Preconfigured mobility with handover preparation information at du

Abstract

Embodiments of the present disclosure relate to pre-configured mobility with handover preparation information at distributed units (DUs). According to an embodiment of the present disclosure, a central unit (CU) of a base station comprises: a transceiver configured to communicate with a network; and a processor communicatively coupled to the transceiver and configured to perform an operation. The operation includes: transmitting handover preparation information of a user equipment (UE) for inter-DU mobility to a second DU of the base station; receiving, after transmitting the handover preparation information, a request for inter-DU mobility from a first DU of the base station serving the UE; and triggering the inter-DU mobility in accordance with a determination that the request for the inter-DU mobility is accepted.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to the field of telecommunications, and particularly to pre-configured mobility with handover preparation information at a distributed unit (DU). Background Art

[0002] A base station (BS) may include a central unit (CU) and one or more DUs. The operation of the DU may be partially controlled by the CU. The CU may terminate the F1 interface connected to the DU. The DU may support one or more cells. A cell is supported by only one DU. The DU may terminate the F1 interface connected to the CU.

[0003] A DU may serve one or more user equipments (UEs) directly connected to the DU. Based on the measurement results, the UE may perform an intra-DU mobility procedure to move from one cell provided by the DU to another cell provided by the DU. Alternatively, the UE may perform an inter-DU mobility procedure to move from a cell provided by one DU to a cell provided by another DU controlled by the same CU. Summary of the invention

[0004] Generally speaking, example embodiments of the present disclosure provide a solution for pre-configured mobility with handover preparation information at a distributed unit (DU).

[0005] In a first aspect, a CU of a BS is provided. The CU includes a transceiver and a processor. The transceiver is configured to communicate with a network. The processor is communicatively coupled to the transceiver and configured to perform operations including: sending handover preparation information for inter-DU mobility of a UE to a second DU of the base station; after sending the handover preparation information, receiving a request for the inter-DU mobility from a first DU of the base station serving the UE; and triggering the inter-DU mobility according to determining that the request for the inter-DU mobility is accepted.

[0006] In a second aspect, a DU of a BS is provided. The DU includes a transceiver and a processor. The transceiver is configured to communicate with a network. The processor is communicatively coupled to the transceiver and configured to perform operations including: receiving handover preparation information for inter-DU mobility of a UE from a CU of the base station; and performing a random access procedure with the UE based on the handover preparation information.

[0007] In a third aspect, a baseband processor of a BS is provided. The baseband processor is configured to perform operations including: sending handover preparation information of a UE for inter-DU mobility to a second DU of the base station; after sending the handover preparation information, receiving a request for the inter-DU mobility from a first DU of the base station serving the UE; and triggering the inter-DU mobility according to determining that the request for the inter-DU mobility is accepted.

[0008] It should be understood that the invention summary is not intended to indicate the key features or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of some embodiments of the present disclosure in the accompanying drawings, in which:

[0010] Figure 1 An example communication network is shown in which example embodiments of the present disclosure may be implemented;

[0011] Figure 2 illustrates a signaling diagram illustrating procedures for mobility according to some example embodiments of the present disclosure;

[0012] Figure 3A illustrates a signaling diagram illustrating a procedure for inter-DU mobility according to some example embodiments of the present disclosure;

[0013] Figure 3B illustrates an exemplary UE CONTEXT MODIFICATION REQUEST message according to some example embodiments of the present disclosure;

[0014] Figure 3C illustrates a signaling diagram illustrating a procedure for inter-DU mobility according to some other example embodiments of the present disclosure;

[0015] Figure 3D illustrates an exemplary UE CONTEXTMODIFICATION REQUEST message according to some other example embodiments of the present disclosure;

[0016] Figure 4A illustrates a signaling diagram illustrating a procedure for inter-DU mobility according to yet other example embodiments of the present disclosure;

[0017] Figure 4B An exemplary UL RRC MESSAGE TRANSFER message according to some exemplary embodiments of the present disclosure is illustrated;

[0018] Figure 4C Another exemplary UL RRC MESSAGETRANSFER message according to some exemplary embodiments of the present disclosure is illustrated;

[0019] Figure 4D illustrates a signaling diagram illustrating a procedure for inter-DU mobility according to further example embodiments of the present disclosure;

[0020] Figure 4E Another exemplary UE CONTEXTMODIFICATION REQUIRED message according to some example embodiments of the present disclosure is illustrated;

[0021] Figure 4F illustrates an exemplary configuration of L2 specific events according to some example embodiments of the present disclosure;

[0022] Figure 4G illustrates another exemplary configuration of L2 specific events according to some other exemplary embodiments of the present disclosure;

[0023] Figure 5 illustrates a signaling diagram illustrating a procedure for inter-DU mobility according to some example embodiments of the present disclosure, in which handover preparation information is pre-configured;

[0024] Figure 6 illustrates a signaling diagram illustrating a procedure for inter-DU mobility with querying using a target DU according to some other example embodiments of the present disclosure;

[0025] Figure 7 illustrates a signaling diagram illustrating a procedure for inter-DU mobility without querying with a target DU according to yet other example embodiments of the present disclosure;

[0026] Fig. 8A illustrates an exemplary IE for configuration of candidate cells for L2 mobility according to some example embodiments of the present disclosure;

[0027] Figure 8B Illustrated are exemplary IEs for configuration of candidate cells for L2 mobility, which are included as part of conditional configuration according to some example embodiments of the present disclosure

[0028] Figure 8C Illustrated are exemplary IEs for configuration of candidate cells for L2 mobility according to some example embodiments of the present disclosure. Fig. 8A and Figure 8B The examples are common;

[0029] Fig.8Dillustrates exemplary IEs for configuration of candidate cells for L1 mobility and L2 mobility according to some example embodiments of the present disclosure;

[0030] Fig. 8E illustrates exemplary IEs for configuration of candidate cells for L1 mobility, which are included as part of conditional configuration according to some example embodiments of the present disclosure;

[0031] Figure 8F Illustrated are exemplary IEs for configuration of candidate cells for L2 mobility and L1 mobility according to some example embodiments of the present disclosure. Fig.8D and Fig. 8E The examples are common;

[0032] Fig. 9A illustrates exemplary IEs for handling configuration of PDCP and RLC according to some example embodiments of the present disclosure;

[0033] Fig. 9B illustrates exemplary IEs for handling configuration of PDCP and RLC according to some other example embodiments of the present disclosure;

[0034] Fig. 9C illustrates exemplary IEs for handling configuration of PDCP and RLC according to yet other example embodiments of the present disclosure;

[0035] Fig.10 illustrates a flow chart illustrating an example method for mobility implemented at a CU of a BS according to some example embodiments of the present disclosure;

[0036] Fig.11 illustrates a flowchart illustrating an example method for mobility implemented at a target DU of a BS according to some example embodiments of the present disclosure; and

[0037] Fig.12 A simplified block diagram of a device suitable for implementing embodiments of the present disclosure is illustrated.

[0038] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0039] The principle of the present disclosure will now be described with reference to some embodiments. It should be understood that these embodiments are described only for the purpose of illustration, and help those skilled in the art to understand and implement the present disclosure, without indicating any limitation to the scope of the present disclosure. In addition to the methods described below, the disclosure described herein can be implemented in various ways.

[0040] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0041] The terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments. For example, as used herein, the singular forms "a", "a kind of" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "include", "have", "include" when used herein specify the presence of stated features, elements and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when describing specific features, structures or characteristics in conjunction with some embodiments, it is considered that it is within the knowledge of those skilled in the art to implement such features, structures or characteristics in conjunction with other embodiments that are explicitly or not explicitly described.

[0042] It should also be understood that, although the terms "first", "second", etc. may be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, the first element can be named as the second element and similarly the second element can be named as the first element without departing from the scope of the example embodiments. As used herein, the term "and / or" includes any combination and all combinations of one or more of the listed terms.

[0043] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, such as long term evolution (LTE), LTE-Advanced (LTE-A), wideband code division multiple access (WCDMA), high speed packet access (HSPA), narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal equipment and the network equipment in the communication network can be performed according to any suitable generation of communication protocol, including but not limited to the first generation (1G) communication protocol, the second generation (2G) communication protocol, the 2.5G communication protocol, the 2.75G communication protocol, the third generation (4C) communication protocol, the fourth generation (4G) communication protocol, the 4.5G communication protocol, the future fifth generation (5G) communication protocol, and / or any other protocol currently known or to be developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communication, there will certainly be communication technologies and systems of future types that can embody the present disclosure. It should not be regarded as limiting the scope of the present disclosure to the above-mentioned systems.

[0044] As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services from it. Depending on the terminology and technology applied, a network device may refer to a base station (BS) or an access point (AP), such as a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, a low power node (such as a femto, pico, etc.).

[0045] The term "terminal device" refers to any terminal device capable of wireless communication. By way of example and not limitation, a terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device (such as a digital camera, a game terminal device, a music storage and playback appliance), a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded equipment (LEE), a laptop mounted equipment (LME), a USB dongle, a smart device, a wireless customer premises equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices running in industrial and / or automated processing chain environments), consumer electronic devices, equipment running on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0046] Figure 1 An example communication network 100 is shown in which embodiments of the present disclosure may be implemented. The network 100 may include a base station. The base station may include a CU and one or more DUs. In some embodiments, the base station may be a gNB, an eNB, etc. Figure 1 In the example of , the base station is illustrated as a gNB. In such an example, the CU of the base station may be referred to as a gNB-CU, and the DU of the base station may be referred to as a gNB-DU.

[0047] like Figure 1As shown, network 100 may include UE 110, gNB-CUs 120 and 150, a first gNB-DU 130, and a second gNB-DU 140. The first gNB-DU 130 and the second gNB-DU 140 are connected to gNB-CU 120. Operations of the first gNB-DU 130 and the second gNB-DU 140 may be partially controlled by gNB-CU 120. gNB-CU 120 may terminate an F1 interface connected to each of the first gNB-DU 130 and the second gNB-DU 140. Each of the first gNB-DU 130 and the second gNB-DU 140 may terminate an F1 interface connected to the gNB-CU 120.

[0048] The gNB-CU 120 may be a logical node for hosting at least one of the radio resource control (RRC), service data adaptation protocol (SDAP), and packet data convergence protocol (PDCP) protocols of a base station. The gNB-CU 150 may be a logical node for hosting at least one of the RRC protocol, SDAP protocol, and PDCP protocol of another base station.

[0049] Each of the first gNB-DU 130 and the second gNB-DU 140 may be a logical node hosting at least one of a radio link control (RLC) layer, a medium access control (MAC) layer, and a physical (PHY) layer of a base station.

[0050] Each of the first gNB-DU 130 and the second gNB-DU 140 may provide or support one or more cells. One cell is supported by only one DU. For example, the first gNB-DU 130 may provide cells 131, 132, and 133, and the second gNB-DU 140 may provide cells 141, 142, and 143.

[0051] The gNB-CU 150 may also provide or support one or more cells. For example, the gNB-CU 150 may provide cells 151 and 152.

[0052] It should be understood that the number of UEs, CUs and / or DUs is for illustration purposes only and does not imply any limitation to the present disclosure. Network 100 may include any suitable number of UEs, CUs and DUs suitable for implementing the present disclosure.

[0053] Communications in the network 100 may conform to any suitable standard, including but not limited to Global System for Mobile Communications (GSM), Long Term Evolution (LTE), LTE-Evolution, LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE Radio Access Network (GERAN), Machine Type Communication (MTC), etc. In addition, communications may be performed according to any generation of communication protocols currently known or to be developed in the future. Examples of communication protocols include but are not limited to first generation (1G) communication protocols, second generation (2G) communication protocols, 2.5G communication protocols, 2.75G communication protocols, third generation (4C) communication protocols, fourth generation (4G) communication protocols, 4.5G communication protocols, and fifth generation (5G) communication protocols.

[0054] UE 110 may access one cell provided by first gNB-DU 130. For example, UE 110 may initially connect to cell 133 provided by first gNB-DU 130. Based on the measurement result, UE 110 may perform an intra-DU mobility procedure to move from cell 133 to another cell provided by first gNB-DU 130. For example, UE 110 may perform an intra-DU mobility procedure to move from cell 133 to one of cells 131 and 132. Hereinafter, intra-DU mobility is also referred to as intra-gNB-DU mobility.

[0055] Alternatively, based on the measurement result, the UE 110 may perform an inter-DU mobility procedure to move from a cell provided by the first gNB-DU 130 to a cell provided by the second gNB-DU 140. For example, the UE 110 may perform an inter-DU mobility procedure to move from a cell 133 provided by the first gNB-DU 130 to one of cells 141, 142, or 143 provided by the second gNB-DU 140. Hereinafter, inter-DU mobility is also referred to as inter-gNB-DU mobility.

[0056] In some embodiments, UE 110 may be in dual connectivity (DC) with gNB-CU 120 and 150. When gNB-CU 120 is configured as a secondary node (SN) and gNB-CU 150 is configured as a master node (MN) in a DC configuration, intra-DU mobility procedures and inter-DU mobility procedures may be allowed.

[0057] Figure 2 A signaling diagram illustrating a process 200 for mobility according to some example embodiments of the present disclosure is illustrated. For the purpose of discussion, reference will be made to Figure 1 Process 200 is described. Process 200 may involve Figure 1UE 110, gNB-CU 120, first gNB-DU 130 and second gNB-DU 140.

[0058] like Figure 2 As shown, UE 110 receives 210 from gNB-CU 120 at least one of a configuration for a first set of candidate cells for intra-DU mobility or a configuration for a second set of candidate cells for inter-DU mobility.

[0059] For example, in an embodiment where UE 110 initially accesses cell 133 provided by first gNB-DU 130, a first set of candidate cells for intra-DU mobility may include cells 131 and 132, and a second set of candidate cells for inter-DU mobility may include cells 141, 142, and 143. FIG. 8A to FIG. 8F Details of the configuration for the first group of candidate cells or the configuration for the second group of candidate cells are described.

[0060] UE 110 receives a handover command (220) from a first gNB-DU 130 serving UE 110. The handover command includes an index of a configuration of a target cell selected from the first group or the second group.

[0061] UE 110 then performs handover to the target cell based on the handover command.

[0062] In process 220, since at least one of the configuration for the first set of candidate cells or the configuration for the second set of candidate cells is provided to UE 110 before handover, mobility delay may be reduced.

[0063] In an implementation where the target cell is selected from the first set of candidate cells for intra-DU mobility, UE 110 may perform a handover to the target cell by performing the intra-DU mobility procedure.

[0064] In an implementation where the target cell is selected from the second set of candidate cells for inter-DU mobility, UE 110 may perform 230 a handover to the target cell by performing an inter-DU mobility procedure.

[0065] In the following, reference will be made to Figures 3A to 6 Some implementations of the inter-DU mobility procedure are described.

[0066] Figure 3A A signaling diagram illustrating a process 300 for inter-DU mobility according to some example embodiments of the present disclosure is illustrated. For discussion purposes, reference will be made to Figure 1 Process 300 is described. Process 300 may involve Figure 1UE 110, gNB-CU 120, first gNB-DU 130 and second gNB-DU 140 in. Process 300 can be regarded as an example implementation of process 200.

[0067] In general, in process 300, a first gNB-DU 130 receives a first message including a first MAC CE from a gNB-CU 120. The first MAC CE includes an index of a configuration of a target cell. A handover command sent from the first gNB-DU 130 to the UE 110 includes the first MAC CE. The first MAC CE includes an index of a configuration of the target cell. Alternatively, the handover command includes first downlink control information (DCI). The first DCI includes an index of a configuration of the target cell.

[0068] In process 300, UE 110 may initially connect to cell 133 provided by first gNB-DU 130. Thus, downlink user data to UE 110 is forwarded to gNB-CU 120 through first gNB-DU 130. In addition, uplink user data transmitted from UE 110 is forwarded to gNB-CU 120 through first gNB-DU 130.

[0069] Based on the measurement result, UE 110 may perform an inter-DU mobility procedure to move from cell 133 to one of cells 141, 142, and 143 provided by the second gNB-DU 140. In this regard, the first gNB-DU 130 may be referred to as a source gNB-DU, and the second gNB-DU 140 may be referred to as a target gNB-DU.

[0070] Specifically, Figure 3A As shown, similar to process 200, UE 110 receives 210 from gNB-CU 120 at least one of a configuration for a first set of candidate cells for intra-DU mobility or a configuration for a second set of candidate cells for inter-DU mobility.

[0071] UE 110 sends 311 an L3 message including the measurement result to gNB-DU 130. gNB-DU 130 sends 312 an UL RRC MESSAGE TRANSFER message to gNB-CU 120 to convey the measurement result.

[0072] The gNB-CU 120 sends 313 a UE CONTEXT SETUP REQUEST message to the second gNB-DU 140 to create a UE context and establish one or more data bearers. The UE CONTEXT SETUP REQUEST message includes HandoverPreparationInformation. In addition, the UE CONTEXT SETUP REQUEST message may include a DL UE Tunnel Endpoint Identifier (TEID).

[0073] The second gNB-DU 314 responds to the gNB-CU 120 with a UE CONTEXT SETUP RESPONSE message.

[0074] The gNB-CU 120 sends 315 a first message to the first gNB-DU 130. The first message may be used to provide the first gNB-DU 130 with a UE context information change. For example, the first message may be a UE CONTEXT MODIFICATION REQUEST message. The UE CONTEXT MODIFICATION REQUEST message includes a first MAC CE. The first MAC CE includes an index of the configuration of the target cell. The first gNB-DU 130 also sends 316 a downlink data delivery status frame to notify the gNB-CU 120 of downlink data that was not successfully sent to the UE 110.

[0075] Upon receiving the UE CONTEXT MODIFICATION REQUEST message from the gNB-CU 120, the first gNB-DU 130 sends 317 a handover command to the UE 110. The handover command includes a first MAC CE. The first MAC CE includes an index of the configuration of the target cell. Alternatively, the handover command includes a first DCI. The first DCI includes an index of the configuration of the target cell.

[0076] Upon receiving the handover command, UE 110 performs 230 a handover to the target cell by performing an inter-DU mobility procedure. For example, UE 110 may initiate a random access (RACH) procedure to the target cell.

[0077] The second gNB-DU 140 sends 318 a UL RRC MESSAGE TRANSFER message to the gNB-CU 120. The UL RRC MESSAGE TRANSFER message may include a MAC CE including a UL UE TEID.

[0078] At the time of switching, downlink user data to UE 110 is forwarded to gNB-CU 120 via the second gNB-DU 140. In addition, uplink user data transmitted from UE 110 is forwarded to gNB-CU 120 via the second gNB-DU 140.

[0079] Figure 3B An exemplary UE CONTEXT MODIFICATION REQUEST message 320 is illustrated according to some example embodiments of the present disclosure. The UE CONTEXT MODIFICATION REQUEST message 320 may be used in the process 300.

[0080] like Figure 3B As shown, a new information element (IE) "RRC-Container-L2-type" 321 is introduced in the UE CONTEXT MODIFICATION REQUEST message 320. The IE "RRC-Container-L2-type" 321 may be a first MAC CE. The first MAC CE includes an index of the configuration of the target cell.

[0081] Figure 3C A signaling diagram illustrating a process 330 for inter-DU mobility according to some other example embodiments of the present disclosure is illustrated. For discussion purposes, reference will be made to Figure 1 Describe process 330. Process 330 may involve Figure 1 UE 110, gNB-CU 120, first gNB-DU 130 and second gNB-DU 140 in. Process 330 can be regarded as another example implementation of process 200.

[0082] In general, in process 330, a first gNB-DU 130 receives a first message from a gNB-CU 120. The first message includes an index of a configuration of a target cell. A handover command sent from the first gNB-DU 130 to the UE 110 includes a first MAC CE. The first MAC CE includes an index of a configuration of the target cell. Alternatively, the handover command includes first downlink control information (DCI). The first DCI includes an index of a configuration of the target cell.

[0083] The actions at 210, 230, 311, 312, 313, 314, 316, 317, and 318 in process 330 are the same as the actions in process 300. Therefore, the details of the actions are omitted for brevity.

[0084] Process 330 differs from process 300 in that upon receiving the UE CONTEXT SETUP RESPONSE message, the gNB-CU 120 sends 335 a first message to the first gNB-DU 130, the first message including an index of the configuration of the target cell. For example, the first message may be a UE CONTEXT MODIFICATION REQUEST message. The UE CONTEXT MODIFICATION REQUEST message includes an index of the configuration of the target cell.

[0085] Figure 3D An exemplary UE CONTEXT MODIFICATION REQUEST message 340 according to some other exemplary embodiments of the present disclosure is illustrated. The UE CONTEXT MODIFICATION REQUEST message 340 may be used in the process 330.

[0086] like Figure 3D As shown, a new IE “L2-1-Mobility-Info” 341 is introduced in the UE CONTEXT MODIFICATION REQUEST message 340. The IE “L2-1-Mobility-Info” 341 may include an index of the configuration of the target cell.

[0087] Figure 4A A signaling diagram illustrating a process 400 for inter-DU mobility according to yet other example embodiments of the present disclosure is illustrated. For discussion purposes, reference will be made to Figure 1 Process 400 is described. Process 400 may involve Figure 1 UE 110, gNB-CU 120, first gNB-DU 130 and second gNB-DU 140 in. Process 400 can be regarded as another example implementation of process 200.

[0088] In general, in process 400, before receiving the handover command, UE 110 sends a second MAC CE or a second DCI to the first gNB-DU 130. The second MAC CE or the second DCI includes a measurement result for at least one candidate cell in the first set of candidate cells for intra-DU mobility or the second set of candidate cells for inter-DU mobility. Upon receiving the measurement result, the first gNB-DU 130 may send a mobility request to the gNB-CU 120. The mobility request may include the second MAC CE, which includes the measurement result. Alternatively, the mobility request may include the measurement result.

[0089] The actions at 210, 230, 313, 314, 316, 317, and 318 in process 400 are the same as the actions in process 300. Therefore, the details of the actions are omitted for brevity.

[0090] Process 400 differs from process 300 in that UE 110 sends 411 a second MAC CE or a second DCI to first gNB-DU 130. The second MAC CE or the second DCI includes a measurement result for at least one candidate cell in the first set of candidate cells for intra-DU mobility or the second set of candidate cells for inter-DU mobility. Upon receiving the measurement result, first gNB-DU 130 sends 412 a mobility request to gNB-CU 120.

[0091] In an implementation where the first gNB-DU 130 receives the measurement results from the UE 110 via the second MAC CE, the first gNB-DU 130 may be identified using the UE C-RNTI and the DCCH logical channel. The first gNB-DU 130 may add the UE TEID to the content from the MAC CE.

[0092] In an embodiment in which the first gNB-DU 130 receives the measurement result from the UE 110 via the second MAC CE, the mobility request may include the second MAC CE, which includes the measurement result. Alternatively, the mobility request may include the measurement result. For example, the first gNB-DU 130 may send the mobility request by sending a UL RRC MESSAGE TRANSFER message to the gNB-CU 120. The UL RRC MESSAGE TRANSFER message may be used to transfer a layer 3 message to the gNB-CU 120 via the F1 interface. The UL RRC MESSAGE TRANSFER message may include the second MAC CE, which includes the measurement result. Alternatively, the first gNB-DU 130 may parse the measurement result in the second MAC CE from the UE 110 and provide the parsed measurement result to the gNB-CU 120 via the UL RRC MESSAGE TRANSFER message.

[0093] In an implementation scheme where the first gNB-DU 130 receives the measurement results from the UE 110 via the second DCI, the first gNB-DU 130 may receive the measurement results using the PUCCH or using CSI punctured in the PUSCH. In such an implementation scheme, the mobility request may include the measurement results. For example, the first gNB-DU 130 may send the mobility request by sending a UL RRC MESSAGE TRANSFER message to the gNB-CU 120. The first gNB-DU 130 may parse the measurement results in the second DCI from the UE 110 and provide the parsed measurement results to the gNB-CU 120 via the UL RRC MESSAGE TRANSFER message. In such an implementation scheme, the gNB-CU 120 does not need to implement the MAC specification.

[0094] Figure 4B An exemplary UL RRC MESSAGE TRANSFER message 420 is illustrated according to some exemplary embodiments of the present disclosure. The UL RRC MESSAGE TRANSFER message 420 may be used in the process 400.

[0095] like Figure 4B As shown, a new IE "RRC-Container-L2-type" 421 is introduced in the UL RRC MESSAGE TRANSFER message 420. The IE "RRC-Container-L2-type" 421 may include a second MAC CE. The second MAC CE includes a measurement result for at least one candidate cell in the first group of candidate cells for intra-DU mobility or the second group of candidate cells for inter-DU mobility.

[0096] Figure 4C Another exemplary UL RRC MESSAGE TRANSFER message 430 is illustrated according to some exemplary embodiments of the present disclosure. The UL RRC MESSAGE TRANSFER message 430 may be used in the process 400.

[0097] like Figure 4C As shown, a new IE “L2-L1-Mobility-Measurement-type” 431 is introduced in the UL RRC MESSAGE TRANSFER message 430. The IE “L2-L1-Mobility-Measurement-type” 431 may include a measurement result for at least one candidate cell in the first group of candidate cells for intra-DU mobility or the second group of candidate cells for inter-DU mobility.

[0098] Figure 4DA signaling diagram illustrating a process 440 for inter-DU mobility according to another example embodiment of the present disclosure is illustrated. For the purpose of discussion, reference will be made to Figure 1 Process 440 is described. Process 440 may involve Figure 1 UE 110, gNB-CU 120, first gNB-DU 130 and second gNB-DU 140 in. Process 440 can be regarded as another example implementation of process 200.

[0099] In general, in process 440, the first gNB-DU 130 may receive at least one of a first configuration for a third group of events for layer 2 (L2) mobility or a second configuration for a fourth group of events for layer 1 (L1) mobility from the gNB-CU 120. If the measurement result received from the UE 110 triggers at least one event in the third group or the fourth group, the first gNB-DU 130 may send a mobility request to the gNB-CU 120. The mobility request may include an index of at least one event. The first gNB-DU 130 may receive a response to the mobility request from the gNB-CU 120. The response includes an index of the configuration of the target cell.

[0100] The actions at 210, 230, 313, 314, 316, 317, and 318 in process 440 are the same as those in process 300. The action at 411 in process 440 is the same as that in process 400. Therefore, the details of the actions are omitted for brevity.

[0101] Process 440 differs from process 400 in that if the measurement results received from UE 110 trigger at least one event in the third group, the first gNB-DU 130 sends 442 a mobility request to the gNB-CU 120.

[0102] For example, the first gNB-DU 130 may send a mobility request by sending a UE CONTEXT MODIFICATION REQUIRED message to the gNB-CU 120. The UE CONTEXT MODIFICATION REQUIRED message may be used to request modification of the UE context. The UE CONTEXT MODIFICATION REQUIRED message may include an index of at least one event. The UE CONTEXT MODIFICATION REQUIRED message may also include measurement results. In some embodiments, the first gNB-DU 130 may trigger a UE CONTEXT MODIFICATION REQUIRED message for the UE 110.

[0103] In response to the UE CONTEXT MODIFICATION REQUIRED message, the gNB-CU 120 sends 315 a UE CONTEXT MODIFICATION REQUEST message to the first gNB-DU 130. The UE CONTEXT MODIFICATION REQUEST message includes a first MAC CE. The first MAC CE includes an index of the configuration of the target cell.

[0104] In some embodiments, the layer 2 message or the layer 1 message may include a unique number or identifier transmitted back by UE 110 in MSG3 as part of the RACH on the second gNB-DU 140, which may be passed to gNB-CU 120 to confirm the handover.

[0105] Figure 4E Another exemplary UE CONTEXT MODIFICATION REQUIRED message 450 according to some example embodiments of the present disclosure is illustrated. The UE CONTEXT MODIFICATION REQUIRED message 450 may be used in the process 440.

[0106] like Figure 4E As shown, a new IE “L2-Info” 451 is introduced in the UL RRC MESSAGE TRANSFER message 450. The IE “L2-Info” 451 may include an index of at least one event triggered by the measurement result.

[0107] In some implementations, UE 110 may receive at least one of a first configuration for a third group of events for layer 2 mobility or a second configuration for a fourth group of events for layer 1 mobility from gNB-CU 120 or first gNB-DU 130. UE 110 may send, to first gNB-DU 130, an index of at least one event in the third group or the fourth group triggered by the measurement result.

[0108] In some embodiments, UE 110 may send an index of at least one event together with the measurement result. For example, UE 110 may send an index of at least one event in the third group triggered by the measurement result in the second MAC CE. For another example, UE 110 may send an index of at least one event in the fourth group triggered by the measurement result in the second DCI.

[0109] In some embodiments, the index of at least one event is associated with a physical cell identifier (PCI) of the target cell.

[0110] In some embodiments, legacy L3 events may be reused.

[0111] In some embodiments, the UE 110 or the first gNB-DU 130 may be configured with an L2 version or an L1 version of the same L3 event.

[0112] In some embodiments, the MAC CE or DCI may carry information about legacy L3 events. Alternatively, new L2 or L1 specific events may be configured.

[0113] Figure 4F An exemplary configuration 460 of L2 specific events according to some example embodiments of the present disclosure is illustrated. In the configuration 460, the same L3 events are used in L2.

[0114] Figure 4G Another exemplary configuration 470 of L2 specific events according to some other exemplary embodiments of the present disclosure is illustrated. In the configuration 470, a new event is defined in L2 with an index reported in a MAC CE.

[0115] Figure 5 A signaling diagram illustrating a process 500 for inter-DU mobility according to some example embodiments of the present disclosure, in which handover preparation information is pre-configured. For discussion purposes, reference will be made to Figure 1 Process 500 is described. Process 500 may involve Figure 1 The gNB-CU 120, the first gNB-DU 130 and the second gNB-DU 140 in the network.

[0116] like Figure 5 As shown, the gNB-CU 120 sends 510 handover preparation information for inter-DU mobility of the UE 110 to the second gNB-DU 140 before the handover starts. Therefore, the second gNB-DU 140 receives the handover preparation information from the gNB-CU 120 before the handover starts.

[0117] After sending the handover preparation information, the gNB-CU 120 receives 520 a request for inter-DU mobility from the first gNB-DU 130 serving the UE 110. In other words, the gNB-CU 120 sends the handover preparation information to the second gNB-DU 140 before receiving the request for inter-DU mobility from the first gNB-DU 130 (i.e., before the handover starts).

[0118] Then, the gNB-CU 120 determines 530 whether the request for inter-DU mobility is accepted. If the request for inter-DU mobility is accepted, the gNB-CU 120 triggers 540 inter-DU mobility.

[0119] In some embodiments, the handover preparation information includes information about at least one of: a context of UE 110, or a data bearer to be established between UE 110 and second gNB-DU 140. Thus, upon receiving the handover preparation information, a context of UE 110 may be created and a data bearer may be established.

[0120] In process 500, because the gNB-CU 120 sends the handover preparation information to the second gNB-DU 140 before the handover starts, the delay for creating the context of the UE 110 and establishing the data bearer can be reduced.

[0121] In some embodiments, before the handover begins, the gNB-CU 120 may send handover preparation information to all candidate target gNB-DUs controlled by the gNB-CU 120.

[0122] Figure 6 A signaling diagram illustrating a process 600 for inter-DU mobility with querying using a target DU according to some other example embodiments of the present disclosure is illustrated. For discussion purposes, reference will be made to Figure 1 Process 600 is described. Process 600 may involve Figure 1 UE 110, gNB-CU 120, first gNB-DU 130 and second gNB-DU 140 in. Process 600 can be regarded as an example implementation of process 500 or 200.

[0123] Generally speaking, in process 600, before receiving a request for inter-DU mobility from a first gNB-DU 130 (i.e., before handover starts), the gNB-CU 120 sends handover preparation information to the second gNB-DU 140. In addition, upon receiving the request for inter-DU mobility, the gNB-CU 120 sends a query for loading conditions to the second gNB-DU 140 to determine whether the request for inter-DU mobility is accepted. If the request for inter-DU mobility is accepted, the gNB-CU 120 triggers 540 inter-DU mobility.

[0124] The second gNB-DU 140 performs 550 a random access (RACH) procedure with the UE 110 based on the handover preparation information.

[0125] The actions at 210, 230, 316, 317, and 318 in process 600 are the same as the actions in process 300. The action at 411 in process 600 is the same as the action in process 400. Therefore, the details of the actions are omitted for brevity.

[0126] Process 600 differs from process 300 and process 400 in that, before receiving a request for inter-DU mobility from the first gNB-DU 130 (i.e., before the handover starts), the gNB-CU 120 sends 600 handover preparation information to the second gNB-DU 140. For example, the gNB-CU 120 may send a UE CONTEXT SETUP REQUEST message to the second gNB-DU 140. The UE CONTEXT SETUP REQUEST message includes the handover preparation information. The second gNB-DU 140 may send 611 a UE CONTEXT SETUP RESPONSE message to the gNB-CU 120 to acknowledge receipt of the handover preparation information.

[0127] The first gNB-DU 130 sends a request for inter-DU mobility by sending 612 a UE CONTEXT MODIFICATION REQUIRED message or a dedicated message. The UE CONTEXT MODIFICATION REQUIRED message or the dedicated message may include a measurement result of the UE 110. Alternatively or additionally, the UE CONTEXT MODIFICATION REQUIRED message or the dedicated message may include an index of at least one event triggered by the measurement result.

[0128] Upon receiving the request for inter-DU mobility, the gNB-CU 120 sends 613 a query for loading conditions to the second gNB-DU 140 to determine whether the request for inter-DU mobility is accepted. For example, the gNB-CU 120 may send a UE CONTEXT SETUP REQUEST message or a first dedicated message including the query to the second gNB-DU 140.

[0129] The gNB-CU 120 receives 614 a response to the query from the second gNB-DU 140. The response includes an indication of the loading condition. For example, the gNB-CU 120 may receive a UE CONTEXT SETUP RESPONSE message or a second dedicated message including a response to the query from the second gNB-DU 140.

[0130] The gNB-CU 120 may determine whether the loading condition is below a threshold. If the loading condition is below the threshold, the gNB-CU 120 may determine that the request for inter-DU mobility is accepted.

[0131] If the request for inter-DU mobility is accepted, the gNB-CU 120 sends 615 a UECONTEXT MODIFICATION REQUEST message or a dedicated message to the first gNB-DU 130 to trigger inter-DU mobility. The UECONTEXTMODIFICATION REQUEST message or the dedicated message may include a MAC CE including an index of the configuration of the target cell.

[0132] Figure 7 A signaling diagram illustrating a process 700 for inter-DU mobility without querying with a target DU according to some other example embodiments of the present disclosure is illustrated. For discussion purposes, reference will be made to Figure 1 Process 700 is described. Process 700 may involve Figure 1 UE 110, gNB-CU 120, first gNB-DU 130 and second gNB-DU 140 in. Process 700 can be regarded as an example implementation of process 500 or 200.

[0133] Process 700 is similar to process 600. Process 700 differs from process 600 in that actions at 613 and 614 are omitted. For example, in the case of a small cell, actions at 613 and 614 may be omitted. In other words, in process 700, the gNB-CU 120 may determine 530 to accept or reject the request for inter-DU mobility without sending a query for the loading condition to the second gNB-DU 140 or receiving a response to the query from the second gNB-DU 140.

[0134] In the following, reference will be made to FIG. 8A to FIG. 8F Some embodiments of configuration of candidate cells are described. The configuration of candidate cells may include at least one of configuration for a first set of candidate cells for intra-DU mobility or configuration for a second set of candidate cells for inter-DU mobility.

[0135] In some embodiments, gNB-CU 120 may send an RRC message to UE 110. The RRC message includes at least one of a configuration for a first set of candidate cells for intra-DU mobility or a configuration for a second set of candidate cells for inter-DU mobility. Thus, the configuration may be provided in a secure manner.

[0136] The configuration of the candidate cells may be provided before the handover, and it is not assumed that the configuration is changed during the handover. The configuration of the candidate cells may be changed when there is no handover.

[0137] Fig. 8AAn exemplary IE 810 for configuration of candidate cells for L2 mobility according to some example embodiments of the present disclosure is illustrated. Fig. 8A In the example of , separate configurations of candidate cells for L2 mobility are used, which can be included as part of the conditional configuration. The configuration of candidate cells for L2 mobility includes a list of candidate L2 cells, as shown in 811.

[0138] Figure 8B An exemplary IE 820 is illustrated for configuration of candidate cells for L2 mobility, which are included as part of the conditional configuration according to some example embodiments of the present disclosure. Figure 8B In the example of , the configuration of candidate cells for L2 mobility is included as part of the conditional configuration, where L2 mobility is conditional. This helps the UE initiate.

[0139] exist Fig. 8A and Figure 8B In the example of , the configuration of candidate cells can be constrained to only include serving cell configurations. DC configuration is allowed.

[0140] Figure 8C An exemplary IE 830 illustrating configuration of candidate cells for L2 mobility according to some example embodiments of the present disclosure is illustrated. Figure 8C The configuration of candidate cells for L2 mobility in Fig. 8A and Figure 8B The examples are common.

[0141] Fig.8D An exemplary IE 840 for configuration of candidate cells for L1 mobility and L2 mobility according to some example embodiments of the present disclosure is illustrated. Fig.8D In the example of , the configuration of candidate cells for L1 mobility and L2 mobility may be included as part of the conditional configuration. The configuration of candidate cells for L2 mobility includes a list of candidate L2 cells, as shown in 841. The configuration of candidate cells for L1 mobility includes a list of candidate L1 cells, as shown in 842.

[0142] Fig. 8E An exemplary IE 850 is illustrated for configuration of candidate cells for L1 mobility, which are included as part of the conditional configuration according to some example embodiments of the present disclosure. Fig. 8E In the example of , the configuration of candidate cells for L1 mobility is included as part of the conditional configuration, where L1 mobility is conditional. This helps the UE to initiate.

[0143] exist Fig.8D and Fig. 8EIn the example of , the configuration of candidate cells can be constrained to only include serving cell configurations. DC configuration is allowed.

[0144] Figure 8F An exemplary IE 860 illustrating configuration of candidate cells for L2 mobility and L1 mobility according to some example embodiments of the present disclosure is illustrated. Figure 8F The configuration of candidate cells for L2 mobility in Fig.8D and Fig. 8E The examples are common.

[0145] In some embodiments, UE 110 may receive a third configuration for handling packet data convergence protocol (PDCP) and radio link control (RLC) from gNB-CU 120 or first gNB-DU 130.

[0146] In such embodiments, the third configuration for handling PDCP and RLC may be used for a first candidate cell in the second set of candidate cells for inter-DU mobility. In other words, the third configuration for handling PDCP and RLC may be used for each target cell. Alternatively, the third configuration for handling PDCP and RLC may be used for a data radio bearer (DRB) or a signaling radio bearer (SRB) in the first candidate cell in the second set.

[0147] In such an embodiment, UE 110 may receive a third configuration for handling PDCP and RLC and a configuration for a second set of candidate cells for inter-DU mobility. In such an embodiment, the third configuration for handling PDCP and RLC may change after handover. Traditional incremental handling applies. Therefore, the field needs to exist as a separate field.

[0148] Fig. 9A An exemplary IE 910 for configurations for handling PDCP and RLC according to some example embodiments of the present disclosure is illustrated. The exemplary IE 910 includes a third configuration for handling PDCP and RLC and a configuration for a second set of candidate cells for inter-DU mobility.

[0149] In some embodiments, the handover command (in L2 or L1) may include a third configuration for handling PDCP and RLC. In such embodiments, UE 110 may only follow the handover command. This is simpler or very safe. For a handover command in L2, the MAC CE may include a third configuration for handling PDCP and RLC. For a handover command in L1, the DCI may include a third configuration for handling PDCP and RLC.

[0150] Fig. 9BAn exemplary IE 920 for handling configuration of PDCP and RLC according to some other example embodiments of the present disclosure is illustrated. The exemplary IE 910 may be included in the handover command from the first gNB-DU 130.

[0151] In some embodiments, the third configuration for handling PDCP and RLC may be used for a set of candidate cells in the first set of candidate cells for intra-DU mobility. In such embodiments, the third configuration for handling PDCP and RLC may be included as a set of PCIs as part of intra-DU mobility.

[0152] In such implementations, the grouping of candidate cells may be accompanied by a bitmap or an explicit group set.Such implementations help the UE save configuration so that subsequent L2 mobility (without network information) does not require reconfiguration.

[0153] Fig. 9C An exemplary IE 930 for configurations for handling PDCP and RLC according to yet other exemplary embodiments of the present disclosure is illustrated. In the exemplary IE 930, a third configuration for handling PDCP and RLC is used for a set of candidate cells in a first set of candidate cells for intra-DU mobility.

[0154] Fig.10 A flowchart illustrating an example method 1000 for mobility according to some example embodiments of the present disclosure is illustrated. For the purpose of discussion, reference will be made to Figure 1 The method 1000 is described from the perspective of the CU 120 .

[0155] At block 1010 , CU 120 sends handover preparation information of the UE for inter-DU mobility to a second DU of a base station.

[0156] At block 1020 , after sending the handover preparation information, the CU 120 receives a request for inter-DU mobility from a first DU of a base station serving the UE.

[0157] At block 1030 , in response to determining that the request for inter-DU mobility is accepted, CU 120 triggers inter-DU mobility.

[0158] In some embodiments, the handover preparation information includes information about at least one of: a context of the UE, or a data bearer to be established between the UE and the second DU.

[0159] In some embodiments, method 1000 further includes: determining whether the request for inter-DU mobility is accepted. Determining whether the request for inter-DU mobility is accepted includes: sending a query for a loading condition to a second DU; receiving a response to the query from the second DU, the response including an indication of the loading condition; and determining that the request for inter-DU mobility is accepted based on determining that the loading condition is below a threshold.

[0160] In some embodiments, sending a query for the loading condition to the second DU includes sending a first dedicated message including a UECONTEXT SETUP REQUEST message or including the query to the second DU.

[0161] In some embodiments, receiving a response to the query from the second DU includes receiving a UE CONTEXT SETUP RESPONSE message or a second dedicated message including a response to the query from the second DU.

[0162] In some embodiments, method 1000 further includes sending to the UE at least one of a configuration for a first set of candidate cells for intra-DU mobility or a configuration for a second set of candidate cells for inter-DU mobility.

[0163] In some embodiments, triggering inter-DU mobility includes: selecting a target cell from the first group or the second group for handover; and sending a configured index of the target cell to the first DU.

[0164] In some embodiments, sending an index of the configuration of the target cell to the first DU includes: sending a first message to the first DU, the first message including one of the following: a first medium access control control element (MAC CE), the first medium access control control element (MAC CE) including an index of the configuration of the target cell; or an index of the configuration of the target cell.

[0165] In some embodiments, the request for inter-DU mobility includes one of: a second MAC CE including a measurement result for at least one candidate cell in the second group; or the measurement result.

[0166] In some embodiments, the method 1000 further includes: receiving, from the first DU, an index of at least one event in a third set of events, the at least one event being triggered by a measurement result, the third set of events being used for layer 2 mobility.

[0167] In some embodiments, the index of at least one event is associated with a physical cell identifier (PCI) of the target cell.

[0168] In some embodiments, the method 1000 further includes sending at least one first configuration of the first configurations for a third set of events for layer 2 mobility to the first DU.

[0169] In some embodiments, the request for inter-DU mobility includes an index to at least one event.

[0170] In some embodiments, sending the index of the configuration of the target cell to the first DU includes: sending a response to the request for inter-DU mobility to the first DU, the response including the index of the configuration of the target cell.

[0171] In some embodiments, the method 1000 further includes sending a third configuration for handling Packet Data Convergence Protocol (PDCP) and Radio Link Control (RLC) to the UE.

[0172] In some embodiments, the third configuration for handling PDCP and RLC is used for at least one of: a first candidate cell in the second group, a data radio bearer or a signaling radio bearer in the first candidate cell in the second group, or a group of candidate cells in the first group.

[0173] Fig.11 A flowchart illustrating an example method 1100 for mobility according to some embodiments of the present disclosure is illustrated. For the purpose of discussion, reference will be made to Figure 1 The method 1100 is described from the perspective of the DU 140 .

[0174] At block 1110 , the DU 140 receives handover preparation information of the UE for inter-DU mobility from the CU of the base station before the handover starts.

[0175] At block 1120, the DU 140 performs a random access procedure with the UE based on the handover preparation information.

[0176] In some embodiments, the handover preparation information includes information about at least one of: a context of the UE, or a data bearer to be established between the UE and the DU.

[0177] In some embodiments, method 1100 also includes: receiving a query for a loading condition from the CU; and sending a response to the query to the CU, the response including an indication of the loading condition.

[0178] In some embodiments, receiving a query for the loading condition from the CU includes: receiving a UE CONTEXTSETUP REQUEST message or a first dedicated message including the query from the CU.

[0179] In some embodiments, sending a response to the query to the CU includes sending a UE CONTEXT SETUPRESPONSE message to the CU or a second dedicated message including the response to the query.

[0180] Fig.12 1 is a simplified block diagram of a device 1200 suitable for implementing embodiments of the present disclosure. For example, the UE 110, the gNB-CU 120, the first gNB-DU 130, or the second gNB-DU 140 may be implemented by the device 1200. As shown, the device 1200 includes a processor 1210, a memory 1220 coupled to the processor 1210, and a transceiver 1240 coupled to the processor 1210.

[0181] The transceiver 1240 is used for bidirectional communication. The transceiver 1240 is coupled to at least one antenna to facilitate communication. The transceiver 1240 may include a transmitter circuit (e.g., associated with one or more transmit chains) and / or a receiver circuit (e.g., associated with one or more receive chains). The transmitter circuit and the receiver circuit may employ common circuit elements, different circuit elements, or a combination thereof.

[0182] Processor 1210 may be of any type suitable for use in a local technology network, and may include one or more of the following as non-limiting examples: a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 1200 may have multiple processors, such as application specific integrated circuit chips, which are time-constrained by a clock that synchronizes a main processor.

[0183] The memory 1220 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 1224, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic storage devices and / or optical storage devices. Examples of volatile memories include, but are not limited to, random access memory (RAM) 1222 and other volatile memories that do not persist during power-off time.

[0184] Computer program 1230 includes computer executable instructions executed by associated processor 1210. Program 1230 may be stored in ROM 1224. Processor 1210 may perform any suitable actions and processes by loading program 1230 into RAM 1222.

[0185] The embodiments of the present disclosure can be implemented with the aid of program 1230, so that the device 1200 can execute the following steps: Figure 10 to Figure 11Any method of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0186] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions (such as those included in a program module) that are executed in a device on a target real or virtual processor to perform the above-referenced Fig.10 The method 1000 and / or as described above with reference to Fig.11 The method 1100 is described.

[0187] Further, although the operations are depicted in a specific order, this should not be understood as requiring such operations to be performed in a sequential order or in the specific order shown, or requiring the execution of all the operations shown to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Although the above discussion contains several specific implementation details, these details should not be understood as limitations on the scope of the present disclosure, but should be regarded as descriptions of features that may be peculiar to a particular embodiment. Certain features described in the context of different embodiments may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in the form of any suitable sub-combination.

[0188] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A central unit (CU) of a base station, the central unit (CU) comprising: a transceiver configured to communicate with a user equipment (UE); and a processor communicatively coupled to the transceiver and configured to perform operations including: sending handover preparation information of the UE for inter-DU mobility to a second distributed unit (DU) of the base station; After sending the handover preparation information, receiving a request for the inter-DU mobility from a first DU of the base station serving the UE; as well as The inter-DU mobility is triggered based on determining that the request for the inter-DU mobility is accepted.

2. The CU according to claim 1, wherein the switching preparation information includes information about at least one of the following: the context of the UE, or A data bearer is to be established between the UE and the second DU.

3. The CU according to claim 1, wherein the operation further comprises: Determining whether the request for the inter-DU mobility is accepted includes: sending a query about the loading condition to the second DU; receiving a response to the query from the second DU, the response comprising an indication of the loading condition; and Based on determining that the loading condition is below a threshold, determining that the request for the inter-DU mobility is accepted.

4. The CU of claim 3, wherein sending the query for loading conditions to the second DU comprises: A first dedicated message or a UECONTEXT SETUP REQUEST message including the query is sent to the second DU.

5. The CU of claim 3, wherein receiving the response to the query from the second DU comprises: A second dedicated message or a UE CONTEXT SETUP RESPONSE message including the response to the query is received from the second DU.

6. The CU according to claim 1, wherein the operation further comprises: At least one of a configuration for a first set of candidate cells for intra-DU mobility or a configuration for a second set of candidate cells for inter-DU mobility is sent to the UE.

7. The CU of claim 6, wherein triggering the inter-DU mobility comprises: selecting a target cell from the first group or the second group for handover; as well as Sending an index of the configuration of the target cell to the first DU.

8. The CU of claim 7, wherein sending the index of the configuration of the target cell to the first DU comprises: Sending a first message to the first DU, where the first message includes one of the following: a first medium access control element (MAC CE) comprising said index of said configuration of said target cell, or The index of the configuration of the target cell.

9. The CU of claim 1 , wherein the request for the inter-DU mobility comprises one of: a second MAC CE, wherein the second MAC CE includes a measurement result for at least one candidate cell in the second group, or The measurement results.

10. The CU according to claim 9, wherein the operation further comprises: An index of at least one event in a third set of events is received from the first DU, the at least one event being triggered by the measurement result, the third set of events being used for layer 2 mobility.

11. The CU of claim 10, wherein the index of at least one event is associated with a physical cell identifier (PCI) of the target cell.

12. The CU according to claim 9, wherein the operations further comprise: At least one first configuration of the first configurations for a third set of events for layer 2 mobility is sent to the first DU. 13 . The CU of claim 10 , wherein the request for the inter-DU mobility includes the index of the at least one event.

14. The CU of claim 13, wherein sending the configured index of the target cell to the first DU comprises: A response to the request for the inter-DU mobility is sent to the first DU, the response including the index of the configuration of the target cell.

15. The CU of claim 1, wherein the operations further comprise: A third configuration for handling Packet Data Convergence Protocol (PDCP) and Radio Link Control (RLC) is sent to the UE.

16. The CU of claim 15, wherein the third configuration for handling the PDCP and the RLC is used for at least one of: a first candidate cell in the second group, a data radio bearer or a signalling radio bearer in the first candidate cell in the second group, or A set of candidate cells in the first group.

17. A distributed unit (DU) of a base station, the distributed unit (DU) comprising: a transceiver configured to communicate with a user equipment (UE); and a processor communicatively coupled to the transceiver and configured to perform operations including: receiving handover preparation information for inter-DU mobility of the UE from a central unit (CU) of the base station; and A random access procedure is performed with the UE based on the handover preparation information.

18. The DU according to claim 17, wherein the handover preparation information includes information on at least one of the following: the context of the UE, or A data bearer to be established between the UE and the DU.

19. The DU of claim 17, wherein the operations further comprise: receiving a query for a loading condition from the CU; as well as A response to the query is sent to the CU, the response including an indication of the loading condition.

20. The DU of claim 19, wherein receiving the query for a loading condition from the CU comprises: A first dedicated message or a UECONTEXT SETUP REQUEST message including the query is received from the CU.

21. The DU of claim 19, wherein sending the response to the query to the CU comprises: A second dedicated message or a UE CONTEXT SETUP RESPONSE message including the response to the query is sent to the CU.

22. A baseband processor of a base station, the baseband processor being configured to perform operations including: sending handover preparation information of a user equipment (UE) for inter-DU mobility to a second distributed unit (DU) of the base station; After sending the handover preparation information, receiving a request for the inter-DU mobility from a first DU of the base station serving the UE; and The inter-DU mobility is triggered based on determining that the request for the inter-DU mobility is accepted.

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