JP2003324496A - Data transmission method, and packet data structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data transmission method with which the number of times of retransmissions between a distribution server and a relay server is reduced. <P>SOLUTION: In the data transmission method for transmitting data for the unit of a packet between the distribution server and a terminal via the relay server and for successively reproducing the data of a received packet on the side of the terminal, when a transmission error occurs between the relay server and the terminal, in the relay server, the error packet is retransmitted based upon a retransmitting instruction from the terminal and when a transmission error occurs between the distribution server and the relay server, in the distribution server, the error packet is retransmitted based upon a retransmitting instruction transmitted from the terminal via the relay server. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a data transmission method,
The present invention relates to a data transmission device, a data reception device, and a packet data structure, and particularly to a process of sequentially reproducing data of a received packet on the terminal side while performing data transmission between the distribution server and the terminal on a packet basis.

[0002]

2. Description of the Related Art At present, there are a download type transmission system and a stream type transmission system for transmitting video (audio and video) data on the Internet. In this download type transmission method, the video file transmitted from the distribution server is once copied on the terminal side, and then the data of the video file (video data) is reproduced. Therefore, in this method, until the file transfer is completed,
Data cannot be reproduced on the terminal side, and the download type transmission method is not suitable for long-time reproduction of video data and the like.

On the other hand, in the stream type transmission system, the received data is reproduced on the terminal side even while the video data and the like are being transmitted from the distribution server to the terminal.
This stream type transmission method is based on IETF (Internet Eng.
The protocol using a protocol called RTP (Real-Time Transport Protocol) defined in RFC1889 of the ineering Task Force is predominant.

FIG. 28 (a) is a diagram for explaining a conventional method of transmitting video data by RTP. Figure 28 (a)
As shown in, the distribution server (sending side) and the terminal (receiving side) such as a personal computer are connected by a wired line such as a modem, ISDN, LAN, etc. on the Internet, and the video data is transmitted by RTP. Be seen.

In the data transmission by the RTP, the process for each packet is synchronized between the transmitting side and the receiving side by the time stamp as the time information, and an out-of-synchronization (arrival delay) packet or a transmission error occurs. The error packet is discarded on the receiving side. Also, the discarded packet or the lost packet is detected by the receiving side due to the missing sequence number given to each packet.

[0006] At present, application of the Internet using mobile phones, such as access to mail and services of character information, is progressing, and third generation mobile communication (W-CDMA: Wide band-Code Division). Multiple A
ccess) for high-speed wireless data communication (~ 38
Infrastructure for high-speed packet communication of 4kbps (infras
tructure) is being prepared.

FIG. 28 (b) is a diagram showing a communication network intended for the W-CDMA visual terminal. Such a communication network includes a wireless transmission section. For example, when data transmission between a video distribution server and a visual terminal is performed via a relay server, wired transmission via the Internet between the distribution server and the relay server. Although it is a section, there is a wireless transmission section by a mobile telephone network such as W-CDMA between the relay server and the visual terminal.

[0008]

However, the bit error rate in the wired section is 10 ^-5 to 10 ^-7 , whereas the bit error rate in the wireless section is 10 ^-3 , and the reproduction quality is low. In the data transmission method of the RTP method, which depends on the transmission quality of the to-end (between the distribution server and the terminal), the transmission quality by wireless becomes a problem.

The present invention has been made to solve the above problems, and an object thereof is to obtain a data transmission method and a packet data structure capable of improving the transmission quality of a wireless section in real-time transmission. To do.

[0010]

A data transmission method according to the present invention (Claim 1) performs data transmission between a distribution server and a terminal on a packet-by-packet basis via a relay server, and the terminal side receives the data. Is a data transmission method for sequentially reproducing the data of the packet, and when a transmission error occurs between the relay server and the terminal, the relay server retransmits the error packet based on a retransmission request from the terminal, When a transmission error occurs between the distribution server and the relay server, the distribution server retransmits the error packet based on the retransmission request transmitted from the terminal via the relay server.

According to the present invention (claim 2), in the data transmission method according to claim 1, when a transmission error occurs between the distribution server and the relay server, the relay server transmits a resend request to the distribution server. The delivery server retransmits the error packet to the relay server.

A packet data structure according to the present invention (claim 3) is a data structure of a packet for performing data transmission from a transmitting side to a receiving side, wherein the packet is related information indicating an attribute of each packet. And a header part that stores
And a data section for storing data to be transmitted, wherein the header section includes first header information indicating a sequence number corresponding to each packet, second header information indicating a priority of each packet, and the above In the configuration, at least the first and second header information of the third header information indicating the reproduction time of the data to be transmitted on the receiving side is included.

According to the present invention (claim 4), in the packet data structure according to claim 3, the header portion of the packet includes the attribute information of the transmitted packet transmitted prior to each packet. is there.

According to the present invention (claim 5), in the packet data structure according to claim 4, the header part of the packet is used as the attribute information of the transmitted packet transmitted prior to each packet. The second information or the first and third information is included.

According to the present invention (claim 6), in the packet data structure according to claim 3, the header part of the packet of a high-priority packet transmitted prior to each packet and having a priority higher than a certain value is transmitted. The configuration includes the value of the high priority sequence number corresponding to the number.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The focus and basic principle of the present invention will be described below. As a result of earnest research on a method for improving transmission quality in a network including a wireless transmission section, the present inventor can improve the transmission quality in the wireless section by retransmitting a packet in real time in the existing real-time transmission method. Found.

That is, the above existing real-time transmission method is for transmitting packet data in real time between a distribution server and a terminal via a relay server or the like, and in order to realize real-time transmission of packet data. Additional information such as required sequence number and time stamp is added to the header of the packet and the like, and the retransmission information of the packet can be controlled in real time by these additional information.

As described above, in the data transmission method of the present invention in which real-time data transmission is performed between the distribution server and the terminal via the relay server and real-time retransmission control is performed, It may also have the function of a distribution server. Further, the present invention can be applied not only in the forward direction from the distribution server to the terminal, but also in the reverse direction from the terminal to the distribution server in the transmission direction of the video data. Furthermore, the present invention realizes control of transmission QoS (Quality of Service) in the relay server in order to effectively function the real-time transmission method.

Next, the outline of real-time retransmission control in the data transmission method of the present invention will be briefly described.

The above-mentioned real-time retransmission control is to recover the error packet in which a wireless transmission error has occurred by retransmitting in consideration of the transmission quality in the wireless section.
The conventional retransmission control is aimed at achieving high reliability in data transmission (error-free transmission), and in order to recover all error packets, it is necessary to retransmit error packets until the data is correctly transmitted to the other party. It was to repeat.

In the conventional retransmission control, when the final retransmission of the error packet fails, the data transmission is abnormally terminated as a communication error. By the way, in the retransmission control required for real-time transmission of video data, even if a transmission error occurs during the transmission of a predetermined packet and an image of several frames is lost, the data transmission must be abnormally terminated. It is not a fatal transmission error. Therefore, in the data transmission method of video data,
Completing real-time transmission with a certain degree of reliability, rather than high reliability, is a top priority.

For example, in the transmission of a video signal conforming to the MPEG standard, when a packet corresponding to an I frame (intra-frame encoded image) which is a reference image becomes an error packet, a subsequent P frame (interframe forward direction) Even if the packets corresponding to the predictive coded image) and the B frame (inter-frame bidirectional predictive coded image) can be correctly received,
It is not possible to reproduce P-frame and B-frame video signals. Therefore, with respect to the I frame, it is necessary to recover the transmission error as much as possible.

Further, in video transmission (stream type communication in which audio signals and video signals are transmitted), unlike conventional retransmission control, it is necessary to perform retransmission while realizing real-time transmission.

In order to realize such real-time transmission, the present invention is a real-time transmission method in which retransmission control for error packets as described below is performed.

The first retransmission control is selective retransmission control,
This is to retransmit only the packet with a high priority among the error packets, and to reduce the number of retransmissions. The second retransmission control is retransmission control with time limit, which is one of the error packets. Retransmission of packets that are not in time for the playback time is stopped, and extra retransmission is reduced.

The embodiments of the present invention will be described below. (Embodiment 1) FIGS. 1 to 3 show Embodiment 1 of the present invention.
3 is a diagram for explaining a data transmission method according to FIG. According to the data transmission method of the first embodiment, the data transmission from the transmission side to the reception side is continuously performed in units of packets that respectively hold corresponding sequence numbers, priorities, and additional information regarding the reproduction time of the data at the reception side. The data transmission method for sequentially reproducing the data of the packet received by the receiving side while retransmitting only the error packet having the priority of a certain value or more.

FIG. 1 (a) is a block diagram showing a data transmission device in a data transmission system for performing real-time data transmission by this data transmission method. The data transmission device 101 constitutes a relay server (transmission side) that relays transmission data between a distribution server and a terminal (reception side). The data transmitting apparatus 101 includes a receiving unit 11 that receives a packet transmitted from a distribution server,
Transmission queue management means 12 for setting the transmission order of received packets and retransmitted packets (retransmission packets) based on the additional information, and transmission means for transmitting the packet data in the transmission order set by the means 12. Thirteen
And have.

Each packet from the transmitting side is composed of a data part storing digital data such as video data, audio data, text data, and a header part storing additional information different from these digital data. Become. Here, each packet has a data structure in which, in its header part, a sequence number corresponding to each packet, a priority, and additional information regarding a reproduction time of the data on the receiving side are stored.

Further, the data transmitting apparatus 101 has a retransmission buffer 17 for storing a predetermined one of the received packets as a retransmission packet, a packet priority determination means 15 for determining the priority of the received packet, and a determination. And a retransmission buffer managing means 18 for controlling the buffer 17 so that the data of the packet having the priority equal to or higher than a certain value is stored in the retransmission buffer 17 based on the priority of the packet. .

Further, the data transmitting apparatus 101 is based on the retransmission instruction receiving means 14 for receiving the retransmission request instruction from the receiving side terminal, the retransmission instruction, and the storage condition of the retransmission packet in the retransmission buffer 17. And a resendability determining means 16 for determining whether or not to resend a packet for which a resend instruction has been issued. The resendability determination means 16 is
Specifically, only when the data of the packet of the sequence number for which a retransmission request is instructed from the receiving side is stored in the retransmission buffer 17, it is determined to retransmit the data of the packet to the receiving side. .

In FIG. 1 (a), the case where the data transmitting device constitutes a relay server has been described. However, when the data transmitting device is a distribution server, the data transmitting device
The receiving means 11 in the data transmitting apparatus 101 encodes the data and outputs the encoded data in units of packets, and the encoded packet generating means 10a, and the priority of each packet output from the means 10a. The configuration is replaced with a priority assigning means 10b for assigning additional information (see FIG. 1 (b)).

FIG. 2 is a block diagram showing a data receiving device in a data transmission system that performs real-time data transmission by the data transmission method of the first embodiment. This data receiving device 201 receives a packet transmitted from a relay server (a data transmitting device on the transmission side), and an error packet in which an error has occurred during transmission based on the output to the receiving device 21. It has an error packet detection means 22 for detecting and outputting a normally transmitted normal packet, and a packet decoding means 23 for receiving the normal packet and decoding the encoded data of the packet.

Further, the data receiving device 201 receives the detection output of the reception history management means 24 for managing the reception history of the packet and the error packet detection means 22, and receives the error packet whose priority is a certain value or more. It has a packet priority determining means 25 for making a decision, and a resending instruction sending means 26 for making a resending request to the transmitting side for an error packet whose priority is decided to be a certain value or more, by giving an instruction for its sequence number. ing.

Next, the function and effect will be described. Figure 3
FIG. 9 is a sequence diagram for explaining selective retransmission control of packets in the data transmission method of the first embodiment. In the data transmission method according to the first embodiment, when a transmission error occurs during packet transmission, the retransmission request is issued from the reception side to the transmission side only for packets having a priority value equal to or higher than a certain value. Retransmission request is not issued for error packets smaller than a certain value.

For example, if a priority higher than a fixed value is a high priority and a priority smaller than a fixed value is a low priority,
As shown in FIG. 3, when an error occurs during the transmission of the high priority packet (S1) having the sequence number S1, a retransmission request is made to the high priority packet, but the low priority packet having the sequence number S2 is issued. When an error occurs during the transmission of the packet (S2), the retransmission request for the low priority packet is not made.

More specifically, each packet transmitted from the distribution server is added with additional information regarding the sequence number and the priority. In the data transmission device 101 as a relay server, the received packet is transmitted. The transmission order is set by the queue management means 12 and the transmission means 13 is set.
Is supplied to. At this time, the packet priority determination means 15
Then, the priority of the received packet is determined. Then, the transmitting means 13 transmits the packets in the set transmission order. Further, the packet whose priority is determined to be equal to or higher than a certain value is stored in the retransmission buffer 17 under the control of the retransmission buffer management means 18. Also,
In the retransmitting packet 17, the data is sequentially released (discarded) by the management unit 18 from the packet which is not in time for the reproduction time.

When the free space in the retransmit buffer 17 is exhausted, the packet data in the retransmit buffer is regenerated based on the replay time of the packet held in the retransmit buffer. Received the first update processing for holding the retransmission data while discarding the earliest packet in order, and the discarding of the data in the retransmission buffer for a predetermined packet after the earliest reproduction time. One of the second update processes for holding the above-mentioned data for retransmission is performed while sequentially performing the reproduction time of the packet on the side at a constant interval. In this way, the packets from the distribution server are sequentially transmitted to the terminal (data receiving device) 201 via the relay server (data transmitting device) 101.

In the data receiving device 201, the packet from the relay server (data transmitting device) 101 is received by the receiving means 21, and the received packet is supplied to the error packet detecting means 22. Then, the normally transmitted packet is output to the packet decoding means 23 by the error packet detection means 22, and the additional information of each packet is supplied to the reception history management means 24. At this time, the priority information of the error packet is supplied to the packet priority determining means 25, and it is determined whether the priority is equal to or higher than a certain value. Then, for error packets having a priority of a certain value or more, the resend instruction sending means 26 makes a resend request to the transmitting side according to the instruction of the sequence number.

Then, in the data transmitting apparatus 101 on the transmitting side, whether or not the resending request is received by the resending instruction receiving means 14, and whether or not the packet of the sequence number for which the resending request is made is stored in the resending buffer 17 or not. The determination is made by the resendability determination means 16. If there is a packet with the sequence number for which a resend request is made in the resending buffer 17, this packet is output from the resending buffer 17 to the sending queue management means 12 as a resending packet. In the transmission queue management means 12, the retransmission packet is set in a predetermined transmission order and is retransmitted to the receiving side via the transmission means 13.

As described above, in the first embodiment, the data transmission from the transmission side to the reception side is continuously performed in units of packets holding the corresponding sequence number, priority, and additional information relating to the data reproduction time. While performing, the data of the packet received by the receiving side is sequentially reproduced, and at this time, for the error packet in which the transmission error occurs, only the packets with the priority of a certain value or more are retransmitted.
It is possible to improve the transmission quality in the wireless section in real-time transmission, and further reduce the number of retransmissions.

It should be noted that, in the above-mentioned embodiment, the priority of the packet is changed to I frame, P frame, B
The type of frame such as a frame may be added as additional information.

Further, there are various methods for determining the priority in the above embodiment, for example, MPEG.
In the case of a video signal conforming to the standard, a packet corresponding to an I frame may be a packet with high priority.

Further, in the packet discarding process when the retransmission buffer is full in the above embodiment, the first or second updating process may be performed in order from the packet with the lowest priority.

(Second Embodiment) FIGS. 4 and 5 are views for explaining a data transmission method according to a second embodiment of the present invention. FIG. 4 is a block diagram showing a data transmission device in a data transmission system that performs real-time data transmission by this data transmission method.

In addition to the configuration of the data transmitting apparatus 101 of the first embodiment, the data transmitting apparatus 102 has an error in the packet output from the transmission queue managing means 12 with respect to additional information such as its sequence number and priority. An error correction means 31 for performing an error correction process for giving a correction code is provided, and the packet subjected to the error correction process is supplied to the transmission means 13. It is the same as the transmitting device 101.

FIG. 5 is a block diagram showing a data receiving device in a data transmission system for performing real-time data transmission by the data transmission method of the second embodiment. In addition to the configuration of the data receiving device 201 of the first embodiment, the data receiving device 202 of the second embodiment has
The packet received by the reception means 21 is provided with an error correction means 41 for performing error correction processing of the additional information by using an error correction code added to the packet, and the packet subjected to this error correction processing. Is output to the error packet detection means 22,
The other configuration is the data receiving device 20 of the first embodiment.
Same as 1.

Next, the function and effect will be described. In the data transmission method according to the second embodiment having such a configuration, the transmission side adds an error correction code to additional information regarding the sequence number and the priority to the transmission packet. Further, on the receiving side, the error correction processing of the additional information is performed by the error correction code, and then the retransmission request of the error packet is performed based on the additional information. As a result, even if there is an error in the sequence number or the priority information, the retransmission request for the error packet can be correctly made.

(Third Embodiment) FIGS. 6 to 9 are diagrams for explaining a data transmission method according to a third embodiment of the present invention and a modification thereof, and FIG. 6 shows the data transmission method of the third embodiment. FIG. 7 is a sequence diagram for explaining selective retransmission control of packets in the data transmission method.

In the data transmission method of the third embodiment,
On the transmitting side, the additional information regarding the sequence number and the priority corresponding to the predetermined packet is also embedded in the subsequent packet transmitted after the predetermined packet. On the receiving side, if a transmission error of the above-mentioned predetermined packet occurs and there is an error in the additional information of the above-mentioned predetermined packet, a resend request for the error packet is sent to the subsequent packet transmitted after the error packet. Is received based on the additional information of the predetermined packet embedded in the subsequent packet.

For example, if a priority higher than a fixed value is a high priority and a priority smaller than a fixed value is a low priority,
As shown in FIG. 6, an error occurs during the transmission of the high priority packet (S1) having the sequence number S1, and the next low priority packet (S1) having the sequence number S2 is transmitted.
If 2) is normally received, the retransmission request for the high priority packet is sent to the next low priority packet (S
It is performed at the time of receiving 2).

On the other hand, an error occurs during the transmission of the low priority packet (S3) having the sequence number S3, and the next high priority packet (S3) having the sequence number S4 is transmitted.
4) is normally received, the next low priority packet (S4) is received when the next high priority packet (S4) is received.
No resend request for 3) is made.

In the data transmission method having such a configuration, even if an error occurs during the transmission of a predetermined packet and the sequence number or priority information of the packet has an error, the succeeding packet transmitted next to this packet is transmitted. Since the packet includes additional information such as the sequence number of the predetermined packet and priority information, it is possible to correctly make a retransmission request with the predetermined packet as an error packet.

In the third embodiment described above, the additional information of each packet is embedded in the next packet that follows it. However, the additional information of each packet is not limited to the next packet, but may include a plurality of subsequent information. It may be embedded in a packet, and a modification of the third embodiment having such a configuration will be described below.

(Modification of Third Embodiment) FIG. 7 is a block diagram showing a data transmission device in a data transmission system for performing real-time data transmission by the data transmission method of the modification of the third embodiment.

In addition to the configuration of the data transmitting apparatus 101 of the first embodiment, this data transmitting apparatus 103 has a sequence number of a packet whose priority is a predetermined value or more among the packets transmitted by the transmitting means 13a. And a sequence number inserting means 32 for outputting the sequence number stored in the storing means 33 to the transmitting means 13a so that the sequence number is stored in the header of the packet to be transmitted. In addition to the function of the transmission means 13 of the first embodiment, the transmission means 13a is configured to transmit the packet from the transmission queue management means 12 by inserting the sequence number from the sequence number insertion means 32 into its header. The other configuration is the same as that of the data transmission device 101 of the first embodiment.

FIG. 8 is a block diagram showing a data receiving device in a data transmission system for performing real-time data transmission by the data transmission method of the modification of the third embodiment.

The data receiving apparatus 203 of the modification of the third embodiment is the same as the data receiving apparatus 201 of the first embodiment.
In addition to the above configuration, the insertion sequence extraction for extracting the sequence number of the high-priority packet inserted in this packet and received before this packet from the normal packet output from the error packet detection means 22. Means 42 are provided, and normal packets are output to the packet decoding means 23 via the insertion sequence extraction means 42. Further, in the data receiving apparatus 203, the packet priority determining means 25a outputs a retransmission request to the retransmission instruction transmitting means 26 when the packet having the sequence number extracted by the insertion sequence extracting means 42 is an error packet. I am trying. Other configurations are the same as those of the data receiving apparatus 201 of the first embodiment.

Next, the function and effect will be described. Figure 9
FIG. 16 is a sequence diagram for explaining selective retransmission control of packets in the data transmission method of the modified example of the third embodiment. In the data transmission device (transmission side) 103, in addition to the transmission operation in the data transmission device 101 according to the first embodiment, the process of embedding the sequence number of the high-priority packet to be transmitted in the subsequent packet is the next high-priority packet. Until the packet is sent once.

For example, if a priority higher than a fixed value is a high priority and a priority lower than a fixed value is a low priority,
As shown in FIG. 9, after the high priority packet (S1) having the sequence number S1 is transmitted, the packets (S2) to (S4) having the sequence numbers S2 to S4 subsequent to this packet are transmitted.
Is transmitted with the sequence number S1 of the high-priority packet (S1) embedded, and the sequence number S4 of the preceding high-priority packet (S4) is added to the next high-priority packet (S5). Is embedded and sent.

At this time, an error occurs during the transmission of the high priority packet (S1) having the sequence number S1 and the subsequent low priority packets (S2) and (S3) having the sequence numbers S2 and S3. When the high priority packet (S4) having the sequence number S4 is normally received, the retransmission request for the first high priority packet (S1) is received as the next high priority packet (S4). Sometimes done.

Further, the data receiving device (reception side) 20
In 3, the sequence number of another packet embedded in the received packet is extracted in addition to the receiving operation in the data receiving apparatus 201 of the first embodiment, and if the packet of this sequence number is an error packet, A retransmission process is performed in which a retransmission request is made to the transmitting side using the sequence number of the error packet.

In the data transmission method according to the modified example of the third embodiment having such a configuration, on the transmitting side, the sequence number of the high priority packet whose priority is equal to or higher than a certain value is followed by the sequence number of the high priority packet. The process of embedding in the packet
The process continues until the transmission of the next high-priority packet of the high-priority packet, and the receiving side extracts the sequence number of another packet (high-priority packet) embedded in the received packet and When a packet transmission error occurs, a resend request for the other packet is issued by instructing the sequence number, so even if two consecutive packets become error packets, the error packet becomes a high priority packet. The sequence number of the priority packet can be detected from the header information of the succeeding packet that has been normally communicated, and thus a retransmission request can be made more reliably when the high priority packet becomes an error packet.

In the third embodiment, the sequence number and the priority information of each packet are embedded in the header of the next packet transmitted next to each packet, and in the modification of the third embodiment, the transmission is performed. The sequence number of the high-priority packet to be embedded is embedded in the subsequent packet until the next high-priority packet is transmitted. However, the information to be embedded in the subsequent packet is not limited to these. The number of retransmissions may be embedded in the subsequent packet together with the sequence number.

In this case, the transmitting side embeds information regarding the number of retransmissions in each packet together with the sequence number. When the receiving side gives an instruction for a retransmission request for an error packet, it gives an instruction to the transmitting side by pairing the number of retransmissions and the sequence number corresponding to the error packet. Further, on the transmitting side, the data of the packet having the sequence number for which the retransmission request is instructed from the receiving side is held in the retransmission buffer, and the sequence number is equal to the packet for which the retransmission request is instructed. If the number of retransmissions matches among the packets in which the data is stored in the retransmission buffer, the error packet for which the retransmission request is made is retransmitted. Then, a selective retransmission process is performed to increment the number of retransmissions corresponding to the packet in the retransmission buffer for which this retransmission has been performed. Hereinafter, a specific configuration example in which such a number of times of retransmission is embedded in a subsequent packet will be described as a fourth embodiment.

(Embodiment 4) FIGS. 10 to 15 are diagrams for explaining a data transmission method according to Embodiment 4 of the present invention. FIG. 10 is a block diagram showing a data transmission device in a data transmission system that performs real-time data transmission by this data transmission method.

In addition to the configuration of the data transmitting apparatus 101 of the first embodiment, this data transmitting apparatus 104 has a sequence number of a packet whose priority is a predetermined value or more among the packets transmitted by the transmitting means 13. And a sequence number for storing the number of retransmissions, and a sequence number for outputting the number of retransmissions storage means 35 and the sequence number and the number of retransmissions stored in the storage means 35 to the transmission means 13a so as to be inserted into the header of the packet to be transmitted. Retransmission count inserting means 34 and a retransmission count clearing means 38 for performing a process of clearing the number of retransmissions on the packet received by the receiving means 11 and outputting the packet to the transmission queue managing means 12 are provided. In addition to the function of the transmission means 13 of the first embodiment, the packet from the transmission queue management means 12
The sequence number and the number of retransmissions from the sequence number inserting means 34 are inserted into the header and transmitted.

Further, the data transmitting apparatus 104 receives the retransmission instruction received by the retransmission instruction receiving means 14, that is, the sequence number and the number of times of retransmission of the packet to be retransmitted, through the reproducibility determining means 16a, and retransmits the instruction. The sequence number of the retransmitted packet and the sequence number of the packet in the retransmission buffer 17, and the number of retransmissions of the packet instructed to be retransmitted and the retransmission of the packet in the retransmission buffer 17 having the sequence number instructed to be retransmitted. It has a sequence number retransmission number comparing means 36 for comparing with the number of times.

In the data transmitting apparatus 104, the resendability determining means 16a, based on the output of the comparing means 36,
If the sequence number of the last received packet is larger than the sequence number of the error packet, selective retransmission processing is performed on the error packet, while if the sequence number of the last received packet is smaller than the sequence number of the error packet, It is configured to determine whether or not retransmission is possible so that selective retransmission processing is performed on a packet having a sequence number that is greater than the sequence number of the last received packet and is less than or equal to the sequence number of the error packet. Further, the retransmission buffer 17a is configured to output a packet to be retransmitted to the transmission queue management unit 12 based on the determination result of the retransmission possibility determination unit 16a.

The retransmission number increment means 37 in the data transmission device 104 increments the number of times of retransmission of the packet in the retransmission buffer 17a which is decided to be retransmitted by the retransmission propriety judging means 16a.

The other structure is the same as that of the data transmitting apparatus 101 of the first embodiment. In addition, FIG. 11 is a block diagram showing a data receiving device in a data transmission system that performs real-time data transmission by the data transmission method of the fourth embodiment.

The data receiving apparatus 204 according to the fourth embodiment
Is a data receiving device 203 of a modification of the third embodiment.
Instead of the resend instruction sending means 26, resend instruction sending means 26 for giving a resend instruction for a packet requesting resend using information having a pair of the sequence number and the resend count.
It has a. Other configurations are the same as those of the data receiving device 203 of the modification of the third embodiment.

Next, the function and effect will be described. 12
FIG. 14 is a sequence diagram for explaining packet selective retransmission control in the data transmission method of the fourth embodiment, and shows a first example of data transmission / reception between a transmission side and a reception side.

In the state shown in FIG. 12, the sequence number S
The high priority packet of 1 has already been normally received by the receiving side. Hereinafter, a packet whose sequence number is Sn and the number of retransmissions is N is referred to as packet (Sn, N) [n,
N is a natural number]. In the figure, the sequence number S
The packets 1, S2 and S4 are high priority packets,
The packets with sequence numbers S3 and S5 are packets other than the high priority packets. Here, only the additional information of the high priority packet is embedded in the subsequent packet.

First, as shown in FIG. 12, at a predetermined transmission timing, a high priority packet (S2, 1) next to the high priority packet (S1) has its header with the sequence number S2 and Along with the number of retransmissions 1, the sequence number S1 of the high priority packet and the number of retransmissions 1
Will be embedded and resent.

At the next transmission timing, the packet (S3) next to the high-priority packet (S2,1) has the sequence number S3 of this packet in its header and the high-priority packet (S2,1). Sequence number S2
Also, the number of retransmissions 1 is embedded and transmitted.

At the next transmission timing, the next high-priority packet (S4, 1) has the header with the sequence number S4 of this packet and the number of retransmissions 1, and the high-priority packet (S2, 1). The sequence number S2 and the number of retransmissions 1 are embedded and retransmitted.

At the next transmission timing, the next packet (S5) contains the sequence number S5 of this packet in its header together with the high priority packet (S4).
The sequence number S4 and the number of retransmissions 1 of 1) are embedded and transmitted.

Here, when the packet transmission is completed four times as described above, a transmission error occurs during the packet transmission from the first time to the third time, and the packet (S2, 1),
(S3) and (S4, 1) are not received by the receiving side,
Only the packet (S5) is received.

In this state, on the receiving side, the last received high priority packet has the sequence number S1, and the error packet has the sequence number S4 and the number of retransmissions is 1
It is known to be the first time, and it is not known what kind of packet is transmitted between the high priority packet (S1) and the packet (S5).

Therefore, on the receiving side, the retransmission instruction of the high-priority packet (S4, 1) is sent together with the sequence number S4 of the packet and the number of retransmissions 1 and the sequence number S1 of the last received high-priority packet. To do.

Then, on the transmitting side, the sequence number S1 of the last received high priority packet is compared with the sequence number S4 of the error packet for which a retransmission instruction has been issued. In this case, since the sequence number S1 of the last received high-priority packet is smaller than the sequence number S4 of the error packet for which the retransmission instruction has been issued, the transmitting side is larger than the sequence number S1 and the sequence number S4.
Selective retransmission processing is performed for packets having the following sequence numbers.

That is, in this case, the high priority packet (S
2, 2) has a high priority packet (S4,
The sequence number S4 and the number of retransmissions 1 of 1) are embedded and transmitted, and then the high priority packets (S4, 2) are
The sequence number S2 of the high priority packet (S2, 2) and the number of retransmissions 2 are embedded in the header and transmitted.

Here, the high priority packet (S2, 2)
Is received, the receiving side sends a retransmission instruction for the high priority packet (S4, 1) together with its sequence number S4 and the number of retransmissions 1 and the sequence number of the last high priority packet (S2, 2). It is performed for the transmission side including S2, but for the high priority packet (S4), 2
Since the second retransmission has been performed, the high priority packet (S
Resending is not performed for the resending instructions of 4 and 1).

Next, a case different from the example of data transfer shown in FIG. 12 will be performed using the sequence diagram of FIG. In the case shown in FIG. 13, the high priority packet (S2, 1)
Data transmission / reception is the same as that shown in FIG. 12 from the transmission of (1) to the transmission of the high priority packet (S2, 2).
In the case shown in FIG. 13, high priority packets (S2,
The transmission of 2) is an error transmission, and the next high priority packet (S4, 2) is normally received.

In this case, on the receiving side, it is known that the last received high priority packet has the sequence number S4 and the error packet has the second retransmission count of the sequence number S2.

Therefore, on the receiving side, the retransmission instruction of the high-priority packet (S2, 2) is sent together with the sequence number S2 of the packet and the number of retransmissions 2 and the sequence number S4 of the last received high-priority packet. To do.

Then, on the transmitting side, the sequence number S4 of the last received high priority packet is compared with the sequence number S2 of the error packet for which a retransmission instruction has been issued. In this case, the sequence number S4 of the last received high-priority packet is larger than the sequence number S2 of the error packet for which a retransmission instruction has been issued, so the transmitting side performs selective retransmission processing only for the error packet.

That is, in this case, the high priority packet (S
2, 3) has a high priority packet (S4,
The sequence number S4 and the number of retransmissions 2 of 2) are embedded and transmitted.

Next, a case different from the example of data exchange shown in FIGS. 12 and 13 is performed using the sequence diagram of FIG. First, as shown in FIG. 14, at a predetermined transmission timing, a high priority packet (S4, 1) has a sequence number S4 of this packet and a retransmission count of 1 in its header, and is transmitted before this packet. Sequence number S2 of priority packet (S2, 1) and retransmission count 1
Will be embedded and resent.

At the next transmission timing, the next packet (S5) has its header with the sequence number S5 of this packet and the high priority packet (S4).
The sequence number S4 and the number of retransmissions 1 of 1) are embedded and transmitted.

Here, a transmission error occurs during the first packet transmission when the two packet transmissions are completed as described above, and the packet (S4, 1) is not received by the receiving side, Only (S5) is received.

In this state, on the receiving side, the last received high priority packet has the sequence number S1, and the error packet has the sequence number S4 and the number of retransmissions is 1
I know it's the first one.

Therefore, on the receiving side, the retransmission instruction of the high priority packet (S4, 1) is sent together with the sequence number S4 of the packet and the number of retransmissions 1 and the sequence number S1 of the last received high priority packet. To do.

Then, on the transmitting side, the sequence number S1 of the last received high priority packet is compared with the sequence number S4 of the error packet for which a retransmission instruction has been issued. In this case, since the sequence number S1 of the last received high-priority packet is smaller than the sequence number S4 of the error packet for which the retransmission instruction has been issued, the transmitting side is larger than the sequence number S1 and the sequence number S4.
Selective retransmission processing is performed for packets having the following sequence numbers.

That is, in this case, the high priority packet (S
2, 2) is transmitted by embedding the sequence number S2 and the retransmission count 2 of this packet (S2, 2) and the sequence number S4 and the retransmission count 1 of the high priority packet (S4, 1) in its header. Then, the high priority packet (S
4, 2) has a high priority packet (S4,
The sequence number S4 and the number of retransmissions 2 of 2) and the sequence number S2 and the number of retransmissions 2 of the high priority packet (S2, 2) are embedded and transmitted.

After that, the packet having the sequence number S6 has the sequence number S6 of this packet in its header.
6, the sequence number S4 of the high priority packet (S4, 2), and the number of retransmissions 2 are embedded and transmitted. At this time, the high priority packets (S2, 2) and (S4,
The transmission of 2) is an error transmission and is not received by the receiving side, and only the packet (S6) is received.

In this state, on the receiving side, the last received high priority packet has the sequence number S1 and the error packet has the sequence number S4 and the number of retransmissions is 2
I know it's the first one.

Therefore, on the receiving side, the retransmission instruction of the high-priority packet (S4, 2) is sent together with the sequence number S4 of the packet and the number of retransmissions 2 and the sequence number S1 of the last received high-priority packet. To do.

Then, on the transmitting side, the sequence number S1 of the last received high priority packet is compared with the sequence number S4 of the error packet for which a retransmission instruction has been issued. In this case, since the sequence number S1 of the last received high-priority packet is smaller than the sequence number S4 of the error packet for which the retransmission instruction has been issued, the transmitting side is larger than the sequence number S1 and the sequence number S4.
Selective retransmission processing is performed for packets having the following sequence numbers.

That is, in this case, the high priority packet (S
2, 3) has a sequence number S2 of this packet and the number of retransmissions 3 in its header, and a high priority packet (S4,
The sequence number S4 and the number of retransmissions 2 of 2) are embedded and transmitted, and subsequently, the high priority packets (S4, 3) are transmitted.
The header includes the sequence number S4 and the number of retransmissions 3
And the sequence number S of the high priority packets (S2, 3)
2 and the number of retransmissions 3 are embedded and transmitted.

As described above, in the fourth embodiment, on the transmitting side, if the sequence number of the last received high priority packet is larger than the sequence number of the error packet,
Since only the error packet is retransmitted, the error packet can be retransmitted efficiently.

In the fourth embodiment, the case where there is one data receiving device for one data transmitting device has been described, but a broadcast communication (multicast) in which there are a plurality of data receiving devices for one data transmitting device. Also, the selective retransmission processing of the above-described Embodiment 4 can be applied to the following, and the following processing in multicast will be performed.
A modification of the fourth embodiment will be described.

(Modification of Fourth Embodiment) FIG. 15 is a sequence diagram for explaining a data transmission method according to a modification of the fourth embodiment, and there are a plurality of data receiving devices for one data transmitting device. An example of the selective retransmission processing according to the fourth embodiment in the above case is shown.

First, as shown in FIG. 15, at a predetermined transmission timing, a high priority packet (S1, 1) has a sequence number S2 of this packet and a retransmission count of 1 in its header, and a high priority packet before this packet. The packet sequence number and the number of retransmissions are embedded and retransmitted. Here, there are two receivers with respect to the transmitter, that is, the receiver I
And the receiving side II, the high priority packet (S1,
The transmission of 1) is an error transmission.

In this case, each receiving side requests the retransmission of the high priority packet (S1, 1) including the sequence number (lastS) of the last received high priority packet. At this time, the transmitting side resends the high priority packets (S1, 2) in response to the resend request from the receiving side I, and after this resending, responds to the resending instruction of the receiving side II arriving at the sending side. Do not resend. This is because the high priority packet (S1, 2) has already been retransmitted in response to the retransmission instruction from the receiving side I.

Then, the high priority packet (S1,
Due to the retransmission of 2), the receiving side I receives the high priority packet (S1), while the receiving side II does not receive the high priority packet (S1). In this case, the receiving side II issues a retransmission instruction of the high priority packet (S1, 2). On the other hand, the transmitting side increments the number of transmissions and retransmits the high priority packets (S1, 3).

In the fourth embodiment and its modifications, the upper limit of the number of retransmissions may be set, or the upper limit of the number of retransmissions of the packet may be changed according to the priority value of the packet. Good.

(Fifth Embodiment) FIGS. 16 and 17 are diagrams for explaining a data transmission method according to a fifth embodiment of the present invention. The data transmission method according to the fifth embodiment is
In the data transmission method according to the first embodiment, a missing sequence number is detected on the receiving side, the transmitting side is instructed to retransmit a packet with the missing sequence number using the missing sequence number, and the transmitting side If the packet having the sequence number for which the receiving side has instructed the retransmission is held in the retransmission buffer 17, the packet is retransmitted. On the transmitting side, only high-priority packets with high priority are stored in the retransmission buffer.

FIG. 16 shows a data transmission device (FIG. (A)) and a data reception device (FIG. 16) in a data transmission system for performing real-time data transmission by this data transmission method.
It is a block diagram which shows (b)).

This data transmitting apparatus 105 has the same structure as the data transmitting apparatus 101 of the first embodiment.
Further, the data receiving device 205, like the data receiving device 201 according to the first embodiment, receives the packet transmitted from the relay server (the data transmitting device on the transmitting side) as the receiving unit 2.
1 and an error packet detecting means 22 for detecting an error packet in which an error has occurred during transmission based on the output to the receiving means 21 and outputting a normally transmitted normal packet; and receiving the normal packet, Packet decoding means 23 for decoding the encoded data of the packet
And reception history management means 2 for managing the reception history of packets
4 and.

The data receiving apparatus 205 of the fifth embodiment replaces the retransmission instruction sending means 26 of the data receiving apparatus 201 of the first embodiment with error packet detecting means 2
It has a resend-instruction sending means 26b which sends out a resend-instruction of the packet corresponding to the missing sequence number detected in 2 to the transmitting side.

Next, the function and effect will be described. FIG. 17
FIG. 16 is a sequence diagram for explaining packet selective retransmission control in the data transmission method of the fifth embodiment. When the high-priority packet (S1) with the sequence number S1 sent from the data transmission device (transmission side) 105 is not received by the data reception device (reception side) 205 due to a transmission error, the data reception device 205 outputs an error packet. The detection means 22 detects that the sequence number S1 is missing, and issues a retransmission instruction for the packet with the sequence number S1 to the transmitting side.

On the transmitting side, it is judged whether or not the packet for which this retransmission instruction has been issued is stored in the retransmission buffer 17. In this case, the packet instructed to be retransmitted is a high priority packet, and is therefore stored in the retransmission buffer 17. Therefore, the transmitting side retransmits the packet for which a retransmission instruction has been issued.

Further, the packet of sequence number S2 sent from the data transmission device (sending side) 105 (S2)
However, due to a transmission error, the data receiving device (reception side) 205
If not received, the error packet detection means 22 of the data reception device 205 detects that the sequence number S2 is missing, and instructs the transmission side to retransmit the packet of this sequence number S2.

On the transmitting side, it is judged whether or not the packet instructed to be retransmitted is stored in the retransmission buffer 17. In this case, the packet for which a retransmission instruction has been issued is not stored in the retransmission buffer 17 because it is not a high priority packet. Therefore, the transmitting side does not retransmit a packet for which a retransmission instruction has been issued.

As described above, according to the fifth embodiment, the receiving side detects a missing sequence number, instructs the transmitting side to retransmit a packet with a missing sequence number using the missing sequence number, and the transmitting side Then, if the packet with the sequence number for which the receiving side has given a retransmission instruction is held in the retransmission buffer, it is retransmitted, so that it is possible to improve the transmission quality of the wireless section in real-time transmission. The number of times can be reduced.

(Sixth Embodiment) FIGS. 18 to 20 are diagrams for explaining a data transmission method according to a sixth embodiment of the present invention. In the data transmission method according to the sixth embodiment, the data transmission from the transmission side to the reception side is continuously performed in units of packets each of which holds a corresponding sequence number, priority, and additional information regarding the data reproduction time. In this data transmission method, the data of the packets received on the receiving side are sequentially reproduced, and at this time, only the packets that meet the packet arrival time limit on the receiving side are retransmitted.

FIG. 18 is a block diagram showing a data transmitter in a data transmission system for performing real-time data transmission by this data transmission method. The data transmission device 106 constitutes a relay server (transmission side) that relays transmission data between a distribution server and a terminal (reception side), and the data transmission device 101 according to the first embodiment.
In addition to the above configuration, a reproduction time determination means 39 for determining a packet that is not in time for the reproduction time on the receiving side among the packets to be transmitted, and the transmission means 13b determines the packet determined by the reproduction time determination means 39. Does not transmit to the receiving side regardless of whether this is stored in the retransmission buffer 17 or not. The other configuration is the same as that of the data transmission device 101 of the first embodiment.

FIG. 19 is a block diagram showing a data receiving device in a data transmission system for performing real-time data transmission by the data transmission method of the sixth embodiment. This data receiving device 206 replaces the packet priority determining means 25 of the data receiving device 201 of the first embodiment, and the reproduction time given to the error packet detected by the error packet detecting means 22 and the error packet The reproduction time determination means 43 for detecting the arrival time at the receiving side, determining the arrival time limit based on the reproduction time, and determining whether or not the arrival time has arrived at the reception side before the arrival time limit, is provided with a retransmission instruction. Based on the result of the determination, the sending means 26 instructs the sending side to use the sequence number to issue a resend request only for error packets that have arrived at the receiving side before the arrival time limit. . In addition,
The arrival time limit is determined by the reproduction time determination means 43.
This is performed based on at least one of the packet allowable delay time determined by the receiving side and the packet transmission delay time between the transmitting side and the receiving side.

The other structure is the same as that of the data receiving apparatus 201 of the first embodiment. The method for determining the arrival time limit in the sixth embodiment is the same as in the eighth embodiment.
Will be described in detail.

Next, the function and effect will be described. Figure 20
FIG. 16 is a sequence diagram for explaining retransmission control with packet time limit in the data transmission method according to the sixth embodiment. In the data transmission device (transmission side) 106, the reproduction time on the reception side is added to each transmission packet.

For example, the data transmission device (transmission side) 106
When the high-priority packets (S1) and (S2) with sequence numbers S1 and S2 transmitted from the data reception device (reception side) 206 are not normally received due to a transmission error,
In the data receiving device 206, the error packet detecting means 2
2, it is determined that the high priority packets (S1) and (S2) are error packets. The reproduction time determination means 43 also reproduces the reproduction time (T
1), (T2) and arrival time are detected, arrival time limits (T1 + α), (T2 + α) are determined based on the reproduction time, and it is determined whether or not the arrival time has arrived at the receiving side before the arrival time limit. .

For the high-priority packet (S1) that has arrived at the receiving side before the arrival time limit, the receiving side issues a retransmission instruction to the transmitting side using this packet as an error packet.

On the other hand, if the packet has not arrived at the receiving side before the arrival time limit, such as the high priority packet (S2),
The receiving side does not instruct the transmitting side to retransmit this packet.

At this time, in the data transmitting apparatus 106, when the data of the packet having the sequence number for which the retransmission request is given from the receiving side is held in the retransmission buffer, the transmission time is the reproduction time. The data of the packet that has not passed is retransmitted to the receiving side, while the data of the packet whose transmission time has exceeded the playback time is discarded without being transmitted, and the data in the retransmission buffer is sent to the receiving side. Packets that are no longer in time for the data reproduction time are discarded in order.

As described above, in the sixth embodiment, the data transmission from the transmission side to the reception side is carried out in units of packets which respectively hold corresponding sequence numbers, priorities, and additional information relating to the reproduction time of the data on the reception side. , The packet data received by the receiving side is sequentially reproduced, and at this time, only the packets that meet the packet arrival time limit at the receiving side are retransmitted. Transmission quality can be improved and the number of retransmissions can be reduced.

In the sixth embodiment, the method of recovering an error in the packet data has been described. However, additional information added to the packet header, that is, the sequence number and the reproduction time. There are some cases where there are errors, and various modification examples are conceivable as a method of recovering these additional information in addition to the recovery of the above-mentioned error of the data, and these modification examples will be described below.

(Modification 1 of Embodiment 6) In Modification 1 of Embodiment 6, in addition to the processing on the transmission side and the reception side in the data transmission method of Embodiment 6 described above, An error correction code for the sequence number and playback time is added to the transmission packet, and the receiving side performs error correction of the sequence number and playback time using the above error correction code, and then based on the determined arrival time limit. Controls retransmission of error packets. In the first modification of the sixth embodiment having such a configuration, even if there is an error in the sequence number or reproduction time of the error packet, these additional information can be corrected.

(Modification 2 of Embodiment 6) In Modification 2 of Embodiment 6, in addition to the processing on the transmitting side and the receiving side in the data transmission method of Embodiment 6, the transmitting side The sequence number and playback time of a given packet,
It is also embedded in the next packet to be transmitted next, and the receiving side extracts the sequence number and the reproduction time information of the previous predetermined packet embedded at the time of receiving the next packet, and based on this information, the predetermined packet The packet arrival limit time is determined, and retransmission control is performed with a predetermined packet as an error packet.

FIG. 21 is a sequence diagram for explaining packet data retransmission control with time limit in the data communication system according to the second modification of the sixth embodiment. On the transmitting side, the sequence number and the playback time on the receiving side are
The sequence number and the reproduction time of the preceding predetermined packet are embedded in the next packet transmitted after the predetermined packet while being given to the predetermined packet.

Then, for example, as shown in FIG. 21, the packets (S) of sequence numbers S1 and S2 are transmitted from the transmitting side.
1) and (S2) are transmitted, and the packet (S1) is not normally received by the receiving side due to a transmission error, but if the packet (S2) is normally received by the receiving side, the packet (S2) is transmitted by the receiving side. The sequence number S1 and the reproduction time (T1) of the packet (S1) before S2) are known.

Therefore, on the receiving side, the error packet (S
1) The arrival time limit (T1) based on the reproduction time (T1)
+ Α) is determined, and a retransmission instruction is given at this point to determine whether or not a retransmission packet can be received within the arrival time limit.
In this case, if the packet (S1) is instructed to be retransmitted when the packet (S2) is received, the packet (S1) may arrive at the receiving side before the time limit. The retransmission instruction of S1) is issued to the transmitting side.

After that, for example, as shown in FIG. 21, packets (S) of sequence numbers S3 and S4 are sent from the transmitting side.
3) and (S4) are transmitted, and the packet (S3) is not normally received by the receiving side due to a transmission error, but if the packet (S4) is normally received by the receiving side, the packet (S4) is transmitted by the receiving side. The sequence number S3 and the reproduction time (T3) of the packet (S3) before S4) can be known.

Therefore, on the receiving side, the error packet (S
3) Based on the reproduction time (T3), the arrival time limit (T3
+ Α) is determined, and it is determined whether or not it has arrived at the receiving side before the arrival time limit. In this case, since the packet (S3) has not arrived at the reception side before the arrival time limit, the retransmission instruction of the packet (S3) from the reception side to the transmission side is not issued.

Modification 2 of Embodiment 6 having such a configuration
Then, on the transmitting side, the sequence number and the reproduction time of a predetermined packet are also embedded in the next packet transmitted next to the predetermined packet. Therefore, due to a transmission error, not only the packet data but also the sequence number Even if an error occurs in the playback time or the playback time, a request for resending the error packet can be issued, and since the receiving side does not issue a resending instruction of the packet that is not in time for the playback time, the number of times of resending can be reduced.

Further, as another modification, a combination of the selective retransmission control of the first to fifth embodiments and these modifications and the time-limited retransmission control of the sixth embodiment and its modifications can be considered. .

For example, a combination of the second embodiment in which the error correction code for the sequence number and the priority information is added to the packet and the first modification of the sixth embodiment in which the error correction code for the sequence number and the reproduction time is added to the packet. It is conceivable that one (first combination example). With this combination, an error correction code for the sequence number, priority information, and reproduction time is added to the packet.

Further, the third embodiment of embedding the sequence number and the priority information of a predetermined packet in the packet next to the predetermined packet to be transmitted, and the predetermined packet in the packet next to the predetermined packet to be transmitted. A combination of the second modification of the sixth embodiment (second combination example) in which the packet sequence number and the reproduction time are embedded can be considered. With this combination, the sequence number of the predetermined packet, the priority information, and the reproduction time are embedded in the packet next to the predetermined packet to be transmitted.

Further, the process of embedding the sequence number and the priority information of the high priority packet to be transmitted in the subsequent packet is performed until the transmission of the next high priority packet, and the modification of the third embodiment. A combination of the second modification of the sixth embodiment (third combination example) in which the sequence number and the reproduction time of the predetermined packet are embedded in the packet next to the predetermined packet is considered.

With this combination, the process of embedding the sequence number, priority information, and reproduction time of a high-priority packet in a subsequent packet is performed until the next high-priority packet is transmitted.

Further, in the combination of the selective retransmission control and the retransmission control with time limit as in the second and third combination examples, the amount of information to be embedded in the packet is large.
A method of embedding the difference between the header information (sequence number, priority information, reproduction time) of a predetermined packet and the header information of the subsequent packet to be embedded in the subsequent packet is effective. Hereinafter, such a configuration example will be described as a modified example 3 of the sixth embodiment.

(Modification 3 of Embodiment 6) FIG. 22 is a sequence diagram for explaining packet time-limited retransmission control in the data transmission method of Modification 3 of Embodiment 6. On the transmission side, the packet transmitted next to the predetermined packet is embedded with the sequence number and the reproduction time of this packet, as well as the difference information regarding the sequence number and the reproduction time of the predetermined packet transmitted before this packet. . This difference information is the difference between the sequence number of a predetermined packet and the sequence number of the next packet (sequence difference), and the difference between the reproduction time of a predetermined packet and the reproduction time of the next packet (time difference).

For example, as shown in FIG. 22, packets (S1) and (S1) of sequence numbers S1 and S2 are sent from the transmitting side.
2) is transmitted and the packet (S1) is not normally received by the receiving side due to a transmission error, the packet (S1)
When 2) is normally received by the receiving side, the receiving side knows the sequence number S1 and the reproduction time (T1) of the packet (S1) before the packet (S2).

That is, the sequence number S1 of the packet (S1) can be obtained by subtracting the sequence difference (S2-S1) from the sequence number S2 of the packet (S2). Also, the reproduction time (T
The reproduction time (T1) of the packet (S1) can be obtained by subtracting the time difference (T2-T1) from 2).

Therefore, on the receiving side, the error packet (S
1) The arrival time limit (T1) based on the reproduction time (T1)
+ Α) is determined, and it is determined whether or not it has arrived at the receiving side before the arrival time limit. For example, packet (S
If 1) arrives at the receiving side before the arrival time limit, the receiving side instructs the transmitting side to retransmit the packet (S1) with the sequence number S1.

Modification 3 of Embodiment 6 having such a configuration
Then, the header information (sequence number,
Since the difference between the priority information and the reproduction time) and the header information of the subsequent packet to be embedded is embedded in the subsequent packet, the amount of information embedded in the packet can be reduced.

In the third modification of the sixth embodiment described above,
Although the sequence number and the reproduction time are shown as the information to be embedded in the packet, the information to be embedded is not limited to these. For example, the number of retransmissions and the priority may be embedded in addition to the sequence number and the reproduction time. next,
An embodiment relating to an application section of retransmission control in the data transmission method according to each of the above-described embodiments will be described.

(Seventh Embodiment) In the data transmission method of the seventh embodiment, data transmission between the distribution server and the terminal is performed in packet units via the relay server.
A data transmission method for sequentially reproducing received packet data, wherein when a transmission error occurs between the relay server and the terminal, the relay server retransmits the error packet based on a retransmission instruction from the terminal. When a transmission error occurs between the delivery server and the relay server, the delivery server sends an error packet based on the resend instruction sent from the terminal via the relay server, based on the resend instruction from the terminal. It is to resend.

FIG. 23 is a diagram for explaining a data transmission method according to the seventh embodiment of the present invention, and shows a configuration of a data transmission device in a system for performing data transmission by the data transmission method.

This data transmission device 107 constitutes a relay server (transmission side) that relays transmission data between a distribution server and a terminal (reception side), and the configuration of the data transmission device 101 of the first embodiment. In addition to the above, there is provided a resend instruction sending unit 51 that sends a resend request of an error packet for which a resend instruction has been issued from the terminal to the distribution server, based on the determination result of the resend availability determination unit 16. The other configuration is the same as that of the data transmission device 101 of the first embodiment.

Next, the function and effect will be described. In the seventh embodiment having such a configuration, when the data transmission between the distribution server and the terminal is performed in packet units, the data transmission device 107 relays the data between the distribution server and the terminal.

When a transmission error occurs between the relay server which is the data transmitting device and the terminal, the relay server retransmits the error packet. In this case, the retransmission instruction for the error packet from the terminal is not relayed to the distribution server.

When a transmission error occurs between the distribution server and the relay server which is the data transmission device, a retransmission instruction of the error packet from the terminal is transmitted to the distribution server,
The error packet retransmitted from the distribution server is relayed by the data transmission device 107 and transmitted to the terminal side.

In the seventh embodiment having such a configuration, when a transmission error occurs between the relay server which is the data transmission device and the terminal, the retransmission instruction for the error packet from the terminal is relayed to the distribution server. Instead, since the error packet is retransmitted by the relay server, the number of retransmissions between the distribution server and the relay server can be reduced.

(Modification of Seventh Embodiment) In the modification of the seventh embodiment, data transmission between the distribution server and the terminal is performed in packet units via the relay server.
A data transmission method for sequentially reproducing data of received packets, wherein when a transmission error occurs between a distribution server and a relay server, the error packet is not transmitted to the terminal, but is transmitted to the distribution server and the relay server. From the distribution server, and the error packet is retransmitted from the distribution server to the relay server.

FIG. 24 is a block diagram showing a data transmitting apparatus in the data communication system according to the modification of the seventh embodiment. The data transmission device 107a of the modification of the seventh embodiment constitutes a relay server (transmission side) that relays transmission data between the distribution server and the terminal (reception side), and the data of the first embodiment In addition to the configuration of the transmission device 101, it is determined whether or not the received packet is an error packet based on the output of the reception means 11 that receives the packet from the distribution server, and the normally received packet is output. Error packet determination means 22,
The reception history management unit 52 that manages the history of normally received packets, the determination result by the resendability determination unit 16, the detection result by the error packet detection unit 22, and the contents of the reception history by the reception history management unit 52. On the basis of this, it is provided with a resend instruction sending means 51a for giving a resend instruction of an error packet to the distribution server, and the other configurations are the same as those of the data sending apparatus 101 of the first embodiment.

Next, the function and effect will be described. In the modified example of the seventh embodiment having such a configuration, when the data transmission between the distribution server and the terminal is performed in packet units, the data transmission device 107a relays the data between the distribution server and the terminal. Done.

When a transmission error occurs between the relay server which is the data transmission device and the terminal, the relay server retransmits the error packet. In this case, the retransmission instruction for the error packet from the terminal is not relayed to the distribution server.

Further, when a transmission error occurs between the distribution server and the relay server which is the data transmission device, the error packet is not transmitted to the terminal, but the retransmission instruction is transmitted from the relay server to the distribution server. The error packet is retransmitted from the distribution server to the relay server. Then, the relay server transmits the error packet retransmitted from the distribution server to the terminal.

In the modification of the seventh embodiment having such a configuration, when a transmission error occurs between the distribution server and the relay server, the error packet is not transmitted to the terminal, but is transmitted from the relay server to the distribution server. Since the retransmission instruction is transmitted and the error packet is retransmitted from the distribution server to the relay server, it is possible to avoid wasteful transmission of the error packet from the relay server to the terminal.

(Embodiment 8) FIGS. 25 to 27 are diagrams for explaining a data transmission method according to Embodiment 8 of the present invention. In this data transmission method, data is transmitted between the distribution server and the terminal on a packet-by-packet basis. On the terminal side, in the data transmission method for sequentially reproducing the data of the received packet, reproduction of the data on the terminal side is performed. Information on the reproduction delay time allowable for time is transmitted from the terminal side to the distribution server, and the distribution server displays the reproduction delay time and
The reproduction time at the terminal is estimated based on the transmission delay time required for data transmission between the distribution server and the terminal.

FIG. 25 is a block diagram showing a data transmission device in a data communication system according to the eighth embodiment of the present invention. The data transmission device 108 constitutes a relay server (transmission side) that relays transmission data between the distribution server and a terminal (reception side), and a reception unit 11 that receives a packet transmitted from the distribution server. , A transmission queue management means 12 for setting the transmission order of the received packets based on additional information such as a sequence number given to each packet, and transmission for transmitting the packets in the transmission order set by the means 12. And means 13.

Further, the data transmitting device 108 allows the time stamps as the time information added to each packet to be extracted from the time stamp extracting means 75 and the receiving side (terminal) via the transmitting means 13. It has a permissible reproduction delay information receiving means 72 for receiving information on the reproduction delay time (arrival time limit).

Further, the data transmission device 108 transmits / receives a packet (transmission delay measurement packet) for measuring the transmission delay, and transmits / receives the transmission delay measurement packet.
1 and a transmission delay measuring means 73 for measuring the transmission delay based on the time required for the transmission delay measurement packet to make a round trip between the transmitting side and the receiving side.

The data transmission method 108 estimates the reproduction time of data on the receiving side based on the transmission delay, the time stamp, and the allowable reproduction delay time (arrival time limit) and outputs the estimated reproduction time. Play time calculation means 7
Have four.

Although not shown in the figure, this data transmitting apparatus 108 stores packets whose priorities are equal to or higher than a certain value in the retransmission buffer, as in the data transmitting apparatus of the first or sixth embodiment. It has a function of discarding a packet that is not in time for the retransmission time and a function of retransmitting a packet for which a retransmission instruction is given from the receiving side.

Specifically, this data transmission device 108
Has a configuration corresponding to the retransmission instruction receiving means 14, the packet priority determination means 15, the retransmission possibility determination means 16, the retransmission buffer 17, and the retransmission buffer management means 18 in the data transmission apparatus 101 according to the first embodiment. However, the transmission queue management unit 12 is configured to set the packet transmission order for all packets to be transmitted, including not only received packets but also retransmitted packets.

FIG. 26 is a block diagram showing a data receiving device in a data transmission system for performing real-time data transmission by the data transmission method of the eighth embodiment. This data receiving device 208 has a receiving means 21 for receiving a packet transmitted from a relay server (a data transmitting device on the transmission side) and a packet decoding means 23 for performing a decoding process on the received packet. is doing.

Further, the data receiving device 208 receives the transmission delay measurement packet transmitted from the transmission delay measurement packet transmitting / receiving means 71 on the transmitting side, and sends it back to the transmitting side, and the allowable reproduction measuring packet transmitting / receiving means 62. It has a permissible reproduction delay determining means 63 for determining a delay time and outputting information related thereto, and a permissible reproduction delay information transmitting means 61 for transmitting information regarding the permissible reproduction delay time to the transmitting side.

Although not shown, this data receiving device 208 detects an error packet and sends a retransmission instruction to the transmission side for those that are in time for retransmission, as in the data receiving devices of the first and sixth embodiments. It has a function to do.

Specifically, this data receiving device 208
Are error packet detection means 22, reception history management means 24, packet priority determination means 25, and retransmission instruction transmission means 26 in the data transmission / reception 201 of the first embodiment.
Has a configuration corresponding to.

Next, the function and effect will be described. FIG. 27
FIG. 27 is a diagram for explaining a method of estimating a data reproduction time at a terminal in the server in the above-mentioned Embodiment 8, and shows a relationship between a packet time stamp and a packet output time (reproduction time) (see FIG. )) And a method for mapping the time stamp to the standard time (Fig. (B)).

In the data transmission device (transmission side) 108, when the transmission means 13 transmits packets based on the transmission order set by the transmission queue management means 12, the time stamp included in each packet tp is extracted by the time stamp extraction means 75, and the reproduction time calculation means 74
Is output to. Further, the data receiving device (reception side) 208
The allowable reproduction delay time dp information determined by the determining means 63 and transmitted by the transmitting means 61 is received by the allowable reproduction delay information receiving means 72 and reproduced time calculating means 74.
Is output to. Further, the transmission delay measurement packet transmitting / receiving means 71 on the transmitting side transmits the transmission delay measurement packet to the transmission delay measuring packet transmitting / receiving means 62 on the receiving side, and the transmission / reception means 62 on the receiving side transmits to the transmitting / receiving means 72 on the transmitting side. The delay measurement packet is returned, the transmission delay measuring means 73 determines the server-terminal transmission delay ds, and outputs it to the reproduction time calculating means 74. At this time, the sending time of each packet to the server is measured on the sending side.

Then, in the reproduction time calculation means 74,
The reproduction time (packet output time) to of each packet on the receiving side is estimated. That is, as shown in FIG. 27A, the packet output time to is obtained by adding the allowable reproduction delay time dp to the time stamp tp, and the server-to-terminal transmission delay ds is added to the server sending time ts. Is added to the terminal reception time tr. Therefore, the reproduction time calculation means 74 calculates the packet output time to as (tp + d)
Then, the terminal reception time tr is calculated by (ts + ds).

Then, in the data transmitter 108, (ts
Based on the magnitude relationship between + ds) and (tp + dp), it is determined whether or not the transmission packet is in time for the reproduction time, that is, whether or not the terminal reception time tr ≦ the packet output time to is satisfied. Based on this determination result, the error packet for which a retransmission instruction has been issued is retransmitted, the packet in the retransmission buffer is discarded, and the like.

Although the reproduction delay dp is transmitted from the receiving terminal to the server in the above description, it may be a constant value. Further, in the above-described Embodiment 8, the time synchronization between the server and the terminal is performed, for example, by the Internet standard NTP (Network Time Protocol).

The time stamp tp of each packet
Is obtained from the time stamp of the RTP header, but this time stamp value needs to be mapped on the same time axis as the server sending time and the like.

The mapping method of the RTP time stamp in the relay server will be briefly described below. Since RTP time stamps are not directly expressed in standard time, other standard protocols RTCP (Real-Time Control)
Protocol), RTSP (Real-TimeStream Protocol)
Is mapped to time information based on standard time using the information contained in. The relay server (data transmission device) 108 needs to know the information for this mapping, and acquires the information (maching information) for this mapping during relay.

For example, as shown in FIG. 27 (b), the RT of the Internet standard protocol sent from the server S
When the time stamp mapping information included in CP and RTSP is relayed by the relay server IS and transmitted to the terminal T,
The relay server IS analyzes the mapping information. Also, the terminal communicates time stamp mapping information at the terminal to the relay server.

As described above, in the eighth embodiment, the server (data transmission device) estimates the actual output time (reproduction time) of the packet at the terminal, so that the packet that is not in time for reproduction is retransmitted from the retransmission buffer. Can be excluded.

In the eighth embodiment, the method of determining the time of the transmission delay and the allowable reproduction delay is not limited to that of the eighth embodiment. For example, the server may be in the middle of reproducing the data on the receiving side. The transmission delay between the terminal and the terminal may be dynamically updated based on the information from the receiving side, and the allowable reproduction delay may be measured dynamically during the data reproduction on the receiving side. It may be changed.

In the above-described Embodiment 8, the method of estimating the actual output time (reproduction time) of the packet at the relay server (data transmission device) has been described. The output time (reproduction time) may be estimated by the distribution server based on an allowable reproduction delay time from the terminal or a transmission delay time required for data transmission between the distribution server and the terminal. Good.

(Ninth Embodiment) FIGS. 29 to 31 are diagrams for explaining a data transmission method according to a ninth embodiment of the present invention. The data transmission method of the ninth embodiment relates to a sequence number, a priority, and a reproduction time of data on the receiving side, which are necessary for realizing data transmission from the transmitting side to the receiving side in real time in packet units. While the additional information is held in packets and continuously transmitted, the data of the packets received by the receiving side are sequentially reproduced. At this time,
This is a data transmission method for retransmitting only error packets whose priority is a certain value or more.

FIG. 29 (a) is a block diagram showing a data transmission device in a data transmission system for performing real-time data transmission by this data transmission method. The data transmission device 109 constitutes a relay server (transmission side) that relays transmission data between a distribution server and a terminal (reception side). The data transmitting device 109 includes a receiving unit 11 that receives a packet transmitted from a distribution server.
And a transmission queue management means 12 for setting the transmission order of the received packet and the packet (retransmission packet) determined to be retransmitted based on the additional information, and the transmission order set by the transmission queue management means 12. And transmitting means 13 for transmitting the packet data.

Further, this data transmitting apparatus 109, when the priority among the packets transmitted by the transmitting means 13 is a certain value or more, the sequence number corresponding to the high priority packet (high priority) High priority sequence number management means 81 for incrementing and storing the value of the high priority packet, the value of the sequence number of the transmitted high priority packet, and the incremented high priority sequence number of this high priority packet. The sequence number correspondence managing means 82 for storing the correspondence relation with the value of the above and the high priority sequence number value of each high priority packet stored in the high priority sequence number managing means 81 are transmitted. It has a high-priority sequence number inserting means 83 for outputting to the transmitting means 13 so as to be inserted into the packet.

Here, the high priority sequence numbers managed by the high priority sequence number management means 81 correspond to the number of high priority packets transmitted from the transmitting side.

Further, the data transmitting apparatus 109 has a retransmission buffer 17 for storing a predetermined one of the received packets as a retransmission packet, a packet priority determination means 15 for determining the priority of the received packet, and a determination. And a retransmission buffer management means 18 for controlling the retransmission buffer 17 so that the data of the packet having the priority equal to or higher than a certain value is stored in the retransmission buffer 17 based on the priority of the transmitted packet. ing.

Further, the data transmitting apparatus 109 retransmits a packet for which a resend request has been made, and resending instruction receiving means 14 for receiving a resend request accompanied by an instruction of a high priority sequence number from the receiving side terminal. Retransmission possibility determining means 16c for determining whether or not there is. Here, the resendability determination means 16c searches for the management information in the sequence number correspondence management means 82 based on the high priority sequence number instructed at the time of the resend request, and at the time of the resend request. A sequence number corresponding to the instructed high priority sequence number is acquired, and it is determined whether or not to retransmit the packet instructed to be retransmitted, depending on whether or not the packet with the sequence number is stored in the retransmission buffer 17. It is configured to do.

In FIG. 29 (a), the case where the packet data is transmitted in real time between the distribution server and the terminal via the relay server or the like, and the data transmission device constitutes the relay server has been described. However, the relay server may also function as the distribution server. That is, when the data transmitting device constitutes a distribution server, the data transmitting device 10
As shown in FIG. 29 (b), reference numeral 9 indicates the data transmission device 1
The receiving means 11 in 09 encodes the data and outputs the encoded data in units of packets. The encoded packet generating means 10a and each packet output from the encoding packet generating means 10a are assigned a priority or the like. The configuration is replaced with the priority assigning means 10b for assigning additional information.

FIG. 30 is a block diagram showing a data receiving device in a data transmission system for performing real-time data transmission by the data transmission method of the ninth embodiment. The data receiving device 209 receives the packet transmitted from the data transmitting device on the transmitting side.
And an error packet detection unit 22a that detects a packet in which an error has occurred during transmission based on the output of the reception unit 21 and outputs a normally transmitted normal packet, and a packet that receives the normal packet Packet decoding means 23 for decoding the encoded data of.

Here, the error packet detection means 22
When the high priority sequence number (transmission side high priority sequence number) inserted in the packet from the data transmission device 109 is correctly extracted, a is the value of the transmission side high priority sequence number and the time And the value of the receiving side high-priority sequence number are output. The value of the receiving side high priority sequence number corresponds to the number of high priority packets received by the receiving side, and this value is incremented each time the receiving side receives the high priority packet. It is a thing.

Also, the data receiving device 209 increments and stores the value of the receiving side high priority sequence number when the error packet detecting means 22a outputs a normal packet. 91 and the value of the transmitting side high priority sequence number output by the error packet detecting means 22a and the value of the receiving side high priority sequence number are compared, and when these values do not match, the receiving side high priority Retransmission sequence number that outputs a value within the range from the value of the sequence sequence number plus 1 to the value of the transmission side high priority sequence number as the value of the retransmission sequence number (transmission side high priority sequence number) It has a determination means 92.

Here, the high priority sequence number management means 91 increments the stored value of the reception side high priority sequence number each time the retransmission sequence number determination means 92 outputs the high priority sequence number. It is configured to do.

Further, the data receiving device 209 issues a retransmission request for a high error packet to the transmission side high priority packet based on the transmission side high priority sequence number output as the retransmission sequence number from the retransmission sequence number judging means 92. It has a resending instruction sending means 26c for sending a priority sequence number to the sending side.

Next, the function and effect will be described. Figure 31
FIG. 19 is a sequence diagram for explaining packet selective retransmission control in the data transmission method of the ninth embodiment.

In the description of FIG. 31, the sequence number [S + n] indicates a sequence number whose value is “S + n”, and the sequence number [H + n] has a value “H”.
+ N ”indicates a high priority sequence number, and packet (S + n) indicates a packet whose sequence number value is“ S + n ”. Also here, n is 0,
The case of 1, 2, 3, 4, and 5 is shown.

For example, if a priority higher than a fixed value is a high priority and a priority lower than a fixed value is a low priority,
As shown in FIG. 31, sequence numbers [S + 1], [S
+2], when an error occurs during the transmission of the high priority packets (S + 1) and (S + 2), a retransmission request for the high priority packet is made, but the sequence number [S +
[3] When an error occurs during the transmission of the low priority packet (S + 3), the retransmission request for the low priority packet (S + 3) is not made.

More specifically, each packet transmitted from the distribution server is added with additional information regarding the sequence number and the priority. In the data transmitting device 109 as a relay server, the received packet is transmitted. The transmission order is set by the queue management means 12 and the transmission means 13 is set.
And the priority is determined by the packet priority determination means 15. Then, the transmitting means 13 transmits the packets in the set transmission order.
Further, the packet whose priority is determined to be equal to or higher than a certain value is stored in the retransmission buffer 17 under the control of the retransmission buffer management means 18. In addition, the packet for retransmission 17
Then, the management unit 18 sequentially releases (discards) the data from the packets that are not in time for the reproduction time.

Next, the sequence number management process during packet transmission will be described. When transmitting a high priority packet, the high priority sequence number is incremented. Specifically, when the high priority packet (S + 0) of the sequence number [S + 0] is transmitted by the transmitting means 13, the transmission side high priority sequence number [H + 0] stored in the high priority sequence number managing means 81. ] Is incremented to “H + 1”. At this time, the value of the sequence number [S + 0] of the high priority packet (S + 0) and the incremented value of the transmitting side high priority sequence number [H + 1] are associated with each other and the sequence number correspondence managing means is associated. 82.

Similarly, when the high-priority packet (S + 1) of sequence number [S + 1] is transmitted by the transmitting means 13, the transmitting-side high-priority sequence number stored in the high-priority sequence number managing means 81 [ The value of [H + 1] is incremented to “H + 2”. At this time, the sequence number [S + 1] of the high priority packet (S + 1)
And the incremented transmission side high priority sequence number [H + 2] are registered in the sequence number correspondence management means 82 in association with each other.

Also, when the high priority packet (S + 2) is transmitted, as in the case of transmitting the high priority packets (S + 0) and (S + 1), the transmission side height in the high priority sequence number management means 81 is increased. The priority sequence number [H + 2] is incremented, the sequence number [S + 2] of the high priority packet (S + 2) and the incremented transmission side high priority sequence number [H +].
3] is associated with the sequence number correspondence managing means 8
Registered in 2.

On the other hand, the low priority sequence number is not incremented when transmitting the low priority packet. Specifically, when the low priority packet (S + 3) having the sequence number [S + 3] is transmitted by the transmission means 13, the transmission side high priority sequence number [H + 3] stored in the high priority sequence number management means 81. ] Value is not updated and is maintained as it is. At this time, the sequence number of the transmitted packet and the transmission side high priority sequence number [H + 3] stored in the high priority sequence number management means 81 are associated and registered in the sequence number correspondence management means 82. Is also not done.

Next, a sequence number embedding process at the time of transmitting a packet will be described. At the time of transmitting the high priority packet (S + 1), the value of the transmission side high priority sequence number [H + 1] stored in the high priority sequence number management means 81 at this point is the insertion of the high priority sequence number. Transmission packet (S + 1) by means 83
Embedded in the header of. Similarly, when transmitting the low priority packet (S + 3), the value of the transmission side high priority sequence number [H + 3] stored in the high priority sequence number management means 81 at this point is the transmission packet. It is embedded in the header of (S + 3). In this way, the transmission packet in which the transmission side high priority sequence number stored in the high priority sequence number management means 81 is embedded in the header is transmitted to the reception side by the transmission means 13.

Thus, the packets from the distribution server are sequentially transmitted to the terminal (data receiving device) 20 via the relay server.
9 is sent. Then, in the data receiving device 209, the packet from the relay server (data transmitting device) 109 is received by the receiving means 21, and the received packet is supplied to the error packet detecting means 22a. The normally transmitted high priority packet (S + 0) is output to the packet decoding means 23 by the error packet detection means 22a, and the reception side high priority sequence number,
That is, the value of the high priority sequence number [H + 0] stored in the high priority sequence number management means 91 is incremented to [H + 1].

Here, it is assumed that a transmission error occurs during transmission of the high priority packets (S + 1) and (S + 2), and then the low priority packet (S + 3) following these packets is normally transmitted.

In this case, the normally transmitted low priority packet (S + 3) is output to the packet decoding means 23 by the error packet detection means 22a, but is stored in the high priority sequence number management means 91. The value of the receiving side high priority sequence number [H + 1] is not incremented.

Further, the error packet detecting means 22a correctly extracts the transmitting side high priority sequence numbers [H + 0] and [H + 3] inserted in the high priority packet (S + 0) and the low priority packet (S + 3). Then, the transmission side high priority sequence numbers [H + 0], [H
+3] is output to the retransmission sequence number determination means 92. Furthermore, at the time when the transmission side high priority sequence numbers [H + 0] and [H + 3] are extracted by the error packet detection means 22a, the reception side high priority sequence numbers stored in the high priority sequence number management means 91 are stored. Value [H +
0] and [H + 1] are output to the retransmission sequence number judging means 92.

For example, at the time when the transmission side high priority sequence number [H + 0] is extracted, the reception side high priority sequence number in the high priority sequence number management means 91 together with the transmission side high priority sequence number [H + 0]. Value [H + 0] of the transmission side high priority sequence number [H + 3] is output to the retransmission sequence number determination means 92, and the transmission side high priority sequence number [H + 3] is extracted at the time when the transmission side high priority sequence number [H + 3] is extracted. Value of the receiving side high priority sequence number in the number management means 91 [H +
1] is output to the retransmission sequence number judging means 92.

Then, the retransmission sequence number judging means 92
Then, the transmission-side high-priority sequence number and the reception-side high-priority sequence number supplied at the same time are compared to determine whether or not to instruct the transmission side to retransmit.

For example, the transmitting side high priority sequence number [H + 0] and the receiving side high priority sequence number [H + 0].
In the comparison process of (1), since a comparison result that both high priority sequence numbers have the same value is obtained, the retransmission instruction is not issued. On the other hand, in the comparison processing of the transmitting side high priority sequence number [H + 3] and the receiving side high priority sequence number [H + 1], a comparison result that the values of both high priority sequence numbers are not equal is obtained. Done. In this case, the value of the receiving side high priority sequence number [H + 1] is 1
From the value with the addition of
[3]] within the range, that is, as the value of the high priority sequence number used for the retransmission instruction, "H + 2", "H"
+3 ”is output to the retransmission instruction sending means 26. At this time, in the high priority sequence number management means 91, the value of the stored reception side high priority sequence number is incremented twice to become "H + 3".

Then, in the retransmission instruction sending means 26, the values of the high priority sequence numbers are "H + 2" and "H + 3".
Is supplied, a retransmission request with a high priority sequence number [H + 2] and a retransmission request with a high priority sequence number [H + 3] are sent to the transmitting side.

Then, in the data transmitting apparatus 109 on the transmitting side, the resend request is received by the resend instruction receiving means 14, and the high priority sequence number [H
+2] and [H + 3], the search processing for the management information of the sequence number correspondence management means 82 is performed, and the sequence number [S + 1] corresponding to the high priority sequence number [H + 2] and the high priority sequence number. [H +
3] corresponding to the sequence number [S + 2] is acquired.

Further, the resendability determining means 16c determines whether or not the packet data corresponding to the sequence numbers [S + 1] and [S + 2] is stored in the resending buffer 17. As a result of this determination, only the packet whose data is stored in the retransmission buffer 17 is
It is output from the retransmission buffer 17 to the transmission queue management means 12 as a retransmission packet. Here, the high priority packets (S + 1) and (S + 2) are output as the retransmission packets.

In the transmission queue management means 12, a predetermined transmission order is set in the retransmission packet, and the transmission means 1
3 is retransmitted to the receiving side. Since the retransmission packet is a high priority packet, each retransmission packet (S +
At the time of transmission of 1) and (S + 2), the value of the transmission side high priority sequence number stored in the high priority sequence number management means 81 is incremented.

Specifically, when transmitting the retransmission packet (S + 1), the transmission side high priority sequence number [H + 3] stored in the high priority sequence number management means 81.
Is incremented to "H + 4", and the sequence number [S + 1] of the retransmission packet (S + 1) and the transmission side high priority sequence number [H + 4] are associated and registered in the sequence number correspondence management means 82.

When the retransmission packet (S + 2) is transmitted, the value of the transmission side high priority sequence number [H + 4] stored in the high priority sequence number management means 81 is incremented to “H + 5”. , The sequence number [S + 2] of the retransmission packet (S + 2) and the transmission side high priority sequence number [H + 5] are associated and registered in the sequence number correspondence management means 82.

As described above, in the ninth embodiment, the data transmission from the transmitting side to the receiving side has additional sequence information, priority, additional information relating to the reproduction time of the data, and high priority managed by the transmitting side. The data of the packets received by the receiving side are sequentially reproduced while the packet holding the sequence number information is continuously performed as a unit, and the value of the sending side high priority sequence number held in the received packets (transmission Number of high-priority packets received) and the value of the reception-side high-priority sequence number managed by the reception side (the number of high-priority packets received), and the missing transmission-side high-priority sequence Since the retransmission request is made by instructing the number, not only can the transmission quality of the wireless section in real-time transmission be improved by retransmitting error packets whose priority is a certain value or more. The retransmission of the error packet can be realized by a simpler procedure.

In the ninth embodiment, when the values of the high-priority sequence numbers corresponding to a plurality of transmitted high-priority packets are continuously missing, on the receiving side, the missing high-priority Although a high-priority packet retransmission request is made to the transmitting side for each sequence number value, a retransmission request for a plurality of high-priority packets is listed, and a plurality of high-priority sequence number values are listed. Alternatively, the range of the value may be designated, and the values may be collectively transmitted to the transmission side.

In this case, on the transmitting side, based on the plurality of high priority sequence numbers for which the receiving side has requested retransmission,
The sequence number associated with each high-priority packet on the transmitting side is acquired by the search process, and the high-priority packet with the acquired sequence number is retransmitted to the receiving side.

(Embodiment 10) The data transmission method of Embodiment 10 is such that the number of times and the interval at which a retransmission request is made to the transmission side are changed in accordance with the transmission state in the wireless section. This is to improve the transmission quality in the wireless section by increasing the probability that the retransmission request is correctly transmitted to the transmitting side.

FIG. 32 is a block diagram showing a data transmission device in a data transmission system for performing real-time data transmission by the data transmission method of the tenth embodiment. This data receiving device 110 is the same as the ninth embodiment.
Resendability determination means 16 in the data transmitter 109 of
Instead of c, processing is performed by this means 16c, and a resendability determination means 16d for outputting the sequence number of the packet decided to be retransmitted is provided, and the sequence number correspondence management means 82 in the data transmission device 109 is further provided. Instead, a sequence number for performing the processing by the means 82 and deleting the value of the transmission side high priority sequence number associated with the value of the sequence number based on the sequence number from the resendability determination means 16d. The correspondence management means 82a is provided. Therefore, the other configuration of the data transmitting apparatus 110 of the tenth embodiment is the same as that of the data transmitting apparatus 109 of the ninth embodiment.
Is the same as

FIG. 33 is a block diagram showing a data receiving device in a data transmission system for performing real-time data transmission by the data transmission method of the tenth embodiment.

This data receiving device 210 performs the same processing as the error packet detection by the means 22a in place of the error packet detecting means 22a in the data receiving device 209 of the ninth embodiment, and detects the error packet It has an error packet detecting means 22b for judging the transmission state of the wireless section from the number.

Further, the data receiving device 210 has a resending instruction sending means 26c in the data receiving device 209.
Instead, it has a resend instruction sending means 26d for performing the same process as the process for sending the resend instruction by the means 26c and outputting the sent resend request as a control signal.

Further, the data receiving device 210 receives the resend request sent as the control signal from the resend instruction sending means 26d, continuously sends the resend request a plurality of times at the predetermined number of times and at the sending interval, and outputs an error. It is provided with a retransmission instruction continuous transmission means 93 that changes the number of times of retransmission request transmission and the transmission interval in accordance with the information output from the packet detection means 22b and indicating the transmission state in the wireless section.

The other structure of the data receiving apparatus 210 of the tenth embodiment is the same as that of the data receiving apparatus 209 of the ninth embodiment.

Next, the function and effect will be described. Since the basic data transmission processing by the data transmission method of the tenth embodiment of the present invention is the same as that of the ninth embodiment, only the processing different from the processing of the ninth embodiment will be described below.

In the tenth embodiment, when the packet received by the receiving means 21 from the transmitting side is output to the error packet detecting means 22b, the error packet detecting means 22b outputs the packet based on the output of the receiving means 21. The transmission state of the wireless section is detected, and information indicating the transmission state of this wireless section is supplied to the retransmission instruction continuous sending means 93.

On the other hand, when the high priority sequence number from the retransmission sequence output means 92 is input to the retransmission instruction sending means 26b, the retransmission instruction sending means 26b gives an instruction for the high priority sequence number and the transmitting side The resend request is sent to the resend instruction continuous sending means 93 as a control signal.

[0230] Then, the retransmission instruction continuous sending means 93 carries out continuous retransmission processing for continuously transmitting the retransmission request to the transmitting side a plurality of times. In this continuous retransmission processing, the number of transmissions of the retransmission request and the transmission interval are adjusted according to the transmission state of the wireless section obtained from the output information of the error packet detecting means 22b with reference to a predetermined default value.

For example, when there are many transmission errors in the wireless section, the number of times of transmission increases and the transmission interval increases. This increases the probability that the retransmission request will be correctly transmitted to the transmission side. On the other hand, when there are few transmission errors in the wireless section, the number of times of transmission is reduced and the transmission interval is narrowed. This shortens the time required for the retransmission process.

On the transmitting side, the packet is retransmitted in response to the retransmission request, and the sequence number correspondence managing means 82a determines the value of the sequence number on the basis of the sequence number from the resendability determining means 16d. A process of deleting the value of the associated transmission side high priority sequence number is performed.

Therefore, with respect to the same retransmission request received again, the sequence number search processing by the retransmission permission / inhibition decision means 16d fails. This is because the correspondence relationship between the transmission side high priority sequence number and the sequence number specified at the time of this retransmission request is deleted from the sequence number correspondence management means 82a.

As a result, in the retransmission determination by the retransmission permission / inhibition decision means 16d, it is decided that the value of the transmitting side high priority sequence number is instructed and the high priority packet for which the retransmission request is made is not retransmitted. This prevents the transmitting side from repeatedly retransmitting the same packet for each retransmission request when the receiving side issues multiple retransmission requests.

As described above, according to the tenth embodiment, the retransmission request for instructing the high-priority sequence number to be transmitted from the reception side is continuously transmitted a plurality of times in preparation for the case where a transmission error occurs during transmission. Therefore, if at least one of the plurality of retransmission request instructions from the receiving side is correctly received, the transmitting side can retransmit an error packet with a priority of a certain value or more, and in the real-time transmission, The transmission quality in the wireless section can be improved more effectively.

The data structure of a packet for transmitting data by the data transmission method of each of the above embodiments will be described below. FIG. 34 is a diagram showing the data structure of the packet. This packet Pa is composed of a header section Ph which stores related information indicating the attribute of each packet and a data section Pd which stores data to be transmitted (FIG. 34 (a)).

The header section Ph includes header information Ia indicating the sequence number corresponding to each packet, header information (time stamp) Ib indicating the reproduction time of the data to be transmitted on the receiving side, and The header information Ic indicating the priority and the extension header information Id are included together with other header information I1 to I10 (FIG. 34).
(b)).

Here, the detailed definition of each header information is described in RFC1889 as shown in FIG. 34 (c). For example, the header information I3 has a value X of X = 1.
, The extension header information Id is the header part Ph
Is added to the. Further, the header information I5 indicates that, when the value PT is PT = 32, the data stored in the data section is encoded data according to the MPEG1 system, and the value PT is P.
When T = 33, it indicates that the data stored in the data section is encoded data by the MPEG2 system. Furthermore, header information I9, Ic,
I10 and I11 are header information added when the encoded data by the MPEG1 system is transmitted by RTP. The value P (P = 1) of the header information Ic indicates that the data in the data part is I frame data, and the packet storing this I frame data should be treated as a high priority packet. (P = 2) is
The data in the data section is P frame data,
It indicates that the packet storing the P frame data should be treated as a low priority packet, and the value P (P = 3)
Indicates that the data in the data section is B frame data, and the packet storing this B frame data should be treated as a low priority packet.

Further, the extension header information Id is the previous sequence number and the previous priority information (FIG. 6) in the third embodiment.
In the fourth embodiment, the sequence number and the number of retransmissions of the high-priority packet transmitted first (see FIGS. 13 and 14), and in the second modification of the sixth embodiment, the previous sequence number and the previous reproduction time (see the figure). 21)), and the third modification of the sixth embodiment.
Then, the difference value of the previous sequence number and the difference value of the previous reproduction time (see FIG. 22) are set, and in the ninth embodiment, the transmission side high priority sequence number (see FIG. 29) is set.

[0240]

As described above, according to the data transmission method of the present invention, the data transmission from the transmission side to the reception side holds the additional information regarding the corresponding sequence number, priority, and data reproduction time. The packet quality is continuously reproduced in units of packets, and the data of the packets received at the receiving side are sequentially reproduced. At this time, only error packets with a priority higher than a certain value are retransmitted. Can be improved, and the number of retransmissions can be reduced.

According to the data transmitting apparatus of the present invention,
Retransmission packet storage means for storing, as a retransmission packet, a packet whose priority is equal to or higher than a certain value, based on the priority of each packet, an instruction of a retransmission request from the receiving side terminal,
Since the resend packet determining means determines whether or not to resend a packet for which a resend instruction is given, based on the resending packet storage state in the resending packet storing means, an error with a priority of a certain value or more Only the packet can be retransmitted, the transmission quality in the wireless section in the real-time transmission can be improved, and the number of retransmissions can be reduced.

According to the data receiving apparatus of the present invention,
A packet priority determining means for determining an error packet whose priority is a fixed value or more, and a resend request for an error packet whose priority is determined to be a fixed value or more, and sends out a sequence number to the transmitting side. Since the re-transmission instruction transmission means is provided, the re-transmission request is sent to the transmission side only for error packets with a priority value of a certain value or more on the reception side, which improves the transmission quality in the wireless section in real-time transmission. It is also possible to reduce the number of retransmissions

According to the data transmission method of the present invention,
Data transmission from the sending side to the receiving side is continuously performed in units of packets holding additional information related to the corresponding sequence numbers, priorities, and data reproduction times, while the data of the packets arriving at the receiving side are sequentially Play,
At this time, since only the error packet that is in time for the packet arrival time limit on the receiving side is retransmitted, it is possible to improve the transmission quality of the wireless section in the real-time transmission and reduce the number of retransmissions.

According to the data transmitting apparatus of the present invention,
A packet for which a retransmission instruction has been issued based on the retransmission packet storage means for storing packets having a priority value of a certain value or more as a retransmission packet, the instruction of the retransmission request, and the storage status of the retransmission packet in the retransmission packet storage means. And a resendability determination means for determining whether or not to resend
Since the data of the retransmission packet other than the packet determined by the reproduction time determination means to be not in time for the reproduction time on the receiving side is retransmitted, the transmission quality of the wireless section in the real-time transmission can be improved, and The number of retransmissions can be reduced.

According to the data receiving apparatus of the present invention,
A reproduction time determination means for determining whether or not the error packet has arrived at the reception side before the arrival time limit is provided, and the retransmission request is issued only for the error packet that has arrived at the reception side before the arrival time limit. Since the sequence number is instructed and sent to the sending side, in real-time transmission,
It is possible to improve the transmission quality in the wireless section and reduce the number of retransmissions.

According to the data transmission method of the present invention,
Data transmission from the sending side to the receiving side is continuously performed in units of packets holding additional information related to the corresponding sequence numbers, priorities, and data reproduction times, while the data of the packets arriving at the receiving side are sequentially Play,
At this time, since only the error packet whose priority is equal to or higher than a certain value and which meets the packet arrival time limit on the receiving side is retransmitted, it is possible to improve the transmission quality of the wireless section in the real-time transmission, The number of times can be greatly reduced.

According to the data transmission method of the present invention,
If a transmission error occurs between the relay server, which is the data transmission device, and the terminal, the retransmission request for the error packet from the terminal is not relayed to the distribution server, but this relay server retransmits the error packet. Therefore, it is possible to reduce the number of retransmissions between the distribution server and the relay server.

According to the present invention, when a transmission error occurs between the distribution server and the relay server, an error packet is not sent to the terminal, but a retransmission request is sent from the relay server to the distribution server, Since the error packet is retransmitted from the relay server to the relay server, there is an effect that wasteful transmission of the error packet from the relay server to the terminal is avoided.

According to the data transmitting apparatus of the present invention,
Based on a retransmission instruction receiving unit that receives an instruction of a retransmission request from the terminal on the receiving side, an instruction of the retransmission request, and a storage state of the retransmission packet in the retransmission packet storage unit,
A resend-possibility determining unit that determines whether or not to resend a packet for which a resend instruction has been issued, and based on the determination result by the resend-possibility determining unit, a resend request for an error packet for which a resend instruction has been issued from the terminal Therefore, if a transmission error occurs between the relay server that is the data transmission device and the terminal, the retransmission request for the error packet from the terminal is not relayed to the distribution server. In addition, the relay server can retransmit the error packet, and the number of retransmissions between the distribution server and the relay server can be reduced.

According to the data transmission method of the present invention,
Additional information related to the sequence number and priority corresponding to the data transmission from the sending side to the receiving side, and the value of the sending side high priority sequence number corresponding to the number of sent high priority packets managed by the sending side The data of the packet received by the receiving side is sequentially reproduced, and the value of the sending side high priority sequence number held in the received packet and the receiving side manage According to the result of comparison with the value of the receiving side high priority sequence number corresponding to the number of received high priority packets, the transmitting side high priority sequence number is instructed and the error packet retransmission request is made. It is possible to retransmit a high-priority packet whose priority is equal to or higher than a certain value by a simpler process.

According to the present invention, since the retransmission request from the receiving side to the transmitting side, which is performed by instructing the value of the transmitting side high priority sequence number, is continuously made a plurality of times. When even one of the multiple retransmission request instructions is correctly received, only the error packet having the priority of a certain value or more can be retransmitted, and the transmission quality of the wireless section in the real-time transmission can be improved more effectively. .

According to the data transmitting apparatus of the present invention,
Sequence number management means for managing the value of the transmission side high priority sequence number corresponding to the number of transmitted high priority packets and the sequence number value of the high priority packet, and the high priority packet And a high-priority sequence number inserting means for embedding the value of the transmission-side high-priority sequence number in the succeeding packet, and retransmits based on a retransmission request from the reception side, instructing the transmission-side high-priority sequence number value. Since the designated packet is retransmitted, only error packets with a priority higher than a certain value will be retransmitted, and high priority packets with a priority higher than a certain value can be retransmitted by a simpler process. You can

According to the data receiving apparatus of the present invention,
Equipped with high priority sequence number management means for managing the value of the high priority sequence number on the receiving side, which corresponds to the number of normally received high priority packets, and is included in the packet from the transmitting side. Number of high-priority packets that correspond to the number of high-priority sequence numbers on the sending side, and the high-priority sequence number on the receiving side, depending on the result of comparison, By specifying the number value and requesting retransmission of error packets having a priority of a certain value or higher, it is possible to perform retransmission of high priority packets having a priority of a certain value or more by a simpler process.

According to the packet data structure of the present invention, a packet for data transmission from the transmitting side to the receiving side is provided with a header section for storing related information indicating the attribute of each packet and data to be transmitted. And a header part for storing the header information, the first information indicating the sequence number corresponding to each packet, the second information indicating the priority of each packet, and the reception of the data to be transmitted. Since it is configured to include at least the first and second information of the third information indicating the reproduction time on the side, it is possible to avoid retransmission of packets with low priority and retransmission of packets that do not meet the reproduction time, It is possible to improve the transmission quality of the wireless section in real-time transmission while reducing the number of retransmissions.

According to the present invention, since the header portion of the packet includes the attribute information of the transmitted packet transmitted prior to each packet, the error packet can be retransmitted more reliably.

According to the present invention, the first and second information or the first and third information is used as the attribute information of the transmitted packet transmitted prior to each packet in the header portion of the packet. Since the configuration is included, the retransmission control based on the priority or the reproduction time can be performed more reliably.

According to the present invention, the header part of the packet is
Since the configuration includes the value of the high-priority sequence number corresponding to the number of high-priority packets that are transmitted prior to each packet and whose priority is higher than a certain value, it is possible to improve the transmission quality of the wireless section in real-time transmission. Instead, error packet retransmission can be realized by a simpler processing procedure.

[Brief description of drawings]

1 is a data transmission device as a relay server in a data transmission system according to a first embodiment of the present invention (FIG.
(a)) is a block diagram for explaining a data transmission device as a distribution server.

FIG. 2 is a block diagram showing a data receiving device (receiving terminal) in the data transmission system according to the first embodiment.

FIG. 3 is a sequence diagram for explaining packet selective retransmission control in the data transmission method according to the first embodiment.

FIG. 4 is a block diagram showing a data transmission device (relay server) in a data transmission system according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a data receiving device (receiving terminal) in the data transmission system of the second embodiment.

FIG. 6 is a sequence diagram for explaining packet selective retransmission control in the data transmission method according to the third embodiment of the present invention.

FIG. 7 is a block diagram showing a data transmission device (relay server) in a data transmission system according to a modification of the third embodiment of the present invention.

FIG. 8 is a block diagram showing a data receiving device (receiving terminal) in a data transmission system of a modified example of the third embodiment.

FIG. 9 is a sequence diagram for explaining packet selective retransmission control in the data transmission method according to the modification of the third embodiment.

FIG. 10 is a block diagram showing a data transmission device (relay server) in a data transmission system according to a fourth embodiment of the present invention.

FIG. 11 is a block diagram showing a data receiving device (receiving terminal) in the data transmission system according to the fourth embodiment.

FIG. 12 is a sequence diagram for explaining a first example of packet selective retransmission control in the data transmission method according to the fourth embodiment.

FIG. 13 is a sequence diagram for explaining a second example of packet selective retransmission control in the data transmission method of the fourth embodiment.

FIG. 14 is a sequence diagram for explaining a third example of selective packet retransmission control in the data transmission method according to the fourth embodiment.

FIG. 15 is a sequence diagram for explaining a fourth example of selective packet retransmission control in the data transmission method according to the modification of the fourth embodiment.

FIG. 16 is a data transmission device as a relay server in the data transmission system according to the fifth embodiment of the present invention (FIG.
(a)) and a data receiving device (Fig. (b)) as a receiving terminal.

FIG. 17 is a sequence diagram for explaining packet selective retransmission control in the data transmission method according to the fifth embodiment.

FIG. 18 is a block diagram showing a data transmission device (relay server) in a data transmission system according to a sixth embodiment of the present invention.

FIG. 19 is a block diagram showing a data receiving device (receiving terminal) in the data transmission system according to the sixth embodiment.

FIG. 20 is a sequence diagram for explaining retransmission control with packet time limit in the data transmission method according to the sixth embodiment.

FIG. 21 is a sequence diagram for explaining packet retransmission control with time limit in the data transmission method according to the second modification of the sixth embodiment.

FIG. 22 is a sequence diagram for explaining retransmission control with packet time limit in the data transmission method according to the third modification of the sixth embodiment.

FIG. 23 is a block diagram showing a data transmission device (relay server) in a data transmission system according to a seventh embodiment of the present invention.

FIG. 24 is a block diagram showing a data transmission device (relay server) in a data transmission system according to a modified example of the seventh embodiment.

FIG. 25 is a block diagram showing a data transmission device (relay server) in a data transmission system according to an eighth embodiment of the present invention.

FIG. 26 is a block diagram showing a data receiving device (receiving terminal) in the data transmission system according to the eighth embodiment.

FIG. 27 is a diagram for explaining a method of estimating a reproduction time of a terminal by the server in the eighth embodiment, and shows a relationship between a packet time stamp and a packet output time and the like (FIG.
(a)) and time stamp mapping method (Figure (b))
Is shown.

28 is a conceptual diagram for conceptually explaining a conventional video transmission system, in which a server and a terminal are connected by a wired line (FIG. (A)), and a server and a terminal are connected by a wireless line. Connected by networks including (Fig.
(b)) is shown.

FIG. 29 is a block diagram for explaining a data transmitting device as a relay server and a data transmitting device as a distribution server in a data transmission system according to a ninth embodiment of the present invention.

FIG. 30 is a block diagram showing a data receiving device (receiving terminal) in the data transmission system of the ninth embodiment.

FIG. 31 is a sequence diagram for explaining packet selective retransmission control in the real-time transmission method according to the ninth embodiment.

FIG. 32 is a block diagram showing a data transmission device (relay server) in the data transmission system according to the tenth embodiment of the present invention.

FIG. 33 is a block diagram showing a data receiving device (receiving terminal) in the data transmission system according to the tenth embodiment of the present invention.

FIG. 34 is a data structure of a packet for transmitting data by the data transmission method according to each of the above embodiments (FIG.
(a)), the structure of the header of the packet (Fig. (b)), and the definition of header information (Fig. (c)).

[Explanation of symbols]

10a Encoded packet generation means 10b Priority assignment means 11, 21 Reception means 12 Transmission queue management means 13, 13a, 13b Transmission means 14 Retransmission instruction reception means 15 Packet priority determination means 16, 16a Retransmission possibility determination means 17, 17a Retransmission Buffer 18 retransmission buffer management means 22 error packet detection means 23 packet decoding means 24 reception history management means 25, 25a packet priority determination means 26, 26a, 26b retransmission instruction transmission means 31, 41 error correction means 32 sequence number insertion Means 33 sequence number storage means 34 sequence number retransmission number insertion means 35 sequence number retransmission number storage means 36 sequence number retransmission number comparison means 37 retransmission number increment means 38 retransmission number clearing means 39, 43 playback time determination means 42 insertion sequence Reproduction extracting means 51, 51a reproduction instruction receiving means 52 reception history managing means 61 allowable reproduction delay information transmitting means 62, 71 transmission delay measurement packet transmitting / receiving means 63 allowable reproduction delay determining means 72 allowable reproduction delay information receiving means 73 transmission delay measuring means 74 Playback time calculation means 75 Time stamp extraction means 81, 91 High priority sequence number management means 82, 82a Sequence number correspondence management means 83 High priority sequence number insertion means 92 Retransmission sequence output means 93 Retransmission instruction continuous transmission means 101-108 107a, 109, 110 Data transmitters 201-210 Data receivers

Continued front page    (72) Inventor Tatsuya Onishi             4-3-1 Tsunashima-higashi, Kohoku-ku, Yokohama-shi Pana             Sonic mobile communications             Within the corporation (72) Inventor Makoto Hakai             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yoshinori Matsui             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Akihiro Miyazaki             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5K034 AA02 AA07 DD01 EE11 FF01                       FF11 FF13 HH01 HH02 MM21                 5K067 AA33 BB21 CC08 EE02 EE06                       EE10 HH28

Claims (6)

[Claims] 1. Data transmission between a distribution server and a terminal is performed in packet units via a relay server, and at the terminal side,
A data transmission method for sequentially reproducing the data of received packets.When a transmission error occurs between the relay server and the terminal, the relay server resends the error packet based on the retransmission request from the terminal. , When a transmission error occurs between the distribution server and the relay server, the distribution server retransmits the error packet based on the retransmission request transmitted from the terminal via the relay server. Method. 2. The data transmission method according to claim 1, wherein when a transmission error occurs between the distribution server and the relay server, the relay server transmits a retransmission request to the distribution server, and the distribution server relays the request. A data transmission method characterized in that an error packet is retransmitted to the device. 3. A data structure of a packet for data transmission from a transmission side to a reception side, wherein the packet includes a header part storing related information indicating attributes of each packet, and data to be transmitted. And a data section that stores the data, and the header section includes first header information indicating a sequence number corresponding to each packet, second header information indicating a priority of each packet, and the data to be transmitted. A packet data structure comprising at least first and second header information of the third header information indicating the reproduction time on the receiving side. 4. The packet data structure according to claim 3, wherein the header portion of the packet includes attribute information of a transmitted packet transmitted prior to each packet. 5. The packet data structure according to claim 4, wherein the header portion of the packet is the first and second information or the first information as attribute information of a transmitted packet transmitted prior to each packet. And a packet data structure comprising third information. 6. The packet data structure according to claim 3, wherein the header part of the packet has a high priority corresponding to the number of high priority packets transmitted prior to each packet and having a priority higher than a fixed value. A packet data structure characterized by containing a sequence number value.