User Equipment Migration in Integrated Access and Backhaul Networks

Abstract

A mechanism for migrating a UE from a node to an R‑IAB node is provided. The method is performed by an S‑IAB node and a D‑IAB node of the R‑IAB node. The method includes obtaining a request to replace the S‑IAB node. The method includes providing an indication to the S‑IAB node to replace the S‑IAB node. The method includes obtaining scheduling information for UEs served by the S‑IAB node from the S‑IAB node. The method includes forwarding the scheduling information to the R‑IAB node. The method includes: initiating migration of at least a subset of UEs from the S‑IAB node to the R‑IAB node by providing an instruction to at least a subset of UEs via the S‑IAB node to switch from being served by the S‑IAB node to being served by the R‑IAB node.

Description

Technical Field

[0001] The presented embodiments relate to methods for migrating a user equipment (UE) from an S-IAB node to an R-IAB node, a donor integrated access and backhaul (D-IAB) node, a serving integrated access and backhaul (S-IAB) node, a replacement integrated access and backhaul (R-IAB) node, a computer program, and a computer program product. Background Art

[0002] In communication networks, obtaining good performance and capacity for a given communication protocol, its parameters, and the physical environment in which the communication network is deployed can be challenging.

[0003] For example, densification via the deployment of more and more base stations (either macro or micro) is one of the mechanisms that can be used to increase coverage, bandwidth and / or capacity in a communication network. However, deploying fiber optic links or other types of cables to small base stations (which is a common way to deploy small base stations) may ultimately be both expensive and impractical. Sampling wireless links to connect small base stations to the core network can be both cheap and practical. One such option is an integrated access and backhaul (IAB) network, in which part of the radio resources can be used for backhaul purposes (i.e., for communication between two IAB nodes).

[0004] In general, an IAB network may include a donor IAB node, a parent IAB node, and a child IAB node. In this regard, the donor IAB node also acts as a parent IAB node, and the child IAB node may act as a parent IAB node of another child IAB node. In order to easily expand network coverage using the IAB network, the child IAB node may be expected to be carried by a vehicle (e.g., a connected and autonomous vehicle (CAV), such as an aircraft and a ground vehicle platform), thereby potentially making the IAB child node portable or mobile. In this case, the currently deployed child IAB node may have to be replaced by another child IAB node. For example, a child IAB node installed on a CAV to expand network coverage during mission-critical (MC) operations may have to be replaced due to exhaustion of its battery.

[0005] Existing procedures for replacement of such a child IAB node may result in unacceptably long interruptions in service to the served UEs.

[0006] Therefore, there remains a need for improved replacement of sub-IAB nodes in an IAB network. Summary of the invention

[0007] The purpose of the embodiments herein is to achieve seamless replacement of sub-IAB nodes in an IAB network.

[0008] According to a first aspect, a method for migrating a UE from a node to an R-IAB node is proposed. The method is performed by an S-IAB node and a D-IAB node of the R-IAB node. The method includes obtaining a request to replace the S-IAB node. The method includes providing an indication of replacing the S-IAB node to the S-IAB node. The method includes obtaining scheduling information for a UE served by the S-IAB node from the S-IAB node. The method includes forwarding the scheduling information to the R-IAB node. The method includes: initiating migration of at least a subset of UEs from the S-IAB node to the R-IAB node by providing an instruction to switch from being served by the S-IAB node to being served by the R-IAB node to at least a subset of UEs via the S-IAB node.

[0009] According to a second aspect, a D-IAB node for migrating a UE from a node to an R-IAB node is proposed. The D-IAB node includes a processing circuit. The processing circuit is configured to enable the D-IAB node to obtain a request for replacing an S-IAB node. The processing circuit is configured to enable the D-IAB node to provide an indication of replacing the S-IAB node to the S-IAB node. The processing circuit is configured to enable the D-IAB node to obtain scheduling information for a UE provided by the S-IAB node from the S-IAB node. The processing circuit is configured to enable the D-IAB node to forward the scheduling information to the R-IAB node. The processing circuit is configured to enable the D-IAB node to: initiate migration of at least a subset of UEs from the S-IAB node to the R-IAB node by providing an instruction to switch from being provided by the S-IAB node to being provided by the R-IAB node to at least a subset of UEs via the S-IAB node.

[0010] According to a third aspect, a computer program for migrating a UE from an S-IAB node to an R-IAB node is provided. The computer program comprises computer program code which, when executed on a processing circuit of a D-IAB node, causes the D-IAB node to perform the method according to the first aspect.

[0011] According to a fourth aspect, a method for migrating a UE from a node to an R-IAB node is proposed. The method is performed by an S-IAB node. The method includes obtaining an indication of replacing the S-IAB node from the S-IAB node and the D-IAB node of the R-IAB node. The method includes providing scheduling information for UEs served by the S-IAB node to the R-IAB node via the D-IAB node. The method includes: initiating migration of at least a subset of UEs from the S-IAB node to the R-IAB node by instructing at least a subset of UEs to switch from being served by the S-IAB node to being served by the R-IAB node according to an instruction from the D-IAB node.

[0012] According to a fifth aspect, an S-IAB node is proposed for migrating a UE from the S-IAB node to an R-IAB node. The S-IAB node includes a processing circuit. The processing circuit is configured to: enable the S-IAB node to obtain an indication of replacing the S-IAB node from the S-IAB node and the D-IAB node of the R-IAB node. The processing circuit is configured to enable the S-IAB node to provide scheduling information for the UE served by the S-IAB node to the R-IAB node and via the D-IAB node. The processing circuit is configured to enable the S-IAB node to: initiate migration of at least a subset of UEs from the S-IAB node to the R-IAB node by instructing at least a subset of UEs to switch from being served by the S-IAB node to being served by the R-IAB node according to an instruction from the D-IAB node.

[0013] According to a sixth aspect, a computer program for migrating a UE from an S-IAB node to an R-IAB node is provided. The computer program comprises computer program code which, when executed on a processing circuit of the S-IAB node, causes the S-IAB node to perform the method according to the first aspect.

[0014] According to a seventh aspect, a method for migrating a UE from a node to an R-IAB node is proposed. The method is performed by the R-IAB node. The method comprises: obtaining scheduling information for a UE served by the S-IAB node from the S-IAB node and via the S-IAB node and the D-IAB node of the R-IAB node. The method comprises: after a subset of UEs has been migrated from being served by the S-IAB node to being served by the R-IAB node, serving at least a subset of UEs according to the scheduling information.

[0015] According to an eighth aspect, an R-IAB node for migrating a UE from a node to an R-IAB node is proposed. The R-IAB node includes a processing circuit. The processing circuit is configured to cause the R-IAB node to: obtain scheduling information for a UE served by the S-IAB node from the S-IAB node and via the S-IAB node and the D-IAB node of the R-IAB node. The processing circuit is configured to cause the R-IAB node to: serve at least a subset of the UEs according to the scheduling information after the subset of the UEs have been migrated from being served by the S-IAB node to being served by the R-IAB node.

[0016] According to a tenth aspect, a computer program for migrating a UE from an S-IAB node to an R-IAB node is provided. The computer program comprises computer program code, which, when executed on a processing circuit of the R-IAB node, causes the R-IAB node to perform the method according to the seventh aspect.

[0017] According to an eleventh aspect, a computer program product is provided, comprising a computer program according to at least one of the third aspect, the sixth aspect and the tenth aspect and a computer-readable storage medium storing the computer program. The computer-readable storage medium may be a non-transitory computer-readable storage medium.

[0018] Advantageously, the methods, the D-IAB node, the S-IAB node, the R-IAB node, the computer programs and the computer program product provide for efficient replacement of S-IAB nodes with R-IAB nodes in an IAB network.

[0019] Advantageously, the methods, the D-IAB node, the S-IAB node, the R-IAB node, the computer programs and the computer program product enable seamless replacement of an S-IAB node with an R-IAB node in an IAB network.

[0020] Advantageously, the methods, the D-IAB node, the S-IAB node, the R-IAB node, the computer programs and the computer program product enable replacement of an S-IAB node with an R-IAB node in an IAB network without interrupting ongoing services of UEs.

[0021] Advantageously, the methods, the D-IAB node, the S-IAB node, the R-IAB node, the computer programs and the computer program product prevent service interruption during migration, which is critical for MC services.

[0022] Other objectives, features and advantages of the attached embodiments will become apparent from the following detailed disclosure, the attached dependent claims as well as the accompanying drawings.

[0023] Generally, unless otherwise explicitly stated herein, all terms used in the claims are interpreted according to their ordinary meaning in the technical field. Unless otherwise explicitly stated, all references to "a / an / the element, device, component, means, module, step, etc." should be openly interpreted as referring to at least one instance of an element, device, component, means, module, step, etc. Unless explicitly stated, the steps of any method disclosed herein do not have to be strictly performed in the exact order disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The inventive concept will now be described by way of example with reference to the accompanying drawings, in which:

[0025] Figure 1 is a schematic diagram showing an IAB network according to an embodiment;

[0026] Figure 2is a schematic illustration of an interface between IAB nodes according to an embodiment;

[0027] Figure 3 , Figure 4 , Figure 5 is a flow chart of a method according to an embodiment;

[0028] Figure 6 is a signaling diagram according to an embodiment;

[0029] Figure 7 is a schematic diagram showing functional units of a D-IAB node according to an embodiment;

[0030] Figure 8 is a schematic diagram showing functional modules of a D-IAB node according to an embodiment;

[0031] Fig. 9 is a schematic diagram showing functional units of an S-IAB node according to an embodiment;

[0032] Fig.10 is a schematic diagram showing functional modules of an S-IAB node according to an embodiment;

[0033] Fig.11 is a schematic diagram showing functional units of an R-IAB node according to an embodiment;

[0034] Fig.12 is a schematic diagram showing functional modules of an R-IAB node according to an embodiment; and

[0035] Fig.13 An example of a computer program product comprising computer readable means according to an embodiment is shown. DETAILED DESCRIPTION

[0036] The inventive concept will now be described more fully below with reference to the accompanying drawings showing certain embodiments of the inventive concept. However, the inventive concept can be embodied in a variety of different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that the disclosure will be thorough and complete and fully convey the scope of the inventive concept to those skilled in the art. Throughout the specification, similar reference numerals refer to similar elements. Any steps or features shown by dashed lines should be considered optional.

[0037] Figure 1is a schematic diagram showing an IAB network 10 to which the embodiments presented herein may be applied. The IAB network 10 comprises a (radio) access network 20, a core network 30 and a service network 40. In turn, the (radio) access network 20 comprises a (radio) access network node in terms of three IAB nodes 100, 200, 300. In this regard, the IAB node 100 is the only node among the IAB nodes 100, 200, 300 that has a wired connection 60 (e.g., an optical fiber connection) to the core network 30. The IAB nodes 200, 300 are configured to communicate with the core network 30 via wireless backhaul links 70a, 70b to the IAB node 100. Therefore, the IAB node 100 provides a wireless backhaul for the IAB nodes 200, 300. The IAB node 100 will therefore be referred to as a donor IAB (D-IAB) node hereinafter, while the IAB nodes 200, 300 may be referred to as child IAB nodes. In Figure 1 In the illustrative example of , it is assumed that UEs 50a:50N are served by IAB node 200 via radio access link 80a, and at least a subset of these UEs 50a:50N are to be migrated to be served by IAB node 300 via radio access link 80b. IAB node 200 will therefore be referred to as a serving IAB (S-IAB) node hereinafter, and IAB node 300 will therefore be referred to as a replacement IAB (R-IAB) node hereinafter. D-IAB node 100 therefore provides backhaul connections to S-IAB node 200 and R-IAB node 300, and is an entry point from core network 30 to (radio) access network 20.

[0038] As defined in the document entitled "NG-RAN; Architecture description" (Release 16.1.0), a gNB is a logical node that can be split into one central unit (CU) and one or more distributed units (DUs). The CU hosts higher layer protocols to the UE 50a:50N and terminates the control plane interface and the user plane interface to the 5G core network (5GC). The CU controls the DU nodes through the F1 interface, where the DU nodes host the lower layer protocols for the NR Uu interface to the UE. The IAB-D node 100 hosts the CU and the DU, while each IAB child node only hosts the DU connected to the donor CU function. The IAB child node with the DU is responsible for providing radio access to the UE 50a:50N and hosts the physical (PHY), medium access control (MAC) and radio link control (RLC) protocol layers. The IAB-D node 100 with the CU is responsible for packet data convergence protocol (PDCP) signaling and radio resource control (RRC) signaling. The mobile terminal (MT) provides a physical interface for the wireless backhaul link between the IAB sub-nodes and the IAB-D node 100 . Figure 2 The interfaces through which the three IAB nodes 100, 200, 300 communicate with each other, with the core network 30, and with the UE 50a:50N are shown in detail. In this regard, the CU in the D-IAB node 100 is configured to communicate with the core network 30. The CU in the D-IAB node 100 is configured to communicate with the DU in each of the S-IAB node 200 and the R-IAB node 300 through the F1 interface. The DU in the D-IAB node 100 is configured to communicate with the MT in each of the S-IAB node 200 and the R-IAB node 300 through the NR Uu interface. The DU in each of the S-IAB node 200 and the R-IAB node 300 is configured to communicate with the UE 50a:50N via the NR Uu interface.

[0039] The embodiments disclosed herein therefore relate to a mechanism for migrating a UE 50a:50N from an S-IAB node 200 to an R-IAB node 300. To achieve such a mechanism, a D-IAB node 100, a method performed by the D-IAB node 100, and a computer program including code (the code is, for example, in the form of a computer program) are provided, which, when executed on a processing circuit of the D-IAB node 100, causes the D-IAB node 100 to perform the method. To achieve such a mechanism, an S-IAB node 200, a method performed by the S-IAB node 200, and a computer program including code (the code is, for example, in the form of a computer program) are also provided, which, when executed on a processing circuit of the S-IAB node 200, causes the S-IAB node 200 to perform the method. In order to obtain such a mechanism, an R-IAB node 300, a method performed by the R-IAB node 300, and a computer program including code (the code is, for example, in the form of a computer program) are also provided. When the code is run on the processing circuit of the R-IAB node 300, the R-IAB node 300 performs the method.

[0040] Reference now Figure 3 , which shows a method performed by the D-IAB node 100 for migrating UE 50a:50N from the S-IAB node 200 to the R-IAB node 300 according to an embodiment.

[0041] S102 : The D-IAB node 100 obtains a request for replacing the S-IAB node 200 .

[0042] S106 : The D-IAB node 100 provides the S-IAB node 200 with an instruction to replace the S-IAB node 200 .

[0043] S108 : The D-IAB node 100 obtains, from the S-IAB node 200 , scheduling information for the UEs 50 a : 50 N served by the S-IAB node 200 .

[0044] S110 : The D-IAB node 100 forwards the scheduling information to the R-IAB node 300 .

[0045] S120: The D-IAB node 100 initiates migration of at least the subset of UEs 50a:50N from the S-IAB node 200 to the R-IAB node 300 by providing instructions to at least the subset of UEs 50a:50N via the S-IAB node 200 to switch from being served by the S-IAB node 200 to being served by the R-IAB node 300.

[0046] Embodiments related to further details of migrating UE 50a : 50N from S-IAB node 200 to R-IAB node 300 performed by D-IAB node 100 will now be disclosed.

[0047] In some examples, the decision to replace the S-IAB node 200 is made by a network administrator, for example, based on a centralized monitoring data pool that collects and stores the status of all IAB nodes, or by a fleet administrator when the IAB node is a portable or mobile node. The decision to replace the S-IAB node 200 can be signaled to the D-IAB node 100 via OAM signaling or fleet management signaling. In other examples, for example, when the S-IAB node 200 has a power exhaustion warning, or when it detects a hardware / software failure that prevents its normal operation, the S-IAB node 200 itself requests replacement. The replacement request can be reported from the S-IAB node 200 to the D-IAB node 100 via the associated F1 interface as high-level signaling. Therefore, in some embodiments, the request to replace the S-IAB node 200 is obtained from the S-IAB node 200, or from an entity outside the D-IAB node 100, the S-IAB node 200, and the R-IAB node 300.

[0048] In some aspects, when the D-IAB node 100 has obtained the request in step S102, the R-IAB node 300 is activated. Specifically, according to an embodiment, the D-IAB node 100 is configured to perform (optional) step S104:

[0049] S104: The D-IAB node 100 provides the R-IAB node 300 with an instruction to activate the R-IAB node 300 after having obtained the request to replace the S-IAB node 200.

[0050] Further aspects of the scheduling information for the UEs 50a : 50N served by the S-IAB node 200 obtained by the D-IAB node 100 from the S-IAB node 200 in step S108 will now be disclosed.

[0051] In a first example, the scheduling information is sent by the S-IAB node 200 to a management system in or connected to the D-IAB node 100 through a logical operation and maintenance (OAM) channel. The D-IAB node 100 will then relay the information to the R-IAB node 300 through its logical OAM channel. The OAM may poll the S-IAB node 200 for any changes in the schedule to forward the information to the R-IAB node 300. In a second example, the S-IAB node 200 sends the scheduling information as a (non-UE associated) F1 application protocol message to the CU in the D-IAB node 100. The CU in the D-IAB node 100 then sends the received scheduling information as an F1 application protocol message to the R-IAB node 300. That is, in some embodiments, the scheduling information is obtained and forwarded through a logical operation and maintenance channel or in an F1 application protocol message.

[0052] In some aspects, downlink (DL) data is sent to the UE 50a:50N via both the S-IAB node 200 and the R-IAB node 300, and / or uplink (UL) data from the UE 50a:50N is received from both the S-IAB node 200 and the R-IAB node 300. Therefore, according to an embodiment, the D-IAB node 100 is configured to perform (optional) step S112 and / or (optional) step S114:

[0053] S112 : The D-IAB node 100 replicates the downlink data message destined for the UE 50 a : 50N to forward the downlink data message to both the S-IAB node 200 and the R-IAB node 300 , while the UE 50 a : 50N is still served by the S-IAB node 200 .

[0054] S114 : The D-IAB node 100 receives uplink messages originating from the UE 50 a : 50N from both the S-IAB node 200 and the R-IAB node 300 , while the UE 50 a : 50N is still served by the S-IAB node 200 .

[0055] Generally speaking, in contrast to the handover of a single UE 50a:50N from the S-IAB node 200 to the R-IAB node 300, the replacement of the S-IAB node 200 involves migrating all UEs 50a:50N from the S-IAB node 200 to the R-IAB node 300 before the S-IAB node 200 ceases to function or is removed. There may be different triggers for performing the actual migration of the UEs 50a:50N from the S-IAB node 200 to the R-IAB node 300. In some non-limiting examples, when a selected signal strength metric (e.g., any one of a received signal strength indicator (RSSI), a reference signal received power (RSRP), a reference signal received quality (RSRQ)) measured by each UE 50a:50N with respect to the R-IAB node 300 exceeds a predefined threshold, the decision to migrate the UE 50a:50N is triggered. The predefined threshold may be selected so that a minimum quality of service (QoS) for a particular service can be guaranteed. In some non-limiting examples, the decision to migrate the UE 50a:50N is triggered when the selected signal strength metric (e.g., any of RSSI, RSRP, RSRQ) measured by each UE 50a:50N with respect to the R-IAB node 300 is better than the same signal strength metric measured from the S-IAB node 200 by a predefined offset value. This triggering criterion can be used in conjunction with reducing the transmit power of the measurement signal sent from the S-IAB node 200. In some non-limiting examples, the decision to migrate the UE 50a:50N is triggered when a certain proportion of the measurement reports of the UE 50a:50N meet a threshold. In some non-limiting examples, the decision to migrate all UEs 50a:50N to the R-IAB node 300 is triggered based on the fraction of UL transmissions successfully decoded at the R-IAB node 300, referred to as the packet success ratio (PSR). Then, when the UL PSR at the R-IAB node 300 exceeds a certain predetermined threshold, or when the UL PSR at the R-IAB node 300 exceeds the UL PSR at the S-IAB node 200, the migration can be triggered. In some embodiments, before initiating the migration of at least the subset of UEs 50a:50N, the D-IAB node 100 verifies that the triggering condition for the migration of at least the subset of UEs 50a:50N is satisfied. In some embodiments, the triggering condition relates to the link quality between the UE 50a:50N and the R-IAB node 300, but not to the link quality between the UE 50a:50N and the S-IAB node 200.

[0056] As will be disclosed in more detail below, in some aspects, the S-IAB node 200 notifies the R-IAB node 300 of the uplink grant for the UE 50a:50N. Specifically, according to an embodiment, the D-IAB node 100 is configured to perform (optional) steps S116 and S118:

[0057] S104: The D-IAB node 100 obtains uplink authorization information from the S-IAB node 200. The UE 50a:50N served by the S-IAB node 200 sends a handover completion message to the R-IAB node 300 after completing the migration according to the uplink authorization.

[0058] S118: The D-IAB node 100 forwards the information of the uplink grant to the R-IAB node 300. When provided with the instruction from the D-IAB node 100 in step S120, the UEs 50a:50N are informed of the uplink grant.

[0059] The uplink grant information may be transmitted via the same manner as the scheduling information is transmitted from the S-IAB node 200 to the R-IAB node 300 (ie, through an OAM channel or using a dedicated F1AP message).

[0060] As disclosed above, the migration of at least a subset of UEs 50a:50N from the S-IAB node 200 to the R-IAB node 300 is initiated. There may be different ways to select which UEs 50a:50N to migrate. In some aspects, the subset of UEs 50a:50N is selected based on a service type (e.g., MC service). Specifically, in some embodiments, the subset of UEs 50a:50N is selected according to criteria related to a priority order given by the service type of the UEs 50a:50N. The migration of UEs 50a:50N with MC services may thus take precedence over the migration of UEs 50a:50N with non-MC services.

[0061] How UE 50a:50N switches from S-IAB node 200 to R-IAB node 300: Switching identifier

[0062] In some embodiments, the UE 50a:50N is instructed to switch from being served by the S-IAB node 200 to being served by the R-IAB node 300 by instructing the UE 50a:50N to use the identifier of the R-IAB node 300 everywhere the identifier of the S-IAB node 200 is used.

[0063] Reference now Figure 4 , which shows a method performed by the S-IAB node 200 for migrating UE 50a:50N from the S-IAB node 200 to the R-IAB node 300 according to an embodiment.

[0064] S204 : The S-IAB node 200 obtains an instruction to replace the S-IAB node 200 from the D-IAB node 100 of the S-IAB node 200 and the R-IAB node 300 .

[0065] S206 : The S-IAB node 200 provides the R-IAB node 300 and via the D-IAB node 100 with scheduling information for the UEs 50 a : 50 N served by the S-IAB node 200 .

[0066] S210 : The S-IAB node 200 initiates migration of at least the subset of UEs 50a : 50N from the S-IAB node 200 to the R-IAB node 300 by instructing at least the subset of UEs 50a : 50N to switch from being served by the S-IAB node 200 to being served by the R-IAB node 300 according to an instruction from the D-IAB node 100 .

[0067] Embodiments related to further details of migrating UE 50a : 50N from S-IAB node 200 to R-IAB node 300 performed by S-IAB node 200 will now be disclosed.

[0068] As disclosed above, in some examples, for example when the S-IAB node 200 has a power exhaustion warning, or when it detects a hardware / software failure that prevents its normal operation, the S-IAB node 200 itself requests replacement. Therefore, according to an embodiment, the S-IAB node 200 is configured to perform (optional) step S202:

[0069] S202 : The S-IAB node 200 provides a request for replacing the S-IAB node 200 to the D-IAB node 100 .

[0070] How scheduling information can be provided from S-IAB node 200 to R-IAB node 300 via D-IAB node 100 has been disclosed above and also applies here. In some embodiments, scheduling information is provided through a logical operation and maintenance channel or in an F1 application protocol message.

[0071] When performing non-coherent joint transmission of the same data, the precoders or beamforming weights at the S-IAB node 200 and the R-IAB node 300 should be selected so that the UE 50a:50N receives power from both the S-IAB node 200 and the R-IAB node 300 and so that the UE 50a:50N is unaware of the transmission from the R-IAB 300 and can still continue to send and receive data. Since the UE 50a:50N is unaware of the transmission from the R-IAB node 300 at this time, the UE 50a:50N cannot report the precoder to be used by the R-IAB node 300 for transmission thereto.

[0072] Therefore, in some examples, in order to simplify the process of selecting a precoder at both the S-IAB node 200 and the R-IAB node 300 when performing simultaneous transmission, the number or rank of transmission spatial layers for all UEs 50a:50N is fixed to 1, and a precoder that performs non-frequency selective wide beam transmission is selected for both the S-IAB node 200 and the R-IAB node 300. In addition, in some examples, in order to simplify the process of selecting a precoder at both the S-IAB node 200 and the R-IAB node 300 when performing simultaneous transmission, the number or rank of transmission spatial layers for all UEs 50a:50N is fixed to 1, and the S-IAB node 200 uses the precoder reported by the UE 50a:50N for rank 1, and the S-IAB node 200 instructs the R-IAB node 300 to perform non-frequency selective wide beam transmission. Therefore, in some embodiments, according to the scheduling information, the number of transmission spatial layers to be used for transmission to UE 50a:50N before UE 50a:50N has been migrated is fixed to 1. Therefore, in some embodiments, according to the scheduling information, R-IAB node 300 uses non-frequency selective wide beam transmission when communicating with UE 50a:50N until UE 50a:50N has been migrated. In some non-limiting examples, the scheduling information for each UE in UE 50a:50N specifies at least one of the following: time / frequency resources, modulation and coding scheme, transmission level, precoder to be used, reference signal configuration.

[0073] In some aspects, the S-IAB node 200 notifies the R-IAB node 300 of the uplink grant for the UE 50a:50N. Specifically, according to an embodiment, the S-IAB node 200 is configured to perform (optional) step S208:

[0074] S208: The S-IAB node 200 provides the uplink authorization information to the R-IAB node 300 and via the D-IAB node 100. The UE 50a:50N served by the S-IAB node 200 will send a handover completion message to the R-IAB node 300 after completing the migration according to the uplink authorization. The instruction from the D-IAB node 100 then includes the notification of the uplink authorization.

[0075] There may be different ways for the UE 50a:50N to switch from being served by the S-IAB node 200 to being served by the R-IAB node 300. In some embodiments, the UE 50a:50N is instructed to switch from being served by the S-IAB node 200 to being served by the R-IAB node 300 by instructing the UE 50a:50N to use the identifier of the R-IAB node 300 everywhere the identifier of the S-IAB node 200 is used.

[0076] Reference now Figure 5 , which shows a method performed by the R-IAB node 300 for migrating UE 50a:50N from the S-IAB node 200 to the R-IAB node 300 according to an embodiment.

[0077] S308 : The R-IAB node 300 obtains S308 scheduling information for the UE 50 a : 50 N served by the S-IAB node 200 from the S-IAB node 200 and via the S-IAB node 200 and the D-IAB node 100 of the R-IAB node 300 .

[0078] S314: After the subset of UEs (50a: 50N) has migrated from being served by the S-IAB node (200) to being served by the R-IAB node (300), the R-IAB node 300 serves at least the subset of UEs (50a: 50N) according to the scheduling information.

[0079] Embodiments related to further details of migrating UE 50a : 50N from S-IAB node 200 to R-IAB node 300 performed by R-IAB node 300 will now be disclosed.

[0080] As disclosed above, in some aspects, when the D-IAB node 100 has obtained the request in step S102, the R-IAB node 300 is activated. Specifically, according to an embodiment, the R-IAB node 300 is configured to perform (optional) steps S302 and S304:

[0081] S302 : The R-IAB node 300 obtains an instruction to activate the R-IAB node 300 from the D-IAB node 100 .

[0082] S304 : The R-IAB node 300 establishes a backhaul connection to the D-IAB node 100 in response thereto (ie, in response to having obtained the instruction).

[0083] After having been activated, the R-IAB node 300 may start sending reference signals and optionally system information identical to the system information sent from the S-IAB node 200. That is, according to an embodiment, the R-IAB node 300 is configured to perform (optional) step S306:

[0084] S306: After having established the backhaul connection to the D-IAB node 100, the R-IAB node 300 starts sending reference signals (and optionally the same system information as sent from the S-IAB node 200) to the UEs 50a:50N.

[0085] Aspects of how scheduling information can be provided from the S-IAB node 200 to the R-IAB node 300 via the D-IAB node 100 have been disclosed above and are also applicable here. In some embodiments, the scheduling information is obtained through a logical operation and maintenance channel, or the scheduling information is obtained in an F1 application protocol message. As disclosed above, in some embodiments, according to the scheduling information, the number of transmission spatial layers to be used for transmission to the UE 50a:50N before the UE 50a:50N has been migrated is fixed to 1. As disclosed above, in some embodiments, according to the scheduling information, the R-IAB node 300 uses non-frequency selective wide beam transmission when communicating with the UE 50a:50N until the UE 50a:50N has been migrated. As disclosed above, in some non-limiting examples, the scheduling information for each UE in the UE 50a:50N specifies at least one of the following: time / frequency resources, modulation and coding scheme, transmission level, precoder to be used, reference signal configuration.

[0086] As disclosed above, in some aspects, DL data is sent to UE 50a:50N via both S-IAB node 200 and R-IAB node 300. Therefore, according to an embodiment, R-IAB node 300 is configured to perform (optional) step S310:

[0087] S310 : The R-IAB node 300 transmits downlink data messages and uplink data messages to the UEs 50 a : 50N according to the scheduling information, while the UEs 50 a : 50N are still served by the S-IAB node 200 .

[0088] As disclosed above, in some aspects, UL data from UE 50a:50N is received by D-IAB node 100 from both S-IAB node 200 and R-IAB node 300. Therefore, according to an embodiment, R-IAB node 300 is configured to perform (optional) step S312:

[0089] S312: The R-IAB node 300 obtains uplink authorization information from the S-IAB node 200 via the D-IAB node 100. The UE 50a:50N served by the S-IAB node 200 will send a handover completion message to the R-IAB node 300 after completing the migration according to the uplink authorization.

[0090] Now refer to Figure 6 The signaling diagram of FIG. 1 discloses in detail a specific embodiment for migrating UE 50a: 50N from S-IAB node 200 to R-IAB node 300 based on at least some of the above disclosed embodiments.

[0091] S400: Data communication.

[0092] Downlink user data and uplink data are transmitted between the S-IAB node 200 and the UEs 50 a : 50 N served by the S-IAB 200 .

[0093] S401: Initiation of the S-IAB node 200 replacement process.

[0094] The D-IAB node 100 obtains a request that the S-IAB node 200 needs to be replaced. As disclosed above, in some examples, the request to replace the S-IAB node 200 is obtained from the S-IAB node 200, while in other examples, the request to replace the S-IAB node 200 is obtained from an external entity (i.e., an entity external to the D-IAB node 100, the S-IAB node 200, and the R-IAB node 300).

[0095] S402, S403: Activate the R-IAB node 300 and establish a connection.

[0096] The D-IAB 100 triggers the R-IAB node to be activated. The IAB integration procedure is performed for the R-IAB 300 to establish a backhaul connection between the R-IAB node 300 and the D-IAB node 100. After the backhaul is established, the R-IAB node 300 starts broadcasting of a reference signal.

[0097] S404, S405, S406, S407: measurement configuration and measurement report.

[0098] The D-IAB node 100 adds the information of the R-IAB node 300 to its neighbor list and includes the information in the RRC reconfiguration message. The message is delivered to all UEs 50a:50N served by the S-IAB node 200 via the S-IAB 200. These UEs 50a:50N can perform measurements on the access link to the R-IAB node 300 and report these measurements to the S-IAB node 200 accordingly.

[0099] The D-IAB node 100 signals an RRC reconfiguration message to the S-IAB node 200 through the F1 interface (step S404 ), and the S-IAB node 200 forwards the RRC reconfiguration message to all UEs (step S406 ).

[0100] The S-IAB node 200 also signals the UE-specific measurement report configuration to each served UE 50a:50N via dedicated RRC signaling.The content of the measurement report includes the time / frequency resources used by the report and the format used by the report.

[0101] After receiving the measurement configuration, the UE 50a:50N measures the link quality with respect to the R-IAB node 300 by measuring the reference signal transmitted by the R-IAB node 300. The UE 50a:50N transmits their measurement reports to the S-IAB node 200 (step S406). The S-IAB node 200 forwards the measurement reports to the D-IAB node 100 (step S407).

[0102] Steps S404 to S407 may be omitted when Automatic Neighbor Relation (ANR) is enabled, in which case the UE 50a:50N discovers new cells (as defined by the R-IAB 300) without being explicitly instructed or configured to do so, and reports measurements of signals from the R-IAB 300 to the serving cell (as defined by the S-IAB 200).

[0103] When the link quality reported by the UE 50a:50N with respect to the R-IAB node 300 meets a certain criterion, for example, when the link quality exceeds a threshold, the D-IAB node 100 triggers the following steps to perform joint transmission and reception.

[0104] S408, S409: UE context establishment.

[0105] The D-IAB 100 sends a UE context establishment request message to the R-IAB node 300 (step S408 ), and the R-IAB node 300 responds to the D-IAB 100 with a UE context establishment response message.

[0106] The UE context setup request message requests the R-IAB node 300 to prepare for the handover of the UE 50a:50N and provides information related to the UE 50a:50N to the R-IAB node 300. The information includes, among other things, necessary information required to maintain network services for the active UE 50a:50N, such as UE state information, UE identity, security information, and UE capability information. When the handover preparation is successful, the R-IAB node 300 responds with a UE context setup response.

[0107] In an example, the UE context establishment request and response process is repeated for all UEs 50a:50N served by the S-IAB node 200. In another example, context establishment requests for all UEs 50a:50N currently served by the S-IAB node 200 are sent to the R-IAB node 300 in a single request message, and the R-IAB node 300 responds with a single response message.

[0108] S410: Joint scheduling.

[0109] In order to perform coordinated transmission and reception, the S-IAB node 200 and the R-IAB node 300 use the same scheduling information. This can be achieved using the different options disclosed above.

[0110] The S-IAB node 200 continues to schedule the served UE 50a:50N, and the scheduling information is forwarded to the R-IAB node 300 via the D-IAB node 100. The scheduling decision is made taking into account the control signaling forwarding delay. For example, in order to account for the delay in forwarding to the R-IAB node 300, the S-IAB node 200 schedules its transmission several time slots in advance.

[0111] The scheduling information sent to the R-IAB node 300 contains information necessary for simultaneous transmission, including but not limited to time / frequency resources for each served UE 50a:50N, the modulation and coding scheme used, the transmission level used, the precoder to be used, the reference signal configuration, etc.

[0112] Examples of how scheduling information may be transmitted from the S-IAB node 200 to the R-IAB node 300 via the D-IAB node 100 have been disclosed above and are also applicable here.

[0113] S411: Coordinated / synchronous DL data transmission.

[0114] For DL ​​transmission, the PDCP packets for UE 50a:50N are duplicated at the D-IAB node 100 and sent to both the S-IAB node 200 and the R-IAB node 300. Using the scheduling information (from step S410) available at both the S-IAB node 200 and the R-IAB node 300, the same signal is sent to the UE 50a:50N from the S-IAB node 200 and the R-IAB node 300. Since the signals sent from the IAB child nodes (i.e., from the S-IAB node 200 and the R-IAB node 300) are the same, the cooperative transmission with different effective channels is transparent to the UE 50a:50N.

[0115] On the UE side, the DL reception timing used to receive the DL transmission from the S-IAB node 200 may also be used to receive the joint transmission from both the S-IAB node 200 and the R-IAB node 300 .

[0116] In order to perform simultaneous transmission without significant inter-symbol interference, the cell timing synchronization accuracy between the S-IAB node 200 and the R-IAB node 300 must be within an expected value, e.g. Existing over-the-air synchronization mechanisms (e.g., variants of the IEEE 1588 Precision Time Protocol) can be used to achieve this.

[0117] S412: Simultaneous UL data reception

[0118] For UL transmission, both the S-IAB node 200 and the R-IAB node 300 decode packets received from the UE 50a:50N independently of each other and forward the decoded packets to the D-IAB node 100. The D-IAB node 100 receives the packets from the S-IAB node 200 and the R-IAB node 300 and removes any duplicate packets received from both the S-IAB node 200 and the R-IAB node 300 before forwarding the packets to the core network.

[0119] In some aspects, the R-IAB node 300 and the S-IAB node 200 are in proximity to each other such that the propagation delay between the S-IAB node 200 and a given UE and the propagation delay between the R-IAB node 300 and the same given UE are similar. This means that the timing advance of the given UE relative to the R-IAB node 300 will be similar to the timing advance of the same given UE relative to the S-IAB node 200. Therefore, when the UE 50a:50N performs an UL transmission to the S-IAB node 200, the R-IAB node 300 can expect that the transmission is aligned in time with the UL transmissions of other UEs within a fraction of the cyclic prefix duration.

[0120] In some aspects, on the UE side, the timing advance (TA) for UL transmissions of the S-IAB node 200 that is already available at the UE 50a : 50N is also used as the TA for UL transmissions to both the S-IAB node 200 and the R-IAB node 300 .

[0121] S413 to S420 : UE 50 a : 50N migrates from the S-IAB node 200 to the R-IAB node 300 .

[0122] When any migration criteria as disclosed above are met, the D-IAB node 100 instructs the S-IAB node 200 to start the migration process (step S413 ).

[0123] The S-IAB node 200 determines a UL grant for the UE 50a:50N to perform an UL transmission carrying a Handover Complete (RRC Reconfiguration Complete) message to the R-IAB node 300 (step S414). The determined UL grant is sent to the R-IAB node 300 via the D-IAB node 100 using the mechanism detailed in step S410.

[0124] The D-IAB node 100 sends a UE handover instruction message to the UE 50a:50N via the S-IAB node 200, instructing the UE 50a:50N to handover to the R-IAB node 300 (step S415). The UE handover instruction message also includes a TA and UL grant to be used by the UE 50a:50N for transmission to the R-IAB node 300.

[0125] When the S-IAB node 200 receives the UE handover instruction message from the D-IAB node 100 , the S-IAB node 200 acknowledges the reception of the message to the D-IAB node 100 (step S416 ).

[0126] UE 50a:50N sends an RRC reconfiguration complete message to R-IAB node 300 confirming that UE 50a:50N has established a connection to R-IAB node 300 (step S417). R-IAB node 300 forwards the received message to D-IAB node 100 (step S418).

[0127] When the RRC reconfiguration complete messages from all UEs 50a:50N are received by the D-IAB node 100, the UE context from the S-IAB node 200 is released (steps S419 and S420) and the S-IAB node 200 may exit operation.

[0128] Figure 7 The components of the D-IAB node 100 according to the embodiment are schematically shown in the form of a plurality of functional units. Fig.13 The processing circuit 110 may be provided by any combination of one or more of a suitable central processing unit (CPU), a multiprocessor, a microcontroller, a digital signal processor (DSP), etc., which may be implemented in accordance with software instructions stored in a storage medium (e.g., in the form of a storage medium 130). The processing circuit 110 may also be provided as at least one application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0129] Specifically, the processing circuit 110 is configured to cause the D-IAB node 100 to perform an operation set or step set as disclosed above. For example, the storage medium 130 may store the operation set, and the processing circuit 110 may be configured to retrieve the operation set from the storage medium 130 so that the D-IAB node 100 performs the operation set. The operation set may be provided as an executable instruction set. Therefore, the processing circuit 110 is thereby arranged to perform the method disclosed herein.

[0130] The storage medium 130 may also include a persistent storage device, which may be, for example, any single memory or any combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory.

[0131] The D-IAB node 100 may also include a communication interface 120 for communicating with the S-IAB node 200, the R-IAB node 300, and the UEs 50a:50N. Thus, the communication interface 120 may include one or more transmitters and receivers including analog and digital components.

[0132] The processing circuit 110 controls the overall operation of the D-IAB node 100, for example, by sending data and control signals to the communication interface 120 and the storage medium 130, by receiving data and reports from the communication interface 120, and by retrieving data and instructions from the storage medium 130. Other components of the D-IAB node 100 and related functions are omitted so as not to obscure the concepts presented herein.

[0133] Figure 8 The components of the D-IAB node 100 according to the embodiment are schematically shown in the form of a plurality of functional modules. Figure 8 The D-IAB node 100 includes multiple functional modules: an obtaining module 110a configured to execute step S102, a providing module 110c configured to execute step S106, an obtaining module 110d configured to execute step S108, a forwarding module 110e configured to execute step S110, and an initiating module 110j configured to execute step S120. Figure 8 The D-IAB node 100 may further include a plurality of optional functional modules, such as any one of the following modules: a providing module 110b configured to execute step S104, a copying module 110f configured to execute step S112, a receiving module 110g configured to execute step S114, an obtaining module 110h configured to execute step S116, and a providing module 110i configured to execute step S118.

[0134] Typically, each functional module 110a to 310j may be implemented in hardware or in software. Preferably, one or more or all functional modules 110a to 110j may be implemented by a processing circuit 110 that may cooperate with a communication interface 120 and a storage medium 130. Therefore, the processing circuit 110 may be arranged to obtain instructions provided by the functional modules 110a to 110j from the storage medium 130 and execute these instructions, thereby performing any steps of the D-IAB node 100 as disclosed herein.

[0135] Fig. 9 The components of the S-IAB node 200 according to the embodiment are schematically shown in the form of a plurality of functional units. Fig.13 The processing circuit 210 may be provided by any combination of one or more of a suitable central processing unit (CPU), a multiprocessor, a microcontroller, a digital signal processor (DSP), etc., which may be implemented in accordance with software instructions stored in a storage medium (e.g., in the form of a storage medium 230). The processing circuit 210 may also be provided as at least one application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0136] Specifically, the processing circuit 210 is configured to cause the S-IAB node 200 to perform a set of operations or steps as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuit 210 may be configured to retrieve the set of operations from the storage medium 230 so that the S-IAB node 200 performs the set of operations. The set of operations may be provided as an executable instruction set. Therefore, the processing circuit 210 is thereby arranged to perform the method disclosed herein.

[0137] The storage medium 230 may also include a persistent storage device, which may be, for example, any single memory or any combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory.

[0138] The S-IAB node 200 may also include a communication interface 220 for communicating with the D-IAB node 100, the R-IAB node 300, and the UEs 50a:50N. Thus, the communication interface 220 may include one or more transmitters and receivers including analog and digital components.

[0139] The processing circuit 210 controls the overall operation of the S-IAB node 200, for example, by sending data and control signals to the communication interface 220 and the storage medium 230, by receiving data and reports from the communication interface 220, and by retrieving data and instructions from the storage medium 230. Other components of the S-IAB node 200 and related functions are omitted to avoid confusing the concepts presented herein.

[0140] Fig.10 The components of the S-IAB node 200 according to the embodiment are schematically shown in the form of a plurality of functional modules. Fig.10 The S-IAB node 200 includes multiple functional modules; an obtaining module 210b configured to execute step S204, a providing module 210c configured to execute step S206, and an initiating module 210e configured to execute step S210. Fig.10 The S-IAB node 200 may also include a plurality of optional functional modules, such as any one of a providing module 210a configured to perform step S202 and a providing module 210d configured to perform step S208. Generally, each functional module 210a-210e may be implemented in hardware or in software. Preferably, one or more or all functional modules 210a to 210e may be implemented by a processing circuit 210 that may cooperate with a communication interface 220 and a storage medium 230. Therefore, the processing circuit 210 may be arranged to obtain instructions provided by the functional modules 210a to 210e from the storage medium 230, and execute these instructions, thereby performing any steps of the S-IAB node 200 as disclosed herein.

[0141] Fig.11 The components of the R-IAB node 300 according to the embodiment are schematically shown in the form of a plurality of functional units. Fig.13 The processing circuit 310 may be provided by any combination of one or more of a suitable central processing unit (CPU), a multiprocessor, a microcontroller, a digital signal processor (DSP), etc., which may be implemented in accordance with software instructions stored in a storage medium (e.g., in the form of a storage medium 330). The processing circuit 310 may also be provided as at least one application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0142] Specifically, the processing circuit 310 is configured to cause the R-IAB node 300 to perform the operations or step set disclosed above. For example, the storage medium 330 can store the operation set, and the processing circuit 310 can be configured to retrieve the operation set from the storage medium 330 so that the R-IAB node 300 executes the operation set. The operation set can be provided as an executable instruction set. Therefore, the processing circuit 310 is thus arranged to perform the method disclosed herein.

[0143] The storage medium 330 may also include a persistent storage device, which may be, for example, any single memory or any combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory.

[0144] The R-IAB node 300 may also include a communication interface 320 for communicating with the S-IAB node 200, the D-IAB node 100, and the UEs 50a:50N. Thus, the communication interface 320 may include one or more transmitters and receivers including analog and digital components.

[0145] The processing circuit 310 controls the overall operation of the R-IAB node 300, for example, by sending data and control signals to the communication interface 320 and the storage medium 330, by receiving data and reports from the communication interface 320, and by retrieving data and instructions from the storage medium 330. Other components of the R-IAB node 300 and related functions are omitted to avoid confusing the concepts presented herein.

[0146] Fig.12 The components of the R-IAB node 300 according to the embodiment are schematically shown in the form of a plurality of functional modules. Fig.12 The R-IAB node 300 includes a plurality of functional modules; an obtaining module 310d configured to execute step S308 and a serving module 310g configured to execute step S314. Fig.12 The R-IAB node 300 may further include a plurality of optional functional modules, such as any one of the following modules: an obtaining module 310a configured to execute step S302, an establishing module 310b configured to execute step S304, a sending module configured to execute step S306, a communication module 310e configured to execute step S310, and an obtaining module 310f configured to execute step S312.

[0147] In general, each functional module 310a to 310g may be implemented in hardware or software. Preferably, one or more or all functional modules 310a to 310g may be implemented by a processing circuit 310 that may cooperate with a communication interface 320 and a storage medium 330. Therefore, the processing circuit 310 may be arranged to obtain instructions provided by the functional modules 310a to 310g from the storage medium 330, and execute these instructions, thereby performing any steps of the R-IAB node 300 as disclosed herein.

[0148] Fig.13An example of a computer program product 1310a, 1310b, 1310c including a computer readable device 1330 is shown. On the computer readable device 1330, a computer program 1320a may be stored, which may cause the processing circuit 110 and entities and devices operatively coupled to the processing circuit 110 (e.g., the communication interface 120 and the storage medium 130) to perform methods according to the embodiments described herein. Therefore, the computer program 1320a and / or the computer program product 1310a may provide means for performing any steps of the D-IAB node 100 disclosed herein. On the computer readable device 1330, a computer program 1320b may be stored, which may cause the processing circuit 210 and entities and devices operatively coupled to the processing circuit 210 (e.g., the communication interface 220 and the storage medium 230) to perform methods according to the embodiments described herein. Therefore, the computer program 1320b and / or the computer program product 1310b may provide means for executing any steps of the S-IAB node 200 disclosed herein. On the computer-readable device 1330, a computer program 1320c may be stored, which may enable the processing circuit 310 and entities and devices (e.g., the communication interface 320 and the storage medium 330) operatively coupled to the processing circuit 310 to perform methods according to the embodiments described herein. Therefore, the computer program 1320c and / or the computer program product 1310c may provide means for executing any steps of the R-IAB node 300 disclosed herein.

[0149] exist Fig.13 In the example of the computer program products 1310a, 1310b, 1310c are shown as an optical disc (e.g., a CD (Compact Disc) or a DVD (Digital Versatile Disc) or a Blu-ray Disc). The computer program products 1310a, 1310b, 1310c may also be embodied as a non-volatile storage medium in the form of a memory (e.g., a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more specifically as an external memory of the device (e.g., a USB (Universal Serial Bus) memory, or a flash memory (e.g., a high-density flash memory)). Thus, although the computer programs 1320a, 1320b, 1320c are schematically shown here as tracks on the described optical disc, the computer programs 1320a, 1320b, 1320c may be stored in any manner suitable for the computer program products 1310a, 1310b, 1310c.

[0150] The inventive concept has been mainly described above with reference to some embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than those disclosed above are also possible within the scope of the inventive concept as defined by the attached patent claims.

Claims

1. A method for migrating a UE (50a:50N) from a serving integrated access and backhaul S-IAB node (200) to a replacement integrated access and backhaul R-IAB node (300), the method being performed by a donor integrated access and backhaul D-IAB node (100) of the S-IAB node (200) and the R-IAB node (300), the method comprising: Obtaining (S102) a request to replace the S-IAB node (200); providing (S106) to the S-IAB node (200) an indication of replacing the S-IAB node (200); Obtaining (S108) from the S-IAB node (200) scheduling information for a UE (50a: 50N) served by the S-IAB node (200); Forwarding (S110) the scheduling information to the R-IAB node (300); as well as Migration of at least the subset of UEs (50a:50N) from the S-IAB node (200) to the R-IAB node (300) is initiated (S120) by providing, via the S-IAB node (200), instructions to at least the subset of UEs (50a:50N) to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300).

2. The method according to claim 1, wherein: The request to replace the S-IAB node (200) is obtained from the S-IAB node (200) or from an entity external to the D-IAB node (100), the S-IAB node (200) and the R-IAB node (300).

3. The method according to claim 1, further comprising: After a request to replace the S-IAB node (200) has been obtained, an instruction to activate the R-IAB node (300) is provided (S104) to the R-IAB node (300).

4. The method according to claim 1, wherein: The scheduling information is obtained and forwarded through a logical operation and maintenance channel or in an F1 application protocol message.

5. The method according to claim 1, further comprising: duplicating (S112) a downlink data message destined for the UE (50a:50N) to forward the downlink data message to both the S-IAB node (200) and the R-IAB node (300), while the UE (50a:50N) is still served by the S-IAB node (200); and / or An uplink message originating from the UE (50a:50N) is received (S114) from both the S-IAB node (200) and the R-IAB node (300) while the UE (50a:50N) is still served by the S-IAB node (200).

6. The method according to claim 1, wherein: Before initiating migration of at least the subset of the UEs (50a:50N), the D-IAB node (100) verifies that a triggering condition for migration of at least the subset of the UEs (50a:50N) is satisfied.

7. The method according to claim 6, wherein: The trigger condition is related to the link quality between the UE (50a:50N) and the R-IAB node (300), but not to the link quality between the UE (50a:50N) and the S-IAB node (200).

8. The method according to claim 1, further comprising: Obtaining (S116) uplink authorization information from the S-IAB node (200), the UE (50a:50N) served by the S-IAB node (200) sending a handover completion message to the R-IAB node (300) after completing the migration according to the uplink authorization; as well as The information of the uplink grant is forwarded (S118) to the R-IAB node (300), and wherein the UE (50a:50N) is informed of the uplink grant when provided with the instruction from the D-IAB node (100).

9. The method according to claim 1, wherein: The subset of the UEs (50a:50N) is selected according to a criterion related to a priority order given according to the service type of the UEs (50a:50N).

10. The method according to claim 1, wherein: By instructing the UE (50a:50N) to use the identifier of the R-IAB node (300) at all places where the identifier of the S-IAB node (200) is used, the UE (50a:50N) is instructed to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300).

11. A method for migrating a UE (50a:50N) from a serving integrated access and backhaul S-IAB node (200) to a replacement integrated access and backhaul R-IAB node (300), the method being performed by the S-IAB node (200), the method comprising: Obtaining (S204) an indication to replace the S-IAB node (200) from a donor integrated access and backhaul D-IAB node (100) of the S-IAB node (200) and the R-IAB node (300); Providing (S206) scheduling information for UEs (50a: 50N) served by the S-IAB node (200) to the R-IAB node (300) and via the D-IAB node (100); as well as Migration of at least the subset of UEs (50a:50N) from the S-IAB node (200) to the R-IAB node (300) is initiated (S210) by instructing at least the subset of UEs (50a:50N) to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300) according to an instruction from the D-IAB node (100).

12. The method according to claim 11, further comprising: A request to replace the S-IAB node (200) is provided (S202) to the D-IAB node (100).

13. The method according to claim 11, wherein: The scheduling information is provided through a logical operation and maintenance channel, or provided in an F1 application protocol message.

14. The method according to claim 11, wherein: According to the scheduling information, the number of transmit spatial layers to be used for transmission to the UE (50a:50N) before the UE (50a:50N) has been migrated is fixed to 1.

15. The method according to claim 11, wherein: According to the scheduling information, the R-IAB node (300) uses non-frequency selective wide beam transmission when communicating with the UE (50a:50N) until the UE (50a:50N) has been migrated.

16. The method according to claim 11, wherein: The scheduling information for each of the UEs (50a:50N) specifies at least one of the following: time / frequency resources, modulation and coding scheme, transmission rank, precoder to be used, reference signal configuration.

17. The method according to claim 11, further comprising: The R-IAB node (300) is provided with uplink authorization information (S208) via the D-IAB node (100), and the UE (50a:50N) served by the S-IAB node (200) will send a handover completion message to the R-IAB node (300) after completing the migration according to the uplink authorization; and wherein the instruction from the D-IAB node (100) includes a notification of the uplink authorization.

18. The method according to claim 11, wherein: By instructing the UE (50a:50N) to use the identifier of the R-IAB node (300) at all places where the identifier of the S-IAB node (200) is used, the UE (50a:50N) is instructed to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300).

19. A method for migrating a UE (50a:50N) from a serving integrated access and backhaul S-IAB node (200) to a replacement integrated access and backhaul R-IAB node (300), the method being performed by the R-IAB node (300), the method comprising: Obtaining (S308) scheduling information for a UE (50a: 50N) served by the S-IAB node (200) from the S-IAB node (200) and via a donor integrated access and backhaul D-IAB node (100) of the S-IAB node (200) and the R-IAB node (300); as well as After the subset of UEs (50a: 50N) has migrated from being served by the S-IAB node (200) to being served by the R-IAB node (300), serving (S314) at least the subset of UEs (50a: 50N) according to the scheduling information.

20. The method according to claim 19, further comprising: Obtaining (S302) an instruction to activate the R-IAB node (300) from the D-IAB node (100), and in response thereto: A backhaul connection to the D-IAB node (100) is established (S304).

21. The method according to claim 20, further comprising: After the backhaul connection to the D-IAB node (100) has been established, reference signals are started to be sent (S306) to the UE (50a: 50N).

22. The method according to claim 19, wherein: The scheduling information is obtained through a logical operation and maintenance channel, or obtained in an F1 application protocol message.

23. The method according to claim 19, wherein: According to the scheduling information, the number of transmit spatial layers to be used for transmission to the UE (50a:50N) before the UE (50a:50N) has been migrated is fixed to 1.

24. The method according to claim 19, wherein: According to the scheduling information, the R-IAB node (300) uses non-frequency selective wide beam transmission when communicating with the UE (50a:50N) until the UE (50a:50N) has been migrated.

25. The method of claim 19, wherein: The scheduling information for each of the UEs (50a:50N) specifies at least one of the following: time / frequency resources, modulation and coding scheme, transmission rank, precoder to be used, reference signal configuration.

26. The method of claim 19, further comprising: A downlink data message and an uplink data message are transmitted (S310) with the UE (50a: 50N) according to the scheduling information, while the UE (50a: 50N) is still served by the S-IAB node (200).

27. The method of claim 19, further comprising: The UE (50a:50N) served by the S-IAB node (200) obtains (S312) uplink authorization information from the S-IAB node (200) via the D-IAB node (100), and sends a handover completion message to the R-IAB node (300) after completing the migration according to the uplink authorization.

28. A donor integrated access and backhaul D-IAB node (100) for migrating a UE (50a:50N) from a serving integrated access and backhaul S-IAB node (200) to a replacement integrated access and backhaul R-IAB node (300), the D-IAB node (100) comprising a processing circuit (110), the processing circuit being configured to cause the D-IAB node (100) to: Obtaining a request to replace the S-IAB node (200); providing an indication to the S-IAB node (200) to replace the S-IAB node (200); Obtaining, from the S-IAB node (200), scheduling information for a UE (50a:50N) served by the S-IAB node (200); forwarding the scheduling information to the R-IAB node (300); and Migration of at least the subset of UEs (50a:50N) from the S-IAB node (200) to the R-IAB node (300) is initiated by providing, via the S-IAB node (200), instructions to at least the subset of UEs (50a:50N) to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300).

29. A serving integrated access and backhaul (S-IAB) node (200) for migrating a UE (50a:50N) from the S-IAB node (200) to a replacement integrated access and backhaul (R-IAB) node (300), the S-IAB node (200) comprising a processing circuit (210), the processing circuit being configured to cause the S-IAB node (200): Obtaining an indication of replacing the S-IAB node (200) from a donor integrated access and backhaul D-IAB node (100) of the S-IAB node (200) and the R-IAB node (300); providing scheduling information for UEs (50a: 50N) served by the S-IAB node (200) to the R-IAB node (300) and via the D-IAB node (100); and Migration of at least the subset of UEs (50a:50N) from the S-IAB node (200) to the R-IAB node (300) is initiated by instructing at least the subset of UEs (50a:50N) to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300) according to an instruction from the D-IAB node (100).

30. A replacement integrated access and backhaul R-IAB node (300) for migrating a UE (50a:50N) from a serving integrated access and backhaul S-IAB node (200) to the R-IAB node (300), the R-IAB node (300) comprising a processing circuit (310), the processing circuit being configured to enable the R-IAB node (300): Obtaining scheduling information for a UE (50a: 50N) served by the S-IAB node (200) from the S-IAB node (200) and via a donor integrated access and backhaul D-IAB node (100) of the S-IAB node (200) and the R-IAB node (300); and After the subset of UEs (50a: 50N) have migrated from being served by the S-IAB node (200) to being served by the R-IAB node (300), at least the subset of UEs (50a: 50N) are served according to the scheduling information.

31. A computer program product (1310a) comprising a computer program (1320a) for migrating a UE (50a:50N) from a serving integrated access and backhaul (S-IAB) node (200) to a replacement integrated access and backhaul (R-IAB) node (300), the computer program comprising computer code which, when executed on a processing circuit (110) of a donor integrated access and backhaul (D-IAB) node (100) of the S-IAB node (200) and the R-IAB node (300), causes the D-IAB node (100) to: Obtaining (S102) a request to replace the S-IAB node (200); providing (S106) to the S-IAB node (200) an indication of replacing the S-IAB node (200); Obtaining (S108) from the S-IAB node (200) scheduling information for a UE (50a: 50N) served by the S-IAB node (200); forwarding (S110) the scheduling information to the R-IAB node (300); and Migration of at least the subset of UEs (50a:50N) from the S-IAB node (200) to the R-IAB node (300) is initiated (S120) by providing, via the S-IAB node (200), instructions to at least the subset of UEs (50a:50N) to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300).

32. A computer program product (1310b) comprising a computer program (1320b) for migrating a UE (50a:50N) from a serving integrated access and backhaul (S-IAB) node (200) to a replacement integrated access and backhaul (R-IAB) node (300), the computer program comprising computer code which, when executed on a processing circuit (210) of the S-IAB node (200), causes the S-IAB node (200) to: Obtaining (S204) an indication to replace the S-IAB node (200) from a donor integrated access and backhaul D-IAB node (100) of the S-IAB node (200) and the R-IAB node (300); providing (S206) scheduling information for UEs (50a: 50N) served by the S-IAB node (200) to the R-IAB node (300) and via the D-IAB node (100); and Migration of at least the subset of UEs (50a:50N) from the S-IAB node (200) to the R-IAB node (300) is initiated (S210) by instructing at least the subset of UEs (50a:50N) to switch from being served by the S-IAB node (200) to being served by the R-IAB node (300) according to an instruction from the D-IAB node (100).

33. A computer program product (1310c) comprising a computer program (1320c) for migrating a UE (50a:50N) from a serving integrated access and backhaul (S-IAB) node (200) to a replacement integrated access and backhaul (R-IAB) node (300), the computer program comprising computer code which, when executed on a processing circuit (310) of the R-IAB node (300), causes the R-IAB node (300) to: obtaining (S308) scheduling information for a UE (50a:50N) served by the S-IAB node (200) from the S-IAB node (200) and via a donor integrated access and backhaul D-IAB node (100) of the S-IAB node (200) and the R-IAB node (300); and After the subset of UEs (50a: 50N) has migrated from being served by the S-IAB node (200) to being served by the R-IAB node (300), serving (S314) at least the subset of UEs (50a: 50N) according to the scheduling information.

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