JP2014014018A - Communication system and node - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system capable of performing communication using an optimum path and a node used in the communication system.SOLUTION: A communication system comprises: a communication confirmation packet transmission unit 12 for intermittently transmitting a communication confirmation packet; a bit error detection unit 13 for detecting a bit error in a communication confirmation packet received from another node; a communication success ratio calculation unit 14 for calculating a communication success ratio of communication with an adjacent node on the basis of the detection result; a RREP reply unit 19 for transmitting a RREP including path information taking one of adjacent nodes stored in a success ratio table 15 as the next node and a success ratio of the next node; a RREP transfer unit 20 for transferring a new RREP including path information taking one of the adjacent nodes stored in the success ratio table 15 as the next node and a success ratio of the next node, according to reception of a RREP; and a data transmission/reception unit 22 for selecting path information having the highest success ratio included in a RREP when a plurality of pieces of path information corresponding to one destination node are acquired.

Description

  The present invention relates to a communication system and a node, and more particularly, to a communication system including a plurality of nodes that perform wireless communication with each other and a node used in the communication system.

  In a scene where wireless communication is performed between nodes, there is a problem that radio waves on a direct communication path are blocked by various factors. In order to cope with this, in the communication system described above, communication including a detour by hopping or the like is performed. In an environment where all of the arrangement positions of nodes and shielding objects are fixed, an appropriate communication path can be set at the time of node installation or the like, and a good communication environment can be obtained. However, such an environment that has not changed from the time of installation is rare, and most of the space is a space in which a person or the like is interposed. In such a space, the radio wave environment used for wireless communication changes at any time. For this reason, it is necessary to set a communication path in accordance with the change.

  As a technique corresponding to this, there is a dynamic routing system as the most used system. A typical route search procedure of this dynamic routing system will be described below with reference to FIG. As shown in the figure, a communication system 100 that performs dynamic routing includes nodes A to D and a node S. The node A is provided so as to be able to communicate with the node B. The node B is provided so as to be able to communicate with the nodes A and S. The node S is provided so as to be able to communicate with the nodes B and C. The node C is provided to be able to communicate with the nodes S and D. The node D is provided so as to be able to communicate with the node C.

Next, an operation when data communication is performed from the node S to the node D will be described.
(1) When communicating from the node S to the node D, first, the node S transmits a Route-Request packet (hereinafter referred to as RREQ) assuming that there is no communication source node S, destination node D, and relay node. This RREQ is received by the nodes B and C (they do not reach other nodes due to the influence of distance, etc.).

(2) Since the destination node of the received RREQ is not the own node and the own node is not stored in the relay node, the nodes B and C store information on the own node in the relay node and transmit the RREQ. The RREQ transmitted from the node B is received by the nodes A and S, and the RREQ transmitted from the node C is received by the nodes S and D.
(3) Since the destination node of the RREQ from the node B is not the own node and the own node is not stored in the relay node, the node A stores the information of the own node in the relay node and transmits the RREQ. Since the destination node of the RREQ from the node C is its own node, the node D knows that communication is performed from the transmission source node and the relay node through the route of the node S → node C → node D. The node S receives the RREQ from the node B and the node C, but ignores this because the source node is its own node.

(4) The node B receives the RREQ from the node A, but ignores this because the relay node has information on its own node.
(5) The node D returns a Route-Reply packet (RREP) including route information based on the route determined from the RREQ. That is, the node D transmits the RREP that is the communication source node S, the destination node D, and the relay node C.
(6) When receiving the RREP from the node D, the node C transmits the received RREP because the relay node has its own node.

(7) Since the node S has obtained a communication route to the node D from the route information included in the RREP received from the node C, the node S performs data communication using the node C as a relay node.
(8) The node C transfers this data to the node D. The communication path is determined by the above flow. As for determination of a route in a communication network, dynamic routing is generally used. In this method, a communication route is determined by investigating a route connected to a target node before starting communication.

  Here, in order to shorten the information acquisition time of the relay node, each node holds the past RREQ-RREP for a certain time, and when the RREQ is received, if the held information can be used, RREP may be returned from the information. In addition, a packet exchange that confirms the state between nodes and that determines the communication path that maximizes the communication success rate to the target node from the communication success rate calculated from the electric field strength at that time is also proposed. (Patent Document 1).

JP 2010-213164 A

  The route obtained by the dynamic routing described above is one of many communication routes in the entire network, such as the shortest route, and is not always optimal. Further, as a method for obtaining an optimum route, in Patent Document 1, an optimum route is selected by acquiring electric field strength and estimating a communication success rate from communication of a packet for performing state confirmation between nodes. There is a problem that the strength does not necessarily match the communication success rate. For example, when radio waves are transmitted from two different nodes, the two radio waves may overlap and the received electric field strength may become strong. However, in this case, the communication data cannot be recognized and fails.

  In addition, the above-described method for obtaining a route by dynamic routing can cope with a change in the communication environment because the node that can communicate immediately before the communication is confirmed. However, the optimum route for the entire network is calculated for each communication. Therefore, there is a problem that the time before the start of communication is very long and it takes time for the data to reach the target node.

  Therefore, an object of the present invention is to provide a communication system that can communicate with an optimum route and a node used in the communication system.

The invention according to claim 1 for solving the above-described problem is a communication confirmation information transmitting means in which each of the nodes intermittently transmits communication confirmation information in a communication system including a plurality of nodes performing wireless communication with each other. And a bit error detection means for detecting a bit error in communication confirmation information received from another node, and a communication for calculating a communication success rate with another node capable of direct communication based on a detection result of the bit error detection means A storage unit for storing the success rate calculating unit, the other node capable of direct communication based on the result calculated by the communication success rate calculating unit, and the communication success rate corresponding to the other node; The first information including the path information in which one of the directly communicable nodes stored in the storage means is the next node and the communication success rate of the next node is transmitted. In response to the reception of the first transmission means and the first information in which the next node is its own node, the path information with one of the nodes stored in the storage means as the next node and the next node Path information included in the first information in response to the reception of the first transfer means for transferring new first information including the communication success rate and the first information in which the next node is the own node. Route information acquisition means for acquiring the first information as route information of the transmission source node, and route information with the highest success rate included in the first information when a plurality of route information for one transmission source node is acquired. Route information selection means to select;
There exists in the communication system characterized by comprising.

  According to the second aspect of the present invention, the communication success rate calculating means determines that the communication is successful if no bit error is detected by the bit error detecting means, and calculates the communication success rate based on the number of times the communication is determined to be successful. The present invention resides in the communication system according to claim 1.

  According to a third aspect of the present invention, the first transfer means multiplies the communication success rate of the received first information by the communication success rate of the next node, and the multiplied value is the communication success rate of the first information. The communication system according to claim 1, wherein the communication system is overwritten.

  According to a fourth aspect of the present invention, when receiving the second information for transmitting the second information for obtaining the route information for the destination node and the second information for which the destination node is not its own node, the second information is transferred. Second transfer means, wherein the first transmission means further includes the first information further including a transmission source node of the second information in response to reception of the second information whose destination node is its own node. When the transmission source node of the second information is included in the other node that can transmit and communicate directly, the first information with another node lower than the communication success rate of the transmission source node as the next node The first transfer means transfers the new first information in response to the reception of the first information in which the transmission source node of the second information is not its own node, and is capable of the direct communication. The source of the second information Is included, the first information is not transferred with another node having a communication success rate lower than that of the transmission source node as the next node, and the path information acquisition unit includes the next node and the first node. The path information included in the first information is acquired as the path information of the transmission source node of the first information only when the first information of the transmission source node of the two information is received. It exists in the communication system of any one of Claims 1-3.

  According to the fifth aspect of the present invention, communication confirmation information transmitting means for intermittently transmitting communication confirmation information and bit errors in communication confirmation information received from other nodes are detected in a wireless communicable node constituting the communication system. Bit error detection means that performs communication success rate calculation means for calculating a communication success rate with other nodes capable of direct communication based on the detection result of the bit error detection means, and results calculated by the communication success rate calculation means One of the nodes capable of direct communication and the communication success rate corresponding to the other node in association with each other, and the directly communicable node stored in the storage means The first transmission means for transmitting the first information including the path information with the next node as the next node and the communication success rate of the next node; and In response to reception of information, first transfer means for transferring new first information including path information in which one of the nodes stored in the storage means is the next node and the communication success rate of the next node. And route information acquisition means for acquiring the route information included in the first information as the route information of the transmission source node of the first information in response to reception of the first information in which the next node is its own node. And a route information selection means for selecting route information having the highest success rate included in the first information when a plurality of route information for one transmission source node is acquired. .

  As described above, according to the first and fifth aspects of the invention, it is possible to select optimum route information having a high communication success rate according to the bit error detection result. In addition, since each node intermittently transmits communication confirmation information, the latest success rate can be obtained each time transmission is performed, and it is not necessary to obtain the success rate at the time of data transmission, thereby reducing the communication time. Can do.

  According to the second aspect of the present invention, the communication success rate can be obtained from the number of successful communications, and more optimal route information can be selected.

  According to the third aspect of the present invention, the data amount of the first information can be suppressed by overwriting the communication success rate.

  According to the fourth aspect of the present invention, when the first transmission unit and the first transfer unit include the transmission source node of the second information in the other directly possible nodes, the communication success rate of the transmission source node Since the first information is not transmitted or transferred with another lower node as the next node, useless first information is not transmitted.

It is a block diagram which shows one Embodiment of the communication system of this invention. It is a block diagram which shows each node which comprises the communication system shown in FIG. It is a figure which shows the structural example of the communication confirmation packet transmitted from each node shown in FIG. It is a flowchart which shows the success rate calculation process procedure of CPU which comprises the node shown in FIG. It is a figure which shows the structural example of RREQ transmitted from each node shown in FIG. It is a figure which shows the structural example of RREP transmitted from each node shown in FIG. It is explanatory drawing for demonstrating operation | movement of the communication system shown in FIG. It is a flowchart which shows the path | route acquisition process procedure of CPU which comprises the node shown in FIG. It is a figure which shows one Embodiment of the conventional communication system.

  The communication system of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the communication system 10 of the present invention includes a plurality of nodes 1 to 8, and these nodes 1 to 8 constitute a wireless mesh network.

  In the communication system 10 shown in FIG. 1, the node 1 is in a state where it cannot wirelessly communicate with the other nodes 2 to 8 due to a failure or the like. The node 2 can communicate wirelessly with the nodes 3, 5 and 6. The node 3 can wirelessly communicate with the nodes 2, 5 and 6. The node 4 is in a state where it cannot wirelessly communicate with the other nodes 1 to 3 and 5 to 8 due to a failure or the like. The node 5 can wirelessly communicate with the nodes 2, 3 and 7. The node 6 can wirelessly communicate with the nodes 2, 3 and 7. The node 7 can wirelessly communicate with the nodes 5, 6 and 8. The node 8 can communicate with the node 7 wirelessly.

  Next, the configuration of the nodes 1 to 8 will be described below with reference to FIG. As shown in the figure, each of the nodes 1 to 8 includes an antenna AT and a communication unit 11 for wirelessly receiving data. Each of the nodes 1 to 8 is a communication confirmation packet transmitting unit 12 (= communication confirmation information transmitting means) for obtaining a communication success rate with other nodes (hereinafter referred to as “adjacent nodes”) that can directly communicate with the own node. , A bit error detection unit 13 (= bit error detection means) and a communication success rate calculation unit 14 (= communication success rate calculation means). With these functions, the success rate table 15 (= storage means) of each of the nodes 1 to 8 stores the adjacent node and the communication success rate corresponding to the adjacent node in association with each other.

  The communication confirmation packet transmitter 12 creates and transmits a communication confirmation packet (= communication confirmation information) as shown in FIG. 3 from the communication unit 11 every time the first timer 16 counts for a first predetermined time. As shown in FIG. 3, the communication confirmation packet includes a type, a transmission source node, a sequence number, data, and an error check code.

  The communication confirmation packet transmission unit 12 stores information indicating a communication confirmation packet as a type. Stores the address of its own node as the source node. As the sequence number, a number obtained by adding 1 to the sequence number when the communication confirmation packet was transmitted last time is stored. When the sequence number reaches the maximum value (for example, 255 if the bit allocation of the sequence number is 8 bits), the next value is 0. As the data, predetermined data such as a PN code that can detect a bit error is stored. As the error check code, a code for error check such as CRC and checksum is stored.

  Each time the communication unit 11 receives a communication confirmation packet from another node, the bit error detection unit 13 confirms the data and error check code of the received communication confirmation packet and detects a bit error. The communication success rate calculation unit 14 calculates the communication success rate with the adjacent node based on the detection result of the bit error detection unit 13. Specifically, the communication success rate calculation unit 14 determines that the communication is successful if no bit error is detected by the bit error detection unit 13 and determines the number of communication success packets (number of communication successes) for the transmission source node. Increment. The communication success rate calculation unit 14 determines that the communication has failed if a bit error is detected by the bit error detection unit 13, and does not increment the number of communication success packets.

Each time the communication success rate calculation unit 14 determines that the communication is successful, the communication success rate calculation unit 14 obtains the number of transmission packets, which is the total number of communication confirmation packets transmitted from the transmission source node so far, from the following equation (1). The communication success rate represented by 2) is updated.
Number of transmitted packets = number of transmitted packets when it was determined that the previous communication was successful + (sequence number when it was determined that the previous communication was successful−sequence number when it was determined that the current communication was successful) (1)
Communication success rate = communication success packet number / transmission packet number (2)
Next, the communication success rate calculating unit 14 stores the adjacent node and the calculated communication success rate corresponding to the adjacent node in the success rate table 15 in association with each other. Each of the nodes 1 to 8 periodically repeats transmission and reception of a communication confirmation packet and calculation of a communication success rate. Thereby, each node 1-8 can grasp | ascertain the newest communication success rate with respect to an adjacent node.

  Moreover, each part 12-14 is comprised by CPU etc. which are not shown in figure, and is performed by the success rate calculation process shown in FIG. 4 which CPU performs. The success rate calculation process will be described. First, the CPU transmits a communication confirmation packet shown in FIG. 3 every time the first timer 16 counts the first predetermined time (Y in step S1) (step S2). ), The process returns to step S1. While the counting of the first predetermined time by the first timer 16 is not yet finished (N in Step S1), the CPU determines whether or not a communication confirmation packet has been received from another node (Step S3).

If the communication confirmation packet has not been received (N in step S3), the CPU returns to step S1 again. If a communication confirmation packet has been received (Y in step S3), the CPU confirms the transmission source node and sequence number of the communication confirmation packet (steps S4 and S5), and then transmits the number of transmitted packets according to the above-described equation (1). Is calculated (step S6). Next, the CPU detects a bit error in the communication confirmation packet (step S7). If no bit error is detected, the CPU determines that the communication is successful, recalculates the communication success rate using equation (2), and in step S4. After the communication success rate with the confirmed transmission source node is stored in the success rate table 15 (step S8), the process returns to step S1. In step S8, the CPU determines that communication has failed if a bit error is detected. Since the sequence number of the confirmation packet at the time of bit error detection is not credible, the CPU adds 1 to the number of transmitted packets every time a bit error is detected without obtaining the number of transmitted packets from equation (1). . Then, as shown in the following formula (3), the communication success rate is calculated again by dividing the number of communication success rate packets by the number of transmission packets to which 1 is added.
Communication success rate = communication success rate packet number / (transmission packet number + 1) (3)

  Next, when the story is returned with respect to the configuration of each of the nodes 1 to 8, each of the nodes 1 to 8 further receives an RREQ transmission unit 17 (= second transmission means), RREQ in order to obtain route information for the other nodes 1 to 8. Transfer unit 18 (= second transfer unit), RREP reply unit 19 (= first transmission unit), RREP transfer unit 20 (= first transfer unit), route information acquisition unit 21 (= route information acquisition unit), data A transmission / reception unit 22 (= route information selection means). With these functions, the routing table 23 stores the route information for other nodes and the communication success rate of the route information in association with each other.

  Each time the second timer 24 counts for a second predetermined time, the RREQ transmission unit 17 creates another RREQ (= second information) for determining route information for the destination node with another node as the destination node. Send. The RREQ transmission unit 17 creates and transmits an RREQ having a frame configuration as shown in FIG. 5, for example. As shown in FIG. 5, the RREQ includes a type, a transmission source node, a destination node, and a relay node. The RREQ transmission unit 17 stores information indicating RREQ as a type. As the source node, the address of the own node that transmits the RREQ is stored. As the destination node, the address of another node to which data is transmitted is stored. As a relay node, nothing is stored and is left blank. Each time the second timer 24 counts for a second predetermined time, the RREQ transmission unit 17 creates and transmits an RREQ in which other nodes stored in the destination node are sequentially switched.

  When the RREQ transfer unit 18 receives an RREQ in which the destination node is not the own node and the own node is not stored in the relay node, the RREQ transfer unit 18 writes the address of the own node to the relay node of the RREQ and then transfers the RREQ. . The RREQ transfer unit 18 writes the address of its own node at the end of the relay node column. Further, when the RREQ transfer unit 18 receives the RREQ in which the address of the own node is stored in the transmission source node or the relay node, the RREQ transfer unit 18 ignores the RREQ and does not transfer the RREQ.

  The RREP reply unit 19 creates and transmits, for example, RREP (= first information) as shown in FIG. 6 in response to reception of RREQ whose destination node is its own node. In the received RREQ, the transmission source node and the relay node up to the local node are already stored, and these are the route information. As shown in FIG. 6, the RREP includes a type, a transmission source node, a destination node, a relay node, and a communication success rate. The RREP reply unit 19 stores information indicating RREP as a type. The address of the source node of the received RREQ is stored as the source node. As the destination node, the address of the destination node of the received RREQ (that is, the address of its own node) is stored.

  In this embodiment, the RREQ destination node is stored as it is in the RREP destination node, and the RREEQ transmission source node is stored as it is in the RREP transmission source node. Therefore, the RREP destination node corresponds to the transmission source node of the first information (RREP) in the claims, and the RREP transmission source node corresponds to the transmission source node of the second information (RREQ) in the claims.

  Further, the RREP reply unit 19 selects one of the adjacent nodes stored in the success rate table 15 as the next node as the relay node, and stores the address thereof. As the communication success rate, the communication success rate of the node stored in the relay node as the next node from the success rate table 15 is written.

  The RREP reply unit 19 basically creates each RREP with all adjacent nodes stored in the success rate table 15 as the next node. If the source node of the RREQ is an adjacent node, An RREP is not created with an adjacent node having a communication success rate lower than that of the transmission source node as the next node.

  When the RREP transfer unit 20 receives the RREP in which the address of its own node is written in the last relay node, that is, the next node is its own node, 1 of the adjacent nodes stored in the success rate table 15 is received. One is selected as the next node and its address is written at the end of the relay node, and a new RREP is created that includes the communication success rate of the received RREP multiplied by the communication success rate of the next node. And transfer. The RREP transfer unit 20 also basically creates an RREP with all adjacent nodes stored in the success rate table 15 as the next node. If the RREP source node is an adjacent node, the RREP transfer unit 20 transmits the RREP. An RREP is not created with an adjacent node having a communication success rate lower than that of the original node as the next node.

  When receiving the RREP in which the transmission source node and the next node are the own nodes, the route information acquisition unit 21 acquires the route information (destination node, relay node) included in the RREP as route information to the destination node, The path information and the communication success rate written in RREP are associated with each other and stored in the routing table 23. The data transmission / reception unit 22 is connected to an application (not shown) via the I / F 25. When transmission data is generated from the application, the data transmission / reception unit 22 selects route information from the routing table 23 to the destination node of the transmission data. Transmission data to which route information is added is transmitted from the communication unit 11. At this time, the data transmitting / receiving unit 22 selects the route information with the highest communication success rate when there are a plurality of route information for one destination node. Each of the nodes 1 to 8 periodically transmits an RREQ and repeats acquisition of route information. Thereby, each node 1-8 can grasp | ascertain the newest route information to another node.

  Next, operations of the RREQ transmission unit 17, the RREQ transfer unit 18, the RREP reply unit 19, the RREP transfer unit 20, the route information acquisition unit 21, and the data transmission / reception unit 22 will be described by taking the network configuration of FIG. 1 as an example. Here, a procedure for determining a communication route when communicating from the node 3 to the node 8 is shown. Each of the nodes 1 to 8 has been confirmed so far, and each node has a communication success rate with a node capable of direct communication as shown in FIG.

  First, the RREQ transmission unit 17 of the node 3 transmits an RREQ with the transmission source node as the node 3 and the destination node as the node 8. Details of the transmission of the RREQ are also described in the background art, and thus detailed description thereof is omitted here.

The RREP reply unit 19 of the node 8 that has received the RREQ whose destination node is its own node creates and returns an RREP accordingly. The RREP reply unit 19 of the node 8 stores the node 3 as the RREQ source node in the RREP source node, and stores the node 8 as the RREQ destination node in the RREP destination node. Also, the RREP reply unit 19 of the node 8 selects the adjacent node 7 from the past communication result as the next node, and writes it as the relay node. Further, the RREP reply unit 19 of the node 8 writes the communication success rate to the node 7 selected as the next node. At this time, a communication success rate of 100% to the node 7 is written in RREP. That is, as shown in FIG. 7, the frame configuration of RREP ₁ created at this time is RREP / source node 3 / destination node 8 / relay node 7 / blank / communication success rate 100%.

When the RREP ₁ is transmitted from the node 8, the node 7 receives it. When the RREP transfer unit 20 of the node 7 receives RREP _{1 in} which the own node is written in the next node (the backmost of the relay node), it creates a new RREP and transmits it. In the node 7, there are three adjacent nodes 3, 5, and 6 (except that the adjacent node 8 is a destination node of RREP ₁ ). The respective communication success rates are 70%, 95%, and 90%. Since the source node stored in RREP ₁ received from the node 8 is the node 3 and is included in the adjacent node of the node 7, the RREP transfer unit 20 of the node 7 first sets the node 3 as the next node. Select and write to the relay node. Further, the RREP transfer unit 20 of the node 7 multiplies the communication success rate 100% of the received RREP ₁ by the communication success rate 70% of the node 3 selected as the next node, and overwrites the value to the communication success rate. . As shown in FIG. 7, the frame configuration of RREP ₂ created in this way is RREP / source node 3 / destination node 8 / relay node 7 / relay node 3 / blank / communication success rate 70%.

In addition, the RREP transfer unit 20 of the node 7 sequentially selects the nodes 5 and 6 as the next nodes because the communication success rate of the other adjacent nodes 5 and 6 is higher than the communication success rate of the transmission source node 3. Write as a relay node. Further, the RREP transfer unit 20 of the node 7 multiplies the communication success rate 100% of the received RREP by the communication success rates 95% and 90% of the nodes 5 and 6 selected as the next node, and succeeds in the communication. Overwrite rate. Thereby, as shown in FIG. 7, the frame structure of RREP ₃ with node 5 as the next node is RREP / source node 3 / destination node 8 / relay node 7 / relay node 5 / blank / communication success rate. The frame configuration of RRPE ₄ with node 6 as the next node is RREP / source node 3 / destination node 8 / relay node 7 / relay node 6 / blank / communication success rate 90%. The RREP transfer unit 20 of the node 7 sequentially transmits the created three RREPs ₂ , ₃ , and ₄ .

When three RREPs ₂ , ₃ , and ₄ are transmitted from the node 7, the nodes 3, 5, 6, 7, and 8 receive them. The node 8 ignores all RREPs ₂ , ₃ , and _{4 in} which the next node is not its own node. The node 3 ignores RREP ₃ and ₄ whose next node is not its own node. The route information acquisition unit 21 of the node 3 acquires the route information included in the RREP ₂ as the route information of the destination node 8 when receiving the RREP _{2 in} which the transmission source node and the next node are its own nodes. Here, node 3 → node 7 → node 8 is acquired from the destination node and relay node written in RREP ₂ as path information, and 70% is acquired as the communication success rate, and this is stored in the routing table 23. In the conventional dynamic routing, the route is determined so far without including the communication success rate.

Further, when _three RREPs ₂ , ₃ , and ₄ are transmitted from the node 7, the node 5 receives them. The node 5 ignores RREP ₂ and ₄ whose next node is not its own node. When the RREP transfer unit 20 of the node 5 receives RREP _{3 in} which the node is written in the next node, it creates and transmits a new RREP. In node 5, there are two adjacent nodes, two and three (excluding adjacent node 7 because it is already written in the relay node of RREP ₁ ). The respective communication success rates are 60% and 75%. Since the transmission source node stored in RREP ₃ received from the node 7 is the node 3 and is included in the adjacent node of the node 5, the RREP transfer unit 20 of the node 5 first sets the node 3 as the next node. Select and write to the relay node. Further, the RREP transfer unit 20 of the node 5 multiplies the communication success rate 95% of the received RREP ₃ by the communication success rate 70% of the node 3 selected as the next node, and overwrites the value on the communication success rate. . As shown in FIG. 7, the frame structure of RREP ₅ created in this way is RREP / source node 3 / destination node 8 / relay node 7 / relay node 5 / relay node 3 / blank / communication success rate 71. 25% (= 95% × 75%).

  In addition, the RREP transfer unit 20 of the node 5 is lower than the communication success rate of the transmission source node 3 for the adjacent node 2 and cannot be expected to be useful via the node 2. do not do.

When RREP ₅ is transmitted from the node 5, the nodes 2, 3, and 7 receive it. Nodes 2 and 7 ignore RREP _{5 in} which the next node is not written. The route information acquisition unit 21 of the node 3 acquires the route information included in the RREP ₅ as the route information of the destination node 8 when the source node and the next node receive the RREP ₅ that is its own node. Here, from the destination node and the relay node written in RREP ₅ , node 3 → node 5 → node 7 → node 8 is acquired as route information, and 71.25% is acquired as the communication success rate, and this is stored in the routing table 23. Remember.

Further, when _three RREPs ₂ , ₃ , and ₄ are transmitted from the node 7, the node 6 also receives them. The node 6 ignores RREP ₂ and ₃ whose next node is not its own node. When the RREP transfer unit 20 of the node 6 receives the RREP _{4 in} which the node is written in the next node, the RREP transfer unit 20 creates and transmits a new RREP. In node 6, there are two adjacent nodes (excluding because adjacent node 7 has already been written as a relay node of RREP ₄ ). The respective communication success rates are 100% and 95%. Since the source node stored in RREP ₄ received from the node 7 is the node 3 and is included in the adjacent node of the node 6, the RREP transfer unit 20 of the node 6 first sets the node 3 as the next node. Select and write to the relay node. Further, the RREP transfer unit 20 of the node 6 multiplies the communication success rate of 90% of the received RREP ₄ by the communication success rate of 95% of the node 3 selected as the next node, and overwrites the value with the communication success rate. . As shown in FIG. 7, the frame structure of RREP ₆ created in this way is RREP / source node 3 / destination node 8 / relay node 7 / relay node 6 / relay node 3 / blank / communication success rate 85. 5% (= 90% × 95%).

Further, the RREP transfer unit 20 of the node 6 selects the node 2 as the next node and writes it as the relay node because the communication success rate of the other adjacent node 2 is higher than the communication success rate of the transmission source node 3. . Further, the RREP transfer unit 20 of the node 6 multiplies the communication success rate 90% of the received RREP ₄ by the communication success rate 100% of the node 2 selected as the next node, and overwrites the value with the communication success rate. The frame configuration of RREP ₇ created in this way is RREP / source node 3 / destination node 8 / relay node 7 / relay node 6 / relay node 2 / blank / communication success rate 90%. The RREP transfer unit 20 of the node 6 sequentially transmits the two created RREPs ₆ and ₇ .

When two RREPs ₆ and ₇ are transmitted from the node 6, the nodes 2, ₃ , and ₇ receive them. The node 7 ignores RREP ₆ and _{7 in} which the next node is not written. Node 3 ignores RREP ₇ whose next node is not its own node. When the route information acquisition unit 21 of the node 3 receives the RREP _{7 in} which the transmission source node and the next node are its own nodes, the route information included in the RREP ₅ is acquired as the route information of the destination node. Here, node 3-> node 6-> node 7-> node 8 is acquired from the destination node and relay node included in RREP ₇ as path information, and 85.5% is acquired as the communication success rate, and this is stored in routing table 23. .

Further, when two RREPs ₆ and ₇ are transmitted from the node 6, the node 2 also receives them. Node 2 ignores RREP ₆ where the next node is not its own node. When the RREP transfer unit 20 of the node 2 receives the RREP ₇ that is the next node, the RREP transfer unit 20 creates and transmits a new RREP. In node 2, there are two adjacent nodes 3 and 5 (excluded because adjacent node 6 has already been written in the relay node). The respective communication success rates are 100% and 60%. Since the source node stored in RREP ₇ received from the node 6 is the node 3 and is included in the adjacent node of the node 2, the RREP transfer unit 20 of the node 2 first sets the node 3 as the next node. Select and write to the relay node. Further, the RREP transfer unit 20 of the node 2 multiplies the communication success rate 90% of the received RREP ₇ by the communication success rate 100% of the node 3 selected as the next node, and overwrites the value with the communication success rate. As shown in FIG. 7, the frame structure of RREP ₈ created in this way is RREP / source node 3 / destination node 8 / relay node 7 / relay node 6 / relay node 2 / relay node 3 / blank / communication. The success rate is 90%.

When two RREPs ₈ are transmitted from the node 2, the nodes 3, 5, and 6 receive them. The nodes 5 and 6 ignore the RREP _{8 in} which the next node is not written. When the route information acquisition unit 21 of the node 3 receives the RREP _{8 in} which the transmission source node and the next node are its own nodes, the route information included in the RREP ₈ is acquired as the route information of the destination node. Here, node 3 → node 2 → node 6 → node 7 → node 8 is acquired as route information from the destination node and relay node included in RREP ₈ , and 90% is acquired as the communication success rate, and this is stored in the routing table 23. Let

  As described above, as shown in FIG. 7, in addition to node 3 → node 7 → node 8 with a communication success rate of 70%, node 3 → node 5 → node 7 → node 8 with a communication success rate of 71.25%, as shown in FIG. The route information of node 3 → node 6 → node 7 → node 8 with communication success rate 85.5% and node 3 → node 2 → node 6 → node 7 → node 8 with communication success rate 90% is obtained from this node. The data transmission / reception unit 22 of No. 3 routes and selects node 3 → node 2 → node 6 → node 7 → node 8 with the highest communication success rate. With the above procedure, each of the nodes 1 to 8 can obtain the optimum route information to other nodes. This path information construction is appropriately performed at a time interval longer than the acquisition of the communication success rate information (that is, the first predetermined time counted by the first timer 16 <the second predetermined time counted by the second timer 24). Next, when a data communication request occurs in the application, the data transmission / reception unit 22 performs data communication according to the route selected above.

  Moreover, each part 17-23 is comprised by CPU etc. which are not shown in figure, and is performed by the route information acquisition process shown in FIG. 8 which CPU performs. The route information acquisition process will be described. First, every time the second timer 24 counts the second predetermined time (Y in step S10), the CPU sequentially transmits the RREQ shown in FIG. 5 (step S11). While the counting of the second predetermined time by the second timer 24 is not yet finished (N in Step S10), the CPU determines whether or not an RREQ from another node has been received (Step S12). If the destination node of the received RREQ is its own node (Y in step S12 and Y in S13), the CPU returns RREP (step S14). On the other hand, if neither the destination node nor the relay node of the received RREQ has its own node (Y in step S12, N in S13, and N in S15), the CPU determines the RREQ obtained by adding the own node to the relay node. After the transfer (step S16), the process returns to step S10.

  Further, when the CPU receives the RREP (Y in step S17), if the next node and the transmission source node of the RREP are its own nodes (Y in step S18), the routing table 23 displays the route information and the success rate of the RREP. (Step S19), the process returns to step S10. On the other hand, if the next node of RREP has its own node and the transmission source node is not its own node (N in step 18 and Y in step S20), the CPU starts from the plurality of adjacent nodes stored in the success rate table 15. Is determined (step S21), the RREP is transferred (step S22), and the process returns to step S10.

  According to the above-described embodiment, in each of the nodes 1 to 8, the communication confirmation packet transmission unit 12 intermittently transmits the communication confirmation packet, and the bit error detection unit 13 receives the bit of the communication confirmation packet received from another node. An error is detected, and the communication success rate calculation unit 14 calculates the communication success rate with the adjacent node based on the detection result. In each of the nodes 1 to 8, the RREP reply unit 19 transmits RREP including the path information in which one of the adjacent nodes stored in the success rate table 15 is the next node and the success rate of the next node. In response to the reception of the RREP in which the next node is the next node, the RREP transfer unit 20 receives the path information and the success of the next node with one of the nodes stored in the success rate table 15 as the next node. Forward a new RREP containing the rate. Further, in each of the nodes 1 to 8, the route information acquisition unit 21 acquires the route information included in the RREP as the route information of the destination node of the RREP, and the data transmission / reception unit 22 receives the route information for one destination node. When a plurality of pieces of information are acquired, route information having the highest success rate included in the RREP is selected. Therefore, it is possible to select optimal route information having a high communication success rate according to the bit error detection result. Moreover, since the nodes 1 to 8 intermittently transmit the success rate data, the latest success rate can be obtained every time data is transmitted, and it is not necessary to obtain the success rate at the time of data transmission, thereby reducing the communication time. Can be planned.

  Further, according to the above-described embodiment, since the communication confirmation packet, RREP, and RREQ are intermittently transmitted, it is possible to cope with a situation in which the radio wave environment changes in the vehicle. Also, since the optimum route is known at the start of communication, communication can be started immediately upon request for communication. Furthermore, the time constraint for obtaining the route does not depend on communication, and the route can be obtained efficiently.

  In the above-described embodiment, since the communication success rate of the next node is added when the RREP is transferred, the optimal communication success rate of the entire network can be known only by the communication success rate with the adjacent nodes.

  According to the embodiment described above, the communication success rate calculation unit 14 of each of the nodes 1 to 8 determines that the communication is successful if no bit error is detected by the bit error detection unit 13, and based on the number of times that the communication is determined to be successful. Calculate the communication success rate. Therefore, the communication success rate can be obtained from the number of successful communications, and more optimal route information can be selected.

  According to the embodiment described above, the RREP transfer unit 20 multiplies the received RREP communication success rate by the communication success rate of the next node, and overwrites the multiplied value on the RREP communication success rate. Therefore, the data amount of RREP can be suppressed by overwriting the communication success rate.

  According to the above-described embodiment, when the RREP reply unit 19 and the RREP transfer unit 20 include an RREQ source node in an adjacent node, the RREP reply unit 19 and the RREP transfer unit 20 follow other nodes having a communication success rate lower than that of the source node. Since no RREP is transmitted or transferred as a node, no useless RREP is transmitted.

  According to the above-described embodiment, the RREP reply unit 19 returns the RREP in response to the reception of the RREQ by the destination node, but the present invention is not limited to this. For example, RREP may be transmitted periodically without transmitting RREQ. When the next node receives an RREP that is the next node, the route information acquisition unit 21 acquires the route information included in the RREP as the route information of the transmission source node of the RREP.

  Further, according to the above-described embodiment, the RREP transfer unit 20 multiplies the communication success rate of the received RREP by the communication success rate of the next node, and overwrites the multiplied value with the communication success rate of the RREP. However, the present invention is not limited to this. For example, the RREP transfer unit 20 may simply add the success rate of the next node without overwriting. Then, the node that finally receives the RREP (node 3 in the above example) may obtain the success rate of the route by multiplying a plurality of success rates included in the RREP.

  Further, the frame configuration of RREQ and RREP is not limited to the above-described embodiment.

  In the embodiment described above, a dedicated communication confirmation packet is transmitted for communication confirmation, but the present invention is not limited to this. For example, it is conceivable to receive data exchanged between other nodes, detect a bit error from the bit error code of the data, and apply this to calculation of the communication success rate. For example, when the node 5 and the node 2 shown in FIG. 1 are communicating, the node 3 can also receive data from the node 5, but the node 3 ignores this because the received data is addressed to the node 2. . In this embodiment, when the node 3 receives data that is not addressed to itself, a bit error is detected using the error check code of the data, and this is used to calculate the communication success rate with the node 5.

  In the embodiment described above, the communication confirmation packet is broadcast, but the present invention is not limited to this. For example, a destination node may be added to the communication confirmation packet, and unicast with the destination node may be performed.

  In this embodiment, the RREQ for obtaining the route information is periodically transmitted. However, the present invention is not limited to this. Other than periodically, RREQ may be transmitted every time there is a change in success rate upon reception of a communication confirmation packet. Then, triggered by reception of this RREQ, other nodes may also start transmitting RREQ for updating route information.

  Further, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

1 to 8 nodes 10 communication system 12 communication confirmation packet transmitter (communication confirmation information transmitter)
13-bit error detector (bit error detection means)
14 Communication success rate calculation unit (communication success rate calculation means)
15 Success rate table (storage means)
17 RREQ transmitter (second transmitter)
18 RREQ transfer unit (second transfer means)
19 RREP reply section (first transmission means)
20 RREP transfer unit (first transfer means)
21 Route information acquisition unit (route information acquisition means)
22 Data transmitter / receiver (route information selection means)

Claims (5)

In a communication system including a plurality of nodes that perform wireless communication with each other,
Each of the nodes
Communication confirmation information transmitting means for intermittently transmitting communication confirmation information;
Bit error detection means for detecting a bit error in communication confirmation information received from another node;
A communication success rate calculating means for calculating a communication success rate with other nodes capable of direct communication based on the detection result of the bit error detecting means;
Storage means for storing the other nodes capable of direct communication based on the result calculated by the communication success rate calculation means and the communication success rates corresponding to the other nodes in association with each other;
First transmission means for transmitting path information having one of the directly communicable nodes stored in the storage means as a next node and first information including a communication success rate of the next node;
In response to the reception of the first information that the next node is its own node, the path information including one of the nodes stored in the storage means as the next node and the communication success rate of the next node are included. First transfer means for transferring new first information;
Path information acquisition means for acquiring path information included in the first information as path information of a transmission source node of the first information in response to reception of the first information in which the next node is the own node;
Route information selection means for selecting route information having the highest success rate included in the first information when a plurality of pieces of route information for one transmission source node are acquired;
A communication system comprising: The communication success rate calculation means determines that communication is successful if no bit error is detected by the bit error detection means, and calculates a communication success rate based on the number of times the communication is determined to be successful. The communication system according to 1. The first transfer means multiplies the communication success rate of the received first information by the communication success rate of the next node, and overwrites the multiplied value on the communication success rate of the first information. The communication system according to claim 1 or 2. Second transmission means for transmitting second information for obtaining route information for the destination node;
A second transfer means for transferring the second information when the destination node receives the second information which is not its own node;
The first transmission means transmits the first information further including a transmission source node of the second information in response to reception of the second information whose destination node is its own node, If the source node of the second information is included in the node, the first information is not transmitted with another node lower than the communication success rate of the source node as the next node,
The first transfer means transfers the new first information in response to the reception of the first information in which the transmission source node of the second information is not its own node, and the second information is transmitted to the other nodes capable of direct communication. When the information source node is included, the first information is not transferred with another node lower than the communication success rate of the source node as the next node,
The route information acquisition means receives the route information included in the first information only when the next node and the source node of the second information receive the first information that is the own node. The communication system according to claim 1, wherein the communication system is acquired as route information of a transmission source node. In a node capable of wireless communication constituting a communication system,
Communication confirmation information transmitting means for intermittently transmitting communication confirmation information;
Bit error detection means for detecting a bit error in communication confirmation information received from another node;
A communication success rate calculating means for calculating a communication success rate with other nodes capable of direct communication based on the detection result of the bit error detecting means;
Storage means for storing the other nodes capable of direct communication based on the result calculated by the communication success rate calculation means and the communication success rates corresponding to the other nodes in association with each other;
First transmission means for transmitting path information having one of the directly communicable nodes stored in the storage means as a next node and first information including a communication success rate of the next node;
In response to the reception of the first information that the next node is its own node, the path information including one of the nodes stored in the storage means as the next node and the communication success rate of the next node are included. First transfer means for transferring new first information;
Path information acquisition means for acquiring path information included in the first information as path information of a transmission source node of the first information in response to reception of the first information in which the next node is the own node;
Route information selection means for selecting route information having the highest success rate included in the first information when a plurality of pieces of route information for one transmission source node are acquired;
A node characterized by comprising:

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