Enhancements to beam management

Abstract

Described herein is a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 protocol of a radio access network, comprising: at least one processor; and at least one memory storing instructions, which when executed by the at least one processor, cause the first network node to determine to initiate an Inter-Cell Beam Management (ICBM) procedure involving at least a source cell of a second network node and a target cell of a third network node; send a first request message to the third network node, the first request message including information indicating a beam of the target cell and information for configuring the third network node to refrain from transmitting a UE-specific reference signal (RS); and receive a first response message from the third network node.

Description

[Technical Field]

[0001] The present disclosure relates to beam management, and in particular to enhancements to inter-cell mobility activation mechanisms for resource reservation. [Background technology]

[0002] Any discussion of background art throughout this specification should in no way be taken as an admission that such art is widely known or forms part of the common general knowledge in the art.

[0003] Roughly speaking, starting from a typical cell topology of a wireless communication system, e.g., 5G, having, e.g., a gNB, the gNB may be implemented using, e.g., at least one DU (Distributed Unit) and a CU (Central Unit). Figure 1 shows, in a simplified manner, an exemplary illustration of a coverage map with 21 (micro)cells (designated as circles).

[0004] When a UE (User Equipment) moves, for example, in a direction as indicated by the arrow in FIG. 1, the UE may travel through several different cells, which may typically result in several handovers.

[0005] Because in some possible cases (e.g., depending on the route) a large number of ping-pong effects, i.e., handovers back and forth between two cells, and a large number of additional signaling, including radio resource control (RRC) signaling, may result, unnecessary handovers and corresponding interruptions and signaling overhead should be reduced or avoided. In addition, it has been observed that the typical topology and coverage of a cell may not be as clear as in FIG. 1 due to reasons such as shadowing, buildings, etc., and may sometimes exhibit coverage islands that encroach on the coverage of other cells. Such more realistic "real-world examples" may result in even more ping-pong effects, for example, due to the presence of cell coverage islands and whether the UE travels through or near these islands. This may be even more true when more and more (narrow) beams are used (e.g., in millimeter wave wireless connections).

[0006] Various technologies / techniques have been proposed that attempt to address at least some of the above challenges, however, some of these conventional techniques may result in increased signaling overhead, wasted resources, time delays, etc., depending on various circumstances. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need to propose a novel beam management mechanism to address some or all of the challenges exemplified above, in particular in an efficient, flexible yet robust manner. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, there is provided a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, the first network node comprising: at least one processor; at least one memory storing instructions; the instructions, when executed by the at least one processor, cause the first network node to receive at least determining to initiate an Inter-Cell Beam Management (ICBM) procedure involving a source cell of a second network node supporting at least one of a Distributed Unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the source cell serving a User Equipment (UE), and a target cell of a third network node supporting at least one of a DU function or a Layer 2 protocol of a radio access network; sending a first request message to a third network node, the first request message including information indicating a beam of the target cell and information for configuring the third network node to refrain from transmitting a UE-specific reference signal (RS); receiving a first response message from a third network node, the first response message including information indicating a beam configuration for the ICBM procedure and information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A first network node is provided that causes:

[0009] In some examples, the first network node: sending a second request message to the second network node, the second request message including information indicating the configuration of the beam and information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; receiving a second response message from the second network node, the second response message including information indicating an acknowledgment that the third network node is configured to refrain from transmitting the UE-specific RS; Further steps will be taken.

[0010] In some examples, the second request message further includes information indicating a request for transmission of a message indicating that the UE is expected to switch to the beam of the target cell; The second response message further includes information indicating an acknowledgment of the information indicating a request for transmission of a message indicating that the UE is expected to switch to the beam of the target cell.

[0011] In some examples, the first network node: receiving a first indication message from a second network node, the first indication message including information indicating that the UE is expected to switch to a beam of the target cell; sending a second indication message to the third network node to enable the third network to start transmitting the UE-specific RS; Further steps will be taken.

[0012] In some examples, the first network node: receiving a third indication message from a third network node, the third indication message including information indicating transmission of the UE-specific RS; sending a fourth indication message including information indicating transmission of the UE-specific RS by the third network node; and Further steps will be taken.

[0013] In some examples, the decision to initiate an ICBM procedure is based on at least one of a measurement report received from the UE or a system operation and maintenance configuration.

[0014] In some examples, the UE-specific RS includes a channel state information reference signal (CSI)-RS.

[0015] In some examples, each of the source cell and the target cell is configurable to operate in at least one bandwidth portion (BWP); The first network node determining that the target cell does not support at least one BWP currently associated with the UE; sending a third request message to a third network node, the third request message including information indicating a beam on a BWP of the target cell; receiving a third response message from the third network node, the third response message including information indicating a BWP configuration of the beam; Further steps will be taken.

[0016] In some examples, the first network node: determining whether the UE is capable of simultaneously supporting two or more BWPs; Based on a determination that the UE is capable of simultaneously supporting two or more BWPs, sending a fourth request message to the second network node, the fourth request message including information indicating a BWP configuration of the beam; Based on a determination that the UE is not capable of simultaneously supporting two or more BWPs, sending a fifth request message to the second network node, the fifth request message including information indicating the BWP configuration of the beam and information for configuring the second network node to indicate when switching to the beam of the target DU is expected; Further steps will be taken.

[0017] In some examples, the first network node: The method is further caused to receive a message from a second network node including information indicating that a switch to the beam of the target DU is expected.

[0018] In some examples, the first network node: The method is further configured to send a configuration message to the UE, the configuration message including information indicating the BWP configuration of the beam.

[0019] According to another aspect of the present disclosure, there is provided a second network node configured by a source cell serving a user equipment (UE), the second network node supporting at least one of a distributed unit (DU) function or a radio access network Layer 2 (L2) protocol, the second network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to: receiving a first request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of the radio access network, the first request message including information indicating a beam configuration of a target cell of the third network node supporting at least one of a DU function or a Layer 2 (L2) protocol of the radio access network and information indicating that the third network node is configured to refrain from transmitting a UE-specific reference signal (RS); transmitting a first response message to the first network node, the first response message including information indicating an acknowledgment of the information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A second network node is provided that causes the

[0020] In some examples, the second network node: determining that the UE is expected to switch to a beam of the target cell; sending a first indication message to a first network node, the first indication message including information indicating an expected switchover; Further steps will be taken.

[0021] In some examples, the second network node is further configured to receive a first measurement report from the UE, and the determination that the UE is expected to switch to the beam of the target cell is based on the first measurement report.

[0022] In some examples, the second network node is further caused to receive a second indication message from the first network node, the second indication message including information indicating transmission of the UE-specific RS by the third network node.

[0023] In some examples, the second network node: receiving a second measurement report from the UE; determining, based on the second measurement report, to switch the UE to a beam of the target cell; The method is further caused to transmit a message to the UE including information indicating a transmission configuration indication (TCI) state change corresponding to the target cell.

[0024] In some examples, each of the source cell and the target cell is configurable to operate in at least one bandwidth portion (BWP).

[0025] In some examples, the second network node is further configured to receive a second request message from the first network node, the second request message including information indicating a BWP configuration of a beam of the target cell.

[0026] In some examples, the second network node is further configured to receive a third request message from the first network node, the third request message including information indicating a BWP configuration of the beam of the target cell and information indicating a configuration of the second network node to indicate when a switch to the beam of the target DU is expected.

[0027] In some examples, the second network node: determining that a switch to the beam of the target DU is expected; sending a third instruction message to the first network node, the third instruction message including information indicating that the target DU is expected to switch to the beam; Further steps will be taken.

[0028] According to yet another aspect of the present disclosure, there is provided a third network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the third network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third network node to: receiving a first request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, the first request message including information indicating a beam of a target cell of the third network node and information for configuring the third network node to refrain from transmitting a UE-specific reference signal (RS); configuring the third network node to refrain from transmitting the UE-specific RS; sending a first response message to the first network node, the first response message including information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A third network node is provided that causes the

[0029] In some examples, the third network node: receiving a first indication message from a first network node, the first indication message including information indicating that a user equipment (UE) served by a source cell of a second network node supporting at least one of a DU function or a Layer 2 protocol of a radio access network is expected to switch to a beam of a target cell; Initiating transmission of a UE-specific RS; sending a second indication message to the first network node, the second indication message including information indicating an expected acknowledgment of the switch; Further steps will be taken.

[0030] In some examples, the UE-specific RS includes a channel state information (CSI)-related RS.

[0031] In some examples, the target cell is configurable to operate in at least one bandwidth portion (BWP).

[0032] In some examples, the third network node: receiving a second request message from the first network node, the second request message including information indicating a beam on a BWP of the target cell; sending a second response message to the first network node, the second response message including information indicating the BWP configuration of the beam; Further steps will be taken.

[0033] According to another aspect of the present disclosure, there is provided a user equipment (UE), comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to perform at least: receiving a configuration message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a layer 3 protocol of the radio access network, the configuration message including information indicating a beam of a target cell of a third network node supporting at least one of a distributed unit (DU) function or a layer 2 protocol of the radio access network and information indicating that the third network node is configured to refrain from transmitting a UE-specific reference signal (RS); Monitoring UE-specific RS; based on determining that the UE-specific RS is being broadcast, transmitting information indicating that the UE-specific RS is being broadcast to a second network node supporting at least one of a DU function or a Layer 2 protocol of the radio access network; A user equipment (UE) is provided that causes the

[0034] According to another aspect of the present disclosure, there is provided a system comprising: a second network node supporting at least one of a distributed unit (DU) function or a radio access network Layer 2 protocol as disclosed in the present disclosure; a user equipment (UE) served by a source cell of a second network node; A system is provided, comprising:

[0035] According to another aspect of the present disclosure, there is provided a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, the first network node comprising: at least one processor; at least one memory storing instructions; the instructions, when executed by the at least one processor, cause the first network node to receive at least determining to initiate an Inter-Cell Beam Management (ICBM) procedure involving a source cell of a second network node supporting at least one of a Distributed Unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the source cell serving a User Equipment (UE), and a target cell of a third network node supporting at least one of a DU function or a Layer 2 protocol of a radio access network; determining that the target cell does not support at least one BWP currently associated with the UE; sending a request message to a third network node, the request message including information indicating a beam on a BWP of the target cell; receiving a response message from the third network node, the response message including information indicating a BWP configuration of the beam; A first network node is provided that causes:

[0036] According to another aspect of the present disclosure, there is provided a second network node configured by a source cell serving a user equipment (UE), the second network node supporting at least one of a distributed unit (DU) function or a radio access network Layer 2 (L2) protocol, the second network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to: receiving a request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a layer 3 protocol of the radio access network, the request message including information indicating a beam width configuration of a target cell of a third network node supporting at least one of a DU function or a layer 2 protocol of the radio access network; or receiving a request message from a first network node, the request message including information indicating a BWP configuration of a beam of the target cell and information indicating a configuration of the second network for indicating to the first network node when a switch to the beam of the target cell is expected; A second network node is provided that causes the

[0037] According to yet another aspect of the present disclosure, there is provided a third network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the third network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third network node to: receiving a request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 protocol of a radio access network, the request message including information indicating a beam on a BWP of a target cell of a third network node; sending a response message to the first network node, the response message including information indicating the BWP configuration of the beam; A third network node is provided that causes the

[0038] In yet another aspect of the present disclosure, a method of a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, comprising: determining to initiate an Inter-Cell Beam Management (ICBM) procedure involving a source cell of a second network node supporting at least one of a Distributed Unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the source cell serving a User Equipment (UE), and a target cell of a third network node supporting at least one of a DU function or a Layer 2 protocol of a radio access network; sending a first request message to a third network node, the first request message including information indicating a beam of the target cell and information for configuring the third network node to refrain from transmitting a UE-specific reference signal (RS); receiving a first response message from a third network node, the first response message including information indicating a beam configuration for the ICBM procedure and information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A method is provided, comprising:

[0039] According to yet another aspect of the present disclosure, there is provided a method of a second network node configured by a source cell serving a user equipment (UE) that supports at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the second network node comprising: receiving a first request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of the radio access network, the first request message including information indicating a beam configuration of a target cell of the third network node supporting at least one of a DU function or a Layer 2 (L2) protocol of the radio access network and information indicating that the third network node is configured to refrain from transmitting a UE-specific reference signal (RS); transmitting a first response message to the first network node, the first response message including information indicating an acknowledgment of the information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A method is provided, comprising:

[0040] According to yet another aspect of the present disclosure, there is provided a method for a third network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the method comprising: receiving a first request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, the first request message including information indicating a beam of a target cell of the third network node and information for configuring the third network node to refrain from transmitting a UE-specific reference signal (RS); configuring the third network node to refrain from transmitting the UE-specific RS; sending a first response message to the first network node, the first response message including information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A method is provided, comprising:

[0041] In yet another aspect of the present disclosure, a method of a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, comprising: determining to initiate an Inter-Cell Beam Management (ICBM) procedure involving a source cell of a second network node supporting at least one of a Distributed Unit (DU) function or a Layer 2 protocol of a radio access network, the source cell serving a User Equipment (UE), and a target cell of a third network node supporting at least one of a DU function or a Layer 2 protocol of a radio access network; determining that the target cell does not support at least one BWP currently associated with the UE; sending a request message to a third network node, the request message including information indicating a beam on a BWP of the target cell; receiving a response message from the third network node, the response message including information indicating a BWP configuration of the beam; A method is provided, comprising:

[0042] According to yet another aspect of the present disclosure, there is provided a method of a second network node configured by a source cell serving a user equipment (UE) that supports at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the second network node comprising: receiving a request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a layer 3 protocol of the radio access network, the request message including information indicating a beam width configuration of a target cell of a third network node supporting at least one of a DU function or a layer 2 protocol of the radio access network; or receiving a request message from a first network node, the request message including information indicating a BWP configuration of a beam of the target cell and information indicating a configuration of the second network for indicating to the first network node when a switch to the beam of the target cell is expected; A method is provided, comprising:

[0043] According to yet another aspect of the present disclosure, there is provided a method for a third network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the method comprising: receiving a request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 protocol of a radio access network, the request message including information indicating a beam on a BWP of a target cell of a third network node; sending a response message to the first network node, the response message including information indicating the BWP configuration of the beam; A method is provided, comprising:

[0044] According to some exemplary embodiments, a computer program product is also provided that includes instructions for causing an apparatus to perform the methods as disclosed in the present disclosure.

[0045] According to some exemplary embodiments, a memory storing computer readable instructions for causing the apparatus to perform the methods as disclosed in this disclosure is also provided.

[0046] Further, according to some example embodiments, there is provided a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, comprising respective suitable means configured to perform respective steps as disclosed in the present disclosure.

[0047] Similarly, according to some example embodiments, there is also provided a second network node and a third network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, comprising respective suitable means configured to perform the respective steps as disclosed in the present disclosure.

[0048] Additionally, according to some other exemplary embodiments, a computer program product for, for example, a wireless communication device having at least one processor is provided, the computer program product including software code portions for performing each of the steps disclosed in the present disclosure when the product is run on the device. The computer program product may include a computer-readable medium on which the software code portions are stored. Furthermore, the computer program product may be directly loadable into the internal memory of a computer and / or transmittable over a network by using at least one of an upload procedure, a download procedure, and a push procedure.

[0049] Although some exemplary embodiments are described herein with particular reference to the above applications, it will be appreciated that the present disclosure is not limited to such fields of use but is applicable in a broader context.

[0050] In particular, it is understood that the methods according to the present disclosure relate to methods of operating the apparatus according to the above exemplary embodiments and various modifications thereof, and that each statement made with respect to the apparatus applies equally to the corresponding method, and vice versa, so that similar statements may be omitted for brevity. In addition, the above aspects may be combined in many ways, even if not explicitly disclosed. As will be understood by those skilled in the art, these combinations of aspects and features / steps are possible unless they create a contradiction that is expressly excluded.

[0051] Implementations of the disclosed apparatus may include, but are not limited to, using one or more processors, one or more application specific integrated circuits (ASICs), and / or one or more field programmable gate arrays (FPGAs). Implementations of the apparatus may also include using other conventional and / or customized hardware, such as software programmable processors, such as graphics processing unit (GPU) processors.

[0052] Other and further exemplary embodiments of the present disclosure will become apparent during the course of the following discussion and by reference to the accompanying drawings.

[0053] Example embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0054] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a cell coverage map illustration. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of a signaling / messaging flow chart according to an exemplary embodiment of the present disclosure. [Figure 3A] FIG. 10 is a schematic diagram illustrating an example of a signaling / messaging flow chart according to another exemplary embodiment of the present disclosure. [Figure 3B] FIG. 10 is a schematic diagram illustrating an example of a signaling / messaging flow chart according to another exemplary embodiment of the present disclosure. [Figure 4A] FIG. 10 is a schematic diagram illustrating an example of a signaling / messaging flow chart according to another exemplary embodiment of the present disclosure. [Figure 4B] FIG. 10 is a schematic diagram illustrating an example of a signaling / messaging flow chart according to another exemplary embodiment of the present disclosure. [Figure 5] FIG. 10 is a schematic diagram illustrating an example of a signaling / messaging flow chart according to yet another exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0055] In the following, several different exemplary embodiments will be described using a communication network architecture based on 3GPP® standards for communication networks such as 5G / NR as an example of a communication network to which the example embodiments may be applied, but the embodiments are not limited to such an architecture. It will be apparent to those skilled in the art that the embodiments may also be applied to other types of communication networks in which mobile communication principles are integrated with D2D (device-to-device) or V2X (vehicle-to-everything) configurations, such as systems using SL (sidelink), e.g., Wi-Fi, Worldwide Interoperable Microwave Access (WiMAX), Bluetooth®, Personal Communications Services (PCS), ZigBee®, Wideband Code Division Multiple Access (WCDMA), Ultra-Wideband (UWB) technologies, Mobile Ad Hoc Networks (MANETs), wired access, etc. Furthermore, without loss of generality, the description of some example embodiments relates to a mobile communication network, but the principles of the present disclosure can be extended and applied to any other type of communication network, such as a wired communication network.

[0056] The following examples and embodiments should be understood as illustrative examples only. Although the specification may refer to "an," "one," or "some" examples or embodiments in some places, this does not necessarily mean that each such reference relates to the same example or embodiment, or that the feature applies only to a single example or embodiment. Single features of different embodiments may be combined to provide other embodiments. Furthermore, the words "comprising" and "including" should be understood as not limiting the described embodiments to consisting only of the recited features; such examples and embodiments may also include features, structures, units, modules, etc. that are not specifically recited.

[0057] A basic system architecture of a (tele)communication network, including a mobile communication system, to which some example embodiments are applicable, may include the architecture of one or more communication networks, including a wireless access network subsystem and a core network. Such architecture may include one or more communication network control elements or functions, access network elements, radio access network elements, access service network gateways or base transceiver stations, such as a base station (BS), an access point (AP), a NodeB (NB), an eNB or a gNB, a distributed unit (DU) or a centralized / central unit (CU), which control respective coverage areas or cells, thereby enabling one or more communication stations, such as a communication element or function, such as a user device or terminal device, such as a user equipment (UE), or another device having similar functionality, such as a modem chipset, chip, module, etc., which may be part of a station, element, function or application capable of communicating, such as a UE, element or function usable in a machine-to-machine communication architecture, or which may be attached as a separate element to such an element, function or application capable of communicating, to communicate over one or more channels via one or more communication beams for transmitting several types of data in multiple access domains. Additionally, core network elements or network functions may be included, such as gateway network elements / functions, mobility management entities, mobile switching centers, servers, databases, etc.

[0058] The following description may provide various details of alternatives, modifications and variations, where the gNB, for example, provides NR user plane and control plane protocol termination towards the UE and includes a node connected to the 5GC via an NG interface, for example in accordance with 3GPP TS 38.300 V16.6.0 (June 2021) Section 3.2, which is incorporated by reference.

[0059] The gNB Central Unit (gNB-CU) comprises a logical node that hosts, for example, the gNB's RRC, SDAP and PDCP protocols or the en-gNB's RRC and PDCP protocols that control the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface that is connected to the gNB-DU.

[0060] The gNB distributed unit (gNB-DU) comprises a logical node that hosts, for example, the RLC, MAC, and PHY layers of a gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0061] The gNB-CU-Control Plane (gNB-CU-CP) includes a logical node that hosts, for example, the control plane portion of the RRC and PDCP protocols of the en-gNB or gNB-CU of the gNB. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU.

[0062] The gNB-CU-User Plane (gNB-CU-UP) includes, for example, a logical node that hosts the user plane portion of the PDCP protocol of the gNB-CU of an en-gNB, as well as the user plane portions of the PDCP protocol and SDAP protocol of the gNB-CU of a gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, in accordance with Section 3.1 of 3GPP TS 38.401 V16.6.0 (July 2021), which is incorporated by reference.

[0063] For example, several different divisions of functionality between the central unit and the distributed units are possible, referred to as options: Option 1 (1A-like division): o The functional division in this option is similar to the 1A architecture in DC: RRC is in the central unit; PDCP, RLC, MAC, physical layer and RF are in distributed units. Option 2 (3C-like division): o The functional division in this option is similar to the 3C architecture in DC: RRC and PDCP are in the central unit; RLC, MAC, physical layer and RF are in the distributed units. Option 3 (Intra-RLC Splitting): o Low RLC (partial functions of RLC), MAC, physical layer and RF are in the distributed units. PDCP and high RLC (other partial functions of RLC) are in the central unit. Option 4 (RLC-MAC Split): o MAC, physical layer and RF are in the distributed units. PDCP and RLC are in the central unit. Or otherwise, for example, according to 3GPP TR 38.801 V14.0.0 (March 2017) Section 11, which is incorporated by reference.

[0064] A gNB supports multiple different protocol layers, such as Layer 1 (L1) - the physical layer.

[0065] Layer 2 (L2) of NR is divided into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP), where, for example, o The physical layer provides transport channels to the MAC sublayer. o The MAC sublayer provides logical channels to the RLC sublayer. o The RLC sublayer provides the RLC channel to the PDCP sublayer. o The PDCP sublayer provides the radio bearer to the SDAP sublayer. ○ The SDAP sublayer provides QoS flows to the 5GC. o Comp. refers to header compression and Segm. refers to segmentation. Control channels include (BCCH, PCCH).

[0066] Layer 3 (L3) includes, for example, Radio Resource Control (RRC) according to 3GPP TS 38.300 V16.6.0 (June 2021) Section 6, which is incorporated by reference.

[0067] For example, a RAN (Radio Access Network) node or network node or portion thereof, such as a gNB, base station, gNB CU or gNB DU, may be implemented using an apparatus having at least one processor and / or at least one memory (with computer readable instructions (computer program)) configured to support and / or provide and / or process, for example, CU and / or DU related functions and / or features, and / or at least one protocol (sub)layer of the RAN (Radio Access Network), for example, Layer 2 and / or Layer 3.

[0068] The gNB CU and gNB DU portions may be co-located, for example, or physically separated. The gNB DU may further be divided, for example, into two portions, e.g., one portion including processing equipment and one portion including antennas. The central unit (CU) may also be referred to as a BBU / REC / RCC / C-RAN / V-RAN, O-RAN, or portions thereof. The distributed unit (DU) may also be referred to as an RRH / RRU / RE / RU, or portions thereof. Hereinafter, in various exemplary embodiments of the present disclosure, the CU-CP (or more generally, the CU) may also be referred to as a (first) network node supporting central unit control plane functions or at least one of Layer 3 protocols of the radio access network, and similarly, the DU may also be referred to as a (second) network node supporting distributed unit functions or Layer 2 protocols of the radio access network.

[0069] The gNB-DU supports one or more cells and may therefore, for example, serve as a serving cell for a user equipment (UE).

[0070] User equipment (UE) may include wireless or mobile devices, devices having a radio interface for interacting with a RAN (Radio Access Network), smartphones, in-vehicle devices, IoT devices, M2M devices, etc. Such UEs or devices may include at least one processor and at least one memory containing computer program code configured by the at least one processor to cause the device to perform at least certain operations, such as, for example, an RRC connection to the RAN. The UE is configured, for example, to generate messages (e.g., including a cell ID) to be transmitted over the air toward the RAN (e.g., to reach and communicate with a serving cell). The UE can generate, send, and receive RRC messages containing one or more RRC PDUs (Packet Data Units).

[0071] The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0 (June 2021) Sections 42.1 and 4.4, which are incorporated by reference).

[0072] A UE may, for example, be in either an RRC_CONNECTED state or an RRC_INACTIVE state when an RRC connection is established.

[0073] In the RRC_CONNECTED state, the UE: ○ Stores the AS context. ○ Transferring unicast data to and from the UE. o Monitor the control channel associated with the shared data channel to determine if data is scheduled for that data channel. o Provides channel quality and feedback information. ○ Perform neighbor cell measurements and measurement reporting.

[0074] The RRC protocol includes, for example, the following main functions: ○ RRC connection control Measurement configuration and reporting Establishing / modifying / releasing measurement configurations (e.g. intra-frequency, inter-frequency and inter-RAT measurements) ○ Measuring gap setup and release ○ Measurement report

[0075] The general functionality and interconnections of the described elements and functions, which also depend on the actual network type, are known to those skilled in the art and are described in the corresponding specifications, and as a result, detailed descriptions thereof may be omitted herein for the sake of brevity. However, several additional network elements and signaling links may be utilized for communication between elements, functions or applications, such as communication endpoints, servers, gateways, communication network control elements such as radio network controllers, and other elements of the same or other communication networks, in addition to those described in detail below.

[0076] The communications network architecture system as considered in the example embodiment may also be capable of communicating with other networks, such as the public switched telephone network or the Internet. It should be noted that the communications network may also be capable of supporting the use of cloud services for virtual network elements or their functions, and that virtual network portions of a telecommunications network may also be provided by non-cloud resources, such as, for example, an internal network. Network elements, such as access systems, core networks, and / or their functions may be implemented by any nodes, hosts, servers, access nodes, or entities, etc., suitable for such use. In general, network functions may be implemented either as network elements on dedicated hardware, software instances running on dedicated hardware, or virtualized functions instantiated on a suitable platform, such as, for example, a cloud infrastructure.

[0077] Furthermore, as described herein, network elements such as communication elements like UEs, terminal devices, control elements or functions such as access network elements like base stations / BSs, gNBs, radio network controllers, core network control elements or functions such as gateway elements, or other network elements or functions, and any other elements, functions or applications, etc. may be implemented by software, e.g., by a computer program product and / or hardware of a computer. For performing their respective processing, the correspondingly used devices, nodes, functions or network elements may include several means, modules, units, components, etc. (not shown) required for control, processing and / or communication / signaling functions. Such means, modules, units and components may include, for example, one or more processors or processor units including one or more processing portions for executing instructions and / or programs and / or processing data, storage or memory units or means (e.g., ROM, RAM, EEPROM, etc.) for storing instructions, programs and / or data to serve as working areas for the processors or processing portions, etc., input or interface means (e.g., floppy disk, CD-ROM, EEPROM, etc.) for inputting data and instructions by means of software, user interfaces (e.g., screen, keyboard, etc.) for providing monitoring and operation capabilities to a user, other interfaces or means for establishing links and / or connections under the control of the processor units or portions (e.g., wired and wireless interface means, e.g., radio interface means including antenna units, etc., means for forming wireless communication portions, etc.), and each means for forming an interface for a wireless communication portion, etc. may also be located at a remote site (e.g., radio head or radio station, etc.).It should be noted that, in this specification, a processing portion should not be considered solely as representing a physical portion of one or more processors, but may also be considered as a logical division of the referenced processing task performed by one or more processors. It should be appreciated that, according to some examples, a so-called "liquid" or flexible network concept may be utilized in which the operations and functions of a network element, network function, or another entity of the network may be flexibly implemented in different entities or functions, such as within a node, host, or server. In other words, the "division of labor" between the involved network elements, functions, or entities may vary from case to case.

[0078] As indicated above, to address issues of signaling overhead, interruptions, and / or delays (e.g., caused by unnecessary back-and-forth handovers), it is known to utilize so-called "borrowed" beams of a (target) cell different from the source / serving cell. The (target) cell may be of (served by) the same serving DU of the source / serving cell or a different DU other than the serving DU; therefore, this may be referred to as an intra-DU or inter-DU ICBM, respectively, in some cases. In some possible cases, a UE may be connected to a serving DU and, while traveling through the cell, may receive good measurements from another cell (e.g., of another DU), which may be a coverage island inside the serving cell or an area overlapping with the serving cell (e.g., at the edge of the serving cell). The connection with the serving cell may, for example, still be good, but the connection to the other cell is / becomes better. In that case, the UE can be served by a borrowed beam of a non-serving DU ("borrowed" in the sense that the UE can be accused of communicating using a beam from another cell without changing the serving cell) without performing a full (traditional) handover to another cell, and therefore no additional RRC signaling overhead and interruption time is observed compared to a (traditional) handover procedure.

[0079] However, broadly speaking, there are two potential challenges associated with such ICBM operations.

[0080] First, in some possible scenarios, a neighboring cell may configure a beam for the UE that is not broadcast but via dedicated signaling (e.g., a finer CSI-RS beam associated with a parent synchronization signal block (SSB) beam, where this association can be dictated by the network). In other words, the beam may be configured not to be scheduled for RS transmission. Therefore, transmitting a UE-specific beam (DL reference signal) before the UE switches to that beam wastes network resources for non-serving DUs and causes unnecessary energy waste (the UE is not using that beam until the DU switches to it) and needs to be avoided.

[0081] Second, in some possible scenarios, the target DU may not support any of the bandwidth portions (BWPs) configurable by the source DU (which may be the basic scenario for inter-frequency lower layer mobility (LLM) scenarios). As a result, ICBM operations cannot be supported in scenarios where the target DU configures a BWP that the CU cannot configure for the UE.

[0082] In view of this, the present disclosure generally proposes apparatuses (such as a DU, a CU, etc.) and corresponding methods for addressing some or all of the above-mentioned problems / observations in a particularly efficient and flexible manner. In particular, it can be seen that in a broad sense, the present disclosure generally seeks to propose a solution for extending the LLM concepts, i.e., ICBM, dynamic switching, and L1-based serving cell change, to inter-DU scenarios where the BWP of the source cell cannot be allocated (as assumed in intra-DU ICBM) or broadcasting neighbor cell resources is unnecessary. In particular, as will become clear in light of the detailed description below, the present disclosure generally attempts to particularly specify information that needs to be exchanged between RAN nodes (such as a serving DU, a CU-CP, and a target DU) to enable initiating and preparing an inter-DU procedure.

[0083] Reference is now made to the drawings. In particular, the same or similar reference numerals used in the drawings of the present disclosure may, unless otherwise indicated, denote the same or similar elements, and as a result, repeated descriptions thereof may be omitted for the sake of brevity. As can be understood and appreciated by those skilled in the art, it is further noted that although the drawings may appear to reference some specific / explicit message names / types, these messages may have different names and / or may be communicated / exchanged in different forms / formats, among other things, depending on various implementations (e.g., underlying technologies).

[0084] In particular, Figure 2 schematically illustrates an example of a signaling / messaging flowchart for an exemplary intra-DU ICBM procedure according to an exemplary embodiment of the present disclosure. As noted above, in an intra-DU ICBM scenario, both the source cell and the target cell (referred to as Cell 1 and Cell 2, respectively, in Figure 2) are under the control of the same serving (source) DU. In the exemplary embodiment of Figure 2, it is also generally assumed that prior to initiating the method, the UE is connected to Cell 1 (i.e., source / serving) and does not have an active inter-cell beam management configuration enabled.

[0085] Here, in step S201, the CU configures the UE with L1 measurements of beam A of neighbor cell 2 (i.e., the target set), for example, through an RRC reconfiguration message (or by using any other appropriate message). Note that while a single beam A is used as a reference in the exemplary embodiment of FIG. 2, those skilled in the art will understand and appreciate that in some other possible implementations, two or more beams may be configured for measurements. In addition, as can also be understood and appreciated by those skilled in the art, if the target DU can operate in another bandwidth portion (BWP) other than the current BWP of the UE (communicating with the serving DU), the CU may also configure the UE with an appropriate measurement gap. The UE can respond to such configuration, for example, by transmitting a corresponding RRCReconfigurationComp (RRC Reconfiguration Complete) message (or the like), as exemplarily shown in step S202.

[0086] Then, in step S203, the UE reports the L1 measurements (eg, reference signal received power (RSRP)) of beam A of cell 2 to the DU.

[0087] The DU may observe the quality of beam A of cell 2 and determine in step S204 that the UE may benefit from radio robustness to initiate an ICBM procedure, and accordingly includes the above beam A of cell 2 for the UE's beam management operations.

[0088] In step S205, the DU can indicate beam A of cell 2 to be included in the UE's beam management operation, e.g., by sending a UE Context Modification Request message (or the like) to the CU. In response, the CU can configure the UE with the beam management information provided by the DU, e.g., by sending another RRCReconfiguration message (or the like) as illustrated in step S206. Upon receiving a corresponding RRCReconfigurationComp message (or the like) from the UE (step S207), the CU can then indicate or acknowledge successful completion of the UE configuration to the DU in step S208, e.g., by sending a corresponding UE Context Modification Confirm / Complete message (or the like).

[0089] The DU may then, in step S209, send a TCI state change message (e.g., as part of a MAC Control Element (CE) or in any other suitable format) to activate Beam A of Cell 2 for the UE, and upon receiving such TCI state information, the UE may switch its operation to Beam A of the cell (as instructed by the TCI state change message), as shown in step S210.

[0090] In particular, as mentioned above, the inter-cell beam management procedure is not intended solely to provide mobility-related functions (e.g., switching, handover, etc.) to different cells, but rather should be understood as being used to provide enhanced radio coverage to the UE as a temporary solution to avoid subsequent (sometimes unnecessary back-and-forth) handovers.

[0091] However, in some cases, the general framework of intra-DU ICBM as presented above may be considered less useful with respect to cell coverage islands, for example, because it has been observed that cell coverage islands can typically be caused by a lack of coverage of other DUs than the serving DU.

[0092] With that in mind, in a broad sense, the present disclosure generally seeks to propose a technique that enables a CU to trigger (inter-DU) ICBMs by cells under the control of a target DU different from the source DU. This allows ICBM operations to be established for inter-DU cells, thereby extending the coverage of ICBM operations to a wider range of use cases. In this way, a UE can dynamically switch back and forth between data connections from different DUs while maintaining a control connection with the serving cell, which is generally faster than a typical inter-DU handover and is also believed to reduce signaling overhead, especially in ping-pong cases. In some possible cases, control signaling generally requires a much lower data rate compared to data transmission, allowing the control connection to be maintained even when the connection to the serving cell is not very good. Furthermore, a UE capable of simultaneously transmitting and receiving two or more BWPs is enabled to use ICBM even if the source and target DUs do not have a common BWP available. This reduces wasted resources (e.g., prepared but not used or not used immediately (e.g., used later)) when, for example, a CSI-RS is prepared by a target DU but a switch to the target DU does not ultimately occur.

[0093] 3 illustrates, in schematic form, an example of a signaling / messaging flowchart according to an exemplary embodiment of the present disclosure, and more particularly, how an (inter-DU) ICBM configuration may be set up at a target DU based on UE measurements, and how the ICBM configuration may be coordinated across source and target DUs. Note that in the exemplary embodiment as illustrated in FIG. 3, it is generally assumed that the source / serving cell (although not explicitly shown in the figure) resides at (or, in other words, is under the control of) the source / serving DU, while the (neighbor) target cell resides at (or, in other words, is under the control of) the target DU.

[0094] Similar to the exemplary embodiment shown in Figure 2, before the message flow begins, it is generally assumed, although not explicitly shown in the figure, that the UE has already established a connection to the serving / source cell of the serving / source DU. In addition, the CU may have already configured the UE to report measurements of beams of neighboring (target) cells controlled by the target DU. In response, the UE may also acknowledge the measurement configuration and begin transmitting measurement reports of beams of neighboring cells (e.g., to the CU via the source DU).

[0095] Here, as shown in FIG. 3 , in step S301, the CU (or more specifically, the CU-CP) can decide to initiate an ICBM procedure for the target DU's cell. This can result in the CU sending a UE context modification request (or any other suitable message, e.g., to request modification of a (previous / preceding) UE configuration) to the serving DU, as illustrated in step S307. In particular, the decision to initiate an ICBM procedure can be based on any suitable criteria. As a (non-limiting) example, such a decision can be based on received UE measurements of the target DU's beam. In another (non-limiting) example, such a decision can also be based on operation and maintenance configuration, in cases where the beam topology is already known to the operator, and thus the RAN nodes are aware of neighboring beams.

[0096] In step S302, the CU sends a UE context setup request (or any other suitable message, e.g., to request the setup or creation of a UE context / configuration) to the target DU and indicates that this is for an ICBM (e.g., by using a predetermined or predefined field / flag, such as "deferred-activation" as illustrated in step S302). Of course, as can be understood and appreciated by those skilled in the art, any other suitable means (e.g., various names, formats, etc.) may be used here to convey information indicating an ICBM.

[0097] Upon receiving such an instruction (e.g., an “activation postponement” instruction as shown in step S302), the target DU may determine in step S303 that the beam allocated to the UE is, for example, an “refined” beam and will not be broadcast (i.e., CSI-RS resources associated with a particular SSB may not be transmitted) to avoid wasting radio resources for transmission, e.g., because, typically, there are no other UEs in the cell using the refined beam (e.g., there may not be any other UEs within the coverage area of the SSB used as the source beam for CSI-RS transmission). In particular, the determination of such an “refined” beam (and, consequently, the decision not to broadcast or schedule UE-specific CSI-RS) may be determined based on various criteria, such as, for example, UE requirements, the ability of the UE to receive the refined beam without extra overhead, UE measurement results indicating that radio resource-efficient transmission is possible, or any other appropriate criteria as can be understood and appreciated by those skilled in the art.

[0098] Thereafter, in step S304, the target DU indicates (e.g., by sending an appropriate message) that it is not broadcasting the beam allocated to the UE and that it needs an instruction to start (or activate) transmission. This instruction may be sent together with the UE context setup response and the beam configuration related to ICBM operation, as illustrated in step S304.

[0099] In steps S305-S306, the CU-CP may also interact with the CU-CP, for example, to perform appropriate bearer setup, as will be understood and appreciated by those skilled in the art.

[0100] Furthermore, the CU indicates the beam configuration obtained from the target DU to the serving DU in step S307. In particular, the CU may specifically indicate that the target DU needs instructions (e.g., such pre-determined or pre-configured) to transmit beams to the UE. In response, the serving DU may acknowledge such instructions in step S308 and provide the UE with a beam management configuration using the beam of cell 2 (the target cell).

[0101] In steps S309-S310, the CU may configure the UE with the corresponding required ICBM configuration (e.g., by sending an RRC reconfiguration message, etc.), and the UE may then acknowledge such configuration (e.g., by sending an RRC reconfiguration complete message, etc.), as can be understood and appreciated by those skilled in the art.

[0102] If, after some time, the assigned beam is still suitable for ICBM based on the UE measurements (step S311), then in step S312 the serving DU may decide to switch to the beam of the target cell (e.g., in response to receiving L1 measurements, which may include target SSB measurements from the UE as illustrated in step S311). For example, the serving DU may determine that a switch to beam A of cell 2 is imminent based on the L1 measurement results. In step S313, the serving DU indicates this to the CU, which further propagates such indication (in a different message) to the target DU.

[0103] Upon receiving the indication, the target DU may decide to start broadcasting a UE-specific beam (e.g., CSI-RS) in response to this indication in step S314. In addition, the target DU may also acknowledge this indication to the CU and further to the source DU in step S315, as illustrated, for example, by using the expression "Ready to switch" (or in any other suitable manner, such as an indication message). In some possible implementations, this indication may also be used by the CU to immediately (early) start data transfer (e.g., downlink data to the UE) towards the target DU.

[0104] The UE may then start receiving the CSI-RS beam being broadcast from (scheduled by) the target DU in step S316, and report the reception of the CSI-RS beam from the target DU to the source DU in step S317.

[0105] In response to the measurements, the source DU may decide to switch the UE to the beam of the target DU in step S318. In particular, such a decision may be based on several L1 measurements, for example, to ensure that the signal strength of beam A in the target cell is constant (or always better than the signal strength of the source beam).

[0106] As a result, the source DU triggers a TCI state switch for the UE (step S319), for example by sending an appropriate message, and instructs the CU-CP to switch (step S321). In response to such a TCI state change instruction, the UE can switch to a "borrowed" beam from the target cell in step S320. Additionally, similar to steps S305 and S306, the CU-CP can contact the CU-UP to complete the bearer context modification.

[0107] Finally, as shown in step S324, user plane data can be transmitted from the target DU and received by the UE.

[0108] To summarize the above, the exemplary embodiment as described above with reference to Figure 3 can be generally considered as proposing to configure a UE with ICBM operation in which the target DU refrains from broadcasting beams related to the ICBM operation. Whenever a beam of the target cell is to be used for ICBM operation, the source DU (through the CU) indicates the impending ICBM operation to the target DU. The target DU can then use this information to activate the broadcast of the relevant beam accordingly.

[0109] The phrase "the target DU refrains from broadcasting" shall mean that the target DU does not broadcast immediately, but is configured or prepared to broadcast and waits until it receives another signal that triggers the actual broadcast, i.e., the activation of the broadcast is postponed until the trigger is received. Thus, the target DU is configured for a conditional broadcast that requires a trigger in order to be activated. Examples of trigger conditions are a change notification or the reception of an activation message sent by the serving DU or the CU-CP. A conditional broadcast can be thought of as a delayed broadcast that is prepared but not sent until the condition is met. The same concept of activation postponement also applies to "refraining from transmitting a UE-specific reference signal".

[0110] In some possible implementations, a source cell (DU) and a target cell (DU) may be configured with one or more BWPs. In such a case, when preparing the target cell for ICBM operation, the CSI-RS resources of all BWPs may be configured in the target cell to a “deactivated” state. Thereafter, whenever a BWP switch is triggered in the source DU, the source DU can instruct the activation of all beams corresponding to a given BWP, for example, by providing only the BWP ID to the target DU (or by any other suitable means). In this case, multiple beams of a given BWP may be activated simultaneously via a single message from the source DU. Notably, this is also schematically reflected in the example of FIG. 3. More specifically, as shown in FIG. 3, when the target DU sends an indication that it is not broadcasting the beams allocated to the UE and that it needs an instruction to start transmission in step S304, the target DU may also send beam configurations related to ICBM operation for all associated BWPs (denoted as “BWP(X,Y,Z)” in step S304). This beam configuration of all BWPs X, Y, and Z is also propagated to the serving DU in step S307. Later, as shown in step S313, the source DU can decide to activate only BWP X (e.g., by indicating BWP ID X to the target DU, as shown above). In response to such an indication, the target DU can start broadcasting CSI-RS only on BWP X, as illustrated in step S316.

[0111] 4 schematically illustrates an example of a signaling / messaging flowchart according to an exemplary embodiment of the present disclosure. In particular, the same or similar reference symbols and / or messages (and the contents contained therein) used in FIG. 4 may refer to the same or similar elements and / or messages (and the respective contents therein) unless otherwise indicated, and as a result, repeated descriptions thereof may be omitted for the sake of brevity.

[0112] In particular, as can be seen from the figure, the exemplary embodiment as shown in Figure 4 is roughly the same as that of Figure 3, except that the procedures / steps related to the UE side are shown in more detail here. More specifically, as shown in Figure 4, as illustrated in step S409 (similar to step S309 in Figure 3), when sending a beam configuration to the UE, for example, in an RRC reconfiguration message (or the like), the CU can additionally also configure the UE (e.g., as part of the RRC reconfiguration message or in any other appropriate separate message) to monitor (e.g., periodically) a UE-specific RS (e.g., CSI-RS) even if the UE-specific RS is configured to refrain from broadcast by the target DU (e.g., in step S302 or S402 where the CU-CP sends a UE context setup request to the target DU indicating that it is for an ICBM with "activation deferral").

[0113] In response to such a configuration (related to monitoring), the UE may start (continuously) monitoring the beam of the target cell (e.g., periodically as configured) in step S411, determine that no UE-specific RS (e.g., CSI-RS) is broadcast on said beam, and report the corresponding measurement results to the serving DU in step S412.

[0114] Since the UE continuously and periodically monitors the beam of the target cell (however, this is not explicitly reflected in the figure, but rather reflected as two separate steps S411 and S417), when the target cell starts broadcasting a UE-specific RS (e.g., CSI-RS) on said beam (as illustrated in step S416, which is similar to step S316 in FIG. 3), the UE determines in step S417 that the UE-specific RS (e.g., CSI-RS) is now broadcast on said beam, and reports to the serving DU accordingly in step S418.

[0115] The serving DU may then decide, based on such measurement reports (especially the instructions contained therein), to change the TCI state at some point, as illustrated in step S419. The subsequent procedures / steps are essentially the same as those shown in Figure 3, and as a result, repeated description thereof may be omitted for the sake of brevity.

[0116] Reference is now made to FIG. 5 , which outlines several further exemplary embodiments that may be used (at least in part) in conjunction with or as an alternative to the exemplary embodiments described above with reference to FIG. 3 and / or FIG. 4 (depending on various implementations). That is, the exemplary embodiments described with reference to FIG. 5 do not necessarily rely on some or all of the procedures as shown in FIG. 3 / FIG. 4 , for example, in implementations that address (only) the issue that the target DU may not support a BWP configurable by the source DU. Therefore, it should be understood that the procedures / steps shown in FIG. 3 / FIG. 4 , particularly with respect to configuring the target DU to refrain from broadcasting UE-specific RSs, do not constitute any limitations on the exemplary embodiments as shown in FIG. 5 . Nevertheless, depending on various implementations, the exemplary embodiments of FIG. 3 / FIG. 4 and FIG. 5 may also be combined, as can be understood and appreciated by those skilled in the art. Notably, in this exemplary embodiment, which will be described in detail below, it is generally assumed that the source / serving cell (DU) and the target cell (DU) may each be capable of operating on (e.g., configured by) one or more BWPs or be configurable by one or more BWPs. For example, the source cell may now be made up of BWPs A, B and C, while the target cell may now be made up of BWPs X, Y and Z.

[0117] Generally, the DU is the owner of the BWP resources that can be provided to the UE. The CU can indicate preferences, but it is the DU that ultimately provides the configuration. The lower layer configuration is provided by the DU. The CU can indicate which lower layer configuration should (preferably) be provided by the DU. However, it is up to the DU to follow the information indicated by the DU. The CU can reconfigure the UE using the lower layer configuration provided by the DU. For example, a target DU decides to configure the UE with BWP Y. At this time, there are two options: (i) the target DU can decide to configure the UE with BWP Y using instructions from the CU, or (ii) the target DU can decide to configure the UE with BWP Y based on the current UE BWP configuration. The UE is later configured by the CU to use the BWP of the target DU.

[0118] Specifically, in step S501, the CU-CP (or more generally, the CU) may decide to initiate an ICBM procedure for the cell of the target DU. Similar to step S301 of FIG. 3, the decision to initiate an ICBM procedure may be based on any suitable criteria, such as (but not necessarily limited to) received UE measurements of the beam of the target DU, operation and maintenance configuration, if the beam topology is already known to the operator and, as a result, the RAN node knows the neighboring beams. Furthermore, in step S501, the CU-CP (or CU) may also determine that the target cell bandwidth does not support at least one BWP of the UE that is configured or configurable by the serving cell. Alternatively, the CU-CP may determine that the target cell bandwidth does not support any BWP currently associated with the UE. Depending on various implementations and / or requirements, this determination may also be based on any suitable criteria, such as (but not necessarily limited to) the overall network topology, the (physical) functional capabilities supported by the target DU, network loading conditions, etc.

[0119] Then, in step S502, the CU-CP instructs the target DU that a specific beam A of the target cell (cell 2) is required on a specific BWP Y. This instruction may be sent, for example, through a UE context setup request message (or any other appropriate message). In some possible embodiments, the CU-CP may also instruct only the requested beam without instructing a specific BWP provided by the DU. It should be noted that the message of S502 may be a separate message or may be merged with message S302 or S402 of Figures 3 and 4. In other words, information about a specific BWP Y may be added to message S302 or S402.

[0120] In step S503, the target DU replies to this request indicating its complete BWP configuration (of the requested BWP Y), since this configuration cannot be provided by the source DU. At the same time, the target DU also indicates the beams allocated by the target cell. As above, the message of S503 may be a separate message or may be merged with message S304 or S404 of Figures 3 and 4. In other words, information about the specific BWP Y may be added to message S304 or S404. Interpreted differently, the procedure of Figure 5 can be considered as an extension of the procedures shown in Figures 3 and 4, in which configurations of source and target cells with different BWPs are handled.

[0121] Here, the CU-CP generally follows two alternative forms (indicated using the wording “capable” and “limited” in FIG. 5 ) depending on the UE capabilities. As can be understood and appreciated by those skilled in the art, such UE capabilities may be determined based on any appropriate criteria, such as the UE category configured by higher layers, the (physical) functions supported by the UE, etc. In a broad sense, generally, in the context of the exemplary embodiment of FIG. 5 , a “capable” UE may generally refer to a UE that is capable of being configured with (operating on) two or more BWPs simultaneously, while a “limited” UE may generally refer to a UE that can be configured with only a single BWP configuration at a time.

[0122] Alternative 1: "Capable" UE

[0123] For this alternative, the CU-CP may indicate the BWP configuration of the target DU to the source / serving DU in step S504. In response, the source DU may incorporate the BWP configuration of the target DU (e.g., into the UE MAC configuration) and return it to the CU-CP in step S505.

[0124] Thereafter, because the UE is capable of operating for two or more BWPs simultaneously, the CU can simply configure the UE (e.g., by sending an RRC reconfiguration message, etc.) with the configurations allocated by the target DU and source DU (step S506), and the UE then confirms the reconfiguration (step S507). Interpreted differently, since the UE generally has the ability to be configured for (and operate on) two or more BWPs simultaneously, the exact timing (or trigger) at which the CU sends each configuration message (e.g., an RRC reconfiguration message, etc.) is not important compared to Alternative 2, as described below. In some possible embodiments, the RRC reconfiguration may also include a measurement gap configuration, thereby facilitating the UE to monitor the broadcast channel of the serving cell (by using such a measurement gap configuration). In particular, as can be understood by those skilled in the art, in some cases (e.g., inter-frequency ICBM scenarios), the UE needs to use this measurement gap to perform necessary L1 RSRP measurements, and therefore an appropriate measurement gap configuration depending on the BWP on which the UE is operating may be required.

[0125] Alternative 2: "Restricted" UE

[0126] In this alternative, steps S508-S509 can generally be considered similar to steps S504-S505 of alternative 1 described above, with the difference that the CU-CP can indicate the target DU's BWP configuration to the source DU (step S508), the source DU can incorporate the target DU's BWP configuration, for example, into the UE MAC configuration and return it to the CU-CP (step S509), and the CU-CP can additionally configure the source DU (in step S508) to indicate when the UE should be reconfigured with a new BWP configuration. More specifically, because a (“restricted”) UE can only be configured with a single BWP configuration, the target DU's beam switching and the BWP configuration generally need to be performed simultaneously. In a different interpretation, compared to alternative 1 described above, in this alternative, the CU needs to know when to send the respective configuration message (e.g., RRC reconfiguration message, etc.) to the UE to ensure proper operation of such a UE with “restricted” capabilities.

[0127] After some time, the source DU may determine in step S510 that a switch to the target cell beam is necessary, for example, based on a measurement report sent to the source DU by the UE (not explicitly shown in the figure). Accordingly, as configured above, the source DU may send an indication to the CU in step S511 indicating that a BWP switch / change is now required. In particular, as can be understood and appreciated by those skilled in the art, such an indication may be sent by using any suitable mechanism (e.g., in an appropriate message).

[0128] Unlike Alternative 1 shown above, in this Alternative 2, only in response to receiving an indication that a BWP switch / change is required (as sent in step S511), the CU can configure the UE with the configurations allocated by the target DU and source DU (step S512), and correspondingly, the UE can acknowledge such reconfiguration (step S513). As above, in this Alternative 2, the RRC reconfiguration may also include an appropriate measurement gap configuration, thereby facilitating the UE to monitor the broadcast channel of the serving cell (by using such measurement gap configuration).

[0129] To summarize the above, the exemplary embodiment as described above with reference to FIG. 5 can be generally considered to address the problem that the target DU may not support any (or at least one) of the BWPs configurable for the UE by the source DU. In other words, there is a mismatch between the BWPs for which the UE is configured (by the source DU) and the available BWPs on the target DU. There are three possible cases: (i) the target cell bandwidth may be completely different from the source cell bandwidth; (ii) a bandwidth portion of the UE provided by the serving cell may be on a bandwidth separate from that of the target cell (thus, the bandwidths of the target and source cells may overlap, but this is not the case for the UE's BWPs, and therefore this is a sub-case of Case 1); or (iii) a bandwidth portion of the UE provided by the serving cell may be on a bandwidth separate from that of the target cell (several bandwidth portions of the UE may be included by the target cell bandwidth, and therefore this case is a sub-case of Case 2).

[0130] More specifically, in some possible exemplary embodiments, the CU (or CU-CP) can determine that the target cell configures the UE with ICBM operation in which the target cell operates in at least one BWP that is not part of the source cell bandwidth. The CU can determine the BWP to which the target cell should allocate a beam for the UE's ICBM operation. In other words, the CU determines the BWP that can be used by the target DU (the DU can be configured for it) and the UE (the UE can be configured for it), and commands both to use this BWP. For example, the CU instructs the target DU that, among all BWPs that can be allocated to the UE, the target DU should allocate a specific preferred BWP "Y" (if possible). The CU also configures the UE with the target DU's BWP information. BWPs that are not part of the target cell's bandwidth or that do not completely overlap with the target cell's bandwidth are indicated by the target DU to the CU. Thus, the CU can use this information to configure a new BWP for the UE. This information is indicated to the target DU via the CU. As a result, the target DU can use this information to decide to switch to the UE's BWP. When configured as suggested above, a UE (either "capable" or "restricted") is generally enabled to use ICBM even if the source and target DUs do not have a common BWP available.

[0131] As mentioned above, in the exemplary embodiments illustrated above (with reference to the drawings), it should be noted that, although the messages communicated / exchanged between network components / elements may be considered to have specific / explicit names, depending on various implementations (e.g., underlying technologies), these messages may have different names and / or may be communicated / exchanged in different forms / formats, as can be understood and appreciated by those skilled in the art.

[0132] According to some example embodiments, corresponding methods suitable to be performed by devices (network elements / components) such as those mentioned above, such as a UE, a CU, a DU, etc., are also provided.

[0133] Nevertheless, it should be noted that features of the above-described devices may not be explicitly described for the sake of brevity, but correspond to features of the respective methods. The disclosure herein is considered to extend to such method features as well. In particular, the disclosure is understood to relate to methods of operating the above-described devices and / or the provision and / or arrangement of the respective elements of these devices.

[0134] Additionally, according to some further exemplary embodiments, there is also provided a respective device (e.g., implementing a UE, CU, DU, etc. as described above) comprising at least one processing circuit and at least one memory for storing instructions executed by the processing circuit, the at least one memory and instructions configured to cause the respective device to perform at least a respective step as described above, by the at least one processing circuit.

[0135] Furthermore, according to some other exemplary embodiments, there is provided a respective apparatus (e.g., implementing a UE, CU, DU, etc. as described above) comprising respective means configured to perform at least the respective steps as described above.

[0136] It should be noted that the example embodiments of the present disclosure are applicable to a variety of different network configurations. In other words, the examples shown in the above figures, which are used as the basis for the above examples, are merely illustrative and do not limit the present disclosure in any way. That is, additional and further existing and proposed new features available within the corresponding operating environment may be used with the example embodiments of the present disclosure based on the defined principles.

[0137] It should also be noted that the disclosed exemplary embodiments can be implemented in many ways using hardware and / or software configurations. For example, the disclosed embodiments may be implemented using dedicated hardware and / or hardware in association with software executable thereon. The components and / or elements in the figures are merely examples and do not limit the scope of use or functionality of any hardware, software in combination with hardware, firmware, embedded logic components, or combinations of two or more such components, implementing particular embodiments of the present disclosure.

[0138] It should further be noted that the present specification and drawings merely illustrate the principles of the present disclosure. Those skilled in the art will be able to implement various configurations that embody the principles of the present disclosure and are within its spirit and scope, even if not explicitly described or shown herein. Moreover, all examples and embodiments outlined in this disclosure are expressly intended to be solely for illustrative purposes to aid the reader in understanding the principles of the proposed method, in principle. Furthermore, all statements herein providing principles, aspects, and embodiments of the present disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.

Claims

1. a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Radio Access Network Layer 3 protocol, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to: determining to initiate an Inter-cell Beam Management, ICBM, procedure involving a source cell of a second network node supporting at least one of a Distributed Unit, DU, function or a Layer 2 protocol of the radio access network, the source cell serving a User Equipment, UE, and a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network; sending a first request message to the third network node, the first request message including information indicating a beam of the target cell and information for configuring the third network node to refrain from transmitting a UE-specific reference signal, RS; receiving a first response message from the third network node, the first response message including information indicating a configuration of the beam for the ICBM procedure and information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A first network node causing

2. The first network node sending a second request message to the second network node, the second request message including information indicating the configuration of the beam and information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; receiving a second response message from the second network node, the second response message including information indicating an acknowledgment of the information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; The first network node of claim 1 , further configured to:

3. the second request message further includes information indicating a request for transmission of a message indicating that the UE is expected to switch to the beam of the target cell; The first network node of claim 2, wherein the second response message further includes information indicating an acknowledgment of the information indicating a request for transmission of a message indicating that the UE is expected to switch to the beam of the target cell.

4. The first network node receiving a first indication message from the second network node, the first indication message including information indicating that the UE is expected to switch to the beam of the target cell; sending a second indication message to the third network node to enable the third network to start transmitting the UE-specific RS; The first network node according to any one of claims 1 to 3, further comprising:

5. The first network node receiving a third indication message from the third network node, the third indication message including information indicating transmission of the UE-specific RS; transmitting a fourth indication message including information indicating the transmission of the UE-specific RS by the third network node; and The first network node of claim 4 further configured to:

6. The first network node according to any one of claims 1 to 5, wherein the decision to initiate the ICBM procedure is based on at least one of a measurement report received from the UE or a system operation and maintenance configuration.

7. The first network node according to any one of claims 1 to 6, wherein the UE-specific RS comprises a Channel State Information Reference Signal, CSI-RS.

8. each of the source cell and the target cell is configurable to operate in at least one bandwidth portion, BWP; The first network node determining that the target cell does not support at least one BWP currently associated with the UE; sending a third request message to the third network node, the third request message including information indicating a beam on a BWP of the target cell; receiving a third response message from the third network node, the third response message including information indicating a BWP configuration of the beam; The first network node according to any one of claims 1 to 7, further adapted to perform:

9. The first network node determining whether the UE is capable of simultaneously supporting two or more BWPs; Based on a determination that the UE is capable of simultaneously supporting two or more BWPs, sending a fourth request message to the second network node, the fourth request message including information indicating the BWP configuration of the beam; Based on determining that the UE is not capable of simultaneously supporting more than one BWP, sending a fifth request message to the second network node, the fifth request message including information indicating the BWP configuration of the beam and information for configuring the second network node to indicate when the target DU is expected to switch to the beam; The first network node of claim 8 , further configured to:

10. The first network node The first network node of claim 9, further configured to receive a message from the second network node including information indicating that the switch to the beam of the target DU is expected.

11. The first network node 11. The first network node of claim 9 or 10, further configured to send a configuration message to the UE, the configuration message including information indicating the BWP configuration of the beam.

12. a second network node supporting at least one of a distributed unit, DU, function or a radio access network Layer 2, L2, protocol and constituted by a source cell serving a user equipment, UE, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to: receiving a first request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 protocol of the radio access network, the first request message including information indicating a beam configuration of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network and information indicating that the third network node is configured to refrain from transmitting a UE-specific reference signal (RS); transmitting a first response message to the first network node, the first response message including information indicating an acknowledgment of the information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; a second network node that causes the

13. The second network node determining that the UE is expected to switch to the beam of the target cell; sending a first indication message to the first network node, the first indication message including information indicating the expected switchover; The second network node of claim 12 further configured to:

14. The second network node 14. The second network node of claim 13, further configured to receive a first measurement message from the UE, and wherein the determination that the UE is expected to switch to the beam of the target cell is based on the first measurement report.

15. The second network node 15. The second network node according to claim 13 or 14, further configured to receive a second indication message from the first network node, the second indication message including information indicating transmission of the UE-specific RS by the third network node.

16. The second network node receiving a second measurement report from the UE; determining, based on the second measurement report, to switch the UE to the beam of the target cell; sending a message to the UE including a transmission configuration indication, a TCI, and information indicating a status change corresponding to the target cell; 16. The second network node according to claim 14 or 15, further adapted to:

17. Each of the source cell and the target cell is configurable to operate in at least one bandwidth portion, BWP, and the second network node is configured to: A second network node according to any one of claims 12 to 16, further configured to receive from the first network node a second request message including information indicating the BWP configuration of the beam of the target cell.

18. Each of the source cell and the target cell is configurable to operate in at least one bandwidth portion, BWP, and the second network node is configured to: A second network node as described in any one of claims 12 to 16, further configured to receive a third request message from the first network node, the third request message including information indicating the BWP configuration of the beam of the target cell and information indicating the configuration of the second network to indicate when switching to the beam of the target DU is expected.

19. The second network node determining that the target DU is expected to switch to the beam; sending a third indication message to the first network node, the third indication message including information indicating that the switch to the beam of the target DU is expected; The second network node of claim 18 further configured to:

20. a third network node supporting at least one of a distributed unit, DU, function or radio access network Layer 2 protocol, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third network node to: receiving a first request message from a first network node supporting at least one of a central unit control plane, CU-CP, function or a Layer 3 protocol of the radio access network, the first request message including information indicating a beam of a target cell of the third network node and information for configuring the third network node to refrain from transmitting a UE-specific reference signal, RS; configuring the third network node to refrain from transmitting UE-specific RS; sending a first response message to the first network node, the first response message including information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; a third network node that causes the

21. The third network node receiving a first indication message from a second network node, the first network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network, comprising information indicating that a user equipment (UE) served by a source cell of the second network node is expected to switch to the beam of the target cell; Initiating transmission of the UE-specific RS; sending a second indication message to the first network node, the second indication message including information indicating an acknowledgment of the expected switchover; 21. The third network node of claim 20, further adapted to:

22. The third network node according to claim 20 or 21, wherein the UE-specific RS comprises channel state information, CSI, and associated RS.

23. A third network node according to any one of claims 20 to 22, wherein the target cell is configurable to operate in at least one bandwidth portion, BWP.

24. The third network node receiving a second request message from the first network node, the second request message including information indicating a beam on a BWP of the target cell; sending a second response message to the first network node, the second response message including information indicating a BWP configuration of the beam; 24. The third network node of claim 23, further adapted to:

25. A user equipment, UE, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to: receiving a configuration message from a first network node supporting at least one of a distributed unit, DU, function or a layer 3 protocol of the radio access network, the configuration message including information indicating a beam of a target cell of a third network node supporting at least one of a distributed unit, DU, function or a layer 2 protocol of the radio access network and information indicating that the third network node is configured to refrain from transmitting UE specific reference signals, RS; monitoring the UE-specific RS; and based on determining that the UE-specific RS is being broadcast, sending a message including information indicating that the UE-specific RS is being broadcast to a second network node supporting at least one of the DU Function or the Layer 2 protocol of the radio access network; The user equipment (UE) performs the above.

26. 1. A system comprising: a second network node supporting at least one of the distributed units, DUs, functions or radio access network layer 2 protocols according to any one of claims 12 to 20; a user equipment, UE, served by a source cell of the second network node; and A system comprising:

27. a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Radio Access Network Layer 3 protocol, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to: determining to initiate an Inter-cell Beam Management (ICBM) procedure involving at least a source cell of a second network node supporting at least one of a Distributed Unit (DU) function or a Layer 2 protocol of the radio access network, the source cell serving a User Equipment (UE), and a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network, wherein each of the source cell and the target cell is configurable to operate in at least one bandwidth portion (BWP); determining that the target cell does not support at least one BWP currently associated with the UE; sending a request message to the third network node, the request message including information indicating a beam on a BWP of the target cell; receiving a response message from the third network node, the response message including information indicating a BWP configuration of the beam; A first network node causing

28. a second network node supporting at least one of a distributed unit, DU, function or a radio access network Layer 2 protocol and configured by a source cell serving a user equipment, UE, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to: receiving a request message from a first network node supporting at least one of a central unit control plane, CU-CP, function or a Layer 3 protocol of the radio access network, the request message including information indicating a BWP configuration of a beam of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network; or receiving a request message from the first network node, the request message including information indicating a BWP configuration of the beam of the target cell and information indicating a configuration of the second network to indicate to the first network node when a switch to the beam of the target cell is expected; a second network node that causes the

29. a third network node supporting at least one of a distributed unit, DU, function or radio access network Layer 2 protocol, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third network node to: receiving a request message from a first network node supporting at least one of a central unit control plane, CU-CP, function or a Layer 3 protocol of the radio access network, the request message including information indicating a beam on a BWP of a target cell of the third network node; sending a response message to the first network node, the response message including information indicating a BWP configuration of the beam; a third network node that causes the

30. 1. A method of a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Layer 3 protocol of a radio access network, comprising: determining to initiate an Inter-cell Beam Management, ICBM, procedure involving a source cell of a second network node supporting at least one of a Distributed Unit, DU, function or a Layer 2 protocol of the radio access network, the source cell serving a User Equipment, UE, and a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network; sending a first request message to the third network node, the first request message including information indicating a beam of the target cell and information for configuring the third network node to refrain from transmitting a UE-specific reference signal, RS; receiving a first response message from the third network node, the first response message including information indicating a configuration of the beam for the ICBM procedure and information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A method comprising:

31. 1. A method of a second network node configured by a source cell supporting at least one of a distributed unit, DU, function or a radio access network Layer 2 protocol and serving a user equipment, UE, comprising: receiving a first request message from a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 protocol of the radio access network, the first request message including information indicating a beam configuration of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network and information indicating that the third network node is configured to refrain from transmitting a UE-specific reference signal (RS); transmitting a first response message to the first network node, the first response message including information indicating an acknowledgment of the information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A method comprising:

32. A method of a third network node supporting at least one of a distributed unit, DU, function or radio access network Layer 2 protocol, comprising: receiving a first request message from a first network node supporting at least one of a central unit control plane, CU-CP, function or a Layer 3 protocol of the radio access network, the first request message including information indicating a beam of a target cell of the third network node and information for configuring the third network node to refrain from transmitting a UE-specific reference signal, RS; configuring the third network node to refrain from transmitting UE-specific RS; sending a first response message to the first network node, the first response message including information indicating that the third network node is configured to refrain from transmitting the UE-specific RS; A method comprising:

33. 1. A method of a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Layer 3 protocol of a radio access network, comprising: determining to initiate an Inter-cell Beam Management, ICBM, procedure involving a source cell of a second network node supporting at least one of a Distributed Unit, DU, function or a Layer 2 protocol of the radio access network, the source cell serving a User Equipment, UE, and a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network; determining that the target cell does not support at least one BWP currently associated with the UE; sending a request message to the third network node, the request message including information indicating a beam on a BWP of the target cell; receiving a response message from the third network node, the response message including information indicating a BWP configuration of the beam; A method comprising:

34. 1. A method of a second network node configured by a source cell supporting at least one of a distributed unit, DU, function or a radio access network Layer 2 protocol and serving a user equipment, UE, comprising: receiving a request message from a first network node supporting at least one of a central unit control plane, CU-CP, function or a Layer 3 protocol of the radio access network, the request message including information indicating a BWP configuration of a beam of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network; or receiving a request message from the first network node, the request message including information indicating a BWP configuration of the beam of the target cell and information indicating a configuration of the second network to indicate to the first network node when a switch to the beam of the target cell is expected; A method comprising:

35. A method of a third network node supporting at least one of a distributed unit, DU, function or radio access network Layer 2 protocol, comprising: receiving a request message from a first network node supporting at least one of a central unit control plane, CU-CP, function or a Layer 3 protocol of the radio access network, the request message including information indicating a beam on a BWP of a target cell of the third network node; sending a response message to the first network node, the response message including information indicating a BWP configuration of the beam; A method comprising:

36. A computer program comprising instructions for causing an apparatus to carry out the method according to any one of claims 30 to 35.

37. A memory storing computer readable instructions for causing an apparatus to carry out a method according to any one of claims 30 to 35.

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