JP5235508B2 - Communication device - Google Patents

Description

  The present invention relates to a communication apparatus that performs information transmission using network coding.

  Network coding (Network Coding) is an information transmission method in which each communication device (node) between End-to-End (between sending node and receiving node) communicates while encoding information using an independent path. Each communication device collectively encodes the received message information and transfers it to one or more communication devices. Each communication device defines an encoding function to be executed by itself so that the information transmitted after encoding can be restored at the receiving node. An independent path is a single communication path (link) that connects adjacent communication apparatuses located on a transmission path from a transmission node to a reception node. In communication using network coding, only one type of data packet is transmitted over one communication path.

  Patent Document 1 below describes a communication system that realizes efficient communication using network coding. The communication system described in Patent Document 1 is realized by mounting a mathematical model described in Non-Patent Document 1 below on a wireless network. Hereinafter, the communication system described in Patent Document 1 will be described.

  In the communication system described in Patent Document 1, when a communication device (transmission node) that is a source of content data transmits content data to another communication device (reception node) that desires distribution of content data, Encodes the content data using the assigned encoding function, generates the same number of encoded data as the number of adjacent nodes constituting the transmission path to the receiving node, and further, for each encoded data A header including information used in the decoding and transmission path information is added, and the encoded data is transmitted to different links (different adjacent nodes).

  A communication device that is not a receiving node (communication device in the middle of a transmission path) that has received encoded data from an adjacent communication device generates a code generated based on the same content data based on information in the header. Judgment is made on whether to receive a plurality of data. If only one piece of encoded data is received, the received encoded data is transferred to the adjacent node indicated by the information in the header. Also, if there are multiple encoded data to be received, after receiving all the encoded data to be received, re-encode them, add a header to the obtained encoded data, To the adjacent node.

  In the communication device corresponding to the receiving node, after receiving all the encoded data necessary for recovering the content data, the content data is recovered using the received encoded data and information in the header thereof.

JP 2006-31693 A R. el. Al “Network Information Flow”, pp.1204-1216, IEEE Trans. On Information Theory, Vol.46, No.4, July 2000

  However, the above conventional technique has a problem in that since the header size is large, the band is compressed to prevent stable information transmission. When the above conventional technique is applied, for example, it is necessary to transmit encoded data using a message having the configuration shown in FIG. In the header constituting this message, a sequence number for identifying content data corresponding to the encoded data, a link transmission node ID indicating the transmission source node of the encoded data, and a link reception indicating the reception node of the encoded data The node ID, the independent path list that is the information of the independent paths constituting each transmission path from the transmission node to the reception node, and the information of the encoding function used when each node on the transmission path performs the re-encoding process. An encoding function list is included. In particular, the independent path list and the encoding function list increase with an increase in the number of communication devices constituting the network, so that sufficient efficiency cannot be realized due to the influence of these pieces of information. The independent path list and the encoding function list are generated by the transmission node, and the node on the transmission path re-encodes the independent path list and the encoding function list included in the header of the received encoded data. Included in the header and send.

  In addition, when the node moves and the topology of the network changes, the transmitting node has to update the independent path list and the encoding function list, which increases the processing load.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a communication apparatus that performs communication using network coding more efficiently than before.

  In order to solve the above-described problems and achieve the object, the present invention configures an ad hoc network and encodes the received data when data generated based on content data addressed to another communication device is received. And a topology management unit that collects topology information of the ad hoc network and a transmission source communication device of the content data based on the topology information when detecting the start of content data transmission. A transmission path calculating means for calculating a data transmission path from a certain first communication apparatus to a second communication apparatus that is a communication apparatus that desires distribution of the content data, and based on the content data based on the transmission path The code used in the encoding process of the received data that is executed when the generated data is received Characterized in that and an encoding function determining means for determining a function.

  According to the present invention, it is possible to reduce the header information to be added to the encoded data as compared with the prior art, and to increase the band usage efficiency.

  Embodiments of a communication apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a first embodiment of a communication device according to the present invention. This communication device includes an application 1 that provides a user with a function of transmitting / receiving content data to / from other communication devices, and a communication device that is a transmission destination from a communication device that is a transmission source of content data (hereinafter referred to as a transmission node). A route management unit 2 that calculates (searches) a data transmission path (hereinafter referred to as a receiving node), and network coding that encodes and transfers content data held by itself or data received from another communication device Unit 3, topology management unit 4 that collects and manages topology information of the network to which it belongs, and coding function determination that determines a coding function used when network coding unit 3 performs coding Part 5. The network coding unit 3 uses a communication protocol when transmitting encoded data obtained by executing the encoding process. The topology management unit 4 uses a topology control protocol that constitutes a control protocol when collecting topology information. The coding function determination unit 5 uses a coding function control protocol (Coding Function Control Protocol) that constitutes a control protocol when determining the coding function.

  The network coding unit 3 also encodes input data, and an independent path management unit 32 that acquires and holds information on each independent path constituting the transmission path calculated by the route management unit 2. And an encoding function management unit 33 that acquires and holds information on the encoding function determined by the encoding function determination unit 5.

  FIG. 2 is a diagram illustrating a configuration example of the topology management unit 4 and the encoding function determination unit 5. The topology management unit 4 communicates a topology management execution unit 41 that collects information on the arrangement state (topology) of communication devices in the network and a control signal (control message) necessary for performing topology management with other communication devices. A communication unit 42 for transmitting and receiving data. The topology management execution unit 41 includes a routing management unit 411 that performs node search in the network and collects topology information, and a topology management table 412 in which the topology information collected by the routing management unit 411 is registered. The communication unit 42 includes a message transmission unit 421 that transmits a control message to another communication device and a message reception unit 422 that receives a control message from another communication device, and executes a topology control protocol. The topology control protocol to be used is, for example, a protocol specified by the MANET (Mobile Ad-hoc Network) working group of IETF (Internet Engineering Task Force).

  The encoding function determination unit 5 includes an encoding function control unit 51 that instructs the determination of the encoding function used by the own device and the determination of the encoding function to the other communication device, and the encoding to the other communication device. And a communication unit 52 that transmits and receives a control signal (control message) necessary for performing an instruction to determine an activation function to and from another communication device. The communication unit 52 includes a message transmission unit 521 that transmits a control message to another communication device and a message reception unit 522 that receives a control message from another communication device, and executes a coding function control protocol.

  Next, a data transmission procedure performed by the communication apparatus configured as described above using network coding will be described with reference to the drawings.

  FIG. 3 is a diagram showing an outline of data transmission using network coding. For example, in an ad hoc network constituted by communication devices T1 to T7, communication device T1 is a transmission node, and communication devices T6 and T7 are reception nodes. The operation outline is shown. The description will be made with ‘s’ attached to the transmitting node and ‘d’ attached to the receiving node. In the example shown in FIG. 3, the communication device T1s that is the transmission node uses the encoding function assigned to itself to transmit the transmission data (content data) to the adjacent node (adjacent communication device) on the transmission path. The data is divided according to the number (in this example, two, hereinafter, the data obtained by the division are referred to as data a and data b, respectively) and transmitted to adjacent nodes (communication devices T2 and T3) on the transmission path. To do. The communication device that has received the data a or the data b transfers the received data to the adjacent node on the transmission path. In addition, in the communication device T4 that has received both the data a and the data b, the received data is synthesized using an exclusive OR as an encoding function. Then, the obtained combined data (aXORb) is sent to the adjacent communication device T5. The communication device T5 transfers the data received from the communication device T4 to the adjacent communication devices T6d and T7d. The communication devices T6d and T7d as receiving nodes perform the following calculation using the respective encoding functions to restore the information of both data a and data b to obtain received data (obtain content data). .

Communication device T6d: received data = (a, b) = (a, aXOR (aXORb))
Communication device T7d: received data = (a, b) = (bXOR (aXORb), b)

  FIG. 4 is a diagram for explaining data transmission using network coding. In FIG. 4, the communication device T10s is a transmission node, and the communication devices T09d, T19d, and T29d are reception nodes. Further, the communication devices T01 to T08, T11 to T18, and T21 to T28 are other nodes (hereinafter referred to as “relay nodes” for convenience of explanation) that constitute a transmission path from the transmission node to each reception node. The operation when content data is transmitted from the transmission node (communication device T10s) to the reception nodes (communication devices T09d, T19d, T29d) will be described with reference to FIG. Note that the encoding function used when each communication apparatus performs the encoding process is “En”. Here, “n” is the same identification number as the communication device. That is, the encoding function of the communication device T10s is E10s, and the encoding function of the communication device T01 is E01.

  For example, in the communication device T24, the received data is input from three independent paths set between the communication devices T03, T13, and T23 (number of input paths L = 3). The data to be transmitted is output to two independent paths to the communication devices T15 and T25 (number of output paths M = 2). Therefore, the communication device T24 encodes the three data from the communication devices T03, T13, and T24 using the encoding function E24, divides the data into two data, and transmits the data to the communication devices T15 and T25. This processing is repeated by each communication device constituting a transmission path from the transmission node (communication device T10s) to each reception node (communication devices T09d, T19d, and T29d), so that data by network coding is end-to-end. Transmission takes place. The encoding function En (n = 0, 02, 03, 04,...) Is configured so that the transmission data (content data) of the transmission node can be restored at the reception node by the encoding rule in accordance with the configuration of the transmission path. It is determined. Note that the present invention does not depend on encoding rules.

  Next, an encoding operation (network coding operation) performed by the communication apparatus according to the present embodiment will be described with reference to FIG. Here, as an example, the operation of the communication device T24 illustrated in FIG. 4 will be described. The received data received from each of the communication devices T03, T13 and T23 connected to the input path to the communication device T24 is data D1, D2 and D3, and the communication devices T15 and T25 connected to the output path The transmission data to be transmitted to each is assumed to be data D4 and D5. However, each reception data and transmission data is transmitted with an encoded header (hereinafter simply referred to as “header”) added thereto. Details of the header will be described later.

  The communication device T24 generates data D4 and D5 by encoding the data D1, D2 and D3 received via each input path using its own encoding function E24, and passes each through the corresponding output path. Send with. Here, as shown in FIG. 5, the encoding function E24 is a matrix having e1, e2, e3, e4, e5, and e6 as elements, for example. Since the communication device T24 has three inputs (number of input paths L = 3) and two outputs (number of output paths M = 2), the encoding function E24 is a matrix with 2 rows and 3 columns.

  The communication device T24 adds a header to each piece of transmission data obtained by executing the above encoding process, and outputs (transmits) the encoded data message to the output path. Although details will be described later, the header (encoded header) includes information necessary for the communication device that has received the encoded data message to encode the data included in the communication device synchronously. For example, the header includes a sequence number for determining whether the encoded data is generated based on the same content data.

  FIGS. 6A and 6B are returned when the configuration example of the encoded data message transmitted by the communication apparatus according to the present embodiment and the communication apparatus according to the present embodiment receive the encoded data message, respectively. It is a figure which shows the structural example of an encoding data response message. As shown, the encoded data message includes a header and encoded data. The header includes a sequence number, a link transmission node ID, a link reception node ID, and a route ID. The encoded data response message includes a header having the same configuration as that included in the encoded data message and a reception result (result) of the encoded data. When a communication device receives an encoded data message and returns an encoded data response message, the communication device adds the header included in the received encoded data message to the reception result of the encoded data as it is. Thus, an encoded data response message is generated.

  The sequence number is a number that identifies the unit encoded by the communication device that is the transmission node. That is, it is information for determining whether or not the encoded data is generated based on the same content data. For example, in the example shown in FIG. 5, the sequence numbers of the data D1, D2, and D3 that are input data are the same. Therefore, in the encoding operation by the communication device T24, these data are encoded synchronously.

  The link transmission / reception node ID is identification information of a communication device that transmits / receives a message. For example, as shown in FIG. 6-3, in an encoded data message transmitted from the communication device T03 to T24 on the link L0324, the ID (identification information) of the communication device T03 is the link transmission node ID and the ID of the communication device T24. Becomes the link receiving node ID. In the encoded data response message transmitted from the communication device T24 to the communication device T03, the ID of the communication device T03 is the link transmission node ID, and the ID of the communication device T24 is the link reception node ID.

  The path ID is information for the communication device that has received the encoded data to determine an encoding function to be used when the received encoded data is further encoded, and is information generated by the transmission node. That is, the same path ID is included in the header of the encoded data message transmitted on the transmission path from the transmission node to the reception node of certain content data.

  FIG. 7 is a diagram for explaining details of the encoding (network coding) operation by the communication apparatus of the present embodiment, and specifically shows an operation example of the communication apparatus 24 shown in FIG. . Details of the encoding operation will be described with reference to FIG.

  When the communication device 24 receives the encoded data message having the same sequence number from each input path, as shown in FIG. 7, the encoded data (encoded data D1, D2, D3) included in each encoded data message is received. Are divided into coding units of a predetermined size. At this time, the encoding function E24 to be used is an encoding function corresponding to the path ID included in the encoded data message. The encoding function is determined in advance by the encoding function determination unit 5 (see FIG. 1) prior to reception of the encoded data message. The encoding function determination operation will be described later. In this example, data D41 and D51 are obtained by inputting data D11, D21, and D31, which are encoding units, and using the communication device encoding function E24. The same processing is executed for the other encoding units, and data D42, D43,..., D52, D53,. These pieces of information are transmitted as encoded data messages addressed to the communication devices T15 and T25. Specifically, the ID of the communication device T24 is set as the link transmission node ID, the ID of the communication device T15 is set as the link reception node ID, and the encoded data includes data D41, D42,. The encoded data message including D4, the ID of the communication device T24 is set as the link transmission node ID, the ID of the communication device T25 is set as the link reception node ID, and the data D51, D52,. The encoded data message including the encoded data D5 included is transmitted.

  Here, an operation in which the encoding function determination unit 5 determines the encoding function prior to reception of the encoded data message will be described. FIG. 8 is a diagram illustrating a sequence example of a coding function control protocol used when the encoding function determination unit 5 determines an encoding function. In FIG. 8, when the number of communication devices constituting the transmission path from the transmission node to each reception node is 7, the communication device T1s that is the transmission node is connected to other communication devices (communication devices T2 to T5 that are relay nodes). The sequence for instructing the communication devices T6d and T7d), which are receiving nodes, to determine the encoding function is shown.

  The communication device T1, which is a transmission node, calculates a transmission path to each reception node by an existing method (any method may be used), and applies an encoding function to all other communication devices constituting the calculated transmission path. Send a decision instruction message. Each communication device (communication devices T2 to T7) that has received this message determines an encoding function to be used based on information contained in the received message, and encodes information indicating that the determination process has been completed. A function determination response message is returned to the communication device T1. When the communication device T1 confirms that the encoding function determination processing has been completed in all the communication devices, the communication device T1 determines that preparation for information transmission has been completed. Details of the encoding function determination instruction message and the encoding function determination response message will be described below with reference to FIGS. 9-1 and 9-2.

  As illustrated in FIG. 9A, the encoding function determination instruction message includes an instruction destination node ID, a transmission node ID, a reception node ID list, the number of independent paths, and a path ID. The instruction destination node ID is identification information of the other party that instructs execution of the encoding function determination process, and is the destination of the encoding function determination instruction message. The transmission node ID is identification information of a transmission node that performs data transmission, and also serves as identification information of the transmission source of the encoding function determination instruction message. The receiving node ID list is information composed of a combination of the number of receiving nodes (number of nodes) and identification information thereof (node ID list including one or more node IDs). The number of independent paths is the number of independent paths constituting the transmission path from the transmission node to each reception node, and is information used when the communication apparatus that has received the encoding function determination instruction message calculates the transmission path. The path ID is information generated by the transmission node, and as described above, the communication device that has received the encoded data message specifies the encoding function used when encoding the data included therein. Information. This information is generated, for example, when the transmission node adds a serial number to its own ID (transmission node ID).

  Also, as illustrated in FIG. 9B, the encoding function determination response message includes an instruction destination node ID, a transmission node ID, a route ID, and a result. The instruction destination node ID is identification information of the transmission source of the encoding function determination response message. The transmitting node identifies the node that has completed the processing from this information. The transmission node ID is identification information of the transmission node that performs data transmission, and also serves as identification information of the destination of the encoding function determination response message. For the path ID, the same value as the path ID sent in the encoding function determination instruction message is set. The transmitting node specifies the corresponding data transmission from this value. The result is information indicating the execution result of the encoding function determination process. For example, “0” is obtained when the encoding function determination is normally completed (successful), and the failure reason is indicated otherwise (failure). Set a value according to.

  In the example of FIG. 9B, when the result field is “−1”, the failure reason is “the transmission node does not exist in the topology table”, and when “−2”, the failure reason is “the reception node is in the topology table”. If "Not exists" is "-3", the reason for failure is "The number of designated independent paths cannot be secured". If "-4", the reason for failure is "Request timeout". If it is "-9", it fails. The reason is “Other”. In the case of “−3”, the encoding function cannot be calculated and the independent path is released. At this time, an encoding function determination response message is returned when it is determined that it cannot be secured. In the case of “−4”, the independent path is also released.

  Note that configuration examples of the encoding function deletion instruction message and the encoding function deletion response message used in the present embodiment are shown in FIGS. 10-1 and 10-2.

  The encoding function deletion instruction message includes an instruction destination node ID, a transmission node ID, and a path ID. The instruction destination node ID is identification information of the other party that instructs to delete the determined encoding function, and is the destination of the encoding function deletion instruction message. The transmission node ID is identification information of a transmission source (transmission node) of transmission data (content data), and also serves as identification information of the transmission source of the encoding function deletion instruction message. The route ID is information generated by the transmission node, and is information for specifying a coding function to be deleted by the communication device that has received this message.

  When receiving the encoding function deletion instruction message, the communication apparatus according to the present embodiment specifies the encoding function indicated by the received message based on the path ID included therein, and deletes the specified encoding function.

  The encoding function deletion response message includes an instruction destination node ID, a transmission node ID, a route ID, and a result. The instruction destination node ID is identification information of the transmission source of the encoding function deletion response message. The transmitting node identifies the node that has completed the processing from this information. The transmission node ID is identification information of a transmission source (transmission node) of transmission data (content data), and also serves as identification information of a destination of the encoding function deletion response message. For the route ID, the same value as the route ID sent in the encoding function deletion instruction message is set. The transmitting node specifies the corresponding data transmission from this value. The result is information indicating whether or not the deletion of the encoding function has been completed normally (whether or not the deletion was successful). For example, “0” is set for success and “−1” is set for failure.

  Next, the data transmission operation in the communication system configured by the communication device of the present embodiment will be described. FIG. 11 is a diagram illustrating an example of a data transmission operation in the communication system according to the present embodiment, and is a diagram illustrating a configuration of processing executed by each node (communication device).

  In the communication device corresponding to the transmission node, routing processing, independent path management processing, encoding function determination processing, data transmission setting processing, and network coding communication processing are executed.

  The routing process is a process for periodically updating the topology (information on the arrangement state of each communication device in the network). In this processing, the routing management unit 411 (see FIGS. 1 and 2) that constitutes the topology management execution unit 41 of the topology management unit 4 performs transmission and reception of control messages with other communication devices in the network according to the topology control protocol, Collect topology information regularly. The collected topology information is registered in the topology management table 412 and the topology management table 412 is updated.

  The independent path management process is a process executed when the application 1 executes a process (nc_open ()) instructing the start of data transmission by network coding communication. In this process, when the route management unit 2 corresponding to the transmission path calculation means receives the information of the receiving node as the communication partner from the application 1, it further acquires the topology information from the topology management unit 4, and these receiving nodes Based on the information and the topology information, a transmission path to each receiving node is calculated. The calculated transmission path information is associated with the path ID which is the management information, and is managed by the independent path management section 32 of the network coding section 3.

  The encoding function determination process is a process executed following the independent path management process. In this process, the encoding function control unit 51 of the encoding function determination unit 5 transmits the transmission calculated by the route management unit 2. Based on the path information, an encoding function to be used when performing network coding communication on the transmission path is determined. Note that the information on the determined encoding function is associated with the path ID and managed by the encoding function management unit 33 of the network coding unit 3.

  The data transmission setting process is a process for instructing other communication devices (relay nodes and reception nodes) to execute a determination process of an encoding function used when performing network coding communication. In this process, the encoding function control unit 51 of the encoding function determination unit 5 generates a control message to be transmitted to another communication device, and transmits the control message via the message transmission unit 521. In addition, when a response message for the transmitted control message is transmitted from another communication device, the encoding function control unit 51 receives the response message via the message reception unit 52. The control messages transmitted and received by the encoding function control unit 51 are the above-described encoding function determination instruction message and the encoding function determination response message (see FIGS. 9-1 and 9-2). The encoding function control unit 51 receives information necessary for the communication apparatus that has received the encoding function determination instruction message to calculate the same transmission path as the transmission path calculated by itself (the communication apparatus corresponding to the transmission node), that is, Information that is used when the route management unit 2 calculates the transmission path and that is not held by the communication device that has received the encoding function determination instruction is included in the encoding function determination instruction message and transmitted. .

  The network coding communication process executes the independent path management process, the encoding function determination process, and the data transmission setting process described above, and after other communication devices execute a predetermined process and prepare for data transmission, This process is executed when it is detected that the application 1 has executed the process (nc_send ()) for instructing the start of data transmission. In this process, the encoding unit 31 of the network coding unit 3 uses the encoding function determined in the encoding function determination process executed by the encoding function determination unit 5 to transmit the content data to be transmitted to the receiving node. The data is encoded, a header is added to the obtained encoded data, and transmitted as an encoded data message (see FIG. 6A). As described above, the encoding unit 31 generates the same number of encoded data as the number of output paths (adjacent nodes on the transmission path calculated by the route management unit 2). Each encoded data message is output to a corresponding path among the output paths indicated by the transmission path information calculated in the independent path management process.

  In the communication device corresponding to the relay node, routing processing, data transmission setting processing, and network coding communication processing are executed. Note that the routing process is the same as the routing process in the transmission node described above. Therefore, explanation is omitted.

  The data transmission setting process is a process that is executed when the transmission node receives a control message (encoding function determination instruction message) transmitted by executing the data transmission setting process.

  In this process, first, information (transmission node ID, reception node ID list and number of independent paths in header) included in the encoding function determination instruction message received from the transmission node by the encoding function determination unit 5 and the topology management unit 4 The route management unit 2 calculates a transmission path from the transmission node to each reception node based on the topology information held by the node. This process is the same as the independent path management process in the transmission node described above. In addition, since the same data (transmission node ID, reception node ID, and topology information) used when the transmission node calculates the transmission path is used, the same result as the calculation result at the transmission node is obtained. The calculated transmission path information is associated with path ID information included in the received encoding function determination instruction message and is managed by the independent path management section 32 of the network coding section 3.

  Next, the encoding function control unit 51 of the encoding function determination unit 5 uses the coding information used when performing network coding communication on the transmission path based on the transmission path information calculated by the route management unit 2. Determine the function. This process is the same process as the encoding function determination process in the transmission node described above, and the information on the determined encoding function is associated with the path ID information included in the received encoding function determination instruction message. It is managed by the encoding function management unit 33 of the network coding unit 3.

  The network coding communication process in the relay node is a process executed when an encoded data message is received from the transmission node or another relay node. In this process, the encoding unit 31 of the network coding unit 3 first determines in advance the encoding function corresponding to the path ID information in the header included in the received encoded data message by the encoding function determination unit 5. It is specified from the encoding function. Next, the data included in the encoded data message is encoded using the specified encoding function. The encoding unit 31 transmits transmission path information corresponding to the path ID information in the header included in the received encoded data message (the path ID in the transmission path information managed by the independent path management unit 32). Based on the corresponding information), after confirming the input path to the device and receiving the encoded data message via all the input paths, the encoding process is performed using the encoded data in each encoded data message. Run. Each generated encoded data message is output to a corresponding path among the output paths indicated by the transmission path information calculated by the route management unit 2.

  In the communication device corresponding to the receiving node, routing processing, data transmission setting processing, and network coding communication processing are executed. The routing process and the data transmission setting process are the same as the routing process and the data transmission setting process in the relay node described above. Therefore, these descriptions are omitted.

  The network coding communication process at the receiving node is a process executed when an encoded data message is received from the relay node. In this process, the encoding unit 31 of the network coding unit 3 first determines in advance the encoding function corresponding to the path ID information in the header included in the received encoded data message by the encoding function determination unit 5. It is specified from the encoding function. Next, the original content data (content data transmitted by the transmission node) is restored from the encoded data included in the encoded data message using the specified encoding function. Note that the encoding unit 31 does not restore the content data, but other components not shown may perform the restoration process. Further, when the content data is restored, the application 1 is notified to that effect, and the application 1 acquires the content data by executing a process (nc_recv ()) for obtaining the restored data.

  FIG. 12 is a diagram illustrating an operation when the encoding function held by each communication device is deleted after the data transmission operation by the communication device according to the present embodiment is completed, and is executed by each node (communication device). It is a figure which shows the structure of the function to perform.

  In the communication device corresponding to the transmission node, routing processing, independent path deletion processing, coding function deletion processing, and data transmission setting cancellation processing are executed. Note that the routing process is the same as the routing process executed by the transmission node in FIG. 11 described above. Therefore, explanation is omitted.

  The independent path deletion process is a process executed when the application 1 executes a process (nc_close ()) for instructing the end of data transmission by network coding communication. In this process, the route management unit 2 specifies the transmission path corresponding to the instruction from the application 1 and instructs the network coding unit 3 to delete the information of the specified transmission path. In the network coding unit 3 that has received the instruction, the encoding unit 31 deletes the transmission path information indicated by the instruction content from the information held by the independent path management unit 32.

  The encoding function deletion process is a process executed following the independent path deletion process. In this process, the encoding function corresponding to the transmission path information deleted in the independent path deletion process (associated with the same path ID as that associated with the transmission path information) is deleted. Specifically, the encoding unit 31 deletes the corresponding information in the information held by the encoding function management unit 33.

  In the data transmission setting release processing, an instruction is given to other communication devices (relay nodes and receiving nodes) so as to delete the encoding function used in the data transmission corresponding to the instruction content from the application 1. This is the process to be performed. In this process, the encoding function control unit 51 of the encoding function determination unit 5 generates a control message to be transmitted to another communication device, and transmits the control message via the message transmission unit 521. In addition, when a response message for the transmitted control message is transmitted from another communication device, the encoding function control unit 51 receives the response message via the message reception unit 52. The control messages transmitted and received by the encoding function control unit 51 are the above-described encoding function deletion instruction message and the encoding function deletion response message (see FIGS. 10-1 and 10-2).

  In a communication device other than the communication device corresponding to the transmission node, a routing process, an encoding function deletion process, and a data transmission setting cancellation process are executed. Note that the routing process is the same as the routing process executed by the transmission node in FIG. 11 described above. Therefore, explanation is omitted.

  The data transmission setting cancellation process is a process executed when the transmitting node receives a control message (encoded function deletion instruction message) transmitted by executing the data transmission setting cancellation process. In this process, first, the transmission path corresponding to the information (path ID) included in the encoding function deletion instruction message received from the transmission node by the encoding function determination unit 5 is specified, and the information of the specified transmission path is deleted. Thus, the network coding unit 3 is instructed. In the network coding unit 3 that has received the instruction, the encoding unit 31 deletes the transmission path information indicated by the instruction content from the information held by the independent path management unit 32. This process is the same process as the independent path deletion process in the transmission node described above.

  Next, the encoding unit 31 deletes the encoding function corresponding to the deleted transmission path information (associated with the same path ID as that associated with the transmission path information). This process is the same as the encoding function deletion process in the transmission node described above.

  As described above, in the communication system according to the present embodiment, when starting data transmission, the transmission node transmits information necessary for calculating the transmission path to each reception node to other nodes (relay nodes and reception nodes). Each node that received the information notification uniquely calculates a transmission path based on the notified information, and further determines an encoding function to be used in data transmission using network coding. I decided to leave. In data transmission, the transmission node performs data transmission together with a header including identification information necessary for each node to specify a transmission path and an encoding function. Performs an encoding process using the determined encoding function, adds a header including the identification information to the encoded data obtained, and then specifies the adjacent specified by the calculated transmission path information The data is transmitted to the node, and the reception node restores the encoded reception data using a predetermined encoding function. Thereby, it is possible to reduce the header information added to the encoded data as compared with the conventional case, and it is possible to increase the use efficiency of the band. As a result, stable communication can be realized.

Embodiment 2. FIG.
FIG. 13 is a diagram illustrating a configuration example of a communication apparatus according to the second embodiment. The communication device according to the second embodiment has a configuration in which the network coding unit 3 of the communication device according to the first embodiment (see FIG. 1) is replaced with a network coding unit 3a and an adjacent node management unit 6 is further added. Other parts are the same as those of the communication apparatus of the first embodiment. In the present embodiment, the description will focus on the operations of the network coding unit 3a and the adjacent node management unit 6, which are different components from the communication device of the first embodiment, and the components already described in the first embodiment will be described. Description is omitted.

  The network coding unit 3a has a configuration in which an independent path complementing unit 34 is added to the network coding unit 3 included in the communication device of the first embodiment. For the other components, the same processing as the corresponding components of the network coding unit 3 is executed.

  The independent path complementing unit 34 determines whether or not it is necessary to search for an alternative route, which will be described later, when an adjacent communication device (adjacent node) moves and the topology changes.

  The adjacent node management unit 6 monitors the connection state of the independent link with the adjacent node (configuration change of the adjacent node), and when detecting that the connection state has changed, notifies the independent path complementing unit 34 to that effect. To do. The adjacent node management unit 6 uses a neighbor discovery control protocol (Neighbor Discovery Control Protocol) that constitutes a control protocol when monitoring the configuration change of the adjacent node.

  FIG. 14 is a diagram illustrating a configuration example of the topology management unit 4, the encoding function determination unit 5, and the adjacent node management unit 6 that execute various processes using the control protocol implemented by the communication apparatus according to the second embodiment. It is. Note that the configurations of the topology management unit 4 and the encoding function determination unit 5 are the same as those of the topology management unit 4 and the encoding function determination unit 5 included in the communication apparatus of the first embodiment. Therefore, in this embodiment, the configuration and operation of the adjacent node management unit 6 will be described.

  The adjacent node management unit 6 transmits and receives an adjacent node management execution unit 61 that monitors the adjacent node and a control signal (control message) necessary for monitoring the adjacent node to and from other communication devices (adjacent nodes). And a communication unit 62. The adjacent node management execution unit 61 includes a connection state monitoring unit 611 that collects information on adjacent nodes, and an adjacent node management table 612 in which information collected by the connection state monitoring unit 611 is registered. The communication unit 62 includes a message transmission unit 621 that transmits a control message to another communication device and a message reception unit 622 that receives a control message from the other communication device, and executes a neighbor search control protocol.

  FIG. 15 is a diagram illustrating an example of a data transmission operation in the communication system configured by the communication apparatus according to the present embodiment. FIG. 15 shows an example in which data is transmitted from the communication device T09 (transmission node) to the communication device T08 (reception node). Specifically, the communication device T05 on the transmission path from the transmission node to the reception node is shown. In the example, the (relay node) moves and the topology changes. In addition, a thick arrow indicates an independent path that constitutes the original transmission path, and a broken arrow indicates an independent path that constitutes an alternative path of the transmission path (T01 → T05 → T06) that is cut off due to a topology change. ing. The illustrated radio wave propagation influence range indicates the reach of radio waves transmitted from the communication device T01, and a communication device located within this range is an adjacent node of the communication device T01.

  Hereinafter, an operation when the communication apparatus according to the present embodiment sets an alternative route will be described with reference to FIG. In addition, since the operation | movement which each communication apparatus sets the illustrated initial independent path (original transmission path) is the same as the operation demonstrated in Embodiment 1, description was abbreviate | omitted and the original independent path was set. The subsequent operation will be described.

  In the communication device T01, when the connection state monitoring unit 611 of the adjacent node management unit 6 monitors the configuration change of the adjacent node using the neighbor search control protocol and detects that the configuration has changed, information indicating the monitoring result is displayed. Register in the adjacent node management table 612. Further, the connection state monitoring unit 611 indicates that the configuration of the adjacent node has changed (in this example, communication with the communication device T05 has become impossible), and independent path interpolation in the topology management unit 4 and the network coding unit 3a. Notification to the unit 34.

  In the independent path complementing unit 34 notified from the connection state monitoring unit 611 that communication with the communication device T05 has become impossible, information held by the independent path management unit 32 (calculated by the route management unit 2). Based on the transmission path information), it is confirmed whether the communication apparatus T05 is a communication apparatus (relay node) on the transmission path. If the communication device T05 is a relay node, the data is transmitted to the adjacent node management unit 6 to the communication device next to the communication device T05 (communication device T06 in the example of FIG. 15) without passing through the communication device T05. An instruction is issued to search for an alternative route for transmitting.

  The adjacent node management unit 6 that has received an alternative route search instruction from the independent path complementing unit 34 operates as an alternative adjacent node selection unit. That is, it is determined whether or not an alternative route can be set (constructed) using a communication device (adjacent node) that can communicate at that time. If it is determined that the alternative route can be set, the alternative route is set. In the example of FIG. 15, it is determined that an alternative route can be constructed, and a route from the communication device T01 to the communication device T06 via the communication devices T10 and T13 is set as an alternative route.

  When the above alternative route is set, the communication devices T10 and T13 newly perform the encoding process using the encoding function E05 performed by the communication device T05. For example, the communication device T10 performs an encoding process using the encoding function E05, and the communication device T13 transfers the received data as it is without encoding, thereby affecting the movement of the communication device T05 and the communication device T10. It can be supplemented with T13. As a result, there is no load for recalculating the end-to-end transmission path from the transmitting node (communication device T09) to the receiving node (communication device T08) or recalculating the encoding function of each communication device.

  The independent path complementing unit 34 instructs the encoding function determining unit 5 to notify the communication devices (communication devices T10 and T13) that configure the alternative route that the communication device is configured to configure the alternative route. Let

  When receiving the above instruction, the encoding function determination unit 5 uses the coding function control protocol to instruct the communication devices T10 and T13 to execute the encoding function determination process.

  In the communication devices T10 and T13 that have received the above instruction, the independent path management unit 32 performs a transmission path search from the transmission node to the reception node, and the encoding function determination unit 5 performs the encoding based on the transmission path search result. The encoding function determination process is executed to determine the encoding function used by itself. However, the communication devices T10 and T13 cooperate to determine the encoding function, and the encoded data output from the communication device T13 is obtained as a result of the encoding process executed by the communication device T05 until now (the code). Data). When the encoding function determination process ends, the communication apparatuses T10 and T13 notify the communication apparatus T01 to that effect.

  In addition, each communication device that configures the alternative route does not determine the encoding function, but the communication device T01 that has searched for the alternative route determines and notifies the encoding function that is used by each communication device that configures the alternative route. You may make it do. This eliminates the need for each communication device constituting the alternative path to determine the encoding function in cooperation with each other.

  As described above, in the communication system according to the present embodiment, each communication device (relay node) on the transmission path from the transmission node to the reception node has its own next relay node (relay node to which the encoded data message is transmitted). ) Moves and communication with the relay node becomes impossible, it is determined whether an alternative route can be set using an adjacent node. If it can be set, an alternative route is set. Data transmission was continued. Thereby, in addition to the effects shown in the first embodiment, it is possible to flexibly cope with a change in topology, and to continue data transmission efficiently while reducing the processing load of the entire system.

Embodiment 3 FIG.
FIG. 16 is a diagram illustrating a configuration example of a communication apparatus according to the third embodiment. The communication device according to the third embodiment has a configuration in which the route management unit 2 of the communication device according to the second embodiment (see FIG. 13) is replaced with a route management unit 2b and a group management unit 7 is further added. Other parts are the same as those of the communication apparatus of the second embodiment. In the present embodiment, description will be made centering on the operations of the route management unit 2b and the group management unit 7, which are different components from the communication device of the second embodiment, and the components already described in the first or second embodiment. Will not be described.

  In the ad hoc network configured by the communication devices of the present embodiment, the communication devices in the network are managed in groups. Each group is constructed by, for example, a collection of communication devices having the same purpose. Therefore, the group management unit 7 manages to which group the communication device in itself and each communication device in the network belong. The group management unit 7 performs group management using a group management protocol that constitutes a control protocol.

  Further, the route management unit 2b refers to the group management information (group information of each communication device in the network) held by the group management unit 7 in the calculation process of the transmission path from the transmission node to the reception node. That is, the transmission path is calculated based on the information on the transmitting node, the information on the receiving node, the topology information, and the group information.

  FIG. 17 illustrates the topology management unit 4, the encoding function determination unit 5, the adjacent node management unit 6, and the group management unit 7 that execute various processes using the control protocol implemented by the communication apparatus according to the third embodiment. It is a figure which shows the example of a structure. The configurations of topology management unit 4, encoding function determination unit 5 and adjacent node management unit 6 are the same as topology management unit 4, encoding function determination unit 5 and adjacent node management unit provided in the communication apparatus of the second embodiment. The same as 6. Therefore, in the present embodiment, the configuration and operation of the group management unit 7 will be described.

  The group management unit 7 sends a signal (control message) necessary for performing group management between the group management execution unit 71 that manages the group to which the device itself and other communication devices belong, and other communication devices. The communication part 72 which transmits / receives by. The method for grouping the communication devices is not particularly defined. For example, the group management unit 7 refers to the topology information, the number of communication devices belonging to each group becomes a predetermined number, and the same group. The communication devices are grouped so that the communication devices are physically close to each other (only a communication device of the same group exists within a certain range). The grouping may be performed individually in all the communication devices, or may be performed on behalf of a specific communication device in the system, and the result may be notified to other communication devices. However, when each communication device performs grouping individually, the same result is obtained in all the communication devices.

  The group management execution unit 71 includes a group control unit 711 and a group management table 712, and the group control unit 711 belongs to itself and other communication devices in the network based on information registered in the group management table 712. It is determined whether or not it is a node (boundary node) located at the boundary with another group. The communication unit 72 includes a message transmission unit 721 that transmits a control signal (control message) to another communication device and a message reception unit 722 that receives a control signal from another communication device, and executes a group management protocol.

  Here, the boundary node is a node that transmits an encoded data message (see FIG. 6-1) to an adjacent node belonging to a group different from the group to which the boundary node belongs, or a group to which the boundary node belongs. Are nodes that receive encoded data messages from neighboring nodes belonging to different groups. In each communication device in the network, after the route management unit 2b calculates the transmission path, the group management unit 7 determines which communication device is a boundary node based on the calculation result. For example, when the transmission path illustrated in FIG. 18 is calculated, the communication device T15 is a boundary node in the group G1, and the communication device T16 is a boundary node in the group G2. The determination result is held in, for example, the group management table 712.

  In this embodiment, an encoding function used when performing network coding is calculated for a path configured by nodes belonging to the same group, and encoding is performed for communication between different groups (communication between boundary nodes). It is assumed that unprocessed data (content data decrypted and restored by the border node on the transmission side) is transmitted. Thereby, the range of the encoding function to be recalculated following the topology change due to the movement of the communication device that occurs locally is limited within the group. When the communication device itself is a boundary node, the communication device performs an operation as a boundary node described later.

  Hereinafter, the operation of the communication apparatus according to the present embodiment will be described separately when it operates as a transmission node, when it operates as a relay node other than the boundary node, when it operates as a boundary node, and when it operates as a reception node. . Note that the description of the same operation as that described in Embodiment 1 or 2 is omitted.

  When operating as a transmission node, in the communication apparatus according to the present embodiment, first, the route management unit 2b uses the reception node information acquired from the application 1, the topology information held in the topology management unit 4, and the group management unit 7. Based on the stored group management information, a transmission path to the receiving node is calculated. At this time, the transmission path is calculated so as to pass only through the communication devices belonging to the same group within a specific range.

  Next, the encoding function determination unit 5 determines the encoding function used by itself based on the transmission path information calculated by the route management unit 2b. However, the encoding function is determined based on the transmission path information to the boundary node of the group to which it belongs. Therefore, first, a boundary node is specified from the information held by the group management unit 7, and further, an encoding function is determined based on the transmission path calculated by the route management unit 2b.

  When the determination process of the encoding function used by itself is completed, the encoding function determination unit 5 instructs each relay node (including the boundary node) in the same group as itself to determine the encoding function. Put out. At this time, an instruction is given by transmitting the control message shown in FIG. FIG. 19 is a diagram illustrating a configuration example of a control message (intra-group encoding function determination instruction message) used when an encoding function determination instruction is issued to a relay node in the same group as itself.

  As shown in FIG. 19, the intra-group encoding function determination instruction message includes an instruction destination node ID, a transmission node ID, a reception node ID list, an intra-group transmission node ID, an intra-group reception node ID list, the number of independent paths, and a route. Includes ID. This message is a configuration in which an intra-group transmission node ID and an intra-group reception node ID list are added to the encoding function determination instruction message (see FIG. 9-1) used in the communication systems of the first and second embodiments. It is. The communication apparatus that has received this message returns an intra-group encoding function determination response message having the same configuration as the encoding function determination response message (see FIG. 9-2) described in the first embodiment as a response message. .

  The intra-group transmission node ID is information indicating a source node of the intra-group encoding function determination instruction message. Note that the same information is set in the transmission node ID and the intra-group transmission node ID of the intra-group encoding function determination instruction message generated by the communication device operating as the transmission node.

  The intra-group receiving node ID list includes identification information (ID) of relay nodes (that is, boundary nodes) that transfer received encoded data messages to relay nodes belonging to other groups among relay nodes in the same group. It is a list.

  When receiving a response to the intra-group encoding function determination instruction message (intra-group encoding function determination response message) from all relay nodes in the same group, the encoding function determination unit 5 performs data transmission (transmission of encoded data message). ) Is ready. The subsequent operation is the same as that of the transmission node shown in the first or second embodiment.

  Further, when operating as a relay node other than the boundary node (hereinafter referred to as a non-boundary relay node), in the communication apparatus of the present embodiment, first, the route management unit 2b receives the received intra-group coding function determination instruction message. Based on the transmission node ID, the reception node ID, the number of independent paths, the topology information held by the topology information management unit 4 and the group management information held by the group management unit 7 The transmission path from the node to the receiving node is calculated. In calculating the transmission path, a condition is used so that the same result as the transmission path calculation result by the transmission node described above can be obtained.

  Next, the encoding function determination unit 5 determines the encoding function used by itself based on the transmission path information calculated by the route management unit 2b. However, as in the case of the transmission node described above, the encoding function is determined based on the transmission path information to the boundary node of the group to which it belongs. When the encoding function determination process is completed, an intra-group encoding function determination response message, which is a control message indicating that, is returned. The subsequent operation is the same as that of the relay node shown in the first or second embodiment.

  When transmitting an encoded data message to a boundary node that operates as a boundary node and belongs to another group, that is, a node ID included in the intra-group reception node ID list of the intra-group encoding function determination instruction message In the case of the boundary node indicated by (hereinafter, referred to as a transmission boundary node), the communication apparatus according to the present embodiment first performs processing similar to that of the non-boundary relay node to determine the transmission path and determine the encoding function. Thereafter, the following processing is executed before returning the intra-group coding function decision response message.

  That is, after determining the encoding function, an instruction is given to the boundary node belonging to another group so as to determine the encoding function used by each communication device in the other group. Specifically, an inter-group encoding function determination instruction message having the same configuration as the encoding function determination instruction message (see FIG. 9-1) shown in the first embodiment is transmitted to the boundary nodes belonging to other groups. . When an inter-group coding function determination response message that is a response to this instruction is received, an intra-group coding function determination response message is returned. The subsequent operation is the same as that of the non-boundary relay node.

  When receiving an encoded data message from a boundary node that operates as a boundary node and belongs to another group, that is, a boundary node (hereinafter referred to as reception) indicated by the intra-group transmission node ID of the intra-group encoding function determination instruction message. In the case of a boundary node), the communication apparatus according to the present embodiment executes a transmission path calculation process and an encoding function determination process when an inter-group encoding function determination instruction message is received from the transmission boundary node.

  Specifically, the transmission node ID, the reception node ID list and the independent path included in the inter-group coding function determination instruction message, the topology information held by the topology information management unit 4, and the group management unit 7 The transmission path from the transmission node to the reception node is calculated based on the group management information. Next, the encoding function determination unit 5 determines the encoding function used by itself based on the transmission path calculation result. It should be noted that the encoding function is determined based on the transmission path information to the transmission boundary node of the group to which the device belongs, as in the case of the communication device operating as the transmission node described above. When the receiving node belongs to the same group as itself, the encoding function is determined based on transmission path information to the receiving node instead of the transmission boundary node. Further, after determining the encoding function, an intra-group encoding function determination instruction message is transmitted to another communication device (non-boundary relay node, transmission boundary node or reception node) in the same group as itself, and the encoding function Instruct to determine. After that, when response messages for all the transmitted intra-group coding function determination instruction messages are received, an inter-group coding function determination response message indicating that is sent as the transmission source (transmission of the inter-group coding function determination instruction message). Return to the border node. The inter-group encoding function determination response message has the same configuration as the encoding function determination response message (see FIG. 9-2) shown in the first embodiment. The subsequent operation is the same as that of the non-boundary relay node.

  When operating as a receiving node, the communication apparatus according to the present embodiment uses the intra-group transmitting node ID and the node ID in the intra-group receiving node ID list included in the received intra-group encoding function determination instruction message. The same operation as that of the receiving node described in the first or second embodiment is performed except that transmission path calculation and coding function determination are performed.

  FIG. 20 is a diagram illustrating an example of a control message transmission sequence when an instruction to determine an encoding function is given. In FIG. 20, the range of transmission paths to be referred to when determining the encoding function (range from the transmission node to the transmission boundary node in the same group, range from the reception boundary node to the transmission boundary node in the same group, the same group The range from the receiving boundary node to the receiving node is defined as an encoding region.

  Thus, in this embodiment, each communication device grasps the group to which it belongs and the group to which the other communication device belongs, and the communication device (boundary node) located at the boundary of each group, The encoding function is determined within a range within the same group. As a result, when the topology changes, the range in which the calculation process of the encoding function occurs again can be limited within the group, reducing the processing load on the entire system and realizing efficient data transmission.

  In the present embodiment, the case where the group management unit 7 is added to the communication device of the second embodiment has been described. However, the group management unit 7 is added to the communication device of the first embodiment. You may do it.

  As described above, the communication apparatus according to the present invention is useful for data transmission using network coding, and is particularly suitable for realizing stable communication following a topology change in an ad hoc network.

It is a figure which shows the structural example of Embodiment 1 of the communication apparatus concerning this invention. It is a figure which shows the structural example of a topology management part and an encoding function determination part. It is a figure which shows the outline | summary of the data transmission using network coding. It is a figure for demonstrating the data transmission using network coding. 6 is a diagram illustrating an example of an encoding operation by the communication apparatus according to Embodiment 1. FIG. It is a figure which shows the structural example of an encoding data message. It is a figure which shows the structural example of an encoding data response message. It is a figure for demonstrating the structure of the header of an encoding data message and an encoding data response message. 6 is a diagram for explaining details of an encoding operation by the communication apparatus according to Embodiment 1. FIG. It is a figure which shows the example of a sequence of a coding function control protocol. It is a figure which shows the structural example of an encoding function determination instruction | indication message. It is a figure which shows the structural example of an encoding function determination response message. It is a figure which shows the structural example of an encoding function deletion instruction | indication message. It is a figure which shows the structural example of an encoding function deletion response message. 3 is a diagram illustrating an example of data transmission operation in the communication system according to Embodiment 1. FIG. FIG. 11 is a diagram illustrating an operation example in the case of deleting an encoding function held by each communication device in the communication system according to the first embodiment. 6 is a diagram illustrating a configuration example of a communication apparatus according to Embodiment 2. FIG. 10 is a diagram illustrating a configuration example of a topology management unit, an encoding function determination unit, and an adjacent node management unit according to Embodiment 2. FIG. 10 is a diagram illustrating an example of a data transmission operation in a second embodiment. FIG. 6 is a diagram illustrating a configuration example of a communication device according to Embodiment 3. FIG. FIG. 10 is a diagram illustrating a configuration example of a topology management unit, an encoding function determination unit, an adjacent node management unit, and a group management unit according to the third embodiment. 6 is a diagram illustrating a configuration example of a network configured by communication apparatuses according to Embodiment 3. FIG. It is a figure which shows the structural example of the encoding function determination instruction message in a group. It is a figure which shows the example of a transmission sequence of the control message in the case of performing the determination function of an encoding function. It is a figure for demonstrating a subject.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Application 2, 2b Route management part 3, 3a Network coding part 4 Topology management part 5 Coding function determination part 6 Adjacent node management part 7 Group management part 31 Coding part 32 Independent path management part 33 Coding function management part 34 Independent Path complementing unit 41 Topology management execution unit 42, 52, 62, 72 Communication unit 51 Coding function control unit 61 Adjacent node management execution unit 71 Group management execution unit 411 Routing management unit 412 Topology management table 421, 521, 621, 721 Message Transmission unit 422, 522, 622, 722 Message reception unit 611 Connection state monitoring unit 612 Adjacent node management table 711 Group control unit 712 Group management table

Claims (4)

A communication device that configures an ad hoc network and receives data generated based on content data addressed to another communication device, and encodes and transfers the received data.
Topology management means for collecting topology information of the ad hoc network;
Before transmission of content data from another communication device is started , an instruction to determine an encoding function to be used in encoding processing for the received data when data generated based on the content data is received It received from the communication device, based on the topology information, a data transmission path to the other is a communication device second is a communication device from the first communication device desires the delivery of the content data of the communication device Transmission path calculation means for calculating;
Based on the data transmission path calculated by the transmission path calculation means , specify the number of input paths to the own apparatus and the number of output paths from the own apparatus of the encoded data generated based on the content data, Encoding function determination means for determining an encoding function for performing network coding on each data received from the input path and generating encoded data of the same number as the number of output paths ;
Equipped with a,
The encoding function determined by the encoding function determination unit and the content data scheduled to start transmission are stored in association with each other and stored when data generated based on the content data is received. A communication apparatus that encodes the received data using an encoding function . When transmitting content data held by itself to other communication devices,
The transmission path calculation means calculates a transmission path to another communication device that desires distribution of the content data based on the topology information before starting transmission of the content data,
The encoding function determination means, for each communication device on the transmission path the calculated, notifies the identification information of other communication devices that want to receive itself and the content data, based on the identification information The communication apparatus according to claim 1, wherein an instruction is given to determine an encoding function to be used in a data transmission process from itself to the other communication apparatus. further,
Based on the topology information, adjacent node management means for monitoring the connection state of adjacent nodes that are adjacent communication devices;
When it is detected that the adjacent node management means is an adjacent node on the transmission path calculated by the transmission path calculation means, and communication with the node that has been the transfer destination of the received data until then becomes impossible, Substitute adjacent node selection means for reselecting an adjacent node as a transfer destination of subsequent received data;
The communication apparatus according to claim 1, further comprising: further,
Group management means for grouping communication devices constituting the ad hoc network based on the topology information so that communication devices existing within a predetermined range are in the same group;
With
The transmission path calculation means is configured to allow the communication devices in the same group to configure a certain range of transmission paths based on the topology information and the group information of each communication device constituting the ad hoc network. Calculating a data transmission path from one communication device to the second communication device;
The encoding function determining unit determines an encoding function based on a transmission path within a range where communication devices belonging to the same group as the transmission path calculated by the transmission path calculating unit exist. The communication device according to claim 1, 2, or 3.

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