Method and apparatus for signaling a cell list in conditional cell addition

Abstract

The disclosure relates to a communication method and system that fuses a fifth generation (5G) communication system supporting a higher data rate than a fourth generation (4G) system with Internet of Things (IoT) technology. The disclosure can be applied to intelligent services based on 5G communication technology and IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. The present invention relates to conditional cell addition, and discloses a method of adding and changing a primary secondary cell (PSCell). The method performed by a first base station in a wireless communication system according to an embodiment of the present invention comprises the steps of: transmitting, to a second base station, a first message for conditional PSCell addition, wherein the first message includes measurement results of at least one cell by a terminal and the second base station operates the at least one cell; receiving, from the second base station, a second message as a response to the first message, wherein the second message includes at least one of frequency information and a cell identifier of a candidate target PSCell selected from the at least one cell and configuration information about the candidate target PSCell; determining an execution condition for conditional PSCell addition related to the candidate target PSCell based on at least one of the frequency information and the cell identifier; and transmitting, to the terminal, a third message including the configuration information about the candidate target PSCell, the execution condition, and information indicating the cell identifier.

Description

Technical Field

[0001] This disclosure relates to methods and apparatus for cell addition. This disclosure also relates to methods and apparatus for conditional cell addition, and to primary / secondary cell (PSCell) addition. Background Technology

[0002] To meet the increased demand for wireless data services since the deployment of 4G communication systems, efforts have been made to develop improved 5G or pre-5G communication systems. Therefore, 5G or pre-5G communication systems are also referred to as "super-4G networks" or "post-LTE systems." 5G communication systems are considered to be implemented in higher frequency (millimeter wave) bands (e.g., the 60GHz band) to achieve higher data rates. To reduce radio wave propagation loss and increase transmission distance, beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive MIMO technologies have been discussed in 5G communication systems. Furthermore, in 5G communication systems, system network improvements are being developed based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, coordinated multipoint (CoMP), and receiver interference cancellation. In 5G systems, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) have been developed as advanced coding and modulation (ACM), and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) have been developed as advanced access technologies.

[0003] The Internet (a human-centric network of connections where humans generate and consume information) is now evolving into the Internet of Things (IoT), where distributed entities such as things exchange and process information without human intervention. The Internet of Everything (IoE), a combination of IoT technology and big data processing technology, has emerged through connection to cloud servers. With technological elements such as sensing technology, wired / wireless communication and network infrastructure, service interface technology, and security technology being required for IoT implementation, sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) have recently been explored. Such an IoT environment can provide intelligent Internet technology services, creating new value for human life by collecting and analyzing data generated between connected things. Through the convergence and integration of existing information technology (IT) and various industrial applications, IoT can be applied to a wide range of fields, including smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart appliances, and advanced medical services.

[0004] Correspondingly, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, machine-type communication (MTC), and machine-to-machine (M2M) communication can be implemented using beamforming, MIMO, and array antennas. Applying cloud radio access networks (RAN) to the aforementioned big data processing technologies can also be seen as an example of the convergence between 5G and IoT technologies. Summary of the Invention

[0005] Technical issues

[0006] The technical objectives to be achieved in the embodiments of this disclosure relate to improved methods and apparatus for cell addition.

[0007] Furthermore, the technical objectives to be achieved in the embodiments of this disclosure relate to conditional cell addition, and to methods and apparatus for adding and changing PSCells (primary SCG cells or primary and secondary cells).

[0008] Furthermore, the technical objective to be achieved in the embodiments of this disclosure relates to a method and apparatus for adding PSCells, which enables a terminal to configure a secondary cell group (SCG) and perform data transmission / reception in a short time when adding a PSCell for dual connectivity (DC) by reducing the delay time that occurs during the process of adding a PSCell when needed.

[0009] Solution to the problem

[0010] According to embodiments of this disclosure, a method performed by a first base station in a wireless communication system may include: sending a first message for conditional primary and secondary cell (PSCell) addition to a second base station operating at least one cell, the first message including measurement results of the at least one cell by a terminal; receiving a second message from the second base station in response to the first message, the second message including configuration information of a candidate target PSCell selected from the at least one cell and at least one of frequency information associated with the candidate target PSCell and a cell identifier of the candidate target PSCell; determining execution conditions for conditional PSCell addition associated with the candidate target PSCell based on at least one of the frequency information and the cell identifier; and sending a third message to the terminal, the third message including configuration information of the candidate target PSCell, information indicating the execution conditions, and a conditional PSCell identifier.

[0011] According to embodiments of this disclosure, a method performed by a second base station in a wireless communication system may include: receiving from a first base station a first message for conditional primary and secondary cell (PSCell) addition, the first message including measurement results of a terminal on at least one cell operated by the second base station; and in response to the first message, sending a second message to the first base station, the second message including configuration information of a candidate target PSCell selected from the at least one cell and at least one of frequency information associated with the candidate target PSCell and a cell identifier of the candidate target PSCell, wherein at least one of the frequency information and the cell identifier is used to determine the execution conditions for conditional PSCell addition associated with the candidate target PSCell, and wherein a third message is sent from the first base station to the terminal, the third message including the configuration information of the candidate target PSCell and information indicating the execution conditions.

[0012] According to embodiments of this disclosure, a first base station in a wireless communication system may include a transceiver and a controller. The controller is configured to: control the transceiver to send a first message for conditional primary and secondary cell (PSCell) addition to a second base station operating at least one cell, the first message including measurement results of the terminal on the at least one cell; control the transceiver to receive a second message from the second base station in response to the first message, the second message including configuration information of a candidate target PSCell selected from the at least one cell and at least one of frequency information associated with the candidate target PSCell and a cell identifier of the candidate target PSCell; determine execution conditions for conditional PSCell addition associated with the candidate target PSCell based on at least one of the frequency information and the cell identifier; and control the transceiver to send a third message to the terminal, the third message including configuration information of the candidate target PSCell and information indicating the execution conditions.

[0013] According to embodiments of this disclosure, a second base station in a wireless communication system may include a transceiver and a controller, the controller being configured to: control the transceiver to receive from a first base station a first message for conditional primary and secondary cell (PSCell) addition, the first message including measurement results of a terminal on at least one cell operated by the second base station; and control the transceiver to send a second message to the first base station in response to the first message, the second message including configuration information of a candidate target PSCell selected from the at least one cell and at least one of frequency information associated with the candidate target PSCell and a cell identifier of the candidate target PSCell, wherein at least one of the frequency information and the cell identifier is used to determine the execution conditions for conditional PSCell addition associated with the candidate target PSCell, and wherein a third message is sent from the first base station to the terminal, the third message including the configuration information of the candidate target PSCell and information indicating the execution conditions.

[0014] Beneficial effects of the invention

[0015] According to embodiments of this disclosure, when a terminal adds a PSCell for dual connectivity (DC), by reducing the latency that occurs during the process of adding the PSCell when necessary, the terminal can configure the secondary cell group (SCG) and perform data transmission / reception in a short time. Attached Figure Description

[0016] Figure 1 This is a diagram illustrating the architecture of an LTE system according to an embodiment of the present disclosure.

[0017] Figure 2 This is a diagram illustrating the structure of a radio protocol in an LTE system according to an embodiment of the present disclosure.

[0018] Figure 3 This is a diagram illustrating the architecture of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0019] Figure 4 This is a diagram illustrating the structure of a radio protocol in a next-generation mobile communication system according to an embodiment of the present disclosure.

[0020] Figure 5 This is a block diagram illustrating the internal structure of a user equipment according to an embodiment of the present disclosure.

[0021] Figure 6 This is a block diagram illustrating the configuration of a base station according to an embodiment of the present disclosure.

[0022] Figure 7 This is a diagram depicting the process of adding a conditional PSCell initiated by the master node (MN) according to an embodiment of the present disclosure.

[0023] Figure 8 This is a flowchart illustrating the operations performed by the MN when the SN does not send an additional threshold for CPA condition information to the MN, according to an embodiment of the present disclosure.

[0024] Figure 9 This is a flowchart illustrating the operations performed by the MN when the SN sends an additional threshold for CPA condition information to the MN according to an embodiment of the present disclosure.

[0025] Figure 10 This is a diagram illustrating a scheme for the UE to store information related to CHO and CPA when both CHO and CPA are configured in the UE according to an embodiment of the present disclosure.

[0026] Figure 11 This is a sequence diagram illustrating a method for performing a CPA operation upon successful execution of a CHO, according to an embodiment of the present disclosure.

[0027] Figure 12 This is a sequence diagram illustrating a method for performing a CPA operation upon successful normal handover according to an embodiment of the present disclosure.

[0028] Figure 13 This is a sequence diagram illustrating a method for performing a CPA operation according to an embodiment of the present disclosure.

[0029] Figure 14 This is a sequence diagram illustrating a method for performing a CPA operation during a normal PSCell addition or SCG addition according to an embodiment of the present disclosure.

[0030] Figure 15 This is a sequence diagram illustrating a method for performing a CPA operation when the process of adding an SCG (or adding a PSCell) or changing a PSCell fails midway, according to an embodiment of the present disclosure.

[0031] Figure 16 This is a sequence diagram illustrating a method for performing a CPA operation when the CPA process fails midway, according to an embodiment of the present disclosure.

[0032] Figure 17 This is a sequence diagram illustrating a method for performing a CPA operation when an SCG failure occurs, in addition to a CPA failure, according to an embodiment of the present disclosure. Detailed Implementation

[0033] In the following description, exemplary embodiments of the present disclosure will be illustrated with reference to the accompanying drawings. It should be noted that, wherever possible, the same reference numerals denote the same components in the drawings. Furthermore, detailed descriptions of well-known functions and configurations that may obscure the subject matter of this disclosure will be omitted.

[0034] In the description of embodiments in this specification, descriptions of technical details that are well-known in the art and not directly related to this disclosure may be omitted. This is to convey the main points of this disclosure more clearly without ambiguity by omitting unnecessary descriptions.

[0035] Similarly, in the accompanying drawings, some elements are exaggerated, omitted, or only briefly outlined. Furthermore, the size of each element may not reflect its actual size. In all the drawings, the same reference numerals are used to refer to the same or corresponding parts.

[0036] The advantages and features of this disclosure, as well as methods of implementing them, will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings. However, this disclosure is not limited to the embodiments disclosed below, but can be implemented in various different ways. The embodiments are provided only to complete this disclosure and to fully inform those skilled in the art of the scope of this disclosure, which is defined only by the scope of the claims. The same reference numerals are used throughout the specification to refer to the same parts.

[0037] Simultaneously, it will be recognized that the blocks of a flowchart and combinations of flowcharts can be executed by computer program instructions. These computer program instructions can be loaded onto the processor of a general-purpose computer, a special-purpose computer, or a programmable data processing device, and the instructions executed by the processor of the computer or programmable data processing device create components for performing the functions described in the blocks of the flowchart. To implement the functions in a certain way, the computer program instructions can also be stored in computer-usable or readable memory applicable to a special-purpose computer or programmable data processing device, and the computer program instructions stored in computer-usable or readable memory can produce an article of manufacture containing components for performing the functions described in the blocks of the flowchart. Since the computer program instructions can be loaded onto a computer or programmable data processing device, when the computer program instructions are executed on the computer or programmable data processing device as a process having a series of operations, they can provide steps for performing the functions described in the blocks of the flowchart.

[0038] Additionally, each block of the flowchart may correspond to a module, segment, or piece of code containing one or more executable instructions for performing one or more logical functions, or a portion thereof. It should also be noted that in some alternative cases, the functions described by the blocks may be executed in an order different from the listed order. For example, two blocks listed sequentially may be executed substantially simultaneously, or in reverse order depending on their corresponding functions.

[0039] Here, the terms "unit," "module," etc., as used in the embodiments can refer to software or hardware components capable of performing functions or operations, such as FPGAs or ASICs. However, "unit," etc., is not limited to hardware or software. Units, etc., can be configured to reside in addressable storage media or drive one or more processors. For example, units, etc., can refer to components, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, or variables, such as software components, object-oriented software components, class components, or task components. The functionality provided by components and units can be a combination of smaller components and units, and can be combined with other components and units to form larger components and units. Furthermore, components and units can be implemented to drive one or more processors in a device or secure multimedia card. Those terms used in the following description to identify access nodes, indicate network entities, indicate messages, indicate interfaces between network entities, and indicate various identification information are used for illustrative purposes. Therefore, this disclosure is not limited to the terminology described later, and other terms referring to objects with equivalent technical meanings can be used.

[0040] For ease of description, this disclosure uses the terms and names defined in the 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) standard. However, this disclosure is not limited to the foregoing terms and names and can be applied equivalently to systems conforming to other standards.

[0041] In various embodiments of this disclosure, the primary node (MN) can be interpreted as the primary base station, and the secondary node (SN) can be interpreted as the secondary base station. Furthermore, in various embodiments of this disclosure, MN and SN can be interpreted as different base stations, as base stations using different Radio Access Technologies (RATs), and in some cases, as base stations using the same RAT. Common terms such as first base station and second base station can be used to distinguish MN and SN.

[0042] In various embodiments of this disclosure, a Radio Resource Control (RRC) message sent by the MN may be referred to as an MNRRC message. Furthermore, an RRC message generated by the SN may be referred to as an SN RRC message.

[0043] Figure 1 This is a diagram illustrating the architecture of an LTE system according to an embodiment of the present disclosure.

[0044] refer to Figure 1As shown in the figure, the radio access network of a Long Term Evolution (LTE) system can consist of next-generation base stations (evolved Node B, ENB, Node B, or base station) 1-05, 1-10, 1-15, or 1-20, a Mobility Management Entity (MME) 1-25, and a Service Gateway (S-GW) 1-30. User equipment (UE or terminal) 1-35 can connect to external networks through ENB 1-05, 1-10, 1-15, or 1-20 and S-GW 1-30.

[0045] exist Figure 1 In this context, ENBs 1-05, 1-10, 1-15, and 1-20 can correspond to existing Node Bs in a UMTS system. The ENB connects to UE 1-35 via a radio channel but can perform more complex functions compared to existing Node Bs. In LTE systems, all user services, including real-time services like VoIP, can be served through a shared channel. Therefore, a mechanism is needed to perform scheduling based on collected state information about the UE's buffers, available transmit power, and the channel, and ENBs 1-05, 1-10, 1-15, and 1-20 can be responsible for this. Typically, one ENB can control multiple cells. To achieve data rates of, for example, 100 Mbps in a bandwidth of, for example, 20 MHz, LTE systems can utilize Orthogonal Frequency Division Multiplexing (OFDM) as the radio access technology. Furthermore, LTE systems can apply Adaptive Modulation and Coding (AMC) to determine the modulation scheme and channel coding rate based on the UE's channel state. S-GW 1-30 is the entity that provides data bearers and can create and remove data bearers under the control of MME 1-25. MME is the entity responsible for various control functions, including UE mobility management functions, and can be connected to multiple ENBs 1-05, 1-10, 1-15, and 1-20.

[0046] Figure 2 This is a diagram illustrating the structure of a radio protocol in an LTE system according to an embodiment of the present disclosure.

[0047] refer to Figure 2 In the UE or ENB, the radio protocol of the LTE system can consist of Packet Data Convergence Protocol (PDCP) 2-05 or 2-40, Radio Link Control (RLC) 2-10 or 2-35, and Media Access Control (MAC) 2-15 or 2-30. PDCP 2-05 or 2-40 can perform IP header compression and decompression. The main functions of PDCP 2-05 or 2-40 can be summarized as follows.

[0048] - Header compression and decompression functions (Header compression and decompression: ROHC only)

[0049] - User data transmission function (transmission of user data)

[0050] - Sequential delivery function (delivering higher-level PDUs sequentially during PDCP reconstruction of RLC AM)

[0051] - Reordering function (for split bearers in DC (RLC AM only): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0052] - Duplicate detection function (duplicate detection of lower-level SDUs during the PDCP reconstruction process of RLC AM)

[0053] - Retransmission function (for RLC AM, retransmit PDCP SDU during handover, and for split bearers in DC, retransmit PDCP PDU during PDCP data recovery)

[0054] - Encryption and decryption functions (encryption and decryption)

[0055] - Timer-based SDU discarding function (timer-based SDU discarding in the uplink)

[0056] The Radio Link Control (RLC) 2-10 or 2-35 can reconfigure PDCP PDUs (Packet Data Units) to an appropriate size and perform Automatic Repeat Request (ARQ) operations. The main functions of the RLC 2-10 or 2-35 can be summarized as follows.

[0057] - Data transmission function (transmission of higher-layer PDUs)

[0058] -ARQ function (error correction via ARQ (for AM data transmission only))

[0059] - Splicing, segmenting, and reassembling functions (splicing, segmenting, and reassembling of RLC SDUs (only for UM and AM data transmission))

[0060] - Re-segmentation function (re-segmentation of RLC data PDUs (only for AM data transmission))

[0061] - Reordering function (Reordering RLC data PDUs (only for UM and AM data transfer))

[0062] - Duplicate detection function (Duplicate detection (only for UM and AM data transmission))

[0063] - Error detection function (protocol error detection (AM data transmission only))

[0064] -RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

[0065] -RLC Reconstruction Function (RLC Reconstruction)

[0066] MAC 2-15 or 2-30 can connect to multiple RLC entities in the UE, and it can multiplex RLC PDUs into MAC PDUs and demultiplex MAC PDUs into RLC PDUs. The main functions of MAC 2-15 or 2-30 can be summarized as follows.

[0067] - Mapping function (mapping between logical channels and transport channels)

[0068] - Multiplexing and demultiplexing functions (multiplexing MAC SDUs belonging to one or different logical channels into transport blocks (TBs) delivered to the physical layer on the transport channel / demultiplexing transport blocks (TBs) delivered from the physical layer on the transport channel into MAC SDUs belonging to one or different logical channels)

[0069] - Scheduling information reporting function (Scheduling Information Report)

[0070] - HARQ (Hybrid Automatic Repeat Request) feature (with HARQ error correction)

[0071] - Priority processing function between logical channels (priority processing between logical channels of a UE)

[0072] - Priority processing function between UEs (priority processing is performed between UEs through dynamic scheduling)

[0073] -MBMS Service Identification Function (MBMS Service Identification)

[0074] -Transmission format selection function (Transmission format selection)

[0075] - Fill function (Fill)

[0076] Physical (PHY) layer 2-20 or 2-25 can convert higher-layer data into OFDM symbols through channel coding and modulation, and transmit OFDM symbols through radio channels. Alternatively, it can demodulate OFDM symbols received through radio channels, perform channel decoding, and forward the results to higher layers.

[0077] Figure 3 This is a diagram illustrating the architecture of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0078] refer to Figure 3The radio access network of a next-generation mobile communication system (hereinafter referred to as NR or 5G) can consist of next-generation base stations (new radio node B, gNB, NR NB, NR gNB, or NR base station) 3-10 and a next-generation core network (new radio core network, NR CN) 3-05. New radio user equipment (NR UE or terminal) 3-15 can connect to external networks via NR gNB 3-10 and NR CN 3-05.

[0079] exist Figure 3 In this context, NR gNB 3-10 can correspond to the evolved Node B (eNB) of an existing LTE system. NR gNB 3-10 can connect to NR UE 3-15 via radio channels and can provide superior service compared to existing Node Bs. In next-generation mobile communication systems, all user services can be served through shared channels. Therefore, an entity is needed to perform scheduling by collecting state information such as the buffer state, available transmit power state, and channel state of each UE, and NR NB 3-10 can be responsible for this. One NR gNB can control multiple cells. In next-generation mobile communication systems, bandwidth exceeding the current maximum bandwidth can be utilized to achieve ultra-high-speed data transmission compared to current LTE. Furthermore, beamforming technology can be additionally combined with Orthogonal Frequency Division Multiplexing (OFDM) as the radio access technology. Additionally, an Adaptive Modulation and Coding (AMC) scheme that determines the modulation scheme and channel coding rate to match the UE's channel state can be applied. NR CN 3-05 can perform functions such as mobility support, bearer configuration, and Quality of Service (QoS) configuration. The NR CN3-05 is an entity responsible not only for mobility management but also for various control functions of the UE, and it can connect to multiple base stations. Furthermore, next-generation mobile communication systems can interoperate with existing LTE systems, and the NR CN 3-05 can connect to the MME 3-25 via a network interface.

[0080] Figure 4 This is a diagram illustrating the structure of a radio protocol in a next-generation mobile communication system according to an embodiment of the present disclosure.

[0081] refer to Figure 4 In the UE or NR gNB, the radio protocol of the next-generation mobile communication system consists of NR Service Data Adaptation Protocol (SDAP) 4-01 or 4-45, NR PDCP 4-05 or 4-40, NR RLC 4-10 or 4-35 and NR MAC 4-15 or 4-30.

[0082] The main functions of NR SDAP 4-01 or 4-45 may include some of the following functions.

[0083] - User data transmission function (transmission of user plane data)

[0084] - Mapping function between uplink and downlink QoS flows and data bearers (mapping between QoS flows and DRB (Data Radio Bearer) for both DL and UL)

[0085] - QoS flow ID tagging function for uplink and downlink (tags QoS flow ID in both DL and UL packets)

[0086] - For uplink SDAP PDUs, the function of mapping reflected QoS flows to data bearers (for UL SDAP PDUs, the function of mapping reflected QoS flows to DRBs).

[0087] Regarding SDAP entities, the UE can be configured via Radio Resource Control (RRC) messages to determine whether to use the SDAP entity header or its functionality for each PDCP entity, bearer, or logical channel. If the SDAP header is configured, the SDAP entity can use the NAS (Non-Access Stratum) reflected QoS 1-bit indication and AS (Access Stratum) reflected QoS 1-bit indication in the SDAP header to instruct the UE to update or reconfigure the mapping information between uplink and downlink QoS flows and data bearers. The SDAP header can include QoS flow ID information indicating QoS. QoS information can be used as data processing priority and scheduling information to support smooth service.

[0088] The main functions of NR PDCP 4-05 or 4-40 may include some of the following functions.

[0089] - Header compression and decompression functions (Header compression and decompression: ROHC only)

[0090] - User data transmission function (transmission of user data)

[0091] - In-order delivery function (in-order delivery of higher-level PDUs)

[0092] - Out-of-order delivery function (out-of-order delivery of higher-level PDUs)

[0093] - Reordering function (for reordering received PDCP PDUs)

[0094] - Duplicate detection function (duplicate detection for lower-level SDUs)

[0095] - Retransmission function (PDCP SDU retransmission)

[0096] - Encryption and decryption functions (encryption and decryption)

[0097] - Timer-based SDU discarding function (timer-based SDU discarding in the uplink)

[0098] In the above description, the reordering function of the NR PDCP entity can mean reordering PDCP PDUs received from lower layers in order based on PDCP sequence numbers (SNs). The reordering function of the NR PDCP entity can include: delivering data to higher layers in a reordered sequence, delivering data directly regardless of order, recording lost PDCP PDUs by reordering them, reporting the status of lost PDCP PDUs to the sender, or requesting retransmission of lost PDCP PDUs.

[0099] The main functions of NR RLC 4-10 or 4-35 may include some of the following functions.

[0100] - Data transmission function (transmission of higher-layer PDUs)

[0101] - In-order delivery function (in-order delivery of higher-level PDUs)

[0102] - Out-of-order delivery function (out-of-order delivery of higher-level PDUs)

[0103] -ARQ functionality (error correction via ARQ)

[0104] - Assembly, segmentation, and reassembly functions (assembly, segmentation, and reassembly of RLC SDUs)

[0105] - Re-segmentation function (re-segmentation of RLC data PDUs)

[0106] - Reordering function (reordering RLC data PDUs)

[0107] - Duplicate detection function (duplicate detection)

[0108] - Error detection function (protocol error detection)

[0109] -RLC·SDU Discard Function (RLC·SDU Discard)

[0110] -RLC Reconstruction Function (RLC Reconstruction)

[0111] In the above description, the in-order delivery of NR RLC entities can mean the in-order delivery of RLC SDUs received from lower layers to higher layers. The in-order delivery of NR RLC entities can include the reassembly and delivery of RLC SDUs when several RLC SDUs belonging to an original RLCSDU are received after segmentation.

[0112] The in-order delivery of NR RLC entities may include: reordering received RLCPDUs based on the RLC sequence number (SN) or PDCP SN; recording lost RLC PDUs by reordering; reporting the status of lost RLC PDUs to the sending side; and requesting retransmission of lost RLC PDUs.

[0113] If a missing RLC SDU exists, the in-order delivery of NR RLC entities may include: delivering only the RLC SDUs preceding the missing RLCSDU to higher layers in order.

[0114] Despite the presence of lost RLC SDUs, if the specified timer has expired, the in-order delivery of NR RLC entities may include: delivering all RLC SDUs received before the timer started to the higher layer in order.

[0115] Despite the presence of lost RLC SDUs, the in-order delivery of NR RLC entities may include delivering all RLC SDUs received so far to higher layers in order, provided that the specified timer has expired.

[0116] The NR RLC entity can process RLC PDUs in the order they are received, regardless of the sequence number order, and transmit them to the NR PDCP entity.

[0117] Upon receiving a segment, the NR RLC entity can reconstruct a complete RLC PDU from the segment stored in the buffer or received later, and transmit it to the NR PDCP entity.

[0118] The NR RLC layer may not include splicing functionality; this functionality can be performed by the NR MAC layer or replaced by the multiplexed functionality of the NR MAC layer.

[0119] In the above description, out-of-order delivery of NR RLC entities can mean the function of directly transmitting RLC SDUs received from a lower layer to the next higher layer regardless of their order. If several RLC SDUs belonging to a single original RLCSDU are received after segmentation, out-of-order delivery of NR RLC entities can include the reassembly and delivery of RLC SDUs. Out-of-order delivery of NR RLC entities may include storing the RLC SN or PDCP SN of the received RLC PDUs and sorting them to record any lost RLC PDUs.

[0120] NR MAC 4-15 or 4-30 can be connected to several NR RLC entities configured in a UE, and the main functions of NR MAC 4-15 or 4-30 may include some of the following functions.

[0121] - Mapping function (mapping between logical channels and transport channels)

[0122] - Multiplexing and demultiplexing functions (MAC SDU multiplexing / demultiplexing)

[0123] - Scheduling information reporting function (Scheduling Information Report)

[0124] - HARQ functionality (error correction via HARQ)

[0125] - Priority processing function between logical channels (priority processing between logical channels of a UE)

[0126] - Priority processing function between UEs (priority processing is performed between UEs through dynamic scheduling)

[0127] -MBMS Service Identification Function (MBMS Service Identification)

[0128] -Transmission format selection function (Transmission format selection)

[0129] - Fill function (Fill)

[0130] NR PHY 4-20 or 4-25 can assemble OFDM symbols from higher-layer data through channel coding and modulation and transmit them through radio channels, or it can demodulate and channel decode OFDM symbols received through radio channels and forward the results to higher layers.

[0131] Figure 5 This is a block diagram illustrating the internal structure of a user equipment according to an embodiment of the present disclosure.

[0132] Referring to the accompanying drawings, the UE may include a radio frequency (RF) processor 5-10, a baseband processor 5-20, a storage device 5-30, and a controller 5-40. Furthermore, the controller 5-40 may include a multi-connection processor 5-42.

[0133] RF processor 5-10 performs functions such as signal band conversion and amplification, transmitting and receiving signals through a radio channel. Specifically, RF processor 5-10 performs up-conversion of the baseband signal provided by baseband processor 5-20 to an RF band signal and transmits it via an antenna, and performs down-conversion of the RF band signal received via the antenna back to a baseband signal. For example, RF processor 5-10 may include transmit filters, receive filters, amplifiers, mixers, oscillators, digital-to-analog converters (DACs), and analog-to-digital converters (ADCs). Although only one antenna is shown in the figures, the UE may be equipped with multiple antennas. Furthermore, RF processor 5-10 may include multiple RF chains. Additionally, RF processor 5-10 can perform beamforming. For beamforming, RF processor 5-10 can adjust the phase and amplitude of signals transmitted and received through multiple antennas or antenna elements. Furthermore, the RF processor can perform MIMO and can receive multiple layers during MIMO operation.

[0134] The baseband processor 5-20 performs the conversion between baseband signals and bitstreams according to the system's physical layer specifications. For example, during data transmission, the baseband processor 5-20 generates complex symbols by encoding and modulating the transmitted bitstream. Furthermore, during data reception, the baseband processor 5-20 recovers the received bitstream by demodulating and decoding the baseband signal provided from the RF processor 5-10. For example, in the case of data transmission using Orthogonal Frequency Division Multiplexing (OFDM), the baseband processor 5-20 generates complex symbols by encoding and modulating the transmitted bitstream, maps the complex symbols to subcarriers, and assembles OFDM symbols through inverse Fast Fourier Transform (IFFT) operations and cyclic prefix (CP) insertion. Furthermore, for data reception, the baseband processor 5-20 divides the baseband signal provided from the RF processor 5-10 into units of OFDM symbols, recovers the signals mapped to subcarriers through Fast Fourier Transform (FFT) operations, and reconstructs the received bitstream through demodulation and decoding.

[0135] As described above, the baseband processor 5-20 and the RF processor 5-10 transmit and receive signals. Therefore, the baseband processor 5-20 and the RF processor 5-10 can be referred to as transmitters, receivers, transceivers, or communication units. Furthermore, to support different radio access technologies, at least one of the baseband processor 5-20 and the RF processor 5-10 may include multiple communication modules. Additionally, to process signals in different frequency bands, at least one of the baseband processor 5-20 and the RF processor 5-10 may include different communication modules. For example, different radio access technologies may include wireless LAN (e.g., IEEE 802.11), cellular networks (e.g., LTE), etc. Furthermore, different frequency bands may include ultra-high frequency (SHF) bands (e.g., 2.0 NRHz, NRhz) and millimeter wave (mmWave) bands (e.g., 60 GHz).

[0136] Storage device 5-30 stores data such as basic programs, application programs, and configuration information for UE operation. Specifically, storage device 5-30 can store information about a second access node performing wireless communication using a second radio access technology. Furthermore, storage device 5-30 provides the stored data in response to requests from controller 5-40.

[0137] Controller 5-40 controls the overall operation of the UE. For example, controller 5-40 transmits and receives signals via baseband processor 5-20 and RF processor 5-10. Furthermore, controller 5-40 writes data to or reads data from storage device 5-40. For this purpose, controller 5-40 may include at least one processor. For example, controller 5-40 may include a communication processor (CP) for controlling communications and an application processor (AP) for controlling higher-level applications such as applications. Furthermore, according to various embodiments of this disclosure, controller 5-40 can control the operation of the UE or a corresponding entity.

[0138] Figure 6 This is a block diagram illustrating the configuration of a base station according to an embodiment of the present disclosure.

[0139] As shown in the figure, the base station may include an RF processor 6-10, a baseband processor 6-20, a backhaul communication unit 6-30, a storage device 6-40, and a controller 6-50. Furthermore, the controller 6-50 may include a multi-connection processor 6-52.

[0140] RF processor 6-10 performs functions for transmitting and receiving signals via a radio channel, such as signal band conversion and amplification. Specifically, RF processor 6-10 performs up-conversion of the baseband signal provided by baseband processor 6-20 to an RF band signal and transmits the converted signal via an antenna, and performs down-conversion of the RF band signal received via an antenna to a baseband signal. For example, RF processor 6-10 may include transmit filters, receive filters, amplifiers, mixers, oscillators, DACs, and ADCs. Although only one antenna is shown in the figures, the first access node may be equipped with multiple antennas. Furthermore, RF processor 6-10 may include multiple RF chains. Additionally, RF processor 6-10 can perform beamforming. For beamforming, RF processor 6-10 can adjust the phase and amplitude of signals transmitted and received through multiple antennas or antenna elements. The RF processor can perform downlink MIMO operation by transmitting one or more layers.

[0141] The baseband processor 6-20 performs the conversion between baseband signals and bitstreams according to the physical layer specifications of the first radio access technology. For example, for data transmission, the baseband processor 6-20 generates complex symbols by encoding and modulating the transmitted bitstream. Furthermore, for data reception, the baseband processor 6-20 recovers the received bitstream by demodulating and decoding the baseband signal provided from the RF processor 6-10. For example, in the case of using OFDM, for data transmission, the baseband processor 6-20 generates complex symbols by encoding and modulating the transmitted bitstream, maps the complex symbols to subcarriers, and assembles OFDM symbols through IFFT operations and CP insertion. Furthermore, for data reception, the baseband processor 6-20 divides the baseband signal provided from the RF processor 6-10 into units of OFDM symbols, recovers the signals mapped to subcarriers through FFT operations, and reconstructs the received bitstream through demodulation and decoding. As described above, the baseband processor 6-20 and the RF processor 6-10 transmit and receive signals. Therefore, the baseband processor 6-20 and the RF processor 6-10 can be referred to as a transmitter, receiver, transceiver, communication unit, or wireless communication unit.

[0142] The backhaul communication unit 6-30 provides an interface for communication with other nodes in the network. That is, the backhaul communication unit 6-30 converts the bit stream to be sent from the base station to another node (e.g., a secondary base station or the core network) into a physical signal, and converts the physical signal received from another node into a bit stream.

[0143] Storage device 6-40 stores data such as basic procedures, applications, and configuration information for base station operation. Specifically, storage device 6-40 can store information about bearers assigned to connected UEs and measurement results reported from connected UEs. Furthermore, storage device 6-40 can store information used as a criterion for determining whether to provide or suspend multi-connectivity to a UE. Additionally, storage device 6-40 provides the stored data in response to requests from controller 6-50.

[0144] Controller 6-50 controls the overall operation of the base station. For example, controller 6-50 transmits and receives signals via baseband processor 6-20 and RF processor 6-10 or via backhaul communication unit 6-30. Furthermore, controller 6-50 writes data to or reads data from storage device 6-40. For this purpose, controller 6-50 may include at least one processor. Moreover, according to various embodiments of this disclosure, controller 6-50 can control the operation of the base station or a corresponding entity.

[0145] In various embodiments of this disclosure, the base station may be a master node (MN) and may be referred to as a first base station. Alternatively, the base station may be a master node (SN) and may be referred to as a second base station. For example, controller 6-50 may be configured to: control transceivers (6-10, 6-20) to send a first message for conditional primary-secondary cell (PSCell) addition to a second base station managing at least one cell, the first message including measurements of the at least one cell by the UE; control transceivers (6-10, 6-20) to receive a second message from the second base station in response to the first message, the second message including at least one of frequency information and cell identifier of a candidate target PSCell selected from the at least one cell and configuration information of the candidate target PSCell; determine execution conditions for conditional PSCell addition associated with the candidate target PSCell based on at least one of the frequency information and cell identifier; and control transceivers (6-10, 6-20) to send a third message to the UE, the third message including configuration information of the candidate target PSCell, information indicating the execution conditions, and a conditional PSCell identifier. As another example, controller 6-50 can be configured to: control transceivers (6-10, 6-20) to receive from a first base station a first message for adding a conditional primary / secondary cell (PSCell), the first message including measurements by the UE of at least one cell managed by a second base station; and control transceivers (6-10, 6-20) to send a second message to the first base station in response to the first message, the second message including at least one of frequency information and cell identifier of the candidate target PSCell selected from at least one cell, and configuration information of the candidate target PSCell. Here, at least one of the frequency information and cell identifier can be used to determine the execution conditions for adding the conditional PSCell associated with the candidate target PSCell, and a third message can be sent from the first base station to the UE, the third message including the configuration information of the candidate target PSCell, information indicating the execution conditions, and the conditional PSCell identifier.

[0146] Dual connectivity mentioned in various embodiments of this disclosure may include both LTE-NR Dual Connectivity (ENDC) with the core network being Evolved Packet Core (EPC) and Multi-RAT Dual Connectivity (MRDC) with the core network being 5GC, and includes network and UE operation based on RAT according to MN and SN.

[0147] Figure 7 This is a diagram depicting the process of adding a conditional primary and secondary cell (PSCell) initiated by the master node (MN) according to an embodiment of the present disclosure.

[0148] Figure 7This is a flowchart illustrating the process of MN adding configuration conditions (CPA) to the UE PSCell and the UE performing the CPA.

[0149] The terminal can be in a connected state with the MN. The UE can receive measurement configuration information of the frequency associated with the SN from the MN.

[0150] In step S700, for the frequency associated with the SN according to the measurement configuration information, the UE can perform measurements on the cells camped on the corresponding frequency, and send a measurement report of the corresponding measurement results to the MN according to the preset measurement report conditions (1). Here, the frequency associated with the SN may mean the frequency where the cell managed by the SN is located.

[0151] After receiving measurement information from the UE for the cell on the frequency managed by the SN, in step S705, the MN can determine the CPA configuration based on the data transmission and measurement information required by the UE as determined by the MN. Furthermore, after determining the CPA configuration, the MN can determine the target SN (2). Here, there can be multiple target SNs.

[0152] After determining the target SN, in steps S710 and S715, MN may send an SgNBAdditionRequest (interchangeable with SNAdditionRequest) message (3-1, 3-2) to the determined SN, which includes at least one of the following information.

[0153] -CPA Instructions

[0154] -CG-ConfigInfo

[0155] CPA indication can be information indicating that CPA should be performed after a specific time when the SN receives the message; CPA is an SCG setting for a specific US. CG-ConfigInfo can include configuration information expected by the MN for the SCG settings. For example, it can include the frequency band of cell operation managed by the target SN and the result values ​​of measurements taken by the UE for cells camped in said frequency band. The measurement result values ​​can include at least one of the frequency of the Absolute Radio Channel Number (ARFCN) associated with the Physical Cell Identifier (PCI) of the measured cell, the cell measurement value, and / or the result value of a beam measurement.

[0156] Upon receiving this message, in steps S720 and S725, the target SN can know that it is a conditional PSCell addition (CPA) based on the CPA indication. Alternatively, the target SN can know that it is not an immediate PSCell addition. Furthermore, the SN can determine candidate target PSCells based on measurements given by the MN for each cell and / or each beam (4-1, 4-2).

[0157] In steps S730 and S735, the target SN may allocate resources for the UE to the target PSCell and send the SCG configuration information to be applied by the UE back to the MN. The SN may include at least one of the following information (5-1, 5-2) in the response message (SgNBAdditionRequestAck message, which is interchangeable with SNAdditionRequestAck).

[0158] -CPA Instructions

[0159] - Configuration information of candidate target PSCell

[0160] -Information about the frequency of operations on candidate target PSCells

[0161] The CPA indication can specify that the information received by the MN is SCG configuration information for CPA. The MN can generate a CPA configuration for the candidate target cell included in the SgNBAdditionRequestACK message containing the CPA indication and send it to the UE. The target SN can include the configuration information of the candidate target PSCell determined by the target SN in an RRC inter-node message called CG-Config and deliver it to the MN. Furthermore, information regarding the frequency on which the candidate target PSCell operates can be an ARFCN value. When the target SN sends the above information, the configuration information and frequency information of each candidate target PSCell can be delivered by being associated separately.

[0162] When the SgNBAdditionRequestACK message is received, in step S740, for each candidate target PSCell included in the SgNBAdditionRequestACK message, MN can generate (or determine) the execution conditions of CPA based on the measurement object having a corresponding frequency as an ssbFrequency or CSI-RS frequency value (6).

[0163] The execution conditions for CPA can be configured using a Synchronization Signal Block (SSB) or Channel State Information Reference Signal (CSI-RS), and can be generated based on Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), or Received Signal Strength Indicator (RSSI). Specifically, as with event A4, the event can be considered satisfied when the cell strength of the candidate target PSCell is greater than or equal to a specific threshold. For example, when event A4 is set as the execution condition for CPA, if the measured values ​​(e.g., RSRP, RSRQ, RSSI) of the signal transmitted through the candidate target PSCell (e.g., SSB or CSI-RS) are greater than or equal to a specific threshold, the UE can determine that the execution conditions for CPA are satisfied. When the UE is configured with E-UTRAN New Radio Dual Connectivity (ENDC), if the cell strength of the NR RAT PSCell is greater than or equal to a specific threshold, as with event B1, the UE can consider the corresponding event satisfied. For example, when setting event B1 as the execution condition for CPA, if the measured value (e.g., RSRP, RSRQ, RSSI) of the signal (e.g., SSB or CSI-RS) transmitted by the candidate target PSCell operating on the NR RAT is greater than or equal to a certain threshold, the UE can determine that the execution condition for CPA is met.

[0164] In an embodiment, the MN can use a measurement ID, formed by a combination of a measurement object corresponding to the frequency value of a candidate target PSCell received from the SN and a reportConfiguration created for CPA, as one of the CPA execution conditions for the candidate target PSCell. Multiple measurement IDs can be used as CPA conditions for a candidate target PSCell; when multiple measurement IDs become CPA conditions, if all measurement IDs are satisfied simultaneously, the CPA conditions for a candidate target PSCell can be considered satisfied. Alternatively, when multiple measurement IDs become CPA conditions, if measurements corresponding to a subset of the multiple measurement IDs are satisfied, the CPA conditions for a candidate target PSCell can be considered satisfied.

[0165] In another embodiment, the SN may include at least one of the following information (5-1, 5-2) in the SgNBAdditionRequestAck message.

[0166] -CPA Instructions

[0167] - Configuration information of candidate target PSCell

[0168] -Information about the frequency of operations on candidate target PSCells

[0169] - Threshold information on cell strength to be considered in the conditions for candidate target PSCells (here, the quantity of the threshold to be used for it can be additionally indicated via the SgNBAdditionRequest message previously received from the MN (e.g., RSRP, RSSQ, RSSI)).

[0170] In this scenario, the three pieces of information above can be used in the operations described in the MN. Furthermore, when the MN receives the threshold information and generates CPA execution conditions for each candidate target PSCell, it can use the threshold information of the cell strength to be considered in the conditions of the candidate target PSCell to ultimately determine the CPA conditions by comparing the threshold considered by the MN for events based on A4 or B1 with the threshold received from the SN. As an example, when the MN receives the above information via the SgNBAdditionRequestACK message, the MN can compare the threshold considered by the MN with the threshold received from the SN to select the larger value, and as a result, use it as the threshold for event A4 or B1 for use in the CPA execution conditions. In this case, the MN may need to send the quantity information to be used for event A4 or B1 to the SN in advance via the SgNBAdditionRequest message, i.e., which value among RSRP, RSRQ, and RSSI to use. Based on these values, the SN can deliver its required threshold back to the MN according to the given quantity information.

[0171] In another embodiment, the SN may include at least one of the following information (5-1, 5-2) in the SgNBAdditionRequestAck message.

[0172] -CPA Instructions

[0173] - Configuration information of candidate target PSCell

[0174] - Information about the frequency at which the candidate target PSCell operates and / or the cell identifier of the candidate target PSCell (e.g., interchangeable with PCI).

[0175] - Threshold information on cell strength to be considered in the conditions for candidate target PSCells

[0176] - In addition to the threshold, offset information to be applied to the corresponding frequency, and / or per-cell offset information (when delivering the threshold information, the amount for which the threshold will be used (e.g., RSRP, RSSQ, RSSI) can be additionally indicated via the SgNBAdditionRequest message previously received from the MN).

[0177] The aforementioned information can be sent to the MN in an associated form for a single candidate target PSCell {configuration information, frequency / PCI information, threshold, and offset information}, and information for multiple candidate target PSCells can be delivered to the MN. Furthermore, this information can be included in specific fields of the X2 / Xn message, or in a separate RRC container field or a traditional CG-Config field.

[0178] In this case, the four pieces of information above can be used in the operations of the MN described above. Furthermore, when the MN receives the threshold information and generates CPA execution conditions for each candidate target PSCell, it can use the threshold information of the cell strength to be considered in the conditions of the candidate target PSCell to ultimately determine the CPA conditions by comparing the threshold considered by the MN for events based on A4 or B1 with the threshold received from the SN. As an example, when the MN receives the above information via the SgNBAdditionRequestACK message, the MN can compare the threshold considered by the MN with the threshold received from the SN to select the larger value, and as a result, it can be used as the threshold to be used in the CPA execution conditions for events A4 or B1. In this case, the MN may need to send the quantity information to be used for events A4 or B1 to the SN in advance via the SgNBAdditionRequest message, i.e., which value among RSRP, RSRQ, and RSSI to use. Based on these values, the SN can deliver the threshold it needs back to the MN according to the given quantity information. Furthermore, when generating conditions based on event A4 or B1, the offset values ​​for each frequency and cell can be used as the corresponding threshold values ​​to be added to the candidate target PSCell for each frequency and cell. For example, the measured cell strength can be compared with the value given by (threshold + per-frequency offset + per-cell offset).

[0179] Upon receiving the above information, in step S745, the MN can send a message (e.g., RRC reconfiguration) including the CPA execution conditions and configuration information for each candidate target PSCell using the given information. For example, for each candidate target PSCell, the configuration ID, CPA execution conditions, and configuration information to be used in the corresponding PSCell (RRCReconfiguration information) can be sent to the UE in an associated form. The configuration ID can be an integer value determined by the MN to indicate the configuration information and conditions for a specific candidate target PSCell. At this time, the MN can send the above information (7) by creating a list in the RRCReconfiguration message.

[0180] In another embodiment, if the MN receives the cell identifier of a candidate target PSCell in step S735, then in step S745, the MN can send a message (e.g., RRC reconfiguration) using given information. For each candidate target PSCell, the message includes the CPA execution conditions of the candidate target PSCell, the configuration information of the candidate target PSCell, and the cell identifier of the candidate target PSCell. For example, for each candidate target PSCell, the MN can send the configuration ID, CPA execution conditions, configuration information to be used in the corresponding PSCell (RRCReconfiguration information generated by the SN), and the cell identifier of the candidate target PSCell to the UE in an associated form. Furthermore, the configuration ID can be an integer value determined by the MN to indicate the configuration information and conditions of a specific candidate target PSCell. In this case, the MN can send the above information (7) by creating a list in the RRCReconfiguration message.

[0181] Upon receiving the above message, in step S750, the UE may perform a measurement (8) for condition evaluation corresponding to the measurement ID indicating each CPA execution condition.

[0182] In another embodiment, if the MN additionally receives the cell identifier of the candidate target PSCell in step S735, then in step S750, when the UE that received the above message performs a measurement for condition evaluation corresponding to the measurement ID indicating each CPA execution condition, it may perform the condition evaluation (8) on the cell residing on the frequency of the measurement object corresponding to the measurement ID and identified by the cell identifier.

[0183] In step S755, the UE may send a response message (9) to the MN indicating that it has received (7) the message (MNRRCReconfiguration). For example, it may send an RRC reconfiguration complete message.

[0184] In step S760, if the CPA execution conditions of a specific candidate target PSCell are met at a specific time, the UE can apply the configuration information (10) of the corresponding PSCell. This configuration information can be configuration information used for SCG settings or SCG additions.

[0185] After applying the configuration information, in step S765, the UE can notify the MN to perform CPA by using a message such as the MNRRCReconfigurationComplete message or the ULInformationTransfer message. Here, in order to indicate the target PSCell for performing CPA via this message, the UE can send a message that includes the configuration ID (config ID) corresponding to the target PSCell among the configuration IDs included in the MNRRCReconfiguration message. In addition, in order for the MN to deliver the SN RRC reconfiguration complete message to the SN of the target PSCell managing CPA, the SNRRC reconfiguration complete message can be sent by being included in the MN RRCReconfigurationComplete message or the ULInformationTransfer message (11). In this case, the SN RRC reconfiguration complete message can be sent as an eight-bit string value.

[0186] When the MN receives the MN RRCReconfigurationComplete, the MN can identify the target SN based on the configuration ID associated with the target PSCell included in it. Thus, when the SNRRCReconfigurationComplete message received in (11) is delivered to the target SN via the Xn message, the target SN can know that the UE performed SCG (PSCell) addition. Figure 7 In this context, assume the target SN is SN 1, but the target SN can be another SN (e.g., Figure 7 (SN 2 in the text).

[0187] In step S770, in order to notify the target SN of the UE's CPA and include the SNRRCReconfigurationComplete message, the MN can use the SgNBRRCReconfigurationComplete message, which is an Xn / X2 message (12-1). For example, the SgNBRRCReconfigurationComplete message including the SN RRCReconfigurationComplete message can be sent to the target SN.

[0188] In step S775, MN may request an SN other than the target SN. Figure 7The SN2 in the M-NG-RAN node can release the resources of the cells to which resources for CPA have been allocated. For this purpose, an Xn / X2 message (e.g., referred to as a CPA release message, but not limited thereto) can be sent. This message may include the M-NG-RAN node UE XnAP ID information. The SN that has received this message can cancel or release all cells selected as CPA candidate PSCells for the corresponding UE and the resources allocated to those cells. In another embodiment, the corresponding message may include information about the cells whose resources will be released. In another embodiment, the MN can only deliver the (12-2) message to the SN2 if the UE has successfully performed CPA. For this purpose, before sending the (12-2) message, the UE may perform random access (13) in step S780; if random access is successful, the target SN (i.e., Figure 7 SN1 in the MN can recognize a successful CPA and deliver a message indicating the success of the CPA to the MN. Upon receiving this message, the MN can send CPA resource release request messages to those SNs that manage the remaining CPA candidate targets PSCell.

[0189] According to the embodiment, when SN sends an SNAddRequestACK message to MN, the TX_nDC_{overall} timer can only be started if there is no CPA indication.

[0190] Figure 8 This is a flowchart illustrating the operations performed by the MN when the SN does not send an additional threshold for CPA condition information to the MN, according to an embodiment of this disclosure.

[0191] Figure 8 The detailed process of the MN sending CPA configuration information to the UE is illustrated. According to an embodiment, Figure 8 This illustrates the case where SN does not send additional thresholds for CPA condition information to MN.

[0192] In step S800, MN can receive the SNAddRequestACK message.

[0193] In one embodiment, the SNAddRequestACK message may include at least one of the following: CPA indication, configuration information of the candidate target PSCell, and frequency information of the candidate target PSCell.

[0194] In step S805, the MN can determine the CPA execution condition for each received candidate target PSCell. Here, for a measurement object (measObject), a measurement object corresponding to the frequency on which the candidate target PSCell resides can be selected, and a threshold determined by the MN for event A4 or B1 can be used in the reportConfig. For example, the measurement object configuration information (measObject) may include frequency information of the candidate target PSCell operating on it, and the measurement result report configuration information (reportConfig) may include event A4 or B1 and the threshold information determined by the MN. One or more measurement IDs created from a pair of measObjects and reportConfigs can constitute a CPA execution condition. For example, one or more measurement IDs are associated with measObjects and reportConfigs respectively, and the UE can identify the CPA execution condition by the measObject and reportConfig associated with each measurement ID.

[0195] In step S810, MN can assign a configuration ID to the candidate target PSCell.

[0196] Here, MN can associate the candidate target PSCell configuration information and CPA execution condition information with the configuration ID.

[0197] In step S815, the MN may send an MN RRCReconfiguration message to the UE, which includes at least one of the following: the configuration ID of the candidate target PSCell received from all target SNs, the candidate target PSCell configuration information, or the CPA execution condition information.

[0198] Figure 9 This is a flowchart illustrating the operations performed by the MN when the SN sends an additional threshold for CPA condition information to the MN according to an embodiment of the present disclosure.

[0199] Figure 9 The detailed process of the MN sending CPA configuration information to the UE is illustrated. According to an embodiment, Figure 8 This illustrates the case where SN sends additional thresholds for CPA condition information to MN.

[0200] In step S900, MN can receive the SNAddRequestACK message.

[0201] In one embodiment, the SNAddRequestACK message may include at least one of a CPA indication, configuration information of the candidate target PSCell, and frequency information of the candidate target PSCell. Additionally, it may include threshold information for event A4 or B1 to be used for CPA execution conditions. In another embodiment, the SNAddRequestACK message may include at least one of a CPA indication, configuration information of the candidate target PSCell, and frequency information of the candidate target PSCell. Additionally, it may include threshold information for event A4 or B1 to be used for CPA execution conditions and offset information for each cell / frequency.

[0202] In step S905 or S910, MN can determine the CPA execution condition for each received candidate target PSCell. Here, if the threshold received from SN is greater than or equal to the threshold determined by MN, then in step S905, as the CPA execution condition for the corresponding candidate target PSCell, MN can select one corresponding to the frequency of the candidate target PSCell's residence for the measurement object, and can use the threshold determined by SN for the event corresponding to event A4 or B1 in reportConfig. A measurement ID created by a pair of measObjects and reportConfig, and / or multiple measurement IDs created by the association between a measObject and different reportConfigs, can constitute a CPA execution condition. If the threshold received from SN is less than the threshold determined by MN, then in step S910, MN can utilize the threshold determined by MN in reportConfig.

[0203] In step S915, MN can assign a configuration ID to the candidate target PSCell.

[0204] MN can associate candidate target PSCell configuration information and CPA execution condition information with configuration ID.

[0205] In step S920, the MN may send an MN RRCReconfiguration message to the UE, which includes at least one of the following: the configuration ID of the candidate target PSCell received from all target SNs, the configuration information of the candidate target PSCell, and the CPA execution condition information.

[0206] As another embodiment of this disclosure, for Figure 7 The SNAddRequest and SNAddRequestACK messages can exchange other information. The following methods are possible. Some or a combination of them can also be used.

[0207] Method 1) If the PSCell frequency information determined by the SN is not present in the SNAddRequestACK message, the MN can decode the CG-Config information, an octet included in the SNAddRequestACK message, to directly extract the frequency of the target PSCell. The MN can use the decoded information to find the measurement object to be sent to the UE for the CPA execution conditions.

[0208] Method 2) When the MN sends information about the frequency managed by the SN and cell strength information measured by the UE on a cell camped on that frequency to the SN via an SNAddRequest message, the MN can assign a specific ID to each cell, associate the ID with the cell in the cell strength information, and send an SNAddRequest message including the association to the SN. Upon receiving the SNAddRequest message, the SN can associate the ID of the candidate target PSCell selected by the SN with the configuration information of the candidate target PSCell, and send an SNAddRequestACK message including the association back to the MN. Based on the included ID, the MN can identify the frequency information of the corresponding cell and create the CPA conditions for the corresponding PSCell.

[0209] Method 3) When the MN sends information about the frequency managed by the SN and cell strength information measured by the UE on the cell camped on that frequency to the SN via an SNAddRequest message, the MN can send an SNAddRequest message containing information about only one cell. The SN can determine whether to accept the cell as a candidate target PSCell and send an ACK or NACK message to the MN. When delivering the ACK message to the MN, since the MN already knows the information about the corresponding single cell, the MN can use the measurement object including the frequency of the corresponding cell as part of the CPA execution condition information based on this information.

[0210] Furthermore, according to another embodiment of this disclosure, when CPA is configured in the UE and other operations (e.g., CHO) are additionally configured in the UE, a method of operating the UE is presented.

[0211] According to embodiments of this disclosure, it can be assumed that both Conditional Handover (CHO) and Conditional Approval (CPA) are configured in the UE. In this case, the UE can determine (or evaluate) whether the execution conditions of both CHO and CPA are met simultaneously, and can prioritize CHO over CPA during operation execution according to specified rules. The following methods can be used to prioritize CHO during execution. However, it is not limited to these methods.

[0212] Method 1) The evaluation of CHO execution conditions continues even while CPA is in progress, and both the CHO configuration and CPA configuration are removed when the CHO is completed.

[0213] Method 2) Remove the CPA configuration instead of the CHO configuration when the CPA is completed.

[0214] Method 3) Perform evaluation / execution / release differently depending on the type of condition reconfiguration.

[0215] According to embodiments of this disclosure, if at least one condition for CHO execution is met while performing CPA, the UE can suspend the ongoing CPA and execute the CHO. Here, the UE can reapply (rollback) the RRC configuration values ​​prior to receiving the RRC message (e.g., an RRCReconfiguration message) applied to the CPA execution. For example, SCG may not yet be set. In this state, the target PCell configuration determined to be the CHO to be executed due to the fulfillment of the CHO execution conditions can be applied.

[0216] Furthermore, according to embodiments of this disclosure, an ongoing CPA can be completed, and then a CHO configuration can be applied.

[0217] Figure 10 This is a diagram illustrating a scheme in which the UE stores information related to CHO and CPA when both CHO and CPA are configured in the UE according to an embodiment of the present disclosure.

[0218] The UE can store information for Conditional Handover (CHO) and information for Conditional PSCell Addition (CPA) together in a variable used to maintain CHO operation (e.g., VarConditionalReconfig). In this case, an indicator can be included to distinguish between the information for CHO and the information for CPA.

[0219] refer to Figure 10The configuration IDs for CHO (e.g., condReconfig ID) and CPA (e.g., condReconfig ID) can be set in association with indicators that distinguish whether they are for CHO or CPA (e.g., CHO indicator and CPA indicator, respectively). Furthermore, each configuration ID (e.g., condReconfig ID) can be set in association with conditional information (e.g., condExecutionCond) and target cell configuration information (e.g., condRRCReconfig) suitable for each situation. When receiving an RRC message (e.g., RRCReconfiguration message) from the network, the UE can use the indicator set in association with the configuration ID (e.g., condReconfigID) included in the configuration information (e.g., conditionalReconfiguration IE) to distinguish whether the configuration is for CHO or CPA.

[0220] Figure 11 This is a sequence diagram illustrating a method for performing a CPA operation upon successful execution of a CHO, according to an embodiment of the present disclosure.

[0221] In step S1105, UE 1110 can receive CPA configuration information from source master node (S-MN) 1120 based on the secondary node (SN) 1140 where the candidate target PSCell is stationed.

[0222] In step S1110, UE 1110 can start from the time point when CPA is configured to evaluate whether the CPA execution conditions are met.

[0223] In step S1115, UE 1110 can be configured with CHO by S-MN 1120 based on the target master node (T-MN) 1140 where the candidate target PCell is located.

[0224] In step S1120, UE 1110 can start from the time point when CHO is configured to evaluate whether the CHO execution conditions are met.

[0225] Alternatively, according to embodiments of this disclosure, UE 1110 may first be configured with CHO, and then configured with CPA based on the SN where the candidate target PSCell resides. For example, in step S1125, UE 1110 may be configured with CPA by S-MN 1120 based on SN 1140 where the candidate target PSCell resides, and in step S1130, the evaluation of whether the CPA execution conditions are met can begin from the time point of CPA configuration.

[0226] If the CHO execution conditions are met, then in step S1135, UE 1110 can execute the CHO for the target PCell and stop evaluating the CPA execution conditions. The target PCell can be a PCell served by T-MN 1130.

[0227] In step S1140, UE 1110 and T-MN 1130 may execute a CHO to the target PCell (or, may execute a random access procedure to the target PCell).

[0228] Upon successful execution of a CHO to the target PCell (or upon successful execution of random access to the target PCell), in step S1145, UE 1110 may remove (release) all configurations classified as CHO and CPA that exist as entries in variables (e.g., VarCondReconfig). Here, a variable may mean the UE's internal storage device, which stores information about specific configuration parameters received from the network. The configuration information for CPA and CHO may be stored separately in a single variable named VarCondReconfig. Furthermore, UE 1110 may remove (release) information associated with the execution conditions (e.g., reportConfig, measurement object, measId) from the variables in the configurations classified as CHO and CPA.

[0229] Figure 12 This is a sequence diagram illustrating a method for performing CPA operations during a successful normal handover according to an embodiment of the present disclosure.

[0230] In step S1205, the source master node (S-MN) 1220 and the slave node (SN) 1240 can perform the SN addition preparation process for CPA.

[0231] In step S1210, UE 1210 can receive CPA configuration information from S-MN 1220 based on SN 1240 where the candidate target PSCell is camped.

[0232] In step S1215, UE 1210 can evaluate whether the CPA execution conditions are met starting from the time point when CPA is configured.

[0233] In step S1220, UE 1210 can receive a message from S-MN 1220 indicating a command switch (HO) to at least one of the candidate PCells of the target master node (T-MN).

[0234] If UE 1210 receives a handover command message from S-MN 1220 during the evaluation process, then in step S1225, UE 1210 can perform a handover to PCell of T-MN 1230 and stop evaluating the CPA execution conditions.

[0235] In step S1230, UE 1210 and T-MN 1230 may perform a handover procedure to the target PCell (or, may perform a random access procedure to the target PCell).

[0236] Upon successful handover to the target PCell (or upon successful random access to the target PCell), in step S1235, UE 1210 may remove all settings classified as CHO and CPA as entries in variables (e.g., VarCondReconfig). Here, a variable may refer to the UE's internal storage, which stores information about specific configuration parameters received from the network. The configuration information for CPA and CHO may be stored separately in a single variable named VarCondReconfig. Furthermore, UE 1210 may remove information set in the settings classified as CHO and CPA that is associated with the execution conditions (e.g., reportConfig, measurement object, measId) from the variables.

[0237] Figure 13 This is a sequence diagram illustrating a method for performing a CPA operation according to an embodiment of the present disclosure.

[0238] In step S1305, the primary node (MN) 1320 and the secondary node (SN) 1330 can perform the SN addition preparation process for CPA. In step S1310, the UE 1310 can receive CPA configuration information from the MN 1320 based on the SN 1330 where the candidate target PSCell is camped.

[0239] In step S1315, UE 1310 can evaluate whether the CPA execution conditions are met starting from the time point when CPA is configured.

[0240] If at least one CPA execution condition is met when UE 1310 performs the evaluation, then in step S1320, UE 1310 may perform CPA on the candidate target PSCell configured in association with the corresponding condition. Alternatively, the evaluation of the CPA execution condition may be stopped.

[0241] In the case of performing CPA, in step S1325, UE 1310 can perform an operation for adding a target PSCell. The target PSCell addition operation may include a random access procedure. When performing the target PSCell addition operation, UE 1310 may send an RRC message for MN 1320 (e.g., an MN RRCReconfigurationComplete message or a ULInformationTransferMRDC message) to MN 1320. The RRC message for MN 1320 may include an RRC message for SN 1330 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message). Furthermore, when performing CPA, a CPA configuration ID (e.g., a CPAconfig ID) set in association with the configuration information of the target PSCell being performed may be included. However, the RRC message does not necessarily include all of the above information or messages; some may be omitted, and other information or messages may be added.

[0242] When an RRC message for MN 1320 is received, in step S1330, MN 1320 may send an Xn message (e.g., an SgNB reconfiguration complete message or an SNReconfigurationComplete message) to SN 1330, which includes the target PSCell. The Xn message may include the RRC message for SN 1330 received from UE 1310 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message).

[0243] In step S1335, UE 1310 and SN 1330 may perform a CPA procedure (or a random access procedure to the target PSCell).

[0244] Upon successful execution of CPA (or upon successful random access to the target PSCell), in step S1340, UE 1310 may remove all settings classified as CPA that exist as entries in variables (e.g., VarCondReconfig). Here, a variable may refer to the UE's internal storage, which stores information about specific configuration parameters received from the network. The configuration information for CPA and CHO may be stored separately in a single variable named VarCondReconfig. Furthermore, UE 1310 may remove information from the variables that is classified as CPA and is only associated with the CPA execution conditions (e.g., reportConfig, measurement object, measId).

[0245] Figure 14 This is a sequence diagram illustrating a method for performing a CPA operation during normal PSCell addition or SCG addition according to an embodiment of the present disclosure.

[0246] In step S1405, the master node (MN) 1420 and the slave node (SN) 1430 can perform the SN addition preparation process for CPA.

[0247] In step S1410, UE 1410 can receive CPA configuration information from MN 1420 based on SN 1430 where the candidate target PSCell is camped.

[0248] In step S1415, UE 1410 can evaluate whether the CPA execution conditions are met starting from the time point when CPA is configured.

[0249] In step S1420, MN 1420 can determine to perform secondary cell group (SCG) addition (or PSCell addition).

[0250] In step S1425, MN 1420 and SN 1430 can perform the SN addition preparation process.

[0251] In step S1430, UE 1410 can receive configuration information for SCG addition (or PSCell addition) from MN 1420. The configuration information for SCG addition (or PSCell addition) can be the SCG configuration including the reconfigurationWithSync IE in the RRCReconfiguration message.

[0252] When UE 1410 receives configuration information for SCG addition from MN 1420 (or, SCG configuration including `reconfigurationWithSync IE` in the `RRCReconfiguration` message) while performing the evaluation, in step S1435, UE 1410 can perform the SCG addition process based on the configuration information for SCG addition. Furthermore, at this time, the evaluation of CPA execution conditions can be stopped. According to the embodiment, SCG addition can also be referred to as PSCell addition. Therefore, upon receiving configuration information for SCG addition or configuration information for PSCell addition, UE 1410 can perform the SCG addition process or PSCell addition process based on the corresponding configuration information. Similarly, at this time, the evaluation of CPA execution conditions can be stopped.

[0253] During the SCG addition procedure, in step S1440, UE 1410 may perform an operation for adding a target PSCell. The target PSCell addition operation may include a random access procedure. When performing the target PSCell addition operation, UE 1410 may send an RRC message for MN 1420 (e.g., an MN RRCReconfigurationComplete message). The RRC message for MN 1420 may include an RRC message for SN 1430 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message).

[0254] Upon receiving an RRC message for MN 1420, in step S1445, MN 1420 may send an Xn message (e.g., an SgNB reconfiguration complete message or an SNReconfigurationComplete message) to SN 1430, which includes the target PSCell. The Xn message may include the RRC message for SN 1430 received from UE 1410 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message).

[0255] In step S1450, UE 1410 and SN 1430 may perform an SCG addition procedure or a PSCell addition procedure (or, may perform a random access procedure to the target PSCell).

[0256] Upon successful execution of the SCG add or PSCell add procedure (or, upon successful random access to the target PSCell), in step S1455, UE 1410 may remove all settings classified as CPA that exist as entries in variables (e.g., VarCondReconfig). Here, a variable may refer to the UE's internal storage, which stores information about specific configuration parameters received from the network. The configuration information for CPA and CHO may be stored separately in a single variable named VarCondReconfig. Furthermore, UE 1410 may remove information from the variables that is classified as CPA and is only set in relation to the CPA execution conditions (e.g., reportConfig, measurement object, measId).

[0257] Figure 15 This is a sequence diagram illustrating a method for performing a CPA operation when the process of adding an SCG (or adding a PSCell) or changing a PSCell fails midway, according to an embodiment of the present disclosure.

[0258] In step S1505, the master node (MN) 1520 and the slave node (SN) 1530 can perform the SN addition preparation process for CPA.

[0259] In step S1510, UE 1510 can receive CPA configuration information from MN 1520 based on SN 1530 where the candidate target PSCell is camped.

[0260] In step S1515, UE 1510 can evaluate whether the CPA execution conditions are met starting from the time point when CPA is configured.

[0261] In step S1520, MN 1520 can determine whether to perform a secondary cell group (SCG) addition (or PSCell addition) or PSCell change.

[0262] In step S1525, MN 1520 and SN 1530 can perform the SN addition preparation process.

[0263] In step S1530, UE 1510 can receive configuration information from MN 1520 for adding an SCG (or adding a PSCell) or changing a PSCell. The configuration information for adding an SCG (or adding a PSCell) or changing a PSCell can be the SCG configuration including the reconfigurationWithSync IE in the RRCReconfiguration message.

[0264] When UE 1510 receives configuration information for SCG addition or PSCell change (or, SCG configuration including `reconfigurationWithSync IE` in the `RRCReconfiguration` message) from MN 1520 while performing the evaluation, in step S1535, UE 1510 can perform SCG addition or PSCell change based on the configuration information for SCG addition or PSCell change. Furthermore, at this time, the evaluation of CPA execution conditions can be stopped. According to the embodiment, SCG addition can also be referred to as PSCell addition. Therefore, upon receiving configuration information for SCG addition (or, configuration information for PSCell addition) or configuration information for PSCell change, UE 1510 can perform the SCG addition (or PSCell addition) process or the PSCell change process based on the corresponding configuration information. Similarly, at this time, the evaluation of CPA execution conditions can be stopped.

[0265] In step S1540, UE 1510 may perform an SCG addition (or PSCell addition) procedure or a PSCell change procedure. The SCG addition (or PSCell addition) procedure or the PSCell change procedure may include a random access procedure. During the execution of the SCG addition (or PSCell addition) procedure or the PSCell change procedure, UE 1510 may send an RRC message (e.g., an MN RRCReconfigurationComplete message) to MN 1520. The RRC message to MN 1520 may include an RRC message to SN 1530 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message).

[0266] Upon receiving an RRC message for MN 1520, in step S1545, MN 1520 may send an Xn message (e.g., an SgNB reconfiguration complete message or an SNReconfigurationComplete message) to SN 1530, which includes the target PSCell. The Xn message may include the RRC message for SN 1530 received from UE 1510 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message).

[0267] In step S1550, UE 1510 and SN 1530 may perform an SCG addition (or PSCell addition) procedure or a PSCell change procedure (or, may perform a random access procedure to the target PSCell).

[0268] In step S1555, UE 1510 may determine that the process for adding an SCG (or adding a PSCell) or changing a PSCell has failed midway based on preset criteria. In this case, the UE may maintain the cessation of the CPA condition assessment while performing the SCG Failure Information procedure. The criteria (or reasons for failure) used to determine the process for adding an SCG (or adding a PSCell) or changing a PSCell may be as follows. However, these are merely illustrative and not limited thereto.

[0269] - While a process for adding an SCG (or adding a PSCell) or changing a PSCell is in progress, a timer (e.g., T304) for the SCG expires.

[0270] - Alternatively, the content of the received RRC message for MN 1520 (e.g., the MN RRCReconfiguration message) is incorrect.

[0271] - Alternatively, a `reconfigurationWithSync` failure may occur during a PSCell change.

[0272] In step S1560, UE 1510 may send an RRC message (e.g., SCGFailureInformation message) including the cause of failure to MN 1520. Here, the cause of failure may be included as a cause value.

[0273] Figure 16 This is a sequence diagram illustrating a method for performing a CPA operation when the CPA process fails midway, according to an embodiment of the present disclosure.

[0274] In step S1605, the master node (MN) 1620 and the slave node (SN) 1630 can perform the SN addition preparation process for CPA.

[0275] In step S1610, UE 1610 can receive CPA configuration information from MN 1620 based on SN 1630 where the candidate target PSCell is camped.

[0276] In step S1615, UE 1610 can evaluate whether the CPA execution conditions are met starting from the time point when CPA is configured.

[0277] If a specific CPA execution condition is met while UE 1610 is performing an evaluation, UE 1610 can perform CPA in step S1620. For example, a process for adding an SCG (or adding a PSCell) to a candidate target PSCell associated with the corresponding condition can be performed. Furthermore, the evaluation of the CPA execution condition can be stopped at this time.

[0278] During CPA execution, in step S1625, UE 1610 may execute an SCG addition (or PSCell addition) procedure for the candidate target PSCell associated with the corresponding condition. The CPA operation may include a random access procedure. During CPA execution, UE 1610 may send an RRC message for MN 1620 (e.g., an MN RRCReconfigurationComplete message or a ULInformationTransferMRDC message). The RRC message for MN 1620 may include an RRC message for SN 1630 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message). Furthermore, it may include a CPA configuration ID (e.g., a CPA config ID) set in association with the configuration information of the target PSCell for which CPA has been performed. However, the RRC message does not necessarily include all of the above information or messages; some may be omitted, and other information or messages may be added.

[0279] When an RRC message for MN 1620 is received, in step S1630, MN 1620 may send an Xn message (e.g., an SgNB reconfiguration complete message or an SNReconfigurationComplete message) to SN 1630, which includes the target PSCell. The Xn message may include the RRC message for SN 1630 received from UE 1610 (e.g., an SgNB reconfiguration complete message or an SN RRCReconfigurationComplete message).

[0280] In step S1635, UE 1610 and SN 1630 may perform a CPA procedure (or a random access procedure to the target PSCell).

[0281] In step S1640, UE 1610 can determine that the CPA process failed midway based on preset criteria. In this case, the UE can maintain the suspension of the CPA condition assessment while performing the SCGFailureInformation procedure. The criteria (or reasons for failure) used to determine the midway failure of the CPA procedure may be as follows. However, these are merely illustrative and not limited thereto.

[0282] - While the CPA process is being executed, a timer used for SCG (e.g., T304) expires.

[0283] - Alternatively, the content of the received RRC message for MN 1620 (e.g., RRCReconfiguration message) is incorrect.

[0284] - Alternatively, a `reconfigurationWithSync` failure may occur during PSCell addition.

[0285] In step S1645, UE 1610 may send an RRC message (e.g., an SCGFailureInformation message) including the cause of failure to MN 1620. Here, the cause of failure may be included as a cause value. Additionally, information (or indicators) indicating that a failure occurred during the CPA procedure may be included in the RRC message (e.g., SCGFailureInformation) including the cause of failure. Furthermore, the CPA configuration ID (e.g., CPA config ID) set in association with the target PSCell configuration information used to perform CPA may be included in the RRC message (e.g., SCGFailureInformation) including the cause of failure. When the CPA procedure fails, UE 1610 may send an RRC message (e.g., an SCGFailureInformation message) including the cause of failure to MN 1620. However, the RRC message does not necessarily need to include all of the above information; some may be omitted, and other information may be added.

[0286] Figure 17 This is a sequence diagram illustrating a method for performing a CPA operation when an SCG failure occurs, in addition to a CPA failure, according to an embodiment of the present disclosure.

[0287] In step S1705, the master node (MN) 1720 and the slave node (SN) 1730 can perform the SN addition preparation process for CPA.

[0288] In step S1710, UE 1710 can receive CPA configuration information from MN 1720 based on SN 1730 where the candidate target PSCell is stationed.

[0289] In step S1715, UE 1710 can evaluate whether the CPA execution conditions are met starting from the time point when CPA is configured.

[0290] In step S1720, UE 1710 can determine, based on a preset standard (or failure reason), that an SCG failure occurred due to a reason other than CPA failure (e.g., SCG RLF, SCG RRCreconfiguration failure, integrity check failure, etc.).

[0291] In step S1725, UE 1710 may execute the SCGFailureInformation procedure and stop the evaluation of CPA execution conditions.

[0292] In step S1730, UE 1710 may send an RRC message (e.g., SCGFailureInformation message) including the cause of failure to MN 1720. Here, the cause of failure may be included as a cause value.

[0293] Furthermore, in the embodiments and methods described above in this disclosure, structures or steps can be selectively applied in combination. Additionally, depending on the system configuration and / or definition, not all of the above steps are mandatory; some steps may be omitted if necessary.

[0294] The embodiments of this disclosure disclosed in this specification and accompanying drawings are presented as specific examples to facilitate the explanation of the technical details of this disclosure and to aid in understanding it, and are not intended to limit the scope of this disclosure. It will be apparent to those skilled in the art to which this disclosure pertains that other modifications based on the technical ideas of this disclosure may be performed in addition to the embodiments disclosed herein.

[0295] Furthermore, the embodiments disclosed in this specification and accompanying drawings are presented only as specific examples to facilitate explanation and understanding of the contents of this disclosure, and are not intended to limit the scope of this disclosure. Therefore, the scope of this disclosure should be interpreted to include the embodiments disclosed herein as well as all changes or modifications derived from the technical features of this disclosure.

Claims

1. A method performed by a first base station in a wireless communication system, the method comprising: Send a first Xn message to the second base station for Conditional Primary and Secondary Cell Group (SCG) Cell Addition (CPA), the first Xn message including measurement results of multiple cells, the multiple cells being determined by the first base station; Receive a second Xn message for CPA from the second base station, the second Xn message including: Configuration information of at least one candidate PSCell, wherein the at least one candidate PSCell is determined by a second base station from among the plurality of cells; and At least one absolute radio frequency channel number (ARFCN) value associated with the configuration information of the at least one candidate PSCell; and Send a first Radio Resource Control (RRC) message to the terminal. The first RRC message includes configuration information of the at least one candidate PSCell and execution condition information for CPA associated with the at least one candidate PSCell.

2. The method of claim 1, further comprising: Receive a second RRC message from the terminal, the second RRC message including information about the configuration identifier (ID) associated with the PSCell used for CPA execution.

3. The method of claim 2, further comprising: When the PSCell is operated by the second base station, a third Xn message is sent to the second base station, the third Xn message indicating that the terminal's RRC reconfiguration is complete; as well as If the PSCell is not operated by the second base station, send a fourth Xn message to the second base station to cancel the CPA.

4. A method performed by a second base station in a wireless communication system, the method comprising: The first base station receives a first Xn message for Conditional Primary and Secondary Cell Group (SCG) Cell Addition (CPA), the first Xn message including measurement results of multiple cells, the multiple cells being determined by the first base station; Identify at least one candidate PSCell from the plurality of cells; as well as Send a second Xn message for CPA to the first base station, the second Xn message including: Configuration information of the at least one candidate PSCell; and At least one absolute radio frequency channel number (ARFCN) value associated with the configuration information of the at least one candidate PSCell.

5. The method of claim 4, further comprising: When the PSCell used for CPA execution is operated by the second base station, a third Xn message is received from the first base station, the third Xn message indicating that the terminal's radio resource control (RRC) reconfiguration is complete; as well as If the PSCell is not operated by the second base station, a fourth Xn message is received from the first base station to cancel the CPA.

6. A first base station in a wireless communication system, the first base station comprising: transceiver; as well as The controller is configured as follows: The terminal sends a first Xn message for Conditional Primary and Secondary Cell Group (SCG) Cell Addition (CPA) to the second base station via a transceiver. The first Xn message includes the terminal's measurement results of multiple cells, which are determined by the first base station. The second Xn message for CPA is received from the second base station via a transceiver. The second Xn message includes: Configuration information of at least one candidate PSCell, wherein the at least one candidate PSCell is determined by a second base station from among the plurality of cells; and At least one absolute radio frequency channel number (ARFCN) value associated with the configuration information of the at least one candidate PSCell; and A first Radio Resource Control (RRC) message is sent to the terminal via a transceiver. The first RRC message includes configuration information of the at least one candidate PSCell and execution condition information for CPA associated with the at least one candidate PSCell.

7. The first base station as described in claim 6, wherein, The controller is also configured to: A second RRC message is received from the terminal via a transceiver. The second RRC message includes information about a configuration identifier (ID) associated with the PSCell used for the execution of CPA.

8. The first base station as described in claim 7, wherein, The controller is also configured to: When the PSCell is operated by the second base station, a third Xn message is sent to the second base station via the transceiver. The third Xn message indicates that the RRC reconfiguration of the terminal is complete. as well as If the PSCell is not operated by the second base station, a fourth Xn message is sent to the second base station via the transceiver to cancel the CPA.

9. A second base station in a wireless communication system, the second base station comprising: transceiver; as well as The controller is configured as follows: The terminal receives a first Xn message from the first base station via a transceiver for Conditional Primary and Secondary Cell Group (SCG) Cell Addition (CPA), the first Xn message including the terminal's measurement results of multiple cells, the multiple cells being determined by the first base station; Identify at least one candidate PSCell from the plurality of cells; as well as A second Xn message for CPA is sent to the first base station via a transceiver. The second Xn message includes: Configuration information of the at least one candidate PSCell; and At least one absolute radio frequency channel number (ARFCN) value associated with the configuration information of the at least one candidate PSCell.

10. The second base station as described in claim 9, wherein, The controller is also configured to: When the PSCell used for CPA execution is operated by the second base station, a third Xn message is received from the first base station via a transceiver. This third Xn message indicates that the terminal's Radio Resource Control (RRC) reconfiguration is complete. If the PSCell is not operated by the second base station, the fourth Xn message is received from the first base station via the transceiver to cancel the CPA.

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