Method and apparatus for estimating user equipment measurement-based timing advance for carrier aggregation operation in next generation mobile communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. According to an embodiment of the present disclosure, a method performed by a user equipment in a wireless communication system may comprise the steps of: acquiring, from a first cell, information about at least one neighboring cell related to user equipment-based timing advance (TA) measurement; receiving, from the first cell on the basis of a result of measurement by the user equipment, a message comprising a second timing advance group (TAG) identity (ID) corresponding to a second cell; determining whether a first TAG ID corresponding to the first cell is the same as the second TAG ID; determining to acquire TA for the second cell if the first TAG ID and the second TAG ID are different from each other as a result of the determination and the second cell is included in the information about the neighboring cell; and acquiring the TA for the second cell.

Description

Method and apparatus for estimating timing advance based on terminal measurement for frequency aggregation operation in next-generation mobile communication systems

[0001] This technology relates to the operation of a terminal in a mobile communication system. Specifically, it relates to a method for obtaining a timing advance value when adding a secondary cell for frequency aggregation 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] The aim is to eliminate the need to unnecessarily perform a random access procedure when a terminal adds a secondary cell to perform frequency aggregation operations.

[0010] According to one embodiment of the present disclosure, a method performed by a terminal in a wireless communication system may include: obtaining information about at least one neighbor cell related to a terminal-based timing advance (TA) measurement from a first cell; receiving a message from the first cell containing a second TAG (timing advance group) identifier (identity, ID) corresponding to a second cell based on the measurement result of the terminal; determining whether the first TAG ID corresponding to the first cell and the second TAG ID are the same; determining that, as a result of the determination, the first TAG ID and the second TAG ID are different and the second cell is included in the information about the neighbor cell, determining to obtain a TA for the second cell; and obtaining a TA for the second cell.

[0011] Meanwhile, according to another embodiment of the present disclosure, a method performed by a first cell in a wireless communication system may include the steps of transmitting information about at least one neighbor cell related to a terminal-based timing advance (TA) measurement to the terminal, transmitting a first TAG (timing advance group) identifier (identity, ID) corresponding to the first cell to the terminal, and transmitting a message including a second TAG ID corresponding to a second cell to the terminal based on the measurement result of the terminal, wherein the terminal determines whether the first TAG ID corresponding to the first cell and the second TAG ID are the same, and if the determination result shows that the first TAG ID and the second TAG ID are different and the second cell is included in the information about the neighbor cell, it is determined to obtain a TA for the second cell, and the TA for the second cell is obtained.

[0012] Meanwhile, according to another embodiment of the present disclosure, in a wireless communication system, a terminal obtains information about at least one neighbor cell related to terminal-based timing advance (TA) measurement from a transceiver and a first cell, receives a message from the first cell through the transceiver that includes a second TAG (timing advance group) identifier (identity, ID) corresponding to a second cell based on the measurement result of the terminal, determines whether the first TAG ID corresponding to the first cell and the second TAG ID are the same, and if the determination result shows that the first TAG ID and the second TAG ID are different and the second cell is included in the information about the neighbor cell, determines to obtain a TA for the second cell and may include a control unit that controls to obtain a TA for the second cell.

[0013] Meanwhile, according to another embodiment of the present disclosure, in a wireless communication system, a first cell transmits information about at least one neighbor cell related to a timing advance (TA) measurement based on a transceiver and a terminal to a terminal through the transceiver, transmits a first TAG (timing advance group) identifier (identity, ID) corresponding to the first cell to the terminal through the transceiver, and includes a control unit that controls the transmission of a message including a second TAG ID corresponding to a second cell to the terminal through the transceiver based on the measurement result of the terminal, and determines by the terminal whether the first TAG ID corresponding to the first cell and the second TAG ID are the same, and if the determination result shows that the first TAG ID and the second TAG ID are different and the second cell is included in the information about the neighbor cell, it is determined to obtain a TA for the second cell, and the TA for the second cell is obtained.

[0014] According to an embodiment of the present invention, any terminal can be added without a random access procedure when adding a secondary cell for frequency aggregation operation.

[0015] Figure 1 is a diagram illustrating the structure of a typical LTE system.

[0016] Figure 2 is a diagram showing the wireless protocol structure of a typical LTE system.

[0017] FIG. 3c is a drawing illustrating the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0018] 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.

[0019] FIG. 5 is a block diagram illustrating the internal structure of a terminal according to one embodiment of the present disclosure.

[0020] FIG. 6 is a block diagram showing the configuration of an NR base station according to one embodiment of the present disclosure.

[0021] FIG. 7 is a diagram illustrating a method of obtaining TA through UE-based TA measurement when two cells are given, according to one embodiment of the present disclosure.

[0022] FIG. 8 is a sequence diagram for specifically explaining the target cell information transfer opt 1 of UE-based TA measurement according to one embodiment of the present disclosure.

[0023] FIG. 9 is a sequence diagram for specifically explaining the target cell information transfer opt 2 of UE-based TA measurement according to one embodiment of the present disclosure.

[0024] FIG. 10 is a sequence diagram for specifically explaining target cell information transfer opt 3 of UE-based TA measurement according to one embodiment of the present disclosure.

[0025] FIG. 11 is a sequence diagram for specifically explaining target cell information transfer opt 4 of UE-based TA measurement according to one embodiment of the present disclosure.

[0026] FIG. 12 is a sequence diagram for specifically explaining the target cell information transfer opt 5 of UE-based TA measurement according to one embodiment of the present disclosure.

[0027] FIG. 13 is a sequence diagram illustrating an example of a case in which, according to one embodiment of the present disclosure, after acquiring a TA in this manner, the TA of the terminal is incorrect when measured by the network and corrected based on RACH.

[0028] FIG. 14 is a sequence diagram illustrating an example of a case in which, according to one embodiment of the present disclosure, after acquiring a TA in this manner, the TA of the terminal is incorrect when measured by the network and corrected without RACH.

[0029] The operating principle of the present invention will be described in detail below with reference to the attached drawings. In describing the present invention below, specific descriptions of related known functions or configurations will be omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the invention. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0030] Terms used in the following description to identify connection 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 invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0031] Hereinafter, a 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), radio access unit, base station controller, or a node on a network. A terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, or a multimedia system capable of performing communication functions. In this disclosure, a downlink (DL) refers to a wireless transmission path of a signal transmitted by a base station to a terminal, and an uplink (UL) refers to a wireless transmission path of a signal transmitted by a terminal to a base station. Furthermore, while an LTE or LTE-A system may be described as an example below, embodiments of this disclosure may be applied to other communication systems having similar technical backgrounds or channel types. For example, 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in a system to which embodiments of this disclosure can be applied, and the 5G below may be a concept that includes existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications made at the discretion of a person with skilled technical knowledge, without departing significantly from the scope of the present disclosure. In this case, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams may be executed by computer program instructions.

[0032] Since these computer program instructions can be loaded onto the processor of a general-purpose computer, a computer for special purposes, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means for performing the functions described in the flowchart 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 functions in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing means of instruction for performing the functions described in the flowchart block(s). Since the computer program instructions can also be loaded onto the computer or other programmable data processing equipment, the instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a computer-executable process can also provide steps for performing the functions described in the flowchart block(s).

[0033] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specific logical function(s). Also, it should be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For example, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order depending on the corresponding function. In this case, the term "part" as used in this embodiment refers to software or hardware components such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), and the "part" may perform 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. Accordingly, as an example, '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'. Furthermore, the components and 'parts' may be implemented to utilize one or more CPUs within a device or secure multimedia card. Additionally, in an embodiment, 'part' may include one or more processors.

[0034] For the convenience of the following explanation, the present invention uses terms and names defined in the 5GS and NR specifications, which are standards defined by the 3GPP (The 3rd Generation Partnership Project) organization among existing communication standards. However, the present invention is not limited by the above terms and names and can be applied in the same way to wireless communication networks according to other standards. For example, the present invention can be applied to 3GPP 5GS / NR (5th generation mobile communication standard).

[0035] Figure 1 is a diagram illustrating the structure of a typical LTE system.

[0036] 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).

[0037] In FIG. 1, the ENB (1-05 to 1-20) can correspond to the existing Node B of the UMTS system. The ENB is 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 ENB (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, for example, in a 20 MHz bandwidth. In addition, an Adaptive Modulation & Coding (AMC) method can be applied to determine the modulation scheme and channel coding rate according to the channel conditions of the terminal. The S-GW (1-30) is a device that provides a data bearer and can create or remove the data bearer under the control of the MME (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.

[0038] Figure 2 is a diagram showing the wireless protocol structure of an existing LTE system.

[0039] Referring to FIG. 2, the wireless protocol of the LTE system may consist of a Packet Data Convergence Protocol (PDCP) (2-05, 2-40), Radio Link Control (RLC) (2-10, 2-35), and Medium Access Control (MAC) (2-15, 2-30) at the terminal and ENB, respectively. PDCP can be responsible for operations such as IP header compression / decompression. The main functions of PDCP can be summarized as follows.

[0040] - Header compression and decompression features (ROHC only)

[0041] - User data transfer function (Transfer of user data)

[0042] - Sequential delivery function (In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM)

[0043] - Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0044] - Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM)

[0045] - 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)

[0046] - Encryption and decryption functions (Ciphering and deciphering)

[0047] - Timer-based SDU discard in uplink.

[0048] Radio Link Control (RLC) (2-10, 2-35) can perform ARQ operations, etc., by reconfiguring PDCP Packet Data Units (PDUs) to an appropriate size. The main functions of RLC can be summarized as follows.

[0049] - Data transfer function (Transfer of upper layer PDUs)

[0050] - ARQ function (Error Correction through ARQ (only for AM data transfer))

[0051] - Concatenation, segmentation, and reassembly functions (Concatenation, segmentation, and reassembly of RLC SDUs (only for UM and AM data transfer))

[0052] - Re-segmentation function (Re-segmentation of RLC data PDUs (only for AM data transfer))

[0053] - Reordering function (Reordering of RLC data PDUs (only for UM and AM data transfer)

[0054] - Duplicate detection function (only for UM and AM data transfer)

[0055] - Error detection function (Protocol error detection (only for AM data transfer))

[0056] - RLC SDU deletion function (RLC SDU discard (only for UM and AM data transfer))

[0057] RLC re-establishment function

[0058] MAC (2-15, 2-30) is connected to multiple RLC layer devices configured in a terminal and can perform operations to multiplex RLC PDUs into MAC PDUs and demultiplex RLC PDUs from MAC PDUs. The main functions of MAC can be summarized as follows.

[0059] - Mapping function (Mapping between logical channels and transport channels)

[0060] - 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)

[0061] - Scheduling information reporting function

[0062] - HARQ function (Error correction through HARQ)

[0063] - Priority handling between logical channels of one UE

[0064] - Priority handling between UEs by means of dynamic scheduling

[0065] - MBMS service identification function

[0066] - Transport format selection function

[0067] - Padding

[0068] The physical layer (2-20, 2-25) can perform the operation of channel coding and modulating upper layer data, making it into OFDM symbols and transmitting it to the wireless channel, or demodulating OFDM symbols received through the wireless channel and channel decoding them to transmit them to the upper layer.

[0069] Figure 3 is a diagram illustrating the structure of a next-generation mobile communication system.

[0070] Referring to FIG. 3, the wireless access network of a next-generation mobile communication system (hereinafter 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).

[0071] In FIG. 3, the NR gNB (3-10) can correspond to the eNB (Evolved Node B) of the 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 the 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 the NR NB (3-10) can handle this scheduling. A single NR gNB can control multiple cells. In the next-generation mobile communication system, to achieve ultra-high-speed data transmission compared to standard LTE, a bandwidth exceeding the standard maximum bandwidth may be applied. Additionally, Orthogonal Frequency Division Multiplexing (OFDM) can be used as the wireless access technology, and beamforming technology can be additionally incorporated. In addition, an Adaptive Modulation & Coding (hereinafter AMC) method may be applied to determine the modulation scheme and 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 configuration. The NR CN 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 the LTE system, and the NR CN can be connected to the MME (3-25) via a network interface. The MME can be connected to the LTE base station eNB (3-30).

[0072] FIG. 4 is a diagram showing the wireless protocol structure of a next-generation mobile communication system to which the present invention can be applied.

[0073] Referring to FIG. 4, the wireless protocol of the next-generation mobile communication system consists of the 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) at the terminal and the NR base station, respectively.

[0074] The main functions of NR SDAP (4-01, 4-45) may include some of the following functions.

[0075] - User data transfer function (transfer of user plane data)

[0076] - Mapping function between a QoS flow and a DRB for both DL and UL for uplink and downlink

[0077] - Marking QoS flow ID in both DL and UL packets for uplink and downlink

[0078] - Function to map reflective QoS flow to data bearers for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0079] For SDAP layer devices, the terminal may receive a Radio Resource Control (RRC) message indicating whether to use the header of the SDAP layer device or to use the functions of the SDAP layer device for each PDCP layer device, for each bearer, or for each logical channel. If the SDAP header is configured, the terminal may be instructed to update or reset the mapping information for the uplink and downlink QoS flows and data bearers using the 1-bit NAS reflective QoS indicator and the 1-bit AS reflective QoS indicator of the SDAP header. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used for data processing priorities, scheduling information, etc., to support seamless service.

[0080] The main functions of NR PDCP (4-05, 4-40) may include some of the following functions.

[0081] - Header compression and decompression features (ROHC only)

[0082] - User data transfer function (Transfer of user data)

[0083] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0084] - Out-of-sequence delivery of upper layer PDUs

[0085] - Reordering function (PDCP PDU reordering for reception)

[0086] - Duplicate detection function (Duplicate detection of lower layer SDUs)

[0087] - Retransmission of PDCP SDUs

[0088] - Encryption and decryption functions (Ciphering and deciphering)

[0089] - Timer-based SDU discard in uplink.

[0090] In the above description, the reordering function of the NR PDCP device may refer to a function that reorders PDCP PDUs received from a lower layer in order based on the PDCP SN (sequence number). The reordering function of the NR PDCP device may include a function that transmits data to an upper layer in the reordered order, or a function that transmits it immediately without considering the order, a function that records lost PDCP PDUs by reordering, a function that reports the status of lost PDCP PDUs to the transmitting side, and a function that requests retransmission of lost PDCP PDUs.

[0091] The main functions of NR RLC(4-10, 4-35) may include some of the following functions.

[0092] - Data transfer function (Transfer of upper layer PDUs)

[0093] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0094] - Out-of-sequence delivery of upper layer PDUs

[0095] - ARQ function (Error Correction through ARQ)

[0096] - Concatenation, segmentation, and reassembly functions of RLC SDUs

[0097] - Re-segmentation function (Re-segmentation of RLC data PDUs)

[0098] - Reordering function (Reordering of RLC data PDUs)

[0099] - Duplicate detection

[0100] - Error detection function (Protocol error detection)

[0101] - RLC SDU discard function

[0102] RLC re-establishment function

[0103] In the above description, the in-sequence delivery function of the NR RLC device may refer to the function of delivering RLC SDUs received from a lower layer to an upper layer in sequence. In the case where a single RLC SDU is received divided into multiple RLC SDUs, the in-sequence delivery function of the NR RLC device may include the function of reassembling and delivering them.

[0104] The in-sequence delivery function of the NR RLC device may include a function to rearrange received RLC PDUs based on an RLC SN (sequence number) or PDCP SN (sequence number), a function to record lost RLC PDUs by rearranging the order, a function to report the status of lost RLC PDUs to the transmitting side, and a function to request retransmission of lost RLC PDUs.

[0105] The in-sequence delivery function of the NR RLC device may include a function that, in the event of a lost RLC SDU, delivers only the RLC SDUs prior to the lost RLC SDU in order to the upper layer.

[0106] 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.

[0107] 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.

[0108] The NR RLC device can process RLC PDUs in the order they are received, regardless of the sequence number (out-of-sequence delivery), and deliver them to the NR PDCP device.

[0109] When an NR RLC device receives a segment, it can receive segments stored in a buffer or to be received later, reconstruct them into a complete RLC PDU, and then transmit it to an NR PDCP device.

[0110] The NR RLC layer may not include a concatenation function, and the function may be performed by the NR MAC layer or replaced by the multiplexing function of the NR MAC layer.

[0111] 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. 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. 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.

[0112] The NR MAC (4-15, 4-30) can be connected to multiple NR RLC layer devices configured in a terminal, and the main functions of the NR MAC may include some of the following functions.

[0113] - Mapping function (Mapping between logical channels and transport channels)

[0114] - Multiplexing and demultiplexing functions (Multiplexing / demultiplexing of MAC SDUs)

[0115] - Scheduling information reporting function

[0116] - HARQ function (Error correction through HARQ)

[0117] - Priority handling between logical channels of one UE

[0118] - Priority handling between UEs by means of dynamic scheduling

[0119] - MBMS service identification function

[0120] - Transport format selection function

[0121] - Padding

[0122] The NR PHY layer (4-20, 4-25) can perform the operation of channel coding and modulating upper layer data, creating OFDM symbols and transmitting them to the wireless channel, or demodulating OFDM symbols received through the wireless channel and channel decoding them to transmit them to the upper layer.

[0123] FIG. 5 is a block diagram illustrating the structure of a terminal according to one embodiment of the present invention.

[0124] Referring to the drawing above, the terminal includes 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).

[0125] The RF processing unit (5-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (5-10) up-converts the baseband signal provided by the baseband processing unit (5-20) into an RF band signal, transmits it through an antenna, and down-converts the 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 the drawing, the terminal may be equipped with multiple antennas. Additionally, the RF processing unit (5-10) may include multiple RF chains. Furthermore, the RF processing unit (5-10) may perform beamforming. For the above 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. In addition, the RF processing unit can perform MIMO and can receive multiple layers when performing MIMO operation.

[0126] The baseband processing unit (5-20) performs 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) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (5-20) restores 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 OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (5-20) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT (inverse fast Fourier transform) operation and CP (cyclic prefix) insertion. Additionally, upon receiving data, the baseband processing unit (5-20) divides the baseband signal provided by the RF processing unit (5-10) into OFDM symbol units, restores the signals mapped to subcarriers through a fast Fourier transform (FFT), and then restores the received bit sequence through demodulation and decoding.

[0127] The baseband processing unit (5-20) and the RF processing unit (5-10) 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, the different wireless access technologies may include wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), etc. In addition, the above different frequency bands may include super high frequency (SHF) bands (e.g., 2 NRHz, NRHz) and millimeter wave (e.g., 60 GHz) bands.

[0128] The storage unit (5-30) stores data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the storage unit (5-30) can store information related to a second connection node that performs wireless communication using a second wireless connection technology. Additionally, the storage unit (5-30) provides the stored data upon request from the control unit (5-40).

[0129] The control unit (5-40) controls the overall operations of the terminal. For example, the control unit (5-40) transmits and receives signals through the baseband processing unit (5-20) and the RF processing unit (5-10). Additionally, the control unit (5-40) writes and reads data to and from the 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.

[0130] FIG. 6 is a block diagram showing the configuration of an NR base station according to one embodiment of the present invention.

[0131] As illustrated in the drawing above, 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).

[0132] The RF processing unit (6-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. The RF processing unit (6-10) upconverts the baseband signal provided by the baseband processing unit (6-20) into an RF band signal, transmits it through an antenna, and downconverts the 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 the drawing, the first connection node 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 above RF processing unit can perform down-to-down MIMO operation by transmitting one or more layers.

[0133] The baseband processing unit (6-20) performs 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) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (6-20) restores 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) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT operation and CP insertion. Additionally, upon receiving data, the baseband processing unit (6-20) divides the baseband signal provided by the RF processing unit (6-10) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operations, and then restores 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.

[0134] The backhaul communication unit (6-30) provides an interface for communicating with other nodes within the network. The backhaul communication unit (6-30) converts a bit sequence transmitted from the main base station to other nodes, such as an auxiliary base station or a core network, into a physical signal, and converts a physical signal received from the other nodes into a bit sequence.

[0135] 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 bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (6-40) can store information that serves as a criterion for determining whether to provide multiple connections to the terminal or to disconnect them. Furthermore, the storage unit (6-40) provides the stored data upon the request of the control unit (6-50).

[0136] The control unit (6-50) controls the overall operations of the base station. For example, the control unit (6-50) transmits and receives 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) writes and reads data to and from the storage unit (6-40). To this end, the control unit (6-50) may include at least one processor.

[0137] Generally, in NR, when adding an Scell, once the network knows that the target cell corresponds to a specific TAG (timing advance group) already configured on the terminal, the terminal can use the value corresponding to the specific TAG as the TA value by indicating the specific TAG. If the target cell is not identical to any existing TAG, the terminal adds the Scell ​​in the RRC message but waits to receive a command via PDCCH from the SpCell (Special Cell) to perform a RACH to the target Scell, while unable to perform UL transmission due to the absence of a TA. If such a command is received, the terminal can perform a RACH on the target Scell ​​to obtain the TA value.

[0138] The above SpCell is a serving cell configured for each MAC (Medium Access Control) entity; if Dual Connectivity is not configured, it refers to a PCell (Primary Cell), and if Dual Connectivity is configured, it refers to a PCell of the MCG (Master Cell Group) or a PSCell (Primary Secondary Cell) of the SCG (Secondary Cell Group), depending on the cell group to which the MAC entity belongs.

[0139] The present invention aims to omit a random access procedure (e.g., RACH operation) by applying a method for obtaining a TA value based on terminal measurement to the Scell ​​addition operation when the target cell is not identical to any previously set TAG.

[0140] In the acquisition of TA values ​​based on terminal measurement, the terminal can first calculate the TA value for a cell that has been instructed to have a TA value, and if it knows the DL timing value of another cell based on the DL timing of that cell, the terminal can calculate the TA value for that cell itself. This method enables autonomous TA calculation of TA values ​​in the case of specific LTM settings in NR, when an idle / inactive mode terminal intends to perform SRS transmission during positioning operations, or due to beam movement in high speed trains.

[0141] For this operation, the terminal must know the TA value of the reference cell, continuously recognize the DL timing of the reference cell, and, when adding the target cell, measure and recognize the DL of the corresponding cell. To meet these conditions, the network must deliver to the terminal the cell corresponding to the UE measurement-based TA measurement target cell, considering the current SpCell as a reference.

[0142] The following options are possible for transmitting this cell information.

[0143] Opt 1. Method to pass to system information of an already added serving cell

[0144] The system information of the serving cell may broadcast information about target cells that can be used as references when performing UE-based TA measurement on this cell. This information may be transmitted by being included in a specific SIB. This cell information may consist of a combination of PCI and AFRCN and / or CGI information, and may include information on multiple cells. Additionally, cells using the same TA as the serving cell may be excluded.

[0145] Opt 2. Method of transmitting via RRC dedicated messages when configuring a Spcell or the first connected cell

[0146] In the case of the SpCell connected to the terminal, information about target cells that can be used as reference cells for UE-based TA measurement can be transmitted in the RRC message (e.g., RRCReconfiguration message, RRC setup message, RRC reestablishment message, RRC resume message) that transmits the settings of this cell. In this case, too, it can be provided in the form of a combination of PCI and AFRCN for each cell.

[0147] Opt 3. Method of transmission included in and linked to the serving cell's measurement configuration

[0148] After the terminal connects to the SpCell, it can receive a measurement for a specific purpose. In this case, regarding specific cells existing at a frequency corresponding to the measurement object among the measurement configuration information, if the cell is a target cell capable of performing a UE-based TA measurement method using the current SpCell as a reference, information about the target cell can be provided through a cell-specific indicator.

[0149] This method has the advantage that the terminal must know the DL timing of the target cell when the UE-based TA measurement method is transmitted in conjunction with configuration information that instructs DL measurement for the cells, so the network does not have to transmit a separate measurement configuration for UE-based TA measurement to the terminal later or previously.

[0150] Opt 4. Method for including Scell ​​addition in messages

[0151] In response to a command to add an Scell, reference cell information for UE-based TA measurements for the added cell may be transmitted. The reference cell may be one of the serving cells currently configured for the terminal. To this end, the reference cell may be indicated by a serving cell ID or a TAG ID.

[0152] Opt 5. Method to include and transmit the added Scell ​​activation MAC CE.

[0153] When Scell ​​is deactivated during Scell ​​addition, a valid TA is not immediately required. Subsequently, when activation is performed, the corresponding activation signal (e.g., Scell ​​activation MAC CE) may include not only the index of the existing target cell for activation but also an indicator to perform UE-based TA measurement. Reference cell information may also be included. In this case, a TAG ID or serving cell index / ID may be indicated as the reference cell.

[0154] The network can instruct the terminal during Scell ​​addition through the PCI and frequency information of the addition target cell. Additionally, if the same TA as a specific cell among the previously configured serving cells is used, the network can instruct the terminal to use the TAG (TA group) ID of the cell having that TA, thereby allowing the terminal to maintain the TA of the newly added Scell ​​identical to the instructed TAG. If the existing TAG ID cannot be used, a TA based on UE-based TA measurement can be instructed, and in this case, the reference cell of the UE-based TA measurement can be instructed using the methods of the above options. Through this, the terminal can determine and use the TA value of the addition target cell by comparing the TA of the reference cell, the DL timing of that cell, and the DL timing of the addition target cell.

[0155] FIG. 7 is a diagram illustrating a method of obtaining TA through UE-based TA measurement when two cells are given, according to one embodiment of the present disclosure.

[0156] In order for a terminal to obtain the initial transmit timing of Cell 1 (710), the base station can estimate the TA through preamble transmission via RACH. Then, the base station can transmit the estimated TA to the terminal via RAR. Upon receiving the value for the TA, the terminal can obtain and retain the TA of the corresponding cell. Subsequently, in order to obtain the TA of another cell, for example, cell 2 (720), the base station of cell 1 (710) and the base station of cell 2 (720) must first recognize each other whether they are cells to which UE-based TA measurement can be applied. Cases where UE-based TA measurement can be applied may include, for example, intra-band co-located cells. If Cell 1 (710) and cell 2 (720) are cells in this relationship, the TA value in cell 2 (720) can be obtained by comparing the DL timing of cell 1 and the DL timing of cell 2 and adding the difference to the TA value of cell 1 (710). In the process of obtaining the TA value of cell 2 (720) in this way, there may be a time error in DL reception and UL reception at the terminal and base station, and an operation to resolve and correct such time terms may be added.

[0157] FIG. 8 is a sequence diagram for specifically explaining target cell information transfer opt 1 of UE-based TA measurement according to one embodiment of the present disclosure.

[0158] For the embodiment illustrated in FIG. 8, the base station of cell 1 (810) and the base station of cell 2 (820) already recognize through each other's signals that they are cells capable of applying the UE-based TA measurement method to each other.

[0159] Cell 1 (810) can broadcast information about target cells that can be used as references when performing UE-based TA measurement methods on cell 1 (810) through its system information. The information may be transmitted by being included in a specific SIB. According to one embodiment, the information about the cells may consist of a combination of PCI and AFRCN and / or CGI information, and may include information about multiple cells. Additionally, cells using the same TA as the serving cell may be excluded.

[0160] For example, the terminal (800) that has obtained the above information connects to the cell as a SpCell, obtains a TA value through RACH, and receives TAG ID 0. After that, the terminal (800) can transmit a capability instruction to the base station of cell 1 (810) that there is a UE-based TA measurement or a UE-based TA measurement-based Scell ​​addition function.

[0161] The terminal (800) can perform normal data transmission and reception with the base station of cell 1 (810).

[0162] The base station of cell 1 (810) can instruct the terminal (800) to a measurement configuration for measuring the signal strength of Scell ​​candidate cells.

[0163] When the terminal (800) receives the above measurement settings, it can perform a measurement corresponding to the relevant frequency and transmit the result to the base station of cell 1 (810).

[0164] Based on the above measurement report, cell 1 (810) may decide to add cell 2 (820) as a secondary cell. According to one embodiment, cell 1 (810) may instruct Scell ​​addition in an RRCReconfiguration message and transmit a configuration including PCI and frequency information of cell 2 (820). Additionally, cell 1 (810) may transmit TAG id 1 for the TA of cell 2 (820). Additionally, cell 1 (810) may instruct Scell ​​to be activated as an initial state.

[0165] The terminal (800) that receives the above message can add an Scell. Also, since the initial state of the Scell ​​is activated, it may attempt to acquire a TA value from the beginning. Also, since the TAG ID was not previously set and maintained (for example, number 0 existed, but number 1 did not), the terminal (800) may recognize / judge / decide that it needs to acquire a new TA for the corresponding target cell. If cell 2 (820) is in the list of target cells capable of UE-based TA measurement transmitted from cell 1 (810), the terminal (800) can check whether it exists, and if it does, the terminal (800) can use cell 1 (810) as a reference to perform DL measurement of the additional target cell and calculate the TA value of the corresponding target cell, cell 2 (820). Then, the terminal (800) can maintain and use the TA value corresponding to TAG ID 1. In this case, the TAT for Tag 1 may not operate. (Alternatively, the TAT can be started by setting the timer value to infinity.)

[0166] The above TA is acquired without a RACH process to the target cell, and the terminal (800) can perform normal data transmission / reception with the Scell ​​(the above Cell 2 (820)).

[0167] As an additional embodiment, after the terminal acquires the TA, the terminal may complete the application of the configuration information of the RRCReconfiguration message that additionally instructs Scell ​​addition with activation. Then, the terminal may transmit the RRCReconfigurationComplete message to the network. In this case, the RRCReconfigurationComplete message may signify that the acquisition of the Scell's TA has expired, and through the message, the Scell ​​can perform data scheduling. Therefore, after receiving the RRCReconfigurationComplete message from the network, the terminal and the network (e.g., Pcell, Scell) can perform normal data transmission and reception. Alternatively, as a signal indicating the completion of the terminal's acquisition of the Scell's TA in the above method, the terminal may send at least one of the signals, such as the acquisition of the Scell's TA or the completion of UL synchronization, to the Pcell via UCI or UL MAC CE. Alternatively, the terminal may notify the Scell ​​that the terminal has completed UL synchronization by transmitting a UCI, UL MAC CE, or dummy UL (e.g., random UL data) to the Scell. In this case, the UCI or UL MAC CE may include information on the acquired TA value. As another method, after transmitting an RRCReconfiguration message indicating the Scell ​​addition with activation, the base station may activate an internal timer. Based on the timer, if a specific time elapses and no random access by the terminal to the Scell ​​is performed during that time, the terminal recognizes that the Scell's UL synchronization has been achieved and may perform scheduling to the Scell.

[0168] FIG. 9 is a sequence diagram for specifically explaining target cell information transfer opt 2 of UE-based TA measurement according to one embodiment of the present disclosure.

[0169] For the embodiment illustrated in FIG. 9, the base station of cell 1 (910) and the base station of cell 2 (920) already recognize through each other's signals that they are cells capable of applying the UE-based TA measurement method to each other.

[0170] The terminal (900) can connect to cell 1 (910) as a SpCell, obtain a TA value through Rach, and start a TAT timer. Subsequently, it is assumed that the TAG ID 0 of the corresponding SpCell, e.g., cell 1 (910), is received via RRCReconfiguration, as an example. The message may additionally include information on target cells capable of performing UE-based TA measurements using cell 1 (910) as a reference. The information may include PCI, AFRCN, and / or CGI information of the target cells.

[0171] After that, the terminal (900) can transmit a capability instruction to the base station of cell 1 (910) that there is a UE-based TA measurement or a UE-based TA measurement-based Scell ​​addition function.

[0172] The terminal (900) can perform normal data transmission and reception with the base station of cell 1 (910).

[0173] The base station of cell 1 (910) can instruct the terminal (900) to a measurement configuration for measuring the signal strength of Scell ​​candidate cells.

[0174] When the terminal (900) receives the measurement configuration, it can perform a measurement corresponding to the relevant frequency and transmit the result to the base station of cell 1 (910).

[0175] Based on the above measurement report, cell 1 (910) may decide to add cell 2 (920) as a secondary cell. According to one embodiment, cell 1 (910) may instruct Scell ​​addition in an RRCReconfiguration message and transmit a configuration including PCI and frequency information of cell 2 (920). Additionally, cell 1 (910) may transmit TAG id 1 for the TA of cell 2 (920). Additionally, cell 1 (910) may instruct Scell ​​to be activated as an initial state.

[0176] The terminal (900) that receives the above message can add an Scell. Also, since the initial state of the Scell ​​is activated, it may attempt to acquire a TA value from the beginning. Also, since the TAG ID was not previously set and maintained (for example, number 0 existed, but number 1 did not), the terminal (900) may recognize / judge / decide that it needs to acquire a new TA for the corresponding target cell. The terminal (900) can check whether cell 2 (920) is in the list of target cells capable of UE-based TA measurement included in the RRCReconfiguration message transmitted from cell 1 (910), and if it is, the terminal (900) can use cell 1 (910) as a reference to perform DL measurement of the additional target cell and calculate the TA value of the corresponding target cell, cell 2 (920). And, the terminal (900) can maintain and use the TA value corresponding to TAG ID 1. In this case, the TAT for Tag 1 may not operate. (Or the TAT may start by setting the timer value to infinity.)

[0177] The above TA is acquired without a RACH process to the target cell, and the terminal (900) can perform normal data transmission / reception with the Scell ​​(the above Cell 2 (920)).

[0178] As an additional embodiment, after the terminal acquires the TA, the terminal may complete the application of the configuration information of the RRCReconfiguration message that additionally instructs Scell ​​addition with activation. Then, the terminal may transmit the RRCReconfigurationComplete message to the network. In this case, the RRCReconfigurationComplete message may signify that the acquisition of the Scell's TA has expired, and through the message, the Scell ​​can perform data scheduling. Therefore, after receiving the RRCReconfigurationComplete message from the network, the terminal and the network (e.g., Pcell, Scell) can perform normal data transmission and reception. Alternatively, as a signal indicating the completion of the terminal's acquisition of the Scell's TA in the above method, the terminal may send at least one of the signals, such as the acquisition of the Scell's TA or the completion of UL synchronization, to the Pcell via UCI or UL MAC CE. Alternatively, the terminal may notify the Scell ​​that the terminal has completed UL synchronization by transmitting a UCI, UL MAC CE, or dummy UL (e.g., random UL data) to the Scell. In this case, the UCI or UL MAC CE may include information on the acquired TA value. As another method, after transmitting an RRCReconfiguration message indicating the Scell ​​addition with activation, the base station may activate an internal timer. Based on the timer, if a specific time elapses and no random access by the terminal to the Scell ​​is performed during that time, the terminal recognizes that the Scell's UL synchronization has been achieved and may perform scheduling to the Scell.

[0179] FIG. 10 is a sequence diagram for specifically explaining target cell information transfer opt 3 of UE-based TA measurement according to one embodiment of the present disclosure.

[0180] For the embodiment illustrated in FIG. 10, the base station of cell 1 (1010) and the base station of cell 2 (1020) already recognize through each other's signals that they are cells capable of applying each other's UE-based TA measurement method.

[0181] The terminal (1000) can connect to cell 1 (1010) as a SpCell, obtain a TA value through Rach, and start a TAT timer. Afterwards, as an example, assume that the TAG ID 0 of the corresponding SpCell, for example, cell 1 (1010), is received via RRCReconfiguration.

[0182] After that, the terminal (1000) can transmit a capability instruction to the base station of cell 1 (1010) that there is a UE-based TA measurement or a UE-based TA measurement-based Scell ​​addition function.

[0183] The terminal (1000) can perform normal data transmission and reception with the base station of cell 1 (1010).

[0184] The base station of cell 1 (1010) may instruct the terminal (1000) to a measurement configuration for measuring the signal strength of Scell ​​candidate cells. The message may additionally include information on target cells capable of performing UE-based TA measurement with cell 1 (1010) as a reference. Among the cells existing at the frequency associated with the measurement object in the measurement configuration information, the information may consist of a UE-based TA measurement capability indicator for each possible cell and PCI, AFRCN, and / or CGI information for the corresponding target cells.

[0185] When the terminal (1000) receives the measurement configuration, it can perform a measurement corresponding to the relevant frequency and transmit the result of the measurement to the base station of cell 1 (1010).

[0186] Based on the above measurement report, cell 1 (1010) may decide to add cell 2 (1020) as a secondary cell. According to one embodiment, cell 1 (1010) may instruct Scell ​​addition in an RRCReconfiguration message and transmit a configuration including PCI and frequency information of cell 2 (1020). Additionally, cell 1 (1010) may transmit TAG id 1 for the TA of cell 2 (1020). Additionally, cell 1 (1010) may instruct Scell ​​to be activated as an initial state.

[0187] The terminal (1000) that receives the above message can add an Scell. Also, since the initial state of the Scell ​​is activated, it may attempt to acquire a TA value from the beginning. Also, since the TAG ID was not previously set and maintained (for example, number 0 existed, but number 1 did not), the terminal (1000) may recognize / judge / decide that it needs to acquire a new TA for the corresponding target cell. The terminal (1000) can check whether cell 2 (1020) exists in the list of target cells capable of UE-based TA measurement included in the measurement configuration information of the RRCReconfiguration message transmitted from cell 1 (1010). If it exists, the terminal (1000) can use cell 1 (1010) as a reference to perform a DL measurement of the additional target cell and calculate the TA value of the corresponding target cell. And, the terminal (1000) can maintain and use the TA value corresponding to TAG ID 1. In this case, the TAT for Tag 1 may not operate. (Or the TAT may start by setting the timer value to infinity.)

[0188] The above TA is acquired without a RACH process to the target cell, and the terminal (1000) can perform normal data transmission / reception with the Scell ​​(the above Cell 2 (1010)).

[0189] As an additional embodiment, after the terminal acquires the TA, the terminal may complete the application of the configuration information of the RRCReconfiguration message that additionally instructs Scell ​​addition with activation. Then, the terminal may transmit the RRCReconfigurationComplete message to the network. In this case, the RRCReconfigurationComplete message may signify that the acquisition of the Scell's TA has expired, and through the message, the Scell ​​can perform data scheduling. Therefore, after receiving the RRCReconfigurationComplete message from the network, the terminal and the network (e.g., Pcell, Scell) can perform normal data transmission and reception. Alternatively, as a signal indicating the completion of the terminal's acquisition of the Scell's TA in the above method, the terminal may send at least one of the signals, such as the acquisition of the Scell's TA or the completion of UL synchronization, to the Pcell via UCI or UL MAC CE. Alternatively, the terminal may notify the Scell ​​that the terminal has completed UL synchronization by transmitting a UCI, UL MAC CE, or dummy UL (e.g., random UL data) to the Scell. In this case, the UCI or UL MAC CE may include information on the acquired TA value. As another method, after transmitting an RRCReconfiguration message indicating the Scell ​​addition with activation, the base station may activate an internal timer. Based on the timer, if a specific time elapses and no random access by the terminal to the Scell ​​is performed during that time, the terminal recognizes that the Scell's UL synchronization has been achieved and may perform scheduling to the Scell.

[0190] FIG. 11 is a sequence diagram for specifically explaining target cell information transfer opt 4 of UE-based TA measurement according to one embodiment of the present disclosure.

[0191] For the embodiment illustrated in FIG. 11, the base station of cell 1 (1110) and the base station of cell 2 (1120) already recognize through each other's signals that they are cells capable of applying each other's UE-based TA measurement method.

[0192] The terminal (1100) can connect to cell 1 (1110) as a SpCell, obtain a TA value through Rach, and start a TAT timer. Afterwards, as an example, assume that the TAG ID 0 of the corresponding SpCell, for example, cell 1 (1110), is received via RRCReconfiguration.

[0193] After that, the terminal (1100) can transmit a capability instruction to the base station of cell 1 (1110) that there is a UE-based TA measurement or a Scell ​​addition function based on UE-based TA measurement.

[0194] The terminal (1100) can perform normal data transmission and reception with the base station of cell 1 (1110).

[0195] The base station of cell 1 (1110) can instruct the terminal (1100) to a measurement configuration for measuring the signal strength of Scell ​​candidate cells.

[0196] When the terminal (1100) receives the measurement configuration, it can perform a measurement corresponding to the relevant frequency and transmit the result to the base station of cell 1 (1110).

[0197] Based on the above measurement report, cell 1 (1110) may decide to add cell 2 (1120) as a secondary cell. According to one embodiment, cell 1 (1110) may instruct Scell ​​addition in an RRCReconfiguration message and transmit a configuration including PCI and frequency information of cell 2 (1120). Additionally, cell 1 (1110) may transmit TAG id 1 for the TA of cell 2 (1120). Additionally, cell 1 (1110) may instruct the initial state of the Scell ​​to be activated. The message may additionally include an indicator indicating that the cell 2 (1120) can obtain a TA through UE-based TA measurement, and may include reference cell information to be used in that case. In this embodiment, cell 1 (1110) may be signaled as defined as the reference cell. Additionally, when indicating a reference cell, if one of the current serving cells is indicated, a serving cell index or SpCell index or indicator may be considered. According to one example, instead of a list of target cells using cell 1 (1110) as a reference, a reference cell for an additional target Scell ​​may be indicated.

[0198] The terminal (1100) that receives the above message can add an Scell. Also, since the initial state of the Scell ​​is activated, it may attempt to acquire a TA value from the beginning. Additionally, since the TAG ID was not previously set and maintained (for example, number 0 existed, but number 1 did not), the terminal (1100) may recognize / judge / decide that it needs to acquire a new TA for the corresponding target cell. Since cell 1 (1110) is indicated as a reference for UE-based TA measurement in the Scell ​​addition message of cell 2 (1120), the terminal (1100) can perform a DL measurement of the target cell to be added using cell 1 (1110) as a reference and calculate the TA value of the corresponding target cell. Then, the terminal (1100) can maintain and use the TA value corresponding to TAG ID 1. In this case, the TAT for Tag 1 may not operate. (Alternatively, TAT can be started by setting the timer value to infinity)

[0199] The above TA is acquired without a RACH process to the target cell, and the terminal (1100) can perform normal data transmission / reception with the Scell ​​(the above Cell 2 (1120)).

[0200] As an additional embodiment, after the terminal acquires the TA, the terminal may complete the application of the configuration information of the RRCReconfiguration message that additionally instructs Scell ​​addition with activation. Then, the terminal may transmit the RRCReconfigurationComplete message to the network. In this case, the RRCReconfigurationComplete message may signify that the acquisition of the Scell's TA has expired, and through the message, the Scell ​​can perform data scheduling. Therefore, after receiving the RRCReconfigurationComplete message from the network, the terminal and the network (e.g., Pcell, Scell) can perform normal data transmission and reception. Alternatively, as a signal indicating the completion of the terminal's acquisition of the Scell's TA in the above method, the terminal may send at least one of the signals, such as the acquisition of the Scell's TA or the completion of UL synchronization, to the Pcell via UCI or UL MAC CE. Alternatively, the terminal may notify the Scell ​​that the terminal has completed UL synchronization by transmitting a UCI, UL MAC CE, or dummy UL (e.g., random UL data) to the Scell. In this case, the UCI or UL MAC CE may include information on the acquired TA value. As another method, after transmitting an RRCReconfiguration message indicating the Scell ​​addition with activation, the base station may activate an internal timer. Based on the timer, if a specific time elapses and no random access by the terminal to the Scell ​​is performed during that time, the terminal recognizes that the Scell's UL synchronization has been achieved and may perform scheduling to the Scell.

[0201] FIG. 12 is a sequence diagram for specifically explaining the target cell information transfer opt 5 of UE-based TA measurement according to one embodiment of the present disclosure.

[0202] For the embodiment illustrated in FIG. 12, the base station of cell 1 (1210) and the base station of cell 2 (1220) already recognize through each other's signals that they are cells capable of applying each other's UE-based TA measurement method.

[0203] The terminal (1200) can connect to cell 1 (1210) as a SpCell, obtain a TA value through Rach, and start a TAT timer. Afterwards, as an example, assume that the TAG ID 0 of the corresponding SpCell, for example, cell 1 (1210), is received via RRCReconfiguration.

[0204] After that, the terminal (100) can transmit a capability instruction to the base station of cell1 (1210) that there is a UE-based TA measurement or a UE-based TA measurement-based Scell ​​addition function.

[0205] The terminal (1200) can perform normal data transmission and reception with the base station of cell 1 (1210).

[0206] The base station of cell 1 (1210) can instruct the terminal (1200) to a measurement configuration for measuring the signal strength of Scell ​​candidate cells.

[0207] When the terminal (1200) receives the measurement configuration, it can perform a measurement corresponding to the relevant frequency based on the measurement configuration and transmit the result to the base station of cell1 (1210).

[0208] Based on the above measurement report, cell 1 (1210) decides to add cell 2 (1220) as a secondary cell, instructs Scell ​​addition in the RRCReconfiguration message, and can transmit a configuration including PCI and frequency information of cell 2 (1220). Additionally, cell 1 (1210) can transmit TAG id 1 for the TA of cell 2 (1220). Additionally, cell 1 (1210) can instruct Scell ​​to be deactivated as its initial state.

[0209] The terminal (1200) that received the above message can add Scell. However, since it is currently in a deactivated state, there is no need to acquire TA.

[0210] Afterward, the base station of cell 2 (1220) can signal the Scell ​​Activation MAC CE to the terminal (1200) to activate the Scell. At this time, the index of the Scell ​​to be activated is included, and as a reference cell for UE-based TA measurement, the serving cell ID of Cell 1, SpCell index / id, or PCI / AFRCN combination information may be included and transmitted.

[0211] The terminal (1200) that receives the message from Cell 2 (1220) must perform activation. And, since the TAG ID was not previously set and maintained (for example, number 0 existed, but number 1 did not), the terminal (1200) can recognize that it needs to obtain a new TA for the corresponding target cell. The terminal (1200) can obtain a TA through UE-based TA measurement in the Scell ​​activation MAC CE. Since cell 1 is indicated as the reference cell at this time, the terminal (1200) can calculate the TA value of the corresponding target cell by performing a DL measurement of cell 2 (1220) using cell 1 (1210) as the reference cell. Then, the terminal (1200) can maintain and use the TA value corresponding to TAG ID 1. In this case, the TAT for Tag 1 may not operate. (Alternatively, TAT can be started by setting the timer value to infinity)

[0212] The above TA is acquired without a RACH process to the target cell, and the terminal (1200) can perform normal data transmission / reception with the Scell ​​(the above Cell 2 (1210)).

[0213] As an additional embodiment, a terminal that has received the Scell ​​activation signal may transmit a signal indicating the completion of the terminal's TA acquisition to the Scell. In this case, the terminal may send at least one of the signals, such as the Scell's TA acquisition or UL synchronization completion, to the Pcell via a UCI or UL MAC CE. Alternatively, the terminal may notify the Scell ​​of the completion of the terminal's UL synchronization by transmitting a UCI, UL MAC CE, or dummy UL (e.g., arbitrary UL data) to the Scell ​​that is the target of the acquired TA. In this case, the UCI or UL MAC CE may include information on the acquired TA value. As another method, after transmitting the Scell ​​activation signal, the base station may activate an internal timer. Based on the timer, if a specific time elapses and the terminal's random access to the Scell ​​is not performed during that time, the terminal recognizes that the Scell's UL synchronization has been achieved and may perform scheduling to the Scell.

[0214] FIG. 13 is a sequence diagram illustrating an example of a case in which, according to one embodiment of the present disclosure, after acquiring a TA in this manner, the TA of the terminal is incorrect when measured by the network and corrected based on RACH.

[0215] As described above, during Scell ​​addition, depending on the methods for acquiring the Scell's TA through UE-based TA measurement, the Scell's base station may detect that the TA value is incorrect while measuring UL transmission during data transmission / reception via the Scell's TA. For example, this is possible by detecting that the timing differs from the expected time when receiving the UL signal.

[0216] In this case, the network (e.g., the base station of cell 1 (1310) or the base station of cell 2 (1320)) can deactivate the UE-based TA measurement method and perform RACH in the following way.

[0217] Opt 1. The RRCRECONFIGURATION message may include the index of the Serving cell to be stopped.

[0218] Opt 2. DL MAC CE may include the index of the Serving cell to be stopped.

[0219] Opt 3. UCI may include the index of the Serving cell to be stopped.

[0220] Opt 4. The index of the Serving cell that is the Rach target can be included in the Rach command through the PDCCH order on the SpCell.

[0221] According to one embodiment among the above options, the terminal (1300) that receives the signal may stop the TAT for the indicated serving cell and stop the UE-based TA measurement operation (for example, the terminal may stop the operation of continuously calculating the TA value by comparing the Scell ​​measurement and the measured DL timing with the DL timing of the ref cell).

[0222] And, the terminal (1300) can perform an operation to newly acquire and maintain a TA value for the Scell ​​based on the transmission of a RACH preamble for the Scell ​​and the reception of a RAR including a TA.

[0223] FIG. 14 is a sequence diagram illustrating an example of a case in which, according to one embodiment of the present disclosure, after acquiring a TA in this manner, the TA of the terminal is incorrect when measured by the network and corrected without RACH.

[0224] As described above, during Scell ​​addition, depending on the methods for acquiring the Scell's TA through UE-based TA measurement, the Scell's base station may detect that the TA value is incorrect while measuring UL transmission during data transmission / reception via the Scell's TA. For example, this is possible by detecting that the timing differs from the expected time when receiving the UL signal.

[0225] In this case, the network (e.g., the base station of cell 2 (1320)) can directly modify the TA value of Scell ​​in the following way.

[0226] Opt 1. Absolute TA command MAC CE signal: The absolute TA value (e.g., a TA value independent of the previous N_{TA} value) and the target serving cell index may be transmitted to the above signal.

[0227] Opt 2. TA command MAC CE signal: The above signal can signal the N_{TA, offset} value, i.e., the delta value, based on the TA value maintained through the existing UE-based TA measurement, and can additionally indicate the serving cell index.

[0228] The terminal (1400) that receives the above signal may stop the TAT for the indicated serving cell and may stop the UE-based TA measurement operation (for example, the terminal (1400) may stop the operation of continuously calculating the TA value by comparing the Scell ​​measurement and the measured DL timing with the DL timing of the ref cell).

[0229] And, the terminal (1400) can perform the operation of newly acquiring and maintaining a TA value by applying the indicated absolute value or delta value to the corresponding Scell.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

Claims

1. A method performed by a terminal in a wireless communication system, A step of obtaining information about at least one neighboring cell related to a terminal-based timing advance (TA) measurement from a first cell; A step of receiving a message from the first cell, based on the measurement result of the terminal, including a second TAG (timing advance group) identifier (identity, ID) corresponding to the second cell; A step of determining whether the first TAG ID corresponding to the first cell and the second TAG ID are the same; A step of determining to obtain a TA for the second cell if, as a result of judgment, the first TAG ID and the second TAG ID are different and the second cell is included in the information regarding the neighboring cell; and A method comprising the step of obtaining a TA for the second cell.

2. In Paragraph 1, The information regarding the neighboring cell above is, Received through at least one of a system information block (SIB), a radio resource control (RRC) reconfiguration message, measurement configuration information, and a secondary cell (Scell) addition command, A method characterized by obtaining a TA for the second cell without performing a RACH (random access channel) procedure for the second cell.

3. In Paragraph 1, The method further includes the step of transmitting terminal capability information to the first cell indicating that it has the terminal-based TA measurement capability; A method characterized in that, based on the acquisition of TA for the second cell above, the timing advance timer is not driven.

4. In Paragraph 1, The method further includes the step of transmitting arbitrary uplink data to the second cell after obtaining a TA for the second cell, and A method characterized by indicating that uplink synchronization for the second cell of the terminal has been completed by the above arbitrary uplink data.

5. A method performed by a first cell in a wireless communication system, A step of transmitting information about at least one neighbor cell related to a terminal-based timing advance (TA) measurement to the terminal; A step of transmitting a first TAG (timing advance group) identifier (identity, ID) corresponding to the first cell to the terminal; and The step of transmitting to the terminal a message including a second TAG ID corresponding to a second cell based on the measurement result of the terminal; A method characterized by determining whether a first TAG ID corresponding to the first cell and the second TAG ID are the same by the terminal, and if the determination result shows that the first TAG ID and the second TAG ID are different and the second cell is included in the information regarding the neighboring cell, determining to obtain a TA for the second cell and obtaining a TA for the second cell.

6. In Paragraph 5, The information regarding the neighboring cell above is, Transmitted via at least one of a system information block (SIB), a radio resource control (RRC) reconfiguration message, measurement configuration information, and a secondary cell (Scell) addition command, A method characterized by obtaining a TA for the second cell without performing a RACH (random access channel) procedure for the second cell.

7. In Paragraph 5, The method further comprises the step of receiving terminal capability information from the terminal indicating that it has the terminal-based TA measurement capability. Based on the TA acquisition for the second cell above, the timing advance timer is not driven, and A method characterized by transmitting any uplink data to the second cell by the terminal after a TA for the second cell is obtained, and indicating that the uplink synchronization of the terminal with respect to the second cell is completed by the any uplink data.

8. In a terminal of a wireless communication system, Transmitter / receiver; and From the first cell, information about at least one neighboring cell related to a terminal-based timing advance (TA) measurement is obtained, and Based on the measurement result of the above terminal, a message including a second TAG (timing advance group) identifier (identity, ID) corresponding to the second cell is received from the first cell through the above transceiver, and Determining whether the first TAG ID corresponding to the first cell and the second TAG ID are the same, If, as a result of the judgment, the first TAG ID and the second TAG ID are different and the second cell is included in the information regarding the neighboring cell, it is decided to obtain a TA for the second cell, and A terminal comprising: a control unit that controls to acquire a TA for the second cell.

9. In Paragraph 8, The information regarding the neighboring cell above is, Received through at least one of a system information block (SIB), a radio resource control (RRC) reconfiguration message, measurement configuration information, and a secondary cell (Scell) addition command, A terminal characterized in that the TA acquisition for the second cell is acquired without performing a RACH (random access channel) procedure for the second cell.

10. In Paragraph 8, The above control unit is, Controls the transmission / reception unit to transmit terminal capability information indicating that the first cell has the terminal-based TA measurement capability, and A terminal characterized in that, based on the acquisition of a TA for the second cell above, the timing advance timer is not driven.

11. In Paragraph 8, The above control unit is, After obtaining the TA for the second cell, control to transmit arbitrary uplink data to the second cell through the transceiver, and A terminal characterized by indicating that uplink synchronization for the second cell of the terminal has been completed by the above arbitrary uplink data.

12. In a first cell of a wireless communication system, Transmitter / receiver; and Information regarding at least one neighbor cell related to terminal-based timing advance (TA) measurement is transmitted to the terminal through the transceiver, and A first TAG (timing advance group) identifier (identity, ID) corresponding to the first cell is transmitted to the terminal through the transceiver, and A control unit that controls the transmission of a message including a second TAG ID corresponding to a second cell to the terminal through the transceiver based on the measurement result of the terminal; comprising A first cell characterized by determining whether a first TAG ID corresponding to the first cell and a second TAG ID are the same by the terminal, and if the determination result shows that the first TAG ID and the second TAG ID are different and the second cell is included in the information regarding the neighboring cell, determining to obtain a TA for the second cell and obtaining a TA for the second cell.

13. In Paragraph 12, The information regarding the neighboring cell above is, Transmitted via at least one of a system information block (SIB), a radio resource control (RRC) reconfiguration message, measurement configuration information, and a secondary cell (Scell) addition command, A first cell characterized in that the TA acquisition for the second cell is acquired without performing a RACH (random access channel) procedure for the second cell.

14. In Paragraph 12, The above control unit is, A first cell characterized by controlling to receive terminal capability information indicating that the terminal-based TA measurement capability is present from the terminal through the transceiver.

15. In Paragraph 12, Based on the TA acquisition for the second cell above, the timing advance timer is not driven, and A first cell characterized by the fact that after a TA for the second cell is obtained, any uplink data is transmitted to the second cell by the terminal, and the uplink synchronization of the terminal with respect to the second cell is completed by the any uplink data.

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