JP4982434B2 - Communication system and decoding apparatus - Google Patents

Description

  The present invention relates to a plurality of communication devices that transfer content data transmitted by multicast from a transmission device to a reception device, an encoding device that encodes content data and generates encoded data, and a decoding that decodes encoded data The present invention relates to a communication system provided with a communication device. The present invention also relates to an encoding device and a decoding device included in the communication system.

  In recent years, with the development of broadband, there is an increasing demand for distributing large-capacity video content over an IP network. Some of such contents are highly broadcast and can be significantly reduced in network bandwidth by being distributed using multicast. On the other hand, in such one-to-many communication, a maximum flow in multicast communication is made one-to-one for each receiving node by coding (encoding) packets arriving from different paths at nodes in the network. “Network coding”, which is a method of minimizing the maximum flow value during communication, is shown (see, for example, Non-Patent Document 1).

  Hereinafter, network coding will be described. As an example, assume the configuration and link capacity (bandwidth) shown in FIG. This network is composed of a transmission node S, reception nodes R1 and R2, and nodes N1, N2, N3 and N4. The numbers written in the vicinity of the links between the nodes indicate the link capacity. For example, the link capacity between the transmission node S and the node N1 is 1.

In normal multicast communication, the content a that consumes capacity 1 is distributed to the receiving nodes R1 and R2 through the route shown in FIG. However, another content data b that consumes capacity 1 cannot be distributed due to the limit of the link capacity. On the other hand, if network coding is used, both content data a and b can be distributed. As shown in FIG. 4C, the node N3 performs encoding of the content data a and b, and generates encoded data a + b. When receiving node R1 receives content data a distributed from transmitting node S and encoded data a + b generated at node N3, receiving node R1 can obtain both content data a and b by decoding. . Similarly, the receiving node R2 can obtain both content data a and b.
R. Ahlswede, et al., "Network Information Flow," IEEE Transactions on Information Theory, Vol. 46, No. 4, pp-1204-1216, Jul. 2000.

  However, since ordinary routers do not have the coding function as described above, it is difficult to apply network coding to IP multicast. Although it is possible to realize network coding by using, for example, active network technology that can enhance the functionality of routers, it is necessary to enhance the functionality of existing routers, which increases costs. .

  The present invention has been made in view of the above problems, and is a communication system and encoding that can realize network coding without increasing the functionality of a communication device constituting an existing communication system that performs multicast transfer. An object is to provide a device and a decoding device.

  The present invention has been made to solve the above problems, and a plurality of communication devices that transfer content data transmitted by multicast from a transmission device to a reception device, and generate encoded data by encoding the content data And a decoding device for decoding the encoded data, wherein the encoding device is connected to a first communication device and transmitted by a first multicast. First data receiving means for receiving the first content data and the second content data transmitted by the second multicast from the first communication device, the first content data and the second content data Encoding means for performing encoding processing based on the content data of the first data and generating encoded data; and the encoded data by means of a third multicast. First data transmission means for transmitting to the first communication device, and the decryption device is connected to a second communication device, the first content data or the second content data and the code Second data receiving means for receiving encoded data from the second communication device, and generating the second content data by performing a decoding process based on the first content data and the encoded data, Alternatively, the communication system includes a decoding unit that performs decoding processing based on the second content data and the encoded data to generate the first content data.

  In the communication system of the present invention, the decoding device further indicates that the communication path to the first multicast transmission device or the second multicast transmission device is in the direction of the decoding device. In order to make the device recognize, the route information transmission unit that transmits the route information about the route to the transmission device to the second communication device, and the first content data generated by the decryption unit or the second content data Second data transmission means for transmitting content data to the second communication device by the first multicast or the second multicast corresponding to the first content data or the second content data It is characterized by that.

  The present invention is also an encoding device connected to a communication device for transferring content data transmitted by multicast from a transmission device to a reception device, the first content data transmitted by the first multicast, Data receiving means for receiving second content data transmitted by the second multicast from the communication device, encoding processing based on the first content data and the second content data, and encoding An encoding apparatus comprising: encoding means for generating data; and data transmission means for transmitting the encoded data to the communication apparatus by a third multicast.

  The present invention is also a decoding device connected to a communication device for transferring content data transmitted by multicast from the transmission device to the reception device, wherein the first content data transmitted by the first multicast, or Encoding generated by receiving second content data transmitted by the second multicast from the communication device and performing encoding processing based on the first content data and the second content data Data receiving means for receiving data from the communication device, and generating the second content data by performing a decoding process based on the first content data and the encoded data, or the second content data and The first content data is generated by performing a decoding process based on the encoded data. A decoding apparatus characterized by comprising a decoding means for.

  In the decoding device of the present invention, in order to make the communication device recognize that the communication path to the first multicast transmission device or the second multicast transmission device is the direction of the own device, Route information transmission means for transmitting route information related to the route to the communication device, and the first content data or the second content data generated by the decryption means, the first content data or the second content data. Data transmission means for transmitting to the communication device by the first multicast or the second multicast corresponding to the content data.

  According to the present invention, an encoding device that encodes the first content data and the second content data to generate encoded data, and the first content data or the second content data by decoding the encoded data. By providing the decoding device that generates the data separately from the existing communication device, an effect that network coding can be realized without increasing the functionality of the communication device is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a communication system according to an embodiment of the present invention. This communication system includes a distribution server 1 (transmitting device), receiving devices 2 and 3, a sender side coding device 4 (encoder), a receiver side coding device 5 (decoder), and routers 6, 7, 8, 9, 10, 11. FIG. 2 shows the link capacity, and the number written in the vicinity of each link is the link capacity. For example, the link capacity between the distribution server 1 and the router 6 is 1.

  A distribution server 1 is installed at the upstream end of the communication system. The distribution server 1 distributes two types of content data a and b by multicast. The content data a is distributed as a multicast (S1, G1) with a source address S1 and a multicast group address G1. The content data b is distributed as a multicast (S2, G2) of the source address S2 and the multicast group address G2.

  The receiving device 2 is connected to the router 10, and the receiving device 3 is connected to the router 11. The receiving devices 2 and 3 participate in the multicast and receive various data. In addition, the receiving device 3 of the present embodiment has a function of decoding content data a + b described later and generating content data a.

  A transmitter coding device 4 and a receiver coding device 5 are connected to routers located at both ends of a section where network coding is performed. The sender side coding device 4 is connected to the router 8, and the receiver side coding device 5 is connected to the router 10.

  The sender side coding apparatus 4 participates in multicast (S1, G1) and (S2, G2), receives the content data a, b from the router 8, and encodes the content data a, b (this In the embodiment, an exclusive OR operation in units of bits between packets is performed to generate encoded data a + b. The sender-side coding device 4 transmits the encoded data a + b to the router 8 as a multicast (C1, G3) of the source address C1 and the multicast group address G3.

  The receiver side coding apparatus 5 participates in multicast (S1, G1) and (C1, G3), receives the content data a and the encoded data a + b from the router 10, and based on the content data a and the encoded data a + b. Then, decryption processing (in this embodiment, exclusive OR operation in units of bits between packets) is performed to generate content data b. Further, the receiver side coding device 5 transmits the content data b to the router 10 as multicast (S2, G2).

  FIG. 3 shows the configuration of the sender side coding device 4. The transmission / reception unit 41 transmits a Join message necessary for multicast participation, receives content data a and b, and transmits encoded data a + b. The encoding unit 42 performs encoding (redundancy) processing on the content data a and b received by the transmission / reception unit 41 to generate encoded data a + b (redundant data). The storage unit 43 temporarily stores content data a and b, encoded data a + b, and the like. The control unit 44 performs information processing as necessary, and controls the operation of each unit in the sender-side coding device 4.

  FIG. 4 shows the configuration of the receiver side coding device 5. The transmission / reception unit 51 transmits a Join message, receives content data a and encoded data a + b, and transmits content data b obtained by decoding the encoded data a + b. The decoding unit 52 decodes the encoded data a + b received by the transmission / reception unit 51 to generate content data b. The storage unit 53 temporarily stores content data a and b and encoded data a + b. The control unit 54 performs information processing as necessary, and controls the operation of each unit in the receiver-side coding device 5.

  Next, the operation of the communication system will be described focusing on the operations of the sender side coding device 4 and the receiver side coding device 5. When the receiving device 2 participates in the multicast (S1, G1) and (S2, G2) and transmits a Join message for receiving the content data a, b toward the upstream side, each router transmits the content data a, b. Multicast packets are forwarded. Similarly, the receiving device 3 participates in the multicast (S2, G2) and (C1, G3) and transmits a Join message for receiving the content data a and the encoded data a + b toward the upstream side.

  The sender-side coding device 4 participates in multicast (S1, G1) and (S2, G2) and receives content data a and b. More specifically, in the sender-side coding device 4, the control unit 44 generates a Join message (reception request) for participating in multicast (S1, G1) and (S2, G2). The transmission / reception unit 41 transmits a Join message to the router 8. The router 8 that has received the Join message transfers the multicast packet of the content data a and b to the sender side coding device 4.

  The transmission / reception unit 41 receives the multicast packet of the content data a and b from the router 8. The encoding unit 42 performs an encoding process based on the received multicast packet of the content data a and b, and generates encoded data a + b. The transmission / reception unit 41 transmits the multicast packet of the encoded data a + b to the router 8. As described above, the encoded data a + b is distributed as multicast (C1, G3).

  The receiver side coding device 5 participates in the multicasts (S1, G1) and (C1, G3), receives the multicast packet of the content data a, and multicasts the encoded data a + b transmitted from the sender side coding device 4. Receive the packet. More specifically, the control unit 54 of the receiver-side coding device 5 generates a Join message for participating in multicast (S1, G1) and (C1, G3). The transmission / reception unit 51 transmits a Join message to the router 10. The router 10 that has received the Join message transfers the multicast packet of the content data a and the encoded data a + b to the receiver side coding device 5.

  In the receiver side coding device 5, the transmission / reception unit 51 receives the multicast packet of the content data a and the encoded data a + b from the router 10. The decoding unit 52 performs a decoding process based on the received multicast packet of the content data a and the encoded data a + b, and generates content data b. The transmission / reception unit 51 transmits the multicast packet of the content data b to the router 10. As described above, the content data b is distributed as multicast (S2, G2).

  The router 10 transfers the multicast packet of the content data a and b to the receiving device 2. The receiving device 2 receives the multicast packet of the content data a and b from the router 10. On the other hand, the router 11 transmits the multicast packet of the content data b and the encoded data a + b to the receiving device 3. The receiving device 3 receives the multicast packet of the content data b and the encoded data a + b from the router 11. As described above, the receiving device 3 has a decoding function, and performs the decoding process based on the received multicast packet of the content data b and the encoded data a + b to generate the content data a. As described above, the receiving devices 2 and 3 can acquire the content data a and b.

  According to RPF (Reverse-Path Forwarding), a router that has received a multicast packet performs a check (RPF check) as to whether or not the multicast packet has been received by an appropriate interface. In this check, a routing table that defines the correspondence between the multicast source address and the receiving interface is referred to. When the interface corresponding to the source address of the received multicast packet on the routing table is the same as the received interface, the router transfers the multicast packet. Also, if the interface corresponding to the source address of the received multicast packet and the routing table is different from the received interface, the router discards the multicast packet.

  When the interface address of the receiver side coding device 5 is S2, the router 10 can recognize that the route in the source address S2 direction is the direction of the receiver side coding device 5. On the other hand, when the address of the interface of the receiver side coding device 5 is not S2, the route in the source address S2 direction is not the direction of the distribution server 1 but the direction of the receiver side coding device 5 with respect to the router 10 as follows. It is necessary to recognize that.

  In the receiver side coding device 5 of the present embodiment, the control unit 54 generates cost information (route information) of a plurality of links regarding the route to the distribution server 1, and the transmission / reception unit 51 transmits the cost information to the router 10. This cost information includes the cost of the link between the receiver side coding device 5 and the router 10 and the cost of the virtual link between the receiver side coding device 5 and the distribution server 1.

  Since the router 10 selects a route with a low cost, a virtual route (router 10-recipient side coding) than the cost of the normal route (router 10-router 9-router 7-distribution server 1) from the router 10 to the distribution server 1 is selected. It is necessary to reduce the cost of the apparatus 5-the distribution server 1) (first condition). Further, it is necessary to set a cost so as not to change the route to the distribution server 1 recognized by the router 8, the router 9, or the like (second condition). Therefore, the cost of the virtual link between the receiver-side coding device 5 and the distribution server 1 is set to a cost of an appropriate size that satisfies the first condition and the second condition.

  Based on the cost information, the router 10 recognizes that the communication path to the distribution server 1 is the direction of the receiver side coding device 5. Thus, the multicast packet of the content data b transmitted from the receiver side coding device 5 is transferred to the receiving device 2 without being discarded by the router 10.

  The Join message related to the content data b transmitted from the receiving device 2 is transferred from the router 10 to the receiver side coding device 5. Receiving side coding apparatus 5 which received this Join message starts participation in multicast (S1, G1) and (C1, G3) as mentioned above.

  In the above description, the receiver-side coding device 5 transmits cost information to the router 10. However, the route setting may be artificially changed on the router 10. In the above description, it is assumed that the receiving device 3 has a decoding function. However, when the receiving device 3 does not have a decoding function, a device similar to the receiver-side coding device 5 is replaced with a router. 11 may be connected. Furthermore, when the receiving device 2 has a decoding function, the receiver-side coding device 5 need not be provided.

  As described above, according to the present embodiment, by providing the sender-side coding device 4 and the receiver-side coding device 5 separately from the existing router, the router that constitutes the existing communication system that performs multicast forwarding is provided. Network coding can be realized without high functionality.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the above-described embodiments, and includes design changes and the like without departing from the gist of the present invention. .

It is a block diagram which shows the structure of the communication system by one Embodiment of this invention. It is a block diagram which shows the link capacity | capacitance of the communication system by one Embodiment of this invention. It is a block diagram which shows the structure of the sender side coding apparatus with which the communication system by one Embodiment of this invention is provided. It is a block diagram which shows the structure of the receiver side coding apparatus with which the communication system by one Embodiment of this invention is provided. It is a block diagram for demonstrating network coding.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Distribution server, 2, 3 ... Receiving device, 4 ... Sender side coding device, 5 ... Recipient side coding device, 6, 7, 8, 9, 10, 11 ... Router, 41, 51 ... Transmission / reception unit, 42 ... Encoding unit, 43, 53 ... Storage unit, 44, 54 ... Control unit, 52 ... Decoding unit

Claims (2)

A plurality of communication devices that transfer content data transmitted by multicast from a transmission device to a reception device, an encoding device that encodes the content data and generates encoded data, and a decoding device that decodes the encoded data A communication system comprising:
The encoding device is connected to the first communication device and transmits the first content data transmitted by the first multicast and the second content data transmitted by the second multicast. First data receiving means for receiving from the communication device;
Encoding means for performing encoding processing based on the first content data and the second content data and generating encoded data;
First data transmission means for transmitting the encoded data to the first communication device by a third multicast;
The decryption device is connected to a second communication device;
Second data receiving means for receiving the first content data or the second content data and the encoded data from the second communication device;
The decoding process is performed based on the first content data and the encoded data to generate the second content data, or the decoding process is performed based on the second content data and the encoded data. Decryption means for generating first content data ;
In order for the second communication device to recognize that the communication path to the transmission device of the first multicast or the second multicast is the direction of the decoding device, a virtual link to the transmission device Route information transmitting means for transmitting, to the second communication device, route information relating to the route to the transmission device, including the cost;
The first multicast data or the second multicast data corresponding to the first content data or the second content data is converted into the first content data or the second content data generated by the decryption means. And a second data transmitting means for transmitting to the second communication device . A decoding device connected to a communication device for transferring content data transmitted by multicast from a transmission device to a reception device,
The first content data transmitted by the first multicast or the second content data transmitted by the second multicast is received from the communication device, and the first content data and the second content data are received. Data receiving means for receiving encoded data generated by performing an encoding process based on the communication device;
The decoding process is performed based on the first content data and the encoded data to generate the second content data, or the decoding process is performed based on the second content data and the encoded data. Decryption means for generating first content data;
Including the cost of a virtual link to the transmission device in order to make the communication device recognize that the communication path to the transmission device of the first multicast or the second multicast is the direction of the own device, Route information transmitting means for transmitting route information related to the route to the transmission device to the communication device;
The first multicast data or the second multicast data corresponding to the first content data or the second content data is converted into the first content data or the second content data generated by the decryption means. Data transmission means for transmitting to the communication device
A decoding apparatus comprising:

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