Device and method for managing terminal context in wireless communication system

Abstract

The present disclosure relates to a wireless communication system and, particularly, to an operating method of a first base station in a wireless communication system, comprising the steps of: RRC-inactivating (RRC INACTIVE) terminals; grouping the terminals on the basis of a discontinuous reception (DRX) period; and transmitting terminal contexts of the terminals to either a second base station or a core network on the basis of a terminal group.

Description

Terminal context management device and method in a wireless communication system

[0001] The present disclosure relates to a wireless communication system, and in particular to an apparatus and method for managing a terminal context in a wireless communication system.

[0002] With the advancement of mobile communication services, Non-Terrestrial Networks (NTNs), which are free from spatial constraints, are attracting attention, and low-orbit satellites, in particular, are expected to play a major role. Accordingly, 3GPP (3 rd The Generation Partnership Project is proceeding with standardization for non-terrestrial networks without spatial constraints to provide effective communication services.

[0003] For example, in 5G NR (New Radio) systems, the RRC_INACTIVE state was introduced to reduce terminal power consumption and support rapid connection resumption. Meanwhile, as satellites in non-terrestrial network environments orbit the Earth at high speeds, the satellite servicing the terminal (User Equipment, UE) may continuously change due to satellite mobility. Consequently, due to this satellite mobility, situations may frequently occur where the terminal context of a terminal in the RRC_INACTIVE state must be transferred to a new satellite.

[0004] The present disclosure is intended to provide a terminal context management device and method in a wireless communication system.

[0005] The present disclosure is intended to provide an apparatus and method for deactivating terminals RRC (RRC INACTIVE).

[0006] The present disclosure is intended to provide an apparatus and method for grouping said terminals based on discontinuous reception (DRX).

[0007] The present disclosure is intended to provide an apparatus and method for transmitting the terminal context of terminals to either a second base station or a core network based on a terminal group.

[0008] The present disclosure is intended to provide an apparatus and method for grouping terminals by comparing a predetermined threshold value and a discontinuous reception period.

[0009] The present disclosure is intended to provide an apparatus and method for adjusting a predetermined threshold value based on the available capacity of an inter-satellite link (ISL) and a feeder link.

[0010] The present disclosure is intended to provide an apparatus and method for transmitting the contexts of terminals included in a first terminal group to a second base station via a satellite link.

[0011] The present disclosure is intended to provide an apparatus and method for transmitting the contexts of terminals included in a second terminal group to a core network via a feeder link.

[0012] The present disclosure is intended to provide an apparatus and method for obtaining the context of a terminal from first terminal contexts when a paging target terminal is included in a first terminal group.

[0013] The present disclosure is intended to provide an apparatus and method for obtaining the context of a terminal among second terminal contexts from a core network when a paging target terminal is included in a second terminal group.

[0014] The present disclosure is intended to provide an apparatus and method for transmitting paging messages to terminals included in a first terminal group based on the disconnection of a satellite link.

[0015] According to one aspect of the present disclosure, a method of operation of a first base station in a wireless communication system is disclosed. The method may include the steps of deactivating terminals RRC (RRC INACTIVE), grouping said terminals based on a discontinuous reception (DRX) period, and transmitting terminal contexts of said terminals based on the terminal group to either a second base station or a core network.

[0016] According to one embodiment of the present disclosure, the step of grouping the terminals may include the step of grouping terminals corresponding to the discontinuous reception period below a predetermined threshold into a first terminal group and the step of grouping terminals corresponding to the discontinuous reception period exceeding the threshold into a second terminal group.

[0017] According to another embodiment of the present disclosure, the threshold value may be adjusted based on the available capacity of the inter-satellite link (ISL) and feeder link of the first base station.

[0018] According to another embodiment of the present disclosure, the transmitting step may include transmitting the first terminal contexts of the terminals included in the first terminal group to the second base station via a satellite link.

[0019] According to another embodiment of the present disclosure, the transmitting step may include transmitting second terminal contexts of the terminals included in the second terminal group to the core network via a feeder link.

[0020] According to another embodiment of the present disclosure, the second base station receives a paging request message for a terminal from the core network, and if the terminal is included in the first terminal group, obtains a first terminal context of the terminal from the first terminal contexts and can transmit a paging message to the terminal using the first terminal context.

[0021] According to another embodiment of the present disclosure, the second base station receives a paging request message for a terminal from the core network, and if the terminal is included in the second terminal group, receives a second terminal context of the terminal among the second terminal contexts from the core network, and can transmit a paging message to the terminal using the second terminal context.

[0022] According to another embodiment of the present disclosure, the transmitting step includes confirming a disconnection of the satellite link with the second base station and, based on the disconnection of the satellite link, transmitting a paging message to the terminals included in the first terminal group, wherein the terminals included in the first terminal group may be induced to update their first terminal contexts by transmitting an RRC connection request message to the second base station.

[0023] According to another embodiment of the present disclosure, the core network assigns a first subgroup to the terminals based on Paging Early Indication (PEI)-based paging control, and the first base station may assign a second subgroup to the terminals based on a paging frame and a paging occasion (PO) within a discontinuous reception cycle.

[0024] According to another embodiment of the present disclosure, when the first subgroup and the second subgroup are valid, the method may include the steps of: assigning priority to the first subgroup; mapping the first subgroup to the discontinuous reception period; and transmitting the terminal contexts to either the second base station or the core network based on the mapping result.

[0025] According to another aspect of the present disclosure, a first base station is disclosed in a wireless communication system. The first base station comprises a transceiver and a processor connected to the transceiver, and the processor may disable RRC inactive terminals, group the terminals based on a discontinuous reception (DRX) period, and transmit terminal contexts of the terminals based on the terminal group to either a second base station or a core network.

[0026] According to another aspect of the present disclosure, a method of operation of a second base station in a wireless communication system is disclosed. The method may include receiving terminal contexts of terminals from a first base station based on a terminal group; receiving a paging request message for a terminal from a core network; obtaining a terminal context of the terminal based on the terminal group including the terminal; and transmitting a paging message to the terminal based on the terminal context.

[0027] According to another aspect of the present disclosure, a second base station is disclosed in a wireless communication system. The second base station comprises a transceiver and a processor connected to the transceiver, and the processor may receive terminal contexts of terminals from a first base station based on a terminal group, receive a paging request message for a terminal from a core network, obtain a terminal context of the terminal based on the terminal group including the terminal, and transmit a paging message to the terminal based on the terminal context.

[0028] According to another aspect of the present disclosure, a method of operating a core network in a wireless communication system is disclosed. The method may include receiving terminal contexts of terminals from a first base station based on a terminal group; confirming the occurrence of downlink data to a terminal; transmitting a paging request message for said terminal to a second base station when the group of said terminals is a first terminal group; transmitting a second terminal context of said terminal to the second base station when the group of said terminals is a second terminal group; and transmitting the paging request message for said terminal based on said second terminal context.

[0029] According to another aspect of the present disclosure, a method of operation of a terminal in a wireless communication system is disclosed. The method comprises the steps of deactivating RRC with a first base station, receiving a paging message from a second base station, and transmitting an RRC connection request message to the second base station, wherein the second base station may obtain a terminal context from either the second base station or a core network based on a terminal group of the terminal.

[0030] According to embodiments of the present disclosure, terminal context management can be effectively performed in a wireless communication system.

[0031] FIG. 1 illustrates an example of a satellite network according to one embodiment of the present disclosure.

[0032] FIG. 2 illustrates another example of a satellite network according to one embodiment of the present disclosure.

[0033] FIG. 3 illustrates the configuration of a device in a wireless communication system according to one embodiment of the present disclosure.

[0034] FIG. 4 illustrates an example of a terminal context management method procedure in a wireless communication system according to one embodiment of the present disclosure.

[0035] FIG. 5 illustrates an example of an operation procedure of a first base station according to one embodiment of the present disclosure.

[0036] FIG. 6 illustrates an example of an operation procedure of a second base station according to one embodiment of the present disclosure.

[0037] FIG. 7 illustrates an example of an operation procedure of a core network according to one embodiment of the present disclosure.

[0038] FIG. 8 illustrates an example of a procedure for a terminal context management method in a wireless communication system when inter-satellite linking is impossible, according to another embodiment of the present disclosure.

[0039] FIG. 9 illustrates an example of an operation procedure of a first base station according to another embodiment of the present disclosure.

[0040] FIG. 10 illustrates an example of an operation procedure of a second base station according to another embodiment of the present disclosure.

[0041] FIG. 11 illustrates an example of an operation procedure of a core network according to another embodiment of the present disclosure.

[0042] FIG. 12 illustrates an example of a terminal context management method procedure in a wireless communication system according to another embodiment of the present disclosure.

[0043] The terms used in these embodiments have been selected to be as widely used and general as possible, taking into account the functions within these embodiments; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, the applicant has arbitrarily selected terms, and in such cases, their meanings will be described in detail in the relevant sections. Therefore, the terms used in these embodiments should be defined not merely by their names, but based on their meanings and the content throughout these embodiments.

[0044] The embodiments are subject to various modifications and may take various forms; therefore, some embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the embodiments to the specific disclosed forms, and it should be understood that the embodiments include all modifications, equivalents, and substitutions that fall within the spirit and scope of the embodiments. The terms used herein are for the description of the embodiments only and are not intended to limit the embodiments.

[0045] Unless otherwise defined, the terms used in these embodiments have the same meaning as generally understood by those skilled in the art to which these embodiments pertain. 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 these embodiments.

[0046]

[0047] The present disclosure relates to a Non-Terrestrial Network (NTN) system and to a method for efficiently partitioning and managing a terminal context corresponding to the Radio Resource Control Inactive (RRC_INACTIVE) state of a User Equipment (UE) in an environment where a base station (gNB) is mounted on a Low Earth Orbit (LEO) satellite. In one embodiment, the present disclosure may be configured to distribute, store, transmit, or maintain the terminal context by utilizing an Xn interface between satellites and an NG interface between a satellite and an Access and Mobility Management Function (AMF) of a core network.

[0048] In 5G NR (New Radio) systems, an RRC-inactive (RRC_INACTIVE) state was introduced to reduce terminal power consumption and support rapid connection resumption. When a terminal is in the RRC-inactive state, the radio connection with the base station (RAN) is terminated, but the connection information (Context) with the AMF, which performs core network access and mobility management functions, is maintained. At this time, the base station stores and manages the terminal context corresponding to the terminal.

[0049] In a conventional terrestrial mobile communication network environment, since base stations are fixed, when downlink data occurs, the core network transmits a paging request to the base station that last serviced the terminal, and the corresponding base station can perform paging for the terminal and initiate data transmission.

[0050] However, in a non-terrestrial network environment based on regenerative payloads where base stations are mounted on satellites, technical problems different from those of terrestrial networks arise because the location of the base station continuously changes as the satellite orbits the Earth.

[0051] Specifically, due to satellite mobility, the serving satellite servicing a terminal continuously changes, and consequently, situations frequently arise where the terminal context for a terminal in an RRC-inactive state must be transferred to a new satellite. Meanwhile, for a terminal to resume the RRC connection or receive paging, the satellite currently servicing the terminal must receive the terminal context of that terminal from the previous satellite. Therefore, the present disclosure aims to provide a method for partitioning and managing terminal contexts by considering the characteristics of terminals in an RRC-inactive state, in order to efficiently utilize limited satellite network resources and ensure stable service continuity for terminals in an RRC-inactive state.

[0052]

[0053] FIG. 1 illustrates an example of a satellite network according to one embodiment of the present disclosure.

[0054] Referring to FIG. 1, the satellite network includes a terminal (110), satellites (120-1, 120-2), and a gateway (130). The terminal (110) is a user device equipped with hardware and software that receives cellular data from a satellite (120-1), and may be a mobile or fixed device. For example, the terminal (110) may include a mobile phone, a smartphone, a wearable device, or a UE (User Equipment). Furthermore, the terminal (110) is not limited to the examples described above, and may include any electronic device capable of cellular communication, such as a laptop or tablet PC. The terminal (110) is not limited to the examples described above. Although the satellite network in FIG. 1 is depicted as including only a single terminal (110), this is merely an exemplary embodiment and is not limited thereto, and it is obvious that it may include multiple terminals (110).

[0055] Specifically, the terminal (110) can support communication protocols defined in 3GPP (3rd generation partnership project) standards (e.g., LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.). Multiple communication nodes (110 to 130) can support CDMA (code division multiple access) technology, WCDMA (wideband CDMA) technology, TDMA (time division multiple access) technology, FDMA (frequency division multiple access) technology, OFDM (orthogonal frequency division multiplexing) technology, Filtered OFDM technology, CP (cyclic prefix)-OFDM technology, DFT-s-OFDM (discrete Fourier transform-spread-OFDM) technology, OFDMA (orthogonal frequency division multiple access) technology, SC (single carrier)-FDMA technology, NOMA (non-orthogonal multiple access) technology, GFDM (generalized frequency division multiplexing) technology, FBMC (filter bank multi-carrier) technology, UFMC (universal filtered multi-carrier) technology, SDMA (space division multiple access) technology, etc.

[0056] Satellites (120-1, 120-2) fly in a fixed orbit and can provide a cell with coverage of a certain size by forming a beam toward the ground. In relation to the present disclosure, satellite (120-1) may mean a serving satellite and satellite (120-2) may mean a target satellite. A gateway (130) provides the satellites (120-1, 120-2) with a link to access a network. That is, the gateway (130) can provide a connection between the satellites (120-1, 120-2) and the core network. The satellites (120-1, 120-2) can interact with the Access and Mobility Management Function (AMF) of the core network through the gateway (130).

[0057] The link between the terminal (110) and the satellite (120-1) is called a service link and may be based on NR standards defined by 3GPP. The link between the satellites (120-1, 120-2) and the gateway (130) is called a feeder link and may be based on a 3GPP or non-3GPP wireless interface. An inter-satellite link (ISL) may be used mainly for regenerative satellites.

[0058] For transparent satellites based on an NR-RAN architecture, the satellite radio interfaces of the feeder link and service link may be NR-Uu. For transparent satellites, the satellite performs radio frequency filtering, frequency conversion, and amplification functions. For regenerative satellites, onboard functions are built into the satellite, and accordingly, the satellite can perform radio frequency filtering, frequency conversion, and amplification, as well as some or all of the base station functions such as switching and routing, coding and modulation, and decoding and demodulation.

[0059] Each of the satellites (120-1, 120-2) according to the present disclosure may provide a cell having a coverage of a certain size to a terminal. Additionally, each of the satellites (120-1, 120-2) may be connected to a gateway (130) via a feeder link. Herein, the link may be a link based on NR standards. Alternatively, a link newly defined in an advanced next-generation wireless communication system may be adaptively applied, or a link based on various interfaces of a communication system introduced by industry needs that are not NR standards may be applied. In the following, in relation to the present disclosure, a serving cell, a target cell, and a candidate cell may be mentioned, each corresponding to a serving satellite, a target satellite, and a candidate satellite, and may be used interchangeably.

[0060] A satellite (120-1) may refer to a satellite currently connected to a terminal in a satellite network to provide communication. For example, a satellite (120-1) may include a geostationary satellite, a low-orbit satellite, a medium-orbit satellite, a polar orbit satellite, an elliptical orbit satellite, etc., and is not limited to any type. In addition, the satellites presented in this disclosure are not limited to a specific satellite configuration and may include any satellite or combination of satellites capable of providing a functional connection between the gateway (130) and the terminal (110).

[0061] The satellite (120-2) may refer to a satellite that is replaced by a serving satellite when the signal strength received by the terminal (110) satisfies the handover condition as the terminal (110) moves out of the beam coverage of the serving satellite or is located near the boundary. The satellite (120-2) may refer to a satellite that can be selected as a target satellite in a satellite network. That is, the satellite (120-2) may be determined based on at least the satellite's visibility, signal strength, connection stability, latency, and network load.

[0062]

[0063] FIG. 2 illustrates another example of a satellite network according to one embodiment of the present disclosure. FIG. 2 illustrates an example of an NTN providing non-ground access to a UE (210) using an NTN payload (220) and an NTN gateway (230). Here, the UE (210) may be substantially the same configuration as the terminal (110) described in FIG. 1. Referring to FIG. 2, the link between the NTN payload (220) and the UE (210) is a service link and may be based on a Uu interface. The link between the NTN payload (220) and the NTN gateway (230) is a feeder link. The link between the NTN gateway (230) and the AMF / UPF (240) may be based on an NG interface. The NTN payload (220) can transparently forward wireless protocols received from the UE (210) to the NTN gateway (230) via the service link. Similarly, the NTN payload (220) can transparently forward wireless protocols received from the NTN gateway (230) via a feeder link to the UE (210).

[0064] To this end, the following connectivity may be supported by the NTN payload (220). A base station may service multiple NTN payloads. An NTN payload may be serviced by multiple base stations.

[0065] The NTN payload (220) can change the carrier frequency before retransmitting data on the service link. That is, the NTN payload (220) can use different carrier frequencies on the service link and the feed link. For the NTN, at least one of the following may be used as a network identifier: AMF name, NCGI (NR cell global identifier), CgNB ID (identifier), global gNB ID, TAI (tracking area identity), S-NSSAI (Single Network Slice Selection Assistance information), NSAG (Network Slice AS Group), NID (Network Identifier), CAG (Closed Access Group) ID, and local NG-RAN node ID (identifier). Additionally, a mapped cell ID may be used. Here, the tracking area may correspond to a fixed geographical area.

[0066] Non-geosynchronous orbits (NGSO) include a low Earth orbit at an altitude of about 300 km to 1500 km and a medium Earth orbit at an altitude of about 7000 km to 25000 km.

[0067] Service links can be classified into the following three types: earth-fixed, quasi-earth-fixed, and earth-moving. The earth-fixed type provides beam(s) that continuously cover the same geographical area at all times. For example, a satellite in a geosynchronous orbit (GSO) can provide an earth-fixed type service link. The quasi-earth-fixed type provides beam(s) that continuously cover the same geographical area for a limited period and beams that cover different geographical areas during different periods. For example, a satellite in a non-earth-synchronous orbit can provide a quasi-earth-fixed type service link using steerable beams. The earth-moving type provides beams where the coverage area slides across the Earth's surface. For example, a satellite with a non-Earth-synchronous orbit can provide an Earth-moving type service link using fixed or steerable beams.

[0068] By using a satellite with a non-Earth-synchronous orbit, the base station can provide quasi-Earth-fixed cell coverage or Earth-mobile cell coverage. By using a satellite with an Earth-synchronous orbit, the base station can provide Earth-fixed cell coverage. In the case of a non-Earth-synchronous orbit, a switch of the service link may be referred to a switch of the satellite (120-1).

[0069]

[0070] FIG. 3 illustrates the configuration of a device in a wireless communication system according to one embodiment of the present disclosure. The device of FIG. 3 may be understood as a part of the structure of any one of the devices described with reference to FIG. 1, for example, a terminal (110), satellites (120-1, 120-2), and a gateway (130).

[0071] Referring to FIG. 3, the device may include a processor (310), a communication unit (220), and a memory (330).

[0072] The processor (310) can control the overall function and operation of the device. The processor (310) may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and / or data processing devices.

[0073] The communication unit (320) is connected to the processor (310) to transmit and receive wireless signals. The communication unit (320) may include a baseband circuit for processing wireless signals. For example, the communication unit (320) may include a short-range communication unit, a mobile communication unit, and a broadcast reception unit. In one embodiment, the communication unit (320) may transmit and receive data to and from other devices, such as a base station, a satellite, etc.

[0074] Memory (330) is hardware that stores various data processed by the processor (310). For example, the memory (330) may store SIR values ​​for the transmission target terminals of the transmitting terminals, information regarding transmission target terminal groups for each transmitting terminal, etc. Additionally, the memory (330) may store applications, drivers, etc. to be driven by the processor (310). The memory (330) may include random access memory (RAM), such as dynamic random access memory (DRAM) and static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), CD-ROM, Blu-ray or other optical disc storage, hard disk drive (HDD), solid state drive (SSD), or flash memory.

[0075] The structure of FIG. 3 can be understood as at least part of a terminal, base station, satellite, or gateway. If the structure of FIG. 3 is part of a satellite, the satellite may further include other hardware devices necessary for orbiting in addition to the components exemplified in FIG. 3. If the structure of FIG. 3 is part of a gateway or base station, the gateway or base station may further include components that support wired communication, etc.

[0076]

[0077] Due to satellite mobility, the serving satellite servicing a terminal continuously changes; consequently, situations may frequently arise where the terminal context for a terminal in an RRC-deactivated state must be passed to a new satellite. For a terminal to resume the RRC connection or receive paging, the satellite currently servicing the terminal must receive the terminal context from the previous satellite.

[0078] In such an environment, if the terminal context of all RRC-disabled terminals is transmitted collectively via inter-satellite links or feeder links, a massive concentration of signaling may occur, potentially leading to a signaling storm. This raises concerns that link capacity may be exceeded or overall network performance may degrade. In particular, if inter-satellite link connections are unstable or disconnected, or if satellites are located in positions where inter-satellite communication is impossible, the transmission of the terminal context itself becomes impossible, making it difficult to guarantee service continuity for RRC-disabled terminals.

[0079] Accordingly, in order to efficiently utilize limited satellite network resources and ensure stable service continuity for terminals in an RRC-disabled state, a method for transmitting and managing terminal contexts by dividing them by considering the characteristics of terminals in an RRC-disabled state is disclosed below.

[0080]

[0081] FIG. 4 illustrates an example of a terminal context management method procedure in a wireless communication system according to one embodiment of the present disclosure.

[0082] Referring to FIG. 4, in step S401, the terminal (410) and the first base station (420) perform the RRC_INACTIVE procedure. Specifically, if data transmission and reception do not occur for a certain period of time or if RRC disconnection is required according to network control, the terminal (410) disconnects the wireless connection with the first base station (420), which is the serving base station, and transitions to an RRC disabled state.

[0083] In step S403, the first base station (420) groups the terminals. Specifically, the first base station (420) determines the group to which the terminal (410) is included in order to divide and manage the terminal context associated with the terminal (410) based on the characteristics of the terminal (410). At this time, according to the embodiment, the location where the terminal context of the terminal (410) is transmitted or stored may be determined by the group to which the terminal (410) is included. For example, the first base station (420) may control the transmission of the terminal context to the second base station (430) or storage on the core network (440) side based on the group to which the terminal (410) is included.

[0084] In step S405, the first base station (420) transmits the context of the terminal (410) to the second base station (430) or the core network (440). Specifically, the first base station (420) transmits the terminal context to the second base station (430) or the core network (440) based on the group to which the terminal (410) is included. According to an embodiment, the first base station (420) may transmit the terminal context of the terminals to the second base station (430) or the core network (440) based on the terminal group to which terminals in an RRC disabled state are included.

[0085] That is, in steps S403 and S405, the first base station (420) groups the RRC-deactivated terminals before leaving the service area and transmits the terminal context to the next satellite, the second base station (430), via the Xn interface (e.g., inter-satellite link), or transmits it to the terrestrial core network (e.g., AMF) via the NG interface (e.g., feeder link). In this way, if the terminal context of a terminal requiring paging is stored in the second base station (430), the second base station (430) can perform the paging procedure using the stored terminal context. Additionally, if the terminal context of a terminal requiring paging is stored in the core network (440), the second base station (430) can perform the paging procedure using the terminal context stored in the core network (440).

[0086] In step S407, the first base station (420) transmits a path switch request message to the core network (440). Specifically, the first base station (420) can transmit the path switch request message to the core network (440) to switch the paths of the User Plane and Control Plane for the terminal (410) based on the second base station (430) as the serving base station of the terminal (410) changes to the second base station (430).

[0087] In step S409, the first base station (420) receives a path switch request confirmation message from the core network (440). Specifically, based on the path switch request message transmitted by the first base station (420), the core network (440) confirms that the transmission paths of the user plane and control plane for the terminal (410) have been updated based on the second base station (430), and can transmit a confirmation message to the first base station (420).

[0088] In step S411, the core network (440) checks for the occurrence of downlink data. Specifically, the core network (440) monitors whether downlink data has been received in a data session or service flow corresponding to the terminal (410), and can recognize if downlink data has occurred. If the occurrence of downlink data is confirmed, the core network (440) prepares a paging procedure or a data delivery procedure for the terminal (410).

[0089] In step S413, the second base station (430) receives a paging request message from the core network (440). At this time, if the terminal to be paged corresponds to a terminal group in which the terminal context is stored in the second base station (430), the second base station (430) can perform a paging procedure using the previously stored terminal context. Meanwhile, if the terminal to be paged corresponds to a terminal group in which the terminal context is stored in the core network (440), the second base station (430) can receive the terminal context from the core network (440).

[0090] In step S415, the second base station (430) transmits a paging message to the terminal (410). Specifically, the second base station (430) can transmit the paging message using the terminal context of the terminal (410) obtained through step S413. At this time, the second base station (430) can transmit the paging message according to the paging occasions available to the terminal (410) by using the terminal identification information and paging-related parameters included in the terminal context.

[0091] In step S417, the terminal (410) transmits an RRC connection request message to the second base station (430). By configuring the RRC connection request message to include previously stored terminal identification information and connection-related parameters, the terminal (410) enables the second base station (430) to resume the connection to the terminal (410). The second base station (430) can quickly resume the connection to the terminal (410) by utilizing the terminal context of the terminal (410).

[0092]

[0093] FIG. 5 illustrates an example of an operation procedure of a first base station according to an embodiment of the present disclosure. The operating entity of FIG. 5 is described as the first base station, and the first base station may be, for example, a serving base station.

[0094] Referring to FIG. 5, in step S501, the first base station performs the RRC_INACTIVE (RRC disabled) procedure. Specifically, if data transmission and reception do not occur for a certain period of time or if RRC connection disconnection is required according to network control, the first base station disconnects the wireless connection with the terminals and transitions the terminals to an RRC disabled state.

[0095] In step S503, the first base station groups terminals based on discontinuous reception (DRX). Specifically, the first base station determines the group to which the terminals are included in order to partition and manage terminal contexts associated with the terminals based on the characteristics of the terminals. At this time, according to the embodiment, the location where the terminal context of the terminals is delivered or stored may be determined by the group to which the terminals are included. For example, the first base station may control the delivery of the terminal context to the next serving base station, the second base station, or to store it in the core network based on the group to which the terminals are included.

[0096] For example, a first base station can determine the group to which each terminal belongs based on the paging frequency of the terminals. Here, the paging frequency of the terminals can be determined based on the Discontinuous Reception (DRX) period, and the shorter the DRX period, the more frequently the terminal is considered to wake up to receive paging, and thus can be classified as a terminal with a relatively high paging frequency.

[0097] According to an embodiment, the first base station may determine the group to which each terminal is included based on whether the discontinuous reception period indicating the paging frequency of the terminals exceeds a predetermined threshold. For example, if a specific terminal has a relatively short DRX period among all terminals in the RRC_disabled state, the terminal may be classified into the first terminal group, and if it is relatively long, the terminal may be classified into the second terminal group. Here, "relatively short" and "long" may be determined by a predetermined threshold. The threshold may be determined based on the ratio of terminals included in each of the total discontinuous reception periods. For example, the threshold may be determined as a value corresponding to the 50% ratio of terminals included in each of the total discontinuous reception periods. For example, the discontinuous reception periods are 2.56 seconds, 5.12 seconds, 10.24 seconds… 8192 seconds, etc., are designated as multiples of 2.56 seconds, and if terminals corresponding to 2.56 seconds and 5.12 seconds account for 50% of all terminals, 5.12 seconds may be designated as the threshold value. The threshold value may be set in a direction that degrades the signaling storm when transmitting terminal context. That is, the threshold value may be determined based on the availability of the satellite link and peer link of the first base station.

[0098] That is, for terminals included in a first terminal group with a relatively high paging frequency, rapid resumption of connection is required; therefore, the first base station currently serving the terminal can directly transmit the terminal contexts of said terminals to the target base station via an inter-satellite link. On the other hand, for terminals included in a second terminal group with a relatively low paging frequency, the first base station currently serving the terminal can transmit the terminal contexts to an entity performing access and mobility management functions of the terrestrial core network via a feeder link for storage. In this way, by distinguishing the transmission paths of terminal contexts according to the terminal group, the present disclosure can distribute the signaling load concentrated on the inter-satellite link to the terrestrial network, thereby preventing the occurrence of signaling storms or mitigating network performance degradation.

[0099] In step S505, the first base station may transmit terminal contexts to either the second base station or the core network based on terminal groups. For example, the first base station may transmit terminal contexts of terminals included in a first group with relatively short discontinuous reception periods to the second base station based on a predetermined threshold. Additionally, for example, the first base station may transmit terminal contexts of terminals included in a second group with relatively long discontinuous reception periods to the core network based on a predetermined threshold. Through this, if the terminal context of a terminal requiring paging is stored in the second base station, the second base station may perform a paging procedure using the stored terminal context. Additionally, if the terminal context of a terminal requiring paging is stored in the core network, the second base station may perform a paging procedure using the terminal context stored in the core network.

[0100]

[0101] FIG. 6 illustrates an example of an operation procedure of a second base station according to an embodiment of the present disclosure. The operating entity of FIG. 6 is described as a second base station, and the second base station may, for example, be a base station configured to serve a terminal after the service provider for the terminal has changed from the first base station. Here, the second base station refers to a base station that performs the role of serving the terminal after the first base station, and may include at least one base station selected to perform service provision to the terminal after the first base station has left the service area, among base stations connected to the first base station via a satellite link.

[0102] Referring to FIG. 6, in step S601, the second base station may receive first terminal contexts of terminals included in a first terminal group from the first base station. For example, the first terminal group may refer to a group of terminals whose discontinuous reception period corresponds to a value less than a predetermined threshold. The first terminal contexts may refer to the contexts of terminals included in the first terminal group. That is, the second base station may receive terminal contexts of terminals whose discontinuous reception period corresponds to a value less than a predetermined threshold.

[0103] In step S603, the second base station receives a paging request. Specifically, the second base station may receive a paging request from the core network when it is confirmed that downlink data has occurred to a specific terminal.

[0104] In step S605, the second base station identifies a group of terminals. Specifically, the second base station identifies a group of terminals for which paging is required.

[0105] In step S607, if the group of terminals corresponds to the first terminal group, the second base station may obtain the first terminal context of the terminal from the first terminal contexts. On the other hand, in step S609, if the group of terminals corresponds to the second terminal group, the second base station may receive the second terminal context of the terminal from the core network. The second terminal context may be obtained from the second terminal contexts of terminals included in the second group stored in the core network.

[0106] In step S611, the second base station transmits a paging message using the terminal context of the terminal. Based on the terminal identification information and paging-related parameters included in the terminal context of the terminal obtained through step S607 or S609, the second base station performs a paging procedure and can transmit a paging message in accordance with the paging opportunity available to the terminal.

[0107]

[0108] FIG. 7 illustrates an example of an operation procedure of a core network according to one embodiment of the present disclosure.

[0109] Referring to FIG. 7, in step S701, the core network receives second terminal contexts of terminals included in a second terminal group from the first base station. For example, the second terminal group may refer to a group of terminals whose discontinuous reception period exceeds a predetermined threshold. The second terminal contexts may refer to the contexts of terminals included in the second terminal group. That is, the core network may receive terminal contexts of terminals whose discontinuous reception period exceeds a predetermined threshold.

[0110] In step S703, the core network checks for the occurrence of downlink data. The core network monitors whether downlink data has been received in a data session or service flow corresponding to a specific terminal, and can recognize if downlink data has occurred. If the occurrence of downlink data is confirmed, the core network prepares a paging procedure or a data delivery procedure for the corresponding terminal.

[0111] In step S705, the core network identifies a group of terminals. Specifically, the core network identifies a group of terminals for which downlink data has been issued and paging is required.

[0112] In step S707, if the terminal group corresponds to the first terminal group, the core network transmits a paging request message to the second base station. Meanwhile, in step S709, if the terminal group corresponds to the second terminal group, the core network transmits the terminal's second terminal context to the second base station. The second terminal context can be obtained from the second terminal contexts of the terminals included in the second group stored in the core network.

[0113]

[0114] The following describes the procedure for the case where the satellite link is disconnected and the first base station cannot directly transmit a terminal contest to the second base station.

[0115] FIG. 8 illustrates an example of a procedure for a terminal context management method in a wireless communication system when inter-satellite linking is impossible, according to another embodiment of the present disclosure.

[0116] Referring to FIG. 8, in step S801, the first terminal (810), the second terminal (820), and the first base station (830) perform the RRC_INACTIVE procedure. Specifically, the first terminal (810) and the second terminal (820) disconnect the wireless connection with the first base station (830), which is the serving base station, and transition to an RRC disabled state when data transmission and reception do not occur for a certain period of time or when RRC disconnection is required according to network control.

[0117] In step S803, the first base station (830) groups the terminals. Specifically, the first base station (830) determines a group to which the first terminal (810) and the second terminal (820) are included in order to divide and manage terminal contexts related to the first terminal (810) and the second terminal (820) based on the characteristics of the first terminal (810) and the second terminal (820). At this time, according to the embodiment, the location where the terminal contexts of the first terminal (810) and the second terminal (820) are transmitted or stored may be determined by the group to which the first terminal (810) and the second terminal (820) are included. Hereinafter, the explanation is based on the premise that the first terminal (810) belongs to the first terminal group and the second terminal (820) belongs to the second terminal group.

[0118] In step S805, the first base station (830) checks for a disconnection of the satellite link with the second base station. Specifically, the first base station (830) can identify a disconnection of the satellite link with the second base station (840) based on the SCTP status, Xn procedure failure, Xn Setup timer, etc.

[0119] In step S807, the first base station (830) transmits a paging message to the first terminal (810). Specifically, the first base station (830) can transmit a paging message to the first terminal (810) having a high-frequency paging period, because the first terminal (810) belonging to the first group cannot directly transmit the terminal context to the second base station (840) via a satellite link.

[0120] In step S809, the first terminal (810) transmits an RRC connection request message to the second base station. Specifically, the first terminal (810), having received the paging message, transmits the RRC connection request message to the second base station (840), thereby connecting to the second base station (840) and inducing the second base station (840) to update the terminal context.

[0121] In step S811, the second base station (840) transmits an RRC connection confirmation message to the first base station and the first terminal. Specifically, the second base station (840) confirms that the wireless connection setup for the first terminal (810) is complete based on the RRC connection request message received from the first terminal (810), and can transmit an RRC connection confirmation message to the first terminal (810). Additionally, the second base station (840) can transmit notification information regarding the completion of the connection to the first base station (830) via a feeder link to indicate that the first terminal (810) has been accepted as a serving terminal of the second base station (840).

[0122] In step S813, the first base station (830) transmits terminal context to the core network (850). Specifically, the first base station (830) transmits the terminal context of the second terminal (820) included in the second terminal group to the core network (850) via a feeder link. Through this, the first base station (830) can prevent data loss by preemptively securing connectivity for important terminals with high paging frequency even when the inter-satellite link is disconnected, and by managing the remaining terminals through the core network.

[0123] In step S815, the first base station (830) transmits a path switch request message to the core network (850). Specifically, the first base station (830) can transmit the path switch request message to the core network (850) to switch the paths of the user plane and control plane for the terminal based on the second base station (840) as the serving base station changes to the second base station (840).

[0124] In step S817, the first base station (830) receives a path switch request acknowledgment message from the core network (850). Specifically, based on the path switch request message transmitted by the first base station (830), the core network (850) confirms that the transmission paths of the user plane and control plane for the terminal have been updated based on the second base station (840), and can transmit an acknowledgment message to the first base station (830).

[0125] In step S819, the core network (850) checks for the occurrence of downlink data. Specifically, the core network (850) monitors whether downlink data has been received in a data session or service flow corresponding to a terminal, and can recognize if downlink data has occurred. When the occurrence of downlink data is confirmed, the core network (850) prepares a paging procedure or a data delivery procedure for the terminal.

[0126] In step S821, the core network (850) transmits a paging request message to the second base station (840). At this time, if the terminal to be paged corresponds to a terminal group in which the terminal context is stored in the second base station (840), the second base station (840) can perform the paging procedure using the previously stored terminal context. Meanwhile, if the terminal to be paged corresponds to a terminal group in which the terminal context is stored in the core network (850), the second base station (840) can receive the terminal context from the core network (850).

[0127] In step S823, the second base station (840) transmits a paging message to the terminal. Specifically, the second base station (840) can transmit the paging message using the terminal context of the terminal to be paged. At this time, the second base station (840) can transmit the paging message in accordance with the paging occasions available to the terminal by using terminal identification information and paging-related parameters included in the terminal context. Here, if the terminal to be paged is the first terminal (810) included in the first group, the terminal context can be obtained from the updated terminal context of the first terminal (810). Meanwhile, if the terminal to be paged is the second terminal (820) included in the second group, the terminal context can be received from the core network (850).

[0128] In step S825, the second base station (840) receives an RRC connection request message from a terminal. The first and second terminals (810, 820) configure an RRC connection request message including previously stored terminal identification information and connection-related parameters, thereby enabling the second base station (840) to perform connection resumption for the first and second terminals (810, 820). The second base station (484) can quickly perform connection resumption for the first and second terminals (810, 820) by using the terminal context of the first and second terminals (810, 820).

[0129]

[0130] FIG. 9 illustrates an example of an operation procedure of a first base station according to another embodiment of the present disclosure. The operating entity of FIG. 9 is described as the first base station, and the first base station may be, for example, a serving base station.

[0131] In step S901, the first base station performs the RRC_INACTIVE procedure. Specifically, if data transmission or reception does not occur for a certain period of time or if RRC disconnection is required under network control, the first base station disconnects the wireless connection with the relevant terminals and transitions the terminals to an RRC-inactive state.

[0132] In step S903, the first base station groups terminals based on discontinuous reception (DRX). Specifically, the first base station determines the group to which the terminals are included in order to partition and manage terminal contexts associated with the terminals based on the characteristics of the terminals. At this time, according to the embodiment, the location where the terminal context of the terminals is delivered or stored may be determined by the group to which the terminals are included. For example, the first base station may control the delivery of the terminal context to the next serving base station, the second base station, or to store it in the core network based on the group to which the terminals are included.

[0133] For example, a first base station can determine the group to which each terminal belongs based on the paging frequency of the terminals. Here, the paging frequency of the terminals can be determined based on discontinuous reception cycles, and the shorter the DRX cycle, the more frequently the terminal is considered to wake up to receive paging, and thus can be classified as a terminal with a relatively high paging frequency.

[0134] According to an embodiment, the first base station may determine the group to which each terminal is included based on whether the discontinuous reception period indicating the paging frequency of the terminals exceeds a predetermined threshold. For example, if a specific terminal has a relatively short DRX period among all terminals in an RRC_disabled state, the terminal may be classified into the first terminal group, and if it has a relatively long period, the terminal may be classified into the second terminal group. Here, "relatively short" and "long" may be determined by a predetermined threshold. The threshold may be determined based on the ratio of terminals included in each of the total discontinuous reception periods.

[0135] In step S905, the first base station checks for a disconnection of the satellite link with the second base station. Specifically, the first base station can identify a disconnection of the satellite link with the second base station based on the SCTP status, Xn procedure failure, Xn Setup timer, etc.

[0136] In step S907, the first base station transmits paging messages to terminals included in the first terminal group. Specifically, since the first base station cannot transmit the first terminal contexts of the terminals included in the first terminal group to the second base station, it transmits paging messages to the terminals included in the first terminal group to preemptively secure connectivity for terminals with high paging frequency. Through this, terminals that receive the paging messages can connect to the second base station by transmitting an RRC connection request message to the second base station, thereby inducing the second base station to update the first terminal context.

[0137] In step S911, the first base station may transmit second terminal contexts included in the second terminal group to the core network. Specifically, the first base station transmits the second terminal context of the second terminal included in the second terminal group to the core network via a feeder link.

[0138]

[0139] FIG. 10 illustrates an example of an operation procedure of a second base station according to another embodiment of the present disclosure. The operating entity of FIG. 10 is described as a second base station, and the second base station may, for example, be a base station configured to serve a terminal after the service provider for the terminal has changed from the first base station. Here, the second base station refers to a base station that performs the role of serving the terminal after the first base station, and may include at least one base station selected to perform service provision to the terminal after the first base station has left the service area, among base stations connected to the first base station via a satellite link.

[0140] Referring to FIG. 10, in step S1001, the second base station receives RRC connection request messages from terminals included in the first terminal group. Specifically, terminals that have received the paging message connect to the second base station by transmitting the RRC connection request message to the second base station, and the second base station can update the first terminal context of the terminals.

[0141] In step S1003, the second base station transmits an RRC connection confirmation message to the terminals included in the first base station and the first terminal group. Specifically, the second base station may confirm that the wireless connection setup for the terminals is complete based on the RRC connection request message received from the terminals of the first terminal group, and transmit an RRC connection confirmation message to the terminals. Additionally, the second base station may transmit notification information regarding the completion of the connection to the first base station via a feeder link to indicate that the terminals have been accepted as serving terminals of the second base station.

[0142] In step S1005, the second base station identifies a group of terminals. Specifically, the second base station identifies a group of terminals for which paging is required.

[0143] In step S1007, if the group of terminals corresponds to the first terminal group, the second base station may obtain the first terminal context of the terminal from the first terminal contexts. On the other hand, in step S1009, if the group of terminals corresponds to the second terminal group, the second base station may receive the second terminal context of the terminal from the core network. The second terminal context may be obtained from the second terminal contexts of terminals included in the second group stored in the core network.

[0144] In step S1011, the second base station transmits a paging message using the terminal context of the terminal. Based on the terminal identification information and paging-related parameters included in the terminal context of the terminal obtained through step S1007 or S1009, the second base station performs a paging procedure and can transmit a paging message in accordance with the paging opportunity available to the terminal.

[0145]

[0146] FIG. 11 illustrates an example of an operation procedure of a core network according to another embodiment of the present disclosure.

[0147] Referring to FIG. 11, in step S1101, the core network receives second terminal contexts of terminals included in a second terminal group from the first base station. For example, the second terminal group may refer to a group of terminals whose discontinuous reception period exceeds a predetermined threshold. The second terminal contexts may refer to the contexts of terminals included in the second terminal group. That is, the core network may receive terminal contexts of terminals whose discontinuous reception period exceeds a predetermined threshold.

[0148] In step S1103, the core network checks for the occurrence of downlink data. The core network monitors whether downlink data has been received in a data session or service flow corresponding to a specific terminal, and can recognize if downlink data has occurred. If the occurrence of downlink data is confirmed, the core network prepares a paging procedure or a data delivery procedure for the corresponding terminal.

[0149] In step S1105, the core network identifies a group of terminals. Specifically, the core network identifies a group of terminals for which downlink data has been issued and paging is required.

[0150] In step S1107, if the terminal group corresponds to the first terminal group, the core network transmits a paging request message to the second base station. Meanwhile, in step S1109, if the terminal group corresponds to the second terminal group, the core network transmits the terminal's second terminal context to the second base station. The second terminal context can be obtained from the second terminal contexts of terminals included in the second group stored in the core network.

[0151]

[0152] The present disclosure discloses a group-based terminal context information element (Information Element, IE) that can be transmitted through a base station-to-base station interface (Xn) and a base station-to-core network interface (NG) in order to efficiently implement the above-described terminal grouping strategy on an actual wireless communication protocol.

[0153] In the following, to group and manage multiple terminals according to paging characteristics, information elements such as group-based context transport containers within XnAP (Xn Application Protocol) and NGAP (NG Application Protocol) messages, and a group determination mechanism using DRX parameters are described.

[0154] Conventionally, a method of transmitting individual terminal contexts for each terminal (e.g., Individual UE Context Transfer) was common, but the present disclosure reduces signaling overhead and promotes the efficient use of link resources by grouping multiple terminals with similar paging characteristics into a single group for transmission. To this end, in one embodiment of the present disclosure, a group-based terminal context information element (UE Context Group Info IE) in the form of a list is defined.

[0155]

[0156] Table 1 shows the structure of a terminal context information element according to one embodiment of the present disclosure.

[0157] IE / Group Name PresenceRange Description UE Context Group Info Mandatory Parent container holding grouped UE context information > Split Strategy Type Mandatory Identifies the strategy type for context splitting (ENUMERATED: ISL-Direct, CN-Relayed, RAN-Paging-Triggered) > DRX Grouping Criteria Optional DRX criteria information used for group classification >> DRX Threshold Mandatory DRX period value (unit: ms / ratio frames) used to distinguish groups (e.g., 10.24s, 5.12s, etc.) >> Paging Probability Optional (Optional) Expected paging probability weight for the corresponding group > UE Context List Mandatory 1.. <maxnoofues>Context list of UEs belonging to the group >> UE XnAP IDM (Mandatory) UE identifier assigned by the source gNB >> UE Specific DRX Cycle (Mandatory) Individual DRX cycle value set for the UE (used by the target satellite to calculate the next paging point) >> I-RNT (Mandatory) RRC_INACTIVE status identifier (for Resume) >> UE Context Container (Mandatory) Actual UE's AS (Access Stratum) Context data (OCTET STRING)

[0158] The group-based terminal context information element of Table 1 is a container for accommodating multiple terminal contexts belonging to the group, enabling group-unit transmission and processing. Specifically, the container may include the following information.

[0159] Split Strategy Type is information for the receiving side (e.g., target satellite base station or Mobility Management Function (AMF)) to identify which context splitting strategy the group is configured according to. For example, Split Strategy Type may be an ISL-Direct type corresponding to a high-frequency paging target terminal group, or a CN-Relayed type corresponding to a low-frequency paging target terminal group.

[0160] The UE Context List contains contexts for one or more terminals belonging to the group in the form of a list. Each item corresponds to an individual terminal and may include a terminal identifier and terminal-specific configuration information.

[0161] UE Specific DRX Cycle is information representing the DRX cycle value set for each terminal, and can be used by the receiving side to calculate the paging occasion for the terminal.

[0162]

[0163] Meanwhile, a serving base station (e.g., a serving satellite base station) can group terminals by comparing a DRX period value set for each terminal with a threshold value set according to network status.

[0164] Each terminal (UEₙ) has a DRX period T_DRX,n agreed upon with the base station at the time of RRC connection disconnection or the time of the last RRC connection establishment. The serving base station queries the T_DRX,n value of each terminal from the stored terminal context database and sets a threshold T_Threshold by considering the current inter-satellite link (ISL) load status, bandwidth conditions, etc. The serving base station can classify terminals according to the following Equation 1.

[0165]

[0166] Referring to mathematical formula 1, In this case, the serving base station may determine that the terminal has a relatively high paging frequency and assign the terminal to Group 1. On the other hand, In this case, the serving base station may determine that the terminal has a relatively low paging frequency and assign the terminal to Group 2. Here, ≠ the median of the entire terminal distribution, the upper ratio point, or a value that can be dynamically adjusted according to network conditions. For example, if ISL bandwidth is limited, adaptive control is possible by lowering the threshold value to reduce the number of terminals included in Group 1. For example, the serving base station may perform adaptive control by setting the threshold value to the upper 50% point of the entire terminal distribution (e.g., 10.24 seconds), or by lowering it to a lower value (e.g., 2.56 seconds) if ISL bandwidth is insufficient, thereby reducing the size of Group 1.

[0167] Based on the grouping results of the terminals, the serving base station may configure each data field of the group-based terminal context information element as follows. For example, for terminals belonging to the first group, the serving base station may set the Split Strategy Type to ISL-Direct, include the context of the terminals in the UE Context List, and transmit it to the target base station via the Xn interface. For terminals belonging to the second group, the serving base station may set the Split Strategy Type to CN-Relayed, include the context of the terminals in the UE Context List, and transmit it to the Mobility Management Function (AMF) via the NG interface. The target base station may parse the UE Specific DRX Cycle information within the received group-based terminal context information element to pre-calculate the next paging time for the terminals and prepare for monitoring. Through this, paging loss can be prevented even after switching between base stations, and continuous communication services can be provided to the terminals.

[0168]

[0169] Hereinafter, another embodiment is described regarding grouping terminals based on subgroups of terminals to support Paging Early Indication (PEI) operation.

[0170] FIG. 12 illustrates an example of a terminal context management method procedure in a wireless communication system according to another embodiment of the present disclosure.

[0171] Referring to FIG. 12, in step S1201, the core network (1230) groups the terminal (1210). Specifically, the terminal (1210) may be grouped based on PEI-based paging control of the core network (1230). For example, the core network (1230) may assign any one of a plurality of groups to the terminal (1210) by considering the characteristics of the terminal (1210). For example, the core network (1230) may assign any one of a total of eight groups from 0 to 7 to the terminal (1210) by considering the characteristics of the terminal (1210). According to one embodiment, the core network (1230) may assign a first sub-group to the terminal (1210) by considering at least one of the mobility characteristics, service type, or paging frequency of the terminal (1210).

[0172] In step S1203, the core network (1230) transmits a terminal group to the terminal (1210) and the first base station (1220). For example, the core network (1230) may notify the terminal (1210) and the first base station (1220) of a first subgroup assigned to the terminal (1210) via a NAS message.

[0173] In step S1205, the first base station (1220) groups the terminal (1210). Specifically, the first base station (1220) may assign a second subgroup to the terminal (1210) based on a paging frame and a paging occasion (PO) within a discontinuous reception cycle. For example, the first base station (1220) may assign the second subgroup using the following Equation 2.

[0174]

[0175] Referring to Equation 2, N represents the total number of paging frames included within the terminal's DRX period, and Nₛ represents the number of available paging occasions (PO) within a single paging frame. SubgroupsNumberForUEID represents the number of subgroups distinguished based on the UE identifier (UE_ID), and SubgroupsNumPerPO represents the total number of subgroups allocated per paging occasion (PO).

[0176] The assignment of the second subgroup may be performed even when the first subgroup of the core network (1230) is assigned to the terminal (1210). Meanwhile, according to an embodiment, the operation of step S1205 may be performed when the core network (1230) does not assign the first subgroup.

[0177] In step S1207, the first base station (1220) can transmit a terminal group to the terminal (1210). For example, the first base station (1220) can notify the terminal (1210) of a second subgroup assigned to the terminal (1210) via a NAS message.

[0178] In step S1209, the first base station (1220) can determine a group of terminals based on priority. Specifically, if both the second sub-group based on the PEI-based paging control of the core network (1230) and the second sub-group assigned by the first base station (1220) are valid for the terminal (1210), the first base station (1220) can preferentially apply the second sub-group based on the core network (1230).

[0179] At this time, the first base station (1220) can determine a split transmission path for the terminal context by mapping the finally determined subgroup to the paging frequency or discontinuous reception cycle characteristics of the terminal (1210). For example, for a terminal (1210) belonging to a subgroup with a relatively high paging frequency, the first base station (1220) can select a context transmission path through a satellite link. On the other hand, for a terminal (1210) belonging to a subgroup with a relatively low paging frequency, the first base station (1220) can select a context transmission path through a feeder link.

[0180]

[0181] Meanwhile, those skilled in the art related to the present embodiment will understand that it may be implemented in modified forms without departing from the essential characteristics of the above description. Therefore, the disclosed methods should be considered in an illustrative rather than a restrictive sense. The scope of the present disclosure is defined by the claims, not by the foregoing description, and all variations within the scope of equivalence should be interpreted as being included in the present disclosure.

[0182] The present disclosure relates to a wireless communication system, and in particular, can be used in a device for transmitting terminal context between base stations in a wireless communication system.< / maxnoofues>

Claims

1. In a method of operating a first base station in a wireless communication system, Step of disabling RRC on terminals (RRC INACTIVE); A step of grouping the terminals based on a Discontinuous Reception (DRX) period; and A method comprising the step of transmitting terminal contexts of the terminals based on a terminal group to either a second base station or a core network.

2. In Paragraph 1, The step of grouping the above terminals is, A step of grouping terminals corresponding to the discontinuous reception period below a predetermined threshold into a first terminal group; and A method comprising the step of grouping terminals corresponding to the discontinuous reception cycles exceeding the threshold value into a second terminal group.

3. In Paragraph 2, The above threshold is, A method that is controlled based on the available capacity of the inter-satellite link (ISL) and feeder link of the first base station.

4. In Paragraph 2, The above-mentioned transmitting step is, A method comprising the step of transmitting the first terminal contexts of the terminals included in the first terminal group to the second base station via a satellite link.

5. In Paragraph 2, The above-mentioned transmitting step is, A method comprising the step of transmitting the second terminal contexts of the terminals included in the second terminal group to the core network via a feeder link.

6. In Paragraph 2, The above-mentioned second base station is, A method for receiving a paging request message for a terminal from the core network, wherein if the terminal is included in the first terminal group, the first terminal context of the terminal is obtained from the first terminal contexts, and the paging message is transmitted to the terminal using the first terminal context.

7. In Paragraph 2, The above-mentioned second base station is, A method for receiving a paging request message for a terminal from the core network, wherein if the terminal is included in the second terminal group, receiving a second terminal context of the terminal among the second terminal contexts from the core network, and transmitting a paging message to the terminal using the second terminal context.

8. In Paragraph 1, The above-mentioned transmitting step is, A step of confirming the disconnection of the satellite link with the second base station; Based on the above satellite link disconnection, the method includes the step of transmitting a paging message to the terminals included in the first terminal group, A method for inducing the terminals included in the first terminal group to update the first terminal contexts of the terminals by transmitting an RRC connection request message to the second base station.

9. In Paragraph 1, The above core network is, A first subgroup is assigned to the above terminals according to PEI (Paging Early Indication) based paging control, and The above-mentioned first base station is, A method for assigning a second subgroup to the terminals based on a paging frame and a paging occasion (PO) within a discontinuous reception period.

10. In Paragraph 9, If the first subgroup and the second subgroup are valid, a step of assigning priority to the first subgroup; A step of mapping the first subgroup and the discontinuous reception period; and A method comprising the step of transmitting the terminal contexts to either the second base station or the core network based on the mapping result above.

11. In a first base station of a wireless communication system, Transmitter / receiver; and It includes a processor connected to the above-mentioned transmitter and receiver, The above processor is, Disable RRC on the terminals (RRC INACTIVE), and Grouping the terminals based on a Discontinuous Reception (DRX) period, and A first base station that transmits terminal contexts of the terminals to either a second base station or a core network based on a terminal group.

12. In a method of operating a second base station in a wireless communication system, A step of receiving terminal contexts of terminals from a first base station based on a terminal group; A step of receiving a paging request message for a terminal from a core network; A step of obtaining a terminal context of the terminal based on the terminal group including the terminal; and A method comprising the step of transmitting a paging message to the terminal based on the terminal context.

13. In Paragraph 12, The above terminals are, When corresponding to a discontinuous reception period below a predetermined threshold, it is grouped into a first terminal group, and A method for grouping into a second terminal group when corresponding to the discontinuous period exceeding the threshold value.

14. In Paragraph 13, The step of receiving the above terminal contexts is, A method comprising the step of receiving first terminal contexts of the terminals included in the first terminal group from the first base station via a satellite link.

15. In Paragraph 13, A method in which the second terminal contexts of the terminals included in the second terminal group are transmitted to the core network via a feeder link.

16. In Paragraph 14, The step of obtaining the terminal context of the above terminal is, A method comprising the step of obtaining a first terminal context of the terminal from the first terminal contexts when the terminal is included in the first terminal group.

17. In Paragraph 15, The step of obtaining the terminal context of the above terminal is, A method comprising the step of receiving a second terminal context of the terminal among the second terminal contexts from the core network when the terminal is included in the second terminal group.

18. In a second base station of a wireless communication system, Transmitter / receiver; and It includes a processor connected to the above-mentioned transmitter and receiver, The above processor is, Based on the terminal group, receive terminal contexts of the terminals from the first base station, and Receive a paging request message for a terminal from the core network, and Based on the terminal group including the terminal, the terminal context of the terminal is obtained, and A second base station that transmits a paging message to the terminal based on the terminal context.

19. In a method of operation of a core network in a wireless communication system, A step of receiving terminal contexts of terminals from a first base station based on a terminal group; Step of confirming downlink data generation to the terminal; If the group of the above terminals is the first terminal group, the step of transmitting a paging request message for the terminals to the second base station; If the group of the above terminals is a second terminal group, the step of transmitting the second terminal context of the above terminals to the second base station; and A method comprising the step of transmitting the paging request message to the terminal based on the second terminal context.

20. In a method of operation of a terminal in a wireless communication system, Step of disabling the first base station and RRC; A step of receiving a paging message from a second base station; and The method includes the step of transmitting an RRC connection request message to the second base station, A method in which the second base station obtains a terminal context from either the second base station or the core network based on a terminal group of the terminal.

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