Communication method, communication apparatus, and communication program

Abstract

To provide a technique capable of reducing a communication waiting time for a communication request generated on a slave device side in UWB communication using a polling manner.SOLUTION: An exemplary communication method is a communication method for performing UWB communication in a polling manner between a master device and a plurality of slave devices. The master device is provided with a first receiver for receiving response transmissions from the plurality of slave devices that have received a transmission from the master device, and a second receiver for receiving interrupt transmissions from the plurality of slave devices. The master device and the plurality of slave devices perform communication using different preamble codes for the response transmissions and the interrupt transmissions.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to UWB (Ultra Wide Band) communication using a polling method. [Background technology]

[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. One type of wireless communication that is on the rise is known as UWB (Ultra Wide Band) communication (see, for example, Patent Document 1).

[0003] UWB communication has the advantages of low interference with radio waves used in Wi-Fi (registered trademark) and mobile devices such as smartphones, and good transmission due to its wide bandwidth of 500 MHz. UWB communication also has the advantage of being easily established in vehicles, which are confined spaces made of metal and have many wires. For these reasons, UWB communication has attracted attention as a communication method advantageous for use in vehicles and outdoors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-166468 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the number of frequency channels permitted for use in UWB communications may be limited, although this varies from country to country. For example, in Japan, only one frequency channel is permitted for use outdoors. When UWB communications are conducted between a parent device and multiple child devices in a situation where only one frequency channel is available, efficient communication can be achieved by using a polling method, in which communications are conducted in a predetermined order.

[0006] However, in a configuration using the polling method, if a slave device issues a communication request to the master device at a time other than its turn, it will have to wait until its turn to communicate before transmitting the communication request to the master device. In particular, when there are a large number of slave devices performing UWB communication with the master device, the waiting time for transmission of the communication request described above can become long, which can cause problems.

[0007] In view of the above, an object of the present invention is to provide a technique that can shorten the waiting time for communication in response to a communication request generated on the slave device side in UWB communication using a polling method. [Means for solving the problem]

[0008] An exemplary communication method of the present invention is a polling-based UWB communication method between a master unit and multiple slave units, in which the master unit is provided with a first receiver that receives response transmissions from the multiple slave units that have received a transmission from the master unit, and a second receiver that receives interrupt transmissions from the multiple slave units. The master unit and the multiple slave units communicate using different preamble codes for the response transmissions and the interrupt transmissions. [Effects of the Invention]

[0009] In the exemplary embodiment of the present invention, a master unit that receives transmissions from slave units includes multiple receivers, enabling the master unit to separately receive transmissions using different preamble codes. The slave units are configured to transmit using different preamble codes for response transmission and interrupt transmission. Therefore, a slave unit that issues a communication request with the master unit out of its turn in a polling system can perform an interrupt transmission using a preamble code different from that used for the response transmission when other slave units issue a response transmission. Because the response transmission and the interrupt transmission use different preamble codes, the master unit, which includes multiple receivers, can receive both transmissions while avoiding interference between the response transmission and the interrupt transmission. In other words, a slave unit that issues a communication request with the master unit out of its turn can communicate with the master unit without waiting for its next turn in the polling system. As can be seen from the above description, the exemplary embodiment of the present invention can shorten the waiting time for communication in response to a communication request issued by a slave unit in UWB communication using a polling system. Furthermore, according to the exemplary configuration of the present invention, there is no need to provide a dedicated period in the master unit for interrupt transmission within the polling cycle, so UWB communication can be performed efficiently. [Brief explanation of the drawings]

[0010] [Figure 1] A diagram showing an example of the configuration of a communication system. [Figure 2] Block diagram showing the general configuration of the parent unit [Figure 3] Block diagram showing the general configuration of the slave unit [Figure 4] FIG. 1 shows a frame format used in UWB communication. [Figure 5] Schematic diagram showing the outline of radio interference countermeasures [Figure 6] FIG. 10 is a schematic diagram illustrating a detailed example of how to set the reception mode start time τstart. [Figure 7] A diagram for explaining UWB communication using a polling method. [Figure 8]FIG. 1 is a diagram for explaining an overview of a communication method according to a first embodiment; [Figure 9] 10 is a flowchart illustrating the flow of a communication method executed by a master unit according to the first embodiment; [Figure 10] 10 is a flowchart illustrating the flow of a communication method executed by a slave device according to the first embodiment; [Figure 11] FIG. 10 is a diagram for explaining an outline of a communication method according to a second embodiment; [Figure 12] FIG. 11 is a block diagram showing the configuration of a master wireless communication unit and a slave wireless communication unit in a third embodiment. [Figure 13] FIG. 10 is a diagram for explaining an outline of a communication method according to a third embodiment; [Figure 14] 10 is a flowchart illustrating the flow of a reception method executed by a master unit according to a third embodiment; [Figure 15A] 10 is a flowchart illustrating the flow of a reception method executed by a slave unit according to a third embodiment; [Figure 15B] 10 is a flowchart illustrating the flow of a transmission method executed by a slave unit according to a third embodiment; [Figure 16] FIG. 10 is a diagram for explaining an outline of a communication method according to a fourth embodiment; [Figure 17] 10 is a flowchart illustrating the flow of a communication method executed by a master unit according to a fourth embodiment; [Figure 18] 10 is a flowchart illustrating the flow of a transmission method executed by a slave unit according to a fourth embodiment; [Figure 19] FIG. 10 is a diagram for explaining a modified example of the fourth embodiment. [Figure 20] FIG. 10 is a diagram for explaining an outline of a communication method according to a fifth embodiment. [Figure 21] 10 is a flowchart illustrating the flow of a communication method executed by a master unit according to a fifth embodiment; [Figure 22] 10 is a flowchart illustrating the flow of a transmission method executed by a slave unit according to a fifth embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the description of the embodiments, the same components are denoted by the same reference numerals, and redundant description will be omitted unless particularly necessary.

[0012] <1. Communication Systems> [1-1. System Overview] FIG. 1 is a diagram showing an example of the configuration of a communication system SYS1 according to an embodiment of the present invention. In this embodiment, as an example, the communication system SYS1 is applied to an automobile C1. However, the communication system of the present invention may be applied to an installation target of communication equipment other than the automobile C1, for example, to general mobile objects other than automobiles, home communication equipment, office communication equipment, or factory communication equipment. In addition to automobiles, general mobile objects include, for example, railroad cars (trains), ships, and aircraft.

[0013] 1, the communication system SYS1 includes a master unit 10 and a plurality of slave units 20a to 20d. The master unit 10 is provided in, for example, a center unit (a so-called head unit) that controls the slave units 20a to 20d, which are various types of in-vehicle equipment in an automobile C1. The center unit is a control unit.

[0014] The communication system SYS1 is, for example, an in-vehicle control system in which a master unit 10 controls each of slave units (in-vehicle devices) 20a to 20d by wireless communication in response to a user's operation on an HMI (Human Machine Interface) 40. As a specific example, each of the slave units 20a to 20d may be configured to control an actuator connected thereto based on a control signal transmitted from the master unit 10. Each of the slave units 20a to 20d may also be configured to transmit to the master unit 10 a sensor value or the like detected by a sensor connected thereto. The transmission from the master unit 10 includes information related to the control of an actuator of a vehicle connected to each of the slave units 20a to 20d, and the response transmission and interrupt transmission transmitted from each of the slave units 20a to 20d to the master unit 10 includes information detected by a sensor of the vehicle connected to each of the slave units 20a to 20d.

[0015] The first sub-unit 20a is, for example, a control device that controls the operation of headlights. The second sub-unit 20b is, for example, a control device that controls the operation of wipers. The third sub-unit 20c is, for example, a control device that controls the operation of power windows. The fourth sub-unit 20d is, for example, a control device that controls the operation of an air conditioner. The first sub-unit 20a, the second sub-unit 20b, the third sub-unit 20c, and the fourth sub-unit 20d are examples of individual control units that control various drive devices.

[0016] Note that wireless communication is performed between the base unit 10 and each of the slave units 20a to 20d. For this reason, the base unit 10 and each of the slave units 20a to 20d can be considered as a communication device. More specifically, the base unit 10 and each of the slave units 20a to 20d can be considered as a wireless communication device. In the following, when it is not necessary to distinguish between the multiple slave units 20a to 20d, each of the slave units 20a to 20d will be simply referred to as a slave unit 20.

[0017] In addition, in this embodiment, there are multiple slave devices 20, but in other embodiments, there may be only one. When there are multiple slave devices 20 as in this embodiment, the master device 10 repeatedly communicates with each of the slave devices 20a to 20d in turn. That is, in this embodiment, wireless communication is performed using a polling method.

[0018] In this embodiment, the base unit 10 not only transmits signals to the slave unit 20 but also receives signals from the base unit 10. The slave unit 20 not only receives signals from the base unit 10 but also transmits signals to the base unit 10. That is, the base unit 10 and the slave unit 20 can be both a transmitter and a receiver of information. Each of the base unit 10 and the slave unit 20 can be either a transmitter that transmits information or a receiver that receives information.

[0019] In this embodiment, the master device 10 and the slave device 20 communicate using a preamble. Specifically, the master device 10 and the slave device 20 communicate using UWB. That is, the communication used by the communication devices 10 and 20 in this embodiment is wireless communication using the UWB communication method. In UWB communication, communication is performed in accordance with a standard such as IEEE 802.15.4 (hereinafter, sometimes simply referred to as a communication standard). Because the master device 10 and each of the slave devices 20a to 20d communicate using UWB, the communication system SYS1 contributes to reducing the number of wire harnesses used in the automobile C1.

[0020] [1-2. Parent unit] Fig. 2 is a block diagram showing a schematic configuration of the base unit 10. Note that Fig. 2 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components.

[0021] As shown in FIG. 2, the master unit 10 includes a master unit controller 11, a master unit memory 12, and a master unit wireless communication unit 13.

[0022] The master controller 11 controls the overall operation of the master device 10. The master controller 11 includes a processor that performs arithmetic processing and the like. The processor may include, for example, a CPU (Central Processing Unit). The master controller 11 may be configured with one processor or multiple processors. When configured with multiple processors, the processors may be connected to each other so that they can communicate with each other.

[0023] The parent device memory 12 is configured to include volatile memory and non-volatile memory. The volatile memory is specifically RAM (Random Access Memory). The non-volatile memory is specifically ROM (Read Only Memory). The non-volatile memory may also be a flash memory, a hard disk drive, or the like. The non-volatile memory stores computer-readable programs and data. The programs include communication programs such as a transmission program and a reception program.

[0024] 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 (for example, an optical disk), a magneto-optical recording medium (for example, 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).

[0025] In this embodiment, the functions of the master controller 11 are realized by a processor executing arithmetic processing in accordance with 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.

[0026] Furthermore, at least some of the functions of the master controller 11 may be realized by other methods than by software as in the present embodiment. At least some of the functions of the master controller 11 may be realized by using, for example, 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 be realized by a combination of software and hardware.

[0027] The master device wireless communication unit 13 is provided so as to be able to perform UWB communication with a slave device wireless communication unit 23 (see FIG. 3 described later) provided in the slave device 20. The master device wireless communication unit 13 has a transmitting function and a receiving function. The master device wireless communication unit 13 may be configured to have, for example, one transmitter and one receiver. Note that the number of transmitters and receivers is not limited to this and may be changed as appropriate. The master device wireless communication unit 13 may also be configured to have a transceiver in which the transmitter and receiver are integrally provided. The transceiver may be configured so that its function as a transmitter and its function as a receiver can be switched by a switching means such as a switch.

[0028] When the master unit wireless communication unit 13 is configured to include a transmitter, the transmitter is configured to be able to select between a transmission mode and an idle mode. When the master unit wireless communication unit 13 is configured to include a receiver, the receiver is configured to be able to select between a reception mode and an idle mode. When the master unit wireless communication unit 13 is configured to include a transceiver, the transceiver is configured to be able to select between the transmission mode, the reception mode, and the idle mode.

[0029] The transmit mode is a mode in which transmission is possible. The receive mode is a mode in which reception is possible. The idle mode is a mode in which neither transmission nor reception is possible. In the idle mode, power is supplied to the necessary circuits, etc., and the mode can be immediately switched to the receive mode or transmit mode.

[0030] [1-3. Handset] Fig. 3 is a block diagram showing a schematic configuration of the slave unit 20. Note that Fig. 3 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components. Note that all of the multiple slave units 20a to 20d have the configuration shown in Fig. 3.

[0031] 3, the slave device 20 includes a slave device controller 21, a slave device memory 22, and a slave device wireless communication unit 23. The configurations of the slave device controller 21, the slave device memory 22, and the slave device wireless communication unit 23 are generally similar to the configurations of the master device controller 11, the master device memory 12, and the master device wireless communication unit 13 described above, and therefore a description of the common parts will be omitted.

[0032] The slave unit controller 21 controls the overall operation of the slave unit 20. In this embodiment, the functions of the slave unit controller 21 are realized by a processor executing arithmetic processing in accordance with a program stored in the slave unit memory 22. However, as in the case of the master unit controller 11, at least some of the functions of the slave unit controller 21 may be realized using a method other than software.

[0033] The slave device wireless communication unit 23 is provided so as to be able to perform UWB communication with the master device wireless communication unit 13 provided in the master device 10. The slave device wireless communication unit 23 has a transmission function and a reception function. The slave device wireless communication unit 23 may be configured to have, for example, one transmitter and one receiver, or may be configured to have a transceiver in which the transmitter and receiver are integrally provided.

[0034] <2. Overview of UWB communication> Next, an overview of UWB communication used in this embodiment will be described. Fig. 4 is a diagram showing a frame format used in UWB communication. The frame format shown in Fig. 4 corresponds to the structure of one unit of transmission data in UWB communication. Hereinafter, one unit of transmission data may be referred to as a communication frame or a communication packet.

[0035] The frame format used in UWB communication is determined by the above-mentioned communication standard. As shown in Figure 4, the frame format used in UWB communication has a structure in which a preamble is first followed by an SFD (Start Frame Delimiter), a PHR (PHY Header), and a data body. Note that the term "data body" is used to make it easier to understand the difference between the preamble, SFD, and PHR.

[0036] 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.

[0037] There are multiple patterns in the preamble. The preamble code is a code for identifying these multiple patterns. Different preamble codes use different code symbols. Code symbols are composed of ternary symbols (for example, -, 0, +). One code symbol (1 symbol) is composed, for example, of "-+0++000-+-++00++0+00-0000-0+0-".

[0038] The SFD is a bit string with a specific pattern that signals the start of data in a communication frame. The PHR contains information necessary for decoding a packet. For example, the PHR contains information such as the address of the communication partner and the data length of the subsequent data. The data body is the main body of information to be sent to the communication partner and contains the actual data to be transmitted. For example, the data body contains information such as ID information of the receiver and sender of the communication frame, instruction information from the parent device 10 to the child device 20, sensor values ​​detected by sensors equipped in the child device 20, and the operating status of the actuator to be controlled by the child device 20.

[0039] In UWB communications, while the strength of radio waves also plays a role, radio waves received earlier are generally given priority. Therefore, when multiple transmission waves are transmitted at the same time, it is possible that an unwanted jamming wave will be received first, rather than the intended target wave. If a jamming wave is received first, it cannot be identified as a jamming wave unless the address in the PHR, which is processed after the preamble and SFD, is demodulated. Once a jamming wave is identified, processing of the jamming wave is stopped, and reception processing of other waves becomes possible. However, if the target wave has already reached the receiver before reception processing identifies the radio wave as a jamming wave, reception of the target wave will be missed. In this embodiment, as a preferred embodiment, measures are implemented to reduce communication failures due to radio interference with jamming waves. An overview of these measures is described below with reference to FIG. 5.

[0040] Figure 5 is a schematic diagram showing an overview of radio interference countermeasures. As shown in Figure 5, the transmitter is capable of switching between a transmission mode and an idle mode. The transmitter is capable of transmitting when in the transmission mode, and is unable to communicate when in the idle mode. The receiver is capable of switching between a reception mode and an idle mode. The receiver is capable of receiving when in the reception mode, and is unable to communicate when in the idle mode.

[0041] In Fig. 5, τstart is the time when the receiver starts receiving (reception mode start time), and τnext is the time when the target wave transmitted from the corresponding transmitter is expected to be received (expected reception time), which is a time previously agreed upon between the transmitter and the receiver.

[0042] The agreement is made, for example, by using wireless communication (UWB communication) or wired communication equipment (not shown) provided in the communication system SYS1. The wired communication equipment is, for example, a PLC (Power Line Communication) communication equipment that uses a power line to start the communication system SYS1.

[0043] The reception mode start time τstart is set slightly before the expected reception time τnext. For example, the reception mode start time τstart is set relative to the expected reception time τnext, taking into consideration the length of time it takes for the receiving circuit to stabilize and achieve good reception after the receiver starts reception mode.

[0044] As shown in Figure 5, the receiver switches from idle mode to receive mode just before the expected reception time τnext agreed upon with the transmitter. The receiver then ends receive mode and switches back to idle mode in synchronization with the end of the transmission wave from the transmitter. Note that the receiver ends receive mode at a pre-programmed timing, for example, based on the receive mode start time τstart.

[0045] In this configuration, the receiver starts receiving at the same time as the transmission start timing of the target wave transmitted from the corresponding transmitter. As a result, it is possible to reduce the possibility that the receiver will receive a transmission wave that arrives at a different time than the target wave. It is preferable to start the reception mode as close as possible to the expected time of reception of the target wave. An example of this is described below.

[0046] FIG. 6 is a schematic diagram for explaining a detailed example of how to set the reception mode start time τstart. In the communication standard for UWB communication, the transmission and reception times (times) can be obtained at the timing of the PHR. Taking this into consideration, as shown in FIG. 6, the expected reception time τnext is determined based on the PHR included in the frame format used in UWB communication. In detail, the expected reception time τnext is set to the start timing of the PHR.

[0047] In the example shown in FIG. 6, the reception mode start time τstart, which is the time immediately before the assumed reception time τnext, is determined by the following equation (1). τstart = τnext -(tSFD +tsym × Nrg ) (1)

[0048] In equation (1), tSFD is the reception period (SFD time) of the SFD included in the frame format. tsym is the reception period (one symbol time) of one symbol of the preamble code in the preamble included in the frame format. As mentioned above, one symbol of the preamble code refers to a sequence symbol formed using pulses of a predetermined pattern (e.g., -, 0, +). Nrg is the required number of times to recognize one symbol of the preamble code. The receiver can receive the transmitted data of UWB communication only after recognizing one symbol of the preamble code the required number of times Nrg.

[0049] The required number of recognition attempts Nrg is a predetermined number that depends on the device. In the example shown in FIG. 6, the required number of recognition attempts Nrg is, for example, four. The minimum recognition period for the preamble can be calculated by multiplying tsym by the device-dependent required number of recognition attempts Nrg. In this embodiment, the reception mode start time τstart is set to a time that is earlier than the expected reception time τnext by the period obtained by the calculation formula (tSFD + tsym × Nrg).

[0050] By determining the receive mode start time in this manner, the start of the period in which UWB communication transmission data can be received can be set as close as possible to the expected reception time. This reduces the possibility of being affected by interference from jamming waves and improves the success rate of communication. Note that the receive mode start time τstart may be set to a time earlier than the expected reception time τnext by the period (time) calculated using the formula (tSFD + tsym × Nrg), or by an appropriate margin time determined through experiments, etc.

[0051] <3. Detailed examples of communication methods> Hereinafter, a method for performing UWB communication between the master device 10 and the slave devices 20a to 20d using the polling method will be described with reference to several examples. Before describing the examples, problems that may occur in UWB communication using the polling method will be described.

[0052] Fig. 7 is a diagram for explaining UWB communication using the polling method. In the example shown in Fig. 7, as in the present embodiment, the number of slave devices 20 performing UWB communication with master device 10 using the polling method is four. Also, the symbol "T" shown in Fig. 7 indicates a polling period. In the example shown in Fig. 7, master device wireless communication unit 13 and slave device wireless communication unit 23 each include one transmitter and one receiver, or one transceiver.

[0053] At the end of each polling period T, the master unit 10 transmits information to one of the four slave units 20a to 20d, which is determined in accordance with a predetermined order (polling order). Specifically, the master unit 10 transmits information to the first slave unit 20a, the second slave unit 20b, the third slave unit 20c, and the fourth slave unit 20d in that order for each polling period. After transmitting information to the first slave unit 20a through the fourth slave unit 20d in that order, the master unit 10 returns to the first slave unit 20a and repeats the information transmission to the slave units 20 in the order described above.

[0054] The master unit 10 switches from idle mode to transmission mode at the start of the polling period T, and starts transmitting information to the slave unit 20 that is the transmission target, determined by the order in the polling method. When a pre-programmed period of time has elapsed since the start of the transmission mode, the master unit 10 switches from transmission mode to idle mode, and ends transmission.

[0055] Each of the slave units 20a to 20d transitions from idle mode to reception mode in accordance with the timing at which the master unit 10 transmits information intended for that unit, according to a schedule previously determined between the slave units 20a to 20d and the master unit 10. As a result, each of the slave units 20a to 20d receives information from the master unit 10. When a predetermined period of time preprogrammed from the start of reception mode has elapsed, each of the slave units 20a to 20d transitions from reception mode to idle mode, and ends reception.

[0056] When each of the slave devices 20a to 20d receives information intended for itself, it switches from idle mode to transmission mode at a timing pre-arranged with the base device 10 and transmits a response to the base device 10. When a pre-programmed period of time has elapsed since the start of transmission mode for transmitting the response, each of the slave devices 20a to 20d switches to idle mode and ends transmission. Meanwhile, the base device 10 switches from idle mode to reception mode in time with the response transmission and receives the response transmission from the slave device 20. When a pre-programmed period of time has elapsed since the start of reception mode for receiving the response transmission, the base device 10 switches to idle mode and ends reception. The response transmission from each of the slave devices 20a to 20d and the reception of the response transmission by the base device 10 are carried out within each polling period T.

[0057] As can be seen from the above explanation, the receiving side starts receiving in accordance with the transmission timing of the transmitting side and is in the receiving state (receiving mode) for only a limited period of time. This reduces the possibility that the receiving side will fail to receive the transmitted wave due to interference from the interfering wave.

[0058] In the example shown in FIG. 7, each of the slave devices 20a to 20d is configured to enter the reception mode only when the master device 10 transmits information intended for that device, but this is merely an example. As shown in FIG. 8, which will be described later, each of the slave devices 20a to 20d may be configured to enter the reception mode even when the master device 10 transmits information intended for another slave device 20, not for that device. In particular, all of the slave devices 20a to 20d may enter the reception mode when the master device 10 transmits information according to the polling period T. Even with this configuration, no particular problem occurs because each of the slave devices 20a to 20d can recognize from the content of the information if the information is not intended for that device. Each of the slave devices 20a to 20d may be configured to transmit a response if the information is intended for that device, and not transmit a response if the information is not intended for that device.

[0059] Incidentally, each of the slave devices 20a to 20d receiving information from the master device 10 may request the master device 10 to transmit information at a timing different from the timing of the response transmission described above. However, in the communication method shown in Fig. 7, each of the slave devices 20a to 20d cannot transmit information to the master device 10 until it is time for it to transmit its next response.

[0060] In the example shown in FIG. 7, the first slave device 20a issues a transmission request to the master device 10 in the polling cycle T (the polling cycle T in which the second slave device 20b's turn comes) after completing the response transmission in its turn (polling order). The portion indicated by the symbol "x" in FIG. 7 corresponds to the timing of the transmission request. In this case, the first slave device 20a transmits the contents of the previously issued transmission request to the master device 10 using the timing of the response transmission to the master device 10 (indicated by (a) in the figure) that occurs in the third polling cycle T counted from the timing of the transmission request.

[0061] Such delayed transmission from the slave device 20 to the master device 10 reduces the real-time nature of communication. For this reason, a communication method is desired that can transmit a transmission request generated by the slave device 20 to the master device 10 as quickly as possible. The following embodiment is configured in consideration of this point.

[0062] [3-1. First Example] 8 is a diagram for explaining an outline of the communication method of the first embodiment. In the first embodiment, each of the master device wireless communication unit 13 and the slave device wireless communication unit 23 includes one transmitter and one receiver. Note that each of the master device wireless communication unit 13 and the slave device wireless communication unit 23 may include one transmitter and one receiver.

[0063] As shown in FIG. 8, master device 10 performs communication (UWB communication) during each polling cycle T, by providing a transmission mode period 51, a first reception mode period 52, and a second reception mode period 53.

[0064] The transmission mode period 51 is set to transmit information to the slave devices 20. The transmission mode period 51 is the same as the period during which the master device 10 is in the transmission mode to transmit information to the slave devices 20 that are the transmission targets in a predetermined polling order, as previously described with reference to FIG. 7. The transmission mode period 51 starts in synchronization with the start timing of the polling cycle T. The transmission mode period 51 ends when a pre-programmed fixed period has elapsed from the start of the period.

[0065] The first reception mode period 52 is the same as the period during which the base unit 10 enters reception mode to receive a response transmission from the slave unit 20 to which information has been transmitted from the base unit 10, as described above with reference to FIG. 7 . The first reception mode period 52 is a period during which the base unit 10 receives a response transmission from the slave unit 20 in response to its own communication request. The first reception mode period 52 is set within the polling period T so that reception begins in synchronization with the response transmission from the slave unit 20 that has received the transmission from the base unit 10. The start timing of the first reception mode period 52 is a period agreed upon between the base unit 10 and the slave unit 20. The first reception mode period 52 ends when a pre-programmed fixed period has elapsed from the start of the period. The first reception mode period 52 begins during the polling period T and ends during the polling period T.

[0066] The second reception mode period 53 is a period that does not exist in FIG. 7 described above. The second reception mode period 53 is a period during which an interrupt transmission from one of the multiple slave units 20 is received. The second reception mode period 53 is set so that reception begins in accordance with the timing of an interrupt transmission that the slave unit 20 performs within the polling period T, which is different from the timing of the response transmission described above. The start timing of the second reception mode period 53 is a period agreed upon between the master unit 10 and the slave unit 20. The second reception mode period 53 ends when a pre-programmed fixed period has elapsed from the start of the period. The second reception mode period 53 begins during the polling period T and ends during the polling period T.

[0067] In detail, the master device 10 performs communication by setting a transmission mode period 51, a first reception mode period 52, and a second reception mode period 53 in that order within the polling cycle T. The master device 10 enters an idle mode period 54 in which it does not perform communication between the transmission mode period 51 and the first reception mode period 52, and between the first reception mode period 52 and the second reception mode period 53. An idle mode period 54 is also set between the second reception mode period 53 and the transmission mode period 51 of the next polling cycle T.

[0068] According to the communication method of the first embodiment, the master device 10 is configured to perform polling-based UWB communication by providing a receive mode period (second receive mode period 53) for interrupt transmission from the slave device 20 to the master device 10 within each polling cycle T. Therefore, even if it is not the slave device's turn to transmit a response, each slave device 20a to 20d can transmit to the master device 10 by utilizing the receive mode period for interrupt transmission. In other words, the slave device 20 can shorten the communication waiting time for a communication request generated in itself. This will be described in more detail with reference to an example shown in FIG. 8.

[0069] In the example shown in FIG. 8, the first slave device 20a issues a transmission request to the master device 10 in the polling cycle T next to its turn (the polling cycle T in which it is the turn of the second slave device 20b). The portions indicated by the symbol "x" in FIG. 8 correspond to the timing at which the transmission request is issued. The first slave device 20a does not wait for the timing of response transmission in the polling cycle T in which it is next its turn (the polling cycle T three cycles later), but transmits information (interrupt transmission) to the master device 10 by utilizing the most recent receive mode period for interrupt transmission. In this example, the most recent receive mode period for interrupt transmission is the second receive mode period 53 (see (a) in FIG. 8) provided in the polling cycle T in which it is the turn of the second slave device 20b.

[0070] The receive mode period for interrupt transmission (second receive mode period 53) in this embodiment is configured to start in synchronization with the interrupt transmission from the slave device 20. This reduces the possibility that the master device 10 will fail to receive the transmission wave for interrupt transmission transmitted from the slave device 20 due to interference with the transmission wave (interference wave) in another system.

[0071] Fig. 9 is a flowchart illustrating the flow of a communication method executed by the parent device 10 of the first embodiment. The flowchart shown in Fig. 9 illustrates the technical content of a computer program (communication program) that causes a computer (parent device controller 11) included in the parent device 10 to function as a means for executing the communication method of the first embodiment.

[0072] As can be seen from the above description, the master device 10 of the first embodiment is a communication device that performs UWB communication using a polling method as a master device with a plurality of slave devices 20. The master device (communication device) 10 is configured to perform communication by providing a first reception mode period 52 (a reception period for response transmission from slave devices 20) and a second reception mode period 53 (a reception period for interrupt transmission from slave devices 20) within a polling cycle. By providing the second reception mode period 53 in addition to the first reception mode period 52 within the polling cycle T, when a transmission request occurs at a timing different from the timing of the response transmission on the slave device 20 side, it is possible to transmit a transmission in response to the transmission request as soon as possible.

[0073] The flowchart shown in Fig. 9 starts after a communication agreement is made in advance between the master unit 10 and the plurality of slave units 20a to 20d. The flowchart shown in Fig. 9 continues until a reason for terminating communication according to the predetermined communication schedule occurs. The start of communication according to the communication schedule may occur, for example, when the ACC is turned on by operating the ignition key of the automobile C1. The reason for terminating communication may occur when the ACC is turned off or when a communication error occurs.

[0074] 9, in step S1, the master controller 11 monitors whether it is the timing to start transmission according to the polling period T. If it is the timing to start transmission (Yes in step S1), the process proceeds to the next step S2. If it is not the timing to start transmission (No in step S1), the monitoring process in step S1 continues.

[0075] In step S2, the master controller 11 transitions the master wireless communication unit 13 (a transceiver in this embodiment) from idle mode to transmission mode. This transition to transmission mode initiates a transmission mode period 51 shown in FIG. 8. With the start of transmission mode period 51, information is transmitted from the master 10 to the slave 20 to be transmitted to in a predetermined polling order. Once the master wireless communication unit 13 has transitioned to transmission mode, the process proceeds to the next step S3.

[0076] In step S3, the parent controller 11 monitors whether it is time to end the transmission of information to the child device 20. The timing to end the transmission is when a certain period of time has elapsed since the start of transmission, and this certain period of time is a predetermined period of time. If it is time to end the transmission (Yes in step S3), the process proceeds to the next step S4. If it is not time to end the transmission (No in step S3), the monitoring process of step S3 continues.

[0077] In step S4, the master controller 11 transitions the master wireless communication unit 13 from the transmission mode to the idle mode, thereby ending the transmission mode period 51. Once the master wireless communication unit 13 has transitioned to the idle mode, the process proceeds to the next step S5.

[0078] In step S5, the master controller 11 monitors whether it is time to receive a response transmission from the slave 20. The reception timing is determined by a prearranged agreement between the master 10 and the slave 20. If it is time to receive a response transmission (Yes in step S5), the process proceeds to the next step S6. If it is not time to receive a response transmission (No in step S5), the monitoring process in step S5 continues.

[0079] In step S6, the master controller 11 transitions the master wireless communication unit 13 from the idle mode to the reception mode. This transition to the reception mode initiates a first reception mode period 52 shown in Fig. 8. The start of the first reception mode period 52 makes it possible to receive a response transmission from the slave device 20, and the response transmission from the slave device 20 is received. Once the master wireless communication unit 13 has transitioned to the reception mode, the process proceeds to the next step S7.

[0080] In step S7, the parent controller 11 monitors whether it is time to end reception of the response transmission from the child device 20. The timing to end reception is when a certain period of time has elapsed since reception began, and this certain period of time is a period that is determined in advance taking into account the period of the response transmission. If it is time to end reception (Yes in step S7), the process proceeds to the next step S8. If it is not time to end reception (No in step S7), the monitoring process of step S7 continues.

[0081] In step S8, the master controller 11 transitions the master wireless communication unit 13 from the reception mode to the idle mode, thereby ending the first reception mode period 52. Once the master wireless communication unit 13 has transitioned to the idle mode, the process proceeds to the next step S9.

[0082] In step S9, the parent controller 11 monitors whether it is time to receive an interrupt transmission from the child device 20. The reception timing is determined by a prearranged agreement between the parent device 10 and the child device 20. If it is time to receive an interrupt transmission (Yes in step S9), the process proceeds to the next step S10. If it is not time to receive an interrupt transmission (No in step S9), the monitoring process in step S9 continues.

[0083] In step S10, the master controller 11 transitions the master wireless communication unit 13 from idle mode to reception mode. This transition to reception mode initiates the second reception mode period 53 shown in FIG. 8. The start of the second reception mode period 53 makes it possible to receive an interrupt transmission from the slave device 20, and if an interrupt transmission occurs, the interrupt transmission is received. Note that an interrupt transmission from the slave device 20 is not always present, and there may be no interrupt transmission. Once the master wireless communication unit 13 has transitioned to reception mode, the process proceeds to the next step S11.

[0084] In step S11, the parent controller 11 monitors whether it is time to end reception of the interrupt transmission from the child device 20. The timing to end reception is when a certain period of time has elapsed since reception began, and this certain period of time is a period that is determined in advance taking into account the period of the interrupt transmission. If it is time to end reception (Yes in step S11), the process proceeds to the next step S12. If it is not time to end reception (No in step S11), the monitoring process of step S11 continues.

[0085] In step S12, the master controller 11 transitions the master wireless communication unit 13 from the reception mode to the idle mode, thereby ending the second reception mode period 53. Upon completion of the transition of the master wireless communication unit 13 to the idle mode, the process returns to step S1 described above, and the processes from step S1 onwards are carried out.

[0086] 10 is a flowchart illustrating the flow of a communication method executed by the slave device 20 of the first embodiment. The flowchart shown in FIG. 10 illustrates the technical content of a computer program (communication program) that causes a computer (slave device controller 21) included in the slave device 20 to function as a means for executing the communication method in the slave device 20.

[0087] As can be seen from the above description, the slave device 20 in the first embodiment is a communication device that performs UWB communication using a polling method as a slave device with the master device 10. The slave device (communication device) 20 performs interrupt transmission at a timing that is set in a second reception mode period 53 that is set separately from a first reception mode period 52 in which the master device 10 receives a response transmission from the slave device 20 (which may be the slave device itself or another device) within the polling period T. By using the second reception mode period 53, the slave device 20 can transmit to the master device 10 at a timing different from the order predetermined by the polling method. Therefore, when a transmission request occurs at a timing different from its own order in the polling method, the slave device 20 can execute transmission in response to the transmission request as soon as possible.

[0088] The flowchart shown in Fig. 10 starts after a communication agreement is made in advance between the master unit 10 and the multiple slave units 20a to 20d. The flowchart shown in Fig. 10 continues until a reason for terminating communication according to the predetermined communication schedule occurs. The start of communication according to the communication schedule may occur, for example, when the ACC is turned on by operating the ignition key of the automobile C1. The reason for terminating communication may occur when the ACC is turned off or when a communication error occurs.

[0089] 10, in step N1, slave unit controller 21 monitors whether it is time to start receiving information in accordance with the timing of transmitting information from master unit 10 according to polling period T. If it is time to start receiving information (Yes in step N1), the process proceeds to the next step N2. If it is not time to start receiving information (No in step N1), the monitoring process in step N1 continues.

[0090] In step N2, the slave device controller 21 transitions the slave device wireless communication unit 23 (a transceiver in this embodiment) from idle mode to reception mode. This transition to reception mode initiates the slave device side reception mode period 55 shown in FIG. 8. With the start of the slave device side reception mode period 55, it becomes possible to receive information transmission in accordance with the polling cycle T of the master device 10, and the transmission from the master device 10 is received. Once the slave device wireless communication unit 23 has transitioned to reception mode, the process proceeds to the next step N3.

[0091] In step N3, slave unit controller 21 monitors whether it is time to end reception of information transmitted from master unit 10 in accordance with polling period T. The timing to end reception is when a certain period of time has elapsed since reception began, and this certain period of time is a period determined in advance in consideration of transmission mode period 51 of master unit 10. If it is time to end reception (Yes in step N3), the process proceeds to the next step N4. If it is not time to end reception (No in step N3), the monitoring process of step N3 continues.

[0092] In step N4, slave device controller 21 transitions slave device wireless communication unit 23 from the reception mode to the idle mode, thereby ending slave device side reception mode period 55. Once slave device wireless communication unit 23 has transitioned to the idle mode, the process proceeds to the next step N5.

[0093] In step N5, slave unit controller 21 determines whether or not a response transmission to master unit 10 is necessary. Slave unit controller 21 determines that a response transmission is necessary if the transmission from master unit 10 received during the previous slave unit side reception mode period 55 is addressed to slave unit controller 21, and determines that a response transmission is unnecessary if the transmission from master unit 10 is not addressed to slave unit controller 21. If it is determined that a response transmission is necessary (Yes in step N5), the process proceeds to the next step N6. If it is determined that a response transmission is not necessary (No in step N5), the process proceeds to step N10.

[0094] In step N6, the slave unit controller 21 monitors whether it is time to start transmitting a response to the master unit 10. The start timing is determined by a prearranged agreement between the master unit 10 and the slave unit 20. If it is time to start transmitting a response (Yes in step N6), the process proceeds to the next step N7. If it is not time to start transmitting a response (No in step N6), the monitoring process in step N6 continues.

[0095] In step N7, the slave device controller 21 transitions the slave device wireless communication unit 23 from the idle mode to the transmission mode. This transition to the transmission mode initiates a response transmission mode period 56 shown in Fig. 8. The start of the response transmission mode period 56 initiates a response transmission from the slave device 20 to the master device 10. Once the slave device wireless communication unit 23 has transitioned to the transmission mode, the process proceeds to the next step N8.

[0096] In step N8, the slave controller 21 monitors whether it is time to end the response transmission. The timing to end the response transmission is when a certain period of time has elapsed since the start of the response transmission, and this certain period of time is a predetermined period of time. If it is time to end the response transmission (Yes in step N8), the process proceeds to the next step N9. If it is not time to end the response transmission (No in step N8), the monitoring process in step N8 continues.

[0097] In step N9, slave device controller 21 transitions slave device wireless communication unit 23 from the transmission mode to the idle mode, thereby ending response transmission mode period 56. Upon completion of transition of slave device wireless communication unit 23 to the idle mode, the process proceeds to the next step N10.

[0098] In step N10, slave unit controller 21 determines whether an interrupt transmission to master unit 10 is necessary. An interrupt transmission is a transmission from slave unit 20 to master unit 10 when information to be transmitted to master unit 10 occurs at slave unit 20 at a timing different from the timing of the response transmission to master unit 10. A request for an interrupt transmission is not always generated, and may not be generated. The timing for checking the necessity of an interrupt transmission can be determined appropriately so that the interrupt transmission is initiated when the interrupt transmission is received during second receive mode period 53 provided within the current polling cycle T. If it is determined that an interrupt transmission is necessary (Yes in step N10), the process proceeds to the next step N11. If it is determined that an interrupt transmission is not necessary (No in step N10), the process returns to step N1 described above, and the processes from step N1 onwards are carried out.

[0099] In step N11, the slave unit controller 21 monitors whether it is time to start an interrupt transmission to the master unit 10. The start timing is determined by a prearranged agreement between the master unit 10 and the slave unit 20 so that the interrupt transmission is received during the second receive mode period 53. If it is time to start the interrupt transmission (Yes in step N11), the process proceeds to the next step N12. If it is not time to start the interrupt transmission (No in step N11), the monitoring process in step N11 continues.

[0100] In step N12, the slave device controller 21 transitions the slave device wireless communication unit 23 from the idle mode to the transmission mode. The transition to the transmission mode initiates an interrupt transmission mode period 57 shown in Fig. 8. The start of the interrupt transmission mode period 57 causes an interrupt transmission from the slave device 20 to the master device 10. Once the slave device wireless communication unit 23 has transitioned to the transmission mode, the process proceeds to the next step N13.

[0101] In step N13, the slave controller 21 monitors whether it is time to end the interrupt transmission. The timing to end the interrupt transmission is when a certain period of time has elapsed since the start of the interrupt transmission, and this certain period of time is a predetermined period of time. If it is time to end the interrupt transmission (Yes in step N13), the process proceeds to the next step N14. If it is not time to end the interrupt transmission (No in step N13), the monitoring process in step N13 continues.

[0102] In step N14, slave device controller 21 transitions slave device wireless communication unit 23 from the transmission mode to the idle mode, thereby ending interrupt transmission mode period 57. Upon completion of transition of slave device wireless communication unit 23 to the idle mode, the process returns to step N1 described above, and the processes from step N1 onwards are carried out.

[0103] [3-2. Second Example] Next, a second embodiment will be described. In describing the second embodiment, explanations of the contents that overlap with the previously described embodiment will be omitted as appropriate.

[0104] FIG. 11 is a diagram for explaining an outline of a communication method of the second embodiment. The communication method of the second embodiment is generally similar to the communication method of the first embodiment described above (see FIG. 8). However, in the second embodiment, a usage restriction is set for each of the multiple slave devices 20a to 20d regarding the second reception mode period 53 used for interrupt transmission. This point differs from the first embodiment. By setting a usage restriction for the second reception mode period 53 that each slave device 20a to 20d can use, it is possible to reduce the possibility that the timing of interrupt transmissions will overlap between multiple slave devices 20. As a result, it is possible to reduce the possibility that the interrupt transmission will fail. Below, this difference from the first embodiment will be explained in detail.

[0105] In the example shown in Fig. 11, the first slave device 20a and the fourth slave device 20d issue transmission requests to the master device 10 within the polling period T in which the second slave device 20b is to be polled. The portions indicated by the symbols "x" in Fig. 11 correspond to the timings at which the transmission requests are issued.

[0106] In this example, as in the first embodiment, it is assumed that no particular restrictions are placed on the second reception mode period 53 used during interrupt transmission. In this case, both the first handset 20a and the fourth handset 20d will perform interrupt transmissions using the second reception mode period 53 that is set within the polling cycle T in which the second handset 20b is to be polled. In other words, the two interrupt transmissions will start transmission at the same time. As a result, interference will occur between the two interrupt transmissions, and the master unit 10 may fail to receive the interrupt transmissions.

[0107] Furthermore, if two interrupt transmissions interfere with each other and the parent device 10 fails to receive either of the interrupt transmissions, the following phenomenon may occur: Both the first child device 20a and the fourth child device 20d perform interrupt transmissions during the second reception mode period 53 in the next polling cycle T (in the example shown in FIG. 11, the polling cycle T in which the third child device 20c is the one to be polled). As a result, interference may occur again between the two interrupt transmissions, and the parent device 10 may fail to receive the interrupt transmissions. In other words, there is a possibility that failure to receive the interrupt transmissions from the parent device 10 may be repeated.

[0108] 11, the fourth slave unit 20d is described as performing an interrupt transmission even when it is its turn to poll. This is merely an example, and when it is its turn to poll, the fourth slave unit 20d may transmit information that was scheduled to be transmitted in an interrupt transmission, including the information in the response transmission to the master unit 10. However, for example, when there is insufficient capacity for data transmission at the time of response transmission, as shown in FIG. 11, the slave unit 20 may perform an interrupt transmission even when it is its turn to poll. Note that an interrupt transmission in its turn to poll may also be performed when a transmission request occurs immediately after a response transmission, for example.

[0109] In consideration of the problem of interference due to interrupt transmission as described above, in this embodiment, as described above, a limit is imposed on the second receive mode period 53 during which each of the slave devices 20a to 20d performs interrupt transmission. Specifically, for each of the multiple slave devices 20a to 20d, the polling period in which the interrupt transmission can be performed is randomly determined from the time when a request for interrupt transmission is generated. The process of randomly determining the polling period T during which the interrupt transmission can be performed is performed separately for each of the slave devices 20a to 20d. For example, the slave device controller 21 included in each of the slave devices 20a to 20d randomly determines the polling period T during which the interrupt transmission can be performed.

[0110] If the timing for interrupt transmission is delayed beyond the number of polling periods T that exist between the first response transmission and the next response transmission in the polling order, the purpose of enabling interrupt transmission by providing second receive mode period 53 is diminished. For this reason, it is preferable to randomly determine the order of interrupt transmission so that interrupt transmission is performed in a polling period T that is within Xth polling period T, including the polling period T at the time the interrupt transmission request is generated. Here, X is a number obtained by subtracting 1 from the number of slave devices 20 that perform UWB communication with master device 10 using the polling method.

[0111] 11, the number of slave devices 20 performing UWB communication with the master device 10 by the polling method is four. Therefore, in a preferred embodiment, the order of interrupt transmission is determined randomly so that the interrupt transmission is performed in a polling period T that is within the first three polling periods T, including the polling period T at which the interrupt transmission request is generated. In detail, it is determined that the first slave device 20a and the fourth slave device 20d will perform interrupt transmission in one of the interrupt transmission mode periods 57 shown in FIG. 11 (a), (b), and (c).

[0112] This reduces the possibility that the timing of the interrupt transmission of the first handset 20a and the timing of the interrupt transmission of the fourth handset 20d will overlap. Even if the timing of the interrupt transmission of the first handset 20a and the interrupt transmission of the fourth handset 20d overlaps at the first random determination, it is considered unlikely that they will overlap at the next random determination. In other words, the method of this embodiment reduces the possibility of an interrupt transmission failure.

[0113] In this embodiment, the method for restricting the use of the second receive mode period 53 used for interrupt transmission is to randomly determine the polling period T for the interrupt transmission, but this is merely an example. The following configuration may also be used as a method for restricting the use of the second receive mode period 53 used for interrupt transmission. That is, for each of the multiple slave devices 20a to 20d, the polling period T in which the interrupt transmission can be performed from the time a request for interrupt transmission is generated may be determined with regularity. Even with such a configuration, it is possible to reduce the possibility of multiple interrupt transmissions overlapping, thereby reducing the possibility of the interrupt transmission failing.

[0114] The above-mentioned regularity may be obtained, for example, by linking it to the number of the slave device 20 to which the master device 10 is to transmit in the polling cycle T in which the request for interrupt transmission is generated. In the example shown in FIG. 11, the number of the first slave device 20a may be "1," the number of the second slave device 20b may be "2," the number of the third slave device 20c may be "3," and the number of the fourth slave device 20d may be "4." In the example shown in FIG. 11, the request for interrupt transmission is generated for the first slave device 20a and the fourth slave device 20d when the second slave device 20b is in the polling order. Therefore, in the example shown in FIG. 11, the number of the slave device 20 to which the master device 10 is to transmit in the polling cycle T in which the request for interrupt transmission is generated is "2."

[0115] For example, a configuration may be adopted in which interrupt transmission is permitted only to a slave unit 20 having the same number as the slave unit 20 to which the master unit 10 is to transmit in the polling period T when the request for interrupt transmission is generated. In this case, in the example shown in FIG. 11, the second slave unit 20b is permitted to perform interrupt transmission. As another example, a configuration may be adopted in which interrupt transmission is permitted only to a slave unit 20 having a number obtained by adding or subtracting N (N is any natural number) from the number of the slave unit 20 to which the master unit 10 is to transmit in the polling period T when the request for interrupt transmission is generated. In this configuration, N=1 is subtracted. In this case, in the example shown in FIG. 11, the first slave unit 20a is permitted to perform interrupt transmission. As another example, a configuration may be adopted in which interrupt transmission is permitted to a slave unit 20 having a number within ±Nth of the number of the slave unit 20 to which the master unit 10 is to transmit in the polling period T when the request for interrupt transmission is generated. In this configuration, N=1. In this case, in the example shown in FIG. 11, the first handset 20a, the second handset 20b, and the third handset 20c are permitted to make interrupt transmission.

[0116] As another example, the slave device 20 that the master device 10 has designated as the transmission target in the polling cycle T at which the request for interrupt transmission has occurred may be used as a reference, and the slave device 20 that will be polled next latest may be permitted to perform the interrupt transmission. In the example shown in Fig. 11, the slave device 20 that the master device 10 has designated as the transmission target in the polling cycle T at which the request for interrupt transmission has occurred is the second slave device 20b. In this case, the slave device 20 that will be polled next latest is determined to be the first slave device 20a, and the first slave device 20a is permitted to perform the interrupt transmission.

[0117] As another example, a configuration may be adopted in which, based on the slave device 20 that the master device 10 has designated as the transmission target in the polling cycle T in which the request for interrupt transmission has occurred, interrupt transmission is permitted for the slave devices 20 up to Nth in order of their next polling. In the example shown in Fig. 11, the slave device 20 that the master device 10 has designated as the transmission target in the polling cycle T in which the request for interrupt transmission has occurred is the second slave device 20b. Here, N = 2. In this case, interrupt transmission is permitted for the first slave device 20a, which has the latest next polling order, and the fourth slave device 20d, which has the next latest next polling order.

[0118] [3-3. Third Example] Next, a third embodiment will be described. In describing the third embodiment, descriptions of content that overlaps with the previously described embodiments will be omitted as appropriate. Also, in this embodiment, as in the first and second embodiments, the master device 10 is a communication device that serves as a master device and performs UWB communication using a polling method with a plurality of slave devices 20. Also, each slave device 20 is a communication device that serves as a slave device and performs UWB communication using a polling method with the master device 10.

[0119] FIG. 12 is a block diagram showing the configuration of the master device wireless communication unit 13A and the slave device wireless communication unit 23A in the third embodiment.

[0120] 12, the master device wireless communication unit 13A includes a transmitter 131, a first receiver 132, and a second receiver 133. The transmitter 131 is used to transmit information to the slave device 20. The first receiver 132 is used to receive a response transmission from the slave device 20 that has received a transmission from the master device 10. The second receiver 133 is used to receive an interrupt transmission that the slave device 20 performs separately from the response transmission.

[0121] That is, the master device 10 includes a first receiver 132 that receives response transmissions from the multiple slave devices 20 that have received a transmission from the master device 10, and a second receiver 133 that receives interrupt transmissions from the multiple slave devices 20. The UWB communication method of this embodiment is performed by providing the master device 10 with the first receiver 132 that receives response transmissions from the multiple slave devices 20 that have received a transmission from the master device 10, and the second receiver 133 that receives interrupt transmissions from the multiple slave devices 20. This embodiment differs from the first and second embodiments described above in that the second receiver 133 is provided.

[0122] The slave device wireless communication unit 23A includes a transmitter 231 and a receiver 232. The transmitter 231 is used for response transmission and interrupt transmission to the master device 10. The receiver 232 is used for receiving transmissions from the master device 10. The configuration of the slave device wireless communication unit 23A is the same as in the first and second embodiments described above.

[0123] In addition, in parent device 10, transmitter 131 and first receiver 132 may be combined into one transceiver. In addition, in child device 20, transmitter 231 and receiver 232 may be combined into one transceiver.

[0124] Fig. 13 is a diagram for explaining an outline of the communication method of the third embodiment. In Fig. 13, "parent transmitter" refers to transmitter 131. Furthermore, "parent receiver 1" refers to first receiver 132, and "parent receiver 2" refers to second receiver 133. Furthermore, "Tx" in the parts indicating first to fourth child devices 20a to 20d refers to transmitter 231, and "Rx" refers to receiver 232.

[0125] In the third embodiment, as in the first and second embodiments, the master device 10 performs UWB communication using a polling method with the four slave devices 20a to 20d. The master device 10 transmits information to the slave devices 20 to be transmitted to at every polling period T in a predetermined polling order. In this embodiment, the polling order is also the first slave device 20a, the second slave device 20b, the third slave device 20c, and the fourth slave device 20d.

[0126] The master device 10 performs UWB communication by providing a transmission mode period 51 within each polling cycle T. During the transmission mode period 51, information is transmitted to the slave device 20 that is the transmission target in a predetermined polling order. The transmission mode period 51 starts in synchronization with the start timing of the polling cycle T. The transmission mode period 51 ends when a pre-programmed fixed period has elapsed from the start of the period. These points are the same as those in the first and second embodiments.

[0127] Furthermore, each of the slave devices 20a to 20d performs UWB communication during each polling cycle T, with a slave device-side reception mode period 55 and a response transmission mode period 56. The slave device-side reception mode period 55 starts in accordance with the timing at which the master device 10 transmits information in accordance with the polling cycle T, and ends when a pre-programmed fixed period has elapsed since the start of the period. The response transmission mode period 56 starts at a timing pre-agreed with the master device 10, and ends when a pre-programmed fixed period has elapsed since the start of the period. These points are the same as those in the first and second embodiments.

[0128] In this embodiment, the first receiver 132 and the second receiver 133 provided in the master unit 10 are always ready to receive. This differs from the first and second embodiments. The always ready to receive state is a state in which the receivers are continuously in reception mode. In this specification, "a state in which reception mode is continuously in operation" also includes a state in which reception mode is momentarily canceled and then immediately resumed, in which the reception mode is essentially considered to be continuously in operation.

[0129] In Fig. 13, "A" and "B" are symbols used to indicate different preamble codes used in communication. As shown in Fig. 13, in this embodiment, the first receiver 132 and the second receiver 133 use different preamble codes for communication. In other words, in the communication method of this embodiment, communication is performed using different preamble codes for response transmission and interrupt transmission.

[0130] With this configuration, even if a response transmission performed by a certain slave device 20 and an interrupt transmission performed by a different slave device 20 are performed at the same time, the preamble codes used for the communications are different, so the possibility of interference between the two can be reduced. That is, according to the configuration of this embodiment, even if the receive mode period for interrupt transmission (second receive mode period 53) shown in the first and second embodiments is not provided, the slave device 20 can perform an interrupt transmission at an early stage after a transmission request to the master device 10 is generated. In other words, according to this embodiment, communication efficiency is improved compared to the first and second embodiments, and each of the slave devices 20a to 20d can perform a transmission to the master device 10 even if it is not its turn to perform a response transmission.

[0131] In the example shown in FIG. 13, preamble code "A" is used for normal communication between the base unit 10 and each of the slave units 20a to 20d in accordance with the polling method. Furthermore, preamble code "B" is used for interrupt transmissions that may occur irregularly in each of the slave units 20a to 20d. In detail, transmitter 131 and first receiver 132 provided in the base unit 10 are always used for communication using preamble code "A". Second receiver 133 provided in the base unit 10 is always used for communication using preamble code "B". Transmitter 231 provided in each of the slave units 20a to 20d is used for communication using preamble code "A" during response transmission, and is used for communication using preamble code "B" during interrupt transmission. The preamble code to be used is switched under the control of slave unit controller 21. The receiver 232 included in the base unit 10 is always used for communication using the preamble code "A".

[0132] In the example shown in Fig. 13, the first slave device 20a issues a transmission request to the master device 10 in the next polling cycle T (the polling cycle T in which it is the second slave device 20b's turn). The part indicated by the symbol "x" in Fig. 13 corresponds to the timing at which the transmission request is issued. After the transmission request is issued, the first slave device 20a immediately sends an interrupt transmission to the master device 10 using the preamble code "B" because it has no plans to send a response.

[0133] In this configuration, there is a possibility that the timing of the interrupt transmission from the first handset 20a and the response transmission from the second handset 20b may overlap. However, the interrupt transmission from the first handset 20a is a transmission using preamble code "B," while the response transmission from the second handset 20b is a transmission using preamble code "A." Due to the difference in the preamble codes used, the two communications are properly received by the receivers 132 and 133 without interference. In particular, the interrupt transmission from the first handset 20a is received by the second receiver 133, and the response transmission from the second handset 20b is received by the first receiver 132.

[0134] Specifically, there are 32 types of preamble codes in UWB communication, from "1" to "32." Preamble codes "1" to "8" are low-code preamble codes with a PRF (Pulse Repletion Frequency) of 16 MHz. Preamble codes "9" to "24" are high-code preamble codes with a PRF of 64 MHz. Preamble codes "25" to "32" are preamble codes with a PRF of 111 MHz that are intended to be used primarily for ranging. Preamble codes "25" to "32" can also be used for data communication and radar communication. Here, to clearly distinguish between low-code and high-code preamble codes, preamble codes "25" to "32" are referred to as ranging preamble codes. Previous research has shown that when multiple UWB communications are performed simultaneously, each communication is more likely to succeed if the preamble codes are different low codes (1 to 8), different high codes (9 to 24), different ranging preamble codes (25 to 32), or different high codes and ranging preamble codes (9 to 32). For this reason, it is preferable that the preamble codes "A" and "B" are different preamble codes selected from a low-code preamble code group, different preamble codes selected from a high-code preamble code group, different preamble codes selected from a ranging preamble code group, or a preamble code selected from a high-code preamble code group and a preamble code selected from a ranging preamble code group.

[0135] 13, the first receiver 132 is in a constant reception state, but this is merely an example. The first receiver 132 may be configured to start reception in synchronization with the timing of a response transmission from the slave device 20 and to end reception after a certain period of time has elapsed. That is, in this embodiment, it is sufficient that, of the first receiver 132 and the second receiver 133, at least the second receiver 133 is in a constant reception state. This configuration ensures flexibility in the timing of interrupt transmission.

[0136] Fig. 14 is a flowchart illustrating the flow of a communication method executed by the parent device 10 of the third embodiment. The flowchart shown in Fig. 14 shows the technical content of a computer program (communication program) that causes a computer (parent device controller 11) included in the parent device 10 to function as a means for executing the communication method of the third embodiment.

[0137] The flowchart shown in Fig. 14 starts after a communication agreement is made in advance between the master unit 10 and the multiple slave units 20a to 20d. The flowchart shown in Fig. 14 continues until a reason for terminating communication according to the predetermined communication schedule occurs. The start of communication according to the communication schedule may occur, for example, when the ACC is turned on by operating the ignition key of the automobile C1. The reason for terminating communication may occur when the ACC is turned off or when a communication error occurs.

[0138] In step S21, the master controller 11 transitions the first receiver 132 and the second receiver 133 from idle mode to reception mode. This allows both the first receiver 132 and the second receiver 133 to be in a state where they can constantly receive transmissions of the corresponding preamble codes. Once the two receivers 132 and 133 have transitioned to reception mode, the process proceeds to step S22.

[0139] In step S22, the master controller 11 monitors whether it is the timing to start transmission according to the polling period T. If it is the timing to start transmission (Yes in step S22), the process proceeds to the next step S23. If it is not the timing to start transmission (No in step S22), the monitoring process in step S22 continues.

[0140] In step S23, the master controller 11 switches the transmitter 131 included in the master wireless communication unit 13A from idle mode to transmission mode. This switch to transmission mode initiates a transmission mode period 51 shown in FIG. 13. When transmission mode period 51 begins, information is transmitted from the master 10 to the slave 20 to be transmitted in a predetermined polling order. In the example shown in FIG. 13, a preamble code "A" is used to transmit the information. Once the transmitter 131 has switched to transmission mode, the process proceeds to the next step S24.

[0141] In step S24, the parent controller 11 monitors whether it is time to end the transmission of information to the child device 20. The timing to end the transmission is when a certain period of time has elapsed since the start of transmission, and this certain period of time is a predetermined period of time. If it is time to end the transmission (Yes in step S24), the process proceeds to the next step S25. If it is not time to end the transmission (No in step S24), the monitoring process of step S24 continues.

[0142] In step S25, the master controller 11 transitions the transmitter 131 from the transmission mode to the idle mode, thereby ending the transmission mode period 51. Upon completion of the transition of the transmitter 131 to the idle mode, the process returns to the above-mentioned step S22, and the processes from step S22 onwards are carried out.

[0143] Fig. 15A is a flowchart illustrating the flow of a reception method (part of a communication method) executed by the slave device 20 of the third embodiment. Fig. 15B is a flowchart illustrating the flow of a transmission method (part of a communication method) executed by the slave device 20 of the third embodiment. Here, the communication method executed by the slave device 20 will be explained separately for ease of understanding, since explaining reception and transmission separately is easier. The flowcharts shown in Figs. 15A and 15B show the technical content of a computer program (communication program) that causes a computer (slave device controller 21) included in the slave device 20 to function as means for executing the communication method of the third embodiment.

[0144] As can be seen from the above explanation, the slave device 20 of the third embodiment uses different preamble codes for communication between a response transmission performed in response to receiving a transmission from the master device 10 and an interrupt transmission performed separately from the response transmission. Because different preamble codes are used for the response transmission and the interrupt transmission, the possibility of interference between the two transmissions can be reduced even when both transmissions are performed simultaneously. As a result, the slave device 20 can perform an interrupt transmission at an early stage after a transmission request to the master device 10 is generated, without providing a reception mode period (second reception mode period 53) for interrupt transmission as shown in the first and second embodiments.

[0145] 15A and 15B are initiated after a communication agreement has been made in advance between the master unit 10 and the slave units 20a to 20d. The flowcharts shown in FIGS. 15A and 15B continue until a reason for terminating communication according to the pre-arranged communication schedule occurs. The start of communication according to the communication schedule may occur, for example, when the ACC is turned on by operating the ignition key of the automobile C1. A reason for terminating communication may occur when the ACC is turned off or when a communication error occurs.

[0146] The processing from step N21 to step N24 related to reception by the slave device 20 shown in Fig. 15A is the same as the processing from step N1 to step N4 shown in Fig. 9. Therefore, detailed description will be omitted. As shown in Fig. 15A, the slave device controller 21 controls the receiver 232 provided in the slave device 20 to periodically repeat processing to set the slave device 20 to a slave device side reception mode period 55 at a timing that matches the timing of the transmission mode period 51 of the master device 10.

[0147] 15B, in step N31 relating to transmission from the slave device 20, the slave device controller 21 determines whether or not a response transmission to the master device 10 is necessary. The slave device controller 21 determines that a response transmission is necessary if the transmission from the master device 10 received during the slave device side reception mode period 55 described above is addressed to the slave device controller 21, and determines that a response transmission is unnecessary if the transmission from the master device 10 is not addressed to the slave device controller 21. If it is determined that a response transmission is necessary (Yes in step N31), the process proceeds to the next step N32. If it is determined that a response transmission is unnecessary (No in step N31), the process proceeds to step N33.

[0148] In step N32, slave unit controller 21 controls transmitter 231 included in slave unit 20 to enter response transmission mode period 56. The process of entering response transmission mode period 56 is, in detail, the same as steps N6 to N9 in Fig. 10 described above. When response transmission mode period 56 ends, the process returns to step N31 described above, and the processes from step N31 onwards are carried out.

[0149] In this embodiment, if there is not enough time to perform both the response transmission and the interrupt transmission within the polling period T, the process returns to step N31 without proceeding to step N33, which will be described below. However, if there is enough time to perform both the response transmission and the interrupt transmission within the polling period T, the process may proceed to the next step N33. Furthermore, in a configuration in which the slave device 20 is separately equipped with the transmitter 231 and the receiver 232 as in this embodiment, the interrupt transmission may be performed at a timing that overlaps with the slave device side reception mode period 55. For this reason, even if there is not enough time to perform both the response transmission and the interrupt transmission within the polling period T, the process may be configured to perform the interrupt transmission after the response transmission. However, with the configuration of this embodiment, even in a configuration in which the slave device 20 is equipped with a transceiver that switches between transmission and reception, it is possible to avoid a situation in which the slave device 20 misses a transmission from the master device 10 due to the slave device 20 performing an interrupt transmission.

[0150] In step N33, the slave unit controller 21 determines whether an interrupt transmission to the master unit 10 is necessary. In this embodiment, the timing for checking whether an interrupt transmission is necessary is set to an appropriate timing so that, if it is determined that an interrupt transmission is necessary, the interrupt transmission is started at a timing that allows it to be completed within the current polling period T. If it is determined that an interrupt transmission is necessary (Yes in step N33), the process proceeds to the next step N34. If it is determined that an interrupt transmission is not necessary (No in step N33), the process returns to the above-mentioned step N31, and the processes from step N31 onwards are carried out.

[0151] In step N34, slave controller 21 determines that an interrupt transmission is required and therefore determines to change the preamble code used for transmission using transmitter 231. In the example shown in Fig. 13, it determines to change preamble code "A" to preamble code "B." When it is determined to change the preamble code, the process proceeds to the next step N35.

[0152] In step N35, slave unit controller 21 transitions transmitter 231 from idle mode to transmission mode. This transition to transmission mode initiates interrupt transmission mode period 57 shown in FIG. 13. With the start of interrupt transmission mode period 57, an interrupt transmission is performed from slave unit 20 to master unit 10. Note that this interrupt transmission is performed using a preamble code different from that used for response transmission. In the example shown in FIG. 13, the interrupt transmission is performed using preamble code "B". Once transmitter 231 has transitioned to transmission mode, processing proceeds to the next step N36.

[0153] In step N36, the slave controller 21 monitors whether it is time to end the interrupt transmission. The timing to end the interrupt transmission is when a certain period of time has elapsed since the start of the interrupt transmission, and this certain period of time is a predetermined period of time. If it is time to end the interrupt transmission (Yes in step N36), the process proceeds to the next step N37. If it is not time to end the interrupt transmission (No in step N36), the monitoring process in step N36 continues.

[0154] In step N37, slave controller 21 transitions transmitter 231 from transmission mode to idle mode, thereby ending interrupt transmission mode period 57. Once transmitter 231 has transitioned to idle mode, the process proceeds to the next step S38.

[0155] In step N38, slave controller 21 decides to restore the preamble code that was previously changed for interrupt transmission. In the example shown in Fig. 13, it is decided to restore preamble code "A" from preamble code "B." If it is decided to restore the preamble code, the process returns to step N31, and the processes from step N31 onward are carried out.

[0156] [3-4. Fourth Example] Next, a fourth embodiment will be described. In describing the fourth embodiment, descriptions of content that overlaps with the previously described embodiments will be omitted as appropriate.

[0157] Fig. 16 is a diagram for explaining an outline of the communication method of the fourth embodiment. In Fig. 16, "parent transmitter" refers to transmitter 131 (see Fig. 12). Also, "parent receiver 1" refers to first receiver 132 (see Fig. 12), and "parent receiver 2" refers to second receiver 133 (see Fig. 12). Also, "Tx" in the parts indicating each of first to fourth child devices 20a to 20d refers to transmitter 231, and "Rx" refers to receiver 232.

[0158] The communication method of the fourth embodiment is generally similar to the communication method of the third embodiment (see FIG. 13). That is, in the fourth embodiment, the slave device 20 also uses different preamble codes for response transmission and interrupt transmission. However, in the fourth embodiment, the first receiver 132 and the second receiver 133 are not in a state where they are always capable of receiving. In this respect, the fourth embodiment differs from the third embodiment.

[0159] The first receiver 132 starts reception in accordance with the transmission timing of a response transmission from the slave device 20 that has received a transmission from the master device 10. The first receiver 132 ends reception at an appropriate timing that coincides with the end of the response transmission. The second receiver 133 starts reception in accordance with the transmission timing of an interrupt transmission performed by the slave device 20. The second receiver 133 ends reception at an appropriate timing that coincides with the end of the interrupt transmission. With this configuration, the probability that the first receiver 132 and the second receiver 133 will receive transmission waves (interference waves) transmitted by other communication systems can be reduced compared to when the reception state is always maintained (as in the third embodiment). As a result, the possibility of failing to receive transmission waves from the own system (communication system SYS1) due to the influence of transmission waves transmitted by other communication systems can be reduced.

[0160] In detail, after the end of the transmission mode period 51 executed in the polling cycle T, the first receiver 132 starts the first reception mode period 52A in synchronization with the response transmission performed by the slave device 20 at a predetermined timing. The first reception mode period 52A ends at a predetermined fixed period. The first reception mode period 52A is performed within the polling cycle T. The first reception mode period 52A is executed in the same cycle as the polling cycle T. The first receiver 132 is configured to be able to receive a transmission wave transmitted with the preamble code "A" during the first reception mode period 52A. Note that the response transmission from the slave device 20 is performed using the preamble code "A," and therefore can be received by the first receiver 132 during the first reception mode period 52A.

[0161] In this embodiment, the timing of an interrupt transmission performed by the slave device 20 overlaps with the timing of a response transmission performed by the slave device 20. That is, the period during which the second receiver 133 receives the interrupt transmission overlaps with the period during which the first receiver 132 receives the response transmission. With this configuration, it is not necessary to provide a new period for the interrupt transmission of the slave device 20, separate from other periods, and it is possible to avoid a situation in which communication efficiency decreases due to the interrupt transmission being enabled.

[0162] In detail, the start timing of the interrupt transmission performed by the slave device 20 is the same as the start timing of the response transmission performed by the slave device 20. In other words, the start timing of the reception of the interrupt transmission by the second receiver 133 is the same as the start timing of the reception of the response transmission by the first receiver 132. The second receiver 133 starts the second reception mode period 53A, which is the reception mode period for receiving the interrupt transmission, at the same timing as the first reception mode period 52. With this configuration, it is possible to simplify the agreement made between the master device 10 and the slave device 20 and prevent the communication processing of UWB communication from becoming complicated.

[0163] The second reception mode period 53A ends after a predetermined period of time and is performed within the polling cycle T. The second reception mode period 53A is executed in the same cycle as the polling cycle T. The second receiver 133 is configured to be able to receive transmission waves transmitted with the preamble code "B" during the second reception mode period 53A. Note that the interrupt transmission from the slave device 20 is performed using the preamble code "B", and therefore can be received by the second receiver 133 during the second reception mode period 53A.

[0164] In the example shown in FIG. 16, the first slave unit 20a issues a transmission request to the master unit 10 in the polling cycle T following its turn (the polling cycle T in which it is the turn of the second slave unit 20b). The portions indicated by the symbols "x" in FIG. 16 correspond to the timing at which the transmission request is issued. The first slave unit 20a performs interrupt transmission in accordance with the second reception mode period 53A executed next by the second receiver 133. In detail, the first slave unit 20a performs interrupt transmission so that the interrupt transmission is received in the second reception mode period 53A executed by the second receiver 133 within the polling cycle T in which it is the turn of the third slave unit 20c.

[0165] In this case, the timing of the interrupt transmission from the first handset 20a and the response transmission from the third handset 20c overlaps. However, the interrupt transmission from the first handset 20a uses preamble code "B," while the response transmission from the third handset 20c uses preamble code "A." Due to the difference in the preamble codes used, the two communications are properly received by the receivers 132 and 133 without interference.

[0166] In the configuration of this embodiment, it may not be possible to immediately perform an interrupt transmission when a transmission request is generated in the slave device 20, and the timing of the interrupt transmission may overlap with the timing of the slave device's own response transmission. In such a case, the interrupt transmission may not be performed, and the information that was scheduled to be transmitted in the interrupt transmission may be included in the response transmission information and transmitted.

[0167] Furthermore, if multiple slave devices 20 perform interrupt transmission simultaneously, there is a possibility that the two transmissions will interfere with each other, resulting in communication failure. In consideration of this, the same restrictions as in the second embodiment may be imposed on the timing at which each of the slave devices 20a to 20d performs interrupt transmission.

[0168] Fig. 17 is a flowchart illustrating the flow of a communication method executed by the parent device 10 of the fourth embodiment. The flowchart shown in Fig. 17 shows the technical content of a computer program (communication program) that causes a computer (parent device controller 11) included in the parent device 10 to function as a means for executing the communication method of the fourth embodiment.

[0169] The flowchart shown in Fig. 17 starts after a communication agreement is made in advance between the parent device 10 and the plurality of child devices 20a to 20d. The flowchart shown in Fig. 17 continues until a reason for terminating communication according to the pre-arranged communication schedule occurs. The start of communication according to the communication schedule may occur, for example, when the ACC is turned on by operating the ignition key of the automobile C1. The reason for terminating communication may occur when the ACC is turned off or when a communication error occurs.

[0170] Steps S31 to S34 in Fig. 17 are control processes for controlling transmitter 131 included in parent device 10 to enter transmission mode period 51, and are the same as the processes of steps S1 to S4 shown in Fig. 9. Therefore, detailed description thereof will be omitted.

[0171] In step S35, the parent controller 11 monitors whether it is time to receive a response transmission from the child device 20. The reception timing is determined by a prearranged agreement between the parent device 10 and the child device 20. As described above, in this embodiment, the timing of the response transmission and the timing of the interrupt transmission are the same. Therefore, the timing of receiving the response transmission is also the timing of receiving the interrupt transmission. If it is time to receive the response transmission (Yes in step S35), the process proceeds to the next step S36. If it is not time to receive the response transmission (No in step S35), the monitoring process of step S35 continues.

[0172] In step S36, the master controller 11 transitions the first receiver 132 and the second receiver 133 from idle mode to reception mode. The transition of the first receiver 132 to reception mode initiates a first reception mode period 52A shown in FIG. 16. The start of the first reception mode period 52A makes it possible to receive a response transmission from the slave device 20, and the response transmission is received. Furthermore, the transition of the second receiver 133 to reception mode initiates a second reception mode period 53A shown in FIG. 16. The start of the second reception mode period 53A makes it possible to receive an interrupt transmission from the slave device 20, and if an interrupt transmission occurs, the interrupt transmission is received. Once the two receivers 132, 133 have transitioned to reception mode, processing proceeds to the next step S37.

[0173] In step S37, the parent controller 11 monitors whether it is time to end reception of the response transmission from the child device 20. The timing to end reception is when a certain period of time has elapsed since reception began, and this certain period of time is a period determined in advance taking into account the period of the response transmission. In this embodiment, the timing to end reception of the response transmission and the timing to end reception of the interrupt transmission are the same. However, this is merely an example, and the two timings may be different. If the two timings are different, each timing must be monitored separately. If it is time to end reception of the response transmission (Yes in step S37), processing proceeds to the next step S38. If it is not time to end reception of the response transmission (No in step S37), the monitoring processing of step S37 continues.

[0174] In step S38, the master controller 11 transitions the first receiver 132 and the second receiver 133 from the reception mode to the idle mode. This ends the first reception mode period 52A and the second reception mode period 53A. As described above, the first reception mode period 52A and the second reception mode period 53A may end at different times. In this case, the first receiver 132 and the second receiver 133 transition to the idle mode at different times. Once the first receiver 132 and the second receiver 133 have transitioned to the idle mode, the process returns to step S31 described above, and the processes from step S31 onwards are performed.

[0175] Fig. 18 is a flowchart illustrating the flow of a transmission method (part of a communication method) executed by the slave device 20 of the fourth embodiment. Note that the reception method (part of a communication method) executed by the slave device 20 is the same as that in Fig. 15A in the third embodiment, and therefore a description thereof will be omitted. The flowchart shown in Fig. 18 illustrates the technical contents of a computer program (communication program) that causes a computer (slave device controller 21) included in the slave device 20 to function as a means for executing the communication method of the fourth embodiment.

[0176] The flowchart shown in Fig. 18 starts after a communication agreement is made in advance between the master unit 10 and the plurality of slave units 20a to 20d. The flowchart shown in Fig. 18 continues until a reason for terminating communication according to the predetermined communication schedule occurs. The start of communication according to the communication schedule occurs, for example, when the ACC is turned on by operating the ignition key of the automobile C1. The reason for terminating communication occurs when the ACC is turned off or when a communication error occurs.

[0177] 18, the slave unit controller 21 determines whether or not a response transmission to the master unit 10 is necessary. The slave unit controller 21 determines that a response transmission is necessary if the transmission from the master unit 10 previously received during the slave unit side reception mode period 55 is addressed to the slave unit controller 21, and determines that a response transmission is unnecessary if the transmission from the master unit 10 is not addressed to the slave unit controller 21. If it is determined that a response transmission is necessary (Yes in step N41), the process proceeds to the next step N42. If it is determined that a response transmission is not necessary (No in step N41), the process proceeds to step N42.

[0178] In step N42, slave unit controller 21 controls transmitter 231 included in slave unit 20 to enter response transmission mode period 56 (see FIG. 16). The process of entering response transmission mode period 56 is, in detail, the same as steps N6 to N9 in FIG. 10 described above. When response transmission mode period 56 ends, the process returns to step N41 described above, and the processes from step N41 onwards are carried out.

[0179] In this embodiment, the interrupt transmission mode period 57 starts at the same timing as the response transmission mode period 56. The slave device 20 has only one transmitter 231. For this reason, response transmission and interrupt transmission cannot be performed within the same polling cycle T. As a result, in this embodiment, after the processing of step N42 ends, the processing returns to step N41 without proceeding to step N43, which will be described next.

[0180] In step N43, the slave unit controller 21 determines whether or not an interrupt transmission to the master unit 10 is necessary. In this embodiment, the timing for checking whether or not an interrupt transmission is necessary is set to an appropriate timing so that the interrupt transmission is started when the interrupt transmission is received during the second receive mode period 53A provided within the current polling cycle T. If it is determined that an interrupt transmission is necessary (Yes in step N43), the process proceeds to the next step N44. If it is determined that an interrupt transmission is not necessary (No in step N43), the process returns to the above-mentioned step N41, and the processes from step N41 onwards are carried out.

[0181] In step N44, because it is necessary to perform interrupt transmission, slave controller 21 decides to change the preamble code used for transmission using transmitter 231. In the example shown in Fig. 16, it decides to change from preamble code "A" to preamble code "B." Once it has been decided to change the preamble code, the process proceeds to the next step N45.

[0182] In step N45, slave unit controller 21 controls transmitter 231 included in slave unit 20 to enter interrupt transmission mode period 57 (see FIG. 16). The process of entering interrupt transmission mode period 57 is, in detail, the same as steps N35 to N37 in FIG. 15B described above. When interrupt transmission mode period 57 ends, the process proceeds to the next step N46.

[0183] In step N46, slave controller 21 decides to restore the preamble code that was previously changed for interrupt transmission. In the example shown in Fig. 16, it is decided to restore preamble code "A" from preamble code "B." If it is decided to restore the preamble code, the process returns to step N41, and the processes from step N41 onward are carried out.

[0184] In this embodiment, the timing of the interrupt transmission is configured to start at the same timing as the timing of the response transmission. However, this is merely an example, and the timing of the interrupt transmission can be changed as appropriate. For example, as shown in FIG. 19 , the timing of the interrupt transmission performed by the slave device 20 may be configured to overlap with the timing of the transmission from the master device 10 to the slave device 20. In other words, the period during which the second receiver 133 receives the interrupt transmission may overlap with the period during which the master device 10 transmits. Even with this configuration, there is no need to provide a separate period for the interrupt transmission by the slave device 20, and it is possible to avoid a situation in which communication efficiency decreases due to the interrupt transmission being enabled.

[0185] 19 is a diagram for explaining a modified example of the fourth embodiment. In FIG. 19, "parent transmitter" refers to transmitter 131 (see FIG. 12). Also, "parent receiver 1" refers to first receiver 132 (see FIG. 12), and "parent receiver 2" refers to second receiver 133 (see FIG. 12). Also, "Tx" in the parts indicating each of first to fourth child devices 20a to 20d refers to transmitter 231, and "Rx" refers to receiver 232.

[0186] In particular, the start timing of the interrupt transmission may be the same as the timing when the parent device 10 starts transmission to the child device 20. The timing when the parent device 10 starts transmission to the child device 20 corresponds to the start timing of the transmission mode period 51 executed every polling period T.

[0187] In this configuration, the arrangement between the master device 10 and the slave device 20 can be simplified, and the UWB communication process can be prevented from becoming complicated. Furthermore, this configuration can prevent the timing of the response transmission and the interrupt transmission performed by the slave device 20 from overlapping. That is, the same slave device 20 can perform both the response transmission and the interrupt transmission within the same polling period T.

[0188] 19, in this modification, the interruption transmission mode period 57 starts at the same timing as the transmission mode period 51 of the parent device 10. Therefore, the second receiver 133 starts the second reception mode period 53B, which is a reception mode period for receiving the interruption transmission, at the corresponding timing.

[0189] The second reception mode period 53B ends after a predetermined fixed period and is performed within the polling cycle T. The second reception mode period 53B is executed in the same cycle as the polling cycle T. The second receiver 133 is configured to be able to receive transmission waves transmitted with the preamble code "B" during the second reception mode period 53B. Note that the interrupt transmission from the slave device 20 is performed using the preamble code "B", and therefore can be received by the second receiver 133 during the second reception mode period 53B.

[0190] In the example shown in FIG. 19, the first slave unit 20a issues a transmission request to the master unit 10 in the polling cycle T following its turn (the polling cycle T in which it is the turn of the second slave unit 20b). Note that the portions indicated by the symbols "x" in FIG. 19 correspond to the timing at which the transmission request is issued. The first slave unit 20a performs interrupt transmission in accordance with the second reception mode period 53B executed next by the second receiver 133. In detail, the first slave unit 20a performs interrupt transmission so that the interrupt transmission is received in the second reception mode period 53B executed by the second receiver 133 within the polling cycle T in which it is the turn of the third slave unit 20c.

[0191] In such a case, the timing of the interrupt transmission from the first handset 20a to the second receiver 133 and the normal transmission from the base unit 10 to the third handset 20c overlap. However, the interrupt transmission from the first handset 20a uses preamble code "B," while the transmission from the base unit 10 to the third handset 20c uses preamble code "A." Due to the difference in the preamble codes used, the two communications do not interfere with each other, reducing the possibility of each communication failing.

[0192] [3-5. Fifth Example] Next, a fifth embodiment will be described. In describing the fifth embodiment, explanations of the contents that overlap with the previously described embodiments will be omitted as appropriate.

[0193] In the first to fourth embodiments described above, when an interrupt transmission is made from the slave device 20, the master device 10 is configured not to respond to the interrupt transmission from the slave device 20. For example, if the slave device 20 is a sensor, this configuration may be acceptable. However, if the slave device 20 is configured to include an actuator, for example, it may be desirable to obtain a response from the master device 10 to the content of the interrupt transmission as quickly as possible.

[0194] Taking this into consideration, in this embodiment, in response to a transmission request from one of the multiple slave devices 20 using interrupt transmission, the master device 10 changes the order of polling and transmits information preferentially to the slave device 20 that made the request. With this configuration, the slave device 20 can obtain information from the master device 10 at a timing earlier than the order scheduled by the polling method.

[0195] Fig. 20 is a diagram for explaining an outline of the communication method of the fifth embodiment. In Fig. 20, "parent transmitter" refers to transmitter 131 (see Fig. 12). Also, "parent receiver 1" refers to first receiver 132 (see Fig. 12), and "parent receiver 2" refers to second receiver 133 (see Fig. 12). Also, "Tx" in the parts indicating first to fourth child devices 20a to 20d refers to transmitter 231, and "Rx" refers to receiver 232.

[0196] The communication method shown in Fig. 20 is configured by applying the idea of ​​preferentially transmitting information from parent device 10 to child device 20 to the communication method shown in Fig. 19 (a communication method according to a modified example of the fourth embodiment). For this reason, explanations that overlap with the contents previously explained regarding Fig. 19 will be omitted as appropriate. However, the idea of ​​preferential transmission performed using Fig. 20 can be applied to, for example, the communication methods of the first embodiment (see Fig. 8), the second embodiment (see Fig. 11), the third embodiment (see Fig. 13), and the fourth embodiment (see Fig. 16) described above. In other words, the communication method shown in Fig. 20 is merely an example.

[0197] 20, the first slave device 20a issues a transmission request to the master device 10 in the next polling cycle T of its turn (the polling cycle T of the second slave device 20b) (see (a) in the figure). In order to perform interrupt transmission, the first slave device 20a must wait for the timing when the second receiver 133 next enters the second reception mode period 53B, and therefore cannot immediately perform interrupt transmission to the master device 10 at this stage.

[0198] After the first handset 20a issues a transmission request, the next polling period T arrives, and the transmitter 131 of the base unit 10 starts a transmission mode period 51 and transmits information to the third handset 20c using a normal preamble code ("A") (see (b) in the figure). At the same time, the first handset 20a, which has issued a transmission request earlier, starts an interrupt transmission mode period 57 and transmits an interrupt transmission using a preamble code ("B") different from the normal preamble code (see (c) in the figure). In order to receive the interrupt transmission, the second receiver 133 of the base unit 10 enters a second reception mode period 53B in accordance with a predetermined arrangement to coincide with the interrupt transmission, and receives the interrupt transmission from the first handset 20a (see (d) in the figure).

[0199] In addition, since the third handset 20c is in the polling order during the polling period T, the third handset 20c, upon receiving the information from the parent device 10, sends a response to the parent device 10 using the normal preamble code ("A") (see (e) in the figure).

[0200] Upon receiving the interrupt transmission from the first handset 20a (see (d) in the figure), the master unit 10 determines that it needs to transmit information to the first handset 20a with priority, based on the information transmission request included in the interrupt transmission. Therefore, during a transmission mode period 51 (see (f) in the figure) in the next polling cycle T, although it should normally transmit information to the fourth handset 20d, it changes the order and transmits information to the first handset 20a with the normal preamble code ("A") instead. In response to this, of the four handset units 20a to 20d that received the information from the master unit 10, the first handset 20a, which is designated by the master unit 10 as the information transmission target, transmits a response to the master unit 10 with the normal preamble code ("A") (see (g) in the figure).

[0201] In the polling cycle T following the priority transmission to the first handset 20a, there is no particular need for priority transmission. For this reason, the master unit 10 returns the transmission order to the handset 20 to the original polling order. That is, the master unit 10 transmits information to the fourth handset 20d, which was in the polling order in the previous polling cycle T, using the normal preamble code ("A") (see (h) in the figure). In response to this, of the four handset units 20a to 20d that have received information from the master unit 10, the fourth handset 20d, which has been designated by the master unit 10 as the information transmission target, transmits a response to the master unit 10 using the normal preamble code ("A") (see (i) in the figure).

[0202] In the example shown above, when the parent device 10 performs priority transmission in response to an interrupt transmission, the parent device 10 performs the priority transmission in the polling cycle T next to the one in which the interrupt transmission was received. However, this is merely an example. For example, after receiving an interrupt transmission, the parent device 10 may perform the interrupt transmission in the polling cycle T within the Nth cycle (N is a predetermined natural number of 2 or more), and may determine the timing of the priority transmission depending on the priority of communication for each of the child devices 20a to 20d.

[0203] Fig. 21 is a flowchart illustrating the flow of a communication method executed by the parent device 10 of the fifth embodiment. The flowchart shown in Fig. 21 shows the technical content of a computer program (communication program) that causes a computer (parent device controller 11) included in the parent device 10 to function as a means for executing the communication method of the fifth embodiment.

[0204] The flowchart shown in Fig. 21 starts after a communication agreement is made in advance between the master unit 10 and the multiple slave units 20a to 20d. The flowchart shown in Fig. 21 continues until a reason for terminating communication according to the predetermined communication schedule occurs. The start of communication according to the communication schedule occurs, for example, when the ACC is turned on by operating the ignition key of the automobile C1. The reason for terminating communication occurs when the ACC is turned off or when a communication error occurs.

[0205] In step S41 in Fig. 21, the master controller 11 determines whether or not it is necessary to change the current order of transmission targets (transmission order). If the order of transmission targets has not been changed before, the current order of transmission targets is the order of transmission targets (polling order) predetermined in the polling method. If the order of transmission targets has been changed before, the current order of transmission targets is the order after the change.

[0206] For example, when a transmission request is made to the master controller 11 by an interrupt transmission from a slave 20, and the slave 20 that made the transmission request is not the next slave to be transmitted, the master controller 11 determines that a change in the polling order is necessary. Note that the method for determining whether a change in the polling order is necessary is merely an example, and may be changed to another method as appropriate. For example, the necessity of changing the transmission order may be determined taking into account the urgency of transmission, etc. If it is determined that a change in the transmission order is necessary (Yes in step S41), the process proceeds to the next step S42. If it is determined that a change in the transmission order is not necessary (No in step S41), the process proceeds to step S43.

[0207] In step S42, the master controller 11 changes the transmission order. Specifically, the master controller 11 changes the transmission order in an interruption manner, with the slave device 20 that has issued a transmission request to the master controller 11 being the next transmission target. That is, the slave device 20 that was originally scheduled to be the next transmission target is reordered by the interruption manner, so that the slave device 20 is placed one step behind its original order. Note that there may be multiple slave devices 20 issuing transmission requests. In such a case, the slave device 20 that will be the next transmission target may be determined according to a predetermined priority order from among the slave devices 20 issuing transmission requests. The predetermined priority order referred to here may be, for example, the order in which the slave device 20 that will be the next transmission target is the earliest, assuming that there will be no subsequent interruption-style order changes. Once the transmission order has been changed, the process proceeds to the next step, step S43.

[0208] In step S43, the master controller 11 sets the transmitter 131 to a transmission mode period 51 in which it transmits information to the slave device 20 that is the transmission target, and sets the second receiver 133 to a second reception mode period 53B in which it receives an interrupt transmission from the slave device 20. Details of the process of setting the transmitter 131 to the transmission mode period 51 are the same as the processes of steps S1 to S4 shown in FIG. 9 described above. Details of the process of setting the second receiver 133 to the second reception mode period 53B are the same as the processes of steps S9 to S12 shown in FIG. 9 described above. When the processes of setting the transmitter 131 to the transmission mode period 51 and the processes of setting the second receiver 133 to the second reception mode period 53B are completed, the process proceeds to the next step S44.

[0209] In step S44, the parent controller 11 sets the first receiver 132 to a first reception mode period 52A in which the first receiver 132 receives a response transmission from the child device 20. Details of the process of setting the first receiver 132 to the first reception mode period 52A are similar to the processes of steps S5 to S8 shown in Fig. 9 described above. When the process of setting the first receiver 132 to the first reception mode period 52A ends, the process returns to the above-mentioned step S41, and the processes from step S41 onwards are performed.

[0210] Fig. 22 is a flowchart illustrating the flow of a transmission method (part of a communication method) executed by the slave device 20 of the fifth embodiment. Note that the reception method (part of a communication method) executed by the slave device 20 is the same as that in Fig. 15A in the third embodiment, and therefore a description thereof will be omitted. The flowchart shown in Fig. 22 illustrates the technical content of a computer program (communication program) that causes a computer (slave device controller 21) included in the slave device 20 to function as a means for executing the communication method of the fifth embodiment.

[0211] The flowchart shown in Fig. 22 starts after a communication agreement is made in advance between the master unit 10 and the multiple slave units 20a to 20d. The flowchart shown in Fig. 22 continues until a reason for terminating communication according to the predetermined communication schedule occurs. The start of communication according to the communication schedule occurs, for example, when the ACC is turned on by operating the ignition key of the automobile C1. The reason for terminating communication occurs when the ACC is turned off or when a communication error occurs.

[0212] 22, the slave unit controller 21 determines whether or not an interrupt transmission to the master unit 10 is necessary. If it is determined that an interrupt transmission is necessary (Yes in step N51), the process proceeds to the next step N52. If it is determined that an interrupt transmission is not necessary (No in step N51), the process proceeds to step N55.

[0213] In step N52, slave controller 21 determines that an interrupt transmission is required and therefore determines to change the preamble code used for transmission using transmitter 231. In the example shown in Fig. 20, it determines to change preamble code "A" to preamble code "B." Once it is determined to change the preamble code, the process proceeds to the next step N53.

[0214] In step N53, slave unit controller 21 controls transmitter 231 included in slave unit 20 to enter interrupt transmission mode period 57 (see FIG. 20). The process of entering interrupt transmission mode period 57 is, in detail, the same as steps N35 to N37 in FIG. 15B described above. When interrupt transmission mode period 57 ends, the process proceeds to the next step N54.

[0215] In step N54, slave controller 21 decides to restore the preamble code that it decided to change for interrupt transmission. In the example shown in Fig. 20, it decides to restore preamble code "B" to preamble code "A." If it is decided to restore the preamble code, the process proceeds to the next step N55.

[0216] In step N55, the slave unit controller 21 determines whether a response transmission to the master unit 10 is necessary. The determination of whether a response transmission is necessary is the same as the processing of step N41 in FIG. 18 described above, and it is determined that a response transmission is necessary when the transmission from the master unit 10 is addressed to the slave unit 21 itself. In this embodiment, when the transmission from the master unit 10 is addressed to the slave unit 21 itself, this includes a case where the master unit 10 has transmitted a message addressed to itself according to a predetermined polling order, and a case where the master unit 10 has transmitted a message addressed to itself in response to a transmission request from the slave unit 20. If it is determined that a response transmission is necessary (Yes in step N55), the process proceeds to the next step N56. If it is determined that a response transmission is not necessary (No in step N55), the process returns to the above-described step N51, and the processes from step N51 onwards are carried out.

[0217] In step N56, slave unit controller 21 controls transmitter 231 included in slave unit 20 to enter response transmission mode period 56 (see FIG. 16). The process of entering response transmission mode period 56 is, in detail, the same as steps N6 to N9 in FIG. 10 described above. When response transmission mode period 56 ends, the process returns to step N51 described above, and the processes from step N51 onwards are carried out.

[0218] <4. Things to keep in mind> Various technical features disclosed in the description of the present invention 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 present invention may be combined to the extent possible. [Explanation of symbols]

[0219] 10. Base unit (communication device) 20. Handset (communication device) 20a···First handset 20b...Second handset 20c···Third handset 20d...4th handset 132···First receiver 133···Second receiver

Claims

1. A communication method for performing UWB communication by polling between a parent device and multiple child devices, comprising: To the parent unit, a first receiver that receives response transmissions from the plurality of slave units that have received the transmission from the master unit; a second receiver for receiving interrupt transmissions from the plurality of slave units; Established The parent device and the plurality of child devices A communication method in which different preamble codes are used for the response transmission and the interrupt transmission.

2. The communication method according to claim 1 , wherein at least the second receiver of the first and second receivers is always in a state where reception is possible.

3. the first receiver starts receiving in accordance with the transmission timing of the response transmission; The communication method according to claim 1 , wherein the second receiver starts reception in synchronization with a transmission timing of the interrupt transmission.

4. The method of claim 3 , wherein a period during which the second receiver receives the interrupt transmission overlaps a period during which the first receiver receives the response transmission.

5. The communication method according to claim 3 , wherein a period during which the second receiver receives the interrupt transmission overlaps with a period during which the master unit transmits.

6. 6. The communication method according to claim 3, wherein, in response to a request for transmission to the parent device using the interrupt transmission from one of the plurality of child devices, the parent device changes the order of the polling methods and performs priority transmission to the one of the child devices that made the request.

7. A communication method for performing UWB communication by polling between a central control unit of a vehicle and a plurality of individual control units that control a plurality of drive devices of the vehicle, comprising: the central control unit has a first receiver that receives a response transmission from the individual control unit in response to its own communication request, and a second receiver that receives an interrupt transmission from any one of the plurality of individual control units, A communication method, wherein the preamble code of the interrupt transmission is different from the preamble code of the response transmission.

8. The communication method according to claim 7, wherein the driving device is a headlight driving device, a wiper driving device, a power window driving device, or an air conditioner driving device.

9. The communication method according to claim 7 or 8, wherein the interrupt transmission and the response transmission include sensor information from sensors of the vehicle connected to the plurality of driving devices.

10. A communication device that performs UWB communication using a polling method as a master device with a plurality of slave devices, a first receiver that receives response transmissions from the plurality of slave units that have received the transmission from the master unit; a second receiver for receiving interrupt transmissions from the plurality of slave units; Equipped with A communications device that utilizes different preamble codes in the first receiver and the second receiver.

11. A computer included in a communication device that performs UWB communication using a polling method as a master device with a plurality of slave devices, a first receiver that receives a response transmission from the plurality of slave devices that has received a transmission from the master device, and a second receiver that receives an interrupt transmission from the plurality of slave devices, communicating using different preamble codes for the response transmission and the interrupt transmission; A communication program that serves as a means to execute the above.

12. A communication device that performs UWB communication using a polling method as a slave device with a master device, A communication device that uses different preamble codes for a response transmission performed in response to a communication request from the parent device and an interrupt transmission performed when an interrupt transmission request to the parent device occurs.

13. A computer included in a communication device that performs UWB communication using a polling method as a slave device with a master device, A different preamble code is used for a response transmission made in response to a communication request from the parent device and an interrupt transmission made when an interrupt transmission request to the parent device occurs. A communication program that serves as a means to execute the above.

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