Communication method, communication device, and communication system

Abstract

To provide a technique that can improve a communication success rate of wireless communication.SOLUTION: An exemplary communication method is a communication method using wireless communication. In the communication method, just before an expected reception time agreed upon between a plurality of devices performing the wireless communication, switching is performed from a mask mode, in which the wireless communication is not possible, to a reception mode, in which the wireless communication is received.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a communication technology using wireless communication. [Background technology]

[0002] In recent years, wireless communication has been increasing in the field of communications due to its advantages in terms of installation, such as the absence of wiring. For example, UWB (Ultra Wide Band) communications, which use radio waves in the 8 GHz band, have little radio interference with radio waves used in Wi-Fi (registered trademark) and mobile terminals such as smartphones, and have good transparency due to their wide bandwidth of 500 MHz, leading to a wide range of applications.

[0003] For example, Patent Document 1 discloses that the vehicle and the electronic key send UWB radio waves to each other in random patterns to perform distance verification. In addition, UWB communication is expected to be a communication method for in-vehicle devices because it is easy to establish communication inside the vehicle, which is a narrow metal space with many wires. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-38332 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if UWB communication becomes widespread, interference between UWB communications will easily occur, which may result in communication interruptions. This communication interruption problem is not limited to the communication means of in-vehicle devices and UWB communication, but may also occur when multiple devices communicate using radio waves in the same frequency band.

[0006] In view of the above, an object of the present invention is to provide a technique capable of improving the communication success rate in wireless communication. [Means for solving the problem]

[0007] An exemplary communication method of the present invention is a communication method that uses wireless communication, and switches from a mask mode, in which the wireless communication is not possible, to a reception mode in which the wireless communication is received, just before an expected reception time agreed upon between multiple devices performing the wireless communication. Effect of the Invention

[0008] According to an exemplary embodiment of the present invention, it is possible to improve the success rate of wireless communication. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 illustrates an example of the configuration of a communication system. [Diagram 2] A schematic diagram to explain problems with reception in UWB communications. [Diagram 3] Schematic diagram showing an overview of radio interference countermeasures in communication systems [Figure 4] FIG. 1 shows an example of the configuration of a master communication device. [Diagram 5] 1 is a flowchart showing an example of the operation of a master communication device. [Figure 6] FIG. 13 is a diagram showing an example of a data format of a wireless communication schedule; [Figure 7] FIG. 1 shows an example of the configuration of a slave communication device. [Figure 8] Flowchart showing an example of the operation of a slave communication device [Figure 9] FIG. 13 is a schematic diagram for explaining a detailed example of how to set the reception mode start time τstart. [Figure 10] FIG. 1 is a schematic diagram showing an example of an operation of a communication system according to a wireless communication schedule; [Figure 11] FIG. 1 is a diagram showing a configuration example of a communication system according to a first modified example; [Figure 12] FIG. 13 is a diagram showing the relationship between a master communication device and a slave communication device included in a communication system according to a first modification; [Figure 13]FIG. 13 is a diagram showing a configuration of a communication system according to a second modified example. [Figure 14] 1 is a flowchart showing an example of a process executed by a master communication device during calibration of radio wave output. [Figure 15] FIG. 15 is a diagram for explaining the operation of the slave communication device when the process shown in FIG. 14 is executed; [Figure 16] An example of a correlation map showing the relationship between device distance and transmission power DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the description of the embodiments, the same components are given the same reference numerals, and duplicated descriptions will be omitted unless particularly necessary.

[0011] <1. Communication Systems> 1 is a diagram showing a configuration example of a communication system SYS1 according to an embodiment of the present invention. In this embodiment, as an example, the communication system SYS1 is mounted on a vehicle C1. However, the communication system SYS1 may be applied to a device other than the vehicle C1, and may be used for home use, office use, or factory use, for example.

[0012] As shown in Fig. 1, the communication system SYS1 includes a master ECU (Electric Control Unit) 10 and a plurality of slave machines 20a to 20d. The communication system SYS1 is, for example, a vehicle control system in which the master ECU 10 controls each of the slave machines 20a to 20d by UWB communication in response to a user operation on an HMI (Human Machine Interface) 40. Specifically, each of the slave machines 20a to 20d transmits a sensor value or the like detected by a sensor connected to the slave machine 20a to 20d to the master ECU 10. Each of the slave machines 20a to 20d controls an actuator connected to the slave machine 20a to 20d based on a control signal transmitted from the master ECU 10.

[0013] The first slave device 20a is, for example, a control device that controls the operation of a headlight. The second slave device 20b is, for example, a control device that controls the operation of a wiper. The third slave device 20c is, for example, a control device that controls the operation of a power window. The fourth slave device 20d is, for example, a control device that controls the operation of an air conditioner.

[0014] Since UWB communication is performed between the master ECU 10 and each of the slave devices 20a to 20d, hereinafter, the master ECU 10 will be referred to as the master communication device 10, and the slave devices 20a to 20d will be referred to as the slave communication devices 20a to 20d. Furthermore, when there is no need to distinguish between the multiple slave communication devices 20a to 20d, each of the slave communication devices 20a to 20d may be simply referred to as the slave communication device 20.

[0015] In this embodiment, there is a plurality of slave communication devices 20, but there may be only one. Furthermore, the communication devices in the communication system do not necessarily have to have a master-slave relationship, and may have an equal relationship.

[0016] In this embodiment, the master communication device 10 and the slave communication device 20 perform UWB communication as described above. That is, the wireless communication in this embodiment is wireless communication by the UWB communication method. The UWB communication is performed according to a standard such as IEEE 802.15.4 (hereinafter, sometimes simply referred to as a communication standard). However, the wireless communication may be other than UWB communication, and may be, for example, Wi-Fi (registered trademark) communication, Bluetooth (registered trademark) communication, BLE (registered trademark, Bluetooth Low Energy) communication, LPWA (Low Power Wide Area) communication, Zigbee (registered trademark) communication, etc.

[0017] The master communication device 10 may transmit a signal to the slave communication device 20 or may receive a signal from the slave communication device 20. The slave communication device 20 may receive a signal from the master communication device 10 or may transmit a signal to the master communication device 10. That is, the communication system SYS1 includes a first wireless communication device that transmits signals by wireless communication and a second wireless communication device that receives signals by wireless communication. Each of the master communication device 10 and the slave communication device 20 can be either the first wireless communication device or the second wireless communication device. That is, the master communication device 10 is the first wireless communication device in a signal transmission state and is the second wireless communication device in a signal reception state. The slave communication device 20 is also the first wireless communication device in a signal transmission state and is the second wireless communication device in a signal reception state.

[0018] In this embodiment, the master communication device 10 and each of the slave communication devices 20a to 20d perform UWB communication. Therefore, the communication system SYS1 contributes to reducing the number of wire harnesses used in the vehicle C1.

[0019] Here, an overview of radio interference countermeasures in the communication system SYS1 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a schematic diagram for explaining problems during reception in UWB communication. Fig. 3 is a schematic diagram showing an overview of radio interference countermeasures in the communication system SYS1. In Fig. 3, "master" refers to the master communication device 10, and "slave" refers to the slave communication device 20. Similar simplified expressions may be used in other figures.

[0020] The format of a communication frame (a unit of transmission data) in UWB communication (hereinafter referred to as the communication frame format) is determined by the above-mentioned communication standard. As shown in Figure 2, the frame format used in UWB communication has a structure in which a preamble is at the beginning, followed by a Start Frame Delimiter (SFD), a PHY Header (PHR), and the data body, in that order. The term "data body" is used to make it easier to understand the difference between the preamble, SFD, and PHR.

[0021] A preamble is a bit string of a specific pattern that is transmitted prior to the data body in digital communication to inform the receiving side that "data is about to be sent." The receiving side uses the preamble signal to start the receiving clock (bit synchronization). There are multiple types of preamble patterns. The multiple types of preamble patterns are identified by a preamble code. Different preamble codes use different code symbols. The code symbols are composed of ternary symbols (e.g., -, 0, +). One code symbol (one symbol) is composed, for example, of "-+0++000-+-++00++0+00-0000-0+0-".

[0022] The SFD is a bit string of a specific pattern for signaling the beginning of data in a communication frame. The PHR includes information required for decoding a packet. For example, the PHR includes the address of the communication partner and information on the data length of the subsequent data. The data body is the main body of information to be transmitted to the communication partner and includes the actual data to be transmitted. For example, the data body includes information such as ID information of the receiver of the communication frame, ID information of the sender, instruction information from the master communication device 10 to the slave communication device 20, sensor values ​​detected by sensors equipped in the slave communication device 20, and the operating state of the actuator to be controlled by the slave communication device 20.

[0023] In FIG. 2, the target wave is a radio wave that is desired to be received by the receiving antenna RA1. The jamming wave is a radio wave that is not desired to be received by the receiving antenna RA1. In UWB communication, the strength of the radio wave also has an effect, but the radio wave that is received earlier is basically processed preferentially. In detail, the communication device enters synchronization processing of the preceding radio wave, and processing of the subsequent radio wave cannot be performed. In FIG. 2, two radio waves arrive at the receiving antenna RA1 in the order of the jamming wave and the target wave. For this reason, the jamming wave is processed preferentially. If the receiving device receives the jamming wave first, it cannot recognize that it is a jamming wave unless it demodulates the address in the PHR that is processed following the preamble and SFD. Note that if it is recognized as a jamming wave, the processing for the jamming wave is stopped, and the receiving processing of other waves (such as the subsequent target wave) becomes possible. There is a possibility that the target wave will arrive at the receiving antenna RA1 before it is determined that the radio wave is a jamming wave by the receiving processing, in which case the target wave will be missed. In this embodiment, measures are taken to reduce communication failures due to such radio interference. An overview of the measures will be described with reference to FIG. 3.

[0024] As shown in Fig. 3, each of the master communication device 10 and the slave communication device 20 can select one of a reception mode, a transmission mode, and a mask mode. In the reception mode, each of the devices 10 and 20 can receive. In the transmission mode, each of the devices 10 and 20 can transmit. The mask mode is a mode that is neither a reception mode nor a transmission mode, and in the mask mode, each of the devices 10 and 20 cannot communicate. The mask mode is a so-called idle mode in which power is supplied to necessary circuits, etc., and the devices can immediately switch to the reception mode or the transmission mode.

[0025] In Figure 3, τ start is the time when the communication devices 10 and 20 start the reception mode (the reception mode start time). next is the time when the target wave is expected to be received (expected reception time), and is a time according to the agreement between the communication devices 10 and 20. start is the expected reception time τnext The mode is set slightly before the expected reception time. As shown in FIG. 3, the master communication device 10 switches from the mask mode to the reception mode just before the expected reception time agreed upon between the slave communication device 20 and the master communication device 10. The slave communication device 20 switches from the mask mode to the reception mode just before the expected reception time agreed upon between the master communication device 10 and the master communication device 10. That is, in the communication method using wireless communication according to the present embodiment, the mask mode in which wireless communication is not possible is switched to the reception mode in which wireless communication is received just before the expected reception time agreed upon between the multiple devices 10 and 20 performing wireless communication. Also, in the communication device using wireless communication according to the present embodiment, the mask mode is switched to the reception mode just before the expected reception time agreed upon between the other device performing wireless communication. The switching process just before the expected reception time may be executed when the transmission mode is switched to the reception mode.

[0026] With this configuration, it is possible to increase the probability that the device receiving the target wave is in mask mode when the jamming wave arrives. In other words, it is possible to reduce the possibility of receiving the jamming wave and increase the probability of properly receiving the target wave. This makes it possible to improve the success rate of wireless communication. Note that it is preferable to set the start time of the receiving mode as close as possible to the expected time of receiving the target wave. A detailed example of this will be described later.

[0027] <2. Master communication device> Fig. 4 is a diagram showing an example of the configuration of the master communication device 10. Note that Fig. 4 shows components necessary for explaining the features of this embodiment, and omits a description of general components.

[0028] As shown in FIG. 2, the master communication device 10 includes a wireless communication unit 11 and a controller 12.

[0029] The wireless communication unit 11 performs wireless communication with the slave communication device 20. Specifically, the wireless communication unit 11 is configured with a UWB communication device that performs UWB communication with the slave communication device 20. The wireless communication unit 11 is capable of receiving when in a receiving mode, is capable of transmitting when in a transmitting mode, and is unable to communicate when in a mask mode that is neither the receiving mode nor the transmitting mode.

[0030] The controller 12 includes a processor that performs arithmetic processing and the like. The processor may include, for example, a CPU (Central Processing Unit). The controller 12 may be configured with one processor or multiple processors. When configured with multiple processors, the processors only need to be connected to each other so that they can communicate with each other. The controller 12 also includes computer components such as memory (RAM, ROM, etc.) necessary for executing programs.

[0031] The controller 12 includes, as its functions, a schedule creation unit 121, a schedule provision unit 122, and a schedule execution unit 123. Each of the functional units 121 to 123 may be realized, for example, by a processor executing arithmetic processing according to one program. However, this is not limited to the above configuration, and each of the functional units 121 to 123 may be realized, for example, by a processor executing arithmetic processing according to a separate program for each functional unit.

[0032] As described above, each of the functional units 121 to 123 may be realized by having a processor execute a program, that is, by software, but may also be realized by other methods. At least a part of each of the functional units 121 to 123 may be realized by using, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). That is, each of the functional units 121 to 123 may be realized by hardware using a dedicated IC or the like. Also, each of the functional units 121 to 123 may be realized by using both software and hardware. Also, each of the functional units 121 to 123 is a conceptual component. A function executed by one component may be distributed to multiple components. Also, functions possessed by multiple components may be integrated into one component.

[0033] The schedule creation unit 121 creates a schedule for UWB communication between the master communication device 10 and the slave communication device 20 (hereinafter referred to as a wireless communication schedule). The wireless communication schedule includes the timing of signal transmission and reception in each of the communication devices 10, 20. In this embodiment, there are multiple slave communication devices 20. For this reason, the schedule creation unit 121 creates a wireless communication schedule between the master communication device 10 and each of the slave communication devices 20a to 20d.

[0034] The schedule providing unit 122 provides the wireless communication schedule created by the schedule creation unit 121 to the slave communication device 20. In this embodiment, there are a plurality of slave communication devices 20. For this reason, the schedule providing unit 122 transmits the wireless communication schedule to each of the slave communication devices 20a to 20d. The wireless communication schedule may be transmitted to each of the slave communication devices 20a to 20d separately for each of the slave communication devices 20a to 20d. However, in this embodiment, the schedule providing unit 122 performs broadcast transmission in which the wireless communication schedule is transmitted simultaneously to the plurality of slave communication devices 20a to 20d.

[0035] The schedule execution unit 123 executes wireless communication in accordance with the wireless communication schedule created by the schedule creation unit 121. The schedule execution unit 123 controls the communication mode of the wireless communication unit 11 when wireless communication is executed.

[0036] Fig. 5 is a flowchart showing an example of the operation of the master communication device 10. The operation shown in Fig. 5 is started, for example, when a body ECU that is installed in the vehicle C1 and controls the body of the vehicle C1 is started. The body ECU specifically controls in-vehicle devices other than the vehicle driving system devices such as an engine. The in-vehicle devices other than the vehicle driving system devices include, for example, an air conditioner, a door lock device, a window opening / closing device, a wiper device, etc.

[0037] The start timing of the body ECU is, as a representative example, the timing when the door of the vehicle C1 is unlocked, and as another example, when the ACC is turned on based on the operation of the ignition key of the vehicle. In the case where the communication system is applied to other moving bodies (for example, when applied to trains, ships, aircraft, etc.), the start timing of the operation shown in FIG. 5 is the timing of the start operation of the moving body drive system, etc. In addition, the operation shown in FIG. 5 may be executed, for example, as a periodic operation (for example, an operation executed immediately after startup, an operation executed at a predetermined time interval) or an exceptional operation (for example, an operation when communication failure occurs or increases, or when there is a change in the vehicle (communication) environment) after the body ECU is started. In addition, at least one of the master communication device 10 and the slave communication devices 20a to 20d may be a body ECU, and all of the master communication device 10 and the slave communication devices 20a to 20d may not be body ECUs. The body ECU may be, for example, an entertainment device such as an audio device.

[0038] In step S1, the schedule creation unit 121 creates a wireless communication schedule. The wireless communication schedule includes the time for transmitting data from the master communication device 10 to each of the slave communication devices 20a to 20d, and the time for receiving data from the master communication device 10 from each of the slave communication devices 20a to 20d. Once the wireless communication schedule is created, the process proceeds to the next step S2. Note that information regarding the wireless communication connections of each of the slave communication devices 20a to 20d, which are wireless communication target devices, is set and registered (stored) in the master communication device 10 by an administrator or the like of the master communication device 10. Furthermore, when a new wireless communication target device is added, the additional device is set and registered (stored) by the administrator or the like.

[0039] In step S2, the schedule providing unit 122 broadcasts (transmits simultaneously) the wireless communication schedule to all the slave communication devices 20a to 20d. That is, in this embodiment, the communication system SYS1 (vehicle communication system) determines an expected reception time between the master communication device 10 and the slave communication device 20 when starting to use the vehicle. The wireless communication schedule is broadcast in accordance with the communication frame format (see FIG. 2) of the UWB communication described above. The wireless communication schedule is included in the data body of the communication frame format.

[0040] Fig. 6 is a diagram showing an example of a data format of a wireless communication schedule. As shown in Fig. 6, the data format of the wireless communication schedule has a structure in which time data D1, first data D2a, second data D2b, third data D2c, fourth data D2d, and cycle data D3 are connected in order.

[0041] The time data D1 is data indicating the time when the broadcast transmission was actually performed (hereinafter referred to as the broadcast transmission time). The broadcast transmission time is measured by the controller 12 based on a timer (not shown) built into the master communication device 10. The timer is composed of a counter or the like that counts at regular time intervals based on an operating clock.

[0042] The first data D2a is data related to the first slave communication device 20a. The second data D2b is data related to the second slave communication device 20b. The third data D2c is data related to the third slave communication device 20c. The fourth data D2d is data related to the fourth slave communication device 20d.

[0043] Each of the data D2a to D2d has a structure in which ID data D21 and time data D22 are sequentially connected. The ID data D21 is data indicating the ID (identification information) of each of the slave communication devices 20a to 20d. The time data D22 is data indicated by a time interval based on a broadcast transmission time or the like, and is data relating to the transmission time of data from the master communication device 10 and the reception time of data by the master communication device 10. The transmission time and reception time are expressed in a format such as how many milliseconds after the broadcast transmission time. The transmission time and reception time are not transmitted as a time because there is a possibility that the recognition times of the communication devices 10, 20a to 20d may not match.

[0044] The cycle data D3 is data indicating the cycle of communication timing between the master communication device 10 and each of the slave communication devices 20a to 20d (for example, see cycle T shown in FIG. 10).

[0045] Returning to FIG. 5, once the wireless communication schedule is broadcast, the process proceeds to the next step S3.

[0046] In step S3, the schedule providing unit 122 judges whether or not there is a reception response from all the slave communication devices 20a to 20d to which the wireless communication schedule has been transmitted. The reception response is a reply to the effect that the wireless communication schedule has been received, and is a process that is requested of each of the slave communication devices 20a to 20d that has received the wireless communication schedule. Since the request is included in the data of the wireless communication schedule described above, the slave communication device 20 that has received the wireless communication schedule will return a response unless it is malfunctioning. However, due to the above-mentioned radio interference or other reasons, there may be a device among the slave communication devices 20a to 20d that fails to receive the wireless communication schedule. In particular, before the broadcast transmission, each of the slave communication devices 20a to 20d does not have a wireless communication schedule, and therefore cannot switch from the mask mode to the reception mode at the appropriate timing described above. For this reason, it is necessary to be in the reception mode for a long period of time, which is easily affected by radio interference.

[0047] If there is a reception response from all the slave communication devices 20a to 20d (Yes in step S3), the process proceeds to the next step S4. On the other hand, if there is no reception response from any of the slave communication devices 20a to 20d (No in step S3), the process returns to step S1. That is, if there is no reception response from all the devices 20a to 20d targeted for the broadcast transmission of the wireless communication schedule, the broadcast transmission of the wireless communication schedule is performed again. With this configuration, it is possible to prevent the wireless communication schedule from being executed in a state in which the wireless communication schedule is not properly transmitted from the master communication device 10 to the slave communication device 20. Note that if the rebroadcast transmission of the wireless communication schedule is performed in the cycle D3, the reception mode timing of each of the slave communication devices 20a to 20d according to the wireless communication schedule in the rebroadcast transmission will be the same as a result. Therefore, it is possible to set the communication timing with each of the slave communication devices 20a to 20d not only when there is a reception response from all the slaves in the same broadcast transmission, but also when there are reception responses from all the slaves in multiple broadcast transmissions.

[0048] In step S4, the schedule providing unit 122 finalizes the wireless communication schedule. When the wireless communication schedule is finalized, the process proceeds to the next step S5.

[0049] In step S5, the schedule execution unit 123 starts wireless communication processing according to the wireless communication schedule. A specific example of the wireless communication processing according to the wireless communication schedule will be described later.

[0050] In the configuration of this embodiment, for example, if at least one of the slave communication devices 20a to 20d is malfunctioning, the process in step S3 will not become "Yes", and the wireless communication schedule will never be finalized. In consideration of this, for example, if the process in step S3 does not become "Yes" even after broadcast transmission is performed a predetermined number of times (e.g., three times), an error may be notified. As another example, a wireless communication schedule may be created that excludes the malfunctioning slave communication devices 20a to 20d, and wireless communication processing may be performed according to the schedule.

[0051] <3. Slave communication device> Fig. 7 is a diagram showing an example of the configuration of the slave communication device 20. Note that Fig. 7 shows components necessary for explaining the features of this embodiment, and a description of general components is omitted. Furthermore, all of the multiple slave communication devices 20a to 20d have the configuration shown in Fig. 7. As shown in Fig. 7, the slave communication device 20 includes a wireless communication unit 21 and a controller 22.

[0052] The wireless communication unit 21 performs wireless communication with the master communication device 10. Specifically, the wireless communication unit 21 is configured with a UWB communication device that performs UWB communication with the master communication device 10 (wireless communication unit 11). The wireless communication unit 21 is capable of receiving when in a receiving mode, capable of transmitting when in a transmitting mode, and is unable to communicate when in a mask mode that is neither the receiving mode nor the transmitting mode.

[0053] The controller 22 includes a processor that performs arithmetic processing and the like. The processor may include, for example, a CPU. The controller 22 may be configured with one processor or multiple processors. When configured with multiple processors, the processors only need to be connected to each other so that they can communicate with each other. The controller 22 also includes computer components such as memory (RAM, ROM, etc.) necessary for executing programs.

[0054] The controller 22 includes, as its functions, a schedule acquisition unit 221 and a schedule execution unit 222. Each of the functional units 221 and 222 may be realized, for example, by a processor executing arithmetic processing according to one program. However, this is not limited to such a configuration, and each of the functional units 221 and 222 may be realized, for example, by a processor executing arithmetic processing according to a separate program for each functional unit.

[0055] As described above, each of the functional units 221 and 222 may be realized by having a processor execute a program, i.e., by software, but may also be realized by other methods. At least a part of each of the functional units 221 and 222 may be realized by using, for example, an ASIC or an FPGA. That is, each of the functional units 221 and 222 may be realized by hardware using a dedicated IC or the like. Also, each of the functional units 221 and 222 may be realized by using both software and hardware. Also, each of the functional units 221 and 222 is a conceptual component. A function executed by one component may be distributed to multiple components. Also, functions possessed by multiple components may be integrated into one component.

[0056] The schedule acquisition unit 221 acquires the wireless communication schedule provided from the master communication device 10 via the wireless communication unit 21. The schedule acquisition unit 221 may perform necessary processing on the acquired wireless communication schedule as appropriate. For example, the schedule acquisition unit 221 may perform processing to convert time data included in transmission data broadcast from the master communication device 10 into the time of its own device.

[0057] The schedule executing unit 222 executes wireless communication in accordance with the wireless communication schedule acquired by the schedule acquiring unit 221. The schedule executing unit 222 controls the communication mode of the wireless communication unit 21 when executing wireless communication.

[0058] Fig. 8 is a flowchart showing an example of the operation of the slave communication device 20. Note that in this embodiment, there are multiple slave communication devices 20, but similar operations are performed in each of the slave communication devices 20a to 20d. The operation shown in Fig. 8 is started in accordance with the operation of the master communication device 10 described above (see Fig. 5). That is, the operation shown in Fig. 8 is started, for example, when the body ECU is started. The operation shown in Fig. 8 may be executed, for example, as a regular operation or an exceptional operation after the body ECU is started.

[0059] In step S11, the schedule acquisition unit 221 determines whether or not a wireless communication schedule has been received. If a wireless communication schedule has been received (Yes in step S11), the process proceeds to the next step S12. On the other hand, if a wireless communication schedule has not been received (No in step S11), the process of step S11 is repeated. That is, in step S11, it is monitored whether or not a wireless communication schedule has been received.

[0060] In step S12, the schedule acquisition unit 221 responds to the reception of the wireless communication schedule. In detail, the schedule acquisition unit 221 responds to the reception of the wireless communication schedule in response to a reply request from the master communication device 10 contained in the data including the wireless communication schedule. The reply is transmitted from the slave communication device 20 to the master communication device 10 using UWB communication. When the reply to the reception of the wireless communication schedule is completed, the process proceeds to the next step S13.

[0061] In step S13, the schedule acquisition unit 221 converts the transmission time and reception time (for example, the time indicated in a format of how many milliseconds later) based on the broadcast transmission time included in the wireless communication schedule into the time of the own device. The schedule acquisition unit 221 performs the time conversion process based on a timer (not shown) built into the own device. When the time conversion process is completed, the process proceeds to the next step S14.

[0062] In step S14, the schedule acquisition unit 221 finalizes the wireless communication schedule. Note that the process of step S14 may be executed before the process of step S13. When the wireless communication schedule is finalized, the process proceeds to the next step S15.

[0063] In step S15, the schedule execution unit 222 starts wireless communication processing according to the wireless communication schedule. A specific example of the wireless communication processing according to the wireless communication schedule will be described later.

[0064] <4. Example of operation of a communication system according to a wireless communication schedule> Next, an example of the operation of the communication system SYS1 according to the wireless communication schedule will be described. During data communication processing according to the wireless communication schedule, the master communication device 10 and the slave communication device 20 start the reception mode at a time τ start As mentioned above, the expected reception time τ next The reception mode start time is immediately before τ start is the time when the mask mode is switched to the receive mode. Also, the expected reception time τ next The process of switching to the receive mode immediately before the broadcast may also be executed when the master communication device 10 receives a reception response from the slave communication device 20 after the broadcast transmission.

[0065] Estimated reception time τ next is calculated according to a wireless communication schedule broadcast from any one of the multiple devices 10, 20a to 20d. In this embodiment, the wireless communication schedule is broadcast from the master communication device 10 as described above. The expected reception time τ next is a time obtained by an agreement between the master communication device 10 and each of the slave communication devices 20a to 20d according to the wireless communication schedule. With this configuration, it is possible to obtain accurate reception timing according to the communication schedule, and it is possible to appropriately start the reception mode.

[0066] Reception mode start time τ start In order to avoid interference from interference waves, the expected reception time τ next In this embodiment, the reception mode start time τ start FIG. 9 shows the reception mode start time τ start FIG. 13 is a schematic diagram for explaining a detailed example of how to set the

[0067] In the UWB communication standard, the time of transmission and reception can be obtained at the timing of the PHR. In consideration of this point, in this embodiment, as shown in FIG. 9, the expected reception time τ next is determined based on the PHR included in the frame format used in wireless communication. According to this, in UWB wireless communication, the reception mode start time τ is set at an appropriate timing that can reduce the probability of interference by jamming waves. start In detail, it is possible to easily set the expected reception time τ next is set to the start timing of the PHR.

[0068] In this embodiment, the expected reception time τ next The receive mode start time τ start is determined by the following equation (1). τ start = τ next -(t SFD +t sym × N rg ) (1)

[0069] In equation (1), t SFD is the reception period (SFD time) of the SFD included in the frame format. sym is the reception period (one symbol time) of one symbol of the preamble code in the preamble included in the frame format. One symbol of the preamble code refers to a code symbol composed of ternary symbols (e.g., -, 0, +) as described above. N rgis the number of times required to recognize one symbol of the preamble code. rg Only when one symbol of the preamble code is recognized can the UWB communication transmission data be received. Note that the number of required recognitions is N rg is a number determined by the devices 10 and 20 (device-dependent number). In the example shown in FIG. 9, the required number of recognitions N rg For example, t is 4 times. sym The number of required recognitions N depends on the device. rg In this embodiment, the minimum recognition period of the preamble can be calculated by multiplying the expected reception time τ next Rather than the formula (t SFD +t sym × N rg ) is the receive mode start time τ start It is as follows.

[0070] By determining the reception mode start time in this way, the start of the period during which transmission data of UWB communication can be received can be set as close as possible to the expected reception time. This reduces the possibility of being affected by interference waves, and improves the success rate of communication. Note that the reception mode start time τ start is the expected reception time τ next than the formula (t SFD +t sym × N rg ) may be set to a time earlier by a margin time obtained by an experiment or the like.

[0071] Fig. 10 is a schematic diagram showing an example of the operation of the communication system SYS1 according to the wireless communication schedule. The operation shown in Fig. 10 corresponds to the execution of the wireless communication schedule in step S5 in Fig. 5 and step S15 in Fig. 8. In Fig. 10, the master communication device 10 and each of the slave communication devices 20a to 20d are in the mask mode when they are not in the reception mode even if they are in the transmission mode.

[0072] 10, the predetermined wireless communication between the master communication device 10 and each of the four slave communication devices 20a to 20d is repeated in sequence in the period T according to the wireless communication schedule, but this is merely an example. The predetermined wireless communication may be performed only once in sequence between the master communication device 10 and each of the four slave communication devices 20 according to the wireless communication schedule. The number of slave communication devices 20 that periodically perform wireless communication with the master communication device 10 may be changed as appropriate, and the communication system SYS1 may be configured such that some of all the slave communication devices 20a to 20d included in the communication system SYS1 periodically perform wireless communication with the master communication device 10.

[0073] 10, the master communication device 10 first starts the transmission mode according to the wireless communication schedule. Then, the master communication device 10 transmits a signal to the first slave communication device 20a after a time (transmission time Ta) agreed upon with the first slave communication device 20a according to the wireless communication schedule has elapsed from the transmission time of the above-mentioned broadcast transmission. The transmission signal includes, for example, instruction information for the first slave communication device 20a. The master communication device 10 completes the transmission mode at a timing that is determined by the time required for data transmission (depending on the amount of data to be transmitted, etc.) based on the start timing of the transmission mode and that is preprogrammed in the device 10.

[0074] The first slave communication device 20a receives the signal at an estimated reception time τ , which is determined by the transmission time Ta that is determined between the first slave communication device 20a and the first slave communication device 20b according to the wireless communication schedule. next From equation (1), the receive mode start time τ start Then, the first slave communication device 20a calculates the reception mode start time τ start The first slave communication device 20a then performs a process of switching from the mask mode to the receive mode, so that the first slave communication device 20a receives the transmission wave transmitted from the master communication device 10 while avoiding reception of interference waves as much as possible.

[0075] The first slave communication device 20a starts the reception mode at a reception mode start time τ start Based on this, the first slave communication device 20a ends the reception mode, starts the transmission mode, and ends the transmission mode in this order, at a timing preprogrammed in the device 20a. After starting the transmission mode, the first slave communication device 20a transmits a signal to the master communication device 10 after a time Ta1 determined between the master communication device 10 and the master communication device 10 according to the wireless communication schedule has elapsed from the transmission timing of the master communication device 10 (see transmission time Ta). The transmission signal includes, for example, sensor information acquired by a sensor provided in the first slave communication device 20a. The first slave communication device 20a completes the transmission mode at a timing preprogrammed in the device 20a, which is determined by the time required for data transmission (depending on the amount of data to be transmitted, etc.) based on the start timing of the transmission mode.

[0076] The master communication device 10 receives the signal at the expected reception time τ 1 determined by the time Ta1 agreed upon with the first slave communication device 20a according to the wireless communication schedule. next From equation (1), the receive mode start time τ start Then, the master communication device 10 calculates the reception mode start time τ start Then, the master communication device 10 performs a process of switching from the mask mode to the receive mode, so that the master communication device 10 receives the transmission wave transmitted from the first slave communication device 20a while avoiding reception of interference waves as much as possible.

[0077] As a result, the communication between the master communication device 10 and the first slave communication device 20a, which is defined in the first time slot TS1, is completed in the wireless communication schedule. Upon completion of the first time slot TS1, the communication between the master communication device 10 and the second slave communication device 20b, which is defined in the second time slot TS2, is executed in the same procedure as in the first time slot TS1. Furthermore, upon completion of the second time slot TS2, the communication between the master communication device 10 and the third slave communication device 20c, which is defined in the third time slot TS3, is executed in the same procedure as in the first time slot TS1. Furthermore, upon completion of the third time slot TS3, the communication between the master communication device 10 and the fourth slave communication device 20d, which is defined in the fourth time slot TS4, is executed in the same procedure as in the first time slot TS1. Upon completion of the fourth time slot TS4, one period T consisting of four time slots TS1 to TS4 is completed, and the first time slot TS1 of the next period is executed.

[0078] In the second time slot TS2, the master communication device 10 transmits a signal to the second slave communication device 20b after a time (transmission time Tb) agreed upon with the second slave communication device 20b has elapsed since the transmission time of the broadcast transmission. The second slave communication device 20b transmits a signal to the second slave communication device 20b after a reception mode start time τ start In addition, the second slave communication device 20b, which has received a transmission wave from the master communication device 10, transmits a signal to the master communication device 10 after a time Tb1 (not shown) agreed upon with the master communication device 10 has elapsed from the transmission timing (see transmission time Tb) of the master communication device 10 described above. The master communication device 10 transmits a signal to the master communication device 10 at a reception mode start time τ start Then, the mask mode is switched to the receive mode.

[0079] In the third time slot TS3, the master communication device 10 transmits a signal to the third slave communication device 20c after a time (transmission time Tc) agreed upon between the master communication device 10 and the third slave communication device 20c has elapsed since the transmission time of the broadcast transmission. The third slave communication device 20c transmits a signal to the third slave communication device 20c after a reception mode start time τ start The third slave communication device 20c, which has received a transmission wave from the master communication device 10, transmits a signal to the master communication device 10 after a time Tc1 (not shown) agreed upon with the master communication device 10 has elapsed from the transmission timing (see transmission time Tc) of the master communication device 10. The master communication device 10 transmits a signal to the master communication device 10 at a reception mode start time τ start Then, the process of switching from mask mode to receive mode is performed.

[0080] In the fourth time slot TS4, the master communication device 10 transmits a signal to the fourth slave communication device 20d after a time (transmission time Td) agreed upon with the fourth slave communication device 20d has elapsed since the transmission time of the broadcast transmission. The fourth slave communication device 20d transmits a signal to the fourth slave communication device 20d after a reception mode start time τ start The fourth slave communication device 20d, which has received a transmission wave from the master communication device 10, transmits a signal to the master communication device 10 after a time Td1 (not shown) agreed upon with the master communication device 10 has elapsed from the transmission timing (see transmission time Td) of the master communication device 10. The master communication device 10 transmits a signal to the master communication device 10 at a reception mode start time τ start Then, the process of switching from mask mode to receive mode is performed.

[0081] As can be seen from the above, in this embodiment, communications between the master communication device 10 and each of the slave communication devices 20a to 20d are performed at different timings, making it possible to avoid radio interference between these communications.

[0082] In this embodiment, the master communication device 10 that has broadcast the wireless communication schedule transmits the wireless communication schedule and then receives the wireless communication schedule. Then, when receiving the wireless communication schedule after transmitting the wireless communication schedule, the time τ start This allows not only the side receiving the wireless communication schedule but also the side transmitting the wireless communication schedule to receive signals while avoiding reception of interference waves as much as possible.

[0083] In this embodiment, the master communication device 10 is configured to perform communication in the order of transmission and reception in each of the time slots TS1 to TS4. However, this is an example, and the master communication device 10 may perform communication in the order of reception and transmission in each of the time slots TS1 to TS4. In this case, the order of transmission and reception of the slave communication devices 20a to 20d in each of the time slots TS1 to TS4 needs to be reversed from that in this embodiment.

[0084] <5. Modifications> [5-1. First modified example] FIG. 11 is a diagram showing a configuration of a communication system SYS1A according to a first modified example. FIG. 12 is a diagram showing the relationship between a master communication device 10A and a slave communication device 20A included in the communication system SYS1A according to the first modified example. Note that in this modified example as well, there are multiple slave communication devices 20A (four in detail), and each of the slave communication devices 20aA, 20bA, 20cA, and 20dA can communicate with the master communication device 10A. Each of the slave communication devices 20aA to 20dA has the same configuration. For this reason, FIG. 12 shows only the first slave communication device 20aA, and omits the second slave communication device 20bA, the third slave communication device 20cA, and the fourth slave communication device 20dA.

[0085] 11 and 12, the thick line L1 is a communication line for wired communication. That is, in the communication system SYS1A of the first modified example, the master communication device 10A and the slave communication device 20A are configured to be able to perform wired communication in addition to UWB communication, which is wireless communication. For this reason, as shown in FIG. 12, the master communication device 10A and the slave communication device 20A each include a wired communication unit 13, 23 that enables wired communication in addition to a wireless communication unit 11, 21 that enables UWB communication.

[0086] In this modification, the communication line L1 is a power line that connects the master communication device 10A and each of the slave communication devices 20aA to 20dA to the battery 30. That is, the wired communication performed between the master communication device 10A and each of the slave communication devices 20aA to 20dA is PLC (Power Line Communication) communication. However, the wired communication used in the communication system SYS1A is not limited to PLC communication, and may be CAN (Registered Trademark, Controller Area Network) communication, LIN (Registered Trademark, Local Interconnect Network) communication, CXPI (Clock Extension Peripheral Interface) communication, etc.

[0087] In this modification, wired communication is used when the master communication device 10A broadcasts the wireless communication schedule. That is, in this modification, in the process shown in Fig. 5, the broadcast of the wireless communication schedule is performed using wired communication (PLC communication) instead of UWB communication.

[0088] In a situation where the wireless communication schedule is not transmitted to each of the slave communication devices 20aA to 20dA, it is difficult to switch from the mask mode to the reception mode at a timing when the UWB communication is unlikely to be affected by radio wave interference. In this modified example, in such a situation where the UWB communication is likely to be affected by radio wave interference, wired communication is used instead of wireless communication. This makes it possible to reduce the possibility of communication failure due to the influence of radio wave interference during reception. The wireless communication schedule may be broadcast using both wireless communication and wired communication.

[0089] As described above, in this modification, the wired communication is PLC communication using the power line L1. The power line L1 is a wire harness that is essential for supplying power to the master communication device 10A and the slave communication devices 20aA to 20dA. In other words, according to the configuration of this modification, the wired communication can be realized using a wire harness that cannot be eliminated, so that the increase in the wire harness can be suppressed and wired communication can be used.

[0090] [5-2. Second modified example] Fig. 13 is a diagram showing a configuration of a communication system SYS1B according to a second modified example. As shown in Fig. 13, the communication system SYS1B includes a master communication device 10B and a plurality of slave communication devices 20B, similar to the communication system SYS1 according to the above-described embodiment. The plurality of slave communication devices 20B include a first slave communication device 20aB, a second slave communication device 20bB, a third slave communication device 20cB, and a fourth slave communication device 20dB.

[0091] The controller 12B included in the master communication device 10B of this modification includes a radio wave learning unit 124 in addition to the functional units 121 to 123 included in the controller 12 of the above-described embodiment. The radio wave learning unit 124 is a functional unit that is realized, for example, by a processor included in the controller 12B executing arithmetic processing according to a program. However, the radio wave learning unit 124 is not limited to a configuration realized by software, and may be realized by hardware using a dedicated IC or the like.

[0092] The radio wave learning unit 124 determines (performs calibration) the optimum value of the radio wave output of the wireless communication (UWB communication) used between the master communication device 10B and each of the slave communication devices 20aB to 20dB. In this modified example, the optimum value is the minimum necessary output of the radio wave. By keeping the radio wave output to the minimum necessary, it is possible to reduce power consumption in the communication system SYS1B. Furthermore, by keeping the radio wave output to the minimum necessary, it is possible to reduce the possibility of interference with other communications.

[0093] In this modification, UWB communication is performed between the master communication device 10B and each of the slave communication devices 20aB to 20dB when the radio wave output is calibrated by the radio wave learning unit 124. When the output of the radio wave used between the devices is calibrated, the device is configured to switch to the reception mode (switch from the mask mode) immediately before the expected reception time agreed upon between the devices.

[0094] This makes it possible to perform calibration of the radio wave output while suppressing the effects of radio wave interference. In other words, wireless communication for calibration can be performed without the effects of radio wave interference, and calibration of the radio wave output can be performed quickly and accurately. Note that calibration of the radio wave output may be performed between devices other than those having a master-slave relationship. Even in this case, switching to the reception mode may be performed immediately before the expected reception time agreed upon between the devices.

[0095] Fig. 14 is a flowchart showing an example of a process executed by the master communication device 10B (radio wave learning unit 124) during calibration of the radio wave output. Fig. 15 is a diagram for explaining the operation of the slave communication device 20B during the process shown in Fig. 14.

[0096] Calibration of the radio wave output (radio wave learning) is performed, for example, when the use of the communication system SYS1B is started. Calibration of the radio wave output is started, for example, when the above-mentioned body ECU is started. Calibration of the radio wave output is usually performed before broadcast transmission of the wireless communication schedule.

[0097] The calibration of the radio wave output is performed in order between the master communication device 10B and each of the slave communication devices 20aB to 20dB. Although the order is not particularly limited, for example, the master communication device 10B calibrates the radio wave output in the order of the first slave communication device 20aB, the second slave communication device 20bB, the third slave communication device 20cB, and the fourth slave communication device 20dB. When each calibration is performed, the processes shown in Figs. 14 and 15 are executed.

[0098] As shown in Fig. 14, in step S21, the master communication device 10B performs a distance measurement process to determine the distance between the master communication device 10B and the slave communication device 20B. The distance measurement process may be performed using a known process. In the distance measurement process, the master communication device 10B transmits a distance measurement signal to the slave communication device 20B using UWB communication. In response to receiving the distance measurement signal, the slave communication device 20B transmits a reply (see Fig. 15). If the time required for radio waves to travel between the devices is obtained from this exchange, the distance X between the master communication device 10B and the slave communication device 20B can be calculated because the speed of the radio waves is known.

[0099] The radio wave output of the UWB communication used in the distance measurement process is preferably close to the maximum power (e.g., -41.3 dBm / MHz) defined by the communication standard. The vicinity of the maximum power is a value equal to or slightly smaller than the maximum power. By setting the radio wave output during the distance measurement process close to the maximum power in this manner, the probability of an incident in which radio waves do not reach the master communication device 10B and the slave communication device 20B can be reduced, and the probability of success in the distance measurement process can be increased.

[0100] When the distance X is determined by the distance measurement process, the master communication device 10B advances the process to step S22.

[0101] In step S22, the master communication device 10B determines the range of transmission power (output range) used to find the optimum value of radio wave output. A correlation map that has been created in advance and shows the relationship between the device-to-device distance and the transmission power (radio wave output) is used to determine the range of transmission power. FIG. 16 is an example of a correlation map that shows the relationship between the device-to-device distance and the transmission power. The correlation map is a map created by experiments, etc., but due to characteristic variations between devices and environmental fluctuations such as temperature, the transmission power found by the correlation map may not necessarily be the optimum value. For this reason, calibration is performed to find the optimum value of radio wave output.

[0102] The master communication device 10B first determines a transmission power Y that is likely to be close to the optimum value, based on the distance X determined in step S21 and the correlation map (see FIG. 16). The master communication device 10B then determines a minimum value a and a maximum value b of the transmission power based on the determined transmission power Y (see FIG. 16). The minimum value a and the maximum value b may be determined using a table or a relational expression prepared in advance. After determining the range of the transmission power, the master communication device 10B proceeds to step S23.

[0103] In step S23, the master communication device 10B sets the variable N to 1. After setting the variable N to 1, the master communication device 10B advances the process to step S24.

[0104] In step S24, the master communication device 10B transmits UWB radio waves at the Nth power to the slave communication device 20B. The Nth power is determined according to a preset criterion. In this modification, the Nth power is a power obtained by adding a value obtained by multiplying a predetermined step power α by (N-1) to the minimum value a of the transmission power range. That is, for example, when N=1 (that is, in the case of the first transmission for power adjustment), the Nth power is "a". Also, for example, when N=2, the Nth power is "a+α". Also, for example, when N=3, the Nth power is "a+2α". Note that in this example, the transmission power is gradually increased based on the minimum value a of the transmission power range, but this is merely an example. It may also be configured such that the transmission power is gradually decreased based on the maximum value b of the transmission power range. After transmitting at the Nth power, the master communication device 10B advances the process to step S25.

[0105] In step S25, the master communication device 10B determines whether or not there is a reply from the slave communication device 20B within a predetermined period determined by an experiment or the like. When the slave communication device 20B receives a transmission wave from the master communication device 10B, it replies to the transmission wave. However, if the transmission power of the transmission wave transmitted from the master communication device 10B is low, the transmission wave may not reach the slave communication device 20B. In this case, the master communication device 10B does not receive a reply from the slave communication device 20B. In the example shown in FIG. 15, the first transmission power and the second transmission power are not received by the slave communication device 20B, and the slave communication device 20B does not reply. On the other hand, the third communication power is received by the slave communication device 20B, and the slave communication device 20B replies.

[0106] If the master communication device 10B receives a reply from the slave communication device 20B (Yes in step S25), the process proceeds to step S26. On the other hand, if the master communication device 10B does not receive a reply from the slave communication device 20B (No in step S25), the process proceeds to step S28.

[0107] In step S26, the master communication device 10B determines the output power of the transmission wave. For example, the master communication device 10B sets the Nth power, which is the power when there is a reply from the slave communication device 20B, as the output power. As another example, the master communication device 10B sets the output power by adding a margin obtained by an experiment or the like to the Nth power. In the example shown in FIG. 15, the output power is set to the third power (a+2α), or the third power (a+2α) plus the margin power. After determining the output power, the master communication device 10B proceeds to step S27.

[0108] In step S27, the master communication device 10B notifies the slave communication device 20B of the determined output power as the utilization power by using UWB communication. This enables UWB communication between the master communication device 10B and the slave communication device 20B at the determined output power.

[0109] In step S28, the master communication device 10B performs a process of adding 1 to the variable N. After performing the process of adding 1 to the variable N, the master communication device 10B returns the process to step S24. This allows the master communication device 10B to output a transmission wave while changing the output power.

[0110] In this modification, when the radio wave output calibration is performed as described above, the estimated reception time τ next The system is configured to switch to reception mode immediately before transmission.

[0111] For example, before transmitting a signal for distance measurement processing (distance measurement signal), the master communication device 10B and the slave communication device 20B make an agreement regarding the transmission time in advance. The agreement may be made using UWB communication, or the above-mentioned PLC communication may be used. Depending on the agreement, the reception mode start time τ startFor example, when radio waves are transmitted from the master communication device 10B to the slave communication device 20B, and when radio waves are transmitted from the slave communication device 20B to the master communication device 10B, the receiving device switches to the receiving mode immediately before the expected reception time. This reduces the possibility of being affected by radio wave interference during the distance measurement process, and enables quick and accurate distance measurement.

[0112] Also, for example, before transmitting a signal for output power adjustment processing, the master communication device 10B and the slave communication device 20B make an agreement regarding the transmission time in advance. The agreement may be made using UWB communication, but the above-mentioned PLC communication may also be used. Depending on the agreement, the reception mode start time τ start For example, when radio waves are transmitted from the master communication device 10B to the slave communication device 20B, and when radio waves are transmitted from the slave communication device 20B to the master communication device 10B, the receiving device switches to the receiving mode immediately before the expected reception time. This reduces the possibility of being affected by radio wave interference during the output power adjustment process, and allows the output power to be determined quickly and appropriately.

[0113] <6. Points to note> Various technical features disclosed in the description of the invention may be modified in various ways without departing from the spirit of the technical creation. Furthermore, the embodiments and modifications disclosed in the description of the invention may be combined to the extent possible. [Explanation of symbols]

[0114] 10, 10A, 10B... Master communication device (first wireless communication device or second wireless communication device) 20, 20A, 20B: Slave communication device (first wireless communication device or second wireless communication device) 20a, 20aA, 20aB: First slave communication device 20b, 20bA, 20bB: Second slave communication device 20c, 20cA, 20cB: Third slave communication device 20d, 20dA, 20dB...Fourth slave communication device SYS1, SYS1A, SYS1B...Communication systems

Claims

1. A communication method using wireless communication, A communication method in which a mask mode in which the wireless communication is impossible is switched to a reception mode in which the wireless communication is received immediately before an expected reception time agreed upon between the plurality of devices performing the wireless communication.

2. The wireless communication is wireless communication according to an UWB communication system, The communication method according to claim 1 , wherein the estimated reception time is determined based on a PHR included in a frame format used for the wireless communication.

3. The communication method according to claim 2 , wherein the time τ start immediately before the expected reception time is calculated by the following formula (1): τstart = τnext - (tSFD + tsym × Nrg) (1) τnext: the estimated reception time tSFD: Reception period of the SFD included in the frame format tsym: reception period of one symbol of the preamble code in the preamble included in the frame format Nrg: the number of times required to recognize one symbol of the preamble code

4. The communication method according to claim 3 , wherein the estimated reception time is calculated according to a wireless communication schedule broadcast from any one of the plurality of devices.

5. 5. The communication method according to claim 4, wherein if there is no response from all devices targeted for broadcast transmission of the wireless communication schedule that they have received the wireless communication schedule, the wireless communication schedule is broadcast again.

6. the device that has broadcast the wireless communication schedule performs wireless communication transmission according to the wireless communication schedule and then receives the wireless communication schedule; The communication method according to claim 4 , wherein, when receiving after transmitting by wireless communication, switching to the receiving mode is performed at the time τ start calculated by the formula (1).

7. The communication method according to claim 4 , wherein wired communication is used when the wireless communication schedule is broadcast.

8. The communication method according to claim 7 , wherein the wired communication is PLC communication.

9. The communication method according to claim 1 , wherein when calibration of the output of the radio wave used between the devices is performed, switching to the reception mode is performed immediately before the expected reception time.

10. A communication device for wireless communication, a communication device that switches from a mask mode in which the wireless communication is not possible to a reception mode in which the wireless communication is received immediately before an expected reception time agreed upon with another device that transmits using the wireless communication;

11. a first wireless communication device that performs wireless communication; a second wireless communication device that receives the signal via wireless communication; A communication system comprising: A communication system in which the second wireless communication device switches from a mask mode, in which wireless communication is not possible, to a reception mode, in which wireless communication is received, just before an expected reception time agreed upon with the first wireless communication device.

12. a first wireless communication device that performs wireless communication; a second wireless communication device that receives the signal via wireless communication; A vehicle communication system comprising: When starting to use the vehicle, an expected reception time is determined between the first wireless communication device and the second wireless communication device; The second wireless communication device switches from a mask mode, in which wireless communication is not possible, to a reception mode, in which wireless communication is received, just before the expected reception time agreed upon with the first wireless communication device.

Images