Method and device for reporting sequence number gap of PDCP layer in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Specifically, the present disclosure relates to a method performed by a terminal of a wireless communication system, the method comprising the steps of: transmitting a first message including first information indicating whether the terminal supports a packet data convergence protocol (PDCP) sequence number (SN) gap report to a base station; receiving a second message including second information for configuring transmission of a PDCP SN gap report from the base station; triggering a PDCP SN gap report for notifying of the discard of a PDCP service data unit (SDU) on the basis of at least one condition; and transmitting the PDCP SN gap report to the base station.

Description

Method and device for reporting sequence number interval of PDCP layer in wireless communication system

[0001] The present disclosure relates to a method and apparatus for reporting a sequence number interval of a PDCP 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 could serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing this technology.

[0008] One aspect of the present disclosure may be to provide a device and method capable of reporting a sequence number interval of a PDCP layer in a wireless communication system.

[0009] A method according to one embodiment of the present disclosure is a method performed by a terminal of a wireless communication system, the method including the steps of: transmitting a first message including first information indicating whether the terminal supports a Packet Data Convergence Protocol (PDCP) SN (Sequence Number) gap report to a base station; receiving a second message including second information setting transmission of a PDCP SN gap report from the base station; triggering a PDCP SN gap report for notifying discard of a PDCP SDU (Service Data Unit) based on at least one condition; and transmitting the PDCP SN gap report to the base station.

[0010] Various embodiments of the present disclosure can provide a device and method capable of effectively providing a service in a wireless communication system.

[0011] The effects that can be obtained from the present disclosure are not limited to the effects mentioned in the various embodiments, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

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

[0013] FIG. 2 is a diagram illustrating a wireless protocol structure in an NR system according to an embodiment of the present disclosure.

[0014] 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.

[0015] FIG. 4 is a diagram illustrating a transmission and reception operation of a PDCP layer device according to an embodiment of the present disclosure.

[0016] FIG. 5 is a diagram illustrating an operation in which a PDCP transmitting device reports an SN Gap to a PDCP receiving device through an SN Gap Report according to one embodiment of the present disclosure.

[0017] FIG. 6 is a diagram illustrating an operation of a terminal and a base station transmitting and receiving a PDCP SN Gap Report according to one embodiment of the present disclosure.

[0018] FIG. 7 is a diagram illustrating the format of a PDCP SN Gap Report according to one embodiment of the present disclosure.

[0019] FIG. 8 is a diagram illustrating a method for selecting AGC when a PDCP transmitting device compiles a PDCP SN Gap Report according to one embodiment of the present disclosure.

[0020] Figure 9 is a diagram illustrating a process in which a PDCP receiving device updates a state variable when receiving a PDCP SN Gap Report.

[0021] FIG. 10 is a diagram showing components of a terminal according to one embodiment of the present disclosure.

[0022] FIG. 11 is a diagram illustrating components of a base station according to one embodiment of the present disclosure.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] At this time, it will be understood that each block of the processing flowchart drawings and combinations of the flowchart drawings 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 flowchart 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 flowchart 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).

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] FIG. 1 is a diagram illustrating the structure of an NR system according to one embodiment of the present disclosure.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] FIG. 2 is a diagram illustrating a wireless protocol structure in an NR system according to one embodiment of the present disclosure.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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).

[0052] In this disclosure, a method for transmitting delay-critical packets using PDCP duplication or split bearer technology is proposed when multiple RLC layer devices are associated with a PDCP layer device, considering a terminal configured with CA or dual connectivity (DC) technology. The proposed method is specified in this disclosure using the following terminology.

[0053] - Pcell (Primary Cell): This refers to the serving cell used when the terminal first establishes a connection with the base station, and the connection is established by transmitting and receiving major RRC messages using the Pcell. In addition, the Pcell always has PUCCH transmission resources, so it can indicate HARQ ACK or NACK, and both uplink and downlink are always configured, and can be used as a reference cell for timing adjustment (Timing Advance, pTAG (Primary Timing Advance Group)). For example, if frequency aggregation technology is configured after the Pcell is configured and an Scell ​​is added, the Scell ​​can perform uplink data transmission by referring to the timing adjustment value of the Pcell. In addition, if dual access technology is configured, the Pcell refers to the PCell of the MCG (Master Cell Group).

[0054] - MCG (Master Cell Group): Refers to the serving cell where the terminal first establishes a connection with the base station or a group of cells supported by the base station. When dual access technology is set, major RRC messages are transmitted or received through the MCG.

[0055] - SCG (Secondary Cell Group): A terminal can establish a connection with a base station and add cells from other base stations in addition to the MCG. This refers to a group of cells supported by other base stations. When dual access technology is set, it can be added to increase additional data transmission rates or efficiently support terminal mobility.

[0056] - PScell ​​(Primary Secondary Cell): When a terminal establishes a connection with a base station and a group of cells from other base stations is added in addition to the MCG and dual access technology is set, the cell corresponding to the Pcell in the SCG is called a PScell.

[0057] - Scell ​​(Secondary Cell): The cells additionally set by the base station to set up carrier aggregation technology after the terminal establishes the initial connection with the base station are called Scells. Depending on the base station settings, the SCell may have PUCCH transmission resources, and depending on the base station settings, the uplink or downlink may be set, and depending on the base station settings, it may be used as a reference cell for timing adjustment (Timing Advance, sTAG (Secondary Timing Advance Group)). For example, if the Pcell is set and then the frequency aggregation technology is set, Scells are added and an sTAG is set, other Scells in the sTAG can perform uplink data transmission by referencing the timing adjustment value of the designated Scell. In addition, if the terminal is set up with dual access technology, the Scell ​​may represent Scells excluding the PCell of the MCG (Master Cell Group) or Scells excluding the PScell ​​of the SCG (Secondary Cell Group).

[0058] - Primary RLC layer device (Primary RLC entity): When the PDCP redundancy function is set, multiple RLC layer devices can be set up in one PDCP layer device, and one RLC layer device that is always used without being deactivated among the multiple RLC layer devices can be called the Primary RLC layer device. In addition, the PDCP layer device can be characterized in that the PDCP Control PDU is not transmitted redundantly and is always transmitted to the Primary RLC layer device. When a PDCP measuring device is associated with two or more RLC measuring devices, the Primary RLC measuring device can be set up by the upper layer (RRC).

[0059] - Split Bearer: In a dual connection situation, this can refer to a bearer that can use the radio resources of both MCG / MgNB and SCG / SgNB.

[0060] - DAPS Bearer: During DAPS Handover, this can refer to a bearer that can use the radio resources of both the source base station and the target base station.

[0061] - Split Secondary RLC layer device (Split RLC entity): In a dual connectivity situation, this can refer to any RLC layer device other than the Primary RLC layer device associated with the Split Bearer. If the PDCP layer device is associated with two RLC layer devices, the Split Secondary RLC layer device can refer to the other RLC layer device among the two associated RLC layer devices, other than the Primary RLC layer device. If the PDCP layer device is associated with more than two RLC layer devices, the Split Secondary RLC layer device can be configured by the upper layer (RRC).

[0062] - Delay-critical PDCP SDU: If pdu-SetDiscard is not set, this may refer to a PDCP SDU whose remaining time before discardTimer expires is shorter than remainingTimeThreshold. If pdu-SetDiscard is set, this may refer to a PDCP SDU that belongs to a PDU Set that contains at least one PDCP SDU whose remaining time before discardTimer expires is shorter than remainingTimeThreshold. The remainingTimeThreshold can be set by the base station for each Cell Group / MAC layer device via an RRC message (RRCSetup, RRCReconfiguration). Therefore, among the data in the PDCP layer device, a delay-critical PDCP SDU for a specific Cell Group / MAC layer device can be determined based on the remainingTimeThreshold of the Cell Group / MAC layer device.

[0063] - PDU Set: It may consist of one or more PDUs corresponding to the payload of one unit of information generated by the application (see TS 23.501). One PDU belonging to the PDU Set can be regarded as one PDCP SDU.

[0064] - Delay-Critical PDCP Data Volume: For the Delay Status Report (DSR) reported in the MAC layer, the transmitting PDCP layer device of the terminal may include all or part of the following Delay-Critical Data-1 to Delay-Critical Data-5 when determining the Delay-Critical PDCP Data Volume.

[0065] 1) Delay-critical Data-1: Delay-critical PDCP SDUs for which no PDCP Data PDUs have been constructed

[0066] 2) Delay-critical Data-2: PDCP Data PDUs that contain delay-critical PDCP SDUs and have not been submitted to lower layers (RLC)

[0067] 3) Delay Critical Data-3: PDCP Control PDUs

[0068] 4) Delay Critical Data-4: For AM DRBs, the PDCP SDUs to be retransmitted according to clause 5.1.2 and clause 5.13 of TS 38.323.

[0069] 5) Delay Critical Data-5: For AM DRBs, the PDCP Data PDUs to be retransmitted according to clause 5.5 of TS 38.323

[0070] - DSR-supporting RLC layer device: The RLC layer device and the MAC layer device associated with the RLC layer device may refer to an RLC layer device that supports DSR. In one embodiment, the RLC layer and the MAC layer device associated with the RLC layer device may be NR RLC layer devices and NR MAC layer devices, respectively, that support DSR.

[0071] In one embodiment, in a PDCP layer device of a terminal, if a specific PDCP SDU becomes a delay-critical PDCP SDU and a PDCP Data PDU containing the PDCP SDU has already been delivered to a lower layer (RLC) of the terminal, a delay-critical indication for the PDCP Data PDU may be provided to the lower layer (RLC) of the terminal through terminal internal signaling.

[0072] 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.

[0073] 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 establishes uplink / downlink transmission synchronization with a base station through a random access process and transmits an RRCSetupRequest message to the base station (300). The RRCSetupRequest message may include an identifier of the terminal and a reason for establishing a connection (EstablishmentCause). The base station transmits an RRCSetup message to the terminal so that the terminal establishes an RRC connection (305).

[0074] 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 the 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. In one embodiment, the PDCP-Config may include the following configuration information.

[0075] - discardTimer: Value in ms of discardTimer specified in TS 38.323. Value ms10 corresponds to 10 ms, value ms20 corresponds to 20 ms and so on. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0076] - pdcp-SN-SizeUL: PDCP sequence number size for uplink, 12 or 18 bits, as specified in TS 38.323. For SRBs only the value len12bits is applicable. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0077] - pdcp-SN-SizeDL: PDCP sequence number size for downlink, 12 or 18 bits, as specified in TS 38.323. For SRBs only the value len12bits is applicable. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer

[0078] - outOfOrderDelivery: Indicates whether or not outOfOrderDelivery specified in TS 38.323 is configured. This field should be either always present or always absent, after the radio bearer is established.

[0079] - statusReportRequired: For AM DRBs, AM MRBs and DAPS UM DRBs, indicates whether the DRB or the multicast MRB is configured to send a PDCP status report in the uplink, as specified in TS 38.323. For DAPS AM DRBs, it also indicates whether the DRB is configured to send a second PDCP status report in the uplink, as specified in TS 38.323.

[0080] - t-Reordering: Value in ms of t-Reordering specified in TS 38.323. Value ms0 corresponds to 0 ms, value ms20 corresponds to 20 ms, value ms40 corresponds to 40 ms, and so on. When the field is absent the UE applies the value infinity. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0081] - pdu-SetDiscard: If set to true, the UE shall perform PDU set based discarding for this PDCP entity, as specified in TS 38.323.

[0082] - discardTimerForLowImportance: Value in ms of discardTimerForLowImportance specified in TS 38.323. Value ms0 corresponds to 0 ms, value ms2 corresponds to 2 ms and so on. The value of this timer for a PDCP entity is always configured shorter than discardTimer, discardTimerExt or discardTimerExt2, whichever is used for the PDCP entity.

[0083] - 해당 PDCP 계층 장치와 연관 / 연결된 RLC 계층 장치가 두 개 이상일 경우:

[0084] 1) Primary RLC layer device indicator (primaryPath): In one embodiment, the Primary RLC layer device can be configured through an indicator that indicates the Cell Group (CellGroupId) to which the RLC layer device belongs and the Logical Channel (LogicalChannelIdentity) corresponding to the RLC layer device in the Cell Group.

[0085] 2) Uplink Split Bearer Threshold (UL-DataSplitThreshold): You can set a threshold that can be used in Split Bearer. When operating as Split Bearer, if the amount of data to be transmitted is less than the threshold, data is transmitted only to the Primary RLC layer device. If the amount of data to be transmitted is more than the threshold, data can be transmitted to the Primary RLC layer device and Split Secondary RLC layer device.

[0086] 3) pdcp-Duplication: When receiving an RRC message / IE, it may indicate whether the PDCP duplication transmission function of the corresponding PDCP layer device is set and activated. The field may be a BOOLEAN indicating TRUE or FALSE. If the field exists, the corresponding PDCP layer device may consider that the duplication transmission function is set. In one embodiment, the PDCP duplication transmission function may not be set for a CA-based LTE RLC Bearer. The setting value of the field may indicate whether the initial state of the PDCP duplication transmission function is activated or deactivated when the terminal receives the corresponding RRC message / IE. For example, if the setting value is TRUE, it may start in an activated state, and if it is FALSE, it may start in a deactivated state. In one embodiment, when the field is set for an SRB, the setting value may be specified to always be set to TRUE. If there are three or more RLC layer devices associated with the corresponding PDCP layer device (moreThanTwoRLC-DRB is present), the field may always be present, and the terminal ignores the setting value of the field, and the initial state of activation / deactivation of the duplication transmission function of RLC layer devices (other than the Primary RLC layer device) associated with the corresponding PDCP layer device may be configured through the duplicationState field. In one embodiment, the duplication transmission function where three or more RLC layer devices (more than two associated RLC entities) are associated with the PDCP layer device may be supported only for NR RLC layer devices (NR RLC Bearer).

[0087] 4) If there are three or more RLC layer devices associated / connected with the corresponding PDCP layer device:

[0088] (1) Split Secondary RLC layer device indicator (splitSecondaryPath): It may include an indicator indicating a Split Secondary RLC layer device. In one embodiment, the base station may indicate the Split Secondary RLC layer device by indicating an LCID (Logical Channel ID) corresponding to the Split Secondary RLC layer device. In one embodiment, the Split Secondary RLC layer indicator may be used for the purpose of indicating the Split Secondary RLC layer device when the PDCP layer device falls back to the Split Bearer and operates when there are three or more RLC layer devices associated with the corresponding PDCP layer device. In one embodiment, the Split Secondary RLC layer device indicator may specify only the LCID corresponding to the corresponding RLC layer device and may not specify the Cell Group to which the corresponding RLC layer device belongs. This may be configured so that the Cell Group to which the corresponding RLC layer device belongs may be designated as a Cell Group other than the Cell Group to which the Primary RLC layer device belongs among MCG and SCG. If there are two RLC layer devices associated with the corresponding PDCP layer device, the Split Secondary RLC layer device indicator may not be required. In one embodiment, since the Primary RLC layer device can be configured via the Primary RLC layer device indicator, one other RLC layer device, excluding the Primary RLC layer device, can be designated as the Split Secondary RLC layer device even without the Split Secondary RLC layer device indicator.

[0089] (2) duplicationState: This is a field that indicates the initial activation / deactivation state of the duplication transmission function for each RLC layer device associated with the corresponding PDCP layer device when the terminal receives the corresponding RRC message / IE. In one embodiment, the field may include three BOOLEAN settings, and each BOOLEAN setting value may correspond to a specific RLC layer device. When the setting value of the field is set to TRUE, the initial activation state may be indicated for the corresponding RLC layer device, and when set to FALSE, the initial deactivation state may be indicated. The determination method for each RLC layer device to which the three BOOLEAN setting values ​​correspond may be such that, among the RLC layer devices associated with the corresponding PDCP layer device, in the order of MCG to SCG, excluding the Primary RLC layer device, the mapping relationship between the RLC layer devices and the BOOLEAN setting values ​​may be in the order of ascending LCID (Logical Channel ID). If there are two RLC layer devices associated with the PDCP layer device, excluding the Primary RLC layer device, the terminal may ignore the BOOLEAN setting with the highest index value. If this field does not exist, the PDCP redundant transmission function may be considered disabled for all associated RLC layer devices.

[0090] Referring to Fig. 3, a terminal that has established an RRC connection enters RRC_CONNECTED mode and transmits 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 determine the terminal capabilities, it can send a message to the terminal asking about the terminal capabilities (315). The terminal can then send a message reporting its capabilities to the base station (320). The message can indicate whether the terminal supports the PDCP duplicate transmission / Split Bearer function and can include an indicator indicating this.

[0091] To set up security with a terminal, the base station transmits a SecurityModeCommand message (325) to the terminal, and the terminal transmits a SecurityModeComplete message (330) to the base station. When the security setting is complete, the base station transmits an RRCReconfiguration message to the terminal (335).

[0092] 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 the 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. In one embodiment, the PDCP-Config may include the following configuration information.

[0093] - discardTimer: Value in ms of discardTimer specified in TS 38.323. Value ms10 corresponds to 10 ms, value ms20 corresponds to 20 ms and so on. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0094] - pdcp-SN-SizeUL: PDCP sequence number size for uplink, 12 or 18 bits, as specified in TS 38.323. For SRBs only the value len12bits is applicable. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0095] - pdcp-SN-SizeDL: PDCP sequence number size for downlink, 12 or 18 bits, as specified in TS 38.323. For SRBs only the value len12bits is applicable. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer

[0096] - outOfOrderDelivery: Indicates whether or not outOfOrderDelivery specified in TS 38.323 is configured. This field should be either always present or always absent, after the radio bearer is established.

[0097] - statusReportRequired: For AM DRBs, AM MRBs and DAPS UM DRBs, indicates whether the DRB or the multicast MRB is configured to send a PDCP status report in the uplink, as specified in TS 38.323. For DAPS AM DRBs, it also indicates whether the DRB is configured to send a second PDCP status report in the uplink, as specified in TS 38.323.

[0098] - t-Reordering: Value in ms of t-Reordering specified in TS 38.323. Value ms0 corresponds to 0 ms, value ms20 corresponds to 20 ms, value ms40 corresponds to 40 ms, and so on. When the field is absent the UE applies the value infinity. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0099] - pdu-SetDiscard: If set to true, the UE shall perform PDU set based discarding for this PDCP entity, as specified in TS 38.323.

[0100] - discardTimerForLowImportance: Value in ms of discardTimerForLowImportance specified in TS 38.323. Value ms0 corresponds to 0 ms, value ms2 corresponds to 2 ms and so on. The value of this timer for a PDCP entity is always configured shorter than discardTimer, discardTimerExt or discardTimerExt2, whichever is used for the PDCP entity.

[0101] - If there are two or more RLC layer devices associated / connected with the corresponding PDCP layer device:

[0102] 1) Primary RLC layer device indicator (primaryPath): In one embodiment, the Primary RLC layer device can be configured through an indicator that indicates the Cell Group (CellGroupId) to which the RLC layer device belongs and the Logical Channel (LogicalChannelIdentity) corresponding to the RLC layer device in the Cell Group.

[0103] 2) Uplink Split Bearer Threshold (UL-DataSplitThreshold): You can set a threshold that can be used in Split Bearer. When operating as Split Bearer, if the amount of data to be transmitted is less than the threshold, data is transmitted only to the Primary RLC layer device. If the amount of data to be transmitted is more than the threshold, data can be transmitted to the Primary RLC layer device and Split Secondary RLC layer device.

[0104] 3) pdcp-Duplication: When receiving an RRC message / IE, it may indicate whether the PDCP duplication transmission function of the corresponding PDCP layer device is set and activated. The field may be a BOOLEAN indicating TRUE or FALSE. If the field exists, the corresponding PDCP layer device may consider that the duplication transmission function is set. In one embodiment, the PDCP duplication transmission function may not be set for a CA-based LTE RLC Bearer. The setting value of the field may indicate whether the initial state of the PDCP duplication transmission function is activated or deactivated when the terminal receives the corresponding RRC message / IE. For example, if the setting value is TRUE, it may start in an activated state, and if it is FALSE, it may start in a deactivated state. In one embodiment, when the field is set for an SRB, the setting value may be specified to always be set to TRUE. If there are three or more RLC layer devices associated with the corresponding PDCP layer device (moreThanTwoRLC-DRB is present), the field may always be present, and the terminal ignores the setting value of the field, and the initial state of activation / deactivation of the duplication transmission function of RLC layer devices (other than the Primary RLC layer device) associated with the corresponding PDCP layer device may be configured through the duplicationState field. In one embodiment, the duplication transmission function where three or more RLC layer devices (more than two associated RLC entities) are associated with the PDCP layer device may be supported only for NR RLC layer devices (NR RLC Bearer).

[0105] 4) If there are three or more RLC layer devices associated / connected with the corresponding PDCP layer device:

[0106] (1) Split Secondary RLC layer device indicator (splitSecondaryPath): It may include an indicator indicating a Split Secondary RLC layer device. In one embodiment, the base station may indicate the Split Secondary RLC layer device by indicating an LCID (Logical Channel ID) corresponding to the Split Secondary RLC layer device. In one embodiment, the Split Secondary RLC layer indicator may be used for the purpose of indicating the Split Secondary RLC layer device when the PDCP layer device falls back to the Split Bearer and operates when there are three or more RLC layer devices associated with the corresponding PDCP layer device. In one embodiment, the Split Secondary RLC layer device indicator may specify only the LCID corresponding to the corresponding RLC layer device and may not specify the Cell Group to which the corresponding RLC layer device belongs. This may be configured so that the Cell Group to which the corresponding RLC layer device belongs may be designated as a Cell Group other than the Cell Group to which the Primary RLC layer device belongs among MCG and SCG. If there are two RLC layer devices associated with the corresponding PDCP layer device, the Split Secondary RLC layer device indicator may not be required. In one embodiment, since the Primary RLC layer device can be configured via the Primary RLC layer device indicator, one other RLC layer device, excluding the Primary RLC layer device, can be designated as the Split Secondary RLC layer device even without the Split Secondary RLC layer device indicator.

[0107] (2) duplicationState: This is a field that indicates the initial activation / deactivation state of the duplication transmission function for each RLC layer device associated with the corresponding PDCP layer device when the terminal receives the corresponding RRC message / IE. In one embodiment, the field may include three BOOLEAN settings, and each BOOLEAN setting value may correspond to a specific RLC layer device. When the setting value of the field is set to TRUE, the initial activation state may be indicated for the corresponding RLC layer device, and when set to FALSE, the initial deactivation state may be indicated. The determination method for each RLC layer device to which the three BOOLEAN setting values ​​correspond may be such that, among the RLC layer devices associated with the corresponding PDCP layer device, in the order of MCG to SCG, excluding the Primary RLC layer device, the mapping relationship between the RLC layer devices and the BOOLEAN setting values ​​may be in the order of ascending LCID (Logical Channel ID). If there are two RLC layer devices associated with the PDCP layer device, excluding the Primary RLC layer device, the terminal may ignore the BOOLEAN setting with the highest index value. If this field does not exist, the PDCP redundant transmission function may be considered disabled for all associated RLC layer devices.

[0108] In one embodiment, the RRCReconfiguration message may include, for each Cell Group (MCG, SCG), RLC Bearer configuration information (RLC-BearerConfig) belonging to the Cell Group. The RLC Bearer configuration information may include the following information:

[0109] - logicalChannelIdentity: Indicates the LCID corresponding to the RLC Bearer / layer device.

[0110] - servedRadioBearer: Indicates the Radio Bearer ID associated with the RLC Bearer / layer device. The Radio Bearer ID can indicate a specific DRB or SRB.

[0111] - rlc-Config: Indicates the RLC layer parameter setting information of the RLC layer device of the corresponding RLC Bearer.

[0112] 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).

[0113] In one embodiment, the RRCReconfiguration message (RRCReconfiguration) may include configuration information (RadioBearerConfig) for each Radio Bearer (DRB or SRB). The Radio Bearer configuration information may include the 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. In one embodiment, the PDCP-Config may include the following configuration information.

[0114] - discardTimer: Value in ms of discardTimer specified in TS 38.323. Value ms10 corresponds to 10 ms, value ms20 corresponds to 20 ms and so on. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0115] - pdcp-SN-SizeUL: PDCP sequence number size for uplink, 12 or 18 bits, as specified in TS 38.323. For SRBs only the value len12bits is applicable. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0116] - pdcp-SN-SizeDL: PDCP sequence number size for downlink, 12 or 18 bits, as specified in TS 38.323. For SRBs only the value len12bits is applicable. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer

[0117] - outOfOrderDelivery: Indicates whether or not outOfOrderDelivery specified in TS 38.323 is configured. This field should be either always present or always absent, after the radio bearer is established.

[0118] - statusReportRequired: For AM DRBs, AM MRBs and DAPS UM DRBs, indicates whether the DRB or the multicast MRB is configured to send a PDCP status report in the uplink, as specified in TS 38.323. For DAPS AM DRBs, it also indicates whether the DRB is configured to send a second PDCP status report in the uplink, as specified in TS 38.323.

[0119] - t-Reordering: Value in ms of t-Reordering specified in TS 38.323. Value ms0 corresponds to 0 ms, value ms20 corresponds to 20 ms, value ms40 corresponds to 40 ms, and so on. When the field is absent the UE applies the value infinity. The value for this field cannot be changed in case of reconfiguration with sync, if the bearer is configured as DAPS bearer.

[0120] - pdu-SetDiscard: If set to true, the UE shall perform PDU set based discarding for this PDCP entity, as specified in TS 38.323.

[0121] - discardTimerForLowImportance: Value in ms of discardTimerForLowImportance specified in TS 38.323. Value ms0 corresponds to 0 ms, value ms2 corresponds to 2 ms and so on. The value of this timer for a PDCP entity is always configured shorter than discardTimer, discardTimerExt or discardTimerExt2, whichever is used for the PDCP entity.

[0122] - If there are two or more RLC layer devices associated / connected with the corresponding PDCP layer device:

[0123] 1) Primary RLC layer device indicator (primaryPath): In one embodiment, the Primary RLC layer device can be configured through an indicator that indicates the Cell Group (CellGroupId) to which the RLC layer device belongs and the Logical Channel (LogicalChannelIdentity) corresponding to the RLC layer device in the Cell Group.

[0124] 2) Uplink Split Bearer Threshold (UL-DataSplitThreshold): You can set a threshold that can be used in Split Bearer. When operating as Split Bearer, if the amount of data to be transmitted is less than the threshold, data is transmitted only to the Primary RLC layer device. If the amount of data to be transmitted is more than the threshold, data can be transmitted to the Primary RLC layer device and Split Secondary RLC layer device.

[0125] 3) pdcp-Duplication: When receiving an RRC message / IE, it may indicate whether the PDCP duplication transmission function of the corresponding PDCP layer device is set and activated. The field may be a BOOLEAN indicating TRUE or FALSE. If the field exists, the corresponding PDCP layer device may consider that the duplication transmission function is set. In one embodiment, the PDCP duplication transmission function may not be set for a CA-based LTE RLC Bearer. The setting value of the field may indicate whether the initial state of the PDCP duplication transmission function is activated or deactivated when the terminal receives the corresponding RRC message / IE. For example, if the setting value is TRUE, it may start in an activated state, and if it is FALSE, it may start in a deactivated state. In one embodiment, when the field is set for an SRB, the setting value may be specified to always be set to TRUE. If there are three or more RLC layer devices associated with the corresponding PDCP layer device (moreThanTwoRLC-DRB is present), the field may always be present, and the terminal ignores the setting value of the field, and the initial state of activation / deactivation of the duplication transmission function of RLC layer devices (other than the Primary RLC layer device) associated with the corresponding PDCP layer device may be configured through the duplicationState field. In one embodiment, the duplication transmission function where three or more RLC layer devices (more than two associated RLC entities) are associated with the PDCP layer device may be supported only for NR RLC layer devices (NR RLC Bearer).

[0126] 4) If there are three or more RLC layer devices associated / connected with the corresponding PDCP layer device:

[0127] (1) Split Secondary RLC layer device indicator (splitSecondaryPath): It may include an indicator indicating a Split Secondary RLC layer device. In one embodiment, the base station may indicate the Split Secondary RLC layer device by indicating an LCID (Logical Channel ID) corresponding to the Split Secondary RLC layer device. In one embodiment, the Split Secondary RLC layer indicator may be used for the purpose of indicating the Split Secondary RLC layer device when the PDCP layer device falls back to the Split Bearer and operates when there are three or more RLC layer devices associated with the corresponding PDCP layer device. In one embodiment, the Split Secondary RLC layer device indicator may specify only the LCID corresponding to the corresponding RLC layer device and may not specify the Cell Group to which the corresponding RLC layer device belongs. This may be configured so that the Cell Group to which the corresponding RLC layer device belongs may be designated as a Cell Group other than the Cell Group to which the Primary RLC layer device belongs among MCG and SCG. If there are two RLC layer devices associated with the corresponding PDCP layer device, the Split Secondary RLC layer device indicator may not be required. In one embodiment, since the Primary RLC layer device can be configured via the Primary RLC layer device indicator, one other RLC layer device, excluding the Primary RLC layer device, can be designated as the Split Secondary RLC layer device even without the Split Secondary RLC layer device indicator.

[0128] (2) duplicationState: This is a field that indicates the initial activation / deactivation state of the duplication transmission function for each RLC layer device associated with the corresponding PDCP layer device when the terminal receives the corresponding RRC message / IE. In one embodiment, the field may include three BOOLEAN settings, and each BOOLEAN setting value may correspond to a specific RLC layer device. When the setting value of the field is set to TRUE, the initial activation state may be indicated for the corresponding RLC layer device, and when set to FALSE, the initial deactivation state may be indicated. The determination method for each RLC layer device to which the three BOOLEAN setting values ​​correspond may be such that, among the RLC layer devices associated with the corresponding PDCP layer device, in the order of MCG to SCG, excluding the Primary RLC layer device, the mapping relationship between the RLC layer devices and the BOOLEAN setting values ​​may be in the order of ascending LCID (Logical Channel ID). If there are two RLC layer devices associated with the PDCP layer device, excluding the Primary RLC layer device, the terminal may ignore the BOOLEAN setting with the highest index value. If this field does not exist, the PDCP redundant transmission function may be considered disabled for all associated RLC layer devices.

[0129] In one embodiment, the RRCReconfiguration message may include, for each Cell Group (MCG, SCG), RLC Bearer configuration information (RLC-BearerConfig) belonging to the Cell Group. The RLC Bearer configuration information may include the following information:

[0130] - logicalChannelIdentity: You can indicate the LCID corresponding to the RLC Bearer / layer device.

[0131] - servedRadioBearer: Indicates the Radio Bearer ID associated with the RLC Bearer / layer device. The Radio Bearer ID can indicate a specific DRB or SRB.

[0132] - rlc-Config: You can indicate the RLC layer parameter setting information of the RLC layer device of the corresponding RLC Bearer.

[0133] 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.

[0134] - 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.

[0135] - 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.

[0136] - 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).

[0137] - 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.

[0138] 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.

[0139] - About SRB:

[0140] 1) Activate PDCP duplicate transmission function

[0141] - About DRB:

[0142] 1) If an activation instruction for the PDCP redundant transmission feature is received (via RRC or MAC CE) for the given DRB:

[0143] (1) Activate PDCP duplicate transmission function for the corresponding DRB.

[0144] 2) If PDCP redundant transmission feature is enabled for at least one associated RLC layer device (via RRC or MAC CE):

[0145] (1) Activate PDCP redundant transmission function for the indicated RLC layer device.

[0146] (2) Activate PDCP duplicate transmission function for the corresponding DRB.

[0147] 3) If a PDCP duplicate transmission feature disable instruction is received (via RRC or MAC CE) for the DRB in question:

[0148] (1) For the DRB in question, disable the PDCP duplicate transmission function.

[0149] 4) If, for at least one associated RLC layer device, a PDCP duplicate transmission feature disablement indication is received (via RRC or MAC CE):

[0150] (1) For the associated RLC layer device that received the instruction, perform PDCP duplicate transmission function deactivation.

[0151] (2) If PDCP redundant transmission feature is disabled for all associated RLC layer devices except the Primary RLC layer device:

[0152] a. Disable PDCP duplicate transmission function for the DRB in question.

[0153] 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.

[0154] 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.

[0155] - 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.

[0156] - 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.

[0157] - When an activation / deactivation instruction (e.g., pdcp-Duplication, duplicationState) is received from the base station via an RRC message

[0158] 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.

[0159] - 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.

[0160] - When an activation / deactivation instruction (e.g., pdcp-Duplication, duplicationState) is received from the base station via an RRC message

[0161] 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:

[0162] - 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.

[0163] 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.

[0164] - When an instruction to activate the PDCP duplicate transmission function for a specific DRB is received via Duplication Activation / Deactivation MAC CE:

[0165] 1) It is possible to instruct the upper layer (PDCP) to activate the PDCP redundant transmission function for the corresponding DRB.

[0166] - When an instruction to disable PDCP duplicate transmission functionality for a specific DRB is received via Duplication Activation / Deactivation MAC CE:

[0167] 1) It is possible to instruct the upper layer (PDCP) to disable the PDCP duplicate transmission function for the corresponding DRB.

[0168] - 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:

[0169] 1) It can instruct the upper layer (PDCP) to enable PDCP redundant transmission function for one or more Secondary RLC layer devices.

[0170] - 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:

[0171] 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.

[0172] - 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:

[0173] 2) It can instruct the upper layer (PDCP) to enable PDCP redundant transmission function for all associated RLC layer devices of the DRB.

[0174] FIG. 4 is a diagram illustrating a transmission and reception operation of a PDCP layer device according to an embodiment of the present disclosure.

[0175] Referring to Figure 4, a PDCP transmitting device (Transmitting PDCP Entity) can operate as follows after receiving a PDCP SDU from an upper layer.

[0176] At reception of a PDCP SDU from upper layers, the transmitting PDCP entity shall:

[0177] - ifdiscardTimerForLowImportanceis configured and PSI based SDU discard is activated, and the PDCP SDU belongs to a low importance PDU Set:

[0178] - start thediscardTimerForLowImportanceassociated with this PDCP SDU;

[0179] - else:

[0180] - start thediscardTimerassociated with this PDCP SDU (if configured).

[0181] For a PDCP SDU received from upper layers, the transmitting PDCP entity shall:

[0182] - associate the COUNT value corresponding to TX_NEXT to this PDCP SDU;

[0183] - set the PDCP SN of the PDCP Data PDU to TX_NEXT modulo 2[pdcp-SN-SizeUL];

[0184] - increment TX_NEXT by one;

[0185] - submit the resulting PDCP Data PDU to lower layer as specified below.

[0186] When submitting a PDCP PDU to lower layer, the transmitting PDCP entity shall:

[0187] - if the transmitting PDCP entity is associated with one RLC entity:

[0188] - submit the PDCP PDU to the associated RLC entity;

[0189] Referring to FIG. 4, a PDCP transmitter can sequentially assign COUNT / SN values ​​1, 2, and 3 to three PDCP SDUs received from an upper layer. In the present disclosure, PDCP SDU X refers to a PDCP SDU with COUNT / SN of X. In one embodiment, a discardTimer can be started for PDCP SDUs 1, 2, and 3, respectively. Accordingly, when the discardTimer expires, the corresponding PDCP SDU can be discarded by the PDCP layer transmitter.

[0190] 일 실시예에서, PDCP 송신 장치의 PDCP SDU 폐기 동작은 아래와 같이 수행될 수 있다.

[0191] When thediscardTimerordiscardTimerForLowImportanceexpires for a PDCP SDU, the transmitting PDCP entity shall:

[0192] - ifpdu-SetDiscardis configured:

[0193] - discard all PDCP SDUs belonging to the PDU Set to which the PDCP SDU belongs along with the corresponding PDCP Data PDUs;

[0194] - else:

[0195] - discard the PDCP SDU along with the corresponding PDCP Data PDU.

[0196] If the corresponding PDCP Data PDU has already been submitted to lower layers, the discard is indicated to lower layers. For SRBs, when upper layers request a PDCP SDU discard, the PDCP entity shall discard all stored PDCP SDUs and PDCP PDUs.

[0197] Referring to Figure 4, PDCP SDU 1 is successfully delivered to the PDCP receiving entity, but due to congestion, PDCP SDU 2 may not be delivered to the PDCP receiving entity until the discardTimer expires. Conversely, due to congestion resolution, PDCP SDU 3 may be successfully delivered to the PDCP receiving entity before the discardTimer expires.

[0198] The following definitions may be utilized in this disclosure.

[0199] - HFN (State Variable): the HFN part (ie the number of most significant bits equal to HFN length) of the State Variable;

[0200] - SN(State Variable): the SN part (ie the number of least significant bits equal to PDCP SN length) of the State Variable;

[0201] - RCVD_SN: the PDCP SN of the received PDCP Data PDU, included in the PDU header;

[0202] - RCVD_HFN: the HFN of the received PDCP Data PDU, calculated by the receiving PDCP entity;

[0203] - RCVD_COUNT: the COUNT of the received PDCP Data PDU = [RCVD_HFN, RCVD_SN].

[0204] In one embodiment of the present disclosure, when receiving a PDCP Data PDU from a lower layer, a PDCP receiving device may operate as follows.

[0205] At reception of a PDCP Data PDU from lower layers, the receiving PDCP entity shall determine the COUNT value of the received PDCP Data PDU, i.e. RCVD_COUNT, as follows:

[0206] - if RCVD_SN < SN(RX_DELIV) - Window_Size:

[0207] - RCVD_HFN = HFN(RX_DELIV) + 1.

[0208] - else if RCVD_SN >= SN(RX_DELIV) + Window_Size:

[0209] - RCVD_HFN = HFN(RX_DELIV) - 1.

[0210] - else:

[0211] - RCVD_HFN = HFN(RX_DELIV);

[0212] - RCVD_COUNT = [RCVD_HFN, RCVD_SN].

[0213] After determining the COUNT value of the received PDCP Data PDU = RCVD_COUNT, the receiving PDCP entity shall:

[0214] - perform deciphering and integrity verification of the PDCP Data PDU using COUNT = RCVD_COUNT;

[0215] - if integrity verification fails:

[0216] - indicate the integrity verification failure to upper layer;

[0217] - discard the PDCP Data PDU and consider it as not received;

[0218] - if RCVD_COUNT < RX_DELIV; or

[0219] - if the PDCP Data PDU with COUNT = RCVD_COUNT has been received before:

[0220] - discard the PDCP Data PDU;

[0221] If the received PDCP Data PDU with COUNT value = RCVD_COUNT is not discarded above, the receiving PDCP entity shall:

[0222] - store the resulting PDCP SDU in the reception buffer;

[0223] - if RCVD_COUNT >= RX_NEXT:

[0224] - update RX_NEXT to RCVD_COUNT + 1.

[0225] - ifoutOfOrderDeliveryis configured:

[0226] - deliver the resulting PDCP SDU to upper layers after performing header decompression using EHC.

[0227] - if RCVD_COUNT = RX_DELIV:

[0228] - deliver to upper layers in ascending order of the associated COUNT value after performing header decompression, if not decompressed before;

[0229] - all stored PDCP SDU(s) with consecutively associated COUNT value(s) starting from COUNT = RX_DELIV;

[0230] - update RX_DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers, with COUNT value > RX_DELIV;

[0231] - ift-Reorderingis running, and if RX_DELIV >= RX_REORD:

[0232] - stop and resett-Reordering.

[0233] - ift-Reorderingis not running (includes the case whent-Reorderingis stopped due to actions above), and RX_DELIV < RX_NEXT:

[0234] - update RX_REORD to RX_NEXT;

[0235] - start t-Reordering.

[0236] t-Reordering 타이머 만료 시, PDCP 수신 장치는 아래와 같이 동작할 수 있다.

[0237] - deliver to upper layers in ascending order of the associated COUNT value after performing header decompression, if not decompressed before:

[0238] - all stored PDCP SDU(s) with associated COUNT value(s) < RX_REORD;

[0239] - all stored PDCP SDU(s) with consecutively associated COUNT value(s) starting from RX_REORD;

[0240] - update RX_DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers, with COUNT value >= RX_REORD;

[0241] - if RX_DELIV < RX_NEXT:

[0242] - update RX_REORD to RX_NEXT;

[0243] - start t-Reordering.

[0244] Referring to FIG. 4, after receiving PDCP SDU 1, the PDCP receiving device can receive PDCP SDU 3 without PDCP SDU 2. When receiving PDCP SDU 3, the PDCP receiving device can set RX_NEXT to 4. At this time, RX_DELIV can be set to 2. Therefore, since RX_DELIV is less than RX_NEXT, RX_REORD can be set to RX_NEXT (4) and the t-Reordering timer can be started. When the t-Reordering timer expires, the PDCP receiving device can forward PDCP SDU 3 to the upper layer.

[0245] In FIG. 4, the PDCP transmitter can know in advance that the PDCP receiver cannot receive PDCP SDU 2 because PDCP SDU 2 has never been transmitted before the expiration of the corresponding discardTimer. Since the PDCP receiver cannot know whether PDCP SDU 2 is unlikely to be received or whether PDCP SDU 3 and PDCP SDU 2 are received out of order during the transmission and reception process, it can start the t-Reordering timer to expect to receive PDCP SDU 2. As such, the PDCP receiver has a basic principle of sequentially delivering PDCP SDUs to the upper layer unless outOfOrderDelivery is set. If the PDCP transmitter can inform the PDCP receiver that it is unlikely to receive a specific COUNT / SN, the PDCP receiver can avoid starting the t-Reordering timer to receive the corresponding SDU, thereby reducing the reordering delay caused by the t-Reordering timer.

[0246] The present disclosure proposes a method by which a PDCP transmitter can inform a PDCP receiver that a PDCP SDU corresponding to a specific COUNT / SN is unlikely to be received by the receiver. In one embodiment of the present disclosure, when a PDCP transmitter discards a PDCP SDU corresponding to a specific COUNT / SN, and the corresponding PDCP SDU is unlikely to be delivered to the receiver, a COUNT / SN Gap can be expressed as occurring due to the discarding of the corresponding PDCP SDU. Accordingly, the PDCP transmitter can report the COUNT / SN Gap to the PDCP receiver through a specific PDCP Control PDU. In one embodiment, the present disclosure refers to the PDCP Control PDU as a COUNT / SN Gap Report or a PDCP COUNT / SN Gap Report. Other names, such as PDCP Discard / Missing Report / Notification / Indication, are also possible, and the present disclosure does not limit the name of the corresponding PDCP Control PDU.

[0247] In one embodiment of the present disclosure, when a PDCP transmitting device discards a PDCP SDU corresponding to a specific COUNT / SN, thereby making it impossible for the corresponding PDCP receiving device to receive the PDCP SDU corresponding to the COUNT / SN, the SN / COUNT of the corresponding PDCP SDU may be expressed as an SN / COUNT Gap, an SN / COUNT that caused the SN / COUNT Gap, a discarded SN / COUNT, or a Missing SN / COUNT. However, the present disclosure does not limit the expression method and all of them can be used with the same meaning.

[0248] FIG. 5 is a diagram illustrating an operation in which a PDCP transmitting device reports an SN Gap to a PDCP receiving device through an SN Gap Report according to one embodiment of the present disclosure.

[0249] Referring to FIG. 5, as in FIG. 4, after a PDCP transmitting device generates PDCP SDU 2, it may not be able to transmit the corresponding SDU until the discardTimer of PDCP SDU 2 expires due to congestion. Therefore, the PDCP transmitting device may inform the PDCP receiving device that the PDCP SDU corresponding to COUNT / SN 2 in the SN Gap Report is unlikely to be received. In one embodiment, the PDCP receiving device that has received the SN Gap Report may know that PDCP SDU 2 is no longer likely to be received, and may no longer start the t-Reordering timer to wait for PDCP SDU 2 after receiving PDCP SDU 3. Therefore, PDCP SDU 3 can be delivered to the upper layer without a t-Reordering delay.

[0250] Figure 6 is a diagram illustrating the operation of a terminal and a base station transmitting and receiving a PDCP SN Gap Report.

[0251] Referring to FIG. 6, when the base station (610) does not know the capability of a terminal (600) in an RRC_CONNECTED state, or when determining the capability of the terminal, the base station (610) may transmit a message (e.g., UECapabilityEnquiry) to the terminal inquiring about the capability of the terminal at step 630.

[0252] The terminal may transmit a message reporting its capabilities (e.g., UECapabilityInformation) to the base station at step 640. The terminal capability report message may include an indicator indicating whether the terminal supports PDCP SN Gap Report. In one embodiment, the terminal may support PDCP SN Gap Report only if it supports pdu-SetDiscard-r18 and / or psi-BasedDiscard-r18. In one embodiment, if the terminal supports pdu-SetDiscard-r18 and / or psi-BasedDiscard-r18, it may be considered to also support PDCP SN Gap Report.

[0253] The base station can determine whether the terminal supports PDCP SN Gap Report through a terminal capability report message (e.g., UECapabilityInformation). If the terminal supports PDCP SN Gap Report, the base station can transmit PDCP SN Gap Report-related configuration information to the terminal through an RRC message (e.g., RRCReconfiguration message (650)).

[0254] The PDCP SN Gap Report related settings set by the base station to the terminal may include the following information.

[0255] - PDCP SN Gap Report can be configured to be transmitted for each DRB / PDCP layer device / QoS Flow / Cell Group. In one embodiment, this configuration can be restricted so that it can be configured only when outOfOrderDelivery is not configured for the corresponding PDCP layer device / DRB.

[0256] - The PDCP SN Gap Report proposed in this disclosure may additionally include configuration information. The configuration information may be set for each DRB / PDCP layer device / QoS Flow / Cell Group. For example, the configuration information may include one or more of the following information: the size of the t-snGapProhibit timer, snGapThreshold, the maximum length of the SN Gap Report, and the maximum length of the Bitmap field of the SN Gap Report.

[0257] Referring to FIG. 6, a PDCP transmitting device (Transmitting PDCP Entity) of a terminal configured to perform a PDCP SN Gap Report can trigger (660) an SN Gap Report when a PDCP SN Gap occurs.

[0258] In one embodiment, a PDCP transmitting device may discard a particular PDCP SDU when the discardTimer or discardTimerForLowImportance of the particular PDCP SDU expires.

[0259] In one embodiment, a PDCP transmitting device may perform PDCP SDU discard as follows.

[0260] PDCP SDU discard behavior:

[0261] When thediscardTimerordiscardTimerForLowImportanceexpires for a PDCP SDU, the transmitting PDCP entity shall:

[0262] -ifpdu-SetDiscardis configured:

[0263] - discard all PDCP SDUs belonging to the PDU Set to which the PDCP SDU belongs along with the corresponding PDCP Data PDUs;

[0264] NOTE 1: PDCP SDUs subsequently received from upper layers are also discarded if they belong to the PDU Set.

[0265] - else:

[0266] - discard the PDCP SDU along with the corresponding PDCP Data PDU.

[0267] If the corresponding PDCP Data PDU has already been submitted to lower layers, the discard is indicated to lower layers.

[0268] For SRBs, when upper layers request a PDCP SDU discard, the PDCP entity shall discard all stored PDCP SDUs and PDCP PDUs.

[0269] In one embodiment of the present disclosure, when a specific PDCP SDU is discarded by a discard operation, one or more of the following conditions may need to be met for a PDCP SN Gap to occur.

[0270] - Condition 1: The discarded PDCP SDU has already been allocated / granted SN / COUNT at the time of discarding.

[0271] - Condition 2: The discarded PDCP SDU is not the last PDCP SDU with an SN / COUNT assigned at the time of discarding. That is, there is at least one PDCP SDU with a SN / COUNT value greater than the discarded PDCP SDU.

[0272] - Condition 3: A discarded PDCP SDU has already been delivered to a lower layer at the time of being discarded. The lower layer may be the RLC layer or the MAC layer. In one embodiment, if the lower RLC layer is in RLC UM or AM mode (i.e., in UM or AM DRB), the discarded PDCP SDU has been delivered to a lower layer, but all or part of the corresponding PDCP SDU (as included in a MAC PDU) must not have been transmitted at all (as included in a MAC PDU). In one embodiment, if the lower layer is in RLC AM mode (i.e., in AM DRB), the discarded PDCP SDU has been delivered to a lower layer, but successful delivery (Acknowledgement) must not have been confirmed by the lower layer. This may include some or all of the following states: never been transmitted at all (waiting for initial transmission), transmitted but waiting for an Acknowledgement, or transmitted but receiving a Negative Acknowledgement and waiting for retransmission.

[0273] - Condition 4: SN re-association must not be performed. In one embodiment, SN re-association may mean the operation of reassigning the SN / COUNT of a PDCP SDU to the next PDCP SDU after the PDCP SDU to which the SN / COUNT was assigned has been discarded. In one embodiment, SN re-association may or may not be implemented by the terminal. Therefore, if the terminal does not implement SN re-association, it may not be performed.

[0274] - Condition 5: In one embodiment of the present disclosure, a PDCP transmitting device can trigger an SN Gap Report only when pdu-SetDiscard is set and all PDCP SDUs in the PDU Set cause discard / SN Gap.

[0275] - Condition 6: In one embodiment of the present disclosure, a PDCP transmitting device can trigger an SN Gap Report only when discardTimerForLowImportance is set and PSI-based SDU discard is activated, and expiration of discardTimerForLowImportance causes discard / SN Gap of PDCP SDU (belonging to low importance PDU Set) / PDU Set (if pdu-SetDiscard is set).

[0276] In one embodiment of the present disclosure, when a specific PDCP SDU is discarded by a discard operation, whether a PDCP SN Gap occurs can be determined by the terminal implementation.

[0277] In one embodiment of the present disclosure, if a PDCP transmitting device confirms successful delivery of a PDCP SDU through a PDCP Status Report, the PDCP transmitting device may discard the corresponding PDCP SDU and the corresponding PDCP Data PDU. That is, the following operation may be performed.

[0278] - When the successful delivery of a PDCP SDU is confirmed by PDCP status report, the transmitting PDCP entity shall discard the PDCP SDU along with the corresponding PDCP Data PDU.

[0279] At this time, even if a successfully delivered PDCP SDU is discarded, it may not generate an SN Gap. Therefore, the SN / COUNT that generated an SN Gap reported through the PDCP SN Gap Report may not include the SN / COUNT corresponding to a PDCP SDU whose successful delivery was confirmed by the PDCP Status Report. In one embodiment, since discarding a PDCP SDU whose successful delivery was confirmed by the PDCP Status Report may not generate an SN Gap, it may not trigger a PDCP SN Gap Report.

[0280] According to one embodiment of the present disclosure, when the discardTimer or discardTimerForLowImportance corresponding to a specific PDCP SDU expires, the PDCP transmitting device may operate as follows.

[0281] - If pdu-SetDiscard is set:

[0282] 1) All PDCP SDUs and corresponding PDCP Data PDUs in the PDU Set to which the PDCP SDU belongs can be discarded. In this case, if the PDU Set includes multiple PDCP SDUs, the following two embodiments may exist.

[0283] (1) Example 1: The number of SN Gap / SN Gap Events may be considered to have occurred as many times as the number of PDCP SDUs that caused SN Gap among multiple PDCP SDUs included in a PDU Set. In other words, if there are N PDCP SDUs that caused SN Gap among discarded PDCP SDUs, the SN Gap / SN Gap Event may be considered to have occurred N times.

[0284] (2) Example 2: Even if there are multiple PDCP SDUs that cause SN Gap among all PDCP SDUs included in the PDU Set, SN Gap / SN Gap Event can be considered to have occurred only once.

[0285] - Otherwise:

[0286] 1) PDCP SDU and corresponding PDCP Data PDU can be discarded. In this case, if an SN Gap occurs due to discarding a PDCP SDU, it can be considered that an SN Gap / SN Gap Event has occurred once.

[0287] In one embodiment of the present disclosure, when an SN Gap / SN Gap Event occurs once in a PDCP transmitter, it can be considered that the SN Gap Report triggering condition is met. In one embodiment, when the PDCP SN Gap Report triggering condition is met once, the PDCP SN Gap Report can be triggered once. In one embodiment, the PDCP SN Gap Report can be triggered only when the base station has configured the corresponding PDCP transmitter to perform the PDCP SN Gap Report.

[0288] In one embodiment of the present disclosure, after a PDCP SN Gap Report triggering condition is satisfied, when the PDCP transmitting device determines at what point to trigger / create (Compile / Construct) a PDCP SN Gap Report, there may be the following embodiments.

[0289] - 실시예 1: If SN Gap Report triggering condition is satisfied, trigger an SN Gap Report, and compile an SN Gap Report and submit it to lower layers as the first PDCP PDU for transmission

[0290] - 실시예 2: If SN Gap Report triggering condition is satisfied, trigger an SN Gap Report, and compile an SN Gap Report at the first transmission opportunity indicated by lower layer. A single SN Gap Report is compiled even if SN Gap Report was triggered several times.

[0291] - 실시예 3: If SN Gap Report triggering condition is satisfied, and if t-snGapProhibit timer is not running, trigger an SN Gap Report, and start t-snGapProhibit. Compile an SN Gap Report, and submit it to lower layers as the first PDCP PDU for transmission after t-snGapProhibit is expired.

[0292] In one embodiment, due to the delay-sensitive nature of the SN Gap Report, the PDCP transmitting device may compile the SN Gap Report and then forward it to the lower layer as the PDCP PDU to be transmitted first. In other words, the SN Gap Report may be given the highest priority, instructing the lower layer to transmit it with priority over other PDCP PDUs.

[0293] In one embodiment of the present disclosure, a new Prohibit Timer (e.g., t-snGapProhibit) may be introduced to prevent SN Gap Reports from being transmitted too frequently. In one embodiment, the size of the timer may be set by the base station through a PDCP SN Gap Report-related setting (included in RRCReconfiguration). In one embodiment, when the timer is running, the PDCP transmitter of the terminal may operate so as not to transmit / trigger the PDCP SN Gap Report. In one embodiment, only when the timer is not running, the PDCP transmitter of the terminal may operate so as to transmit / trigger the PDCP SN Gap Report.

[0294] In one embodiment, a PDCP transmitting device of a terminal with t-snGapProhibit set may operate as follows.

[0295] When an SN Gap Report is triggered:

[0296] -if t-snGapProhibit is not running

[0297] 1) at the first transmission opportunity indicated by lower layer, compile / construct a missing report, and submit it to lower layer

[0298] - else

[0299] 1) at the first transmission opportunity indicated by lower layer after t-snGapProhibit timer expires, a single SN Gap report is compiled / constructed and submitted to lower layer even if SN Gap report was triggered several times while t-snGapProhibit was running

[0300] When an SN Gap Report has been compiled / constructed / submitted to lower layer, the transmission PDCP entity shall:

[0301] - start t-snGapProhibit

[0302] In one embodiment of the present disclosure, in order to prevent SN Gap Reports from being transmitted too frequently, when a SN Gap / SN Gap Event or SN Gap Report trigger (SN Gap Report triggering condition / event) or the number of PDCP SDU / PDU Sets that cause SN Gap occurs more than a certain threshold, an SN Gap Report may be triggered or transmitted / compiled. At this time, the threshold (e.g., snGapThreshold) may be set by the base station through a PDCP SN Gap Report related setting (included in RRCReconfiguration). In one embodiment, the PDCP transmitting device of the terminal may introduce a counter (e.g., GAP_WITHOUT_REPORT) that counts the number / number of SN Gap / SN Gap Event / SN Gap Report trigger / SN Gap causing PDCP SDU / PDU Sets. In one embodiment, the PDCP transmitting device of the terminal with snGapThreshold set may operate as follows.

[0303] - When an SN Gap / SN Gap triggering condition / event occurs (or SN Gap Report is triggered), or a PDCP SDU / PDU set causes SN Gap increment GAP_WITHOUT_REPORT by one

[0304] - if GAP_WITHOUT_REPORT >= snGapThreshold

[0305] 1) compile / construct / trigger an SN Gap Report and submit it to lower layers

[0306] 2) set GAP_WITHOUT_REPORT to 0

[0307] FIG. 7 is a diagram illustrating the format of a PDCP SN Gap Report according to one embodiment of the present disclosure.

[0308] Referring to FIG. 7, the first byte of the PDCP SN Gap Report may be composed of a D / C field (700), a PDU Type field (710), and a Reserved (R) field. In one embodiment, the D / C field may be defined as follows.

[0309] - Length: 1 bit.

[0310] - This field indicates whether the corresponding PDCP PDU is a PDCP Data PDU or a PDCP Control PDU.

[0311] In one embodiment, the PDU Type field may be defined as follows:

[0312] - Length: 3 bits

[0313] - This field indicates the type of control information included in the corresponding PDCP Control PDU.

[0314] In one embodiment, the PDU Type field may indicate that the corresponding PDCP Control PDU is a PDCP SN Gap Report, as shown in Table 1. In one embodiment, the PDU Type field value indicating a PDCP SN Gap Report may be indicated as one of the Reserved values ​​in Table 1.

[0315]

[0316] Referring to FIG. 7, in one embodiment, the Anchor Gap Count (AGC) (720-750) may be indicated as 4 bytes from Oct 2 to Oct 5 of the PDCP SN Gap Report. In one embodiment, the AGC may be referred to as First Discarded COUNT (FDC), First Missing COUNT (FMC), First SN Gap COUNT (FSC), or in other ways. In the present disclosure, the field is referred to as AGC, but the name of the field is not limited. In one embodiment, the length of the AGC field may be shorter than 4 bytes. If shorter than 4 bytes, the field may include only some bits of the COUNT corresponding to the AGC. For example, it may include only bits corresponding to the SN among the COUNT. In one embodiment, when the length of SN is 12 bits, the AGC field for Byte Alignment may have a length of 2 bytes, and in this case, other bits except the SN bit may be set to 0. In one embodiment, when the length of SN is 18 bits, the AGC field for Byte Alignment may have a length of 3 bytes, and in this case, other bits except the SN bit may be set to 0.

[0317] Referring to FIG. 7, the PDCP SN Gap Report may additionally include a Bitmap field (760-770). In one embodiment, each bit of the Bitmap may indicate whether an SN Gap is generated or discarded for the SN / COUNT assigned to a specific PDCP SDU determined by the position of the corresponding bit.

[0318] In one embodiment, if a specific bit is set to 1, it may indicate that the PDCP SDU with the SN / COUNT corresponding to that bit has caused an SN Gap or has been discarded. In one embodiment, if a specific bit is set to 0, it may indicate that the PDCP SDU with the SN / COUNT corresponding to that bit has not (yet) caused an SN Gap or has not been discarded.

[0319] In one embodiment, if a specific bit is set to 0, it may indicate that the PDCP SDU with the SN / COUNT corresponding to that bit has caused an SN gap or has been discarded. In one embodiment, if a specific bit is set to 1, it may indicate that the PDCP SDU with the SN / COUNT corresponding to that bit has not (yet) caused an SN gap or has not been discarded.

[0320] In one embodiment, the length of the Bitmap can be 0 bytes.

[0321] In one embodiment, the meaning of the Nth Bit (bit position = N) in the Bitmap may be as shown in Table 2 below.

[0322]

[0323] Referring to FIG. 6, in a PDCP transmitting device, after an SN Gap Report is triggered (660), the SN Gap Report can be compiled (670).

[0324] FIG. 8 is a diagram illustrating a method for a PDCP transmitting device to select an AGC of a PDCP SN Gap Report according to one embodiment of the present disclosure.

[0325] Referring to FIG. 8, the AGC (720-750) setting / determination / selection method of FIG. 7 may have the following embodiments.

[0326] - Example 1 (810): COUNT value of the first PDCP SDU that is discarded / causing SN Gap / missing and not covered by previous SN Gap Report. That is, it can be set to the smallest / first COUNT among the COUNTs of PDCP SDUs that caused SN Gap and that have not yet been reported through SN Gap Report. At this time, if one or more PDCP SDUs among the PDCP SDUs with a COUNT value greater than AGC caused / discarded SN Gap, the Bitmap field of FIG. 7 can be added in addition to the AGC field to report the SN Gap / discarding status for the COUNT of the corresponding PDCP SDU. In one embodiment, the Bitmap field can be set as follows.

[0327] 1) Option 1: Allocating a Bitmap field of length in bits equal to the number of COUNTs from and not including the PDCP SDU corresponding to AGC, up to and including the last PDCP SDUs, rounded up to the next multiple of 8, or up to and including a PDCP SDU for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0328] 2) Option 2: Allocating a Bitmap field of length in bits equal to the number of COUNTs from and not including the PDCP SDU corresponding to AGC, up to and including the last PDCP SDUs causing SN Gap / discarded / missing, rounded up to the next multiple of 8, or up to and including a PDCP SDU causing SN Gap / discarded / missing, rounded up to the next multiple of 8, for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0329] - Embodiment 2 (820): COUNT value of the last discarded PDCP SDU due to discardTimer expiry, or the next COUNT value of the last discarded PDCP SDU due to discardTimer expiry. That is, it can be set to the COUNT of the PDCP SDU with the largest COUNT value among the PDCP SDUs discarded due to discardTimer expiration, or the corresponding COUNT + 1. In one embodiment, a PDCP receiving device that receives a PDCP SN Gap Report can know that all PDCP SDUs corresponding to the COUNT before AGC (with or without AGC) are discarded. If there is a PDCP SDU corresponding to discard / SN Gap among the PDCP SDUs with a COUNT value greater than AGC, the Bitmap field can be used to report the discard status / SN Gap status of the corresponding PDCP SDU. In one embodiment, the Bitmap field can be set as follows.

[0330] 1) Option 1: Allocating a Bitmap field of length in bits equal to the number of COUNTs from and not including the PDCP SDU corresponding to AGC, up to and including the last PDCP SDUs, rounded up to the next multiple of 8, or up to and including a PDCP SDU for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0331] 2) Option 2: Allocating a Bitmap field of length in bits equal to the number of COUNTs from and not including the PDCP SDU corresponding to AGC, up to and including the last PDCP SDUs causing SN Gap / discarded / missing, rounded up to the next multiple of 8, or up to and including a PDCP SDU causing SN Gap / discarded / missing, rounded up to the next multiple of 8, for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0332] - Embodiment 3 (830): COUNT of the PDCP SDU triggered the SN Gap Report, or the COUNT of the first PDCP SDU triggered the pending SN Gap Reports, or the COUNT of the first PDCP SDU triggered the SN Gap Reports since(after) the last transmission of SN Gap Report / PDCP establishment / PDCP re-establishment. In one embodiment, it may be set to the COUNT value of the PDCP SDU that triggered the corresponding PDCP SN Gap Report. In one embodiment, it may be set to the COUNT value of the PDCP SDU that triggered the PDCP SN Gap Report first after the most recent point in time among the most recent PDCP SN Gap Report transmission, PDCP establishment, and PDCP re-establishment. In one embodiment, it may be set to the COUNT value of the smallest / first PDCP SDU among the PDCP SDUs that triggered the pending PDCP SN Gap Report. In one embodiment, when a PDCP SN Gap Report is transmitted, all pending PDCP SN Gap Reports may be canceled. If there is a PDCP SDU with a COUNT value greater than the AGC that corresponds to a discard / SN Gap, the Bitmap field may be used to report the discard / SN Gap status of the corresponding PDCP SDU. In one embodiment, the Bitmap field may be set as follows.

[0333] 1) Option 1: Allocating a Bitmap field of length in bits equal to the number of COUNTs from and not including the PDCP SDU corresponding to AGC, up to and including the last PDCP SDUs, rounded up to the next multiple of 8, or up to and including a PDCP SDU for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0334] 2) Option 2: Allocating a Bitmap field of length in bits equal to the number of COUNTs from and not including the PDCP SDU corresponding to AGC, up to and including the last PDCP SDUs causing SN Gap / discarded / missing, rounded up to the next multiple of 8, or up to and including a PDCP SDU causing SN Gap / discarded / missing, rounded up to the next multiple of 8, for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0335] - Example 4 (840): COUNT of the last PDCP SDU discarded / causing SN gap. That is, it can be set to the COUNT value of the PDCP SDU that was most recently / last discarded / caused an SN Gap. In one embodiment, if there is a PDCP SDU among the PDCP SDUs with a COUNT value smaller than the AGC that caused / discarded an SN Gap, but there is a PDCP SDU for which an SN Gap / discard situation has not yet been reported through an SN Gap Report, the SN Gap / discard situation of the PDCP SDU can be reported through the Bitmap field. In one embodiment, the Bitmap field can be set as follows. In one embodiment, the meaning of the Nth Bit (bit position = N) in the Bitmap can be as shown in Table 3 below.

[0336] 1) Option 1: Allocating a Bitmap field of length in bits equal to the number of COUNTs backwards from and not including the PDCP SDU corresponding to AGC, up to and including the first PDCP SDUs that have not been reported by SN Gap Report, rounded up to the next multiple of 8, or up to and including a PDCP SDU for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0337] 2) Option 2: Allocating a Bitmap field of length in bits equal to the number of COUNTs backwards from and not including the PDCP SDU corresponding to AGC, up to and including the first PDCP SDUs that cause SN Gap / discarded / missing but have not been reported by SN Gap Report, rounded up to the next multiple of 8, or up to and including a PDCP SDU that causes SN Gap / discarded / missing but has not been reported by SN Gap Report, rounded up to the next multiple of 8, for which the resulting PDCP Control PDU size is equal to [length limit of SN Gap Report], whichever comes first;

[0338]

[0339] In one embodiment of the present disclosure, the maximum length of the PDCP SN Gap Report (length limit of SN Gap Report) may be 9000 bytes. In one embodiment of the present disclosure, the maximum length of the PDCP SN Gap Report (length limit of SN Gap Report) may be set by the base station through an RRC message (e.g., RRCReconfiguration). In one embodiment, the base station may set the maximum length of the PDCP SN Gap Report (length limit of SN Gap Report) in units of bytes. In one embodiment, the base station may set the maximum length of the Bitmap field (length limit of Bitmap field) in the PDCP SN Gap Report in units of bytes. In this case, the maximum length of the PDCP SN Gap Report (length limit of SN Gap Report) may be determined as a value obtained by adding the maximum length of the Bitmap field (length limit of Bitmap field) to the length of other fields of the PDCP SN Gap Report (e.g., AGC field (e.g., 4 bytes) and 1 byte).

[0340] In addition to the PDCP SN Gap Report format presented in Figure 7, the PDCP SN Gap Report may have other formats. For example, it may include one or more indicators indicating a COUNT range for a number of consecutive discarded / missing / SN Gap occurrences. The indicators may include the following examples.

[0341] - Example 1: It is possible to indicate multiple COUNTs that cause consecutively discarded / missing / SN Gap, starting and ending with the first and last COUNT values ​​(including or excluding the first COUNT, including or excluding the last COUNT).

[0342] - Example 2: It is possible to indicate the number of COUNTs that have been discarded / missed / SN Gap-caused consecutively starting from the first COUNT and that COUNT.

[0343] In one embodiment, even if the PDCP SN Gap Report does not have the format presented in FIG. 7, among the discarded / missing / SN Gap-causing COUNTs reported through the PDCP SN Gap Report, the first or last discarded / missing / SN Gap-causing COUNT can be set / determined / selected by the AGC setting / determination / selection method.

[0344] In one embodiment of the present disclosure, a PDCP transmitting device may operate as follows.

[0345] When submitting a PDCP PDU to lower layer, the transmitting PDCP entity shall:

[0346] - if the transmitting PDCP entity is associated with one SRAP entity:

[0347] 1) submit the PDCP PDU to the associated SRAP entity;

[0348] - else, if the transmitting PDCP entity is associated with one RLC entity:

[0349] 1) submit the PDCP PDU to the associated RLC entity;

[0350] - else, if the transmitting PDCP entity is associated with one or more RLC entities and, either one SRAP entity or the N3C:

[0351] 1) if PDCP duplication is activated for the RB:

[0352] (1) if the PDCP PDU is a PDCP Data PDU or PDCP SN Gap Report:

[0353] a. duplicate the PDCP Data PDU or PDCP SN Gap Report and submit the PDCP Data PDU or PDCP SN Gap Report to both the primary path and secondary path, including any associated Uu RLC entities activated for PDCP duplication;

[0354] (2) else:

[0355] a. submit the PDCP Control PDU to the primary path;

[0356] 2) else (i.e., PDCP duplication is deactivated for the RB):

[0357] (1) if the total amount of PDCP data volume, RLC data volume pending for initial transmission (as specified in TS 38.322 [5]) in the RLC entity, and data volume pending for either transmission in the N3C (if available) or mapped SL RLC entity associated with the SRAP entity, is equal to or larger than ul-DataSplitThreshold:

[0358] a. submit the PDCP PDU to either the primary path or secondary path;

[0359] (2) else:

[0360] a. submit the PDCP PDU to the primary path;

[0361] - else, if the transmitting PDCP entity is associated with at least two RLC entities:

[0362] 1) if the PDCP duplication is activated for the RB:

[0363] (1) if the PDCP PDU is a PDCP Data PDU or PDCP SN Gap Report:

[0364] a. duplicate the PDCP Data PDU or PDCP SN Gap Report and submit the PDCP Data PDU to the associated RLC entities activated for PDCP duplication;

[0365] (2) else:

[0366] a. submit the PDCP Control PDU to the primary RLC entity;

[0367] 2) else (i.e. the PDCP duplication is deactivated for the RB or the RB is a DAPS bearer):

[0368] (1) if the split secondary RLC entity is configured; and

[0369] (2) if the total amount of PDCP data volume and RLC data volume pending for initial transmission (as specified in TS 38.322 [5]) in the primary RLC entity and the split secondary RLC entity is equal to or larger than ul-DataSplitThreshold:

[0370] a. submit the PDCP PDU to either the primary RLC entity or the split secondary RLC entity;

[0371] (3) else, if the transmitting PDCP entity is associated with the DAPS bearer:

[0372] a. if the uplink data switching has not been requested:

[0373] a) submit the PDCP PDU to the RLC entity associated with the source cell;

[0374] b. else:

[0375] a) if the PDCP PDU is a PDCP Data PDU or PDCP SN Gap Report:

[0376] (a) submit the PDCP Data PDU or PDCP SN Gap Report to the RLC entity associated with the target cell;

[0377] b) else:

[0378] (a) if the PDCP Control PDU is associated with source cell:

[0379] - submit the PDCP Control PDU to the RLC entity associated with the source cell;

[0380] (b) else:

[0381] - submit the PDCP Control PDU to the RLC entity associated with the target cell;

[0382] (4) else:

[0383] a. submit the PDCP PDU to the primary RLC entity.

[0384] 도 9는 PDCP 수신 장치가 PDCP SN Gap Report 수신 시, 상태 변수(State Variable)를 업데이트 하는 과정을 도시한 도면이다.

[0385] In one embodiment of the present disclosure, after receiving a PDCP SN Gap Report, a PDCP receiving device may consider the PDCP SDU corresponding to the COUNT that caused / discarded the SN Gap reported through the PDCP SN Gap Report as having been (successfully) received and / or delivered to the upper layer, or as not expecting to be received (Not Expect to Receive).

[0386] In one embodiment of the present disclosure, a PDCP receiving device may ignore the following cases for the PDCP SDUs that caused / discarded the SN Gap reported through the PDCP SN Gap Report:

[0387] - Case 1: if the PDCP SDU is already stored in reception buffer or has been received before and delivered to upper layer

[0388] - Case 2: if the COUNT of the PDCP SDU is outside of reordering window (ie, < RX_DELIV or >= RX_DELIV+Window_Size)

[0389] In one embodiment, a PDCP receiving device may report (indicate) an HFN desynchronization problem to a higher layer when there is a COUNT (e.g., GAP_COUNT) that satisfies the following conditions among the discarded / missing / SN Gap-causing COUNTs reported through a PDCP SN Gap Report.

[0390] - HFN desynchronization condition: GAP_COUNT < RX_DELIV - Window_Size and / or GAP_COUNT >= RX_DELIV + Window_Size

[0391] In one embodiment of the present disclosure, the state variables / Constants of the PDCP receiving device can be defined as follows.

[0392] - RX_NEXT: This state variable indicates the COUNT value of the next PDCP SDU expected to be received. The initial value is 0, except for sidelink broadcast and groupcast, for SRBs configured with state variables continuation, for multicast MRBs whose PDCP COUNT is not synchronized as indicated by upper layer, and for broadcast MRBs. For NR sidelink communication for broadcast and groupcast or sidelink SRB4 for NR sidelink discovery, the initial value of the SN part of RX_NEXT is (x +1) modulo (2[sl-PDCP-SN-Size]), where x is the SN of the first received PDCP Data PDU. For multicast MRBs whose PDCP COUNT is not synchronized as indicated by upper layer, and for broadcast MRBs, the initial value of the SN part of RX_NEXT is (x +1) modulo (2[PDCP-SN-SizeDL]), where x is the SN of the first received PDCP Data PDU. For target SRB configured with state variables continuation, the initial value is the value stored in PDCP entity for the corresponding source SRB.For source SRB configured with state variables continuation, the initial value is the value stored in PDCP entity for the corresponding target SRB.

[0393] - RX_DELIV: This state variable indicates the COUNT value of the first PDCP SDU not delivered to the upper layers, but still waited for. The initial value is 0, except for sidelink broadcast and groupcast, for SRBs configured with state variables continuation, and for MRBs. For NR sidelink communication for broadcast and groupcast or sidelink SRB4 for NR sidelink discovery, the initial value of the SN part of RX_DELIV is (x - 0.5 Х 2[sl-PDCP-SN-Size-1]) modulo (2[sl-PDCP-SN-Size]), where x is the SN of the first received PDCP Data PDU. For multicast MRBs whose PDCP COUNT is not synchronized as indicated by upper layer, and for broadcast MRBs, the initial value of the SN part of RX_DELIV is set to (x - 0.5 Х 2[PDCP-SN-SizeDL-1]) modulo (2[PDCP-SN-SizeDL]), where x is the SN of the first received PDCP Data PDU. For multicast MRBs, the initial value of RX_DELIV is set, if provided, by initialRX-DELIV in TS 38.331.For target SRB configured with state variables continuation, the initial value is the value stored in PDCP entity for the corresponding source SRB. For source SRB configured with state variables continuation, the initial value is the value stored in PDCP entity for the corresponding target SRB.

[0394] - RX_REORD: This state variable indicates the COUNT value following the COUNT value associated with the PDCP Data PDU which triggered t-Reordering. For target SRB configured with state variables continuation, the initial value is the value stored in PDCP entity for the corresponding source SRB. For source SRB configured with state variables continuation, the initial value is the value stored in PDCP entity for the corresponding target SRB.

[0395] - Window_Size: This constant indicates the size of the reordering window. The value equals to 2[pdcp-SN-SizeDL] - 1for SRB / DRB / MRB and 2[sl-PDCP-SN-Size] - 1for SLRB.

[0396] In one embodiment of the present disclosure, when a PDCP receiving device receives a PDCP SN Gap Report, it can update RX_NEXT as follows.

[0397] - if [the largest COUNT that is reported as missing / discarded / causing SN Gap by the SN Gap Report] >= RX_NEXT:

[0398] 1) update RX_NEXT to the COUNT value of

[0399] (1) [the largest COUNT that is reported as missing / discarded / causing SN gap by the SN Gap Report], added by 1 (+1)

[0400] In one embodiment of the present disclosure, when a PDCP receiving device receives a PDCP SN Gap Report, it can update RX_DELIV as follows.

[0401] - if RX_DELIV is reported as missing / discarded / causing SN gap (by the SN Gap Report):

[0402] 1) deliver to upper layers in ascending order of the associated COUNT value after performing header decompression, if not decompressed before;

[0403] (1) all stored PDCP SDU(s) (if any), with COUNT value > RX_DELIV, and < the first PDCP SDU that has not delivered to the upper layer and / or has not successfully received and has not been reported as missing / discarded / causing SN gap.

[0404] (2) update RX_DELIV to the COUNT value of the first PDCP SDU, which has not reported as missing / discarded / causing SN gap and has not delivered to upper layer and / or has not successfully received, with COUNT value > RX_DELIV

[0405] - if t-Reordering is running, and if RX_DELIV >= RX_REORD:

[0406] 1) stop and reset t-Reordering.

[0407] - if t-Reordering is not running (includes the case when t-Reordering is stopped due to actions above), and RX_DELIV < RX_NEXT:

[0408] 1) update RX_REORD to RX_NEXT;

[0409] 2) start t-Reordering.

[0410] In one embodiment of the present disclosure, when a PDCP receiving device receives a PDCP SN Gap Report, it may perform the following operations for each SN Gap cause / discard COUNT (e.g., GAP_COUNT) reported in the Report.

[0411] - if GAP_COUNT >= RX_NEXT:

[0412] 1) update RX_NEXT to GAP_COUNT + 1.

[0413] - if GAP_COUNT = RX_DELIV:

[0414] 1) deliver to upper layers in ascending order of the associated COUNT value after performing header decompression, if not decompressed before;

[0415] (1) all stored PDCP SDU(s) with consecutively associated COUNT value(s) starting from (but not include) COUNT = RX_DELIV (if any);

[0416] 2) update RX_DELIV to the COUNT value of the first PDCP SDU which has not been delivered to upper layers, with COUNT value > RX_DELIV;

[0417] In one embodiment of the present disclosure, upon receiving a PDCP SN Gap Report, the PDCP receiving device may operate as follows after processing updating state variables RX_NEXT / RX_DELIV for all or each SN Gap caused / discarded COUNT reported in the Report.

[0418] - if t-Reordering is running, and if RX_DELIV >= RX_REORD:

[0419] 1) stop and reset t-Reordering.

[0420] - if t-Reordering is not running (includes the case when t-Reordering is stopped due to actions above), and RX_DELIV < RX_NEXT:

[0421] 1) update RX_REORD to RX_NEXT;

[0422] 2) Start t-Reordering.

[0423] Referring to FIG. 9, when a PDCP receiving device receives a PDCP SN Gap Report, it can update RX_DELIV and RX_NEXT as follows.

[0424] - When RX_DELIV is set to COUNT D (900), if COUNT D is reported as a discarded / missing / SN Gap-causing COUNT, RX_DELIV can be set to the first COUNT (D+4 (940)) that has not yet been received among COUNTs greater than COUNT D and has not been reported as a discarded / missing / SN Gap-causing COUNT. Referring to Fig. 9, D+1 and D+3 are PDCP SDUs that have already been successfully received, and D+2, like D, is reported as a discarded / missing / SN Gap-causing COUNT. Therefore, D+1 and D+3 can be delivered to the upper layer without a re-ordering delay.

[0425] - When RX_NEXT is set to COUNT N (950), COUNT N and COUNT N+1 can be reported as discarded / missing / SN Gap causing COUNT. In this case, RX_NEXT can be set to the next COUNT value (N+2) after N+1.

[0426] In the present disclosure, a PDCP transmitting device may be a terminal or a base station. If the PDCP transmitting device is a terminal, the PDCP receiving device may be a base station. If the PDCP transmitting device is a base station, the PDCP receiving device may be a terminal.

[0427] In one embodiment of the present disclosure, when a PDCP SN Gap Report is triggered / compiled, the PDCP transmitting device may deliver the PDCP SN Gap Report to the lower layer first before other PDCP PDUs / PDCP Data PDUs in the buffer due to its delay-sensitive nature.

[0428] In one embodiment of the present disclosure, the base station may enable (e.g., SNGapReportEnabled) a specific PDCP layer device (AM / UM DRB) of the terminal to perform PDCP SN Gap Report via an RRC message (e.g., RRCReconfiguration).

[0429] For example, a transmitting PDCP layer device (AM / UM DRB) of a terminal with SNGapReportEnabled set can indicate that a PDCP SDU corresponding to the SN / COUNT included in the PDCP SN Gap Report has been discarded by transmitting a PDCP SN Gap Report to a receiving PDCP layer device of a base station. In addition, a transmitting PDCP layer device (AM / UM DRB) of a base station with SNGapReportEnabled set can indicate that a PDCP SDU corresponding to the SN / COUNT included in the PDCP SN Gap Report has been discarded by transmitting a PDCP SN Gap Report to a receiving PDCP layer device of a terminal. In addition, a receiving PDCP layer device (AM / UM DRB) of a terminal with SNGapReportEnabled set can receive an SN Gap Report from a transmitting PDCP layer device of a base station.

[0430] In one embodiment of the present disclosure, the base station may enable transmission / reception of header-only PDCP Data PDUs for a specific PDCP layer device (AM / UM DRB) of the terminal (e.g., headerOnlyPduEnabled) via an RRC message (e.g., RRCReconfiguration).

[0431] For example, a transmitting PDCP layer device (AM / UM DRB) of a terminal with headerOnlyPduEnabled set can indicate that a PDCP SDU corresponding to the SN / COUNT included in the PDCP Header is discarded by transmitting a header-only PDCP Data PDU to a receiving PDCP layer device of a base station. In addition, a transmitting PDCP layer device (AM / UM DRB) of a base station with headerOnlyPduEnabled set can indicate that a PDCP SDU corresponding to the SN / COUNT included in the PDCP Header is discarded by transmitting a header-only PDCP Data PDU to a receiving PDCP layer device of a terminal. In addition, a receiving PDCP layer device (AM / UM DRB) of a terminal with headerOnlyPduEnabled set can receive a header-only PDCP Data PDU from a transmitting PDCP layer device of a base station.

[0432] For example, a PDCP layer device (AM / UM DRB) with SNGapReportEnabled / headerOnlyPduEnabled set can perform or trigger PDCP SN Gap Report / header-only PDCP Data PDU related actions when discarding a specific PDCP SDU, if some or all of at least one of the following conditions are met:

[0433] - A COUNT value is assigned to the PDCP SDU to be discarded.

[0434] - There is at least one PDCP SDU assigned a COUNT value greater than the COUNT value assigned to the PDCP SDU to be discarded by the PDCP layer device.

[0435] - The PDCP SDU to be discarded has never been delivered to a lower layer.

[0436] - The PDCP SDU has been delivered to a lower layer, but has not been transmitted by the lower layer.

[0437] In one embodiment of the present disclosure, when a header-only PDCP Data PDU related operation is triggered, a transmitting PDCP layer device may perform an operation of configuring a header-only PDCP Data PDU and transmitting it to a lower layer as follows.

[0438] - The transmitting PDCP layer device can remove the Data field of the PDCP Data PDU (if present) corresponding to the PDCP SDU to be discarded. For example, the transmitting PDCP layer device can also remove the MAC-I (Message Authentication Code for Integrity) field (if present) of the PDCP Data PDU.

[0439] - After removing the Data field and / or MAC-I field, the transmitting PDCP layer device can newly generate MAC-I for Integrity Protection of the PDCP Header (e.g., including some or all of the D / C bit, one or more Reserved bits, and PDCP SN field) of the header-only PDCP Data PDU and add it after the PDCP Header field if the corresponding PDCP layer device (UM / AM DRB) has Integrity Protection enabled (e.g., integrityProtection is set to enabled in pdcp-Config via an RRC message). That is, the header-only PDCP Data PDU can include the PDCP Header and the MAC-I field generated for Integrity Protection of the corresponding PDCP Header.

[0440] - If the transmitting PDCP layer device (AM / UM DRB) has ciphering enabled (e.g., if cipheringDisabled is not set in pdcp-Config of the PDCP layer device via an RRC message), the transmitting PDCP layer device may perform ciphering on the MAC-I field of the header-only PDCP Data PDU. For example, the transmitting PDCP layer device may not perform ciphering on the PDCP Header field (since the corresponding PDCP SN / COUNT must be verified by the receiving PDCP layer device before de-ciphering).

[0441] A transmitting PDCP layer device can pass header-only PDCP Data PDUs to lower layers for transmission.

[0442] FIG. 10 is a diagram illustrating components of a terminal (UE) according to one embodiment of the present disclosure.

[0443] Referring to FIG. 10, a terminal according to one embodiment may include a transceiver (1010), a memory (1020), and a processor (1030). The transceiver (1010), the memory (1020), and the processor (1030) of the UE may operate according to the communication method of the terminal described above. However, the components of the terminal are not limited thereto. For example, the terminal may include more or fewer components than those described above. In addition, the processor (1030), the transceiver (1010), and the memory (1020) may be implemented as a single chip. In addition, the processor (1030) may include at least one processor. In addition, the terminal of FIG. 10 may correspond to the terminal of FIG. 1, FIG. 2, FIG. 3, or FIG. 6.

[0444] The transceiver (1010) collectively refers to the UE receiver and the UE transmitter, and can transmit and receive signals with a base station or network entity. The signals transmitted and received with the base station or network entity may include control information and data. The transceiver (1010) may include an RF transmitter for up-converting and amplifying the frequency of a transmission signal, and an RF receiver for low-noise amplification and down-converting the frequency of a reception signal. However, this is merely an example of the transceiver (1010), and the components of the transceiver (1010) are not limited to the RF transmitter and RF receiver.

[0445] In addition, the transceiver (1010) can receive a signal through a wireless channel and output it to the processor (1030), and transmit the signal output from the processor (1030) through the wireless channel. The memory (1020) can store programs and data necessary for the operation of the UE. In addition, the memory (1020) can store control information or data included in a signal acquired by the UE. The memory (1020) can be a storage medium such as a read-only memory (ROM), a random access memory (RAM), a hard disk, a CD-ROM, and a DVD, or a combination of storage media.

[0446] The processor (1030) can control a series of processes to enable the terminal to operate. For example, the transceiver (1010) can receive a data signal including a control signal transmitted by a base station or a network entity, and the processor (1030) can determine the result of receiving the control signal and data signal transmitted by the base station or the network entity.

[0447] FIG. 11 is a diagram illustrating components of a base station (BS) according to one embodiment of the present disclosure.

[0448] Referring to FIG. 11, a base station according to one embodiment may include a transceiver (1110), a memory (1120), and a processor (1130). The transceiver (1110), the memory (1120), and the processor (1130) of the base station may operate according to the communication method of the base station described above. However, the components of the base station are not limited thereto. For example, the base station may include more or fewer components than the components described above. In addition, the processor (1130), the transceiver (1110), and the memory (1120) may be implemented as a single chip. In addition, the processor (1130) may include at least one processor. In addition, the base station of FIG. 11 may correspond to the base station of FIG. 1, FIG. 2, FIG. 3, or FIG. 6.

[0449] The transceiver (1110) collectively refers to a base station receiver and a base station transmitter, and can transmit and receive signals with a terminal (UE) or a network entity. The signals transmitted and received with the terminal or network entity may include control information and data. The transceiver (1110) may include an RF transmitter for up-converting and amplifying the frequency of a transmission signal and an RF receiver for low-noise amplifying and down-converting the frequency of a reception signal. However, this is only an example of the transceiver (1110), and the components of the transceiver (1110) are not limited to the RF transmitter and RF receiver. In addition, the transceiver (1110) may receive a signal through a wireless channel and output it to the processor (1130), and transmit a signal output from the processor (1130) through the wireless channel.

[0450] The memory (1120) can store programs and data required for the operation of the base station. In addition, the memory (1120) can store control information or data included in a signal acquired by the base station. The memory (1120) can be a storage medium such as a read-only memory (ROM), a random access memory (RAM), a hard disk, a CD-ROM, a DVD, or a combination of storage media. The processor (1130) can control a series of processes so that the base station operates as described above. For example, the transceiver (1110) can receive a data signal including a control signal transmitted by a terminal, and the processor (1130) can determine the result of receiving the control signal and the data signal transmitted by the terminal.

Claims

1. In a method performed by a terminal of a wireless communication system, A step of transmitting a first message to a base station, the first message including first information indicating whether the terminal supports a PDCP (Packet Data Convergence Protocol) SN (Sequence Number) gap report; A step of receiving a second message including second information for setting transmission of the PDCP SN gap report from the base station; A step of triggering the PDCP SN gap report to indicate discard of a PDCP SDU (Service Data Unit) based on at least one condition; and A method comprising the step of transmitting the PDCP SN gap report to the base station.

2. In paragraph 1, The above second information is included in the configuration information for DRB (Data Radio Bearer), The above configuration information does not include the outOfOrderDelivery field.

3. In paragraph 1, A method according to claim 1, wherein the at least one condition comprises a first condition that at least one PDCP SDU is discarded, a second condition that there is a PDCP SDU associated with a count value greater than a count value associated with the at least one discarded PDCP SDU, and a third condition that the at least one discarded PDCP SDU is not delivered to a lower layer by an RLC (Radio Link Control) entity of the terminal.

4. In paragraph 1, A method wherein the PDCP SN gap report is included in a PDCP PDU (Protocol Data Unit), and the PDCP PDU includes a field for indicating that the PDCP PDU is a PDCP Control PDU, a field for indicating that the type of the PDCP Control PDU is a PDCP SN gap report, a field for indicating a smallest value among count values ​​associated with at least one discarded PDCP SDU that triggered the PDCP SN gap report, and a bitmap field for indicating the at least one discarded PDCP SDU.

5. In a method performed by a base station of a wireless communication system, A step of receiving, from a terminal, a first message including first information indicating whether the terminal supports a PDCP (Packet Data Convergence Protocol) SN (Sequence Number) gap report; A step of transmitting a second message including second information for setting transmission of the PDCP SN gap report to the terminal; A method comprising the step of receiving the PDCP SN gap report from the terminal.

6. In paragraph 5, The above second information is included in the configuration information for DRB (Data Radio Bearer), The above configuration information does not include the outOfOrderDelivery field.

7. In paragraph 5, The above PDCP SN gap report is triggered by at least one condition, A method according to claim 1, wherein the at least one condition includes a first condition that at least one PDCP Service Data Unit (SDU) is discarded, a second condition that there is a PDCP SDU associated with a count value greater than a count value associated with the at least one discarded PDCP SDU, and a third condition that the at least one discarded PDCP SDU is not delivered to a lower layer by an RLC (Radio Link Control) entity of the terminal.

8. In paragraph 5, A method wherein the PDCP SN gap report is included in a PDCP PDU (Protocol Data Unit), and the PDCP PDU includes a field for indicating that the PDCP PDU is a PDCP Control PDU, a field for indicating that the type of the PDCP Control PDU is a PDCP SN gap report, a field for indicating a smallest value among count values ​​associated with at least one discarded PDCP SDU that triggered the PDCP SN gap report, and a bitmap field for indicating the at least one discarded PDCP SDU.

9. In the terminal of a wireless communication system, Transmitter and receiver; and Includes a control unit connected to the above transmitter and receiver, The above control unit, Transmitting a first message to the base station, the first message including first information indicating whether the terminal supports a PDCP (Packet Data Convergence Protocol) SN (Sequence Number) gap report, Receive a second message from the base station, including second information for setting up transmission of the PDCP SN gap report, Triggering the PDCP SN gap report to indicate discard of a PDCP SDU (service data unit) based on at least one condition, and A terminal configured to transmit the PDCP SN gap report to the base station.

10. In paragraph 9, The above second information is included in the configuration information for DRB (Data Radio Bearer), The above configuration information does not include the outOfOrderDelivery field.

11. In paragraph 9, A terminal, wherein the at least one condition includes a first condition that at least one PDCP SDU is discarded, a second condition that there is a PDCP SDU associated with a count value greater than a count value associated with the at least one discarded PDCP SDU, and a third condition that the at least one discarded PDCP SDU is not delivered to a lower layer by a radio link control (RLC) entity of the terminal.

12. In paragraph 9, A terminal, wherein the PDCP SN gap report is included in a PDCP PDU (Protocol Data Unit), and the PDCP PDU includes a field for indicating that the PDCP PDU is a PDCP Control PDU, a field for indicating that the type of the PDCP Control PDU is a PDCP SN gap report, a field for indicating a smallest value among count values ​​associated with at least one discarded PDCP SDU that triggered the PDCP SN gap report, and a bitmap field for indicating the at least one discarded PDCP SDU.

13. In a base station of a wireless communication system, Transmitter and receiver; and Includes a control unit connected to the above transmitter and receiver, The above control unit, Receive a first message from a terminal, the first message including first information indicating whether the terminal supports a PDCP (Packet Data Convergence Protocol) SN (Sequence Number) gap report, Transmitting a second message including second information for instructing the terminal to transmit the PDCP SN gap report, A base station configured to receive the PDCP SN gap report from the terminal.

14. In paragraph 13, The above second information is included in the configuration information for DRB (Data Radio Bearer), The above configuration information does not include the outOfOrderDelivery field, the base station.

15. In paragraph 13, The above PDCP SN gap report is triggered by at least one condition, The at least one condition includes a first condition that at least one PDCP Service Data Unit (SDU) is discarded, a second condition that there is a PDCP SDU associated with a count value greater than a count value associated with the at least one discarded PDCP SDU, and a third condition that the at least one discarded PDCP SDU is not delivered to a lower layer by an RLC (Radio Link Control) entity of the terminal. A base station, wherein the PDCP SN gap report is included in a PDCP PDU (Protocol Data Unit), and the PDCP PDU includes a field for indicating that the PDCP PDU is a PDCP Control PDU, a field for indicating that the type of the PDCP Control PDU is a PDCP SN gap report, a field for indicating a smallest value among count values ​​associated with at least one discarded PDCP SDU that triggered the PDCP SN gap report, and a bitmap field for indicating the at least one discarded PDCP SDU.

Images