Enhancements for beam management

Abstract

It is described a first network node supporting at least one of a 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 that, when executed by the at least one processor, cause the first network node to at least: determine to initiate an ICBM process, the ICBM procedure involves at least a source cell of a second network node serving the UE supporting at least one of a DU function or a Layer 2 protocol of a radio access network 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; transmitting, to a third network node, a first request message including information indicating a beam of the target cell and information for configuring the third network node to avoid transmitting a UE-specific RS; and receiving, from the third network node, a first response message including information indicating a configuration of a beam for the ICBM process and information indicating that the third network node is configured to avoid transmitting the UE-specific RS.

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 Art

[0002] Throughout the specification, any discussion of the background art should not be considered as an admission that this art is widely known or forms part of the common general knowledge in the field.

[0003] Broadly speaking, starting from a normal cell topology of a radio communication system (such as e.g. 5G, e.g. gNB etc.), a gNB may be implemented, for example, using at least one DU (distributed unit) and a CU (central unit). Figure 1 An example illustration of a coverage map with 21 (micro) cells (such as those indicated by circles) is schematically shown.

[0004] When UE (user equipment) Figure 1 When moving in the direction indicated by the arrow, the UE may pass through different cells, which usually causes several handovers.

[0005] Unnecessary handovers and the corresponding interruptions and signaling overhead should be reduced or avoided, since in some possible cases (e.g., depending on the route), it may cause a large number of ping-pong handovers, i.e., switching back and forth between two cells, and a large amount of additional signaling, including Radio Resource Control (RRC) signaling. In addition, it has been observed that the normal topology and coverage of the cells may not be as good as expected due to reasons such as shadows, buildings, etc. Figure 1 , but may sometimes show coverage islands that penetrate the coverage of other cells. Such a more realistic "real world example" may cause more ping-pong phenomena, e.g. due to the presence of cell coverage islands etc. and if the UE passes through or gets close to these islands. This may even become more and more the case if more and more (narrow) beams are used (e.g. in mmWave radio connections).

[0006] Various techniques / methods have been proposed to try to solve at least some of the above problems. However, depending on various situations, some of these conventional techniques may cause increased signaling overhead, resource waste, time delay, etc.

[0007] Therefore, new beam management mechanisms need to be proposed to solve some or all of the above problems in an efficient, flexible and reliable manner. Summary of the invention

[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, comprising:

[0009] at least one processor; and

[0010] At least one memory storing instructions that, when executed by at least one processor, cause the first network node to at least:

[0011] 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 (L2) protocol of a radio access network and 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;

[0012] sending a first request message to a third network node, wherein the first request message includes information indicating a beam of a target cell and information for configuring the third network node to avoid sending a UE-specific reference signal (RS); and

[0013] A first response message is received from the third network node, wherein the first response message includes information indicating configuration of a beam for an ICBM process and information indicating that the third network node is configured to avoid transmitting a UE-specific RS.

[0014] In some examples, the first network node is further caused to:

[0015] sending a second request message to the second network node, wherein the second request message includes information indicating configuration of the beam, and information indicating that the third network node is configured to avoid sending a UE-specific RS; and

[0016] A second response message is received from the second network node, wherein the second response message includes information indicating confirmation of the information indicating that the third network node is configured to avoid sending the UE-specific RS.

[0017] In some examples, the second request message also includes information indicating requesting transmission of a message instructing the UE to switch a beam to the target cell; and

[0018] The second response message also includes information indicating confirmation of the information of the message indicating the request to instruct the UE to switch the beam to the target cell.

[0019] In some examples, the first network node is further caused to:

[0020] receiving a first indication message from the second network node, the first indication message including information indicating switching of the UE to the beam of the target cell; and

[0021] A second indication message is sent to the third network node to enable the third network node to start sending the UE-specific RS.

[0022] In some examples, the first network node is also caused to:

[0023] receiving a third indication message from a third network node, the third indication message including information indicating transmission of a UE-specific RS; and

[0024] A fourth indication message is sent, the fourth indication message including information indicating transmission of the UE-specific RS by the third network node.

[0025] In some examples, initiating an ICBM procedure is determined based on at least one of: a measurement report received from a UE, or a system operations and maintenance configuration.

[0026] In some examples, the UE-specific RS includes a channel state information reference signal (CSI)-RS.

[0027] In some examples, wherein each of the source cell and the target cell is configurable to operate in at least one bandwidth part (BWP); and

[0028] The first network node is further caused to:

[0029] Determining that the target cell does not support at least one BWP currently associated with the UE;

[0030] sending a third request message to a third network node, wherein the third request message includes information indicating a beam on the BWP of the target cell; and

[0031] A third response message is received from the third network node, the third response message including information indicating the BWP configuration for the beam.

[0032] In some examples, the first network node is further caused to:

[0033] Determine whether the UE is capable of supporting more than one BWP simultaneously;

[0034] Based on determining that the UE is capable of supporting more than one BWP simultaneously:

[0035] sending a fourth request message to the second network node, wherein the fourth request message includes information indicating a BWP configuration for the beam; and

[0036] Based on determining that the UE is not capable of supporting more than one BWP simultaneously:

[0037] A fifth request message is sent to the second network node, wherein the fifth request message includes information indicating a BWP configuration for the beam, and information for configuring the second network node to indicate when a switch to the beam of the target DU is expected.

[0038] In some examples, the first network node is further caused to:

[0039] A message including information indicating a switch to a beam of a target DU is received from the second network node.

[0040] In some examples, the first network node is further caused to:

[0041] A configuration message is sent to the UE, the configuration message including information indicating the BWP configuration for the beam.

[0042] According to another aspect of the present disclosure, there is provided 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 and configured with a source cell serving a user equipment (UE), comprising:

[0043] at least one processor; and

[0044] at least one memory storing instructions that, when executed by at least one processor, cause the second network node to at least:

[0045] 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 configuration of a beam for a target cell of a third network node and information indicating that the third network node is configured to avoid transmitting a UE-specific reference signal (RS), the third network node supporting at least one of a DU function or a layer 2 (L2) protocol of the radio access network; and

[0046] A first response message is sent to the first network node, wherein the first response message includes information indicating confirmation of the information indicating that the third network node is configured to avoid sending the UE-specific RS.

[0047] In some examples, the second network node is further caused to:

[0048] determining that a handover of the UE to the beam of the target cell is expected; and

[0049] A first indication message is sent to a first network node, the first indication message including information indicating a handover to be expected.

[0050] In some examples, the second network node is further caused to:

[0051] A first measurement report is received from the UE, wherein determining that a switching of the UE to a beam of a target cell is to be expected is based on the first measurement report.

[0052] In some examples, the second network node is further caused to:

[0053] A second indication message is received from the first network node, the second indication message including information indicating transmission of a UE-specific RS by a third network node.

[0054] In some examples, the second network node is further caused to:

[0055] receiving a second measurement report from the UE;

[0056] Determining, based on the second measurement report, a beam to which the UE is to be handed over to the target cell; and

[0057] A message including information indicating a change in a transmission configuration indication (TCI) state corresponding to a target cell is sent to the UE.

[0058] In some examples, each of the source cell and the target cell can be configured to operate in at least one bandwidth part (BWP).

[0059] In some examples, the second network node is also caused to receive a second request message from the first network node, the second request message including information indicating a BWP configuration for the beam of the target cell.

[0060] In some examples, the second network node is also caused to receive a third request message from the first network node, the third request message including information indicating a BWP configuration for a beam for the target cell and information indicating a configuration for the second network to indicate when a switch to the beam to the target DU will be expected.

[0061] In some examples, the second network node is further caused to:

[0062] determining that a switch to the beam of the target DU is expected; and

[0063] A third indication message is sent to the first network node, the third indication message including information indicating that a beam to the target DU is to be expected.

[0064] 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, comprising:

[0065] at least one processor; and

[0066] at least one memory storing instructions that, when executed by at least one processor, cause the third network node to at least:

[0067] 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 a third network node, and information for configuring the third network node to avoid transmitting a UE-specific reference signal (RS);

[0068] configuring the third network node to avoid sending the UE-specific RS; and

[0069] A first response message is sent to the first network node, wherein the first response message includes information indicating that the third network node is configured to avoid sending the UE-specific RS.

[0070] In some examples, the third network node is further caused to:

[0071] receiving a first indication message from the first network node, the first indication message including information indicating that a handover of a beam of 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 to a target cell is to be expected;

[0072] Start sending UE-specific RS; and

[0073] A second indication message is sent to the first network node, the second indication message comprising information indicating confirmation that the handover is to be expected.

[0074] In some examples, the UE-specific RS includes a channel state information (CSI)-related RS.

[0075] In some examples, the target cell can be configured to operate in at least one bandwidth part (BWP).

[0076] In some examples, the third network node is further caused to:

[0077] receiving a second request message from the first network node, the second request message including information indicating a beam on the BWP of the target cell; and

[0078] A second response message is sent to the first network node, the second response message including information indicating the BWP configuration for the beam.

[0079] According to another aspect of the present disclosure, there is provided a user equipment (UE), including:

[0080] at least one processor; and

[0081] At least one memory storing instructions that, when executed by at least one processor, cause the UE to at least:

[0082] 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 a radio access network, the configuration message including information indicating a beam of a target cell of a third network node and information indicating that the third network node is configured to avoid transmitting a UE-specific reference signal (RS), the third network node supporting at least one of a distributed unit (DU) function or a layer 2 protocol of the radio access network;

[0083] Monitoring UE-specific RS; and

[0084] Based on determining that the UE-specific RS is broadcast, a message including information indicating that the UE-specific RS is broadcast is sent to a second network node supporting at least one of a DU function or a layer 2 protocol of a radio access network.

[0085] According to another aspect of the present disclosure, there is provided a system, comprising:

[0086] a second network node supporting at least one of a distributed unit (DU) function disclosed in the present disclosure or a layer 2 protocol of a radio access network; and

[0087] A user equipment (UE) served by a source cell of the second network node.

[0088] 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, comprising:

[0089] at least one processor; and

[0090] at least one memory storing instructions that, when executed by at least one processor, cause the first network node to at least:

[0091] 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 (L2) protocol of a radio access network and 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;

[0092] Determining that the target cell does not support at least one BWP currently associated with the UE;

[0093] sending a request message to a third network node, wherein the request message includes information indicating a beam of the target cell; and

[0094] A response message is received from the third network node, the response message including information indicating a BWP configuration for the beam.

[0095] According to another aspect of the present disclosure, there is provided 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 and configured with a source cell serving a user equipment (UE), including:

[0096] at least one processor; and

[0097] at least one memory storing instructions that, when executed by at least one processor, cause the second network node to at least:

[0098] receiving a request message from a first network node supporting at least one of a central unit control plane CU-CP functionality or a layer 3 protocol of a radio access network, the request message including information indicating a BWP configuration of a beam for a target cell of a third network node, the third network node supporting at least one of a DU functionality or a layer 2 protocol of the radio access network; or

[0099] A request message is received from the first network node, the request message comprising information indicating a BWP configuration for a beam of the target cell and information indicating a configuration for the second network to indicate to the first network node when a switch to the beam of the target cell is expected.

[0100] According to 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, comprising:

[0101] at least one processor; and

[0102] at least one memory storing instructions that, when executed by at least one processor, cause the third network node to at least:

[0103] 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; and

[0104] A response message is sent to the first network node, wherein the response message includes information indicating the BWP configuration for the beam.

[0105] According to yet another aspect of the present disclosure, there is provided a method of a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Radio Access Network Layer 3 (L3) protocol, the method comprising:

[0106] 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 (L2) protocol of a radio access network and 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;

[0107] sending a first request message to a third network node, wherein the first request message includes information indicating a beam of a target cell and information for configuring the third network node to avoid sending a UE-specific reference signal (RS); and

[0108] A first response message is received from the third network node, wherein the first response message includes information indicating configuration of a beam for the ICBM process and information indicating that the third network node is configured to avoid transmitting a UE-specific RS.

[0109] According to yet another aspect of the present disclosure, there is provided a method 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 and configured with a source cell serving a user equipment (UE), the method comprising:

[0110] 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 configuration of a beam for a target cell of a third network node and information indicating that the third network node is configured to avoid transmitting a UE-specific reference signal (RS), the third network node supporting at least one of a DU function or a layer 2 (L2) protocol of the radio access network; and

[0111] A first response message is sent to the first network node, wherein the first response message includes information indicating confirmation of the information indicating that the third network node is configured to avoid sending the UE-specific RS.

[0112] According to yet another aspect of the present disclosure, a method of 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 is provided, the method comprising:

[0113] 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 a third network node, and information for configuring the third network node to avoid transmitting a UE-specific reference signal (RS);

[0114] configuring the third network node to avoid sending the UE-specific RS; and

[0115] A first response message is sent to the first network node, wherein the first response message includes information indicating that the third network node is configured to avoid sending the UE-specific RS.

[0116] According to yet another aspect of the present disclosure, there is provided 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, the method comprising:

[0117] 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 and serving a user equipment UE, and a target cell of a third network node supporting at least one of the DU function or a layer 2 protocol of the radio access network;

[0118] Determining that the target cell does not support at least one BWP currently associated with the UE;

[0119] sending a request message to a third network node, wherein the request message includes information indicating a beam of the target cell; and

[0120] A response message is received from the third network node, wherein the response message includes information indicating a BWP configuration for the beam.

[0121] According to yet another aspect of the present disclosure, there is provided a method 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 and configured with a source cell serving a user equipment (UE), the method comprising:

[0122] receiving a request message from a first network node supporting at least one of a central unit control plane CU-CP functionality or a layer 3 protocol of a radio access network, the request message including information indicating a BWP configuration of a beam for a target cell of a third network node, the third network node supporting at least one of a DU functionality or a layer 2 protocol of the radio access network; or

[0123] A request message is received from the first network node, the request message comprising information indicating a BWP configuration for a beam of the target cell and information indicating a configuration for the second network to indicate to the first network node when a switch to the beam of the target cell is expected.

[0124] According to yet another aspect of the present disclosure, a method of 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 is provided, the method comprising:

[0125] 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; and

[0126] A response message is sent to the first network node, wherein the response message includes information indicating the BWP configuration for the beam.

[0127] According to some example embodiments, there is also provided a computer program comprising instructions for causing an apparatus to perform the method as disclosed in the present disclosure.

[0128] According to some example embodiments, there is also provided a memory storing computer-readable instructions for causing an apparatus to execute the method disclosed in the present disclosure.

[0129] Furthermore, 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 corresponding appropriate components configured to perform corresponding steps as disclosed in the present disclosure.

[0130] Similarly, according to some example embodiments, there is also provided a second network node and a third network node, which support at least one of a distributed unit (DU) function or a layer 2 (L2) protocol of a radio access network, and include corresponding appropriate components configured to perform the corresponding steps disclosed in the present disclosure.

[0131] In addition, according to some other example embodiments, for example, a computer program product for a wireless communication device includes at least one processor, including a software code portion for executing the corresponding 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 portion is stored. In addition, the computer program product may be directly loaded into the internal memory of the computer and / or may be sent via a network through at least one of an upload, download, and push process.

[0132] Although some example embodiments will be described herein with particular reference to the above-mentioned applications, it will be appreciated that the present disclosure is not limited to such fields of use and may be applied in a wider context.

[0133] It is worth noting that it should be understood that the method according to the present disclosure relates to a method of operating a device according to the above-mentioned example embodiments and variations thereof, and the corresponding statements made about the device are also applicable to the corresponding method, and vice versa, so similar descriptions can be omitted for the sake of brevity. In addition, even if not explicitly disclosed, the above aspects can be combined in a variety of ways. Those skilled in the art will understand that the combination of these aspects and features / steps is possible unless it produces a contradiction that is explicitly excluded.

[0134] Implementation of the disclosed apparatus may include the use of, but is not limited to, one or more processors, one or more application specific integrated circuits (ASICs), and / or one or more field programmable gate arrays (FPGAs). Implementation of the apparatus may also include the use of other conventional and / or custom hardware, such as a software programmable processor, such as a graphics processing unit (GPU) processor.

[0135] Other and further example embodiments of the present disclosure will become apparent during the course of the following discussion and with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0136] Example embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0137] Figure 1 schematically shows an example of a diagram of a cell coverage map;

[0138] Figure 2 schematically illustrates an example of a signaling / message flow diagram according to an example embodiment of the present disclosure;

[0139] FIG3 schematically illustrates an example of a signaling / message flow diagram according to another example embodiment of the present disclosure;

[0140] FIG4 schematically illustrates an example of a signaling / message flow diagram according to another example embodiment of the present disclosure; and

[0141] Figure 5 An example of a signaling / message flow diagram according to yet another example embodiment of the present disclosure is schematically illustrated. DETAILED DESCRIPTION

[0142] In the following, different exemplary embodiments will be described using a communication network architecture based on 3GPP standards (such as 5G / NR) as an example of a communication network to which the exemplary embodiments can be applied, but the exemplary embodiments are not limited to such an architecture. It is obvious to those skilled in the art that the exemplary embodiments can also be applied to other types of communication networks, where the mobile communication principle is combined with D2D (device to device) or V2X (vehicle to everything) configurations (such as SL (side link)), for example Wi-Fi, Worldwide Interoperability for Microwave Access (WiMAX), Personal Communications Service (PCS), Wideband Code Division Multiple Access (WCDMA), systems using ultra-wideband (UWB) technology, mobile ad hoc networks (MANET), wired access, etc. In addition, without loss of generality, the description of some embodiment examples is related to mobile communication networks, 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.

[0143] 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 several places, this does not necessarily mean that each such reference is related to the same (multiple) examples or (multiple) embodiments, or that the feature applies only to a single example or embodiment. Individual features of different embodiments may also be combined to provide other embodiments. In addition, it should be understood that terms such as "comprising" and "including" do not limit the embodiments to only the features mentioned; these examples and embodiments may also include features, structures, units, modules, etc. that have not been specifically mentioned.

[0144] The basic system architecture of a (telecommunication) communication network including a mobile communication system (in which some example embodiments apply) may include the architecture of one or more communication networks, including (multiple) radio access network subsystems and (multiple) core networks. Such an 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 base stations (BS), access points (AP), NodeBs (NBs), eNBs or gNBs, distributed units (DUs) or centralized / central units (CUs), which control the corresponding coverage area or (multiple) cells, and one or more communication stations (such as communication elements or functions, such as user equipment or terminal equipment, such as user equipment (UE), or another device with similar functions, such as a modem chipset, chip, module, etc., which may also be part of a station, element, function or application capable of communication, such as a UE, an element or function that can be used for a machine-to-machine communication architecture, or as a separate element attached to such an element, function or application capable of communication, etc.) and can communicate with it via one or more communication beams via one or more channels to send several types of data in multiple access domains. Furthermore, core network elements or network functions such as gateway network elements / functions, mobility management entities, mobile switching centers, servers, databases, etc. may be included.

[0145] The following description may provide further details of alternatives, modifications and variants: The gNB includes, for example, a node that provides NR user plane and control plane protocol terminations towards the UE and is connected to the 5GC via an NG interface, for example in accordance with 3GPP TS 38.300 V16.6.0 (2021-06) section 3.2 incorporated by reference.

[0146] The gNB Central Unit (gNB-CU) includes, for example, logical nodes hosting, for example, RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB, which controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU.

[0147] The gNB distributed unit (gNB-DU) includes logical nodes such as the RLC, MAC, and PHY layers that host the gNB or en-gNB, and its operation is partially 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.

[0148] The gNB-CU control plane (gNB-CU-CP) includes, for example, a logical node that hosts the control plane part of the RRC and PDCP protocols for an en-gNB or a gNB-CU of a gNB. The gNB-CU-CP terminates the E1 interface with the gNB-CU-UP and the F1-C interface with the gNB-DU.

[0149] The gNB-CU-User Plane (gNB-CU-UP) includes, for example, a logical node hosting, for example, the user plane part of the PDCP protocol for the gNB-CU of the en-gNB and the user plane parts of the PDCP protocol and the SDAP protocol for the gNB-CU of the 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 according to 3GPP TS 38.401 V16.6.0 (2021-07) section 3.1 incorporated by reference.

[0150] Different functional splits between central and distributed units are possible, for example, known as options:

[0151] Option 1 (similar split to 1A):

[0152] oThe functional split in this option is similar to 1A architecture in DC. RRC is located in the central unit. PDCP, RLC, MAC, physical layer, and RF are located in the distributed unit.

[0153] Option 2 (similar to 3C split):

[0154] oThe functional split in this option is similar to the 3C architecture in DC. RRC and PDCP are located in the central unit. RLC, MAC, physical layer, and RF are located in the distributed unit.

[0155] Option 3 (RLC internal split):

[0156] o Low RLC (part of the RLC functionality), MAC, physical layer and RF are located in the distributed unit. PDCP and High RLC (another part of the RLC functionality) are located in the central unit.

[0157] Option 4 (RLC-MAC Split):

[0158] o MAC, physical layer and RF are located in the distributed unit. PDCP and RLC are located in the central unit.

[0159] Or, for example, according to 3GPP TR 38.801 V14.0.0, incorporated by reference

[0160] (2017-03)Part 11.

[0161] gNB supports different protocol layers, such as Layer 1 (L1) - physical layer.

[0162] 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:

[0163] oThe physical layer provides transport channels to the MAC sublayer;

[0164] o The MAC sublayer supplies logical channels to the RLC sublayer;

[0165] o The RLC sublayer supplies RLC channels to the PDCP sublayer;

[0166] o The PDCP sublayer supplies radio bearers to the SDAP sublayer;

[0167] o SDAP sublayer provides 5GC QoS flows;

[0168] o Comp. refers to header compression and Segm. refers to segmentation;

[0169] oControl channels include (BCCH, PCCH).

[0170] Layer 3 (L3) includes, for example, Radio Resource Control (RRC), for example according to 3GPP TS 38.300 V16.6.0 (2021-06) part 6, incorporated by reference.

[0171] A RAN (Radio Access Network) node or network node, such as, for example, a gNB, a base station, a gNB CU or a gNB DU or a part thereof, may be implemented using, for example, a device 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 CU and / or DU related functions and / or features, and / or at least one protocol (sub)layer of a RAN (Radio Access Network), such as layer 2 and / or layer 3.

[0172] The gNB CU and gNB DU parts may be, for example, co-located or physically separated. The gNB DU may be even further split, for example, into two parts, for example, one part including a processing device and one part including an antenna. The central unit (CU) may also be referred to as BBU / REC / RCC / C-RAN / V-RAN, O-RAN or a part thereof. The distributed unit (DU) may also be referred to as RRH / RRU / RE / RU or a part thereof. Hereinafter, in various example embodiments of the present disclosure, the CU-CP (or more generally CU) may also be referred to as a (first) network node supporting at least one of the central unit control plane functions or the layer 3 protocols of the radio access network; similarly, the DU may be referred to as a (second) network node supporting at least one of the distributed unit functions or the layer 2 protocols of the radio access network.

[0173] A gNB-DU supports one or more cells and can thus be used, for example, as a serving cell for a user equipment (UE).

[0174] User equipment (UE) may include a wireless or mobile device, a device with a radio interface to interact with a RAN (radio access network), a smartphone, an in-vehicle device, an IoT device, an M2M device, etc. Such a UE or device may include: at least one processor; and at least one memory, including computer program code; wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the device to perform at least certain operations, such as, for example, an RRC connection with the RAN. The UE is, for example, configured to generate a message (e.g., including a cell ID) to be sent to the RAN via radio (e.g., to arrive at a serving cell and communicate with it). The UE may generate, send and receive an RRC message containing one or more RRC PDUs (packet data units).

[0175] The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0 (2021-06) sections 42.1 and 4.4, incorporated by reference).

[0176] When the RRC connection has been established, the UE is in, for example, the RRC_CONNECTED state or the RRC_INACTIVE state.

[0177] In the RRC_CONNECTED state, the UE may:

[0178] oStore AS context;

[0179] oTransmit unicast data to / from UE;

[0180] o monitoring a control channel associated with a shared data channel to determine whether data is scheduled for the data channel;

[0181] oProvide channel quality and feedback information;

[0182] oPerform neighbor cell measurements and measurement reporting.

[0183] The RRC protocol includes the following main functions:

[0184] o RRC connection control;

[0185] oMeasurement configuration and reporting;

[0186] o Establishment / modification / release of measurement configurations (e.g. intra-frequency, inter-frequency and inter-RAT measurements);

[0187] o Measuring gap creation and release;

[0188] o Measurement report.

[0189] The general functionality and interconnection of the elements and functions (also depending on the actual network type) are known to those skilled in the art and are described in the corresponding specifications, and therefore, for the sake of brevity, their detailed description may be omitted herein. However, it should be noted that in addition to the elements, functions or applications described in detail below, several additional network elements and signaling links may be employed for communication to or from the elements, functions or applications, such as communication endpoints, communication network control elements (such as servers, gateways, radio network controllers) and other elements of the same or other communication networks.

[0190] The communication network architecture as considered in the example embodiments may also be able to communicate with other networks such as a public switched telephone network or the Internet. The communication network may also support the use of cloud services for virtual network elements or their functions, wherein it should be noted that the virtual network portion of the telecommunications network may also be provided by non-cloud resources (e.g., an internal network, etc.). It should be understood that the network elements and / or corresponding functions of the access system, core network, etc. may be implemented using any node, host, server, access node or entity, etc. suitable for such use. Typically, the network functions may be implemented as network elements on dedicated hardware, as software instances running on dedicated hardware, or as virtualized functions instantiated on an appropriate platform (e.g., a cloud infrastructure).

[0191] In addition, network elements (such as communication elements, such as UE, terminal equipment), control elements or functions (such as access network elements, such as base stations / BS, gNB, radio network controllers), core network control elements or functions (such as gateway elements) or other network elements or functions (as described herein) and any other elements, functions or applications may be implemented by software (e.g., by a computer program product for a computer) and / or by hardware. In order to perform their corresponding processing, the correspondingly used devices, nodes, functions or network elements may include several components, modules, units, components, etc. (not shown) required for control, processing and / or communication / signaling functions. Such components, modules, units and components may include, for example, one or more processors or processor units, including one or more processing parts for executing instructions and / or programs and / or for processing data, storage or memory units or components for storing instructions, programs and / or data, for use as a work area of ​​a processor or processing part, etc. (e.g. ROM, RAM, EEPROM, etc.), input or interface components for inputting data and instructions by software (e.g. floppy disk, CD-ROM, EEPROM, etc.), user interfaces for providing monitoring and operation possibilities for users (e.g. screen, keyboard, etc.), other interfaces or components for establishing links and / or connections under the control of the processor unit or part (e.g. wired and wireless interface components, radio interface components including, for example, antenna units, etc., components for forming a radio communication part, etc.), etc., wherein the corresponding components forming the interface (such as the radio communication part) may also be located at a remote site (e.g. a radio head or a radio station, etc.). It should be noted that in this specification, a processing part should not be regarded as representing only a physical part of one or more processors, but should be regarded as a logical division of the indicated processing tasks performed by one or more processors. It should be understood that according to some examples, a so-called "fluid" or flexible network concept may be adopted, wherein the operations and functions of a network element, a network function, or another entity of the network may be performed in a flexible manner in different entities or functions (such as nodes, hosts, or servers). In other words, the "division of labor" between the network elements, functions, or entities involved may vary from case to case.

[0192] As described above, in order to solve the problem of signaling overhead, interruption and / or delay (e.g. caused by unnecessary handovers), it is known that a so-called "borrowed" beam of a (target) cell different from the source / serving cell can be utilized. The (target) cell can be the same serving DU of (operated by) the source / serving cell or a different DU other than the serving DU, so in some cases, they can be referred to as intra-DU ICBM or inter-DU ICBM respectively. In some possible cases, the UE can be connected to the serving DU, and while traversing the cell, it may experience good measurements from another cell (e.g., of another DU), which may be a coverage island within 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 with the other cell is / becomes better. In this case, the UE can be served by a borrowed beam of a non-serving DU ("borrowed" means that the UE can be instructed to communicate with a beam from another cell without a serving cell change) without performing a complete (conventional) handover to another cell, so no additional RRC signaling overhead and interruption time are observed compared to a (conventional) handover.

[0193] But broadly speaking, there are two possible problems with such ICBM operations.

[0194] First, in some possible scenarios, a neighboring cell may configure a beam (e.g., a finer CSI-RS beam associated with a parent synchronization signal block (SSB) beam, and the association may be indicated by the network) that is not broadcast but configured to the UE via dedicated signaling. In other words, the beam may be configured not to be scheduled for RS transmission. Therefore, sending a UE-specific beam (DL reference signal) before the UE switches to the beam will be considered as a waste of network resources for non-serving DUs and cause additional energy waste (because the UE does not use the beam until the UE is switched to the beam by the DU), and needs to be avoided.

[0195] Second, in some possible scenarios, the target DU may not support any bandwidth part (BWP) configurable by the source DU (this may be the basic scenario for inter-frequency lower layer mobility (LLM) scenarios). Therefore, in the scenario where the target DU configures a BWP that the CU cannot configure for the UE, ICBM operation cannot be supported.

[0196] In view of this, the present disclosure generally proposes apparatus (such as DU, CU, etc.) and corresponding methods to address some or all of the above-mentioned issues / comments in a particularly efficient and flexible manner. In particular, in a broad sense, it can be seen that the present disclosure generally attempts to propose solutions to extend LLM concepts (i.e. ICBM, dynamic switching and L1-based serving cell changes) 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 not required. In particular, as will become apparent from the detailed description below, the present disclosure generally attempts to specify, among other things, the information that must be exchanged between RAN nodes (such as serving DU, CU-CP and target DU) in order to be able to initiate and prepare inter-DU procedures.

[0197] Reference is now made to the drawings. In particular, it should be noted that, unless otherwise noted, the same or similar reference numerals used in the drawings of the present disclosure may indicate the same or similar elements, so that repeated descriptions thereof may be omitted for the sake of brevity. It should also be noted that, as can be understood and appreciated by those skilled in the art, even though the drawings may appear to reference some specific / clear message names / types, these messages may of course have different names and / or be communicated / exchanged in different forms / formats depending on various implementations (e.g., underlining techniques).

[0198] Specifically, Figure 2 An example of a signaling / message flow chart for an exemplary intra-DU ICBM process according to an exemplary embodiment of the present disclosure is schematically shown. As shown above, in the intra-DU ICBM scenario, the source cell and the target cell (in Figure 2 are both under the control of the same serving (source) DU. It is also generally assumed that Figure 2 In the example embodiment, before the method starts, the UE is connected to cell 1 (i.e., the source / serving) and does not have an active inter-cell beam management configuration enabled.

[0199] Now, in step S201, the CU configures the L1 measurement of beam A for neighbor cell 2 (i.e., the target set) for the UE via, for example, an RRC reconfiguration message (or by using any other suitable message). It should be noted that although a single beam A is Figure 2The example embodiments of are used as reference, but those skilled in the art will understand and appreciate that in some other possible implementations, more than one beam may be configured for measurement. In addition, as those skilled in the art may also understand and appreciate, if the target DU may be operating in another bandwidth part (BWP) other than the current BWP of the UE (communicating with the serving DU), the CU may also configure appropriate measurement gaps for the UE. The UE may respond to such a configuration, for example, by sending a corresponding RRCReconfigurationComp message (or similar) to the serving CU, as exemplarily shown in step S202.

[0200] Then in step S203 , the UE reports L1 measurements (eg, reference signal received power (RSRP), etc.) for beam A of cell 2 to the DU.

[0201] 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 correspondingly include said beam A of cell 2 for beam management operations of the UE.

[0202] In step S205, the DU may indicate that beam A of cell 2 is included in the beam management operation of the UE, for example, by sending a UE CONTEXT MODIFICATION REQUEST message (or similar) to the CU. In response, the CU may configure the UE using the beam management information provided by the DU, for example, by sending another RRCReconfiguration message (or similar), as shown in step S206. Upon receipt of a corresponding RRCReconfigurationComp message (or similar) from the UE (step S207), the CU may in turn indicate or confirm the successful completion of the UE configuration to the DU, for example, by sending a corresponding UE CONTEXT MODIFICATION CONFIRM / COMPLETE message (or similar) in step S208.

[0203] The DU may then send a TCI state change message (e.g., as part of a MAC control unit (CE) or in any other suitable form) in step S209 to activate beam A of cell 2 for the UE, and the UE may, upon receipt of such TCI state information, switch its operation to beam A of cell 2 (as indicated by the TCI state change message), as shown in step S210.

[0204] It is noteworthy that, as mentioned above, it should be understood that the purpose of the inter-cell beam management process is not solely to provide mobility-related functions (e.g., switching, handover, etc.) to different cells, but is used to provide enhanced radio coverage to the UE as a temporary solution to avoid subsequent (sometimes unnecessary back and forth) handovers.

[0205] However, in some cases, the general framework of intra-DU ICBM as described above may be considered to be of little help in terms of cell coverage islands, for example because it has been observed that those cell coverage islands may typically be caused by lack of coverage of other DUs than the serving DU.

[0206] In view of this, in a broad sense, the present disclosure generally attempts to propose a technique that enables a CU to trigger (inter-DU) ICBM, where the cell is under the control of a target DU different from the source DU. This allows the UE to establish ICBM operations to the inter-DU cell, thereby extending the coverage of ICBM operations to a wider range of use cases. In this way, the UE can dynamically switch data connections back and forth between different DUs while maintaining a control connection with the serving cell, which is generally considered to be faster than a normal inter-DU handover, and can also reduce signaling overhead, especially in ping-pong situations. In some possible cases, since control signaling generally requires a much lower data rate than data transmission, the control connection can also be maintained in the case of a less good connection with the serving cell. In addition, even if the source and target DUs do not have a common BWP available, the Ue with the ability to send / receive on more than one BWP at the same time is also enabled to use ICBM. Thus, resource waste (e.g., prepared but not used, or not used immediately (e.g., delayed use)) is reduced, such as when the CSI-RS has been prepared by the target DU but the switch to the target DU does not ultimately occur.

[0207] 3 schematically illustrates an example of a signaling / message flow diagram according to an example embodiment of the present disclosure, and more specifically illustrates how an (inter-DU) ICBM configuration may be set at a target DU based on UE measurements and how the ICBM configuration may be aligned between source and target DUs. It is noteworthy that in the example embodiment illustrated in FIG3 , 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, and the (neighboring) target cell resides at (or in other words, is under the control of) the target DU.

[0208] and Figure 2 Similar to the example embodiment shown, before the message flow starts, although not explicitly shown in the figure, it is generally assumed that the UE has established a connection with the serving / source cell of the serving / source DU. In addition, the CU may have configured the UE to report measurements of the beams of the neighbor (target) cells controlled by the target DU. And in response, the UE may also confirm the measurement configuration and start sending measurement reports of the beams of the neighbor cells (e.g., via the source DU to the CU).

[0209] As now shown in FIG. 3 , in step S301 , the CU (or more specifically, the CU-CP) may determine to initiate an ICBM procedure for a cell of a target DU. Thereby, the CU may send, for example, a UE context modification request (or any other suitable message, for example, to request modification of a (previous / earlier) UE configuration) to the serving DU, as shown in step S307. It is worth noting that the determination of the initiation of the ICBM procedure may be based on any suitable criteria. As a (non-limiting) example, such a determination may be based on received UE measurements of the beam of the target DU. As another (non-limiting) example, such a determination may also be based on an operation and maintenance configuration, where the beam topology may already be known to the operator so that the RAN node will be aware of the neighbor beams.

[0210] 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 ICBM (e.g., by using a predetermined or predefined field / flag, such as "delayed 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., in various names, forms, etc.) may be used herein to convey information indicating ICBM.

[0211] Upon receipt of such an indication (e.g., a “delayed activation” indication as shown in step S302), the target DU may determine in step S303 that the allocated beam to the UE is, for example, a “refined” beam and will not be broadcast (i.e., CSI-RS resources associated with a particular SSB may not be sent) so as not to waste radio resources for transmission, for example because there are typically no other UEs in the cell using the refined beam (e.g., there may not be any other UEs in the coverage area of ​​the SSB used as the source beam for CSI-RS transmission). It is worth noting that such determination of a “refined” beam (and therefore not broadcasting or scheduling UE-specific CSI-RS) may be determined, for example, based on various criteria, such as UE requirements, the UE's ability to receive a refined beam without additional overhead, UE measurement results indicating that efficient transmission of radio resources is possible, or any other suitable criteria, as may be understood and appreciated by those skilled in the art.

[0212] Subsequently, in step S304, the target DU indicates (e.g., by sending a suitable message) that it does not broadcast the beam assigned to the UE and that the target DU requires an indication to start (or activate) transmission. The indication may be sent together with the UE context setup response and the beam configuration associated with the ICBM operation, as shown in step S304.

[0213] In steps S305-S306, the CU-CP may also interact with the CU-UP, for example, to perform appropriate bearer setup, as may be understood and appreciated by those skilled in the art.

[0214] In addition, the CU indicates the acquired beam configuration from the target DU to the serving DU in step S307. Specifically, the CU may specifically indicate that the target DU needs to be indicated (e.g., predetermined or preconfigured) for sending UE beams. In response, the serving DU may confirm such an indication and provide a beam management configuration for the UE with the beam of cell 2 (target cell) in step S308.

[0215] In steps S309-S310, the CU may configure the corresponding necessary ICBM configuration for the UE (for example, by sending an RRC reconfiguration message, etc.); then, the UE may confirm such configuration (for example, by sending an RRC reconfiguration completion message, etc.), as can be understood and recognized by those skilled in the art.

[0216] After a period of time, if the assigned beam is still suitable for ICBM based on the UE measurement results (step S311), then in step S312, the serving DU may determine (e.g., in response to receiving L1 measurements from the UE that may include target SSB measurements, as shown in step S311) to switch to the beam of the target cell. For example, the serving DU may determine to switch to beam A of cell 2 based on the L1 measurement results. In step S313, the serving DU indicates this to the CU, which further propagates such an indication (in the same or different message) to the target DU.

[0217] Upon receipt of the indication, the target DU may determine in step S314 to start broadcasting a UE-specific beam (e.g., CSI-RS) as a response to the indication. In addition, the target DU may also confirm the indication to the CU and further to the source DU, for example, as illustrated in step S315 by using the expression "prepare for switching" (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 start forwarding (early) data (e.g., downlink data to the UE) to the target DU.

[0218] Subsequently, the UE may start receiving the CSI-RS beam broadcasted from the target DU (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.

[0219] In response to the measurement(s), the source DU may determine the beam to which to switch the UE to the target DU in step S318. It is worth noting that such a determination 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).

[0220] Therefore, the source DU triggers the TCI state switch to the UE, for example, by sending a suitable message (step S319), and also indicates the switch to the CU-CP (step S321). In response to such a TCI state change indication, the UE can switch to the "borrowed" beam A from the target cell in step S320. In addition, similar to steps S305 and S306, the CU-CP can contact the CU-UP to complete the bearer context modification.

[0221] Finally, user plane data may be sent from the target DU and received by the UE, as shown in step S324.

[0222] In summary, the example embodiment described above with reference to FIG. 3 can generally be regarded as proposing to configure ICBM operation for UE, wherein the target DU avoids broadcasting beams related to ICBM operation. Whenever the beam of the target cell is to be used for ICBM operation, the source DU (through the CU) indicates the upcoming ICBM operation to the target DU. The target DU can then use this information to activate the broadcast-related beams accordingly.

[0223] The term "target DU avoids broadcast" shall mean that the target DU will not broadcast immediately, but is configured or prepared to broadcast and waits until it receives another signal position that triggers the actual broadcast, i.e., the activation of the broadcast is postponed until the trigger is received. The target DU is therefore configured for a conditional broadcast that requires a trigger to be initiated. Examples of triggering conditions include the receipt of a change notification, or an activation message sent by the serving DU or CU-CP. Conditional broadcasts can be considered as delayed broadcasts, i.e. prepared but not sent until the condition is met. The same concept of delayed activation applies to "avoiding transmission of UE-specific reference signals".

[0224] In some possible implementations, the source cell (DU) and the 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 for all BWPs may be configured in the target cell as a "deactivated" state. Subsequently, whenever BWP switching is triggered in the source DU, the source DU may indicate 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. It is worth noting that this is also reflected in the example of FIG. 3 in the form of a schematic diagram. More specifically, as shown in FIG. 3, when the target DU sends an indication, it indicates that it has not broadcast the beam assigned to the UE and it will need an indication to start transmission in step S304. The target DU may also send a beam configuration related to ICBM operation for all relevant BWPs (represented as "BWP (X, Y, Z)" in step S304). This beam configuration for 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 may determine 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 may in turn begin broadcasting CSI-RS only on BWP X, as shown in step S316.

[0225] FIG4 schematically illustrates an example of a signaling / message flow chart according to an example embodiment of the present disclosure. It is noteworthy that, unless otherwise specified, the same or similar reference numbers and / or messages (and the contents included therein) used in FIG4 may represent the same or similar elements and / or messages (and the corresponding contents therein), so that for the sake of brevity, repeated descriptions thereof may be omitted.

[0226] Specifically, as can be seen from the figure, the example embodiment shown in FIG. 4 is substantially the same as the example embodiment in FIG. 3 , except that those processes / steps related to the UE side are now shown in more detail. More specifically, as shown in FIG. 4 , when sending a beam configuration to the UE, for example, in an RRC reconfiguration message (or similar), as shown in step S409 (similar to step S309 of FIG. 3 ), the CU may also additionally configure the UE (e.g., as part of the RRC reconfiguration message or any other suitable separate message) to monitor (e.g., periodically) a UE-specific RS, even if the UE-specific RS (e.g., CSI-RS) has been configured not to be broadcast by the target DU (e.g., in steps S302 or S402, where the CU-CP sends a UE context setup request to the target DU and indicates that this is for an ICBM with “delayed activation”).

[0227] In response to such a configuration (related to monitoring), the UE may start (continuously) monitoring (e.g., periodically as configured) the beam of the target cell in step S411, and determine that the UE-specific RS (e.g., CSI-RS) is not broadcast on the beam, and report the corresponding measurement results to the serving DU in step S412.

[0228] Since the UE continuously and periodically monitors the beam of the target cell (although not explicitly reflected in the figure, but as two separate steps S411 and S417), once the target cell starts broadcasting the UE-specific RS (e.g., CSI-RS) on the beam (as shown in step S416, similar to step S316 of Figure 3), the UE will determine in step S417 that the UE-specific RS (e.g., CSI-RS) is now broadcast on the beam; and report accordingly to the serving DU in step S418.

[0229] The serving DU may then determine to change the TCI state at a certain point in time based on such a measurement report (particularly the indication contained therein), as shown in step S419. The subsequent process / steps are substantially the same as those shown in FIG3 , and therefore, for the sake of brevity, a repeated description thereof may be omitted.

[0230] Reference now Figure 5 , which schematically describes some further example embodiments, which may (depending on various implementations) be used in conjunction with (at least partially) or as an alternative to the example embodiments described above with reference to FIG. 3 and / or FIG. 4 . Figure 5 The described example embodiments do not necessarily rely on some or all of the procedures shown in FIG. 3 / 4, for example in implementations that address the problem that (only) the target DU may not support the BWP configurable by the source DU. Therefore, it should be understood that those procedures / steps shown in FIG. 3 / 4, especially those procedures / steps regarding configuring the target DU to avoid broadcasting UE-specific RS, should not constitute a reliance on the above. Figure 5 However, depending on various implementations, FIG. 3 / 4 and Figure 5 The example embodiments of the present invention may also be combined, as can be understood and appreciated by those skilled in the art. It is worth noting that in this example 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 operate on (e.g., be configured with) or be configurable with one or more BWPs. For example, the source cell may currently be configured with BWPs A, B, and C; and the target cell may currently be configured with BWPs X, Y, and Z.

[0231] Typically, the DU is the owner of the BWP resources that it can provide to the UE. The CU can indicate preferences, but it is the DU that ultimately provides the configuration. The low-level configuration is provided by the DU. The CU can indicate which low-level configuration should (preferably) be provided by the DU. But this depends on whether the DU complies with the information indicated by the DU. The CU can reconfigure the UE using the low-level configuration provided by the DU. For example, the target DU determines to configure the UE with BWP Y. Then there are 2 options: (i) the target DU can use the indication from the CU to determine to configure the UE with BWP Y, or (ii) the target DU can determine 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.

[0232] Specifically, in step S501, the CU-CP (or more generally, the CU) may determine to initiate an ICBM procedure for the cell of the target DU. Similar to step S301 in Figure 3, the determination of the initiation of the ICBM procedure may be based on any appropriate criteria, such as (but certainly not limited to): UE measurements of the received beams of the target DU, operation and maintenance configurations where the beam topology may already be known to the operator, so that the RAN node knows the neighbor beams, etc. In addition, 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, the determination may also be made based on any appropriate criteria, such as (but certainly not limited to): the overall network topology, (physical) functional capabilities supported by the target DU, network load conditions, etc.

[0233] Subsequently, in step S502, the CU-CP indicates to the target DU that a specific beam A of the target cell (cell 2) is required on a specific BWP Y. The indication may be sent, for example, via a UE context setup request message (or any other suitable message). In some possible implementations, the CU-CP may also indicate only the requested beam without indicating a specific BWP to be provided by the DU. It should be noted that the message of S502 may be a separate message or may be merged with the message S302 or S402 in Figures 3 and 4. In other words, the message S302 or S402 may be added with information about the specific BWP Y.

[0234] The target DU answers this request in step S503 (e.g., as a UE context setup response, etc.), indicating its complete BWP configuration (for the requested BWP Y), because this configuration cannot be provided by the source DU. At the same time, the target DU also indicates the beam allocated by the target cell. Similar to the above, the message of S503 can be a separate message or combined with the message S304 or S404 in Figures 3 and 4. In other words, the message S304 or S404 can be added with information about the specific BWP Y. In other words, Figure 5 The process of can be viewed as an extension of the process shown in Figures 3 and 4, where configurations of source and target cells with different BWPs are considered.

[0235] Now, CU-CP usually depends on UE capabilities (in Figure 5 As can be understood and appreciated by those skilled in the art, such UE capabilities can be determined based on any suitable criteria, such as UE categories configured by higher layers, (physical) functions supported by the UE, etc. In a broad sense, it can generally be considered that in Figure 5 In the context of the example embodiments of , a "capable" UE may generally refer to a UE that is capable of being configured with (operating on) more than one BWP at the same time; while a "limited" UE may generally refer to a UE that can only be configured with a single BWP configuration at a time.

[0236] Alternative 1: “Capable” UE.

[0237] 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 (eg, in the UE MAC configuration) and send it back to the CU-CP in step S505.

[0238] Subsequently, since the UE is capable of operating on more than one BWP at the same time, the CU can simply configure (e.g., by sending an RRC reconfiguration message, etc.) the UE with the configuration allocated by the target DU and the source DU (step S506); and then, the UE confirms the reconfiguration (step S507). In other words, it can be generally understood that since the UE has the ability to be configured (and operate) on two or more BWPs at the same time, the exact time (or trigger) for the CU to send the corresponding configuration message (e.g., RRC reconfiguration message, etc.) is not so important compared to alternative 2 to be described below. In some possible implementations, 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). It is worth noting that, as can be understood by those skilled in the art, in some cases (e.g., inter-frequency ICBM scenarios), it may be necessary to perform appropriate measurement gap configuration depending on the BWP on which the UE is operating, because the UE must use this measurement gap to perform the necessary L1 RSRP measurement.

[0239] Alternative 2: “Limited” UE.

[0240] In this alternative, steps S508-S509 are generally considered to be similar to steps S504-S505 in alternative 1 above, i.e., the CU-CP may indicate the BWP configuration of the target DU to the source DU (step S508), and the source DU may incorporate the BWP configuration of the target DU into, for example, the UE MAC configuration and send it back to the CU-CP (step S509), except that the CU-CP may additionally configure (in step S508) the source DU to indicate when the UE should be reconfigured with a new BWP configuration. More specifically, since a ("limited") UE can only be configured with a single BWP configuration, the switching of the beam to the target DU and the BWP configuration generally must occur at the same time. In other words, compared to alternative 1 above, in this alternative, the CU needs to know when to send the corresponding configuration message (e.g., RRC reconfiguration message, etc.) to the UE to ensure normal operation of such a UE with "limited" capabilities.

[0241] After a period of time, the source DU may determine in step S510 that a switch to the target cell beam is required, for example based on a measurement report sent by the UE to the source DU (not explicitly shown in the figure). Therefore, as configured above, the source DU sends an indication to the CU in step S511 indicating that a BWP switch / change is now required. It is worth noting that such an indication may be sent using any appropriate mechanism (e.g., in an appropriate message), as can be understood and appreciated by those skilled in the art.

[0242] Unlike the above-mentioned alternative 1, in this alternative 2, only upon receiving an indication that a BWP needs to be switched / changed (such as sent in step S511), the CU can configure the UE with the configuration allocated by the target DU and the source DU (step S512); and correspondingly, the UE can confirm such reconfiguration (step S513). Similar to the above, in this alternative 2, the RRC reconfiguration can also include appropriate measurement gap configuration, thereby facilitating the UE (by using such measurement gap configuration) to monitor the broadcast channel of the serving cell.

[0243] In summary, reference Figure 5 The described example embodiments can generally be viewed as addressing the problem that the target DU may not support any (or at least one) of the BWPs configured for the UE by the source DU. In other words, there may be a mismatch between the BWP configured for the UE (by the source DU) and the available BWP on the target DU. There are three possible scenarios: (i) The target cell bandwidth may be completely different from the source cell bandwidth. (ii) A portion of the UE's bandwidth provided by the serving cell may be located on a separate bandwidth from the bandwidth of the target cell (thus the target cell and source cell bandwidths may overlap, but this is not the case for the UE's BWP, so it is a sub-case of scenario 1). (iii) A portion of the UE's bandwidth provided by the serving cell may be located on a separate bandwidth from the bandwidth of the target cell (some portions of the UE's bandwidth may be included by the target cell bandwidth, so this scenario is a sub-case of scenario 2).

[0244] More specifically, in some possible example embodiments, the CU (or CU-CP) may determine to configure the UE to have ICBM operation, where the target cell operates in at least one BWP that is not part of the bandwidth of the source cell. The CU may determine which BWP the target cell should allocate for ICBM operation of the UE. In other words, the CU determines the BWP that can be used by the target DU (the DU may be configured to) and by the UE (the UE may be configured to), and instructs both to use this BWP. For example, the CU indicates to the target DU that among all the 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 BWP information of the target DU. BWPs that are not part of the bandwidth of the target cell or that do not completely overlap with the bandwidth of the target cell are indicated to the CU from the target DU. Therefore, the CU can use this information to configure a new BWP to the UE. This information is indicated to the target DU by the CU. Therefore, the target DU can use this information to determine the BWP to switch to the UE. As configured as proposed above, even if the source and target DUs do not have a common BWP available, the UE ("capable" or "limited") is generally enabled to use ICBM.

[0245] As has been described above, although in the above-mentioned example embodiments (refer to the accompanying drawings), the messages transmitted / exchanged between network components / elements may appear to have specific / clear names, depending on various implementations (e.g., underline technology), these messages may have different names and / or be transmitted / exchanged in different forms / formats, as can be understood and recognized by those skilled in the art.

[0246] According to some example embodiments, corresponding methods suitable for being performed by an apparatus (network element / component) as described above, such as a UE, CU, DU, etc., are also provided.

[0247] However, it should be noted that the above-mentioned device (equipment) features correspond to corresponding method features, but for the sake of brevity, may not be explicitly described. The disclosure of this document is considered to also extend to such method features. Specifically, the disclosure is understood to relate to methods of operating the above-mentioned devices, and / or providing and / or arranging the corresponding elements of these devices.

[0248] In addition, according to some other example embodiments, a corresponding device (for example, implementing the UE, CU, DU, etc. as described above) is also provided, which includes at least one processing circuit system and at least one memory for storing instructions to be executed by the processing circuit system, wherein the at least one memory and the instructions are configured to enable the corresponding device to perform at least the corresponding steps as described above together with the at least one processing circuit system.

[0249] However, in some other example embodiments, a corresponding apparatus (eg, implementing the UE, CU, DU, etc. as described above) is provided, which includes corresponding components configured to at least perform the corresponding steps as described above.

[0250] It should be noted that the examples of the embodiments of the present disclosure are applicable to various network configurations. In other words, the examples shown in the above-mentioned figures (which are used as the basis for the examples discussed above) are only illustrative and do not limit the present disclosure in any way. That is, based on the defined principles, additional existing and proposed new functions available in the corresponding operating environment can be used in conjunction with the examples of the embodiments of the present disclosure.

[0251] It should also be noted that the disclosed example embodiments can be implemented in a variety of ways using hardware and / or software configurations. For example, the disclosed embodiments can be implemented using dedicated hardware and / or hardware associated with software executable thereon. The components and / or elements in the figures are only examples and do not limit the scope of use or functionality of any hardware, software combined with hardware, firmware, embedded logic components, or combinations of two or more such components that implement a particular embodiment of the present disclosure.

[0252] It should also be noted that the description and drawings illustrate only the principles of the present disclosure. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or shown herein, embody the principles of the present disclosure and are included in its spirit and scope. In addition, all examples and embodiments summarized in this disclosure are primarily and explicitly used only for explanatory purposes to help the reader understand the principles of the proposed method. In addition, all statements of the principles, aspects and embodiments of the present disclosure and their specific examples provided herein are intended to cover their equivalents.

Claims

1. A first network node, the 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 first network node comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to at least: 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 and 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, wherein the first request message includes: information indicating a beam of the target cell, and information for configuring the third network node to avoid sending a UE-specific reference signal (RS); and A first response message is received from the third network node, wherein the first response message includes information indicating configuration of a beam used for the ICBM process and information indicating that the third network node is configured to avoid transmitting the UE-specific RS.

2. The first network node according to claim 1, wherein the first network node is further caused to: Sending a second request message to the second network node, wherein the second request message includes: information indicating the configuration of the beam, and information indicating that the third network node is configured to avoid sending the UE-specific RS; as well as A second response message is received from the second network node, wherein the second response message includes information indicating confirmation of the information indicating that the third network node is configured to avoid sending the UE-specific RS.

3. The first network node according to claim 2, wherein the second request message further comprises: information indicating a request for transmission of a message instructing the UE to switch the beam to the target cell; as well as The second response message also includes: information indicating confirmation of the information of the message indicating the request to instruct the UE to switch the beam to the target cell.

4. The first network node according to any one of claims 1 to 3, wherein the first network node is further caused to: A first indication message is received from the second network node, where the first indication message includes: Information indicating switching of the beam of the UE to the target cell; as well as and sending a second indication message to the third network node to enable the third network node to start sending the UE-specific RS.

5. The first network node according to claim 4, wherein the first network node is further caused to: A third indication message is received from the third network node, where the third indication message includes: Information indicating transmission of the UE-specific RS; as well as A fourth indication message is sent, the fourth indication message comprising: information indicating the transmission of the UE-specific RS by the third network node.

6. The first network node according to any one of claims 1 to 5, wherein initiating the ICBM process is determined based on at least one of the following items: 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: Channel State Information Reference Signal CSI-RS.

8. The first network node according to any one of claims 1 to 7, wherein each of the source cell and the target cell is configurable to operate in at least one bandwidth part (BWP); and The first network node is further configured to: 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, wherein the third request message includes: information indicating a beam on the BWP of the target cell; and A third response message is received from the third network node, the third response message comprising information indicating a BWP configuration for the beam.

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

10. The first network node according to claim 9, wherein the first network node is further caused to: A message including information indicating the switching of the beam to the target DU is received from the second network node.

11. The first network node according to claim 9 or 10, wherein the first network node is further caused to: Sending a configuration message to the UE, the configuration message including: Information indicative of the BWP configuration for the beam.

12. A second network node, the second network node supporting at least one of a distributed unit DU function or a layer 2 protocol of a radio access network and configured with a source cell serving a user equipment UE, the second network node comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to at least: 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 comprising: information indicating a configuration of a beam for a target cell of a third network node, and information indicating that the third network node is configured to avoid sending a UE-specific reference signal (RS), the third network node supporting at least one of the DU function or the layer 2 protocol of the radio access network; and A first response message is sent to the first network node, wherein the first response message includes information indicating confirmation of the information indicating that the third network node is configured to avoid sending the UE-specific RS.

13. The second network node according to claim 12, wherein the second network node is further caused to: determining that a handover of the UE to the beam of the target cell is expected; and Sending a first indication message to the first network node, where the first indication message includes: Information indicating the handover to be expected.

14. The second network node according to claim 13, wherein the second network node is further caused to: A first measurement report is received from the UE, wherein determining that a handover of the UE to the beam of the target cell is to be expected is based on the first measurement report.

15. The second network node according to claim 13 or 14, wherein the second network node is further caused to: A second indication message is received from the first network node, the second indication message comprising information indicating transmission of the UE-specific RS by the third network node.

16. The second network node according to claim 14 or 15, wherein the second network node is further caused to: 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; and A message including information indicating a change in the transmission configuration indication (TCI) state corresponding to the target cell is sent to the UE.

17. The second network node according to any one of claims 12 to 16, wherein each of the source cell and the target cell is configurable to operate in at least one bandwidth part B WP, wherein the second network node is further caused to: A second request message is received from the first network node, where the second request message includes: Information indicating the BWP configuration of the beam for the target cell.

18. The second network node according to any one of claims 12 to 16, wherein each of the source cell and the target cell is configurable to operate in at least one bandwidth part B WP, wherein the second network node is further caused to: A third request message is received from the first network node, where the third request message includes: Information indicating a BWP configuration for the beam of the target cell, and information indicating a configuration for the second network to indicate when a switch to the beam of the target DU is expected.

19. The second network node according to claim 18, wherein the second network node is further caused to: determining that a switch of the beam to the target DU is expected; and Sending a third indication message to the first network node, where the third indication message includes: Information indicating that the beam to the target DU is to be expected.

20. A third network node, the third network node supporting at least one of a distributed unit DU function or a layer 2 protocol of a radio access network, the third network node comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the third network node to at least: 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 comprising: information indicating a beam of a target cell of the third network node, and information for configuring the third network node to avoid sending a UE-specific reference signal RS; configuring the third network node to avoid sending a UE-specific RS; and A first response message is sent to the first network node, wherein the first response message includes: information indicating that the third network node is configured to avoid sending the UE-specific RS.

21. The third network node according to claim 20, wherein the third network node is further caused to: A first indication message is received from the first network node, where the first indication message includes: information indicating that a handover of a user equipment UE served by a source cell of a second network node to the beam of the target cell is to be expected, the second network node supporting at least one of the DU functionality or the layer 2 protocol of the radio access network; Start sending the UE-specific RS; as well as A second indication message is sent to the first network node, the second indication message comprising information indicating confirmation of the expected handover.

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

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

24. The third network node according to claim 23, wherein the third network node is further caused to: A second request message is received from the first network node, where the second request message includes: Information indicating a beam on the BWP of the target cell; as well as A second response message is sent to the first network node, the second response message comprising: information indicating a BWP configuration for the beam.

25. A user equipment UE, comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the UE to 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 a radio access network, the configuration message comprising: information indicating a beam of a target cell of a third network node, and information indicating that the third network node is configured to avoid sending a UE-specific reference signal (RS), the third network node supporting at least one of a distributed unit (DU) function or a layer 2 protocol of the radio access network; monitoring the UE-specific RS; and Based on determining that the UE-specific RS is broadcast, a message including information indicating that the UE-specific RS is broadcast is sent to a second network node supporting at least one of the DU function or the layer 2 protocol of the radio access network.

26. A system comprising: The second network node according to any one of claims 12 to 20, the second network node supporting at least one of a distributed unit DU functionality or a layer 2 protocol of a radio access network; as well as A user equipment UE served by a source cell of the second network node.

27. A first network node, the 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 first network node comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to at least: 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 and 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 part (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, wherein the request message includes: information indicating the beam of the target cell; and A response message is received from the third network node, wherein the response message includes information indicating a BWP configuration for the beam.

28. A second network node, the second network node supporting at least one of a distributed unit DU function or a layer 2 protocol of a radio access network and configured with a source cell serving a user equipment UE, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by at least one processor, cause the second network node to at least: 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 comprising: information indicating a BWP configuration of a beam for a target cell of a third network node, the third network node supporting at least one of the DU function or the layer 2 protocol of the radio access network; or A request message is received from the first network node, the request message comprising information indicating a BWP configuration for the beam of the target cell and information indicating a configuration for the second network to indicate to the first network node when a switch to the beam of the target cell is expected.

29. A third network node, the third network node supporting at least one of a distributed unit DU function or a layer 2 protocol of a radio access network, the third network node comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the third network node to at least: 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 comprising: information indicating a beam on a BWP of a target cell of the third network node; and A response message is sent to the first network node, wherein the response message includes information indicating a BWP configuration for the beam.

30. A method of a first network node, the first network node supporting at least one of a Central Unit Control Plane (CU-CP) functionality or a Radio Access Network Layer 3 protocol, the method comprising: determining to initiate an inter-cell beam management (ICBM) procedure, the inter-cell beam management 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 and 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, wherein the first request message includes: information indicating a beam of the target cell, and information for configuring the third network node to avoid sending a UE-specific reference signal (RS); and A first response message is received from the third network node, wherein the first response message includes information indicating configuration of a beam used for the ICBM process and information indicating that the third network node is configured to avoid transmitting the UE-specific RS.

31. A method of a second network node, the second network node supporting at least one of a distributed unit DU function or a layer 2 protocol of a radio access network and configured with a source cell serving a user equipment UE, 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 protocol of the radio access network, the first request message comprising: information indicating a configuration of a beam for a target cell of a third network node, and information indicating that the third network node is configured to avoid sending a UE-specific reference signal (RS), the third network node supporting at least one of the DU function or the layer 2 protocol of the radio access network; and A first response message is sent to the first network node, wherein the first response message includes information indicating confirmation of the information indicating that the third network node is configured to avoid sending the UE-specific RS.

32. A method of a third network node, the third network node supporting at least one of a distributed unit (DU) functionality or a layer 2 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 protocol of the radio access network, the first request message comprising information indicating a beam of a target cell of the third network node and information for configuring the third network node to avoid sending a UE-specific reference signal (RS); configuring the third network node to avoid sending a UE-specific RS; as well as A first response message is sent to the first network node, wherein the first response message includes: information indicating that the third network node is configured to avoid sending the UE-specific RS.

33. A method of a first network node, the first network node supporting at least one of a Central Unit Control Plane (CU-CP) functionality or a layer 3 protocol of a radio access network, the method comprising: 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 and 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 part (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, wherein the request message includes: information indicating the beam of the target cell; and A response message is received from the third network node, wherein the response message includes information indicating a BWP configuration for the beam.

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

35. A method of a third network node, the third network node supporting at least one of a distributed unit (DU) functionality or a layer 2 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 functionality or a layer 3 protocol of the radio access network, the request message comprising information indicating a beam on a BWP of a target cell of the third network node; as well as A response message is sent to the first network node, wherein the response message includes information indicating a BWP configuration for the beam.

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

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

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