Method and apparatus for inter-CU l1 / l2 layer-based mobility for secondary cell group in next generation mobile communication system

Abstract

The present disclosure relates to a method and an apparatus for inter-central unit(CU) L1 / L2 layer-based mobility (LTM) for a secondary cell group (SCG). The method performed by a source master node (S-MN) comprises the steps of: receiving, from a CU of a candidate secondary node (C-SN), SCG configuration information of LTM candidate PSCells corresponding to each CU of the C-SN; transmitting, to a terminal, an RRC reconfiguration message including the SCG configuration information and master cell group (MCG) configuration information; and receiving, from the terminal, an MN RRC reconfiguration complete message on the basis of the message.

Description

Method and device for inter-CU L1 / L2 layer-based mobility for secondary cell groups in next-generation mobile communication systems

[0001] This technology relates to the operation of base stations and terminals in mobile communication systems. More specifically, it relates to technology for mobility between terminals.

[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 the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz band (for example, the 3 terahertz (3THz) band at 95GHz) is being considered to achieve a transmission speed that is 50 times faster than 5G mobile communication technology and an ultra-low latency time that is reduced to one-tenth.

[0003] In the early stages of 5G mobile communication technology, the goal is to support services and satisfy performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). These include beamforming and massive MIMO to mitigate path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of BWP (Bidth Part), new channel coding methods such as LDPC (Low Density Parity Check) codes for large-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2). Standardization has been made for network slicing, which provides dedicated networks specialized for specific services, and pre-processing.

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

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

[0006] Once these 5G mobile communication systems are commercialized, an explosive increase in connected devices will be connected to the communication network, necessitating enhanced functionality and performance of 5G mobile communication systems and integrated operation of these connected devices. To this end, new research will be conducted on improving 5G performance and reducing complexity, supporting AI services, supporting metaverse services, and drone communications by utilizing eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0008] As described above and with the development of mobile communication systems, various services have become available, and methods for effectively providing these services are required.

[0009] As a terminal moves, a handover operation can be performed from the source cell to the target cell. When performing a handover operation, the network can instruct the terminal to use a preferred beam in the target cell based on a specific beam.

[0010] These L1 / L2 triggered cell switch operations are structured so that, from a network perspective, the DU (distributed unit) issues commands. Therefore, terminal movement is guaranteed only between DUs connected to a single CU.

[0011] In order to solve the above problem, we propose a method and device that can exchange information necessary for the movement of a terminal between a source CU, a target CU, and a DU linked to each CU, and as a result, the terminal can perform cell switching even in cells of an inter CU. In particular, in the case of SN, we propose a specific signaling system between a source SN-CU and a candidate SN CU.

[0012] The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0013] In order to solve the above problems, the present disclosure provides a method performed by a source master node (S-MN) in a communication system, the method comprising: receiving, from a central unit (CU) of at least one candidate secondary node (C-SN), secondary cell group (SCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate primary secondary cell (PSCell) corresponding to each of the at least one CU of the C-SN; generating and transmitting, to a terminal, a first radio resource control (RRC) reconfiguration message (RRC Reconfiguration Message) including SCG configuration information and Master Cell Group (MCG) configuration information of an LTM candidate PSCell corresponding to each of the at least one CU of the C-SN; And, based on the RRC reconfiguration message, it is characterized by including a step of receiving an MN RRC Reconfiguration Complete Message including an SN RRC Reconfiguration Complete Message from the terminal.

[0014] In order to solve the above problem, the present disclosure provides a method performed by a terminal in a communication system, the method comprising the steps of: receiving, from a source master node (S-MN), a first radio resource control (RRC) reconfiguration message including secondary cell group (SCG) configuration information and master cell group (MCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) triggered mobility (LTM) candidate primary secondary cell (PSCell) corresponding to each central unit (CU) of at least one candidate secondary node (C-SN); And, based on the RRC reconfiguration message, it is characterized by including a step of transmitting an MN RRC Reconfiguration Complete Message including an SN RRC Reconfiguration Complete Message to the CU of the S-MN.

[0015] In order to solve the above problems, the present disclosure provides a method performed by a source master node (S-MN) in a communication system, comprising: a transceiver for transmitting and receiving a signal; And a control unit, wherein the control unit receives, from a central unit (CU) of at least one candidate secondary node (C-SN), secondary cell group (SCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate primary secondary cell (PSCell) corresponding to each of the at least one CU of the C-SN, and generates and transmits, to a terminal, a first radio resource control (RRC) reconfiguration message (RRC Reconfiguration Message) including SCG configuration information and Master Cell Group (MCG) configuration information of an LTM candidate PSCell corresponding to each of the at least one CU of the C-SN, and, based on the RRC reconfiguration message, transmits, from the terminal, a MN RRC reconfiguration complete message (MN RRC Reconfiguration Complete Message) including an SN RRC reconfiguration complete message. It is characterized by receiving a Reconfiguration Complete Message.

[0016] In order to solve the above problems, the present disclosure provides a source master node (S-MN) in a communication system, comprising: a transceiver for transmitting and receiving signals; And a control unit, wherein the control unit receives, from a central unit (CU) of at least one candidate secondary node (C-SN), secondary cell group (SCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate primary secondary cell (PSCell) corresponding to each of the at least one CU of the C-SN, and generates and transmits, to a terminal, a first radio resource control (RRC) reconfiguration message (RRC Reconfiguration Message) including SCG configuration information and Master Cell Group (MCG) configuration information of an LTM candidate PSCell corresponding to each of the at least one CU of the C-SN, and, based on the RRC reconfiguration message, transmits, from the terminal, a MN RRC reconfiguration complete message (MN RRC Reconfiguration Complete Message) including an SN RRC reconfiguration complete message. It is characterized by receiving a Reconfiguration Complete Message.

[0017] In order to solve the above problems, the present disclosure provides a terminal in a communication system, comprising: a transceiver for transmitting and receiving signals; And a control unit, wherein the control unit receives, from a source master node (S-MN), a first radio resource control (RRC) reconfiguration message (RRC Reconfiguration Message) including secondary cell group (SCG) configuration information and master cell group (MCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate primary secondary cell (PSCell) corresponding to each central unit (CU) of at least one candidate secondary node (C-SN), and transmits, based on the RRC reconfiguration message, a MN RRC Reconfiguration Complete Message including an SN RRC Reconfiguration Complete Message to a CU of the S-MN.

[0018] According to an embodiment of the present disclosure, a terminal may not experience communication interruption when moving to a different cell.

[0019] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0020] FIG. 1 is a diagram illustrating the structure of a long term evolution (LTE) system according to one embodiment of the present disclosure.

[0021] FIG. 2 is a diagram illustrating a wireless protocol structure of a long term evolution (LTE) system according to an embodiment of the present disclosure.

[0022] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0023] FIG. 4 is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0024] FIG. 5 is a block diagram illustrating the internal structure of a terminal according to an embodiment of the present disclosure.

[0025] FIG. 6 is a block diagram illustrating the structure of a new radio (NR) base station according to one embodiment of the present disclosure.

[0026] FIG. 7A is a diagram illustrating an inter central unit (CU) secondary cell group (SCG) L1 / L2 triggered mobility (LTM) operation according to one embodiment of the present disclosure.

[0027] FIG. 7b is a diagram illustrating an inter central unit (CU) secondary cell group (SCG) L1 / L2 triggered mobility (LTM) operation according to one embodiment of the present disclosure.

[0028] FIG. 8 is a diagram illustrating the structure of a radio resource control (RRC) reconfiguration message according to one embodiment of the present disclosure.

[0029] The operating principles of the present invention will be described in detail below with reference to the attached drawings. In the following description of the present invention, detailed descriptions of known functions or components will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Furthermore, the terms described below are defined based on their functions in the present invention and may vary depending on the intentions or practices of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0030] In the following description of the present invention, detailed descriptions of known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the present invention. Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

[0031] The operating principles of the present invention are described in detail with reference to the attached diagram. The terms described below are defined based on their functions within the present invention. These terms may vary depending on the intent or custom of the user or operator, and therefore their definitions should be determined based on the overall content of this specification.

[0032] For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted. Furthermore, the dimensions of each component do not entirely reflect its actual size.

[0033] The advantages and features of the present disclosure, and methods for achieving them, will become clearer with reference to the embodiments described below in detail with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure is complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Like reference numerals designate like elements throughout the disclosure.

[0034] Certain terms used in the following description are provided to aid in understanding the present disclosure, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present disclosure.

[0035] The 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, and terms referring to various identification information are provided for convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms referring to objects with equivalent technical meanings may be used.

[0036] Hereinafter, the base station is an entity that performs resource allocation of the terminal, and may be at least one of a gNode B, an eNode B, a Node B, a BS (Base Station), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In the present disclosure, downlink (DL) refers to a wireless transmission path of a signal transmitted from a base station to a terminal, and uplink (UL) refers to a wireless transmission path of a signal transmitted from a terminal to a base station. In addition, although the LTE or LTE-A system may be described below as an example, the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, the 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included in a system to which the embodiments of the present disclosure may be applied, and 5G below may also 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, as determined by a person skilled in the art, without significantly departing from the scope of the present disclosure. It will be appreciated that each block of the processing flow diagrams and combinations of the flow diagrams can be executed by computer program instructions.

[0037] These computer program instructions may be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, so that the instructions executed by the processor of the computer or other programmable data processing apparatus create means for performing the functions described in the flowchart block(s). These computer program instructions may also be stored in a computer-available or computer-readable memory that can be directed to a computer or other programmable data processing apparatus to implement functions in a particular manner, so that the instructions stored in the computer-available or computer-readable memory can produce an article of manufacture that includes instruction means for performing the functions described in the flowchart block(s). The computer program instructions may also be installed on a computer or other programmable data processing apparatus, so that a series of operational steps are performed on the computer or other programmable data processing apparatus to create a computer-implemented process, so that the instructions executing on the computer or other programmable data processing apparatus can provide steps for performing the functions described in the flowchart block(s).

[0038] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for executing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order depending on the corresponding function. In this case, the term '~unit' used in the present embodiment means software or a hardware component such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), and the '~unit' may perform certain roles. However, the '~unit' is not limited to software or hardware. The '~unit' may be configured to be on an addressable storage medium and may be configured to execute one or more processors. Thus, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, the components and '~ units' may be implemented to reproduce one or more CPUs within a device or a secure multimedia card. Also, in an embodiment, the '~ unit' may include one or more processors.

[0039] For convenience of explanation, the present invention uses terms and names defined in the 5GS and NR standards, which are standards defined by the 3rd Generation Partnership Project (3GPP) among the existing communication standards. However, the present invention is not limited to the above terms and names and can be equally applied to wireless communication networks that follow other standards. For example, the present invention can be applied to the 3GPP 5GS / NR (5th generation mobile communication standard).

[0040] FIG. 1 is a diagram illustrating the structure of a long term evolution (LTE) system according to one embodiment of the present disclosure.

[0041] Referring to FIG. 1, as illustrated, a wireless access network of a long term evolution (LTE) system may be composed of next-generation base stations (Evolved Node Bs, hereinafter referred to as ENBs, eNBs, Node Bs or base stations) (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 equipment (UE or terminal) (1-35) may access an external network through the ENBs (1-05 to 1-20) and the S-GW (1-30).

[0042] In Fig. 1, ENBs (1-05 to 1-20) may correspond to existing Node Bs of a UMTS system. ENBs (1-05 to 1-20) are connected to UEs (1-35) via a wireless channel and may perform a more complex role than existing Node Bs. 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 that collects status information such as buffer status, available transmission power status, and channel status of UEs (1-35) and performs scheduling is required, and ENBs (1-05 to 1-20) may be responsible for this. One ENB (1-05 to 1-20) can typically control multiple cells. For example, in order to achieve a transmission rate of 100 Mbps, an LTE system may use, for example, Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology in a 20 MHz bandwidth. Additionally, an adaptive modulation and coding (AMC) method can be applied, which determines the modulation scheme and channel coding rate according to the channel condition of the terminal. The S-GW (1-30) is a device that provides a data bearer and can create or remove a data bearer according to 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.

[0043] FIG. 2 is a diagram illustrating a wireless protocol structure of a long term evolution (LTE) system according to an embodiment of the present disclosure.

[0044] Referring to FIG. 2, the wireless protocol of the LTE system may be composed of 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) in the terminal and ENB, respectively. PDCP (2-05, 2-40) may be responsible for operations such as IP header compression / decompression. The main functions of PDCP (2-05, 2-40) can be summarized as follows.

[0045] - Header compression and decompression (ROHC only)

[0046] - User data transfer function

[0047] - In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

[0048] - Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0049] - Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM)

[0050] - 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)

[0051] - Encryption and decryption functions (Ciphering and deciphering)

[0052] - Timer-based SDU discard in uplink.

[0053] 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 (2-10, 2-35) can be summarized as follows.

[0054] - Data transfer function (Transfer of upper layer PDUs)

[0055] - ARQ function (Error Correction through ARQ (only for AM data transfer))

[0056] - Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

[0057] - Re-segmentation of RLC data PDUs (only for AM data transfer)

[0058] - Reordering of RLC data PDUs (only for UM and AM data transfer)

[0059] - Duplicate detection (only for UM and AM data transfer)

[0060] - Error detection function (Protocol error detection (only for AM data transfer))

[0061] - RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

[0062] - RLC re-establishment function

[0063] MAC(2-15, 2-30) is connected to multiple RLC layer devices configured in a single terminal, and can perform the operation of multiplexing RLC PDUs into MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC(2-15, 2-30) can be summarized as follows.

[0064] - Mapping function (Mapping between logical channels and transport channels)

[0065] - 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)

[0066] - Scheduling information reporting function

[0067] - HARQ function (Error correction through HARQ)

[0068] - Priority handling between logical channels of one UE

[0069] - Priority handling between UEs by means of dynamic scheduling

[0070] - MBMS service identification function

[0071] - Transport format selection function

[0072] - Padding function

[0073] The physical layer (2-20, 2-25) can perform the operation of channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it through a wireless channel, or demodulating and channel decoding OFDM symbols received through a wireless channel and transmitting them to a higher layer.

[0074] FIG. 3 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0075] Referring to FIG. 3, a wireless access network of a next-generation mobile communication system (hereinafter referred to as NR or 5g) may be composed of a next-generation base station (New Radio Node B, hereinafter referred to as NR gNB, gNB, or NR base station) (3-10) and a next-generation radio core network (New Radio Core Network, NR CN) (3-05). A next-generation radio user equipment (New Radio User Equipment, NR UE or terminal) (3-15) may access an external network through the NR gNB (3-10) and the NR CN (3-05).

[0076] In Fig. 3, the NR gNB (3-10) can correspond to the eNB (Evolved Node B) of the existing LTE system. The NR gNB (3-10) is connected to the NR UE (3-15) via a wireless channel and can provide a service that is superior 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 that collects status information such as buffer status, available transmission power status, and channel status of the UEs (3-15) and performs scheduling is required, and the scheduling can be performed by the NR NB (3-10). One NR gNB (3-10) can control multiple cells. In the next-generation mobile communication system, in order to implement ultra-high-speed data transmission compared to the general LTE, a bandwidth exceeding the general maximum bandwidth can be applied. In addition, beamforming technology can be additionally grafted using Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology. In addition, an adaptive modulation and coding (AMC) method that determines a modulation scheme and a channel coding rate according to the channel status of the terminal may be applied. NR CN (3-05) can perform functions such as mobility support, bearer setup, and QoS setup. NR CN 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. In addition, the next-generation mobile communication system can also be linked with the LTE system, and NR CN can be connected to MME (3-25) through a network interface. MME can be connected to eNB (3-30), which is an LTE base station.

[0077] FIG. 4 is a diagram illustrating a wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0078] Referring to FIG. 4, the wireless protocol of the next-generation mobile communication system may be composed of 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) in the terminal and NR base station, respectively.

[0079] Key features of NR SDAP (4-01, 4-45) may include some of the following:

[0080] Transfer of user plane data

[0081] Mapping between a QoS flow and a DRB for both DL and UL

[0082] QoS flow ID marking function for both uplink and downlink (marking QoS flow ID in both DL and UL packets)

[0083] Ability to map relective QoS flow to data bearer for the UL SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0084] For an SDAP layer device, a terminal can be configured by a Radio Resource Control (RRC) message for each PDCP layer device, per bearer, or per logical channel, whether to use the header of the SDAP layer device or whether to use the function of the SDAP layer device. When the SDAP header is configured, the terminal can instruct the terminal to update or reset the mapping information for the QoS flow and data bearer of the uplink and downlink by using a 1-bit indicator for reflecting the Non-Access Stratum (NAS) Quality of Service (QoS) in the SDAP header (NAS reflective QoS) and a 1-bit indicator for reflecting the Access Stratum (AS) QoS in the SDAP header. The SDAP header can include QoS flow ID information indicating QoS. The QoS information can be used as data processing priority, scheduling information, etc. to support a smooth service.

[0085] The main functions of NR PDCP (4-05, 4-40) may include some of the following functions:

[0086] - Header compression and decompression (ROHC only)

[0087] - User data transfer function

[0088] - In-sequence delivery of upper layer PDUs

[0089] - Out-of-sequence delivery of upper layer PDUs

[0090] - PDCP PDU reordering for reception

[0091] - Duplicate detection of lower layer SDUs

[0092] - Retransmission function (Retransmission of PDCP SDUs)

[0093] - Encryption and decryption functions (Ciphering and deciphering)

[0094] - Timer-based SDU discard in uplink.

[0095] In the above, the reordering function of the NR PDCP device may refer to 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 may include a function of transmitting data to an upper layer in the reordered order, or a function of transmitting data directly without considering the order, a function of recording lost PDCP PDUs by reordering the order, a function of reporting a status of lost PDCP PDUs to the transmitting side, and a function of requesting retransmission of lost PDCP PDUs.

[0096] The main functions of NR RLC(4-10, 4-35) may include some of the following functions:

[0097] - Data transfer function (Transfer of upper layer PDUs)

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

[0099] - Out-of-sequence delivery of upper layer PDUs

[0100] - ARQ function (Error Correction through ARQ)

[0101] - Concatenation, segmentation and reassembly of RLC SDUs

[0102] - Re-segmentation of RLC data PDUs

[0103] - Reordering of RLC data PDUs

[0104] - Duplicate detection function

[0105] - Protocol error detection

[0106] - RLC SDU discard function

[0107] - RLC re-establishment function

[0108] In the above, the in-sequence delivery function of the NR RLC device may refer to the function of sequentially delivering RLC SDUs received from the lower layer to the upper layer. If a single RLC SDU is originally 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.

[0109] The in-sequence delivery function of the NR RLC device may include a function to reorder received RLC PDUs based on the RLC SN (sequence number) or PDCP SN (sequence number), a function to record lost RLC PDUs by reordering them, a function to report status of lost RLC PDUs to the transmitter, and a function to request retransmission of lost RLC PDUs.

[0110] The in-sequence delivery function of the NR RLC device may include a function to sequentially deliver only the RLC SDUs up to the lost RLC SDU to the upper layer when there is a lost RLC SDU.

[0111] The in-sequence delivery function of the NR RLC device may include a function to deliver all RLC SDUs received before a predetermined timer starts to the upper layer in sequence, even if there are lost RLC SDUs, if the timer has expired.

[0112] The in-sequence delivery function of the NR RLC device may include a function to deliver all RLC SDUs received up to now to the upper layer in sequence if a predetermined timer has expired, even if there are lost RLC SDUs.

[0113] An NR RLC device can process RLC PDUs in the order they are received and deliver them to an NR PDCP device, regardless of the order of the sequence number (out-of-sequence delivery).

[0114] When an NR RLC device receives a segment, it can receive segments that are stored in a buffer or will be received later, reconstruct them into a complete RLC PDU, and then transmit them to the NR PDCP device.

[0115] The NR RLC layer may not include concatenation functionality, and the functionality may be performed by the NR MAC layer or replaced by the multiplexing functionality of the NR MAC layer.

[0116] In the above, the out-of-sequence delivery function of the NR RLC device may refer to the function of directly delivering RLC SDUs received from a lower layer to an upper layer regardless of the order. The out-of-sequence delivery function of the NR RLC device may include the function of reassembling and delivering the RLC SDUs when an original RLC SDU is received fragmented into multiple RLC SDUs. The out-of-sequence delivery function of the NR RLC device may include the function of storing and arranging the RLC SN or PDCP SN of the received RLC PDUs to record the lost RLC PDUs.

[0117] NR MAC (4-15, 4-30) can be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of NR MAC can include some of the following functions.

[0118] - Mapping function (Mapping between logical channels and transport channels)

[0119] - Multiplexing / demultiplexing of MAC SDUs

[0120] - Scheduling information reporting function

[0121] - HARQ function (Error correction through HARQ)

[0122] - Priority handling between logical channels of one UE

[0123] - Priority handling between UEs by means of dynamic scheduling

[0124] - MBMS service identification function

[0125] - Transport format selection function

[0126] - Padding function

[0127] The NR PHY layer (4-20, 4-25) can perform operations such as channel coding and modulating upper layer data, converting it into OFDM symbols and transmitting it over a wireless channel, or demodulating and channel decoding OFDM symbols received over a wireless channel and transmitting them to a higher layer.

[0128] FIG. 5 is a block diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

[0129] 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), a control unit (5-40), etc.

[0130] 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 from the baseband processing unit (5-20) into an RF band signal and 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 digital to analog convertor (DAC), an analog to digital convertor (ADC), etc. In the drawing, only one antenna is shown, but 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 the above beamforming, the RF processing unit (5-10) can adjust the phase and size of each signal 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 the MIMO operation.

[0131] The baseband processing unit (5-20) above performs a conversion function between a baseband signal and a bit stream 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 a transmission bit stream. In addition, when receiving data, the baseband processing unit (5-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from 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 a transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit (5-20) divides the baseband signal provided from the RF processing unit (5-10) into OFDM symbol units, restores signals mapped to subcarriers through FFT (fast Fourier transform), and then restores the received bit string through demodulation and decoding.

[0132] 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 transmitter, a receiver, a transceiver, 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. In addition, 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), a cellular network (e.g., LTE), etc. Additionally, the different frequency bands may include a super high frequency (SHF) (e.g., 2.NRHz, NRhz) band and a millimeter wave (mm wave) (e.g., 60GHz) band.

[0133] 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 access node that performs wireless communication using a second wireless access technology. In addition, the storage unit (5-30) provides the stored data at the request of the control unit (5-40).

[0134] The above 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). In addition, the control unit (5-40) records and reads data in the storage unit (5-40). For this purpose, 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 application programs.

[0135] FIG. 6 is a block diagram illustrating the structure of a new radio (NR) base station according to an embodiment of the present disclosure.

[0136] Referring to FIG. 6, the base station may be 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), a control unit (6-50), etc.

[0137] 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) up-converts the baseband signal provided from the baseband processing unit (6-20) into an RF band signal and 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 (6-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. In the drawing, only one antenna is shown, but the first access node may have multiple antennas. In addition, the RF processing unit (6-10) may include multiple RF chains. Furthermore, the RF processing unit (6-10) may perform beamforming. For the beamforming, the RF processing unit (6-10) may adjust the phase and magnitude of each signal transmitted and received through multiple antennas or antenna elements. The above RF processing unit can perform a downlink MIMO operation by transmitting one or more layers.

[0138] The baseband processing unit (6-20) above performs a conversion function between a baseband signal and a bit stream 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 a transmission bit stream. In addition, when receiving data, the baseband processing unit (6-20) restores the reception bit stream by demodulating and decoding the baseband signal provided from the RF processing unit (6-10). For example, in the case of OFDM, when transmitting data, the baseband processing unit (6-20) generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols through IFFT operation and CP insertion. In addition, when receiving data, the baseband processing unit (6-20) divides the baseband signal provided from the RF processing unit (6-10) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operation, and then restores the received bit string 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 transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

[0139] The above backhaul communication unit (6-30) provides an interface for communicating with other nodes within the network. The above backhaul communication unit (6-30) converts a bit string transmitted from the main base station to other nodes, such as auxiliary base stations and core networks, into a physical signal, and converts a physical signal received from the other nodes into a bit string.

[0140] The storage unit (6-40) stores data such as basic programs, application programs, and configuration information for the operation of the main base station. In particular, the storage unit (6-40) can store information on bearers assigned to connected terminals, measurement results reported from connected terminals, and the like. In addition, the storage unit (6-40) can store information that serves as a judgment criterion for whether to provide or terminate multiple connections to a terminal. In addition, the storage unit (6-40) provides the stored data at the request of the control unit (6-50).

[0141] 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). In addition, the control unit (6-50) records and reads data in the storage unit (6-40). For this purpose, the control unit (6-50) may include at least one processor.

[0142] The following terms and abbreviations may be used in the specification below.

[0143] LTM: L1 / L2 triggered mobility

[0144] CU: central unit

[0145] DU: distributed unit

[0146] MCG: master cell group

[0147] MN: master node

[0148] SCG: secondary cell group

[0149] SN: secondary node

[0150] S-MN: source MN

[0151] S-SN: source SN

[0152] C-SN: candidate SN

[0153] In this disclosure, we propose operations necessary for preparing and performing LTM on inter-CU cells when a terminal performs LTM. In particular, we propose a method for performing LTM on an SCG, i.e., movement of a primary secondary cell (PSCell). Existing LTM operations assume only intra-CU operations, thus lacking inter-node signaling.

[0154] As a basic prerequisite, since the execution order of LTM is decided (or issued) by the DU, a DU ready for LTM (candidate DU, target DU) must have at least one of the following as information about all candidate cells:

[0155] - LTM candidate ID

[0156] - Mapping information between LTM candidate ID and corresponding cell ID

[0157] - Beam information to be used for each candidate (TCI state)

[0158] ■ In this case, the meaning of use may include all meanings such as a beam that is linked to a RACH occasion when performing downlink (DL) and / or uplink (UL) synchronization and / or random access channel (RACH), and / or a beam to be used for first UL data transmission. If necessary, an indicator for each case may be accompanied (or set together) to perform a cell switch.

[0159] - RACH preamble index

[0160] - synchronization signal block (SSB) index: This is the index of the SSB used to determine the RACH occasion in each candidate cell, and can mean the occasion for transmitting the RACH preamble of contention free random access (CFRA).

[0161] The above information is information that must be displayed when issuing a cell switch command MAC (medium access control) CE (control element) instruction to a candidate cell that has made an LTM decision.

[0162] As a preparatory step before the cell switch, each candidate cell will transmit CSI (channel state information) for LTM, and each DU must also possess RS (reference signal) information for the corresponding CSI. Before instructing the LTM cell switch, the source DU transmits CSI information for specific candidate cells to the UE, and the UE can measure and report the corresponding CSI RS. The source DU, which receives the CSI measurement result report from the UE, can decide whether to move to the corresponding cell and / or which beam to use. To this end, each DU may need at least one of the following information for its concerned cell.

[0163] - CSI resource settings for each candidate cell (required when transmitting L1 measurement settings to the terminal as a source DU), individual resource settings and / or setting ID for each cell, CSI resource settings for LTM, etc.

[0164] - CSI report configuration considering the CSI resources of each candidate cell above

[0165] ■ The purpose of this is that when a candidate DU creates the above information and passes it to the CU, this information can be used as the CSI report configuration within the target cell configuration (RRCReconfiguration) of the concerned cell (i.e., target cell) created by the CU.

[0166] ■ That is, when a terminal moves from another cell to this cell (concerned cell), it can be used as a CSI report configuration with that cell as the serving cell. This can be used to include it in the target cell config (configuration) without providing a separate L1 setting for subsequent LTM.

[0167] - RACH configuration and lower layer setting information to be used in the concerned cell

[0168] ■ This information is transmitted from the candidate DU to the CU, and can be written as the settings required for performing RACH within the target cell configuration of the concerned cell, the lower layer settings to be applied when moving to the cell, and / or the reference settings including them, and can be transmitted to the terminal later.

[0169] ■ In particular, some of the RACH settings can be used to include the RACH preamble index, mask, and occasion decision information in the cell switch command mac CE described above.

[0170] Based on the above-mentioned information, the inter-CU signaling system is described.

[0171] FIG. 7A and FIG. 7B are diagrams illustrating inter central unit (CU) secondary cell group (SCG) L1 / L2 triggered mobility (LTM) operation according to one embodiment of the present disclosure.

[0172] The actions at each step of the drawing are as follows.

[0173] The user equipment (UE) is connected to a source master node (MN) (or S-MN CU), receives configuration for L3 measurements and / or reports, and performs measurements on the frequency associated with the secondary node (SN) and reports them. (L3 measurement control and reports)

[0174] Through the above report, the MN (or S-MN CU) can select a candidate PSCell and perform the SN addition procedure to configure the PSCell and its corresponding SCG (SCG config). As a result, the UE can establish a dual connection (DC) with the network (e.g., S-MN CU, S-SN DU, and / or S-SN CU).

[0175] Afterwards, if the S-SN (or S-SN CU) wants to configure the LTM settings to replace the current PSCell by performing measurements according to the settings of the PCell, it can determine the LTM candidate cell. Then, it can perform LTM preparation.

[0176] 1. S-SN (or S-SN CU) determines LTM candidate cells (LTM candidate decision), and information on each LTM candidate cell can be transmitted to each C-SN (e.g., CU-SN1, CU-SN2, ...) through MN (or S-MN CU).

[0177] More specifically, the S-SN CU can determine candidate cells based on measurement results (or L3 measurement reports) received from the terminal, and transmit (or can send) information about each candidate cell to at least one C-SN (e.g., CU-SN1, CU-SN2, ...) serving each candidate cell via the MN.

[0178] The above S-SN CU can convey (or transmit) information on each candidate cell to the MN (or S-MN CU) through an SN change required message, and the SN change required message can include at least one of the following information.

[0179] A. Indicators indicating the preparation and / or initiation of LTM and / or LTM SCG (LTM preparation / initiation)

[0180] B. RRM (radio resource management) measurement result information of the terminal at the frequency of the SN band (meas result on SN freq)

[0181] C. Candidate PSCell information existing in C-SN proposed by S-SN (proposed PSCells)

[0182] i. Physical cell identifier (PCI) and / or cell group identifier (CGI) with absolute radio frequency channel number (AFRCN)

[0183] ii. C-SN gNB ID where each candidate cell exists

[0184] D. CSI resource configuration used in cells existing in S-SN among the proposed candidate cells

[0185] E. Current source DU ID

[0186] F. Request for PRACH (physical random access channel) resources used by each candidate cell

[0187] G. Request for the candidate DU of C-SN to provide the lower layer configuration for the purpose of generating the reference configuration

[0188] H. Information for intra-SN LTM already configured [optional], i.e., information about LTM candidate cells that were operating in the S-SN that are not operating in other SNs.

[0189] i. List of candidate PSCell ID confirmed / generated by S-SN

[0190] ii. List of the mapping info between LTM config ID and corresponding candidate PSCell ID (in i above) generated by S-SN

[0191] iii. CSI resource configuration per PSCell,

[0192] iv. CSI report configuration per PSCell

[0193] v. TCI states configuration per PSCell

[0194] vi. RACH config of each candidate PSCell

[0195] vii. Lower layer configuration (for generating reference config at each C-SN)

[0196] I. Information for S-SNs maintained LTM candidate cells if SN maintains [optional], i.e., information on candidate cells on the inter-SN that the S-SN maintained before the preparation step of the terminal.

[0197] i. List of candidate PSCell ID confirmed / generated by S-SN or MN and its indicator of MN or SN

[0198] ii. List of the mapping info between LTM config ID and corresponding candidate PSCell ID generated by S-SN

[0199] iii. CSI resource configuration per PSCell,

[0200] iv. CSI report configuration per PSCell

[0201] v. TCI states configuration per PSCell

[0202] vi. RACH config of each candidate PSCell

[0203] vii. Lower layer configuration (for generating reference config at each C-SN)

[0204] 2. The MN that has obtained information on the above LTM candidate cells can perform the SN Addition procedure.

[0205] More specifically, when the MN (or S-MN CU) receives the SN change required message, it may perform a separate SN Addition procedure for each C-SN of each proposed candidate PSCell (e.g., CU of C-SN1, CU of C-SN2, ...).

[0206] The SN Addition procedure may use an SN ADD request message. The SN ADD request message may include and transmit at least one of the following information for each C-SN (or CU of C-SN1, CU of C-SN2, ...).

[0207] A. Indicator indicating LTM preparation / initiation: Upon receiving this indicator, the C-SN (or CU of C-SN1, CU of C-SN2, ...) may request LTM setup for a given candidate PSCell to the DU serving the PSCell.

[0208] B. All the proposed candidate PSCell in that C-SN

[0209] i. ID of each candidate PSCell (PCI and / or CGI with AFRCN can be used)

[0210] ii. C-SN gNB ID where each candidate cell exists

[0211] iii. LTM configuration ID assigned by MN or S-SN to each candidate cell.

[0212] iv. Request for lower layer configuration for the purpose of generating the ref config

[0213] v. Request PRACH resource

[0214] C. All the proposed candidate PSCells in the other C-SN, including S-SN: This information is not admission control, but rather information about other candidate PSCells that the DU should be aware of during subsequent LTM operations. After the SN Addition procedure, the DU can erase all of these candidate cells, leaving only the finally admitted candidate cells.

[0215] i. ID of each candidate PSCell (PCI and / or CGI with AFRCN can be used)

[0216] ii. C-SN gNB ID where each candidate cell exists

[0217] iii. LTM configuration ID assigned by MN or S-SN to each candidate cell.

[0218] iv. For the proposed candidate cell of S-SN, CSI resource configuration, TCI state configuration, and RACH configuration

[0219] D. Information for LTM already configured [optional] (the following information about candidate PSCells maintained by S-SN, including intra-SN and inter-SN in step 1)

[0220] i. List of candidate PSCell ID confirmed / generated by S-SN or MN and its indicator of MN or SN

[0221] ii. List of the mapping info between LTM config ID and corresponding candidate PSCell ID generated by S-SN

[0222] iii. CSI resource configuration per PSCell,

[0223] iv. CSI report configuration per PSCell

[0224] v. TCI states configuration per PSCell

[0225] vi. RACH config of each candidate PSCell

[0226] vii. Lower layer configuration (for generating reference config at each C-SN)

[0227] 3. The C-SN (e.g., CU of C-SN1, CU of C-SN2, ...) may receive the above information and transmit some or all of the received information to the C-DU (e.g., candidate DU of C-SN1, or candidate DU of C-SN2, ...) operating each candidate PSCell.

[0228] At this time, the F1 UE context modification message or setup request message can be used.

[0229] A. Current source DU ID information

[0230] B. Among the proposed candidate cells allocated to C-SN, the candidate cells corresponding to the C-DU can be down-selected and the corresponding information can be transmitted.

[0231] i. These cells may include a request directive for LTM resource allocation.

[0232] C. Information related to candidate PSCells allocated to DUs other than the above C-DU and other C-SNs (cell ID, gNB ID, LTM config ID)

[0233] D. The following information about the remaining already confirmed LTM candidate PSCells:

[0234] i. List of candidate PSCell ID confirmed / generated by S-SN or MN and its indicator of MN or SN

[0235] ii. List of the mapping info between LTM config ID and corresponding candidate PSCell ID generated by S-SN

[0236] iii. CSI resource configuration per PSCell,

[0237] iv. CSI report configuration per PSCell

[0238] v. TCI states configuration per PSCell

[0239] vi. RACH config of each candidate PSCell

[0240] vii. Lower layer configuration (for generating reference config at each C-SN)

[0241] 4. C-DUs (e.g., candidate DU of C-SN1, or candidate DU of C-SN2, etc.) that have received the above information can perform the following actions through (or based on) the received information and transmit the relevant information to the C-SN. At this time, the F1 UE context set response message and / or modification response message can be used.

[0242] A. LTM resource allocation for the proposed candidate PSCells can be determined.

[0243] i. For each admitted candidate cell, at least one of the following information may be transmitted to the C-SN.

[0244] 1. Cell ID and / or associated LTM configuration ID

[0245] 2. TCI state configuration

[0246] 3. RACH configuration

[0247] 4. CSI resource configuration

[0248] 5. CSI report Configuration: This is determined by referring to the information of all other LTM candidate cells below.

[0249] 6. Generated lower layer configuration if requested,

[0250] B. The cell ID, mapping of cell, and LTM configuration ID of all candidate PSCells received from MN can be stored.

[0251] C. The following information about all LTM candidate cells that have already been confirmed is stored and can be used when performing subsequent LTM.

[0252] i. List of candidate PSCell ID confirmed / generated by S-SN or MN and its indicator of MN or SN

[0253] ii. List of the mapping info between LTM config ID and corresponding candidate PSCell ID generated by S-SN

[0254] iii. CSI resource configuration per PSCell,

[0255] iv. CSI report configuration per PSCell

[0256] v. TCI states configuration per PSCell

[0257] vi. RACH config of each candidate PSCell

[0258] vii. Lower layer configuration (for generating reference config at each C-SN)

[0259] 5. The C-SN that receives the above information can share information related to the admitted candidate cell with other C-DUs within the C-SN. This enables subsequent LTM execution within the C-SN between the newly confirmed candidate cells in this LTM preparation.

[0260] 6. Each C-DU that receives the above information can update the CSI report configuration of the candidate cells it operates by adding the CSI resource configuration of the newly confirmed candidate cells. The newly updated CSI report configuration of each candidate cell can be transmitted to the C-SN. The updated lower layer configuration can also be transmitted.

[0261] 7. Each C-SN can transmit the following information to the MN (or S-MN CU). At this time, the SN ADD request acknowledgement message (SN ADD REq ACK message) can be used.

[0262] A. PCI and / or LTM candidate configuration ID of Admitted candidate PSCell

[0263] B. As information for each admitted candidate PSCell

[0264] i. RRCReconfiguration message as target PSCell configuration information including updated lower layer information.

[0265] ii. An indicator of whether the above message is a complete message or not.

[0266] iii. CSI resource configuration

[0267] iv. CSI report configuration

[0268] v. RACH configuration

[0269] vi. TCI state configuration

[0270] C. The allocated resources of the above accepted PSCells can be maintained until a separate release instruction or cancel instruction is received from Mn or another SN.

[0271] D. A reference configuration for this C-SN can be created and transmitted. The gNB ID of the C-SN can be associated with this reference configuration.

[0272] 8. The MN (or S-MN CU) may receive the above information and confirm that the LTM configuration ID previously assigned to the unadmitted candidate cells can be reused later. The MN (or S-MN CU) may also store the received information.

[0273] A. MN (or S-MN CU) can transmit (or forward) information of finally admitted candidate cells in C-SNs other than its own to all other C-SNs (e.g., CU of C-SN1, CU of C-SN2, ...) including S-SN. Information of finally admitted candidate cells can include at least one of the following information, and the message used at this time can be an Xn SN Modification request message.

[0274] i. PCI and / or LTM candidate config ID of the admitted and / or not admitted candidate cells.

[0275] ii. CSI resource configuration of other C-SNs containing admitted candidate cells.

[0276] iii. Updated CSI report configuration, TCI state config, and RACH config of candidate cells of each C-SN

[0277] B. The C-SN (e.g., CU of C-SN1, CU of C-SN2, ...) that has received (or has received) the above information can then transmit the information to its C-DU (e.g., DU of C-SN1, DU of C-SN2, ...) to update the necessary information.

[0278] C. The above information must be transmitted even if all proposed candidate cells are admitted.

[0279] 9. The MN (or S-MN CU) can generate ltm-configuration and transmit it to the terminal. (generate ltm-Config including SCG ltm configuration in MN format RRCReconfiguration) More specifically, ltm config including SCG ltm configuration can be generated and transmitted by including it in the ltm-Config field in the RRCReconfiguration message.

[0280] A. The MN (or S-MN CU) may transmit the aforementioned information to each SN, and then configure ltm-configuration using information including target cell settings (config) of each candidate cell, and transmit it to the UE by including it in the ltm-Config field in the RRCReconfiguration message. The ltm-config field may include at least one of the following information.

[0281] i. For each candidate cell

[0282] 1. LTM candidate ID

[0283] 2. PCI

[0284] 3. SSB config

[0285] 4. Candidate config with reference ID below

[0286] 5. Complete config indicator

[0287] 6. DL TCI state info

[0288] 7. Using early TA indicator

[0289] 8. RACH-less execution indicator

[0290] ii. LTM reference list

[0291] 1. Each reference config per C-SN having SN related ID

[0292] B. When the MN (or S-MN CU) transmits the ltm-config to the terminal, it may be transmitted by including it in RRCReconfiguration of MN format. The RRCReconfiguration may be transmitted using signaling radio bearer 1 (SRB1).

[0293] i. In particular, candidate config in ltm-config may mean RRCReconfiguration that includes RRCReconfiguration written by each C-SN as SCG configuration and adds corresponding MCG configuration to it.

[0294] ii. If the terminal is instructed to switch through the inter-CU cell switch command MAC CE and successfully connects, the terminal can notify the MN (or S-MN CU) through the RRCReconfigurationComplete or ULInformationTransferMRDC message through SRB1 of the MN (or S-MN CU). In this case, the SN RRCReconfigurationComplete message can be encapsulated in the RRCReconfigurationComplete and / or ULInformationTransferMRDC. Afterwards, the MN (or S-MN CU) that receives the RRCReconfigurationComplete and / or ULInformationTransferMRDC in which the SN RRCReconfigurationComplete message is encapsulated can transmit the SN Reconfiguration complete message including the SN RRCReconfigurationComplete message to the C-SN (e.g., CU of C-SN1).

[0295] C. The RRCReconfiguration message in MN format delivered to the terminal may include at least one of the following: master cell group configuration, secondary cell group configuration, measurement configuration, radio bearer configuration, and LTM configuration. In particular, the LTM configuration may be composed of fields separate from the above.

[0296] The specific MN format RRCReconfiguration message structure is shown in Fig. 8. In Fig. 8, a field called Ltm-Config is included in RRCReconfiguration, and in Ltm-Config, configuration information related to one candidate cell can be mapped to one LTM candidate configuration ID and transmitted. Information mapped to each LTM candidate configuration ID may include RRCReconfiguration to be applied when moving to the corresponding target PSCell. In addition, an indicator indicating whether the configuration is a complete configuration or a delta configuration and, if it is a delta configuration, an index indicator of the reference configuration to be applied may be included. This RRCReconfiguration may include MCG config and SCG config. SCG config is a target PSCell configuration created by C-SN through the inter node signaling, and MCG config is configuration information on MCG corresponding to the corresponding target PSCell configuration, and is created by MN. (Or generate.) Regardless of the above LTM candidate ID, there may be a reference configuration as configuration information that is universally applied, and this reference configuration may be transmitted with an indicator indicating the C-SN along with reference configuration information created for each C-SN.

[0297] 10. The terminal that receives the above MN format RRC Reconfiguration message can store the corresponding ltm-config information in the UE variable. In addition, if a specific LTM candidate ID is indicated through the cell switch command MAC CE in the serving cell, the terminal can move to the corresponding PSCell by applying the corresponding candidate configuration.

[0298] At this time, an early TA acquisition procedure may be performed, and the specific operation of the early TA acquisition procedure may be as follows.

[0299] (1) The source DU of the MN can indicate an early TA indicator. More specifically, the source DU of the MN can transmit early TA acquisition through a physical downlink control channel (PDCCH).

[0300] (2) Afterwards, the terminal can perform the Early TA acquisition procedure. More specifically, the terminal can transmit the preset RACH preamble to the LTM candidate cell (e.g., candidate DU of C-SN1) associated with the corresponding indicator.

[0301] (3) The target C-DU (e.g., candidate DU of C-SN1) can measure the preamble to estimate the TA value, and can transmit (or notify) the measured TA value to the C-SN (e.g., CU of C-SN1) as a DU-CU TA info transfer message.

[0302] (4) Afterwards, the C-SN (e.g., CU of C-SN1) must inform the MN (e.g., S-MN CU) of the information again. At this time, a new Xn message and / or Xn TA info transfer message may be used. The Xn message and / or Xn TA info transfer message may include all or part of the following information.

[0303] A. XnAP UE ID, Rach preamble index, C-SN ID, TA value, PCI of the candidate cell, LTM candidate config ID of the candidate cell

[0304] (5) The MN (or S-MN CU) that has received the above information must then notify this to the current S-SN (or S-SN CU). At this time, a new Xn message or SN MOD request message may be used, and the information that may be included in the new Xn message or SN MOD request message is as follows.

[0305] A. C-SN id or corresponding gNB CU ID, TA value, candidate LTM cell ID, LTM config ID

[0306] (6) The S-SN (or S-SN CU) that has received the above information can inform its S-DU of the TA value.

[0307] The early TA acquisition procedures (1) to (6) may be omitted. For example, if it is determined that preamble transmission is likely to fail in a cell belonging to a specific CU based on L3 measurement values, the early TA procedure may be omitted. In this case, the omission of the early TA procedure may be determined by the candidate SN (inter CU) and / or MN (or S-MN CU).

[0308] 11. If the S-DU (or Source DU of SN) instructs the UE to switch to a candidate cell, the S-DU (or Source DU of SN) can simultaneously or later notify the S-SN (or S-SN CU) by transmitting an LTM cell switch notification. This is to prevent the S-SN from additionally instructing L3 PSCell change. In addition, the potential target DU (e.g., candidate DU of C-SN1) that receives this message can determine whether the UE has performed and completed access based on the enclosed TCI state information after receiving this message.

[0309] For the same operation, the S-SN (or S-SN CU) that received the above indication can give the same indication to the C-DU of the target PSCell through the MN (or S-MN CU). Accordingly, the S-SN (or S-SN CU) can notify the C-SN of the target PSCell using an Xn SN Cell switch notification message (or its corresponding Xn message) to the MN (or S-MN CU).

[0310] The above Xn SN Cell switch notification message (or the corresponding Xn message) may include at least one of a UE ID (e.g., Xn AP UE ID, or its corresponding GUPI, SUPI, ...) that is instructed to the cell switch, a target cell ID (LTM candidate ID or PCI, or CGI with AFRCN), and a TCI state ID.

[0311] 12. The MN (or S-MM CU) that has received the above information can notify the C-SN of the target PSCell using Xn LTM Cell switch notification (or the corresponding unidirectional message of Xn).

[0312] The above Xn LTM Cell switch notification (or the corresponding Xn unidirectional message) may include at least one of a UE ID, a target cell ID, and a TCI state ID, similar to the above-described Xn SN Cell switch notification message (or the corresponding Xn message).

[0313] Although not shown in the drawing, the S-SN (or S-SN CU) can directly transmit the same instruction (or information about the LTM sell switch, or notification) to the C-CN1, without going through the MN. In this case, it can be transmitted through a separate Xn message.

[0314] The C-SN (e.g., CU of C-SN1, ...) that receives the above message can inform the DU operating the target cell of the above information. Based on this, the target C-DU can detect the access of the terminal and determine the success and / or failure of the access.

[0315] 13. When the C-SN (e.g., C-SN1 CU) recognizes the LTM success of the terminal, it can inform the MN (S-MN CU) of the content (or the terminal's access success and / or failure information) through an Xn message. The Xn message can include PSCell change success, and the Xn message (or PSCell change success message) can include at least one piece of information from among the UE ID, target cell ID, and used TCI state ID.

[0316] FIG. 8 is a diagram illustrating the structure of a radio resource control (RRC) reconfiguration message according to one embodiment of the present disclosure.

[0317] The RRCReconfiguration message in MN format delivered to the terminal may include master cell group (MCG) configuration, secondary cell group (SCG) configuration, measurement configuration (measConfig), radio bearer configuration (RBconfig), l1 / l2 triggered mobility configuration (LTM config), etc. In particular, the LTM configuration (LTM config) may be configured as a separate field from the aforementioned MCG configuration, SCG configuration, measConfig, and RB config.

[0318] Referring to FIG. 8, RRCReconfiguration may include a field called Ltm-Config. In the Ltm-Config, configuration information associated with one candidate cell may be mapped to one LTM candidate configuration ID (e.g., LTM candidate id1, LTM candidate id2, LTM candidate id3, LTM candidate id4, ...) and transmitted. Information mapped to the LTM candidate configuration ID may include RRCReconfiguration to be applied when moving to the corresponding target PSCell. In addition, an indicator indicating whether the configuration is a complete configuration or a delta configuration may be included, and if it is a delta configuration, an index indicator of a reference configuration to be applied may be included.

[0319] When moving to the target PSCell, the RRCReconfiguration to be applied may include MCG config and SCG config. The MCG config is the configuration information on the MCG corresponding to the target PSCell configuration, and is configured (or created) by the MN. The SCG config is the target PSCell configuration created by the C-SN through the inter-node signaling.

[0320] Additionally, Ltm-Config may include a reference configuration. The reference configuration is configuration information that is universally applied regardless of the LTM candidate ID, and reference configuration information created for each C-SN may be transmitted along with an indicator.

[0321] The 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.

[0322] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present invention.

[0323] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage device, magnetic cassette. Or, they may be stored in a memory configured as a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

[0324] Additionally, the program may be stored in an attachable storage device that is accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present invention via an external port. Additionally, a separate storage device on the communication network may be connected to a device implementing an embodiment of the present invention.

[0325] In the specific embodiments of the present invention described above, components included in the invention are expressed in the singular or plural form depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present invention is not limited to singular or plural components. Even components expressed in the plural form may be composed of singular elements, or even components expressed in the singular form may be composed of plural elements.

[0326] While the detailed description of the present invention has described specific embodiments, it is clear that various modifications are possible without departing from 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 not only by the scope of the following claims but also by equivalents thereof.

Claims

1. In a method performed by a source master node (S-MN) in a communication system, A step of receiving secondary cell group (SCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate primary secondary cell (PSCell) corresponding to each CU of at least one candidate secondary node (C-SN) from a central unit (CU) of at least one candidate secondary node (C-SN); A step of generating and transmitting a first radio resource control (RRC) reconfiguration message including SCG configuration information and Master Cell Group (MCG) configuration information of an LTM candidate PSCell corresponding to each CU of at least one C-SN, to a terminal; and A method characterized by comprising the step of receiving, from the terminal, an MN RRC Reconfiguration Complete Message including an SN RRC Reconfiguration Complete Message based on the RRC reconfiguration message.

2. In paragraph 1, A step of determining whether to change the LTM cell based on the L1 measurement result received from the terminal; and A method characterized in that it further comprises a step of transmitting, to the terminal, a cell change command Media Access Control (MAC) control information (Control Element, CE) including an identifier (ID) of a specific LTM candidate cell.

3. In paragraph 1, A method further comprising the step of receiving a secondary node change request message (SN Change Required Message) including at least one LTM candidate cell information from a CU of a source secondary node (S-SN).

4. In paragraph 3, A step of receiving at least one of channel state information (CSI) related configuration information or transmission configuration indicator (TCI) configuration information from a CU of at least one C-SN; and A method characterized in that it further comprises a step of transmitting at least one of the received CSI-related setting information or TCI setting information to the CU of the S-SN.

5. In paragraph 1, The first RRC reconfiguration message includes an identifier of the LTM candidate PSCell and a second RRC reconfiguration message to be applied when changing the LTM cell to the LTM candidate PSCell. A method characterized in that the second RRC reconfiguration message includes SCG configuration information and Master Cell Group (MCG) configuration information of the LTM candidate PSCell.

6. In a method performed by a terminal in a communication system, A step of receiving a first Radio Resource Control (RRC) reconfiguration message (RRC Reconfiguration Message) including Secondary Cell Group (SCG) configuration information and Master Cell Group (MCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate Primary Secondary Cell (PSCell) corresponding to each central unit (CU) of at least one candidate secondary node (C-SN) from a source master node (S-MN); and A method characterized in that it comprises a step of transmitting an MN RRC Reconfiguration Complete Message including an SN RRC Reconfiguration Complete Message to a CU of the S-MN based on the RRC reconfiguration message.

7. In paragraph 6, A step of reporting the results of L1 measurements for at least one LTM candidate cell to the above S-MN; A step of receiving, from the S-MN, a cell change command Media Access Control (MAC) control information (Control Element, CE) including an identifier (ID) of a specific LTM candidate cell; and A method characterized by comprising a step of changing to the specific LTM candidate cell based on the first RRC reconfiguration message and the MAC CE.

8. In paragraph 6, The first RRC reconfiguration message includes an identifier of the LTM candidate PSCell and a second RRC reconfiguration message to be applied when changing the LTM cell to the LTM candidate PSCell. A method characterized in that the second RRC reconfiguration message includes SCG configuration information and Master Cell Group (MCG) configuration information of the LTM candidate PSCell.

9. In the communication system, in the Source Master Node (S-MN), A transceiver for transmitting and receiving signals; and It includes a control unit, wherein the control unit is: Receive secondary cell group (SCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate primary secondary cell (PSCell) corresponding to each CU of at least one candidate secondary node (C-SN) from a central unit (CU) of at least one candidate secondary node (C-SN), A terminal generates and transmits a first radio resource control (RRC) reconfiguration message including SCG configuration information and Master Cell Group (MCG) configuration information of an LTM candidate PSCell corresponding to each CU of at least one C-SN, An S-MN characterized in that, based on the RRC reconfiguration message, an MN RRC Reconfiguration Complete Message including an SN RRC Reconfiguration Complete Message is received from the terminal.

10. In paragraph 9, the control unit, Based on the L1 measurement results received from the above terminal, determine whether to change the LTM cell, An S-MN characterized in that it transmits a cell change command media access control (MAC) control information (Control Element, CE) including an identifier (ID) of a specific LTM candidate cell to the terminal.

11. In paragraph 9, the control unit, An S-MN characterized in that it receives a secondary node change request message (SN Change Required Message) including at least one LTM candidate cell information from a CU of a source secondary node (S-SN).

12. In paragraph 9, the control unit, Receive at least one of channel state information (CSI) related configuration information or transmission configuration indicator (TCI) configuration information from the CU of at least one C-SN, An S-MN characterized in that it transmits at least one of the received CSI-related setting information or TCI setting information to the CU of the S-SN.

13. In paragraph 9, The first RRC reconfiguration message includes an identifier of the LTM candidate PSCell and a second RRC reconfiguration message to be applied when changing the LTM cell to the LTM candidate PSCell. An S-MN characterized in that the second RRC reconfiguration message includes SCG configuration information and Master Cell Group (MCG) configuration information of the LTM candidate PSCell.

14. In a terminal in a communication system, A transceiver for transmitting and receiving signals; and It includes a control unit, wherein the control unit is: Receive a first Radio Resource Control (RRC) reconfiguration message (RRC Reconfiguration Message) including Secondary Cell Group (SCG) configuration information and Master Cell Group (MCG) configuration information of a Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM) candidate Primary Secondary Cell (PSCell) corresponding to each central unit (CU) of at least one candidate secondary node (C-SN) from a source master node (S-MN), A terminal characterized in that, based on the RRC reconfiguration message, a MN RRC Reconfiguration Complete Message including an SN RRC Reconfiguration Complete Message is transmitted to the CU of the S-MN.

15. In paragraph 14, the control unit, With the above S-MN, report the results of L1 measurements for at least one LTM candidate cell, From the S-MN, a cell change command Media Access Control (MAC) control information (Control Element, CE) including an identifier (ID) of a specific LTM candidate cell is received, Based on the first RRC reconfiguration message and the MAC CE, changing to the specific LTM candidate cell, The first RRC reconfiguration message includes an identifier of the LTM candidate PSCell and a second RRC reconfiguration message to be applied when changing the LTM cell to the LTM candidate PSCell. A terminal characterized in that the second RRC reconfiguration message includes SCG configuration information and Master Cell Group (MCG) configuration information of the LTM candidate PSCell.

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