JP2011234399A - Wireless communication device and wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable important data to be transmitted reliably by a periodic transmission communication device by separation between a communication period of the periodic transmission communication device and that of a random transmission communication device in a wireless communication system including mixed two types of communication devices which are the periodic transmission communication device and the random transmission communication device.SOLUTION: In a wireless communication system transmitting/receiving data by using a same communication channel, a random transmission communication device 2B receives a periodical transmission information indicating a periodical transmission period which is transmitted by a periodic transmission communication device 2A directly from the communication device or via such as another random transmission communication device 2C depending on the position of the communication device 2B inside or outside of an area where a transmission radio wave from the communication device 2A is reachable. A random transmission inhibition period is set based on the periodical transmission period of the data obtained from the periodical transmission information received; and a random transmission in the random transmission inhibition period is inhibited.

Description

  The present invention relates to a wireless communication system including a plurality of communication devices including a communication device having a periodic transmission function and a communication device having a random transmission function as a communication device that performs wireless communication using a common communication channel, and The present invention relates to a communication apparatus suitable for configuring this system.

  Conventionally, as a wireless communication system in which a plurality of communication devices perform wireless communication with each other using the same communication channel, access control in which each communication device detects a free state of a communication channel by carrier sense when a transmission request occurs There is known a CSMA wireless communication system that starts data transmission when a free state of a communication channel is detected by this access control (see, for example, Patent Document 1).

  In addition, in such a CSMA wireless communication system, since a plurality of communication devices perform random data transmission, for example, when applied to wireless communication in a safe driving support system of an automobile, the importance of road devices to in-vehicle devices is great. Even if high information is to be transmitted, it may take time for the roadside device to acquire the transmission right on the communication channel, and important information may not be transmitted to surrounding vehicles.

  Therefore, conventionally, in a CSMA wireless communication system, it has also been proposed that a communication device that transmits highly important information can periodically transmit important data using a communication method such as TDMA.

  That is, for example, an arbitrary communication device declares the start of TDMA communication to another communication device, thereby operating as a TDMA communication control station, assigning a transmission time (period) of each communication device, and then When there is no transmission from another communication device, the communication device returns to CSMA communication (see, for example, Patent Document 2), or each communication device autonomously determines its own transmission time. It is proposed that each communication device can periodically transmit data by notifying the communication device (see, for example, Patent Document 3).

JP 2000-196597 A JP 2002-112345 A JP 2007-235445 A

  However, among the proposed wireless communication systems, in the former system, all communication devices are switched to TDMA wireless communication. Therefore, when the number of communication devices increases, it becomes impossible to assign a transmission time to all communication devices. There is a problem that the radio communication system fails.

  In the latter wireless communication system, each communication device notifies the other communication devices of the transmission time so that the communication channel becomes idle at the timing of periodic transmission. Since a CSMA communication is started when a transmission request is generated, there is a problem that each communication device cannot reliably ensure a regular transmission opportunity.

  The present invention has been made in view of such problems, and in a wireless communication apparatus and a wireless communication system in which two types of communication apparatuses, that is, a communication apparatus that performs random transmission and a communication apparatus that performs periodic transmission, coexist. It is an object of the present invention to make it possible for a communication device that performs periodic transmission to reliably transmit important data by temporally separating communication from random transmission.

  The wireless communication device according to claim 1, which has been made to achieve the object, determines whether or not a communication channel is free when a data transmission request is generated, and the communication channel is free. Sometimes in a wireless communication device that performs random transmission by radio, the wireless communication device itself transmits periodic transmission information representing a periodic transmission period transmitted from an external communication device that performs periodic transmission of data using the communication channel. Random if the wireless communication device itself is located outside the area where the transmission radio wave from the external communication device reaches directly when the radio communication device is located in an area where the radio wave transmission from the external communication device reaches Receiving means that can be received via another wireless communication device that performs transmission, and when the periodic transmission information is received by the receiving means, the received periodic transmission Set the own random transmission prohibition period in the periodic transmission period of data obtained from the information, prohibit the random transmission in the set random transmission prohibition period, and the periodic transmission information received by the receiving means, Transmission means capable of transmitting to the wireless communication device.

  Here, in the present invention (Claim 1), the wireless communication device itself transmits the periodic transmission information indicating the periodic transmission period transmitted from the external communication device that performs the periodic transmission of data from the external communication device. Other wireless communication devices that perform random transmission directly from an external communication device when located in an area where radio waves reach, or when the wireless communication device itself is located outside an area where transmission waves from an external communication device reach And receiving means capable of receiving the periodic transmission information received by the receiving means to other wireless communication devices.

  For this reason, the periodic transmission information transmitted by the external communication device can be transmitted over a wide range from the external communication device to the wireless communication device itself and from the wireless communication device itself to another wireless communication device. Therefore, random transmission from another wireless communication device that does not receive the transmission radio wave from the external communication device overlaps with periodic transmission from the external communication device, and the wireless communication device located between the two communication devices Therefore, it is possible to prevent a problem that transmission data from each communication device collide and both data cannot be received.

  Further, according to the present invention (Claim 1), when the periodic transmission information is received by the receiving means, the random transmission prohibition period of the wireless communication device itself is set in the periodic transmission period of the data obtained from the received periodic transmission information. ing. That is, the random transmission prohibition period is set by applying the NAV period (transmission prohibition period) notification and reflection technique adopted in the CSMA method. In this way, since the wireless communication apparatus itself can appropriately set the random transmission prohibition period, it is possible to favorably avoid data collision between regular transmission and random transmission.

  The transmission means in the wireless communication device according to claim 1 may be configured to transmit the periodical transmission information received by the reception means by including in other transmission data, as described in claim 3. As described in claim 4, the periodic transmission information received by the receiving means may be transmitted alone as one transmission data.

  When the transmission means is configured as described in claim 3, it is possible to prevent an increase in the number of packets transmitted and received in the entire wireless communication system due to the transfer of the periodic transmission information. When the means is configured as described in claim 4, the periodic transmission information can be promptly transferred to another communication device.

  Further, as in claim 5, the wireless communication device of the present invention (claims 1, 3, 4) is an in-vehicle device mounted on a vehicle, and external communication devices are distributed and installed in the vicinity of the traveling path of the vehicle. It is possible to use an on-road device mounted on a vehicle with another wireless communication device.

  Next, in the radio communication system according to claim 2, the communication channel is free when a data transmission request is generated and a first communication device that periodically transmits transmission data using a predetermined communication channel. A wireless communication system in which a second communication device and a third communication device having a random transmission function for performing random transmission by radio when the communication channel is free are mixed, The first communication device includes means for periodically transmitting transmission data including regular transmission information indicating a regular transmission period in an area where the transmission radio wave reaches, and the second communication device transmits from the first communication device. When transmission data including periodic transmission information transmitted from the first communication device is received in an area where radio waves reach, data obtained from the received periodic transmission information Means for setting its own random transmission prohibition period in the period transmission period, prohibiting the random transmission in the set random transmission prohibition period, and means for transmitting the received periodic transmission information to the third communication device. The third communication device sets its own random transmission prohibition period in the periodic transmission period obtained from the periodic transmission information based on the periodic transmission information received from the second communication device, and sets the set random transmission prohibition period And means for prohibiting random transmission.

  Here, in the present invention (Claim 2), the second communication device is located in an area where the transmission radio wave from the first communication device reaches, and includes the periodic transmission information transmitted from the first communication device. Since it has means capable of receiving data and transmitting the received periodic transmission information to the third communication device, the first communication device to the second communication device, the second communication device to the third communication device, Periodic transmission information transmitted by the communication device can be transmitted over a wide range. Accordingly, random transmission from the third communication device that does not reach the transmission radio wave from the first communication device overlaps with periodic transmission from the first communication device, and in the first communication device located between the two communication devices, It is possible to prevent such a problem that transmission data from each communication apparatus collide and both data cannot be received.

  Further, according to the present invention (Claim 2), the second communication device is located in an area where the transmission radio wave from the first communication device reaches and includes transmission data including the periodic transmission information transmitted from the first communication device. Means for setting its own random transmission prohibition period in the periodic transmission period of data obtained from the received periodic transmission information, and prohibiting random transmission in the set random transmission prohibition period, and the received periodic Means for transmitting the transmission information to the third communication device, and the third communication device is based on the periodic transmission information received from the second communication device, and has its own random transmission period in the periodic transmission period obtained from the periodic transmission information. There is provided means for setting a transmission prohibition period and prohibiting random transmission in the set random transmission prohibition period.

  Thus, in the present invention (Claim 2), the random transmission prohibition period is set on the second communication device side by transmitting the periodic transmission information from the first communication device to the second communication device, and the second communication device. The random transmission prohibition period is set on the third communication device side by transmitting periodic transmission information to the third communication device. That is, the random transmission prohibition period is set by applying the NAV period (transmission prohibition period) notification and reflection technique adopted in the CSMA method.

  In this way, the random transmission prohibition period can be appropriately set on the second communication device side and the third communication device side, respectively, so that it is possible to satisfactorily avoid data collision between regular transmission and random transmission.

  In the present invention (Claim 2), as in Claim 6, when a data transmission request is generated, it is determined whether or not the communication channel is free, and the communication channel is free. A fourth communication device having a random transmission function for performing random transmission wirelessly is provided, and the third communication device is configured to include means capable of transmitting periodic transmission information received from the second communication device to the fourth communication device. May be.

  Moreover, the 2nd communication apparatus in the radio | wireless communications system of Claim 2 or 6 includes the periodical transmission information transmitted from the 1st communication apparatus in other transmission data, as described in Claim 7, and transmits. Alternatively, as described in claim 8, the second communication device may transmit the periodic transmission information transmitted from the first communication device alone as one transmission data.

  When the second communication device is configured as described in claim 7, it is possible to prevent an increase in the number of packets transmitted and received in the entire wireless communication system due to the transfer of the periodic transmission information. When the second communication device is configured as described in claim 8, the periodic transmission information can be promptly transferred to another communication device.

  Further, as in claim 9, in the present invention (claims 2, 7, and 8), the first communication device is a road device installed in the vicinity of the traveling path of the vehicle, and the second communication device and the first communication device The three communication devices can be an in-vehicle device mounted on the vehicle.

It is explanatory drawing showing the outline | summary of a structure and operation | movement of the radio | wireless communications system of embodiment. It is a block diagram showing the structure of the communication apparatus of embodiment. It is explanatory drawing showing the guard time G which considered the time synchronization shift | offset | difference. It is explanatory drawing showing guard time A and B which considered the time required for data transmission / reception. It is explanatory drawing explaining the division | segmentation operation | movement of a random transmission prohibition period. It is explanatory drawing showing the functional block which operate | moves when using a communication apparatus for regular transmission. It is explanatory drawing showing the functional block which operate | moves when using a communication apparatus for random transmission. It is a flowchart showing a regular transmission information transfer process. It is a flowchart showing a periodic transmission information update / time synchronization process and a time correction operation of a clock. It is a flowchart showing an asynchronous setting process. It is explanatory drawing showing the change of the frequency | count of a transfer updated by a regular transmission information transfer process. It is explanatory drawing showing the offset amount used for the time correction of a timepiece. It is explanatory drawing showing the change of the register for correction | amendment accompanying the time correction of a timepiece. It is explanatory drawing showing the change of the frequency | count of a transfer updated by an asynchronous setting process. It is explanatory drawing showing an example of the periodical transmission period table produced | generated with the communication apparatus for random transmission when there exist multiple communication apparatuses for periodical transmission. FIG. 10 is a block diagram illustrating a configuration of a communication device according to a first modification. FIG. 10 is an explanatory diagram illustrating a dividing operation of a random transmission prohibition period in Modification Example 1. 10 is a time chart for explaining a synchronization operation in a regular transmission period in Modification 2.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment]
(Outline of wireless communication system)
FIG. 1 is an explanatory diagram showing an outline of the configuration and operation of a wireless communication system according to an embodiment to which the present invention is applied.

  As shown in FIG. 1 (a), the wireless communication system of the present embodiment includes a plurality of communication devices 2A installed as road devices in the vicinity of the road of a vehicle, and mounted on the vehicle. Are configured from communication devices 2B, 2C,... That perform wireless communication with other vehicles.

  The communication device 2A has a periodic transmission function for periodically transmitting various information such as traffic information to surrounding vehicles, and the communication devices 2B, 2C,... Send a transmission request from a control device mounted on the vehicle. In response, it has a random transmission function for transmitting the state of the host vehicle and the like to a road machine and other vehicles.

  In addition, a common communication channel is used for communication between these communication devices 2A, 2B, 2C,..., And when the communication devices 2B, 2C,. It is determined whether or not the communication channel is free by access control, and data transmission is started when the communication channel is free.

  The communication device 2A performs periodic transmission. The period of this periodic transmission is determined in advance, and the communication device 2A is assigned which period within one period of periodic transmission is used for periodic transmission. ing.

  Then, the communication device 2A notifies the other communication devices 2B, 2C,... Of the assigned periodic transmission period by the periodic transmission, and the other communication devices 2B, 2C,. During the regular transmission period, random transmission is prohibited.

  That is, in this embodiment, the communication apparatus 2A having the periodic transmission function, as shown in FIG. 1B, periodic transmission period information indicating the start timing of the periodic transmission period and the length of the periodic transmission period (period length). In addition, periodic transmission information to which the device ID, which is identification information of the communication device 2A, and the number of transfers described below are added is added to other or transmission data and periodically transmitted to the surroundings.

  Then, when the other communication devices 2B, 2C,... Having the random transmission function receive the periodic transmission information transmitted by the communication device 2A, based on the periodic transmission information, as shown in FIG. A random transmission prohibition period is set so as not to start random transmission within the regular transmission period of the communication device 2A, and random transmission is performed within a period other than the random transmission prohibition period (random transmission period). .

  Further, as shown in FIG. 1A, the communication device 2B is located in an area (area indicated by hatching in the figure) where the transmission radio wave from the communication device 2A reaches, and the communication device 2C is located outside the area. In this case, the periodic transmission information transmitted from the communication device 2A does not reach the communication device 2C, the communication device 2C starts random transmission within the regular transmission period of the communication device 2A, and on the communication device 2B side, the communication device 2A, It is conceivable that transmission radio waves from 2C arrive at the same time, and the respective transmission data cannot be received.

  Therefore, in this embodiment, when the communication devices 2B, 2C,... Receive the periodic transmission information, the periodic transmission information is retransmitted to another communication device remote from the communication device 2A. Has been to notify you.

  When each communication device 2B, 2C,... Retransmits the periodic transmission information to another communication device, the periodic transmission information is updated by updating (+1) the number of transfers given to the periodic transmission information. The periodic transmission information can be identified by the communication device that has received the first transmission from the first transmission by the communication device 2A.

  In order to set the random transmission prohibition period based on the periodic transmission information on the communication devices 2B, 2C,..., The periodic transmission period recognized on the communication device 2A side, and the communication devices 2B, 2C,. ... It is necessary to match the periodic transmission period recognized on the side.

  Therefore, in this embodiment, when the communication device 2A transmits periodic transmission information, or when the communication devices 2B, 2C,... Transfer periodic transmission information, the transmission time is read from its own clock and periodically transmitted. The communication devices 2B, 2C,..., Which are attached to the information and have received the periodic transmission information, compare the transmission time given to the periodic transmission information with the reception time read from its own clock, The time of the clock is synchronized with the time of the communication device 2A, 2B,... That has transmitted the periodic transmission information.

  That is, for example, in FIG. 1A, the periodic transmission information transmitted from the communication device 2A reaches the communication device 2B, and the communication device 2B transfers the periodic transmission information to the communication device 2C. When the devices 2B and 2C receive the periodic transmission information, each communication device that has received the periodic transmission information by synchronizing the time of its own clock with the clock of the communication devices 2A and 2B that transmitted the periodic transmission information. The clocks 2B, 2C,... Are time-synchronized so that all of the clocks of the communication device 2A have the same time.

As a result, each communication device 2A, 2B, 2C,... Can detect one period of periodic transmission at the same timing using its own clock.
(Configuration of communication device)
Next, FIG. 2 is a block diagram showing a configuration of the communication apparatus 2 used for constructing the above-described wireless communication system of the present embodiment.

  2 has both a regular transmission function and a random transmission function. The communication apparatus 2A as a roadside device and the communication devices 2B, 2C,. It can be used.

  As shown in FIG. 2, the communication device 2 includes a data transmission unit 12 that outputs additional data such as a header added to transmission data input from an external control device, and a transmission output from the data transmission unit 12. Modulation processing unit 14 that converts data into a transmission signal (high-frequency signal) on a predetermined communication channel and outputs the signal to a communication antenna (not shown); receives a received signal received by the communication antenna; The demodulating processor 16 for restoring the transmission data from the receiver, and additional information such as a header is extracted from the received data restored by the demodulating processor 16, and the received data is transmitted to the communication device 2. For example, a data receiving unit 18 that outputs received data to an external control device is provided.

  Further, the communication device 2 stores the periodic transmission information set when the communication device 2 performs periodic transmission or the periodic transmission information acquired from another communication device when the communication device 2 performs random transmission. Periodical transmission period table (specifically, memory) 20, periodic transmission period in which data is actually transmitted when the communication apparatus 2 performs periodic transmission, periodical transmission information (communication apparatus) in the periodical transmission period table 20 A periodical transmission period determining unit 30 that is determined on the basis of its own periodic transmission period information) and that is output to the data transmission unit 12; Is determined based on the periodic transmission information in the periodic transmission period table 20 (periodic transmission period information acquired from other communication devices), and is prohibited from random transmission that is output to the data transmission unit 12 And while determining unit 40, it is provided.

  Then, when the periodic transmission period information is input from the periodic transmission period determination unit 30, the data transmission unit 12 can transmit the transmission data only during the periodic transmission period corresponding to the information, and the random transmission prohibition period determination unit When random transmission prohibition period information is input from 40, random transmission of transmission data is prohibited for the random transmission prohibition period corresponding to the information.

  In addition, the communication device 2 is provided with a clock 4 that counts the time by counting an internal clock, and the data transmission unit 12 determines the period of periodic transmission based on the time measured by the clock 4 and A periodic transmission period or a random transmission prohibition period within the cycle is detected, and the periodic transmission or random transmission is controlled.

  The timepiece 4 resets the timepiece 4 when the time measured by the timepiece 4 (specifically, the count value) becomes a predetermined integer multiple of the count value for one periodical transmission, and the count value is reset. Is connected to the timer reset unit 6.

  The timer reset unit 6 can receive an external signal representing an absolute time as a reference. When the external signal is input, the timer reset unit 6 can obtain a reference time obtained from the external signal. By resetting the timepiece 4 in this manner, the timepiece 4 is time-synchronized with another communication device to which the same external signal is input.

(Guard time setting)
Next, the communication device 2 includes a guard time determination unit that determines a guard time G provided between the regular transmission period and the random transmission period based on synchronization accuracy information indicating the synchronization accuracy with the other communication devices of the watch 4. 22 is provided.

  That is, the clock 4 of the communication device 2 and the clocks of other communication devices are time-synchronized by time synchronization processing described later, but the time synchronization processing cannot completely match the times of the clocks, resulting in errors. Arise.

  Therefore, in the present embodiment, even if there is an error due to time synchronization, the periodic transmission period and the random transmission prohibition period do not overlap with each other as shown in FIG. In addition, a guard time G corresponding to the synchronization accuracy of the clock is provided, and after the random transmission prohibition period ends, the guard transmission period starts after the guard time G has elapsed, and after the end of the periodic transmission period, the guard time G After the elapse of time, the random transmission prohibition period ends, and random transmission is permitted.

  Further, in the present embodiment, when the guard time G is provided, it is not necessary to set the random transmission prohibition period in consideration of the guard time G on the communication devices 2B, 2C,... As described above, the periodic transmission period including the guard time G is set in the periodic transmission information transmitted by the communication device 2A.

  As a result, in the communication device 2, the periodic transmission period information input to the periodic transmission period determining unit 30 represents the periodic transmission period including the guard time G, and the periodic transmission period determining unit 30 stores the periodic transmission period information. If the periodical transmission period in which data transmission from the data transmission unit 12 is permitted is set as it is, the guard time G will disappear.

  Therefore, in this embodiment, the periodic transmission period determining unit 30 corrects the periodic transmission period information by shortening the period before and after the periodic transmission period obtained from the periodic transmission period information by the card time G, and the data transmitting unit 12 is output.

  Also, the modulation processing unit 14 is configured to set a transmission data modulation scheme (BPSK, QPSK, 16QAM, etc.) in accordance with a command from the data transmission unit 12. It is necessary for the modulation processing unit 14 to modulate the transmission data by one packet based on the modulation information representing the modulation method and based on the modulation information and the data length of the transmission data output from the data transmission unit 12 to the modulation processing unit 14. A transmission time determination unit 24 for calculating time (transmission time) is provided.

  Then, the transmission time information obtained by the transmission time determination unit 24 is output to the regular transmission period determination unit 30 and the random transmission prohibition period determination unit 40, and the regular transmission period determination unit 30 obtains from the regular transmission period information. The periodic transmission period information to be output to the data transmission unit 12 is determined by moving the end timing of the periodic transmission period to the previous transmission time and shortening the periodic transmission period.

  In addition, the random transmission prohibition period determination unit 40 moves the start timing of the periodic transmission period obtained from the periodic transmission period information by the transmission time to increase the random transmission prohibition period, thereby allowing the data transmission unit 12 to Random transmission prohibition period information to be output is determined.

  In other words, in the present embodiment, by separating the periodic transmission period in which the communication apparatus 2A performs periodic transmission and the random transmission period in which the communication apparatuses 2B, 2C,. The transmission data due to random transmission is prevented from colliding, and the periodic transmission period and the random transmission period do not overlap due to the clock synchronization difference between the communication devices 2A, 2B, 2C,. A guard time G is provided between the regular transmission period and the random transmission period.

  However, with such measures alone, when the periodic transmission period ends during data transmission by periodic transmission, or when the random transmission period ends during data transmission by random transmission, the data transmission is continued. It is conceivable that data transmission by transmission and data transmission by random transmission are executed simultaneously.

  Therefore, in the present embodiment, as shown in FIG. 4, transmission data by periodic transmission is between the end timing of the regular transmission period and the end timing of the random transmission prohibition period (in other words, the start timing of the random transmission period). A guard time A corresponding to the transmission time for one packet is provided, and transmission by random transmission is performed between the start timing of the random transmission prohibition period (in other words, the end timing of the random transmission period) and the start timing of the regular transmission period. By providing a guard time B corresponding to the transmission time for one packet of data, it is possible to prevent data transmission by regular transmission and data transmission by random transmission from overlapping.

  For this reason, in this embodiment, as the periodic transmission information transmitted by the communication device 2A, a guard time G corresponding to the time synchronization error is added before and after the regular periodic transmission period, and further, the periodic transmission period Finally, when the transmission apparatus 2A adds a guard time A corresponding to the transmission time required to transmit one packet of transmission data, the communication apparatus 2A actually performs periodic transmission. The regular transmission period determination unit 30 subtracts the guard time G and the guard time A from the regular transmission period obtained from the regular transmission information, so that the period during which the data transmission unit 12 outputs transmission data during regular transmission is determined as a regular regular period. On the side of the communication devices 2B, 2C,..., The random transmission prohibition period determination unit 40 performs a regular transmission period (that is, a regular periodic period) obtained from the regular transmission information. By setting the guard time B to the regular transmission period in which the guard time G and the guard time A are added to the transmission period, a random transmission prohibition period is set by adding the guard times G, A, and B to the regular periodic transmission period. Have been to.

  The random transmission prohibition period determining unit 40 sets the random transmission prohibition period by adding the guard time B, which is its own data transmission time, to the periodic transmission period corresponding to the periodic transmission information, as shown in FIG. In addition, when this random transmission prohibition period spans one period of periodic transmission, the random transmission prohibition period is separated into two along the period, and the separated transmission prohibition periods 1 and 2 are divided into two. The data transmission unit 12 is instructed as a random transmission prohibition period.

  This is a period during which random transmission is prohibited (in other words, a period during which transmission data is output) for each period of periodic transmission based on the time measured by the clock 4 (in other words, the count value) on the data transmission unit 12 side. This is to enable setting. That is, in this way, the data transmission unit 12 is a simple digital circuit composed of a gate circuit that switches output / stop of transmission data, a timing circuit that switches opening and closing of the gate circuit at a predetermined timing every predetermined period, and the like. It can be configured.

(Function blocks realized by software processing)
Next, the communication device 2 includes a periodical transmission period update unit 50 that updates the periodical transmission information in the periodical transmission period table 20 based on the periodical transmission information extracted from the reception data by the data reception unit 18, and a data reception The time difference calculation unit 52 that takes in the transmission time of the periodic transmission information extracted from the reception data and the reception time of the reception data by the unit 18 and calculates the time difference (reception time−transmission time), and the time difference calculation unit 52 Based on the time difference and the synchronization accuracy information, it is determined whether or not the time difference is within an allowable range corresponding to the synchronization accuracy, and if it is not within the allowable range, the time correction information is output to the clock 4. Thus, a time correction determination unit 54 for correcting the time is provided.

  The regular transmission period update unit 50, the time difference calculation unit 52, and the time correction determination unit 54 are functional blocks realized by software processing by a microcomputer. The regular transmission period update unit 50 is software processing of the microcomputer. Thus, the transmission processing of the periodic transmission information by the communication device 2A and the retransmission processing of the periodic transmission information by the communication devices 2B, 2C,.

  In FIG. 2, functional blocks other than the periodic transmission period update unit 50, the time difference calculation unit 52, and the time correction determination unit 54, that is, the clock 4, the timer reset unit 6, the data transmission unit 12, the modulation processing unit 14, and the demodulation The processing unit 16, the regular transmission period table 20, the guard time determination unit 22, the transmission time determination unit 24, the regular transmission period determination unit 30, and the random transmission prohibition period determination unit 40 all have a hardware configuration including a digital circuit. Realized.

  Next, FIG. 6 shows functional blocks for periodic transmission that operate when the communication apparatus 2 is used as a road device that performs periodic transmission in the communication apparatus 2 of the present embodiment. The functional block for random transmission which operate | moves when the communication apparatus 2 is used as a vehicle-mounted apparatus which performs random transmission is represented.

  As shown in FIG. 6, when the communication device 2 is used as a communication device 2A that performs periodic transmission, the clock 4, the timer reset unit 6, the data transmission unit 12, the modulation processing unit 14, the periodic transmission period table 20, the guard The time determination unit 22, the transmission time determination unit 24, the regular transmission period determination unit 30, and the regular transmission period update unit 50 operate, and the output period of transmission data from the data transmission unit 12 is changed to the regular transmission period determination unit 30. The periodical transmission period determined by

  In this case, the periodic transmission period table 20 stores periodic transmission information indicating the periodic transmission period when the communication apparatus 2 itself performs periodic transmission, and the periodic transmission period update unit 50 includes software by a microcomputer. By reading the periodic transmission information from the periodic transmission period table 20 and outputting it to the data transmission unit 12 by processing, the periodic transmission information is transmitted periodically as a single transmission data or a header of other transmission data. . In addition, when transmitting the regular transmission information, the data transmission unit 12 reads the transmission time from the clock 4 and gives it to the regular transmission information.

  On the other hand, as shown in FIG. 7, when the communication device 2 is used as communication devices 2B, 2C,... That perform random transmission, all functional blocks except for the regular transmission period determination unit 30 and the guard time determination unit 22 are used. And the transmission of transmission data from the data transmitter 12 is prohibited during the random transmission prohibition period determined by the random transmission prohibition period determination unit 40.

  In this case, the regular transmission period update unit 50 updates the regular transmission information in the regular transmission period table 20 based on the regular transmission information extracted from the reception data by the data reception unit 18 by software processing by the microcomputer. At the same time, by outputting the updated periodic transmission information to the data transmission unit 12, the periodic transmission information is added to a header of other transmission data to be randomly transmitted and transferred to another communication device.

  Further, the time difference calculation unit 52 and the time correction determination unit 54 calculate the time of the clock 4 based on the time difference between the transmission time and the reception time of the periodic transmission information received by the data reception unit 18 by software processing by the microcomputer. to correct.

  Therefore, next, when the communication device 2 is used as the communication devices 2B, 2C,... That perform random transmission, the functions of the periodic transmission period update unit 50, the time difference calculation unit 52, and the time correction determination unit 54 Software processing executed by the microcomputer to realize the above will be described with reference to the flowcharts shown in FIGS.

(Periodic transmission information transfer processing)
First, FIG. 8 is a flowchart showing a periodical transmission information transfer process executed in the microcomputer to transfer the periodical transmission information extracted from the received data by the data receiving unit 18 to another communication device.

  As shown in FIG. 8, in the periodic transmission information transfer process, in S110 (S represents a step), it is determined whether or not the data receiving unit 18 has received data including the periodic transmission information. After waiting for the transmission of periodic transmission information from the communication device, when the data receiving unit 18 receives data including the periodic transmission information, the process proceeds to S120, and the number of times C of transmission of the periodic transmission information is read.

  If the data reception unit 18 receives periodic transmission information having the same device ID and different transfer count C at substantially the same time (for example, within one period of periodic transmission), the plurality of periodic transmissions are performed in S120. Periodic transmission information with a small transfer count C is selected from the information, and the transfer count C is read.

  Next, in subsequent S130, it is determined whether or not the transfer count C of the periodic transmission information read in S120 is smaller than a preset threshold value Cmax, and the transfer count C is smaller than the threshold value Cmax. In this case, the process proceeds to S140, where the number of times C of regular transmission information is transferred is updated (+1), and the process proceeds to S150.

  In S150, the periodic transmission information after the update of the number of transfers is output to the data transmission unit 12, so that the periodic transmission information is added as one of the headers of the transmission data to be randomly transmitted and transmitted to other communication devices. Let In addition, the data transmission part 12 gives periodic transmission information to transmission data, reads the transmission time from the clock 4 and transmits it to the periodic transmission information when transmitting to other transmission apparatuses.

  If it is determined in S130 that the transfer count C is greater than or equal to the threshold value Cmax, or if the periodic transmission information after the transfer count update is output to the data transmission unit 12 in S150, The periodic transmission information transfer process is once ended, and the processes after S110 are executed again.

  In this way, in the periodic transmission information transfer process, the periodic transmission information is transferred after updating (+1) the transfer count C of the periodic transmission information extracted by the data receiver 18 with the threshold Cmax as an upper limit. Further, as shown in FIG. 11, the periodic transmission information transmitted by the communication device 2A is not only sequentially transferred by the surrounding communication devices 2B, 2C,. Value: 0) is counted up for each transfer. In the periodic transmission information transfer process, if the number of times C of periodic transmission information transfer is equal to or greater than the threshold value Cmax, the transfer of the periodic transmission information is stopped.

  Therefore, the periodic transmission information can be transmitted not only to the communication devices 2C,... Located outside the area where the transmission radio wave from the communication device 2A reaches, but also the transmission range within the desired range using the transfer count C. Can be limited.

(Regular transmission information update / time synchronization processing)
Next, FIG. 9 shows that the microcomputer updates the periodic transmission period table 20 based on the periodic transmission information extracted from the received data by the data receiving unit 18, and further transmits the transmission time and data assigned to the periodic transmission information. 10 is a flowchart showing a periodical transmission information update / time synchronization process that is executed to correct the time of the clock 4 based on the reception time at the reception unit 18.

  As shown in FIG. 9, when this process is started, first, in S210, the data reception unit 18 determines whether or not data including the periodic transmission information has been received, thereby periodically transmitting from another communication device. When the data receiving unit 18 receives data including the periodic transmission information after waiting for the information to be transmitted, the process proceeds to S220, and the periodic transmission information is already registered in the periodic transmission period table 20. It is determined whether it is what is. This determination is made based on the device ID of the periodic transmission information.

  If it is determined in S220 that the periodic transmission information is unregistered, in S230, the unregistered periodic transmission information is newly registered in the periodic transmission period table 20, and then the process proceeds to S240. If it is determined in S220 that the periodic transmission information is already registered in the periodic transmission period table 20, the process proceeds to S240 as it is.

  In S240, the transfer count C (reception transfer count C) of the periodic transmission information received this time is the transfer count C of the regular transmission information registered in the periodic transmission period table 20 (specifically, the periodic transmission information having the same device ID). It is determined whether or not it is smaller than the registered transfer count C). If the received transfer count C is smaller than the registered transfer count C, the process proceeds to S260.

  If the periodic transmission information received this time is not registered in the periodic transmission period table 20 and is newly registered in S230, it is assumed that the registered transfer count C is the maximum value in S240, and the received transfer count C is compared with the registered transfer count C. As a result, if the periodic transmission information received this time is newly registered, the process proceeds from S240 to S260.

  Next, when it is determined in S240 that the reception transfer count C is equal to or greater than the registration transfer count C, the process proceeds to S250, where the reception transfer count C and the registered transfer count C are the same, and this time It is determined whether the device ID of the received periodic transmission information is equal to or less than the device ID of the periodic transmission information used for the time synchronization of the previous clock 4. The device IDs are compared in order to determine the priority order of the periodic transmission information used for time synchronization from the device ID value.

  The periodic transmission information transfer count C received this time and the periodic transmission information transfer count C stored in the periodic transmission period table are the same, and the device ID of the periodic transmission information used for the previous time synchronization is the device ID. If smaller, the process proceeds to S260; otherwise, the process is temporarily terminated and the process proceeds to S210 again.

  Next, in S260, the transmission time of the periodic transmission information received this time and the reception time of the periodic transmission information are fetched from the data receiving unit 18, and the time difference between the fetched transmission time and the reception time is represented by the clock 4. Is calculated as the amount of synchronization deviation.

  In S260, when calculating the amount of synchronization deviation, as shown in FIG. 12, after the communication device transmits the periodic transmission information, the offset required for other communication devices to receive the periodic transmission information. The amount of synchronization deviation is calculated as “amount of synchronization deviation = reception time−transmission time−offset amount”.

  That is, the transmission time of the periodic transmission information is given when the data transmission unit 12 outputs transmission data, but the transmission data is converted into a transmission signal by being modulated by the modulation processing unit 14. Therefore, there is a delay time (modulation processing delay) required for the modulation process until the transmission data is converted into a transmission signal and emitted from the communication antenna.

  Also, a delay time (propagation delay) occurs due to radio wave propagation until the transmission signal (radio wave) radiated from the communication antenna reaches the communication antenna of another communication device, and the received signal is demodulated. A delay time (demodulation process delay) required for the demodulation process also occurs until the demodulating process by the unit 16 and the periodical transmission information is restored.

  Therefore, in this embodiment, a delay time (modulation processing delay, propagation delay, demodulation processing delay) generated between the transmission time and the reception time is set in advance as an offset amount, and the clock is determined from the transmission time and the reception time. When calculating the amount of synchronization deviation 4, the true amount of synchronization deviation of the timepiece 4 is calculated by using this offset amount.

  Next, when the synchronization deviation amount of the timepiece 4 is calculated in S260, the process proceeds to S270, and whether or not the calculated synchronization deviation amount is within the allowable range corresponding to the synchronization accuracy described above. If the amount of synchronization deviation is within the allowable range, the process is temporarily terminated and the process proceeds to S210. If the amount of synchronization deviation is not within the allowable range, the process proceeds to S280. It is determined whether or not the previous time correction has been completed by determining whether or not the synchronization deviation amount (that is, the time correction amount) set in the correction register of the previous clock 4 remains in the correction register. .

  If the previous time correction amount remains in the correction register of the clock 4, the processing is temporarily ended and the process proceeds to S210 again. Conversely, the correction register of the clock 4 is “0”. If the previous time correction amount does not remain, the process proceeds to S290, and the time shift amount calculated this time is written in the correction register of the clock 4 in S260.

  The timepiece 4 is provided with a correction circuit that corrects its own clock time (in other words, a count value) in accordance with the time correction operation procedure shown in FIG.

  Then, the correction circuit initializes the internal circuit with the activation of the communication device 2 (S310), and then determines whether or not the correction register is “0”, whereby the time correction amount is stored in the correction register. (I.e., the time lag amount) is written (S320), and when the time lag amount is written in the correction register, the time keeping time (in other words, the count value) is calculated based on the written time lag amount. The time of the time 4 is set to the clock of the communication device that has transmitted the periodic transmission information by the procedure of correcting (S330), initializing the correction register to “0”, and shifting to the standby operation of S310 again. Synchronize with.

  Accordingly, when the microcomputer writes the time lag amount in the correction register of the timepiece 4 in S290, the timepiece 4 automatically corrects the time according to the time lag amount.

  Then, after writing the time lag amount in the correction register of the timepiece 4 in S290, the microcomputer proceeds to S300 and used this time for the time synchronization of the timepiece 4 in the processing of S260 and S290. Based on the periodical transmission information, the periodical transmission information registered in the periodical transmission period table 20 is updated. Thereafter, the process is temporarily terminated, and the process proceeds to S210 again.

  The periodic transmission information is updated by S300 by rewriting the number of times C of transmission of the periodic transmission information.

  In S280, when the previous time correction amount remains in the correction register (in other words, when the correction register is not “0”), the time shift amount calculated this time is not written to the correction register. The process is temporarily terminated, as shown in FIG. 13, by writing the time lag amount in the correction register of the clock 4 by software processing and then writing it by the time correction processing on the clock 4 side. It takes time until the time is corrected according to the amount of time lag, and when the time lag calculated in the meantime is written to the correction register, the time of the clock 4 is corrected again with the time lag and new This is because there is a risk of causing a time lag.

  That is, in the present embodiment, when the time lag amount is calculated in S260, if the previous time lag amount remains in the correction register and the time correction based on the time lag amount is not completed, the time lag amount is calculated this time. By discarding the time lag amount, it is possible to prevent the time lag of the timepiece 4 from being unnecessarily executed and causing a time lag.

(Asynchronous setting process)
Next, FIG. 10 shows the periodical transmission information of the communication device 2A when the vehicle is separated from the communication device 2A that performs periodic transmission and the random transmission can be executed in the periodical transmission period of the communication device 2A. 10 is a flowchart showing an asynchronous setting process executed for rewriting as asynchronous information not used for setting a random transmission prohibition period.

  As shown in FIG. 10, this asynchronous setting process is a process executed for each period of periodic transmission. When this process is started, first, the periodic registration registered in the periodic transmission period table 20 in S410. It is determined whether there is periodic transmission information that could not be received within one period of the periodic transmission among the transmission information.

  If there is periodic transmission information that could not be received within one period of periodic transmission, the number of transfers C of the periodic transmission information is read in S420, and the number of transfers C of the read periodic transmission information is read in S430. Is smaller than a preset threshold value Cmax.

  If the transfer count C is smaller than the threshold value Cmax, the process proceeds to S440, where the transfer count C of the periodic transmission information is updated (+1), and the process proceeds to S450.

  In S450, it is determined whether or not the transfer count C updated (+1) in S440 has reached the threshold value Cmax. If the transfer count C has reached the threshold value Cmax, the software timer is determined in S460. Is started, the elapsed time thereafter is started, and the asynchronous setting process is temporarily terminated. If the transfer count C does not reach the threshold value Cmax, the asynchronous setting process is temporarily terminated.

  It should be noted that the elapsed time started by starting the software timer in S460 is a period in which the transfer count C reaches the threshold value Cmax in the periodical transmission information registered in the periodical transmission period table 20. This is performed for each transmission information, and when the number of times C of transmission of the periodic transmission information is updated to a value smaller than the threshold value Cmax, the elapsed time measurement ends.

  Also, when there are a plurality of periodic transmission information that has been registered and could not be received within one period of the periodic transmission, the processes of S420 to S460 and the processes of S470 and S480 described below are also performed. It is executed for each transmission information.

  Next, in S430, when it is determined that the number of times C of periodic transmission information is transferred is greater than or equal to the threshold value Cmax, the process proceeds to S470, and the elapsed time when the time measurement is started in S460 described above is set in advance. It is determined whether or not the asynchronous determination time Tout is exceeded.

  If the elapsed time is not equal to or longer than the asynchronous determination time Tout, the asynchronous setting process is temporarily terminated. Conversely, if the elapsed time is equal to or longer than the asynchronous determination time Tout, the process proceeds to S480 and the transfer count C is set to the threshold. The number of transfers of the periodic transmission information whose elapsed time after reaching the value Cmax is equal to or greater than the asynchronous determination time Tout is set to a specified value (fixed value greater than the threshold Cmax: for example, value 15) representing the asynchronous information. Thus, the periodic transmission information is rewritten as asynchronous information, and the asynchronous setting process is temporarily ended.

  The periodical transmission information rewritten as asynchronous information in the periodical transmission period table 20 is not used for setting a transfer or random transmission prohibition period, but is stored in the periodical transmission period table 20 as a past history.

  As described above, in the asynchronous setting process, as illustrated in FIG. 14, in the communication device 2B that performs random transmission, when the periodic transmission information stored in the periodic transmission period table 20 cannot be received, the transfer count C Is counted up every periodic transmission, and the number of transfers C reaches a threshold value Cmax for stopping the transmission of the periodic transmission information. After that, when the asynchronous determination time Tout elapses, the vehicle It is determined that there is no problem even if the communication device 2A is separated from the communication device 2A corresponding to the transmission information, and random transmission is performed during the periodic transmission period of the communication device 2A, and the periodic transmission information is rewritten to asynchronous information.

  Therefore, even if the periodic transmission information from a large number of communication devices 2A that perform periodic transmission is registered in the periodic transmission period table 20, the communication devices 2B, 2C,. The random transmission prohibition period can be set only for the periodic transmission period that affects the periodic transmission of the other communication device 2A, and the random transmission period can be prevented from being restricted more than necessary.

  That is, for example, in the periodic transmission period table 20 of the communication device 2B, periodic transmission information from a large number of communication devices 2A provided around the travel route is registered as the automobile moves. Of these, the periodic transmission information that cannot be received even when the number of transfers C reaches the threshold value Cmax and the asynchronous determination time Tout elapses is excluded from the periodic transmission information used for control as asynchronous information. As illustrated, in the periodic transmission period table 20 of the communication device 2B, only the periodic transmission information of the communication devices 2A1, 2A2, and 2A3 that the transmission radio waves may interfere with each other remains as the periodic transmission information used for control. Therefore, the random transmission prohibition period is set based on the periodic transmission information, and the random transmission prohibition period is secured while preventing the periodic transmission from being affected. It is possible to become.

(Effect of embodiment)
As described above, in the wireless communication system according to the present embodiment, the communication device 2A having the periodic transmission function transmits the periodic transmission information indicating the periodic transmission period, and the communication devices 2B, 2C having the random transmission function.・ ・ Sets a random transmission prohibition period based on the periodic transmission information.

  In addition, the transmission time is given to the periodic transmission information, and the communication devices 2B, 2C,... That have received the periodic transmission information have the clock 4 between the devices based on the transmission time and their own reception time. Is calculated, and the time of the clock 4 is corrected.

  Therefore, according to the wireless communication system of the present embodiment, the communication devices 2B, 2C,... Are prevented from starting random transmission during the regular transmission period of the communication device 2A, and important by the communication device 2A. Periodic transmission of data can be preferentially executed.

  Further, since a guard time is provided between the random transmission prohibition period set by the communication apparatuses 2B, 2C,... And the regular transmission period, each communication apparatus 2A, 2B, 2C,. If the time of the clock 4 does not need to coincide with high accuracy and the time lag is within the allowable error range, the periodic transmission period in the communication device 2A and the random transmission in the communication devices 2B, 2C,. By synchronizing the prohibition period, it is possible to prevent collision between transmission data by regular transmission and transmission data by random transmission.

  Further, since the communication devices 2B, 2C,... Having the random transmission function retransmit the received periodic transmission information while updating the transfer count C, the periodic transmission information from the communication device 2A is transmitted within the transmission range. Can be transmitted to other communication devices that do not receive the transmission radio wave from the communication device 2A, and the probability that the transmission data that is periodically transmitted collides with the transmission data that is randomly transmitted is reduced. be able to.

  Here, in the present embodiment, the communication device 2A corresponds to the first communication device of the present invention, and the communication devices 2B and 2C correspond to the second communication device of the present invention. In the communication device 2, the data transmission unit 12 corresponds to the data transmission unit of the present invention, the modulation processing unit 14 corresponds to the modulation processing unit of the present invention, and the demodulation processing unit 16 includes the modulation processing of the present invention. The data receiving unit 18 corresponds to the data receiving unit and the transmission time giving unit of the present invention, the periodic transmission period table 20 corresponds to the storage unit of the present invention, and the transmission time determining unit 24 This corresponds to time setting means.

  Similarly, the periodic transmission period determination unit 30 corresponds to the periodic transmission permission unit of the present invention, the random transmission prohibition period determination unit 40 corresponds to the random transmission prohibition period setting unit and the random transmission prohibition unit of the present invention, The periodic transmission period update unit 50 corresponds to the periodic transmission information transmission control unit, the periodic transmission information registration unit, and the transfer control unit of the present invention. The timer reset unit 6 includes the first clock control unit and the second clocking unit of the present invention. The time difference calculation unit 52 and the time correction determination unit 54 correspond to the control unit, and correspond to the synchronization control unit of the present invention. Of these, the time correction determination unit 54 corresponds to the time correction unit of the present invention.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can take various forms without departing from the gist of the present invention.

[Modification 1]
For example, in the above embodiment, since the guard times G, A, and B are provided between the regular transmission period and the random transmission period, the regular transmission information transmitted by the communication device 2A includes a guard in the original regular transmission period. A period G and a guard time A corresponding to the transmission time of transmission data transmitted by the communication device 2A are set, and the communication device 2B, 2C,. In the above description, the random transmission prohibition period is set by adding the guard time B corresponding to the transmission time of the transmission data transmitted by itself.

  However, in order to provide the guard times G, A, and B between the regular transmission period and the random transmission period, it is not always necessary to do this, and the regular transmission information assigned to the communication device 2A is included in the regular transmission information. The communication devices 2B, 2C,... That receive the periodic transmission information and set the random transmission prohibition period while setting the period as it is, the guard times G, A, B in the periodic transmission period obtained from the periodic transmission information. The random transmission prohibition period may be determined by adding

  In this case, the communication devices 2B, 2C,... Include, as shown in FIG. 16, the data length (reception data length information) of the transmission data transmitted from the communication device 2A that performs periodic transmission, and the data. Is provided with a reception time determination unit 26 (corresponding to the reception time setting means of the present invention) for setting the reception time (guard time A) based on the demodulation method used when demodulating the signal by the demodulation processing unit 16. 26, the reception time information (guard time A) set by the transmission time determination unit 24, the transmission time information (guard time B) set by the transmission time determination unit 24, and the guard time information determined by the guard time determination unit 22 ( The guard time G) may be input to the random transmission prohibition period determining unit 40.

  That is, if the communication devices 2B, 2C,... Are configured in this way, the random transmission prohibition period determination unit 40 adds the guard times G, A, and B to the regular transmission period obtained from the regular transmission information. The random transmission prohibition period can be determined.

  In this case, on the communication device 2A side, the regular transmission period determination unit 30 may output the regular transmission period obtained from the regular transmission information stored in the regular transmission period table 20 to the data transmission unit 12 as it is. The configuration of the regular transmission period determination unit 30 can be simplified.

  As described above, in the communication devices 2B, 2C,..., When the guard times G, A, and B are added to the regular transmission period, the finally obtained random transmission prohibition period is shown in FIG. As shown in FIG. 17B, it is conceivable that both the guard time B side and the guard time A side as shown in FIG.

  However, when the random transmission prohibition period crosses the period of one periodical transmission as described above, the random transmission prohibition period is divided into two along the period and each transmission prohibition is performed as in the above embodiment. If the periods 1 and 2 are commanded to the data transmission unit 12 as random transmission prohibition periods, respectively, the circuit configuration for controlling the random transmission prohibition period can be simplified.

[Modification 2]
In addition, in order to provide the guard times A and B between the regular transmission period and the random transmission period, it is not always necessary to perform the guard time A and B as in the above-described embodiment and modification example 1. The periodic transmission information including A and B is transmitted, and the communication apparatus 2B, 2C,... May set the random transmission prohibition period using the periodic transmission period obtained from the periodic transmission information. Or alternatively, the communication device 2A transmits the periodic transmission information obtained by adding the guard time B to the periodic transmission period, and the communication devices 2B, 2C,... Receive the periodic transmission period obtained from the periodic transmission information. The random transmission prohibition period may be set by adding the guard time A.

  If the guard time G is added to the periodical transmission period of the periodical transmission information, especially in the case of the former configuration, the communication devices 2B, 2C,. The transmission period can be set as the random transmission prohibition period as it is, and the configuration of the random transmission prohibition period determination unit 40 can be simplified.

  However, in this case, the regular transmission period determination unit 30 sets the regular transmission period information to be output to the data transmission unit 12 by subtracting the guard times G, A, and B from the regular transmission period obtained from the regular transmission information. It is necessary to configure as follows.

[Modification 3]
On the other hand, in the above embodiment, in order to synchronize the periodic transmission period of the communication device 2A and the random transmission prohibition period of the communication devices 2B, 2C,..., The time of the clock 4 provided in each communication device is set. Although described as what is synchronized, as shown in FIG. 18, when the communication device 2A transmits periodic transmission information by periodic transmission and when the communication device 2B retransmits periodic transmission information by random transmission, Instead of the transmission time, the synchronization information indicating the time from the transmission time to the start timing of the next periodic transmission period is added to the periodic transmission information, and on the communication devices 2B and 2C side that received the periodic transmission information, The start time of the next periodic transmission is predicted based on the reception time of the periodic transmission information and the synchronization information, and the periodic transmission period of the communication device 2A is recognized based on the predicted start time and the periodic transmission information. It may be.

  Then, without synchronizing the time of the clock 4, the periodical transmission period of the communication device 2A and the random transmission prohibition period of the communication devices 2B, 2C,... Can be preferentially executed.

  Such an operation can be easily realized in the communication device 2 by changing the software processing as the periodic transmission period update unit 50 executed by the microcomputer, and thus detailed description thereof is omitted here. In this case, the periodic transmission period update unit 50 functions as a synchronization control unit (specifically, a synchronization information adding unit, a start time predicting unit, and a second synchronization information adding unit) of the present invention.

[Modification 4]
Next, in the above embodiment, in the periodic transmission information transfer process shown in FIG. 8, when the periodic transmission information is output to the data transmission unit 12 and the periodic transmission information is transferred, the periodic transmission information is random transmission. Although it has been described that it is given as one of the headers to the transmission data to be transmitted, when the periodic transmission information is transferred, the periodic transmission information is transmitted as single transmission data (in this case, similarly to the communication device 2A that performs the periodic transmission). (Random transmission).

[Modification 5]
Moreover, in the said embodiment, when communication apparatus 2B, 2C, ... receives periodic transmission information, it is judged whether it retransmits from the transfer frequency C of the periodic transmission information, and received periodic transmission Although the information has been described as being retransmitted, for example, when periodic transmission information is received or every periodic transmission period, all the periodic transmission information (asynchronous information is stored in the periodic transmission period table 20). May be retransmitted.

  In this case, the periodic transmission information to be retransmitted may be limited to the periodic transmission information in which the transfer count C is smaller than the threshold value Cmax among the periodic transmission information stored in the periodic transmission period table 20. .

[Modification 6]
Next, in the above embodiment, in order to limit the transmission range of the periodic transmission information, the number of transfers C is provided in the periodic transmission information, and the communication devices 2B, 2C,. Although it has been described that the received periodic transmission information is transferred until Cmax is reached, in order to limit the transmission range of the periodic transmission information, for example, the reception time at which the periodic transmission information is received is the same as the previous time when the device ID is the same. Based on the time difference from the reception time when the transmission information was received, the elapsed time from the previous reception of the periodic transmission information is obtained. If that time is longer than the threshold value, the retransmission of the periodic transmission information (transfer) ) May be canceled.

  And even if it does in this way, since communication apparatus 2B, 2C, ... will stop transfer of periodical transmission information, when distance between communication apparatuses 2A becomes long, periodical transmission information The transmission range can be limited.

[Modification 7]
In the above embodiment, when calculating the synchronization deviation amount of the clock 4 from the time difference between the transmission time and the reception time of the periodic transmission information in S260 of the periodic transmission information update / time synchronization processing shown in FIG. Explanation is made assuming that a preset offset amount is used based on the modulation processing delay generated in the modulation processing unit 14 on the transmission side, the propagation delay generated in the radio wave propagation path, and the demodulation processing delay generated in the demodulation processing unit 16 on the reception side. However, the offset amount is determined by the transmission time (that is, modulation processing delay) set by the transmission time determination unit 24 and the reception time (that is, demodulation processing delay) set by the reception time determination unit 26 (see FIG. 16). ) And a preset propagation delay.

  In this way, the offset amount can be set corresponding to the operations of the modulation processing unit 14 and the demodulation processing unit 16, and the synchronization deviation amount can be more accurately determined from the transmission time and the reception time of the periodic transmission information. Can be calculated.

[Modification 8]
In the above embodiment, when the periodic transmission information is sequentially transmitted from the communication device 2A to the communication device 2B and from the communication device 2B to the communication device 2C, a transmission time is added to the periodic transmission information. The communication apparatus that has received the transmission information has been described as performing time synchronization of the clock 4 based on the transmission time transmitted together with the periodic transmission information and the reception time of the periodic transmission information. May be transmitted as time information at a timing different from the periodic transmission information.

  2, 2A, 2B, 2C ... communication device, 4 ... watch, 6 ... timer reset unit, 12 ... data transmission unit, 14 ... modulation processing unit, 16 ... demodulation processing unit , 18 ... Data reception unit, 20 ... Periodic transmission period table, 22 ... Guard time determination unit, 24 ... Transmission time determination unit, 26 ... Reception time determination unit, 30 ... Periodic Transmission period determination unit, 40... Random transmission prohibition period determination unit, 50... Regular transmission period update unit, 52.

Claims (9)

When a data transmission request occurs, it is determined whether or not a communication channel is vacant, and a radio communication device that performs random transmission by radio when the communication channel is vacant,
Periodic transmission information representing a periodic transmission period transmitted from an external communication device that performs periodic transmission of data using the communication channel, and an area in which the radio communication device itself receives transmission radio waves from the external communication device Directly from the external communication device when it is located, or via another wireless communication device that performs random transmission when the wireless communication device itself is located outside the area where the transmission radio wave from the external communication device reaches And receiving means capable of receiving,
When the periodic transmission information is received by the receiving means, the random transmission prohibition period is set in the periodic transmission period of data obtained from the received periodic transmission information, and the random transmission in the set random transmission prohibition period Prohibiting means to prohibit,
A wireless communication apparatus comprising: transmission means capable of transmitting periodic transmission information received by the reception means to the other wireless communication apparatus. A first communication device that periodically transmits transmission data using a predetermined communication channel;
A second communication device having a random transmission function for determining whether or not the communication channel is free when a data transmission request is generated, and performing random transmission wirelessly when the communication channel is free and third; A communication device;
A wireless communication system in which
The first communication device includes means for periodically transmitting transmission data including regular transmission information representing a regular transmission period in a fixed period within an area where transmission radio waves reach,
When the second communication device is located in an area where the transmission radio wave from the first communication device reaches and receives transmission data including the periodic transmission information transmitted from the first communication device, the received periodic Means for setting a random transmission prohibition period of itself in a periodic transmission period of data obtained from transmission information, and prohibiting the random transmission in the set random transmission prohibition period;
Means for transmitting the received periodic transmission information to the third communication device;
Based on the periodic transmission information received from the second communication device, the third communication device sets its own random transmission prohibition period in the periodic transmission period obtained from the periodic transmission information, and the set random transmission prohibition A wireless communication system comprising means for prohibiting the random transmission during a period.   The wireless communication apparatus according to claim 1, wherein the transmission unit transmits the periodical transmission information received by the reception unit by including it in other transmission data.   The wireless communication apparatus according to claim 1, wherein the transmission unit independently transmits the regular transmission information received by the reception unit as one transmission data.   The wireless communication device is an in-vehicle device mounted on a vehicle, the external communication device is a road device installed in the vicinity of a traveling path of the vehicle, and the other wireless communication device is mounted on the vehicle. The wireless communication device according to claim 1, wherein the wireless communication device is a vehicle-mounted device. Further, a fourth communication device having a random transmission function for determining whether or not the communication channel is free when a data transmission request occurs and performing random transmission by radio when the communication channel is free is provided. Prepared,
The wireless communication system according to claim 2, wherein the third communication device includes means capable of transmitting the periodic transmission information received from the second communication device to the fourth communication device.   The wireless communication system according to claim 2 or 6, wherein the second communication device transmits the periodical transmission information transmitted from the first communication device including other transmission data.   The wireless communication system according to claim 2 or 6, wherein the second communication device transmits the periodic transmission information transmitted from the first communication device alone as one transmission data.   8. The first communication device is a road device installed in a distributed manner near a vehicle traveling path, and the second communication device and the third communication device are in-vehicle devices mounted on the vehicle. , 8. The wireless communication system according to claim 1.

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