KR20080073553A - Apparatus for syncronizing a transmission of multicast/broadcast service data and method using the same - Google Patents

Abstract

An MBS(Multicast/Broadcast Service) data transmission synchronization device and a method thereof are provided to enable RASs(Radio Access Stations) within the same MBS zone to synchronize transmission time for MBS contents received from MBS contents sources, while a mobile terminal is capable of seamlessly receiving the MBS contents. A information receiver receives transmission synchronization from an ACR(Access Control Router). A contents receiver(230) sequentially receives contents packets including contents time information from MBS contents sources. A transmission time determiner(220) determines transmission time of the received contents packets based on the contents time information and transmission synchronization. A contents transmitter(240) transmits the received contents packets to mobile terminals at the transmission time.

Description

Multicast / broadcast service data transmission synchronization device and method thereof {APPARATUS FOR SYNCRONIZING A TRANSMISSION OF MULTICAST / BROADCAST SERVICE DATA AND METHOD USING THE SAME}

1 is a diagram illustrating an exemplary system for explaining a multicast / broadcast service data transmission synchronization apparatus according to the present invention.

2 is a block diagram illustrating an apparatus for synchronizing a multicast / broadcast service data transmission according to an embodiment of the present invention.

3 is an exemplary view for explaining the operation of the MBS data transmission synchronization device of the present invention.

4 is another exemplary view for explaining the operation of the MBS data transmission synchronization device of the present invention.

5 is a flowchart illustrating a method of synchronizing MBS data transmission according to an embodiment of the present invention.

FIG. 6 is a detailed operation flowchart of step S530 illustrated in FIG. 5.

7 is an exemplary view for explaining an operation of the MBS data transmission synchronization method of the present invention.

<Explanation of symbols for the main parts of the drawings>

210: information receiving unit

220: transmission time determining unit

230: content receiving unit

240: content transmission unit

The present invention relates to a multicast / broadcast service (MBS), and more particularly, to a multicast / broadcast service that performs transmission synchronization of multicast / broadcast service data transmitted from a wireless network to a mobile terminal. The present invention relates to a cast service data transmission synchronization apparatus and a method thereof.

In a WiBro / WiMax network, mobile terminals belonging to the same multicast group receive the same MBS contents. MBS content is transmitted in the MBS flow indicated by the connection indicator (CID) and the security association (SA) at the base station. The MBS zone represents an area in which one MBS flow is valid, and MBS contents transmitted to mobile terminals in the same MBS zone must be synchronized to obtain macro diversity gain.

In a WiBro / WiMax network, a mobile terminal receives MBS content of an MBS content source through an access control router (ACR) and a radio access station (RAS).

Here, the MBS content source, ACR, ACR, and RAS are connected by wire, and the mobile terminal and RAS are connected by wireless.

That is, the RAS transmits the MBS contents received through the ACR to the mobile terminals located in the cell through the wireless network.

However, even if the MBS content source transmits MBS content to different RASs in the same MBS zone at the same time, each of the different RASs may have different times for receiving MBS content. For example, depending on the path from the MBS content source to different RASs in the same MBS zone, each of the RASs may have a different time to receive the MBS content.

Since different RASs receive different MBS content from each other, content packets received by mobile terminals located in cells of each of the RASs may be different. For example, when the first RAS in the same MBS zone transmits MBS contents two frames earlier than the time in which the second RAS transmits MBS contents, when the mobile terminals located in the second RAS receive the first packet of the MBS contents. Mobile terminals located in the first RAS receive the third packet of MBS content.

Since the MBS content transmission time of each of the RASs is different, when the mobile terminal receives the MBS content and hands over to another RAS in the same MBS zone, seamless reception of the MBS content becomes impossible. In other words, the mobile terminal receives duplicate or lost MBS contents.

In addition, since RAS does not have a retransmission function for MBS content loss in a wireless section, quality of experience (QoE) cannot be guaranteed when MBS content loss occurs.

Therefore, there is a need for an apparatus capable of synchronizing the transmission time of MBS content to the RAS and retransmitting lost MBS content packets.

The present invention has been made to solve the problems of the prior art as described above, and aims to synchronize transmission times for MBS content received from MBS content sources by RASs in the same MBS zone.

In addition, an object of the present invention is to enable seamless reception of MBS content in a mobile terminal through transmission synchronization of MBS content.

It is also an object of the present invention to retransmit the lost MBS content packet to ensure QoE.

In order to achieve the above object and solve the problems of the prior art, the multicast / broadcast service data transmission synchronization apparatus of the present invention is an information receiver for receiving transmission synchronization information from an access control router (ACR); A content receiver for sequentially receiving a content packet including content time information from a cast / broadcast service (MBS) content source, and a transmission for determining a transmission time of the received content packet based on the transmission synchronization information and the content time information. And a time transmitter and a content transmitter for transmitting the received content packet to mobile terminals at the transmission time.

In this case, the transmission synchronization information is transmitted from a Tx reference time for transmitting the content packet, a cycle time (Tx interval time) for checking whether the content packet can be transmitted, and the multicast / broadcast service content source. It may include a predetermined threshold time (Tmax) or more than the maximum time required to receive the received content packet.

In this case, the content time information may include a time when the content packet is transmitted from the multicast / broadcast service content source and a sequence number of the content packet.

In this case, the transmission time determiner may determine the current time as the transmission time of the content packet when a current time for transmitting the content packet and a time difference transmitted from the content source of the content packet is greater than the threshold time. .

At this time, the transmission time determiner is the current time for transmitting the content packet and if the time difference transmitted from the content source of the content packet is less than the threshold time of the content packet after the cycle time has elapsed from the current time. The transmission time can be determined.

In this case, when the retransmission of the lost content packet is requested from the mobile terminal, the content transmitter may retransmit the lost content packet to the mobile terminal.

In this case, the content transmitter may retransmit the lost content packet to the mobile terminal in a unicast manner.

The multicast / broadcast service data transmission synchronization method of the present invention comprises the steps of receiving transmission synchronization information from an access control router (ACR) and including content time information from a multicast / broadcast service (MBS) content source. Receiving a content packet sequentially; determining a transmission time of the received content packet based on the transmission synchronization information and the content time information; and transmitting the received content packet to mobile terminals at the transmission time. Characterized in that it comprises a step.

In this case, the multicast / broadcast service data transmission synchronization method may further include retransmitting the lost content packet to the mobile terminal when retransmission of the lost content packet is requested from the mobile terminal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an exemplary system for explaining a multicast / broadcast service data transmission synchronization apparatus according to the present invention.

Referring to FIG. 1, the system includes mobile terminals 110, wireless access stations 120-140, access control routers 150, 160, MBS content source 180, and MBS controller 190. .

Each of the mobile terminals 100 displays the MBS content received through the radio section, and determines whether the content packet is lost. When the content packet is lost, the mobile terminals 100 transmit the retransmission of the lost content packet to the RAS of the corresponding cell. request.

In this case, each of the mobile terminals may determine whether the content packet is lost by checking a sequence number included in the content packet.

Each of the RASs 120 to 140 performs a function of the MBS data transmission synchronization device according to the present invention.

That is, each of the RASs includes a content packet including transmission synchronization information transmitted from the MBS control unit 190 and content time information transmitted from the MBS content source 180 through the IP core network 170 and the ACRs 150 and 160. And determine the transmission time of the content packet based on the transmission synchronization information and the content time information, and then transmit the content packet to the mobile terminals located in the cell at the transmission time.

In this case, when the ACR performs the function of the MBS control unit, the ACR may transmit transmission synchronization information, and the RAS may receive transmission synchronization information transmitted from the ACR. For example, if only one ACR is included in the same MBS zone, the function of the MBS control unit is added to the ACR, so that the RAS receives the transmission synchronization information transmitted from the ACR or configures the MBS control unit separately from the ACR to transmit the RAS from the MBS control unit. Transmitted synchronization information may be received through the ACR.

Of course, when two or more ACRs are included in the same MBS zone, it is preferable to configure the MBS control unit separately so that the RAS receives the transmission synchronization information transmitted from the MBS control unit through the ACR.

Each of the RASs 120 to 140 transmits the lost content packet to the mobile terminal requesting retransmission when the retransmission of the lost content packet is requested from the mobile terminal.

At this time, each of the RAS retransmits the lost content packet to the mobile terminal in a unicast manner.

Each of the ACRs 150 and 160 receives transmission synchronization information transmitted from the MBS control unit 190 and transmits the transmission synchronization information to each of the RASs.

In this case, each of the ACRs 150 and 160 may receive the MBS zone identifier and the multicast IP address from the MBS controller 190 and transmit the received MBS zone identifiers to the RASs.

Here, in the same MBS zone, transmission synchronization information is provided for the same MBS flow, and the MBS flow is distinguished through a multicast IP address.

At this time, the transmission synchronization information receives a reference time (Tx reference time) for transmitting the content packet in the RAS, a cycle time (Tx interval time) for checking whether the content packet can be transmitted in the RAS and a content packet transmitted from the MBS content source It may include a predetermined threshold time (Tmax) or more than the maximum time taken to.

Each of the ACRs 150 and 160 receives a content packet including content time information transmitted from the MBS content source 180 and transmits it to each of the RASs.

In this case, the content time information may include a time when the content packet is transmitted from the MBS content source and a sequence number of the content packet.

2 is a block diagram illustrating an apparatus for synchronizing MBS data transmission according to an embodiment of the present invention.

Referring to FIG. 2, the MBS data transmission synchronization apparatus includes an information receiver 210, a transmission time determiner 220, a content receiver 230, and a content transmitter 240.

The information receiver 210 receives the transmission synchronization information transmitted from the MBS controller through the ACR.

In this case, the information receiver 210 may receive the MBS zone identifier and the multicast IP address transmitted from the MBS controller through the ACR.

Here, the transmission synchronization information is information necessary for determining a transmission time so that all RASs having the same MBS zone identifier can transmit a content packet at the same time to mobile terminals located in a corresponding cell through a wireless section.

In this case, the transmission synchronization information includes a reference time (Tx reference time) for the RAS to transmit the content packet, a cycle time (Tx interval time) for checking whether the RAS can transmit the content packet, and a content packet transmitted from the MBS content source by the RAS. It may include a predetermined threshold time (Tmax) or more than the maximum time required to receive the.

That is, the RAS checks whether the content packet can be transmitted at a periodic time period starting from the reference time. Here, the reference time is equally applied to all RASs included in the same MBS zone.

In this case, the reference time may be the sum of the time at which the transmission of the content packet starts from the MBS content source, the threshold time, and the buffering time in the De-jitter buffer of the RAS.

In addition, the RAS may determine whether the content packet is lost using the threshold time. For example, if the RAS does not receive the content packet transmitted from the MBS content source within the threshold time, the RAS determines that the content packet is lost in the IP core network section or the section between the ACR and the RAS.

Here, an example threshold time may be 2 to 3 seconds, the threshold time is not limited but may vary depending on a situation, and this value may be determined by an MBS content provider or a mobile terminal provider.

The content receiver 230 receives the content packet transmitted from the MBS content source through the ACR.

In this case, the content packet may include content time information, and the content time information may include a time when the content packet is transmitted from the MBS content source and a sequence number of the content packet.

In this case, the content receiving unit 230 may sequentially store content packets sequentially received from the MBS content source in a circular buffer or a static buffer.

That is, the content receiver 230 receives a content packet including a time and a sequence number transmitted from the MBS content source from the MBS content source through the ACR.

The transmission time determiner 220 determines the transmission time of the content packet based on the transmission synchronization information received by the information receiver 210 and the content time information received by the content receiver 230.

In this case, the transmission time determiner 220 determines the difference between the current time for transmitting the corresponding content packet received by the content receiving unit 230 and the time transmitted from the content source of the corresponding content packet and the threshold time included in the transmission synchronization information. The transmission time can be determined based on the comparison result.

That is, the transmission time determiner 220 determines the current time as the transmission time of the content packet when the difference between the current time for transmitting the content packet and the time transmitted from the content source of the content packet is greater than the threshold time. .

On the other hand, if the difference between the current time for transmitting the content packet and the time transmitted from the content source of the content packet is less than the threshold time, the transmission time determiner 220 waits for the period time included in the transmission synchronization information. The transmission time of the content packet is determined.

That is, the transmission time determiner 220 determines the transmission time of the content packet again by using the time after the cycle time as the current time.

The content transmitter 240 transmits the content packet to the mobile terminals in the cell at the transmission time determined by the transmission time determiner 220.

In this case, when the retransmission of the lost content packet is requested from the mobile terminal, the content transmitter 240 may retransmit the lost content packet to the mobile terminal in a unicast manner.

Description of the MBS data transmission synchronization apparatus according to the present invention will be described with reference to FIGS.

3 is an exemplary view for explaining the operation of the MBS data transmission synchronization device of the present invention.

Referring to FIG. 3, RAS1 and RAS2 receive content packets P1 through P4 that include transmission times T1 through T4 transmitted from MBS content sources.

Here, RAS1 and RAS2 receive transmission synchronization information transmitted from the MBS control unit, that is, a reference time (Tr: Tx reference time), a cycle time (Tp: Tx interval time), and a threshold time (Tmax) transmitted from the MBS controller before receiving the content packet. .

At this time, each content packet includes a time and a sequence number transmitted from the MBS content source. That is, the content packet P1 includes the time T1 transmitted from the MBS content source and the first sequence number.

It can be seen that RAS1 and RAS2 have different times of receiving content packets transmitted from MBS content sources. That is, RAS1 receives content packets P1, P2, P3, and P4 transmitted from MBS content sources at R1, R2, R3, and R4 times, and RAS2 receives content packets P1, P2, P3, and P4 transmitted from MBS content sources. Receive at R1 + k, R2 + l, R3 + m and R4 + n times. The reason that RAS1 and RAS2 receive the content packet is different because the paths from the MBS content source to RAS1 and RAS2 are different.

RAS1 and RAS2 respectively store the content packets received from the MBS content source in the reception buffer and determine the transmission time for transmitting the content packets to mobile terminals in the cell.

Here, since the transmission times of the content packets determined by the RAS1 and the RAS2 are the same, an operation in which the RAS1 determines the transmission time and transmits the content packet at the determined transmission time will be described.

The RAS1 determines the transmission time of the content packet at the reference time Tr or at a time after the cycle time at the reference time (for example, Tα = Tr + Tp). That is, RAS1 determines whether the difference (Tα-T1) between Tα and the content packet P1 transmitted from the MBS content source (Tα-T1) is greater than the threshold time (Tmax), and if Tα-T1> Tmax, Tα is the transmission time of the content packet P1. Determine and transmit the content packet P1 to mobile terminals located in the cell of RAS1.

Whereas if T1 ≤ Tα-cycle time Tmax is the last time Tp at Tα (Tα + Tp) that is, it is determined greater than a threshold time (Tmax) the difference (T _β -T1) for _β T and _β T T1 -T1> Tmax In this case, T _β is determined as the transmission time of the content packet P1, and T _β is transmitted to the mobile terminals located in the cell of the RAS1.

Of course, if the contents packet P1 is sent to the mobile terminals in Tα determines the transmission time of the content packet P2 from T _β. That is, T _β -T2> Tmax is determined the T _β to the transmission time of the packet P2, and transmits the content to mobile terminals located in the cell of the contents packet P2 RAS1 in T _β.

This series of procedures is performed for all content packets stored in the receive buffer of RAS1, and transmits the content packets to the mobile terminals at the determined transmission time. In the example of Figure 3 sends the P1 in Tα and transmits P2 in T _β, and transmitting from the P3 T _γ.

Of course, RAS2 also performs the same operation as RAS1 and transmits the same packet to mobile terminals located in the cells of RAS2 at the same time.

At this time, each of the mobile terminals requesting the MBS content determines whether the content packet is lost through the sequence number included in the received content packet, and if the lost content packet occurs, retransmits the lost content packet to the RAS by unicast method. You can request

An operation of RAS receiving a request for a lost content packet from a mobile terminal and transmitting the requested content packet will be described with reference to FIG. 4.

4 is another exemplary view for explaining the operation of the MBS data transmission synchronization device of the present invention.

4, the RAS transmits a content packet received from an MBS content source to mobile terminals located in the RAS at a determined transmission time.

The mobile terminal receiving the content packet determines whether there is a lost content packet through the sequence number included in the content packet. That is, the mobile terminal may extract the sequence number included in the received content packet and determine whether the content packet is lost based on the extracted sequence number.

When a lost content packet occurs, the mobile terminal transmits a message requesting retransmission of the lost content packet P4 to the RAS in a unicast manner, as shown in FIG. 4.

The RAS reads a content packet requested to be retransmitted from the mobile terminal in a circular buffer or a static buffer, which is a reception buffer, and transmits the content packet to the mobile terminal in a unicast manner.

Of course, in order to perform such an operation, the mobile terminal preferably includes a configuration for determining whether a content packet is lost from the received content packet and a configuration for requesting and receiving the lost content packet from the RAS.

5 is a flowchart illustrating a method of synchronizing MBS data transmission according to an embodiment of the present invention.

Referring to FIG. 5, the MBS data transmission synchronization method receives transmission synchronization information from the MBS controller (S510).

In this case, the transmission synchronization information may be received from the ACR. That is, when a single ACR is included in the MBS zone, the MBS controller is added to the ACR, and when the ACR performs the function of the MBS controller without receiving a separate MBS controller, the transmission synchronization information is received from the ACR. Of course, when two or more ACRs are included in the MBS zone, it is preferable to separately configure the MBS control unit to receive transmission synchronization information from the MBS control unit.

In this case, the transmission synchronization information is a predetermined time or more than a reference time for the RAS to transmit the content packet, a cycle time for checking whether the RAS can transmit the content packet, and a maximum time required for the RAS to receive the content packet transmitted from the MBS content source. May include a threshold time.

A content packet including content time information is received from the MBS content source (S520).

At this time, the content time information includes the time when the content packet was transmitted from the MBS content source and the sequence number of the content packet.

On the basis of the transmission synchronization information received from the MBS control unit and the content time information received from the MBS content source, a transmission time for transmitting a content packet to a wireless section is determined (S530).

The content packet is transmitted to mobile terminals located in the cell at the determined transmission time (S540).

After transmitting the content packet to the mobile terminals and receiving a message requesting retransmission of the content packet from the mobile terminal in unicast manner, the content packet requested for retransmission is transmitted to the mobile terminal in unicast manner (S550 and S560).

FIG. 6 is a detailed operation flowchart of step S530 illustrated in FIG. 5.

Referring to FIG. 6, in step S530 of determining a transmission time of a content packet, a time Tm transmitted from MBS content of a content packet included in the content packet is checked (S610).

The difference between the current time Tc and the time Tm transmitted from the MBS content of the corresponding content packet at the reference time included in the transmission synchronization information or the current time after the reference time is compared with the threshold time Tmax included in the transmission synchronization information. (S620).

The difference between the two times, that is, Tc-Tm is greater than Tmax (S630). If Tc-Tm> Tmax, the current time is determined as the transmission time of the content packet (S640).

On the other hand, if it is determined in S630 that Tc-Tm ≤ Tmax, the processor waits for the period time Tp included in the transmission synchronization information (S650), and that time, that is, Tc + Tp as the current time (Tc = Tc + Tp). Perform S620 again.

This is done for all content packets received.

The MBS data transmission synchronization method according to the present invention will be further described with reference to FIG. 7.

7 is an exemplary view for explaining an operation of the MBS data transmission synchronization method of the present invention.

Referring to FIG. 7, RASs located in the same MBS zone, that is, RAS1 and RAS2, receive MBS Zone Information transmitted from the MBS control unit through ACR.

In this case, the MBS zone information includes an MBS zone identifier (ID), a multicast IP address, and transmission synchronization information.

Although only one ACR is shown in FIG. 7, another ACR included in the same MBS zone is also performed in the same operation as FIG. 7.

As shown in FIG. 7, when the MBS zone is configured in one ACR, the MBS controller function may be performed in the ACR.

After receiving the MBS zone information, the RAS1 and RAS2 receive the content packet transmitted from the MBS content source through the ACR.

At this time, the content packet includes a time and a sequence number transmitted from the MBS content source.

Each of RAS1 and RAS2 stores the received content packet in a buffer for MBS contents.

Each of RAS1 and RAS2 determines the transmission time of the content packet stored in the MBS content buffer based on the transmission synchronization information and the content time information included in the MBS zone information, and transmits the content packet to the wireless section at the determined transmission time.

In this case, RAS1 and RAS2 may sequentially transmit the content packet stored in the MBS content buffer for the longest time.

The method for synchronizing multicast / broadcast service data transmission according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like including a carrier wave for transmitting a signal specifying a program command, a data structure, or the like. Examples of program instructions include machine code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

The apparatus and method for synchronizing multicast / broadcast service data transmission of the present invention can synchronize transmission times for MBS content received from MBS content sources by RASs in the same MBS zone.

In addition, the present invention may enable seamless reception of MBS content in a mobile terminal through transmission synchronization of MBS content.

In addition, the present invention may retransmit lost MBS content packets to ensure QoE.

Claims (19)

An information receiver configured to receive transmission synchronization information from an access control router (ACR); A content receiving unit sequentially receiving a content packet including content time information from a multicast / broadcast service (MBS) content source; A transmission time determiner configured to determine a transmission time of the received content packet based on the transmission synchronization information and the content time information; And A content transmitter which transmits the received content packet to mobile terminals at the transmission time Multicast / broadcast service data transmission synchronization apparatus comprising a. The method of claim 1, The transmission synchronization information Tx reference time for transmitting the content packet, Tx interval time for checking whether the content packet can be transmitted, and time required for receiving the content packet transmitted from the multicast / broadcast service content source. And a predetermined threshold time (Tmax) equal to or more than a maximum time period. The method of claim 2, The content time information is And a sequence number of the content packet and the time at which the content packet was transmitted from the multicast / broadcast service content source. The method of claim 3, The transmission time determiner And if the current time for transmitting the content packet and the time difference transmitted from the content source of the content packet is greater than the threshold time, determine the current time as the transmission time of the content packet. Cast service data transmission synchronization device. The method of claim 3, The transmission time determiner Determining a transmission time of the content packet after the cycle time has elapsed from the current time when a current time for transmitting the content packet and a time difference transmitted from the content source of the content packet is less than or equal to the threshold time. Multicast / broadcast service data transmission synchronization device. The method of claim 1, The information receiving unit And receiving the transmission synchronization information transmitted from the multicast / broadcast service control unit through the access control router. The method of claim 1, The information receiving unit And receiving the transmission synchronization information transmitted from the access control router. The method of claim 1, The content transmission unit And retransmitting the lost content packet to the mobile terminal when retransmission of the lost content packet is requested from the mobile terminal. The method of claim 8, The content transmission unit And retransmitting the lost content packet to the mobile terminal in a unicast manner. Receiving transmission synchronization information from an access control router (ACR); Sequentially receiving a content packet containing content time information from a multicast / broadcast service (MBS) content source; Determining a transmission time of the received content packet based on the transmission synchronization information and the content time information; And Transmitting the received content packet to mobile terminals at the transmission time Multicast / broadcast service data transmission synchronization method comprising a. The method of claim 10, The transmission synchronization information Receiving a Tx reference time for transmitting the content packet, a Tx interval time for checking whether the content packet can be transmitted, and a content packet transmitted from the multicast / broadcast service content source. And a predetermined threshold time (Tmax) that is greater than or equal to the maximum time required. The method of claim 11, The content time information is And the sequence number of the content packet and the time at which the content packet was transmitted from the multicast / broadcast service content source. The method of claim 12, Determining a transmission time of the content packet And if the current time for transmitting the content packet and the time difference transmitted from the content source of the content packet is greater than the threshold time, determine the current time as the transmission time of the content packet. How to Synchronize Cast Service Data Transfers. The method of claim 12, Determining a transmission time of the content packet Determining a transmission time of the content packet after the cycle time has elapsed from the current time when the current time for transmitting the content packet and the time difference transmitted from the content source of the content packet is less than or equal to the threshold time. A multicast / broadcast service data transmission synchronization method. The method of claim 10, Receiving the transmission synchronization information And receiving the transmission synchronization information transmitted from the multicast / broadcast service control unit through the access control router. The method of claim 10, Receiving the transmission synchronization information And receiving the transmission synchronization information transmitted from the access control router. The method of claim 10, The multicast / broadcast service data transmission synchronization method Retransmitting the lost content packet to the mobile terminal when retransmission of the lost content packet is requested from the mobile terminal; The multicast / broadcast service data transmission synchronization method further comprising. The method of claim 17, Retransmitting the lost content packet to the mobile terminal And retransmitting the lost content packet to the mobile terminal in a unicast manner. A computer-readable recording medium in which a program for executing the method of any one of claims 10 to 18 is recorded.

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