Configuration of L1 beam measurements for lower layer mobility

Abstract

Described herein is a first network node supporting at least one of a central unit control plane (CU-CP) function or a layer 3 protocol of a radio access network, 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; obtaining association between the cell identifier of the target cell and the first identifier; and transmitting a configuration message to a user equipment (UE) served by the source cell, the configuration message including information indicating an 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 enhancements to the configuration of L1 beam measurements for lower layer mobility. Background Art

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

[0003] Broadly speaking, L1 / 2 inter-cell mobility is one of the upcoming mobility enhancement goals in the next 3rd Generation Partnership Project (3GPP) release, such as Release 18. Compared to the conventional / legacy L3 mobility procedure where the handover between two cells is usually decided by the Radio Resource Control (RRC) layer, L1 / 2 inter-cell mobility is usually performed by the Medium Access Control (MAC) layer, which usually terminates in the Distributed Unit (DU) of the 5G / NR (New Radio) gNB.

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

[0005] However, due to UE mobility, the configured SSB index list may no longer be applicable to lower layer inter-cell mobility, because some SSB indexes that are not part of the configured CSI-SSB-ResourceSet may become more relevant. On the other hand, as can be appreciated by those skilled in the art, continuous updating of the CSI-SSB-ResourceSet will result in high signaling overhead for the radio and network interfaces, including:

[0006] Radio Overhead: The update of CSI-SSB-ResourceSet usually requires the transmission of RRC Reconfiguration message from the network to the UE and the transmission of the corresponding RRC Reconfiguration Complete from the UE to the network.

[0007] Network interface overhead: To update a CSI-SSB-ResourceSet, the CU typically needs to coordinate the new configuration with the serving / source and target DUs over the F1 interface.

[0008] In addition to the signaling overhead, the UE may also face the risk of mobility failure (eg, due to missed cell changes) if the update of the CSI-SSB-ResourceSet is not performed in time while the UE still has a good serving radio link.

[0009] Furthermore, it is also worth mentioning that, compared to some technologies 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 can be configured with multiple cells (e.g., up to 8 or even more prepared target cells), which makes this problem more obvious.

[0010] Therefore, there is a need to propose new measurement-related mechanisms / techniques for L1 / 2 (lower layer) inter-cell mobility management to address some or all of the above issues, especially in an efficient, flexible yet reliable manner. Summary of the invention

[0011] According to one aspect of the present disclosure, there is provided a first network node, the first network node supporting at least one of a central unit control plane (CU-CP) function or a layer 3 (L3) protocol of a radio access network, the first network node comprising:

[0012] at least one processor; and

[0013] at least one memory storing instructions that, when executed by at least one processor, cause the first network node to at least:

[0014] determining to prepare a target cell of the third network node for a lower layer mobility (LLM) with a source cell of the second network node, wherein each of the second network node and the third network node supports at least one of a distributed unit (DU) functionality of a radio access network or a layer 2 (L2) protocol;

[0015] acquiring an association between a cell identifier of the target cell and the first identifier; and

[0016] A configuration message including information indicating an association between a cell identifier of the target cell and the first identifier is sent to a user equipment UE served by the source cell.

[0017] In some examples, the first network node is further caused to:

[0018] A message including information indicating an association between a cell identifier of the target cell and the first identifier is sent to the third network node.

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

[0020] Information indicating a number of synchronization signal block (SSB) indexes configured in the target cell is received from the third network node.

[0021] In some examples, the first network node is further caused to:

[0022] Information indicating a number of SSB indexes configured in the target cell is sent to at least one of the second network node, the third network node, or the UE.

[0023] In some examples, the first identifier is a cell index used to distinguish beam measurements of different cells.

[0024] In some examples, obtaining the association between the cell identifier of the target cell and the first identifier includes:

[0025] sending a request message including information indicating a cell identifier of the target cell to the second network node; and

[0026] A response message including information indicating an association between a cell identifier of the target cell and the cell index is received from the second network node.

[0027] In some examples, obtaining the association between the cell identifier of the target cell and the first identifier includes:

[0028] determining, by the first network node, an association between a cell identifier and a cell index of the target cell; and

[0029] The first network node is further caused to:

[0030] A request message including information indicating an association between a cell identifier of the target cell and a cell index is sent to the second network node.

[0031] In some examples, the first identifier is a configuration identifier associated with and used to identify a configuration of a prepared target cell used by the UE to perform a handover from a source cell.

[0032] In some examples, obtaining the association between the cell identifier of the target cell and the first identifier includes:

[0033] determining, by the first network node, an association between a cell identifier of the target cell and the configuration identifier; and

[0034] The first network node is further caused to:

[0035] A request message including information indicating an association between the PCI of the target cell and the configuration identifier is sent to the second network node.

[0036] In some examples, the configuration message also includes information indicating measurement-related configuration.

[0037] In some examples, 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.

[0038] In some examples, the measurement-related configuration includes information for configuring the UE to independently determine the SSB index for UE measurement and reporting.

[0039] In some examples, the cell identifier is a physical cell identifier (PCI).

[0040] In some examples, the first identifier has a bit length that is shorter than a bit length of the cell identifier.

[0041] According to another aspect of the present disclosure, there is provided a second network node, the 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:

[0042] at least one processor; and

[0043] at least one memory storing instructions that, when executed by at least one processor, cause the second network node to at least:

[0044] obtaining an association between 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 the radio access network and the first identifier, wherein the target cell is prepared by the first network for lower layer mobility (LLM) with a source cell of the second network node, the first network supporting at least one of a central unit control plane (CU-CP) function or a layer 3 (L3) protocol of the radio access network; and

[0045] A message is received from a user equipment (UE) served by a source cell, the message including information indicative of a measurement report related to at least one beam of a target cell, and a first identifier.

[0046] In some examples, the second network node is also caused to receive information from the first network node indicating the number of synchronization signal block SSB indexes configured in the prepared target cell.

[0047] In some examples, the first identifier is a cell index used to distinguish beam measurements of different cells.

[0048] In some examples, obtaining the association between the cell identifier of the target cell and the first identifier includes:

[0049] receiving, from the first network node, a request message including information indicating a cell identifier of a target cell; and

[0050] determining, by the second network node, an association between a cell identifier and a cell index of the target; and

[0051] The second network node is further caused to:

[0052] A response message including information indicating an association between the PCI of the target and the cell index is sent to the first network node.

[0053] In some examples, obtaining the association between the cell identifier of the target cell and the first identifier includes:

[0054] A message including information indicating an association between a cell identifier of a target cell and a cell index is received from the first network node.

[0055] In some examples, the first identifier is a configuration identifier associated with a configuration of the target cell and used to identify the configuration of the target cell, the configuration of the target cell being issued by the first network node to configure the UE to hand over to the target cell; and

[0056] Acquiring the association between the cell identifier of the target cell and the first identifier includes:

[0057] A message including information indicating an association between a cell identifier of a target cell and a configuration identifier is received from the first network node.

[0058] In some examples, the second network node is further caused to:

[0059] generating a measurement-related configuration including information for configuring the UE to report the prepared N strongest beam measurements of the target cell without reference to an SSB index or a channel state information reference signal (CSI-RS) index included in the measurement-related configuration; and

[0060] A message including information indicating a measurement related configuration is sent to the first network node.

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

[0062] generating a measurement-related configuration including information for configuring the UE to self-determine an SSB index for UE measurement and reporting; and

[0063] A message including information indicating a measurement related configuration is sent to the first network node.

[0064] In some examples, the message received from the UE also includes information indicating an index of an SSB detected by the UE for measuring at least one beam of the target cell.

[0065] In some examples, the second network node is further caused to send a message including information indicative of an instruction for the UE to hand over from the source cell to the target cell.

[0066] In some examples, the cell identifier is a physical cell identifier (PCI).

[0067] In some examples, the first identifier has a bit length that is shorter than a bit length of the cell identifier.

[0068] According to another aspect of the present disclosure, there is provided a user equipment (UE), the UE being 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 UE comprising:

[0069] at least one processor; and

[0070] at least one memory storing instructions that, when executed by at least one processor, cause the UE to at least:

[0071] obtaining an association between 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 the radio access network and the first identifier; and

[0072] A message is sent to the second network node, the message comprising information indicative of a measurement report related to at least one beam of the target cell, and the first identifier.

[0073] In some examples, the first identifier is a cell index for distinguishing beam measurements of different cells, and obtaining an association between a cell identifier of the target cell and the first identifier includes:

[0074] A configuration message is received from a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a layer 3 protocol of a radio access network, the configuration message comprising information indicating an association between a cell identifier and a cell index of a target cell.

[0075] In some examples, the received configuration message is an RRC reconfiguration message, which also includes a CSI measurement-related configuration suitable for supporting L1 / 2 mobility function, and the number of SSB indexes configured in the target cell, and the sent message is an L1 measurement report, which includes a cell index, an SSB index and information about L1-RSRP.

[0076] In some examples, the first identifier is a configuration identifier associated with a configuration of a target cell and used to identify the configuration of the target cell, the configuration of the target cell being used for handover by the UE; and acquiring the association between the cell identifier of the target cell and the first identifier includes:

[0077] A configuration message is received from a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a layer 3 protocol of a radio access network, the configuration message comprising information indicating an association between a cell identifier and a cell index of a target cell.

[0078] In some examples, the received configuration message is an RRC reconfiguration message, which also includes a CSI measurement-related configuration suitable for supporting L1 / 2 mobility functions, and the number of SSB indexes configured in the target cell, and the sent message is an L1 measurement report, which includes a configuration identifier, an SSB index, and information about L1-RSRP.

[0079] In some examples, the configuration message also includes information indicating a measurement-related configuration, which measurement-related configuration includes information for configuring the UE to report N strongest beam measurements of the target cell without reference to a synchronization signal block (SSB) index or a channel state information reference signal (CSI-RS) index included in the configuration message.

[0080] In some examples, the configuration message also includes information indicating a measurement-related configuration, which includes information for configuring the UE to independently determine a synchronization signal block (SSB) index for UE measurement and reporting.

[0081] In some examples, sending the message includes sending a message including information indicating a measurement report related to the strongest beam measurement of the target cell.

[0082] In some examples, the configuration message also includes information indicating the number of SSB indexes configured in the target cell.

[0083] In some examples, the message sent to the second network node also includes information indicating an index of an SSB detected by the UE for measurement.

[0084] In some examples, the UE is also caused to:

[0085] A message including information indicative of an instruction for handover of the UE from the source cell to the target cell is received from the second network node.

[0086] In some examples, the cell identifier is a physical cell identifier (PCI).

[0087] In some examples, the first identifier has a bit length that is shorter than a bit length of the cell identifier.

[0088] According to another aspect of the present disclosure, there is provided a method of a first network node supporting at least one of a Central Unit Control Plane (CU-CP) function or a Layer 3 (L3) protocol of a radio access network, the method comprising:

[0089] determining to prepare a target cell of the third network node for lower layer mobility (LLM) with a source cell of the second network node, wherein each of the second network node and the third network node supports at least one of a distributed unit (DU) functionality or a layer 2 protocol of a radio access network;

[0090] acquiring an association between a cell identifier of the target cell and the first identifier; and

[0091] A configuration message including information indicating an association between a cell identifier of a target cell and the first identifier is sent to a user equipment (UE) served by the source cell.

[0092] According to another aspect of the present disclosure, there is provided a method of a second network node, the second network node supporting at least one of a distributed unit (DU) function or a layer 2 (L2) protocol of a radio access network, the method comprising:

[0093] obtaining an association between 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 the radio access network and the first identifier, wherein the target cell is prepared by a first network supporting at least one of a central unit control plane (CU-CP) function or a layer 3 (L3) protocol of the radio access network for lower layer mobility (LLM) with a source cell of a second network node; and

[0094] A message including information indicative of a measurement report related to at least one beam of a target cell and a first identifier is received from a user equipment (UE) served by a source cell.

[0095] According to another aspect of the present disclosure, there is provided a method of a user equipment (UE), the UE being 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:

[0096] obtaining an association between 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 the radio access network and the first identifier; and

[0097] A message is sent to the second network node, the message comprising information indicative of a measurement report related to at least one beam of the target cell, and the first identifier.

[0098] According to some example embodiments, there is also provided a computer program comprising instructions for causing an apparatus to execute the method disclosed in the present disclosure.

[0099] According to some example embodiments, there is also provided a memory storing computer-readable instructions for causing an apparatus to execute the method disclosed in the present disclosure.

[0100] In addition, according to some example embodiments, a first network node is provided, which supports at least one of a central unit control plane (CU-CP) function or a layer 3 (L3) protocol of a radio access network, and the first network node includes appropriate components configured to perform the corresponding steps disclosed in the present disclosure.

[0101] Similarly, according to some example embodiments, a second network node and a third network node are also provided, which support at least one of a distributed unit (DU) function or a layer 2 (L2) protocol of a radio access network, and the second network node and the third network node include appropriate components configured to perform the corresponding steps disclosed in the present disclosure.

[0102] In addition, according to some other example embodiments, for example, a computer program product for a wireless communication device is provided, which includes at least one processor, and at least includes a software code portion for executing the corresponding steps disclosed in the present disclosure when the above-mentioned product is run on the device. The computer program product may include a computer-readable medium having the above-mentioned software code portion stored thereon. In addition, the computer program product can be directly loadable into the internal memory of the computer and / or can be sent via a network by means of at least one of an upload, download and push process.

[0103] Although some example embodiments will be described herein with particular reference to the above-mentioned applications, it will be appreciated that the present disclosure is not limited to such fields of use, but is applicable in a wider context.

[0104] It is worth noting that it should be understood that the method according to the present disclosure relates to a method of operating a device according to the above-mentioned example embodiments and variations thereof, and corresponding statements made about the device are also applicable to the corresponding method, and vice versa, so similar descriptions may be omitted for the sake of brevity. In addition, even if not explicitly disclosed, the above aspects may be combined in a variety of ways. Those skilled in the art will understand that these aspects and feature / step combinations are possible unless they produce a contradiction that is explicitly excluded.

[0105] The implementation of the disclosed apparatus may include, but is not limited to, the use of one or more processors, one or more application specific integrated circuits (ASICs), and / or one or more field programmable gate arrays (FPGAs). The implementation of the apparatus may also include the use of other conventional and / or custom hardware, such as a software programmable processor, such as a graphics processing unit (GPU) processor.

[0106] Other and further example embodiments of the present disclosure will become apparent during the following discussion and by reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Example embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0108] Figure 1 schematically illustrates an example of a signaling / messaging flow diagram according to an example embodiment of the present disclosure;

[0109] Figure 2 schematically illustrates an example of a channel state information (CSI) measurement configuration according to an example embodiment of the present disclosure;

[0110] Figure 3 schematically illustrates an example of a CSI measurement related configuration according to an example embodiment of the present disclosure;

[0111] Figure 4 Schematically illustrates another example of a signaling / message flow diagram according to an example embodiment of the present disclosure;

[0112] Figure 5 schematically illustrates another example of a signaling / message flow diagram according to another example embodiment of the present disclosure; and

[0113] Figure 6 An example of a signaling / messaging flow diagram according to another example embodiment of the present disclosure is schematically illustrated. DETAILED DESCRIPTION

[0114] In the following, 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 an example communication network to which the embodiments may be applied, without however limiting the embodiments to such an architecture. It will be apparent to those skilled in the art that the embodiments may also be applicable 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 SL (side link), e.g. Wi-Fi, Worldwide Interoperability for Microwave Access (WiMAX), Personal Communications Service (PCS), Wideband Code Division Multiple Access (WCDMA), systems using ultra-wideband (UWB) technology, mobile ad hoc networks (MANET), wired access, etc. In addition, without loss of generality, the description of some examples of the embodiments is related to mobile communication networks, but the principles of the present disclosure can be extended and applied to any other type of communication network, such as a wired communication network.

[0115] 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 multiple places, this does not necessarily mean that each such reference is related to the same (multiple) examples or (multiple) embodiments, nor does it necessarily mean that the feature only applies to a single example or embodiment. Individual features of different embodiments may also be combined to provide other embodiments. In addition, terms such as "comprising" and "including" should be understood as not limiting the described embodiments to only those features that have been mentioned; such examples and embodiments may also include features, structures, units, modules, etc. that are not specifically mentioned.

[0116] The basic system architecture of a communication (telecommunication) network including a mobile communication system (in which some examples of embodiments are applicable) may include the architecture of one or more communication networks, including (multiple) radio access network subsystems and (multiple) core networks. Such an architecture may include one or more communication network control elements or functions, access network elements, radio access network elements, access service network gateways or base transceiver stations (such as base stations (BS), access points (AP), NodeBs (NBs), eNBs or gNBs), distributed units (DUs) or centralized / central units (CUs), which control the corresponding coverage area or (multiple) cells and which communicate with one or more communication stations (such as communication elements or functions, such as user equipment or terminal equipment, such as user equipment (UE), or another device with similar functions, such as a modem chipset, chip, module, etc., which may also be part of a station, element, function or application capable of communication, such as a UE, an element or function that can be used in a machine-to-machine communication architecture, or as a separate element attached to an element, function or application capable of communication, etc.) via one or more channels via one or more communication beams to send several types of data in multiple access domains. Furthermore, core network elements or network functions may be included, such as gateway network elements / functions, mobility management entities, mobile switching centers, servers, databases, etc.

[0117] The following description may provide further details of alternatives, modifications and variations: The gNB includes, for example, a node that provides NR user plane and control plane protocol termination towards the UE and which is connected to the 5GC via an NG interface, for example, in accordance with Section 3.2 of 3GPP TS 38.300 V16.6.0 (2021-06) incorporated by reference.

[0118] The gNB Central Unit (gNB-CU) comprises, for example, a logical node that hosts, for example, the RRC, SDAP and PDCP protocols of a gNB, or the RRC and PDCP protocols of an en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU.

[0119] The gNB distributed unit (gNB-DU) comprises, for example, a logical node that hosts, for example, the RLC, MAC, and PHY layers of a gNB or en-gNB, and whose operation is partially controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0120] The gNB-CU control plane (gNB-CU-CP) comprises, for example, a logical node that hosts the control plane portion of the RRC and PDCP protocols, for example, for a gNB-CU of an en-gNB or gNB. The gNB-CU-CP terminates the E1 interface with the gNB-CU-UP and the F1-C interface with the gNB-DU.

[0121] The gNB-CU user plane (gNB-CU-UP) includes, for example, a logical node that hosts, for example, the user plane part of the PDCP protocol for the gNB-CU of the en-gNB, and the user plane parts of the PDCP protocol and the SDAP protocol for the gNB-CU of the gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, according to Section 3.1 of 3GPP TS 38.401 V16.6.0 (2021-07) incorporated by reference.

[0122] There may be different functional splits between central and distributed units, called options for example:

[0123] Option 1 (Class 1A Split):

[0124] The functional split in this option is similar to the 1A architecture in DC. RRC is located in the central unit. PDCP, RLC, MAC, physical layer and RF are located in the distributed unit.

[0125] Option 2 (Class 3C Split):

[0126] The functional split in this option is similar to the 3C architecture in DC. RRC and PDCP are located in the central unit. RLC, MAC, physical layer and RF are located in the distributed unit.

[0127] Option 3 (split within RLC):

[0128] • Low RLC (part of the RLC functions), MAC, physical layer and RF are located in the distributed unit. PDCP and High RLC (another part of the RLC functions) are located in the central unit.

[0129] Option 4 (RLC-MAC Split):

[0130] MAC, physical layer and RF are located in the distributed unit. PDCP and RLC are located in the central unit.

[0131] Otherwise, for example, according to 3GPP TR 38.801 V14.0.0 incorporated by reference

[0132] (2017-03) Section 11.

[0133] gNB supports different protocol layers, such as Layer 1 (L1) - the physical layer.

[0134] NR’s Layer 2 (L2) is split 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:

[0135] The physical layer provides transport channels to the MAC sublayer;

[0136] The MAC sublayer provides logical channels to the RLC sublayer;

[0137] The RLC sublayer provides RLC channels to the PDCP sublayer;

[0138] The PDCP sublayer provides radio bearers to the SDAP sublayer;

[0139] The SDAP sublayer provides QoS flows to the 5GC;

[0140] Comp. refers to header compression and Segm. refers to segmentation;

[0141] Control channels include (BCCH, PCCH).

[0142] Layer 3 (L3) includes, for example, Radio Resource Control (RRC), for example according to Section 6 of 3GPP TS 38.300 V16.6.0 (2021-06), incorporated by reference.

[0143] A RAN (Radio Access Network) node or network node (such as a gNB, base station, gNB CU or gNB DU or part thereof) may be implemented using, for example, a device having at least one processor and / or at least one memory having computer-readable instructions (computer program) configured to support and / or provide and / or process CU and / or DU related functions and / or features, and / or at least one protocol (sub) layer of a RAN (Radio Access Network), such as Layer 2 and / or Layer 3.

[0144] The gNB CU and gNB DU parts may be, for example, co-located or physically separated. The gNB DU may be even further split into two parts, for example, one part including a processing device and the other part including an antenna. The central unit (CU) may also be referred to as BBU / REC / RCC / C-RAN / V-RAN, O-RAN or a part thereof. The distributed unit (DU) may also be referred to as RRH / RRU / RE / RU or a part thereof. Hereinafter, in various example embodiments of the present disclosure, the CU-CP (or more generally, CU) may also be referred to as a (first) network node supporting at least one of the central unit control plane functions or layer 3 protocols of the radio access network; and similarly, the DU may be referred to as a (second) network node supporting at least one of the distributed unit functions or layer 2 protocols of the radio access network.

[0145] The gNB-DU supports one or more cells and can thus serve as, for example, a serving cell for a user equipment (UE).

[0146] User equipment (UE) may include a wireless or mobile device, a device having a radio interface that interacts with a RAN (Radio Access Network), a smartphone, an in-vehicle device, an IoT device, an M2M device, etc. Such a UE or device may include: at least one processor; and at least one memory including a computer program code; wherein the at least one memory and the computer program code are configured to, together with the at least one processor, enable the device to perform at least certain operations, such as an RRC connection with the RAN. The UE is configured, for example, to generate a message (e.g., including a cell ID) to send to the RAN via radio (e.g., to reach a serving cell and communicate with it). The UE can generate, send and receive RRC messages containing one or more RRC PDUs (packet data units).

[0147] The UE may have different states (e.g., according to sections 42.1 and 4.4 of 3GPP TS 38.331 V16.5.0 (2021-06), incorporated herein by reference).

[0148] When the RRC connection has been established, the UE is in, for example, an RRC_CONNECTED state or an RRC_INACTIVE state.

[0149] In the RRC_CONNECTED state, the UE may:

[0150] Store AS context;

[0151] ·Transmit unicast data to / from UE;

[0152] Monitor the control channel associated with the shared data channel to determine if it is data

[0153] Channel scheduling data;

[0154] Provide channel quality and feedback information;

[0155] Perform neighbor cell measurements and measurement reporting.

[0156] The RRC protocol includes the following main functions:

[0157] RRC connection control;

[0158] Measurement configuration and reporting;

[0159] · Establish / modify / publish measurement configurations (e.g., intra-frequency, inter-frequency, and inter-RAT)

[0160] Measurement);

[0161] ·Measure the establishment and release of the gap;

[0162] Measurement report.

[0163] The general functionality and interconnection of the described elements and functions (which also depends on the actual network type) are known to those skilled in the art and are described in the corresponding specification, so for the sake of brevity, a detailed description thereof may be omitted here. However, it should be noted that in addition to those described in detail below, several additional network elements and signaling links may be employed to communicate with elements, functions or applications (such as communication endpoints), communication network control elements (such as servers, gateways, radio network controllers), and other elements of the same or other communication networks.

[0164] The communication network architecture considered in the examples of embodiments may also be able to communicate with other networks such as a public switched telephone network or the Internet. The communication network may also support the use of cloud services for virtual network elements or their functions, wherein it should be noted that the virtual network portion of the telecommunications network may also be provided by non-cloud resources, such as an internal network, etc. It should be understood that the network elements and / or corresponding functions of the access system, core network, etc. may be implemented by using any node, host, server, access node or entity, etc. suitable for such purpose. In general, the network functions may be implemented as network elements on dedicated hardware, software instances running on dedicated hardware, or virtualized functions instantiated on an appropriate platform (e.g., a cloud infrastructure).

[0165] In addition, network elements such as communication elements (such as UE, terminal equipment), control elements or functions (such as access network elements (such as base stations / BS, gNB), radio network controllers, core network control elements or functions (such as gateway elements)), or other network elements or functions described herein, and any other elements, functions or applications may be implemented by software (e.g., by a computer program product of a computer) and / or by hardware. In order to perform its corresponding processing, the corresponding device, node, function or network element may include several parts, modules, units, components, etc. (not shown) required for control, processing and / or communication / signaling functions. For example, such components, modules, units and components may include: one or more processors or processor units, including one or more processing parts for executing instructions and / or programs and / or for processing data; storage or memory units or components used as work areas of processors or processing parts for storing instructions, programs and / or data (e.g., ROM, RAM, EEPROM, etc.), input or interface components for inputting data and instructions by software (e.g., floppy disks, CD-ROMs, EEPROMs, etc.), user interfaces for providing users with monitoring and manipulation possibilities (e.g., screens, keyboards, etc.), other interfaces or components for establishing links and / or connections under the control of processor units or parts (e.g., wired and wireless interface components, radio interface components including, for example, antenna units, etc., components for forming radio communication parts, etc.), etc., wherein the corresponding components forming the interface (such as radio communication parts) may also be located at remote sites (e.g., radio heads or radio stations, etc.). It should be noted that in this specification, a processing part should not be regarded as representing only a physical part of one or more processors, but may also be regarded as a logical division involving processing tasks performed by one or more processors. It should be understood that according to some examples, a so-called "fluid" or flexible network concept may be adopted, wherein the operations and functions of a network element, a network function, or another entity of the network may be performed in a flexible manner in different entities or functions (such as in a node, a host, or a server). In other words, the "division of labor" between the network elements, functions, or entities involved may vary from case to case.

[0166] As mentioned above, technology related to L1 / 2 inter-cell mobility (or sometimes also referred to as lower layer mobility, LLM) is one of the upcoming targets for mobility enhancements considered, for example, in Release 18 of the 3rd Generation Partnership Project (3GPP). In contrast to the (conventional) L3 mobility procedure, in which the handover procedure between two cells is usually decided by the RRC layer, L1 / 2 inter-cell mobility is usually performed by the MAC layer, which usually terminates in the DU of the 5G / NR gNB.

[0167] Figure 1An exemplary implementation of a signaling diagram for L1 / 2 inter-cell mobility from a serving / source cell in DU 1 (sometimes also referred to as source / serving DU) to a target cell in DU 2 (sometimes also referred to as target DU) is schematically shown, which can also be considered as an inter-DU intra-CU scenario. The same diagram can also be applied (with adjustments if necessary) in the case of intra-DU intra-CU cell change / switching, where DU 1 is the same as DU 2. In this case, DU 1 (or DU 2) itself can be referred to as both a source / serving cell and a target cell.

[0168] In particular, the main steps of this L1 / 2 inter-cell mobility procedure can be summarized as follows.

[0169] In step S101, the UE may issue a measurement report, which may contain, for example, cell quality measurements of the serving / source and (multiple) neighboring cells. In some possible cases, the UE may be configured by the serving cell to issue a measurement report in advance when it still has a good connection with the serving cell. The measurement report is received by DU 1 (source / serving DU) and then further propagated to the CU (as illustrated in step S102).

[0170] Using the reported cell quality measurements, the CU can identify a set of potential candidate target cells (from the overall neighboring cells controlled by the same or different DU(s)) to which the UE can switch. Figure 1 In the example shown, the CU identifies candidate target cells served by DU 1 (controlling the serving DU / cell) and another DU 2 controlled by the same CU.

[0171] In step S103 , the CU may request to prepare a candidate target cell controlled by the DU 1 , for example, by issuing a UE context establishment request message (or any other suitable message).

[0172] In step S104, DU 1 may provide the configuration of the UE in a corresponding UE context establishment response message (or any other suitable message) containing a message container from the DU to the CU.

[0173] Similarly, steps S105 and S106 may also be performed by DU 2 so as to prepare target cell(s) controlled by DU 2.

[0174] After receiving the UE configuration of the candidate target cell(s) (as illustrated in steps S104 and S106), the CU may generate an RRC reconfiguration message (or similar message) in step S107, which will be sent to the UE in step S108. Among other possible / appropriate information, the RRC reconfiguration message may include:

[0175] Measurement reporting configuration for L1 / 2 handover / mobility, e.g. configuration(s) on how to report L1 beam measurements of serving and target cells in step S110;

[0176] as well as

[0177] As shown in step S111, upon receiving a MAC CE command such as changing / switching the serving cell (i.e., performing a handover), the UE needs to execute the prepared (multiple)

[0178] Configuration(s) of candidate cells.

[0179] After confirming the RRC reconfiguration to the network in step S109 (e.g., by issuing a corresponding RRC reconfiguration complete message, etc.), as shown in step S110, the UE can now start reporting (e.g., periodically, etc.) L1 beam measurements of the serving and candidate target cells.

[0180] Upon determining that there is a target candidate cell with a better radio link / beam measurement than the serving cell's radio link / beam measurement (e.g., based on determining that the L1-RSRP (reference signal received power) measured by the target beam is greater than the L1-RSRP measured by the serving beam, possibly with an offset of a period of time, such as a trigger time (TTT), or based on any other suitable criteria), the serving cell may issue a MAC control element (MAC CE) or a suitable L1 message in step S111 to trigger a cell change / handover to the target candidate cell. In some possible cases, the MAC CE may, for example, include transmission configuration indication (TCI) state change information indicating the beam of the target candidate cell, or any other suitable information.

[0181] As a result of such a MAC CE or a suitable L1 message, a (lower layer) handover is performed by the UE from the serving cell to the target cell in step S112.

[0182] For beam management (including the process of switching between beams of the same cell), a channel state information (CSI) measurement configuration (sometimes referred to as "CSI-MeasConfig") shall be provided in a higher layer (e.g., RRC) configuration information element (IE), such as ServingCellConfig IE, which is shared from the DU to the CU as an RRC container (e.g., as Figure 1 ), as part of an F1 (which is typically an interface between a CU and a DU) message (such as a UE context establishment response message).

[0183] In general, CSI-MeasConfig may be understood to contain CSI measurement related configurations, which may include, among other possibilities:

[0184] (multiple) CSI reporting related configurations, which include, for example, information about how the UE should report

[0185] Report L1 beam measurement information; and

[0186] • CSI resource related configuration(s), which contains information such as that the UE needs to report beam measurements for a reference signal (RS) such as a synchronization signal block (SSB) or CSI-RS.

[0187] exist Figure 2 In the example shown, the exemplary CSI-MeasConfig can be viewed as containing two CSI reporting configurations associated with different RSs: SSB (left side) and CSI-RS (right side).

[0188] In Release 17 of 3GPP, the CSI measurement related configuration has been extended so that the UE may be able to report L1 beam measurements of (multiple) non-serving cells so that inter-cell beam management (ICBM) can be better supported to allow the UE to be served by a beam from another cell ("borrowed"). As a result of this extension, the CSI-SSB-ResourceSet may also be extended to include, in addition to the configuration of the SSB index that the UE should measure and use to report the L1 beam measurement, the physical cell identifier (PCI) associated with each configured SSB index. Figure 3 An illustrative example of such a possible (extended) configuration is shown in (above).

[0189] Those skilled in the art will understand and appreciate that L1 beam measurements are typically provided by the UE to the network (e.g., to the DU, or to the CU via the DU) in a CSI report (or any other suitable form / message), which is typically part of the uplink control information (UCI) sent via the physical uplink common control channel (PUCCH) or the physical uplink shared channel (PUSCH). Figure 3 An example of such a possible UCI is schematically shown in the lower left figure.

[0190] In a broad sense, Figure 3 As shown in the lower right figure of FIG. , in some possible (non-limiting) examples, the CSI report may include the following elements (such as Figure 3 )

[0191] Channel State Information Reference Signal Resource Indicator (CRI) or SS / PBCH Block Resource Indicator (SSB-RI). In general, the length of the SSB-RI may depend on the number of SSB indices configured in the CSI-SSB-ResourceSet (e.g. Figure 3 As a simple illustrative example, if a total of 64 SSB indices are defined, the length of the SSB-RI will be 6 bits.

[0192] RSRP for each CRI or SSB-RI. Among some possible (non-limiting)

[0193] In implementation, the length of the RSRP of the first reported CRI or SSB-RI may be 7 bits, while the length of the remaining different RSRPs, for example three indexes (if reported), may be 4 bits.

[0194] In conventional techniques, a UE can only report L1 beam measurements of synchronization signal blocks (SSBs) indexed by the network in the configuration of CSI-SSB-ResourceSet. Currently, the SSB index list is usually limited to 64 to meet UE capabilities. In other words, the UE can theoretically measure up to 64 indexes simultaneously. In addition, the maximum number N of L1 beam measurements to be reported is configured by the network. Figure 3 In the example, N is equal to 4 and is much smaller than the number of SSB indices configured in the CSI-SSB-ResourceSet.

[0195] However, due to UE mobility, the configured SSB index list may no longer be applicable to lower layer inter-cell mobility, because some SSB indexes that are not part of the configured CSI-SSB-ResourceSet may become more relevant, for example, if they now have a higher received power. For example, the network may configure the UE to report an L3 measurement report issued to the CU. It is worth noting that the L3 measurement configuration is typically controlled by the RRC and is completely separate from the CSI measurement configuration, which is 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 indexes and whether the CSI-SSB-ResourceSet needs to be updated. Therefore, the network can provide another L3 measurement configuration to the UE, in which the UE is not forced to measure a specific set of SSB indexes. However, it will be appreciated by those skilled in the art that continuous updating of the CSI-SSB-ResourceSet will result in high signaling overhead for the radio and network interfaces, including:

[0196] Radio Overhead: The update of CSI-SSB-ResourceSet usually requires the transmission of, for example, an RRC Reconfiguration message from the network to the UE and the transmission of a corresponding RRC Reconfiguration Complete from the UE to the network.

[0197] Network interface overhead: To update a CSI-SSB-ResourceSet, the CU typically needs to coordinate the new configuration with the serving / source and target DUs over the F1 interface.

[0198] In addition to the signaling overhead, the UE may also face the risk of mobility failure (eg, due to missed cell changes) if the update of the CSI-SSB-ResourceIndex is not performed in time while the UE still has a good serving radio link.

[0199] Furthermore, it is worth mentioning 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 8 or even more prepared target cells), which makes this problem more obvious. That is, depending on various implementations, the CU may be able to be configured to extract the configurations of up to 8 (potential) target cells from various DUs and issue these configurations to the UE (for L1 measurements and subsequent handover / mobility).

[0200] Thus, in general, the present disclosure may be seen as seeking to propose techniques / mechanisms for configuring network nodes (and UEs) to support L1 / 2 mobility (or referred to as lower layer mobility LLM) to address at least some or all of the above-mentioned issues.

[0201] In a broad sense, according to some example embodiments, the present disclosure generally proposes that the network (CU and / or DU) can configure the UE to report N (e.g., 1, 2, 4, or any other suitable number) strongest L1 beam measurements of a set of prepared target cells without reference to an explicit list of SSB (or CSI-RS) indices (SSB-RI or CRI) to be measured. Here, depending on various circumstances and / or requirements, in some possible implementations, it may be left to the UE implementation to determine and decide to measure in these detected relevant SSB (or CSI-RS) SSBs. More specifically, according to some possible (but non-limiting) implementations, the UE may decide entirely on its own which SSB indices it should measure and report.

[0202] The list of target cells (e.g., up to 8) that the UE should measure may be fixed and correspond to cells prepared for L1 / 2 centric mobility. The cell list may be updated by the CU based on, e.g., L3 measurement reports, e.g., to prepare new target cells, replace or remove target cells.

[0203] According to some other possible (but non-limiting) implementations, the number Q of SSB indices to be measured and used for L1 beam measurement reporting can still be a number lower than 64 (or any other suitable maximum number of SSB indices configured by higher layers), and Q+M=64, where M generally refers to the number of SSB indices configured by the network in the CSI-SSB-ResourceSet for the UE to perform measurements as described above. As an illustrative example for understanding, Q can be configured to 24. Then, for the remaining M=64-24=40 measurements, the measurement configuration and reporting provided by the network can apply; and for the remaining Q=24 measurements, the UE can decide what to measure and report, for example, depending on various implementations, it is also possible to capture unconfigured SSBs that become strong in between. According to some other possible (but non-limiting) implementations, the UE can be configured to measure up to 64 SSB indices configured by the network; in addition, there are the Q strongest L1 beam measurements (e.g., for those indices for which SSBs are not configured). After being configured as described above, the UE can still comply with the maximum UE capability of measuring up to 64 SSB indices simultaneously as configured / required according to the standardization.

[0204] In the report, in general, the UE may include a suitable (cell-specific) identifier to enable the serving DU to distinguish L1 beam measurements of different cells, where the cell identifier may be determined / designed to be associated with each prepared cell (e.g. identified by PCI, or identified by any other suitable identifier / ID available within the gNB or within the entire network). This has the advantage that the UE may be able to send only 3 bits (or any other suitable number of bits, which may depend on the total number of cells to be distinguished from) for the cell identifier (e.g. for up to a maximum of 8 prepared target cells), instead of the normal / typical longer per-cell or per-network identifier (e.g. 10 bits for PCI). Of course, depending on various implementations and / or requirements, any other suitable (existing or new) identifier (which is shorter in length compared to the normal / typical cell identifier (such as PCI)) may be considered (or proposed), as long as it can be generally used by network nodes (e.g. CU and DU) and UE to be able to distinguish L1 beam measurements of different cells.

[0205] Broadly speaking, the present disclosure generally proposes three different possible example methods to coordinate appropriate (cell-specific) identifiers (e.g., cell indexes, etc., such as PCI) between UE, CU and (serving and target DU), which will now be described in more detail with reference to the accompanying drawings. It should be noted that, unless otherwise stated, the same or similar reference numerals used in the drawings of the present disclosure may represent the same or similar elements. Similarly, unless otherwise stated, the same or similar messages (and the contents included therein) used in the drawings of the present disclosure may represent the same or similar messages (and the contents therein), so for the sake of brevity, repeated descriptions thereof may be omitted.

[0206] first, Figure 4 Another example of a signaling / messaging flow diagram according to some example embodiments of the present disclosure is schematically illustrated.

[0207] Usually, in Figure 4 In the example embodiment of , it will be appreciated that the (source) DU is configured to determine a cell identifier (here a cell index) to distinguish L1 measurements of a cell. The DU is therefore also responsible for associating the prepared PCI(s) of the target cell(s) (or any other suitable cell identifier, such as available within the gNB or across the network) with the cell index. Of course, in this case, the DU must also provide the determined association between the cell index and the PCI to the CU, which in turn can issue the association to the UE (and, if necessary, to other DU(s)).

[0208] More specifically, in steps S401 and S402, the UE may report measurements to the source / serving DU (DU 1), and then the source / serving DU (DU 1) may also propagate such measurement reports to the CU (similar to Figure 1 1 and 2).

[0209] Subsequently, based on the measurement report(s), the CU may identify and decide in step S403 to prepare a (target) cell (or a set of potential target cells) in DU 2 (or in some possible implementations, even in DU 1) to achieve L1 / 2 inter-cell mobility.

[0210] Similar to Figure 1 In steps S103 and S104 or steps S105 and S106, the CU may then request preparation of candidate target cells controlled by DU 2, for example by issuing 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.

[0211] In step S406, the CU may send the prepared PCI of the target cell (e.g., received from the DU, or obtained by the CU using any other suitable means) to DU 1. The information may be sent from the CU to DU 1 in (e.g., as part of) any suitable message, such as the CSI measurement configuration request message illustrated in step S406.

[0212] After receiving such CSI measurement configuration request from the CU, in step S407, DU 1 may be configured to generate a CSI measurement configuration for supporting L1 / 2 inter-cell mobility. Specifically, as described above, DU 1 may generate a configuration for indicating / configuring / enabling the UE to report the N strongest L1 beam measurements of the prepared target cell without an explicit indication of the SSB / CSI-RS index configured by a higher layer.

[0213] In addition, in this example embodiment, DU 1 will also determine in step S408 the association between the PCI (received from the CU in step S406) and the cell index (which, as described above, is designed in an appropriate manner to enable measurements of different cells to be distinguished). Depending on various implementations and / or requirements, this association may be determined in any suitable manner. For example, a (predetermined or preconfigured) mapping function / algorithm or a lookup table (LUT) may be used to map the (10-bit) PCI to an appropriate cell index (e.g., a 3-bit cell index, which is typically determined based on the number of cells to be distinguished). Of course, as will be understood and appreciated by those skilled in the art, any other suitable manner may be used as long as the measurements of the cell can be correctly identified.

[0214] After the association between (multiple) PCIs and (multiple) cell indexes has been created / generated, such association will be propagated to the CU as shown in step S409. In some possible implementations, in order to support, for example, dynamic switching between prepared target cells (or between a target cell and an original source / serving cell), such association information may be further propagated to DU 2 (and other appropriate (multiple) DUs, if deemed necessary), as exemplarily shown in step S410.

[0215] Then, in step S411 (similar to Figure 1In step S108 in the figure), the CU will generate an RRC reconfiguration message (or similar message) and send it to the UE. Similar to what is shown above, such a configuration message may include CSI measurement related configuration suitable for supporting L1 / 2 mobility functions. In addition, the association between the PCI and the cell index already generated by DU 1 may also be notified by the CU in the configuration message (or in any other suitable manner). It is also worth noting that, although not explicitly shown in the figure, those skilled in the art will understand and recognize that the configuration for the UE to report the N strongest L1 beam measurements of the prepared target cell in the absence of an explicit indication of the SSB / CSI-RS index configured by a higher layer (in step S407) will also be propagated from DU 1 to the CU (for example, as part of a CSI measurement configuration response message or in any other suitable message); and, in turn, from the CU to the UE (for example, as part of an RRC reconfiguration message or in any other suitable message).

[0216] The above process, in particular steps S403 to S409, may be repeated for multiple target cells (e.g., PCell and / or PSCell) prepared for L1 / 2 inter-cell mobility, thereby generating an association list between the PCI of the target cell and the cell index, wherein one cell index is associated with one target cell. The configurations of all prepared target cells may be merged by the CU into one collective measurement configuration and sent out in one RRC reconfiguration message, or whenever the CU prepares a target cell, the CU may send out a corresponding RRC reconfiguration message containing the corresponding measurement configuration of the target cell.

[0217] Therefore, as shown in step S412, the UE may now start reporting (e.g., periodically, aperiodically, etc.) L1 beam measurements. This time, the UE may report at least a cell index (for DU identification of the corresponding target cell) and an SSB index for identifying the corresponding beam together with the L1-RSRP. More specifically, as described above with reference to Figure 3 As shown, the UE can report the SSB index detected by the physical layer in the CSI report (containing L1 beam measurement) instead of the SSB-RI, which usually refers to the running index (entry index) of the SSB configured in the CSI-SSB-ResourceSet configuration. The SSB index is needed because, in the proposed embodiment, the network does not indicate a specific list of SSB indices to be measured, and therefore, the SSB-RI (which is used in conventional techniques) cannot be used.

[0218] Finally, with Figure 1Similar to step S111 in , upon determining that there is a target candidate cell with better radio link / beam measurement than the serving cell (for example, based on determining that the L1-RSRP of the target beam measurement is greater than the L1-RSRP of the serving beam measurement, or any other suitable criterion), DU 1 may issue a suitable MAC CE (or L1 message) in step S413 to trigger a cell change / handover to the target candidate cell.

[0219] In some possible implementations, the CSI report may be further enhanced to 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 may request the DU (controlling the prepared target cell, such as Figure 4 DU 2 in the example of ) to provide the number of RS indexes (e.g., SSB indexes) supported in the prepared target cell. This information (i.e., the number of SSB indexes of the target cell) can be sent to the CU as part of the exemplary UE context establishment response message as shown in step S405 (or in any other suitable manner). This information will also be propagated to the serving DU (i.e., Figure 4 DU 1 in the current example), other suitable target DUs (if necessary), and UEs (as exemplarily shown in steps S406, S410, and part of S411), which can derive the number of bits that can be allocated for reporting based on such information, such as the SSB index of the corresponding prepared target cell (for example, as shown in step S412).

[0220] Secondly, Figure 5 Another example of a signaling / message flow chart according to some other example embodiments of the present disclosure is schematically illustrated. As described above, unless otherwise specified, the same or similar reference numerals or messages (and the contents included therein) used in the drawings of the present disclosure may represent the same or similar element messages (and the corresponding contents therein), and therefore, for the sake of brevity, repeated descriptions thereof may be omitted.

[0221] Generally speaking, Figure 4 In the example embodiment of , it can be understood that the CU is now configured to determine the cell index to distinguish the L1 measurement of the cell. Therefore, the CU is also responsible for associating the prepared (multiple) PCIs of the target cell (or any other per-cell or per-network cell identifier as described above) with the corresponding cell index. Of course, in this case, the CU must provide the determined association between the cell index and the PCI to the (source) DU and the UE (and, if necessary, to the (multiple) other (target) DUs).

[0222] More specifically, it can be seen from the figure that Figure 5The example embodiments shown are Figure 4 Basically the same, except that instead of DU 1 being configured to associate the PCI with the cell index (step S408), now, it is the CU that is configured to determine the association between the PCI and the corresponding cell index of the prepared target cell (eg Figure 5 (as illustrated in step S506 of FIG. 1 ).

[0223] Similarly, the above process can be repeated for multiple target cells (e.g., PCell and / or PSCell) prepared for L1 / 2 inter-cell mobility, thereby generating an association list between the PCI of the target cell and the cell index, where one cell index is associated with one target cell. The configurations of all prepared target cells can be merged by the CU into one collective measurement configuration and sent out in one RRC reconfiguration message, or whenever the CU prepares a target cell, the CU can send a corresponding RRC reconfiguration message containing the corresponding measurement configuration of the target cell.

[0224] at last, Figure 6 Another example of a signaling / message flow chart according to some other example embodiments of the present disclosure is schematically illustrated. As described above, unless otherwise specified, the same or similar reference numerals or messages (and the contents included therein) used in the drawings of the present disclosure may represent the same or similar element messages (and the corresponding contents therein), and therefore, for the sake of brevity, repeated descriptions thereof may be omitted.

[0225] Generally speaking, Figure 6 In the example embodiment, it will be appreciated that the CU is configured to determine the association of the PCI (or any other per-cell or per-network cell identifier as described above) of the prepared target cell. However, in this example embodiment, instead of using a (newly introduced) cell index, a configuration identifier (ID) associated with the configuration of the prepared target cell (similar to the cell index, which is typically shorter than other cell identifiers such as PCI) is (re)used to identify the L1 beam measurements reported by the UE for the target cell. The configuration of the prepared target cell 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 a configuration identifier may be pre-existing, pre-configured, predetermined or configured to the UE, as shown in step S611, etc., as long as the network nodes (CU and DU) and the UE are able to use such a configuration identifier to identify or distinguish measurements of different cells.

[0226] As an illustrative example (but not to be construed as limiting in any way), Figure 6In the illustrated example embodiment, as shown in step S606, the CU may associate the PCI of the 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. Therefore, as can be understood and appreciated by those skilled in the art, such a "reconfiguration ID" may have different names according to various implementations. Since the CU may 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. As shown in step S613, when the UE receives a MAC CE command from DU 1, the UE applies one of the target cell configurations. In step S611, the CU will also send the reconfiguration ID of the prepared target cell with a given PCI and the corresponding target cell configuration to the UE. In this example, it can generally be assumed that the reconfiguration ID itself may be sufficient for the UE to associate the measurement with the corresponding cell, so an explicit and complete association between the PCI and the reconfiguration ID may not be required. For example, the UE can decode the target cell configuration associated with the reconfiguration ID to derive the PCI of the target cell. In this case, in step S611, the CU does not explicitly signal the PCI, but the UE obtains the PCI by decoding the target cell configuration. However, in some other examples, the CU may issue 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 not indicate the cell index (e.g. Figure 4 and Figure 5 ), but instead reports the reconfiguration ID together with the L1-RSRP measurement (and possibly the SSB index for identifying the beam). This reconfiguration ID can then be used by DU 1 (or any other suitable (multiple) DUs, if necessary) to identify the corresponding cell associated with the L1 measurement (because the CU has already notified this association between PCI and reconfiguration ID in step S607).

[0227] Similar to before, the above process can be repeated for multiple target cells (e.g., PCell and / or PSCell) prepared for L1 / 2 inter-cell mobility, thereby generating an association list between the cell configuration of the target cell and the cell identifier, where one cell identifier is associated with one target cell. The configurations of all prepared target cells can be merged by the CU into one collective measurement configuration and sent out in one RRC reconfiguration message, or whenever the CU prepares a target cell, the CU can send a corresponding RRC reconfiguration message containing the corresponding measurement configuration of the target cell.

[0228] For the sake of completeness, it should be noted that in the above reference Figures 4 to 6In any of the example embodiments described, in the case of releasing or replacing a target cell, the UE may generally be configured to release and / or replace a cell index corresponding to the target cell being released or replaced.

[0229] It should also be noted that even in Figures 4 to 6 In the example embodiment of the present invention, the association between the (longer) PCI (or any other per-cell or per-network cell identifier) ​​and the appropriate (shorter) identifier (cell index or reconfiguration ID, etc.) appears to be propagated between the network node and the UE at a specific timing / sequence, but this is not necessarily always the case. Depending on various implementations and / or requirements, this association between the prepared cell's PCI and the cell index (or reconfiguration ID) may also be issued at a later (or even earlier) point in time (e.g. upon a cell change trigger).

[0230] It should also be noted that although it may appear that only examples of cell index or reconfiguration ID are described, those skilled in the art can understand and appreciate that any other suitable identifier can also be used as long as the identifier allows the network node and the UE to identify and distinguish measurements of different cells.

[0231] In summary, when configured as recommended above, the network generally no longer needs to maintain the correct configuration of the SSB index for L1 / 2 inter-cell mobility. Therefore, mobility failures caused by possible misconfiguration of the SSB index can be avoided, thereby saving the signaling overhead associated with the RRC reconfiguration for configuring / updating the SSB index list, and also reducing the signaling overhead associated with the reporting of the PCI (10 bits) of each L1-RSRP.

[0232] According to another aspect of the present disclosure, the CU allocates a temporary dynamic mapping table to report the cell id + related measurements. The table includes a shorter length code than the normal PCI to identify the measured cell and reduce signaling traffic, such as in the following example process:

[0233] The UE sends L3 measurements of the detected (strongest) cells to the CU. The CU selects a number (e.g., 8) of cells to be further measured by the UE, such as the 8 strongest and / or best available cells, in view of load conditions, etc. The CU can report this to the DU for LLM. Each of the selected 8 cells has its own physical cell identifier PCI number, such as PC1, PC2, ..., PCI8. Each PCI typically has a length of 10 bits. This would require the UE to have sent 80 bits to identify the cell (+ related measurement results sent by the UE).

[0234] For example, allocating new cell IDs only for measurement purposes can reduce signaling traffic. For example, for 8 cells to be measured, only 3 bits are needed to distinguish the 8 cells:

[0235] 001——PCI1

[0236] 010——PCI2

[0237] 100——PCI3

[0238] …

[0239] 111——PCI8

[0240] The CU may update the cell list based on, for example, L3 measurement reports, for example, to prepare new target cells, replace or remove target cells. For example, PCI1 to PCI5 should still be measured, but if PCI6 to PCI8 need to be replaced by PCI9 to PCI11, a new updated allocation will be provided, for example:

[0241] 001——PCI1

[0242] 010——PCI2

[0243] 100——PCI3

[0244] …

[0245] 101——PCI9

[0246] 110——PCI10

[0247] 111——PCI11

[0248] Using only 3 bits (instead of 10 bits) only requires the UE to send 24 bits instead of 80 bits to identify the 8 cells to measure (+ the associated measurements sent by the UE) and thereby significantly reduces signaling.

[0249] If more than 8 cells should be measured, for example up to 16, 4 bits may be used for encoding.

[0250] If the UE wants to report on unconfigured / unprepared cells, it uses, for example, normal PCI and aperiodic L1 reporting or L3 measurement reporting.

[0251] According to another example process, the UE sends an L3 measurement of the detected (strongest) cell to the CU. The CU selects the number (e.g., 8) to be further measured by the UE, such as the 8 strongest and / or best available cells, in view of load conditions, etc. The CU configures the UE to report 8 cells in a (pre-)determined order, such as PCI1, PCI2, ..., PCI8. The UE then first sends a measurement report for the measurements related to PCI1, and then sends a measurement report for the measurements related to PCI2, and so on. The DU (or CU) will inherently know from the received report which measurement refers to which cell. In this case, even a 3-bit cell identifier is not required. In this case, the UE needs to always report a predefined number of measurements for each prepared cell. Otherwise, the network may not know how to interpret the results.

[0252] To provide more flexibility in reporting different numbers of measurements, the following variations of this process may be employed.

[0253] If the UE reports measurements of e.g. only 7 cells, the unreported cells may be marked as "unmeasured" (e.g. by XXX) so that no misjudgment occurs on the receiving side. The (predefined) protocol for reporting may then include e.g. measure1 bit, measure2 bit, ... The reporting of the actual measurements for cell 1, cell 2 (which is not reported), cell 3, ... may include:

[0254] 01010100111, XXXXXXXXXXX, 11001100110,…

[0255] XXXXXXXXXXX = reserved bits for indicating that cell 2 has no measurements reported, which may be, for example, a predefined sequence such as 00000000000, 11111111111, 10101010101, ... Alternatively, if no actual measurements are available, previous measurements may be reported again.

[0256] Alternatively, an additional flag (1 bit) may also be used to indicate whether to report the actual measurement.

[0257] According to another example procedure, the network associates the PCI of the prepared target cell with the cell identifier (as described above). The network configures the UE to report X L1 beam measurements for the prepared target cell, the PCI of which is associated with the cell identifier in a predefined sequence, for example, X=2, i.e., two beam measurements are performed for each cell starting from the cell with the smallest cell identifier (or vice versa, from the cell with the largest cell identifier to the cell with the smallest cell identifier) ​​or in any predefined sequence indicated by the network. The DU implicitly derives the association between the reported L1 beam measurements and the PCI using the predefined sequence for reporting beam measurements. In the event that the UE skips measurements of one prepared cell, it may indicate this to the network using a flag or a predefined sequence as described above.

[0258] Finally, although in the above-described example embodiments (with reference to the accompanying drawings), the messages passed / exchanged between network components / elements may appear to have specific / unambiguous names, depending on various implementations (e.g., underlining technology), as understood and appreciated by those skilled in the art, these messages may have different names and / or be passed / exchanged in different forms / formats.

[0259] According to some example embodiments, corresponding methods suitable for being performed by an apparatus (network element / component) as described above, such as a UE, a CU, (multiple) DUs, etc., are also provided.

[0260] It should also be noted that the above-mentioned device (equipment) features correspond to corresponding method features, but for reasons of simplicity, these method features may not be explicitly described. The disclosure of this document is considered to also extend to such method features. In particular, the present disclosure is understood to relate to methods of operating the above-mentioned devices and / or providing and / or arranging corresponding elements of these devices.

[0261] In addition, according to some other example embodiments, a corresponding device (for example, implementing the UE, CU, DU, etc. as described above) is also provided, which includes at least one processing circuit system and at least one memory for storing instructions executed by the processing circuit system, wherein the at least one memory and the instructions are configured to be together with the at least one processing circuit system so that the corresponding device performs at least the corresponding steps as described above.

[0262] However, in some other example embodiments, a corresponding apparatus (eg, implementing the UE, CU, DU, etc. described above) is provided, the apparatus comprising corresponding components configured to at least perform the corresponding steps described above.

[0263] It should be noted that the examples of the embodiments of the present disclosure are applicable to a variety of different network configurations. In other words, the examples shown in the above figures used as the basis for the above examples are merely illustrative and do not limit the present disclosure in any way. That is, based on the defined principles, other existing and proposed new functions available in the corresponding operating environment can be used in conjunction with the examples of the embodiments of the present disclosure.

[0264] It should also be noted that the disclosed example embodiments can be implemented in a variety of ways using hardware and / or software configurations. For example, the disclosed embodiments can be implemented using dedicated hardware and / or hardware associated with software that can be executed thereon. The components and / or elements in the accompanying drawings are merely examples and do not limit the scope of use or functionality of any hardware, software combined with hardware, firmware, embedded logic components, or a combination of two or more such components that implement a specific embodiment of the present disclosure.

[0265] It should be further noted that the description and the accompanying drawings illustrate only the principles of the present disclosure. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or illustrated herein, embody the principles of the present disclosure and are included in its spirit and scope. In addition, all examples and embodiments outlined in the present disclosure are primarily and explicitly intended to be used only for explanatory purposes to help the reader understand the principles of the proposed method. In addition, all statements of the principles, aspects, and embodiments of the present disclosure and specific examples thereof provided herein are intended to cover their equivalents.

Claims

1. A first network node, the first network node supporting at least one of a central unit control plane CU-CP function or a layer 3 protocol of a radio access network, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the first network node to at least: determining to prepare a target cell of a third network node for a 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) functionality or a layer 2 protocol of the radio access network; Acquire an association between a cell identifier of the target cell and the first identifier; as well as A configuration message is sent to a user equipment UE served by the source cell, the configuration message comprising: information indicating the association between the cell identifier of the target cell and the first identifier.

2. The first network node according to claim 1, wherein the first network node is further caused to: Sending a message to the third network node, the message comprising: Information indicating the association between the cell identifier of the target cell and the first identifier.

3. The first network node according to claim 1 or 2, wherein the first network node is further caused to: Information indicating the number of synchronization signal block (SSB) indexes configured in the target cell is received from the third network node.

4. The first network node according to claim 3, wherein the first network node is further caused to: and sending the information indicating the number of the SSB indexes 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 of the preceding claims, wherein the first identifier is a cell index for distinguishing beam measurements of different cells.

6. The first network node according to claim 5, wherein 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 comprising: information indicating the cell identifier of the target cell; and A response message is received from the second network node, the response message comprising information indicating an association between the cell identifier of the target cell and the cell index.

7. The first network node according to claim 5, wherein 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 cell index; and The first network node is further configured to: A request message is sent to the second network node, the request message comprising: information indicating the association between the cell identifier of the target cell and the cell index.

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

9. The first network node according to claim 8, wherein the obtaining of the association between the cell identifier of the target cell and the first identifier comprises: determining, by the first network node, an association between the cell identifier of the target cell and the configuration identifier; and The first network node is further configured to: A request message is sent to the second network node, the request message comprising information indicating the association between the cell identifier of the target cell and the configuration identifier.

10. The first network node according to any one of the preceding claims, wherein the configuration message further comprises: Indicates information about measurement-related configuration.

11. The first network node according to claim 10, wherein the measurement-related configuration comprises: Used to configure the UE to report the prepared N strongest beam measurements of the target cell without referring to the SSB index or channel state information reference signal CSI-RS index included in the configuration message.

12. The first network node according to any one of claims 10 or 11, wherein the measurement-related configuration comprises: Information used to configure the UE to independently determine the SSB index measured and reported by the UE.

13. The first network node according to any of the preceding claims, wherein the cell identifier is a physical cell identifier (PCI).

14. The first network node according to any of the preceding claims, wherein the first identifier has a bit length shorter than a bit length of the cell identifier.

15. A second network node, the second network node supporting at least one of a distributed unit DU function or a layer 2 protocol of a radio access network, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the second network node to at least: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU functionality or the layer 2 protocol of the radio access network and a first identifier, wherein the target cell is prepared by a first network node for lower layer mobility (LLM) with a source cell of the second network node, the first network node supporting at least one of the central unit control plane (CU-CP) functionality or the layer 3 protocol of the radio access network; as well as A message is received from a user equipment (UE) served by the source cell, the message comprising: information indicating a measurement report related to at least one beam of the target cell, and the first identifier.

16. The second network node according to claim 15, wherein the second network node is further caused to: Information is received from the first network node, the information indicating the number of synchronization signal block (SSB) indexes configured in the prepared target cell.

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

18. The second network node according to claim 17, wherein 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 comprising information indicating the cell identifier of the target cell; as well as determining, by the second network node, an association between the cell identifier of the target cell and the cell index; and The second network node is further configured to: A response message is sent to the first network node, the response message including information indicating an association between the cell identifier of the target cell and the cell index.

19. The second network node according to claim 17, wherein the obtaining of the association between the cell identifier of the target cell and the first identifier comprises: A message is received from the first network node, the message comprising information indicating the association between the cell identifier of the target cell and the cell index.

20. The second network node according to claim 15 or 16, wherein the first identifier is a configuration identifier associated with a configuration of the target cell and used to identify the configuration of the target cell, the configuration of the target cell being issued by the first network node to configure the UE to switch to the target cell; and The acquiring of the association between the cell identifier of the target cell and the first identifier comprises: A message is received from the first network node, the message comprising information indicating an association between the cell identifier of the target cell and the configuration identifier.

21. The second network node according to any one of claims 15 to 20, wherein the second network node is further caused to: Generate a measurement-related configuration, the measurement-related configuration comprising: Used to configure the UE to report the prepared N strongest beam measurements of the target cell without referring to the SSB index or the channel state information reference signal CSI-RS index included in the measurement related configuration; as well as A message including information indicating the measurement-related configuration is sent to the first network node.

22. The second network node according to any one of claims 15 to 20, wherein the second network node is further caused to: Generate a measurement-related configuration, the measurement-related configuration comprising: Information for configuring the UE to independently determine the SSB index measured and reported by the UE; as well as A message including information indicating the measurement-related configuration is sent to the first network node.

23. The second network node according to any one of claims 15 to 22, wherein the message received from the UE further comprises: Information indicating an index of an SSB detected by the UE for measuring at least one beam of the target cell.

24. The second network node according to any one of claims 15 to 23, wherein the second network node is further caused to: A message including information indicating an instruction for the UE to switch from the source cell to the target cell is sent.

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 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, the UE comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the UE to at least: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU functionality or the layer 2 protocol of the radio access network and a first identifier; as well as A message is sent to the second network node, the message comprising: information indicating a measurement report related to at least one beam of the target cell, and the first identifier.

28. The UE according to claim 27, wherein the first identifier is a cell index for distinguishing beam measurements of different cells; and The acquiring of the association between the cell identifier of the target cell and the first identifier comprises: A configuration message is received 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 comprising information indicating an association between the cell identifier and the cell index of the target cell.

29. The UE according to claim 28, wherein the received configuration message is an RRC reconfiguration message, and the RRC reconfiguration message further comprises: The CSI measurement related configuration is suitable for supporting L1 / 2 mobility function, and the number of SSB indexes configured in the target cell, and the message sent is an L1 measurement report, and the L1 measurement report includes: the cell index, SSB index and information about L1-RSRP.

30. The UE according to claim 27, wherein the first identifier is a configuration identifier associated with a configuration of the target cell and used to identify the configuration of the target cell, the configuration of the target cell being used for handover by the UE; and wherein the acquiring of the association between the cell identifier of the target cell and the first identifier comprises: A configuration message is received 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 comprising information indicating an association between the cell identifier of the target cell and the configuration identifier.

31. The UE according to claim 30, wherein the received configuration message is an RRC reconfiguration message, and the RRC reconfiguration message further comprises: The CSI measurement related configuration is suitable for supporting L1 / 2 mobility function, and the number of SSB indexes configured in the target cell, and the message sent is an L1 measurement report, and the L1 measurement report includes: the configuration identifier, SSB index and information about L1-RSRP.

32. The UE according to any one of claims 28 to 31, wherein the configuration message further includes information indicating measurement-related configuration, and the measurement-related configuration includes: Used to configure the UE to report information on the N strongest beam measurements of the target cell without referring to the synchronization signal block SSB index or the 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 measurement-related configuration, and the measurement-related configuration includes: Information used to configure the UE to independently determine the synchronization signal block SSB index measured and reported by the UE.

34. The UE according to any one of claims 27 to 33, wherein the sending of the message comprises: A message including information indicative of a measurement report related to the strongest beam measurement of the target cell is sent.

35. The UE according to any one of claims 28 to 34, wherein the configuration message further comprises: Information indicating the number of SSB indexes configured in the target cell.

36. The UE according to any one of claims 27 to 35, wherein the message sent to the second network node further comprises: Information indicating an index of an SSB detected by the UE and used for the measurement.

37. The UE according to any one of claims 27 to 36, wherein the UE is further caused to: A message including information indicating an instruction for the UE to hand over from the source cell to the target cell is received from the second network node.

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. A method of a first network node, the first network node supporting at least one of a Central Unit Control Plane (CU-CP) functionality or a layer 3 protocol of a radio access network, the method comprising: determining to prepare a target cell of a third network node for a 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) functionality or a layer 2 protocol of the radio access network; Acquire an association between a cell identifier of the target cell and the first identifier; as well as A configuration message is sent to a user equipment UE served by the source cell, the configuration message comprising: information indicating the association between the cell identifier of the target cell and the first identifier.

41. A method of a second network node, the second network node supporting at least one of a distributed unit (DU) function or a layer 2 protocol of a radio access network, the method comprising: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU functionality or the layer 2 protocol of the radio access network and a first identifier, wherein the target cell is prepared by a first network node for lower layer mobility (LLM) with a source cell of the second network node, the first network node supporting at least one of the central unit control plane (CU-CP) functionality or the layer 3 protocol of the radio access network; and A message is received from a user equipment (UE) served by the source cell, the message comprising information indicating a measurement report related to at least one beam of the target cell and the first identifier.

42. A method for a user equipment (UE), the UE being served by a source cell of a second network node supporting at least one of a distributed unit (DU) function of a radio access network or a layer 2 protocol, the method comprising: obtaining an association between a cell identifier of a target cell of a third network node supporting at least one of the DU functionality or the layer 2 protocol of the radio access network and a first identifier; as well as A message is sent to the second network node, the message comprising: information indicating a measurement report related to at least one beam of the target cell, and the first identifier.

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

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

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