Communication device, communication method, communication program, and communication system

Abstract

An exemplary communication device is a communication device mounted on a mobile body and capable of realizing a plurality of types of functions by UWB communication. The communication device comprises a control unit that changes a preamble code of the UWB communication allocated to each of the plurality of types of functions in accordance with a state of the mobile body.

Description

COMMUNICATION DEVICE, COMMUNICATION METHOD, COMMUNICATION PROGRAM, AND COMMUNICATION SYSTEM

[0001] The present disclosure relates to communication technology using UWB (Ultra Wide Band) communication.

[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 communication, which uses wideband radio waves, has the advantages of low radio wave interference with radio waves used in Wi-Fi (registered trademark) and mobile devices such as smartphones, and good transparency, leading to an expansion of its applications. Furthermore, UWB communication is expected to be a communication method for devices mounted on mobile devices, since it is easy to establish communication even in a narrow metal space and with many wires inside a vehicle such as an automobile.

[0003] A known prior art technique related to UWB communication is a time-division transmission and reception technique for UWB signals to realize various functions, such as a vehicle key function, a radar function, and a beacon ranging function (see, for example, Patent Document 1). Patent Document 1 discloses that the time-division schedule for each function is changed depending on the vehicle state (whether the vehicle is stopped or moving).

[0004] Japanese Patent Application Laid-Open No. 2021-503178

[0005] If UWB signal transmission and reception is configured to be time-division shared to achieve multiple functions, there is a concern that the responsiveness of the communication performed to achieve each function will deteriorate. Also, if the time-division schedule for each function is changed, all communication devices will need to be aware of the schedule for each function, which may make synchronization difficult. There is also a concern that the processing load on each communication device will increase.

[0006] When UWB communication is used, interference between UWB communications may cause communication interruptions. In other words, if UWB signals are not transmitted and received in a time-division manner, there is a concern that the success rate of communication may decrease due to interference between UWB communications. In this regard, when there are multiple functions (uses) realized by transmitting and receiving UWB signals, it is considered desirable that the success rate of communication for functions with high priority (importance) is higher than that of communication for functions with low priority.

[0007] In view of the above, an object of the present disclosure is to provide a technology that can increase the success rate of UWB communication for high-priority usage applications while suppressing deterioration in UWB communication responsiveness.

[0008] An exemplary communication device of the present disclosure is a communication device that is mounted on a mobile body and is capable of realizing multiple types of functions through UWB communication, and is equipped with a control unit that changes the UWB communication preamble code assigned to each of the multiple types of functions depending on the state of the mobile body.

[0009] According to an exemplary configuration of the present disclosure, a preamble code is assigned to each of multiple types of functions (usage applications) realized by UWB communication. In a situation where the communication timings of UWB communications overlap, the success rate of UWB communications is related to the preamble code used for the communication. Therefore, according to the configuration of the present disclosure, by assigning a preamble code that increases the success rate of communication to a high-priority usage application, it is possible to increase the success rate for the high-priority usage application while suppressing a deterioration in communication responsiveness. Furthermore, the high-priority usage application may change depending on the state of the mobile device. In this regard, according to the configuration of the present disclosure, the preamble code assigned to each function is changed depending on the state of the mobile device, so it is possible to increase the success rate of communication for the high-priority usage application even if the state of the mobile device changes.

[0010] 1 is a diagram showing the configuration of a communication system that is an example of a communication system according to an embodiment of the present disclosure; FIG. 2 is a diagram showing the configuration of a communication system that is another example of a communication system according to an embodiment of the present disclosure; FIG. 3 is a block diagram showing the general configuration of a parent device; FIG. 4 is a block diagram showing the general configuration of a child device; FIG. 5 is a block diagram showing the general configuration of a wireless tag; FIG. 6 is a diagram showing a frame format used in UWB communication; FIG. 7 is a diagram showing the tendency of communication success rate for each combination of preamble codes when two UWB communications are performed simultaneously; FIG. 8 is a diagram showing a preamble code allocation pattern for multiple types of functions that can be realized by transmitting and receiving UWB signals; FIG. 9 is a diagram showing a preamble code allocation pattern different from the example shown in FIG. 8; FIG. 10 is a diagram illustrating a communication schedule for a data communication function; FIG. 11 is a diagram illustrating a communication schedule for a ranging function; FIG. 12 is a diagram illustrating a communication schedule for a radar function; 17A and 17B are diagrams illustrating the relationship between the state of a moving body and the preamble codes assigned to each function; FIG. 17B is a diagram illustrating an example of the relationship between the state of a moving body and the preamble codes assigned to each function; FIG. 17C is a diagram illustrating the relationship between the state of a moving body and the preamble codes assigned to each function; FIG. 17D is a diagram illustrating the relationship between the state of a moving body and the preamble codes assigned to each function;

[0011] Hereinafter, exemplary embodiments of the present disclosure 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.

[0012] <1. Communication System> [1-1. System Overview] Fig. 1 is a diagram showing a configuration of a communication system SYS1 as an example of a communication system SYS according to an embodiment of the present disclosure. Fig. 2 is a diagram showing a configuration of a communication system SYS2 as another example of a communication system SYS according to an embodiment of the present disclosure. Both of the two example communication systems SYS1 and SYS2 are applied to a mobile object M1. Specifically, the mobile object M1 is a vehicle such as an automobile, a bus, or a railroad car. However, the mobile object M1 may be something other than a vehicle, such as an airplane or a ship.

[0013] As shown in FIGS. 1 and 2, the communication systems SYS1 and SYS2 include a master unit 10, a slave unit 20, and a wireless tag 30.

[0014] The base unit 10 is mounted on the moving object M1. Specifically, the base unit 10 constitutes a central control unit mounted on the moving object M1.

[0015] The slave 20 is mounted on the mobile unit M1. Specifically, the slave 20 constitutes an individual control unit controlled by the center control unit, and is connected by wire to the devices 40 arranged on the mobile unit M1. The slave 20 transmits and receives UWB signals to and from the base unit 10. That is, the slave 20 performs UWB communication with the base unit 10 and is controlled by the base unit 10 using the UWB communication. The slave 20 controls each device 40 connected to it in accordance with instructions from the base unit 10. The base unit 10 and the slave 20 can be said to be communication devices performing UWB communication.

[0016] 1 and 2, in this embodiment, the communication systems SYS1 and SYS2 include a plurality of slave devices 20. The master device 10 performs UWB communication with each of the slave devices 20. Note that the dashed lines connecting the master device 10 and each slave device 20 in FIGS. 1 and 2 indicate that UWB communication is performed between the master device 10 and each slave device 20.

[0017] 1 illustrates an example of an arrangement in which the devices 40 connected to each slave device 20 are sensors, actuators, or ECUs (Electronic Control Units). Specifically, the sensors are, for example, light receiving sensors, power window switches, accelerator sensors, brake sensors, or wiper switches. The actuators are, for example, power window motors, headlamps, or wiper motors. The ECUs are, for example, airbag ECUs or air conditioner ECUs.

[0018] 2 also shows an example of a layout configuration in which the devices 40 connected to each slave unit 20 are assumed to be devices arranged around seats. Examples of devices arranged around seats include call buttons used by passengers, displays that display information about the location where the passenger is sitting (such as the name of the station or bus stop), and reclining control devices that control the reclining of seats and the position of the reclining seats. Reclining control may include, for example, control to return the reclining position of a seat to its initial position in response to an instruction from the master unit 10. Reclining seat control may also include, for example, control to change the reclining position of a seat in response to a change in the direction of travel of a moving object M1, such as a railway vehicle, in response to an instruction from the master unit 10.

[0019] Furthermore, the arrangements shown in FIGS. 1 and 2 are merely examples, and for example, an arrangement in which the arrangements of both FIGS. 1 and 2 are combined may also be used.

[0020] The wireless tag 30 transmits and receives UWB signals to and from the slave 20. That is, the wireless tag 30 performs UWB communication with the slave 20. The wireless tag 30 can be said to be a communication device that performs UWB communication. In this embodiment, the wireless tag 30 performs UWB communication with each of the multiple slaves 20. Note that the dashed dotted lines connecting each slave 20 and the wireless tag 30 in FIGS. 1 and 2 indicate that UWB communication is performed between each slave 20 and the wireless tag 30. Note that, as another example, the wireless tag 30 may be configured to transmit and receive UWB signals to and from the master 10.

[0021] The wireless tag 30 is configured to be able to measure distances to each of the multiple slave units 20 by transmitting and receiving UWB signals. In this embodiment, three or more slave units 20 are provided, and therefore the position of the wireless tag 30 can be detected by triangulation using the slave units 20 as anchors. The wireless tag 30 may be configured to be attached to a key of the mobile unit M1, or to a cleaning robot that boards the mobile unit M1 and cleans the inside of the mobile unit M1, for example.

[0022] [1-2. Configuration of Base Unit] Fig. 3 is a block diagram showing a general configuration of base unit 10. Note that Fig. 3 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components.

[0023] As shown in FIG. 3, the master unit 10 includes a master unit controller 11 , a master unit memory 12 , and a master unit wireless communication unit 13 .

[0024] The master controller 11 controls the overall operation of the master 10. In other words, the master controller 11 constitutes a control unit. The master controller 11 includes a processor that performs arithmetic processing and the like. The processor includes, for example, a CPU (Central Processing Unit). The master controller 11 may be composed of one processor or multiple processors. When composed of multiple processors, the processors only need to be connected to each other so that they can communicate with each other.

[0025] The base unit memory 12 is configured to include volatile memory and nonvolatile memory. The volatile memory is specifically RAM (Random Access Memory). The nonvolatile memory is specifically ROM (Read Only Memory). The nonvolatile memory may also be a flash memory, a hard disk drive, or the like. The nonvolatile memory stores computer-readable programs and data. The programs include a communication program 121 used when performing UWB communication.

[0026] The program stored in the parent device memory 12 may be provided by, for example, a computer-readable nonvolatile recording medium. The nonvolatile recording medium may be, for example, an optical recording medium (e.g., an optical disk), a magneto-optical recording medium (e.g., a magneto-optical disk), a USB memory, or an SD card, in addition to the nonvolatile memory described above. As another example, the program may be provided from a program providing server via a communication line such as the Internet (provided by so-called download).

[0027] In this embodiment, the functions of the master controller 11 are realized by the processor executing arithmetic processing in accordance with the programs stored in the master memory 12. The number of programs that realize the functions of the master controller 11 may be one or more.

[0028] Furthermore, at least some of the functions of the master controller 11 may be realized by other methods than software as in the present embodiment. At least some of the functions of the master controller 11 may be realized, for example, by using an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). That is, at least some of the functions of the master controller 11 may be realized by hardware using a dedicated IC or the like. At least some of the functions of the master controller 11 may also be realized by a combination of software and hardware.

[0029] The master device wireless communication unit 13 is provided to be able to perform UWB communication with a slave device wireless communication unit 23 (see FIG. 4 described later) provided in the slave device 20. The master device wireless communication unit 13 has a transmitting function for transmitting UWB signals and a receiving function for receiving UWB signals. In the present embodiment, as an example, the master device wireless communication unit 13 includes a transmitter 131 and a receiver 132.

[0030] 3, in this embodiment, the parent controller 11 includes, as its functional units, a preamble code management unit 111, a communication processing unit 112, and an application unit 113. Note that each of the functional units 111 to 113 is a conceptual component. A function performed by one component may be distributed among multiple components. Furthermore, functions possessed by multiple components may be integrated into one component.

[0031] The preamble code management unit 111 manages the preamble codes used when the base device 10 itself performs UWB communication with the slave device 20. The preamble code management unit 111 appropriately determines the preamble code that the base device 10 itself should use during UWB communication, and also performs processing to instruct the slave device 20 on the preamble code that should be used. The preamble codes and their management will be described in detail later.

[0032] The communication processing unit 112 executes communication processing related to UWB communication performed between the base unit 10 and the slave unit 20. This communication processing allows the base unit 10 to perform data communication with the slave unit 20. In detail, the communication processing unit 112 controls the transmitter 131 to perform processing for transmitting a UWB signal from the base unit 10 to the slave unit 20. The communication processing unit 112 also controls the receiver 132 to perform processing for receiving a UWB signal sent from the slave unit 20 to the base unit 10. A detailed example of UWB communication performed between the base unit 10 and the slave unit 20 will be described later.

[0033] The application unit 113 realizes various functions to be provided to the user of the mobile body M1 on which the base unit 10 is mounted, based on information (data) received from the slave unit 20. The various functions to be provided to the user include, for example, alerting the user using a notification means, controlling in-vehicle devices such as an air conditioner, and automatically unlocking doors using a smart entry system.

[0034] [1-3. Configuration of Child Device] Fig. 4 is a block diagram showing a general configuration of child device 20. Note that Fig. 4 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components.

[0035] 4, the slave device 20 includes a slave device controller 21, a slave device memory 22, and a slave device wireless communication unit 23. Note that the configuration of the slave device 20 is similar to that of the master device 10 in many respects, and therefore, a description of the similar parts will be omitted as appropriate.

[0036] The slave controller 21 controls the overall operation of the slave 20. That is, the slave controller 21 constitutes a control unit. The slave controller 21 includes a processor, similar to the master controller 11, and has the same hardware configuration as the master controller 11.

[0037] The slave device memory 22 includes a volatile memory and a nonvolatile memory, similar to the master device memory 12. The nonvolatile memory stores programs and data, similar to the master device memory 12. The programs include a communication program 221 used when performing UWB communication.

[0038] The slave device wireless communication unit 23 is provided to be able to perform UWB communication between the master device wireless communication unit 13 (see FIG. 3 ) included in the master device 10 and the tag communication unit 33 (see FIG. 5 , which will be described later) included in the wireless tag 30. The slave device wireless communication unit 23 has a transmitting function for transmitting UWB signals and a receiving function for receiving UWB signals, and like the master device wireless communication unit 13, has a transmitter 231 and a receiver 232.

[0039] The functions of slave controller 21 are realized by a processor executing arithmetic processing in accordance with a program stored in slave memory 22. As shown in Fig. 4, in this embodiment, slave controller 21 includes, as its functional units, a preamble code management unit 211, a communication processing unit 212, a ranging processing unit 213, and a radar processing unit 214.

[0040] At least some of the functions of slave controller 21 may be realized by other methods rather than by software, as in the case of master controller 11. Furthermore, each of functional units 211 to 214 is a conceptual component, and the functions executed by these components may be distributed among multiple components, or multiple functions may be integrated, as in the case of master controller 11 described above.

[0041] The preamble code management unit 211 manages the preamble code used by the device itself (child device 20) when performing UWB communication with the base device 10 and the wireless tag 30. The preamble code management unit 211 changes the preamble code used by the device itself (child device 20) in response to instructions from the base device 10 and the wireless tag 30. In other words, the child device 20 can be said to be a communication device that receives instructions to change the preamble code from other communication devices (the base device 10 or the wireless tag 30). With this configuration, when the base device 10 or the wireless tag 30 changes the preamble code, the child device 20 can appropriately perform UWB communication by matching the preamble code used for UWB communication with the base device 10 or the wireless tag 30.

[0042] The communication processing unit 212 executes communication processing related to UWB communication performed between the device itself (child device 20) and the base device 10 or the wireless tag 30. Through this communication processing, for example, the child device 20 can perform data communication with the base device 10. In detail, the communication processing unit 212 controls the transmitter 231 to perform processing for transmitting a UWB signal from the device itself (child device 20) to the base device 10 or the wireless tag 30. The communication processing unit 212 also controls the receiver 232 to perform processing for receiving a UWB signal sent from the base device 10 or the wireless tag 30 to the device itself (child device 20).

[0043] The ranging processing unit 213 estimates the distance to the object to be measured based on the reception result of the UWB signal transmitted by the object to be measured. For example, when the ranging processing unit 213 receives a UWB signal from the object to be measured, it calculates the difference between the transmission time and the reception time of the UWB signal. The ranging processing unit 213 calculates the distance to the object to be measured from the calculated time difference and the known speed of the radio waves. In this embodiment, the object to be measured is a wireless tag 30. A specific example of the object to be measured is a smart key (electronic key) in a smart entry system. In this case, the wireless tag 30 is attached to the electronic key. Note that the ranging processing unit may be provided on the wireless tag 30 depending on the purpose of distance measurement. In this case, the slave 20 may not be provided with the ranging processing unit 213.

[0044] The radar processing unit 214 transmits pulse waves composed of pulsed UWB signals using the transmitter 231 of the slave wireless communication unit 23, and receives reflected waves of the transmitted pulse waves. The radar processing unit 214 then detects the heartbeat of the living body based on the received radar reflection. In other words, the radar processing unit 214 can detect the living body based on the received radar reflection.

[0045] As can be seen from the above description, the slave device 20 can realize a data communication function, a ranging function, and a radar function by transmitting and receiving UWB signals (i.e., UWB communication). In other words, the slave device 20 can be said to be a communication device mounted on the mobile unit M1 and capable of realizing multiple functions by transmitting and receiving UWB signals. The base device 10 can also realize a data communication function by transmitting and receiving UWB signals. However, the base device 10 may also be configured to realize a ranging function or a radar function by transmitting and receiving UWB signals. From this perspective, the base device 10 can be said to be a communication device mounted on the mobile unit M1 and capable of realizing at least some of the multiple functions that can be realized by transmitting and receiving UWB signals. Furthermore, the base device 10 can be said to be a communication device mounted on the mobile unit M1 and capable of realizing multiple functions by transmitting and receiving UWB signals. Furthermore, the base device 10 can be said to be capable of realizing multiple functions by UWB communication with multiple slave devices 20.

[0046] [1-4. Configuration of Wireless Tag] Fig. 5 is a block diagram showing a schematic configuration of the wireless tag 30. Note that Fig. 5 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components.

[0047] 5, the wireless tag 30 includes a tag controller 31, a tag memory 32, and a tag communication unit 33. Note that the configuration of the wireless tag 30 is similar to that of the base unit 10 in many respects, and therefore, a description of the similar parts will be omitted as appropriate.

[0048] The tag controller 31 controls the overall operation of the wireless tag 30. In other words, the tag controller 31 constitutes a control unit. The tag controller 31 includes a processor, similar to the master controller 11, and its hardware configuration is similar to that of the master controller 11.

[0049] The tag memory 32 includes a volatile memory and a nonvolatile memory, similar to the base unit memory 12. The nonvolatile memory stores programs and data, similar to the base unit memory 12. The programs include a communication program 321 used when performing UWB communication.

[0050] The tag communication unit 33 is provided so as to be able to perform UWB communication with the slave device wireless communication unit 23 (see FIG. 4 ) provided in the slave device 20. The tag communication unit 33 has a transmitting function for transmitting UWB signals and a receiving function for receiving UWB signals, and like the master device wireless communication unit 13, has a transmitter 331 and a receiver 332.

[0051] The functions of the tag controller 31 are realized by the processor executing arithmetic processing in accordance with the programs stored in the tag memory 32. As shown in Fig. 5, in this embodiment, the tag controller 31 includes, as its functional units, a preamble code management unit 311, a communication processing unit 312, and a ranging processing unit 313.

[0052] At least some of the functions of tag controller 31 may be realized by other methods rather than by software, as in the case of parent controller 11. Also, each of functional units 311 to 313 is a conceptual component, and the functions performed by these components may be distributed across multiple units or multiple functions may be integrated, as in the case of parent controller 11 described above.

[0053] The preamble code management unit 311 manages the preamble code used when the device itself (wireless tag 30) performs UWB communication with the slave device 20. The preamble code management unit 311 appropriately determines the preamble code that the device itself (wireless tag 30) should use when performing UWB communication, and also performs processing to instruct the slave device 20 on the preamble code to be used.

[0054] The communication processing unit 312 executes communication processing related to UWB communication performed between the wireless tag 30 itself and the slave 20. This communication processing allows, for example, the wireless tag 30 to perform data communication with the slave 20. In detail, the communication processing unit 312 controls the transmitter 331 to perform processing for transmitting a UWB signal from the wireless tag 30 itself to the slave 20. The communication processing unit 312 also controls the receiver 332 to perform processing for receiving a UWB signal sent from the slave 20 to the wireless tag 30 itself.

[0055] Similar to the ranging processor 213 provided in the slave unit 20, the ranging processor 313 estimates the distance to the object to be measured based on the reception result of the UWB signal transmitted by the object to be measured. Here, unlike the case of the ranging processor 213 of the slave unit 20 described above, the object to be measured is the slave unit 20. The ranging processor 313 estimates the distances between three or more slave units 20 and the wireless tag 30. This makes it possible to detect the position of the wireless tag 30. A specific example is a case where a cleaning robot that cleans the inside of the moving body M1 uses the wireless tag 30 mounted thereon to determine its own position. Note that the ranging processor may be provided on the slave unit 20 side depending on the purpose of measuring the distance. In this case, the ranging processor 313 may not be provided on the wireless tag 30.

[0056] The wireless tag 30 can achieve both a data communication function and a distance measurement function by transmitting and receiving UWB signals. However, the wireless tag 30 may also be configured to achieve, for example, only a distance measurement function by transmitting and receiving UWB signals. From this perspective, the wireless tag 30 can be said to be a communication device that is mounted on the mobile unit M1 and can achieve at least some of the multiple functions that can be achieved by transmitting and receiving UWB signals. The wireless tag 30 can also be said to be a communication device that is mounted on the mobile unit M1 and can achieve multiple functions by transmitting and receiving UWB signals.

[0057] 2. UWB Communication Next, UWB communication used in the communication system SYS will be described.

[0058] [2-1. Overview] UWB communication is wireless communication using a UWB communication system, and is performed in accordance with a standard such as IEEE 802.15.4 (hereinafter sometimes simply referred to as a communication standard).

[0059] Fig. 6 is a diagram showing a frame format F1 used in UWB communication. The frame format F1 shown in Fig. 6 corresponds to the structure of one unit of transmission data in UWB communication. The frame format F1 used in UWB communication is determined by the above-mentioned communication standard.

[0060] As shown in Fig. 6, the frame format F1 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.

[0061] A preamble is a sequence of bits or pulses (e.g., -, 0, +) 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 synchronize the receiving clock.

[0062] The SFD is a bit string with a specific pattern that signals the start of data in a communication frame. The PHR includes information necessary for decoding the packet. For example, the PHR includes the address of the communication partner and information on the data length of the subsequent data. The data body is the main body of information to be transmitted to the communication partner and includes the actual data to be transmitted. For example, the data body includes information such as ID information of the recipient and sender of the communication frame, instruction information from the master device 10 to the slave device 20, sensor values ​​detected by sensors equipped in the slave device 20, and the operating status of actuators to be controlled by the slave device 20.

[0063] [2-2. Preamble Code] There are multiple patterns for the preamble included in the frame format F1 of UWB communication. The preamble code is a parameter that identifies these multiple patterns.

[0064] There are 24 types of preamble codes, codes "1" to "24." Codes "1" to "8" are preamble codes with a PRF (Pulse Repletion Frequency) of 16 MHz. Codes "9" to "24" are preamble codes with a PRF of 64 MHz. The preamble codes can be divided into two groups based on the PRF. Codes "1" to "8" are a group of low codes with low PRF. Codes "9" to "24" are a group of high codes with high PRF. In other words, the preamble codes include a group of high codes and a group of low codes with different PRF levels.

[0065] Figure 7 shows the trends in the communication success rate for each combination of preamble codes when two UWB communications are performed simultaneously. The trends shown in Figure 7 are derived from experimental results. As shown in Figure 7, there are four patterns in the trends in the communication success rate.

[0066] Pattern (1) is a case where the preamble codes (code values) in the two UWB communications are the same, and in this case, there is a high possibility that both of the two UWB communications will fail.

[0067] In addition, pattern (2) is a case where the preamble codes in each UWB communication are different low-code values. In this case, there is a high possibility that both of the two UWB communications will be successful.

[0068] In addition, pattern (3) is a case where one preamble code in each UWB communication is a high code and the other is a low code. In this case, there is a high possibility that communication using the high code preamble will be successful.

[0069] Pattern (4) is a case where the preamble codes in each UWB communication are different high-value codes. In this case, there is a high possibility that both of the two UWB communications will be successful.

[0070] By utilizing the characteristics of the preamble codes shown in Fig. 7 in terms of their superiority and inferiority in terms of communication interference, it is conceivable to assign preamble codes to multiple types of functions that can be realized by transmitting and receiving UWB signals, as shown in Fig. 8. Fig. 8 is a diagram showing a preamble code assignment pattern for multiple types of functions that can be realized by transmitting and receiving UWB signals. In Fig. 8, the multiple types of functions that can be realized by transmitting and receiving UWB signals are assumed to be a data communication function, a ranging function, and a radar function. These functions are available in the communication system SYS of this embodiment.

[0071] In "Pattern 1" shown in Figure 8, a preamble code belonging to a high code is assigned to the data communication function, and a preamble code belonging to a low code is assigned to the ranging function and the radar function. In this case, even if data communication is performed at a timing that overlaps with communication for realizing the ranging function and the radar function, there is a high possibility that communication will be successful. In other words, "Pattern 1" is suitable when it is desired to prioritize the data communication function over other functions.

[0072] In "Pattern 2" shown in Figure 8, a preamble code belonging to the high code range is assigned to the ranging function, and a preamble code belonging to the low code range is assigned to the data communication function and the radar function. In this case, even if communication for realizing the ranging function overlaps with communication for realizing the data communication function and the radar function, there is a high possibility that communication will be successful. In other words, "Pattern 2" is suitable when it is desired to prioritize the ranging function over other functions.

[0073] In "Pattern 3" shown in Figure 8, a preamble code belonging to a high code is assigned to the radar function, and a preamble code belonging to a low code is assigned to the data communication function and the radar function. In this case, there is a high possibility that communication for realizing the radar function will be successful even if it is performed at a timing that overlaps with communications for realizing the data communication function and the radar function. In other words, "Pattern 2" is suitable when it is desired to prioritize the radar function over other functions.

[0074] In the IEEE 802.15.4z communication standard, the preamble code types are expanded to include the above-mentioned codes "1" to "24" and codes "25" to "32." In other words, in accordance with the IEEE 802.15.4z communication standard, there are 32 preamble code types, codes "1" to "32."

[0075] Codes "25" to "32" are preamble codes with a PRF of 111 MHz that are intended to be used primarily for ranging. Note that preamble codes "25" to "32" can also be used for data communication and radar functions. Here, to clarify that this group of preamble codes is separate from the low and high codes described above, preamble codes "25" to "32" are referred to as ranging codes or preamble codes for ranging.

[0076] Previous research has revealed that when two UWB communications are conducted simultaneously, ranging codes have the following characteristics (A) to (D): (A) If the preamble codes of the two UWB communications are the same ranging code (same code value), there is a high probability that both of the two UWB communications will fail. (B) If the preamble codes of the two UWB communications are different ranging code values, there is a high probability that both of the two UWB communications will be successful. (C) If one of the preamble codes of the two UWB communications is a ranging code and the other is a low code, there is a high probability that the communication using the ranging code will be successful. (D) If one of the preamble codes of the two UWB communications is a ranging code and the other is a high code, there is a high probability that both of the two UWB communications will be successful.

[0077] In view of the above findings, when complying with the communication standard IEEE 802.15.4z, it is conceivable to assign preamble codes to the data communication function, ranging function, and radar function in the pattern shown in Fig. 9. Note that Fig. 9 is a diagram showing a preamble code assignment pattern different from the example shown in Fig. 8.

[0078] In "Pattern 1" shown in Figure 9, a preamble code belonging to a high code is assigned to the data communication function, a preamble code belonging to a ranging code is assigned to the ranging function, and a preamble code belonging to a low code is assigned to the radar function. In this case, data communication is likely to be successful even if it is performed at a timing that overlaps with communications for implementing the ranging function and the radar function. Furthermore, communication for implementing the ranging function is likely to be successful even if it is performed at a timing that overlaps with communications for implementing the data communication function and the radar function. Furthermore, communication for implementing the radar function is likely to fail if it is performed at a timing that overlaps with communications for implementing the data communication function and the ranging function. In other words, "Pattern 1" is suitable when the priority of the data communication function is higher than that of the radar function. Note that the priority of the ranging function may be high or low.

[0079] In "Pattern 2" shown in Figure 9, a preamble code belonging to a low code is assigned to the data communication function, a preamble code belonging to a ranging code is assigned to the ranging function, and a preamble code belonging to a high code is assigned to the radar function. In this case, if data communication is performed at a timing that overlaps with communication for realizing the ranging function and the radar function, the communication is likely to fail. Furthermore, communication for realizing the ranging function is likely to be successful even if it is performed at a timing that overlaps with communication for realizing the data communication function and the radar function. Furthermore, communication for realizing the radar function is likely to be successful even if it is performed at a timing that overlaps with communication for realizing the data communication function and the ranging function. In other words, "Pattern 2" is suitable when the radar function has a higher priority than the data communication function. Note that the priority of the ranging function may be high or low.

[0080] As can be seen from the above, when a ranging code is used for the ranging function, there is a high possibility that the ranging function will be obtained even if UWB communication for obtaining other functions is executed at the same time. For this reason, when a ranging code is used for the ranging function, the priority of the ranging function does not need to be particularly considered, and the preamble codes to be assigned to the data communication function and the radar function can be determined based on which of the data communication function and the radar function has a higher priority.

[0081] 3. Communication Schedule Next, a communication schedule executed in the communication system SYS of this embodiment will be described. As described above, in the communication system SYS, functions realized by transmitting and receiving UWB signals include a data communication function, a ranging function, and a radar function. Each of these functions has a communication schedule.

[0082] 3-1. Data Communication Function] Fig. 10 is a diagram illustrating a communication schedule for the data communication function. In Fig. 10, as an example, the number of slave devices 20 performing UWB communication with the base device 10 is three. For the sake of convenience, the three slave devices 20 are designated as a first slave device 20a, a second slave device 20b, and a third slave device 20c in order to distinguish between them.

[0083] 10 , the base unit 10 performs UWB communication with multiple slave units 20 using a polling method. Specifically, the base unit 10 transmits data to the multiple slave units 20 in turn at a fixed period T (polling period; for example, 5 ms). The slave units 20 that receive the data transmitted from the base unit 10 transmit a response to the base unit 10.

[0084] Each polling period T includes a normal communication time slot t1 and a re-communication time slot t2. The normal communication time slot t1 is a time slot for communication in accordance with the polling period T. The re-communication time slot t2 is a time slot for re-communication if communication fails in the normal communication time slot t1. Note that it is preferable to provide the re-communication time slot t2, but it is not essential.

[0085] In the example shown in FIG. 10 , the base unit 10 transmits data to the first handset 20a, the second handset 20b, and the third handset 20c in that order. Although not shown in FIG. 10 , once the third handset 20c's turn is finished, the data communication returns to the first handset 20a and is repeated in the order described above. In FIG. 10 , in the communication order with the first handset 20a and the second handset 20b, communication is successful in the normal communication time slot t1, and the re-communication time slot t2 is not used. However, in the communication order with the third handset 20c, the base unit 10 does not receive a reply (response transmission) from the third handset 20c, so it transmits data to the third handset 20c using the re-communication time slot t2. The third handset 20c replies to the re-transmission, indicating successful communication.

[0086] The master unit 10 transmits, for example, an actuator operation request and a sensor information acquisition request to each of the slave units 20 a to 20 c. In response, the slave unit 20 issues an operation request to the actuator connected by a wire, acquires sensor information from the sensor connected by a wire, and sends the information back to the master unit 10.

[0087] Specific examples of requests from the base unit 10 to the slave unit 20 include a request to acquire a sensor value of a light receiving sensor, a request to operate a power window motor, a request to acquire power window operation information, a request to turn on headlamps, etc. Specific examples of return information from the slave unit 20 to the base unit 10 include light receiving sensor information, power window motor operation information, power window operation information, headlamp operation information, etc.

[0088] 11 is a diagram illustrating a communication schedule for the ranging function. In FIG. 11, as an example, three slave devices 20 are used for UWB communication with the wireless tag 30. For convenience, the three slave devices 20 are designated as a first slave device 20a, a second slave device 20b, and a third slave device 20c in order to distinguish between them.

[0089] As shown in Fig. 11, UWB communication for realizing the ranging function is performed when ranging is required. In other words, communication for realizing the ranging function is not performed constantly at a fixed cycle like data communication. In the example shown in Fig. 11, UWB communication for realizing the ranging function is performed when it is desired to detect the position of the wireless tag 30.

[0090] For example, if the moving object M1 is a bus, a train, or the like, the cleaning robot performs cleaning when the moving object M1 stops for a long period of time (such as when the moving object M1 arrives at its destination). The cleaning robot needs to detect its own position as appropriate while in operation. For this purpose, the wireless tag 30 attached to the cleaning robot sends a ranging request to the slave unit 20 as appropriate to detect its position. Since the distances of three points are required to detect the position, the wireless tag 30 sends ranging requests to at least three slave units 20 in sequence. When a slave unit 20 receives a ranging request from the wireless tag 30, it transmits a ranging response to the wireless tag 30 so that the distance can be calculated.

[0091] In the example shown in FIG. 11 , when the need for position detection arises, the wireless tag 30 first performs UWB communication for distance measurement with the first slave device 20a, and the distance measurement communication is successful. The wireless tag 30 then performs UWB communication for distance measurement with the second slave device 20b, and the distance measurement communication is successful. The wireless tag 30 then performs UWB communication for distance measurement with the third slave device 20c, but fails in the distance measurement communication, so performs UWB communication for distance measurement again, and the communication is successful. This allows the wireless tag 30 to detect the distances to the three points. The wireless tag 30 or the controller (not shown) of the cleaning robot detects the position of the cleaning robot from the detected distances to the three points.

[0092] Although three distance points are sufficient for position detection, the more points from which distances are detected, the more accurate the position can be detected, so the wireless tag 30 may perform UWB communication for distance measurement with more than three sub-units 20.

[0093] Furthermore, location detection using the wireless tag 30 is not limited to the location detection of the cleaning robot described above, but may also be, for example, the location detection of a smart key in an automobile. In this configuration, for example, while the automobile is parked, the wireless tag 30 attached to the smart key requests the slave unit 20 to unlock the door. Upon receiving the unlock request, the slave unit 20 transmits a distance measurement signal to the wireless tag 30 and determines the distance to the smart key by receiving a distance measurement response from the wireless tag 30. When the wireless tag 30 (i.e., the smart key) is within a certain range, the door is unlocked. Note that the door unlocking process is executed by the master unit 10, which receives the distance measurement result from the slave unit 20 via data communication, for example.

[0094] [3-3. Radar Function] Fig. 12A is a diagram illustrating a communication schedule for the radar function. Note that the base unit 10 in Fig. 12A may be a wireless tag 30. In Fig. 12A, as an example, the number of slave units 20 performing UWB communication with the base unit 10 (wireless tag 30) is three. For the sake of convenience, the three slave units 20 are designated as a first slave unit 20a, a second slave unit 20b, and a third slave unit 20c in order to distinguish between them.

[0095] The radar function is initiated when the parent device 10 or the wireless tag 30 issues an instruction to the child device 20 using UWB communication. The UWB communication for realizing the radar function is performed when radar information is needed. In other words, the communication for realizing the radar function is not performed constantly at a fixed cycle like data communication. In the example shown in Fig. 12A, the UWB communication for realizing the radar function is performed when it is desired to perform a biological detection process.

[0096] For example, if the moving object M1 is a bus, a train, or the like, it is possible to detect whether a passenger has been abandoned by performing a living body detection process when the moving object M1 arrives at its destination. For this abandonment detection, a living body detection process using a radar function is performed. That is, UWB communication for realizing the radar function is performed, for example, when the moving object M1 arrives at its destination. Note that the detection of whether a person has been abandoned may also be performed in other moving objects, such as automobiles. For example, in the case of an automobile, the detection may be performed when the doors of the automobile are locked and the automobile has been parked for a certain period of time or more.

[0097] In the example shown in FIG. 12A , the base unit 10 (or the wireless tag 30) broadcasts a radar command to multiple slave units 20a-20c using a UWB signal at a timing when a living body detection process is required. As a result, each slave unit 20a-20c transmits radar waves, which are pulsed UWB signals, and receives reflected waves of the transmitted radar waves. Each slave unit 20a-20c performs a living body detection process based on the results of the radar wave transmission and reception, and returns (transmits a response) the results to the base unit 10 (or the wireless tag 30). The replies from each slave unit 20a-20c are staggered so that they can be received by the receiver 132 of the base unit 10 (the receiver 332 of the wireless tag 30). The response timing information may be included in the radar command. For example, when a request to detect a living body is returned to the base unit 10, the base unit 10 performs a process to notify the slave units 20a-20c that a passenger has been abandoned. Also, for example, if the wireless tag 30 is replied with a request to detect a living organism, the cleaning robot equipped with the wireless tag 30 performs processing to notify the user that it has detected that a passenger has been left behind.

[0098] When performing a biological detection process using the radar function, it is preferable that the slave units 20 are placed near each of the multiple seats of the moving object M1. For this reason, when the moving object M1 is a bus or a train, the number of slave units 20 is usually more than three. In the example shown in Fig. 12A, multiple slave units 20 are used for the radar function, but in some cases, only one slave unit 20 may be used for the radar function.

[0099] In the example shown in Fig. 12A, the radar instructions are broadcast, but this is merely an example. As shown in Fig. 12B, the radar instructions may be sent in order from the master unit 10 (which may be a wireless tag 30 as in Fig. 12A) to each of the slave units 20a to 20c.

[0100] <4. Operation when communication interference occurs] When the data communication function, ranging function, and radar function are executed according to the communication schedule described above, communication interference may occur when the communication timing of each function overlaps. The operation when communication interference occurs will be described below.

[0101] Here, it is assumed that the wireless tag 30 is attached to a cleaning robot that cleans the mobile object M1, and that it performs radar instructions in addition to distance measurement. Furthermore, the preamble code of the UWB signal (UWB communication) is assigned such that the data communication function has a high code and the distance measurement function and radar function have a low code. As a detailed example, the code value of the preamble code for the high code is "9," and the code value of the preamble code for the low code is "3." In other words, it is assumed here, as an example, that the data communication function has a higher priority than other functions.

[0102] 13 is a diagram for explaining the operation when radio wave interference occurs between data communication and ranging communication. In the example shown in FIG. 13, the communication system SYS includes three slave devices 20: a first slave device 20a, a second slave device 20b, and a third slave device 20c, but the number may be changed as appropriate.

[0103] 13, the base unit 10 uses a high code (code value "9") as the preamble code. The wireless tag 30 uses a low code (code value "3") as the preamble code. Each of the slave units 20a to 20c uses a high code (code value "9") preamble code only during period T, which is its own polling order, in data communication with the base unit 10 using the polling method, and uses a low code (code value "3") preamble code during other periods. By switching the preamble code in each of the slave units 20a to 20c in this way, each of the slave units 20a to 20c can perform UWB communication with both the base unit 10 and the wireless tag 30.

[0104] 13, data communication is taking place between the parent unit 10 and the first child unit 20a. During this period (a), the wireless tag 30 mounted on the cleaning robot issues a distance measurement request to the first child unit 20a to detect the position of the cleaning robot. However, because the first child unit 20a uses a high code for data communication with the parent unit 10, the distance measurement request using the low code of the wireless tag 30 is not accepted because the preamble code used is different.

[0105] Also, during period (a), the wireless tag 30 also sends a ranging request to the second handset 20b and the third handset 20c. However, because the base unit 10 and the first handset 20a are communicating using a high code, the radio waves of the ranging request using a low code, which is inferior in terms of preamble code superiority (see FIG. 7), are lost. In other words, the ranging request from the wireless tag 30 to the second handset 20b and the third handset 20c is not established. Note that, because the data communication between the base unit 10 and the first handset 20a has a superior preamble code superiority, the communication is successful without being affected by the ranging request communication sent by the wireless tag 30.

[0106] During period (a), communication between the base unit 10 and the first handset 20a was successful, so no data communication took place during period (b), which corresponds to the re-communication time slot t2. However, during period (b), a distance measurement request using a low code from the wireless tag 30 to the first handset 20a is not accepted because the preamble code of the first handset 20a is set to a high code. On the other hand, distance measurement requests using a low code from the wireless tag 30 to the second handset 20b and the third handset 20c do not cause radio wave interference because no data communication is taking place. Therefore, the distance measurement requests made by the wireless tag 30 to the second handset 20b and the third handset 20c during period (b) are accepted, and the wireless tag 30 receives replies to the distance measurement requests from the second handset 20b and the third handset 20c.

[0107] During periods (c) and (d), the wireless tag 30 sends a ranging request to the first handset 20a, with which it previously failed in ranging communication. However, in both cases, because the base unit 10 and the second handset 20b are communicating using a high code, the radio waves of the ranging request, which uses a low code that is inferior in terms of preamble code superiority, are lost. In other words, during periods (c) and (d), the wireless tag 30 also fails in ranging communication with the first handset 20a. Note that during period (c), data communication between the base unit 10 and the second handset 20b fails for some reason. However, it should be noted that the failure of this communication is not due to a loss in the superiority of the preamble code.

[0108] During period (e), the wireless tag 30 again sends a distance measurement request to the first handset 20a. However, in this case, the base unit 10 and the third handset 20c are communicating using a high code, so the radio waves of the distance measurement request using a low code, which is inferior in terms of the superiority of the preamble code, are lost. In other words, during period (e), the wireless tag 30 fails to perform distance measurement communication with the first handset 20a.

[0109] During period (f), the wireless tag 30 again sends a distance measurement request to the first slave unit 20a. This distance measurement request does not cause radio wave interference because no data communication is taking place. Therefore, the distance measurement request sent by the wireless tag 30 to the first slave unit 20a during period (f) is accepted, and the wireless tag 30 receives a reply to the distance measurement request from the first slave unit 20a. This allows the distances from three points to the wireless tag 30 to be obtained, enabling the cleaning robot's position to be detected by three-point positioning.

[0110] 14 is a diagram for explaining the operation when radio wave interference occurs between data communication and radar communication. In the example shown in FIG. 14, the communication system SYS includes three slave devices 20: a first slave device 20a, a second slave device 20b, and a third slave device 20c, but the number may be changed as appropriate.

[0111] 14, the base unit 10 uses a high code (code value "9") as the preamble code. The wireless tag 30 uses a low code (code value "3") as the preamble code. Each of the slave units 20a to 20c uses a high code (code value "9") preamble code only during period T, which is its own polling order, in data communication with the base unit 10 using the polling method, and uses a low code (code value "3") preamble code during other periods.

[0112] During the period (a) shown in Figure 14, data communication is taking place between the parent unit 10 and the first child unit 20a. During this period (a), the wireless tag 30 mounted on the cleaning robot broadcasts radar instructions to each of the child units 20a to 20c to perform a living organism detection process. However, because the parent unit 10 and the first child unit 20a are communicating using a high code, the radio waves of the laser instruction using a low code, which is inferior in terms of the superiority of the preamble code, are lost. In other words, the laser instruction broadcast from the wireless tag 30 to each of the child units 20a to 20c is not successful.

[0113] The radar instruction from the wireless tag 30 to the first slave unit 20a is not accepted because it is transmitted using a preamble code different from the preamble code set in the first slave unit 20a. Furthermore, the data communication between the master unit 10 and the first slave unit 20a is successful without being affected by the communication for the radar instruction from the wireless tag 30 because the superiority of the preamble code is superior.

[0114] During period (b), data communication is taking place between the base unit 10 and the second slave unit 20b. During this period (b), the wireless tag 30 broadcasts a radar command to each of the slave units 20a-20c in order to perform the biological detection process again, since the previous radar command failed. However, because the base unit 10 and the second slave unit 20b are communicating using a high code, the radio waves of the laser command, which uses a low code that is inferior in terms of preamble code superiority, are lost. In other words, the laser command broadcast from the wireless tag 30 to each of the slave units 20a-20c is not successful again. Note that the radar command from the wireless tag 30 to the second slave unit 20b is not accepted because it is transmitted using a preamble code different from the preamble code set in the second slave unit 20b.

[0115] Because communication between the base unit 10 and the second slave unit 20b was successful during period (b), no data communication was performed during period (c) corresponding to the re-communication time slot t2. Therefore, the radar instruction broadcast by the wireless tag 30 for the biological detection process during period (c) did not cause radio wave interference. Therefore, the radar instruction issued by the wireless tag 30 to the first slave unit 20a and the third slave unit 20c during period (c) was accepted, and the wireless tag 30 received replies to the radar instruction (results of the biological detection process using radar) from the first slave unit 20a and the third slave unit 20c. However, the radar instruction from the wireless tag 30 to the second slave unit 20b was not accepted due to the difference in the preamble code used. As a result, the radar instruction from the wireless tag 30 to the second slave unit 20b failed.

[0116] During period (d), the wireless tag 30 sends a radar command to the first slave unit 20a, which previously failed to issue a radar command. However, because the master unit 10 and the third slave unit 20c are communicating using a high code, the radio wave of the radar command using the low code, which is inferior in terms of the superiority of the preamble code, is defeated. In other words, during period (d), the wireless tag 30 also fails to send a radar command to the first slave unit 20a.

[0117] During period (e), the wireless tag 30 again sends a radar instruction to the first slave unit 20a. In this case, the radar instruction does not cause radio wave interference because no data communication is taking place. Therefore, the radar instruction sent by the wireless tag 30 to the first slave unit 20a during period (e) is accepted, and the wireless tag 30 receives a response to the radar instruction (the result of the living body detection process using radar) from the first slave unit 20a. As a result, the wireless tag 30 acquires the results of the living body detection process from all of the slave units 20a to 20c. When the controller of the cleaning robot acquires the results of the living body detection process from the wireless tag 30 and detects that a person has been left behind based on the results of the living body detection process, the controller outputs an alarm using the notification means (speaker, etc.) provided in the cleaning robot.

[0118] In this embodiment, the wireless tag 30 issues distance measurement instructions and radar instructions to each of the slave units 20 a to 20 c. This prevents distance measurement instructions and radar instructions from being issued simultaneously, and communication interference between the two is not anticipated.

[0119] [4-3. First Modification] As described above, the radar instruction may be performed by the base unit 10 instead of the wireless tag 30. Fig. 15 is a diagram for explaining the relationship between data communication and radar communication when the base unit 10 performs the radar instruction. When the base unit 10 performs the data communication, simultaneous data communication and radar communication are avoided, and communication interference between the two is not anticipated.

[0120] In a configuration in which the master device 10 issues radar instructions, when it becomes necessary to perform biological detection processing, an interrupt process such as that shown in Fig. 15 may be performed. Specifically, one system period P for radar communication may be inserted between two system periods P for data communication that were scheduled to be performed consecutively. One system period P corresponds to the period required to communicate with all slave devices 20 included in the communication system SYS in polling order. In the example shown in Fig. 15, the period for communicating with each of the slave devices 20a to 20c in polling order is "T", and since there are three slave devices 20, one system period is "3T".

[0121] 15 , in one system cycle P for radar communication, the base unit 10 first transmits a radar instruction to the first slave unit 20a in the normal communication time slot t1. The first slave unit 20a receives the transmission and transmits radar waves, receives the reflected waves of the radar waves, and performs a living body detection process. The first slave unit 20a returns the result of the living body detection process to the base unit 10 in the re-communication time slot t2. Similar processing is performed in turn for the second slave unit 20b and the third slave unit 20c, completing one system cycle P for radar communication. Once one system cycle for radar communication is completed, data communication resumes.

[0122] In this configuration, a preamble code belonging to the high code group (in the example shown in FIG. 15, the code value "9") can be used for radar communication, just as in data communication. Also, during radar communication, each of the slave units 20a to 20c sets the preamble code to a low code (in a specific example, the code value "3") if it is not its own polling order, just as in data communication. This allows each of the slave units 20a to 20c to perform UWB communication with both the base unit 10 and the wireless tag 30. Note that a low code may always be assigned to radar communication, for example, when communication with the wireless tag 30 is not occurring.

[0123] [4-4. Second Modification] As described above, when complying with the IEEE 802.15.4z communication standard, a ranging code is used during ranging communication to detect the position of the wireless tag 30. In light of this, the preamble code assignment for UWB communication can be such that the data communication function has a high code (a detailed example is code value "9"), the ranging function has a ranging code (a detailed example is code value "25"), and the radar function has a low code (a detailed example is code value "3"). Figure 16 is a diagram illustrating the operation when radio wave interference occurs between data communication and ranging communication, assuming such preamble code settings.

[0124] In the example shown in Fig. 16, the base unit 10 uses a high code (code value "9") as the preamble code. The wireless tag 30 uses a ranging code (code value "25") as the preamble code during ranging communication and a low code (code value "3") during radar communication. In addition, each of the slave units 20a to 20c generally uses a high code (code value "9") preamble code only during period T, which is its own polling order, in data communication with the base unit 10 using the polling method, and uses a ranging code (code value "25") during other periods. However, when radar communication becomes necessary, the slave unit 20 receives an instruction from the wireless tag 30 to change the preamble code using ranging communication and uses the low code instead of the ranging code.

[0125] 16, data communication is taking place between the parent unit 10 and the first child unit 20a. During this period (a), the wireless tag 30 mounted on the cleaning robot issues a distance measurement request to the first child unit 20a to detect the position of the cleaning robot. However, because the first child unit 20a uses a high-speed code for data communication with the parent unit 10, the distance measurement request using the distance measurement code of the wireless tag 30 is not accepted because the preamble code used is different.

[0126] Furthermore, during period (a), the wireless tag 30 also sends a ranging request to the second handset 20b and the third handset 20c. While the base unit 10 and the first handset 20a are communicating using the high-frequency code, the ranging request is accepted by the second handset 20b and the third handset 20c because there is no difference in the quality of the preamble code between the high-frequency code and the ranging code. As a result, the wireless tag 30 receives replies to the ranging request from the second handset 20b and the third handset 20c. Note that the data communication between the base unit 10 and the first handset 20a is successful without being affected by the ranging request communication sent by the wireless tag 30 because there is no difference in the quality of the preamble code between the high-frequency code and the ranging code.

[0127] During period (b), the wireless tag 30 requests distance measurement from the first slave unit 20a, with which the distance measurement communication failed earlier. However, the distance measurement communication fails for the same reason as in period (a).

[0128] During period (c), the wireless tag 30 again sends a distance measurement request to the first slave unit 20a. In this case, the master unit 10 and the second slave unit 20b are communicating using the high-frequency code, but since there is no difference in the superiority of the preamble code between the high-frequency code and the distance measurement code, the distance measurement request is accepted by the first slave unit 20a. As a result, the wireless tag 30 receives a reply to the distance measurement request from the first slave unit 20a. Since the distances from three points on the wireless tag 30 can be obtained, the position of the cleaning robot can be detected by three-point positioning.

[0129] In this modification, the operation when radio wave interference occurs between data communication and radar communication is the same as in the above-described embodiment (see FIG. 14), and therefore a description thereof will be omitted.

[0130] 5. Relationship between the State of the Mobile Body and the Preamble Code For example, in the above-described Figures 13 and 14, data communication is not affected by other communications and has a high probability of success. On the other hand, ranging communication and radar communication are likely to fail due to interference with data communication, making it difficult to quickly obtain the desired function. This is not a problem when data communication is highly important, such as when UWB communication is primarily used for data communication. However, in reality, depending on the state of the mobile body M1, ranging communication and radar communication may be more important than data communication.

[0131] In view of this, in this embodiment, the preamble codes of at least some of the UWB signal (UWB communication) preamble codes assigned to each of the multiple types of functions are configured to be changed according to the state of the mobile unit M 1. With this configuration, even if the functions with high importance among the multiple types of functions change according to the state of the mobile unit M 1, it is possible to determine the preamble codes to be assigned to each function so as to improve the success rate of communication and responsiveness of the functions with high importance.

[0132] 17 is a diagram illustrating the relationship between the state of a moving object M1 and preamble codes assigned to each function. Each function is one of multiple types of functions that can be realized by transmitting and receiving UWB signals. In this embodiment, the multiple types of functions include a data communication function, a ranging function, and a radar function.

[0133] In FIG. 17 , "moving" shown as the state of the mobile unit M1 means that the mobile unit M1 is moving if the mobile unit M1 is a vehicle such as an automobile, bus, or railroad vehicle. Furthermore, "stopped" shown as the state of the mobile unit M1 means that the mobile unit M1 is stopped if the mobile unit M1 is a vehicle such as an automobile, bus, or railroad vehicle. Furthermore, "end of use" shown as the state of the mobile unit M1 means that the use of the mobile unit M1 has ended. Specific examples of "end of use" include, if the mobile unit M1 is an automobile, a state in which the mobile unit M1 has arrived at its destination and been parked, or a state in which the mobile unit M1 is parked in a garage. Specific examples of "end of use" include, if the mobile unit M1 is a bus or railroad vehicle, a state in which the last bus or train has arrived at its terminal, a state in which the next vehicle to be used for out-of-service has arrived at its destination, or a state in which the mobile unit M1 is parked in a garage.

[0134] In the example shown in Figure 17, when the mobile unit M1 is moving, a high code is assigned to the data communication function and a low code is assigned to the ranging function. Also, when the mobile unit M1 is stopped, a low code is assigned to the data communication function and a high code is assigned to the ranging function. However, when the use of the mobile unit M1 is finished, a low code may be assigned to the data communication function and a high code may be assigned to the ranging function. In other words, when the mobile unit M1 is stopped or when the use is finished, a low code may be assigned to the data communication function and a high code may be assigned to the ranging function. With this configuration, the priority of communication for realizing each function can be changed according to the importance of each function, which changes depending on the state of the mobile unit M1.

[0135] For example, in buses and railroad vehicles, data communication between the powertrain and body systems is important while the vehicle is traveling. The powertrain system includes drive systems such as the accelerator and brake. The body system includes devices operated by the driver, such as headlights and wipers. On the other hand, cleaning robots usually do not move while the vehicle is traveling, so the location information of the cleaning robot is not important. For this reason, it is preferable to set the data communication function to a high code and the ranging function to a low code while the bus or railroad vehicle is traveling.

[0136] Similarly to buses and trains, data communication between the powertrain and body systems is important for automobiles while the vehicle is in motion. However, the vehicle key (smart key) is inside the vehicle while it is in motion, and its location information is not important. For this reason, it is preferable to use high-code data communication functions and low-code distance measurement functions while the vehicle is in motion.

[0137] Furthermore, for example, in the case of buses and railroad vehicles, data communication for the powertrain and body systems is not necessarily important when the vehicle is stopped or at the end of use. However, when the vehicle is stopped (especially when the stop is long) or at the end of use, the cleaning robot's location must be known in order to perform cleaning, and distance measurement communication becomes important. For this reason, it is preferable to set the data communication function to low code and the distance measurement function to high code when the bus or railroad vehicle is stopped or at the end of use. Note that the cleaning robot can determine the timing for cleaning (such as a long stop or the end of service) from, for example, a timetable stored in memory, and distance measurement communication using the wireless tag 30 is initiated based on the determined timing.

[0138] For example, in the case of an automobile, data communication for the powertrain system and body system is not necessarily important when the automobile is stopped or when use is finished. On the other hand, when the automobile is stopped or when use is finished, there is a possibility that the vehicle key (smart key) to which the wireless tag 30 is attached may be taken out of the automobile, making it necessary to know the location information, and distance measurement communication becomes important. For this reason, it is preferable to set the data communication function to low code and the distance measurement function to high code when the automobile is stopped or when use is finished.

[0139] 17, when the mobile unit M1 is moving, a high code is assigned to the data communication function and a low code is assigned to the radar function. Furthermore, when the use of the mobile unit M1 is terminated, a low code is assigned to the data communication function and a high code is assigned to the radar function. However, when the mobile unit M1 is stopped, a low code may be assigned to the data communication function and a high code may be assigned to the radar function. That is, when the mobile unit M1 is stopped or when the use of the mobile unit M1 is terminated, a low code may be assigned to the data communication function and a high code may be assigned to the radar function. With such a configuration, the priority of communication for realizing each function can be changed according to the importance of the function, which changes depending on the state of the mobile unit M1.

[0140] As mentioned above, data communication is important for buses and railroad vehicles while they are moving. However, the presence or absence of passengers in seats in the vehicle does not change significantly while the vehicle is moving, so the live person detection process is not necessarily important. For this reason, it is preferable to set the data communication function to a high code and the radar function to a low code while the bus or railroad vehicle is moving.

[0141] As mentioned above, data communication is important for automobiles while they are traveling. However, like buses and trains, the presence or absence of passengers in seats in automobiles does not change significantly while the automobile is traveling, so the liveness detection process is not necessarily important. For this reason, it is preferable to set the data communication function to a high code and the ranging function to a low code while the automobile is traveling.

[0142] As mentioned above, data communication is not necessarily important for buses and railcars when the bus is stopped or when the vehicle has finished being used. However, passengers get on and off when the bus is stopped or when the vehicle has finished being used, and passenger boarding and alighting information is necessary to detect, for example, unauthorized boarding or abandonment. In other words, the radar function used to perform living body detection processing becomes important when the bus or railcar is stopped or when the vehicle has finished being used. For this reason, it is preferable to set the data communication function to low code and the radar function to high code when the bus or railcar is stopped or when the vehicle has finished being used.

[0143] As mentioned above, data communication is not necessarily important when the vehicle is stopped or when the vehicle has finished operating. However, when the vehicle is stopped or when the vehicle has finished operating, the radar function used to perform the living body detection process becomes important because people may move from their seats. For this reason, it is preferable to set the data communication function to low code and the radar function to high code when the vehicle is stopped or when the vehicle has finished operating.

[0144] 17, when the mobile unit M1 is moving, among the data communication function, the ranging function, and the radar function, the preamble code of the data communication function is set to a high code, and the preamble codes of the other functions are set to a low code. Therefore, when the mobile unit M1 is moving, the data communication function is given priority.

[0145] Furthermore, when the mobile unit M1 is stopped, among the data communication function, the ranging function, and the radar function, the preamble code of the ranging function is set to a high code, and the preamble codes of the other functions are set to a low code. Therefore, when the mobile unit M1 is stopped, the ranging function is given priority. However, when the mobile unit M1 is stopped, the preamble code of the radar function may be set to a high code, and the preamble codes of the other functions may be set to a low code. By doing this, for example, in a bus or a train, it is possible to detect the presence or absence of passengers and to detect unauthorized boarding or disembarking of passengers.

[0146] Furthermore, when the use of the mobile unit M1 is terminated, among the data communication function, ranging function, and radar function, the preamble code of the radar function is set to a high code, and the preamble codes of the other functions are set to a low code. Therefore, when the mobile unit M1 is stopped, the radar function is given priority. This configuration is advantageous when performing a living body detection process to prevent people from being left behind. However, when the use of the mobile unit M1 is terminated, the preamble code of the ranging function may be set to a high code, and the preamble codes of the other functions may be set to a low code. This allows, for example, the operation of a cleaning robot that cleans the vehicle to be given priority.

[0147] [5-2. Second Example] Fig. 18 is a diagram showing an example of the relationship between the state of the mobile station M1 and the preamble codes assigned to each function, which is different from Fig. 17. Fig. 18 shows a configuration conforming to the communication standard IEEE 802.15.4z.

[0148] In the example shown in Figure 18, a preamble code for ranging (ranging code) is used for the ranging function. Specifically, for the ranging function, the preamble code does not change depending on the state of the mobile unit M1, and the ranging code is used whether the mobile unit M1 is moving, stopping, or has finished using the function. The ranging code is superior to low codes in terms of the superiority of preamble codes, and there is no difference in superiority between the ranging code and high codes. In other words, communication for the ranging function using the ranging code (ranging communication) is likely to be successful without being affected by communication for other functions, regardless of the state of the mobile unit M1.

[0149] When a ranging code is used, among the multiple functions that can be realized by transmitting and receiving UWB signals, the ranging function does not require changing the preamble code depending on the state of the moving body M1, thereby reducing the burden of control processing. In particular, among the data communication function, ranging function, and radar function, it is only necessary to change the preamble code depending on the state of the moving body M1 for only the data communication function and the radar function, thereby reducing the burden of control processing.

[0150] In the example shown in Fig. 18, when the state of the mobile unit M1 is "moving" or "use completed", the preamble code settings for the data communication function and the radar function are the same as those described in Fig. 17. For this reason, detailed description will be omitted.

[0151] 18, when the state of the moving body M1 is "stopped," the preamble code of the data communication function is set to a low code, and the preamble code of the radar function is set to a high code. With this configuration, for example, in a bus or a train, it is possible to detect the presence or absence of passengers and to detect unauthorized boarding or disembarking of passengers.

[0152] However, when the state of the moving body M1 is "stopped," the preamble code for the data communication function may be set to a high code, and the preamble code for the radar function may be set to a low code. For example, in the case of a car that does not need to monitor passengers getting on and off, such a configuration can eliminate the need to switch the preamble code when the car changes from moving to stopped, or from stopped to moving. As a result, a reduction in the load on the control process can be expected.

[0153] 6. Specific Application Examples of the Technology of the Present Disclosure> Next, specific application examples of the technology of the present disclosure will be described.

[0154] [6-1. First Application Example] In the first application example, the multiple types of functions that can be realized by transmitting and receiving UWB signals are a data communication function, a ranging function, and a radar function. Furthermore, the mobile object M1 is a railway vehicle, and the wireless tag 30 is attached to a cleaning robot. Furthermore, it is the wireless tag 30 that issues radar instructions. Furthermore, the preamble code does not include a ranging code, and each function is assigned a high code or a low code. Note that, for example, the code value when a high code is assigned is "9," and, for example, the code value when a low code is assigned is "3."

[0155] FIG. 19 is a flowchart illustrating a preamble code change process executed by the master unit 10. Specifically, the process shown in FIG. 19 is executed by the master unit controller 11. The flowchart shown in FIG. 19 illustrates the technical content of a computer program (communication program 121) that causes the master unit controller 11 (computer) to function as a means for executing the communication method of this embodiment. The process shown in FIG. 19 can be widely implemented, for example, in a state where a mobile unit M1 (railroad vehicle) is capable of UWB communication. The process shown in FIG. 19 may also be executed by the wireless tag 30 in some cases.

[0156] In step S1, the base unit 10 (preamble code management unit 111; see FIG. 3 ) acquires the status of the mobile unit M1 on which it is mounted. The base unit 10 periodically acquires the status of the mobile unit M1. The status of the mobile unit M1 may be acquired as a result of a determination made by the base unit 10 based on, for example, information acquired using UWB communication or wired communication, or information input by an occupant. However, the status of the mobile unit M1 may also be determined by a device other than the base unit 10 and acquired from that device. The acquired status of the mobile unit M1 may be, for example, "driving," "parked," or "end of use." Once the status of the mobile unit M1 has been acquired, processing proceeds to the next step S2.

[0157] In step S2, the base unit 10 (preamble code management unit 111) determines whether or not the preamble code needs to be changed based on table information and the like previously stored in the base unit memory 12. Note that the table information referred to here may have a configuration similar to that of the table shown in Fig. 17 described above. In this description, it is assumed that the table information similar to that shown in Fig. 17 is stored in the base unit memory 12.

[0158] For example, if the state of the moving body M1 acquired in step S1 is "moving," the preamble code assignment requires that the data communication function be assigned a high code and the ranging function and radar function be assigned a low code. If the current preamble code setting is not in such a state, the base unit 10 determines that a preamble code change is necessary. On the other hand, if the current preamble code setting is the same as the setting obtained from the table information, the base unit 10 determines that a preamble code change is not necessary. If it is determined that a preamble code change is necessary (Yes in step S2), processing proceeds to the next step S3. If it is determined that a preamble code change is not necessary (No in step S2), processing returns to step S1.

[0159] As can be seen from the above, the communication device (specifically, the base unit 10) determines whether to change the preamble code of the UWB signal assigned to a function realized by transmitting and receiving a UWB signal, depending on the state of the mobile unit M1. In this configuration, the preamble code assigned to the communication used for each function can be determined depending on the importance of each function, which is determined based on the state of the mobile unit M1.

[0160] In step S3, the base unit 10 (preamble code management unit 111) changes the setting of the preamble code it uses based on the table information. For example, if the state of the mobile unit M1 changes from stopped to moving, the setting that assigns low codes to the data communication function and radar function and high codes to the ranging function is changed to a setting that assigns high codes to the data communication function and low codes to the ranging function and radar function. Furthermore, when the base unit 10 changes the setting of its own preamble code, it instructs each slave unit 20 to change the preamble code setting using UWB communication (data communication) or the like. As can be seen from the above, when the preamble code management unit 111 (first controller 11) determines to change the preamble code, it operates as follows. The preamble code management unit 111 (first controller 11) changes the preamble code assigned to the function to be changed among the multiple types of functions, and instructs other communication devices to change the preamble code assigned to the function to be changed. Each slave device 20 changes the setting of the preamble code in response to the instruction. Each slave device 20 communicates with the base device 10 using the changed preamble code. As can be seen from the above, in the communication method in each slave device 20 that can realize multiple types of functions by transmitting and receiving UWB signals, the preamble codes of at least some of the UWB signal preamble codes assigned to each of the multiple types of functions are changed in accordance with the state of the mobile body M1 on which the slave device 20 is mounted. This communication method is realized by the slave device controller 21 executing arithmetic processing in accordance with the communication program 221. When the processing of step S3 is completed, the processing returns to step S1, and the processing from step S1 onwards is carried out.

[0161] In this example, the wireless tag 30 can grasp the status of the moving object M1 based on operation information (such as a timetable) that is pre-stored in the memory of the cleaning robot. For this reason, the base unit 10 does not instruct the wireless tag 30 to change the preamble code setting, and the wireless tag 30 determines the status of the moving object M1 based on the operation information and automatically switches the preamble code setting. However, a configuration in which the base unit 10 instructs the wireless tag 30 to change the preamble code setting may also be adopted.

[0162] Here, an example of communication operation when the preamble code setting is changed will be described. Fig. 20 is a diagram for explaining operation when radio wave interference occurs between data communication and ranging communication, and illustrates operation when the preamble code setting is different from that in Fig. 13 . In Fig. 13 , a high code (code value "9") is assigned to the data communication function and a low code ("3") is assigned to the ranging function. However, in Fig. 20 , a low code (code value "3") is assigned to the data communication function and a high code (code value "9") is assigned to the ranging function. The situation in Fig. 20 can be imagined, for example, when a moving object M1, such as a railway vehicle, stops at a station for a long period of time and a cleaning robot performs cleaning during this long stop. On the other hand, the situation in Fig. 13 can be imagined when the moving object M1 is traveling.

[0163] 20, the base unit 10 uses a low code (code value "3") as the preamble code. The wireless tag 30 uses a high code (code value "9") as the preamble code. Each of the slave units 20a to 20c uses a low code (code value "3") preamble code only during period T, which is its own polling order, in data communication with the base unit 10 using the polling method, and uses a high code (code value "9") preamble code during other periods.

[0164] 20 , data communication is taking place between the parent unit 10 and the first child unit 20a. During this period (a), the wireless tag 30 mounted on the cleaning robot issues a distance measurement request to the first child unit 20a to detect the cleaning robot's position. In this case, the first child unit 20a uses a low code for data communication with the parent unit 10, and therefore the distance measurement request using the high code of the wireless tag 30 is not accepted because the preamble code used is different. Furthermore, the data communication using the low code of the parent unit 10 is inferior to the distance measurement communication using the high code of the wireless tag 30 in terms of preamble code superiority, and therefore fails due to the influence of the distance measurement communication using the high code of the wireless tag 30.

[0165] During period (a), the wireless tag 30 also sends distance measurement requests to the second handset 20b and the third handset 20c. Because the communication for the distance measurement request (distance measurement communication) has a superior preamble code, the communication is successful without being affected by the data communication performed by the base unit 10. As a result, the wireless tag 30 receives replies from the second handset 20b and the third handset 20c and successfully measures the distance.

[0166] During period (b), since the parent device 10 failed to communicate with the first child device 20a, it uses the re-communication time slot t2 to perform data communication. During this period (b), there is no ranging communication, so the data communication between the parent device 10 and the first child device 20a is successful without being affected by the ranging communication.

[0167] During period (c), data communication is taking place between the base unit 10 and the second slave unit 20b. During this period (c), the wireless tag 30 issues a distance measurement request to the first slave unit 20a, with which it previously failed to communicate. Here, the preamble codes of the wireless tag 30 and the first slave unit 20a are the same. Furthermore, the communication for the distance measurement request (distance measurement communication) is superior in terms of preamble code superiority, so the communication is successful without being affected by the data communication performed by the base unit 10. As a result, the wireless tag 30 receives a reply from the first slave unit 20a and successfully measures the distance. This allows the distances from three points to the wireless tag 30 to be obtained, enabling the cleaning robot's position to be detected by triangulation.

[0168] During period (c), the radio tag 30 and the first handset 20a are communicating using the high code, so the radio waves for data communication using the low code, which is inferior in terms of the superiority of the preamble code, are lost. In other words, data communication between the base unit 10 and the second handset 20b is not established. For this reason, after period (c), the base unit 10 performs data communication with the second handset 20b using the re-communication time slot t2.

[0169] Comparing Figure 20 with Figure 13, it can be seen that the responsiveness of ranging communication improves by changing the preamble code assigned to the data communication function from a high code to a low code and by changing the preamble code assigned to the ranging function from a low code to a high code.

[0170] In this example, when the moving object M1, which is a railway vehicle, reaches its end of use (for example, when the last train arrives at the terminal station), a liveness detection process is performed to prevent passengers from being left behind in the vehicle. For this reason, when the moving object M1 is in the "end of use" state, the liveness detection process is an important item, and a high code is assigned to the radar function to facilitate successful radar communication for the liveness detection process (see FIG. 17 ). Depending on the result of the liveness detection process using the radar function, which of the multiple functions realized using UWB communication is important will differ. A preamble code change process that takes this into consideration will now be described.

[0171] Fig. 21 is a flowchart showing an example of operation after a living body detection process using a radar function. The process shown in Fig. 21 is executed by the parent device 10. In detail, the process shown in Fig. 21 is executed by the parent device controller 11. The process shown in Fig. 21 is started, for example, when radar communication between the wireless tag 30 and the child device 20 is completed and the result of the living body detection process is transmitted from the child device 20 to the parent device 10 in response to a request from the parent device 10 using data communication. At the start of the process shown in Fig. 21, the preamble code is set to a low code for the data communication function and the ranging function, and a high code for the radar function.

[0172] In step S11, the base unit controller 11 (preamble code management unit 111; see FIG. 3) determines whether or not a passenger has been abandoned based on the result of the living body detection process. If the base unit controller 11 determines that a passenger has been abandoned (Yes in step S11), the process proceeds to step S12. On the other hand, if the base unit controller 11 determines that a passenger has not been abandoned (No in step S11), the process proceeds to step S13.

[0173] In step S12, the master controller 11 (preamble code management unit 111) changes the preamble codes for the data communication function and the radar function from their current settings. Specifically, the preamble code for the data communication function is changed from a low code to a high code, and the preamble code for the radar function is changed from a high code to a low code. Accordingly, the master controller 10 instructs the slave controller 20, via data communication or the like, to similarly change the preamble code settings. That is, after the master controller 10 and the slave controller 20 complete the processing using the radar function that was executed upon the end of use of the mobile unit M1, a high code is assigned to the data communication function and a low code is assigned to the radar function. The wireless tag 30 also obtains the results of the biological detection processing through radar communication and recognizes that radar communication is no longer necessary. Therefore, the wireless tag 30 switches the preamble code setting for the radar function to a low code.

[0174] When it is detected that a passenger has been abandoned, it is necessary to notify the crew of the moving object M1 (railroad vehicle), the railway administrator, etc. In order to perform this notification process, the priority of the data communication function between the base unit 10 and the slave unit 20 is increased. By the process of step S12, the priority of the data communication function is increased, and the occurrence of abandonment can be quickly notified.

[0175] In step S13, the base unit controller 11 (application unit 113 and communication processing unit 112) performs a notification process to notify the user that a passenger has been abandoned. The notification process includes issuing an alarm output instruction to the slave unit 20 using a data communication function. The slave unit 20, which has an alarm output function (e.g., a speaker function, etc.), outputs an alarm in response to an instruction from the base unit 10 via data communication. The alarm may be, for example, a buzzer sound, a voice, a screen display, etc. The notification process may also include sending an email to a terminal device managed by a railway administrator, etc.

[0176] 22 is a diagram showing an example of a display screen 100 that notifies that a passenger has been abandoned. The display screen 100 is, for example, the display screen of a display device provided in a control room provided in a railway vehicle, or the display screen of a terminal device (PC, tablet terminal, smartphone, etc.) owned by a person located away from the railway vehicle.

[0177] 22 includes a content display area 101 that notifies the user that an item has been left behind, a first occurrence location display area 102 that notifies the user of the location of the item left behind in text, and a second occurrence location display area 103 that notifies the user of the location of the item left behind in a graphic form. The use of text and graphics to notify the user of the location of the item left behind makes it easy to identify the location of the item left behind.

[0178] In step S14, the master controller 11 (preamble code management unit 111) changes the preamble codes for the ranging function and the radar function from their current settings. Specifically, the preamble code for the ranging function is changed from a low code to a high code, and the preamble code for the radar function is changed from a high code to a low code. The master controller 10 instructs the slave controller 20, via data communication or the like, to perform the same preamble code setting change. That is, after the master controller 10 and the slave controller 20 complete the processing using the radar function executed in response to the end of use of the mobile unit M1, a high code is assigned to the ranging function and a low code is assigned to the radar function. The wireless tag 30 also obtains the results of the biological detection processing through radar communication and recognizes that radar communication is no longer necessary and that ranging communication is important. Therefore, the wireless tag 30 switches the preamble code setting for the measuring function to a high code and the preamble code setting for the radar function to a low code.

[0179] In this example, the result of the living body detection process using the radar function is transmitted from the slave unit 20 to the wireless tag 30 as part of radar communication. This allows the cleaning robot to determine whether or not a passenger has been left behind. The cleaning robot then decides whether or not to start cleaning depending on whether or not a passenger has been left behind. If any passenger has been left behind, the cleaning robot decides to temporarily suspend cleaning. If no passenger has been left behind, the cleaning robot decides to start cleaning. When cleaning, the cleaning robot's own location information is important. The processing of step S14 increases the priority of the ranging function, so the cleaning robot can determine its own location with good responsiveness and perform cleaning work appropriately.

[0180] [6-2. Second Application Example] In the second application example, as in the first application example, the multiple functions that can be realized by transmitting and receiving UWB signals are a data communication function, a ranging function, and a radar function. However, the mobile unit M1 is an automobile, and the wireless tag 30 is attached to a smart key. Furthermore, the base unit 10 issues radar instructions. Furthermore, the communication standard is IEEE 802.15.4z, and a ranging code is assigned to the ranging function. While high and low codes can be assigned to the data communication function and the radar function, the base unit 10 is configured to assign high codes to both the data communication function and the radar function in order to issue instructions for both functions (see FIG. 15 above). Therefore, in this example, the preamble code setting is not changed depending on the state of the mobile unit M1. However, this is merely an example, and the preamble code setting for the data communication function and the radar function may be changed depending on the state of the mobile unit M1.

[0181] Fig. 23 is a flowchart showing an example of a suspicious person detection process using transmission and reception of UWB signals in an automobile. The process shown in Fig. 23 is executed by a base unit 10 (more specifically, a base unit controller 11) mounted on an automobile, which is a moving object M1. The process shown in Fig. 23 is started, for example, when the ACC power supply of the automobile is turned on.

[0182] In step S21, the master controller 11 monitors whether the ACC power supply has been turned off. The master controller 11 can acquire ACC power supply on / off information, for example, via wired communication. If it detects that the ACC power supply has been turned off (Yes in step S21), the process proceeds to the next step S22. If it does not detect that the ACC power supply has been turned off (No in step S21), the monitoring process of step S21 is maintained.

[0183] In step S22, the parent controller 11 determines whether a certain time has elapsed since the ACC power was turned off. The certain time is a time stored in advance in the parent controller memory 12, and may be, for example, 5 minutes. If the certain time has elapsed since the ACC power was turned off (Yes in step S22), the process proceeds to the next step S23. If the certain time has not elapsed since the ACC power was turned off (No in step S22), the process returns to step S21.

[0184] In step S23, the master controller 11 determines whether a smart key has been detected. The master controller 11 determines whether a smart key has been detected or not based on the results of ranging communication using transmission and reception of UWB signals between the slave 20 and the wireless tag 30 attached to the smart key. The master 10 requests the slave 20 to perform ranging communication. The slave 20 transmits the results of the ranging communication to the master 10 in response to a request from the master 10. However, ranging communication may be performed between the master 10 and the wireless tag 30.

[0185] When the smart key is near the vehicle, the transmission for distance measurement from the slave unit 20 is received by the wireless tag 30, and a reply is sent from the wireless tag 30 to the slave unit 20. As a result, the master controller 11, which acquires the result of the distance measurement communication from the slave unit 20, detects the smart key. On the other hand, if the smart key is far away from the vehicle, the slave unit 20 does not receive a reply to the distance measurement request from the wireless tag 30. As a result, the master controller 11, which acquires the result of the distance measurement communication, does not detect the smart key. If the smart key is detected (Yes in step S23), the process returns to step S21. If the smart key is not detected (No in step S23), the process proceeds to step S24.

[0186] In step S24, the master controller 11 determines whether or not a body system input signal has been received. A body system input signal is a signal input from a device that starts operating when operated by a human, such as when a door lock, door handle, wiper, or headlamp switch is operated. The master controller 10 acquires the body system input signal by using data communication (communication using UWB signals) with the slave controller 20. If the master controller 11 determines that a body system input signal has been received (Yes in step S24), the process proceeds to the next step S25. On the other hand, if the master controller 11 determines that a body system input signal has not been received (No in step S24), the process proceeds to step S26.

[0187] In step S25, the master controller 11 performs a suspicious person notification process to notify the master controller 11 of the presence of a suspicious person. The reason for performing such a notification process is that, even though the smart key is not nearby, an input signal from the vehicle's body system is detected, and it is determined that a suspicious person has likely entered the vehicle. The suspicious person notification process may be, for example, a process of sounding the vehicle's horn using a data communication function using a UWB signal, or a process of sending an email to the vehicle owner's mobile device (such as a smartphone) notifying the owner of the vehicle of the presence of a suspicious person. The suspicious person notification process may also include a process of contacting the police using an email, etc.

[0188] In step S26, the master controller 11 checks whether a living organism has been detected. Specifically, the master controller 11 issues a command (radar command) to the slave 20, which is installed near the seat of the vehicle, to perform a living organism detection process using radar. As described above, the radar command is a process included in the radar function that uses the transmission and reception of UWB signals. The master controller 11 determines whether a living organism has been detected based on the result of the living organism detection process returned from the slave 20 in response to the radar command. If the master controller 11 determines that a living organism has been detected (Yes in step S26), the process proceeds to the next step S27. On the other hand, if the master controller 11 determines that a living organism has not been detected (No in step S26), the process returns to step S21.

[0189] In step S27, the parent controller 11 performs an abandonment notification process to notify the parent that a person has been left behind. The reason for performing such a notification process is that the presence of a living body that is not a suspicious person was confirmed in the vehicle even though the smart key was not nearby, and therefore it can be determined that a child or the like has been left behind in the vehicle. The abandonment notification process may be, for example, a process of sounding the vehicle's horn using a data communication function using an UWB signal, or a process of sending an email to the vehicle owner's mobile device (such as a smartphone) notifying them of the presence of a suspicious person. The abandonment notification process may be the same as the suspicious person notification process described above, but it is preferable to use a different process so that the two can be distinguished.

[0190] 7. 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.

[0191] For example, in the above description, each of the base unit 10, the slave unit 20, and the wireless tag 30 is configured to have one transmitter and one receiver (see, for example, FIGS. 3 to 5). However, this is merely an example, and each of the base unit 10, the slave unit 20, and the wireless tag 30 may be configured to have separate sets of transmitters and receivers corresponding to multiple types of functions that can be realized by transmitting and receiving UWB signals.

[0192] Fig. 24 is a diagram illustrating a wireless communication unit WC according to another embodiment. The example shown in Fig. 24 is a diagram assuming a case where a communication device is used for all of the data communication function, the ranging communication function, and the radar function. The wireless communication unit WC includes a data communication unit WC1, a ranging communication unit WC2, and a radar communication unit WC3, and each of the communication units WC1 to WC3 includes one set of a transmitter Tx and a receiver Rx.

[0193] The configuration of the communication unit included in the wireless communication unit WC may be changed depending on the type of function used by the communication device. For example, assume that the data communication function is used only between the base unit 10 and the slave unit 20, and the ranging function and radar function are used only between the slave unit 20 and the wireless tag 30. In this case, the wireless communication unit WC of the base unit 10 may be configured to include only a data communication unit WC1. Furthermore, in this case, the wireless communication unit WC of the slave unit 20 may be configured to include a data communication unit WC1, a ranging communication unit WC2, and a radar communication unit WC3. Furthermore, in this case, the wireless communication unit WC of the wireless tag 30 may be configured to include a ranging communication unit WC2 and a radar communication unit WC3.

[0194] When a different wireless communication unit WC is provided for each function (usage), the preamble codes assigned to the data communication function, ranging function, and radar function can be high-value codes with different code values, as shown in pattern 1 in Fig. 25. In this case, UWB communication for any function is likely to be successful without being affected by communication for the other functions, and therefore, overlapping timing communications can be performed.

[0195] 25 shows an example of preamble code allocation when the communication standard is IEEE 802.15.4z. In this case, UWB communication for any function is likely to be successful without being affected by communication for other functions, so communication can be performed at overlapping times.

[0196] Fig. 26 is a diagram showing an example of communication operation when a preamble code of pattern 1 or pattern 2 of Fig. 25 is assigned. Fig. 26 shows the operation when data communication between the base unit 10 and the slave unit 20 and distance measurement communication between the slave unit 20 and the wireless tag 30 are performed at approximately the same time.

[0197] Specifically, during data communication between the base unit 10 and the first handset 20a, the wireless tag 30 requests the first handset 20a to measure distance. Even in such a case, there is no difference between the preamble code used for data communication and the preamble code used for distance measurement communication, and furthermore, the first handset 20a has a receiver Rx for each function, so in principle both communications will be successful. More specifically, as long as the request timings of the base unit 10 and the wireless tag 30 are not completely simultaneous, each of the handset 20a to 20c can send a reply to both the base unit 10 and the wireless tag 30.

[0198] <8. Supplementary Notes> The following supplementary notes are further disclosed regarding the above-described embodiments, examples, and modifications.

[0199] The present disclosure can have the following configurations (1) to (11).

[0200] (1) A communication device mounted on a mobile body and capable of realizing multiple types of functions through UWB communication, the communication device comprising a control unit, the control unit changing the UWB communication preamble code assigned to each of the multiple types of functions depending on the state of the mobile body.

[0201] (2) The communication device described in (1), wherein the control unit determines whether to change the UWB communication preamble code assigned to each of the multiple types of functions depending on the state of the mobile body, and if it determines to change it, changes the preamble code assigned to a function to be changed among the multiple types of functions, and instructs other communication devices to change the preamble code assigned to the function to be changed.

[0202] (3) The communication device described in (1) or (2), wherein the preamble code includes a high code preamble code and a low code preamble code having different pulse repetition frequencies, the multiple types of functions include a data communication function and a ranging function, and the control unit assigns the high code to the data communication function and the low code to the ranging function when the mobile body is moving, and assigns the low code to the data communication function and the high code to the ranging function when the mobile body is stopped or usage is terminated.

[0203] (4) The communication device according to (1) or (2), wherein the preamble code includes a high code preamble code and a low code preamble code having different high and low pulse repetition frequencies, the plurality of types of functions include a data communication function and a radar function, and the control unit assigns the high code to the data communication function and the low code to the radar function when the mobile body is moving, and assigns the low code to the data communication function and the high code to the radar function when the mobile body is stopped or has finished using it.

[0204] (5) The communication device according to (4), wherein the plurality of types of functions further includes a distance measurement function, and the control unit assigns a distance measurement preamble code to the distance measurement function.

[0205] (6) The communication device according to (4) or (5), wherein the control unit assigns the high code to the data communication function and the low code to the radar function after completion of processing using the radar function that is executed in response to the end of use of the mobile body.

[0206] (7) The communication device described in (4), wherein the multiple types of functions further include a ranging function, and the control unit assigns the high code to the ranging function and the low code to the radar function after completion of processing using the radar function executed in conjunction with the end of use of the mobile body.

[0207] (8) A communication method in a communication device capable of realizing multiple types of functions through UWB communication, the communication method comprising: changing the preamble codes of at least some of the UWB communication preamble codes assigned to each of the multiple types of functions according to the state of a mobile body in which the communication device is mounted.

[0208] (9) A communication program that causes a computer provided in a communication device capable of realizing multiple types of functions through UWB communication to function as a means for executing the following: changing the preamble codes of the UWB communication assigned to each of the multiple types of functions according to the state of a mobile body on which the communication device is mounted.

[0209] (10) A communication system comprising: a base unit mounted on a mobile body and capable of realizing multiple types of functions through UWB communication with multiple slave units; and slave units mounted on the mobile body and performing UWB communication with the base unit, wherein the base unit determines whether to change the UWB communication preamble codes assigned to each of the multiple types of functions according to the state of the mobile body, and if it is determined to change the preamble codes, changes the preamble codes assigned to functions to be changed among the multiple types of functions and instructs the multiple slave units to change the preamble codes assigned to the functions to be changed based on the instruction, and communicates with the base unit using the changed preamble codes.

[0210] (11) The communication system described in (10) further includes a wireless tag that performs UWB communication with the multiple handset devices, wherein the wireless tag determines whether or not to change the UWB communication preamble code assigned to the function of the wireless tag depending on the state of the mobile body, and if it determines to change the preamble code, changes the preamble code and instructs the multiple handset devices to change the preamble code assigned to the function of the wireless tag, and the multiple handset devices communicate with the wireless tag using the changed preamble code based on instructions from the wireless tag.

[0211] (12) The communication system described in (10) further includes a wireless tag that performs UWB communication with the plurality of slave units, wherein the master unit determines whether to change the preamble code of the UWB signal assigned to each of the plurality of types of functions according to the state of the mobile body, and if it determines to change the preamble code, changes the preamble code assigned to a function to be changed among the plurality of types of functions and instructs the plurality of slave units and the wireless tag to change the preamble code assigned to the function to be changed, based on the instruction from the master unit, and communicates with the master unit and the wireless tag using the changed preamble code, and the wireless tag changes the preamble code for the function to be changed based on the instruction from the master unit, and communicates with the plurality of slave units using the changed preamble code.

[0212] REFERENCE SIGNS LIST 10: Master unit (communication device) 20: Child unit (communication device) 20a: First child unit 20b: Second child unit 20c: Third child unit 30: Wireless tag 121, 221, 321: Communication program M1: Mobile unit SYS: Communication system

Claims

1. A communication device that is mounted on a mobile body and can realize multiple types of functions through UWB communication, and that includes a control unit, wherein the control unit changes the UWB communication preamble codes assigned to each of the multiple types of functions depending on the state of the mobile body.

2. The communication device described in claim 1, wherein the control unit determines whether or not to change the UWB communication preamble code assigned to each of the multiple types of functions depending on the state of the mobile body, and if it determines to change it, changes the preamble code assigned to the function to be changed among the multiple types of functions, and instructs other communication devices to change the preamble code assigned to the function to be changed.

3. The communication device of claim 2, wherein the preamble codes include a high code preamble code and a low code preamble code having different high and low pulse repetition frequencies, the multiple types of functions include a data communication function and a ranging function, and the control unit assigns the high code to the data communication function and the low code to the ranging function when the mobile body is moving, and assigns the low code to the data communication function and the high code to the ranging function when the mobile body is stopped or usage has ended.

4. The communication device of claim 2, wherein the preamble codes include a high code preamble code and a low code preamble code having different high and low pulse repetition frequencies, the multiple types of functions include a data communication function and a radar function, and the control unit assigns the high code to the data communication function and the low code to the radar function when the mobile body is moving, and assigns the low code to the data communication function and the high code to the radar function when the mobile body is stopped or usage has ended.

5. The communication device according to claim 4, wherein the plurality of types of functions further includes a distance measurement function, and the control unit assigns a distance measurement preamble code to the distance measurement function.

6. The communication device described in claim 4, wherein the control unit assigns the high code to the data communication function and the low code to the radar function after completion of processing using the radar function executed in response to the end of use of the mobile body.

7. The communication device of claim 4, wherein the multiple types of functions further include a ranging function, and the control unit assigns the high code to the ranging function and the low code to the radar function after completion of processing using the radar function executed upon termination of use of the mobile body.

8. A communication method for a communication device capable of realizing multiple types of functions through UWB communication, wherein the preamble codes of at least some of the UWB communication preamble codes assigned to each of the multiple types of functions are changed according to the state of a mobile body in which the communication device is installed.

9. A communication program that causes a computer equipped with a communication device capable of realizing multiple types of functions through UWB communication to function as a means for changing the preamble codes of the UWB communication assigned to each of the multiple types of functions according to the state of the mobile body on which the communication device is installed.

10. A communications system comprising: a base unit mounted on a mobile body and capable of realizing multiple types of functions through UWB communications with multiple slave units; and slave units mounted on the mobile body and performing UWB communications with the base unit, wherein the base unit determines whether to change the UWB communication preamble codes assigned to each of the multiple types of functions according to the state of the mobile body; if it determines to change the preamble codes, it changes the preamble codes assigned to the functions to be changed among the multiple types of functions and instructs the multiple slave units to change the preamble codes assigned to the functions to be changed based on the instructions; and communicates with the base unit using the changed preamble codes.

11. A communication system as described in claim 10, further comprising a wireless tag that performs UWB communication with the plurality of handset units, wherein the wireless tag determines whether or not to change the preamble code for UWB communication assigned to the function of the wireless tag depending on the state of the mobile body, and if it determines to change the preamble code, changes the preamble code and instructs the plurality of handset units to change the preamble code assigned to the function of the wireless tag, and the plurality of handset units communicate with the wireless tag using the changed preamble code based on instructions from the wireless tag.

12. A communication system as described in claim 10, further comprising a wireless tag that performs UWB communication with the plurality of slave units, wherein the master unit determines whether or not to change the preamble code of the UW signal assigned to each of the plurality of types of functions according to the state of the mobile body, and if it determines to change it, changes the preamble code assigned to a function among the plurality of types of functions that is to be changed, and instructs the plurality of slave units and the wireless tag to change the preamble code assigned to the function that is to be changed, based on the instruction from the master unit, and communicates with the master unit and the wireless tag using the changed preamble code, and the wireless tag changes the preamble code for the function that is to be changed based on the instruction from the master unit, and communicates with the plurality of slave units using the changed preamble code.

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