Method and device for controlling timing advance timer for conditional lower layer handover in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting higher data transmission rates.

Description

Method and apparatus for controlling a lead time timer for conditional lower layer handover in a wireless communication system

[0001] This technology relates to the operation of a terminal in a wireless (or mobile) communication system. Specifically, it relates to technology related to communication control during the movement of the terminal.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in frequency bands below 6 GHz ('Sub 6 GHz'), such as 3.5 gigahertz (3.5 GHz), but also in ultra-high frequency bands called millimeter waves (mmWave), such as 28 GHz and 39 GHz ('Above 6 GHz'). In addition, for 6G mobile communication technology, which is referred to as a system beyond 5G, implementation in the terahertz band (e.g., the 3 terahertz (3 THz) band at 95 GHz) is being considered to achieve transmission speeds 50 times faster and ultra-low latency reduced to one-tenth compared to 5G mobile communication technology.

[0003] In the early stages of 5G mobile communication technology, aiming to satisfy service support and performance requirements for enhanced Mobile BroadBand (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), technologies such as beamforming and Massive MIMO to mitigate path loss and increase transmission distance in ultra-high frequency bands, support for various numerologies (such as the operation of multiple subcarrier spacings) and dynamic operation of slot formats for the efficient utilization of ultra-high frequency resources, initial access techniques to support multi-beam transmission and broadband, definition and operation of Band-Width Parts (BWP), Low Density Parity Check (LDPC) codes for high-volume data transmission, new channel coding methods such as Polar Codes for the reliable transmission of control information, and L2 pre-processing (L2 Standardization has been carried out for pre-processing, network slicing which provides a dedicated network specialized for specific services, and other methods.

[0004] Currently, discussions are underway to improve and enhance the performance of the initial 5G mobile communication technology, taking into account the services that the 5G mobile communication technology was intended to support. Additionally, standardization of the physical layer is in progress for technologies such as V2X (Vehicle-to-Everything), which helps autonomous vehicles make driving decisions and enhance user convenience based on their own location and status information transmitted by the vehicle; NR-U (New Radio Unlicensed), which aims for system operation in unlicensed bands to comply with various regulatory requirements; NR terminal low power consumption technology (UE Power Saving); Non-Terrestrial Network (NTN), which is direct terminal-satellite communication for securing coverage in areas where communication with the terrestrial network is impossible; and positioning.

[0005] In addition, standardization is underway in the field of wireless interface architecture / protocols for technologies such as the Industrial Internet of Things (IIoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) which provides nodes to expand network service areas by integrating wireless backhaul links and access links, Mobility Enhancement including Conditional Handover and Dual Active Protocol Stack (DAPS) Handover, and 2-step Random Access (2-step RACH for NR) which simplifies random access procedures. Standardization is also underway in the field of system architecture / services for 5G baseline architectures (e.g., Service based Architecture, Service based Interface) to incorporate Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC), which provides services based on the location of the terminal.

[0006] When such 5G mobile communication systems are commercialized, connected devices, which are increasing explosively, will be connected to communication networks. Accordingly, it is expected that there will be a need to enhance the functionality and performance of 5G mobile communication systems and to integrate the operation of connected devices. To this end, new research is planned to be conducted on 5G performance improvement and complexity reduction, support for AI services, support for metaverse services, and drone communication using eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] Furthermore, the advancement of these 5G mobile communication systems encompasses multi-antenna transmission technologies such as new waveforms to guarantee coverage in the terahertz band of 6G mobile communication technology, Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas; metamaterial-based lenses and antennas to improve terahertz band signal coverage; high-dimensional spatial multiplexing technology using OAM (Orbital Angular Momentum); and Reconfigurable Intelligent Surface (RIS) technology; as well as Full Duplex technology for enhancing frequency efficiency and system networks in 6G mobile communication technology; AI-based communication technologies that realize system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions; and the realization of services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources. It could serve as a foundation for the development of next-generation distributed computing technologies.

[0008] As a result of the aforementioned developments and advancements in mobile communication systems, it has become possible to provide a variety of services, and thus measures to effectively provide these services are required.

[0009] Since the timing of a conditional L1 / 2 (layer 1 / 2) handover is not fixed, the necessary timing advance value must be delivered to the candidate cell in advance to perform the handover without random access, and the network must continuously manage this. In this case, a method to manage the timing advance timer at the time the handover to the target cell is performed may be required.

[0010] The present invention, for solving the above-mentioned problems, is characterized in that a method for processing a control signal in a wireless communication system comprises: a step of receiving a first control signal transmitted from a base station; a step of processing the received first control signal; and a step of transmitting a second control signal generated based on the processing to the base station.

[0011] According to an embodiment of the present disclosure, when any terminal performs a conditional L1 / 2 handover, it can synchronize the validity of the TA (timing advance) timer required for the corresponding target cell connection with the base station by stopping or maintaining the TA value.

[0012] FIG. 1 is a drawing illustrating the structure of an LTE system according to one embodiment of the present disclosure.

[0013] FIG. 2 is a diagram showing the wireless protocol structure of an LTE system according to one embodiment of the present disclosure.

[0014] FIG. 3 is a drawing illustrating the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0015] FIG. 4 is a diagram showing the wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0016] FIG. 5 is a block diagram illustrating the internal structure of a terminal according to one embodiment of the present disclosure.

[0017] FIG. 6 is a block diagram showing the configuration of an NR (new radio) base station according to one embodiment of the present disclosure.

[0018] FIG. 7 illustrates the starting operation of the Timing Advance Timer (TAT) in the existing LTM (L1 / L2 triggered mobility) in relation to one embodiment of the present disclosure.

[0019] FIG. 8 illustrates a TAT processing method in a serving cell and a candidate cell in a wireless communication system according to one embodiment of the present disclosure.

[0020] FIG. 9 illustrates the operation of a target cell and other candidate cells in a wireless communication system according to one embodiment of the present disclosure.

[0021] FIG. 10 illustrates the operation of a target cell and a remaining candidate cell in a wireless communication system according to one embodiment of the present disclosure.

[0022] FIG. 11 illustrates the operation of a target cell and a remaining candidate cell in a wireless communication system according to one embodiment of the present disclosure.

[0023] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In describing the embodiments, technical details that are well known in the art to which the present disclosure belongs and are not directly related to the present disclosure will be omitted. This is intended to convey the essence of the present disclosure more clearly without obscuring it by omitting unnecessary explanations.

[0024] For the same reason, some components in the attached drawings have been exaggerated, omitted, or schematically depicted. Additionally, the dimensions of each component do not entirely reflect their actual dimensions. Identical or corresponding components in each drawing have been assigned the same reference numbers.

[0025] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure is complete and to fully inform those skilled in the art of the scope of the invention, and the present disclosure is defined only by the scope of the claims. Throughout the specification, like reference numerals refer to like components.

[0026] At this point, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flow diagram block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing the means of instruction to perform the function described in the flow diagram block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0027] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specified logical function(s). It should also be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For instance, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order according to their corresponding functions.

[0028] In this embodiment, the term "part" refers to a software or hardware component such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium or configured to run one or more processors. Thus, as an example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." In addition, the components and 'parts' may be implemented to utilize one or more CPUs within the device or secure multimedia card. Also, in the embodiments, 'parts' may include one or more processors.

[0029] In describing the embodiments of the present disclosure, the focus is primarily on the New Radio (NR), which is a wireless access network, and the Packet Core 5G System, 5G Core Network, or NG Core (Next Generation Core), which is a core network, as specified by the 3rd Generation Partnership Project (3GPP), a mobile communication standardization organization. However, the main point of the present disclosure is that it can be applied to other communication systems having a similar technical background with slight modifications without significantly departing from the scope of the present disclosure, and this will be possible at the judgment of a person with skilled technical knowledge in the technical field of the present disclosure.

[0030] For convenience of explanation, some terms and names defined in 3GPP standards (specifications for 5G, NR, LTE, or similar systems) may be used below. However, the present disclosure is not limited by these terms and names and may be applied equally to systems conforming to other standards.

[0031] Terms used in the following description to identify connected nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc., are examples provided for the convenience of explanation. Accordingly, the present disclosure is not limited to the terms used herein, and other terms referring to objects having equivalent technical meanings may be used.

[0032] Hereinafter, the base station is an entity that performs resource allocation for terminals and may be at least one of a gNode B, eNode B, Node B, BS (Base Station), wireless access unit, base station controller, or a node on a network. The terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, or a multimedia system capable of performing communication functions. Of course, it is not limited to the above examples.

[0033] In particular, the present disclosure is applicable to 3GPP NR (5th generation mobile communication standard). Furthermore, the present disclosure is applicable to intelligent services based on 5G communication technology and IoT-related technology (e.g., smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail, security and safety-related services, etc.). In the present disclosure, eNB may be used interchangeably with gNB for convenience of explanation. That is, a base station described as eNB may represent a gNB. Additionally, the term terminal may refer to mobile phones, NB-IoT devices, sensors, as well as other wireless communication devices.

[0034] Wireless communication systems are evolving from providing early voice-oriented services to broadband wireless communication systems that provide high-speed, high-quality packet data services, such as communication standards like 3GPP’s HSPA (High Speed ​​Packet Access), LTE (Long Term Evolution or E-UTRA (Evolved Universal Terrestrial Radio Access)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2’s HRPD (High Rate Packet Data), UMB (Ultra Mobile Broadband), and IEEE’s 802.16e.

[0035] As a representative example of a broadband wireless communication system, the LTE system employs the Orthogonal Frequency Division Multiplexing (OFDM) method for the downlink (DL) and the Single Carrier Frequency Division Multiple Access (SC-FDMA) method for the uplink (UL). The uplink refers to a wireless link through which a terminal (User Equipment; UE or Mobile Station; MS) transmits data or control signals to a base station (eNode B or BS; Base Station), and the downlink refers to a wireless link through which a base station transmits data or control signals to a terminal. The above multiple access method distinguishes the data or control information of each user by allocating and operating time-frequency resources to be transmitted for each user so that they do not overlap, that is, so that orthogonality is established.

[0036] As a future communication system following LTE, that is, a 5G communication system, it must be able to freely reflect the diverse requirements of users and service providers, and therefore, services that satisfy various requirements simultaneously must be supported. Services being considered for the 5G communication system include Enhanced Mobile BroadBand (eMBB), massive Machine Type Communication (mMTC), and Ultra Reliability Low Latency Communication (URLLC).

[0037] According to some embodiments, eMBB may aim to provide data transmission speeds that are higher than those supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, eMBB must be able to provide a peak data rate of 20 Gbps in the downlink and a peak data rate of 10 Gbps in the uplink from the perspective of a single base station. In addition, the 5G communication system may need to provide a user-perceived data rate while simultaneously providing the peak data rate. To satisfy these requirements, the 5G communication system may require improvements in various transmission and reception technologies, including enhanced Multi-Input Multi-Output (MIMO) transmission technology. Furthermore, while current LTE transmits signals using a maximum transmission bandwidth of 20 MHz in the 2 GHz band, the 5G communication system can satisfy the data transmission speeds required by the 5G communication system by using a frequency bandwidth wider than 20 MHz in frequency bands of 3 to 6 GHz or above 6 GHz.

[0038] Simultaneously, mMTC is being considered to support application services such as the Internet of Things (IoT) in 5G communication systems. To efficiently provide IoT services, mMTC may require support for a large number of terminal connections within a cell, improved terminal coverage, enhanced battery life, and reduced terminal costs. Since IoT devices are attached to various sensors and equipment to provide communication functions, the system must be able to support a large number of terminals within a cell (e.g., 1,000,000 terminals / km²). Furthermore, due to the nature of the service, terminals supporting mMTC are likely to be located in dead zones not covered by cells, such as building basements; therefore, wider coverage may be required compared to other services provided by 5G communication systems. Terminals supporting mMTC must consist of low-cost devices, and since it is difficult to frequently replace terminal batteries, a very long battery life of 10 to 15 years may be required.

[0039] Finally, URLLC is a mission-critical cellular-based wireless communication service that can be used for services such as remote control of robots or machinery, industrial automation, unmanned aerial vehicles, remote health care, and emergency alerts. Therefore, the communication provided by URLLC may need to offer very low latency and very high reliability. For example, services supporting URLLC must satisfy an air interface latency of less than 0.5 milliseconds and may simultaneously require a packet error rate of 10⁻⁵ or less. Consequently, for services supporting URLLC, 5G systems must provide a Transmit Time Interval (TTI) smaller than other services, and design considerations may be required to allocate wide resources in the frequency band to ensure the reliability of the communication link.

[0040] The three services considered in the aforementioned 5G communication system, namely eMBB, URLLC, and mMTC, can be multiplexed and transmitted within a single system. In this case, different transmission and reception techniques and parameters may be used between the services to satisfy the different requirements of each service. However, the aforementioned mMTC, URLLC, and eMBB are merely examples of different service types, and the service types to which this disclosure applies are not limited to the examples mentioned above. In an embodiment of this disclosure, a master node (MN) can be interpreted as a master base station, and a secondary node (SN) can be interpreted as a secondary base station. Furthermore, in an embodiment of this disclosure, the MN and SN may be different base stations or base stations using different RATs (radio access technologies), and in some cases, they may be base stations using the same RAT. The MN and SN may also be distinguished using general expressions such as a first base station, a second base station, etc.

[0041] In an embodiment of the present disclosure, a radio resource control (RRC) message transmitted by an MN may be named an MN RRC message. Additionally, an RRC message generated by an SN may be named an SN RRC message.

[0042] In Release 16, the intra-SN conditional PScell ​​change (CPC) is initiated by the SN, which then transmits the configuration of the candidate target PScell ​​to the terminal via the SN's RRC message. In contrast, in Release 17, the inter-SN conditional PScell ​​change is initiated by either the MN or the SN, which then transmits the configuration of the candidate target PScell ​​to the terminal via the MN's RRC message. If the network intends to configure both Rel-16 intra-SN conditional PScell ​​changes and Rel-17 inter-SN conditional PScell ​​changes for the terminal, the configuration, measurement, and condition evaluation of the terminal's candidate target PScell ​​may be performed in units of a specific number of candidate PScells. Therefore, the MN and SN must agree on the maximum number of conditional PScell ​​change configurations they are responsible for. This ensures that the number of conditional PScell ​​change configurations and measurements does not exceed the maximum operational limit based on the terminal's capabilities.

[0043] In addition, when transmitting conditional PScell ​​change settings to the terminal, the ID designating each candidate target PScell ​​setting is assigned by the SN in the case of intra-SN, and by the MN in the case of inter-SN. If all candidate PScell ​​change settings are stored in a single storage, i.e., a variable, there may be conflicts between IDs because the entities assigning the IDs are different.

[0044] In addition, when the two aforementioned conditional PScell ​​changes are set and operated on the terminal, if the intra-SN CPC is successfully performed, the inter-SN CPC setting may be deleted according to specific conditions.

[0045] According to embodiments of the present disclosure, it is possible to prevent a terminal from performing operations that exceed the terminal's capability based on the CPC settings of the MN and SN. Additionally, errors caused by ID duplication between multiple CPC settings can be prevented. Furthermore, inter-SN CPC settings resulting from intra-SN CPC execution can be efficiently managed.

[0046] FIG. 1 is a drawing illustrating the structure of an LTE system according to one embodiment of the present disclosure.

[0047] Referring to FIG. 1, as illustrated, the wireless access network of the LTE system may be composed of a next-generation base station (Evolved Node B, hereinafter ENB, Node B or base station) (1-05, 1-10, 1-15, 1-20), a Mobility Management Entity (MME) (1-25), and an S-GW (1-30, Serving-Gateway). A user terminal (User Equipment, hereinafter UE or terminal) (1-35) can connect to an external network through the ENB (1-05 to 1-20) and the S-GW (1-30).

[0048] In FIG. 1, the ENBs (1-05 to 1-20) can correspond to the existing Node B of a UMTS (universal mobile telecommunication system) system. The ENBs are connected to the UE (1-35) via a wireless channel and can perform more complex roles than the existing Node B. In an LTE system, all user traffic, including real-time services such as VoIP (Voice over IP) via the Internet Protocol, can be serviced through a shared channel. Therefore, a device is required to collect status information such as the buffer status, available transmission power status, and channel status of the UEs to perform scheduling, and this can be handled by the ENBs (1-05 to 1-20). A single ENB can typically control multiple cells. For example, to achieve a transmission speed of 100 Mbps, the LTE system can use Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology in a 20 MHz bandwidth. Of course, it is not limited to the above example. Additionally, the ENB (1a-05 to 1a-20) can apply an Adaptive Modulation & Coding (AMC) method that determines the modulation scheme and channel coding rate according to the channel conditions of the terminal. The S-GW (serving gateway) (1-30) is a device that provides a data bearer and can create or remove the data bearer under the control of the MME (mobility management entity) (1-25). The MME is a device that is responsible for various control functions as well as mobility management functions for the terminal and can be connected to multiple base stations.

[0049] FIG. 2 is a diagram showing the wireless protocol structure of an LTE system according to one embodiment of the present disclosure.

[0050] Referring to FIG. 2, the wireless protocol of the LTE system may include Packet Data Convergence Protocol (PDCP) (2-05, 2-40), Radio Link Control (RLC) (2-10, 2-35), Medium Access Control (MAC) (2-15, 2-30), and Physical (2-20, 2-25) layers at the terminal and ENB, respectively. Of course, the wireless protocol of the LTE system may include more or fewer layers than the configuration shown in FIG. 2.

[0051] According to one embodiment of the present disclosure, PDCP may be responsible for operations such as IP header compression / recovery. The main functions of PDCP can be summarized as follows. Of course, the following examples are not limited.

[0052] - Header compression and decompression (ROHC (robust header compression) only)

[0053] - User data transfer function (Transfer of user data)

[0054] - Sequential delivery function (In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM (acknowledge mode)

[0055] - Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0056] - Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM)

[0057] - Retransmission function (Retransmission of PDCP SDUs at handover and, for split bearers in DC, of ​​PDCP PDUs at PDCP data-recovery procedure, for RLC AM)

[0058] - Encryption and decryption functions (Ciphering and deciphering)

[0059] - Timer-based SDU discard in uplink.

[0060] According to one embodiment of the present disclosure, Radio Link Control (RLC) (2-10, 2-35) can reconfigure a PDCP Packet Data Unit (PDU) to an appropriate size to perform ARQ operations, etc. The main functions of the RLC can be summarized as follows. Of course, it is not limited to the following examples.

[0061] - Data transfer function (Transfer of upper layer PDUs)

[0062] - ARQ function (Error Correction through ARQ (only for AM data transfer))

[0063] - Concatenation, segmentation, and reassembly functions (Concatenation, segmentation, and reassembly of RLC SDUs (only for UM and AM data transfer))

[0064] - Re-segmentation function (Re-segmentation of RLC data PDUs (only for AM data transfer))

[0065] - Reordering function (Reordering of RLC data PDUs (only for UM and AM data transfer)

[0066] - Duplicate detection function (only for UM and AM data transfer)

[0067] - Error detection function (Protocol error detection (only for AM data transfer))

[0068] - RLC SDU deletion function (RLC SDU discard (only for UM and AM data transfer))

[0069] RLC re-establishment function

[0070] According to one embodiment of the present disclosure, a MAC (2-15, 2-30) is connected to multiple RLC layer devices configured in a terminal and can perform operations of multiplexing RLC PDUs to a MAC PDU and demultiplexing RLC PDUs from a MAC PDU. The main functions of the MAC can be summarized as follows. Of course, it is not limited to the following examples.

[0071] - Mapping function (Mapping between logical channels and transport channels)

[0072] - Multiplexing and demultiplexing function (Multiplexing / demultiplexing of MAC SDUs belonging to one or different logical channels into / from transport blocks (TB) delivered to / from the physical layer on transport channels)

[0073] - Scheduling information reporting function

[0074] - HARQ function (Error correction through HARQ)

[0075] - Priority handling between logical channels of one UE

[0076] - Priority handling between UEs by means of dynamic scheduling

[0077] - MBMS service identification

[0078] - Transport format selection function

[0079] - Padding

[0080] According to one embodiment of the present disclosure, the physical layer (2-20, 2-25) may perform the operation of channel coding and modulating upper layer data, creating OFDM symbols and transmitting them over a wireless channel, or demodulating OFDM symbols received through a wireless channel and channel decoding them to transmit them to an upper layer. Of course, it is not limited to the above examples.

[0081] FIG. 3 is a drawing illustrating the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0082] Referring to FIG. 3, the wireless access network of a wireless communication system (hereinafter, next-generation mobile communication system, NR or 5G) may be composed of a next-generation base station (New Radio Node B, hereinafter NR gNB or NR base station) (3-10) and a next-generation wireless core network (New Radio Core Network, NR CN) (3-05). A next-generation wireless user terminal (New Radio User Equipment, NR UE or terminal) (3-15) can connect to an external network through the NR gNB (3-10) and the NR CN (3-05).

[0083] In FIG. 3, the NR gNB (3-10) can correspond to the eNB (Evolved Node B) of an existing LTE system. The NR gNB is connected to the NR UE (3-15) via a wireless channel and can provide superior service compared to the existing Node B. In a next-generation mobile communication system, all user traffic can be serviced through a shared channel. Therefore, a device is required to collect status information such as the buffer status, available transmission power status, and channel status of the UEs to perform scheduling, and this can be handled by the NR NB (3-10). A single NR gNB can control multiple cells.

[0084] According to one embodiment of the present disclosure, in a next-generation mobile communication system, a bandwidth greater than the current maximum bandwidth may be applied to achieve ultra-high-speed data transmission compared to current LTE. Additionally, beamforming technology may be used by using Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology.

[0085] In addition, according to one embodiment of the present disclosure, an Adaptive Modulation & Coding (hereinafter referred to as AMC) method may be applied to determine a modulation scheme and a channel coding rate according to the channel conditions of the terminal. The NR CN (3-05) can perform functions such as mobility support, bearer configuration, and QoS (quality of service) configuration. The NR CN (3-05) is a device responsible for various control functions as well as mobility management functions for the terminal and can be connected to multiple base stations. In addition, the next-generation mobile communication system can be interoperable with an existing LTE system, and the NR CN (3-05) can be connected to the MME (3-25) via a network interface. The MME (3-25) can be connected to an existing base station, eNB (3-30).

[0086] FIG. 4 is a diagram showing the wireless protocol structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0087] Referring to FIG. 4, the wireless protocol of the next-generation mobile communication system may include NR Service Data Adaptation Protocol (SDAP) (4-01, 4-45), NR PDCP (4-05, 4-40), NR RLC (4-10, 4-35), NR MAC (4-15, 4-30), and NR PHY (4-20, 4-25) layers at the terminal and the NR base station, respectively. Of course, the wireless protocol of the next-generation mobile communication system may include more or fewer layers than the configuration shown in FIG. 4.

[0088] According to one embodiment of the present disclosure, the main functions of the NR SDAP (4-01, 4-45) may include some of the following functions. Of course, it is not limited to the following examples.

[0089] User data transfer function (transfer of user plane data)

[0090] Mapping function between a QoS flow and a DRB for both DL and UL for uplink and downlink

[0091] Marking QoS flow ID in both DL and UL packets for uplink and downlink

[0092] A feature that maps reflective QoS flow to the data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs)

[0093] For an SDAP device (hereinafter referred to interchangeably as layer or layer device) (4-01, 4-45), the terminal may receive a Radio Resource Control (RRC) message indicating whether to use the header of the SDAP layer device or the functions of the SDAP device (4-01, 4-45) for each PDCP layer device, for each bearer, or for each logical channel. When the SDAP header is configured, the terminal may be instructed to update or reset the mapping information for the QoS flows of the uplink and downlink and the data bearer using the Non-Access Stratum (NAS) Quality of Service (QoS) reflective setting 1-bit indicator (NAS reflective QoS) and the Access Stratum (AS) QoS reflective setting 1-bit indicator (AS reflective QoS) of the SDAP header. According to one embodiment, the SDAP header may include QoS flow ID information indicating QoS. In addition, according to one embodiment, QoS information can be used for data processing priority, scheduling information, etc. to support smooth service.

[0094] According to one embodiment of the present disclosure, the main functions of an NR PDCP (4-05, 4-40) device may include some of the following functions. Of course, it is not limited to the following examples.

[0095] - Header compression and decompression features (ROHC only)

[0096] - User data transfer function (Transfer of user data)

[0097] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0098] - Out-of-sequence delivery of upper layer PDUs

[0099] - Reordering function (PDCP PDU reordering for reception)

[0100] - Duplicate detection function (Duplicate detection of lower layer SDUs)

[0101] - Retransmission of PDCP SDUs

[0102] - Encryption and decryption functions (Ciphering and deciphering)

[0103] - Timer-based SDU discard in uplink.

[0104] According to one embodiment of the present disclosure, the reordering function of the NR PDCP device (4-05, 4-40) may mean a function of reordering PDCP PDUs received from a lower layer in order based on a PDCP SN (sequence number). The reordering function of the NR PDCP device (4-05, 4-40) may include at least one of a function of transmitting data to an upper layer in the reordered order, a function of transmitting immediately without considering the order, a function of recording lost PDCP PDUs by reordering the order, a function of reporting the status of lost PDCP PDUs to the transmitting side, and a function of requesting retransmission of lost PDCP PDUs.

[0105] According to one embodiment of the present disclosure, the main functions of an NR RLC (4-10, 4-35) device may include some of the following functions. Of course, it is not limited to the following examples.

[0106] - Data transfer function (Transfer of upper layer PDUs)

[0107] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0108] - Out-of-sequence delivery of upper layer PDUs

[0109] - ARQ function (Error Correction through ARQ)

[0110] - Concatenation, segmentation, and reassembly functions of RLC SDUs

[0111] - Re-segmentation function (Re-segmentation of RLC data PDUs)

[0112] - Reordering function (Reordering of RLC data PDUs)

[0113] - Duplicate detection

[0114] - Error detection function (Protocol error detection)

[0115] - RLC SDU discard function

[0116] RLC re-establishment function

[0117] According to one embodiment of the present disclosure, the in-sequence delivery function of the NR RLC device (4-10, 4-35) may mean a function of delivering RLC SDUs received from a lower layer to an upper layer in sequence. The in-sequence delivery function of the NR RLC device may include a function of reassembling and delivering RLC SDUs when an original RLC SDU is received divided into multiple RLC SDUs.

[0118] According to one embodiment of the present disclosure, the in-sequence delivery function of the NR RLC device (4-10, 4-35) may include at least one of the following: a function of rearranging received RLC PDUs based on an RLC SN (sequence number) or a PDCP SN (sequence number); a function of recording lost RLC PDUs by rearranging the order; a function of reporting the status of lost RLC PDUs to the transmitting side; and a function of requesting retransmission of lost RLC PDUs.

[0119] According to one embodiment of the present disclosure, the in-sequence delivery function of the NR RLC device (4-10, 4-35) may include at least one of the following: a function of delivering only the RLC SDUs prior to the lost RLC SDU in order to the upper layer when there is a lost RLC SDU; a function of delivering all RLC SDUs received before the timer started in order to the upper layer when there is a lost RLC SDU and a predetermined timer has expired; and a function of delivering all RLC SDUs received up to the present in order to the upper layer when there is a lost RLC SDU and a predetermined timer has expired.

[0120] The in-sequence delivery function of the NR RLC device may include the function of delivering all RLC SDUs received before the timer started to the upper layer in order, even if there are lost RLC SDUs, if a predetermined timer has expired.

[0121] The in-sequence delivery function of the NR RLC device may include the function of delivering all RLC SDUs received up to that point to the upper layer in order when a predetermined timer expires, even if there are lost RLC SDUs.

[0122] According to one embodiment of the present disclosure, the NR RLC device (4-10, 4-35) can process RLC PDUs in the order in which they are received and deliver them to the NR PDCP device regardless of the sequence number (Out-of-sequence delivery).

[0123] According to one embodiment of the present disclosure, when an NR RLC device (4-10, 4-35) receives a segment, it may receive segments stored in a buffer or to be received later, reconstruct them into a single complete RLC PDU, and then transmit it to an NR PDCP device.

[0124] According to one embodiment of the present disclosure, the NR RLC device (4-10, 4-35) may not include a concatenation function and may perform a function in the NR MAC layer or be replaced by a multiplexing function of the NR MAC layer.

[0125] In the above description, the out-of-sequence delivery function of the NR RLC device may refer to a function of delivering RLC SDUs received from a lower layer directly to an upper layer regardless of order. Additionally, the out-of-sequence delivery function of the NR RLC device may include a function of reassembling and delivering RLC SDUs when a single RLC SDU is received divided into multiple RLC SDUs. Furthermore, the out-of-sequence delivery function of the NR RLC device may include a function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording the lost RLC PDUs.

[0126] According to one embodiment of the present disclosure, an NR MAC device (4-15, 4-30) may be connected to multiple NR RLC layer devices configured in a terminal, and the main functions of the NR MAC (4-15, 4-30) may include some of the following functions. Of course, it is not limited to the following examples.

[0127] - Mapping function (Mapping between logical channels and transport channels)

[0128] - Multiplexing and demultiplexing functions (Multiplexing / demultiplexing of MAC SDUs)

[0129] - Scheduling information reporting function

[0130] - HARQ function (Error correction through HARQ)

[0131] - Priority handling between logical channels of one UE

[0132] - Priority handling between UEs by means of dynamic scheduling

[0133] - MBMS service identification

[0134] - Transport format selection function

[0135] - Padding

[0136] According to one embodiment of the present disclosure, the NR PHY layer (4-20, 4-25) may perform the operation of channel coding and modulating upper layer data, creating OFDM symbols and transmitting them over a wireless channel, or demodulating OFDM symbols received through a wireless channel and channel decoding them to transmit them to an upper layer. Of course, the above examples are not limited.

[0137] FIG. 5 is a block diagram illustrating the internal structure of a terminal to which the present invention is applied.

[0138] Referring to FIG. 5, the terminal may include an RF (Radio Frequency) processing unit (5-10), a baseband processing unit (5-20), a storage unit (5-30), and a control unit (5-40). Of course, it is not limited to the above example, and the terminal may include fewer or more configurations than the configuration shown in FIG. 5.

[0139] The RF processing unit (5-10) can perform functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (5-10) can up-convert a baseband signal provided by the baseband processing unit (5-20) into an RF band signal and transmit it through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (5-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC (digital to analog converter), an ADC (analog to digital converter), etc. Although only one antenna is shown in FIG. 5, the terminal may be equipped with multiple antennas. In addition, the RF processing unit (5-10) may include multiple RF chains. Furthermore, the RF processing unit (5-10) may perform beamforming. For beamforming, the RF processing unit (5-10) can adjust the phase and magnitude of each of the signals transmitted and received through multiple antennas or antenna elements. Additionally, the RF processing unit (5-10) can perform MIMO and can receive multiple layers when performing MIMO operation. The RF processing unit (5-10) can perform receiving beam sweeping by appropriately setting multiple antennas or antenna elements according to the control of the control unit, or can adjust the direction and beam width of the receiving beam so that the receiving beam is coordinated with the transmitting beam.

[0140] According to one embodiment of the present disclosure, the baseband processing unit (5-20) can perform a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (5-20) can generate complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (5-20) can restore the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (5-10). For example, in the case of following the orthogonal frequency division multiplexing (OFDM) method, when transmitting data, the baseband processing unit (5-20) can generate complex symbols by encoding and modulating the transmitted bit sequence, map the complex symbols to subcarriers, and then construct OFDM symbols through inverse fast Fourier transform (IFFT) operations and cyclic prefix (CP) insertion. Additionally, upon receiving data, the baseband processing unit (5-20) can divide the baseband signal provided by the RF processing unit (5-10) into OFDM symbol units, restore the signals mapped to subcarriers through a fast Fourier transform (FFT), and then restore the received bit sequence through demodulation and decoding.

[0141] According to one embodiment of the present disclosure, the baseband processing unit (5-20) and the RF processing unit (5-10) can transmit and receive signals as described above. Accordingly, the baseband processing unit (5-20) and the RF processing unit (5-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, or a communication unit. Furthermore, at least one of the baseband processing unit (5-20) and the RF processing unit (5-10) may include a plurality of communication modules to support a plurality of different wireless access technologies. Additionally, at least one of the baseband processing unit (5-20) and the RF processing unit (5-10) may include different communication modules to process signals of different frequency bands. For example, different wireless access technologies may include wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), etc. In addition, different frequency bands may include super high frequency (SHF) bands (e.g., 2.NRHz, NRHz) and millimeter wave (e.g., 60GHz) bands. The terminal can transmit and receive signals with a base station using a baseband processing unit (5-20) and an RF processing unit (5-10), and the signals may include control information and data.

[0142] The storage unit (5-30) stores data such as basic programs, application programs, and configuration information for the operation of the terminal. In particular, the storage unit (5-30) may store information related to a second connection node that performs wireless communication using the second wireless connection technology. Additionally, the storage unit (5-30) provides the stored data upon a request from the control unit (5-40). Furthermore, the storage unit (5-30) may be composed of multiple memories. According to one embodiment, the storage unit (5-30) may store a program for performing the conditional PSCell change method described in this disclosure.

[0143] According to one embodiment of the present disclosure, a control unit (5-40) controls the overall operations of the terminal. For example, the control unit (5-40) can transmit and receive signals through a baseband processing unit (5-20) and an RF processing unit (5-10). Additionally, the control unit (5-40) can write and read data to and from a storage unit (5-40). To this end, the control unit (5-40) may include at least one processor. For example, the control unit (5-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as applications. Additionally, at least one component within the terminal may be implemented as a single chip. Also, according to one embodiment of the present disclosure, the control unit (5-40) may include a multiple connection processing unit (5-42) that performs processing for operating in a multiple connection mode.

[0144] FIG. 6 is a block diagram showing the configuration of an NR base station according to one embodiment of the present disclosure.

[0145] As illustrated in FIG. 6, the base station is configured to include an RF processing unit (6-10), a baseband processing unit (6-20), a backhaul communication unit (6-30), a storage unit (6-40), and a control unit (6-50). Of course, it is not limited to the above example, and the base station may include fewer or more configurations than the configuration illustrated in FIG. 6.

[0146] According to one embodiment of the present disclosure, the RF processing unit (6-10) can perform functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (6-10) can up-convert a baseband signal provided by the baseband processing unit (6-20) into an RF band signal and transmit it through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (6-10) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in FIG. 6, the base station may be equipped with multiple antennas. Additionally, the RF processing unit (6-10) may include multiple RF chains. Furthermore, the RF processing unit (6-10) may perform beamforming. For beamforming, the RF processing unit (6-10) may adjust the phase and magnitude of each of the signals transmitted and received through multiple antennas or antenna elements. The RF processing unit (6-10) can perform down-to-down MIMO operation by transmitting one or more layers.

[0147] According to one embodiment of the present disclosure, the baseband processing unit (6-20) can perform a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (6-20) can generate complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (6-20) can restore the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (6-10). For example, in the case of following the OFDM method, when transmitting data, the baseband processing unit (6-20) can generate complex symbols by encoding and modulating the transmitted bit sequence, map the complex symbols to subcarriers, and then construct OFDM symbols through IFFT operation and CP insertion. Additionally, upon receiving data, the baseband processing unit (6-20) can divide the baseband signal provided by the RF processing unit (6-10) into OFDM symbol units, restore the signals mapped to subcarriers through FFT operations, and then restore the received bit sequence through demodulation and decoding. The baseband processing unit (6-20) and the RF processing unit (6-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (6-20) and the RF processing unit (6-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0148] According to one embodiment of the present disclosure, the communication unit (6-30) may provide an interface for performing communication with other nodes within the network. That is, the communication unit (6-30) may convert a bit sequence transmitted from the main base station to another node, e.g., an auxiliary base station, a core network, etc., into a physical signal, and convert a physical signal received from another node into a bit sequence.

[0149] The storage unit (6-40) stores data such as basic programs, application programs, and configuration information for the operation of the main station. In particular, the storage unit (6-40) can store information regarding a bearer assigned to a connected terminal, measurement results reported from the connected terminal, etc. Additionally, the storage unit (6-40) can store information that serves as a criterion for determining whether to provide or discontinue multiple connections to the terminal. Furthermore, the storage unit (6-40) can provide the stored data upon a request from the control unit (6-50). The storage unit (6-40) can provide the stored data upon a request from the control unit (6-50). The storage unit (6-40) may be composed of a storage medium or a combination of storage media such as ROM, RAM, a hard disk, CD-ROM, and DVD. Additionally, the storage unit (6-40) may be composed of multiple memories. According to one embodiment, the storage unit (6-40) may store a program for performing the conditional pscell change method described in this disclosure.

[0150] The control unit (6-50) can control the overall operations of the base station. For example, the control unit (6-50) can transmit and receive signals through the baseband processing unit (6-20) and the RF processing unit (6-10) or through the backhaul communication unit (6-30). Additionally, the control unit (6-50) can write and read data to and from the storage unit (6-40). To this end, the control unit (6-50) may include at least one processor. Additionally, at least one component of the base station may be implemented as a single chip. According to one embodiment of the present disclosure, the control unit (6-50) may include a multiple connection processing unit (6-52) that performs processing for operating in a multiple connection mode. Additionally, the control unit (6-50) can control the operation of the base station or the corresponding entity according to various embodiments of the present disclosure.

[0151] The Layer 1 / Layer 2 handover or L1 / L2 mobility mentioned in the present disclosure may be referred to as LTM (L1 / 2 triggered mobility). Also, TAT refers to Timing Advance timer.

[0152] In the LTM introduced in 3GPP NR R18 and R19, when a cell switch command MAC CE containing CFRA (contention-based random access) settings is received, and a TA value included in a RAR (random access response) is received from the corresponding cell via random access, the terminal initiates TAT ​​for that TA value. When a cell switch command is given without CFRA settings, the TA value may or may not be included. If the TA value is included, the terminal establishes a connection to the target cell using the included TA value. If the TA value is not included, the terminal establishes a connection to the target cell using a TA value measured by itself. In both of the aforementioned cases, the terminal initiates TAT ​​the moment it receives the cell switch command.

[0153] FIG. 7 illustrates the TAT start operation in a conventional LTM in relation to one embodiment of the present disclosure.

[0154] Referring to Figure 7, the conditional LTM (CLTM) introduced in R19 allows the terminal to perform the LTM on its own without a cell switch command. Therefore, the network cannot know when the terminal starts performing the LTM. Since the TA value must be known to the terminal in advance to perform RACH-less LTM, the network informs the terminal of the TA value for each candidate cell through a serving cell and introduces a timer for the corresponding TA.

[0155] However, it is necessary to discuss whether the TA value can be continuously updated through the serving cell. Additionally, it is necessary to discuss how to handle the TAT value when LTM is performed. Accordingly, the following includes a proposal regarding the aforementioned issues.

[0156] In one embodiment, the TA value used by the terminal can be expressed by the following mathematical formula 1. Of course, it is not limited to the following examples.

[0157] [Mathematical Formula 1]

[0158] T TA = (N TA + N TA,offset )·T c

[0159] In mathematical equation 1, T c = 1 / (480kHz · 4096) = 0.509 ns, and N TA is an absolute value, which can be a 12-bit integer or the value pointed to by that integer. N TA In NR, it can refer to the TA command value included in RAR or the TA command value included in LTM cell switch command.

[0160] N TA,offse is a delta value, where the terminal is the above N TA It can be a value added additionally after receiving the value. N TA,offse can be an integer indicated by 6 bits included in the Timing Advance command MAC CE.

[0161] The terminal can derive the T_{TA} value through the above signals.

[0162] As a value proposed in this disclosure, T_c value or N TA , N TA,offset ​The number of bits it can have may vary depending on the frequency and subcarrier spacing. Also, N pointed to by the integer indicated by each bit TA , N TA,offset There may be a mapping / linking of the value to a real or integer value. In this case, the terminal constructs the above formula based on the linked value to T TA The value can be derived.

[0163] Regarding the first problem of the problem to be solved (for example, the problem of whether the TA value can be continuously updated through the serving cell), the following suggestion may be made.

[0164] The terminal may operate on updating the TA value of the CLTM through any one of the following methods. Of course, the following embodiments are merely examples and are not limited thereto.

[0165] Opt 1. (In the absence of a delta signal) When the terminal receives a CLTM TA command MAC CE through the serving cell, the terminal may always derive a TA value using the absolute TA value or N_{TA} value included in the TA MAC CE, or, if the existing TA value has been received, overwrite the N_{TA} value with the newly derived value. Additionally, whenever a CLTM TA MAC CE is received, the terminal may start a new TAT.

[0166] Opt 2. (If there is a delta signal)

[0167] Opt 2-1. If the terminal receives the N_{TA} value via the CLTM TA command MAC CE for each candidate cell, then N via a separate CLTM delta TA command thereafter TA,offse When a value is received, the existing TA value (e.g., N TA or T TA Newly received N in ) TA,offseA new TA value can be derived and maintained by applying it. When the terminal receives the separate CLTM delta TA command MAC CE, it can restart the CLTM TAT for the candidate cell.

[0168] Opt 2-2. If the terminal receives the N_{TA} value via the CLTM TA command MAC CE for each candidate cell, thereafter, delta (e.g., N) to the said CLTM TA command MAC CE TA,offse A 1-bit or N-bit indicator indicating the value and N TA,offse Given a value, the existing maintained TA value (e.g., N TA or T TA In addition to ), newly received N TA,offse A new TA value can be derived and maintained by applying it. If the existing CLTM TA command includes a value indicating that it is delta, the terminal can restart the CLTM TAT for the candidate cell.

[0169] In the method of configuring the above CLTM TA command MAC CE, as described above, N TA And / or N TA,offse When expressing a value, the network additionally indicates a specific TAG ID, and the N of that TAG TA N based on the value TA,offse The value can also be instructed to the terminal.

[0170] According to the above-described terminal and network operations, the terminal may start TAT when it first receives the CLTM TA command MAC CE from the network. Additionally, the terminal may restart TAT by means of the above options.

[0171] For a specific CLTM candidate cell, until the TAT starts and expires, the terminal may consider the TA value associated with the TAT to be valid for the CLTM candidate cell. Conversely, if the CLTM TA command MAC CE has never been given, or if it is given but the associated timer expires, the terminal may consider or determine that there is no valid TA value for the CLTM candidate cell.

[0172] If the TAT starts and is not restarted before expiration, the timer may expire, and upon timer expiration, the terminal may perform the following actions. Of course, it is not limited to the examples below.

[0173] - Opt 1. The terminal does not perform RACH on its own, and the terminal may perform at least one of the following operations.

[0174] -- Can wait from the serving cell for a PDCCH order that commands a RACH operation to an expired candidate cell.

[0175] In addition, when the timer expires and the conditions of the target cell are satisfied, if the terminal is given a CBRA or CFRA setting in the target cell setting of the candidate cell, it can perform CLTM by performing a CBRA or CFRA operation using the setting.

[0176] -- If the conditions are met and the timer has expired, and there is no CBRA or CFRA setting in the target cell settings, the terminal's MAC is,

[0177] If the cell is set to an L3-based condition, MAC can notify RRC of an invalid TA, and RRC can stop evaluating the relevant condition.

[0178] If the cell is set to an L1-based condition, MAC can notify PHY of an invalid TA, and PHY can stop evaluating the relevant condition.

[0179] In this case, the terminal can retain the N_{TA} value for the corresponding candidate cell.

[0180] - Opt 2. The terminal can perform RACH on candidate cells on its own.

[0181] -- You can send an RA preamble to the target cell using the RACH resource settings associated with the target cell settings.

[0182] -- After that, you can wait for the reception of CLTM TA information from the serving cell.

[0183] - Opt 3. The terminal may transmit a signal to the serving cell regarding the expiration of the candidate cell TA timer. In this case, the signal regarding the expiration of the candidate cell TA timer may be transmitted via UCI or UL MAC CE.

[0184] As a next issue, when CLTM is performed, the processing method of the above CLTM TAT may be problematic.

[0185] In this case, there are two aspects to consider: TAT processing for the target cell for LTM execution, and TAT processing for other candidate cells.

[0186] As part of the TAT processing for a target cell, if the CLTM condition for the target cell is satisfied, the terminal executes a CLTM that applies the target cell settings for the corresponding candidate cell. At this time, the T304 timer may start. Additionally, a case may be considered where the TA value for the target cell has already been indicated through the serving cell and the TAT timer is operating. When T304 starts, the terminal may process the CLTM TAT timer for the target cell as follows. Of course, it is not limited to the examples below.

[0187] Opt 1. When T304 starts, the terminal may stop the TAT timer. The stopped timer may then perform the following actions.

[0188] Opt 1-1. When the CLTM to the target cell is successfully executed, the stopped TAT timer can be restarted. For example, the terminal can restart by initializing the TAT timer value.

[0189] Opt 1-2. When the CLTM to the target cell is successfully executed, the stopped TAT timer can be resumed. For example, the terminal can restart from the previously stopped TAT value.

[0190] Opt 1-3. When CLTM is successfully executed on the target cell and CLTM TA command MAC CE is received from the cell, or a general TA command MAC CE is received, or an absolute TA command MAC CE is received, or RAR's TAC(TA command) is received, TAT may be restarted according to the serving cell TAT value of the target cell.

[0191] Since the synchronization between the terminal and the base station of the TAT timer may be disrupted due to the execution of CLTM according to the methods of opt 1 above, after the terminal has completed moving to the target cell, the terminal may need to provide a management signal regarding TA.

[0192] Opt 2. If T304 starts, the TAT timer may continue. In this case, the TAT timer may expire before T304 expires (e.g., CLTM failure) or stops (e.g., CLTM successful completion). In this case, the following terminal actions are possible.

[0193] Opt 2-1. If the TAT expires before the T304 expires or the terminal stops, the terminal may consider or identify this as a handover failure (HOF) or a reconfigurationWithSync failure. Accordingly, the terminal may perform an RRC Reestablishment operation or a separate HOF processing operation.

[0194] Opt 2-2. If the TAT expires before the complete message (e.g., HO complete, or CLTM execution completion message) is transmitted to the target cell, and based on the time when the terminal transmits the complete message to the target cell, the terminal may consider or determine it to be a HOF. The terminal may then perform HOF processing operations such as RRCReestablishment. If the TAT expires after the complete message is transmitted and before the expiration or suspension of the T304, the terminal may not consider it to be a HOF. Instead, since the current target cell configuration is applied, the terminal may not perform release and deconfiguration operations related to the UL-related configurations and resources of the target cell. (Note: If the TAT expires in the existing serving cell state, the terminal must perform release / deconfiguration operations.) For example, the terminal may perform at least one of the following operations. In the following, "serving cell" may refer to the target cell that executed the CLTM.

[0195] keep all HARQ buffers for the serving Cells;

[0196] (Maintain all HARQ buffers for the serving cell)

[0197] keep PUCCH for the Serving Cells, if configured;

[0198] (If configured, retain PUCCH for serving cell)

[0199] keep SRS for the Serving Cells, if configured;

[0200] (If configured, maintain SRS for the serving cell)

[0201] keep any configured downlink assignments and configured uplink grants;

[0202] (Maintain configured downlink allocations and configured uplink grants)

[0203] keep any PUSCH resource for semi-persistent CSI reporting;

[0204] (Maintaining PUSCH resources for semi-persistent CSI reporting)

[0205] maintain N TA of all CLTM candidate cells.

[0206] (N of all CLTM candidate cells TA (maintain)

[0207] Additionally, when the network receives an RRCReconfigurationComplete message from the terminal, it may send a TA command MAC CE in the very next message. This allows the terminal to use the received TA value to transmit the necessary UL data using the UL configuration it maintains.

[0208] Although Opt 2 methods synchronize the TAT for the CLTM target cell between the terminal and the network, if the TAT expires during transit to the target cell, an agreement on the operation regarding whether the corresponding TA can be used may be required. Accordingly, we propose options.

[0209] Opt 3. When T304 starts, the terminal can restart TAT using a previously set timer value. The network can prevent TAT from expiring in the middle of CLTM execution by setting the timer value to a value greater than T304.

[0210] If the above options are operations related to the TAT of the target cell performing CLTM, the terminal may have a CLTM candidate setting other than the target cell before performing CLTM, and among these candidate cells, there may be a candidate cell that has received a TA setting for CLTM. Below, a method for processing the TAT of another candidate cell while CLTM is being performed on the target cell is proposed.

[0211] Opt 1. When the T304 of the target cell starts, if any of the CLTM candidate cells have already received TA settings and TAT is in operation, the TAT timers of the corresponding candidate cells, excluding the target cell, may be stopped. Stopped TAT timers may be restarted in the following cases.

[0212] Opt 1-1. If the CLTM to the target cell is successfully executed, the TAT timers of the stopped candidate cells may be restarted. For example, the terminal restarts by initializing the TAT timer value.

[0213] Opt 1-2. If the CLTM to the target cell is successfully executed, the TAT timers of the candidate cells that were stopped can be resumed. For example, the terminal can restart from the previously stopped TAT value.

[0214] Opt 1-3. When CLTM is successfully performed on the target cell and the terminal receives the CLTM TA command MAC CE of each candidate cell, the general TA command MAC CE of each candidate cell, the absolute TA command MAC CE, or the TAC of the RAR from the serving cell (e.g., the target cell during CLTM execution) for the TA of the candidate cells that was stopped, the terminal may restart the TAT by applying the TAT value maintained in the candidate cell.

[0215] Since the methods of opt 1 above are methods in which the synchronization between the terminal and the base station of the TAT timer is disrupted due to the execution of CLTM, the terminal may need to provide a management signal regarding TA after completing movement to the target cell. However, since it is based on TAT control of the other candidate cells rather than TAT control with the target cell, TAT control of the candidate cells is relatively less critical to time and thus may be highly feasible to implement.

[0216] Opt 2. If T304 starts, the TAT timer may continue as is. In this case, the TAT timer of another candidate cell may expire before T304 expires (e.g., CLTM failure) or stops (e.g., CLTM successful completion). In this case, the following terminal actions may be possible.

[0217] Opt 2-1. If the TAT of another candidate cell expires before the T304 expires or the terminal stops, the terminal may record certain information and report that information to the serving cell if the CLTM to the target cell is successfully performed. The information recorded / reported by the terminal may include at least one of the configuration ID of the CLTM candidate cell whose TAT expired or information from PCI and AFRCN. Additionally, such information may include at least one of the configuration ID of the target cell that was subject to the CLTM execution, PCI / ARFCN, the configuration ID of the source cell, or information from PCI / ARFCN. Such information may be reported using UCI or UL MAC CE after moving to the target cell without issue.

[0218] Opt 2-2. If the TAT of another candidate cell expires before the terminal T304 expires or stops, the terminal retains that TA value, but may wait for a PDCCH order to perform RACH to that candidate cell.

[0219] Opt 3. When T304 starts, the terminal may restart TAT for all CLTM candidate cells where TAT is running, using a previously set timer value. The network may prevent TAT from expiring in the middle of CLTM execution by setting the timer value to a value greater than T304.

[0220] When performing CLTM, the TAT processing method in the target cell and the TAT processing method of other candidate cells can be considered independently of each other.

[0221] FIG. 8 illustrates a TAT processing method in a serving cell and a candidate cell in a wireless communication system according to one embodiment of the present disclosure.

[0222] In step 810, the network prepares the terminal and CLTM candidate cell configurations, and can transmit each CLTM candidate cell configuration and condition information to the terminal via an RRCReconfiguration message.

[0223] In step 820, the network can additionally transmit the TA value to the terminal via the CLTM TA command MAC CE.

[0224] In step 830, the terminal can start TAT based on the TAT value for the corresponding candidate cell given in the preparation step (e.g., step 810).

[0225] In step 840, the serving cell can obtain TA values ​​for the target cell and candidate cell and, if necessary, transmit them to the terminal via the CLTM TA command MAC CE.

[0226] In step 850, the terminal that receives the TA values ​​for the target cell and the candidate cell can apply the TA values ​​for each corresponding cell and simultaneously start the TAT for the corresponding cell.

[0227] In step 860, if the condition for a specific cell is satisfied and CLTM is performed, the terminal can start T304 to move to that cell and simultaneously stop TAT for the target cell and TAT for other CLTM candidate cells.

[0228] In step 870, the terminal can send an RRCReconfigComplete message to the target cell.

[0229] In step 880, if the terminal successfully transmits a complete message to the target cell, the TAT for the target cell and candidate cells may be restarted or resumed from the existing paused state by opt 1-1 and opt 1-2. Through this, the terminal can have a valid TA for each candidate cell and use it for uplink transmission as needed.

[0230] FIG. 9 illustrates the operation of a target cell and other candidate cells in a wireless communication system according to one embodiment of the present disclosure.

[0231] In step 905, the network prepares the terminal and CLTM candidate cell configurations, and can transmit each CLTM candidate cell configuration and condition information to the terminal via an RRCReconfiguration message.

[0232] In step 910, the network can additionally transmit the TA value to the terminal via the CLTM TA command MAC CE.

[0233] In step 915, the terminal can start TAT based on the TAT value for the corresponding candidate cell given in the preparation step (e.g., step 905).

[0234] In step 920, the serving cell can obtain TA values ​​for the target cell and candidate cell and, if necessary, transmit them to the terminal via the CLTM TA command MAC CE.

[0235] In step 925, the terminal that receives the TA values ​​for the target cell and the candidate cell can apply the TA values ​​for each corresponding cell and simultaneously start the TAT for the corresponding cell.

[0236] In step 930, if the condition for a specific cell is satisfied and CLTM is performed, the terminal may start T304 to move to that cell and simultaneously stop TAT for the target cell and TAT for other CLTM candidate cells.

[0237] In step 935, the terminal can send an RRCReconfigComplete message to the target cell.

[0238] In step 940, if the terminal successfully transmits a complete message to the target cell, the TAT for the target cell and candidate cells may be restarted or resumed from the existing paused state by opt 1-1 and opt 1-2. Through this, the terminal can have a valid TA for each candidate cell and use it for uplink transmission as needed.

[0239] In step 945, until the terminal receives a separate CLTM TA command MAC CE, an absolute value TA, or a MAC CE or RAR indicating a delta value for a previously maintained TA value from the target cell, the TAT in the target cell may remain suspended.

[0240] In step 950, after receiving TA-related information from the target cell, the terminal can restart the TAT of the target cell, and at that time, the received TA value can be considered as a new valid TA value and used for uplink data transmission of the target cell.

[0241] FIG. 10 illustrates the operation of a target cell and a remaining candidate cell in a wireless communication system according to one embodiment of the present disclosure.

[0242] In step 1010, the network prepares the terminal and CLTM candidate cell configurations, and can transmit each CLTM candidate cell configuration and condition information to the terminal via an RRCReconfiguration message.

[0243] In step 1020, the network can additionally transmit the TA value to the terminal via the CLTM TA command MAC CE.

[0244] In step 1030, the terminal can start TAT based on the TAT value for the corresponding candidate cell given in the preparation step (e.g., step 1010).

[0245] In step 1040, the serving cell can obtain TA values ​​for the target cell and candidate cell and, if necessary, transmit them to the terminal via the CLTM TA command MAC CE.

[0246] At step 1050, the terminal can apply a TA value for the cell and simultaneously start a TAT for the cell.

[0247] In step 1060, if the condition for a specific cell is satisfied and CLTM is performed, the terminal initiates T304 to move to that cell, and at the same time, TAT for the target cell and TAT for other CLTM candidate cells can proceed as before.

[0248] In step 1070, before the terminal successfully transmits a complete message to the target cell and before T304 expires, the TAT for the target cell may expire. In this case, the terminal may consider or determine that it is a HOF.

[0249] In step 1080, the terminal can perform an RRC reestablishment operation.

[0250] FIG. 11 illustrates the operation of a target cell and a remaining candidate cell in a wireless communication system according to one embodiment of the present disclosure.

[0251] In step 1105, the network prepares the terminal and CLTM candidate cell configurations, and can transmit each CLTM candidate cell configuration and condition information to the terminal via an RRCReconfiguration message.

[0252] In step 1110, the network can additionally transmit the TA value through the CLTM TA command MAC CE.

[0253] In step 1115, the terminal can start TAT based on the TAT value for the corresponding candidate cell given in the preparation step (e.g., step 1105).

[0254] In step 1120, the serving cell can obtain TA values ​​for the target cell and candidate cell and, if necessary, transmit them to the terminal via the CLTM TA command MAC CE.

[0255] In step 1125, the terminal can apply a TA value for the cell and simultaneously start a TAT for the cell.

[0256] In step 1130, if the condition for a specific cell is satisfied and CLTM is performed, the terminal initiates T304 to move to that cell, and at the same time, TAT for the target cell and TAT for other CLTM candidate cells can proceed as before.

[0257] In step 1135, the terminal can send an RRCReconfigComplete message to the target cell.

[0258] In step 1140, after the terminal has transmitted a complete message to the target cell and before T304 expires, the TAT for the target cell may expire. In this case, the terminal is not considered to be a HOF and may retain resources and related settings for UL transmission in the target cell. A specific explanation regarding this is as described above.

[0259] In step 1145, if the TAT for another cell expires before T304 expires, the terminal may store information about the expired cell and store the context for CLTM execution. At this time, the specific information stored is as described above.

[0260] In step 1150, the terminal can receive a DL or UL grant from the target cell.

[0261] In step 1155, T304 may be stopped at the time when CLTM execution is completed by receiving a DL or UL grant.

[0262] In step 1160, a CLTM TA command can be received from the target cell.

[0263] In step 1165, the terminal can consider the TA value included in the corresponding MAC CE as the TA value for the target cell and use it, and can start the TAT anew.

[0264] In step 1170, if a UL grant is received, the terminal may report information logged in relation to TAT expiration to the target cell using the TA value of the target cell obtained in the above process. At this time, it may be transmitted via a UL RRC message, UL MAC CE, or UCI.

[0265] Methods according to the embodiments described in the claims or specification of the present invention may be implemented in the form of hardware, software, or a combination of hardware and software.

[0266] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present invention.

[0267] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, ROM (Read Only Memory), Electrically Erasable Programmable Read Only Memory (EEPROM), magnetic disc storage devices, Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0268] In addition, the above program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), or Storage Area Network (SAN), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present invention through an external port. Additionally, a separate storage device on a communication network may be connected to a device performing an embodiment of the present invention.

[0269] In the specific embodiments of the present invention described above, the components included in the invention are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present invention is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed in the singular form, or even if a component is expressed in the singular form, it may be composed in the plural form.

[0270] Meanwhile, although specific embodiments have been described in the detailed description of the present invention, it is understood that various modifications are possible within the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

[0271] In the drawings describing the embodiments of the present disclosure, the order of description does not necessarily correspond to the order of execution, and the order of execution may be changed or executed in parallel. Additionally, the drawings describing the embodiments of the present disclosure may omit some components and include only some components to the extent that the essence of the present disclosure is not impaired.

[0272] The embodiments of the present disclosure may be practiced by combining some or all of the contents included in each embodiment to the extent that the essence of the present disclosure is not impaired.

[0273] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples provided to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is obvious to those skilled in the art that other variations based on the technical concept of the present disclosure are possible in addition to the embodiments disclosed herein.

Claims

In a method performed by a terminal in a wireless communication system, A step of receiving configuration information regarding CLTM (conditional L1 / L2 Triggered Mobility) from a base station; Based on the above setting information, a step of evaluating the triggering condition of the CLTM and receiving a TA (timing advance) value for the CLTM candidate cell; and The method includes the step of performing a CLTM cell change when the event for the above CLTM is satisfied and the timer associated with the CLTM candidate cell is running, and A method in which the TA value for the CLTM candidate cell is valid for the remaining time of the timer. In paragraph 1, the above method is: The method further includes the step of starting the timer for the above CLTM candidate cell, A method in which the TA value associated with the above CLTM candidate cell is included in the MAC (medium access control) CE (control element). In paragraph 2, A method in which the above MAC CE includes an index value for indicating the above TA value. In paragraph 1, A method in which a RACH (random access channel)-less CLTM cell change is performed on the above CLTM candidate cell. In paragraph 1, A method in which a RACH-based CLTM cell change for the CLTM candidate cell is performed when the timer associated with the CLTM candidate cell is not operating. In paragraph 1, A method in which a timer running for other CLTM candidate cells, excluding the above CLTM candidate cell, is maintained. In paragraph 1, the above method is: A method comprising the step of releasing a setting or resource associated with the target cell when the timer associated with the CLTM candidate cell is not operating. Regarding the terminal: At least one transceiver; At least one processor communicatively coupled to the above at least one transceiver; and It includes at least one memory that is communicationally coupled to the above at least one processor and stores instructions, and The above instructions are executed individually or in any combination by the above at least one processor, so that the terminal: Receive configuration information regarding CLTM (conditional L1 / L2 Triggered Mobility) from the base station, and Based on the above configuration information, the triggering conditions of the CLTM are evaluated and the TA (timing advance) value for the CLTM candidate cell is received, and If the event for the above CLTM is satisfied and the timer associated with the CLTM candidate cell is running, perform a CLTM cell change, and A terminal in which the TA value for the above CLTM candidate cell is valid for the remaining time of the timer. In paragraph 8, the above commands are the terminal: Start the timer for the above CLTM candidate cell, and A terminal in which the TA value associated with the above CLTM candidate cell is included in the MAC (medium access control) CE (control element). In Paragraph 9, A terminal in which the above MAC CE includes an index value for indicating the above TA value. In paragraph 8, A terminal in which a RACH (random access channel)-less CLTM cell change is performed for the above CLTM candidate cell. In paragraph 8, A terminal in which a RACH-based CLTM cell change for the CLTM candidate cell is performed when the timer associated with the CLTM candidate cell is not operating. In paragraph 8, A terminal in which a timer running for other CLTM candidate cells, excluding the above CLTM candidate cell, is maintained. In paragraph 8, the above commands are the terminal: A terminal that releases settings or resources associated with the target cell when the timer associated with the CLTM candidate cell is not operating.

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