JPH10308932A - Data transmitting method/device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a real time video, to ensure a short end-to-end delay, to reduce a buffer size and to improve the video quality by collecting plural transmission packets for transmission as a block, copying/retransmitting in a block unit only a packet which needs to be retransmitted when the NAK signal of illegal reception is obtained in a recognition response to a transmission side. SOLUTION: When a NAK signal is contained in a recognition response which a recognition response reception means 16 receives, a block number is set to be a key and an address where the block is preserved is retrieved and obtained by using the table of a preservation place storage means 15. A relative address is calculated from the address by the intra-block packet number of the transmission packet to which transmission is requested and the address where the transmission packet is preserved is obtained. The plural transmission packets to which retransmission is requested are copied and they are transmitted again through a transmission packet transmission means 14. Then, an area where the block is preserved is opened after retransmission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method and a data transmission apparatus, and more particularly to a real-time video transmission method and a real-time video transmission for performing low-delay and high-quality bidirectional video communication even when a network error occurs. The present invention relates to technology effective when applied to a video transmission device.

[0002]

2. Description of the Related Art Conventionally, the transmission of video, which is real-time information, involves a time constraint, and thus, in many cases, recovery from errors and loss of video data occurring during transmission is not performed. However, in this case, the influence to the image quality due to errors and loss of image data that remains is inevitable, in recent years, encodes transmission information in FEC (F orward E rror C rrection ) method (the transmitting side to the recovery, the received (A non-feedback method in which an error is detected and corrected on the side), or an approach in which an existing retransmission control method is applied.

[0003] In the FEC system, dedicated hardware for performing error correction processing is required, and there is a problem that the cost is high. Therefore, a retransmission control system is applied to recover from errors and loss of video data. Is considered to be influential.

When an existing retransmission control method is applied to the transmission of real-time video, a buffer for storing video data is provided on the video transmission side and the video reception side, and a time margin for retransmission is provided. The video transmitting side generates a transmission packet for each fixed unit of video data and transmits the packet to the video receiving side. The video receiving side returns an acknowledgment of transmission packet reception to the video transmitting side every time a transmission packet is received. At this time, if there is a transmission packet in which an error or a loss has occurred during transmission, the video transmission side requests the video transmission side to retransmit the transmission packet, and the video transmission side retransmits the transmission packet for which the retransmission was requested. Normally, in the existing retransmission control method, in order to guarantee that all transmission packets are received by the video receiving side in the correct order, transmission packets having an error or loss during transmission are repeatedly retransmitted until they are received correctly. It is.

[0005]

However, when the existing retransmission control method is applied to real-time video transmission, the following problems occur.

(1) In the case of end-to-end transmission, retransmission of an error or loss transmission packet during transmission is
If it is not completed by the display time of the video data contained in it, until the transmission packet is received correctly,
Even if transmission packets subsequent to the transmission packet are correctly received by the video receiving side, the video data included therein is not displayed, so that the video is interrupted. Similarly, in the case of node-to-node transmission, if the completion of retransmission of an error or loss packet during transmission is delayed, video data to be transmitted to the next node or video display device is interrupted, and finally There are cases where the video is interrupted.

(2) In order to reduce the frequency of occurrence of the problem (1), it is necessary to increase the sizes of buffers on the video transmission side and the video reception side, but this increases end-to-end delay. I will.

(3) Normally, in the existing retransmission control method, a long unit is used for the size of the transmission packet, but the longer the transmission packet size, the higher the packet error rate. Conversely, if the transmission packet is shortened in order to lower the packet error rate, the number of acknowledgments increases, causing an increase in the amount of transmitted words and an increase in processing load accompanying an increase in acknowledgment processing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a data transmission method and a data transmission apparatus in which all video data are free from errors and losses. The present invention provides a technology that can recover an error and a loss of video data while guaranteeing low delay and real-time performance of a video, rather than ensuring that the video data is transmitted to a video receiving side. It is in.

Another object of the present invention is to provide a data transmission method and a data transmission apparatus which have a low delay and real-time video not only when an error occurs in a forward transmission path but also when an error occurs in a backward transmission path. It is an object of the present invention to provide a technique capable of recovering an error and a loss of video data while suppressing a network load while guaranteeing performance.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0012]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

In a data transmission method for transmitting video data generated in real time between nodes or end to end in high quality and in real time, a plurality of transmission packets are grouped together as a block, and And an acknowledgment including an ACK signal indicating that all transmission packets in one block have been correctly received, or an acknowledgment including a NAK signal indicating that any transmission packet in one block has not been correctly received. A response is generated in units of blocks and sent back to the transmitting side. When the acknowledgment in block units from the receiving side includes a NAK signal, the transmitting side copies and transmits only a plurality of transmission packets requiring retransmission. It is characterized by resending to the side.

In the data transmission method, the receiving side may generate, for each of a plurality of blocks received in the past, 1-bit history information indicating whether or not the block has been correctly received, and Generates an acknowledgment including the block of the history information and returns it to the transmitting side,
The transmitting side detects the presence or absence of an error in the received acknowledgment, and when there is an acknowledgment containing an error or a lost acknowledgment, uses the block number included in the acknowledgment correctly received before and after that. The acknowledgment containing the error and the lost acknowledgment are identified for which block, and the history information of the identified block is identified by the block number included in the acknowledgment correctly received thereafter. An acknowledgment that can be obtained from the history information list and contains an error or a lost acknowledgment is NAK
Only when it is determined that the packet includes a signal, a plurality of all transmission packets included in a block for an acknowledgment containing an error or a lost acknowledgment are copied and retransmitted to a receiving side. I do.

[0015] In a data transmission apparatus for transmitting video data generated in real time between nodes and nodes or between end and end in high quality and in real time, the transmission apparatus includes a transmission side buffer and video data input thereto. Input means, video data temporary storage means for temporarily storing input video data in a transmission-side buffer, and generating a transmission packet for each fixed unit of video data in the transmission-side buffer. Is generated, and header information including a block number for identifying the block and an in-block packet number for identifying a transmission packet in the block is added to the transmission packet. Uses a transmission packet and block generation means and a table using the block number as a key Te, a storage location storage means for storing the location in the transmission side buffer of the generated block,
Transmission packet transmitting means for transmitting the transmission packet to a receiving device, acknowledgment receiving means for receiving an acknowledgment from the receiving device, and selecting a transmission packet having a retransmission request,
Retransmitting means for instructing the transmission packet transmitting means to copy a plurality of the transmission packets and retransmitting the transmission packets only once for each transmission packet; and A receiving buffer, a transmission packet receiving unit for receiving a transmission packet transmitted from the transmission device, an error detection unit for detecting an error in the received transmission packet, and detecting an error using the block number and the in-block packet number. Error and loss packet specifying means for specifying a transmission packet including and a lossy transmission packet, and a block for storing a packet number in a block of the transmission packet including an error-containing transmission packet or a lossy transmission packet when the transmission packet includes an error or a lossy transmission packet Packet number storage means and, if one block is received correctly, the block of the received block. If an acknowledgment including the number and the ACK signal is received, if there is a transmission packet containing an error or a lost transmission packet in one received block, it becomes a transmission packet or a loss containing the block number of the received block and the error. Acknowledgment generating means for generating an acknowledgment including the packet number in the block of the transmitted packet and the NAK signal only for the first transmitted block every time one block is received, and transmitting the generated acknowledgment to the transmitting device. Acknowledgment transmitting means for transmitting, video data extracting means for extracting video data included in the received transmission packet, and video data storage for storing the extracted video data in a receiving buffer for a time required for one retransmission Means, and output means for outputting video data.

In the data transmission device, the acknowledgment generation means of the reception device generates, for each of a plurality of blocks received in the past, 1-bit history information indicating whether or not the block was correctly received. The transmitting device generates an acknowledgment including the history information for the past several blocks, and the transmitting device determines whether or not the received acknowledgment has an error. If there is an acknowledgment, an error acknowledgment is used to identify the block to which the acknowledgment containing the error and the lost acknowledgment correspond to the acknowledgment using the block numbers included in the acknowledgment correctly received before and after the acknowledgment. The response specifying means, and the block information and the history information included in the acknowledgment correctly received thereafter, by using the history information of the specified block. Can be obtained from the sequence and acknowledgment NA became acknowledgment or loss contains the error
Block retransmitting means for copying and retransmitting a plurality of all transmission packets included in the block corresponding to the acknowledgment including the error or the lost acknowledgment only when it is determined that the acknowledgment includes the K signal. , Are further provided.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, components having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted.

[Embodiment] FIG. 1 is a block diagram showing a schematic configuration of a real-time video transmission apparatus according to an embodiment of the present invention.

As shown in FIG. 1, in the present embodiment, transmitting apparatus 100 and receiving apparatus 200
00 is connected. The transmission device 100 including the transmission-side buffer 10 includes input means 11 for inputting video data.
A video data temporary storage unit 12 for temporarily storing input video data, a transmission packet and block generation unit 13 for generating transmission packets and blocks, and a transmission packet transmission unit 14 for transmitting the generated transmission packets to the receiving device 200 And the transmission buffer 10 of the generated block
Storage location storage means 15 for storing storage locations in
It comprises an acknowledgment receiving unit 16 for receiving an acknowledgment from the receiving device 200, and a retransmitting unit 17 for retransmitting a transmission packet when a retransmission request is received from the receiving device 200.

Receiving device 20 provided with receiving buffer 20
0 is a transmission packet receiving unit 21 that receives a transmission packet from the transmission device 100, an error detection unit 22 that detects an error in the received transmission packet, and an error and loss packet that specifies an error or loss transmission packet. Identifying means 23, in-block packet number storing means 24 for storing the in-block packet number of an error or loss transmission packet, video data extracting means 25 for extracting video data from the transmission packet, and generating an acknowledgment. Acknowledgment generating means 26, acknowledgment transmitting means 27 for transmitting the generated acknowledgment to transmitting apparatus 100, and video data storage means for storing the extracted video data in receiving buffer 20 for the time required for one retransmission And output means 29 for outputting video data.

Here, when the real-time video transmission is a node-to-node transmission, the input means 11 is connected to the network 111,
The output unit 29 is a network 291, and in the case of end-to-end transmission, the input unit 11 is a video generation and encoding device 112, and the output unit 29 is a decoding and video display device 292.

FIG. 2 is a diagram showing an example of generation of a transmission packet and a block in the present embodiment, and an example of a format of header information included in the transmission packet.

In the example shown in FIG. 2, N bytes are used.
A transmission packet is generated for each of the coded data, and header information H0 is added to the coded data C0 to generate a transmission packet P0. Similarly, by adding header information H1 to the encoded data C1, the transmission packet P1 is added to the encoded data C1.
The transmission packet P4 is generated by adding header information H4 to the transmission packet P4. A block is a group of a plurality of transmission packets. In the example shown in FIG.
A block of transmission packets from 0 to the transmission packet P4 is referred to as a block B1.

The header information H0 to H4 includes a block number F1 for identifying each block, a block packet number F2 for identifying a transmission packet included in the block in each block, and a transmission packet number for each block. Is a retransmission packet F3 indicating whether the packet is a retransmission packet. Here, the block generation means that the block numbers F1 included in the header information of all the transmission packets put together are set to the same number.

FIG. 3 is a diagram for explaining a method of adding the block number F1 and the intra-block packet number F2 in the present embodiment.

In the example shown in the figure, five transmission packets are grouped together into one block, and the upper block and the transmission packet have a longer generation time. As shown in FIG. 3, when the block number for the block B2 is M-1, the transmission packets P11 to P15 included in the block B2 all have the same block number M-1. Since the block number is continuously added to the sequence of the encoded data, the block number for the block B3 is M, and the block number for the block B4 is M + 1. Like the block B2, the transmission packets included in the blocks B3 and B4 Will have the same block number for each block.

On the other hand, the intra-block packet number is independently added in each block, and is continuously added to the arrangement of encoded data in each block. Therefore, block B
2, transmission packet P11 is 0, transmission packet P
12 is 1, transmission packet P13 is 2, transmission packet P1
4 has an intra-block packet number of 3 and the transmission packet P15 has an intra-block packet number of 4.

FIG. 4 is a diagram showing an example of the format of an acknowledgment in the present embodiment.
It is generated by the acknowledgment generation unit 26.

In the figure, the acknowledgment includes a block number O2 indicating which block the acknowledgment is for, and whether or not each transmission packet in each block was correctly received (ACK) or not (NAK). Is included in the response O1. Here, the block number O2 corresponds to the block number F1 of the block corresponding to the acknowledgment, and the response O1 outputs an ACK signal if the acknowledgment is ACK.
If it is AK, it contains a NAK signal. If the acknowledgment is an ACK, the acknowledgment is composed of the block number O2 and the response O1.

When there is a transmission packet in which an error or a loss occurs in the block, a request for retransmission of the transmission packet is made. In addition to the block number O2 and the response O1,
The acknowledgment further includes the number of packets O3 that need to be retransmitted and the identification number O4 in the block of the transmission packet that needs to be retransmitted, that is, a transmission packet containing an error or a lost transmission packet. The in-block identification number O4 is
This is the in-block packet number of the packet that needs to be retransmitted.

FIG. 5 shows a configuration of the video data storage means 28 of the present embodiment for storing the encoded data extracted from the received transmission packet in the reception buffer 20 for the time required for one retransmission. It is a block diagram showing an example.

In the example shown in the figure, a method of providing a queue in the buffer 20 on the receiving side is shown, and the queue from the coded data D1 to the coded data D6 is stored on the receiving side with one block of coded data as one unit. It is provided in the buffer 20. In the queue shown in FIG. 5, the storage time of the coded data at the head of the queue located at the lower side is longer,
Next, when new coded data comes to the end of the queue, the coded data D1 is output to the output means 29, and the coded data D2 to the coded data D6 are respectively shifted by one unit toward the head of the queue. You will slide.

In this queue, when new encoded data comes to the end of the queue, output the encoded data at the head of the queue to the output means 29 regardless of the validity of the encoded data; and By setting the length of this queue to the time required for one retransmission, the encoded data extracted from the received transmission packet can be stored in the reception buffer 20 for the time required for one retransmission.

FIG. 6 is a flowchart showing a processing procedure of transmitting apparatus 100 for transmitting encoded data according to the present embodiment.

The processing of the transmitting apparatus 100 for transmitting coded data is roughly divided into two processings, that is, processing for generating and transmitting transmission packets and blocks and processing after receiving an acknowledgment.
With reference to FIG. 6, a process of generating and transmitting the transmission packet and the block in the transmission device 100 will be described.

As shown in FIG. 6, the encoded data from the input means 11 is stored in the transmission buffer 10 by the video data temporary storage means 12 (602). When the encoded data capable of generating one block is stored, the transmission packet and block generation means 13 generates the transmission packet and the block in the transmission buffer 10 (603).
The generated transmission packet is transmitted by the transmission packet transmitting means 14 to the receiving device 200 via the network 300 (604).

The generated block is stored in the transmission buffer 10 until an acknowledgment corresponding to the block is received from the receiving device 200. The storage location is stored in the storage location storage means 15 in a table using the block number as a key. (605).

Next, the processing after receiving the acknowledgment will be described. When the acknowledgment receiving unit 16 receives the acknowledgment from the receiving device 200 (601), it determines whether the acknowledgment is an ACK or a NAK (606).

If the received acknowledgment is ACK, the address where the block is stored is searched and obtained using the table in the storage location storage unit 15 using the block number as a key, and the area is opened. (60
7). If the received acknowledgment is a NAK, using the table in the storage location storage unit 15, the block number is used as a key to search and acquire the address where the block is stored, and further, the transmission packet requested to be retransmitted. Using the packet number in the block, a relative address from the above address is calculated to obtain an address where the transmission packet is stored, and a plurality of transmission packets for which retransmission has been requested are copied. (608). After retransmission, the area where the block is stored is released.

FIG. 7 is a flowchart showing a processing procedure of receiving apparatus 200 for receiving encoded data according to the present embodiment. With reference to FIG. 7, the processing of receiving apparatus 200 will be described.

The transmission packet transmitted via the network 300 is received by the transmission packet receiving means 21 (701), and as a result of detecting the error of the transmission packet received by the error detecting means 22 (702), there is an error. In this case, the transmission packet is discarded (703). When the transmission packet is correctly received, the retransmission bit F3 included in the header information of each transmission packet is checked, and it is determined whether the transmission packet is the first transmission packet or the retransmitted transmission packet. (70
4).

When the transmission packet transmitted for the first time is received, the encoded data contained in the transmission packet is extracted by the video data extracting means 25, stored in the receiving buffer 20 (705), and contained in the transmission packet. Header information is retrieved.

Since the block number F1 and the intra-block packet number F2 are continuously added to the sequence of the encoded data, the block number F1 and the intra-block packet number F2 included in the header information of the transmission packet,
By comparing the block number F1 and the intra-block packet number F2 included in the header information of the first transmitted transmission packet correctly received immediately before, the presence or absence of an error or a lost transmission packet is determined as an error. And can be checked by the lost packet specifying means 23 (706).

If there is an error or loss transmission packet, the in-block packet number storage means 24 uses the in-block packet number storage unit 24 until the acknowledgment is generated in order to request the transmission apparatus 100 to retransmit the transmission packet. The in-block packet number F2 of the transmission packet is stored (707). When one block has been received (708),
The acknowledgment generation unit 27 generates an acknowledgment for the block.
(709), and the acknowledgment is transmitted to the transmitting device 100 by the acknowledgment transmitting means 27 (710).

When a retransmission packet is received, it is checked whether the same retransmission packet as the retransmission packet has already been correctly received (711). If the same retransmitted packet has not been correctly received before the retransmitted packet, the encoded data included in the retransmitted packet is stored in a predetermined location of the receiving buffer 20 (712), and the same retransmitted packet is already correctly received. If the packet has been received, the retransmission packet is discarded (713).

After the processing for the received transmission packet and the processing for the acknowledgment, if there is encoded data to be outputted in the video data storage means 28 (714), the encoded data is outputted to the output means 29 (715). .

FIG. 8 is a diagram showing a transmission procedure of a transmission packet in the present embodiment. With reference to FIG. 8, a procedure for transmitting a transmission packet in the real-time video transmission device of the present embodiment will be described.

The packet S50 has a block number F1 of 5,
The transmission packet in which the packet number F2 in the block is 0 is 0. Similarly, each transmission packet in FIG. 8 is the block number F1 of each transmission packet in parentheses, and the transmission number is the block number F1 of the transmission packet in the right. It represents the packet number F2.

Transmission packet S50, transmission packet S5
2. Although the transmission packet S59 was correctly received by the receiving device 200, the transmission packet S51 is discarded by the receiving device 200 because an error occurred during transmission.

When the transmission packet S59 is received, an acknowledgment for the block whose block number F1 is 5 is generated and transmitted to the transmitting device 100. The acknowledgment in this case is a NAK, and the receiving device 200 requests the transmitting device 100 to retransmit the transmission packet S51.

The transmitting apparatus 100 copies a plurality of transmission packets S51, and in this case, copies three transmission packets S511, S512, and S513 and retransmits them. The transmission packet S511 is discarded because an error occurs again during transmission.
2 has been received correctly, and at this point the transmission packet S
The retransmission of 51 is successful once. Transmission packet S513
However, since the retransmission of the transmission packet S51 has already been successful in the reception of the transmission packet S512, the transmission packet S513 is discarded. Note that generation and transmission of an acknowledgment from the retransmitted transmission packet S511 to the transmission packet S513 are not performed.

In the transmission packet and block generation means 13 in the present embodiment, for example, when the structured coding method is applied to the coding method, the structure of the coded stream is taken into consideration and the encoded data of one data structure is There is a method for generating a transmission packet. In this case, even if an error or a lost transmission packet cannot be recovered by retransmission, the effect only affects the encoded data for one data structure and extends over the encoded data for two data structures. It has the characteristic that the influence can be minimized.

In the error / loss packet specifying means 23 in this embodiment, for example, the block number F1 of the first transmitted packet correctly received immediately before is 5, and the packet number F2 in the block is 2, if the block number F1 of the subsequently received transmission packet is the same 5 and the intra-block packet number F2 is 4, the block number F1 is 5 and the intra-block packet number F2 is 3 It can be seen that the transmission packet to be received has an error or loss during transmission.
As described above, the continuity of the block number F1 and the intra-block packet number F2 allows the receiving apparatus 200 to specify a transmission packet that has become an error or a loss during transmission immediately after the arrival of the transmission packet.

FIG. 9 is a system configuration diagram showing a schematic configuration of an experimental system according to the real-time video transmission device of the present embodiment.

In the figure, reference numeral 91 denotes a camera, 92 denotes an encoder (ENC), and 93 denotes a personal computer (P).
C) a transmission terminal, 94 is a network, 95 is a network emulator (NEM: device that generates transmission delay and cell loss), 96 is a reception terminal composed of a personal computer (PC), and 97 is a decoder (DE).
C) and 98 are monitors (display devices).

This experimental system assumes an ATM network as a high-speed broadband network. As shown in FIG.
The video from the camera 91 is encoded by the encoder (ENC) 92 in real time in the MPEG2 system, and is actually transmitted by the AAL type 5.

On the network 94, a cell loss (random) and a delay (10 ms) are generated by using a network emulator (NEM) 95, and a transmission terminal including two personal computers (PCs) sandwiching the cell loss is generated. The real-time video transmission device of the present embodiment is mounted. The transmission unit is one transport packet (TS), one packet is five cells (1TS), and one block is ten packets (Case 1). For comparison, one packet is 40 cells (10TS) and one block is one packet (Case 2).

In the present experimental system, 4
Min about the video (Case 1 10 ⁶ packets, Case 2
10 ⁵ packets), and the real-time video transmission apparatus of the present embodiment was evaluated in terms of video quality.

FIGS. 10A and 10B show the actual measurement results. FIG. 10A shows the case 1 and FIG. here,
The packet error rate indicates the ratio of the number of packets containing an error at the time of decoding to the total number of packets (excluding retransmitted packets). The following evaluation can be performed from FIG.

(1) In the case 1, an environment where the cell loss rate is 10 to ³ only by setting the number of copies (the number of retransmissions) to 2
(The image quality is so disturbing that you can't see it.)
In this case, the packet error rate is improved to 10 to ⁵ (the image quality is such that the image is disturbed once or twice per minute).

(2) When compared at the same copy number, the packet error rates of Case 1 and Case 2 are about 10 times different, and Case 1 having a smaller packet size has a greater improvement in video quality.

(3) Since the packet containing the error is discarded, the effect on the video quality when the packet cannot be remedied by retransmission is larger in Case 2 where the packet size is large.

(4) In the method of the present experimental system, the retransmission is limited to one time. However, the image quality can be considerably improved by copy transmission of the retransmitted packet, and the smaller the packet size is, the better. The improvement in video quality was found to be greater.

As described above, according to the present embodiment, the retransmission of a transmission packet having an error or a loss during transmission is 1
Time-to-end, in the case of end-to-end transmission, the time from the arrival of video data to the display of that video data,
In the case of node-to-node transmission, the time from the arrival of video data to the transmission of the video data to the next node or video display device is the time required for one retransmission, and the low end-to-end delay is low. The amount of video data that can be guaranteed and is stored in the receiving buffer 20 of the receiving device 200 that is the video receiving side is within the time required for one retransmission.
The amount of video data arriving at 00 may be sufficient, and the buffer size can be reduced.

When the video data received by the receiving apparatus 200 is stored in the receiving buffer 20 for a time corresponding to the time for performing one retransmission, the video data is irrespective of its own or the validity of the previous video data. Output means 29
Since the video data is output to the output unit 29, it is guaranteed that the video data reaches the output unit 29 stably, and the video is not interrupted, and the real-time performance of the video can be guaranteed.

In addition, if even one of the transmission packets copied and retransmitted in plural copies is correctly received by the receiving apparatus 200, the retransmission is successful, and the recovery of the error or loss of the video data becomes impossible. Therefore, the quality of the displayed image can be improved.

Further, transmitting apparatus 100 generates a packet as a transmission unit and a block in which a plurality of the transmission packets are put together. That is, the receiving apparatus 200 has a two-layer structure of a packet and a block, and the receiving apparatus 200 generates an acknowledgment in block units, that is, returns an acknowledgment of each transmission packet included in one block as one acknowledgment. By not returning an acknowledgment of the retransmitted transmission packet, it is possible to reduce the amount of transmitted pack words, that is, to reduce the number of acknowledgments, thereby reducing acknowledgment processing.

Thus, according to the real-time video transmission apparatus of the present embodiment, when applied to real-time transmission of video data generated in real time, a forward transmission path for transmitting a transmission packet from a transmission apparatus to a reception apparatus. , Real-time video communication with low delay and high quality is possible.

[Second Embodiment] In the real-time video transmission apparatus of the first embodiment, the receiving apparatus 200
No countermeasures are taken for the case where an error occurs in the backward transmission path for transmitting the acknowledgment to 0 and the acknowledgment becomes erroneous. Therefore, if the transmitting device 100 fails to correctly receive an acknowledgment, the transmitting device 100 cannot know whether the acknowledgment was ACK or NAK. In this case, as the processing method of the transmitting apparatus 100, there are the following two methods.

(Method 1) It is determined that all acknowledgments that resulted in errors are NAKs, and all transmission packets included in the block corresponding to the acknowledgment are retransmitted.

(Method 2) It is determined that all of the acknowledgments that resulted in errors were ACKs, and the transmission packet included in the block corresponding to the acknowledgment is not retransmitted.

In the above (method 1), all the transmission packets included in the block corresponding to the erroneous acknowledgment are retransmitted. Therefore, even if the erroneous acknowledgment is actually NAK, retransmission is performed as requested. That is, it is possible to recover an error or lost transmission packet.

However, since the probability of being an ACK is higher than the probability of being an NAK in a normal acknowledgment, a large number of useless retransmissions of retransmitting one block in spite of the fact that an ACK is actually performed are performed. A network load problem may occur, and in the worst case, unnecessary retransmission may cause congestion.

In the above (method 2), since unnecessary retransmission is not performed, there is no influence on the network load. However, conversely, in spite of the fact that the incorrect acknowledgment is actually a NAK, the requested transmission packet may not be retransmitted, and the error or loss of the transmission packet cannot be recovered. There is.

The real-time video transmission apparatus of this embodiment guarantees low delay and real-time video not only when an error occurs in the forward transmission path but also when an error occurs in the backward transmission path. Thus, error and loss of video data are recovered while suppressing the network load.

FIG. 11 is a block diagram showing a schematic configuration of a real-time video transmission apparatus according to another embodiment of the present invention.

As shown in the figure, the real-time video transmission apparatus according to the present embodiment includes an acknowledgment error detecting means 18 for detecting an error in an acknowledgment received by the transmitting apparatus 100, An error acknowledgment specifying unit 19 for specifying which block the acknowledgment that resulted in the loss was an acknowledgment, and the history information of the specified block is stored in the acknowledgment that is correctly received thereafter. Only when it is determined that the acknowledgment containing the error or the lost acknowledgment was obtained from the sequence of information and was a NAK, the block for the acknowledgment containing the error or the lost acknowledgment is Copy and resend all of the included transmission packets, and if the history information of the specified block cannot be obtained, confirm the error including the error. Or acknowledgment became Ross A
A block retransmitting means 30 that is considered to have been a CK,
The acknowledgment generation unit 26 of the receiving device 200 generates history information for the past m blocks, generates an acknowledgment including the history information for the past m blocks, and returns the acknowledgment to the transmitting device 100. , Is different from the real-time video transmission device of the embodiment.

FIG. 12 shows an example of the format of an acknowledgment generated by the acknowledgment generating means 26 of the present embodiment.

In the format example shown in the figure, the acknowledgment includes a block number O2 indicating which block the acknowledgment is for, and whether each transmission packet in each block was correctly received (ACK). No (NA
K) and response information O5 for the past m blocks. If the acknowledgment is a NAK,
To make a retransmission request to the transmitting device, the number of packets O3 requiring retransmission and the intra-block packet number O4 of the packet requiring retransmission are further included in the acknowledgment.

As described above, the format example shown in FIG. 12 differs from the format example of the acknowledgment shown in FIG. 4 in that the history information O5 for the past m blocks is added to the format of the acknowledgment.

As described above, the response O1 includes the ACK signal if the acknowledgment is ACK, and includes the NAK signal if the acknowledgment is NAK, and can be represented by 1 bit. Also, the history information of the past block, that is, the block is ACK
Or NAK can also be represented by 1 bit, and the history information for m blocks is m
It can be represented by bits.

The history information O5 for the past m blocks in the format example shown in FIG. 12 is history information for m blocks from the block corresponding to the immediately preceding acknowledgment to the block corresponding to the m acknowledgments going back m times.
Therefore, the history information O5 for the past m blocks shown in FIG.
In, the bit located to the left, that is, the history information located to the left is the history information of the block corresponding to the earlier acknowledgment, and the history information of the block corresponding to the immediately preceding acknowledgment is the history information located to the far right. It has become.

Therefore, the transmitting apparatus 100 determines from the block number of the correctly received acknowledgment and the sequence of this history information that the acknowledgment containing the error or the history information of the block corresponding to the lost acknowledgment has been correctly received. It is possible to check whether it is included in the response and to know where the history information is.

That is, when an erroneous acknowledgment is detected by the acknowledgment error detecting means 18 of the transmitting apparatus 100, or when there is a lost acknowledgment, the error acknowledgment specifying means 19 includes the acknowledgment in the acknowledgment. Due to the continuity of the block numbers, before and after the acknowledgment that was not received correctly (the acknowledgment including the error or the acknowledgment that was lost), the acknowledgment that could not be received correctly is obtained from the block number of the acknowledgment received correctly Can be easily identified.

Further, the block retransmitting means 30 checks the block history information for the acknowledgment that could not be received correctly, which is included in the acknowledgment correctly received thereafter, and the transmitting apparatus 100 could not receive the acknowledgment correctly. It is possible to know whether the acknowledgment was an ACK or a NAK.

In the example shown in FIG. 12, since one acknowledgment includes the history information of the past m blocks, the m acknowledgments following the acknowledgment that could not be received correctly are included in the correct acknowledgment. Block history information for an acknowledgment that could not be received is always included. Therefore, as long as there is no situation in which m consecutive acknowledgments cannot be correctly received, transmitting apparatus 100 can obtain the history information of the block corresponding to the acknowledgment that could not be correctly received. If m consecutive acknowledgments cannot be received correctly, it is not possible to obtain the block history information for the acknowledgment that could not be received correctly. (Generally, the acknowledgment error is small).

FIG. 13 is a diagram showing a transmission procedure of a transmission packet and an acknowledgment in this embodiment. With reference to FIG. 13, a transmission procedure of a transmission packet and an acknowledgment in the present embodiment will be described.

In the example shown in FIG. 13, one block is composed of five transmission packets.
The figure shows a case where the transmission packet and the acknowledgment are transmitted.

The transmitting apparatus 100 generates a transmission packet and a block, and sequentially transmits the generated transmission packet to the receiving apparatus 200. When the receiving apparatus 200 finishes receiving one block, it generates an acknowledgment for the block. Then, it transmits to transmitting apparatus 100.

The transmission packet (6-
Since 1) results in an error during transmission, it is discarded in the receiving device 200, and the receiving device 200 generates an acknowledgment for the block 6 as a NAK and transmits it to the transmitting device 100.

Since the acknowledgment to block 6 has an error during transmission, the transmitting apparatus 100 cannot correctly receive the acknowledgment, and the transmitting apparatus 100 cannot know the contents of the acknowledgment to block 6; 7, the error acknowledgment specifying means 19
Then, it is detected that the acknowledgment of the block 6 has been lost, and the block retransmitting means 30 determines that the acknowledgment of the block 6 is NAK based on the history information of the block 6 included in the acknowledgment of the block 7 received correctly. It is possible to know what happened.

Therefore, transmitting apparatus 100 copies a plurality of transmission packets included in block 6 (two copies in the example shown in FIG. 13) and retransmits them to receiving apparatus 200 by block retransmitting means 30. I do. Here, if it is determined that the acknowledgment of block 6 is ACK, in that case, there is no need to retransmit, so that the transmission packet included in block 6 is not retransmitted.

The transmitting apparatus 100 cannot know from the history information which transmission packet included in the block 6 should be retransmitted, and therefore retransmits all the transmission packets included in the block 6 and once. In order to increase the success rate of retransmission of a transmission packet limited to the above, a plurality of retransmission packets are copied and retransmitted.

Here, in the example shown in FIG. 13, the retransmitted transmission packet (6-0) and the transmission packet (6-1) have an error during transmission, but the transmission packet (6 Since 1) was correctly received, the retransmission of the transmission packet (6-1) that originally required retransmission has succeeded. Here, in the data transmission method of the present embodiment, retransmission of a transmission packet is limited to one time, so that an acknowledgment for the retransmission packet is not required.

As described above, in the present embodiment, when there is an acknowledgment that could not be correctly received by transmitting apparatus 100, transmitting apparatus 100 cannot correctly receive the acknowledgment due to the continuity of the block numbers included in the acknowledgment. From the block number of the acknowledgment correctly received before and after the unacknowledged acknowledgment, the unacknowledged acknowledgment can be easily specified. For example, in the example shown in FIG. 13, the block 6 can be specified from the block numbers of the blocks 5 and 7.

FIG. 14 and FIG. 15 are diagrams showing actual measurement results of an experimental system according to the real-time video transmission apparatus of the present embodiment.

As shown in FIG. 9, the experimental system assumes an ATM network as a high-speed broadband network.
The video from the camera 91 was encoded in real time by the encoder (ENC) 92 in the MPEG2 system, and actually transmitted by AAL type 5. On the network 94, a cell loss (random) and a delay (10 ms) are generated using a network emulator (NEM) 95, and two personal computers (P
The real-time video transmission device of the present embodiment is mounted on the transmitting terminal C).

In this experimental system, cell loss and delay of 10 m were applied to both the forward transmission path and the backward transmission path.
sec was generated and an actual measurement was performed. Here, the cell loss in the forward transmission path is a random cell loss with a cell loss rate of 10 to ³ . The transmission unit is 5 transport cells (1TS) for each transport stream (TS) and 10 transport packets for one block. Further, the number of copies of the retransmission packet is 3, and the history information included in each acknowledgment is the history information of the past 4 blocks.

In this experimental system, each video of about 4 minutes, that is, 10 ⁶ transmission packets is transmitted,
In the case where a random cell loss occurs in the backward transmission path (Case 1) and a case where a burst cell loss of 1 to 8 continuous cells occurs (Case 2), in terms of video quality and network load. The real-time video transmission device of the present embodiment was evaluated.

FIG. 14 shows the case 1 and FIG. 15 shows the case 2. 14 (a) and FIG.
In (a), the number of residual error packets indicates the number of transmission packets that could not be rescued by retransmission at the time of decoding, and the packet increase rate in FIGS. 14 (b) and 15 (b). Represents the percentage of the number of retransmission packets to the number of transmission packets to be transmitted. The following evaluations can be made from FIG. 14 and FIG.

(1) According to FIG. 14A, in case 1, in the conventional method without history information, there are several error packets remaining in an environment with a cell loss rate of 10 to ⁴ or more in the conventional method. Therefore, the number of residual error packets is 0 in the real-time video transmission device of this embodiment with history information, and the video quality is improved by using the real-time video transmission device of this embodiment with history information. It is possible to

(2) As shown in FIG. 15 (a), in case 2, the number of acknowledgments that are continuously in error may be larger than the number of history information included in the acknowledgment. Although there are several transmission packets that cannot be rescued by using the real-time video transmission device of the present embodiment, the real-time video transmission device of the present embodiment with history information can be used for real-time video without history information. It is possible to improve the video quality over the transmission device.

(3) From FIGS. 14 (b) and 15 (b),
In both cases 1 and 2, the packet growth rate of the real-time video transmission device with history information according to the present embodiment is substantially the same as that of the real-time video transmission device without history information. The rate of increase is less than 2%.

In this embodiment, since the acknowledgment is one cell, the number of ATM cells transmitted on the backward transmission path does not increase by including 4 bits of history information in the acknowledgment. , There was no effect on the amount of backward transmission.

As described above, according to the present embodiment, even if there is an acknowledgment containing an error or a lost acknowledgment in transmitting apparatus 100, the acknowledgment correctly received thereafter will be included in the acknowledgment. If the block history information for the acknowledgment including the error or the lost acknowledgment is included, the transmitting apparatus 100 determines whether the acknowledgment including the error or the lost acknowledgment is ACK or NAK. It is possible to know. Therefore,
Only when it is known to be NAK, by retransmitting all transmission packets included in the block for the acknowledgment including the error or the lost acknowledgment, it is possible to reduce the amount of unnecessary retransmission, that is, keep the network load low. Meanwhile, it is possible to recover an error or loss of the transmission packet.

Also, by including the history information of the past several blocks in one acknowledgment, the acknowledgment containing the error or the history information of the block corresponding to the lost acknowledgment can be confirmed after that. Since it is not included in the response, it is possible to reduce the probability of occurrence of a case where it is not known whether the acknowledgment including the error or the lost acknowledgment was ACK or NAK.

This is because whether the acknowledgment containing the error or the lost acknowledgment is ACK or not.
Even in the case where it is not known whether or not the AK is AK, the probability that the acknowledgment including the error or the lost acknowledgment is NAK can be reduced.

Further, since the history information of each past block is represented by one bit, the past m
Even if the history information for the block is included, the increase in the acknowledgment size due to it is m bits, and the influence on the backward transmission amount by including the history information in the acknowledgment is small.

As described above, the invention made by the present inventor is:
Although a specific description has been given based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the invention.

For example, the video data used in the description so far includes, of course, all data composed of audio data and image data, only data composed of image data, or all composed only of audio data.

[0111]

The effects obtained by typical ones of the inventions disclosed by the present application will be briefly described as follows.

(1) According to the present invention, retransmission of a transmission packet is limited to one time, and video data is stably output to an output unit, thereby real-time performance of video and low end-to-end delay. And the buffer size can be reduced.

(2) According to the present invention, a plurality of retransmission packets are copied and retransmitted, so that the video quality can be improved.

(3) According to the present invention, by returning an acknowledgment of a transmission packet included in one block as one acknowledgment, it is possible to reduce the number of acknowledgments and reduce acknowledgment processing.

(4) According to the present invention, each acknowledgment
Since multiple pieces of history information of past blocks represented by bits are included, even if there is an acknowledgment that could not be received correctly at the transmitting device, an acknowledgment that contains errors correctly after that If the history information of the block corresponding to the response or the lost acknowledgment is included, the transmitting apparatus transmits the acknowledgment including the error or the lost acknowledgment to the ACK signal or the NAK.
It is possible to know whether a signal was included.

(5) According to the present invention, the transmitting apparatus responds to the acknowledgment only when it is determined that the acknowledgment including the error or the lost acknowledgment includes the NAK signal based on the history information. Since a plurality of transmission packets included in the block are copied and retransmitted, it is possible to improve the video quality while keeping the network load low.

(6) According to the present invention, the history information of each past block is represented by one bit. Therefore, even if the history information of the past m blocks is included in each acknowledgment, the confirmation by that is confirmed. The increase in the response size is m bits, and it is possible to reduce the influence on the backward transmission amount caused by including the history information in the acknowledgment.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a real-time video transmission device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of generation of a transmission packet and a block and an example of a format of header information included in the transmission packet according to the first embodiment.

FIG. 3 is a diagram for explaining a method of adding a block number F1 and an intra-block packet number F2 according to the first embodiment.

FIG. 4 is a diagram showing an example of a format of an acknowledgment in the first embodiment.

FIG. 5 is a block diagram illustrating an example of a configuration for storing encoded data extracted from a received transmission packet in a receiving buffer for a time necessary for one retransmission in the video data storage unit according to the first embodiment; FIG.

FIG. 6 is a flowchart showing a processing procedure of a transmitting apparatus for transmitting encoded data according to the first embodiment.

FIG. 7 is a flowchart illustrating a processing procedure of a receiving device that receives encoded data according to the first embodiment.

FIG. 8 is a diagram showing a transmission procedure of a transmission packet in the first embodiment.

FIG. 9 is a system configuration diagram showing a schematic configuration of an experimental system according to the real-time video transmission device of the first embodiment.

FIG. 10 is a diagram showing actual measurement results of the experimental system shown in FIG.

FIG. 11 is a block diagram showing a schematic configuration of a real-time video transmission device according to another embodiment of the present invention.

FIG. 12 is a diagram showing an example of a format of an acknowledgment according to the second embodiment.

FIG. 13 is a diagram showing a transmission procedure of a transmission packet and an acknowledgment in the second embodiment.

FIG. 14 is a diagram showing actual measurement results by an experimental system according to the real-time video transmission device of the second embodiment.

FIG. 15 is a diagram showing actual measurement results by an experimental system according to the real-time video transmission device of the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Transmission side buffer, 11 ... Input means, 12 ... Video data temporary storage means, 13 ... Transmission packet and block generation means, 14 ... Transmission packet transmission means, 15 ... Storage location storage means, 16 ... Confirmation response receiving means, 17 ... retransmission means,
18 acknowledgment error detection means, 19 error acknowledgment identification means, 30 block retransmission means, 20 reception buffer, 21 transmission packet reception means, 22 error detection means, 23 error and loss packet identification means, 24: Packet number storage unit in block, 25: Video data extraction unit, 26: Confirmation response generation unit, 27: Confirmation response transmission unit, 28: Video data storage unit, 29: Output unit, 91
... Camera, 92 ... Encoder (ENC), 93 ... Transmission terminal, 94 ... Network, 95 ... Network emulator (NEM), 96 ... Reception terminal, 97 ... Decoder (D
EC), 98 monitor, 100 transmitter, 112 video generator and encoder, 111, 291, 300 network, 200 receiver, 292 decoding and video display, O1 response, O2 block No., O3: number of packets requiring retransmission, O4: packet number in a block of packets requiring retransmission, O5: history information of past m blocks, C0, C1, C4: coded data, H0, H
1, H4: header information, P0, P1, P4, P11 to P
15, P21 to P25, P31 to P35, S50, S5
1, S52, S59, S511, S512, S513 ...
Transmission packet, B1 to B4 block, F1 block number, F2 packet number within block, F3 retransmission bit, D1 to D6 encoded data.

Claims (9)

[Claims] An image data generated in real time is stored in a node
A data transmission method for transmitting high-quality and real-time data between nodes or end-to-end. In a data transmission method, a set of multiple transmission packets is grouped into blocks, and the reception side receives all transmission packets in one block correctly. An acknowledgment including an ACK signal indicating that the transmission has been performed or an acknowledgment including a NAK signal indicating that any transmission packet in one block has not been correctly received is generated in block units and returned to the transmission side. ,
A data transmission method on the transmitting side, wherein when the block-based acknowledgment from the receiving side includes a NAK signal, only a plurality of transmission packets requiring retransmission are copied and retransmitted to the receiving side. 2. A method for transmitting video data generated in real time to a node
In a data transmission method for transmitting high-quality and real-time between nodes, a transmission side transmitting input video data temporarily stores video data input from a network in a transmission side buffer,
In the transmission-side buffer, a transmission packet is generated for each fixed unit of video data, and further, a block in which a plurality of the transmission packets are grouped together is generated, and the transmission packet includes a block for identifying a block. A header information including a number and a packet number in a block for identifying a transmission packet in the block is added, and the storage location of the generated block in the transmission buffer is stored using a table using the block number as a key. Transmitting the transmission packet to a receiving device, receiving an acknowledgment from the receiving device, selecting a transmission packet for which a retransmission request has been made, and instructing that a plurality of the transmission packets be copied and retransmitted. Retransmission processing is performed only once for each transmission packet, and the receiving side that receives video data The transmission packet transmitted from the transmitting side is received, an error of the received transmission packet is detected, and the transmission packet including the error and the transmission packet having the loss are identified using the block number and the packet number in the block, and the error is identified. If there is a transmission packet including a transmission packet or a lossy transmission packet, the packet number in the block of the transmission packet is stored. If one block is correctly received, the block number of the received block and A
If the received acknowledgment including the CK signal includes a transmission packet containing an error or a lost transmission packet in one received block, the block number of the received block and a transmission packet containing an error or a lost transmission packet are included. An acknowledgment including the packet number in the block of the packet and the NAK signal is generated only for the first transmitted block every time one block is received and transmitted to the transmitting device, and included in the received transmission packet. A data transmission method, comprising extracting video data to be extracted, storing the extracted video data in the reception buffer for a time required for one retransmission, and outputting the video data to a network. 3. End-time video data generated in real time
In a data transmission method for transmitting high-quality and real-time between ends, the input video data on the transmission side is video data from a video generation and encoding device, and the output video data on the reception side is decoded and 3. The data transmission method according to claim 2, wherein the data is video data output to a video display device. 4. The reception side generates, for each of a plurality of blocks received in the past, 1-bit history information indicating whether or not the block has been correctly received,
An acknowledgment including the history information for the past several blocks is generated and returned to the transmitting side. The transmitting side detects the presence or absence of an error in the received acknowledgment, and confirms the acknowledgment including the error or the loss. If there is a response, use the block number included in the acknowledgment correctly received before and after that to identify the block to which the acknowledgment containing the error and the lost acknowledgment were the acknowledgment, and specify the identification. Can be obtained from the block number and the sequence of the history information included in the acknowledgment correctly received thereafter, and the acknowledgment including the error or the acknowledgment that has been lost is NAK.
Only when it is determined that the packet includes a signal, a plurality of all transmission packets included in a block for an acknowledgment containing an error or a lost acknowledgment are copied and retransmitted to a receiving side. The data transmission method according to any one of claims 1, 2 and 3, wherein 5. The transmitting side, if the history information of the block specified by the acknowledgment including the error or the lost acknowledgment cannot be obtained, the acknowledgment including the error or the lost acknowledgment. 5. The data transmission method according to claim 4, wherein the response is regarded as including an ACK signal. 6. A data transmission device, comprising a transmission device and a reception device, for transmitting video data generated in real time between nodes with high quality and in real time, wherein the transmission device comprises: a transmission buffer; Input means for inputting video data from the network, video data temporary storage means for temporarily storing the input video data in a transmission buffer, and generating a transmission packet for each fixed unit of video data in the transmission buffer. Further, a block in which a plurality of the transmission packets are grouped together is generated, and the transmission packet includes a block number for identifying the block and an in-block packet number for identifying the transmission packet in the block. Transmission packet and block generation means for adding header information including A storage location storing means for storing a storage location of the generated block in the transmission-side buffer, a transmission packet transmitting means for transmitting the transmission packet to a receiving device, and receiving an acknowledgment from the receiving device. One acknowledgment receiving unit and a retransmission process for selecting a transmission packet for which a retransmission request has been made, and instructing the transmission packet transmission unit to copy a plurality of the transmission packets and retransmit the same are performed for each transmission packet. A retransmission unit that performs transmission only on a transmission basis, the reception device detects a reception buffer, a transmission packet reception unit that receives a transmission packet transmitted from the transmission device, and detects an error in the received transmission packet. A transmission packet including an error and a transmission packet having a loss using an error detection unit, a block number and a packet number in a block. And error and loss packet specifying means for specifying, when there is transmission packet that the transmission packet or loss includes an error, the block packet number storage means for storing the block packet number of the transmission packet, 1
If the block is received correctly, an acknowledgment including the block number of the received block and the ACK signal is sent. If there is an erroneous or lost transmission packet in one of the received blocks, the received block is returned. Block number and NAK and the packet number in the block of a transmission packet containing an error or a lost transmission packet
An acknowledgment generating means for generating an acknowledgment including a signal only for each block transmitted for the first time each time one block is received, an acknowledgment transmitting means for transmitting the generated acknowledgment to the transmitting device, Video data extraction means for extracting video data included in the transmission packet from the transmission packet, video data storage means for storing the extracted video data in a receiving buffer for a time required for one retransmission, and outputting the video data to a network A data transmission device comprising output means. 7. A data transmission device comprising a transmission device and a reception device for transmitting video data generated in real time between end and end with high quality and in real time, wherein the input means of the transmission device includes: 7. The data transmission device according to claim 6, wherein the video data from the video generation and encoding device is input, and the output unit of the receiving device outputs the video data to a decoding and video display device. 8. The acknowledgment generation means of the receiving device generates, for each of a plurality of blocks received in the past, 1-bit history information indicating whether or not the block has been correctly received, The transmitting device generates an acknowledgment including the history information of the acknowledgment, and the transmitting device has an acknowledgment error detecting means for detecting the presence or absence of an error in the received acknowledgment, and an acknowledgment including an error or an acknowledgment that has been lost In the case, using the block number included in the acknowledgment correctly received before and after the acknowledgment, error acknowledgment identification means for identifying to which block the acknowledgment including the error and the acknowledgment that has resulted in a loss, and , The history information of the identified block can be obtained from the block number and the sequence of the history information included in the acknowledgment correctly received thereafter, and NA acknowledgment that became the acknowledgment or loss including the error of
Block retransmitting means for copying and retransmitting a plurality of all transmission packets included in the block corresponding to the acknowledgment including the error or the lost acknowledgment only when it is determined that the acknowledgment includes the K signal. The data transmission device according to claim 6, further comprising: 9. The block retransmitting means, if the history information of the block specified by the acknowledgment containing the error or the lost acknowledgment cannot be obtained, returns the acknowledgment containing the error or a loss. Acknowledgment is ACK
9. The data transmission apparatus according to claim 8, wherein all the transmission packets included in the specified block are not retransmitted assuming that the data transmission includes a signal.