Method for energy-efficient NTN communications

Abstract

The present invention is related to a method for energy-efficient 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 recieves from a source NTN node a NTN node identifier as an indication of a target NTN node, as well as a wait timer value.

Description

[0001] 202500619

[0002] 1

[0003] Description

[0004] Method for Energy-Efficient NTN Communications

[0005] The present invention relates to a method and system for energy-efficient NTN communications, generally related to mobile communications.

[0006] TECHNNICAL FIELD

[0007] Non-Terrestrial Networks (NTN) enhance the reliability of loT devices in several key ways. NTNs provide connectivity in remote and underserved areas where traditional terrestrial networks are unavailable. This ensures loT devices can maintain communication regardless of their location. By incorporating satellite connectivity, NTNs offer an additional layer of redundancy. If terrestrial networks fail due to natural disasters or other disruptions, NTNs continue to provide reliable service. NTNs are less susceptible to local infrastructure issues, such as power outages or physical damage to cell towers. Also, NTNs support a large number of loT devices over vast areas, reducing the likelihood of network congestion and ensuring consistent performance. Overall, NTNs enhance the robustness and dependability of loT services, making them more resilient to various challenges.

[0008] BACKGROUND

[0009] Standardization of Non-Terrestrial Networks (NTN) for future 3GPP releases focuses on transparent and regenerative payload architectures, requiring satellite platforms to connect to ground stations for loT services. In this context, NTN deployments targeting delay tolerant loT applications benefit from architectures based on the use of support for store-and-forward (S&F) operations, where satellite access remains operational even at times when the satellite is not connected to a ground station. Received data packets will be stored at the satellite and forwarded to a ground station, when a feeder link can be re-established.202500619

[0010] 2

[0011] 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-visit 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.

[0012] 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.

[0013] 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.202500619

[0014] 3

[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 procedure.

[0016] However, in store and forward mode, NTN node broadcasts time indication when real-time mode starts or resumes. All UEs receive and apply same time indication for accessing or re-connecting to the network. This may result in congestion and potentially high network load. In case of colliding access attempts, UEs will retry connecting, which consumes additional energy.

[0017] The technical problem is to avoid congestion and to improve UE's energy consumption.

[0018] Therefore, it is an objective of the present invention to solve the mentioned technical problem. This objective is achieved according to the invention by means of the technical characteristics mentioned in the independent claims.

[0019] The invention relies on defining method steps of receiving by UE an indication of next NTN node identifier and corresponding wait timer before store-and-forward mode starts.

[0020] The dependent claims include advantageous further developments and improvements of the present invention.

[0021] According to a first aspect of the invention, there is provided a method for energyefficient NTN communication, performed by a UE in wireless communication with a network comprising at least a source NTN node and a target NTN node.202500619

[0022] 4

[0023] The method comprises the following steps: UE receives from a source NTN node a NTN node identifier as indication of a target NTN node, as well as a timer value. While the wait timer is running, the UE refrains from performing idle mode tasks, such as cell (re-)selection or measurements. When timer expires, UE performs measurements, cell (re-)selection or resumes connection to the target NTN node. When the network decides to start the store and forward operations, it determines the target NTN node identifier (e.g., using constellation characteristics) and UE-specific wait timer value. The source NTN node provides the target NTN node identifier and the corresponding wait timer information to the UE, e.g., using RRC connection release message.

[0024] By applying these method steps, the network determines the most suitable next satellite (i.e., target NTN node) and configures wait timer in UE-specific manner, e.g., based on data traffic pattern. Thus, congestion when accessing next satellite is avoided or mitigated. Further, UE-specific wait timer settings improve UE’s energy consumption in idle mode, since UE will not perform measurements or cell (re-)selection. Further, UEs with rather low data transfer frequencies can be configured to wait longer than UEs requiring more frequent data transfer.

[0025] In one exemplary embodiment, when the network (e.g., via source NTN node) decides to start store-and-forward operations, it determines the target NTN node identifier using constellation characteristics and UE-specific wait timer value. The source NTN node provides the UE and wait timer information to a corresponding target NTN node, e.g., via X2 interface. If resource reservation indication and UL grant are received from the target NTN node, the source NTN node provides the target NTN node identifier and the corresponding wait timer information as well as indication on reserved resources and UL grant to the UE. Otherwise, the source NTN provides the target NTN node identifier and the corresponding wait timer information to UE, e.g., using RRC connection release message.

[0026] Furthermore, in another embodiment, the UE receives the target NTN node identifier and corresponding wait timer, as well as information on reserved radio resources and grant for UL data transfer, e.g., via RRC message, and more202500619

[0027] 5

[0028] specific, via RRC connection release message. While the wait timer is running, the UE refrains from performing idle mode tasks, e.g., intra- / inter-frequency measurements and / or cell (re-) selection. When the wait timer expires, the UE connects to the indicated NTN node and performs UL data transfer based on UL grant.

[0029] Moreover, when the target NTN node receives the UE and wait timer information, it determines resurse reservation, i.e. , radio resources for random access and grant for UL data transfer. Resource reservation is performed based on wait timer and / or UE information (e.g., including service priorities, data traffic characteristics). If no resources are available, the target NTN node provides an indication that the resource reservation was rejected. Otherwise, the target NTN node provides information on the reserved resources and grant for UL data transfer to source NTN node, e.g., via X2 interface.

[0030] According to a second aspect of the invention, there is provided an apparatus for energy efficient 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.

[0031] According to a third aspect of the invention, there is provided a user equipment for energy-efficient 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.

[0032] According to a fourth aspect of the invention, there is provided a NTN node comprising an apparatus for energy-efficient NTN communications.

[0033] According to a fifth aspect of the invention, there is provided a wireless communication system comprising at least one NTN node with a processor coupled with a memory in which computer program instructions are stored, said202500619

[0034] 6

[0035] instructions being configured to implement steps of method claims, in communication with at least one UE configured to implement steps of the method claims.

[0036] Figures

[0037] 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.

[0038] Figures 1 presents an illustration of a feeder link switch over (FLSO) in a non-geostationary network scenario,

[0039] 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 intermitent available or not available, and store and forward mode is activated,

[0040] Fig. 1c illustrates a subsequent moment when NTN coverage is non-contiguous, and UEs are temporarily out of coverage,

[0041] Fig. 2 presents a first embodiment of a method for energy-efficient NTN communications, performed at UE,

[0042] Fig. 3 presents the first embodiment of the method for energy-efficient NTN communications, performed at network node,

[0043] Fig. 4 presents a second embodiment of a method for energy-efficient NTN communications, performed at UE,

[0044] Fig. 5 presents the second embodiment of the method for energy-efficient NTN communications, performed at a source NTN node,

[0045] Fig. 6 presents the second embodiment of the method for energy-efficient NTN communications, performed at a target NTN node.

[0046] Detailed description202500619

[0047] 7

[0048] 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.

[0049] 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.

[0050] 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.202500619

[0051] 8

[0052] 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 & 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.

[0053] 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.

[0054] Additionally, terminologies such as base station / gNB 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. The same applies to “first base station” and “second base station”; throughout this description, at some point, “first base station” is202500619

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[0056] equivaled with a source or serving gNB / cell, and “second base station” is equivaled with a target gNB / cell.

[0057] 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.

[0058] For example, the disclosed embodiments may be implemented as a hardware circuit comprising custom very-large-scale integration (“VLSI”) circuits or gate 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.

[0059] 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.

[0060] 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.202500619

[0061] 10

[0062] 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.

[0063] 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”)).

[0064] 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,202500619

[0065] 11

[0066] 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 not 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.

[0067] 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.

[0068] 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.202500619

[0069] 12

[0070] 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.

[0071] The flowchart diagrams and / or block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of 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).

[0072] 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.

[0073] 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 (e.g., NTN) 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 36.304.202500619

[0074] 13

[0075] The mentioned indicators are either included or derived from SIB3, SIB31 , SIB32, SIB33, SIB31-NB, SIB31-NB, SIB32-NB, SIB33-NB data, for example:

[0076] t-Service-r17 (indicates the time information on when a cell provided via NTN quasi-Earth fixed system is going to stop serving the area it is currently covering), t-ServiceStart-r18 indicates the time information on when the target satellite is going to start serving the area currently covered by the serving satellite.

[0077] Fig. 1b presents a scenario when the current serving NTN node or source NTN node (e.g., satellite Sat ID#1) still covers UE location, but feeder link is not or only intermittently available. The NTN 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 NTN 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 NTN node (e.g., satellite).

[0078] 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.

[0079] According to invention, there is provided a method for energy-efficient communications, performed by a UE in wireless communication with at least one NTN node integrated in a wireless communication system.

[0080] Fig. 2 and 3 show the first embodiment of the method for energy-efficient NTN communications, according to invention, whereby the behaviour of UE and NTN nodes, respectively, are illustrated.

[0081] When the source NTN node decides to start store-and-forward operations, it determines a suitable target NTN node ID (by using constellation characteristics)202500619

[0082] 14

[0083] and UE-specific wait timer value. The source NTN node provides the target NTN node ID and a corresponding wait timer information to UE, e.g., using RRC connection release message. While the wait timer is running, the UE refrains from performing idle mode tasks, e.g., intra- / inter-frequency measurements and / or cell (re-)selection. When timer expires, the UE performs measurements, cell (re-) selection or resumes connection to the target NTN node.

[0084] List of satellites (including respective identifiers and ephemeris data) is provided by the source NTN node (e.g., via SIB31). Source NTN node is aware when the next NTN node (e.g., target NTN node) will cover a geographical area and can provide time indication when real-time mode starts / resumes. In addition, the source NTN node is aware which services (e.g., data traffic pattern) a UE requested. The source NTN node determines satellite identifier based on movement data of neighboring satellites. Further on, the source NTN node determines wait timer based on UE service history, data traffic pattern, distance, timing advance, capabilities, or further assistance information provided by the UE (e.g., UE mobility, energy status).

[0085] Upon receiving the RRC release message including target satellite identifier and wait timer, UE moves to idle mode and refrains from cell search, intra-Zinter-frequency measurements, and / or cell re-selection procedures until the wait timer expires. UE wait timer configuration is exchanged between the source and target NTN nodes, which enables to manage or reserve random access resources at target NTN node.

[0086] Fig. 4, 5 and 6 show the second embodiment of the method for energy-efficient NTN communications, according to invention, whereby the behaviour of UE, the source and target NTN nodes, respectively, are illustrated.

[0087] In this second embodiment, UE receives the target NTN node identifier and corresponding wait timer, as well as information on reserved radio resources and grant for UL data transfer, e.g., via RRC message, or more specific, via RRC connection release message. While the wait timer is running, the UE refrains from202500619

[0088] 15

[0089] performing idle mode tasks, e.g., intra- / inter-frequency measurements and / or cell (re-) selection. When timer expires, the UE connects to the indicated target NTN node and performs UL data transfer based on UL grant.

[0090] Fig. 5 illustrates the source NTN node behavior. When the source NTN node (e.g., Sat ID#1 in Fig. 1c, for example), decides to start store-and-forward operations, it determines a suitable target NTN node identifier (e.g., using constellation characteristics) and UE-specific wait timer value. The source NTN node provides the UE and wait timer information to the corresponding target NTN node, e.g., via X2 interface. If the resource reservation indication and UL grant are received from the target NTN node, the source NTN node provides the target NTN node identifier and corresponding wait timer information as well as indication on reserved resources and UL grant to the UE. Otherwise, the source NTN node provides the target NTN node identifier and corresponding wait timer information to the UE, e.g., using RRC connection release message.

[0091] Behavior of the target NTN node is shown in Fig. 6. When the target NTN node (e.g., Sat ID#2 in Fig. 1c) receives the UE and wait timer information from the source NTN node, it determines resources reservation, meaning radio resources for random access and grant for UL data transfer. Resources reservation is performed based on wait timer and / or UE information (e.g., including service priorities, data traffic characteristics). If no resources are available, the target NTN node provides an indication that the resource reservation was rejected. Otherwise, the target NTN node provides information on reserved resources and grant for UL data transfer to source NTN node, e.g., via X2 interface.202500619

[0092] Abbreviations list:

[0093] UE User Equipment

[0094] NTN Non-Terrestrial Network RRC Radio Resource Control UL Uplink

[0095] SIB System Information Block S&F Store-and-Forward

[0096] Cited patent literature:

[0097] D1: US 2024063896 A1

[0098] D2: US 2024276213 A1

[0099] D3: WO 2024159793 A1

[0100] D4: WO 2024108921 A1

Claims

20250061917Patent claims1. A method for energy-efficient NTN communications, performed by a UE in communication with a wireless communication network comprising at least one NTN node, c h a ra cte r i z e d i n that, a UE recieves from a source NTN node a NTN node identifier as an indication of a target NTN node, as well as a wait timer value.

2. Method of claim 1 , c h a r a c t e r i z e d i n that, while the wait timer is running, the UE refrains from performing idle mode tasks, such as intra-, interfrequency measurements or cell (re-)selection.

3. Method of the previous claim, c h a ra ct e r i z e d i n that, when the wait timer expires, the UE performs measurements, cell (re-)selection or resumes connection to the target NTN node.

4. Method of the previous claims, c h a r a ct e r i z e d i n that, the target NTN node identifier and the wait timer value are provided by the source NTN node in a RRC configuration message, more specifically in the RRC connection release message.

5. Method of the previous claim, c h a ra ct e r i z e d i n that, when the source NTN node decides to start store-and-forward operations, it determines the target NTN node identifier by using constellation characteristics such as NTN node identifiers and ephemeris data.

6. Method of the previous claim 5, c h a r a ct e r i z e d i n that, the source network node determines the wait timer as UE-specific value.

7. Method of claim ^ ch a racte rized i n that, in addition, the UE receives information on reserved radio resources and grant for UL data transfer.202500619188. Method of claims 1 and 7, c h a r a c t e r i z e d i n that, while the wait timer is running, the UE refrains from performing idle mode tasks, such as intra-, interfrequency measurements or cell (re-)selection, and when the wait timer expires, the UE connects to the target NTN node and performs UL data transfer based on UL grant.

9. Method of claims 1 , 7 and 8, c h a r a c t e r i z e d i n that, the source NTN node provides the UE and UE-specific wait timer information to the target NTN node, via X2 interface.

10. Method of the previous claims 1 , 7-9, c h a r a c t e r i z e d i n that, when the target NTN node receives the UE and wait timer information, it determines radio resources allocation for random access and grant for UL data transfer.11 . Method of previous claims 7- 10, c h a r a c t e r i z e d i n that, the radio resource allocation is performed based on the received wait timer and UE information, the received information including service priorities, data traffic characteristics.

12. Method of previous claim 1 and 7, c h a r a c t e r i z e d i n that, if the resource reservation indication and UL grant are not received from the target NTN node, the source NTN node provides the target NTN node identifier and the wait timer information to UE via RRC connection release message.

13. The method of claims 1 , 7 and 12, c h a r a c t e r i z e d i n that, if no radio resources are available, the target NTN node provides an indication that the resource allocation was rejected.

14. Apparatus for store and forward operations, 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 13.

15. User Equipment (UE) comprising an apparatus according to claim 14.2025006191916. NTN node comprising an apparatus according to claim 14.

17. Wireless communication system comprising a NTN node according to claim 16 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 13, in communication with at least one UE according to claim 15, 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 13.

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