Conditional handover

Abstract

In some examples, a method for preparing a handover of a user equipment (UE) in dual connectivity (DC), performed in a target master node (MN) of a wireless network, where the handover is between primary cells (PCells) of a source MN and a target MN and between primary secondary cells (PSCells) between a source secondary node (SN) and a target SN, includes: transmitting to the source MN a secondary cell group (SCG) delta configuration config1 of a CHO and a target SN having a DC configuration including a unique identifier of the UE defined between the source master node and the target secondary node; receiving from the source MN an indication representing a CPC procedure configured after transmitting the CHO having the DC configuration, the unique identifier of the UE, and an identifier of the target SN; and transmitting to the target SN a request to prepare a second delta SCG configuration config2 to be used by the UE when a source MN-initiated CPC procedure is performed.

Description

Technical Field

[0001] The present invention generally relates to a fifth generation (5G) New Radio (NR) system. Aspects relate to conditional handover in a 5G NR system.

Background Art

[0002] The fifth generation (5G) New Radio (NR) system is designed to provide flexibility and configurability to optimize network services and types for various use cases. With the new handover procedure provided as part of the 5G NR system, a User Equipment (UE) can decide to perform a handover when certain conditions are met. This NR handover procedure is called conditional handover (CHO) and is executed in contrast to conventional handover procedures, where the network was tasked with determining whether to perform a handover. Therefore, handover was a reactive process and handover failures were likely to occur.

[0003] On the other hand, CHO is a handover executed by the UE when one or more handover execution conditions are met. Specifically, the UE can start evaluating the execution conditions when receiving the CHO configuration and can end the evaluation of the execution conditions when the handover is executed.

Summary of the Invention

[0004] The objective of the present disclosure is to enable the effectiveness of the CHO-DC configuration and the avoidance of double resource reservation for the target delta SCG configuration in the situation of CHO-CPC coexistence.

[0005] The above objective and other objectives are achieved by the features of the independent claims.

[0006] Further embodiments are apparent from the dependent claims, the specification, and the drawings.

[0007] A first aspect of this disclosure provides a method for preparing a handover of user equipment (UE) in dual connectivity (DC) performed at a target master node (MN) of a wireless network, the handover being between primary cells (PCells) of the source MN and the target MN, and between primary secondary cells (PSCells) of a source secondary node (SN) and the target SN, and comprising: transmitting to the source MN a secondary cell group (SCG) delta configuration config1 of the CHO and target SN having a DC configuration including a unique identifier of the UE defined between the source master node and the target secondary node; receiving from the source MN an indication representing a CPC procedure configured after the transmission of the CHO, the unique identifier of the UE, and the identifier of the target SN having a DC configuration; and transmitting to the target SN a request to prepare a second delta SCG configuration, config2, to be used by the UE once the source MN-initiated CPC procedure has been performed.

[0008] In an embodiment of the first aspect, the method may further include receiving config2 from a target SN, and the second delta SCG configuration is effective when the UE applies the SCG configuration after the CPC procedure has been performed. The method may further include generating a second CHO having a DC configuration using the second delta SCG configuration. The method may further include sending a handover request update message to the source MN to update an existing CHO having a DC configuration. The second CHO having a DC configuration can be maintained and used by the UE when the CPC procedure is performed. The method may further include providing the second CHO having a DC configuration to the UE and instructing the UE to maintain the second CHO having a DC configuration after the CPC procedure has been performed.

[0009] A second aspect of the present disclosure provides a source master node in a wireless network, the source master node comprising a processor and a memory coupled to the processor, configured to store program code executable by the processor, the program code comprising one or more instructions, thereby causing the source master node to receive from a target MN a secondary cell group (SCG) delta configuration config1 of the target SN and a CHO having a DC configuration including a unique identifier of the UE defined between the source master node and the target SN; to send to the target MN an indication comprising a CPC procedure configured after the transmission of the CHO having a DC configuration, a unique identifier of the UE, and an identifier of the target SN; and to receive from the target MN a handover request update message including a second CHO having a DC configuration.

[0010] In a second embodiment, the program code may include one or more further instructions that cause the source master node to update an existing CHO having a DC configuration with a second CHO having a DC configuration. The program code may include one or more further instructions that cause the source master node to send the second CHO having a DC configuration to the UE and instruct the UE to maintain the second CHO having a DC configuration after the CPC procedure has been executed. The program code may include one or more further instructions that cause the source master node to send the CHO condition ID associated with the second CHO having a DC configuration to the UE.

[0011] A third aspect of the present disclosure provides a user device UE comprising a processor and a memory coupled to the processor, configured to store program code executable by the processor, wherein the program code comprises one or more instructions, thereby causing the UE to receive a second CHO having a DC configuration from a source MN and to maintain the second CHO having a DC configuration after a CPC procedure has been performed.

[0012] In an embodiment of the third aspect, the program code may comprise one or more further instructions that cause the UE to receive a CHO condition ID from the source MN relating to a second CHO having a DC configuration.

[0013] A fourth aspect of the present disclosure provides a machine-readable storage medium encoding instructions for preparing a handover of user equipment (UE) in dual connectivity (DC), wherein the handover is between the primary cell (PCell) of a source MN and the primary cell (PCell) of a target MN, and between the primary secondary cell (PSCell) of a source secondary node (SN) and the target SN, wherein the instructions are executable by the processor of the target master node, thereby causing the target master node to send to the source MN a secondary cell group (SCG) delta configuration config1 of the CHO and target SN having a DC configuration including a unique identifier of the UE defined between the source master node and the target secondary node, to receive from the source MN an indication representing a CPC procedure configured after the transmission of the CHO, the unique identifier of the UE, and the identifier of the target SN having a DC configuration, and to send to the target SN a request to prepare a second delta SCG configuration, config2, to be used by the UE when the source MN-initiated CPC procedure is executed.

[0014] In the fourth embodiment, the machine-readable storage medium can further encode instructions that can be executed by the processor of the target master node, thereby causing the target master node to receive config2 from the target SN, where the second delta SCG configuration is effective when the UE applies the SCG configuration after the CPC procedure has been performed. The machine-readable storage medium can further encode instructions that can be executed by the processor of the target master node, thereby causing the target master node to generate a second CHO having a DC configuration using the second delta SCG configuration.

[0015] Here, the embodiments will be described with reference to the drawings as illustrative examples. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram of the message flow according to one embodiment. [Figure 2] This is a schematic diagram of the message flow according to one embodiment. [Figure 3] This is a schematic diagram of a machine according to one embodiment. [Figure 4] This is a flowchart of the method according to one embodiment. [Modes for carrying out the invention]

[0017] Exemplary embodiments are described below in sufficient detail to enable those skilled in the art to embody and implement the systems and methods described herein. It is important to understand that embodiments can be provided in many alternative forms and should not be construed as being limited to the embodiments described herein.

[0018] Accordingly, the embodiments can be modified in various ways and take on various alternative forms, but the particular embodiments are shown in the drawings as examples and are described in detail below. There is no intention to limit ourselves to the specific forms disclosed. Rather, all modifications, equivalents, and alternative forms included in the appended claims should be included. Elements of the exemplary embodiments are consistently shown by the same reference figures throughout the drawings and detailed description, where appropriate.

[0019] The terms used herein to describe embodiments are not intended to limit the scope of the invention. The articles “a,” “an,” and “the” are singular in that they refer to a single object, but the use of singularity herein should not exclude the existence of two or more objects. In other words, an element referred to in the singular can refer to one or more objects unless the context clearly indicates otherwise. Furthermore, it will be understood that, when used herein, the terms “equipped,” “equipped,” “contains,” and / or “contains” indicate the presence of a described feature, item, step, action, element, and / or component, but do not exclude the presence or addition of one or more other feature parts, items, steps, actions, elements, components, and / or groups thereof. The terms “and / or” are merely correlations to describe the objects in question, indicating that there may be three possible relationships such that A and / or B can indicate that A exists alone, A and B exist together, or B exists alone. The letter “ / ” generally indicates that the objects in question are in an “or” relationship.

[0020] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall be interpreted as convention in the relevant art. Furthermore, it will be understood that commonly used terms, unless expressly defined herein, should also be interpreted as convention in the relevant art and not as idealized or overly formal.

[0021] The following includes specific information related to embodiments of the present disclosure. The drawings and the detailed disclosure accompanying them are merely directed to the embodiments. However, the present disclosure is not limited to these embodiments. Other variations and embodiments of the present disclosure will be apparent to those skilled in the art.

[0022] The phrases "in one embodiment" or "in some embodiments" can each refer to one or more of the same or different embodiments. The term "coupled" is defined as being directly or indirectly connected through intervening components and is not necessarily limited to physical connections. The expression "at least one of A, B, and C" or "the following: at least one of A, B, and C" means "only A, or only B, or only C, or any combination of A, B, and C".

[0023] The terms "system" and "network" can be used synonymously.

[0024] For purposes of explanation and not limitation, specific details of functional entities, technologies, protocols, and specifications, etc. are described to provide an understanding of the present disclosure. In other examples, detailed disclosure of well-known methods, technologies, systems, and architectures is omitted so as not to obscure the present disclosure with unnecessary details.

[0025] Those skilled in the art will immediately recognize that any network function or algorithm disclosed can be implemented by hardware, software, or a combination of software and hardware. The disclosed functions can correspond to modules that can be software, hardware, firmware, or a combination thereof.

[0026] The software implementation can include machine-readable and / or computer-readable and / or executable instructions stored on a machine-readable and / or computer-readable medium such as a memory or other type of storage device. One or more microprocessors or general-purpose computers having communication processing capabilities can be programmed with the corresponding executable instructions to implement the disclosed network functions or algorithms.

[0027] The microprocessor or general-purpose computer can include a dedicated integrated circuit (ASIC), a programmable logic array, and / or one or more digital signal processors (DSPs). Some of the disclosed embodiments are directed to software installed and executed on computer hardware, but alternative embodiments implemented as firmware or as hardware or as a combination of hardware and software are well within the scope of the present disclosure. The computer-readable medium includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, compact disc read-only memory (CD-ROM), magnetic cassettes, magnetic tapes, magnetic disk storage devices, or any other equivalent medium capable of storing computer-readable instructions.

[0028] A wireless communication network architecture such as a Long Term Evolution (LTE) system, LTE-Advanced (LTE-A) system, LTE-Advanced Pro system, or 5G NR radio access network (RAN) typically includes at least one base station (BS), at least one user equipment (UE), and one or more optional network elements that provide connectivity within the network. The UE communicates with networks such as a core network (CN), an evolved packet core (EPC) network, an evolved universal terrestrial RAN (E-UTRAN), a 5G core (5GC), or the Internet via the RAN established by one or more BSs.

[0029] The UE may include, but is not limited to, a mobile station, mobile terminal or device, or user communication radio terminal. The UE may also include, but is not limited to, a mobile radio device having radio communication capabilities, such as a mobile phone, tablet, wearable device, sensor, vehicle, or PDA (Personal Digital Assistant). The UE is configured to receive and transmit signals via an air interface to one or more cells in the RAN.

[0030] BS can provide communication services in accordance with at least radio access technologies (RATs), including Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM), often called 2G, GSM Enhanced Data rates for GSM Evolution (EDGE)RAN (GERAN), General Packet Radio Service (GPRS), Universal Mobile Telecommunication System (UMTS), often called 3G based on basic broadband code division multiple access (W-CDMA), High Speed ​​Packet Access (HSPA), LTE, LTE-A, Evolved LTE (eLTE), which is LTE connected to 5GC, NR (often called 5G), and / or LTE-A Pro. However, the scope of this disclosure is not limited to these protocols.

[0031] A BS may include, but is not limited to, a Node B (NB) in UMTS, an evolved Node B (eNB) in LTE or LTE-A, a Radio Network Controller (RNC) in UMTS, a BS Controller (BSC) in GSM / GERAN, a next-generation (ng)-eNB in ​​E-UTRA (Evolved Universal Terrestrial Radio Access) BS connected to 5GC, a next-generation Node B (gNB) in 5G-RAN, or any other device capable of controlling radio communications within a cell and managing radio resources. A BS can provide services to one or more UEs via a radio interface.

[0032] A BS (Band Station) can provide wireless coverage to a specific geographic area using multiple cells that form a RAN (Range Range). The BS supports the operation of these cells. Each cell operates to serve at least one UE (User Environment) within its wireless coverage.

[0033] Each cell (often called a serving cell) can serve one or more UEs in its radio coverage, such that each cell schedules downlink (DL) and optionally uplink (UL) resources to at least one UE in its radio coverage for DL ​​and optionally uplink (UL) packet transmission. A BS can communicate with one or more UEs in a radio communication system via multiple cells.

[0034] Cells can allocate sidelink (SL) resources to support proximity services (ProSe) or Vehicle to Everything (V2X) services. Each cell may have overlapping coverage areas with other cells.

[0035] The NR frame structure supports flexible configurations to meet various next-generation (e.g., 5G) communication requirements, such as Extended Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC), and Ultra-High Reliability Low Latency Communications (URLLC), meeting high reliability, high data rate, and low latency requirements. The Orthogonal Frequency Division Multiplexing (OFDM) technology of the Third Generation Partnership Project (3GPP) can serve as the baseline for NR waveforms. Scalable OFDM numerical processing such as adaptive subcarrier spacing, channel bandwidth, and cyclic prefixes (CPs) can also be used.

[0036] Examples of some of the terms used in this disclosure are as follows:

[0037] Primary Cell (PCell): A PCell is a Master Cell Group (MCG) cell that operates at the primary frequency, and the UE performs the initial connection establishment procedure or initiates the connection re-establishment procedure. A PCell is a Special Cell (SpCell) of an MCG.

[0038] Primary SCG Cell (PSCell): In dual connectivity (DC) operation, the PSCell is a secondary cell group (SCG) cell that the UE accesses randomly when performing the Reconfiguration with Sync procedure. The PSCell is a SpCell of the SCG. In some embodiments, the term PSCell may refer to a primary secondary cell. The terms “primary SCG cell” and “primary secondary cell” may be used synonymously in this disclosure.

[0039] Special Cell (SpCell): In DC operation, the term Special Cell (SpCell) refers to the PCell of the MCG or the PSCell of the SCG, or the term Special Cell refers to the PCell.

[0040] Secondary cell (SCell): In a UE configured with carrier aggregation (CA), an SCell is a cell that provides additional radio resources on top of a special cell.

[0041] Serving Cell: In an UE in RRC_CONNECTED where CA / DC is not configured, there is only one serving cell containing a primary cell. In an UE in RRC_CONNECTED where CA / DC is configured, the term "serving cell" is used to refer to the set of cells containing special cells and all secondary cells.

[0042] Master Cell Group (MCG): In MR-DC, an MCG is a group of serving cells associated with a master node, comprising SpCell (PCell) and optionally one or more SCells.

[0043] Master Node (MN): In MR-DC, the MN, or primary node, is a radio access node that provides control plane connectivity to the core network. The MN is a master eNB (EN-DC), master ng-eNB (NGEN-DC), or master gNB (NR-DC and NE-DC). In some embodiments, the MN, or primary node, may comprise a source node or target node of the UE.

[0044] Secondary Cell Group (SCG): In MR-DC, an SCG is a group of serving cells associated with a secondary node, comprising a SpCell (PSCell) and optionally one or more SCells.

[0045] Secondary Node (SN): In MR-DC, the SN is a radio access node that does not have control plane connectivity to the core network and provides additional resources to the UE. This is an en-gNB (in EN-DC), a secondary ng-eNB (in NE-DC), or a secondary gNB (in NR-DC and NGEN-DC). In some embodiments, the SN or secondary node may comprise a source node or a target node of the UE.

[0046] In wireless communication networks such as E-UTRAN, one of the main causes of handover (HO) failures is that the UE does not receive a handover command message from the source base station (e.g., source eNB or source gNB) or the serving base station (e.g., serving eNB or serving gNB). Conventional handover procedures are typically triggered by a measurement report from the UE. For example, if the quality of a serving cell (e.g., signal strength and / or quality of service) is below a preset threshold and the quality of an adjacent cell (e.g., signal strength and / or quality of service) is above a preset threshold, the UE can send a measurement report to the source base station below the serving cell based on the received measurement configuration. Upon receiving the measurement report, the source base station can send a handover request message to several target base stations (e.g., eNB or gNB) for admission control and receive a handover acknowledgment message from the target base stations. The source base station can then select and send a handover command message (which may be included in the handover acknowledgment message from one of the target base stations) to the UE so that the UE can connect to the target cell.

[0047] The success of the entire handover procedure depends on several factors. One of these factors is that the serving cell quality does not deteriorate rapidly in a short period of time, which can be determined by backhaul latency (e.g., X2 / Xn / Xx interfaces), target base station processing time, and signaling transmission time. However, in real-world situations, the serving cell quality can deteriorate rapidly in a short period of time, and the UE may not be able to successfully receive the handover command message before the serving cell quality deteriorates significantly. As a result, the UE may detect a radio link failure. Consequently, in response to the detected radio link failure, the UE may initiate a Radio Resource Control (RRC) connection re-establishment procedure, resulting in a considerable service interruption.

[0048] In next-generation wireless networks (e.g., 5G NR networks), large-scale antenna beamforming is used in higher frequency bands, and the quality of serving cells may degrade even faster, especially when narrow beams are used to serve UEs. Shielding is another problem in NR deployment.

[0049] 3GPP introduced the concept of Conditional Handover (CHO) to improve the overall reliability of handover procedures. CHO procedures can be considered complementary to conventional handover procedures in order to reduce the handover failure rate.

[0050] To execute a conditional reset command, the UE can evaluate the trigger conditions associated with the conditional reset command to determine whether one or more trigger conditions (or execution conditions) of the conditional reset command are met. If the UE determines that the trigger conditions are met, it can apply the corresponding conditional reconfiguration command and connect to the target cell. Existing measurement events (e.g., A3 and A5) can be used to determine whether the trigger conditions for a conditional reconfiguration command are met.

[0051] CHO can help improve the reliability of the entire handover procedure. Applying a similar concept to CHO can also be beneficial to PSCell addition procedures, PSCell modification procedures, SN addition procedures, or SN modification procedures in MR-DC mode, as preparation between MN and SN and RRC signaling for adding the SN may be completed beforehand.

[0052] When the concept of CHO (or conditional configuration) is applied to a normal HO (e.g., PCell modification) procedure or a PSCell addition / modification (or SN addition / modification) procedure, the UE may behave differently. For example, if the executed conditional reconfiguration command is for a PSCell addition / modification, the UE may not need to release the link to the current PCell (or MN). Some information or guidelines (e.g., implicitly) may be needed to determine what the UE should do when a conditional reconfiguration command is executed. Also, the principles for applying CHO (or conditional configuration) to PCell modifications and the principles for applying CHO (or conditional configuration) to PSCell addition / modification may differ because they serve different purposes.

[0053] A conditional reconfiguration procedure can be a reconfiguration procedure that is executed by the UE when one or more execution conditions (also called trigger conditions) are met. There are three types of conditional reconfigurations. The first type is a conditional reconfiguration for PCell change, also called a conditional reconfiguration for handover or conditional handover (CHO). The second type is a conditional reconfiguration for PSCell change, also called a conditional PSCell change (CPC). The third type is a conditional reconfiguration for PSCell addition, also called a conditional PSCell addition (CPA).

[0054] A CHO can be a handover procedure executed by the UE when one or more handover execution conditions are met. The UE can start evaluating the execution conditions when it receives the CHO setting and stop evaluating the execution conditions when the conditions are met. In some embodiments, the execution conditions can include, for example, A3 / A5 events. In some embodiments, the execution conditions can consist of one or two trigger conditions.

[0055] In relation to the CHO-CPC coexistence framework, there are two configurations: one provided to the UE and another that runs in parallel. That is, the UE monitors both measurements for both configurations. One configuration is the CHO configuration with CHO execution conditions (including the presence or absence of DC connections, i.e., SN connections), and the other configuration is the Conditional PSCell Change (CPC) configuration and CPC execution conditions, which are provided to the UE and run in parallel.

[0056] In a CHO-CPC coexistence scenario, if the target MN prepares a CHO-DC with an SN delta configuration, a CPC effectiveness issue arises. Thus, the UE is serviced by the source MN and source SN (i.e., DC setup). The source MN can initiate the target MN's CHO preparation when the target MN prepares a target SN with a target SN delta configuration (i.e., CHO-DC preparation). The target SN delta configuration is maintained by the source SN during the target MN's CHO preparation and execution, and is applied when the UE applies the target SN delta configuration to the source SN configuration to obtain the complete configuration required for the target SN connection.

[0057] However, if the source SN is changed after CHO preparation (before CHO execution), the UE's serving SN changes, rendering the delta configuration invalid and preventing its application to the new SN configuration. This invalidity is observed when the source MN prepares a CPC between the source SN and target SN after CHO-DC preparation, and the CPC is executed before CHO-DC execution. In this case, i.e., if the source SN is changed before CHO-DC execution, the delta SN configuration prepared during CHO-DC preparation becomes invalid. Therefore, CHO preparation must be repeated.

[0058] In some cases, both the serving MN and the target MN may prepare the same target SN for the UE; that is, the target MN may prepare the target SN for a CHO-DC handover, and the source MN may prepare a CPC for the same target SN. In this case, the target SN will not realize that the same UE for the CHO-DC preparation is also being prepared as part of the CPC preparation initiated by the source MN. Therefore, even if the bearer configuration is the same, the target SN will end up with duplicate resources.

[0059] Therefore, in a CHO-CPC coexistence scenario, a serving MN can initiate CHO preparation for a target MN. The target MN can then prepare a CHO-DC, i.e., a CHO-DC for a target SN with a delta configuration. Subsequently, the target MN can prepare a CPC for the UE, directed towards the same target SN. In this case, the serving MN prepares the same SN that the target MN has already prepared for the CHO-DC configuration, resulting in the same target SN reserving resources twice for the same UE. Furthermore, the target SN delta configuration included in the CHO-DC configuration becomes invalid if the serving SN is modified before the CHO-DC execution (by a CPC prepared after the CHO-DC preparation), because the delta configuration is prepared for the initial serving SN. To avoid SN failures (due to invalid configuration use), CHO-DC preparation is restarted at the expense of extra signaling overhead and the delay of the CHO-DC configuration given to the UE.

[0060] In this given scenario, the source MN first prepares the CHO on the target MN, and then the CPC on the target SN. If the target MN prepares the CHO-DC (with SN connection), and the CPC configured by the source MN is executed first, the delta SCG configuration of the target MN's CHO-DC configuration becomes invalid. This is because the target MN's delta SCG configuration is configured to be used only if the serving SN does not change before or after the CHO-DC preparation. However, from the perspective of signaling sequences, the solution is different because the CPC preparation follows the CHO preparation, and the CHO preparation needs to be updated after the CPC preparation is complete.

[0061] For example, in a scenario where a source MN prepares a CHO-DC first, and then a target SN is prepared in the CPC, if the CPC preparation is handled after the CHO-DC preparation, the target MN's CHO-DC can be updated. Furthermore, the target SN can provide information related to previous CHO-DC or CPC preparations for the same UE to prevent the target SN from reserving resources twice for the same UE.

[0062] Figure 1 is a schematic diagram of a message flow according to one embodiment. In the example of Figure 1, the message flow is a method for preparing a handover of user equipment (UE) in dual connectivity (DC) performed at a target master node (MN) of a wireless network, wherein the handover is between primary cells (PCell) of the source MN and the target MN, and between primary-secondary cells (PSCell) of the source secondary node (SN) and the target secondary node (SN).

[0063] UE101 sends a measurement report (1) to source master node 103 and starts preparing target master node 109 for CHO. Subsequently, source master node 103 sends a CHO request (2) to target master node 109.

[0064] Target MN109 prepares Target SN107 for CHO-DC preparation and generates CHO-DC configuration config1 in block 5, which includes Delta SCG configuration 1 of Target SN107. A handover request acknowledgment message (6) is sent from Target MN109 to Source MN103, which includes the CHO-DC configuration prepared by Target MN109.

[0065] According to one embodiment, as part of message (6), the target MN109 also includes an SN UE XnAP ID which is determined between the target secondary node 107 and the source MN103 during the UE's CPC-1 preparation for communication via the Xn interface.

[0066] The CHO-DC configuration of UE101 is complete, and UE101 monitors the CHO status towards the target PCell of target MN109 in block 10. UE101 sends another measurement report (11) to source MN103 to begin CPC preparation of the target PSCell in target SN107.

[0067] Source MN109 sends an SN change request (12) to prepare CPC-1 between source SN105 and target SN107. Since this request is sent to target SN107 (i.e., specified by the SN ID) as indicated above, source MN103 forwards the SN UE XnAP ID to target SN107 so that target SN can identify the UE that was already prepared by target MN109 in CHO-DC preparation.

[0068] Target SN107 will recognize that a CPC is being requested for UE101, which has already been prepared by Target MN during CHO-DC preparation. Therefore, if the bearer configuration allows it, resource allocation (13) can be optimized. In other words, duplicate resources will not be allocated to Target SN107.

[0069] Target SN107 responds to the source MN's SN change request (12) with an acknowledgment (14). In one example, target SN107 also indicates that the same UE101 has been prepared for CHO-DC operation with target MN109.

[0070] The CPC preparation configuration and conditions are provided to the UE, and CPC preparation is completed between UE101, source MN103, and target SN107 (15-17). Accordingly, the UE begins monitoring the CPC-1 conditions in order to execute CPC-1 (18).

[0071] Source MN105 notifies target MN109 of the UE's conditional PSCell change CPC-1 preparation so that target MN may be aware that if CPC is executed before CHO is executed, the delta secondary cell group SCG configuration of target MN's CHO-DC configuration may be invalidated (12). To this end, source MN103 indicates CPC-1 along with the SN ID and SN UE XnAP ID sent from target MN109 to source MN103 in message 6.

[0072] Target MN109 requests Target SN107 to prepare a second delta SCG configuration to be used by UE101 when CPC-1 is executed (20).

[0073] Target SN107 sends target delta SCG configuration configu2 to target MN109, which becomes effective when UE101 applies SCG configuration 2 after CPC-1 has been executed (21).

[0074] Target MN109 generates a second CHO-DC configuration using target delta SCG configuration 2 (block 22) and sends a handover request update message (23) to source MN103 to update the previous CHO-DC configuration. That is, target MN109 sends a second CHO-DC configuration to be maintained and used by UE101 if CPC-1 is executed.

[0075] Source MN103 relays the second CHO-DC configuration to UE101 along with the CHO condition IDs that are coupled to the CHO-DC configuration (24), and instructs UE101 to maintain the second CHO-DC configuration after CPC-1 has been executed.

[0076] UE101 notifies source MN103 that RRC reconstruction is complete (25), and source MN103 relays this information to target MN109 (26).

[0077] Figure 2 is a schematic diagram of the message flow according to one embodiment, and is a continuation of the message flow described above with reference to Figure 1.

[0078] In block 27, the CPC-1 condition is met, and UE101 hands over from source SN105 to target SN107 without changing source MN from source MN103 (CPC execution, 28-31). Target SN107 becomes the new serving SN for UE101 (SN changed). Target MN109 is notified of the execution of CPC-1, i.e., that the PSCell has been changed from source SN105 to target SN107 (32).

[0079] After the execution of CPC-1, UE101 retains the CHO-DC config 2 in block 33 as instructed (24), and therefore, after the execution of CPC-1, has a valid delta SCG configuration 2 (delta SCG configuration 2 is generated when target SN107 becomes the serving SN of UE101).

[0080] UE101 continues to monitor the CHO conditions for target MN109 toward target PCell, and when the conditions are met, the UE executes CHO-DC toward target MN109 and target SN107, completing the handover procedure (34-41).

[0081] The embodiments described herein may be provided as methods, systems, or machine-readable instructions, such as any combination of software, hardware, firmware, etc. Machine-readable instructions can be executed, for example, by machines such as general-purpose computers, platforms with user devices such as smart devices, such as smartphones, and / or network entities such as base stations or nodes of wireless networks. Modules of the device (e.g., modules that generate CHO configurations, CHOs with DC configurations, CPC configurations, etc.) can be implemented by generators that execute machine-readable instructions stored in memory, or by processors that operate according to instructions embedded in logic circuits. The methods and modules may all be executed by a single processor or divided among multiple processors.

[0082] Figure 3 is a schematic diagram of a machine according to one embodiment. Machine 300 can be, for example, a node in a wireless network. For example, machine 300 can be a source master node 103 or a target master node 109 in a wireless network 301. Machine 300 comprises a processor 303 and memory 305 for storing instructions 307 that can be executed by the processor 303. The machine also comprises storage 309 that can be used to store data 311 representing one or more of the following: a CHO configuration, a DC configuration, a CPC configuration, a UE, and / or node identifiers. In one example, instructions 307 that can be executed by the processor 303 can cause machine 300 to implement a method for preparing a handover of user equipment, UE in dual connectivity (DC), where the handover is between primary cells (PCells) of a source MN and a target MN, and between primary secondary cells (PSCells) of a source secondary node (SN) and a target SN. When executed by processor 303, the instruction can cause a machine such as a target master node to perform the following steps: send a secondary cell group (SCG) delta configuration config1 of a CHO and a target SN having a DC configuration that includes a unique identifier of the UE defined between the source master node and the target secondary node to the source MN; receive an indicator from the source MN representing the CPC procedure configured after the transmission of the CHO, the unique identifier of the UE, and the identifier of the target SN having a DC configuration; and send a request to the target SN to prepare a second delta SCG configuration config2 to be used by the UE when the source MN-initiated CPC procedure is executed.

[0083] In this embodiment, the machine can be a target master node or a source master node, and instructions can be executed by the processor of the target master node or the processor of the source master node.

[0084] In some cases, several methods can be implemented in a cloud computing environment or a network-based environment. A cloud computing environment can provide a variety of services and applications over the internet. These cloud-based services (e.g., software as a service, platform as a service, infrastructure as a service, etc.) can be accessed, for example, through a web browser on a user's device or other remote interface. The various functions described herein can be provided through a remote desktop environment or other cloud-based computing environment.

[0085] While various embodiments have been described and / or illustrated herein in relation to fully functional computer systems, one or more of these exemplary embodiments can be deployed as various forms of program products, regardless of the specific type of computer-readable storage medium used to actually implement the deployment. Furthermore, embodiments disclosed herein can also be implemented using software modules that perform specific tasks. These software modules may include scripts, batches, or other executable files that can be stored on computer-readable storage medium or within a computer system. In some embodiments, these software modules can configure a computer system to perform one or more of the exemplary embodiments disclosed herein. Moreover, one or more modules described herein can convert data, physical devices, and / or representations of physical devices from one form to another.

[0086] Figure 4 is a flowchart of an example method. In the example in Figure 4, the method is suitable for preparing a handover of user equipment (UE) in dual connectivity (DC) where the handover is between the primary cell (PCell) of the source MN and the primary cell (PCell) of the target MN, and between the primary secondary cell (PSCell) of the source secondary node (SN) and the target SN. In block 401, the target MN sends a secondary cell group (SCG) delta configuration config1 of the CHO and target SN, which has a DC configuration including a unique identifier for the UE defined between the source master node and the target secondary node. In block 403, the target MN receives an indication from the source MN representing the CPC procedure configured after the transmission of the CHO, the unique identifier for the UE, and the identifier of the target SN, which have the DC configuration. In block 405, a request is sent to the target SN to prepare a second delta SCG configuration config2, which the UE will use when the source MN-initiated CPC procedure is executed.

[0087] The foregoing description is provided to enable those skilled in the art to make optimal use of the various embodiments of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exclusive or to limit to any exact form disclosed. Many modifications and variations are possible without departing from the spirit and scope of this disclosure. The embodiments disclosed herein should be considered in all respects to be exemplary and non-restrictive. In determining the scope of this disclosure, refer to the appended claims and their equivalents. [Explanation of Symbols]

[0088] 103 Source MN 105 Source SN 107 Target SN 109 Target MN 1. Send the measurement report. 2 CHO request 3 SN addition request 4 SN additional request ACK 5. Config1: Generates a CHO configuration consisting of MCG configuration 1 + target delta SCG configuration 1 (delta relative to source SCG). 6. Handover Request Acknowledgment Message (CHO Configuration) 7 RRC Reconfiguration 8 RRC reconfiguration completed 9 RRC reconfiguration completed 10 UE evaluates CHO conditions 11. Measurement Report 12. SN Change (CPC-1) Request 13. Duplicate resources will not be allocated. 14. SN Change (CPC-1) Request ACK (CHO-DC in progress) 15 RRC Reconfiguration (CPC-1) 16 RRC reconfiguration completed 17 SN reconfiguration completed 18 UE evaluates CPC-1 conditions 20 SN change request SN-2 UE XnAP ID, CPC-1 SCG configuration 21 SN Change Request ACK Target Delta SCG Configuration 2 22 Config2: Generates a CHO configuration consisting of MCG configuration 1 + target delta SCG configuration 2 (delta relative to the applied target SCG) (if CPC-1 is executed) 23. Handover Request Update (Previous SCG configured for CPC-1) 24. Maintain Configuration 2 after RRC Reconfiguration CPC-1 execution. 25 RRC reconfiguration completed 26 RRC reconfiguration completed

Claims

1. A method for preparing a handover of user equipment (UE) in dual connectivity (DC) performed at a target master node (MN) of a wireless network, wherein the handover is between the primary cells (PCell) of the source MN and the target MN, and between the primary secondary cells (PSCell) of the source secondary node (SN) and the target SN. The source MN is to transmit a secondary cell group (SCG) delta configuration config1 of the CHO and the target SN, which has a DC configuration including a unique identifier of the UE defined between the source master node and the target secondary node. The source MN receives an indication representing the CPC procedure configured after the transmission of the CHO having the DC configuration, the unique identifier of the UE, and the identifier of the target SN. When the source MN initiation CPC procedure is executed, a request is sent to the target SN to prepare a second delta SCG configuration, config2, to be used by the UE. Methods that include...

2. The method according to claim 1, further comprising receiving configure2 from the target SN, wherein the second delta SCG configuration is effective when the UE applies the SCG configuration after the CPC procedure has been performed.

3. The method according to claim 1 or 2, further comprising generating a second CHO having a DC configuration using the second delta SCG configuration.

4. The method according to claim 3, further comprising sending a handover request update message to the source MN to update the existing CHO having a DC configuration.

5. The method according to claim 4, wherein the second CHO having a DC configuration is maintained and used by the UE when the CPC procedure is performed.

6. To provide the UE with the second CHO having a DC configuration, After the CPC procedure is performed, the UE is instructed to maintain the second CHO having a DC configuration. The method according to claim 5, further comprising:

7. A source master node in a wireless network, Processor and A memory coupled to the processor, configured to store program code executable by the processor, Equipped with, The program code includes one or more instructions, thereby sending to the source master node: The system receives a CHO having a DC configuration that includes a unique identifier for the UE defined between the source master node and the target SN, and a secondary cell group (SCG) delta configuration config1 of the target SN from the target MN. To transmit to the target MN an indication representing the CPC procedure configured after the transmission of the CHO having a DC configuration, the unique identifier of the UE, and the identifier of the target SN, The recipient receives a handover request update message from the target MN, including a second CHO having a DC configuration. The source master node that performs this task.

8. The program code comprises one or more further instructions, thereby enabling the source master node to: The existing CHO having the DC configuration is to be replaced with the second CHO having the DC configuration. The source master node according to claim 7.

9. The program code comprises one or more further instructions, thereby enabling the source master node to: Transmitting the second CHO having the DC configuration to the UE, After the CPC procedure is performed, the UE is instructed to maintain the second CHO having the DC configuration, To have them do it, The source master node according to claim 7 or 8.

10. The program code comprises one or more further instructions, thereby enabling the source master node to: The UE is instructed to transmit a CHO condition ID related to the second CHO having the DC configuration described above. The source master node according to claim 9.

11. A machine-readable storage medium encoding instructions for preparing a handover of user equipment (UE) in dual connectivity (DC), wherein the handover is between the primary cells (PCell) of a source MN and a target MN, and between the primary secondary cells (PSCell) of a source secondary node (SN) and a target SN. The aforementioned instruction is executable by the processor of the target master node, thereby allowing the target node to: The source MN is instructed to transmit a secondary cell group (SCG) delta configuration config1 of the CHO and the target SN, which has a DC configuration including a unique identifier of the UE defined between the source master node and the target secondary node. The source MN receives an indication representing the CPC procedure configured after the transmission of the CHO having the DC configuration, the unique identifier of the UE, and the identifier of the target SN. When the source MN initiation CPC procedure is executed, the UE sends a request to the target SN to prepare a second delta SCG configuration, config2, to be used by the UE. Machine-readable storage medium.

12. Instructions that can be executed by the processor of the target master node are further coded, thereby enabling the target master node to: A machine-readable storage medium that receives config2 from the target SN, wherein the second delta SCG configuration is effective when the UE applies the SCG configuration after the CPC procedure has been executed. The machine-readable storage medium according to claim 11.

13. Instructions that can be executed by the processor of the target master node are further coded, thereby enabling the target master node to: Using the second delta SCG configuration described above, a second CHO having a DC configuration is generated. The machine-readable storage medium according to claim 11 or 12.

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