Communication method and communication system

Abstract

An exemplary communication method is a communication method using a preamble between a first communication device and a second communication device, wherein the first communication device communicates with the second communication device using the type of the preamble determined according to the use purpose of communication from among a plurality of preamble types determined by the pulse repetition frequency of the preamble or the length of the preamble.

Description

Communication method and communication system

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

[0002] In recent years, wireless communication has been on the rise in the field of communications due to its advantages in terms of installation, such as the elimination of wiring. For example, UWB (Ultra Wide Band) communication, which uses broadband radio waves, has low radio wave interference with Wi-Fi (registered trademark) and radio waves used in mobile devices such as smartphones, and has good transparency, leading to an expansion of its applications. Furthermore, UWB communication is expected to be a communication method for in-vehicle devices because it is easy to establish communication even in a vehicle, which has a narrow metal space and many wires.

[0003] JP 2016-38332 A

[0004] However, as UWB communication becomes more widespread, interference between UWB communications is likely to occur, which may result in communication disruptions. This communication disruption problem is not limited to the communication means of in-vehicle devices and UWB communications, but may also occur when multiple devices communicate using radio waves in the same frequency band.

[0005] To address this problem, Patent Document 1 discloses a technique for preventing interference by lowering the communication rate. However, it is desirable to be able to prevent interference without lowering the communication rate. Furthermore, when there are multiple communication usage purposes, it is desirable for communication for usage purposes with high priority (importance) to have a higher communication success rate than communication for usage purposes with low priority (importance).

[0006] In view of the above, an object of the present invention is to provide a technique that can improve the success rate of communication in high-priority use applications.

[0007] An exemplary communication method of the present invention is a communication method using a preamble between a first communication device and a second communication device, in which the first communication device communicates with the second communication device using a preamble type determined from a plurality of preamble types determined by the pulse repetition frequency or length of the preamble, depending on the intended use of the communication.

[0008] According to the exemplary embodiment of the present invention, the preamble used in communication can be appropriately set depending on the intended use of the communication, thereby improving the success rate of communication in communication for intended uses with high priority.

[0009] FIG. 1 is a diagram showing an example of the configuration of a communication system; FIG. 2 is a diagram showing a frame format used in UWB communication; FIG. 3 is a diagram showing a first determined pattern included in a first determined example of a preamble type; FIG. 4 is a diagram showing a second determined pattern included in a first determined example of a preamble type; FIG. 5 is a diagram showing a fifth determined pattern included in a second determined example of a preamble type; FIG. 6 is a diagram showing a sixth determined pattern included in a second determined example of a preamble type; FIG. 7 is a diagram showing a seventh determined pattern included in a third determined example of a preamble type; FIG. 8 is a diagram showing a modification of the fourth determined pattern; FIG. 9 is a diagram showing a modification of the fourth determined pattern; FIG. 10 is a diagram showing a seventh determined pattern included in a third determined example of a preamble type; ｓｔａｒｔ 18 is a schematic diagram for explaining a detailed example of how to set the wireless communication schedule. Schematic diagram showing an example of the operation of a communication system according to a wireless communication schedule. Schematic diagram showing an example of the configuration of a communication system according to a first modified example. Schematic diagram showing the relationship between a master communication device and a slave communication device provided in a communication system according to a first modified example. Schematic diagram showing the configuration of a communication system according to a second modified example ... for explaining a detailed example of how to set the wireless communication schedule.

[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 denoted by the same reference numerals, and redundant description will be omitted unless particularly necessary.

[0011] 1 is a diagram showing an example of the configuration 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 vehicle other than the vehicle C1, and may be used, for example, for general mobile objects other than automobiles, or for home, office, or factory use.

[0012] 1, the communication system SYS1 includes a master ECU (Electric Control Unit) 10 and a plurality of slave devices 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 devices 20a to 20d via UWB communication in response to a user operation on an HMI (Human Machine Interface) 30. Specifically, each of the slave devices 20a to 20d transmits sensor values ​​and the like detected by sensors connected to the slave devices 20a to 20d to the master ECU 10. Each of the slave devices 20a to 20d controls an actuator connected to the slave device 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 headlights. The second slave device 20b is, for example, a control device that controls the operation of wipers. The third slave device 20c is, for example, a control device that controls the operation of power windows. The fourth slave device 20d is, for example, a control device that controls the operation of an air conditioner.

[0014] Because 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 it is not necessary 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 are multiple slave communication devices 20, but there may be only one. Furthermore, the multiple communication devices in the communication system do not necessarily have to be in a master-slave relationship, but may be in an equal relationship with each other.

[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 using the UWB communication method. The UWB communication is performed in accordance with a standard such as IEEE 802.15.4 (hereinafter, sometimes simply referred to as the communication standard). However, the wireless communication may be communication that uses a preamble other than UWB communication, such as 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 transmitting device that transmits signals via wireless communication and a receiving device that receives signals via wireless communication. The master communication device 10 and the slave communication device 20 can each be either the transmitting device or the receiving device. That is, the master communication device 10 is a transmitting device in a signal transmission state and a receiving device in a signal reception state. The slave communication device 20 is also a transmitting device in a signal transmission state and a receiving device in a signal reception state.

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

[0019] The master communication device 10 and the slave communication device 20 are communication devices whose communication use is data communication.

[0020] The communication system SYS1 further includes a ranging communication device 40 and a radar communication device 50.

[0021] In this embodiment, the ranging communication device 40 and the radar communication device 50 each perform UWB communication. That is, the wireless communication in each of the ranging communication device 40 and the radar communication device 50 is wireless communication according to the UWB communication method. However, the wireless communication in each of the ranging communication device 40 and the radar communication device 50 may be communication using a preamble other than UWB communication, such as Wi-Fi communication, Bluetooth communication, BLE communication, LPWA communication, or Zigbee communication.

[0022] The ranging communication device 40 is a communication device used for distance measurement communication. The ranging communication device 40 communicates wirelessly with the electronic key 60. The ranging communication device 40 transmits a signal to the electronic key 60. After receiving the signal from the ranging communication device 40, the electronic key 60 transmits a reply signal back to the ranging communication device 40. The ranging communication device 40 receives the reply signal from the electronic key 60, measures the time required from sending the signal to receiving the reply signal, and calculates the distance to the electronic key 60 based on the measured time required.

[0023] The radar communication device 50 is a communication device used for radar communication. The radar communication device 50 emits (transmits) a signal and detects (receives) the signal reflected by an object. The radar communication device 50 measures the time required from emitting the signal to receiving the reflected signal, and calculates the distance to the (reflecting) object based on the measured time required. When the radar communication device 50 emits (transmits) a signal into the passenger compartment of the vehicle C1, the radar communication device 50 can be used as a device for monitoring the presence, movement, etc. of occupants. On the other hand, when the radar communication device 50 emits (transmits) a signal outside the vehicle C1, the radar communication device 50 can be used as a device for monitoring the presence, movement, etc. of obstacles located around the vehicle C1.

[0024] <2. Determining the Preamble Type> [2-1. Frame Format] Here, the format of a communication frame (a unit of transmission data) in UWB communication (hereinafter referred to as frame format) will be explained using Fig. 2. The frame format used in UWB communication is determined by the above-mentioned communication standard.

[0025] As shown in Fig. 2, the frame format F used in UWB communication has a structure in which a preamble is first followed by a Start Frame Delimiter (SFD), a PHY Header (PHR), and a data body, in that order. Note that the term "data body" is used to make it easier to understand the difference between the preamble, SFD, and PHR.

[0026] A preamble is a sequence of bits or pulses (e.g., -, 0, +) of a specific pattern that is sent before the data itself in digital communications to inform the receiving end that "data is about to be sent." The receiving end uses the preamble signal to start (synchronize) the receiving clock. There are multiple types of preamble patterns. In other words, there are multiple types of preambles.

[0027] The configurable physical layer parameters of the preamble include the preamble code and the length of the preamble (preamble length).

[0028] There are 24 types of preamble codes, codes 1 to 24. Codes 1 to 8 have a PRF (Pulse Repletion Frequency) of 16 MHz. Codes 9 to 24 have a PRF of 64 MHz.

[0029] The preamble length is determined by the number of symbols included in the preamble, and is selected from patterns such as 16 symbols, 64 symbols, 128 symbols, 256 symbols, 512 symbols, 1024 symbols, 2048 symbols, and 4096 symbols.

[0030] A preamble is a sequence composed of a predetermined pattern of bits or pulses (e.g., -, 0, +) such as "10101010...", and the preamble length is a size (length) that increases as the number of symbols included in the preamble increases.

[0031] The SFD is a bit string with a specific pattern that signals the start of data in a communication frame. The PHR contains information necessary for decoding the packet. For example, the PHR contains information such as the address of the communication partner and the data length of the subsequent data. The data body is the main body of information to be transmitted to the communication partner and contains the actual data to be transmitted. For example, the data body contains information such as ID information of the destination 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 status of the actuator to be controlled by the slave communication device 20.

[0032] In this embodiment, the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each use a preamble type determined based on the intended use of communication from among multiple preamble types determined by the preamble pulse repetition frequency or preamble length. Because different preamble types have different resistance to radio wave interference, using a preamble type with superior resistance to radio wave interference for communication in a high-priority application can improve the success rate of communication in the high-priority application. Therefore, the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine a preamble type based on the priority of the intended use and use the determined preamble type.

[0033] [2-2. First Determination Example] For example, each of the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 uses a preamble type determined according to the intended use of communication from among a plurality of preamble types determined by the pulse repetition frequency of the preamble. Since resistance to radio wave interference varies depending on the pulse repetition frequency of the preamble, the success rate of communication in the intended use of high priority can be improved by setting the pulse repetition frequency of the preamble used in communication for the intended use of high priority to a frequency that is highly resistant to radio wave interference.

[0034] More specifically, since the higher the pulse repetition frequency of the preamble, the better the resistance to radio wave interference, setting a high pulse repetition frequency for the preamble used in communications for high-priority applications can improve the success rate of communications for high-priority applications. Such a relationship between the pulse repetition frequency of the preamble and the resistance to radio wave interference is thought to be due to the fact that preambles with high pulse repetition frequencies are analyzed preferentially in the receiving section of the communication device.

[0035] For this reason, the first usage purpose is a usage purpose that is given priority (importance) over the second usage purpose, and the pulse repetition frequency determined when the usage purpose for communication is the first usage purpose is preferably set higher than the pulse repetition frequency determined when the usage purpose for communication is the second usage purpose. Similarly, the first usage purpose is a usage purpose that is given priority over the third usage purpose, and the pulse repetition frequency determined when the usage purpose for communication is the first usage purpose is preferably set higher than the pulse repetition frequency determined when the usage purpose for communication is the third usage purpose.

[0036] In the first determination example, the preamble length may be set to a single length regardless of the intended use of the communication.

[0037] 3A is a diagram showing a first determination pattern included in determination example 1. The first determination pattern is a determination pattern when the first use purpose is data communication, the second use purpose is one of distance measurement communication and radar communication, and the third use purpose is the other of distance measurement communication and radar communication.

[0038] When the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble in accordance with the first determination pattern, the preamble code of the preamble used in the communication performed by the master communication device 10 and the slave communication device 20 will be any one of Code 9 to Code 24, and therefore the pulse repetition frequency of the preamble used in the communication performed by the master communication device 10 and the slave communication device 20 will be 64 MHz. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble in accordance with the first determination pattern, the preamble code of the preamble used in the communication performed by the ranging communication device 40 and the radar communication device 50 will be any one of Code 1 to Code 8, and therefore the pulse repetition frequency of the preamble used in the communication performed by the ranging communication device 40 and the radar communication device 50 will be 16 MHz.

[0039] 3B is a diagram showing a second determination pattern included in the first determination example, in which the first use is distance measurement communication, the second use is one of data communication and radar communication, and the third use is the other of data communication and radar communication.

[0040] When the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the second determination pattern, the preamble code of the preamble used in the communication performed by the ranging communication device 40 will be any one of Code 9 to Code 24, and therefore the pulse repetition frequency of the preamble used in the communication performed by the ranging communication device 40 will be 64 MHz. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the second determination pattern, the preamble code of the preamble used in the communication performed by the master communication device 10, the slave communication device 20, and the radar communication device 50 will be any one of Code 1 to Code 8, and therefore the pulse repetition frequency of the preamble used in the communication performed by the master communication device 10, the slave communication device 20, and the radar communication device 50 will be 16 MHz.

[0041] 3C is a diagram showing a third determination pattern included in the first determination example, in which the first use is radar communication, the second use is one of data communication and distance measurement communication, and the third use is the other of data communication and distance measurement communication.

[0042] When the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the third determination pattern, the preamble code of the preamble used in communication by the radar communication device 50 will be any one of Code 9 to Code 24, and therefore the pulse repetition frequency of the preamble used in communication by the radar communication device 50 will be 64 MHz. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the third determination pattern, the preamble code of the preamble used in communication by the master communication device 10, the slave communication device 20, and the ranging communication device 40 will be any one of Code 1 to Code 8, and therefore the pulse repetition frequency of the preamble used in communication by the master communication device 10, the slave communication device 20, and the ranging communication device 40 will be 16 MHz.

[0043] In the first determination example, the preamble types are the same for the second and third usage purposes. That is, in the first determination example, even if the usage purposes of the communication are different, the determined preamble types are allowed to be the same. This increases the number of preamble types permitted for use in the second and third usage purposes, thereby increasing the degree of freedom in setting the preamble types.

[0044] [2-3. Second Determination Example] For example, the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each use a preamble type determined according to the intended use of communication from among a plurality of preamble types determined by the preamble length. Since resistance to radio wave interference varies depending on the preamble length, the success rate of communication in the intended use of high priority can be improved by setting the length of the preamble used in communication for the intended use to a length that provides excellent resistance to radio wave interference.

[0045] More specifically, the longer the preamble length, the better the resistance to radio interference. Therefore, by setting the length of the preamble used in communications for high-priority applications to be longer, the success rate of communications for high-priority applications can be improved.

[0046] For this reason, the first usage purpose is a usage purpose that is given priority (importance) over the second usage purpose, and the preamble length determined when the communication usage purpose is the first usage purpose should be set longer than the preamble length determined when the communication usage purpose is the second usage purpose. Similarly, the first usage purpose is a usage purpose that is given priority over the third usage purpose, and the preamble length determined when the communication usage purpose is the first usage purpose should be set longer than the preamble length determined when the communication usage purpose is the third usage purpose.

[0047] In the second determination example, the pulse repetition frequency of the preamble may be set to a single frequency regardless of the intended use of the communication.

[0048] 4A is a diagram showing a fourth determination pattern included in determination example 2. The fourth determination pattern is a determination pattern when the first use purpose is data communication, the second use purpose is one of distance measurement communication and radar communication, and the third use purpose is the other of distance measurement communication and radar communication.

[0049] When the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the fourth determination pattern, the length of the preamble used in communication by each of the master communication device 10 and the slave communication device 20 will be 4096 symbols. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the fourth determination pattern, the length of the preamble used in communication by each of the ranging communication device 40 and the radar communication device 50 will be 16 symbols, 64 symbols, or 1024 symbols.

[0050] 4B is a diagram showing a fifth determination pattern included in determination example 2. The fifth determination pattern is a determination pattern when the first intended use is distance measurement communication, the second intended use is one of data communication and radar communication, and the third intended use is the other of data communication and radar communication.

[0051] When the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the fifth determination pattern, the length of the preamble used in communication by the ranging communication device 40 will be 4096 symbols. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the fifth determination pattern, the length of the preamble used in communication by the master communication device 10, the slave communication device 20, and the radar communication device 50 will be 16 symbols, 64 symbols, or 1024 symbols.

[0052] 4C is a diagram showing a sixth determination pattern included in determination example 2. The sixth determination pattern is a determination pattern when the first intended use is radar communication, the second intended use is one of data communication and distance measurement communication, and the third intended use is the other of data communication and distance measurement communication.

[0053] When the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the sixth determination pattern, the length of the preamble used in communication by the radar communication device 50 will be 4096 symbols. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the sixth determination pattern, the length of the preamble used in communication by the master communication device 10, the slave communication device 20, and the ranging communication device 40 will be 16 symbols, 64 symbols, or 1024 symbols.

[0054] In the fourth to sixth determination patterns described above, the preamble length corresponding to the prioritized usage is 4096 symbols, and the preamble lengths corresponding to the other usages are either 16 symbols, 64 symbols, or 1024 symbols. However, these patterns are not limited to these. As in the modified example of the fourth determination pattern shown in Figure 4D, the preamble length corresponding to the prioritized usage may be either 1024 symbols or 4096 symbols, and the preamble lengths corresponding to the other usages may be either 16 symbols or 64 symbols. Furthermore, as in another modified example of the fourth determination pattern shown in Figure 4E, the preamble length corresponding to the prioritized usage may be either 64 symbols, 1024 symbols, or 4096 symbols, and the preamble length corresponding to the other usages may be 16 symbols.

[0055] In the second determination example, the preamble type is different for the second intended use. Similarly, in the second determination example, the preamble type is different for the third intended use. In other words, in the second determination example, even if the intended use of communication is the same, the determined preamble type is allowed to be different. This allows the preamble type to be subdivided based on other factors (e.g., type of data, type of device to be measured, type of obstacle (obstacle inside the vehicle, obstacle outside the vehicle), etc.) even if the intended use of communication is the same, thereby increasing the flexibility in setting the preamble type.

[0056] [2-4. Third Determination Example] For example, each of the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 uses a preamble type determined according to the intended use of communication from among a plurality of preamble types determined by the pulse repetition frequency and the length of the preamble. Since the resistance to radio wave interference varies depending on the pulse repetition frequency and the length of the preamble, the success rate of communication in the intended use of high priority can be improved by setting the pulse repetition frequency of the preamble used in communication for the intended use to a frequency that is highly resistant to radio wave interference and setting the length of the preamble used in communication for the intended use of high priority to a length that is highly resistant to radio wave interference.

[0057] More specifically, the higher the pulse repetition frequency of the preamble, the better the resistance to radio wave interference, so by setting the pulse repetition frequency of the preamble used in communications for high-priority applications to a higher frequency, and also by setting the length of the preamble to a longer length, the better the resistance to radio wave interference, the communication success rate for communications for high-priority applications can be improved.

[0058] For this reason, the first usage purpose is a usage purpose that is given priority (importance) over the second usage purpose, and the pulse repetition frequency determined when the communication usage purpose is the first usage purpose may be set higher than the pulse repetition frequency determined when the communication usage purpose is the second usage purpose. Furthermore, the preamble length determined when the communication usage purpose is the first usage purpose may be set longer than the preamble length determined when the communication usage purpose is the second usage purpose. Similarly, the first usage purpose is a usage purpose that is given priority over the third usage purpose, and the pulse repetition frequency determined when the communication usage purpose is the first usage purpose may be set higher than the pulse repetition frequency determined when the communication usage purpose is the third usage purpose. Furthermore, the preamble length determined when the communication usage purpose is the first usage purpose may be set longer than the preamble length determined when the communication usage purpose is the third usage purpose.

[0059] 5 is a diagram showing a seventh determination pattern included in determination example 3. The seventh determination pattern is a determination pattern when the first use purpose is data communication, the second use purpose is one of distance measurement communication and radar communication, and the third use purpose is the other of distance measurement communication and radar communication.

[0060] When the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the seventh determination pattern, the preamble code of the preamble used in the communication performed by the master communication device 10 and the slave communication device 20 will be any one of Code 9 to Code 24, and therefore the pulse repetition frequency of the preamble used in the communication performed by the master communication device 10 and the slave communication device 20 will be 64 MHz. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the seventh determination pattern, the length of the preamble used in the communication performed by the master communication device 10 and the slave communication device 20 will be any one of 64 symbols, 1024 symbols, or 4096 symbols. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the seventh determination pattern, the preamble code of the preamble used in the communications performed by the ranging communication device 40 and the radar communication device 50 will be any one of Code 1 to Code 8, and therefore the pulse repetition frequency of the preamble used in the communications performed by the ranging communication device 40 and the radar communication device 50 will be 16 MHz. Furthermore, when the master communication device 10, the slave communication device 20, the ranging communication device 40, and the radar communication device 50 each determine the type of preamble according to the seventh determination pattern, the length of the preamble used in the communications performed by the ranging communication device 40 and the radar communication device 50 will be 16 symbols.

[0061] In the seventh determination pattern, the preamble length types are subdivided according to the type of data in the first usage purpose: When communicating "safety data related to driving operations," which has the highest priority in data communication, the preamble length is set to 4096 symbols to enhance resistance to radio wave interference; when communicating "body device data (such as a wiper device)," which has the second highest priority in data communication, the preamble length is set to 1096 symbols; and when communicating "entertainment data (such as audio content, video content, etc.)," ​​which has the lowest priority in data communication, the preamble length is set to 64 symbols.

[0062] [2-5. Modifications] Unlike the present embodiment, the ranging communication device 40 may be configured to operate as a slave communication device 20 that performs data communication with the master communication device 10 immediately after startup, and to switch the communication usage from data communication to distance measurement communication when the master communication device 10 instructs the device 40 to switch the communication usage from data communication to distance measurement communication. A ranging communication device 40 configured in this manner may include, for example, a storage unit that stores a data table indicating the correspondence between the communication usage and the preamble type used in the communication, and the current settings of at least one of the communication usage and the preamble type. The type of preamble used in the communication may be switched depending on the communication usage. If the configuration allows the type of preamble used in the communication to be switched depending on the communication usage, the preamble used in the communication may be appropriately set depending on the communication usage, even when the communication usage is switched.

[0063] Similarly, unlike the present embodiment, the radar communication device 50 may be configured to operate as a slave communication device 20 that performs data communication with the master communication device 10 immediately after startup, and then switch the communication usage from data communication to radar communication when the master communication device 10 instructs the radar communication device 50 to switch the communication usage from data communication to radar communication. A radar communication device 50 configured in this manner may include, for example, a storage unit that stores a data table indicating the correspondence between the communication usage and the preamble type used in the communication, and the current settings of at least one of the communication usage and the preamble type. The radar communication device 50 may switch the preamble type used in the communication depending on the communication usage. If the radar communication device 50 is configured in this way to switch the preamble type used in the communication depending on the communication usage, the preamble used in the communication can be appropriately set depending on the communication usage, even when the communication usage is switched.

[0064] 3. Mask Mode The master communication device 10 and the slave communication device 20 of the communication system SYS1 may each be configured to be able to select a mask mode. By combining the above-described preamble determination and the mask mode, it is possible to further improve the communication success rate in communications for high-priority applications.

[0065] Here, an overview of radio wave interference countermeasures in the communication system SYS1 will be described with reference to Figs. 6 and 7. Fig. 6 is a schematic diagram for explaining problems that occur during reception in UWB communication. Fig. 7 is a schematic diagram showing an overview of radio wave interference countermeasures in the communication system SYS1. Note that in Fig. 7, "master" refers to the master communication device 10, and "slave" refers to the slave communication device 20. Similar simplified expressions may also be used in other figures.

[0066] In FIG. 6 , the target wave is a radio wave desired to be received by the receiving antenna RA1. The jamming wave is a radio wave not desired to be received by the receiving antenna RA1. In UWB communication, although the strength of the radio wave also plays a role, the radio wave received first is generally processed first. Specifically, the communication device enters synchronization processing for the preceding radio wave and is unable to process the subsequent radio wave. In FIG. 6 , two radio waves arrive at the receiving antenna RA1 in the order of the jamming wave and the target wave. Therefore, the jamming wave is processed first. If the receiving device receives the jamming wave first, it cannot recognize it as a jamming wave unless it demodulates the address in the PHR, which is processed after the preamble and SFD. Note that once it is recognized as a jamming wave, processing of the jamming wave is stopped, and reception 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 the reception processing identifies the radio wave as a jamming wave, resulting in a missed reception of the target wave. In this embodiment, measures are implemented to reduce communication failures due to such radio wave interference. The outline of this measure will be explained with reference to FIG.

[0067] As shown in Figure 7, each of the master communication device 10 and the slave communication device 20 can select one of reception mode, transmission mode, and mask mode. In reception mode, each device 10, 20 can receive. In transmission mode, each device 10, 20 can transmit. Mask mode is a mode that is neither reception mode nor transmission mode, and in mask mode, each device 10, 20 cannot communicate. Note that mask mode is an idle mode in which power is supplied to necessary circuits, etc., and the device can immediately switch to reception mode or transmission mode.

[0068] In FIG. ｓｔａｒｔ is the time when the communication devices 10 and 20 start the reception mode (reception mode start time). ｎｅｘｔ is the time when the target wave is expected to be received (expected reception time), and is a time that conforms to the agreement between the communication devices 10 and 20. ｓｔａｒｔ is the estimated reception time τ ｎｅｘｔThe mask mode is set slightly before the expected reception time. As shown in FIG. 7 , the master communication device 10 switches from mask mode to reception mode just before the expected reception time agreed upon with the slave communication device 20. The slave communication device 20 switches from mask mode to reception mode just before the expected reception time agreed upon with the master communication device 10. That is, in the communication method using wireless communication according to this embodiment, just before the expected reception time agreed upon between the multiple devices 10, 20 performing wireless communication, switching is performed from mask mode, in which wireless communication is not possible, to reception mode, in which wireless communication is performed, just before the expected reception time agreed upon between the multiple devices 10, 20 performing wireless communication. Also, in the communication device using wireless communication according to this embodiment, switching from mask mode to reception mode just before the expected reception time agreed upon with other devices performing wireless communication. Note that the switching process just before the expected reception time may be performed when switching from transmission mode to reception mode.

[0069] This configuration increases the probability that the device receiving the target wave will be in mask mode when a jamming wave arrives. In other words, it reduces the possibility of receiving a jamming wave and increases the probability that the target wave will be properly received. This improves the success rate of wireless communication. Note that it is preferable to start the receive mode as close as possible to the expected time of reception of the target wave. A detailed example of this will be described later.

[0070] 4. Master Communication Device Fig. 8 is a diagram showing an example of the configuration of the master communication device 10. Note that Fig. 8 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components.

[0071] As shown in FIG. 8, the master communication device 10 includes a wireless communication unit 11 and a controller 12 .

[0072] 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 reception when in a reception mode, capable of transmission when in a transmission mode, and is unable to communicate when in a mask mode that is neither a reception mode nor a transmission mode.

[0073] 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.

[0074] The controller 12 has, 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 in accordance with a single program. However, this configuration is not limited thereto, and each of the functional units 121 to 123 may be realized, for example, by a processor executing arithmetic processing in accordance with a separate program for each functional unit.

[0075] As described above, each of the functional units 121 to 123 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 portion of each of the functional units 121 to 123 may be realized 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 a combination of software and hardware. Also, each of the functional units 121 to 123 is a conceptual component. The function performed by one component may be distributed among multiple components. Also, the functions of multiple components may be integrated into one component.

[0076] The schedule creation unit 121 creates a schedule for UWB communication between the master communication device 10 and the slave communication devices 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.

[0077] The schedule providing unit 122 provides the wireless communication schedule created by the schedule creation unit 121 to the slave communication devices 20. In this embodiment, there are multiple 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. However, in this embodiment, the schedule providing unit 122 performs broadcast transmission, which transmits the wireless communication schedule simultaneously to the multiple slave communication devices 20a to 20d.

[0078] 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 executing wireless communication.

[0079] 9 is a flowchart showing an example of the operation of the master communication device 10. The operation shown in FIG. 9 is initiated, for example, when a body ECU installed in the vehicle C1 that controls the body of the vehicle C1 is started. The body ECU specifically controls on-board devices other than vehicle driving devices such as the engine. On-board devices other than vehicle driving devices include, for example, an air conditioner, door lock devices, window opening / closing devices, wiper devices, etc.

[0080] The body ECU is typically activated when the doors of the vehicle C1 are unlocked. Another example is when the ACC is turned on by operating the vehicle's ignition key. In the case of applying the communication system to other mobile objects (e.g., trains, ships, aircraft, etc.), the start timing of the operations shown in FIG. 9 may be the start timing of the mobile object drive system. The operations shown in FIG. 9 may be executed periodically after the body ECU is activated (e.g., immediately after activation, or at predetermined intervals), or as exceptional operations (e.g., when communication failures occur or increase frequently, or when there is a change in the vehicle (communication) environment). At least one of the master communication device 10 and the slave communication devices 20a to 20d may be a body ECU. However, not all of the master communication device 10 and the slave communication devices 20a to 20d may be body ECUs. The body ECU may be, for example, an entertainment device such as an audio device.

[0081] 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 has been 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, has been 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.

[0082] In step S2, the schedule providing unit 122 broadcasts (simultaneously transmits) the wireless communication schedule to all of 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 devices 20 when the vehicle starts to be used. The wireless communication schedule is broadcast in accordance with the communication frame format of the UWB communication described above (see FIG. 2). The wireless communication schedule is included in the data body of the communication frame format.

[0083] 10 is a diagram showing an example of a data format of a wireless communication schedule. As shown in Fig. 10, 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.

[0084] The time data D1 indicates 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 configured with a counter or the like that counts at regular time intervals based on an operating clock.

[0085] 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.

[0086] Each of the data D2a to D2d has a structure in which ID data D21 and time data D22 are connected in order. 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 the 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 a number of 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 may not match among the communication devices 10, 20a to 20d.

[0087] The cycle data D3 indicates 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. 14).

[0088] Returning to FIG. 9, once the wireless communication schedule has been broadcast, the process proceeds to the next step S3.

[0089] In step S3, the schedule providing unit 122 determines whether or not a reception response has been received from all of the slave communication devices 20a to 20d to which the wireless communication schedule was transmitted. The reception response is a reply indicating that the wireless communication schedule was received and is a process requested of each of the slave communication devices 20a to 20d that received the wireless communication schedule. Since this request is included in the wireless communication schedule data described above, the slave communication device 20 that received the wireless communication schedule will return a response unless it is malfunctioning. However, due to reasons such as the occurrence of radio wave interference described above, it is possible that some of the slave communication devices 20a to 20d will fail to receive the wireless communication schedule. In particular, before broadcast transmission, each of the slave communication devices 20a to 20d does not have a wireless communication schedule and therefore cannot switch from mask mode to receive mode at the appropriate timing described above. Therefore, it is necessary to remain in receive mode for a long period of time, which makes them susceptible to radio wave interference.

[0090] If a reception response has been received from all of the slave communication devices 20a to 20d (Yes in step S3), the process proceeds to the next step S4. On the other hand, if a reception response has not been received 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 of the devices 20a to 20d targeted for the broadcast transmission of the wireless communication schedule, the wireless communication schedule is broadcast again. This configuration can prevent the wireless communication schedule from being executed in a state in which the wireless communication schedule has not been properly transmitted from the master communication device 10 to the slave communication devices 20. Note that if the wireless communication schedule is rebroadcast at period D3, the receive mode timing of each of the slave communication devices 20a to 20d according to the wireless communication schedule in the rebroadcast transmission will ultimately be the same. Therefore, it is possible to set the communication timing with each of the slave communication devices 20a to 20d not only when a reception response is received from all slaves in the same broadcast transmission, but also when a reception response is received from all slaves in multiple broadcast transmissions.

[0091] In step S4, the schedule providing unit 122 finalizes the wireless communication schedule. Once the wireless communication schedule is finalized, the process proceeds to step S5.

[0092] In step S5, the schedule execution unit 123 starts wireless communication processing according to the wireless communication schedule. A specific example of wireless communication processing according to the wireless communication schedule will be described later.

[0093] In the configuration of this embodiment, for example, if at least one of the multiple slave communication devices 20a to 20d is malfunctioning, the process in step S3 will not return "Yes," and the wireless communication schedule will never be finalized. Taking this into consideration, for example, if the process in step S3 does not return "Yes" even after broadcast transmission has been 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 in accordance with that schedule.

[0094] 5. Slave Communication Device Fig. 11 is a diagram showing an example of the configuration of the slave communication device 20. Note that Fig. 11 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components. Furthermore, all of the multiple slave communication devices 20a to 20d have the configuration shown in Fig. 11. As shown in Fig. 11, the slave communication device 20 includes a wireless communication unit 21 and a controller 22.

[0095] 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 reception when in the reception mode, capable of transmission when in the transmission mode, and is unable to communicate when in a mask mode that is neither the reception mode nor the transmission mode.

[0096] 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.

[0097] 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 in accordance with a single program. However, this configuration is not limited thereto, and each of the functional units 221 and 222 may be realized, for example, by a processor executing arithmetic processing in accordance with separate programs for each functional unit.

[0098] As described above, the functional units 221 and 222 may be realized by causing a processor to execute a program, i.e., by software, but may also be realized by other methods. At least a portion of the functional units 221 and 222 may be realized using, for example, an ASIC or an FPGA. That is, the functional units 221 and 222 may be realized by hardware using a dedicated IC or the like. Furthermore, the functional units 221 and 222 may be realized by a combination of software and hardware. Furthermore, the functional units 221 and 222 are conceptual components. The function performed by one component may be distributed among multiple components. Furthermore, the functions of multiple components may be integrated into one component.

[0099] 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 convert time data included in transmission data broadcast from the master communication device 10 into the time of its own device.

[0100] The schedule execution unit 222 executes wireless communication in accordance with the wireless communication schedule acquired by the schedule acquisition unit 221. The schedule execution unit 222 controls the communication mode of the wireless communication unit 21 when executing wireless communication.

[0101] FIG. 12 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 by each of the slave communication devices 20a to 20d. The operation shown in FIG. 12 is initiated in synchronization with the operation of the master communication device 10 described above (see FIG. 9). That is, the operation shown in FIG. 12 is initiated, for example, when the body ECU is started. The operation shown in FIG. 12 may also be executed, for example, as a regular operation or an exceptional operation after the body ECU is started.

[0102] 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.

[0103] In step S12, the schedule acquisition unit 221 replies that it has received the wireless communication schedule. In detail, the schedule acquisition unit 221 replies that it has received 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 receive the wireless communication schedule is completed, the process proceeds to the next step S13.

[0104] In step S13, the schedule acquisition unit 221 converts the transmission time and reception time (for example, the time indicated in a format such as "after how many milliseconds") based on the broadcast transmission time or the like included in the wireless communication schedule into the time of its own device. The schedule acquisition unit 221 performs the time conversion process based on a timer (not shown) built into its own device. When the time conversion process is complete, the process proceeds to the next step S14.

[0105] In step S14, the schedule acquisition unit 221 determines the wireless communication schedule. Note that the process of step S14 may be executed before the process of step S13. Once the wireless communication schedule is determined, the process proceeds to the next step S15.

[0106] In step S15, the schedule execution unit 222 starts wireless communication processing according to the wireless communication schedule. A specific example of wireless communication processing according to the wireless communication schedule will be described later.

[0107] 6. Example of Operation of Communication System According to Wireless Communication Schedule Next, an example of 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 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.

[0108] Estimated reception time τ ｎｅｘｔ is calculated according to the wireless communication schedule broadcast from any one of the plurality of devices 10, 20a to 20d. In this embodiment, the wireless communication schedule is broadcast from the master communication device 10 as described above. The estimated reception time τ ｎｅｘｔ is the 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, accurate reception timing according to the communication schedule can be obtained, and the start time of the reception mode can be set appropriately.

[0109] Receive mode start time τ ｓｔａｒｔ In order to avoid interference from jamming waves, the expected reception time τ ｎｅｘｔIn this embodiment, the reception mode start time τ ｓｔａｒｔ 13 is a diagram showing the reception mode start time τ ｓｔａｒｔ 10 is a schematic diagram for explaining a detailed example of how to set the

[0110] In the UWB communication standard, the transmission and reception times (times) can be acquired at the timing of the PHR. In consideration of this point, in this embodiment, as shown in FIG. 13, the estimated 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 estimated reception time τ ｎｅｘｔ is set to the start timing of the PHR.

[0111] In this embodiment, the estimated reception time τ ｎｅｘｔ The receive mode start time τ, which is the time immediately before ｓｔａｒｔ is determined by the following equation (1): ｓｔａｒｔ = τ ｎｅｘｔ　 -(t ＳＦＤ　 +t ｓｙｍ　 × N ｒｇ ) (1)

[0112] In formula (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. As described above, one symbol of the preamble code refers to a sequence symbol configured using pulses of a predetermined pattern (for example, -, 0, +). N ｒｇ is the required number of times of recognition of one symbol of the preamble code. ｒｇ Only when one symbol of the preamble code is recognized can the transmitted data of UWB communication be received. ｒｇis the number of times (device-dependent number of times) determined by the apparatuses 10 and 20. In the example shown in FIG. 13, the required number of times of recognition N ｒｇ For example, t is four times. ｓｙｍ The number of required recognition times N depends on the device. ｒｇ In this embodiment, the minimum recognition period of the preamble can be calculated by multiplying the estimated reception time τ ｎｅｘｔ Rather than the calculation formula (t ＳＦＤ　 +t ｓｙｍ　 × N ｒｇ ) is the receive mode start time τ ｓｔａｒｔ It is as follows.

[0113] By determining the reception mode start time in this way, the start of the period in 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 from jamming waves, and improves the success rate of communication. Note that the reception mode start time τ ｓｔａｒｔ is the estimated reception time τ ｎｅｘｔ than the formula (t ＳＦＤ　 +t ｓｙｍ　 × N ｒｇ ) and may be set to a time that is further earlier by a margin time obtained by an experiment or the like.

[0114] Fig. 14 is a schematic diagram showing an example of operation of the communication system SYS1 according to the wireless communication schedule. The operation shown in Fig. 14 corresponds to the execution of the wireless communication schedule in step S5 in Fig. 9 and step S15 in Fig. 12. In Fig. 14, 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 receive mode even if they are in the transmit mode.

[0115] 14 shows a configuration in which predetermined wireless communication between the master communication device 10 and each of the four slave communication devices 20a to 20d is repeated in sequence at a period T in accordance with the wireless communication schedule, but this is merely an example. A configuration in which predetermined wireless communication is performed only once in sequence between the master communication device 10 and each of the four slave communication devices 20 in accordance with the wireless communication schedule may also be used. Furthermore, the number of slave communication devices 20 that periodically perform wireless communication with the master communication device 10 may be changed as appropriate, and a configuration in which only some of all of the slave communication devices 20a to 20d included in the communication system SYS1 periodically perform wireless communication with the master communication device 10 may also be used.

[0116] 14 , the master communication device 10 first starts the transmission mode in accordance with 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 in accordance with 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 preprogrammed in the device 10, which is determined based on the time required for data transmission (which depends on the amount of data to be transmitted, etc.) relative to the start timing of the transmission mode.

[0117] The first slave communication device 20a receives the signal at the estimated reception time τ determined by the transmission time Ta agreed 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 reception 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 switches from the mask mode to the receive mode, thereby receiving the transmission wave transmitted from the master communication device 10 while avoiding reception of interference waves as much as possible.

[0118] The first slave communication device 20a starts the reception mode at the reception mode start time τ ｓｔａｒｔBased 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 timings 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 agreed upon with the master communication device 10 in accordance with 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. Note that the first slave communication device 20a completes the transmission mode at a timing preprogrammed in the device 20a, which is determined based on the time required for data transmission (which depends on the amount of data to be transmitted, etc.) based on the start timing of the transmission mode.

[0119] The master communication device 10 receives the signal at the estimated 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 reception mode start time τ ｓｔａｒｔ Then, the master communication device 10 calculates the reception mode start time τ ｓｔａｒｔ The master communication device 10 then switches from the mask mode to the receive mode, thereby receiving the transmission wave transmitted from the first slave communication device 20a while avoiding reception of interference waves as much as possible.

[0120] As a result, communication between the master communication device 10 and the first slave communication device 20a, which is defined in the first time slot TS1 in the wireless communication schedule, is completed. Upon completion of the first time slot TS1, communication between the master communication device 10 and the second slave communication device 20b, which is defined in the second time slot TS2, is performed in the same manner as in the first time slot TS1. Furthermore, upon completion of the second time slot TS2, communication between the master communication device 10 and the third slave communication device 20c, which is defined in the third time slot TS3, is performed in the same manner as in the first time slot TS1. Furthermore, upon completion of the third time slot TS3, communication between the master communication device 10 and the fourth slave communication device 20d, which is defined in the fourth time slot TS4, is performed in the same manner 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 performed.

[0121] 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 at a reception mode start time τ ｓｔａｒｔ 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 since the transmission timing of the master communication device 10 (see transmission time Tb) described above. The master communication device 10 starts the reception mode at a reception mode start time τ ｓｔａｒｔ Then, the mask mode is switched to the receive mode.

[0122] 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 at 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 between the master communication device 10 and the third slave communication device 20c has elapsed since the transmission timing (see transmission time Tc) of the master communication device 10. The master communication device 10 starts the reception mode at a reception mode start time τ ｓｔａｒｔ Then, the mask mode is switched to the receive mode.

[0123] 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 at 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 since the transmission timing of the master communication device 10 (see transmission time Td). The master communication device 10 starts the reception mode at a reception mode start time τ ｓｔａｒｔ Then, the mask mode is switched to the receive mode.

[0124] 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 times, so that radio wave interference between these communications can be avoided.

[0125] In this embodiment, the master communication device 10 that has broadcast the wireless communication schedule performs reception after transmitting wirelessly according to the wireless communication schedule. Then, when receiving after transmitting wirelessly, 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.

[0126] 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 must be reversed from the order in this embodiment.

[0127] 7. Modifications [7-1. First Modification] Fig. 15 is a diagram showing the configuration of a communication system SYS1A according to a first modification. Fig. 16 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 modification. Note that in this modification, there are also multiple slave communication devices 20A (four in particular), and each of the slave communication devices 20aA, 20bA, 20cA, and 20dA can communicate with the master communication device 10A. The slave communication devices 20aA to 20dA have the same configuration. For this reason, Fig. 16 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.

[0128] 15 and 16, 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. 16, the master communication device 10A and the slave communication device 20A each include wireless communication units 11 and 21 that enable UWB communication, as well as wired communication units 13 and 23 that enable wired communication.

[0129] In this modification, the communication line L1 is a power supply line connecting the master communication device 10A and each of the slave communication devices 20aA to 20dA to the battery 70. 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.

[0130] 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. 9, the broadcast of the wireless communication schedule is performed using wired communication (PLC communication) instead of UWB communication.

[0131] 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 mask mode to reception mode at a time when UWB communication is less susceptible to radio wave interference. In this modified example, wired communication is used instead of wireless communication in such a situation where there is a high possibility of radio wave interference. This reduces the possibility of communication failure due to radio wave interference during reception. Note that the wireless communication schedule may be broadcast using both wireless and wired communication.

[0132] As described above, in this modification, the wired communication is PLC communication using the power supply line L1. The power supply 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, the configuration of this modification allows wired communication to be achieved using a wire harness that cannot be eliminated, thereby suppressing an increase in the number of wire harnesses and enabling wired communication to be used.

[0133] [7-2. Second Modification] Fig. 17 is a diagram showing the configuration of a communication system SYS1B according to a second modification. As shown in Fig. 17, 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 includes 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. Like the communication system SYS1 according to the above-described embodiment, the communication system SYS1B includes a ranging communication device 40 and a radar communication device 50, but the ranging communication device 40 and the radar communication device 50 are not shown in Fig. 17.

[0134] 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 in accordance with a program. However, the radio wave learning unit 124 is not limited to being realized by software, and may also be realized by hardware using a dedicated IC or the like.

[0135] The radio wave learning unit 124 determines (performs calibration) the optimum value of the radio wave output for wireless communication (UWB communication) used between the master communication device 10B and each of the slave communication devices 20aB to 20dB. In this modification, the optimum value is the minimum necessary output of the radio waves. By limiting the radio wave output to the minimum necessary, it is possible to reduce power consumption in the communication system SYS1B. Furthermore, by limiting the radio wave output to the minimum necessary, it is possible to reduce the possibility of interference with other communications.

[0136] In this modified example, 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 waves used between the devices is calibrated, the devices are configured to switch to the receive mode (switch from the mask mode) immediately before the expected reception time agreed upon between the devices.

[0137] This allows radio wave output calibration to be performed while suppressing the effects of radio wave interference. In other words, radio communication for calibration can be performed without the effects of radio wave interference, allowing radio wave output calibration to be performed quickly and accurately. Note that radio wave output calibration may also be performed between devices other than those having a master-slave relationship. Even in this case, the devices may switch to reception mode immediately before the expected reception time agreed upon between them.

[0138] Fig. 18 is a flowchart showing an example of processing executed by the master communication device 10B (radio wave learning unit 124) during calibration of the radio wave output. Fig. 19 is a diagram for explaining the operation of the slave communication device 20B during the processing shown in Fig. 18.

[0139] The calibration of the radio wave output (radio wave learning) is performed, for example, when the communication system SYS1B is first used. The calibration of the radio wave output is started, for example, when the body ECU described above is started. The calibration of the radio wave output is usually performed before broadcast transmission of the wireless communication schedule.

[0140] The radio wave output calibration is performed in order between the master communication device 10B and each of the slave communication devices 20aB to 20dB. The order is not particularly limited, but for example, the master communication device 10B calibrates the radio wave output 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 in that order. When each calibration is performed, the processes shown in Figures 18 and 19 are executed.

[0141] As shown in Figure 18, in step S21, the master communication device 10B performs a distance measurement process to determine the distance to the slave communication device 20B. Note that a known process may be used for the distance measurement 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. The slave communication device 20B replies in response to receiving the distance measurement signal (see Figure 19). If the time required for radio waves to travel between the devices is determined 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.

[0142] It is preferable that the radio wave output of the UWB communication used in the ranging process be near the maximum power (e.g., -41.3 dBm / MHz) specified by the communication standard. Near the maximum power is a value equal to or slightly smaller than the maximum power. By setting the radio wave output during ranging process to near the maximum power in this way, the probability of a situation occurring in which radio waves do not reach the master communication device 10B and the slave communication device 20B can be reduced, thereby increasing the probability of the ranging process being successful.

[0143] Once the distance X is determined by the distance measurement process, the master communication device 10B proceeds to step S22.

[0144] In step S22, the master communication device 10B determines the range of transmission power (output range) used to find the optimal value of radio wave output. A correlation map showing the relationship between the device-to-device distance and transmission power (radio wave output), created in advance, is used to determine the range of transmission power. FIG. 20 is an example of a correlation map showing the relationship between the device-to-device distance and transmission power. The correlation map is created through experiments, etc., but due to variations in characteristics between devices and environmental fluctuations such as temperature, the transmission power found from the correlation map may not necessarily be the optimal value. For this reason, calibration is performed to find the optimal value of radio wave output.

[0145] The master communication device 10B first determines the 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. 20). The master communication device 10B then determines the minimum and maximum values ​​a and b of the transmission power, using the determined transmission power Y as a reference (see FIG. 20). The minimum and maximum values ​​a and b may be determined using a table or relational expression prepared in advance. Once the transmission power range has been determined, the master communication device 10B proceeds to step S23.

[0146] 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.

[0147] In step S24, the master communication device 10B transmits UWB radio waves at the Nth power level to the slave communication device 20B. The Nth power level is determined according to a preset standard. In this modification, the Nth power level is the minimum value a of the transmission power range plus a predetermined step power α multiplied by (N-1). That is, for example, when N = 1 (i.e., the first transmission for power adjustment), the Nth power level is "a." For example, when N = 2, the Nth power level is "a + α." For example, when N = 3, the Nth power level is "a + 2α." Note that in this example, the transmission power level is gradually increased based on the minimum value a of the transmission power range, but this is merely an example. The transmission power level may also be gradually decreased based on the maximum value b of the transmission power range. After transmitting at the Nth power level, the master communication device 10B proceeds to step S25.

[0148] In step S25, the master communication device 10B determines whether or not a reply has been received from the slave communication device 20B within a predetermined period determined through experiments 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. Note that in the example shown in FIG. 19 , 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 replies. On the other hand, the third communication power is received by the slave communication device 20B, and the slave communication device 20B replies.

[0149] 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.

[0150] 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 output power to the Nth power, which is the power when a reply is received from the slave communication device 20B. As another example, the master communication device 10B sets the output power by adding a margin determined by experiments or the like to the Nth power. In the example shown in FIG. 19, the output power is set to the third power (a+2α), or the power obtained by adding the margin power to the third power (a+2α). Once the output power is determined, the master communication device 10B proceeds to step S27.

[0151] In step S27, the master communication device 10B notifies the slave communication device 20B of the determined output power as the power to be used, using UWB communication. This allows UWB communication between the master communication device 10B and the slave communication device 20B to be performed at the determined output power.

[0152] In step S28, the master communication device 10B adds 1 to the variable N. After adding 1 to the variable N, the master communication device 10B returns to step S24. This allows the master communication device 10B to output transmission waves while changing the output power.

[0153] 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.

[0154] 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. This 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, or when radio waves are transmitted from the slave communication device 20B to the master communication device 10B, the receiving device switches to reception mode immediately before the expected reception time. This reduces the possibility of being affected by radio wave interference during the distance measurement process, allowing for quick and accurate distance measurement.

[0155] Furthermore, 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. This agreement may be made using UWB communication, or the above-mentioned PLC communication may be used. In accordance with 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, or when radio waves are transmitted from the slave communication device 20B to the master communication device 10B, the receiving device switches to reception 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.

[0156] The ranging process indicated by the dashed frame W1 in Fig. 19 is preprocessing for data communication performed between the master communication device 10B and the slave communication device 20B. Therefore, the usage of the master communication device 10B and the slave communication device 20B when performing the ranging process indicated by the dashed frame W1 in Fig. 19 may be data communication rather than distance measurement communication. Note that the usage of the master communication device 10B and the slave communication device 20B when performing the ranging process indicated by the dashed frame W1 in Fig. 19 may be distance measurement communication, and after performing the ranging process indicated by the dashed frame W1 in Fig. 19, the master communication device 10B and the slave communication device 20B may switch the preamble type from a type corresponding to distance measurement communication to a type corresponding to data communication.

[0157] 8. Points to Note, etc. The various technical features disclosed in the description of the invention in this specification may be modified in various ways without departing from the spirit of the technical creation. Furthermore, multiple embodiments and modifications disclosed in the description of the invention in this specification may be combined to the extent possible.

[0158] 10, 10A, 10B... Master communication device 20, 20A, 20B... Slave 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 40... Ranging communication device 50... Radar communication device SYS1, SYS1A, SYS1B... Communication system

Claims

1. A communication method using a preamble between a first communication device and a second communication device, in which the first communication device communicates with the second communication device using a preamble type determined from a plurality of preamble types determined by the pulse repetition frequency or length of the preamble according to the intended use of the communication.

2. The communication method according to claim 1, wherein the first purpose of use is a purpose of use that has priority over the second purpose of use, and the pulse repetition frequency determined when the purpose of use for the communication is the first purpose of use is higher than the pulse repetition frequency determined when the purpose of use for the communication is the second purpose of use.

3. The communication method according to claim 1, wherein the first purpose of use is a purpose of use that has priority over the second purpose of use, and the length of the preamble determined when the purpose of use of the communication is the first purpose of use is longer than the length of the preamble determined when the purpose of use of the communication is the second purpose of use.

4. The communication method according to claim 1, further comprising determining a pulse repetition frequency of the preamble and a length of the preamble used in the communication in accordance with an intended use of the communication.

5. The communication method according to claim 4, wherein the first purpose of use is a purpose of use that has priority over the second purpose of use, the pulse repetition frequency determined when the purpose of use of the communication is the first purpose of use is higher than the pulse repetition frequency determined when the purpose of use of the communication is the second purpose of use, and the length of the preamble determined when the purpose of use of the communication is the first purpose of use is longer than the length of the preamble determined when the purpose of use of the communication is the second purpose of use.

6. The communication method according to claim 5, wherein the first purpose of use is data communication, and the second purpose of use includes at least one of distance measurement communication and radar communication.

7. The communication method according to claim 1, wherein the communication is wireless communication according to an UWB communication system, and the usage of the communication includes at least one of data communication, distance measurement communication, and radar communication.

8. The communication method according to claim 1, wherein the pulse repetition frequency is 16 MHz or 64 MHz.

9. The communication method according to claim 1, wherein the length of the preamble is any one of 16 symbols, 64 symbols, 128 symbols, 256 symbols, 512 symbols, 1024 symbols, 2048 symbols, and 4096 symbols.

10. The communication method according to claim 1, wherein the use of the communication can be switched.

11. A communication method according to any one of claims 1 to 10, in which a switch is made from a mask mode in which wireless communication is impossible to a reception mode in which wireless communication is received immediately before an expected reception time agreed upon between the first communication device and the second communication device.

12. A communication system comprising: a first communication device; and a second communication device, wherein the first communication device communicates with the second communication device using a preamble type determined according to the intended use of the communication from among a plurality of preamble types determined by a pulse repetition frequency or a length of the preamble.

13. The communication system according to claim 12, wherein the communication is wireless communication using an UWB communication system, and the usage of the communication includes at least one of data communication, distance measurement communication, and radar communication.

14. The communication system according to claim 13, wherein the first communication device and the second communication device are mounted in a vehicle.

15. A communication method between a first communication device and a second communication device performing UWB communication, wherein the first communication device determines a pulse repetition frequency to be 64 MHz when the intended use of the communication is data communication, and determines the pulse repetition frequency to be 16 MHz when the intended use of the communication is distance measurement communication or radar communication, and communicates with the second communication device using the determined pulse repetition frequency.

16. A communication method between a first communication device and a second communication device performing UWB communication, wherein the first communication device determines the length of a preamble to be 4096 symbols when the intended use of the communication is data communication, and determines the length of the preamble to be less than 4096 symbols when the intended use of the communication is distance measurement communication or radar communication, and communicates with the second communication device using the determined preamble length.

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