) of the network may operate. However, the components of the network are not limited to the examples described above. For example, the network may include more components or fewer components than the components described above. Furthermore, the transceiver, memory, and processor may be implemented in the form of a single chip.

[0172] The transceiver (1000, 1010) can transmit and receive signals with a base station. Here, the signal may include control information and data. According to one embodiment, the transceiver (1000, 1010) can transmit a signal to a base station or receive a signal from a base station via a wired IP network. However, this is merely one embodiment of the transceiver, and the components of the transceiver are not limited thereto.

[0173] Additionally, the transmitting and receiving unit (1000, 1010) can output the received signal to the processor (1005) and transmit the signal output from the processor (1005) through a wired IP network.

[0174] Memory can store programs and data necessary for the operation of a network. Additionally, memory can store control information or data included in signals transmitted and received by the network. Memory can be composed of storage media or combinations of storage media, such as ROM, RAM, hard disks, CD-ROMs, and DVDs. Additionally, there may be multiple memory units.

[0175] Additionally, the processor (1005) can control a series of processes to enable the network to operate according to the above-described embodiment. There may be multiple processors (1005), and the processor (1005) can perform control operations on the components of the network by executing a program stored in memory.

[0176] The methods according to the claims of the present disclosure or the embodiments described in the disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0177] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or description of the present disclosure.

[0178] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disc storage devices, compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0179] Additionally, the program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, LAN (local area network), WAN (wide area network), or SAN (storage area network), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port. Additionally, a separate storage device on a communication network may be connected to a device performing an embodiment of the present disclosure.

[0180] In the specific embodiments of the present disclosure described above, the components included in the disclosure are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present disclosure is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed of a singular form, and even if a component is expressed in the singular form, it may be composed of a plural form.

[0181] Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, it is understood that various modifications are possible within the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

1. A method performed by a terminal in a wireless communication system, wherein the method comprises: A step of transmitting a Registration Request message to a network that includes information indicating that the terminal supports operation according to the satellite's S&F (Store and Forward) mode; A step of receiving a Registration Accept message from the above network containing information indicating that an operation according to the S&F mode is supported or provided; A step of transmitting a request message for a request associated with an always-on protocol data unit session to the above network; and The method includes the step of receiving a rejection message from the above network to reject a request associated with an always-on PDU session, wherein A method in which the above rejection message includes a reason value indicating that the always-on PDU session is not supported as the operation according to the above S&F mode is supported or provided.

2. In Paragraph 1, The above rejection message further includes a back-off timer, and A method further comprising the step of retransmitting a request message for a request associated with the always-on PDU session to the above network after the back-off timer has expired.

3. In Paragraph 1, A method further comprising the step of exploring a second network different from the network that supports requests associated with the always-on PDU session, based on the above reason value.

4. In Paragraph 3, The step of exploring the second network above is, A method comprising the step of searching for the second network based on PLMN (Public Land Mobile Network) and / or RAT (Radio Access Technology).

5. In Paragraph 1, The above rejection message further includes a back-off timer, and A step of searching for a second network different from the network that supports requests related to the always-on PDU session based on the reason value after the back-off timer has expired; and A method further comprising the step of sending a request message for a request associated with an always-on PDU session to the discovered second network.

6. In Paragraph 1, The above rejection message further includes a back-off timer, and Based on the above reason value, a step of searching for a second network different from the network that supports requests related to the always-on PDU session until the back-off timer expires; A method further comprising the step of sending a request message for a request associated with a PDU session that is always on to the second network when the second network is discovered before the back-off timer expires.

7. In Paragraph 6, A method further comprising the step of retransmitting a request message for a request associated with a PDU session that is always turned on to the network if the second network is not discovered until the back-off timer expires.

8. In Paragraph 1, The above rejection message further includes a back-off timer and a search timer, and Based on the above reason value, the step of searching for a second network different from the network that supports requests associated with the always-on PDU session until the back-off timer and the search timer expire; and A method further comprising the step of sending a request message for a request associated with a PDU session that is always on to the second network when the back-off timer and the search timer expire.

9. In Paragraph 8, A step of stopping the operation of searching the second network when the search timer expires; A method further comprising the step of retransmitting a request message for a request associated with a PDU session that is always turned on to the network if the second network is not discovered until the back-off timer expires.

10. A method performed by a network in a wireless communication system, wherein the method comprises: A step of receiving a Registration Request message from a terminal, the message including information indicating that the terminal supports operation according to the satellite's S&F (Store and Forward) mode; A step of transmitting a Registration Accept message to the terminal containing information indicating that an operation according to the S&F mode is supported or provided; A step of receiving a request message from the terminal for a request related to an always-on protocol data unit session; and The method includes the step of sending a rejection message to the terminal to reject a request associated with an always-on PDU session, wherein A method in which the above rejection message includes a reason value indicating that the always-on PDU session is not supported as the operation according to the above S&F mode is supported or provided.

11. In Paragraph 10, The step of transmitting the above rejection message The method includes the step of transmitting a rejection message that further includes a back-off timer, wherein A method in which the back-off timer is intended to prevent the terminal from retransmitting a request message for a request associated with the always-on PDU session before it expires.

12. In a terminal of a wireless communication system, transceiver; and It includes a controller connected to the above transceiver, and The above controller is, Transmit a Registration Request message to the network containing information indicating that the terminal supports operation according to the satellite's S&F (Store and Forward) mode, and Receive a Registration Accept message from the above network containing information indicating that operation according to the S&F mode is supported or provided, and Send a request message for a request related to an always-on protocol data unit session to the above network, and Configured to receive a rejection message from the above network to reject requests associated with an always-on PDU session, A terminal in which the above rejection message includes a reason value indicating that the always-on PDU session is not supported as the operation according to the above S&F mode is supported or provided.

13. In Paragraph 12, The above rejection message further includes a back-off timer, and The above controller is, A terminal that retransmits a request message for a request associated with the always-on PDU session to the above network after the back-off timer has expired.

14. In Paragraph 12, The above controller is, A terminal further configured to search for a second network different from the network that supports requests associated with the always-on PDU session, based on the above reason value.

15. In Paragraph 14, The above controller is, A terminal further configured to search the second network based on PLMN (Public Land Mobile Network) and / or RAT (Radio Access Technology).

16. In Paragraph 12, The above rejection message further includes a back-off timer, and The above controller is, After the back-off timer expires, based on the reason value, search for a second network different from the network that supports requests related to the always-on PDU session, and A terminal further configured to send a request message for a request associated with an always-on PDU session to the discovered second network.

17. In Paragraph 12, The above rejection message further includes a back-off timer, and The above controller is, Based on the above reason value, search for a second network different from the network that supports requests related to the always-on PDU session until the back-off timer expires, and A terminal further configured to send a request message for a request associated with a PDU session that is always on to the second network when the back-off timer expires.

18. In Paragraph 17, The above controller is, A terminal further configured to resend a request message for a request associated with a PDU session that is always on to the network if the second network is not discovered until the back-off timer expires.

19. In Paragraph 12, The above rejection message further includes a back-off timer and a search timer, and The above controller is, Based on the above reason value, search for a second network different from the network that supports requests related to the always-on PDU session until the back-off timer and the search timer expire, and A terminal further configured to send a request message for a request associated with a PDU session that is always on to the second network when the back-off timer and the search timer expire.

20. In Paragraph 19, The above controller is, When the above search timer expires, the operation of searching the second network is stopped, and A terminal configured to resend a request message for a request associated with a PDU session that is always turned on to the network if the second network is not discovered until the back-off timer expires.

21. A method performed by a terminal in a wireless communication system, wherein the method comprises: A step of transmitting a Registration Request message to a network that includes information indicating that the terminal supports operation according to the satellite's S&F (Store and Forward) mode; A step of receiving a Registration Accept message from the above network containing information indicating that an operation according to the S&F mode is supported or provided; A step of transmitting and receiving data to and from the above network and the above S&F mode; A method comprising the step of, when there is a request associated with an always-on protocol data unit session, searching for a second network different from the network that supports the request associated with the always-on protocol data unit session.

22. In a terminal of a wireless communication system, transceiver; and It includes a controller connected to the above transceiver, and The above controller is, Transmit a Registration Request message to the network containing information indicating that the terminal supports operation according to the satellite's S&F (Store and Forward) mode, and Receive a Registration Accept message from the above network containing information indicating that operation according to the S&F mode is supported or provided, and Sending and receiving data to and from the above network and the above S&F mode, A terminal that, when there is a request associated with an always-on protocol data unit session, searches for a second network different from the network that supports the request associated with the always-on protocol data unit session.

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