JP6606484B2 - Communication apparatus and communication control method - Google Patents

Description

  The present invention relates to a communication device and a communication control method in a communication system that performs multi-hop communication.

  In a wireless sensor network, which is a communication system composed of multiple communication devices, sensor data from sensors installed at various locations on the monitoring target is transferred and aggregated to a predetermined target device by multi-hop communication via the communication device. (For example, refer to Patent Document 1).

JP 2009-206749 A

  In such a wireless communication system, when performing a dynamic route search for selecting a communication device through which communication is performed, in order to reduce the number of transfers until reaching the target device for the purpose of power saving of the communication device, Designed to preferentially select the communication device closest to the target device. For example, the priority of the communication device to be selected is set according to the distance between the communication devices, and first, the communication device having the highest priority is selected to transfer data. A method of selecting a high communication device and transferring data again can be considered.

  However, there is no problem when the radio wave environment hardly changes, but when it changes frequently, the priority is fixed, and there is a problem that the number of data retransmissions increases and the power consumption increases. There is. This is because data transmission is attempted by sequentially selecting communication devices in accordance with a predetermined priority, and therefore it is not possible to cope with fluctuations in the radio wave environment, and data retransmission is simply repeated. As a specific example in which the radio wave environment changes, for example, a vehicle monitoring system in which a sensor is installed in each vehicle of a long train train to monitor the state of each vehicle. The radio wave environment such as geography such as mountainous areas where the track passes, track structure such as tunnels, and radio waves that cause noise such as urban areas fluctuate greatly as the train travels, leading vehicle and tail The radio wave environment can be different from the vehicle.

  The present invention has been made in view of the above circumstances, and its object is to reduce the number of transfers until reaching the target device in a wireless communication system that performs multi-hop communication between the communication devices. It is possible to realize a route search in which a communication device with high communication reliability is preferentially selected.

The first invention for solving the above-described problems is
A communication device constituting a wireless communication system that performs multi-hop communication in which given data is transmitted to a given target device by multiple hop communications,
First hop destination information (for example, the route table 50 in FIG. 2) in which candidates of other communication devices (hereinafter referred to as “other devices”) as the first hop communication (hereinafter referred to as “first hop”) are registered. Storage means for storing (for example, the storage unit 300 in FIG. 6);
Each time the first hop is performed, transmission history information (for example, the transmission history 60 in FIG. 3) is recorded for each of the other devices registered in the first hop destination information. ) Recording control means for performing update control (for example, transmission history update unit 202 in FIG. 6)
Based on the transmission history information, selection means (for example, the first hop destination selection unit 204 in FIG. 6) for selecting another device as the next first hop destination,
It is a communication apparatus provided with.

As another invention,
A communication control method for a communication device constituting a wireless communication system for performing multi-hop communication in which given data is transmitted to a given target device by multiple hop communication,
The communication device stores first hop destination information in which candidates for other communication devices (hereinafter referred to as “other devices”) as first hop communication (hereinafter referred to as “first hop”) are registered,
Each time the first hop is performed, update control of transmission history information in which the communication success or failure of the first hop for the predetermined number of times in the past is recorded for each other device registered in the first hop destination information;
Based on the transmission history information, selecting another device as the next first hop destination;
A communication control method including the above may be configured.

  According to the first aspect of the present invention, the other device to be the next first hop destination is selected based on the transmission history information in which the success or failure of the first hop for the predetermined number of times in the past is recorded for each other device. As a result, for example, by preferentially selecting other devices with a high past communication success rate or other devices with a large number of successful communication, the number of transfers until reaching the target device is reduced as much as possible. It is possible to realize a route search in which a highly reliable communication device is preferentially selected.

As a second invention, the communication device of the first invention,
The selecting means is a calculating means for calculating a communication success probability for the predetermined number of times in the past in the past for each other device registered in the first hop destination information based on the transmission history information (for example, FIG. 6). A communication success probability calculation unit 206), and based on the communication success probability, selects another device as the next first hop destination,
A communication device may be configured.

  According to the second aspect of the invention, the other device to be the next first hop destination is selected based on the communication success probability for each other device calculated based on the transmission history information. Thereby, for example, by preferentially selecting a communication device having a high communication success probability, that is, a high communication reliability, the number of times of data retransmission due to communication failure is suppressed, and the communication time and power consumption are reduced. be able to.

As a third invention, the communication device of the second invention,
The calculation means adds the number of successful successes (for example, “success / failure of communication in routing table” in FIG. 3) that the predetermined number of first hops are considered to be successful for each other device registered in the first hop destination information. Above, calculating the communication success probability,
A communication device may be configured.

  According to the third aspect of the invention, the communication success probability for each other device is calculated after adding the number of successes that the predetermined number of first hops are considered successful. As a result, even if another device in which the success or failure of communication is not recorded in the transmission history information, i.e., another device that has not been communicated as the first hop destination in the past is included. The communication success probability can be calculated.

As a fourth invention, the communication device of the second or third invention,
The storage means stores information (for example, connection information 304 in FIG. 6) that can determine the perspective order of each other device registered in the first hop destination information to the target device,
The selection means sets another device that satisfies the predetermined high probability of communication success as the next first hop destination, and when there are a plurality of other devices that satisfy the high probability, Select the device as the next first hop destination,
A communication device may be configured.

  According to the fourth aspect of the invention, the other device closest to the target device is selected as the next first hop destination among the other devices whose communication success probability satisfies the predetermined high probability condition. In other words, it is possible to preferentially select other devices that have high communication reliability and are close to the target device, thereby suppressing the number of data retransmissions due to communication failure and transferring data until reaching the target device. The number of times (the number of hops) can be suppressed, and the communication time and power consumption can be reduced.

As a fifth invention, the communication device of the fourth invention,
The selection means, when there is no other device that satisfies the high probability condition, selects the communication other device having the highest communication success probability as the next first hop destination,
A communication device may be configured.

  According to the fifth aspect, when there is no other device that satisfies the high probability condition, the other device having the highest communication success probability is selected as the next first hop destination. As a result, the number of data retransmissions due to communication failure can be suppressed, and the communication time and power consumption can be reduced.

As a sixth invention, the communication device of the first invention,
The selection means includes a calculation means for calculating a communication failure probability for the predetermined number of times in the past in the past for each other device registered in the first hop destination information based on the transmission history information, Based on the failure probability, select another device as the next first hop destination,
A communication device may be configured.

  According to the sixth aspect of the invention, the other device to be the next first hop destination is selected based on the communication failure probability for each other device calculated based on the transmission history information. As a result, for example, by dynamically selecting a communication device having a low communication failure probability, that is, a high communication reliability, the number of times of data retransmission due to communication failure is suppressed, thereby reducing communication time and power consumption. be able to.

An application example of a wireless communication system. An example of a routing table. Explanatory drawing of selection of a 1st hop destination. A specific example of selection of the first hop destination. A specific example of selection of the first hop destination. The function block diagram of a communication apparatus. The flowchart of a communication control process.

[System configuration]
The wireless communication system according to the present embodiment is an application of the present invention to a vehicle monitoring system that collects sensor data by sensors attached to each vehicle in a railway train formed by a plurality of vehicles.

  FIG. 1 is an application example of a wireless communication system 1 for a vehicle monitoring system. As shown in FIG. 1, the radio | wireless communications system 1 is provided with the some communication apparatus 20 mounted in each vehicle 10 of a train. The communication device 20 has a wireless communication function, and wireless communication between the communication devices 20 is possible. Further, the communication device 20 can perform wireless communication or wired communication with each sensor 30 attached to the vehicle 10 on which the device is mounted, and sensor data from each sensor 30 passes through the communication device 20. Then, for example, they are collected into a predetermined target device such as the communication device 20 mounted on the leading vehicle 10. Communication in the wireless communication system 1 is realized by multi-hop communication, and is a dynamic communication network that searches for a route to a target device for each communication.

[principle]
(A) Route Search In the wireless communication system 1, a route search at the time of communication is performed according to a route table stored in each communication device 20. FIG. 2 is an example of the route table 50. In FIG. 2, the route table 50-1 of the communication device 20-1 mounted on the leading vehicle 10 in the train of N cars (N ≧ 2) and the communication device mounted on the i-th vehicle 10-i from the beginning. 20-i route table 50-i. The routing table 50 stores, in correspondence with each other communication device that is the destination, a candidate for the communication device that is the first hop destination when performing communication with the other communication device as the target device. This route table 50 corresponds to the first hop destination information. The identification information is stored in order of the communication device candidates to be the first hop destination in the order closer to the target device.

  In the route search, in the route table 50, the first hop destination candidate associated with the destination communication device 20 as the target device is selected based on the transmission history stored in the communication device 20. The communication device 20 that is the hop destination is selected.

  FIG. 3 is a diagram illustrating selection of the first hop destination. In FIG. 3, the communication device 20-i mounted on the i-th vehicle 10-i from the head in the train of N cars is shown as an example. The communication device 20-i stores a route table 50 (route table 50-i in FIG. 2) destined for each of the other communication devices 1 to i-1, i + 1 to N, and the latest α times. The transmission history 60 which is data of success or failure (success and failure) of communication with the first hop destination communication device 20 is stored.

  The transmission history 60 records the success or failure of communication with other communication devices 20 that can be the first hop destination, that is, with each communication device 20 defined as a candidate for the first hop destination of any destination in the route table 50. Data. In FIG. 3, the transmission history 60 is data indicating success or failure of communication with each of the communication devices i-3 to i−1 and 1 + 1 to i + 3 determined as the first hop destination candidates in the route table 50. That is, the communication device 20 mounted on the vehicle 10 for three vehicles before and after the vehicle 10-i on which the communication device 20-i is mounted is set as a first hop destination candidate. Further, the success or failure of the communication performed with the communication device 20-1 of the leading vehicle as the target device, that is, the communication device 1- defined as the first hop destination candidate of the communication device 20-1 that is the destination in the route table 50. The success or failure of communication performed by using any one of 3 to i-1 as the first hop destination is shown as an example.

  Successful communication with respect to the number of times of communication for each communication device 20 that is a candidate for the first hop destination is added to the communication success / failure of the past α times as the transmission history 60 by adding only one success / failure of communication based on the route table 50. The communication success probability that is the ratio of the number of times is calculated. The route table 50 defines other communication devices 20 that can communicate with the own device as candidates for the first hop destination. That is, the communication device 20 determined as the first hop destination candidate in the route table 50 can communicate with its own device. For this reason, for the communication device 20 defined as the first hop destination in the route table 50, the communication success / failure regarded as a communication success (deemed success) is regarded as a communication success / failure based on the route table 50 (deemed communication success / failure). to add. If it is not actually selected as the first hop destination, the actual communication success probability becomes zero. Therefore, by adding the deemed communication success / failure (deemed success), the communication success probability is made non-zero.

  Then, based on the calculated communication success probability for each of the other communication devices 20, the next first hop destination communication device is selected. Specifically, among the communication devices 20 defined as candidates for the first hop destination of the communication device 20 as the target device in the route table 50, the communication success probability satisfies a predetermined high probability condition, and The nearest communication device 20 is selected as the next first hop destination communication device 20. If there is no communication device 20 whose communication success probability satisfies the high probability, the communication device 20 having the highest communication success probability is selected. The high probability condition is that it is equal to or higher than a predetermined threshold value β. The threshold value β can be arbitrarily set as a value in the range of 0 to 1 (0 ≦ β ≦ 1).

[Concrete example]
4 and 5 are specific examples of selection of the next first hop destination communication apparatus based on the transmission history 60. FIG. 4 and 5, the communication device 20-i mounted on the i-th vehicle 10-i from the head in the train of N cars is targeted, and the communication device 20-1 mounted on the head vehicle is the target device. The case where repeated communication is repeatedly performed is shown as an example. Further, in the route table 50 of the communication device 20-i, as the first hop destination candidates of the communication device 20-1 that is the target device, the communication devices i-3 and i-2 are arranged in order from the communication device 20-1. , I-1 are determined, and the first hop destination communication device 20 is selected from these. For this reason, FIGS. 4 and 5 show the success or failure of communication only for the communication devices i-1 to i-3 that are candidates for the first hop destination. Further, as the transmission history 60, communication success / failure for the past 10 times (α = 10) is stored. The communication success / failure based on the route table 50 (deemed communication success / failure) is successful (1) for all the communication devices i-1 to i-3, and this is fixed. Further, the threshold value β = 0.9.

  FIG. 4A shows the success or failure of each of the communication devices i-1 to i-3 at a certain time point t1. At this time t1, the communication success probabilities of the communication devices i-1 to i-3 are 2 / 3≈0.67, 6 / 7≈0.86, and 2 / 3≈0.67. Accordingly, the communication success probability of the communication devices i-1 to i-3 is less than the threshold β, and the communication device i-2 having the highest communication success probability is selected as the next first hop destination.

  FIG. 4B shows the communication devices i-1 to i-3 after the communication with the selected communication device i-2 at the time t1 and at the time t2 when the next communication is to be performed. The success or failure of each communication. As the transmission history 60, the oldest α success communication data (successful communication with the communication device i-3) at the time point t1 is deleted, and the communication success or failure (communication with the communication device i-2 selected at the time point t1). Success) is added as data on the success or failure of the previous communication. As a result, the communication success probabilities of the communication devices i-1 to i-3 are 2 / 3≈0.67, 7 / 8≈0.86, and 1/2 = 0.5, both of which are less than the threshold β. Therefore, the communication device i-2 having the highest communication success probability is selected as the next first hop destination.

  FIG. 4C shows the communication devices i-1 to i-3 after the communication with the selected communication device i-2 at the time t2, and at the time t3 when the next communication is to be performed. The success or failure of each communication. Similarly, the transmission success / failure data (communication failure with the communication device i-3) of the oldest α times before the time t2 is deleted as the transmission history 60, and communication with the communication device i-2 selected at the time t2 is performed. Success / failure (communication failure) is added as data on the success or failure of the previous communication. As a result, the communication success probabilities of the communication devices i-1 to i-3 are 2 / 3≈0.67, 7 / 9≈0.78, and 1/1 = 1. Here, the communication success probability of the communication device i-3 is equal to or higher than the threshold value β, but only the communication device i-3 is equal to or higher than the threshold value β, so that the communication device i is the next first hop destination. -3 is selected.

  FIG. 4D shows the communication devices i-1 to i after the communication with the communication device i-3 selected at the time t3, and at the time t4 when the next communication is to be performed. -3 is the success or failure of each communication. Similarly, the communication success / failure data (successful communication with the communication device i-2) of the oldest α times before the time t3 is deleted as the transmission history 60, and communication with the communication device i-3 selected at the time t3 is performed. Success / failure (communication success) is added as data on the success or failure of the previous communication. As a result, the communication success probabilities of the communication devices i-1 to i-3 are 2 / 3≈0.67, 6/8 = 0.75, and 2/2 = 1. Although the communication success probability of the communication device i-3 is equal to or higher than the threshold value β, only the communication device i-3 is equal to or higher than the threshold value β. Therefore, the communication device i-3 is the next first hop destination. Selected.

  Thus, for each communication with the other communication device 20 selected as the first hop destination, the communication success / failure data is newly added, and the oldest communication success / failure data is deleted and the transmission history 60 is updated. The next first hop destination communication device 20 is selected based on the communication success probability calculated from the updated transmission history 60.

  By the way, in the train, the route table 50 is updated with the increase / decrease of the vehicle (addition / disconnection, or both). In this case, the transmission history 60 is cleared and new transmission is performed. A history 60 is created. That is, the vehicle organization is changed due to the increase / decrease of the vehicle, and the combination and positional relationship of the communication devices 20 mounted on one train are changed.

  FIG. 5A shows the success or failure of each of the communication devices i-1 to i-3 at time t11 immediately after the new creation of the route table 50. At this time t11, no data is stored in the transmission history 60, and the communication success probability is calculated based only on the communication success / failure (deemed communication success / failure) based on the route table 50. That is, since the communication success probabilities of the communication devices i-1 to i-3 are all 1 = 1/1, both of which are equal to or greater than the threshold value β, the communication device i closest to the communication device 20-1 that is the target device. -3 is selected as the next first hop destination.

  FIG. 5B shows the success or failure of each of the communication devices i-1 to i-3 at the time t12 after the communication with the communication device i-3 is performed twice after the time t11. As the transmission history 60, data on the success or failure of communication with the communication device i-3 is stored. As a result, the communication success probabilities of the communication devices i-1 to i-3 are 1/1 = 1, 1/1 = 1, 2 / 3≈0.67. Of the communication devices i-1 and i-2 that are equal to or greater than the threshold β, the communication device i-2 that is closest to the communication device 20-1 that is the target device is selected as the next first hop destination.

  FIG. 5C shows the communication devices i-1 to i-3 after the communication with the selected communication device i-2 at the time t12 and at the time t13 when the next communication is to be performed. The success or failure of each communication. As the transmission history 60, communication success / failure data for a total of three times, that is, two communication success / failure data with the communication device i-3 and one communication success / failure data with the communication device i-2 are stored. . As a result, the communication success probability of each of the communication devices i-1 to i-3 is 1/1 = 1, 2/2 = 1, 2 / 3≈0.67. Of the communication devices i-1 and i-2 that are equal to or greater than the threshold β, the communication device i-2 that is closest to the communication device 20-1 that is the target device is selected as the next first hop destination.

  In this way, each time a communication device with another communication device 20 selected as the first hop destination is performed, the communication success / failure data is added to the transmission history 60. Then, α times (here, 10 times) communication is performed, and as shown in FIG. 5D, after the communication success / failure data for 10 times is stored as the transmission history 60, as shown in FIG. Every time a new communication is performed, the oldest communication success / failure data is deleted and new communication success / failure data is added to the transmission history 60.

  In this way, immediately after the new creation of the routing table 50, since the communication success / failure data is not stored in the transmission history 60, the communication device 20 closest to the target device is selected as the first hop destination. Thereafter, while the communication with the communication device 20 selected as the first hop destination is successful, the communication with the communication device 20 as the first hop destination is repeated, but if the communication fails, the communication device Accordingly, another communication device 20 with the next highest communication success probability or another communication device 20 that is next closest to the target device can be selected as the next first hop destination.

  Furthermore, when a plurality of communication times are performed, the communication device 20 with the highest communication success probability or the communication device 20 closest to the target device is selected as the first hop destination based on the past α transmission history 60 Can be done. Thus, by using the communication success / failure data for the past α times and the communication success / failure data based on the routing table 50, the communication success probability is high to some extent, that is, the communication reliability is high and close to the target device. Communication that dynamically selects the communication device 20 as the first hop destination can be realized.

[Function configuration]
FIG. 6 is a functional configuration diagram of the communication device 20. According to FIG. 6, the communication device 20 includes an operation unit 102, a display unit 104, a sound output unit 106, a wireless communication unit 108, a sensor data input unit 110, a processing unit 200, and a storage unit 300. It is a kind of computer control apparatus comprised.

  The operation unit 102 is an input device realized by an input device such as a touch panel or various switches, for example, and outputs an operation signal corresponding to an operation input by the administrator to the processing unit 200. The display unit 104 is a display device realized by, for example, an LCD (Liquid Crystal Display) or the like, and performs various displays according to display signals from the processing unit 200. The sound output unit 106 is an audio output device realized by a speaker or the like, for example, and outputs various sounds according to the audio signal from the processing unit 200. The wireless communication unit 108 is a wireless communication device realized by a wireless communication module or the like for performing wireless communication by multi-hop communication with another communication device 20.

  The sensor data input unit 110 is a wireless communication device or a wired communication device, and inputs sensor data from the sensor 30 attached to the vehicle 10 on which the communication device 20 is mounted. The sensor data input by the sensor data input unit 110 is accumulated and stored as a sensor data group 306.

  The processing unit 200 is an arithmetic unit realized by, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), and the like. The processing unit 200 stores programs, data, and the like stored in the storage unit 300. Based on this, an instruction and data transfer to each unit constituting the communication device 20 are performed, and the overall control of the communication device 20 is performed. Further, the processing unit 200 includes a transmission history update unit 202, a first hop destination selection unit 204, and a communication execution control unit 208 when classified as a functional configuration. These functional units may be realized by software by the processing unit 200 executing a program, or may be realized by a dedicated processor or circuit. In the present embodiment, the former will be described.

  The transmission history update unit 202 updates / manages communication success / failure data with the other communication devices 20 of the latest α times as the first hop destination as the transmission history 60. Specifically, every time the communication execution control unit 208 performs communication with the other communication device 20 as the first hop destination, old communication success / failure data exceeding the past α times is deleted, and the communication performed The success / failure is added as the latest communication success / failure data, and the transmission history 60 is updated. When the routing table 50 is updated, the transmission history 60 up to that point is cleared, and the communication device 20 defined as a candidate for the first hop destination of any destination in the updated routing table 50. Update the transmission history for.

  The first hop destination selection unit 204 includes a communication success probability calculation unit 206, and the next first hop destination is selected from among the communication devices 20 defined as candidates for the first hop destination of the target device in the route table 50. The communication device 20 is selected.

  The communication success probability calculation unit 206 calculates a communication success probability for each communication device 20 based on the transmission history 60. That is, for each communication device 20 defined as a first hop destination candidate in the route table 50, based on the past communication success / failure stored in the transmission history 60 and the communication success / failure defined in the route table 50. In addition, the ratio of the number of successful communications to the number of communications (which can also be called the number of trials) is calculated as the communication success probability (see FIG. 3).

  Then, the first hop destination selection unit 204 selects the communication device 20 as the next first hop destination based on the communication success probability for each communication device calculated by the communication success probability calculation unit 206. That is, among the communication devices 20 defined as candidates for the first hop destination of the target device in the route table 50, a communication device 20 having a communication success probability equal to or higher than the predetermined threshold β and closest to the target device. , Select as first hop destination. When there is no communication device 20 having a communication success probability equal to or higher than the predetermined threshold β, the communication device 20 having the highest communication success probability is selected as the first hop destination.

  The perspective order, which is the degree of proximity (or distance) between each communication device including its own device and the target device, can be determined by the connection information 304. The connection information 304 stores identification information of a communication device mounted on the vehicle in association with the connection order of the vehicles constituting the train.

  The communication execution control unit 208 transmits the data of its own device such as the sensor data group 306 to the other communication device 20 selected as the first hop destination by the first hop destination selection unit 204, or from the other communication device 20 It controls communications such as receiving data with its own device as the first hop destination.

  The storage unit 300 is a storage device realized by, for example, a hard disk, a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and a system program for the processing unit 200 to control the communication device 20 in an integrated manner, Stores programs, data, and the like for realizing various functions, and is used as a work area for the processing unit 200, and temporarily stores calculation results and the like executed by the processing unit 200 according to the various programs. The storage unit 300 stores a communication control program 302, connection information 304, a route table 50, a transmission history 60, and a sensor data group 306.

[Process flow]
FIG. 7 is a flowchart for explaining the communication control process. This process is realized by the processing unit 200 executing the communication control program 302.

  First, the transmission history update unit 202 determines whether or not the routing table 50 has been updated, and if updated (step S1: YES), clears the previous transmission history 60, and in the updated routing table 50 The transmission history 60 for the communication device 20 determined as the first hop destination candidate of the destination is updated (step S3).

  Next, it is determined whether the transmission timing of the data of the own device such as the sensor data group 306, which is determined in advance, has arrived. If the data transmission timing of the own device has not arrived (step S5: NO), it is further determined whether or not data has been received from another communication device 20 by communication with the own device as the first hop destination. Then, when the data transmission timing of the own device has arrived (step S5: YES) or when data has been received from another device (step S7: YES), the communication success probability calculation unit 206 refers to the route table 50. Then, the communication device 20 (hereinafter referred to as “candidate device”) defined as the first hop destination candidate of the target device is determined (step S9), and each of these candidate devices is determined based on the transmission history 60. The communication success probability is calculated (step S11).

  Next, the first hop destination selection unit 204 determines whether there is a candidate device with a communication success probability equal to or higher than the predetermined threshold β (step S13: YES), and if there is a candidate device with a communication success probability equal to or higher than the threshold β. Among these, the candidate device closest to the target device is selected as the next first hop destination (step S15). If there is no candidate device with a communication success probability equal to or higher than the threshold β (step S13: NO), the candidate device with the highest communication success probability is selected as the next first hop destination (step S17). Thereafter, the communication execution control unit 208 executes communication with the candidate device selected as the first hop destination (step S19).

  Then, the transmission history update unit 202 updates the transmission history 60 by determining whether the communication has been successful. That is, if the communication is successful (step S21: NO), “success” is added as the communication success / failure of the communication device 20 that has performed the communication, and the transmission history 60 is updated (step S23). (Step S21: NO), “failure” is added as the success or failure of communication of the communication device 20 that has performed communication, and the transmission history 60 is updated (Step S25). If the above process is performed, it will return to step S1 and the same process will be repeated.

[Function and effect]
Thus, according to the wireless communication system 1 of the present embodiment, the communication device 20 with high communication reliability is preferentially selected while minimizing the number of transfers until reaching the target device by multi-hop communication. Route search can be realized. That is, the communication device 20 stores a transmission history 60 in which the communication success / failure of the first hop for the latest α times is recorded for each of the other communication devices 20. Based on the communication success probability for each other communication device 20 calculated by adding one communication success to the past communication success / failure recorded in the transmission history 60 as communication success / failure based on the route table 50. The first hop destination communication device 20 is selected. That is, among communication devices 20 defined as candidates for the first hop destination of the target device in the route table 50, a communication device 20 having a communication success probability equal to or higher than the predetermined threshold β and closest to the target device is selected. To do. If there is no communication device having a communication success probability equal to or higher than the threshold β, the communication device 20 having the highest communication success probability is selected. As a result, the number of data retransmissions due to communication failure can be suppressed, and the number of transfers (the number of hops) until reaching the target device can be suppressed, thereby shortening the communication time and power consumption.

  In addition, since the radio wave environment can change as the train travels, it is possible to perform communication via an appropriate communication device 20 that is presumed to be more reliable by not using old communication success / failure data. It becomes.

  Further, by adding the success or failure of communication for one time based on the route table 50 (deemed success), even if communication according to the latest route table 50 is not performed, the communication success probability for each communication device 20 Can be calculated, and the communication device 20 of the next first hop destination can be appropriately selected.

[Modification]
It should be noted that embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can of course be changed as appropriate without departing from the spirit of the present invention.

(A) Number of communication times α recorded in transmission history 60
The communication frequency α for recording the success / failure of communication in the transmission history 60 may be changed according to the radio wave environment, for example. That is, the communication frequency α is set so that past communication success or failure in a radio wave environment similar to the current time is recorded in the transmission history. Specifically, areas of a certain size (several kilometers to several tens of kilometers) such as mountainous areas, tunnels, urban areas, and plain areas are roughly defined, and for each area, Based on the area size, the train traveling speed, the communication frequency of the communication device 20, and the like, the standard number of communication by the communication device 20 when passing through this area is obtained. And based on the standard communication frequency corresponding to the area according to the current traveling position of the train, the communication frequency α for recording communication success / failure is set in the transmission history.

(B) Deemed Success Number In the above-described embodiment, when the communication success probability for each communication device is calculated, the communication success / failure based on the route table 50 is compared with the communication success / failure for the latest α times stored in the transmission history 60. As described above, the communication success for one time, that is, the success without only one time is added, but it may be zero times instead of one time, or may be two times or more.

(C) Communication failure probability It is good also as calculating the communication failure probability which is not a communication success probability but the ratio of the communication failure frequency with respect to the communication frequency. In this case, the communication device 20 whose communication failure probability is equal to or less than the predetermined threshold γ and closest to the target device can be selected as the next first hop destination. If there is no communication device having a threshold value γ or less, the communication device 20 with the lowest communication failure probability can be selected.

(D) System to be applied In the above-described embodiment, the case where the present invention is applied to a vehicle monitoring system has been described. However, for example, in a monitoring system configured by attaching a sensor to another monitoring object such as a bridge or a tunnel. Is equally applicable.

DESCRIPTION OF SYMBOLS 1 Wireless communication system 20 Communication apparatus 102 Operation part, 104 Display part, 106 Sound output part 108 Wireless communication part, 10 Sensor data input part 200 Processing part 202 Transmission history update part 204 1st hop destination selection part, 206 Communication success probability calculation Unit 208 Communication execution control unit 300 Storage unit 302 Communication control program 304 Connection information, 306 Sensor data group 50 Route table, 60 Transmission history 10 Vehicle, 30 Sensor

Claims (4)

A communication device constituting a wireless communication system that performs multi-hop communication in which given data is transmitted to a given target device by multiple hop communications,
Storage means for storing first hop destination information in which candidates for other communication devices (hereinafter referred to as “other devices”) as first hop communication (hereinafter referred to as “first hop”) are registered;
Recording control means for performing update control of transmission history information in which the communication success or failure of the first hop for the most recent predetermined number of times in the past is recorded for each other device registered in the first hop destination information each time the first hop is performed; ,
Based on the transmission history information, selection means for selecting another device as the next first hop destination;
Equipped with a,
Based on the transmission history information, the selection unit adds the number of successes that the predetermined number of first hops are considered to be successful for each of the other devices registered in the first hop destination information, and Having calculation means for calculating a communication success probability for a predetermined number of times, and selecting another device as the next first hop destination based on the communication success probability;
Communication device. The storage means stores information capable of determining a perspective order to each target device of each other device registered in the first hop destination information,
The selection means sets another device that satisfies the predetermined high probability of communication success as the next first hop destination, and when there are a plurality of other devices that satisfy the high probability, Select the device as the next first hop destination,
The communication apparatus according to claim 1 . The selection means selects the other device having the highest communication success probability as the next first hop destination when there is no other device satisfying the high probability condition.
The communication apparatus according to claim 2 . A communication control method for a communication device constituting a wireless communication system for performing multi-hop communication in which given data is transmitted to a given target device by multiple hop communication,
The communication device stores first hop destination information in which candidates for other communication devices (hereinafter referred to as “other devices”) as first hop communication (hereinafter referred to as “first hop”) are registered,
Each time the first hop is performed, update control of transmission history information in which the communication success or failure of the first hop for the predetermined number of times in the past is recorded for each other device registered in the first hop destination information;
Based on the transmission history information, for each other device registered in the first hop destination information, after adding a deemed number of successful times that a predetermined number of first hops are considered to be successful, Calculating the communication success probability of
Selecting another device as the next first hop destination based on the communication success probability ;
Including a communication control method.

Images