KR102186906B1 - Method for reducing uplink transmission delay in dual-connectivity network and terminal applying same - Google Patents

Abstract

The uplink transmission delay reduction method performed by a terminal connected to a master base station and a secondary base station in a packet split-type dual connection network environment according to an embodiment of the present invention comprises a plurality of packets to be transmitted according to a predetermined transmission order. Securing data to be transmitted, of the data to be transmitted, an amount of packets that can be transmitted to the master base station during a backhaul delay time, which is a time required to transmit data from the secondary base station to the master base station. Selecting from the beginning of the target data in the transmission order and designating it as a master data block, which is a data block to be transmitted by the master base station, from a predetermined transmission start point to a transmission time interval (TTI), the Transmitting a packet of a master data block from the first packet to the master base station in the transmission order, and a packet following the master data block in the transmission order of the transmission target data during the unit transmission time from the transmission start time In the transmission order, the first packet may be transmitted to the secondary base station.

Description

A method for reducing uplink transmission delay in a dual connectivity network and a terminal to which the method is applied {METHOD FOR REDUCING UPLINK TRANSMISSION DELAY IN DUAL-CONNECTIVITY NETWORK AND TERMINAL APPLYING SAME}

The present invention is a dual-connectivity network system of a packet split method in which a mobile communication terminal can simultaneously access a master base station (MeNB) and a secondary base station (SeNB) to transmit and receive data. In the following, 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.

Thanks to the improvement of living standards and the development of information and communication technology, the vast majority of people have and use personal mobile communication terminals such as cell phones. In addition, contents that can be used through such a mobile communication terminal are also increasing in capacity day by day. Therefore, the amount of data used by mobile communication subscribers is increasing exponentially.

To overcome this situation, a dual link technology was devised. According to the dual connectivity technology, a terminal can simultaneously use radio resources provided from two or more different network nodes, such as 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. As described above, when the terminal is connected to two base stations at the same time, the uplink and downlink data transmission rates of the terminal are greatly improved, thereby enabling a more improved communication environment.

1 is a diagram conceptually showing a dual connection network. In the mobile communication system 10 supporting the dual connectivity network as shown in FIG. 1, the terminal 20 may 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 through a backhaul called an X2 interface to exchange data with each other. Here, the master base station 11 has to provide a seamless connection to the terminal 20 while performing a role as an anchor when the secondary base station 12 is changed, compared to the secondary base station 12. It is desirable to have wide coverage.

In the mobile communication system 10 supporting the dual connectivity network as described above, 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, splitting is performed in the master base station 11 for one communication service. However, in the bearer split method, splitting is performed in a core network located at a rear end of the master base station 11 for different communication services. The packet split method can have an advantage in terms of performance such as data transmission speed compared to the bearer split method because adaptive splitting in consideration of the radio environment of the master base station 11 and the secondary base station 12 is possible.

When the terminal 20 simultaneously transmits data for a specific service through the master base station 11 and the secondary base station 12, a portion of the data transmitted to the secondary base station 12 is the master base station ( 11). At this time, since the backhaul is a non-ideal backhaul that requires a certain level of delay in data transmission, the portion transmitted from the terminal 20 to the secondary base station 12 is directly transferred to the master base station 11 at the same time. It arrives at the master base station 11 late by the delay time of the backhaul compared to the transmitted part.

The master base station 11 sequentially aggregates the packet data convergence protocol (PDCP) protocol data unit (PDCP) PDU (protocol data unit) directly received by the master base station 11 and the PDCP PDU delivered from the secondary base station 12 according to the serial number, It supports reordering function so that it can be delivered to. However, due to the delay in the backhaul as described above, the PDCP PDU directly received from the master base station 11 is, when a PDCP PDU whose serial number precedes itself is transmitted to the secondary base station 12, the PDCP PDU precedes the serial number. There may be a problem in that the PDCP buffer of the master base station 11 has to wait until it arrives at the master base station 11 through a backhaul.

2A and 2B are diagrams illustrating a data transmission method in a dual connection network according to the prior art. For convenience, assuming that each packet size to be transmitted from the terminal 20 is the same and that the transmission rate to the master base station 11 and the secondary base station 12 is the same, according to FIG. 2A, the terminal 20 transmits 0 Packets (eg, PDCP packets) having a serial number of the above integer are alternately allocated to the master base station 11 and the secondary base station 12. For example, even-numbered packets are assigned to the master base station 11, and odd-numbered packets are assigned to the secondary base station 12, respectively. For convenience, the terminal 20 may transmit one packet for a period of time as much as one transmission time interval (TTI). Here, it is assumed that TTI = 1 ms and the backhaul delay (T) is 10 ms. Then, 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 delivered to the core network based on the serial number. 2A, since packet 0 is the packet with the most advanced serial number, it can be directly transmitted to the core network. However, in packet 2, packet 1, which is the packet immediately preceding the serial number, passes through the backhaul to the master base station 11 9ms must be waited in the PDCP buffer of the master base station 11 until it is transmitted. 2B, it can be seen that all packets except for the 0th packet out of the even-numbered packets directly transmitted to the master base station 11 wait for an odd-numbered packet with a serial number faster than itself for 9ms. . Of course, the odd-numbered packets transmitted through the secondary base station 12 may be transferred to an upper layer without a separate waiting time in the master base station 11. In general, when there is a backhaul delay of T, a packet directly received to the master base station 11 must wait at 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 up to a level of 60 ms, a packet directly received to the master base station 11 must wait for a maximum of 59 ms without being delivered to an upper layer. This amount of delay can be said to be a number that can sufficiently affect the quality of delay-sensitive services such as real-time services and streaming services.

Korean Patent Application Publication No. 10-2015-0088746 (published on Aug. 3, 2015)

The problem to be solved by the present invention is, in the case of transmitting data through uplink in a packet split-type dual connection network system, a packet configured in consideration of the backhaul delay is appropriately distributed to one of a master base station and a secondary base station. By doing so, the uplink transmission delay reduction method and the terminal to which the method is applied to solve the data transmission delay caused by waiting for packets with a fast serial number transmitted to the secondary base station before the packets transmitted to the master base station are delivered to the core network. Is to provide.

The uplink transmission delay reduction method performed by a terminal connected to a master base station and a secondary base station in a packet split-type dual connection network environment according to an embodiment of the present invention comprises a plurality of packets to be transmitted according to a predetermined transmission order. Securing data to be transmitted, of the data to be transmitted, an amount of packets that can be transmitted to the master base station during a backhaul delay time, which is a time required to transmit data from the secondary base station to the master base station. Selecting from the beginning of the target data in the transmission order and designating it as a master data block, which is a data block to be transmitted by the master base station, from a predetermined transmission start point to a transmission time interval (TTI), the Transmitting a packet of a master data block from the first packet to the master base station in the transmission order, and a packet following the master data block in the transmission order of the transmission target data during the unit transmission time from the transmission start time In the transmission order, the first packet may be transmitted to the secondary base station.

A terminal connected to a master base station (MeNB) and a secondary base station (SeNB) in a dual connection network environment of a packet split method according to an embodiment of the present invention uses a plurality of packets to be transmitted according to a predetermined transmission order. Among the configured data to be transmitted, the amount of packets that can 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, is transmitted from the front of the data to be transmitted. Packets of the master data block during a transmission time interval (TTI) from a predetermined transmission start point and a data block generator that is selected in order and designated as a master data block, which is a data block to be transmitted by the master base station Is transmitted from the first packet to the master base station in the transmission order, and during the unit transmission time from the transmission start time, the packet next to the master data block in the transmission order among the transmission target data is first in the transmission order. It may include a data transmission unit for transmitting to the secondary base station from the previous packet.

According to an embodiment of the present invention, the terminal constructs a master data block, which is a set of packets that can be transmitted to the master base station during the backhaul delay time, and transmits it to the master base station first, and packets transmitted to the master base station wait at the master base station. By distributing subsequent packets to each base station so that the average waiting time is shorter than the backhaul delay time between the master base station and the secondary base station, the optimal dual connectivity service is provided to the terminal by solving the problem of uplink transmission delay due to non-ideal backhaul. Can provide. In addition, the terminal may estimate a 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 through the secondary base station.

1 is a diagram conceptually showing a dual connection network.
2A and 2B are diagrams illustrating a data transmission method in a dual connection network according to the prior art.
3 is a diagram schematically showing a configuration of a mobile communication system providing a dual connection service according to an embodiment of the present invention.
4 is a diagram showing 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 sequence of a method for reducing an uplink transmission delay 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 using the uplink transmission delay reduction method according to the second embodiment of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, and only these embodiments make the disclosure of the present invention complete, and are common knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have, and the invention is only defined by the scope of the claims.

In describing the embodiments of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in an embodiment of the present invention, which may vary according to the intention or custom of users or operators. Therefore, the definition should be made based on the contents throughout this specification.

3 is a diagram schematically showing a configuration of a mobile communication system 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 constituent elements of the mobile communication system 100 of FIG. 3 and the connection relationship between the constituent elements to be described below are only an embodiment of the present invention, the technical idea of the present invention is limitedly interpreted by FIG. no.

First, the terminal 200 is a device for providing mobile communication services such as data transmission and reception to a user by accessing a mobile communication network using the master base station 110 or the secondary base station 120. For example, the terminal 200 may include a hand-held-based mobile communication device, such as a smartphone, a tablet PC, and a smart watch, which ensures portability and mobility. . 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 may 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 equipment that connect the core network 130 and the terminal 200 to provide a mobile communication service to the terminal 200. Each base station may exchange data with each other through a backhaul such as an X2 interface, and may exchange data with the terminal 200 through a wireless channel. In addition, each base station may be connected to the core network 130 through a wired network such as optical communication.

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

4 is a diagram showing 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 generation unit 210, a data transmission unit 220, a speed information acquisition unit 230, and a delay information acquisition unit 240. However, since the description of the components of the terminal 200 of FIG. 4 is only an embodiment of the present invention, the technical idea of the present invention is not limitedly interpreted by FIG. 4.

The data block generator 210 may construct a plurality of unit data from packets to be transmitted by the terminal 200. The packet to be transmitted may be, for example, in the form of a PDCP packet. The PDCP packet may have a respective serial number, communication standard of 3GPP (3 ^rd Generation Partnership Project) when, based on the Release 13, the size of the sequence number is five bits in accordance with the type of service, 7 bits, It can be selected from 12 bits or 15 bits. Hereinafter, a description will be made on the assumption that "packet" refers to a PDCP packet, but is not limited thereto.

Since one unit data is transmitted from the terminal 200 to the base station at one unit transmission time, the size of the unit data may be determined based on a data transmission rate from the terminal 200 to the base station to be described later. In addition, since the sizes of packets may be all different, a plurality of packets may be included in one unit data, 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 a method of configuring a data block may be variously applied according to exemplary embodiments, which will be described in detail with reference to FIGS. 5 to 7B below. The data block generation unit 210 may be implemented by a computing device including a microprocessor.

The data transmission unit 220 may distribute the data blocks generated by the data block generation unit 210 to each base station so that they can be transmitted through either the master base station 110 or the secondary base station 120. The data transmission unit 220 may be configured in hardware to include a communication module capable of performing wired or wireless communication in addition to a computing device including a microprocessor, which is a speed information acquisition unit 220 to be described later. And the transmission information acquisition unit 230. A detailed implementation method of such a communication module is apparent to those of ordinary skill in the art, and thus further detailed description thereof will be omitted.

The rate information acquisition unit 230 may acquire information on a data transmission rate to the master base station 110 or the secondary base station 120. In the present invention, although the uplink transmission rate is mainly acquired by the rate information acquisition unit 230, it is not limited thereto. The delay information acquisition unit 240 may acquire a delay time due to a backhaul between the master base station 110 and the secondary base station 120. Detailed operations of the speed information acquisition unit 230 and the delay information acquisition unit 240 will be described in detail with reference to FIG. 5 below.

5 is a diagram illustrating a sequence of a method for reducing an uplink transmission delay according to an embodiment of the present invention. However, since the method shown in FIG. 5 is only an embodiment of the present invention, the spirit of the present invention is not limitedly interpreted by FIG. 5, and each step of the method shown in FIG. It goes without saying that it can be performed in a different order. Hereinafter, a method for reducing an uplink transmission delay according to the present invention will be generally described with reference to FIG. 5, and two exemplary embodiments of the present invention will be described in detail with reference to FIGS. 6A to 7B.

First, in the absence of information such as a backhaul delay time, the data transmission unit 220 may cross-transmit unit data to the master base station 110 and the secondary base station 120 (S101). It has been previously described that the unit data is data of a size that can be transmitted during one unit transmission time, and the transmission target data stored in the transmission buffer of the terminal 200 is regarded as a set of unit data that can be transmitted in a predetermined order. I can. For convenience of explanation, it is assumed from now on that one unit data is composed of one packet. 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 that is an integer greater than or equal to 0. In this case, the data transmission unit 220 may transmit the even-numbered packet to the master base station 110 and the odd-numbered packet to the secondary base station 120. While performing the cross-transmission, the rate information acquisition unit 230 obtains an uplink transmission rate (R _M and R _S , respectively) per unit transmission time (TTI) of the master base station and the secondary base station, and the delay information acquisition unit 240 ) May each attempt to obtain a backhaul delay time T (S102).

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 packets included in the transmission target data based on the obtained values. . According to the conventional method described with reference to FIGS. 2A and 2B, when the length of the unit transmission time is TTI, the packet transmitted from the terminal 200 to the secondary base station 120 is the master base station 110 before being transmitted to the upper layer. Although there is no need to wait at, it has been previously discussed that packets transmitted to the master base station 110 must wait for a time as much as T-TTI. Accordingly, the uplink transmission delay reduction method of the present invention aims to reduce the waiting time of packets transmitted to the master base station 110 to less than the T-TTI level. In order to achieve the above goal, first, the data block generation unit 210 generates an amount of packets that can be transmitted to the master base station 110 for a time corresponding to the backhaul delay time (T) among the data to be transmitted. It is possible to select in order from the top of the packet, and designate the selected set of packets as a master data block, which is a data block to be transmitted to the master base station 110 (S103). For example, when the backhaul delay time is 10ms and the unit transmission time is 1ms, 10 units of data that can be transmitted for a period of 10ms, that is, 10 packets with serial numbers 0 to 9 are selected from the beginning of the transmission target data. And can be designated as a master data block.

When the amount of packets that can be transmitted to the master base station 110 during the backhaul delay time is designated as a master data block, the average waiting time of the packets transmitted to the master base station 110 is reduced compared to cross-transmission in the prior art. I can. This focuses on the principle that packets with adjacent serial numbers must reach the master base station 110 at a time similar to each other as possible to reduce the waiting time.

In order to explain the above principle in more detail, packets 9 and 10 in the data to be transmitted are taken as examples. According to the prior art of FIGS. 2A and 2B, packets 9 adjacent to each other are transmitted from the terminal to the secondary base station 120 at TTI 4 and to the master base station 110 at TTI 5 based on the transmission start time. do. At this time, the 10th packet directly transmitted to the master base station 110 reaches the master base station 110 at the 5th TTI, but the 9th packet transmitted to the secondary base station 120 is sent to the master base station 110 through the backhaul. Since it needs to be transmitted, the backhaul delay time of 10 ms is further consumed to reach the master base station 110 at TTI 14. That is, even though it is transmitted from the terminal 200 at a similar point in time, it arrives at the master base station 110 as late as 9 ms compared to the 10th packet. Accordingly, for packet 10, the master base station 110 must wait for 9 ms, which is approximately the same as the backhaul delay time, until the packet 9, which is the packet with the preceding number, reaches the master base station 110.

On the other hand, according to an embodiment of the present invention, as described above, packet 9 is included in the master data block, and the master base station 110 from the terminal 200 to the ninth TTI based on the transmission start time of the transmission target data. Is sent to. Packet 10, which is a packet having the earliest serial number among 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, packet 9 reaches the master base station 110 immediately at the ninth TTI, and packet 10 reaches the master base station 110 at the 10th TTI through a backhaul delay time. In other words, even though the packet number 9 preceded by the serial number is transmitted later from the terminal 200 than the packet number 10, it may arrive at the master base station 110 earlier than the packet number 10. Therefore, in this case, packet 10 does not need to wait for packet 9 preceded by the serial number.

In short, according to the prior art, while "the order of transmission from the terminal 200" is in the order of packet serial number, according to an embodiment of the present invention, by considering the backhaul delay time, "reaching the master base station 110" The waiting time can be reduced by making the "order" as possible in the order of the packet serial number.

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

However, in the process of generating a data block from the packet of the data to be transmitted and transmitting the packet to each base station as described above, each time a specific repetition condition is satisfied, for example, every time a backhaul delay time (T) elapses, It may be repeatedly performed each time the unit transmission time (TTI) elapses or each data block transmission is completed, because the backhaul delay time, the uplink transmission rate of each base station, etc. may be updated.

If the repetition condition is satisfied while the data block is being generated and transmitted (S105), if the residual data of the data stream that has not yet been transmitted in the transmission buffer of the terminal 200 remains enough to exceed a preset threshold. (S106), the backhaul delay time (T) and the uplink transmission rate (R _M , R _S ) of each base station are updated by remeasurement (S107), and the next conference data block generation (update) and transmission process can be performed. have. If the residual data is less than or equal to the threshold value, all residual data may be transmitted to the master base station (S108) and transmission may be terminated.

Hereinafter, a method of finding 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 may use a method of crossing and transmitting unit data for the master base station 110 and unit data for the secondary base station 120 in a transmission buffer of the terminal 200. In this way, the rate information acquisition unit 230 of the terminal 200 may 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 an uplink transmission rate based on the accumulated transmission history. The uplink transmission rate for each base station thus obtained can be used when determining the amount of unit data and data blocks to be transmitted to each base station, which will be described in detail later.

Next, the estimation of the backhaul delay time will be described. As the simplest method for knowing the backhaul delay time, the master base station 110 directly checks the backhaul delay time with the secondary base station 120 when adding the secondary base station 120 and transmits it to the terminal 200. Can be lifted. As a specific implementation method, a message capable of self-checking the backhaul delay time immediately after connection to the secondary base station 120 is exchanged between both base stations, or between the master base station 110 and the secondary base station 120 through a system management function of a network operator. It is possible to transmit the backhaul delay of to each base station.

Next, assuming that information on the backhaul delay is not exchanged between the master base station 110 and the secondary base station 120, a method of checking the backhaul delay time through the active measurement operation of the terminal is as follows. Can be mentioned.

First, a method of repeatedly transmitting a packet (eg, PDCP PDU) having a specific serial number from the master base station 110 and the secondary base station 120 to the terminal 200 may be mentioned. To this end, the master base station 110 needs to transmit the corresponding data directly to the terminal 200 and at the same time transmit the data to the secondary base station 120 through a backhaul. Since the secondary base station 120 transmits the data to the terminal as soon as it receives the data if there is not much traffic, it can be considered that the difference in arrival time of the duplicated packets in the terminal is the backhaul delay time. However, the difference in arrival time of redundant data may differ from the actual backhaul delay time depending on the amount of network load, scheduling policy, and buffer status. To compensate for this, the terminal 200 may perform backhaul delay time estimation a plurality of times and average the results of performing the plurality of times. Meanwhile, in order to secure 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 repeatedly, a data packet having a specific serial number can be determined and used in advance. However, if there are many duplicated transmission packets, radio resources may be wasted because the same data is transmitted by two base stations, so it is necessary to keep the redundant transmission packets used for backhaul delay time estimation to a minimum. In addition, since the terminal 200 reflects only the first packet and discards the redundant packet when packets are repeatedly received in the PDCP layer, it can be said that there is no operational problem due to the redundant packet transmission of the base station.

Second, the master base station 110 determines a reference packet to help compare the arrival time of the terminal, and then directly transmits the reference packet to the terminal and transfers the subsequent packet immediately following the reference packet to the secondary base station 120. There is a method. The terminal 200 may regard a time difference between the reception time of the reference packet and the reception time of the subsequent packet as the backhaul delay time. As the reference packet, an RRC control message for measuring the backhaul delay time or a PDCP control PDU (Control PDU) may be used.

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

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

In addition, the delay information acquisition unit 240 may calculate a plurality of delay time candidate values by performing the above-described delay time estimation a plurality of times, and obtain a backhaul delay time by averaging the plurality of delay time candidate values. have. In this case, a delay time candidate value that exceeds a threshold value prepared for setting an 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 a generally conceivable maximum of the backhaul delay time.

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

[ First Example ]

6A and 6B are diagrams illustrating data stream transmission by the uplink transmission delay reduction method according to the first embodiment of the present invention. According to the first embodiment, after determining data that can be transmitted to the two base stations during the backhaul delay time (T) from the current point from among the data in the transmission buffer of the terminal 200, the preceding data is a master base station as a master data block. For (110), the data of the latter part may be allocated to the secondary base station 120 as a secondary data block, respectively.

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 respectively obtained by the transmission information acquisition unit 230, the master base station 110 during the backhaul delay time ) The amount of data to be transmitted (B _M ) and the amount of data to be transmitted to the secondary base station (B _S ) can be B _M = R _M × T and B _S = R _S × T, respectively. The data block generation unit 210 may generate a data block enough to be sent to each base station for a time T based on the calculation result.

That is, when referring to FIG. 6A, assuming that each unit data is composed of one packet with a serial number of an integer greater than or equal to 0, the UE has a size of B _M + B _S that can be transmitted for T time to both base stations An integrated data block may be secured, and the integrated data block may be divided into a master data block having a size B _M and a secondary data block having a size B _S located at the front. The data blocks generated in this way may be transmitted to the master base station 110 and the secondary base station 120 respectively by the data transmission unit 220. Each data block, 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. If there is a difference, transmission may be completed earlier or additional time may be required. Even if transmission of the data block is not completed according to the backhaul delay time T, the terminal 200 may 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, one TTI, that is, packets that can be transmitted one by one per 1 ms (assuming that it is the same as the unit data in this example) may include 10 packets in one data block transmitted during the backhaul delay time T, that is, 10 ms. Considering the example of FIG. 6A, packets from 0 to 9 are sequentially transferred to the master base station 110 during the first 10 ms, and packets from 10 to 19 are sequentially transferred to the secondary base station 120. Each may be transmitted by the data transmission unit 220. Then, the unit data from 0 to 9 are immediately received in the reception buffer of the master base station 110, and the unit data from 10 to 19 are received by the master base station 110 after 10 ms elapsed from the time of transmission. Can be received in the buffer. Likewise, unit data from 20 to 29 are also immediately received in the reception buffer of the master base station 110, and unit data from 30 to 39 are received by the master base station 110 after 10 ms elapsed from the time of transmission. Can be received in the buffer.

Packets transmitted to the secondary base station 120 arrive at the reception buffer of the master base station 110 after 10 ms elapses, 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, When the time point of arrival at the reception buffer of the master base station 110 is checked, it can be confirmed that the serial number of the packet continues after the backhaul delay time (T).

According to the first embodiment as described above, the average waiting time of the unit data transmitted to the master base station 110 is reduced to less than half compared to the prior art described with reference to FIGS. 2A and 2B. According to the prior art, all unit data except for packet 0 has a waiting time of 9 ms for a packet received by the master base station 110, but according to the first embodiment of the present invention, packets from 0 to 9 are not waited. It can be passed directly to the upper layer. In addition, packets 10 to 19 transmitted to the secondary base station 120 can be directly transferred to an upper layer without waiting because all previous packets have been received. However, since each of packets 20 to 29 is paired with each of packets 10 to 19 and is received by the master base station 110, packets from 20 to 29 are all packets from 10 to 19. It can be delivered to an upper layer immediately after it is received. Accordingly, the waiting time for the packet 20 located at the front is 9 ms, and the waiting time for subsequent packets is reduced by 1 ms as in the prior art. That is, the average waiting time between the 20th to 29th unit data and the subsequent unit data transmitted to the master base station 110 to the upper layer is 4.5ms, which can be confirmed through FIG. 6B.

Meanwhile, if the backhaul delay time can be accurately estimated, the data block can 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 network configuration information related to the backhaul delay time or use the backhaul delay time information measured by various methods previously described, and the data block generator ( 210) may generate a data block by reflecting the result of the new measurement.

On the other hand, if data transmission to at least one of each base station is completed, the terminal immediately constructs an additional new data block by reflecting the latest average transmission rate, and re-distributes packets for the master base station 110 and the secondary base station 120 to transmit. You can continue. At this time, if data transmission allocated to a specific base station is completed, but data allocated to another base station remains, this may be considered when configuring a new data block. For example, assuming that transmission of the master data block is completed and a total of 100 kbytes of data remains in the secondary data block, the size of the new data block reflecting the new average transmission rate is the master base station 110 and the secondary base station 120 For each 1Mbyte, when a secondary data block is newly configured, only 900kbyte can be additionally secured and configured as 1Mbyte plus the previous 100kbyte. Through this process, the transmission completion timing of the data blocks transmitted to the two base stations may be adaptively matched.

[ Second Example ]

7A and 7B are diagrams showing data stream transmission by the uplink transmission delay reduction method according to the second embodiment of the present invention. First, in the same manner as in the first embodiment, the uplink transmission rate (R _M ) to the master base station 110 per unit transmission time (TTI) by the transmission information acquisition unit 230 and the uplink transmission rate to the secondary base station (R _S ) can be obtained respectively. Among the data in the transmission buffer of the terminal 200, data that can be transmitted by the master base station during the backhaul delay time (T) from the current point of time is allocated to the master base station 110 as a master data block, and the subsequent data is secondary. It may be configured as unit data transmitted by the base station 120 during a unit transmission time (TTI). In the second embodiment, a data block may be configured only for the master base station 110 and a separate data block may not be configured for the secondary base station 120. In addition, the master data block for the master base station 110 and the unit data for the secondary base station 120 may be updated every unit transmission time (TTI).

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. In addition, it is assumed that each unit data is composed of one packet having a serial number of an integer greater than or equal to 0.

In the present invention, data that can be transmitted for a time as much as the backhaul delay time (T) from the front of the transmission target data based on the unit transmission time (TTI) at a specific moment is allocated to the master base station 110 as a master data block. , Then, subsequent data may be configured as one unit data and allocated to the secondary base station 120. That is, based on 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 acquisition unit 230 at the moment when TTI = n (n is an integer). After securing the data to be transmitted up to the time point TTI = n + T-1 as a master data block based on the uplink transmission rate, the secured master data blocks are sequentially configured as unit data and transmitted to the master base station 110. I can. At the same time, at the moment TTI = n, the terminal 200 secures data located at the front of the portion excluding the secured master data block, configures unit data that can be transmitted to the secondary base station 120, and immediately configures the secondary base station ( 120).

Referring to FIG. 7A, the terminal 200 secures packets from 0 to 9, which are expected to be transmitted for T = 10 ms in the transmission buffer, as a master data block for transmission to the master base station 110, Among them, packet 0 may be transmitted to the master base station 110 in TTI 0, which is the first TTI. In addition, the moment the master data block is secured, the packet 10 immediately following the packets 0 to 9 may be transmitted to the secondary base station 120. This process can be repeated in the next TTI, TTI 1, and packet 11 is added for the master base station 110 in order to secure data expected to be transmitted for the next 10 ms. Packet 1 may be transmitted 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, may be transmitted to the secondary base station 120. That is, the master data block and data to be transmitted to the secondary base station 120 in the corresponding TTI may be updated every unit transmission time (TTI). This process may be continued until all data in the transmission buffer of the terminal 200 is transmitted on a per transmission time basis.

As a result of the above-described process, as can be seen in FIG. 7A, even packets from No. 10 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 as late as the backhaul delay time, and the terminal 200 simultaneously transmits two packets having a time difference by the backhaul delay time on the transmission buffer. Because of the transmission, it can be seen that two packets having consecutive serial numbers are simultaneously received in the reception buffer of the master base station 110. Accordingly, as can be seen in FIG. 7B, all packets can be transmitted to the upper layer without waiting time in the master base station 110.

According to an embodiment of the present invention, the time that a packet transmitted to the master base station 110 through an uplink waits at the master base station 110 by estimating the backhaul delay time and reflecting the estimated backhaul delay time. Can be reduced. Accordingly, since the problem caused by data transmission delay can be largely solved, the quality of service can be improved by applying the present invention to a real-time service or streaming service sensitive to transmission delay.

Combinations of each block in the block diagram attached to the present invention and each step in the flowchart may be performed by computer program instructions. Since these computer program instructions can be mounted on the encoding processor of a general-purpose computer, special purpose computer or other programmable data processing equipment, the instructions executed by the encoding processor of the computer or other programmable data processing equipment are each block of the block diagram or Each step of the flow chart will create a means to perform the functions described. These computer program instructions can also be stored in computer-usable or computer-readable memory that can be directed to a computer or other programmable data processing equipment to implement a function in a particular way, so that the computer-usable or computer-readable memory It is also possible to produce an article of manufacture in which the instructions stored in the block diagram contain instruction means for performing the functions described in each block or flow chart. Computer program instructions can also be mounted on a computer or other programmable data processing equipment, so that a series of operating steps are performed on a computer or other programmable data processing equipment to create a computer-executable process to create a computer or other programmable data processing equipment. It is also possible for the instructions to perform the processing equipment to provide steps for performing the functions described in each block of the block diagram and each step of the flowchart.

In addition, each block or each step may represent a module, segment, or part of code comprising one or more executable instructions for executing the specified logical function(s). In addition, it should be noted that in some alternative embodiments, functions mentioned in blocks or steps may occur out of order. For example, two blocks or steps shown in succession may in fact be performed substantially simultaneously, or the blocks or steps may sometimes be performed in the reverse order depending on the corresponding function.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential quality of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, 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 interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

The present invention can be used to increase the efficiency of operation of a dual connection network. Specifically, it can be used to improve the mobile communication service quality of a terminal in a heterogeneous network environment in which a macro base station and a small base station are mixed. In particular, since the present invention can solve the problem of data transmission delay to a large extent, the problem of perceived quality of service can be improved by applying the present invention to a real-time service or streaming service sensitive to transmission delay. .

100: mobile communication system
110: master base station
120: secondary base station
121: communication department
122: control signal generation unit
123: control unit
130: core network
131: control node
132: serving gateway
133: PDN gateway
200: terminal
300: external network

Claims (20)

◈ Claim 1 was abandoned upon payment of the set registration fee. As a method for reducing uplink transmission delay performed in a terminal connected to a master base station and a secondary base station in a packet split-type dual connection network environment,
Securing transmission target data composed of a plurality of packets to be transmitted according to a predetermined transmission order;
Among the transmission target data, the amount of packets that can be transmitted to the master base station during a backhaul delay time, which is a time required for data transmission from the secondary base station to the master base station, is transmitted from the front of the transmission target data. Selecting in order and designating 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 to the master base station from the first packet in the transmission order during a transmission time interval (TTI) from a predetermined transmission start point; And
For the unit transmission time from the start of transmission, transmitting a packet next to the master data block in the transmission order among the transmission target data from the first packet to the secondary base station in the transmission order.
Uplink transmission delay reduction method. ◈ Claim 2 was abandoned upon payment of the set registration fee. The method of claim 1,
The designating may include, among the packets following the master data block in the transmission order in the transmission target data, an amount of packets that can be transmitted to the secondary base station during the backhaul delay time, the first packet in the transmission order. Selecting from and designating a secondary data block that is a data block to be transmitted by the secondary base station
Uplink transmission delay reduction method. ◈ Claim 3 was abandoned upon payment of the set registration fee. The method of claim 2,
The step of transmitting to the master base station includes transmitting a packet of the master data block to the master base station from the first packet in the transmission order during the backhaul delay time from the start of transmission,
The transmitting of the secondary base station to the secondary base station includes transmitting a packet of the secondary data block to the secondary base station from the first packet in the transmission order during the backhaul delay time from the start of transmission.
Uplink transmission delay reduction method. ◈ Claim 4 was abandoned upon payment of the set registration fee. The method of claim 1,
When the unit transmission time has elapsed from the predetermined transmission start time, the transmission order among untransmitted packets not belonging to the master data block in the transmission target data excluding packets previously transmitted from the master data block Depending on the amount of packets added from the first packet to the back of the master data block, the master data block may re-include an amount of packets that can be transmitted to the master base station during the backhaul delay time. Redirecting the data block further comprising
Uplink transmission delay reduction method. ◈ Claim 5 was abandoned upon payment of the set registration fee. The method of claim 4,
Transmitting a packet of the redesignated master data block to the master base station in the transmission order from the time point when the unit transmission time has elapsed and during the unit transmission time; And
Transmitting a packet next to the redesignated master data block in the transmission order to the secondary base station from the first packet in the transmission order during the unit transmission time from the lapse of the unit transmission time.
Uplink transmission delay reduction method. ◈ Claim 6 was abandoned upon payment of the set registration fee. The method according to any one of claims 2 and 4,
Further comprising the step of obtaining transmission rate information about the data transmission rate to the master base station and the data transmission rate to the secondary base station,
The designation or reassignment of the data block is performed so that the data block includes a maximum amount of data packets that can be transmitted within the backhaul delay time based on the transmission rate information.
Uplink transmission delay reduction method. ◈ Claim 7 was abandoned upon payment of the set registration fee. The method of claim 1,
Further comprising the step of obtaining information on a backhaul delay time required for data transmission from the secondary base station to the master base station,
The obtaining step includes a time point at which the master base station receives the data transmitted to the terminal at a first time point, and a time point at which the master base station receives the data transmitted to the secondary base station at a second time point from the secondary base station. Based on the difference, comprising the step of estimating the backhaul delay time
Uplink transmission delay reduction method. ◈ Claim 8 was abandoned upon payment of the set registration fee. The method of claim 7,
In the estimating step, a plurality of delay time candidate values are calculated based on a difference between the received time points, and an average of the remaining delay time candidate values excluding a value exceeding a predetermined threshold among the plurality of delay time candidate values is calculated. Estimating as the backhaul delay time
Uplink transmission delay reduction method. ◈ Claim 9 was abandoned upon payment of the set registration fee. The method according to any one of claims 2 and 4,
Further comprising the step of obtaining information on a backhaul delay time required for data transmission from the secondary base station to the master base station,
The designation or reassignment of the data block is performed so that the data block includes a maximum amount of data packets that can be transmitted within the backhaul delay time, based on the information on the backhaul delay time.
Uplink transmission delay reduction method. In a terminal connected to a master base station (MeNB) and a secondary base station (SeNB) in a dual connection network environment of a packet split method,
Among the transmission target data consisting of a plurality of packets to be transmitted according to a predetermined transmission order, the amount that can be transmitted to the master base station during a backhaul delay time, which is the time required to transmit data from the secondary base station to the master base station. A data block generator for selecting a packet in the order of transmission from the front of the transmission target data and designating a master data block, which is a data block to be transmitted by the master base station; And
During a transmission time interval (TTI) from a predetermined transmission start time, the packet of the master data block is transmitted from the first packet to the master base station in the transmission order, and the unit transmission time from the transmission start time In the meantime, a data transmission unit for transmitting a packet next to the master data block in the transmission order among the transmission target data from the first packet to the secondary base station in the transmission order.
A terminal to which the uplink transmission delay reduction method is applied. The method of claim 10,
The data block generator may generate a quantity of packets that can be transmitted to the secondary base station during the backhaul delay time from among the packets following the master data block in the transmission order in the transmission target data, the first packet in the transmission order Selecting from and designating a secondary data block that is a data block to be transmitted by the secondary base station
A terminal to which the uplink transmission delay reduction method is applied. The method of claim 11,
The data transmission unit transmits the packet of the master data block to the master base station from the first packet in the transmission order during the backhaul delay time from the transmission start time, and during the backhaul delay time from the transmission start time, Transmitting the packet of the secondary data block from the first packet to the secondary base station in the transmission order
A terminal to which the uplink transmission delay reduction method is applied. The method of claim 10,
When the unit transmission time has elapsed from the predetermined transmission start point, the data block generation unit is configured to exclude a packet previously transmitted from the master data block and not belong to the master data block. Of the transport packets, by adding a predetermined amount of packets from the first packet to the back of the master data block according to the transmission order, the amount of packets that can be transmitted to the master base station during the backhaul delay time by the master data block Reassigning the master data block to be included again
A terminal to which the uplink transmission delay reduction method is applied. The method of claim 13,
The data transmission unit transmits the packet of the redesignated master data block to the master base station in the transmission order from the time the unit transmission time has elapsed during the unit transmission time, and the unit transmission time is During the unit transmission time from the elapsed point in time, the packet following the redesignated master data block in the transmission order is transmitted from the first packet to the secondary base station in the transmission order.
A terminal to which the uplink transmission delay reduction method is applied. The method according to any one of claims 11 and 13,
Further comprising a rate information acquisition unit for acquiring transmission rate information about the data transmission rate to the master base station and the data transmission rate to the secondary base station,
The designation or reassignment of the data block is performed so that the data block includes a maximum amount of data packets that can be transmitted within the backhaul delay time based on the transmission rate information.
A terminal to which the uplink transmission delay reduction method is applied. 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,
The delay information acquisition unit includes a time point at which the master base station receives data transmitted to the terminal at a first time point, and a time point at which the master base station receives data transmitted to the secondary base station at a second time point from the secondary base station. Based on the difference, to estimate the backhaul delay time
A terminal to which the uplink transmission delay reduction method is applied. The method of claim 16,
The delay information obtaining unit calculates a plurality of delay time candidate values based on a difference between the received time points, and calculates an average of the remaining delay time candidate values excluding a value exceeding a predetermined threshold among the plurality of delay time candidate values. Estimated as the backhaul delay time
A terminal to which the uplink transmission delay reduction method is applied. The method according to any one of claims 11 and 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 reassignment of the data block is performed so that the data block includes a maximum amount of data packets that can be transmitted within the backhaul delay time, based on the information on the backhaul delay time.
A terminal to which the uplink transmission delay reduction method is applied. ◈ Claim 19 was abandoned upon payment of the set registration fee. As a computer program stored in a computer-readable recording medium,
The computer program,
A computer program comprising instructions for causing a processor to perform a method according to any one of claims 1 to 5, 7 and 8. ◈ Claim 20 was waived upon payment of the set registration fee. As a computer-readable recording medium storing a computer program,
The computer program,
A computer-readable recording medium comprising instructions for causing a processor to perform the method according to any one of claims 1 to 5, 7 and 8.

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