JP2004349891A - Packet transmitting device, packet receiving device, method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improved the communication quality of communication processing for data packets by increasing a frequency of resending using encoded packets for forward error correction. <P>SOLUTION: A transmitting device 3 is equipped with an original data storage part 31 which stores original data regarding transmission, an encoding part 32 which encodes redundant data for error correction from the original data regarding the transmission, a resending data storage part 33 which stores part of the encoded redundant data as data for resending, a data packet transmission part 35 which transmits the original data and part or the whole of the redundant data, and a request-to-resend reception part 37 which receives a request to resend from a transmission destination. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a packet transmission device, a packet reception device, a method, and a program related to error recovery of data in packet communication.
[0002]
[Prior art]
As one form of packet communication, there is a multicast method for collectively distributing the same packet to a plurality of clients. In this multicast method, as shown in FIG. 10, a packet 15 transmitted from a server 11 is distributed to a plurality of client terminals 14 via an access point 13 such as a router 12 or a wireless LAN router.
[0003]
By the way, in such a multicast system, there is a case where any one of the plurality of client terminals 14 cannot receive a necessary packet. In this case, a retransmission request is made to the server 11, but if a retransmission request is made to the server 11 every time a reception packet is lost, the server load and the consumption of communication resources become excessive. An error recovery technique is employed so that a lost packet can be recovered on the client terminal 14 side.
[0004]
Forward error correction (FEC) is one of error recovery techniques. In transmitting and receiving a data packet, a transmitting side adds redundant data by encoding to original data to be transmitted and transmits the data packet. This is a method in which, on the side side, the received original data and redundant data are used to recover the insufficient packets that could not be received and to perform error correction (for example, see Non-Patent Documents 1 and 2).
[0005]
Conventionally, several encoding algorithms are known, but when one of them, Reed-Solomon Erasure Code, is used, the total number of encoded data packets for generating redundant data is up to 256. (Non-Patent Document 2).
[0006]
Further, the encoding method developed by Digital Foundation can generate encoded data for redundant data indefinitely. If a specific number of data packets are collected from arbitrary encoded data, the original data packet can be obtained. Can be decoded. However, such a unique method has a problem of license fee and has not been widely used.
[0007]
[Non-patent document 1]
Nagayoshi Nagauchi, “Reliable Multicast”, IPSJ Magazine, pp. 754-759, Vol. 42, no. 8, Aug. 2001
[0008]
[Non-patent document 2]
Weimoto Suzuki, et al., "Study of FEC / ARQ Hybrid Control Method for Mobile Multicast Communication," IEICE Technical Report, SST 2001-139, A.P. 2001.287, pp. 75-82
[0009]
[Problems to be solved by the invention]
When forward error correction is used as error recovery in data packet communication as described above, the number of data packets that can be used for retransmission is limited to the range of the number of data packets encoded and generated at the first transmission. There is a problem that the number of retransmissions for recovery is limited.
[0010]
In view of the above, the present invention has been made in view of the above points, and increases the number of redundant data packets by repeating forward error correction encoding of data packets. An object of the present invention is to provide a packet transmission device, a packet reception device, a method, and a program that can increase the number of retransmissions using a packet and improve communication quality.
[0011]
[Means for Solving the Problems]
In order to solve the above problem, the present invention generates redundant data for error correction from original data related to transmission when packet data is transmitted, and stores a part of the redundant data as data for retransmission. At the same time, part or all of the original data and the redundant data are transmitted. Until the necessary data is transmitted, a retransmission request for the insufficient data is received from the transmission destination, and new redundant data is further generated from the accumulated retransmission data, and the new redundant data is transmitted to the retransmission data. And transmit some or all of the redundant data and part or all of the new redundant data.
[0012]
Further, the present invention, when receiving the packet data, receives the original data for transmission, and redundant data for error correction generated from the original data, until the necessary data is received, the shortage of A data retransmission request is transmitted to the transmission source, and part or all of the redundant data accumulated on the transmission side as data for retransmission, and part or all of new redundant data further generated from the data for retransmission, The data is received as redundant data related to retransmission, and original data related to transmission is generated from the original data, the redundant data, and the redundant data related to retransmission.
[0013]
It should be noted that the data transmission in the above invention can be performed by a multicast method in which a plurality of other communication devices connected to the packet transmitting device are collectively transmitted.
[0014]
According to the present invention, on the transmission side, the data packet is encoded for forward error correction, the number of redundant data packets is increased and transmitted, and when a retransmission request is received, the data packet is already encoded. Redundant data can be further forward-error-corrected encoded, and transmitted with more redundant data packets.
[0015]
In the above invention, the transmitting side stores the number of retransmissions, describes the number of retransmissions in data related to transmission, and detects the number of retransmissions of the data described in the received data on the receiving side. However, it is preferable to generate original data according to the detected number of retransmissions.
[0016]
Thus, in a communication protocol that does not guarantee ordering, even when the order of data packets may be changed due to network delay or error, the information on the number of retransmissions is described in the data packet so that The data packet required for decoding can be identified, and the original data packet can be obtained by repeating decoding sequentially using data having the same number of retransmissions.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
(System configuration)
FIG. 1 is a configuration diagram illustrating the overall configuration of the packet communication system according to the embodiment of the present invention.
[0019]
As shown in the figure, in the packet communication system according to the present embodiment, a server 21 and a client terminal 24 are connected via a router HUB 22 and an access point 23. Note that the data transmission in the present embodiment is performed by a multicast method in which a plurality of other client terminals 24 connected to the server 21 are collectively transmitted. That is, the data packet 25 distributed from the server 21 reaches the client terminal 24 via the router HUB 22 and the access point 23.
[0020]
The server 21 includes the transmitting device 3 of the present invention, and each client terminal 24 includes the receiving device 4. FIG. 2 is a block diagram illustrating an internal configuration of the transmission device 3 according to the present embodiment.
[0021]
As shown in the figure, the transmission device 3 includes an original data storage unit 31 for storing original data for transmission, an encoding unit 32 for encoding redundant data for error correction from the original data for transmission, A retransmission data storage unit 33 for storing a part of the redundant data as retransmission data, a data packet transmission unit 35 for transmitting the original data and a part or all of the redundant data, and receiving a retransmission request from a transmission destination. And a retransmission request receiving unit 37 that performs the retransmission request.
[0022]
Further, the transmission device 3 includes a retransmission number storage unit 34 that stores the number of retransmissions by the data packet transmission unit 35, a multiplicity management unit 38 that describes the number of retransmissions in data related to transmission, and data transmission / reception that transmits / receives various data. A section 36 and a control section 39 for controlling each of the above sections are provided.
[0023]
The encoding unit 32 has a function of generating new redundant data from retransmission data in response to the retransmission request received by the retransmission request receiving unit 37. Also, the retransmission data storage unit 33 stores the new redundant data as retransmission data,
The data packet transmitting unit 35 has a function of transmitting a part or all of the redundant data and a part or all of the new redundant data in response to the retransmission request received by the retransmission request receiving unit 37.
[0024]
FIG. 3 is a block diagram illustrating an internal configuration of the receiving device 4 in the present embodiment.
[0025]
As shown in the figure, the receiving device 4 is capable of receiving an original data storage unit 31 for storing received original data 41, a data packet receiving unit 45 for receiving original data and redundant data, and receiving necessary data. A retransmission request transmitting unit 47 that transmits a retransmission request for the insufficient data to the server 21 when there is no redundant data; a redundant data storage unit 43 that stores the received redundant data and the retransmitted redundant data; , Redundant data and a retransmitted redundant data, and a decoding unit 42 for decoding original data related to transmission.
[0026]
Further, the receiving device 4 includes a multiplicity interpreting unit 44 for detecting the number of retransmissions of the data described in the received data, a data transmitting / receiving unit 46 connected to a network for transmitting and receiving various data, A control unit 48 for performing control.
[0027]
The decoding unit 42 has a function of decoding the original data according to the number of retransmissions detected by the multiplicity interpretation unit 44.
[0028]
(System operation)
FIG. 4 is an overall sequence diagram for explaining an example of the distribution operation of the data communication system according to the present embodiment.
[0029]
First, at the time of transmitting packet data, the server 21 generates redundant data 1 ′ to s ′ for error correction based on the original data 1 to n related to the transmission, and t redundant data (α + 1) among them. '~ S' is stored in the retransmission data storage unit 33 as retransmission data (S101).
[0030]
Then, all original data 1 to n and α redundant data 1 ′ to α ′ (0 ≦ α ≦ s) are transmitted to each client terminal 24 (S102). On the other hand, the client terminal 24 attempts to receive the original data 1 to n and the redundant data 1 ′ to α ′ related to the transmission (S103). Here, it is assumed that nk packet data has been received without receiving necessary packet data. Therefore, in the client terminal 24, the retransmission request transmission unit 47 transmits a retransmission request for the insufficient data (k: k ≦ t) to the server 21 (S104).
[0031]
In the server 21, the retransmission request receiving unit 37 receives the retransmission request from the client terminal 24 and reads out the retransmission data (α + 1) ′ to s ′ stored in the retransmission data storage unit 33. Encoding is performed by the encoding unit 32 using the k pieces of retransmission data (α + 1) ′ to (α + k) ′, and new redundant data 1 ″ to u ″ are generated (S105). Then, v new redundant data (β + 1) ″ to u ″ are stored as retransmission data in the retransmission data storage unit 33, and k retransmission redundant data (α + 1) ′ to (α + k) ′, And β new redundant data 1 ″ to β ″ (0 ≦ β ≦ u) are transmitted to the client terminal 24 (S106).
[0032]
The client terminal 24 receives the transmitted k pieces of redundant data for retransmission (α + 1) ′ to (α + k) ′ and β pieces of new redundant data 1 ″ to β ″ as redundant data for retransmission ( S107). Here, it is assumed that the necessary packet data has not been received and kh packet data have been received. Therefore, in the client terminal 24, the retransmission request transmitting unit 47 transmits a retransmission request for the insufficient data (h pieces: h ≦ v) to the server 21 (S108).
[0033]
In the server 21, the retransmission request receiving unit 37 receives the retransmission request from the client terminal 24, reads out the retransmission data (β + 1) ”to“ u ”stored in the retransmission data storage unit 33, and reads out Encoding is performed by the encoding unit 32 using the retransmission data (β + 1) ″ to (β + h) ″ for the number, and new redundant data 1 ′ ″ to w ′ ″ are generated (S109). Then, x pieces of new redundant data (γ + 1) ′ ″-w ′ ″ are stored as retransmission data in the retransmission data storage unit 33, and h pieces of redundant data for retransmission (β + 1) ″-( β + h) ″ and γ pieces of new redundant data 1 ′ ″ to γ ′ ″ (0 ≦ γ ≦ w) are transmitted to the client terminal 24 (S110).
[0034]
The above-described processing is repeated until necessary data is transmitted. Here, it is assumed that all the necessary data has been received by the client terminal 24 by the transmission in step S110 (S111). The client terminal 24 generates original data for transmission from the received original data, redundant data, and redundant data for retransmission (S112 and S113).
[0035]
(Transmission processing in server 21)
FIG. 5 is a flowchart showing a transmission process of the server 21 in the present embodiment.
[0036]
First, n original packets (original data) are generated based on data to be transmitted (S201). The generated original packet is encoded by the encoding unit 32 to generate s (s ≧ n) redundant packets (S202), and the number of retransmissions of the data packet is described in the data packet by the multiplicity management unit 38. , The original packet and α (0 ≦ α ≦ s) redundant packets are transmitted (S203). At this time, of the generated redundant packet, a part that has not been transmitted is stored in the retransmission data storage unit 33 as retransmission data (S204).
[0037]
Next, it is determined whether there is a retransmission request from the client terminal 24 (S205). If there is no retransmission request from the client terminal 24, the distribution process ends there (S206).
[0038]
On the other hand, if it is determined in step S205 that there has been a retransmission request from the client terminal 24, a new redundant packet is generated based on the stored redundant packet (retransmission data) (S207), and the multiplicity management unit 38, the number of retransmissions of the data packet is described in the data packet, and the redundant packet and the redundant packet β (0 or more) of the redundant packet are transmitted (S208).
[0039]
The part of the generated redundant packet that has not been transmitted is stored in the retransmission data storage unit 33 (S209). Thereafter, steps S205 to S209 are repeated until there is no retransmission request from the client.
[0040]
(Reception processing in client terminal 24)
FIG. 6 is a flowchart showing the receiving process of the client terminal 24 in the present embodiment.
[0041]
First, a data packet is received from the server 21 (S301), and the number of retransmissions described in the reception data is detected by the multiplicity interpretation unit 44, and the number of data packets required for decoding is received at the number of retransmissions. Is checked (S302). If the data packet has been successfully received, the data packet is sequentially decoded in accordance with the number of retransmissions of the data packet, the original packet is reproduced, and the process is terminated (S304).
[0042]
On the other hand, if it is determined in step S302 that the number required for decoding has not been received, a request is made to the server to retransmit as many data packets as necessary for decoding (S303). Thereafter, steps S302 to S303 are repeated until a data packet sufficient for decoding is received.
[0043]
(Action / Effect)
According to the system and method according to the present embodiment described above, the server 21 encodes the data packet for forward error correction, increases the number of redundant data packets and transmits the data packets, and requests the retransmission request from the client terminal 24. Is received, the already encoded redundant data is further encoded for forward error correction, and the number of redundant data packets can be further increased and transmitted.
[0044]
In the present embodiment, the server 21 stores the number of retransmissions, describes the number of retransmissions in data related to transmission, and the client terminal 24 stores the number of retransmissions described in the received data. Since the number of retransmissions is detected and the original data is generated according to the detected number of retransmissions, in a communication protocol that does not guarantee ordering, the order of data packets may be changed due to network delay or error. Even in some cases, by describing information on the number of retransmissions in the data packet, the data packet required for decoding can be identified on the receiving side, and decoding is sequentially repeated using the same data of the number of retransmissions. The original data packet can be obtained.
[0045]
(Example of change)
Note that the present invention is not limited to the above-described embodiment, and the following changes can be made.
[0046]
(1) Modification example 1
FIG. 7 is an explanatory diagram for describing an example of a distribution operation of the data communication system in the first modification.
[0047]
In the above-described embodiment, when there is a retransmission request from the client terminal 24, encoding is performed on the insufficient number of data associated with the retransmission request among the retransmission data stored in the retransmission data storage unit 33. Alternatively, all of the retransmission data stored in the retransmission data storage unit 33 may be encoded.
[0048]
More specifically, in step S105, when a retransmission request is received from the client terminal 24, the retransmission data (α + 1) ′ to s ′ stored in the retransmission data storage unit 33 are read, and the shortage k Encoding is performed by the encoding unit 32 using the pieces of retransmission data (α + 1) ′ to (α + k) ′, new redundant data 1 ″ to u ″ are generated, and k pieces of retransmission redundant data (α + 1) are generated. ) ′ To (α + k) ′ and β new redundant data 1 ″ to β ″ (0 ≦ β ≦ tk) are transmitted to the client terminal 24.
[0049]
On the other hand, in the present modified example, encoding is performed using all (s′−α) pieces of retransmission data (α + 1) ′ to s ′ stored in the retransmission data storage unit 33, and the new redundant data 1 “〜U” is generated, and k + β pieces of data are retransmitted from the retransmission data (α + 1) ′ to s ′ and the new redundant data 1 ″.
[0050]
That is, the β pieces of data related to the retransmission include the retransmission data already stored in the retransmission data storage unit 33 and the newly encoded new redundant data. In this case, (β + 1) ″ to u ″ among the new redundant data 1 ″ to u ″ are stored in the retransmission data storage unit 33 as retransmission data for the next encoding.
[0051]
If s′−α is sufficiently large and s′−α ≧ 2k + β, the retransmission data (α + 1) already stored in the retransmission data storage unit 33 without encoding new redundant data. ) Retransmit k + β in '~ s'.
[0052]
According to the first modification, new redundant data for retransmission can be generated by making maximum use of data already encoded and stored in the retransmission data storage unit 33. The load on the server 21 can be reduced.
[0053]
(2) Modification example 2
FIG. 8 is a flowchart illustrating a transmission process of the server 21 in the second modification. In the above-described embodiment, during a festival in which a retransmission request is received from the client terminal 24, the retransmission data stored in the retransmission data storage unit 33 is always encoded, and the retransmission data and the encoded redundant data are retransmitted. However, according to the number of insufficient data requested to be retransmitted, it is possible to select whether to transmit the retransmission data stored in the retransmission data storage unit 33 as it is or to transmit an encoded version of the retransmission data. Is also good.
[0054]
More specifically, as shown in FIG. 8A, first, the transmission data is divided into transmission packet sizes, an original packet is generated, and this is stored in the original data storage unit 31 (S401). Next, redundant data is generated from the stored data (original data) (S402), and a packet header describing the number of encodings (the number of retransmissions) of the data is added to the transmission packet (S403). Then, a desired number (for example, n original data and α redundant packets) of the generated transmission packets is transmitted (S404).
[0055]
Then, it is determined whether or not there is a retransmission request from the client terminal 24 (S405). If there is no retransmission request, the distribution process is terminated (S406). Here, it is assumed that K retransmission requests have been made in step S405.
[0056]
If it is determined in step S405 that there is a retransmission request, the number of retransmission data stored in the retransmission data storage unit 33 (the number of remaining data: x) and the number of insufficient data relating to the retransmission request (threshold: 2K + C) Are compared (S406). This threshold is a value obtained from the table shown in FIG. 4B, and is obtained from C associated with the number K of requests. This correspondence table may be stored in the server 21 in advance, and the correspondence table may be referred to at the time of retransmission.
[0057]
In step S406, when the number x of remaining data is larger than the threshold (2K + C) (x ≧ 2K + C in S407 in the figure), the processing after step S404 is executed without performing encoding, and the number of remaining data becomes larger than the threshold (2K + C). If the number is less (x <2K + C in S408 in the figure), the processing after step S402 for performing encoding is executed.
[0058]
According to the second modification, it is possible to prevent unnecessary encoding processing from being executed, and it is possible to reduce the processing load on the server 21.
[0059]
(Packet communication program)
In addition, the packet communication system and the method in the above-described embodiment and the modification can be a program described in a predetermined computer language. That is, by installing the program in the server 21 or the computer provided in the client terminal 24, the transmitting device 3 and the receiving device 4 having the above-described functions can be easily constructed. This program can be, for example, an application that runs on a communication service and a standalone computer.
[0060]
Such a program can be recorded on recording media 116 to 119 that can be read by the general-purpose computer 120 as shown in FIG. More specifically, as shown in the figure, in addition to a magnetic recording medium such as a flexible disk 116 and a cassette tape 119, an optical disk such as a CD-ROM and a DVD-ROM 117, and a recording medium such as a RAM card 118, various recording media are used. can do.
[0061]
According to the computer-readable recording medium on which the program is recorded, the program synchronization system and the program synchronization method described above can be performed using a general-purpose computer or a special-purpose computer, and the program can be stored and stored. It can be easily transported and installed.
[0062]
【The invention's effect】
According to the present invention, since redundant data packets can be increased by repeating forward error correction encoding of data packets, the number of retransmissions using forward error correction encoded packets can be reduced in communication processing of data packets. Thus, the communication quality can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an overall configuration of a packet communication system according to an embodiment.
FIG. 2 is a block diagram illustrating an internal configuration of a transmission device 3 according to the embodiment.
FIG. 3 is a block diagram illustrating an internal configuration of a receiving device 4 in the embodiment.
FIG. 4 is an overall sequence diagram for explaining an example of a distribution operation of the data communication system according to the embodiment.
FIG. 5 is a flowchart illustrating a transmission process of a server 21 according to the embodiment.
FIG. 6 is a flowchart showing a receiving process of the client terminal 24 in the embodiment.
FIG. 7 is an explanatory diagram illustrating an example of a distribution operation of a data communication system according to a modification of the embodiment.
FIG. 8 is a flowchart illustrating a transmission process of a server 21 according to a modification of the embodiment.
FIG. 9 is a perspective view of a computer-readable recording medium on which a packet communication program according to the embodiment is recorded.
FIG. 10 is a configuration diagram showing an overall configuration of a conventional packet communication system using a multicast method.
[Explanation of symbols]
α: redundant packet β, γ: new redundant packet t, v, x: data for retransmission 3: transmitting device 4, receiving device 21, server 22, router HUB
23 access point 24 client terminal 25 data packet 31 original data storage unit 32 encoding unit 33 retransmission data storage unit 34 retransmission count storage unit 35 data packet transmission unit 36 data transmission / reception unit 37 retransmission request Reception unit 38 Multiplicity management unit 39 Control unit 41 Original data 42 Decoding unit 43 Redundant data storage unit 44 Multiplicity interpretation unit 45 Data packet reception unit 46 Data transmission / reception unit 47 Retransmission request transmission unit 48 ... Control units 116 to 119 ... Recording medium 120 ... General purpose computer

Claims (10)

A packet transmitting device for transmitting packet data,
An encoding unit that generates redundant data for error correction from original data related to transmission,
A retransmission data storage unit that stores a part of the redundant data as retransmission data, and a transmission unit that transmits a part or all of the original data and the redundant data,
A retransmission request receiving unit that receives a retransmission request from a transmission destination,
The encoding unit, in response to the retransmission request received by the retransmission request receiving unit, further generates new redundant data from the retransmission data,
The retransmission data storage unit stores the new redundant data as retransmission data,
The packet transmission device, wherein the transmission unit transmits a part or all of the redundant data and a part or all of the new redundant data in response to the retransmission request received by the retransmission request receiving unit. A retransmission count storage unit that stores the number of retransmissions by the transmission unit,
The packet transmission device according to claim 1, further comprising: a multiplicity management unit that describes the number of retransmissions in data related to transmission. The encoding unit compares the number of retransmission data stored in the retransmission data storage unit with the number of insufficient data related to a retransmission request, and generates the new redundant data according to the comparison result. 3. The packet transmitting apparatus according to claim 1, wherein a process of outputting retransmission data already stored in the retransmission data storage unit as new retransmission data is selected. 4. The packet transmitting apparatus according to claim 1, wherein the transmission of the data by the transmitting unit is a multicast method in which the data is transmitted to a plurality of other communication apparatuses connected to the packet transmitting apparatus at a time. . A packet receiving device for receiving packet data,
Original data pertaining to transmission, and a receiving unit that receives redundant data for error correction generated from the original data,
A retransmission request transmission unit that transmits a retransmission request for the insufficient data to the transmission source when the necessary data cannot be received;
A received data storage unit that stores the received original data, the redundant data, and the retransmitted redundant data;
The original data stored in the reception data storage unit, the redundant data, and from the retransmitted redundant data, comprising a decoding unit that generates the original data pertaining to the transmission, the retransmitted redundant data,
On the transmission side, a part or all of the redundant data stored as retransmission data,
A packet receiving apparatus comprising a part or all of new redundant data further generated from the retransmission data. The multiplicity interpretation unit that detects the number of retransmissions of the data, described in the data received by the reception unit, further includes:
The packet receiving device according to claim 5, wherein the decoding unit generates the original data according to the number of retransmissions detected by the multiplicity interpretation unit. A packet transmission method for transmitting packet data,
(1) generating redundant data for error correction from original data related to transmission;
(2) storing a part of the redundant data as retransmission data and transmitting a part or all of the original data and the redundant data;
(3) receiving a request for retransmission of the insufficient data from the transmission destination;
(4) further generating new redundant data from the stored retransmission data and storing the new redundant data as retransmission data;
(5) transmitting a part or all of the redundant data and a part or all of the new redundant data;
A packet transmission method characterized by repeating steps (3) to (5) until necessary data is transmitted. A packet receiving method for receiving packet data,
Receiving (1) original data for transmission and redundant data for error correction generated from the original data;
(2) transmitting a request for retransmission of the insufficient data to the transmission source;
Receiving a part or all of the redundant data accumulated on the transmission side as retransmission data and a part or all of new redundant data further generated from the retransmission data as redundant data for retransmission ( 3) and
(4) generating original data related to the transmission from the original data, the redundant data, and the redundant data related to retransmission,
A packet receiving method comprising repeating steps (2) to (4) until necessary data is received. A packet transmission program for transmitting packet data, comprising:
(1) generating redundant data for error correction from original data related to transmission;
(2) storing a part of the redundant data as retransmission data and transmitting a part or all of the original data and the redundant data;
(3) receiving a request for retransmission of the insufficient data from the transmission destination;
(4) further generating new redundant data from the stored retransmission data and storing the new redundant data as retransmission data;
Transmitting a part or all of the redundant data and a part or all of the new redundant data (5).
A packet transmission program for repeating steps (3) to (5) until necessary data is transmitted. A packet receiving program for receiving packet data, the method comprising: receiving (1) original data to be transmitted to a computer and redundant data for error correction generated from the original data;
(2) transmitting a request for retransmission of the insufficient data to the transmission source;
Receiving a part or all of the redundant data accumulated on the transmission side as retransmission data and a part or all of new redundant data further generated from the retransmission data as redundant data for retransmission ( 3) and
Generating (4) the original data related to the transmission from the original data, the redundant data, and the redundant data related to the retransmission;
A packet receiving program for repeating steps (2) to (4) until necessary data is received.

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