Device and method for distributing packets in wireless communication system, and non-transitory computer-readable storage medium

Abstract

This communication device for providing functions of a packet data convergence protocol (PDCP) entity is configured to: acquire a first desired buffer size (DBS) for a first radio link control (RLC) entity of a split bearer and a second DBS for a second RLC entity of the split bearer; identify the ratio of a first throughput to a second throughput on the basis of the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS; as a result of the identification that the ratio of the first throughput to the second throughput is less than a threshold ratio, refrain from transmitting packets through the first RLC entity while the split bearer is maintained; and transmit the packets through the second RLC entity on the basis of the second throughput.

Description

Device, method, and non-transient computer-readable storage medium for distributing packets in a wireless communication system

[0001] The following descriptions relate to an apparatus, a method, and a non-transient computer-readable storage medium for distributing packets in a wireless communication system.

[0002] In a wireless communication system, a split bearer may be used for dual connectivity. A base station may transmit packets to a terminal through the split bearer. The terminal may reorder the packets by performing sequence number (SN) renumbering.

[0003] The information described above may be provided as related art for the purpose of aiding understanding of the present disclosure. No claim or determination is made as to whether any of the foregoing may be applied as prior art related to the present disclosure.

[0004] A communication device is provided that provides functions of a PDCP (packet data convergence protocol) entity. The communication device may include at least one processor comprising a processing circuit. The communication device may include a memory that stores instructions and includes one or more storage media. When the instructions are executed individually or collectively by the at least one processor, the communication device may cause to acquire a first DBS (desired buffer size) for a first RLC (radio link control) entity of a split bearer and a second DBS for a second RLC entity of the split bearer. When the above instructions are executed individually or collectively by the at least one processor, the communication device may cause to identify the ratio of the first throughput to the second throughput based on the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS. Upon identifying that the ratio of the first throughput to the second throughput is below a threshold ratio, the communication device may cause to refrain from transmitting packets through the first RLC entity while the split bearer is maintained. When the above instructions are executed individually or collectively by the at least one processor, the communication device may cause to transmit packets through the second RLC entity based on the second throughput.

[0005] A method is provided to be performed by a communication device that provides functions of a PDCP (packet data convergence protocol) entity. The method may include an operation of obtaining a first DBS (desired buffer size) for a first RLC (radio link control) entity of a split bearer and a second DBS for a second RLC entity of the split bearer. The method may include an operation of identifying a ratio of the first throughput to the second throughput based on a first throughput for the first RLC entity corresponding to the first DBS and a second throughput for the second RLC entity corresponding to the second DBS. The method may include an operation of refraining from transmitting packets through the first RLC entity while the split bearer is maintained, upon identifying that the ratio of the first throughput to the second throughput is less than a threshold ratio. The above method may include the operation of transmitting packets through the second RLC entity based on the second throughput.

[0006] A non-transient computer-readable storage medium is provided for storing one or more programs. The one or more programs may cause the communication device to obtain a first desired buffer size (DBS) for a first radio link control (RLC) entity of a split bearer and a second DBS for a second RLC entity of the split bearer when executed by at least one processor of the communication device. The one or more programs may cause the communication device to identify a ratio of the first throughput to the second throughput based on a first throughput for the first RLC entity corresponding to the first DBS and a second throughput for the second RLC entity corresponding to the second DBS when executed by the at least one processor of the communication device. The above one or more programs may cause the communication device to refrain from transmitting packets through the first RLC entity while the split bearer is maintained, upon identification that the ratio of the first throughput to the second throughput is less than a threshold ratio when executed by the at least one processor of the communication device. The above one or more programs may cause the communication device to transmit packets through the second RLC entity based on the second throughput when executed by the at least one processor of the communication device.

[0007] In relation to the description of the drawings, the same or similar reference numerals may be used for identical or similar components.

[0008] Figure 1 illustrates an example of a wireless communication system.

[0009] Figure 2a illustrates an example of a protocol stack in the control plane.

[0010] Figure 2b illustrates an example of a protocol stack in the user plane.

[0011] FIGS. 3A and FIGS. 3B illustrate examples of dual connections in a wireless communication system.

[0012] FIGS. 4a and 4b illustrate examples of a method for transmitting downlink packets to a terminal through a split bearer by a PDCP entity.

[0013] Figure 5 illustrates an example of reordering performed at the PDCP layer.

[0014] Figure 6 illustrates a simplified block diagram of a communication device.

[0015] FIGS. 7a through 7c illustrate examples of transmitting packets through a split bearer.

[0016] FIG. 8 is a flowchart showing the operations of a communication device for transmitting packets through a split bearer.

[0017] FIG. 9 is a flowchart illustrating the operations of a communication device for transmitting packets through a split bearer.

[0018] FIG. 10 is a flowchart illustrating the operations of a communication device for transmitting packets through a split bearer.

[0019] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit the scope of other embodiments. A singular expression may include a plural expression unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as generally understood by those skilled in the art described in this disclosure. Terms used in this disclosure that are defined in a general dictionary may be interpreted as having the same or similar meaning as they have in the context of the relevant technology, and are not to be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure. In some cases, even terms defined in this disclosure are not to be interpreted to exclude the embodiments of this disclosure.

[0020] In the various embodiments of the present disclosure described below, a hardware-based approach is described as an example. However, since the various embodiments of the present disclosure include techniques using both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach.

[0021] Terms referring to signals used in the following description (e.g., packet, message, signal, information, signaling), terms referring to resources (e.g., section, symbol, slot, subframe, radio frame, subcarrier, RE (resource element), RB (resource block), BWP (bandwidth part), occasion)), terms for operation states (e.g., step, operation, procedure)), terms referring to data (e.g., packet, message, user stream, information, bit, symbol, codeword)), terms referring to channels, terms referring to network entities (DU (distributed unit), RU (radio unit), CU (central unit), CU-CP (control plane), CU-UP (user plane), O-DU (O-RAN (open radio access network) DU), O-RU (O-RAN RU), O-CU (O-RAN CU), Terms such as O-CU-UP (O-RAN CU-CP), O-CU-CP (O-RAN CU-CP), and terms referring to components of the device are examples provided for convenience of explanation. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used. Furthermore, terms such as '...part', '...device', '...object', '...body' used below may refer to at least one shape structure or a unit that processes a function.

[0022] Additionally, in this disclosure, expressions of "greater than" or "less than" may be used to determine whether a specific condition is satisfied or fulfilled; however, this is merely for the purpose of expressing an example and does not exclude descriptions of "greater than" or "less than." Conditions described as "greater than" may be replaced with "greater than," conditions described as "less than" may be replaced with "less than," and conditions described as "greater than and less than" may be replaced with "greater than and less than." Furthermore, "A" to "B" below refer to at least one of elements from A (including A) to B (including B). Below, "C" and / or "D" refers to including at least one of "C" or "D," i.e., {"C", "D", "C" and "D"}.

[0023] The present disclosure describes embodiments using terms used in some communication standards (e.g., 3GPP (3rd Generation Partnership Project)), but this is merely illustrative. The embodiments of the present disclosure may also be applied to other communication and broadcasting systems.

[0024] Figure 1 illustrates an example of a wireless communication system.

[0025] Referring to FIG. 1, FIG. 1 illustrates a base station (110) and a terminal (120) as part of nodes using a wireless channel in a wireless communication system. FIG. 1 illustrates only one base station, but the wireless communication system may include other base stations identical or similar to the base station (110).

[0026] A base station (110) is a network infrastructure that provides wireless access to a terminal (120). The base station (110) has coverage defined based on the distance over which it can transmit signals. In addition to being a base station, the base station (110) may be referred to as an 'access point (AP)', 'eNodeB (eNB)', '5G node (5th generation node)', 'next generation nodeB (gNB)', 'wireless point', 'transmission / reception point (TRP)', or other terms having an equivalent technical meaning.

[0027] A terminal (120) is a device used by a user and communicates with a base station (110) via a wireless channel. The link from the base station (110) to the terminal (120) is referred to as a downlink (DL), and the link from the terminal (120) to the base station (110) is referred to as an uplink (UL). Additionally, although not shown in FIG. 1, the terminal (120) and another terminal can communicate with each other via a wireless channel. In this case, the link between the terminal (120) and another terminal (device-to-device link, D2D) is referred to as a sidelink, and the sidelink may be used interchangeably with the PC5 interface. In some other embodiments, the terminal (120) may be operated without user involvement. For example, the terminal (120) may be a device that performs machine type communication (MTC) and may not be carried by the user. In addition, for example, the terminal (120) may be a narrowband (NB) IoT (internet of things) device.

[0028] The terminal (120) may be referred to as 'user equipment (UE)', 'customer premises equipment (CPE)', 'mobile station', 'subscriber station', 'remote terminal', 'wireless terminal', 'electronic device', or 'user device' or other terms having an equivalent technical meaning.

[0029] The base station (110) can perform beamforming with the terminal (120). The base station (110) and the terminal (120) can transmit and receive wireless signals in a relatively low frequency band (e.g., FR 1 (frequency range 1) of NR). Additionally, the base station (110) and the terminal (120) can transmit and receive wireless signals in a relatively high frequency band (e.g., FR 2 (or FR 2-1, FR 2-2, FR 2-3), FR 3) of NR) and a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz)). To improve channel gain, the base station (110) and the terminal (120) can perform beamforming. Here, beamforming may include transmit beamforming and receive beamforming. The base station (110) and the terminal (120) can impart directivity to the transmitted signal or the received signal. To this end, the base station (110) and the terminal (120) can select serving beams through a beam search or beam management procedure. After the serving beams are selected, subsequent communication can be performed through a resource that has a QCL relationship with the resource that transmitted the serving beams.

[0030] If large-scale characteristics of the channel that transmitted the symbol on the first antenna port can be inferred from the channel that transmitted the symbol on the second antenna port, the first antenna port and the second antenna port can be evaluated as being in a QCL relationship. For example, the large-scale characteristics may include at least one of a delay spread, a Doppler spread, a Doppler shift, an average gain, an average delay, and a spatial receiver parameter.

[0031] In FIG. 1, it is described that both the base station (110) and the terminal (120) perform beamforming, but the embodiments of the present disclosure are not necessarily limited thereto. In some embodiments, the terminal may or may not perform beamforming. Also, the base station may or may not perform beamforming. That is, either the base station or the terminal may perform beamforming, or neither the base station nor the terminal may perform beamforming.

[0032] In the present disclosure, a beam refers to a spatial flow of a signal in a wireless channel, formed by one or more antennas (or antenna elements), and this formation process may be referred to as beamforming. Beamforming may include at least one of analog beamforming or digital beamforming (e.g., precoding). A reference signal transmitted based on beamforming may include, for example, a demodulation-reference signal (DM-RS), a channel state information-reference signal (CSI-RS), a synchronization signal / physical broadcast channel (SS / PBCH), or a sounding reference signal (SRS). Additionally, an IE such as a CSI-RS resource or an SRS-resource may be used as a configuration for each reference signal, and such a configuration may include information associated with the beam. Information associated with a beam may refer to whether the configuration (e.g., CSI-RS resource) uses the same spatial domain filter as other configurations (e.g., other CSI-RS resources within the same CSI-RS resource set) or a different spatial domain filter, or which reference signal it is quasi-colocated with, and if so, what type (e.g., QCL type A, B, C, D).

[0033] Conventionally, in communication systems with a relatively large cell radius of base stations, each base station was installed to include the functions of a digital processing unit (or DU (distributed unit)) and an RF (radio frequency) processing unit (RF processing unit, or RU (radio unit)). However, as high frequency bands are used in 4G (4th generation) and / or subsequent communication systems (e.g., 5G) and the cell coverage of base stations decreases, the number of base stations required to cover a specific area has increased. Consequently, the burden of installation costs for operators to install base stations has also increased. To minimize base station installation costs, a structure has been proposed in which the DU and RU of a base station are separated, with one or more RUs connected to a single DU via a wired network and one or more geographically distributed RUs deployed to cover a specific area.

[0034] Figure 2a illustrates an example of a protocol stack in the control plane.

[0035] Referring to FIG. 2a, in a communication system, the wireless protocol of the control plane of a terminal (120) may include a PHY (physical) layer (211), a MAC (medium access control) layer (212), an RLC (radio link control) layer (213), a PDCP (packet data convergence protocol) layer (214), and an RRC (radio resource control) layer (215). The wireless protocol of the control plane of a base station (110) may include a PHY layer (221), a MAC layer (222), an RLC layer (223), a PDCP layer (222), and an RRC layer (225).

[0036] The main functions of the RRC layer (215, 225) may include at least one of the following functions.

[0037] - Broadcast system information related to AS (Access Stratum) and NAS (Non Access Stratum)

[0038] - Paging initiated by 5GC or NG-RAN

[0039] - Establish, maintain, and release the RRC connection between the UE and NG-RAN, including the following:

[0040] 1) Adding, modifying, and removing carrier aggregation

[0041] 2) Add, modify, and disable Dual Connectivity within NR or between E-UTRA and NR.

[0042] - Security functions including key management

[0043] - Setup, configuration, maintenance, and release of SRB (Signaling Radio Bearer) and DRB (Data Radio Bearer)

[0044] - Mobility features including the following:

[0045] 1) Handover and context transfer

[0046] 2) UE cell selection and reselection and control of cell selection and reselection

[0047] 3) Inter-RAT mobility

[0048] - QoS (Quality of Service) management function

[0049] - UE measurement reporting and reporting control;

[0050] - Detection of and recovery from radio link failure

[0051] - Send messages from / to / from the UE to / from the NAS.

[0052] The main functions of the PDCP layer (214, 224) may include some of the following functions.

[0053] - Header compression and decompression features (ROHC only)

[0054] - User data transfer function (Transfer of user data)

[0055] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0056] - Out-of-sequence delivery of upper layer PDUs

[0057] - Reordering function (PDCP PDU reordering for reception)

[0058] - Duplicate detection function (Duplicate detection of lower layer SDUs)

[0059] - Retransmission of PDCP SDUs

[0060] - Encryption and decryption functions (Ciphering and deciphering)

[0061] - Timer-based SDU discard in uplink.

[0062] In the above description, the reordering function of the PDCP layer (214, 224) may mean a function that reorders PDCP PDUs received from a lower layer in order based on the PDCP SN (sequence number). In one example, the reordering function of the PDCP layer (214, 224) may include a function that transmits data to an upper layer in the reordered order. In one example, the reordering function of the PDCP layer (214, 224) may include a function that transmits data to an upper layer without considering the order. In one example, the reordering function of the PDCP layer (214, 224) may include a function that records lost PDCP PDUs by reordering them. In one example, the reordering function of the PDCP layer (214, 224) may include a function that transmits a status report regarding lost PDCP PDUs to the transmitting side. In one example, the reordering function of the PDCP layer (214, 224) may include a function to request retransmission of lost PDCP PDUs.

[0063] The main functions of the RLC layer (213, 223) may include at least one of the following functions.

[0064] - Data transfer function (Transfer of upper layer PDUs)

[0065] - Sequential delivery function (In-sequence delivery of upper layer PDUs)

[0066] - Out-of-sequence delivery of upper layer PDUs

[0067] - ARQ function (Error Correction through ARQ)

[0068] - Concatenation, segmentation, and reassembly functions of RLC SDUs

[0069] - Re-segmentation function (Re-segmentation of RLC data PDUs)

[0070] - Reordering function (Reordering of RLC data PDUs)

[0071] - Duplicate detection

[0072] - Error detection function (Protocol error detection)

[0073] - RLC SDU discard function

[0074] RLC re-establishment function

[0075] In the above description, the in-sequence delivery function of the RLC layer (213, 223) may mean a function of delivering RLC SDUs received from a lower layer to an upper layer in order. When a single RLC SDU is received divided into multiple RLC SDUs, the in-sequence delivery function of the RLC layer (213, 223) may include a function of reassembling and delivering the multiple RLC SDUs. In one example, the in-sequence delivery function of the RLC layer (213, 223) may include a function of rearranging the received RLC PDUs based on an RLC SN or PDCP SN. In one example, the in-sequence delivery function of the RLC layer (213, 223) may include a function of recording lost RLC PDUs by rearranging the order. In one example, the sequential delivery function of the RLC layer (213, 223) may include a function to deliver a status report for lost RLC PDUs to the transmitting side. In one example, the sequential delivery function of the RLC layer (213, 223) may include a function to request retransmission of lost RLC PDUs. In one example, the sequential delivery function of the RLC layer (213, 223) may include a function to deliver only the RLC SDUs prior to the lost RLC SDU in order to the upper layer if there is a lost RLC SDU. In one example, the sequential delivery function of the RLC layer (213, 223) may include a function to deliver all RLC SDUs received before the timer started to the upper layer in order if a predetermined timer has expired even if there is a lost RLC SDU. In one example, the sequential delivery function of the RLC layer (213, 223) may include the function of delivering all RLC SDUs received up to now to the upper layer in order when a predetermined timer expires, even if there are lost RLC SDUs.

[0076] The RLC layer (213, 223) can process the RLC PDUs in the order they are received, regardless of the order of the SN (out of sequence delivery), and deliver them to the PDCP layer (214, 224).

[0077] When the RLC layer (213, 223) receives a segment, it can receive segments stored in a buffer or subsequent segments, reconstruct them into a single complete RLC PDU, and then transmit it to the PDCP layer (214, 224).

[0078] The RLC layer (213, 223) may or may not include a concatenation function. The concatenation function may be performed in the MAC layer (212, 222) or replaced by the multiplexing function of the MAC layer (212, 222).

[0079] The MAC layer (212, 222) may be connected to one or more RLC layers configured in the terminal (120), and the main function of the MAC layer (212, 222) may include at least one of the following functions.

[0080] - Mapping function (Mapping between logical channels and transport channels)

[0081] - Multiplexing and demultiplexing functions (Multiplexing / demultiplexing of MAC SDUs)

[0082] - Scheduling information reporting function

[0083] - HARQ function (Error correction through HARQ)

[0084] - Priority handling between logical channels of one UE

[0085] - Priority handling between UEs by means of dynamic scheduling

[0086] - MBMS service identification function

[0087] - Transport format selection function

[0088] - Padding

[0089] The PHY layer (211, 221) can perform the operation of channel coding and modulating upper layer data, creating OFDM (orthogonal frequency division multiplexing) symbols and transmitting them to the wireless channel, or demodulating OFDM symbols received through the wireless channel and channel decoding them to transmit them to the upper layer.

[0090] Figure 2b illustrates an example of a protocol stack in the user plane.

[0091] Referring to FIG. 2b, the wireless protocol of the user plane of the terminal (120) may include a PHY (physical) layer (261), a MAC (medium access control) layer (262), an RLC (radio link control) layer (263), a PDCP (packet data convergence protocol) layer (264), and an SDAP (service data adaptation protocol) layer (265). The wireless protocol of the control plane of the base station (110) may include a PHY layer (271), a MAC layer (272), an RLC layer (273), a PDCP layer (274), and an SDAP layer (275).

[0092] The main functions of the SDAP layer (265, 276) may include at least one of the following functions.

[0093] - User data transfer function (transfer of user plane data)

[0094] - Mapping function between a QoS flow and a DRB for both DL and UL for uplink and downlink

[0095] - Marking QoS flow ID in both DL and UL packets for uplink and downlink

[0096] - Function to map reflective QoS flow to data bearers for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

[0097] For SDAP layers (265, 275), the terminal (120) may receive a radio resource control (RRC) message indicating whether to use the header of the SDAP layer (265, 275) or the function of the SDAP layer (265, 275) for each PDCP layer, for each bearer, or for each logical channel. If the SDAP header is set, the terminal (120) may be instructed to update or reset the mapping information for the QoS flows of the uplink and downlink and the data bearer using the NAS (non-access stratum) QoS (quality of service) reflective setting 1-bit indicator (NAS reflective QoS) and the AS (access stratum) QoS reflective setting 1-bit indicator (AS reflective QoS) of the SDAP header. The SDAP header may include QoS flow ID (identifier) ​​information indicating QoS. QoS information can be used for data processing priorities, scheduling information, etc., to support smooth service.

[0098] For the PDCP layers (264, 274) in the user plane, the contents of the PDCP layers (214, 224) in the control plane of FIG. 2a can be applied substantially identically. For the RLC layers (263, 273) in the user plane, the contents of the RLC layers (213, 223) in the control plane of FIG. 2a can be applied substantially identically. For the MAC layers (262, 272) in the user plane, the contents of the MAC layers (212, 222) in the control plane of FIG. 2a can be applied substantially identically. For the PHY layers (261, 271) in the user plane, the contents of the PHY layers (211, 221) in the control plane of FIG. 2a can be applied substantially identically.

[0099] Referring to FIGS. 2a and 2b, a radio protocol of a new radio (NR) communication system in a radio access network is described as an example, but the present disclosure is not limited thereto. For example, the description of FIGS. 2a and 2b may be applied to other communication systems (e.g., a long term evolution (LTE) communication system or a 6G (6th generation) communication system).

[0100] In FIG. 2a and FIG. 2b, a protocol stack of a base station (110) is illustrated, but the present disclosure is not limited thereto. For example, the base station (110) may be implemented in a distributed deployment according to a central unit (or control unit) configured to perform the functions of the upper layer (e.g., PDCP, RRC) of the access network and a distributed unit (DU) configured to perform the functions of the lower layer.

[0101] FIGS. 3A and FIGS. 3B illustrate examples of dual connections in a wireless communication system.

[0102] FIG. 3a illustrates an example (300) of dual connectivity (DC) between a terminal (120) and a plurality of base stations (110-1, 110-2). Referring to the example (300), the terminal (120) may be configured in a dual connectivity using a first base station (110-1) and a second base station (110-2). The dual connectivity technology is a technology that increases frequency usage efficiency by simultaneously connecting the terminal (120) to two independent heterogeneous or homogeneous radio communication cell groups having separate radio resource control entities, thereby utilizing frequency resources on the component carriers of cells within each cell group located in different frequency bands for the transmission and reception of signals. For example, a terminal (120) may be connected to two different radio resource entities (e.g., a first base station (110-1) and a second base station (110-2)) and may use radio resources allocated by each radio resource entity. In a multi-radio DC (MR-DC), a terminal (120) in a radio resource control (RRC) connection state (e.g., RRC_CONNECTED) may be configured to use radio resources provided by two independent schedulers. Each scheduler may be located at an NG-RAN node (e.g., a first base station (110-1), a second base station (110-2)). One of the nodes may be a master node (MN) and the other may be a secondary node (SN). The MN and the SN are connected via a network interface, and the MN may be connected to a core network (CN). The SN may be connected to the core network or may not be connected.

[0103] MN may provide a master cell group (MCG). In addition to MN, MN may be referred to as an M-NODE, M-NG-RAN node, or other terms having an equivalent technical meaning. MCG may include one or more cells. MCG may include a primary cell (PCell). MCG may include a plurality of aggregated cells. MCG may include a PCell and one or more secondary cells (SCell). SN may provide a secondary cell group (SCG). In addition to SN, SN may be referred to as an S-NODE, S-NG-RAN node, or other terms having an equivalent technical meaning. SCG may include one or more cells. SCG may include a plurality of aggregated cells. SCG, like MCG, may include a PCell and / or SCell. A cell functioning as a PCell within an SCG may be referred to as a primary secondary cell (PSCell). Hereinafter, the term SpCell (special cell) may be used as a term including PCell and PSCell. For example, SpCell in MCG may represent PCell, and SpCell in SCG may represent PSCell.

[0104] The types of DC can be defined as follows.

[0105] 1) EN-DC (EUTRA (evolved universal terrestrial radio access) NR (new radio) dual connectivity): dual connectivity in which an eNB is connected to an EPC (evolved packet core) and a terminal is connected to an Enb operating as an MN and a gNB operating as an SN (act as). The gNB may be referred to as an en-gNB, and the en-gNB may or may not be connected to an EPC.

[0106] 2) NGEN-DC: A dual connection in which an eNB is connected to a 5GC (5G core), and a terminal is connected to an eNB operating as an MN and a Gnb operating as an SN. Here, the eNB may be referred to as ng-eNB.

[0107] 3) NE-DC: A dual connection in which a gNB is connected to a 5GC, and a terminal is connected to a gNB operating as an MN and an eNB operating as an SN. Here, the eNB may be referred to as ng-eNB.

[0108] 4) NR-DC: A dual connection in which gNBs are connected to 5GC, and terminals are connected to a gNB operating as an MN and a gNB operating as an SN. NR-DC can also be used when a UE is connected to a single gNB to perform both the roles of MN and SN and to configure both MCG and SCG.

[0109] The terminal (120) may support MR-DC. The terminal (120) may be connected to a first base station (110-1) and a second base station (110-2). The first base station (110-1) may be connected to the terminal (120) as an MN and the second base station (110-2) as an SN. However, this is merely an example and the present disclosure is not limited thereto. For example, the first base station (110-1) may be connected to the terminal (120) as an SN and the second base station (110-2) as an MN.

[0110] FIG. 3b illustrates an example (350) of a dual connection between a terminal (120), a first DU (371), a second DU (372), and a CU (360). Referring to the example (350), base stations (e.g., base station (110), first base station (110-1), second base station (110-2)) may be separated into CUs and DUs. Unlike multiple independent base stations (e.g., first base station (110-1), second base station (110-2)) serving the terminal (120), one CU and multiple DUs may serve the terminal (120). For example, the CU (360) may be connected to the first DU (371) and the second DU (372). The CU (360) may be connected to each of the first DU (371) and the second DU (372) via an F1 interface. The first DU (371) may provide one or more cells. For example, one or more cells provided by the first DU (371) may be referred to as MCG (or SCG). The second DU (372) may provide one or more cells. For example, one or more cells provided by the second DU (372) may be referred to as SCG (or MCG). In terms of the terminal (120), the CU (360) and the first DU (371) may operate as logical nodes corresponding to one base station. In terms of the terminal (120), the CU (360) and the second DU (372) may operate as logical nodes corresponding to another base station different from the one base station.

[0111] In the present disclosure, base stations (e.g., base station (110), first base station (110-1), second base station (110-2)) may be implemented in a distributed arrangement according to a CU configured to perform upper-layer functions of an access network and a DU configured to perform lower-layer functions. The CU and DU may represent independent network entities (or network nodes, network equipment, network devices) for the access network. A CU may be connected to one or more DUs. A CU may perform functions of a layer higher than a DU (e.g., packet data convergence protocol (PDCP), radio resource control (RRC)). A DU may perform functions of a lower layer (e.g., radio link control (RLC), medium access control (MAC), and physical (PHY)).

[0112] FIGS. 4a and 4b illustrate examples of a method for transmitting downlink packets to a terminal through a split bearer by a PDCP entity.

[0113] FIG. 4a illustrates an example (400) of a base station (410) connected to an evolved packet core (EPC). Referring to the example (400), the base station (410) and the node (420) may be configured to provide dual connectivity (DC) (e.g., EN-DC) to a terminal (540). In the example (400), the base station (410) may be a gNB and the node (420) may be an eNB. However, the present disclosure is not limited thereto. For example, the base station (510) may be implemented as a central unit (CU) (or control unit) or a distributed unit (DU). The base station (410) may be connected to a serving-gateway (S-GW) (430) which is an entity of the EPC. For example, the S-GW (430) may be an entity (or node) that provides packets (or data) to the base station (410) in the user plane.

[0114] For example, a base station (410) may include NR (new radio) PDCP (packet data convergence protocol) (or, PDCP, PDCP layer) (411), NR RLC (radio link control) (or, RLC, RLC layer) (412), and NR MAC (medium access control) (or, MAC, MAC layer) (413). In example (400), the base station (410) is illustrated as including NR PDCP (411), NR RLC (412), and NR MAC (413), but the present disclosure is not limited thereto. For example, the base station (410) may further include at least one of NR RRC (radio resource control), NR SDAP (service data adaptation protocol), or NR PHY (physical). For NR PDCP (411), the contents of the PDCP layers (224, 274) of FIGS. 2a and 2b can be applied substantially identically. For NR RLC (412), the contents of the RLC layers (223, 273) of FIGS. 2a and 2b can be applied substantially identically. For NR MAC (413), the contents of the MAC layers (222, 272) of FIGS. 2a and 2b can be applied substantially identically.

[0115] For example, a node (420) may include an EUTRA (evolved universal terrestrial radio access) RLC (or, RLC, RLC layer) (422) and an EUTRA MAC (or, MAC, MAC layer) (423). In example (400), the node (420) is depicted as including an EUTRA RLC (422) and an EUTRA MAC (423), but the present disclosure is not limited thereto. For example, the node (420) may further include at least one of an EUTRA RRC, an EUTRA SDAP, an EUTRA PDCP, or an EUTRA PHY. For the EUTRA RLC (422), the contents regarding the RLC layer (223, 273) of FIG. 2B may be substantially applicable. For the EUTRA MAC (423), the contents regarding the MAC layer (222, 272) of FIG. 2B may be substantially applicable.

[0116] Referring to Example (400), to support a split bearer, the NR PDCP (411) of the base station (410) may be connected to the NR RLC (412) of the base station (410) and the EUTRA RLC (422) of the node (420). The base station (410) may perform packet distribution for the split bearer using the downlink data delivery status (DDDS) obtained from each of the NR RLC (412) and the EUTRA RLC (422). In one example, the DDDS may be referred to as PDU type 1. For example, the NR PDCP (411) of the base station (410) may obtain a first DDDS from the corresponding node, the NR RLC (412), via an uplink path (402). For example, the NR PDCP (411) of the base station (410) may obtain a second DDDS via the uplink path (402) from the corresponding node, the EUTRA RLC (422). For example, the DDDS may include a desired buffer size (DBS). For example, the DBS may indicate a buffer size for the data radio bearer (DRB). For example, the DBS may be used to identify the number of packets according to the buffer size in the NR PDCP (411). For example, the base station (410) (or the NR PDCP (411)) may perform distribution of downlink packets received from the S-GW (430) based on the first DBS of the first DDDS obtained from the NR RLC (412) and the second DBS of the second DDDS obtained from the EUTRA RLC (422).

[0117] The downlink path (401) may include paths for split bearers. For example, the paths for split bearers may include a first path (401-1) and a second path (401-2). The first path (401-1) may include an NR PDCP (411) of a base station (410), an NR RLC (412) of a base station (410), an NR MAC (413) of a base station (410), an NR MAC (441) of a terminal (440), an NR RLC (442) of a terminal (440), and an NR PDCP (445) of a terminal (440). The second path (401-2) may include the NR PDCP (411) of the base station (410), the EUTRA RLC (422) of the node (420), the EUTRA MAC (423) of the node (420), the EUTRA MAC (443) of the terminal (440), the EUTRA RLC (444) of the terminal (440), and the NR PDCP (445) of the terminal (440).

[0118] For example, the first path (401-1) may be associated with a cell group provided by the base station (410). For example, if the base station (410) is composed of a CU and a DU, the first path (401-1) may be associated with a cell group provided by the DU. For example, the cell group associated with the first path (401-1) may include a secondary cell group (SCG). For example, the second path (401-2) may be associated with a cell group provided by the node (420). For example, the cell group associated with the second path (401-2) may include a master cell group (MCG).

[0119] For example, the base station (410) (or, NR PDCP (411)) may provide downlink packets to the NR RLC (412) and EUTRA RLC (422) via a split bearer. The downlink packets provided from the NR PDCP (411) to the NR RLC (412) (or, EUTRA RLC (422)) may include a PDCP protocol data unit (PDU). The header of the PDCP PDU may include a PDCP sequence number (SN). The terminal (440) (or, NR PDCP (445)) may reorder downlink packets obtained via paths (401-1, 401-2) to the split bearer. For example, the terminal (440) (or NR PDCP (445)) can sort the order of downlink packets using the PDCP SN included in the acquired downlink packet.

[0120] In FIG. 4a, an example (400) of the user plane of a base station (410), a node (420), and a terminal (440) is illustrated, but the present disclosure is not limited thereto. For example, the base station (410), the node (420), and the terminal (440) may establish a connection in the control plane for dual connection. For example, the upper layer of the node (420) (e.g., RRC) may be connected to an entity of the EPC.

[0121] FIG. 4b illustrates an example (450) of a base station (460) connected to a 5th generation core (5GC). Referring to the example (450), the base station (460) and the node (470) may be configured to provide dual connectivity to a terminal (490). In the example (450), the base station (460) may be a gNB and the node (470) may be a gNB. However, the present disclosure is not limited thereto. For example, the base station (460) and / or the node (470) may be implemented as a CU and a DU. The base station (460) may be connected to a user plane function (UPF) (480) which is an entity of the 5GC. For example, the UPF (480) may be an entity (or node) that provides packets (or data) to the base station (460) in the user plane.

[0122] For example, the base station (460) may include NR PDCP (or, PDCP, PDCP layer) (461), NR RLC (or, RLC, RLC layer) (462), and NR MAC (or, MAC, MAC layer) (463). In example (450), the base station (460) is depicted as including NR PDCP (461), NR RLC (462), and NR MAC (463), but the present disclosure is not limited thereto. For example, the base station (460) may further include at least one of NR RRC, NR SDAP, or NR PHY. With respect to the NR PDCP (461), the contents of the PDCP layer (224, 274) of FIG. 2a and FIG. 2b may be applied substantially the same way. For NR RLC (462), the content of the RLC layers (223, 273) of FIG. 2a and FIG. 2b can be applied substantially the same way. For NR MAC (463), the content of the MAC layers (222, 272) of FIG. 2a and FIG. 2b can be applied substantially the same way.

[0123] For example, a node (470) may include an NR RLC (or, RLC, RLC layer) (472) and an NR MAC (or, MAC, MAC layer) (473). In example (450), the node (470) is depicted as including an NR RLC (472) and an NR MAC (473), but the present disclosure is not limited thereto. For example, the node (470) may further include at least one of an NR RRC, an NR SDAP, an NR PDCP, or an NR PHY. For the NR RLC (472), the details regarding the RLC layers (223, 273) of FIG. 2a and FIG. 2b may be substantially applicable. For the NR MAC (473), the details regarding the MAC layers (222, 272) of FIG. 2a and FIG. 2b may be substantially applicable.

[0124] Referring to example (450), to support a split bearer, the NR PDCP (461) of the base station (460) may be connected to the NR RLC (462) of the base station (460) and the NR RLC (472) of the node (470). The base station (460) may perform packet distribution for the split bearer using the DDDS obtained from each of the NR RLC (462) and the NR RLC (472). In one example, the DDDS may be referred to as PDU type 1. For example, the NR PDCP (461) of the base station (460) may obtain a first DDDS from the corresponding node, the NR RLC (462), via an uplink path (452). For example, the NR PDCP (461) of the base station (460) can obtain a second DDDS from the corresponding node, the NR RLC (472), via the uplink path (452). For example, the DDDS may include a DBS. For example, the DBS may indicate a buffer size for the DRB. For example, the DBS may be used to identify the number of packets according to the buffer size in the NR PDCP (461). For example, the base station (460) (or the NR PDCP (461)) may perform distribution for downlink packets received from the UPF (480) based on the first DBS of the first DDDS obtained from the NR RLC (462) and the second DBS of the second DDDS obtained from the NR RLC (472).

[0125] The downlink path (451) may include paths for a split bearer. For example, the paths for a split bearer may include a first path (451-1) and a second path (451-2). The first path (451-1) may include an NR PDCP (461) of a base station (460), an NR RLC (462) of a base station (460), an NR MAC (463) of a base station (460), an NR MAC (491) of a terminal (490), an NR RLC (492) of a terminal (490), and an NR PDCP (495) of a terminal (490). The second path (451-2) may include the NR PDCP (461) of the base station (460), the EUTRA RLC (472) of the node (470), the EUTRA MAC (473) of the node (470), the EUTRA MAC (493) of the terminal (490), the EUTRA RLC (494) of the terminal (490), and the NR PDCP (495) of the terminal (490).

[0126] For example, the first path (451-1) may be associated with a cell group provided by the base station (460). For example, if the base station (460) is composed of a CU and a DU, the first path (451-1) may be associated with a cell group provided by the DU. For example, the cell group associated with the first path (451-1) may include an SCG (or, MCG). For example, the second path (451-2) may be associated with a cell group provided by the node (470). For example, the cell group associated with the second path (451-2) may include an MCG (or, SCG).

[0127] For example, a base station (460) (or, NR PDCP (461)) may provide downlink packets to NR RLC (462) and NR RLC (472) via a split bearer. The downlink packets provided from NR PDCP (461) to NR RLC (462) (or, NR RLC (472)) may include a PDCP PDU. The header of the PDCP PDU may include a PDCP SN. A terminal (490) (or, NR PDCP (495)) may rearrange downlink packets obtained via paths (451-1, 451-2) to the split bearer. For example, a terminal (490) (or, NR PDCP (445)) may rearrange the order of downlink packets using the PDCP SN included in the obtained downlink packets.

[0128] In FIG. 4b, an example (450) of the user plane of the base station (460), node (470), and terminal (490) is illustrated, but the present disclosure is not limited thereto. For example, the base station (460), node (470), and terminal (490) may establish a connection in the control plane for dual connection. For example, the upper layer of the node (470) (e.g., RRC) may be connected to an entity of 5GC.

[0129] FIG. 5 illustrates an example of reordering performed at the PDCP layer. The PDCP (packet data convergence protocol) layer can provide a reordering function to ensure the packet order of uplink packets in the NR (new radio) standard. In referring to data at the PDCP layer, the terms SDU (service data unit) or PDU (protocol data unit) may be used. For example, data containing a PDCP header may be referred to as a PDU. For example, data not containing a PDCP header may be referred to as an SDU. Hereinafter, as a term to distinguish between data packets and control packets, a PDCP PDU may be a PDCP data PDU or a PDCP control PDU. In the present disclosure, unless otherwise specified, PDU and PDCP PDU may refer to a PDCP data PDU.

[0130] Referring to FIG. 5, communication can be performed between a transmitting PDCP entity (510) and a receiving PDCP entity (560). The transmitting PDCP entity (510) and the receiving PDCP entity (560) can be distinguished according to the entity transmitting data and the entity receiving data. For example, in downlink data transmission, the transmitting PDCP entity (510) may correspond to a base station (110) (or a central unit (CU) (360)), and the receiving PDCP entity (560) may correspond to a terminal (120). For example, in uplink data transmission, the transmitting PDCP entity (510) may correspond to a terminal (120), and the receiving PDCP entity (560) may correspond to a base station (110) (or a central unit (360)).

[0131] The transmitting PDCP entity (510) can obtain data (e.g., PDCP SDU) from an upper layer (e.g., SDAP (service data adaptation protocol) layer, RRC (radio resource control) layer). The transmitting PDCP entity (510) can perform sequence numbering (515). The transmitting PDCP entity (510) can determine a count value for the data through sequence numbering (515). For example, the transmitting PDCP entity (510) can determine a count value corresponding to the state variable 'TX_NEXT'. The transmitting PDCP entity (510) can associate the count value with the data. The transmitting PDCP entity (510) can determine a sequence number (SN) for the data. For example, the transmitting PDCP entity (510) can determine the SN of the PDCP PDU based on the state variable 'TX_NEXT' and a modulo operation. The SN may be an integer greater than or equal to 0 and less than [2[PDCP_size]-1]. 'PDCP_size' may be configured by an upper layer (e.g., RRC). 'PDCP_size' may be 12-bit or 18-bit. For example, if the PDCP PDU is uplink data, the 'PDCP_size' for the uplink may be configured by an upper layer (e.g., RRC). For example, if the PDCP PDU is downlink data, the 'PDCP_size' for the downlink may be configured by an upper layer (e.g., RRC). Subsequently, the transmitting PDCP entity (510) may increase the state variable 'TX_NEXT' by 1. That is, the status variable 'TX_NEXT' can be the count value of the next PDCP SDU to be transmitted.

[0132] Although not illustrated in FIG. 5, the transmitting PDCP entity (510) can perform various functions in addition to sequence numbering (515). For example, the transmitting PDCP entity (510) can perform header compression on the data using ROHC (robust header compression). For example, the transmitting PDCP entity (510) can perform integrity protection and ciphering. For example, the transmitting PDCP entity (510) can generate a PDCP PDU by adding a PDCP header to the data. The transmitting PDCP entity (510) can transmit the result of the functions performed (e.g., PDCP PDU) to the receiving PDCP entity (560). For example, the above results may be provided to other nodes (e.g., terminal (120) in the downlink, base station (110) in the uplink, CU (360)) via RLC entities, MAC entities, and wireless interfaces.

[0133] A receiving PDCP entity (560) can receive data (e.g., PDCP PDU) from a lower layer (e.g., RLC layer). Variables may be defined to describe the operations of the receiving PDCP entity (560).

[0134] - HFN (hyper frame number): The HFN portion of the state variable (i.e., the number of MSBs (most significant bits) equal to the HFN length)

[0135] - SN (sequence number): The SN portion of the state variable (i.e., the number of LSB (least significant bits) equal to the PDCP SN length)

[0136] - RCVD_SN: The PDCP SN of the received PDCP data PDU included in the PDU header

[0137] - RCVD_HFN: HFN of the received PDCP data PDU calculated by the receiving PDCP entity (560)

[0138] - RCVD_COUNT: COUNT of received PDCP data PDU = [RCVD_HFN, RCVD_SN].

[0139] A receiving PDCP entity (560) may receive a PDCP PDU from a lower layer (e.g., RLC). The PDCP PDU may be data transmitted from a transmitting PDCP entity (510). The receiving PDCP entity (560) may determine a count value (e.g., 'RCVD_COUNT') of the received PDCP PDU. After determining the count value (e.g., 'RCVD_COUNT') of the received PDCP PDU, the receiving PDCP entity (560) may perform deciphering and integrity verification. If the integrity verification fails, the receiving PDCP entity (560) may discard the PDCP PDU. The receiving PDCP entity (560) may discard the PDCP PDU if it has previously received a PDCP PDU corresponding to the count value, or if the count value is smaller than the count value ('RX_DELIV') (hereinafter, waiting start count value) of the first PDCP SDU that is still waiting and has not been passed to an upper layer (e.g., SDAP, RRC).

[0140] The receiving PDCP entity (560) can perform a sequential delivery function and a reordering procedure (565) for said sequential delivery function. The receiving PDCP entity (560) can store a PDCP SDU corresponding to the PDCP PDU in a receiving buffer if the PDCP PDU is not deleted by the procedures described above. The receiving PDCP entity (560) can determine whether the count value of the received PDCP PDU (e.g., 'RCVD_COUNT') is greater than or equal to the count value (RX_NEXT) of the PDCP SDU expected to be received (hereinafter, expected count value). If the count value of the received PDCP PDU (e.g., 'RCVD_COUNT') is greater than or equal to the expected count value (RX_NEXT), the receiving PDCP entity (560) may update the expected count value to the value of the received PDCP PDU (e.g., 'RCVD_COUNT') plus 1. This is because the receiving PDCP entity (560) expects the reception of PDCP SDUs having consecutive count values. The receiving PDCP entity (560) may determine whether the count value of the received PDCP PDU (e.g., 'RCVD_COUNT') is equal to the starting count value ('RX_DELIV'). The receiving PDCP entity (560) can forward all stored PDCP SDUs corresponding to consecutive count values ​​starting from the starting count value ('RX_DELIV') to the upper layer (e.g., SDAP, RRC) if the count value (e.g., 'RCVD_COUNT') of the received PDCP PDU is equal to the starting count value ('RX_DELIV'). The starting count value ('RX_DELIV') can be updated to the count value of the first PDCP SDU that is greater than the current starting count value ('RX_DELIV') and has not been forwarded to the upper layer (e.g., SDAP, RRC).

[0141] If the receiving PDCP entity (560) is running a reorder timer and the start count value is greater than or equal to the count value ('RX_REORD') (hereinafter referred to as the reorder start value) following the count value associated with the PDCP PDU that triggered the reorder timer, the receiving PDCP entity (560) may stop and reset the reorder timer. If the receiving PDCP entity (560) is not running a reorder timer and the start count value ('RX_DELIV') is less than the expected count value (RX_NEXT), the receiving PDCP entity (560) may update the reorder start value ('RX_REORD') to the expected count value (RX_NEXT). If the start count value ('RX_DELIV') is less than the expected count value (RX_NEXT), the receiving PDCP entity (560) may start the reorder timer. Even though there is data that has not yet been transmitted to the upper layer (e.g., SDAP), since the expected count value points to the PDCP SDU following the data, the receiving PDCP entity (560) can start the reorder timer as a reorder procedure (465).

[0142] When the reorder timer expires, the receiving PDCP entity (560) may forward all stored PDCP SDUs associated with count values ​​smaller than the reorder start value ('RX_REORD') to the upper layer (e.g., SDAP, RRC). Even if the intended data (e.g., PDCP SDU) has not been received because the reorder timer has expired, the PDCP SDUs currently stored in the receiving buffer may be reported to the upper layer. When the reorder timer expires, the receiving PDCP entity (560) may forward all stored PDCP SDUs having consecutive count values ​​starting from the reorder start value ('RX_REORD') to the upper layer (e.g., SDAP, RRC). The start count value ('RX_DELIV') may be updated to the count value of the first PDCP SDU that is larger than the reorder start value ('RX_REORD') and has not been forwarded to the upper layer (e.g., SDAP, RRC). The receiving PDCP entity (560) can update the reorder start value ('RX_REORD') to the expected count value (RX_NEXT) if the start count value ('RX_DELIV') is less than the expected count value (RX_NEXT). If the start count value ('RX_DELIV') is less than the expected count value (RX_NEXT), the receiving PDCP entity (560) can start a reorder timer. Even though there is data that has not yet been delivered to the upper layer (e.g., SDAP, RRC), the expected count value points to the PDCP SDU following the data, so the receiving PDCP entity (560) can start the reorder timer as a reorder procedure (565).

[0143] When the reorder timer is reconfigured, the receiving PDCP entity (560) can update the reorder start value ('RX_REORD') to the expected count value (RX_NEXT). When the reorder timer is reconfigured, the receiving PDCP entity (560) can stop and restart the reorder timer.

[0144] The transmitting PDCP entity (510) can sequentially transmit data with count values ​​of 2, 3, 4, …, 9. The receiving PDCP entity (560) can receive a PDCP PDU with a count value of '2'. The receiving PDCP entity (560) can obtain a PDCP SDU from the above PDCP PDU. The receiving PDCP entity (560) can forward the above PDCP SDU with a count value of '2' to an upper layer (e.g., SDAP, RRC). Subsequently, the receiving PDCP entity (560) can expect a PDCP PDU with a count value of '3'. The receiving PDCP entity (560) can receive a PDCP PDU with a count value of '3'. The receiving PDCP entity (560) can obtain a PDCP SDU from the above PDCP PDU. The receiving PDCP entity (560) can forward the PDCP SDU with a count value of '3' to an upper layer (e.g., SDAP, RRC). Subsequently, the receiving PDCP entity (560) can expect a PDCP PDU with a count value of '4'. The receiving PDCP entity (560) can receive a PDCP PDU with a count value of '4'. The receiving PDCP entity (560) can obtain a PDCP SDU from the PDCP PDU. The receiving PDCP entity (560) can forward the PDCP SDU with a count value of '4' to an upper layer (e.g., SDAP, RRC). Subsequently, the receiving PDCP entity (560) can set the starting count value ('RX_DELIV') to '5'. The receiving PDCP entity (560) can expect a PDCP PDU with a count value of '5'.

[0145] In Example (571), a situation is described where a PDCP PDU with a count value of '5' is lost. A receiving PDCP entity (560) may receive a PDCP PDU with a count value of '6' while expecting a PDCP PDU with a count value of '5'. Since a PDCP PDU with a count value of '6' has been received but the starting count value ('RX_DELIV') is '5', the receiving PDCP entity (560) may not perform data transfer to an upper layer (e.g., SDAP, RRC). This is because a PDCP SDU with a count value of '5' has not yet been received. The receiving PDCP entity (560) may store the PDCP SDU corresponding to the PDCP PDU with a count value of '6' in the receiving buffer (581). The receiving PDCP entity (560) may start a reordering timer. Since a PDCP PDU with a count value of '6' has been received, the receiving PDCP entity (560) can expect a PDCP PDU with a count value of '7'. For example, the receiving PDCP entity (560) can set the expected count value (RX_NEXT) to '7'. The receiving PDCP entity (560) can update the reorder start value ('RX_REORD') to the expected count value (RX_NEXT) (e.g., '7').

[0146] The receiving PDCP entity (560) may receive a PDCP PDU with a count value of '7' while expecting a PDCP PDU with a count value of '7'. Since the PDCP PDU with a count value of '7' has been received but the starting count value ('RX_DELIV') is '5', the receiving PDCP entity (560) may not perform data transfer to the upper layer (e.g., SDAP, RRC). This is because a PDCP SDU with a count value of '5' has not yet been received. The receiving PDCP entity (560) may store the PDCP SDU corresponding to the PDCP PDU with a count value of '7' in the receiving buffer (581). The reordering timer may be running. Since a PDCP PDU with a count value of '7' has been received, the receiving PDCP entity (560) may expect a PDCP PDU with a count value of '8'.

[0147] The receiving PDCP entity (560) may receive a PDCP PDU with a count value of '8' while expecting a PDCP PDU with a count value of '8'. Since the PDCP PDU with a count value of '8' has been received but the starting count value ('RX_DELIV') is '5', the receiving PDCP entity (560) may not perform data transfer to the upper layer (e.g., SDAP, RRC). This is because a PDCP SDU with a count value of '5' has not yet been received. The receiving PDCP entity (560) may store the PDCP SDU corresponding to the PDCP PDU with a count value of '8' in the receiving buffer (581). Afterward, the reorder timer may expire. When the above reorder timer expires, the receiving PDCP entity (560) may forward the stored PDCP SDU having a count value smaller than the reorder start value ('RX_REORD') (e.g., 7) (e.g., a PDCP SDU with a count value of 6) and the stored PDCP SDU having consecutive count values ​​greater than or equal to the reorder start value ('RX_REORD') '7' (e.g., a PDCP SDU with a count value of '7', a PDCP SDU with a count value of '8') to the upper layer (e.g., SDAP, RRC).

[0148] In Example (572), a situation is described where a PDCP PDU with a count value of '5' is received late. As in Example (571), the receiving PDCP entity (560) may receive a PDCP PDU with a count value of '6' while expecting a PDCP PDU with a count value of '5'. Since the PDCP PDU with a count value of '6' has been received but the starting count value ('RX_DELIV') is '5', the receiving PDCP entity (560) may not perform data transfer to the upper layer (e.g., SDAP, RRC). This is because the PDCP SDU with a count value of '5' has not yet been received. The receiving PDCP entity (560) may store the PDCP SDU corresponding to the PDCP PDU with a count value of '6' in the receiving buffer (582). The receiving PDCP entity (560) may start a reordering timer. Since a PDCP PDU with a count value of '6' has been received, the receiving PDCP entity (560) can expect a PDCP PDU with a count value of '7'. For example, the receiving PDCP entity (560) can set the expected count value (RX_NEXT) to '7'. The receiving PDCP entity (560) can update the reorder start value ('RX_REORD') to the expected count value (RX_NEXT) (e.g., '7').

[0149] The receiving PDCP entity (560) may receive a PDCP PDU with a count value of '7' while expecting a PDCP PDU with a count value of '7'. Since the PDCP PDU with a count value of '7' has been received but the starting count value ('RX_DELIV') is '5', the receiving PDCP entity (560) may not perform data transfer to the upper layer (e.g., SDAP, RRC). This is because a PDCP SDU with a count value of '5' has not yet been received. The receiving PDCP entity (560) may store the PDCP SDU corresponding to the PDCP PDU with a count value of '7' in the receiving buffer (582). The reordering timer may be running. Since a PDCP PDU with a count value of '7' has been received, the receiving PDCP entity (560) may expect a PDCP PDU with a count value of '8'.

[0150] The receiving PDCP entity (560) may receive a PDCP PDU with a count value of '5' while expecting a PDCP PDU with a count value of '8'. The receiving PDCP entity (560) may receive a PDCP PDU corresponding to the start count value ('RX_DELIV') before the reorder timer expires. Since the start count value ('RX_DELIV') is '5', the receiving PDCP entity (560) may perform data transfer to an upper layer (e.g., SDAP, RRC). The receiving PDCP entity (560) may store a PDCP SDU corresponding to the PDCP PDU with a count value of '5' in the receiving buffer (582). The receiving buffer (582) may store a PDCP SDU associated with a count value of '6', a PDCP SDU associated with a count value of '7', and a PDCP SDU associated with a count value of '5'. The receiving PDCP entity (560) can forward the stored PDCP SDUs to the upper layer (e.g., SDAP, RRC) in ascending order starting from '5'. Meanwhile, a PDCP PDU with a count value of '5' is received, but since the expected count value (RX_NEXT) is '8', the expected count value (RX_NEXT) is not updated.

[0151] The PDCP layer of the NR specification may provide a reordering function (e.g., reordering procedure (565)) that guarantees the packet order for uplink packets. The reordering function may be performed by a receiving PDCP entity (560). When the reordering timer expires or the intended PDCP PDU is received, the receiving PDCP entity (560) may correct the packet order by sorting the PDCP SDUs in ascending order of count values ​​(values ​​corresponding to SN) and delivering the sorted PDCP SDUs to the upper layer (e.g., SDAP, RRC). Referring to the usual procedures, if the PDCP SDU of a specific SN is not received while the reordering timer is operating, the receiving PDCP entity (560) may wait without delivering the PDCP SDU(s) to the upper layer until the reordering timer expires. Afterwards, when the reorder timer expires, the PDCP SDU(s) stored in the receive buffer of the receiving PDCP entity (560) can be transferred to the upper layer (e.g., SDAP, RRC).

[0152] FIG. 6 illustrates a simplified block diagram of a communication device. The communication device (610) may be configured to provide functions of a PDCP (packet data convergence protocol) layer (e.g., PDCP layer (411), PDCP layer (461)). For example, the communication device (610) may correspond to a base station (110). In another example, the communication device (610) may correspond to an upper network node in a distributed deployment. In one example, the communication device (610) may be a CU (central unit) (or CU (control unit)) (360). In one example, the communication device (610) may correspond to a node for performing a reordering procedure in the user plane.

[0153] Referring to FIG. 6, the communication device (610) may include a processor (611), a memory (612), and a transceiver (613).

[0154] The processor (611) controls the overall operations of the communication device (610). The processor (611) may be referred to as a control unit. For example, the processor (611) transmits and receives signals through the transceiver (613) (or through the backhaul communication unit). Additionally, the processor (611) writes and reads data to and from memory (612). Furthermore, the processor (611) can perform functions of the protocol stack required by the communication standard (e.g., functions according to the protocol layer of FIG. 2a, FIG. 2b, FIG. 4a, and FIG. 4b, functions of the PDCP layer). Although only the processor (611) is shown in FIG. 6, according to other implementation examples, the communication device (610) may include two or more processors.

[0155] Memory (612) stores data such as basic programs, application programs, and configuration information for the operation of the communication device (610). Memory (612) may be referred to as a storage unit. Memory (612) may be composed of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. Additionally, memory (612) may provide stored data upon request from the processor (611). Memory (612) represents a storage space as a functional component. For example, memory (612) may be understood not only as representing memory (e.g., hard disk, flash memory, RAM) placed as a component within the communication device (610), but also as representing a space for storing instructions and / or programs.

[0156] The transceiver (613) can perform functions for transmitting and receiving signals in a wired communication environment. The transceiver (613) may include a wired interface for controlling a direct connection between devices through a transmission medium (e.g., copper wire, optical fiber). For example, the transceiver (613) can transmit an electrical signal to another device through a copper wire or perform conversion between an electrical signal and an optical signal. According to one embodiment, the communication device (610) can communicate with a DU (distributed unit) (e.g., a first DU (371), a second DU (372)) through the transceiver (613). The transceiver (613) may also perform functions for transmitting and receiving signals in a wireless communication environment. For example, the transceiver (613) can perform conversion between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the transceiver (613) generates complex symbols by encoding and modulating the transmitted bit sequence. Also, when receiving data, the transceiver (613) restores the received bit sequence by demodulating and decoding the baseband signal. Additionally, the transceiver (613) may include a plurality of transmission and reception paths. According to one embodiment, the communication device (610) may be a base station (110) and may communicate with the terminal (120) directly through a wireless access network or through a radio unit (RU).

[0157] The transceiver (613) transmits and receives signals as described above. Accordingly, all or part of the transceiver (613) may be referred to as a 'communication unit', 'transmitter', 'receiver', or 'transmitter / receiver'. Furthermore, in the following description, transmission and reception performed via a wireless channel are used to mean that processing as described above is performed by the transceiver (613). Although only the transceiver (613) is shown in FIG. 6, according to other embodiments, the communication device (610) may include two or more transceivers.

[0158] The configuration of the communication device (610) shown in FIG. 6 is merely an example, and examples of components of the communication device for performing embodiments of the present disclosure are not limited to the configuration shown in FIG. 6. In some embodiments, some components may be added, deleted, or changed.

[0159] FIGS. 7a through 7c illustrate examples of transmitting packets through a split bearer. In FIGS. 7a through 7c, a communication device (610) may be configured to provide functions of the Packet Data Convergence Protocol (PDCP) layer. For example, the communication device (610) may correspond to a node hosting a PDCP entity (701). The PDCP entity (701) of the communication device (610) may be connected to a first RLC entity (702) and a second RLC entity (703) based on dual connectivity (DC). In FIGS. 7a through 7c, the communication device (610) may include the first RLC entity (702), and another communication device may include the second RLC entity (703). However, this is merely an example and the present disclosure is not limited thereto. For example, a communication device (610) may include a second RLC entity (702), and another communication device may include a first RLC entity (702). In another example, both the first RLC entity (701) and the second RLC entity (702) may be configured within the communication device (610). In yet another example, the communication device (610) may be connected to a first DU (distributed unit) (371) including the first RLC entity (701) and a second DU (372) including the second RLC entity (702).

[0160] Referring to FIG. 7a, the PDCP entity (701) of the communication device (610) can obtain a first DBS (desired buffer size) for the first RLC entity (702) from the first RLC entity (702). The first DBS may directly or indirectly indicate a first channel state (710) between the first RLC entity (702) and the terminal (120). The PDCP entity (701) of the communication device (610) can identify a first throughput based on the first DBS for the first RLC entity (702). In one example, the first throughput may be 200 Mbps (megabits per second).

[0161] The PDCP entity (701) of the communication device (610) can obtain a second DBS for the second RLC entity (703) from the second RLC entity (703). The second DBS may directly or indirectly indicate the second channel state (720) between the second RLC entity (703) and the terminal (120). The PDCP entity (701) of the communication device (610) can identify a second throughput based on the second DBS for the second RLC entity (703). In one example, the second throughput may be 1 Gbps (gigabits per second).

[0162] The PDCP entity (701) of the communication device (610) can identify the ratio of the first throughput to the second throughput. In one example, the ratio of the first throughput to the second throughput may be 20 percent (%). The PDCP entity (701) of the communication device (610) can transmit packets through the first RLC entity (702) and the second RLC entity (703) upon identifying that the ratio of the first throughput to the second throughput exceeds a threshold ratio (e.g., 10%).

[0163] Referring to FIG. 7b, the PDCP entity (701) of the communication device (610) can obtain a third DBS (desired buffer size) for the first RLC entity (702) from the first RLC entity (702). The third DBS may directly or indirectly indicate a third channel state (730) between the first RLC entity (702) and the terminal (120). The PDCP entity (701) of the communication device (610) can identify a third throughput based on the third DBS for the first RLC entity (702). In one example, the first throughput may be 90 Mbps (megabits per second).

[0164] The PDCP entity (701) of the communication device (610) can obtain a fourth DBS for the second RLC entity (703) from the second RLC entity (703). The fourth DBS may directly or indirectly indicate a fourth channel state (740) between the second RLC entity (703) and the terminal (120). The PDCP entity (701) of the communication device (610) can identify a fourth throughput based on the fourth DBS for the second RLC entity (703). In one example, the fourth throughput may be 1 Gbps (gigabits per second).

[0165] The PDCP entity (701) of the communication device (610) can identify the ratio of the third throughput to the fourth throughput. In one example, the ratio of the third throughput to the fourth throughput may be 9%. The ratio below a threshold ratio (e.g., 10%) may indicate a degradation or deterioration of the third channel condition (or air condition) (730) between the first RLC entity (702) and the terminal (120).

[0166] In the above third channel state (730), when the PDCP entity (701) of the communication device (610) transmits packets through both the first RLC entity (702) and the second RLC entity (703), the transmission control protocol (TCP) performance may be degraded by the sequence number (SN) reordering performed at the terminal (120). For example, at least some of the packets transmitted through the first RLC entity (702) may be lost (or delayed) in the air between the first RLC entity (702) and the terminal (120) according to the degraded third channel state (730). If the PDCP entity (701) of the communication device (610) transmits packets through both the first RLC entity (702) and the second RLC entity (703), a delay caused by SN reordering may occur at the terminal (120) due to the loss (or delay) of packets transmitted through the first RLC entity (702). This delay may cause a degradation in TCP performance when packets are transmitted through both the first RLC entity (702) and the second RLC entity (703). Therefore, as illustrated in FIG. 7c, the PDCP entity (701) of the communication device (610) needs to ensure TCP performance according to at least the fourth throughput by refraining from transmitting packets through the first RLC entity (702) and transmitting packets using only the second RLC entity (703).

[0167] FIG. 8 is a flowchart illustrating the operations of a communication device for transmitting packets through a split bearer. The operations of FIG. 8 can be performed by the communication device (610) of FIG. 6. For example, at least some of the operations can be controlled by the processor (611) of the communication device (610). In the following, each operation may be performed sequentially, but is not necessarily performed sequentially. For example, the order of each operation may be changed. For example, at least two operations may be performed in parallel.

[0168] In FIG. 8, the communication device (610) may be configured to provide functions of the packet data convergence protocol (PDCP) layer. The communication device (610) may correspond to a node hosting a PDCP entity. For example, the communication device (610) may correspond to a base station (110). In another example, the communication device (610) may correspond to a higher network node in a distributed deployment. In one example, the communication device (610) may correspond to a central unit (CU) (360). In one example, the communication device (610) may be a node for performing a reordering procedure in the user plane. The communication device (610) may be connected to other communication devices based on dual connectivity (DC). The radio link control (RLC) entity of the communication device (610) is referred to as the first RLC entity, and the RLC entity of another communication device may be referred to as the second RLC entity. However, this is merely an example and the present disclosure is not limited thereto. For example, both the first RLC entity and the second RLC entity may be configured within the communication device (610). In another example, the communication device (610) may be connected to a first distributed unit (DU) containing the first RLC entity and a second DU containing the second RLC entity. In FIG. 8, a situation is described in which the communication device (610) corresponding to the transmitting PDCP entity transmits downlink packets to the terminal (120) through the first RLC entity and / or the second RLC entity.

[0169] Referring to FIG. 8, in operation 801, a communication device (610) according to one embodiment can obtain a first DBS (desired buffer size) for a first RLC entity and a second DBS for a second RLC entity.

[0170] In one embodiment, the communication device (610) may provide a first message for requesting a first downlink data delivery status (DDDS) (or a first protocol data unit (PDU) type 1) for a first RLC entity of a split bearer. For example, the first message may be provided periodically. For example, the first message may be provided with or without a PDCP PDU. In one example, the first message may be referred to as first downlink user data or first PDU type 0. For example, the first message may include an information element (IE) (or parameter) for requesting the first DDDS. The IE (or parameter) may indicate whether to request the provision of the first DDDS. In one example, the IE (or parameter) may be referred to as report polling. For example, the communication device (610) may obtain a first DDDS from a first RLC entity in response to a first message. The first DDDS may include a first DBS of the first RLC entity. For example, the first DBS may directly or indirectly indicate the channel state between the communication device (610) and the terminal (120) including the first RLC entity.

[0171] In one embodiment, the communication device (610) may provide a second message for requesting a second DDDS (or a second PDU type 1) for a second RLC entity of the split bearer. For example, the second message may be provided periodically. For example, the second message may be provided with or without a PDCP PDU. In one example, the second message may be referred to as second DL user data or second PDU type 0. For example, the second message may include an IE (or parameter) for requesting the second DDDS. The IE (or parameter) may indicate whether to request the provision of the second DDDS. In one example, the IE (or parameter) may be referred to as a report polling. For example, the communication device (610) may obtain the second DDDS from the second RLC entity in response to the second message. The second DDDS may include a second DBS of the second RLC entity. For example, the second DBS may directly or indirectly indicate the channel state between the terminal (120) and another communication device including the second RLC entity.

[0172] In operation 802, a communication device (610) according to one embodiment can identify a first throughput and a second throughput.

[0173] In one embodiment, the communication device (610) may identify a first throughput based on a first DBS. For example, the first throughput may represent the amount of data that the communication device (610) can transmit to the terminal (120) through the first RLC entity. For example, the first throughput may correspond to the first DBS. In one example, the first throughput may be indicated based on bits per second (bps). In one example, if the communication device (610) including the first RLC entity corresponds to a master cell group (MCG), the first throughput may be referred to as the MCG throughput. In another example, if the communication device (610) including the first RLC entity corresponds to a secondary cell group (SCG), the first throughput may be referred to as the SCG throughput.

[0174] In one embodiment, the communication device (610) may identify a second throughput based on a second DBS. For example, the second throughput may represent the amount of data that the communication device (610) can transmit to the terminal (120) through the second RLC entity. For example, the second throughput may correspond to a second DBS. In one example, the second throughput may be indicated based on bps. In one example, if another communication device including the second RLC entity corresponds to an SCG, the second throughput may be referred to as SCG throughput. In another example, if another communication device including the second RLC entity corresponds to an MCG, the second throughput may be referred to as MCG throughput.

[0175] In operation 803, a communication device (610) according to one embodiment can identify whether the first throughput is less than the second throughput.

[0176] In operation 804, a communication device (610) according to one embodiment can identify whether the ratio of the first throughput to the second throughput is less than a threshold ratio. In one example, the threshold ratio may be 10 percent (%). However, this is merely an example and the present disclosure is not limited thereto. The communication device (610) can identify the ratio of the first throughput to the second throughput based on the identification that the first throughput is less than the second throughput. The communication device (610) can identify whether the ratio of the first throughput to the second throughput is less than a threshold ratio. For example, whether the ratio of the first throughput to the second throughput is less than a threshold ratio can be identified according to [Equation 1] below.

[0177]

[0178] In operation 805, a communication device (610) according to one embodiment may refrain from transmitting packets through a first RLC entity. For example, the communication device (610) may refrain from transmitting packets to a terminal (120) through the first RLC entity upon identifying that the ratio of the first throughput to the second throughput is less than a threshold ratio. For example, the communication device (610) may refrain from transmitting packets through the first RLC entity even if the first DBS is not zero. For example, the ratio less than the threshold ratio may indicate a degradation or deterioration of the channel condition (or air condition) between the communication device (610) including the first RLC entity and the terminal (120). When the communication device (610) transmits packets through both the first RLC entity and the second RLC entity in the above channel state, the transmission control protocol (TCP) performance may be degraded by sequence number (SN) reordering performed at the terminal (120). In one example, at least some of the packets transmitted through the first RLC entity may be lost (or delayed) in the air between the first RLC entity and the terminal (120). When the communication device (610) transmits packets through both the first RLC entity and the second RLC entity, delays caused by SN reordering at the terminal (120) may occur due to the loss (or delay) of packets transmitted through the first RLC entity. Such delays may cause a decrease in the first throughput for the first RLC entity as well as the second throughput for the second RLC entity. The above delay may cause a decrease in total throughput (e.g., the sum of the first throughput and the second throughput).The above delay may cause a degradation in TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity. In one example, the TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity may be lower than the TCP performance when packets are transmitted through the second RLC entity. Therefore, the communication device (610) can ensure TCP performance according to at least the second throughput by transmitting packets using only the second RLC entity.

[0179] In one embodiment, the split bearer may be maintained even if packets are not transmitted through the first RLC entity. For example, the first RLC bearer between the PDCP entity of the communication device (610) and the first RLC entity may be maintained while packets are not transmitted through the first RLC entity. When the channel condition (or air condition) between the communication device (610) and the terminal (120) improves, the communication device (610) may resume transmitting packets through the first RLC entity. The operations of the communication device (610) to resume transmitting packets through the first RLC entity are described in FIG. 9.

[0180] In operation 806, a communication device (610) according to one embodiment may transmit packets through a first RLC entity and a second RLC entity. For example, the communication device (610) may transmit packets to a terminal (120) through the first RLC entity and the second RLC entity upon identification that the ratio of the first throughput to the second throughput is greater than or equal to a threshold ratio. The communication device (610) may transmit first packets determined based on the first throughput to the terminal (120) through the first RLC entity. The communication device (610) may transmit second packets determined based on the second throughput to the terminal (120) through the second RLC entity. For example, the first packets and the second packets may have consecutive SNs. The first packets and the second packets may be reordered at the terminal (120).

[0181] In operation 807, a communication device (610) according to one embodiment can identify whether the ratio of a second throughput to a first throughput is less than a threshold ratio. In one example, the threshold ratio may be 10 percent (%). However, this is merely an example and the present disclosure is not limited thereto. The communication device (610) can identify the ratio of a second throughput to a first throughput based on the identification that the second throughput is less than the first throughput. The communication device (610) can identify whether the ratio of a second throughput to a first throughput is less than a threshold ratio. For example, whether the ratio of a second throughput to a first throughput is less than a threshold ratio can be identified according to [Equation 2] below.

[0182]

[0183] In operation 808, a communication device (610) according to one embodiment may refrain from transmitting packets through a second RLC entity. For example, the communication device (610) may refrain from transmitting packets to a terminal (120) through a second RLC entity upon identifying that the ratio of the second throughput to the first throughput is below a threshold ratio. For example, the communication device (610) may refrain from transmitting packets through the second RLC entity even if the second DBS is not zero. For example, the ratio below the threshold ratio may indicate a deterioration of the channel condition (or air condition) between another communication device including the second RLC entity and the terminal (120). In the channel condition, if the communication device (610) transmits packets through both the first RLC entity and the second RLC entity, TCP performance may be degraded by SN reordering performed on the terminal (120). In one example, at least some of the packets transmitted through the second RLC entity may be lost (or delayed) in the air between the second RLC entity and the terminal (120). When the communication device (610) transmits packets through both the first RLC entity and the second RLC entity, a delay due to SN reordering may occur at the terminal (120) due to the loss (or delay) of packets transmitted through the second RLC entity. This delay may cause a degradation in TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity. In one example, the TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity may be lower than the TCP performance when packets are transmitted through the first RLC entity. Therefore, the communication device (610) can ensure TCP performance according to at least the first throughput by transmitting packets using only the first RLC entity.

[0184] In one embodiment, the split bearer may be maintained even if packets are not transmitted through the second RLC entity. For example, the second RLC bearer between the PDCP entity of the communication device (610) and the second RLC entity may be maintained while packets are not transmitted through the second RLC entity. When the channel condition (or air condition) between the terminal (120) and another communication device including the second RLC entity improves, the communication device (610) may resume transmitting packets through the second RLC entity. The operations of the communication device (610) to resume transmitting packets through the second RLC entity are described in FIG. 10.

[0185] In operation 809, a communication device (610) according to one embodiment may transmit packets through a second RLC entity. For example, the communication device (610) may transmit packets to a terminal (120) through a first RLC entity and a second RLC entity upon identification that the ratio of the second throughput to the first throughput is greater than or equal to a threshold ratio. The communication device (610) may transmit first packets determined based on the first throughput to the terminal (120) through the first RLC entity. The communication device (610) may transmit second packets determined based on the second throughput to the terminal (120) through the second RLC entity. For example, the first packets and the second packets may have consecutive SNs. The first packets and the second packets may be rearranged at the terminal (120).

[0186] FIG. 9 is a flowchart illustrating the operations of a communication device for transmitting packets through a split bearer. The operations of FIG. 9 can be performed by the communication device (610) of FIG. 6. For example, at least some of the operations can be controlled by the processor (611) of the communication device (610). In the following, each operation may be performed sequentially, but is not necessarily performed sequentially. For example, the order of each operation may be changed. For example, at least two operations may be performed in parallel. The operations according to FIG. 9 may be performed following operation 805 of FIG. 8.

[0187] Referring to FIG. 9, in operation 901, a communication device (610) according to one embodiment can obtain a first DBS (desired buffer size) for a first RLC (radio link control) entity and a second DBS for a second RLC entity while refraining from transmitting packets through a first RLC entity.

[0188] In one embodiment, the communication device (610) may provide a first message for requesting a first DDDS (downlink data delivery status) (or, a first PDU (protocol data unit) type 1) to the first RLC entity of the split bearer while refraining from transmitting packets through the first RLC entity. For example, the first message may be provided without a PDCP PDU. In one example, the first message may be referred to as first DL (downlink) user data or first PDU type 0. For example, the first message may include an IE (information element) (or parameter) for requesting the first DDDS. The IE (or parameter) may indicate whether to request the provision of the first DDDS. In one example, the IE (or parameter) may be referred to as report polling. For example, the communication device (610) may obtain a first DDDS from a first RLC entity in response to a first message. The first DDDS may include a first DBS of the first RLC entity. For example, the first DBS may directly or indirectly indicate the channel state between the communication device (610) and the terminal (120) including the first RLC entity.

[0189] In one embodiment, the communication device (610) may provide a second message for requesting a second DDDS (or a second PDU type 1) for a second RLC entity of the split bearer. For example, the second message may be provided with or without a PDCP PDU. In one example, the second message may be referred to as second DL user data or second PDU type 0. For example, the second message may include an IE (or parameter) for requesting the second DDDS. The IE (or parameter) may indicate whether to request the provision of the second DDDS. In one example, the IE (or parameter) may be referred to as report polling. For example, the communication device (610) may obtain the second DDDS from the second RLC entity in response to the second message. The second DDDS may include the second DBS of the second RLC entity. For example, the second DBS can directly or indirectly indicate the channel state between the terminal (120) and another communication device including the second RLC entity.

[0190] In operation 902, a communication device (610) according to one embodiment can identify a first throughput and a second throughput.

[0191] In one embodiment, the communication device (610) may identify a first throughput based on a first DBS. For example, the first throughput may represent the amount of data that the communication device (610) can transmit to the terminal (120) through the first RLC entity. For example, the first throughput may correspond to the first DBS. In one example, the first throughput may be indicated based on bits per second (bps). In one example, if the communication device (610) including the first RLC entity corresponds to a master cell group (MCG), the first throughput may be referred to as the MCG throughput. In another example, if the communication device (610) including the first RLC entity corresponds to a secondary cell group (SCG), the first throughput may be referred to as the SCG throughput.

[0192] In one embodiment, the communication device (610) may identify a second throughput based on a second DBS. For example, the second throughput may represent the amount of data that the communication device (610) can transmit to the terminal (120) through the second RLC entity. For example, the second throughput may correspond to a second DBS. In one example, the second throughput may be indicated based on bps. In one example, if another communication device including the second RLC entity corresponds to an SCG, the second throughput may be referred to as SCG throughput. In another example, if another communication device including the second RLC entity corresponds to an MCG, the second throughput may be referred to as MCG throughput.

[0193] In operation 903, a communication device (610) according to one embodiment can identify whether the ratio of the first throughput to the second throughput exceeds a threshold ratio.

[0194] In operation 904, a communication device (610) according to one embodiment may resume transmitting packets through a first RLC entity. For example, the communication device (610) may resume transmitting packets through a first RLC entity upon identification that the ratio of the first throughput to the second throughput exceeds a threshold ratio.

[0195] In one embodiment, the communication device (610) can transmit packets through a first RLC entity and a second RLC entity. The communication device (610) can transmit first packets, determined based on a first throughput, to a terminal (120) through the first RLC entity. The communication device (610) can transmit second packets, determined based on a second throughput, to a terminal (120) through the second RLC entity. For example, the first packets and the second packets may have consecutive SNs. The first packets and the second packets may be rearranged at the terminal (120).

[0196] In operation 905, a communication device (610) according to one embodiment may refrain from transmitting packets through a first RLC entity. For example, the communication device (610) may refrain from transmitting packets through a first RLC entity upon identifying that the ratio of the first throughput to the second throughput is less than a threshold ratio.

[0197] In one embodiment, the communication device (610) may refrain from transmitting packets to the terminal (120) through the first RLC entity upon identifying that the ratio of the first throughput to the second throughput is below a threshold ratio. For example, the communication device (610) may refrain from transmitting packets through the first RLC entity even if the first DBS is not zero. For example, the ratio below the threshold ratio may indicate a degradation or deterioration of the channel condition (or air condition) between the communication device (610) and the terminal (120) including the first RLC entity. When the communication device (610) transmits packets through both the first RLC entity and the second RLC entity in the channel condition, the transmission control protocol (TCP) performance may be degraded by sequence number (SN) reordering performed at the terminal (120). In one example, at least some of the packets transmitted through the first RLC entity may be lost (or delayed) in the air between the first RLC entity and the terminal (120). When the communication device (610) transmits packets through both the first RLC entity and the second RLC entity, a delay due to SN reordering may occur at the terminal (120) due to the loss (or delay) of the packets transmitted through the first RLC entity. This delay may cause a degradation in TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity. In one example, the TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity may be lower than the TCP performance when packets are transmitted through the second RLC entity. Therefore, the communication device (610) can ensure TCP performance according to at least the second throughput by transmitting packets using only the second RLC entity.

[0198] FIG. 10 is a flowchart illustrating the operations of a communication device for transmitting packets through a split bearer. The operations of FIG. 10 can be performed by the communication device (610) of FIG. 6. For example, at least some of the operations can be controlled by the processor (611) of the communication device (610). In the following, each operation may be performed sequentially, but is not necessarily performed sequentially. For example, the order of each operation may be changed. For example, at least two operations may be performed in parallel. The operations according to FIG. 10 may be performed following operation 808 of FIG. 8.

[0199] Referring to FIG. 10, in operation 1001, a communication device (610) according to one embodiment can obtain a first DBS (desired buffer size) for a first RLC entity and a second DBS for a second RLC entity while refraining from transmitting packets through a second RLC (radio link control) entity.

[0200] In one embodiment, the communication device (610) may provide a first message for requesting a first DDDS (downlink data delivery status) (or, a first PDU (protocol data unit) type 1) to the first RLC entity of the split bearer while refraining from transmitting packets through the first RLC entity. For example, the first message may be provided without a PDCP PDU. In one example, the first message may be referred to as first DL (downlink) user data or first PDU type 0. For example, the first message may include an IE (information element) (or parameter) for requesting the first DDDS. The IE (or parameter) may indicate whether to request the provision of the first DDDS. In one example, the IE (or parameter) may be referred to as report polling. For example, the communication device (610) may obtain a first DDDS from a first RLC entity in response to a first message. The first DDDS may include a first DBS of the first RLC entity. For example, the first DBS may directly or indirectly indicate the channel state between the communication device (610) and the terminal (120) including the first RLC entity.

[0201] In one embodiment, the communication device (610) may provide a second message for requesting a second DDDS (or a second PDU type 1) for a second RLC entity of the split bearer. For example, the second message may be provided with or without a PDCP PDU. In one example, the second message may be referred to as second DL user data or second PDU type 0. For example, the second message may include an IE (or parameter) for requesting the second DDDS. The IE (or parameter) may indicate whether to request the provision of the second DDDS. In one example, the IE (or parameter) may be referred to as report polling. For example, the communication device (610) may obtain the second DDDS from the second RLC entity in response to the second message. The second DDDS may include the second DBS of the second RLC entity. For example, the second DBS can directly or indirectly indicate the channel state between the terminal (120) and another communication device including the second RLC entity.

[0202] In operation 1002, a communication device (610) according to one embodiment can identify a first throughput and a second throughput.

[0203] In one embodiment, the communication device (610) may identify a first throughput based on a first DBS. For example, the first throughput may represent the amount of data that the communication device (610) can transmit to the terminal (120) through the first RLC entity. For example, the first throughput may correspond to the first DBS. In one example, the first throughput may be indicated based on bits per second (bps). In one example, if the communication device (610) including the first RLC entity corresponds to a master cell group (MCG), the first throughput may be referred to as the MCG throughput. In another example, if the communication device (610) including the first RLC entity corresponds to a secondary cell group (SCG), the first throughput may be referred to as the SCG throughput.

[0204] In one embodiment, the communication device (610) may identify a second throughput based on a second DBS. For example, the second throughput may represent the amount of data that the communication device (610) can transmit to the terminal (120) through the second RLC entity. For example, the second throughput may correspond to a second DBS. In one example, the second throughput may be indicated based on bps. In one example, if another communication device including the second RLC entity corresponds to an SCG, the second throughput may be referred to as SCG throughput. In another example, if another communication device including the second RLC entity corresponds to an MCG, the second throughput may be referred to as MCG throughput.

[0205] In operation 1003, a communication device (610) according to one embodiment can identify whether the ratio of the second throughput to the first throughput exceeds a threshold ratio.

[0206] In operation 1004, a communication device (610) according to one embodiment may resume transmitting packets through a second RLC entity. For example, the communication device (610) may resume transmitting packets through a second RLC entity upon identification that the ratio of the second throughput to the first throughput exceeds a threshold ratio.

[0207] In one embodiment, the communication device (610) can transmit packets through a first RLC entity and a second RLC entity. The communication device (610) can transmit first packets, determined based on a first throughput, to a terminal (120) through the first RLC entity. The communication device (610) can transmit second packets, determined based on a second throughput, to a terminal (120) through the second RLC entity. For example, the first packets and the second packets may have consecutive SNs. The first packets and the second packets may be rearranged at the terminal (120).

[0208] In operation 1005, a communication device (610) according to one embodiment may refrain from transmitting packets through a second RLC entity. For example, the communication device (610) may refrain from transmitting packets through a second RLC entity upon identifying that the ratio of the second throughput to the first throughput is less than a threshold ratio.

[0209] In one embodiment, the communication device (610) may refrain from transmitting packets to the terminal (120) through the second RLC entity upon identifying that the ratio of the second throughput to the first throughput is below a threshold ratio. For example, the communication device (610) may refrain from transmitting packets through the second RLC entity even if the second DBS is not zero. For example, the ratio below the threshold ratio may indicate a degradation or deterioration of the channel condition (or air condition) between the second RLC entity and the terminal (120). When the communication device (610) transmits packets through both the first RLC entity and the second RLC entity in the channel condition, the transmission control protocol (TCP) performance may be degraded by sequence number (SN) reordering performed at the terminal (120). In one example, at least some of the packets transmitted through the second RLC entity may be lost (or delayed) in the air between the second RLC entity and the terminal (120). When the communication device (610) transmits packets through both the first RLC entity and the second RLC entity, a delay due to SN reordering may occur at the terminal (120) due to the loss (or delay) of packets transmitted through the second RLC entity. This delay may cause a degradation in TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity. In one example, the TCP performance when packets are transmitted through both the first RLC entity and the second RLC entity may be lower than the TCP performance when packets are transmitted through the first RLC entity. Therefore, the communication device (610) can ensure TCP performance according to at least the first throughput by transmitting packets using only the first RLC entity.

[0210] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure pertains.

[0211] A communication device providing the functions of a PDCP (packet data convergence protocol) entity as described above may include at least one processor including a processing circuit. The communication device may include a memory that stores instructions and includes one or more storage media. When the instructions are executed individually or collectively by the at least one processor, the communication device may cause the first DBS (desired buffer size) for a first RLC (radio link control) entity of a split bearer and a second DBS for a second RLC entity of the split bearer. When the above instructions are executed individually or collectively by the at least one processor, the communication device may cause to identify the ratio of the first throughput to the second throughput based on the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS. Upon identifying that the ratio of the first throughput to the second throughput is below a threshold ratio, the communication device may cause to refrain from transmitting packets through the first RLC entity while the split bearer is maintained. When the above instructions are executed individually or collectively by the at least one processor, the communication device may cause to transmit packets through the second RLC entity based on the second throughput.

[0212] For example, when the above instructions are executed individually or collectively by the at least one processor, the communication device may cause the first RLC entity to provide a message to the first RLC entity to request a DDDS (downlink data delivery status) including DBS for the first RLC entity of the split bearer while refraining from transmitting packets through the first RLC entity of the split bearer.

[0213] For example, when the above instructions are executed individually or collectively by the at least one processor, the communication device may cause to acquire a third DBS for the first RLC entity and a fourth DBS for the second RLC entity while refraining from transmitting packets through the first RLC entity of the split bearer. When the above instructions are executed individually or collectively by the at least one processor, the ratio of the third throughput to the fourth throughput may be identified based on a third throughput for the first RLC entity corresponding to the third DBS and a fourth throughput for the second RLC entity corresponding to the fourth DBS. The above instructions may cause packets to be transmitted through a first RLC bearer between the PDCP entity and the first RLC entity while refraining from transmitting packets through the first RLC entity, upon identification that the ratio of the third throughput to the fourth throughput exceeds the threshold ratio when executed individually or collectively by the at least one processor.

[0214] For example, when the instructions are executed individually or collectively by the at least one processor, the communication device may be caused to identify the ratio of the second throughput to the first throughput based on the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS. When the instructions are executed individually or collectively by the at least one processor, the communication device may be caused to refrain from transmitting packets through the second RLC entity while the split bearer is maintained, upon identifying that the ratio of the second throughput to the first throughput is less than the threshold ratio.

[0215] For example, when the above instructions are executed individually or collectively by the at least one processor, the communication device may cause the second RLC entity to provide a message to the second RLC entity for requesting a DDDS including a DBS for the second RLC entity of the split bearer while refraining from transmitting packets through the second RLC entity of the split bearer.

[0216] For example, when the above instructions are executed individually or collectively by the at least one processor, the communication device may cause to acquire a fifth DBS for the first RLC entity and a sixth DBS for the second RLC entity while refraining from transmitting packets through the second RLC entity of the split bearer. When the above instructions are executed individually or collectively by the at least one processor, the communication device may cause to identify the ratio of the sixth throughput to the fifth throughput based on the fifth throughput for the first RLC entity corresponding to the fifth DBS and the sixth throughput for the second RLC entity corresponding to the sixth DBS. When the above instructions are executed individually or collectively by the at least one processor, the communication device may cause packets to be transmitted through a second RLC bearer between the PDCP entity and the second RLC entity while refraining from transmitting packets through the second RLC entity upon identification that the ratio of the sixth throughput to the fifth throughput exceeds the threshold ratio.

[0217] For example, when the instructions are executed individually or collectively by the at least one processor, the communication device may be caused to identify whether the ratio of the first throughput to the second throughput is less than a threshold ratio, upon identifying that the first throughput is less than the second throughput. When the instructions are executed individually or collectively by the at least one processor, the communication device may be caused to transmit consecutive packets to a terminal through the first RLC entity and the second RLC entity, upon identifying that the ratio of the first throughput to the second throughput exceeds the threshold ratio. The packets of the consecutive packets may include a sequence number (SN) indicating the order of the packets in the consecutive packets.

[0218] For example, the SNs of the above consecutive packets can be used for reordering the above consecutive packets performed at the terminal.

[0219] For example, the first DBS may represent the state of the channel between the first RLC entity and the terminal. The second DBS may represent the state of the channel between the second RLC entity and the terminal.

[0220] For example, the communication device may include a central unit (CU).

[0221] A method performed by a communication device providing the functions of a PDCP (packet data convergence protocol) entity as described above may include an operation of obtaining a first DBS (desired buffer size) for a first RLC (radio link control) entity of a split bearer and a second DBS for a second RLC entity of the split bearer. The method may include an operation of identifying the ratio of the first throughput to the second throughput based on a first throughput for the first RLC entity corresponding to the first DBS and a second throughput for the second RLC entity corresponding to the second DBS. The method may include an operation of refraining from transmitting packets through the first RLC entity while the split bearer is maintained, upon identifying that the ratio of the first throughput to the second throughput is less than a threshold ratio. The above method may include the operation of transmitting packets through the second RLC entity based on the second throughput.

[0222] For example, the above method may include the operation of providing a message to the first RLC entity to request a DDDS (downlink data delivery status) including DBS for the first RLC entity of the split bearer while refraining from transmitting packets through the first RLC entity of the split bearer.

[0223] For example, the method may include the operation of obtaining a third DBS for the first RLC entity and a fourth DBS for the second RLC entity while refraining from transmitting packets through the first RLC entity of the split bearer. The method may include the operation of identifying the ratio of the third throughput to the fourth throughput based on the third throughput for the first RLC entity corresponding to the third DBS and the fourth throughput for the second RLC entity corresponding to the fourth DBS. The method may include the operation of transmitting packets through a first RLC bearer between the PDCP entity and the first RLC entity, which is maintained while refraining from transmitting packets through the first RLC entity, upon identification that the ratio of the third throughput to the fourth throughput exceeds the threshold ratio.

[0224] For example, the method may include an operation of identifying the ratio of the second throughput to the first throughput based on the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS. The method may include an operation of refraining from transmitting packets through the second RLC entity while the split bearer is maintained, upon identifying that the ratio of the second throughput to the first throughput is less than the threshold ratio.

[0225] For example, the above method may include the operation of providing a message to the second RLC entity to request a DDDS including a DBS for the second RLC entity of the split bearer while refraining from transmitting packets through the second RLC entity of the split bearer.

[0226] For example, the method may include the operation of obtaining a fifth DBS for the first RLC entity and a sixth DBS for the second RLC entity while refraining from transmitting packets through the second RLC entity of the split bearer. The method may include the operation of identifying the ratio of the sixth throughput to the fifth throughput based on the fifth throughput for the first RLC entity corresponding to the fifth DBS and the sixth throughput for the second RLC entity corresponding to the sixth DBS. The method may include the operation of transmitting packets through a second RLC bearer between the PDCP entity and the second RLC entity, which is maintained while refraining from transmitting packets through the second RLC entity, upon identification that the ratio of the sixth throughput to the fifth throughput exceeds the threshold ratio.

[0227] For example, the method may include an operation of identifying whether the ratio of the first throughput to the second throughput is less than a threshold ratio, based on the identification that the first throughput is less than the second throughput. The method may include an operation of transmitting consecutive packets to a terminal through the first RLC entity and the second RLC entity, based on the identification that the ratio of the first throughput to the second throughput exceeds the threshold ratio.

[0228] For example, the SNs of the above consecutive packets can be used for reordering the above consecutive packets performed at the terminal.

[0229] For example, the first DBS may represent the state of the channel between the first RLC entity and the terminal. The second DBS may represent the state of the channel between the second RLC entity and the terminal.

[0230] For example, the communication device may include a central unit (CU).

[0231]

[0232] A communication device according to the present disclosure can transmit packets through a split bearer. A communication device according to the present disclosure can prevent a decrease in total throughput by stopping packet distribution for one of the paths of the split bearer when the channel condition (or air condition) deteriorates for that path. A communication device according to the present disclosure can guarantee TCP (transmission control protocol) performance based on the throughput of another path by stopping packet distribution for that path when the channel condition (or air condition) deteriorates for one of the paths of the split bearer. A communication device according to the present disclosure can reduce the frequency of sequence number (SN) renumbering operations performed at a terminal by stopping packet distribution for that path when the channel condition (or air condition) deteriorates for one of the paths of the split bearer.

[0233] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs.

[0234] Methods according to the claims or embodiments described in the specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0235] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of this disclosure. The one or more programs may be provided as a computer program product. The computer program product may be traded between a seller and a buyer as a product. The computer program product may be distributed in the form of a device-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or distributed online (e.g., download or upload) through an application store (e.g., Play Store™) or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product may be temporarily stored or temporarily created on a device-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or a relay server.

[0236] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disc storage devices, compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0237] Additionally, the program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, LAN (local area network), WAN (wide area network), or SAN (storage area network), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port. Additionally, a separate storage device on a communication network may be connected to a device performing an embodiment of the present disclosure.

[0238] In the specific embodiments of the present disclosure described above, the components included in the disclosure are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present disclosure is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed of a singular form, and even if a component is expressed in the singular form, it may be composed of a plural form.

[0239] According to the embodiments, one or more of the aforementioned components or operations may be omitted, or one or more other components or operations may be added. Generally or additionally, a plurality of components (e.g., a module or a program) may be integrated into a single component. In this case, the integrated component may perform one or more functions of each of the plurality of components in the same or similar manner as those performed by the corresponding component among the plurality of components prior to the integration. According to the embodiments, operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order, omitted, or one or more other operations may be added.

[0240] Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, it is understood that various modifications are possible within the scope of the present disclosure.

Claims

1. In a communication device that provides the functions of a PDCP (packet data convergence protocol) entity, At least one processor including a processing circuit; and Memory that stores instructions and includes one or more storage media, When the above instructions are executed individually or collectively by the at least one processor, the communication device, Obtain a first DBS (desired buffer size) for a first RLC (radio link control) entity of a split bearer and a second DBS for a second RLC entity of the split bearer, and Based on a first throughput for the first RLC entity corresponding to the first DBS and a second throughput for the second RLC entity corresponding to the second DBS, the ratio of the first throughput to the second throughput is identified, and Upon identification that the ratio of the first throughput to the second throughput is below a threshold ratio, while the split bearer is maintained, refrain from transmitting packets through the first RLC entity, and Causing to transmit packets through the second RLC entity based on the second throughput, Communication device.

2. In Paragraph 1, When the above instructions are executed individually or collectively by the at least one processor, the communication device, Causing to provide the first RLC entity with a message requesting a DDDS (downlink data delivery status) including DBS for the first RLC entity of the split bearer while refraining from transmitting packets through the first RLC entity of the split bearer, Communication device.

3. In Paragraph 1, When the above instructions are executed individually or collectively by the at least one processor, the communication device, While refraining from transmitting packets through the first RLC entity of the split bearer, obtain a third DBS for the first RLC entity and a fourth DBS for the second RLC entity, Based on the third throughput for the first RLC entity corresponding to the third DBS and the fourth throughput for the second RLC entity corresponding to the fourth DBS, the ratio of the third throughput to the fourth throughput is identified, and Causing to transmit packets through a first RLC bearer between the PDCP entity and the first RLC entity, which is maintained while refraining from transmitting packets through the first RLC entity, upon identification that the ratio of the third throughput to the fourth throughput exceeds the threshold ratio. Communication device.

4. In Paragraph 1, When the above instructions are executed individually or collectively by the at least one processor, the communication device, Based on the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS, the ratio of the second throughput to the first throughput is identified, and Causing to refrain from transmitting packets through the second RLC entity while the split bearer is maintained, upon identification that the ratio of the second throughput to the first throughput is less than the threshold ratio. Communication device.

5. In Paragraph 4, When the above instructions are executed individually or collectively by the at least one processor, the communication device, Causing to provide the second RLC entity with a message for requesting a DDDS including a DBS for the second RLC entity of the split bearer while refraining from transmitting packets through the second RLC entity of the split bearer, Communication device.

6. In Paragraph 4, When the above instructions are executed individually or collectively by the at least one processor, the communication device, While refraining from transmitting packets through the second RLC entity of the split bearer, obtain the fifth DBS for the first RLC entity and the sixth DBS for the second RLC entity, Based on the fifth throughput for the first RLC entity corresponding to the fifth DBS and the sixth throughput for the second RLC entity corresponding to the sixth DBS, the ratio of the sixth throughput to the fifth throughput is identified, and Causing to transmit packets through a second RLC bearer between the PDCP entity and the second RLC entity, which is maintained while refraining from transmitting packets through the second RLC entity, upon identification that the ratio of the sixth throughput to the fifth throughput exceeds the threshold ratio. Communication device.

7. In Paragraph 1, When the above instructions are executed individually or collectively by the at least one processor, the communication device, Based on the identification that the first throughput is less than the second throughput, the ratio of the first throughput to the second throughput is identified as being less than a threshold ratio, and Upon identification that the ratio of the first throughput to the second throughput exceeds the threshold ratio, continuous packets are transmitted to the terminal through the first RLC entity and the second RLC entity, and The packet of the above consecutive packets includes a sequence number (SN) indicating the order of the packets in the above consecutive packets, Communication device.

8. In Paragraph 7, The SNs of the above consecutive packets are used for reordering the above consecutive packets performed at the terminal, Communication device.

9. In Paragraph 1, The above first DBS indicates the state of the channel between the above first RLC entity and the terminal, and The above second DBS indicates the state of the channel between the above second RLC entity and the terminal, Communication device.

10. In Paragraph 1, The above communication device includes a CU (central unit), Communication device.

11. A method performed by a communication device that provides the functions of a PDCP (packet data convergence protocol) entity, An operation to obtain a first DBS (desired buffer size) for a first RLC (radio link control) entity of a split bearer and a second DBS for a second RLC entity of the split bearer; An operation to identify the ratio of the first throughput to the second throughput based on the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS; An operation to refrain from transmitting packets through the first RLC entity while the split bearer is maintained, upon identification that the ratio of the first throughput to the second throughput is less than a threshold ratio; and Based on the second throughput, the operation of transmitting packets through the second RLC entity, method.

12. In Paragraph 11, further comprising the operation of providing a message to the first RLC entity to request a DDDS (downlink data delivery status) including DBS for the first RLC entity of the split bearer while refraining from transmitting packets through the first RLC entity of the split bearer. method.

13. In Paragraph 11, The operation of obtaining a third DBS for the first RLC entity and a fourth DBS for the second RLC entity while refraining from transmitting packets through the first RLC entity of the split bearer; An operation to identify the ratio of the third throughput to the fourth throughput based on the third throughput for the first RLC entity corresponding to the third DBS and the fourth throughput for the second RLC entity corresponding to the fourth DBS; and Further including the operation of transmitting packets through a first RLC bearer between the PDCP entity and the first RLC entity, which is maintained while refraining from transmitting packets through the first RLC entity, upon identification that the ratio of the third throughput to the fourth throughput exceeds the threshold ratio. method.

14. In Paragraph 11, An operation to identify the ratio of the second throughput to the first throughput based on the first throughput for the first RLC entity corresponding to the first DBS and the second throughput for the second RLC entity corresponding to the second DBS; and A further operation comprising refraining from transmitting packets through the second RLC entity while the split bearer is maintained, upon identification that the ratio of the second throughput to the first throughput is less than the threshold ratio. method.

15. In Paragraph 14, The method further includes the operation of providing a message to the second RLC entity to request a DDDS including a DBS for the second RLC entity of the split bearer while refraining from transmitting packets through the second RLC entity of the split bearer. method.

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