Method and apparatus for dual connectivity condition switch recovery

Abstract

Methods and apparatus for dual connectivity conditional switching recovery are presented. A user equipment supporting dual connectivity and configured for conditional handover (CHO) is presented, the user equipment being configured to establish a connection to a primary cell of a source primary node and a primary secondary cell of a source secondary node. The user equipment is further configured to: receive a plurality of CHOs; receiving auxiliary information for CHO recovery; and determining a primary cell of the target primary node and an associated CHO configuration from the plurality of CHO configurations based on the secondary information for CHO recovery. Finally, the user equipment is configured to perform CHO recovery to a primary cell of the target primary node based on the determined associated CHO configuration. Methods, network nodes, and functional units of the network nodes involved in the presented dual connectivity condition switching recovery process are also presented.

Description

Technical Field

[0001] The subject disclosure relates generally to wireless communication systems, and more particularly to conditional handover in wireless communication systems. More particularly, the subject disclosure provides a method and apparatus for dual connectivity conditional handover recovery. Background Art

[0002] Wireless telecommunication systems are constantly evolving. Higher data rates and high quality of service are required. Reliability requirements are increasing, and methods and means for ensuring reliable connections and data services while keeping transmission delays to a minimum are also evolving.

[0003] The evolving network offers new services to customers. One service is dual connectivity, where the user equipment connects to both the primary node base station and the secondary node base station for communication. Dual connectivity improves data throughput and mobility robustness. Another service is conditional handover, which further improves mobility robustness. For conditional handover, the network can prepare multiple target cells, for which conditional handover configurations are associated with execution conditions evaluated by the user equipment. These configurations can also be used to restore and reestablish connections in the event of a radio link failure.

[0004] Using dual connectivity and conditional handover may require advanced techniques for dual connectivity conditional handover recovery. Summary of the invention

[0005] According to a first aspect of the subject disclosure, a user equipment (UE) is presented, the UE being configured to support operation with dual connectivity of a primary cell of a source primary node and a primary secondary cell of a source secondary node of a radio access network, and being configured to support conditional handover CHO. The user equipment comprises: at least one processor; and at least one memory, the at least one memory comprising computer program code, which, when executed with at least one processor, causes the user equipment to perform the process described herein. In particular, the UE is caused to: establish a connection to a primary cell of the source primary node; and establish a connection to a primary secondary cell of the source secondary node. In addition, the UE is caused to: receive a plurality of CHO configurations from the source primary node, the plurality of CHO configurations comprising: configurations for conditional handover to at least one target primary node and at least one target secondary node; and receive auxiliary information for CHO recovery from the source primary node. The UE is caused to: in response to the user equipment experiencing a radio link failure on a primary cell of the source primary node, or a handover failure to a primary cell of a first target primary node, determine a primary cell of a second target primary node, and an associated CHO configuration from a plurality of CHO configurations based on the auxiliary information for CHO recovery. In addition, the UE is caused to perform CHO recovery to the primary cell of the second target primary node based on the determined associated CHO configuration.

[0006] In an embodiment, the UE is further caused to: in response to the determined CHO configuration being a dual connectivity CHO configuration, perform CHO recovery to a primary secondary cell of a target secondary node, wherein the primary secondary cell of the target secondary node is different from the primary secondary cell of the source secondary node.

[0007] In some embodiments, the auxiliary information includes: a single-dual connectivity priority flag for prioritizing single connectivity or dual connectivity for CHO recovery. In another embodiment, the auxiliary information includes: information about pending traffic on the secondary cell group bearer, wherein determining the CHO configuration includes: prioritizing the single connectivity CHO configuration in response to the single connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target primary node, and prioritizing the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target secondary node.

[0008] In some embodiments, the auxiliary information indicates that: when the primary and secondary cells of the source secondary node are maintained, the dual connectivity CHO configuration is given priority. In another embodiment, the auxiliary information includes a CHO recovery primary and secondary cell selection condition, wherein determining the CHO configuration includes: selecting a CHO configuration whose primary and secondary cells meet the primary and secondary cell selection condition.

[0009] In an embodiment, determining the CHO configuration includes: in response to none of the at least one primary and secondary cells satisfying the primary and secondary cell selection condition, selecting a single connectivity CHO configuration. In some further embodiments, the user equipment is further caused to: in response to selecting the single connectivity CHO configuration with the second target primary node, send cell selection information to the second target primary node, the cell selection information including: an indication that none of the at least one primary and secondary cells associated with the second target primary node satisfies the primary and secondary cell selection condition. In some further embodiments, the cell selection information also includes: measurements related to at least one primary and secondary cell associated with the second target primary node.

[0010] In some embodiments, the cell selection information further includes measurements performed at the user equipment and related to another cell. In another embodiment, the auxiliary information includes a single-dual connectivity indicator, which indicates whether the corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration. In an embodiment, the auxiliary information includes an identifier of a primary and secondary cell, which indicates which primary and secondary cell is included in the corresponding CHO configuration.

[0011] According to a second aspect of the subject disclosure, a source master node (source MN) is presented, the source MN being configured to support establishing a connection to a user equipment, the user equipment being configured to support operating with dual connectivity with a primary cell of the source master node and a primary and secondary cell of a source secondary node, and supporting conditional handover CHO. The source MN comprises: at least one processor; and at least one memory, the at least one memory comprising computer program code, which, when executed using at least one processor, causes the source MN to perform the process described herein. In particular, the source MN is caused to: send a plurality of CHO configurations to the user equipment, the plurality of CHO configurations comprising: configurations for conditional handover to at least one target master node and at least one target secondary node; and send auxiliary information for CHO recovery to the user equipment, wherein the auxiliary information is used by the user equipment to determine a CHO configuration for CHO recovery from a plurality of CHO configurations.

[0012] In an embodiment, the auxiliary information includes: a single-dual connectivity priority flag for prioritizing single connectivity or dual connectivity for CHO recovery. In some embodiments, the single-dual connectivity priority flag is determined based on the pending traffic on the secondary cell group bearer, for prioritizing the single connectivity CHO configuration in response to the single connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target primary node, and for prioritizing the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target secondary node.

[0013] In some embodiments, the auxiliary information indicates that when the primary and secondary cells of the source secondary node are maintained, the dual connectivity CHO configuration is given priority. In some embodiments, the auxiliary information includes a CHO recovery primary and secondary cell selection condition, which is used to determine the CHO configuration in which the primary and secondary cells meet the primary and secondary cell selection condition. In another embodiment, the auxiliary information includes a single and dual connectivity indicator, which indicates whether the corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration. In some further embodiments, the auxiliary information includes an identifier of the primary and secondary cell, which indicates which primary and secondary cell is included in the corresponding CHO configuration.

[0014] According to a third aspect of the subject disclosure, a network node is presented, the network node supporting at least one of a central unit control plane function, or a layer 3 protocol of a radio access network, the network node being configured to support a connection with a user equipment, the user equipment operating with dual connectivity with a primary cell of the network node and a primary secondary cell of a source secondary node, and being configured for conditional handover (CHO). The network node comprises: at least one processor; and at least one memory, the at least one memory comprising computer program code, the computer program code when executed by at least one processor, causing the network node to perform the process described herein. In particular, the network node is caused to: generate a radio resource control (RRC) message, the radio resource control (RRC) message comprising auxiliary information for CHO recovery; and send an RRC message comprising the auxiliary information to a user equipment, wherein the auxiliary information is used by the user equipment to determine a CHO configuration for CHO recovery from a plurality of CHO configurations, the plurality of CHO configurations comprising: a configuration for conditional handover to at least one target primary node and at least one target secondary node.

[0015] In an embodiment, the auxiliary information includes: a single-dual connectivity priority flag for prioritizing single connectivity or dual connectivity for CHO recovery. In some embodiments, the single-dual connectivity priority flag is determined based on the pending traffic on the secondary cell group bearer, for prioritizing the single connectivity CHO configuration in response to the single connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target primary node, and for prioritizing the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target secondary node.

[0016] In some embodiments, the auxiliary information indicates that when the primary and secondary cells of the source secondary node are maintained, the dual connectivity CHO configuration is given priority. In some embodiments, the auxiliary information includes a CHO recovery primary and secondary cell selection condition, which is used to determine the CHO configuration in which the primary and secondary cells meet the primary and secondary cell selection condition. In another embodiment, the auxiliary information includes a single and dual connectivity indicator, which indicates whether the corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration. In some further embodiments, the auxiliary information includes an identifier of the primary and secondary cell, which indicates which primary and secondary cell is included in the corresponding CHO configuration.

[0017] According to a fourth aspect of the subject disclosure, a method for conditional switching CHO recovery is presented, which is performed by a user equipment configured to operate with dual connectivity within at least one radio access network RAN. The method includes: establishing a connection to a primary cell of a source primary node; establishing a connection to a primary and secondary cell of a source secondary node; receiving a plurality of CHO configurations from the source primary node, the plurality of CHO configurations including: a configuration for conditional switching to at least one target primary node and at least one target secondary node; and receiving auxiliary information for CHO recovery from the source primary node. The method also includes: in response to the user equipment experiencing a radio link failure on the primary cell of the source primary node, or a switching failure to the primary cell of the first target primary node, based on the auxiliary information for CHO recovery, determining the primary cell of the second target primary node, and an associated CHO configuration from a plurality of CHO configurations; and performing CHO recovery to the primary cell of the second target primary node based on the determined associated CHO configuration.

[0018] In an embodiment, the method further comprises: in response to the determined CHO configuration being a dual connectivity CHO configuration, performing CHO recovery to a primary secondary cell of a target secondary node, wherein the primary secondary cell of the target secondary node is different from the primary secondary cell of the source secondary node.

[0019] In some embodiments, the auxiliary information includes: a single-dual connectivity priority flag for prioritizing single connectivity or dual connectivity for CHO recovery. In another embodiment, the auxiliary information includes: information about pending traffic on the secondary cell group bearer, wherein determining the CHO configuration includes: prioritizing the single connectivity CHO configuration in response to the single connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target primary node, and prioritizing the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having a secondary cell group bearer mapped to the corresponding target secondary node.

[0020] In some embodiments, the auxiliary information indicates that: when the primary and secondary cells of the source secondary node are maintained, the dual connectivity CHO configuration is given priority. In another embodiment, the auxiliary information includes a CHO recovery primary and secondary cell selection condition, wherein determining the CHO configuration includes: selecting a CHO configuration whose primary and secondary cells meet the primary and secondary cell selection condition.

[0021] In an embodiment, determining the CHO configuration includes: in response to none of the at least one primary and secondary cells satisfying the primary and secondary cell selection condition, selecting a single connectivity CHO configuration. In some further embodiments, the user equipment is further caused to: in response to selecting the single connectivity CHO configuration with the second target primary node, send cell selection information to the second target primary node, the cell selection information including: an indication that none of the at least one primary and secondary cells associated with the second target primary node satisfies the primary and secondary cell selection condition. In some further embodiments, the cell selection information also includes: measurements related to at least one primary and secondary cell associated with the second target primary node.

[0022] In some embodiments, the cell selection information further includes measurements performed at the user equipment and related to another cell. In another embodiment, the auxiliary information includes a single-dual connectivity indicator, which indicates whether the corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration. In an embodiment, the auxiliary information includes an identifier of a primary and secondary cell, which indicates which primary and secondary cell is included in the corresponding CHO configuration.

[0023] According to a fifth aspect of the subject disclosure, there is presented a method for conditional switching CHO recovery performed by a source master node connected to a user equipment, the user equipment operating with dual connectivity with a master cell of the source master node and a master and slave cell of a source slave node, the method comprising: sending a plurality of CHO configurations to the user equipment, the plurality of CHO configurations comprising: a configuration for conditional switching to at least one target master node and at least one target slave node; and sending auxiliary information for CHO recovery to the user equipment, wherein the auxiliary information is used by the user equipment to determine a CHO configuration for CHO recovery from the plurality of CHO configurations.

[0024] In an embodiment, the auxiliary information includes: a single-dual connectivity priority flag for prioritizing the priority of determining single connectivity or dual connectivity for CHO recovery. In some embodiments, the single-dual connectivity priority flag is determined based on the pending traffic on the secondary cell group bearer, so as to prioritize the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target primary node, and prioritize the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node.

[0025] In some embodiments, the auxiliary information indicates that when the primary and secondary cells of the source secondary node are maintained, the dual connectivity CHO configuration is given priority. In some embodiments, the auxiliary information includes a CHO recovery primary and secondary cell selection condition, which is used to determine the CHO configuration in which the primary and secondary cells meet the primary and secondary cell selection condition. In another embodiment, the auxiliary information includes a single and dual connectivity indicator, which indicates whether the corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration. In some further embodiments, the auxiliary information includes an identifier of the primary and secondary cell, which indicates which primary and secondary cell is included in the corresponding CHO configuration.

[0026] The above aspects and features can be implemented in systems, apparatuses, methods, articles, and non-transitory computer-readable media depending on the desired configuration. The subject disclosure can be implemented in and used with a variety of different types of devices, including but not limited to any of cellular phones, tablet computers, wearable computing devices, portable media players, and various other computing devices.

[0027] The present invention is intended to provide a brief overview of some aspects and features disclosed in accordance with the present subject matter. Therefore, it will be appreciated that the above-mentioned features are merely examples and should not be interpreted as narrowing the scope of the present subject matter disclosure in any way. Other features, aspects and advantages disclosed in the present subject matter will become apparent from the following detailed description, drawings and claims.

[0028] List of abbreviations

[0029] In the subject disclosure, the following abbreviations are used and should be understood in light of the definitions given:

[0030] 3GPP Third Generation Partnership Project

[0031] 5G Fifth Generation (mobile communication network)

[0032] 5GC 5G Core Network

[0033] NG-RAN Next Generation Radio Access Network

[0034] NR New Radio, 5G

[0035] LTE Long Term Evolution, 4G

[0036] BS Base Station

[0037] UE User Equipment

[0038] HO Switchover

[0039] CHO Condition Switch

[0040] DC Dual Connectivity

[0041] gNB gNodeB(NR)

[0042] eNB eNodeB(LTE)

[0043] SCG Secondary Cell Group

[0044] MCG Master Cell Group

[0045] PCell Primary Cell

[0046] PSCell primary and secondary cells

[0047] MN Master / Primary Node

[0048] SN Secondary Node

[0049] RRC Radio Resource Control Reconfiguration

[0050] SRB Signalling Radio Bearer

[0051] gNB-CU-CP gNodeB Central Unit Control Plane

[0052] gNB-CU-UP gNodeB Central Unit User Plane

[0053] gNB-DU gNodeB distributed unit

[0054] CPC Condition PSCell Change BRIEF DESCRIPTION OF THE DRAWINGS

[0055] A better understanding of the subject disclosure may be obtained when the following detailed description of various embodiments is considered in conjunction with the following drawings, in which:

[0056] Figure 1 A schematic diagram of an example communication system including a base station and a plurality of communication devices is shown;

[0057] Figure 2 A schematic diagram of an example mobile communication device is shown;

[0058] Figure 3 A schematic diagram of an example control device is shown;

[0059] Figure 4A and Figure 4B Describes the NG-RAN architecture;

[0060] Figure 5 A flow chart of dual connectivity conditional handover recovery performed by a user equipment is presented;

[0061] Figure 6A flow chart of dual connectivity conditional handover recovery performed by a source master node is presented;

[0062] Figure 7 A flow chart of dual connectivity conditional handover recovery performed by a network node supporting layer 3 functions is presented;

[0063] Figure 8 A message flow diagram showing an exemplary overall dual connectivity conditional handover recovery;

[0064] Fig. 9 Another message flow diagram illustrating an exemplary overall dual connectivity conditional handover recovery; and

[0065] Fig.10 A flow chart of an embodiment for overall dual connectivity conditional handover recovery is presented. DETAILED DESCRIPTION

[0066] Before explaining the examples in detail, refer to Figures 1 to 3 Certain general principles of wireless communication systems and mobile communication devices are briefly explained to assist in understanding the technology behind the described examples.

[0067] In such Figure 1 In the wireless communication system 100 shown in , wireless access is provided to mobile communication devices, user devices, user equipment (UE) 102, 104, 105 via at least one base station (e.g., next generation NB, gNB), similar wireless transmission and / or receiving nodes or network nodes. The base station can be controlled or assisted by at least one appropriate controller device to achieve its operation and management of mobile communication devices communicating with the base station. The controller device can be located in a radio access network (RAN) (e.g., the wireless communication system 100) or in a core network (CN) (not shown), and can be implemented as a central device, or its functions can be distributed over several devices. The controller device can be part of the base station and / or provided by a separate entity (such as a radio network controller (RNC)). In Figure 1 In the embodiment, control means 108 and 109 are shown as controlling the respective macro-level base stations 106 and 107. The control means of the base station may be interconnected with other control entities. The control means are typically provided with memory capacity and at least one data processor. The control means and functions may be distributed among a plurality of control units. In some systems, the control means may be additionally or alternatively provided in the RNC.

[0068] exist Figure 1 In FIG. 1 , base stations 106 and 107 are shown as being connected to a wider communications network 113 via a gateway 112. A further gateway function may be provided to connect to another network.

[0069] 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 at a fixed location and is used to communicate as part of a wireless telephone system or a radio system. The communication area (or coverage area) of a base station may be referred to as a "cell". A base station and UE may be configured to communicate over a transmission medium using any of a variety of radio access technologies (RATs), also referred to as wireless communication technologies, or any of the telecommunication standards described below. Figure 1 As illustrated in the figure, although one of the base stations may act as a "serving cell" for the UE, the UE may also be able to receive signals from (and possibly within its communication range of) one or more other cells (which may be provided by the base station and / or any other base station), which may be referred to as "neighboring cells."

[0070] Smaller base stations 116, 118 and 120 may also be connected to the network 113, for example, through a separate gateway function and / or via a controller of a macro-level station. Base stations 116, 118 and 120 may be micro-level base stations or femto-level base stations, etc. In this example, stations 116 and 118 are connected via gateway 111, while 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, such as a wireless local area network (WLAN), and may be WLAN access points (APs). Communication devices 102, 104, 105 may access the communication system based on various access technologies, such as code division multiple access (CDMA) or wideband CDMA (WCDMA). Other non-limiting examples include time division multiple access (TDMA), frequency division multiple access (FDMA) and its various schemes such as interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA), etc.

[0071] An example of a wireless communication system is an architecture standardized by the Third Generation Partnership Project (3GPP). The latest 3GPP-based development is generally referred to as the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology. The various development stages of the 3GPP specification are referred to as releases. The newer development of LTE is generally referred to as LTE Advanced (LTE-A). LTE (or LTE-A) adopts a radio mobile architecture referred to as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and a core network referred to as the Evolved Packet Core (EPC). The base station of such a system is referred to as an evolved or enhanced Node B (eNB), and provides E-UTRAN features to communication devices, such as user plane packet data convergence / radio link control / media access control / physical layer protocol (PDCP / RLC / MAC / PHY) and control plane radio resource control (RRC) protocol termination. Other examples of radio access systems include systems provided by base stations of systems based on technologies such as WLAN and / or Worldwide Interoperability for Microwave Access (WiMax). The base station can provide coverage for an entire cell or similar radio service area. The core network elements include the Mobility Management Entity (MME), the Serving Gateway (S-GW) and the Packet Gateway (P-GW).

[0072] An example of a suitable communication system is the 5G or NR concept. The network architecture in NR can be similar to LTE-A. The base station of the NR system can be called the next generation node B (gNB). Changes in the network architecture may depend on the demand for various radio technologies and more refined quality of service (QoS) support, as well as some on-demand requirements for QoS levels to support the quality of experience (QoE) from the user's perspective. In addition, network-aware services and applications, as well as service and application-aware networks, can bring changes to the architecture. These are related to the information-centric network (ICN) and user-centric content delivery network (UC-CDN) approaches. NR can use multiple-input multiple-output (MIMO) antennas, have more base stations or nodes than LTE (the so-called small cell concept), including macro sites that operate in cooperation with smaller stations, and may also adopt various radio technologies to achieve better coverage and enhanced data rates.

[0073] Future networks may utilize network function virtualization (NFV), a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that can be operatively connected or linked together to provide services. A virtualized network function (VNF) may include one or more virtual machines that run computer program code using standard or general-purpose servers rather than custom hardware. Cloud computing or data storage may also be utilized. In radio communications, this may mean that node operations are at least partially performed in servers, hosts, or nodes that are operatively coupled to remote radio heads. Node operations may also be distributed among multiple servers, nodes, or hosts. It should also be understood that the allocation of labor between core network operations and base station operations may be different from the case of LTE, or even non-existent.

[0074] An example 5G core network (CN) includes functional entities. The CN is connected to the UE via the radio access network (RAN). The user plane function (UPF), whose role is called the PDU session anchor (PSA), can be responsible for forwarding frames back and forth between the data network (DN) and the tunnels established over 5G, which are towards the UE exchanging traffic with the DN.

[0075] The UPF is controlled by a Session Management Function (SMF), which receives policies from a Policy Control Function (PCF). The CN may also include an Access and Mobility Function (AMF).

[0076] Now refer to Figure 2 To describe a possible (mobile) communication device 200 in more detail, Figure 2 A schematic, partially cutaway view is shown. Such a mobile communication device 200 is generally referred to as a user equipment (UE), a user device or a terminal device. A suitable mobile communication device 200 can be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) or a mobile device, such as a mobile phone or a so-called smart phone, a computer provided with a wireless interface card or other wireless interface facilities (e.g., a USB dongle), a personal data assistant (PDA) or a tablet computer provided with wireless communication capabilities, or any combination of these, etc. For example, the communication device 200 can provide communication for carrying data such as voice, e-mail (e-mail), text messages, multimedia, etc. Therefore, a variety of services can be provided to the user via the user's communication device. Non-limiting examples of these services include two-way or multi-directional calls, data communications or multimedia services or simply access to a data communication network system, such as the Internet. Broadcast or multicast data can also be provided to the user. Non-limiting examples of content include downloads, television and radio programs, videos, advertisements, various alarms and other information.

[0077] In industrial applications, the communication device can be a modem integrated into an industrial actuator (e.g., a robotic arm) and / or a modem acting as an Ethernet hub, which will act as a connection point for one or several connected Ethernet devices (the connection can be wired or wireless).

[0078] The communication device 200 is typically provided with at least one data processing entity 201, at least one memory 202, and other possible components 203 for software and hardware assistance in performing the tasks it is designed to perform, including controlling access to and communication with access systems and other communication devices. The data processing, storage and other related control means may be provided on appropriate circuit boards and / or in a chipset 204. The user may control the operation of the communication device 200 through a suitable user interface (such as a keyboard 205, voice commands, a touch-sensitive screen or pad, a combination thereof, etc.). A display 208, a speaker and a microphone may also be provided. In addition, the communication device 200 may include appropriate connectors (wired or wireless) to other devices and / or for connecting external accessories (such as a hands-free device) thereto.

[0079] The communication device 200 may receive signals over the air or radio interface 207 via appropriate means for receiving, and may transmit signals via appropriate means for transmitting radio signals. Figure 2 In the communication device 200, the transceiver means is schematically designated by the block 206. The transceiver means 206 may be provided, for example, by a radio part and an associated antenna means. The antenna means may be arranged inside or outside the communication device 200.

[0080] If desired, the communication device 200 may also or alternatively be configured to communicate using one or more global navigation satellite systems (GNSS, such as GPS or GLONASS), one or more mobile television broadcast standards (e.g., ATSC-M / H or DVB-H), and / or any other wireless communication protocol. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

[0081] generally, Figure 2 The communication device 200 illustrated in the figure includes a component set configured to perform core functions. For example, the component set can be implemented as a system on a chip (SoC), which can include parts for various purposes. Alternatively, the component set can be implemented as a separate component or a group of components for various purposes. The component set can be (e.g., directly or indirectly) (communicatively) coupled to various other circuits of the communication device 200.

[0082] The communication device 200 may include at least one antenna for communicating with a transmitter and a receiver (e.g., a transceiver device 206). Alternatively, the transmitting and receiving antennas 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 and the receiver, respectively, and to receive signals from the transmitter and the receiver, and to control the functions of the communication device 200. The processor may be configured to control the functions of the transmitter and the receiver by implementing control signaling via electrical leads to the transmitter and the receiver. Likewise, the processor may be configured to control other elements of the communication device 200 by implementing control signaling via electrical leads connecting the processor to the other elements, such as a display (e.g., display 208) or a memory (e.g., at least one memory 202). For example, the processor may be embodied in a variety of ways, including circuitry, at least one processing core, one or more microprocessors with accompanying digital signal processor(s), one or more processors without accompanying digital signal processor(s), one or more coprocessors, one or more multi-core processors, one or more controllers, processing circuitry, one or more computers, various other processing elements, including integrated circuits, such as, for example, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), etc., or some combination thereof. Thus, in some examples, the processor may include multiple processors or processing cores.

[0083] The communication device 200 may be capable of operating with one or more air interface standards, communication protocols, modulation types, access types, etc. The signals sent and received by the processor may include signaling information in accordance with the air interface standard of the applicable cellular system, and / or any number of different wired or wireless networking technologies, including but not limited to Wi-Fi, WLAN technologies, such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, 802.16, 802.3, ADSL, DOCSIS, etc. In addition, these signals may include voice data, user-generated data, user-requested data, etc.

[0084] For example, the communication device 200 and / or the cellular modem therein may be capable of operating in accordance with various third generation (3G) communication protocols, fourth generation (4G) communication protocols, fifth generation (5G) communication protocols, Internet Protocol Multimedia Subsystem (IMS) communication protocols (such as, for example, Session Initiation Protocol (SIP)), or 5G and above protocols. For example, the communication device 200 may be capable of operating in accordance with 4G wireless communication protocols (such as LTE-A, 5G, etc.), as well as similar wireless communication protocols that may be subsequently developed.

[0085] It is understood that the processor may include a circuit system 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, etc. The control and signal processing functions of the communication device 200 may be allocated between these devices according to their respective capabilities. The processor may additionally include an internal voice encoder, an internal data modem, etc. In addition, the processor may include functions for operating one or more software programs, which may be stored in a memory. Typically, the processor and the stored software instructions may be configured to enable the communication device 200 to perform actions. For example, the processor may be able to operate a connectivity program, such as a Web browser. The connectivity program may allow the communication device 200 to send and receive Web content, such as location-based content, according to protocols such as a wireless application protocol (WAP), a hypertext transfer protocol (HTTP), etc.

[0086] The communication device 200 may also include a user interface, for example, including a headset or speaker, a ringer, a microphone, a display, a user input interface, etc., which may be operatively coupled to the processor. As described above, the display may include a touch-sensitive display, where the user can touch and / or make gestures to make selections, input values, etc. The processor may also include a user interface circuit system, which is configured to control at least some functions of one or more elements of the user interface (such as a speaker, a ringer, a microphone, a display, etc.). The processor and / or the user interface circuit system including the processor may be configured to control one or more functions of one or more elements of the user interface by computer program instructions (such as software and / or firmware) stored on a memory accessible to the processor (such as a volatile memory, a non-volatile memory, etc.). The communication device 200 may include a battery for powering various circuits associated with the mobile terminal, for example, a circuit for providing mechanical vibration as a detectable output. The user input interface may include a device that allows the communication device 200 to receive data, such as a keyboard (e.g., keyboard 206) and / or other input devices. The keyboard may also be a virtual keyboard presented on the display or an externally coupled keyboard.

[0087] The communication device 200 may also include one or more mechanisms for sharing and / or obtaining data. For example, the communication device 200 may include a short-range radio frequency (RF) transceiver and / or interrogator, so that data can be shared with and / or obtained from electronic devices based on RF technology. The communication device 200 may include other short-range transceivers, such as infrared (IR) transceivers, Bluetooth TM Wireless technology operated by Bluetooth TM (BT) transceiver, wireless universal serial bus (USB) transceiver, BluetoothTM Low energy transceiver, ZigBee transceiver, ANT transceiver, cellular device to device transceiver, wireless local area link transceiver, and / or any other short-range radio technology. The communication device 200, and more specifically, the short-range transceiver, can be capable of sending data to and / or receiving data from electronic devices near the device (such as within 10 meters). The communication device 200 including a Wi-Fi or WLAN modem can also send data to and / or receive data from electronic devices according to various wireless networking technologies (including 6LoWPAN, Wi-Fi, Wi-Fi low power, WLAN technology (such as IEEE 802.11 technology), IEEE 802.15 technology, IEEE 802.16 technology, etc.).

[0088] The communication device 200 may include a 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), etc., which may store information elements related to mobile subscribers. In addition, the communication device 200 may include other removable and / or fixed memories. The communication device 200 may include volatile memory and / or non-volatile memory. For example, the volatile memory may include random access memory (RAM), including dynamic and / or static RAM, on-chip or off-chip cache memory, etc. The non-volatile memory may be embedded and / or removable, and may include, for example, read-only memory, flash memory, magnetic storage devices (such as hard disks, floppy disk drives, tapes, optical drives and / or media), non-volatile random access memory (NVRAM), etc. Like volatile memory, non-volatile memory may include a cache area for temporarily storing data. At least a portion of the volatile and / or non-volatile memory may be embedded in the processor. The memory may store one or more software programs, instructions, information segments, data, etc., which may be used by the apparatus to perform the operations disclosed herein.

[0089] The memory may include an identifier, such as an International Mobile Equipment Identity (IMEI) code, that can uniquely identify the communication device 200. In an example embodiment, the processor may be configured using computer code stored in the memory to cause the processor to perform the operations disclosed herein.

[0090] Some embodiments disclosed herein may be implemented in software, hardware, application logic, or a combination of software, hardware, and application logic. The software, application logic, and / or hardware may reside in a memory, a processor, or an electronic component. In some example embodiments, the application logic, software, or an instruction set is maintained on any of a variety of conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any non-transitory medium that can contain, store, communicate, propagate, or transmit instructions for use by or in conjunction with an instruction execution system, apparatus, or device (such as a computer or data processor circuit system), examples of which are described in detail in the accompanying drawings. Figure 2 As depicted, computer-readable media may include non-transitory computer-readable storage media, which may be any medium that can contain or store instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0091] In some embodiments, the communication device 200 (i.e., UE or user equipment in the network) includes a processor (e.g., at least one data processing entity 201) and a memory (e.g., at least one memory 202). The memory includes a computer program code that causes the communication device 200 to perform the following operations according to the reference Figure 5 Describes the method to perform the processing.

[0092] Figure 3 An example embodiment of a control device of a communication system is shown, which control device is coupled to and / or used to control a station of an access system, such as a RAN node, such as a base station, 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 a host. The method can be implanted in a single control device, or across more than one control device. The control device can be integrated with a node or module of a core network or RAN, or located outside it. In some embodiments, the base station includes a separate control device unit or module. In other embodiments, the control device can be another network element, such as an RNC or a spectrum controller. In some embodiments, the base station can have such a control device, as well as a control device provided in the RNC. The control device 300 can be arranged to provide control of communications in a 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. Via the interface, the control device 300 can be coupled to a receiver and a transmitter of the base station. The receiver and / or the transmitter may be implemented as a radio front end or a remote radio head.

[0093] Typically, the control device 300 has an antenna that sends 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 sends 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 out to the antenna. The processor processes the received baseband signals and calls different functional modules to execute features in the control device 300. A memory (e.g., at least one memory 301) stores program instructions and data to control the operation of the control device 300. In Figure 3 In the example of , the control device 300 also includes a protocol stack, and a collection of control function modules and circuits. The PDU session processing circuit processes the PDU session establishment and modification process. The policy control module configures policy rules for the UE. The configuration and control circuits provide different parameters to configure and control the UE of related functions (including mobility management and session management). For example, suitable processors include 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) and / or state machines.

[0094] In some embodiments, the control device 300 (i.e., a base station, a wireless transmission and / or reception point device, or a network node in a network) includes a processor (e.g., at least one data processing unit 302, 303) and a memory (e.g., at least one memory 301). The memory includes a computer program code, which enables the control device 300 to perform the following reference Figure 6 Describes the method to perform the processing.

[0095] Figure 4A and Figure 4B A next generation radio access network (NG-RAN) architecture 400 with gNB 402 according to 3GPP TS38.401 V17.0.0 is depicted. The gNB 402 employs NR user / control plane protocols to serve UEs and is connected to the 5GC 401 via an NG interface and to other gNBs 402 through an Xn interface. Figure 4AThe gNB 402 in the embodiment 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, and controls the operation of one or more gNB-DUs 404. The gNB-CU 403 terminates the F1 interface connected to the gNB-DU 404. The dNB-DU 404 is a logical node that hosts the RLC, MAC, and PHY layers of the gNB 402 or en-gNB, and its operation is partially controlled by the gNB-CU 403. One gNB-DU 404 supports one or more cells. One cell is supported by one gNB-DU 404. The gNB-DU 404 terminates the F1 interface connected to the gNB-CU 403.

[0096] One gNB-DU 404 is connected to one gNB-CU 403 via the F1 interface. NG, Xn, and F1 are logical interfaces. The Xn-C interface interconnects the gNB-CU 403 of different gNBs 402. The gNB 402 may also include a gNB-CU control plane (gNB-CU-CP), multiple gNB-CU user planes (gNB-CU-UP), and multiple gNB-DUs, which are connected in Figure 4B is described in more detail in .

[0097] It should be noted that NG-RAN may also include a group of ng-eNBs, which may include ng-eNB-CU and one or more ng-eNB-DUs. The ng-eNB-CU and ng-eNB-DU are connected via the W1 interface.

[0098] Figure 4BThe diagram illustrates a separated architecture of the control plane and the user plane of the gNB-CU (i.e., gNB-CU-CP and gNB-CU-UP) 403. The gNB-CU-CP 405 is a logical node that hosts the control plane portion of the RRC and PDCP protocols of the gNB-CU 403 for an en-gNB or gNB 402. The gNB-CU-CP 405 terminates the E1 interface connected to the gNB-CU-UP 406 and the F1-C interface connected to the gNB-DU 404. The gNB-CU-UP 406 is a logical node that hosts the user plane portion of the PDCP protocol of the gNB-CU 403 for an en-gNB and the user plane portion of the PDCP protocol and the SDAP protocol of the gNB-CU 403 for the gNB 402. The gNB-CU-UP 406 terminates the E1 interface connected to the gNB-CU-CP 405 and the F1-U interface connected to the gNB-DU 404. The gNB-CU-UP 406 is connected to one gNB-CU-CP 405, and multiple gNB-DUs 404 and multiple gNB-CU-UPs 406 under the control of the same gNB-CU-CP 405.

[0099] In some embodiments, the gNB-CU-CP 405 is associated with a processor and a memory. The memory includes computer program code that causes the gNB to support the functions of the gNB-CU-CP 405 according to the following reference Figure 7 Describes the method to perform the processing.

[0100] The following description may provide further details of alternatives, modifications and variants: The gNB may include, for example, a node that provides NR user plane and control plane protocol terminals to the UE and is connected to the 5GC via an NG interface, for example in accordance with 3GPP TS 38.300 V17.0.0, which is incorporated herein by reference.

[0101] The gNB Central Unit (gNB-CU) includes, for example, a logical node hosting, for example, RRC, SDAP and PDCP protocols of a gNB or RRC and PDCP protocols of an en-gNB, which controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU. The gNB Distributed Unit (gNB-DU) includes, for example, hosting, for example, RLC, MAC and PHY layers of a gNB or en-gNB, and its operation is partially controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0102] The gNB-CU-Control Plane (gNB-CU-CP) comprises a logical node hosting, for example, the control plane portion of the RRC and PDCP protocols of a gNB-CU of an en-gNB or gNB. The gNB-CU-CP terminates an E1 interface connected to a gNB-CU-UP and an F1-C interface connected to a gNB-DU. The gNB-CU-User Plane (gNB-CU-UP) comprises, for example, the user plane portion of the PDCP protocol of a gNB-CU of an en-gNB, and the user plane portion of the PDCP protocol and SDAP protocol of a gNB-CU of a gNB. The gNB-CU-UP terminates an E1 interface connected to a gNB-CU-CP and an F1-U interface connected to a gNB-DU, for example according to 3GPP TS 38.401 V17.0.0, Section 3.1, which is incorporated herein by reference.

[0103] Different functional divisions between the central unit and the distributed units are possible, for example referred to as options: Option 1 (1A-type division), in which the functional division is similar to the 1A architecture in DC. RRC is in the central unit. PDCP, RLC, MAC, physical layer and RF are in the distributed units. Option 2 (3C-type division), in which the functional division is similar to the 3C architecture in DC. RRC and PDCP are in the central unit. RLC, MAC, physical layer and RF are located in the distributed units. Option 3 (intra-RLC split), in which the low RLC (part of the functions of the RLC), MAC, physical layer and RF are located in the distributed units. PDCP and high RLC (another part of the functions of the RLC) are located in the central unit. Option 4 (RLC-MAC split), in which MAC, physical layer and RF are located in the distributed units. PDCP and RLC are located in the central unit. Or, for example, according to 3GPP TR 38.801 V14.0.0, section 11, which is incorporated herein by reference.

[0104] gNB supports different protocol layers, such as Layer 1 (L1) - physical layer. Layer 2 (L2) of NR is divided into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP). The physical layer can provide transport channels to the MAC sublayer; the MAC sublayer can provide logical channels to the RLC sublayer, the RLC sublayer can provide RLC channels to the PDCP sublayer, the PDCP sublayer can provide radio bearers to the SDAP sublayer, and the SDAP sublayer can provide QoS flows to the 5GC. Control channels include, for example, BCCH and PCCH. Layer 3 (L3) includes, for example, Radio Resource Control (RRC), for example according to 3GPP TS 38.300 V17.0.0, Section 6, which is incorporated herein by reference.

[0105] 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, for example, a device having at least one processor and / or at least one memory with computer-readable instructions (computer program) configured to support and / or provide and / or process CU and / or DU related functions and / or features, and / or at least one protocol (sub)layer of the RAN (Radio Access Network), such as Layer 2 and / or Layer 3.

[0106] The gNB-CU and gNB-DU parts may be, for example, co-located or physically separated. The gNB-DU may be even further split, for example into two parts, for example one part comprising a processing device and one part comprising an antenna. The central unit (CU) may also be referred to as BBU / REC / RCC / C-RAN / V-RAN, O-RAN or parts thereof. The distributed unit (DU) may also be referred to as RRH / RRU / RE / RU or parts thereof. The gNB-DU supports one or more cells and may thus act as a serving cell for, for example, a user equipment (UE).

[0107] User equipment (UE) may include a wireless or mobile device, a device with a radio interface to interact with a RAN (Radio Access Network), a smart phone, an in-vehicle device, an IoT device, an M2M device, etc. Such a UE or device may include: at least one processor; and at least one memory, including computer program code; wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the device to at least perform certain operations, such as, for example, an RRC connection to the RAN. The UE is, for example, configured to generate a message (e.g., including a cell ID) to be sent to the RAN via radio (e.g., to arrive at a serving cell and communicate with the serving cell). The UE can generate, send and receive RRC messages, which contain one or more RRC PDUs (packet data units).

[0108] The UE may have different states (e.g., according to 3GPP TS 38.331 V17.0.0, sections 4.2.1 and 4.4, which are incorporated herein by reference). When an RRC connection has been established, the UE is in, for example, an RRC_CONNECTED state or in an RRC_INACTIVE state. In the RRC_CONNECTED state, the UE may store an AS context, transmit unicast data to / from the UE, monitor a control channel associated with a shared data channel to determine whether it is data channel scheduling data, provide channel quality and feedback information, and / or perform neighbor cell measurements and measurement reporting. The RRC protocol includes, for example, the following main functions: RRC connection control, measurement configuration and reporting, establishment / modification / release of measurement configuration (e.g., intra-frequency, inter-frequency, and inter-RAT measurements), setting and release of measurement gaps, and / or measurement reporting.

[0109] In reference Figures 5 to 8 Before describing dual connectivity conditional handover recovery according to some embodiments of the present disclosure, some background information and aspects related to the present disclosure will be provided.

[0110] For example, the subject disclosure may be incorporated into a network that supports dual connectivity (DC) and conditional handover (CHO). The CHO procedure has been introduced in 3GPP Rel.16 to improve mobility robustness. In the case of CHO, the network may prepare multiple target cells, where the conditional handover reconfiguration is associated with a CHO execution condition evaluated by the UE. The CHO execution condition refers to a measurement ID configured by the source gNB (associating the measurement object with the reporting configuration). The reporting configuration defines the measurement events that trigger the CHO execution (e.g., measurement events A3 or A5 as defined in the 3GPP standard). Whenever the CHO execution condition is met, the corresponding target CHO configuration is selected, and the handover is performed towards the selected target cell.

[0111] In CHO, the UE is served by the primary cell (PCell) in the source master node (MN) and the primary secondary cell (PSCell) in 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, and the CHO execution conditions in the RRC reconfiguration message to the UE. Once the CHO execution conditions for one of the target PCells are met, the UE detaches from the source PCell, i.e., stops TX / RX to / 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 of the target MN notifies the source PCell of the source MN of the successful completion of the switching procedure. After receiving the switching success indication from the target MN, the source PCell in the source MN initiates data forwarding to the target PCell of the target MN. Once the data forwarding process is completed, the UE will continue its data transmission / reception with the network.

[0112] However, it may happen that even with CHO, the UE experiences poor radio link quality for a given period of time.Currently, the UE declares a failure and initiates a re-establishment procedure to reconnect to the network, which incurs additional signaling overhead and delays in the re-establishment process.

[0113] To address this issue, 3GPP introduced CHO recovery in Release 16 of the NR standard. CHO recovery (e.g., as described in 3GPP TS 38.311 V17.0.0 Section 5.3.7.3) reduces the outage time due to failures for UEs configured with conditional reconfiguration for multiple target cells. Although CHO minimizes the probability of mobility failures, the UE may still detect failures due to misconfiguration of mobility parameters or handover execution to the wrong cell. A UE supporting the CHO recovery feature can recover from a failure using the stored conditional reconfiguration of the prepared target cell instead of performing a reestablishment.

[0114] After detecting a failure, the UE initiates a cell reselection procedure, and if the selected cell is one of the prepared target cells in CHO, the UE uses the CHO configuration previously provided by the network to perform a handover towards that cell. Otherwise, if the selected cell does not have a corresponding CHO configuration, the UE initiates a reestablishment procedure to the selected cell. Thus, using CHO recovery, the UE can initiate a CHO execution using the stored CHO configuration of the target cell instead of an expensive reestablishment procedure, thereby reducing the interruption time after a failure.

[0115] The CHO recovery mechanism allows the UE to recover on a cell with a stored CHO configuration. In case of CHO with DC, i.e., CHO with multiple candidate secondary cell groups (SCGs) and / or multiple CHO configurations for target PCell and target PSCell, where the UE can apply a dual connectivity CHO (CHO-DC) configuration when the CHO conditions are met, CHO recovery does not consider which SCG should be considered during CHO execution or whether SCG should be considered at all. If CHO preparation with the correct SCG configuration is not selected, this may result in SCG failures and outage time on MN / SN terminated SCG bearers.

[0116] Currently, the signaling of the target CHO configuration is selected based solely on the radio signal measurements of the target PCell that meets certain cell selection criteria, without considering the signal strength / quality of the target PSCell. If more than one CHO configuration is available for the same PCell, the UE does not further distinguish between different dual connectivity CHO (CHO-DC) and single connectivity CHO (CHO-SC) configurations during the CHO recovery procedure. Selecting the appropriate configuration with the same PCell is critical to minimize performance impact and disruption to current bearers.

[0117] Furthermore, in the case where one of the CHO-DC configurations has both the appropriate PCell and PSCell, the UE does not know which CHO configuration is DC or SC because the configuration details are not transparent to the UE unless the UE decodes the configuration. Furthermore, the UE does not know in which CHO-DC configuration the appropriate PSCell is configured before decoding the configuration.

[0118] The technical solutions to these problems according to the present disclosure are summarized as follows: The network provides auxiliary information to the UE to improve the recovery process in the CHO-DC scenario.

[0119] In an embodiment, the network may provide an SC / DC priority flag for prioritizing CHO configurations of the same PCell during the recovery process. In additional or alternative embodiments, the criteria for prioritizing SC or DC configurations may also be based on the pending traffic volume of a specific SCG bearer, rather than a direct indication of a DC / SC configuration. Thus, the network may indicate the pending traffic volume to the UE. Alternatively, if the SC configuration has current SCG bearers mapped to a target SC configuration, the network may configure the SC / DC priority flag and select SC instead of DC. If the current SCG bearers are only mapped to a target SCG, the network may select DC instead of SC since there is no benefit in switching to SC.

[0120] In another embodiment, the network may also or alternatively indicate that a target DC configuration with the same PSCell (DC switching maintained by SCG) is preferred, which will minimize the interruption of the current service. In another embodiment, the network may also or alternatively provide the UE with a PSCell selection criterion to be met when selecting a cell for recovery. This enables the UE to select a target DC configuration with better radio conditions for the secondary cell group. In another embodiment, the network may also or alternatively provide an SC / DC indication outside the CHO configuration so that the UE can identify which CHO configurations are SC or DC. In another embodiment, the network may also or alternatively provide the ID of the PSCell together with the CHO-DC configuration or outside the CHO-DC configuration so that the UE can identify in which CHO-DC configuration the PSCell is configured. In addition, a fallback from CHO-DC to CHO-SC can be used to allow the UE to continue to exist on the PCell if no PSCell is suitable on the CHO-DC configuration.

[0121] exist Figure 5 A flow chart for dual connectivity conditional handover recovery performed by a UE is presented in the specification. The user equipment includes at least one processor and at least one memory, the memory including computer program code, the computer program code causing the UE to perform the process described herein. In other words, the UE is configured to perform the process described herein.

[0122] The UE operates with dual connectivity, i.e. it is connected to a source base station (also referred to as source MN) as a master node and a secondary base station (also referred to as source SN or SN). Figure 5 The described process is performed during a conditional handover, for example, after the UE has been configured with one or more possible target primary nodes (also referred to as target MNs) and / or target secondary nodes (also referred to as target SNs) for CHO. For example, the source MN may have determined (for example, based on measurements performed and reported by the UE in a measurement report) that a conditional handover with one or more target MNs is expected to occur. Thereafter, the source MN may have sent a CHO request to the one or more target MNs. The one or more (or at least some of those) target MNs may have confirmed the CHO request. In future communication systems, before performing the CHO request, Figure 5 Other steps may also be performed before or after the described processes.

[0123] Starting from box 501, the UE receives multiple CHO configurations from the source master node. The CHO configurations are at least related to the primary cell of the target master node, but may also include the primary and secondary cells of the target master node. The CHO configurations can be sent to the UE in one message (such as an RRC reconfiguration message). Alternatively, the CHO configurations can be sent in at least two separate messages, one message for each CHO configuration, or one message for each target master node, including one or more CHO configurations of the target master node. Compared to using the RRC reconfiguration message of layer 3, other messages of layer 2 or layer 1 (such as MAC signaling, or signaling CHO execution conditions via PDCCH) can also be used.

[0124] In block 502, the UE receives assistance information for CHO recovery from a primary cell of a source primary node. The assistance information may be any information, and the UE may select a CHO configuration from a plurality of CHO configurations according to the information.

[0125] The auxiliary information may include a single-dual connectivity priority flag. Such a flag may be used to configure the UE to prioritize a single connectivity CHO configuration over a dual connectivity CHO configuration, and vice versa. For example, if the single-dual connectivity priority flag is set to 1, the UE prioritizes a dual connectivity (DC) CHO configuration over a single connectivity CHO configuration. Otherwise, if the single-dual connectivity priority flag is set to 0, the UE prioritizes an SC-CHO configuration over a DC-CHO configuration.

[0126] Additionally or alternatively, the auxiliary information may include: information about pending traffic on the secondary cell group bearer. Then, the UE may be configured to: prioritize the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target primary node, and prioritize the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node.

[0127] Additionally or alternatively, the auxiliary information may include an indication that, in the case where the primary and secondary cells of the source secondary node are maintained, a dual connectivity CHO configuration is prioritized. In such a configuration, the UE will maintain its connection to the source SN. Thereby reducing the data forwarding required between nodes while having a stable connection to the source SN.

[0128] The auxiliary information may additionally or alternatively include a primary and secondary cell selection condition. Then, the UE may be configured to select a CHO configuration in which the primary and secondary cells satisfy the primary and secondary cell selection condition. For example, the primary and secondary cell selection condition may include a threshold for cell quality and / or any selection condition based on RSRP, RSRQ or SINR conditions.

[0129] Additionally or alternatively, the auxiliary information may include information about which information is encoded in which CHO configuration. For example, the auxiliary information may include a single-dual connectivity indicator, which indicates which type of CHO configuration is encoded in the corresponding CHO configuration. In another additional or alternative example, the auxiliary information may include an identifier of a primary and secondary cell, which indicates which primary and secondary cell is encoded in the CHO configuration. In alternative embodiments, the information about the CHO configuration may also be indicated in different ways, for example, by including the information in an additional field accompanying the CHO configuration, or by signaling them separately to the auxiliary information.

[0130] Then, the UE selects a CHO configuration for CHO recovery from a plurality of CHO configurations based on the auxiliary information, as shown in block 503. This selection is typically performed in response to the user equipment experiencing a radio link failure on a primary cell of a source primary node, or a handover failure on a primary cell of a handover target primary node. The selected CHO configuration is associated with (at least) the primary cell of the target primary node, and may additionally be associated with possible primary and secondary cells of the target secondary node, which may be used in conjunction with the primary cell for DC.

[0131] Finally, and as depicted in block 504, the UE performs CHO recovery on the primary cell of the target primary node according to the selected CHO configuration. In an embodiment, where the selected CHO is a dual connectivity CHO configuration, where the primary secondary cell of the target secondary node is different from the primary secondary cell of the source secondary node, the UE may also be configured to perform CHO recovery on the primary secondary cell of the target secondary node (in addition to the primary cell of the target primary node for enabling DC connection).

[0132] In addition, if none of the primary and secondary cells configured with DC-CHO are suitable, a fallback can be used, which allows the UE to continue to exist on the primary cell using single connectivity. For example, if none of the primary and secondary cells in at least one primary and secondary cell meets the above-mentioned primary and secondary cell selection conditions, the UE can be configured to select (or apply) the single connectivity CHO configuration of the target primary node. In such an example, the UE may also be configured to send cell selection information to the target primary node, the cell selection information including an indication that none of the at least one primary and secondary cell configured for the target primary node meets the primary and secondary cell selection conditions. In another embodiment, the cell selection information may also include measurements related to at least one primary and secondary cell configured for the target primary node. This information can be used by the network for root cause analysis. In other additional or alternative embodiments, the cell selection information also includes measurements related to other cells, for example, all cells or at least multiple cells available for measurement at the user equipment.

[0133] The UE may also include components for performing the processes described herein. For example, the UE may include: components for receiving multiple CHO configurations from a source master node, and components for receiving CHO recovery assistance information from a primary cell of the source master node. The UE may also include: components for selecting a CHO configuration from multiple CHO configurations based on the recovery assistance information for CHO in response to the user equipment experiencing a radio link failure on the primary cell of the source master node, or a switching failure on the primary cell of the second target master node, wherein the selected CHO configuration is related to the primary cell of the target master node. Finally, the UE may include: components for performing CHO recovery on the primary cell of the target master node. Components for other processes described herein may also be provided.

[0134] exist Figure 6 A flow chart for dual connectivity conditional handover recovery performed by a source MN is presented in the specification. The source MN includes at least one processor and at least one memory, the at least one memory including a computer program code, the computer program code causing the source MN to perform the process described herein. In other words, the source MN is configured to perform the process described herein. The source MN is connected to a user equipment, the user equipment operates with dual connectivity with a primary cell of a source primary node and a primary and secondary cell of a source secondary node, and is configured for conditional handover CHO.

[0135] To implement the improved CHO recovery mechanism described herein, the source MN sends multiple CHO configurations to the user equipment, for example, in response to measurements performed and reported by the UE in a measurement report indicating that a conditional handover with one or more target MNs is expected to occur. Figure 6 The CHO configuration is shown in box 601 of . The CHO configuration is at least related to the primary cell of the target primary node, but may also include the primary and secondary cells of the target primary node. The CHO configuration may be sent to the UE in one message, such as an RRC reconfiguration message. Alternatively, the CHO configuration may be sent in at least two separate messages, one message for each CHO configuration, or one message for each target primary node, including one or more CHO configurations of the target primary node. In addition to using the RRC reconfiguration message of layer 3, other messages of layer 2 or layer 1 (such as MAC signaling, or signaling the CHO execution conditions via the PDCCH) may also be used.

[0136] As shown in block 602, the source MN also sends auxiliary information for CHO recovery to the user equipment. The auxiliary information is used by the user equipment to select a CHO configuration for CHO recovery from a plurality of CHO configurations, as described above with respect to Figure 5 As described.

[0137] The auxiliary information may include a single-dual connectivity priority flag. Such a flag may be used to configure the UE to prioritize a single connectivity CHO configuration over a dual connectivity CHO configuration, and vice versa. For example, if the single-dual connectivity priority flag is set to 1, the UE prioritizes a dual connectivity (DC) CHO configuration over a single connectivity CHO configuration. Otherwise, if the single-dual connectivity priority flag is set to 0, the UE prioritizes an SC-CHO configuration over a DC-CHO configuration.

[0138] The single-dual connectivity priority flag may be determined based on the pending traffic volume on the secondary cell group bearer. Then, the source MN may be configured to prioritize the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target primary node, and prioritize the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node.

[0139] Additionally or alternatively, the auxiliary information may include an indication that, in the case where the primary and secondary cells of the source secondary node are maintained, a dual connectivity CHO configuration is prioritized. In such a configuration, the UE will maintain its connection to the source SN. This reduces the data forwarding required between nodes while having a stable connection to the source SN.

[0140] The auxiliary information may additionally or alternatively include a primary and secondary cell selection condition. Then, the UE may be configured to select a CHO configuration in which the primary and secondary cells satisfy the primary and secondary cell selection condition. For example, the primary and secondary cell selection condition may include a threshold for cell quality and / or any selection condition based on RSRP, RSRQ or SINR conditions.

[0141] Additionally or alternatively, the auxiliary information may include information about which information is encoded in which CHO configuration. For example, the auxiliary information may include a single-dual connectivity indicator indicating which type of CHO configuration is encoded in the corresponding CHO configuration. In another additional or alternative example, the auxiliary information may include an identifier of a primary and secondary cell indicating which primary and secondary cell is encoded in the CHO configuration. In alternative embodiments, the information about the CHO configuration may also be indicated in different ways, for example, by including the information in an additional field accompanying the CHO configuration, or by signaling them separately to the auxiliary information.

[0142] The source master node may also include components for performing the processes described herein. For example, the source master node may include: components for sending multiple CHO configurations to a user device, and components for sending auxiliary information for CHO recovery to the user device, wherein the auxiliary information is used by the user device to select a CHO configuration for CHO recovery from the multiple CHO configurations. Components for other processes described herein may also be provided.

[0143] exist Figure 7 A flow chart for dual connectivity conditional switching with on-time data forwarding performed by a network node supporting gNB-CU-CP functionality is presented in.

[0144] The network node supports at least one of a central unit control plane (gNB-CU-CP) functionality or a layer 3 protocol of a radio access network and is configured to support a connection with a user equipment operating with dual connectivity with a primary cell of the network node and a primary secondary cell of a source secondary node.

[0145] Starting from block 701, a network node, in particular a gNB-CU-CP of the network node, generates a radio resource control RRC message including CHO recovery assistance information. Thereafter, the network node sends an RRC message including the assistance information to a user equipment. The assistance information is used by the user equipment to select a CHO configuration for CHO recovery from a plurality of CHO configurations. The RRC message is sent to the UE via the gNB-DU. As will be appreciated by those skilled in the art, the embodiments described with respect to the source MN may also be applicable to Figure 7 network nodes.

[0146] Figure 8 An overall message flow diagram of an embodiment of dual connectivity conditional handover recovery is presented in. The message flow diagram depicts a UE 801 acting during CHO recovery according to the present disclosure, a source MN 802 with an associated primary cell PCell-0, a source SN 803 with an associated primary secondary cell PSCell-0, a first target MN 804 with an associated primary cell PCell-1, a first target SN 805 with associated primary secondary cells PCell-1 and PCell-3, a second target MN 806 with an associated primary cell PCell-2, and a second target SN 807 with an associated primary secondary cell PCell-2.

[0147] The overall process of this example embodiment is as follows. In number 1, UE 801 is served by PCell-0 of source MN 802 (S-MN) and PSCell-0 of source SN 803 (S-SN), that is, UE 801 operates with dual connectivity. Number 2 indicates that UE 801 is configured with 3 CHO configurations of the same target PCell-1 of T-MN1804. These CHO configurations are called configuration 1a, configuration 1b, and configuration 1c. Configuration 1a includes CHO configuration information for conditional PSCell change (CPC) of CHO toward PCell-1 and PSCell-1 toward T-SN1 805 (MN+SN bearer, CHO-DC). Configuration 1b includes CHO configuration information for CHO only for PCell-1 (all MN bearers, CHO-SC). Configuration 1c includes CHO configuration information for CHO towards PCell-1 and CPC towards PSCell-3 (MN+SN bearer, CHO-DC) of T-SN1 805 .

[0148] In addition to these three configurations towards PCell-1, UE 801 is also configured with another CHO-DC configuration towards PCell-2 of T-MN2 806, and a CPC configuration towards PSCell-2 of T-SN2 807. This is highlighted in the box with number 3. The configurations provided to UE 801 in numbers 2 and 3 can also be provided in a single step (using a single RRC reconfiguration).

[0149] Number 4 depicts that the serving PCell-0 provides auxiliary information to the UE 801 for a CHO recovery process, as described with respect to the embodiments disclosed herein. In this example, the auxiliary information is considered to include an SC / DC priority flag to configure the recovery behavior of the UE 801 and indicate which type of configuration should be prioritized during the CHO recovery process. The auxiliary information is also considered to include a PSCell selection condition for the CHO recovery process, which may be based on any or all of RSRP, RSRQ, or SINR measurements. In addition, the auxiliary information also includes an indication related to CHO-DC or CHO-SC, so that the UE 801 can identify whether the configuration includes a PSCell, so that the UE can determine which configurations should be considered / decoded during the CHO recovery process. In addition, the auxiliary information also includes an ID of a PSCell outside the CHO-DC configuration, which is configured with a PSCell ID, so that the UE 801 can select / decode the desired configuration. As will be appreciated by those skilled in the art, the auxiliary information may also include a portion of the information as needed.

[0150] In number 5, UE 801 experiences a radio link failure on source PCell-0 and / or a handover failure during CHO execution towards the initially selected target PCell-2. In this example, we assume that UE 801 experiences a handover failure to PCell-2. Thereafter, UE 801 selects a suitable cell for recovery, such as PCell-1. Suitable means, for example, that measurements indicate that the radio conditions of the cell are sufficient for a stable connection, or that any other conditions for establishing a connection are met. In summary, PCell-1 is one of the prepared cells for CHO and is suitable for recovering the connection.

[0151] According to the auxiliary information, UE 801 prioritizes (shown in number 7) the DC configuration rather than the SC configuration because it is configured by the serving PCell-0 in number 4. Then, UE 801 detects the CHO-DC configuration associated with PCell-1 in number 8 by using the SC / DC indicator provided in number 4. UE 801 recognizes that configuration 1a and configuration 1c are CHO-DC configurations associated with PCell-1.

[0152] In number 9, UE 801 recognizes that PSCell-1 and PSCell-3 are PSCells of the target SN configured together with the CHO configuration of PCell-1 by using the auxiliary information provided in number 4. In number 10, UE 801 selects one of the CHO-DC configurations associated with PCell-1, that is, one of configuration 1a and configuration 1c. The selection criterion is based on the PSCell selection condition provided in number 4. In this example, PSCell-3 satisfies the selection condition during recovery, and UE 801 selects configuration 1c associated with PSCell-3.

[0153] Afterwards, and as shown in number 11, UE 801 decodes configuration 1c, which is selected as a suitable configuration based on the auxiliary information in number 4 and is used in numbers 7 to 11. In the final number 12, UE 801 recovers on PCell-1 and PSCell-3 using the CHO configuration configuration 1c selected in step 10 and decoded in step 11. As explained above, during the recovery process in the CHO-DC scenario, UE 801 is provided and configured with sufficient information to minimize the interruption time on the SCG bearer.

[0154] Fig. 9An overall message flow diagram of an embodiment of dual connectivity conditional handover recovery is presented in. The message flow diagram depicts a UE 901 acting during CHO recovery according to the present disclosure, a source MN 902 with an associated primary cell PCell-0, a source SN 903 with an associated primary secondary cell PSCell-0, a first target MN 904 with an associated primary cell PCell-1, a first target SN 905 with associated primary secondary cells PCell-1 and PCell-3, a second target MN 906 with an associated primary cell PCell-2, and a second target SN 907 with an associated primary secondary cell PCell-2.

[0155] The overall process of this example embodiment is as follows. In number 1, UE 901 is served by PCell-0 of source MN 902 (S-MN) and PSCell-0 of source SN 903 (S-SN), that is, UE 901 operates with dual connectivity. Number 2 indicates that UE 901 is configured with 3 CHO configurations of the same target PCell-1 of T-MN1904. These CHO configurations are called configuration 1a, configuration 1b, and configuration 1c. Configuration 1a includes CHO configuration information for conditional PSCell change (CPC) for CHO toward PCell-1 and PSCell-1 (MN+SN bearer, CHO-DC) toward T-SN1 905. Configuration 1b includes CHO configuration information only for CHO toward PCell-1 (all MN bearers, CHO-SC). Configuration 1c includes CHO configuration information for CHO towards PCell-1 and CPC towards PSCell-3 (MN+SN bearer, CHO-DC) of T-SN1 905.

[0156] In addition to these three configurations towards PCell-1, the UE 901 is also configured with another CHO-DC configuration towards PCell-2 of T-MN2 906, and a CPC configuration towards PSCell-2 of T-SN2 907. This is highlighted in the box with number 3. The configurations provided to the UE 901 in numbers 2 and 3 can also be provided in a single step (using a single RRC reconfiguration).

[0157] Number 4 depicts that the service PCell-0 provides auxiliary information to the UE 901 for the CHO recovery process, as described with respect to the embodiments disclosed herein. In this example, the auxiliary information is considered to include an SC / DC priority flag to configure the recovery behavior of the UE 901 and indicate which type of configuration is to be prioritized during the CHO recovery process. The auxiliary information is also considered to include a PSCell selection condition for the CHO recovery process, which may be based on any or all of RSRP, RSRQ, or SINR measurements. In addition, the auxiliary information also includes an indication related to CHO-DC or CHO-SC, so that the UE 901 can identify whether the configuration includes a PSCell, so that the UE can determine which configurations to consider / decode during the CHO recovery process. In addition, the auxiliary information also includes the ID of the PSCell outside the CHO-DC configuration configured with the PSCell ID, so that the UE 901 can select / decode the desired configuration. As will be appreciated by those skilled in the art, the auxiliary information may also include a portion of the information as needed.

[0158] In number 5, UE 901 experiences a radio link failure on source PCell-0 and / or a handover failure during CHO execution towards the initially selected target PCell-2. In this example, we assume that UE 901 experiences a PCell-2 handover failure. Thereafter, UE 901 selects a suitable cell for recovery, such as PCell-1. Suitable means, for example, that measurements indicate that the radio conditions of the cell are sufficient for a stable connection, or that any other conditions for establishing a connection are met. In summary, PCell-1 is one of the prepared cells for CHO and is suitable for recovering the connection.

[0159] According to the auxiliary information, the UE 901 prioritizes (shown in number 7) the DC configuration rather than the SC configuration because it is configured by the serving PCell-0 in number 4. Then, the UE 901 detects the CHO-DC configuration associated with the PCell-1 in number 8 by using the SC / DC indicator provided in number 4. The UE 901 recognizes that configuration 1a and configuration 1c are CHO-DC configurations associated with the PCell-1.

[0160] In number 9, UE 901 recognizes that PSCell-1 and PSCell-3 are PSCells of the target SN, which are configured together with the CHO configuration of PCell-1, by using the auxiliary information provided in number 4. In number 10, UE 901 does not select any CHO-DC configuration associated with PCell-1, that is, does not select configuration 1a or configuration 1c, because none of them meets the PSCell selection condition.

[0161] Afterwards, and as shown in number 11, UE 901 selects CHO-SC configuration configuration 1b as the appropriate configuration based on the auxiliary information provided in number 4 and used in numbers 7 to 11. Since there is an available CHO-SC configuration for PCell-1, the UE falls back from CHO-DC recovery to CHO-SC recovery. In number 12, UE 901 recovers on PCell-1 by using the CHO-SC configuration (i.e., configuration 1b).

[0162] Finally, after successfully completing the CHO recovery procedure, UE 901 reports to T-MN1 904 that none of the PSCells configured in the CHO-DC configuration are suitable for the CHO recovery procedure. In one embodiment, UE 901 also reports measurements related to PSCell-1 and PSCell-3, which are identified as PSCells associated with the CHO-DC configuration of PCell-1, which can be used for root cause analysis. In another embodiment, UE 901 reports all available measurements that can be used by the network for root cause analysis.

[0163] Fig.10 Finally, a flow chart of an embodiment for overall dual connectivity conditional handover recovery is presented, which illustrates the decision mechanism that the UE may follow.

[0164] Starting from box 1001, the UE determines (and self-declares) a radio quality failure, such as RLF or HOF as explained with respect to the embodiments described herein. Thereafter, and shown in box 1002, the PCell of the target master node is selected for CHO recovery, for example, based on current measurements. PCell configurations, i.e., CHO configurations for this PCell are available and are detected in box 1003. These CHO configurations are classified into configurations for SC and DC based on the information sent with the auxiliary information, as described above. If the auxiliary information indicates that DC takes precedence over SC (shown in box 1005), the UE proceeds to box 1006. If not, the UE proceeds to box 1010 (described below).

[0165] In block 1006, the UE detects a PSCell for the corresponding DC configuration. This may also be done based on information sent with the assistance information, as described above. If any PSCell satisfies the PSCell selection condition (shown in block 1007), the UE proceeds to block 1008. If not, the UE proceeds to block 1010 (described below). The PSCell selection condition may be as described above for other embodiments (e.g., Figure 5In block 1008, the UE selects a PSCell based on the PSCell condition (e.g., the PSCell with the best condition is determined). The PSCell condition may also be included in the PSCell selection condition. If only one PSCell satisfies the selection condition, the process of block 1008 may be skipped.

[0166] Finally, the UE either selects the corresponding DC configuration in box 1009 and establishes a connection on the corresponding PCell and PSCell, or selects the corresponding SC configuration in box 1010 and establishes a connection only on the corresponding PCell.

[0167] It should be understood that the devices described herein may include, or be coupled to, other units or modules used in transmission and / or reception, such as radio components or radio heads. Although these devices have been described as one entity, different modules and memories may be implemented in one or more physical or logical entities.

[0168] It is worth noting that although embodiments related to LTE and 5G NR have been described, similar principles can be applied to other networks and communication systems that require forced fast connection reestablishment. Therefore, although certain embodiments are described above by way of example with reference to certain example architectures of wireless networks, technologies and standards, the embodiments can be applied to any other suitable form of communication system other than the communication system shown and described herein.

[0169] It is also noted herein that while exemplary embodiments are described above, several variations and modifications may be made to the disclosed solution without departing from the scope of the subject disclosure.

[0170] In general, various exemplary embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects of the subject disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device, but the subject disclosure is not limited thereto. Although various aspects of the subject disclosure may be illustrated and described in block diagrams, flow charts, or using other graphical representations, it is fully understood that, as non-limiting examples, these boxes, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or combinations thereof.

[0171] The example embodiments disclosed in the subject matter may be implemented by computer software executable by a data processor of a mobile device, such as implemented in a processor entity, or by hardware, or by a combination of software and hardware. Computer software or programs, also referred to as program products, include software routines, applets, and / or macros, which may be stored in a data storage medium readable by any device, and which include program instructions for performing specific tasks. A computer program product may include one or more computer executable components that are configured to perform an embodiment when the program is run. One or more computer executable components may be at least one software code or a portion thereof.

[0172] In addition, in this regard, it should be noted that any block of the logic flow shown in the figure can represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software can be stored on physical media, such as memory chips or memory blocks implemented in processors, magnetic media (such as hard disks or floppy disks), and optical media (such as, for example, DVDs and their data variants CDs). Physical media are non-transient media.

[0173] The memory may be of any type suitable for the local technical environment and may 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. The data processor may be of any type suitable for the local technical environment and may include, as non-limiting examples, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), an FPGA, a gate level circuit, and a processor based on a multi-core processor architecture.

[0174] Example embodiments of the subject disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available to convert a logic level design into a semiconductor circuit design that is ready to be etched and formed on a semiconductor substrate.

[0175] The foregoing description has provided, by way of non-limiting example, a complete and informative description of the exemplary embodiments of the subject disclosure. However, in view of the foregoing description, various modifications and adaptations may become apparent to those skilled in the relevant art when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of the present disclosure will still fall within the scope of the subject disclosure as defined in the appended claims. In fact, there are additional embodiments that include a combination of one or more embodiments with any other embodiments previously discussed.

Claims

1. A user equipment, the user equipment being configured to support operation with dual connectivity with a primary cell of a source primary node and a primary secondary cell of a source secondary node of a radio access network, and being configured to support conditional handover (CHO), the user equipment comprising: at least one processor, and at least one memory comprising computer program code, which, when executed by the at least one processor, causes the user equipment to: - Establishing a connection to the primary cell of the source primary node; - Establishing a connection to the primary and secondary cells of the source secondary node; - receiving a plurality of CHO configurations from the source master node, the plurality of CHO configurations comprising: configurations for conditional handover to at least one target master node and at least one target secondary node; - receiving auxiliary information for CHO recovery from the source master node; - in response to the user equipment experiencing a radio link failure on the primary cell of the source primary node, or a handover failure to the primary cell of a first target primary node, determining a primary cell of a second target primary node and an associated CHO configuration from the plurality of CHO configurations based on the auxiliary information for CHO recovery; and - Based on the determined associated CHO configuration, performing CHO recovery towards the primary cell of the second target primary node.

2. The user equipment according to claim 1 is further configured to: in response to the determined CHO configuration being a dual connectivity CHO configuration, perform CHO recovery to a primary and secondary cell of a target secondary node, wherein the primary and secondary cells of the target secondary node are different from the primary and secondary cells of the source secondary node.

3. The user equipment according to claim 1 or claim 2, wherein the auxiliary information comprises: Single and dual connectivity priority flag used to prioritize single connectivity or dual connectivity for CHO recovery.

4. The user equipment according to any one of the preceding claims, wherein the assistance information comprises: Information about pending traffic on the secondary cell group bearer, wherein determining the CHO configuration includes: giving priority to the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target primary node, and giving priority to the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node. 5 . The user equipment according to claim 1 , wherein the auxiliary information indicates that, in the case where the primary and secondary cells of the source secondary node are maintained, a dual connectivity CHO configuration is given priority.

6. The user equipment according to any one of the preceding claims, wherein the auxiliary information includes a CHO recovery primary and secondary cell selection condition, wherein determining the CHO configuration comprises: A CHO configuration in which the primary and secondary cells satisfy the primary and secondary cell selection condition is selected.

7. The user equipment of claim 6, wherein determining the CHO configuration comprises: In response to none of the at least one primary and secondary cells satisfying the primary and secondary cell selection condition, a single connectivity CHO configuration is selected.

8. The user equipment according to claim 7, wherein the user equipment is further caused to: - In response to selecting a single connectivity CHO configuration with the second target master node, sending cell selection information to the second target master node, the cell selection information comprising: An indication that none of the at least one primary and secondary cell associated with the second target primary node satisfies the primary and secondary cell selection condition.

9. The user equipment according to claim 8, wherein the cell selection information further comprises: Measurements related to the at least one primary secondary cell associated with the second target primary node.

10. The user equipment according to claim 8 or claim 9, wherein the cell selection information further comprises: Measurements performed at the user equipment relating to further cells.

11. The user equipment according to any one of the preceding claims, wherein the auxiliary information comprises a single-dual connectivity indicator, the single-dual connectivity indicator indicating whether a corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration.

12. The user equipment according to any one of the preceding claims, wherein the auxiliary information comprises identifiers of primary and secondary cells, and the indicator indicates: which primary and secondary cell is included in the corresponding CHO configuration.

13. A source master node, the source master node being configured to support establishing a connection to a user equipment, the user equipment being configured to support operating with dual connectivity with a primary cell of the source master node and a primary and secondary cell of a source secondary node, and supporting conditional handover CHO, the source master node comprising: at least one processor, and at least one memory including computer program code, which, when executed by the at least one processor, causes the source master node to: - sending a plurality of CHO configurations to the user equipment, the plurality of CHO configurations comprising: configurations for conditional handover to at least one target primary node and at least one target secondary node; and - sending assistance information for CHO recovery to the user equipment, wherein the assistance information is used by the user equipment to determine a CHO configuration for CHO recovery from the plurality of CHO configurations.

14. The source master node according to claim 13, wherein the auxiliary information comprises: Single and dual connectivity priority flag used to prioritize single connectivity or dual connectivity for CHO recovery.

15. A source master node according to claim 14, wherein the single-dual connectivity priority flag is determined based on the pending traffic on the secondary cell group bearer, so as to give priority to the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target master node, and to give priority to the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node. 16 . The source primary node according to claim 13 , wherein the auxiliary information indicates that, in the case where the primary and secondary cells of the source secondary node are maintained, a dual connectivity CHO configuration is given priority.

17. The source master node according to any one of claims 13 to 16, wherein the auxiliary information comprises a CHO recovery primary and secondary cell selection condition, and the CHO recovery primary and secondary cell selection condition is used to determine a CHO configuration in which the primary and secondary cells meet the primary and secondary cell selection condition.

18. The source master node according to any one of claims 13 to 17, wherein the auxiliary information comprises a single-dual connectivity indicator, the single-dual connectivity indicator indicating whether a corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration.

19. The source master node according to any one of claims 13 to 18, wherein the auxiliary information comprises an identifier of a primary and a secondary cell, the identifier indicating which primary and secondary cell is included in a corresponding CHO configuration.

20. A network node, the network node supporting at least one of a central unit control plane function, or a layer 3 protocol of a radio access network, the network node being configured to support a connection with a user equipment, the user equipment operating with dual connectivity with a primary cell of the network node and a primary secondary cell of a source secondary node, and being configured for conditional handover (CHO), the network node comprising: at least one processor, and at least one memory comprising computer program code which, when executed by the at least one processor, causes the network node to: - generating a radio resource control RRC message, the radio resource control RRC message comprising assistance information for CHO recovery; as well as -Sending the RRC message including the auxiliary information to the user equipment, wherein the auxiliary information is used by the user equipment to determine a CHO configuration for CHO recovery from a plurality of CHO configurations, the plurality of CHO configurations comprising: a configuration for conditional switching to at least one target primary node and at least one target secondary node.

21. The network node according to claim 20, wherein the auxiliary information comprises: Single and dual connectivity priority flag used to prioritize single connectivity or dual connectivity for CHO recovery.

22. A network node according to claim 21, wherein the single-dual connectivity priority flag is determined based on the pending traffic on the secondary cell group bearer, so as to give priority to the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target primary node, and to give priority to the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node.

23. The network node according to any one of claims 20 to 22, wherein the auxiliary information indicates that: in the case where the primary and secondary cells of the source secondary node are maintained, dual connectivity CHO configuration is given priority.

24. The network node according to any one of claims 20 to 23, wherein the auxiliary information comprises a CHO recovery primary and secondary cell selection condition, and the CHO recovery primary and secondary cell selection condition is used to determine a CHO configuration in which the primary and secondary cells meet the primary and secondary cell selection condition.

25. The network node according to any one of claims 20 to 24, wherein the assistance information comprises a single-dual connectivity indicator, the single-dual connectivity indicator indicating whether a corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration.

26. The network node according to any one of claims 20 to 25, wherein the auxiliary information comprises an identifier of a primary and a secondary cell, the identifier indicating which primary and secondary cell is included in the corresponding CHO configuration.

27. A method for conditional handover (CHO) recovery, performed by a user equipment configured to operate with dual connectivity within at least one radio access network (RAN), comprising: - Establish a connection to the primary cell of the source primary node; - Establish a connection to the primary and secondary cells of the source secondary node; - receiving a plurality of CHO configurations from the source master node, the plurality of CHO configurations comprising: configurations for conditional handover to at least one target master node and at least one target secondary node; - receiving auxiliary information for CHO recovery from the source master node; - in response to the user equipment experiencing a radio link failure on the primary cell of the source primary node, or a handover failure to the primary cell of a first target primary node, determining a primary cell of a second target primary node and an associated CHO configuration from the plurality of CHO configurations based on the auxiliary information for CHO recovery; and - Based on the determined associated CHO configuration, performing a CHO recovery towards the primary cell of the second target primary node.

28. The method according to claim 27, further comprising: In response to the determined CHO configuration being a dual connectivity CHO configuration, CHO recovery is performed to a primary secondary cell of a target secondary node, wherein the primary secondary cell of the target secondary node is different from the primary secondary cell of the source secondary node.

29. The method according to claim 27 or claim 28, wherein the auxiliary information comprises: Single and dual connectivity priority flag used to prioritize single connectivity or dual connectivity for CHO recovery.

30. The method according to any one of claims 27 to 29, wherein the auxiliary information comprises: Information about pending traffic on the secondary cell group bearer, wherein determining the CHO configuration includes: giving priority to the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target primary node, and giving priority to the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node.

31. The method according to any one of claims 27 to 30, wherein the auxiliary information indicates that: in the case where the primary and secondary cells of the source secondary node are maintained, dual connectivity CHO configuration is given priority.

32. The method according to any one of claims 27 to 31, wherein the auxiliary information includes a CHO recovery primary and secondary cell selection condition, wherein determining the CHO configuration comprises: A CHO configuration in which the primary and secondary cells satisfy the primary and secondary cell selection condition is selected.

33. The method of claim 32, wherein determining the CHO configuration comprises: In response to none of the at least one primary and secondary cells satisfying the primary and secondary cell selection condition, a single connectivity CHO configuration is selected.

34. The method of claim 33, wherein the user equipment is further caused to: - In response to selecting a single connectivity CHO configuration with the second target master node, sending cell selection information to the second target master node, the cell selection information comprising: An indication that none of the at least one primary and secondary cell associated with the second target primary node satisfies the primary and secondary cell selection condition.

35. The method according to claim 34, wherein the cell selection information further comprises: Measurements related to the at least one primary secondary cell associated with the second target primary node.

36. The method according to claim 34 or claim 35, wherein the cell selection information further comprises: Measurements performed at the user equipment relating to further cells.

37. The method according to any one of claims 27 to 36, wherein the auxiliary information comprises a single-dual connectivity indicator, and the single-dual connectivity indicator indicates whether a corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration.

38. The method according to any one of claims 27 to 37, wherein the auxiliary information comprises identifiers of primary and secondary cells, and the indicator indicates: which primary and secondary cell is included in the corresponding CHO configuration.

39. A method for conditional handover (CHO) recovery performed by a source primary node connected to a user equipment, the user equipment operating with dual connectivity with a primary cell of the source primary node and a primary secondary cell of a source secondary node, the method comprising: - sending a plurality of CHO configurations to the user equipment, the plurality of CHO configurations comprising: configurations for conditional handover to at least one target primary node and at least one target secondary node; and - sending assistance information for CHO recovery to the user equipment, wherein the assistance information is used by the user equipment to determine a CHO configuration for CHO recovery from the plurality of CHO configurations.

40. The method of claim 39, wherein the auxiliary information comprises: Single and dual connectivity priority flag used to prioritize single connectivity or dual connectivity for CHO recovery.

41. A method according to claim 40, wherein the single-dual connectivity priority flag is determined based on the pending traffic on the secondary cell group bearer, so as to give priority to the single connectivity CHO configuration in response to the single connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target primary node, and to give priority to the dual connectivity CHO configuration in response to the dual connectivity CHO configuration having the secondary cell group bearer mapped to the corresponding target secondary node.

42. The method according to any one of claims 39 to 41, wherein the auxiliary information indicates that: in the case where the primary and secondary cells of the source secondary node are maintained, dual connectivity CHO configuration is given priority.

43. The method according to any one of claims 39 to 42, wherein the auxiliary information comprises a CHO recovery primary and secondary cell selection condition, and the CHO recovery primary and secondary cell selection condition is used to determine a CHO configuration in which the primary and secondary cells meet the primary and secondary cell selection condition.

44. The method according to any one of claims 39 to 43, wherein the auxiliary information comprises a single-dual connectivity indicator, and the single-dual connectivity indicator indicates whether the corresponding CHO configuration is a single connectivity configuration or a dual connectivity configuration.

45. The method according to any one of claims 39 to 44, wherein the auxiliary information comprises an identifier of a primary and a secondary cell, the identifier indicating which primary and secondary cell is included in the corresponding CHO configuration.

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