User equipment, methods for user equipment, network nodes, and methods for network nodes

Abstract

A communication system (1) is disclosed in which a user equipment (UE) communicates using beams via a non-terrestrial network. A UE (3) receives information from a network node via the non-terrestrial network identifying a set of at least one candidate beam for beam switching, performs measurements of reference signals transmitted via the at least one candidate beam in the set, initiates the beam switching to a beam in the set based on results of the measurements, and transmits an indication of the beam switching to the network node via the non-terrestrial network.

Description

Technical Field

[0001] The present invention relates to a wireless communication system operating in accordance with 3rd Generation Partner Project (3GPP) standards or their equivalents or derivatives, and devices thereof. The present disclosure is particularly relevant, but not limited to, improvements in beam management in so-called "5G" (or "next generation") systems that employ a non-terrestrial portion including aircraft or spaceborne network nodes.

Background Art

[0002] In 3GPP standards, NodeB (or "eNB" in LTE, "gNB" in 5G) is a base station through which communication devices (user equipment or "UE") connect to a core network and communicate with other communication devices or remote servers. End-user communication devices are generally referred to as user equipment (UE) and are either operated by humans or composed of automated devices. Such communication devices can be, for example, mobile communication devices such as mobile phones, smartphones, smartwatches, personal digital assistants, laptop / tablet computers, web browsers, e-book readers, connected vehicles, etc. Such mobile (or generally fixed) devices are usually operated by users (thus, they are often collectively referred to as user equipment, "UE"), but it is also possible to connect Internet of Things (IoT) devices and similar machine type communication (MTC) devices to the network. For simplicity, in this application, the term base station is used to refer to such base stations, and the terms mobile device or UE are used to refer to such communication devices.

[0003] The latest development in 3GPP standards is the so-called "5G" or "New Radio" (NR) standard, which refers to an evolving communication technology expected to support a variety of applications and services, including MTC, IoT / Industrial IoT (IIoT) communications, vehicle communications and autonomous vehicles, high-definition video streaming, and smart city services. 3GPP plans to support 5G through the so-called 3GPP Next Generation (NextGen) Radio Access Network (RAN) and 3GPP NextGen Core (NGC) networks. Various details about 5G networks are explained, for example, in the Next Generation Mobile Network (NGMN) Alliance's "NGMN 5G White Paper" V1.0, which is available at https: / / www.ngmn.org / 5g-white-paper.html.

[0004] 3GPP is also working on specifying integrated satellite and terrestrial network infrastructure in the context of 4G and 5G. The term Non-Terrestrial Networks (NTN) refers to networks or segments of networks that use aircraft or spacecraft for transmission. Satellites refer to spacecraft in non-geostationary Earth orbits (NGEO), such as geostationary Earth orbit (GEO), low Earth orbit (LEO), medium Earth orbit (MEO), and highly elliptical orbit (HEO). Aircraft refer to high-altitude platforms (HAPs), including unmanned aircraft systems (UAS). This includes tethered UASs, lighter UASs than aircraft, and heavier UASs than aircraft. All of these typically operate in a quasi-geostationary state at altitudes of 8 to 50 kilometers.

[0005] 3GPP TR38.811 V15.4.0 is a study on new radios that support such non-terrestrial networks. This study includes, in particular, descriptions of NTN deployment scenarios and related system parameters (architecture, altitude, orbit, etc.), and the adaptation of 3GPP channel models for non-terrestrial networks (propagation conditions, mobility, etc.). 3GPP TR38.821 V16.1.0 contains further details on NTN.

[0006] The following is expected from non-terrestrial networks: - To improve the performance of terrestrial networks by facilitating the deployment of 5G services in areas where services are not available or are not adequately available. - To enhance the reliability of services by providing continuity of service to user devices or mobile platforms (passenger vehicles, aircraft, ships, high-speed rail, buses, etc.). - To enhance the availability of services everywhere, especially in critical communications, and future rail / maritime / air communications. - To achieve 5G network scalability by providing efficient multicast / broadcast resources for delivering data directly to the network edge or user equipment.

[0007] NTN access typically includes the following elements in particular: -NTN terminal: May refer to a 3GPP UE, or a terminal specific to the satellite system if the satellite does not directly serve the 3GPP UE. - A service link refers to a radio link between user equipment and a space / aviation platform (and may be in addition to a radio link with a ground-based RAN). -Space or aerial platform. - A gateway ("NTN Gateway") connecting satellite or air access networks to the core network. It will be understood that the gateway will likely be installed in the same location as the base stations. - Feeder link. Refers to the wireless link between the gateway and the space / aviation platform.

[0008] Satellites or aircraft may generate multiple beams over a given area to provide separate NTN cells. These beams typically have an elliptical footprint on the Earth's surface.

[0009] 3GPP plans to support the following three types of NTN beams or cells: - Earth-fixed cells (e.g., GEO satellites and HAPS) that feature beams that always cover the same geographical area. - A quasi-Earth-fixed cell characterized by a beam that covers one geographic area for a finite period and a different geographic area for another period (e.g., NGEO satellites that generate steerable beams). - Earth-moving cells characterized by beams that cover one geographical area at one moment and another geographical area at another (e.g., NGEO satellites that generate fixed or unsteerable beams).

[0010] A satellite or aircraft maintains a fixed position at a specific point on Earth in terms of altitude / azimuth. For GEOs and UASs, the beam footprint is fixed to Earth.

[0011] If a satellite orbits the Earth (e.g., a low-earth orbit), or in an elliptical orbit around the Earth (e.g., a high-earth orbit), the beam footprint may move across the Earth in accordance with the movement of the satellite or aircraft in its orbit. Alternatively, the beam footprint can be temporarily fixed to the Earth (or a quasi-Earth), in which case an appropriate beampointing mechanism (mechanical or electronic steering) can be used to compensate for the movement of the satellite or aircraft.

[0012] LEO satellites may have steerable beams, in which case the beam is temporarily directed to a substantially fixed footprint on Earth. In other words, the beam footprint (representing an NTN cell) remains stationary on the ground for a certain period of time before changing its focal area to a different NTN cell (due to the satellite's movement in orbit). From a cell coverage / UE perspective, cell changes occur periodically at discrete intervals because a different Physical Cell Identity (PCI) and / or Synchronization Signal / Physical Broadcast Channel (PBCH) block (SSB) must be assigned after each service link change, even if these beams serve the same land area (have the same footprint). In LEO satellites without steerable beams, the beam (cell) is always moving across the ground in a sweeping motion as the satellite moves along its orbit. Also, as with steerable beams, service link changes and the resulting cell changes occur periodically at discontinuous intervals. Similar to service link changes, feeder link changes also occur periodically due to the satellite's movement in orbit. Both service and feeder link changes can occur between different base stations / gateways (sometimes referred to as "inter-gNB radio link switches") or within the same base station / gateway ("intra-gNB radio link switches").

[0013] 3GPP is working on specifying enhanced beam management and bandwidth part (BWP) operation capabilities for NTN. Beam-level mobility (or "beam switching") is handled at lower layers (Physical: PHY and Media Access Control: MAC) without incurring the additional radio resource control (RRC) signaling overhead associated with conventional handover procedures. Therefore, 3GPP prefers UE-connected mode mobility over handover-based mobility, at least in the case of multi-beam Earth mobile cells. Currently proposed beam-level mobility mechanisms include periodic transmission of Channel State Information Reference Signals (CSI-RS) by base stations and associated measurement reports by UEs, especially in the case of frequent beam switching. Issues related to beam switching have been widely discussed at 3GPP meetings, but no conclusions or agreements have been reached.

[0014] Current measurement-based beam management has been shown to have at least the following problems. - Significant signaling overhead and long delays due to periodic exchange of CSI-RS transmissions and corresponding reports to NTN. -Especially with high-speed moving LEO satellites, the complexity / power consumption at the UE for performing measurements increases.

[0015] When using BWP for NTN, the following issues also need to be addressed. - To cope with frequent and relatively predictable satellite beam switching, appropriate mechanisms such as configured BWP switching may be necessary. -NR BWP switching / beam switching uses UE-specific signaling as the UE moves. This is inefficient in NTN scenarios where satellite BWP / beam switching is common to a set of UEs (serviced by the same satellite). [Prior art documents]

Non-Patent Literature

[0016]

Non-Patent Literature 1

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Non-Patent Literature 4

Patent Literature

[0017]

Patent Literature 1

Summary of the Invention

Problems to be Solved by the Invention

[0018] Therefore, the present disclosure aims to provide a method and related apparatus that address at least a part of the above problems and reduce / optimize, in particular, signaling overhead and measurement effort on the UE side.

Means for Solving the Problems

[0019] In one embodiment, the Disclosure provides a method performed by User Equipment (UE) configured to communicate using beams over a non-terrestrial network, the method comprising: receiving information from a network node over the non-terrestrial network identifying a set of at least one candidate beams for beam switching; performing a measurement of a reference signal transmitted over the at least one candidate beam in the set; initiating the beam switching to a beam in the set based on the results of the measurement; and transmitting an instruction to the network node over the non-terrestrial network to indicate the beam switching.

[0020] In one embodiment, the Disclosure provides a method performed by a network node configured to communicate with User Equipment (UE) using beams over a non-terrestrial network, the method comprising: transmitting information to the UE identifying a set of at least one candidate beams for beam switching; and receiving instructions from the UE when the UE initiates beam switching to a beam in the set based on the result of measuring a reference signal transmitted over the at least one candidate beam in the set.

[0021] In one embodiment, the Disclosure provides User Equipment (UE) configured to communicate using beams over a non-terrestrial network, the UE comprising: means for receiving information from a network node over the non-terrestrial network identifying a set of at least one candidate beams for beam switching; means for performing a measurement of a reference signal transmitted over the at least one candidate beam in the set; means for initiating the beam switching to a beam in the set based on the results of the measurement; and means for transmitting instructions to the network node over the non-terrestrial network to indicate the beam switching.

[0022] In one embodiment, the Disclosure provides a network node configured to communicate with User Equipment (UE) using beams over a non-terrestrial network, the network node comprising means for transmitting information to the UE identifying a set of at least one candidate beams for beam switching, and means for receiving instructions from the UE when the UE initiates beam switching to a beam in the set based on the result of measuring a reference signal transmitted over the at least one candidate beam in the set. [Effects of the Invention]

[0023] For the convenience of those skilled in the art, this disclosure will be described in detail in relation to 3GPP systems (including NTN's 5G network), but the principles of this disclosure can be similarly applied to other systems. Aspects of this disclosure include corresponding systems, apparatus, and computer program products such as computer-readable storage media storing instructions operable to program a programmable processor to perform the methods described in the above aspects, and programming a computer appropriately adapted to provide the apparatus described in the claims and / or any of the claims. Each feature disclosed herein and / or shown in the drawings may be incorporated into this disclosure independently of (or in combination with) other disclosed and / or illustrated features. In particular, but not limited to, any feature of a claim dependent on a particular independent claim may be introduced into that independent claim in any combination or individually. [Brief explanation of the drawing]

[0024] Next, embodiments of the present disclosure will be described as examples with reference to the attached drawings.

[0025] [Figure 1] Figure 1 is a schematic diagram illustrating a mobile (cellular or wireless) telecommunications system to which embodiments of the present disclosure may be applied.

[0026] [Figure 2] Figure 2 is a schematic block diagram of mobile devices that form part of the system shown in Figure 1.

[0027] [Figure 3] Figure 3 is a schematic block diagram of an NTN node (e.g., a satellite / UAS platform) that forms part of the system shown in Figure 1.

[0028] [Figure 4] Figure 4 is a schematic block diagram of an access network node (e.g., a base station) that forms part of the system shown in Figure 1.

[0029] [Figure 5] Figure 5 is a schematic diagram illustrating an exemplary scenario to which the present invention is applied.

[0030] [Figure 6] Figure 6 schematically illustrates several exemplary architectural options for providing NTN functionality in the system shown in Figure 1. [Modes for carrying out the invention]

[0031] <Overview> Figure 1 schematically shows a mobile (cellular or wireless) telecommunications system 1 to which embodiments of the present invention may be applied.

[0032] In this system 1, users of mobile devices 3 (UEs) can communicate with each other and with other users via access network nodes, their respective satellites 5 and / or base stations 6, and data network 7, using appropriate 3GPP radio access technology (RAT), such as Evolved Universal Terrestrial Radio Access (E-UTRA) or 5G RAT. As will be understood by those skilled in the art, Figure 1 shows three mobile devices 3, one satellite 5, and one base station 6 for illustrative purposes, but the system, when implemented, would typically include other satellite / UAS platforms, base station / RAN nodes, and mobile devices (UEs).

[0033] It will be understood that a number of base stations 6 form a (radio) access network or (R)AN, and a number of NTN nodes 5 (satellite and / or UAS platforms) form a non-terrestrial network (NTN). Each NTN node 5 is connected to a suitable gateway (in this case, located in the same place as the base station 6) using a so-called feeder link, and then connected to its respective UE3 via a corresponding service link. Thus, when serviced by an NTN node 5, a mobile device 3 communicates data to and from 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, NTN forms part of the (R)AN but may also provide satellite communication services independently of E-UTRA (or "4G") and / or New Radio (or "5G") communication services.

[0034] Although not shown in Figure 1, adjacent base stations 6 are connected to each other via appropriate inter-base station interfaces (so-called "X2" interfaces, "Xn" interfaces, etc.). Base stations 6 are also connected to data network nodes via appropriate interfaces (so-called "S1", "NG-C", "NG-U" interfaces, etc.).

[0035] The data (or core) network 7 (e.g., EPC for LTE, NGC for NR / 5G) typically supports communications in the telecommunications system 1 and includes logical nodes (or “functions”) for subscriber management, mobility management, charging, security, and call / session management (among other things). For example, the data network 7 in a “next-generation” / 5G system would include user plane entities and control plane entities, such as one or more control plane functions (CPFs) and one or more user plane functions (UPFs). The so-called Access and Mobility Management Function (AMF) in 5G, or Mobility Management Entity (MME) in 4G, is responsible for handling the connection and mobility management tasks of the mobile device 3. The data network 7 is also coupled to other data networks, such as the Internet or similar Internet Protocol (IP) based networks (not shown in Figure 1).

[0036] Each NTN node 5 controls a number of directional beams that may be provided by associated NTN cells. Specifically, each beam has an associated footprint on the Earth's surface corresponding to an 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 fixed to the Earth, in which case the movement of the NTN node 5 can be compensated for using an appropriate beam pointing mechanism (mechanical or electronic steering).

[0037] Each cell is associated with an "NR Cell Global Identifier" (NCGI) for global identification. The NCGI is constructed from the Public Land Mobile Network (PLMN) Identity (PLMN Identity: ID) to which the cell belongs and the cell's NR Cell Identity (NR Cell Identity: NCI). The PLMN ID included in the NCGI is the first PLMN ID in the set of PLMN IDs associated with the NR Cell Identity of System Information Block Type 1 (SIB1). The "gNB identifier" (gNB ID) is used to identify a specific gNB within the PLMN. The gNB ID is included in the cell's NCI. The "global gNB ID" is used to globally identify a gNB and is constructed from the PLMN ID to which the gNB belongs and the gNB ID. The Mobile Country Code (MCC) and Mobile Network Code (MNC) are the same as those included in the NCGI.

[0038] When UE3 first establishes an RRC connection with base station 6 via the cell, UE3 registers with the appropriate AMF9 (or Mobility Management Entity: MME). UE3 is in a so-called RRC connection state, and the associated UE context is maintained by the network.

[0039] When UE3 is serviced via NTN node 5, UE3 sends and receives data through one of NTN node 5's beams (NTN cells). Over time, as UE3 moves and / or the serving NTN node 5 moves, UE3 switches from beam to beam using appropriate mobility procedures. To do this, base station 6 provides UE3 with appropriate configuration data and / or supporting information that enables UE3 to determine which beam to use and when to switch from one beam to another.

[0040] In this system 1, beam-level mobility (or "beam switching") is handled at lower layers (physical layer (PHY) and medium access control (MAC) layer) without requiring additional RRC signaling for each beam switch. Beam-level mobility is based on periodic Channel State Information Reference Signal (CSI-RS) transmissions in each cell (by base station 6, via NTN node 5), taking into account the support information and settings provided by the network (for example, when UE3 establishes or reconfigures its RRC connection).

[0041] To enable efficient beam switching (which requires reduced / optimized measurement work in UE3) while maintaining some degree of control over beam selection, the nodes of this System 1 are configured as follows: - Base station 6 / NTN node 5 allocates mutually exclusive CSI-RS resources to adjacent beams. -Base station 6 / NTN node 5 configures an appropriate resource set, including possible combinations of candidate CSI-RS resources, depending on the beam layout. - Base station 6 displays a set of candidate beams for UE3 measurement and beam switching. - Base station 6 / NTN node 5 transmits appropriate support information, including any information necessary for UE3 to perform the candidate beam measurement. -UE3 indicates to base station 6 the beam selected for switching based on the measurement results of candidate beams from the configured CSI-RS set.

[0042] More specifically, UE3 performs measurements on candidate beams for beam selection and initiates beam switching only if the quality of the reference signal in the current beam falls below a certain threshold, and if UE3 determines, based on the resource set being measured, that it is within (or approaching) the coverage area of ​​another beam. Based on the measurements performed on the reference signal transmitted through that beam (and the other beams in the candidate set), UE3 indicates the strongest beam (i.e., the best candidate for switching) to base station 6.

[0043] Before triggering beam indication toward base station 6, UE3 monitors whether certain conditions are met (or at least one condition is met). For example, the conditions include, but are not limited to, that the Reference Signal Received Power (RSRP) of the candidate beam is higher than the RSRP of the serving beam by a predetermined value (or that the RSRP of the candidate beam is above a threshold). The predetermined value may be given as "X" dB, where X can be set by base station 6. UE3 is configured to transmit appropriate instructions to identify the selected beam via Layer 1 (L1) or the MAC layer (or, where appropriate, using RRC signaling).

[0044] Advantageously, the above approach reduces / optimizes signaling overhead and measurement work on the UE side without introducing unnecessary overhead (such as RRC signaling associated with traditional handovers). However, the network / base station can control the measurement / beam switching process by setting up appropriate candidate beams and providing supporting information (e.g., X values) for the UE to consider. When performing beam switching, the network (base station / AMF / MME) can track the beam currently being used by the UE based on instructions from the UE.

[0045] <User Equipment (UE)> Figure 2 is a block diagram showing the main components of the mobile device (UE) 3 shown in Figure 1. As illustrated, the UE 3 includes a transceiver circuit 31 capable of transmitting signals to and receiving signals from connected nodes via one or more antennas 33. Although not necessarily shown in Figure 2, the UE 3 naturally has all the usual functions of a conventional mobile device (such as a user interface 35), which can be provided by hardware, software, and firmware, or any suitable combination thereof. The controller 37 controls the operation of the UE 3 according to software stored in memory 39. The software may be pre-installed in memory 39 and / or downloaded via the communication network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 41, a communication control module 43, and a positioning module 45 (optional in some UEs).

[0046] 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 the NTN node 5, the (R)AN node 6, and the core network node. Although not shown in FIG. 2, the communication control module 43 has appropriate sub-modules for, among other things, the PHY layer, the MAC layer, and the RRC layer. The signaling may include control signaling (such as RRC signaling) related to the configuration and support of the beam-level mobility of the UE 3.

[0047] When present, the positioning module 45 is responsible for determining the position of the UE 3, for example, based on signals from a Global Navigation Satellite System (GNSS).

[0048] <NTN Node (Satellite / UAS Platform)> FIG. 3 is a block diagram showing the main components of the NTN node 5 (satellite or UAS platform) shown in FIG. 1. As shown, the NTN node 5 includes a transceiver circuit 51 operable to transmit signals to and receive signals from the connected UE 3 via one or more antennas 53, and to transmit and receive signals (directly or indirectly) to and from other network nodes such as gateways and base stations. The controller 57 controls the operation of the NTN node 5 according to software stored in the memory 59. The software may be pre-installed in the memory 59 and / or downloaded via the communication network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 61 and a communication control module 63.

[0049] The communication control module 63 is responsible for processing (generating / transmitting / receiving / relaying) signaling between the NTN node 5 and other nodes such as the UE3, base station 6, gateway, and core network nodes (via the base station / gateway). The signaling may include control signaling (such as RRC signaling) related to setting up and assisting the beam level mobility of the UE3.

[0050] <Base station / gateway (access network node)> Figure 4 is a block diagram showing the main components of the gateway 6 (base station (gNB) or similar access network node) shown in Figure 1. As shown, the gateway / gNB 6 includes transceiver circuitry 71 capable of transmitting and receiving signals to and from UE3 connected via one or more antennas 73, and also transmitting and receiving signals (directly or indirectly) to and from other network nodes via network interface 75. Signals may be transmitted to and from UE3 directly and / or via NTN node 5, as needed. Network interface 75 typically includes appropriate base station-to-base station interfaces (such as X2 / Xn) and appropriate base station-to-core network interfaces (such as S1 / NG-C / NG-U). Controller 77 controls the operation of base station 6 according to software stored in memory 79. The software may be pre-installed in memory 79 and / or downloaded via communication network 1 or from removable data storage (RMD). The software includes, among other things, an operating system 81 and a communication control module 83.

[0051] The communication control module 83 is responsible for processing (generating / transmitting / receiving) signaling between the base station 6 and other nodes such as UE3, NTN node 5, and core network nodes. Although not shown in Figure 4, the communication control module 83 has appropriate submodules for the PHY layer, MAC layer, and RRC layer, among other things. The signaling may include control signaling (such as RRC signaling) related to setting and assisting the beam level mobility of UE3.

[0052] <Detailed explanation> The following is a description of exemplary procedures performed by the system nodes shown in Figure 1, with reference to the exemplary scenario shown in Figure 5. As can be seen, Figure 5 shows a cluster of seven beams (NTN cells) and two UEs moving relative to the cluster of beams. The same scenario (or a scenario in which both beams and UEs are moving) is also applicable to stationary UEs, in which case it will be understood that the beams are moving relative to the UEs.

[0053] The following procedure benefits from the predictability of beam switching (including the expected timing of switching and possible candidate cells) by either base station 6 or UE3, in order to reduce signaling overhead and measurement effort in UE3. Furthermore, the following procedure also takes into account the channel state of UE3.

[0054] More specifically, the network (base station 6 using communication control module 83) configures different CSI-RS resources for different beams within the satellite footprint. All beams surrounding a particular beam are assigned mutually exclusive CSI-RS resources. For example, the CSI-RS resources assigned to the seven beams in Figure 5 are not shared among the beams within this cluster (although they may be shared with beams in other beam clusters).

[0055] Note that "Beam 1" to "Beam 7" in Figure 5 do not represent the actual beam numbers or beam indices used by satellite 5. However, for the purposes of this explanation, for a given UE3, Beam 1 represents the UE's serving beam, and Beams 2 through 7 represent the logical indices of the surrounding beams in the corresponding direction. In Figure 5, for illustrative purposes, the serving beam is shown to have six adjacent beams, but it will be understood that depending on the beam footprint and the associated network parameters or geographical aspects, a beam may have a different number of adjacent beams (i.e., more than six or fewer than six adjacent beams).

[0056] The base station 6 (using its communication control module 83) transmits support information to the UE3 to determine which candidate beams the UE3 can switch to when it reaches the end of the current serving beam. This support information includes all the information necessary for the UE3 to perform measurements on each candidate beam (and the serving beam, if applicable).

[0057] For example, support information may be transmitted via a properly formatted MAC Control Element (MAC-CE) scheduled via DCI (which could be beam-specific Downlink Control Information (DCI) for all UEs in a particular beam or cluster of beams) common to a group of UEs. In this case, the support information is related to candidate beams around the current beam and can be used by all UEs served by that beam. Alternatively, where appropriate, UE-specific DCI / MAC-CE can be used to support information for a specific UE. Such UE-specific support information may be appropriate depending on the number of UEs served by a given beam (e.g., if the number of UEs is relatively small) and / or depending on the movement of a particular UE relative to the serving beam (e.g., if it is a fast-moving UE, a stationary UE, or a UE moving in a different direction from other UEs served by the same beam).

[0058] In another example, relevant support information could be applicable to all beams (or a subset of all beams) of satellite 5 and transmitted to all UE3s served by satellite 5. For instance, the support information could be broadcast in system information, allowing any UE3 in a serving beam to obtain the information necessary to perform measurements on the surrounding beams (beam switching candidates).

[0059] It will be understood that the CSI-RS resource set can be defined so that, based on its associated resource set, UE3 can determine what measurements it needs to perform for beam switching and also determine any target candidate beam. Applicable resource sets (for each UE or for groups of UEs) can be configured via RRC signaling or broadcast in system information.

[0060] For example, referring to the beam layout in Figure 5, the following CSI-RS resource set can be defined. TIFF0007910612000001.tif95150

[0061] The base station 6 indicates candidate beams for switching to each UE3 by, for example, transmitting information that identifies the set of resources used by its UE3 for signal measurement.

[0062] Using the exemplary resource sets in the table above, if base station 6 configures “UE1” in Figure 5 with resource set F, the UE can determine that its candidate beams for beam switching include the beams indicated as “beam2” and “beam7”. UE1 can also determine that the beams indicated as “beam3,” “beam4,” “beam5,” and “beam6” are not included in the set of candidate beams, and therefore it is not necessary to perform measurements of the reference signal transmitted through those beams. Alternatively, base station 6 may configure “UE1” with resource set M, in which case the UE can determine that it only needs to measure “beam7” (in addition to the current serving beam, i.e., “beam1” in Figure 5).

[0063] Using the example of "UE2" in Figure 5, base station 6 can configure this UE with resource set E, in which case the candidate beams for that UE include "beam 6" and "beam 7". UE2 may also determine that it does not need to perform measurements on the reference signal transmitted through the beams indicated by "beam 2", "beam 3", "beam 4", and "beam 5", because these beams are not included in the set of candidate beams for that UE. Alternatively, base station 6 may configure "UE2" with resource set M, in which case the UE may determine that it only needs to measure "beam 7" (in addition to the current serving beam, i.e., "beam 1" in Figure 5).

[0064] It is understood that various other options are possible; for example, UE3 may be configured using multiple resource sets (for example, by signaling sets K, L, and M, base station 6 can configure "beam 5", "beam 6", and "beam 7" as candidate beams for a given UE3). This approach is useful, for example, when the movement of UE3 is not very predictable, in which case it may be beneficial to configure a relatively large number of candidate beams.

[0065] Once UE3 obtains information to identify the candidate beams, it performs measurements on those beams for beam selection and switching. In particularly favorable cases, UE3 performs signal measurements on candidate beams only if the quality of the reference signal (or multiple signals) on the UE's current serving beam falls below a certain threshold, and UE determines that it is substantially within (or approaching) the coverage area of ​​another beam (of the set of candidate beams). The results of the signal measurement (CSI-RS measurement) for a particular beam are given as the RSRP value (in dB) for that beam.

[0066] Based on the signal measurement results, UE3 indicates to base station 6 the strongest beam (e.g., the beam with the highest RSRP) as the beam selected by UE3 for beam switching. UE3 may be configured to transmit appropriate instructions to identify the strongest / selected beam via Layer 1 (L1) or MAC layer (or, if appropriate, using RRC signaling).

[0067] UE3 may indicate the selected beam at the time of switching to that beam (e.g., immediately before or after the switch) so that base station 6 can record (and, if appropriate, confirm) that UE3 is being serviced by the new beam. Alternatively, UE3 may indicate the selected beam before initiating the beam switch, in which case base station 6 may be configured to send appropriate instructions on whether UE3 is permitted to switch to that beam. However, it will be understood that such explicit approval from base station 6 may not be required, at least when UE3 is configured with a particular set of candidate beams.

[0068] In either case, this approach could result in reduced overhead because it eliminates the need to send measurement reports for each candidate beam to base station 6 in order to select the appropriate new serving beam for UE3. Furthermore, the beam switching decision (beam selection) is based on measurements of signals from candidate beams within the candidate CSI-RS set configured for UE3, so the channel state of the UE is taken into account in the beam switching process.

[0069] Conveniently, appropriate beam designation can be triggered by UE3 when certain predetermined conditions are met. Such conditions include, but are not limited to, that the RSRP of a candidate beam is higher than a threshold or the RSRP of a serving beam by a predetermined value. The predetermined value may be given as "X" dB, and the value of X may be set by base station 6 (per UE or per beam).

[0070] <Advantages> Advantageously, the above approach reduces / optimizes signaling overhead and measurement work on the UE side without introducing unnecessary overhead (such as RRC signaling associated with traditional handovers). This is achieved by performing measurements on a specific candidate beam (selected and signaled by the base station via appropriate resource set instructions) and configuring the UE to indicate the selected / best beam when the UE needs to perform a beam switch. This also reduces overhead as it eliminates the need to send measurement reports to the base station (only switch instructions). However, the beam switch decision is still based on measurements of signals from the candidate beams, so the UE's channel state is taken into account in the beam switch procedure.

[0071] Another advantage is that the network / base station can control the measurement / beam switching process by setting up appropriate candidate beams and providing supporting information (such as the value of X) for the UE to consider. When performing beam switching, the network (base station / AMF / MME) can track the beam currently being used by the UE based on instructions from the UE.

[0072] This approach avoids switching decisions made purely by the UE based on RSRP measurements, which can lead to undesirable outcomes (at least from a network perspective), and can waste measurement effort at the UE when the UE needs to re-select a different beam. Since the base station is aware of the UE's movement (and / or beam movement), it can reduce measurement effort and switching frequency by directing the UE to the appropriate resource set.

[0073] <Revisions and Alternatives> Detailed embodiments have been described above. As those skilled in the art will understand, many modifications and substitutions can be made to the above embodiments while still enjoying the benefits of the invention as embodied therein. Some of these substitutions and modifications are described here as examples.

[0074] Assistance information may include information identifying the beam layout, or information from which the beam layout is derived by the UE. Such information may include, but is not limited to, information regarding beam width, information identifying applicable BWP / beams, and information identifying the beam center altitude and / or azimuth. However, it will be understood that assistance information does not necessarily have to include such beam layout information. Instead, assistance information may include information identifying pre-configured resource and / or candidate resource instructions for a given UE (or group of UEs) (as shown in the table above). In this case, assistance information only needs to include beam-specific parameters necessary for the UE (or group of UEs) to perform measurements on the appropriate candidate beam. Base station control over candidate beam display allows each UE to select and display an appropriate candidate beam for load balancing purposes or interference adjustment purposes (for beams / cells controlled by a particular base station, or beams / cells controlled by adjacent base stations). For example, in the scenario shown in Figure 5, if UE2 is located at the edge of "Beam 1" or within the overlapping region between "Beam 6" and "Beam 7", the base station may be able to select a more suitable target beam (e.g., "Beam 6") for UE2, for example, load balancing and / or interference coordination.

[0075] Base stations for 5G / NR communication systems are generally called new radio base stations ("NR-BS") or "gNB," but it is understood that they may also be referred to using the term "eNB" (or 5G / NR eNB), which is more commonly associated with Long Term Evolution (LTE) base stations (also commonly called "4G" base stations). 3GPP Technical Specifications (TS) 38.300V16.6.0 and TS37.340V16.6.0 define the following nodes in particular:

[0076] A node that provides NR user plane and control plane protocol termination to gNB:UE and connects to the 5G core network (5GC) via the NG interface.

[0077] A node that provides NR user plane and control plane protocol termination to gNB:UE and connects to the 5G core network (5GC) via the NG interface.

[0078] This node provides NR user plane and control plane protocol termination to En-gNB:UE and functions as a secondary node in E-UTRA-NR dual connectivity (EN-DC).

[0079] NG-RAN node: Either gNB or ng-eNB.

[0080] It will be understood that the above embodiments are applicable to both 5G new wireless systems and LTE systems (E-UTRAN). Base stations (gateways) that support the E-UTRAN / 4G protocol are sometimes called "eNBs," and base stations that support the next-generation / 5G protocol are sometimes called "gNBs." It will be understood that some base stations may be configured to support both 4G and 5G protocols, and / or other 3GPP or non-3GPP communication protocols.

[0081] (Table 1) Types of satellites and UAS platforms [Table 1]

[0082] It will be understood that there are various architectural options for implementing NTN in 5G systems, some of which are schematically shown in Figure 6. The first option shown is an NTN that serves the UE and features an access network based on satellite / antennas with bent pipe payloads and ground gNBs (satellite hub or gateway level). The second option is an NTN that serves the UE and features an access network based on satellite / antennas with gNBs. The third option is an NTN based on satellite / antennas with bent pipe payloads that features an access network that serves relay nodes. The fourth option is an NTN that serves relay nodes and features an access network based on satellite / air with gNBs. It will be understood that other architectural options, such as combinations of two or more of the above options, can also be used. Alternatively, the relay nodes may have satellite / UASs. Similar architectural options can be used in 4G / LTE systems, but it will be understood that eNBs are used instead of gNBs, EPCs are used instead of NGCs, and appropriate LTE interfaces are used instead of the NG interfaces shown in Figure 6.

[0083] For the sake of clarity, the above description assumes that the UE, NTN node (satellite / UAS platform), and access network node (base station) have numerous individual modules (such as communication control modules). These modules may be provided in this way for specific applications, for example, when an existing system is modified to implement the present invention, or for other applications, for example, in a system designed from the outset with the features of the present invention in mind. However, these modules may not be recognizable as individual entities because they may be integrated into the entire operating system or code. These modules can also be implemented in software, hardware, firmware, or a combination thereof.

[0084] Each controller may comprise 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) circuits, internal memory / cache (programs and / or data), register processing, communication buses (e.g., control buses, data buses, address buses, etc.), direct memory access (DMA) functions, hardware or software-implemented counters, pointers, and / or timers, and / or similar.

[0085] In the embodiments described above, numerous software modules have been explained. As those skilled in the art will understand, software modules can be provided in compiled or uncompiled form and supplied as signals to UEs, NTN nodes, and access network nodes (base stations) via a computer network or on a recording medium. Furthermore, some or all of the functions performed by this software can be performed using one or more dedicated hardware circuits. However, the use of software modules is recommended because it facilitates updates to update the functions of UEs, NTN nodes, and access network nodes (base stations).

[0086] The embodiments described above are also applicable to “non-mobile” or generally fixed user devices. The aforementioned mobile devices may include MTC / IoT devices, etc.

[0087] The methods performed by the UE may include receiving information from network nodes via a non-terrestrial network that identifies at least one set of candidate beams, using at least one of the following: radio resource control (RRC) signaling (e.g., via RRC connection reconfiguration messages), medium access control (MAC) signaling (e.g., via MAC control elements scheduled via downlink control information (DCI) common to a group of UEs), or system information (e.g., system information common to all UEs that receive service via multiple beams of a non-terrestrial network). The system information can identify each set of at least one candidate beam for each of the multiple possible serving beams.

[0088] The method performed by the UE may further include receiving supporting information for measurements of at least one set of candidate beams (e.g., information identifying beam layout such as beam width, central altitude, azimuth angle, and / or information identifying one of a set of pre-configured resources).

[0089] Each beam in at least one set of candidate beams can use a mutually exclusive Channel State Information Reference Signal (CSI-RS) resource for CSI-RS resources used by other beams in the set.

[0090] The indication allows the UE to identify the beam being switched. Based on the results of previous measurements, the indication may show the strongest beam in the set. The method performed by the UE may further include initiating beam switching to the beams in the set based on the measurement results.

[0091] The method performed by the UE further comprises sending instructions to a network node via a non-terrestrial network when the Reference Signal Received Power (RSRP) of a candidate beam is higher than a relevant threshold or at least a predetermined value (e.g., a dB value) higher than the RSRP of a serving beam. In this case, the predetermined value may be set by a base station providing services to the UE.

[0092] The method performed by the UE may further comprise sending an instruction when the quality of the reference signal in the current serving beam used by the UE falls below a relevant threshold based on measurements of the reference signal transmitted through the current serving beam.

[0093] The methods performed by the UE may further include sending instructions via at least one of the following: Layer 1 (L1) signaling, MAC layer signaling, and RRC signaling.

[0094] The method performed by the UE may further include receiving a response to the instruction from the serving base station before initiating the beam switching.

[0095] The method performed by the UE may further include initiating beam switching if the quality of at least one reference signal transmitted over the serving beam falls below a threshold based on relevant measurements.

[0096] The method performed by the UE may include initiating beam switching if, based on the results of the measurement, the UE determines that it is within or substantially within the coverage of another beam.

[0097] The method performed by the UE may further include initiating the beam switching if the RSRP of the candidate beam is higher than a relevant threshold, or if it is at least a predetermined value (e.g., a dB value) higher than the RSRP of the serving beam.

[0098] Other various modifications are obvious to those skilled in the art and will not be described in further detail here.

[0099] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above.

[0100] Various modifications can be made to the structure and details of this disclosure that would be understandable to those skilled in the art within the scope of the disclosure.

[0101] Programs can be stored and provided to computer devices using any type of non-temporary computer-readable medium. Non-temporary computer-readable medium includes all types of tangible storage media. Examples of non-temporary computer-readable medium include magnetic storage media (floppy disks, magnetic tapes, hard disk drives, etc.), magneto-optical storage media (magneto-optical disks, etc.), CD-ROMs (read-only memory), CD-Rs, CD-R / Ws, and semiconductor memory (mask ROMs, programmable ROMs (PROMs), erasable PROMs (EPROMs), flash ROMs, Random Access Memory (RAMs), etc.). Programs can also be provided to computer devices using any type of temporary computer-readable medium. Examples of temporary computer-readable medium include electrical signals, optical signals, and electromagnetic waves. Temporary computer-readable medium can provide programs to computer devices via wired communication lines such as electric wires and optical fibers, or via wireless communication lines.

[0102] For example, all or part of the embodiments disclosed above may also be described as follows, but are not limited to these. (Note 1) A method performed by User Equipment (UE) configured to communicate using beams over a non-terrestrial network, Receiving information from a network node via the aforementioned non-terrestrial network to identify at least one set of candidate beams for beam switching, Performing a measurement of the reference signal transmitted through at least one candidate beam in the set, Based on the results of the measurement, the switching of the beam to the beam in the set is initiated. Transmitting instructions to the network node via the non-terrestrial network to indicate the beam switching, A method for providing a UE. (Note 2) The above instruction identifies the beam, The method described in Appendix 1. (Note 3) The aforementioned indication shows the strongest beam in the set based on the results of the measurement. The method described in Appendix 1 or 2. (Note 4) The instruction is transmitted when the Reference Signal Received Power (RSRP) of the beam is higher than a threshold, or at least higher than the RSRP of the current serving beam by a parameter value. The method described in any one of the appendices 1 to 3. (Note 5) The parameter value is set by the base station providing the service to the UE. The method described in Appendix 4. (Note 6) The transmission of the aforementioned instruction is performed when the quality of the reference signal in the current serving beam is below a threshold based on the measurement of the reference signal. The method described in any one of the appendices 1 to 5. (Note 7) The initiation of the beam switching is performed when the quality of the reference signal in the current serving beam is below a threshold based on the measurement of the reference signal. The method described in any one of the appendices 1 to 6. (Note 8) The initiation of the beam switching is performed when, based on the results of the measurement, it is determined that the UE is within or substantially within the coverage of another beam in the set. The method described in Appendix 7. (Note 9) The initiation of the beam switching is performed when the RSRP of a candidate beam in the set is higher than a threshold, or at least higher than the RSRP of the current serving beam by a parameter value. The method described in any one of the appendices 1 to 8. (Note 10) The aforementioned reception, Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling, System information and, It is executed using at least one of the following: The method described in any one of the appendices 1 through 9. (Note 11) The system information identifies, for each of the multiple possible serving beams, each set of at least one candidate beams. The method described in Appendix 10. (Note 12) The system further comprises receiving support information for the measurement of the set of at least one candidate beams from the network node via the non-terrestrial network, The method described in any one of the appendices 1 through 11. (Note 13) Each beam in the set of at least one candidate beams uses a mutually exclusive Channel State Information Reference Signal (CSI-RS) resource with respect to the Channel State Information Reference Signal (CSI-RS) resource used by the other beams in the set. The method described in any one of the appendices 1 to 12. (Note 14) The aforementioned transmission Layer 1 (L1) signaling, MAC layer signaling and RRC signaling and Executed via at least one of the following: The method described in any one of the appendices 1 to 13. (Note 15) The system further comprises receiving a response to the instruction from the network node via the non-terrestrial network before initiating the beam switching, The method described in any one of the appendices 1 through 14. (Note 16) A method performed by a network node configured to communicate with User Equipment (UE) using beams over a non-terrestrial network, Transmitting information to the UE that identifies at least one set of candidate beams for beam switching, Receiving instructions from the UE when the UE initiates beam switching to a beam in the set based on the results of measuring a reference signal transmitted through the at least one candidate beam in the set, A method for a network node that includes the following features. (Note 17) User Equipment (UE) configured to communicate using beams over a non-terrestrial network, Means for receiving information from a network node via the aforementioned non-terrestrial network that identifies at least one set of candidate beams for beam switching, Means for performing a measurement of a reference signal transmitted through at least one candidate beam in the set, Means for initiating the beam switching to the beam in the set based on the results of the measurement, means for transmitting instructions to the network node to indicate the beam switching via the non-terrestrial network, A UE equipped with [unclear]. (Note 18) A network node configured to communicate with User Equipment (UE) using beams over a non-terrestrial network, Means for transmitting information to the UE that identifies at least one set of candidate beams for beam switching, Means for receiving instructions from the UE when the UE initiates beam switching to a beam in the set based on the result of measuring a reference signal transmitted through the at least one candidate beam in the set, A network node equipped with the following features.

[0103] This application claims priority based on UK Patent Application No. 2110935.0, filed on 29 July 2021, the entirety of which disclosures are incorporated herein by reference. [Explanation of Symbols]

[0104] 1. Communication System 3. User Equipment (UE) 5 satellites 6 Gateways 7. Data Network 31, 51, 71 Transceiver Circuits 33, 53, 73 antennas 35, 75 User Interface 37, 57, 77 Controllers 39, 59, 79 memory 41, 61, 81 Operating Systems 43, 63, 83 Communication control modules 45 Positioning Modules

Claims

1. User equipment (UE) configured to communicate over a non-terrestrial network, The system includes means for receiving information from network nodes via the non-terrestrial network that identifies a set of at least one candidate beams for beam switching, wherein the set of at least one candidate beams corresponds to the movement of network nodes within the non-terrestrial network. Means for performing a measurement of a reference signal transmitted through at least one candidate beam in the set, Means for initiating beam switching to the beam in the set based on the results of the measurement, means for transmitting instructions to the network node to indicate the beam switching via the non-terrestrial network, A UE equipped with [unclear].

2. Each beam in the set of at least one candidate beams uses a Channel State Information Reference Signal (CSI-RS) resource that is mutually exclusive with respect to the Channel State Information Reference Signal (CSI-RS) resource used by the other beams in the set. The UE according to claim 1.

3. The set of at least one candidate beams is configured based on load balancing or interference adjustment at the network node. The UE according to claim 1 or 2.

4. The means for initiating the beam switching is configured to initiate the beam switching without transmitting a measurement report relating to the measurement to the network node. The UE according to claim 1 or 2.

5. The beam switching is performed taking into consideration the channel state of the UE. The UE according to claim 1 or 2.

6. The means for initiating beam switching is configured to initiate beam switching when it is determined, based on the results of the measurement, that the UE is within or substantially within the coverage of another beam in the set. The UE according to claim 1 or 2.

7. The means for receiving the information is: Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling, System information and, Configured to receive using at least one of the following: The UE according to claim 1 or 2.

8. The means for transmitting the instruction is: Layer 1 (L1) signaling, MAC layer signaling and RRC signaling and Configured to transmit via at least one of the following: The UE according to claim 1 or 2.

9. A network node configured to communicate with a user device (UE) via a non-terrestrial network, The system includes means for transmitting information to the UE identifying a set of at least one candidate beams for beam switching, wherein the set of at least one candidate beams corresponds to the movement of network nodes in the non-terrestrial network. Means for receiving instructions from the UE when the UE initiates beam switching to a beam in the set based on the results of measuring a reference signal transmitted through the at least one candidate beam in the set, A network node equipped with the following features.

10. A method performed by a user device (UE) configured to communicate over a non-terrestrial network, The system includes receiving information from a network node via the non-terrestrial network that identifies a set of at least one candidate beams for beam switching, wherein the set of at least one candidate beams corresponds to the movement of a network node within the non-terrestrial network. Performing a measurement of the reference signal transmitted through at least one candidate beam in the set, Based on the results of the measurement, the switching of the beam to the beam in the set is initiated. Transmitting instructions to the network node via the non-terrestrial network to indicate the beam switching, A method of UE that includes [a specific feature].

11. A method performed by a network node configured to communicate with a user device (UE) via a non-terrestrial network, The system comprises transmitting information to the UE identifying a set of at least one candidate beams for beam switching, wherein the set of at least one candidate beams corresponds to the movement of a network node in the non-terrestrial network. To receive instructions from the UE when the UE initiates beam switching to a beam in the set based on the results of measuring a reference signal transmitted through the at least one candidate beam in the set, A method for a network node that includes [a specific feature].

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