JP4877993B2 - Transmission device, transmission method, and transmission / reception system - Google Patents

Description

The present invention is the transmitting apparatus, transmitting method, and a transmission and reception system, in particular, for a large number of users, the transmission apparatus, transmission method for such data can be distributed in an efficient and high reliability, and transmission and reception About the system.

  As a method for efficiently distributing data to a large number of users, for example, a transmission medium used for so-called broadcasting such as terrestrial waves, a satellite line, and a CATV network is used. There are teletexts and others that send data.

  On the other hand, recently, there has been proposed a method for efficiently distributing data to a large number of users by using, for example, the Internet as a computer network instead of a transmission medium used for broadcasting.

  For example, as a method for efficiently distributing data to a large number of users on the Internet, there is a method of broadcasting data called IP (Internet Protocol) multicast.

  That is, FIG. 8 shows a data distribution system that distributes data by IP multicast (a system is a system in which a plurality of devices are logically assembled, and whether or not each component device is in the same housing). An example configuration is shown.

  In IP multicast, a multicast address (generally referred to as a class D is generally used as a multicast address) for performing simultaneous broadcasting to a receiving device group that is a collection of receiving devices as a delivery destination as an IP address of a data delivery destination. An IP address having a value in the range of 224.0.0.0 to 239.255.255.255 is assigned. The transmitting device 101 such as a server that broadcasts data designates a specific multicast address to transmit data, and the receiving devices 103 to 107 such as computers that receive the data broadcast receive the multicast address. Specify. In this case, when an IP packet with a specified multicast address is received in an IP multicast compatible router on the communication line 102 that performs communication according to the TCP / IP protocol such as the Internet, the multicast address is specified. A route in which a receiving device is present is determined, and the packet is copied and transmitted.

  Therefore, in the transmission apparatus 101, only one address (multicast address) is designated without being conscious of the large number of reception apparatuses (the reception apparatuses 103 to 107 in FIG. 8) that distribute data, and the large number of reception apparatuses. In contrast, data can be distributed.

  For example, in the communication line 102 which is the Internet, in order to reduce the traffic, data transfer suitable for IP multicast, such as omitting the transfer of duplicate data or transferring the data only to a necessary address, is performed. Route control may be performed.

  Here, the details of the IP multicast are described in Non-Patent Document 1, for example.

  In IP multicast, data transfer is performed according to UDP (User Datagram Protocol), which is one of connectionless protocols for performing communication without confirming the data reception status at the other party (in FIG. 8, the receiving apparatuses 103 to 107). Is called. In UDP communication, the load at the time of transmission / reception is small and processing can be performed at a high speed. However, at that level (protocol level), data can be received normally as in the case of communication performed by so-called handshake. Signal ACK (ACKnowledgment) (hereinafter referred to as confirmation signal ACK as appropriate) and signal NAK (Negative AcKnowledgment) (hereinafter referred to as retransmission request signal NAK as appropriate) requesting retransmission because data could not be normally received. In either case, since the data is not returned from the receiving side to the transmitting side, the data reliability is low.

  In order to improve data reliability, for example, a communication protocol such as RMTP (Reliable Multicast Transport Protocol) has been proposed.

  In communication using RMTP, first, as shown in FIG. 9A, data is broadcast by IP multicast from the transmission apparatus 101 to the reception apparatuses 103 to 107 via the communication line 102 by UDP. Is done. Then, as shown in FIG. 9B, among the receiving apparatuses 103 to 107, those that have received data normally can receive confirmation signals ACK, and those that have not received data correctly can receive retransmission request signals NAK. Each is transmitted to the transmission apparatus 101 by UDP via the communication line 102.

  Here, in FIG. 9B, since the receiving devices 104 and 106 have successfully received the data, the confirmation signal ACK is transmitted to the transmitting device 101, and the receiving devices 103, 105, In 107 and 107, data could not be received normally, and therefore a retransmission request signal NAK is transmitted to the transmission apparatus 101.

  When receiving the retransmission request signal NAK, the transmitting apparatus 101 transmits (retransmits) the requested data again by UDP as shown in FIG. 9A. Data retransmission is repeated until the retransmission request signal NAK is transmitted until it is not transmitted or until a predetermined time.

  In communication using RMTP, since either the confirmation signal ACK or the retransmission request signal NAK is always returned, the reliability of the data can be improved while maintaining the efficiency of data distribution to many users by IP multicast. Can be improved.

  The details of RMTP are described in Non-Patent Document 2, for example.

NIKKEI ELECTRONICS, 1994. 3.24 (no. 685), pages 146 to 157 Shiroshita, Takahashi, Yamashita, Yamauchi, Kushida, “Reliable simultaneous distribution system applicable to the Internet”, Information Processing Society of Japan Report AVM11-2, December 1995, etc.

  When data is distributed using transmission media such as terrestrial, satellite, and CATV networks, it is possible to broadcast data over a wide range, but for now, it has been adopted as a standard in computer networks. For example, when a protocol based on IP (Internet Protocol) such as UDP or TCP (Transmission Control Protocol) is not supported, and an unrecoverable missing or other error occurs during data transmission The error cannot be dealt with. Therefore, the data reliability is low.

  On the other hand, when performing IP multicast using one of the computer networks, for example, the Internet, data reliability can be improved by adopting the above-described RMTP or the like. However, in the current Internet, when IP multicast is performed, the same data is transmitted over a wide range, so that limited resources are wasted.

  Therefore, as a technique for reducing traffic on the network, there is a method of controlling a data transfer route suitable for IP multicast such as omitting transfer of duplicate data or transferring data only to a necessary partner. In this case, a router that performs such control needs to be arranged on the network. However, assuming that, for example, the world-scale Internet is used as a network, it is not realistic to replace all routers on the Internet with such special routers.

  In addition, many companies connected to the Internet often have so-called firewalls to prevent third parties from entering the company's network. In addition, it is blocked by this fire wall. Therefore, in a network surrounded by a firewall, in many cases, IP multicast packets cannot be received.

  On the other hand, in RMTP, in order to increase the reliability of data, as described in FIG. 9B, it is required to always return either the confirmation signal ACK or the retransmission request signal NAK. .

  Therefore, a network capable of at least two-way communication is required as a network connecting the transmitting device and each of a large number of receiving devices. Further, in order to receive a data distribution service based on RMTP, all receiving apparatuses must be able to transmit an acknowledgment signal ACK and a retransmission request signal NAK to the transmitting apparatus.

  Furthermore, for example, when data is distributed to a large number of users such as the national scale and the global scale, any one of the confirmation signal ACK or the retransmission request signal NAK must be sent to all the users (user reception devices). If the transmission is performed, the network becomes congested, and as a result, efficient data distribution becomes difficult.

  The present invention has been made in view of such a situation, and in particular, enables data to be distributed efficiently and highly reliably to a large number of users.

A transmitting apparatus according to a first aspect of the present invention includes a packetizing unit that packetizes data into one or more packets of a predetermined data unit, and a broadcast line using a broadcast wave that can transmit the packets only in one direction. Transmitting means for transmitting to a plurality of receiving devices including a receiving device connected to a communication line different from the broadcasting line and a receiving device not connected to the communication line, and the connecting to the communication line If the receiving device cannot correctly receive the packet transmitted via the broadcast line, the receiving device transmits a retransmission request for retransmitting the packet in units of data, and does not transmit reception information if the packet is correctly received. a device, the reception is not connected to the communication line device is a device in which the unused function of transmitting the retransmission request if it can not correctly receive the packet, one Receiving means for receiving the retransmission request for the packet transmitted in units of data from the receiving device connected to the communication line via the communication line different from the broadcast line that can be transmitted only in the direction A summing means for calculating a logical sum of the retransmission requests of the packets from each of the plurality of receiving devices connected to the communication line received by the receiving means; and the logic obtained by the summing means Control means for controlling the transmission means so as to retransmit all the packets requested to be retransmitted to a plurality of the receiving apparatuses via the broadcast line based on the sum.

  When the data is retransmitted, the transmission unit can repeat the retransmission under a predetermined condition.

  The receiving means can receive the retransmission request transmitted according to UDP.

In the transmission method according to the first aspect of the present invention, data is packetized into one or more packets of a predetermined data unit, and the broadcast line is transmitted via a broadcast line using broadcast waves that can be transmitted only in one direction. To a plurality of receiving devices including a receiving device connected to a different communication line and a receiving device not connected to the communication line, and the receiving device connected to the communication line If the packet transmitted through the network cannot be correctly received, a retransmission request for retransmitting the packet is transmitted in units of data, and if received correctly, the received information is not transmitted to the communication line. connected though not receiving apparatus is an apparatus which unused function of transmitting the retransmission request if it can not correctly receive the packet, only one direction to be transmitted as the broadcast times And receiving the retransmission request for the packet transmitted in units of data from the receiving device connected to the communication line via the communication line different from the communication line, and connecting to the communication line Calculate a logical sum of the retransmission requests of the packets from each of the receiving devices, and retransmit all of the packets requested for retransmission to the plurality of receiving devices via the broadcast line based on the logical sum. A step of controlling the transmission.

In the first aspect of the present invention, data is packetized into one or more packets of a predetermined data unit, and the packet is different from the broadcast line via a broadcast line by a broadcast wave that can be transmitted only in one direction. Transmitted to a plurality of receiving devices including a receiving device connected to the communication line and a receiving device not connected to the communication line. The receiving device connected to the communication line receives the packet transmitted via the broadcasting line. transmits if not correctly received retransmission request for retransmitting the packet data unit is a device that does not transmit the reception information if correctly received, the receiving device that is not connected to the communication line, a packet correctly and a function of transmitting a retransmission request if it can not receive an apparatus unused, and only allows transmission broadcast line direction via different communication lines, are connected to the communication line A packet retransmission request transmitted in data units from the receiving device is received, and a logical sum of packet retransmission requests from each of a plurality of receiving devices connected to the communication line is calculated, and retransmission is performed based on the logical sum. Transmission is controlled so that all the requested packets are retransmitted to a plurality of receiving apparatuses via the broadcast line.

A transmission / reception system according to a second aspect of the present invention includes a transmission device that transmits data via a broadcast line that can transmit data only in one direction, and a reception device that is connected to a communication line different from the broadcast line. And a plurality of receiving apparatuses including a receiving apparatus not connected to the communication line, wherein the transmitting apparatus packetizes the data into one or more packets of a predetermined data unit. Data transmitting means for transmitting the packet to the plurality of receiving devices via the broadcast line, and the receiving device connected to the communication line is transmitted via the broadcast line. If the packet cannot be received correctly, a retransmission request for retransmitting the packet is transmitted in the data unit. If the packet is received correctly, the reception information is not transmitted. The receiving device that is not connected to the communication line is a device that was unused function of transmitting the retransmission request if it can not correctly receive the packet, different from said only allows transmission of the broadcast channel in one direction Retransmission request receiving means for receiving the retransmission request for the packet transmitted in units of data from the receiving device connected to the communication line via the communication line, and received by the retransmission request receiving means Aggregating means for calculating the logical sum of the retransmission requests of the packets from each of the plurality of receiving devices connected to the communication line, and the retransmission request is made based on the logical sum obtained by the aggregation means. And a control means for controlling the data transmission means so as to retransmit all the packets to the plurality of receiving devices via the broadcast line. The reception device connected to a communication line different from the broadcast line receives the packet transmitted from the transmission device via the broadcast line, and receives the packet normally. A confirmation means for confirming whether the packet has been successfully received, and a retransmission request for retransmitting the packet that could not be received when the packet could not be received normally, A retransmission request transmission unit that transmits the data unit to the transmission device via a communication line, and the data reception unit further includes the retransmission request from itself and the other connected to the communication line. Based on the logical sum of the retransmission request from the receiving device, the retransmission data retransmitted from the transmitting device is received.

In the second aspect of the present invention, in the transmission device, data is packetized into one or more packets of a predetermined data unit, and the packets are broadcast via a broadcast line using broadcast waves that can be transmitted only in one direction. Sent to a plurality of receiving devices including a receiving device connected to a communication line different from the line and a receiving device not connected to the communication line, and the receiving device connected to the communication line transmits via the broadcast line. been if you can not correctly received packet to transmit a retransmission request for retransmitting the packet data unit is a device that does not transmit the reception information if correctly received, the receiving device that is not connected to the communication line It is a device that is unused the ability to send a retransmission request if it can not correctly receive the packet, and only allows transmission broadcast line direction via different communication lines, through A packet retransmission request transmitted in units of data from a receiving device connected to the line is received, and a logical sum of packet retransmission requests from each of a plurality of receiving devices connected to the communication line is calculated. Based on the logical sum, transmission is controlled so that all the packets for which retransmission is requested are retransmitted to a plurality of receiving apparatuses via the broadcast line. In a receiving apparatus connected to a communication line different from the broadcast line, a packet transmitted via the broadcast line is received, and it is confirmed whether or not the packet can be normally received. When a packet cannot be normally received, a retransmission request for retransmitting the packet that could not be received is transmitted in units of data to the transmission device via a communication line different from the broadcast line, The retransmission data retransmitted from the transmission device is received based on the logical sum of the retransmission request from the transmission request and the retransmission request from another reception device connected to the communication line.

  According to the first aspect of the present invention, data can be distributed efficiently and with high reliability.

  According to the second aspect of the present invention, data can be distributed efficiently and with high reliability.

  FIG. 1 shows a configuration example of an embodiment of a data distribution system to which the present invention is applied.

In this data distribution system, data is transmitted by the transmission device 1 and received by the reception devices 3 ₁ , 3 ₂ , 3 ₃ ,... The transmission of data by the transmission apparatus 1 is, for example, a satellite line, a CATV network, a terrestrial wave, or a network that can be broadcast simultaneously to at least a large number of users (a broadcast line to distinguish it from a communication line 4 described later) 2), and in this embodiment, the receiving devices 3 ₂ , 3 ₃ , 3 ₅ of the receiving devices 3 ₁ , 3 ₂ , 3 ₃ ,... Is, for example, an analog public network, ISDN (Integrated System Digital Network), the Internet, or any other network that can transmit information to the transmission device 1 (referred to as a communication line to distinguish it from the broadcast line 2) 4 The retransmission request signal NAK can be transmitted to the transmission device 1 via.

  Next, the operation will be described with reference to FIG.

In the transmission device 1, as shown in FIG. 2A, data is transmitted via the broadcast line 2 by, for example, IP multicast. Data transmitted (distributed) via the broadcast line 2 is received by the receiving devices 3 ₁ , 3 ₂ , 3 ₃ ,. These receiving devices 3 ₁ , 3 ₂ , 3 ₃ ,... May be dispersed in a network (in different domains) or in one network.

Here, in the following, for simplicity of explanation, as the user side of the receiving device, consider only the receiving apparatus 3 ₁ to 3 _5. Hereinafter, the receiving devices 3 _{1 to} 3 ₅ are collectively referred to as a receiving device 3 as appropriate.

The receiving devices 3 _{1 to} 3 ₅ check whether or not the data transmitted via the broadcast line 2 has been normally received, and store the data if the data has been normally received. To do.

The data stored in the receiving devices 3 _{1 to} 3 ₅ is displayed, for example, or output as sound when the user performs a predetermined operation.

As described above, among the receiving devices 3 _{1 to} 3 ₅ , in the present embodiment, the receiving devices 3 ₂ , 3 ₃ , and 3 ₅ transmit information to the transmitting device 1 via the communication line 4. And the communication line 4 can be used (therefore, the remaining receiving apparatuses 3 ₁ and 3 ₄ do not have such a function, or have such a function. The communication line 4 is temporarily not used) (hereinafter simply referred to as having or not having the function of transmitting information as appropriate), the receiving devices 3 ₂ , 3 ₃ , in or _35, when it is not possible to receive the data normally only retransmission request signal NAK, via the communication line 4, it is sent to the transmitter 1.

That is, in FIG. 2, as shown in FIG. (B), of the receiving apparatus 3 ₁ to 3 _5, in the receiving apparatus 3 _1, 3 ₃ and 3 ₅ (in FIG. 2 (B) indicated by mark ●) can not receive the data normally, to the transmitting apparatus 1 from the receiving device 3 ₃ and 3 ₅ have the function of transmitting the retransmission request signal NAK of which retransmission request signal NAK is, via the communication line 4 Have been sent.

  For example, when the transmission apparatus 1 receives the retransmission request signal NAK via the communication line 4 after a predetermined time elapses after transmission of data via the broadcast line 2, FIG. As shown in A), the data requested to be retransmitted by the retransmission request signal NAK is transmitted again via the broadcast line 2.

Here, as described above, the receiving devices 3 ₁ and 3 ₄ do not have a function of transmitting information to the transmitting device 1 (or the communication line 4 is connected even if it has a function of transmitting information). Therefore, in these receiving apparatuses 3 ₁ and 3 ₄ , only data transmitted from the transmitting apparatus 1 via the broadcast line 2 is received. A connection as in the case of performing communication by handshake is not established (not established) with each of the receiving devices 3 ₁ or 3 ₄ . Therefore, it can be said that the transmission of data from the transmission device 1 to each of the reception devices 3 ₁ or 3 ₄ is performed by connectionless communication as in the case where data is transmitted by the above-described UDP.

In addition, the receiving device 3 ₂ has a function of transmitting information to the transmitting device 1, but in FIG. 2B, the receiving device 3 ₂ was able to receive data normally. Thus, the retransmission request signal NAK is not transmitted. Accordingly, in this case as well as in the receiving apparatuses 3 ₁ and 3 ₄ , since no connection is established with the transmitting apparatus 1, data transmission from the transmitting apparatus 1 to the receiving apparatus 3 ₂ is also a connection. It can be said that it is performed by less communication.

On the other hand, in the remaining receiving devices 3 ₃ and 3 ₅ having a function of transmitting information to the transmitting device 1, data could not be normally received in FIG. Thus, the retransmission request signal NAK is transmitted to the transmission device 1. That is, at the time of data reception, a retransmission request signal NAK as a response is returned to the transmission apparatus 1. Accordingly, in this case, a connection is established as in the case of performing communication by handshake. However, the response to the transmission device 1 is not transmitted in any case, whether the data can be received normally or not, and the data can be received normally. Only in the case of failure, the retransmission request signal NAK is transmitted. That is, the connection with the transmission apparatus 1 is not always established, and is established only when data cannot be normally received. In this sense, the transmission of data from the transmitting device 1 to the receiving device 3 ₃ or 3 ₅ in this case is a so-called slow connection communication (when the data can be normally received, the connection is not established and If it cannot be received, it can be said that the connection is established).

Of the receiving apparatuses 3 ₂ , 3 ₃ , or 3 ₅ , the one that has transmitted the retransmission request signal NAK and the function of transmitting the retransmission request NAK (or the function of transmitting the retransmission request NAK may be included). Of the receiving devices 3 ₁ or 3 ₃ that are not using the communication line 4, the data that has not been received normally can be received as described above. Then, it is confirmed whether or not the data has been successfully received. Thereafter, the same processing is repeated.

  On the other hand, in the transmission apparatus 1, when the retransmission request signal NAK is transmitted again after the data is retransmitted, the data retransmission is repeated. When the retransmission request signal NAK is no longer transmitted, the next data is transmitted, and the same processing is repeated thereafter.

  As described above, since only the retransmission request signal NAK is transmitted from the receiving device 3 to the transmitting device 1 via the communication line 4, the number of receiving devices is smaller than that in the case where the confirmation signal ACK is also transmitted. For example, even if the population increases to the national scale, congestion of the communication line 4 can be reduced, and as a result, efficient data distribution can be performed.

In the data distribution system of FIG. 1, all the receiving devices (in this embodiment, the receiving devices 3 _{1 to} 3 ₅ ) that receive data transmitted from the transmitting device 1 via the broadcast line 2 are requested to send retransmission requests. It is not necessary to have a function of transmitting the signal NAK. Therefore, even a receiving apparatus that does not have such a function can receive data from the transmitting apparatus 1.

In FIG. 1, when all the receiving apparatuses 3 _{1 to} 3 ₅ do not have the function of transmitting the retransmission request signal NAK (or even if they have the communication line 4 not used). simply, as in the case of the delivery of data in IP multicast, regardless of whether it was possible to normally receive data at the receiving apparatus 3 ₁ to 3 _5, retransmission of data is not performed. Therefore, in this case, since the reliability of data is lowered, it is preferable that one or more of the receiving apparatuses 3 _{1 to} 3 ₅ have a function of transmitting the retransmission request signal NAK. .

  Furthermore, it is preferable that the number of receiving apparatuses (hereinafter, appropriately referred to as retransmission requestable receiving apparatuses) having a function of transmitting the retransmission request signal NAK is larger. That is, a receiving apparatus that does not have a function of transmitting a retransmission request signal NAK (hereinafter referred to as a retransmission request disabled receiving apparatus) transmits a retransmission request signal NAK when data cannot be received normally. If there is a re-transmission requestable receiving device that could not normally receive the same data as that (if such a situation, the cause of the failure of normal reception is the individual receiving device The retransmission request signal NAK is transmitted from the re-transmission request possible receiving device via the broadcast line 2 by the re-transmission request possible receiving device. The data is retransmitted. Therefore, as a result, the data is also retransmitted to the retransmission request impossible receiving device that has not been able to receive the data normally, and not only the data received at the retransmission requestable receiving device but also the retransmission request is received. The reliability of the data received by the request impossible receiving device can also be improved.

  Here, since only the retransmission request signal NAK can be transmitted, it is expected that an error may occur during the transmission and the retransmission request signal NAK may not be received by the transmission apparatus 1. The However, when the transmitter 1 cannot receive the retransmission request signal NAK transmitted by a certain receiver, the receiver is not a receiver that can request retransmission but a receiver that cannot request retransmission. Therefore, in order to deal with such a case, it is preferable that the number of retransmission requestable receiving apparatuses is larger.

  However, even if there is no re-transmission requestable receiving device among the receiving devices, it is difficult to maintain data reliability, but data can be distributed.

  The broadcast line 2 and the communication line 4 do not need to be physically separate networks. That is, when the broadcast line 2 is configured by, for example, a CATV network, the CATV network can also be used as the communication line 4. Further, in the case where data distribution via the broadcast line 2 is performed by, for example, IP multicast using the Internet or the like, the communication line 4 can also be configured by the Internet.

  However, it is desirable that the broadcasting line 2 is suitable for so-called broadcasting, which can broadcast simultaneously over a wide area, such as a satellite line, a terrestrial wave, or a CATV network. This is due to the following reason. That is, according to such a broadcast line 2, the transmitting apparatus 1 and each of a large number of receiving apparatuses are directly connected in a network, so that all receiving apparatuses are equivalent from the viewpoint of the transmitting apparatus 1. become. Therefore, for example, the above-described problems in path control and the problem of wasting network resources when performing IP multicast using the current Internet can be avoided. Further, for example, when a wireless line such as a satellite line or a terrestrial wave is used as the broadcast line 2, the reception connected to the network provided with the firewall is within the range in which the radio wave can reach. Data can also be distributed to a computer as an apparatus.

  Next, the operation of the data distribution system of FIG. 1 will be further described with reference to FIG.

  In the transmission apparatus 1, data is transmitted according to a predetermined schedule, but before transmitting the data, information necessary for restoring the data on the receiving side (hereinafter referred to as transmission conditions as appropriate). For example, information for identifying the data, data content, data amount, data transmission time, transmission rate, protocol, number of transmissions (as will be described later, data is repeatedly transmitted one or more times. The number of times of transmission means the number of times of repetition) is transmitted via the broadcast line 2 by, for example, IP multicast.

  The transmission condition is received by the reception device 3, and the reception device 3 then waits until data is transmitted. Note that the receiving device 3 subsequently receives and restores data based on the transmission conditions.

  On the other hand, in the transmission apparatus 1, according to a predetermined schedule, the data to be transmitted is packetized into one or more packets, and information necessary for restoring the original data is added to each packet. Configure. Here, in FIG. 3, the data is packetized into five packets of packets a, b, c, d, and e.

  Thereafter, the transmission device 1 sequentially transmits the packets a to e via the broadcast line 2 by, for example, IP multicast.

  The receiving device 3 receives the packets a to e transmitted sequentially as described above. In the receiving device 3, the packets a to e are reconstructed into the original data based on the information added thereto. At this time, the receiving device 3 confirms whether or not the packets a to e have been normally received.

Here, in FIG. 3, all of the packets a to e are normally received by the receiving apparatuses 3 ₂ and 3 ₄ . On the other hand, the receiving apparatus 3 _1, packet b, the receiving apparatus 3 ₃ In the packet b and d, the receiving apparatus 5, a packet d and e, can not be normally received, respectively, to reconstruct the original data (In FIG. 3, the packets that could not be normally received are indicated by shadows).

Of the receiving devices 3 ₁ , 3 ₃ , or 3 ₅ that have not been able to normally receive any of the packets a to e necessary to reconstruct the data, the retransmission requestable receiving device In some receiving apparatuses 3 ₃ and 3 ₅ , a packet that could not be normally received after a predetermined time has elapsed since the last packet reception, even though data reconfiguration has not been completed. A retransmission request signal NAK requesting retransmission in units of data is transmitted to the transmission apparatus 1 via the communication line 4 by, for example, UDP. That is, in FIG. 3, the retransmission of the receiving apparatus 3 ₃ packet b and d, the retransmission of the receiving apparatus 3 ₅ packets d and e, the retransmission request signal NAK for requesting collectively respectively, for example, by UDP, the transmission device 1 to send.

The transmission device 1 waits for a predetermined waiting time after the transmission of the packets a to e, and receives and aggregates the retransmission request signals NAK transmitted during that time. That is, in the transmission apparatus 1, for example, a logical sum of the packets requested to be retransmitted by the retransmission request signal NAK is obtained, and thereby the packet to be retransmitted is recognized. In FIG. 3, the receiving apparatus 3 ₃ packet retransmission b and d from the receiving apparatus 3 ₅ retransmission packet d and e from and because they are respectively requested packet b is the logical OR, d, and e is recognized as a packet to be retransmitted.

  Then, in the transmitting apparatus 1, the recognized packets b, d, and e are sequentially transmitted (retransmitted) via the broadcast line 2 in the same manner as described above.

In the receiving apparatuses 3 ₂ and 3 ₄ that have already received all the packets a to e normally, the packets b, d, and e retransmitted from the transmitting apparatus 1 are ignored (discarded). Also, the receiving apparatus 3 ₃ was a retransmission request for the packet b and d, the only packets b and d are received, the packet e is ignored. Similarly, the receiving apparatus 3 ₅ to a retransmission request for the packet d and e, the only packets d and e are received, the packet b is ignored.

Moreover, it was not possible to successfully receive a packet b, the receiving apparatus 3 ₁ a retransmission request not receiving apparatus, a retransmission is requested by the receiving device 3 _3, only packet b which has been retransmitted from the transmitting device 1 is received And packets d and e are ignored.

In the receiving apparatuses 3 ₁ , 3 ₃ , and 3 ₅ that have received the retransmitted packet as described above, the original data is reconstructed using the packet and the already received packet.

  Therefore, in the case where the retransmission request capable receiving apparatus cannot normally receive the packet, it can obtain the packet by transmitting the retransmission request signal NAK for the packet. In addition, even when a packet cannot be normally received in a retransmission request impossible receiving device, another receiving device that is a retransmission request capable receiving device transmits a retransmission request signal NAK for the packet. In other words, the packet can be obtained in the form of a piggyback.

  Further, in FIG. 3, when a packet from the transmission apparatus 1 cannot be normally received, the retransmission request signal NAK is not immediately transmitted, but after receiving a series of packets constituting certain data. In other words, retransmission request signals NAK requesting packets that could not be normally received are transmitted in a batch. When the retransmission request signal NAK is transmitted in such data units, the traffic on the communication line 4 can be reduced as compared with the case where the retransmission request signal NAK is transmitted in packet units.

  In addition, every time the retransmission request signal NAK is received, the transmission apparatus 1 does not retransmit the packet requested by the retransmission request signal NAK, but aggregates the retransmission request signals NAK received within a predetermined period. The packets are retransmitted according to the result of counting. Therefore, more efficient retransmission can be performed compared to the case where the packet is retransmitted corresponding to each retransmission request signal NAK.

  In addition, after retransmission of a packet, if any of the retransmission requestable receiving apparatuses that request the retransmission again fails to normally receive the packet, the retransmission requestable receiving apparatus again transmits the retransmission request signal NAK. Send. On the other hand, when receiving the retransmission request signal NAK, the transmission device 1 repeats retransmission of the packet. When the transmission apparatus 1 cannot receive the retransmission request signal NAK, that is, when the retransmission request signal NAK is not transmitted from the reception apparatus, the packet constituting the next data (in accordance with a predetermined schedule) ).

  However, if the retransmission of the packet is repeated until the retransmission request signal NAK is not transmitted from the one retransmission requestable receiving apparatus, in an extreme case, only the one retransmission requestable receiving apparatus receives the packet. The retransmission may be repeated many times and is not efficient. Therefore, it is possible to limit the number of times and time for performing retransmission of a packet.

  Next, FIG. 4 shows a configuration example of the transmission apparatus 1 of FIG.

The database 11 stores data to be distributed. The packet configuration unit 12 reads data from the database 11 under the control of the schedule management unit 14, packetizes it into one or more IP packets, and supplies the packet to the transmission unit 13. The transmission unit 13 is configured to transmit a packet from the packet configuration unit 12 through the broadcast line 2 by IP multicast or the like under the control of the schedule management unit 14. The schedule management unit 14 configures and transmits a packet by controlling the packet configuration unit 12 and the transmission unit 13 according to a predetermined schedule. Further, the schedule management unit 14 controls the transmission unit 13 in accordance with the totalization result of the retransmission request signal NAK by the retransmission request totaling unit 15, thereby retransmitting necessary packets. The retransmission request totaling unit 15 totals the retransmission request signals NAK received by the communication control unit 16 and supplies the totaled result to the schedule management unit 14. The communication control unit 16 controls communication with the receiving device (in the embodiment shown in FIG. 1, the receiving devices 3 ₂ , 3 ₃ , and 3 ₅ ) via the communication line 4. The retransmission request signal NAK transmitted by UDP or the like is received via the communication line 4 and supplied to the retransmission request counting unit 15.

  Next, the operation will be described with reference to the flowchart of FIG.

  First, in step S <b> 1, the schedule management unit 14 controls the transmission unit 13 to transmit transmission conditions for data to be transmitted according to a predetermined schedule via the broadcast line 2. Then, the schedule management unit 14 controls the packet configuration unit 12 according to a predetermined schedule, thereby reading data to be transmitted from the database 11 and configuring an IP packet in step S2. The IP packets are sequentially supplied to the transmission unit 13 and transmitted via the broadcast line 2 in step S3.

  Then, the process proceeds to step S4, where the schedule management unit 14 determines whether or not the transmission of the packet constituting the data has been repeated a predetermined number of times. If it is determined that the packet has not been repeated a predetermined number of times, the process proceeds to step S3. Return and the packet transmission is repeated.

That is, among the receiving devices 3 that receive data transmitted via the broadcast line 2, there are receiving devices 3 ₁ and 3 ₄ that do not make a retransmission request, and the receiving devices 3 ₂ , 3 ₃ that make a retransmission request, When the data can be normally received in all of 3 and 3 ₅ , the retransmission request is not performed. Therefore, in this case, the receiving devices 3 ₁ and 3 ₄ can normally receive the data. If not, the receiving apparatuses 3 ₁ and 3 ₄ cannot request retransmission, and thus cannot obtain the data. Further, even if the receiving apparatus 3 ₂ , 3 ₃ , 3 ₅ cannot receive data normally and the retransmission request signal NAK is transmitted, the transmitting apparatus 1 transmits the retransmission request signal NAK. There are times when normal reception is not possible. Also in this case, data is not retransmitted.

  Therefore, the transmission device 1 is configured to repeat transmission of a packet constituting the data one or more times, thereby improving the probability that the reception device 3 can normally receive the data. It is made like that.

  The packet transmission may be repeated until a predetermined time elapses instead of being repeated a predetermined number of times.

  If it is determined in step S4 that the transmission of the packet constituting the data has been repeated a predetermined number of times, the process proceeds to step S5, and the communication control unit 16 determines whether or not the retransmission request signal NAK has been received. If it is determined in step S5 that the retransmission request signal NAK has not been received, the process returns to step S1, the transmission condition for the data to be transmitted next is transmitted, and the same processing is repeated thereafter.

On the other hand, if it is determined in step S5 that the retransmission request signal NAK has been received, the process proceeds to step S6, where the retransmission request signal NAK is aggregated. That is, the retransmission request signal NAK received by the communication control unit 16 is supplied to the retransmission request totaling unit 15, and the retransmission request totaling unit 15 requests a retransmission by the retransmission request signal NAK from the communication control unit 16. Is obtained as a packet to be retransmitted. For example, in the example shown in FIG. 3 described above, the retransmission from the receiving apparatus 3 ₃ packets b and d are retransmitted from the receiving apparatus 3 ₅ packets d and e are, since they are respectively requested by the logical OR Certain packets b, d, and e are obtained as packets to be retransmitted. Information indicating the packet to be retransmitted (the result of counting the retransmission request signal NAK) (hereinafter referred to as retransmission information as appropriate) is supplied from the retransmission request counting unit 15 to the schedule management unit 14.

  When receiving the retransmission information from the retransmission request counting unit 15, the schedule management unit 14 controls the transmission unit 13 in step S7 to retransmit the packet corresponding to the retransmission information, and returns to step S5. If the retransmission request signal NAK is transmitted as a result of the retransmission, the processes in steps S5 to S7 are repeated, and when the retransmission request signal NAK is not transmitted, the process returns from step S5 to step S1. Note that, as described above, the packet retransmission processing in steps S5 to S7 can be terminated at a predetermined number of times or at a predetermined time and returned to step S1.

  Next, FIG. 6 shows a configuration example of the receiving device 3 of FIG.

  The reception unit 21 receives information (packets, transmission conditions, etc.) transmitted from the broadcast line 2 and supplies the information to the data configuration unit 22. The data configuration unit 22 reconfigures the packet supplied from the data reception unit 21 into the original data according to the transmission conditions supplied from the data reception unit 21. The data confirmation unit 23 monitors a packet supplied to the data configuration unit 22 and confirms whether the packet is normally received. In addition, the data confirmation unit 23 controls the reception unit 21 so as to discard the duplicately received packet. The recording medium 24 is, for example, a hard disk, a magneto-optical disk, or the like, and stores (records) the data reconstructed by the data configuration unit 22. The reading unit 25 reads data from the recording medium 24 according to the operation of the operation unit 27 and supplies the data to the output unit 26. The output unit 26 includes, for example, a display and a speaker, and is configured to display, print, or output data from the reading unit 25 as sound. The operation unit 27 is operated when reading data recorded on the recording medium 24.

  When the data confirmation unit 23 confirms that the packet has not been normally received, the retransmission request unit 28 requests the retransmission. That is, the retransmission request unit 28 generates a retransmission request signal NAK that requests retransmission of a packet that could not be normally received, and controls the communication control unit 29 to transmit the transmission device 1 via the communication line 4. To be sent to. Note that, as described above, the retransmission request unit 28 generates the retransmission request signal NAK in units of data. That is, after the reception unit 21 finishes receiving a series of packets that constitute certain data, a retransmission request signal NAK is generated for the packets that constitute that data that could not be normally received. It is made like that.

  The communication control unit 29 is configured to control communication with the transmission device 1 via the communication line 4, whereby the retransmission request signal NAK supplied from the retransmission request unit 28 is transmitted to the communication line 4. Is transmitted to the transmission device 1 by UDP or the like.

Among the receiving apparatuses 3, the receiving apparatuses 3 ₂ , 3 ₃ , and 3 ₅ , which are receiving apparatuses that make a retransmission request (receivable receiving apparatus), are as described above, but the receiving apparatuses that do not perform a retransmission request. (retransmission request not receiving apparatus) receiver 3 ₁ and 3 ₄ a is either one of the configurations, or they retransmission requesting unit 28 and the communication control unit 29 shown enclosed by the dotted line is not provided in FIG. 6 Or both functions are paused.

  Next, the operation will be described with reference to the flowchart of FIG.

  In the reception device 3, in step S <b> 11, the reception unit 21 receives the transmission condition from the transmission device 1 via the broadcast line 2 and then receives the transmission condition. The reception unit 21 supplies the received transmission condition to the data confirmation unit 23 via the data configuration unit 22, and thereafter, the data confirmation unit 23 from the reception unit 21 until the next transmission condition is supplied. Based on the transmission conditions supplied via the data configuration unit 22, the reception unit 21 and the data configuration unit 22 are controlled.

  When the transmission condition is received, the process proceeds to step S12, where the reception unit 21 receives the series of packets constituting the data from the transmission device 1 via the broadcast line 2. When the reception unit 21 receives the packet, the process proceeds to step S13, in which whether the packet is the same as a packet that has already been received (hereinafter, referred to as a received packet as appropriate). Determined. That is, as described above, in the transmission device 1, since the packet is repeatedly transmitted several times, the reception unit 21 may receive the same packet as the received packet in duplicate. In this case, the data confirmation unit 23 controls the reception unit 21 so as to ignore the packet, and therefore, the duplicate packet is discarded in the reception unit 21.

  If it is determined in step S13 that the received packet is the same as the received packet, the process proceeds to step S14, and the data confirmation unit 23 determines that the received packet is the same as the received packet. The receiving unit 21 is controlled so as to discard, and the process proceeds to step S15. As a result, the receiving unit 21 discards the same received packet as the received packet. Note that packets that are not discarded by the reception unit 21 are supplied to the data configuration unit 22.

  In step S13, if it is determined that there is no packet received by the receiving unit 21 that is the same as the received packet, all the packets received by the receiving unit 21 are supplied to the data configuration unit 22. The In step S15, the data construction unit 22 reconstructs the original data using the packet supplied from the reception unit 21.

  In step S16, the data confirmation unit 23 determines whether all the packets supplied to the data configuration unit 22 have been normally received. If it is determined that all packets have been normally received, The unit 22 supplies the reconstructed data to the recording medium 24 for storage. Then, after waiting for the next transmission condition to be transmitted from the transmission apparatus 1 via the broadcast line 2, the process returns to step S11.

  Here, the data recorded on the recording medium 24 as described above is read by the reading unit 25 when the operation unit 27 is operated, supplied to the output unit 26, and displayed. Thereby, the user can use the data recorded on the recording medium 24.

  On the other hand, if it is determined in step S16 that one of the packets supplied to the data configuration unit 22 has not been successfully received, the process proceeds to step S17, where the data confirmation unit 23 The packets (missing packets) that could not be normally received are counted. That is, the data confirmation unit 23 detects all of the packets necessary for reconstructing certain data that could not be normally received and supplies the packets to the retransmission request unit 28. Then, the process proceeds to step S18, and all retransmissions of the packets that could not be normally received are requested collectively. That is, in step S 18, the retransmission request unit 28 generates a retransmission request signal NAK for collectively requesting packets that could not be normally received, and supplies the request to the communication control unit 29. In step S 18, the communication control unit 29 transmits the retransmission request signal NAK from the retransmission request unit 28 to the transmission device 1 via the communication line 4.

  Thereafter, the process returns to step S12, and the packet requested by the retransmission request signal NAK is received by the receiving unit 21 after waiting for the packet to be retransmitted via the broadcast line 2. At this time, if the receiving unit 21 has received all the packets requested by the retransmission request signal NAK, in step S15, using the packet and the packet that has already been normally received, Data will be reconstructed.

Here, in the receiving apparatuses 3 ₁ and 3 ₄ that do not have the retransmission request unit 28 and the communication control unit 29, the processes in steps S17 and S18 are skipped. Accordingly, in the receiving devices 3 ₁ and 3 ₄ , when it is determined in step S 16 that one of the packets supplied to the data configuration unit 22 cannot be normally received, The process of step S12 is performed after waiting for a packet that could not be normally received to be retransmitted by the retransmission request signal NAK by the receiving apparatuses 3 ₂ , 3 ₃ , and 3 ₅ . Note that, when a packet that could not be normally received is not retransmitted, the data including the packet is discarded without being recorded in the recording medium 24, for example.

  The case where the present invention is applied to a data distribution system has been described above. Such a data distribution system is, for example, a broadcast line 2 or a network introduced as 97.3, Nikkei Multimedia. The communication line 4 can be applied to a multimedia content distribution business by digital broadcasting using a satellite or the Internet.

  Here, with the spread of information devices with built-in computers to general households, transmissions that can be broadcast simultaneously over a wide area, such as satellite links, terrestrial waves, and CATV networks, which are used for television broadcasting and radio broadcasting. Attempts to use not only media (hereinafter referred to as “broadcast media” where appropriate) for distribution of images and audio but also various types of digital data handled by computers and the like have become active. Thus, it is expected that the use of data for distributing data (including computer programs in addition to image and audio data) to computers will become increasingly popular.

  On the other hand, with the spread of terminals that can be connected to the Internet, which is one of the computer networks, and the increase in the capacity of the lines for the connection, using the Internet, like television broadcasting and radio broadcasting, Attempts to broadcast data such as images (especially videos) and audio in real time are also active, and it is expected that the movement to use computer networks for so-called broadcasting will become more and more popular in the future. The

  As described above, with the current situation where the boundary between the broadcasting medium and the computer network is disappearing, AV broadcasting can be performed by combining the characteristics of the broadcasting medium with the wide-area broadcast and the bidirectionality of the computer network. (Audio Visual) Technology that efficiently distributes various types of multimedia information ranging from content to computer software to users on a national and global scale is extremely important. According to the above, it is possible to provide an efficient and highly reliable multicast service to a large number of users.

  In the case where radio is used as the broadcast line 2, the receiving device 3 may be installed indoors or may be a so-called portable device such as a mobile computer. Also good.

  Further, in the data distribution system as described above, data can be distributed either for a fee or free of charge, and further, a pay user and a free user can be mixed. In addition, data can be distributed regardless of the number of receiving apparatuses 3, but the present invention is particularly useful when the number of receiving apparatuses 3 is large.

It is a block diagram which shows the structural example of one Embodiment of the data delivery system to which this invention is applied. It is a figure for demonstrating operation | movement of the data delivery system of FIG. It is a figure for demonstrating operation | movement of the data delivery system of FIG. It is a block diagram which shows the structural example of the transmitter 1 of FIG. 6 is a flowchart for explaining the operation of the transmission apparatus 1 of FIG. FIG. 2 is a block diagram illustrating a configuration example of a receiving device 3 in FIG. 1. 7 is a flowchart for explaining the operation of the receiving device 3 of FIG. 6. It is a block diagram which shows the structure of an example of the conventional data delivery system. It is a block diagram which shows the structure of an example of the data delivery system using RMTP.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter, 2 Broadcast line, 3 ₁ thru | or 3 ₅ Receiver, 4 Communication line, 11 Database, 12 Packet structure part, 13 Transmission part, 14 Schedule management part, 15 Retransmission request total part, 16 Communication control part, 21 Reception Unit, 22 data configuration unit, 23 data confirmation unit, 24 recording medium, 25 reading unit, 26 output unit, 27 operation unit, 28 retransmission request unit, 29 communication control unit

Claims (7)

Packetizing means for packetizing data into one or more packets of a predetermined data unit;
A plurality of receivers including a receiver connected to a communication line different from the broadcast line and a receiver not connected to the communication line via a broadcast line using a broadcast wave that can be transmitted in only one direction. Transmitting means for transmitting to the receiving device;
If the receiving device connected to the communication line cannot correctly receive the packet transmitted via the broadcast line, the receiving device transmits a retransmission request for retransmitting the packet in units of data, and receives the packet correctly. If not, it is a device that does not transmit reception information, and the reception device that is not connected to the communication line is a device that has not used the function of transmitting the retransmission request when the packet cannot be received correctly,
Reception for receiving the retransmission request for the packet transmitted in units of data from the receiving device connected to the communication line via the communication line different from the broadcast line that can be transmitted only in one direction Means,
Aggregating means for calculating a logical sum of the retransmission requests of the packets from each of the plurality of receiving devices connected to the communication line received by the receiving means;
Control means for controlling the transmission means so as to retransmit all of the packets requested to be retransmitted to the plurality of receiving devices via the broadcast line based on the logical sum obtained by the aggregation means. A transmission device comprising: The transmission device according to claim 1, wherein the transmission unit repeats retransmission under a predetermined condition when the data is retransmitted. The transmission apparatus according to claim 1, wherein the broadcast line is a line that performs communication without confirming a reception state in the reception apparatus. The transmission device according to claim 1, wherein the communication line is a communication line capable of bidirectional communication. The transmission device according to claim 1, wherein the reception unit receives the retransmission request transmitted according to UDP. Packetize data into one or more packets of a given data unit;
A plurality of receivers including a receiver connected to a communication line different from the broadcast line and a receiver not connected to the communication line via a broadcast line using a broadcast wave that can be transmitted in only one direction. To the receiving device,
If the receiving device connected to the communication line cannot correctly receive the packet transmitted via the broadcast line, the receiving device transmits a retransmission request for retransmitting the packet in units of data, and receives the packet correctly. If not, it is a device that does not transmit reception information, and the reception device that is not connected to the communication line is a device that has not used the function of transmitting the retransmission request when the packet cannot be received correctly,
Receiving the retransmission request of the packet transmitted in units of data from the receiving device connected to the communication line via the communication line different from the broadcast line that can be transmitted in only one direction;
Calculate a logical sum of the retransmission requests of the packets from each of the plurality of receiving devices connected to the communication line, and based on the logical sum, all the packets for which the retransmission request has been made are transmitted to the broadcast line. A transmission method including the step of controlling transmission so as to be retransmitted to a plurality of the reception devices via the network. A transmission device for transmitting data via a broadcast line by a broadcast wave capable of transmitting data in only one direction;
A transmission / reception system comprising a receiving device connected to a communication line different from the broadcast line and a plurality of receiving devices including a receiving device not connected to the communication line,
The transmitter is
Packetizing means for packetizing the data into one or more packets of a predetermined data unit;
Data transmitting means for transmitting the packet to the plurality of receiving devices via the broadcast line;
If the receiving device connected to the communication line cannot correctly receive the packet transmitted via the broadcast line, the receiving device transmits a retransmission request for retransmitting the packet in units of data, and receives the packet correctly. If not, it is a device that does not transmit reception information, and the reception device that is not connected to the communication line is a device that has not used the function of transmitting the retransmission request when the packet cannot be received correctly,
Retransmission for receiving the retransmission request for the packet transmitted in units of data from the receiving device connected to the communication line via the communication line different from the broadcast line that can be transmitted in only one direction A request receiving means;
Aggregating means for calculating a logical sum of the retransmission requests of the packets from each of the plurality of receiving devices connected to the communication line received by the retransmission request receiving means;
Control for controlling the data transmission means so as to retransmit all the packets requested for retransmission to a plurality of receiving devices via the broadcast line based on the logical sum obtained by the aggregation means. Means and
The receiving device connected to a communication line different from the broadcast line,
Data receiving means for receiving the packet transmitted from the transmitting device via the broadcast line;
Confirmation means for confirming whether or not the packet was successfully received;
If the packet cannot be normally received, a retransmission request for retransmitting the packet that could not be received is sent to the transmitting device via the communication line different from the broadcast line. And a retransmission request transmission means for transmitting at
The data receiving means is further retransmitted from the transmitting device based on the logical sum of the retransmission request from itself and the retransmission request from another receiving device connected to the communication line. A transmission / reception system that receives data.

Images