Conditional switching in dual connectivity systems

Abstract

Various example embodiments relate to signaling and execution of conditional switching in dual connectivity systems. Different conditional switching connection configurations may be provided for client nodes such that an appropriate connection configuration may be selected upon triggering execution of conditional switching. An apparatus, method and computer program are disclosed.

Description

[0001] This application is a divisional application of the Chinese invention patent application with international application number PCT / EP2020 / 081099, international application date November 5, 2020, entering the Chinese national stage on May 7, 2022, Chinese national application number 202080077715.0, and invention name “Conditional switching in a dual connection system”. Technical Field

[0002] Various example embodiments relate generally to the field of wireless communications. In particular, some example embodiments relate to signaling and execution of conditional handover in a cellular communication network with dual connectivity. Background Art

[0003] In various wireless communication technologies such as 3GPP Long Term Evolution (LTE), 4G and 5G New Radio (NR), a client node such as a mobile phone can be handed over from one base station to another. In addition, the handover can be performed in a dual connectivity scenario, where the client node can communicate with two base stations simultaneously to increase data throughput. Summary of the invention

[0004] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0005] The exemplary embodiment provides an improved conditional switching process that can reduce the signaling overhead of the dual-connection system and improve the reliability and throughput of the dual-connection system. These benefits can be achieved by the features of the independent claims. Additional implementation forms are provided in the dependent claims, the description and the drawings.

[0006] According to one aspect, a device includes: at least one processor and at least one memory including computer program code, the at least one memory and the computer code being configured to, together with the at least one processor, enable the device to at least: establish a first connection to a source master node; establish a second connection to a source slave node; receive at least one indication of multiple conditional switching connection configurations from the source master node; detect a trigger for execution of conditional switching; select a conditional switching connection configuration from the multiple conditional switching connection configurations based on at least one condition associated with the second connection; and perform conditional switching based on the selected conditional switching connection configuration.

[0007] According to one aspect, a method includes: establishing a first connection to a source master node; establishing a second connection to a source slave node; receiving at least one indication of multiple conditional switching connection configurations from the source master node; detecting a trigger for execution of conditional switching; selecting a conditional switching connection configuration from multiple conditional switching connection configurations based on at least one condition associated with the second connection; and performing conditional switching based on the selected conditional switching connection configuration.

[0008] According to one aspect, a computer program is configured to, when executed by an apparatus, cause the apparatus to at least: establish a first connection to a source master node; establish a second connection to a source slave node; receive at least one indication of a plurality of conditional switching connection configurations from the source master node; detect a trigger for execution of a conditional switching; select a conditional switching connection configuration from a plurality of conditional switching connection configurations based on at least one condition associated with the second connection; and execute conditional switching based on the selected conditional switching connection configuration.

[0009] According to one aspect, a device includes: a component for establishing a first connection to a source master node; a component for establishing a second connection to a source slave node; a component for receiving at least one indication of multiple conditional switching connection configurations from the source master node; a component for detecting a trigger for execution of a conditional switching; a component for selecting a conditional switching connection configuration from multiple conditional switching connection configurations based on at least one condition associated with the second connection; and a component for executing conditional switching based on the selected conditional switching connection configuration.

[0010] According to one aspect, a device includes: at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer code are configured to, together with the at least one processor, enable the device to at least: receive a switching request associated with a client node from a source master node, wherein the switching request includes an indication of a source slave node associated with the client node and a switching type indicating a conditional switching; prepare multiple conditional switching connection configurations for the client node; transmit to the source master node indications of the multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations when the conditional switching is triggered.

[0011] According to one aspect, a method includes: receiving a switching request associated with a client node from a source master node, wherein the switching request includes an indication of a source slave node associated with the client node and a switching type indicating a conditional switching; preparing multiple conditional switching connection configurations for the client node; transmitting to the source master node indications of the multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations when the conditional switching is triggered.

[0012] According to one aspect, a computer program is configured to, when executed by an apparatus, cause the apparatus to at least: receive a switching request associated with a client node from a source master node, wherein the switching request includes an indication of a source slave node associated with the client node and a switching type indicating a conditional switching; prepare multiple conditional switching connection configurations for the client node; and transmit to the source master node indications of multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations when the conditional switching is triggered.

[0013] According to one aspect, a device includes: a component for receiving a switching request associated with a client node from a source master node, wherein the switching request includes an indication of a source slave node associated with the client node and a switching type indicating a conditional switching; a component for preparing multiple conditional switching connection configurations for the client node; and a component for transmitting to the source master node an indication of multiple conditional switching connection configurations and an indication of at least one condition of the conditional switching connection configuration from the multiple conditional switching connection configurations when the conditional switching is triggered.

[0014] According to one aspect, a device includes: at least one processor and at least one memory including computer program code, the at least one memory and the computer code being configured to, together with the at least one processor, enable the device to at least: transmit a switching request to a target master node, the switching request including an indication of a source slave node associated with a client node and a switching type indicating a conditional switching; receive from the target master node an indication of multiple conditional switching connection configurations of the client node and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations; transmit to the client node an indication of multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration.

[0015] According to one aspect, a method includes: transmitting a switching request to a target master node, the switching request including an indication of a source slave node associated with a client node and a switching type indicating a conditional switching; receiving from the target master node an indication of multiple conditional switching connection configurations of the client node and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations; transmitting to the client node an indication of multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration.

[0016] According to one aspect, a computer program is configured to, when executed by an apparatus, cause the apparatus to at least: transmit a switching request to a target master node, the switching request including an indication of a source slave node associated with a client node and a switching type indicating a conditional switching; receive from the target master node an indication of multiple conditional switching connection configurations of the client node and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations; and transmit to the client node an indication of multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration.

[0017] According to one aspect, an apparatus includes: a component for transmitting a switching request to a target master node, the switching request including an indication of a source slave node associated with a client node and a switching type indicating a conditional switching; a component for receiving from the target master node an indication of multiple conditional switching connection configurations of the client node and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations; and a component for transmitting to the client node an indication of multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration.

[0018] Many of the additional features will be more readily appreciated as the same become better understood by reference to the following detailed description considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are used to provide a further understanding of the exemplary embodiments and constitute a part of this specification, illustrate the exemplary embodiments and together with the description help to understand the exemplary embodiments. In the drawings:

[0020] Figure 1 An example of a network including network nodes and client nodes according to an example embodiment is shown.

[0021] Figure 2 An example of an apparatus configured to perform a handover procedure according to an example embodiment is shown;

[0022] Figure 3 An example of a conditional handover process involving a client node, a source network node, and a target network node according to an example embodiment is shown;

[0023] Figure 4A and Figure 4B An example of a handover process in a dual connectivity scenario according to an example embodiment is shown;

[0024] Figure 5 An example of a conditional handover process with different conditional handover connection configurations according to an example embodiment is shown;

[0025] Figure 6A client node is shown communicating with a source master node and a source slave node according to an example embodiment.

[0026] Figure 7 A client node is shown communicating with a target master node according to an example embodiment.

[0027] Figure 8 A client node is shown communicating with a target master node and a source secondary node according to an example embodiment.

[0028] Fig. 9 A client node is shown communicating with a target primary node and a target secondary node according to an example embodiment.

[0029] Fig.10 A client node is shown communicating with a target primary node and an alternate secondary node according to an example embodiment.

[0030] Fig.11 An example of a method for performing a handover at a client node according to an example embodiment is shown.

[0031] Fig.12 An example of a method for performing a handover at a network node according to an example embodiment is shown.

[0032] Fig.13 An example of a method for performing a handover at a network node according to an example embodiment is shown.

[0033] In the drawings, like reference numerals are used to denote like parts. DETAILED DESCRIPTION

[0034] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in conjunction with the accompanying drawings is intended as a description of this example and is not intended to represent the only form in which this example can be constructed or utilized. This specification describes the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be implemented by different examples.

[0035] According to an example embodiment, a client node may communicate with a network in a dual connection configuration including a connection to a source master node and a source secondary node. The client node may be mobile and may therefore need to be switched to a target master node. In the case of a conditional switch, the client node may be instructed in a switch command to perform a switch based on at least one condition that triggers the execution of the switch. Due to the conditional nature of the switch, radio conditions may not be predicted when the switch is performed. Therefore, different conditional switching connection configurations may be provided so that an appropriate connection configuration may be selected when the execution of the conditional switch is triggered. Different conditional switching connection configurations may include a single connection configuration with a target master node and a dual connection configuration with a target master node and a secondary node.

[0036] Figure 1 An example embodiment of a network 100 is shown. The network 100 may include one or more core network elements 140. For example, the core network element may include one or more access and mobility management functions (AMFs) and / or user plane functions (UPFs), for example according to the 3GPP 5G-NR (3rd Generation Partnership Project 5G New Radio) standard. Alternatively or additionally, the core network element 140 may include one or more mobility management entities (MMEs) and / or serving gateways (S-GWs), for example according to the 3GPP LTE (Long Term Evolution) standard. The network 100 may also include at least one client node 110 (also referred to as a user node or user equipment (UE)). The UE 110 may communicate with one or more base stations 120, 122, 130, 132 via (multiple) radio channels. The base station may also be referred to as a radio access network (RAN) node. In general, a base station may include any suitable radio access point.

[0037] The network 100 may be configured to support dual connectivity (DC), which enables data throughput to be increased by allowing the UE 110 to utilize resources of two base stations (e.g., the primary node 120 and the secondary node 122 or the primary node 130 and the secondary node 132) at the same time. The responsibility for communicating with the UE 110 may be shared between the primary node and the secondary node. For example, the primary node 120 may be configured to handle at least a portion of the control plane communications associated with the UE 110 and the user plane communications associated with the UE 110. The secondary node 122 may be configured to provide additional radio resources for the user plane communications of the UE 110 in parallel with the primary node 120. The UE 110 may be connected to the primary node 120 and the secondary node 122 at the same time. Similarly, the UE 110 may be connected to the primary node 130 and the secondary node 132 at the same time. When the UE is connected to a base station, it may be in a specific radio resource control (RRC) state, such as an RRC_CONNECTED state. A master cell group (MCG) may include a group of serving cells associated with the primary nodes 120 and 130. The MCG may include a primary cell and optionally one or more secondary cells. A secondary cell group (SCG) may include a group of serving cells associated with a secondary node 122, 132. The SCG may also include a primary cell and optionally one or more secondary cells.

[0038] Dual connectivity may enable UE 110 to establish simultaneous connections with the same or different types of network nodes. For example, UE 110 may be configured to communicate with a 5G primary node (primary gNB (MgNB)) and a 4G secondary node (secondary eNB (SeNB)), or vice versa. In general, UE 110 may be connected to more than two network nodes, and therefore the example embodiments described herein are not limited to dual connectivity. For example, UE 110 may be simultaneously connected to one primary node and multiple secondary nodes to utilize the radio resources of multiple additional base stations.

[0039] Primary nodes 120 and 130 may be associated with respective coverage areas 121, 131. When dual connectivity enabled UE 110 moves from coverage area 121 to coverage area 131, network 100 may be configured to perform a handover from primary node 120 and secondary node 122 to primary node 132 and optionally secondary node 132 or another secondary node.

[0040] The master nodes 120, 130 and the slave nodes 122, 132 may be configured to communicate with the core network element 140 via a communication interface, such as, for example, a control plane or user plane interface NG-C / U of a 5G system or an X2 interface of a 4G E-UTRAN (Evolved Universal Terrestrial Radio Access Network). The functionality of a RAN node may be distributed between a central unit (CU) (e.g., a gNB-CU) and one or more distributed units (DU) (e.g., one or more gNB-DUs). Network elements such as eNBs, gNBs, gNB-CUs and gNB-DUs, AMFs, UPFs, MMEs, or S-GWs may generally be referred to as network nodes or network devices. Although depicted as a single device, a network node may not be a standalone device. Instead, a network node may, for example, include a distributed computing system coupled to a remote radio head. For example, a cloud radio access network (cRAN) may be applied to split control of wireless functions to optimize performance and cost.

[0041] Various signaling information may be exchanged in the network 100 to provide information related to transmission parameters and allocation of radio resources for data transmission. The signaling information may be provided at various levels of the protocol stack.

[0042] Radio Resource Control (RRC) may refer to providing radio resource related control data. Radio resource control messages may be transmitted on various logical control channels, such as, for example, a Common Control Channel (CCCH) or a Dedicated Control Channel (DCCH). Logical control channels may be mapped to one to multiple Signaling Radio Bearers (SRBs).

[0043] Although some example embodiments have been described using specific RRC messages as examples, it should be understood that any suitable (multiple) messages may be configured to carry the handover-related signaling information described herein. Although some example embodiments have been described using 4G and / or 5G networks as examples, it should be understood that the example embodiments presented herein are not limited to these example networks and may be applied to any current or future communication networks, such as other types of cellular networks, short-range wireless networks, broadcast networks, etc.

[0044] Figure 2 An example embodiment of an apparatus 200 is shown, for example, a client node such as UE 110, a network node such as primary node 120, 130 or secondary node 122, 132, or another network node acting as a secondary node. The apparatus 200 may include at least one processor 202. The at least one processor may include, for example, one or more of a variety of processing devices, such as, for example, a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), processing circuitry with or without an accompanying DSP, or a variety of other processing devices, including integrated circuits, such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a dedicated computer chip, etc.

[0045] The apparatus may also include at least one memory 204. The memory may be configured to store, for example, computer program code, such as operating system software and application software. The memory may include one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination thereof. For example, the memory may be embodied as a magnetic storage device (such as a hard disk drive, a floppy disk, a magnetic tape, etc.), an optical magnetic storage device, or a semiconductor memory (such as a mask ROM, a PROM (programmable ROM), an EPROM (erasable PROM), a flash ROM, a RAM (random access memory), etc.).

[0046] The apparatus 200 may also include a communication interface 208 configured to enable the apparatus 200 to transmit and / or receive information, such as signaling information or data packets, to / from other devices. In one example, the apparatus 200 may use the communication interface 208 to transmit or receive signaling information and data according to at least one cellular communication protocol. The communication interface may be configured to provide at least one radio connection, such as, for example, a 3GPP mobile broadband connection (e.g., 3G, 4G, 5G). However, the communication interface may be configured to provide one or more other types of connections, such as a wireless local area network (WLAN) connection, such as, for example, standardized by the IEEE 802.11 series or the Wi-Fi Alliance; a short-range wireless network connection, such as, for example, Bluetooth, NFC (near field communication) or RFID connection; a wired connection, such as, for example, a local area network (LAN) connection, a universal serial bus (USB) connection, or an optical network connection, etc.; or a wired Internet connection. The communication interface 208 may include or be configured to be coupled to at least one antenna to transmit and / or receive radio frequency signals. One or more of the various types of connections may also be implemented as a separate communication interface, which may be coupled or configured to be coupled to multiple antennas.

[0047] The device 200 may also include a user interface 210, which includes an input device and / or an output device. The input device may take various forms, such as a keyboard, a touch screen, or one or more embedded control buttons. The output device may include, for example, a display, a speaker, a vibration motor, etc.

[0048] When the device is configured to implement a certain function, a certain component and / or certain components of the device (such as, for example, at least one processor and / or memory) can be configured to implement the function. In addition, when at least one processor is configured to implement each function, the function can be implemented using, for example, the program code 206 included in the memory 204.

[0049] The functions described herein may be performed at least in part by one or more computer program product components (such as software components). According to one embodiment, the device includes a processor or processor circuit system, such as, for example, a microcontroller, which is configured by program code to perform the described operations and embodiments of the functions when executed. Alternatively or additionally, the functions described herein may be performed at least in part by one or more hardware logic components. For example, and not limitation, illustrative types of hardware logic components that may be used include field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chip (SOCs), complex programmable logic devices (CPLDs), and graphics processing units (GPUs).

[0050] The device includes a component for performing at least one method described herein. In one example, the component includes at least one processor and at least one memory, the at least one memory including a program code configured to cause the device to perform the above method when executed by at least one processor.

[0051] The apparatus 200 may include, for example, a computing device, such as, for example, a base station, a server, a mobile phone, a tablet computer, a laptop computer, an Internet of Things (IoT) device, etc. Examples of IoT devices include, but are not limited to, consumer electronics, wearable devices, sensors, and smart appliances. In one example, the apparatus 200 may include a vehicle, such as, for example, a car. Although the apparatus 200 is shown as a single device, it should be understood that, where applicable, the functionality of the apparatus 200 may be distributed to multiple devices, for example to implement the example embodiments as a cloud computing service.

[0052] Figure 3 An example of a conditional handover process involving UE 110, source node 120, and target node 130 is shown. Generally, the source node may include a network node that initially serves the UE. The target node may include a network node that initially does not serve the UE but will be responsible for serving the UE after the handover. The handover may be performed when the UE 110 transfers from the coverage area of ​​the source node 120 to the coverage area of ​​the target node 130. The conditional handover (CHO) may include performing the handover in response to detecting a trigger of at least one condition or event. In the case of an unconditional handover, the UE 110 may immediately perform the handover in response to receiving a handover command. However, in the case of a conditional handover, the UE 110 may wait until a specific condition or event is detected, and perform the handover after the condition or event is detected. The conditional handover may include a conditional handover preparation phase and a conditional handover execution phase, such as Figure 3 shown.

[0053] Prior to the handover, the UE 110 and the source node 120 may transmit and / or receive data to / from each other, for example as one or more data packets. The UE 110 may be configured to receive downlink signals from the source node 120 and transmit uplink signals to the source node 120, and vice versa. At 301, the source node 120 may transmit a measurement control message to the UE 110, for example to configure the UE 110 to measure the strength and / or quality of (multiple) signals received from one or more network nodes. The measurement control message may include an indication of at least one conditional handover-related measurement event, which the UE 110 may add to the measurement event list in operation 302 in response to receiving the measurement control message 301. At 303, the UE 110 may transmit at least one measurement report to the source node 120, for example in response to detecting a trigger of a conditional handover-related measurement event. For example, if the measured signal strength or quality associated with the source node 120 and / or other network nodes meets at least one condition, for example, a threshold indicated in the measurement control message, the sending of the measurement report may be triggered. The measurement event added at 302 need not be related to a conditional handover. A conditional handover may also be performed after sending a measurement report for any configured handover measurement event, for example, if the conditional handover type is indicated later in a handover command message.

[0054] Based on the measurement report received from the UE 110, the source node 120 may be configured to prepare the target node 130 or a plurality of candidate target cells associated with the target node 130 for handover. At 304, the source node 120 may transmit a handover request message to the target node 130 to prepare the target node 130 for handover. At 305, the target node 130 may confirm receipt of the handover request message by sending a handover request message confirmation to the source node 120. At 306, the target node 130 may reserve resources for the UE 110.

[0055] At 307, in response to receiving the handover request confirmation from the target node 130, the source node 120 may send a handover command message to the UE 110. The handover command message may include a ready cell list, which may indicate one or more target cells of the target node 130. At 308, the source node 120 may confirm the receipt of the handover command with a handover command confirmation message. This may end the conditional handover preparation phase.

[0056] The handover command message 307 may include at least one handover execution condition. The handover execution condition may be different from the conditional handover measurement event added in operation 302 (which may be associated with triggering a measurement report rather than associated with the execution of a handover). At 309, the UE 110 may determine whether the handover execution condition is satisfied. If the handover execution condition is satisfied, the UE may determine that a handover to the target node 130 is to be performed. This may include synchronizing with the target node 130 at 310. The transmitted synchronization information may include signaling information (such as, for example, one or more system information blocks) and / or one or more synchronization signals (such as, for example, reference signals embedded in a transmission waveform). In addition, a random access (RA) procedure may be used to connect to the target node 130. For example, the UE 110 may transmit a random access preamble, which may be in various formats and, for example, may include a signature identifying the UE 110. Typically, the random access procedure may include a connection request to the target node 130. The RA preamble may be transmitted, for example, on a physical random access channel (PRACH) and may be used to acquire uplink synchronization between UE 110 and target node 130 and to acquire resources for transmitting additional signaling messages. If the handover execution condition is not satisfied, UE 110 may determine that the handover cannot be performed at this time.

[0057] At 311, UE 110 may send a handover completion message to target node 130. At 312, the conditional handover execution phase may end when target node 130 transmits a handover completion confirmation message. After the handover is completed, the old handover preparation work may no longer be valid. Therefore, UE 110 and / or source node 120 may be configured to delete or ignore handover preparation data, such as a cell list associated with the handover command sent at 307.

[0058] One advantage of conditional handover execution is that the handover command can be sent in advance, for example when the UE 110 is still safely within the coverage area 121 of the source node 120. It also reduces the risk of losing access to the target node 130 and enhances the stability of the radio link to the target node 130.

[0059] Figure 4A and Figure 4B An example of a handover process in a dual connectivity scenario is shown, where the source node 120 may include a source master node (MN) and where the target node 130 may include a target master node. UE 110 may initially establish connections to source MN 120 and source secondary node (SN) 122. Figure 3In operations 301 to 303, source MN 120 may configure UE 110 to provide measurement reports associated with source MN 120, source SN 122, and / or one or more other base stations. Based on the received measurement reports, source MN 120 may determine to request a handover to target MN 130.

[0060] At 401, the source MN 120 may transmit a handover request to the target MN 130. In response to receiving the handover request, the target MN 130 may determine whether to add the target SN 132 to maintain dual connectivity after the handover. If the target MN 130 determines to add the target SN 132, the target MN 130 may initiate a secondary node addition procedure, for example, using the same X2-AP-ID that the source MN 120 has used. The X2-AP-ID may identify the UE 110 during the handover. At 402, the target MN 130 may transmit a secondary node addition request, for example, an SgNB addition request, to the target SN 132. At 403, the target SN 132 may confirm receipt of the message by sending a secondary node addition request confirmation message (e.g., an SgNB addition request Ack message). At 404, the target MN 130 may transmit a handover request confirmation message, for example, in response to receiving the secondary node addition request confirmation message from the target SN 132.

[0061] At 405, source MN 120 may transmit a secondary node release request, such as an SgNB Release Request message, to source SN 122. In response to receiving the secondary node release request message, source SN 122 may terminate transmission to UE 110. At 406, source SN 122 may transmit a secondary node release request confirmation message, such as an SgNB Release Request Ack message.

[0062] At 407, source MN 120 may transmit an RRC connection reconfiguration message to UE 110. The RRC connection reconfiguration message may include a handover command. In response to receiving the handover command, UE 110 may perform a handover to target MN 130. UE 110 may, for example, initiate a random access procedure 408 between UE 110 and target MN 130 to request a connection to target MN 130. At 409, UE 110 may transmit an RRC connection reconfiguration complete message to target MN 130.

[0063] refer to Figure 4BContinuing with the process, UE 110 may also synchronize with target SN 132 to maintain dual connectivity, for example, in response to receiving a message indicating a secondary node or secondary cell group configuration. UE 110 may initiate a random access procedure 410 between UE 110 and target SN 132. In general, UE 110 may be configured to select a connection configuration to be applied after handover, for example, switching connection options based on a plurality of conditions provided by target MN 130 and one or more conditions configured at UE 110 or received from source MN 120.

[0064] At 411, the target MN 130 may transmit a secondary node reconfiguration complete message, such as an SgNB reconfiguration complete message, to the target SN 132. The message may indicate that the UE 110 has successfully completed the reconfiguration process. At 412, the source SN 122 may transmit a secondary node data volume report, such as a secondary RAT (radio access technology) data volume report. The report message may, for example, indicate the uplink and downlink data volume of the secondary node resources used. At 413, the source MN 120 may forward the information to the MME 144 or AMF, such as in a secondary RAT report message.

[0065] At 414, source MN 120 may transmit a sequence number (SN) state transfer message to target MN 130. At 416, source MN 120 may forward the data packet provided by S-GW 142 at 415 to target MN 130. At 417, target MN 130 may transmit a request for path switching to MME 144. A transmission path may refer to a path along which a core network delivers data to be delivered to a specific UE. For example, path switching may include switching a transmission path for data of UE 110 from source MN 120 and source SN 122 to target MN 130 and target SN 132. After the path switching, target MN 130 and target SN 132 may communicate with the core network to obtain data to be transmitted to UE 110. The path switching process may include transmitting a bearer modification message by MME 144 at 418, and initiating the provision of data to target MN 130 and target SN 132 over a new path at 419 and 420, respectively. Completion of the path switch request may be indicated by MME 144 at 421 via a Path Switch Request Acknowledge message.

[0066] At 422, target MN 130 may transmit a UE context release message. At 423, source MN 120 may forward the UE context release message to source SN 122. In response to receiving the UE context release message from target MN 130, source SN 122 may release radio resources associated with UE 110.

[0067] As discussed above, the conditional handover process enables early provision of a handover command and thereby improves the reliability of the handover. However, in a dual-connection scenario, the radio conditions between the UE 110 and the source SN 122 may change before the handover is performed, such as between the transmission of the conditional handover command by the source MN 120 and the triggering of the conditional handover execution at the UE 110. For example, the connection to the source SN 122 may be lost or degraded, and therefore it may not be desirable to configure the UE 110 to use the same secondary node (source SN 122) after the handover. In this example, preferably, the UE 110 is configured to apply a single connection with the target MN 130, or the UE is configured to connect to a new secondary node (e.g., target SN 132) to maintain dual connectivity after the handover.

[0068] However, if the source SN 122 is still active when the handover is performed, the UE 110 may need to be configured to use the same secondary node except the target MN 130 after the handover. This can avoid service interruption because the connection to the source SN 122 can be maintained throughout the handover process. In addition, this can reduce the operational load caused by the handover, for example because there is no need to transfer the path to the secondary node or release the secondary node. However, since the target MN 130 may not know the future state of the source SN 122 at the time of the handover request, the target MN 130 may not be able to select the best conditional handover connection configuration for the UE 110. Some example embodiments relate to providing conditional handover signaling, which enables a dual-connection device to select between different conditional handover connection configurations according to the secondary node or secondary cell group state when the conditional handover is performed.

[0069] Figure 5 Examples of conditional handover procedures with different conditional handover connection configurations according to example embodiments are shown. Figure 5 The exemplary embodiment of can be combined with the above exemplary embodiments, for example with Figure 4A and Figure 4B Initially, UE 110 may establish a first connection to source MN 120 and a second connection to source SN 122 ( Figure 5 At 501, UE 110 may be configured to send a handover measurement report, such as an RRC measurement report message, to source MN 120, similar to Figure 3 , Figure 4A and Figure 4B switching process.

[0070] At 502, source MN 120 may determine that a handover is to be performed and transmit a handover request to target MN 130. The handover request may include an identifier of target MN 130, (multiple) identifiers of one or more target cells, and / or an indication of a source SN 122 associated with UE 110. The handover request may include a handover type indicating a conditional handover. The handover type may be indicated by a value of a signaling field (e.g., a set of bits) in a handover request message or a separate handover type indication message. The handover type may also be indicated in this manner in other types of messages (e.g., messages sent to UE 110). The handover request may include information about source SN 122, such as one or more measurement results associated with source SN 122. The results may be provided to source MN 120 by UE 110. The measurement results may be transmitted to target MN 130 in a handover request message or a separate message, for example, as part of UE context information. Target MN 130 may receive (multiple) handover request messages from source MN 120.

[0071] According to an example embodiment, the source MN 120 may be configured to transmit to the target master node 130 an indication that the source MN 120 supports the delivery of multiple conditional handover configurations to the UE 110. The indication may be included in a handover request or a separate message. In response to receiving the indication, the target MN may determine to prepare and provide multiple conditional handover connection options. In some example embodiments, in response to not receiving such an indication, the target MN 130 may be configured to prepare a single connection configuration without a dual connection configuration. According to an example embodiment, if no indication is received that the source MN 120 supports the delivery of two or more conditional handover conditions, the target MN 130 may be configured to provide a single conditional handover connection configuration or multiple conditional handover connections as a default configuration.

[0072] At 503, the target MN 130 may send a secondary node addition request to at least one target secondary node 132, for example, in response to receiving the handover request and the indication of the conditional handover type. Figure 5 Only one target secondary node, namely, target SN 132, is shown, but it should be understood that when a conditional handover configuration including source SN 122 and / or alternative SN 134 is applied, similar operations and communications may be applied at or with respect to source SN 122 or alternative SN 134, such as with respect to Figure 8 or Fig.10 As described.

[0073] At 504, the target MN 130 may determine to prepare multiple conditional handover connection configurations, for example, in response to receiving a handover request and / or an indication of a conditional handover type. The target node may determine, for example, based on resource conditions at the target MN 130 and / or an indication of a secondary node included in the handover request, whether to prepare resources only with the target MN 130 or with the target MN 130 and the secondary node. For example, if the target MN 130 cannot allocate all required resources to complete the handover request, the target MN 130 may determine to prepare resources with the target MN 130 and the secondary node. If the early mobility performance or other information at the target MN 130 indicates the possibility of losing the secondary cell group during the handover, the target MN 130 may also prepare two configurations, including only the target MN 130 and the target MN 130 and the secondary node. For example, if one or more previous dual-connection handovers fail due to the loss of connection with the secondary node, the target MN 130 may determine to include a single connection option in the conditional handover connection configuration. The target MN 130 may then prepare multiple conditional handover connection configurations for the UE 110.

[0074] At 505, the target MN 130 may transmit an indication of multiple conditional handover connection configurations to the source MN 120. The target MN 130 may also transmit an indication of at least one condition for selecting a specific conditional handover connection configuration from multiple conditional handover connection configurations when a conditional handover is triggered at the UE 110. This enables the target MN 130 to control the selection of the conditional handover connection configuration at the UE 110 in various situations. The (multiple) indications may be included in a handover request confirmation message, which may be transmitted in response to receiving a handover request. Each conditional handover connection configuration may be associated with an indication of whether the configuration should be selected when the source SN 122 is active or inactive. Typically, each conditional handover connection configuration may be associated with at least one condition for selecting the configuration. The (multiple) indications of the conditional handover connection configuration may be transmitted in a single message or multiple messages, such as in two separate messages. The source MN 120 may receive the (multiple) indications of the conditional handover configuration of the UE 110 and the (multiple) conditions associated therewith.

[0075] According to an example embodiment, the plurality of conditional handover connection configurations may include a single connection configuration and a dual connection configuration. The single connection configuration may be with the target MN 130. The dual connection configuration may be with the target MN 130 and the target secondary node. Alternatively or additionally, the dual connection configuration may be with the target primary node and the source secondary node.

[0076] Figure 6An example is shown in which UE 110 initially communicates with source MN 120 and source SN 122 via radio links 601 and 602, respectively. UE 110 may move toward coverage area 131 of target MN 130 and may send one or more measurement reports associated with source MN 120, source SN 122, and one or more other network nodes (such as target MN 130 and target SN 132) to source MN 120. When moving to coverage area 131 of target MN 130, UE 110 may handover from source MN 120 to target MN 130.

[0077] Figure 7 An example of a single connection configuration after handover is shown. UE 110 may communicate with target MN 130 via radio link 701. For example, this configuration may be applied if radio link 602 to source SN 122 is released, lost, or degraded before handover is performed.

[0078] Figure 8 An example of a dual connectivity configuration after a handover is shown. UE 110 can communicate with target MN 130 and source secondary node, source SN 122. Communications to target MN 130 and source SN 122 can be provided via radio links 801 and 802, respectively. This configuration enables dual connectivity to be maintained after a handover. For example, this configuration can be applied if radio link 602 to source SN 122 is still active when a handover is performed. This configuration also enables the connection to source SN 122 to be maintained throughout the handover process, thereby reducing the risk of service interruption.

[0079] Fig. 9 Another example of a dual connectivity configuration after handover is shown. UE 110 can communicate with target MN 130 and target SN 132 via radio links 901 and 902, respectively. Target SN 132 can be different from source SN 122. This configuration enables dual connectivity to be maintained after handover. For example, if radio link 602 to source SN 122 is released, lost or degraded before the execution of conditional handover and a new secondary node is available, this configuration can be applied. The availability of the new secondary node can be determined by target MN 130, for example, based on measurement results sent by UE 110 and forwarded to target MN 130 by source MN 120.

[0080] Fig.10Another example of a dual connection configuration after switching is shown. According to an exemplary embodiment, multiple conditional switching connection configurations may include a first dual connection configuration with a target MN 130 and a source SN 122. Multiple conditional switching connection configurations may also include a second dual connection configuration with a target MN 130 and a target SN 132. Multiple conditional switching configurations may also include a single connection configuration with a target MN 130. Based on at least one condition when a conditional switching is triggered, the UE 100 may select one of the configurations for the execution of the conditional switching. When the alternative SN 134 is selected as the secondary node, the UE 110 may communicate with the target MN 130 and the alternative SN 134 via radio links 1001 and 1002, respectively. This enables multiple secondary node options to be provided, and thereby increases the possibility of finding an available secondary node to maintain dual connectivity after switching.

[0081] According to an example embodiment, for example, the plurality of conditional handover connection configurations may include a first dual connectivity configuration with a target MN 130 and a target SN 132 and a second dual connectivity configuration with a target MN 130 and a source SN 122. This provides an opportunity to maintain dual connectivity through the source SN 122 without interrupting service, while providing an option to access a new secondary node (target SN 132) to maintain dual connectivity when the radio link to the source SN 122 is released, lost, or degraded.

[0082] According to an example embodiment, at least one condition for selecting a conditional handover configuration may include detecting or not detecting a secondary node change from the source SN 122 to the target SN 132 or the alternative SN 134 before triggering the execution of the conditional handover. For example, in response to not detecting a secondary node change before triggering the execution of the conditional handover, the UE 110 may be configured to select a first dual connectivity configuration including connections with the target MN 130 and the source SN 122. The UE 110 may also be configured to select a second configuration including connections with the target MN 130 and the target SN 132 in response to not detecting a secondary node change before triggering the execution of the conditional handover. If both the target SN 132 and the alternative SN 134 are included in a plurality of conditional handover configurations, the UE may select the secondary node based on measurement results, a priority order of the secondary nodes, or other predetermined criteria.

[0083] Reference again Figure 5, at least one condition sent at 505 for selecting a specific conditional handover connection configuration from a plurality of conditional handover connection configurations may include an active state or an inactive state of the source SN 122. For example, if the source SN 122 is active when performing the conditional handover, the UE 110 may be instructed to select a dual connectivity option, in which the source SN 122 still serves as a secondary node. If the source SN 122 is inactive, the UE 110 may be instructed to select a single connectivity configuration with the target MN 130 or a dual connectivity option with the target MN 130 and another secondary node.

[0084] The inactive state of source SN 122 may refer to a situation in which UE 110 has lost connection with source SN 122 or in which application data is not transmitted between UE 110 and source SN 122. The active state of source SN 122 may refer to a situation in which UE 110 is connected to source SN 122 so that application data can be transmitted between devices. If UE 110 is in the RRC_CONNECTED state with source SN 122, UE 110 may, for example, determine that source SN 122 or a source secondary cell group has an active state. If UE 110 is not in the RRC_CONNECTED state with source SN 122, UE 110 may, for example, determine that source SN 122 has an inactive state.

[0085] According to an example embodiment, at least one condition for selecting a specific conditional handover connection configuration from a plurality of conditional handover connection configurations may include detecting the release of the source SN 122. For example, if the source SN 122 has been released, the UE 110 may determine that the state of the source SN 122 is inactive. The at least one condition may also include detecting that the signal strength or signal quality associated with the source SN 122 is lower than or equal to a threshold. For example, if the UE 110 determines that the signal strength or quality is no longer sufficient, then when selecting one of the conditional handover connection configurations, the UE 110 may determine that the connection to the source SN 122 is to be considered inactive. The at least one condition may also include detecting one or more out-of-sync indications associated with the source SN 122, such as one or more out-of-sync indications generated at the UE 110. The at least one condition may also include detecting the start of a radio link monitoring (RLM) timer associated with the source SN 122. The radio link monitoring timer may, for example, include a T313 timer in accordance with the 3GPP specification. Applying one or more of these conditions makes it possible to avoid performing dual connectivity handover and maintain the same source SN 122 when the connection to the source SN 122 is lost, expected to be lost, or degrades to an insufficient level.

[0086] At least one condition may also include detecting a radio link failure associated with the source SN 122 or detecting a beam failure associated with the source SN 122. If the UE 110 cannot maintain synchronization with the source SN 122, if the reference signal received power (RSRP) is below a threshold or drops below a threshold, or if the UE 110 cannot decode a specific channel, such as a physical downlink control channel (PDCCH) or a physical downlink service channel (PDSCH), the UE 110 may determine that a radio link failure has occurred. A beam failure may be detected based on similar criteria, but associated with a specific beam. In response to detecting at least one condition, the UE 110 may be configured to select a single connection configuration or a dual connection configuration without the source SN 122.

[0087] At 506, source MN 120 may transmit an indication of a plurality of conditional handover connection configurations to UE 110. Source MN 120 may also transmit an indication of at least one condition for selecting a conditional handover connection configuration to UE 110. Source MN 120 may also transmit an indication of at least one condition for triggering execution of a conditional handover to UE 110. Source MN 120 may also transmit an indication of a handover type to UE 110. The handover type may indicate a conditional handover. The conditional handover connection configuration, the condition(s) for selecting such a configuration, the handover execution condition, and / or the handover type may be included in one or more control messages. Figure 5 The RRC reconfiguration message of is an example of such a control message. The control message(s) may include a handover command. The UE 110 may receive the indication(s) from the source MN 120.

[0088] According to an example embodiment, the condition for triggering the execution of the conditional handover may include the detection of an A3 event. According to the 3GPP specification, for example, if the neighboring cell becomes a better offset than the current cell in terms of signal strength, an A3 event may be detected. The condition(s) for triggering the execution of the conditional handover may also include an inactive state of the source SN 122 or a threshold(s) associated with the radio condition (e.g., signal strength or quality) between the UE 110 and the source SN 122.

[0089] Figure 5A first example is shown, i.e., case A, in which a conditional handover is performed after detecting that the source SN 122 is inactive, e.g., based on a radio link failure or a release of the source SN 122. However, the operations associated with case A may also be applied when a degradation of the radio link with the source SN 122 is detected, e.g., based on one or more of the conditions associated with the connection to the source SN 122. For example, the UE 110 may be configured to determine that the state of the source SN 122 or the state of the connection to the source SN 122 is inactive based on detecting one or more of the following conditions: release of the source SN 122, detecting that a signal strength or a signal quality associated with the source SN 122 is lower than or equal to a threshold, detecting one or more out-of-sync indications associated with the source SN 122, detecting the start of a radio link monitoring (RLM) timer associated with the source SN 122, detecting a radio link failure associated with the SN 122, or detecting a beam failure associated with the source SN 122. In response to determining that the source SN 122 is inactive, or at least one of the above conditions is detected, the UE 110 may select a single connection configuration or a dual connection configuration that does not involve the source SN 122 .

[0090] According to an example embodiment, source MN 120 may determine that the state of source SN 122 is inactive relative to UE 110, for example, based on an indication of the inactive state received from source SN 122 or UE 110. Source MN 120 may transmit an indication of the inactive state of source SN 122 to target MN 130. In response to determining that the state of source SN 122 is inactive, for example, based on the indication received from source MN 120, target MN 130 may transmit a secondary node release request to target SN 132. This enables the release of unnecessary resources prepared for the dual connectivity configuration.

[0091] For example, at 507, UE 110 and / or source MN 120 may detect a radio link failure associated with source SN 122 or a release of source SN 122. Source MN 120 may transmit an indication of the release or radio link failure to target MN 130. Therefore, both target MN 130 and UE 110 may be aware of the inactive state of source SN 122. This enables target MN 130 to perform a handover of UE 110 using the conditional handover connection configuration selected by UE 110 when performing a handover. Therefore, explicit signaling of the selected conditional handover connection configuration from UE 110 to target MN 130 may be avoided, which reduces the required capacity at the air interface between UE 110 and target MN 130. Furthermore, since the single connectivity configuration has already been prepared and indicated to UE 110, target MN 130 does not need to send an explicit reconfiguration to reflect the removal of the secondary node or SCG in the target configuration, since alternatives not involving source SN 122 may have been provided in the conditional handover command itself at 506. Thus, an additional RRC reconfiguration message to UE 110 for modifying the conditional handover preparation information may be avoided.

[0092] At 508, UE 110 may, for example, detect a trigger for the execution of a conditional handover based on detecting that a handover execution condition is satisfied. In response to detecting the trigger for the conditional handover, UE 110 may select a conditional handover connection configuration from a plurality of conditional handover connection configurations based on at least one condition associated with the connection to source SN 122. UE 110 may determine which of the conditional handover connection configurations is to be selected for executing the triggered conditional handover based on the state of the connection to source SN 122. For example, UE 110 may select a single connection configuration in response to determining that the state of the source secondary node is inactive. Alternatively, if an option for a dual connection configuration not involving source SN 122 is provided in a plurality of conditional handover connection configurations, UE 110 may select a dual connection configuration not involving source SN 122.

[0093] At 509, UE 110 may initiate a handover access to target MN 130, for example, by sending a connection request to target MN 130. The connection request may include one or more control messages, such as, for example, an RRC reconfiguration complete message. The control message may include a handover complete message, which may be included in the RRC reconfiguration complete message. UE 110 may use a single connection configuration without any secondary node. At 510, the target MN may apply a single connection configuration without any secondary node.

[0094] In the example of case A, the source SN 122 is released or a radio link failure is detected. Based on this information, the UE 110 may select a single connection configuration with the target MN 130. The UE 110 may perform conditional handover based on the single connection configuration. In response to receiving a connection request, the target MN 130 may perform conditional handover based on the single connection configuration. The target MN 130 may, for example, select a conditional handover configuration to be applied based on information about the source SN 122 that may be received from the source MN 120. For example, if the target MN 130 receives an indication of an inactive state of the source SN 122, the target MN 130 may perform conditional handover based on the single connection configuration.

[0095] Figure 5 A second example is further shown, i.e., case B, in which conditional handover is performed when the source SN 122 or the source secondary cell group is active relative to the UE 110. At 511, the UE 110 may detect a trigger for conditional handover, for example, based on determining that a handover execution condition is satisfied. In response to the trigger for conditional handover, the UE 110 may determine a state of the source SN 122, for example, that the source SN 122 is active, and / or determine whether one or more conditions associated with the selection of a conditional handover connection configuration are satisfied. According to an example embodiment, the source MN 120 may determine whether the source SN 122 is active relative to the UE 110 based on an indication of an active state received from the source SN 122 or the UE 110. The source MN 120 may transmit an indication of the active state of the source SN 122 to the target MN 130. Therefore, both the target MN 130 and the UE 110 may know the active state of the source SN 122. Alternatively, if no indication of an inactive state is received from the source MN 120, the target MN 130 may determine that the source SN 122 has an active state.

[0096] At 511, UE 110 may also determine which of the conditional handover connection configurations is to be selected for performing the triggered conditional handover. In example case B, source SN 122 is still in an active state. In response to determining that the state of source SN 122 is active, UE 110 may select a dual connection configuration. For example, UE 110 may select a dual connection configuration with target MN 130 and source SN 122. Alternatively, UE 110 may select a dual connection configuration with target MN 130 and new target SN 132, or select a dual connection configuration with target MN 130 and alternative SN 134, which may be provided as an option in addition to target SN 132.

[0097] The selection of the target secondary node may be based on one or more criteria associated with the radio link conditions between UE 110 and the secondary node in question, such as signal strength and / or quality. According to an example embodiment, the criteria for selecting between the plurality of secondary nodes may be known to both UE 110 and target MN 130, and thus UE 110 may not need to inform target MN 130 of the selection. However, UE 110 may also send an indication of the selected conditional handover connection configuration to target MN 130, for example, in the event that there are multiple secondary nodes that meet the selection criteria.

[0098] UE 110 may initiate a handover access to target MN 130, for example, by sending a connection request to target MN 130 at 512. The connection request may include one or more control messages, such as, for example, an RRC reconfiguration complete message. The control message may include a handover complete message, which may be included in the RRC reconfiguration complete message. At 513, UE 110 may initiate a handover access to target SN 132, similar to the handover access to target MN 130. UE 110 may synchronize with target SN 132 while synchronizing with target MN 130. UE 110 may use the selected dual connectivity (DC) configuration.

[0099] Target MN 130 may receive an indication of an active state of source SN 122 from source MN 120. Target MN 130 may also receive a connection request from UE 110. At 514, target MN 130 may perform a conditional handover based on the dual connectivity configuration, e.g., in response to receiving the connection request from UE 110 and the indication of an active state of source SN 122 received from source MN 120. For example, if target MN 130 has valid preparation for dual connectivity configuration with target MN 130 and target SN 132, target MN 130 may send an SN reconfiguration complete message to target SN 132. This may be done to notify target SN 132 of the execution of the conditional dual connectivity handover.

[0100] Example embodiments enable different connection options to be prepared according to the radio conditions when the execution of the conditional handover is triggered. For example, if the target MN 130 estimates the possible change of the secondary node or the secondary cell group (SCG) when the conditional handover is performed, the target MN 130 can prepare multiple configurations, such as with and without the secondary node or SCG, as described above. If the secondary node changes before the conditional handover is performed, there is no need to change the preparation at the target MN 130 because the target MN 130 can apply a single connection configuration. When the change of the secondary node is applied to the source configuration, the source MN 120 can also notify the ready target MN 130 to switch to the single connection configuration.

[0101] As described above, the target MN 130 may prepare a plurality of dual-connection configurations for selection at the time of conditional handover execution. For example, if the target MN 130 identifies potential (multiple) new secondary nodes or (multiple) SCGs before the execution of the conditional handover, a dual-connection configuration with an alternative SN 134 may be prepared. For example, the target MN 130 may provide two dual-connection configurations: a first configuration with a current secondary node (e.g., source SN 122), and a second configuration with a new secondary node (e.g., target SN 132 or alternative SN 134). The RRC signaling toward the UE 110 may include an indication of the secondary node and a conditional handover execution condition, such as, for example, comparing the primary cell group with a new secondary cell group associated with the new secondary node in terms of an A3 event. In response to determining that the conditional handover execution condition is satisfied, the UE 110 may check the secondary node. If the secondary node has not changed, the UE 110 may apply the first configuration. If the secondary node is changed and matches the secondary node indicated together with the conditional handover execution condition, the UE 110 may apply the second configuration.

[0102] Various example embodiments disclose methods, computer programs, and apparatus for applying side-link communications to achieve seamless handover, avoid service interruption during handover, and improve communication reliability during handover.

[0103] Fig.11 An example of a method 1100 for performing a handover at a client node according to an example embodiment is shown.

[0104] At 1101, the method may include establishing a first connection to the source master node.

[0105] At 1102, the method may include establishing a second connection to the source auxiliary node.

[0106] At 1103, the method may include receiving at least one indication of a plurality of conditional switching connection configurations from the source master node.

[0107] At 1104, the method may include detecting a trigger for the execution of a condition switching.

[0108] At 1105, the method may include selecting a conditional switch connection configuration from among the plurality of conditional switch connection configurations based on at least one condition associated with the second connection.

[0109] At 1106, the method may include performing conditional switching based on the selected conditional switching connection configuration.

[0110] According to an example embodiment, the plurality of conditional switching connection configurations may include: a single connection configuration with a target primary node, and a dual connection configuration with a target primary node and a source secondary node. At least one condition associated with the second connection may include an active state or an inactive state of the source secondary node.

[0111] The method may also include selecting a single connection configuration in response to determining that the state of the source auxiliary node is inactive, and / or selecting a dual connection configuration in response to determining that the state of the source auxiliary node is active. At least one condition associated with the second connection may include at least one of the following: detecting the release of the source auxiliary node, detecting that the signal strength or signal quality associated with the source auxiliary node is lower than or equal to a threshold, detecting one or more out-of-sync indications associated with the source auxiliary node, detecting the start of a radio link monitoring timer associated with the source auxiliary node, detecting a radio link failure associated with the source auxiliary node, or detecting a beam failure associated with the source auxiliary node. The method may also include selecting a single connection configuration in response to detecting at least one condition.

[0112] According to an example embodiment, the plurality of conditional switching connection configurations may include at least two of the following: a first dual connection configuration with a target primary node and a source secondary node; a second dual connection configuration with a target primary node and a target secondary node; and a single connection configuration with a target primary node. The method may also include selecting the first dual connection configuration in response to not detecting a secondary node change from the source secondary node to the target secondary node before triggering the execution of the conditional switching, and / or selecting the second dual connection configuration in response to detecting a secondary node change before triggering the execution of the conditional switching.

[0113] According to an example embodiment, the method may further include receiving at least one control message from the source master node, the at least one control message including at least one of the following: an indication of a plurality of conditional handover connection configurations; at least one condition associated with the second connection for selecting the conditional handover connection configuration; or at least one second condition for triggering the execution of the conditional handover. The at least one second condition for triggering the execution of the conditional handover may include an A3 event. The at least one control message may include a handover type indicating the conditional handover. The at least one control message includes a radio resource control connection reconfiguration message. The radio resource control connection reconfiguration message may include a handover command message.

[0114] Fig.12 An example of a method 1200 for performing a handover at a network node (eg, target master node 130) according to an example embodiment is shown.

[0115] At 1201, the method may include receiving a handover request associated with a client node from a source primary node. The handover request may include an indication of a source secondary node associated with the client node and a handover type indicating a conditional handover.

[0116] At 1202, the method may include preparing a plurality of conditional handoff connection configurations for a client node.

[0117] At 1203, the method may include transmitting, to the source master node, an indication of a plurality of conditional handover connection configurations and an indication of at least one condition for selecting a conditional handover connection configuration from the plurality of conditional handover connection configurations upon triggering of conditional handover.

[0118] According to an example embodiment, the plurality of conditional switching connection configurations may include a single connection configuration with a target primary node, and a dual connection configuration with a target primary node and a target secondary node.

[0119] According to an example embodiment, a plurality of conditional switching connection configurations may include: a single connection configuration with a target master node, and a dual connection configuration with a target master node and a source slave node. At least one condition for selecting a conditional switching connection configuration may include an active state or an inactive state of a source slave node. At least one condition for selecting a conditional switching connection configuration includes at least one of the following: detecting the release of a source slave node, detecting that a signal strength or a signal quality associated with a source slave node is less than or equal to a threshold, detecting one or more out-of-sync indications associated with a source slave node, detecting the start of a radio link monitoring timer associated with a source slave node, detecting a radio link failure associated with a source slave node, or detecting a beam failure associated with a source slave node.

[0120] According to an example embodiment, the method may further include receiving an indication of an active status of the source secondary node from the source primary node; receiving a connection request from the client node; and performing a conditional switch based on the dual connectivity configuration.

[0121] According to an example embodiment, the method may further include receiving an indication of an inactive state of the source secondary node from the source primary node; receiving a connection request from the client node; and performing a conditional switch based on the single connection configuration.

[0122] According to an example embodiment, the method may further include transmitting a secondary node release request to the target secondary node in response to receiving an indication of the inactive state of the source secondary node.

[0123] According to an example embodiment, the multiple conditional switching connection configurations may include at least two of the following: a first dual connection configuration with a target primary node and a source secondary node; a second dual connection configuration with a target primary node and a target secondary node; and a single connection configuration with the target primary node.

[0124] Fig.13 An example of a method 1300 for performing a handover at a network node (eg, source master node 120) according to an example embodiment is shown.

[0125] At 1301 , the method may include transmitting a handover request to a target primary node, the handover request including an indication of a source secondary node associated with a client node and a handover type indicating a conditional handover.

[0126] At 1302, the method may include receiving, from a target master node, an indication of a plurality of conditional handoff connection configurations for a client node and an indication of at least one condition for selecting the conditional handoff connection configuration from the plurality of conditional handoff connection configurations.

[0127] At 1303, the method may include transmitting, to a client node, an indication of a plurality of conditional handover connection configurations and an indication of at least one condition for selecting the conditional handover connection configuration.

[0128] According to an example embodiment, the plurality of conditional switching connection configurations may include a single connection configuration with a target primary node, and a dual connection configuration with a target primary node and a target secondary node.

[0129] According to an example embodiment, the plurality of conditional switching connection configurations may include a single connection configuration with a target master node, and a dual connection configuration with the target master node and a source secondary node.

[0130] According to an example embodiment, the method may further include transmitting to the target master node an indication that the source master node supports delivery of the plurality of conditional switching configurations to the client node.

[0131] According to an example embodiment, at least one condition for selecting a conditional handover connection configuration includes an active state or an inactive state of a source auxiliary node. At least one condition for selecting a conditional handover connection configuration may include at least one of the following: detecting the release of the source auxiliary node; detecting that a signal strength or signal quality associated with the source auxiliary node is less than or equal to a threshold; detecting one or more out-of-sync indications associated with the source auxiliary node; detecting the start of a radio link monitoring timer associated with the source auxiliary node; detecting a radio link failure associated with the source auxiliary node; or detecting a beam failure associated with the source auxiliary node.

[0132] According to an example embodiment, the method may further include transmitting an indication of an active state or an inactive state of the source secondary node to the target primary node.

[0133] According to an example embodiment, the multiple conditional switching connection configurations may include at least two of the following: a first dual connection configuration with a target primary node and a source secondary node; a second dual connection configuration with a target primary node and a target secondary node; and a single connection configuration with the target primary node.

[0134] According to an example embodiment, the method may further include receiving at least one control message from the target master node, the at least one control message including at least one of the following: an indication of a plurality of conditional handover connection configurations; at least one condition associated with the second connection for selecting the conditional handover connection configuration; or at least one second condition for triggering execution of the conditional handover. The control message includes a handover request confirmation message.

[0135] Different variations of the methods may also be applied, as described in connection with the various exemplary embodiments.

[0136] An apparatus (e.g., a client node such as UE 110, or a network node such as source master node 120 or target master node 130) may be configured to perform or cause the performance of any aspect of the method(s) described herein. In addition, a computer program may include instructions for causing the apparatus to perform any aspect of the method(s) described herein when executed. In addition, an apparatus may include a component for performing any aspect of the method(s) described herein. According to an example embodiment, the component includes at least one processor and a memory including program code, the at least one processor and the program code being configured to cause the performance of any aspect of the method(s) described above when executed by the at least one processor.

[0137] Any range or device value given herein may be expanded or changed without losing the effect sought. In addition, unless explicitly prohibited, any embodiment may be combined with another embodiment.

[0138] Although the subject matter has been described in language specific to structural features and / or actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Instead, the specific features and actions described above are disclosed as examples of implementing the claims, and other equivalent features and actions are intended to fall within the scope of the claims.

[0139] It should be understood that the above benefits and advantages may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to embodiments that solve any or all of the above problems or embodiments that have any or all of the above benefits and advantages. It will be further understood that reference to "an" item may refer to one or more of these items.

[0140] The steps or operations of the methods described herein may be performed in any suitable order, or simultaneously where appropriate. In addition, individual blocks may be deleted from any method without departing from the scope of the subject matter described herein. Aspects of any of the above-described embodiments may be combined with aspects of any other embodiment described to form additional embodiments without losing the effects sought.

[0141] The term "comprising" is used herein to mean including the identified methods, blocks or elements, but such blocks or elements do not comprise an exclusive list and the method or apparatus may contain additional blocks or elements.

[0142] Although a topic may be referred to as the "first" or "second" topic, this does not necessarily indicate any order or importance of the topics. Rather, such an attribute may simply serve to distinguish the topics.

[0143] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) a hardware circuit implementation only (such as an implementation using only analog and / or digital circuitry), and (b) a combination of hardware circuitry and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) any portion of a hardware processor(s) with software (including digital signal processor(s), software, and memory(s)) that work together to enable a device (such as a mobile phone or server) to perform various functions, and (c) hardware circuitry and / or processor(s), such as microprocessor(s) or a portion of microprocessor(s) that requires software (e.g., firmware) to operate, but that software may not be present when such software is not required to operate. This definition of circuitry applies to all uses of the term in this application, including in any claims.

[0144] As a further example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device, if applicable to a particular claim element.

[0145] It should be understood that the above description is given as an example only, and various modifications may be made by those skilled in the art. The above description, examples and data provide a complete description of the structure and use of the exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity or with reference to one or more individual embodiments, those skilled in the art may make various changes to the disclosed embodiments without departing from the scope of this specification.

Claims

1. A device comprising: at least one processor; as well as at least one memory including computer program code; The at least one memory and the computer code are configured to, with the at least one processor, cause the apparatus to at least: Establishing a first connection to a source master node; establishing a second connection to the source secondary node; Receiving at least one indication of a plurality of conditional handover connection configurations from the source master node, wherein the plurality of conditional handover connection configurations comprises: A single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; Detecting the triggering of the execution of the conditional switching; selecting a conditional handover connection configuration from the plurality of conditional handover connection configurations based on at least one condition associated with the second connection; and Based on the selected conditional switching connection configuration, the conditional switching is performed. 2 . The apparatus of claim 1 , wherein the at least one condition associated with the second connection comprises an active state or an inactive state of the source secondary node.

3. The device according to claim 1 or 2, wherein the device is further caused to: In response to determining that the state of the source secondary node is inactive, selecting the single connection configuration; or In response to determining that the state of the source secondary node is active, the dual connectivity configuration is selected.

4. The apparatus of claim 1 , wherein the at least one condition associated with the second connection comprises at least one of the following: detecting the release of the source secondary node, detecting that a signal strength or a signal quality associated with the source secondary node is less than or equal to a threshold, detecting one or more out-of-sync indications associated with the source secondary node, detecting the initiation of a radio link monitoring timer associated with the source secondary node, a radio link failure associated with the source secondary node is detected, or detecting a beam failure associated with the source secondary node; and Wherein the apparatus is further caused to select the single connection configuration in response to detecting the at least one condition.

5. The apparatus according to any one of the preceding claims, wherein the plurality of conditional switching connection configurations comprises: a first dual connection configuration with the target primary node and the source secondary node; a second dual connection configuration with the target primary node and the target secondary node; as well as The single connection configuration with the target master node.

6. The apparatus of claim 5, wherein the apparatus is further caused to: In response to not detecting a secondary node change from the source secondary node to the target secondary node prior to the triggering of the execution of the conditional switching, selecting the first dual connectivity configuration; and In response to detecting the secondary node change prior to the triggering of the execution of the conditional handover, selecting the second dual connectivity configuration.

7. The apparatus according to any one of the preceding claims, wherein the apparatus is further caused to: Receive at least one control message from the source master node, the at least one control message comprising at least one of the following: said indication of said plurality of conditional handover connection configurations; the at least one condition associated with the second connection for selecting the conditional switching connection configuration; or At least one second condition for triggering said execution of said conditional switching. 8 . The apparatus of claim 7 , wherein the at least one second condition for triggering the execution of the conditional switching comprises an A3 event.

9. The apparatus according to claim 7 or 8, wherein the at least one control message comprises a handover type indicating a conditional handover.

10. The apparatus according to any one of claims 7 to 9, wherein the at least one control message comprises a Radio Resource Control Connection Reconfiguration message.

11. The apparatus of claim 10, wherein the radio resource control connection reconfiguration message comprises a handover command message.

12. An apparatus comprising: at least one processor; as well as at least one memory including computer program code; The at least one memory and the computer code are configured to, with the at least one processor, cause the apparatus to at least: receiving a handover request associated with a client node from a source primary node, wherein the handover request includes an indication of a source secondary node associated with the client node and a handover type indicating a conditional handover; A plurality of conditional switching connection configurations are prepared for the client node, wherein the plurality of conditional switching connection configurations include: A single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; An indication of the plurality of conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration from the plurality of conditional switching connection configurations when the conditional switching is triggered are transmitted to the source master node. 13 . The apparatus according to claim 12 , wherein the at least one condition for selecting the conditional handover connection configuration comprises an active state or an inactive state of the source secondary node.

14. The apparatus according to claim 12 or 13, wherein the at least one condition for selecting the conditional handover connection configuration comprises at least one of the following: detecting the release of the source secondary node; detecting that a signal strength or a signal quality associated with the source secondary node is less than or equal to a threshold; detecting one or more out-of-sync indications associated with the source secondary node; detecting a start of a radio link monitoring timer associated with the source secondary node; detecting a radio link failure associated with the source secondary node; or A beam failure associated with the source secondary node is detected.

15. The apparatus according to claim 13 or 14, wherein the apparatus is further caused to: receiving, from the source primary node, an indication of the active state of the source secondary node; receiving a connection request from the client node; and Based on the dual connectivity configuration, the conditional switching is performed.

16. The apparatus according to claim 13 or 14, wherein the apparatus is further caused to: receiving, from the source primary node, an indication of the inactive state of the source secondary node; receiving a connection request from the client node; and Based on the single connection configuration, the conditional switching is performed.

17. The apparatus of claim 16, wherein the apparatus is further caused to: In response to receiving the indication of the inactive state of the source secondary node, transmitting a secondary node release request to the target secondary node.

18. The apparatus according to any one of claims 12 to 17, wherein the plurality of conditional switching connection configurations comprises: a first dual connection configuration with the target primary node and the source secondary node; a second dual connection configuration with the target primary node and the target secondary node, and The single connection configuration with the target master node.

19. The device according to any one of claims 12 to 18, wherein the device is further caused to: Transmitting at least one control message to the source master node, the at least one control message comprising at least one of the following: said indication of said plurality of conditional handover connection configurations; the at least one condition associated with the second connection for selecting the conditional switching connection configuration; or At least one second condition for triggering said execution of said conditional switching.

20. The apparatus of claim 19, wherein the control message comprises a handover request confirm message.

21. An apparatus comprising: at least one processor; as well as at least one memory including computer program code; The at least one memory and the computer code are configured to, with the at least one processor, cause the apparatus to at least: transmitting a handover request to a target primary node, the handover request including an indication of a source secondary node associated with the client node and a handover type indicating a conditional handover; Receiving, from the target master node, an indication of a plurality of conditional switching connection configurations of the client node and an indication of at least one condition for selecting a conditional switching connection configuration from the plurality of conditional switching connection configurations, wherein the plurality of conditional switching connection configurations comprises: a single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; The indication of the plurality of conditional handover connection configurations and the indication of at least one condition for selecting the conditional handover connection configuration are transmitted to the client node.

22. The apparatus of claim 21, wherein the apparatus is further caused to: An indication that the source master node supports delivery of the plurality of conditional switching configurations to the client node is transmitted to the target master node.

23. The apparatus according to claim 21 or 22, wherein the at least one condition for selecting the conditional handover connection configuration comprises an active state or an inactive state of the source secondary node.

24. The apparatus according to any one of claims 21 to 23, wherein the at least one condition for selecting the conditional handover connection configuration comprises at least one of the following: detecting the release of the source secondary node; detecting that a signal strength or a signal quality associated with the source secondary node is less than or equal to a threshold; detecting one or more out-of-sync indications associated with the source secondary node; detecting a start of a radio link monitoring timer associated with the source secondary node; detecting a radio link failure associated with the source secondary node; or A beam failure associated with the source secondary node is detected.

25. The apparatus according to claim 23 or 24, wherein the apparatus is further caused to: An indication of the active state or the inactive state of the source secondary node is transmitted to the target primary node.

26. The apparatus according to any one of claims 21 to 25, wherein the plurality of conditional switching connection configurations comprises: a first dual connection configuration with the target primary node and the source secondary node; a second dual connection configuration with the target primary node and the target secondary node; as well as The single connection configuration with the target master node.

27. The device according to any one of claims 21 to 26, wherein the device is further caused to: At least one control message is received from the target master node, the at least one control message comprising at least one of the following: said indication of said plurality of conditional handover connection configurations; the at least one condition associated with the second connection for selecting the conditional handover connection configuration; or At least one second condition for triggering said execution of said conditional switching.

28. The apparatus of claim 27, wherein the control message comprises a handover request confirm message.

29. A method for communication, comprising: Establishing a first connection to a source master node; establishing a second connection to the source secondary node; Receiving at least one indication of a plurality of conditional handover connection configurations from the source master node, wherein the plurality of conditional handover connection configurations comprises: a single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; Detecting the triggering of the execution of the conditional switching; selecting a conditional handover connection configuration from the plurality of conditional handover connection configurations based on at least one condition associated with the second connection; and The conditional switching is performed based on the selected conditional switching connection configuration.

30. A method for communication, comprising: receiving a handover request associated with a client node from a source primary node, wherein the handover request includes an indication of a source secondary node associated with the client node and a handover type indicating a conditional handover; A plurality of conditional switching connection configurations are prepared for the client node, wherein the plurality of conditional switching connection configurations include: a single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; as well as An indication of the plurality of conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration from the plurality of conditional switching connection configurations when the conditional switching is triggered are transmitted to the source master node.

31. A method for communication, comprising: transmitting a handover request to a target primary node, the handover request including an indication of a source secondary node associated with the client node and a handover type indicating a conditional handover; Receiving, from the target master node, an indication of a plurality of conditional switching connection configurations of the client node and an indication of at least one condition for selecting a conditional switching connection configuration from the plurality of conditional switching connection configurations, wherein the plurality of conditional switching connection configurations comprises: a single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; and transmitting to the client node the indication of the plurality of conditional handover connection configurations and the indication of at least one condition for selecting the conditional handover connection configuration.

32. A computer program comprising program code configured to cause an apparatus to at least: Establishing a first connection to a source master node; establishing a second connection to the source secondary node; Receiving at least one indication of a plurality of conditional handover connection configurations from the source master node, wherein the plurality of conditional handover connection configurations comprises: a single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; Detecting the triggering of the execution of the conditional switching; selecting a conditional handover connection configuration from the plurality of conditional handover connection configurations based on at least one condition associated with the second connection; and The conditional switching is performed based on the selected conditional switching connection configuration.

33. A computer program comprising program code configured to cause an apparatus to at least: receiving a handover request associated with a client node from a source primary node, wherein the handover request includes an indication of a source secondary node associated with the client node and a handover type indicating a conditional handover; A plurality of conditional switching connection configurations are prepared for the client node, wherein the plurality of conditional switching connection configurations include: a single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; And transmitting to the source master node an indication of the multiple conditional switching connection configurations and an indication of at least one condition for selecting a conditional switching connection configuration from the multiple conditional switching connection configurations when the conditional switching is triggered.

34. A computer program comprising program code configured to cause an apparatus to at least: transmitting a handover request to a target primary node, the handover request including an indication of a source secondary node associated with the client node and a handover type indicating a conditional handover; Receiving, from the target master node, an indication of a plurality of conditional switching connection configurations of the client node and an indication of at least one condition for selecting a conditional switching connection configuration from the plurality of conditional switching connection configurations, wherein the plurality of conditional switching connection configurations comprises: a single connection configuration to the target master node, and Dual connection configuration with the target primary node and the target secondary node; and transmitting to the client node the indication of the plurality of conditional handover connection configurations and the indication of at least one condition for selecting the conditional handover connection configuration.

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