Method for multi-connection

Abstract

The present invention provides a method for multi-connection. The method for implementing multi-connection between a plurality of base stations and a user equipment includes: estimating, at the user equipment, a first round-trip time (RTT) spent on sending first data to a first base station; estimating, at the user equipment, a second round-trip time spent on sending second data to a second base station; and determining, based on the first round-trip time and the second round-trip time, the size of the first data to be sent to the first base station.

Description

[0001] [Cross - reference to related applications]

[0002] This application claims the priority of Korean Patent Application No. 10 - 2018 - 0123273, filed on October 16, 2018, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0003] The present inventive concept relates to wireless communication, and more particularly, to a method and an apparatus for splitting data in multi - connection. Background Art

[0004] In wireless communication between a user equipment and a base station, various techniques can be used to send a larger amount of data at a higher speed. For example, multi - connection may represent a process in which one user equipment communicates with two or more base stations. In multi - connection, data can be sent and / or received via multiple channels between the user equipment and two or more base stations, and thus the data throughput can be increased and the communication quality can be prevented from deteriorating due to a poor - quality channel. To improve the efficiency of multi - connection, it is desirable to efficiently distribute the transmitted data to multiple channels. Summary of the Invention

[0005] The present inventive concept provides a method and an apparatus for efficiently splitting data in multi - connection.

[0006] According to an aspect of the present inventive concept, there is provided a method for implementing multi - connection between a plurality of base stations and a user equipment, the method including: estimating, at the user equipment, a first round - trip time (RTT) taken to send first data to a first base station; estimating, at the user equipment, a second round - trip time taken to send second data to a second base station; and determining, at the user equipment, a size of the first data to be sent to the first base station based on the first round - trip time and the second round - trip time.

[0007] According to another aspect of the present inventive concept, there is provided a method for implementing multi - connection between a plurality of base stations and a user equipment, the method including: estimating, at the first base station, a first round - trip time taken to send first data from the first base station to the user equipment; obtaining, at the first base station, a second round - trip time taken to send second data from a second base station to the user equipment; and determining, at the first base station, a size of the first data to be sent from the first base station to the user equipment based on the first round - trip time and the second round - trip time.

[0008] According to another aspect of the inventive concept, there is provided a method for implementing multi-connection between a plurality of base stations and a user equipment, the method comprising: estimating a plurality of round-trip times (RTTs) spent on transmitting data and receiving an acknowledgement response (ACK) via a plurality of channels between the plurality of base stations and the user equipment; obtaining respective channel bandwidths of the plurality of channels; and determining sizes of a plurality of divided data to be transmitted via the plurality of channels based on the plurality of round-trip times and the channel bandwidths. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments of the inventive concept will be more clearly understood by reading the following detailed description in conjunction with the accompanying drawings, in which:

[0010] Figure 1 is a diagram illustrating multi-connection according to an exemplary embodiment.

[0011] Figure 2 is a diagram illustrating Figure 1 the structure of a wireless protocol in the multi-connection shown according to an exemplary embodiment.

[0012] Figure 3 is a diagram illustrating the structure of a wireless protocol in a user equipment according to an exemplary embodiment.

[0013] Figure 4 is a flowchart illustrating a method for implementing multi-connection according to an exemplary embodiment.

[0014] Figure 5 is a flowchart illustrating a method for implementing multi-connection according to an exemplary embodiment.

[0015] Figure 6 is a diagram illustrating Figure 4 a flowchart of operation S200 shown according to an exemplary embodiment.

[0016] Figure 7A and Figure 7B is a diagram illustrating Figure 6 a flowchart of operation S240 shown according to an exemplary embodiment.

[0017] Figure 8 is a diagram illustrating Figure 4 a flowchart of operation S600 shown according to an exemplary embodiment.

[0018] Figure 9A and Figure 9B is a diagram illustrating Figure 8 a flowchart of operation S640 shown according to an exemplary embodiment.

[0019] Figure 10 is a block diagram of a user equipment according to an exemplary embodiment.

[0020] Figure 11A and Figure 11B is a diagram showing a method for implementing multi-connection with respect to a time flow according to an exemplary embodiment.

[0021] Figure 12 is a diagram showing multi-connection according to an exemplary embodiment.

[0022] Figure 13A and Figure 13B is a diagram showing a method for implementing multi-connection with respect to a time flow according to an exemplary embodiment. Detailed Description

[0023] Figure 1 is a diagram showing multi-connection according to an exemplary embodiment. Specifically, Figure 1 is a diagram showing a plurality of wireless communication systems, the plurality of wireless communication systems including a first wireless communication system RAT1 and a second wireless communication system RAT2 that respectively include a user equipment (UE) 30 and a plurality of base stations, and the plurality of base stations including a first base station 10 and a second base station 20.

[0024] In a non-limiting embodiment, each of the first wireless communication system RAT1 and the second wireless communication system RAT2 may be a fifth-generation (5 th generation, 5G) system, a fifth-generation new radio (5G NR) system, a long term evolution (LTE) system, a code division multiple access (CDMA) system, a global system for mobile communication (GSM) system, a wireless local area network (WLAN) system, or any other arbitrary wireless communication system. Herein, a wireless communication system may be referred to as a radio access technology (RAT).

[0025] The first base station 10 and the second base station 20 may communicate with the UE 30 based on multi-connection. For example, as Figure 1As shown, a first channel CH1 can be established between the UE 30 and the first base station 10 according to the first radio access technology RAT1 of the first radio communication system, and communication can be performed with each other via the first channel CH1. A second channel CH2 can be established between the UE 30 and the second base station 20 according to the second radio access technology RAT2 of the second radio communication system, and communication can be performed with each other via the second channel CH2. In some embodiments, the first radio access technology RAT1 of the first radio communication system can be the same as the second radio access technology RAT2 of the second radio communication system. In some other embodiments, the first radio access technology RAT1 of the first radio communication system can be different from the second radio access technology RAT2 of the second radio communication system. Hereinafter, in an exemplary embodiment, an example in which the first radio access technology RAT1 is a 5G NR system (i.e., the first base station 10 is a 5G NR base station) and the second radio access technology RAT2 is an LTE system (i.e., the second base station 20 is an LTE base station) will be mainly described. However, it should be understood that the exemplary embodiment is not limited thereto.

[0026] A base station (for example, the first base station 10 and / or the second base station 20) can represent a fixed station and can communicate with the UE 30 and / or another base station to exchange data and control information. For example, a base station can be referred to as a Node B, an evolved Node B (eNB), a next-generation Node B (gNB), a sector, a site, a base transceiver system (BTS), an access point (AP), a relay node, a remote radio head (RRH), a radio unit (RU), or a small cell. Herein, a base station or a cell can be regarded as representing the comprehensive meaning of the function implemented by a base station controller (BSC) in CDMA, a Node B in wideband code division multiple access (WCDMA), an eNB in LTE, or a gNB or a sector (site) in 5G NR, and can cover various coverage areas such as: a mega cell, a micro cell, a pico cell, a femto cell, a relay node, an RRH, an RU, and the communication range of a small cell.

[0027] UE 30 may be a wireless communication device and may be fixed or mobile. In addition, UE 30 may represent various devices that communicate with a base station to send or receive data and / or control information. For example, UE 30 may be referred to as a terminal device, a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, or a handheld device. In addition, UE 30 may support multiple connections, and therefore, as shown in FIG. Figure 1 As shown, UE 30 can be connected to two or more base stations, such as a first base station 10 and a second base station 20. Specifically, as Figure 1 As shown, a UE 30 connected to two base stations (e.g., a first base station 10 and a second base station 20) may be referred to as dual connectivity. Hereinafter, in exemplary embodiments, dual connectivity will be mainly described, but it should be understood that exemplary embodiments are applicable to multi-connectivity in which the UE 30 communicates with three or more base stations.

[0028] The wireless communication network between the first base station 10 and the second base station 20 and the UE 30 can share available network resources and, therefore, can support multiple users. For example, information can be transmitted via the wireless communication network using various multiple access schemes such as CDMA, frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), orthogonal frequency division multiplexing (OFDM)-FDMA, OFDM-TDMA and OFDM-CDMA. The first base station 10 can communicate with the second base station 20 via the interface IF. In some embodiments, the first base station 10 can access the second base station 20 via a double (X2) interface. In some other embodiments, as described below with reference to Figure 12 As described above, the first base station 10 can access the second base station 20 via the core network.

[0029] In multi-connection, data can be segmented and transmitted, and the segmented parts of the data (e.g., first data and second data) can be transmitted via a first channel CH1 and a second channel CH2, respectively. For example, in the downlink, the first base station 10 and the second base station 20 can transmit the first data and the second data obtained by segmenting the data to be transmitted to the UE 30 via the first channel CH1 and the second channel CH2, respectively. In addition, in the uplink, the UE 30 can segment the data to be transmitted into the first data and the second data and can transmit the first data and the second data to the first base station 10 and the second base station 20 via the first channel CH1 and the second channel CH2, respectively. Hereinafter, according to an exemplary embodiment, as described below with reference to the drawings, the UE 30, and the first base station 10 and the second base station 20 can efficiently segment data based on the state of each of the first channel CH1 and the second channel CH2. Therefore, the delay caused by reordering the data can be reduced, and an improved quality of experience (QoE) can be provided to the user of the UE 30.

[0030] Figure 2 is a diagram showing Figure 1 the structure of the radio protocol in the multi-connection shown according to an exemplary embodiment.

[0031] As referred to above Figure 1 stated, the UE 30' can access the first base station 10' and the second base station 20'. In Figure 2 this case, it can be assumed that the first base station 10' is a base station of a 5G NR system (e.g., gNB), and the base station 20' is a base station of an LTE system (e.g., eNB). As Figure 2 shown, the UE 30' (or the packet data convergence protocol (PDCP) of the UE 30') can support the radio protocol of the first radio communication system RAT1 (e.g., 5G NR system) and the radio protocol of the second radio communication system RAT2 (e.g., LTE system). Hereinafter, with reference to Figure 1 it will be described Figure 2 .

[0032] Referring to Figure 2, in each of the first base station 10' and the UE 30', the radio protocol of the first radio communication system RAT1 may include a physical (PHY) layer 11 and 31a, a medium access control (MAC) 12 and 32a, a radio link control (RLC) 13 and 33a, and a PDCP 14 and 34. Each of the PHY layer 11 and 31a, the MAC 12 and 32a, the RLC 13 and 33a, and the PDCP 14 and 34 may perform its unique function based on the provisions of the first radio communication system RAT1. For example, the PHY layer 11 and 31a may encode and modulate the data of the MAC 12 and 32a, generate OFDM symbols to transmit the generated OFDM symbols to the first channel CH1, demodulate and decode the OFDM symbols received via the first channel CH1, and transmit the data to the MAC 12 and 32a. The MAC 12 and 32a may perform functions including hybrid automatic repeat request (HARQ) retransmission, the RLC 13 and 33a may perform functions including automatic repeat request (ARQ), and the PDCP 14 and 34 may perform functions including reordering.

[0033] In each of the second base station 20' and the UE 30', the radio protocol of the second radio communication system RAT2 may include a PHY layer 21 and 31b, a MAC 22 and 32b, an RLC 23 and 33b, and a PDCP 24 and 34. Each of the PHY layer 21 and 31b, the MAC 22 and 32b, the RLC 23 and 33b, and the PDCP 24 and 34 may perform its unique function based on the provisions of the second radio communication system RAT2. For example, the PHY layer 21 and 31b may encode and modulate the data of the MAC 22 and 32b, generate OFDM symbols to transmit the generated OFDM symbols to the second channel CH2, demodulate and decode the OFDM symbols received via the second channel CH2, and transmit the data to the MAC 22 and 32b. The MAC 22 and 32b may perform functions including HARQ retransmission, the RLC 23 and 33b may perform functions including ARQ, and the PDCP 24 and 34 may perform functions including reordering.

[0034] PDCP 34 may include a split bearer in dual connectivity. The split bearer may distribute data packets to multiple different RLC entities in one PDCP to transmit data via multiple channels, and thus, may represent a data radio bearer (DRB) for improving the data transmission rate. For example, in the uplink, PDCP 34 may process data packets (or PDCP service data units (SDUs)) into PDCP protocol data units (PDUs) and may transmit the PDCP PDUs to two RLC entities 33a and 33b. Here, when the PDCP PDUs transmitted to the two RLC entities 33a and 33b are not properly distributed (i.e., when the size of the split data is not properly determined), the delay caused by reordering in PDCP 34 may increase. When the delay caused by reordering increases, a delay may occur in the upper layer of PDCP 34 (e.g., the application layer (e.g., Figure 3 as shown in 35)), deteriorating the user QoE of the UE 30'. In addition, a problem similar to the above problem may occur in the downlink.

[0035] Figure 3 is a diagram showing the structure of a radio protocol in the UE 30'' according to an exemplary embodiment. Specifically, Figure 3 shows the structure of the radio protocol in the uplink. Hereinafter, reference will be made to Figure 1 elaborate Figure 3 and when elaborating Figure 3 the description identical or similar to that provided with reference to Figure 2 will be omitted.

[0036] Referring to Figure 3 the radio protocol may include a first PHY layer 31a' of a first radio access technology (RAT) 1 of a first wireless communication system, a first MAC 32a', and a first RLC 33a', and may include a second PHY layer 31b' of a second RAT 2 of a second wireless communication system, a second MAC 32b', and a second RLC 33b', and PDCP 34' may support the first RAT 1 of the first wireless communication system and the second RAT 2 of the second wireless communication system. In addition, an application 35 corresponding to the upper layer of PDCP 34' may provide data packets to be transmitted via the uplink to PDCP 34'.

[0037] As referred to above with reference to Figure 2As described above, PDCP 34' can determine data to be transmitted via a first channel CH1 and a second channel CH2 in a multi-connection (e.g., the size of first data and the size of second data), and thus, can split data packets provided from application 35 and can provide multiple pieces of split data to a first RLC (or a first RLC entity) 33a' and a second RLC (or a second RLC entity) 33b' respectively. For example, according to the recently released NR PDCP standard (3GPP TS38.323 V15.2.0, 2018-06), means for minimizing the PDCP reordering delay caused by the data splitting operation performed by UE 30” is defined as the capability of UE 30”.

[0038] In some embodiments, multiple indicators can be provided to PDCP 34' from a lower layer, and data can be distributed to the first RLC 33a' and the second RLC 33b' based on the multiple indicators. For example, as Figure 3 shown, a first indicator IND1 can be provided to PDCP 34' from a first PHY layer 31a', a first MAC 32a' and a first RLC 33a', and a second indicator IND2 can be provided to PDCP 34' from a second PHY layer 31b', a second MAC 32b' and a second RLC 33b'. PDCP 34' can detect the state of the first channel CH1 and the state of the second channel CH2 based on the first indicator IND1 and the second indicator IND2, and can distribute data to the first RLC 33a' and the second RLC 33b' based on the state of the first channel CH1 and the state of the second channel CH2. The exemplary operations of PDCP 34' will be described below with reference to Figure 4 FIG.

[0039] Figure 4 FIG. Figure 4 is a flowchart showing a method for implementing a multi-connection according to an exemplary embodiment. For example, Figure 3 the method shown can be performed by Figure 5 the PDCP 34' shown, and as described below with reference to Figure 4 FIG. Figure 1 and Figure 3 the method shown can be triggered by various factors. Hereinafter, with reference to Figure 4 FIG.

[0040] Referring to Figure 4, in operation S200, an operation for estimating the round-trip time can be performed. The round-trip time (RTT) can be defined as the time it takes for a sender to send data to a receiver and receive a response to the sent data (e.g., an acknowledgement response (ACK)) from the receiver. The document "Stability of end-to-end algorithms for joint routing and rate control" (F. Kelly and T. Voice, Association for Computing Machinery Special Interest Group on Data Communication Computer Communication Review, ACM SIGCOMM CCR, 35, 2005) has proposed a method for maximizing network efficiency in the transmission control protocol (TCP), and the proposed method can be expressed as the following equation (1). The sender can change the congestion window "cwnd" of the corresponding path by Δw in the following equation (1). p Change the congestion window "cwnd" of the corresponding path:

[0041]

[0042] In equation (1), P can represent the total set of paths formed by a single host, w i can represent the current sending window of the i-th path, and RTT i can represent the round-trip time of the i-th path. In some embodiments, in a multi-connection, data segmentation can be performed based on the change in the sending window provided in equation (1). In TCP, the round-trip time can be determined based on the network traffic, and thus, the sender can measure the difference between the time when data is sent and the time when an ACK is received as the round-trip time. On the other hand, in a multi-connection, the round-trip time can depend on the state of the channel and can be estimated as described below.

[0043] For applying equation (1) to the Figure 1 shown multi-connection, the first round-trip time RTT1 and the second round-trip time RTT2 corresponding to the first channel CH1 and the second channel CH2 can be estimated. For example, as referred to above Figure 3As described above, the PDCP 34' of the "UE 30" can estimate the first round-trip time RTT1 based on the first indicator ID1 provided by the lower layer, and can estimate the second round-trip time RTT2 based on the second indicator ID2 provided by the lower layer. The following will refer to Figure 6 illustrate an example of operation S200.

[0044] In operation S400, an operation of obtaining the channel bandwidth can be performed. As Figure 1 shown, in the multi-connection where the UE 30 communicates with the first base station 10 and the second base station 20, the UE 30 and one base station (e.g., the first base station 10 or the second base station 20) can be regarded as a 1-hop network, and the w in Equation (1) i can be expressed as the multiplication of the channel bandwidth and the round-trip time as in the following Equation (2):

[0045] wi = BWi × RTTi (2)

[0046] Therefore, in Equation (1), "BW i × RTT i " can be used to replace w i , and in operation S400, an operation of obtaining the channel bandwidth (i.e., the first channel bandwidth BW1 of the first channel CH1 and the second channel bandwidth BW2 of the second channel CH2) can be performed. For example, the first PHY layer 31a' and the second PHY layer 31b' can measure the first channel bandwidth BW1 and the second channel bandwidth BW2 respectively, and the PDCP 34' can obtain the first channel bandwidth BW1 based on the indicator provided by the first PHY layer 31a' in the first indicator IND1, and can obtain the second channel bandwidth BW2 based on the indicator provided by the second PHY layer 31b' in the second indicator IND2.

[0047] In operation S600, an operation of determining the sizes of multiple pieces of segmented data (e.g., the first data and the second data) can be performed. When the first channel bandwidth BW1 and the second channel bandwidth BW2 correspond to the channel bandwidths of the first channel CH1 and the second channel CH2 respectively, in the Figure 1 multi-connection shown, Equation (1) can be expressed as the following Equation (3):

[0048]

[0049] In addition, in a multi-connection based on M (where M is an integer greater than one) number of channels, Equation (1) can be expressed as the following Equation (4):

[0050]

[0051] In operation S200, a first round-trip time RTT1 and a second round-trip time RTT2 can be estimated, and in operation S400, a first channel bandwidth BW1 and a second channel bandwidth BW2 can be obtained. Thus, in operation S600, PDCP 34' can calculate a change in data size (i.e., Δw) based on Equation (3), and can reflect the change Δw in the segmentation of data packets to be transmitted. An example of operation S600 will be described below with reference to Figure 8 be elaborated.

[0052] Figure 5 is a flowchart showing a method for implementing multi-connection according to an exemplary embodiment. Specifically, in Figure 5 the shown operation S100, the method for implementing multi-connection described above with reference to Figure 4 can be triggered, and after performing operation S100, operation S200 shown in Figure 4 can be sequentially performed. Additionally, after performing Figure 4 the shown operation S600, operation S100 shown in Figure 5 can be performed. As shown in Figure 5 operation S100 can include operations S120, S140, and S160. In some embodiments, when at least one of operations S120, S140, and S160 of operation S100 is performed, the method can proceed to operation S200. In some other embodiments, operation S100 can include only some of operations S120, S140, and S160. Hereinafter, it will be described with reference to Figure 3 be elaborated Figure 5 .

[0053] In operation S120, an operation of receiving a data packet can be performed. For example, when a data packet is received from an application 35 corresponding to an upper layer, PDCP 34' can trigger Figure 4 the shown method. The data packet received from application 35 can be data to be transmitted by application 35 through wireless communication and can be referred to as a PDCP SDU, and in some embodiments, the data packet can include a header and a payload.

[0054] In operation S140, an operation of receiving an ACK can be performed. For example, when an ACK corresponding to an RLC PDU in RLC acknowledge mode (AM) is received, PDCP34' can trigger Figure 4 the shown method. In some embodiments, when a predefined number of ACKs are received, PDCP 34' can trigger Figure 4 the shown method. Additionally, in some embodiments, as described below with reference to Equation (8), PDCP 34' can trigger based on a predefined period or another factorFigure 4 the method shown, and in such a case, the number of received ACKs can be used.

[0055] In operation S160, an operation of receiving updated retransmission parameters can be performed. As will be described below with reference to Figure 6 stated, in Figure 4 the operation S200 shown, the round-trip time can be estimated based on retransmissions. A wireless communication system can specify the value of the retransmission parameter, some wireless communication systems (e.g., 5G NR systems) can specify that the value of the retransmission parameter changes, and the base station can update the retransmission parameter based on the channel state. When the value of the retransmission parameter changes, the estimated round-trip time can change, and thus, when the updated retransmission parameter is received from the base station, the PDCP 34' can trigger Figure 4 the method shown.

[0056] Figure 6 is a flowchart showing Figure 4 the operation S200 shown according to an exemplary embodiment. As described above with reference to Figure 4 stated, in Figure 6 the operation S200' shown, an operation of estimating the round-trip time can be performed. Specifically, in Figure 6 the operation S200' shown, a round-trip time corresponding to one channel can be estimated, and based on multiple channels, Figure 6 the operation S200' can be performed multiple times sequentially or in parallel. As Figure 6 shown, the operation S200' can include operation S220 and operation S240. Hereinafter, with reference to Figure 1 and Figure 3 will be described, and based on Figure 6 the assumption that the UE 30 shown in Figure 1 is the Figure 3 UE 30” shown, an example of estimating the first round-trip time RTT1 corresponding to the first channel CH1 will be described.

[0057] In operation S220, an operation of obtaining retransmission parameters can be performed. For example, a first indicator IND1 provided from the first base station 10 can be provided to the PDCP 34', and the first indicator IND1 includes a first retransmission parameter. In some embodiments, the PDCP 34' can reflect the HARQ retransmission in the estimation of the first round-trip time RTT1, and for example, the first retransmission parameter can include a retransmission period c1 and a maximum retransmission number N1. In some other embodiments, the PDCP 34' can reflect the RLC retransmission in the estimation of the first round-trip time RTT1, and for example, the first retransmission parameter can include the RLC maximum retransmission number R1.

[0058] In operation S240, an operation of calculating a round-trip time can be performed. For example, the PDCP 34' can calculate a first round-trip time RTT1 based on the retransmission parameters obtained in operation S220. The first round-trip time RTT1 is used to calculate a change Δw in data size in equation (3). In some embodiments, the PDCP 34' can calculate a round-trip time that includes HARQ retransmissions provided by the first MAC 32a'. In some embodiments, the PDCP 34' can calculate a round-trip time that further includes RLC retransmissions provided by the first RLC 33a'. Examples of operation S240 will be described below with reference to Figure 7A and Figure 7B An example of operation S240 will be described.

[0059] Figure 7A and Figure 7B are flowcharts showing operation S240 according to an exemplary embodiment Figure 6 as shown.

[0060] In Figure 7A operation S240a as shown and Figure 7B operation S240b as shown, the operation of calculating the first round-trip time RTT1 as described above with reference to Figure 6 can be performed. Repeated descriptions will be omitted when describing the embodiments shown in Figure 7A and Figure 7B Examples of estimating the first round-trip time RTT1 corresponding to the first channel CH1 based on the assumption that the UE 30 shown in Figure 1 is the same as the UE 30” shown in Figure 3 will be described with reference to Figure 7A and Figure 7B , and examples of estimating the first round-trip time RTT1 corresponding to the first channel CH1 based on the assumption that the UE 30 shown in Figure 1 is the same as the UE 30” shown in Figure 3 will be described.

[0061] Referring to Figure 7A , operation S240a can include operation S242a and operation S244a, and in operation S242a, an operation of calculating a round-trip time including HARQ retransmissions can be performed. For example, the PDCP 34' can use the block error rate BLER to calculate the first round-trip time RTT including HARQ retransmissions as in the following equation (5): S1 :

[0062]

[0063] In equation (5), the first block error rate BLER1 can represent the block error rate measured in the first channel CH1. In some embodiments, the PDCP 34' can obtain the first block error rate BLER1 from an indicator provided by the first PHY layer 31a' in the first indicator IND1.

[0064] The first propagation delay p1 may represent the propagation delay that occurs in the first channel CH1. In some embodiments, PDCP 34' may obtain the first propagation delay p1 from the first MAC 32a'. For example, the first base station 10 may allocate a dedicated random access preamble to the UE 30", and when the UE 30" does not include radio resources for accessing the first base station 10 first or for transmitting a signal to the first base station 10, the UE 30" may perform a random access procedure (RACH) based on the random access preamble. The first base station 10 may use the random access preamble (or sounding reference signal (SRS)) to measure the transmission time of the UE 30", calculate a correction timing value, and notify the UE 30" of the calculated correction timing value. The correction timing value provided from the first base station 10 to the UE 30" (i.e., the timing advance value) may be referred to as a timing advance command (TAC), and the TAC may be processed at the MAC layer. Therefore, the first MAC 32a' of the UE 30" may generate the first propagation delay p1 based on the TAC and may provide the first propagation delay p1 to the PDCP 34' as one of the first indicators IND1.

[0065] In some embodiments, the first propagation delay p1 may be omitted in the process of calculating the first round-trip time RTT including HARQ retransmission S1 . For example, in Equation (5), the first propagation delay p1 may have a value smaller than 'n1×c1', and thus, the first round-trip time RTT including HARQ retransmission may be calculated as in the following Equation (6) S1 . In such a case, the operation of obtaining the first propagation delay p1 from the first MAC 32a' as the first retransmission parameter may be omitted in the Figure 6 operation S220 shown.

[0066]

[0067] In some embodiments, in the RLC unacknowledged mode (UM), the PDCP 34' may determine the first round-trip time RTT S1 as the first propagation delay p1. For example, when the first block error rate BLER1 is approximately maintained at zero, the RLC UM may be set, and the PDCP 34' may determine the first round-trip time RTT S1Determined as the first propagation delay p1. Additionally, in some other embodiments, the PDCP 34' may reflect the change Δw every first propagation delay p1 (i.e., the first round-trip time RTT S1 ).

[0068] It should be understood that the second round-trip time RTT including HARQ retransmissions and corresponding to the second channel CH2 S2 is similarly calculated based on Equation (5) and / or Equation (6).

[0069] In operation S244a, an operation of calculating the round-trip time including RLC retransmissions may be performed. For example, the PDCP 34' may calculate the first round-trip time RTT including RLC retransmissions as in the following Equation (7) T1 :

[0070]

[0071] In Figure 7A the illustrated embodiment, the PDCP 34' may use the first round-trip time RTT calculated based on Equation (7) T1 as the data change Δw in Equation (3). Additionally, it should be understood that the second round-trip time RTT including HARQ retransmissions and corresponding to the second channel CH2 S2 is similarly calculated based on Equation (7).

[0072] Referring to Figure 7B , operation S240b may include operation S242b, operation S243b, and operation S244b. Compared with Figure 7A the illustrated operation S240a, Figure 7B the illustrated operation S240b may further include operation S243b. Similar to Figure 7A the illustrated operation S242a, an operation of calculating the round-trip time including HARQ retransmissions may be performed in operation S242b. Therefore, the first round-trip time RTT S1 including HARQ retransmissions and the second round-trip time RTT S2 may be calculated respectively.

[0073] In operation S243b, an operation of comparing the block error rate BLER with a predefined first threshold THR1 may be performed. For example, during the process of calculating the first round-trip time RTT S1 , the first block error rate BLER1 may be compared with the predefined first threshold THR1, and as Figure 7BAs shown, when the first block error rate BLER1 is less than the first threshold THR1, operation S240b may end. On the other hand, when the first block error rate BLER1 is equal to or greater than the first threshold THR1, operation S244b may be executed, and in operation S244b, the first round-trip time RTT including RLC retransmission may be calculated. T1 operation.

[0074] Therefore, in Figure 7B the embodiment shown, when the first block error rate BLER1 is less than the first threshold THR1, the first round-trip time RTT including HARQ retransmission in Equation (5) or Equation (6) S1 may be determined as the final first round-trip time RTT1. On the other hand, when the first block error rate BLER1 is equal to or greater than the first threshold THR1, the first round-trip time RTT including RLC retransmission T1 may be determined as the final first round-trip time RTT1. In a state where the block error rate is low, the possibility of RLC retransmission may be low, and thus, in Figure 7B the embodiment shown, operation S244b (e.g., calculation based on Equation (7)) may be omitted.

[0075] Figure 8 is a flowchart showing operation S600 according to an exemplary embodiment. As referred to above with reference to Figure 4 In operation S600 shown, an operation of determining the sizes of a plurality of divided data (e.g., first data and second data) may be executed. As Figure 4 described, in Figure 8 operation S600' shown, an operation of determining the sizes of a plurality of divided data (e.g., first data and second data) may be executed. As Figure 8 shown, operation S600' may include operation S620 and operation S640. Hereinafter, with reference to Figure 3 and Figure 4 will be described Figure 8 .

[0076] In operation S620, an operation of calculating a change in data size may be executed. For example, the change in data size Δw may be calculated as in Equation (3) based on the round-trip time obtained through operation S200 and the channel bandwidth obtained through operation S400. In some embodiments, the change Δw may be equally applicable to multiple channels.

[0077] In some embodiments, when the change in data size is not calculated every time an ACK appears, the change in data size Δw1 corresponding to the first channel CH1 may be calculated as in the following Equation (8):

[0078]

[0079] In Equation (8), N ACK1may represent the number of ACKs received from the first base station 10 via the first channel CH1. For example, PDCP 34' may calculate the change Δw1 in the data size in RLC AM based on Equation (8). Similarly, N representing the number of ACKs received from the second base station 20 via the second channel CH2 may be used ACK2 to calculate the change Δw2 in the data size corresponding to the second channel CH2.

[0080] In multi-connection based on M number of channels, the change Δw in the data size corresponding to the i-th channel CHi may be calculated as in Equation (9) below i :

[0081]

[0082] In operation S640, an operation of changing the data size may be performed. For example, PDCP 34' may add the change Δw calculated through operation S620 to the data size set in the multiple channels to change the data size. In some embodiments, when the change Δw is equally applicable to the multiple channels, the same change Δw may be added to the data size set in the multiple channels. For example, retransmissions may rarely occur in channels with sufficient quality, and thus, even when the change Δw has a negative value, a large amount of data may still be transmitted via a channel having sufficient quality (or channel state) compared to a channel with lower quality. Additionally, retransmissions may frequently occur in channels with poor quality, and thus, even when the change Δw has a positive value, a small amount of data may still be transmitted via a channel having lower quality compared to a channel with sufficient quality.

[0083] Figure 9A and Figure 9B are flowcharts showing operation S640 according to an exemplary embodiment. Specifically, Figure 8 operation S640a shown in Figure 9A and operation S640b shown in Figure 9B may respectively include operations S644a and S644b of blocking data transmission via channels with poor channel states. As described below with reference to Figure 8 , in Figure 9A operation S640a shown in Figure 9B and operation S640b shown in Figure 9A and Figure 9B , an operation of changing the data size may be performed. Hereinafter, repeated descriptions will be omitted when explaining Figure 3 and Figure 9A and Figure 9B .

[0084] Referring to Figure 9A, operation S640a may include operations S641a to S646a, and an initialization operation may be performed in operation S641a. For example, as Figure 9A shown, a variable i representing an index of a channel may be set to 1. In Figure 9A the illustrated embodiment, the sizes of a plurality of data to be transmitted via M channels may be determined, and thus, the variable i may have a value of "1 to M".

[0085] In operation S642a, an operation of comparing the block error rate (BLER) of the i-th channel i with a predefined second threshold THR2 may be performed. As Figure 9A shown, when the block error rate (BLER) of the i-th channel i is greater than the second threshold THR2, operation S644a may be performed, and an operation of determining the data size to be zero may be performed in operation S644a. On the other hand, when the block error rate (BLER) of the i-th channel i is equal to or less than the second threshold THR2, operation S643a may be performed, and an operation of reflecting a change in the data size in the data distribution may be performed in operation S643a. Therefore, when the block error rate (BLER) of a channel is high, PDCP 34' may block data transmission via the corresponding channel.

[0086] In operation S645a, an operation of comparing the variable i with M may be performed. As Figure 9A shown, when the variable i does not match M (i.e., when the variable i is less than M), the variable i may be incremented by one in operation S646a, and operation S642a may be performed again. On the other hand, when the variable i matches M (i.e., when the data sizes corresponding to the M channels have all been determined), operation S640a may end.

[0087] Referring to Figure 9B , operation S640b may include operations S641b to S646b. In Figure 9B some of the operations S641b and S643b to S646b shown, operations similar to those performed in Figure 9A some of the operations S641a and S643a to S646a shown may be performed.

[0088] In operation S642b, an operation of comparing a predefined threshold THR3 with a ratio NACK% of negative unacknowledge responses (NACK) occurring in the i-th channel may be performed. As Figure 9BAs shown, when the ratio NACK% of NACKs occurring in the i-th channel is higher than the threshold THR3, operation S644b can be performed, and when the ratio NACK% of NACKs occurring in the i-th channel is equal to or lower than the threshold THR3, operation S643b can be performed. Accordingly, when the NACK ratio NACK% of the channel is high, the PDCP 34' can block data transmission via the corresponding channel.

[0089] Figure 10 is a block diagram showing a UE 100 according to an exemplary embodiment. As referred to above Figure 1 above, Figure 10 shown, the UE 100 can support multi-connection and can perform wireless communication with two or more base stations. As Figure 10 shown, the UE 100 may include an antenna 110, a transceiver 120, a data processor 130, a memory 140, and a main processor 150. In Figure 10 the UE 100's elements are shown independently, but in some embodiments, two or more elements may be implemented as one entity (e.g., a semiconductor chip).

[0090] The antenna 110 may receive a radio frequency (RF) signal from a base station or may transmit an RF signal to a base station. In some embodiments, the antenna 110 may be configured to include an antenna array of multiple antennas and may support multiple input multiple output (MIMO) and beamforming.

[0091] The transceiver 120 may process signals between the antenna 110 and the data processor 130. For example, the transceiver 120 may include a duplexer, a switch, a filter, a multiplexer, and an amplifier. Additionally, the transceiver 120 may process the RF signal received via the antenna 110 to generate a received signal RX and may provide the received signal RX to the data processor 130. Additionally, the transceiver 120 may process the transmit signal TX provided from the data processor 130 to generate an RF signal and may provide the generated RF signal to the antenna 110. In some embodiments, the transceiver 120 may be referred to as a radio frequency integrated circuit (RFIC).

[0092] The data processor 130 may process the data packet PKT received from the main processor 150 to generate a transmission signal TX, process the received signal RX received from the transceiver 120 to generate a data packet PKT, and provide the generated data packet PKT to the main processor 150. The data processor 130 may perform operations corresponding to at least one layer in the wireless protocol architecture. For example, the data processor 130 may be referred to as a communication protocol and may perform Figure 3 the functions of the first PHY layer 31a' and the second PHY layer 31b', the first MAC 32a' and the second MAC 32b', the first RLC 33a' and the second RLC 33b', and the PDCP 34' shown. In some embodiments, the data processor 130 may include hardware, including a processing unit, and a combination of hardware and a processing unit. The hardware includes logic blocks designed based on logical combinations, and the processing unit includes software and at least one core (or at least one processor) for executing the software. For example, the data processor 130 may include hardware blocks and / or software blocks corresponding to Figure 3 the first PHY layer 31a' and the second PHY layer 31b', the first MAC 32a' and the second MAC 32b', the first RLC 33a' and the second RLC 33b', and the PDCP 34' shown respectively. The method according to the exemplary embodiments described above with reference to the drawings and at least one operation included in the method may be performed by the data processor 130. In some embodiments, a base station (e.g., Figure 1 10 and / or 20 shown) may have a structure similar to that of the Figure 10 UE 100 shown, and the data processor included in the base station may perform the method for implementing dual connectivity and at least one operation included in the method.

[0093] The memory 140 may store data required for the process of the processing performed by the data processor 130, and may store signals and / or data. In some embodiments, the memory 140 may store software (i.e., a series of instructions) executed by the data processor 130.

[0094] The main processor 150 may include at least one core (or processor). Additionally, the main processor 150 may transmit the data packet PKT to be transmitted via wireless communication to the data processor 130 and may receive data transmitted from the base station based on the data packet PKT provided by the data processor 130. The main processor 150 may control the operation of the UE 100, and may generate a data packet PKT or may perform operations based on the received data packet PKT.

[0095] Figure 11A and Figure 11BFIG. is a diagram illustrating a method for implementing multi-connection with respect to a time stream. Specifically, Figure 11A and Figure 11B FIG. is an example diagram illustrating a method for implementing multi-connection in a downlink. In some embodiments, one of the base stations connected to the UE may perform segmentation of data for multi-connection, and the following will be described with reference to Figure 11A and Figure 11B to illustrate an example in which the first base stations 10a and 10b (i.e., base stations of a 5G NR system (e.g., gNB)) perform segmentation of data for multi-connection. However, it should be understood that the exemplary embodiments are not limited thereto. Hereinafter, with reference to Figure 1 will be described Figure 11A and Figure 11B , and it can be assumed that Figure 1 the first base station 10, the second base station 20, and the UE 30 shown in FIG. correspond to Figure 11A the first base station 10a, the second base station 20a, and the UE 30a shown in FIG. and correspond to Figure 11B the first base station 10b, the second base station 20b, and the UE 30b shown in FIG. Repeated descriptions will be omitted when describing Figure 11A and Figure 11B .

[0096] Referring to Figure 11A , the second base station 20a that establishes the second channel CH2 with the UE 30a may estimate the second round-trip time RTT2 corresponding to the second channel CH2, and the estimated second round-trip time RTT2 may be provided from the second base station 20a to the first base station 10a.

[0097] In operation S11a, the first base station 10a may estimate the first round-trip time RTT1. The first base station 10a may establish the first channel CH1 with the UE 30a, and thus, as described above with reference to the diagram, the first base station 10a may estimate the first round-trip time RTT1 in a manner similar to the way the UE 30a estimates the first round-trip time RTT1. Additionally, in operation S12a, the first base station 10a may obtain the first channel bandwidth BW1.

[0098] In operation S13a, the second base station 20a may estimate the second round-trip time RTT2. The second base station 20a may establish the second channel CH2 with the UE 30a, and thus, as described above with reference to the diagram, the second base station 20a may estimate the second round-trip time RTT2 in a manner similar to the way the UE 30a estimates the second round-trip time RTT2. Additionally, in operation S14a, the second base station 20a may obtain the second channel bandwidth BW2.

[0099] In operation S15a, the second base station 20a may provide the second round-trip time RTT2 and the second channel bandwidth BW2 to the first base station 10a. For example, as described above with reference to Figure 1 the second base station 20a may provide the second round-trip time RTT2 and the second channel bandwidth BW2 to the first base station 10a via the interface IF.

[0100] In operation S16a, the first base station 10a may calculate the data size. For example, in operations S11a to S15a, the first base station 10a may collect information about the first channel CH1 and the second channel CH2 and may calculate the change Δw in the data size based on the collected information as in Equation (3). The first base station 10a may reflect the change Δw in the data size in the calculation of the size of the first data to be sent from the first base station 10a to the UE 30a and the size of the second data to be sent from the second base station 20a to the UE 30a.

[0101] In operation S17a, the first base station 10a may send the first data to the UE 30a via the first channel CH1 based on the calculated size of the first data. Additionally, in operation S18a, the first base station 10a may provide the second data to the second base station 20a. In operation S19a, the second base station 20a may send the second data provided by the first base station 10a to the UE 30a via the second channel CH2.

[0102] Referring to Figure 11B , the second base station 20b that establishes the second channel CH2 with the UE 30b may provide information about the second channel CH2 to the first base station 10b, and the first base station 10b may estimate the second round-trip time RTT2 based on the information about the second channel CH2.

[0103] In operation S11b, the first base station 10b may estimate the first round-trip time RTT1, and in operation S12b, the first base station 10b may obtain the first channel bandwidth BW1.

[0104] In operation S13b, the second base station 20b may provide the second channel information to the first base station 10b. For example, as described above with reference to the diagrams, the second base station 20b may provide the first base station 10b with information for estimating the second round-trip time RTT2 (e.g., the second retransmission parameter corresponding to the second channel CH2) and information for calculating the change Δw in the data size (e.g., the second channel information including the second channel bandwidth BW2). In some embodiments, the second base station 20b may provide the first base station 10b with the propagation delay corresponding to the second channel CH2 (i.e., the second propagation delay p2).

[0105] In operation S14b, the first base station 10b may estimate a second round-trip time RTT2. For example, the first base station 10b may estimate the second round-trip time RTT2 based on the second channel information provided in operation S13b using Equation (5), Equation (6), and / or Equation (7).

[0106] In operation S15b, the first base station 10b may calculate a data size. In operation S16b, the first base station 10b may transmit the first data to the UE 30b via the first channel CH1 based on the calculated size of the first data. Additionally, in operation S17b, the first base station 10b may provide second data to the second base station 20b. In operation S18b, the second base station 20b may transmit the second data provided from the first base station 10b to the UE 30b via the second channel CH2.

[0107] Figure 12 is a diagram showing multi-connection according to an exemplary embodiment. Specifically, Figure 12 shows a structure including cores (e.g., a first core and a second core) 70 and 80 connected to base stations (e.g., a first base station and a second base station) 40 and 50. Hereinafter, when Figure 12 is described, a repeated description related to Figure 1 will be given.

[0108] Referring to Figure 12 , the UE 60 may access the first base station 40 via the first channel CH1 and may access the second base station 50 via the second channel CH2. The first base station 40 may access the first core 70, and the second base station 50 may access the second core 80. For example, the first base station 40 may be a base station of a 5G NR system, and the second base station 50 may be a base station of an LTE system. In such a case, the second core 80 may be referred to as an evolved packet core (EPC).

[0109] The first core 70 and the second core 80 may access a general Internet protocol (IP) anchor 90, and the general IP anchor 90 may be a network entity and may perform a function of routing data transmitted from a data network to a UE 60. In some embodiments, the general IP anchor 90 may perform data splitting in multi-connection, and related embodiments will be described hereinafter with reference to Figure 13A and Figure 13B will be given.

[0110] Figure 13A and Figure 13B is a diagram showing a method for implementing multi-connection with respect to a time flow according to an exemplary embodiment. Specifically, Figure 13A and Figure 13BAn example of a method for implementing multi-connection in the downlink is shown. In some embodiments, general IP anchors 90a and 90b may perform segmentation of data for multi-connection, and the following will refer to Figure 13A and Figure 13B to illustrate an example in which data is distributed to first base stations 40a and 40b of a 5G NR system and second base stations 50a and 50b of an LTE system. However, it should be understood that the exemplary embodiments are not limited thereto.

[0111] Referring to Figure 13A , general IP anchor 90a may segment data based on round-trip times and channel bandwidths provided from first base station 40a and second base station 50a. In operation S21a, first base station 40a may provide general IP anchor 90a with a first round-trip time RTT1 and a first channel bandwidth BW1 corresponding to a first channel CH1, respectively. In operation S22a, second base station 50a may provide general IP anchor 90a with a second round-trip time RTT2 and a second channel bandwidth BW2 corresponding to a second channel CH2, respectively. For example, first base station 40a and second base station 50a may calculate first round-trip time RTT1 and second round-trip time RTT2 based on Equation (5), Equation (6), and / or Equation (7), respectively.

[0112] In operation S23a, general IP anchor 90a may calculate the sizes of multiple segmented data based on the round-trip times and channel bandwidths provided from first base station 40a and second base station 50a. For example, general IP anchor 90a may calculate a change Δw in data size based on Equation (3), and may reflect the change Δw in data size in the calculation of the size of first data to be transmitted via first channel CH1 and the size of second data to be transmitted via second channel CH2. Subsequently, in operation S24a, general IP anchor 90a may provide the first data to first base station 40a, and in operation S25a, general IP anchor 90a may provide the second data to second base station 50a.

[0113] Referring to Figure 13B , general IP anchor 90b may segment data based on channel information provided from each of first base station 40b and second base station 50b. In operation S21b, first base station 40b may provide general IP anchor 90b with first channel information corresponding to first channel CH1. In operation S22b, second base station 50b may provide general IP anchor 90b with second channel information corresponding to second channel CH2. For example, the first channel information may include a first retransmission parameter and a first channel bandwidth, and the second channel information may include a second retransmission parameter and a second channel bandwidth.

[0114] In operation S23b, the general IP anchor 90b may estimate the round-trip time. For example, the general IP anchor 90b may use Equation (5), Equation (6), and / or Equation (7) to estimate the first round-trip time RTT1 and the second round-trip time RTT2 based on the first channel information and the second channel information. In operation S24b, the general IP anchor 90b may calculate the sizes of multiple pieces of segmented data. For example, the general IP anchor 90b may calculate the change Δw in the data size based on Equation (3), and may reflect the change Δw in the data size in the calculation of the size of the first data to be transmitted via the first channel CH1 and the size of the second data to be transmitted via the second channel CH2. In operation S25b, the general IP anchor 90b may provide the first data to the first base station 40b, and in operation S26b, the general IP anchor 90b may provide the second data to the second base station 50b.

[0115] Although the inventive concept has been specifically shown and described with reference to embodiments of the inventive concept, it will be understood that various changes in form and detail may be made herein without departing from the spirit and scope of the above claims.

Claims

1. A method for implementing multi - connection between multiple base stations and a user equipment, the method comprising: estimating, at the user equipment, a first round - trip time taken to send first data to a first base station; estimating, at the user equipment, a second round - trip time taken to send second data to a second base station; and determining, at the user equipment, a size of the first data to be sent to the first base station based on the first round - trip time and the second round - trip time; wherein determining the size of the first data to be sent to the first base station specifically includes: obtaining a first channel bandwidth corresponding to the first base station; and obtaining a second channel bandwidth corresponding to the second base station, wherein determining the size of the first data includes obtaining the size of the first data based on the first round - trip time, the second round - trip time, the first channel bandwidth, and the second channel bandwidth, and wherein determining the size of the first data includes changing the size of the first data based on a variation Δw expressed in the following equation: wherein the RTT1, the RTT2, the BW1, and the BW2 are the first round - trip time, the second round - trip time, the first channel bandwidth, and the second channel bandwidth respectively.

2. The method according to claim 1, wherein estimating the first round - trip time includes: obtaining a re - transmission parameter corresponding to the first base station; and obtaining the first round - trip time based on the re - transmission parameter.

3. The method according to claim 2, wherein the re - transmission parameter includes a re - transmission period c1 and a maximum re - transmission number N1, and Obtaining the first round-trip time includes obtaining the RTT expressed in the following equation S1 : wherein the BLER1 and the p1 are a block error rate and a signal moving time in a channel corresponding to the first base station respectively.

4. The method according to claim 3, wherein obtaining the first round-trip time includes determining the RTT as the first round-trip time in response to the BLER1 being less than a first threshold. S1 ​ 5. The method according to claim 3, wherein determining the size of the first data includes determining the size of the first data to be zero in response to the BLER1 being greater than a second threshold.

6. The method according to claim 2, wherein obtaining the re - transmission parameter includes obtaining an updated re - transmission parameter received from the first base station, and obtaining the first round - trip time includes obtaining the first round - trip time based on the updated re - transmission parameter.

7. The method according to claim 1, wherein the method is implemented in a packet data convergence protocol layer.

8. The method according to claim 1, wherein determining the size of the first data includes determining the size of the first data to be zero in response to a ratio of negative acknowledgments from the first base station being greater than a third threshold.

9. The method according to claim 1, further comprising determining a size of the second data to be sent to the second base station based on the first round - trip time and the second round - trip time.

10. The method according to claim 1, wherein the first base station and the second base station communicate with the user equipment based on the same radio access technology.

11. The method according to claim 1, wherein the first base station and the second base station communicate with the user equipment based on different radio access technologies.

12. A method for implementing multi-connection between multiple base stations and a user equipment, the method comprising: estimating, at the user equipment, a first round-trip time taken to send first data to a first base station; estimating, at the user equipment, a second round-trip time taken to send second data to a second base station; and determining, at the user equipment, a size of the first data to be sent to the first base station based on the first round-trip time and the second round-trip time; wherein determining the size of the first data to be sent to the first base station specifically comprises: obtaining a first channel bandwidth corresponding to the first base station; and obtaining a second channel bandwidth corresponding to the second base station, wherein determining the size of the first data comprises obtaining the size of the first data based on the first round-trip time, the second round-trip time, the first channel bandwidth, and the second channel bandwidth, and wherein determining the size of the first data comprises changing the size of the first data based on a variation Δw expressed in the following equation: wherein the RTT1, the RTT2, the BW1, the BW2, and the N ACK1 are the first round-trip time, the second round-trip time, the first channel bandwidth, the second channel bandwidth, and the number of acknowledgement responses received from the first base station, respectively.

13. A method for implementing multi-connection between multiple base stations and a user equipment, the method comprising: estimating, at a first base station, a first round-trip time taken to send first data from the first base station to the user equipment; obtaining, at the first base station, a second round-trip time taken to send second data from a second base station to the user equipment; and determining, at the first base station, a size of the first data to be sent from the first base station to the user equipment based on the first round-trip time and the second round-trip time; obtaining a first channel bandwidth corresponding to the first base station; and obtaining a second channel bandwidth corresponding to the second base station, wherein determining the size of the first data comprises obtaining the size of the first data based on the first round-trip time, the second round-trip time, the first channel bandwidth, and the second channel bandwidth, and wherein determining the size of the first data comprises changing the size of the first data based on a variation Δw expressed in the following equation: wherein the RTT1, the RTT2, the BW1, and the BW2 are the first round-trip time, the second round-trip time, the first channel bandwidth, and the second channel bandwidth respectively.

14. The method according to claim 13, wherein obtaining the second round-trip time comprises receiving, from the second base station, the second round-trip time estimated by the second base station.

15. The method according to claim 13, wherein obtaining the second round-trip time comprises: receiving, from the second base station, channel information about a channel established by the second base station and the user equipment; and estimating the second round-trip time based on the channel information.

16. A method for implementing multi-connection between multiple base stations and a user equipment, the method comprising: estimating multiple round-trip times taken to send data via multiple channels between the multiple base stations and the user equipment; obtaining respective channel bandwidths of the multiple channels; and Determine the sizes of multiple pieces of segmented data to be transmitted via the multiple channels based on the multiple round-trip times and the channel bandwidths, Determining the size of the plurality of segmented data includes changing the size of the segmented data transmitted via the i-th channel based on a variation Δw expressed in the following equation: i ​ wherein the RTT i and the BW i are respectively the round-trip time and the channel bandwidth corresponding to the i-th channel in the multi-connection respectively based on M channels between M base stations and the user equipment, where M is an integer greater than one, and 1 ≤ i ≤ M.

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