Method and apparatus for conditional handover recovery of dual connectivity

Abstract

A method and apparatus for dual connectivity conditional handover recovery are presented. A user equipment (UE) is presented that supports dual connectivity and is configured for conditional handover CHO, where the UE is configured to establish a connection to a primary cell of a source master node and a primary secondary cell of a source secondary node. The UE is further configured to receive a plurality of CHOs, receive assistance information for CHO recovery, and determine a primary cell of a target master node and an associated CHO configuration from the plurality of CHO configurations based on the assistance information for CHO recovery. Finally, the UE is configured to perform CHO recovery to the primary cell of the target master node based on the determined associated CHO configuration. Methods, network nodes, and functional units of the network nodes involved in the presented dual connectivity conditional handover recovery process are also presented.

Description

Technical Field

[0001] The present disclosure generally relates to a wireless communication system, and more particularly to conditional handover in a wireless communication system. Even more particularly, the present disclosure provides a method and apparatus for dual connectivity conditional handover recovery.

Background Art

[0002] Wireless telecommunication systems are continuously being developed. Higher data rates and high-quality services are demanded. The requirements for reliability are constantly increasing, and methods and means for ensuring reliable connections and data traffic while minimizing transmission delays are continuously being developed.

[0003] The development of networks enables new services for customers. One service is dual connectivity, where a user equipment is connected to a master node base station and a secondary node base station for communication. Dual connectivity improves data throughput and mobility robustness. Another service is conditional handover, which further improves the mobility robustness. For conditional handover, the network may prepare a plurality of target cells whose conditional handover settings are associated with execution conditions evaluated by the user equipment. These settings can also be used for connection recovery and re-establishment in case of a radio link failure.

[0004] To use dual connectivity and conditional handover, advanced techniques for dual connectivity conditional handover recovery may be required.

Summary of the Invention

[0005] According to a first aspect of this disclosure, user equipment (UE) is presented which is configured to support operation in dual connectivity with the primary cell of a source master node and the primary secondary cell of a source secondary node of a wireless access network, and which is configured to support conditional handover CHO. The user equipment comprises at least one processor and at least one memory containing computer program code, which, when executed by at least one processor, causes the user equipment to perform the processes described herein. Specifically, the UE is configured to establish a connection to the primary cell of the source master node and to establish a connection to the primary secondary cell of the source secondary node. Furthermore, the UE is configured to receive a plurality of CHO settings from the source master node, including setting up conditional handovers to at least one target master node and at least one target secondary node, and to receive support information for CHO recovery from the source master node. In response to a user device experiencing a radio link failure in the primary cell of the source master node, or a failure to hand over to the primary cell of the first target master node, the UE is prompted to determine the primary cell of the second target master node and the associated CHO configuration from among several CHO configurations, based on supporting information for CHO recovery. Furthermore, the UE is prompted to perform CHO recovery to the primary cell of the second target master node based on the determined associated CHO configuration.

[0006] In one embodiment, the UE may be further prompted to perform CHO recovery to the primary secondary cell of the target secondary node in response to the determined CHO configuration being a dual connectivity CHO configuration having a primary secondary cell of the target secondary node that is different from the primary secondary cell of the source secondary node.

[0007] In some embodiments, the support information includes a single-dual connectivity prioritization flag for prioritizing single or dual connectivity for CHO recovery. In further embodiments, the support information includes information about the amount of pending traffic on a secondary cell group bearer, and determining the CHO setting includes prioritizing a single connectivity CHO setting in response that the single connectivity CHO setting has secondary cell group bearers mapped to their respective target master nodes, and prioritizing a dual connectivity CHO setting in response that the dual connectivity CHO setting has secondary cell group bearers mapped to their respective target secondary nodes.

[0008] In some embodiments, the support information indicates a preference for a dual connectivity CHO configuration in which the primary secondary cell of the source secondary node is maintained. In further embodiments, the support information includes CHO recovery primary secondary cell selection criteria, and determining the CHO configuration includes selecting a CHO configuration that has a primary secondary cell that satisfies the primary secondary cell selection criteria.

[0009] In some embodiments, determining the CHO setting includes selecting a single connectivity CHO setting in response to none of the at least one primary secondary cell meeting the primary secondary cell selection criteria. In some further embodiments, the user device may further transmit cell selection information to the second target master node, including an indication that none of the at least one primary secondary cell associated with the second target master node meets the primary secondary cell selection criteria, in response to selecting a single connectivity CHO setting with the second target master node. In some yet other embodiments, the cell selection information further includes measurements related to at least one primary secondary cell associated with the second target master node.

[0010] In some embodiments, the cell selection information further includes measurements related to additional cells performed on the user device. In further embodiments, the support information includes a single-dual connectivity indicator indicating whether each CHO setting is a single or dual connectivity setting. In embodiments, the support information includes primary and secondary cell identifiers indicating which primary and secondary cells are included in each CHO setting.

[0011] A second aspect of this disclosure presents a source master node (source MN) configured to support the establishment of a connection to user equipment, wherein the user equipment supports operation in dual connectivity with the primary cell of the source master node and the primary secondary cell of the source secondary node, and is configured to support conditional handover CHO. The source MN comprises at least one processor and at least one memory containing computer program code, the computer program code, when executed by at least one processor, causes the source MN to perform the operations described herein. Specifically, the source MN is caused to transmit a plurality of CHO settings to the user equipment, including setting up conditional handovers to at least one target master node and at least one target secondary node, and to transmit support information for CHO recovery to the user equipment, the support information being used by the user equipment to determine a CHO setting from the plurality of CHO settings for CHO recovery.

[0012] In some embodiments, the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery. In some embodiments, the single-dual connectivity preference flag is determined based on the amount of pending traffic on the secondary cell group bearer to prioritize a single connectivity CHO configuration in response that the single connectivity CHO configuration has secondary cell group bearers mapped to each target master node, and to prioritize a dual connectivity CHO configuration in response that the dual connectivity CHO configuration has secondary cell group bearers mapped to each target secondary node.

[0013] In some embodiments, the support information indicates that a dual connectivity CHO configuration is preferred in which the primary secondary cell of the source secondary node is maintained. In some embodiments, the support information includes primary secondary cell selection criteria to determine a CHO configuration that has a primary secondary cell that satisfies the CHO recovery primary secondary cell selection criteria. In further embodiments, the support information includes a single-dual connectivity indicator indicating whether each CHO configuration is a single or dual connectivity configuration. In yet another embodiment, the support information includes a primary secondary cell identifier indicating which primary secondary cells are included in each CHO configuration.

[0014] A third aspect of this disclosure presents a network node that supports at least one of the central unit control plane functions or Layer 3 protocols of a radio access network, and is configured to operate with dual connectivity to the primary cell of the network node and the primary secondary cell of a source secondary node, and to support connection to user equipment configured for conditional handover CHO. The network node comprises at least one processor and at least one memory containing computer program code, the computer program code, when executed by at least one processor, causes the network node to perform the operations described herein. Specifically, the network node is caused to generate a radio resource control RRC message containing support information for CHO recovery and to transmit the RRC message containing the support information to the user equipment, the support information being used by the user equipment to determine a CHO configuration from a plurality of CHO configurations, including a configuration for conditional handover to at least one target master node and at least one target secondary node for CHO recovery.

[0015] In some embodiments, the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery. In some embodiments, the single-dual connectivity preference flag is determined based on the amount of pending traffic on the secondary cell group bearer to prioritize a single connectivity CHO configuration in response that the single connectivity CHO configuration has secondary cell group bearers mapped to each target master node, and to prioritize a dual connectivity CHO configuration in response that the dual connectivity CHO configuration has secondary cell group bearers mapped to each target secondary node.

[0016] In some embodiments, the support information indicates that a dual connectivity CHO configuration is preferred in which the primary secondary cell of the source secondary node is maintained. In some embodiments, the support information includes primary secondary cell selection criteria to determine a CHO configuration that has a primary secondary cell that satisfies the CHO recovery primary secondary cell selection criteria. In further embodiments, the support information includes a single-dual connectivity indicator indicating whether each CHO configuration is a single or dual connectivity configuration. In yet another embodiment, the support information includes a primary secondary cell identifier indicating which primary secondary cells are included in each CHO configuration.

[0017] A fourth aspect of this disclosure presents a method for conditional handover CHO recovery performed by user equipment configured to operate with dual connectivity within at least one radio access network RAN. The method includes establishing a connection to the primary cell of a source master node, establishing a connection to the primary secondary cell of a source secondary node, receiving a plurality of CHO settings from the source master node, including conditional handover settings to at least one target master node and at least one target secondary node, and receiving support information for CHO recovery from the source master node. The method further includes, in response to the user equipment experiencing a radio link failure in the primary cell of the source master node or experiencing a failure to hand over to the primary cell of a first target master node, determining the primary cell of a second target master node and an associated CHO setting from the plurality of CHO settings based on the support information for CHO recovery, and performing CHO recovery to the primary cell of the second target master node based on the determined associated CHO setting.

[0018] In an embodiment, this method further includes performing CHO recovery to the primary secondary cell of the target secondary node in response to the determined CHO setting being a dual connectivity CHO setting having a primary secondary cell of the target secondary node that is different from the primary secondary cell of the source secondary node.

[0019] In some embodiments, the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery. In further embodiments, the support information includes information about the amount of pending traffic on a secondary cell group bearer, and determining the CHO setting includes prioritizing a single connectivity CHO setting in response that the single connectivity CHO setting has secondary cell group bearers mapped to their respective target master nodes, and prioritizing a dual connectivity CHO setting in response that the dual connectivity CHO setting has secondary cell group bearers mapped to their respective target secondary nodes.

[0020] In some embodiments, the support information indicates a preference for a dual connectivity CHO configuration in which the primary secondary cell of the source secondary node is maintained. In further embodiments, the support information includes CHO recovery primary secondary cell selection criteria, and determining the CHO configuration includes selecting a CHO configuration that has a primary secondary cell that satisfies the primary secondary cell selection criteria.

[0021] In some embodiments, determining a CHO setting includes selecting a single connectivity CHO setting in response to the fact that none of the at least one primary secondary cell meets the primary secondary cell selection criteria. In some further embodiments, the user device may further cause the user device to transmit cell selection information to the second target master node, including an indication that none of the at least one primary secondary cell associated with the second target master node meets the primary secondary cell selection criteria, in response to selecting a single connectivity CHO setting with the second target master node. In some yet other embodiments, the cell selection information further includes measurements related to the at least one primary secondary cell associated with the second target master node.

[0022] In some embodiments, the cell selection information further includes measurements related to additional cells performed on the user device. In further embodiments, the support information includes a single-dual connectivity indicator indicating whether each CHO setting is a single or dual connectivity setting. In embodiments, the support information includes primary and secondary cell identifiers indicating which primary and secondary cells are included in each CHO setting.

[0023] A fifth aspect of the present disclosure presents a method for conditional handover CHO recovery performed by a source master node connected to a user device, wherein the user device operates with dual connectivity to the primary cell of the source master node and the primary secondary cell of the source secondary node. The method includes transmitting a plurality of CHO configurations to the user device, which include configurations for conditional handover to at least one target master node and at least one target secondary node; and transmitting support information for CHO recovery to the user device, which is used by the user device to determine a CHO configuration from the plurality of CHO configurations for CHO recovery.

[0024] In some embodiments, the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery. In some embodiments, the single-dual connectivity preference flag is determined based on the amount of pending traffic on the secondary cell group bearer to prioritize a single connectivity CHO configuration in response that the single connectivity CHO configuration has secondary cell group bearers mapped to each target master node, and to prioritize a dual connectivity CHO configuration in response that the dual connectivity CHO configuration has secondary cell group bearers mapped to each target secondary node.

[0025] In some embodiments, the assistance information indicates a preference for a dual connectivity CHO setting in which the primary secondary cell of the source secondary node is maintained. In some embodiments, the assistance information includes its primary secondary cell selection criteria to determine a CHO setting having a primary secondary cell that meets the CHO recovery primary secondary cell selection criteria. In further embodiments, the assistance information includes a single-dual connectivity indicator indicating whether each CHO setting is in a single or dual connectivity setting. In still other embodiments, the assistance information includes an identifier of the primary secondary cell indicating which primary secondary cell is included in each CHO setting.

[0026] The above aspects and features can be implemented in a system, apparatus, method, article, and non-transitory computer-readable medium according to a desired setting. The present disclosure can be implemented in and used with a number of types of devices including, but not limited to, mobile phones, tablet computers, wearable computing devices, portable media players, and any other various computing devices.

[0027] This summary is intended to provide a brief overview of some of the aspects and features according to the present disclosure. Accordingly, it will be understood that the above features are merely examples and should not be construed as narrowing the scope of the present disclosure in any way. Other features, aspects, and advantages of the present disclosure will become apparent from the following detailed description, drawings, and claims.

[0028] List of Abbreviations In the present disclosure, the following abbreviations are used and should be understood according to the provided definitions. 3GPP 3rd Generation Partnership Project 5G 5th Generation (Mobile Communication Network) 5GC 5G Core Network NG-RAN Next Generation Radio Access Network NR New Radio, 5G LTE Long Term Evolution, 4G BS Base Station UE User Equipment HO Handover CHO Conditional Handover DC Dual Connectivity gNB gNodeB (NR) eNB eNodeB (LTE) SCG Secondary Cell Group MCG Master Cell Group PCell Primary Cell PSCell Primary Secondary Cell MN Master / Main Node SN Secondary Node RRC Radio Resource Control Reconfiguration SRB Signaling Radio Bearer gNB-CU-CP gNodeB Central Unit Control Plane gNB-CU-UP gNodeB Central Unit User Plane gNB-DU gNodeB Distributed Unit CPC Conditional PSCell Change

[0029] In conjunction with the following drawings, the following detailed description of various embodiments can be considered to better understand the present disclosure.

Brief Description of the Drawings

[0030] [Figure 1] It is a schematic diagram of an exemplary communication system including a base station and a plurality of communication devices. [Figure 2] It is a schematic diagram of an exemplary mobile communication device. [Figure 3] It is a schematic diagram of an exemplary control device. [[ID=6l]] [Figure 4A] It is a diagram showing the NG-RAN architecture. [Figure 4B]This is a diagram showing the NG-RAN architecture. [Figure 5] This is a flowchart for dual connectivity conditional handover recovery performed by user equipment. [Figure 6] This is a flowchart of dual connectivity conditional handover recovery performed by the source master node. [Figure 7] This is a flowchart of dual connectivity conditional handover recovery performed by network nodes that support Layer 3 functionality. [Figure 8] This is an exemplary overall message flow diagram for dual connectivity conditional handover recovery. [Figure 9] This is another message flow diagram illustrating an exemplary overall dual connectivity conditional handover recovery. [Figure 10] This is a flowchart of one embodiment of overall dual connectivity conditional handover recovery. [Modes for carrying out the invention]

[0031] Before detailing the examples, we will briefly explain the specific general principles of wireless communication systems and mobile communication devices, referring to Figures 1-3, to help understand the underlying technologies of the examples we will describe.

[0032] In a wireless communication system 100 as shown in Figure 1, mobile communication devices, user devices, and user equipment (UEs) 102, 104, and 105 are provided with wireless access via at least one base station (e.g., next-generation NB, gNB), similar wireless transmit and / or receive nodes, or network nodes. The base station may be controlled or assisted by at least one suitable controller device to enable the operation of the base station and the management of mobile communication devices communicating with the base station. The controller device may be located in a radio access network (RAN) (e.g., wireless communication system 100) or a core network (CN) (not shown), and may be implemented as a single central device, or its functions may be distributed among several devices. The controller device may be part of the base station and / or provided by a separate entity such as a radio network controller (RNC). In Figure 1, controllers 108 and 109 for controlling macro-level base stations 106 and 107, respectively, are shown. The base station controllers may be interconnected with other control entities. The controllers are typically provided with memory capacity and at least one data processor. Control devices and functions may be distributed across multiple control units. In some systems, control devices may be located within the RNC, either additionally or alternatively.

[0033] In Figure 1, base stations 106 and 107 are shown as being connected to a wider communication network 113 via gateway 112. Further gateway functionality may be provided for connecting to other networks.

[0034] As used herein, the term “base station” has the full scope of its ordinary meaning and includes at least a wireless communication station that is installed in a fixed location and used to communicate as part of a wireless telephone system or radio system. The communication area (or coverage area) of a base station may be called a “cell.” Base stations and UEs may be configured to communicate over a transmission medium using any of the following radio access technologies (RATs), also called wireless communication technologies, or telecommunication standards. As shown in Figure 1, one of the base stations may function as a “serving cell” to a UE, and the UE may also receive signals from one or more other cells (which may be provided by the base station and / or any other base station) (possibly within their communication range), which may be called “adjacent cells.”

[0035] Smaller base stations 116, 118, and 120 may also be connected to network 113, for example, by a separate gateway function and / or via a controller of a macro-level station. Base stations 116, 118, and 120 may be pico-level or femto-level base stations, etc. In this example, stations 116 and 118 are connected via gateway 111, and station 120 is connected via controller device 108. In some embodiments, smaller stations may not be provided. Smaller base stations 116, 118, and 120 may be part of a second network, for example, a wireless local area network (WLAN), and may be WLAN access points (APs). Communication devices 102, 104, and 105 may access the communication system based on various access technologies, such as code division multiplexing access (CDMA) or wideband CDMA (WCDMA). Other non-exclusive examples include Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), and various schemes thereof, such as Interleaved Frequency Division Multiple Access (IFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and Space Division Multiple Access (SDMA).

[0036] An example of a wireless communication system is the architecture standardized by the Third Generation Partnership Project (3GPP). The latest 3GPP-based developments are often referred to as the Long-Term Evolution of Universal Mobile Telecommunications System (UMTS) Radio Access Technology (LTE). Various development stages of 3GPP standards are called releases. More recent developments of LTE are often referred to as LTE Advanced (LTE-A). LTE (or LTE-A) uses a radio mobile architecture known as Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and a core network known as Evolved Packet Core (EPC). Base stations in such systems are known as evolved or extended node B (eNB) and provide E-UTRAN functions to communication devices, such as user-plane packet data convergence / radio link control / medium access control / physical layer protocol (PDCP / RLC / MAC / PHY) and control plane radio resource control (RRC) protocol termination. Other examples of wireless access systems include those provided by base stations in systems based on technologies such as WLAN and / or WiMAX (Worldwide interoperability for microwave access). Base stations can provide coverage across a cell or similar wireless service area. Core network elements include Mobility Management Entities (MMEs), Serving Gateways (S-GWs), and Packet Gateways (P-GWs).

[0037] Examples of suitable communication systems include 5G or the NR concept. The NR network architecture may be similar to LTE-A. Base stations in an NR system may also be known as next-generation node B (gNB). Changes to the network architecture may depend on the need to support various radio technologies and finer-grained Quality of Service (QoS) support, as well as on-demand requirements for QoS levels to support Quality of Experience (QoE) from the user's perspective. Network-aware services and applications, as well as service and application-aware networks, may also lead to architectural changes. These relate to Information Centric Network (ICN) and User-Centric Content Delivery Network (UC-CDN) approaches. NR may use MIMO (Multiple Input-Multiple Output) antennas and more base stations or nodes than LTE (the so-called small cell concept), including macrosites that work in conjunction with smaller stations and, in some cases, also use various radio technologies for better coverage and enhanced data rates.

[0038] In future networks, Network Functions Virtualization (NFV) may be utilized. NFV is a network architecture concept that proposes virtualizing network node functions into “building blocks” or entities that can be connected or linked together to operate collectively in order to provide services. A Virtualized Network Function (VNF) may include one or more virtual machines that run computer program code using standard or common types of servers instead of customized hardware. Cloud computing or data storage may also be utilized. In wireless communication, this may mean that node operations are performed at least partially on servers, hosts, or nodes operably coupled to a remote radio head. Node operations can also be distributed across multiple servers, nodes, or hosts. It should also be understood that the distribution of work between core network operations and base station operations may differ from, and may not even exist, in LTE.

[0039] An exemplary 5G core network (CN) includes functional entities. The CN is connected to the UE via a radio access network (RAN). A User Plane Function (UPF), which may have a role called a PDU session anchor (PSA), may be responsible for forwarding frames between the data network (DN) and tunnels established over 5G to the UE that exchange traffic with the DN.

[0040] The UPF is controlled by the Session Management Function (SMF), which receives policies from the Policy Control Function (PCF). The CN may also include the Access and Mobility Function (AMF).

[0041] The following describes a possible (mobile) communication device 200 in more detail with reference to Figure 2, which shows a schematic partial cross-sectional view. Such a mobile communication device 200 is often called a user equipment (UE), user device, or terminal device. A suitable mobile communication device 200 can be provided by any device capable of transmitting and receiving radio signals. Non-limiting examples include a mobile station (MS) or mobile device, such as a mobile phone or smartphone, a computer equipped with a wireless interface card or other wireless interface equipment (such as a USB dongle), a personal data assistant (PDA) or tablet with wireless communication capabilities, or any combination thereof. The communication device 200 may provide data communication to carry communications such as voice, email, text messages, and multimedia. This allows the user to be offered and provided with various services through their communication device. Non-limiting examples of these services include two-way or multi-way calls, data communications or multimedia services, or simply access to data communication network systems such as the Internet. The user may also be provided with broadcast data or multicast data. Non-exclusive examples of content include downloads, television and radio programs, videos, advertisements, various alerts, and other information.

[0042] In industrial applications, communication devices may be modems integrated into industrial actuators (such as robot arms), and / or modems that function as Ethernet hubs, acting as connection points for one or more connected Ethernet devices (these connections may be wired or unwired).

[0043] The communication device 200 typically includes at least one data processing entity 201, at least one memory 202, and other possible components 203 for use in software and hardware-assisted execution of tasks designed to be performed, including control of access to and communication with access systems and other communication devices. Data processing, storage, and other related control devices may be located on a suitable circuit board and / or within a chipset 204. The user may control the operation of the communication device 200 using a suitable user interface, such as a keypad 205, voice commands, a touch-sensitive screen or pad, or a combination thereof. A display 208, speaker, and microphone may also be provided. Furthermore, the communication device 200 may include suitable connectors (wired or wireless) for other devices and / or suitable connectors (wired or wireless) for connecting external accessories such as hands-free devices.

[0044] The communication device 200 may receive signals via an air or radio interface 207 through a suitable receiving device and transmit signals via a suitable radio signal transmitting device. In Figure 2, the transceiver device is schematically represented by block 206. The transceiver device 206 may be provided, for example, by a radio unit and an associated antenna device. The antenna device may be located inside or outside the communication device 200.

[0045] The communication device 200 may be configured to communicate using, additionally or alternatively, one or more global navigation satellite systems (GNSS such as GPS or GLONASS), one or more mobile television broadcasting standards (such as ATSC-M / H or DVB-H), and / or any other wireless communication protocol, as needed. Other combinations of wireless communication standards (including two or more wireless communication standards) are also possible.

[0046] Generally, the communication device 200 shown in Figure 2 includes a set of components configured to perform core functions. For example, this set of components may be implemented as a system-on-a-chip (SoC) which may include parts for various purposes. Alternatively, this set of components may be implemented as individual components or groups of components tailored to various purposes. The set of components may be coupled (communicatively) to various other circuits of the communication device 200 (for example, directly or indirectly).

[0047] The communication device 200 may include at least one antenna that communicates with a transmitter and a receiver (e.g., a transceiver device 206). Alternatively, the transmitting antenna and the receiving antenna may be separate. The communication device 200 may also include a processor (e.g., at least one data processing entity 201) configured to provide signals to the transmitter, receive signals from the receiver, and control the functions of the communication device 200. The processor may be configured to control the functions of the transmitter and receiver by generating control signaling via electrical leads to the transmitter and receiver. Similarly, the processor may be configured to control other elements of the communication device 200 by generating control signaling via electrical leads connecting the processor to other elements such as a display (e.g., a display 208) or memory (e.g., at least one memory 202). A processor can be embodied in various ways, such as a circuit, at least one processing core, one or more microprocessors with accompanying digital signal processors, one or more processors without accompanying digital signal processors, one or more coprocessors, one or more multicore processors, one or more controllers, processing circuits, one or more computers, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and / or similar integrated circuits, or a combination thereof. Therefore, in some examples, a processor may comprise multiple processors or processing cores.

[0048] The communication device 200 may operate with one or more air interface standards, communication protocols, modulation types, access types, and / or similar. Signals transmitted and received by the processor may include signaling information in accordance with the applicable cellular system air interface standards, and / or various wired or wireless network technologies, including but not limited to Wi-Fi, WLAN technologies, e.g., IEEE 802.11, 802.16, 802.3, ADSL, DOCSIS, and / or similar. Furthermore, these signals may include voice data, user-generated data, user-requested data, and / or similar.

[0049] For example, the communication device 200 and / or the cellular modem within it may be capable of operating according to various third-generation (3G), fourth-generation (4G), fifth-generation (5G), Internet Protocol Multimedia Subsystem (IMS) communication protocols, such as Session Initiation Protocol (SIP), and / or similar, or 5G and beyond. For example, the communication device 200 may be capable of operating according to 4G wireless communication protocols, such as LTE-A, 5G, and / or similar, as well as similar wireless communication protocols that may be developed in the future.

[0050] It is understood that the processor may include circuitry for implementing the audio / video and logic functions of the communication device 200. For example, the processor may include a digital signal processor device, a microprocessor device, an analog-to-digital converter, a digital-to-analog converter, and / or similar. The control and signal processing functions of the communication device 200 may be assigned among these devices according to their respective functions. The processor may further include an internal voice coder, an internal data modem, and / or similar. Furthermore, the processor may include the ability to run one or more software programs that can be stored in memory. In general, the processor and the stored software instructions may be configured to cause the communication device 200 to perform actions. For example, the processor may be capable of running a connectivity program such as a web browser. The connectivity program may enable the communication device 200 to transmit and receive web content, such as location-based content, according to protocols such as Wireless Application Protocol (WAP), Hypertext Transfer Protocol (HTTP), and / or similar.

[0051] The communication device 200 may also include a user interface, such as an earphone or speaker, a ringer, a microphone, a display, a user input interface, and / or similar, which may be operably coupled to the processor. The display may include a touch-sensitive display as described above, allowing the user to make selections, input values, and / or similar actions by touch and / or gestures. The processor may also include user interface circuitry configured to control the functionality of at least some of the elements of the user interface, such as the speaker, ringer, microphone, display, and / or similar. The processor and / or user interface circuitry including the processor may be configured to control one or more of the functionality of one or more elements of the user interface through computer program instructions, such as software and / or firmware, stored in memory accessible to the processor, such as volatile memory, non-volatile memory, and / or similar. The communication device 200 may include a battery for powering various circuits associated with the mobile terminal, such as a circuit for providing mechanical vibration as a detectable output. The user input interface may include devices that enable the communication device 200 to receive data, such as a keypad (e.g., keypad 206) and / or other input devices. The keypad may be a virtual keyboard displayed on the display or an externally coupled keyboard.

[0052] The communication device 200 may also include one or more mechanisms for sharing and / or acquiring data. For example, the communication device 200 may include a short-range radio frequency (RF) transceiver and / or interrogator, which may share data with and / or acquire data from an electronic device according to RF technology. The communication device 200 may also include other short-range transceivers such as, for example, an infrared (IR) transceiver, a Bluetooth® (BT) transceiver operating using Bluetooth® wireless technology, a wireless universal serial bus (USB) transceiver, a Bluetooth® low-energy transceiver, a ZigBee transceiver, an ANT transceiver, a cellular device-to-device transceiver, a wireless local area link transceiver, and / or any other short-range wireless technology. The communication device 200, more specifically, the short-range transceiver may be capable of transmitting and / or receiving data to and from an electronic device in the vicinity of the device, for example, within 10 meters. A communication device 200, including a Wi-Fi or WLAN modem, may also transmit and / or receive data to and from electronic devices in accordance with various wireless network technologies, including LoWPAN, Wi-Fi, Wi-Fi Low Power, WLAN technologies, such as IEEE 802.11 technology, IEEE 802.15 technology, IEEE 802.16 technology, and / or similar technologies.

[0053] The communication device 200 may include memory such as one or more Subscriber Identity Modules (SIMs), one or more Universal Subscriber Identity Modules (USIMs), one or more removable User Identity Modules (R-UIMs), one or more Embedded Universal Integrated Circuit Cards (eUICCs), one or more Universal Integrated Circuit Cards (UICCs), and / or similar, which are capable of storing information elements related to a mobile subscriber. Furthermore, the communication device 200 may include other removable memory and / or fixed memory. The communication device 200 may also include volatile memory and / or non-volatile memory. For example, volatile memory may include random access memory (RAM), such as dynamic RAM and / or static RAM, on-chip or off-chip cache memory, and / or similar. Non-volatile memory, which may be embedded and / or removable, may include, for example, read-only memory, flash memory, magnetic storage devices such as hard disks, floppy disk drives, magnetic tapes, optical disk drives and / or media, non-volatile random-access memory (NVRAM), and / or similar. Like volatile memory, non-volatile memory may include cache areas for temporarily storing data. At least a portion of the volatile memory and / or non-volatile memory may be embedded in the processor. The memory may store one or more software programs, instructions, information, data, and / or similar that may be used by the device to perform the operations disclosed herein.

[0054] The memory may contain identifiers such as an International Mobile Equipment Identification (IMEI) code that uniquely identifies the communication device 200. In exemplary embodiments, the processor may be configured using computer code stored in memory to cause the processor to perform the operations disclosed herein.

[0055] Some of the embodiments disclosed herein may be implemented using software, hardware, application logic, or a combination of software, hardware, and application logic. The software, application logic, and / or hardware may reside, for example, on memory, a processor, or an electronic component. In some exemplary embodiments, the application logic, software, or instruction set is held in one of a variety of conventional computer-readable media. In the context of this document, “computer-readable media” can be any non-temporary medium that can contain, store, communicate, propagate, or transfer instructions used by or in connection with an instruction execution system, apparatus, or device, such as a computer or data processor circuit. In the example shown in Figure 2, the computer-readable media may include any non-temporary computer-readable storage medium that can contain or store instructions used by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0056] In some embodiments, the communication device 200 (i.e., a UE or user device in the network) includes a processor (e.g., at least one data processing entity 201) and memory (e.g., at least one memory 202). The memory contains computer program code that causes the communication device 200 to perform processing in the manner described below with reference to Figure 5.

[0057] Figure 3 shows an exemplary embodiment of a control device for a communications system, which is coupled to and / or controls, for example, a base station, an access system station such as an eNB or gNB, a relay node or a core network node such as an MME or S-GW or P-GW, or a core network function such as an AMF / SMF, or a server or host. This method may be incorporated into a single control device or into two or more control devices. The control device may be integrated into a node or module of the core network or RAN, or it may be outside of these. In some embodiments, the base station includes a separate control device unit or module. In other embodiments, the control device may be another network element such as an RNC or spectrum controller. In some embodiments, the base station may have such a control device in addition to the control device provided within the RNC. The control device 300 may be configured to provide control of communications within the service area of ​​the system. The control device 300 includes at least one memory 301, at least one data processing unit 302, 303, and an input / output interface 304. The control device 300 may be coupled to the receivers and transmitters of the base station via the interface. The receiver and / or transmitter may be implemented as a wireless front end or remote radio head.

[0058] Generally, the control unit 300 has an antenna that transmits and receives radio signals. A radio frequency (RF) transceiver module coupled to the antenna receives RF signals from the antenna, converts them to baseband signals, and transmits them to a processor (e.g., at least one data processing unit 302, 303). The RF transceiver also converts baseband signals received from the processor, converts them to RF signals, and sends them back to the antenna. The processor processes the received baseband signals and invokes various function modules to perform functions within the control unit 300. Memory (e.g., at least one memory 301) stores program instructions and data for controlling the operation of the control unit 300. In the example in Figure 3, the control unit 300 also includes a protocol stack as well as a set of control function modules and circuits. PDU session processing circuitry handles PDU session establishment and modification procedures. Policy control modules set policy rules for the UE. Configuration and control circuits provide various parameters for related functions, including mobility management and session management, for configuring and controlling the UE. Suitable processors include, for example, dedicated processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, ASICs, FPGA circuits, and other types of integrated circuits (ICs), as well as / or state machines.

[0059] In some embodiments, the control unit 300 (i.e., a base station, a wireless transmit and / or receive point device, or a network node in the network) includes a processor (e.g., at least one data processing unit 302, 303) and memory (e.g., at least one memory 301). The memory contains computer program code that causes the control unit 300 to perform processing in the manner described below with reference to Figure 6.

[0060] Figures 4A and 4B show a next-generation radio access network (NG-RAN) architecture 400 with a gNB402 compliant with 3GPP TS38.401 V17.0.0. The gNB402 serves the UE using the NR user / control plane protocol, is connected to the 5GC401 via the NG interface, and is connected to other gNB402s via the Xn interface. The gNB402 in Figure 4A includes a central unit (i.e., gNB-CU) 403 and one or more distributed units (i.e., gNB-DU) 404. The gNB-CU is a logical node that hosts the RRC, SDAP, and PDCP protocols of the gNB, or the RRC and PDCP protocols of the en-gNB, controlling the operation of one or more gNB-DU 404s. The gNB-CU 403 terminates the F1 interface connected to the gNB-DU 404. The dNB-DU404 is a logical node that hosts the RLC, MAC, and PHY layers of the gNB402 or en-gNB, and its operation is partially controlled by the gNB-CU403. One gNB-DU404 supports one or more cells. One cell is supported by one gNB-DU404. The gNB-DU404 terminates the F1 interface connected to the gNB-CU403.

[0061] One gNB-DU404 is connected to one gNB-CU403 via the F1 interface. NG, Xn, and F1 are logical interfaces. The Xn-C interface interconnects gNB-CU403s of different gNB402s. A gNB402 can also include a gNB-CU control plane (gNB-CU-CP), multiple gNB-CU user planes (gNB-CU-UP), and multiple gNB-DUs, which are shown in more detail in Figure 4B.

[0062] Note that NG-RAN may also include a set of ng-eNBs, and an ng-eNB may include an ng-eNB-CU and one or more ng-eNB-DUs. The ng-eNB-CU and ng-eNB-DUs are connected via the W1 interface.

[0063] Figure 4B shows an architecture where the control plane and user plane (i.e., gNB-CU-CP and gNB-CU-UP) of the gNB-CU403 are separated. gNB-CU-CP405 is a logical node that hosts the control plane portion of the RRC and PDCP protocols of the gNB-CU403 in en-gNB or gNB402. gNB-CU-CP405 terminates the E1 interface connected to gNB-CU-UP406 and the F1-C interface connected to gNB-DU404. gNB-CU-UP406 is a logical node that hosts the user plane portion of the PDCP protocol of the gNB-CU403 in en-gNB, and the user plane portion of the PDCP protocol and the SDAP protocol of the gNB-CU403 in gNB402. gNB-CU-UP406 terminates the E1 interface connected to gNB-CU-CP405 and the F1-U interface connected to gNB-DU404. The gNB-CU-UP406 is connected to one gNB-CU-CP405, multiple gNB-CU-UP406s, and multiple gNB-DU404s under the control of the same gNB-CU-CP405.

[0064] In some embodiments, the gNB-CU-CP405 is associated with a processor and memory. The memory contains computer program code that causes the gNB, which supports the functions of the gNB-CU-CP405, to perform processing in the manner described below with reference to Figure 7.

[0065] The following description may provide further details of alternative, modified, and modified examples, and the gNB may include a node connected to the 5GC via an NG interface that provides NR user plane and control plane protocol termination to the UE, for example, in accordance with 3GPP TS38.300 V17.0.0 incorporated herein by reference.

[0066] A gNB Central Unit (gNB-CU) includes, for example, a logical node that hosts the RRC, SDAP, and PDCP protocols of gNB, or the RRC and PDCP protocols of en-gNB, and controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DUs. A gNB Distributed Unit (gNB-DU) includes, for example, a logical node that hosts the RLC, MAC, and PHY layers of gNB or en-gNB, and its operation is partially controlled by the gNB-CU. A single gNB-DU supports one or more cells. A single cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0067] The gNB-CU control plane (gNB-CU-CP) includes, for example, a logical node that hosts the control plane portions of the RRC and PDCP protocols of the gNB-CU of the en-gNB or gNB. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU. The gNB-CU user plane (gNB-CU-UP) includes, for example, a logical node that hosts the user plane portion of the PDCP protocol of the gNB-CU of the en-gNB, and the user plane portion of the PDCP protocol and the SDAP protocol of the gNB-CU of the gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, in accordance with 3GPP TS38.401 V17.0.0, Section 3.1, which is incorporated herein by reference.

[0068] Between the central and distributed units, various functional partitions, sometimes called options, are possible. In Option 1 (1A-like partition), the functional partition resembles the 1A architecture of the DC. The RRC resides in the central unit. The PDCP, RLC, MAC, physical layer, and RF reside in the distributed units. In Option 2 (3C-like partition), the functional partition resembles the 3C architecture of the DC. The RRC and PDCP reside in the central unit. The RLC, MAC, physical layer, and RF reside in the distributed units. In Option 3 (intra-RLC partition), the low RLC (a partial function of the RLC), MAC, physical layer, and RF reside in the distributed units. The PDCP and high RLC (another partial function of the RLC) reside in the central unit. In Option 4 (RLC-MAC partition), the MAC, physical layer, and RF reside in the distributed units. The PDCP and RLC reside in the central unit. Alternatively, follow section 11 of 3GPP TR38.801 V14.0.0, which is incorporated by reference, for example.

[0069] gNB supports various protocol layers, including Layer 1 (L1) – the physical layer. Layer 2 (L2) of NR is divided into the following sublayers: Media Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP). The physical layer may provide a transport channel to the MAC sublayer, the MAC sublayer may provide a logical channel to the RLC sublayer, the RLC sublayer may provide an RLC channel to the PDCP sublayer, the PDCP sublayer may provide a radio bearer to the SDAP sublayer, and the SDAP sublayer may provide QoS flows to the 5GC. Control channels include, for example, BCCH, PCCH, etc. Layer 3 (L3) includes, for example, Radio Resource Control (RRC) according to Section 6 of 3GPP TS38.300 V17.0.0, which is incorporated herein by reference.

[0070] A RAN (Radio Access Network) node or network node, such as a gNB, base station, gNB-CU, or gNB-DU, or a part thereof, may be implemented using a device having, for example, CU and / or DU-related functions and / or features, and / or at least one processor and / or at least one memory (including computer-readable instructions (computer programs)) configured to support and / or provide and / or process at least one protocol (sub)layer of the RAN (Radio Access Network), such as Layer 2 and / or Layer 3.

[0071] The gNB-CU and gNB-DU components may, for example, be located in the same place or be physically separated. The gNB-DU may be further divided, for example, into two parts, for example, a part containing processing equipment and a part containing antennas. The central unit (CU) may also be called BBU / REC / RCC / C-RAN / V-RAN, O-RAN, or a part thereof. The distributed unit (DU) may also be called RRH / RRU / RE / RU, or a part thereof. The gNB-DU supports one or more cells, thereby functioning as a serving cell to, for example, user equipment (UE).

[0072] User equipment (UE) may include wireless or mobile devices, devices having a radio interface for interacting with a RAN (Radio Access Network), smartphones, in-vehicle devices, IoT devices, M2M devices, etc. Such UE or device may include at least one processor and at least one memory containing computer program code, the at least one memory and computer program code configured by at least one processor to cause the device to perform certain operations, such as making an RRC connection to at least one RAN. The UE is configured to generate messages (e.g., including a cell ID) that are transmitted radioly toward the RAN (for example, to reach a serving cell and communicate). The UE may generate, transmit, and receive RRC messages containing one or more RRC PDUs (Packet Data Units).

[0073] A UE can have different states (for example, according to 3GPP TS38.331 V17.0.0, sections 4.2.1 and 4.4, incorporated herein by reference). For example, when an RRC connection is established, the UE is in either the RRC_CONNECTED state or the RRC_INACTIVE state. In the RRC_CONNECTED state, the UE may store the AS context, transfer unicast data to and from the UE, monitor the control channel associated with the shared data channel to determine whether data is scheduled to the data channel, provide channel quality and feedback information, and / or perform adjacent cell measurements and measurement reporting. The RRC protocol includes, for example, the following main functions: RRC connection control, measurement setup and reporting, establishment / modification / release of measurement settings (e.g., in-frequency, inter-frequency, and inter-RAT measurements), setup and release of measurement gaps, and / or measurement reporting.

[0074] Before describing dual connectivity conditional handover recovery according to some embodiments of the present disclosure with reference to Figures 5-8, we will provide some background information and aspects relevant to the present disclosure.

[0075] For example, this disclosure may be incorporated into a network that supports dual connectivity (DC) and conditional handover (CHO). The CHO procedure was introduced in 3GPP Rel.16 to improve mobility robustness. In the case of CHO, the network may prepare multiple target cells associated with CHO execution conditions that are evaluated by the UE for conditional handover reconfiguration. The CHO execution conditions refer to a measurement ID (which associates the measurement with a reporting configuration) set by the source gNB. The reporting configuration defines a measurement event (e.g., measurement event A3 or A5 as defined in the 3GPP standard) that triggers a CHO execution. Each time a CHO execution condition is met, a corresponding target CHO configuration is selected and a handover is performed to the selected target cell.

[0076] In a CHO, the UE is serviced by the primary cell (PCell) of the source master node (MN) and the primary secondary cell (PSCell) of the source secondary node (SN). The UE sends a measurement report to its serving PCell to initiate CHO preparation for the PCell in the target MN. The source PCell prepares the target PCell and sends the CHO preparation, i.e., the CHO configuration of the target PCell and / or target PSCell, to the UE in an RRC reconfiguration message along with the CHO execution conditions. Once the CHO execution conditions for one of the target PCells are met, the UE disconnects from the source PCell, i.e., stops TX / RX to and from the source PCell. The UE initiates a random access procedure to the target PCell. Once the random access procedure is successfully completed, the target PCell in the target MN notifies the source PCell in the source MN that the handover procedure has been successfully completed. Upon receiving the handover success instruction from the target MN, the source PCell in the source MN begins data transfer to the target PCell in the target MN. Once the data transfer procedure is complete, the UE continues sending / receiving data to / from the network.

[0077] However, even with CHO, the wireless link quality of the UE may degrade over a given period. Currently, the UE declares a failure and initiates a re-establishment procedure to reconnect to the network, which results in additional signaling overhead and delay during the re-establishment procedure.

[0078] To overcome this problem, 3GPP introduced CHO recovery in Release 16 of the NR standard. CHO recovery (for example, as described in 3GPP TS38.311 V17.0.0, Section 5.3.7.3) reduces the downtime caused by a failure in a UE configured with conditional reconfiguration of multiple target cells. While CHO minimizes the possibility of mobility failures, a UE can still detect a failure due to misconfiguration of mobility parameters or performing a handover to the wrong cell. Instead of performing a re-establishment, a UE supporting the CHO recovery feature can recover from a failure by utilizing the stored conditional reconfiguration of prepared target cells.

[0079] After a failure is detected, the UE initiates a cell reselection procedure. If the selected cell is one of the target cells prepared by the CHO, the UE performs a handover to that cell using the CHO configuration provided by the network. If it does not have a corresponding CHO configuration, the UE initiates a re-establishment procedure to the selected cell. Thus, with CHO recovery, the UE can leverage the stored CHO configuration of the target cell to initiate CHO execution instead of going through the costly re-establishment procedure, thus reducing downtime after a failure.

[0080] The CHO recovery mechanism allows the UE to recover in the cell where the CHO setting is stored. In the case of a DC-based CHO, i.e., a CHO with multiple candidate secondary cell groups (SCGs) and / or multiple CHO settings for target PCell and target PSCell, the UE may apply a dual connectivity CHO (CHO-DC) setting when the CHO conditions are met, but CHO recovery does not take into account which SCGs to consider or whether to consider them at all during CHO execution. Therefore, if the appropriate SCG setting is not selected for CHO preparation, SCG failures and interruptions may occur in SCG bearers terminated at MN / SN.

[0081] Currently, the target CHO setting is selected based solely on radio signal measurements of the target PCell that meet specific cell selection criteria, and does not consider the signal strength / quality of the target PSCell. If two or more CHO settings are available for the same PCell, the UE does not further distinguish between different dual connectivity CHO (CHO-DC) and single connectivity CHO (CHO-SC) settings during the CHO recovery procedure. To minimize performance impact and current bearer disruption, it is essential to select the appropriate setting for the same PCell.

[0082] Furthermore, if one of the CHO-DC settings has both the appropriate PCell and PSCell, the setting details are not transparent to the UE, so the UE does not know which CHO setting is DC or SC until it decodes the setting. Moreover, the UE does not know which CHO-DC setting has the appropriate PSCell set until the setting is decoded.

[0083] The solutions to these issues provided by this disclosure can be summarized as follows: The network provides the UE with supporting information to improve recovery procedures in the CHO-DC scenario.

[0084] In some embodiments, the network may provide an SC / DC preference flag to prioritize the same PCell's CHO setting during the recovery procedure. In additional or alternative embodiments, the criterion for prioritizing an SC setting or a DC setting may be based on the amount of pending traffic on a particular SCG bearer, rather than a direct indication of a DC / SC setting. Thus, the network may indicate the amount of pending traffic to the UE. Alternatively, if the current SCG bearer has an SC setting mapped to a target SC setting, the network may set an SC / DC preference flag and choose SC over DC. If the current SCG bearer is mapped only to a target SCG, there is no benefit to switching to SC, and the network may choose DC over SC.

[0085] In further embodiments, the network may, additionally or alternatively, indicate a preference for selecting a target DC configuration with the same PSCell that minimizes disruption to current traffic (SCG maintain DC handover). In further embodiments, the network may, additionally or alternatively, provide the UE with PSCell selection criteria to be met when selecting a cell for recovery. This allows the UE to select a target DC configuration with better radio conditions for the secondary cell group. In further embodiments, the network may, additionally or alternatively, provide SC / DC indication outside of the CHO configuration so that the UE can identify which CHO configuration is SC or DC. In further embodiments, the network may, additionally or alternatively, provide PSCell IDs with or outside of the CHO-DC configuration so that the UE can identify which CHO-DC configuration has that PSCell configured in it. Furthermore, if there is no suitable PSCell in the CHO-DC configuration, a fallback from CHO-DC to CHO-SC may be used, allowing the UE to remain in the PSCell.

[0086] Figure 5 shows a flowchart of the dual connectivity conditional handover recovery performed by the UE. The user device includes at least one processor and at least one memory containing computer program code that causes the UE to perform the processing described herein. In other words, the UE is configured to perform the processing described herein.

[0087] The UE operates with dual connectivity, meaning it is connected to a source base station acting as a master node, also called a source MN, and a secondary base station, also called a source SN or SN. The process described with respect to Figure 5 is performed during a conditional handover, for example, after one or more possible target master nodes (also called target MNs) and / or target secondary nodes (also called target SNs) for a CHO have been configured in the UE. For example, the source MN may determine, based on measurements performed by the UE and reported in a measurement report, that a conditional handover with one or more target MNs is expected. The source MN may then send a CHO request to one or more target MNs. One or more (or at least some of them) target MNs may acknowledge the CHO request. In future communication systems, other steps may be performed before or after the process described with respect to Figure 5.

[0088] Starting with box 501, the UE receives multiple CHO settings from the source master node. The CHO settings relate to at least the primary cell of the target master node, but may also include the primary secondary cell of the target master node. The CHO settings may be sent to the UE in a single message, such as an RRC reconfiguration message. Alternatively, the CHO settings may be sent in at least two separate messages, i.e., one message per CHO setting, or one message per target master node, each containing one or more CHO settings for that target master node. Instead of using a Layer 3 RRC reconfiguration message, other Layer 2 or 1 messages, such as MAC signaling or signaling of CHO execution conditions via PDCCH, may be used.

[0089] In Box 502, the UE receives support information for CHO recovery from the primary cell of the source master node. This support information may be any information that allows the UE to select a CHO configuration from multiple configurations.

[0090] Support information may include a single-dual connectivity preference flag. Such a flag can be used to configure the UE to prioritize single connectivity CHO settings over dual connectivity CHO settings, and vice versa. For example, if the single-dual connectivity preference flag is set to 1, the UE will prioritize dual connectivity (DC) CHO settings over single connectivity CHO settings. Conversely, if the single-dual connectivity preference flag is set to 0, the UE will prioritize SC-CHO settings over DC-CHO settings.

[0091] Supporting information may, additionally or alternatively, include information about the amount of pending traffic on secondary cell group bearers. In this case, the UE may be configured to prioritize the single connectivity CHO setting in response to the single connectivity CHO setting having secondary cell group bearers mapped to each target master node, and to prioritize the dual connectivity CHO setting in response to the dual connectivity CHO setting having secondary cell group bearers mapped to each target secondary node.

[0092] Support information may include, additionally or alternatively, instructions to prioritize a dual connectivity CHO configuration in which the primary secondary cell of the source secondary node is maintained. In such a configuration, the UE maintains connectivity to the source SN. This reduces the data transfer required between nodes while maintaining a stable connection to the source SN.

[0093] Supporting information may additionally or alternatively include primary / secondary cell selection criteria. In this case, the UE may be configured to select a CHO setting that has primary / secondary cells that satisfy the primary / secondary cell selection criteria. For example, primary / secondary cell selection criteria may include cell quality thresholds and / or any selection criteria based on RSRP, RSRQ, or SINR conditions.

[0094] Support information may additionally or alternatively include information about which information is coded in which CHO settings. For example, support information may include a single-dual connectivity indicator that shows which type of CHO setting is coded in each CHO setting. In other additional or alternative examples, support information may include primary / secondary cell identifiers that show which primary / secondary cells are coded in the CHO setting. In alternative embodiments, information about CHO settings may be indicated in different ways, for example, by including the information in an additional field accompanying the CHO setting, or by signaling separately from the support information.

[0095] The UE then selects a CHO configuration from several CHO configurations based on supporting information for CHO recovery, as shown in box 503. Such a selection is typically made in response to user equipment experiencing a radio link failure in the primary cell of the source master node or a handover failure in the primary cell of the handover target master node. The selected CHO configuration is (at least) related to the primary cell of the target master node and may also be related to the possible primary and secondary cells of the target secondary node used in conjunction with the primary cell.

[0096] Finally, as shown in box 504, the UE performs CHO recovery using the primary cell of the target master node according to the selected CHO configuration. In one embodiment, where the selected CHO is a dual connectivity CHO configuration having a primary-secondary cell of the target secondary node that is different from the primary-secondary cell of the source secondary node, the UE may also be configured to perform CHO recovery using the primary-secondary cell of the target secondary node (in addition to the primary cell of the target master node to enable DC connectivity).

[0097] Furthermore, if none of the primary and secondary cells in the DC-CHO configuration are suitable, a fallback may be used, allowing the UE to persist with single connectivity on the primary cell. For example, if none of at least one primary and secondary cells meet the primary and secondary cell selection criteria described above, the UE may be configured to select (or apply) a single connectivity CHO configuration for the target master node. In such an example, the UE may also be configured to send cell selection information to the target master node, indicating that none of the at least one primary and secondary cells configured for the target master node meet the primary and secondary cell selection criteria. In a further embodiment, this cell selection information may also include measurements related to at least one primary and secondary cell configured for the target master node. This information may be used for root cause analysis by the network. In other additional or alternative embodiments, the cell selection information may further include measurements related to additional cells, such as all cells or at least several cells that can be measured on the user equipment.

[0098] The UE may also include means for performing the processes described herein. For example, the UE may include means for receiving a plurality of CHO settings from a source master node and means for receiving support information for CHO recovery from the primary cell of the source master node. The UE may further include means for selecting a CHO setting from the plurality of CHO settings based on support information for CHO recovery in response to a user device experiencing a radio link failure in the primary cell of the source master node or a handover failure in the primary cell of a second target master node, the selected CHO setting relating to the primary cell of the target master node. Finally, the UE may include means for performing CHO recovery using the primary cell of the target master node. Means for other processes described herein may also be provided.

[0099] Figure 6 shows a flowchart of the dual connectivity conditional handover recovery performed by the source MN. The source MN includes at least one processor and at least one memory containing computer program code that causes the source MN to perform the operations described herein. In other words, the source MN is configured to perform the operations described herein. The source MN operates with dual connectivity to the primary cell of the source master node and the primary secondary cell of the source secondary node and is connected to user equipment configured for conditional handover CHO.

[0100] To enable the improved CHO recovery mechanism described herein, the source MN sends multiple CHO settings to the user instrument in response to measurements performed by the UE and reported in a measurement report, for example, indicating that a conditional handover with one or more target MNs is expected. This is shown in box 601 of Figure 6. The CHO settings relate to at least the primary cell of the target master node, but may also include the primary secondary cells of the target master node. The CHO settings may be sent to the UE in a single message, such as an RRC reconfiguration message. Alternatively, the CHO settings may be sent in at least two separate messages, i.e., one message per CHO setting, or one message per target master node, containing one or more CHO settings for that target master node. Instead of using a Layer 3 RRC reconfiguration message, other Layer 2 or 1 messages, such as MAC signaling or signaling of CHO execution conditions via PDCCH, may be used.

[0101] As shown in box 602, the source MN further transmits support information for CHO recovery to the user device. This support information is used by the user device to select a CHO setting from several CHO settings for CHO recovery, as previously described with respect to Figure 5.

[0102] Support information may include a single-dual connectivity preference flag. Such a flag can be used to configure the UE to prioritize single connectivity CHO settings over dual connectivity CHO settings, and vice versa. For example, if the single-dual connectivity preference flag is set to 1, the UE will prioritize dual connectivity (DC) CHO settings over single connectivity CHO settings. Conversely, if the single-dual connectivity preference flag is set to 0, the UE will prioritize SC-CHO settings over DC-CHO settings.

[0103] The single-dual connectivity preference flag may be determined based on the amount of pending traffic on the secondary cell group bearers. In this case, the source MN may be configured to prefer the single connectivity CHO setting in response to having secondary cell group bearers mapped to their respective target master nodes, and the dual connectivity CHO setting in response to having secondary cell group bearers mapped to their respective target secondary nodes.

[0104] Support information may include, additionally or alternatively, instructions to prioritize a dual connectivity CHO configuration in which the primary secondary cell of the source secondary node is maintained. In such a configuration, the UE maintains connectivity to the source SN. This reduces the data transfer required between nodes while maintaining a stable connection to the source SN.

[0105] Supporting information may additionally or alternatively include primary / secondary cell selection criteria. In this case, the UE may be configured to select a CHO setting that has primary / secondary cells that satisfy the primary / secondary cell selection criteria. For example, primary / secondary cell selection criteria may include cell quality thresholds and / or any selection criteria based on RSRP, RSRQ, or SINR conditions.

[0106] Support information may additionally or alternatively include information about which information is coded in which CHO settings. For example, support information may include a single-dual connectivity indicator that shows which type of CHO setting is coded in each CHO setting. In other additional or alternative examples, support information may include primary / secondary cell identifiers that show which primary / secondary cells are coded in the CHO setting. In alternative embodiments, information about CHO settings may be indicated in different ways, for example, by including the information in an additional field accompanying the CHO setting, or by signaling separately from the support information.

[0107] The source master node may also include means for performing the processes described herein. For example, the source master node may include means for sending a plurality of CHO settings to a user device and means for sending support information for CHO recovery to the user device, the support information being used by the user device to select a CHO setting from the plurality of CHO settings for CHO recovery. Means for other processes described herein may also be provided.

[0108] Figure 7 shows a flowchart of a dual connectivity conditional handover using on-time data transfer performed by a network node that supports the gNB-CU-CP function.

[0109] The network node is configured to support at least one of the following: the central unit control plane (gNB-CU-CP) functionality of the wireless access network or a Layer 3 protocol, and to support connection with user equipment operating with dual connectivity between the network node's primary cell and the primary / secondary cell of the source secondary node.

[0110] Starting from box 701, the network node, in particular the gNB-CU-CP of the network node, generates a radio resource control RRC message containing support information for CHO recovery. The network node then sends the RRC message containing the support information to the user equipment. The support information is used by the user equipment to select a CHO setting from several CHO settings for CHO recovery. The RRC message is sent to the UE via the gNB-DU. The embodiments described with respect to the source MN can also be applied to the network node in Figure 7, as will be understood by those skilled in the art.

[0111] Figure 8 shows an overall message flow diagram of one embodiment of dual connectivity conditional handover recovery. The message flow diagram shows UE801, source MN802 associated with primary cell PCell-0, source SN803 associated with n primary secondary cells PSCell-0, first target MN804 associated with primary cell PCell-1, first target SN805 associated with primary secondary cells PCell-1 and PCell-3, second target MN806 associated with primary cell PCell-2, and second target SN807 associated with primary secondary cell PCell-2, which operate during CHO recovery in accordance with this disclosure.

[0112] The overall process of this exemplary embodiment is as follows: In number 1, UE801 is serviced by PCell-0 from source MN802 (S-MN) and PSCell-0 from source SN803 (S-SN), i.e., UE801 is operating with dual connectivity. Number 2 indicates that UE801 is configured with three CHO settings for the same target PCell-1 of T-MN1 804. These CHO settings are referred to as Config 1a, Config 1b, and Config 1c. Config 1a contains CHO setting information for CHO to PCell-1 and conditional PSCell change (CPC) to PSCell-1 of T-SN1 805 (MN+SN bearer, CHO-DC). Config 1b contains CHO setting information for CHO to PCell-1 only (all MN bearer, CHO-SC). Config 1c contains CHO configuration information for PCell-1 and CPC for PSCell-3 of T-SN1 805 (MN+SN bearer, CHO-DC).

[0113] In addition to these three settings for PCell-1, the UE801 is configured with the other CHO-DC settings for PCell-2 (T-MN2 806) along with the CPC settings for PSCell-2 (T-SN2 807). This is highlighted in box number 3. The settings provided to the UE801 in numbers 2 and 3 can also be provided in a single step (using a single RRC reconfiguration).

[0114] Number 4 indicates that the serving PCell-0 provides UE801 with support information for the CHO recovery procedure described in relation to the embodiments disclosed herein. In this example, the support information may include SC / DC preference flags that configure the recovery operation of UE801 and indicate the type of configuration preferred during the CHO recovery procedure. The support information may further include PSCell selection criteria for the CHO recovery procedure, which may be based on one or all of the RSRP, RSRQ, or SINR measurements. Furthermore, the support information may also include instructions related to CHO-DC or CHO-SC so that UE801 can identify whether a configuration contains a PSCell, allowing the UE to determine which configuration to consider / decode during the CHO recovery procedure. The support information may also include PSCell IDs outside of CHO-DC configurations configured by PSCell ID so that UE801 can select / decode the desired configuration. As will be understood by those skilled in the art, the support information may include parts of this information as needed.

[0115] In step 5, UE801 experiences either a radio link failure on source PCell-0, and / or a failure of the handover during CHO execution to the originally selected target PCell-2. In this example, we assume that UE801 experienced a handover failure on PCell-2. UE801 then selects one cell suitable for recovery, for example, PCell-1. Suitable means, for example, that measurements indicate this cell's radio state is sufficient for a stable connection, or that other conditions for establishing a connection are met. In short, PCell-1 is one of the cells prepared for CHO and is suitable for recovering the connection.

[0116] According to the support information, as shown in number 7, UE801 prioritizes the DC setting over the SC setting, as set by serving PCell-0 in number 4. Then, in number 8, UE801 detects the CHO-DC setting associated with PCell-1 by using the SC / DC indicator provided in number 4. UE801 identifies Config 1a and Config 1c as the CHO-DC settings associated with PCell-1.

[0117] In step 9, UE801 identifies PSCell-1 and PSCell-3 as PSCells of the target SN configured with the CHO setting for PSCell-1, using the support information provided in step 4. In step 10, UE801 selects one of the CHO-DC settings associated with PSCell-1, namely Config 1a and Config 1c. The selection criteria are based on the PSCell selection conditions provided in step 4. In this example, PSCell-3 meets the selection conditions during recovery, and UE801 selects Config 1c associated with PSCell-3.

[0118] Subsequently, as shown in number 11, UE801 decodes Config 1c, which was selected as the appropriate setting based on the supporting information in number 4 used in numbers 7-11. In the final step 12, UE801 recovers PCell-1 and PSCell-3 using the CHO setting Config 1c selected in step 10 and decoded in step 11. As described above, UE801 is provided with and configured with enough information to minimize SCG bearer downtime during the recovery procedure in the CHO-DC scenario.

[0119] Figure 9 shows an overall message flow diagram of one embodiment of dual connectivity conditional handover recovery. The message flow diagram shows UE901, source MN902 associated with primary cell PCell-0, source SN903 associated with n primary secondary cells PSCell-0, first target MN904 associated with primary cell PCell-1, first target SN905 associated with primary secondary cells PCell-1 and PCell-3, second target MN906 associated with primary cell PCell-2, and second target SN907 associated with primary secondary cell PCell-2, which operate during CHO recovery in accordance with this disclosure.

[0120] The overall process of this exemplary embodiment is as follows: In number 1, UE901 is serviced by PCell-0 from source MN902 (S-MN) and PSCell-0 from source SN903 (S-SN), i.e., UE901 is operating with dual connectivity. Number 2 indicates that UE901 is configured with three CHO settings for the same target PCell-1 of T-MN1 904. These CHO settings are referred to as Config 1a, Config 1b, and Config 1c. Config 1a contains CHO setting information for CHO to PCell-1 and conditional PSCell change (CPC) to PSCell-1 of T-SN1 905 (MN+SN bearer, CHO-DC). Config 1b contains CHO setting information for CHO to PCell-1 only (all MN bearer, CHO-SC). Config 1c contains CHO configuration information for PCell-1 and CPC for PSCell-3 with T-SN1 905 (MN+SN bearer, CHO-DC).

[0121] In addition to these three settings for PCell-1, the UE901 is configured with the other CHO-DC settings for PCell-2 (T-MN2 906) along with the CPC settings for PSCell-2 (T-SN2 907). This is highlighted in box number 3. The settings provided to the UE901 in numbers 2 and 3 can also be provided in a single step (using a single RRC reconfiguration).

[0122] Number 4 indicates that the serving PCell-0 provides UE901 with support information for the CHO recovery procedure described in relation to the embodiments disclosed herein. In this example, the support information may include SC / DC preference flags that configure the recovery operation of UE901 and indicate the type of configuration preferred during the CHO recovery procedure. The support information may further include PSCell selection criteria for the CHO recovery procedure, which may be based on one or all of the RSRP, RSRQ, or SINR measurements. Furthermore, the support information may also include instructions related to CHO-DC or CHO-SC so that UE901 can identify whether a configuration contains a PSCell, and so that the UE can determine which configuration to consider / decode during the CHO recovery procedure. The support information may also include PSCell IDs outside of CHO-DC configurations configured by PSCell ID so that UE901 can select / decode the desired configuration. As will be understood by those skilled in the art, the support information may include parts of this information as needed.

[0123] In step 5, UE901 experiences either a radio link failure at source PCell-0, and / or a failure of the handover during CHO execution to the originally selected target PCell-2. In this example, we assume that UE901 experienced a handover failure to PCell-2. UE901 then selects one cell suitable for recovery, for example, PCell-1. Suitable means, for example, that measurements indicate this cell's radio state is sufficient for a stable connection, or that other conditions for establishing a connection are met. In short, PCell-1 is one of the cells prepared for CHO and is suitable for recovering the connection.

[0124] According to the support information, as shown in number 7, UE901 prioritizes the DC setting over the SC setting, as set by serving PCell-0 in number 4. Then, in number 8, UE901 detects the CHO-DC setting associated with PCell-1 by using the SC / DC indicator provided in number 4. UE901 identifies Config 1a and Config 1c as the CHO-DC settings associated with PCell-1.

[0125] In step 9, UE901 identifies PSCell-1 and PSCell-3 as PSCells of the target SN configured with the CHO setting for PCell-1, by using the support information provided in step 4. In step 10, UE901 does not select any of the CHO-DC settings associated with PCell-1, i.e., neither Config 1a nor Config 1c is selected, because neither of them satisfies the PSCell selection criteria.

[0126] Subsequently, as shown in number 11, UE901 selects CHO-SC configuration Config 1b as the appropriate configuration based on the support information provided in number 4 and used in numbers 7-11. Since an available CHO-SC configuration exists for PCell-1, the UE falls back from CHO-DC recovery to CHO-SC recovery. In number 12, UE901 recovers on PCell-1 by using the CHO-SC configuration, i.e., Config 1b.

[0127] Finally, after the CHO recovery procedure is successful, UE901 reports to T-MN1 904 that none of the PSCells configured in the CHO-DC setting were suitable for the CHO recovery procedure. In one embodiment, UE901 also reports measurements related to PSCell-1 and PSCell-3, which are identified as PSCells associated with the CHO-DC setting of PCell-1, which can be used for root cause analysis. In other embodiments, UE901 reports all available measurements that the network can use for root cause analysis.

[0128] Finally, Figure 10 shows a flowchart of one embodiment of the overall dual connectivity conditional handover recovery, illustrating the decision mechanism that the UE may follow.

[0129] Starting from box 1001, the UE determines (and declares) a radio quality fault, such as RLF or HOF, as described with respect to the embodiments described herein. Then, as shown in box 1002, a PCell of the target master node is selected for CHO recovery, for example, based on current measurements. The PCell configuration, i.e., the CHO configuration of this PCell, is available and detected in box 1003. These CHO configurations are classified for SC and DC according to the information transmitted with the supporting information described above. If the supporting information indicates that DC takes precedence over SC (as shown in box 1005), the UE proceeds to box 1006. Otherwise, the UE proceeds to box 1010 (described below).

[0130] In box 1006, the UE detects the PSCell for each DC configuration. This may be done according to the information transmitted along with the support information described above. If any of the PSCells satisfy the PSCell selection criteria (shown in box 1007), the UE proceeds to box 1008. Otherwise, the UE proceeds to box 1010 (described below). The PSCell selection criteria may be one of the conditions described above for other embodiments, for example, the embodiment in Figure 5. In box 1008, the UE selects a PSCell based on the PSCell criteria, for example, selecting the PSCell with the best condition determined. The PSCell criteria may also be included in the PSCell selection criteria. If only one PSCell satisfies the selection criteria, the process in box 1008 may be skipped.

[0131] Finally, the UE selects the corresponding DC setting in box 1009 and establishes connections on each PCell and PSCell, or selects the corresponding SC setting in box 1010 and establishes connections only on each PCell.

[0132] It should be understood that the apparatus described herein may include, or be combined with, other units or modules such as radio components or radio heads used in or for transmitting and / or receiving. Although the apparatus is described as a single entity, different modules and memories may be implemented in one or more physical or logical entities.

[0133] While the embodiments are described in relation to LTE and 5G NR, it should be noted that similar principles can be applied to other networks and communication systems that require high-speed connection re-establishment. Thus, although specific embodiments have been described above as examples with reference to specific exemplary architectures of wireless networks, technologies, and standards, the embodiments may be applied to any other suitable form of communication system other than those illustrated and described herein.

[0134] While the above describes exemplary embodiments, it should be noted that there are several variations and modifications that can be added to the disclosed solutions without departing from the scope of this disclosure.

[0135] In general, various exemplary embodiments may be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. Some aspects of this disclosure may be implemented in hardware, while others may be implemented in firmware or software that can be executed by a controller, microprocessor, or other computing device, but this disclosure is not limited to these. Various aspects of this disclosure may be illustrated and described using block diagrams, flowcharts, or other graphic representations, but it should be understood that these blocks, apparatus, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers, or other computing devices, or a combination thereof, as non-limiting examples.

[0136] The exemplary embodiments of this disclosure may be implemented by computer software or hardware, or a combination of software and hardware, that can be executed by a data processor of a mobile device, such as a processor entity. Computer software or programs, also called program products, which include software routines, applets, and / or macros, may be stored on any device-readable data storage medium and include program instructions for performing a particular task. A computer program product may include one or more computer executable components configured to perform embodiments when the program is executed. One or more computer executable components may be at least one piece of software code or part thereof.

[0137] Furthermore, it should be noted that in this regard, the logic flow blocks shown in the diagram may represent program steps, interconnected logic circuits, blocks, and functions, or combinations of program steps and logic circuits, blocks, and functions. Software can be stored on physical media such as memory chips or memory blocks implemented within the processor, magnetic media such as hard disks or floppy disks, optical media such as DVDs and their data variants, and CDs. Physical media are non-temporary media.

[0138] Memory can be any type appropriate to the local technical environment and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. Data processors can be any type appropriate to the local technical environment and may include, but are not limited to, one or more general-purpose computers, dedicated computers, microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), FPGAs, gate-level circuits, and processors based on multi-core processor architectures.

[0139] The exemplary embodiments of this disclosure can be implemented in various components, such as integrated circuit modules. Designing integrated circuits is generally a highly automated process. Complex and powerful software tools are available to translate logic-level designs into semiconductor circuit designs ready for etching onto semiconductor substrates.

[0140] The foregoing description has provided a complete and informative description of exemplary embodiments of the present disclosure, as non-limiting examples. However, various modifications and adaptations may become apparent to those skilled in the art by reading the foregoing description in conjunction with the accompanying drawings and claims. However, all such modifications and similar modifications of the teachings of the present disclosure remain within the scope of the present disclosure as defined in the accompanying claims. In fact, further embodiments exist, including combinations of one or more embodiments with any of the other embodiments described above.

Claims

1. User equipment configured to support operation in dual connectivity with the primary cell of a source master node and the primary secondary cell of a source secondary node of a wireless access network, and configured to support conditional handover CHO, At least one processor, At least one memory containing computer program code and The computer program code, when executed by the at least one processor, is transmitted to the user device. Establishing a connection to the primary cell of the aforementioned source master node, To establish a connection between the source secondary node and the primary secondary cell, Receiving multiple CHO configurations from the source master node, including the configuration of conditional handover to at least one target master node and at least one target secondary node, Receiving support information for CHO recovery from the aforementioned source master node, In response to the user equipment experiencing a wireless link failure in the primary cell of the source master node or experiencing a failure to hand over to the primary cell of the first target master node, the primary cell of the second target master node and the associated CHO setting among the plurality of CHO settings are determined based on the CHO recovery support information. Based on the associated CHO settings determined above, perform CHO recovery of the second target master node to the primary cell. User equipment that executes the command.

2. The user device according to claim 1, which can be further made to perform CHO recovery to the primary secondary cell of the target secondary node in response to the determined CHO setting being a dual connectivity CHO setting having a primary secondary cell of the target secondary node that is different from the primary secondary cell of the source secondary node.

3. The user device according to claim 1, wherein the support information includes a single-dual connectivity priority flag for prioritizing single or dual connectivity for CHO recovery.

4. The user equipment according to claim 1, wherein the support information includes information regarding the amount of pending traffic on a secondary cell group bearer, and determining the CHO setting includes prioritizing the single connectivity CHO setting in response that the single connectivity CHO setting has secondary cell group bearers mapped to each target master node, and prioritizing the dual connectivity CHO setting in response that the dual connectivity CHO setting has secondary cell group bearers mapped to each target secondary node.

5. The user device according to claim 1, wherein the support information indicates that a dual connectivity CHO setting is preferred in which the primary secondary cell of the source secondary node is maintained.

6. The user device according to claim 1, wherein the support information includes CHO recovery primary secondary cell selection conditions, and determining the CHO setting includes selecting a CHO setting having primary secondary cells that satisfy the primary secondary cell selection conditions.

7. The user device according to claim 6, wherein determining the CHO setting includes selecting a single connectivity CHO setting in response to none of at least one primary secondary cell satisfying the primary secondary cell selection criteria.

8. The aforementioned user equipment is In response to selecting a single connectivity CHO setting with the second target master node, send cell selection information to the second target master node, including an indication that none of the at least one primary secondary cell associated with the second target master node satisfies the primary secondary cell selection criteria. The user device according to claim 7, which can be further made to perform the following.

9. The user device according to claim 8, wherein the cell selection information further includes measurements related to the at least one primary secondary cell associated with the second target master node.

10. The user device according to claim 8, wherein the cell selection information further includes measurements related to further cells performed on the user device.

11. The user device according to claim 1, wherein the support information includes a single-dual connectivity indicator indicating whether each CHO setting is a single or dual connectivity setting.

12. The user device according to any one of claims 1 to 11, wherein the support information includes a primary / secondary cell identifier indicating which primary / secondary cells are included in each CHO setting.

13. A source master node configured to support establishing a connection to user equipment, wherein the user equipment is configured to support operation in dual connectivity with the primary cell of the source master node and the primary secondary cell of the source secondary node, and to support conditional handover CHO, and the source master node is configured to support conditional handover CHO. At least one processor, At least one memory containing computer program code and The computer program code, when executed by at least one processor, is sent to the source master node. Sending multiple CHO configurations to the user device, including the configuration of conditional handover to at least one target master node and at least one target secondary node, Transmitting support information for CHO recovery to the user equipment, wherein the support information is used by the user equipment to determine a CHO setting from the plurality of CHO settings for CHO recovery. The source master node that executes the command.

14. The source master node according to claim 13, wherein the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery.

15. The source master node according to claim 14, wherein the single-dual connectivity preference flag is determined based on the amount of pending traffic on the secondary cell group bearer in order to prefer the single connectivity CHO setting in response that the single connectivity CHO setting has secondary cell group bearers mapped to each target master node, and to prefer the dual connectivity CHO setting in response that the dual connectivity CHO setting has secondary cell group bearers mapped to each target secondary node.

16. The source master node according to claim 13, wherein the support information indicates that a dual connectivity CHO setting is preferred in which the primary secondary cell of the source secondary node is maintained.

17. The source master node according to claim 13, wherein the support information includes the primary / secondary cell selection criteria for determining a CHO configuration having primary / secondary cells that satisfy the CHO recovery primary / secondary cell selection criteria.

18. The source master node according to claim 13, wherein the support information includes a single-dual connectivity indicator indicating whether each CHO setting is a single or dual connectivity setting.

19. The source master node according to any one of claims 13 to 18, wherein the support information includes a primary / secondary cell identifier indicating which primary / secondary cells are included in each CHO configuration.

20. A network node supporting at least one of the central unit control plane functions or Layer 3 protocols of a wireless access network, operating with dual connectivity between the primary cell of the network node and the primary secondary cell of a source secondary node, and configured to support connection with user equipment configured for conditional handover CHO, wherein the network node At least one processor, At least one memory containing computer program code and The computer program code, when executed by the at least one processor, is transmitted to the network node. To generate a wireless resource control RRC message containing support information for CHO recovery, Transmitting the RRC message containing the support information to the user device, wherein the support information is used by the user device to determine a CHO configuration from a plurality of CHO configurations, including a configuration for conditional handover to at least one target master node and at least one target secondary node for CHO recovery. The network node that executes the command.

21. The network node according to claim 20, wherein the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery.

22. The network node according to claim 21, wherein the single-dual connectivity preference flag is determined based on the amount of pending traffic on the secondary cell group bearer in order to prefer the single connectivity CHO setting in response that the single connectivity CHO setting has secondary cell group bearers mapped to each target master node, and to prefer the dual connectivity CHO setting in response that the dual connectivity CHO setting has secondary cell group bearers mapped to each target secondary node.

23. The network node according to claim 20, wherein the support information indicates that a dual connectivity CHO configuration is preferred in which the primary secondary cell of the source secondary node is maintained.

24. The network node according to claim 20, wherein the support information includes the primary / secondary cell selection criteria for determining a CHO configuration having primary / secondary cells that satisfy the CHO recovery primary / secondary cell selection criteria.

25. The network node according to claim 20, wherein the support information includes a single-dual connectivity indicator indicating whether each CHO setting is a single or dual connectivity setting.

26. The network node according to any one of claims 20 to 25, wherein the support information includes a primary / secondary cell identifier indicating which primary / secondary cells are included in each CHO configuration.

27. A conditional handover CHO recovery method performed by user equipment configured to operate with dual connectivity within at least one wireless access network RAN, Establishing a connection to the primary cell of the source master node, Establishing a connection between the source secondary node and the primary secondary cell, Receiving multiple CHO configurations from the source master node, including the configuration of conditional handover to at least one target master node and at least one target secondary node, Receiving support information for CHO recovery from the aforementioned source master node, In response to the user equipment experiencing a wireless link failure in the primary cell of the source master node or experiencing a failure to hand over to the primary cell of the first target master node, the primary cell of the second target master node and the associated CHO setting among the plurality of CHO settings are determined based on the CHO recovery support information. Based on the associated CHO settings determined above, perform CHO recovery of the second target master node to the primary cell. Methods that include...

28. The method according to claim 27, further comprising performing CHO recovery to the primary secondary cell of the target secondary node in response to the determined CHO setting being a dual connectivity CHO setting having a primary secondary cell of the target secondary node that is different from the primary secondary cell of the source secondary node.

29. The method according to claim 27, wherein the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery.

30. The method according to claim 27, wherein the support information includes information regarding the amount of pending traffic on a secondary cell group bearer, and determining the CHO setting includes prioritizing the single connectivity CHO setting in response that the single connectivity CHO setting has secondary cell group bearers mapped to each target master node, and prioritizing the dual connectivity CHO setting in response that the dual connectivity CHO setting has secondary cell group bearers mapped to each target secondary node.

31. The method according to claim 27, wherein the support information indicates that a dual connectivity CHO setting is preferred in which the primary secondary cell of the source secondary node is maintained.

32. The method according to claim 27, wherein the support information includes CHO recovery primary secondary cell selection criteria, and determining the CHO setting includes selecting a CHO setting having primary secondary cells that satisfy the primary secondary cell selection criteria.

33. The method according to claim 32, wherein determining the CHO setting includes selecting a single connectivity CHO setting in response to none of at least one primary secondary cell satisfying the primary secondary cell selection criteria.

34. The aforementioned user equipment is In response to selecting a single connectivity CHO setting with the second target master node, send cell selection information to the second target master node, including an indication that none of the at least one primary secondary cell associated with the second target master node satisfies the primary secondary cell selection criteria. The method according to claim 33, which allows for further execution of the above.

35. The method according to claim 34, wherein the cell selection information further includes measurements relating to the at least one primary secondary cell associated with the second target master node.

36. The method according to claim 34, further comprising the cell selection information, which further includes measurements related to further cells performed on the user device.

37. The method according to claim 27, wherein the support information includes a single-dual connectivity indicator indicating whether each CHO setting is a single or dual connectivity setting.

38. The method according to any one of claims 27 to 37, wherein the support information includes a primary / secondary cell identifier indicating which primary / secondary cells are included in each CHO setting.

39. A conditional handover CHO recovery method performed by a source master node connected to a user device, wherein the user device operates with dual connectivity to the primary cell of the source master node and the primary secondary cell of the source secondary node, and the method is: Sending multiple CHO configurations to the user device, including the configuration of conditional handover to at least one target master node and at least one target secondary node, Transmitting support information for CHO recovery to the user equipment, wherein the support information is used by the user equipment to determine a CHO setting from the plurality of CHO settings for CHO recovery. Methods that include...

40. The method according to claim 39, wherein the support information includes a single-dual connectivity preference flag for prioritizing single or dual connectivity for CHO recovery.

41. The method according to claim 40, wherein the single-dual connectivity preference flag is determined based on the amount of pending traffic on the secondary cell group bearer in order to prefer the single connectivity CHO setting in response that the single connectivity CHO setting has secondary cell group bearers mapped to each target master node, and to prefer the dual connectivity CHO setting in response that the dual connectivity CHO setting has secondary cell group bearers mapped to each target secondary node.

42. The method according to claim 39, wherein the support information indicates that a dual connectivity CHO setting is preferred in which the primary secondary cell of the source secondary node is maintained.

43. The method according to claim 39, wherein the support information includes primary and secondary cell selection conditions for determining a CHO setting having primary and secondary cells that satisfy the CHO recovery primary and secondary cell selection conditions.

44. The method according to claim 39, wherein the support information includes a single-dual connectivity indicator indicating whether each CHO setting is a single or dual connectivity setting.

45. The method according to any one of claims 39 to 44, wherein the support information includes a primary / secondary cell identifier indicating which primary / secondary cells are included in each CHO setting.

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