KR20180107649A - Method for reducing uplink transmission delay in dual-connectivity network and terminal applying same - Google Patents

Abstract

According to an embodiment of the present invention, a method for reducing uplink transmission delay, which is performed in a terminal connected to a master base station and a secondary base station in a dual connection network environment of a packet split mode, comprises the steps of: securing transmission target data composed of a plurality of packets to be transmitted according to a predetermined transmission order; selecting packets in the amount which can be transmitted to the master base station, from the foremost side of the transmission target data in the transmission order, for a backhaul delay time which is a time required for data to be transmitted from the secondary base station to the master base station, among the transmission target data, and designating the selected packets as a master data block which is a data block to be transmitted by the master base station; transmitting packets of the master data block to the master base station in the transmission order during a transmission time interval (TTI) from a predetermined transmission start time point; and transmitting a packet, which is next to the master data block on the transmission order among the transmission target data, in the transmission order to the secondary base station from the transmission start point during the TTI.

Description

METHOD FOR REDUCING UPLINK TRANSMISSION DELAY IN DUAL-CONNECTIVITY NETWORK AND TERMINAL APPLICATION SAME Technical Field [1] The present invention relates to a method for reducing an uplink transmission delay in a dual-

The present invention relates to a packet split dual-connectivity network system in which a mobile communication terminal can simultaneously access a master base station (MeNB) and a secondary base station (SeNB) A method for improving a mobile communication environment by reducing an uplink transmission delay due to a backhaul delay between a master base station and a secondary base station, and a terminal to which the method is applied.

BACKGROUND ART [0002] With the improvement of living standards and the development of information and communication technologies, a great number of people are using personal mobile communication terminals such as cell phones. In addition, contents available through such mobile communication terminals are also increasing in capacity. Thus, the amount of data used by mobile communication subscribers is increasing exponentially.

To overcome this situation, a dual connection technology has been devised. According to the dual connection technique, a terminal can simultaneously use two or more different network nodes, for example, a radio resource provided from a master base station and a secondary base station. The master base station performs both transmission and reception of user plane data and control plane data, and the secondary base station mainly performs transmission and reception of user plane data. Thus, if the terminal is connected to both base stations at the same time, the uplink and downlink data transmission speeds of the terminal are greatly improved, thereby enabling a more improved communication environment to be enjoyed.

Figure 1 is a diagrammatic representation of a dual-link network. In the mobile communication system 10 supporting the dual connection network as shown in FIG. 1, the terminal 20 can perform data communication through both the master base station 11 and the secondary base station 12. The master base station 11 and the secondary base station 12 are connected to each other via a backhaul called X2 interface and can exchange data with each other. Here, since the master base station 11 plays a role as an anchor when changing the secondary base station 12 and provides a seamless connection to the terminal 20, It is desirable to have a wide coverage.

In the mobile communication system 10 supporting the above-described dual connection network, there are a packet split method and a bearer split method as a method of splitting data to different base stations. According to the packet split method, one communication service is split in the master base station 11, but according to the bearer split method, split is performed in the core network located at the rear end of the master base station 11 for different communication services. Since the packet split scheme allows adaptive splitting considering the radio environment of the master base station 11 and the secondary base station 12, the packet split scheme can have advantages in performance in terms of data transmission speed and the like compared to the bearer split scheme.

When the terminal 20 simultaneously transmits data for a specific service via the master base station 11 and the secondary base station 12, a portion of the data transmitted to the secondary base station 12 is transmitted to the master base station 12 11). In this case, since the backhaul is a non-ideal backhaul requiring a certain level of delay in data transmission, the portion transmitted from the terminal 20 to the secondary base station 12 is directly transmitted to the master base station 11 at the same time And reaches the master base station 11 later than the transmitted portion by the delay time of the backhaul.

The master base station 11 sequentially collects a packet data convergence protocol (PDCP) PDU (protocol data unit) directly received from the master base station 11 and a PDCP PDU delivered from the secondary base station 12 according to a serial number, And a reordering function is provided so as to be able to be transmitted to the user. However, due to the delay in the backhaul as described above, when the PDCP PDU directly received by the master base station 11 is transmitted to the secondary base station 12, the PDCP PDU having the serial number preceded by the serial number is transmitted to the PDCP PDU The master base station 11 may wait in the PDCP buffer of the master base station 11 until it arrives at the master base station 11 via the backhaul.

FIGS. 2A and 2B are diagrams illustrating a conventional data transmission method in a dual connection network. Assuming that the sizes of all the packets to be transmitted from the terminal 20 are the same and the transmission rates to the master base station 11 and the secondary base station 12 are the same for convenience, (For example, a PDCP packet) having a serial number of an integer equal to or greater than the integer is alternately allocated to the master base station 11 and the secondary base station 12. For example, an even-numbered packet is allocated to the master base station 11 and an odd-numbered packet is allocated to the secondary base station 12, respectively. For convenience, the terminal 20 can transmit one packet for a time corresponding to one transmission time interval (TTI). Here, it is assumed that TTI = 1 ms and the backhaul delay T is 10 ms. The packet transmitted to the secondary base station 12 is received by the PDCP of the master base station 11 10 ms later than the packet transmitted to the master base station 11 based on the same transmission time. That is, the data transmitted to the secondary base station 12 is received by the master base station 11 after a delay time of 10 ms.

As described above, each packet must be sequentially transmitted to the core network based on the serial number. In FIG. 2A, the packet No. 0 is the packet with the highest serial number, so it can be directly transmitted to the core network. However, the packet No. 2, which is the packet immediately before the serial number, is transmitted to the master base station 11 via the backhaul It should wait 9 ms in the PDCP buffer of the master base station 11 until it is transmitted. 2B, it can be seen that all of the even-numbered packets transmitted directly to the master base station 11 except the packet No. 0 wait for an odd-numbered packet having a serial number higher than the self-numbered packet, . Of course, the odd-numbered packets transmitted through the secondary base station 12 can be transferred to the upper layer without a separate waiting time in the master base station 11. [ In general, when there is a backhaul delay of T, the packet received directly to the master base station 11 must wait in the master base station 11 for a time of T-TTI.

According to the current standard, since the delay in the backhaul is assumed to be a maximum of 60 ms, packets received directly to the master base station 11 must wait for a maximum of 59 ms without being transmitted to the upper layer. This level of latency is a number that can fully affect the quality of delay-sensitive services such as real-time services or streaming services.

Korean Unexamined Patent Publication No. 10-2015-0088746 (published on Aug. 20, 2015)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a packet split duplex network system in which when a data is transmitted through an uplink, a packet configured in consideration of a backhaul delay is appropriately distributed to either a master base station or a secondary base station A method for reducing an uplink transmission delay for solving a data transmission delay caused by waiting for packets having a serial number transmitted to a secondary base station before packets transmitted to a master base station are transmitted to a core network, .

The uplink transmission delay reduction method performed in a terminal connected to a master base station and a secondary base station in a packet split duplex network environment according to an embodiment of the present invention includes a plurality of packets to be transmitted according to a predetermined transmission order The method comprising the steps of: acquiring data to be transmitted; transmitting a positive packet, which can be transmitted to the master base station during a backhaul delay time which is a time required for data to be transmitted from the secondary base station to the master base station, Selecting a master data block as a master data block to be transmitted by the master base station in accordance with the transmission order from the top of the target data; The packet of the master data block is And transmitting the packet after the master data block to the master base station in the order of the transmission from the transmission start time to the master base station in the transmission order, To the secondary base station.

A terminal connected to a master base station (MeNB) and a secondary base station (SeNB) in a packet split duplex network environment according to an exemplary embodiment of the present invention transmits a plurality of packets to be transmitted according to a predetermined transmission order The master base station transmits a positive packet which can be transmitted to the master base station during a backhaul delay time which is a time required for data to be transmitted from the secondary base station to the master base station, A data block generation unit for sequentially selecting the master data block as a master data block which is a data block to be transmitted by the master base station and a data block generation unit for selecting a packet of the master data block during a transmission time interval From the first packet in the transmission order to the master And transmits data packets following the master data block in the transmission order from the first packet to the secondary base station in the transmission order during the unit transmission time from the transmission start time, Section.

According to an embodiment of the present invention, a terminal constructs a master data block, which is a set of packets that can be transmitted during a backhaul delay time, to a master base station and transmits the master data block to the master base station. An optimal waiting time is distributed to each base station so that the average waiting time becomes shorter than the backhaul delay time between the master base station and the secondary base station, thereby solving the problem of uplink transmission delay due to non-ideal backhaul, . In addition, the terminal can estimate the backhaul delay time based on a difference in arrival time between a packet directly transmitted from the master base station to the terminal and a packet transmitted from the master base station to the terminal via the secondary base station.

Figure 1 is a diagrammatic representation of a dual-link network.
FIGS. 2A and 2B are diagrams illustrating a conventional data transmission method in a dual connection network.
3 is a diagram schematically illustrating a configuration of a mobile communication system for providing a dual connection service according to an embodiment of the present invention.
4 is a diagram illustrating a configuration of a terminal receiving a dual connection service from a mobile communication system according to an embodiment of the present invention.
5 is a diagram illustrating a procedure of an uplink transmission delay reduction method according to an embodiment of the present invention.
6A and 6B are diagrams illustrating data transmission by the uplink transmission delay reduction method according to the first embodiment of the present invention.
7A and 7B are diagrams illustrating data transmission by an uplink transmission delay reduction method according to a second embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

3 is a diagram schematically illustrating a configuration of a mobile communication system for providing a dual connection service according to an embodiment of the present invention. The mobile communication system 100 of FIG. 3 is a system for providing a mobile communication service to the terminal 200 and may include a master base station 110, a secondary base station 120, and a core network 130. However, since the components of the mobile communication system 100 of FIG. 3 and the connection relationships of the respective components to be described below are only one embodiment of the present invention, the technical idea of the present invention is limited to FIG. 3 no.

The terminal 200 is a device for connecting to a mobile communication network using the master base station 110 or the secondary base station 120 and providing mobile communication services such as data transmission and reception to the user. For example, the terminal 200 may include a hand-held mobile communication device, such as a smart phone, a tablet PC, and a smart watch, . In addition, the terminal 200 according to an embodiment of the present invention is required to be a terminal capable of dual connection. That is, the terminal 200 can simultaneously access the master base station 110 and the secondary base station 120 to perform data communication.

The master base station 110 and the secondary base station 120 are devices for connecting the core network 130 and the terminal 200 in order to provide a mobile communication service to the terminal 200. Each base station can exchange data with each other through a backhaul such as an X2 interface, and can exchange data with a terminal 200 through a wireless channel. In addition, each base station can be connected to the core network 130 through a wired network such as optical communication.

The core network 130 may be responsible for managing the mobile communication system 100. Specifically, the core network 130 may perform procedures for authentication and security for the user of the terminal 200. The core network 130 can transmit a data packet transmitted from the terminal 200 to the master base station 110 or the secondary base station 120 through the uplink to the external network 300 such as the Internet, 200 may transmit the data packet to be received from the external network 300 to the terminal 200 via the downlink to the master base station 100 or the secondary base station 120.

4 is a diagram illustrating a configuration of a terminal receiving a dual connection service from a mobile communication system according to an embodiment of the present invention. The terminal 200 of FIG. 4 may include a data block generator 210, a data transmitter 220, a rate information acquirer 230, and a delay information acquirer 240. However, the description of the components of the terminal 200 of FIG. 4 is only an embodiment of the present invention, and therefore the technical idea of the present invention is not limited to FIG.

The data block generation unit 210 may construct a plurality of unit data from the packets that the terminal 200 should transmit. The packet to be transmitted may be in the form of a PDCP packet, for example. The PDCP packet may have a respective serial number. When the 3GPP (3 ^rd Generation Partnership Project) Release 13, which is a communication standard, is used, the size of the serial number may be 5 bits, 7 bits, 12 bits, or 15 bits. Hereinafter, it is assumed that "packet" refers to a PDCP packet, but the present invention is not limited thereto.

Since one unit data is transmitted from the terminal 200 to the base station in one unit transmission time, the size of the unit data can be determined based on the data transmission rate from the terminal 200 to the base station, which will be described later. In addition, since the sizes of the packets may be all different, one unit data may include a plurality of packets, or one packet may be divided into a plurality of unit data.

The data block generator 210 may generate a plurality of data blocks to be transmitted to the master base station 110 or the secondary base station 120 from the unit data. In this case, the data block may include one or more unit data, and the method of configuring the data block may be variously applied according to the embodiment, which will be described in detail with reference to FIGS. 5 to 7B below. The data block generator 210 may be implemented by a computing device including a microprocessor.

The data transmission unit 220 can distribute the data blocks generated by the data block generation unit 210 to each base station so that the data blocks can be transmitted through either the master base station 110 or the secondary base station 120. The data transmitting unit 220 may be configured to include a communication module capable of performing wired or wireless communication in addition to a computing device including a microprocessor. The data transmitting unit 220 may include a speed information acquiring unit 220, And transmission information acquisition unit 230 are the same. A detailed implementation method of such a communication module will be obvious to a person skilled in the art, and a detailed description thereof will be omitted here.

The speed information acquisition unit 230 may acquire information on the data transmission speed to the master base station 110 or the secondary base station 120. [ In the present invention, the uplink transmission rate will be mainly acquired by the rate information acquisition unit 230, but the present invention is not limited thereto. The delay information obtaining unit 240 may obtain the delay time due to the backhaul between the master base station 110 and the secondary base station 120. [ The detailed operation of the speed information obtaining unit 230 and the delay information obtaining unit 240 will be described in detail with reference to FIG.

5 is a diagram illustrating a procedure of an uplink transmission delay reduction method according to an embodiment of the present invention. However, since the method shown in Fig. 5 is only one embodiment of the present invention, the concept of the present invention is not limited to Fig. 5, and each step of the method shown in Fig. But may be performed in different orders. Hereinafter, an uplink transmission delay reduction method of the present invention will be described with reference to FIG. 5, and two representative embodiments of the present invention will be described in detail with reference to FIGS. 6A to 7B.

First, in a state where there is no information such as a backhaul delay time, the data transfer unit 220 can cross-transfer unit data to the master base station 110 and the secondary base station 120 (S101). The unit data is a data size that can be transmitted during one unit transmission time. The transmission data stored in the transmission buffer of the terminal 200 is a set of unit data that can be transmitted in a predetermined order. . For convenience of explanation, it is assumed that one unit data is composed of one packet in the future. Such cross-transmission may be performed, for example, as described with reference to FIGS. 2A and 2B. Each packet constituting the unit data has a serial number which is an integer of 0 or more. At this time, the data transmission unit 220 can transmit the even-numbered packets to the master base station 110 and the odd-numbered packets to the secondary base station 120. While performing the crossing transmission, the rate information acquisition unit 230 acquires the uplink transmission rates (R _M and R _S , respectively) per unit transmission time (TTI) of the master base station and the secondary base station through the delay information acquisition unit 240 May attempt to acquire the backhaul delay time T (S102), respectively.

When the values of R _M , R _S, and T are obtained, the data block generator 210 may generate a data block including at least one of the packets included in the transmission target data, based on the obtained values . 2A and 2B, when the length of the unit transmission time is TTI, a packet transmitted from the UE 200 to the secondary base station 120 is transmitted to the master base station 110 before being transmitted to the upper layer, But the packets transmitted to the master base station 110 should wait for a time of T-TTI. Therefore, the method of reducing the uplink transmission delay of the present invention aims at reducing the waiting time of the packets transmitted to the master base station 110 to less than the T-TTI level. In order to achieve the above object, first, the data block generator 210 transmits a packet, which can be transmitted to the master base station 110, for a time corresponding to the backhaul delay time T, And selects a set of the selected packets as a master data block that is a data block to be transmitted to the master base station 110 (S103). For example, when the backhaul delay time is 10 ms and the unit transmission time is 1 ms, 10 unit data that can be transmitted for a time of 10 ms, that is, 10 packets of serial numbers 0 to 9 are selected from the beginning of the transmission object data And can be designated as a master data block.

In this manner, when designating packets of a quantity that can be transmitted to the master base station 110 during the backhaul delay time as master data blocks, the average waiting time of packets transmitted to the master base station 110 is reduced compared to the cross- . This is based on the principle that the standby time is reduced when the serial number reaches the master base station 110 at a point in time when adjacent packets are as close to each other as possible.

In order to explain the above principle in more detail, a packet 9 and a packet 10 in the data to be transmitted are exemplified. According to the prior art of FIGS. 2A and 2B, the 9th packet adjacent to each other is transmitted from the terminal to the secondary base station 120 in the 4th TTI and to the master base station 110 in the 5th TTI, do. At this time, the 10th packet transmitted directly to the master base station 110 reaches the master base station 110 in the 5th TTI, but the 9th packet transmitted to the secondary base station 120 is transmitted to the master base station 110 through the backhaul Therefore, the backhaul delay time of 10 ms is further consumed and reaches the master base station 110 in the TTI of 14 times. That is, even though it is transmitted from the terminal 200 at a similar point in time, it reaches the master base station 110 by 9 ms later than the 10th packet. Accordingly, the 10th packet must wait for 9ms, which is almost the same as the backhaul delay time, in the master base station 110 until the 9th packet, the numbered packet, arrives at the master base station 110. [

In contrast, according to an embodiment of the present invention, the 9th packet is included in the master data block, and the 9th TTI is transmitted from the terminal 200 to the master base station 110 on the basis of the transmission start time of the data to be transmitted, Lt; / RTI > The packet 10, which is the packet with the highest serial number among the packets not included in the master data block, is transmitted from the terminal 200 to the secondary base station 120 at the 0th TTI. Then, the ninth packet reaches the master base station 110 immediately after the ninth TTI, and the tenth packet reaches the master base station 110 via the backhaul delay time at the tenth TTI. That is, the 9th packet having the serial number earlier than the 10th packet can be arrived earlier than the 10th packet to the master base station 110 even though it is later than the 10th packet. Therefore, in this case, the 10th packet will not have to wait for the 9th packet that precedes the serial number.

In other words, according to the related art, "the order transmitted from the terminal 200" is made in the order of the packet serial number, whereas the backhaul delay time is considered according to the embodiment of the present invention, Quot; sequence "can be made in the order of the packet serial number as much as possible, thereby reducing the waiting time.

When the data block is generated, the data transmission unit 220 can transmit the packets included in the master data block from the predetermined transmission start point to the master base station 110 in order from the first packet, and in parallel, Packets in the following order of the master data block can be transmitted to the secondary base station 120 from the transmission start time in order from the first packet (S104).

However, the process of generating a data block from a packet of data to be transmitted and transmitting a packet to each base station is performed every time a specific repetition condition is satisfied, for example, every time the backhaul delay time T elapses, This is because it is possible to perform repetition every time a unit transmission time (TTI) elapses or at a time point when each data block is completed, because there may be updates such as a backhaul delay time and an uplink transmission rate of each base station.

If the repetition condition is satisfied (S105) while the generation and transmission of the data block is being performed, if the residual data of the data stream not yet transmitted in the transmission buffer of the terminal 200 remains to a level exceeding a predetermined threshold value (Update) and transmission process of the next data block (S107), the backhaul delay time (T) and the uplink transmission rate (R _M , R _S ) have. If the remaining data is less than the threshold value, all remaining data may be transmitted to the master base station (S108) and the transmission may be terminated.

Hereinafter, a method for determining the backhaul delay time and the uplink transmission rate of each base station will be described. First, the uplink transmission rate for each base station can be transmitted by crossing the unit data for the master base station 110 and the unit data for the secondary base station 120 in the transmission buffer of the terminal 200. In this way, the rate information acquisition unit 230 of the terminal 200 can continuously measure and update the uplink transmission rate. After the transmission history is accumulated to some extent, the rate information acquisition unit 230 may predict the uplink transmission rate based on the accumulated transmission history. The thus obtained uplink transmission rate for each base station can be used to determine the amount of data to be transmitted to each base station and the data amount of the data block, which will be described later in detail.

Next, the backhaul delay time estimation will be described. The simplest method for determining the backhaul delay time is to directly check the backhaul delay time with the secondary base station 120 when the master base station 110 adds the secondary base station 120 and transmit the backhaul delay time to the terminal 200 . As a specific implementation method, a message enabling the backhaul delay time itself to be confirmed immediately after connection with the secondary base station 120 may be exchanged between the base stations, or a message may be exchanged between the master base station 110 and the secondary base station 120 The backhaul delay of each base station can be transmitted to each base station.

Next, assuming that no information regarding the backhaul delay is exchanged between the master base station 110 and the secondary base station 120, a method of confirming the backhaul delay time through performing the active measurement operation of the terminal may be as follows And so on.

First, a method of redundantly transmitting a packet (for example, a PDCP PDU) having a specific serial number from the master base station 110 and the secondary base station 120 to the terminal 200 can be mentioned. For this, the master base station 110 needs to transmit the data directly to the terminal 200 and also to the secondary base station 120 through the backhaul. If the secondary base station 120 does not have a large amount of traffic, the secondary base station 120 transmits the data to the mobile station as soon as it receives the data, so that the arrival time difference of the overlapped packets in the mobile station can be considered as the backhaul delay time. However, depending on the network load, scheduling policy, and buffer status, the arrival time difference of the redundant data may be different from the actual backhaul delay time. In order to compensate for this, the terminal 200 may perform the backhaul delay time estimation a plurality of times and averages the results of performing a plurality of times. Meanwhile, in order to ensure higher accuracy, the master base station 110 may transmit redundant data when the data in the transmission buffer of the secondary base station 120 is empty.

For data to be transmitted redundantly, a data packet having a specific serial number can be determined and used in advance. However, if there are many packets to be transmitted redundantly, since the same data is transmitted from two base stations, radio resources may be wasted. Therefore, it is necessary to keep the redundant transmission packets used for backhaul delay time estimation as small as possible. In addition, when the PDCP layer receives a packet repeatedly in the PDCP layer, the terminal 200 reflects only the packet arriving at the beginning and discards the duplicate packet, so that there is no problem in operation due to packet duplication transmission of the base station.

Second, the master base station 110 determines a reference packet that assists the comparison of the arrival time of the UE, directly transmits the reference packet to the UE, and transmits the subsequent packet immediately following the reference packet to the secondary base station 120 Method. The terminal 200 can regard the time difference between the reception time of the reference packet and the reception time of the subsequent packet as a backhaul delay time. As the reference packet, an RRC control message or a PDCP control PDU (Control PDU) for measuring the backhaul delay time can be used.

A PDCP control PDU defined in the PDCP layer can be used as a method that can be utilized without separately defining the reference packet. The PDCP control PDU is a message informing the transmitting side of the reception state of the PDCP layer, and each field can be utilized based on the existing PDCP control PDU format. First, a field value indicating the measurement of the backhaul delay time may be added to the PDU Type field (3 bits) indicating the PDU type and used as a reference packet. For example, if the value of the PDU Type field is set to 111, the UE considers the PDCP control PDU as a reference packet. Next, the first missing PDCP sequence number (FMS) field of the PDCP control PDU may include the serial number of the PDCP data PDU (Data PDU) transmitted to the secondary base station 120 immediately after transmission of the PDCP control PDU. In summary, when the UE receives a PDCP control PDU having a PDU Type field value of 111, it regards the PDCP control PDU as a reference packet for estimating the backhaul delay time, and determines the PDCP control PDU from the reception time of the PDCP control PDU The time difference until the packet having the serial number included in the FMS field is received from the secondary base station can be regarded as the backhaul delay time.

The delay information acquisition unit 240 of the terminal 200 determines the timing at which the terminal 200 receives the packet transmitted from the master base station 110 to the terminal 200 at the first time, The backhaul delay time can be estimated using the difference between the time when the terminal 200 receives the packet transmitted from the secondary base station 120 by the base station 100 to the secondary base station 120 at the second time point. Here, the first viewpoint and the second viewpoint may be the same or different. For example, according to the first method of using the redundant packet among the above-described methods, the first point and the second point of time may be the same.

The delay information acquiring unit 240 may calculate the plurality of delay time candidate values by performing the delay time estimation as described above a plurality of times and calculate the backhaul delay time by a method of averaging the plurality of delay time candidate values have. At this time, the delay time candidate value exceeding the threshold value set for setting the upper limit of the backhaul delay time may be excluded from the average calculation. Such a threshold value can be set to, for example, 60 ms which is the maximum value of the generally considered backhaul delay time.

Hereinafter, with reference to FIG. 6A to FIG. 7B, two exemplary embodiments of the downlink transmission delay reduction method of the present invention will be described.

[ 1st Example ]

6A and 6B are diagrams illustrating data stream transmission by an uplink transmission delay reduction method according to the first embodiment of the present invention. According to the first embodiment, data that can be transmitted to the two base stations during the backhaul delay time T from the current time is determined from the data in the transmission buffer of the terminal 200, To the secondary base station 120, and the latter data can be allocated to the secondary base station 120 as a secondary data block.

When the uplink transmission rate R _M to the master base station 110 and the uplink transmission rate R _S to the secondary base station are obtained by the transmission information acquisition unit 230, (B _M ) to be transmitted to the secondary base station and the data amount (B _S ) to be transmitted to the secondary base station can be maximum B _M = R _M × T and B _S = R _S × T, respectively. Based on the calculation result, the data block generator 210 can generate a data block to be transmitted to each base station for a time T (T).

That is, referring to FIG. 6A, assuming that each unit data is composed of one packet having a sequence number of an integer equal to or greater than 0, the terminal transmits a B _M + B _S size The integrated data block may be allocated and the integrated data block may be divided into a master data block of the B _M size and a secondary data block of the B _S size located in the front portion. The data blocks thus generated may be transmitted to the master base station 110 and the secondary base station 120 by the data transmission unit 220, respectively. Each of the data blocks, i.e., the master data block and the secondary data block, can be transmitted during the backhaul delay time T when the uplink transmission rate predicted by the terminal 200 is maintained. However, If there is a difference, the transfer may be completed earlier or take an additional time. Even if the data block transmission is not completed in accordance with the backhaul delay time T, the terminal 200 can repeat the process of configuring the data block again based on the uplink transmission rate according to the previous data block transmission.

In FIG. 6A, it is assumed that the length of the unit transmission time (TTI) is 1 ms and the length of the backhaul delay time (T) is 10 ms. Accordingly, a packet (which is assumed to be the same unit data in this example) that can be transmitted in one TTI, i.e., 1 ms, may include 10 backhaul delay time T, i.e., 10 data blocks transmitted in 10 ms. 6A, the packets 0 to 9 are sequentially transmitted to the master base station 110 and the packets 10 to 19 are sequentially transmitted to the secondary base station 120 for the first 10 ms. Respectively, by the data transmission unit 220. Then, the unit data of 0 to 9 are directly received in the reception buffer of the master base station 110, and the unit data of 10th to 19th are respectively transmitted to the master base station 110 Lt; / RTI > buffer. Likewise, the unit data of 20 to 29 are immediately received in the reception buffer of the master base station 110, and the unit data of 30 to 39 are transmitted to the master base station 110 after 10 ms from the transmission time Lt; / RTI > buffer.

The packets transmitted to the secondary base station 120 arrive at the reception buffer of the master base station 110 after lapse of 10 ms but since the packets located behind the serial number in the transmission buffer of the terminal 200 are transmitted to the secondary base station 120, It can be confirmed that the sequence number of the packet is continued after the backhaul delay time (T) when the arrival time of the master base station 110 in the reception buffer is confirmed.

According to the first embodiment, the average waiting time of the unit data transmitted to the master base station 110 is reduced to less than half of the prior art described with reference to FIGS. 2A and 2B. According to the prior art, all the unit data except the packet No. 0 has a waiting time of 9 ms with respect to the packet received by the master base station 110. However, according to the first embodiment of the present invention, It can be delivered to the upper layer immediately. The 10th to 19th packets transmitted to the secondary base station 120 can be transmitted to the upper layer without waiting because all the previous packets have been received. However, since the 20th to 29th packets are received by the master base station 110 in pairs with the 10th to 19th packets, packets from 20th to 29th packets are transmitted from the 10th to the 19th packets It can be delivered to the upper layer immediately after it is received. Accordingly, the 20th packet located at the forefront has a waiting time of 9ms and the waiting time of the subsequent packets is reduced by 1ms as in the prior art. That is, the average waiting time from the 20th to the 29th unit data and the unit data transmitted to the master base station 110 thereafter to the upper layer is 4.5ms, which can be confirmed from FIG. 6b.

Meanwhile, if the backhaul delay time can be accurately estimated, the data block may be configured according to the backhaul delay time, but the terminal 200 may not know the backhaul delay time between the two base stations in advance. To this end, the delay information acquisition unit 240 of the terminal 200 may receive the network configuration information related to the backhaul delay time or utilize the backhaul delay time information measured by various methods described previously, 210 may generate a data block reflecting the result of the new measurement.

Meanwhile, if data transmission to at least one of the base stations is completed, the terminal immediately constructs an additional new data block reflecting the latest average transmission rate, and distributes the packets for the master base station 110 and the secondary base station 120 again Can continue. At this time, if the data transmission assigned to the particular base station is completed but data allocated to another base station remains, this can be taken into account when constructing a new data block. For example, assuming that the transmission of the master data block has been completed and that a total of 100 kbytes of data remain in the secondary data block, the size of the new data block reflecting the new average transmission rate is smaller than the size of the master base station 110 and the secondary base station 120 , If the secondary data block is newly constructed, only 900 kbytes can be additionally secured and it can be constituted by the previous 100 kbytes plus 1 Mbyte. Through this process, the transmission completion time of the data block transmitted to the two base stations can be adaptively matched.

[ Second Example ]

7A and 7B are diagrams illustrating a data stream transmission according to an uplink transmission delay reduction method according to a second embodiment of the present invention. The transmission information acquiring unit 230 acquires the uplink transmission rate R _M to the master base station 110 and the uplink transmission rate R to the secondary base station TTI per unit transmission time TTI in the same way as in the first embodiment, _S ), respectively. Data that can be transmitted from the current time in the transmission buffer of the terminal 200 during the backhaul delay time T by the master base station is assigned to the master base station 110 as a master data block, And unit data transmitted by the base station 120 during a unit transmission time (TTI). In the second embodiment, a data block is formed only for the master base station 110, and a separate data block for the secondary base station 120 is not formed. In addition, the master data block for the master base station 110 and the unit data for the secondary base station 120 can be updated at every TTI.

Also in FIG. 7A, it is assumed that the length of the unit transmission time (TTI) is 1 ms and the length of the backhaul delay time (T) is 10 ms. It is also assumed that each unit data is composed of one packet having a serial number of 0 or more integer.

In the present invention, data that can be transmitted for a time corresponding to the backhaul delay time (T) from the top of the transmission object data is allocated to the master base station 110 as a master data block on the basis of a unit transmission time (TTI) , And the subsequent data may be composed of one piece of unit data and allocated to the secondary base station 120. That is, on the basis of the backhaul delay time T in units of TTI, the terminal 200 transmits to the master base station 110 already secured by the speed information obtaining unit 230 at the moment TTI = n (n is an integer) The data to be transmitted up to the time point of TTI = n + T - 1 is secured as a master data block based on the uplink transmission rate for the uplink data, and then the secured master data blocks are sequentially formed as unit data and transmitted to the master base station 110 . At the same time, the terminal 200 acquires the data located at the front of the portion excluding the secured master data block at the moment of TTI = n and forms the unit data that can be transmitted to the secondary base station 120, 120).

Referring to FIG. 7A, the MS 200 secures the 0th to 9th packets, which are expected to be transmitted for T = 10ms in the transmission buffer, as a master data block for transmission to the master base station 110, The 0th packet can be transmitted to the master base station 110 at the TTI of the first TTI. In addition, at the instant of securing the master data block, the 10th packet immediately following the packets 0 to 9 can be transmitted to the secondary base station 120. This process can be repeated in the first TTI, which is the next TTI. In order to secure data expected to be transmitted in the next 10 ms, a packet 11 is added for the master base station 110, 1 to the master base station 110. At the same time, the 12th packet immediately following the 11th packet, which is the last packet of the newly updated master data block, can be transmitted to the secondary base station 120. That is, the data to be transmitted to the secondary base station 120 can be updated in the master data block and the corresponding TTI for each unit transmission time (TTI). This process can be continued until all the data in the transmission buffer of the UE 200 is transmitted in units of transmission time units.

As a result of the above-described process, as shown in FIG. 7A, even-numbered packets from 10th are allocated to the secondary base station 120 and odd packets are allocated to the master base station 110. [ In particular, the packet transmitted to the secondary base station 120 arrives at the reception buffer of the master base station 110 late by the backhaul delay time. In the terminal 200, two packets having a time difference of the backhaul delay time It can be seen that two consecutive packets of the serial number are simultaneously received in the master base station 110 receiving buffer. Therefore, as can be seen in FIG. 7B, all packets can be transmitted to the upper layer without waiting time at the master base station 110.

According to an embodiment of the present invention, the backhaul delay time is estimated, and the time that the packet transmitted to the master base station 110 on the uplink is reflected in the master base station 110 . As a result, the problem due to the data transmission delay can be largely solved. Therefore, the present invention can be applied to the real-time service or the streaming service sensitive to the transmission delay, thereby improving the service quality.

Combinations of each step of the flowchart and each block of the block diagrams appended to the present invention may be performed by computer program instructions. These computer program instructions may be embedded in an encoding processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, so that the instructions, performed through the encoding processor of a computer or other programmable data processing apparatus, Thereby creating means for performing the functions described in each step of the flowchart. These computer program instructions may also be stored in a computer usable or computer readable memory capable of directing a computer or other programmable data processing apparatus to implement the functionality in a particular manner so that the computer usable or computer readable memory It is also possible for the instructions stored in the block diagram to produce a manufacturing item containing instruction means for performing the functions described in each block or flowchart of the block diagram. Computer program instructions may also be stored on a computer or other programmable data processing equipment so that a series of operating steps may be performed on a computer or other programmable data processing equipment to create a computer- It is also possible that the instructions that perform the processing equipment provide the steps for executing the functions described in each block of the block diagram and at each step of the flowchart.

Also, each block or each step may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative embodiments, the functions mentioned in the blocks or steps may occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially concurrently, or the blocks or steps may sometimes be performed in reverse order according to the corresponding function.

The above description is merely illustrative of the technical idea of the present invention, and various modifications and changes may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as falling within the scope of the present invention.

The present invention can be utilized for efficient operation of a dual connection network. More specifically, the present invention can be utilized to improve mobile communication service quality of a mobile station in a heterogeneous network environment in which a macro base station and a small base station are mixed. Particularly, since the present invention can solve a problem caused by a data transmission delay to a considerable part of the problem of quality of service, the present invention can be applied to a real-time service or a streaming service sensitive to a transmission delay, .

100: mobile communication system
110: Master base station
120: Secondary base station
121:
122: control signal generating unit
123:
130: core network
131: control node
132: Serving gateway
133: PDN gateway
200: terminal
300: External network

Claims (20)

A downlink transmission delay reduction method performed in a terminal connected to a master base station and a secondary base station in a packet split duplex network environment,
Comprising the steps of: acquiring transmission target data composed of a plurality of packets to be transmitted according to a predetermined transmission order;
The transmission of the data to be transmitted to the master base station during the backhaul delay time, which is the time required for data to be transmitted from the secondary base station to the master base station, Selecting as a master data block which is a data block to be transmitted by the master base station;
Transmitting a packet of the master data block from the first packet in the transmission order to the master base station during a transmission time interval (TTI) from a predetermined transmission start time; And
And transmitting the packet following the master data block in the transmission order from the first packet to the secondary base station in the transmission order during the unit transmission time from the transmission start time
A method for reducing uplink transmission delay. The method according to claim 1,
Wherein the step of designating comprises the step of selecting, from among the packets to be transmitted, a packet after the master data block in the transmission order, a packet which can be transmitted to the secondary base station during the backhaul delay time, And designating the secondary data block as a secondary data block to be transmitted by the secondary base station
A method for reducing uplink transmission delay. 3. The method of claim 2,
Wherein the transmitting of the master data block to the master base station includes transmitting the packet of the master data block from the first packet to the master base station in the transmission order during the backhaul delay time from the transmission start time,
The step of transmitting to the secondary base station includes transmitting the packet of the secondary data block from the first packet to the secondary base station in the transmission order during the backhaul delay time from the transmission start time
A method for reducing uplink transmission delay. The method according to claim 1,
Wherein, when the unit transmission time elapses from the predetermined transmission start time, a packet transmitted from the master data block is excluded, and among the untransmitted packets not belonging to the master data block in the transmission target data, The master data block is added to the master data block in such a way that the master data block again includes a packet that can be transmitted to the master base station during the backhaul delay time, Further comprising redirecting the data block
A method for reducing uplink transmission delay. 5. The method of claim 4,
Transmitting a packet of the redirected master data block from the first packet in the transmission order to the master base station during the unit transmission time from the time when the unit transmission time elapses; And
And transmitting the packet following the reconfigured master data block in the transmission order from the first packet to the secondary base station in the transmission order during the unit transmission time from the time when the unit transmission time elapses
A method for reducing uplink transmission delay. 5. The method according to any one of claims 2 and 4,
Further comprising the step of acquiring transmission rate information on a data transmission rate to the master base station and a data transmission rate to the secondary base station,
The designation or re-designation of the data block is performed so that the data block includes a positive data packet that can be transmitted at maximum within the backhaul delay time, based on the transmission rate information
A method for reducing uplink transmission delay. The method according to claim 1,
Further comprising acquiring information on a backhaul delay time required for data transmission from the secondary base station to the master base station,
Wherein the acquiring step comprises the steps of: when the master base station receives the data transmitted to the terminal at the first time point and when the master base station receives the data transmitted to the secondary base station at the second time point from the secondary base station And estimating the backhaul delay time based on the difference
A method for reducing uplink transmission delay. 8. The method of claim 7,
Wherein the estimating step includes a step of calculating a plurality of delay time candidate values based on the difference of the received time points and calculating an average of the remaining delay time candidate values excluding those exceeding a predetermined threshold value among the plurality of delay time candidate values And estimating the backhaul delay time as the backhaul delay time
A method for reducing uplink transmission delay. 5. The method according to any one of claims 2 and 4,
Further comprising acquiring information on a backhaul delay time required for data transmission from the secondary base station to the master base station,
The designation or re-designation of the data block is performed such that the data block includes a maximum amount of data packets that can be transmitted within the backhaul delay time, based on information about the backhaul delay time
A method for reducing uplink transmission delay. In a terminal connected to a master base station (MeNB) and a secondary base station (SeNB) in a packet split duplex network environment,
The amount of data to be transmitted to the master base station during a backhaul delay time, which is the time required for data to be transmitted from the secondary base station to the master base station, among transmission target data composed of a plurality of packets to be transmitted according to a predetermined transmission order A data block generation unit for selecting a packet from the top of the transmission target data in the transmission order and designating the packet as a master data block to be transmitted by the master base station; And
And transmits the packet of the master data block from the first packet to the master base station in the transmission order during a transmission time interval (TTI) from a predetermined transmission start time, And a data transfer unit for transferring the packet following the master data block in the transfer order from the first packet to the secondary base station in the transfer order,
A terminal to which an uplink transmission delay reduction method is applied. 11. The method of claim 10,
Wherein the data block generation unit is configured to generate a data packet that is a packet after the master data block in the transmission order and that can be transmitted to the secondary base station during the backhaul delay time, And designates this as a secondary data block which is a data block to be transmitted by the secondary base station
A terminal to which an uplink transmission delay reduction method is applied. 12. The method of claim 11,
Wherein the data transmission unit transmits a packet of the master data block from the first packet to the master base station in the transmission order during the backhaul delay time from the transmission start time, And transmits the packet of the secondary data block to the secondary base station from the first packet in the transmission order
A terminal to which an uplink transmission delay reduction method is applied. 11. The method of claim 10,
Wherein the data block generator excludes packets previously transmitted from the master data block when the unit transmission time elapses from the predetermined transmission start time, Adding a predetermined amount of packets from the first packet to the last part of the master data block according to the transmission order of the transmission packets so that the master data block can transmit a positive packet that can be transmitted to the master base station during the backhaul delay time And reassigning the master data block to include the master data block again
A terminal to which an uplink transmission delay reduction method is applied. 14. The method of claim 13,
Wherein the data transmission unit transmits the packets of the redirected master data block from the first packet to the master base station in the transmission order from the time point when the unit transmission time elapses to the master base station during the unit transmission time, And transmits the packet following the reconfigured master data block in the transmission order from the first packet to the secondary base station in the transmission order during the unit transmission time
A terminal to which an uplink transmission delay reduction method is applied. The method according to any one of claims 11 to 13,
Further comprising a speed information acquiring unit for acquiring transmission speed information on a data transmission speed to the master base station and a data transmission speed to the secondary base station,
The designation or re-designation of the data block is performed so that the data block includes a positive data packet that can be transmitted at maximum within the backhaul delay time, based on the transmission rate information
A terminal to which an uplink transmission delay reduction method is applied. 11. The method of claim 10,
Further comprising a delay information obtaining unit for obtaining information on a backhaul delay time required for data transmission from the secondary base station to the master base station,
Wherein the delay information obtaining unit obtains the delay information from the time when the master base station receives the data transmitted to the terminal at the first time point and the time when the master base station receives the data transmitted from the secondary base station at the second time, Based on the difference, the backhaul delay time is estimated
A terminal to which an uplink transmission delay reduction method is applied. 17. The method of claim 16,
Wherein the delay information obtaining unit calculates a plurality of delay time candidate values based on the difference of the received time points and calculates an average of the remaining delay time candidate values except for the plurality of delay time candidate values exceeding a predetermined threshold value And estimates the backhaul delay time
A terminal to which an uplink transmission delay reduction method is applied. The method according to any one of claims 11 to 13,
Further comprising a delay information obtaining unit for obtaining information on a backhaul delay time required for data transmission from the secondary base station to the master base station,
The designation or re-designation of the data block is performed such that the data block includes a maximum amount of data packets that can be transmitted within the backhaul delay time, based on information about the backhaul delay time
A terminal to which an uplink transmission delay reduction method is applied. 10. A program stored on a computer-readable medium for performing the respective steps according to the method of any one of claims 1 to 9. 10. A computer-readable recording medium having recorded thereon instructions for performing the respective steps according to the method of any one of claims 1 to 9.

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