JP2011066812A - Communication system and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system and a method capable of improving the reliability of transmitting and receiving information according to a communication environment for each path between communication devices and improving the quality of communication, in communication between and among a plurality of communication devices which transmit and receive information for traffic control. <P>SOLUTION: In communication between and among a plurality of communication devices in a wireless communication system by time division multiplex communication, each communication device determines the number of time slots assigned to the transmission and reception of the same data in the communication path according to the communication environment in a communication path between the device and a communication device as a communication counterpart. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to wireless communication between traffic equipment on a road or communication devices installed in the vicinity of the traffic equipment, and in particular, improves the reliability of information transmission / reception according to the communication environment for each route between the communication devices. The present invention relates to a communication system and a communication method that can improve communication quality.

  Traffic signal control is planarly controlled by traffic lights on a plurality of intersections. It is necessary to send and receive traffic signal control information between the signal controllers of each traffic light, between the vehicle detectors, and the central device of the control center. Conventionally, the signal controller, the vehicle detector, and the control center are configured to transmit and receive information by wire. FIG. 14 is an upper perspective view of a road showing an example in which traffic signal control information is transmitted and received between devices installed in the vicinity of traffic facilities on the road.

  In FIG. 14, 91 is a communication device installed in the vicinity of the signal controller, and 92 is a communication device installed in the vehicle detector. A sensing result obtained by the vehicle sensor is transmitted from the communication device 92 to another communication device 91. In order to perform signal control in cooperation with the signal controller, information on the detection result is transmitted from the vehicle detector to the communication device 91 from the communication device 92 and further to a device for determining signal control parameters or a traffic control center. . At this time, conventionally, as shown by the broken line in FIG. 14, the communication devices 91 and 92 and other devices are connected by the communication line 90, and the information from the communication device 92 installed in the vehicle detector is the communication device. 91, and information such as signal control parameters is transmitted and received between the communication devices 91.

  On the other hand, for the purpose of reducing the cost of installation work and facilitating maintenance, a transition is being made so that communication between devices for traffic control is performed wirelessly instead of wired (Patent Document 1). However, there are some problems in performing wireless communication using a 2.4 GHz band frequency used in a wireless LAN. If there are base stations that use the same frequency, or if there are microwave ovens or high-frequency heating medical devices in buildings along the road, these will emit radio waves in the 2.4 GHz band. Communication quality deteriorates.

  Thus, in wireless communication between devices for traffic control, there is an interference wave (jamming wave) because it is outdoors. In particular, urban areas tend to have many interference waves. Moreover, since a traffic road is not necessarily a straight line, as shown in FIG. 14, there is an obstacle such as a building in which communication apparatuses are linear, which greatly affects communication quality. In the current system using wireless communication, an optimum communication frequency is set in advance in each communication device manually.

JP 2008-205765 A

  However, traffic equipment such as vehicle detectors and signal controllers or communication devices installed in the vicinity thereof may be several tens to several hundreds meters apart even when adjacent to each other. Therefore, the communication environment may change depending on the day of the week or the time zone in each section. The situation changes both spatially and temporally, for example, a communication error occurs only in a certain section and the communication error disappears depending on the time zone. Furthermore, since information transmitted / received between devices for traffic control is information for traffic signal control, real-time performance is required. When a failure occurs in communication between devices, there is a problem such as inducing a traffic jam and causing a traffic trouble.

  In the conventional method of the wireless LAN, communication is performed in units of frames including a time slot that is basically allocated once for transmission / reception of each communication device. When a communication error such as reception failure in any communication device occurs, it cannot be received until the next frame unit. In particular, traffic signal control information transmitted and received between signal control devices may be delayed in the conventional method, although real-time characteristics are required.

  The present invention has been made in view of such circumstances, and in communication between a plurality of communication apparatuses that transmit and receive information for traffic control, the certainty of transmission and reception according to the individual communication environment for each path between the communication apparatuses. It is an object to provide a communication system and a communication method that can improve communication quality and communication quality.

  The communication system according to the first aspect of the present invention includes a traffic facility provided at a plurality of points on the road or a plurality of communication devices installed in the vicinity of the traffic facility, and each communication device performs a wireless communication. And measuring means for measuring a communication environment by wireless communication, and the communication means communicates in a time slot assigned to itself in a frame unit including a plurality of time slots assigned to communication between the communication devices. A communication system configured to perform time division multiplex communication, comprising: a determining unit that determines the number of time slots allocated to transmission of the same data in the frame according to a measured communication environment. Features.

  A communication system according to a second invention includes, in the first invention, three or more communication devices, and each communication device measures a communication environment for each communication path between the communication devices by the measuring means. The determining means determines the number of time slots allocated to transmission of the same data on the communication path according to the communication environment for each communication path.

  In the communication system according to the third invention, the determining means in the second invention judges the quality of the communication environment measured for each communication path, and transmits the same data on the communication path judged to be defective based on a predetermined standard The decision is made to increase the number of time slots allocated to.

  In the communication system according to a fourth aspect of the invention, when the communication environment is determined to be bad, the determining means in the third aspect of the invention is based on the number of received packet losses, the received signal level, or the error rate, The decision is made to increase the number of time slots more.

  In the communication system according to the fifth invention, the determining means in the third or fourth invention increases the number of time slots allocated to transmission of the same data in one communication path, and then communicates in the one communication path. When the environment is judged to be good for a predetermined time or more, a decision is made to reduce the number of time slots.

  The communication system according to a sixth aspect of the present invention is the communication system according to any one of the first to fifth aspects, wherein the determination means determines that the number of time slots allocated for transmission of the same data is plural within a frame. The slots are allocated so as to be continuous.

The communication system according to a seventh aspect of the present invention is the communication system according to any one of the first to fifth aspects, wherein the determination means determines that the number of time slots allocated to transmission of the same data in the frame is plural. The slots are allocated so that other time slots can be included between the slots.

  In a communication system according to an eighth invention, the determining means in the first to seventh inventions transmits the same data based on the number of empty time slots in the frame and the number of time slots allocated to another communication path. The number of time slots to be allocated is determined.

  A communication method according to a ninth aspect of the present invention includes a traffic facility provided at a plurality of points on a road or a plurality of communication devices installed in the vicinity of the traffic facility, and each communication device performs a wireless communication. And measuring means for measuring a communication environment by wireless communication, wherein the communication means performs communication in a time slot assigned to itself in a frame unit including a plurality of time slots assigned to communication between the communication devices. Each communication apparatus measures a communication environment between itself and a communication partner, and determines the number of time slots allocated to transmission of the same data in the frame according to the measurement result. Each communication device performs communication according to a time slot assigned based on the determined number.

  In the first invention and the ninth invention, a traffic facility including a signal controller, a vehicle detector, a signal controller, etc. at each point on the road or a plurality of communication devices fixedly installed in the vicinity thereof relates to traffic signal control. When information is communicated wirelessly by time division multiplex communication, the number of time slots assigned to transmission of the same data in a frame is determined according to the wireless communication environment between communication devices. That is, the number of transmissions is determined by increasing / decreasing depending on the quality of the communication environment and the presence / absence of a communication error. Thereby, according to the individual communication environment for every path | route between communication apparatuses, since the reliability of transmission / reception can be improved, it is possible to improve communication quality and to perform stable wireless communication.

  In the second invention, for each of two or more communication paths between a plurality of communication apparatuses and at least three or more communication apparatuses, the number of transmissions of the same information in the frame is individually determined according to the communication environment in each communication path. To be determined. Therefore, the number of transmissions of information transmitted through the different paths may be different for different communication paths. This improves the certainty of transmission and reception, for example, information transmitted on a route determined to be defective based on a predetermined standard is transmitted multiple times even if it is the same information.

  In the third invention, the quality of the communication environment for each communication path between the communication devices is determined, and the number of time slots in the frame allocated to the transmission of the same data in the communication path determined to be poor is increased. . Specifically, in a communication path that is highly likely to be affected by interference waves based on information indicating communication quality, such as communication error, for example, the number of received packets (loss), the signal level of wireless communication, or the error rate. The number of transmissions of the same data within the frame is increased. This improves the certainty of data transmission / reception.

  In the fourth aspect of the invention, the quality of the communication environment for each communication path between the communication devices is determined, and the number of transmissions is determined to increase as the degree of the failure of the communication environment of the communication path increases. Specifically, the increase in the number of transmissions increases according to the comparison result with a reference value given in advance to numerical information indicating communication quality such as the number of received packet loss, radio communication signal level, or error rate. . This improves the certainty of data transmission / reception.

In the fifth aspect of the present invention, after the number of time slots in a frame allocated for transmission of the same data in the communication environment that has been determined to be poor, the communication environment of the communication path is determined to be good for a predetermined time or more. If done, it will be reduced. As a result, it is possible to avoid a situation in which the number of times of transmission on the communication path once determined to be poor is constant. It is possible to improve the certainty of transmission / reception in each communication path according to the communication environment that can vary depending on the time zone and day of the week in each communication path.

  In the sixth aspect of the present invention, when there are a plurality of time slots assigned to the transmission of the same data within the frame, the same data is continuously transmitted within the frame. Depending on the communication environment, the certainty of successful reception may be improved.

  In the seventh invention, when there are a plurality of time slots assigned to the transmission of the same data in the frame, transmission / reception in other paths or empty time slots are included between the plurality of time slots. As a result, an interval is provided between time slots assigned to transmission of the same data within the frame. Depending on the communication environment, when transmission is performed at non-continuous timing, there is a possibility that the certainty of successful reception is improved.

  In the eighth invention, the number to be increased is determined according to the number of empty time slots included in the frame or the number of other communication paths in which the number of time slots may increase. For example, with the number of empty time slots included in the frame as the upper limit, the number obtained by subtracting the number of other communication paths from the upper limit is increased so that the number of transmissions can be increased one by one in other communication paths. When increasing the number of time slots assigned to a communication path determined to have a bad communication environment, if all available time slots are used, the number of time slots assigned to other communication paths cannot be increased. obtain. However, according to the present invention, it is possible to avoid a situation in which the number of time slots corresponding to a communication path that is determined to have a poor communication environment is unnecessarily increased to cause other problems.

  According to the present invention, in communication between communication devices that transmit and receive information for traffic control, the reliability of transmission and reception can be improved according to the individual communication environment for each route between communication devices. Improved and stable wireless communication can be performed.

  Communication devices installed in or near traffic facilities that transmit and receive information related to traffic signal control may be several tens to hundreds of tens of meters and several hundred meters apart even when adjacent to each other. May be different. In the case of the present invention, when an interference occurs in some communication paths and an error occurs, the same data can be transmitted at a number of times suitable for the communication environment of the path, so that stable wireless communication is realized. It is possible to improve the reliability of transmission / reception of information relating to traffic signal control.

1 is an upper perspective view schematically showing a traffic signal control system in Embodiment 1. FIG. 3 is a block diagram showing an internal configuration of a communication device that constitutes the traffic signal control system in Embodiment 1. FIG. It is explanatory drawing which shows typically the time slot of the time division multiplex communication by a communication apparatus. FIG. 3 is an explanatory diagram illustrating an example of time slots assigned in advance to the communication apparatuses that are the master station, the slave station 1, the slave station 2, the slave station 3, and the slave station 4 in the first embodiment. 3 is a flowchart illustrating an example of processing in which a communication device that is a master station in Embodiment 1 determines the number of transmissions and instructs slave stations 1 to 4; 3 is a flowchart illustrating an example of details of a transmission count determination process by a communication device of a main station in the first embodiment. 6 is an explanatory diagram illustrating an example in which the number of transmissions is changed when an interfering wave exists in the communication path between the master station and the slave station 2 in Embodiment 1. FIG. 6 is an explanatory diagram illustrating another example of the number of transmissions that is changed when an interfering wave exists on the communication path between the master station and the slave station 2 in Embodiment 1. FIG. 6 is an explanatory diagram illustrating another example of the number of transmissions that is changed when an interfering wave exists on the communication path between the master station and the slave station 2 in Embodiment 1. FIG. 4 is a flowchart illustrating an example of a processing procedure including processing performed when a communication environment by a communication device that is a main station in Embodiment 1 returns to a favorable state. 7 is a flowchart illustrating another example of details of a transmission count determination process performed by a main station communication device according to the first embodiment. 10 is a flowchart illustrating an example of a procedure of a transmission frequency determination process and a time slot allocation determination process performed by a communication apparatus that is a main station in the second embodiment. In Embodiment 2, it is explanatory drawing which shows the example in which the frequency | count of transmission is changed when the error occurs frequently in communication from the master station to the slave station. It is an upper perspective view of a road showing an example in which traffic signal control information is transmitted and received between devices installed in the vicinity of traffic equipment on a road.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. In the following embodiments, an example in which the communication system according to the present invention is applied to communication between devices related to traffic signal control will be described.

(Embodiment 1)
FIG. 1 is an upper perspective view schematically showing the traffic signal control system in the first embodiment. The traffic signal control system according to the first embodiment is installed in the vicinity of a signal controller on the road, and includes a communication device 1 and communication devices 2 and 2 that transmit and receive signal control information used by the signal controller, an optical beacon, and the like. It includes communication devices 3 and 3 that are installed in a vehicle sensor and transmit / receive information used for signal control including a sensing result.

  In the first embodiment, the communication apparatus 1 operates as a master station, the communication apparatuses 2 and 2 operate as slave stations 1 and 2, and the communication apparatuses 3 and 3 operate as slave stations 3 and 4, respectively. The communication device 1 that is the master station and the communication devices 2, 2, 3, and 3 that are the slave stations 1 to 4 communicate with each other wirelessly.

  Information transmitted / received between the communication devices 1, 2, 3 includes signal control execution information indicating a history of operation of each signal controller, and signal control command information which is an instruction regarding display of a signal lamp color transmitted from the traffic control center. and so on. In addition, there are vehicle information transmitted from the vehicle detector to the traffic control center, VICS information provided from the traffic control center to the vehicle via an optical beacon, and the like. In addition, information on the vehicle number read by the vehicle number reader may be transmitted / received by any one of the communication devices 1, 2, 3 or other similar communication device (not shown).

  The wireless communication between the communication apparatuses 1, 2 and 3 uses a 2.4 GHz band called an ISM band (Industrial Scientific Medical Band). Use the same frequency band as the frequency for wireless LAN devices based on IEEE802.11b / g (2.4 GHz band: 2.4000 to 2.4835 HGz), and use any of the communication frequency channels divided into 13 or 14 channels. Do it. Here, a device conforming to “ARIB STD-T66 (second generation low power data communication system / wireless LAN system standard)” is also used for 13 channels of the frequency band, “RCR STD-33 (low power data communication system / wireless). A device conforming to the “LAN system standard”) can also use the 14-channel frequency of the frequency band. Therefore, when these wireless LAN devices exist in the vicinity of the communication devices 1, 2, 3, it is difficult to avoid radio wave interference.

FIG. 2 is a block diagram showing an internal configuration of the communication devices 1, 2, and 3 constituting the traffic signal control system in the first embodiment. The communication devices 1, 2, and 3 have basically the same internal configuration. The communication devices 2 and 3 are denoted by reference numerals corresponding to those of the communication device 1 and detailed description of the internal configuration is omitted.

The communication device 1 includes a control unit 10, a storage unit 11, and a wireless communication unit 12. The control unit 10 uses a CPU (Central Processing Unit). The control unit 10 is configured to execute various communication control processes described below based on the computer program stored in the storage unit 11. The storage unit 11 has an EEPROM (Electrically Erasable and Programmable).
In addition to a computer program executed by the control unit 10, information used for control by the control unit 10 is stored so that it can be referred to.

  The wireless communication unit 12 includes a frequency channel selection circuit in addition to an antenna, a transmission / reception circuit, a modulation / demodulation circuit, and a modulation / spreading / encoding processing circuit for transmitting and receiving time division multiplex communication radio waves (none of which are shown). ). The wireless communication unit 12 selects any channel from 1CH to 14CH in the frequency band for wireless LAN and realizes communication with other communication devices.

  The control unit 10 has a function of performing wireless communication environment measurement, specifically noise measurement, using the wireless communication unit 12. Specifically, the control unit 10 measures a reception level or a noise level in a communication frequency channel selected by the wireless communication unit 12. Further, the control unit 10 transmits a signal of the same standard as the communication by the wireless communication unit 12 even though the wireless communication unit 12 should not have transmitted a signal from any of the communication devices 1, 2, 3. Measure the presence and strength of jamming radio waves depending on whether or not they are received. Note that the wireless communication environment measurement may be configured to use a circuit capable of performing wireless communication environment measurement based on an instruction.

  As described above, the communication devices 1, 2, and 3 are used for traffic signal control by hardware such as FPGA, ASIC, DPU, etc., in addition to the configuration in which the CPU executes the computer program to realize each function in software. A configuration for realizing wireless communication of information may be employed.

  The communication devices 1, 2, 3 configured in this way perform transmission / reception only in the time slot allocated in advance between the respective stations by time division multiplex communication. Basic allocation of time slots is preset in each communication device.

  FIG. 3 is an explanatory diagram schematically showing a time slot of time division multiplex communication by the communication devices 1, 2, 3. The communication devices 1, 2, and 3 transmit and receive information in units of time slots of 4 milliseconds, for example. A plurality of time slots form one frame. In the first embodiment, each frame includes a “maintenance slot” at the beginning of each frame, and each of the communication devices 1, 2, and 3 has information indicating a communication frequency channel used for communication in the “maintenance slot”, a response to the instruction, and the like. Send and receive maintenance information for communication. Note that the first “maintenance slot” includes a synchronization signal for frame synchronization. In the first synchronization “maintenance slot”, the control unit 10 of the communication device 1 that is the master station starts transmission, and the communication devices 2 and 3 that are the slave stations 1 to 4 The head of the frame is recognized by the synchronization signal of the “maintenance slot”.

  Also, as shown in FIG. 3, after the “maintenance slot”, time slots are assigned to the respective communications from the master station to the slave stations 1 to 4 or from the slave stations 1 to 4 to the master station. Communication is performed in the time slot assigned to. Time slot assignment is set in advance in each of the communication devices 1, 2, and 3. Specifically, it is stored in advance in the storage unit 11 and the like, and the control unit 10 can determine its own communication timing with reference to it.

FIG. 4 is an explanatory diagram illustrating an example of time slots allocated in advance to the communication apparatuses 1, 2, and 3 that are the master station and slave stations 1 to 4 in the first embodiment. Each rectangle represents a time slot, and represents a “maintenance slot” in which maintenance information is transmitted and received by hatching. FIG. 4 shows which of the master station and the slave stations 1 to 4 becomes a sender and a receiver below each slot. In FIG. 4, “S” means transmission by the corresponding device, and “R” means reception by the corresponding device.

  In the first embodiment, as shown in FIG. 2, the communication devices 1, 2, 3 are called between the communication device 1 of the master station and each of the communication devices 2, 2, 3, 3 of the slave stations 1 to 4. Communication is performed via four communication paths. The communication devices 1, 2 and 3 are basically set to transmit and receive information used for signal control acquired from traffic equipment such as signal controllers or vehicle detectors once a frame. is there.

  In the example shown in FIG. 4, the first to fourth time slots of the frame k are allocated as “maintenance slots”. In the time slot, the communication device 1 that is the master station transmits (S), and the communication devices 2 and 3 that are the slave stations 1 to 4 receive (R). The fifth to eighth time slots of frame k are also assigned as “maintenance slots”. In the time slot, the communication devices 2 and 3 of the slave stations 1 to 4 transmit responses to the master station (S) in response to maintenance information from the master station in the “maintenance slot”, and the communication device 1 serving as the master station. Receive (R).

  As shown in FIG. 4, one frame (frame k) is transmitted / received in the upstream / downstream of the “maintenance slot” and the information time slot between the master station and the slave stations 1 to 4 and the noise measurement period. Consists of assigned time slots. Basically, each of the “maintenance slot” and the information time slot is assigned at least one to all the upstream and downstream communications in the four communication paths between the master station and the slave stations 1 to 4. Therefore, the frame includes at least 16 time slots.

  In addition, as shown in FIG. 4, the allocation of time slots is predetermined. In the example of FIG. 4, in the first eight “maintenance slots”, maintenance information including instruction information for instructing the number of transmissions is transmitted from the master station to each of the slave stations 1 to 4 as described later. In the “maintenance slot”, the communication devices 2 and 3 of the slave stations 1 to 4 that have received the maintenance information including the instruction information from the communication device 1 as the master station are informed by the number of transmissions indicated by the received instruction information. Can be recognized. With a total of eight “maintenance slots” for uplink and downlink corresponding to the four communication paths, transmission / reception of maintenance information related to specific communication control such as instructing the number of times of transmission of the same information in the frame is completed. In this way, communication of maintenance information such as information related to the change of the communication frequency channel and a response to it can be completed within one frame.

  As shown in FIG. 4, in the first embodiment, after completion of transmission / reception of the maintenance information in the “maintenance slot”, in the time slots “9” to “12”, from the communication device 1 as the master station to the slave stations 1 to 4. State information indicating a control state in a signal controller in the vicinity of each communication device 2, 3, signal control command information from a traffic control center, control parameters, and the like are transmitted to a certain communication device 2, 3.

  Thereafter, in the time slots “13” and “14”, the communication devices 1, 2, and 3 each perform wireless reception environment measurement (noise measurement). After the noise measurement, in the time slots “15” to “18”, the signal controllers or vehicles in the vicinity of the communication devices 2 and 3 from the communication devices 2 and 3 that are the slave stations 1 to 4 respectively. Status information indicating the control status of the sensor, vehicle detection results, noise measurement results (communication error rate), and the like are transmitted and received.

Basically, each of the communication devices 1, 2, and 3 performs wireless communication with maintenance information based on the assigned time slots as shown in FIG. However, if an error has occurred in wireless communication in any communication path due to noise measurement results, the reliability of reception is increased by increasing the number of times the same data is transmitted in the communication path by the process described below. Improve.

  In the first embodiment, communication between the communication device 1 that is the master station and the communication devices 2 and 3 that are the slave stations 1 to 4 is performed in a one-to-many relationship between the master station and the slave stations 1 to 4. It is. Therefore, the communication device 1 as the master station determines whether or not an error has occurred in the wireless communication with each of the slave stations 1 to 4, determines the number of transmissions of the same data within the same frame according to the presence or absence, and It is set as the structure which directs to ~ 4. However, the present invention is not limited to this, and other communication devices that determine signal control parameters can be connected to the communication device 1 that is the main station, and the communication device determines the number of transmissions and transmits it to the communication device 1. You may do it.

  FIG. 5 is a flowchart illustrating an example of processing in which the communication apparatus 1 as the master station in the first embodiment determines the number of transmissions and instructs the slave stations 1 to 4.

  The communication device 1 starts transmission / reception of maintenance information in the “maintenance slot” using the wireless communication unit 12 by the control unit 10 (step S101). Transmission / reception is started based on the synchronization signal of the first “maintenance slot” of the frame from the communication device 1 of the main station. At this time, in the other communication apparatuses 2 and 3, the control units 20 and 30 start transmission / reception in the “maintenance slot” using the wireless communication units 22 and 32.

  The communication device 1 determines whether or not it is necessary to change the number of transmissions when the control unit 10 communicates with each of the slave stations 1 to 4 in the “maintenance slot” (step S102). Whether or not it is necessary to change the number of transmissions in step S102 is determined based on the results of processing in steps S108 to S112 described later.

  If it is determined in step S102 that the change is not necessary (S102: NO), the communication device 1 continues to transmit / receive maintenance information in the “maintenance slot” and proceeds to the next step S107.

  If the communication device 1 determines that the number of transmissions needs to be changed in communication with any of the slave stations 1 to 4 in step S102 (S102: YES), the communication device 1 stores the information including the same data with the slave station determined to be necessary. Processing for determining the number of transmissions is performed (step S103). Details of the process of determining the number of transmissions will be described later.

  The communication device 1 transmits the number of transmissions determined in step S103, including information on the number of transmissions instructed to the slave station that is the counterpart of the communication, in the maintenance information (step S104). At this time, since the communication devices 1, 2, and 3 automatically determine the allocation of the time slot in the frame according to the change in the number of transmissions, the communication devices 2, 3 that are the slave stations 1 to 4 are also connected to the slave station 2. It is desirable to send a notification of the change in the number of transmissions in the maintenance information.

  The communication device 1 determines whether or not a response to the transmitted transmission count instruction information has been received in the “maintenance slot” after transmission of the maintenance information from itself (step S105). At this time, it may be determined whether or not a response is received only from the slave station of the communication partner whose number of transmissions is to be changed. However, since the change in the number of transmissions relates to the entire allocation of time slots in the frame, it is desirable to determine whether or not responses have been received from all the communication devices 2 and 3 of the slave stations 1 to 4. If the communication device 1 determines that no response has been received in the “maintenance slot” in the frame (S105: NO), the communication device 1 stops changing the number of transmissions and proceeds directly to step S107.

When the communication device 1 determines that a response has been received in the “maintenance slot” in the frame (S105: YES), it changes the subsequent number of transmissions of information relating to traffic signal control to the determined number of transmissions (step S106). . At this time, if the communication devices 2 and 3 of the slave stations 1 to 4 also receive an instruction or notification for changing the number of transmissions in the “maintenance slot” and return a response, the corresponding slave station returns the number of transmissions (and The number of receptions) is changed, and other slave stations automatically change the allocation of time slots accordingly.

  Note that the communication devices 1, 2, and 3 recognize the time slot assigned to their own communication when the number of transmissions is changed. Specifically, in principle, information from the master station is in ascending order from slave station 1, slave station 2, slave station 3, slave station 4, and information from slave stations 1-4 to the master station is slave station 4, slave station 3, slave station 2, The communication devices 1, 2, and 3 recognize that the time slots are assigned in descending order from the slave station 1. Then, it is assumed that continuous transmission is performed on the communication path in which the number of transmissions is determined to be plural. The slave stations 1 to 4 can recognize the change in the allocation of the time slot based on the maintenance information indicating the number of transmissions from the master station, respectively, so that the time slot allocated to itself after the change can be recognized without error. .

  Next, the communication device 1 starts transmission / reception of information according to the number of transmissions for each communication path with the communication devices 2 and 3 of the slave stations 1 to 4 in the information slot (step S107). In other communication apparatuses 2 and 3, when the number of transmissions is changed through any one of the communication paths, transmission / reception of information is started in accordance with the assignment of the changed time slot.

  The communication device 1 determines whether there is a communication path in which communication errors frequently occur during transmission / reception in the information slot (step S108). Specifically, the communication device 1 compares with a condition value given in advance based on information indicating communication quality such as the number of received packets in communication with each of the slave stations 1 to 4, a signal level of wireless communication, or an error rate. Identify frequently occurring communication paths. The quality of the communication environment in each communication path from the slave stations 1 to 4 to the master station can be determined based on the number of received packets of information transmitted from the slave station. Further, the quality of the communication environment in each communication path from the master station to the slave stations 1 to 4 is similarly determined by the number of received packets in the communication devices 2 and 3 of the slave stations 1 to 4, and the determination result is displayed as an information slot. May be transmitted to the communication device 1 of the main station.

  When the communication device 1 determines that there is no communication path in which communication errors frequently occur (S108: NO), the process proceeds to the next step S110.

  When the communication device 1 determines that there is a communication path in which communication errors frequently occur (S108: YES), it stores that the number of transmissions in the communication path in which the communication errors frequently occur needs to be changed (step S109). ), The process proceeds to the next step S110.

  The communication device 1 performs noise measurement by the function of wireless communication environment measurement in the noise measurement time slot (step S110), and determines the presence or absence of an interfering wave (step S111). If the communication device 1 determines that there is no interfering wave (S111: NO), it continues to transmit and receive information in the other information time slot as it is, and ends the process. Note that the processing in steps S111 and S112 is actually performed in a time slot for noise measurement included between information slots in a frame as shown in FIG. That is, in practice, the processing of step S108 and step S109 is performed again after the processing of step S111 and step S112.

  When the communication device 1 determines that there is an interference wave (S111: YES), it stores that the number of transmissions in the communication path in which the communication error frequently occurs needs to be changed (step S112), and other information as it is. The transmission / reception of information is continued in the time slot for processing, and the process ends. In this case as well, the processes of step S108 and step S109 are actually performed again.

  And the communication apparatus 1 moves to the process in the next frame, and returns to step S101. The processing procedure from step S101 to step S112 is repeated.

  FIG. 6 is a flowchart showing an example of details of the transmission frequency determination process by the main station communication device 1 according to the first embodiment. The processing procedure shown in FIG. 6 corresponds to the details of step S103 in the flowchart of FIG.

  When determining the number of transmissions, the communication device 1 first determines whether there is an empty slot (step S31). When the communication device 1 determines that there is no time slot enough to increase the number of transmissions in the frame and there is no empty slot (S31: NO), the number of transmissions remains as it is and the processing is performed in the steps of the flowchart of FIG. The process returns to S104.

  When determining that there is an empty slot (step S31: YES), the communication device 1 determines whether the communication error rate is high or low (step S32). The communication apparatus 1 determines whether a communication error rate, for example, the number of received packets is equal to or higher than a predetermined lower limit value, whether the signal level is equal to or higher than a predetermined lower limit level, and whether the error rate is equal to or lower than a predetermined threshold value. Judge whether or not. When the communication device 1 determines that the communication error rate is lower than the reference value based on a preset lower limit value or threshold value (S32: NO), the communication device 1 increases the number of increases by 1 and determines the number of transmissions. (Step S33), the process is returned to Step S104 of the flowchart of FIG.

  When the communication device 1 determines that the communication error rate is higher than the reference value based on a preset lower limit value or threshold value (S32: YES), the number of transmissions increases from the number of empty slots in the frame. The number obtained by subtracting the number of communication paths other than the target communication path is obtained, and the number of transmissions is determined using this number as the number of increases (step S34), and the process returns to step S104 in the flowchart of FIG.

  In the first embodiment, the communication device 1 of the master station 1 determines the quality of the communication environment in the communication path between each of the slave stations 1 to 4, and the uplink / downlink in the communication path is determined according to the quality of the communication environment. Determine the number of transmissions.

  By determining the number of transmissions in this manner, the number of transmissions is determined to increase as the degree of the failure of the communication environment of the communication path increases. If the communication environment is bad and the number of timeslots is increased a plurality of times, the number to be increased is determined according to the number of other communication paths that may increase the number of time slots. Thereby, the number of transmissions can be increased one by one in other communication paths. A situation in which the number of time slots corresponding to a communication path determined to have a bad communication environment is unnecessarily increased to cause other problems is avoided.

  Note that step S34 is not indispensable in the transmission count determination process, and it is increased either one by one in advance or according to the number of empty slots or the number of other communication paths. May be.

  A specific example in the case where the number of transmissions is changed according to the communication environment by the processing procedure shown in the flowcharts of FIGS. 5 and 6 will be described. FIG. 7 is an explanatory diagram illustrating an example in which the number of transmissions is changed when an interfering wave exists on the communication path between the master station and the slave station 2 in the first embodiment. FIG. 7 shows an example in an arbitrary k-th frame. FIG. 7 shows the receivers and senders in each time slot indicated by a rectangle, as in FIG.

If it is determined that the communication path between the communication apparatus 1 of the master station and the communication apparatus 2 of the slave station 2 is a communication path in which communication errors frequently occur in the (k-1) th frame (S108: YES), FIG. As shown, an instruction on the number of transmissions is transmitted from the main station in the “maintenance slot” of the k-th frame (S104). In the example shown in FIG. 7, in particular, when the maintenance information is transmitted from the communication device 1 of the master station to which the time slot “2”, which is the “maintenance slot”, is transmitted to the communication device 2 of the slave station 2.
The number of transmissions of the same data in the communication path between the main station and the main station is increased by 1, and an instruction of the number of transmissions determined to be twice each for uplink and downlink is transmitted. Further, when the maintenance information is transmitted from the communication device 2 of the slave station 2 to which the time slot “7”, which is the “maintenance slot”, is transmitted to the communication device 1 of the master station, a response from the slave station 2 is received. (S105).

  As a result, as shown in FIG. 7, the transmission from the master station to the slave station 2 is changed from once in the time slot “10” (see FIG. 4) to twice in the time slots “10” and “11”. It is changed (S106) and is continuously sent. The transmission from the slave station 2 to the master station is also changed from once in the time slot “17” (see FIG. 4) to twice in the time slots “18” and “19” (S106), and the assignment is also automatic. Has been changed continuously.

  By such processing, when there is a communication path in which communication errors frequently occur in the time division multiplex communication between the communication apparatuses 1, 2, and 3 of the signal control system in the first, second, and third embodiments, until the next frame. There is an increased probability of successful transmission and reception within one frame without waiting. Since transmission / reception of traffic signal control information is not allowed to have excessive delays, it is possible to improve speediness and reliability by adopting a configuration in which transmission can be performed multiple times within the same frame as in the present invention. I can expect.

  In addition, it is possible to increase the number of transmissions before it becomes possible to clearly determine that there are jamming waves by judging whether there are frequent communication errors as well as jamming waves. And reliability can be improved.

  FIG. 8 is an explanatory diagram illustrating another example of the number of transmissions that is changed when an interfering wave exists on the communication path between the master station and the slave station 2 in the first embodiment. The configuration of the explanatory diagram of FIG. 9 is the same as the configuration of the explanatory diagram of FIG.

  The example illustrated in FIG. 8 is an example in which it is determined that the communication error rate is high as illustrated in the flowchart of FIG. 6 and the number of transmissions is determined to be increased twice instead of being increased once. is there. Thus, according to the comparison result with the reference value given in advance for the numerical information indicating the communication quality such as the number of received packets, the signal level of the wireless communication, or the error rate, the number of transmissions is set for a route with low communication quality. By further increasing, the certainty of transmission / reception of information regarding signal control can be further improved.

  FIG. 9 is an explanatory diagram showing another example of the number of transmissions that is changed when an interfering wave exists on the communication path between the master station and the slave station 2 in the first embodiment. The configuration of the explanatory diagram of FIG. 9 is the same as the configuration of the explanatory diagram of FIG.

  In the example shown in FIG. 7 and FIG. 8 described above, the transmission is continuously performed when the number of transmissions is increased. However, there is a case where the probability of successful transmission / reception increases when the timing for transmitting the same data is shifted as much as possible. Therefore, as shown in FIG. 9, it may be added to the end of each upstream and downstream information slot, including time slots assigned to transmission / reception in other communication paths. If there is an empty slot, an empty slot may be included. As a result, an interval can be provided between time slots assigned to transmission of the same data. Depending on the communication environment, when transmission is performed at non-continuous timing, there is a possibility that the certainty of successful reception is improved. In this case, the rules for changing the allocation should be shared by the communication devices 1, 2 and 3 of the master station and slave stations 1 to 4, so that there is no contradiction.

As shown in FIG. 7 to FIG. 9, the number of transmissions is increased and the reliability is improved in the communication path in which it is determined that communication errors frequently occur. However, the communication environment may change depending on the day of the week or the time zone. It is conceivable that a communication error that has occurred in a certain communication path is resolved depending on the time zone, but changes every moment, such as a communication error occurring in another communication path. At this time, if the number of transmissions is increased, the number of transmissions may not be increased effectively when the communication environment of other communication paths deteriorates even though the communication environment returns to a favorable state. obtain.

  Therefore, when the communication environment returns to a favorable state, processing for decreasing the number of transmissions that has been increased may be performed. FIG. 10 is a flowchart illustrating an example of a processing procedure including processing performed when the communication environment by the communication device 1 serving as the main station in Embodiment 1 returns to a favorable state. Note that, among the processing procedures shown in the flowchart of FIG. 10, the steps common to the processing procedure shown in the flowchart of FIG. 5 are given the same step numbers, and detailed description thereof is omitted.

  If the communication device 1 determines in step S108 that there is no communication path in which communication errors frequently occur (S108: NO), the number of transmissions is increasing and there is no communication error for a predetermined time or more on the communication path. It is determined whether or not there is a communication path in which the (less) situation continues (step S113).

  If the communication device 1 determines that it is present in step S113 (S113: NO), the process proceeds to step S110. If the communication device 1 determines that there is nothing in step S113 (S113: YES), it stores that it is necessary to change (decrease) the number of transmissions in the communication path (step S114), and advances the processing to step S110. .

  Further, when the communication device 1 determines in step S111 that there is no interference wave (S111: NO), the communication device 1 is increasing the number of transmissions and a good situation without the interference wave in the communication path is a predetermined time. The presence / absence of a communication path continuing as described above is determined (step S115).

  If the communication device 1 determines that there is nothing in step S115 (S115: NO), it ends the process. If the communication device 1 determines that it is present in step S115 (S115: YES), it stores that it is necessary to change (decrease) the number of transmissions in the communication path (step S116), and ends the process.

  FIG. 11 is a flowchart illustrating another example of the details of the transmission frequency determination process by the main station communication device 1 according to the first embodiment. The processing procedure shown in FIG. 11 corresponds to the details of step S103 in the flowchart of FIG. Of the processing procedures shown in the flowchart of FIG. 11, the steps common to the processing procedure shown in the flowchart of FIG. 6 are given the same step numbers, and detailed description thereof is omitted.

  When determining the number of transmissions, the communication device 1 determines whether or not the change in the number of transmissions is an increase (step S35). If the communication device 1 determines that the increase has occurred (S35: YES), the communication device 1 appropriately performs the processing from step S31 to step S34.

  If the communication device 1 determines that the number is reduced (S35: NO), it determines that the number of transmissions is the original number, that is, "1 time" (step S36), and returns the process to step S104 in the flowchart of FIG.

  By determining the number of transmissions in this way, when the communication environment of the communication path returns satisfactorily, it is returned to the initial number of transmissions set in advance. Although the communication environment has become favorable, a situation in which the number of time slots corresponding to the communication path once determined to be poor is unnecessarily increased is avoided.

  As a result of such processing, there is a communication error between the communication apparatuses 1, 2, and 3 that perform wireless communication that is fixed in or near traffic facilities that may be several tens to several hundreds of meters away. In the case of frequent occurrence, the number of transmissions is automatically increased / decreased when there are jamming waves. Even when a communication between devices is disturbed by an interference wave, the reliability of the communication is improved. By improving the certainty according to the communication environment that can be different for each communication path, it is possible to improve the reliability of transmission and reception of information relating to traffic signal control.

  In the first embodiment, an instruction for the number of times of both uplink and downlink transmission is transmitted from the communication apparatus 1 of the main station. However, an instruction on the number of transmissions may also be transmitted from the slave station using the maintenance information in the “maintenance slot” so that the number of transmissions can be determined for each of the upstream and downstream. In this case, the communication apparatuses 2 and 3 that are the slave stations 1 to 4 also execute the processing procedure shown in the flowcharts of FIGS. 5, 6, 10, and 11. In this case as well, the change in the number of transmissions is related to the change in allocation in one entire frame. It is desirable to change the number of transmissions when it is possible to receive responses from the communication devices 2 and 3 of the master station and other slave stations that are communication partners. Therefore, in this case, the response from the master station is received in the “maintenance slot” from the master station to the slave stations 1 to 4 in the next frame.

(Embodiment 2)
In the first embodiment, each communication device 1, 2 and 3 has been described as automatically recognizing a change in the time slot assigned to its own transmission / reception according to the change in the number of transmissions. In the second embodiment, the communication apparatus 1 as the master station also determines the scheduling of the time slot and instructs each of the communication apparatuses 2 and 3 of the slave stations 1 to 4. In the second embodiment, the master station communication device 1 can also transmit a transmission count instruction based on a request for changing the transmission count from each of the communication devices 2 and 3 of the slave stations 1 to 4. To do.

  The configuration of the signal control system in the second embodiment is the same as that in the first embodiment. Accordingly, the same reference numerals are assigned and detailed description of the hardware configuration is omitted. Hereinafter, differences from the first embodiment among the processes performed in the communication apparatuses 1, 2, and 3 will be described with reference to flowcharts and specific examples.

  FIG. 12 is a flowchart illustrating an example of a procedure of a transmission count determination process and a time slot allocation determination process performed by the communication apparatus 1 as the main station in the second embodiment.

  After starting transmission / reception of maintenance information in the “maintenance slot” by the control unit 10 (S101), the communication device 1 determines the number of transmissions (S102: YES) and determines the number of transmissions (S103). ). The communication apparatus 1 serving as the main station uses the control unit 10 to re-determine the allocation of time slots in the frame as the number of transmissions is changed (step S121). Specifically, the storage units 11, 21, 31 store different pattern assignments according to the increase / decrease of the number of transmissions in each communication path, and the communication device 1 determines which pattern to change to. To do. At this time, the time slot allocated for transmission of information including the same data includes a continuous pattern (continuous transmission) and the time slot includes a time slot allocated to another communication path or an empty slot. Each of the patterns may be stored, and one of them may be selected.

  Based on the determination, the communication device 1 transmits an instruction for the number of transmissions and an allocation instruction to the communication devices 2 and 3 of each of the slave stations 1 to 4 through the “maintenance slot” (step S122). It is determined from all 1 to 4 whether or not a response has been received (S105).

If the communication device 1 determines that a response has been received (S105: YES), it changes the number of transmissions and time slot assignment (step S123), and starts transmission / reception of information in the information slot thereafter (S107). . The subsequent processing from step S108 to step S112 is the same as in the first embodiment.

  If the communication apparatus 1 determines that the change in the number of transmissions is not required in step S102 (S102: NO), the communication apparatus 1 uses the “maintenance slot” in which maintenance information from the slave stations 1 to 4 is transmitted. It is determined whether a request for changing the number of transmissions has been received from the communication devices 2 and 3 (step S124). Here, the communication devices 2 and 3 of the slave stations 1 to 4 do not perform the transmission count determination process (S103) and the allocation determination process (S121) in the processing procedure shown in the flowchart of FIG. 12 (FIG. 5). However, almost the same processing is performed. When the communication devices 2 and 3 start transmission / reception in the information slot (S107), whether or not communication errors occur frequently during reception of information from the main station (S108), communication with the main station The necessity or non-necessity of changing the number of transmissions is determined based on the presence / absence of interfering waves on the path (S111) and stored (S109, S112). When the communication devices 2 and 3 determine that the transmission count needs to be changed based on the storage in the next frame (S102: YES), the communication devices 2 and 3 transmit a transmission count change request instead of the transmission count instruction (S104).

  Therefore, if the communication apparatus 1 as the main station does not store the change in the number of transmissions according to its own determination and determines that the change in the number of transmissions is unnecessary (S102: NO), the “maintenance slot” Then, it is determined whether or not a request for changing the number of transmissions has been received from the slave stations 1 to 4 (step S124). If the communication device 1 determines that no change request has been received (S124: NO), the process proceeds to step S107. On the other hand, when the communication device 1 receives a change request in the “maintenance slot” from the slave stations 1 to 4 (S124: YES), the “maintenance slot” from the master station must wait for the next frame thereafter. Therefore, the fact that the number of transmissions needs to be changed is stored in the storage unit 11 (step S125), and the process proceeds to the next step S107.

  A specific example in the case where the number of transmissions is changed according to the quality of the communication environment determined by the slave station 2 by the processing procedure shown in the flowchart of FIG. FIG. 13 is an explanatory diagram illustrating an example in which the number of transmissions is changed when errors frequently occur in communication from the master station to the slave station 2 in the second embodiment. In FIG. 13, when frequent communication errors are observed in an arbitrary k−1th frame, a transmission count change request is transmitted from the subordinate in the kth frame shown in the upper stage, and the next An example in which the number of transmissions is changed in the (k + 1) th frame is shown. Note that FIG. 12 shows the receiver and the sender in each time slot indicated by a rectangle, as in FIG. 4 or FIG.

  When it is determined by the communication device 2 of the slave station 2 at the time point of the (k−1) th frame that communication errors occur frequently in communication in the information slot from the communication device 1 of the master station, it is shown in FIG. As described above, the transmission count change request is transmitted to the communication apparatus 1 of the main station in the “maintenance slot” of the k-th frame. When the communication device 1 of the main station receives a request for changing the number of transmissions (S124: YES), even if the communication device 1 itself does not determine that many communication errors have occurred, the next k + 1th frame Thus, it is determined that it is necessary to change the number of transmissions at the time of transmission from the master station to the slave station 2 (S102: YES).

Thus, in the next (k + 1) th frame, the number of transmissions and the allocation instruction are transmitted in the “maintenance slot” from the communication device 1 of the master station to the communication devices 2 and 3 of the slave stations 1 to 4 (S122). ). Responses are transmitted in the “maintenance slot” from the communication devices 2 and 3 of the slave stations 1 to 4 to the communication device 1 of the master station, and the communication device 1 receives these responses. Transmission to the slave station 2 is changed from once in the time slot “10” (see FIG. 4) to twice in the time slots “10” and “11” (S123), and is continuously transmitted. The transmission from the slave station 2 to the master station is also changed from once in the time slot “17” (see FIG. 4) to twice in the time slots “18” and “19” (S123), and the assignment is also automatic. Has been changed continuously.

  Thus, the number of transmissions can be flexibly changed even based on the request for changing the number of transmissions from the communication devices 2 and 3 of the slave stations 1 to 4. As a result, if there is an interfering wave between communication devices 1, 2, and 3 that perform wireless communication that is fixed in the vicinity of traffic facilities that may be several tens to several hundreds of meters away, The number of transmissions is increased or decreased. When a failure occurs in communication between devices due to an interference wave, the reliability of the communication is improved. By improving the certainty according to the communication environment that can be different for each communication path, it is possible to improve the reliability of transmission and reception of information relating to traffic signal control.

  The disclosed embodiments should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1, 2, 3 Communication device 11 Storage unit 12 Wireless communication unit

Claims (9)

Including a plurality of communication devices installed at or near a traffic facility provided at a plurality of points on the road, each communication device having a communication means for performing wireless communication, and a communication environment by wireless communication Measuring means for measuring, wherein the communication means performs time-division multiplex communication in which communication is performed in a time slot allocated to itself in a frame unit including a plurality of time slots allocated to communication between the communication devices. A communication system,
A communication system comprising: determining means for determining the number of time slots allocated to transmission of the same data in the frame according to a measured communication environment. Including three or more communication devices,
Each communication device is configured to measure the communication environment for each communication path between the communication devices by the measurement means,
The communication system according to claim 1, wherein the determining means determines the number of time slots allocated to transmission of the same data in the communication path according to a communication environment for each communication path. . The determination unit determines whether the communication environment measured for each communication path is good or bad, and determines to increase the number of time slots allocated to the transmission of the same data on the communication path determined to be defective based on a predetermined criterion. The communication system according to claim 2, wherein the communication system is configured as described above. If the communication environment is determined to be poor, the determination means determines to increase the number of time slots as the level of failure is higher based on the number of received packet losses, the received signal level, or the error rate. The communication system according to claim 3, wherein the communication system is configured as follows. The determining means increases the number of time slots allocated to transmission of the same data in one communication path, and then determines that the communication environment of the one communication path is good for a predetermined time or more. The communication system according to claim 3 or 4, wherein a decision is made to reduce the number of time slots. 6. The time slot is allocated so that the number of time slots allocated to the transmission of the same data is plural in a frame, the time slots are allocated consecutively. The communication system in any one. When the determining means determines that the number of time slots allocated to transmission of the same data in the frame is plural, the time is allocated so that other time slots are included between the time slots. The communication system according to any one of claims 1 to 5. The determining means determines the number of time slots allocated to transmission of the same data based on the number of empty time slots in the frame and the number of time slots allocated to other communication paths. A communication system according to any one of claims 1 to 7. Including a plurality of communication devices installed at or near a traffic facility provided at a plurality of points on the road, each communication device having a communication means for performing wireless communication, and a communication environment by wireless communication A communication method comprising measuring means for measuring, and performing communication in a time slot assigned to itself in a frame unit including a plurality of time slots assigned to communication between communication devices by the communication means,
Each communication device measures the communication environment between itself and the communication partner,
According to the measurement result, determine the number of time slots allocated for transmission of the same data in the frame,
Each communication apparatus performs communication according to a time slot assigned based on the determined number.

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