User equipment, access network node, and methods therein

Abstract

A communication system is disclosed in which a user equipment (UE) communicates with a base station via a non-terrestrial network, the UE obtains information identifying a threshold associated with a timing advance value applied to communication between the UE and a network node via the non-terrestrial network, obtains a timing advance value for communication with the network node, and determines whether to transmit a timing advance report to the network node based on the timing advance value and the threshold.

Description

[Technical field]

[0001] The present disclosure relates to communication systems. [Background technology]

[0002] The present disclosure relates to wireless communication systems and apparatus therefor that operate in accordance with 3GPP (3rd Generation Partnership Project) standards or equivalents or derivatives thereof. The present disclosure relates in particular, but not exclusively, to improvements relating to so-called "5G" (or "next generation") systems that employ non-terrestrial portions that include airborne or space network nodes.

[0003] In 3GPP standards, a NodeB (or "eNB" in LTE, "gNB" in 5G) is a base station through which communication devices (user equipment or UE) connect to the core network and communicate with other communication devices or remote servers. The communication devices can be, for example, mobile communication devices such as mobile phones, smartphones, smart watches, personal digital assistants, laptop / tablet computers, web browsers, e-book readers, etc. Although such mobile (or generally fixed) devices are typically operated by users (and thus they are often collectively referred to as user equipment, "UE"), it is also possible for IoT devices and similar MTC devices to connect to the network. For simplicity, this specification will use the term base station to refer to such base stations and the term mobile device or UE to refer to such communication devices.

[0004] The latest development in 3GPP standards is the so-called "5G" or "New Radio" (NR) standard, which refers to evolved communications technologies that are expected to support various applications and services such as Machine Type Communication (MTC), Internet of Things (IoT) / Industrial Internet of Things (IIoT) communications, vehicular communications and autonomous vehicles, high-definition video streaming, and smart city services. 3GPP plans to support 5G via the so-called 3GPP NextGen radio access network (RAN) and 3GPP NextGen core (NGC) networks. Various details of the 5G network are described, for example, in the "NGMN 5G White Paper" V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which is available at https: / / www.ngmn.org / 5g-white-paper.html.

[0005] End-user communication devices are commonly referred to as User Equipment (UE) and may be operated by humans or may be automated (MTC / IoT) devices. Base stations in 5G / NR communication systems are commonly referred to as New Radio Base Stations ("NR-BS") or "gNBs", although it is understood that they are referred to using the term "eNB" (or 5G / NR eNB), which is more typically associated with Long Term Evolution (LTE) base stations (also commonly referred to as "4G" base stations). 3GPP Technical Specification (TS) 38.300 V16.4.0 and TS 37.340 V16.4.0 define, among other things, the following nodes: gNB: A node that provides NR user plane and control plane protocol termination for the UE and is connected to the 5G core network (5GC) via the NG interface. ng-eNB: A node that provides Evolved Universal Terrestrial Radio Access (E-UTRA) user plane and control plane protocol termination for the UE and is connected to the 5GC via the NG interface. En-gNB: A node that provides NR user plane and control plane protocol termination for the UE and acts as a secondary node for E-UTRA-NR Dual Connectivity (EN-DC). NG-RAN node: Either gNB or ng-eNB.

[0006] 3GPP is also working on the specification of integrated satellite and terrestrial network infrastructure in the context of 5G. The term Non-Terrestrial Network (NTN) refers to a network, or a segment of a network, that uses aircraft or spacecraft for communication. A satellite refers to a spacecraft in Geostationary Earth Orbit (GEO) or Non-Geostationary Earth Orbit (NGEO), such as Low Earth Orbit (LEO), Medium Earth Orbit (MEO), or Highly Elliptical Orbit (HEO). An aircraft refers to a High Altitude Platform (HAP), including Unmanned Aircraft System (UAS). This includes tethered UAS, lighter than aerial UAS, and heavier than aerial UAS, all of which typically operate in a quasi-geostationary manner at altitudes between 8 km and 50 km.

[0007] 3GPP Technical Report (TR) 38.811 V15.4.0 is a study on New Radio to support such non-terrestrial networks. This study includes, among other things, a description of NTN deployment scenarios and related system parameters (architecture, altitude, orbit, etc.) and adaptation of 3GPP channel models for non-terrestrial networks (propagation conditions, mobility, etc.). 3GPP TR 38.821 V16.0.0 provides further details on NTN.

[0008] In non-terrestrial networks, the following is expected: -Facilitate the rollout of 5G services in unserved and underserved areas and improve terrestrial network performance. -Enhancing service reliability by providing service continuity for user equipment and mobile platforms (e.g. passenger cars, aircraft, ships, high-speed trains, buses). -Improve service availability everywhere, especially for critical communications and future rail / maritime / air communications. - Achieving 5G network scalability through the provision of efficient multicast / broadcast resources for delivering data towards the network edge or directly to user equipment.

[0009] NTN Access typically includes (among other things): NTN terminal: may refer to a 3GPP UE, or a terminal specific to a satellite system in cases where the satellite does not directly provide a 3GPP UE. Service Link: refers to the radio link between user equipment and a space / airborne platform (which may be in addition to the radio link with the ground-based RAN). -Space or airborne platforms. -Gateway (NTN Gateway): connects satellite or aeronautical access networks to the core network. Gateways are almost always co-located with base stations. Feeder link: Refers to the radio link between the gateway and the space / airborne platform.

[0010] A satellite or aircraft can generate multiple beams over a given area to provide each NTN cell, with the beams having a typical elliptical footprint on the Earth's surface.

[0011] 3GPP intends to support three types of NTN beams or cells. -Earth fixed cell: characterized by at least one beam that always covers the same geographic area (e.g. GEO satellites or HAPS) - Quasi-Earth fixed cell: characterized by at least one beam that covers one geographic area during a limited period of time and a different geographic area during another period of time (e.g., an NGEO satellite producing a steerable beam). -Earth moving cell: characterized by at least one beam that covers one geographical area at one moment and a different geographical area at another moment (e.g. NGEO satellites generating fixed or non-steerable beams).

[0012] If the satellite or aircraft has a fixed position in altitude / azimuth relative to a given point, such as GEO and UAS, the beam footprint is Earth-fixed.

[0013] If the satellite orbits the Earth (e.g., LEO) or is in an elliptical orbit around the Earth (e.g., HEO), the beam footprint may move over the Earth with the orbital motion of the satellite or aircraft. Alternatively, the beam footprint may be temporarily Earth-fixed (or quasi-Earth-fixed), in which case an appropriate beam-pointing mechanism (mechanical or electronic steering) can be used to compensate for the motion of the satellite or aircraft.

[0014] The term "Timing Advance" (TA) refers to a parameter used to control the transmission timing of a signal on the uplink towards the base station to ensure that the signal arrives at the base station at the right time. The larger the value of TA, the earlier the UE must transmit a signal in order for that signal to arrive at the base station at the correct time. In NTN systems, signals are relayed via satellites and therefore must travel a longer distance than in non-NTN wireless networks. Thus, the applied Timing Advance (TA) of the UE may be affected (change) by one or more of the UE's location, the serving satellite's location, and the applied Timing Offset. Summary of the Invention [Problem to be solved by the invention]

[0015] Due to the fast moving nature of LEO and MEO satellites, the uplink TA of a UE may be adversely affected when communicating through an NTN. Although it is not clear how fast the satellites move towards or away from the UE, it will be appreciated that the associated round trip delay (RTD) in an NTN will change faster than in legacy (non-NTN) networks. For example, in terrestrial NR networks, the UE uplink timing is controlled by the so-called timing advance command (parameter N TA_offset ) by the base station (gNB) via a closed loop using the LTE-20 ...

[0016] Incorrect time alignment adversely affects decodability of the uplink signal at the base station due to inter-system interface (ISI) and / or frame ambiguity. Furthermore, the TA value is also used to apply the appropriate timing offset between the UE and the base station, e.g., for UE scheduling in the uplink and for determining the start of the response window in the downlink.

[0017] The inventors have noticed that with the more frequent TA adjustments required in an NTN system, the associated signaling between the UE and its serving base station increases. Although it is possible for the UE to derive an appropriate TA value by itself, there are concerns regarding the accuracy of such self-computed TA values, and additional signaling from the network to the UE may be required for TA refinement (e.g., during initial access and / or TA maintenance).

[0018] Furthermore, the UE and base station need to have the same timing offset. However, the information on which the timing offset is based is not symmetrical without reporting by the UE or using traditional closed-loop adjustment by the base station, which would be inefficient in NTN and wasteful of resources. If the UE implicitly determines the timing offset to be applied (e.g., from a Timing Advance Command (TAC)), it is not clear what happens if the UE misses a TAC or if the base station needs to send multiple TACs (which could result in asymmetric knowledge levels at the UE and base station).

[0019] Currently proposed methods to maintain proper time alignment require excessive signaling between the UE and the base station (e.g., TA reports by the UE to maintain uplink alignment at the gNB side) and / or additional processing / increased battery usage at the UE (e.g., open-loop TA maintenance by the UE based on Global Navigation Satellite System (GNSS) positioning).

[0020] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS The present invention therefore provides a method, and associated apparatus, that addresses or at least alleviates (at least some of) the problems set forth above.

[0021] For ease of understanding by those skilled in the art, the present invention will be described in detail in the context of 3GPP systems (5G networks including NTN), however, the principles of the present invention can be applied to other systems as well. [Means for solving the problem]

[0022] In one aspect, the present invention provides a method performed by a user equipment (UE) configured to communicate over a non-terrestrial based network, the method comprising obtaining information identifying a threshold corresponding to a timing advance value to be applied to communications with a network node over the non-terrestrial based network, obtaining a timing advance value for communications with the network node, and determining whether to transmit a timing advance report to the network node based on the timing advance value and the threshold.

[0023] In one aspect, the present invention provides a method performed by a user equipment (UE) configured to communicate over a non-terrestrial based network, the method comprising obtaining information for use in predicting a timing advance value to be used for communication with a network node, obtaining a timing advance value, deriving a predicted timing advance value based on the obtained information, and determining whether to transmit a timing advance report to the network node based on the obtained timing advance value and the predicted timing advance value.

[0024] In one aspect, the present invention provides a method performed by a network node configured to communicate with a user equipment (UE) over a non-terrestrial based network, the method comprising transmitting information to the UE identifying a threshold value corresponding to a timing advance value to be applied for communications with the UE over the non-terrestrial based network, obtaining a timing advance value for communications with the UE, and receiving a timing advance report from the UE based on the threshold value and the timing advance value obtained by the UE.

[0025] In one aspect, the present invention provides a method performed by a network node configured to communicate with a user equipment (UE) over a non-terrestrial based network, the method comprising transmitting to the UE information for use in predicting a timing advance value to be used in communications between the UE and the network node, and receiving a timing advance report from the UE based on a timing advance value obtained by the UE and the predicted timing advance value.

[0026] In one aspect, the present invention provides a user equipment (UE) configured to communicate over a non-terrestrial based network, the UE having means for obtaining information identifying a threshold corresponding to a timing advance value to be applied for communication with a network node over the non-terrestrial based network, means for obtaining a timing advance value for communication with the network node, and means for determining whether to transmit a timing advance report to the network node based on the timing advance value and the threshold.

[0027] In one aspect, the present invention provides a user equipment (UE) configured to communicate over a non-terrestrial based network, the UE having means for obtaining information used in predicting a timing advance value to be used for communication with a network node, means for obtaining a timing advance value, means for deriving a predicted timing advance value based on the obtained information, and means for determining whether to send a timing advance report to the network node based on the obtained timing advance value and the predicted timing advance value.

[0028] In one aspect, the present invention provides a network node configured to communicate with a user equipment (UE) via a non-terrestrial based network, the network node having means for transmitting information to the UE identifying an associated threshold value corresponding to a timing advance value to be applied for communications with the UE via the non-terrestrial based network, means for obtaining a timing advance value for communications with the UE, and means for receiving a timing advance report from the UE based on the threshold value and the timing advance value obtained by the UE.

[0029] In one aspect, the present invention provides a network node arranged to communicate with a user equipment (UE) via a non-terrestrial based network, the network node having means for transmitting to the UE information for use in predicting a timing advance value for use in communication between the UE and the network node, and means for receiving a timing advance report from the UE based on a timing advance value obtained by the UE and the predicted timing advance value.

[0030] In one aspect, the present invention provides a user equipment (UE) configured to communicate over a non-terrestrial based network, the UE having a processor, a transceiver, and a memory storing instructions, the controller configured to obtain information identifying a threshold value corresponding to a timing advance value to be applied to communication with a network node over the non-terrestrial based network, obtain a timing advance value for communication with the network node, and determine whether to transmit a timing advance report to the network node based on the timing advance value and the threshold value.

[0031] In one aspect, the present invention provides a user equipment (UE) configured to communicate over a non-terrestrial based network, the UE having a processor, a transceiver, and a memory storing instructions, and a controller configured to obtain information used in predicting a timing advance value to be used in communicating with a network node, obtain a timing advance value, derive a predicted timing advance value based on the obtained information, and determine whether to transmit a timing advance report to the network node based on the obtained timing advance value and the predicted timing advance value.

[0032] In one aspect, the present invention provides a network node configured to communicate with a user equipment (UE) over a non-terrestrial based network, the network node having a processor, a transceiver, and a memory storing instructions, the controller is configured to control the transceiver to send information to the UE identifying a threshold value corresponding to a timing advance value to be applied to communications with the UE over the non-terrestrial based network, obtain a timing advance value for communications with the UE, and control the transceiver to receive a timing advance report from the UE based on the threshold value and the timing advance value obtained by the UE.

[0033] In one aspect, the present invention provides a network node configured to communicate with a user equipment (UE) over a non-terrestrial network, the network node having a processor, a transceiver, and a memory storing instructions, the controller is configured to control the transceiver to transmit to the UE information used in predicting a timing advance value to be used in communication between the UE and the network node, and to receive a timing advance report from the UE based on a timing advance value obtained by the UE and a predicted timing advance value.

[0034] Aspects of the present invention extend to corresponding systems, apparatus, and computer program products, such as a computer-readable storage medium operable to program a programmable processor to perform the methods described in the above aspects and possibilities or as claimed, and / or having instructions stored thereon to program a computer suitably adapted to provide an apparatus as described in any of the claims.

[0035] Each feature disclosed in this specification (including the claims) and / or illustrated in the drawings may be incorporated in the present invention independently of (or in combination with) other disclosed and / or illustrated features. In particular, but not limited to, features of any claim that are dependent on a particular independent claim may be introduced in any combination or individually in the independent claim.

[0036] term -TAC=Timing Advance Command TAT=Time Alignment Timer (timer that determines how long a TA can remain valid before the UE is considered to be out of sync). -NTA indicates the absolute TAC (initialized by a 12-bit number sent by the gNB in ​​the random access response (RAR) message during initial access). -N TA_offset is a 6-bit number that notifies the UE of the misalignment between the base station and the UE (N TA_offset is sent by the gNB via the appropriate Medium Access Control Element (MAC CE) when the gNB detects a misalignment (see 3GPP TS 38.213 V16.4.0 and 3GPP TS 38.321 V16.3.0). TA_offset may be used to update an old NTA used by the UE (N TA_new =N TA_old +NTA_offset ). -Common TA (exact definition not yet agreed by 3GPP) --May be equal to the feeder link duration plus the service link duration to a terrestrial reference point (see, for example, Figure 6.3.4-1 of 3GPP TR 38.821). May refer to feeder link RTDs only (see, for example, 3GPP draft R1-2102215). -K_offset (also called common TA) is common to all UEs in a cell and is used as an offset (given as a number of subframes) for uplink misalignment before initial access (may be updated after initial access, see 3GPP draft R1-2102078). - K_mac: Used by the UE to adjust the downlink response window in case of frame timing misalignment on the gNB side (when the UE is uplink synchronized but not frame synchronized). Timing offset is the term used herein to describe the offset, in frames, used for uplink (UL) scheduling and downlink (DL) response windows. (UE and gNB may use the same timing offset, which may initially be equal to K_offset). [Brief description of the drawings]

[0037] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0038] [Figure 1] FIG. 1 illustrates diagrammatically a mobile (cellular or wireless) communication system in which embodiments of the present invention are applicable. [Diagram 2] FIG. 2 is a schematic block diagram of a mobile device forming part of the system shown in FIG. [Diagram 3] FIG. 3 is a schematic block diagram of an NTN node (e.g., a satellite / UAS platform) forming part of the system shown in FIG. [Figure 4] FIG. 4 is a schematic block diagram of an access network node (eg a base station) forming part of the system shown in FIG. [Diagram 5] FIG. 5 shows a schematic diagram of the change over time in the round trip time of a feeder link. [Figure 6] FIG. 6 illustrates a schematic diagram of a timing advance adjustment procedure during an initial access. [Figure 7] FIG. 7 is a flow chart that illustrates generally a timing advance update procedure performed by a mobile device. [Figure 8] FIG. 8 illustrates diagrammatically some exemplary architectural options for providing NTN functionality in the system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] overview FIG. 1 illustrates diagrammatically a mobile (cellular or wireless) communication system 1 in which embodiments of the present invention can be applied.

[0040] In this system 1, a user of a mobile device 3 (UE) communicates with an access network node using a suitable 3GPP radio access technology (RAT), for example E-UTRA and / or 5G RAT. ( Each satellite 5 and / or base station 6 ) and data network 7. As one skilled in the art will appreciate, while FIG. 1 shows three mobile devices 3, one satellite 5 and one base station 6 for illustrative purposes, the system when implemented will typically include other satellite / UAS platforms, base stations / RAN nodes, and mobile devices (UE).

[0041] It will be understood that several base stations 6 form a (radio) access network or (R)AN, and several NTN nodes 5 (satellite and / or UAS platforms) form a non-terrestrial based network (NTN). Each NTN node 5 is connected to an appropriate gateway (in this case collocated with the base station 6) using a so-called feeder link and connected to each UE 3 via a corresponding service link. Thus, if the NTN node 5 provides a service, the mobile device 3 communicates data to and from the base station 6 via the NTN node 5 using the appropriate service link (between the mobile device 3 and the NTN node 5) and the feeder link (between the NTN node 5 and the gateway / base station 6). In other words, the NTN forms part of the (R)AN, but can also provide satellite communication services independently of E-UTRA and / or 5G communication services.

[0042] Although not shown in Figure 1, neighbouring base stations 6 are connected to each other via appropriate inter-base station interfaces (so-called "X2" interfaces, "Xn" interfaces, etc.) and the base stations 6 are connected to data network nodes via appropriate interfaces (so-called "S1", "NG-C", "NG-U" interfaces, etc.).

[0043] A data (or core) network 7 (e.g., EPC in LTE, NGC in NR / 5G) typically supports communications in the communication system 1 and includes logical nodes (or functions) for subscriber management, mobility management, charging, security, call / session management, etc. For example, the data network 7 in a "next generation" / 5G system includes user plane entities and control plane entities, such as one or more control plane functions (CPF) and one or more user plane functions (UPF). The data network 7 is also coupled to other data networks, such as the Internet or a similar Internet Protocol (IP)-based network (not shown in FIG. 1). Each NTN node 5 controls a number of directional beams in which an associated NTN cell may be provided. Specifically, each beam has an associated footprint on the Earth's surface that corresponds to the NTN cell. Each NTN cell (beam) has an associated Physical Cell Identity (PCI) and / or beam ID. The beam footprint may move as the NTN node 5 moves along its orbit. Alternatively, the beam footprint may be Earth-fixed, in which case an appropriate beam pointing mechanism (mechanical or electronic steering) can be used to compensate for movement of the NTN node 5.

[0044] Due to the movement of the satellite along its orbit, the distance between the UE 3 and the current NTN node 5 changes relatively quickly, and the characteristics of the service link (e.g. delay) change accordingly. The characteristics of the feeder link change as well, due to the change in the distance between the NTN node 5 and the base station 6 as the satellite moves. These changes affect the overall RTD between the UE 3 and the base station 6, necessitating appropriate adjustments of the timing advance / time offset used between them.

[0045] To support proper time and frequency synchronization between the UE 3 and the base station 6, when the UE 3 is connected via the NTN node 5 (RRC connected state), it is configured to perform UE-specific TA calculations based at least on GNSS acquired positions and serving satellite ephemeris. To update TA in the RRC connected state, the UE 3 can use an open control loop (e.g., UE autonomous TA estimation, common TA estimation, etc.), or a closed control loop (e.g., received TA command), or a combination thereof.

[0046] Specifically, the UE3 is configured to use one of the following approaches: - Optimized TAT values ​​and configurable thresholds to minimize the need for TA reports to base station 6. - An optimized TAT value, and a TA that is calculated autonomously and reported to the base station 6 only if the difference from the prediction affects the timing offset beyond a configurable threshold. - the TA obtained using the optimized TAT value and a prediction model that may be modified over time (if necessary). The TA is reported to the base station 6 only if the difference from the prediction affects the timing offset beyond a configurable threshold.

[0047] Beneficially, the above techniques allow for reducing / minimizing signaling related to TA updates without causing misalignment between the UE 3 and the base station 6. Furthermore, reduced / more efficient timing offset signaling can be achieved by employing implicit offset derivation techniques from the TA, reported and / or predicted from the UE.

[0048] For example, for a UE 3 with good GNSS / autonomous TA updates, no signaling is required (no TA report) as long as the TA does not affect the timing offset. The base station 6 can set an appropriate (flexible) TAT value for the UE 3 depending on the situation, which can further reduce the signaling required by the UE 3 and / or improve the TA correction by the UE 3.

[0049] Since the timing offset is derived from the (perfect) TA, there is no need to use signaling to indicate the actual timing offset (implicit solution) if both the UE 3 and the base station 6 have this information. If a predictive model is used, the timing offset can be updated with reduced / removed signaling.

[0050] User Equipment (UE) FIG. 2 is a block diagram showing the main components of the mobile device (UE) 3 shown in FIG. 1. As shown in the figure, the UE 3 includes a transceiver circuit 31 operable to transmit and receive signals to and from at least one connected node via one or more antennas 33. Although not necessarily shown in FIG. 2, the UE 3 of course has all the usual functions of a normal mobile device (such as a user interface 35), which may be provided by any one or any suitable combination of hardware, software, and firmware. A controller 37 controls the operation of the UE 3 according to software stored in a memory 39. The software may be pre-installed in the memory 39 or may be downloaded via the communication network 1, for example from a removable data storage device (RMD). The software includes, among other things, an operating system 41 and a communication control module 43.

[0051] The communication control module 43 is responsible for processing (generating / sending / receiving) signaling messages and uplink / downlink data packets between the UE 3 and other nodes including NTN nodes 5, (R)AN nodes 6, and core network nodes. The signaling may include control signaling related to time and frequency synchronization between the UE 3 and the base station / gateway 6.

[0052] NTN Node (Satellite / UAS Platform) FIG. 3 is a block diagram showing the main components of the NTN node 5 (satellite / UAS platform) shown in FIG. 1. As shown in the figure, the NTN node 5 includes a transceiver circuit 51 operable to transmit and receive signals to and from at least one connected UE 3 via one or more antennas 53, and to transmit and receive signals to and from other network nodes, such as gateways and base stations (directly or indirectly). A controller 57 controls the operation of the NTN node 5 according to software stored in a memory 59. The software may be pre-installed in the memory 59 or may be downloaded via the communication network 1, for example from a removable data storage device (RMD). The software includes, among other things, an operating system 61 and a communication control module 63.

[0053] The communication control module 63 is responsible for handling (generating / sending / receiving) signaling between the NTN node 5 and other nodes such as the UE 3, base stations 6, gateways, and (via the base stations / gateways) core network nodes. The signaling may include control signaling for time and frequency synchronization between the UE 3 and the base stations / gateways 6.

[0054] Base Station / Gateway (Access Network Node) FIG. 4 is a block diagram showing the main components of the gateway 6 (base station (gNB) or similar access network node) shown in FIG. 1. As shown in the figure, the gateway / gNB 6 includes a transceiver circuit 71 operable to transmit and receive signals to and from at least one connected UE 3 via one or more antennas 73, and to transmit and receive signals to and from other network nodes (directly or indirectly) via a network interface 75. Signals may be transmitted and received directly and / or via NTN nodes 5 to and from at least one UE 3. The network interface 75 typically includes a suitable base station-base station interface (such as X2 / Xn) and a suitable base station-core network interface (such as S1 / NG-C / NG-U). The controller 77 controls the operation of the base station 6 according to software stored in the memory 79. The software may be pre-installed in the memory 79 or may be downloaded via the communication network 1, for example from a removable data storage device (RMD). The software includes, among other things, an operating system 81 and a communication control module 83.

[0055] The communication control module 83 is responsible for handling (generating / sending / receiving) signaling between the base station 6 and other nodes (such as the UE 3, the NTN node 5, and the core network nodes). The signaling may include control signaling related to time and frequency synchronization between the UE 3 and the base station / gateway 6.

[0056] Detailed Description The timing advance used by the UE 3 may be influenced (changed) by one or more of the following: the UE's location, the serving satellite's location, and the timing offset. The following assumptions can be made regarding these parameters: The UE's location is not known to the base station 6 without a large amount of signaling (although location information may be needed for reasons other than TA decisions). Also, some UEs are not able to derive or are not configured to derive their location (or are not able to or are not configured to provide their location to the base station 6). However, the TA reporting process may give the base station 6 sufficient information about the UE's location. At least for initial access, the position of the serving satellite is obtained by the UE 3 from the satellite's orbital information data, which also includes information identifying the satellite's future position (or path), from which the specific part of the serving link of the complete TA can be determined. The base station 6 can broadcast common TA parameters, which also include TA information for the feeder link (also called the specific part of the feeder link of the complete TA). - The UE 3 and base station 6 need to use the same timing offset (e.g. given by K_Offset = service link + feeder link delay). The base station 6 needs to know the location of the UE 3 (or at least the complete TA) and the UE 3 needs to have information about the feeder link used by the base station 6 (which may not be as predictable as the service link). Typically the base station 6 broadcasts information about the feeder link via the system information, but the feeder link may not be known in advance.

[0057] The system is able to reduce / minimize signaling associated with TA updates through one or more (combinations of) key features.

[0058] Downlink TAC signaling can be reduced (or avoided altogether) by having an accurately calculated or estimated TA, which can be achieved by the following features: Using GNSS capability, the UE 3 is always UL synchronized (the base station 6 only needs to adjust the UE's TA in case of an incorrect estimation). Even without using GNSS during the RRC connected state, the UE 3 can be UL synchronized without requiring signaling from the base station 6, for example by using an appropriate TA prediction model (broadcast by the base station 6 in the system information or provided over-the-air). In either case, there is no need for the base station 6 to transmit the TAC (or transmit it less frequently if the TAT is set to a relatively high value), since an accurate TA estimation could potentially lead to an infinite TAT. It will be appreciated that the accuracy of the TA estimation may vary (over time and from UE to UE), but if the TA estimation is good, the TAT may be set to infinity.

[0059] Uplink TA reporting can be reduced (or avoided altogether) using appropriate thresholds. -UE3 may be configured to use GNSS and compare GNSS-based location information with predictive models. - If the GNSS and predictive model based positions are substantially the same or the difference is within a threshold, then UE3 can use either the GNSS based position information (to improve accuracy and avoid TA adjustments) or the predictive model of the TA, and the offset information will be symmetric.

[0060] To achieve efficient signaling of timing offsets, the nodes of the system benefit from one or more (combinations of) the following: In traditional closed loop control, the UE 3 is TA aligned and the base station 6 has full knowledge of the UE's situation to update the timing offset as needed. However, this approach requires a lot of DL signaling. -TA is more sensitive to misalignment (0.52 μs) than to timing offset (1 subframe or 1 ms). As long as the UE's UL TA is correct, decodability / ISI is not an issue for the base station 6. Therefore, the base station 6 does not need to know the exact TA.

[0061] Figure 5 shows a schematic of how the RTT of a feeder link varies over time during one pass of a satellite (in this example the VLEO 200 satellite). The feeder link is known in advance and is periodically broadcast by the gNB. The service link is UE specific but has a similar U-shape to the feeder link shown in Figure 5. It is therefore easily predictable (e.g. it can be stored by trial and error).

[0062] The advantage associated with using such prediction is that the UE 3 and the base station 6 have the same level of information without signaling by independently predicting the same TA. The UE 3 can be configured to make fine corrections to the TA while knowing if the timing offset is affected by these corrections. The goal is to reduce the triggering of explicit TA or offset updates between the UE 3 and the base station 6.

[0063] In the following, we describe some exemplary ways (solutions 1 to 2b) in which the above procedure can be implemented in the system shown in FIG.

[0064] Solution 1: Minimal TA reporting using reporting thresholds In this case, the initial access procedure is used to provide more efficient signaling options for the remaining communications. The UE 3 may indicate, implicitly or explicitly, whether to perform open-loop TA control (e.g. to avoid the use of GNSS) or traditional closed-loop. Alternatively, in the absence of such an indication from the UE 3, open-loop (or closed-loop) TA control may be applied by default. The base station 6 may set an appropriate TA reporting period, at least one threshold and at least one TAT value, which may also be based on the TA modification for the initial access.

[0065] The parameters can be changed later by the base station 6 if required.

[0066] In this example, the UE 3 is configured to autonomously acquire its TA and triggers a TA report only if the acquired TA affects the timing offset, as configured by an associated threshold provided by the base station 6.

[0067] Beneficially, only minimal and necessary TA reporting is performed between the UE 3 and the base station 6. The amount of TA updates and the appropriate TAT are configured during the initial connection setup.

[0068] Solution 2 This solution also uses a prediction model. The parameters of the prediction model are agreed during initial connection and the parameters of the prediction model may be broadcast or stored in a database accessible to the UE 3. The base station 6 may update the parameters of the prediction model from time to time (if necessary). A few (e.g. three) measurements may be sufficient to provide a "U-shaped" interpolation curve (see Figure 5) for predicting the evolution of the UE's TA over time.

[0069] The base station 6 and the UE 3 use the predicted TA (which is based on the same prediction model parameters) to derive the same timing offset and apply this offset when communicating with each other.

[0070] The UE 3 may apply TA using an estimated TA (eg, derived using GNSS) or a predicted TA (eg, corrected by TAC) to maintain UL synchronization with a relatively fine granularity.

[0071] It will be appreciated that the optimum change in estimated timing offset will not occur simultaneously with the predicted and common change with base station 6. However, if this remains within the margin of error (e.g. predicted=14.9ms->offset=17ms but estimated=15.3ms), then there is no need to inform base station 6 and the current offset can be used.

[0072] The UE 3 can know if the actual TA is likely to differ from the predicted TA in such a way that the agreed timing offset is inappropriate (e.g. predicted=14.9ms->offset=17ms, estimated=17.3ms), in which case the UE 3 can inform the base station 6 that the current offset cannot be used. A sufficiently large error (i.e. predicted=14.9ms->offset=15, 16, 17, 18ms?) can reduce the need for signalling, but further increase the associated round trip delay which is already large in the NTN.

[0073] If the UE 3 needs to inform the base station 6 that the prediction model is too inaccurate, the prediction model needs to be updated at both the UE 3 and the base station 6 to allow the same level of knowledge (and timing offset derivation).

[0074] Solution 2a In this case, the prediction model is only used to derive the timing offset. Both the UE 3 and the base station 6 have access to the same level of information (initial TA and prediction model), which is not affected by potential mistakes in the TAC. The UE 3 can obtain an accurate TA using other TA estimation methods (e.g. GNSS). The UE 3 can derive which offset (derived from the same predicted TA) is used by the base station 6 and compare it with the accurately estimated TA (or an offset derived from the estimated TA).

[0075] The UE 3 only notifies the base station 6 if it determines that the derived base station 6 offset is not appropriate (i.e., the prediction model is too off). In many cases, even a slightly erroneous prediction model, where there is a sufficient margin of error in the offset, can give good results in making the predicted offset appropriate.

[0076] The advantage of this solution is that the signaling related to TA reports can be further reduced (or completely removed).

[0077] Solution 2b

[0078] In this case, the prediction model is also used for the actual TA adjustment. Both the UE 3 and the base station 6 have access to the same level of initial information (prediction model and initial TA). The UE 3 applies the TA using the prediction model. Consistent failure to decode the TAC may result in misalignment of the TA information between the base station 6 and the UE 3 (e.g., the base station 6 may think that the UE 3 corrected the TA three times based on three TACs, when the UE failed to decode twice and corrected only once). However, misalignment of the TA information does not affect the applied timing offset, since it is derived from the prediction model.

[0079] Advantages associated with this solution include reduced signaling between the UE 3 and the base station 6, improved UE battery consumption (as GNSS is not required after initial access), and no need for GNSS-related measurement gaps.

[0080] TA Coordination Protocol: Initialization (common to all solutions) The following initialization procedures are common to the three solutions mentioned above, with the exception that prediction model signaling in step 2 / 7 is optional for solution 1.

[0081] In detail, the initialization stage includes the following steps: 1. The UE 3 determines whether it is accessing an NTN cell (or a non-NTN cell, i.e. a terrestrial network cell). If the UE 3 is under the coverage of an NTN cell, it becomes aware of the satellite movement with respect to the reference position. This information can be obtained via OTA configuration (from the core network using Non-Access Stratum signaling) or broadcast signaling. 2. The UE 3 obtains from the base station 6 (or a database) information about the RTT prediction model to use in the NTN cell and the appropriate formula for deriving the timing offset from the TA. 3. UE3 calculates (using an algorithm) the optimal uplink TA based on, for example, its current position (GNSS derived), broadcast information and data obtained as part of step 1. 4. The UE 3 applies the TA derived in step 2 to access the Random Access Channel (RACH). The UE 3 receives a timing advance command as part of the RAR from the base station 6 (for RAR, the value of TAC ranges from 0 to 1282). The UE 3 adjusts the TA based on the TAC, applies the adjusted TA command to the uplink timing and starts the associated TAT. A timing alignment timer is started even if NTA=0. 5. The UE 3 notifies the base station 6 of the TA to be used (calculated in step 3). 6. The UE 3 indicates to the base station 6 which TA update mechanism to use (optionally including prediction model information since the UE 3 knows its location and can set a more accurate prediction model). 7. As part of the initial access handshake, the base station 6 indicates a dedicated TAT and optionally a TA reporting period and / or threshold to be used by the UE 3 to trigger a TA report.

[0082] TA Coordination Protocol: During RRC_CONNECTED (Solution 1) The threshold for triggering a TA report can be set by the base station 6 (e.g., step 7 above), but may also be pre-configured for the UE 3. The threshold may be given, for example, as a particular difference (value or percentage) in TA since the last report or a periodic timer. For example, the threshold may be the point at which an update to the TA causes or requires a change in the timing offset (this corresponds to the TA having changed by approximately 1 ms since the last update).

[0083] This stage consists of the following steps: 8. Before the time alignment timer expires, UE3 performs the following actions: - a. Monitor for new TA modifications (if any) from base station 6 and modify the TA accordingly for subsequent communications with base station 6. b. In the absence of any corrections from the base station 6, update the calculated TA according to step 3 and use it during subsequent communications with the base station 6. - c. Derive the timing offset corresponding to the calculated TA using the equation in step 2. -d. During communication with base station 6, apply the offset derived in step 8.c. e. Update the TA to the base station 6 if the autonomously calculated TA changes beyond a threshold (configurable by the base station 6). - f. After the TA update, the corresponding offset is derived autonomously and applied during further communication with the base station 6. 9. Before the time alignment timer expires, the base station 6 performs the following actions: -a. Monitor whether TA needs adjustment and correct as necessary. -b. Monitor the UE's TA reports. -c. If a new TA is received from UE3, update the timing offset from step 9.b. - d. Apply the updated timing offset from step 9.c during subsequent communications with the UE 3 (without needing to signal the timing offset to the UE 3). 10. If a TA revision is received (before the TAT expires), the base station 6 may change the TAT value and / or the TA report period / threshold depending on the TA revision etc.

[0084] TA Coordination Protocol: During RRC_CONNECTED (Solution 2a) In this case, both the UE 3 and the base station 6 independently update the timing offset from the prediction model. Beneficially, the trigger for updating TA can be relaxed and the UE 3 can report TA only when necessary (e.g., when inaccurate information on the gNB side affects the validity of the offset). For example, instead of "TA changed by a certain value (e.g., 1 ms) since the last update", the trigger can be "TA is greater than a certain value (e.g., 1 ms) compared to the predicted TA".

[0085] This stage includes the following steps: 8. Before the time alignment timer expires, UE3 performs the following actions: - a. Monitor new TA corrections (if any) from base station 6 and correct the TA accordingly. b. In the absence of any corrections from the base station 6, update the calculated TA according to step 3 and use it during subsequent communications with the base station 6. - c. Derive the estimated timing offset corresponding to the calculated TA using the equation in step 2. - d. Monitor for new prediction model revisions (if any) from base station 6 and revise the prediction model accordingly. - e. Calculate the predicted TA from step 2 / 7 and derive the predicted timing offset. -f. During subsequent communications with base station 6, apply the predicted offset obtained in step 8.d. -g. TA update condition for base station 6: The autonomously calculated TA, taking into account the predicted TA, has been changed beyond a threshold configurable by the base station 6. The UE 3 can assume that the base station 6 has the same predicted TA knowledge. 9. Before the time alignment timer expires, the base station 6 performs the following actions: -a. Monitor whether TA needs adjustment and correct as necessary. -b. Monitor the UE's TA reports. -c. Update the prediction model with the TA from step 9.b and signal the changes to UE3 (optional). -d. Estimate the forecast TA from step 2 / 7 using the current forecast model. -e. Update the timing offset from the TA derived in step 9.d. -f. Apply the timing offset of step 9.e during communication with the UE 3 (no need to signal the timing offset to the UE 3). 10. If a TA correction is received (before the TAT expires), the base station 6 can: - a. Based on the TA correction, correct the prediction model taking this value into account (e.g., if the value is greater than a threshold). -b. Change the TAT value according to the TA correction value.

[0086] TA Coordination Protocol: During RRC_CONNECTED (Solution 2b) In this case, the UE 3 uses the predicted TA for the actual TA adjustment, and the timing offset is derived from the prediction model (rather than the predicted and corrected TA as above). This approach can be followed, for example, when the incremental TA adjustment is inaccurate because the UE 3 is missing or unable to decode one or more TACs. Beneficially, by updating / correcting the prediction model, the appropriate timing offset is always used.

[0087] This stage includes the following steps: 8. Before the time alignment timer expires, UE3 performs the following actions: - a. Monitor new TA corrections (if any) from base station 6 and correct the TA accordingly. b. Calculate the predicted TA from step 2 / 7 and derive the predicted timing offset using the equation in step 2. - c. Apply the offset derived in step 8.b. - d. Apply the TA from the TA predicted in step 8.b and correct it (if any) from the TAC received during communication with the base station 6. - e.g. Condition for updating TA for a NB: The predicted + corrected TA has changed beyond a threshold (configurable by the base station 6), taking into account also the predicted TA. The UE 3 can assume that the base station 6 has the same predicted TA knowledge (but not necessarily the predicted + corrected TA). 9. Before the time alignment timer expires, the base station 6 performs the following actions: -a. Monitor whether TA needs adjustment and correct as necessary. -b. Monitor the UE's TA reports. -c. Update the prediction model in the TA from step 9.b and signal the changes to UE3 (optional). - d. Estimate the predicted TA from the latest prediction model (not including the TAC sent to UE3). - e. Derive a timing offset from the TA in step 9.d and apply it during communication with UE3. 10. If a TA modification is received (before the TAT expires), the base station 6 may: - a. Based on the TA correction, correct the prediction model taking this value into account (e.g., if the value is greater than a threshold). -b. Change the TAT value according to the TA correction value.

[0088] operation Figure 6 is a schematic diagram of a timing advance adjustment procedure during initial access in a 5G (NR) radio access network. In fact, the steps shown in Figure 6 correspond to the general procedure described above in the section "TA Adjustment Protocol: Initialization (common to all solutions)".

[0089] In this example, in step S01, the base station or gNB 6 signals NTN satellite information to the UE 3. The NTN satellite information includes feeder link information and information about satellite movement relative to a reference position.

[0090] Optionally, in step S02, the gNB 6 may send to the UE 3 information about the RTT prediction model used in the NTN cell and the appropriate formula for deriving the timing offset from the TA. The information sent to the UE 3 may depend on the solution used.

[0091] In step S03, the UE 3 calculates an optimal uplink TA (UE specific TA) based on, for example, its current location (derived using GNSS if available), broadcast information and acquired NTN satellite information.

[0092] In step S04, the UE 3 derives and applies a timing offset based on the TA, and in step S05 reports the TA to the gNB 6 (e.g., as part of a RACH procedure). Optionally, as generally indicated in step S06, the UE 3 may send information regarding the TA update mechanism and prediction model to be used.

[0093] Based on the TA from UE3, the gNB6 also derives and applies a timing offset in step S07, and indicates an appropriate dedicated TAT value (as well as a TA reporting period, if necessary) to the UE3 in step S08.

[0094] This completes the initialization phase where UE3 and gNB6 apply the same TA value / timing offset and have the same level of knowledge to subsequently update the TA according to the applicable TA adjustment protocol.

[0095] FIG. 7 is a flow chart that illustrates a schematic timing advance update procedure performed by a mobile device during the RRC Connected state (i.e., after initial access). In particular, the flow chart illustrates an example in which the UE 3 determines when to send a TA report to the gNB 6 (e.g., based on a threshold according to solution 1 (see step S16) or based on a prediction model according to solutions 2a or 2b). Although the flow chart illustrates various options, such as solution 2a and solution 2b, the UE 3 may be configured to perform only one of the options, in which case the branches of the flow chart corresponding to the other options are ignored. Alternatively, if the UE 3 is configured to use GNSS measurements in addition to the prediction model, the steps related to the UE predictions and the UE measurements may be performed substantially simultaneously.

[0096] Modifications and Substitutions Detailed embodiments have been described above. As will be appreciated by those skilled in the art, the above embodiments are susceptible to several modifications and variations while still benefiting from the invention embodied therein. By way of example, some of these alternatives and variations are described.

[0097] It will be understood that the above embodiments are applicable to both 5G New Radio and LTE systems (E-UTRAN). A base station (gateway) supporting E-UTRAN / 4G protocols can be referred to as an "eNB", and a base station supporting next-generation / 5G protocols can be referred to as a "gNB". It will be understood that some base stations can be configured to support both 4G and 5G protocols, and / or other 3GPP or non-3GPP communication protocols.

[0098] LEO satellites may have steerable beams, in which case the beams are temporarily directed to a substantially fixed footprint on the Earth. In other words, the beam footprint (representing the NTN cell) is stationary on the ground for a certain time before changing focal area to another NTN cell (due to the orbital movement of the satellite). From a cell coverage / UE point of view, this results in cell changes occurring periodically at discrete intervals, even if these beams serve the same land area (have the same footprint), since different Physical Cell Identity (PCI) and / or Synchronization Signal / Physical Broadcast Channel (SSB) blocks must be assigned after each service link change. LEO satellites without steerable beams have beams (cells) constantly moving in a sweeping motion over the Earth as the satellite moves along its orbit, and service link changes, and therefore cell changes, occur periodically at discrete intervals, just as in the case of steerable beams.

[0099] Similar to the service link change, the feeder link change also occurs periodically due to the orbital movement of the satellite. Both the service link and the feeder link change may be performed between different base stations / gateways (sometimes called inter-gNB radio link switch) or within the same base station / gateway (intra-gNB radio link switch). The above method may be performed upon service and / or feeder link change, as required.

[0100] It will be appreciated that there are various architecture options for implementing NTNs in 5G systems, some of which are shown diagrammatically in FIG. 8. The first option shown is a satellite / aircraft based NTN featuring an access network serving UEs, with bent-pipe payloads and terrestrial (satellite hub or gateway level) gNBs. The second option is a satellite / aircraft based NTN featuring an access network serving UEs, with gNBs. The third option is a satellite / aircraft based NTN featuring an access network serving relay nodes, with bent-pipe payloads. The fourth option is a satellite / aircraft based NTN featuring an access network serving relay nodes, with gNBs. Other architecture options may also be used, for example a combination of two or more of the above options. Alternatively, the relay nodes may include satellites / UAS. [Table 1]

[0101] An appropriate TAT value may be set by default in the system information block type 1 (SIB1) and can be reconfigured if necessary as described in 3GPP TS 38.331 V16.3.1. Specifically, the TAT can be (re)configured using appropriate information elements (IEs) of the RRC Reconfiguration message (e.g., rrcReconfiguration IE > secondaryCellGroup IE > CellGroupConfig IE > mac-CellGroupConfig IE > TAG-Config IE > tag-ToAddMod IE > timeAlignmentTimer IE). TIFF0007670160000002.tif76162

[0102] The value of the TimeAlignmentTimer field is specified in milliseconds, allowing the UE to configure a dedicated TAT (for a particular cell / carrier) in the range of 500 ms to 10240 ms, or to infinity.

[0103] In the above description, for ease of understanding, the UE, NTN node (satellite / UAS platform), and access network node (base station) have been described as having several separate modules (such as communication control modules). These modules may be provided in this way for certain applications, such as when an existing system is modified to implement the present invention, but in other applications, such as systems designed from the beginning with the features of the present invention in mind, these modules may be incorporated into the overall operating system or code, and therefore, these modules may not be identified as separate entities. These modules may also be implemented in software, hardware, firmware, or a combination of these.

[0104] Each controller may include any suitable form of processing circuitry including, but not limited to, one or more hardware implemented computer processors, microprocessors, central processing units (CPUs), arithmetic logic units (ALUs), input / output (IO) circuitry, internal memory / cache (program and / or data), processing registers, communications buses (e.g., control buses, data buses, and / or address buses), direct memory access (DMA) facilities, hardware or software implemented counters, pointers, and / or timers, etc.

[0105] In the above embodiment, several software modules have been described. As can be understood by those skilled in the art, the software modules may be provided in compiled or uncompiled form and provided to the UE, NTN node, and access network node (base station) as a signal via a computer network or on a recording medium. Furthermore, the functions performed by some or all of the software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred because it facilitates updates to update the functionality of the UE, NTN node, and access network node (base station).

[0106] The above embodiments are also applicable to "non-mobile" or generally fixed user equipment. Such mobile devices may include MTC / IoT devices and / or the like.

[0107] The method performed by the UE may further include deriving a timing offset for communication with the network node based on the timing advance value.

[0108] The method performed by the UE may further include transmitting a timing advance report to a network node when the timing advance value is determined to have changed beyond a threshold.

[0109] The method performed by the UE may further include obtaining a time alignment timer (TAT) associated with the timing advance value.

[0110] The method performed by the UE may further include indicating whether the UE is configured to use open loop timing advance control or closed loop timing advance control.

[0111] The method performed by the UE may further include obtaining a timing advance value based on a position of the UE obtained using a Global Navigation Satellite System (GNSS).The method performed by the UE may further include obtaining the timing advance value based on a prediction model for at least one of a service link and a feeder link associated with communication with a network node over a non-terrestrial based network.

[0112] The information used to predict the timing advance value may include a set of parameters (e.g., a prediction model) for predicting the timing advance. The set of parameters may be used to derive a timing offset for communication with the network node. The information (or parameters) used to predict the timing advance value may be sent by the network node at initial access or upon receiving a timing advance report from the UE.

[0113] The method performed by the network node may further include transmitting a TAT associated with the timing advance value to the UE.

[0114] The network nodes may include gateways, base station equipment, or satellites having gateway or base station functionality.

[0115] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0116] For example, all or part of the exemplary embodiments disclosed above can be described as follows, but are not limited to these. (Appendix 1) 1. A method performed by a user equipment (UE) configured to communicate over a non-terrestrial based network, comprising: receiving information from a network node identifying threshold values ​​corresponding to respective timing advance values ​​for communications with said network node via said non-terrestrial based network; obtaining a timing advance value for said communication; determining whether to send a timing advance report to the network node based on the timing advance value and the threshold. (Appendix 2) 2. The method of claim 1, further comprising deriving a timing offset for the communication based on the timing advance value. (Appendix 3) determining whether the timing advance value has changed beyond the threshold; 3. The method of claim 1 or 2, further comprising sending the timing advance report to the network node based on the determination of whether the timing advance value has changed by more than the threshold. (Appendix 4) 4. The method of claim 1, further comprising receiving a Time Alignment Timer (TAT) from the network node, the Time Alignment Timer corresponding to the Timing Advance value. (Appendix 5) 5. The method of any one of claims 1 to 4, further comprising transmitting, to the network node, information indicating whether the UE is configured to use open loop timing advance control or closed loop timing advance control. (Appendix 6) 6. The method according to any one of claims 1 to 5, wherein the obtaining of the timing advance value is performed based on the position of the UE obtained using a Global Navigation Satellite System (GNSS). (Appendix 7) 7. The method of any one of claims 1 to 6, wherein the obtaining of the timing advance value is performed based on a prediction model for at least one of a service link and a feeder link corresponding to the communication. (Appendix 8) 1. A method performed by a user equipment (UE) configured to communicate over a non-terrestrial based network, comprising: receiving information from a network node for predicting a timing advance value for communications with said network node; Get the timing advance value, deriving a predicted timing advance value based on said information; determining whether to send a timing advance report to the network node based on a timing advance value and the predicted timing advance value. (Appendix 9) 9. The method of claim 8, wherein the information includes a set of parameters for predicting the timing advance value. (Appendix 10) 10. The method of claim 9, wherein the set of parameters is used to derive a timing offset for the communication. (Appendix 11) 11. The method of any one of claims 8 to 10, wherein the receiving of the information is performed upon initial access or in response to sending the timing advance report. (Appendix 12) 1. A method performed by a network node configured to communicate with User Equipment (UE) over a non-terrestrial based network, comprising: transmitting, to the UE, information identifying threshold values ​​corresponding to respective timing advance values ​​to be applied to communications with the UE via the non-terrestrial network; obtaining a timing advance value for said communication; The method includes receiving a timing advance report from the UE based on the threshold and the timing advance value. (Appendix 13) 13. The method of claim 12, further comprising transmitting a Time Alignment Timer (TAT) corresponding to the timing advance value to the UE. (Appendix 14) 1. A method performed by a network node configured to communicate with a user equipment (UE) over a non-terrestrial based network, comprising: sending, to the UE, information for predicting a timing advance value for communication between the UE and the network node; The method includes receiving a timing advance report from the UE based on the predicted timing advance value. (Appendix 15) 15. The method of claim 14, wherein the transmitting of the information is performed upon initial access or upon receipt of the timing advance report. (Appendix 16) 16. The method of any one of claims 12 to 15, wherein the network node comprises a gateway, a base station, or a satellite having gateway or base station functionality. (Appendix 17) A user equipment (UE) configured to communicate over a non-terrestrial network, means for receiving, from a network node, information identifying threshold values ​​corresponding to respective timing advance values ​​for communications with said network node via said non-terrestrial based network; means for obtaining a timing advance value for said communication; and means for determining whether to send a timing advance report to the network node based on the timing advance value and the threshold. (Appendix 18) A user equipment (UE) configured to communicate over a non-terrestrial network, means for receiving information from a network node for predicting a timing advance value for communications with said network node; A means for obtaining a timing advance value; means for deriving a predicted timing advance value based on said information; and means for determining whether to send a timing advance report to the network node based on the timing advance value and the predicted timing advance value. (Appendix 19) A network node configured to communicate with a User Equipment (UE) via a non-terrestrial network, comprising: means for transmitting, to the UE, information identifying threshold values ​​corresponding to respective timing advance values ​​to be applied for communications with the UE via the non-terrestrial network; means for obtaining a timing advance value for said communication; and means for receiving a timing advance report from the UE based on the threshold and the timing advance value. (Appendix 20) A network node configured to communicate with a User Equipment (UE) via a non-terrestrial network, comprising: means for transmitting, to the UE, information for predicting a timing advance value for communication between the UE and a network node; and means for receiving a timing advance report from the UE based on the predicted timing advance value.

[0117] This application is based on and claims the benefit of priority to UK patent application No. 2104780.8, filed April 1, 2021, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0118] 1. Mobile communication systems 3. Mobile device users 5 satellites 6 base station 7 Data Network 31 Transceiver Circuit 33 Antenna 35 User Interface 37 Controller 39 Memory 41 Operating Systems 43 Communication Control Module 51 Transceiver Circuit 53 Antenna 57 Controller 59 Memory 61 Operating Systems 63 Communication Control Module 71 Transceiver Circuit 73 Antenna 75 Network Interface 77 Controller 79 Memory 81 Operating Systems 83 Communication Control Module

Claims

1. 1. A User Equipment (UE) configured to communicate over a non-terrestrial based network, comprising: means for receiving, from an access network node, information indicative of a threshold value corresponding to a timing advance value for communications with said access network node; means for calculating a UE-specific timing advance estimate based on a current location of the UE and ephemeris of a satellite handling communication of the non-terrestrial network; means for determining whether to send a timing advance report to the access network node based on whether a difference between the timing advance estimate and a previously reported timing advance value is equal to or greater than the threshold; A UE comprising: means for transmitting the timing advance report to the access network node if the difference is equal to or greater than the threshold. The UE of claim 1.

3. The calculating means calculates the timing advance estimate based on a position of the satellite relative to a reference point.

3. The UE according to claim 1 or 2.

4. 1. An access network node configured to communicate with User Equipment (UE) via a non-terrestrial based network, comprising: means for transmitting, to the UE, information indicative of a threshold value corresponding to a timing advance value for communication with the access network node; means for receiving from the UE a timing advance estimate specific to the UE, the timing advance estimate being calculated by the UE based on a current location of the UE and ephemeris of a satellite handling communication of the non-terrestrial network; means for receiving a timing advance report from the UE based on whether a difference between the timing advance estimate and a previously reported timing advance value is equal to or greater than the threshold; An access network node comprising:

5. The access network node comprises a gateway, a base station, or a satellite having the functionality of a gateway or a base station; An access network node according to claim 4.

6. 1. A method in User Equipment (UE) configured to communicate over a non-terrestrial based network, comprising: receiving, from an access network node, information indicative of a threshold value corresponding to a timing advance value for communications with said access network node; calculating a UE-specific timing advance estimate based on a current location of the UE and ephemeris of a satellite handling communication of the non-terrestrial network; determining whether to send a timing advance report to the access network node based on whether a difference between the timing advance estimate and a previously reported timing advance value is equal to or greater than the threshold; A method in a UE, comprising:

7. 1. A method in an access network node arranged to communicate with User Equipment (UE) over a non-terrestrial based network, comprising: transmitting, to the UE, information indicative of a threshold value corresponding to a timing advance value for communication with the access network node; receiving from the UE a UE-specific timing advance estimate calculated by the UE based on a current location of the UE and ephemeris of a satellite handling communication of the non-terrestrial network; receiving a timing advance report from the UE based on whether a difference between the timing advance estimate and a previously reported timing advance value is equal to or greater than the threshold; A method in an access network node comprising:

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