JP5532786B2 - Communication system and communication method - Google Patents

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, stable wireless communication can be performed according to a reception environment for each route between communication devices. The present invention relates to a communication system and a communication method.

  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. 13 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 a traffic facility on a road.

  In FIG. 13, 91 is a communication device installed in the vicinity of the signal controller, and 92 is a communication device installed in the vehicle detector. The sensing result obtained by the vehicle sensor is transmitted from the communication device 92 to the other communication devices 91 and 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 devices 91 and 91 from the communication device 92 and further to the device for determining the signal control parameter or the traffic control center. Is done. At this time, conventionally, as shown by the broken line in FIG. 13, the communication devices 91, 91, 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 Received or relayed by the communication devices 91, 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 devices emit 2.4 GHz band radio waves. 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. In the current system using wireless communication, an optimum communication frequency is set in advance in each communication device manually.

JP 2008-205765 A JP 2006-0667462 A

  However, since traffic devices 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, each communication as shown in FIG. It is troublesome to manually change the settings so that the devices 91, 91, and 92 use the optimum communication frequency. In addition, the communication environment may change depending on the day of the week or the time zone. It is unrealistic to manually change the setting whenever the communication environment changes due to a change in the communication frequency. Furthermore, since information transmitted / received between devices for traffic control is information for traffic signal control, real-time performance is required. When communication between devices is disturbed by jamming waves, there is a problem that traffic congestion is caused by causing traffic congestion.

  Patent Document 2 proposes a method for automatically selecting a frequency that is most unlikely to be affected when there is an interfering wave and changing the communication frequency as a whole to the selected frequency for wireless communication control. By applying the wireless communication control in Patent Document 2 to communication between devices for traffic control, it is possible to use a frequency that is not easily affected by interference waves. When automation can be realized, the complexity of manual setting can be eliminated, and since it can be automatically changed, real-time characteristics are also satisfied.

  However, as described above, even when the traffic control devices that cooperate with each other are adjacent to each other, they may be several tens to several hundreds meters apart, so there is a possibility that interference waves with different frequencies may exist depending on the location. The communication environment can vary depending on the time zone and day of the week.

  In this case, in the configuration in which communication device frequencies between devices that cooperate with each other are the same frequency as in the past, even if automation can be realized by the method of Patent Document 2, interference waves having different frequencies exist. In this case, there is a possibility that the optimum frequency that can avoid the interference wave cannot be selected.

  The present invention has been made in view of such circumstances, and in communication between a plurality of communication devices that transmit and receive information for traffic control, stable wireless communication according to individual reception environments for each path between the communication devices. It is an object of the present invention to provide a communication system and a communication method capable of performing the above.

  The communication system according to the first aspect of the present invention includes traffic facilities provided at a plurality of points on the road or three or more communication devices installed in the vicinity of the traffic facilities, each of which is a single wireless device. A communication means for performing wireless communication on a communication frequency channel of communication, and a means for measuring a communication environment when each communication frequency channel is used, and each communication device is based on a time slot assigned to each communication path. A communication system configured to perform time division multiplex communication by the communication means, comprising a selection means for selecting a communication frequency channel for each communication path according to a communication environment measured for each communication path, and each communication The apparatus is characterized in that wireless communication is performed on the communication frequency channel selected by the selection means for each communication path with the communication partner.

  A communication system according to a second aspect of the present invention comprises a determination means for determining time slot allocation for each communication path within one frame including a plurality of time slots respectively allocated to communication between the plurality of communication devices. When a communication device that requires switching to a different communication frequency channel depending on a communication path with a communication partner exists on the basis of a selection result by the selection device, the means is assigned to communication via one communication path of the communication device. The allocation is determined by including other time slots equal to or longer than the switching time required for switching between the assigned time slot and the time slot allocated for communication via another communication path. And

  The communication system according to a third aspect of the present invention is a means for determining whether or not the other time slot can be included in the one frame, and when the determination is negative by the means, the communication apparatus needs to be switched. Means for changing a communication frequency channel to a different communication frequency channel selected by the selection means in a time slot assigned to communication via the communication path and a time slot assigned to communication via another communication path. It is characterized by providing.

In the communication system according to a fourth aspect of the present invention, the determining means includes a specific information including information indicating an instruction to change the communication frequency channel selected by the selecting means or information indicating a response to the change instruction in the one frame. A specific time slot is allocated to information communication, and the determination means includes the change instruction and response for all communication paths in the one frame to determine allocation. .

  In a communication system according to a fifth aspect of the present invention, the plurality of communication devices include one master device and a plurality of slave devices, and the master device is a communication selected by the selection unit based on the assignment determined by the determination unit. And a means for transmitting instruction information indicating a frequency channel to the slave apparatus side. When the slave apparatus receives the instruction information from the master apparatus side, the slave apparatus transmits a response to the instruction information to the master apparatus side. Means for transmitting the instruction information to another slave device that is a communication partner, and means for transmitting to the master device when the response is received from another slave device. The one frame is determined so as to include all the time slots corresponding to the instruction information from the master apparatus and the responses from the plurality of slave apparatuses to the instruction information. .

  A communication method according to a sixth aspect of the present invention includes a traffic facility provided at a plurality of points on a road or three or more communication devices installed in the vicinity of the traffic facility, each of which is a single wireless device. A communication means for performing wireless communication on a communication frequency channel of communication, and a means for measuring a communication environment when each communication frequency channel is used, and each communication device is based on a time slot assigned to each communication path. A communication method for performing time division multiplex communication by the communication means, wherein each communication device measures a communication environment using a communication frequency channel in use and determines whether or not the communication frequency channel needs to be changed according to the measurement result. When it is determined that it is necessary, the communication frequency channel is selected according to the communication environment of each communication path, and the communication frequency channel is switched to the selected communication frequency channel for each communication path. To.

  In the first invention and the sixth invention, a plurality of communication devices fixedly installed in or near a traffic facility including a signal controller, a vehicle detector, a signal control device, etc. are related to traffic signal control by time division multiplex communication. When communicating information wirelessly, a communication frequency channel corresponding to the wireless communication environment in each communication path is selected between three or more communication devices, that is, for each of two or more communication paths. That is, a different communication frequency channel can be selected for each communication in a different time slot assigned to each communication path.

In the second invention, time division multiplex communication is performed in units of one frame including a plurality of time slots assigned to communication between a plurality of communication devices, and the assignment of time slots to each communication path in one frame is determined. Determined by. The determination means may be configured to function in a specific communication device, may be configured to function in a specific determination device other than the communication device, or selected and determined by each communication device from a predetermined allocation. It is good also as a structure to be made. When determining a time slot allocation corresponding to each communication path in one frame by the determining means, if a communication frequency channel different from the other is selected in one communication path according to the wireless communication environment, the one communication path is selected. A communication device that communicates via a communication path and also communicates via another communication path requires a communication means that uses one frequency to switch communication frequency channels depending on the communication partner. In the second invention, at this time, an amount of time required for switching the frequency between the time slot of communication via the one communication path of the communication device and the time slot of communication via the other communication path. The other time slots are included and determined.
That is, a communication apparatus that needs to switch to a different communication frequency channel is given a grace period equal to or longer than the time required for switching. As a result, it is possible to reduce the cost by using one communication means for one communication device to communicate at one frequency, and switch to a different communication frequency channel according to the communication environment for each communication path. This can be done without any problem. Here, the other time slot may be an empty slot that is not allocated to communication of any communication apparatus in one frame, or if there is no empty slot, a communication apparatus that performs communication on the communication path to be switched. It may be a time slot assigned to communication between other communication devices on a communication path not related to. Also, it may be a time slot scheduled to perform a specific process such as noise measurement.

In the third invention, communication is performed in units of one frame including all time slots allocated to at least one communication between a plurality of communication devices that perform communication. That is, each communication is performed at least once within one frame, and the communication is repeated in units of frames. When one communication device communicates with different communication partners via a plurality of communication paths, and different communication frequency channels are selected for communication with different communication partners, it is assigned to communication with each communication partner. Need more than the switching time between the time slots.
Therefore, in the third aspect of the invention, it is determined whether or not a grace period equal to or longer than the switching time can be included between time slots allocated to communication of a communication device that requires switching of communication frequency channels. Each communication device performs communication repeatedly in units of frames and transmits / receives information related to traffic signal control. Since the repetition period is a length suitable for communication of information relating to traffic signal control, the number of time slots included in one frame is limited according to the period. Therefore, there may be a case in which a grace period equal to or longer than the switching time cannot be provided between time slots assigned to communication performed by the communication device related to switching. In the third invention, when it is determined that a time longer than the switching time cannot be provided between the time slots, any communication in the time slot is changed to the selected communication frequency channel. As a result, it is possible to switch to a different communication frequency channel according to the communication environment for each communication path in a configuration that achieves cost reduction in which one communication device uses one communication means that performs communication using a single frequency channel. Can be performed flexibly without hindrance.

  In the fourth invention, communication of specific information including information indicating a change instruction to the communication frequency channel selected according to the communication environment in each communication path or information in response to the change instruction is performed in a specific time slot. Is called. However, in the fourth invention, when there is a change instruction, the time slot allocation is determined so that the change instruction and its response are completed within one frame. And the response is completed quickly. Information relating to traffic signal control is required to be safe and quick. However, according to the present invention, it is possible to perform switching to a different communication frequency channel according to the communication environment with a low cost configuration.

  In the fifth invention, a plurality of communication devices have a relationship of a master device (master station) and a slave device (slave station). Based on the assignment determined by the determining means, instruction information indicating the communication frequency channel selected by the selecting means is transmitted from the master station side to the slave station, and a response to the instruction information is transmitted from the slave station side to the master station side. Further, all time slots corresponding to the communication of instruction information from the master station side to the slave station side and the response communication from the slave station side to the master station side in one frame are included in one frame. As a result, communication of information regarding the change of the communication frequency channel is completed within one frame, and it is possible to switch to a different communication frequency channel according to the communication environment in a safe and quick configuration with low cost. It is.

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

Even in the case where they are adjacent to each other, the communication devices that are installed in the traffic facility or in the vicinity thereof and transmit and receive information relating to traffic signal control may be several tens to hundreds of meters or several hundred meters apart. According to the present invention, when a communication frequency channel that interferes with an interfering wave is used in a part of communication paths, it is possible to avoid the channel and select another communication frequency channel only in the communication path. . Without changing the entire communication frequency channel, it is possible to realize stable wireless communication at a frequency suitable for the communication environment of each route, and 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. 3 is an explanatory diagram illustrating an example of time slots allocated in advance to communication devices that are a master station, a slave station 1, and a slave station 2 in Embodiment 1. FIG. 4 is a flowchart illustrating an example of processing performed by each communication device in Embodiment 1. It is explanatory drawing which shows the frequency allocation of wireless LAN. 6 is an explanatory diagram illustrating an example of switching of communication frequency channels when an interference wave is present on a communication path between communication devices in Embodiment 1. FIG. 6 is a flowchart illustrating an example of processing performed by each communication device in Embodiment 2. FIG. 10 is an explanatory diagram illustrating an example of switching of communication frequency channels and changing allocation when there is an interfering wave on a communication path between communication devices in the second embodiment. 10 is a flowchart showing an example of processing performed by each communication device in Embodiment 3. FIG. 10 is an explanatory diagram illustrating an example of switching of communication frequency channels and changing allocation when there is an interfering wave on a communication path between communication apparatuses in the third embodiment. It is explanatory drawing which shows the example of the content of the pattern table memorize | stored in the memory | storage part of a communication apparatus. 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 communicates with a communication device 1 and a communication device 2 that transmit and receive signal control information used by the signal controller, and vehicle sensing such as an optical beacon. And a communication device 3 that transmits and receives information used for signal control including a sensing result. The communication device 1 and the communication device 2 at a short distance communicate with each other, and the communication device 2 and the communication device 3 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).

  In the first embodiment, the communication device 1 operates as a master station, the communication device 2 operates as a slave station 1, the communication device 3 operates as a slave station 2, and the communication device 2 (slave station 1) is basically the communication device 1 ( A description will be given assuming that the device relays transmission / reception of information between the master station) and the communication device 3 (slave station 2).

  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.

  In the first embodiment, the communication devices 1, 2, and 3 avoid the influence of radio waves from other wireless LAN devices, and are stable according to the individual reception environment for each path between the communication devices 1, 2, and 3. Configured to implement wireless communication. Hereinafter, the configuration of the communication devices 1, 2, and 3 for realizing stable wireless communication according to the individual reception environment for each path will be described.

  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 the reception level in the communication frequency channel selected by the wireless communication unit 12, the reception level when the reception frequency is switched to another frequency, or the noise level, and the like. The band of the radio signal is investigated, and the presence / absence and the strength of the jamming radio wave are measured depending on whether or not the signal of the same standard as the communication by the radio communication unit 12 is 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, and 3 basically use a preset communication frequency channel (1CH: 2, 412 MHz in FIG. 2) for signal control acquired from traffic equipment such as a signal controller or a vehicle detector. Send and receive information used. The communication devices 1, 2 and 3 perform transmission / reception only in the time slot allocated in advance between the respective stations by time division multiplex communication. Time slot assignment 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 “maintenance slot” for synchronization, 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 station 1 or the slave station 2 The head of the frame is recognized by the synchronization signal of “maintenance slot”.

  As shown in FIG. 3, after the “maintenance slot”, a time slot is assigned to each communication from the master station to the slave station 1, the slave station 2, or from the slave station 1, the slave station 2 to the master station. Communicates in the time slot assigned to itself. 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, the slave station 1, and the slave station 2 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. In FIG. 4, below each slot, the communication frequency channel to be used and which of the master station, the slave station 1 and the slave station 2 is the sender and the receiver are shown. 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, and 3 are connected between the communication device 1 of the master station and the communication device 2 of the slave station 1 at a short distance from the master station, and the slave station 1. The communication device 2 and the communication device 3 of the other slave station 2 communicate with each other via two communication paths. For example, the first time slot of the frame k shown in FIG. 4 is allocated as a “maintenance slot”, and in this time slot, the communication device 1 that is the master station transmits (S) and the communication device 2 that is the slave station. , 3 receive (R).

  Then, the communication devices 1, 2, and 3 initially perform communication using a preset communication frequency channel. In the first embodiment, the initially set communication frequency channel is “1CH”.

  As shown in FIG. 4, one frame (frame k) is transmitted / received in the “maintenance slot” from the master station to the slave station 1 and in the uplink / downstream of the information time slot, and “maintenance” from the slave station 1 to the slave station 2. "Slot" and transmission / reception of information time slots, and time slots assigned to noise measurement periods. Both the “maintenance slot” and the information time slot are allocated to all uplink and downlink communications on the two communication paths between the master station and the slave station 1 and between the slave station 1 and the slave station 2. Therefore, the frame includes at least 8 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 four “maintenance slots”, maintenance information including instruction information for instructing a communication frequency channel is transmitted from the master station to the slave station 2 via the slave station 1, and a response to the instruction is slave station 2. To the master station via the slave station 1. The communication device 2 of the slave station 1 that has received the maintenance information including the instruction information from the communication device 1 that is the master station in the “maintenance slot” should communicate on the communication frequency channel indicated by the received instruction information. Can be recognized. With a total of four “maintenance slots” for uplink and downlink in two communication paths, transmission / reception of maintenance information related to specific communication control such as indicating a communication frequency channel is completed in the frame. 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 “5” and “6”, the communication from the communication device 1 as the master station to the communication from the slave station 1 is performed first. State information indicating the control state in the signal controller in the vicinity of each communication device 1, 2 as well as signal control command information, control parameters, etc. are transmitted to the device 2, to the communication device 3 which is the slave station 2 by relaying the communication device 2. Sent and received.

  Thereafter, in the time slots “7” to “10”, the communication devices 1, 2, and 3 each perform wireless reception environment measurement (noise measurement). After the noise measurement, in the time slots “11” and “12”, the communication device 2 from the communication device 3 that is the slave station 2 to the communication device 2 that is the slave station 1 and the communication device 2 that is the master station by relaying the communication device 2 , 3 in the vicinity of the signal controller or vehicle detector, state information indicating a control state, vehicle detection result, noise measurement result (communication error rate), and the like are transmitted and received.

  Basically, the communication apparatuses 1, 2, and 3 perform wireless communication based on the time slots assigned as shown in FIG. However, when an error occurs in wireless communication in any communication path based on the noise measurement result, the channel of wireless communication in the communication path is changed by the process described below.

  FIG. 5 is a flowchart showing an example of processing performed by each communication device 1, 2, 3 in the first embodiment. The communication apparatuses 1, 2, and 3 repeat the following processing procedure for each frame.

  Each of the communication devices 1, 2, and 3 starts transmission / reception of maintenance information in the “maintenance slot” at the head of the frame using the wireless communication units 12, 22, and 32 by the control units 10, 20, and 30 (steps). S1). Specifically, transmission / reception is started based on the synchronization signal of the first “maintenance slot” of the frame from the communication apparatus 1 of the main station.

  Each of the communication devices 1, 2, and 3 determines whether or not it is necessary to switch the communication frequency channel before the time slot assigned to itself among the “maintenance slots” arrives by the control units 10, 20, and 30. (Step S2). Whether or not it is necessary to switch the communication frequency channel in step S2 is determined based on the results of processes in steps S7 to S9 described later.

  If the communication devices 1, 2, and 3 determine that switching is not necessary in step S2 (S2: NO), the communication information is continuously transmitted / received and relayed in the “maintenance slot”, and the process proceeds to the next step S6.

If the communication devices 1, 2 and 3 determine that switching is required in step S2 (S2: YES), the communication devices 1, 2 and 3 transmit a communication frequency channel switching request in the “maintenance slot” assigned to them (step S3). For example, when the communication device 2 determines that many errors have occurred in communication with the communication device 3 in the previous frame (cycle), the communication frequency channel is switched in the communication path with the communication device 3. This request is transmitted in a “maintenance slot” that transmits maintenance information to the communication apparatus 3 that is the communication partner.

  In the first embodiment, the communication frequency channel switching request can be transmitted only from the master station side to the slave station side so that the request and the response to the request can be completed within one frame. However, it is also possible to transmit a switching request from the slave station side to the master station side. Only in the communication device 3, when a communication error with the communication device 2 is detected, a switching request can be transmitted to the communication device 2 on the main station side. However, in this case, a response from the communication apparatus 2 is received in the “maintenance slot” of the next frame, and switching is performed in the next frame.

  When the communication devices 1, 2, and 3 transmit the request for switching the communication frequency channel, whether or not the response from the communication devices 1, 2, and 3 corresponding to the request has been received in the subsequent “maintenance slot” Is determined (step S4).

  If it is determined that no response has been received (S4: NO), the communication devices 1, 2, and 3 proceed to the next step S6, similarly to the case where it is determined that switching is not necessary.

  When it is determined that a response has been received from the communication partner (S4: YES), the communication devices 1, 2, and 3 switch the communication frequency channel with the communication partner (step S5). The switching is executed at the time of communication with the corresponding communication apparatus in the time slot for transmitting / receiving information after the “maintenance slot”. Details will be described later with an example. Note that the communication frequency channels are switched at least 5 channels apart. Specifically, since the communication apparatuses 1, 2, and 3 are initially performing wireless communication with “1CH”, “6CH” is selected when it is determined that switching is necessary.

  FIG. 6 is an explanatory diagram showing frequency allocation of the wireless LAN. The horizontal axis of FIG. 6 is a communication frequency, and indicates a frequency range assigned to each communication frequency channel by a rounded rectangle. As shown in FIG. 6, each channel is divided every 5 MHz, and one channel uses a total of 22 MHz for 11 MHz before and after the center frequency. Therefore, interference occurs in adjacent communication frequency channels such as “1CH” and “2CH”. In order to avoid interference between radio waves, it is necessary to prevent the frequencies from overlapping. In the case of switching, switching to a communication frequency channel separated by 5 channels or more.

  Returning to FIG. 5, the description of the processing procedure will be continued. The communication devices 1, 2 and 3 execute switching of communication channels as necessary, and start transmission / reception of information such as a control state in an information time slot (step S6).

  Each of the communication devices 1, 2, and 3 performs its own noise measurement in a time slot for noise measurement during information transmission / reception (step S7). The communication devices 1, 2 and 3 also measure the interference wave by noise measurement, and determine the presence or absence of the interference wave from the measurement result (step S8). Specifically, like the control unit 10 described above, the wireless communication environment measurement function is used based on measurement results such as reception levels in each communication frequency channel and whether or not signals of the same standard are received. It is determined whether or not there is an interfering wave that interferes with the communication frequency channel (1CH).

  If the communication devices 1, 2, and 3 determine that there is no interfering wave (S8: NO), the communication devices 1, 2 and 3 continue to transmit and receive information in the other information time slots, and the processing ends. In this case, the process moves to the process in the next frame and returns to step S1.

If the communication devices 1, 2 and 3 determine that there is an interference wave (S8: YES), the communication devices 1, 2 and 3 store that switching from the communication frequency channel in use is necessary (step S9), and time for other information After the transmission / reception of information is continued in the slot, the process is terminated. Also in this case, the processing moves to the processing in the next frame and returns to step S1.

  A specific example will be described in which the communication frequency channel is switched according to the presence or absence of an interfering wave by the processing procedure shown in the flowchart of FIG. FIG. 7 is an explanatory diagram showing an example of switching of communication frequency channels when an interference wave is present on the communication path between the communication devices 2 and 3 in the first embodiment. FIG. 7 shows an example in which the communication frequency channel is switched in the next k + 1-th frame shown in the lower stage when an interference wave is observed in the noise measurement slot of the arbitrary k-th frame shown in the upper stage. ing. FIG. 7 shows the receiver and sender in each time slot indicated by a rectangle and the communication frequency channel used, as in FIG.

  In the upper k-th frame (frame k), communication between the communication device 2 of the slave station 1 and the communication device 3 of the slave station 2 in the time slots “6” and “11” is all “1CH”. "Is done using. However, the noise measurement between the time slots “7” to “10” determines that there is an interference wave in the communication device 2 (S8: YES), and the necessity for switching the communication frequency channel is stored. At this time, many communication errors occur in communication from the communication device 3 of the slave station 2 to the communication device 2 of the slave station 1 in the time slot “11”.

  In the lower k + 1-th frame (frame k + 1), after the maintenance information is transmitted from the main communication apparatus 1 to the communication apparatus 2 in the “maintenance slot”, the communication apparatus 2 communicates with the communication apparatus 3. It is determined that the communication frequency channel of the communication path needs to be switched (S2: YES). The communication device 2 transmits a switching request together with maintenance information from the communication device 1 to the communication device 3 of the slave station 2 in the next time slot “2” (S3). In response to the switching request from the communication device 2, the communication device 3 of the slave station 2 transmits a response in the time slot “3” allocated to itself. In this time slot “3”, the communication device 2 determines that a response to the switching request has been received (S4: YES). Therefore, the communication devices 2 and 3 perform communication by switching the communication frequency channel in the time slots “6” and “11” in which communication is performed next between the communication devices 2 and 3 to “6CH”.

  As described above, in the communication between the communication devices 1, 2, and 3 of the signal control system in the first embodiment, the communication frequency channel is automatically switched from the original “1CH” to “6CH” for each communication path. To do. That is, the situation where the communication frequency channel used for every communication path differs is also permitted. If there is an interfering wave that interferes with the communication frequency channel of “1CH” only on the communication path between the communication device 2 and the communication device 3, it is not necessary to change all the communication frequency channels in each communication route. Communication according to the communication environment is possible.

  As a result, the communication frequency channel is automatically switched when there is an interfering wave between communication devices that perform radio communication fixed in or near traffic facilities that may be several tens to several hundreds of meters away. Is done. Even when a communication failure occurs between devices due to an interference wave, it is not necessary to manually reset the communication frequency so that the optimum communication frequency is used as in the conventional case. Further, it is possible to select different communication frequency channels depending on the communication environment for each communication path. Stable wireless communication can be performed individually for each communication path, and the reliability of transmission / reception of information relating to traffic signal control can be improved.

(Embodiment 2)
In the first embodiment, the communication frequency channel is switched. On the other hand, in the second embodiment, each of the communication devices 1, 2, and 3 is configured to include one wireless communication unit, so that the time slot scheduling is also changed in consideration of the time required for channel switching.

  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. 8 is a flowchart showing an example of processing performed by each communication device 1, 2, 3 in the second embodiment. Of the processing procedures shown in the flowchart of FIG. 8, the steps common to the processing procedure shown in the flowchart of FIG. 5 of the first embodiment are given the same step numbers, and detailed description thereof is omitted.

  The communication apparatuses 1, 2, and 3 repeat the following processing procedure for each frame.

  The communication devices 1, 2, 3 start transmission / reception of maintenance information in the “maintenance slot” using the wireless communication units 12, 22, 32 by the control units 10, 20, 30 (S 1), and then the communication frequency channel It is determined whether or not it is necessary to change the allocation of time slots within a frame (step S21). The necessity of time slot allocation is determined based on the results of steps S7, S8 and S25 described later.

  If the communication devices 1, 2, and 3 determine that switching and allocation change are unnecessary in step S21 (S21: NO), the communication devices continue to transmit / receive maintenance information in the “maintenance slot” and relay to the next step S6. To proceed.

  If the communication devices 1, 2 and 3 determine that switching or allocation change is required in step S21 (S21: YES), the communication device 1 and the communication frequency channel switching request in the “maintenance slot” allocated to itself A slot allocation change request is transmitted (step S22). Specifically, the communication frequency channel switching request is transmitted from the master station side to the slave station side in order to complete the response within one frame. The allocation change request is transmitted from the slave station side to the master station side.

  Here, the communication apparatus 1 as the main station re-determines the allocation of time slots in the frame based on the allocation change request transmitted by the control unit 10 (step S23). Specifically, when any one of the communication devices 1, 2, and 3 that performs communication on the communication path for which the communication frequency channel is to be switched uses a different communication frequency channel depending on a different communication partner, it is assigned to each communication. The allocation is determined so that an empty slot or another time slot such as a time slot for noise measurement is included between the time slots. Not only the configuration determined only by the control unit 10 of the communication apparatus 1 that is the main station, but also different allocation patterns are stored in the storage units 11, 21, and 31, which pattern is changed to each. Thus, it may be determined based on the same standard.

  The communication apparatuses 1, 2, and 3 determine whether a response has been received for both the communication frequency channel switching request and the allocation change request (S4). The allocation change request is received in the next frame because the response (instruction) from the communication apparatus 1 as the main station corresponds. When it is determined that the communication apparatuses 1, 2, and 3 have not received a response (S4: NO), the process proceeds to the next step S6, similarly to the case where it is determined that switching and allocation change are unnecessary.

If the communication devices 1, 2, and 3 determine that a response has been received from the communication partner that transmitted the request (S4: YES), the communication device 1 switches the communication frequency channel with the communication partner, and the communication device 1 performs step S23. Based on this determination, the time slot allocation is changed (step S24). The switching of the communication frequency channel is performed at the time of communication with the corresponding communication partner communication device in the information transmission / reception time slot after the “maintenance slot”. The time slot allocation is changed by the communication apparatus 1 as the main station including the change instruction in the maintenance information transmitted in the “maintenance slot” and transmitted using the wireless communication unit 12. Receive instructions to recognize changes. Transmission / reception (S6) in the subsequent information time slot is performed based on the time slot after the allocation change.

  The communication devices 1, 2, and 3 start transmission / reception of information such as the control state in the information time slot (S6), and perform their own noise measurement in the noise measurement time slot (S7). The communication devices 1, 2, and 3 determine the presence or absence of an interference wave based on the noise measurement result (S8).

  If the communication devices 1, 2, and 3 determine that there is no interfering wave (S8: NO), the communication devices 1, 2 and 3 continue to transmit and receive information in the other information time slots, and the processing ends. In this case, the process proceeds to the process in the next frame, and returns to step S1.

  When the communication devices 1, 2 and 3 determine that there is an interference wave (S8: YES), the communication devices 1, 2 and 3 store the fact that switching from the communication frequency channel in use is necessary, and the time required for switching when switching is performed. Since it is necessary to wait for more than one minute, it is necessary to change the allocation of time slots within one frame (step S25), and after continuing transmission / reception of information in other information time slots The process is terminated. Also in this case, the processing moves to the processing in the next frame and returns to step S1.

  A specific example in the case where the communication frequency channel is switched and the time slot allocation is changed according to the presence or absence of an interfering wave according to the processing procedure shown in the flowchart of FIG. 8 will be described. FIG. 9 is an explanatory diagram illustrating an example of switching of communication frequency channels and changing allocation when there is an interference wave on the communication path between the communication apparatuses 2 and 3 according to the second embodiment. 9 shows the receiver and sender in each time slot indicated by a rectangle and the communication frequency channel used, as in FIG.

  In FIG. 9, when an interference wave is observed in a noise measurement slot of an arbitrary k-th frame shown in the upper stage, maintenance is transmitted / received in the “maintenance slot” in the next k + 1-th frame shown in the middle stage. Based on the information, an example is shown in which the communication frequency channel is switched and the time slot allocation is changed in the next k + 2th frame shown in the lower part.

  In the upper k-th frame (frame k), communication between the communication device 2 of the slave station 1 and the communication device 3 of the slave station 2 in the time slots “6” and “11” is all “1CH”. "Is done using. However, the noise measurement between the time slots “7” to “10” determines that there is an interfering wave in the communication device 2 (S8: YES), the necessity of switching the communication frequency channel is stored, and the switching is required. It is stored that the time slot allocation needs to be changed in consideration of time. At this time, many communication errors have occurred in the communication from the communication device 3 to the communication device 2 in the time slot “11”.

  In the middle (k + 1) th frame (frame k + 1), after the maintenance information is transmitted from the communication device 1 as the main station to the communication device 2 in the “maintenance slot”, the communication device 2 communicates with the communication device 3. It is determined that it is necessary to switch the communication frequency channel of the communication path and change the allocation of the time slot (S21: YES). Then, the communication device 2 of the slave station 1 transmits a switching request together with the maintenance information from the communication device 1 to the communication device 3 of the slave station 2 in the next time slot “2” (S22). In response to the switching request from the communication device 2, the communication device 3 of the slave station 2 transmits a response in the time slot “3” allocated to itself. In this time slot “3”, the communication device 2 determines that a response to the switching request has been received (S4: YES).

  In the middle (k + 1) th frame (frame k + 1), the communication apparatus 2 further determines that the time slot allocation needs to be changed (S21: YES). Therefore, a time slot allocation change request is transmitted in time slot “4” to communication device 1 which is the main station that determines the allocation of time slots (S22). The communication apparatus 1 of the main station receives this and re-determines time slot allocation. The communication device 1 that is the main station recognizes that the communication device 2 that performs communication via the communication path to be switched of the communication frequency channel communicates with different communication partners using different communication frequency channels. Further, the communication device 1 has time slots “5” and “6”, and “11” and “12” that are assigned to communications performed by the communication device 2 using different communication frequency channels with different communication partners. Recognize that they are next to each other in the frame. Therefore, the communication device 1 re-determines the allocation so that the time slot for noise measurement is included between the time slots allocated for communication with different communication partners of the communication device 2 (S23).

  In the lower k + 2th frame (frame k + 2), the communication device 1 as the main station uses the “maintenance slot” “1” “2” as a response to the allocation change request to communicate the information indicating the determined allocation. 2 and 3 are transmitted. The communication device 2 of the slave station 1 and the communication device 3 of the slave station 2 each receive this as a response or an assignment change instruction, and change the communication frequency channel and change the assignment of the time slot from the subsequent time slot (S24).

  As shown in FIG. 9, a time slot for noise measurement is included after the time slot “5” allocated to transmission using “1CH” from the communication device 1 of the master station to the communication device 2 of the slave station 1. It comes to be. During the time slot for noise measurement, the communication device 2 performs noise measurement at the wireless communication unit 22 and switches the communication frequency channel to “6CH”. The communication device 2 of the slave station 1 transmits information to the communication device 3 of the slave station 2 using the communication frequency channel of “6CH” in the time slot “8”. Since the communication device 3 of the slave station 2 communicates only with the communication device 2, the communication frequency channel in the wireless communication unit 32 is switched to “6CH”. Then, the communication device 3 of the slave station 2 transmits information to the communication device 2 using “6CH” in the time slot “9”, and the communication device 2 receives information on “6CH”. In the time slots “10” and “11”, the communication apparatus 2 performs noise measurement and switches the communication frequency channel in the wireless communication unit 22 from “6CH” to “1CH” again. Then, in the next time slot “12”, the communication device 2 of the slave station 1 transmits information to the communication device 1 of the master station using the communication frequency channel “1CH”.

  In this way, in the second embodiment, the cost is reduced by using one wireless communication unit 22 for one communication device 2, and different communication frequency channels “depending on the communication environment for each communication path”. When switching from “1CH” to “6CH”, the switching time required for switching is provided, so that switching can be performed without any problem.

  In the second embodiment, the communication device 2 is reassigned so as to include a time slot for noise measurement for switching between communication with the communication device 1 and communication with the communication device 3 by one wireless communication unit 22. The configuration. The present invention is not limited to this, and when there is an empty slot in the frame, the empty slot or a time slot assigned to communication between other communication apparatuses not related to switching of communication frequency channels may be included. .

(Embodiment 3)
In the second embodiment, when one communication device 2 switches to a different communication frequency channel in accordance with communication on a different communication path, another time corresponding to the switching time required for switching between the time slots assigned to each communication is obtained. The layout is changed to include slots. On the other hand, in the third embodiment, considering that there is a possibility that the allocation of the time slot cannot be changed because there is no room for an empty slot in one frame, a process for determining whether or not the change can be made is added. When the change cannot be made, all the communication frequency channels of all the communication paths are switched.

  The configuration of the signal control system in the third 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. In the following, differences from Embodiments 1 and 2 among the processing performed in each communication device 1, 2 and 3 will be described with reference to flowcharts and specific examples.

  FIG. 10 is a flowchart illustrating an example of processing performed by each communication device 1, 2 and 3 according to the third embodiment. Note that, in the processing procedure shown in the flowchart of FIG. 10, the procedure common to the processing procedure shown in the flowchart of FIG. 5 of the first embodiment and the processing procedure shown in the flowchart of FIG. 8 of the second embodiment are common. The procedure is given the same step number and detailed description is omitted.

  The communication apparatuses 1, 2, and 3 repeat the following processing procedure for each frame.

  After starting transmission / reception of maintenance information in the “maintenance slot” (S 1), the control units 10, 20, and 30 of the communication apparatuses 1, 2, and 3, the necessity of switching the communication frequency channel, and time slot assignment It is determined whether or not the change is necessary (S21). The necessity of time slot allocation is determined based on the results of steps S7, S8 and S25 described later.

  If the communication devices 1, 2, and 3 determine that switching and allocation change are unnecessary in step S21 (S21: NO), the communication devices continue to transmit / receive maintenance information in the “maintenance slot” and relay to the next step S6. To proceed.

  If the communication devices 1, 2, and 3 determine that switching or allocation change is necessary in step S21 (S21: YES), the communication frequency channel switching request and time slot are assigned to the “maintenance slot” allocated to itself. The allocation change request is transmitted (S22).

  Here, when the communication apparatus 1 as the main station receives the allocation change request to be transmitted, the communication apparatus 1 is allocated to communication via the channel switching target communication path in one frame when the allocation of the time slot in the frame is changed. It is determined whether or not another time slot can be included between the time slot and the time slot allocated for communication via another communication path by an amount equal to or longer than the switching time (step S31).

  When determining that another time slot can be included in step S31 (S31: YES), the communication apparatus 1 as the main station re-determines the allocation of the time slot in the frame based on the transmitted allocation change request (step S31: YES). S23). Then, the communication devices 1, 2, and 3 determine whether or not a response has been received for both the communication frequency channel switching request and the allocation change request (S4). The allocation change request is received in the next frame because the response (instruction) from the communication apparatus 1 as the main station corresponds. When it is determined that the communication apparatuses 1, 2, and 3 have not received a response (S4: NO), the process proceeds to the next step S6, similarly to the case where it is determined that switching and allocation change are unnecessary.

  If the communication devices 1, 2, and 3 determine that a response has been received from the communication partner that transmitted the request (S4: YES), the communication device 1 switches the communication frequency channel with the communication partner, and the communication device 1 performs step S23. Based on this determination, the time slot allocation is changed (step S24), and the process proceeds to the next step S6.

  If the communication device 1 determines in step S31 that other time slots cannot be included (S31: NO), the communication frequency channel should be changed in order to avoid interference and perform stable communication. Therefore, the communication device 1 transmits an instruction to switch communication frequency channels in all communication paths (step S32). The instruction is transmitted in the “maintenance slot” in the next frame. The communication apparatuses 1 and 2 determine whether or not a response has been received from the communication apparatuses 2 and 3 of the communication partner in the “maintenance slot” of the next frame (step S33). When it is determined that no response has been received (S33: NO), each of the communication devices 1 and 2 proceeds to the next step S6, similarly to the case where it is determined that switching and allocation change are unnecessary (S21: NO). When it is determined that each of the communication devices 1, 2, and 3 has received a response (S33: YES), the communication frequency channel is switched (S34), and the process proceeds to the next step S6.

  The communication devices 1, 2, and 3 start transmission / reception of information such as the control state in the information time slot (S6), and perform their own noise measurement in the noise measurement time slot (S7). The communication devices 1, 2, and 3 determine the presence or absence of an interference wave based on the noise measurement result (S8).

  If the communication devices 1, 2, and 3 determine that there is no interfering wave (S8: NO), the communication devices 1, 2 and 3 continue to transmit and receive information in the other information time slots, and the processing ends. In this case, the process proceeds to the process in the next frame, and returns to step S1.

  When the communication devices 1, 2 and 3 determine that there is an interference wave (S8: YES), the communication devices 1, 2 and 3 store the fact that switching from the communication frequency channel in use is necessary, and the time required for switching when switching is performed. Since a grace period of more than one minute is necessary, it is necessary to change the allocation of time slots within one frame (S25), and after continuing transmission / reception of information in time slots for other information, End the process. Also in this case, the processing moves to the processing in the next frame and returns to step S1.

  A specific example in the case where the communication frequency channel is switched and the time slot allocation is changed in accordance with the presence or absence of an interfering wave according to the processing procedure shown in the flowchart of FIG. 10 will be described. FIG. 11 is an explanatory diagram illustrating an example of switching of the communication frequency channel and changing the assignment when there is an interference wave on the communication path between the communication devices 2 and 3 according to the third embodiment.

  In FIG. 10, when an interference wave is observed in a noise measurement slot of an arbitrary k-th frame shown in the upper stage, maintenance is transmitted / received in the “maintenance slot” in the next k + 1-th frame shown in the middle stage. Based on the information, an example is shown in which all communication frequency channels are switched in the next k + 2th frame shown in the lower part.

  In the upper k-th frame (frame k), communication between the communication device 2 of the slave station 1 and the communication device 3 of the slave station 2 in the time slots “6” and “11” is all “1CH”. "Is done using. However, the noise measurement between the time slots “7” to “10” determines that there is an interfering wave in the communication device 2 (S8: YES), the necessity of switching the communication frequency channel is stored, and the switching is required. It is stored that the time slot allocation needs to be changed in consideration of time. At this time, many communication errors have occurred in the communication from the communication device 3 to the communication device 2 in the time slot “11”.

In the middle (k + 1) th frame (frame k + 1), after the maintenance information is transmitted from the communication device 1 as the main station to the communication device 2 in the “maintenance slot”, the communication device 2 communicates with the communication device 3. It is determined that it is necessary to switch the communication frequency channel of the communication path and change the allocation of the time slot (S21: YES). Then, the communication device 2 of the slave station 1 transmits a switching request together with the maintenance information from the communication device 1 to the communication device 3 of the slave station 2 in the next time slot “2” (S22). In response to the switching request from the communication device 2, the communication device 3 of the slave station 2 transmits a response in the time slot “3” allocated to itself. In this time slot “3”, the communication device 2 determines that a response to the switching request has been received (S4: YES).

  In the middle (k + 1) th frame (frame k + 1), the communication apparatus 2 further determines that the time slot allocation needs to be changed (S21: YES). Therefore, a time slot allocation change request is transmitted in time slot “4” to communication device 1 which is the main station that determines the allocation of time slots (S22). As a result, the communication apparatus 1 as the main station is required to re-determine the time slot assignment. However, the communication device 1 does not change the time slot allocated for communication via the communication path to be switched to the time slot allocated for communication via another communication path by an amount equal to or longer than the switching time. It is determined whether or not a time slot can be included (S31). Here, the communication device 1 of the master station is assigned to each of communication with the communication device 1 of the communication device 2 that is the slave station 1 and communication with the communication device 3 that is the slave station 2 that is the channel switching target. It is determined that other time slots cannot be included between consecutive time slots (“5” and “6” and “11” and “12”) (S31: NO). In this case, it is difficult for the communication device 2 of the slave station 1 to switch to a different communication frequency channel in successive time slots in the wireless communication unit 22 using a single communication frequency channel. The communication device 1 switches the communication frequency channel of communication in the time slot related to the communication device 2 in the frame and the time slot continuous with the time slot to the selected channel “6CH”.

  In the lower k + 2 frame (frame k + 2), the communication apparatus 1 as the main station uses the time slot “5”, “6”, “11” in the first “maintenance slot” (time slot “1”). And maintenance information instructing switching of the communication frequency channel at “12” to “6CH”. On the other hand, the communication device 2 of the slave station 1 and the communication device 3 of the slave station 2 transmit responses in “maintenance slots” (time slots “3” and “4”). As a result, in the subsequent time slots “5” to “12”, communication between the communication apparatuses 1, 2, and 3 is performed using the communication frequency channel “6CH”.

  In this way, in the third embodiment, the cost is reduced by using one wireless communication unit 22 for one communication device 2, and the communication frequency channel varies depending on the communication environment for each communication path. When switching is performed, it is determined whether or not a grace period for the switching time required for the switching can be provided. Thereby, it is possible to flexibly switch to a different communication frequency channel according to the communication environment for each communication path without any trouble.

  With the configuration of the first to third embodiments, even if the communication environment deteriorates between the wireless communication devices related to traffic signal control fixed at a distant place, the communication frequency being used can be changed as a whole. It is also possible to improve the reliability of transmission / reception of information relating to traffic signal control by selecting a communication frequency suitable for the communication environment of each route to realize stable wireless communication.

In the second or third embodiment, the time slot allocation for each communication of the communication devices 1, 2, and 3 is set in advance, and if the allocation needs to be changed, the change is also necessary. When the change is possible, the control unit 10 of the communication device 1 serving as the main station re-determines the assignment. At this time, when the allocation determined according to which communication path has deteriorated in the communication environment is previously made into a pattern table, the communication device 1 can set another time slot between communication time slots related to switching. Can be easily determined or omitted.

  FIG. 12 is an explanatory diagram illustrating an example of the contents of the pattern table stored in the storage unit 11 of the communication device 1. In the example shown in FIG. 12, pattern A that is initially set in the first to third embodiments is illustrated. FIG. 12 illustrates a pattern B that is a candidate for changing the allocation of time slots. In addition, the pattern C which is a candidate for changing the allocation of the time slot when an interference wave exists between the communication device 1 and the communication device 2 may be stored.

  In each pattern, for each time slot, the type of the time slot and which station (communication device) is the sender (S) and receiver (R) are shown. Except for the “maintenance slot” and the time slot for noise measurement, the type of time slot is omitted.

  In the pattern A, the first four are “maintenance slots”, and after information is transmitted from the master station side to the slave station side between the communication devices 1, 2 and 3 in the time slots “5” and “6”, Noise measurement is performed in time slots “7” to “10”, and information is assigned so that information is transmitted from the slave station to the master station in time slots “11” and “12”.

  The pattern B is a candidate after the assignment change when an interference wave exists between the communication device 2 of the slave station 1 and the communication device 3 of the slave station 2. This corresponds to the changed assignment shown in FIG. 9 of the second embodiment. Pattern B is also common to Pattern A in that the first four are “maintenance slots”. Pattern B differs in that time slot “6” in pattern A is replaced with time slot “8” and time slot “11” is replaced with time slot “9”.

  As shown in FIG. 12, since the allocation candidates after the change are tabulated, complicated processing for the change instruction is unnecessary. If each communication device 1, 2, 3 stores a pattern table, the main communication device 1 transmits in the “maintenance slot” instruction information indicating which pattern is changed. The other communication devices 2 and 3 can easily recognize the changed assignment.

  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 (6)

It includes three or more communication devices installed in the vicinity of traffic facilities provided at a plurality of points on the road or in the vicinity of the traffic facilities, and each communication device performs wireless communication using a single communication frequency channel. And means for measuring a communication environment when each communication frequency channel is used, and each communication device performs time division multiplex communication by the communication means based on a time slot assigned to each communication path. A communication system that is designed to perform,
According to the communication environment measured for each communication path, a selection means for selecting a communication frequency channel for each communication path is provided.
Each communication device is configured to perform wireless communication on a communication frequency channel selected by the selection unit for each communication path with a communication partner. Determining means for determining allocation of time slots to each communication path within one frame including a plurality of time slots respectively allocated to communication between the plurality of communication devices;
The determination means, based on the selection result by the selection means, when there is a communication apparatus that needs to be switched to a different communication frequency channel depending on the communication path with the communication partner, the communication via one communication path of the communication apparatus The allocation is determined by including other time slots more than the switching time required for switching between the time slot allocated to the communication and the time slot allocated for communication via other communication paths. The communication system according to claim 1. Means for determining whether or not the other time slot can be included in the one frame;
If it is determined by the means to be negative, a communication frequency channel between a time slot assigned to communication via one communication path that needs to be switched by the communication device and a time slot assigned to communication via another communication path The communication system according to claim 2, further comprising: means for changing to a different communication frequency channel selected by the selection means. The determination means includes a specific time slot for communication of specific information including information indicating a change instruction to the communication frequency channel selected by the selection means or information indicating a response to the change instruction in the one frame. Is assigned,
4. The communication system according to claim 2, wherein the determining unit determines allocation by including the change instruction and the response regarding all communication paths in the one frame. 5. The plurality of communication devices includes one master device and a plurality of slave devices,
The master apparatus includes means for transmitting instruction information indicating the communication frequency channel selected by the selection means to the slave apparatus based on the assignment determined by the determination means;
The slave device is
Means for transmitting a response to the instruction information to the main apparatus when receiving the instruction information from the main apparatus;
Means for transmitting the instruction information to another slave device that is a communication partner;
Means for transmitting to the master device side when the response is received from another slave device;
The determining means determines to include all time slots corresponding to the instruction information from the master device and responses from the plurality of slave devices to the instruction information in the one frame. A communication system according to any one of claims 2 to 4. It includes three or more communication devices installed in the vicinity of traffic facilities provided at a plurality of points on the road or in the vicinity of the traffic facilities, and each communication device performs wireless communication using a single communication frequency channel. And means for measuring a communication environment when each communication frequency channel is used, and each communication device performs time division multiplex communication by the communication means based on a time slot assigned to each communication path. A communication method to perform,
Each communication device measures the communication environment by the communication frequency channel in use,
Based on the measurement results, determine whether it is necessary to change the communication frequency channel,
If determined to be necessary, select the communication frequency channel according to the communication environment of each communication path,
A communication method characterized by switching to a selected communication frequency channel for each communication path.

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