Method and apparatus for reporting sequence number gap of radio link control layer in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. An operation method of a user equipment in a wireless communication system, according to an embodiment of the present disclosure, may comprise the operations of: receiving, from a base station, a first radio resource control (RRC) message inquiring about whether or not a report on a radio link control (RLC) sequence number (SN) gap is supported; transmitting, to the base station, a second RRC message including information regarding whether or not the report on the RLC sequence number gap is supported; receiving, from the base station, a third RRC message configuring, with respect to an RLC layer device, whether or not occurrence of the RLC sequence gap is allowed or whether or not transmission of the RLC sequence number gap is possible; and transmitting the report on the RLC sequence number gap to the base station.

Description

Method and device for reporting sequence number intervals of a radio link control layer in a wireless communication system

[0001] The present disclosure relates to a method and apparatus for reporting a sequence number interval of a radio link control (RLC) layer in a wireless communication system.

[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] One aspect of the present disclosure may be to provide a device and method capable of reporting a sequence number interval of an RLC layer in a wireless communication system.

[0009] A method of operating a terminal in a wireless communication system according to one embodiment of the present disclosure may include: receiving, from a base station, a first radio resource control (RRC) message inquiring about whether reporting of a radio link control (RLC) sequence number gap (SN Gap) is supported; transmitting, to the base station, a second RRC message including information about whether the RLC sequence number gap report is supported; receiving, from the base station, a third RRC message that sets, for an RLC layer device, whether generation of an RLC sequence number gap is permitted or whether RLC sequence number gap transmission is possible; and transmitting the RLC sequence number gap report to the base station.

[0010] The method and device according to the embodiment of the present disclosure can increase communication transmission and reception efficiency by reporting the sequence number interval of the RLC layer in a wireless communication system.

[0011] FIG. 1 is a diagram illustrating the structure of an NR system according to one embodiment of the present disclosure.

[0012] FIG. 2 is a diagram illustrating a wireless protocol structure in an NR system according to an embodiment of the present disclosure.

[0013] FIG. 3 is a diagram illustrating a procedure for a terminal to establish a connection with a network according to an embodiment of the present disclosure.

[0014] FIG. 4 is a diagram illustrating an operation in which an RLC transmitting device reports an RLC SN Gap to an RLC receiving device through an RLC SN Gap Report according to an embodiment of the present disclosure.

[0015] FIG. 5 is a diagram illustrating the format of an RLC SN Gap report / PDU according to one embodiment of the present disclosure.

[0016] FIG. 6 is a diagram illustrating the format of an RLC SN Gap report / PDU according to one embodiment of the present disclosure.

[0017] FIG. 7 is a diagram illustrating a procedure in which a terminal and a base station report an RLC SN Gap through an RLC SN Gap report according to one embodiment of the present disclosure.

[0018] Figure 8 shows the structure of a terminal according to an embodiment of the present disclosure.

[0019] Figure 9 shows the structure of a base station according to an embodiment of the present disclosure.

[0020] The operating principles of the present disclosure are described in detail below with reference to the attached drawings. In the following description of the present disclosure, detailed descriptions of related known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, the terms described below are defined based on the functions of the present disclosure and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0021] In describing the embodiments of this disclosure, descriptions of technical details that are well known in the technical field to which this disclosure pertains and are not directly related to this disclosure will be omitted. This is to more clearly convey the gist of this disclosure without obscuring it by omitting unnecessary explanations.

[0022] 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. Identical or corresponding components in each drawing are assigned the same reference numbers.

[0023] 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 together 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 present 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 specification.

[0024] At this time, it will be understood that each block of the processing flow diagrams and combinations of the flow diagrams can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment create a means for performing the functions described in the flow diagram block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to implement the functions in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce a manufactured item that includes an instruction means for performing the functions described in the flow diagram block(s). Since the computer program instructions may be installed on a computer or other programmable data processing device, a series of operational steps may be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) may also provide steps for performing the functions described in the flowchart block(s).

[0025] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0026] Here, the term '~ part' used in the present embodiment means software or hardware components such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit), and the '~ part' performs certain roles. However, the '~ part' is not limited to software or hardware. The '~ part' may be configured to be on an addressable storage medium and may be configured to play one or more processors. Therefore, as an example, the '~ part' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, 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'. Additionally, components and '~parts' may be implemented to regenerate one or more CPUs within a device or secure multimedia card.

[0027] Hereinafter, the base station is an entity that performs resource allocation of the terminal, and may be at least one of a Node B, a BS (Base Station), an eNB (eNode B), a gNB (gNode B), 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 addition, the embodiments of the present disclosure may be applied to other communication systems having a similar technical background or channel type to the embodiments of the present disclosure described below. In addition, the embodiments of the present disclosure may be applied to other communication systems with some modifications without significantly departing from the scope of the present disclosure at the discretion of a person having skilled technical knowledge. For example, the 5th generation mobile communication technology (5G, new radio, NR) developed after LTE-A may be included here, and the 5G below may also be a concept that includes existing LTE, LTE-A, and other similar services. In addition, the present disclosure may be applied to other communication systems through some modifications within a scope that does not significantly deviate from the scope of the present disclosure, as judged by a person having skilled technical knowledge.

[0028] In the following description, terms used to identify connection nodes, terms referring to network entities or network functions (NFs), terms referring to messages, terms referring to interfaces between network objects, terms referring to various identification information, etc. are provided as examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0029] For convenience of explanation below, some terms and names defined in the 3rd generation partnership project (3GPP) LTE (long term evolution) standard and / or 3GPP NR (new radio) standard may be used. However, the present disclosure is not limited by these terms and names, and can be equally applied to systems conforming to other standards.

[0030] FIG. 1 is a diagram illustrating the structure of an NR system according to one embodiment of the present disclosure.

[0031] Referring to FIG. 1, the wireless communication system may be composed of multiple base stations (e.g., gNB (100), ng-eNB (110), ng-eNB (120), gNB (130)), an Access and Mobility Management Function (AMF) (140), and a User Plane Function (UPF) (150). Of course, the wireless communication system is not limited to the configuration illustrated in FIG. 1, and may include more or fewer components.

[0032] According to one embodiment of the present disclosure, a user equipment (hereinafter referred to as UE or terminal) (160) can access an external network through base stations (100, 110, 120, 130) and UPF (150).

[0033] In Fig. 1, base stations (100, 110, 120, 130) can serve as access nodes of a cellular network and provide wireless access to terminals accessing the network. For example, base stations (100, 110, 120, 130) can collect status information such as buffer status, available transmission power status, and channel status of terminals to schedule the collected information and support connections between terminals and a core network (CN; in particular, the CN of NR is referred to as 5GC) in order to service user traffic.

[0034] In Fig. 1, gNB (100, 130) can control multiple cells, and 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 can be applied.

[0035] The core network, which handles various control functions as well as mobility management for terminals, can be connected to multiple base stations. 5GC can also be integrated with existing LTE systems.

[0036] Meanwhile, in a wireless communication system, a user plane (UP) related to transmission of actual user data and a control plane (CP) such as connection management may be configured separately. The gNB (100) and gNB (130) of FIG. 1 may use the UP and CP technologies defined in NR technology, and the ng-eNB (110) and ng-eNB (120), although connected to 5GC, may use the UP and CP technologies defined in LTE (Long Term Evolution) technology.

[0037] AMF (140) is a device that is responsible for various control functions as well as mobility management functions for terminals and can be connected to multiple base stations.

[0038] UPF (150) may refer to a type of gateway device that provides data transmission. Although not illustrated in FIG. 1, the NR wireless communication system may also include a Session Management Function (SMF). The SMF can manage packet data network connections, such as PDU (protocol data unit) sessions provided to terminals.

[0039] FIG. 2 is a diagram illustrating a wireless protocol structure in an NR system according to one embodiment of the present disclosure.

[0040] Referring to FIG. 2, the wireless protocol of the NR system may be composed of SDAP (Service Data Adaptation Protocol) (200) (290), PDCP (Packet Data Convergence Protocol) (210) (280), RLC (Radio Link Control) (220) (270), MAC (Medium Access Control) (230) (260), and PHY (Physical) (240) (250) in the terminal and the base station, respectively.

[0041] SDAP (Service Data Adaptation Protocol) (200) (290) can perform operations for transmitting user data, mapping QoS flows to specific DRBs for uplink and downlink, marking QoS flow IDs for uplink and downlink, and mapping reflective QoS flows to data bearers for uplink SDAP PDUs. SDAP settings corresponding to each DRB can be provided from a higher RRC layer. Of course, the present invention is not limited to the above examples.

[0042] PDCP (Packet Data Convergence Protocol) (210) (280) can handle operations such as IP header compression / decompression. Furthermore, PDCP (210) (280) can provide sequential and out-of-order transmission functions, reordering, duplicate detection, retransmission, encryption, and decryption functions. Of course, the examples are not limited thereto.

[0043] Radio Link Control (220)(270) can reconfigure PDCP Protocol Data Units (PDUs) to an appropriate size. Furthermore, RLC (220)(270) can provide sequential and out-of-order transmission functions, and can provide ARQ functions, concatenation, segmentation, reassembly functions, re-segmentation functions, reordering functions, duplicate detection functions, and error detection functions. Of course, the examples are not limited thereto.

[0044] MAC (230) (260) is connected to multiple RLC layer devices configured in one terminal, and can perform operations of multiplexing RLC PDUs into MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. In addition, MAC (230) (260) can provide a mapping function, a scheduling information reporting function, a HARQ function, a priority control function between logical channels, a priority control function between terminals, an MBMS service confirmation function, a transmission format selection function, and a padding function. Of course, the present invention is not limited to the above examples.

[0045] The physical (PHY) layer (240)(250) channels and modulates upper layer data, converts it into OFDM symbols, and transmits it over a wireless channel, or demodulates and channel decodes OFDM symbols received over a wireless channel and transmits them to the upper layer. In addition, the physical layer uses HARQ (Hybrid ARQ) for additional error correction, and the receiver transmits 1 bit whether or not it has received a packet transmitted by the transmitter. The 1 bit information is called HARQ ACK / NACK information.

[0046] Downlink HARQ ACK / NACK information for uplink data transmission is transmitted through the PHICH (Physical Hybrid-ARQ Indicator Channel) physical channel in the case of LTE, and in the case of NR, whether retransmission is necessary or new transmission can be performed through the UE's scheduling information in the PDCCH (Physical Dedicated Control CHannel), which is a channel through which downlink / uplink resource allocation, etc. are transmitted. This is because NR applies asynchronous HARQ. Uplink HARQ ACK / NACK information for downlink data transmission can be transmitted through the PUCCH (Physical Uplink Control Channel) or PUSCH (Physical Uplink Shared Channel) physical channel. PUCCH is generally transmitted in the uplink of the PCell, which will be described later, but if the UE supports it, the base station may additionally transmit it to the SCell, which will be described later, to the UE, and this is called the PUCCH SCell.

[0047] Although not shown in Figure 2, an RRC (Radio Resource Control) layer exists above the PDCP layer of each terminal and base station, and the RRC layer can transmit and receive connection and measurement-related setting control messages for radio resource control.

[0048] Meanwhile, the physical layer can be composed of one or more frequencies / carriers, and the technology that sets and uses multiple frequencies simultaneously is called carrier aggregation (CA). CA technology can dramatically increase the transmission capacity by using the primary carrier and one or more secondary carriers in addition to a single carrier for communication between a terminal (or User Equipment, UE) and a base station (eNB or gNB). Meanwhile, in LTE / NR, a cell within a base station that uses a primary carrier is called a primary cell or PCell (Primary Cell), and a cell within a base station that uses a secondary carrier is called a secondary cell or SCell (Secondary Cell).

[0049] FIG. 3 is a diagram illustrating a procedure for a terminal to establish a connection with a network according to an embodiment of the present disclosure.

[0050] Figure 3 illustrates a procedure in which a terminal establishes a connection with a network by switching from RRC idle mode (RRC_IDLE) to RRC connected mode (RRC_CONNECTED) in the present disclosure. In Figure 3, the terminal can establish uplink / downlink transmission synchronization with a base station through a random access process and transmit an RRCSetupRequest message to the base station (300). The RRCSetupRequest message can include an identifier of the terminal and a reason for establishing a connection (EstablishmentCause). The base station can transmit an RRCSetup message to the terminal to establish an RRC connection (305).

[0051] In one embodiment, the RRCSetup message may include configuration information (RadioBearerConfig) for each Radio Bearer (DRB or SRB). The Radio Bearer configuration information may include an ID of each Radio Bearer, configuration information (PDCP-Config) for the PDCP layer device of the Radio Bearer, and an indicator indicating whether the Radio Bearer is a Dual Active Protocol Stack (DAPS) Bearer.

[0052] In one embodiment, the RRCSetup message may include configuration information (e.g., CellGroupConfig) for each Cell Group (Master Cell Group and / or Secondary Cell Group). The Cell Group configuration information (CellGroupConfig) may include configuration information (e.g., RLC-BearerConfig) for each RLC bearer to be configured in the corresponding Cell Group.

[0053] In one embodiment, the RLC bearer configuration information (RLC-BearerConfig) may include the following fields. The description of each field may be as follows.

[0054] - logicalChannelIdentity: ID commonly used for the MAC logical channel and for the RLC bearer. Value 4 is not configured for DRBs if SRB4 is configured.

[0055] - servedRadioBearer: Associates an RLC bearer with a specific SRB or DRB. The UE must forward downlink (RX) RLC SDUs received through the RLC entity of this RLC bearer to the PDCP entity of the corresponding servedRadioBearer. In addition, the PDCP PDUs generated in the PDCP entity of the uplink (UL) servedRadioBearer must be notified and forwarded to the uplink RLC entity of this RLC bearer, except when this is not allowed by uplink scheduling constraints (moreThanOneRLC of PDCP-Config and constraints of LogicalChannelConfig). (Associates the RLC Bearer with an SRB or a DRB. The UE shall deliver DL RLC SDUs received via the RLC entity of this RLC bearer to the PDCP entity of the servedRadioBearer. Furthermore, the UE shall advertise and deliver uplink PDCP PDUs of the uplink PDCP entity of the servedRadioBearer to the uplink RLC entity of this RLC bearer unless the uplink scheduling restrictions (moreThanOneRLC in PDCP-Config and the restrictions in LogicalChannelConfig) forbid it to do so.)

[0056] - reestablishRLC: Indicates that RLC should be re-established. The network shall set this value to true if: the security key of the radio bearer associated with the corresponding RLC entity has changed; for SRB2, multicast MRB and DRB, if full configuration was not used, set to true on RRC connection resumption or the first reconfiguration after RRC connection re-establishment; for SRB1, this field shall not be set to true on RRC connection resumption or the first reconfiguration after RRC connection re-establishment. This field shall not be included if an RLC-BearerConfig Information Element (IE) is included in the RRCReconfiguration message within the LTM-Config IE. (Indicates that RLC should be re-established. Network sets this to true at least whenever the security key used for the radio bearer associated with this RLC entity changes. For SRB2, multicast MRBs and DRBs, unless full configuration is used, it is also set to true during the resumption of the RRC connection or the first reconfiguration after reestablishment. For SRB1, when resuming an RRC connection, or at the first reconfiguration after RRC connection reestablishment, the network does not set this field to true.The network does not include this field if the RLC-BearerConfig IE is part of an RRCReconfiguration message within the LTM-Config IE.).

[0057] - rlc-Config: Determines the RLC mode (UM or AM) and provides corresponding parameters. RLC mode reconfiguration is only possible by releasing / adding DRB or multicast MRB or by fully configuring them. The network can configure rlc-Config-v1610 only when the existing rlc-Config is in AM mode. (Determines the RLC mode (UM, AM) and provides corresponding parameters. RLC mode reconfiguration can only be performed by releasing / adding DRB / multicast MRB or by fully configuring it. The network may configure rlc-Config-v1610 only when rlc-Config (without suffix) is set to AM.)

[0058] - mac-LogicalChannelConfig: May contain Logical Channel configuration information for the RLC bearer.

[0059] In one embodiment, the rlc-Config may include RLC layer device configuration information of the RLC bearer. For example, the rlc-Config may include the following fields. The description of each field may be as follows.

[0060] - When the RLC layer device is set to AM (acknowledged mode):

[0061] ■ ul-AM-RLC configuration information: sn-FieldLength (Sequence Number length), t-PollRetransmit (Poll retransmission timer size), pollPDU (Poll trigger PDU count threshold), pollByte (Poll trigger byte threshold), maxRetxThreshold (maximum number of retransmissions).

[0062] ■ dl-AM-RLC configuration information: sn-FieldLength (Sequence Number length), t-Reassembly (Reassembly timer size), t-StatusProhibit (Status PDU prohibit timer size).

[0063] - When the RLC layer device is set to UM (unacknowledged mode) Bi-Directional mode:

[0064] ■ ul-UM-RLC configuration information: sn-FieldLength (Sequence Number length)

[0065] ■ dl-UM-RLC configuration information: sn-FieldLength (Sequence Number length), t-Reassembly (Reassembly timer size)

[0066] - When the RLC layer device is set to UM Uni-Directional-UL mode:

[0067] ■ ul-UM-RLC configuration information: sn-FieldLength (Sequence Number length)

[0068] - When the RLC layer device is set to UM Uni-Directional-DL mode:

[0069] ■ dl-UM-RLC configuration information: sn-FieldLength (Sequence Number length), t-Reassembly (Reassembly timer size)

[0070] Referring to FIG. 3, a terminal that has established an RRC connection can enter RRC_CONNECTED mode and transmit an RRCSetupComplete message to the base station (310). If the base station does not know the terminal capabilities of the terminal that is currently establishing a connection or wants to check the terminal capabilities, it can transmit a message (e.g., UECapabilityEnquiry) to the terminal to inquire about the terminal's capabilities (315). In addition, the terminal can transmit a message (e.g., UECapabilityInformation) to the base station to report its capabilities (320).

[0071] To set up security with a terminal, the base station may transmit a SecurityModeCommand message (325) to the terminal, and the terminal may transmit a SecurityModeComplete message (330) to the base station. Once the security setting is complete, the base station may transmit an RRCReconfiguration message to the terminal (335).

[0072] In one embodiment, the RRCReconfiguration message may include configuration information (RadioBearerConfig) for each Radio Bearer (DRB or SRB). The Radio Bearer configuration information may include an ID of each Radio Bearer, configuration information (PDCP-Config) for the PDCP layer device of the Radio Bearer, and an indicator indicating whether the Radio Bearer is a DAPS Bearer.

[0073] In one embodiment, the RRCReconfiguration message may include configuration information (e.g., CellGroupConfig) for each Cell Group (Master Cell Group and / or Secondary Cell Group). The Cell Group configuration information (CellGroupConfig) may include configuration information (e.g., RLC-BearerConfig) for each RLC bearer to be configured in the corresponding Cell Group.

[0074] In one embodiment, the RLC bearer configuration information (RLC-BearerConfig) may include the following fields. The description of each field may be as follows.

[0075] - logicalChannelIdentity: An ID commonly used for the MAC logical channel and the RLC bearer. If SRB4 is configured, the value 4 is not configured for DRBs.

[0076] - servedRadioBearer: An entry that associates an RLC bearer with a specific SRB or DRB. The UE shall forward downlink (RX) RLC SDUs received through the RLC entity of this RLC bearer to the PDCP entity of the corresponding servedRadioBearer. Furthermore, the UE shall advertise and forward PDCP PDUs generated in the PDCP entity of the uplink (UL) servedRadioBearer to the uplink RLC entity of this RLC bearer, except when prohibited by uplink scheduling restrictions (moreThanOneRLC in PDCP-Config and restrictions in LogicalChannelConfig). (Associates the RLC Bearer with an SRB or a DRB. The UE shall deliver DL RLC SDUs received via the RLC entity of this RLC bearer to the PDCP entity of the servedRadioBearer. Furthermore, the UE shall advertise and deliver uplink PDCP PDUs of the uplink PDCP entity of the servedRadioBearer to the uplink RLC entity of this RLC bearer unless the uplink scheduling restrictions (moreThanOneRLC in PDCP-Config and the restrictions in LogicalChannelConfig) forbid it to do so.)

[0077] - reestablishRLC: Indicates whether to reset RLC. The network shall set this value to true if: the security key of the radio bearer associated with the corresponding RLC entity has changed. For SRB2, multicast MRB and DRB, in a non-full configuration state: at the first RRC reconfiguration after RRC connection resumption or reset. For SRB1, this value shall not be set to true at RRC connection resumption or at the first reconfiguration after RRC reset. This field is not included if an RLC-BearerConfig Information Element (IE) is included in the RRCReconfiguration message within the LTM-Config IE. (Indicates that RLC should be re-established. Network sets this to true at least whenever the security key used for the radio bearer associated with this RLC entity changes. For SRB2, multicast MRBs and DRBs, unless full configuration is used, it is also set to true during the resumption of the RRC connection or the first reconfiguration after reestablishment. For SRB1, when resuming an RRC connection, or at the first reconfiguration after RRC connection reestablishment, the network does not set this field to true.The network does not include this field if the RLC-BearerConfig IE is part of an RRCReconfiguration message within the LTM-Config IE.).

[0078] - rlc-Config: Determines the RLC mode (UM, AM) and provides the corresponding parameters. RLC mode changes can only be performed by releasing / adding DRBs or multicast MRBs, or by performing a full configuration. The network can configure rlc-Config-v1610 only when rlc-Config (without a suffix) is set to AM mode.

[0079] - mac-LogicalChannelConfig: May contain Logical Channel configuration information for the RLC bearer.

[0080] In one embodiment, the rlc-Config may include RLC layer device configuration information of the RLC bearer. For example, the rlc-Config may include the following fields. The description of each field may be as follows.

[0081] - When the RLC layer device is set to AM (acknowledged mode):

[0082] ■ ul-AM-RLC configuration information: sn-FieldLength (Sequence Number length), t-PollRetransmit (Poll retransmission timer size), pollPDU (Poll trigger PDU count threshold), pollByte (Poll trigger byte threshold), maxRetxThreshold (maximum number of retransmissions).

[0083] ■ dl-AM-RLC configuration information: sn-FieldLength (Sequence Number length), t-Reassembly (Reassembly timer size), t-StatusProhibit (Status PDU prohibit timer size).

[0084] - When the RLC layer device is set to UM (unacknowledged mode) Bi-Directional mode:

[0085] ■ ul-UM-RLC configuration information: sn-FieldLength (Sequence Number length)

[0086] ■ dl-UM-RLC configuration information: sn-FieldLength (Sequence Number length), t-Reassembly (Reassembly timer size)

[0087] - When the RLC layer device is set to UM Uni-Directional-UL mode:

[0088] ■ ul-UM-RLC configuration information: sn-FieldLength (Sequence Number length)

[0089] - When the RLC layer device is set to UM Uni-Directional-DL mode:

[0090] ■ dl-UM-RLC configuration information: sn-FieldLength (Sequence Number length), t-Reassembly (Reassembly timer size)

[0091] As such, the general data transmission process largely consists of three steps: RRC connection setup, security setup, and DRB setup. Additionally, the base station may transmit an RRCReconfiguration message to the terminal to update, add, or change settings for a specific reason (350).

[0092] In one embodiment of the present disclosure, upon receiving an RRC message (RRCReconfiguration), each Radio Bearer is set up by the Radio Bearer setting of the corresponding message, a corresponding PDCP layer device is set up, and an RLC Bearer / layer device having an association with each Radio Bearer / PDCP layer device is set up, and then an association between the RLC layer device and the PDCP layer device can be established. In one embodiment, one Radio Bearer corresponds to one PDCP layer device. In one embodiment, each PDCP layer device can be associated with one, two, three, four, six, or eight RLC layer devices as follows.

[0093] - A PDCP layer device of a Split Bearer can be associated with two uplink or two downlink UM RLC layer devices, four UM RLC layer devices (two downlink and two uplink), or two AM RLC layer devices.

[0094] - An RB with PDCP redundancy transmission enabled can be associated with N UM RLC layer devices (all downlink or all uplink), 2 × N UM RLC layer devices (N uplink and N downlink), or N AM RLC layer devices, where N can be greater than or equal to 2 and less than or equal to 4.

[0095] - A PDCP layer device of a DAPS Bearer can be associated with two UM RLC layer devices (both uplink or both downlink, one for the Source cell and one for the Target cell), four UM RLC layer devices (uplink and downlink of the Source cell, uplink and downlink of the Target cell), or two AM RLC layer devices (one for the Source cell and one for the Target cell).

[0096] - In other cases, each PDCP layer device may be associated with one UM RLC layer device, two UM RLC layer devices (one each for uplink and downlink), or one AM RLC layer device.

[0097] In one embodiment of the present disclosure, a transmitter of a PDCP layer device of a terminal for which pdcp-Duplication is set may operate as follows.

[0098] - About SRB:

[0099] 1) Activate PDCP duplicate transmission function

[0100] - About DRB:

[0101] 1) If an activation instruction for the PDCP redundant transmission feature is received (via RRC or MAC CE) for the given DRB:

[0102] (1) Activate PDCP duplicate transmission function for the corresponding DRB.

[0103] 2) If PDCP redundant transmission feature is enabled for at least one associated RLC layer device (via RRC or MAC CE):

[0104] (1) Activate PDCP redundant transmission function for the indicated RLC layer device.

[0105] (2) Activate PDCP duplicate transmission function for the corresponding DRB.

[0106] 3) If a PDCP duplicate transmission feature disable instruction is received (via RRC or MAC CE) for the DRB in question:

[0107] (1) For the DRB in question, disable the PDCP duplicate transmission function.

[0108] 4) If, for at least one associated RLC layer device, a PDCP duplicate transmission feature disablement indication is received (via RRC or MAC CE):

[0109] (1) For the associated RLC layer device that received the instruction, perform PDCP duplicate transmission function deactivation.

[0110] (2) If PDCP redundant transmission feature is disabled for all associated RLC layer devices except the Primary RLC layer device:

[0111] a. Disable PDCP duplicate transmission function for the DRB in question.

[0112] In one embodiment of the present disclosure, when the PDCP redundant transmission function is set for one or more DRBs, the base station can instruct, through MAC CE, to activate / deactivate the PDCP redundant transmission function of all or some of the associated RLC layer devices for the DRBs for which the PDCP redundant transmission function is set.

[0113] In one embodiment, in the following cases, the terminal may activate or deactivate the PDCP redundancy transmission function for the DRB for which the function is configured.

[0114] - When an activation / deactivation indication is received from the base station via the Duplication Activation / Deactivation MAC CE of TS 38.321 section 6.1.3.11. In one embodiment, the Duplication Activation / Deactivation MAC CE may indicate activation / deactivation of the PDCP duplicate transmission function only when the number of associated RLC layer devices is two.

[0115] - When an activation / deactivation indication is received from the base station via the Duplication RLC Activation / Deactivation MAC CE of TS 38.321 section 6.1.3.32.

[0116] - When an activation / deactivation instruction (e.g., pdcp-Duplication, duplicationState) is received from the base station via an RRC message

[0117] In one embodiment, in the following cases, the terminal may enable / disable the PDCP redundancy transmission function for all or some RLC layer devices associated with the DRB for which the function is enabled.

[0118] - When an activation / deactivation indication is received from the base station via the Duplication RLC Activation / Deactivation MAC CE of TS 38.321 section 6.1.3.32.

[0119] - When an activation / deactivation instruction (e.g., pdcp-Duplication, duplicationState) is received from the base station via an RRC message

[0120] In one embodiment, the terminal may enable the PDCP redundancy transmission function for all associated RLC layer devices for the DRB for which the function is configured, in the following cases:

[0121] - When receiving an Uplink Grant, which is specified by CS-RNTI and has NDI (New Data Indicator) = 1, for a Logical Channel associated with a DRB with survivalTimeStateSupport set.

[0122] In one embodiment of the present disclosure, a MAC layer device of a terminal may operate as follows for each DRB for which a PDCP redundant transmission function is set.

[0123] - When an instruction to activate the PDCP duplicate transmission function for a specific DRB is received via Duplication Activation / Deactivation MAC CE:

[0124] 1) It is possible to instruct the upper layer (PDCP) to activate the PDCP redundant transmission function for the corresponding DRB.

[0125] - When an instruction to disable PDCP duplicate transmission functionality for a specific DRB is received via Duplication Activation / Deactivation MAC CE:

[0126] 1) It is possible to instruct the upper layer (PDCP) to disable the PDCP duplicate transmission function for the corresponding DRB.

[0127] - When an indication to activate the PDCP duplicate transmission feature for a specific DRB is received via a Duplication RLC Activation / Deactivation MAC CE for one or more Secondary RLC layer devices associated with that DRB:

[0128] 1) It can instruct the upper layer (PDCP) to enable PDCP redundant transmission function for one or more Secondary RLC layer devices.

[0129] - When an instruction to disable PDCP duplicate transmission functionality for a specific DRB is received via Duplication RLC Activation / Deactivation MAC CE for one or more Secondary RLC layer devices associated with that DRB:

[0130] 1) It is possible to instruct the upper layer (PDCP) to disable the PDCP redundant transmission function for one or more Secondary RLC layer devices.

[0131] - For a Logical Channel associated with a DRB with survivalTimeStateSupport set, when receiving an Uplink Grant specified by CS-RNTI and with New Data Indicator (NDI) = 1:

[0132] It is possible to instruct the upper layer (PDCP) to enable PDCP redundant transmission function for all associated RLC layer devices of the DRB.

[0133] In one embodiment of the present disclosure, the RLC layer device can operate in one of Transparent Mode (TM), Unacknowledged Mode (UM), or Acknowledged Mode (AM). Accordingly, the RLC layer device may be referred to as a TM RLC layer device, an UM RLC layer device, or an AM RLC layer device, depending on the mode.

[0134] For example, a UM RLC layer entity can operate as either a transmitting UM RLC entity or a receiving UL RLC entity. The transmitting UM RLC layer entity and the receiving UM RLC layer entity can operate as follows.

[0135] - The transmitting UM RLC entity receives RLC SDUs from the upper layer and transmits them to the receiving UM RLC entity in the form of RLC PDUs via the lower layer. The receiving UM RLC entity receives RLC PDUs from the transmitting UM RLC entity via the lower layer and delivers them to the upper layer in the form of RLC SDUs. (The transmitting UM RLC entity receives RLC SDUs from the upper layer and sends RLC PDUs to its peer receiving UM RLC entity via lower layers. The receiving UM RLC entity delivers RLC SDUs to the upper layer and receives RLC PDUs from its peer transmitting UM RLC entity via lower layers.)

[0136] For example, an AM RLC layer device may be configured with a transmitting side and a receiving side. The transmitting side and receiving side of the AM RLC layer device may operate as follows.

[0137] - The transmitting side of an AM RLC entity receives RLC SDUs from the upper layer and transmits them to the counterpart AM RLC entity in the form of RLC PDUs via the lower layer. The receiving side of an AM RLC entity receives RLC PDUs from the counterpart AM RLC entity via the lower layer and delivers them to the upper layer in the form of RLC SDUs. (The transmitting side of an AM RLC entity receives RLC SDUs from the upper layer and sends RLC PDUs to its peer AM RLC entity via lower layers. The receiving side of an AM RLC entity delivers RLC SDUs to the upper layer and receives RLC PDUs from its peer AM RLC entity via lower layers.)

[0138] In one embodiment of the present disclosure, each RLC SDU can be formed into an RLC PDU without a transmission opportunity notification from a lower layer (e.g., MAC). Based on the transmission opportunity notification from the lower layer, a UM or AM RLC layer device can segment one RLC SDU into two or more segments and transmit them as two or more RLC PDUs. For example, an RLC layer device can submit an RLC PDU to a lower layer after receiving a transmission opportunity notification from the lower layer.

[0139] In one embodiment of the present disclosure, a PDCP SDU discard operation in a PDCP layer device may be performed as follows.

[0140] - When the successful delivery of a PDCP SDU is confirmed by the PDCP status report, the transmitting PDCP entity shall discard the PDCP SDU along with the corresponding PDCP Data PDU.

[0141] - When the discardTimer or discardTimerForLowImportance expires for a PDCP SDU, the transmitting PDCP entity shall:

[0142] ■ If pdu-SetDiscard is configured:

[0143] ◆ All PDCP SDUs and their corresponding PDCP Data PDUs included in the PDU Set to which the corresponding PDCP SDU belongs must be discarded. PDCP SDUs subsequently received from upper layers must also be discarded if they belong to the same PDU Set. (Discard all PDCP SDUs belonging to the PDU Set to which the PDCP SDU belongs along with the corresponding PDCP Data PDUs; PDCP SDUs subsequently received from upper layers are also discarded if they belong to the PDU Set.)

[0144] ■ Otherwise (pdu-SetDiscard not set) (else):

[0145] ◆ Only the corresponding PDCP SDU and the associated PDCP Data PDU must be discarded. (Discard the PDCP SDU along with the corresponding PDCP Data PDU.)

[0146] In one embodiment of the present disclosure, a PDCP layer device may issue a discard instruction for a PDCP Data PDU to a lower layer (e.g., RLC) if the discarded PDCP Data PDU has already been submitted to a lower layer (e.g., RLC).

[0147] In the present disclosure, an RLC transmitting device may refer to a transmitting UM RLC layer device. In the present disclosure, an RLC receiving device may refer to a receiving UM RLC layer device.

[0148] In the present disclosure, an RLC transmitting device may refer to a transmitting side of an AM RLC layer device. In the present disclosure, an RLC receiving device may refer to a receiving side of an AM RLC layer device.

[0149] In one embodiment of the present disclosure, an RLC transmitter may discard a specific RLC SDU if it receives a discard instruction for the specific RLC SDU from a higher layer (e.g., PDCP). For example, discarding the RLC SDU may be performed only if the corresponding RLC SDU or a segment of the corresponding RLC SDU has not yet been delivered to a lower layer (e.g., MAC). Otherwise, if the corresponding RLC SDU is discarded, an RLC SN (Sequence Number) Gap may occur. An RLC SN Gap may refer to a case where an RLC SDU having a specific RLC SN cannot be (permanently) received by an RLC receiver due to discarding an RLC SDU having the corresponding SN by the RLC transmitter.

[0150] If the SN of a discarded RLC SDU is assigned to an RLC SDU that has not yet been delivered to another (non-discarded) lower layer, an RLC SN Gap may not occur. However, if the SN of an RLC SDU that has already been delivered to a lower layer is assigned to another RLC SDU, multiple RLC SDUs with the same SN may be received by the RLC receiver. In this case, the later-arriving RLC SDU may be treated as a duplicate reception and may be discarded. This may result in data loss. Therefore, the AM RLC layer device may operate so that the RLC SDU that has already been delivered to the lower layer cannot be discarded.

[0151] When an AM RLC layer device receives a NACK (Negative Acknowledgement) from a receiver for a transmitted RLC SDU, it can retransmit the RLC SDU. If a discard instruction is received from an upper layer for the RLC SDU, it may not be discarded because it is an RLC SDU that has already been delivered to a lower layer. Therefore, even an RLC SDU that has already been discarded (already discarded by an upper layer and has no transmission value) can be retransmitted. This may delay the transmission / retransmission of other RLC SDUs before discarding. In addition, it may cause waste of radio resources. As a method for solving the above problem, the present invention can operate so that even an RLC SDU that has already been delivered to a lower layer can be discarded. Therefore, in order to avoid the stalling phenomenon of the Receiving Window at the RLC receiving device due to the RLC SN Gap that occurs at this time, a method is proposed in which an RLC transmitting device can report an RLC SN Gap to the RLC receiving device through an RLC SN Gap Report. For example, the RLC SN Gap Report can be transmitted and received only to AM RLC layer devices.

[0152] In one embodiment of the present disclosure, the RLC SN Gap Report may have the form of a specific RLC Control PDU. In the present disclosure, the RLC SN Gap Report and the RLC SN Gap PDU may be used interchangeably. The RLC SN Gap Report proposed in the present disclosure may have other names (e.g., RLC Discard / Missing Report / Notification / Indication), and the present disclosure does not limit the name of the corresponding RLC Control PDU. The RLC SN Gap in the present disclosure may be replaced with other expressions such as RLC SN / SDU / PDU Loss / Discard / Missing, and the present disclosure does not limit the expressions.

[0153] In one embodiment of the present disclosure, a base station may include configuration information that allows / enables transmission / reception of RLC SN Gap and / or RLC SN Gap Report for each RLC layer device of a terminal via an RRC message (e.g., RRCReconfiguraiton). As an example, the configuration information may be referred to as rlcSnGapEnabled.

[0154] In one embodiment of the present disclosure, the base station may include configuration information, via an RRC message (e.g., RRCReconfiguraiton), indicating that transmission / reception of RLC SN Gap and / or RLC SN Gap Report is not allowed / disabled for each RLC layer device of the terminal. For example, the configuration information may be referred to as rlcSnGapNotEnabled.

[0155] In an embodiment of the present disclosure, when rlcSnGapEnabled is set, it may mean that rlcSnGapNotEnabled is not set.

[0156] In one embodiment of the present disclosure, if a base station sets rlcSnGapEnabled to a specific RLC device of a terminal through an RRC message (e.g., RRCReconfiguration), the RLC transmitting device may discard an RLC SDU that has been instructed to be discarded by a higher layer. For example, the discarding may be performed both when the RLC SDU or a segment of the RLC SDU has not yet been delivered to a lower layer and when it has already been delivered. For example, the following embodiment may be considered.

[0157] - When indicated from an upper layer (e.g. PDCP) to discard a particular RLC SDU, the transmitting side of an AM RLC entity shall discard the indicated RLC SDU (if a positive acknowledgment has not been received for the RLC SDU), if rlcSnGapEnabled is configured.

[0158] - When indicated from an upper layer (e.g. PDCP) to discard a particular RLC SDU, the transmitting side of an AM RLC entity shall discard the indicated RLC SDU if neither the RLC SDU nor a segment thereof has been submitted to the lower layers, if rlcSnGapEnabled is not configured. The transmitting side of an AM RLC entity shall not introduce an RLC SN gap when discarding an RLC SDU, if rlcSnGapEnabled is not configured.

[0159] The following embodiments may exist for UM RLC layer devices.

[0160] - When indicated from an upper layer (e.g., PDCP) to discard a particular RLC SDU, the transmitting UM RLC entity shall discard the indicated RLC SDU.

[0161] - When rlcSnGapEnabled is configured, the transmitting UM RLC entity shall discard the indicated RLC SDU if indicated from an upper layer (i.e. PDCP) to discard a particular RLC SDU.

[0162] - If rlcSnGapEnabled is not configured, the transmitting UM RLC entity shall discard the indicated RLC SDU only when it receives an instruction from an upper layer (i.e. PDCP) to discard a particular RLC SDU, and neither the RLC SDU nor a segment thereof has been submitted to the lower layers, if rlcSnGapEnabled is not configured.

[0163] FIG. 4 is a diagram illustrating an operation in which an RLC transmitting device reports an RLC SN Gap to an RLC receiving device through an RLC SN Gap Report according to an embodiment of the present disclosure.

[0164] The state variables / Counters / Timers used in this disclosure can be used for the following purposes / meanings / rules.

[0165] - All state variables and all counters are non-negative integers.

[0166] - All state variables related to AM data transmission can have values ​​from 0 to 4095 when using a 12-bit sequence number (SN), and from 0 to 262143 when using an 18-bit sequence number. All arithmetic operations on AM-related state variables of the present disclosure are affected by AM modulo operations (e.g., final value = [operation result] mod 4096 (12-bit SN), or mod 262144 (18-bit SN)). (All state variables related to AM data transfer can take values ​​from 0 to 4095 for 12 bit SN or from 0 to 262143 for 18 bit SN. All arithmetic operations contained in the present document on state variables related to AM data transfer are affected by the AM modulus (ie final value = [value from arithmetic operation] modulo 4096 for 12 bit SN and 262144 for 18 bit SN).)

[0167] - All state variables related to UM data transfer can take values ​​from 0 to 63 for 6-bit SN, and from 0 to 4095 for 12-bit SN. All arithmetic operations on UM-related state variables of the present disclosure are affected by the UM modulus (i.e., final value = [operation result] modulo 64 (6-bit SN), or modulo 4096 (12-bit SN)). (All state variables related to UM data transfer can take values ​​from 0 to 63 for 6-bit SN or from 0 to 4095 for 12-bit SN. All arithmetic operations contained in the present document on state variables related to UM data transfer are affected by the UM modulus (i.e., final value = [value from arithmetic operation] modulo 64 for 6-bit SN and 4096 for 12-bit SN).)

[0168] - When comparing state variables or SN values, a modulus base must be used for arithmetic comparisons.

[0169] - In the AM RLC entity, the transmitting side uses TX_Next_Ack and the receiving side uses RX_Next as the module base. This base value is subtracted from the values ​​to be compared, and then an absolute comparison is performed. (TX_Next_Ack and RX_Next shall be assumed as the modulus base at the transmitting side and receiving side of an AM RLC entity, respectively. This modulus base is subtracted from all the values ​​involved, and then an absolute comparison is performed) (e.g., RX_Next <= SN < RX_Next + AM_Window_Size is evaluated as [RX_Next - RX_Next] modulo 2[sn-FieldLength] <= [SN - RX_Next] modulo 2[sn-FieldLength] < [RX_Next + AM_Window_Size - RX_Next] modulo 2[sn-FieldLength]), where sn-FieldLength is 12 for 12-bit SN and 18 for 18-bit SN (where sn-FieldLength is 12 or 18 for 12 bit SN and 18 bit SN, respectively).

[0170] - On the UM RLC receiving side, RX_Next_Highest - UM_Window_Size is used as the module base. After subtracting this base value from the comparison target, an absolute comparison is performed. (RX_Next_Highest- UM_Window_Size shall be assumed as the modulus base at the receiving UM RLC entity. This modulus base is subtracted from all the values ​​involved, and then an absolute comparison is performed) (For example, (RX_Next_Highest- UM_Window_Size) <= SN < RX_Next_Highest is evaluated as [(RX_Next_Highest-UM_Window_Size) - (RX_Next_Highest- UM_Window_Size)] modulo 2[sn-FieldLength] <= [SN - (RX_Next_Highest-UM_Window_Size)] modulo 2[sn-FieldLength] < [RX_Next_Highest- (RX_Next_Highest- UM_Window_Size)] modulo 2[sn-FieldLength]), where sn-FieldLength is 6 for 6-bit SN and 12 for 12-bit SN (where sn-FieldLength is 6 or 12 for 6-bit SN and 12-bit SN, respectively).

[0171] - AM RLC transmitting side state variables (The transmitting side of each AM RLC entity shall maintain the following state variables):

[0172] ■ a) TX_Next_Ack - Stores the SN value of the next RLC SDU to receive a positive acknowledgment for sequential transmission, and serves as the lower edge of the transmitting window. The initial value is 0, and it is updated when an ACK is received for the corresponding SN. (Acknowledgement state variable. This state variable holds the value of the SN of the next RLC SDU for which a positive acknowledgment is to be received in-sequence, and it serves as the lower edge of the transmitting window. It is initially set to 0, and is updated whenever the AM RLC entity receives a positive acknowledgment for an RLC SDU with SN = TX_Next_Ack.)

[0173] ■ b) TX_Next - Stores the SN value to be assigned to the newly generated AMD PDU. The initial value is 0, and is updated when the AMD PDU contains an RLC SDU or the last segment. (Send state variable. This state variable holds the value of the SN to be assigned for the next newly generated AMD PDU. It is initially set to 0, and is updated whenever the AM RLC entity constructs an AMD PDU with SN = TX_Next and contains an RLC SDU or the last segment of an RLC SDU.)

[0174] ■ c) POLL_SN - Stores the highest SN value among the AMD PDUs submitted to the lower layer with the Poll bit set. The initial value is 0. (Poll send state variable. This state variable holds the value of the highest SN of the AMD PDU among the AMD PDUs submitted to the lower layer when POLL_SN is set according to clause 5.3.3.2. It is initially set to 0.)

[0175] - AM RLC transmitting side counters (The transmitting side of each AM RLC entity shall maintain the following counters):

[0176] ■ a) PDU_WITHOUT_POLL - Counter. Counts the number of AMD PDUs transmitted since the last poll bit was transmitted. Default: 0 (This counter is initially set to 0. It counts the number of AMD PDUs sent since the most recent poll bit was transmitted).

[0177] ■ b) BYTE_WITHOUT_POLL - Counter. Counts the number of data bytes transmitted since the last poll bit was transmitted. Default: 0 (This counter is initially set to 0. It counts the number of data bytes sent since the most recent poll bit was transmitted.)

[0178] ■ c) RETX_COUNT - Counter. Maintained per RLC SDU or segment, it counts the number of retransmissions of each data. (This counter counts the number of retransmissions of an RLC SDU or RLC SDU segment (see clause 5.3.2). There is one RETX_COUNT counter maintained per RLC SDU.)

[0179] - AM RLC receiving side state variables (The receiving side of each AM RLC entity shall maintain the following state variables):

[0180] ■ a) RX_Next - Receive state variable. Stores the SN value following the last in-sequence completely received RLC SDU, which is the lower edge of the receiving window. Initial value: 0 (This state variable holds the value of the SN following the last in-sequence completely received RLC SDU, and serves as the lower edge of the receiving window. It is initially set to 0 and is updated whenever the AM RLC entity receives an RLC SDU with SN = RX_Next.)

[0181] ■ b) RX_Next_Status_Trigger - t-Reassembly state variable. This state variable holds the value of the SN following the SN of the RLC SDU that triggered t-Reassembly.

[0182] ■ c) RX_Highest_Status - Maximum STATUS transmit state variable. Stores the highest possible SN value that can be used as ACK_SN when a STATUS PDU is constructed. Initial value: 0 (This state variable holds the highest possible SN value that can be indicated by "ACK_SN" when a STATUS PDU needs to be constructed. It is initially set to 0.)

[0183] ■ d) RX_Next_Highest - Highest received state variable. Stores the SN value following the highest SN among received RLC SDUs. Initial value: 0 (This state variable holds the value of the SN following the SN of the RLC SDU with the highest SN among received RLC SDUs. It is initially set to 0.)

[0184] - UM RLC transmitting side state variables (Each transmitting UM RLC entity shall maintain the following state variables):

[0185] ■ a) TX_Next - UM send state variable. Stores the SN value to be assigned to the newly generated UMD PDU. Initial value: 0, updated after the UMD PDU containing the last segment of an RLC SDU is submitted to the lower layer. (This state variable holds the value of the SN to be assigned for the next newly generated UMD PDU with segment. It is initially set to 0 and is updated after the UM RLC entity submits a UMD PDU containing the last segment of an RLC SDU to lower layers.)

[0186] - UM RLC receiving side state variables (Each receiving UM RLC entity shall maintain the following state variables):

[0187] ■ a) RX_Next_Reassembly - UM receive state variable. Stores the earliest SN value considered for reassembly. The initial value is 0, but can be set differently depending on the following conditions: NR sidelink groupcast / broadcast or SL-SRB4: SN of the first received UMD PDU containing the SN value. When configured on MCCH or MTCH: The initial value can be set to the previous value of RX_Next_Highest (depending on terminal implementation) (This state variable holds the value of the earliest SN that is still considered for reassembly. It is initially set to 0. For groupcast and broadcast of NR sidelink communication or for SL-SRB4 for broadcast and groupcast based sidelink discovery, it is initially set to the SN of the first received UMD PDU containing an SN. For the receiving UM RLC entity configured for MCCH or MTCH, it is up to UE implementation to set the initial value of RX_Next_Reassembly to a value before RX_Next_Highest.)

[0188] ■ b) RX_Timer_Trigger - UM t-Reassembly state variable. This state variable holds the value of the SN following the SN that triggered t-Reassembly.

[0189] ■ c) RX_Next_Highest- UM reception state variable. This state variable stores the next SN value of the PDU with the highest SN among the received UMD PDUs. This variable is used as the higher edge of the reassembly window. The initial value is 0, and in case of groupcast and broadcast or broadcast / groupcast based SL-SRB4 discovery of NR sidelink communication, it is set to the SN of the first received UMD PDU containing an SN value. Also, in case of a receiving UM RLC entity configured on MCCH or MTCH, the initial value is set to the SN of the first received UMD PDU. (UM receive state variable. This state variable holds the value of the SN following the SN of the UMD PDU with the highest SN among received UMD PDUs. It serves as the higher edge of the reassembly window. It is initially set to 0. For groupcast and broadcast of NR sidelink communication or for SL-SRB4 for broadcast and groupcast based sidelink discovery, it is initially set to the SN of the first received UMD PDU containing an SN. For the receiving UM RLC entity configured for MCCH or MTCH, it is initially set to the SN of the first received UMD PDU containing an SN.)

[0190] - a) AM_Window_Size. This constant is used by both the transmitting side and the receiving side of each AM RLC entity. When a 12-bit SN is set: AM_Window_Size = 2048, when an 18-bit SN is set: AM_Window_Size = 131072 (This constant is used by both the transmitting side and the receiving side of each AM RLC entity. AM_Window_Size = 2048 when a 12-bit SN is used, AM_Window_Size = 131072 when an 18-bit SN is used.)

[0191] - b) UM_Window_Size. This constant is used by the UM RLC receiver to define the reassembly window range. This value determines the SN range of UMD SDUs that can be received without exceeding the receiving window. When a 6-bit SN is configured: UM_Window_Size = 32. When a 12-bit SN is configured: UM_Window_Size = 2048 (This constant is used by the receiving UM RLC entity to define the SNs of those UMD SDUs that can be received without causing an advancement of the receiving window. UM_Window_Size = 32 when a 6-bit SN is configured, UM_Window_Size = 2048 when a 12-bit SN is configured.)

[0192] - a) t-PollRetransmit. This timer is used by the transmitting side of an AM RLC entity to determine whether to retransmit a poll bit. (This timer is used by the transmitting side of an AM RLC entity in order to retransmit a poll.)

[0193] - b) t-Reassembly. This timer is used by the AM RLC receiving side and the UM RLC receiving side to detect loss of RLC PDUs at lower layers (see 3GPP TS 38.322 5.2.2.2 and 5.2.3.2). If t-Reassembly is already running, another t-Reassembly timer will not be started at the same time, and only one timer can be active per RLC entity. (This timer is used by the receiving side of an AM RLC entity and the receiving UM RLC entity in order to detect loss of RLC PDUs at lower layers (see clauses 5.2.2.2 and 5.2.3.2). If t-Reassembly is running, t-Reassembly shall not be started additionally, i.e. only one t-Reassembly per RLC entity is running at a given time.)

[0194] - c) t-StatusProhibit. This timer is used by the AM RLC receiving side to prohibit the transmission of a STATUS PDU for a certain period of time. (This timer is used by the receiving side of an AM RLC entity in order to prohibit the transmission of a STATUS PDU.)

[0195] Referring to FIG. 4, when an RLC transmitter receives a discard instruction for a specific RLC SDU from a higher layer, the RLC SDU can be in one of three states as follows.

[0196] - State 1 (435): The RLC SDU has not been submitted to the lower layer (MAC) or has not been transmitted (by lower layer / MAC PDU)). For example, the RLC SDU in State 1 may not have been included in an RLC Data PDU or may be included in an RLC Data PDU that is pending for initial transmission.

[0197] - State 2 (445, 455): The RLC SDU or a segment of the RLC SDU has already been submitted to the lower layer (MAC)) or has already been transmitted (by the lower layer / MAC PDU) but a Positive Acknowledgement has not yet been received for the RLC SDU or at least one segment of the RLC SDU. This state may include the following cases:

[0198] ■ State 2-1 (445): The above RLC SDU or a segment of the RLC SDU is included in an RLC Data PDU that is pending for retransmission.

[0199] ■ State 2-2 (455): Included in the RLC Data PDU waiting for Acknowledgement after the above RLC SDU or RLC SDU segment has been transmitted.

[0200] - State 3: A state in which a Positive Acknowledgement has already been received for the RLC SDU or all Segments of the RLC SDU. For example, an RLC SDU or all Segments of an RLC SDU in this state may no longer exist in the RLC transmitter. Therefore, the presence of an RLC SDU or a Segment of an RLC SDU in the RLC transmitter may mean that a Positive Acknowledgement has not yet been received for the RLC SDU or the Segment of the RLC SDU.

[0201] In one embodiment of the present disclosure, for an RLC SN Gap to occur when an RLC SDU is discarded in an RLC layer device or for an RLC SN Gap occurrence condition to be met, some or all of the following conditions may need to be met.

[0202] - Condition 1: When discarding the above RLC SDU, an RLC SN must already be assigned to the RLC SDU.

[0203] - Condition 2: When discarding the RLC SDU, the RLC SDU or a segment of the RLC SDU must have already been submitted to a lower layer (MAC) or has already been transmitted (via a lower layer) (by a lower layer / MAC PDU). For example, an RLC SDU satisfying Condition 2 must be an RLC SDU (state 2) that has not yet received a Positive Acknowledgement for the RLC SDU or for (at least) one segment of the RLC SDU. In other words, an RLC SDU (state 3) that has already received a Positive Acknowledgement for an RLC SDU or all segments of the RLC SDU is either not present in the RLC transmitter and therefore cannot be discarded, or even if it exists, it can be considered not to satisfy Condition 2.

[0204] - Condition 3: When discarding the RLC SDU, the discarded RLC SDU must not be the RLC SDU last assigned a SN by the corresponding RLC layer device. For example, when discarding the RLC SDU, the RLC SN may be less than TX_Next - 1. For example, when discarding the RLC SDU, at least one RLC SDU must have been assigned an RLC SN greater than the RLC SN of the discarded RLC SDU, or in another embodiment, at least one RLC SDU must have been assigned an RLC SN greater than the RLC SN of the discarded RLC SDU and then delivered (transmitted) to a lower layer.

[0205] In one embodiment of the present disclosure, when an RLC SDU is discarded at an RLC layer device, if the above condition 1 is satisfied, it can be said that an RLC SN Gap has occurred or an RLC SN Gap occurrence condition has been satisfied. For example, when an RLC SDU is discarded at an RLC layer device, if both the above conditions 1 and 3 are satisfied, it can be said that an RLC SN Gap has occurred or an RLC SN Gap occurrence condition has been satisfied. For example, when an RLC SDU is discarded at an RLC layer device, if the above conditions 1, 2, and 3 are all satisfied, it can be said that an RLC SN Gap has occurred or an RLC SN Gap occurrence condition has been satisfied.

[0206] In one embodiment of the present disclosure, when an RLC SDU is discarded in an RLC transmitting device, whether an RLC SN Gap occurs or whether an RLC SN Gap occurrence condition is satisfied can be determined by the implementation of the terminal / base station (up to UE / network implementation).

[0207] Referring to FIG. 4, when discarding an RLC SDU (430) in state 1, an RLC SN Gap may not occur. Therefore, the RLC SN Gap report may not report the SN of the corresponding RLC SDU. Referring to FIG. 4, when discarding an RLC SDU (440, 450) in state 2-1 (445) and / or state 2-2 (455), an RLC SN Gap may occur. Therefore, to report the RLC SN Gap, an RLC transmitting device may transmit an RLC SN Gap report (460). An RLC receiving device that receives an RLC SN Gap report (460) may perform all or part of the operations to be performed when successfully receiving an RLC SDU (470, 480) corresponding to the RLC SN reported as the SN Gap. Therefore, a transmitting and receiving RLC layer device operating in RLC AM mode can continue to perform transmitting and receiving operations without a Transmitting / Receiving Window pause even if an RLC SN Gap occurs.

[0208] In one embodiment of the present disclosure, the RLC transmitting device can trigger an RLC SN Gap Report when the RLC SN Gap occurs or when the RLC SN Gap occurrence condition is met.

[0209] In one embodiment of the present disclosure, at the transmitting side of an AM RLC layer device, transmission of an RLC Control PDU may have a higher priority than transmission of an AMD PDU (AM Data PDU). For example, the following operation may be performed.

[0210] - The transmitting side of an AM RLC entity shall prioritize transmission of RLC control PDUs over AMD PDUs.

[0211] For example, the RLC Control PDU may correspond to an RLC STATUS PDU (RLC STATUS Report) or an RLC SN Gap PDU (RLC SN Gap Report).

[0212] In one embodiment of the present disclosure, when both an RLC STATUS Report and an RLC SN Gap Report are triggered, transmission of the RLC STATUS Report / PDU may have a higher priority than transmission of the RLC SN Gap Report / PDU. For example, the following may be performed. This is because the RLC STATUS Report / PDU may be more urgent than the RLC SN Gap Report / PDU.

[0213] - The transmitting side of an AM RLC entity shall prioritize transmission of RLC STATUS PDU(s) over RLC SN Gap PDU(s).

[0214] In one embodiment of the present disclosure, when both the RLC STATUS Report and the RLC SN Gap Report are triggered, transmission of the RLC SN Gap Report / PDU may have a higher priority than transmission of the RLC STATUS Report / PDU. For example, the following may be performed. This is because the RLC SN Gap Report may be more urgent than the RLC STATUS Report.

[0215] - The transmitting side of an AM RLC entity shall prioritize transmission of RLC SN Gap Report / PDU(s) over RLC STATUS Report / PDU(s).

[0216] In one embodiment of the present disclosure, after an RLC SN Gap Report is triggered, the RLC transmitting device may have the following embodiments when determining when to Compile / Construct the RLC SN Gap Report / PDU.

[0217] - Example 1: After the RLC SN Gap report is triggered, at the first transmission opportunity indicated by the lower layer, the RLC SN Gap PDU can be constructed / compiled and then delivered to the lower layer. For example, the following operation can be performed.

[0218] ■ When an RLC SN Gap report has been triggered, the transmitting side of an AM RLC entity shall:

[0219] ◆ At the first transmission opportunity indicated by the lower layer, construct / compile an RLC SN Gap PDU and submit it to the lower layer.

[0220] - Example 2: After the RLC SN Gap report is triggered, the RLC SN Gap PDU can be immediately compiled / constructed. For example, it can operate as follows.

[0221] ■ If the SN Gap Report is triggered, the SN Gap Report is constructed / compiled immediately and pending for transmission.

[0222] In one embodiment of the present disclosure, a new transmission prevention timer (e.g., t-snGapProhibit) may be introduced to prevent excessive transmission of RLC SN Gap Reports. In one embodiment, the use / size of the timer may be set by the base station to the corresponding RLC layer device via an RRC message (e.g., RRCReconfiguration).

[0223] In one embodiment, when the t-snGapProhibit timer is running, the RLC transmitter of the terminal may operate so as not to transmit (forward to a lower layer) an RLC SN Gap Report. In one embodiment, only when the t-snGapProhibit timer is not running, the RLC transmitter of the terminal may operate so as to transmit (forward to a lower layer) an RLC SN Gap Report.

[0224] In one embodiment, the RLC transmitting device of a terminal in which the size of the t-snGapProhibit is set to a value greater than 0 may operate as follows.

[0225] When an RLC SN Gap Report has been triggered, the transmitting side of an AM RLC entity shall:

[0226] - If the t-snGapProhibit timer is not running: At the first transmission opportunity indicated by the lower layer, compile / construct an RLC SN Gap PDU and submit it to the lower layer.

[0227] - If the t-snGapProhibit timer is running: At the first transmission opportunity indicated by the lower layer after the t-snGapProhibit timer expires, only one RLC SN Gap report / PDU shall be generated or compiled and submitted to the lower layer, even if the RLC SN Gap report was triggered several times while the t-snGapProhibit was running. (else: At the first transmission opportunity indicated by the lower layer after the t-snGapProhibit timer expires, only one RLC SN Gap report / PDU shall be generated or compiled and submitted to the lower layer, even if the RLC SN Gap report was triggered several times while the t-snGapProhibit was running.)

[0228] When an RLC SN Gap Report has been submitted to a lower layer, the transmitting side of an AM RLC entity shall:

[0229] - start t-snGapProhibit)

[0230] In one embodiment of the present disclosure, in order to prevent RLC SN Gap Reports from being transmitted too frequently, an RLC SN Gap report / PDU may be transmitted (delivered to a lower layer) only when the number of times the RLC SN Gap report is triggered is greater than or equal to a certain threshold. For example, the threshold (e.g., snGapThreshold) may be set by the base station to the corresponding RLC layer device of the terminal via an RRC message (e.g., RRCReconfiguraiton).

[0231] In one embodiment, the RLC transmitter may introduce an RLC SN Gap Report trigger COUNTER (e.g., SN_GAP_WITHOUT_REPORT, initially set to 0).

[0232] In one embodiment, an RLC transmitter with snGapThreshold set may operate as follows.

[0233] - When an RLC SN gap report is triggered, increment SN_GAP_WITHOUT_REPORT by one.

[0234] ■ If SN_GAP_WITHOUT_REPORT is greater than or equal to snGapThreshold (if SN_GAP_WITHOUT_REPORT >= snGapThreshold)

[0235] ◆ At the first transmission opportunity indicated by the lower layer, compile / construct an RLC SN Gap PDU and submit it to the lower layer.

[0236] ◆ Set SN_GAP_WITHOUT_REPORT value to 0 (set GAP_WITHOUT_REPORT to 0)

[0237] As one embodiment of the present disclosure, FIG. 5 is a diagram illustrating the format of an RLC SN Gap report / PDU.

[0238] Referring to FIG. 5, an RLC SN Gap PDU may be composed of an RLC SN Gap PDU payload and an RLC control PDU header. For example, the RLC control PDU header may be composed of a D / C (Data / Control) field / bit (500) and a CPT (Control PDU Type) field (510).

[0239] In one embodiment, the D / C bit / field (500) can be interpreted as follows.

[0240] - The D / C field indicates whether the RLC PDU is an RLC data PDU or an RLC control PDU. The interpretation of the D / C field is as follows: 0 can indicate a control PDU, and 1 can indicate a data PDU. (The D / C field indicates whether the RLC PDU is an RLC data PDU or an RLC control PDU. The interpretation of the D / C is: 0 can indicate a control PDU, and 1 can indicate a data PDU.)

[0241] In one embodiment, the CPT field (510) may be interpreted as follows.

[0242] - The CPT field indicates the type of the RLC control PDU.

[0243] In one embodiment, the CPT field (510) may be interpreted as shown in Table 1 below. The RLC SN Gap PDU may have a Reserved value other than 001. The present disclosure does not limit the CPT value.

[0244] [Table 1: CPT field interpretation]

[0245]

[0246] Referring to FIG. 5, the payload of the RLC SN Gap PDU may start from the first bit (520) following the RLC control PDU header. For example, the payload of the RLC SN Gap PDU may be composed of at least one of the fields below. The present disclosure does not limit the names or lengths of the fields below. If they can be replaced with fields having different names or different lengths indicating information with the same meaning, the present disclosure proposes the meaning of the information conveyed through the fields.

[0247] - First_GAP_SN field (520, 521)

[0248] ■ Length: 12 bits or 18 bits (configured by NW)

[0249] ■ The First_GAP_SN field indicates

[0250] ◆ Option 1: Not previously reported by RLC SN Gap PDU / report,

[0251] The first / smallest SN of the RLC SDU that is discarded / whose discarding causes an SN gap, and not previously reported as discarded by an RLC SN Gap PDU / report.

[0252] ◆ Option 2: The first / smallest SN of the RLC SDU that has been discarded / caused an SN gap, from (and including) TX_Next_Ack

[0253] ◆ Option 3: The first / smallest SN of the RLC SDU which is discarded / whose discarding causes RLC SN gap, and not previously reported as discarded by RLC SN Gap PDU / report, from (and including) TX_Next_Ack

[0254] - Extension bit 1 (E1) field (530, 551)

[0255] ■ Length: 1 bit

[0256] ■ The E1 field indicates whether a set of GAP_SN, E1, E2, and E3 follows. Value 0: The set does not follow. Value 1: The set follows. (The E1 field can indicate whether or not a set of GAP_SN, E1, E2, and E3 follows: 0 can indicate a set of GAP_SN, E1, E2, and E3 does not follow. 1 can indicate a set of GAP_SN, E1, E2, and E3 follows.)

[0257] - GAP_SN field (540, 541)

[0258] ■ Length: 12 bits or 18 bits (configured by NW)

[0259] ■ The GAP_SN field indicates the SN of the RLC SDU (or RLC SDU segment) that has been discarded / whose discarding causes an SN Gap at the transmitting side of the AM RLC entity and is larger than First_GAP_SN.

[0260] - Extension bit 2 (E2) field (531, 552)

[0261] ■ Length: 1 bit

[0262] ■ The E2 field indicates whether the GAP_SOstart and GAP_SOend fields follow the corresponding GAP_SN. Value 0: No GAP_SOstart and GAP_SOend follow. Value 1: The GAP_SOstart and GAP_SOend follow. (The E2 field can indicate whether or not a set of GAP_SOstart and GAP_SOend follows. 0 can indicate a set of GAP_SOstart and GAP_SOend does not follow for this GAP_SN. 1 can indicate a set of GAP_SOstart and GAP_SOend follows for this GAP_SN.)

[0263] - GAP_SOstart field (560, 561)

[0264] ■ The GAP_SOstart field, together with the GAP_SOend field, indicates the starting position (offset) in bytes of the byte that was discarded or caused an SN Gap due to discarding within an RLC SDU with SN = GAP_SN. The first byte of the RLC SDU is indicated by the value "0000000000000000", and the byte position starts from 0. (The GAP_SOstart field (together with the GAP_SOend field) indicates the portion of the RLC SDU with SN = GAP_SN (the GAP_SN for which the GAP_SOstart is related to) that has been discarded / whose discarding causes RLC SN gap at the transmitting side of the AM RLC entity. Specifically, the GAP_SOstart field can indicate the position of the first byte of the portion of the RLC SDU in bytes within the original The first byte of the original RLC SDU can be referred to by the GAP_SOstart field value "0000000000000000", ie, numbering starts at zero.)

[0265] - GAP_SOend field (570, 571)

[0266] ■ When E3 = 0: The GAP_SOend field, together with the GAP_SOstart field, indicates the position, in bytes, of the last byte of the section that was discarded or caused an SN Gap within an RLC SDU with SN = GAP_SN. The first byte of the original RLC SDU is referenced by the value "0000000000000000", and the byte number starts from 0. The special value "1111111111111111" indicates that all up to the last byte of the corresponding RLC SDU has been discarded (When E3 is 0, the GAP_SOend field (together with the GAP_SOstart field) can indicate the portion of the RLC SDU with SN = GAP_SN (the GAP_SN for which the GAP_SOend is related to) that has been discarded / whose discarding causes RLC SN gap at the transmitting side of the AM RLC entity. Specifically, the GAP_SOend field indicates the position of the last byte of the RLC SDU in bytes within the first byte of the original RLC SDU is referred to by the GAP_SOend field value "0000000000000000", ie, numbering starts at zero. "1111111111111111" can be used to indicate that the discarded portion of the RLC SDU includes all bytes to the last byte of the RLC SDU).

[0267] When E3 = 1: The GAP_SOend field indicates the position, in bytes, of the last byte within an RLC SDU where SN = GAP_SN + GAP_SN range - 1 that was discarded or caused an SN Gap. The first byte is identically referenced as "0000000000000000". "111111111111111" means that all bytes up to the last byte were discarded. (When E3 is 1, the GAP_SOend field indicates the portion of the RLC SDU with SN = GAP_SN + GAP_SN range - 1 that has been discarded / whose discarding causes RLC SN gap at the transmitting side of the AM RLC entity. Specifically, the GAP_SOend field indicates the position of the last byte of the portion of the RLC SDU in bytes within the original RLC SDU. The first byte of the original RLC SDU is referred by the GAP_SOend field value "0000000000000000", ie, numbering starts at zero. The special GAP_SOend value "1111111111111111" can be used to indicate that the discarded portion of the RLC SDU includes all bytes to the last byte of the RLC SDU.)

[0268] - Extension bit 3 (E3) field (532, 553)

[0269] ■ Length: 1 bit.

[0270] ■ The E3 field indicates whether or not information about a continuous sequence of RLC SDUs that have been discarded or caused an SN gap follows. Value 0: The GAP_SN range field does not follow this GAP_SN. Value 1: The GAP_SN range field follows this GAP_SN. (The E3 field can indicate whether or not information about a continuous sequence of RLC SDUs that have been discarded / causing an RLC SN gap follows. 0 can indicate the GAP_SN range field does not follow this GAP_SN. 1 can indicate the GAP_SN range field follows this GAP_SN.)

[0271] - GAP_SN range field (580)

[0272] ■ The GAP_SN range field indicates the number of consecutively discarded / causing RLC SN gap RLC SDUs starting from and including GAP_SN.

[0273] In one embodiment of the present disclosure, when creating an RLC SN Gap PDU, an AM RLC layer device may operate as follows.

[0274] - First_GAP_SN setting conditions (setting the First_GAP_SN to):

[0275] ■ Option 1: The first / smallest SN of which the RLC SDU has been discarded / caused RLC SN gap, and not previously reported as discarded / RLC SN gap by RLC SN Gap report.

[0276] ■ Option 2: The first / smallest SN of which the RLC SDU has been discarded / caused RLC SN gap, from (and including) TX_Next_Ack

[0277] ■ Option 3: Starting from (and including) TX_Next_Ack, the first / smallest SN of RLC SDU which is discarded / whose discarding causes RLC SN gap, and not previously reported as discarded by RLC SN Gap PDU / report, from (and including) TX_Next_Ack

[0278] - Option 1: For RLC SDUs with SN greater than First_GAP_SN that were discarded or caused an SN Gap and were not previously reported, include the GAP_SN in SN order of the RLC SDUs, up to whichever of the following conditions is met first: up to the last / highest SN, or until all RLC SDUs in a contiguous SN range that can fit within the lower layer-specified total RLC PDU size limit were discarded or caused an SN Gap and were already reported, include the GAP_SN and GAP_SN range set. (for the RLC SDUs with SN larger than First_GAP_SN, and have been discarded / caused RLC SN gap, and have not been previously reported as discarded / RLC SN gap by RLC SN gap report, include GAP_SN for each of them in increasing SN order of RLC SDUs up to the last / largest RLC SN, of which the RLC SDU has been discarded / caused RLC SN gap and not previously reported as discarded / RLC SN gap, or up to the point where the resulting RLC SN gap PDU still fits to the total size of RLC PDU(s) indicated by lower layer, whichever comes first.For a continuous sequence of RLC SDUs that have been discarded / caused RLC SN gap, and have been reported as discarded / RLC SN gap, include in the RLC SN gap PDU a set of GAP_SN and GAP_SN range.).

[0279] - Option 2: For all RLC SDUs with SN greater than First_GAP_SN that were discarded or caused an SN Gap, include the GAP_SN in that SN order, up to whichever of the following conditions is met first: If consecutive RLC SDUs in that sequence were discarded or caused an SN Gap, up to the last / highest SN or until the total RLC PDU size allowed by the lower layer is not exceeded, include the GAP_SN and GAP_SN range set for that interval. (for the RLC SDUs with SN larger than First_GAP_SN, and have been discarded / caused RLC SN gap, include GAP_SN for each of them in increasing SN order of RLC SDUs up to the last / largest RLC SN, of which the RLC SDU has been discarded / caused RLC SN gap, or up to the point where the resulting RLC SN gap PDU still fits to the total size of RLC PDU(s) indicated by lower layer, whichever comes first. For a continuous sequence of RLC SDUs that have been discarded / caused RLC SN gap, include in the RLC SN gap PDU a set of GAP_SN and GAP_SN range.)

[0280] As one embodiment of the present disclosure, FIG. 6 is a diagram illustrating the format of an RLC SN Gap report / PDU.

[0281] Referring to FIG. 6, an RLC SN Gap PDU may be composed of an RLC SN Gap PDU payload and an RLC control PDU header. For example, the RLC control PDU header may be composed of a D / C (Data / Control) field / bit (600) and a CPT (Control PDU Type) field (610).

[0282] In one embodiment, the D / C bit / field (600) can be interpreted as follows.

[0283] - The D / C field indicates whether the RLC PDU is an RLC data PDU or an RLC control PDU. The interpretation of the D / C field is as follows: 0 can indicate a control PDU, and 1 can indicate a data PDU. (The D / C field indicates whether the RLC PDU is an RLC data PDU or an RLC control PDU. The interpretation of the D / C. 0 can indicate a control PDU, and 1 can indicate a data PDU.)

[0284] In one embodiment, the CPT field (610) may be interpreted as follows.

[0285] - The CPT field indicates the type of the RLC control PDU.

[0286] In one embodiment, the CPT field (610) may be interpreted as shown in Table 1 above. The RLC SN Gap PDU may have a Reserved value other than 001. The present disclosure does not limit the CPT value.

[0287] Referring to FIG. 6, the payload of the RLC SN Gap PDU / report may start from the first bit (620) following the RLC control PDU header. For example, the payload of the RLC SN Gap PDU may be composed of at least one of the fields below. The present disclosure does not limit the names or lengths of the fields below. If they can be replaced with fields having different names or different lengths indicating information with the same meaning, the present disclosure proposes the meaning of the information conveyed through the fields.

[0288] - First_GAP_SN field (620, 630)

[0289] ■ Length: 12 bits or 18 bits (configured by NW)

[0290] ■ The First_GAP_SN field indicates

[0291] ◆ Option 1: The first / smallest SN of which the RLC SDU has been discarded / caused RLC SN gap, and not previously reported as discarded / RLC SN gap by RLC SN Gap report.

[0292] ◆ Option 2: The first / smallest SN of which the RLC SDU has been discarded / caused RLC SN gap, from (and including) TX_Next_Ack

[0293] ◆ Option 3: The first / smallest SN of RLC SDU which is discarded / whose discarding causes RLC SN gap, and not previously reported as discarded by RLC SN Gap PDU / report, from (and including) TX_Next_Ack

[0294] - GAP_Bitmap field (640, 650): The meaning of the Nth bit (bit position = N) in GAP_Bitmap can be as shown in Table 2 below.

[0295] [Table 2] Bitmap

[0296]

[0297] In one embodiment of the present disclosure, when creating an RLC SN Gap PDU, an AM RLC layer device may operate as follows.

[0298] - Setting the First_GAP_SN to:

[0299] ■ Option 1: The smallest SN among the RLC SDUs that have been discarded or caused an RLC SN Gap and that were not previously reported through an RLC SN Gap report (PDU / report) (the first / smallest SN, of which the RLC SDU has been discarded / caused an RLC SN gap, and not previously been reported as discarded / RLC SN gap by an RLC SN Gap report.)

[0300] ■ Option 2: The first / smallest SN of which the RLC SDU has been discarded / caused RLC SN gap, from (and including) TX_Next_Ack

[0301] ■ Option 3: The first / smallest SN of RLC SDU which is discarded / whose discarding causes RLC SN gap, and not previously reported as discarded by RLC SN Gap PDU / report, from (and including) TX_Next_Ack

[0302] - The bit length of the Bitmap field is set based on the following range: from the First_GAP_SN (excluding that SN); up to the SN containing the last RLC SDU that caused the SN Gap or was discarded. This bit length is rounded up to a multiple of 8, subject to the following conditions: Allocating a Bitmap field of length in bits equal to the number of SNs from and not including the RLC SDU corresponding to First_GAP_SN, up to and including the last RLC SDUs causing SN Gap / discarded, rounded up to the next multiple of 8, or up to and including a RLC SDU causing SN Gap / discarded, rounded up to the next multiple of 8, for which the resulting RLC SN Gap PDU size still fits to the total size of RLC PDU(s) indicated by lower layers, whichever comes first.

[0303] In one embodiment of the present disclosure, an RLC transmitting device configured to transmit / receive an RLC SN Gap Report may operate as follows when transmitting / compiling / constructing / delivering an RLC SN Gap Report to a lower layer.

[0304] - If TX_Next_Ack is / was / has been reported as discarded / discarded by the RLC SN Gap Report / PDU, or is discarded by the RLC SN Gap Report / PDU, then the TX_Next_Ack value shall be set to the smallest SN of the RLC SDU whose SN falls within the range TX_Next_Ack ≤ SN ≤ TX_Next and for which a positive acknowledgment has not been received yet and has not been discarded and has not been reported as an RLC SN Gap or discard (if TX_Next_Ack is / was / has been reported as discarded / discarded by the RLC SN Gap Report / PDU, set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN, whose SN falls within the range TX_Next_Ack <= SN <= TX_Next and for which a positive acknowledgment has not been received yet and has not been discarded / has not been reported as discard / RLC SN gap.)

[0305] In one embodiment of the present disclosure, an RLC transmitter may operate as follows.

[0306] When receiving a positive acknowledgement for an RLC SDU with SN = x, the transmitting side of an AM RLC entity shall:

[0307] ■ Notifies the upper layers that the RLC SDU has been successfully delivered (send an indication to the upper layers of successful delivery of the RLC SDU;)

[0308] ■ Set TX_Next_Ack to the smallest SN among the RLC SDUs that satisfy the following conditions: SN value is greater than or equal to TX_Next_Ack and less than or equal to TX_Next, and a positive acknowledgment has not been received yet and has not been discarded / has not been reported as discard / RLC SN gap. (set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN, whose SN falls within the range TX_Next_Ack <= SN <= TX_Next and for which a positive acknowledgment has not been received yet and has not been discarded / has not been reported as discard / RLC SN gap.)

[0309] In one embodiment of the present disclosure, an RLC receiving device configured to transmit / receive an RLC SN Gap Report may receive an RLC SDU discard / RLC SN Gap for one or more SNs by receiving an RLC SN Gap Report / PDU from a peer RLC transmitting device. For example, an RLC receiving device that has received an RLC SN Gap report / PDU may operate as follows.

[0310] - If the SN of the RLC SDU reported as RLC SN Gap / Discard is outside of the receiving window, the RLC SN Gap / Discard report for the RLC SDU can be ignored.

[0311] - If all bytes of an RLC SDU reported as RLC SN Gap / Discard have already been successfully received and / or the RLC SDU has already been delivered to the upper layer, the RLC SN Gap / Discard report of the RLC SDU can be ignored.

[0312] - If some Byte Segment(s) of an RLC SDU reported as RLC SN Gap / Discard have already been received, the already received Byte Segment(s) may be discarded (from the reception buffer). Alternatively, the Byte Segment(s) may be forwarded to the upper layer.

[0313] - Among the RLC SDUs discarded / reported as RLC SN gap with the above RLC SN Gap report, if the value with the largest SN is indicated as Xmax:

[0314] ■ If Xmax is >= RX_Next_Highest:

[0315] ◆ RX_Next_Highest can be updated to Xmax + 1.

[0316] - if RX_Highest_Status is reported as discarded / RLC SN Gap by the RLC SN Gap PDU / report:

[0317] ■ Update RX_Highest_Status to the SN of the first RLC SDU with SN > current RX_Highest_Status for which not all bytes have been received and has not been reported as discarded / RLC SN gap by RLC SN gap report(s).

[0318] - if RX_Next is reported as discarded / RLC SN Gap by the RLC SN Gap PDU / report:

[0319] ■ Update RX_Next to the SN of the first RLC SDU with SN > current RX_Next for which not all bytes have been received and has not been reported as discarded / RLC SN gap by RLC SN gap report(s).

[0320] - If the t-Reassembly timer is running:

[0321] ■ if RX_Next_Status_Trigger = RX_Next; or

[0322] ■ if RX_Next_Status_Trigger = RX_Next + 1 and there is no missing byte segment of the SDU associated with SN = RX_Next before the last byte of all received segments of this SDU; or

[0323] ■ If RX_Next_Status_Trigger falls outside of the receiving window and RX_Next_Status_Trigger is not equal to RX_Next + AM_Window_Size):

[0324] ◆ Stop and reset t-Reassembly.

[0325] - if t-Reassembly is not running (includes the case t-Reassembly is stopped due to actions above)):

[0326] ■ if RX_Next_Highest> RX_Next + 1; or

[0327] ■ In the SDU corresponding to if RX_Next_Highest = RX_Next + 1 and SN = RX_Next

[0328] If there is at least one missing byte segment of the SDU associated with SN = RX_Next before the last byte of all received segments of this SDU:

[0329] ◆ Start t-Reassembly;

[0330] ◆ Set RX_Next_Status_Trigger to RX_Next_Highest.

[0331] In one embodiment of the present disclosure, an RLC receiving device configured to transmit / receive an RLC SN Gap Report may operate as follows.

[0332] When the t-Reassembly timer expires, the receiving side of an AM RLC entity shall:

[0333] - Update RX_Highest_Status to the SN of the first RLC SDU with SN >= RX_Next_Status_Trigger for which not all bytes have been received and that has not been reported as discarded / RLC SN gap;

[0334] - if RX_Next_Highest> RX_Highest_Status + 1: or

[0335] - if RX_Next_Highest = RX_Highest_Status + 1 and there is at least one missing byte segment of the SDU associated with SN = RX_Highest_Status before the last byte of all received segments of this SDU:

[0336] ■ start t-Reassembly;

[0337] ■ set RX_Next_Status_Trigger to RX_Next_Highest

[0338] In one embodiment of the present disclosure, an AM RLC entity configured to transmit / receive an RLC SN Gap Report may operate as follows.

[0339] When constructing a STATUS PDU, the AM RLC entity shall:

[0340] - Among the RLC SDUs with SN values ​​greater than or equal to RX_Next and less than RX_Highest_Status, the RLC SDUs that have not been completely received yet and have not been reported as discarded or gapped by an RLC SN Gap PDU / report are processed sequentially in increasing SN order and in byte segment order within each SDU, starting with SN = RX_Next, until the resulting STATUS PDU can be contained within the total size limit of the RLC PDU specified by the lower layer (for the RLC SDUs with SN such that RX_Next <= SN < RX_Highest_Status that has not been completely received yet and has not been reported as discarded / RLC SN gap (by RLC SN Gap report / PDU), in increasing SN order of RLC SDUs and increasing byte segment order within RLC SDUs, starting with SN = RX_Next up to the point where the resulting STATUS PDU still fits to the total size of the RLC PDU. PDU(s) indicated by lower layer:

[0341] ■ For an RLC SDU that satisfies the following conditions and for which no byte segments have been received yet and that has not been reported as discarded / RLC SN gap:

[0342] ◆ Include in the STATUS PDU a NACK_SN which is set to the SN of the RLC SDU as the SN of the corresponding SDU.

[0343] ■ For a continuous sequence of byte segments of a partly received RLC SDU that have not been received yet and that has not been reported as discarded / RLC SN gap:

[0344] ◆ Include in the STATUS PDU a set of NACK_SN, SOstart and SOend.

[0345] ■ For a continuous sequence of RLC SDUs that have not been received yet and that has not been reported as discarded / RLC SN gap:

[0346] ◆ Include in the STATUS PDU a set of NACK_SN and NACK range;

[0347] ◆ Include in the STATUS PDU, if required, a pair of SOstart and SOend.

[0348] ■ ACK_SN is set to the SN of the RLC SDU that satisfies the following conditions: the earliest SN that has not yet been received, has not been indicated as missing in the resulting STATUS PDU, and has not been reported as discarded / RLC SN gap.

[0349] FIG. 7 is a diagram illustrating a procedure in which a terminal and a base station report an RLC SN Gap through an RLC SN Gap report according to one embodiment of the present disclosure.

[0350] Referring to FIG. 7, a base station (710) can transmit an RRC message (e.g., UECapabilityEnquiry (730)) to a terminal (700) in an RRC_CONNECTED state (720) to request confirmation of whether RLC SN Gap report is supported. The terminal (700) can report to the base station whether RLC SN Gap report is supported by transmitting an RRC message (e.g., UECapabilityInformation (740)) to the base station.

[0351] For a terminal (700) that supports RLC SN Gap report, the base station (710) can transmit an RRC message (e.g., RRCReconfiguration) (750) to the terminal (700) to set whether to allow RLC SN Gap generation for a specific RLC layer device (i.e., whether to perform RLC SDU discard that may generate RLC SN Gap) and / or whether to enable RLC SN Gap report transmission (e.g., set rlcSnGapEnabled). The RLC layer device of the terminal (700) with rlcSnGapEnabled set can perform RLC SDU discard that may generate RLC SN Gap. The RLC layer device of the terminal (700) with rlcSnGapEnabled set can trigger an RLC SN Gap report when an RLC SN Gap occurs (760). The RLC layer device of the terminal (700) with rlcSnGapEnabled set can trigger and transmit an RLC SN Gap report to the compile / construct / lower layer when an RLC SN Gap occurs (770). The RLC layer device of the terminal (700) with rlcSnGapEnabled set can transmit the RLC SN Gap report to the counterpart RLC layer device of the base station (710) (780). The base station (710) can receive the RLC SN Gap report and update a reception status variable (790). According to one embodiment, the base station can transmit the RLC SN Gap report to the RLC layer device of the terminal (700) with rlcSnGapEnabled set (795). The RLC layer device of the terminal (700) with rlcSnGapEnabled set can update a reception status variable when receiving the RLC SN Gap report (796).

[0352] In one embodiment of the present disclosure, a terminal may operate as follows when calculating a delay-reporting RLC data volume. For the purpose of MAC delay status reporting, the terminal (UE) shall evaluate the dsr-ReportingThreshold values ​​in ascending order and consider the following as delay-reporting RLC data volume associated with the i:th dsr-ReportingThreshold:

[0353] - delay-reporting RLC SDUs and delay-reporting RLC SDU segments that are associated with the i:th dsr-ReportingThreshold and have not yet been included in an RLC data PDU, and are not considered as delay-reporting RLC data volume associated with any of the k:th dsr-ReportingThreshold where k < i);

[0354] - Among the RLC data PDUs pending for initial transmission, and containing a delay-reporting RLC SDU or a delay-reporting RLC SDU segment associated with the i:th dsr-ReportingThreshold, and are not considered as delay-reporting RLC data volume associated with any of the k:th dsr-ReportingThreshold where k < i);

[0355] - RLC data PDUs that are pending for retransmission (RLC AM mode) ([if i=1,] RLC data PDUs that are pending for retransmission (RLC AM)).

[0356] If dsr-ReportNonDelayCriticalData is configured, the UE shall further consider the following as delay-reporting RLC data volume associated with the i:th dsr-ReportingThreshold:

[0357] - non-delay-reporting RLC SDUs and non-delay-reporting RLC SDU segments that are associated with the i:th dsr-ReportingThreshold and have not yet been included in an RLC data PDU, and are not considered as delay-reporting RLC data volume associated with any of the k:th dsr-ReportingThreshold where k < i);

[0358] - RLC data PDUs pending for initial transmission, and containing non-delay-reporting RLC SDU or non-delay-reporting RLC SDU segment(s) associated with the i:th dsr-ReportingThreshold, and are not considered as delay-reporting RLC data volume associated with any of the k:th dsr-ReportingThreshold where k < i);

[0359] When receiving a negative acknowledgment for an RLC SDU or an RLC SDU segment by a STATUS PDU from its peer AM RLC entity, the transmitting side of the AM RLC entity shall:

[0360] - The SN of the corresponding RLC SDU is greater than or equal to TX_Next_Ack and is within the range of the highest SN of the AMD PDUs submitted to the lower layer (if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack <= SN <= the highest SN of the AMD PDU among the AMD PDUs submitted to the lower layer); and

[0361] - If stopReTxObsoleteSDU is enabled and no discard indication for the RLC SDU SN has been received from upper layers:

[0362] - The RLC SDU or RLC SDU segment for which a negative acknowledgment was received must be considered for retransmission.

[0363] In one embodiment of the present disclosure, a transmitting side of an RLC layer device having a specific RRC setting (e.g., stopReTxObsoleteSDU) set to Enabled may operate as follows when a Discard Indication is received for a specific RLC SDU from a higher layer (PDCP layer).

[0364] Option 1:

[0365] If stopReTxObsoleteSDU is set to enabled, when receiving a discard indication for an RLC SDU from the upper layer, the transmitting side of an AM RLC entity shall not consider the corresponding RLC SDU or RLC SDU segment(s) for transmission or retransmission.

[0366] Option 2:

[0367] If stopReTxObsoleteSDU is set to enabled, when receiving a discard indication for an RLC SDU with SN = x from the upper layer, if x falls within the transmitting window (i.e., TX_Next_Ack <= SN < TX_Next_Ack + AM_Window_Size), the transmitting side of an AM RLC entity shall not consider the corresponding RLC SDU or RLC SDU segment(s) for transmission or retransmission.

[0368] Option 3:

[0369] If stopReTxObsoleteSDU is set to enabled, when receiving a discard indication for an RLC SDU with SN = x from the upper layer, if the RLC SDU or the corresponding RLC SDU segment(s) have been submitted to the lower layers, the transmitting side of an AM RLC entity shall not consider the corresponding RLC SDU or RLC SDU segment(s) for transmission or retransmission.

[0370] Option 4:

[0371] If stopReTxObsoleteSDU is set to enabled, when receiving a discard indication for an RLC SDU with SN = x from the upper layer, if x falls within the transmitting window (i.e., TX_Next_Ack <= SN < TX_Next_Ack + AM_Window_Size), and / or if the RLC SDU or the corresponding RLC SDU segment(s) have been submitted to the lower layers, the transmitting side of an AM RLC entity shall not consider it for transmission or retransmission. the corresponding RLC SDU or RLC SDU segment(s) for transmission or retransmission).

[0372] Option 5

[0373] If stopReTxObsoleteSDU is set to enabled, when receiving a discard indication for an RLC SDU from the upper layer, if the RLC SDU or the corresponding RLC SDU segment(s) have been submitted to the lower layers, the transmitting side of an AM RLC entity shall not consider the corresponding RLC SDU or RLC SDU segment(s) for transmission or retransmission.

[0374] Option 6:

[0375] If stopReTxObsoleteSDU is set to enabled, when receiving a discard indication for an RLC SDU from the upper layer, if the RLC SDU or the corresponding RLC SDU segment(s) have been submitted to the lower layers, and / or for which a positive acknowledgment has not been received yet, the transmitting side of an AM RLC entity shall not consider the corresponding RLC SDU or RLC SDU segment(s) for transmission or retransmission.

[0376] Figure 8 shows the structure of a terminal according to an embodiment of the present disclosure.

[0377] The terminal of Fig. 8 may be any one of the terminals (or UEs) described in Figs. 1 to 7. Referring to Fig. 8, the terminal may be composed of a transceiver unit (810), a memory (820), and a control unit (830).

[0378] Depending on the communication method of the device described above, the transceiver (810), control unit (830), and memory (820) of the terminal may operate. However, the components of the terminal are not limited to the examples described above. For example, the terminal may include more or fewer components than the components described above. In addition, the transceiver (810), control unit (830), and memory (820) may be implemented in the form of a single chip. Furthermore, the control unit (830) may include one or more processors.

[0379] The transceiver (810) may also be referred to as a transceiver. The transceiver (810) is a general term for the receiving unit of a terminal and the transmitting unit of an electronic device, and can transmit and receive signals with other devices. To this end, the transceiver (810) may be configured with an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and frequency-converts a received signal. However, this is only one embodiment of the transceiver (810), and the components of the transceiver (810) are not limited to the RF transmitter and RF receiver.

[0380] In addition, the transmitter / receiver unit (810) can receive a signal through a wireless channel and output it to the control unit (830), and transmit the signal output from the control unit (830) through the wireless channel.

[0381] The memory (820) can store programs and data necessary for the operation of the terminal. In addition, the memory (820) can store control information or data included in signals acquired from the terminal. The memory (820) can be configured as a storage medium or a combination of storage media, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, the memory (820) may not exist separately but may be configured as part of the control unit (830).

[0382] The control unit (830) can control a series of processes so that the terminal can operate according to the embodiments of the present disclosure described above.

[0383] Figure 9 shows the structure of a base station according to an embodiment of the present disclosure.

[0384] The base station of FIG. 9 may be implemented as any one of the base stations (or gNBs) described in FIGS. 1 to 7. Referring to FIG. 9, the base station may be composed of a transceiver unit (910), a memory (920), and a control unit (930).

[0385] Depending on the communication method of the above-described device, the base station's transceiver (910), control unit (930), and memory (920) may operate. However, the base station may include more or fewer components than the above-described components. In addition, the transceiver (910), control unit (930), and memory (920) may be implemented in the form of a single chip. Furthermore, the control unit (930) may include one or more processors.

[0386] The transceiver (910) may also be referred to as a transceiver. The transceiver (910) is a general term for the receiver of the second electronic device and the transmitter of the electronic device, and can transmit and receive signals with other devices. To this end, the transceiver (910) may be configured with an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and down-converts the frequency of a received signal. However, this is only one embodiment of the transceiver (910), and the components of the transceiver (910) are not limited to the RF transmitter and RF receiver.

[0387] In addition, the transmitter / receiver unit (910) can receive a signal through a wireless channel and output it to the control unit (930), and transmit the signal output from the control unit (930) through the wireless channel.

[0388] The memory (920) can store programs and data required for the operation of the base station. In addition, the memory (920) can store control information or data included in signals acquired from the base station. The memory (920) can be configured as a storage medium or a combination of storage media, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, the memory (920) may not exist separately but may be configured as part of the control unit (930).

[0389] The control unit (930) can control a series of processes so that the base station can operate according to the embodiments of the present disclosure described above.

[0390] The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0391] 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 disclosure.

[0392] These programs (software modules, software) may be stored in a non-volatile memory including random access memory, flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage devices, compact disc ROMs (CD-ROMs), digital versatile discs (DVDs) or other forms of optical storage devices, magnetic cassettes, or 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.

[0393] Additionally, the program may be stored on 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 disclosure 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 disclosure.

[0394] In the specific embodiments of the present disclosure described above, components included in the present disclosure 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 disclosure is not limited to singular or plural components. Components expressed in the plural form may be composed of singular elements, or components expressed in the singular form may be composed of plural elements.

[0395] While the detailed description of this disclosure has described specific embodiments, it should be understood that various modifications are possible without departing from the scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the described embodiments, but should be defined not only by the scope of the claims described below, but also by equivalents thereof.

Claims

1. In a method of operating a terminal in a wireless communication system, An operation of receiving an RRC (radio resource control) message from a base station that includes configuration information (rlcSnGapEnabled) indicating that the RLC (radio link control) sequence number gap (SN Gap) function is enabled; and A method characterized by comprising an operation of setting the setting information (rlcSnGapEnabled) in the RLC layer device of the terminal based on the RRC message, and discarding the first RLC SDU (service data unit) instructing the PDCP (packet data convergence protocol) layer device of the terminal to be discarded in the RLC layer device.

2. In paragraph 1, A method characterized in that it further includes an operation of setting the second RLC SDU not to be retransmitted to the RLC layer device when a discard timer for the second RLC SDU has expired in the PDCP layer device.

3. In paragraph 1, A method characterized by further including an operation of evaluating a plurality of thresholds (dsr-ReportingThreshold) in ascending order for MAC (medium access control) delay status reporting, and considering data satisfying a condition set for an ith threshold among the plurality of thresholds as a delay-reporting RLC data amount.

4. In the third paragraph, the set conditions are: When evaluating the delay-reporting RLC data amount for the i-th threshold, the k-th (k <i) 임계값에 관련된 상기 지연-보고 RLC 데이터량을 고려하지 않는 것임을 특징으로 하는 방법.

5. In paragraph 1, A method characterized in that it further includes an operation of determining that the first RLC SDU or a segment of the first RLC SDU, which has been instructed to be discarded by the PDCP layer device of the terminal, is not a target for retransmission.

6. In paragraph 1, A method characterized in that it further includes an operation of determining a third RLC SDU or a segment of the third RLC SDU that is not instructed to be discarded by the PDCP layer device of the terminal as a target for retransmission.

7. In paragraph 1, An operation of receiving a message from the base station inquiring about whether the report of the RLC SN Gap is supported; and A method further comprising the action of transmitting a message including information on whether the report of the RLC SN Gap is supported to the base station.

8. In paragraph 7, A method characterized in that it further includes an operation of transmitting a report of the RLC SN Gap to the base station.

9. In a wireless communication system, at the terminal, Transmitter and receiver; and A control unit comprising: Receive an RRC (radio resource control) message from a base station that includes configuration information (rlcSnGapEnabled) indicating that the RLC (radio link control) sequence number gap (SN Gap) function is enabled, A terminal characterized in that, based on the RRC message, the RLC layer device of the terminal sets the setting information (rlcSnGapEnabled), and the RLC layer device of the terminal discards the first RLC SDU (service data unit) that instructs the PDCP (packet data convergence protocol) layer device of the terminal to discard.

10. In paragraph 9, the control unit, A terminal characterized in that the second RLC SDU is set not to be retransmitted to the RLC layer device when the discard timer for the second RLC SDU expires in the PDCP layer device.

11. In paragraph 9, the control unit, A terminal characterized in that it evaluates multiple thresholds (dsr-ReportingThreshold) in ascending order for MAC (medium access control) delay status reporting, and regards data that satisfies a condition set for the ith threshold among the multiple thresholds as a delay-reporting RLC data amount.

12. In paragraph 11, the set conditions are: When evaluating the delay-reporting RLC data amount for the i-th threshold, the k-th (k <i) 임계값에 관련된 상기 지연-보고 RLC 데이터량을 고려하지 않는 것임을 특징으로 하는 단말.

13. In paragraph 9, the control unit, A terminal characterized in that the PDCP layer device of the terminal determines that the first RLC SDU or a segment of the first RLC SDU, which has been instructed to be discarded, is not a target for retransmission.

14. In paragraph 9, the control unit, A terminal characterized in that the terminal determines the third RLC SDU or the segment of the third RLC SDU, which is not instructed to be discarded by the PDCP layer device of the terminal, as a target for retransmission.

15. In paragraph 9, the control unit, Receive a message from the base station asking whether the report of the above RLC SN Gap is supported, Transmitting a message containing information on whether the report of the RLC SN Gap is supported to the base station, A terminal characterized in that it transmits a report of the above RLC SN Gap to the base station.

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