Methods and apparatus for a wireless communication system

Abstract

Methods and apparatus for use in a wireless communication system including a network entity, such as a Wireless Access Backhaul, WAB, node and a Non-Terrestrial Network, NTN, backhaul link, are disclosed. The method at the WAB node includes transmitting to or receiving from, a network entity, a message including first information related to the NTN backhaul link associated with the WAB node. The method at an NG-RAN node of the network includes receiving an indication that the backhaul link uses an NTN connection, and sending, to a network entity, first information including an indication that the backhaul link uses an NTN connection.

Description

[0001] METHODS AND APPARATUS FOR A WIRELESS COMMUNICATION SYSTEM

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to methods and apparatus for use in managing a NonTerrestrial Network backhaul link in a wireless communication system. In particular, the disclosure relates to methods and apparatus for use in managing notification of the presence of a NonTerrestrial Network backhaul link in a wireless communication system involving at least one Wireless Access Backhaul, WAB, node.

[0004] BACKGROUND

[0005] Wireless communication systems are largely deployed to address a wide range of applications, from mobile broadband, massive machine type communications to Ultra Reliable Low Latency Communications (URLLC). Such systems allow a plurality of user equipment (UE) or mobile terminals to share the wireless medium to exchange several types of data content (e.g. video, voice, messaging ...) over a radio access network (RAN) through one or more base stations (gNBs). The base stations are conventionally wired-connected (e.g. through fiber) to a core network, forming an intermediate network, named backhaul (BH).

[0006] Examples of such wireless multiple-access communication systems include systems based on 3rd generation partnership project (3GPP - RTM) standards, such as fourth-generation (4G) Long Term Evolution (LTE) or recent fifth-generation (5G) New Radio (NR) systems, or systems-based IEEE 802.11 standards, such as WiFi.

[0007] The demand for network densification increases due to the rising number of users and higher throughput requirement.

[0008] Facing the issues of high deployment costs and time of the wired backhaul networks with network densification, 3GPP has proposed, from release 16 for 5GNR, a wireless backhaul, also known as Integrated Access and Backhaul, IAB, where part of the wireless (i.e. radio) spectrum is used for the backhaul connection of base stations instead of fiber. The wireless backhaul communications (between base stations) may use the same radio resources as access communications (between a base station and UEs).

[0009] IAB turns out to be a competitive alternative to the fiber-based backhauling in dense areas or areas difficult to cover, as it allows scalable and rapid installations without the burden of cabling the base stations.IAB is most likely to operate in the millimeter wave (mmWave) band to achieve the required Gbps (gigabits per second) data rate.

[0010] Urban environments are usually characterised by a high density of users along with the presence of a significant number of vehicles (e.g. public / private passengers transportation, goods delivery, food trucks ...).

[0011] 3 GPP considers that such vehicles could offer an opportunity to increase network coverage and connectivity to the UEs inside the vehicles, or even to UEs in proximity to the vehicles, by installing on these vehicles on-board base stations (or base station elements) that would act as relays. These relays would rely on 5G wireless backhaul (typically IAB, or Integrated Access & Backhaul) for connecting to a fixed donor device. Thus, based upon the fixed IAB foundations set out in Releases 16 and 17, 3 GPP considers mobile IAB systems and architecture, as a part of the Release 18 framework, in order to address scenarios focusing on mobile lAB-nodes mounted on vehicles (for example, a bus, a train, a taxi). In such scenarios, mobile lAB-nodes can also be referred to as Vehicle Mounted Relays (VMR), providing 5G coverage / capacity to on-board and / or surrounding UEs.

[0012] Some further enhancements for Release 19, concern the need for 5G access for UEs onboard aircrafts, cruise ships, helicopters and vehicles in remote areas with limited sky visibility (e.g. where terrestrial cellular coverage or Wi-Fi coverage is not available), support for onboard / on-site mobile edge computing (MEC), local services, and direct local inter-UE communications, or local gNB deployment in public safety or disaster recovery scenarios. The backhauling links for the base stations providing the 5G access in such scenarios would then be operated over either a terrestrial network (TN), or a non-terrestrial network (NTN), with a possibility to handover communications from a terrestrial network to a non-terrestrial network and vice-versa. Such base stations can be referred to as Wireless Access Backhaul (WAB) nodes, or mobile WAB nodes, or WAB nodes.

[0013] WAB nodes serving UEs use backhaul links to exchange data (in the user plane and the control plane), these backhaul links are wireless in the context of WAB networks. In some situations these backhaul links may use a Non-Terrestrial Network (NTN) as specified by 3GPP (e.g. in TS 38.300 section 16.14) meaning that the data packets exchanged between a WAB node and a 5G core network, and between the base station of a WAB node and other base stations of the Radio Access Network (RAN), are transmitted through Uncrewed Aircraft Systems (UAS) like drones, or High Altitude Platforms (HAPs), or satellites.

[0014] SUMMARYThe inventors have appreciated that where Non-Terrestrial Networks are used in the context of WAB networks, this can significantly impact network functionality if the presence of the NTN links is not accounted for. When an NTN entity such as a satellite is used to form part of a backhaul link between a WAB node (i.e. the MT component of a WAB node) and its core network, another core network serving the WAB node (i.e. the gNB component of the WAB node) is not aware that the NTN backhaul link exists. This is because the gNB component of the WAB node, for example, is not an NTN entity. Therefore, the WAB node may communicate with the core network serving the gNB component of the WAB node over an NTN connection without being aware of the NTN connection. Accordingly, among other issues that may arise the WAB node and core network may not expect messages to be subject to long propagation delays associated with NTN transmissions. Therefore, in order to avoid service interruption at the UEs served by WAB nodes, the presence of NTN backhaul links in the data path should be correctly managed. In particular, the long propagation delay to transfer data wirelessly through a satellite, and the mobility of a satellite relative to the WAB nodes should be taken into account.

[0015] In general, the present invention addresses the above problems by informing the network of the presence of an NTN link within the network. In particular, a first entity (i.e. network entity) in the network sends, to a second entity (i.e. network entity) information related to the NTN link and / or an indication that the network includes the NTN link. The first entity and second entity may be any network nodes within the network.

[0016] In accordance with a first aspect of the present invention, there is provided a method for use in a wireless communication system including a wireless access backhaul, WAB, node, including a gNB component and an MT component, the method at the gNB component comprising: sending, to a network entity, a message including first information related to a Non-Terrestrial Network, NTN, backhaul link associated with the WAB node. The network entity may be, for example, an Access and Management Function (AMF) managing a User Equipment (UE) served by the gNB component of the WAB node. The NTN backhaul link may be a backhaul link used by the WAB node, such as a backhaul link between the WAB node and a core network. The WAB node may not be an NTN entity. For example, one or more UEs served by the WAB node may not be satellite-enabled UEs.

[0017] In accordance with a second aspect of the present invention, there is provided a method for use in a wireless communication system including a wireless access backhaul, WAB, node, including a gNB component and an MT component, the method at the WAB node comprising: receiving, from a network entity, a message including first information related to a Non-Terrestrial Network, NTN, backhaul link associated with the WAB node. The WAB node may not be an NTN entity. For example, one or more UEs served by the WAB node may not be satellite-enabled UEs.The network entity may be an NTN base station serving the MT component of the WAB node. The network entity may be a backhaul gNB.

[0018] In accordance with a third aspect of the present invention, there is provided a method for use in a wireless network, the method comprising at an NG-RAN node: receiving an indication that a backhaul link uses an NTN connection; and sending, to a network entity, first information including an indication that the backhaul link uses an NTN connection. The backhaul link may be a backhaul link used by the NG-RAN node, or may be a backhaul link used by another NG-RAN node in the network.

[0019] In accordance with a fourth aspect of the present invention, there is provided a method for use in a wireless network comprising a Non-Terrestrial Network, NTN, backhaul link, the method comprising at an Access and Management Function, AMF, of a core network: receiving, from an NG-RAN node, an indication that the backhaul link uses an NTN connection; and configuring one or more parameters associated with communication with the NG-RAN node over the NTN backhaul link based on the indication. The configuring of the one or more parameters may comprise managing (i.e. controlling, such as controlling the timing and configuration of) one or more parameters used for transmitting and receiving NG protocol messages over the NTN backhaul link.

[0020] In accordance with a fifth aspect of the present invention, there is provided a method for use in a wireless network comprising a Non-Terrestrial Network, NTN, backhaul link, the method comprising at an NTN entity connected to the NTN backhaul link: admitting an MT component of a network node through the NTN backhaul link; and sending, to the network node, a message including first information related to the NTN backhaul link.

[0021] In accordance with a sixth aspect of the present invention, there is provided a method for use in a wireless communication system including a network entity and a wireless access backhaul, WAB, node, the method at the network entity comprising: receiving, from the WAB node, a message including first information related to a Non-Terrestrial Network, NTN, backhaul link associated with the WAB node.

[0022] In accordance with a seventh aspect of the present invention, there is provided a method for use in a wireless communication system including a wireless access backhaul, WAB, node, a first network entity and a second network entity, the method comprising at the first network entity: sending, to the second network entity, a message including first information related to a NonTerrestrial Network, NTN, backhaul link associated with the WAB node. The first network entity may be the WAB node (or the gNB component of the WAB node, or the MT component of the WAB node) or another network node in the network.In accordance with an eighth aspect of the present invention, there is provided a computer program comprising instructions which, when the program is executed by at least one processor unit, cause the at least one processing unit to carry out the method according to any of the aspects of the present disclosure.

[0023] In accordance with an ninth aspect of the present invention, there is provided a computer-readable medium carrying a computer program according to the eighth aspect.

[0024] In accordance with a tenth aspect of the present invention, there is provided an apparatus for a network entity for a wireless communication system, the apparatus comprising one or more processing units configured to perform the method.

[0025] Optional features will now be set out. These are applicable singly or in any combination with any aspect of the disclosure.

[0026] The first information may include an indication that a communication path between the WAB node and a network entity includes the NTN backhaul link. The network entity may be, for example, an Access and Management Function (AMF) of one or more UEs served by the gNB component of the WAB node, or the network entity may be an NG-RAN node.

[0027] The first information may include an indication that the NTN backhaul link uses an NTN satellite.

[0028] The first information may further include an indication of an orbit type of the NTN satellite. The first information may include tracking area information indicating one or more tracking areas associated with the NTN entity connected to the NTN backhaul link.

[0029] The tracking area information may indicate a plurality of tracking areas associated with the NTN backhaul link, and the first information may further include an indication of a tracking area of the plurality of tracking areas associated with a current location of the WAB node or associated with a current location of the NG-RAN node.

[0030] The first information may include one or more configuration parameters associated with the NTN backhaul link.

[0031] The first information may include cell identity information, the cell identity information indicating a current geographical coverage area associated with the NTN backhaul link.

[0032] The first information may include location information, the location information specifying the current location of the WAB node and / or velocity information associated with the WAB node.

[0033] The first information may include an indication of an Access and Management Function, AMF, serving the MT component of the WAB node.

[0034] The message may further include information for identifying the MT component of the WAB node. The information for identifying the MT component of the WAB node may be, for example, a5GS mobile identity as defined in 3GPP Technical Specification document TS 24.501 section 9.11.3.4, or an AMF UENGAP ID as defined in 3GPP Technical Specification document TS 38.413 section 9.3.3.1. The MT component may be the MT component of a WAB node that uses one or more NTN connections as part of a backhaul link between the WAB node and the core network. For example, where the information is being sent by a gNB component of a WAB node, the MT component may be the MT component co-located with the gNB component. The information for identifying the MT component of the WAB node may be included in the messages described herein in connection with any one of Figures 5 to 12 inclusive.

[0035] The message may further include information for identifying a backhaul NG-RAN node serving the MT component. The information for identifying the backhaul NG-RAN node may be, for example, a Global RAN Node ID as defined in 3 GPP Technical Specification document TS 38.413 section 9.3.1.5 The information for identifying the backhaul NG-RAN node serving the MT component of the WAB node may be included in the messages described herein in connection with any one of Figures 5 to 12 inclusive.

[0036] The message may further comprise second information for identifying the WAB node and / or the gNB component of the WAB node.

[0037] The message may further comprise second information including an indication that the network entity sending the message (i.e. the gNB component of the WAB node) is a gNB component of a WAB node. The indication may be implemented as an Additional ULI (User Location Information) providing information to help the core network to localize the network entity (i.e. the WAB node). Optionally, the Additional ULI IE (Information Element) may be composed of one or more of an NR CGI (New Radio Cell Group Identity) as defined in TS 38.413 section 9.3.1.7, and a TAI (Tracking Area Identity) as defined in TS 38.413 section 9.3.3.11.

[0038] The second information may include an identifier of the WAB node and or the gNB component of the WAB node.

[0039] The message may comprise a request to establish a connection between the gNB component and the network entity, the method further comprising receiving, from the network entity, a response message indicating whether the connection has been successfully established.

[0040] In a case where the connection has not been successfully established, the response message may include an indication of the reason why the connection has not been successfully established.

[0041] The message may comprise (or be included within) a request to update a configuration of a connection between the gNB component and the network entity, and the method may further comprise receiving, from the network entity, a response message indicating whether the request to update the configuration has been successful.In a case where the request to update the configuration has not been successful, the response message may include an indication of the reason why the request to update the configuration was not successful.

[0042] The message may comprise (or be included within) one of

[0043] a message providing the current location of one or more UEs served by the WAB node; a message providing Non Access Stratum, NAS, information;

[0044] a path switch request message; or

[0045] a message related to the setup or modification of a PDU Session associated with one or more UEs served by the WAB node.

[0046] The network entity may be an Access and Management Function, AMF, or an NG-RAN node. The AMF may be an AMF of one or more UEs served by the gNB component of the WAB node. The WAB node may not be an NTN entity. For example, the one or more UEs served by the (gNB component of the) WAB node may not be satellite-enabled UEs.

[0047] The network entity may be an Access Management Function, AMF, and the connection may be an NG interface connection. The AMF may be an AMF of one or more UEs served by the gNB component of the WAB node.

[0048] The network entity may be an NG-RAN node and the connection may be an Xn interface connection.

[0049] The method may further comprise sending, to the network entity, an indication that the WAB node is a WAB node before receiving the message from the network entity.

[0050] The message may further comprises second information for identifying the network entity. The second information may include an identifier of the network entity.

[0051] The network entity may be an NTN base station serving the MT component of the WAB node. The method may be performed by the MT component of the WAB node.

[0052] The method may further comprise sending the first information to the gNB component of the WAB node.

[0053] The method may be performed by the gNB component of the WAB node.

[0054] The network entity may be an Access and Management Function, AMF, or another NG-RAN node. The AMF may, for example, be an AMF of one or more UE’s served by the NG-RAN node.

[0055] The method may further comprise receiving information related to the NTN backhaul link before sending the first information to the network entity.

[0056] The method may further comprise receiving a response from the network entity.

[0057] The response may comprise an acknowledgement that the first information was received (i.e. received successfully) by the network entity.The NG-RAN node may be one of:

[0058] a gNB component of a Wireless Access Backhaul, WAB, node;

[0059] an MT component of a WAB node;

[0060] a WAB node; or

[0061] a backhaul gNB, BH-gNB.

[0062] Configuring one or more parameters associated with communication with the NG-RAN node may comprise adjusting one or more Quality of Service, QoS, parameters for one or more PDU sessions of one or more UEs served by the AMF.

[0063] The method may further comprise receiving, from the NG-RAN node, first information related to the NTN backhaul link.

[0064] The configuring one or more parameters associated with communication with the NG-RAN node may be further based on the received first information.

[0065] The method may further comprise sending a response to the NG-RAN node.

[0066] The response may comprise an acknowledgement that the indication and / or first information was received (i.e. was received successfully).

[0067] Sending the message to the network node may comprise sending the message to the MT component of the network node (for example, the MT component of a WAB node).

[0068] The method may further comprise establishing an Xn connection with a gNB component colocated with the MT component of the network node.

[0069] Sending the message to the network node may comprise sending the message to a gNB component co-located with the MT component of the network node.

[0070] The NTN entity may be an NTN NG-RAN node.

[0071] The first information may include an indication that a communication path between the network node and a core network entity comprises the NTN backhaul link.

[0072] The message may further comprise second information for identifying the NTN entity.

[0073] The second information may include an identifier of the NTN entity.

[0074] The method may further comprise receiving a response from the MT component.

[0075] The method may further comprise receiving, from the network node, an indication that the network node is a Wireless Access Backhaul, WAB, node prior to sending the information related to the NTN backhaul link to the network node.

[0076] The term ‘backhaul link’ is used herein to describe a link between two backhaul nodes. It will be appreciated that a backhaul link need not be limited to a single link between two nodes, but may refer to a ‘backhaul connection’ comprising one or multiple backhaul links. The same logic may be applied to the term ‘non-terrestrial network (NTN) backhaul link’ as used herein. Embodiments ofthe present invention described herein may equally be applied to backhaul connections comprising one or multiple backhaul links.

[0077] Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus / device / unit aspects, and vice versa.

[0078] Furthermore, features implemented in hardware may be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly. For example, in accordance with other aspects of the invention, there are provided a computer program comprising instructions which, when the program is executed by one or more processing units, cause the one or more processing units to carry out the method of any aspect or example described above and a computer readable storage medium carrying the computer program.

[0079] BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Different aspects of the invention will now be described, by way of example only, and with reference to the following drawings in which:

[0081] Figure 1 is a schematic diagram of a communication system in which the present invention may be implemented according to one or more example embodiments;

[0082] Figure 2 is a simplified schematic diagram of a 5G system in which the present invention may be implemented according to one or more example embodiments;

[0083] Figure 3 is a simplified schematic diagram of a 5G system involving a Wireless Access Backhaul (WAB) node, and in which the present invention may be implemented according to one or more example embodiments.

[0084] Figure 4 is a block schematic diagram of an example network node or base station in accordance with one or more embodiments of the invention;

[0085] Figure 5 is a simplified schematic diagram showing an example of a wireless communication system, including a WAB network or WAB network system, in which embodiments and examples of embodiments of the present invention may be implemented;

[0086] Figure 6a is a schematic diagram illustrating the protocol stack associated with the NG or Xn interface in the user plane (NG-U or Xn-U);

[0087] Figure 6b is a schematic diagram illustrating the protocol stack associated with the NG or Xn interface in the control plane (NG-C or Xn-C);

[0088] Figure 7a is a schematic diagram showing an example message flow on an NG interface for indicating the presence of an NTN backhaul link to convey NGAP messages, and for providing information related to this NTN backhaul link;Figure 7b is a schematic diagram showing an example message flow on an Xn interface for indicating the presence of an NTN backhaul link to convey XnAP messages, and for providing information related to this NTN backhaul link;

[0089] Figure 8a is a schematic diagram showing an example message flow on a Uu interface for providing information related to an NTN backhaul link;

[0090] Figure 8b is a schematic diagram showing an example message flow on an Xn interface for providing information related to an NTN backhaul link;

[0091] Figure 9a is a flowchart of an example method for managing, at an NG-RAN node, the presence of an NTN backhaul link;

[0092] Figure 9b is a flowchart of another example method for managing, at an NG-RAN node, the presence of an NTN backhaul link;

[0093] Figure 10 is a flowchart of an example method for managing, at an Access and Management Function (AMF) of a core network, the presence of an NTN backhaul link;

[0094] Figure 1 la is a flowchart of an example method for managing, at an NTN NG-RAN node, the presence of an NTN backhaul link;

[0095] Figure 1 lb is a flowchart of another example method for managing, at an NTN NG-RAN node, the presence of an NTN backhaul link;

[0096] Figure 12 is a simplified schematic diagram showing another example of a wireless communication system, including a WAB network or WAB network system, in which embodiments and examples of embodiments of the present invention may be implemented.

[0097] DETAILED DESCRIPTION

[0098] Figure 1 illustrates an example communication system 100 in which the present invention may be implemented according to one or more embodiments.

[0099] As depicted, the example system 100 is a wireless communication system, in particular a mobile radio communication system such as a fifth-generation (5G) New Radio (NR) system including a Wireless Access Backhaul (WAB) communication system or network. Although in the following description, embodiments and examples of embodiments of the present invention will be described with respect to a 5G NR system, it will be appreciated that it is not intended that the present invention is limited to 5G NR systems and may be used in any wireless communication systems having an integrated access and backhaul communication system which shares radio resources for wireless access links and wireless backhaul links.

[0100] The system 100 comprises a plurality of UEs (User Equipment) 111, 112, 113, 121, 122, 123, 131, 132, 133, 134, 141, 142, 143, 151, 152, 153 and 154, a communication satellite 160, a satellite dish 101, a remote core network 170, three fixed Base Stations 102, 103 and 104, a plurality ofWireless Access Backhaul (WAB) nodes 110 (mounted on plane 161), 120a and 120b (mounted on train 162), 140 (mounted on Unmanned Aerial Vehicle (UAV) UAV 164) and 150 (mounted on backpack 165 or other carrier that can be carried by a user (e.g. in a disaster zone)), and a Wireless Access Backhaul node 130 (or Home gNB, mounted in house 163) which is fixed but based on the same architecture as a WAB node. In more general terms, the WAB node may be mounted on or in a vehicle (such as a train, bus, taxi, tram, etc.) and / or an aircraft or flying vehicle (such as a plane, UAV, helicopter, etc. ) and / or a building (such as a house, enterprise / company / office building, hotel building, airport building, sports / event buildings, shopping centre building, etc..) and / or a portable carrier that can be carried by a user (such as a backpack, bag, etc), for example, in a disaster zone or for public safety or for emergency services, and / or public infrastructure elements or units (such as lamp posts, traffic lights, etc.). In an example where the WAB node is implemented in a Femto network, the WAB node functions as a 5G Femto node and may be mounted at a building (such as a house, enterprise / company / office building, hotel building, airport building, sports / event buildings, shopping centre building, etc..) and / or public infrastructure elements or units (such as lamp posts, traffic lights, etc.). When it is a mobile base station, a WAB node is also referred to as a Mobile WAB (MWAB) node.

[0101] Some examples of UEs include smartphones / tablets (such as UEs 111, 123, 134, 142, 152), XR headsets (such as UEs 112, 122, 132), cameras (such as UEs 141 and 151), fixed video cameras (such as UEs 113, 121, 133, 153) or mobile / wearable video cameras (such as UEs 143 and 154). In general, the UE may be any portable or handheld or mobile telephone, a smartphone, a tablet, a portable or fixed computer, fixed or mobile camera, portable television or other similar wireless communication device. In the following description, the term UE will be used and it is not intended to limit the description to any particular type of wireless communication device.

[0102] Base stations 102, 103 and 104 are interconnected through a wired link infrastructure 180, preferably based on optical fiber or any other wired means.

[0103] Base stations 102, 103 and 104 are also connected to the core network 170 through a wired link infrastructure 190, preferably based on optical fiber or any other wired means. In embodiments and examples of embodiments of the invention, base stations 102, 103 and 104 are 5G NR base stations (referred to as a gNB), as defined in 3GPP TS 38.300 specification document.

[0104] Satellite dish 101 (e.g. satellite gateway or Earth station) is also connected to wired link infrastructure 180 or 190, or to both infrastructures. Besides, in some cases infrastructures 180 and 190 may be the same infrastructure. In a first example, a part of a base station is embedded in the satellite 160 while another part is embedded in the gateway 101, meaning that the base station is split between the satellite 160 and the gateway 101. This first Non-Terrestrial Network (NTN)architecture may be referred to as “transparent payload”. In a second example, a full base station is embedded in the satellite 160, and the gateway 101 connects the base station 160 with the infrastructure 180 and / or 190. This second NTN architecture may be referred to as “regenerative payload”. In case of non-geostationary satellite, the satellite 160 may connect to different gateways, like the gateway 101, while the satellite 160 is moving around the earth. A constellation of satellites is one of the possible deployments of NTN, which also covers the use of Uncrewed Aircraft Systems (UAS) like drones, or High-Altitude Platforms (HAPs).

[0105] In order to extend the network coverage of base stations 102, 103, 104 and 160 / 101, and reach the remote UEs 111, 112, 113, 121, 122, 123, 131, 132, 133, 134, 141, 142, 143, 151, 152, 153 and 154, mobile WAB nodes or WAB nodes, or WAB-nodes, 110, 120a, 120b, 130, 140 and 150, have been installed on vehicles / mobile equipment 161, 162, 163, 164 and 165. By acting as relaying nodes between the base stations 102, 103,104, and 160 / 101 and the UEs 111, 112, 113, 121, 122, 123, 131, 132, 133, 134, 141, 142, 143, 151, 152, 153 and 154, WAB-nodes 110, 120a, 120b, 130, 140 and 150 allow overcoming the reachability issue resulting from limited sky visibility while ensuring support for onboard / on-site mobile edge computing (MEC), local services, and direct local inter-UE communications. This allows further communication between base stations 102, 103 and 104 and the UEs 111, 112, 113, 121, 122, 123, 131, 132, 133, 134, 141, 142, 143, 151, 152, 153 and 154 and / or communications between the UEs served by a same WAB-node (e.g., UEs 151, 152, 153 and 154 connected to WAB node 150).

[0106] The base stations 102, 103 and 104, the WAB nodes 110, 120a, 120b, 130, 140 and 150, the satellite 160, the satellite dish 101 (satellite dish 160 and satellite dish 101 may act as part of, or all of, a base station as described above) are thus forming a backhaul network or WAB network (also referred to as WAB topology), or WAB network (also referred to as WAB topology), which accommodates UEs 111, 112, 113, 121, 122, 123, 131, 132, 133, 134, 141, 142, 143, 151, 152, 153 and 154. Although Figure 1 shows the satellite 160 connected to the WAB node 110 installed on vehicle 161 , it will be appreciated that the satellite 160 may connect to any WAB node in the system 100. Additionally, although the NTN is embodied by the satellite 160 in Figure 1, it will be appreciated that the NTN may comprise one or more satellites, one or more UASs, one or more HAPs, and / or one or more other entities configured to act as NTN architecture.

[0107] The terms WAB network, WAB network, WAB topology and WAB topology will be used interchangeably in the following. The WAB network is part of the Radio Access Network (RAN) or as referred to with respect to 5G, the Next Generation (NG) RAN.

[0108] The base stations 102, 103 and 104, the WAB nodes 110, 120a, 120b, 130, 140 and 150, the satellite 160, the satellite dish 101 (satellite dish 160 and satellite dish 101 may act as part of, or allof, a base station as described above), and the core network 170 are thus forming a WAB system, , which accommodates UEs 111, 112, 113, 121, 122, 123, 131, 132, 133, 134, 141, 142, 143, 151, 152, 153 and 154.

[0109] A base station, or gNB, such as base station 102, 103, 104, or 160 / 101 is a logical node that provides NR-connectivity, hosting both higher layer protocols, such as PDCP (Packet Data Convergence Protocol) and RRC (Radio Resource Control) protocols, and lower layer protocols, such as the RLC (Radio Link Control), MAC (Medium Access Control) and physical layer protocols.

[0110] The WAB nodes 110, 120a, 120b, 130, 140 and 150, which may serve multiple radio sectors, are wireless backhauled to the base station 102, 103 or 104, via a single logical hop associated to a single radio link (i.e., radio links D1041a, D1041b, D1031, D1022, D1021), or split into two radio links in the case of satellite relaying (radio links DI 60 la and DI 60 lb). The link DI 60 la between the satellite 160 and the WAB node 110 is called the service link, and the link D1601b between the satellite 160 and the gateway 101 is called the feeder link. These names, service link and feeder link, apply to both NTN architectures (transparent payload and regenerative payload).

[0111] Although a single logical hop is shown in figure 1, it will be appreciated that the WAB nodes could be wirelessly backhauled to the base station over multiple logical hops (for example, similar to the multiple hops provided in an IAB network).

[0112] Each WAB node consists of or includes a gNB or RAN node or base station component or entity which is referred to as a WAB-gNB, or WAB base station, and a Mobile Termination (MT) component or entity which is referred to as an IAB-MT, or WAB-Mobile Termination. The WAB-gNB functionality of an WAB-node allows or enables the WAB-node to serve UEs. The WAB-MT functionality includes, e.g., physical layer, layer-2, RRC and Non-Access Stratum (NAS) functionalities and allows or enables the WAB-MT to connect to a base station, or gNB, such as base station 102, 103, 104, or 160 / 101 and to support backhauling of traffic related to the WAB-gNB of the WAB node. The WAB-gNB may also be referred to as a NG-RAN node (of a WAB node) and the WAB-MT may also be referred to as a UE (of a WAB node).

[0113] WAB nodes 110, 120a, 120b, 140 and 150 are intended to be mobile devices that will move along with the vehicle they are mounted on. However, these WAB nodes may remain at a fixed location for a significant duration when their associated vehicle is remaining still (e.g., a train may stop at a railway station, a plane may be parked at an airport for a while, a car / truck / fire engine or any other emergency vehicle may be parked nearby a disaster area).

[0114] WAB node 130 is likely to remain at fixed location and may be a 5G Femto node, which provides NR access at home or at enterprise premises. In such case, the 5G Femto node 130 mayhave a direct connection DI 700 to the Core Network 170 through the wired link infrastructure 190, which is preferably based on optical fiber or any other wired means.

[0115] For satellites, such as Satellite 160 shown in Figure 1, there are several classes of orbit:

[0116] Geostationary (GEO) where the satellite rotates at the same speed as the Earth’s rotation providing continuous coverage of the same geographical area on Earth.

[0117] - Non-Geostationary (NGSO) where the satellite rotates at a speed different from the Earth’ s rotation. In that case, a satellite covers a geographical area that is continuously changing. There are three types of orbits for NGSO, depending on the altitude range of the satellite:

[0118] • LEO (Low-Earth Orbiting)

[0119] • MEO (Medium-Earth Orbiting)

[0120] • HEO (Highly -Eccentric Orbiting)

[0121] The propagation delay for radio signals to cover the distance between the satellite and a device on Earth (e.g. between the satellite 160 and the Earth station 101) depends on the altitude of the satellite above the Earth (i.e. it depends on the class of orbit), and on the elevation angle under which the satellite is seen by the device on Earth (i.e. the angle measured between the location of the remote device above the horizon of the Earth). This propagation delay may vary between a few milliseconds (ms) and up to around 140ms. Such long propagation delay may also be present for radio signal transmission between the satellite 160 and the WAB node 110. As with any base station, an NTN satellite base station broadcasts some information to be used by a served User Equipment (UE). However, there are some differences compared to a TN (Terrestrial Network) base station. For instance, for an NTN cell, an NTN satellite base station does not broadcast a single Tracking Area Code (TAC) identifying the geographical area corresponding to the radio coverage of the cell, but a list of TACs. Indeed, the radio beam of an NTN satellite may cover a large geographical area on Earth gathering several tracking areas. Also, a NSGO satellite may move at high speed relative to the surface of the Earth, thus covering a geographical area during a few seconds or a few minutes. Then, instead of continuously changing the broadcasted TAC, an NTN satellite broadcasts a list of TACs.

[0122] Figure 2 is a simplified schematic diagram of a 5G system 200 in which the present invention may be implemented according to one or more example embodiments. This figure illustrates the possible standardized interfaces between the various elements composing the system. First, it represents a User Equipment (UE) 201 having a Uu interface with the New Generation (NG) Radio Access Network (RAN or NG-RAN) 202, and a N1 interface with an Access and Mobility management Function (AMF) entity or AMF 212 in a 5G core network (5GC) 210. Each base station (TN or NTN base station) composing the RAN 202 has a N2 interface with one or more Access andMobility management Function (AMF) entity or AMF, like AMF 212, and a N3 interface with one or more User Plane Function (UPF) entity or UPF, like UPF 211.

[0123] The N1 interface is used to convey Non-Access Stratum (NAS) protocol messages between a UE 201 and an AMF 212. NAS messages are used for the signaling between the UE and the core network for various procedures such as registration, session establishment, security, and mobility management. Although the N1 connection is shown as a direct link between the UE 201 and AMF 212, NAS messages are in fact conveyed through the Uu interface between the UE 201 and the RAN 202, and the N2 interface between the RAN 202 and the AMF 212.

[0124] An AMF 212 is responsible for handling registration, authentication, connection and mobility management tasks for a UE. For a WAB node, the AMF may apply the procedures defined in NAS protocol specifications (TS 24.502 section 5), considering the WAB node is a Mobile Base Station Relay (MBSR) introduced in Release 18. There may be several AMFs in a 5G core network, a standardized interface N14 enables the communications between AMFs. When a UE registers to the network through a serving base station, the serving base station will connect to an AMF suitable to handle the UE.

[0125] When the UE 201 is registered, one or more Protocol Data Unit (PDU) session(s) can be set up to transfer data flows between the UE 201 and the Data Network (DN) 220 providing internet access. A PDU session is established between a UE 201 and a User Plane Function (UPF) 211 in the 5G core network 210. In the user plane, the UPF 211 connects to the Data Network (DN) 220 through the interface N6, and it is responsible for data packets routing with the required Quality of Service (QoS). There may be several UPFs on the data path with a N9 interface between UPFs. The user data between a UE 201 and the Data Network 220 are thus conveyed through interfaces Uu, N3, N6 and potentially N9.

[0126] In the control plane, the setup of PDU sessions is handled through NAS messages involving the Session Management Function (SMF) entity or SMF 213 in the 5G core network 210. The NAS messages are still exchanged between the UE 201 and the AMF 212 through the N1 interface, but an additional interface N11 between an AMF 212 and the SMF 213 is used to reach the SMF 213. In a 5G core network, the SMF is responsible for the setup, modification, and release of PDU sessions for a UE, as well as the Internet Protocol (IP) address allocation for the UE. To manage a PDU session, the SMF 213 controls the UPF 211 (configuration) based on QoS policy defined for the PDU session. For this purpose, a N4 interface exists between the SMF 213 and the UPF 211.

[0127] A base station in RAN 202 operating in a first Public Land Mobile Network (PLMN) may serve a UE having a subscription for a second PLMN (called home PLMN) different from the first PLMN (called visited PLMN). In such a roaming case, there are two options to provide the UE 201with an access to the Data Network 220. In a first option called home routed, the UPF and its controlling SMF to access the Data Network 220 are located in the 5G core network for the home PLMN. However, the SMF of the visited PLMN controls the intermediate UPF(s) of the visited PLMN, and interacts with the SMF of the home PLMN. In a second option called local breakout, the UPF and its controlling SMF to access the Data Network 220 are located in the 5G core network for the visited PLMN. However, the SMF interacts with the home 5G core network to get QoS policies associated with the UE’s PDU session(s).

[0128] Nl, N2, N3, N4, N6, N9, Nil, N14 may also be called reference points as defined in TS 23.501.

[0129] When NTN satellites are involved to serve satellite-enabled UEs (UEs that are specifically configured for satellite communications), the core network must configure the PDU session(s) of the UEs taking into account the long propagation delay to transmit radio signals between the NTN satellite and the UEs and between the NTN satellite and the Earth station (or gateway). In particular, the QoS flows transmitted with a PDU session via an NTN satellite must be set with a QoS profile provisioning a large Packet Delay Budget (PDB). This profile corresponds to the value 10 among the list of 5G QoS Identifier (5QI) values defined TS 23.501 section 5.7.4. To be aware that an NTN satellite is used for data transmission, the NTN satellite base station shall inform the AMF(s) managing the served UE(s) when a NG connection is established between the AMF(s) and the NTN satellite base station. For this purpose, the information element RAT information specified in TS 38.413 section 9.3.1.125 and included in the message NG SETUP REQUEST, is set to a value indicating the use of satellite NTN and the type of orbit.

[0130] To assist the Location Management Function (LMF) of the core network (not represented in Figure 2), any base station reports the broadcasted Tracking Area Code (TAC) of the selected PLMN to the AMF as part of User Location Information (ULI). The ULI may also enable the AMF to determine whether the UE is allowed to operate at its present location. With an NTN satellite base station, a list of broadcasted TACs is broadcasted in the controlled cell(s), and the NTN satellite base station reports the list of broadcasted TACs to the AMF. Besides, when the NTN satellite base station knows the UE's location, the NTN satellite base station may determine the TAC corresponding to the geographical area the UE is currently located, and it may provide that determined TAC to the AMF as part of ULI. To assist the NTN satellite base station, a UE may provide to the NTN satellite base station its location based on GNSS (Global Navigation Satellite System) coordinates.

[0131] Figure 3 is a simplified schematic diagram of a 5G system 300 involving a Wireless Access Backhaul (WAB) node (or a MW AB node), and in which the present invention may be implementedaccording to one or more example embodiments. This figure first represents a User Equipment (UE) 301 served by a WAB node 310 through the Uu interface. The WAB node 310 is composed of or includes a MT or WAB-MT or MWAB-MT unit / component / entity 311 (also called WAB-UE), and a gNB or WAB-gNB, or MWAB-gNB unit / component / entity 312. Through the WAB-gNB 312, a WAB node acts as a gNB for UEs providing access to the 5G network, i.e. providing a NR access link to the UEs that can be located inside or outside the entity, such as a vehicle, equipped with the WAB node 310 (e.g. on entering / leaving the vehicle). In other words, the WAB-gNB 312 includes full base station or gNB function (including both Central Unit (CU) and distributed unit (DU)) and MT function, where the gNB function is used to communicate with UEs for access service and the MT function is used to communicate with another gNB for backhauling purpose. The WAB node 310 wirelessly connects to the 5G Core Network (using NR Uu interface) through IP connectivity provided by PDU session(s) established by the WAB-MT 311 via a gNB 320, which can be called a backhaul RAN node, BH RAN node, backhaul base station, backhaul gNB or BH gNB. Acting as a legacy UE, the WAB-MT 311 connects via a NG-RAN cell of the BH gNB 320, through a backhaul link (e.g. a wireless backhaul link) that may be a direct link or via a satellite (e.g. when the WAB node 310 is embedded in an airplane). Thus, a PDU session is provided either by a Terrestrial Network (TN) or by a Non-Terrestrial Network (NTN). In addition, the WAB node 310 may embed some core network functions, like a UPF 313, to enable local services to the served UEs. The traffic associated to these local services does not need to use the links to / from the core network via the BH gNB 320, which has the advantages to reduce the load on these links and to run applications having very low latency requirements. For example, where the WAB node 310 includes a UPF 313, the WAB node can connect to one or more local servers (e.g. mounted at the same entity as the WAB 310) enabling a UE served by the WAB access to local services provided by the local servers with no traffic required outside of the WAB node / server environment.

[0132] The BH gNB 320 provides N3 and N2 interfaces so that the WAB-MT 311 can access the functions of its 5G core network 330 (or backhaul 5GC or BH 5GC). Indeed, a WAB-MT 311 may have access to some or several PLMNs through the appropriate subscriptions, and it may connect in a non-roaming manner to one PLMN, e.g. PLMN1 supported by the BH gNB 320, and may then have access to the corresponding 5G core network 330. In particular the WAB-MT 311 interacts with the AMF 332, which can be called the WAB AMF or backhaul AMF or BH AMF, and establishes PDU session(s) with the UPF 331, which can be called the WAB UPF or backhaul UPF or BH UPF. The WAB UPF 331 is controlled by the SMF 333 (through N4 interface), which can be called the WAB SMF or backhaul SMF of BH SMF, and which also interacts with the WABAMF 332 (through N11 interface). There may be one or several intermediate UPFs between the BH gNB 320 and the WAB UPF 331 as mentioned in Figure 2.

[0133] An interface internal to the WAB node 310 exists between the WAB-gNB 312 and the WAB-MT 311, which may be implemented on different or the same hardware resources. For instance, these two functions are implemented on the same processing unit 402 of Figure 4, and interactions exist between the two functions.

[0134] Once the WAB-MT 311 has established a PDU session with the WAB UPF 331, the WAB node is ready to serve UEs and the WAB-gNB 312 can start operating as a legacy gNB. The WAB-gNB may support various PLMNs and the UE 301 connects to one PLMN, e.g. PLMN2, which may be different from the PLMN 1 the WAB-MT 311 connects to. In the case where PLMN 1 and PLMN2 are different, the UE 301 connects to the 5G core network 340 (or UE 5GC), including a UPF 341, which can be called the UE UPF, an AMF 342, which can be called the UE AMF, and a SMF 343, which can be called the UE SMF. The UE SMF 343 interacts with the UE AMF 342 (through N11 interface) and the UE UPF 341 (through N4 interface). In the case where the PLMN1 and the PLMN2 are the same, the UE UPF 341, the UE AMF 342, the UE SMF 343, the WAB UPF 331, the WAB AMF 332, and the WAB SMF 333 belong to the same 5G core network 350. In addition, the UE UPF 341 and the WAB UPF 331 may be the same UPF, the UE AMF 342 and the WAB AMF 332 may be the same AMF, the UE SMF 343 and the WAB SMF 333 may be the same SMF.

[0135] The connections between the UE 301 to the UE UPF 341 and to the UE AMF 342 are possible thanks to the N6 interface between the UE UPF 341 and the WAB UPF 331, and thanks to the N6 interface between the WAB UPF 331 and the UE AMF 342. These N6 interfaces enable the establishment of N2 interface between the WAB-gNB 312 and the UE AMF 342, and the establishment of N3 interface between the WAB-gNB 312 and the UE UPF 341, which allows the UE 301 to access the Data Network 360.

[0136] In case the WAB-MT 311 connects to the 5G network in a roaming manner corresponding to the home routed option, then the PLMN1 is the visited PLMN and the WAB UPF 331 connects to another UPF not represented in Figure 3 in the home PLMN through a N9 interface. It is this other UPF that provides the connection to the UE UPF 341 and the UE AMF 342 through N6 interfaces.

[0137] In case the WAB-MT 311 connects to the 5G network in a roaming manner corresponding to the local breakout option, then the PLMN1 is the visited PLMN and the WAB UPF 331 directly connects to the UE UPF 341 and the UE AMF 342 through N6 interfaces as shown in Figure 3.

[0138] When the BH gNB 320, or part of BH gNB 320, is embedded in a satellite, the WAB-MT 311 uses Non-Terrestrial Network (NTN) to connect to the core network 330. As the BH gNB 320 informs the WAB AMF 332 that it is an NTN satellite (through System Information Blocks asdefined in TS 38.331), the core network 330 can configure the QoS flows transmitted over the backhaul (BH) PDU session(s) established between the WAB-MT 311 and the WAB UPF 331, taking into account the long propagation delay induced by the NTN backhaul link. However, the core network 340 is not aware of the presence of an NTN backhaul link, as the UE AMF 342 is not aware the backhaul link uses NTN because the WAB-gNB 312 is not an NTN base station. Thus, the QoS flows transmitted over the PDU session(s) established between the UE 301 and the UE UPF 341 may not be configured correctly. For instance, the Packet Delay Budget (PDB) may be set to a value too low compared to the actual latency to transmit data between the UE 301 and the UE UPF 341.

[0139] In some cases, the BH gNB 320 is not an NTN base station but rather connects to the core network 330 through an NTN connection. For instance, a satellite (or other NTN entity) may be involved in the interface between the BH-gNB 320 and the BH UPF 331, and / or between the BH-gNB 320 and the BH AMF 332. This configuration raises the same issue as described above.

[0140] Furthermore, when the backhaul link connecting the WAB node 310 uses NTN, the core network 340 is not aware of this information and the actual location of UE 301 served by the WAB-gNB 301 may not be accessible to the core network 340. Indeed, the WAB-gNB 312 should report a Tracking Area code (TAC) that corresponds to the TAC broadcasted by the BH gNB 320, but when the BH gNB 320 is an NTN satellite base station, the BH gNB 320 broadcasts several TACs, and then the WAB-gNB 312 node has no information to select the appropriate TAC to report.

[0141] For a WAB node like WAB node 310, the NG protocol messages exchanged between the WAB-gNB 312 and the core network 340, and the Xn protocol messages exchanged between the WAB-gNB 312 and other base stations of the Radio Access Network, are transmitted through a wireless backhaul link. When the BH gNB 320, or part of BH gNB 320, is embedded in a satellite, the NG and Xn protocol messages exchanged at the WAB-gNB 312 may experience a long transmission latency. Actually, NG and Xn protocols are designed for wired networks, meaning that these protocols assumed that the medium used for the transmission of messages is reliable with low transmission latency. When applied to communication through a wireless backhaul link, these protocols are not resilient to degradation of the link quality, including the increase of transmission latency in case of NTN satellite. As a consequence, some NG and Xn procedures may fail in the context of WAB networks because of poor radio conditions, and / or high load (congestion), and / or long propagation delay of the radio signals on the wireless backhaul link. This situation may lead to system failure and interruption of service at the UEs served by a WAB node. More generally, when NG and Xn application protocols are applied to communication through links that can becomedegraded, some NG and Xn signalling procedures may fail, because of degradation of the link quality, which may lead to system failure and interruption of service.

[0142] The inventors have appreciated that to solve the above issues, the core network 340 may be informed when NTN is used for the wireless backhaul link connecting the WAB node 310 to the network. For this purpose, the WAB-gNB 310 may inform the UE AMF 342 when NTN is used at the wireless backhaul link. Information related to the NTN configuration may be provided to the UE AMF 342 so that the QoS flows of the UE 301 can be correctly configured, the UE 301 can be correctly localized, and the NG protocol is correctly managed (e.g. taking into account the long transmission latency with NTN satellite). Besides, the WAB-gNB 312 may inform the NG-RAN nodes having an Xn connection with the WAB-gNB 312 when an NTN backhaul link is used to convey the Xn protocol messages. This would enable the NG-RAN nodes to take into account the specificities of the NTN backhaul link, for instance the long transmission latency with NTN satellite. Methods to provide NTN backhaul link information to an AMF or to a NG-RAN node are described with the help of the following figures. As described above, these methods may be applied to other network entities within the network.

[0143] Figure 4 is a block schematic diagram of an example network node or RAN node or base station 400, such as base stations or gNBs or WAB nodes shown in Figure 1, in accordance with one or more embodiments of the invention. Each of a WAB node 110, 120a, 120b, 130, 140, or 150 of figure 1 may comprise the elements of the base station of figure 4. Also, the satellite 160 of figure 1 may comprise some of or all of the elements of the base station of figure 4. In the following description, the network node 400 will be referred to generally as a base station. As will be apparent to a skilled person, Figure 4 is a simplified schematic diagram and shows only some of the functional components of an example base station 400 for use in describing the one or more embodiments of the invention.

[0144] The base station 400 includes components for transmitting and receiving communications. As shown in Figure 4, the base station 400 includes a processing unit 402, a wireless interface 404, one or more antennas 410, a network interface 432, and memory 418.

[0145] The network interface 432 manages communications of the base station 400 with the core network, other base stations, local network functions (like UPF), or local servers. It may provide a standardized interface, wired (e.g. fiber) or wireless, to support these communications. Through this network interface 432, the base station 400 may implement the standardized interfaces N2 (based on NGAP protocol) and N3 (based on GPRS tunneling protocol) with the core network, and the standardized interface Xn (based on XnAP protocol) with other base station of the Radio Access Network (RAN), all defined by the 3GPP standard. The network interface 432 may not be presentor active in case the base station 400 is a WAB node that does not support local services, that is not used as a legacy base station like base station 102, 104 in Figure 1, and that is not used as a home base station providing Femto cells like base station 130 in Figure 1.

[0146] The wireless interface 404 is configured to provide wireless communication via communication links (414) with other wireless devices, such as one or more UEs, e.g. link D1041b between base station 104 and the MT / UE unit of WAB node 120b, or link DI 202 between the gNB unit of WAB node 120b and the UE 122. In case of WAB node, the wireless interface 404 may then be used both for the wireless backhaul link(s) with backhaul base station(s) and for the wireless link(s) with the UE(s) served by the WAB node. The wireless interface 404 may be compliant with a fifth-generation (5G) New Radio (NR) system and thus implementing the Uu interface defined by 3GPP standard, or with other wireless communication system. The wireless interface 404 is coupled to the processing unit 402 and to one or more antennas (such as the antenna 410). The wireless interface 404 typically includes a receiving unit 406 and a transmitting unit 408. The configuration of the wireless interface 404 may be limited to connect to one antenna, but preferably several antennas are used, in order to provide beamforming capability. Although not shown in Figure 4, the receiving unit 406 typically includes elements such as a receiver, demodulator, decoder, and the transmitting unit 408 typically includes elements such as a transmitter, modulator, coder. The receiving unit 406 and transmitting unit 408 may together be referred to as a transceiver.

[0147] The processing unit 402 is configured to carrying out processing for operation of the base station 400. The processing unit 402 may be a single processor (e.g. Central Processing Unit) or may comprise two or more processors. The number of processors and the allocation of processing functions to the processors is a matter of design choice for a skilled person. The base station 400 includes memory 418 for storing data and computer programs containing instructions for the operation of the base station 400. Memory 418 includes RAM (Random Access Memory), ROM (Read Only Memory), or combination of both or as a non-limiting example a mass storage device such as a disk or a Solid-State Drive. Memory 418 includes a program memory in which are stored programs containing processor instructions for operation of the base station 400 and for implementing the methods in accordance with one or more embodiments of the invention. The programs may contain a number of different program elements or sub-routines (represented by element 420 in memory 418) containing processor instructions for a variety of different tasks, for example, an element for sending a message as part of a Xn or NG protocol procedure, an element for receiving a message as part of a Xn or NG protocol procedure, an element for sending a message including information related to an NTN backhaul link, an element for receiving a messageincluding information related to an NTN backhaul link. Memory 418 may further include memory (e.g. RAM) for storing information such as information related to an NTN backhaul link, .

[0148] The operation of the program elements or sub-routines 420 will be described in more detail below.

[0149] In an example arrangement, a communication bus 424 provides communication and interoperability between the various elements included in the base station 400 or connected to it. The representation of the bus is not limiting and in particular, the processing unit 402 is operable to communicate instructions to any element of the base station 400 directly or by means of another element of the base station 400.

[0150] In an example implementation, the base station 400 may be or may include an apparatus comprising one or more processing units or processors for performing or implementing the methods in accordance with one or more embodiments of the invention. In other words, the apparatus is capable of performing one or more functions of the base station including performing the methods in accordance with one or more embodiments of the invention by means of the one or more processing units. For example, the one or more processing units uses software to implement the one or more embodiments of the invention as described above with reference to the processing unit 402 of Figure 4. Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, a CPU of a microcontroller Unit (MCU), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated (e.g. on an Integrated Circuit) or discrete logic circuitry. However, alternatively, the one or more processing units for performing or implementing the methods may be implemented in hardware: for example, in the form of an Application Specific Integrated Circuit or ASIC or other hardware comprising logic element (s). Accordingly, the term “processing unit” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein.

[0151] In a 5G core network, an AMF (Access and Mobility management Function) like the WAB AMF 332 or the UE AMF 342, may be implemented with the apparatus described in Figure 4 where the Wireless Interface 404 and the antenna 410 is not present.

[0152] Figure 5 illustrates an example of a wireless communication system 500, including a WAB network or WAB network system, in which embodiments and examples of embodiments of the present invention may be implemented.

[0153] A WAB network will also be referred to as a WAB network system, WAB topology, WAB system, topology or system and so in this application, the terms WAB network system, WAB network, WAB topology, WAB system, topology or system will be used interchangeably.The WAB network system of Figure 5, is composed of three base stations 501, 502 and 503, also referred to as backhaul base stations, or backhaul RAN nodes (also referred to as BH RAN nodes), or backhaul gNBs (also referred to as BH-gNB), two core networks 510 and 520, with the respective AMF entities 511a and 511b (for Core Network 510) and 521a and 521b (for Core Network 520) and the respective UPF entities 512a and 512b (for Core Network 510) and 522a and 522b (for Core Network 520), and two WAB nodes 530 and 540.

[0154] A wired backhaul IP network 590 interconnects the base stations 501, 502 and 503 and the Core Networks 510 and 520. For instance, this wired link consists of optical fiber cable(s). In some cases, one or more of base stations 501, 502, and 503 may be connected to Core Networks 510 and 520 via a wireless connection, including an NTN connection (see Figure 12 and accompanying description).

[0155] As discussed above, each WAB node comprises a Mobile Termination (MT) component or part or unit (WAB-MT 531 for WAB node 530 and WAB-MT 541 for WAB node 540) and a RAN node or base station or gNB component or part or unit (WAB-gNB 532 for WAB node 530 and WAB-gNB 542 for WAB node 540).

[0156] WAB node 530 and WAB node 540 may also embed a UPF entity, respectively UPF entity 533 and UPF 543, as previously discussed in figure 3, allowing WAB-node 530 to provide UEs 551, 552 and 561 with some local services, such as for instance inter-UE communication where the user data exchanged between the two UEs would be routed through UPF entity 533 / 543 instead of being routed through a UPF entity belonging to Core Network 510 or 520.

[0157] WAB node 530 is connected to the serving backhaul base station referred to as BH-gNBl, 501 through the wireless backhaul (BH) link 5011.

[0158] WAB node 540 may be connected to the serving backhaul base station referred to as BH-gNB2, 502 through the wireless backhaul (BH) link 5021 or to the serving backhaul base station referred to as BH-gNB3, 503 through wireless backhaul (BH) links 5031a and 5031b (with the satellite 580 in between) or, in case of dual connectivity, to both the serving backhaul base station BH-gNB2, 502 through BH link 5021 and the serving backhaul base station BH-gNB3, 503 through BH links 5031a and 503 lb (with the satellite 580 in between).

[0159] WAB-gNB 532 of WAB node 530 is also connected to UE 551 through communication link or radio link 5301 and to UE 552 through communication link or radio link 5302.

[0160] Similarly, WAB-gNB 542 of WAB node 540 is also connected to UE 561 through communication link or radio link 5401.Although Figure 5 shows only UE 561 connected to WAB node 540, it will be appreciated that there may be a plurality of UEs connected to WAB nodes of the wireless communication system.

[0161] WAB-gNB 532 and WAB-MT 531 may be connected to a same AMF function or entity (e.g., AMF 511a) or to different AMF functions or entities belonging to the same Core Network (e.g., AMF 511a and AMF 511b) or to different Core Network (e.g., AMF 511a and AMF 521a).

[0162] Some AMF functions may be implementing WAB-specific features for managing a WAB node (e.g., advanced mobility features). Some AMF functions may not implement such features but may still be capable of serving a WAB node with a limited set of basic features. Some AMF functions may not be capable of serving a WAB node.

[0163] In this example, it is assumed that BH-gNB3 503 is an NTN satellite base station (based on NTN transparent payload architecture) while BH-gNBl 501 and BH-gNB2 are TN (Terrestrial Network) base stations. When the NTN architecture is transparent payload, the NTN base station BH-gNB3 503 is embedded in an Earth station and the satellite 580 is a relay between the WAB-MT 541 and the BH-gNB3 503. It can be noted that the regenerative payload architecture could be used as well. In this case, the BH-gNB3 503 is fully embedded in the satellite 580 and the Earth station (or gateway) connects the BH-gNB3 503 to the 5G core network 510 with a wired backhaul link between the Earth station and the core network 510. With both NTN architectures, the NTN backhaul link is actually composed of two wireless backhaul links: the link 5031a between the WAB-MT 541 and the satellite 580, and the link 5031b between the satellite 580 and the Earth station.

[0164] As a first scenario, and taking the example of WAB node 540, a dual-connectivity configuration may be applied to the WAB-MT 541, initially connected to BH-gNB2 502 only through the link 5021. Indeed, the WAB-MT 541 periodically performs a cell search procedure, as defined in 3GPP TS 38.300, trying to detect PSS (Primary Synchronization Signal) and SSS (Secondary Synchronization Signal). The WAB-node may report to BH-gNB2 502 the presence of a new cell, for instance one cell managed by the BH-gNB3 503, through a measurement report. Based on the analysis of the measurement report, the BH-gNB2 502 may request to the BH-gNB3 503 the establishment of a dual connectivity for the WAB-MT 541 with an additional connection through the links 503 la / 503 lb. The BH-gNB3 503 may accept the request and proceed to the connection of the WAB-MT 541 according to the procedure described in TS 37.340 section 10.2.2. As a result, the WAB-MT 541, and thus the WAB node 540 is dual-connected. The BH-gNB2 502 may take benefit of the dual connectivity of WAB node 540 to balance the traffic load by offloading some traffic (data / user traffic or control traffic) initially planned to be transmittedthrough the link 5021. Some or all the traffic associated to the WAB node 540 (i.e. control data related to the WAB node, and control and user data related to the UEs served by the WAB node 540) may be transmitted through the links 5031a / 5031b and through the IP connectivity between BH-gNB2502 and BH-gNB3 503. Dual-connectivity configuration is however transparent for the WAB-gNB 542 and for the UEs served by the WAB-gNB 542.

[0165] As a second scenario, the radio link 5021 may experience radio link deficiency due to some unexpected interference or shadowing phenomena. For such reasons, the WAB-MT 541 may lose the connection with the BH-gNB2 502 and declare a Radio Link Failure (RLF). Then, the WAB-MT 541 will try to reestablish the connection in the same or a different cell controlled by BH gNB2502 or by another gNB. Thus, the WAB-MT 541 may try to connect to a cell controlled by BH-gNB3 503 by requesting the establishment of the link 5031a. In this case, the reestablishment procedure described in TS 38.300 section 9.2.3.3 may be applied, which enables a UE to maintain the RRC connection. With such procedure, the BH gNB3 503 sends to the BH gNB2502 a request to retrieve the context of the WAB-MT 541. Based on the response from the BH gNB2502, the BH gNB3 503 may accept the connection of the WAB-MT 541. Then, all the traffic related to the WAB node 540 (and the served UEs) will now transit through the BHgNB 503. The reestablishment procedure does not involve the WAB-gNB 542 and its served UEs. If the reestablishment is rapidly performed after RLF, the service interruption at the UE 561 may be avoided or limited.

[0166] As a third scenario, the WAB-MT 541 may be handed over from the current serving cell to a new cell. Indeed, based on the measurement reports provided by the WAB-MT 541, the BH-gNB2502 may detect that the WAB-MT 541 would have a better connection through a cell managed by the BH-gNB3 503. Then, the BH-gNB2 502 may trigger a handover procedure described in TS 38.300 section 9.2.3.2. In this procedure, the BH-gNB2 502 sends a handover request to the BH-gNB3 503 along with information related to the WAB-MT 541. Based on this information, the BH gNB3 503 may accept the handover request and proceed to the admission of the WAB-MT 541. Then, all the traffic related to the WAB node 540 (and the served UEs) will now transit through the BH-gNB 503. The handover procedure does not involve the WAB-gNB 542 and its served UEs, and it may be transparent for the WAB-gNB and the served UEs (no interruption of service).

[0167] With this example of figure 5, it is further assumed that, when the WAB-MT 541 accesses the network via the BH-gNB 502 and / or the BH-gNB 503, it is served by the AMF 51 la of the 5G core network 510, and when the WAB-gNB 542 serves the UE 561, the WAB-gNB 542 establishes a NG connection with the AMF 521a of the 5G core network 520. Still in this example, it is assumed that the WAB-gNB 542 establishes an Xn connection with BH-gNB 1 501, BH-gNB2 502, BH-gNB3 503, and WAB-gNB 532. In the configuration where the WAB-MT 541 accesses the networkthrough the BH-gNB3 503 only, AMF 521a, BH-gNBl 501 and WAB-gNB 532 may not be aware that an NTN backhaul link is present in the path to communicate with the WAB-gNB 542. In that case, the WAB-gNB 532 provides information related to the NTN backhaul link to the AMF 521a using a NG Application Protocol (NGAP) message described at figure 7a. The WAB-gNB 532 provides information related to the used NTN backhaul link to the BH-gNBl 501, and WAB-gNB 532 using a Xn Application Protocol (XnAP) message described at figure 7b.

[0168] To be able to provide information, the WAB-gNB 542 may first retrieve information related to the used NTN backhaul link. For that purpose, the WAB-gNB 542 may rely on either or both of a Radio Resource Control (RRC) protocol message received at the WAB-MT 541 and described in figure 8a, and a Xn Application Protocol (XnAP) message described in figure 8b.

[0169] Figure 6a is a schematic diagram 600 illustrating the protocol stack associated to the NG or Xn interface in the user plane, referred to as NG-U or Xn-U. The NG-U interface and the associated Transport Network Layer (TNL) protocol stack are described in the following 3GPP specifications: TS 38.410, TS 38.411, TS 38.414. The Xn-U interface and the associated TNL protocol stack are described in the following 3GPP specifications: TS 38.420, TS 38.421, TS 38.424

[0170] The NG user plane interface (NG-U) is defined between a NG-RAN node and a UPF. The Xn user plane interface (Xn-U) is defined between two NG-RAN nodes. Both interfaces are built on IP (Internet Protocol) transport. GTP-U (GPRS (General Packet Radio Service) Tunnelling Protocol for User Plane) 601 is used on top of UDP (User Datagram Protocol) 602 and IP 603 to carry the user plane PDUs between the NG-RAN node and the UPF (for NG-U), or user plane PDUs between two NG-RAN nodes (for Xn-U).

[0171] GTP-U 601 is defined in TS 29.281, while UDP 602 is defined in IETF RFC 768, and IP 603 is defined in IETF RFC 8200 (for IPv6) and IETF RFC 791 (for IPv4).

[0172] Any data link layer 604 and physical layer 605 that fulfil the requirements toward the upper layers 601, 602, 603 may be used. For instance, they can be implemented with Ethernet protocol over fiber cables.

[0173] Figure 6b is a schematic diagram 610 illustrating the protocol stack associated to the NG or Xn interface in the control plane, referred to as NG-C or Xn-C. The NG-C interface and the associated Transport Network Layer (TNL) protocol stack are described in the following 3GPP specifications: TS 38.410, TS 38.411, TS 38.412, TS 38.413. The Xn-C interface and the associated TNL protocol stack are described in the following 3GPP specifications: TS 38.420, TS 38.421, TS 38.422, TS 38.423.

[0174] The NG control plane interface (NG-C) is defined between a NG-RAN node and an AMF. The NG control plane interface may also be called or provides the N2 interface discussed above.The Xn control plane interface (Xn-C) is defined between two NG-RAN nodes. Both interfaces are built on IP (Internet Protocol) transport. NGAP (Next Generation Application Protocol) or XnAP (Xn Application Protocol) 611 is used on top of SCTP (Stream Control Transmission Protocol) 612 and IP 613 to carry the control plane data between the NG-RAN node and the AMF (for NG-C), or between two NG-RAN nodes (for Xn-C).

[0175] NGAP 611 is defined in TS 38.413, XnAP 611 is defined in TS 38.423, while SCTP 612 is defined in IETF RFC 4960, IP 603 is defined in IETF RFC 8200 (for IPv6) and IETF RFC 791 (for IPv4).

[0176] Any data link layer 614 and physical layer 615 that fulfil the requirements toward the upper layers 611, 612, 613 may be used. For instance, they can be implemented with Ethernet protocol over fiber cables.

[0177] Details of exampleNGAP procedures are set out in section 8 of TS 38.413. NGAP procedures may also be referred to as NG protocol procedures or signalling procedures of NG application protocol. Several NGAP elementary procedures to manage a NG-C interface are specified in TS 38.413.

[0178] Details of example XnAP procedures are set out in section 8 of TS 38.423. XnAP procedures may also be referred to as Xn protocol procedures or signalling procedures of Xn application protocol.

[0179] Figure 7a is a schematic diagram showing an example message flow 700 on a NG interface for indicating the presence of an NTN backhaul link to convey NGAP messages, and for providing information related to this NTN backhaul link in accordance with one or more embodiments of the present invention. This figure shows a NG-RAN node 701 like WAB-gNB 542 of figure 5, and an AMF 702 like the AMF 521a of figure 5 in a 5G core network (5GC) like the core network 520 of figure 5.

[0180] The NG-RAN node 701 sends the message NTN BH LINK INDICATION 703 to the AMF 702, which may respond by sending the message NTN BH LINK INDICATION RESPONSE 705.

[0181] In addition to an identifier of the sender of the message (for instance a Global RAN Node ID as defined in TS 38.413 section 9.3.1.5 and corresponding to an identifier of the NG-RAN node 701), and an optional indication that the NG-RAN 701 is the gNB component of a WAB node, the message NTN BH LINK INDICATION 703 includes an indication that an NTN backhaul link is used at the NG interface. The indication (e.g. NTN BH link Indication) may be limited to one bit set to value ‘ 1 ’ when the NG interface uses an NTN backhaul link and value ‘0’ otherwise.

[0182] The optional indication that the NG-RAN 701 is the gNB component of a WAB node may be the Additional ULI (User Location Information) providing some information to help the corenetwork to localize the WAB node (and thus to localize the UEs served by the WAB node). This Additional ULI IE (Information Element) may be composed of an NR CGI (New Radio Cell Group Identity) as defined in TS 38.413 section 9.3.1.7, and of a TAI (Tracking Area Identity) as defined in TS 38.413 section 9.3.3.11, both reflecting the location of the WAB node.

[0183] Besides, the message 703 may include NTN backhaul link information composed of at least one of the following information elements (IES):

[0184] An NTN BH link information indicating whether the NTN backhaul link uses NTN satellite, and it may also indicate the type of orbit of the NTN satellite;

[0185] A BH NTN TAI (Tracking Area Identity) information, which may correspond to the NTN TAI Information IE defined in TS 38.413 section 9.3.3.53. The presence of this IE also indicates that the NG interface between the NG-RAN node 701 and the AMF 702 uses an NTN satellite backhaul link. It may include a list of TACs associated to a PLMN and broadcasted by the NTN satellite base station between the NG-RAN node 701 and the AMF 702 (for instance the BH-gNB3 503 between the WAB-gNB 542 and the AMF 521a). It may also indicate a specific TAC among the list of broadcasted TACs, which corresponds to the geographical area where the NG-RAN node 701 is estimated to be actually located;

[0186] An NTN configuration composed of several NTN parameters, which may correspond to parameters included in the SIB 19 (System Information Block 19) defined in TS 38.331. For a UE receiving SIB 19, these parameters such as satellite ephemeris data can be used by the UE to access the network via NTN satellite. The presence of this IE also indicates that the NG interface between the NG-RAN node 701 and the AMF 702 uses an NTN satellite backhaul link;

[0187] An NTN NR CGI (New Radio Cell Global Identity), which may correspond to the NR CGI IE defined in TS 38.413 section 9.3.1.7. This NR CGI may correspond to the mapped cell ID that the NTN base station reports to the AMF(s) it is connected to. This mapped cell ID corresponds to the geographical area the NTN satellite base station is currently covering (for instance the mapped cell ID reported by the BH-gNB3 503 to the AMF 511a);

[0188] A Location information related to the RAN node 701. This IE may correspond to the CommonLocationlnfo IE defined in TS 38.331, which may include coordinates, and / or velocity information related to the NG-RAN node 701;

[0189] An identifier of the AMF serving a MT component co-located with the NG-RAN node 701. For instance, this IE is a GUAMI as defined in TS 38.413 section 9.3.3.3. Taking theexample figure 5, it corresponds to the identity of the AMF 511a serving the WAB-MT 541 co-located with the WAB-gNB 542 in the WAB node 540. This identifier may then be used by the AMF 702 (e.g. the AMF 521a in figure 5) to request NTN backhaul link information to the identified AMF;

[0190] - An identifier of the MT component co-located with the NG-RAN node 701. For instance, this IE may be a 5GS mobile identity as defined in TS 24.501 section 9.11.3.4, or an AMF UENGAP ID as defined in TS 38.413 section 9.3.3.1. In addition, the identifier of the MT component may include a NR CGI (New Radio Cell Group Identity) as defined in TS 38.413 section 9.3.1.7, corresponding to the identity of the cell where the MT component co-located with the NG-RAN node 701 is being served. Taking the example of figure 5, it corresponds to an identity of the WAB-MT 541 co-located with the WAB-gNB 542 in the WAB node 540. This identifier may then be used by the AMF 702 (e.g., the AMF 521a in figure 5) to request NTN backhaul link information to the AMF serving the WAB-MT 541. This IE may be used in association with an identifier, as described above, of the AMF serving the MT component of the NG-RAN node 701. This MT’ s identifier is then provided by the AMF 702 to the AMF serving the MT component of the NG-RAN node 701, along with a request to obtain NTN backhaul link information;

[0191] - An identifier of the backhaul NG-RAN node serving the MT component co-located with the NG-RAN node 701. For instance, this IE may be a Global RAN Node ID, as defined in TS 38.413 section 9.3.1.5. Taking the example of figure 5, it corresponds to an identity of the BH-gNB3 503 serving the WAB-MT 541 co-located with the WAB-gNB 542 in the WAB node 540. NTN backhaul link is used, it means that the backhaul NG-RAN node serving the MT component may be embedded in a satellite (or a drone, or high-altitude platform) or it may be connected to the core network through a satellite (or a drone, or a high-altitude platform). As this identifier uniquely identifies a NG-RAN node, the AMF 702 may use this identifier when accessing a database in the core network storing information related to each NG-RAN node. Then, the AMF 702 may retrieve NTN parameters associated with the identified backhaul NG-RAN node. In an alternative method, the AMF 702 may use this identifier in association with an identifier, as described above, of the AMF serving the MT component of the NG-RAN node 701. This identifier of the backhaul NG-RAN node is then provided by the AMF 702 to the AMF serving the MT component of the NG-RAN node 701, along with a request to obtain NTN backhaul link information.The IES BH NTN TAI information, NTN NR CGI, Location information may be used by the AMF 702 to estimate the transmission latency between the AMF 702 and the NG-RAN node 701. These IEs may also be used by the AMF 702 to assist the LMF (Location Management Function) of the core network to locate the NG-RAN node 701, and thus to locate the UE(s) served by the NG-RAN node 701.

[0192] According to embodiments of the disclosure, figure 7a may correspond to the procedure NG Setup described in TS 38.413 section 8.7.1, where the message 703 is the message NG SETUP REQUEST, the message 705 is the message NG SETUP RESPONSE or the message NG SETUP FAILURE, these 3 messages being described in TS 38.413 sections 9.2.6.1, 9.2.6.2, 9.2.6.3 respectively. The message NG SETUP REQUEST is sent by the NG-RAN node 701 to establish a NG connection with the AMF 702. For instance, once the WAB-MT 541 connects to the BH-gNB3 503 (which is an NTN satellite base station) while moving to a new geographical area, the WAB-gNB 542 may need to establish an NG connection to a new AMF which is the AMF 521a in the example. Thus, the WAB-gNB 542 sends to the AMF 521a a NG SETUP REQUEST message that includes NTN backhaul link information as defined above. Then, the AMF 521a can take into account the presence of an NTN backhaul link to, for instance, correctly manage the PDU session(s) of UE(s) served by the WAB-gNB 542.

[0193] According to embodiments of the disclosure, figure 7a may correspond to the procedure RAN Configuration Update described in TS 38.413 section 8.7.2, the message 703 is the message RAN CONFIGURATION UPDATE, the message 705 is the message RAN CONFIGURATION UPDATE ACKNOWLEDGE or the message RAN CONFIGURATION UPDATE FAILURE, these 3 messages being described in TS 38.413 sections 9.2.6.4, 9.2.6.5, 9.2.6.6 respectively. The message RAN CONFIGURATION UPDATE is sent by the NG-RAN node 701 to provide configuration information to the AMF 702. For instance, once the WAB-MT 541 connects to the BH-gNB3 503 (which is an NTN satellite base station) while moving to a new geographical area, the WAB-gNB 542 may already have established a NG connection with the AMF 521a and may want to maintain this NG connection. In case of handover of the WAB-MT 541 from the BH-gNB2 502 to the BH-gNB3 503, the wireless backhaul link becomes an NTN backhaul link. Thus, the WAB-gNB 542 sends to the AMF 521a a RAN CONFIGURATION UPDATE message that includes NTN backhaul link information as defined above, and the AMF 521a can take into account the presence of an NTN backhaul link to, for instance, correctly manage the PDU session(s) of UE(s) served by the WAB-gNB 542.

[0194] According to other embodiments of the disclosure, the message 703 corresponds to a UE-associated message containing User Location Information (ULI) related to a UE served by the NG-RAN node 701. For instance, the message 703 is the message LOCATION REPORT defined in TS 38.413 section 9.2.11.3, or the message UPLINK NAS TRANSPORT defined in TS 38.413 section 9.2.5.3, or the message INITAIL UE MESSAGE defined in TS 38.413 section 9.2.5.1, or the message PATH SWITCH REQUEST defined in TS 38.413 section 9.2.3.8, or the message UE CONTEXT RESUME REQUEST defined in TS 38.413 section 9.2.2.19, or a message related to the setup or the modification of a PDU Session associated with the UE as defined in TS 38.413 section 9.2.1. Each of these messages may be enhanced to included additional ULI (User Location Information) which corresponds to the NTN backhaul link information defined above.

[0195] Figure 7b is a schematic diagram showing an example message flow 710 on a Xn interface for indicating the presence of an NTN backhaul link to convey XnAP messages, and for providing information related to this NTN backhaul link in accordance with embodiments of the disclosure. This figure shows a NG-RAN node 1, 711, like WAB-gNB 542 of figure 5, and a NG-RAN node 2, 712, like the BH-gNBl 501 or the WAB-gNB 532 of figure 5.

[0196] The NG-RAN node 711 sends the message NTN BH LINK INDICATION 713 to the NG-RAN node 712, which may respond by sending the message NTN BH LINK INDICATION RESPONSE 715.

[0197] In addition to an identifier of the sender of the message (for instance a Global RAN Node ID, as defined in TS 38.413 section 9.3.1.5 and corresponding to an identifier of the NG-RAN node 711), and an optional indication that the NG-RAN node 711 is the gNB component of a WAB node, the message NTN BH LINK INDICATION 713 includes an indication that an NTN backhaul link is used at the Xn interface. The indication (e.g. NTN BH link Indication) may be limited to one bit set to value ‘ 1 ’ when the Xn interface uses an NTN backhaul link and value ‘0’ otherwise.

[0198] Besides, the message 713 may include NTN backhaul link information composed of at least one of the following information elements (IES):

[0199] An NTN BH link information indicating whether the NTN backhaul link uses NTN satellite, and it may also indicate the type of orbit of the NTN satellite;

[0200] An NTN configuration composed of several NTN parameters, which may correspond to parameters included in the SIB 19 (System Information Block 19) defined in TS 38.331. For a UE receiving SIB 19, these parameters such as satellite ephemeris data can be used by the UE to access the network via NTN satellite. The presence of this IE also indicates that the NG interface between the NG-RAN node 711 and the NG-RAN node 712 uses an NTN satellite backhaul link;

[0201] An NTN NR CGI (New Radio Cell Global Identity), which may correspond to the NR CGI IE defined in TS 38.413 section 9.3.1.7. This NR CGI may correspond to the mappedcell ID that the NTN base station reports to the AMF(s) it is connected to. This mapped cell ID corresponds to the geographical area the NTN satellite base station is currently covering (for instance the mapped cell ID reported by the BH-gNB3 503 to the AMF 511a).

[0202] A Location information related to the NG-RAN node 711. This IE may correspond to the CommonLocationlnfo IE defined in TS 38.331, which may include coordinates, and / or velocity information related to the NG-RAN node 711;

[0203] The IES BH NTN TAI information, NTN NR CGI, Location information may be used by the NG-RAN node 712 to estimate the transmission latency between the NG-RAN node 711 and the NG-RAN node 712.

[0204] According to embodiments of the disclosure, figure 7b may correspond to the procedure Xn Setup described in TS 38.423 section 8.4.1, where the message 713 is the message XN SETUP REQUEST, the message 715 is the message XN SETUP RESPONSE or the message XN SETUP FAILURE, these 3 messages being described in TS 38.423 sections 9.1.3.1, 9.1.3.2, 9.1.3.3 respectively. The message XN SETUP REQUEST is sent by the NG-RAN node 711 to establish a Xn connection with the NG-RAN node 712. For instance, once the WAB-MT 541 connects to the BH-gNB3 503 (which is an NTN satellite base station) while moving to a new geographical area, the WAB-gNB 542 may establish a Xn connection with BH-gNBl 501. Thus, the WAB-gNB 542 sends to the BH-gNBl 501 XN SETUP REQUEST message that includes NTN backhaul link information as defined above, and the BH-gNBl 501 can take into account the presence of an NTN backhaul link to correctly manage the Xn protocol messages exchanged with the WAB-gNB 542 (for instance by taking into account the long transmission latency).

[0205] According to embodiments of the disclosure, figure 7b may correspond to the procedure NG-RAN Configuration Update described in TS 38.423 section 8.4.2, the message 713 is the message NG-RAN CONFIGURATION UPDATE, the message 715 is the message NG-RAN CONFIGURATION UPDATE ACKNOWLEDGE or the message NG-RAN CONFIGURATION UPDATE FAILURE, these 3 messages being described in TS 38.423 sections 9.1.3.4, 9.1.3.5, 9.1.3.6 respectively. The message NG-RAN CONFIGURATION UPDATE is sent by the NG-RAN node 711 to provide configuration information to the NG-RAN node 712. For instance, once the WAB-MT 541 connects to the BH-gNB3 503 (which is an NTN satellite base station) while moving to a new geographical area, the WAB-gNB 542 may already have established a Xn connection with the BH-gNBl 501 and may want to maintain this Xn connection. In case of handover of the WAB-MT 541 from the BH-gNB2 502 to the BH-gNB3 503, the wireless backhaul link uses NTN. Thus, the WAB-gNB 542 sends to the BH-gNB 1 501 a NG-RAN CONFIGURATION UPDATE messagethat includes NTN backhaul link information as defined above, and the BH-gNBl 501 can take into account the presence of an NTN backhaul link to correctly manage the Xn protocol messages exchanged with the WAB-gNB 542.

[0206] Figure 8a is a schematic diagram showing an example message flow 800 on a Uu interface for providing information related to an NTN backhaul link in accordance with embodiments of the disclosure. This figure shows a UE 801, like WAB-MT 541 of figure 5, and a NG-RAN node 802, like the BH-gNB3 503 of figure 5.

[0207] The NG-RAN node 802 sends the message NTN BH LINK INFORMATION 803 to the UE 801, which may respond by sending the message NTN BH LINK INFORMATION RESPONSE 805. The message 803 includes information related to an NTN backhaul link. Taking the example of figure 5, the WAB-MT 541 receives the message 803 from the BH-gNB3 503. Then, the WAB-MT 541 relays the received information to the WAB-gNB 542 (through an interface internal to the WAB node 540).

[0208] According to embodiments of the disclosure, the message 803 corresponds to the SIB1 (System Information Block 1) defined in TS 38.331. When broadcasted by an NTN base station, SIB1 does not include a Tracking Area Code (TAC) but a list of TACs, with the tracking AreaList-rl7 field only present in an NTN cell.

[0209] According to embodiments of the disclosure, the message 803 corresponds to the SIB 19 (System Information Block 19) defined in TS 38.331 and broadcasted only by an NTN satellite base station. SIB19 contains satellite assistance information for NTN access.

[0210] Both SIB1 and SIB 19 may be enhanced to include the NTN backhaul link information defined in figure 7a.

[0211] According to embodiments of the disclosure, the message 803 corresponds to the RRCReconfiguration message defined in TS 38.331 but including NTN backhaul link information as defined in figure 7a, and the message 805 corresponds to the RRCReconfigurationComplete message defined in TS 38.331. Taking the example of figure 5, when the WAB-MT 541 connects to the BH-gNB3 503, the WAB-MT 541 may indicate that the connection is related to a WAB node and not to legacy UE. When the BH-gNB3 503 receives this WAB node indication and supports WAB system, the BH-gNB3 503 includes NTN backhaul link information as defined in figure 7a in the RRCReconfiguration message sent to the WAB-MT 541. Then, the WAB-MT 541 relays the received NTN backhaul link information to the WAB-gNB 542 (through an interface internal to the WAB node 540).

[0212] Figure 8b is a schematic diagram showing an example message flow 810 on a Xn interface for providing information related to an NTN backhaul link in accordance with embodiments of thedisclosure. This figure shows a NG-RAN node 1, 811, like WAB-gNB 542 of figure 5, and a NG-RAN node 2, 812, like the BH-gNB3 503 of figure 5.

[0213] The NG-RAN node 812 sends the message NTN BH LINK INFORMATION 813 to the NG-RAN node 811, which may respond by sending the message NTN BH LINK INFORMATION RESPONSE 815.

[0214] In addition to an identifier of the sender of the message (for instance a Global RAN Node ID, as defined in TS 38.413 section 9.3.1.5 and corresponding to an identifier of the NG-RAN node 812), the message NTN BH LINK INFORMATION 813 comprised information related to an NTN backhaul link. Thus, NTN backhaul link information includes at least one of the information elements (IES) defined in figure 7a.

[0215] Figure 8b may correspond to the procedure Xn Setup described in TS 38.423 section 8.4.1, where the message 813 is the message XN SETUP REQUEST, the message 815 is the message XN SETUP RESPONSE or the message XN SETUP FAILURE, these 3 messages being described in TS 38.423 sections 9.1.3.1, 9.1.3.2, 9.1.3.3 respectively. The message XN SETUP REQUEST is sent by the NG-RAN node 812 to establish a Xn connection with the NG-RAN node 811. For instance, once the WAB-MT 541 connects to the BH-gNB3 503 (which is an NTN satellite base station) while moving to a new geographical area, the BH-gNBl 501 may establish a Xn connection with the gNB component co-located with the WAB-MT 541, i.e. the WAB-gNB 542. Thus, the sends BH-gNB3 503 to the WAB-gNB 542 XN SETUP REQUEST message that includes NTN backhaul link information, and the WAB-gNB 542 can then inform the AMF(s) it is connected to via a NG interface, and / or inform other NG-RAN node(s) it is connected to via a Xn interface. It can be noted that the message 813 may correspond to the XN SETUP RESPONSE message or the message XN SETUP FAILURE, as a reply to a XN SETUP REQUEST message sent by the NG-RAN node 811. With the example of figure 5, the WAB-gNB 542 may send the request to establish Xn connection with the backhaul base station serving the MT component co-located with the WAB-gNB 542, and the BH-gNB3 503 replies with XN SETUP RESPONSE or XN SETUP FAILURE including NTN backhaul link.

[0216] Alternatively or additionally, figure 8b may correspond to the procedure NG-RAN Configuration Update described in TS 38.423 section 8.4.2, the message 813 is the message NG-RAN CONFIGURATION UPDATE, the message 815 is the message NG-RAN CONFIGURATION UPDATE ACKNOWLEDGE or the message NG-RAN CONFIGURATION UPDATE FAILURE, these 3 messages being described in TS 38.423 sections 9.1.3.4, 9.1.3.5, 9.1.3.6 respectively. The message NG-RAN CONFIGURATION UPDATE is sent by the NG-RAN node 812 to provide configuration information to the NG-RAN node 811. For instance, once theWAB-MT 541 connects to the BH-gNB3 503 (which is anNTN satellite base station) while moving to a new geographical area, the BH-gNB3 503 may already have established a Xn connection with the WAB-gNB 542 and may want to maintain this Xn connection. In case of handover of the WAB-MT 541 from the BH-gNB2 502 to the BH-gNB3 503, the wireless backhaul link uses NTN. Thus, the BH-gNB3 503 sends to the WAB-gNB 542 a NG-RAN CONFIGURATION UPDATE message that includes NTN backhaul link information as defined above, and the WAB-gNB 542 can then inform the AMF(s) it is connected to via a NG interface, and / or inform other NG-RAN node(s) it is connected to via a Xn interface. It can be noted that the message 813 may correspond to the NG-RAN CONFIGURATION UPDATE ACKNOWLEDGE message or the message NG-RAN CONFIGURATION UPDATE FAILURE, as a reply to a NG-RAN CONFIGURATION UPDATE message sent by the NG-RAN node 811. With the example of figure 5, the WAB-gNB 542 may send a configuration update to the BH-gNB3 503, and the BH-gNB3 503 replies with NG-RAN CONFIGURATION UPDATE ACKNOWLEDGE or NG-RAN CONFIGURATION UPDATE FAILURE including NTN backhaul link.

[0217] Figure 9a is a flowchart of an example method 900 for managing, at a NG-RAN node, the presence of an NTN backhaul link. For example, with reference to the communication system 500 shown in and described with respect to figure 5, the NG-RAN node may be the WAB-gNB 542, and the AMF 521a is a UE’s AMF (i.e. an AMF managing UE(s) served by the WAB-gNB 542). The method 900 as shown in and described with respect to figure 9a may be performed by software elements and / or hardware elements. The NG-RAN node may be implemented in a network node 400 as shown in and described with reference to figure 4 with the method as shown in and described with respect to figure 9a being performed by an apparatus for the NG-RAN node including one or more processing units, such as the processing unit 402.

[0218] At step 901, the NG-RAN node receives an indication that a backhaul link uses NTN.

[0219] At step 902, the NG-RAN node may receive information related to the NTN backhaul link. The indication and information provided at steps 901 and 902 may be received in the same message from the same entity or from different message from the same entity or from different entities. Taking the example of figure 5, the WAB-gNB 542 may receive the NTN backhaul link indication and / or information from the WAB-MT 541 (based on the description of figure 8a) and / or from the BH-gNB3 503 (based on the description of figure 8b).

[0220] At step 903, the NG-RAN node sends to a UE’s AMF, indication that a backhaul link uses NTN. If available, the NG-RAN node sends information related to the NTN backhaul link.

[0221] At step 904, the NG-RAN node may receive a response from the UE’s AMF, for instance to acknowledge the reception of the indication / information.The steps 903 and 904 corresponds to the procedure described with figure 7a.

[0222] In addition to these steps 901 to 904, the NG-RAN node may use the received NTN backhaul link information to correctly manage the NG protocol messages exchanged with the UE’ s AMF over the NTN backhaul link, for instance taking into account the long transmission latency.

[0223] Figure 9b is a flowchart of another example method for managing, at a NG-RAN node, the presence of an NTN backhaul link. For example, with reference to the communication system 500 shown in and described with respect to figure 5, the NG-RAN node may be the WAB-gNB 542, and the BH-gNBl 501 is a NG-RAN node communicating via a Xn interface with the WAB-gNB 542. The method 910 as shown in and described with respect to figure 9b may be performed by software elements and / or hardware elements. The NG-RAN node may be implemented in a network node 400 as shown in and described with reference to figure 4 with the method as shown in and described with respect to figure 9b being performed by an apparatus for the NG-RAN node including one or more processing units, such as the processing unit 402.

[0224] At step 911, the NG-RAN node receives an indication that a backhaul link uses NTN.

[0225] At step 912, the NG-RAN node may receive information related to the NTN backhaul link. The indication and information provided at steps 911 and 912 may be received in the same message from the same entity or from different message from the same entity or from different entities. Taking the example of figure 5, the WAB-gNB 542 may receive the NTN backhaul link indication and / or information from the WAB-MT 541 (based on the description of figure 8a) or from the BH-gNB3 503 (based on the description of figure 8b).

[0226] At step 913, the NG-RAN node sends to another NG-RAN node, an indication that a backhaul link uses NTN. If available, the NG-RAN node sends information related to the NTN backhaul link.

[0227] At step 914, the NG-RAN node may receive a response from the other NG-RAN node, for instance to acknowledge the reception of the indication / information.

[0228] The steps 913 and 914 corresponds to the procedure described with figure 8a.

[0229] In addition to these steps 911 to 914, the NG-RAN node may use the received NTN backhaul link information to correctly manage the Xn protocol messages exchanged with the other NG-RAN node over the NTN backhaul link, for instance taking into account the long transmission latency.

[0230] Figure 10 is a flowchart of an example method 1000 for managing, at an Access and Management Function (AMF) of a core network, the presence of an NTN backhaul link. For example, with reference to the communication system 500 shown in and described with respect to figure 5, the AMF is the AMF 521a, and the WAB-gNB 542 is the NG-RAN node the AMF can connect to manage the UE(s) served by the NG-RAN node. The method 1000 as shown in and described with respect to figure 10 may be performed by software elements and / or hardwareelements. The AMF may be implemented in a network node 400 as shown in and described with reference to figure 4 with the method as shown in and described with respect to figure 10 being performed by an apparatus for the AMF including one or more processing units, such as the processing unit 402.

[0231] At step 1001, the AMF receives an indication from a NG-RAN node that a backhaul link uses NTN.

[0232] At step 1002, the AMF may receive from the NG-RAN node information related to the NTN backhaul link.

[0233] The indication and information provided at steps 1001 and 1002 may be received in the same message from the same entity. Taking the example of figure 5, the AMF 521a may receive the NTN backhaul link indication and / or information from the WAB-gNB 542 (based on the description of figure 7a).

[0234] At step 1003, the AMF may send a response to the NG-RAN node, for instance to acknowledge the reception of the indication / information.

[0235] The steps 1001, 1002, 10003 corresponds to the procedure described with figure 7a.

[0236] At step 1004, the AMF may use the received NTN backhaul link information to correctly manage the NG protocol messages exchanged with the NG-RAN over the NTN backhaul link, for instance taking into account the long transmission latency. The AMF may also use the NTN backhaul link information to localize the UE served by the NG-RAN node. The AMF may assist the Location Management Function (LMF) in the core network. The AMF may also assist the Session Management Function (SMF) in the core network to configure the QoS flows transmitted over the NTN backhaul link.

[0237] Figure Ila is a flowchart of an example method 1100 for managing, at an NTN NG-RAN node, the presence of an NTN backhaul link. For example, with reference to the communication system 500 shown in and described with respect to figure 5, the NTN NG-RAN node may be the BH-gNB3 503, and the WAB-MT 541 is the MT component of a network node which is the WAB-node 540. The method 1100 as shown in and described with respect to figure 1 la may be performed by software elements and / or hardware elements. The NTN NG-RAN node may be implemented in a network node 400 as shown in and described with reference to figure 4 with the method as shown in and described with respect to figure 1 la being performed by an apparatus for the NTN NG-RAN node including one or more processing units, such as the processing unit 402.

[0238] At step 1101, the NTN NG-RAN node admits the MT component of a network node through an NTN backhaul link.At step 1102, the NTN NG-RAN sends to the MT component information related to the NTN backhaul link.

[0239] At step 1103, the NTN NG-RAN may receive a response from the MT component, for instance to acknowledge the reception of the information.

[0240] The steps 1102, 1103 correspond to the procedure described with figure 8a. Taking the example of figure 5, once the WAB-MT 531 connects to the 5G network via the BH-gNB3 503, the BH-gNB3 503 provides information related to the NTN backhaul link (5031a / 5031b). Then, the WAB-MT 541 relays the NTN backhaul link information to the WAB-gNB 542.

[0241] Figure 11b is a flowchart of another example method 1110 for managing, at an NTN NG-RAN node, the presence of an NTN backhaul link. For example, with reference to the communication system 500 shown in and described with respect to figure 5, the NTN NG-RAN node may be the BH-gNB3 503, the WAB-MT 541 is the MT component of a network node which is the WAB-node 540, and the WAB-gNB 542 is the gNB component co-located with the WAB-MT 541 in the network node. The method 1110 as shown in and described with respect to figure 1 lb may be performed by software elements and / or hardware elements. The NTN NG-RAN node may be implemented in a network node 400 as shown in and described with reference to figure 4 with the method as shown in and described with respect to figure 1 lb being performed by an apparatus for the NTN NG-RAN node including one or more processing units, such as the processing unit 402.

[0242] At step 1111, the NTN NG-RAN node admits the MT component of a network node through an NTN backhaul link.

[0243] At step 1112, the NTN NG-RAN may establish a Xn connection with the gNB component colocated with the MT component in the network node. This step is not necessary in case the NTN NG-RAN node has already setup a Xn connection with the gNB component.

[0244] At step 1113, the NTN NG-RAN sends information related to the NTN backhaul link to the gNB component co-located with the MT component in the network node.

[0245] At step 1114, the NTN NG-RAN node may receive a response from the gNB component, for instance to acknowledge the reception of the information.

[0246] The steps 1113, 1114 correspond to the procedure described with figure 8b. Taking the example of figure 5, once the WAB-MT 531 connects to the 5G network via the BH-gNB3 503, the BH-gNB3 503 establishes a Xn connection with the WAB-gNB 542 (if the Xn connection is not yet established), and provides information related to the NTN backhaul link (503 la / 503 lb) to the WAB-gNB 542.Figure 12 illustrates another example of a wireless communication system 1200, including a WAB network or WAB network system, in which embodiments and examples of embodiments of the present invention may be implemented.

[0247] The WAB network system of Figure 12, is composed of three base stations 1201, 1202 and 1203, also referred to as backhaul base stations, or backhaul RAN nodes (also referred to as BH RAN nodes), or backhaul gNBs (also referred to as BH-gNB), two 5G core networks 1210 and 1220, with the respective AMF entities 1211a and 1211b (for the core network 1210) and 1221a and 1221b (for the core network 1220), and the respective UPF entities 1212a and 1212b (for the core network 1210) and 1222a and 1222b (for the core network 1220), and two WAB nodes 1230 and 1240.

[0248] A wired backhaul IP network 1290 interconnects the base stations 1201, 1202 and 1203 and the core networks 1210 and 1220. For instance, this wired infrastructure uses optical fiber cables. BH-gNB 1 1201, BH-gNB2 1202 and BH-gNB3 1203 are all TN (Terrestrial Network) base stations. However, as illustrated in Figure 12, the BH-gNB3 1203 is connected to the backhaul network 1290 through NTN (Non-Terrestrial Network), with a satellite 1205 relaying radio signals to / from the Earth station of NTN gateway 1204 (other NTN connection types using different NTN entities are equally possible). The BH-gNB3 1203 is connected to the satellite 1205 with the wireless link 1283b, and the satellite 1205 is connected to the NTN gateway 1204 with the wireless link 1283c.

[0249] As discussed above, each WAB node comprises a Mobile Termination (MT) component or part or unit (WAB-MT 1231 for WAB node 1230 and WAB-MT 1241 for WAB node 1240) and a RAN node or base station or gNB component or part or unit (WAB-gNB 1232 for WAB node 1230 and WAB-gNB 1242 for WAB node 1240).

[0250] WAB node 1230 is connected to the serving backhaul base station referred to as BH-gNBl, 1201 through the wireless backhaul (BH) link 1273.

[0251] WAB node 1240 may be connected to the serving backhaul base station referred to as BH-gNB2, 1202 through the wireless backhaul (BH) link 1282 or to the serving backhaul base station referred to as BH-gNB3, 1203 through wireless backhaul (BH) link 1283a.

[0252] WAB-gNB 1232 of WAB node 1230 serves the UE 1251 through communication link or radio link 1271.

[0253] Similarly, WAB-gNB 1242 of WAB node 1240 serves the UE 1261 through communication link or radio link 1281, and the UE 1262 through communication link or radio link 1282.

[0254] WAB node 1230 and WAB node 1240 may each also embed a UPF entity as previously discussed in Figure 3, respectively UPF entity 1233 and UPF 1243, allowing these WAB-nodes to provide UEs 1251, 1261 and 1262 with some local services, or inter-UE communications, such asfor instance, where the user data exchanged between the two UEs 1261 and 1262 would be routed through UPF entity 1243 instead of being routed through a UPF entity belonging to the core network 1210 or 1220.

[0255] Although Figure 12 shows only one UE 1251 connected to WAB node 1230, it will be appreciated that there may be a plurality of UEs connected to WAB nodes of the wireless communication system.

[0256] Still by way of example, WAB-MT 1241 may initially be connected to BH-gNB2 1202 only, through the link 1282, and WAB-MT 1241 may be served by the AMF function or entity 1221a of the 5G core network 1220. This AMF 1221a can be referred to as the backhaul AMF (or BH AMF) for the WAB node 1240, while the core network 1220 can be referred to as the backhaul core network (or BH 5GC) for the WAB node 1240. At the same time, the WAB-gNB 1242 may be connected to AMFs 1211a and 1211b of the 5G core network 1210. The UE 1261 may be served by the AMF 121 la and the UE 1262 may be served by the AMF 1211b. These AMFs 1211a and 1211b can be referred to as UE’s AMF (or UE AMF) for the WAB node 1240, while the core network 1210 can be referred to as the UE’s core network (or UE’s 5GC or UE 5GC) for the WAB node 1240.

[0257] As a possible scenario, the radio link 1202 may experience radio link deficiency due to some unexpected interference or shadowing phenomena, or because the WAB-node 1240 is moving away from the radio coverage of cell(s) controlled by the BH-gNB2 1202. For such reasons, the WAB-MT 1241 may be handed over by the BH-gNB2 1202 to a new serving cell managed by the BH-gNB3 1203. Then, the BH-gNB2 1202 may trigger the handover procedure described in TS 38.300 section 9.2.3.2. In this procedure, the BH-gNB2 1202 sends a handover request to the BH-gNB3 1203 along with information related to the WAB-MT 1241. Based on this information, the BH gNB3 1203 may accept the handover request and proceed to the admission of the WAB-MT 1241. Then, the whole traffic related to the WAB node 1240 (and the served UEs 1261, 1262) will transit through the BH-gNB 1203, and thus through the satellite 1205 and the NTN gateway 1204. After the handover of WAB-MT 1241, there may be no change for the serving AMFs: WAB-MT 1241 may still be served by the AMF 1221a, while the UE 1261 may still be served by the AMF 1211a and the UE 1262 may still be served by the AMF 1211b. In some cases, there may be a change of serving AMF for the WAB-MT 1241 and / or the UEs 1261, 1262. In any case, because of the presence of NTN backhaul link (with the satellite 1205 and the NTN gateway 1204), the propagation delay between the WAB-MT 1241 and its core network may be larger than when the WAB-MT 1241 was served by the BH-gNB2 1202. This is the same situation for the communications between the WAB-gNB 1242 and its core network (via the NG interface), between the WAB-gNB 1242 and other NG-RAN nodes (via the Xn interface), and between the UEs 1261, 1262 and their core network. The presence of an NTN backhaul link to connect the WAB node 1240 is not known at the BH AMF 1221a or at the UE’s AMFs 1211a, 1211b. Accordingly, BH AMF 1221a or UE’s AMFs 1211a, 1211b will not be expecting the longer network delay associated with the NTN backhaul link.

[0258] There may be two solutions to inform the BH AMF 1221a about the presence of NTN, either by the BH-gNB3 1203 (first option with NGAP protocol) or by the WAB-MT 1241 (second option with NAS protocol). In the first option, when the BH-gNB3 1203 is connected via an NTN backhaul link, the BH-gNB3 1203 sends the related information to all the AMFs connected to BH-gNB3 1203. The BH-gNB3 1203 may use the procedure described at figure 7a. In the second option, the WAB-MT 1241 may use the UE-initiated NAS transport procedure specified in TS 24.501 section 5.4.5.2 to provide in a NAS message the information related to the NTN backhaul link. As the WAB-MT 1241 cannot detect by itself the presence of the NTN backhaul link (composed of links 1283a and 1283b), the WAB-MT 1241 shall first be informed by the BH-gNB3 1203, for instance with the procedure described above in relation to Figure 8a.

[0259] To inform the UE’s AMFs 1211a and 1211b of the presence of the NTN backhaul link (composed of links 1283a and 1283b), the WAB-gNB 1242 may use the procedure described above in relation to Figure 7a. To inform other NG-RAN nodes, the WAB-gNB 1242 may use the procedure described above in relation to Figure 7b. As the WAB-gNB 1242 cannot detect by itself the presence of the NTN backhaul link, the WAB-gNB 1242 shall first be informed. There may be two options to inform the WAB-gNB 1242, either by the BH-gNB3 1203 (first option with XnAP protocol) or by the WAB-MT 1241 (second option with NAS protocol). In the first option, when the BH-gNB3 1203 is connected via an NTN backhaul link, the BH-gNB3 1203 sends the related information to the WAB-gNB 1242, using for instance the procedure described at figure 8b. In the second option, the WAB-MT 1241 provides the related information through the interface internal to the WAB node 1240. This second option assumes that the WAB-MT 1241 was previously informed by the BH-gNB3 1203 as described above. As a summary for NTN satellite backhaul link notification:

[0260] When NTN satellites are involved to serve satellite-enabled UEs, the core network establishes the PDU session(s) of the UEs taking into account this configuration. In particular, the QoS flows transmitted with a PDU session via an NTN satellite can be configured with a large Packet Delay Budget (PDB) when long propagation delays are expected to transmit radio signals between the NTN satellite and the UEs and between the NTN satellite and the Earth station.

[0261] In order to ensure that the core network is aware of long propagation delays introduced by NTN satellite, the NTN satellite base station shall inform the AMF(s) managing the served UE(s)when an NG connection is established between the AMF(s) and the NTN satellite base station. For this purpose, the information element RAT (Radio Access Technology) Information (as specified in TS 38.413 section 9.3.1.125) may be included in the message NG SETUP REQUEST with a value indicating the type of orbit. This IE may also be included in the RAN CONFIGURATION UPDATE message.

[0262] Moreover, the User Location Information providing location information of a served UE embeds NR NTN TAI Information when the UE is served by an NTN satellite base station.

[0263] When an NTN satellite is involved in the backhaul link for a WAB node, the WAB-gNB is not an NTN entity. Hence, the RAT Information in an NG SETUP REQUEST message or in a RAN CONFIGURATION UPDATE message sent by the WAB-gNB to an AMF would not indicate the presence of NTN satellite and would not indicate a potential long propagation delay to reach the WAB-gNB. Therefore, an indication that NTN satellite is used for the backhaul link should be sent by the WAB-gNB to the serving AMF(s).

[0264] It can be noted that the format of the additional ULI to be introduced for WAB is not specifically adapted in case of backhaul link using NTN satellite. Thus, a network function receiving additional ULI from a WAB node would not deduce any information related to the NTN nature of the backhaul link.

[0265] Therefore, an indication that NTN satellite is used for the backhaul link may be included in the NG SETUP REQUEST message and in the RAN CONFIGURATION UPDATE message sent by the WAB-gNB to the serving AMF(s). The indication may be in the form of a new information element BH RAT Information. This information element BH RAT Information may correspond to the NTN backhaul link information described at Figure 7a.

[0266] When the Additional ULI IE is included in the NG SETUP REQUEST message, this WAB specific IE can thus be used as a WAB indication for the AMF. Consequently, if the Additional ULI IE is included in the NG SETUP REQUEST message, the AMF shall, if supported, consider that the transmitting NG-RAN node is a WAB-gNB.

[0267] In other words, if the Additional ULI IE is included in the NG SETUP REQUEST message, the AMF shall, if supported, store this information, consider that the transmitting NG-RAN node is a WAB-gNB, and take it into account for determining the location of the UEs served by the NG-RAN node.

[0268] Besides, considering a WAB Supported IE as an indication of support for WAB, if the AMF supports WAB, the AMF shall include the WAB Supported IE in the NG SETUP RESPONSE message. If the WAB Supported IE is included in the NG SETUP RESPONSE message, the NG-RAN node shall, if supported, store this information and further use it for AMF selection.When NTN is used for the backhaul connection of a WAB node, the WAB-gNB may be first informed by the BH-gNB serving the WAB-MT co-located with the WAB-gNB in the WAB node. For this purpose, the information element BH RAT Information may be introduced in various Xn messages.

[0269] For this purpose, the information element BH RAT Information may be introduced in various Xn messages: XN SETUP REQUEST, XN SETUP RESPONSE, NG-RAN NODE CONFIGURATION UPDATE and NG-RAN NODE CONFIGURATION UPDATE ACK.

[0270] Thus, an indication that NTN satellite is used in the backhaul may be included in various Xn messages (XN SETUP REQUEST, XN SETUP RESPONSE, NG-RAN NODE CONFIGURATION UPDATE and NG-RAN NODE CONFIGURATION UPDATE ACK), sent to a WAB-gNB by the BH-gNB serving the WAB-MT co-located with the WAB-gNB.

[0271] Besides, to allow a BH-gNB to provide BH RAT Information to the WAB-gNB co-located to a served WAB-MT, the BH-gNB shall first discover the WAB-MT / WAB-gNB co-location.

[0272] For the purpose of NTN satellite backhauling notification to a WAB node, the WAB-gNB may be informed via Xn by the BH-gNB serving the co-located WAB-MT. Hence, the BH-gNB needs to discover the WAB-MT / WAB-gNB co-location. For co-location discovery, Co-location information (i.e., a WAB-MT identifier) may be provided by the WAB-gNB via the XN SETUP REQUEST or XN SETUP RESPONSE message at the establishment of a Xn connection with the BH-gNB, or via NG-RAN NODE CONFIGURATION UPDATE or NG-RAN NODE CONFIGURATION UPDATE ACK if the Xn connection is already established. Besides, at the handover of the WAB-MT to a target BH-gNB involving the use of NTN for the backhaul link, the WAB node should be informed as soon as possible, with the objective to inform AMF(s) and to correctly handle the QoS flows. Therefore, the target BH-gNB may inform the WAB-gNB via Xn once the WAB-MT’s handover is accepted. To speed up the process, the target BH-gNB may be informed by the source BH-gNB of the identifier of the WAB-gNB co-located with the WAB-MT to be handed over.

[0273] Then, it can be noted that to allow a BH-gNB to provide NTN backhaul link information to a WAB-gNB, it is beneficial to consider:

[0274] - a WAB-MT identifier optionally included in the messages XN SETUP REQUEST, XN SETUP RESPONSE, NG-RAN NODE CONFIGURATION UPDATE and NG-RAN NODE CONFIGURATION UPDATE ACK),

[0275] - a WAB-gNB identifier optionally included in the HANDOVER REQUEST message related to the handover of the co-located WAB-MT.For WAB resource coordination with a BH-gNB serving a WAB-MT, it is also necessary for the BH-gNB to discover the WAB-gNB co-located with the WAB-MT. For this purpose, a WAB-MT identifier (known by the BH-gNB) may be provided by the WAB-gNB in various Xn messages: XN SETUP REQUEST, XN SETUP RESPONSE, NG-RAN NODE CONFIGURATION UPDATE and NG-RAN NODE CONFIGURATION UPDATE ACK.

[0276] To allow a smooth implementation of WAB resource coordination between a WAB-gNB and the BH-gNB serving the co-located WAB-MT, it is beneficial to consider:

[0277] - a WAB-MT identifier optionally included in the messages XN SETUP REQUEST, XN SETUP RESPONSE, NG-RAN NODE CONFIGURATION UPDATE and NG-RAN NODE CONFIGURATION UPDATE ACK,

[0278] - a WAB-gNB identifier optionally included in the HANDOVER REQUEST message related to the handover of the co-located WAB-MT.

[0279] As a conclusion, for the purpose of informing that NTN is used for a WAB backhaul link, or for enabling the implementation of WAB resource coordination, a BH-gNB has to discover the WAB-MT / WAB-gNB co-location at a WAB node.

Claims

CLAIMS1. A method for use in a wireless communication system including a wireless access backhaul, WAB, node, including a gNB component and an MT component, the method at the gNB component comprising:sending, to a network entity, a message including first information related to a NonTerrestrial Network, NTN, backhaul link associated with the WAB node.

2. The method of claim 1, wherein the first information includes an indication that a communication path between the WAB node and a network entity includes the NTN backhaul link.

3. The method of claim 1 or claim 2, wherein the first information includes an indication that the NTN backhaul link uses an NTN satellite.

4. The method of claim 3, wherein the first information further includes an indication of an orbit type of the NTN satellite.

5. The method of any one of the preceding claims, wherein the first information includes tracking area information indicating one or more tracking areas associated with an NTN entity connected to the NTN backhaul link.

6. The method of claim 5, wherein the tracking area information indicates a plurality of tracking areas associated with the NTN backhaul link, and the first information further includes an indication of a tracking area of the plurality of tracking areas associated with a current location of the WAB node.

7. The method of any one of the preceding claims, wherein the first information includes one or more configuration parameters associated with the NTN backhaul link.

8. The method of any one of the preceding claims, wherein the first information includes cell identity information, the cell identity information indicating a current geographical coverage area associated with the NTN backhaul link.

459. The method of any one of the preceding claims, wherein the first information includes location information, the location information specifying the current location of the WAB node and / or velocity information associated with the WAB node.

10. The method of any one of the preceding claims, wherein the first information includes an indication of an Access and Management Function, AMF, serving the MT component of the WAB node.

11. The method of any one of the preceding claims, wherein the message further includes information for identifying the MT component of the WAB node.

12. The method of any one of the preceding claims, wherein the message further includes information for identifying a backhaul NG-RAN node serving the MT component of the WAB node.

13. The method of any one of the preceding claims, wherein the message further comprises second information for identifying the WAB node and / or the gNB component of the WAB node.

14. The method of claim 13, wherein the second information includes an identifier of the WAB node and / or the gNB component of the WAB node.

15. The method of any one of the preceding claims, wherein the message comprises a request to establish a connection between the gNB component and the network entity, the method further comprising receiving, from the network entity, a response message indicating whether the connection has been successfully established.

16. The method of claim 15 wherein, in a case where the connection has not been successfully established, the response message includes an indication of the reason why the connection has not been successfully established.

17. The method of any one of claims 1 to 14, wherein the message comprises a request to update a configuration of a connection between the gNB component and the network entity, the method further comprising receiving, from the network entity, a response message indicating whether the request to update the configuration has been successful.

18. The method of claim 13, wherein, in a case where the request to update the configuration has not been successful, the response message includes an indication of the reason why the request to update the configuration was not successful.

19. The method of any one of claims 1 to 14, wherein the message comprises one of:a message providing the current location of one or more UEs served by the WAB node; a message providing Non Access Stratum, NAS, information;a path switch request message; ora message related to the setup or modification of a PDU Session associated with one or more UEs served by the WAB node.

20. The method of any one of the preceding claims wherein the network entity is an Access and Management Function, AMF, or an NG-RAN node.

21. The method of any one of the preceding claims, wherein the network entity is an Access Management Function, AMF, and the connection is an NG interface connection; or wherein the network entity is an NG-RAN node and the connection is an Xn interface connection.

22. A method for use in a wireless communication system including a wireless access backhaul, WAB, node, including a gNB component and an MT component, the method at the WAB node comprising:receiving, from a network entity, a message including first information related to a NonTerrestrial Network, NTN, backhaul link associated with the WAB node.

23. The method of claim 22, further comprising sending, to the network entity, an indication that the WAB node is a WAB node before receiving the message from the network entity.

24. The method of claim 22 or claim 23, wherein the first information includes an indication that a communication path between the WAB node and a core network entity comprises the NTN backhaul link.

25. The method of any one of claims 22 to 23, wherein the message further comprises second information for identifying the network entity.

26. The method of claim 25, wherein the second information includes an identifier of the network entity.

27. The method of any one of claims 22 to 26, wherein the first information includes an indication that the NTN backhaul link uses an NTN satellite.

28. The method of claim 27, wherein the first information further includes an indication of an orbit type of the NTN satellite.

29. The method of any one of claims 22 to 28, wherein the first information includes tracking area information indicating one or more tracking areas associated with an NTN entity connected to the NTN backhaul link.

30. The method of claim 29, wherein the tracking area information indicates a plurality of tracking areas associated with the NTN backhaul link, and the first information further includes an indication of a tracking area of the plurality of tracking areas associated with a current location of the WAB node.

31. The method of any one of claims 22 to 30, wherein the first information includes one or more configuration parameters associated with the NTN backhaul link.

32. The method of any one of claims 22 to 31, wherein the first information includes cell identity information, the cell identity information indicating a current geographical coverage area associated with the NTN backhaul link.

33. The method of any one of claims 22 to 32, wherein the network entity is an NTN base station serving the MT component of the WAB node.

34. The method of any one of claims 22 to 33, wherein the method is performed by the MT component of the WAB node.

35. The method of claim 34, further comprising sending the first information to the gNB component of the WAB node.

36. The method of any one of claims 22 to 33, wherein the method is performed by the gNB component of the WAB node.

37. A method for use in a wireless network, the method comprising at an NG-RAN node: receiving an indication that a backhaul link uses an NTN connection; andsending, to a network entity, first information including an indication that the backhaul link uses an NTN connection.

38. The method of claim 37, wherein the network entity is an Access and Management Function, AMF, or another NG-RAN node.

39. The method of claim 37 or claim 38, further comprising receiving information related to the NTN backhaul link before sending the first information to the network entity.

40. The method of any one of claims 37 to 38, further comprising receiving a response from the network entity.

41. The method of claim 40, wherein the response comprises an acknowledgement that the first information was received by the network entity.

42. The method of any one of claims 37 to41, wherein the first information includes an indication that the NTN backhaul link uses an NTN satellite.

43. The method of claim 42, wherein the first information further includes an indication of an orbit type of the NTN satellite.

44. The method of any one of claims 37 to 43, wherein the first information includes tracking area information indicating one or more tracking areas associated with an NTN entity connected to the NTN backhaul link.

45. The method of claim 44, wherein the tracking area information indicates a plurality of tracking areas associated with the NTN backhaul link, and the first information further includes an indication of a tracking area of the plurality of tracking areas associated with a current location of the NG-RAN node.

46. The method of any one of claims 37 to 45, wherein the first information includes one or more configuration parameters associated with the NTN backhaul link.

47. The method of any one of claims 37 to 46, wherein the first information includes cell identity information, the cell identity information indicating a current geographical coverage area associated with the NTN backhaul link.

48. The method of any one of claims 37 to 47, wherein the NG-RAN node is a gNB component of a Wireless Access Backhaul, WAB, node.

49. A method for use in a wireless network comprising a Non-Terrestrial Network, NTN, backhaul link, the method comprising at an Access and Management Function, AMF, of a core network:receiving, from an NG-RAN node, an indication that the backhaul link uses an NTN connection;configuring one or more parameters associated with communication with the NG-RAN node over the NTN backhaul link based on the indication.

50. The method of claim 49, wherein configuring one or more parameters comprises adjusting one or more Quality of Service, QoS, parameters for one or more PDU sessions of one or more UEs served by the AMF.

51. The method of claim 49 or claim 50, further comprising receiving, from the NG-RAN node, first information related to the NTN backhaul link.

52. The method of claim 51, wherein the configuring one or more parameters is further based on the received first information.

53. The method of claim 51 or claim 52, wherein the first information includes an indication that the NTN backhaul link uses an NTN satellite.

54. The method of claim 53, wherein the first information further includes an indication of an orbit type of the NTN satellite.

55. The method of any one of claims 51 to 54, wherein the first information includes tracking area information indicating one or more tracking areas associated with an NTN entity connected to the NTN backhaul link.

56. The method of claim 55, wherein the tracking area information indicates a plurality of tracking areas associated with the NTN backhaul link, and the first information further includes an indication of a tracking area of the plurality of tracking areas associated with a current location of the NG-RAN node.

57. The method of any one of claims 51 to 56, wherein the first information includes one or more configuration parameters associated with the NTN backhaul link.

58. The method of any one of claims 51 to 57, wherein the first information includes cell identity information, the cell identity information indicating a current geographical coverage area associated with the NTN backhaul link.

59. The method of any one of claims 49 to 58, further comprising sending a response to the NG-RAN node.

60. The method of claim 59, wherein the response comprises an acknowledgement that the indication and / or first information was received.

61. The method of any one of claims 49 to 60, wherein the NG-RAN node is the gNB component of a WAB node comprising the gNB component and an MT component, the method further comprising receiving, from the NG-RAN node, information for identifying the MT component.

62. The method of any one of claim 61, further comprising receiving, from the NG-RAN node, information for identifying a backhaul NG-RAN node serving the MT component of the WAB node.

63. The method of any one of claims 49 to 60, wherein the NG-RAN node is the gNB component of a WAB node comprising the gNB component and an MT component, the methodfurther comprising receiving, from the NG-RAN node, information for identifying a backhaul NG-RAN node serving the MT component of the WAB node.

64. A method for use in a wireless network comprising a Non-Terrestrial Network, NTN, backhaul link, the method comprising at an NTN entity connected to the NTN backhaul link: admitting an MT component of a network node through the NTN backhaul link; sending, to the network node, a message including first information related to the NTN backhaul link.

65. The method of claim 64, wherein sending the message to the network node comprises sending the message to the MT component of the network node.

66. The method of claim 64 or claim 65, further comprising establishing an Xn connection with a gNB component co-located with the MT component of the network node.

67. The method of claim 64 or claim 66, wherein sending the message to the network node comprises sending the message to a gNB component co-located with the MT component of the network node.

68. The method of any one of claims 64 to 67, wherein the NTN entity is an NTN NG-RAN node.

69. The method of any one of claims 64 to 68, wherein the first information includes an indication that a communication path between the network node and a core network entity comprises the NTN backhaul link.

70. The method of any one of claims 64 to 69, wherein the message further comprises second information for identifying the NTN entity.

71. The method of claim 70, wherein the second information includes an identifier of the NTN entity.

72. The method of any one of claims 64 to 71, wherein the first information includes an indication that the NTN backhaul link uses an NTN satellite.

73. The method of claim 72, wherein the first information further includes an indication of an orbit type of the NTN satellite.

74. The method of any one of claims 64 to 73, wherein the first information includes tracking area information indicating one or more tracking areas associated with an NTN entity connected to the NTN backhaul link.

75. The method of claim 74, wherein the tracking area information indicates a plurality of tracking areas associated with the NTN backhaul link, and the first information further includes an indication of a tracking area of the plurality of tracking areas associated with a current location of the network node.

76. The method of any one of claims 64 to 75, wherein the first information includes one or more configuration parameters associated with the NTN backhaul link.

77. The method of any one of claims 64 to 76, wherein the first information includes cell identity information, the cell identity information indicating a current geographical coverage area associated with the NTN backhaul link.

78. The method of any one of claims 64 to 77, further comprising receiving a response from the MT component.

79. The method of any one of claims 64 to 78, further comprising receiving, from the network node, an indication that the network node is a Wireless Access Backhaul, WAB, node prior to sending the information related to the NTN backhaul link to the network node.

80. A computer program comprising instructions which, when the program is executed by at least one processor unit, cause the at least one processing unit to carry out the method according to any one of claims 1 to 79.

81. A computer-readable medium carrying a computer program according to claim 80.

82. An apparatus for a network entity for a wireless communication system, the apparatus comprising one or more processing units configured to perform the method as recited in any one of claims 1 to 79.54

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