JP5835178B2 - Communications system - Google Patents

Description

  The present invention relates to a communication system that implements network coding.

Network coding is known as a communication method for realizing efficient communication.
This network coding is applied to a communication system in which nodes are connected by individual transmission paths. In each node (relay node) existing between the providing node that provides the content data and the user node that receives the provision of the content data, data received from one or more adjacent nodes is set in advance. Are encoded using the encoding function and transferred to one or more other adjacent nodes. Further, the user side node restores the content data by decoding the data received from the plurality of adjacent nodes and having been encoded differently.

  In the use side node, when decoding data, information on what route is used in the network and what encoding function is used in each relay node is required.

  As one method for realizing this, the following is known. That is, when the provision of content data is started, the providing side node notifies each node (relay node and using side node) of the route ID as information for specifying the transmission route to the using side node. Each node that has received the notification of information determines the transmission path and the encoding function to be used based on the notified information, and stores them in association with the path ID. Then, the providing side node includes the path ID in the header of the communication data used for transmitting the content data, and the using side node encodes the transmission path and each relay node used from the path ID indicated in the header. A function is specified, and content data is restored using information about the specified transmission path and encoding function (see, for example, Patent Document 1).

JP 2009-296251 A

  However, in the conventional apparatus described in Patent Document 1, the header of communication data used for transmission of content data includes a route ID that is unnecessary information for transferring the communication data. However, there is a problem that the transmission efficiency of the content data is reduced, which is a factor that hinders the efficiency of communication.

  In order to solve the above problems, an object of the present invention is to further improve communication efficiency in a communication system using network coding.

  In the communication system of the present invention, the providing node uses a vector having K (K is an integer of 2 or more) bits cut out from the content data as a transmission vector, and is a matrix of K rows and K columns set in advance. The transmission vector is sequentially encoded using the expressed encoding function, communication data is generated for each of K types of data sequences obtained by the encoding, and the communication data is transmitted to separate adjacent nodes for each data sequence. To do.

  Further, the relay node is a vector having M and N as integers equal to or greater than 1, and a total M bits of data extracted from each piece of communication data addressed to other nodes received from M adjacent nodes. As an input vector, the input vector is encoded using a preset encoding function represented by a matrix of M rows and N columns, and communication data is generated for each of N types of data series obtained by the encoding, The communication data is transferred to a separate adjacent node for each data series.

  Then, the usage-side node uses a K-order vector having K-bit data extracted from each of the communication data addressed to its own node received from K adjacent nodes as a reception vector as a reception vector. The content data is restored by decoding the received vector using a decoding function represented by a matrix of rows and columns.

That is, the communication system of the present invention realizes communication using so-called network coding.
Then, when the function estimation unit of the use side node requests the providing side node to transmit the initialization vector, the initialization vector transmission unit of the providing side node returns the initialization vector in response to the request as described above. Transmit as a transmission vector. However, the initialization vector is composed of K unit vectors (vectors in which any one component becomes 1 and the other components become 0) related to a vector having K-bit data as a component.

This initialization vector is encoded at the provider side node, transferred while being re-encoded at the relay node, and received at the user side node.
When the function estimation means of the user side node receives communication data addressed to the own node based on its own request, the function estimation means arranges the received vectors as column vectors based on K received vectors extracted from the received communication data. An overall coding function that represents a conversion characteristic from a transmission vector to a reception vector is estimated by a matrix of rows and K columns.

  That is, when a unit vector (column vector) in which the i-th row is set to 1 is applied to a matrix of K rows and K columns, a column vector equal to the i-th component of the matrix is obtained as its output. Further, it can be said that the reception vector received by the use side node is a result of applying the entire encoding function to the transmission vector provided by the providing side node. From this, for the K types of unit vectors transmitted from the providing side node, the receiving vectors obtained at the using side node each represent one of the column vectors constituting the overall coding function. The entire encoding function can be estimated by appropriately arranging the received vectors.

In the usage-side node, the decoding function setting unit sets the inverse function obtained from the encoding function estimated by the function estimation unit as the decoding function.
Thereafter, the use side node restores the content data by decoding the encoded data transmitted from the providing side node using this decoding function.

  As described above, in the communication system according to the present invention, the initialization vector is transmitted to the providing side node, and the entire encoding function, and thus the decoding function, is determined from the encoded initialization vector received at the using side node. Thereafter, the content data is restored from the received vector using the determined decoding function.

As described above, according to the communication system of the present invention, before the content data is transmitted, the decoding function is determined using the newly devised initialization vector. It is not necessary to include information for specifying the decryption function, and the path ID included in the communication data in the prior art can be omitted.
As a result, content data can be transmitted efficiently, and the effect becomes more prominent when short data is frequently transmitted.

  In the communication system according to claim 2, the consultation vector generation unit of the user side node transmits the consultation vector generated based on the entire coding function estimated by the function estimation unit to the providing side node. This requests the providing node to transmit the consultation vector. The consultation vector refers to a vector that is converted into a preset unit vector when applied to the entire encoding function.

  The consultation vector transmission means of the providing side node performs transmission using the consultation vector provided from the usage side node as a transmission vector in response to a request from the usage side node.

  As a result, the consultation vector is encoded by the providing side node, transferred while being re-encoded by the relay node, and received by the using side node, as in the case of the initialization vector.

  When the function correction means of the user side node receives the communication data addressed to its own node based on its own request, the received vector extracted from the received communication data does not match the expected unit vector. The overall encoding function is corrected by changing the arrangement order of the row vectors constituting the overall encoding function estimated by the function estimation means (that is, the arrangement order of the components constituting the column vector).

  Specifically, as a result of receiving a consultation vector expected to be converted to a unit vector (column vector) in which i row is set to 1, a unit vector in which j (i ≠ j) row is set to 1 In this case, the j-th row vector constituting the estimated overall encoding function may be moved to the i-th row. Then, by repeating this operation for the consultation vectors corresponding to the K-1 types of unit vectors, it is possible to correct the erroneously estimated overall coding function.

  Therefore, according to the communication system of the present invention, even when the correct arrangement order of each component constituting the reception vector is unknown at the user side node, the correct arrangement order is grasped by using the newly devised consultation vector. And thus the overall coding function can be uniquely determined.

1 is an overall configuration diagram of a communication system. It is explanatory drawing which shows the content of the message transmitted / received between nodes. It is a block diagram which shows the internal structure of a node. It is a flowchart which shows the content of the provision side process which the decoding function determination part of a provision side node performs. It is a flowchart which shows the content of the utilization side process which the decoding function determination part of a utilization side node performs. It is a sequence diagram which shows the initialization procedure performed when a utilization side node determines a decoding function. It is explanatory drawing about the uncertain element at the time of estimating a whole encoding function.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
<Overall configuration>
The communication system 1 executes communication using network coding.
As shown in FIG. 1, a plurality of communication devices (nodes) 2 are connected to each other via a transmission line (link) 3 that performs one-to-one communication. Each node 2 is connected to one or more transmission paths.

  Hereinafter, a node connected to the other end of the link 3 connected to the own node 2 is also referred to as an adjacent node. In addition, among the nodes 2, a node that provides content data is configured as a providing side node, a node that receives the provision of content data, and a node that uses the content data is configured as a usage side node, and a network that extends from the providing side node to the usage side node A node that relays content data is called a relay node.

  The providing side node transmits data to K adjacent nodes via K (K is an integer of 1 or more) links, and the relay node transmits M (M is an integer of 1 or more) links ( Encode data input from M adjacent nodes via (input link), and N adjacent via N (N is an integer of 1 or more) links (output links) different from the input link Output the encoded data to the node. Then, the user side node is configured to receive data from K adjacent nodes via K links and to decrypt the received data to restore the content data.

<Message>
Here, the contents of communication data (hereinafter referred to as “message”) transmitted and received between the nodes 2 will be described.

  The message includes at least an encoded data message used for transmission of content data, and a control message used to determine a decoding function used when decoding data encoded by network coding to restore content data Exists.

  As shown in FIG. 2A, the encoded data message includes a sequence area for setting a sequence number, a transmission ID area for setting a transmission node ID indicating a transmission source, and a reception ID for setting a reception node ID indicating a reception destination. It consists of an area and a data area for setting data.

  Note that the same sequence number is assigned to the K encoded data messages transmitted in parallel from the providing side node. Each relay node encodes data set in the data area for M encoded data messages having the same transmission node ID, reception node ID, and sequence number. The N encoded data messages in which the encoded data is set in the data area include the same transmission node ID, reception node ID, and the same as those given to the encoded data message to be encoded. Transferred with a sequence number. Further, the user side node decodes the data set in the data area for K encoded data messages having the same transmission node ID, reception node ID, and sequence number, and content data. To restore.

  On the other hand, as shown in FIGS. 2B to 2E, the control message is the same as the encoded data message except that a command area for designating the type of control is provided instead of the sequence area. . However, the data area may be omitted depending on the setting contents of the command area.

  FIG. 2B shows an initialization request message, when a request is made from the use side node to the providing side node to start a series of processes for determining a decoding function used in the use side node. Used for. This initialization request message is omitted because the data area is not necessary.

  FIG. 2C shows an initialization start notification message, which is used when the providing side node notifies the user side node that the initialization request message is received and the initialization process is started. This initialization start notification message is also omitted because the data area is not necessary.

  FIG. 2D shows an initialization vector transmission message which is transmitted from the providing side node to the usage side node, and data obtained by encoding an initialization vector (described later) is set in the data area. .

  FIG. 2E shows a consultation vector notification message, which is used when notifying data necessary for verification of the entire encoding function estimated by the user side node from the user side node to the providing side node. In the data area of this consultation vector notification message, a consultation vector (described later) generated using the estimated overall encoding function is set.

  FIG. 2F shows a consultation vector transmission message, which is transmitted from the provider side node to the user side node using the consultation vector acquired by the consultation vector notification message. In the data area of this consultation vector transmission message, data obtained by encoding the consultation vector is set.

  Note that the data area of the control message (here, initialization vector transmission message, consultation vector transmission message) transmitted from the provider side node to the user side node is encoded by the provider side node and the relay node in the same manner as the encoded data message. (Network coding). Hereinafter, the encoded data message, the initialization vector transmission message, and the consultation vector transmission message are collectively referred to as an encoding target message.

  On the other hand, control messages other than the encoding target message (here, an initialization start request message, an initialization start notification message, and a consultation vector notification message) are transferred according to a known routing technique that does not use network coding.

<Node>
As shown in FIG. 3, the node 2 is connected to a plurality of links 3, and a transmission / reception unit 21 that individually performs communication (message transmission / reception) with an adjacent node 2 via each link 3 and the own node 2 belong to the node 2. And a topology management unit 22 that collects and stores information (hereinafter referred to as “topology information”) relating to the arrangement state (topology) of nodes in the network (that is, the communication system 1).

  Further, when the node 2 receives an encoding target message addressed to another node from a predetermined adjacent node (input side adjacent node) via the transmission / reception unit 21, the data set in the data area is set in advance. An encoding target message, which is encoded using an encoding function and the encoded data is set in a data area, is transmitted to a predetermined adjacent node (output-side adjacent node) different from the input-side adjacent node via the transmission / reception unit 21. ) And a relay processing unit 23 that realizes a function as a relay node and data to be transmitted when transmitting a message to be encoded (content data, initialization vector, consultation vector held by itself) Is cut out in K-bit units (hereinafter, data in K-bit units is also referred to as “transmission vector”), encoded using an encoding function, and encoded. A transmission processing unit 24 that realizes a function as a providing side node by outputting an encoding target message in which the data is set in the data area to a predetermined adjacent node via the transmission / reception unit 21, and a topology management unit 22 An encoding function determination unit 25 that determines an encoding function (also referred to as an individual encoding function) used in the relay processing unit 23 and the transmission processing unit 24 based on the collected topology information is provided.

Further, when the node 2 receives the encoding target message addressed to itself via the transmitting / receiving unit 21, the node 2 decodes the data set in the data area using a preset decoding function, A series of initialization procedures between the reception processing unit 26 that realizes the function as the user side node by restoring the content data provided by the node, the topology information collected by the topology management unit 22, and the providing side node A decoding function determining unit 27 that determines a decoding function based on information obtained by executing (described later).

  Furthermore, the node 2 is a content data providing process that is an application that provides the content data of the node 2 to the user side node using the encoded message, either spontaneously or in response to a request from another node. An application processing unit 28 that executes at least content data use processing that is an application that uses content data restored by the reception processing unit 26 is provided.

That is, the node 2 is configured to operate as any of the providing side node, the usage side node, and the relay node.
<Transmission processing unit>
When transmitting the encoding target message, the transmission processing unit 24 encodes the data to be transmitted using the data area by an encoding function expressed by a matrix of K rows and K columns determined by the encoding function determination unit 25. Are sequentially encoded in units of transmission vectors. Then, a separate encoding target message is generated for each of the K types of data series obtained by the encoding, and the encoding target message is transmitted to a separate adjacent node for each data series via the transmission / reception unit 21.

  In addition, when transmitting a control message other than the encoding target message, the transmission processing unit 24 does not perform encoding by the encoding function even if the data area exists, and does not execute any encoding specified in advance. To one adjacent node.

<Relay processing unit>
When the relay processing unit 23 receives an encoding target message addressed to another node from the M adjacent nodes via the transmission / reception unit 21, the relay processing unit 23 receives 1 bit from the data area of the received encoding target message addressed to the other node. By extracting and arranging them in a predetermined order, an input vector composed of M-bit data is generated. That is, if P data is set in the data area of each message, P input vectors are generated. Then, the input function is sequentially encoded using the encoding function expressed by the matrix of M rows and N columns determined by the encoding function determination unit 25, and separately for each of the N types of data series obtained by the encoding. The encoding target message is generated, and the encoding target message is transferred to a separate adjacent node for each data series via the transmission / reception unit 21.

  Further, when receiving a control message other than the encoding target message, the relay processing unit 23 transfers the control message to any one of the adjacent nodes determined by a known routing process.

<Reception processing unit>
When the reception processing unit 26 receives the encoding target message addressed to the own node from the K adjacent nodes via the transmission / reception unit 21, the reception processing unit 26 receives 1 bit from the data area of the received encoding target message addressed to the own node. By extracting and arranging them in a predetermined order, a reception vector composed of K-bit data is generated. That is, if P data is set in the data area of each message, P reception vectors are generated. Then, the content data is restored by sequentially decoding the received vector using the decoding function expressed by the matrix of K rows and K columns determined by the decoding function determination unit 27.

<Topology management unit>
The topology management unit 22 collects topology information by transmitting and receiving control messages (not shown) prepared in advance for topology management to and from other nodes, and stores the collected information in the topology management table. To do. Thereby, all the nodes 2 having the topology management unit 22 hold common topology information.

The protocol used for collecting the topology information is well known and is not directly related to the main part of the present invention, and therefore the description thereof is omitted here.
When the topology management unit 22 detects that the topology information has changed, for example, when a new node 2 is added to the communication system 1 or the connected node 2 is removed, the topology information To the encoding function determination unit 25 and the decoding function determination unit 27 that execute processing based on the above, a topology update notification that notifies the fact is output.

<Encoding function determination unit>
The encoding function determination unit 25 operates to determine an encoding function (individual encoding function) when the encoding function has not been calculated or when a topology update notification is received from the topology management unit 22.

  Specifically, input links and output links used in network coding are determined based on topology information stored in the topology management table. Then, the number of output links to be used when the own node 2 operates as the providing side node is set as K, and an encoding function of K rows and K columns used by the transmission side processing unit 24 is set. Assuming that the number of input links to be used is M and the number of output links is N, an encoding function expressed by a matrix of M rows and N columns used in the relay processing unit 23 is set.

  These encoding functions are provided for each node 2 so that the entire encoding function obtained by synthesizing the encoding functions has an inverse matrix and has a characteristic that a decoding function can be obtained from the entire encoding function. Set arbitrarily. An encoding function having such characteristics is well known in network coding.

<Decoding function determination unit>
The decryption function determination unit 27 executes a providing process when the node 2 is a providing node that provides content data, and a using process when it is a using node that uses content data. Note that the node 2 serving as the user side node holds in advance a node ID that is information for specifying the node 2 serving as the providing side node.

Hereinafter, the process in the decryption function determination unit 27 will be described in detail by dividing it into a providing side process and a using side process.
A procedure realized by executing the provider side process and the user side process is referred to as an initialization procedure.

<< Providing processing >>
The provider side process is started when the topology management unit 22 collects the topology information and the encoding function determination unit 25 determines the encoding function and then receives the initialization start request message from the user side node. . When there are a plurality of usage-side nodes, an initialization start request message is individually transmitted from each usage-side node, and the same processing is executed for each of the usage-side nodes.

  When this processing is started, as shown in FIGS. 4 and 6, first, an initialization start notification message is sent to the use side node (hereinafter referred to as “request source node”) that is the transmission source of the initialization start request message. Is transmitted (S110), and then an initialization vector notification message is transmitted to the requesting node (S120).

The initialization vector notification message is output from each of the K output links of the own node.
Here, the initialization vector is composed of K-bit data having the same number as the number of output links as components, and any one component is set to 1 and all other components are set to 0. Consists of various unit vectors. For example, when K = 3, the initialization vectors are represented by [1, 0, 0] [0, 1, 0] [0, 0, 1], respectively.

If the encoded data (output vector) obtained by applying these initialization vectors to the unit encoding function is represented by [x ₁ , x ₂ ,... X _K ], the output vector component x _i (i = 1, 2,... K) is set in the data area of the initialization vector notification message output from the i-th output link. That is, since K types of initialization vectors exist here, K data are set in the data area of the initialization vector notification message output from each output link.

  After that, it waits until a consultation vector notification message is received from the requesting node (S130). When a consultation vector notification message is received, a consultation vector transmission message based on the consultation vector set in the message is transmitted (S140). This process is terminated.

  The consultation vector transmission message is output from each of the K output links as in the case of the initialization vector notification message. That is, the initialization vector is replaced with the consultation vector, and the same encoding as when the initialization vector notification message is transmitted and the setting of the encoded data in the data area are performed.

  After this processing, transmission of content data using the encoded data message is started in response to a request from the requesting node or periodically. In the case of transmitting content data, the same processing as in the case of the initialization vector and the consultation vector is performed below using the data cut out in K bits from the content data as a transmission vector. However, the same sequence number is assigned to K encoded data messages in which encoded data based on the same transmission vector is set in the data area.

<< User side processing >>
In the use side process, there is a change in the topology information collected by the topology management unit 22 (input of topology update information), and the own node 2 is a use side node that uses content data provided by another node. (For example, when the node ID of the providing node is stored in a predetermined storage area). The case where there is a change in topology information includes the case where topology information acquired and stored in the past does not exist and topology information is acquired for the first time.

Further, when it is necessary to acquire content data from a plurality of providing side nodes, this processing is individually executed for each providing side node.
When this process starts, as shown in FIGS. 5 and 6, first, an initialization start request message is transmitted to the providing side node (S210).

  Thereafter, it waits until an initialization start notification message is received from the providing side node (S220), and upon receiving this, it waits until it receives an initialization vector notification message (S230).

When receiving an initialization vector notification message in which the transmission node ID, the reception node ID, and the sequence number all match from all K input links used for receiving the content data, the reception vector is extracted from the data area of those messages, Based on the extracted received vector, an overall encoding function which is an encoding function of the entire network (a function obtained by combining encoding functions used in the providing side node and all relay nodes) is estimated (S240).

  Here, since K data is set in the data area of each initialization vector notification message, the i-th (i = 1, 2,... K) set data is extracted from each message. Is extracted as the i-th received vector. An i-th received vector arranged as a column vector of i columns in a matrix of K rows and K columns is used as an estimated value (hereinafter referred to as “estimation function”) of the entire coding function.

  Next, a consultation vector is calculated based on the estimation function obtained in S240 (S250), and a consultation vector notification message in which the calculated consultation vector is set in the data area is transmitted to the providing side node (S260).

  Note that the consultation vector is a K-bit vector that is encoded into a K-bit unit vector when applied to the estimation function, and is composed of K vectors corresponding to each of K types of unit vectors.

  After that, it waits until receiving a consultation vector transmission message from the providing side node (S270). When initialization vector notification messages are received from all of the K input links used for receiving content data, from the data area of those messages. The received vector is extracted, and the estimated function is verified by determining whether or not the extracted received vector matches the expected unit vector (S280).

  If even one received vector does not match the expected unit vector, the estimated function is corrected by appropriately replacing column vectors constituting the estimated function according to the contents of the received vector (S290).

  If all the received vectors match the expected unit vector, the estimation function is used as the whole encoding function as it is. If the two do not match, the estimation function modified in S290 is used. Is used as the overall encoding function, an inverse function of the overall encoding function is obtained as a decoding function (S300), and the process is terminated.

  Thereafter, when the reception processing unit 26 receives, through the transmission / reception unit 21, encoded data messages having the same transmission node ID and reception node ID sequence number from all K input links, the data area of those messages The reception vector extracted from the data set in (2) is decrypted using the decryption function determined by the decryption function determination unit 27, and the content data restored by the decryption is provided to the application processing unit 28.

<Operation example>
An operation example of the communication system 1 will be described.
In FIG. 1, it is assumed that the node N1 operates as a providing side node, the nodes N2 and N as relay nodes, and the node N4 as a usage side node.

  Here, as shown in the equations (1) to (3), the encoding functions set in the nodes N1 to N3 are represented by H1 to H3.

Further, a transmission vector composed of 2-bit data cut out from the content data provided by the providing side node N1 is represented by [b ₁ , b ₂ ], and the encoded data output from the node Ni is represented by [S _iL , S _iR ], the encoding executed at each of the nodes N1 to N3 is expressed by the equations (4) to (6).

The received vector [b ₁ , b ₂ ] provided by the provider side node N1 and the received vector [S _2R , S _3L ] extracted from the encoded data message received by the user side node N4 are encoded in the entire network. If the overall coding function as a function is H, the relationship shown in the equation (7) is obtained. Further, the overall coding function H can be obtained from (4) to (7), and is represented by the equation (8). Is done.

As can be seen from the equation (7), if the individual encoding functions H1 to H3 are set so that the overall encoding function H has an inverse matrix, a decoding function that is an inverse matrix of the overall encoding function H is used. Thus, the transmission vector [b ₁ , b ₂ ] can be obtained from the reception vector [S _2R , S _3L ], and the content data can be restored.

  Further, as is clear from the equations (7) and (8), when the transmission vector transmitted from the providing side node N1 is the initialization vector [1, 0], the reception vector received at the using side node N4 is , When the transmission vector is the initialization vector [0, 1], the received vector is the column vector of the second column of the overall encoding function H. Is equal to

  Therefore, the use side node N4 can estimate the entire encoding function H by appropriately arranging received vectors extracted from the values set in the data area of the initialization vector transmission message.

  However, the correspondence relationship between the arrangement order of the components constituting the transmission vector and the arrangement order of the components constituting the reception vector is collected into two patterns shown in FIG. 7 when K = 2.

  That is, when the received vector arrangement order is correct, the correct overall encoding function estimated using the initialization vector is H, and when the received vector arrangement order is incorrect (replaced), the initialization vector Assuming that the erroneous overall coding function estimated using the Herr is Herr, both functions are expressed by the equations (9) and (10), and the relationship between them uses the transformation matrix T expressed by the equation (12). (11).

  When unit vectors E1 and E2 of two-component vectors are expressed by equations (13) and (14) and the estimation function is expressed by Hs (= H or Herr), the unit vector E1 obtained from the estimation function Hs is expressed as The converted diagnostic vector Vex is expressed by equation (15).

When this diagnostic vector Vex is transmitted from the providing side node N1 as a transmission vector, the reception vector obtained at the use side node N4 is represented by H · Vex. When the estimation function Hs is correctly estimated (when Hs = H), the received vector is expressed by equation (16), and when the estimation function Hs is estimated incorrectly (when Hs = Herr), The reception vector is expressed by equation (17).

That is, the received vector obtained by network coding the diagnostic vector Vex is the unit vector E1 that is an expected value if the estimation function Hs is correct, and matches the expected value if the estimation function Hs is incorrect. It turns out that it becomes unit vector E2 which does not.

  For this reason, when the received vector based on the diagnostic vector Vex does not match the expected unit vector, it is assumed that the estimation function Hs is incorrect, and the correct whole coding function is obtained by replacing the row vectors constituting the estimation function Hs. Will be obtained.

Here, the case of K = 2 has been described, but when K> 3, the following correction may be performed.
That is, when a unit vector whose i-th row is expected to be 1 but a received vector is a unit vector whose 1-th row is j (i ≠ j), j rows constituting the estimation function Hs The eye row vector is moved to the i-th row. By performing this operation for all received vectors that do not match the expected value, a correct overall coding function can be obtained.

<Effect>
As described above, the communication system 1 causes the providing side node N1 to transmit the initialization vector and the consultation vector, and the encoded data (received vector) received by the using side node N4 is used as an overall encoding function H, As a result, a decoding function is specified, and thereafter, the content data is restored from the received vector using the specified decoding function.

As described above, according to the communication system 1, before starting transmission of content data, a decoding function is determined using “initialization vector” and “consultation vector” which are new concepts in network coding. Therefore, when transmitting the content data, there is no need to include information for specifying the decoding function in the encoded data message, and the path ID included in the message can be omitted in the prior art.
For this reason, content data can be transmitted efficiently, and the effect becomes more prominent when short data is frequently transmitted.

  The communication system 1 is configured to reset the individual encoding function and re-specify the overall encoding function H (and thus the decoding function) when the network topology information changes. It can be suitably used even in a system in which 2 may be retrofitted or removed.

<Other embodiments>
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be implemented in various modes without departing from the gist of the present invention.

  For example, in the above-described embodiment, each node 2 is configured to be operable as any of the providing side node, the usage side node, and the relay node, but may be configured for any one of them. Specifically, if it is dedicated to the providing side node, the use side process in the relay processing unit 23, the reception processing unit 26, the decryption function determining unit 27, and the content use process in the application processing unit 28 may be omitted. If the node is dedicated to the use side node, the providing side process in the relay processing unit 23, the transmission processing unit 24, the encoding function determining unit 25, the decoding function determining unit 27, and the content providing process in the application processing unit 28 are omitted. Also good. If the relay node is dedicated, the transmission processing unit 24, the reception processing unit 26, the decoding function determination unit 27, and the application processing unit 28 may be omitted.

DESCRIPTION OF SYMBOLS 1 ... Communication system 2 ... Node 3 ... Link 21 ... Transmission / reception part 22 ... Topology management part 23 ... Relay processing part 24 ... Transmission processing part 25 ... Coding function determination part 26 ... Reception processing part 27 ... Decoding function determination part 28 ... Application processing section

Claims (4)

A transmission vector is a vector having K (K is an integer greater than or equal to 2) bits extracted from the content data as a transmission vector, and the transmission vector is expressed using an encoding function expressed in a preset matrix of K rows and K columns. Sequentially providing, generating communication data for each of the K types of data sequences obtained by the encoding, and providing the communication data to separate adjacent nodes for each data sequence,
M and N are both integers greater than or equal to 1, and a vector whose components are M-bit data extracted from each of the communication data addressed to other nodes received from M adjacent nodes is set in advance as an input vector. The input vector is encoded using an encoding function represented by a matrix of M rows and N columns, communication data is generated for each of N types of data series obtained by the encoding, and the communication data is converted to the data A plurality of relay nodes that transfer to different neighboring nodes for each sequence;
A vector having K-bit data extracted from each of the communication data addressed to its own node received from K adjacent nodes as a component is represented as a reception vector, and is expressed by a matrix of preset K rows and K columns. A user side node that restores the content data by decoding the received vector using a decoding function;
With
The provider node is
In response to a request from the user side node, a vector in which any one component is 1 and the other component is 0 is a unit vector, and K unit vectors related to a vector composed of K-bit components are initialization vectors. Initialization vector transmission means for performing transmission with the initialization vector as the transmission vector,
The user side node is
When requesting the provider node to transmit the initialization vector and receiving communication data addressed to the own node based on the request, the reception vector is determined based on K received vectors extracted from the communication data. Function estimation means for estimating an overall encoding function expressed by a matrix of K rows and K columns arranged as a column vector and representing a conversion characteristic from the transmission vector to the reception vector;
Decoding function setting means for setting an inverse function obtained from the encoding function estimated by the function estimation means as the decoding function;
A communication system comprising: The provider node is
In response to a request from the user side node, comprising a consultation vector transmission means for performing transmission with the consultation vector provided from the user side node as the transmission vector,
The user side node is
When the entire encoding function estimated by the function estimation unit is operated, a consultation vector generation unit that generates a vector that is converted into a preset unit vector as the consultation vector;
By transmitting the consultation vector generated by the consultation vector generation means to the providing side node, the transmission side node is requested to transmit the consultation vector, and communication data addressed to the own node based on the request is transmitted. When received, if the received vector extracted from the communication data does not match the expected unit vector, the column vector of the overall coding function estimated by the function estimating means is replaced according to the content of the received vector. A function correcting means for correcting the entire encoding function;
The communication system according to claim 1, further comprising: The providing side node and the relay node are:
Topology information management means for collecting network topology information;
Encoding function setting means for setting an encoding function based on the topology information collected by the topology information management means;
The communication system according to claim 1, further comprising: The user side node is
A topology information management means for collecting network topology information is provided.
4. The communication system according to claim 1, wherein the function estimation unit is activated when a change occurs in the content of the topology information collected by the topology information management unit. 5. .

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