JP2010239196A - Data delivery method, radio communication system, and data relay terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for reducing the number of packet transmission to deliver data efficiently, even when network coding is performed when data is delivered in a radio multi-hop network. <P>SOLUTION: The method includes the steps of: extracting for each data source, at least two minimum hop routes among a plurality of routes from the data source to at least one data sink of destination; determining for each combination of at least two cross routes among the minimum hop routes, coding propriety of data which flows at each cross route of the combination; establishing the coding-enabled minimum hop route from the data source to the data sink of destination, according to the determined result of coding propriety obtained; and, according to the determined result of coding propriety corresponding to the coding-enabled minimum hop route, coding the data and delivering it from the data source to the data sink of destination through the coding-enabled minimum hop route established about the data source. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention comprises a plurality of wireless communication terminals capable of wireless communication with each other, and each wireless communication terminal independently transmits data as a data generation source or receives data as a data termination side, and these The present invention relates to a data distribution method, a wireless communication system, and a data relay terminal in a multi-hop network having a hop transfer function for relaying transmitted / received data.

  In a wireless multi-hop network including a plurality of wireless communication terminals, a link is formed because a plurality of communication paths are formed between terminals functioning as data transmission terminals and terminals functioning as data reception terminals among the wireless communication terminals. High reliability against failures. However, on the other side, there is a possibility of redundant transmission, so the network load accompanying an increase in data amount becomes a problem.

  In this regard, a method for reducing the number of transmissions by multicast routing is known. However, since such a method aggregates and transfers links, there is a high risk that the amount of data lost when a link failure occurs is high, and there is a risk that the overhead of data delivery will be concentrated on a specific terminal. As a method of reducing the number of data packet transmissions, a method of consolidating a plurality of data packets and transmitting them in one data packet is also considered. However, in this method, although the overhead for each packet is reduced, the size of each packet is increased and a sufficient improvement in efficiency cannot be expected.

  In view of this, a concept called network coding has been introduced, and it has been proposed to apply a specific encoding algorithm to data to reduce the amount of data. For example, Non-Patent Document 1 discloses a technique for reducing the amount of data by transmitting encoded data obtained by performing an exclusive OR operation that is a kind of linear combination operation on data of a plurality of packets. ing.

  1A-1C illustrate the advantages of network coding using exclusive OR operations. Network coding improves reliability by reducing the amount of data to be transmitted and the number of transmissions by transmitting data obtained by calculating an exclusive OR of a plurality of data. As a background explanation, FIGS. 1A and 1B show a situation where network coding is not performed. Here, it is assumed that among the wireless communication terminals, two data transmission terminals S1 and S2, two data reception terminals R1 and R2, and four data relay terminals T1 to T4 are arranged. The data transmitting terminal S1 tries to deliver data D_S1 that is its own generated data to the data receiving terminal R1, and the data transmitting terminal S2 tries to deliver data D_S2 that is its own generated data to the data receiving terminal R2.

  Referring to FIG. 1A, two D_S1 transfers are performed from the data transmission terminal S1 to the data reception terminal R1, while four D_S1 transfers are performed from the data transmission terminal S1 to the data reception terminal R2. Since the transfer from the data transmission terminal S1 to the data relay terminals T1 and T2 is a broadcast communication (broadcast), it is counted as one transmission, and a total of five transmissions are performed. Referring to FIG. 1B, a total of five transmissions are similarly performed for the transfer from the data transmission terminal S2 to D_S2. Eventually, it can be seen that a total of 10 transmissions are required to deliver the data D_S1 and D_S2 to the data receiving terminals R1 and R2.

  FIG. 1C shows a case where network coding is used. The data D_S1 reaches the data receiving terminal R1 through two transmissions via the data relay terminal T3. Further, the data D_S2 reaches the data receiving terminal R2 through two transmissions via the data relay terminal T4. Since transmission of the data transmission terminals S1 and S2 is broadcast communication, the data relay terminal T1 receives data D_S1 and data D_S2 from the data transmission terminals S1 and S2, respectively. Next, the data relay terminal T1 transmits data D_S1 XOR D_S2, which is an exclusive OR of the data D_S1 and the data D_S2, to the data relay terminal T2 (one transmission). The data relay terminal T2 transmits the received data D_S1 XOR D_S2 as it is to both the data relay terminals T3 and T4 (one transmission). The data relay terminals T3 and T4 transmit the received data D_S1 XOR D_S2 to the data receiving terminal R1 and the data receiving terminal R2, respectively (two transmissions).

  The data receiving terminal R1 obtains data D_S2 by performing decoding by calculating an exclusive OR of the data D_S1 XOR D_S2 and the data D_S1. On the other hand, the data receiving terminal R1 obtains data D_S1 by performing decoding by calculating an exclusive OR of the data D_S1 XOR D_S2 and the data D_S2. As a result, the desired data delivery requires a total of eight transmissions, with the number of transmissions at the data relay terminals T1 and T2 being reduced by one each. The amount of data transmission can be reduced by transmitting data obtained by exclusive OR. That is, it can be seen that the number of data transmissions and the data transmission amount are reduced as compared with the case where network coding is not performed.

  The technology disclosed in Non-Patent Document 1 states that “each wireless communication terminal selects a packet to be encoded in accordance with data holding information notified by an adjacent terminal, and becomes an exclusive OR of the data of the selected packet. The data is encoded and transmitted. " Then, a specific algorithm for taking the exclusive OR is “when sending n data packets p1, p2,... Pn to n destination next-hop terminals r1, r2,. Only when each next-hop terminal r holds n−1 data other than pi, the data of exclusive OR of n data packets p1, p2,. Is based. By following such rules, it is possible to guarantee the decodability of the encoded data.

  Further, as disclosed in Non-Patent Document 2, many existing routing protocols that operate in a wireless multi-hop network set the hop count as a metric for path construction, and the hop count from the data transmission terminal to the data reception terminal. The path that minimizes is constructed.

S. Katti, H. Rahul, W. Hu, D. Katabi, M. Medard, and J. Crowcroft, "XORs in The Air: Practical Wireless Network Coding," in Proc. Of ACM, SIGCOMM 2006, Pisa, Italy, Sept. 2006. C. Perkins, E. Belding-Royer, and S. Das, `` Ad-Hoc On-Demand Distance Vector (AODV) Routing ,, '' RFC 3561, http://www.ietf.org/rfc/rfc3561. TXT

  However, as in Non-Patent Document 2, route control in which individual terminals construct a minimum hop route does not consider route control between end-to-end data transmission data receiving terminals when performing network coding. Therefore, when network coding is performed in a form where there are a plurality of data transmission terminals, there is a case where the total number of hops is not minimized even if a minimum hop route is constructed between each data transmission terminal and data reception terminal. There is a problem.

  In addition, when there are a plurality of data transmission terminals and data reception terminals, it is conceivable to reduce the number of packet transmissions by performing multicast. However, since data is aggregated and delivered, there is a problem that the delivery rate to the data receiving terminal is likely to decrease when a certain link is disconnected.

  Referring now to FIG. 2A, in the form of multicast, when data is distributed to a plurality of data receiving terminals R1 and R2, data is transmitted only once in a common link, and data is copied at a terminal at a branch point. This is a method of delivering data to the route. In FIG. 2A, data transmission terminals S1 and S2 deliver data Da and Db to data reception terminals R1 and R2, respectively. Since the route is shared, the number of transmissions is reduced compared to the case where the route is not shared. The data relay terminal Ta can encode the data Da and data Db, the data receiving terminal R1 has data Da and data (Da XOR Db), and the data receiving terminal R2 has data Db and data (Da XOR Db). )) Respectively. Then, for example, the data Da and the data (Da XOR Db) are exclusive-ORed to obtain the data Db, and the data is decoded at the respective data receiving terminals R1 and R2, and the data Da and the data Db are respectively obtain. In the example of FIG. 2A, the total number of transmissions is 23. When the data relay terminal Tx that relays certain data fails for some reason, only the data Db reaches the data receiving terminals R1 and R2. When network coding is performed on a multicast route in this way, the total number of transmissions is suppressed, but the routes to which the same data is delivered are aggregated, so the problem is low resistance to terminal failures and link errors There is.

  Still referring to FIG. 2B, in the minimum hop routing, a minimum path from the data transmission terminals S1 and S2 to the data reception terminals R1 and R2 is established. In FIG. 2B, data can be encoded by the data relay terminal Ta. Similarly to the case of the multicast described above, the data receiving terminal R1 has data Da and data (Da XOR Db)), and the data receiving terminal R2 has Data Db and data (Da XOR Db)) arrive. Then, the data is decoded at each of the terminals R1 and R2 to obtain data Da and data Db. In the example of FIG. 2B, the total number of transmissions is 35. Even if the data relay terminal Tx breaks down for some reason, the data receiving terminals R1 and R2 can obtain the data Da and data Db, respectively, and the data receiving terminals R1 and R2 cooperate to allow the user to receive both data. Can be acquired. Therefore, when performing network coding on the minimum hop route, compared to a case where network coding is performed on a multicast route where data Da cannot be obtained by either data receiving terminal, it is possible to cope with terminal failures and link errors. Although the tolerance is high, there is a problem that the total number of transmissions is large.

  The present invention has been made in view of the above-described problems, and the object of the present invention is even when the data transmission terminal performs network coding when delivering data addressed to the data reception terminal via the data relay terminal. Another object of the present invention is to provide a data delivery method, a wireless communication system, and a data relay terminal capable of efficiently delivering data by reducing the number of packet transmissions.

  The invention according to claim 1 is a data delivery method in a wireless communication system in which a plurality of terminals each connected between adjacent ones via a wireless communication link constitute a multi-hop network, and the data of the terminals For each transmitting terminal, a path extracting step for extracting at least two minimum hop paths from a plurality of paths from the data transmitting terminal to at least one data receiving terminal as a transmission destination, and a minimum obtained for each data transmitting terminal For each combination of at least two of the hop paths, an encoding determination step for determining whether or not data flowing in each intersection path of the combination is encoded, and determination of whether or not encoding is obtained for each of the intersection paths Depending on the result, for each data transmission terminal, the minimum hop path corresponding to the encoding from the data transmission terminal to the destination data reception terminal A path setting step to be set, and for each data transmission terminal, the data is transmitted from the data transmission terminal to the destination data reception terminal via the encoding-compatible minimum hop path set for the data transmission terminal. And a data distribution step of performing distribution according to the determination result of whether or not encoding corresponding to the corresponding minimum hop route is performed.

  The invention according to claim 15 is a wireless communication system in which a plurality of terminals, each of which is connected between adjacent ones via a wireless communication link, constitutes a multi-hop network, and is provided for each data transmission terminal among the terminals. A path extracting means for extracting at least two minimum hop paths from a plurality of paths from the data transmitting terminal to at least one data receiving terminal as a transmission destination, and a minimum hop path obtained for each data transmitting terminal For each combination of at least two crossing paths, encoding determination means for determining whether or not data flowing in each crossing path of the combination can be encoded, and according to the determination result of encoding propriety obtained for each of the crossing paths A path setting means for setting a minimum hop path for encoding from the data transmitting terminal to the destination data receiving terminal for each data transmitting terminal; For each data transmission terminal, the data corresponding to the minimum hop path corresponding to the encoding is transmitted from the data transmission terminal to the destination data reception terminal via the minimum hop path corresponding to the encoding set for the data transmission terminal. And data delivery means for delivering the data after performing encoding according to the determination result.

  The invention according to claim 16 is a data relay terminal that is connected between adjacent ones via a wireless communication link and has a data relay function among a plurality of terminals constituting a multi-hop network, Route extracting means for extracting at least two minimum hop routes from a plurality of routes from the data transmitting terminal to at least one data receiving terminal of the transmission destination for each data transmitting terminal, and obtained for each data transmitting terminal For each combination of at least two crossing paths among the minimum hop paths determined, encoding determination means for determining whether or not data flowing in each crossing path of the combination can be encoded, and encoding obtained for each crossing path Depending on the determination result, an encoding-compatible minimum hop route from the data transmitting terminal to the destination data receiving terminal is set for each data transmitting terminal. For each data transmission terminal, the data is transmitted from the data transmission terminal to the destination data reception terminal via the encoding-compatible minimum hop path set for the data transmission terminal. And a data delivery means for delivering by performing encoding according to a determination result of whether or not encoding corresponding to the minimum hop route is possible.

  According to the data delivery method, the wireless communication system, and the data relay terminal according to the present invention, a code-aware routing scheme in which an arbitrary terminal constructs a route suitable for network coding in an autonomous distributed manner is used. As a result, the reliability of data delivery is higher than when using conventional multicast, and it is possible to reduce the number of transmissions and the number of transmissions compared to the case where each terminal constructs a route to the data receiving terminal with the minimum path. Become.

It is a block diagram which shows the condition which does not perform network coding. It is a block diagram which shows the other situation which does not perform network coding. It is a block diagram which shows the condition which performed network coding. It is a figure which shows the example of the network coding in a multicast. It is a figure which shows the example of the network coding in the minimum hop routing. 1 is a block diagram illustrating an overall configuration of a wireless communication system according to an embodiment of the present invention. FIG. 4 is a block diagram showing an internal configuration of each wireless communication terminal shown in FIG. 3. It is a sequence diagram which shows the process sequence of the setting method of a route information table. It is a figure which shows the example of a setting of the path | route information table updated as a result of the process sequence shown by FIG. It is a figure which shows the format of the data packet produced | generated when a data transmission terminal performs data delivery. It is a flowchart which shows the process sequence at the time of reception of a data packet. It is a flowchart which shows the more detailed process sequence of the data transfer process shown by FIG. It is explanatory drawing explaining the actual mode of the process sequence shown by FIG. It is a figure which shows the example of the network coding in an encoding corresponding | correspondence (code-aware) routing. It is a block diagram which shows the example of many-to-many communication in a 2nd Example. It is a block diagram which shows the structure of the radio | wireless communication terminal in a 2nd Example. It is a figure which shows the construction example of the minimum hop path | route in a 2nd Example. It is a figure which shows the example of the intersection of the path | route in a 2nd Example. It is a figure which shows the example which detects the intersection of the path | route in a 2nd Example. It is a figure which shows the example of a notification from the encoding determination terminal in a 2nd Example to the data relay terminal on a path | route. It is a figure which shows the example of flooding of the control packet of each terminal on a network from the data relay terminal on the path | route in a 2nd Example. It is a figure which shows the construction example of the minimum hop path | route from the transmission data receiving terminal in a 2nd Example on a path | route. It is a figure which shows the example of determination of the data encoding terminal in a 2nd Example, and a multicast terminal. It is a figure which shows the example of data delivery from the transmission data receiving terminal in a 2nd Example to a data receiving terminal. It is a figure which shows the construction example of the recursive encoding corresponding | compatible minimum hop path | route in a 2nd Example. It is a figure which shows the effect of the encoding corresponding | correspondence (code-aware) routing in a 2nd Example. It is a block diagram which shows the example of many-to-one communication in a 3rd Example. It is a figure which shows the example which detects the intersection of the path | route in a 3rd Example. It is a figure which shows the example of the encoding determination by the path | route information in many-to-one communication in a 3rd Example. It is a figure which shows the example of the network coding in the many-to-one communication in a 3rd Example. It is a figure which shows the effect of the network coding in the many-to-one communication in a 3rd Example. It is a figure which shows the example of data encoding on the same path | route in many-to-many communication in a 4th Example. It is a figure which shows the 1st data encoding of the data encoding example of the multiple times in the same path | route in a 4th Example. It is a figure which shows the 2nd data encoding of the example of multiple times data encoding in the same path | route in a 4th Example. It is a figure which shows the example of many-to-many communication in which the path | route to a certain data transmission terminal in a 5th Example or a certain data receiving terminal exists. It is a figure which shows the encoding determination example by the packet information in the many-to-many communication in 5th Example. It is a figure which supplements the example of an encoding determination by the packet information in many-to-many communication in 5th Example.

  A first embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  In the following description, various names such as a data encoding determination terminal, a multicast terminal, a data relay terminal, a data receiving terminal, and a data transmitting terminal are used as the names of the wireless communication terminals. In this example, each terminal means a wireless communication terminal having basically the same function unless the function is particularly limited.

<First embodiment>
FIG. 3 shows an embodiment of the present invention and shows the overall configuration of the wireless communication system. Here, there are a plurality of wireless communication terminals T1 to T10 connected to each other via a wireless link in a network form. In this figure, ten wireless communication terminals T1 to T10 are shown as an example, but the number is an example, and a large number of two or more wireless communication terminals can be assumed.

  Each of the wireless communication terminals T1 to T10 can transmit and receive data and can relay data. That is, on the premise of a plurality of wireless communication terminals T1 to T10, data generated by any one of them as a data transmitting terminal is relayed to any other data receiving terminal by any of the remaining data Deliver via terminal. Data transmission / reception means end-to-end transmission / reception at the application layer. The data transmission terminal functions as a sensor terminal that measures sensor data, for example, and the data reception terminal collects the collected sensor data. Can function as a terminal. On the other hand, data relay basically means that data is transferred as it is in a layer lower than the application layer, and data is encoded or decoded as required according to an algorithm described later.

  In the first embodiment, it is assumed that a plurality of data transmitting terminals transmit data to a plurality of data receiving terminals. As an advantage of this form, for example, when sensor data is collected by a plurality of data receiving terminals, even if a failure occurs in one data receiving terminal, the data can be collected by another operating data receiving terminal, Even if the link route of data delivery up to this point disappears due to a failure or the like, data can be collected through another available link route.

  FIG. 4 shows the internal configuration of each wireless communication terminal shown in FIG. Each of the wireless communication terminals T1 to T10 includes a route information table 205, a route information control unit 201, a data packet holding unit 202, a data packet processing unit 203, and a wireless communication unit 204. The route information control unit 201 sets the route information table 205, and performs route control for data delivery to the data receiving terminal according to the setting contents. The packet holding unit 202 temporarily holds data packets to be transmitted / received. The data packet processing unit 203 generates a new data packet by generating a new data packet or calculating an exclusive OR based on a predetermined function such as sensing. The wireless communication unit 204 transmits and receives route control packets and data packets by wireless communication with other adjacent wireless communication terminals.

  FIG. 5 shows the processing procedure of the setting method of the route information table 205. This processing procedure is executed by the route information control unit 201 (see FIG. 4) of each wireless communication terminal, and is executed prior to the delivery of the data packet. In the following description, a terminal that performs data transmission among a plurality of wireless communication terminals is represented as a data transmission terminal S1 or S2, and a terminal that performs data reception is represented as a data reception terminal R1 or R2. Terminals that perform relaying are represented by data relay terminals T1 to Tn (n is a positive number).

  First, the data receiving terminal R1 periodically floods a route control message including its own terminal ID (own terminal ID), a sequence number, and the number of hops. That is, the data receiving terminal R1 determines the regular arrival (step S11), and if it has arrived, floods the route control packet (step S12). If it has not arrived, it waits until regular arrival (step S13), and repeats the processing procedure after step S11 repeatedly.

  Here, flooding means that a route control packet is sent to all transmittable wireless communication terminals connected on the wireless multi-hop network. 0 is set as the initial value for the number of hops in the route control message. The sequence number of the routing message is incremented every flooding. That is, the routing packet with the same sequence number is scattered on the network in one flooding among a plurality of floodings performed periodically. Therefore, there is a possibility that a plurality of route control packets having the same sequence number reach a certain data relay terminal via different link routes.

  In response to reception of the flooded routing control packet, the data relay terminal T1 determines whether or not the sequence number of the packet is the first sequence number for the data receiving terminal (data receiving terminal R1) (step S14). If it is the same as previously received, discard it. On the other hand, if it is the first sequence number, the data relay terminal T1 adds its own terminal ID to the route control message and increments the hop count by 1 (step S15). Next, the route control packet is further flooded, for example, transferred to another data relay terminal T2 shown in the figure (step S16). Next, the data relay terminal T1 selects the path with the shortest hop from the data receiving terminal R and updates the control information table (step S17).

  The data relay terminal T2 executes the same processing procedure (steps S14 to S17) according to the route control packet transferred from the data relay terminal T1 (step S18).

  FIG. 6 shows a setting example of the route information table 205 updated as a result of the processing procedure shown in FIG. In the route information table 205, the terminal ID (next hop terminal ID) of the next hop terminal that becomes the shortest hop is set for each terminal ID (data receiving terminal ID) of the data receiving terminal. Here, the terminal ID is shown in place of the reference symbol of each wireless communication terminal. Referring to the figure, for example, delivery of a data packet to the data receiving terminal R1 means that transfer to the data relay terminal T1 gives the shortest hop.

  FIG. 7 shows a format of a data packet generated when the data transmission terminal performs data delivery. Assuming that data is generated at a certain data transmitting terminal, the data transmitting terminal is a unit route information piece consisting of a combination of all data receiving terminal IDs to which the data is destined and the next hop terminal ID of the data receiving terminal. 1 to n are created. The unit route information pieces 1 to n constitute planned route information and give future planned routes of the data packet.

  The correspondence between the data receiving terminal ID and the next hop terminal ID is created based on the setting contents of the route information table 205 (see FIG. 6) held by the data transmitting terminal. The unit route information pieces 1 to n are created by the number of destination data receiving terminals (n: positive number) and constitute a part of the header portion of the data packet. The header part further includes a data identification part Did, and the data part D is described immediately after the header part. The data identification part Did includes the identification information of the data stored in the data part D and the identification information of the original data to be encoded. As an example of the identification information of the original data before encoding, the source terminal ID and sequence number of the data can be mentioned.

  FIG. 8 shows a processing procedure when a data packet is received. The subject of this processing procedure is one of the wireless communication terminals, which may be any one of the data transfer terminals T1 to Tn, or the data receiving terminal R1 or R2 that is the destination of the final data packet. It can be.

  First, it is assumed that the wireless communication terminal receives a data packet transmitted (broadcasted) by the data transmitting terminal (step S21). It is determined whether or not the data receiving terminal ID included in each unit path information piece of the data packet matches the own terminal ID (step S22). If they coincide with each other, since it is a data receiving terminal, a desired application process is performed on the data of the data packet (step S24). If the data of the data packet is data-encoded, application processing is performed (step S24) after performing decoding processing in network coding (step S23).

  On the other hand, if they do not match in step S22, the wireless communication terminal further determines whether or not the next hop terminal ID included in each unit route information piece of the data packet matches its own terminal ID (step S25). . If they do not match, the data packet is discarded because it is neither a data receiving terminal nor a data relay terminal (step S26).

  On the other hand, if they match in step S25, since the wireless communication terminal itself is a data relay terminal, after encoding the data packet, the wireless communication terminal transfers (broadcasts) the data packet to another adjacent wireless communication terminal ( Step S27).

  FIG. 9 shows a more detailed processing procedure of the data transfer processing shown in FIG. Such a processing procedure is executed in a data relay terminal among the wireless communication terminals.

  First, the data relay terminal waits for a certain waiting period T and waits for and holds a plurality of data packets that need to be transferred (step S31). The held data packet is stored in the data packet holding unit. As a premise, as a result of the processing procedure shown in FIG. 8, one of the next hop terminal IDs in the unit route information piece of the data packet includes one that matches the own terminal ID.

  Next, the data relay terminal extracts a coding target group that satisfies the extraction condition from the plurality of data packets held in the data packet holding unit (step S32). The extraction condition of the data packet set to belong to the encoding target group is “at least one matching the data receiving terminal ID of the unit route information piece including the next hop terminal ID matching the own terminal ID of the data relay terminal. The ID is in the data receiving terminal ID of one of the unit route information pieces of all the data packets, and for each ID that matches the data receiving terminal ID, the ID is the same as the next hop terminal ID of the unit route information including the ID. It is a condition that “there is only one data packet that matches the terminal ID”. Satisfaction of such an extraction condition is that, in a data receiving terminal of general data Di (1 ≦ i ≦ N), all N−1 pieces of data other than Di among data D1, D2,. If any data including Di in the linear combination is received in a state where the signal is received, Di can be decoded. "

  Next, the data relay terminal performs data encoding on the data of the plurality of data packets belonging to the encoding target group, and generates and transfers a new combined encoded data packet (step S33). . At this time, in the header portion of the new encoded data packet, the data receiving terminal ID in the unit path information piece including the next hop terminal ID that matches the own terminal ID in the original data packet before encoding, A combination with the next hop terminal ID referenced from the route information table is described as a new unit route information piece. Also, identification information (Da_id, Db_id, Dc_id) of exclusive OR of data in each original data packet is described in the data identification unit. A new encoded data packet is broadcast and transferred to another wireless communication terminal.

  Next, the data relay terminal determines whether or not all encoding target groups have been extracted for the held data packet (step S34), and if not extracted, repeats steps S32 to S33. If extracted, the data relay terminal reassigns the remaining single data packet to the next hop terminal ID referenced from the path information table and leaves the data as it is. Transfer (step S35).

  The selection of the waiting time T in the above processing procedure is performed appropriately so that the number of data packets transmitted and the transmission amount can be reduced by extracting as many data packets that satisfy the conditions as possible, and excessive data delay does not occur. Need to be adjusted.

  FIG. 10 shows an actual state of the processing procedure shown in FIG. It is assumed that the data relay terminal T1 receives the data packet a, the data packet b, and the data packet c during a certain period T.

  For each data packet, the data relay terminal T1 transmits a unit route information piece, that is, a unit route information piece 1, a unit route information piece 2, and a unit route information piece 3 in which the next hop terminal ID in the data packet matches the own terminal ID. locate. The data receiving terminal ID of the unit path information piece 1 present in the data packet a is R1, but R1 is also present in the data packet b and the data packet c. The data receiving terminal ID of the unit path information piece 2 present in the data packet b is R3, but R3 is also present in the data packet a and the data packet c. The data receiving terminal ID of the unit path information piece 3 present in the data packet c is R4, but R4 also exists in the data packet a and the data packet b. Therefore, the data packet a, the data packet b, and the data packet c are candidates for the encoding target group.

  Next, for each data receiving terminal ID of each unit route information piece, the data relay terminal T1 determines whether or not there is only one data packet that matches the next hop terminal ID and the own terminal ID. If attention is paid to the data receiving terminal ID = R1 of the unit path information piece 1, only one of the data packets a is equal to T1 whose next hop terminal ID is its own terminal ID. In data packet b, the next hop terminal ID of data receiving terminal ID = R1 is T3, and in data packet c, the next hop terminal ID of data receiving terminal ID = R1 is T2, both of which are other than T1. .

  Similarly, the data receiving terminal ID = R3 of the unit route information 2 and the data receiving terminal ID = R4 of the unit route information 3 also satisfy the above conditions.

  As a result, the data packet a, the data packet b, and the data packet c are grouped into one encoding target group. Therefore, the data relay terminal T1 performs data encoding by exclusive OR operation of the data Da, Db, Dc included in each data packet of the data packets a, b, c, and the next hop terminal ID is the own terminal. Create new unit route information pieces 4 to 6 by referring to the own route information table from the terminals R1, R3, and R4 of the data receiving terminals of the unit route information pieces 1 to 3 that match the ID, and further, the original data packet Are added to create a new data packet.

  As a result of the above processing procedure being executed by a plurality of data relay terminals, data encoded data packets including the exclusive OR of data Da and data Db and data Dc arrive at data receiving terminals R1, R3 and R4. become.

  Decoding of data Da at the data receiving terminal R1 will be described. To the data receiving terminal R1, a data packet in which data including exclusive OR of data Da, data Db, and data Dc is encoded is delivered via the data relay terminal T1, while a data packet b including data Db A data packet c including data Dc is delivered via a route other than the data relay terminal T1. Therefore, the data receiving terminal R1 can decode the data Da by performing an operation of Da = (Da XOR Db XOR Dc) XOR Db XOR Dc. Similarly, the data receiving terminal R3 receives the data packet a and the data packet c in addition to the data encoded data packet. The data receiving terminal R4 also receives the data packet a and the data packet b in addition to the data encoded data packet. Therefore, each data can be obtained similarly.

  As is clear from the first embodiment described above, the data distribution method and the wireless communication system according to the present invention have several operational effects. First, in the present invention, it is not necessary for the adjacent terminal to hold data or to manage the held information. Each wireless communication terminal performs data encoding by determining whether or not data encoding is possible from the data reception information of the final data receiving terminal, and the data reception information of the adjacent terminal becomes unnecessary. Can be spread. Second, the present invention can reduce power consumption. In general, wireless sensor networks consume more power when transmitting packets than when performing calculations. In the present invention, the amount of data transmission can be reduced, although the amount of calculation increases as the data increases. Third, the present invention can perform network coding in an autonomous and distributed manner without centralized control by a specific terminal. Fourthly, according to the present invention, network coding can be performed so that data can be decoded at a terminal to which each data arrives.

<Second embodiment>
FIG. 11 shows the principle of code-aware routing used in the present invention. Code-aware routing is routing that minimizes the total number of transmissions in consideration of network coding when distributing data to a plurality of data receiving terminals R1 and R2. Data relay terminal A encodes data Da and data Db. The encoded data (Da XOR Db) is multicast to the data receiving terminals R1 and R2. Although the route from the data transmission terminal S1 to the data reception terminal R2 and the route from the data transmission terminal S2 to the data reception terminal R1 are not the shortest route, the total number of transmissions is 30 by encoding data upstream of the route. The total number of transmissions is smaller than when performing network coding on the minimum hop route. Similarly to the case of performing network coding on the minimum hop route, even if the data relay terminal X fails for some reason, the data receiving terminals R1 and R2 can receive the data Da and data Db, respectively.

  In this way, when performing network coding on a code-aware route, the minimum hop route is more resistant to terminal failures and link errors than when performing network coding on a multicast route. The effect is that the total number of transmissions is smaller than in the case of performing network coding above.

  FIG. 12 shows an example of many-to-many communication in the second embodiment. As shown in the figure, a plurality of data transmission terminals S1 to S5 in the network transmit data to a plurality of data reception terminals R1 to R4.

  FIG. 13 shows the configuration of a wireless communication terminal in the second embodiment. As with the first embodiment, each of the wireless communication terminals T1 to Tn includes a route information table 205, a route information control unit 201, a data packet holding unit 202, a data packet processing unit 203, and a wireless communication unit 204. It consists of. Unlike the first embodiment, the route information control unit 201 in the second embodiment further includes a minimum hop route construction control unit 601, a data encoding determination unit 602, and a route reconstruction control unit 603. . The minimum hop route construction control unit 601 realizes route extraction means that is a component of the present invention, and has a function of constructing a minimum hop route from a data transmission terminal to a data reception terminal. The data encoding determination unit 602 implements an encoding determination unit that is a component of the present invention, and has a function of determining whether or not data flowing through a path can be encoded when a plurality of paths intersect. The route reconstruction control unit 603 realizes route setting means that is a component of the present invention, and has a function of constructing a route based on the determination result of the data encoding determination unit.

  The construction of a code-aware path is performed through three phases. That is, as the first phase, the “phase for constructing the minimum hop route from the data transmission terminal to the data reception terminal” executed by the minimum hop route construction control unit 601 and the data encoding determination unit as the second phase 3, which is a “phase detection determination of path intersection and data encoding determination” executed by 602, and a “phase reconfiguration phase” executed by the path reconfiguration control unit 603 as a third phase. There are two phases.

<Construction of minimum hop route from data transmitting terminal to data receiving terminal>
FIG. 14 shows a construction example of the minimum hop route in the second embodiment. In the second embodiment, a method that is more effective in reducing transmission costs than the ordinary minimum hop route construction method will be described. That is, when there are a plurality of shortest paths from a certain data transmission terminal to a certain data reception terminal, the number of link duplications is minimized so that links on the path from a certain data transmission terminal do not overlap as much as possible. Generate a route.

  Referring to the figure, the data receiving terminal R1 and the data receiving terminal R2 flood a control packet describing the number of hops from the data receiving terminal R1 and the terminal ID of the data relay terminal. Each time the data relay terminal passes, the number of hops of the control packet increases by 1, and the terminal ID of the data relay terminal is added. The data transmission terminal S1 receives the control packet flooded by the data reception terminal R1 via the data relay terminals T1 and T2. The data transmission terminal S1 receives the control packet flooded by the data reception terminal R2 via the data relay terminals T1 and T2 and the data relay terminals T3 and T4. As a minimum hop route from the data transmission terminal S1 to the data reception terminal R2, there is a route A passing through the data relay terminals T1 and T2, and as a minimum hop route from the data reception terminal R2, the data relay terminals T1 and T2 2 and the route C via the data relay terminals T3 and T4 are found to exist. In this case, some links on the route A and the route B overlap. On the other hand, since the route A and the route C do not have overlapping links, the data transmission terminal S1 adopts the route C instead of the route B as the minimum hop route to the data reception terminal R2. Each data transmitting terminal notifies the terminal on the route to each data receiving terminal adopted by itself that it is a “terminal on the route”.

  In this way, when a plurality of routes from a certain data transmission terminal to a certain data reception terminal are constructed so as not to overlap as much as possible, when terminals on a route constructed between different data transmission data reception terminals are duplicated, It is possible to increase the chances of encoding.

<Detection of path intersection and determination of data encoding>
FIG. 15 shows an example of a route intersection in the second embodiment. When a plurality of data transmission data receiving terminals construct a minimum hop route as described above, the routes may intersect. In the example of this figure, the route A from the data transmission terminal S1 to the data reception terminal R2 and the route B from the data transmission terminal S2 to the data reception terminal R1 intersect. In such a case, the data relay terminal detects the intersection of the route as follows.

  FIG. 16 shows an example of detecting an intersection of routes in the second embodiment. In the case of FIG. 16A, when a certain terminal becomes the data relay terminal T1 of a plurality of routes, the data relay terminal T1 can detect the intersection of the routes. The data relay terminal T1 becomes the encoding determination terminal Td. On the other hand, in the case of FIG. 16B, a certain terminal may not be a data relay terminal of a plurality of routes at a portion where two routes intersect. Each data relay terminal advertises information such as the ID of the data transmission terminal that is the transmission source of the data that it relays and the data reception terminal that is the data destination. Thereby, the data relayed by the adjacent terminal and the IDs of the data transmitting terminal and data receiving terminal can be known, and the intersection of the routes is detected. The data relay terminal that has detected the intersection of the routes becomes an encoding determination terminal that determines whether or not the data flowing on the intersecting route can be encoded. In the case of FIG. 16B, the two data relay terminals T1 and T2 detect the crossing of the route, but the two data relay terminals T1 and T2 exchange information, and thus one of the data relay terminals. (T1 in this figure) is the coding determination terminal Td. An algorithm for determining whether or not encoding is possible follows, for example, the algorithm described in the first embodiment.

<Reconstruction of route>
In the encoding determination terminal, when it is determined that encoding is possible, at least one of the crossing routes is fixedly set as a reference route, and from the data transmission terminal of at least one other route other than the reference route A terminal that becomes the contact point of the route that gives the minimum hop to the fixed route is set as the data encoding terminal, and the terminal that becomes the contact point of the route that gives the minimum hop from the data receiving terminal of the other route to the reference route Is set as a multicast terminal to reconstruct the route. Such reconstruction of the route can be performed using either of the following two methods. The following route A indicates a reference route.

<First construction method>
17 to 19 show a first construction method in the second embodiment. As illustrated in FIG. 17, the encoding determination terminal Td transfers a control packet to each data relay terminal of one path A. The starting point of the route A is the data transmitting terminal S1, and the ending point is the data receiving terminal R2.

  As shown in FIG. 18, each data relay terminal Ti (i = 1 to n, n is the number of data relay terminals on the route) corresponds to its own terminal ID in accordance with the transfer of the control packet from the encoding determination terminal Td. And floods the entire control packet with the number of hops. The number of hops in the control packet is set to 0 at the outgoing data relay terminal Ti, and is incremented by 1 every time it passes through the intermediate data relay terminal Ti.

  As shown in FIG. 19, in response to receiving the control packet from the data relay terminal, the data transmission terminal S2 knows the number of hops from the data relay terminal of the route A and knows the minimum hop route C to the route A. . Then, the data transmission terminal S2 notifies the data relay terminal that is the contact point of the minimum hop route from itself to the route C, and the notified data relay terminal becomes the data encoding terminal Tc. On the other hand, the data receiving terminal R1 notifies the data relay terminal that is the contact point of the minimum hop path D from itself to the path A, and the notified data relay terminal becomes the multicast terminal Tm. The data encoding terminal Tc is a terminal that encodes data, and the multicast terminal Tm is a terminal that multicasts the encoded data.

<Second construction method>
FIG. 20 shows a second construction method in the second embodiment. The second construction method is an example in which each terminal in the network floods control packets throughout the network in advance. As a premise, it is assumed that each terminal in the network knows the next hop terminal ID and the number of hops of the route to the partner terminal.

  First, in the second construction method, similarly to the first construction method, the data encoding determination terminal Td transfers a control packet to the terminal on the route A. The data relay terminal on the path A adds its own terminal ID and the number of hops to the data transmission terminal S1 and the data reception terminal R2 to the control packet, and the control packet is transmitted to the data relay terminals Ta and Tb at both ends of the path A. It is transferred (circle 1 in FIG. 20).

  Next, each of the data relay terminals Ta and Tb at the end of the route A has the ID of the data relay terminal having the smallest number of hops to the data transmission terminal S2 among the data relay terminals on the route A and the number of hops thereof, And the ID of the data relay terminal with the smallest number of hops to the data receiving terminal R1 and the number of hops are notified to the data encoding determination terminal Td (circle 2 in FIG. 20).

  Next, the data encoding determination terminal Td is based on the information from both terminals, and the data relay terminal having the smallest number of hops to the data transmission terminal S2 and the smallest number of hops to the data reception terminal R1. Is determined. Next, the data relay terminal having the smallest number of hops to the data transmitting terminal is determined as the data encoding terminal Tc, and the data relay terminal having the smallest hop number to the data receiving terminal is determined as the multicast terminal Tm. Then, the data encoding determination terminal Td notifies the determination result to the data encoding terminal Tc and the multicast terminal Tm (circle 3 in FIG. 20).

  Next, the data encoding terminal Tc notifies the data transmitting terminals S1 and S2 that it is a data encoding terminal, and the multicast terminal Tm notifies the data receiving terminals R1 and R2 that it is a multicast terminal. .

  In the second construction method described above, since each terminal is flooded throughout the network when the network is initialized, the number of transmissions of control packets is larger than that in the first construction method. However, in the operation of reconstructing the route, it is not necessary to flood each time the data relay terminal reconstructs the route as in the first construction method, so the route is reconstructed as compared with the first construction method. The number of control packet transmissions is small.

  FIG. 21 shows an example of data delivery from the data transmitting terminal to the data receiving terminal in the second embodiment. Here, a state is shown in which data flows on the constructed path through the execution of the first construction method or the second construction method. Data Da and data Db transmitted from the data transmission terminal S1 and the data transmission terminal S2, respectively, are encoded by the data encoding terminal Tc to become data (Da XOR Db). The data (Da XOR Db) is delivered to the multicast terminal Tm via the common route from the data transmission terminals S1 and S2. In the multicast terminal Tm, the data (Da XOR Db) is multicast to each of the data receiving terminals R1 and R2.

  FIG. 22 shows a construction example of a recursive minimum hop route in the second embodiment. As shown in the figure, the path constructed by the above method may further cross another path C. In this case, first, a data coding determination terminal having a small number of hops from the data transmission terminal performs reconstruction as a starting point of the path reconstruction operation. In the reconstructed route, the route is recursively reconstructed in the same manner.

  Referring to FIG. 22, a route E indicated by a dotted line in the figure indicates a route from the data transmission terminal to the data reception terminal toward the end closer to the start point of the arrow and closer to the end point. The route E intersects with the route indicated by the solid line at three points. Assuming that the intersections are intersection 1, intersection 2, and intersection 3 in the direction from the start point of the arrow to the end point, the data relay terminal corresponding to intersection 1 is a data coding determination terminal with a small number of hops from the data transmission terminal. Become. Therefore, the data encoding determination terminal becomes the starting point of the route reconstructing operation, and the route is reconstructed by the same method as in the case where the two routes intersect at one point.

  When the route is reconstructed, the reconstructed route may intersect with another route at another intersection (the intersection is not necessarily the intersections 1 to 3). In this case as well, the data relay terminal corresponding to the intersection close to the data transmission terminal side becomes the data encoding determination terminal and reconstructs the route. This operation is performed recursively until the reconstructed route does not intersect another route.

  FIG. 23 shows the effect of code-aware routing in the second embodiment. FIG. 23A shows a case where a minimum hop path is established from the data transmission terminal S1 and the data transmission terminal S2 to the data reception terminal R1 and the data reception terminal R2, and the data encoding terminal Tc and the multicast terminal Tm match. . In this case, the total number of transmissions is 35. On the other hand, in the case of code-aware routing in FIG. 23B, the number of hops from the data transmission terminal S2 and the data reception terminal R1 to the path A (data transmission terminal S1 → data reception terminal R2) is short. Become. Since the number of common links through which encoded data (Da XOR Db) flows increases, the total number of transmissions decreases to 32.

  As described above, according to the second embodiment, first, there is less possibility of data loss when a terminal or link error occurs than when performing network coding on a multicast route. Second, each terminal can construct a route (encoding-compatible minimum hop route) suitable for network coding in an autonomous and distributed manner, and the amount of data transmission and the number of transmissions can be reduced.

<Third embodiment>
In the third embodiment, a code-aware routing method in many-to-one communication in which a plurality of paths from a certain data transmission terminal to a certain data reception terminal exist and a plurality of data transmission terminals exist will be described. Moreover, the effect is demonstrated.

  FIG. 24 shows an example of many-to-one communication in the third embodiment. As shown in the figure, the third embodiment differs from the second embodiment in that a plurality of data transmission terminals S1 to S5 distribute data through a plurality of routes to one data reception terminal R1. The configuration of each wireless communication terminal is the same as that of the second embodiment.

  First, each data transmission terminal S1 to S5 constructs a plurality of paths through which the same data flows to the data reception terminal R1. The construction algorithm uses existing multipath routing. At this time, if a route in which the data transmission terminals S1 to S5 intersect with each other as much as possible is constructed, a route having a great effect of code-aware routing is easily constructed. The data transmission terminals S1 to S5 determine one or more non-encoded paths through which unencoded data flows, among a plurality of paths to the data receiving terminal R1. Also, routes other than the non-encoded route are set as a codeable route. Although it is possible to encode data flowing on the encoding possible path, the data is not necessarily encoded. The selection of which path is the non-encoding path is arbitrary, but needs to be set in advance.

  As a method for selecting which route is to be an unencoded route, for example, a code of data relay terminals in which a route from which a data transmission terminal is a transmission source and a route from which another data transmission terminal is a transmission source intersect It is conceivable that the number of data relay terminals that can be converted is obtained, a path whose number is less than a threshold is set as an uncoded path, and a path that is equal to or greater than a certain threshold is set as a codeable path.

  Also, for example, among a plurality of routes from the data transmitting terminal to the data receiving terminal, a route having the smallest number of links or terminals intersecting with other routes is set as an uncoded route, and other routes are set as a codeable route. . Among the paths with different data transmission terminals, when the codeable paths intersect, it is determined that the data can be encoded.

  FIG. 25 shows an example of intersection of routes in the third embodiment. As shown in the figure, the data relay terminal Td that performs the coding determination is a data relay terminal that detects the intersection of the routes, as in the second embodiment. A method for determining whether data can be encoded from the contents of the data packet will be described below.

  FIG. 26 illustrates an example in which encoding determination using path information in many-to-one communication is performed. As shown in the figure, the data packet includes unit route information including a data receiving terminal ID, a terminal ID of the next hop to the route, and an encoded route flag indicating whether or not the route is an encodeable route. At least one piece is included. The encoding path flag is set to 1 for a path that can be encoded, and is set to 0 for a path that can be encoded.

  Therefore, first, the terminal ID of the next hop of each data packet received by the data relay terminal matches its own terminal ID, the encoded route flag of the route is 1, and the next hop other than itself is included in each data packet. If there is a terminal ID of which the encoding path flag is 0, it is determined that the data of those data packets can be encoded. “The encoded route flag of the route in which the terminal ID of the next hop is located with the own terminal ID is 1” means that the data relayed by the device can be encoded. Also, “Each data packet has a terminal ID of the next hop other than itself and the encoded route flag of the route passing through them is 0” means that the original data is not encoded and passes through another route. Means to reach the data receiving terminal.

  In the example of FIG. 26, the data packet a and the data packet b received by the data relay terminal N1 include the terminal ID (ie, N1) of the data relay terminal N1, and the encoding path flag in each data packet is 1. Each of the data packet a and the data packet b has NA and NC, which are terminal IDs of the next hop other than the data relay terminal N1, respectively, and the encoded route flag in the route passing through them is 0. Therefore, it is determined that the data packet a and the data packet b can be encoded.

  Referring again to FIG. 25, the data transmission terminals S1 and S2 construct each of the data Da and data Db by two routes and deliver the data to the terminal R1. As a result of the determination, the data transmission terminal S1 has a codeable path A and a non-coding path C, and the data transmission terminal S2 has a codeable path B and a non-coding path D. The codeable path A and the codeable path B intersect. In this case, as in the second embodiment, the terminal that detected the intersection becomes the data encoding determination terminal Td and reconstructs the route.

  FIG. 27 shows an example of network coding in many-to-one communication in the third embodiment. As shown in the figure, the data transmission terminal S2 constructs a minimum hop route C to the codeable route A extended from the data transmission terminal S1, and a terminal serving as a contact is set as the data encoding terminal Tc.

  FIG. 28 shows the effect of network coding in many-to-one communication in the third embodiment. FIG. 28A shows a case where a minimum hop path from the data transmission terminals S1 and S2 to the data reception terminal R1 is constructed, and data encoding is performed at the data encoding terminal Tc. The total number of transmissions is 35 times. Become. On the other hand, FIG. 28B shows a case where code-aware routing is performed, and the number of hops from the data transmission terminal S2 to the path A (data transmission terminal S1 → data reception terminal R1) is shortened. In addition, since the number of common links through which data (Da XOR Db) encoded by the data encoding terminal Tc flows increases, the total number of transmissions decreases to 30.

  As described above, according to the third embodiment, each terminal can construct a route suitable for network coding in an autonomous distributed manner, and the amount of data transmission and the number of transmissions can be reduced.

  In the third embodiment, as shown in FIG. 26, the example in which the path information is described for each data packet has been described. However, this information is not described for each data packet. May be previously notified to the data relay terminal by a control packet.

<Fourth embodiment>
In the fourth embodiment, a description will be given of an extended method of the data encoding determination method of the first embodiment. In the first embodiment, an example in which data flowing on a certain path is encoded once has been described. In the fourth embodiment, an example in which data is encoded a plurality of times on the same path will be described. The terminal configuration in the fourth embodiment is the same as that of the second embodiment except for many-to-many communication (see FIG. 13).

  FIG. 29 shows an example of data encoding on the same path in the many-to-many communication in the fourth embodiment. As shown in the figure, each of a plurality of data flowing through a certain path is encoded. Data Da, Db, and Dc are delivered from the data transmission terminals S1, S2, and S3 to the data reception terminals R1, R2, and R3, respectively. The data relay terminals N1 and N4 on the path from the data transmission terminal S1 to the data reception terminal R3 can respectively encode data. Similarly, the data relay terminals N2, N3, N4, and N5 can also encode data. As a result, since the data receiving terminals R1, R2, and R3 receive three linearly independent data including the data Da, Db, and Dc as elements, the data Da, Db, and Dc can be obtained. Hereinafter, a method for determining data encoding from path information in order to perform encoding a plurality of times in a path from a data transmitting terminal to a data receiving terminal will be described.

  FIG. 30 shows the first data encoding of a plurality of data encoding examples on the same path in the fourth embodiment. Here, the data relay terminal N1 receives the data Da and Db from the data transmission terminals S1 and S2, respectively. Each packet of data Da and Db includes a sequence number, and further includes at least one unit path information piece including a data receiving terminal ID and a next hop terminal ID. Since the data Da and Db have not been encoded yet, the determination of the encoding is performed according to the method described in the first embodiment. In the fourth embodiment, unlike the first embodiment, it is assumed that data is encoded a plurality of times in the same path. Therefore, in the encoded data packet, the sequence number of the encoded data, the data receiving terminal ID, and the next hop terminal ID are described, and further, the sequence number of the original data packet and the data receiving terminal The ID and the next hop terminal ID of the route to the data receiving terminal are described.

  FIG. 31 shows the second data encoding of a plurality of data encoding examples on the same path in the fourth embodiment. Here, the data relay terminal N4 receives the encoded data (Da XOR Db) and (Db XOR Dc). If the data packet is transferred without encoding, the data (Da XOR Db) reaches the data receiving terminal R3 and the data (Db XOR Dc) reaches the data receiving terminal R1. On the other hand, when data is encoded, the encoded data is (Da XOR Dc).

  Referring again to FIG. 29, element data Db that is lost by encoding and element data Dc that is newly added based on data (Da XOR Db) to the data receiving terminal R3 when encoding is not performed. Since the data packet (Db XOR Dc) including the data Db and Dc as the original data reaches the data receiving terminal R3 via another route D that does not pass through the terminal N4, the data Db at the data receiving terminal R3 respectively. And Dc.

  Similarly, with reference to data (Db XOR Dc) to the data receiving terminal R1 when encoding is not performed, a data packet (Da XOR) including data Db and Da, which are original data changed by encoding. Since Db) reaches the data receiving terminal R1 through another route C that does not pass through the terminal N4, the data receiving terminal R1 can decode the data Da and Db, respectively.

  Therefore, even if the encoded data (Da XOR Dc) is delivered to the data receiving terminal R1 through the path A and delivered to the data receiving terminal R3 through the path B, the data Da, Db, and Dc are transmitted. Can be decrypted. Therefore, it is understood that the data relay terminal N1 can encode the data (Da XOR Db) and the data (Db XOR Dc).

  According to the fourth embodiment described above, since the data flowing through the path is encoded a plurality of times, the total number of data transmissions is reduced as compared to encoding once.

<Fifth embodiment>
In the fifth embodiment, combining the many-to-many communication and the many-to-one communication in which a plurality of routes to one data receiving terminal exist as described in each of the second and third embodiments, A data encoding determination method in many-to-many communication in which a plurality of paths from a certain data transmission terminal to a data reception terminal exist will be described. The terminal configuration in the fifth embodiment is the same as that of the second embodiment (see FIG. 13).

  FIG. 32 shows an example of many-to-many communication in which a plurality of routes to a certain data transmitting terminal or a certain data receiving terminal exist in the fifth embodiment. As shown in the figure, there are a plurality of paths from each of the data transmission terminals R1 to R3 to a certain data reception terminal R1 or R2. Further, as in the third embodiment, the plurality of paths to a certain data receiving terminal R1 or R2 include a codeable path and a non-coding path.

  In the first embodiment, as an extraction condition for determining a packet that can be encoded, “the extraction condition is“ data of a unit route information piece including a next hop terminal ID that matches the own terminal ID of the data relay terminal ”. At least one ID that matches the receiving terminal ID is in the data receiving terminal ID of any unit route information piece of all data packets, and for each ID that matches the data receiving terminal ID, a unit that includes the ID The condition that “there is only one data packet in which the next hop terminal ID of the route information matches the own terminal ID” has been set.

  On the other hand, in the third embodiment, since there are a plurality of paths from a certain data transmitting terminal to a certain data receiving terminal, the present invention is not limited to the case of “only one matching data packet”. Or, even when there are multiple matching data packets, in those matching data packets, the route that becomes the data relay terminal is a codeable route, and the next hop terminal ID is other than the own terminal ID. The route that includes the terminal ID and the terminal other than its own terminal becomes a data relay terminal is an unencoded route.

  In the third embodiment, there are a plurality of routes from a certain data transmitting terminal to a certain data receiving terminal, and there are a plurality of data packets whose next hop terminal ID and own terminal ID match. This is because it is determined that the data can be encoded because it is known that the original data that is not encoded reaches the corresponding data receiving terminal via another path.

  FIG. 33 shows an encoding determination example based on packet information in the many-to-many communication in the fifth embodiment. Assume that the data relay terminal N1 receives data packets a and b. In each of the data packets a and b, a unit route information piece whose data receiving terminal ID is R1 as a unit route information piece whose next hop ID is the ID of the data relay terminal N1, and a next hop terminal ID is its own terminal ID As a unit route information piece including a terminal ID other than that, a unit route information piece having a data receiving terminal ID R2 is included. That is, the condition that “there are a plurality of data packets in which the next hop terminal ID and the own terminal ID match” is met.

  Further, paying attention to the data packet a, in the unit route information piece of the data receiving terminal R1, the data encoding enable flag is 1 for the route having the next hop terminal ID N1, and the next hop ID is set to the other data packet b. Includes a unit route information piece of terminal IDs other than itself (ND and NE), and the encoding possible flag of the route having the next hop ID as NE is 0. The same applies to the data packet b. The determination is made as described above because the unencoded data Da and Db are delivered to the data receiving terminals R1 and R2 through paths other than the data relay terminal N1, respectively, and the encoded data (Da XOR Db) arrives. Is also based on the principle that it can be decoded.

  FIG. 34 supplementarily explains the coding determination example shown in FIG. Here, the data Da is delivered to the data receiving terminal R1 via the data relay terminals N1, NA, NB, and is delivered to the data receiving terminal R2 via the data relay terminal NC. On the other hand, the data Db is delivered to the data receiving terminal R1 via the data relay terminals N1, ND, NE, and is delivered to the data receiving terminal R2 via the data relay terminals N1, NF. The route through which the data Db is delivered to the data receiving terminals R1 and R2 via the data relay terminal N1 is one common route. Further, in this figure, when the encoding path flag is 1, it is expressed as “encoding ○”, and when it is 0, it is expressed as “encoding ×”. The data relay terminal N1 receives the data packet a and the data packet b including the data Da.

  One of the conditions for determining that encoding is possible "the encoded path flag of the unit path information piece that is the data relay terminal N1 of the next hop among the unit path information pieces in the data packet a" The data receiving terminal is R1 and the data packet b also includes the data receiving terminal R1 and includes a data relay terminal other than N1 in the next hop ID and a unit path information piece (data “There is a unit route information piece including the relay terminal NE” indicates that the data Db reaches R1 without being encoded by a route other than itself (N1) (route passing through NE).

  Another “for determining that encoding is possible” Among the unit route information pieces in the data packet b, the data is received when the encoded route flag of the unit route information piece which is the data relay terminal N1 of the next hop is 1. The terminals are R1 and R2. The data packet a also includes data receiving terminals R1 and R2, and includes a data relay terminal other than N1 in the next hop ID, and a unit path information piece (data relay terminal) whose encoded path flag is 0. “The unit route information piece including the NA and the unit route information including the data relay terminal NC” is encoded with the data Da other than its own (N1) (the route via the NA and the route via the NC). Without reaching R1 and R2, respectively. That is, since it can be seen that data to be relayed to each data receiving terminal by itself (N1) reaches Da and Db without being encoded, it can encode the data. According to the fifth embodiment described above, it is possible to determine data encoding in many-to-many communication in which a plurality of routes to the data receiving terminal exist.

  The fifth embodiment and the fourth embodiment can be used in combination. That is, when there are a plurality of data transmission terminals and data is delivered from each data transmission terminal to at least one data reception terminal via a plurality of paths, a plurality of data transmission terminals are provided on the path from the data transmission terminal to the data reception terminal. Code-aware routing that performs one-time data encoding is possible.

DESCRIPTION OF SYMBOLS 201 Path | route control part 202 Data packet holding | maintenance part 203 Data packet processing part 204 Radio | wireless communication part 205 Path | route information table 601 Minimum hop path | route construction control part 602 Data encoding determination part 603 Path | route reconstructability control part N1-N5 Data relay terminal R1- R5 data receiving terminal S1 to S5 data transmitting terminal T1 to T10 Wireless communication terminal (various terminals)
Tc Data encoding terminal Tx Failure terminal Td Data encoding determination terminal Tm Multicast terminal

Claims (16)

A data delivery method in a wireless communication system in which a plurality of terminals each connected between adjacent ones via a wireless communication link constitute a multi-hop network,
A path extracting step for extracting at least two minimum hop paths from a plurality of paths from the data transmitting terminal to at least one data receiving terminal of the transmission destination for each data transmitting terminal of the terminals;
An encoding determination step for determining, for each combination of at least two crossing paths among the minimum hop paths obtained for each data transmission terminal, whether or not data flowing in each crossing path of the combination can be encoded;
A path setting step for setting, for each data transmission terminal, an encoding-compatible minimum hop path from the data transmission terminal to the transmission destination data reception terminal in accordance with the determination result of the encoding availability obtained for each of the intersection paths. When,
For each data transmission terminal, the data is transmitted from the data transmission terminal to the destination data reception terminal via the encoding-compatible minimum hop path set for the data transmission terminal, and the data corresponds to the encoding-compatible minimum hop path. A data delivery step of performing coding according to the determination result of coding availability and delivering;
A data delivery method comprising:   In the route setting step, when there are a plurality of encoding-compatible minimum hop routes for the data transmitting terminal, the number of overlapping links in the plurality of routes from the data transmitting terminal to the plurality of data receiving terminals of the transmission destination is minimized. The data delivery method according to claim 1, further comprising: setting a minimum hop route corresponding to encoding.   The encoding determination step detects, in a data relay terminal located on the minimum hop route, that it is a data relay terminal of a plurality of routes from a control packet or a data packet transmitted by an adjacent terminal, and performs the data relay 2. The data delivery method according to claim 1, wherein the terminal determines whether the encoding is possible or not as an encoding determination terminal.   In the encoding determination terminal, when the encoding determination terminal determines that the encoding is possible, at least one of the intersecting paths is fixedly set as a reference path, and other than the reference path A terminal serving as a contact point of a path that gives a minimum hop from a data transmission terminal of at least one other path to the reference path is set as a data encoding terminal, and a minimum hop from the data reception terminal of the other path to the reference path is set. 4. The data delivery method according to claim 3, wherein a terminal serving as a contact point of a given route is set as a multicast terminal.   The route setting step transmits a control packet to each data relay terminal on the reference route in the data encoding determination terminal, and each time the data relay terminal that receives it relays it with its own terminal ID. By flooding the entire network with a control packet including the number of hops incremented by one, the data transmission terminal and the data reception terminal other than the above-described path that has received the control packet have the minimum hop to the reference path. A data relay terminal that discovers a given route and serves as a contact point of a minimum hop route from the reference route to a data transmission terminal on the other route receives data on the other route from the data encoding terminal or the reference route 5. The data relay terminal as a contact point of the minimum hop route to the terminal is a multicast terminal. Data delivery method.   In the route setting step, each terminal of the network recognizes each other's route and the number of hops in advance, and the data encoding determination terminal transmits a control packet to each data relay terminal on the reference route. Each received data relay terminal on the reference path adds its own terminal ID and the number of hops to the data transmitting terminal and data receiving terminal of a path other than the above path, and the data relay serving as the terminal on the reference path In the terminal, the data encoding determination terminal is notified of the ID and the hop number of the data relay terminal on the reference route that minimizes the number of hops to the data transmitting terminal and data receiving terminal of the other route, and the data In the coding determination terminal, a data relay terminal serving as a contact point of a minimum hop route from the reference route to a data transmission terminal on the other route is designated as the data code. Of terminal or data delivery method according to claim 4, characterized in that the data relay terminal as the contact point of the minimum hop path from the reference path to the data receiving terminal on the other path as the multicast terminal.   When delivering the same data via a plurality of routes to a data receiving terminal of a certain data transmission terminal, at least one of the plurality of routes is set in advance as an uncoded route and 2. The data distribution method according to claim 1, further comprising a presetting step of presetting the others as encoding possible paths.   The pre-setting step obtains the number of data relay terminals that can be encoded among data relay terminals intersecting a path that is a source of the data transmission terminal and a path that is a source of another data transmission terminal. 8. The data delivery method according to claim 7, wherein a path whose number is less than a certain threshold is set as an uncoded path, and a path greater than a certain threshold is set as a codeable path.   In the encoding determination step, in the data relay terminal existing on the path from the certain data transmitting terminal to the certain data receiving terminal or a terminal adjacent thereto, the terminal is set as an encoding determination terminal to determine whether the encoding is possible. 8. The data delivery method according to claim 7, wherein the determination is made according to a setting of the non-encoding path and / or the encoding-enabled path. Each data packet constituting the data includes a destination data receiving terminal, a next hop terminal ID on a route to the data receiving terminal, and a flag indicating whether or not the route is a codeable route. Each including at least one unit path information piece,
The data distribution step includes the terminal ID of the next hop terminal ID in the unit route information piece including the terminal ID of a certain data receiving terminal among the plurality of received packets in the data encoding terminal, The corresponding route is an encodable route and includes a terminal ID other than its own terminal ID, and the corresponding route is a non-encodable route, and the packets are encoded. The data distribution method according to claim 9.   The route setting step, when the encoding determination terminal determines that the encoding is possible, fixedly sets at least one of the intersection routes as a reference route, 4. The data delivery method according to claim 3, wherein a terminal serving as a contact point of a path that gives a minimum hop to the reference path from a data transmission terminal of at least one other path is set as a data encoding terminal.   In the data encoding terminal, in the data encoding terminal, the encoded data packet includes a data sequence number of the original data packet, a data receiving terminal ID, and a next hop in the route to the destination data receiving terminal. In another data encoding terminal that describes the ID and receives the encoded data packet, the data packet is further encoded in accordance with the description content of the encoded data packet. The wireless communication system according to claim 4.   In the data encoding terminal, in the data encoding terminal, as the element data before and after encoding, the element data before encoding and the element data after encoding, from the description content of the received data packet When it is recognized that data including element data other than included as an element of exclusive OR is delivered to a destination data receiving terminal via another path that does not relay the data encoding terminal, 5. The data delivery method according to claim 4, wherein the element data is determined to be decodable at the destination data receiving terminal, and the received data packet is further encoded. Each data packet constituting the data includes a plurality of unit route information pieces each consisting of a combination of a data receiving terminal ID and a next hop terminal ID,
In the data distribution step, at the data encoding terminal, for the received data packet, at least one ID that matches the data receiving terminal ID of the unit path information piece including the next hop terminal ID that matches the terminal ID of the terminal Is in the data receiving terminal ID of any unit path information piece of all data packets, and for each ID that matches the data receiving terminal ID, the next hop terminal ID of the unit path information including the ID and the own terminal When there is only one data packet with a matching ID, the received data packet is encoded,
Furthermore, when there are a plurality of data packets in which the next hop terminal ID and the own terminal ID match, the corresponding route is a codeable route, and the next hop terminal ID matches the own terminal ID. 5. The data distribution method according to claim 4, wherein the received data packet is encoded even when at least one terminal ID whose corresponding route is an unencoded route is included. A wireless communication system in which a plurality of terminals, each connected between neighbors via a wireless communication link, constitutes a multi-hop network,
Path extracting means for extracting at least two minimum hop paths from a plurality of paths from the data transmitting terminal to at least one data receiving terminal of the transmission destination for each data transmitting terminal of the terminals;
Encoding determination means for determining, for each combination of at least two crossing paths among the minimum hop paths obtained for each data transmission terminal, whether or not data flowing in each crossing path of the combination can be encoded;
Route setting means for setting, for each data transmission terminal, an encoding-compatible minimum hop route from the data transmission terminal to the transmission destination data reception terminal for each data transmission terminal, in accordance with the determination result of the encoding availability obtained for each intersection route When,
For each data transmission terminal, the data is transmitted from the data transmission terminal to the destination data reception terminal via the encoding-compatible minimum hop path set for the data transmission terminal, and the data corresponds to the encoding-compatible minimum hop path. A data delivery means for delivering by performing encoding according to the determination result of encoding availability;
A wireless communication system comprising: A data relay terminal that is connected between adjacent ones via a wireless communication link, and has a data relay function among a plurality of terminals constituting a multi-hop network,
Path extracting means for extracting at least two minimum hop paths from a plurality of paths from the data transmitting terminal to at least one data receiving terminal of the transmission destination for each data transmitting terminal of the terminals;
Encoding determination means for determining, for each combination of at least two crossing paths among the minimum hop paths obtained for each data transmission terminal, whether or not data flowing in each crossing path of the combination can be encoded;
Route setting means for setting, for each data transmission terminal, an encoding-compatible minimum hop route from the data transmission terminal to the transmission destination data reception terminal for each data transmission terminal, in accordance with the determination result of the encoding availability obtained for each intersection route When,
For each data transmission terminal, the data is transmitted from the data transmission terminal to the destination data reception terminal via the encoding-compatible minimum hop path set for the data transmission terminal, and the data corresponds to the encoding-compatible minimum hop path. A data delivery means for delivering by performing encoding according to the determination result of encoding availability;
A data relay terminal comprising:

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