JP2006237968A - System and method for communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a communication system capable of data transmission with both real-time response and reliability. <P>SOLUTION: A transmitting device 10 has a transmitting buffer 12 which stores transmitted data, a real-time transmission section 11 which transmits the transmitted data in real time one after another and stores them in the transmitting buffer 12, and a re-transmission section 13 which takes re-transmitted data corresponding to a request for re-transmission out of the transmitting buffer 12 and transmits the data, and a receiving device 30 has a reception section 31 which receives transmitted data and re-transmitted data, a real-time output section 32 which takes out transmitted data having been received normally and outputs the data one after another, and an error-free output section 33 which sends a request to re-transmit lost data when there is the lost data to receive re-transmitted data, and combines the transmitted data having been received normally with the re-transmitted data to output received data in the order of the transmitted data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication system and a communication method for transmitting data that requires real-time properties from a transmitting device to a receiving device via a transmission path and transmitting data that requires quality.

  Conventional communication methods include real-time communication methods such as UDP (User Datagram Protocol) that may cause errors in data, and TCP (Transmission Control Protocol) that has no real-time property but data reliability. And non-real-time communication methods existed. That is, UDP has a feature that the transfer rate can be freely set but the reliability is not guaranteed, while TCP has the feature that the reliability is guaranteed but the transfer rate cannot be set.

  Therefore, there is a communication system in which only data that cannot be normally received is retransmitted while transmitting data in real time (see, for example, Patent Document 1). In this communication method, after the end of communication or during communication, a request is made to retransmit the data of the part that could not be normally received on the receiving side, and the data on the corresponding part is retransmitted on the transmitting side. For this reason, the transmission side needs to prepare for retransmission of all data until communication is completed.

Japanese Patent Laid-Open No. 10-313350 (first page, FIG. 1)

  However, the prior art has the following problems. The conventional communication system has a problem in that a large amount of memory is required for holding because all the data needs to be held for retransmission on the transmission side. In addition, since there is no function for rate control in the part that communicates in real time, there is a problem in that once the congestion state occurs, retransmission operations frequently occur and a more serious congestion state is generated.

  In addition, in the communication method that emphasizes reliability, the real-time property is impaired. On the other hand, in the communication method that emphasizes real-time property, the reliability is impaired.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a communication system capable of performing data transmission having both real-time properties and reliability.

  A communication system according to the present invention is a communication system including a transmission device that transmits data via a transmission line and a reception device that receives data via the transmission line. The transmission device is sequentially transmitted in real time. A transmission buffer for storing transmission data, a real-time transmission unit that sequentially transmits transmission data in real time and stores the transmission data in the transmission buffer, and transmission corresponding to lost data in response to a retransmission request for lost data from the receiving device A retransmission unit that extracts data from the transmission buffer and transmits the retransmission data, and the reception device receives the transmission data transmitted from the real-time transmission unit and the retransmission data transmitted from the retransmission unit as reception data; Of the received data, it can be normally received from the transmission data transmitted from the real-time transmitter. A real-time output unit that extracts only the transmission data and outputs it sequentially, and for the received data, the presence or absence of lost data that could not be received normally is judged in sequence. If there is no lost data, the received data is output in sequence, and the lost data If there is, the transmission data from the transmission device is transmitted by transmitting a retransmission request for lost data to the transmission device, and extracting and outputting the retransmission data transmitted from the retransmission unit as a response to the retransmission request. And an error-free output unit that outputs received data in order.

  The communication method according to the present invention is a communication method including a transmission method for transmitting data via a transmission line and a reception method for receiving data via a transmission line. Real-time transmission processing step for transmitting the packet data in the transmission buffer and dividing the packet data into large-sized packet data, and erasing in response to the retransmission request for the lost packet data generated by the receiving method Normal processing based on the retransmission processing step of retrieving packet data corresponding to the packet data from the transmission buffer and transmitting it as retransmission packet data, and normal reception information indicating the packet data generated by the reception method up to the point where reception was successful Transmission buffer that discards packet data in the transmission buffer corresponding to received information A reception processing step for receiving packet data and retransmission packet data transmitted by the transmission method, and extracting only packet data that can be normally received from the packet data and sequentially outputting them. A real-time output processing step, a determination processing step for sequentially determining presence / absence of lost packet data that could not be normally received for the packet data and retransmission packet data received in the reception processing step, and loss if there is lost packet data The retransmission request transmission processing step for transmitting a retransmission request for packet data and the packet data that can be normally received and the retransmission packet data that can be normally received when there is no lost packet data, are combined in accordance with the transmission order from the transmission method. Output packet data sequentially And Furi output processing step, when there is no lost packet data is one having a normal reception information transmission processing step of transmitting the normal reception information indicating the packet data up to where it can be received correctly.

  According to the present invention, real-time output is provided by providing two outputs that can output transmission data transmitted in real time in real time while receiving error-free output based on retransmission data when a reception error occurs. A communication system capable of performing data transmission having reliability can be obtained.

Hereinafter, preferred embodiments of a communication system of the present invention will be described with reference to the drawings.
The communication system of the present invention is characterized in that it can supply two types of data transmission methods that require real-time characteristics and data transmission methods that require quality.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a communication system according to Embodiment 1 of the present invention. In FIG. 1, the transmission device 10 acquires transmission data from the outside and outputs it to the network 20 as communication data. The receiving device 30 acquires the communication data via the network 20 and outputs it as received data to the outside.

  Here, the transmission apparatus 10 includes a real-time transmission unit 11, a transmission buffer 12, and a retransmission unit 13. The real-time transmission unit 11 outputs (transmits) data input from the outside to the network 20 as transmission data in accordance with a communication protocol. The transmission buffer 12 is a storage unit that temporarily accumulates data transmitted by the real-time transmission unit 11. The retransmission unit 13 retrieves corresponding data from the transmission buffer 12 in response to the retransmission request from the receiving device 30, and outputs the data to the network 20 as retransmission data according to the communication protocol.

  On the other hand, the receiving device 30 includes a receiving unit 31, a real-time output unit 32, and an error-free output unit 33. The reception unit 31 receives communication data output from the transmission device 10 via the network 20. This communication data includes transmission data transmitted in real time from the real-time transmission unit 11 and retransmission data transmitted from the retransmission unit 13 in response to a retransmission request.

  The real-time output unit 32 receives data from the reception unit 31 and outputs only the transmission data transmitted in real time to the outside. On the other hand, the error-free output unit 33 receives communication data from the receiving unit 31 and transmits a retransmission request to the transmitting apparatus 10 when data omission or error is found, and in response to the transmission data transmitted in real time and the retransmission request Combined with the retransmitted data that has been transmitted, the data successfully received is output to the outside in time series.

Next, a specific operation will be described.
First, the transmission device 10 acquires a data string to be transmitted from the outside, and outputs the acquired data string to the network 20 as transmission data in accordance with a communication protocol by the real-time transmission unit 11. This transmission data is referred to herein as real-time data.

  The real-time transmission unit 11 divides the data string into an appropriate length for transmission for transmission. Further, the real-time transmission unit 11 gives a serial number or the like to each packet data so that the packet data can be identified. The real-time transmission unit 11 stores the transmitted real-time data in the transmission buffer 12 in preparation for a retransmission request from the receiving device.

  When the retransmission unit 13 receives a retransmission request for specific packet data from the receiving device 30, the retransmission unit 13 reads out the corresponding packet data stored in the transmission buffer 12, and retransmits the network 20 as retransmission data according to the communication protocol. Output to. A serial number can be used to identify the packet data.

  On the other hand, the receiving device 30 receives the real-time data and the retransmission data from the transmitting device 10 via the network 20 by the receiving unit 31 according to the communication protocol. The receiving unit 31 transfers the received packet data to the real-time output unit 32 and the error-free output unit 33. The real-time output unit 32 outputs only packet data that can be normally received and is not retransmitted out of the transferred data. That is, the real-time output unit 32 outputs only real-time data that can be normally received.

  Here, the real-time output unit 32 refers to the serial number given to the packet data, and outputs only the packet data whose value is monotonically increasing, thereby determining whether or not the received packet data has been retransmitted. Can be determined. In this way, the data output from the real-time output unit 32 is output only with data having a small transmission delay (that is, the real-time property is ensured).

  On the other hand, the error-free output unit 33 detects packet data having an error in data or lost packet data for transmitted packet data including both real-time data and retransmission data, and transmits a retransmission request for the packet. This is performed for the apparatus 10.

  The error-free output unit 33 can request retransmission of packet data of the serial number by detecting unreceived packet data from the serial number of the received packet. The retransmission request is transmitted to the transmission device 10 using a control communication protocol. The error-free output unit 33 accumulates the received data inside and outputs up to the point where it can be normally received.

  Thereafter, when unreceived packet data can be received by retransmission from the transmission device 10, the error-free output unit 33 outputs data up to a portion that can be normally received at that time. In this way, the error-free output unit 33 outputs, as needed, data up to the point where it can be normally received based on the real-time data and the retransmission data, and outputs error-free (ie, quality ensured) data. Can do.

  FIG. 2 is a sequence diagram showing a state of output data by the real-time output unit 32 and the error-free output unit 33 when a retransmission request is generated in the first embodiment of the present invention. Specifically, the operation of the communication system when data D1 to D5 are transmitted as real-time data from the real-time transmission unit 11 and D2 of them is lost during transmission is shown. In FIG. 2, portions not related to the communication sequence such as the network 20 and the transmission buffer 12 are omitted.

  Data D1 to D5 periodically transmitted from the real-time transmission unit 11 are processed and output by the real-time output unit 32 and the error-free output unit 33 via the reception unit 31, respectively. Here, it is assumed that among the data D1 to D5, D2 does not reach the receiving unit 31 and a transmission error occurs midway.

  The first D1 is simultaneously output by the real-time output unit 32 and the error-free output unit 33. D2 having a transmission error does not reach the receiving unit 31, and then D3 that can be received is output by the real-time output unit 32. On the other hand, the error-free output unit 33 notices that D2 is not received because D3 is received next to D1, and notifies the transmitter 10 of the retransmission request R2 of D2.

  Thereafter, the retransmission unit 13 in the transmission apparatus 10 receives the retransmission request R2, and transmits D2 as retransmission data. D2 is already recognized by the real-time output unit 32 as past data (because D3 has already been received) and is not output. On the other hand, the error-free output unit 33 outputs D3 received earlier simultaneously with the reception of D2. Thereafter, D4 and D5 are output together by the real-time output unit 32 and the error-free output unit 33.

  As a result, the real-time output unit 32 sequentially outputs data other than D2 in which a transmission error has occurred in the order of D1, D3, D4, and D5 as data requiring a real-time property with a small transmission delay. On the other hand, the error-free output unit 33 receives D2 in response to a retransmission request, and sequentially outputs it as data requiring error-free quality in the order of D1, D2, D3, D4, and D5.

  As described above, according to the first embodiment, the receiving apparatus can perform two outputs, an output that emphasizes real-time characteristics and an output that emphasizes quality, and outputs data with two characteristics in one communication. A communication device that can be used is obtained.

  1, the output of the real-time transmission unit 11 is output to two of the network 20 and the transmission buffer 12, but the output from the real-time transmission unit 11 is set to one and the destination is 2 The same effect can be obtained by branching to one and going to the network 20 and the transmission buffer 12.

  Further, the receiving device 30 of FIG. 1 distributes data to the real-time output unit 32 and the error-free output unit 33 after receiving data once by the receiving unit 31, but the function of the receiving unit 31 is error-free. The same effect can be obtained by providing the output unit 33 to distribute the real-time data from the error-free output unit 33 to the real-time output unit 32. On the contrary, the same effect can be obtained by distributing from the real-time output unit 32 to the error-free output unit 33.

Embodiment 2. FIG.
In the first embodiment, the communication system that transmits a predetermined amount of generated data has been described. On the other hand, this Embodiment 2 demonstrates the communication system which can control the information generation amount.

  FIG. 3 is a configuration diagram of a communication system according to Embodiment 2 of the present invention. In FIG. 3, the communication system includes transmission device 10, network 20, and reception device 30 as in the first embodiment, and transmits data to be transmitted to reception device 30 to transmission device 10. The information generator 40 is further provided.

  The retransmission unit 13 in the transmission device 10 retransmits data and controls the information generation amount of the information generation device 40. The functions relating to the other parts are the same as in the first embodiment, and the description thereof is omitted.

Next, a specific operation will be described.
First, the transmitting apparatus 10 acquires a data string to be transmitted from the information generating apparatus 40, and outputs the acquired data string to the network 20 as real-time data according to a communication protocol by the real-time transmitting unit 11. The real-time transmission procedure and the retransmission procedure are the same as in the first embodiment, and a description thereof is omitted.

  The retransmission unit 13 detects the reception status of the retransmission request and outputs an information generation amount control command to the information generation device 40 so as to suppress or increase the information generation amount according to the reception status. Specifically, the retransmission unit 13 outputs an information generation amount control command based on the frequency of occurrence of retransmission requests or the time interval at which retransmission requests are received.

  When communication data is discarded due to network congestion, the retransmission unit 13 in the transmission device 10 frequently receives retransmission requests from the reception device 30. In this case, if retransmission is repeated by the transmission apparatus 10, the congestion state will be further deteriorated. Thus, for example, when the frequency of occurrence of retransmission requests exceeds a predetermined allowable value, the retransmission unit 13 determines that the congestion state has deteriorated and controls the information generation apparatus 40 to suppress the information generation amount. By outputting the generation amount control command, a congestion state can be avoided.

  As described above, according to the second embodiment, the retransmission unit in the transmission device can control the information generation amount of the information generation device based on the reception status of the retransmission request, and avoid the network congestion state. can do.

  In the second embodiment, the case where the information generation device 40 that generates transmission data is provided outside the transmission device 10 has been described. However, the information generation amount similar to that of the information generation device 40 is set in the transmission device 10. It is also possible to incorporate functions that can be controlled.

Embodiment 3 FIG.
In the third embodiment, when the error-free output unit 33 sequentially determines the presence / absence of packet data that could not be normally received, normal reception information indicating the packet data information up to the point of normal reception is generated. A case of transmitting to the transmission device 10 will be described.

  The error-free output unit 33 in the receiving device 30 can request retransmission of packet data that could not be normally received, and can notify the transmitting device 10 of packet data up to the point where it was successfully received as normal reception information. . As a notification method in this case, the error-free output unit 33 can notify up to the point of normal reception using the serial number of the packet data or the like.

  Further, by notifying the transmitting device 10 of data up to a portion that can be normally received as the normal reception information, the transmitting device 10 determines whether or not the real-time data and the retransmission data that have been transmitted before reach the receiving device 30 normally. Can be confirmed. FIG. 4 is a sequence diagram showing a state of output data by the real-time output unit 32 and the error-free output unit 33 when a retransmission request and normal reception information are generated in the third embodiment of the present invention.

  Specifically, data D1 to D4 are transmitted as real-time data from the real-time transmission unit 11, D2 of them is lost during transmission, a retransmission request is generated, and D2 is transmitted as retransmission data. It shows the operation of the communication system when normal reception information up to is generated. In FIG. 4, portions not related to the communication sequence such as the network 20 and the transmission buffer 12 are omitted.

  The process up to the first retransmission procedure of D2 is the same as in FIG. After that, the error-free output unit 33 in the receiving device 30 transmits normal reception information C1 indicating that it has been successfully received up to D1 at an arbitrary timing to the transmitting device 10. The retransmission unit 13 in the transmission apparatus 10 that has received the normal reception information C1 recognizes that the D2 that has been retransmitted does not arrive and can transmit D2 again.

  Since the receiving apparatus 30 does not know when the transmitting apparatus 10 retransmits D2 after transmitting the retransmission request R2, it recognizes that the first retransmission in FIG. 4 has not been retransmitted even if it does not arrive in error. Therefore, there is a possibility that the second retransmission request cannot be made immediately. Therefore, by notifying the transmission device 10 of the normal reception information C1 at a certain timing as described above, the transmission device 10 can recognize that the first retransmission is an error and can quickly retransmit D2. .

  Further, the difference between the real-time data being sent in real time and the data up to the point where it was successfully received corresponds to the output delay of the error-free output unit 33. Therefore, the transmitter 10 calculates the output delay approximate value by obtaining the output delay approximate value from the difference between the normal reception information received by the retransmission unit 13 and the real-time data output from the real-time transmission unit 11 at this stage. It is also possible to devise retransmission control so as not to increase or to reduce the amount of information generated.

  Further, the normal reception information transmitted by the receiving device 30 eliminates the need for the transmitting device 10 to retransmit the packet data up to that portion, so that the corresponding packet data in the transmission buffer 12 can be discarded. The capacity of 12 can be reduced. In particular, in the case of usage such as monitoring, since communication is not interrupted, the transmission buffer 12 becomes insufficient without means for releasing the transmission buffer 12.

  FIG. 5 is a sequence diagram showing how the transmission buffer 12 is released when normal reception information is generated in the third embodiment of the present invention. Specifically, as in FIG. 2, after data D1 to D5 are transmitted as real time data from the real time transmission unit 11, D2 of them is lost during transmission and a retransmission request is generated, and then D1 to D4 are further generated. The operation of the communication system when the normal reception information is generated is shown.

  The retransmission procedure is the same as that in FIG. The real-time transmission unit 11 writes the data in the transmission buffer 12 at the same time as transmitting the data to the receiving device 30. When receiving the retransmission request R2 for D2, the retransmission unit 13 extracts the corresponding data from the transmission buffer 12, and transmits the retransmission data for D2.

  The error-free output unit 33 in the receiving device 30 transmits to the transmitting device normal reception information C4 indicating that it has been successfully received up to D4 at an arbitrary timing after normally receiving the D2 retransmission data. Receiving this, the retransmission unit 13 in the transmission apparatus 10 can determine that the retransmission of D1 to D4 is no longer necessary, can discard the data of D1 to D4 in the transmission buffer 12, and can release the transmission buffer 12. . Thereby, the free capacity of the transmission buffer 12 increases.

  As described above, according to the third embodiment, the transmission device can quickly confirm the delivery of the retransmission data by notifying the transmission device of the packet data up to the part that can be normally received as normal reception information. it can. Further, the transmission device can release the transmission buffer based on the received normal reception information, and as a result, the capacity of the transmission buffer can be reduced.

Embodiment 4 FIG.
In the third embodiment, the case where the normal reception information indicating the packet data information up to the point of normal reception is used has been described. In the fourth embodiment, a case will be described in which information corresponding to the normal reception information is added to a retransmission request as necessary.

  In a situation where retransmission requests do not occur frequently, the retransmission request itself can be used as information indicating that reception has been successful. That is, when the retransmission request is received, the retransmission unit 13 can also mean that the data before the data corresponding to the retransmission request has been successfully received by the receiving device 30. However, in consideration of the case where a plurality of retransmission requests are generated, it is not possible to determine that data from the retransmission request alone to the data before the data corresponding to the retransmission request has been normally received.

  Therefore, when transmitting the retransmission request, if the previous data has been successfully received, the receiving device 30 adds the immediately previous data normal reception information as information to that effect to the retransmission request. 10 can be notified. The immediately preceding data normal reception information functions in the same manner as the normal reception information described in the third embodiment. When the immediately preceding data normal reception information is included in the received retransmission request, the transmitting device 10 knows how far packet data has been successfully received by the receiving device 30 based on the immediately preceding data normal reception information. Can do.

  As an implementation method, it is conceivable to add 1-bit delivery confirmation information to the retransmission request information. The retransmission request to which this 1-bit information corresponding to the previous data normal reception information is added can indicate whether or not the data can be normally received up to the data number included in the retransmission request.

  As described above, according to the fourth embodiment, by adding to the retransmission request sent from the receiving apparatus to the transmitting apparatus, the immediately preceding data normal reception information indicating that the data up to immediately before can be normally received, The transmission device can confirm the delivery of data up to the place where the reception device has successfully received the data. Furthermore, the transmission device can release the transmission buffer based on the received normal data reception information immediately before reception, and as a result, the capacity of the transmission buffer can be reduced.

Embodiment 5. FIG.
In the fifth embodiment, a method for reducing the delay of data output from the error-free output unit 33 by transmitting retransmission data in duplicate (multi-feed) at a time according to the reception status of the retransmission request will be described. To do.

  If it happens that the retransmission data of the same packet data is wrong or lost, and the retransmission is repeated many times, new real-time data is sent more and more in the meantime. For this reason, the transmission buffer 12 in the transmission apparatus 10 is in a state where all packet data from the packet data for which retransmission is repeated to the latest packet data is accumulated, and the reception apparatus 30 repeats retransmission. During this time, the error-free output unit 33 cannot output any data.

  In order to improve such a situation quickly, in the fifth embodiment, when the same packet data is retransmitted, the number of retransmission packet data (the number of double feeds) to be sent at a time is increased according to the number of retransmissions. I do. By doing this, even if there is an influence of an error or loss, a plurality of desired packet data are sent at a time, so that the probability of successfully reaching the receiving device is increased. However, if the number of multi-feeds is always increased, it will lead to network congestion. Therefore, only packet data with a large number of retransmissions will be multi-feed.

  In a situation where retransmission of the same data is repeated many times, it is difficult for the transmission apparatus 10 to count the number of retransmissions for each packet data. Therefore, as an alternative, the transmission device 10 can determine the number of double feeds according to the elapsed time from the time of the first transmission to the retransmission. For example, assuming that the number of packet transmissions per unit time is almost constant, the transmitting apparatus 10 estimates the approximate elapsed time from the difference between the serial number of the packet data currently being transmitted and the serial number of the packet data to be retransmitted. The number of double feeds can be increased as the elapsed time increases.

  As another alternative, data that may be retransmitted (data portion that has not been notified from the receiving device that it has been successfully received) remains in the transmission buffer 12, so that the transmitting device 10 It is also possible to estimate the elapsed time from the amount of data stored in the transmission buffer 12 from the packet data to the latest packet data and determine the number of double feeds.

  If the retransmission data is continuously transmitted during retransmission, if a burst-like error or loss occurs, all of the overlapped data cannot be received normally by the receiving device. Therefore, even if a burst-like error or loss occurs due to double feeding at a certain interval when double feeding, all data will not be damaged, and retransmitted data will be delivered to the receiving device be able to.

As described above, according to the fifth embodiment, by increasing the number of double feeds according to the number of retransmissions of the same packet data, the capacity of the transmission buffer can be reduced and the output delay of error-free data in the receiving apparatus can be reduced. can do. Further, the same effect can be obtained by increasing the number of double feeds according to the elapsed time at the time of retransmission of the same packet data. Furthermore, when the retransmission data is double-transferred, it is possible to realize retransmission that is strong against burst errors and losses by double-feeding at a fixed time interval.
Embodiment 6 FIG.

  In the sixth embodiment, a method for reducing the delay of data output from the error-free output unit 33 by controlling the amount of information generated according to normal reception information will be described.

  Transmitting apparatus 10 in the sixth embodiment is configured to transmit a time difference between packet data currently being transmitted and packet data of a portion confirmed to be received by a retransmission request to which normal reception information or previous data normal reception information is added. To control the amount of information generated. When the time difference between the data transmitted from the transmission device 10 but not confirmed on the reception device 30 side increases, the amount of data accumulated in the transmission buffer 12 on the transmission device 10 side increases, and the error on the reception device 30 side increases. The delay of the output data from the free output unit 33 becomes larger.

  In order to avoid such a situation, the transmission apparatus 10 controls the amount of information generated based on the above-described time difference. Specifically, when the time difference becomes large, the retransmission unit 13 generates an information generation amount control command so as to reduce the information generation amount. Conversely, when the time difference becomes small, the retransmission unit 13 sets the information generation amount. An information generation amount control command is generated so as to increase, and the information generation amount control command is output to the information generation device 40. By reducing the amount of information generated, the congestion state of the network is alleviated, the frequency of retransmission data is reduced, the time difference is reduced, and the amount of data stored in the transmission buffer 12 is also reduced.

  Also, instead of the time difference, the amount of data transmitted between the currently transmitted packet data and the packet data of the portion confirmed to be received by the retransmission request to which the normal reception information or the previous data normal reception information is added is used. Similarly, the amount of information generated can be controlled. When the total amount of data that has been transmitted from the transmission device 10 but has not yet been confirmed by the reception device 30 increases, the amount of data that accumulates in the transmission buffer 12 on the transmission device 10 side increases, and an error occurs on the reception device 30 side. The delay of the output data from the free output unit 33 becomes larger.

  In order to avoid such a situation, the transmission apparatus 10 controls the amount of information generated based on the above-described data amount. Specifically, the retransmission unit 13 generates an information generation amount control command so as to reduce the information generation amount when the data amount increases, and conversely when the data amount decreases, the information generation amount control instruction is generated. An information generation amount control command is generated so as to increase the amount, and the information generation amount control command is output to the information generation device 40. By reducing the information generation amount, the congestion state of the network is alleviated, the frequency of retransmission data is reduced, the time difference and the data amount are reduced, and the data amount stored in the transmission buffer 12 is also reduced.

As described above, according to the sixth embodiment, by controlling the amount of information generated based on the amount of time difference based on the portion of data that has not been acknowledged on the transmission side, the transmission buffer can be reduced and the reception device The output delay of error-free data can be reduced.
Furthermore, the same effect can be obtained by controlling the information generation amount using the total data amount instead of the time difference.

Embodiment 7 FIG.
In the seventh embodiment, a case will be described in which the amount of information generation is controlled in consideration of a usable transmission band. When a best effort type network is used, the usable transmission band changes constantly. When data is transmitted over a band that can be transmitted, a part of the data is discarded due to the congestion, and further, the congestion becomes worse as the data of the discarded part is retransmitted.

  Therefore, it is conceivable to calculate the bandwidth that can be transmitted using the information of the retransmission request and to obtain the information generation amount by subtracting the data bandwidth scheduled for retransmission. That is, the retransmission unit 13 according to the seventh embodiment obtains the information generation amount of the real-time data by subtracting the data band necessary for transmitting the retransmission data, and the calculated information generation to the information generation device 40. An information generation amount control command based on the amount is output.

  As described above, according to the seventh embodiment, it is possible to avoid a congestion state due to retransmission by controlling the amount of information generation in consideration of the retransmission bandwidth.

  Note that the communication systems in the above-described first to seventh embodiments can also be realized as software, and the transmission device 10 and the reception device 30 are only operations related to communication. It can be mounted on the device.

  The transmission method in the transmission device 10 can be realized by each processing of a real-time transmission processing step, a retransmission processing step, and a transmission buffer release processing step. In addition, the reception method in the reception device 30 can be realized by each process of a reception processing step, a real-time output processing step, a determination processing step, a retransmission request transmission processing step, an error-free output processing step, and a normal reception information transmission processing step.

  Specifically, the real-time transmission processing step divides transmission data into packet data of an appropriate size, sequentially transmits the packet data, and stores the transmitted packet data in the transmission buffer. 11 and the transmission buffer 12.

  In the retransmission processing step, the packet data corresponding to the lost packet data is extracted from the transmission buffer in response to the retransmission request for the lost packet data generated on the receiving side, and the retransmission packet data is transmitted. 12 can be realized.

  The transmission buffer release processing step discards the packet data in the transmission buffer corresponding to the normal reception information based on the normal reception information generated on the receiving side and indicating the packet data up to the point where the reception was successful. This can be realized by the retransmission unit 13 and the transmission buffer 12.

  In the reception method, the reception processing step receives packet data and retransmission packet data transmitted from the transmission side, and can be realized by the reception unit 31. The real-time output processing step is to extract only the packet data that can be normally received from the packet data and sequentially output it, and can be realized by the real-time output unit 32.

  The determination processing step sequentially determines the presence or absence of lost packet data that could not be normally received for the packet data and retransmission packet data received in the reception processing step, and can be realized by the error-free output unit 33. The retransmission request transmission processing step is to transmit a retransmission request for lost packet data when there is lost packet data, and can be realized by the error-free output unit 33.

  The error-free output processing step combines packet data that can be received normally and retransmitted packet data that can be received normally when there is no lost packet data, and sequentially outputs packet data according to the transmission order from the transmission side. It can be realized by the error-free output unit 33. Further, the normal reception information transmission processing step is to transmit normal reception information indicating packet data up to the point where data can be normally received when there is no lost packet data, and can be realized by the error-free output unit 33.

It is a block diagram of the communication system in Embodiment 1 of this invention. It is a sequence diagram which shows the mode of the output data by the real-time output part and error free output part when the resending request | requirement in Embodiment 1 of this invention generate | occur | produces. It is a block diagram of the communication system in Embodiment 2 of this invention. It is a sequence diagram which shows the mode of the output data by the real-time output part and error free output part when the resending request | requirement and normal reception information in Embodiment 3 of this invention generate | occur | produce. It is a sequence diagram which shows a mode that the transmission buffer is released when the normal reception information occurs in Embodiment 3 of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Transmission apparatus, 11 Real time transmission part, 12 Transmission buffer, 13 Retransmission part, 20 Network, 30 Reception apparatus, 31 Reception part, 32 Real time output part, 33 Error free output part, 40 Information generation apparatus.

Claims (11)

In a communication system comprising a transmitting device that transmits data via a transmission line and a receiving device that receives the data via the transmission line,
The transmitter is
A transmission buffer for storing transmission data sequentially transmitted in real time;
A transmission unit that sequentially transmits transmission data in real time, and stores the transmission data in the transmission buffer;
A retransmission unit that extracts the transmission data corresponding to the lost data from the transmission buffer in response to the lost data retransmission request from the receiving device, and transmits the retransmission data;
The receiving device is:
A reception unit that receives transmission data transmitted from the real-time transmission unit and retransmission data transmitted from the retransmission unit as reception data;
Among the received data, a real-time output unit that takes out only the transmission data that can be normally received from the transmission data transmitted from the real-time transmission unit and sequentially outputs the data;
With respect to the received data, the presence / absence of lost data that could not be normally received is sequentially determined, and when there is no lost data, the received data is sequentially output. In response to the transmission request from the transmitting apparatus, the retransmission request is transmitted from the transmitting unit in response to the retransmission request, and the retransmission data transmitted from the retransmission unit is extracted from the receiving unit and output. An error-free output unit for outputting data. The communication system according to claim 1,
The error-free output unit, when transmitting the retransmission request, if the data up to immediately before the lost data can be normally received, transmits the previous data normal reception information added to the retransmission request,
The retransmission unit discards transmission data in the transmission buffer corresponding to the immediately preceding data normal reception information when the retransmission request received includes the immediately preceding data normal reception information. Communications system. The communication system according to claim 1 or 2,
The error-free output unit generates normal reception information indicating data up to a place where the data can be normally received based on a result of sequentially determining the presence or absence of lost data that could not be normally received, and Sending the normal reception information;
The re-transmission unit discards transmission data in the transmission buffer corresponding to the received normal reception information. The communication system according to any one of claims 1 to 3,
Further comprising an information generator for generating transmission data and transmitting the transmission data to the transmitter;
The retransmission unit outputs an information generation amount control command to the information generation device according to a reception status of the retransmission request from the reception device,
The information generation device changes a generation amount of transmission data to be transmitted to the transmission device based on the information generation amount control command. The communication system according to claim 4,
The retransmission unit generates the information generation amount control command from a time difference between transmission data corresponding to the retransmission request and current transmission data being transmitted by the real-time transmission unit according to a reception status of the retransmission request. A communication system characterized by the above. The communication system according to claim 4,
The retransmission unit generates the information from the amount of data transmitted between the transmission data corresponding to the retransmission request and the current transmission data being transmitted by the real-time transmission unit according to the reception status of the retransmission request. A communication system characterized by generating a quantity control command. The communication system according to claim 4,
The re-transmission unit generates the information generation amount control command by calculating a data rate that can be transmitted by subtracting a data rate based on retransmission data according to a reception status of the retransmission request. The communication system according to any one of claims 1 to 7,
The retransmission unit, based on the retransmission request from the receiving device, increases the number of duplicates of the retransmission data according to the number of times of transmission of the same retransmission data, and double-transmits the retransmission data. system. The communication system according to any one of claims 1 to 7,
Based on the retransmission request from the receiving device, the retransmission unit increases the number of duplicates of the retransmission data according to an elapsed time from the previous transmission time to the current transmission time of the same retransmission data, and A communication system characterized by multi-feeding data. The communication system according to claim 8 or 9,
The retransmission unit transmits the retransmission data at intervals of a certain time or more when the retransmission data is double-transmitted. In a communication method comprising a transmission method for transmitting data via a transmission line, and a reception method for receiving the data via the transmission line,
The transmission method is:
Real-time transmission processing step of dividing the transmission data into packet data of an appropriate size, sequentially transmitting the packet data, and storing the transmitted packet data in a transmission buffer;
Retransmission processing step of extracting packet data corresponding to the lost packet data from the transmission buffer and transmitting it as retransmission packet data in response to a retransmission request of lost packet data generated by the reception method;
A transmission buffer release processing step of discarding packet data in the transmission buffer corresponding to the normal reception information based on normal reception information indicating packet data up to a place where the reception was successful generated by the reception method; Have
The reception method includes a reception processing step of receiving the packet data and the retransmission packet data transmitted by the transmission method;
A real-time output processing step of taking out only the packet data that has been successfully received from the packet data and sequentially outputting the packet data;
A determination processing step for sequentially determining the presence or absence of lost packet data that could not be normally received for the packet data and the retransmission packet data received in the reception processing step;
When there is the lost packet data, a retransmission request transmission processing step of transmitting a retransmission request for the lost packet data;
An error-free output processing step of combining packet data that has been successfully received and retransmission packet data that has been successfully received in the absence of the lost packet data, and sequentially outputting packet data in accordance with the transmission order from the transmission method; ,
And a normal reception information transmission processing step of transmitting normal reception information indicating packet data up to a place where reception was successful when there is no lost packet data.

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