JP2000307580A - Data distributing method and recording medium therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data distributing method by which the area of a buffer for securing a resending time required for restoring one piece of data within a finite buffer area is reduced by reducing the resending time without regard to the generating place of a data error or a loss and to provide a recording medium therefor. SOLUTION: At the time of detecting an error in received data and receiving resending data (step 129, Yes), a selectively receiving terminal judges whether a resending request is received or not from another selectively receiving terminal (step 131). When the resending request is received from another selectively receiving terminal (step 132, Yes), transmission of the received resending data is stopped when the received resending data was simultaneously distributed (step 135). The received resending data is simultaneously distributed to all the other selectively receiving terminals when the received resending data was not simultaneously distributed (step 136).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data distribution method in which a transmitting terminal simultaneously distributes real-time media to a plurality of receiving terminals, and a recording medium therefor.

[0002] At present, demands for remote education, remote monitoring, and the like by real-time media distribution are increasing. The network used at this time may not guarantee reliability. By applying the data distribution method according to the present invention to such a network, it is possible to improve the data recovery rate.

[0003]

2. Description of the Related Art Generally, in a data distribution method for simultaneously transmitting data from a transmitting terminal to a plurality of receiving terminals, when a receiving terminal receives data distributed from the transmitting terminal, a data error or loss is detected. In this case, a method is often employed in which a receiving terminal requests retransmission to a transmitting terminal, and the transmitting terminal retransmits correct data only to the receiving terminal that has requested retransmission. In this case, the receiving terminal has a buffer to secure the retransmission time,
If the retransmission time is long and it is necessary to use the entire area of the buffer to recover one of the data, if a new error is detected before the data is recovered, the error data cannot be recovered. .

If such a situation occurs continuously, it becomes difficult for the receiving terminal to recover a large amount of data. In addition, if all the receiving terminals are retransmission-requested destinations, the transmitting terminal and the transmission path cannot be transmitted. As a problem, traffic may be concentrated and may cause a new data error and data loss.

Therefore, conventionally, a relay terminal that receives data temporarily distributed by a transmitting terminal in a distribution route, temporarily stores the data, and retransmits correct data to a request source when a retransmission request is received,
Installed for each of a plurality of receiving terminals connected to one or more nodes, and retransmitted between a transmitting terminal and a relay terminal, between a relay terminal and a relay terminal, and between a relay terminal and a receiving terminal. There is a way to do it.

[0006] According to this method, retransmission requests concentrated only on the transmitting terminal are distributed to a plurality of relay terminals, so that traffic concentration is reduced. Further, the receiving terminal does not request the transmitting terminal to perform retransmission via a plurality of nodes, but requests the relay terminal located at a position where the number of passing nodes is smaller than the transmitting terminal to perform retransmission. Therefore, when a data error or loss occurs in the receiving terminal, the number of nodes that pass to complete retransmission decreases, and the retransmission time can be reduced.

Further, when data loss occurs at a node to which the receiving terminal and the relay terminal are connected, the relay terminal detects the loss before the receiving terminal detects the data loss, and a higher-order node. A retransmission request is made to the relay terminal connected to the (node having a smaller number of nodes with the transmitting terminal than that node). After the retransmission is performed, in response to a retransmission request from a relay terminal connected to a lower node (a node having a larger number of nodes with the transmitting terminal than the node), retransmission to the relay terminal is performed. I do. By performing these processes, when the receiving terminal detects a data error or loss and requests retransmission to the nearest relay terminal, the relay terminal has correct data at an early stage.
Therefore, retransmission time can be reduced.

[0008]

In the data distribution method described above, when a data error or loss occurs in a certain node, the relay terminal connected to that node is connected to the relay terminal connected to a higher-order node. A retransmission request is sent to the terminal or the transmitting terminal. As a result, when correct data is retransmitted, the relay terminal next performs retransmission to the relay terminal in response to a retransmission request from a relay terminal connected to a lower node. By performing such processing hierarchically, correct data is received at the relay terminal close to the receiving terminal.

For this reason, for example, when a data error or loss occurs at a node installed closest to the transmitting terminal, the relay terminal connected to the lowest node needs to transmit data to the transmitting terminal in order to receive correct data. A retransmission operation performed between a plurality of relay terminals provided up to the relay terminal connected to the lowest node must be performed. That is, if the number of relay terminals existing between the receiving terminal and the node where the data error or loss has occurred is large, it takes a long time until the relay terminal connected to the same node as the receiving terminal receives correct data. , It is difficult to reduce the retransmission time.

[0010] On the other hand, if the number of relay terminals is reduced, for example, when the receiving terminal detects a data error or loss and the cause is the receiving terminal itself, the same node or the next higher node If there is no relay terminal connected to the terminal, it is difficult to reduce the retransmission time. In addition, when the number of relay terminals is reduced, the number of retransmission requests received by each relay terminal increases, which causes a problem of traffic concentration.
Therefore, it is an issue to apply the existing method of installing a plurality of relay terminals and to reduce the retransmission time even when a data error or loss occurs in a higher-order node.

[0011] Therefore, the present invention has been made in view of the above-mentioned circumstances, and can reduce the retransmission time regardless of the location where a data error or loss has occurred. Within the finite buffer area, the receiving terminal can reduce the buffer area to secure the retransmission time required to recover one data, and the receiving terminal improves the data recovery rate even when continuous errors are detected. An object of the present invention is to provide a data distribution method and a recording medium for the data distribution method.

[0012]

According to a first aspect of the present invention, there is provided a data transmitting apparatus for simultaneously transmitting video data generated in real time to a plurality of receiving terminals connected to one or more nodes. In the distribution method, at least one of the plurality of receiving terminals is selected as a selected receiving terminal, and each of the receiving terminals is determined as a retransmission request destination when an error or loss is detected in received video data. Requesting the selected receiving terminal or the transmitting terminal to perform retransmission, and when the selected receiving terminal detects an error or loss in the received video data, retransmitting to the transmitting terminal or another selected receiving terminal determined as the retransmission request destination. Request,
When the transmitting terminal receives a retransmission request from the selected receiving terminal or the receiving terminal, the transmitting terminal transmits correct video data only to the selected receiving terminal or the receiving terminal.

According to a second aspect of the present invention, in the data distribution method according to the first aspect, each of the receiving terminals measures the number of nodes between itself and the transmitting terminal, and the selected receiving terminal Measuring the number of nodes between the transmitting terminal and transmitting the measured value to the transmitting terminal, the transmitting terminal, the measured value of each selected receiving terminal sent from the selected receiving terminal all the Transmit to the selected receiving terminal and the receiving terminal, the receiving terminal compares the measured value transmitted from the transmitting terminal with the measured value of the number of nodes between the own terminal and the transmitting terminal, If there is no selected receiving terminal that is a measurement value less than the number of nodes between the transmitting terminal and the retransmission request destination to the transmitting terminal, if there is, measure the number of nodes between those selected receiving terminals, Selective reception of the smallest number of nodes It is characterized in that the end of the retransmission request destination.

According to a third aspect of the present invention, in the data distribution method according to the first aspect, the selective receiving terminal measures the number of nodes between the terminal itself and the transmitting terminal, and compares the measured value with the number of nodes. Transmitting to the transmitting terminal, the transmitting terminal transmits the measurement value sent from each of the selective receiving terminals to all selective receiving terminals and receiving terminals, the selective receiving terminal,
The measured value transmitted from the transmitting terminal and the measured value between the own terminal and the transmitting terminal are compared, and the selected receiving terminal is a measured value smaller than the number of nodes between the own terminal and the transmitting terminal. If does not exist, the sending terminal is the retransmission request destination,
If there is, the number of nodes located between the selected receiving terminals is measured, and the selected receiving terminal having the smallest number of nodes is set as the retransmission request destination.

According to a fourth aspect of the present invention, in the data distribution method according to the first aspect, the selected receiving terminal does not detect an error or loss in the data received from the transmitting terminal. If the retransmission request is received from another selected receiving terminal or receiving terminal, it is determined that a data error or loss has occurred in the receiving terminal, and retransmission data is transmitted only to the terminal of the retransmission request source. If an error or loss is detected in the data received from the terminal, and if a request for retransmission of the data is received from another selected receiving terminal, it is determined that the error or loss has occurred in the node, and the retransmission request source is selected. If it is a receiving terminal, determine whether the retransmission data received from the transmitting terminal or the selected receiving terminal connected to the upper node is the one that has been broadcast, If the received retransmitted data has been delivered simultaneously aborts the transmission of the retransmission data, if not been broadcasted it is characterized by concurrently delivers the retransmission data thus received.

Here, retransmission data refers to correct data transmitted in response to a retransmission request.

The invention according to claim 5 is executed by a computer functioning as the transmission terminal in a network including a transmission terminal connected to one or more nodes, a plurality of reception terminals and a selective reception terminal, A computer-readable recording medium on which a program for simultaneously distributing video data generated in real time to the plurality of receiving terminals and the selective receiving terminal is recorded. Upon receiving a measurement of the number of nodes between the terminal and the sending terminal,
Transmitting the measurement value to the all-selected receiving terminal and the receiving terminal; and, when receiving a retransmission request from the selected receiving terminal, transmitting retransmission data to the selected receiving terminal of the retransmission request source. Is a computer-readable recording medium on which a program to be executed by a computer is recorded.

The invention according to claim 6 is executed by a computer functioning as the selective receiving terminal in a network including a transmitting terminal connected to one or more nodes, a plurality of receiving terminals, and a selective receiving terminal. Is a computer-readable recording medium that records a program that receives video data generated in real time broadcast from the transmitting terminal, and measures the number of nodes between the own terminal and the transmitting terminal. Transmitting the measured value to the transmitting terminal, measuring values of all selected receiving terminals transmitted from the transmitting terminal, and comparing measured values between the own terminal and the transmitting terminal; and Determining whether there is a selected receiving terminal having a measured value smaller than the number of nodes between the own terminal and the transmitting terminal; If there is no selected receiving terminal that is a measurement value less than the number of nodes between the transmission terminal and the transmission terminal, and the measurement value less than the number of nodes between the own terminal and the transmission terminal. And measuring the number of nodes between the selected receiving terminals when there is a selected receiving terminal, and setting the selected receiving terminal having the smallest number of nodes as a retransmission request destination. Computer-readable recording medium.

According to a seventh aspect of the present invention, the program recorded on the computer-readable recording medium according to the sixth aspect does not detect any error or loss in the data received from the transmitting terminal. A step of, when receiving the data retransmission request from another selected receiving terminal or receiving terminal, determining that the data error or loss has occurred in the receiving terminal and transmitting the retransmission data only to the retransmission requesting terminal; If an error or loss is detected in the data received from the transmitting terminal, and if a request for retransmission of the data is received from another selected receiving terminal, it is determined that the error or loss has occurred in the node, and the retransmission If the request source is the selective receiving terminal, the retransmission data received from the transmitting terminal or the selective receiving terminal connected to the upper node is broadcast simultaneously. Judging whether or not the received retransmission data is broadcast, stopping the transmission of the retransmission data if the received retransmission data has been broadcast, and broadcasting the received retransmission data if the reception has not been broadcast Are executed by the computer.

The invention according to claim 8 is executed by a computer functioning as the receiving terminal in a network including a transmitting terminal connected to one or more nodes, a plurality of receiving terminals, and a selective receiving terminal. A computer-readable recording medium that records a program for receiving video data generated in real time that is broadcast from the transmitting terminal, and measuring the number of nodes between the own terminal and the transmitting terminal; Receiving the measured value of the number of nodes between the transmitting terminal and the selected receiving terminal measured by the selected receiving terminal respectively transmitted from the transmitting terminal; and measuring each of the measurements transmitted from the transmitting terminal. Comparing the measured value with the measured value of the number of nodes between the own terminal and the transmitting terminal; If there is no selected receiving terminal having a measured value smaller than the number of nodes, the transmitting terminal is set to the retransmission request destination; andthe selected receiving terminal having a measured value smaller than the number of nodes between the own terminal and the transmitting terminal. If there is, measuring the number of nodes between the selected receiving terminal, and the step of making the selected receiving terminal of the smallest number of nodes a retransmission request destination; and It is a recording medium.

In the above data distribution method and its recording medium, the retransmission request destination of the selected receiving terminal connected to the highest-order node is the transmitting terminal, and the retransmission request of the selected receiving terminal or the receiving terminal connected to the lower-order node. The request destination is a selected receiving terminal that is connected to a higher-level node and has the least number of nodes existing between itself and the terminal. Also, if a certain receiving terminal detects a data error or loss,
When a retransmission is requested from the transmitting terminal or the selected receiving terminal connected to the upper node closer to the transmitting terminal, and a retransmission request is received from the selected receiving terminal connected to the lower node, the received retransmitted data is broadcast simultaneously. It is determined whether or not the retransmission data has been broadcast. If the broadcast has been broadcast, the transmission of the retransmission data is stopped. If the broadcast has not been broadcast, the retransmission data is broadcast.

As described above, by using this method, the retransmission time can be reduced irrespective of the location where a data error or loss occurs. Also, by shortening the retransmission time, the receiving terminal can reduce the buffer area for securing the retransmission time required for recovering one data within the limited buffer area. Therefore, the receiving terminal can improve the data recovery rate even when a continuous error is detected.

[0023]

1 to 3 are flowcharts showing one embodiment of a data distribution method according to the present invention.
The system targeted for the processing of the flowcharts shown in FIGS. 1 to 3 includes a transmitting terminal and a plurality of receiving terminals,
Each terminal is assumed to be connected to the same network.

The transmitting terminal distributes data (for example, real-time video data) to the plurality of receiving terminals simultaneously, and the plurality of receiving terminals respectively receive the data distributed from the transmitting terminal. Also, some of the plurality of receiving terminals are appropriately selected in advance, and the selected receiving terminal (hereinafter, referred to as a selected receiving terminal) is correctly selected in response to a retransmission request from the receiving terminal or another selected receiving terminal. Causes retransmission of data.

First, a processing procedure when each receiving terminal determines a retransmission request destination in the above-described system will be described with reference to FIG. FIG. 1A shows the processing in the receiving terminal, FIG. 1B shows the processing in the selective receiving terminal, and FIG.
(C) shows the processing in the transmitting terminal.

First, each selected receiving terminal measures the number of nodes with the transmitting terminal (step 107), and sends the measured value to the transmitting terminal (step 108). The transmitting terminal receives the measurement value from the selected receiving terminal (Step 109)
Then, the measured values are simultaneously distributed to all the receiving terminals (step 110). Each receiving terminal measures the number of nodes existing between the receiving terminal and the transmitting terminal (step 101). Thereafter, the process waits until a measurement value (described later) of the selected receiving terminal is received from the transmitting terminal (step 102).

When the receiving terminal receives the measured value of the selected receiving terminal from the transmitting terminal (Step 102, Yes), it compares the received measured value with the value measured in Step 101 (Step 103). Then, the selected receiving terminal having a measured value smaller than the measured value measured in step 101 is selected (step 104). Here, if there is no selected receiving terminal whose measured value is smaller than the measured value measured in step 101, the transmitting terminal is set as the retransmission request destination. next,
The number of nodes existing between the terminal itself and each of the selected receiving terminals is measured (step 105). Finally, the selected receiving terminal having the smallest number of nodes between each selected receiving terminal and the own terminal is set as the retransmission request destination (step 1).
06).

Next, with reference to FIG. 2, a description will be given of a processing procedure when each selected receiving terminal determines a retransmission request destination in the system described above. FIG. 2A shows the processing in the selected receiving terminal, and FIG. 2B shows the processing in the transmitting terminal.

First, the process waits until a measurement value (described later) of all the selected receiving terminals is received from the transmitting terminal (step 11).
3). On the other hand, the transmitting terminal waits until receiving the measured value from the selected receiving terminal (step 120), and upon receiving the measured value from the selected receiving terminal, simultaneously distributes the measured values to all receiving terminals including the selected receiving terminal (step 120). Step 12
1).

The selected receiving terminal receives the measurement values of all the selected receiving terminals from the transmitting terminal (step 113, Ye).
s), each received measurement value, and step 10 in FIG.
The measured value is compared with the measured value in step 7 (step 114).
As a result of the comparison, if the measured value measured in step 107 is the smallest (step 115, Yes), the transmitting terminal is set as the retransmission request destination (step 117). If the measured value measured in step 107 is not the minimum (step 115, No), the selected receiving terminal having a measured value smaller than the measured value measured in step 107 is selected (step 116). Next, the number of nodes existing between the selected selected receiving terminal and the self-selected receiving terminal is measured (step 11).
8) The selected receiving terminal having the smallest number of nodes is set as the retransmission request destination (step 119).

Next, a processing procedure when the transmitting terminal retransmits correct data in the above-described system will be described with reference to FIG. FIG. 3A shows the processing in the transmitting terminal, and FIG. 3B shows the processing in the selective receiving terminal.

First, the transmitting terminal waits until receiving a retransmission request from the selected receiving terminal or the receiving terminal (step 1).
22). On the other hand, the selective receiving terminal waits until an error is detected (step 124). If an error is detected (Step 124, Yes), retransmission is requested to another selected receiving terminal or transmitting terminal (Step 125).
When the transmitting terminal receives the retransmission request (step 122, Ye
s) The correct data is sent only to the retransmission request source (step 123). Hereinafter, correct data transmitted in response to a retransmission request is referred to as retransmission data.

Next, with reference to FIG. 4, a description will be given of a processing procedure when the selected receiving terminal retransmits correct data to another selected receiving terminal or another receiving terminal in the system described above.

First, the selected receiving terminal determines whether an error has been detected in the received data (step 12).
6). If no error is detected (step 126,
No), it is determined whether a retransmission request has been received from another selected receiving terminal or receiving terminal (step 128). If no retransmission request has been received (step 128, N
o), the process of FIG. 4 ends. On the other hand, if a retransmission request has been received (step 128, Yes), retransmission data is sent only to the receiving terminal or the selected receiving terminal that has transmitted the retransmission request (step 130).

If an error is detected in the received data (step 126, Yes), a retransmission request is sent to the transmitting terminal or the selected receiving terminal connected to the upper node (step 127), and until the retransmission data is received. It waits (step 129). When retransmission data is received (step 129, Yes), it is determined whether a retransmission request has been received from another selected receiving terminal or receiving terminal (step 1).
31).

If no retransmission request has been received (step 1
31, No), and terminates the processing in FIG. On the other hand, when a retransmission request is received (Step 131, Yes), it is determined whether or not the terminal of the transmission source of the retransmission request is the selected receiving terminal (Step 132). If it is not the selected receiving terminal (step 132, No), retransmission data is sent only to the receiving terminal that has requested retransmission (step 134).

If the source of the retransmission request is the selected receiving terminal (step 132, Yes), step 13
It is determined whether or not the retransmission data received in step 1 has been broadcast simultaneously (step 133). If it is broadcasted all at once (step 133, Yes), step 131
Stops the transmission of the retransmission data received in step (step 13)
5). On the other hand, if the retransmission data has not been broadcast (step 133, No), the retransmission data received in step 131 is broadcast to all other selected receiving terminals and all receiving terminals (step 136).

Next, the processing shown in FIGS. 1 to 4 will be described with reference to a specific network configuration example. FIG. 5 shows an example of a target network. This network includes a transmitting terminal 1 and nodes 10, 11, and 1.
2, 13, 14 and receiving terminals 20, 21, 22, 23,
24, 25, 26, and 27. Before real-time media distribution is performed on this network, the receiving terminal 2 of the receiving terminals 20 to 27 is specified in advance by the user.
It is assumed that 0 and 24 are set as the selective receiving terminals.

Further, as shown in FIG.
Is connected to the transmitting terminal 1 and the node 11, and the node 11 is connected to the node 10, the selective receiving terminal 20, the receiving terminal 21, and the node 12. The node 12 is connected to the node 11, the receiving terminals 22 and 23, and the node 13, and the node 13 is connected to the node 12, the selective receiving terminal 24, the receiving terminal 25, and the node 14. . In addition, node 14
Is connected to the node 13 and the receiving terminals 26 and 27.

Next, the procedure (see FIG. 2) in which the selective receiving terminals 20 and 24 each determine the retransmission request destination in the network configuration shown in FIG. 5 will be described below. At first,
Each of the selective receiving terminals 20 and 24 measures the number of nodes existing between itself and the transmitting terminal 1 (step 111),
The measured value is sent to the transmitting terminal 1 (step 112). Here, nodes 10 and 11 exist between the transmitting terminal 1 and the selective receiving terminal 20, and the transmitting terminal 1 and the selective receiving terminal 24
Since the nodes 10, 11, 12, and 13 exist between the two, the measured value of the selected receiving terminal 20 is "2" and the measured value of the selected receiving terminal 24 is "4" (see Table 1).

[Table 1]

Further, the transmitting terminal 1 includes a selective receiving terminal 20,
24 (step 120, Ye
s), and sends the measured values to the selected receiving terminals 20, 24 and all the receiving terminals 21, 22, 23, 25, 26, 27 (step 121).

Thus, the selective receiving terminal 20 obtains the measured value of the own terminal (the number of nodes between the own terminal and the transmitting terminal 1),
The measured value of the selected receiving terminal 24 (the number of nodes between the selected receiving terminal 24 and the transmitting terminal 1) is compared (step 11).
4). As shown in Table 1, the measured value of the own terminal ("2")
Is the smallest (step 115, Yes), the selective receiving terminal 20 sets the transmitting terminal 1 as the retransmission request destination (step 117).

On the other hand, the selected receiving terminal 24 also compares the measured value of its own terminal with the measured value of the selected receiving terminal 20 (step 114). Then, as shown in Table 1, since the measurement value (“2”) of the selected receiving terminal 20 is the smallest (Step 115, No), the selected receiving terminal whose measured value is smaller than the measured value of its own terminal (in this case, , Inevitably becomes the selection receiving terminal 20) (step 116). Then, the number of nodes existing between the own terminal and the selective receiving terminal 20 is measured (step 118).

As a result, as shown in Table 2 below, the measured value between the selected receiving terminals 20 and 24 is “3”, and the number of nodes existing between the own terminal and the transmitting terminal 1 (“4”) ), The selected receiving terminal 20 is set as the retransmission request destination (step 119).

[Table 2]

Next, a method (see FIG. 1) in which each of the receiving terminals 21, 22, 23, 25, 26, 27 determines a retransmission request destination in the network configuration shown in FIG. 6 will be described below. First, the selective receiving terminals 20 and 24 each measure the number of nodes with the transmitting terminal 1 (step 10).
7), send it to transmitting terminal 1 (step 108). Accordingly, when receiving the measured values of the selected receiving terminals 20 and 24 (step 109, Yes), the transmitting terminal 1 transmits the measured values to all the receiving terminals 21, 22, 23, 25, 26, and 2.
7 (step 110).

Here, the receiving terminals 21, 22, 23, 2
The method of determining the retransmission request destination in each of 5, 26, and 27 will be described individually. First, the receiving terminal 21 measures the number of nodes with the transmitting terminal (step 101). Then, when the measured values of the selective receiving terminals 20 and 24 are received (Step 102, Yes), those measured values ("2", "4")
And the measured value of the terminal itself ("2") (step 103).

From Table 1 shown above and Table 3 shown below, among the above-mentioned measured values, the measured value of the selected receiving terminal 20 and the measured value measured in step 101 (the transmitting terminal 1 and the receiving terminal 21 is the same and the smallest.

[Table 3]

Then, the selected receiving terminal 20 is selected (step 104), and the number of nodes between the selected receiving terminal 20 and the own terminal is measured (step 105). Then, as shown in Table 4 below, the measured value (“1”) between the selective receiving terminal 20 and the own terminal is the measured value measured in step 107,
That is, the number is smaller than the number of nodes ("2") between the transmitting terminal 1 and the own terminal. Therefore, the receiving terminal 21 sets the selected receiving terminal 20 as the retransmission request destination (step 106).

[Table 4]

Next, a method of determining the retransmission request destination of the receiving terminal 22 will be described. The receiving terminal 22 measures the number of nodes with the transmitting terminal 1. And this measured value ("3")
And the measured values of the selected receiving terminals 20 and 24 received from the transmitting terminal 1 are compared. As shown in Tables 1 and 3, among these measured values, the measured value of the selective receiving terminal 20 is the smallest.

For this reason, the receiving terminal 22 measures the number of nodes between itself and the selected receiving terminal 20. Table 3, Table 4
, The measured value (“2”) of the selected receiving terminal 20 is smaller than the number of nodes (“3”). Therefore, the receiving terminal 22 sets the selected receiving terminal 20 as a retransmission request destination.
Further, by the same processing as above, the receiving terminal 23 also sets the selected receiving terminal 20 as the retransmission request destination.

Next, a method of determining the retransmission request destination of the receiving terminal 25 will be described. The receiving terminal 25 measures the number of nodes with the transmitting terminal 1. And this measured value ("4")
And the measured values of the selected receiving terminals 20 and 24 received from the transmitting terminal 1 are compared. As shown in Tables 1 and 3, the measured value (“2”) of the selected receiving terminal 20 and the measured value (“4”) of the selected receiving terminal 24 are between the transmitting terminal 1 and the receiving terminal 25. Is equal to or smaller than the number of nodes (“4”).

The receiving terminal 25 measures the number of nodes between the own terminal and the selective receiving terminal 20 and between the own terminal and the selective receiving terminal 24, respectively. When these measured values are compared, as shown in Tables 3 and 4, the number of nodes between the own terminal and the transmitting terminal 1 ("4") and the number of nodes between the own terminal and the selected receiving terminal 20 are determined. Than the number of nodes ("3")
Number of nodes between own terminal and selective receiving terminal 24 ("1")
Is smaller. Therefore, the receiving terminal 25 sets the selected receiving terminal 24 as a retransmission request destination.

Next, a method of determining the retransmission request destination of the receiving terminal 26 will be described. The receiving terminal 26 measures the number of nodes with the transmitting terminal 1. And this measurement ("5")
The measured values (“2”, “4”) of the selected receiving terminals 20 and 24 received from the transmitting terminal 1 are compared. As shown in Tables 1 and 3, each measured value of the selected receiving terminals 20 and 24 is smaller than the measured value between the receiving terminal 26 and the transmitting terminal 1. Therefore, the receiving terminal 26 measures the number of nodes between the own terminal and the selected receiving terminals 20 and 24, respectively.

As shown in Tables 3 and 4, the measured value between the own terminal and the transmitting terminal 1 ("5") and the measured value between the own terminal and the selected receiving terminal 20 ("5") The measured value (“2”) between the own terminal and the selected receiving terminal 24 is smaller than that. Therefore, the receiving terminal 26 sets the selected receiving terminal 24 as a retransmission request destination. By the same processing as above, the receiving terminal 27 also sets the selected receiving terminal 24 as the retransmission request destination.

Next, FIG. 6 shows a configuration example of a network different from that of FIG. In this figure, the same components as those shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. In the network configuration shown in this figure, the transmitting terminal 1, the nodes 10 to 14, and the receiving terminals 30, 3
The connection relation among 1, 32, 33, 34, 35, 36, and 37 is the same as the connection relation shown in FIG. 5, but in FIG. 6, among the reception terminals 30 to 37, the reception terminals 30, 3
2, 34 and 36 are defined as selective receiving terminals.

When the method of determining the retransmission request destination shown in FIGS. 1 and 2 is executed in the network configuration shown in FIG. 6, the retransmission request destination of each terminal is as shown in Table 5 below.

[Table 5]

In the network configuration shown in FIG. 6, when real-time media is simultaneously distributed from the transmitting terminal 1 to the selected receiving terminals and the receiving terminals 30 to 37, for example, when an error or loss occurs in the receiving terminal 37, Table 5 above
As shown in (2), the receiving terminal 37 sends a selection request to the selection receiving terminal 36. Therefore, the retransmission in that case is performed within the local area L1 indicated by the broken line in FIG. 6, and as a result, the retransmission time is shorter than when the receiving terminal 37 requests retransmission to the transmitting terminal 1. It is possible to shorten it. Further, since the traffic is limited to the local area L1, it is possible to reduce the traffic affecting the entire network.

In the network configuration example shown in FIG. 6, for example, as shown in FIG. When an error or loss occurs in the node 11, first, an error in the node 11 is detected by the selective reception terminal 30 (FIG. 4, step 126, Yes). Thereby, the selection receiving terminal 30
Request retransmission to transmission terminal 1 (FIG. 4, step 1
27). As a result, when receiving the retransmission request (step 122, Yes), transmitting terminal 1 transmits correct data to selected receiving terminal 30 (FIG. 3, step 1).
23).

If an error or loss is detected in the data received by the selective receiving terminal 32 due to an error or loss occurring at the node 11 (step 126 in FIG. 4, Yes), the selective receiving terminal 32 performs selective reception. Terminal 3
0 is requested for retransmission (FIG. 4, step 127).
Thereby, in the selective receiving terminal 30, FIG.
31 is Yes, and the source terminal of the retransmission request is the selected receiving terminal 32 (FIG. 4, step 13).
1, Yes), and since the retransmission data received from the transmitting terminal 1 has not been broadcast (step 133, No in FIG. 4), the selective receiving terminal 30 broadcasts the retransmission data received from the transmitting terminal 1. Deliver (Figure 4, Step 1
36).

According to the above processing, as shown in FIG. 7, when an error or loss occurs in the node 11, the error or loss of the node 11 is detected in the local area L2, and The retransmission data is transmitted by simultaneous distribution. As a result, the retransmission time can be reduced as compared with each receiving terminal requesting the transmitting terminal 1 to perform retransmission.

Next, the transmitting terminal, the selective receiving terminal described above,
The specific configuration of the receiving terminal will be described with reference to FIG. In FIG. 8, the target system includes a transmitting terminal 100, nodes 110, 111, 112, and a plurality of receiving terminals 120, 130, 140.
Each terminal is connected to the same network 200. Also, among the receiving terminals 120, 130 and 140,
It is assumed that the receiving terminals 120 and 130 are determined to be the selective receiving terminals in advance.

The transmitting terminal 100 has a selection receiving terminal 120,
A simultaneous distribution means 101 for simultaneously distributing data to 130 and the receiving terminal 140;
Transmitting means 102 for transmitting a measurement value (described later) transmitted from the receiving apparatus 30 to all receiving terminals including the selected receiving terminal;
When a measurement command (to be described later) is sent from the selective receiving terminals 120 and 130, retransmission data is returned, and when a retransmission request is received, retransmission means 103 for retransmitting correct data to the requesting terminal. And

Each of the selective receiving terminals 120 and 130 has a measuring means 121 for measuring the number of nodes existing between the transmitting terminal 100 and another selective receiving terminal, and a measurement value measured by the measuring means 121, respectively. A reporting unit 122 for reporting to the transmitting terminal 100 and a deciding unit 1 for deciding whether a data error or loss has occurred is a node or a terminal
23, determining means 124 for determining whether or not the received retransmission data has been broadcast, and retransmission means 125 for retransmitting correct data when receiving a retransmission request from another selected receiving terminal or receiving terminal. Have. The receiving terminal 140 includes the measuring unit 121 described above.

Further, the network 200 is provided with a node 110, a node 111, and a node 112 in the order of proximity to the transmitting terminal 100. The node 110 has the transmitting terminal 100, and the node 111 has the selected receiving terminal 12.
0, the selective receiving terminal 130 and the receiving terminal 140 are connected to the node 112, respectively.

Next, a description will be given, with reference to FIGS. 9 to 16, of a data flow accompanying processing performed in each terminal in the network having the configuration shown in FIG.

FIG. 9 shows a data flow when video data is simultaneously distributed from transmitting terminal 100 to selective receiving terminals 120 and 130 and receiving terminal 140. In this figure, video data is simultaneously broadcast from a broadcasting means 101 of a transmitting terminal 100 to selective receiving terminals 120 and 130 and a receiving terminal 140 via a network 200.

FIG. 10 shows a diagram for determining a retransmission request destination when an error or a loss is detected by the selective receiving terminal 110.
4 shows a data flow when measuring the number of nodes existing with the transmission terminal 100. First, the measuring means 121 of the selective receiving terminal 120 sends a measuring command to the transmitting terminal 100. This measurement command is a command for measuring the number of nodes existing between the terminal transmitting the measurement command and the destination terminal of the measurement command.

Thus, retransmission means 1 of transmitting terminal 100
03 returns the measurement data to the selected receiving terminal (in this case, selected receiving terminal 120) that transmitted the measurement command. Here, the measurement data is data indicating a preset initial value (natural number), and each time the measurement data passes through the node, the value of the data is decremented by one. However, when passing from the transmitting terminal to the selected receiving terminal, the measurement data is not decremented. It is also assumed that the measuring means 121 has previously recognized the initial value of the measurement data.

The measuring means 1 of the selective receiving terminal 120
21 receives the measurement data returned from the transmitting terminal 100, and calculates the value reduced from the initial value of the measurement data,
It is recognized as the number of nodes existing with the transmission terminal 100. Similarly, the selective receiving terminal 130 measures the number of nodes existing with the transmitting terminal 100. Note that the measured value at this time is “2” because the nodes 110 and 111 exist between the transmitting terminal 100 and the transmitting terminal 100. Also, the method of measuring the number of nodes is not limited to the above-described method, and any other method may be used as long as the number of nodes existing between the own terminal and the transmitting terminal (or another selected receiving terminal) can be measured. Is also good.

Next, the selected receiving terminal 12 measured in FIG.
The measured value of the number of nodes between 0 and the transmitting terminal 100 is transmitted to the transmitting terminal 100, and the transmitting terminal 100 transmits the measured number of nodes of the selected receiving terminal 120 to the selected receiving terminals 120, 130 and the receiving terminal 140. Figure 11 shows the data flow
Shown in The selection receiving terminal 120 sends the measured value of the number of nodes obtained by the measuring unit 121 to the transmitting terminal 100 by the reporting unit 122. The transmitting terminal 100 is a selective receiving terminal 12
The selected number of receiving terminals 120 and 130 and the receiving terminal 140
Send to The same applies to the selection receiving terminal 130.

Next, the selective receiving terminal 130 is
FIG. 12 shows a data flow until the number of nodes existing between 00 and 00 is measured. The selection receiving terminal 130 is shown in FIG.
The measurement value (“2”) of the selected receiving terminal 120 received at
Since it is smaller than the number of nodes ("3") between the own terminal and the transmitting terminal 100, the selected receiving terminal 120 is set as a candidate for a retransmission request destination. Next, the measuring means 121 of the selective receiving terminal 130
A measurement command for measuring the number of nodes with the selected receiving terminal 120 is sent to the selected receiving terminal 120.

Receiving this, the selective receiving terminal 120 sends the measurement data to the selective receiving terminal 130 by the retransmitting means 125. The selection receiving terminal 130 receives the returned measurement data by the measuring means 121 and measures the number of nodes existing between the selection receiving terminal 130 and the selection receiving terminal 120 from the content thereof. By this processing, “2” is obtained as the measurement value, and the selected receiving terminal 130 and the transmitting terminal 100
From the number of nodes (“3”) between
Since the number of nodes between the selected receiving terminal 120 and the selected receiving terminal 120 is smaller, the selected receiving terminal 120 is set as a retransmission request destination of the selected receiving terminal 130.

The number of nodes between the selected receiving terminal 130 and the transmitting terminal 100 (“3”) received in FIG. 11 is determined by the number of nodes between the own terminal and the transmitting terminal 100 (“3”). Since “2”), the transmission terminal 100 is set as the retransmission request destination.

Next, FIG. 13 shows a data flow until the receiving terminal 140 determines the retransmission request destination. Receiving terminal 14
0 indicates that each of the selective receiving terminals 120, 1 is connected as shown in FIG.
The number of nodes from 30 to the transmission terminal 100 was received. Therefore, the receiving terminal 140 measures the number of nodes between itself and the transmitting terminal 100.
Send measurement command to 0. In response, the transmitting terminal 100
Transmits the measurement data from the retransmission unit 103 to the receiving terminal 140
Send to

The receiving terminal 140 receives the returned measurement data by the measuring means 121, and measures the number of nodes existing between the receiving terminal 140 and the transmitting terminal 100 from the content thereof. Then, the number of nodes, the selected receiving terminals 120 and 130 and the transmitting terminal 100 obtained in FIG.
And the number of nodes between. As a result of the comparison, the number of nodes (“3”) between the own terminal and the transmitting terminal is larger or equal to the number of nodes between the selected receiving terminals 120 and 130 and the transmitting terminal 100. Receiving terminal 1
20, 130 are candidates for the retransmission request destination.

Next, the receiving terminal 140 sends a measurement command from the measuring means 121 to each of the selected receiving terminals 120 and 130 in order to measure the number of nodes with each of the selected receiving terminals 120 and 130. In response to this, each selection receiving terminal 120,
130 sends the measurement data to the receiving terminal 140 by the retransmitting means 125. The receiving terminal 140 receives the measurement data returned by the measuring unit 121, and, based on the contents, receives the receiving data 140 and the selected receiving terminals 12
The number of each node between 0 and 130 is measured.

As a result, the number of nodes (“2”) between the receiving terminal 140 and the selected receiving terminal 120,
The number of nodes (“1”) between the receiving terminal 130 and the selected receiving terminal 130 and the number of nodes (“3”) between the receiving terminal 140 and the transmitting terminal 100 are compared. As a result, the number of nodes between the receiving terminal 140 and the selective receiving terminal 130 is the smallest. Therefore, the receiving terminal 140 sets the selected receiving terminal 130 as a retransmission request destination.

Next, FIG. 14 shows a flow of retransmission data when a data error or loss is detected only by the receiving terminal 140. When the receiving terminal 140 detects a data error or loss, it requests the selected receiving terminal 130 to retransmit. When the selective receiving terminal 130 receives this retransmission request,
The determining unit 123 determines the location where the data error or the loss occurs as the receiving terminal 140 because no data error or loss has been detected in the selective receiving terminal 130. Then, the retransmitting means 125 retransmits the correct data only to the receiving terminal 140.

Next, FIG. 15 shows a flow of a retransmission request when a data error or a loss occurs in the node 110 or the node 111. First, the selective receiving terminal 120 requests the transmitting terminal 100 to perform retransmission. Next, the selective receiving terminal 130 requests retransmission to the selective receiving terminal 120. Further, the receiving terminal 140 requests the selected receiving terminal 130 to retransmit.

Next, FIG. 16 shows the flow of retransmission after the retransmission request is made in FIG. First, when the transmitting terminal 100 receives a retransmission request from the selective receiving terminal 120, the retransmitting means 103 retransmits correct data to the selective receiving terminal 120. As a result, the selective receiving terminal 120 receives the retransmission data, and when receiving a retransmission request from another selective receiving terminal (here, the selective receiving terminal 130), the node 110 or the node 1
At 11, it is determined that a loss has occurred. Next, determination means 12
No. 4 determines that the retransmission data has been transmitted only from the transmitting terminal 100 to the own terminal, whereby the selective receiving terminal 120 recognizes that the retransmission data has not been broadcast.

Here, it is easy to determine whether the retransmission data has been transmitted only to the own terminal or has been distributed simultaneously, for example, in the case of an IP network, by determining the address of the retransmission data. It is possible. That is,
In the IP network, a unicast address is used when data is transmitted to one terminal, and a multicast address is used when broadcasting data simultaneously. Since the multicast address is completely different from the unicast address, it is easy to determine from the difference between the two.

The selection receiving terminal 120 is connected to the decision unit 12.
3 determines that an error or loss has occurred in the node 110 or the node 111, and furthermore, it is determined by the determination unit 124 that the retransmission data is not the one that was broadcast at once. Broadcast retransmission data.

In order to confirm the effect of reducing the retransmission time and the concentration of retransmission traffic by the data distribution method of the present embodiment, various conditions are set, and the data distribution method of the present embodiment is compared with the existing data distribution method. RMT method
The retransmission time and the number of retransmission packets for P (A Reliable Multicast Trfansport Protocol) were calculated on the desk.

[Evaluation 1] Conditions are shown below. In [Evaluation 1], it is assumed that the selective receiving terminals are connected to all the nodes. Network model: five nodes pass from the transmitting terminal to the receiving terminal, and “node 0”, “node 1”, “node 2”, “node 3”, “node 4 (receiving Node to which the terminal is connected) ". Possible error locations: each node and receiving terminal. Probability of occurrence of loss at each receiving terminal and node:
0E-3. Packet transit time: 1 unit time. Terminals to be calculated: 10 receiving terminals connected to the node farthest from the transmitting terminal. Number of transmitted packets: 2.7E + 6. Number of retransmissions: once (however, retransmission is performed a plurality of times to ensure error-free in RMTP).

FIG. 17 is a graph showing the relationship between the error occurrence location and the retransmission time in the data distribution method and RMTP (hereinafter referred to as the conventional method) of the present embodiment. FIG. 18 is a graph showing the relationship between the error occurrence location and the number of retransmitted packets in the data distribution method of the present embodiment and the conventional method.

As shown in FIG. 17, in the data distribution method of the present embodiment, the retransmission time is shortened irrespective of the location where an error occurs, as compared with the conventional method. That is, unlike the conventional method, there is almost no difference in the retransmission time between the case where an error occurs in a higher-order node and the case where an error occurs in a lower-order node. It can be said that the effect of reducing the retransmission time becomes more remarkable as the error occurs in the node.

Also, as shown in FIG. 18, when an error occurs in a node higher than the node (“node 4”) to which the receiving terminal is directly connected, the number of retransmitted packets is significantly larger than in the conventional method. It can be seen that the effect of reducing the concentration of retransmission traffic is remarkable.

[Evaluation 2] Next, in the data distribution method of the present embodiment, several patterns are used to confirm how the location of the selected receiving terminal affects the retransmission time and the number of retransmission packets. Was calculated on the desk. The conditions are the same as in [Evaluation 1] described above. Table 6 shows installation patterns when the number of selected receiving terminals is one and two.

[Table 6]

FIG. 19 shows the effect of shortening the retransmission time when the number of selected receiving terminals is one and the arrangement is changed. FIG. 20 shows the effect of shortening the retransmission time when the number of selected receiving terminals is two and the arrangement is changed. FIG. 21 shows the effect of reducing retransmission traffic when the number of selected receiving terminals is two and the arrangement is changed.

As shown in FIG. 19, the number of selected receiving terminals is 1
If you set one, the longest time required for retransmission is the shortest.
This is the case when the selected receiving terminal is connected to the intermediate node (“node 2”) (case 2). Similarly, as shown in FIG. 20, when the number of the selected receiving terminals is two, each of the selected receiving terminals is placed above the intermediate node (“node 2”) and the intermediate node (“node 1”), respectively. When placed (Case 5)
In addition, the longest time required for retransmission is the shortest. Therefore, when reducing the retransmission time is the first priority and connecting limited selected receiving terminals, it is better to connect from a position close to the intermediate node.

Further, as shown in FIG. 21, for each error location, the most repetitive traffic is reduced by the node farthest from the transmitting terminal (“node 4”) and the next higher node. This is a case where a selective receiving terminal is connected to each of the nodes (“node 3”) (case 7). Therefore, when reducing retransmission traffic is the first priority, when connecting two or more selected receiving terminals, it is better to connect from a node close to the receiving terminal.

[Evaluation 3] Next, retransmission is required when the selected receiving terminal is provided in each node shown in [Evaluation 1] and when the number of selected receiving terminals is one and two in [Evaluation 2]. The retransmission time was compared between Case 2 and Case 5 having the shortest time respectively. Furthermore, in order to confirm the effect of error recovery when the number of retransmissions is limited,
The error residual rate was calculated on the desk. The condition was [Evaluation 1]
Is the same as

FIG. 22 is a graph showing the relationship between the error occurrence location and the retransmission time in the above three cases. FIG. 23 is a graph showing the relationship between the error occurrence location and the error residual rate in the above three cases.

As shown in FIG. 22, the maximum time required for retransmission hardly changes between a case where a selective receiving terminal is connected to each node and a case where two selective receiving terminals are connected. Therefore, a sufficient effect can be obtained even when the number of selected receiving terminals is two. Further, as shown in FIG. 23, when the number of retransmissions is limited to two, when a selective reception terminal is connected to each node,
In the optimal arrangement when the number of selected receiving terminals is one (case 2), and in the optimal arrangement when the number of selected receiving terminals is two (case 5), the respective error residual rates can clear the error tolerance rate. it can.

A program for realizing the processing in the transmitting terminal, the selective receiving terminal, and the receiving terminal shown in FIGS. 1 to 4 is recorded on a computer-readable recording medium, and is recorded on this recording medium. The program may be read by a computer system and executed to communicate with another user terminal.

Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” also includes a homepage providing environment (or a display environment) if a WWW system is used. The “computer-readable recording medium” is a floppy disk, a magneto-optical disk, a ROM, a CD-ROM, a DV
D and other storage devices such as a hard disk built into the computer system, as well as communication lines for transmitting programs via a network such as the Internet or a communication line such as a telephone line. This includes programs that hold programs dynamically for a period of time (transmission medium or transmission wave), and those that hold programs for a fixed period of time, such as volatile memory inside a computer system serving as a server or client in that case. Shall be considered.

Further, the above-mentioned program may be for realizing a part of the above-mentioned functions, or may be for realizing the above-mentioned functions in combination with a program already recorded in a computer system. That is, it may be a so-called difference file (difference program).

[0098]

As described above, according to the present invention,
The retransmission request destination of the selected receiving terminal connected to the highest node is the transmitting terminal, and the retransmission request destination of the selected receiving terminal or receiving terminal connected to the lower node is connected to the upper node, and the own terminal. And the selected receiving terminal having the least number of nodes existing between the selected receiving terminal and the receiving terminal. Also, when a certain selected receiving terminal detects a data error or loss, it requests retransmission to the transmitting terminal or a selected receiving terminal connected to an upper node closer to the transmitting terminal, and further, from the selected receiving terminal connected to a lower node, When a retransmission request is received, it is determined whether the received retransmission data has been broadcast or not.If the retransmission data has been broadcast, the transmission of the retransmission data is stopped. Since the retransmission data is distributed all at once, the retransmission time can be reduced irrespective of the location of the data error or loss. Also, by reducing the retransmission time, the receiving terminal can reduce the buffer area for securing the retransmission time required for recovering one data within the limited buffer area. Therefore, the receiving terminal can improve the data recovery rate even when a continuous error is detected.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure until a receiving terminal determines a retransmission request destination in the data distribution method of the present invention.

FIG. 2 is a flowchart showing a procedure until a selected receiving terminal determines a retransmission request destination in the data distribution method of the present invention.

FIG. 3 is a flowchart showing a retransmission procedure of a transmitting terminal in the data distribution method of the present invention.

FIG. 4 is a flowchart showing a retransmission procedure of a selected receiving terminal in the data distribution method of the present invention.

FIG. 5 is a diagram showing a configuration example of a network referred to for specifically explaining a retransmission destination determination procedure in the data distribution method of the present invention.

FIG. 6 is a diagram showing another configuration example of a network referred to for specifically describing a retransmission procedure in the data distribution method of the present invention.

FIG. 7 shows a configuration of the network shown in FIG.
FIG. 11 is an explanatory diagram for specifically describing a retransmission procedure when a data error or loss occurs in another part.

FIG. 8 is a block diagram illustrating a configuration of a transmitting terminal, a selective receiving terminal, and a receiving terminal according to an embodiment when the data distribution method of the present invention is applied.

9 is a diagram showing a data flow when video data is simultaneously distributed to a plurality of receiving terminals in the configuration shown in FIG.

FIG. 10 is a diagram showing a data flow when measuring the number of nodes between transmitting terminals in the configuration shown in FIG. 8;

11 is a diagram showing a flow of data when the measurement values of the selected receiving terminal are distributed to all the selected receiving terminals and the receiving terminals in the configuration shown in FIG. 8;

FIG. 12 is a diagram showing a data flow when a selected receiving terminal measures the number of nodes existing between the selected receiving terminal and another selected receiving terminal in the configuration shown in FIG. 8;

FIG. 13 is a diagram showing a data flow until a receiving terminal determines a retransmission request destination in the configuration shown in FIG. 8;

14 is a diagram illustrating a flow of retransmission data when a loss is detected only by a receiving terminal in the configuration illustrated in FIG. 8;

FIG. 15 is a diagram showing a data flow indicating a flow of a retransmission request when a loss occurs in a node between a transmitting terminal and a selected receiving terminal in the configuration shown in FIG. 8;

FIG. 16 is a diagram showing a flow of retransmission data after a retransmission request is made in FIG.

FIG. 17 is a graph showing a relationship between an error occurrence location and a retransmission time in the data distribution method of the present embodiment and the conventional data distribution method.

FIG. 18 is a graph showing a relationship between an error occurrence location and the number of retransmission packets in the data distribution method of the present embodiment and the conventional data distribution method.

FIG. 19 is a graph showing the effect of reducing the retransmission time when the number of selected receiving terminals is set to 1 and the arrangement is changed.

FIG. 20 is a graph showing the effect of reducing the retransmission time when the number of selected receiving terminals is set to two and the arrangement is changed.

FIG. 21 is a graph showing the effect of reducing retransmission traffic when the number of selected receiving terminals is set to two and the arrangement is changed.

FIG. 22 is a graph showing a relationship between an error occurrence location and a retransmission time in the data distribution method of the present embodiment.

FIG. 23 is a graph showing a relationship between an error occurrence location and an error remaining rate in the data distribution method of the present embodiment.

[Explanation of symbols]

1,100 transmitting terminal 10-14,110-112 node 20,24,30,32,34,36,120,130
Selection receiving terminal 21, 22, 23, 25, 26, 27, 31, 33, 3
5, 37, 140 Receiving terminal 101 Simultaneous distribution means 102 Transmission means 103, 125 Retransmission means 121 Measurement means 122 Reporting means 123 Determination means 124 Determination means 200 Network

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (8)

[Claims] 1. A data distribution method in which a transmitting terminal simultaneously distributes video data generated in real time to a plurality of receiving terminals connected to one or more nodes, wherein at least one of the plurality of receiving terminals One receiving terminal as a selective receiving terminal, each of the receiving terminals, when detecting an error or loss in the received video data, requests retransmission to the selected receiving terminal or transmitting terminal defined as a retransmission request destination If the selected receiving terminal detects an error or loss in the received video data, requests retransmission to a transmitting terminal or another selected receiving terminal determined as a retransmission request destination, the transmitting terminal is the selected receiving terminal or When receiving a retransmission request from a receiving terminal, the data is characterized in that correct video data is transmitted only to the selected receiving terminal or only the receiving terminal. Shin method. 2. Each of the receiving terminals measures the number of nodes between itself and the transmitting terminal, and the selected receiving terminal measures the number of nodes between the transmitting terminal and the measured value. To the transmitting terminal, the transmitting terminal transmits the measurement value of each selected receiving terminal sent from the selected receiving terminal to all the selected receiving terminals and the receiving terminals, and the receiving terminal is the transmitting terminal And the measured value of the number of nodes between the own terminal and the transmitting terminal, and the selected receiving terminal, which is a measured value smaller than the number of nodes between the own terminal and the transmitting terminal. If there is no, the transmitting terminal is the retransmission request destination, if there is, the number of nodes between the selected receiving terminal is measured, and the selected receiving terminal with the smallest number of nodes is the retransmission request destination. The data distribution according to claim 1, How to trust. 3. The selective receiving terminal measures the number of nodes between the own terminal and the transmitting terminal, and transmits the measurement value to the transmitting terminal. The transmitted measurement values are transmitted to all the selected reception terminals and the reception terminals, and the selection reception terminal is a measurement value transmitted from the transmission terminal, and a measurement value between the own terminal and the transmission terminal. If there is no selected receiving terminal whose measured value is smaller than the number of nodes between the own terminal and the transmitting terminal, the transmitting terminal is set as the retransmission request destination. The data distribution method according to claim 1, wherein a certain number of nodes is measured, and the selected receiving terminal having the smallest number of nodes is set as a retransmission request destination. 4. The receiving apparatus according to claim 1, wherein the selective receiving terminal receives a request for retransmission of the data from another selective receiving terminal or receiving terminal even though no error or loss is detected in the data received from the transmitting terminal. It is determined that the data error or loss occurred in the terminal, retransmission data is transmitted only to the terminal of the retransmission request source, an error or loss is detected in the data received from the transmitting terminal, and If a retransmission request is received from another selected receiving terminal, it is determined that an error or loss has occurred in the node. Further, if the retransmission requesting source is the selected receiving terminal, the selection connected to the transmitting terminal or an upper node is determined. It is determined whether or not the retransmission data received from the receiving terminal has been broadcast, and if the received retransmission data has been broadcast, the transmission of the retransmission data is performed. Data distribution method according to claim 1 canceled, if they were not being broadcasted, characterized in that concurrently delivers the retransmission data thus received the. 5. In a network including a transmitting terminal connected to one or more nodes, a plurality of receiving terminals, and a selective receiving terminal, the network is executed by a computer functioning as the transmitting terminal, and the plurality of receiving terminals and the selective receiving terminal are selected. A computer-readable recording medium on which a program for simultaneously distributing video data generated in real time to a receiving terminal is recorded, wherein all of the selected receiving terminals are connected to each other between a selected receiving terminal and a transmitting terminal. Receiving the measured value of the number of nodes in the step, transmitting the measured value to the all-selected receiving terminal and the receiving terminal, and when receiving a retransmission request from the selected receiving terminal, the selected receiving terminal of the retransmission request source Transmitting the retransmitted data by the computer. A recording medium that can be. 6. In a network including a transmitting terminal connected to one or more nodes, a plurality of receiving terminals, and a selective receiving terminal, the network is executed by a computer functioning as the selective receiving terminal, and simultaneously transmitted from the transmitting terminal. A computer-readable recording medium on which a program for receiving video data generated in real time is recorded, wherein the transmission terminal measures the number of nodes between its own terminal and a transmission terminal and transmits the measured value to the transmission terminal. And transmitting the measurement values of all the selected reception terminals transmitted from the transmission terminal, and comparing the measurement values between the own terminal and the transmission terminal. Determining whether there is a selected receiving terminal having a measurement value smaller than the number of nodes in between, and a node between the own terminal and the transmitting terminal. When there is no selected receiving terminal having a measured value less than the number, the transmitting terminal is set as a retransmission request destination; and there is a selected receiving terminal having a measured value smaller than the number of nodes between the own terminal and the transmitting terminal. Measuring the number of nodes between the selected receiving terminals, and setting the selected receiving terminal having the smallest number of nodes as a retransmission request destination. . 7. A program recorded on the computer-readable recording medium according to claim 6, wherein the program receives a request for retransmission of the data even though the program does not detect an error or loss in the data received from the transmitting terminal. When receiving from the receiving terminal or the receiving terminal, determining that the data error or loss occurred in the receiving terminal and transmitting retransmission data only to the terminal of the retransmission request source, receiving from the transmitting terminal If an error or loss is detected in the received data, and if a request for retransmission of the data is received from another selected receiving terminal, it is determined that the error or loss has occurred in the node. If there is, it is determined whether the retransmission data received from the transmitting terminal or the selected receiving terminal connected to the upper node has been broadcast. Stopping the transmission of the retransmitted data if the received retransmitted data has been broadcasted, and broadcasting the received retransmitted data if the received retransmitted data has not been broadcasted. A computer-readable recording medium on which is recorded. 8. In a network including a transmitting terminal connected to one or a plurality of nodes, a plurality of receiving terminals, and a selective receiving terminal, the network is executed by a computer functioning as the receiving terminal, and is simultaneously broadcast from the transmitting terminal. A computer-readable recording medium recording a program for receiving video data generated in real time, wherein the step of measuring the number of nodes between the own terminal and the transmitting terminal; and Receiving the measurement value of the number of nodes between the transmission terminal and the selection reception terminal each of which is measured by the selection reception terminal, and each measurement value transmitted from the transmission terminal, Comparing the measured value of the number of nodes between the transmitting terminal and the measured number of nodes less than the number of nodes between the own terminal and the transmitting terminal; If the selected receiving terminal does not exist, the transmitting terminal is set to the retransmission request destination, and if there is a selected receiving terminal having a measured value smaller than the number of nodes between the own terminal and the transmitting terminal, A step of measuring the number of nodes between the selected receiving terminal and the selected receiving terminal having the smallest number of nodes as a retransmission request destination.