Coexistence of conditional switching and dual connectivity

Abstract

In some examples, a method performed in a target primary node of a radio network for preparing a handover of a user equipment (UE) in a dual connectivity (DC), where the handover is between respective primary cells (PCells) of a source primary node and the target primary node and respective primary secondary cells (PSCells) of a source secondary node and the target secondary node, the method includes receiving a conditional handover (CHO) request message from a source master node, the CHO request message including a unique identifier for a UE defined between the source master node and a target secondary node, and an identifier for the target secondary node, transmitting the unique identifier for the UE to the target secondary node, as part of a secondary node add request for a CHO with DC preparation, an acknowledgement message is received from a target secondary node to acknowledge CPC preparation for the UE, the acknowledgement message including a complete secondary cell group (SCG) configuration.

Description

Technical Field

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

[0002] Fifth Generation (5G) New Radio (NR) systems are designed to provide flexibility and configurability to optimize network services and types to suit a variety of use cases. As part of the 5G NR system, a new handover procedure is provided that 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 deciding whether a handover should be performed. Therefore, this is a passive 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 the execution condition(s) after receiving the CHO configuration, and may stop evaluating the execution condition(s) once the handover is performed. 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] These and other objects are achieved by the features of the independent claims.

[0006] Further implementations are apparent 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 of a radio network, for preparing a handover of a user equipment UE in a dual-connection DC, wherein the handover is between corresponding primary cells PCell of a source master node and a target master node and corresponding primary secondary cells PSCell of a source secondary node and a target secondary node, the method comprising: receiving a conditional handover CHO request message from the source master node, the CHO request message comprising: a unique identifier for the UE defined between the source master node and the target secondary node, and an identifier for the target secondary node, sending the unique identifier for the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation, and receiving a confirmation message from the target secondary node to confirm CPC preparation for the UE, the confirmation message comprising a complete secondary cell group SCG configuration.

[0008] The target primary node and the target secondary node are informed of the ongoing CPC preparation. Therefore, the target secondary node will not reserve duplicate resources for the same UE. In addition, the complete SCG configuration is provided instead of incremental SCG configuration, thereby preventing SCG configuration validity issues in case of serving secondary node changes.

[0009] In an implementation of the first aspect, a handover request confirmation message is sent to the source master node, the handover request confirmation message including data representing the following items: an indication that the CHO with DC contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after execution of the UE's ongoing CPC configuration.

[0010] The method may further include: receiving, from the source primary node, confirmation of UE handover from the source secondary node to the target secondary node. The method may further include: receiving, from the target secondary node, confirmation of UE handover from the source secondary node to the target secondary node.

[0011] In an example, the complete SCG configuration may be valid before and after execution of a UE handover from a source secondary node to a target secondary node.

[0012] 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 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, so that the source master node: sends a CHO request message to a target master node of the radio network, the CHO request message comprising: a unique identifier for the UE defined between the source master node and the target secondary node, and an identifier for the target secondary node, and receives a switching request confirmation message from the target master node of the radio network, the switching request confirmation message comprising data representing the following items: an indication that the CHO configuration contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after execution of the UE's ongoing CPC configuration.

[0013] In the implementation of the second aspect, the program code may also include one or more instructions so that the source master node: sends a confirmation of the UE switching to the target master node. The program code may also include one or more instructions so that the source master node: sends data including the following items to the UE: an indication that the CHO with DC configuration is to be maintained after the execution of CPC.

[0014] A third aspect of the present disclosure provides a machine-readable storage medium encoded with instructions for preparing for switching of a user equipment UE in a dual-connection DC, wherein the switching is between corresponding primary cells PCell of a source primary node and a target primary node and corresponding primary secondary cells PSCell of a source secondary node and a target secondary node, and the instructions are executable by a processor of the target primary node, so that the target primary node: receives a conditional switching CHO request message from the source primary node, the CHO request message includes: a unique identifier for the UE defined between the source primary node and the target secondary node, and an identifier for the target secondary node, sends the unique identifier for the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation, and receives a confirmation message from the target secondary node to confirm the CPC preparation for the UE, the confirmation message including a complete secondary cell group SCG configuration.

[0015] 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: send a switching request confirmation message to the source master node, the switching request confirmation message including data representing the following items: an indication that the CHO with DC contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after execution of the UE's ongoing CPC configuration.

[0016] The machine-readable storage may also be encoded with instructions executable by a processor of the target primary node, thereby causing the target primary node to: receive, from the source primary node, confirmation of the UE handover from the source secondary node to the target secondary node.

[0017] The machine-readable storage medium may also be encoded with instructions executable by a processor of the target primary node, thereby causing the target primary node to: receive, from the target secondary node, confirmation of UE handover from the source secondary node to the target secondary node.

[0018] A fourth aspect of the present disclosure provides a target master node in a radio network, the target master node comprising: a processor, a memory 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, so that the target master node: receives a conditional switching CHO request message from a source master node, the CHO request message comprising: a unique identifier for the UE defined between the source master node and the target secondary node, and an identifier for the target secondary node, sends the unique identifier for the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation, and receives a confirmation message from the target secondary node to confirm CPC preparation for the UE, the confirmation message comprising a complete secondary cell group SCG configuration.

[0019] The program code may also include one or more instructions to cause the target master node to: send a switching request confirmation message to the source master node, the switching request confirmation message including data representing the following items: an indication that the CHO with DC contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after execution of the UE's ongoing CPC configuration.

[0020] The program code may also include one or more instructions to cause the target primary node to: receive, from the source primary node, a confirmation of the UE handover from the source secondary node to the target secondary node. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0022] Figure 1 is a schematic diagram of a message flow according to an example;

[0023] Figure 2 is a schematic diagram of a machine according to an example; and

[0024] Figure 3 is a flow chart of a method according to an example. DETAILED DESCRIPTION

[0025] Example embodiments are described below in sufficient detail to enable one of ordinary skill in the art to embody and implement 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 described herein.

[0026] Therefore, although the embodiments may be modified in various ways and in various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. It is not intended to limit the specific form disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. The elements of the example embodiments are always represented by the same reference numerals in the drawings and detailed description.

[0027] The terminology used in this article to describe the embodiment is not intended to limit the scope. The articles "one", "an" and "the" are singular because they have a single referent, but the use of the singular form in this document should not exclude the presence of more than one referent. In other words, unless the context clearly states otherwise, the elements mentioned in the singular form can be numbered one or more. It will also be understood that when used in this article, the terms "include", "comprise", "comprises" and / or "comprises" specify the presence of the features, projects, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, projects, steps, operations, elements, components and / or their combinations. The term "and / or" is only used to describe the association relationship of the associated object, and represents that there can be three kinds of relationships, so that A and / or B can indicate that A exists alone, A and B exist simultaneously or B exists alone. The character " / " usually represents that the associated object is in an "or" relationship.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used herein should be interpreted according to common usage in the art. It will also be understood that, unless explicitly defined herein, commonly used terms should also be interpreted according to common usage in the relevant art, rather than in an idealized or overly formal sense.

[0029] The following contains specific information related to the implementation of the present disclosure. The drawings and the detailed disclosure attached thereto are only for the implementation. However, the present disclosure is not limited to these implementations. Other variations and implementations of the present disclosure will be obvious to those skilled in the art.

[0030] The phrases "in one implementation" or "in some implementations" may each refer to one or more of the same or different implementations. The term "coupled" is defined as directly connected or indirectly connected through intermediate components, and is not necessarily limited to physical connections. The expression "at least one of A, B, and C" or "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."

[0031] The terms "system" and "network" may be used interchangeably.

[0032] For the purpose of explanation and non-limiting, specific details such as functional entities, technologies, protocols and standards are set forth to provide an understanding of the present disclosure. In other examples, detailed disclosures of well-known methods, technologies, systems and architectures are omitted to avoid obscuring the present disclosure with unnecessary details.

[0033] Those skilled in the art will immediately recognize that any network function(s) or algorithm(s) disclosed may be implemented by hardware, software, or a combination of software and hardware. The disclosed functions may correspond to a module, which may be software, hardware, firmware, or any combination thereof.

[0034] 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 can be programmed with corresponding executable instructions and execute the disclosed (multiple) network functions or (multiple) algorithms.

[0035] 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 oriented toward software installed and executed on computer hardware, alternative implementations implemented as firmware or hardware or a combination of hardware and software are fully 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), cassettes, magnetic tape, disk storage, or any other equivalent medium capable of storing computer readable instructions.

[0036] 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), 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 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) via a RAN established by one or more BSs.

[0037] A UE may include, but is not limited to, a mobile station, a mobile terminal or device, or a user communication radio terminal. A UE may be a portable radio device, including, but 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. A UE is configured to receive and send signals to one or more cells in a RAN over an air interface.

[0038] The BS may provide communication services according to at least 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) of LTE 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.

[0039] 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 associated with 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.

[0040] A BS may provide radio coverage for a particular geographical area using multiple cells forming a RAN. The BS supports the operation of cells. Each cell is operable to provide service to at least one UE within its radio coverage.

[0041] Each cell (usually referred to as a serving cell) can provide services to serve one or more UEs within its radio coverage, so that each cell schedules downlink (DL) and optionally uplink (UL) resources to at least one UE within its radio coverage for DL ​​and optionally UL packet transmission. A BS can communicate with one or more UEs in a radio communication system via multiple cells.

[0042] The cell can allocate side link (SL) resources to support ProSe or V2X services. Each cell can have overlapping coverage areas with other cells.

[0043] The frame structure for NR supports flexible configuration to accommodate various next-generation (e.g., 5G) communication requirements, such as enhanced mobile broadband (eMBB), massive machine type communication (mMTC), and ultra-reliable and low-latency communication (URLLC), while meeting high reliability, high data rate, and low latency requirements. The Orthogonal Frequency Division Multiplexing (OFDM) technology in the 3rd Generation Partnership Project (3GPP) can serve as a baseline for the NR waveform. Scalable OFDM parameter sets can also be used, such as adaptive subcarrier spacing, channel bandwidth, and cyclic prefix (CP).

[0044] Some examples of terms used in this disclosure are as follows:

[0045] Primary Cell (PCell): PCell is a Master Cell Group (MCG) cell operating on a primary frequency, in which a UE performs an initial connection establishment procedure or initiates a connection re-establishment procedure. PCell is a Special Cell (SpCell) of an MCG.

[0046] Primary SCG cell (PSCell): For dual connectivity (DC) operation, the PSCell is a secondary cell group (SCG) cell in which the UE performs random access when performing a synchronous reconfiguration procedure. 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.

[0047] 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.

[0048] 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.

[0049] Serving cell: For a UE in RRC_CONNECTED not configured with CA / DC, there is only one serving cell including the primary cell. For a UE in RRC_CONNECTED configured with CA / DC, the term "serving cell" is used to denote the set of cells including the special cell(s) and all secondary cells.

[0050] Master Cell Group (MCG): In MR-DC, MCG is a group of serving cells associated with a master node, including a SpCell (PCell) and optionally one or more SCells.

[0051] Master Node (MN): In MR-DC, the MN or master node is the radio access node that provides the control plane connection with 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 a source node or a target node for a UE.

[0052] Secondary Cell Group (SCG): In MR-DC, an SCG is a group of serving cells associated with a secondary node, including a SpCell (PSCell) and optionally one or more SCells.

[0053] Secondary Node (SN): In MR-DC, the SN is a radio access node with no control plane connection to the core network, providing additional resources for the UE. It can be an en-gNB (in EN-DC), secondary ng-eNB (in NE-DC), or secondary gNB (in NR-DC and NGEN-DC). In some implementations, the SN or secondary node may include a source node or a target node for the UE.

[0054] 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 procedure is usually triggered by a measurement report from the UE. For example, when the quality of the serving cell (e.g., signal strength and / or service quality) is lower than a preconfigured threshold and the quality of the neighboring cell (e.g., signal strength and / or service quality) is higher than the preconfigured threshold, the UE may send a measurement report to the source base station under the serving cell based on the received measurement configuration. After 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.

[0055] 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 may be mainly determined by the latency 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 the real world, the quality of the serving cell may drop rapidly in a short period of time, and the UE may not be able to successfully receive the handover command message before the quality of the serving cell drops significantly. Therefore, the UE may detect a radio link failure. Therefore, in response to the detected radio link failure, the UE may initiate a radio resource control (RRC) connection reestablishment process, which in turn may cause a considerable service interruption time.

[0056] In next generation wireless networks (e.g. 5G NR networks), due to the large number of antenna beamforming at higher frequencies, the service cell quality may degrade faster, especially when narrow beams are used to serve the UE. Blocking is another issue in NR deployments.

[0057] 3GPP has introduced the concept of Conditional Handover (CHO) to improve the reliability of the overall handover process. The CHO process can be regarded as a supplementary process to the traditional handover process, which helps to reduce the handover failure rate.

[0058] In order to execute the conditional reconfiguration command, the UE may evaluate the triggering condition(s) 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 condition is 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 condition of the conditional reconfiguration command is met.

[0059] CHO can help improve the reliability of the overall handover process. Applying concepts similar to CHO may also be beneficial for 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 can be completed in advance.

[0060] 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 behavior of the UE may be different. 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). Some information or guidance (e.g., in an implicit way) may be required for the UE to determine what to do when the conditional reconfiguration command is executed. In addition, due to different purposes, the principles for applying CHO (or conditional configuration) to PCell changes and the principles for applying CHO (or conditional configuration) to PSCell addition / change may be different.

[0061] The conditional reconfiguration process can be a reconfiguration process performed by the UE when one or more execution conditions (also referred to as triggering conditions) are met. There are three types of conditional reconfiguration. The first type is conditional reconfiguration for PCell change, also referred to as conditional reconfiguration for handover or conditional handover (CHO). The second type is conditional reconfiguration for PSCell change, also referred to as conditional PSCell change (CPC). The third type is conditional reconfiguration for PSCell addition, also referred to as conditional PSCell addition (CPA).

[0062] 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) after receiving the CHO configuration, and may stop evaluating the execution condition(s) once 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.

[0063] 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 both of the 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 also run in parallel.

[0064] If the UE is connected to a PCell under a MN and a PSCell under a SN (ie, in a DC setup), the UE may be handed over to a target cell in another MN, and the target cell requests to maintain the UE's serving PSCell.

[0065] However, if the source MN initially prepares the CPC of the UE from the source SN to the target SN, the source MN initiates CHO preparation of the target MN, where the target MN provides CHO-DC configuration, i.e., it prepares the target SN with an incremental (i.e., partial) configuration for CHO preparation (the source MN also prepares for CPC). In this case, a CHO-CPC coexistence validity problem occurs because if CPC is executed first, the CHO-DC configuration is invalidated, i.e., CPC execution causes a serving SN change, and the SN incremental configuration of the CHO-DC configuration cannot be applied to the new serving SN. In order to avoid SN failure, CHO-DC preparation is re-initiated at the cost of additional signaling overhead and delayed CHO-DC configuration provided to the UE.

[0066] In addition, both the serving and target MNs prepare the same target SN for UE handover. Therefore, the source MN first prepares the CPC towards the target SN, and the target MN prepares the same target SN for CHO-DC handover. In this case, the target SN does not know that the same UE will be prepared during the CHO-DC of the target MN, so the target SN will double reserve the required resources even if the bearer configuration is the same.

[0067] In the given scenario, it is assumed that the source MN initially configures the UE with CPC from the source SN to the target SN. Then, the source MN initiates CHO preparation towards the target MN, where the target MN prepares CHO-DC configuration.

[0068] According to the example, in order to prevent incremental configuration and thus avoid CHO-CPC coexistence validity issues, the source MN provides existing CPC-related information to the target MN as part of the CHO request. That is, the source primary node provides existing CPC-related information to the target primary node as part of the CHO request. The existing CPC-related information can be relayed to the target secondary node so that the target primary node and the target secondary node can understand the ongoing CPC configuration. Therefore, the target secondary node can configure the complete SCG configuration prepared by the source primary node, which will be valid both before and after CPC execution. Therefore, dual resource reservation is prohibited.

[0069] Figure 1 is a schematic representation of a message flow according to an example, wherein in the context of a source primary node first preparing CPC and then initiating target primary node preparation using CHO-DC, the target primary node provides a complete SCG configuration, rather than an incremental SCG configuration, in order to prevent SCG configuration validity issues in the event of a serving secondary node change. In the example, the target primary node and the target secondary node are informed of the ongoing CPC preparation so that the target secondary node will not reserve duplicate resources for the same UE.

[0070] refer to Figure 1, in blocks 1 and 2, the source master node 103 prepares the CPC, CPC-1, for the UE 101 to change its serving SN from the source secondary node SN-1 105 to the target secondary node SN-2 107. The UE 101 evaluates the CPC-1 condition in block 2. The UE 101 sends a measurement report (3) to its source master node 103 to initiate CHO preparation of the target master node 109. The source master node 103 then sends (4) a CHO request to the target master node 109.

[0071] According to an example, as part of the CHO request message (4), the source master node also includes: the SN UE XnAP ID defined between the target secondary node SN-2 107 during the CPC-1 preparation of the UE for communication with the source master node 103 over the Xn interface. The source master node 103 also sends the ID of SN-2 (107) to the target master node 109 to indicate to the UE 101 between which source master node 103 and the secondary node the XnAP ID is defined. The target secondary node (107) is the same secondary node for which the source master node configures the CPC (i.e., it is not any arbitrary secondary node identifier).

[0072] The target master node 109 sends (5) a secondary node add request to the target SN-2 (107) to prepare the target SN-2 for CHO-DC. The target master node 109 includes the UE XnAP ID of the target SN-2 in the message because the target master node 109 knows that the target secondary node 107 needs this information (the SN-2 ID has been sent in the message (4)).

[0073] The target secondary node SN-2 (107) knows that the UE 101 configured for CPC from the source secondary node SN-1 105 to the target secondary node SN-2 107 is requested for SN addition by the target primary node 109, since the SN-2UE XnAP ID is provided as part of the SN Add Request message (5). Therefore, if the bearer configuration allows optimization, the target secondary node SN-2 107 does not reserve resources twice for the same UE 101. In addition, it provides a complete SCG configuration instead of an incremental configuration, because if the CPC is performed by the UE 101, the incremental configuration may become invalid, but the complete SCG configuration will not.

[0074] The target secondary node SN-2 107 confirms (7) that it is ready for the requested UE 101 and sends (7) the complete SCG configuration it has generated. The target primary node 109 then generates (8) a CHO-DC configuration, which includes: the MCG configuration for the target primary node 109 and the complete SCG configuration for the target secondary node 107.

[0075] The target master node 109 sends (9) a Handover Request Confirmation message to the source master node 103. It also indicates that the CHO-DC configuration will be valid even if the CPC-1 prepared by the source master node 103 is executed by the UE 101. This enables the source master node 103 to avoid canceling the CHO if the CPC is executed first.

[0076] UE 101 sends (11) an RRC Reconfiguration Complete message to source master node 103, which relays this information (12) to target master node 109. After receiving CHO-DC, UE 101 starts monitoring CHO execution conditions in block 13. If CPC-1 conditions are met in block 14, UE 101 performs CPC-1, i.e., it switches (15) from source secondary node SN-1 105 (old secondary node 16) to target secondary node SN-2 107 (new secondary node 17) without changing its source master node. As indicated in message 10, UE 101 retains the CHO-DC configuration because it will still be valid due to the complete SCG configuration.

[0077] According to an example, since the target master node 109 needs to be notified about the serving secondary node change, the source master node 103 may notify (19) the target master node 109. In another example, the target secondary node SN-2 107 (now the new secondary node 17) may notify (20) the target master node 109.

[0078] Since the CHO-DC configuration is valid after CPC-1 is executed, UE 101 can continue to monitor the CHO-DC condition (21). If the condition is met (22), UE 101 can perform CHO to the target master node 109 and apply the complete SCG configuration to connect the target secondary node SN-2 with the new configuration (22-28). During the UE context release (27), if the CHO has the same target SN, the secondary node 107 can be notified not to release the UE context. Such an indication can be sent from the target master node 109 to the source master node 103, and from the source master node to the target secondary node 107. In the example, this can be an alternative to 4-5 to avoid the UE context being released by the target secondary node. Alternatively, the indication can be sent from the source master node 103 to the target secondary node SN-2107 (28) to avoid the UE context being released.

[0079] 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 a smart device (e.g., a smartphone), and / or a network entity such as, for example, a base station or node in a radio network. The modules of the apparatus (e.g., a module 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 methods and modules may all be executed by a single processor or divided into multiple processors.

[0080] Figure 2 201. The machine 200 may be, for example, a node in a radio network. For example, the machine 200 may be a source master node 103 or a target master node 109 in a radio network 201. The machine 200 includes a processor 203 and a memory 205, the memory 205 storing instructions 207 executable by the processor 203. The machine includes a storage 209, which may be used to store data 211 representing one or more of a CHO configuration, a CHO configuration with DC, a CPC configuration, an identifier for a UE and / or a node, etc., as described above. In the example, the instructions 207 executable by the processor 203 may cause the machine 200 to: receive a conditional handover CHO request message from a source master node, the CHO request message including: a unique identifier for a UE defined between a source master node and a target secondary node, and an identifier for a target secondary node, and send a unique identifier for the UE to the target secondary node as part of a secondary node add request for a CHO with DC preparation.

[0081] In an example, the instructions 207 executable by the processor 203 may cause the machine 200 to: receive a confirmation message from a target secondary node to confirm CPC preparation for the UE, the confirmation message including a complete secondary cell group SCG configuration.

[0082] The machine 200 may implement a method for preparing a handover of a user equipment UE in a dual-connection DC, wherein the handover is between corresponding primary cells PCell of a source primary node and a target primary node and corresponding primary secondary cells PSCell of a source secondary node and a target secondary node. In one implementation, the machine is a target primary node, and the instructions are executable by a processor of the target primary node.

[0083] In some examples, some methods can be performed in a cloud computing or network-based environment. A cloud computing environment can 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.) can be accessed, for example, through a web browser or other remote interface of a user device. The various functions described herein can be provided through a remote desktop environment or any other cloud-based computing environment.

[0084] Although various embodiments have been described and / or illustrated in the context of a fully functional computing system herein, one or more of these exemplary embodiments can be distributed as various forms of program products, regardless of the specific type of the computer-readable storage medium that is used to actually perform the distribution. The embodiments disclosed herein can also be implemented using software modules that perform certain tasks. These software modules can include scripts, batch processing or other executable files, which can be stored on a computer-readable storage medium or in a computing system. In some embodiments, these software modules can configure a computing system to perform one or more exemplary embodiments disclosed herein. In addition, one or more of the modules described herein can convert data, physical devices and / or representations of physical devices from one to another.

[0085] Figure 3 is a flow chart of a method according to an example. Figure 3 In the example of , the method is applicable to preparing a handover of a user equipment UE in a dual connection DC, wherein the handover is between the corresponding primary cells PCell of the source primary node and the target primary node and the corresponding primary secondary cells PSCell of the source secondary node and the target secondary node. In block 301, a conditional handover CHO request message is received by the target primary node from the source primary node, the CHO request message including: a unique identifier for the UE defined between the source primary node and the target secondary node, and an identifier for the target secondary node. The target secondary node in question is a secondary node for which the source primary node has configured CPC.

[0086] In block 303, a unique identifier for the UE is sent to the target secondary node as part of a secondary node add request for CHO with DC preparation. In block 305, a confirmation message (by the target primary node) confirming CPC preparation for the UE is received from the target secondary node, the confirmation message including the complete secondary cell group SCG configuration.

[0087] The foregoing description has been provided to enable those 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 are possible without departing from the spirit and scope of the present disclosure. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. In 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 primary node of a radio network, for preparing a handover of a user equipment UE in a dual connectivity DC, wherein the handover is between respective primary cells PCell of a source primary node and a target primary node and respective primary secondary cells PSCell of a source secondary node and a target secondary node, the method comprising: receiving a conditional handover CHO request message from the source primary node, the CHO request message including: a unique identifier for the UE defined between the source primary node and the target secondary node, and an identifier for the target secondary node; sending the unique identifier for the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation; A confirmation message is received from the target secondary node to confirm CPC preparation for the UE, the confirmation message including a complete secondary cell group (SCG) configuration.

2. The method according to claim 1, further comprising: A handover request confirmation message is sent to the source master node, the handover request confirmation message including data representing the following items: an indication that the CHO with DC contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after the execution of the ongoing CPC configuration of the UE.

3. The method according to claim 1 or 2, further comprising: A confirmation of UE switching from the source SN to the target SN is received from the source master node.

4. The method according to claim 1 or 2, further comprising: A confirmation of UE handover from the source secondary node to the target secondary node is received from the target SN.

5. A method according to any preceding claim, wherein the complete SCG configuration is valid before and after execution of a UE handover from the source secondary node to the target secondary node.

6. A source master node in a radio network, the source master node comprising: processor; A memory 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, so that the source master node: sending a CHO request message to a target primary node of the radio network, the CHO request message comprising: a unique identifier for the UE defined between the source primary node and the target secondary node, and an identifier for the target secondary node; as well as A handover request confirmation message is received from a target master node of the radio network, the handover request confirmation message including data representing the following items: an indication that the CHO configuration contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after the execution of the ongoing CPC configuration of the UE.

7. The source master node according to claim 6, wherein the program code further comprises one or more instructions, so that the source master node: Sending a confirmation of UE switching to the target master node.

8. The source master node according to claim 6 or 7, wherein the program code further comprises one or more instructions, so that the source master node: Data including: an indication that the CHO with the DC configuration is to be maintained after execution of the CPC is sent to the UE.

9. A machine-readable storage medium encoded with instructions for preparing a handover of a user equipment UE in a dual-connectivity DC, wherein the handover is between respective primary cells PCell of a source primary node and a target primary node and respective primary secondary cells PSCell of a source secondary node and a target secondary node, wherein the instructions are executable by a processor of the target primary node, thereby causing the target primary node to: A conditional handover CHO request message is received from the source master node, the CHO request message comprising: a unique identifier for the UE defined between the source primary node and the target secondary node, and an identifier for the target secondary node; sending the unique identifier for the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation; A confirmation message is received from the target secondary node to confirm CPC preparation for the UE, the confirmation message including a complete secondary cell group (SCG) configuration.

10. The machine-readable storage medium of claim 9, further encoded with instructions executable by the processor of the target host node, thereby causing the target host node to: A handover request confirmation message is sent to the source master node, the handover request confirmation message including data representing the following items: an indication that the CHO with DC contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after the execution of the ongoing CPC configuration of the UE.

11. The machine-readable storage medium according to claim 9 or 10, further encoded with instructions executable by a processor of a target master node, so that the target master node: A confirmation of UE switching from the source SN to the target SN is received from the source master node.

12. The machine-readable storage medium of claim 9 or 10, further encoded with instructions executable by the processor of the target host node, so that the target host node: A confirmation of UE handover from the source secondary node to the target secondary node is received from the target SN.

13. A target master node in a radio network, the target master node comprising: processor; A memory 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, so that the target master node: receiving a conditional handover CHO request message from a source primary node, the CHO request message including: a unique identifier for the UE defined between the source primary node and a target secondary node, and an identifier for the target secondary node; sending the unique identifier for the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation; A confirmation message is received from the target secondary node to confirm CPC preparation for the UE, the confirmation message including a complete secondary cell group (SCG) configuration.

14. The target master node according to claim 13, wherein the program code further comprises one or more instructions, so that the target master node: A handover request confirmation message is sent to the source master node, the handover request confirmation message including data representing the following items: an indication that the CHO with DC contains a complete SCG configuration, and an indication that the provided configuration will be maintained by the UE after the execution of the ongoing CPC configuration of the UE.

15. The target master node according to claim 13 or 14, wherein the program code further comprises one or more instructions, so that the target master node: A confirmation of UE switching from the source SN to the target SN is received from the source master node.

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