Condition switching

Abstract

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

Description

Technical Field

[0001] The present invention generally relates to fifth generation (5G) New Radio (NR) systems. Various aspects relate to conditional handover in 5G NR systems. Background Art

[0002] The fifth generation (5G) New Radio (NR) system is designed to provide flexibility and configurability to optimize network services and types to suit various use cases. A new handover procedure provided as part of the 5G NR system enables the user equipment (UE) to decide to perform a handover when certain conditions are met. This NR handover procedure is called conditional handover (CHO) and is performed in contrast to the traditional handover procedure, in which the network is responsible for making the decision as to whether a handover should be performed. Therefore, this is a reactive process and is prone to handover failures.

[0003] On the other hand, CHO is a handover performed by the UE when one or more handover execution conditions are met. Specifically, the UE may start evaluating (multiple) execution conditions upon receiving the CHO configuration, and after performing the handover, may stop evaluating (multiple) execution conditions. Summary of the invention

[0004] The purpose of the present disclosure is to enable CHO-DC configuration validity for target incremental SCG configuration in the context of CHO-CPC coexistence and avoid double resource reservation.

[0005] The aforementioned and other objects are achieved by the features of the independent claims.

[0006] Further implementation forms are evident from the dependent claims, the description and the drawings.

[0007] A first aspect of the present disclosure provides a method performed in a target master node (MN) of a radio network for preparing a handover of a user equipment UE in a dual-connection DC, wherein the handover is performed between a primary cell (PCell) of a source MN and a target MN, and between a primary secondary cell (PSCell) of a source secondary node (SN) and a target SN, the method comprising: sending a CHO with a DC configuration to the source MN, the DC configuration comprising: a unique identifier of the UE defined between the source master node and the target secondary node, and a secondary cell group (SCG) incremental configuration config1 of the target SN; receiving an indication from the source MN, the indication indicating a CPC process configured after transmitting the CHO with the DC configuration, a unique identifier of the UE, and an identifier of the target SN; and sending a request to the target SN, the request being used to prepare a second incremental SCG configuration config2, which will be used by the UE when the CPC process initiated by the source MN is executed.

[0008] In the implementation of the first aspect, it may also include: receiving config2 from the target SN, wherein the second incremental SCG configuration is valid when the UE applies the SCG configuration after the CPC process is executed. The method may also include: using the second incremental SCG configuration to generate a second CHO with a DC configuration. The method may also include: sending a switching request update message to the source MN, thereby updating the existing CHO with a DC configuration. When the CPC process is executed, the second CHO with a DC configuration is maintained and used by the UE. The method also includes: providing the UE with a second CHO with a DC configuration; and after the CPC process is executed, instructing the UE to maintain the second CHO with a DC configuration.

[0009] A second aspect of the present disclosure provides a source master node in a radio network, the source master node comprising: a processor; a memory, the memory being coupled to the processor, the memory being configured to store a program code executable by the processor, the program code comprising one or more instructions, thereby enabling the source master node to: receive a CHO with a DC configuration from a target MN, the DC configuration comprising: a unique identifier of a UE defined between the source master node and a target SN, and a secondary cell group (SCG) incremental configuration config1 of the target SN; send an indication to the target MN, the indication indicating a CPC process configured after transmitting the CHO with the DC configuration, a unique identifier of the UE, and an identifier of the target SN; and receive a switching request update message from the target MN, the switching request update message comprising a second CHO with a DC configuration.

[0010] In an implementation of the second aspect, the program code may include one or more additional instructions, thereby causing the source master node to: update an existing CHO with a DC configuration using a second CHO with a DC configuration. The program code may include one or more additional instructions, thereby causing the source master node to: send the second CHO with a DC configuration to the UE; and after the CPC process is executed, instruct the UE to maintain the second CHO with a DC configuration. The program code includes one or more additional instructions, thereby causing the source master node to: send a CHO condition ID related to the second CHO with a DC configuration to the UE.

[0011] A third aspect of the present disclosure provides a user equipment UE, comprising: a processor; a memory, the memory being coupled to the processor, the memory being configured to store a program code executable by the processor, the program code comprising one or more instructions, thereby enabling the UE to: receive a second CHO with a DC configuration from a source MN; and maintain the second CHO with a DC configuration after a CPC process is executed.

[0012] In an implementation of the fourth aspect, the program code includes one or more further instructions, thereby causing the UE to: receive, from the source MN, a CHO condition ID associated with the second CHO having a DC configuration.

[0013] A fourth aspect of the present disclosure provides a machine-readable storage medium, encoded with instructions for preparing switching of a user equipment UE in a dual-connection DC, wherein the switching is performed between the primary cells (PSCells) of a source MN and a target MN, and between the primary and secondary cells (PSCells) of a source secondary node (SN) and a target SN, and the instructions can be executed by a processor of the target primary node, thereby causing the target primary node to: send a CHO with a DC configuration to the source MN, the DC configuration including: a unique identifier of the UE defined between the source primary node and the target secondary node, and an incremental configuration config1 of a secondary cell group (SCG) of the target SN; receive an indication from the source MN, the indication indicating a CPC process configured after transmitting the CHO with the DC configuration, a unique identifier of the UE, and an identifier of the target SN; and send a request to the target SN, the request being used to prepare a second incremental SCG configuration config2, which will be used by the UE when the CPC process initiated by the source MN is executed.

[0014] In the implementation of the fourth aspect, the machine-readable storage medium may also be encoded with instructions executable by a processor of the target master node, thereby causing the target master node to: receive config2 from the target SN, wherein after the CPC process is executed and when the UE applies the SCG configuration, the second incremental SCG configuration is valid. The machine-readable storage medium may also be encoded with instructions executable by a processor of the target master node, thereby causing the target master node to: use the second incremental SCG configuration to generate a second CHO with a DC configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0016] Figure 1 is a schematic representation of a message flow according to an example;

[0017] Figure 2 is a schematic representation of a message flow according to an example;

[0018] Figure 3 is a schematic representation of a machine according to an example; and

[0019] Figure 4 is a flow chart of a method according to an example. DETAILED DESCRIPTION

[0020] The following describes exemplary embodiments in sufficient detail to enable one of ordinary skill in the art to implement and practice the systems and processes described herein.It is important to understand that the embodiments may be provided in many alternative forms and should not be construed as limited to the examples set forth herein.

[0021] Therefore, although the embodiments can be modified in various ways and take various alternative forms, specific embodiments thereof are shown in the drawings and described in detail as examples below. It is not intended to limit the specific forms disclosed. On the contrary, all modifications, equivalents, and substitutes falling within the scope of the appended claims should be included. Where appropriate, the elements of the exemplary embodiments are consistently represented by the same reference numerals in the drawings and detailed description.

[0022] The terminology used to describe the embodiments herein is not intended to limit the scope. The articles "one", "an" and "the" are singular forms because they have referents, but the use of singular forms in this document should not exclude the presence of multiple referents. In other words, the elements referred to by the singular form can be numbered as one or more unless the context clearly indicates otherwise. It will also be understood that the terms "include", "comprise", "contain", and / or "contain" when used in this article specify the presence of stated features, projects, steps, operations, elements, and / or components, but do not exclude the presence or increase of one or more other features, projects, steps, operations, elements, components, and / or combinations thereof. The term "and / or" is only a kind of association relationship describing associated objects, and represents that there can be three kinds of relationships, A and / or B can indicate A: exist alone, A and B exist simultaneously, or B exists alone. The character " / " generally represents that it is an "or" relationship between associated objects.

[0023] Unless otherwise defined, all terms (including technical and scientific terms) used in this document should be interpreted according to the common practice in the field. It will also be understood that unless otherwise clearly defined in this document, commonly used terms should also be interpreted according to the common practice in the relevant field, rather than idealized or overly formal meanings.

[0024] The following contains specific information related to the implementation of the present disclosure. The accompanying drawings and the detailed disclosure attached thereto are only for implementation. However, the present disclosure is not limited to these implementations. Other variations and implementations of the present disclosure will be apparent to those skilled in the art.

[0025] The phrases "in one implementation" or "in some implementations" may refer to one or more of the same or different implementations, respectively. The term "coupled" is defined as connected directly or indirectly through an access component, and is not necessarily limited to a physical connection. The expression "at least one of A, B, and C" or "at least one of the following: A, B, and C" means "only A, or only B, or only C, or any combination of A, B, and C".

[0026] The terms "system" and "network" are used interchangeably.

[0027] For the purpose of explanation and non-limitation, specific details such as functional entities, technologies, protocols and standards 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 to avoid confusing the present disclosure with unnecessary details.

[0028] 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 any combination thereof.

[0029] Software implementations may include machine and / or computer readable and / or executable instructions stored on machine and / or computer readable media (such as memory or other types of storage devices). One or more microprocessors or general-purpose computers with communication processing capabilities may be programmed with corresponding executable instructions and execute the disclosed (multiple) network functions or (multiple) algorithms.

[0030] The microprocessor or general purpose computer may include an application specific integrated circuit (ASIC), a programmable logic array, and / or use one or more digital signal processors (DSPs). Although some of the disclosed implementations are for software installed and executed on computer hardware, alternative implementations implemented as firmware or hardware or a combination of hardware and software are also within the scope of the present disclosure. Computer readable media include, but are 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 disk read-only memory (CD-ROM), flash memory, magnetic tape, disk storage, or any other equivalent medium capable of storing computer readable instructions.

[0031] A radio communication network architecture such as a long term evolution (LTE) system, an advanced LTE (LTE-A) system, an advanced LTE Pro system, or a 5G NR radio access network (RAN) generally 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 a network 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 through a RAN established by one or more BSs.

[0032] UE may include but is not limited to a mobile station, a mobile terminal, or a device, or a user communication radio terminal. UE may be a portable radio device, which includes but is not limited to a mobile phone, a tablet, a wearable device, a sensor, a vehicle, or a personal digital assistant (PDA) with wireless communication capabilities. UE is configured to receive and send signals to one or more cells in the RAN over an air interface.

[0033] The BS may provide communication services according to a radio access technology (RAT), such as Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile Communications (GSM), commonly referred to as 2G, GSM Enhanced Data Rates for GSM Evolution (EDGE) RAN (GERAN), General Packet Radio Service (GPRS); Universal Mobile Telecommunications System (UMTS) (commonly referred to as 3G based on basic Wideband Code Division Multiple Access (W-CDMA)), High Speed ​​Packet Access (HSPA), LTE, LTE-A, Evolved LTE (eLTE) connected to 5GC, NR (commonly referred to as 5G), and / or LTE-A Pro. However, the scope of the present disclosure is not limited to these protocols.

[0034] The 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 ​​an Evolved Universal Terrestrial Radio Access (E-UTRA) BS connected to a 5GC, a Next Generation Node B (gNB) in 5G-RAN, or any other device capable of controlling radio communications and managing radio resources within a cell. The BS may serve one or more UEs via a radio interface.

[0035] A BS may use multiple cells forming a RAN to provide radio coverage to a specific geographical area. The BS supports the operation of cells. Each cell is operable to provide service to at least one UE within its radio coverage.

[0036] Each cell (usually referred to as a serving cell) can provide services to one or more UEs within its radio coverage, so that each cell schedules downlink (DL) and optional uplink (UL) resources to at least one UE within its radio coverage for DL ​​and optional UL packet transmission. A BS can communicate with one or more UEs in a radio communication system via multiple cells.

[0037] The cell may allocate sidelink (SL) resources to support Proximity Services (ProSe) or Vehicle-to-Everything (V2X) services. Each cell may have a coverage area that overlaps with other cells.

[0038] NR's frame structure supports flexible configuration to accommodate various next-generation (e.g., 5G) communication requirements, such as enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable and low-latency communications (URLLC), while meeting high reliability, high data rate, and low latency requirements. The Orthogonal Frequency Division Multiplexing (OFDM) technology in the Third Generation Partnership Project (3GPP) can be used as a baseline for the NR waveform. Scalable OFDM numerology, such as adaptive subcarrier spacing, channel bandwidth, and cyclic prefix (CP), can also be used.

[0039] Some examples of terms used in this disclosure are as follows:

[0040] Primary Cell (PCell): PCell is a Master Cell Group (MCG) cell operating on a primary frequency, where a UE performs an initial connection establishment procedure or initiates a connection reestablishment procedure. PCell is a Special Cell (SpCell) of an MCG.

[0041] Primary SCG cell (PSCell): For dual connectivity (DC) operation, the PSCell is a secondary cell group (SCG) cell where the UE performs random access when performing reconfiguration with synchronization procedures. The PSCell is the SpCell of the SCG. In some implementations, the term PSCell may refer to a primary secondary cell. The term "primary SCG cell" and the term "primary secondary cell" may be used interchangeably in the present disclosure.

[0042] Special cell (SpCell): For DC operation, the term special cell (SpCell) refers to the PCell of the MCG or the PSCell of the SCG, otherwise the term special cell refers to the PCell.

[0043] Secondary Cell (SCell): For a UE configured with carrier aggregation (CA), a SCell is a cell that provides additional radio resources on top of a special cell.

[0044] Serving cell: For UEs without CA / DC configured in RRC-CONNECTED, there is only one serving cell including the primary cell. For UEs with CA / DC configured in RRC-CONNECTED, the term "serving cell" is used to refer to the set of cells including (multiple) dedicated cells and all secondary cells.

[0045] Master Cell Group (MCG): In MR-DC, MCG is a serving cell group associated with a master node, including: SpCell (PCell) and optionally one or more SCells.

[0046] Master Node (MN): In MR-DC, the MN or master node is the radio access node that provides the control plane connection to the core network. It can be a master eNB (in EN-DC), a master ng-eNB (in NGEN-DC), or a master gNB (in NR-DC and NE-DC). In some implementations, the MN or master node may include the source node or target node of the UE.

[0047] Secondary Cell Group (SCG): In MR-DC, SCG is a serving cell group associated with a secondary node, including: SpCell (PSCell) and optionally one or more SCells.

[0048] Secondary Node (SN): In MR-DC, the SN is a radio access node that has no control plane connection to the core network and provides additional resources for the UE. It can be 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 implementations, the SN or secondary node may include: the source node or the target node of the UE.

[0049] In a wireless communication network such as E-UTRAN, one of the main reasons for handover (HO) failure is that the UE does not receive a handover command message from a source base station (e.g., source eNB or source gNB) or a serving base station (e.g., serving eNB or serving gNB). A conventional handover process is usually triggered by a measurement report from the UE. For example, when the quality (e.g., signal strength and / or service quality) of a serving cell is lower than a pre-configured threshold and the quality (e.g., signal strength and / or service quality) of a neighboring cell is higher than a pre-configured threshold, the UE may send a measurement report to the source base station under the serving cell based on the received measurement configuration. Upon receiving the measurement report, the source base station may send a handover request message to multiple target base stations (e.g., eNB or gNB) for admission control, and receive a handover confirmation message from the target base station. The source base station may select and send a handover command message (which may be included in a handover confirmation message from one of the target base stations) to the UE so that the UE can connect to the target cell.

[0050] The success of the entire handover process depends on several factors. One of the factors is that the quality of the serving cell will not drop rapidly in a short period of time, which can be dominated by the delay of the backhaul (for example, for the X2 / Xn / Xx interface), the processing time of the target base station, and the signaling transmission time. However, in actual situations, the quality of the serving cell can drop rapidly in a short period of time, and the UE may not successfully receive the handover command message before the quality of the serving cell drops significantly. As a result, the UE can detect a radio link failure. Therefore, in response to the detected radio link failure, the UE can initiate a radio resource control (RRC) connection reestablishment process, which in turn results in a considerable service interruption time.

[0051] In next generation wireless networks (e.g., 5G NR networks), with extensive antenna beamforming in higher frequency bands, the serving cell quality may degrade even faster, especially when narrow beams are used to serve UEs. Blocking is another issue in NR deployments.

[0052] 3GPP introduced the concept of Conditional Handover (CHO) to improve the reliability of the entire handover process. The CHO process can be regarded as a supplementary process to the traditional handover process to help reduce the handover failure rate.

[0053] In order to execute the conditional reconfiguration command, the UE may evaluate the triggering conditions associated with the conditional reconfiguration command to determine whether one or more triggering conditions (or execution conditions) for the conditional reconfiguration command are met. When the UE determines that the triggering conditions are met, the UE may apply the corresponding conditional reconfiguration command to connect to the target cell. Existing measurement events (e.g., A3 and A5) may be used to determine whether the triggering conditions of the conditional reconfiguration command are met.

[0054] CHO can help improve the reliability of the entire handover process. Applying concepts similar to CHO can also benefit the PSCell addition process, PSCell change process, SN addition process, or SN change process for MR-DC mode, because the preparation between the MN and the SN, and the RRC signaling for adding the SN may be completed in advance.

[0055] When the concept of CHO (or conditional configuration) is applied to a normal HO (e.g., PCell change) process or a PSCell addition / change (or SN addition / change) process, the UE may behave differently. For example, if the conditional reconfiguration command executed is for PSCell addition / change, the UE may not need to release the link to the current PCell (or MN). The UE may need some information or guidance (e.g., implicitly) to determine how to operate when executing the conditional reconfiguration command. In addition, due to different purposes, the principle of applying CHO (or conditional configuration) to PCell changes and the principle of applying CHO (or conditional configuration) to PSCell addition / change.

[0056] The conditional reconfiguration process can be a reconfiguration process performed by the UE when one or more execution conditions (also called triggering conditions) are met. There are three types of conditional reconfiguration. The first type is conditional reconfiguration for PCell change, also called conditional reconfiguration for switching or conditional switching (CHO). The second type is conditional reconfiguration for PSCell change, also called conditional PSCell change (CPC). The third type is conditional reconfiguration for PSCell addition, also called conditional PSCell addition (CPA).

[0057] CHO may be a handover procedure performed by the UE when one or more handover execution conditions are met. The UE may start evaluating the execution condition(s) upon receiving the CHO configuration, and may stop evaluating the execution condition(s) after the execution condition(s) are met. In some implementations, the execution condition(s) may include, for example, an A3 / A5 event. In some implementations, the execution condition(s) may include one or two trigger conditions.

[0058] In the context of the CHO-CPC coexistence framework, there will be two configurations provided to the UE and run in parallel. That is, the UE in question monitors two measurements for the two configurations. One configuration is a CHO configuration with CHO execution conditions (with or without DC connection, i.e. including SN connection), and the other configuration is a conditional PSCell change (CPC) configuration and CPC execution conditions provided to the UE, and these configurations and conditions also run in parallel.

[0059] In a CHO-CPC coexistence scenario, CPC validity issues occur if the target MN prepares CHO-DC with SN incremental configuration. In this way, the UE is served by the source MN and the source SN (i.e., DC establishment). The source MN can initiate CHO preparation of the target MN, where the target MN prepares the target SN with target SN incremental configuration (i.e., CHO-DC preparation). If the source SN is retained during the CHO preparation and execution of the target MN, and the UE applies the target SN incremental configuration on the source SN configuration to obtain the full configuration required for the target SN connection, the target SN incremental configuration will be applicable.

[0060] However, if the source SN changes after CHO preparation (but before CHO execution), the incremental configuration becomes invalid as the UE's serving SN changes, and the incremental configuration can no longer be applied to the configuration of the new SN. This invalidity is observed if the source MN prepares CPC between the target SN and the target SN after CHO-DC preparation, and if CPC is performed before CHO-DC execution. In this case, i.e., the source SN changes before CHO-DC execution, the incremental SN configuration prepared by CHO-DC becomes invalid. Therefore, CHO preparation should be repeated.

[0061] In some cases, both the serving MN and the target MN may prepare the same target SN for the UE, i.e., the target MN prepares the target SN for CHO-DC handover, and the source MN prepares CPC for the same target SN. In this case, the target SN will not be aware that the same UE prepared by CHO-DC is also prepared as part of CPC preparation initiated by the source MN. Therefore, the target SN will double reserve resources even if the bearer configuration is the same.

[0062] Therefore, in a CHO-CPC coexistence scenario, the serving MN may initiate CHO preparation to the target MN. The target MN may prepare CHO-DC, i.e., for a target SN with an incremental configuration. The target MN may then prepare the UE in question with CPC to the same target SN. In this case, since the serving MN prepares the same SN that the target MN has prepared for CHO-DC configuration, the same target SN will reserve resources twice for the same UE. In addition, if the serving SN changes before CHO-DC is executed (due to CPC prepared after CHO-DC preparation), the incremental configuration of the target SN included in the CHO-DC configuration will become invalid because this incremental configuration is prepared for the initial serving SN. In order to avoid SN failure (due to invalid configuration usage), CHO-DC preparation is re-initiated at the expense of additional signaling overhead and delayed CHO-DC configuration given to the UE.

[0063] In the given scenario, the source MN first prepares the target MN with CHO, and only later prepares the target SN with CPC. In the case where the target MN prepares CHO-DC (with SN connection), if the CPC configured by the source MN is performed first, the incremental SCG configuration of the CHO-DC configuration of the target MN becomes invalid. The invalidation reason is that the incremental SCG configuration of the target MN will be configured to be used when the serving SN is unchanged before and after the CHO-DC preparation. However, this solution is different from the signal sequence point of view because the CPC preparation is performed after the CHO preparation, and the CHO preparation needs to be updated after the CPC preparation is completed.

[0064] According to an example, in the context that the source MN first prepares CHO-DC and then prepares the target SN with CPC, if CPC preparation is processed after CHO-DC preparation, the CHO-DC of the target MN can be updated. In addition, the target SN can be provided with information related to the previous CHO-DC or CPC preparation for the same UE so that the target SN does not reserve duplicate resources for the same UE.

[0065] Figure 1 is a schematic representation of a message flow according to an example. Figure 1 In the example, the message flow relates to a method performed in a target master node (MN) of a radio network for preparing a handover of a user equipment UE in a dual-connection DC, wherein the handover is performed between primary cells (PCells) of source and target MNs, and between primary secondary cells (PSCells) of source and target SNs.

[0066] UE 101 sends a measurement report (1) to its source master node 103 to initiate CHO preparation of target master node 109. Then, source master node 103 sends (2) a CHO request to target master node 109.

[0067] Target MN 109 prepares target SN 107 for CHO-DC preparation and generates CHO-DC configuration config1 in block 5, which contains incremental SCG configuration 1 of target SN 107. A Handover Request Ack message (6) is sent from target MN 109 to source MN 103 and includes the CHO-DC configuration prepared by target MN 109.

[0068] According to one example, as part of message (6), the target MN 109 also includes the SN UE XnAP ID, which is defined between the target secondary node 107 and the source MN 103 during the preparation of the UE's CPC-1 for communication over the Xn interface.

[0069] In box 10, the CHO-DC configuration of UE 101 is completed and UE 101 starts monitoring the CHO condition towards the target PCell of target MN 109. UE 101 sends another measurement report (11) to source MN 103 to initiate CPC preparation of the target PSCell in target SN 107.

[0070] The source MN 109 sends an SN Modification Request (12) to prepare CPC-1 between the source SN 105 and the target SN 107. When the request is sent to the target SN 107 indicated above (i.e., specified using the SN ID), the source MN 103 forwards the SN UE XnAPID to the target SN 107 so that the target SN can identify the UE that has been prepared by the target MN 109 in the CHO-DC preparation.

[0071] If the bearer configuration allows, the target SN 107 can optimize resource allocation (13) because it will become aware that the CPC requested for UE 101 has already been prepared by the target MN in CHO-DC preparation. That is, no duplicate resources are allocated at the target SN 107.

[0072] The target SN 107 replies to the source MN's SN modification request (12) with an acknowledgement (14). In one example, it will also instruct the same UE 101 to prepare for CHO-DC operation with the target MN 109.

[0073] The CPC preparation configuration and conditions are provided to the UE, and CPC preparation is completed between the UE 101, the source MN 103, and the target SN 107 (15-17). Therefore, the UE starts monitoring the CPC-1 conditions to perform CPC-1 (18).

[0074] The source MN 105 notifies the target MN 109 (19) of the conditional PSCell change CPC-1 preparation of the UE (12) so that the target MN knows that if CPC is performed before CHO is performed, the incremental secondary cell group SCG configuration of the CHO-DC configuration of the target MN may become invalid. To this end, the source MN 103 indicates CPC-1 and the SN ID and SN UE XnAP ID sent from the target MN 109 to the source MN 103 message 6.

[0075] If CPC-1 is performed, the target MN 109 requests (20) the target SN 107 to prepare a second incremental SCG configuration, which will then be used by the UE 101.

[0076] The target SN 107 sends (21) a target incremental SCG configuration config2 to the target MN 109, which will be valid if the UE 101 applies SCG config2 after CPC-1 execution.

[0077] The target MN 109 (box 22) generates a second CHO-DC configuration using the target incremental SCG config2 and sends a handover request update message (box 23) to the source MN 103 to update the previous CHO-DC configuration. That is, if CPC-1 is executed, it sends the second CHO-DC configuration to be maintained and used by the UE 101.

[0078] The source MN 103 relays (24) the second CHO-DC configuration to the UE 101 together with the CHO Condition ID bound to the CHO-DC configuration, and instructs the UE 101 to maintain the second CHO-DC configuration after CPC-1 is executed.

[0079] UE 101 notifies source MN 103 of the RRC reconfiguration completion (25), and source MN 103 relays the information to target MN 109 (26).

[0080] Figure 2 is a schematic representation of a message flow according to an example and is a reference to Figure 1 A continuation of the message flow described.

[0081] In block 27, the CPC-1 condition is satisfied and UE 101 switches from source SN 105 to target SN 107 without changing the source MN from source MN 103 (CPC execution, 28-31). Target SN 107 becomes the new serving SN for UE 101 (SN change). Target MN 109 is notified (32) about the CPC-1 execution, i.e., the PSCell has been changed from source SN 105 to target SN 107.

[0082] In box 33, after CPC-1 execution, UE 101 saves CHO-DC config2 as it is instructed (24), and thus has a valid incremental SCG config2 after CPC-1 execution (incremental SCG config2 is generated for the case where target SN 107 becomes the serving SN of UE 101).

[0083] UE 101 continues to monitor the CHO condition towards the target PCell of target MN 109, and after the condition is met, the UE performs CHO-DC towards target MN 109 and target SN 107, and completes the handover process (34-41).

[0084] Examples in the present disclosure may be provided as methods, systems, or machine-readable instructions, such as any combination of software, hardware, firmware, etc. The machine-readable instructions may be executed, for example, by a machine such as a general-purpose computer, a platform including a user device such as an intelligent device (e.g., a smart phone), and / or a network entity such as a base station or node in a radio network. The modules of the device (e.g., modules for generating a CHO configuration, a CHO with a DC configuration, a CPC configuration, etc.) may be implemented by a processor executing machine-readable instructions stored in a memory or a processor operating according to instructions embedded in a logic circuit system. The method and modules may be executed entirely by a single processor or divided among several processors.

[0085] Figure 3 is a schematic representation of a machine according to an example. The machine 300 may be, for example, a node in a wireless network. For example, the machine 300 may be a source master node 103 or a target master node 109 in a wireless network 301. The machine 300 includes: a processor 303 and a memory 305 for storing instructions 307 executable by the processor 303. As described above, the machine includes: a memory 309, which may be used to store data 311 representing any one or more of a CHO configuration, a CHO with a DC configuration, a CPC configuration, an identifier of a UE and / or a node, and the like. In one example, the instructions 307 executable by the processor 303 may enable the machine 300 to implement a method for preparing a handover of a user equipment UE in a dual-connection DC, wherein the handover is performed between a primary cell (PCell) of a source MN and a target MN, and between a primary secondary cell (PSCell) of a source secondary node (SN) and a target SN. When the instruction is executed by the processor 303, it can cause: a machine such as a source master node to send a CHO with a DC configuration to a source MN, the DC configuration including: a unique identifier of the UE defined between the source master node and the target secondary node, and an incremental configuration config1 of the secondary cell group SCG of the target SN; receive an indication from the source MN, the indication indicating a CPC process configured after transmitting the CHO with a DC configuration, a unique identifier of the UE, and an identifier of the target SN; and send a request to the target SN, the request being used to prepare a second incremental SCG configuration config2, which will be used by the UE when the CPC process initiated by the source MN is executed.

[0086] In one implementation, the machine may be a target host node or a source host node, and the instructions may be executed by a processor of the target host node or the source host node.

[0087] In some examples, some methods may be performed in a cloud computing or web-based environment. A cloud computing environment may provide various services and applications via the Internet. These cloud-based services (e.g., software as a service, platform as a service, infrastructure as a service, etc.) may be accessed through, for example, a web browser or other remote interface of a user device. The various functions described herein may be provided through a remote desktop environment or any other cloud-based computing environment.

[0088] Although various embodiments are described and / or shown in the context of the fully functional computing system herein, one or more of these exemplary embodiments can be distributed as various forms of process products, regardless of the specific type of the computer-readable storage medium used to actually perform the distribution. The embodiments disclosed herein can also be implemented using software modules that perform specific tasks. These software modules can include scripts, batch processing or other executable files that can be stored on a computer-readable storage medium or in a computing system. In certain embodiments, these software modules can configure a computing system to perform one or more exemplary embodiments disclosed herein. In addition, one or more modules described herein can convert the representation of data, physical devices, and / or physical devices from one form to another.

[0089] Figure 4 is a flow chart of a method according to an example. Figure 4 In the example, the method is suitable for preparing a handover of a user equipment UE in a dual-connection DC, wherein the handover is performed between the primary cells (PCell) of the source MN and the target MN, and between the primary and secondary cells (PSCell) of the source secondary node (SN) and the target SN. In box 401, a CHO with a DC configuration is sent from the target MN to the source MN, and the DC configuration includes: a unique identifier of the UE defined between the source primary node and the target secondary node, and a secondary cell group SCG incremental configuration config1 of the target SN. In box 403, the target MN receives an indication from the source MN, indicating a CPC process configured after transmitting the CHO with a DC configuration, a unique identifier of the UE, and an identifier of the target SN. In box 405, a request is sent to the target SN, the request being used to prepare a second incremental SCG configuration config2, which will be used by the UE when the CPC process initiated by the source MN is executed.

[0090] The above description is provided to enable other persons skilled in the art to best utilize the various aspects of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exhaustive or limited to any precise form disclosed. Many modifications and variations may be made without departing from the spirit and scope of the present disclosure. The embodiments disclosed herein should be considered illustrative and non-restrictive in all respects. When determining the scope of the present disclosure, reference should be made to the attached claims and their equivalents.

Claims

1. A method performed in a target master node (MN) of a radio network for preparing a handover of a user equipment UE in dual connectivity DC, wherein the handover is performed between a primary cell (PCell) of a source MN and a target MN, and between a primary secondary cell (PSCell) of a source secondary node (SN) and a target SN, the method comprising: Sending a CHO with a DC configuration to the source MN, the DC configuration including: a unique identifier of the UE defined between the source primary node and the target secondary node, and a secondary cell group (SCG) incremental configuration config1 of the target SN; receiving an indication from the source MN, the indication indicating a CPC procedure configured after transmitting the CHO with DC configuration, the unique identifier of the UE, and the identifier of the target SN; and A request is sent to the target SN, the request being used to prepare a second incremental SCG configuration config2, which will be used by the UE when the CPC procedure initiated by the source MN is executed.

2. The method according to claim 1, further comprising: config2 is received from the target SN, wherein the second incremental SCG configuration is valid if the UE applies the SCG configuration after the CPC procedure is performed.

3. The method according to claim 1 or 2, further comprising: Using the second incremental SCG configuration, a second CHO with a DC configuration is generated.

4. The method according to claim 3, further comprising: A handover request update message is sent to the source MN, thereby updating the existing CHO with DC configuration. 5 . The method according to claim 4 , wherein in a case where the CPC procedure is performed, the second CHO having a DC configuration is maintained and used by the UE.

6. The method according to any one of claims 5, further comprising: providing the second CHO having a DC configuration to the UE; as well as After the CPC process is executed, the UE is instructed to maintain the second CHO with DC configuration.

7. A source master node in a radio network, the source master node comprising: processor; A memory, the memory being coupled to the processor, the memory being configured to store a program code executable by the processor, the program code comprising one or more instructions, thereby causing the source master node to: receiving a CHO with a DC configuration from a target MN, the DC configuration comprising: a unique identifier of the UE defined between the source master node and the target SN, and a secondary cell group (SCG) incremental configuration config1 of the target SN; sending an indication to the target MN, the indication indicating a CPC procedure configured after transmitting the CHO with DC configuration, the unique identifier of the UE, and the identifier of the target SN; and A handover request update message is received from the target MN, the handover request update message including a second CHO having a DC configuration.

8. The source master node according to claim 7, wherein the program code comprises one or more further instructions, thereby causing the source master node to: The existing CHO with DC configuration is updated by using the second CHO with DC configuration.

9. A source master node according to claim 7 or 8, wherein the program code comprises one or more further instructions, thereby causing the source master node to: sending the second CHO with DC configuration to the UE; and After the CPC process is executed, the UE is instructed to maintain the second CHO with DC configuration.

10. The source master node of claim 9, wherein the program code includes one or more further instructions, thereby causing the source master node to: A CHO condition ID associated with the second CHO with DC configuration is sent to the UE.

11. A user equipment UE, comprising: processor; a memory, the memory being coupled to the processor, the memory being configured to store a program code executable by the processor, the program code comprising one or more instructions, thereby causing the UE to: receiving a second CHO having a DC configuration from a source MN; as well as After the CPC process is executed, the second CHO having the DC configuration is maintained.

12. The UE of claim 11, wherein the program code comprises one or more further instructions, thereby causing the UE to: A CHO condition ID associated with the second CHO having a DC configuration is received from the source MN.

13. A machine-readable storage medium, encoded with instructions for preparing a handover of a user equipment UE in dual connectivity DC, wherein the handover is performed between a primary cell (PSCell) of a source MN and a target MN, and between a primary secondary cell (PSCell) of a source secondary node (SN) and a target SN, and the instructions are executable by a processor of the target primary node, thereby causing the target primary node to: Sending a CHO with a DC configuration to the source MN, wherein the DC configuration includes: A unique identifier of the UE defined between the source primary node and the target secondary node, and a secondary cell group (SCG) incremental configuration config1 of the target SN; receiving an indication from the source MN, the indication indicating a CPC procedure configured after transmitting the CHO with DC configuration, the unique identifier of the UE, and the identifier of the target SN; as well as A request is sent to the target SN, the request being used to prepare a second incremental SCG configuration config2, which will be used by the UE when the CPC procedure initiated by the source MN is executed.

14. The machine-readable storage medium of claim 13, further encoded with instructions executable by the processor of the target host node, thereby causing the target host node to: config2 is received from the target SN, wherein the second incremental SCG configuration is valid if the UE applies the SCG configuration after the CPC process is performed.

15. The machine-readable storage medium of claim 13 or 14, further encoded with instructions executable by the processor of the target host node, thereby causing the target host node to: Using the second incremental SCG configuration, a second CHO with a DC configuration is generated.

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