Method for reducing congestion in NTN communications

Abstract

The present invention is related to a method for reducing congestion in NTN communications, performed by a UE in communication with a wireless communication network comprising at least one NTN node. According to the invention, the UE receives a specific group identifier information from a network node, where each group identifier (ID) is associated with a group ID-specific store-and-forward wait timer, and a mapping between group ID and group ID-specific store-and-forward timer is broadcast through system information message.

Description

[0001] 202500617

[0002] 1

[0003] Description

[0004] Method for Reducing Congestion in NTN Communications

[0005] The present invention relates to a method and system for reducing congestion in NTN communications, generally related to mobile communications.

[0006] TECHNNICAL FIELD

[0007] The 3rd Generation Partnership Project (3GPP) has been actively working on standardizing NTN for loT applications. Releases 17 and 18 include enhancements specifically for NTN, focusing on improving support for loT devices. Non-Terrestrial Networks (NTNs) are advanced wireless communication systems that operate above the Earth's surface using satellites, high-altitude platform stations (HAPS), or drones. They are designed to extend connectivity to remote and underserved areas, complementing terrestrial networks.

[0008] BACKGROUND

[0009] With the increasing number of loT devices and applications requiring connectivity, NTNs may experience high traffic loads, leading to congestion. Satellites and other non-terrestrial platforms have limited bandwidth compared to terrestrial networks, which can result in congestion when demand exceeds capacity. In addition, the distance between satellites and ground stations can introduce latency, and inefficient routing can exacerbate congestion.

[0010] US 2024063896 A1 [D1] describes methods and devices for wireless communication of an apparatus, e.g., a UE, a network entity, and / or a base station. The apparatus receives, from a network, an indication of at least one of a coverage re-visit time or a backhaul connection unavailability. The apparatus also identifies, based on the received indication, whether to initiate at least one of a signaling procedure or a data packet procedure, the signaling procedure and the data packet procedure being associated with at least one of the coverage re-visit202500617

[0011] 2

[0012] time or the backhaul connection unavailability. The apparatus also initiates at least one of a signaling procedure or a data packet procedure based on the indication of the coverage re-visit time or the backhaul connection unavailability, the signaling procedure and the data packet procedure being associated with the coverage revisit time or the backhaul connection unavailability.

[0013] US 2024276213 A1 [D2] discloses ystems, methods, and software of performing a store and forward service for mobile terminated messages to user equipment via satellite access. According to [D2], a home network of user equipment (UE) receives a first message request from an application server that includes a secured packet destined for the user equipment via satellite access, and determines whether the user equipment supports the store and forward service via satellite access. When the user equipment supports the store and forward service, the home network provides integrity protection of the secured packet at the home network by deriving a message authentication code based on the secured packet and a home network key, and send a second message request to a serving network of the user equipment with the secured packet and the message authentication code contained in a home network container.

[0014] WO 2024159793 A1 [D3] relates to store and forward operations. According to [D3], a user equipment receives a configuration for a store and forward operation from a network device. Based on the configuration, the user equipment determines to initiate the store and forward operation. In this way, the store and forward operation is initiated at appropriate occasions.

[0015] WO 2024108921 A1 [D4] presents systems and methods for timing enhancement in store and forward mode. A wireless communication node configures a waiting duration indicative of a duration to a next service period of a satellite, and a serving duration indicative of a duration of a service period of the satellite. The wireless communication node sends the waiting duration and the serving duration, to be used by a wireless communication device during a random access

[0016] procedure.202500617

[0017] 3

[0018] However, in store-and-forward mode, the NTN node broadcasts time indication when real-time mode starts or resumes. All UEs receive and apply the same time indication for accessing or re-connecting to the network, which means network congestion and potentially high network load. In case of colliding access attempts, UEs will retry connecting, which consumes additional energy.

[0019] The technical problem is how to avoid congestion, reduce DL overhead and improve UE’s energy consumption.

[0020] Therefore, it is an objective of the present invention to solve the mentioned technical problem.

[0021] This objective is achieved according to the invention by means of the technical characteristics mentioned in the independent claims.

[0022] The invention solves the technical problem by defining method steps of receiving by UE a group identifier information from network, where each group ID is associated with group ID-specific store-and-forward wait timer, and a mapping between the group identifier and group ID-specific store-and-forward wait timer is broadcast through system information message.

[0023] The dependent claims include advantageous further developments and improvements of the present invention.

[0024] According to a first aspect of the invention, there is provided a method for reducing congestion in NTN communication, performed by a UE in wireless communication with a network including at least one NTN node.

[0025] The method comprises the following steps: during RRC setup or in RRC connected state, UE receives group ID information from network, where each group ID is associated with a group ID-specific store-and-forward wait timer, and a mapping between group ID and group ID-specific store-and-forward timer is broadcast through system information message.202500617

[0026] 4

[0027] By applying these method steps, the network determines customized associations of group IDs and group ID-specific store-and-forward wait timers. Thus, RACH congestion is avoided or mitigated. Further, group ID-specific timer settings improve UE’s energy consumption in idle mode, since UE don't perform measurements or cell (re-)selection.

[0028] In one exemplary embodiment, the network (e.g., via network / gNB / NTN node) provides a mapping between group ID and group ID-specific store-and-forward wait timer. The mapping is broadcast through system information message, and the mapping concerns one or a combination of the following indicators: each group ID and cell-specific UL data transfer timer; each group ID and group ID-specific UL data transfer timer; or each group ID and group ID-specific UL data transfer timer value range.

[0029] UE receives group ID information from network node during RRC setup or in RRC connected state. If store-and-forward mode is activated, the UE checks if the assigned group ID is included in the received broadcast message and starts the group ID-specific store-and-forward wait timer value. While the store-and-forward wait timer is running, the UE refrains from performing measurements, cell (re-election, or random access procedure. When the store-and-forward timer expires, the UE starts UL data transfer wait timer. When UL data transfer timer expires, the UE starts to perform UL data transfer, meaning intra- / inter-frequency measurements, cell (re-)selection or random access procedure.

[0030] In some embodiments, when the group ID-specific store-and-forward wait timer value expires, the UE starts UL data transfer timer, according to one of the following options:

[0031] - if the network configured the UL data transfer timer as cell-specific, UE applies cell-specific UL data transfer timer (option #1 ),

[0032] - if the network configured the UL data transfer timer as group ID-specific, the UE applies the group ID-specific UL data transfer timer (option #2),202500617

[0033] 5

[0034] - if the network configured the UL data transfer timer as group ID-specific, the UE applies the group ID-specific UL data transfer timer value, by selecting a random value from the indicated value range (option #3).

[0035] In some embodiments, the network / gNB / NTN node determines the group ID’s number and size of UEs as well as corresponding group-specific timer values or timer value ranges, e.g., depending on network load and / or number of connected UEs. Further on, the network / gNB / NTN node determines group ID based on UE service type, UE service history, data traffic pattern, distance, timing advance, capabilities, or further assistance information provided by the UE (e.g., UE mobility, energy status).

[0036] According to a second aspect of the invention, there is provided an apparatus for reducing congestion in NTN communications, comprising a wireless transceiver, a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the method claims.

[0037] According to a third aspect of the invention, there is provided a user equipment for reducing congestion in NTN communications, comprising a wireless transceiver, a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the method claims.

[0038] According to a fourth aspect of the invention, there is provided a network node comprising an apparatus for reducing congestion in NTN communications.

[0039] According to a fifth aspect of the invention, there is provided a wireless communication system comprising a network node with a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of method claims, in communication with at least one UE configured to implement steps of the method claims.202500617

[0040] 6

[0041] Figures

[0042] For a better understanding of the principle of the present invention, embodiments of the invention will be explained in more detail below with reference to the figures. Like reference numerals are used in the figures for the same or equivalent elements and are not necessarily described again for each figure. It is to be understood that the invention is not limited to the illustrated embodiments and that the features described may also be combined or modified without departing from the scope of the invention as defined in the appended claims.

[0043] Figures 1 presents an illustration of a feeder link switch over (FLSO) in a non-geostationary network scenario,

[0044] Fig. 1a shows a standard scenario with both feeder link and service link available, Fig. 1 b shows a moment when the feeder link is only intermittent available or not available, and store-and-forward mode is activated,

[0045] Fig. 1c illustrates a subsequent moment when network coverage is noncontiguous, and UEs are temporarily out of coverage,

[0046] Fig. 2 presents one embodiment of a method for reducing congestion in NTN communications, performed at UE,

[0047] Fig. 3 presents the embodiment of the method for reducing congestion in NTN communications, performed at network node.

[0048] Detailed description

[0049] The detailed description set forth below, with reference to annexed drawings, is intended as a description of various configurations and is not intended to represent only the configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. Although terminology from 3GPP LTE NTN may be used in this disclosure to exemplify embodiments herein, this should not be seen as limiting the scope of the invention.202500617

[0050] 7

[0051] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0052] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

[0053] In some embodiments, a more general term “network node” may be used and may correspond to any type of radio network node or any network node, which communicates with a UE (directly or via another node) and / or with another network node. Examples of network nodes are NodeB, MeNB, eNB, Integrated Access and Backhaul (IAB) node, a network node belonging to MCG or SCG, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNodeB, gNodeB, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g. Mobile Switching Center (MSC), Mobility Management Entity (MME), etc.), Operations &202500617

[0054] 8

[0055] Maintenance (O&M), Operations Support System (OSS), Self-Optimized Network (SON), positioning node (e.g. Evolved- Serving Mobile Location Centre (E-SMLC)), Minimization of Drive Tests (MDT), test equipment (physical node or software), etc. In addition, examples of NTN nodes are Low Earth Orbit (LEO) satellites (orbiting the Earth at altitudes between 500 to 2000 km), Unmanned Aerial Vehicles (UAVs) (providing broadband links between UEs at lower altitude), or High-Altitude Platform Systems (HAPS) (operating at altitudes between 17 and 22 km, higher than UAVs but lower than satellites).

[0056] In some embodiments, the non-limiting term user equipment (UE) or wireless device may be used and may refer to any type of wireless device communicating with a network node and / or with another UE in a cellular or mobile communication system. Examples of UE are target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, PDA, PAD, tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, UE category Ml, UE category M2, ProSe UE, V2V UE, V2X UE, etc.

[0057] Additionally, terminologies such as base station / gNB / cell and UE should be considered non-limiting and do in particular not imply a certain hierarchical relation between the two; in general, “gNB” could be considered as device 1 and “UE” could be considered as device 2 and these two devices communicate with each other over some radio channel. And in the following the transmitter or receiver could be either gNB, or UE.

[0058] As will be appreciated by one skilled in the art, aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects.

[0059] For example, the disclosed embodiments may be implemented as a hardware circuit comprising custom very-large-scale integration (“VLSI”) circuits or gate202500617

[0060] 9

[0061] arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. The disclosed embodiments may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, or the like. As another example, the disclosed embodiments may include one or more physical or logical blocks of executable code which may, for instance, be organized as an object, procedure, or function.

[0062] Furthermore, embodiments may take the form of a program product embodied in one or more computer readable storage devices storing machine readable code, computer readable code, and / or program code, referred hereafter as code. The storage devices may be tangible, non- transitory, and / or non-transmission. The storage devices may not embody signals. In a certain embodiment, the storage devices only employ signals for accessing code.

[0063] Any combination of one or more computer readable medium may be utilized. The computer readable medium may be a computer readable storage medium. The computer readable storage medium may be a storage device storing the code. The storage device may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

[0064] More specific examples (a non-exhaustive list) of the storage device would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (“RAM”), a read-only memory (“ROM”), an erasable programmable read-only memory (“EPROM” or Flash memory), a portable compact disc read-only memory (“CD-ROM”), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.202500617

[0065] 10

[0066] Code for carrying out operations for embodiments may be any number of lines and may be written in any combination of one or more programming languages including an object- oriented programming language such as Python, Ruby, Java, Smalltalk, C++, or the like, and conventional procedural programming languages, such as the “C” programming language, or the like, and / or machine languages such as assembly languages. The code may execute entirely on the user’s computer, partly on the user’s computer, partly on the user’s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user’s computer through any type of network, including a local area network (“LAN”), wireless LAN (“WLAN”), or a wide area network (“WAN”), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider (“ISP”)).

[0067] Furthermore, the described features, structures, or characteristics of the embodiments may be combined in any suitable manner. In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of an embodiment. Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. An enumerated listing of items does not202500617

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[0069] imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise.

[0070] Aspects of the embodiments are described below with reference to schematic flowchart diagrams and / or schematic block diagrams of methods, apparatuses, systems, and program products according to embodiments. It will be understood that each block of the schematic flowchart diagrams and / or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and / or schematic block diagrams, can be implemented by code. This code may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart diagrams and / or block diagrams.

[0071] The code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture including instructions which implement the function / act specified in the flowchart diagrams and / or block diagrams.

[0072] The code may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices to produce a computer implemented process such that the code which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart diagrams and / or block diagrams.

[0073] The flowchart diagrams and / or block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of202500617

[0074] 12

[0075] apparatuses, systems, methods, and program products according to various embodiments. In this regard, each block in the flowchart diagrams and / or block diagrams may represent a module, segment, or portion of code, which includes one or more executable instructions of the code for implementing the specified logical function(s).

[0076] It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more blocks, or portions thereof, of the illustrated figures.

[0077] Fig. 1a schematically shows standard routing data by means of feeder link switches for Earth-moving cells, as described by 3GPP standard specifications. Feeder link is required for routing data to packet gateway and / or cloud services. A network node provides a UE with a time indication when the feeder link will disappear (expressed by t-Service). Most precisely, t-Service is the time information on when an NTN cell is going to stop serving the area it is currently covering, as specified in TS 36.304.

[0078] Fig. 1b presents a scenario when the network node (e.g., satellite Sat ID#1) still covers UE location, but feeder link is not or only intermittently available. The network node, e.g., satellite, activates Store-and-Forward (S&F) mode and receives and stores user data. UEs receive and store broadcast time indication when the feeder link becomes available and the network node resumes real-time data transfer as well as forward stored user data to ground segment. As a mention, all UEs store the same time value indicated by the network node (e.g., satellite). Providing UEs with individual time indications via UE-specific signaling, e.g., RRC messages, consumes a considerable amount of DL resources and results in network signaling overhead.202500617

[0079] 13

[0080] Fig. 1c illustrates the same scenario from Fig. 1b, but at the moment when satellite coverage is non-contiguous, i.e. , UEs are temporarily out of coverage. UEs store the broadcasted time indication when real-time mode starts / resumes. While UEs move to idle mode, next satellite is approaching UE location(s). The issue is that many UEs will try to access next satellite (Sat ID #2) simultaneously, resulting in high congestion and network load.

[0081] According to invention, there is provided a method for reducing congestion in NTN communications, performed by a UE in wireless communication with at least one NTN node integrated in a wireless communication system.

[0082] Fig. 2 shows one embodiment of the method for reducing congestion in NTN communications, according to invention, whereby the behaviour of UE is illustrated.

[0083] The behaviour of UE is described as follows: during RRC setup or in RRC connected state, UE receives a specific group ID information from network / gNB / NTN node, where each group ID is associated with group ID-specific store-and-forward wait timer, and a mapping between group ID and group ID-specific S&F timer is broadcast through system information message.

[0084] The mapping includes one or a combination of the following indicators: each group ID and cell-specific UL data transfer timer; each group ID and group ID-specific UL data transfer timer; or each group ID and group ID-specific UL data transfer timer value range.

[0085] If store-and-forward mode is activated, the UE checks the system information message and if UE determines that its assigned group ID is included in the received broadcast message, the UE starts the group ID-specific store-and-forward timer value. While the store-and-forward wait timer is running, the UE refrains from performing measurements, cell (re-)selection, or random access procedure. When the store-and-forward wait timer expires, the UE starts the UL data transfer wait timer. When the UL data transfer timer expires, the UE starts202500617

[0086] 14

[0087] performing UL data transfer, which means performing tasks such as intra- / inter-frequency measurements, cell (re-)selection, random access procedure.

[0088] The behavior of network node is illustrated in Fig. 3. The network / gNB / NTN node determines the number and size of UEs per group ID, as well as corresponding group-specific timer values or timer value ranges, e.g., depending on network load and / or number of connected UEs.

[0089] More specific, the network / gNB / NTN node determines the group identifier based on UE service type, UE service history, data traffic pattern, distance, timing advance, capabilities, and further assistance information provided by the UE (e.g., UE mobility, energy status).

[0090] During connection setup or via RRC re-configuration process, the network / gNB / NTN node configures the UE with specific group identifier for store-and-forward mode. When network / gNB / NTN node decides to start store-and-forward operations, it indicates store-and-forward mode per group identifier.

[0091] Further on, the network / gNB / NTN node provides the mapping between group ID, store-and-forward wait timer, and UL data transfer timer value or timer value range through system information message.

[0092] When the group ID-specific S&F timer value expires, the UE starts UL data transfer timer, according to one of the following options:

[0093] - If the network configured the UL data transfer timer as cell-specific, UE applies cell-specific UL data transfer timer (option #1 ),

[0094] If the network configured the UL data transfer timer as group ID-specific, the UE applies the group ID-specific UL data transfer timer (option #2). For example, the network configures lower UL data transfer timer value for higher priority group ID.

[0095] - If the network configured the UL data transfer timer as group ID-specific, the UE applies the group ID-specific UL data transfer timer value, by selecting a random value from the indicated value range (option #3). For example, the202500617

[0096] 15

[0097] network configures lower UL data transfer timer value range for higher priority group ID.

[0098] The mentioned options are illustrated as exemplary embodiments in Table 1.

[0099] Table 1

[0100] &

[0101]

[0102] 202500617

[0103] 16

[0104] List of abbreviations

[0105] UE User Equipment

[0106] NTN Non-Terrestrial Network RRC Radio Resource Control DL Downlink

[0107] UL Uplink

[0108] SIB System Information Block S&F Store-and-Forward

[0109] Cited patent literature:

[0110] D1: US 2024063896 A1

[0111] D2: US 2024276213 A1

[0112] D3: WO 2024159793 A1

[0113] D4: WO 2024108921 A1

Claims

20250061717Patent claims1. A method for reducing congestion in NTN communications, performed by a UE in communication with a wireless communication network comprising at least one NTN node, c h a r a c t e r i z e d i n that, the UE receives a specific group identifier information from network node, where each group identifier (ID) is associated with a group ID-specific store-and-forward wait timer, and a mapping between group ID and group ID-specific store-and-forward timer is broadcast through system information message.

2. Method of claim ^ ch a racte rized i n that, the UE receives the specific group identifier information during connection setup or in RRC connected state.

3. Method of previous claims, c h a r a ct e r i z e d i n that, during connection setup, the UE is configured by the network node with specific group identifier for store-and-forward mode.

4. Method of claim ^ ch a racte rized i n that, the mapping between group identifier and group ID-specific store-and-forward wait timer includes one or more combinations of the following indicators:- each group ID and cell-specific UL data transfer timer;- each group ID and group ID-specific UL data transfer timer; or- each group ID and group ID-specific UL data transfer timer value range.

5. Method of claims 1-4, c h a r a c t e r i z e d i n that, if store-and-forward mode is activated, the UE checks the system information message, and if the UE determines that the specific group identifier is included in the received broadcast message, the UE starts the group ID-specific store-and-forward wait timer.

6. Method of the previous claims, c h a r a ct e r i z e d i n that, while the group ID-specific store-and-forward timer is running, the UE refrains from performing measurements, cell (re-)selection, random access procedure.202500617187. Method of the previous claims, c h a r a ct e r i z e d i n that, when the group ID-specific store-and-forward wait timer expires, the UE starts UL data transfer timer by applying one or more of the following:- if the network configured the UL data transfer timer as cell-specific, UE applies cell-specific UL data transfer timer (option #1 ),- if the network configured the UL data transfer timer as group ID-specific, the UE applies the group ID-specific UL data transfer timer (option #2),- if the network configured the UL data transfer timer as group ID-specific, the UE applies the group ID-specific UL data transfer timer value, by selecting a random value from the indicated value range (option #3).

8. Method of the previous claims, c h a r a ct e r i z e d i n that, when the UL data transfer timer expires, the UE starts performing UL data transfer by performing tasks such as intra- / inter-frequency measurements, cell (re-)selection, random access procedure.

9. Method of claim ^ ch a racte rized i n that, the specific group identifier is determined by the network node based on UE service type, UE service history, data traffic pattern, distance, timing advance, capabilities, or further assistance information provided by the UE such as UE mobility, energy status.

10. Method of claim ^ ch a racte rized i n that, the number and size of UEs per group, as well as corresponding group ID and group ID-specific timer values or timer value ranges are determined by the network node depending on network load or the number of connected UEs.

11. Apparatus for reducing congestion in NTN communications, comprising a wireless transceiver, a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the claims 1 to 10.

12. User Equipment (UE) comprising an apparatus according to claim 11.2025006171913. NTN node comprising an apparatus according to claim 12.

14. Wireless communication system comprising a NTN node according to claim 13 with a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of claims 1 to 10, in communication with at least one UE according to claim 12, wherein the UE comprises a processor coupled with a memory in which computer program instructions are stored, said instructions being configured to implement steps of the claims 1 to 10.

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