Method and apparatus for supporting lower layer mobility

Abstract

The present application relates to a method and an apparatus for supporting lower layer mobility. One embodiment of the present disclosure provides a distributed unit (DU), including: a transceiver; and a processor coupled to the transceiver, configured to: determine a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of one or more candidate cells, where the index of the candidate cell configuration is generated by the DU or received from another network node; and send an instruction to a user equipment (UE), indicating to the UE to hand over from the serving cell to the candidate cell of the one or more candidate cells.

Description

[Technical Field]

[0001] The present disclosure relates to wireless communications, and more particularly to methods and apparatus for supporting lower layer mobility. [Background technology]

[0002] A user equipment (UE) may move from one cell to another and therefore, at some point, a serving cell change needs to be performed.

[0003] Currently, serving cell changes are implemented by explicit Radio Resource Control (RRC) reconfiguration signaling to trigger target cell synchronization based on Layer 3 (L3) measurement reports, which results in longer latency, higher overhead, and longer disruption times than beam-level mobility.

[0004] In 3rd Generation Partnership Project (3GPP) Release 18, a new work item was approved on further New Radio (NR) mobility enhancements that enable serving cell change via lower layer signaling, e.g., Layer 1 (L1) or Layer 2 (L2) signaling, to reduce latency, overhead, and disruption time.

[0005] Therefore, how to support lower layer mobility will be considered and solved. Summary of the Invention [Problem to be solved by the invention]

[0006] One objective of this disclosure is to propose some solutions to support lower layer mobility. [Means for solving the problem]

[0007] One embodiment of the present disclosure provides a distributed unit (DU), including: a transceiver; and a processor coupled to the transceiver and configured to: determine a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among one or more candidate cells, where the index of the candidate cell configuration is generated by the DU or received from another network node; and send an instruction to a user equipment (UE), indicating to the UE to handover from the serving cell to the candidate cell among the one or more candidate cells.

[0008] In some embodiments, the indication is transmitted via a Medium Access Control (MAC) Control Element (CE) or Downlink Control Information (DCI).

[0009] In some embodiments, the indication indicates at least one of the following: an index of a candidate cell configuration corresponding to the candidate cell, or an indicator indicating whether the candidate cell configuration should be maintained.

[0010] In some embodiments, the processor is further configured to receive, from a central unit (CU), a first message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of a set of candidate cells, where the set of candidate cells includes one or more candidate cells; and to send to the CU a second message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of the one or more candidate cells.

[0011] In some embodiments, the processor is further configured to receive, from the CU, a first message indicating a candidate cell configuration for each candidate cell of the set of candidate cells, determine one or more candidate cells from the set of candidate cells, generate an index for each candidate cell configuration for each candidate cell of the one or more candidate cells, and send, to the CU, a second message indicating the candidate cell configuration for each candidate cell of the one or more candidate cells and the index of the candidate cell configuration.

[0012] In some embodiments, the processor is further configured to receive, from the CU, a first message indicating a set of candidate cells; determine one or more candidate cells from the set of candidate cells; generate a candidate cell configuration for each candidate cell among the one or more candidate cells and an index for each candidate cell configuration; and send, to the CU, a second message indicating the candidate cell configuration for each candidate cell among the one or more candidate cells and an index for the candidate cell configuration.

[0013] In some embodiments, the processor is further configured to receive, from the CU, a first message indicating a set of candidate cells; determine one or more candidate cells from the set of candidate cells; generate a candidate cell configuration for each candidate cell of the one or more candidate cells; and send, to the CU, a second message indicating the candidate cell configuration for each candidate cell of the one or more candidate cells.

[0014] In some embodiments, the candidate cell configuration includes at least one of the following: a channel state information (CSI) resource configuration, or a state of a transmission configuration indicator.

[0015] Another embodiment of the present disclosure provides a CU including a transceiver and a processor coupled to the transceiver and configured to: transmit a first message indicating at least a set of candidate cells; and receive a second message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among one or more candidate cells in the set of candidate cells.

[0016] In some embodiments, the first message further indicates a candidate cell configuration for each candidate cell of the set of candidate cells, and the processor is further configured to: send, to the candidate DU, a request message indicating the at least one candidate cell; and receive, to the candidate DU, a response message indicating a candidate cell configuration for each candidate cell of at least a portion of the at least one candidate cell.

[0017] In some embodiments, the first message further indicates an index of each candidate cell configuration for each candidate cell in the set of candidate cells.

[0018] In some embodiments, the processor is further configured to determine an index of each candidate cell configuration for at least a portion of the at least one candidate cell.

[0019] In some embodiments, the processor is further configured to: send a request message to the candidate DU indicating at least one candidate cell and an index range; and receive a response message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of at least some of the at least one candidate cell.

[0020] In some embodiments, the processor is further configured to send, to the UE, a message indicating a candidate cell configuration for each candidate cell of the one or more candidate cells and an index of the candidate cell configuration.

[0021] In some embodiments, the candidate cell configuration includes at least one of the following: a CSI resource configuration, or a state of a transmission configuration indicator.

[0022] Yet another embodiment of the present disclosure provides a UE including: a transceiver; and a processor coupled to the transceiver and configured to receive a message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of one or more candidate cells; and, in response to receiving an indication indicating to the UE to hand over from the serving cell to the candidate cell of the one or more candidate cells, perform a random access procedure toward the candidate cell.

[0023] In some embodiments, the indication is received via a MAC CE or a DCI.

[0024] In some embodiments, the indication indicates at least one of the following: an index of a candidate cell configuration corresponding to the candidate cell, or an indicator indicating whether the candidate cell configuration should be maintained.

[0025] In some embodiments, the candidate cell configuration includes at least one of the following: a CSI resource configuration, or a state of a transmission configuration indicator.

[0026] Yet another embodiment of the present disclosure provides a method for supporting lower layer mobility, the method including: determining a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among one or more candidate cells, wherein the index of the candidate cell configuration is generated by the DU or received from another network node; and transmitting an indication to the UE indicating to the UE to hand over from the serving cell to the candidate cell among the one or more candidate cells.

[0027] Yet another embodiment of the present disclosure provides a method for supporting lower layer mobility, the method including: transmitting a first message indicating at least a set of candidate cells; and receiving a second message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among one or more candidate cells in the set of candidate cells.

[0028] Yet another embodiment of the present disclosure provides a method for supporting lower layer mobility, the method including: receiving a message indicating a candidate cell configuration for each candidate cell of one or more candidate cells and an index of the candidate cell configuration; and performing a random access procedure towards the candidate cell in response to receiving an indication indicating to the UE to hand over from the serving cell to the candidate cell of the one or more candidate cells.

[0029] To explain the manner in which the advantages and features of the present application can be obtained, the present application will be described by reference to specific embodiments thereof that are illustrated in the accompanying drawings. These drawings merely illustrate exemplary embodiments of the present application and therefore should not be considered as limiting its scope. [Brief explanation of the drawings]

[0030] [Figure 1A] FIG. 1 is a schematic diagram of an intra-CU, intra-DU mobility scenario according to some embodiments of the present disclosure. [Figure 1B] FIG. 1 is a schematic diagram of an intra-CU inter-DU mobility scenario according to some embodiments of the present disclosure. [Figure 2] FIG. 2 illustrates a method performed by a source DU according to some embodiments of the present disclosure. [Figure 3] FIG. 1 illustrates a method performed by a CU according to some embodiments of the present disclosure. [Figure 4] FIG. 1 illustrates a method performed by a UE in accordance with some embodiments of the present disclosure. [Figure 5]1 is a flowchart for supporting lower layer mobility in an inter-DU mobility scenario according to some embodiments of the present disclosure. [Figure 6] 1A-1C illustrate the structure of instructions according to some embodiments of the present disclosure. [Figure 7] 1 is a flowchart for supporting lower layer mobility in an inter-DU mobility scenario according to some embodiments of the present disclosure. [Figure 8] 1 is a flowchart for supporting lower layer mobility in an inter-DU mobility scenario according to some embodiments of the present disclosure. [Figure 9] 1 is a flowchart for supporting lower layer mobility in an intra-DU mobility scenario according to some embodiments of the present disclosure. [Figure 10] 1 is a flowchart for supporting lower layer mobility in an intra-DU mobility scenario according to some embodiments of the present disclosure. [Figure 11] FIG. 1 is a simplified block diagram of an apparatus according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0031] The detailed description of the accompanying drawings is intended as an illustration of the presently preferred embodiment of the invention and is not intended to represent the only form in which the invention may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments which are intended to be encompassed within the spirit and scope of the invention.

[0032] Although operations are illustrated in the figures in a particular order, those skilled in the art will readily recognize that such operations need not be performed in the particular order shown or in sequential order, or that not all illustrated operations need be performed, and that in some cases one or more operations may be skipped, to achieve desirable results. Additionally, the figures may schematically illustrate one or more exemplary processes in the form of a flow diagram. However, other operations not shown may be incorporated into the schematically illustrated exemplary process. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In certain situations, multitasking and parallel processing may be advantageous.

[0033] Reference will now be made in detail to several embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as cellular telephone networks, time division multiple access (TDMA)-based networks, code division multiple access (CDMA)-based networks, orthogonal frequency division multiple access (OFDMA)-based networks, LTE networks, 3GPP-based networks, LTE, LTE-Advanced (LTE-A), 3GPP 4G, 3GPP 5G NR, 3GPP Release 16 or later, satellite communication networks, and high altitude platform networks. With the development of network architectures and new service scenarios, it is contemplated that all embodiments in the present disclosure are also applicable to similar technical challenges, and further, the terms listed in the present disclosure may change, without affecting the principles of the present disclosure.

[0034] The main objectives for further mobility expansion are: - Configuration and maintenance for multiple candidate cells to enable rapid application of configuration for candidate cells - Dynamic switching mechanism between candidate serving cells for potential applicable scenarios may include:

[0035] Potential applicable scenarios of lower layer mobility may include intra-CU intra-DU mobility and intra-CU inter-DU mobility. In this disclosure, lower layer mobility, for example, L1 or L2 mobility based on L1 or L2 signaling, is compared with legacy L3 mobility based on RRC signaling.

[0036] FIG. 1A illustrates a schematic diagram of an intra-CU, intra-DU mobility scenario according to some embodiments of the present disclosure.

[0037] The wireless communication system of FIG. 1A includes a DU (e.g., DU 102A), a UE (e.g., UE 101A), and several access nodes (e.g., access node 103A1 and access node 103A2). The access node 103A1 and access node 103A2 are controlled by the DU 102A and serve UEs in cell #1A and cell #2A, respectively. Although FIG. 1A shows only one UE and two access nodes, those skilled in the art will recognize that any number of UEs and access nodes may be included in the wireless communication system.

[0038] The UE 101A may include a computing device such as a desktop computer, a laptop computer, a personal digital assistant (PDA), a tablet computer, a smart television (e.g., a television connected to the Internet), a set-top box, a game console, a security system (including a security camera), an in-vehicle computer, a network device (e.g., a router, a switch, a modem), etc. According to an embodiment of the present disclosure, the UE 101A may include a portable wireless communication device, a smartphone, a cellular telephone, a flip phone, a device with a subscriber identity module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals over a wireless network. In some embodiments, the UE 101A includes a wearable device such as a smart watch, a fitness band, an optical head-mounted display, etc. Furthermore, the UE 101A may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, a device, or by other terms used in the art.

[0039] The access nodes 103A1 and 103A2 may be distributed throughout a geographic region. In particular embodiments, the access nodes may also be referred to as access points, access terminals, base stations, macrocells, Node Bs, enhanced Node Bs (eNBs), gNBs, Home Node Bs, relay nodes, devices, or any other terminology used in the art. The access nodes 103A1 and 103A2 may generally be part of a wireless access network that may include one or more controllers communicatively coupled to one or more corresponding base stations.

[0040] The wireless communication system may be compatible with any type of network capable of transmitting and receiving wireless communication signals, for example, a wireless communication network, a cellular telephone network, a TDMA-based network, a CDMA-based network, an OFDMA-based network, a Long Term Evolution (LTE) network, a 3GPP-based network, a 3GPP 5G network, a satellite communication network, a high altitude platform network, and / or other communication networks.

[0041] In one implementation, the wireless communication system is compatible with the 3GPP protocol NR, and transmissions may be performed using OFDM modulation schemes. More generally, the wireless communication system may implement some other open or proprietary communication protocol, such as WiMAX, among other protocols.

[0042] In other embodiments, the transmission may be performed using other communication protocols, such as the IEEE 802.11 family of wireless communication protocols. Additionally, in some embodiments, the transmission may be performed over a licensed spectrum, while in other embodiments, the transmission may be performed over an unlicensed spectrum. This disclosure is not intended to be limited to any particular wireless communication system architecture or protocol implementation. In another embodiment, the transmission may be performed using 3GPP 5G protocols.

[0043] In Figure 1A, UE 101A is moving from cell #1A to cell #2A and may perform a handover procedure from cell #1A to access cell #2A, which is a handover procedure performed between different cells within a DU. This scenario may be called intra-CU intra-DU mobility. For short, this scenario may be called intra-DU mobility.

[0044] FIG. 1B illustrates a schematic diagram of an intra-CU inter-DU mobility scenario according to some embodiments of the present disclosure.

[0045] The wireless communication system of FIG. 1B includes a CU (e.g., CU 104B), a UE (e.g., UE 101B), and several DUs (e.g., DU 102B1 and DU 102B2). DU 102B1 and DU 102B2 are controlled by CU 104B and serve UEs in cell #1B and cell #2B, respectively. Although FIG. 1B shows only one UE and two DUs, those skilled in the art will recognize that any number of UEs and DUs may be included in the wireless communication system.

[0046] In Figure 1B, UE 101B is moving from cell #1B to cell #2B and may perform a handover procedure from cell #1B to access cell #2B, which is a handover procedure performed between different cells belonging to different DUs but within the same CU. This scenario may be called intra-CU inter-DU mobility. For short, this scenario may be called inter-DU mobility.

[0047] For lower layer mobility, the following issues are addressed:

[0048] Problem 1: If mobility to a different cell is required for the UE, the network may trigger the UE to change from the current source cell to a target candidate cell. A Cell ID having 32 bits and a Physical Cell Identity (PCI) having 10 bits are used in legacy L3 signaling, which causes overhead in L1 or L2 signaling.

[0049] Therefore, the present disclosure proposes a more efficient solution to reduce signaling overhead in L1 or L2 signaling. Specifically, the present disclosure proposes introducing an index that indicates the candidate cell configuration.

[0050] Problem 2: In an inter-DU mobility scenario, for example, as shown in FIG. 1B, the candidate cell configuration is generated by the candidate DU and sent to the CU via an information element (IE), for example, CellGroupConfig, that is transparent to the CU.

[0051] When an index-based approach such as that proposed in Problem 1 is used, it is necessary that there is no collision or confusion between the generated indices of the candidate cell configurations of different candidate DUs. Furthermore, it is necessary that the source DU and the UE have a common understanding of the indices.

[0052] Question 3: In intra-DU mobility scenarios, it is also necessary to determine which node generates the index of the candidate cell configuration.

[0053] The present disclosure proposes some solutions to solve at least the above problems.

[0054] FIG. 2 illustrates a method performed by a DU, eg, a source DU, according to some embodiments of the present disclosure.

[0055] In operation 201, the source DU may determine a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among one or more candidate cells (e.g., N candidate cells, where N is an integer), where the index of the candidate cell configuration is generated by the DU or received from another network node, and in operation 202, the source DU may send an indication to the UE indicating to the UE to hand over from the serving cell to the candidate cell among the one or more candidate cells.

[0056] In some embodiments, the indication is sent via the MAC CE or DCI.

[0057] In some embodiments, the instructions include: - the index of the candidate cell configuration corresponding to the candidate cell, or - an indicator of whether the candidate cell configuration should be maintained may indicate at least one of:

[0058] In some embodiments, the DU may receive from the CU a first message (e.g., a UE CONTEXT MODIFICATION REQUEST message) indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among a set of candidate cells (e.g., M candidate cells, where M is an integer greater than or equal to N), where the set of candidate cells includes one or more candidate cells (e.g., M candidate cells), and send to the CU a second message (e.g., a UE CONTEXT MODIFICATION RESPONSE message) indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among the one or more candidate cells.

[0059] In some embodiments, the DU may receive from the CU a first message (e.g., a UE CONTEXT MODIFICATION REQUEST message) indicating a candidate cell configuration for each candidate cell among a set of candidate cells (e.g., M candidate cells), determine one or more candidate cells (e.g., N candidate cells) from the set of candidate cells (e.g., M candidate cells), generate an index for each candidate cell configuration for each candidate cell among the one or more candidate cells, and send to the CU a second message (e.g., a UE CONTEXT MODIFICATION RESPONSE message) indicating the candidate cell configuration for each candidate cell among the one or more candidate cells and the index of the candidate cell configuration.

[0060] In some embodiments, the DU may receive a first message (e.g., a UE CONTEXT MODIFICATION REQUEST message) from the CU indicating a set of candidate cells (e.g., M candidate cells), determine one or more candidate cells (e.g., N candidate cells) from the set of candidate cells, generate a candidate cell configuration for each candidate cell among the one or more candidate cells and an index for each candidate cell configuration, and send a second message to the CU indicating the candidate cell configuration for each candidate cell among the one or more candidate cells and an index for the candidate cell configuration.

[0061] In some embodiments, the DU may receive a first message (e.g., a UE CONTEXT MODIFICATION REQUEST message) from the CU indicating a set of candidate cells, determine one or more candidate cells (e.g., N candidate cells) from the set of candidate cells (e.g., M candidate cells), generate a candidate cell configuration for each candidate cell among the one or more candidate cells, and send a second message (e.g., a UE CONTEXT MODIFICATION RESPONSE message) to the CU indicating the candidate cell configuration for each candidate cell among the one or more candidate cells.

[0062] In some embodiments, the candidate cell configuration is: - CSI resource configuration, or - Transmit Configuration Indicator Status It includes at least one of the following:

[0063] FIG. 3 illustrates a method performed by a CU according to some embodiments of the present disclosure.

[0064] In operation 301, the CU may send a first message (e.g., a UE CONTEXT MODIFICATION REQUEST message) indicating at least a set of candidate cells (e.g., M candidate cells), and in operation 302, the CU may receive a second message (e.g., a UE CONTEXT MODIFICATION RESPONSE message) indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell among one or more candidate cells (e.g., N candidate cells) of the set of candidate cells.

[0065] In some embodiments, the first message (e.g., a UE CONTEXT MODIFICATION REQUEST message) further indicates a candidate cell configuration for each candidate cell in the set of candidate cells, and the CU is further configured to send, to the DU, a request message indicating at least one candidate cell (e.g., K candidate cells, where K is an integer) and receive a response message indicating a candidate cell configuration for each candidate cell of at least a portion of the at least one candidate cell (e.g., L candidate cells, where L is an integer and L≦K).

[0066] In some embodiments, the first message further indicates an index of each candidate cell configuration for each candidate cell in the set of candidate cells.

[0067] In some embodiments, the CU may determine an index for each candidate cell configuration for at least a portion of the at least one candidate cell.

[0068] In some embodiments, the CU may send a request message (e.g., a UE CONTEXT SETUP REQUEST message) to a candidate DU indicating at least one candidate cell and an index range, and receive a response message (e.g., a UE CONTEXT SETUP RESPONSE message) indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of at least some of the at least one candidate cell.

[0069] In some embodiments, the CU may send to the UE a message (e.g., an RRCReconfiguration message) indicating a candidate cell configuration for each candidate cell of the one or more candidate cells and an index of the candidate cell configuration.

[0070] FIG. 4 illustrates a method performed by a UE according to some embodiments of the present disclosure.

[0071] In operation 401, the UE may receive a message (e.g., an RRCReconfiguration message) indicating a candidate cell configuration for each candidate cell among one or more candidate cells and an index of the candidate cell configuration, and in operation 402, in response to receiving an indication indicating to the UE to hand over from the serving cell to a candidate cell among the one or more candidate cells, the UE may perform a random access procedure toward the candidate cell.

[0072] FIG. 5 illustrates a flowchart for supporting lower layer mobility in an inter-DU mobility scenario according to some embodiments of the present disclosure.

[0073] Figure 5 includes four components: a UE, a source DU, one or more candidate DUs (referred to as "candidate DUs" in Figure 5), and a CU. The source DU and one or more candidate DUs are in the CU, and the UE is moving from the source DU to one of the one or more candidate DUs. The source DU manages the serving cell of the UE, and one of the one or more candidate DUs manages a candidate cell to which the UE is handed over. In some embodiments, the candidate cell to which the UE is handed over may be referred to as a "candidate target cell."

[0074] In this solution, the index of the candidate cell configuration is generated by the CU. The candidate DU (one or more candidate DUs) may provide the cell configuration of each candidate cell to the CU. In response to receiving the cell configuration of the candidate cell (short, candidate cell configuration), the CU may generate (or assign) an index for each candidate cell configuration. The CU may send the candidate cell configuration and the generated index to the source DU. The CU may also send the candidate cell configuration and the generated index to the UE. A detailed flow is presented as follows:

[0075] In operation 501, the CU may send a message, e.g., a UE CONTEXT SETUP REQUEST message, to a candidate DU (or to multiple candidate DUs) indicating the number of candidate cell IDs (denoted as K candidate cell IDs for simplicity). Note that the K candidate cells may be controlled by the same candidate DU or by different candidate DUs. The message may request preparation of the K candidate cells controlled by the candidate DU for creating a UE context and setting up one or more data bearers.

[0076] In some embodiments, a UE CONTEXT SETUP REQUEST message may be sent for each candidate cell, i.e., the CU may send K UE CONTEXT SETUP REQUEST messages, and each UE CONTEXT SETUP REQUEST message may indicate a candidate cell ID.

[0077] In some other embodiments, the UE CONTEXT SETUP REQUEST message may include multiple candidate cell IDs (eg, a list of K candidate cell IDs) and is sent to candidate DUs that control multiple candidate cells.

[0078] In operation 502, if the preparation request is accepted, the candidate DU may send a response message, for example, a UE CONTEXT SETUP RESPONSE message, to the CU. The UE CONTEXT SETUP RESPONSE message may indicate the candidate cell IDs as well as the candidate cell configurations that were requested by the CU.

[0079] The candidate cell configurations may include cell configurations used for lower layer mobility. For example, the candidate cell configurations may include the following: - A CSI resource configuration, sometimes called CSI-ResourceConfig, or - TCI state associating one or two downlink reference signals with the corresponding quasi-colocation type may include at least one of:

[0080] The CSI resource configuration may define at least one of the following in a candidate cell: 1) a group of one or more non-zero power (NZP) CSI reference signal (RS) resource sets, which may be referred to as NZP-CSI-RS-ResourceSet; 2) a CSI interference management (IM) resource set, which may be referred to as CSI-IM-ResourceSet; or 3) a CSI synchronization signal / physical broadcast channel (SSB) resource set, which may be referred to as CSI-SSB-ResourceSet.

[0081] The NZP-CSI-RS-ResourceSet is a set of NZP CSI-RS resources and set-specific parameters, where each NZP CSI-RS resource is used to configure an NZP CSI-RS transmitted in a cell on which the UE may be configured to measure. The CSI-IM-ResourceSet is used to configure one or more CSI IM resources and a set of set-specific parameters. The CSI-SSB-ResourceSet is used to configure one SS / PBCH block resource set.

[0082] Among the K requested candidate cells, some candidate cells may be accepted, while other candidate cells may not be accepted. For simplicity, the total number of accepted candidate cells is denoted as L, where L may be an integer greater than or equal to 1 and is assumed to be L≦K. A candidate DU may, for example, send a UE CONTEXT SETUP RESPONSE message indicating the L candidate cell configurations. In some embodiments, a UE CONTEXT SETUP RESPONSE message may be sent for each requested candidate cell, i.e., one UE CONTEXT SETUP RESPONSE message may be sent for each candidate cell, and the candidate DU may send L UE CONTEXT SETUP RESPONSE messages to the CU. In some other embodiments, if there is one candidate DU, the one candidate DU may send one UE CONTEXT SETUP RESPONSE message indicating the L candidate cell configurations. In some other embodiments, each candidate DU among multiple DUs may send one UE CONTEXT SETUP RESPONSE message to the CU indicating all of its own candidate cell configurations.

[0083] In operation 503, after receiving the L candidate cell configurations, the CU may generate an index for each candidate cell configuration among the L candidate cell configurations, where the index is used to identify the candidate cell configuration.

[0084] For example, the index may be a numeric value, e.g., 0, 1, 2, 3, etc. A maximum value for the index may be preconfigured, such as 8, 16, 32, 64, 128, etc. In another example, the index may be a candidate cell configuration ID used to identify a candidate cell configuration.

[0085] In operation 504, the CU may send a message, e.g., a UE CONTEXT MODIFICATION REQUEST message or a DL RRC MESSAGE TRANSFER message, to the source DU, which may indicate the number of candidate cell configurations (denoted as M candidate cell configurations for simplicity, where M may be an integer equal to or greater than 1) and corresponding indexes. The M candidate cell configurations may be from one candidate DU or from multiple candidate DUs. For simplicity, the UE CONTEXT MODIFICATION REQUEST message is used to describe the solution.

[0086] In some embodiments, a UE CONTEXT MODIFICATION REQUEST message may be sent for each candidate cell, i.e., the CU may send M UE CONTEXT MODIFICATION REQUEST messages, and each UE CONTEXT MODIFICATION REQUEST message may indicate one candidate cell configuration and corresponding index.

[0087] In some other embodiments, the UE CONTEXT MODIFICATION REQUEST message may indicate multiple candidate cell configurations and corresponding indices (eg, a list of M candidate cell configurations and corresponding indices) and is sent to the source DU.

[0088] In some cases, the CU may identify a potential set of candidate cells to which the UE may be handed over from L candidate cells, e.g., based on reported L3 measurements, where M is less than the total number of candidate cells from one or more candidate DUs, i.e., M≦L.

[0089] In operation 505, if the modification request is accepted, the source DU may send a response message, for example, a UE CONTEXT MODIFICATION RESPONSE message or a UL RRC MESSAGE TRANSFER message, to the CU that may indicate that the N candidate cell configurations and corresponding indices are accepted, where N≦M.

[0090] In some embodiments, a UE CONTEXT MODIFICATION RESPONSE message may be sent for each accepted candidate cell, i.e., the source DU may send M UE CONTEXT MODIFICATION RESPONSE messages, and each UE CONTEXT MODIFICATION RESPONSE message may indicate one accepted candidate cell configuration and corresponding index.

[0091] In some other embodiments, the UE CONTEXT MODIFICATION RESPONSE message may include a list of N accepted candidate cell IDs, which may indicate that the candidate cell configurations and indices are accepted, where N < M. Alternatively, the UE CONTEXT MODIFICATION RESPONSE message may indicate N candidate cell configurations and corresponding indices, where N < M.

[0092] In operation 506, upon receiving the N candidate cell configurations and corresponding indices from the source DU, the CU may generate the required RRC reconfiguration and send an RRC reconfiguration message to the UE. The RRC reconfiguration message may indicate the N candidate cell configurations and corresponding indices.

[0093] In some embodiments, the CU may send the number of candidate cell configurations (this number may be less than or equal to N) and corresponding indexes to the UE. For example, the CU may exclude some candidate cells to which the UE cannot be handed over (for simplicity, the number of these candidate cells is denoted as A, where A may be an integer greater than or equal to 1), and then send information of the N A candidate cells to the UE, including the N A candidate cell configurations and the corresponding N A indexes.

[0094] In operation 507, the UE may respond to the CU with an RRC reconfiguration complete message, which may be represented as RRCReconfigurationComplete.

[0095] In operation 508, the UE may start reporting L1 measurements of the serving cell and the candidate cell to the source DU.

[0096] In operation 509, the source DU may determine that lower layer mobility to the candidate cell is required.

[0097] In operation 510, the source DU may send an indication, e.g., a lower layer mobility command, to the UE to trigger the UE to handover from the current serving cell to a candidate cell. The candidate cell may also be referred to as a candidate target cell. The indication may be sent via a MAC CE, or DCI, or other message or signaling.

[0098] The indication may indicate an index that may indicate a candidate cell configuration to be applied (or used, or activated) by the UE when the UE receives the indication. The indication may further include an indicator that may indicate whether the candidate cell configuration is to be maintained by the UE when the UE connects to the candidate cell.

[0099] In operation 511, the UE may perform a random access procedure towards the target cell indicated by the source DU.

[0100] FIG. 6 illustrates the structure of an instruction according to some embodiments of the present disclosure.

[0101] 6, the instruction may be a MAC CE command having a fixed size of one octet. In particular, the octet may include at least one of the following: Lower Layer Handover (HO) Command: This field may indicate the index value used for the candidate cell configuration that the UE must apply. The size of the field may be 6 bits. - M: This field may indicate whether the candidate cell configuration is maintained by the UE when the UE connects to the candidate cell. The length of the field may be 1 bit. If the M field is set to 1, the candidate cell configuration is maintained by the UE. - R: Reserved bit, may be set to 0.

[0102] The MAC CE for the indication may have a logical channel ID (LCID) value in the MAC subheader. For example, a code point of 35 is used for the indication. Other code points may also be used for the indication.

[0103] The MAC CE illustrated in Figure 6 is an example of the structure of the MAC CE, and other formats of the MAC CE may also be used, such as a MAC CE consisting of 2 octets, 3 octets, or a lower layer HO command field size of 3 bits.

[0104] In some other embodiments, the indication may be a DCI command. For example, DCI format 2_8 may be used to indicate the candidate cell configuration that the UE must apply and, optionally, whether the candidate cell configuration is to be maintained by the UE when the UE connects to the candidate cell. At least one of the following information is transmitted by DCI format 2_8: Lower Layer Handover (HO) Command: This field may indicate the index value used for the candidate cell configuration that the UE must apply. The size of the field may be 6 bits. - M: This field may indicate whether the candidate cell configuration is maintained by the UE when the UE connects to the candidate cell. The length of the field may be 1 bit. If the M field is set to 1, the candidate cell configuration is maintained by the UE.

[0105] DCI format 2_8 is an example of a DCI structure, and other formats of DCI may also be used, for example, the size of the lower layer HO command field may be 3 bits.

[0106] As can be seen, compared to legacy L3 signaling in which a cell ID having 32 bits and a physical cell identity (PCI) having 10 bits are used, one octet may be sufficient to indicate the candidate cell configuration, and the solution of the present application significantly reduces the signaling overhead.

[0107] 7 shows a flowchart for supporting lower layer mobility in an inter-DU mobility scenario according to some embodiments of the present disclosure. The components included in FIG. 7 are similar to those in FIG. 5, and details are omitted here.

[0108] In this solution, an index of the candidate cell configuration for each candidate cell is generated by the source DU. The candidate DU may provide the candidate cell configuration to the CU. The CU may send the candidate cell configuration from the candidate DU to the source DU. In response to receiving the candidate cell configuration, the source DU may generate (or assign) an index for each candidate cell configuration. The source DU may send the candidate cell configuration and the generated index to the CU. The CU may send the candidate cell configuration and the generated index to the UE. A detailed flow is presented as follows:

[0109] Operations 701, 702, and 706 to 711 are similar to operations 501, 502, and 506 to 511, respectively, described in FIG. 5, and will not be described in detail here.

[0110] In operation 703, the CU may send a message to the source DU, such as a UE CONTEXT MODIFICATION REQUEST message or a DL RRC MESSAGE TRANSFER message, that may indicate M candidate cell configurations. The M candidate cell configurations may be from one candidate DU or multiple candidate DUs.

[0111] In some embodiments, a UE CONTEXT MODIFICATION REQUEST message may be sent for each candidate cell, i.e., the CU may send M UE CONTEXT MODIFICATION REQUEST messages, and each UE CONTEXT MODIFICATION REQUEST message may indicate one candidate cell configuration.

[0112] In some other embodiments, the UE CONTEXT MODIFICATION REQUEST message may include multiple candidate cell configurations (eg, a list of M candidate cell configurations) and is sent to the source DU.

[0113] In another example, the CU may identify a potential set of candidate cells to which the UE may be handed over, e.g., based on reported L3 measurements, where M is less than the total number of candidate cells (i.e., L) from one or more candidate DUs, i.e., M≦L.

[0114] In operation 704, after receiving the M candidate cell configurations, the source DU may generate an index for each candidate cell configuration among the M candidate cell configurations, where the index is used to identify the candidate cell configuration.

[0115] For example, the index may be a numeric value, e.g., 0, 1, 2, 3, etc. A maximum value for the index may be preconfigured, such as 8, 16, 32, 64, 128, etc. In another example, the index may be a candidate cell configuration ID used to identify a candidate cell configuration.

[0116] In operation 705, the modification request may be accepted, and the source DU may send a response message, for example, a UE CONTEXT MODIFICATION RESPONSE message or a UL RRC MESSAGE TRANSFER message to the CU, that may indicate that the N candidate cell configurations and corresponding indices are accepted, where N≦M.

[0117] In some embodiments, a UE CONTEXT MODIFICATION RESPONSE message may be sent for each accepted candidate cell, i.e., the source DU may send N UE CONTEXT MODIFICATION RESPONSE messages, each of which may indicate one accepted candidate cell configuration and the corresponding generated index.

[0118] In some other embodiments, the UE CONTEXT MODIFICATION RESPONSE message may include a list of N accepted candidate cell IDs and corresponding generated indices, which may indicate that the candidate cell configurations and indices are accepted, where N < M. Alternatively, the UE CONTEXT MODIFICATION RESPONSE message may include N candidate cell configurations and corresponding generated indices, where N < M.

[0119] 8 shows a flowchart for supporting lower layer mobility in an inter-DU mobility scenario according to some embodiments of the present disclosure. The components included in FIG. 8 are similar to those in FIG. 5, and details are omitted here.

[0120] In this solution, an index for a candidate cell configuration is generated by the candidate DU (or each of the multiple candidate DUs). The CU may assign an index range for the candidate cell configuration to each candidate DU. The candidate DU (or each of the multiple candidate DUs) may select an index from the index range for each candidate cell configuration and send the selected index and the corresponding candidate cell configuration to the CU. The CU may send the index and the corresponding candidate cell configuration received from the candidate DU (or each of the multiple candidate DUs) to the source DU. The CU may also send the index and the corresponding candidate cell configuration to the UE. A detailed flow is presented as follows:

[0121] In operation 801, the CU may send a message, e.g., a UE CONTEXT SETUP REQUEST message, to the candidate DU, including a number of candidate cell IDs (denoted as K candidate cell IDs for simplicity, where K may be an integer equal to or greater than 1). Note that the K candidate cells may be controlled by the same candidate DU or by different candidate DUs. The message may also indicate an index range assigned by the CU, and indices within the index range may be used by the candidate DU.

[0122] In some embodiments, a UE CONTEXT SETUP REQUEST message may be sent for each candidate cell, i.e., the CU may send K UE CONTEXT SETUP REQUEST messages, and each UE CONTEXT SETUP REQUEST message may indicate a candidate cell ID and index range.

[0123] In some other embodiments, the UE CONTEXT SETUP REQUEST message may indicate multiple candidate cell IDs (e.g., a list of K candidate cell IDs) and index ranges and is sent to a candidate DU that may control multiple candidate cells.

[0124] The preparation request may be accepted at operation 802. The candidate DU may prepare candidate cell configurations and select an index from the index range for each candidate cell configuration.

[0125] For example, one index range may be 0 to 5, and the selected index may be a number, e.g., 0, 1, 2, 3, etc. The maximum value of the index range may be preconfigured, such as 8, 16, 32, 64, 128, etc. In another example, the index range may be a set of candidate cell configuration IDs, and the selected index may be one ID from that set that is used to identify the candidate cell configuration.

[0126] In operation 803, the candidate DU may send a response message, for example, a UE CONTEXT SETUP RESPONSE message, to the CU. The UE CONTEXT SETUP RESPONSE message may indicate the candidate cell IDs, candidate cell configurations, and the corresponding selected index of the candidate cell configuration for each candidate cell that have been requested by the CU.

[0127] Among the K requested candidate cells, some candidate cells may be accepted, while others may not. The number of accepted candidate cells is denoted as L, and it is assumed that L≦K. The candidate DU may send a UE CONTEXT SETUP RESPONSE message indicating the L candidate cell configurations and the corresponding L selected indices. In some embodiments, a UE CONTEXT SETUP RESPONSE message may be sent for each requested candidate cell, i.e., one UE CONTEXT SETUP RESPONSE message may be sent for each candidate cell, and the candidate DU may send L UE CONTEXT SETUP RESPONSE messages to the CU. In some other embodiments, if there is one candidate DU, the one candidate DU may send one UE CONTEXT SETUP RESPONSE message indicating the L candidate cell configurations and the corresponding selected indices. In some other embodiments, each candidate DU among the multiple DUs may send one UE CONTEXT SETUP RESPONSE message to the CU indicating all of its own candidate cell configurations and the corresponding selected indices.

[0128] Operations 804 to 811 are similar to operations 504 to 511, respectively, described in FIG. 5, and will not be detailed here.

[0129] 9 illustrates a flowchart for supporting lower layer mobility in an intra-DU mobility scenario according to some embodiments of the present disclosure. Figure 9 includes three components: a UE, a DU, and a CU. The DU may also be referred to as a source DU, and the UE is performing a handover procedure from a source cell to a target cell, both cells being managed by the DU.

[0130] In this solution, the index is generated by the DU. The DU may provide the candidate cell configurations and the index of each candidate cell configuration to the CU. The CU may send the index and the corresponding candidate cell configuration to the UE. The detailed flow is presented as follows:

[0131] In operation 901, the CU may send a message, such as a UE CONTEXT MODIFICATION REQUEST message, to the DU, which may include M candidate cell IDs. The CU may request preparation of the M candidate cells by sending a message to the DU to modify the UE context.

[0132] In some embodiments, a UE CONTEXT MODIFICATION REQUEST message may be sent for each candidate cell, i.e., the CU may send M UE CONTEXT MODIFICATION REQUEST messages, and each UE CONTEXT MODIFICATION REQUEST message may include one candidate cell ID.

[0133] In some other embodiments, the UE CONTEXT MODIFICATION REQUEST message may include multiple candidate cell IDs (eg, a list of M candidate cell configurations) and is sent to the DU.

[0134] In operation 902, a modification request may be accepted, e.g., N out of M candidate cells are accepted, where N≦M, and the DU may prepare the N candidate cell configurations and generate an index for each candidate cell configuration among the N candidate cell configurations, the index being used to identify the candidate cell configuration. In some embodiments, the index may be a numeric value, e.g., 0, 1, 2, 3, etc. A maximum value for the index, such as 8, 16, 32, 64, 128, etc., may be preconfigured. In other embodiments, the index may be a candidate cell configuration ID used to identify the candidate cell configuration.

[0135] In operation 903, the DU may send a response message, for example, a UE CONTEXT MODIFICATION RESPONSE message, to the CU, which may indicate the N candidate cell configurations and corresponding indices.

[0136] In some embodiments, a UE CONTEXT MODIFICATION RESPONSE message may be sent for each accepted candidate cell, i.e., the DU may send N UE CONTEXT MODIFICATION RESPONSE messages, and each UE CONTEXT MODIFICATION RESPONSE message may indicate one accepted candidate cell configuration and corresponding index.

[0137] In some other embodiments, the UE CONTEXT MODIFICATION RESPONSE message may indicate N candidate cell configurations and corresponding indices, where N≦M.

[0138] Operations 904 to 909 are similar to operations 506 to 511, respectively, described in FIG. 5, and will not be detailed here.

[0139] 10 shows a flowchart for supporting lower layer mobility in an intra-DU mobility scenario according to some embodiments of the present disclosure. The components included in FIG. 10 are similar to those in FIG. 9, and details are omitted here.

[0140] In this solution, the index is generated by the CU. The DU may provide the cell configuration of each candidate cell to the CU. In response to receiving the candidate cell configuration, the CU may generate (or assign) an index for each candidate cell configuration. The CU may send the candidate cell configuration and the generated index to the DU. The CU may also send the candidate cell configuration and the generated index to the UE. A detailed flow is presented as follows:

[0141] In operation 1001, the CU may send a message including K candidate cell IDs, for example, a UE CONTEXT MODIFICATION REQUEST message, to the DU. The CU may request preparation of the K candidate cells by sending a message to the DU to modify the UE context.

[0142] In some embodiments, a UE CONTEXT MODIFICATION REQUEST message may be sent for each candidate cell, i.e., the CU may send K UE CONTEXT MODIFICATION REQUEST messages, and each UE CONTEXT MODIFICATION REQUEST message may indicate a candidate cell ID.

[0143] In some other embodiments, the UE CONTEXT MODIFICATION REQUEST message may include multiple candidate cell IDs (eg, a list of M candidate cell configurations) for the DU.

[0144] In operation 1002, if the modification request is accepted, e.g., L out of K candidate cells are accepted candidate cells, where L≦K, the DU may send a response message, e.g., a UE CONTEXT MODIFICATION RESPONSE message, to the CU. The UE CONTEXT MODIFICATION RESPONSE message may include the candidate cell configuration for each of the L candidate cells.

[0145] In operation 1003, after receiving the L candidate cell configurations, the CU may generate an index for each candidate cell configuration among the L candidate cell configurations, where the index is used to identify the candidate cell configuration.

[0146] In operation 1004, the CU may send a message, eg, a UE CONTEXT MODIFICATION REQUEST message, to the DU that may indicate the M candidate cell configurations and corresponding indices.

[0147] In some embodiments, a UE CONTEXT MODIFICATION REQUEST message may be sent for each candidate cell, i.e., the CU may send M UE CONTEXT MODIFICATION REQUEST messages, each UE CONTEXT MODIFICATION REQUEST message including one candidate cell configuration and a corresponding index.

[0148] In some other embodiments, the UE CONTEXT MODIFICATION REQUEST message may include multiple candidate cell configurations and corresponding indices for the source DU (eg, a list of M candidate cell configurations and corresponding indices).

[0149] In operation 1005, if the modification request is accepted, the source DU may send a response message, for example, a UE CONTEXT MODIFICATION RESPONSE message, to the CU that may indicate that the N candidate cell configurations and corresponding indices have been accepted.

[0150] In some embodiments, a UE CONTEXT MODIFICATION RESPONSE message may be sent for each accepted candidate cell, i.e., the DU may send N UE CONTEXT MODIFICATION RESPONSE messages, and each UE CONTEXT MODIFICATION RESPONSE message may indicate one accepted candidate cell configuration and corresponding index.

[0151] In some other embodiments, the UE CONTEXT MODIFICATION RESPONSE message may indicate a list of N accepted candidate cell IDs, which may indicate that the candidate cell configurations and indices are accepted, where N < M. Alternatively, the UE CONTEXT MODIFICATION RESPONSE message may indicate N candidate cell configurations and corresponding indices, where N < M.

[0152] Operations 1006 to 1011 are similar to operations 506 to 511, respectively, described in FIG. 5, and will not be detailed here.

[0153] FIG. 11 shows a simplified block diagram of an apparatus according to some embodiments of the present disclosure.

[0154] 11, an example of an apparatus 1100 may include at least one processor 1104 and at least one transceiver 1102 coupled to the processor 1104. The apparatus 1100 may be a UE, a BS, a CU, a candidate DU, a source DU, a target DU, a candidate target DU, or any other device having similar functionality.

[0155] In this figure, elements such as at least one transceiver 1102 and processor 1104 are described in the singular, but the plural is contemplated unless limitation to the singular is explicitly stated. In some embodiments of the present disclosure, the transceiver 1102 may be divided into two devices, such as a receiving circuit and a transmitting circuit. In some embodiments of the present disclosure, the apparatus 1100 may further include an input device, a memory, and / or other components.

[0156] In some embodiments of the present disclosure, the apparatus 1100 may be a UE. The transceiver 1102 and the processor 1104 may interact with each other to perform the operations of a UE described in any of FIGS. 1-10. In some embodiments of the present disclosure, the apparatus 1100 may be a CU, a candidate DU, a source DU, a target DU, a candidate-target DU, etc. The transceiver 1102 and the processor 1104 may interact with each other to perform the operations of a node described in any of FIGS. 1-10.

[0157] In some embodiments of the present disclosure, the apparatus 1100 may further include at least one non-transitory computer-readable medium.

[0158] For example, in some embodiments of the present disclosure, a non-transitory computer-readable medium may store computer-executable instructions that cause the processor 1104 to implement the methods described above for a UE. For example, the computer-executable instructions, when executed, cause the processor 1104 interacting with the transceiver 1102 to perform the operations of a UE described in any of FIGS.

[0159] In some embodiments of the present disclosure, a non-transitory computer-readable medium may store computer-executable instructions that cause the processor 1104 to implement the methods described above for a CU, a candidate DU, a source DU, a target DU, or a candidate target DU. For example, the computer-executable instructions, when executed, cause the processor 1104 interacting with the transceiver 1102 to perform the operations of the node described in any of FIGS.

[0160] The methods of the present disclosure may be implemented on a programmed processor. However, the controllers, flowcharts, and modules may also be implemented on hardware electronic or logical circuitry, such as a general-purpose or special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, integrated circuits, discrete component circuits, programmable logic devices, etc. In general, any device having a finite state machine capable of implementing the flowcharts shown in the figures may be used to implement the processor functions of the present disclosure.

[0161] While the present disclosure has been described using specific embodiments thereof, it is apparent that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, various components of the embodiments may be exchanged, added, or substituted in other embodiments. Also, not all elements shown in the figures are necessary for the operation of the disclosed embodiments. For example, one skilled in the art of the disclosed embodiments would be able to make and use the teachings of the present disclosure by simply employing the elements of the independent claims. Accordingly, the embodiments of the present disclosure described herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0162] In this disclosure, relational terms such as “first,” “second,” and the like may be used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. The terms “includes,” “including,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements not only includes those elements, but may also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “a,” “an,” etc., does not, without further constraint, preclude the presence of additional identical elements in a process, method, article, or apparatus that includes that element. Also, the term “another” is defined as at least a second or more. Terms such as “including,” “having,” and the like, as used herein, are defined as “comprising.” [Explanation of symbols]

[0163] 101A UE 101B UE 102A DU 102B1DU 102B2DU 103A1 Access Node 103A2 Access Node 104B CU 1100 equipment 1102 Transceiver 1104 processor

Claims

1. A distributed unit (DU), A transceiver; coupled to the transceiver, determining a candidate cell configuration for each candidate cell among one or more candidate cells and an index of the candidate cell configuration, wherein the index of the candidate cell configuration is generated by the DU or received from another network node; sending an indication to a user equipment (UE) indicating to the UE to handover from a serving cell to a candidate cell of the one or more candidate cells; a processor configured to: Equipped with DU.

2. The DU of claim 1 , wherein the instruction is transmitted via a Medium Access Control (MAC) control element (CE) or downlink control information (DCI).

3. The instructions are as follows: an index of a candidate cell configuration corresponding to said candidate cell; or an indicator indicating whether the candidate cell configuration should be maintained; 2. The DU of claim 1, wherein the DU exhibits at least one of:

4. the processor: receiving, from a central unit (CU), a first message indicating a candidate cell configuration and an index of the candidate cell configuration for each candidate cell of a set of candidate cells, the set of candidate cells including the one or more candidate cells; sending, to the CU, a second message indicating the candidate cell configuration for each candidate cell of the one or more candidate cells and the index of the candidate cell configuration; The DU of claim 1 , further configured to:

5. the processor: receiving a first message from a central unit (CU) indicating a candidate cell configuration for each candidate cell in a set of candidate cells; determining the one or more candidate cells from the set of candidate cells; generating an index for each candidate cell configuration for each candidate cell of the one or more candidate cells; sending, to the CU, a second message indicating the candidate cell configuration for each candidate cell of the one or more candidate cells and the index of the candidate cell configuration; The DU of claim 1 , further configured to:

6. the processor: receiving a first message from a central unit (CU) indicating a set of candidate cells; determining the one or more candidate cells from the set of candidate cells; generating a candidate cell configuration for each candidate cell of the one or more candidate cells and an index for each candidate cell configuration; sending, to the CU, a second message indicating the candidate cell configuration for each candidate cell of the one or more candidate cells and the index of the candidate cell configuration; The DU of claim 1 , further configured to:

7. the processor: receiving a first message from a central unit (CU) indicating a set of candidate cells; determining the one or more candidate cells from the set of candidate cells; generating a candidate cell configuration for each candidate cell of the one or more candidate cells; sending, to the CU, a second message indicating the candidate cell configuration for each candidate cell of the one or more candidate cells; The DU of claim 4 , further configured to:

8. The candidate cell configuration is one of the following: Channel State Information (CSI) resource configuration, or Transmission Configuration Indicator State The DU of claim 1 , comprising at least one of:

9. a central unit (CU), A transceiver; coupled to the transceiver, transmitting a first message indicating at least a set of candidate cells; receiving a second message indicating a candidate cell configuration for each candidate cell among one or more candidate cells in the set of candidate cells and an index of the candidate cell configuration; a processor configured to: Equipped with CU.

10. the first message further indicates a candidate cell configuration for each candidate cell in the set of candidate cells, and the processor: sending a request message indicating at least one candidate cell to a candidate distribution unit (DU); receiving a response message indicating a candidate cell configuration for each of at least some of the at least one candidate cell; The CU of claim 9 , further configured to:

11. The CU of claim 10 , wherein the first message further indicates an index of each candidate cell configuration of each candidate cell in a set of candidate cells.

12. the processor: determining an index of each candidate cell configuration for at least some of the at least one candidate cell; The CU of claim 11 , further configured to:

13. the processor: sending a request message to a candidate DU indicating at least one candidate cell and an index range; receiving a response message indicating a candidate cell configuration for each of at least some of the at least one candidate cell and an index of the candidate cell configuration; The CU of claim 11 , further configured to:

14. the processor: and transmitting to the UE a message indicating the candidate cell configuration for each candidate cell of the one or more candidate cells and the index of the candidate cell configuration. The CU of claim 9, further configured to:

15. A user equipment (UE), A transceiver; coupled to the transceiver, receiving a message indicating a candidate cell configuration for each candidate cell of one or more candidate cells and an index of the candidate cell configuration; In response to receiving an indication indicating to the UE to hand over from a serving cell to a candidate cell of the one or more candidate cells, performing a random access procedure toward the candidate cell. a processor configured to: UE equipped with.

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