Cross-cell reference signal beam mapping and measurement

Abstract

A technical solution is provided that allows for reducing unnecessary reference signal (RS) transmissions and configurations associated with each target or non-serving cell, thereby reducing unnecessary RS measurements performed by multiple UEs. To this end, a mapping is used that associates each RS of a serving cell with one or more RSs of each non-serving cell. The mapping can be created by a network node based on past RS measurements related to previous handover events, or a UE can be configured by a network node to do so. By using the mapping, the UE determines which RS(s) of each non-serving cell is associated with the strongest RS(s) of the serving cell, whereupon the UE starts performing measurements on each determined RS of the non-serving cell. In another alternative embodiment, the mapping created by the network node is provided to another network node instead of the UE, and said another network node configures and broadcasts only those RSs that are associated with the strongest RS(s) of the serving cell.

Description

Technical Field

[0001] This disclosure generally relates to the field of wireless communications. In particular, this disclosure relates to techniques for cross-cell reference signal (RS) mapping and measurement, for example, in lower-level (i.e., Level 1 (L1) or Level 2 (L2)) mobility scenarios. Background Technology

[0002] L1 / 2 inter-cell mobility is one of the targets of mobility enhancements in Release 18, and further enhancements are being discussed in Release 19. Unlike the Level 3 (L3) mobility process, where handover between two cells is determined by the Radio Resource Control (RRC) layer, L1 / 2 inter-cell mobility is performed by the Media Access Control (MAC) layer, which terminates, for example, in the Distribution Unit (DU) within the split or decomposed architecture of the Radio Access Network (RAN) node (e.g., gNB).

[0003] In the context of Channel State Information RS (CSI-RS) configuration and transmission in L1 / L2 inter-cell mobility scenarios, the target DU (i.e., the DU from which the User Equipment (UE) should switch) typically configures all CSI-RS for the UE to ensure that the UE measures all CSI-RS. However, this leads to the following disadvantages: (1) the serving DU must send all CSI-RS indices, even when they are not needed (e.g., if their parent SSB indices cannot be detected by the UE); and (2) the UE needs to perform measurements on all configured CSI-RS indices of the target cell, which can be a limiting factor considering that multiple cells can be prepared in L1 / L2 triggered mobility (LTM). Summary of the Invention

[0004] The present invention is provided to present, in a simplified form, the selection of concepts further described below in the detailed embodiments. The present invention is not intended to identify key features of this disclosure, nor is it intended to limit the scope of this disclosure.

[0005] The purpose of this disclosure is to provide a technical solution to reduce unnecessary RS (e.g., CSI-RS) transmissions and configurations associated with each prepared target or candidate cell, thereby reducing unnecessary RS (e.g., CSI-RS) measurements performed by multiple UEs.

[0006] The above-mentioned objectives are achieved by the features of the independent claims in the appended claims. Further embodiments and examples will be apparent from the dependent claims, detailed descriptions, and drawings.

[0007] According to a first aspect, a serving network node in a radio access network (RAN) is provided. The serving network node includes at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the serving network node to operate at least as follows: First, the serving network node collects past RS measurements performed by a UE during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of a non-serving cell. Then, the serving network node uses the past RS measurements to generate control information, which includes a mapping between the first set of RSs and the second set of RSs. Next, the serving network node sends the control information and the past RS measurements to the UE and a non-serving network node. By using this mapping, the relationship between the RSs of the serving cell and the RSs of the non-serving cell (which may be a potential target cell for the next handover event) can be established. This knowledge of the relationship allows the non-serving network node to configure itself and allows the UE to measure only the most relevant RS(s) of the non-serving cell(s), thereby reducing the number of unnecessary RS measurements that the UE would otherwise perform.

[0008] In one example embodiment of the first aspect, the mapping between the first group of RSs and the second group of RSs includes at least one of the following: a one-to-one mapping between an RS from the first group of RSs and an RS from the second group of RSs; a one-to-many mapping between an RS from the first group of RSs and a subset of RSs from the second group of RSs; a many-to-one mapping between a subset of RSs from the first group of RSs and an RS from the second group of RSs; and a many-to-many mapping between a subset of RSs from the first group of RSs and a subset of RSs from the second group of RSs. These different types of mapping can provide flexibility in determining which(s) of the non-serving RSs should be measured, which can be beneficial in some use cases. For example, in a scenario where a cell handover occurs in an area where at least two beams of a serving cell are receiving at similar power, for most observations, the mapping between the serving cell's RSs and the non-serving cell's RSs should involve all such multiple RSs from the serving cell, as the mapping then becomes more accurate.

[0009] According to a second aspect, a non-serving network node in a RAN is provided. The non-serving network node includes at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the non-serving network node to operate at least as follows: First, the non-serving network node receives control information and past RS measurements from a serving network node. The past RS measurements are performed by the UE during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of the non-serving cell. The control information includes a mapping between the first set of RSs and the second set of RSs. Then, the non-serving network node uses the past RS measurements to determine at least one strongest RS in terms of signal strength within the first set of RSs. Next, the non-serving network node uses the determined at least one strongest RS and the mapping to determine at least one target RS to be measured by the UE within the second set of RSs. Thereafter, the non-serving network node configures and transmits the at least one target RS in the RAN during the next handover event for the UE. By using the mapping, a relationship between the RSs of the serving cell and the RSs of the non-serving cell (which may be a potential target cell for the next handover event) can be established. This knowledge of relationships allows non-serving network nodes to configure themselves and allows the UE to measure only the most relevant RS(s) of the non-serving cell, thereby reducing the number of unnecessary RS measurements that the UE would otherwise perform.

[0010] In one example embodiment of the second aspect, the mapping between the first group of RSs and the second group of RSs includes at least one of the following: a one-to-one mapping between an RS from the first group of RSs and an RS from the second group of RSs; a one-to-many mapping between an RS from the first group of RSs and a subset of RSs from the second group of RSs; a many-to-one mapping between a subset of RSs from the first group of RSs and an RS from the second group of RSs; and a many-to-many mapping between a subset of RSs from the first group of RSs and a subset of RSs from the second group of RSs. These different types of mapping can provide flexibility in determining which(s) of the non-serving RSs should be measured, which can be beneficial in some use cases. For example, in a scenario where a cell handover occurs in an area where at least two beams of a serving cell are receiving at similar power, for most observations, the mapping between the serving cell's RSs and the non-serving cell's RSs should involve all such multiple RSs from the serving cell, as the mapping then becomes more accurate.

[0011] In one example embodiment of the second aspect, a non-serving network node is instructed to identify at least two strongest RSs in terms of signal strength from a first set of RSs. In this embodiment, the non-serving network node determines at least one target RS based on which of the at least two strongest RSs is stronger. In other words, this embodiment involves sorting at least two strongest RSs according to their signal strength, and the ordered list of at least two strongest RSs is then used by the non-serving network node in conjunction with a received mapping to determine one or more target RSs in a second set of RSs. This embodiment may be advantageous when a mapping between multiple RSs serving a cell and multiple RSs serving a non-serving cell is required.

[0012] In an alternative example embodiment of the second aspect, the non-serving network node is caused to identify at least two strongest RSs in terms of signal strength from the first set of RSs. In this embodiment, the non-serving network node is caused to determine at least one target RS based on the relative value of the signal strength between the at least two strongest RSs. This embodiment may also be advantageous when a mapping between multiple RSs serving a cell and multiple RSs serving a non-serving cell is required.

[0013] In one example embodiment of the second aspect, the non-serving network node is further configured to notify the serving network node when the non-serving network node starts and ends the transmission of at least one target RS.

[0014] According to a third aspect, a method for operating a serving network node in a RAN is provided. The method begins with a step of collecting past RS measurements performed by a UE during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of a non-serving cell. The method then proceeds to a step of generating control information, which includes a mapping between the first and second sets of RSs. Next, the method proceeds to a step of sending the control information and past RS measurements to the UE and the non-serving network node. Using this mapping, the relationship between the RSs of the serving cell and the RSs of the non-serving cell (which may be a potential target cell for the next handover event) can be established. This knowledge of the relationship allows the non-serving network node to configure itself and allows the UE to measure only the most relevant RS(s) of the non-serving cell(s), thereby reducing the number of unnecessary RS measurements that the UE would otherwise perform.

[0015] According to a fourth aspect, a method for operating a non-serving network node in a wireless communication network is provided. The method begins with receiving control information and past RS measurements from the serving network node. The past RS measurements are performed by the UE during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of the non-serving cell. The control information includes a mapping between the first set of RSs and the second set of RSs. The method then proceeds to the step of determining at least one strongest RS in terms of signal strength within the first set of RSs using the past RS measurements. Next, the method proceeds to the step of determining at least one target RS to be measured by the UE in the second set of RSs using the determined at least one strongest RS and the mapping. Afterward, the method proceeds to the step of configuring and transmitting at least one target RS in the RAN during the next handover event for the UE. By using the mapping, the relationship between the RSs of the serving cell and the RSs of the non-serving cell (which may be a potential target cell for the next handover event) can be established. This knowledge of the relationship allows the non-serving network node to be configured and allows the UE to measure only the most relevant RS(s) of the non-serving cell(s), thereby reducing the number of unnecessary RS measurements that the UE would otherwise perform.

[0016] According to a fifth aspect, a computer program product is provided. The computer program product includes a computer-readable storage medium storing computer code. The computer code is executed by at least one processor, causing the at least one processor to perform the method according to the third aspect. By using such a computer program product, the implementation of the method according to the third aspect in any service network node (such as the service network node according to the first aspect) can be simplified.

[0017] According to a sixth aspect, a computer program product is provided. The computer program product includes a computer-readable storage medium storing computer code. The computer code is executed by at least one processor, causing the at least one processor to perform the method according to the fourth aspect. By using such a computer program product, implementation of the method according to the fourth aspect in any non-serving network node (such as the non-serving network node according to the second aspect) can be simplified.

[0018] According to a seventh aspect, a serving network node in a wireless communication network is provided. The serving network node includes components for collecting past RS measurements performed by a UE during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of a non-serving cell. The serving network node also includes components for generating control information, which includes a mapping between the first set of RSs and the second set of RSs. The serving network node also includes components for transmitting the control information and past RS measurements to the UE and non-serving network nodes. By using this mapping, a relationship between the RSs of the serving cell and the RSs of non-serving cells (which may be potential target cells for the next handover event) can be established. This knowledge of the relationship allows the non-serving network node to be configured and allows the UE to measure only the most relevant RS(s) of the non-serving cell(s), thereby reducing the number of unnecessary RS measurements that the UE would otherwise perform.

[0019] According to an eighth aspect, a non-serving network node in a wireless communication network is provided. The non-serving network node includes components for receiving control information and past RS measurements from a serving network node. The past RS measurements are performed by the UE during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of the non-serving cell. The control information includes a mapping between the first set of RSs and the second set of RSs. The non-serving network node also includes components for determining at least one strongest RS in terms of signal strength in the first set of RSs using the past RS measurements. The non-serving network node also includes components for determining at least one target RS to be measured by the UE in the second set of RSs using the determined at least one strongest RS and the mapping. The non-serving network node also includes components for configuring and transmitting at least one target RS in the RAN during the next handover event for the UE. By using the mapping, a relationship between the RSs of the serving cell and the RSs of the non-serving cell (which may be a potential target cell for the next handover event) can be established. This knowledge of relationships allows non-serving network nodes to configure themselves and allows the UE to measure only the most relevant RS(s) of the non-serving cell, thereby reducing the number of unnecessary RS measurements that the UE would otherwise perform.

[0020] Other features and advantages of this disclosure will become apparent from reading the following detailed description and viewing the accompanying drawings. Attached Figure Description

[0021] This disclosure is explained below with reference to the accompanying drawings, in which: Figure 1 A signaling diagram of L1 / L2 inter-cell mobility according to the prior art is shown; Figure 2 A block diagram of a UE in a wireless communication network according to an example embodiment is shown; Figure 3 An example of operation according to a first example embodiment is shown. Figure 2 The flowchart of the UE method; Figure 4 A block diagram of a serving network node in a wireless communication network according to an example embodiment is shown; Figure 5 An example of operation according to a first example embodiment is shown. Figure 4 A flowchart of the method for serving network nodes; Figure 6 The signaling diagram of mobility between L1 and L2 cells is shown, in which Figure 2 UE and Figure 4 The service network nodes are respectively based on Figure 3 and Figure 5 The methods interact with each other; Figure 7 The diagram schematically illustrates a CSI-RS beam spanning two adjacent cells, where Figure 2 The UE switches from one cell to another; Figure 8 The probability quality function (PMF) of the target cell CSI-RS index for a given serving cell CSI-RS index is shown. Figure 9 An example of operation according to a second example embodiment is shown. Figure 2 The flowchart of the UE method; Figure 10 An example of operation according to a second example embodiment is shown. Figure 4 A flowchart of the method for serving network nodes; Figure 11 The signaling diagram of mobility between L1 and L2 cells is shown, in which Figure 2 UE and Figure 4 The service network nodes are respectively based on Figure 9 and Figure 10 The methods interact with each other; Figure 12 An example of operation according to a third example embodiment is shown. Figure 4 A flowchart of the method for serving network nodes; Figure 13 A block diagram of adjacent network nodes in a wireless communication network according to an example embodiment is shown; Figure 14 An example embodiment of operation is shown. Figure 12 A flowchart of the method for using adjacent network nodes; and Figure 15 The signaling diagram of mobility between L1 and L2 cells is shown, in which Figure 2 UE and Figure 4 The service network nodes are respectively based on Figure 12 and Figure 14 The methods interact with each other. Detailed Implementation

[0022] Various embodiments of the present disclosure are described in further detail with reference to the accompanying drawings. However, the present disclosure may be embodied in many other forms and should not be construed as limited to any particular structure or function discussed in the following description. Rather, these embodiments are provided to make the description of the present disclosure detailed and complete.

[0023] As will be apparent to those skilled in the art from the detailed description, the scope of this disclosure covers any embodiment thereof disclosed herein, whether implemented independently or in conjunction with any other embodiment of this disclosure. For example, the apparatus and methods disclosed herein can be implemented in practice using any number of the embodiments provided herein. Furthermore, it should be understood that any embodiment of this disclosure can be implemented using one or more elements presented in the appended claims.

[0024] Unless otherwise stated, any embodiment described herein as an "example embodiment" should not be construed as preferred or having an advantage over other embodiments.

[0025] According to the example embodiments disclosed herein, a User Equipment (UE) can refer to an electronic computing device configured to perform wireless communication. A UE can be implemented as a mobile station, mobile terminal, mobile subscriber unit, mobile phone, cellular phone, smartphone, cordless phone, personal digital assistant (PDA), wireless communication device, desktop computer, laptop computer, tablet computer, gaming device, netbook, smartbook, ultrabook, medical mobile device or equipment, biometric sensor, wearable device (e.g., smartwatch, smart glasses, smart wristband, etc.), entertainment device (e.g., audio player, video player, etc.), vehicle component or sensor (e.g., driver assistance system), smart meter / sensor, unmanned vehicle (e.g., industrial robot, quadcopter, etc.) and its components (e.g., self-driving car computer), industrial manufacturing equipment, Global Positioning System (GPS) device, Internet of Things (IoT) device, Industrial IoT (IIoT) device, Machine-Type Communication (MTC) device, a set of Massive IoT (MIoT) or Massive MTC (mMTC) devices / sensors, or any other suitable mobile device configured to support wireless communication. In some embodiments, a UE can refer to at least two juxtaposed and interconnected UEs as defined herein.

[0026] As used in the example embodiments disclosed herein, a network node can refer to a node in either the Radio Access Network (RAN) or the Core Network (CN). It should be noted that a CN can refer to a network designed to connect different RAN nodes by providing appropriate interfaces therebetween. A CN can also provide gateways to other networks, such as data networks (DNs).

[0027] As part of the RAN, a network node can be implemented as a fixed point for communication / communication nodes of a UE in a specific wireless communication network. More specifically, a RAN node can be used to connect a UE to a DN via a CN, and may be referred to as a Base Transceiver Station (BTS) for 2G communication technology, a NodeB for 3G communication technology, an Evolved NodeB (eNodeB) for 4G communication technology, and a gNB for 5G New Radio (NR) communication technology. RAN nodes can serve different types of cells, such as macrocells, microcells, picocells, femtocells, and / or other cell types. Macrocells can cover relatively large geographic areas (e.g., a radius of at least several kilometers). For example, a microcell can cover a geographic area with a radius of less than two kilometers. Picocells can cover relatively small geographic areas, such as offices, shopping malls, train stations, stock exchanges, etc. Femtocells can cover even smaller geographic areas (e.g., homes).

[0028] As part of the CN, a network node can also refer to any CN network function, such as Access and Mobility Management Function (AMF), Session Management Function (SMF), Unified Data Management (UDM), User Plane Function (UPF), Policy Control Function (PCF), etc. AMF supports the termination of Non-Access Stratum (NAS) signaling, NAS encryption and integrity protection, registration management, connection management, mobility management, access authentication and authorization, and security context management. SMF supports session management (session establishment, modification, and release), UE IP address allocation and management, Dynamic Host Configuration Protocol (DHCP) functions, termination of NAS signaling related to session management, downlink (DL) data notification, and UPF service redirection configuration for appropriate service routing. UDM supports Authentication and Key Agreement (AKA) credential generation, user identity processing, access authorization, and subscription management. UPF supports packet routing and forwarding, packet inspection, Quality of Service (QoS) processing, acts as an external Protocol Data Unit (PDU) session point interconnected with the DN, and serves as an anchor point for mobility within and between Radio Access Technologies (RATs). PCF supports a unified policy framework, providing policy rules to control plane (CP) functions and accessing subscription information for policy decisions in the unified data repository (UDR).

[0029] According to the example embodiments disclosed herein, the wireless communication network through which the UE and network nodes communicate with each other can refer to a cellular or mobile network, a wireless local area network (WLAN), a wireless personal area network (WPAN), a wireless wide area network (WWAN), a satellite communication (SATCOM) system, or any other type of wireless communication network. Each of these types of wireless communication networks supports wireless communication according to one or more communication protocol standards. For example, a cellular network can operate according to the Global System for Mobile Communications (GSM) standard, the Code Division Multiple Access (CDMA) standard, the Wideband Code Division Multiple Access (WCDM) standard, the Time Division Multiple Access (TDMA) standard, or any other communication protocol standard; a WLAN can operate according to one or more versions of the IEEE 802.11 standard; a WPAN can operate according to the Infrared Data Association (IrDA), Wireless USB, Bluetooth, or ZigBee standards; and a WWAN can operate according to the Global Microwave Access Interoperability (WiMAX) standard.

[0030] Figure 1 Signaling diagram 100 for L1 / L2 inter-cell mobility according to the prior art is shown. More specifically, signaling diagram 100 relates to an exemplary implementation of L1 / 2 inter-cell mobility from the serving cell in distribution unit 1 (DU1) to the target cell in DU2 (i.e., an intra-DU control unit (CU) scenario). The same diagram will also be applied if DU1 changes the same intra-DU CU cell as DU2.

[0031] Signaling diagram 100 begins at step S102, where the UE sends a measurement report to DU1. The measurement report contains cell quality measurements of the serving cell and neighboring cells. The UE can be configured by DU1 (in this case, its serving network node) to send the measurement report early while it still has a good connection to DU1.

[0032] Then, signaling diagram 100 proceeds to step S104, where DU1 forwards the measurement report to CU. CU uses the reported cell quality measurements to identify a potential set of candidate target cells that the UE can hand over to. In this example, CU identifies candidate target cells served by DU1 and another DU2 controlled by the same CU.

[0033] Next, signaling diagram 100 proceeds to step S106, where the CU requests the preparation of a candidate target cell controlled by DU1 by sending a UE context modification request message.

[0034] In response, in step S108, DU1 provides the UE configuration in a UE context modification response message containing the container from DU1 to CU.

[0035] The next steps S110 and S112 of signaling diagram 100 are similar to steps S106 and S108, respectively, except that they are performed using DU2 to prepare the target cells (multiple) controlled by DU2.

[0036] After receiving the UE configuration of the candidate target cells controlled by DU1 and DU2, the CU generates an RRC reconfiguration message in step S114. In step S116, the RRC reconfiguration message is also sent to the UE. Among other information, the RRC reconfiguration message includes: (1) a measurement reporting configuration for L1 / 2 handover, i.e., a configuration on how to report L1 beam measurements of the serving cell and the target cell (in step S120), and (2) a configuration of the prepared candidate cells that the UE needs to execute when it receives a MAC control element (CE) command to change the serving cell (i.e., perform a handover) (in step S122).

[0037] After confirming the RRC reconfiguration to the CU in step S118, the UE begins to periodically report the L1 beam measurement of the serving cell and the L1 beam measurement of the candidate target cell in step S120.

[0038] Subsequently, signaling diagram 100 proceeds to step S122, where, upon determining the existence of a target candidate cell with better radio link / beam measurement than the serving cell (e.g., [Target beam measurement L1-RSRP] > [Serving beam measurement L1-RSRP] + [Offset of time quantity, e.g., Trigger Time (TTT)]), DU1 sends a MAC CE command or L1 message to the UE to trigger a cell change to the target candidate cell. In the final step S124, the UE performs a handover from the serving cell to the target cell.

[0039] To trigger a cell change in step S122, the serving DU (i.e., DU1) needs to indicate the Transport Configuration Index (TCI) status, which includes QCL information for receiving from the target cell on the Physical Downlink Control Channel (PDCCH) / Physical Downlink Shared Channel (PDSCH) (DL Reception) and / or for transmitting on the Physical Uplink Control Channel (PUCCH) / Physical Uplink Shared Channel (PUSCH) (UL Transmission). The QCL information includes: 1) a Reference Signal (RS), 2) a QCL type (which can be any of type A, type B, type C, and type D), and 3) the bandwidth portion (bwp) where the RS resides. The definition of the QCL type is provided in TS 38.214 as follows: -'Type A': {Doppler frequency shift, Doppler spread, average delay, delay spread} -'Type B': {Doppler frequency shift, Doppler spread} -'Type C': {Doppler shift, average delay} -'Type D': {Space Rx parameter}.

[0040] To switch serving beams, the QCL information allows one of the following options: (1) qcl-type 1: reference signal = trace RS (TRS) index, where TRS is a special configuration of CSI-RS index (see TS 38.331), and qcl-type = A, qcl-type 2 (only applicable to frequency range 2 (FR2)): reference signal = same TRS index and qcl-type = D.

[0041] (2) qcl-type 1: reference signal = trace RS (TRS) index and qcl-type = A, qcl-type 2 (only applicable to FR2): reference signal = with repeating CSI-RS index and qcl-type = D.

[0042] For example, in option (1) and for FR1, DU1 points to the TRS index as the QCL source, and the UE should use the QCL source to estimate the channel attributes (i.e., Doppler shift, Doppler spread, average delay, delay spread) for receiving PDCCH / PDSCH and / or transmitting PUCCH / PUSCH.

[0043] However, in order for the serving DU (i.e., DU1) to indicate the TCI state containing QCL information, where the QCL information uses the CSI-RS index as the source RS, the target DU (i.e., DU2) that controls the prepared target cell can provide a list of CSI-RS that should be measured by the UE. Here, DU2 should also be aware of the corresponding configuration to select the appropriate TCI state of the target cell for the UE to use during cell handover.

[0044] To account for all possible target CSI-RSs measured by the UE, DU2 needs to configure them for the UE. In other words, even if some of the CSI-RS indices are not needed (e.g., if the UE cannot detect its parent SSB index), DU2 must still send all CSI-RS indices. All of this will cause the UE to perform unnecessary RS measurements.

[0045] The example embodiments disclosed herein provide a technical solution to reduce unnecessary RS (e.g., CSI-RS) transmissions and configurations associated with each prepared target (candidate or non-serving) cell, thereby reducing unnecessary RS (e.g., CSI-RS) measurements performed by multiple UEs. To this end, a mapping (e.g., in the form of a mapping table) is used, which associates each RS of the serving cell with one or more RSs of each non-serving cell in a wireless communication network (e.g., RAN). This mapping may be created by a network node of the RAN based on past measurements related to previous handover events, or the UE may be configured by the network node to do so. By using the mapping, the UE determines a subset of RSs for each non-serving cell, which is associated with the serving cell's... The strongest RS (or the RS with the best signal strength, and / or RSs arranged in a specified order according to signal strength) is associated, and the UE then performs measurements on the determined subset of RSs. In another alternative embodiment, the mapping created by the network node is provided to the target network node instead of the UE, and the target network node is only configured with the serving cell's... The RSs associated with the strongest RS.

[0046] Figure 2 A block diagram of a UE 200 in a RAN according to an example embodiment is shown. Figure 2 As shown, UE 200 includes a processor 202 and a memory 204. Memory 204 stores processor-executable instructions 206, which, when executed by processor 202, cause processor 202 to perform various aspects of this disclosure, as will be described in more detail below. It should be noted that in Figure 2 The number, arrangement, and interconnection of the building elements constituting UE 200 shown are not intended to be any limitation of this disclosure, but are merely intended to provide a general idea of ​​how the building elements can be implemented within UE 200. For example, processor 202 may be replaced by several processors, and memory 204 may be replaced by several removable and / or fixed storage devices, depending on the specific application. Furthermore, in some embodiments, processor 202 may perform different operations required for data reception and transmission, such as signal modulation / demodulation, encoding / decoding, etc. Alternatively, UE 200 may also include an individual transceiver that can be configured to perform the required operations for data reception and transmission based on commands from processor 202.

[0047] Processor 202 can be implemented as a CPU, a general-purpose processor, a single-purpose processor, a microcontroller, a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), a complex programmable logic device, etc. It should also be noted that processor 202 can be implemented as any combination of one or more of the foregoing. As an example, processor 202 can be a combination of two or more microprocessors.

[0048] Memory 204 can be implemented as a classic non-volatile or volatile memory used in modern electronic computing machines. As examples, non-volatile memory may include read-only memory (ROM), ferroelectric random access memory (RAM), programmable ROM (PROM), electrically erasable PROM (EEPROM), solid-state drives (SSD), flash memory, disk storage devices (such as hard disk drives and magnetic tape), optical disk storage devices (such as CDs, DVDs, and Blu-ray discs), etc. As for volatile memory, examples include dynamic RAM, synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), static RAM, etc.

[0049] The processor-executable instructions 206 stored in memory 204 can be configured to cause processor 202 to execute computer-executable program code of various aspects of this disclosure. The computer-executable program code for performing the operations or steps of various aspects of this disclosure can be written in any combination of one or more programming languages, such as Java, C++, Python, etc. In some examples, the computer-executable program code can be in the form of a high-level language or in a pre-compiled form, and is generated on the fly by an interpreter (also pre-stored in memory 204).

[0050] Figure 3 A flowchart of a method 300 for operating a UE 200 according to a first example embodiment is shown. Method 300 begins at step S302, where the processor 202 receives control information from a network node (e.g., a gNB) of the RAN. Step S302 can be performed, for example, using RRC signaling. Alternatively, step S302 can be performed after the UE 200 has established a connection to the network node. Alternatively, the network node can broadcast the control information, for example, as part of a System Information Block (SIB) message. The control information includes a first set of RSs (i.e., {RS1, ..., RS2}) associated with multiple beams of the serving cell. M}) and a second set of RS (i.e., {RS'1, ..., RS') associated with multiple beams of non-serving cells. N A mapping between {RS1, ..., RS) where M and N are natural numbers. For example, the mapping can be used to map {RS1, ..., RS) to ... M Each RS in} is related to {RS'1, ..., RS'}N One or more RSs in {RS1, ..., RS} can be associated, or a mapping can be used to associate {RS1, ..., RS}. M The RS subset in} (ordered appropriately according to signal strength) and {RS'1, ..., RS'} N The RS subset in {RS1, ..., RS} is associated. Both the serving cell and non-serving cells can be controlled by the network node with which the UE 200 has established a connection. Alternatively, the serving cell can be controlled by the network node, while the non-serving cell can be controlled by different network nodes of the RAN. Next, method 300 proceeds to step S306, where the processor 202 in {RS1, ..., RS} M In the process 300, one or more strongest RSs are determined based on signal strength. Signal strength can refer to signal-to-interference-plus-noise ratio (SINR), reference signal received quality (RSRQ), and / or reference signal received power (RSRP). Furthermore, method 300 proceeds to step S308, where processor 202 uses the one or more strongest RSs and the received mapping to determine the maximum RS in {RS'1, ..., RS'}. N In step S300, one or more target RSs to be measured are identified. Then, method 300 proceeds to step S310, where processor 202 begins performing measurements on the target RSs(s). The measurements may involve SINR, RSRQ, and / or RSRP measurements on a subset of RSs.

[0051] This mapping can represent a one-to-one mapping between an RS from a first set of RS and an RS from a second set of RS (e.g., RS1->RS'2, meaning RS1 is mapped to RS'2). This mapping can also additionally or alternatively represent a one-to-many mapping between an RS from the first set of RS and a subset of RS from the second set of RS (e.g., RS1->{RS'2, RS'3}). This mapping can also additionally or alternatively represent a many-to-one mapping between a subset of RS from the first set of RS and an RS from the second set of RS (e.g., {RS'1, RS'2}->RS'2). This mapping can also additionally or alternatively represent a many-to-many mapping between a subset of RS from the first set of RS and a subset of RS from the second set of RS (e.g., {RS1, RS3}->{RS'2, RS'3}).

[0052] In one example embodiment, the processor 202 may determine {RS1, ..., RS1} in step S306. MThe processor 202 determines at least two of the strongest RSs in the list of at least two strongest RSs in step S308, and determines (multiple) target RSs based on which of the at least two strongest RSs is stronger. That is, the processor 202 can first sort the at least two strongest RSs according to their signal strength, so it can use the ordered list or subset of the at least two strongest RSs in step S308. Alternatively, the processor 202 can determine {RS1, ..., RS2} in step S306. M At least two of the strongest RSs in}, but now in step S308, target RSs are determined based on the relative values ​​of the signal strengths of the at least two strongest RSs.

[0053] In one example embodiment, method 300 may include additional steps, wherein processor 202 sends a measurement report to the network node including measurements of the determined subset of RSs, and in response, processor 202 receives a handover instruction from the network node. The handover instruction may cause processor 202 of UE 200 to switch to a target beam among multiple beams in the non-serving cell. The network node selects the target beam based on measurements of the target RS(s). Alternatively, the handover instruction may cause processor 202 of UE 200 to determine the beam with the best beam quality among the multiple beams in the non-serving cell and switch to that beam. The measurement report may be sent to the network node, for example, using L1 signaling.

[0054] Figure 4 A block diagram of a serving network node 400 in a wireless communication network according to an example embodiment is shown. The serving network node 400 is intended to communicate with a UE 200 in the RAN. Figure 4 As shown, network node 400 includes processor 402 and memory 404 coupled to processor 402. Memory 404 stores processor-executable instructions 406, which, when executed by processor 402, cause processor 402 to implement various aspects of this disclosure, as will be described in more detail below. It should be noted again that in Figure 4 The number, arrangement, and interconnection of the building elements constituting the service network node 400 shown are not intended to be any limitation of this disclosure, but are merely intended to provide a general concept of how the building elements can be implemented within the service network node 400. Typically, the processor 402, memory 404, and processor executable instructions 406 can be implemented in the same or similar manner as processor 202, memory 204, and processor executable instructions 206, respectively.

[0055] Figure 5A flowchart of a method 500 for operating a serving network node 400 according to a first example embodiment is shown. Method 500 begins at step S502, where processor 402 collects past RS measurements, which are performed by UE 200 (i.e., processor 202) during one or more past handover events in the RAN. The past RS measurements are associated with a set of RS (i.e., {RS1, ..., RS200}). M}) and the second group RS (i.e., {RS'1, ..., RS') N The RS measurement in the past may involve {RS1, ..., RS}. M One or more RS and {RS'1, ..., RS'} in} N One or more RSs in the serving cell and / or non-serving cell. Additionally or alternatively, past measurements may involve one or more RSs in one or more cells similar to the serving cell and / or non-serving cell. Furthermore, past measurements may be performed by UE 200 and / or any other UE in the serving cell and non-serving cell. In the next step S504, processor 402 uses the past RS measurements to generate control information for UE 200. The mapping included in the control information can be obtained by applying a conditional probability quality function or a joint probability quality function to the past RS measurements. As a non-limiting example, the mapping may be in the form of a mapping table. Next, method 500 proceeds to step S504, where processor 402 sends the control information to UE 200 (i.e., processor 202). As previously described, step S504 can be performed using RRC signaling.

[0056] In one example embodiment, method 500 may include additional steps, wherein processor 402 receives a measurement report from UE 200, determines whether UE 200 needs to switch to one of a plurality of beams of a non-serving cell, and if so, sends a handover instruction to UE 200.

[0057] Figure 6 Signaling diagram 600 for L1 / L2 inter-cell mobility is shown, in which UE 200 and serving network node 400 interact with each other according to methods 300 and 500, respectively. In signaling diagram 600, it is assumed that network node 400 has a split or decomposed architecture, where DU1 serves the serving cell currently in which UE 200 exists, DU2 serves at least one non-serving cell, and CU controls each of DU1 and DU2. It should be noted that this disclosure is not limited to [specific details] without departing from the teachings of this disclosure. Figure 6 In other embodiments of the split or decomposed architecture shown, the CU may be absent, and DU1 may be replaced by network node 400, and DU2 may be replaced by another (e.g., adjacent) network node.

[0058] Signaling diagram 600 begins at step S602, where the CU generates control information for the UE 200 according to step S502 of method 500. In this example, it is assumed that the mapping is in the form of a mapping table associating each CSI-RS of the serving cell with one or more CSI-RSs of the non-serving cell, and the mapping table itself is obtained based on past handover-related measurements related to the serving cell(s) CSI-RS(s) at the point where handover is triggered (equivalently, at the point where the MAC CE command is sent in step S626 of signaling diagram 600). The next steps S604-S614 of signaling diagram 600 are the same as steps S102-S112 of signaling diagram 100, respectively. In the next step S616, the CU generates an RRC reconfiguration message and indicates the control information in the RRC reconfiguration message using the mapping table. Then, in step S618, the CU sends the RRC reconfiguration message to the UE 200. Typically, step S618 of signaling diagram 600 is similar to step S116 of signaling diagram 100, except that the RRC reconfiguration message also includes a mapping table. In the next step S620 (similar to step S118 of signaling diagram 100), UE 200 confirms the RRC reconfiguration to CU, and then UE 200 applies the mapping table (or in other words, the mapping rules indicated in the mapping table) in step S622 to associate each strongest CSI-RS of the serving cell with one or more CSI-RSs of the non-serving cell (hereinafter also referred to as the (multiple) target CSI-RSs of the non-serving cell). After step S622, signaling diagram 600 proceeds to step S624, where UE 200 begins to periodically report the measurements of the (multiple) target RSs of the non-serving cell to DU1. In the next step S626 (which is similar to step S122 of signaling diagram 100), UE 200 receives a MAC CE command from DU1. Signaling diagram 600 ends at step S628, in which UE 200 performs a handover from the serving cell to a selected (via DU1) non-serving cell controlled by DU2.

[0059] Figure 7 The diagram schematically illustrates a CSI-RS beam spanning two adjacent cells, where UE 200 is switching from one cell to another. Figure 7 In this context, we assume that the serving cell is served by network node 400. Figure 7 The diagram illustrates a typical inter-cell mobility scenario, where a mobility event is triggered (e.g., when UE 200 receives a MAC CE command, see [link]). Figure 1 Step S122 and Figure 6In step S626), UE 200 switches from the serving cell to a neighboring (or non-serving) cell. This typically occurs once UE 200 has "good enough" access to the coverage area of ​​a neighboring cell, such that the received signal power from the neighboring cell is sufficiently greater than the received signal power from the serving cell.

[0060] according to Figure 7 The transition from the serving cell to a neighboring cell occurs at the cell edge and is typically associated with a given combination of serving CSI-RS and neighboring CSI-RS. This means that unnecessary CSI-RS measurements of neighboring cells (prepared for handover) can be reduced by appropriately associating (multiple) neighboring CSI-RS with the serving CSI-RS (i.e., the serving CSI-RS measured by UE 200 as the optimal CSI-RS and reported to network node 400 before leaving the serving cell).

[0061] More specifically, according to method 500, the serving network node 400 can use past measurements from UE 200 (or other UEs) to configure only a subset of neighboring CSI-RSs, which is mapped to the last reported CSI-RS of the serving cell before the MAC CE command that triggers a cell change. By doing so, network node 400 creates a mapping table through which UE 200 can be configured to perform measurements only on the CSI-RS(s) of neighboring cells. In this case, the mapping table can represent a subset of the serving CSI-RSs from the serving cell (i.e., those strongest CSI-RSs measured above a threshold, see...). Figure 8 (and its description below) is associated with a subset of neighboring CSI-RS from neighboring cells (i.e., those CSI-RS that are associated with the strongest CSI-RS of the serving cell according to the mapping table). This can help filter and select only those neighboring CSI-RS that need to be measured.

[0062] like Figure 7 As shown, CSI-RS 3, 4, and 5 of neighboring cells are of particular interest because UE 200 locates along their propagation paths and may decide on handover based on measurements of these CSI-RS. This, in turn, means that other CSI-RS (especially CSI-RS 10-12) can be excluded from consideration (i.e., UE 200 does not need to perform measurements on these CSI-RS).

[0063] refer to Figure 7 The mapping table can be as follows (in this example embodiment, the mapping table associates a serving CSI-RS of a serving cell with a set of neighboring CSI-RS of (at least one) neighboring cells):

[0064] In another example embodiment, the mapping table can associate a set of serving CSI-RSs of a serving cell (e.g., an ordered list of serving CSI-RSs sorted according to their quality, such as CSI-RSRP or CSI-RSRQ) with a set(s) of neighboring CSI-RSs of at least one neighboring cell. Reference Figure 7 Such a mapping table can be as follows:

[0065] Figure 8 The probability quality function (PMF) for a target (or non-serving) cell CSI-RS index given a serving cell CSI-RS index is shown. Figure 8 In this model, each target cell CSI-RS is represented as an "ingress CSI-RS," while the serving cell CSI-RS is represented as an "exgress CSI-RS." As mentioned above, a PMF can be used to create a mapping table. A PMF can also be a conditional PMF. In this form, it provides a given strongest output CSI-RS (beam). Time-entry CSI-RS (beam) The probability. Alternative sites could be joint PMF (Probability Factor). In this form, it provides export CSI-RS (beams). With entrance CSI-RS (beam) The joint probability.

[0066] refer to Figure 7 The strongest egress CSI-RS is CSI-RS 4, and the ingress CSI-RS configured for UE 200 are those ingress CSI-RS with a PMF higher than a predefined threshold (see [link]). Figure 8 ).like Figure 8 As shown, the configured ingress CSI-RS index from the candidate cell is an index with indexes #3, #4 and #5 (i.e., CSI-RS 3, 4 and 5).

[0067] Therefore, the association between the outgoing (serving cell) CSI-RS beams and the incoming (candidate cell) CSI-RS beams is achieved by defining incoming CSI-RS beams with PMF above a given threshold based on past measurements and configuring these incoming CSI-RS beams according to the reported outgoing CSI-RS.

[0068] Figure 9A flowchart of a method 900 for operating a UE 200 according to a second example embodiment is shown. In the second example embodiment, it is implied that the mapping (e.g., in the form of a mapping table discussed above) can be created by the UE 200 itself, if the network node 400 allows the UE 200 to do so. In this case, the UE 200 is configured with a conventional CSI-RS measurement procedure for candidate cells, but it applies a filtering mechanism to select only a subset of candidate CSI-RS for measurement based on a pre-created mapping table. This alternative embodiment is particularly suitable for scenarios where the UE 200 learns its mobility patterns and the relevant transitions of CSI-RS measurements from the serving cell to the target (non-serving) cell. For example, the UE 200 may be configured with a large number of CSI-RS for one or more candidate cells for measurement. Using the proposed mapping table-based filtering mechanism, the UE 200 may attempt to perform RRM measurements only on a subset of the CSI-RS. Then, if needed and if the UE 200 is configured to do so, the measurement results can be reported to the network node 400.

[0069] refer to Figure 9 Method 900 begins at step S902, where processor 202 receives control information from processor 402 of network node 400. The control information includes a first indication for UE 200 to collect RS measurements to be performed by processor 202 during one or more handover events within a predefined time period. The collected RS measurements relate to a first set of RSs (i.e., {RS1, ..., RS2}) associated with multiple beams of the serving cell. M}) and a second set of RS (i.e., {RS'1, ..., RS') associated with multiple beams of non-serving cells. N Similarly, serving and non-serving cells can be controlled by network node 400, or serving cells can be controlled by network node 400 while non-serving cells can be controlled by different (e.g., adjacent) network nodes. The control information also includes a second instruction for processor 202 to create a mapping based on RS measurements collected after and / or during a predefined time period, for example, in the form of a mapping table (as discussed above). Next, method 900 proceeds to step S904, where processor 202 creates a mapping table based on the control information and the collected RS measurements. For example, as described above, a PMF can be used to perform step S904, and the control information can also instruct UE 200 to use a certain PMF type. Afterwards, method 900 proceeds to step S906, where processor 202 creates a mapping table in {RS1, ..., RS...} MIn the process}, one or more strongest RSs are determined based on signal strength. Furthermore, method 900 proceeds to step S908, where processor 202 uses the determined strongest RS(s) and the created mapping to define the mapping in {RS'1, ..., RS'}. N In step S910, processor 202 determines one or more target RSs to be measured. In the next step S910, processor 202 performs subsequent measurements on the target RSs(s).

[0070] Therefore, if UE 200 is permitted and configured to store past RS measurements across multiple (i.e., serving and non-serving) cells, the mapping from a set of egress (serving cell) CSI-RS to a set of ingress (target / candidate cell) CSI-RS can be performed at UE 200 itself. In this case, UE 200 can deploy any training procedure (depending on the UE implementation) to determine the PMF of the ingress CSI-RS beam for each egress CSI-RS beam.

[0071] In one example embodiment, method 900 may include additional steps in which processor 202 sends a measurement report to network node 400 similar to that discussed above with reference to method 300, and in response receives a switching instruction similar to that discussed above.

[0072] Figure 10 A flowchart of a method 1000 for operating a serving network node 400 according to a second example embodiment is shown. In this embodiment, it is assumed that the serving network node 400 interacts with a UE 200 operating according to method 900. Method 1000 begins at step S1002, where processor 402 generates control information including the aforementioned first and second instructions for processor 202. Then, method 1000 proceeds to step S1004, where processor 402 sends the control information to processor 202 of UE 200.

[0073] In one example embodiment, method 1000 may include additional steps, wherein processor 402 receives a measurement report from processor 202 of UE 200, determines whether UE 200 needs to switch to one of a plurality of beams of a non-serving cell, and if so, sends a handover instruction to UE 200.

[0074] Figure 11Signaling diagram 1100 for L1 / L2 inter-cell mobility is shown, in which UE 200 and serving network node 400 interact with each other according to methods 900 and 1000, respectively. Similar to signaling diagram 600, in signaling diagram 1100, it is assumed that network node 400 has a split or decomposed architecture, where DU1 serves the serving cell currently in which UE 200 exists, DU2 serves at least one non-serving cell, and CU controls each of DU1 and DU2. It should be noted again that this disclosure is not limited to [specific details] without departing from the teachings of this disclosure. Figure 11 In other embodiments of the split or decomposed architecture shown, the CU may be absent, and DU1 may be replaced by network node 400, and DU2 may be replaced by another (e.g., adjacent) network node.

[0075] Signaling diagram 1100 begins at step S1102, where it is assumed that UE 200 has received control information from the CU and created a mapping in the form of a mapping table (as discussed above). That is, the mapping table associates each CSI-RS of the serving cell with one or more CSI-RSs of the non-serving cell, and the mapping table itself is based on past handover-related measurements relating to the (multiple) CSI-RSs of the serving cell when handover is triggered (equivalently, when the MAC CE command is sent in step S1126 of signaling diagram 1100). The subsequent steps S1104-S1120 of signaling diagram 1100 are identical to steps S102-S118 of signaling diagram 100, respectively. In the next step S1122, UE 200 applies the mapping table (or, in other words, the mapping rules indicated in the mapping table) to associate each strongest CSI-RS of the serving cell with one or more CSI-RSs of the non-serving cell (hereinafter also referred to as the (multiple) target CSI-RSs of the non-serving cell). Following step S1122, signaling diagram 1100 proceeds to step S1124, where UE 200 begins periodically reporting measurements of the target RS(s) of the non-serving cell(s) to DU1. In the next step S1126 (which is similar to step S122 of signaling diagram 100), UE 200 receives a MAC CE command from DU1. Signaling diagram 1100 ends at step S1128, where UE 200 performs a handover from the serving cell to a selected non-serving cell (via DU1) controlled by DU2.

[0076] Figure 12A flowchart of a method 1200 for operating a (serving) network node 400 according to a third example embodiment is shown. In this embodiment, network node 400 is again responsible for creating a mapping table (similar to the mapping table discussed above), but sends it to neighboring (non-serving) network nodes instead of UE 200. By using the mapping table, non-serving network nodes can configure and broadcast only those RSs associated with a particular strongest RS of the serving cell, according to the mapping table.

[0077] More specifically, method 1200 begins at step S1202, where processor 402 collects past RS measurements, which were performed by UE 200 during one or more previous handover events in the RAN. The past RS measurements are associated with the set of RS (i.e., {RS1, ..., RS2}). M}) and the second group RS (i.e., {RS'1, ..., RS') N The process involves the following steps: In the next step S1204, the processor 402 uses past RS measurements to create a mapping table. The mapping table will associate the first set of RSs (i.e., {RS1, ..., RS2}) with multiple beams of the serving cell. M}) is mapped to a second set of RS (i.e., {RS'1, ..., RS') associated with multiple beams of the non-serving cell. N For example, as described above, step S1204 can be performed using PMF. Thereafter, method 1200 proceeds to step S1206, where processor 402 sends the mapping table and past RS measurements to the non-serving network node.

[0078] Figure 13 A block diagram of a non-serving network node 1300 in a RAN according to an example embodiment is shown. The non-serving network node 1300 is intended to communicate with a UE 200 and a serving network node 400 in the RAN. Figure 13 As shown, the non-service network node 1300 includes a processor 1302 and a memory 1304 coupled to the processor 1302. The memory 1304 stores processor-executable instructions 1306, which, when executed by the processor 1302, cause the processor 1302 to implement various aspects of this disclosure, as will be described in more detail below. It should be noted again that... Figure 13 The number, arrangement, and interconnection of the building elements constituting the non-service network node 1300 shown are not intended to limit the scope of this disclosure, but are merely intended to provide general ideas on how building elements can be implemented within the non-service network node 1300. Typically, the processor 1302, memory 1304, and processor executable instructions 1306 can be implemented in the same or similar manner as the processor 202, memory 204, and processor executable instructions 206, respectively.

[0079] Figure 14 A flowchart of a method 1400 for operating a non-serving network node 1300 according to an example embodiment is shown. Method 1400 begins at step S1402, where processor 1302 receives control information having a mapping table from processor 402 of the serving network node 400, and past RS measurements performed by UE 200 during previous handover events(s) in the RAN. Method 1400 further proceeds to step S1404, where processor 1302 uses the past RS measurements to perform calculations in {RS1, ..., RS...} M In the process 1400, one or more strongest RSs are determined based on signal strength. Then, method 1400 proceeds to step S1406, where processor 1302 uses the determined strongest RS(s) and a mapping table to locate the RS(s) in {RS'1, ..., RS'1}. N In the process 1400, one or more target RSs to be measured by UE 200 are determined. In other words, the target RSs are associated with the strongest RSs via a mapping table. Next, method 1400 proceeds to step S1408, where processor 1302 configures and sends each target RS during the next handover event of UE 200.

[0080] In one example embodiment, method 1400 may include an additional step in which processor 1302 of non-serving network node 1300 notifies processor 402 of network node 400 when it starts and ends the transmission toward target RS(s) of UE 200.

[0081] Figure 15 Signaling diagram 1500 for L1 / L2 inter-cell mobility is shown, in which serving network node 400 and non-serving network node 1300 interact with each other according to methods 1200 and 1400, respectively. Similar to signaling diagrams 600 and 1100, in signaling diagram 1500, it is assumed that network node 400 has a split or decomposed architecture, where DU1 serves the serving cell currently in which UE 200 exists, DU2 serves at least one non-serving cell, and CU controls each of DU1 and DU2. It should be noted again that this disclosure is not limited to [specific details] without departing from the teachings of this disclosure. Figure 15 In other embodiments of the split or decomposed architecture shown, the CU may be absent, and DU1 may be replaced by network node 400, and DU2 may be replaced by another (e.g., adjacent) network node.

[0082] Signaling diagram 1500 begins at S1502, where the CU generates control information for UE 200 and DU2 according to step S1202 of method 1200. In this example, it is assumed that the mapping is in the form of a mapping table associating each CSI-RS of the serving cell with one or more CSI-RSs of the non-serving cell, and the mapping table itself is obtained based on past handover-related measurements associated with the serving cell(s) CSI-RS(s) at the point where handover is triggered (equivalently, at the point where the MAC CE command is sent in step S1530 of signaling diagram 1500). The next steps S1504-S1514 of signaling diagram 1500 are the same as steps S102-S112 of signaling diagram 100, respectively. In the next step S1516, the CU generates an RRC reconfiguration message and indicates the control information in the RRC reconfiguration message using the mapping table. Then, in step S1518, the CU sends the RRC reconfiguration message to UE 200. In the following steps S1520 and S1522, the CU sends the same mapping table to DU2, thereby triggering DU2 to send one or more target CSI-RS of the non-serving cell (according to method 1400), and in response, DU2 sends CSI-RS transmission ACK / NACK, and (if ACK) begins broadcasting (multiple) target CSI-RS. It should be noted that steps S1518 and S1520 can be performed in parallel by the CU if necessary. Furthermore, signaling diagram 1500 proceeds to step S1524 (similar to step S118 of signaling diagram 100), where UE 200 confirms the RRC reconfiguration to the CU, and then in step S1526, UE 200 applies the mapping table (or, in other words, the mapping rules indicated in the mapping table) to associate each strongest CSI-RS of the serving cell with one or more CSI-RS of the non-serving cell (hereinafter also referred to as (multiple) target CSI-RS of the non-serving cell). Following step S1526, signaling diagram 1500 proceeds to step S1528, where UE 200 begins periodically reporting measurements of the target RS(s) of the non-serving cell(s) to DU1. In the next step S1530 (which is similar to step S122 of signaling diagram 100), UE 200 receives a MAC CE command from DU1. Signaling diagram 1500 ends at step S1532, where UE 200 performs a handover from the serving cell to a selected non-serving cell (via DU1) controlled by DU2.

[0083] It should be noted that each step or operation of methods 300, 500, 900, 1000, 1200, and 1400, and signaling diagrams 600, 1100, and 1500, or any combination of steps or operations, can be implemented by various means, such as hardware, firmware, and / or software. As an example, one or more of the above steps or operations can be embodied by processor-executable instructions, data structures, program modules, and other suitable data representations. Furthermore, the processor-executable instructions embodying the above steps or operations can be stored on a corresponding data carrier and executed by the corresponding processor 202, 402, or 1202. This data carrier can be implemented as any computer-readable storage medium configured to be readable by the at least one processor to execute the processor-executable instructions. Such a computer-readable storage medium can include volatile and non-volatile media, removable and non-removable media. As an example, and not a limitation, a computer-readable medium includes media implemented in any method or technology suitable for storing information. More specifically, practical examples of computer-readable media include, but are not limited to, information delivery media, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD), holographic media or other optical disc storage, magnetic tape, tape cassette, disk storage and other magnetic storage devices.

[0084] Although exemplary embodiments of this disclosure have been described herein, it should be noted that various changes and modifications may be made to the embodiments of this disclosure without departing from the scope of legal protection defined by the appended claims. In the appended claims, the word "comprising" does not exclude other elements or operations, and the indefinite articles "a" or "an" do not exclude a plurality. The fact that certain measures are recited in mutually different dependent claims does not imply that a combination of these measures cannot be used advantageously.

Claims

1. A serving network node in a radio access network (RAN), 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 service network node to at least: Collect past reference signal (RS) measurements, which are performed by the user equipment (UE) during one or more past handover events in the RAN, and the past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of the non-serving cell; Based on the past RS measurements, control information is generated, which includes a mapping between the first group of RS and the second group of RS. as well as The control information and the past RS measurements are sent to the UE and non-serving network nodes.

2. The service network node according to claim 1, wherein the mapping between the first group of RSs and the second group of RSs includes at least one of the following: A one-to-one mapping between an RS from the first group of RSs and an RS from the second group of RSs; A one-to-many mapping between an RS from the first group of RSs and a subset of RSs from the second group of RSs; A many-to-one mapping between a subset of RSs from the first group of RSs and an RS from the second group of RSs; as well as A many-to-many mapping between a subset of RS from the first group of RSs and a subset of RS from the second group of RSs.

3. A non-serving network node in a radio access network (RAN), 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 non-serving network node to at least: Control information and past reference signal (RS) measurements are received from the serving network node. The past RS measurements are performed by the user equipment (UE) during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of the non-serving cell. The control information includes a mapping between the first set of RSs and the second set of RSs. Based on the past RS measurements, at least one strongest RS in terms of signal strength is determined from the first group of RSs; Based on the determined strongest RS and the mapping, at least one target RS to be measured by the UE is determined from the second set of RSs; as well as The at least one target RS is configured and transmitted in the RAN during the next handover event for the UE.

4. The non-service network node according to claim 3, wherein the mapping between the first group of RSs and the second group of RSs includes at least one of the following: A one-to-one mapping between an RS from the first group of RSs and an RS from the second group of RSs; A one-to-many mapping between an RS from the first group of RSs and a subset of RSs from the second group of RSs; A many-to-one mapping between a subset of RSs from the first group of RSs and an RS from the second group of RSs; as well as A many-to-many mapping between a subset of RS from the first group of RSs and a subset of RS from the second group of RSs.

5. The non-service network node according to claim 3 or 4, wherein the non-service network node is configured to: Identify at least two of the strongest RSs in terms of signal strength from the first set of RSs; and The at least one target RS is determined based on which of the at least two strongest RSs is stronger.

6. The non-service network node according to claim 3 or 4, wherein the non-service network node is configured to: Identify at least two of the strongest RSs in terms of signal strength from the first set of RSs; and The at least one target RS is determined based on the relative value of the signal strength between the at least two strongest RSs.

7. The non-serving network node according to any one of claims 3 to 6, wherein the non-serving network node is further configured to notify the serving network node when the non-serving network node starts and ends the transmission of the at least one target RS.

8. A method for operating a serving network node in a radio access network (RAN), comprising: Collect past reference signal (RS) measurements, which are performed by the user equipment (UE) during one or more past handover events in the RAN, and the past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of the non-serving cell; Generate control information, the control information including a mapping between the first group of RS and the second group of RS; as well as The control information and the past RS measurements are sent to the UE and non-serving network nodes.

9. A method for operating a non-serving network node in a radio access network (RAN), comprising: Control information and past reference signal (RS) measurements are received from the serving network node. The past RS measurements are performed by the user equipment (UE) during one or more past handover events in the RAN. The past RS measurements involve a first set of RSs associated with multiple beams of the serving cell and a second set of RSs associated with multiple beams of the non-serving cell. The control information includes a mapping between the first set of RSs and the second set of RSs. Based on the past RS measurements, at least one strongest RS in terms of signal strength is determined from the first group of RSs; Based on the determined strongest RS and the mapping, at least one target RS to be measured by the UE is determined from the second set of RSs; as well as The at least one target RS is configured and transmitted in the RAN during the next handover event for the UE.

10. A computer program product comprising a computer-readable storage medium storing computer code that, when executed by at least one processor, causes the at least one processor to perform the method of claim 8.

11. A computer program product comprising a computer-readable storage medium storing computer code that, when executed by at least one processor, causes the at least one processor to perform the method of claim 9.

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