Coexistence of conditional switching with 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 performed 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 comprises: receiving a conditional handover (CHO) request message from a source master node, the CHO request message comprising: a unique identifier of a UE defined between the source master node and a target secondary node, and an identifier of the target secondary node; transmitting, to a target secondary node, a unique identifier of the UE as part of a secondary node addition request for a CHO having a DC preparation; and receiving a first delta secondary cell group (SCG) configuration and a second delta SCG configuration from the target secondary node, each of the first delta SCG configuration and the second delta SCG configuration being generated to accommodate a different CPC execution state.

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] 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. 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. As a result, it 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 (one or more) execution conditions upon receiving the CHO configuration, and may stop evaluating (one or more) execution conditions 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] The aforementioned and other objects are achieved by the features of the independent claims.

[0006] Further forms of implementation 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, the method being used to prepare for switching of a user equipment UE in a dual-connection DC, wherein the switching is performed between corresponding primary cells PCells of a source master node and a target master node and corresponding primary secondary cells PSCells of a source secondary node and a target secondary node, the method comprising: receiving a conditional switching CHO request message from the source master node, the CHO request message comprising: a unique identifier of the UE defined between the source master node and the target secondary node, and an identifier of the target secondary node; sending the unique identifier of the UE to the target secondary node as part of a secondary node add request for a CHO with DC preparation; and receiving a first incremental secondary cell group SCG configuration and a second incremental SCG configuration from the target secondary node, each of the first incremental SCG configuration and the second incremental SCG configuration being generated to accommodate different CPC execution states.

[0008] In an implementation of the first aspect, the first incremental SCG configuration may be generated for an execution state in which an ongoing CPC configuration is not executed. The second incremental SCG configuration may be generated for an execution state in which an ongoing CPC configuration is executed. The method may further include: generating a first CHO with a DC configuration based on the first incremental SCG configuration; and when the ongoing CPC configuration is not executed, using the first CHO with a DC configuration, the ongoing CPC configuration is configured by the source master node, and defines a switch from a source PSCell of a source secondary node to a target PSCell of a target secondary node. The method may further include: generating a second CHO with a DC configuration based on the second incremental SCG configuration; and when the ongoing CPC configuration is executed, using the second CHO with a DC configuration, the ongoing CPC configuration is configured by the source master node, and defines a switch from a source PSCell of a source secondary node to a target PSCell of a target secondary node. The method may also include: sending at least one of the first CHO and the second CHO with a DC configuration to the source master node; and providing the source master node with an indication that the second CHO with a DC configuration includes a temporary SCG configuration, which will be used in the event that the UE performs a CPC, which is prepared by the source master node for the UE to switch from the source PSCell of the source secondary node to the target PSCell of the target secondary node. The method may also include: receiving a confirmation from the source master node that the UE switches from the source secondary node to the target secondary node. The method may also include: receiving a confirmation from the target secondary node that the UE switches from the source secondary node to the target secondary node. The method may also include: providing a corresponding condition for selecting one of the first CHO and the second CHO with a DC configuration. The method may also include: selecting one of the first CHO and the second CHO with a DC configuration based on the condition.

[0009] A second aspect of the present disclosure provides a target master node of 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 to enable the target master node to: receive a conditional switching CHO request message from a source master node, the CHO request message comprising: a unique identifier of a UE defined between the source master node and a target secondary node, and an identifier of the target secondary node; send the unique identifier of the UE to the target secondary node as part of a secondary node add request for a CHO with DC preparation; and receive a first incremental secondary cell group SCG configuration and a second incremental SCG configuration from the target secondary node, each of the first incremental SCG configuration and the second incremental SCG configuration being generated to accommodate different CPC execution states.

[0010] In an implementation of the second aspect, the program code may also include one or more instructions to enable the target master node to: generate a first CHO with a DC configuration based on a first incremental SCG configuration for use when an ongoing CPC configuration is not executed, the ongoing CPC configuration is configured by the source master node, and defines switching from a source PSCell of a source secondary node to a target PSCell of a target secondary node. The program code may also include one or more instructions to enable the target master node to: generate a second CHO with a DC configuration based on a second incremental SCG configuration for use when an ongoing CPC configuration is executed, the ongoing CPC configuration is configured by the source master node, and defines switching from a source PSCell of a source secondary node to a target PSCell of a target secondary node.

[0011] A third aspect of the present disclosure provides a machine-readable storage medium, which encodes instructions for preparing switching of a user equipment UE in a dual-connection DC, wherein the switching is performed between corresponding primary cells PCells of a source primary node and a target primary node and corresponding primary secondary cells PSCells 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: sends at least one of a first CHO and a second CHO with a DC configuration to the source primary node; and provides an indication to the source primary node that the second CHO with a DC configuration includes a temporary SCG configuration, which will be used in the event that the UE performs CPC, which is prepared by the source primary node for the UE to switch from a source PSCell of a source secondary node to a target PSCell of a target secondary node.

[0012] In an implementation of the third aspect, the machine-readable storage medium may also be encoded with instructions executable by a processor of the target master node to enable the target master node to: generate corresponding conditions for selecting one of the first CHO and the second CHO having a DC configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0014] Figure 1 is a schematic diagram of a message flow according to an example;

[0015] Figure 2 is a schematic diagram of a message flow according to an example;

[0016] Figure 3 is a schematic diagram of a machine according to an example; and

[0017] Figure 4 is a flow chart of a method according to an example. DETAILED DESCRIPTION

[0018] 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.

[0019] 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 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.

[0020] The terminology used to describe the embodiments herein is not intended to limit the scope. The articles "one", "an" and "the (described)" are in the singular form 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, the elements referred to in 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", "include" and / or "include" 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 an associated object, and represents that three kinds of relationships can exist, so that A and / or B can indicate that A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally represents that it is an "or" relationship between associated objects.

[0021] 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 in an idealized or overly formal meaning.

[0022] 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 the implementation. However, the present disclosure is not limited to these implementations. Other variations and implementations of the present disclosure are obvious to those skilled in the art.

[0023] 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 intervening 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."

[0024] The terms "system" and "network" are used interchangeably.

[0025] For the purpose of explanation and non-limitation, 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 disclosure of well-known methods, technologies, systems and architectures is omitted to avoid obscuring the present disclosure with unnecessary details.

[0026] 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, which can be software, hardware, firmware, or any combination thereof.

[0027] 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 network functions or algorithms.

[0028] 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), cassettes, magnetic tape, disk storage, or any other equivalent medium capable of storing computer readable instructions.

[0029] 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 network connectivity. 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.

[0030] UE may include, but is not limited to, a mobile station, a mobile terminal or device, or a user communication radio terminal. 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. UE is configured to receive and send signals to one or more cells in the RAN over an air interface.

[0031] The BS may provide communication services based on at least one 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) based on basic Wideband Code Division Multiple Access (W-CDMA) commonly referred to as 3G, High Speed ​​Packet Access (HSPA), LTE, LTE-A, Evolved LTE (eLTE) (i.e., 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.

[0032] 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.

[0033] A BS may provide radio coverage to a specific geographic 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.

[0034] 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.

[0035] A cell may allocate sidelink (SL) resources for supporting Proximity Services (ProSe) or Vehicle-to-Everything (V2X) services. Each cell may have a coverage area that overlaps with other cells.

[0036] 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.

[0037] Some examples of terms used in this disclosure are as follows:

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Serving cell: For a UE in RRC-CONNECTED without CA / DC configured, there is only one serving cell including the primary cell. For a UE in RRC-CONNECTED state with CA / DC configured, the term "serving cell" is used to refer to the set of cells including the dedicated cell(s) and all secondary cells.

[0043] Master Cell Group (MCG): In MR-DC, MCG is a group of serving cells associated with a master node, including SpCell (PCell) and optionally one or more SCells.

[0044] 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.

[0045] Secondary Cell Group (SCG): In MR-DC, SCG is a group of serving cells associated with a secondary node, including SpCell (PSCell) and optionally one or more SCells.

[0046] 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), 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 target node of the UE.

[0047] 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). The 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.

[0048] 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 waiting time of the backhaul (e.g., 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 may 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 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 results in a large amount of service interruption time.

[0049] In next generation wireless networks (e.g., 5G NR networks), with extensive antenna beamforming in higher frequency bands, serving cell quality may degrade even faster, especially when narrow beams are used to serve UEs. Blocking is another issue in NR deployments.

[0050] 3GPP has 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.

[0051] 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.

[0052] 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 can be completed in advance.

[0053] 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, the principles of applying CHO (or conditional configuration) to PCell changes, and the principles of applying CHO (or conditional configuration) to PSCell addition / change may differ depending on the purpose.

[0054] 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 known as conditional reconfiguration for switching or conditional switching (CHO). The second type is conditional reconfiguration for PSCell change, also known as conditional PSCell change (CPC). The third type is conditional reconfiguration for PSCell addition, also known as conditional PSCell addition (CPA).

[0055] 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) 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.

[0056] 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 also run in parallel.

[0057] In the case where the UE is connected to a PCell under a MN and a PSCell under a SN (ie, in a DC setting), it is possible for the UE to hand over to a target cell in another MN, and it is possible for the target cell to request maintenance of the UE's serving PSCell.

[0058] 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 is also prepared for CPC). In this case, since the CHO-DC configuration becomes invalid if CPC is performed first, a CHO-CPC coexistence validity problem occurs, i.e., CPC execution causes a change in the serving SN, 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 expense of giving the UE additional signaling overhead and delayed CHO-DC configuration.

[0059] In addition, both the serving MN and the target MN prepare the same target SN for UE handover. Therefore, the source MN first prepares CPC toward 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.

[0060] In the given scenario, it is assumed that initially the source MN configures CPC from the source SN to the target SN for the UE. Then, the source MN initiates CHO preparation to the target MN, where the target MN prepares CHO-DC configuration.

[0061] According to one example, the target master node and the target secondary node may be notified of the ongoing CPC preparation of the source master node. The target secondary node may provide two incremental SCG configurations. The first configuration is valid before CPC execution, and the second configuration is valid after CPC execution. Since the second configuration is generated by considering CPC execution and is valid after CPC execution, if CPC is executed, the UE may be configured to maintain the second configuration.

[0062] In one implementation, the target secondary node and the target primary node may prepare two incremental SCG configurations. However, in addition, the target primary node may be configured with two conditions (one condition in each incremental SCG configuration). In this way, the UE can check the serving PSCell and decide which CHO-DC configuration to select. This ensures that the UE uses the correct configuration before and after CPC execution. That is, in the case of CHO-CPC coexistence, the target secondary node is not prohibited from providing incremental configuration. Instead, the target secondary node may provide two incremental configurations. One incremental SCG configuration may be provided for the secondary node currently serving the UE, and another incremental SCG configuration (temporary) may be provided for a candidate target secondary node that may be a serving secondary node in the future (for example, if CPC is executed).

[0063] Figure 1 is a schematic representation of a message flow according to an example. In boxes 1 and 2, the source master node 103 prepares a 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. In box 2, the UE 101 evaluates the CPC-1 condition. 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.

[0064] According to one 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 between which source master node 103 and the secondary node the UE 101 XnAP ID is defined. The target secondary node (107) is the same secondary node as the source master node configured the CPC to the target secondary node (i.e., it is not any arbitrary secondary node identifier).

[0065] The target master node 109 sends (5) a secondary node add request to the target SN-2 (107) to prepare the target SN-2 with 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 (SN-2 ID is sent in message (4)).

[0066] 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 due to the SN-2UE XnAP ID provided as part of the SN Add Request message (5). Therefore, if the bearer configuration allows optimization (6), the target secondary node SN-2 107 does not reserve double resources for the same UE 101. That is, the target secondary node 107 can optimize resource allocation because it knows that the UE 101 is the same UE that has been prepared for CPC.

[0067] The target secondary node 107 then provides the two incremental configurations to the target primary node 109 (7). In one example, the two incremental configurations may be provided as part of a secondary node add request message acknowledgment sent from the target secondary node 107 to the target primary node 109.

[0068] If the source primary node 103 CPC is not executed, that is, if the serving secondary node (of UE 101) is still the source secondary node 105, the first incremental configuration (incremental SCG configuration 1 (default)) may be the configuration to be applied during CHO-DC. If CPC-1 is not executed, this configuration is valid (box 1).

[0069] The second incremental configuration (incremental SCG configuration 2) may be the configuration to be applied during CHO-DC if the source primary node 103 CPC is performed, ie if the serving secondary node (of UE 101) is the target secondary node 107. This is valid if CPC-1 is performed.

[0070] Therefore, the target master node 109 compiles two CHO-DC configurations in box 8. The first configuration is based on incremental SCG configuration 1, and the second configuration is based on incremental SCG configuration 2. Therefore, there are two configurations on the UE side. In this way, the UE 101 will always have a valid configuration before or after the CPC of the source master node is executed. That is, in one example, if the CPC of the source master node is not executed, the first CHO-DC configuration is valid, and if the CPC of the source master node is executed, the second CHO-DC configuration is valid.

[0071] The target master node sends (9) two CHO-DC configurations to the source master node 103 and indicates that the second configuration contains a temporary SCG configuration, which is used if the CPC of the source master node (CPC-1) is executed.

[0072] The source master node 103 then forwards (10) the RRC reconfiguration of the target master node 109 to the UE 101 and indicates to the UE 101 that it maintains and activates the second configuration only after performing CPC-1.

[0073] UE 101 sends (11) an RRC reconfiguration complete message to source master node 103, and source master node 103 relays (12) the information to target master node 109. After receiving CHO-DC, UE 101 starts monitoring CHO execution conditions in box 13. If CPC-1 conditions are met in box 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 primary node.

[0074] After the serving secondary node is changed from source SN-1 105 to target SN-2 107 by performing CPC-1 of the source primary node, UE 101 will retain the second CHO-DC configuration prepared by the target primary node for the UE to use after performing CPC on target SN-2 107.

[0075] According to one example, when the target master node 109 needs to be notified about a change in the serving source node, 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.

[0076] 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 towards the target primary node 109 and apply the full 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 that the UE context may not be released. This indication can be sent from the target primary node 109 to the source primary node 103, or from the source primary node to the target secondary node 107. In one 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 (28) from the source primary node 103 to the target secondary node SN-2 107 to avoid the UE context being released. UE 101 will use the second CHO-DC configuration during CHO execution because this is the configuration that the UE has retained and is valid after CPC-1 is executed.

[0077] Depending on the CPC execution state, the UE 101 is therefore instructed to select one of the provided CHO-DC configurations that is valid at the CHO-DC execution time.

[0078] In one implementation, as described above, the target master node may prepare two incremental SCG configurations. However, the selection criteria for the configuration may be based on the serving PSCell of the UE when CHO-DC is executed.

[0079] Figure 2 is a diagram of the message flow according to the example. Figure 1 , in blocks 1 and 2, the source master node 103 prepares 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. In block 2, the UE 101 evaluates the CPC-1 condition. 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.

[0080] According to one example, as part of the CHO request message (4), the source master node also includes the SN UE XnAP ID that was assigned at the target secondary node SN-2 107 during the CPC 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 at which secondary node the UE 101 XnAP ID was assigned. The target secondary node (107) is the same secondary node as the source master node configured the CPC to the target secondary node (i.e., it is not any arbitrary secondary node identifier).

[0081] The target master node 109 sends (5) a Secondary Node Add Request to prepare the target SN-2 with CHO-DC to the target SN-2 107. 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 is sent in the message (4)).

[0082] 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 due to the SN-2UE XnAP ID provided as part of the SN Add Request message (5). Therefore, if the bearer configuration allows optimization (6), the target secondary node SN-2 107 does not reserve double resources for the same UE 101. That is, the target secondary node 107 can optimize resource allocation because it knows that the UE 101 is the same UE that has been prepared for CPC.

[0083] The target secondary node 107 then provides the two incremental configurations to the target primary node 109 (7). In one example, the two incremental configurations may be provided as part of a secondary node add request message acknowledgment sent from the target secondary node 107 to the target primary node 109.

[0084] If the source primary node 103 CPC is not executed, that is, if the serving secondary node (of UE 101) is still the source secondary node 105, the first incremental configuration (incremental SCG configuration 1 (default)) may be the configuration to be applied during CHO-DC. If CPC-1 is not executed, this configuration is valid (box 1).

[0085] The second incremental configuration (incremental SCG configuration 2) may be the configuration to be applied during CHO-DC if the source primary node 103 CPC is performed, ie if the serving secondary node (of UE 101) is the target secondary node 107. This is valid if CPC-1 is performed.

[0086] As described above, the target master node compiles two CHO-DC configurations in block 8, wherein the first configuration is based on delta SCG configuration 1, and the second configuration is based on delta SCG configuration 2. Furthermore, in one example, the target master node defines additional conditions for each configuration, such that when the CHO-DC conditions are met, the UE 101 will check the serving PSCell to select one of the CHO-DC configurations.

[0087] According to an example, if the serving PSCell is the PSCell of the source primary node 103 served by the UE 101 before the CPC-1 execution, the UE 101 will select the first CHO-DC configuration. If the serving PSCell is the PSCell of the target secondary node 107 (SN-2) after the CPC-1 execution, the UE 101 will select the second CHO-DC configuration.

[0088] The CHO-DC configuration generated by the target master node 109 is sent (9) to the source master node 103, for example as part of a handover request confirmation message, and is forwarded (10) to the UE 101, the CHO-DC configuration including a CHO-DC configuration selection condition based on the serving PSCell at the time of CHO-DC execution. The condition also indicates to the UE 101 that it should retain the CHO-DC configuration that is valid after CPC-1 execution. An RRC reconfiguration complete message (11) is sent from the UE 101 to the source master node 103, and the RRC reconfiguration complete message is forwarded (12) to the target master node 109.

[0089] UE 101 evaluates (13) CHO and CPC-1 conditions and it performs CPC-1 to change from source secondary node 105 to target secondary node 107 without changing its serving primary node. Thus, target primary node 109 is informed about the change of secondary node.

[0090] In box 13, UE 101 starts monitoring CHO execution conditions. If CPC-1 conditions are met in box 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 primary node.

[0091] The source master node 103 notifies (18) the target master node 109 that the CPC-1 execution is complete. Once the CPC-1 execution is complete, the UE 101 retains the valid CHO-DC configuration, i.e., Configuration 2, as indicated in message 10. The UE 101 may delete the CHO-DC Configuration 1 as it is invalid after the CPC-1 execution.

[0092] After CPC-1 execution has been completed, UE 101 continues to monitor the CHO condition of the target PCell towards the target master node in block 20. When the CHO condition of the target PCell towards the target master node 109 is met (block 21), UE 101 initiates the CHO execution procedure. UE 101 evaluates the CHO-DC configuration selection criteria to decide which CHO-DC configuration will be selected. Figure 2 In the example of , since CPC-1 execution has changed the serving PSCell when the CHO condition is met, UE 101 selects the second CHO-DC configuration (configuration 2), where the incremental SCG configuration of configuration 2 is valid for the current serving PSCell. Figure 2 The final part of the process shown in Figure 1 Same as described.

[0093] 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. The method and modules may be executed entirely by a single processor or divided between several processors.

[0094] Figure 3 is a schematic diagram of a machine according to an example. The machine 300 can be, for example, a node in a radio network. For example, the machine 300 can be a target master node 109 in a radio network 301. The machine 300 includes a processor 303 and a memory 305 for storing instructions 307 executable by the processor 303. The machine includes a storage device 309, which can 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, etc., as described above. The instructions 307 executable by the processor 303 can cause the machine 300 to: send at least one of a first CHO and a second CHO with a DC configuration to a source master node; and provide an indication to the source master node that the second CHO with a DC configuration includes a temporary SCG configuration, which will be used in the event that the UE executes the CPC, which is prepared by the source master node for the UE to switch from a source PSCell of a source secondary node to a target PSCell of a target secondary node.

[0095] Therefore, the machine 300 can implement a method for preparing a handover of a user equipment UE in a dual connection DC, wherein the handover is performed between the corresponding primary cells PCells of the source primary node and the target primary node and the corresponding primary secondary cells PSCells of the source secondary node and the target secondary node. In one implementation, the machine is the target primary node, and the instruction can be executed by a processor of the target primary node.

[0096] 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 through, for example, 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.

[0097] Although various embodiments are described and / or shown in the context of a fully functional computing system herein, one or more of these exemplary embodiments may be distributed as process products in various forms, regardless of the specific type of computer-readable storage medium used to actually perform the distribution. The embodiments disclosed herein may also be implemented using software modules that perform specific tasks. These software modules may include scripts, batches, or other executable files that may be stored on a computer-readable storage medium or in a computing system. In some embodiments, these software modules may configure a computing system to perform one or more exemplary embodiments disclosed herein. In addition, one or more modules described herein may convert data, physical devices, and / or representations of physical devices from one form to another.

[0098] 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 corresponding primary cells PCells of a source master node and a target master node and corresponding primary secondary cells PSCells of a source secondary node and a target secondary node.

[0099] In block 401, the target master node receives a conditional handover CHO request message from the source master node, the CHO message including: a unique identifier of a UE defined between the source master node and the target secondary node, and an identifier of the target secondary node, which is a secondary node with which the source master node has configured CPC.

[0100] In block 403, the unique identifier of the UE is sent to the target secondary node as part of a secondary node add request for CHO with DC preparation. In block 405, a first incremental secondary cell group SCG configuration and a second incremental SCG configuration are received from the target secondary node, each of the first incremental SCG configuration and the second incremental SCG configuration being generated to accommodate different CPC execution states.

[0101] 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 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 master node of a radio network, the method being used to prepare a handover of a user equipment UE in a dual connectivity DC, wherein the handover is performed between respective primary cells PCells of a source master node and a target master node and respective primary secondary cells PSCells 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 of the UE defined between the source primary node and the target secondary node, and an identifier of the target secondary node; sending the unique identifier of the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation; A first incremental secondary cell group (SCG) configuration and a second incremental SCG configuration are received from the target secondary node, each of the first incremental SCG configuration and the second incremental SCG configuration being generated to accommodate different CPC execution states.

2. The method of claim 1, wherein the first incremental SCG configuration is generated for an execution state in which an ongoing CPC configuration is not executed.

3. The method according to claim 1 or 2, wherein the second incremental SCG configuration is generated for an execution state of an ongoing CPC configuration being executed.

4. The method according to claim 2, further comprising: generating a first CHO having a DC configuration based on the first incremental SCG configuration; as well as The first CHO with DC configuration is used when an ongoing CPC configuration is not performed, the ongoing CPC configuration being configured by the source primary node and defining a handover from the source PSCell of the source secondary node to the target PSCell of the target secondary node.

5. The method according to claim 3, further comprising: generating a second CHO having a DC configuration based on the second incremental SCG configuration; as well as The second CHO with DC configuration is used when an ongoing CPC configuration is executed, the ongoing CPC configuration being configured by the source primary node and defining a handover from the source PSCell of the source secondary node to the target PSCell of the target secondary node.

6. The method according to claim 4 or 5, further comprising: sending at least one of the first CHO and the second CHO having a DC configuration to the source master node; as well as Providing the second CHO with DC configuration to the source master node includes an indication of a temporary SCG configuration, which will be used in the event that the UE executes the CPC, and the CPC is prepared by the source master node for the UE to switch from the source PSCell of the source secondary node to the target PSCell of the target secondary node.

7. The method according to any preceding claim, further comprising: A confirmation of the UE switching from the source secondary node to the target secondary node is received from the source primary node.

8. The method according to any one of claims 1 to 6, further comprising: A confirmation of the handover of the UE from the source secondary node to the target secondary node is received from the target secondary node.

9. The method according to any preceding claim, further comprising: A corresponding condition for selecting one of the first CHO and the second CHO having a DC configuration is provided.

10. The method according to claim 9, further comprising: Based on the condition, one of the first CHO and the second CHO having a DC configuration is selected.

11. A target master node of 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 to cause the target master node to: Receiving a conditional handover CHO request message from a source primary node, the CHO request message including: a unique identifier of a UE defined between the source primary node and a target secondary node, and an identifier of the target secondary node; sending the unique identifier of the UE to the target secondary node as part of a secondary node add request for CHO with DC preparation; A first incremental secondary cell group (SCG) configuration and a second incremental SCG configuration are received from the target secondary node, each of the first incremental SCG configuration and the second incremental SCG configuration being generated to accommodate different CPC execution states.

12. The target master node according to claim 11, wherein the program code further comprises one or more instructions to enable the target master node to: Based on the first incremental SCG configuration, a first CHO with a DC configuration is generated for use when an ongoing CPC configuration is not executed, wherein the ongoing CPC configuration is configured by the source master node and defines a switch from the source PSCell of the source secondary node to the target PSCell of the target secondary node.

13. The target master node according to claim 11 or 12, wherein the program code further comprises one or more instructions to enable the target master node to: Based on the second incremental SCG configuration, a second CHO with a DC configuration is generated for use when an ongoing CPC configuration is executed, wherein the ongoing CPC configuration is configured by the source master node and defines a switch from the source PSCell of the source secondary node to the target PSCell of the target secondary node.

14. A machine-readable storage medium encoding instructions for preparing a handover of a user equipment UE in a dual connectivity DC, wherein the handover is performed between the respective primary cells PCells of a source primary node and a target primary node and the respective primary secondary cells PSCells 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: sending at least one of a first CHO and a second CHO having a DC configuration to the source master node; and Providing the second CHO with DC configuration to the source master node includes an indication of a temporary SCG configuration, which will be used in the event that the UE executes the CPC, and the CPC is prepared by the source master node for the UE to switch from the source PSCell of the source secondary node to the target PSCell of the target secondary node.

15. The machine-readable storage medium of claim 10, further encoded with instructions executable by a processor of the target host node to cause the target host node to: A corresponding condition for selecting one of the first CHO and the second CHO having a DC configuration is generated.

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