Method and device for performing dual connectivity in heterogeneous networks

Abstract

The present disclosure relates to a communication method and system for converging a fourth generation (4G) communication system or a fifth generation (5G) communication system to support a higher data rate beyond the fourth generation (4G) system and use the Internet of Things (IoT) technology. The present disclosure can be applied to smart services based on 5G communication technology and IoT-related technologies, such as smart homes, smart buildings, smart cities, smart cars, connected cars, healthcare, digital education, smart retail, security and safety services. In a wireless communication system supporting Evolved Universal Terrestrial Radio Access and New Air Interface Dual Connectivity (EN‑DC), a method of a central unit control plane (CU‑CP) included in a secondary node (SN) (or a secondary gNB (SgNB)) includes receiving a first message for requesting the SgNB to allocate radio resources for a bearer from a master node (MN) (or a master eNB (MeNB)), and sending a second message to a central unit user plane (CU‑UP) included in the SgNB, the message including indication information indicating whether a packet data convergence protocol (PDCP) version of the bearer has been changed. The indication information is generated based on the first message.

Description

Technical Field

[0001] The present disclosure relates to a method and apparatus for performing dual connectivity in a heterogeneous network. Background Art

[0002] In order to meet the growing demand for wireless data traffic since the deployment of 4G communication systems, efforts have been made to develop improved 5G or pre-5G communication systems. Therefore, 5G or pre-5G communication systems are also referred to as "beyond 4G networks" or "post-LTE systems." 5G communication systems are considered to be implemented in higher frequency (mmWave) bands (e.g., 60GHz bands) to achieve higher data rates. In order to reduce the propagation loss of wireless waves and increase the transmission distance, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, massive antennas and other technologies discussed in 5G communication systems. In addition, in the 5G communication system, development of system network improvements based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, coordinated multi-points (CoMP), receiving end interference elimination, etc. is underway. In the 5G system, hybrid FSK and QAM modulation (FSK and QAM Modulation, FQAM) and sliding window superposition coding (SWSC) as advanced coding modulation (ACM) have been developed, as well as filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) as advanced access technologies.

[0003] The Internet is a human-centered connected network in which humans generate and consume information, and is now evolving towards the Internet of Things (IoT), in which distributed entities (such as things) can exchange and process information without human intervention. The Internet of Everything (IoE) has emerged, which is a combination of IoT technology and big data processing technology through connection with cloud servers. With the demand for technical elements such as "sensing technology", "wired / wireless communication and network infrastructure", "service interface technology", and "security technology" in IoT implementation, sensor networks, machine-to-machine (M2M) communication, machine type communication (MTC), etc. have been studied recently. Such an IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing data generated between connected things. IoT can be applied to various fields, including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart appliances, and advanced medical services through the convergence and combination between existing information technology (IT) and various industrial applications.

[0004] In light of this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, machine type communications (MTC), and machine-to-machine (M2M) communications can be implemented through beamforming, MIMO, and array antennas. The application of cloud radio access networks (RANs) as the above-mentioned big data processing technology can also be considered as an example of convergence between 5G technologies and IoT technologies.

[0005] The LTE system has a data processing structure different from that of the next generation mobile communication system. Specifically, in the LTE system, because the cascade (RLC concatenation, RLC cascade) function is placed in the radio link control (radio link control, RLC) layer, the terminal cannot perform a given data preprocessing before receiving the uplink transmission resource from the network. When receiving the uplink transmission resource, the packet data convergence protocol (PDCP) layer forms an RLC PDU by cascading PDCP packet data units (PDU) and sends the RLC PDU to the medium access control (MAC) layer for data transmission. In contrast, the next generation mobile communication system has a data processing structure in which the RLC layer forms the RLC PDU by processing the PDCP PDU received from the PDCP layer before receiving the uplink transmission resource, because the cascade (RLC cascade) function is not included in the RLC layer, and the MAC subheader and MAC SDU can be generated before the RLC PDU is sent to the MAC layer and the MAC layer.

[0006] Meanwhile, in the next generation communication system, various types of research are being conducted in order to achieve the purpose of improving the data processing speed.

[0007] Public Content

[0008] Technical issues

[0009] The CU-CP included in the SgNB can receive information about the PDCP version change from the MeNB through the SgNB add request message. However, the CU-UP responsible for the PDCP layer cannot recognize the information about the PDCP version change because a field for forwarding the information about the PDCP version change is not generated in the message sent and received on the E1 interface between the CU-CP and the CU-UP.

[0010] Therefore, the CU-UP included in the SgNB inevitably sets the PDCP sequence number based on the SN status transfer message.

[0011] That is, when the MeNB using only LTE PDCP requests SgNB addition, a mismatch occurs in the setting of the PDCP sequence number between the CU-UP included in the UE and the SgNB, and therefore, there is a problem of data loss.

[0012] Technical Solution

[0013] To solve this problem, an embodiment of the present disclosure may provide a method capable of preventing a mismatch in the setting of a PDCP sequence number between a CU-UP responsible for the PDCP layer and a UE by generating a field for forwarding indication information (indicating whether the PDCP version has been changed) in a message sent and received on an E1 interface between a CU-CP and a CU-UP included in an SgNB.

[0014] The present disclosure may provide a method and apparatus for sending a message (including indication information indicating whether a carried packet data convergence protocol (PDCP) version has been changed) to a control unit control plane (CU-UP) included in a secondary node (SN) (or a secondary gNB (SgNB)) in a wireless communication system supporting evolved universal terrestrial radio access and new air interface dual connectivity (EN-DC) to the CU-UP included in the secondary node.

[0015] The present disclosure may provide a method and apparatus for allocating a PDCP sequence number (SN) to at least one downlink (DL) packet based on whether a PDCP version of a bearer has been changed in a CU-UP included in a secondary node in a wireless communication system supporting EN-DC.

[0016] The present disclosure may provide a method and apparatus for aligning an order of at least one uplink (UL) packet based on whether a PDCP version of a bearer has been changed in a CU-UP included in a secondary node in a wireless communication system supporting EN-DC.

[0017] According to an embodiment of the present disclosure, in a wireless communication system supporting Evolved Universal Terrestrial Radio Access and New Air Interface Dual Connectivity (EN-DC), a method of a central unit control plane (CU-CP) included in a secondary node (SN) (or a secondary gNB (SgNB)) includes receiving a first message for requesting the SgNB to allocate radio resources for a bearer from a master node (MN) (or a master eNB (MeNB)), and sending a second message (including indication information indicating whether a Packet Data Convergence Protocol (PDCP) version of the bearer has been changed) to a CU-UP included in the SgNB. The indication information is generated based on the first message.

[0018] According to an embodiment of the present disclosure, in a wireless communication system supporting Evolved Universal Terrestrial Radio Access and New Air Interface Dual Connectivity (EN-DC), a method of a central unit user plane (CU-UP) included in a secondary node (SN) (or a secondary gNB (SgNB)) includes receiving a first message (including indication information indicating whether a packet data convergence protocol (PDCP) version of a bearer has been changed) from a central unit control plane (CU-CP) including the SgNB, receiving a second message including counting information from the CU-CP, and based on at least one of the indication information or the counting information, assigning a PDCP sequence number to at least one downlink packet received through the bearer.

[0019] According to an embodiment of the present disclosure, in a wireless communication system supporting Evolved Universal Terrestrial Radio Access and New Air Interface Dual Connectivity (EN-DC), a method of a central unit user plane (CU-UP) included in a secondary node (SN) (or a secondary gNB (SgNB)) includes receiving a first message (including indication information indicating whether a packet data convergence protocol (PDCP) version of a bearer has been changed) from a central unit control plane (CU-CP) included in the SgNB, receiving a second message including counting information from the CU-CP, and assigning a PDCP sequence number to at least one downlink packet received through the bearer based on at least one of the indication information or the counting information.

[0020] According to an embodiment of the present disclosure, in a wireless communication system supporting Evolved Universal Terrestrial Radio Access and New Air Interface Dual Connectivity (EN-DC), a central unit control plane (CU-CP) included in a secondary node (SN) (or a secondary gNB (SgNB)) includes a transceiver and at least one processor. The processor may be configured to control the transceiver to receive a first message for requesting the SgNB to allocate radio resources for a bearer from a master node (MN) (or a master eNB (MeNB)) and send a second message (the second message includes indication information indicating whether a Packet Data Convergence Protocol (PDCP) version of the bearer has been changed) to a CU-UP included in the SgNB. The indication information may be generated based on the first message.

[0021] According to a disclosed embodiment, in a wireless communication system supporting Evolved Universal Terrestrial Radio Access and New Air Interface Dual Connectivity (EN-DC), a Central Unit User Plane (CU-UP) included in a Secondary Node (SN) (or Secondary gNB (SgNB)) includes a transceiver and at least one processor. The processor may be configured to control the transceiver to receive a first message (including indication information indicating whether a Packet Data Convergence Protocol (PDCP) version of a bearer has been changed) from a Central Unit Control Plane (CU-CP) included in the SgNB, and to receive a second message including counting information from the CU-CP. The processor may be configured to control the allocation of a PDCP sequence number to at least one downlink packet received through the bearer based on at least one of the indication information or the counting information.

[0022] Beneficial Effects

[0023] According to various embodiments of the present disclosure, if an SgNB using NR-PDCP allocates wireless resources to a bearer using LTE-PDCP in a wireless communication system supporting EN-DC, a method and apparatus may be provided for preventing data loss due to a mismatch in the PDCP version of the bearer.

[0024] According to various embodiments of the present disclosure, a method and apparatus can be provided, which are capable of preventing a mismatch in PDCP sequence number settings between a CU-CP included in an SgNB and a UE, because if the MeNB issues an SgNB add request message so that the SgNB allocates wireless resources to a bearer in a wireless communication system supporting EN-DC, the CU-CP included in the SgNB sends a message (including indication information indicating whether the PDCP version of the bearer has been changed) to the CU-UP wireless included in the SgNB. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts:

[0026] Figure 1 A diagram showing the architecture of an LTE system;

[0027] Figure 2 A diagram showing a radio protocol structure in an LTE system;

[0028] Figure 3 A diagram showing the architecture of a next generation mobile communication system according to an embodiment of the present disclosure;

[0029] Figure 4 A diagram showing a radio protocol structure of a next generation mobile communication system according to an embodiment of the present disclosure;

[0030] Figure 5A A diagram showing SgNB addition and release scenarios in a wireless communication system supporting EN-DC;

[0031] Figure 5B Figure 2 shows a diagram of SgNB addition and release scenarios in a wireless communication system supporting EN-DC

[0032] Figure 6 A diagram showing a structure of a network element included in a wireless communication system supporting EN-DC;

[0033] Fig. 7A and 7B A flowchart showing an operation for a terminal supporting EN-DC to add a secondary node so that radio resources of an SgNB can be allocated to the terminal;

[0034] Figure 8 A flowchart showing an operation for a CU-CP included in a secondary node to send indication information (indicating whether a PDCP version has been changed) to a CU-UP according to various embodiments of the present disclosure;

[0035] Fig. 9 A flowchart showing various exemplary operations according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node assigns a PDCP sequence number (SN) to a DL packet based on indication information indicating whether a PDCP version has been changed;

[0036] Fig.10 A flowchart showing various exemplary operations according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node assigns a PDCP sequence number (SN) to a DL packet based on indication information indicating whether a PDCP version has been changed;

[0037] Fig.11 A flowchart showing various exemplary operations according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed;

[0038] Fig.12 A flowchart showing various exemplary operations according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed;

[0039] Fig.13A diagram showing various examples according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node allocates a PDCP sequence number to a DL packet based on indication information indicating whether a PDCP version has been changed;

[0040] Fig.14 A diagram showing various examples according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node allocates a PDCP sequence number to a DL packet based on indication information indicating whether a PDCP version has been changed;

[0041] Fig.15 A diagram showing various examples in which a CU-UP included in a secondary node aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed according to various embodiments of the present disclosure;

[0042] Fig.16 A diagram showing various examples in which a CU-UP included in a secondary node aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed according to various embodiments of the present disclosure;

[0043] Fig.17 A block diagram of a CU-CP included in a secondary node according to an embodiment of the present disclosure is shown;

[0044] Fig.18 A block diagram showing a CU-UP included in a secondary node according to an embodiment of the present disclosure; and

[0045] Fig.19 A block diagram of a terminal according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0046] According to an embodiment of the present disclosure, in a wireless communication system supporting Evolved Universal Terrestrial Radio Access and New Air Interface Dual Connectivity (EN-DC), a Central Unit User Plane (CU-UP) included in a Secondary Node (SN) (or Secondary gNB (SgNB)) includes a transceiver and at least one processor. The processor may be configured to control the transceiver to receive a first message (including indication information indicating whether a Packet Data Convergence Protocol (PDCP) version of a bearer has been changed) from a Central Unit Control Plane (CU-CP) included in the SgNB, and to receive a second message including counting information from the CU-CP. The processor may be configured to control to align sequence information of at least one uplink packet received through the bearer based on at least one of the indication information or the count. Before proceeding with the following detailed description, it may be helpful to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprising," and their derivatives, mean including but not limited to; the term "or" is inclusive, meaning and / or; the phrases "associated with" and "associated with," and their derivatives, may mean including, included within, interconnected with, containing, contained within, connected or connected with, coupled or coupled with, communicable with, cooperating with, interwoven, parallel, proximate, combined or combined with, having, having the properties of, and the like. The term "controller" means any device, system, or part thereof that controls at least one operation. Such a device may be implemented in hardware, firmware, or software, or in a combination of at least two thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0047] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, processes, functions, objects, classes, instances, related data, or a portion thereof suitable for implementation in a suitable computer-readable program code. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. "Non-transitory" computer-readable media does not include wired, wireless, optical, or other communication links that transmit temporary electrical signals or other signals. Non-transitory computer-readable media include media in which data can be permanently stored and media in which data can be stored and then overwritten, such as rewritable optical discs or erasable memory devices.

[0048] Definitions for certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

[0049] Described below Figures 1 to 19 , and the various embodiments used to describe the principles of the present disclosure in this patent document are only for illustration and should not be interpreted in any way to limit the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged system or device.

[0050] Hereinafter, the operating principle of the present disclosure is described in detail with reference to the accompanying drawings. When describing the present disclosure, if the detailed description of the known functions or configurations is considered to make the main points of the disclosure unnecessarily obscure, it will be omitted. In addition, the terms described below are defined by considering the functions in the present disclosure and may vary depending on the intention or practice of the user or operator. Therefore, each term should be defined based on the content of the entire specification.

[0051] In describing the present disclosure, if a detailed description about a known function or configuration is deemed to make the gist of the disclosure unnecessarily obscure, it will be omitted. Embodiments of the present disclosure are described below with reference to the accompanying drawings.

[0052] In the following description, for the convenience of description, terms for identifying access nodes, terms representing network entities, terms representing messages, terms representing interfaces between network entities, and terms representing various types of identification information have been shown. Therefore, the present disclosure is not limited to the following terms, and other terms may be used to represent objects with equivalent technical meanings.

[0053] For ease of description, in the present disclosure, terms and names are defined in the Long Term Evolution (LTE) of the 3rd Generation Partnership Project (hereinafter referred to as "3GPP"), and the New Radio (NR) standard is used. However, the present disclosure is not limited to the terms and names and can be equally applied to systems conforming to other standards.

[0054] First, the terms used in this specification are defined.

[0055] In this specification, a radio bearer may include a data radio bearer (DRB) and a signaling radio bearer (SRB).

[0056] For example, a data radio bearer (DRB) provided in a wireless interface between a terminal and a base station is a path through which data of a user plane is forwarded. A signaling radio bearer (SRB) may be a path through which data of a control plane is forwarded, such as a radio resource control (RRC) layer and a non-access-stratum (NAS) control message.

[0057] In this specification, a wireless communication system supported in a network (on which multiple communication systems are interconnected) can support interworking between heterogeneous technologies and frequency bands (multi-RAT interworking). In this specification, systems supporting different communication networks can basically be divided into terminals, radio access networks and multiple core networks (CNs).

[0058] In this specification, the terminal may be an integrated terminal supporting all of 4G radio access technology (E-UTRA), radio access technology evolved from 4G (Evolved E-UTRA), and 5G radio access technology (New Radio (NR)).

[0059] In this specification, a radio access network may support multiple radio access technologies (RATs) and may support interworking between heterogeneous technologies and frequency bands (multi-RAT interworking).

[0060] For example, the radio access technology may be all new air access networks (new RAN) supporting 4G radio access technology (E-UTRA), radio access technology evolved from 4G (Evolved E-UTRA) and 5G radio access technology (New Radio (NR)).

[0061] In this specification, radio access network, base station and network node may be used as the same meaning. The base station may include a 5G base station (or new air interface base station or gNB) using 5G radio access technology (new air interface radio (NR)), a 4G base station (LTE-eNB) using 4G radio access technology (E-UTRA), and a base station (eLTE eNB) using a radio access technology evolved from 4G (evolved E-UTRA). In addition, the base station (eLTE eNB) can support both 4G radio access technology and 5G radio access technology.

[0062] According to the specification of the present disclosure, a wireless communication system, in which a terminal can perform communication with at least one cell associated with a first base station and at least one cell associated with a second base station, may involve the following situations: the first and second base stations associated with dual connectivity (DC) involve a 4G system; or a first base station associated with a 4G system and a second base station supporting an NR system (E-UTRA-NR dual connectivity, EN-DC). In addition, even if the wireless communication system disclosed in the present specification involves an EN-DC system, the system is not necessarily limited thereto and may also include a multi-radio dual connectivity (Multi-RadioDual Connectivity, MR-DC) system.

[0063] In the EN-DC system disclosed in this specification, the main base station can be used as the same meaning as the main base station, the main node (MN) or the main eNB (MeNB). The sub-base station can be used as the same meaning as the auxiliary base station, the auxiliary node (SN) or the auxiliary gNB (SgNB).

[0064] In the EN-DC system disclosed in this specification, if the terminal moves to the coverage of the secondary node, a handover may occur. At this time, the primary node may become the source base station, and the secondary node may become the target base station.

[0065] Likewise, in the EN-DC system disclosed in this specification, if the terminal deviates from the coverage of the secondary node, a handover may occur. At this time, the secondary node may become the source base station, and the primary node may become the target base station.

[0066] The terms described in TS 38.401, i.e., gNB central unit (gNB-CU), gNB-CU control plane (gNB-CU-CP), gNB-CU user plane (gNB-CU-UP) and gNB distributed unit (gNB-DU), may correspond to a central unit included in a secondary node (SN) (or secondary gNB (SgNB)), a CU-UP included in a secondary node (SN) (or secondary gNB (SgNB)), a CU-UP included in a secondary node and a distributed unit (DU) included in a secondary node in the EN-DC system disclosed in the present specification.

[0067] That is, in this specification, the gNB-CU control plane (gNB-CU-CP), gNB-CU user plane (gNB-CU-UP) and gNB distributed unit (gNB-DU) may be indicated as CU-CP, CU-UP and DU, respectively.

[0068] In this specification, in the EN-DC system, a terminal can be connected to one eNB operating as a master node and one en-gNB operating as a slave node.

[0069] The eNB can be connected to the EPC through the S1 interface and to the en-gNB through the X2 interface. The en-gNB can be connected to the EPC through the S1. The en-gNB can be connected to the EPC through the S1-U interface, and other en-gNBs can be connected to the EPC through the X2-U interface.

[0070] Figure 1 Diagram showing the architecture of an LTE system.

[0071] refer to Figure 1 , the radio access network of the LTE system is configured with next generation evolved Node Bs (hereinafter referred to as “ENBs”, “Node Bs” or “base stations”) 105, 110, 115 and 120, a mobility management entity (MME) 125 and a serving gateway (S-GW) 130. User equipment (hereinafter referred to as “UE or terminal”) 135 accesses an external network through the ENBs 105-120 and the S-GW 130.

[0072] exist Figure 1In the LTE system, ENB 105-120 corresponds to an existing node B of a universal mobile telecommunication system (UMTS) system. The ENB is connected to the UE 135 through a wireless channel and performs more complex functions than the existing node B. In the LTE system, all types of user services including real-time services (such as voice over IP (VoIP)) through the Internet protocol are served through a shared channel. Therefore, a device that performs scheduling by collecting status information such as the buffer status of the UE, the available transmission power status, and the channel status is used. ENB 105-120 is responsible for such a device. In general, one ENB controls multiple cells. For example, in order to implement a transmission rate of 100Mbps, the LTE system uses orthogonal frequency division multiplexing (hereinafter referred to as "OFDM") as a wireless access technology with a bandwidth of 20MHz. In addition, the LTE system adopts an adaptive modulation and coding (hereinafter referred to as "AMC") scheme for determining a modulation scheme and a channel coding rate based on the channel status of the UE. The S-GW 130 provides a data bearer and generates or removes a data bearer under the control of the MME 125. The MME 125 is responsible for various control functions in addition to a mobility management function for UEs, and is connected to a plurality of ENBs.

[0073] Figure 2 A diagram showing a wireless protocol structure in which the present disclosure is applied to an LTE system.

[0074] refer to Figure 2 , the wireless protocols of the LTE system include the Packet Data Convergence Protocol (PDCP) 205 and 240 in the UE and ENB, the Radio Link Control (RLC) 210 and 235, and the Medium Access Control (MAC) 215 and 230. The PDCP 205 and 240 are responsible for operations such as IP header compression / recovery. The main functions of the PDCP are summarized as follows.

[0075] -Header compression and decompression: ROHC only

[0076] - User data transmission

[0077] - In-sequence delivery of upper layer PDUs during PDCP re-establishment for RLC-AM

[0078] - Reordering functionality (applicable to split bearers in DC (supports RLC AM only): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

[0079] - Used for duplication detection of lower layer SDUs during PDCP reestablishment of RLC-AM

[0080] - For split bearers in DC, retransmit PDCP SDUs during handover and for RLC-AM, retransmit PDCP PDUs during PDCP data recovery procedure

[0081] -Encryption and decryption

[0082] - Timer based SDU discard in uplink.

[0083] The RLC 210, 235 reconfigures PDCP packet data units (PDUs) with appropriate sizes and performs ARQ operations. The main functions of the RLC are summarized as follows.

[0084] -Transmission of upper layer PDU

[0085] -ARQ function (error correction through ARQ (only applicable to AM data transmission))

[0086] -RLC SDU concatenation, segmentation and reassembly (only for UM and AM data transmission)

[0087] - Re-segmentation of RLC data PDU (only for AM data transmission)

[0088] - Reordering of RLC data PDUs (only for UM and AM data transmission)

[0089] - Duplicate detection (for UM and AM data transmission only)

[0090] -Protocol error detection (for AM data transmission only)

[0091] -RLC SDU discard (only for UM and AM data transmission)

[0092] -RLC reconstruction

[0093] MAC 215, 230 is connected to a plurality of RLC layer devices configured in one UE, and performs operations of multiplexing and demultiplexing RLC PDUs with and from MAC PDUs. The main functions of MAC are summarized as follows.

[0094] - Mapping between logical channels and transport channels

[0095] - Multiplexing MAC SDUs belonging to one or different logical channels into transport blocks (TBs) delivered to the physical layer on a transport channel, and / or demultiplexing MAC SDUs belonging to one or different logical channels from transport blocks delivered to the physical layer on a transport channel

[0096] -Dispatch information report

[0097] - Error correction through HARQ

[0098] - Priority handling between logical channels of a UE

[0099] - Priority handling between UEs through dynamic scheduling

[0100] -MBMS service identification

[0101] -Transmission format selection

[0102] -Padding

[0103] The physical layers 220, 225 perform operations of channel coding and modulating higher layer data, generating higher layer data into OFDM symbols, and transmitting OFDM symbols through a wireless channel, or perform operations of demodulating OFDM symbols received through a wireless channel, channel decoding OFDM symbols, and transmitting OFDM symbols to a higher layer.

[0104] Figure 3 A diagram showing the architecture of a next generation mobile communication system to which the present disclosure may be applied.

[0105] refer to Figure 3 , the radio access network of the next generation mobile communication system (hereinafter referred to as "NR" or "5G") is configured as a new radio node B (hereinafter referred to as "NR gNB" or "NR base station") 310 and a new radio core network (NR CN) 305. The new radio user equipment (hereinafter referred to as "NR UE" or "terminal") 315 accesses the external network through the NR gNB 310 and the NR CN 305.

[0106] exist Figure 3In the NR gNB 310, the NR gNB 310 corresponds to the existing evolved Node B (eNB) of the LTE system. The NR gNB is connected to the NR UE 315 through the wireless channel 320 and can provide better services than the existing Node B. In the next generation mobile communication system, a device that performs scheduling by collecting status information such as the buffer status, available transmission power status, and channel status of the UE is used because all types of user services are served through a shared channel. The NR gNB 310 is responsible for the device. In general, one NR-gNB controls multiple cells. In order to implement ultra-high-speed data transmission compared to the existing LTE, the next generation mobile communication system may have the existing maximum bandwidth or more bandwidth and may introduce beamforming technology using OFDM as a wireless access technology. In addition, the next generation mobile communication system adopts an AMC scheme that determines the modulation scheme and channel coding rate based on the channel status of the UE. The NR CN 305 performs functions such as mobility support, bearer configuration, and QoS configuration. In addition to the mobility management function for the UE, the NR-CN is also responsible for various control functions and is connected to multiple eNBs. In addition, the next generation mobile communication system can also operate in conjunction with the existing LTE system. The NR-CN is connected to the MME 325 through a network interface. The MME is connected to the eNB 330, ie, an existing base station.

[0107] Figure 4 A diagram showing a radio protocol structure of a next generation mobile communication system to which the present disclosure can be applied.

[0108] refer to Figure 4 , the NR radio protocol is configured with NR PDCPs 405 and 440, NRRLC 410 and 435, and NR MAC 415 and 430 in the NR UE and NR base station, respectively. The main functions of NR PDCP 405 and 440 may include the following functions.

[0109] -Header compression and decompression: ROHC only

[0110] - User data transmission

[0111] -Sequential delivery of upper layer PDUs

[0112] - Reordering of received PDCP PDUs

[0113] - Duplicate detection of lower layer SDU

[0114] -Retransmission of PDCP-SDU

[0115] -Encryption and decryption

[0116] - Timer based SDU discard in uplink.

[0117] The reordering function of the NR-PDCP entity refers to a function for sequentially reordering the PDCP PDUs received from the lower layer based on the PDCP sequence number (SN). The reordering function may include a function for sending data to a higher layer in the reordered sequence. In addition, the reordering function of the NR PDCP entity may include a function for reordering the sequence and recording the lost PDCP PDUs, a function for making a status report of the lost PDCP PDU to the transmission side, and a function for requesting retransmission of the lost PDCP PDU.

[0118] The main functions of NR RLC 410, 435 may include the following functions.

[0119] -Transmission of upper layer PDU

[0120] -Sequential delivery of upper layer PDUs

[0121] -Out-of-order delivery of upper layer PDUs

[0122] - Error correction via ARQ

[0123] -RLC SDU concatenation, segmentation and reassembly

[0124] - Re-segmentation of RLC data PDUs

[0125] - Reordering of RLC data PDUs

[0126] - Duplicate detection

[0127] -Protocol error detection

[0128] -RLC SDU discarded

[0129] -RLC reconstruction

[0130] The sequential delivery function of the NR RLC entity refers to a function for sending the RLC SDU received from the lower layer to the higher layer in sequence, and may include a function for reassembling and sending multiple RLC SDUs if one RLC SDU is initially segmented into multiple RLC SDUs and received. In addition, the sequential delivery function of the NRRLC entity may include a function for reordering the RLC PDUs received based on the RLC sequence number (SN) or the PDCP sequence number (SN) and a function for reordering the sequence and recording the lost RLC PDUs. In addition, the sequential delivery function of the NRRLC entity may include a function for sending a status report about the lost RLC PDU to the transmission side, a function for requesting retransmission of the lost RLC PDU, and a function for sending the RLC SDU to the higher layer only before the lost RLC SDU (if the lost RLC SDU exists). In addition, the sequential delivery function of the NR RLC entity may include a function for sending all RLC SDUs received before the expiration of a given timer to a higher layer in sequence when the timer expires, although the RLC SDU is lost, or a function for sending all RLC SDUs received so far when the given timer expires to a higher layer, although the RLC SDU is lost. In addition, in the above, the RLC PDUs can be processed in the order in which they are received (regardless of the order of sequence numbers, in the order of arrival) and sent to the PDCP entity regardless of their order (i.e., out-of-order delivery). In the case of segmentation, the segments stored in the buffer or (multiple) segments to be received subsequently can be received and reconfigured into a complete RLC PDU. A complete RLC PDU can be processed and sent to the PDCP entity. The NR RLC layer may not include a concatenation function. The concatenation function may be performed in the NR-MAC layer, or may be replaced by a multiplexing function of the NR-MAC layer.

[0131] The out-of-order delivery function of the NR RLC entity refers to a function for directly sending the RLC SDUs received from the lower layer to the higher layer without considering their sequence. The out-of-order delivery function may include a function for reassembling multiple RLC SDUs if one RLC SDU is initially segmented into multiple RLC SDUs and received, and a function for storing the RLC SN or PDCP SN of the received RLC PDU, reordering its sequence, and recording the lost RLC PDU.

[0132] NR MAC 415, 430 can be connected to multiple NR RLC layer devices configured in one UE. The main functions of NR MAC may include the following functions.

[0133] - Mapping between logical channels and transport channels

[0134] -Multiplexing / demultiplexing of MAC SDU

[0135] -Dispatch information report

[0136] - Error correction through HARQ

[0137] - Priority handling between logical channels of a UE

[0138] - Priority handling between UEs through dynamic scheduling

[0139] -MBMS service identification

[0140] -Transmission format selection

[0141] -filling

[0142] The NR PHY layer 420, 425 may perform the following operations: channel coding and modulating higher layer data, generating higher layer data into OFDM symbols, sending OFDM symbols to a wireless channel or demodulating OFDM symbols received through a wireless channel, channel decoding OFDM symbols, and transmitting OFDM symbols to a higher layer.

[0143] Figure 5A is a diagram for SgNB addition and release scenarios in a wireless communication system supporting EN-DC. Figure 5B Diagram applicable to SgNB addition and release scenarios in a wireless communication system supporting EN-DC

[0144] For example, in an LTE system, when a terminal performs a handover from a source base station to a target base station, the source base station may support data forwarding by forwarding current configuration information of the terminal to the target base station.

[0145] Data forwarding means providing data services to users without delay in a manner in which a source base station forwards a received packet (eg, PDCP SDU) to a target base station through an X2 interface.

[0146] In the LTE system, if the standard specification versions between the source base station and the target base station are different, the current configuration information of the terminal may be reset, and the terminal may be configured as new configuration information.

[0147] For example, during switching, the source base station can reset the current configuration information of the terminal via an RRC connection reconfiguration message, can use new configuration information to send information indicating the configuration (e.g., full configuration), and can send new configuration information to the target base station via a switching request message.

[0148] The EN-DC system is a system that connects a 4G (E-UTRA) base station and a 5G (New Radio (hereinafter referred to as NR)) base station to a 4G core network.

[0149] like Figure 5A and 5B As shown, in the EN-DC system, the 4G base station can play the role of the master node (MN) (or MeNB) 510a, 510b that processes the control signal. The 5G base station can play the role of the secondary node (SN) (or SgNB) 520a, 520b that processes the data based on the control signal received from the MeNB.

[0150] like Figure 5A and 5B As shown, SgNB has a smaller coverage area than MeNB but may have high data rates because it uses a wide bandwidth at a relatively higher frequency.

[0151] The terminals 500a, 500b supporting EN-DC are basically connected to the MeNB and can use the wireless resources with high data rate of the SgNB through processes such as SgNB addition / release / modification depending on the situation.

[0152] For example, Figure 5A As shown, in the EN-DC system, when the terminal 500a moves to the coverage of the SgNB 520a, the SgNB addition process can be performed. Figure 5B As shown, in the EN-DC system, when the terminal is out of the coverage of the SgNB, the SgNB release process can be performed.

[0153] like Figure 5A As shown, in the EN-DC system, the terminal can add multi-access to MeNB 510a and SgNB through SgNB. At this time, the bearer added for SgNB can support data forwarding.

[0154] In the LTE system, all bearer information of the terminal is forwarded at the time of handover. In contrast, in the EN-DC system, only information about the bearer added by the SgNB can be forwarded so that the SgNB allocates radio resources for the bearer. For example, the source base station in the EN-DC system can forward the change configuration information (delta configuration) of the bearer (i.e., the object of data forwarding) to the terminal and the target base station.

[0155] Figure 6 A diagram showing a structure of a network element included in a wireless communication system supporting EN-DC.

[0156] like Figure 6As shown, the 4G eNB is configured with one network element (NE), and the 5G gNB is configured with CU-CP, CU-UP and DU, i.e., three network elements.

[0157] like Figure 6 As shown, CU-CP as the control plane, CU-UP as the user plane, and DU including MAC / RLC / PHY layers can be connected to E1, F1 control plane interface (F1-C) / F1 user plane interface (F1-U), i.e., external interfaces, respectively.

[0158] Fig. 7A and 7B This is a flowchart of operations for a UE supporting EN-DC to add a secondary node so that the radio resources of the SgNB can be allocated to the UE.

[0159] In operation S700, the UE sends a measurement report to the MeNB. In operation S701, the MeNB makes an SgNB addition decision. In operation S703, the MeNB may send an SgNB addition request message through the CU-CP included in the SgNB.

[0160] In operations S705 to S715, the CU-CP may send messages to and receive messages from the CU-UP of the MeNB via the E1 interface (e.g., bearer context setup request, bearer context setup response, bearer modification request, bearer modification response), and may send messages to and receive messages from the DU via the F1 interface (e.g., UE context setup request, UE context setup response).

[0161] In operation S717, the CU-CP may send an SgNB add request confirmation to the MeNB. In operation S719, the MeNB may send an RRC connection reconfiguration message to the UE. In operation S721, the UE may send an RRC connection reconfiguration completion message to the MeNB.

[0162] In operation S723, the MeNB may send an SgNB reconfiguration completion message to the CU-CP. In operation S725, a random access procedure may be performed between the UE and the SgNB.

[0163] In operation S727, the MeNB may send a sequence number (SN) status transfer message to the CU-CP. In operation S729, the CU-CP may forward the SN status transfer message to the CU-UP.

[0164] In operation S731, a data forwarding process may be performed. In operation S707, a path updating process may be performed.

[0165] In a wireless system supporting EN-DC, in order to perform dual connectivity, the MeNB may send an SgNB add request message to the SgNB. The CU-CP of the SgNB may send information to be used in the user plane, belonging to the received SgNB add request information, to the CU-UP of the SgNB through the E1 interface, and may send information to be used in the RLC / MAC / PHY to the DU of the SgNB through the F1 interface.

[0166] The MeNB may use either LTE PDCP or NR PDCP, and the SgNB may use only NR PDCP.

[0167] For example, if the MeNB requests the SgNB using NR PDCP to use LTE PDCP to allocate wireless resources for a bearer (hereinafter referred to as "LTE PDCP version bearer"), that is, if the MeNB performs SgNB addition, then because the type of the bearer is changed to use NR PDCP (hereinafter referred to as NR PDCP version bearer), a change in the PDCP version of the bearer may occur.

[0168] In this case, the MeNB can send information about the change of the PDCP version of the bearer that the SgNB has been requested to add through the incremental configuration information to the UE and the CU-CP included in the SgNB (e.g., the target SgNB) so as to allocate the wireless resources of the SgNB to the MeNB.

[0169] For example, the UE may receive information about the PCDP version change from the MeNB through an RRC connection reconfiguration message, may reset the PDCP based on the received information about the PCDP version change, and may initialize the PDCP sequence number of the downlink / UL packet to "0".

[0170] For example, the CU-CP included in the SgNB can receive information about the PDCP version change from the MeNB through the SgNB add request message. However, the CU-UP responsible for the PDCP layer cannot recognize the information about the PDCP version change because a field for forwarding information about the PDCP version change is not generated in the message sent and received on the E1 interface between the CU-CP and the CU-UP.

[0171] Therefore, the CU-UP included in the SgNB inevitably sets the PDCP sequence number based on the SN status transfer message.

[0172] That is, when the MeNB using only LTE PDCP requests SgNB addition, a mismatch occurs in the setting of the PDCP sequence number between the CU-UP included in the UE and the SgNB, and therefore, there is a problem of data loss.

[0173] In order to solve this problem, an embodiment of the present disclosure can provide a method that is capable of preventing a mismatch in the setting of the PDCP sequence number between the CU-UP responsible for the PDCP layer and the UE by generating a field for forwarding indication information (indicating whether the PDCP version is changed) in a message sent and received on the E1 interface between the CU-CP and the CU-UP included in the SgNB.

[0174] Figure 8 A flowchart of an operation for a CU-CP included in an SgNB to send indication information (indicating whether the PDCP version has been changed) to a CU-UP of the SgNB according to various embodiments of the present disclosure is shown.

[0175] In operation 800, the CU-CP may receive a first message from a master node (MN) (or a master eNB (MeNB)) for requesting the SgNB to allocate wireless resources for a bearer.

[0176] According to various embodiments of the present disclosure, the first message may include an SgNB add request message.

[0177] For example, the SgNB add request may include incremental configuration information. The incremental configuration information may include information about the bearer added by the SgNB.

[0178] For example, the SgNB add request may include information about the bearers to which the SgNB has been requested to be added and information about the PDCP version of at least one bearer (e.g., a bearer of NR PDCP version).

[0179] For example, information about the bearer for which the SgNB has been requested to be added can be identified by E-RAB To Be Added List>E-RAB To Be Added Item>>E-RAB ID of the SgNB Add Request message described in 3GPP LTE document TS 36.423. In addition, information about the bearer of the NR PDCP version can be identified by E-RAB ID within CG-ConfigInfo>mcg-RB-Config of the MeNB to SgNBContainer of the SgNB Add Request message described in 3GPP NR document 38.331.

[0180] exist Fig. 7AIn operation S703, the E-RAB information included in the SgNB add request sent through X2 signaling is information about the bearer to which the SgNB has been requested to be added. CG ConfigInfo is the bearer information of the NR-PDCP version.

[0181] In operation 810, the CU-CP may send a second message to the CU-UP included in the SgNB, the message including indication information indicating whether a Packet Data Convergence Protocol (PDCP) version of the bearer has been changed.

[0182] According to various embodiments of the present disclosure, the indication information may be generated based on the first message.

[0183] For example, whether the PDCP version has been changed can be identified based on information about at least one bearer for which the SgNB has been requested to be added and included in the first message, and information about the PDCP version of the at least one bearer.

[0184] For example, information about the PDCP version of at least one bearer relates to the version of the radio access technology of the PDCP used by the bearer, and can be referred to as a "bearer of LTE PDCP version" in a bearer using LTE supported PDCP, and can be referred to as a "bearer of NR PDCP version" in a bearer using NR supported PDCP.

[0185] According to various embodiments of the present disclosure, indication information indicating whether the PDCP version of the bearer has been changed can be generated based on information about the bearer to which the SgNB has been requested to add and information about the NR PDCP version of the bearer included in the SgNB add request received at operation 800.

[0186] For example, a bearer that is a bearer to which the SgNB has been requested to add and is not a bearer of the NR-PDCP version is a bearer type of the LTE-PDCP version. In order to use the radio resources allocated by the SgNB, the type of the bearer inevitably changes because it should become a bearer of the NR-PDCP version type.

[0187] That is, if the bearer type using the wireless resources allocated by the SgNB changes from the LTE PDCP version to the NR PDCP version, it can be said that there is a change in the PDCP version of the bearer.

[0188] For each bearer to which the SgNB has been requested to add, indication information may be generated indicating whether the PDCP version of the bearer has been changed according to various embodiments.

[0189] The indication information indicating whether the PDCP version of the bearer according to various embodiments has been changed may be represented as 1 bit. For example, if the bit value is 0, this may be information indicating a situation where there is no PDCP version change. If the bit value is 1, this may be information indicating a situation where a PDCP version change has occurred.

[0190] The second message including the indication information indicating whether the PDCP version of the bearer according to various embodiments has been changed may be included in the bearer context setup request message sent and received on the E1 interface. Fig. 7A As shown, a bearer context setup request message may be sent at operation S705.

[0191] Fig. 9 A flowchart of various exemplary operations according to various embodiments of the present disclosure is shown, in which a CU-UP included in a secondary node allocates a PDCP sequence number (SN) to a DL packet based on indication information indicating whether a PDCP version has been changed. Fig.10 A flowchart of various exemplary operations according to various embodiments of the present disclosure is shown, in which a CU-UP included in a secondary node allocates a PDCP sequence number (SN) to a DL packet based on indication information indicating whether a PDCP version has been changed.

[0192] In operation 900, the CP-UP may receive a first message from a CU-CP included in the SgNB, the first message including indication information indicating whether a PDCP version of a bearer has been changed.

[0193] For example, the first message may include Fig. 7A The bearer context setup request message received at operation S705.

[0194] In this case, the indication information indicating whether the PDCP version of the bearer has been changed is 1 bit and may be included in a field within the bearer context setup request message.

[0195] In operation 910, the CP-UP may receive a second message including counting information from the CU-CP.

[0196] For example, the counting information is information that notifies the SgNB that it should send packets to the UE and receive packets from the UE. The counting information may include information indicating a count of the first DL packets to be sent to the UE (e.g., DL count) and information indicating a count of the first UL packets to be received from the UE (e.g., UL count).

[0197] For example, the second message may include Figure 7B The SN status transfer message received at operation S729.

[0198] The SN status transfer message according to various embodiments of the present disclosure is a message used in the handover operation step, and is sent from the source base station (in Figure 7B In the case of MeNB) is sent to the target base station (in Figure 7B The SN status transmission message may include notifying the target base station (in the case of Figure 7B In the case of SgNB, the counting information notifies the target base station that it should send packets to the UE and receive packets from the UE.

[0199] For example, Figure 7B As shown, the SN status transfer message is a message sent from the MeNB to the CU-CP included in the SgNB and from the CU-CP to the CU-UP.

[0200] For example, the counting information is a count value of a PDCP protocol data unit (PDU) and may be represented as a 32-bit value configured as a hyper frame number (HFN) and a PDCP sequence number (SN). The counting information may include information indicating a count of first packets to be sent to the UE (e.g., a DL count) and information indicating a count of first packets to be received from the UE (e.g., a UL count).

[0201] At operation 920 , the CP-UP may assign a PDCP sequence number to at least one DL packet received through the bearer based on at least one of the indication information received at operation 900 or the counting information received at operation 910 .

[0202] For example, the CP-UP may identify whether there is a change in the PDCP version of the bearer based on the indication information. If the PDCP version of the bearer changes, the CP-UP may initialize the PDCP sequence number and assign the PDCP sequence number to at least one DL packet. If the PDCP version of the bearer does not change, the CP-UP may assign the PDCP sequence number to at least one DL packet based on the counting information.

[0203] Specific reference Fig.10 Provide explanation.

[0204] Operations 1000 and 1010 correspond to Fig. 9 Operations 900 to 910.

[0205] At operation 1020 , the CU-UP may identify whether there is a change in the PDCP version of the bearer based on the indication information received at operation 1000 .

[0206] If a change in the PDCP version of the bearer is identified at operation 1030 , then at operation 1040 , the CU-UP may initialize a PDCP sequence number and assign the PDCP sequence number to at least one DL packet.

[0207] That is, if it is recognized that there is a change in the PDCP version of the bearer, the CU-UP may reset the PDCP sequence number to “0” regardless of the counting information received at operation 1010 .

[0208] For example, initializing the PDCP sequence number may include assigning a PDCP sequence number of 0 to a first DL packet transmitted by the UE and then performing PDCP sequence numbering.

[0209] The at least one DL packet according to various embodiments of the present disclosure may include at least one DL packet data forwarded from the MeNB and at least one DL packet, ie, a new packet received from a core network (eg, a 4G core network in an EN-DC system).

[0210] For example, the first DL packet sent from the SgNB to the UE may be the first DL packet data forwarded from the MeNB.

[0211] As above Figure 7B As described in, if according to various embodiments of the present disclosure, the PDCP version of the bearer changes, the UE may receive information about the PDCP version change from the MeNB through an RRC connection reconfiguration message, may reset the PDCP based on the received information about the PDCP version change, and may initialize the PDCP sequence number of the DL packet to "0"

[0212] That is, if the PDCP version of the bearer changes, the CU-UP included in the SgNB according to various embodiments of the present disclosure can initialize the PDCP sequence number to "0". Therefore, a mismatch in the setting of the PDCP sequence number between the CU-UP responsible for the PDCP layer and the UE can be prevented, thereby preventing data loss.

[0213] Specific reference Fig.14 Provide explanation.

[0214] If it is identified at operation 1030 that the PDCP version of the bearer has not changed, at operation 1050, the CU-UP may assign a PDCP sequence number to at least one DL packet based on the counting information.

[0215] For example, if it is identified that the PDCP version of the bearer has not changed, the CU-UP may assign a PDCP sequence number to at least one DL packet (e.g., DL count) based on counting information indicating a count of first packets to be sent to the UE included in the SN status transmission message received at operation 1010.

[0216] Specific reference Fig.13 Provide explanation.

[0217] Fig.11 A flowchart of various exemplary operations according to various embodiments of the present disclosure is shown, in which a CU-UP included in a secondary node aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed. Fig.12 A flowchart of various exemplary operations according to various embodiments of the present disclosure is shown, in which a CU-UP included in a secondary node aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed.

[0218] Operations 1100 to 1120 correspond to Fig. 9 Operations 900 and 910.

[0219] At operation 1120 , a sequence of at least one UL packet received through the bearer is aligned based on at least one of the indication information received at operation 1100 or the counting information received at operation 1110 .

[0220] The at least one UL packet according to various embodiments of the present disclosure may include at least one UL packet data forwarded from the MeNB and at least one UL packet received from the UE.

[0221] For example, a PDCP sequence number of at least one UL packet received from the UE may be allocated in the UE.

[0222] In this case, the UE may assign a PDCP sequence number to at least one UL packet, and may forward at least one UL packet to which the PDCP sequence number has been assigned to the SgNB.

[0223] In this case, the CU-UP of the SgNB may align the sequence of at least one UL packet received from the UE to which a PDCP sequence number has been assigned and at least one UL packet data forwarded from the MeNB. The CU-UP according to various embodiments of the present disclosure may identify whether there is a change in the PDCP version of the bearer based on the indication information. If a change in the PDCP version of the bearer is identified, the CU-UP may align the sequence of at least one UL packet using a first-in-first-out (FIFO) scheme. If it is identified that the PDCP version of the bearer has not changed, the CU-UP may align the sequence of at least one UL packet based on the counting information.

[0224] Specific reference Fig.12 Provide explanation.

[0225] Operations 1200 to 1230 correspond to Fig.10 Operations 1000 to 1030.

[0226] If a change in the PDCP version of the bearer is identified at operation 1230, the CU-UP may align a sequence of at least one UL packet using a FIFO scheme at operation 1240. Fig.16 For example, the at least one UL packet may include at least one UL packet to which a PDCP sequence number has been allocated and received from the UE and at least one UL packet data forwarded from the MeNB.

[0227] As above Figure 7B As described in, if according to various embodiments of the present disclosure, the PDCP version of the bearer changes, the UE may receive information about the PDCP version change from the MeNB through an RRC connection reconfiguration (RRC connection reconfiguration) message, may reset the PDCP based on the information about the version change on the received PDCP, and may initialize the PDCP sequence number of the UL packet to "0"

[0228] That is, the UE may initialize the PDCP sequence number to '0' and may allocate the PDCP sequence number to at least one UL packet. The CU-UP included in the SgNB may receive at least one UL packet to which the PDCP sequence has been allocated from the UE.

[0229] If the PDCP version of the bearer changes according to various embodiments of the present disclosure, at least one UL packet aligned using the FIFO scheme in the CP-UP may be sent to the core network. In this case, multiple UL packets aligned using the FIFO scheme in the CP-UP may be aligned based on the PDCP sequence number in the transmission control protocol (TCP) layer of the core network.

[0230] At operation 1220 , the CU-UP may identify whether there is a change in the PDCP version of the bearer based on the indication information received at operation 1000 .

[0231] If it is identified at operation 1230 that the PDCP version of the bearer has not changed, the CU-UP may align a sequence of at least one UL packet based on the counting information received at operation 1210 at operation 1250 .

[0232] For example, the at least one UL packet may include at least one UL packet data forwarded from the MeNB and at least one UL packet received from the UE.

[0233] Specific reference Fig.15 Provide explanation.

[0234] like Figures 13 to 16 As shown, one PDCP entity exists according to a radio bearer (hereinafter referred to as "RB" for short). One PDCP entity may be connected to one RLC entity.

[0235] According to various embodiments, the PDCP entity can be connected to all acknowledged mode (AM) (acknowledged mode, a mode in which it is checked whether data has been sent), unacknowledged mode (UM) (unacknowledged mode, a mode in which it is not checked whether data has been sent), and transparent mode (TM) (a mode in which data is simply transmitted), i.e., three entities of RLC.

[0236] That is, each RLC entity can operate in transparent mode (TM), unacknowledged mode (UM) or acknowledged mode (AM) based on the processing and transmission method of RLC SDU. In the case of RLC acknowledged mode (AM), RLC PDU can be configured using the separation / connection function of RLC SDU, and RLC PDU can be retransmitted when the transmission of the packet fails.

[0237] Fig.13 A diagram illustrating various examples according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node allocates a PDCP sequence number to a DL packet based on indication information indicating whether a PDCP version has been changed. Fig.14 A diagram illustrating various examples according to various embodiments of the present disclosure, in which a CU-UP included in a secondary node allocates a PDCP sequence number to a DL packet based on indication information indicating whether a PDCP version has been changed.

[0238] Fig.13A diagram showing an example of allocating a PCDP sequence number to a DL packet if a target eNB using NRPDCP allocates radio resources for a bearer using NR-PDCP (ie, if the PDCP version of the bearer has not changed) in a wireless communication system supporting EN-DC.

[0239] That is, included in Fig.13 The PDCP 1311 in the source eNB 1310 shown supports NR-PDCP, the RLC 1313 is E-UTRARLC, the PDCP 1331 included in the target eNB 1330 is NR-PDCP, and the RLC 1333 is NR-RLC.

[0240] If in Fig.13 There is no PDCP version change in the target eNB, and the method for CU-UP for processing DL packets included in the target eNB may include a case where the PDCP entity is connected to the RLC-AM entity. When transmission of the DL packet fails, the DL packet may be retransmitted.

[0241] like Fig.13 As shown, in a state where the UE has not yet sent ACK / NACK information for packet 1340 (PDCP sequence number 4) from the source eNB and packet 1341 (PDCP sequence number 5) from the source eNB to the source eNB, the CU-CP included in the target eNB may receive an SgNB add request message from the source eNB. The CU-CP of the target eNB may identify whether a Packet Data Convergence Protocol (PDCP) version of the bearer has been changed based on the SgNB add request, and may send a bearer context setup request message including indication information indicating whether the PDCP version has been changed to the CU-UP of the target eNB.

[0242] In addition, the CU-UP of the target eNB may receive an SN status transfer message including count information indicating a count of first packets to be transmitted to the UE (eg, DL count=6) from the CU-CP.

[0243] As described above, the CU-UP may recognize that the PDCP version of the bearer has not changed based on the indication information received from the CU-CP, and may allocate a PDCP sequence number to at least one DL packet based on 6 (ie, the counting information).

[0244] like Fig.13 As shown, the target eNB may receive at least one DL packet 1340, 1341, 1342, 1344, and 1345 forwarded from the source eNB data. Fig.13 As shown, at least one DL packet of data forwarding may be configured with an end marker (EndMarker) packet.

[0245] In the handover completion step of the handover process, if the traffic sent by the S-GW is from the source base station ( Fig.13 The source eNB in ​​the example becomes the target eNB ( Fig.13 In the example of FIG. 1340 , if the target eNB receives the “end marker” packet, the “end marker” packet may be used to prevent the loss of packets or the change of the packet sequence during the process. When the target eNB receives the “end marker” packet, it may receive at least one DL packet 1346, 1347, 1348, i.e., a new packet, from the S-GW.

[0246] like Fig.13 As shown, in the PDCP layer of the target eNB, PDCP sequence numbers "4" and "5" have been allocated to DL packets 1340 and 1341 that belong to data forwarding at least one DL packet and are retransmitted in the PDCP of the source eNB. Therefore, "6", that is, the counting information included in the SN status transfer message, can be allocated to the PDCP sequence numbers of packets 1342, 1343, 1344, 1345, 1346, 1347, and 1348 that have not been allocated PDCP sequence numbers.

[0247] Therefore, if Fig.13 As shown, PDCP sequence numbers from "6" to "12" can be assigned to at least one DL packet 1342, 1343, 1344 and 1345, i.e., data forwarding packets, and at least one DL packet 1346, 1347 and 1348, i.e., new packets received by the PDCP layer of the target eNB from the S-GW.

[0248] Fig.14 A diagram showing an example of allocating PDCP sequence numbers to DL packets if a secondary node using NR-PDCP allocates radio resources for a bearer using LTE-PDCP (i.e., if the PDCP version of the bearer changes) in a wireless communication system supporting EN-DC.

[0249] That is, included in Fig.14 The PDCP 1411 in the source eNB 1410 is LTE PDCP, the RLC 1413 is E-UTRA RLC, the PDCP 1431 included in the SgNB is NR PDCP, and the RLC 1433 is NR RLC.

[0250] like Fig.14As shown, in a state where the UE has not yet sent ACK / NACK information of the packet 1440 with a PDCP sequence number of 4 sent by the source eNB and the packet 1441 with a PDCP sequence number of 5 sent by the source eNB to the source eNB, the CU-CP of the SgNB may receive an SgNB add request message from the source eNB. The CU-CP of the SgNB may identify whether the PDCP version of the bearer has been changed based on the SgNB add request, and may send a bearer context setup request message including indication information indicating whether the PDCP version has been changed to the CU-UP of the SgNB.

[0251] In addition, the CU-UP of the SgNB may receive an SN status transfer message from the CU-CP, which includes counting information indicating a count of first packets to be sent to the UE (e.g., DL count = 6).

[0252] like Fig.14 As shown, the bearer type has changed from the LTE PDCP version to the NR PDCP version. Therefore, the source eNB can reset the current configuration information of the UE through the RRC connection reconfiguration message, and can send information indicating the configuration (e.g., complete configuration) as new configuration information. Therefore, the UE can receive information about the PDCP version change from the source eNB through the RRC connection reconfiguration message, can reset the PDCP based on the received information about the PDCP version change, and can initialize the PDCP sequence number of the DL packet to "0"

[0253] like Fig.14 As shown, the target eNB may receive at least one DL packet 1440, 1441, 1442, 1444, and 1445 forwarded from the source eNB data. Fig.14 As shown, at least one DL packet of data forwarding may be configured as an end marker packet.

[0254] In the handover completion step of the handover process, if the traffic sent by the S-GW is from the source base station ( Fig.14 The source eNB in ​​the example becomes the target eNB ( Fig.14 In the example of FIG. 1440 , if the target eNB receives the “end marker” packet, the “end marker” packet may be used to prevent the loss of packets or the change of the packet sequence during the process. When the target eNB receives the “end marker” packet, it may receive at least one DL packet 1446, 1447, 1448, i.e., a new packet, from the S-GW.

[0255] In addition, if Fig.14As shown, the type of the bearer has been changed from the LTE PDCP version to the NR PDCP version. Therefore, the CU-UP may initialize the PDCP sequence number without considering the counting information included in the SN status transfer message, and may allocate the PDCP sequence number to at least one DL packet.

[0256] For example, initializing the PDCP sequence number may include assigning a PDCP sequence number of 0 to a first DL packet transmitted to the UE and then performing PDCP sequence numbering.

[0257] At least one DL packet according to various embodiments of the present disclosure may include at least one DL packet data forwarded from a source eNB and at least one DL packet received from a core network (eg, a 4G core network in an EN-DC system), ie, a new packet.

[0258] For example, the first DL packet sent from the SgNB to the UE may be the first DL packet data forwarded from the source eNB.

[0259] like Fig.14 As shown, the CU-UP included in the SgNB can assign PDCP sequence number 0 to the first DL packet 1440, which is the first DL packet sent to the UE and is forwarded from the source eNB data.

[0260] Therefore, if Fig.14 As shown, PDCP sequence numbers from "0" to "8" may be sequentially assigned to data forwarding DL packets 1440, 1441, 1442, 1443, 1444, and 1445, including retransmitted DL packets, and DL packets 1446, 1447, and 1448, i.e., new packets sent by the S-GW.

[0261] That is, according to various embodiments of the present disclosure, according to Fig.15 According to the algorithm shown in , data loss can be prevented because the PDCP sequence numbers between the CU-UP of the UE and the SgNB are set to the same.

[0262] Fig.15 A diagram illustrating various examples according to various embodiments of the present disclosure, in which a CU-UP included in a target eNB aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed. Fig.16 A diagram illustrating various examples according to various embodiments of the present disclosure, in which a CU-UP included in a target eNB aligns a sequence of UL packets based on indication information indicating whether a PDCP version has been changed.

[0263] Fig.15A diagram showing an example in which, in a wireless communication system supporting EN-DC, if a target eNB using NRPDCP allocates radio resources to a bearer using NRPDCP, that is, if a PDCP version of the bearer is changed, a sequence of at least one UL packet is aligned.

[0264] That is, included in Fig.15 The PDCP 1513 in the source eNB 1510 supports NR PDCP, the RLC 1511 is E-UTRA RLC, the PDCP 1533 included in the target eNB 1530 is NR PDCP, and the RLC 1531 is NR RLC.

[0265] like Fig.15 As shown, the UE may send at least one UL packet 1540, 1541, 1542, and 1543 to the source eNB. In a state where the UE has not received ACK / NACK information of the UL packet 1542 sent to the source eNB from the source eNB, the CU-CP included in the target eNB may receive an SgNB add request message from the source eNB. The CU-CP may identify whether the group PDCP version of the bearer has been changed based on the SgNB add request, and may send a bearer context setup request message including indication information indicating whether the PDCP version has been changed to the CU-UP of the target eNB.

[0266] In addition, the CU-UP of the target eNB may receive an SN status transfer message including count information indicating a count of first UL packets to be received from the UE (eg, UL count=6) from the CU-CP.

[0267] like Fig.15 As shown, the UE may retransmit to the target eNB the UL packet 1542 for which ACK / NACK information has not yet been received from the source eNB. Therefore, the UE may send at least one UL packet 1542, 1544, and 1545 including the retransmitted UL packet 1542 to the CU-UP of the target eNB.

[0268] As described above, the CU-UP may recognize that the PDCP version of the bearer has not changed based on the indication information obtained from the CU-CP. Fig.15 As shown, the CU-UP can align a sequence of at least one UL packet 1543 forwarded from the source eNB data and a sequence of at least one UL packet 1542, 1544 and 1545 received from the UE based on "6", i.e., the counting information included in the SN status transmission message.

[0269] Fig.16A diagram showing an example in which a sequence of at least one UL packet is aligned if a target eNB using NR PDCP allocates radio resources to a bearer using LTE PDCP, i.e., if the PDCP version of the bearer is changed, in a wireless communication system supporting EN-DC.

[0270] That is, included in Fig.16 The PDCP 1613 in the source eNB 1610 is LTE PDCP, the RLC 1611 is E-UTRA RLC, the PDCP 1633 included in the target eNB is NR PDCP, and the RLC 1631 is NR RLC.

[0271] like Fig.16 As shown, the UE may send at least one UL packet 1640, 1641, 1642, and 1643 to the source eNB. In a state where the UE has not received ACK / NACK information of the UL packet 1642 sent to the source eNB from the source eNB, the CU-CP included in the target eNB may receive an SgNB add request message from the source eNB. The CU-CP may identify whether the PDCP version of the bearer has been changed based on the SgNB add request, and may send a bearer context setup request message including indication information indicating whether the PDCP version has been changed to the CU-UP of the target eNB.

[0272] In addition, the CU-UP of the target eNB may receive an SN status transfer message including information indicating a count of first UL packets to be received from the UE (eg, UL count=6) from the CU-CP.

[0273] like Fig.16 As shown, the UE may retransmit the UL packet 1642 for which ACK / NACK information has not been received from the source eNB to the target eNB. Therefore, the UE may send at least one UL packet 1642, 1644, and 1645 including the retransmitted UL packet 1642 to the CU-UP of the target eNB.

[0274] like Fig.16 As shown, the bearer type has been changed from the LTE PDCP version to the NR PDCP version. Therefore, the source eNB can reset the current configuration information of the UE through the RRC connection reconfiguration message, and can send information indicating the configuration (eg, complete configuration) as new configuration information.

[0275] Therefore, the UE may receive information about the PDCP version change from the source eNB through the RRC connection reconfiguration message, may reset the PDCP based on the received information about the PDCP version change, and may initialize the PDCP sequence number of the UL packet to "0".

[0276] That is, if the PDCP version of the bearer changes, the UE can initialize the PDCP sequence number to "0". Fig.16 As shown, the UE can assign PDCP sequence numbers "0", "1" and "2" to at least one UL packet 1642, 1644 and 1645, and can send at least one UL packet 1642, 1644 and 1645 to which the PDCP sequence number has been assigned to the CU-UP of the target eNB.

[0277] In addition, if Fig.16 As shown, the bearer type has been changed from the LTE PDCP version to the NR PDCP version. Therefore, the CU-UP can use the FIFO scheme to align the sequence of at least one UL packet 1642, 1644 and 1645 received from the UE and the sequence of at least one UL packet 1643 forwarded from the source eNB data without considering the counting information included in the SN status transfer message.

[0278] like Fig.16 As shown, examples of a sequence of at least one UL packet aligned using the FIFO scheme may be various.

[0279] In this case, at least one UL packet aligned using the FIFO scheme may be transmitted to the core network.The PDCP sequence number of the at least one UL packet aligned using the FIFO scheme may be aligned in a TCP layer of the core network.

[0280] That is, according to various embodiments of the present disclosure, according to Fig.16 According to the algorithm shown in , data loss can be prevented because the PDCP sequence numbers between the CU-UP of the UE and the target eNB are set to be the same.

[0281] Fig.17 is a block diagram of a CU-CP included in an SgNB according to an embodiment of the present disclosure.

[0282] like Fig.17 As shown, the CU-CP according to various embodiments may include a transceiver 1710 , a controller 1720 , and a memory or storage unit 1730 .

[0283] These elements are described below in order.

[0284] The transceiver according to various embodiments may send and receive signals, information or data to and from the MeNB or CU-UP and DU, i.e., an external network element included in the SgNB according to various embodiments of the present disclosure.

[0285] The controller according to various embodiments may include at least one processor.

[0286] The processor according to various embodiments may control the overall operation of the CU-CP.The processor may control the overall operation of the CU-CP according to the above-described various embodiments of the present disclosure.

[0287] According to various embodiments, at least one processor may control the transceiver to receive, from the MeNB, an SgNB add request for requesting the SgNB to allocate radio resources for the bearer.

[0288] At least one processor according to various embodiments may control the transceiver to receive an SN status transfer message including counting information from the MeNB.

[0289] According to various embodiments, at least one processor may control the transceiver to send the SN status transfer message (including the counting information received from the MeNB) to the CU-UP.

[0290] For example, the counting information is information that notifies the SgNB that it should send packets to and receive packets from the UE, and may include information indicating a count of the first DL packets to be sent to the UE (e.g., DL count) and information indicating a count of the first UL packets received from the UE (e.g., UL count).

[0291] At least one processor according to various embodiments may control a bearer context setup request message to be sent to the CU-UP to include indication information indicating whether a PDCP version of the bearer has been changed.

[0292] For example, the indication information indicating whether the PDCP version has been changed can be identified based on information about at least one bearer to which the SgNB has been requested to add and information about the PDCP version of at least one bearer (for example, information about the NR PDCP version of the bearer) included in the SgNB add request message.

[0293] For example, the indication information indicating whether the PDCP version has been changed may be represented as 1 bit. If each bearer has a PDCP version change, the value of this bit is 1. If there is no PDCP version change, the value of this bit may be 0.

[0294] The memory may store data, such as basic programs, applications, or configuration information for CU-CP operation. In addition, the memory may include at least one of the following storage media: flash memory type, hard disk type, multimedia card micro type, card type memory (e.g., SD or XD memory), magnetic memory, disk, optical disk, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), programmable read-only memory (PROM), or electrically erasable programmable read-only memory (EEPROM). In addition, the processor may use various programs, content, or data stored in the memory to perform various operations.

[0295] Fig.18 This is a block diagram of a CU-UP included in an SgNB according to an embodiment of the present disclosure.

[0296] like Fig.18 As shown, the CU-UP according to various embodiments may include a transceiver 1810 , a controller 1820 , and a memory or storage unit 1830 .

[0297] These elements are described below in order.

[0298] The transceiver according to various embodiments may send and receive signals, information or data to and from the MeNB or CU-CP and DU, i.e., an external network element included in the SgNB according to various embodiments of the present disclosure.

[0299] The controller according to various embodiments may include at least one processor. For example, the at least one processor 1820 may include a packet processor 1821.

[0300] The processor according to various embodiments may control the overall operation of the CU-UP. According to the above-described various embodiments of the present disclosure, the processor may control the overall operation of the CU-UP.

[0301] At least one processor according to various embodiments may control the transceiver to receive a bearer context setup request message from the CU-CP, including indication information indicating whether a PDCP version of the bearer has been changed.

[0302] At least one processor according to various embodiments may control the transceiver to receive an SN status transfer message including counting information from the CU-CP.

[0303] For example, the counting information is information that notifies the SgNB that it should send packets to and receive packets from the UE, and may include information indicating a count of the first DL packets to be sent to the UE (e.g., DL count) and information indicating a count of the first UL packets received from the UE (e.g., UL count).

[0304] At least one processor according to various embodiments may assign a PDCP sequence number to at least one DL packet received through a bearer based on at least one of indication information indicating whether a PDCP version received from the CU-CP has changed or counting information received from the CU-CP.

[0305] At least one processor according to various embodiments may identify whether the PDCP version of the bearer has been changed based on indication information received from the CU-CP indicating whether the PDCP version has been changed.

[0306] For example, information indicating whether the PDCP version has changed may be represented as 1 bit. If the PDCP version of each bearer has changed, the value of the bit may be 1, and if there is no change in the PDCP version, the value of the bit may be 0.

[0307] If a PDCP version of a bearer is changed, at least one processor according to various embodiments may initialize a PDCP sequence number and may assign the PDCP sequence number to at least one DL packet.

[0308] For example, if the PDCP version of the bearer changes, at least one processor according to various embodiments may assign a PDCP sequence number of 0 to a first DL packet sent to the UE. The first DL packet may be packet data forwarded from the MeNB.

[0309] If the PDCP version of the bearer has not changed, at least one processor according to various embodiments may assign a PDCP sequence number to at least one DL packet based on the counting information.

[0310] At least one processor according to various embodiments may align a sequence of at least one UL packet received through the bearer based on at least one of indication information indicating whether the PDCP version has been changed or counting information received from the CU-CP.

[0311] For example, the at least one UL packet may include at least one UL packet data forwarded from the MeNB and at least one UL packet received from the UE.

[0312] At least one processor according to various embodiments may identify whether the PDCP version of the bearer has changed based on indication information received from the CU-CP indicating whether the PDCP version has been changed. If the PDCP version of the bearer has changed, the at least one processor may align the sequence of at least one UL packet using a FIFO scheme. If the PDCP version of the bearer has not changed, the at least one processor may align the sequence of at least one UL packet based on the counting information.

[0313] According to various embodiments, if the PDCP version of the bearer changes, at least one UL packet aligned in the CU-UP using the FIFO scheme may be sent to the core network. For example, the PDCP sequence number of at least one UL packet aligned using the FIFO scheme may be aligned in the transmission control protocol (TCP) layer of the core network.

[0314] The memory may store data, such as basic programs, applications, or configuration information for CU-UP operation. In addition, the memory may include at least one of the following storage media: flash memory type, hard disk type, multimedia card micro type, card type memory (e.g., SD or XD memory), magnetic memory, disk, optical disk, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), programmable read-only memory (PROM), or electrically erasable programmable read-only memory (EEPROM). In addition, the processor may use various programs, content, or data stored in the memory to perform various operations.

[0315] Fig.19 is a block diagram of a UE according to an embodiment of the present disclosure.

[0316] like Fig.19 As shown, the UE according to various embodiments may include a transceiver 1910 , a controller 1920 , and a memory or storage unit 1930 .

[0317] These elements are described below in order.

[0318] According to various embodiments, the transceiver can send signals, information or data to the MeNB or SgNB of various embodiments of the present disclosure, and receive signals, information or data from the MeNB or SgNB.

[0319] The controller according to various embodiments may include at least one processor.

[0320] The processor according to various embodiments may control the overall operation of the UE.The processor may control the overall operation of the UE according to the above-mentioned various embodiments of the present disclosure.

[0321] The UE according to various embodiments is a UE supporting EN-DC. The UE is basically connected to the MeNB, and can use the high data rate wireless resources of the SgNB through a process such as SgNB addition / release / modification depending on the situation.

[0322] According to various embodiments, at least one processor may control the transceiver to simultaneously send and receive packets to and from the MeNB and the SgNB.

[0323] The UE according to various embodiments is a UE supporting data retransmission.

[0324] At least one processor according to various embodiments may control the transceiver to receive change configuration information (incremental configuration) of a bearer (ie, an object of data forwarding) from the MeNB.

[0325] For example, at least one processor according to various embodiments may control the transceiver to receive information about the PDCP version change from the MeNB through an RRC connection reconfiguration message.

[0326] In this case, at least one processor according to various embodiments may reset the PDCP based on the received information about the PDCP version change, and may initialize the PDCP sequence number of the DL / UL packet to "0".

[0327] The memory may store data used for the operation of the UE, such as basic programs, applications, or configuration information. In addition, the memory may include at least one of the following storage media: a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (e.g., an SD or XD memory), a magnetic memory, a disk, an optical disk, a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), a programmable read-only memory (PROM), or an electrically erasable programmable read-only memory (EEPROM). In addition, the processor may use various programs, contents, or data stored in the memory to perform various operations.

[0328] In the above-mentioned detailed embodiment of the present disclosure, by virtue of the proposed detailed embodiment, the elements included in the present disclosure can be expressed in singular form or plural form. However, singular or plural expression has been appropriately selected to facilitate the description of the proposed situation, and the present disclosure is not limited to singular or plural elements. Although the element has been expressed in plural form, it can be configured as a singular form. Although the element has been expressed in singular form, it can be configured as a plural form. The embodiments described in this specification have been described individually, but two or more embodiments can be combined and practiced.

[0329] According to various embodiments of the present disclosure, if an SgNB using NR PDCP allocates wireless resources to a bearer using LTE PDCP in a wireless communication system supporting EN-DC, a method and apparatus may be provided for preventing data loss due to a mismatch in the PDCP version of the bearer.

[0330] According to various embodiments of the present disclosure, a method and apparatus can be provided, which are capable of preventing a mismatch in PDCP sequence number settings between a CU-CP included in an SgNB and a UE, because if the MeNB issues an SgNB add request message so that the SgNB allocates wireless resources to a bearer in a wireless communication system supporting EN-DC, the CU-CP included in the SgNB sends a message (including indication information indicating whether the PDCP version of the bearer has been changed) to the CU-UP included in the SgNB.

[0331] Although detailed embodiments have been described in the detailed description of the present disclosure, the present disclosure may be modified in various ways without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the above embodiments, but should be defined not only by the claims but also by their equivalents.

[0332] The embodiments of the present disclosure and the terms used in the embodiments are not intended to limit the technology described in this document to specific embodiments, but should be interpreted as including various changes, equivalents and / or alternatives of corresponding embodiments. Regarding the description of the accompanying drawings, similar reference numerals may be used in similar reference numerals. Singular expressions may include plural expressions, unless otherwise clearly defined in the context. In this document, expressions such as "A or B", "at least one of A and / or B", "A, B or C" or "at least one of A, B and / or C" may include all possible combinations of listed items. Expressions, such as "first", "second", can modify corresponding elements, without considering sequence and / or importance, and are only used to distinguish one element from other elements, without limiting corresponding elements. When describing a (e.g., first) element "(operably or communicatively) connected to" or "coupled" other (e.g., second) elements, an element may be directly connected to other elements, or may be connected to other elements by another element (e.g., the third element).

[0333] The "module" used in the present disclosure includes a unit configured as hardware, software or firmware, and can be used interchangeably with terms such as logic, logic block, component or circuit. A module can be an integrated component, a minimum unit that performs one or more functions, or a part thereof. For example, the module can be configured as an application specific integrated circuit (ASIC).

[0334] Various embodiments of the present disclosure may be implemented as a machine (e.g., computer) readable storage medium (e.g., software (e.g., program), including instructions stored in an internal memory or an external memory). A device is a device that can acquire instructions stored in a storage medium and operate according to the acquired instructions, and may include a base station or a UE according to various embodiments. If the instructions are executed by a processor (e.g., Fig.17Controller 1720 or Fig.18 Controller 1820 or Fig.19 If the instruction is executed by the controller 1920 of the processor, the function corresponding to the instruction can be directly executed by the processor, or can be executed using other elements under the control of the processor. The instruction may include code generated or executed by a compiler or interpreter.

[0335] The machine-readable storage medium may be provided in the form of a non-transitory storage medium. In this case, the term "non-transitory" means that the storage medium does not include a signal and is tangible, and is not limited to whether data is stored in the storage medium semi-permanently or temporarily.

[0336] The methods according to various embodiments disclosed in the present disclosure may be included in a computer program product and provided. The computer program product may be traded as a product between a buyer and a seller. The computer program product may be distributed in a device-readable storage medium (e.g., a compact disc read-only memory (CD-ROM)) or through an application store (e.g., PlayStore). TM ) Online distribution. In the case of online distribution, at least some of the computer program product may be at least temporarily stored or temporarily generated in a storage medium, such as a memory of a manufacturer's server, an application store's server, or a relay server.

[0337] Each element (for example, module or program) according to various embodiments can be configured as a single entity or multiple entities. Some of the above-mentioned sub-elements can be omitted, and other sub-elements can also be included in various embodiments. Alternatively or additionally, some elements (for example, modules or programs) can be integrated into an entity, and the function performed by each corresponding element before integration can be performed, identical or similar. The operation performed by modules, programs or other elements according to various embodiments can be run sequentially, in parallel, repeatedly or heuristically, or at least some operations can be run in different orders or can be omitted, or other operations can be added.

[0338] Although the present disclosure has been described with various embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to include such changes and modifications within the scope of the appended claims.

Claims

1. A method of a central unit control plane (CU-CP), the central unit control plane (CU-CP) being included in a secondary node (SN) or a secondary gNB (SgNB) in a wireless communication system supporting evolved universal terrestrial radio access and new air interface dual connectivity (EN-DC), the method comprising: Receiving a first message from a master node (MN) or a master eNB (MeNB) for requesting an SgNB to allocate radio resources for a bearer; and Sending a second message to a central unit user plane (CU-UP) included in the SgNB, the second message including indication information indicating whether a packet data convergence protocol (PDCP) version of the bearer has been changed, sending a third message to the CU-UP, the third message including counting information about PDCP sequence numbers of packets received through the bearer, in, The indication information is generated based on the first message, and Therein, based on at least one of the indication information or the counting information, packets received through the bearer are aligned at the CU-UP.

2. The method according to claim 1, wherein: Based on information about at least one bearer for which the SgNB has been requested to add and information about the PDCP version of the at least one bearer included in the first message, it is identified whether the PDCP version has been changed.

3. A method of a central unit user plane (CU-UP), the central unit user plane (CU-UP) being included in a secondary node (SN) or a secondary gNB (SgNB) in a wireless communication system supporting evolved universal terrestrial radio access and new air interface dual connectivity (EN-DC), the method comprising: receiving a second message from a central unit control plane (CU-CP) included in the SgNB, the second message including indication information indicating whether a packet data convergence protocol (PDCP) version of the bearer has been changed; receiving a third message from the CU-CP, the third message including counting information about PDCP sequence numbers of packets received through the bearer; and assigning a PDCP sequence number to at least one downlink packet received via the bearer based on at least one of the indication information or the counting information, and in, The indication information is generated based on a first message requesting the SgNB to allocate radio resources for the bearer, the first message being received from a master node (MN) or a master eNB (MeNB).

4. The method according to claim 3, wherein: Allocating a PDCP sequence number to at least one downlink packet received via the bearer based on at least one of the indication information or the counting information comprises: Based on the indication information, identifying whether the PDCP version of the bearer has changed; Initializing a PDCP sequence number based on a change in the PDCP version of the bearer, and assigning the PDCP sequence number to the at least one downlink packet; and Based on the PDCP version of the bearer not being changed, a PDCP sequence number is assigned to the at least one downlink packet based on the counting information.

5. The method according to claim 4, wherein: Initializing a PDCP sequence number and assigning the PDCP sequence number to the at least one downlink packet based on a change of a PDCP version of the bearer, including assigning a PDCP sequence number of 0 to a first downlink packet sent to the terminal.

6. A method of a central unit user plane (CU-UP), the central unit user plane (CU-UP) being included in a secondary node (SN) or a secondary gNB (SgNB) in a wireless communication system supporting evolved universal terrestrial radio access and new air interface dual connectivity (EN-DC), the method comprising: receiving a first message from a central unit control plane (CU-CP) included in the SgNB, the first message including indication information indicating whether a packet data convergence protocol (PDCP) version of the bearer has been changed; receiving a second message from the CU-CP, the second message including counting information about PDCP sequence numbers of packets received through the bearer; and Based on at least one of the indication information or the counting information, a sequence of at least one uplink packet received through the bearer is aligned.

7. The method according to claim 6, wherein: The at least one uplink packet includes at least one uplink packet data forwarded from the master node and at least one uplink packet received from the terminal.

8. The method according to claim 6, wherein: Based on at least one of the indication information or the counting information, aligning a sequence of at least one uplink packet received via the bearer, comprising: Identify whether the PDCP version of the bearer has changed based on the indication information; as well as aligning a sequence of the at least one uplink packet using a first-in-first-out (FIFO) scheme based on a change of a PDCP version of the bearer; as well as Based on the PDCP version of the bearer not being changed, a sequence of the at least one uplink packet is aligned based on the counting information.

9. The method according to claim 8, wherein: The PDCP sequence number of the at least one uplink packet aligned using the FIFO scheme is aligned in a Transmission Control Protocol (TCP) layer.

10. A central unit control plane (CU-CP) (1700), the central unit control plane (CU-UP) being included in a secondary node (SN) or a secondary gNB (SgNB) in a wireless communication system supporting evolved universal terrestrial radio access and new air interface dual connectivity (EN-DC), the CU-CP comprising: a transceiver (1710); and A controller (1720) configured to control the transceiver: receiving a first message from a master node (MN) or a master eNB (MeNB) for requesting the SgNB to allocate radio resources for the bearer, and sending a second message to a CU-UP included in the SgNB, the second message including indication information indicating whether a Packet Data Convergence Protocol (PDCP) version of the bearer has been changed, and sending a third message to the CU-UP, the third message including counting information about PDCP sequence numbers of packets received through the bearer, in, The indication information is generated based on the first message, and Therein, based on at least one of the indication information or the counting information, packets received through the bearer are aligned at the CU-UP.

11. The central unit control plane according to claim 10, wherein: The controller is configured to identify whether the PDCP version has been changed based on information about at least one bearer for which the SgNB has been requested to be added and information about the PDCP version of the at least one bearer included in the first message.

12. A central unit user plane (CU-UP) (1800), the central unit user plane (CU-UP) being included in a secondary node (SN) or a secondary gNB (SgNB) in a wireless communication system supporting evolved universal terrestrial radio access and new air interface dual connectivity (EN-DC), the CU-UP comprising: a transceiver (1810); and The controller (1820) is configured to: The control transceiver receives a second message from a central unit control plane (CU-CP) included in the SgNB, the second message including indication information indicating whether a packet data convergence protocol (PDCP) version of the bearer has been changed, controlling the transceiver to receive a third message from the CU-CP, the third message including counting information about PDCP sequence numbers of packets received through the bearer; and controlling to assign a PDCP sequence number to at least one downlink packet received through the bearer based on at least one of the indication information or the counting information, in, The indication information is generated based on a first message requesting the SgNB to allocate radio resources for the bearer, the first message being received from a master node (MN) or a master eNB (MeNB).

13. The central unit user plane according to claim 12, wherein: The controller is configured as: Identify whether the PDCP version of the bearer has changed based on the indication information, initializing a PDCP sequence number and assigning the PDCP sequence number to the at least one downlink packet based on a change in the PDCP version of the bearer, and Based on the PDCP version of the bearer not being changed, a PDCP sequence number is assigned to the at least one downlink packet based on the counting information.

14. A central unit user plane (CU-UP) (1800), the central unit user plane (CU-UP) being included in a secondary node (SN) or a secondary gNB (SgNB) in a wireless communication system supporting evolved universal terrestrial radio access and new air interface dual connectivity (EN-DC), the CU-UP comprising: a transceiver (1810); and The controller (1820) is configured to: The control transceiver receives a first message from a central unit control plane (CU-CP) included in the SgNB, the first message including indication information indicating whether a packet data convergence protocol (PDCP) version of the bearer has been changed, and controlling the transceiver to receive a second message from the CU-CP, the second message including counting information about PDCP sequence numbers of packets received through the bearer; and Control is performed to align a sequence of at least one uplink packet received through the bearer based on at least one of the indication information or the counting information.

15. The central unit user plane according to claim 14, wherein: The controller is configured as: Identify whether the PDCP version of the bearer has changed based on the indication information, aligning a sequence of the at least one uplink packet using a first-in-first-out (FIFO) scheme based on a change in the PDCP version of the bearer, and Based on the PDCP version of the bearer not being changed, a sequence of the at least one uplink packet is aligned based on the counting information.

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