L1 beam measurement configuration for lower layer mobility

Abstract

SUMMARY [0003] Described herein is a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Layer 3 protocol of a radio access network, the first network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to at least: determine to prepare a target cell of a third network node for Lower Layer Mobility (LLM) with a source cell of a second network node, wherein each of the second network node and the third network node supports at least one of a Distributed Unit (DU) function or a Layer 2 protocol of the radio access network; obtain an association between a cell identifier of the target cell and a first identifier; and transmit a configuration message to a user equipment (UE) served by the source cell, the configuration message including information indicating the association between the cell identifier of the target cell and the first identifier.

Description

[Technical Field]

[0001] The present disclosure relates to lower layer (L1 / 2) mobility, and in particular to enhancing the configuration of L1 beam measurements for lower layer mobility. [Background technology]

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

[0003] Broadly speaking, L1 / 2 inter-cell mobility is one of the immediate goals for mobility enhancements in upcoming Third Generation Partnership Project (3GPP) releases (e.g., Release 18). In contrast to regular / traditional L3 mobility procedures, where handover between two cells is typically decided by the Radio Resource Control (RRC) layer, L1 / 2 inter-cell mobility is generally performed by the Medium Access Control (MAC) layer, which typically terminates in the Distributed Unit (DU) of a 5G / NR (New Radio) gNB.

[0004] For beam measurements (including procedures for switching between beams of the same cell), a channel state information (CSI) measurement configuration (sometimes simply referred to as "CSI-MeasConfig") is provided from the DU to the CU in a higher layer (e.g., RRC) configuration information element (IE), such as the ServingCellConfig IE, shared as an RRC container as part of an F1 (which is the interface between the CU and DU) message, such as a UE Context Setup Response message. In the prior art, a UE can only report L1 beam measurements of synchronization signal block (SSB) indices configured by the network in the CSI-SSB-ResourceSet configuration. Currently, the list of SSB indices is typically limited to 64 to accommodate UE capabilities, i.e., the UE can measure up to 64 indices simultaneously.

[0005] However, due to UE mobility, some SSB indices that were not part of the configured CSI-SSB-ResourceSet may become more relevant, and so the list of configured SSB indices may no longer be appropriate / valid for lower layer inter-cell mobility. On the other hand, as can be appreciated by those skilled in the art, continuous configuration of the CSI-SSB-ResourceSet will cause high signaling overhead over the radio and network interfaces, including: Over-the-air overhead: Updating the CSI-SSB-ResourceSet typically requires, for example, sending an RRC reconfiguration message from the network to the UE and a corresponding RRC reconfiguration complete from the UE to the network. · Overhead across network interfaces: To update the CSI-SSB-ResourceSet, the CU generally needs to coordinate the new configuration with the serving / source and target DUs across the F1 interface.

[0006] In addition to the signaling overhead, the UE may also be at risk of mobility failure (e.g., due to a failed cell change) if the CSI-SSB-ResourceSet update is not performed in a timely manner when the UE still has a good serving radio link.

[0007] It may also be beneficial to note that in L1 / 2 inter-cell mobility, compared to some techniques (such as inter-cell beam measurement (ICBM)) where the UE is typically configured with only one non-serving cell (or in other words, one target cell), the UE may be configured with multiple cells (e.g., up to eight or even more prepared target cells), which poses even more significant problems.

[0008] Therefore, there is a need to propose new measurement-related mechanisms / techniques for use in L1 / 2 (lower layer) inter-cell mobility management to address some or all of the challenges exemplified above, in particular in an efficient, flexible yet robust manner. Summary of the Invention

[0009] According to one aspect of the present disclosure, there is provided a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, the first network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to: determining to prepare a target cell of a third network node for lower layer mobility (LLM) with a source cell of a second network node, wherein each of the second network node and the third network node supports at least one of a distributed unit (DU) function or a radio access network Layer 2 (L2) protocol; obtaining an association between a cell identifier of the target cell and the first identifier; transmitting a configuration message to a user equipment (UE) served by the source cell, the configuration message including information indicating an association between a cell identifier of the target cell and the first identifier; A first network node is provided that causes:

[0010] In some examples, the first network node: The method is further caused to transmit a message to a third network node, the message including information indicating an association between a cell identifier of the target cell and the first identifier.

[0011] In some examples, the first network node: The method is further caused to receive information from a third network node indicating a number of synchronization signal block (SSB) indices configured in the target cell.

[0012] In some examples, the first network node: The method is further caused to transmit information indicating the number of SSB indices configured in the target cell to at least one of the second network node, the third network node, or the UE.

[0013] In some examples, the first identifier is a cell index for distinguishing between beam measurements of multiple different cells.

[0014] In some examples, obtaining an association between a cell identifier of the target cell and the first identifier includes: sending a request message to a second network node, the request message including information indicating a cell identifier of the target cell; receiving a response message from the second network node, the response message including information indicating an association between a cell identifier and a cell index of the target cell; Includes.

[0015] In some examples, obtaining an association between a cell identifier of the target cell and the first identifier includes: determining, by the first network node, an association between a cell identifier and a cell index of the target cell; The first network node The method is further caused to send a request message to a second network node, the request message including information indicating an association between a cell identifier and a cell index of the target cell.

[0016] In some examples, the first identifier is a configuration identifier associated with and for identifying a configuration of a prepared target cell used by the UE to perform a handover from the source cell.

[0017] In some examples, obtaining an association between a cell identifier of the target cell and the first identifier includes: determining, by the first network node, an association between a cell identifier of the target cell and a configuration identifier; The first network node The method is further caused to send a request message to a second network node, the request message including information indicating an association between the PCI of the target cell and the configuration identifier.

[0018] In some examples, the configuration message further includes information indicating a measurement related configuration.

[0019] In some examples, the measurement-related configuration includes information for configuring the UE to report the N strongest beam measurements of the prepared target cell without reference to the SSB index or the channel state information reference signal (CSI-RS) index included in the configuration message.

[0020] In some examples, the measurement-related configuration includes information for configuring the UE to make its own decisions regarding SSB indices that the UE will measure and report.

[0021] In some examples, the cell identifier is a physical cell identifier (PCI).

[0022] In some examples, the first identifier has a bit length that is shorter than that of the cell identifier.

[0023] 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, the second network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to: obtaining an association between the first identifier and a cell identifier of a target cell of a third network node supporting at least one of a DU function or a Layer 2 protocol of a radio access network, the target cell being prepared for Lower Layer Mobility (LLM) with a source cell of a second network node by 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; receiving a message from a user equipment (UE) served by the source cell, the message including information indicating a measurement report associated with at least one beam of the target cell and a first identifier; A second network node is provided that causes the

[0024] In some examples, the second network node is further caused to receive from the first network node information indicating the number of synchronization signal block (SSB) indices configured in the prepared target cell.

[0025] In some examples, the first identifier is a cell index for distinguishing between beam measurements of multiple different cells.

[0026] In some examples, obtaining an association between a cell identifier of the target cell and the first identifier includes: receiving a request message from a first network node, the request message including information indicating a cell identifier of a target cell; determining, by a second network node, an association between a target cell identifier and a cell index; Including, The second network node The method is further caused to send a response message to the first network node, the response message including information indicating the association between the target PCI and the cell index.

[0027] In some examples, obtaining an association between a cell identifier of the target cell and the first identifier includes: receiving a message from the first network node that includes information indicating an association between a cell identifier and a cell index of the target cell;

[0028] In some examples, the first identifier is a configuration identifier associated with and identifying a configuration of the target cell sent by the first network node to configure the UE for handover to the target cell; Obtaining an association between a cell identifier of the target cell and the first identifier includes: receiving a message from the first network node that includes information indicating an association between a cell identifier and a configuration identifier of the target cell;

[0029] In some examples, the second network node: generating a measurement-related configuration including information for configuring the UE to report N strongest beam measurements of the prepared target cell without reference to an SSB index or a Channel State Information Reference Signal (CSI-RS) index included in the measurement-related configuration; sending a message to a first network node, the message including information indicative of a measurement-related configuration; Further steps will be taken.

[0030] In some examples, the second network node: generating a measurement-related configuration including information for configuring the UE to make its own decisions regarding SSB indices that the UE will measure and report; sending a message to a first network node, the message including information indicative of a measurement-related configuration; Further steps will be taken.

[0031] In some examples, the message received from the UE further includes information indicating an index of an SSB detected by the UE for measurement of at least one beam of the target cell.

[0032] In some examples, the second network node is further caused to transmit a message including information indicating an instruction for the UE to switch from the source cell to the target cell.

[0033] In some examples, the cell identifier is a physical cell identifier (PCI).

[0034] In some examples, the first identifier has a bit length that is shorter than that of the cell identifier.

[0035] According to yet another aspect of the present disclosure, there is provided a user equipment (UE) served by a source cell of a second network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the second network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to perform at least: obtaining an association between the first identifier and a cell identifier of a target cell of a third network node supporting at least one of a DU function or a Layer 2 protocol of a radio access network; sending a message to a second network node, the message including information indicative of the measurement report associated with at least one beam of the target cell and the first identifier; A user equipment (UE) is provided that causes the

[0036] In some examples, the first identifier is a cell index for distinguishing beam measurements of a plurality of different cells, and obtaining an association between the cell identifier of the target cell and the first identifier includes: The method includes 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 an association between a cell identifier and a cell index of the target cell.

[0037] In some examples, the received configuration message is an RRC reconfiguration message that further includes a CSI measurement-related configuration suitable for supporting L1 / 2 mobility functionality and the number of SSB indices configured in the target cell, and the transmitted message is an L1 measurement report that includes information about the cell index, SSB index, and L1-RSRP.

[0038] In some examples, the first identifier is a configuration identifier for associating with and identifying a configuration of a target cell for handover by the UE, and obtaining the association between the cell identifier of the target cell and the first identifier includes: The method includes receiving, 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, a configuration message from the first network node, the configuration message including information indicating an association between a cell identifier and a cell index of the target cell.

[0039] In some examples, the received configuration message is an RRC reconfiguration message that further includes a CSI measurement-related configuration suitable for supporting L1 / 2 mobility functionality and the number of SSB indices configured in the target cell, and the transmitted message is an L1 measurement report that includes information regarding the configuration identifier, the SSB indices, and the L1-RSRP.

[0040] In some examples, the configuration message further includes information indicating a measurement-related configuration including information for configuring the UE to report the N strongest beam measurements of the target cell without referencing a synchronization signal block (SSB) index or a channel state information reference signal (CSI-RS) index included in the configuration message.

[0041] In some examples, the configuration message further includes information indicating a measurement-related configuration, including information for configuring the UE to make its own decisions regarding synchronization signal block (SSB) indices that the UE will measure and report.

[0042] In some examples, transmitting the message includes transmitting a message including information indicative of a measurement report associated with a strongest beam measurement value of the target cell.

[0043] In some examples, the configuration message further includes information indicating the number of SSB indices configured in the target cell.

[0044] In some examples, the message transmitted to the second network node further includes information indicating an index of the SSB detected by the UE for measurement.

[0045] In some examples, the UE The UE is further caused to receive a message from the second network node, the message including information indicating an instruction for the UE to switch from the source cell to the target cell.

[0046] In some examples, the cell identifier is a physical cell identifier (PCI).

[0047] In some examples, the first identifier has a bit length that is shorter than that of the cell identifier.

[0048] In yet another aspect of the present disclosure, a method of a first network node supporting at least one of a central unit control plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, comprising: determining to prepare a target cell of a third network node for lower layer mobility (LLM) with a source cell of a second network node, wherein each of the second network node and the third network node supports at least one of a distributed unit (DU) function or a radio access network layer 2 protocol; obtaining an association between a cell identifier of the target cell and the first identifier; transmitting a configuration message to a user equipment (UE) served by the source cell, the configuration message including information indicating an association between a cell identifier of the target cell and the first identification information; A method is provided, comprising:

[0049] 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, the method comprising: obtaining an association between the first identifier and a cell identifier of a target cell of a third network node supporting at least one of a DU function or a Layer 2 (L2) protocol of a radio access network, wherein the target cell is prepared for Lower Layer Mobility (LLM) with a source cell of a second network node by 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; receiving a message from a user equipment (UE) served by the source cell, the message including information indicative of a measurement report associated with at least one beam of the target cell and a first identifier; A method is provided, comprising:

[0050] According to yet another aspect of the present disclosure, there is provided a method for a user equipment (UE) served by a source cell of a second network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, the method comprising: obtaining an association between the first identifier and a cell identifier of a target cell of a third network node supporting at least one of a DU function or a Layer 2 (L2) protocol of a radio access network; sending a message to a second network node, the message including information indicative of the measurement report associated with at least one beam of the target cell and the first identifier; A method is provided, comprising:

[0051] According to some exemplary embodiments, a computer program product is also provided that includes instructions for causing an apparatus to perform the methods as disclosed in the present disclosure.

[0052] According to some exemplary embodiments, a memory storing computer readable instructions for causing the apparatus to perform the methods as disclosed in this disclosure is also provided.

[0053] Further, according to some example embodiments, there is provided a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, comprising respective suitable means configured to perform respective steps as disclosed in the present disclosure.

[0054] Similarly, according to some example embodiments, there is also provided a second network node and a third network node supporting at least one of a distributed unit (DU) function or a Layer 2 (L2) protocol of a radio access network, comprising respective suitable means configured to perform the respective steps as disclosed in the present disclosure.

[0055] Additionally, according to some other exemplary embodiments, a computer program product for, for example, a wireless communication device having at least one processor is provided, the computer program product including software code portions for performing each of the steps disclosed in the present disclosure when the product is run on the device. The computer program product may include a computer-readable medium on which the software code portions are stored. Furthermore, the computer program product may be directly loadable into the internal memory of a computer and / or transmittable over a network by using at least one of an upload procedure, a download procedure, and a push procedure.

[0056] Although some exemplary embodiments are described herein with particular reference to the above applications, it will be appreciated that the present disclosure is not limited to such fields of use but is applicable in a broader context.

[0057] In particular, it is understood that the methods according to the present disclosure relate to methods of operating the apparatus according to the above exemplary embodiments and various modifications thereof, and that each statement made with respect to the apparatus applies equally to the corresponding method, and vice versa, so that similar statements may be omitted for brevity. In addition, the above aspects may be combined in many ways, even if not explicitly disclosed. Those skilled in the art will understand that these combinations of aspects and features / steps are possible unless they create a contradiction that is expressly excluded.

[0058] Implementations of the disclosed apparatus may include, but are not limited to, using one or more processors, one or more application specific integrated circuits (ASICs), and / or one or more field programmable gate arrays (FPGAs). Implementations of the apparatus may also include using other conventional and / or customized hardware, such as software programmable processors, such as graphics processing unit (GPU) processors.

[0059] Other and further exemplary embodiments of the present disclosure will become apparent during the course of the following discussion and by reference to the accompanying drawings.

[0060] Example embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0061] [Figure 1] FIG. 2 is a schematic diagram illustrating an example of a signaling / messaging flow chart according to an exemplary embodiment of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram illustrating an example of a channel state information (CSI) measurement configuration according to an exemplary embodiment of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram illustrating an example of a CSI measurement-related configuration according to an exemplary embodiment of the present disclosure. [Figure 4] FIG. 10 is a schematic diagram illustrating another example of a signaling / messaging flow chart according to an exemplary embodiment of the present disclosure. [Figure 5] FIG. 10 is a schematic diagram illustrating another example of a signaling / messaging flowchart according to another exemplary embodiment of the present disclosure. [Figure 6] FIG. 10 is a schematic diagram illustrating a further example of a signaling / messaging flow chart according to yet another exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0062] In the following, several different exemplary embodiments will be described using a communication network architecture based on 3GPP standards for communication networks such as 5G / NR as an example of a communication network to which the example embodiments can be applied, but the embodiments are not limited to such an architecture. It will be apparent to those skilled in the art that the embodiments may also be applied to other types of communication networks in which mobile communication principles are integrated with D2D (device-to-device) or V2X (vehicle-to-everything) configurations, such as systems using SL (sidelink), e.g., Wi-Fi, Worldwide Interoperable Microwave Access (WiMAX), Bluetooth®, Personal Communications Services (PCS), ZigBee®, Wideband Code Division Multiple Access (WCDMA), Ultra-Wideband (UWB) technologies, Mobile Ad Hoc Networks (MANETs), wired access, etc. Furthermore, without loss of generality, the description of some example embodiments relates to a mobile communication network, but the principles of the present disclosure can be extended and applied to any other type of communication network, such as a wired communication network.

[0063] The following examples and embodiments should be understood as illustrative examples only. Although the specification may refer to "an," "one," or "some" examples or embodiments in some places, this does not necessarily mean that each such reference relates to the same example or embodiment, or that the feature applies only to a single example or embodiment. Single features of different embodiments may be combined to provide other embodiments. Furthermore, the words "comprising" and "including" should be understood as not limiting the described embodiments to consisting only of the recited features; such examples and embodiments may also include features, structures, units, modules, etc. that are not specifically recited.

[0064] A basic system architecture of a (tele)communication network, including a mobile communication system, to which some example embodiments are applicable, may include the architecture of one or more communication networks, including a wireless access network subsystem and a core network. Such architecture may include one or more communication network control elements or functions, access network elements, radio access network elements, access service network gateways or base transceiver stations, such as a base station (BS), an access point (AP), a NodeB (NB), an eNB or a gNB, a distributed unit (DU) or a centralized / central unit (CU), which control respective coverage areas or cells, thereby enabling one or more communication stations, such as a communication element or function, such as a user device or terminal device, such as a user equipment (UE), or another device having similar functionality, such as a modem chipset, chip, module, etc., which may be part of a station, element, function or application capable of communicating, such as a UE, element or function usable in a machine-to-machine communication architecture, or which may be attached as a separate element to such an element, function or application capable of communicating, to communicate over one or more channels via one or more communication beams for transmitting several types of data in multiple access domains. Additionally, core network elements or network functions may be included, such as gateway network elements / functions, mobility management entities, mobile switching centers, servers, databases, etc.

[0065] The following description may provide various details of alternatives, modifications and variations, where the gNB, for example, provides NR user plane and control plane protocol termination towards the UE and includes a node connected to the 5GC via an NG interface, for example in accordance with 3GPP TS 38.300 V16.6.0 (June 2021) Section 3.2, which is incorporated by reference.

[0066] The gNB Central Unit (gNB-CU) comprises a logical node that hosts, for example, the gNB's RRC, SDAP and PDCP protocols or the en-gNB's RRC and PDCP protocols that control the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface that is connected to the gNB-DU.

[0067] The gNB distributed unit (gNB-DU) comprises a logical node that hosts, for example, the RLC, MAC, and PHY layers of a gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0068] The gNB-CU-Control Plane (gNB-CU-CP) includes a logical node that hosts, for example, the control plane portion of the RRC and PDCP protocols of the en-gNB or gNB-CU of the gNB. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU.

[0069] The gNB-CU-User Plane (gNB-CU-UP) includes, for example, a logical node that hosts the user plane portion of the PDCP protocol of the gNB-CU of an en-gNB, as well as the user plane portions of the PDCP protocol and SDAP protocol of the gNB-CU of a gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, in accordance with Section 3.1 of 3GPP TS 38.401 V16.6.0 (July 2021), which is incorporated by reference.

[0070] For example, several different divisions of functions between the central unit and the distributed units are possible, referred to as options: Option 1 (1A-like division): o The functional division in this option is similar to the 1A architecture in DC: RRC is in the central unit; PDCP, RLC, MAC, physical layer and RF are in distributed units. Option 2 (3C-like division): o The functional division in this option is similar to the 3C architecture in DC: RRC and PDCP are in the central unit; RLC, MAC, physical layer and RF are in the distributed units. Option 3 (Intra-RLC Splitting): o Low RLC (partial functions of RLC), MAC, physical layer and RF are in the distributed units. PDCP and high RLC (other partial functions of RLC) are in the central unit. Option 4 (RLC-MAC Split): o MAC, physical layer and RF are in the distributed units. PDCP and RLC are in the central unit. Or otherwise, for example, according to 3GPP TR 38.801 V14.0.0 (March 2017) Section 11, which is incorporated by reference.

[0071] A gNB supports multiple different protocol layers, such as Layer 1 (L1) - the physical layer.

[0072] Layer 2 (L2) of NR is divided into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP), where, for example, o The physical layer provides transport channels to the MAC sublayer. o The MAC sublayer provides logical channels to the RLC sublayer. o The RLC sublayer provides the RLC channel to the PDCP sublayer. o The PDCP sublayer provides the radio bearer to the SDAP sublayer. ○ The SDAP sublayer provides QoS flows to the 5GC. o Comp. refers to header compression and Segm. refers to segmentation. Control channels include (BCCH, PCCH).

[0073] Layer 3 (L3) includes, for example, Radio Resource Control (RRC) according to 3GPP TS 38.300 V16.6.0 (June 2021) Section 6, which is incorporated by reference.

[0074] For example, a RAN (Radio Access Network) node or network node or portion thereof, such as a gNB, base station, gNB CU or gNB DU, may be implemented using an apparatus having at least one processor and / or at least one memory (with computer readable instructions (computer program)) configured to support and / or provide and / or process, for example, CU and / or DU related functions and / or features, and / or at least one protocol (sub)layer of the RAN (Radio Access Network), for example, Layer 2 and / or Layer 3.

[0075] The gNB CU and gNB DU portions may be co-located, for example, or physically separated. The gNB DU may further be divided, for example, into two portions, e.g., one portion including processing equipment and one portion including antennas. The central unit (CU) may also be referred to as a BBU / REC / RCC / C-RAN / V-RAN, O-RAN, or portions thereof. The distributed unit (DU) may also be referred to as an RRH / RRU / RE / RU, or portions thereof. Hereinafter, in various exemplary embodiments of the present disclosure, the CU-CP (or more generally, the CU) may also be referred to as a (first) network node supporting central unit control plane functions or at least one of Layer 3 protocols of the radio access network, and similarly, the DU may also be referred to as a (second) network node supporting distributed unit functions or Layer 2 protocols of the radio access network.

[0076] The gNB-DU supports one or more cells and may therefore, for example, serve as a serving cell for a user equipment (UE).

[0077] User equipment (UE) may include wireless or mobile devices, devices having a radio interface for interacting with a RAN (Radio Access Network), smartphones, in-vehicle devices, IoT devices, M2M devices, etc. Such UEs or devices may include at least one processor and at least one memory containing computer program code configured by the at least one processor to cause the device to perform at least certain operations, such as, for example, an RRC connection to the RAN. The UE is configured, for example, to generate messages (e.g., including a cell ID) to be transmitted over the air toward the RAN (e.g., to reach and communicate with a serving cell). The UE can generate, send, and receive RRC messages containing one or more RRC PDUs (Packet Data Units).

[0078] The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0 (June 2021) Sections 42.1 and 4.4, which are incorporated by reference).

[0079] A UE may, for example, be in either an RRC_CONNECTED state or an RRC_INACTIVE state when an RRC connection is established.

[0080] In the RRC_CONNECTED state, the UE: ○ Stores the AS context. ○ Transferring unicast data to and from the UE. o Monitor the control channel associated with the shared data channel to determine if data is scheduled for that data channel. o Provides channel quality and feedback information. ○ Perform neighbor cell measurements and measurement reporting.

[0081] The RRC protocol includes, for example, the following main functions: ○ RRC connection control Measurement configuration and reporting Establishing / modifying / releasing measurement configurations (e.g. intra-frequency, inter-frequency and inter-RAT measurements) ○ Measuring gap setup and release ○ Measurement report

[0082] The general functionality and interconnections of the described elements and functions, which also depend on the actual network type, are known to those skilled in the art and are described in the corresponding specifications, and as a result, detailed descriptions thereof may be omitted herein for the sake of brevity. However, several additional network elements and signaling links may be utilized for communication between elements, functions or applications, such as communication endpoints, servers, gateways, communication network control elements such as radio network controllers, and other elements of the same or other communication networks, in addition to those described in detail below.

[0083] The communications network architecture as considered in the example embodiments may also be capable of communicating with other networks, such as the public switched telephone network or the Internet. It should be noted that the communications network may also be capable of supporting the use of cloud services for virtual network elements or their functions, and that virtual network portions of a telecommunications network may also be provided by non-cloud resources, such as, for example, an internal network. Network elements, such as access systems, core networks, and / or their functions may be implemented by any nodes, hosts, servers, access nodes, or entities, etc., suitable for such use. In general, network functions may be implemented either as network elements on dedicated hardware, software instances running on dedicated hardware, or virtualized functions instantiated on a suitable platform, such as, for example, a cloud infrastructure.

[0084] Furthermore, as described herein, network elements such as communication elements like UEs, terminal devices, control elements or functions such as access network elements like base stations / BSs, gNBs, radio network controllers, core network control elements or functions such as gateway elements, or other network elements or functions, and any other elements, functions or applications may be implemented by software, e.g., by a computer program product and / or hardware of a computer. For performing their respective processing, the correspondingly used devices, nodes, functions or network elements may include several means, modules, units, components, etc. (not shown) required for control, processing and / or communication / signaling functions. Such means, modules, units and components may include, for example, one or more processors or processor units including one or more processing portions for executing instructions and / or programs and / or for processing data, storage or memory units or means (e.g., ROM, RAM, EEPROM, etc.) for storing instructions, programs and / or data to serve as working areas for the processors or processing portions etc., input or interface means (e.g., floppy disk, CD-ROM, EEPROM, etc.) for inputting data and instructions by means of software, user interfaces (e.g., screen, keyboard, etc.) for providing monitoring and operation capabilities to a user, other interfaces or means for establishing links and / or connections under the control of the processor units or portions (e.g., wired and wireless interface means, e.g., wireless interface means including antenna units, etc., means for forming wireless communication portions, etc.), and each means for forming an interface for a wireless communication portion, etc. may also be located at a remote site (e.g., radio head or radio station, etc.).It should be noted that, in this specification, a processing portion should not be considered solely as representing a physical portion of one or more processors, but may also be considered as a logical division of the referenced processing task performed by one or more processors. It should be appreciated that, according to some examples, a so-called "liquid" or flexible network concept may be utilized in which the operations and functions of a network element, network function, or another entity of the network may be flexibly implemented in different entities or functions, such as within a node, host, or server. In other words, the "division of labor" between the involved network elements, functions, or entities may vary from case to case.

[0085] As exemplified above, techniques related to L1 / 2 inter-cell mobility (or sometimes referred to as Lower Layer Mobility (LLM)) are one of the immediate mobility enhancement goals being considered, for example, in Third Generation Partnership Project (3GPP) Release 18. In contrast to (traditional) L3 mobility procedures, where handover procedures between two cells are typically determined by the RRC layer, L1 / 2 inter-cell mobility is generally performed by the MAC layer, which typically terminates in the DU of a 5G / NR gNB.

[0086] 1 shows a schematic diagram of one exemplary embodiment of a signaling diagram for L1 / 2 inter-cell mobility from a serving / source cell in DU1 (sometimes referred to as the source / serving DU) to a target cell in DU2 (sometimes referred to as the target DU), which may also be considered as an inter-DU, intra-CU scenario. The same diagram may also apply (with possible adaptations, if necessary) to the case of an intra-DU, intra-CU cell change / switch, where DU1 becomes the same as DU2. In such a case, DU1 (or DU2) may itself be referred to as both the source / serving cell and also the target cell.

[0087] In particular, the main steps of such an L1 / 2 inter-cell mobility procedure can be summarized as follows:

[0088] In step S101, the UE may send a measurement report containing, for example, cell quality measurements of the serving / source cell and also of neighboring cells. In some possible cases, the UE may be configured by the serving cell to send the measurement report early if it still has a good connection to the serving cell. This measurement report is received by DU1 (source / serving DU) and then further propagated to the CU (as illustrated in step S102).

[0089] Using the reported cell quality measurements, the CU can identify a potential set of candidate target cells (across neighboring cells controlled by the same or different DUs) to which the UE can be handed over. In this example as shown in Figure 1, the CU identifies candidate target cells served by DU1 (controlling the serving DU / cell) and by another DU2 controlled by the same CU.

[0090] In step S103, the CU may request the preparation of candidate target cells controlled by DU1, for example, by sending a UE context setup request message (or any other suitable message).

[0091] In step S104, DU1 may provide the configuration of the UE in a corresponding UE context setup response message (or any other suitable message) containing a DU-to-CU message container.

[0092] Similarly, steps S105 and S106 may also be performed by DU2 to prepare the target cell controlled by DU2.

[0093] Once the UE configuration for the candidate target cell is received (as illustrated in steps S104 and S106), the CU may generate an RRC reconfiguration message (or the like) in step S107 to be sent to the UE in step S108. Among other possible / appropriate information, the RRC reconfiguration message may include: L1 / 2 handover / mobility measurement reporting configurations, such as configurations on how to report L1 beam measurements of the serving cell and the target cell in step S110, and · Configuration of prepared candidate cells that the UE needs to perform when receiving a MAC CE command to change / switch serving cell (i.e. to perform handover), e.g. as shown in step S111.

[0094] After confirming the RRC reconfiguration to the network in step S109 (e.g., by sending a corresponding RRC reconfiguration complete message, etc.), the UE can now begin reporting (e.g., periodically, etc.) L1 beam measurements for the serving cell and candidate target cells, as shown in step S110.

[0095] Upon determining that there is a target candidate cell with better radio link / beam measurements than those of the serving cell (e.g., based on a determination that the L1-RSRP (Reference Signal Received Power) of the target beam measurements is greater than the L1-RSRP of the serving beam measurements, possibly plus an offset over a certain amount of time, such as, for example, Time-to-Trigger (TTT), or based on any other suitable criteria), the serving cell may send a MAC Control Element (MAC CE) or appropriate L1 message in step S111 to trigger a cell change / switch to the target candidate cell. In some possible cases, the MAC CE may include, for example, Transmission Configuration Indicator (TCI) state change information indicating the beam of the target candidate cell.

[0096] As a result of such a MAC CE or appropriate L1 message, a (lower layer) handover from the serving cell to the target cell is performed by the UE in step S112.

[0097] For beam measurements (including procedures for switching between beams of the same cell), the channel state information (CSI) measurement configuration (sometimes simply referred to as "CSI-MeasConfig") is provided from the DU to the CU in a higher layer (e.g., RRC) configuration information element (IE), such as the ServingCellConfig IE, shared as an RRC container (e.g., as shown with reference to steps S104 and S106 of Figure 1), as part of an F1 (which is generally the interface between the CU and DU) message, such as a UE Context Setup Response message.

[0098] Generally speaking, CSI-MeasConfig can be understood as encompassing CSI measurement related configurations, which may include, among other possibilities: CSI reporting related configurations, which contain, for example, example information on how the UE should report L1 beam measurements; and A CSI resource related configuration encompassing exemplary information for which the UE should report beam measurements for its reference signals (RS), e.g., synchronization signal blocks (SSBs) or CSI-RSs.

[0099] In the example as shown in FIG. 2, it can be seen that the exemplary CSI-MeasConfig encompasses two CSI reporting configurations associated with different RSs, namely SSB (left side) and CSI-RS (right side).

[0100] In 3GPP Release 17, the CSI measurement-related configuration was extended so that it may be enabled to report L1 beam measurements of non-serving cells, potentially to better support inter-cell beam management (ICBM), which allows a UE to be served by a (“borrowed”) beam from another cell. As a result of such an extension, the CSI-SSB-ResourceSet may also be extended to include the configuration of SSB indices that the UE should measure and use to report L1 beam measurements, as well as possibly the physical cell identifier (PCI) associated with each configured SSB index. An example of such a possible (extended) configuration is shown in Figure 3 (top diagram).

[0101] As can be understood and appreciated by those skilled in the art, the L1 beam measurements are typically provided by the UE to the network (e.g., the DU, or the CU via the DU) in a CSI-Report (or any other suitable format / message) that is part of the Uplink Control Information (UCI) sent by the UE over either the Physical Uplink Common Control Channel (PUCCH) or the Physical Uplink Shared Channel (PUSCH). An example of such a possible UCI is shown schematically in the bottom left diagram of FIG. 3.

[0102] In a broad sense, as also shown schematically in the bottom right diagram of FIG. 3, in some possible (non-limiting) examples, the CSI report may include the following elements (as shown schematically in the bottom right diagram of FIG. 3): Channel State Information Reference Signal Resource Indicator (CRI) or SS / PBCH Block Resource Indicator (SSB-RI). Generally, the length of the SSB-RI may depend on the number of SSB indices configured in the CSI-SSB-ResourceSet (as shown schematically in the upper diagram of Figure 3). As a simple example, if a total of 64 SSB indices are defined, the length of the SSB-RI will be 6 bits. RSRP of each CRI or SSB-RI. In some possible (non-limiting) embodiments, the RSRP of the first reported CRI or SSB-RI may be 7 bits in length, while the different RSRPs of the remaining, e.g., three, indexes (if reported) are 4 bits in length.

[0103] In the prior art, a UE can only report L1 beam measurements of synchronization signal block (SSB) indices configured by the network in the configuration of the CSI-SSB-ResourceSet. Currently, the list of SSB indices is typically limited to 64 to accommodate UE capabilities. In other words, the UE can theoretically measure up to 64 indices simultaneously. Furthermore, the maximum number N of reported L1 beam measurements is configured by the network. In the example of Figure 3, N is equal to 4, which is much smaller than the number of SSB indices configured in the CSI-SSB-ResourceSet.

[0104] However, due to UE mobility, for example, if it has higher received power at this point, some SSB indices that were not part of the configured CSI-SSB-ResourceSet may become more relevant, and the list of configured SSB indices may no longer be appropriate / valid for lower-layer inter-cell mobility. For example, the network can configure the UE to report an L3 measurement report to be sent to the CU. It may be useful to note that the L3 measurement configuration is completely separate from the CSI measurement configuration, which is generally controlled by the RRC and at least partially controlled by the MAC. The L3 measurement report may include cell quality measurements (derived by the UE based on beam measurements) and L3 beam measurements (L3 filtered L1 beam measurements). Using this measurement report, the network can know whether there are more relevant SSB indices and whether the CSI-SSB-ResourceSet needs to be updated. As a result, if the UE is not instructed to measure a specific SSB index set, the network may provide the UE with another L3 measurement configuration. However, as can be appreciated by those skilled in the art, continuous configuration of the CSI-SSB-ResourceSet will cause high signaling overhead over the radio and network interfaces, including: Over-the-air overhead: Updating the CSI-SSB-ResourceSet typically requires, for example, sending an RRC reconfiguration message from the network to the UE and a corresponding RRC reconfiguration complete from the UE to the network. · Overhead across network interfaces: To update the CSI-SSB-ResourceSet, the CU generally needs to coordinate the new configuration with the serving / source and target DUs across the F1 interface.

[0105] In addition to the signaling overhead, the UE may also be at risk of mobility failure (e.g., due to a failed cell change) if the CSI-SSB-ResourceIndex update is not performed in a timely manner when the UE still has a good serving radio link.

[0106] Furthermore, it may also be useful to mention that compared to some techniques (such as inter-cell beam management (ICBM)) where the UE is typically configured with only one non-serving cell (or in other words, one target cell), in L1 / 2 inter-cell mobility the UE may be configured with multiple cells (e.g., up to eight or even more prepared target cells), which poses even more significant problems. That is, depending on various implementations, the CU may be configured to fetch configurations of up to eight (potential) target cells from various DUs and send those configurations to the UE (for L1 measurements and subsequent switching / mobility).

[0107] Generally speaking, therefore, the present disclosure may be seen as seeking to propose techniques / mechanisms for configuring network nodes (and UEs) to support L1 / 2 mobility (also referred to as Lower Layer Mobility (LLM)) to address at least some or all of the challenges exemplified above.

[0108] In broad aspects, according to some exemplary embodiments, the present disclosure generally proposes that the network (CU and / or DU) can configure a UE to report N (e.g., one, two, four, or any other suitable number) strongest L1 beam measurements of a set of prepared target cells without referring to an explicit list of SSB (or CSI-RS) indices (SSB-RI or CRI) for measurement. Herein, depending on various circumstances and / or requirements, in some possible implementations, the decision and judgment regarding which relevant SSB (or CSI-RS) to measure from among those detected may be left to the UE implementation. More specifically, according to some possible (but non-limiting) implementations, the UE may make a completely independent decision regarding which SSB indices to measure and report.

[0109] The list of target cells to be measured by the UE (e.g., up to eight) can be fixed and correspond to cells prepared for L1 / 2-centric mobility. This cell list can be updated by the CU, e.g., based on L3 measurement reports, to prepare new target cells, replace or remove target cells, for example.

[0110] According to some other possible (but non-limiting) embodiments, the number Q of SSB indices to measure and use for L1 beam measurement reporting may still be lower than 64 (or any other suitable maximum number of SSB indices configured by higher layers), such that Q + M = 64, where M generally refers to the number of SSB indices the UE is configured to measure by the network in the CSI-SSB-ResourceSet, as described above. As a concrete example for understanding, Q may be configured as 24. Then, for the remaining M = 64 - 24 = 40 measurements, the measurement configuration and reporting provided by the network as described above may be applied, while for the remaining Q = 24 measurements, the UE may determine what to measure and report according to various embodiments, for example, to capture unconfigured SSBs that have become stronger in between. According to some further possible (but non-limiting) embodiments, the UE may be configured to measure up to 64 SSB indices configured by the network, plus another number Q of the strongest L1 beam measurements (e.g., of unconfigured SSB indices). When configured as suggested above, the UE can still meet the maximum UE capability of simultaneously measuring up to 64 SSB indices as configured / required according to the above standardization.

[0111] In the report, generally speaking, the UE may include a suitable (cell-specific) identifier to enable the serving DU to distinguish between L1 beam measurements of multiple different cells, where the cell identifier may be determined / designed to be associated with each prepared cell (e.g., identified by a PCI or any other suitable identifier / ID available within the gNB or globally throughout the network). This has the advantage that the UE may be able to send only 3 bits for the cell identifier (e.g., for up to a maximum of 8 prepared target cells) (or any other suitable number of bits, depending on the total number of cells to be distinguished from, as the case may be) instead of a usual / typical much longer per-cell or per-network identifier (e.g., 10 bits for a PCI). Of course, depending on various implementations and / or requirements, any other suitable (existing or new) identifier (having a shorter length compared to a usual / typical cell identifier, such as a PCI) may be considered (or proposed) as long as it can be used to enable the network nodes (e.g., the CU and DU) and the UE to distinguish between L1 beam measurements of multiple different cells.

[0112] In a broad sense, the present disclosure generally proposes three different possible exemplary methods for coordinating appropriate (cell-specific) identifiers (e.g., cell indexes or the like, such as PCIs) among UEs, CUs, and (serving DUs and target DUs), which will now be described in more detail with reference to the drawings. Identical or similar reference symbols used in the drawings of the present disclosure may refer to identical or similar elements unless otherwise indicated. Similarly, it should also be noted that identical or similar messages (and content contained therein) used in the drawings of the present disclosure may refer to identical or similar messages (and content therein) unless otherwise indicated, and as a result, repeated descriptions thereof may be omitted for the sake of brevity.

[0113] First, FIG. 4 illustrates, in schematic form, another example of a signaling / messaging flowchart according to some exemplary embodiments of the present disclosure.

[0114] Generally, it can be seen that in the exemplary embodiment of Figure 4, the (source) DU is configured to determine a cell identifier (here, a cell index) to distinguish between the L1 measurements of the cells. It is therefore the DU that is responsible for associating the PCI of the prepared target cell (or any other suitable cell identifier available, for example, within the gNB or globally throughout the network) with the cell index. Of course, in such a case, the DU would also need to provide the determined association between the cell index and the PCI to the CU, which may send this association to the UE (and to other DUs, if necessary).

[0115] More specifically, in steps S401 and S402, the UE may report measurements to the source / serving DU (DU1), which may then also propagate such measurement reports to the CU (similar to steps S101 and S102 in FIG. 1).

[0116] Based on the measurement report, the CU may then decide in step S403 to identify a (target) cell (or a set of possible target cells) within DU2 (or, in some possible implementations, even within DU1) and prepare it to enable L1 / 2 inter-cell mobility.

[0117] Similar to steps S103 and S104 or steps S105 and S106 of FIG. 1, the CU may then request the preparation of candidate target cells controlled by DU2, for example by sending a UE context setup request message (or any other suitable message), and in return receive the configuration in a corresponding UE context setup response message (or any other suitable message) containing a message container from the DU to the CU.

[0118] In step S406, the CU may send the PCI of the prepared target cell (e.g., received from the DU or obtained by the CU by using any other suitable means) to DU1. This information may be sent from the CU to DU1 in (e.g., as part of) any suitable message, such as a CSI measurement configuration request message as illustrated in step S406.

[0119] When such a CSI measurement configuration request is received from the CU, DU1 can be configured to generate a CSI measurement configuration to support L1 / 2 inter-cell mobility in step S407. Specifically, as exemplified above, DU1 can generate a configuration to instruct / configure / enable the UE to report N strongest L1 beam measurements of the prepared target cell without explicitly indicating the SSB / CSI-RS indexes configured by higher layers.

[0120] In addition, in this exemplary embodiment, DU1 also determines in step S408 an association between the PCI (received from the CU in step S406) and a cell index (designed in a manner suitable for enabling distinction between measurements of multiple different cells, as exemplified above). Depending on various implementations and / or requirements, such association may be determined by any suitable means. For example, a (predetermined or preconfigured) mapping function / algorithm or a look-up table (LUT) may be used to map the PCI (10 bits) to an appropriate cell index (e.g., 3 bits, generally determined based on the number of cells to be distinguished). Of course, as can be understood and appreciated by those skilled in the art, any other suitable means may be used as long as the cell measurements can be appropriately identified.

[0121] Once an association between a PCI and a cell index is created / generated, such association is propagated to the CU, as shown in step S409. In some possible implementations, for example, to support dynamic switching between prepared target cells (or between a target cell and the original source / serving cell), this association information may also be propagated further to DU2 (and other appropriate DUs, if deemed necessary), as exemplarily shown in step S410.

[0122] The CU then generates an RRC reconfiguration message (or the like) and sends it to the UE in step S411 (similar to step S108 in FIG. 1 ). As illustrated above, such a configuration message may include CSI measurement-related configuration suitable for supporting L1 / L2 mobility functionality. Furthermore, the association between the PCI and cell index generated by DU1 may also be signaled by the CU in this configuration message (or in any other appropriate manner). Although not explicitly shown in the drawings, as can be understood and appreciated by those skilled in the art, it may also be beneficial to note that the configuration for the UE to report the N strongest L1 beam measurements of the prepared target cell without explicitly indicating the SSB / CSI-RS index configured by higher layers (in step S407) is also propagated from DU1 to the CU (e.g., as part of a CSI measurement configuration response message or in any other appropriate message) and then from the CU to the UE (e.g., as part of an RRC reconfiguration message or in any other appropriate message).

[0123] The above process, in particular steps S403-S409, may be repeated for multiple target cells (e.g., PCells (PCells) and / or PSCells (PS cells)) that are prepared for L1 / 2 inter-cell mobility, thereby generating a list of associations between PCIs and cell indices of target cells, with one cell index associated with one target cell. The configurations of all prepared target cells may be combined by the CU into one collective measurement configuration and sent in one RRC reconfiguration message, or the CU may send respective RRC reconfiguration messages containing the respective measurement configurations of the target cells whenever the CU prepares the target cells.

[0124] As a result, the UE can start reporting L1 beam measurements (e.g., periodically, aperiodically, etc.) at this point, as shown in step S412. At this point, the UE can report, along with the L1-RSRP, at least a cell index (for the DU to identify the corresponding target cell) and an SSB index for identifying the corresponding beam. More specifically, in the CSI report (containing the L1 beam measurements), the UE can report the SSB index detected by the physical layer instead of the SSB-RI, which generally refers to the active index (entry index) of the SSB configured in the CSI-SSB-ResourceSet configuration as illustrated above with reference to FIG. 3. This SSB index is necessary because, in the proposed embodiment, the network does not dictate a specific list of SSB indices to measure and therefore cannot use the SSB-RI (used in conventional techniques).

[0125] Finally, similar to step S111 of FIG. 1, if it is determined that there is a target candidate cell that has better radio link / beam measurements than that of the serving cell (e.g., based on determining that the L1-RSRP of the target beam measurements is greater than the L1-RSRP of the serving beam measurements, or based on any other suitable criteria), DU1 may send an appropriate MAC CE (or L1 message) in step S413 to trigger a cell change / switch to the target candidate cell.

[0126] In some possible implementations, the CSI report can be further enhanced to potentially minimize the number of bits used to report the SSB index associated with the target cell index. For example, as an illustrative (non-limiting) example, the CU can request a DU (such as DU2 in the example of FIG. 4, which controls the prepared target cell) to provide the number of RS indices (e.g., SSB indices) supported in the prepared target cell. This information, i.e., the number of SSB indices of the target cell, can be sent to the CU as part of an exemplary UE context step response message as shown in step S405 (or in any other suitable manner). This information can also be propagated to the serving DU (i.e., DU1 in the present example of FIG. 4), other appropriate target DUs as needed, and the UE (as illustratively shown as part of steps S406, S410, and S411), which can derive, based on such information, the number of bits that can be allocated to reporting the SSB index of each prepared target cell (e.g., as shown in step S412).

[0127] 5 schematically illustrates another example of a signaling / messaging flowchart according to some other exemplary embodiments of the present disclosure. As mentioned above, the same or similar reference symbols or messages (and the contents contained therein) used in the drawings of the present disclosure may refer to the same or similar element messages (and the respective contents therein) unless otherwise indicated, and as a result, repeated descriptions thereof may be omitted for the sake of brevity.

[0128] Roughly speaking, it can be seen that in the exemplary embodiment of Fig. 4, the CU is now configured to determine the cell index in order to distinguish the L1 measurements of the cells. It is therefore also the CU that is responsible for associating the PCI of the prepared target cell (or any other per-cell or per-network cell identifier as exemplified above) with the respective cell index. Of course, in such a case, the CU will need to provide the determined association between cell index and PCI to the (source) DU and the UE (and also to other (target) DUs, if necessary).

[0129] More specifically, as can be seen, the exemplary embodiment as shown in FIG. 5 is essentially the same as that shown in FIG. 4, except that instead of DU1 being configured to associate PCIs with cell indices (step S408), here the CU is configured to determine the association between the PCIs of the prepared target cells and the respective cell indices (as exemplarily shown in step S506 of FIG. 5).

[0130] Again, the above process may be repeated for multiple target cells (e.g., PCells (PCells) and / or PSCells (PS cells)) that are prepared for L1 / 2 inter-cell mobility, thereby generating a list of associations between PCIs and cell indices of the target cells, with one cell index associated with one target cell. The configurations of all prepared target cells may be combined by the CU into one collective measurement configuration and sent in one RRC reconfiguration message, or the CU may send respective RRC reconfiguration messages containing the respective measurement configurations of the target cells whenever the CU prepares a target cell.

[0131] Finally, Figure 6 schematically illustrates yet another example of a signaling / messaging flowchart according to some further exemplary embodiments of the present disclosure. As mentioned above, the same or similar reference symbols or messages (and the contents contained therein) used in the drawings of the present disclosure may refer to the same or similar element messages (and the respective contents therein) unless otherwise indicated, and as a result, repeated descriptions thereof may be omitted for the sake of brevity.

[0132] Broadly speaking, it can be seen that in the exemplary embodiment of FIG. 6, the CU is configured to determine the association of the PCI (or any other per-cell or per-network cell identifier) ​​of the prepared target cell. However, in this exemplary embodiment, instead of using a (newly introduced) cell index, a configuration identifier (ID) (which, like the cell index, is generally shorter compared to other cell identifiers such as the PCI) associated with the configuration of the prepared target cell is (re)used to identify the L1 beam measurements reported by the UE for the target cell. The prepared target cell configuration is used by the UE to perform a handover from the source cell to the target cell. Depending on various implementations and / or requirements, such configuration identifier may pre-exist, pre-configured, predetermined, or configured for the UE, as shown in step S611, etc., as long as the network nodes (CU and DU) and the UE, as the case may be, are able to identify or distinguish measurements of multiple different cells using such configuration identifier.

[0133] As a specific example (which should not be understood as any kind of limitation), in an exemplary embodiment as shown in FIG. 6 , the CU can associate the PCI of a prepared target cell with a so-called “reconfiguration ID,” which itself is associated with the configuration of the target cell used by the UE to perform a handover from the source cell to the target cell, as shown in step S606. Therefore, depending on various implementations, such a “reconfiguration ID” may have multiple different names, as can be understood and appreciated by those skilled in the art. Because the CU can prepare multiple target cells for L1 / 2-centric mobility (using steps S604 and S605), a different reconfiguration ID is associated with each target cell configuration. Upon receiving a MAC CE command from DU1, the UE applies one of the target cell configurations, as shown in step S613. The CU also sends the reconfiguration ID of the prepared target cell with a given PCI to the UE along with the corresponding target cell configuration in step S611. In this example, it can be generally assumed that the reconfiguration ID itself may be sufficient for the UE to possibly associate measurements with the respective cells, such that an explicit and complete association between the PCI and the reconfiguration ID may not be necessary. For example, the UE may decode the target cell configuration associated with the reconfiguration ID to derive the PCI of the target cell. In this case, the PCI is not explicitly signaled by the CU in step S611 but is obtained by the UE by decoding the target cell configuration. However, in some other examples, it may be possible for the CU to send an explicit and complete association between the PCI and the reconfiguration ID in the RRC reconfiguration message. On the other hand, when reporting measurements in step S612, the UE may now report the reconfiguration ID together with the L1-RSRP measurements (and possibly also an SSB index to identify the beam) instead of indicating the cell index (as in the exemplary embodiments of FIGS. 4 and 5).Such reconfiguration ID can then be used by DU1 (or any other suitable DU, if desired) to identify the corresponding cell with which this L1 measurement is associated (since such association, i.e., between PCI and reconfiguration ID, has already been signaled by the CU in step S607).

[0134] Similar to before, the above process may be repeated for multiple target cells (e.g., PCells (PCells) and / or PSCells (PS cells)) that are being prepared for L1 / 2 inter-cell mobility, thereby generating a list of associations between cell configurations and cell identifiers for the target cells, with one cell identifier being associated with one target cell. The configurations of all prepared target cells may be combined by the CU into one collective measurement configuration and sent in one RRC reconfiguration message, or the CU may send respective RRC reconfiguration messages containing the respective measurement configurations of the target cells whenever the CU prepares a target cell.

[0135] For the sake of completeness, it should be noted that in any of the exemplary embodiments as described above with reference to Figures 4 to 6, in the event of a release or replacement of a target cell, the UE may generally be configured to release and / or replace the cell index corresponding to the target cell being released or replaced.

[0136] It should also be noted that even though in the exemplary embodiments of Figures 4-6 it may be considered that the association between the (longer) PCI (or any other per-cell or per-network cell identifier) ​​and the appropriate (shorter) identifier (such as either a cell index or a reconfiguration ID) is propagated between the network node and the UE at a particular timing / sequence, this does not necessarily have to be the case all the time. Depending on various implementations and / or requirements, such an association between the PCI of the prepared cell and the cell index (or reconfiguration ID) can also be sent at a later (or even earlier) point in time, such as upon a cell change trigger.

[0137] It can be appreciated that only examples of cell index or reconfiguration ID are given, but it is further noted that any other suitable identifier may also be employed as long as that identifier is capable of enabling the network node and the UE to identify and distinguish between measurements of possibly multiple different cells, as can be understood and appreciated by those skilled in the art.

[0138] To summarize the above, once the network is configured as proposed above, it generally does not need to maintain proper configuration of SSB indices anymore for L1 / 2 inter-cell mobility. As a result, mobility failures caused by possible misconfiguration of SSB indices can be avoided, thereby saving the signaling overhead associated with RRC reconfiguration for configuring / updating the list of SSB indices and also reducing the signaling overhead associated with reporting PCI (10 bits) for each L1-RSRP.

[0139] According to another aspect of the present disclosure, the CU allocates a temporary dynamic mapping table for reporting cell id+related measurements. The table includes coding with a shorter length compared to normal PCI to identify the measured cell and reduce signaling traffic, for example, in the following exemplary procedure:

[0140] The UE sends the L3 measurements of the (strongest) detected cells to the CU. The CU selects some (e.g., eight) cells to be further measured by the UE, e.g., the eight strongest cells and / or the best available cell, taking into account load conditions, etc. The CU can report this to the DU for LLM. Each of the eight selected cells has its own physical cell identification PCI number, e.g., PC1, PC2, ..., PCI8. Each PCI typically has a length of 10 bits. This requires that 80 bits are already transmitted by the UE to identify the cell (+ associated measurement results transmitted by the UE).

[0141] For example, new cell ids are allocated for measurement purposes only, resulting in less signaling traffic; for example, if eight cells are measured, only three bits are needed to distinguish between the eight cells.

[0142] 001-PCI1

[0143] 010-PCI2

[0144] 100-PCI3

[0145] ...

[0146] 111-PCI8

[0147] This cell list can be updated by the CU, e.g., based on L3 measurement reports, to prepare new target cells, replace or delete target cells, etc. For example, if PCIs 1 to 5 still need to be measured, but PCIs 6 to 8 need to be replaced by PCIs 9 to 11, a new updated allocation is provided, e.g., as follows:

[0148] 001-PCI1

[0149] 010-PCI2

[0150] 100-PCI3

[0151] ...

[0152] 101-PCI9

[0153] 110-PCI10

[0154] 111-PCI11

[0155] By using only 3 bits (instead of 10 bits) to identify the 8 cells to be measured (+ the associated measurement results transmitted by the UE), only 24 bits are required to be transmitted by the UE instead of 80 bits, thus significantly reducing signaling.

[0156] For example, if more than eight cells are measured, such as up to 16, four bits may be used for encoding.

[0157] If the UE wishes to report unconfigured / unprepared cells, it may use, for example, normal PCI and aperiodic L1 or L3 measurement reports.

[0158] According to another exemplary procedure, the UE sends L3 measurements of the (strongest) detected cell to the CU. The CU selects several (e.g., eight) cells to be further measured by the UE, e.g., the eight strongest cells and / or the best available cell, taking into account load conditions, etc. The CU configures the UE to report on the eight cells in a (pre)determined order, e.g., PCI1, PCI2, ..., PCI8. The UE then sends measurement reports with measurements related to PCI1 first, then measurements related to PCI2, etc. The DU (or CU) then essentially knows which measurements refer to which cells from the received reports. In this case, even a 3-bit cell identifier is not necessary. In this case, the UE only needs to always report a predefined number of measurements for each prepared cell. Otherwise, the network would not know how to interpret the results.

[0159] To allow for more flexible reporting of varying numbers of measurements, the following variation of the procedure can be adopted.

[0160] If the UE reports measurements for, for example, only seven cells, the non-reported cells can for example be marked as "not measured" (e.g. by XXX), so that no misinterpretation occurs at the receiving side. The (predefined) reporting protocol may then include, for example, a measure1 bit, a measure2 bit, ... A report on the actual measurements for cell1, cell2 (not reported), cell3, ... may include:

[0161] 01010100111, XXXXXXXXXXX, 11001100110,...

[0162] XXXXXXXXXXX=cell2 may be a reserved bit used to indicate that no measurements are to be reported, e.g., a predefined sequence, e.g., 00000000000, 11111111111, 10101010101, ... Alternatively, if there are no actual measurements available, the previous measurements may be reported again.

[0163] Alternatively, an additional flag (1 bit) may also be used to indicate whether the actual measurement is being reported or not.

[0164] According to another exemplary procedure, the network associates the PCI of a prepared target cell with a cell identifier (as described above). The network configures the UE to report X L1 beam measurements of the prepared target cell whose PCI is associated with a cell identifier in a predefined sequence, such as two beam measurements for each cell, X=2, starting with the cell with the smallest cell identifier (or conversely from largest cell identifier to smallest), or in any predefined sequence dictated by the network. The DU implicitly derives the association between the reported L1 beam measurements and the PCI using the predefined sequence for reporting the beam measurements. If the UE skips measurements of one prepared cell, it can indicate this to the network using a flag or a predefined sequence, as described above.

[0165] Finally, it should nevertheless be noted that, although in the exemplary embodiments illustrated above (with reference to the drawings), the messages communicated / exchanged between network components / elements may be considered to have specific / explicit names, depending on various implementations (e.g., underlying technologies), these messages may have different names and / or may be communicated / exchanged in different forms / formats, as can be understood and appreciated by those skilled in the art.

[0166] According to some example embodiments, corresponding methods suitable to be performed by devices (network elements / components) such as those mentioned above, such as a UE, a CU, a DU, etc., are also provided.

[0167] It should also be noted that features of the above-described apparatus (devices) may not be explicitly described for the sake of brevity, but correspond to features of the respective methods. The disclosure herein is considered to extend to such method features as well. In particular, the disclosure is understood to relate to methods of operating the above-described devices and / or the provision and / or arrangement of the respective elements of these devices.

[0168] Additionally, according to some further exemplary embodiments, there is also provided a respective device (e.g., implementing a UE, CU, DU, etc. as described above) comprising at least one processing circuit and at least one memory for storing instructions executed by the processing circuit, the at least one memory and instructions configured to cause the respective device to perform at least a respective step as described above, by the at least one processing circuit.

[0169] Furthermore, according to some other exemplary embodiments, there is provided a respective apparatus (e.g., implementing a UE, CU, DU, etc. as described above) comprising respective means configured to perform at least the respective steps as described above.

[0170] It should be noted that the example embodiments of the present disclosure are applicable to a variety of different network configurations. In other words, the examples shown in the above figures, which are used as the basis for the above examples, are merely illustrative and do not limit the present disclosure in any way. That is, additional and further existing and proposed new features available within the corresponding operating environment may be used with the example embodiments of the present disclosure based on the defined principles.

[0171] The disclosed exemplary embodiments can be implemented in many ways using hardware and / or software configurations. For example, the disclosed embodiments may be implemented using dedicated hardware and / or hardware in association with software executable thereon. The components and / or elements in the figures are merely examples and do not limit the scope of use or functionality of any hardware, software in combination with hardware, firmware, embedded logic components, or combinations of two or more such components, implementing particular embodiments of the present disclosure.

[0172] It should further be noted that the present specification and drawings merely illustrate the principles of the present disclosure. Those skilled in the art will be able to implement various configurations that embody the principles of the present disclosure and are within its spirit and scope, even if not explicitly described or shown herein. Moreover, all examples and embodiments outlined in this disclosure are expressly intended to be solely for illustrative purposes to aid the reader in understanding the principles of the proposed method, in principle. Furthermore, all statements herein providing principles, aspects, and embodiments of the present disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.

Claims

1. a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Radio Access Network Layer 3 protocol, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to: determining to prepare a target cell of a third network node for Lower Layer Mobility, LLM, with a source cell of a second network node, wherein each of the second network node and the third network node supports at least one of a distributed unit, DU, function or a Layer 2 protocol of the radio access network; obtaining an association between a cell identifier of the target cell and a first identifier; sending a configuration message to a user equipment, UE, served by the source cell, the configuration message including information indicating the association between the cell identifier of the target cell and the first identifier; A first network node causing

2. The first network node 2. The first network node of claim 1, further configured to: send a message to the third network node, the message including information indicating the association between the cell identifier of the target cell and the first identifier.

3. The first network node 3. The first network node of claim 1 or 2, further adapted to receive from the third network node information indicating the number of synchronization signal block, SSB, indices configured in the target cell.

4. The first network node 4. The first network node of claim 3, further configured to transmit the information indicating the number of SSB indices configured in the target cell to at least one of the second network node, the third network, or the UE.

5. The first network node according to any one of claims 1 to 4, wherein the first identifier is a cell index for distinguishing between beam measurements of a plurality of different cells.

6. The obtaining of the association between the cell identifier of the target cell and the first identifier comprises: sending a request message to the second network node, the request message including information indicating the cell identifier of the target cell; receiving a response message from the second network node, the response message including information indicating the association between the cell identifier and the cell index of the target cell; 6. The first network node according to claim 5, comprising:

7. The obtaining of the association between the cell identifier of the target cell and the first identifier comprises: determining, by the first network node, the association between the cell identifier and the cell index of the target cell; The first network node 6. The first network node of claim 5, further configured to: send a request message to the second network node, the request message including information indicating the association between the cell identifier and the cell index of the target cell.

8. The first network node according to any one of claims 1 to 4, wherein the first identifier is a configuration identifier associated with and for identifying a configuration of the prepared target cell used by the UE to perform a handover from the source cell.

9. The obtaining of the association between the cell identifier of the target cell and the first identifier comprises: determining, by the first network node, the association between the cell identifier of the target cell and the configuration identifier; The first network node 9. The first network node of claim 8, further configured to: send a request message to the second network node, the request message including information indicating the association between the cell identifier and the configuration identifier of the target cell.

10. The first network node according to any one of claims 1 to 9, wherein the configuration message further comprises information indicating a measurement-related configuration.

11. The first network node of claim 10, wherein the measurement-related configuration includes information for configuring the UE to report N strongest beam measurements of the prepared target cell without reference to an SSB index or a channel state information reference signal, CSI-RS, index included in the configuration message.

12. 12. The first network node according to claim 10 or 11, wherein the measurement related configuration comprises information for configuring the UE to make its own decisions regarding SSB indices that it measures and reports.

13. The first network node according to any one of claims 1 to 12, wherein said cell identifier is a physical cell identifier, PCI.

14. The first network node according to any one of claims 1 to 13, wherein the first identifier has a bit length that is shorter than a bit length of the cell identifier.

15. a second network node supporting at least one of a distributed unit, DU, function or radio access network Layer 2 protocol, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network and the first identifier, wherein the target cell is prepared for Lower Layer Mobility, LLM, with a source cell of the second network node by 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; receiving a message from a user equipment (UE) served by the source cell, the message including information indicative of a measurement report associated with at least one beam of the target cell and the first identifier; a second network node that causes the

16. The second network node 16. The second network node of claim 15, further configured to receive from the first network node information indicating the number of synchronization signal block, SSB, indices configured in the prepared target cell.

17. 17. The second network node according to claim 15 or 16, wherein the first identifier is a cell index for distinguishing between beam measurements of different cells.

18. The obtaining of the association between the cell identifier of the target cell and the first identifier comprises: receiving a request message from the first network node, the request message including information indicating the cell identifier of the target cell; determining, by the second network node, the association between the cell identifier and the cell index of the target cell; The second network node 18. The second network node of claim 17, further configured to: send a response message to the first network node, the response message including information indicating the association between the cell identifier and the cell index of the target cell.

19. The obtaining of the association between the cell identifier of the target cell and the first identifier comprises:

18. The second network node of claim 17, comprising receiving a message from the first network node including information indicating the association between the cell identifier and the cell index of the target cell.

20. the first identifier is a configuration identifier associated with and identifying a configuration of the target cell sent by the first network node to configure the UE for handover to the target cell; The obtaining of the association between the cell identifier of the target cell and the first identifier comprises:

17. The second network node of claim 15 or 16, comprising receiving from the first network node a message including information indicating the association between the cell identifier and the configuration identifier of the target cell.

21. The second network node generating a measurement-related configuration including information for configuring the UE to report N strongest beam measurements of the prepared target cell without reference to an SSB index or a channel state information reference signal, CSI-RS, index included in the measurement-related configuration; sending a message to the first network node including information indicative of the measurement-related configuration; The second network node according to any one of claims 15 to 20, further adapted to perform:

22. The second network node generating a measurement-related configuration including information for configuring the UE to make its own decisions regarding SSB indices that the UE will measure and report; sending a message to the first network node including information indicative of the measurement-related configuration; The second network node according to any one of claims 15 to 20, further adapted to perform:

23. A second network node according to any one of claims 15 to 22, wherein the message received from the UE further includes information indicating an index of an SSB detected by the UE for the measurement of at least one beam of the target cell.

24. The second network node The second network node according to any one of claims 15 to 23, further adapted to send a message including information indicating an instruction for the UE to switch from the source cell to the target cell.

25. The second network node according to any one of claims 15 to 24, wherein the cell identifier is a physical cell identifier, PCI.

26. The second network node according to any one of claims 15 to 25, wherein the first identifier has a bit length shorter than a bit length of the cell identifier.

27. a user equipment, UE, served by a source cell of a second network node supporting at least one of a distributed unit, DU, function or a Layer 2 protocol of a radio access network, at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network and the first identifier; sending a message to the second network node, the message including information indicative of a measurement report associated with at least one beam of the target cell and the first identifier; A user equipment (UE) performs the above.

28. the first identifier is a cell index for distinguishing beam measurements of a plurality of different cells; The obtaining of the association between the cell identifier of the target cell and the first identifier comprises:

28. The UE of claim 27, comprising receiving a configuration message from a first network node supporting at least one of a central unit control plane, CU-CP, function or a Layer 3 protocol of the radio access network, the configuration message including information indicating the association between the cell identifier and the cell index of the target cell.

29. 29. The UE of claim 28, wherein the received configuration message is an RRC reconfiguration message further including a CSI measurement-related configuration suitable for supporting an L1 / 2 mobility function and the number of SSB indices configured in the target cell, and the transmitted message is an L1 measurement report including information about the cell index, SSB index, and L1-RSRP.

30. The first identifier is a configuration identifier associated with a configuration of the target cell for handover by the UE and for identifying the configuration, and obtaining the association between the cell identifier of the target cell and the first identifier includes:

28. The UE of claim 27, comprising receiving, 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, a configuration message including information indicating the association between the cell identifier of the target cell and the configuration identifier.

31. 31. The UE of claim 30, wherein the received configuration message is an RRC reconfiguration message further including a CSI measurement-related configuration suitable for supporting an L1 / 2 mobility function and the number of SSB indices configured in the target cell, and the transmitted message is an L1 measurement report including information regarding the configuration identifier, SSB indices, and L1-RSRP.

32. A UE as described in any of claims 28 to 31, wherein the configuration message further includes information indicating a measurement-related configuration including information for configuring the UE to report N strongest beam measurement values ​​of the target cell without referencing a synchronization signal block, SSB, index, or a channel state information reference signal, CSI-RS, index included in the configuration message.

33. The UE according to any one of claims 28 to 32, wherein the configuration message further includes information indicating a measurement-related configuration including information for configuring the UE to make its own decisions regarding synchronization signal blocks, SSBs, and indices that the UE measures and reports.

34. The UE of any one of claims 27 to 33, wherein transmitting the message comprises transmitting a message including information indicating a measurement report associated with the strongest beam measurement value of the target cell.

35. The UE according to any one of claims 28 to 34, wherein the configuration message further includes information indicating the number of SSB indices configured in the target cell.

36. The UE according to any one of claims 27 to 35, wherein the message transmitted to the second network node further includes information indicating an index of an SSB detected by the UE for the measurement.

37. The UE 37. The UE of any one of claims 27 to 36, further configured to receive a message from the second network node, the message including information indicating an instruction for the UE to switch from the source cell to the target cell.

38. The UE according to any one of claims 27 to 37, wherein the cell identifier is a physical cell identifier, PCI.

39. The UE according to any one of claims 27 to 38, wherein the first identifier has a bit length shorter than a bit length of the cell identifier.

40. 1. A method of a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Layer 3 protocol of a radio access network, comprising: determining to prepare a target cell of a third network node for Lower Layer Mobility, LLM, with a source cell of a second network node, wherein each of the second network node and the third network node supports at least one of a distributed unit, DU, function or a Layer 2 protocol of the radio access network; obtaining an association between a cell identifier of the target cell and a first identifier; sending a configuration message to a user equipment (UE) served by the source cell, the configuration message including information indicating the association between the cell identifier of the target cell and the first identity; A method comprising:

41. A method of a second network node supporting at least one of a distributed unit, DU, function or radio access network Layer 2 protocol, comprising: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network and the first identifier, wherein the target cell is prepared for Lower Layer Mobility, LLM, with a source cell of the second network node by 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; receiving a message from a user equipment (UE) served by the source cell, the message including information indicative of a measurement report associated with at least one beam of the target cell and the first identifier; A method comprising:

42. 1. A method of a user equipment, UE, served by a source cell of a second network node supporting at least one of a distributed unit, DU, function or a Layer 2 protocol of a radio access network, comprising: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU function or the Layer 2 protocol of the radio access network and the first identifier; sending a message to the second network node, the message including information indicative of a measurement report associated with at least one beam of the target cell and the first identifier; A method comprising:

43. A computer program comprising instructions for causing an apparatus to carry out the method according to any one of claims 40 to 42.

44. A memory storing computer readable instructions for causing an apparatus to carry out a method according to any one of claims 40 to 42.

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