WO2025152121A1

WO2025152121A1 - Method and apparatus for feeder link switchover in communication network

Info

Publication number: WO2025152121A1
Application number: PCT/CN2024/073092
Authority: WO
Inventors: Xiang Xu; Jeroen Wigard; Saubhagya Baliarsingh
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Priority date: 2024-01-18
Filing date: 2024-01-18
Publication date: 2025-07-24
Anticipated expiration: 2026-07-18
Also published as: WO2025152121A9

Abstract

Embodiments of the present disclosure provide a method and an apparatus for feeder link switchover in communication network. A method (300) performed by a first network node comprises: communicating (S302) with a second network node and a third network node using a first feeder link; performing (S304) the feeder link switchover by setting up a second feeder link; transmitting (S306), to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and switching (S308) a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link. The second message comprises a transport network layer, TNL, parameter related to the second feeder link. The interruption or even loss of the data transmission caused by the feeder link switchover may be reduced.

Description

METHOD AND APPARATUS FOR FEEDER LINK SWITCHOVER IN COMMUNICATION NETWORK

TECHNICAL FIELD

Various example embodiments of the present disclosure relate generally to the technology of communication, and in particular to a method and apparatus for feeder link switchover in communication network.

BACKGROUND

In current communication system, such as the 3^rd generation partnership project (3GPP) the 5^th generation (5G) , new radio (NR) , etc., a communication link for transmitting signalling or data between a transmitter and a receiver may be changed/switched during the communication of signalling or data due to many reasons, while the transmitter and the receiver are unchanged.

During such change of the communication link, the signalling or data transmission may be interrupted or even lost. Thus, it is desired that influence caused by such link switchover could be further reduced.

SUMMARY

This summary is provided to introduce some aspects in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Certain aspects of the present disclosure and their embodiments may provide solutions to these or other challenges. There are, proposed herein, various embodiments which address one or more of the issues disclosed herein. Specific method and apparatus for feeder link switchover in communication network.

A first aspect of the present disclosure provides a method performed by a first network node for a feeder link switchover in a communication network. The method comprises: communicating with a second network node and a third network node using a first feeder link; performing the feeder link switchover by setting up a second feeder link; transmitting, to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and switching a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link. The second message comprises a transport network layer, TNL, parameter (or, TNL parameters) related to the second feeder link.

In exemplary embodiments of the present disclosure, performing the feeder link switchover comprises: transmitting, to the second network node, a first message to indicate that the feeder link switchover from the first feeder link to the second feeder link is to be performed by the first network node.

In exemplary embodiments of the present disclosure, the first message comprises a TNL parameter related to the first feeder link. The TNL parameter in the first message comprises: a TNL address (or, TNL addresses) of the first network node before the feeder link switchover; and the TNL parameter in the second message comprises: a TNL address (or, TNL addresses) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, at least one of the first message or the second message further comprises: an identifier, ID, of the first network node, and/or a list of at least an identifier of a terminal device connected with the first network node.

In exemplary embodiments of the present disclosure, the TNL parameter in the second message further comprises: a mapping between the TNL address (or, TNL addresses) of the first network node before the feeder link switchover and the TNL address (or, TNL addresses) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, the first message or the second message is a next generation, NG, Setup Request message, or a radio access network, RAN, Configuration Update message, or S1 Setup Request message, or an eNB Configuration Update message, or any S1 or NG application protocol, AP, message.

In exemplary embodiments of the present disclosure, the first feeder link comprises a first gateway; the second feeder link comprises a second gateway; and the first message further comprises a time parameter, indicating a time point for the first feeder link to become unavailable, and/or a time point for the second feeder link to become available, and/or a time period for both the first feeder link and the second feeder link to be available.

In exemplary embodiments of the present disclosure, the first network node transmits the first message and the second message to a plurality of second network nodes.

In exemplary embodiments of the present disclosure, the method further comprises: receiving, control plane message from the second network node and/or user plane traffic from the third network node, via the second feeder link, after transmitting the second message.

In exemplary embodiments of the present disclosure, the first network node comprises a base station; the second network node comprises an access and mobility management function, AMF, or a mobility management entity, MME; the third network node comprises a user plane function, UPF, or a serving gateway, S-GW; and the communication between the first network node and the third network node comprises a user plane transmission suspended before the feeder link switchover and resumed after the feeder link switchover.

In exemplary embodiments of the present disclosure, wherein the communication network is a non-terrestrial network.

A second aspect of the present disclosure provides a method performed by a second network node for a feeder link switchover in a communication network. The method comprises: communicating with a first network node using a first feeder link; receiving, from the first network node, a second message to manage a control plane interface between the first network node and the second network node, the second message comprises a transport network layer, TNL, parameter (or, TNL parameters) related to a second feeder link; initiating, to the third network node, a second request comprising the transport network layer parameter, for the third network node to switch a communication between the first network node and the third network node to use the transport network layer parameter, for a list of terminal devices connected with the first network node; switching a communication between the first network node and the second network node from the first feeder link to the second feeder link.

In exemplary embodiments of the present disclosure, communicating with the first network node using the first feeder link comprises: receiving, from the first network node, a first message to indicate that the feeder link switchover from the first feeder link to the second feeder link is to be performed by the first network node; and initiating, to a third network node, a first request for the third network node to suspend communication between the first network node and the third network node for a list of terminal devices connected with the first network node.

In exemplary embodiments of the present disclosure, at least one of the first message or the first request comprises: a TNL address (or, TNL addresses) of the first network node before the feeder link switchover; and at least one of the TNL parameter (or, TNL parameters) in the second message or the TNL parameter in the second request comprises: a TNL address (or, TNL addresses) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, at least one of the first message, the second message, the first request or the second request further comprises: an identifier, ID, of the first network node, and/or a list of identifiers for at least a terminal device connected with the first network node.

In exemplary embodiments of the present disclosure, at least one of the TNL parameter (or, TNL parameters) in the second message or the TNL parameter in the second request further comprises: a mapping between the TNL address of the first network node before the feeder link switchover and the TNL address (or, TNL addresses) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, the first message or second message is a next generation, NG, Setup Request message, or a radio access network, RAN, Configuration Update message, or S1 Setup Request message, or an eNB Configuration Update message, or an application protocol, AP, message.

In exemplary embodiments of the present disclosure, the first feeder link comprises a first gateway; the second feeder link comprises a second gateway; the first message further comprises a time parameter, indicating a time point for the first feeder link to become unavailable, and/or a time point for the second feeder link to become available, and/or a time period for both the first feeder link and the second feeder link to be available; and the first request comprises a time parameter, indicating a time point for the third network node to suspend the communication, and/or a time period for third network node to suspend the communication.

In exemplary embodiments of the present disclosure, the method further comprises: stopping a transmission for control plane message via the first feeder link to the first network node, upon receiving the first message; and resuming the transmission for the control plane message via the second feeder link to the first network node, upon receiving the second message.

In exemplary embodiments of the present disclosure, the second network node transmits the first request and the second request to a plurality of third network nodes.

In exemplary embodiments of the present disclosure, the first network node comprises a base station; the second network node comprises an access and mobility management function, AMF, or a mobility management entity, MME; the third network node comprises a user plane function, UPF, or a serving gateway, S-GW; and the communication comprises a user plane transmission suspended before the feeder link switchover and resumed after the feeder link switchover.

In exemplary embodiments of the present disclosure, initiating a first request or a second request by the AMF comprises: invoking a service request including a list of terminal devices to a session management function, SMF. The SMF initiates an N4 request including a list of identifiers for the list of terminal devices, to the UPF.

In exemplary embodiments of the present disclosure, the communication network is a non-terrestrial network.

A third aspect of the present disclosure provides a method performed by a third network node for a feeder link switchover in a communication network. The method comprises: receiving, from the second network node, a second request comprising a transport network layer, TNL, parameter, for the third network node to update a communication for a list of terminal devices connected with the first network node; updating stored information about the communication, by using the transport network layer parameter; and starting the communication, by using the updated information about the communication, for the list of terminal devices connected with the first network node.

In exemplary embodiments of the present disclosure, the method further comprises: receiving, from a second network node, a first request for the third network node to suspend a communication between a first network node and the third network node, for a list of terminal devices connected with the first network node; suspending the communication between a first network node and the third network node, for the list of terminal devices connected with the first network node.

In exemplary embodiments of the present disclosure, the first request comprises: a TNL address (or, TNL addresses) of the first network node before a feeder link switchover; and the TNL parameter (or, Parameters) in the second request comprises: a TNL address (or, TNL addresses) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, at least one of the first request or the second request further comprises: an identifier, ID, of the first network node, and/or a list of at least an identifier of a terminal device connected with the first network node.

In exemplary embodiments of the present disclosure, the TNL parameter in the second request further comprises: a mapping from the TNL address (or, TNL addresses) of the first network node before the feeder link switchover to the TNL address (or, TNL addresses) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, the first request comprises a time parameter, indicating a time point for the third network node to suspend the communication, and/or a time period for the third network node to suspend the communication.

In exemplary embodiments of the present disclosure, the stored information comprises at least a user plane transport network layer address of a user plane tunnel for a terminal device connected with the first network node.

In exemplary embodiments of the present disclosure, the third network node updates at least one IP address for next generation user plane, NG-U, tunnels related to the first network node, based at least on the second request.

In exemplary embodiments of the present disclosure, the first network node comprises a base station; the second network node comprises an access and mobility management function, AMF, or a mobility management entity, MME; the communication comprises a user plane transmission suspended before the feeder link switchover and resumed after the feeder link switchover; the communication is resumed over a Transport Network Layer, TNL, connection using the second feeder link; and the third network node comprises a user plane function, UPF, or a serving gateway, S-GW.

In exemplary embodiments of the present disclosure, a first request or a second request received by the UPF is an N4 request transmitted by a session management function, SMF, and the SMF transmits the N4 request as a response to a reception of a service request including a list of identifiers for terminal devices and a list of protocol data unit, PDU, needing reactivation, from the AMF.

A fourth aspect of the present disclosure provides a first network node. The first network node comprises means configured for: communicating with a second network node and a third network node using a first feeder link; performing the feeder link switchover by setting up a second feeder link; transmitting, to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and switching a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link. The second message comprises a transport network layer, TNL, parameter (or, TNL parameters) related to the second feeder link. The means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the first network node.

In exemplary embodiments of the present disclosure, the means are further configured for performing the method according to any exemplary embodiment of the first aspect.

A fifth aspect of the present disclosure provides a second network node. The second network node comprises means configured for: communicating with a first network node using a first feeder link; receiving, from the first network node, a second message to manage a control plane interface between the first network node and the second network node, the second message comprises a transport network layer, TNL, parameter (or, TNL parameters) related to a second feeder link; initiating, to the third network node, a second request comprising the transport network layer parameter, for the third network node to switch a communication between the first network node and the third network node to use the transport network layer parameter, for a list of terminal devices connected with the first network node; and switching a communication between the first network node and the second network node from the first feeder link to the second feeder link. The means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the second network node.

In exemplary embodiments of the present disclosure, the means are further configured for performing the method according to any exemplary embodiment of the second aspect.

A sixth aspect of the present disclosure provides a third network node. The third network node comprises means configured for: receiving, from the second network node, a second request comprising a transport network layer, TNL, parameter related to the second feeder link, for the third network node to update a communication for a list of terminal devices connected with the first network node; updating stored information about the communication, by using the transport network layer parameter; and starting the communication, by using the updated information about the communication, for the list of terminal devices connected with the first network. The means comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the third network node.

In exemplary embodiments of the present disclosure, the means are further configured for performing the method according to any exemplary embodiment of the third aspect.

A seventh aspect of the present disclosure provides a computer-readable storage medium. The computer-readable storage medium stores instructions, which when executed by at least one processor of a network node, cause the at least one processor of a network node to perform the method according to any exemplary embodiment of the first, second, and third aspects.

According to embodiments of the present disclosure, the exemplary embodiments of the present disclosure propose a mechanism that allows a faster and more accurate approach to suspend/resume the communication in the communication network when a feeder link switchover is performed. The interruption or even loss of the data transmission caused by the feeder link switchover may be reduced.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and benefits of various embodiments of the present disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements. The drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:

FIG. 1 is a diagram showing an exemplary architecture of regenerative NTN deployment.

FIG. 2 is a diagram showing an example of Feeder Link Switch Over (FLSO) .

FIG. 3A is a flow chart showing a method performed by a first network node, according to exemplary embodiments of the present disclosure.

FIG. 3B is a flow chart showing further steps of the method as shown in FIG. 3A, according to exemplary embodiments of the present disclosure.

FIG. 3C is a flow chart showing further steps of the method as shown in FIG. 3A, according to exemplary embodiments of the present disclosure.

FIG. 4A is a flow chart showing a method performed by a second network node, according to exemplary embodiments of the present disclosure.

FIG. 4B is a flow chart showing further steps of the method as shown in FIG. 4A, according to exemplary embodiments of the present disclosure.

FIG. 4C is a flow chart showing further steps of the method as shown in FIG. 4A, according to exemplary embodiments of the present disclosure.

FIG. 4D is a flow chart showing further steps of the method as shown in FIG. 4A, according to exemplary embodiments of the present disclosure.

FIG. 5A is a flow chart showing a method performed by a third network node, according to exemplary embodiments of the present disclosure.

FIG. 5B is a flow chart showing further steps of the method as shown in FIG. 5A, according to exemplary embodiments of the present disclosure.

FIG. 6 is a diagram showing an example call flow, according to embodiments of the present disclosure.

FIG. 7 is a block diagram showing an exemplary structure for a first network node, according to exemplary embodiments of the present disclosure.

FIG. 8 is a block diagram showing an exemplary structure for a second network node, according to exemplary embodiments of the present disclosure.

FIG. 9 is a block diagram showing an exemplary structure for a third network node, according to exemplary embodiments of the present disclosure.

FIG. 10 is a block diagram showing an apparatus/computer readable storage medium, according to embodiments of the present disclosure.

FIG. 11 is a block diagram showing exemplary apparatus units for a first network node, which is suitable for performing the method according to embodiments of the disclosure.

FIG. 12 is a block diagram showing exemplary apparatus units for a second network node, which is suitable for performing the method according to embodiments of the disclosure.

FIG. 13 is a block diagram showing exemplary apparatus units for a third network node, which is suitable for performing the method according to embodiments of the disclosure.

DETAILED DESCRIPTION

The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for better understanding, rather than limitations on the scope of the present disclosure. The described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments.

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless clearly given and/or implied from the context. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate.

As used herein, the term “network” or “communication network” refers to a network following any suitable communication standards (such for an internet network, or any wireless network) . For example, wireless communication standards may comprise WLAN (Wireless Local Area Network) , new radio (NR) , long term evolution (LTE) , LTE-Advanced, 5G NR, etc. In the following description, the terms “network” and “system” can be used interchangeably.

The term “node/network node” refers to a computing device or computing entity or computing function or any other devices (physical or virtual) in a communication network. For example, the node in the network may include a base station (BS) , an access point (AP) , or any other suitable device in a wireless communication network. The BS may be, for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNodeB or gNB) , a remote radio unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth. Further, the node may include other core network node, such as an Access and Mobility Management Function, AMF, a Session Management Function, SMF, a User Plane Function, UPF, a mobility management entity, MME, or a serving gateway, S-GW, etc.

The term “terminal device” refers to any end device that can access a communication network and receive services therefrom. By way of example and not limitation, the terminal device refers to a mobile terminal, user equipment (UE) , a non-AP device (such as a non-AP Station (STA) ) , or other suitable devices. The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, a wearable device, a vehicle-mounted wireless terminal device, a vehicle, and the like.

As one example, a terminal device may represent a device configured for communication in accordance with one or more communication standards promulgated by any standard organization, such as 3^rd generation partnership project, 3GPP.

As yet another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another terminal device and/or network equipment. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, for example refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed terms.

As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or” , mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

Exemplary embodiments of the disclosure are relevant to a method and an apparatus for feeder link switchover in communication network.

For illustration, some embodiments are targeted for Hard Feeder Link Switch Over (FLSO) or Soft Feeder Link Switch Over (FLSO) in Non Terrestrial Network (NTN) Regenerative architecture with gNB on satellite. In such scenarios, the gNB and satellite are used interchangeably. However, it should be noted that, the embodiments of the present disclosure may be also applied to other scenarios, in which communication link changes/switches. It should also be noted that, gNB is just an example. A base station can also be an eNB, or ng-eNB, or any other type of base stations.

As shown in FIG. 1, a UE may be connected to a data network via a gNB and 5G CN (5^th generation core network) . The NR Uu may be the interface between the UE and the gNB. The gNB is connected to the 5G CN via a feeder link between the satellite and a gateway, for example an NTN Gateway1. The NG interface between the gNB and 5G CN is transferred via NG over SRI (Satellite Radio Interface) . N6 is an interface between the 5G CN and the data network.

The NTN-Gateway (GW) or gateway or NTN-GW is a transport network node. When the satellite/gNB connects with an NTN-GW, the gNB is assigned with one or more transport network layer, TNL, addresses, for example, one or more IP address (es) , anchored in the NTN-GW. This ensures that, the downlink (DL) control plane/user plane (CP/UP) traffic with the destination internet protocol (IP) address set to the gNB’s IP address is routed to the right NTN-GW, then further forwarded to the satellite/gNB. The gNB may be assigned with separate IP addresses for the control plane and user plane. Namely, the gNB may have more than one IP addresses.

During NTN operation, it may become necessary to switch the feeder link between different NTN GWs (such as from the NTN Gateway1 to NTN Gateway2) serving the same satellite. This may be due to e.g., maintenance, traffic offloading, or (for Low-Earth Orbit (LEO) ) due to the satellite moving out of visibility with respect to the current NTN GW. After the FLSO, the gNB is assigned with one or more new IP address (es) anchored in the new NTN-GW.

In hard feeder link switchover (Hard FLSO) , an NTN payload (e.g. satellite) connects to only one NTN Gateway at any given time, i.e. a radio link interruption may occur during the transition between the feeder links. In soft feeder link switchover (Soft FLSO) , an NTN payload (e.g. satellite) may connects with both NTN Gateway during a period.

The FLSO may not change the base station, e.g., gNB, and/or the core network, e.g., access and mobility management function (AMF) , and thus there may still be the same base station and core network (for example, gNB and AMF) serving the UE. The satellite can be Earth-Fixed or Earth-Moving.

FIG. 2 is a diagram showing an example of FLSO.

● AT T1, before FLSO, Satellite1/gNB1 connects with NTN-GW1, and further connects with AMF. The satellite is far away from NTN-GW1, and thus needs to be changed to an NTN-GW2 which is closer.

● At T1+0.5 (s) , after FLSO, Satellite1/gNB1 changes the feeder link to use NTN-GW2. The UE is still served by the same gNB and same AMF.

It should be noted that, the feeder link switch can be done on a cell by cell basis, such that for instance for a satellite with 16 beams, one by one, the cells are switched from one feeder link to the other feeder link. For a single cell this is still seen as a hard switch, but for the satellite both feeder links are available during the switching time.

In current next generation (NG) interface, the Transport Network Layer (TNL) connection may be lost for a short period, e.g., due to IP network problem. After the TNL connection is recovered, the gNB initiate a NG Setup procedure. The NG SETUP REQUEST message includes a UE Retention Information IE with value set to “ues-retained” . 3GPP Technical Specification (TS) 38.413 V17.6.0 (2023-09) defines following behavior:

If the UE Retention Information IE set to “ues-retained” is included in the NG SETUP REQUEST message, the AMF may accept the proposal to retain the existing UE related contexts and signalling connections by including the UE Retention Information IE set to “ues-retained” in the NG SETUP RESPONSE message.

By using the UE Retention Information IE, both gNB and AMF can retain the existing UE contexts, and do not affect the UE during the short TNL connection loss and recovery.

In NTN transparent architecture, hard FLSO can also be performed, but the issue mentioned above does not happen. In transparent architecture, the gNB is on the ground. So, the gNB can buffer the DL packet during the hard FLSO.

- In case a new satellite serves the UE, the gNB forward the buffered DL packet to new satellite.

- In case the existing satellite still serves the UE, the gNB forward the buffered DL packet to the existing satellite via the new NTN-GW.

So, the issue is not applicable to NTN Transparent architecture. However, such solutions are not useful when the satellite embarks a gNB.

3GPP TS 23.401 V18.4.0 (2023-12) /3GPP TS 23.501 V18.4.0 (2023-12) and TS 29.502 V18.4.0 (2023-09) defines some suspend procedure.

In such resume procedure, “UPF is instructed to remove DL N3 Tunnel Info of Access Network (AN) during Connection Suspend procedure, while UPF keeps UL N3 Tunnel Info (i.e. UPF accepts and forwards UL data) . ” Later, the UE-triggered Service Request (or Network triggered Service Request) is performed to provide the DL N3 Tunnel Info of AN to the UPF.

In such procedures, the Service Request procedure includes many procedures to be performed.

In embodiments of the present disclosure, the UPF still keeps the DL N3 Tunnel Info of AN for each UE, but just stops the DL transmission. After FLSO, UPF updates the stored DL N3 Tunnel Info to use the new TNL address of gNB.

In embodiments of the present disclosure, a single procedure is performed to update the UPF with the new DL N3 TNL address Info of AN (e.g., the DL Tunnel Endpoint Identifier (TEID) assigned by the gNB remains unchanged, but just the IP address of the gNB is changed) .

Particularly, in NTN Regenerative architecture, the FLSO changes the NTN-GW. The gNB/AMF may remain unchanged but can also be changed.

Following embodiments discuss the FLSO scenario that gNB/AMF is not changed.

● Step 1: gNB1 connects with NTN-GW1. gNB1 is assigned with an IP address #1 anchored in NTN-GW1.

● Step 2: gNB1 sets up TNL connection and NG interface with AMF1.

● Step 3: UEs are connected to gNB1.

● Step 4: When AMF/UPF sends DL NG-Control Plane/User Plane (NG-C/U) IP packet to gNB1, it uses the IP address #1 as the destination IP address of the DL NG-C/U IP packet, so the DL NG-C/U IP packets are routed to NTN-GW1, which are further transmitted to gNB1.

● Step 5: gNB1 performs hard FLSO, i.e., disconnects from NTN-GW1, and connects with NTN-GW2. gNB1 is assigned with a new IP address #2 anchored in NTN-GW2.

● Step 6: gNB1 sets up TNL connection with AMF1.

● Step 7: gNB1 sends an NG SETUP REQUEST message including UE Retention Information IE set to “ues-retained” . Both gNB1 and AMF1 maintains the existing UE contexts.

● Step 8: gNB1 use the new IP address #2 as the destination IP address of the DL NG-C IP packet, the DL NG-C IP packets are routed via NTN-GW2, which are further transmitted to gNB1. There is no problem for NG-C.

However, the UPF does not know the FLSO, nor that gNB1’s IP address has been changed. The UPF continues to send the DL NG-U traffic using the old IP address #1, which is routed to NTN-GW1. Since gNB1 does not connect with NTN-GW1 anymore, the NTN-GW1 has no way to send the DL data to gNB1. This causes packet loss and service interruption to the existing UEs.

The present disclosure may provide some exemplary embodiments for reducing such packet loss and service interruption.

As shown in FIG. 3A, the method 300 comprises: a step S302, communicating with a second network node and a third network node using a first feeder link; a step S304, performing the feeder link switchover by setting up a second feeder link; a step S306, transmitting, to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and a step S308, switching a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link. The second message comprises a transport network layer, TNL, parameter related to the second feeder link.

According to embodiments of the present disclosure, when the first network performs a feeder link switchover, it can notify the second network node and the third network node. Thus, unexpected interruption or data loss may be reduced.

In exemplary embodiments of the present disclosure, the step S304 performing the feeder link switchover comprises: a step S3042, transmitting, to the second network node, a first message to indicate that the feeder link switchover from the first feeder link to the second feeder link is to be performed by the first network node.

According to embodiments of the present disclosure, the indication about the feeder link switchover may be performed implicitly, such as by the second message, or explicitly, such as by the first message.

In exemplary embodiments of the present disclosure, the first message comprises a TNL parameter related to the first feeder link. The TNL parameter in the first message comprises: a TNL address (for example, an internet protocol, IP, address) of the first network node before the feeder link switchover; and the TNL parameter in the second message comprises: a TNL address (for example, an IP address) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, the TNL parameter in the second message further comprises: a mapping between the TNL address (for example, IP address) of the first network node before the feeder link switchover and the TNL address (for example, IP address) of the first network node after the feeder link switchover.

According to embodiments of the present disclosure, the first feeder link and/or the second may be indicated by different parameters, such as TNL address (for example, IP addresses) , or an identifier.

In exemplary embodiments of the present disclosure, the first message or the second message is a next generation, NG, Setup Request message, or a radio access network, RAN, Configuration Update message, or a S1 Setup Request message, or an eNB Configuration Update message, or any application protocol, AP, message.

According to embodiments of the present disclosure, different kinds of second message may be used for different scenario. For example, when the control plane interface needs to be set up, the second message may be NG, Setup Request message or S1 Setup Request message. When the control plane interface needs to be updated, the RAN, Configuration Update message or eNB Configuration Update message may be used.

In exemplary embodiments of the present disclosure, the first feeder link comprises a first gateway; the second feeder link comprises a second gateway; and the first message further comprises a time parameter, indicating a time point for the first network node to be disconnected from the first gateway or a time point for the first feeder link to become unavailable, and/or a time point for the second feeder link to become available, and/or a time period for both the first feeder link and second feeder link to be available.

According to embodiments of the present disclosure, with the time parameter, it can be accurately controlled to suspend and resume the communication during the feeder link switchover. The interruption to the communication may be reduced.

According to embodiments of the present disclosure, even when a plurality of second network nodes is involved, the related communications can be also suspended.

As shown in FIG. 3C, the method 300 further comprises: a step S310, receiving, control plane message from the second network node and/or user plane traffic from the third network node, via the second feeder link, after transmitting the second message.

According to embodiments of the present disclosure, the interruption or loss of the user plane transmission between the base station and the core network (for example, UPF or S-GW) may be reduced.

According to embodiments of the present disclosure, as a specifical example, the proposed technical solution may be applied to non-terrestrial network. However, it should be noted that, the proposed technical solution may be also appliable to other kinds of networks.

As shown in FIG. 4A, the method 400 comprises: a step S402, communicating with a first network node using a first feeder link; a step S404, receiving, from the first network node, a second message to manage a control plane interface between the first network node and the second network node, the second message comprises a transport network layer, TNL, parameter related to a second feeder link; a step S406, initiating, to the third network node, a second request comprising the transport network layer parameter, for the third network node to switch a communication between the first network node and the third network node to use the transport network layer parameter, for a list of terminal devices connected with the first network node; and a step S408, switching a communication between the first network node and the second network node from the first feeder link to the second feeder link.

As shown in FIG. 4B, the step S402 communicating with the first network node using the first feeder link comprises: a step S4022, receiving, from the first network node, a first message to indicate that the feeder link switchover from the first feeder link to the second feeder link is to be performed by the first network node; and a step S4024, initiating, to a third network node, a first request for the third network node to suspend communication between the first network node and the third network node for a list of terminal devices connected with the first network node.

In exemplary embodiments of the present disclosure, at least one of the first message or the first request comprises: a TNL address (for example, IP address) of the first network node before the feeder link switchover; and at least one of the TNL parameter in the second message or the TNL parameter in the second request comprises: a TNL address (for example, IP address) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, at least one of the first message, the second message, the first request or the second request further comprises: an identifier, ID, of the first network node, and/or a list of identifier for at least a terminal device connected with the first network node.

In exemplary embodiments of the present disclosure, at least one of the TNL parameter in the second message or the TNL parameter in the second request further comprises: a mapping between the TNL address (for example, IP address) of the first network node before the feeder link switchover and the TNL address (for example, IP address) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, the first message or the second message is a next generation, NG, Setup Request message, or a radio access network, RAN, Configuration Update message, or S1 Setup Request message, or an eNB Configuration Update message, or an application protocol, AP, message (e.g., any S1 or NG AP message) .

As shown in FIG. 4C, the method 400 further comprises: a step S412, stopping a transmission for control plane message via the first feeder link (or via the first gateway) to the first network node, upon receiving the first message; and a step S414, resuming the transmission for control plane message via the second feeder link (or via the second gateway) to the first network node, upon receiving the second message.

In exemplary embodiments of the present disclosure, the second network node initiates the first request and the second request to a plurality of third network nodes.

In exemplary embodiments of the present disclosure, the initiating a first request or a second request by the AMF comprises a step S416, invoking a service request including a list of identifiers for the terminal devices to a session management function, SMF . The SMF then initiates an N4 request including a list of identifiers for the terminal devices, to the UPF. The service request and the N4 request may further include at least a TNL parameter, for example, a TNL address of the first network node before the feeder link switchover, and/or a TNL address of the first network node after the feeder link switchover, and/or a mapping from the TNL address of the first network node before the feeder link switchover to the TNL address of the first network node after the feeder link switchover.

For example, SMF may receive Suspend from AMF, then send N4 Suspend to UPF. SMF may further receive Update from AMF, then send N4 Update to UPF.

As shown in FIG. 5A, the method 500 comprises: a step S506, receiving, from the second network node, a second request comprising a transport network layer parameter related to the second feeder link, for the third network node to update a communication for a list of terminal devices connected with the first network node; S508, updating stored information about the communication, by using the transport network layer parameter; and S510, starting the communication, by using the updated information about the communication, for the list of terminal devices connected with the first network node.

As shown in FIG. 5B, the method 500 further comprises: a step S502, receiving, from a second network node, a first request for the third network node to suspend a communication between a first network node and the third network node, for the list of terminal devices connected with the first network node; a step S504, suspending the communication between a first network node and the third network node, for the list of terminal devices connected with the first network node.

According to embodiments of the present disclosure, the third network node may suspend and then resume the communication in response to the messages from the second node. Therefore, the interruption or even the loss of the communication may be reduced.

In exemplary embodiments of the present disclosure, the first request comprises: a TNL address (for example, IP address) of the first network node before the feeder link switchover; and the TNL parameter in the second request comprises: a TNL address (for example, IP address) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, at least one of the first request or the second request further comprises: an identifier, ID, of the first network node, and/or at least an identifier of a terminal device connected with the first network node.

In exemplary embodiments of the present disclosure, the TNL parameter in the second request further comprises: a mapping from the TNL address (for example, IP address) of the first network node before the feeder link switchover to the TNL address (for example, IP address) of the first network node after the feeder link switchover.

In exemplary embodiments of the present disclosure, the first request comprises a time parameter, indicating a time point for the third network node to suspend the communication, and/or a time period for third network node to suspend the communication.

In exemplary embodiments of the present disclosure, the stored information comprises at least a user plane transport network layer address of one or more user plane tunnel for one or more terminal device (s) connected with the first network node. For example, the stored information may include the downlink Full Qualified Tunnel Endpoint Identifier, F-TEID for one or more terminal device (s) connected with the first network node.

In exemplary embodiments of the present disclosure, the third network node updates at least one TNL address (for example, IP address) for next generation user plane, NG-U, tunnels related to the first network node, based at least on the second request. In another example embodiment, the third network node updates at least one TNL address (for example, IP address) for user plane, for example, S1-U tunnels, related to the first network node, based at least on the second request.

In exemplary embodiments of the present disclosure, the first network node comprises a base station; the second network node comprises an access and mobility management function, AMF, or a mobility management entity, MME; the communication comprises a user plane transmission suspended before the feeder link switchover and resumed after the feeder link switchover; the communication is resumed over a Transport Network Layer, TNL, connection in the second feeder link; and the third network node comprises a user plane function, UPF, or a serving gateway, S-GW.

In exemplary embodiments of the present disclosure, a first request or a second request received by the UPF is an N4 request transmitted by a session management function, SMF. The SMF transmits the N4 request as a response to a reception of a service request including a list of identifiers for terminal devices (e.g. with a list of PDU needing reactivation) , from the AMF. The N4 request and the service request may further include a TNL parameter, for example, a TNL address of the first network node before the feeder link switchover, and/or a TNL address of the first network node after the feeder link switchover, and/or a mapping from the TNL address of the first network node before the feeder link switchover to the TNL address of the first network node after the feeder link switchover.

Embodiments of the present disclosure provide means to minimize packet loss and service interruption during a hard FLSO in an NTN system.

More specifically, the network nodes may perform as follows.

gNB1 may perform following actions.

● When detecting a need to perform hard FLSO, gNB1 sends a notification about the upcoming hard FLSO to AMF1. (Step 1 in FIG. 6)

● After gNB1 connects with new NTN-GW2 and new IP address (es) is assigned, gNB1 initiates a NG procedure, for example, an NG Setup procedure, requesting the UPF to use the new IP address (es) for DL NG-U. (Step 5 in FIG. 6)

● The uplink/downlink NG-C/U are resumed using the new IP address (es) anchored in the new NTN-GW. The NG-C/U traffic are transferred via the new feeder link related to the new IP address (es) .

AMF may perform following actions.

● Upon the reception of a notification for the upcoming hard FLSO from gNB, AMF requests the UPF (via SMF) to suspend all DL transmission to the gNB1 or specific IP address (es) . (Steps 1 and 2 and 3 in FIG. 6)

- AMF also stops the DL NG-C transmission to gNB1 via the existing (or first) feeder link related to IP address #1.

● Upon the reception of the NG SETUP REQUEST, including the new IP address (es) , AMF sends an update to UPF (via SMF) to update the IP address (es) for the NG-U tunnels related to gNB1 or related to the existing IP address of gNB1 or a list of terminal devices connected with gNB1. (Steps 5 and 6 and 7 in FIG. 6)

● AMF resumes the DL NG-C transmission to gNB1 using the new IP address. The NG-C traffic are transferred via the new feeder link related to the new IP address (es) .

UPF may perform following actions.

● Upon the reception of the suspend request, the UPF suspends DL transmission for all NG-U tunnels related to gNB1 or specific IP address (es) of gNB1 or a list of terminal devices connected with gNB1, but keeps the DL Full Qualified Tunnel Endpoint Identifier (F-TEID) for the related UEs/PDU Sessions. (Steps 2 and 3 in FIG. 6)

● Upon the reception of the update request, the UPF updates all related NG-U tunnels to use the new IP address (es) , and resumes DL transmission for all related NG-U tunnels towards the new IP address (es) for the list of terminal devices. (Steps 6 and 7 in FIG. 6) The NG-U traffic are transferred via the new feeder link related to the new IP address (es) .

Further, the steps of the call flow in FIG. 3 will be illustrated in details as follows.

Step 0: gNB1 is connected with AMF1 via NTN-GW1. gNB1 is assigned with IP address (es) , e.g. IP address #1, anchored in NTN-GW1. The DL/UL NG-C/U uses the IP address #1, and is routed via NTN-GW1.

● Step 1: gNB1 decides to perform a hard FLSO. gNB1 sends a notification for Upcoming Hard FLSO to AMF1. The purpose is to ask the AMF/UPF to stop the DL NG-C/U transmission using the existing IP address (es) , e.g., IP address #1, i.e. using the first feeder link.

- The notification may indicate a specific time that first feeder link to be become unavailable or gNB1 will be disconnected from NTN-GW1, such as a time point to start a disconnection procedure, or a specific time point that the second feeder link to become available, or a time period for both the first feeder link and the second feeder link network node are available. AMF1 can use this time to determine when it need to stop DL NG-C and perform Step 2 to stop DL NG-U. Therefore, the communication may be suspended at such time point/time period, or just before it.

The AMF stops the DL NG-C transmission to gNB1.

In case gNB1 connects with multiple AMFs, Step 1 is repeated for every connected AMF.

● Step 2 and step 3: AMF1 initiates a suspend request to the UPF via SMF to suspend the DL transmission for a list of UEs or all UEs served by gNB1. The Request may include the gNB1’s IP address, e.g., #1, or an ID of the gNB, or a list of IDs for at least one UE connected with gNB1 and served by this UPF.

- Upon the reception of the suspend request, the UPF stops the DL NG-U transmission for all related NG-U tunnels which can be identified using gNB1’s IP address, e.g. #1, or the ID of the gNB, or the list of the IDs of UEs, and keeps the DL F-TEID information for those UEs connected with the satellite/gNB1. It should be noted that, this is different to connection suspend procedure above mentioned, which releases the DL F-TEID information in the UPF. In embodiments of the present disclosure, the UPF still keeps the DL F-TEID for all UEs connected with the satellite/gNB1. During the hard FLSO, only the IP address of the gNB is changed and TEID assigned by the gNB can remain unchanged (since it is the same gNB before FLSO and after FLSO) .

- In addition, the changing of IP address in DL F-TEID is applicable to a list of UEs or all UEs connected with the satellite/gNB. So, it may be better to use a non-UE associated signaling (for example, only indicating the satellite/gNB in the signalling may be enough) since it is possible that many UEs may be connected with gNB1. Using a non-UE associated signaling can avoid the signaling storm to SMF/UPF. The required change is applicable to AMF-SMF interface and SMF-UPF interface.

- It is possible that multiple UPFs may be used for UEs connected with the satellite/gNB1. Step 2/3 are repeated for all related SMF/UPF serving the UE (s) connected with the satellite/gNB1.

Alternatively or additionally, AMF1 may also send the specific time information to SMF/UPF, so the UPF may stop the DL transmission at (or just before) the specific time that the satellite/gNB1 disconnects from NTN-GW1.

● Step 4: gNB1 performs hard FLSO, i.e. disconnects from NTN-GW1, and connects with NTN-GW2. gNB1 is assigned with new IP address (es) , e.g., IP address #2, anchored in NTN-GW2. The first feeder link is disconnected, and the second feeder link is established.

● Step 5: gNB1 uses the new IP address to set up TNL connection with AMF via NTN-GW2. gNB1 sends an NG SETUP REQUEST message to AMF1. The message includes

- UE Retention Information IE set to “ues-retained” ;

- gNB1’s new IP address (es) for NG-U. In case gNB1 uses multiple IP addresses for NG-U, it can be a mapping from gNB1’s old IP address (anchored in NTN-GW1) to gNB1’s new IP address (anchored in NTN-GW2) .

Upon the reception of the NG SETUP REQUEST message, AMF1 accept the proposal to retain the existing UE-related contexts and knows the NG-U IP address (es) which need to be updated. AMF1 also resumes DL NG-C transmission to gNB1 via NTN-GW2. In other words, the NG-C communication between AMF1 and gNB1 is switched from the first feeder link using NTN-GW1 to the second feeder link using NTN-GW2.

● Step 6 and step 7: AMF initiates an update procedure via SMF to request the UPF to update the IP address (es) for NG-U tunnels related to gNB1. The Request message includes a mapping from gNB1’s old IP address (related to the first feeder link and anchored in NTN-GW1) to gNB1’s new IP address (related to the second feeder link and anchored in NTN-GW2) .

- Alternatively or additionally, the Request may include the gNB ID of gNB1, which indicating the update is applicable to all NG-U tunnels to this gNB.

UPF updates all NG-U tunnels related to gNB1 or a list of terminal devices connected with gNB1, to use the new IP address (es) anchored in NTN-GW2. UPF resume the DL transmission via NTN-GW2 for all related NG-U tunnels using the new IP address (es) . The NG-U traffic is switched from using the old IP address (es) anchored in NTN-GW1, to new IP address (es) anchored in NTN-GW2.

At the completion of Step 5, the uplink/downlink NG-C/U between gNB1 and 5GC (AMF1, UPF) are routed via NTN-GW2. In other words, the communication between gNB1 and AMF1, and the communication between gNB1 and UPF1, are switched from the first feeder link to the second feeder link.

The embodiments of the present disclosure provide benefits, such as that, the DL NG-U packet loss is avoided during the hard FLSO. It provides a fast approach to suspend/resume the DL NG-U for all UEs served by the gNB/satellite. It is to be understood that step 5, 6 and 7 can also be performed in case of soft FLSO, which enables a single procedure to update the user plane tunnels for a list of terminal devices connected with the same gNB/satellite, from the old IP address related to the old NTN-GW and first feeder link before feeder link switchover, to new IP address related to the new NTN-GW and second feeder link after feeder link switchover.

Such embodiments may be specifically applicable to improve the standardization in the related 3GPP specifications (e.g., TS23.501 V18.4.0 (2023-12) , TS23.502 V18.4.0 (2023-12) , TS38.413 V17.6.0 (2023-09) , etc. ) .

As shown in FIG. 7, the first network node 70 comprises means 700 configured for: communicating with a second network node and a third network node using a first feeder link; performing the feeder link switchover by setting up a second feeder link; transmitting, to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and switching a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link. The second message comprises a transport network layer, TNL, parameter related to the second feeder link.

In exemplary embodiments of the present disclosure, the means 700 comprise: at least one processor 702; and at least one memory 704 storing instructions that, when executed by the at least one processor 702, cause the performance of the first network node 70.

In exemplary embodiments of the present disclosure, the means 700 are further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 3A, 3B, 3C, 6.

As shown in FIG. 8, the second network node 80 comprises means 800 configured for: communicating with a first network node using a first feeder link; receiving, from the first network node, a second message to manage a control plane interface between the first network node and the second network node, the second message comprises a transport network layer, TNL, parameter related to a second feeder link; initiating, to the third network node, a second request comprising the transport network layer parameter, for the third network node to switch a communication between the first network node and the third network node to use the transport network layer parameter, for a list of terminal devices connected with the first network node; and switching a communication between the first network node and the second network node from the first feeder link to the second feeder link.

In exemplary embodiments of the present disclosure, the means 800 comprise: at least one processor 802; and at least one memory 804 storing instructions that, when executed by the at least one processor 802, cause the performance of the third network node 80.

In exemplary embodiments of the present disclosure, the means 800 are further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 4A, 4B, 4C, 4D, 6.

As shown in FIG. 9, the third network node 90 comprises means 900 configured for: receiving, from the second network node, a second request comprising a transport network layer, TNL, parameter related to the second feeder link, for the third network node to update a communication for a list of terminal devices connected with the first network node; updating stored information about the communication, by using the transport network layer parameter; and starting the communication, by using the updated information about the communication, for the list of terminal devices connected with the first network node.

In exemplary embodiments of the present disclosure, the means 900 comprise: at least one processor 902; and at least one memory 904 storing instructions that, when executed by the at least one processor 902, cause the performance of the fourth node 90.

In exemplary embodiments of the present disclosure, the means 900 are further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 5A, 5B, 6.

The processor 702, 802, 902 may be any kind of processing component, such as one or more microprocessor or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs) , special-purpose digital logic, and the like. The memory 704, 804, 904 may be any kind of storage component, such as read-only memory (ROM) , random-access memory, cache memory, flash memory devices, optical storage devices, etc.

As shown in FIG. 10, a computer-readable storage medium 100 storing instructions 101, which when executed by at least one processor of a network node (such as the first, second, third, fourth, fifth node) , cause the at least one processor of the node to perform the method according to any of the embodiments above mentioned, such as shown in FIG. 3A, 3B, 3C, 4A, 4B, 4C, 4D, 5A, 5B, 6.

In addition, the present disclosure may also provide a carrier containing the computer program/instructions as mentioned above. The carrier is one of an electronic signal, optical signal, radio signal, or the above computer readable storage medium. The computer readable storage medium can be, for example, an optical compact disk or an electronic memory device like a RAM (random access memory) , a ROM (read only memory) , Flash memory, magnetic tape, CD-ROM, DVD, Blue-ray disc and the like.

FIG. 11 is a block diagram showing exemplary apparatus units for a first network node, which is suitable for performing the method according to embodiments of the disclosure. As shown in FIG. 11, the first network node 110 may include: a communicating unit 1102, for communicating with a second network node and a third network node using a first feeder link; a performing unit 1104, for performing the feeder link switchover by setting up a second feeder link; a transmitting unit 1106, for transmitting, to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and a switching unit 1108, for switching a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link. The second message comprises a transport network layer, TNL, parameter related to the second feeder link.

In exemplary embodiments of the present disclosure, the first network node 170 is further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 3A, 3B, 3C, 6.

As shown in FIG. 12, the second network node 120 may include: a communicating unit 1202, for communicating with a first network node using a first feeder link; a receiving unit 1204, for receiving, from the first network node, a second message to manage a control plane interface between the first network node and the second network node, the second message comprises a transport network layer, TNL, parameter related to a second feeder link; an initiating unit 1206, for initiating, to the third network node, a second request comprising the transport network layer parameter, for the third network node to switch a communication between the first network node and the third network node to use the transport network layer parameter, for a list of terminal devices connected with the first network node; and a switching unit 1208, for switching a communication between the first network node and the second network node from the first feeder link to the second feeder link.

In exemplary embodiments of the present disclosure, the second network node 120 is further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 4A, 4B, 4C, 4D, 6.

As shown in FIG. 13, the third network node 130 may include: a receiving unit 1306, for receiving, from the second network node, a second request comprising a transport network layer, TNL, parameter related to the second feeder link, for the third network node to update a communication for a list of terminal devices connected with the first network node; an updating unit 1308, for updating stored information about the communication, by using the transport network layer parameter; and a starting unit 1310, for resuming the communication, by using the updated information about the communication, for the list of terminal devices connected with the first network node.

In exemplary embodiments of the present disclosure, the third network node 130 is further configured for performing the method according any of the embodiments above mentioned, such as shown in FIG. 5A, 5B, 6.

The term ‘unit’ may have conventional meaning in the field of electronics, electrical devices and/or electronic devices and may include, for example, electrical and/or electronic circuitry, devices, modules, processors, memories, logic solid state and/or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and/or displaying functions, and so on, as such as those that are described herein.

As used in the present disclosure, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analogy and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analogy and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. ”

This definition of circuitry applies to all uses of this term in the present disclosure, including in any claims. As a further example, as used in the present disclosure, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

With these units, the apparatus may not need a fixed processor or memory, any kind of computing resource and storage resource may be arranged from at least one node/device/entity/apparatus relating to the communication system. The virtualization technology and network computing technology (e.g., cloud computing) may be further introduced, so as to improve the usage efficiency of the network resources and the flexibility of the network.

The techniques described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding apparatus described with an embodiment comprises not only prior art means, but also means for implementing the one or more functions of the corresponding apparatus described with the embodiment and it may comprise separate means for each separate function, or means that may be configured to perform two or more functions. For example, these techniques may be implemented in hardware (one or more apparatuses) , firmware (one or more apparatuses) , software (one or more modules/units) , or combinations thereof. For a firmware or software, implementation may be made through modules (e.g., procedures, functions, and so on) that perform the functions described herein.

In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionalities may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and/or by end users and a wireless network generally.

The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

As described in above exemplary embodiments of this disclosure, embodiments herein afford many advantages. According to embodiments of the present disclosure, the exemplary embodiments of the present disclosure propose a mechanism that allows a faster and more accurate approach to suspend/resume the communication in the communication network when a feeder link switchover is performed. The interruption or even loss of the data transmission caused by the feeder link switchover may be reduced.

It should be understood that the above embodiments are only for illustration but not limitation. The present disclosure may be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the disclosure. All changes to these embodiments not departing from the meaning and equivalency of the appended claims are intended to be comprised herein.

REFERENCES

The followings are the references which are incorporated herein in their entirety:

3GPP TS 38.413 V17.6.0 (2023-09) ;

3GPP TS 23.401 V18.4.0 (2023-12) ;

3GPP TS 23.501 V18.4.0 (2023-12) ;

3GPP TS 23.502 V18.4.0 (2023-12) ;

3GPP TS 29.502 V18.4.0 (2023-09) .

ABBREVIATION    EXPLANATION
FLSO     Hard Feeder Link Switch Over
AMF      Access and Mobility Management Function
DL       Downlink
CP       Control Plane
UP       User Plane
SMF      Session Management Function
UPF      User Plane Function
NTN      Non Terrestrial Network
LEO      Low-Earth Orbit
NG       Next Generation
TNL      Transport Network Layer
AN       Access Network
TEID     Tunnel Endpoint Identifier
F-TEID   Full Qualified Tunnel Endpoint Identifier

Claims

A method (300) performed by a first network node for a feeder link switchover in a communication network, comprising:

communicating (S302) with a second network node and a third network node using a first feeder link;

performing (S304) the feeder link switchover by setting up a second feeder link;

transmitting (S306) , to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and

switching (S308) a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link;

wherein the second message comprises a transport network layer, TNL, parameter related to the second feeder link.
The method (300) according to claim 1,

wherein performing (S304) the feeder link switchover comprises: transmitting (S3042) , to the second network node, a first message to indicate that the feeder link switchover from the first feeder link to the second feeder link is to be performed by the first network node.
The method (300) according to claim 2,

wherein the first message comprises a TNL parameter related to the first feeder link;

wherein the TNL parameter in the first message comprises: a TNL address of the first network node before the feeder link switchover; and

wherein the TNL parameter in the second message comprises: a TNL address of the first network node after the feeder link switchover.
The method (300) according to claim 3,

wherein at least one of the first message or the second message further comprises: an identifier, ID, of the first network node, and/or a list of at least an identifier of a terminal device connected with the first network node.
The method (300) according to claim 3 or 4,

wherein the TNL parameter in the second message further comprises: a mapping between the TNL address of the first network node before the feeder link switchover and the TNL address of the first network node after the feeder link switchover.
The method (300) according to any of claims 2 to 5,

wherein the first message or the second message is a next generation, NG, Setup Request message, or a radio access network, RAN, Configuration Update message, or S1 Setup Request message, or an eNB Configuration Update message, or an application protocol, AP, message.
The method (300) according to any of claims 2 to 6,

wherein the first feeder link comprises a first gateway;

wherein the second feeder link comprises a second gateway; and

wherein the first message further comprises a time parameter, indicating a time point for the first feeder link to become unavailable, and/or a time point for the second feeder link to become available, and/or a time period for both the first feeder link and the second feeder link to be available.
The method (300) according to any of claims 2 to 7,

wherein the first network node transmits the first message and the second message to a plurality of second network nodes.
The method (300) according to any of claims 1 to 8, further comprising:

receiving (S310) , control plane message from the second network node and/or user plane traffic from the third network node, via the second feeder link, after transmitting the second message.
The method (300) according to any of claims 1 to 9,

wherein the first network node comprises a base station;

wherein the second network node comprises an access and mobility management function, AMF, or a mobility management entity, MME;

wherein the third network node comprises a user plane function, UPF, or a serving gateway, S-GW; and

wherein the communication between the first network node and the third network node comprises a user plane transmission suspended before the feeder link switchover and resumed after the feeder link switchover.
The method (300) according to any of claims 1 to 10,

wherein the communication network is a non-terrestrial network.
A method (400) performed by a second network node for a feeder link switchover in a communication network, comprising:

communicating (S402) with a first network node using a first feeder link;

receiving (S404) , from the first network node, a second message to manage a control plane interface between the first network node and the second network node, wherein the second message comprises a transport network layer, TNL, parameter related to a second feeder link;

initiating (S406) , to the third network node, a second request comprising the transport network layer parameter, for the third network node to switch a communication between the first network node and the third network node to use the transport network layer parameter, for a list of terminal devices connected with the first network node; and

switching (S408) a communication between the first network node and the second network node from the first feeder link to the second feeder link.
The method (400) according to claim 12,

wherein communicating (S402) with the first network node using the first feeder link comprises: receiving (S4022) , from the first network node, a first message to indicate that the feeder link switchover from the first feeder link to the second feeder link is to be performed by the first network node; and

initiating (S4024) , to a third network node, a first request for the third network node to suspend communication between the first network node and the third network node for a list of terminal devices connected with the first network node.
The method (400) according to claim 13,

wherein at least one of the first message or the first request comprises: a TNL address of the first network node before the feeder link switchover; and

wherein at least one of the TNL parameter in the second message or the TNL parameter in the second request comprises: a TNL address of the first network node after the feeder link switchover.
The method (400) according to claim 13 or 14,

wherein at least one of the first message, the second message, the first request or the second request further comprises: an identifier, ID, of the first network node, and/or a list of identifier for at least a terminal device connected with the first network node.
The method (400) according to any of claims 13 to 15,

wherein at least one of the TNL parameter in the second message or the TNL parameter in the second request further comprises: a mapping between the TNL address of the first network node before the feeder link switchover and the TNL address of the first network node after the feeder link switchover.
The method (400) according to any of claims 13 to 16,

wherein the first message or the second message is a next generation, NG, Setup Request message, or a radio access network, RAN, Configuration Update message, or S1 Setup Request message, or an eNB Configuration Update message, or an application protocol, AP, message.
The method (400) according to any of claims 13 to 17,

wherein the first feeder link comprises a first gateway;

wherein the second feeder link comprises a second gateway;

wherein the first message further comprises a time parameter, indicating a time point for the first feeder link to become unavailable, and/or a time point for the second feeder link to become available, and/or a time period for both the first feeder link and the second feeder link to be available; and

wherein the first request comprises a time parameter, indicating a time point for the third network node to suspend the communication, and/or a time period for third network node to suspend the communication.
The method (400) according to any of claims 13 to 18, further comprising:

stopping (S412) a transmission for control plane message via the first feeder link to the first network node, upon receiving the first message; and

resuming (S414) the transmission for control plane message via the second feeder link to the first network node, upon receiving the second message.
The method (400) according to any of claims 13 to 19,

wherein the second network node initiates the first request and the second request to a plurality of third network nodes.
The method (400) according to any of claims 12 to 20,

wherein the first network node comprises a base station;

wherein the second network node comprises an access and mobility management function, AMF, or a mobility management entity, MME;

wherein the third network node comprises a user plane function, UPF, or a serving gateway, S-GW; and

wherein the communication comprises a user plane transmission suspended before the feeder link switchover and resumed after the feeder link switchover.
The method (400) according to claim 21,

wherein initiating a first request or a second request by the AMF comprises:

invoking (S416) a service request including a list of terminal devices to a session management function, SMF; and

wherein the SMF initiates an N4 request including a list of identifiers for the list of terminal devices, to the UPF.
The method (400) according to any of claims 12 to 22,

wherein the communication network is a non-terrestrial network.
A method (500) performed by a third network node for a feeder link switchover in a communication network, comprising:

receiving (S506) , from the second network node, a second request comprising a transport network layer, TNL, parameter, for the third network node to update a communication for a list of terminal devices connected with the first network node;

updating (S508) stored information about the communication, by using the transport network layer parameter; and

starting (S510) the communication, by using the updated information about the communication, for the list of terminal devices connected with the first network node.
The method (500) according to claim 24, further comprising:

receiving (S502) , from a second network node, a first request for the third network node to suspend the communication between a first network node and the third network node, for the list of terminal devices connected with the first network node; and

suspending (S504) the communication between a first network node and the third network node, for the list of terminal devices connected with the first network node.
The method (500) according to claim 25,

wherein the first request comprises: a TNL address of the first network node before a feeder link switchover; and

wherein the TNL parameter in the second request comprises: a TNL address of the first network node after the feeder link switchover.
The method (500) according to claim 26,

wherein at least one of the first request or the second request further comprises: an identifier, ID, of the first network node, and/or a list of at least an identifier of a terminal device connected with the first network node.
The method (500) according to claim 26 or 27,

wherein the TNL parameter in the second request further comprises: a mapping from the TNL address of the first network node before the feeder link switchover to the TNL address of the first network node after the feeder link switchover.
The method (500) according to any of claims 25 to 28,

wherein the first request comprises a time parameter, indicating a time point for the third network node to suspend the communication, and/or a time period for third network node to suspend the communication.
The method (500) according to any of claims 24 to 29,

wherein the stored information comprises at least a user plane transport network layer address of a user plane tunnel for a terminal device connected with the first network node.
The method (500) according to any of claims 24 to 30,

wherein the third network node updates at least one IP address for next generation user plane, NG-U, tunnel related to the first network node, based at least on the second request.
The method (500) according to any of claims 24 to 31,

wherein the first network node comprises a base station;

wherein the second network node comprises an access and mobility management function, AMF, or a mobility management entity, MME;

wherein the communication comprises a user plane transmission suspended before the feeder link switchover and resumed after the feeder link switchover;

wherein the communication is resumed over a Transport Network Layer, TNL, connection using the second feeder link; and

wherein the third network node comprises a user plane function, UPF, or a serving gateway, S-GW.
The method (500) according to claim 32,

wherein a first request or a second request received by the UPF is an N4 request transmitted by a session management function, SMF, and

wherein the SMF transmits the N4 request as a response to a reception of a service request including a list of identifiers for terminal devices, from the AMF.
The method (500) according to any of claims 24 to 33,

wherein the communication network is a non-terrestrial network.
A first network node (70) comprising means (700) configured for:

communicating with a second network node and a third network node using a first feeder link;

performing the feeder link switchover by setting up a second feeder link;

transmitting, to the second network node, a second message to manage a control plane interface between the first network node and the second network node; and

switching a communication between the first network node and the second network node, and/or a communication between the first network node and the third network node, to the second feeder link;

wherein the second message comprises a transport network layer, TNL, parameter related to the second feeder link;

wherein the means (700) comprise:

at least one processor (702) ; and

at least one memory (704) storing instructions that, when executed by the at least one processor (702) , cause the performance of the first network node (70) .
The first network (70) node according to claim 35, wherein the means (700) are further configured for performing the method according to any of the claims 2 to 11.
A second network node (80) comprising means (800) configured for:

communicating with a first network node using a first feeder link;

receiving, from the first network node, a second message to manage a control plane interface between the first network node and the second network node, wherein the second message comprises a transport network layer, TNL, parameter related to a second feeder link; and

initiating, to the third network node, a second request comprising the transport network layer parameter, for the third network node to switch a communication between the first network node and the third network node to use the transport network layer parameter, for a list of terminal devices connected with the first network node; and

switching a communication between the first network node and the second network node from the first feeder link to the second feeder link;

wherein the means (800) comprise:

at least one processor (802) ; and

at least one memory (804) storing instructions that, when executed by the at least one processor (802) , cause the performance of the second network node (80) .
The second network node (80) according to claim 37, wherein the means (800) are further configured for performing the method according to any of the claims 13 to 23.
A third network node (90) comprising means (900) configured for:

receiving, from the second network node, a second request comprising a transport network layer, TNL, parameter related to the second feeder link, for the third network node to update a communication for a list of terminal devices connected with the first network node;

updating stored information about the communication, by using the transport network layer parameter; and

starting the communication, by using the updated information about the communication, for the list of terminal devices connected with the first network;

wherein the means comprise:

at least one processor (902) ; and

at least one memory (904) storing instructions that, when executed by the at least one processor (902) , cause the performance of the third network node (90) .
The third network node (90) according to claim 39, wherein the means (900) are further configured for performing the method according to any of the claims 25 to 34.
A computer-readable storage medium (100) storing instructions (101) , which when executed by at least one processor of a network node, cause the at least one processor of a network node to perform the method according to any of claims 1 to 34.