KR101631104B1 - Method and device for transmitting multimedia data in wireless communication system - Google Patents

Abstract

In the method of transmitting multimedia broadcasting data in the wireless communication system of the present invention, in the process of generating a MAC PDU for transmission in an MBMS subframe corresponding to a current SYNC period, before the RLC PDU payload is configured, Calculating a size of the non-received RLC SDUs by using a POC or a PPS stored in a previous SYNC frame when the RLC SDUs are not present, Determining which MBMS subframes corresponding to the missing RLC SDUs should be accommodated in the MAC PDU corresponding to the received MBMS subframes and stopping transmission in the MBMS subframe corresponding to the MAC PDUs in which the missing RLC SDUs should be received, And transmitting the MAC PDU in the corresponding MBMS subframe. It shall be.
According to the method and apparatus for transmitting multimedia broadcast data in the wireless communication system of the present invention, it is possible to stably transmit data by maintaining the homogeneity of multimedia broadcast data transmitted over a wireless channel.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus and a method for transmitting multimedia broadcast data in a wireless communication system,

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for generating and transmitting multimedia broadcasting data in a wireless communication system.

Generally, a wireless communication system has been developed for providing communication while ensuring user mobility. This wireless communication system has reached the stage of providing high-speed data communication service as well as voice communication due to the breakthrough of the technology.

Recently, as one of the next generation wireless communication systems, standard works for LTE (Long Term Evolution) are underway in 3GPP. LTE is a technology that realizes high-speed packet-based communication with a transfer rate of up to 100 Mbps, which is higher than the currently available data rate, with the aim of commercialization in 2010 or so. For example, there are discussions on how to reduce the number of nodes on the communication path by simplifying the structure of the network, and to make the wireless protocols as close as possible to the wireless channel.

Unlike the voice service, the data service determines the amount of data to be transmitted and the resources that can be allocated according to the channel status. Therefore, in a wireless communication system such as a wireless communication system, the scheduler manages allocation of transmission resources in consideration of the amount of resources to be transmitted, the channel status, and the amount of data. This is the same in LTE, one of the next generation wireless communication systems, and the scheduler located in the base station manages and allocates wireless transmission resources. A two-layer protocol such as MAC and RLC is also located in the base station.

In wireless communication systems that provide increased radio capacity and improved quality, such as the LTE wireless communication system, there is a sufficient condition to provide a multimedia broadcasting service, and therefore attempts to combine multimedia broadcasting service with wireless communication have continued. In LTE, the multimedia broadcasting service is referred to as an MBMS (Multimedia Broadcast Multicast Service), and data generated from the MBMS server is defined as being transmitted from a plurality of base stations. When the base stations providing the MBMS service transmit the same data over the radio, the transmission efficiency on the radio is maximized. However, since the second layer protocol such as MAC (Medium Access Control) or RLC (Radio Link Control) is located at the base station as described above, data generated at the MBMS server is processed at the second layer of the base station, May be broken.

The present invention aims to propose a method and apparatus for transmitting multimedia broadcasting data transmitted through a wireless channel while maintaining homogeneity.

In order to solve the above problems, a method for transmitting multimedia broadcast data in a wireless communication system according to the present invention includes: receiving a Medium Access Control Protocol Data (MAC PDU) for transmission in a Multimedia Broadcast Multicast Service (MBMS) Determining whether radio link control service data units (RLC SDUs) are discontinuously present before all the payloads of the RLC PDUs are configured in the process of generating the RLC SDUs, Calculating a size of the non-received RLC SDU using an OC (Octet Counter) of neighboring RLC SDUs of the missing RLC SDU if the RLC SDUs are discontinuously present; Determining if an RLC SDU should be stored in a MAC PDU corresponding to which MBMS subframe; In the MBMS sub-frame corresponding to a MAC PDU that should have been lead to stop the transmission, by constructing a MAC PDU for storing only valid RLC SDU it is characterized in that it comprises the step of transmitting from the MBMS subframe.

According to another aspect of the present invention, there is provided a method for transmitting multimedia broadcast data in a wireless communication system including a Medium Access Control Protocol (MAC) PDU (Medium Access Control Protocol) for transmission in a Multimedia Broadcast Multicast Service (MBMS) (RLC SDU) before configuring all the payloads of an RLC PDU in a process of generating RLC SDUs (Data Units), determining whether or not there are RLC SDUs Calculating a size of the non-received RLC SDUs by using a POC (Previous Octet Count) or a PPS (Previous Payload Size) stored in a previous SYNC frame when RLC SDUs are present; Determining whether an unreceived RLC SDU should be stored in a MAC PDU corresponding to which MBMS subframe, And stopping transmission in an MBMS subframe corresponding to an MAC PDU to which RLC SDUs should be stored, and constructing a MAC PDU storing only valid RLC SDUs, and transmitting the MAC PDU in the corresponding MBMS subframe.

According to another aspect of the present invention, there is provided a method for transmitting multimedia broadcast data in a wireless communication system, the method comprising: receiving a MAC PDU (Medium Access Control (MAC) PDU) for transmission in a Multimedia Broadcast Multicast Service (MBMS) Determining whether or not there are RLC SDUs before configuring all the payloads of the RLC PDU in the process of generating the RLC PDUs, Determining whether a control message containing the RLC SDU size information has been received for the SYNC period if RLC SDUs are present, determining whether the RLC SDU size information is included in the RLC SDU size information received in the control message, Determining which MBMS subframe should be accommodated in a MAC PDU corresponding to the MBMS subframe, And stopping the transmission in the MBMS subframe corresponding to the MAC PDU to which the SDUs should be stored, and constructing a MAC PDU storing only the valid RLC SDUs, and transmitting the MAC PDU in the corresponding MBMS subframe.

In order to solve the above problems, the apparatus for transmitting multimedia broadcast data in the wireless communication system of the present invention stores an RLC SDU (Radio Link Control Service Data Unit) or a part of the RLC SDU according to a PN (Packet Number) An RLC SDU storage unit for generating a payload of an RLC PDU using the size of the RLC SDUs, and a RLC SDU storing unit for calculating a size of the RLC SDU, And an RLC PDU generation unit for determining an amount of data to be stored in the RLC PDU payload and instructing the RLC SDU storage unit to generate a payload of an RLC PDU of a corresponding size, If the size of an unreceived RLC SDU can not be calculated after a specific RLC SDU in the calculation unit, the RLC SDU storage unit stores RLC SDUs after the specific RLC SDU in the RLC SDU, When the RLC SDU size calculation unit of the RLC SDU size calculation unit calculates the size of the RLC SDU size, the RLC SDU storage unit stores the size of the RLC SDU, And generates the RLC PDU payload and transfers the payload to the RLC PDU generating unit.

According to the method and apparatus for transmitting multimedia broadcast data in the wireless communication system of the present invention, it is possible to stably transmit data by maintaining the homogeneity of multimedia broadcast data transmitted over a wireless channel.

Brief Description of the Drawings Fig. 1 shows the structure of an LTE mobile communication system. Fig.
2 is a diagram illustrating a protocol structure in an LTE mobile communication system;
3 is a diagram illustrating a general MBMS service providing method;
4 is a diagram illustrating an operation of a general base station when some data among MBMS data is not received.
5 is a diagram showing a structure of a general SYNC frame;
6 is a diagram for explaining a general method of setting PN and OC in a SYNC frame;
FIG. 7 is a diagram for explaining a general method of determining the amount and the number of data not received using PN and OC. FIG.
8 is a view for explaining a first embodiment of the present invention.
FIG. 9 is another diagram illustrating the first embodiment of the present invention. FIG.
10 is a flowchart showing the operation of the base station apparatus according to the first embodiment of the present invention;
11 is a view for explaining a second embodiment of the present invention.
FIG. 12 illustrates a SYNC frame structure according to a second embodiment of the present invention; FIG.
13 is a flowchart showing the operation of the base station apparatus according to the second embodiment of the present invention;
14 is a view for explaining a third embodiment of the present invention;
15 is a flowchart showing the operation of the base station apparatus according to the third embodiment of the present invention;
16 illustrates a base station apparatus in accordance with embodiments of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same components are denoted by the same reference numerals as possible in the accompanying drawings. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

Also, the terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor is not limited to the concept of terms in order to describe his invention in the best way. It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be properly defined.

Before describing the present invention in full, LTE mobile communication system will be described in more detail with reference to FIG. 1 and FIG.

1 is a diagram showing the structure of an LTE system.

Referring to FIG. 1, an LTE system includes an Evolved Radio Access Network (E-RAN) 110 and an Evolved Radio Access Network (hereinafter referred to as E-RAN) , 124, 126, and 128) and an upper node (referred to as an Access Gateway) 130 and 132, respectively. A User Equipment (UE) 101 accesses an Internet Protocol (IP) network by an E-RAN 110 or 112.

The ENBs 120 to 128 correspond to the Node B of the existing UMTS system. The ENBs 120 to 128 are connected to the UE 101 through a radio channel and perform a more complex role than the Node B of the existing UMTS system. In the LTE system, all user traffic including a real-time service such as Voice over IP (VoIP) over the Internet protocol is serviced through a shared channel. Therefore, a device for collecting and scheduling situation information of UEs 101 is required And the ENBs 120 to 128 take charge thereof. One ENB 120-128 typically controls a number of cells.

In order to realize a transmission rate of up to 100 Mbps, LTE uses Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in a bandwidth of up to 20 MHz. In addition, Adaptive Modulation and Coding (AMC) scheme is used to determine a modulation scheme and a channel coding rate in accordance with a channel state of a UE.

1, there is an MBMS server for generating multimedia broadcast multicast service (MBMS) data and transmitting the MBMS data to the ENBs 120 to 128 in the LTE system. The MBMS server and the ENBs 120 to 128 are connected to an IP network.

2 is a diagram illustrating a protocol structure in an LTE mobile communication system.

2, a wireless protocol of the LTE system includes Packet Data Convergence Protocol (PDCP) layers 205 and 240, Radio Link Control (RLC) layers 210 and 235, a MAC (Medium Access Control) layer 215 , 230).

The PDCP layers 205 and 240 perform operations such as IP header compression / decompression and the RLC layers 210 and 235 reconfigure PDCP protocol data units (PDUs) to an appropriate size to perform ARQ operations. In order to perform the ARQ operation or the like, an RLC header is added in the RLC layers 210 and 235.

The MAC layers 215 and 230 are connected to the devices of the RLC layers 210 and 235 configured in a terminal, multiplex RLC PDUs into MAC PDUs, and demultiplex RLC PDUs from MAC PDUs. For the multiplexing and demultiplexing, a MAC header is added in the MAC layer 215 and 230.

The PHY layers 220 and 225 perform channel coding and modulation on the data of the upper layer and transmit them to a wireless channel by making OFDM symbols or demodulate OFDM symbols received through a wireless channel, . Data to be input to the protocol entity based on transmission is referred to as SDU (Service Data Unit), and data to be output is referred to as PDU (Protocol Data Unit).

Hereinafter, Multimedia Broadcast Multicast Service (MBMS) will be briefly described.

3 is a view for explaining a general MBMS service providing method.

3, MBMS service data is generated in the MBMS server 305, and the data is transmitted to all the ENBs 310, 315, 320, 325, and 330 participating in the MBMS transmission. The ENBs 310, 315, 320, 325, and 330 store data received from the MBMS server 305 and simultaneously transmit the received data.

315, 320, 325, and 330, the terminals located in the reception areas of the ENBs 310, 315, 320, 325, and 330 may receive the ENBs 310, 315, 320, 325, 330, it is possible to enjoy a much higher reception quality than that of receiving only a signal transmitted by one ENB. In order for the ENBs 310, 315, 320, 325, and 330 to transmit the same signal, the same conditions as above must be assumed.

First, the ENBs 310, 315, 320, 325 and 330 must receive the same data, the second ENBs 310, 315, 320, 325 and 330 must generate the same data from the received data, The ENBs 310, 315, 320, 325, and 330 must transmit the same data at the same time.

4 is a view for explaining an operation of a general base station when some data among MBMS data is not received.

Referring to FIG. 4, a normal MBMS server transmits an RLC SDU to an ENB after an IP packet has undergone a PDCP process. RLC SDUs are IP packets because, unlike general data, header compression or non-mapping is not applied to MBMS data. In the present invention, it is described that the RLC SDU is input to the ENB, but this is the same as the IP packet is input to the ENB.

The ENB divides or concatenates the RLC SDUs received from the MBMS server into an appropriate size, forms an RLC PDU by adding an RLC header, multiplexes the RLC PDU with another RLC PDU, and adds a MAC header to the MAC PDU. The MAC PDU is transmitted through a wireless channel. More specifically, since only one RLC PDU is stored in one MAC PDU, an RLC header 415 and a MAC header 410 are added to an RLC SDU divided or concatenated to an appropriate size, Is generated.

Since all ENBs have the same version of RLC protocol and MAC protocol, if all ENBs receive all RLC SDUs in full, the MAC PDUs generated from RLC SDUs in each ENB have exactly the same contents. However, if an ENB fails to receive an arbitrary RLC SDU, the ENB can not generate a MAC PDU from the RLC SDU not received.

The best way to solve this problem is to transmit the MAC PDU to which the RLC SDU has been received, but not the next MAC PDU. For example, if an ENB receives only the remaining RLC SDUs except for the RLC SDU [m + 1] 425, the ENB also receives the MAC PDUs, i.e. MAC PDU [n + 1] N 420] and MAC PDU [n + 1] 425, but resumes transmission from the MAC PDU [n + 2] 430.

On the other hand, in order for the ENB to resume transmission from the MAC PDU [n + 2], the ENB must determine from which byte of the RLC SDUs the MAC PDU [n + 2] should be stored. In this case, if the overhead of the MAC header added to each RLC SDU and the overhead of the RLC header can be predicted, the ENB determines how many bytes of data the RLC SDUs which have not been received from the sum of the number of RLC SDUs that have not been received, And included in the MAC PDU can be calculated. It is also possible to determine which RLC SDUs are included in the MAC PDUs that should not be transmitted and how many bytes in which RLC SDUs should be stored in the MAC PDUs to start transmission.

Also, if the amount of RLC overhead generated from one RLC SDU and the amount of MAC overhead can be predicted, the information required for the ENB to perform the above operation is the sum and the number of the sizes of RLC SDUs that have not been received. Therefore, the MBMS server stores the RLC SDU in the SYNC frame so that the ENB can know the total number and the number of the RLC SDUs that have not been received. Hereinafter, the SYNC frame will be described in more detail.

5 is a diagram showing a structure of a general SYNC frame.

Referring to FIG. The SYNC frame 505 includes a header 510 and a payload 520, and one RLC SDU is stored in the payload 520. The data stored in the payload 520 of the SYNC frame 505 and the RLC SDU are mixed for convenience of explanation.

Packet Number, Octet Counter, SYNC period related information, and the like are stored in the header 510. Packet Number (PN) is information indicating how many SYNC frames the corresponding SYNC frame is, and Octet Counter (OC) is information indicating the total amount of payloads of the SYNC frame transmitted until the corresponding SYNC frame is transmitted . The SYNC period related information is information indicating which SYNC period the RLC SDU stored in the SYNC frame is to be transmitted. Here, the SYNC period is a predetermined period defined on the radio channel.

One or more subframes are designated as an MBMS subframe during one SYNC period, and only an MAC PDU containing only MBMS data is transmitted in the MBMS subframe. The amount of MBMS data that can be transmitted during the corresponding SYNC period is determined according to the number of MBMS subframes allocated in the SYNC period. Also, the network determines the number of MBMS subframes to be allocated to the SYNC period in consideration of the data rate of the MBMS service and the like.

Meanwhile, the MBMS server manages the PN and the OC based on the SYNC period in order to maintain the sizes of the PN and the OC at an appropriate level. For example, the MBMS server transmits SYNC frames containing the amount of data to be transmitted during one SYNC period, and initializes PN and OC of the SYNC protocol to zero. Then, the MBMS server repeats the operation of increasing PN and OC while transmitting SYNC frames by the amount of data to be transmitted during the next SYNC period, and initializing PN and OC to 0 for the next SYNC period.

6 is a diagram illustrating a general method of setting PN and OC in a SYNC frame.

Referring to FIG. 6, if the amount of data to be transmitted during the SYNC period is 700 bytes, the MBMS server stores 700 bytes of data from the SYNC frame 610 to the SYNC frame 635 for any one SYNC period. SYNC frames. PN and OC of the first SYNC frame 610 are set to 0 and PN and OC of the fifth SYNC frame 630 are set to 4 and 500, respectively. Since the next SYNC frame 640 is transmitted in the new SYNC period, PN and OC are initialized to 0, respectively. For reference, the amount of data to be transmitted during one SYNC period is generally constant. In the above example, the RLC header and the MAC header are not considered for convenience of explanation.

The ENB can calculate the sum of the number of SYNC frames not received using the PN and OC and the size of the RLC SDUs stored in the SYNC frame, and reconstruct the MAC PDU to resume transmission based on the information .

7 is a diagram for explaining a general method of determining the amount and the number of data not received using PN and OC.

7, when the ENB fails to receive SYNC frames between the SYNC frame 705 and the SYNC frame 710, the ENB uses the PN and OC of the SYNC frame 705 and the SYNC frame 710 The three SYNC frames are not received, and the sum of the unreceived data is calculated to be 400 bytes.

In this case, if it is assumed that the RLC / MAC overhead added per RLC SDU is 4 bytes, the ENB knows that a total of 412 bytes of data should be stored in the MAC PDU by the RLC SDUs not received. For example, if 50 bytes of the MAC PDU [n] 715 are already occupied by the RLC SDU 705, the 412 bytes are stored in the remaining 450 bytes of the MAC PDU [n] Able to know. At this time, since the first 38 bytes of the RLC SDU 710 are stored in the extra space, the MAC PDU [n + 1] is stored in the 39th byte of the RLC SDU 710. Therefore, the ENB does not transmit the MAC PDU [n] that has received the RLC SDU that has not been received, and constructs and transmits the MAC PDU normally from the MAC PDU [n + 1].

In order to resume transmission from certain MAC PDUs using the sum of the number and size of RLC SDUs not received as described above and to calculate the number of bytes of an RLC SDU to be stored in the MAC PDU, The size of the head and MAC overhead should be predictable. However, in the current RLC protocol and the MAC protocol, the size of the RLC / MAC overhead may vary depending on how the RLC SDU is stored in the RLC PDU and whether the size of the RLC PDU exceeds a specific value. For example, if the last byte of a specific RLC SDU is received to match the last byte of the RLC PDU, an RLC field called LI (Length Indicator) is omitted.

The size of the overhead caused by the LI varies depending on the number of LIs stored in the RLC PDU. When only one LI is stored, the overhead due to the LI is 2 bytes. However, when two LIs are stored, the overhead due to the LI is 3 bytes. Therefore, it is necessary to change the current RLC standard and the MAC standard so that the size of the RLC / MAC overhead added per RLC SDU can be predicted. However, considering that the RLC protocol and the MAC protocol are also applied to terminals that do not support MBMS, it is not desirable to change the protocols for the MBMS service.

In order to solve such a problem, the present invention proposes a method and an apparatus for enabling ENBs to construct and transmit MAC PDUs in the same manner as conventional ones without changing the RLC protocol and the MAC protocol.

≪ Embodiment 1 >

In the first embodiment of the present invention, when the ENB does not consecutively receive SYNC frames, the ENB calculates the size of the RLC SDU received in the SYNC frame not received using the PN and OC values of the SYNC frame, It is determined whether to retransmit a MAC PDU from which MAC PDU is to be transmitted and from which MAC PDU to resume transmission and from which byte of a certain RLC SDU the MAC PDU to be retransmitted to be retransmitted.

Also, when the ENB detects that SYNC frames are not received consecutively for a certain SYNC period, the ENB does not construct MAC PDUs from SYNC frames that are subsequently received, including consecutively not received SYNC frames. That is, the MBMS transmission is stopped during the period in which the unconfigured MAC PDU is to be transmitted. When the next SYNC period starts, the MAC PDU configuration and transmission are resumed.

If the ENB recognizes the size of an RLC SDU that has not been received, it can calculate which RLC PDU the RLC SDU is stored in and how many bytes of overhead are generated from the RLC PDU. However, when one SYNC frame is not received in the current SYNC protocol, the size of the RLC SDU received in the SYNC frame may be calculated. However, if more than one SYNC frame is not received consecutively, It is unknown how many bytes of overhead will occur from the RLC SDUs. Therefore, when the ENB does not consecutively receive the SYNC frames, the transmission of the MAC PDU is stopped, the PN and the OC are initialized to 0, and the MAC PDU is started from the start of the next SYNC period in which the MAC PDU is configured from the first RLC SDU. Lt; / RTI >

8 is a view for explaining the first embodiment of the present invention. In particular, FIG. 8 shows the operation of the ENB when the SYNC frame is not received consecutively.

Referring to FIG. 8, RLC SDUs 810 through 830 of the five RLC SDUs 820 are successfully received for any SYNC period except for the RLC SDU 820. The ENB constructs RLC PDUs and MAC PDUs successfully received RLC SDUs using the conventional RLC protocol and MAC protocol, and transmits the MAC PDUs 865 to a predetermined MBMS subframe.

The size of the RLC SDU 820 that has not been received is calculated using the PN and OC of the SYNC frame, and the RLC PDU and the MAC PDU configuration are continued as if the corresponding RLC SDU was received. For example, it is possible to arbitrarily generate an RLC SDU having the same size as an RLC SDU that has not been received, and to continue the RLC PDU configuration and the MAC PDU configuration using the randomly generated RLC SDU. Method. The MAC PDU 870, which has received the randomly generated RLC SDU, does not transmit in the corresponding MBMS subframe but discards it.

As a result, the MAC PDU is not transmitted in the MBMS subframe. The ENB resumes transmission in a predetermined MBMS subframe from the MAC PDU 875 that is not affected by the RLC SDU that it has not received, i.e., only the received RLC SDU has been received. In more detail, if the size of the RLC SDU received in the SYNC frame is not calculated even if the SYNC frame is not received, the ENB continues the RLC PDU and MAC PDU configuration considering the size of the RLC SDU not received, The MAC PDUs that do not include the RLC SDUs not received are transmitted in a predetermined MBMS subframe and the MAC PDUs that do not include the RLC SDUs that have not been received are not transmitted in the MBMS subframe to which the MAC PDUs are to be transmitted.

9 is another drawing for explaining the first embodiment of the present invention. In particular, Figure 9 illustrates the operation of the ENB when one or more RLC SDUs are not received in succession.

Referring to FIG. 9, among the 5 RLC SDUs 910 to 930 for an arbitrary SYNC period, the RLC SDU 920 and the RLC SDU 925 are not received. The ENB successfully configures RLC SDU 910 and RLC SDU 915 as RLC PDU 945 and MAC PDU 965 using the conventional RLC protocol and MAC protocol and transmits the MAC PDU (965). The ENB interprets the PN and OC of the RLC SDU 915 and the RLC SDU 930 and recognizes that the sum of the sizes of the RLC SDUs that have not been received consecutively since the two RLC SDUs are not received consecutively.

In the case where one or more RLC SDUs are not received consecutively, the ENB can not know the individual sizes of the RLC SDUs that have not been received. Therefore, the RLC SDUs can not calculate how much of the space the MAC PDUs will occupy, The MAC PDU can not be correctly configured from the RLC SDUs. Therefore, if the ENB detects that the RLC SDU is not received consecutively, it stops configuring the MAC PDU until the next SYNC period starts. And does not perform transmission in the MBMS subframe in which unconfigured MAC PDUs are scheduled to be transmitted. The ENB resumes the transmission of the MBMS data when the next SYNC period starts.

10 is a flowchart showing the operation of the base station apparatus according to the first embodiment of the present invention.

Referring to FIG. 10, when an arbitrary SYNC period starts in step 1005, the ENB proceeds to step 1010 and determines whether or not a first MBMS subframe among the MBMS subframes allocated during the SYNC period, And starts an operation for configuring the MAC PDU. The ENB sequentially segments or concatenates a part of the RLC SDU or the RLC SDU that has not yet been stored in the MAC PDU according to the size of the RLC PDU to be stored in the MAC PDU.

In step 1015, the ENB checks whether an unreceived RLC SDU is found before all payloads of the RLC PDU are filled. If all the payloads of the RLC PDUs are filled without the missing RLC SDUs, the process proceeds to step 1020, and if an RLC SDU is detected before the payload of the RLC PDUs is found, the process proceeds to step 1030. The presence of an unreceived RLC SDU in step 1015 means that the PNs of two adjacent RLC SDUs are not contiguous.

In step 1020, the ENB constructs an RLC PDU by adding a predetermined header to an RLC payload segmented / concatenated by the RLC SDUs, and multiplexes the RLC PDUs to form a MAC PDU. In step 1025, the ENB transmits the configured MAC PDU in the corresponding MBMS subframe and proceeds to step 1055.

On the other hand, if an unreceived RLC SDU is found before the payload of the RLC PDU is completely filled, the ENB proceeds to step 1030 to check whether one of the RLC SDUs is missing or one or more RLC SDUs are continuously lost. This can be determined by examining the PNs of RLC SDUs adjacent to the missing RLC SDUs. If there is one unreceived RLC SDU, the ENB proceeds from step 1030 to step 1035.

In step 1035, the ENB calculates the size of the RLC SDU that has not been received by using the OCs of neighboring RLC SDUs of the RLC SDUs that have not been received, and determines the RLC SDU that has not been received in consideration of the size of the RLC SDU It is determined which MAC PDU corresponding to which MBMS subframe should be stored. It is possible to arbitrarily generate an RLC SDU having the same size as that of an unreceived RLC SDU to proceed with a normal MAC PDU generation process and to determine which MAC PDU the RLC SDU having the same size as that of an unreceived RLC SDU is received. Also, the ENB stops transmission in the MBMS subframe corresponding to the MAC PDU in which the RLC SDU not received in step 1040 has been received, configures the first MAC PDU storing only the valid RLC SDUs in step 1045, and transmits do. For example, an RLC SDU having the same size as an unreceived RLC SDU may be arbitrarily generated, and a normal MAC PDU generation process may be performed until a first MAC PDU that does not contain an RLC SDU of the same size as the RLC SDU of the unreceived RLC SDU is generated Do.

If it is determined in step 1030 that one or more consecutive unsent RLC SDUs are present, the ENB transmits only the MAC PDUs generated so far in step 1050 in the corresponding MBMS subframe and ceases to generate further MAC PDUs. Transmission is stopped in the MBMS subframe corresponding to the MAC PDU that has not been generated and waits until the next SYNC period starts in step 1060. [

In step 1055, the ENB determines whether the SYNC period has expired. If the MAC PDUs not generated due to the missing RLC SDUs are excluded, the ENB proceeds to step 1060 if all the MAC PDUs to be transmitted in the MBMS subframe allocated in the corresponding SYNC period are generated. If there are MAC PDUs not yet generated, the ENB returns to step 1010.

≪ Embodiment 2 >

In the second embodiment of the present invention, a method and apparatus for normally generating MAC PDUs other than MAC PDUs corresponding to non-received RLC SDUs, even if one or more RLC SDUs are not received consecutively. As described above, the reason why the ENB can not normally generate the MAC PDU when one or more RLC SDUs are not received consecutively is because the individual sizes of the RLC SDUs not received are unknown. If the RLC SDU is transmitted together with the RLC SDU information, the ENB can generate a normal MAC PDU for the received RLC SDUs even if several RLC SDUs are not received consecutively.

Information that can calculate the size of an RLC SDU that has not been received may include information indicating an octet count (hereinafter, referred to as POC) of a previous SYNC frame or information indicating a size of data stored in a payload of a previous SYNC frame PPS). For example, if information for calculating the size of the [n + 2] -th RLC SDU is stored in the SYNC frame containing an arbitrary [n + 3] -th RLC SDU, And the [n + 2] -th RLC SDU are not received consecutively, the ENB can calculate the individual sizes of the RLC SDUs not received. Hereinafter, a method of calculating the individual sizes of the RLC SDUs not received when the SYNC frames are not received consecutively will be described in more detail.

11 is a view for explaining a second embodiment of the present invention.

Referring to FIG. 11, the current SYNC frame is transmitted together with the OC of the immediately preceding SYNC frame. Information contained in each SYNC frame is the same as reference numeral 1105 to 1120. In particular, reference numerals 1105 to 1120 assume that the Octet Count (POC) of the previous SYNC frame is stored in the SYNC frame.

In this case, when the RLC SDU [n + 2] is received and the RLC SDU [n + 2] is not received, the size of the RLC SDU [n + 2] (n + 3) of the RLC SDU [n + 3] is obtained by subtracting the OC (y3) of the RLC SDU [n + 2] from the OC y4-y3) can be calculated. Similarly, the size of the RLC SDU [n + 1] is a value obtained by subtracting OC (y2) of RLC SDU [n + 1] from OC (y3) of RLC SDU [n + 2].

If the size (PPS) of the data stored in the payload of the SYNC frame immediately before the SYNC frame, that is, the size of the RLC SDU, is transmitted together with the size of the RLC SDU [n + 2] n + 3].

In this case, since OC of RLC SDU [n + 1] is a value obtained by summing the size of RLC SDU [n] with the OC of RLC SDU [n], only information given to RLC SDU [n] and RLC SDU [n + 3] RLC SDU [n + 1] size calculation is possible. That is, the size of the RLC SDU [n + 1] is the sum of the RLC SDU [n + 1] and the RLC SDU [n + 2] And the size of the RLC SDU [n + 1] minus the size of the RLC SDU [n + 2].

As described above, if the POC or the PPS of the previous n SYNC frames are stored in the SYNC frame, the size of the RLC SDUs not received may be calculated even if [n + 1] SYNC frames are not received consecutively.

A method for calculating the sizes of RLC SDUs not received using POC when m RLC SDUs are successively received from RLC SDU [n + 1] to RLC SDU [n + m] is as follows. OC_ [x] denotes the size of the x-th RLC SDU, and OC_ [x] denotes the size of the x-th RLC SDU.

Assuming that the OCs of the previous [m-1] RLC SDUs, that is, OC_ [n + 2] to OC_ [n + m] are stored in the SYNC frame in which the RLC SDU [n + m + 1] , Can be summarized as shown in Table 1 below.

The size of the RLC SDU [n + m] = OC_ [n + m + 1] - OC_ [n + m] The size of the RLC SDU [n + m-1] = OC_ [n + m] - OC_ [n + m- ........... The size of the RLC SDU [n + 2] = OC_ [n + 3] - OC_ [n + 2] (OC_ [n + m + 1] - OC_ [n + 2]) of the sizes of RLC SDU [n + OC_ [n] + rlc sdu size_ [n] = sum of the sizes of RLC SDUs that have not been received = OC_ [n +

In Table 1, OC_ [n + m + 1] - OC_ [n + 2] is the sum of the sizes of all RLC SDUs from RLC SDU [n + 2] to RLC SDU [n + m].

The sizes of the immediately preceding [m-1] RLC SDUs, that is, rlc sdu size_ [n + 2] to rlc sdu size_ [n + m] are stored in the SYNC frame in which the RLC SDU [n + m + The size of each RLC SDU can be summarized as shown in Table 2 below.

Size of RLC SDU [n + m] = rlc sdu size_ [n + m] Size of RLC SDU [n + m-1] = rlc sdu size_ [n + m-1] ........... Size of RLC SDU [n + 2] = rlc sdu size_ [n + 2] The size of RLC SDU [n + 1] = the sum of sizes of RLC SDUs not received - RLC SDU [n + 2]
The sum of the sizes of all RLC SDUs up to RLC SDU [n + m]

12 is a diagram illustrating a SYNC frame structure according to a second embodiment of the present invention

Referring to FIG. In the SYNC frame 1205, PN and OC information 1210 and an RLC SDU 1220 are stored. In addition, information for calculating the size of the immediately preceding RLC SDUs is stored. The size of the data (i.e., the RLC SDUs) accommodated in the payload of the immediately preceding n SYNC frames or the OCs previously stored in n SYNC frames is stored sequentially do.

If the OC values of n previous SYNC frames are stored in an arbitrary RLC SDU or the sizes of data stored in payloads of n previous SYNC frames are accommodated, the ENB stores [n + 1] SYNC It is possible to individually calculate the sizes of [n + 1] RLC SDUs to be accommodated in the [n + 1] SYNC frames, even if the frames are not received consecutively.

The number of POCs or PPSs that can be stored in the 'information for calculating the size of previous RLC SDUs' is related to the stability of the link between the MBMS server and the ENB. For example, if the link is sufficiently good that the rate of packet not received is very low, there is little chance of two or more consecutive packet not received. In this case, it is also possible to accommodate only one immediately preceding POC or PSS in the 'information for calculating the size of the immediately preceding RLC SDUs', and prepare only when two SYNC frames are not received consecutively. Or if the performance of the link is unstable, a large number of POCs or PSSs may be accommodated to prepare for the case where a large number of SYNC frames are not received consecutively.

The number of POCs or PSSs to be stored in the SYNC frame may be preset to a predetermined value between the MBMS server and the ENBs, and the MBMS server may arbitrarily adjust the value as needed. For example, an MBMS server typically accommodates only one POC or PSS, but may store multiple POCs or PSSs when link load is low.

13 is a flowchart showing the operation of the base station apparatus according to the second embodiment of the present invention.

Referring to FIG. 13, when an arbitrary SYNC period starts in step 1305, the ENB proceeds to step 1310, where the first MBMS subframe in which the MAC PDU is not yet configured among the MBMS subframes allocated during the arbitrary SYNC period Lt; RTI ID = 0.0 > MAC PDU < / RTI > That is, the ENB sequentially divides or concatenates a part of the RLC SDU or the RLC SDU that has not yet been stored in the MAC PDU according to the size of the RLC PDU to be stored in the MAC PDU.

In step 1315, the ENB checks whether an unreceived RLC SDU is found before the payload of the RLC PDU is completely filled. If the payload of the RLC PDU is filled up with no RLC SDU, the ENB proceeds to step 1320. In step 1320, If an unreceived RLC SDU is found previously, the process proceeds to step 1330.

In step 1320, the ENB constructs an RLC PDU by adding a predetermined header to the RLC payload of the RLC SDUs, and constructs a MAC PDU by multiplexing the RLC PDUs. In step 1325, the ENB transmits the configured MAC PDU in the corresponding MBMS subframe and proceeds to step 1355.

If an unreceived RLC SDU is found before filling the payload of the RLC PDU, the ENB proceeds from step 1315 to step 1330. Also, in step 1330, the ENB checks whether the sizes of the above-mentioned missing RLC SDUs can be calculated. If n is greater than m + 1 when the number of consecutive missing RLC SDUs is n and the number of POC or PSS received in the SYNC frame of the RLC SDU next to the last missing RLC SDU is m, then the ENB may include some of the missing RLC SDUs The size of the SDU can not be computed, and if n is less than or equal to m + 1, the ENB can calculate the size of all missing RLC SDUs. If it is possible to calculate the size of all missing RLC SDUs, the ENB proceeds to step 1335 and proceeds to step 1350 if it can not calculate the size of some missing RLC SDUs.

The ENB that has proceeded to step 1335 determines whether the RLC SDU that has not been received should be received in the MAC PDU corresponding to which MBMS subframe in consideration of the size of the RLC SDU that it has not received. It is possible to arbitrarily generate an RLC SDU having the same size as that of an unreceived RLC SDU to proceed with a normal MAC PDU generation process and determine based on which MAC PDU the RLC SDU having the same size as the non-received RLC SDU is received. In step 1340, the ENB stops the transmission in the MBMS subframe corresponding to the MAC PDU in which the RLC SDU that has not been received is received, and proceeds to step 1345.

Subsequently, in step 1345, the ENB constructs a first MAC PDU containing only valid RLC SDUs and transmits it in the corresponding MBMS subframe. For example, an RLC SDU having the same size as an unreceived RLC SDU is arbitrarily generated, and a normal MAC PDU is generated until a first MAC PDU is received, the RLC SDU having the same size as the non-received RLC SDU is generated It is possible.

If the size of some missing RLC SDUs can not be computed, the ENB proceeds from step 1330 to step 1350. In step 1350, the ENB transmits only the MAC PDUs generated so far in the corresponding MBMS subframe and stops further MAC PDU generation. In the MBMS subframe corresponding to the non-generated MAC PDU, transmission is stopped, and the process proceeds to step 1360.

In step 1355, the ENB determines whether the SYNC period has expired. If the MAC PDUs not generated due to the missing RLC SDUs are excluded, the ENB proceeds to step 1360 if all the MAC PDUs to be transmitted in the MBMS subframe allocated in the corresponding SYNC period are generated. If there are MAC PDUs not yet generated, the ENB returns to step 1310.

≪ Third Embodiment >

In the third embodiment of the present invention, the MBMS server transmits to the ENB a separate control message containing the size information of the payload stored in the SYNC frames corresponding to the predetermined SYNC period. When receiving the control message, the ENB can grasp the size of all the RLC SDUs in the corresponding SYNC period. Therefore, even when a large number of SYNC frames are not received consecutively, the ENB can normally generate MAC PDUs corresponding to the received RLC SDUs.

14 is a view for explaining a third embodiment of the present invention.

Referring to Fig. The MBMS server 1410 transmits n SYNC frames from the SYNC frame 1415 with PN = 0 to the SYNC frame 1425 with PN = n stored in the RLC SDUs to be transmitted in an arbitrary SYNC period x to the ENB 1405, Lt; / RTI > And transmits to the ENB a control message 1430 for the SYNC period x indicating the size of the payload stored in the SYNC frames or the size of the received RLC SDUs at an arbitrary point in time.

In the control message 1430, the sizes of the RLC SDUs stored in the SYNC frame for the SYNC period x are stored. The size of all the RLC SDUs stored in the SYNC frame for the SYNC period x, such as the size of the RLC SDU [0] stored in the SYNC frame [0] and the size of the RLC SDU [1] stored in the SYNC frame [ Can be accommodated.

If a separate control message 1430 indicating the size of the RLC SDU is provided, it is not necessary to separately store the OC information in the SYNC frames. Therefore, in the third embodiment of the present invention, the header of the SYNC frames containing the RLC SDU The OC information is not stored. Therefore, an ENB that has not received a separate control message 1430 indicating the size of the RLC SDU can not correctly generate a MAC PDU after the missing RLC SDU even if only one missing RLC SDU is generated, And stops transmission in the MBMS subframe until it is started.

On the other hand, if a separate control message 1430 indicating the size of the RLC SDU is received, the ENB can generate MAC PDUs from the correctly received RLC SDUs, regardless of how many unreceived RLC SDUs are generated, The MAC PDUs are transmitted in the corresponding MBMS subframe.

15 is a flowchart showing the operation of the base station apparatus according to the third embodiment of the present invention.

Referring to FIG. 15, when an arbitrary SYNC period starts in step 1505, the ENB proceeds to step 1510 and selects one of the MBMS subframes allocated for the arbitrary SYNC period, the first MBMS sub- And starts an operation for configuring the MAC PDU for the frame. The ENB sequentially segments or concatenates a part of the RLC SDU or the RLC SDU that has not yet been stored in the MAC PDU according to the size of the RLC PDU to be stored in the MAC PDU.

In step 1515, the ENB checks if an unreceived RLC SDU is found before all the payloads of the RLC PDU are found. If the payload of the RLC PDU is not filled with an unreceived RLC SDU, the ENB proceeds to step 1520, If an unreceived RLC SDU is found before filling, the process proceeds to step 1530.

In step 1520, the ENB constructs an RLC PDU by adding a predetermined header to an RLC payload segmented / concatenated by the RLC SDUs, and multiplexes the RLC PDUs to form a MAC PDU. In step 1525, the ENB transmits the configured MAC PDU in the corresponding MBMS subframe and proceeds to step 1555. If an unreceived RLC SDU is found before the payload of the RLC PDU is filled, the ENB proceeds from step 1515 to step 1530.

In step 1530, the ENB determines whether a control message containing the size information of the RLC SDUs is available for the SYNC period. If the control message is available, the ENB proceeds to step 1535, and if not, proceeds to step 1550.

In step 1535, the ENB determines the size of the RLC SDU that has not been received using the information stored in the control message, and determines, based on the size of the RLC SDU that has not been received, It is determined whether the MAC PDU has been received. For example, it is possible to arbitrarily generate an RLC SDU having the same size as that of an unreceived RLC SDU and to perform a normal MAC PDU generation process to determine which MAC PDU the RLC SDU having the same size as the non-received RLC SDU is stored in. In step 1540, the ENB stops transmission in the MBMS subframe corresponding to the MAC PDU in which the RLC SDU that it has not received is received, and proceeds to step 1545.

Subsequently, in step 1545, the ENB constructs a first MAC PDU containing only valid RLC SDUs and transmits the MAC PDU in the corresponding MBMS subframe. For example, an RLC SDU having the same size as an unreceived RLC SDU is arbitrarily generated, and a normal MAC PDU is generated until a first MAC PDU is received, the RLC SDU having the same size as the non-received RLC SDU is generated It is possible.

If a control message informing the size of the RLC SDUs for the corresponding SYNC period is not available, the ENB proceeds from step 1530 to step 1550. In step 1550, the ENB transmits only the MAC PDUs generated so far in the corresponding MBMS subframe and stops further MAC PDU generation. In the MBMS subframe corresponding to the MAC PDU that has not been generated, the transmission is stopped and the process proceeds to step 1560.

In step 1555, the ENB determines whether or not the SYNC period has expired. If the MAC PDUs not generated due to the non-received RLC SDUs are excluded, the ENB proceeds to step 1560 if all the MAC PDUs to be transmitted in the MBMS subframe allocated in the corresponding SYNC period are generated. If there are MAC PDUs not yet generated, the ENB returns to step 1510.

16 is a diagram illustrating a base station apparatus according to an embodiment of the present invention.

Referring to FIG. 16, the L1 receiving apparatus 1605 is an apparatus for receiving data transmitted from an MBMS server. Depending on the type of the wired link connected to the ENB, the L1 receiving apparatus 1605 may be an Ethernet receiving apparatus or an optical receiving apparatus. The data received by the L1 receiving apparatus 1605 is input to the demultiplexer 1607. [ The demultiplexer 1607 serves to distribute the received data to a suitable upper layer device. The demultiplexer 1607 transfers the SYNC frame corresponding to the specific MBMS service to the SYNC frame processor of the corresponding MBMS service.

The SYNC frame processing unit 1615 receives the SYNC frame and delivers the RLC SDU and related information, for example, PN, OC, etc., stored in the payload to the RLC SDU storage unit 1620. In addition, the SYNC frame processing unit 1615 transfers the POC or PPS stored in the SYNC frame to the RLC SDU size calculation unit 1610. The SYNC frame processing unit 1615 also receives the control message containing the RLC SDU size information, and transmits the control information to the not-received RLC SDU size calculation unit 1610. [

In the RLC SDU storage unit 1620, a portion of the RLC SDU or RLC SDU that has not yet been transmitted is stored in the order of PN. If the PNs of two adjacent RLC SDUs are not consecutive, the RLC SDU storage unit 1620 delivers the non-consecutive PNs and the OCs corresponding to the PNs to the missing RLC SDU size calculation unit 1610. And performs RLC PDU payload generation operation in consideration of the size of non-received RLC SDUs reported by the missing RLC SDU size calculation unit 1610. [ The RLC SDU storage unit 1620 divides / concatenates a part of the RLC SDU or the RLC SDU into a size required by the RLC PDU generation unit 1625 to form an RLC PDU payload, and transmits the payload to the RLC PDU generation unit 1625 .

If the RLC PDU payload can not be filled due to an unreceived RLC SDU, the RLC SDU storage unit 1620 notifies the RLC PDU generation unit 1625 that there is no data to be transmitted. If the RLC SDU size calculation unit 1610 notifies the RLC SDU storage unit 1620 that the size of an unreceived RLC SDU can not be calculated after a specific RLC SDU, the RLC SDU storage unit 1620 stores the specific RLC SDU size In the subsequent RLC SDU, the RLC PDU generation unit 1625 does not generate an RLC payload any more and notifies that there is no data to be transmitted. On the other hand, if the RLC SDU size calculation unit 1610 notifies the RLC SDU storage unit 1620 of the size of the non-received RLC SDU, the RLC SDU storage unit 1620 stores the RLC PDU payload in consideration of the size of the non- The RLC PDU generation unit 1625 generates an RLC PDU payload from the generation time point.

The unreceived RLC SDU size calculation unit 1610 calculates the size of an unreceived RLC SDU based on the information transmitted from the SYNC frame processing unit 1615 and the RLC SDU storage unit 1620 and transmits the calculated size to the RLC SDU storage unit 1620 . The unreceived RLC SDU size calculation unit 1610 notifies the RLC SDU storage unit 1620 of information indicating that the size of an unreceived RLC SDU can not be calculated.

The RLC PDU generation unit 1625 generates an RLC PDU of a size indicated by the transmission control unit 1635. The RLC PDU generation unit 1625 determines the amount of data to be stored in the RLC PDU payload in accordance with the size instructed by the transmission control unit 1635 and instructs the RLC SDU storage unit 1620 to create and deliver a payload of a corresponding size do. The RLC PDU generation unit 1625 attaches an RLC header to the payload delivered from the RLC SDU storage unit 1620, creates an RLC PDU, and transmits the RLC PDU to the MAC PDU generation unit 1630. If the RLC PDU generation unit 1625 does not transmit the RLC PDU payload in the RLC SDU storage unit 1620, the RLC PDU generation unit 1625 does not transmit the RLC PDU to the MAC PDU generation unit 1630.

The MAC PDU generation unit 1630 stores the RLC PDU received from the RLC PDU generation unit 1625 in the payload and adds a predetermined MAC header to the MAC PDU. And transfers the MAC PDU generation unit 1630 to the L1 transmission apparatus 1640 at a timing indicated by the transmission control unit 1635. If the RLC PDU generation unit 1625 does not forward the RLC PDU, the MAC PDU does not generate the MAC PDU.

The L1 transmission apparatus 1640 transmits the MAC PDUs delivered by the MAC PDU generation unit 1630 to the predetermined transmission resources in a predetermined modulation / channel coding scheme at the time when the transmission control unit 1635 instructs transmission. If there is no MAC PDU delivered by the MAC PDU generation unit 1630 at the time the transmission control unit 1635 instructs the transmission, the L1 transmission apparatus 1640 does not perform transmission at this point in time.

The transmission control unit 1635 recognizes the MBMS subframe and controls the RLC PDU generation unit 1625, the MAC PDU generation unit 1630, and the L1 transmission apparatus 1640 at an appropriate time before the start of the MBMS subframe, Thereby allowing the MAC PDU to be transmitted to the MBMS subframe.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative examples of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

Claims (24)

A method of transmitting a multimedia broadcast multicast service (MBMS) data of a base station,
Receiving service data units (SDUs) to be transmitted in an MBMS subframe from a core network node;
Receiving a control message including length information of each SDU transmitted from the core network node to the base station;
And processing the SDUs using length information included in the control message,
Wherein the control message is transmitted from the core network node to the base station after the SDUs are transmitted from the core network node to the base station. 2. The method of claim 1, wherein processing the SDUs comprises:
Identifying at least one SDU loss,
Determining an MBMS subframe including a MAC PDU (protocol data unit) for the at least one lost SDU, and
And blocking transmission of the MAC PDU in the determined MBMS subframe. 3. The method of claim 2,
Generating a MAC PDU comprising a valid SDU; And
And transmitting the generated MAC PDU in a corresponding MBMS subframe. 2. The method of claim 1, wherein the SDUs and the control message are received separately. 2. The method of claim 1, wherein processing the SDUs comprises:
Processes the SDUs using a length indicator of each SDU included in each SDU,
When loss of consecutive SDUs occurs, processing using length information included in the control message. 2. The method of claim 1, wherein processing the SDUs comprises:
Identifying a loss of at least two consecutive SDUs,
Confirming an MBMS subframe including a MAC PDU for the at least two SDUs using the length information, and
And blocking transmission of the MAC PDU in the identified MBMS subframe. 2. The method of claim 1, wherein the control message further comprises length information for each of the other SDUs transmitted from the core network node in one synchronization period. In the base station,
A transmitting and receiving unit for transmitting and receiving signals; And
Receiving from a core network node SDUs (service data units) to be transmitted in a MBMS subframe, receiving a control message including length information of each SDU transmitted from the core network node to the base station, And a control unit for controlling the SDUs to be processed using the length information included in the control message,
Wherein the control message is transmitted from the core network node to the base station after the SDUs are transmitted from the core network node to the base station. 9. The apparatus according to claim 8,
Determining at least one SDU loss, determining an MBMS subframe including a MAC PDU (protocol data unit) for the at least one lost SDU, preventing transmission of the MAC PDU in the determined MBMS subframe, To the base station. 10. The apparatus according to claim 9,
Generates an MAC PDU including a valid SDU, and controls the generated MAC PDU to be transmitted in a corresponding MBMS subframe. 9. The base station of claim 8, wherein the SDUs and the control message are received separately. 9. The apparatus according to claim 8,
Processes the SDUs using a length indicator of each SDU included in each SDU,
And controls to process using the length information included in the control message if a loss of consecutive SDUs occurs. 9. The apparatus according to claim 8,
Confirms a loss of at least two consecutive SDUs, identifies an MBMS subframe including a MAC PDU for the at least two SDUs using the length information, and transmits the MAC PDU in the confirmed MBMS subframe And to process the SDUs. The base station of claim 8, wherein the control message further comprises length information for each of the other SDUs transmitted from the core network node in one synchronization period. A method of transmitting a multimedia broadcast multicast service (MBMS) data of a core network node,
Transmitting service data units (SDUs) to be transmitted in an MBMS subframe to a base station; And
And transmitting a control message including length information of each SDU to the base station,
Wherein the control message is transmitted after the SDUs are transmitted. 16. The method of claim 15, wherein the SDUs and the control message are transmitted separately. 16. The method of claim 15, wherein the length information is used for synchronization in the synchronization interval if the base station checks loss of an SDU in a synchronization interval,
The MBMS subframe including the MAC PDU (protocol data unit) for the lost SDU is confirmed on the basis of the length information,
Wherein the transmission of the MAC PDU is prohibited by the base station in the identified MBMS subframe. 18. The method of claim 17,
Wherein the base station generates an MAC PDU including a valid SDU and uses the generated MAC PDU for transmission of the MAC PDU in a corresponding MBMS subframe. delete In a core network node,
A transmitting and receiving unit for transmitting and receiving signals; And
A control unit for transmitting service data units (SDUs) to be transmitted in a MBMS subframe to a base station and transmitting a control message including length information of each SDU to the base station,
Wherein the control message is transmitted after the SDUs are transmitted. 21. The core network node of claim 20, wherein the SDUs and the control message are transmitted separately. 21. The method of claim 20, wherein the length information is used for synchronization in the synchronization interval if the base station identifies loss of an SDU in the synchronization interval,
The MBMS subframe including the MAC PDU (protocol data unit) for the lost SDU is confirmed on the basis of the length information,
Wherein the transmission of the MAC PDU is prohibited by the BS in the identified MBMS subframe. 21. The method of claim 20,
Wherein the base station generates a MAC PDU including a valid SDU and uses the generated MAC PDU to transmit the MAC PDU in a corresponding MBMS subframe. delete

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