Communication device and communication program

Abstract

An exemplary communication device is a communication device used as a master apparatus capable of UWB communication with a plurality of slave apparatuses, the communication device comprising a control unit. The control unit determines a preamble code used for the UWB communication with a new slave apparatus on the basis of connection information including preamble code information about a slave apparatus connected for communication.

Description

Communication Device and Communication Program

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

[0002] In recent years, in the field of communication, wireless communication has been increasing due to its advantages in terms of installation area, such as not requiring wiring. For example, UWB communication using wideband radio waves has advantages such as less radio wave interference with radio waves used in mobile terminals such as Wi-Fi (registered trademark) and smartphones, and good permeability, and its applications are expanding. In addition, UWB communication is expected to be a communication means for devices mounted on moving bodies because communication is likely to be established even within a moving body such as an automobile, which has a narrow metal space and many wirings.

[0003] When UWB communication becomes widely popular, in a narrow space such as inside a vehicle, radio wave interference may occur between devices performing UWB communication, and communication may become unstable. As a prior art that discloses countermeasures against radio wave interference in UWB communication, for example, the technology disclosed in Patent Document 1 can be cited.

[0004] In the technology disclosed in Patent Document 1, in communication using a preamble, the preamble used by a communication target device for communication is selected and determined from among predetermined standard preambles. In making this determination, first, information on the usage state preambles used in the communication being executed around the communication target device is collected. Then, based on the collected information on the usage state preambles, the usage state preamble is detected, and based on the detected usage state preamble, the preamble used by the communication target device for communication is determined.

[0005] Japanese Unexamined Patent Application Publication No. 2024 - 33445

[0006] In the technology disclosed in Patent Document 1, a UWB communication device needs to switch to UWB radio wave reception mode and collect preamble code information from communication devices in its vicinity in order to determine the preamble code to be used for communication. When collecting preamble codes using UWB radio wave reception mode, the received radio waves are analyzed each time a UWB communication radio wave is received in order to recognize the preamble code. For this reason, the time required to collect preamble code information may be long. If the collection time is long, the real-time capability of the connection between communication devices may be lost. In addition, when collecting preamble code information by switching to UWB radio wave reception mode, there is a possibility that information cannot be collected properly due to the effects of radio wave interference, etc.

[0007] In view of the above, this disclosure aims to provide a technology that can efficiently and appropriately determine the preamble code used between UWB communication devices.

[0008] An exemplary communication device of this disclosure is a communication device used as a master unit capable of UWB communication with a plurality of slave units, comprising a control unit, the control unit determines a preamble code to be used for UWB communication with a new slave unit based on connection information including preamble code information of a slave unit that has already been connected.

[0009] In the exemplary configuration of this disclosure, the communication device is configured as a master unit that performs UWB communication with multiple slave units. When the master unit performs UWB communication with a slave unit, it makes an agreement with the slave unit regarding the preamble code to be used. For this purpose, if there is a slave unit that is already connected to the master unit, the master unit has connection information including the preamble code information of that slave unit. That is, the control unit of the communication device of this disclosure can use the connection information of the connected slave unit when a new slave unit requests a new communication connection. As a result, the control unit of the communication device can quickly determine the preamble code to be used for UWB communication with the new slave unit in a way that minimizes radio interference with UWB communication with other slave units. In other words, according to the configuration of this disclosure, the preamble code used between UWB communication devices can be determined efficiently and appropriately.

[0010] Figures illustrating the configuration of a communication system according to the embodiment of this disclosure; Block diagram showing the schematic configuration of the master unit; Figure showing the frame format used for UWB communication; Figure showing the trend of communication success rates for each combination of preamble codes when two UWB communications are performed simultaneously; Figure showing the trend of communication success rates for each combination of preamble codes when two UWB communications are performed simultaneously, at least one of which uses a distance measuring code; Figure showing the main characteristics of UWB communication used in the communication system; Schematic diagram for explaining the preamble code determination operation in the communication system; Figure showing the connection information table after the preamble code assigned to a new slave unit has been determined in the example shown in Figure 7; Figure for explaining a different example from Figure 7 regarding the preamble code determination operation in the communication system; Flowchart illustrating the flow of the preamble code determination process performed by the master unit to assign to a new slave unit; Figure for explaining the preamble code change operation in the communication system; Flowchart illustrating the flow of the preamble code change process performed according to vehicle information to assign to an already connected slave unit; Figure showing an example of an arrangement based on the type and number of preamble codes.

[0011] Hereinafter, exemplary embodiments of this disclosure will be described in detail with reference to the drawings. In the description of the embodiments, the same parts will be denoted by the same reference numerals, and redundant descriptions will be omitted unless particularly necessary.

[0012] <1. Communication System> [1-1. System Overview] Figure 1 is a diagram showing the configuration of the communication system SYS1 according to an embodiment of the present disclosure. In this embodiment, as an example, the communication system SYS1 is applied to a vehicle C1. The vehicle C1 is specifically an automobile, but may be a vehicle other than an automobile. Vehicles other than automobiles may include, for example, work vehicles or railway vehicles (trains). Furthermore, the communication system of the present disclosure may be applied to objects other than the vehicle C1 where communication equipment is installed. The communication system of the present disclosure may be applied to, for example, all mobile objects other than vehicles, home communication equipment, office communication equipment, or factory communication equipment. Note that all mobile objects other than vehicles may include, for example, ships, aircraft, robots, etc.

[0013] As shown in Figure 1, the communication system SYS1 comprises a master unit 10 and a plurality of slave units 20. The master unit 10 is mounted on the vehicle C1 and constitutes a central control unit (so-called head unit). Each slave unit 20 is mounted on the vehicle C1 and constitutes an individual control unit controlled by the central control unit, and is connected by wire to equipment 30 located on the vehicle C1.

[0014] The master unit 10 and each of the multiple slave units 20 communicate via UWB. In other words, the master unit 10 and each slave unit 20 can be said to be communication devices that perform UWB communication. The master unit 10 is a communication device that can communicate with multiple slave units 20. The master unit 10 controls each slave unit 20 using UWB communication. Each slave unit 20 controls the devices 30 connected to it in response to instructions from the master unit 10.

[0015] Each of the devices 30 is, for example, a sensor, actuator, or antenna. Sensors are, for example, a light sensor, power window switch, accelerator sensor, brake sensor, wiper switch, G sensor (accelerometer), or GPS (Global Positioning System) sensor. Actuators are, for example, a power window motor, headlamp, or wiper motor. Antennas are broadcasting antennas, communication antennas, or radar antennas.

[0016] The transmission from the master unit 10 to each slave unit 20 includes information related to the control of devices 30 such as actuators connected to each slave unit 20. Furthermore, the transmission from each slave unit 20 to the master unit 10 includes information detected or acquired by devices 30 such as sensors connected to each slave unit 20. For example, one of the multiple slave units 20 may be the air conditioning ECU (Electric Control Unit) of an air conditioning system that provides air conditioning in the vehicle cabin, and another of the multiple slave units 20 may be the navigation ECU of a navigation system that provides road guidance.

[0017] In this example, the air conditioning ECU (slave unit 20) transmits the recirculation status signal of the air conditioning to the head unit (master unit 10) via UWB communication. The navigation ECU (slave unit 20) also transmits the tunnel driving status of vehicle C1 to the head unit (master unit 10) via UWB communication. Based on the recirculation status information of the air conditioning received via UWB communication and the tunnel driving status information of vehicle C1, the head unit (master unit 10) generates a control signal for switching between recirculation and outside air for the air conditioning. The head unit (master unit 10) transmits the generated switching control signal to the air conditioning ECU (slave unit 20) using UWB communication. This allows the head unit (master unit 10) to control the air conditioning to operate according to various conditions of the vehicle.

[0018] Furthermore, the master unit 10 and the slave unit 20 capable of UWB communication may include a portable device brought into the vehicle by the occupants of vehicle C1. The portable device may be, for example, a smartphone, a tablet device, or a laptop computer.

[0019] [1-2. Overview of the Communication Device] Figure 2 is a block diagram showing the general configuration of the master unit 10. In Figure 2, the components necessary to explain the features of the master unit 10 of this embodiment are shown, and components that do not require explanation are omitted.

[0020] As shown in Figure 2, the master unit 10 comprises a control unit 11, a storage unit 12, and a communication unit 13.

[0021] The control unit 11 controls the overall operation of the master unit 10. In this embodiment, the control unit 11 is a computer device. That is, the communication device 10 configured as the master unit includes a computer. The control unit 11 includes a processor that performs calculations and the like. The processor is configured to include, for example, a CPU (Central Processing Unit). The control unit 11 may consist of one processor or multiple processors. If it consists of multiple processors, those processors only need to be connected to each other so that they can communicate with one another.

[0022] The storage unit 12 is composed of 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 flash memory or a hard disk drive, etc. The non-volatile memory stores programs and data that can be read by the computer. The programs include a communication program 121 used when performing UWB communication.

[0023] The program stored in the memory unit 12 may be provided, for example, on a computer-readable non-volatile recording medium. The non-volatile recording medium may be, for example, an optical recording medium (e.g., optical disc), a magneto-optical recording medium (e.g., magneto-optical disc), a USB memory, or an SD card, in addition to the non-volatile memory described above. As another example, the program may be provided from a program provision server via a communication line such as the Internet (a configuration provided by so-called download).

[0024] In this embodiment, the functions of the control unit 11 are realized by the processor executing arithmetic processing according to the program stored in the storage unit 12. The number of programs that realize the functions of the control unit 11 may be one or more.

[0025] Furthermore, at least a portion of the functions of the control unit 11 may be implemented by methods other than software, as in this embodiment. At least a portion of the functions of the control unit 11 may be implemented using, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). In other words, at least a portion of the functions of the control unit 11 may be implemented by hardware using a dedicated IC or the like. Also, at least a portion of the functions of the control unit 11 may be implemented by using both software and hardware.

[0026] The communication unit 13 performs UWB communication with the communication unit (not shown) of the slave unit 20. More specifically, the communication unit 13 includes a transmission function for transmitting UWB signals and a reception function for receiving UWB signals. Such a communication unit 13 can be realized, for example, by a NIC (Network Interface Card) equipped with a UWB communication interface (UWB communication circuit).

[0027] The general configuration of each slave unit 20 is the same as that of the master unit 10. That is, the general configuration of the slave unit 20 can be represented in the same way as the schematic configuration diagram of the master unit 10 shown in Figure 2. Like the master unit 10, the slave unit 20 includes a control unit, a storage unit, and a communication unit. Since the details of these are the same as those of the master unit 10, a detailed explanation will be omitted.

[0028] <2. UWB Communication> Next, we will explain the UWB communication used in the SYS1 communication system.

[0029] [2-1. Overview] UWB communication is a wireless communication method using the UWB communication protocol. UWB communication is carried out in accordance with standards such as IEEE 802.15.4 (hereinafter sometimes simply referred to as communication standards).

[0030] Figure 3 shows the frame format F1 used in UWB communication. The frame format F1 shown in Figure 3 corresponds to the structure of one unit (one packet) of transmitted data in UWB communication. The frame format F1 used in UWB communication is determined by the communication standard described above.

[0031] As shown in Figure 3, the frame format F1 used in UWB communication has a structure in which the preamble is at the beginning, followed by the SFD (Start Frame Delimiter), PHR (PHY Header), and the data body in that order. Note that the term "data body" is used to make the differences between the preamble, SFD, and PHR easier to understand.

[0032] A preamble is a sequence of bits in a predetermined pattern, or pulses (e.g., -, 0, +), that are sent before the data itself to inform the receiver that data is about to be sent in digital communication. The receiver uses the preamble signal to synchronize its receiving clock.

[0033] The SFD is a specific pattern of bits used to signal the start of data in a communication frame. The PHR contains information necessary for decoding the packet. For example, the PHR includes the address of the communication partner and information about the data length of the data that follows. The data body is the main body of the information to be sent to the communication partner and includes the actual data to be transmitted. For example, the data body includes information such as the ID information of the recipient of the communication frame, the ID information of the sender, instruction information from the master unit 10 to the slave unit 20, sensor values ​​detected by sensors on the slave unit 20, and the operating status of the actuator controlled by the slave unit 20.

[0034] [2-2. Preamble Code] The preamble included in the UWB communication frame format F1 has multiple patterns. The preamble code is a parameter that identifies these multiple patterns.

[0035] In this embodiment, UWB communication is performed in accordance with the IEEE 802.15.4 communication standard, and there are 24 types of preamble codes, code "1" to "24". Codes "1" to "8" are preamble codes with a PRF (Pulse Repletion Frequency) of 16 MHz. Codes "9" to "24" are preamble codes with a PRF of 64 MHz. The preamble codes can be divided into two groups, focusing on the PRF. Codes "1" to "8" are the low-code group with a low PRF. Codes "9" to "24" are the high-code group with a high PRF. In other words, the preamble codes are stratified into multiple groups with different PRFs. The preamble codes include high-code and low-code preamble codes with different PRFs.

[0036] Figure 4 shows the trend in communication success rates for each preamble code combination when two UWB communications are performed simultaneously. Here, the two UWB communications use radio waves in the same frequency band (e.g., 8 GHz). The trends shown in Figure 4 are derived from experimental results. As shown in Figure 4, there are four patterns in the trend of communication success rates.

[0037] Pattern (1) is when the preamble code (code value) is the same for each UWB communication. In this case, there is a high probability that both of the two UWB communications will fail.

[0038] Furthermore, pattern (2) is when the preamble codes in each UWB communication are low-code and have different code values. In this case, there is a high probability that both of the two UWB communications will succeed.

[0039] Furthermore, pattern (3) is the case where the preamble code in each UWB communication is high code and the other is low code. In this case, the communication using the high code preamble is more likely to succeed.

[0040] Also, the pattern in (4) is a case where the preamble codes in each UWB communication have high codes and different code values from each other. In this case, it is highly likely that either of the two UWB communications will succeed.

[0041] In the communication system SYS1 of the present embodiment, by utilizing the communication characteristics of the preamble code as described above, stable communication that is less affected by radio wave interference is achieved. In the present embodiment, in each of the plurality of UWB communications performed in the communication system SYS1, by selecting an appropriate preamble code, stable communication that is less affected by radio wave interference is achieved. Details thereof will be described later.

[0042] In addition to the above IEEE 802.15.4, there are also standards such as IEEE 802.15.4z for the UWB communication standard. In the communication standard IEEE 802.15.4z, as types of preamble codes, codes "25" to "32" are added to the above codes "1" to "24". That is, when following the communication standard IEEE 802.15.4z, the types of preamble codes are 32 types of codes "1" to "32".

[0043] Codes "25" to "32" are preamble codes mainly assumed to be used for ranging applications with a PRF of 111 MHz. Note that the preamble codes "25" to "32" may also be used for applications other than ranging, such as data communication and radar communication. In this specification, in order to clarify that the preamble codes "25" to "32" are a different group from the above low codes and high codes as a group of preamble codes, the preamble codes "25" to "32" are described as ranging codes.

[0044] FIG. 5 is a diagram showing the tendency of the communication success rate for each combination of preamble codes when two UWB communications in which at least one uses a ranging code are simultaneously performed. Here, the two UWB communications are UWB communications using radio waves in the same frequency band (for example, 8 GHz, etc.). Also, the tendency shown in FIG. 5 summarizes the findings obtained from previous research.

[0045] The pattern in (A) is the case where the preamble codes of two UWB communications are the same ranging code (the code values are the same). In this case, it is highly likely that either of the two UWB communications will fail.

[0046] The pattern in (B) is the case where the preamble codes of two UWB communications are ranging codes and have different code values from each other. In this case, it is highly likely that either of the two UWB communications will succeed.

[0047] The pattern in (C) is the case where, among the preamble codes of two UWB communications, one is a ranging code and the other is a low code. In this case, it is highly likely that the communication using the ranging code among the two UWB communications will succeed.

[0048] The pattern in (D) is the case where, among the preamble codes of two UWB communications, one is a ranging code and the other is a high code. In this case, it is highly likely that either of the two UWB communications will succeed.

[0049] When performing UWB communication according to the communication standard IEEE 802.15.4z, in addition to the communication characteristics shown in FIG. 4, by utilizing the communication characteristics shown in FIG. 5, it is possible to achieve stable communication that is less affected by radio wave interference.

[0050] <3. Communication Operation> Next, the communication operation in the communication system SYS1 will be described. FIG. 6 is a diagram showing the main characteristics of the UWB communication used in the communication system SYS1. As shown in FIG. 6, in the communication system SYS1, channel "9" is used among a plurality of frequency channels (16 channels from 0 to 15) determined in advance according to the communication standard. FIG. 6 is, in other words, a communication characteristic table showing the outline of the UWB communication of channel "9".

[0051] As shown in Figure 6, channel "9" is a UWB communication with a center frequency of 7987.2 MHz and a bandwidth of 499.2 MHz. Furthermore, six preamble codes (3, 4, 9, 10, 11, and 12) are available for selection on channel "9". As mentioned above, code values ​​3 and 4 are low-code preamble codes, while code values ​​9, 10, 11, and 12 are high-code preamble codes. The method for determining which preamble codes are available will be described later.

[0052] As described above, in this embodiment, IEEE 802.15.4 is used as the communication standard for UWB communication. However, this is an example, and IEEE 802.15.4z may also be used as the communication standard for UWB communication. In this case, eight preamble codes with code values ​​from 25 to 32 are added to the preamble codes that can be selected and used on channel "9".

[0053] Furthermore, in this embodiment, the channel for UWB communication is "9," but this is merely an example. The channel used for UWB communication may be other than "9." By changing the channel, the center frequency, bandwidth, and the types of preamble codes that can be selected and used will be changed accordingly.

[0054] [3-1. Preamble Code Determination Operation] When a new slave unit 20 requests a new communication connection, the control unit 11 of the master unit 10 determines the preamble code to be used for UWB communication with the new slave unit 20 based on the connection information with the slave unit 20 that is already connected at the time of the new communication connection request. Here, the connection information is information necessary for the master unit 10 to perform UWB communication with the slave unit 20, and includes preamble code information. The master unit 10 stores the connection information of the slave unit 20 that is already connected in the storage unit 12. Also, the slave unit 20 that is already connected at the time of the new communication connection request can be rephrased as the already connected slave unit 20.

[0055] According to this embodiment, the master unit 10 can quickly determine the preamble code to be used for UWB communication with a new slave unit 20 by utilizing the connection information of communication with a slave unit 20 that it owns, thereby minimizing radio interference with UWB communication with other slave units 20.

[0056] The following provides a more detailed explanation with specific examples. Figure 7 is a schematic diagram illustrating the preamble code determination process in the communication system SYS1.

[0057] In Figure 7, the master unit 10 has a connection information table T1. More specifically, the connection information table T1 is stored in the storage unit 12. The connection information table T1 is a table that shows information related to communication between the master unit 10 and the slave unit 20, and includes information on "ID", "preamble code", and "priority".

[0058] "ID" is identification information provided to identify multiple slave units 20. "Preamble code" is the preamble code used when the slave unit 20 performs UWB communication with the master unit 10. The preamble code is given by the above code value in detail, and in this example it is one of "3", "4", "9", "10", "11", or "12".

[0059] The "priority" is determined by the importance of the communication performed by the slave unit 20; the higher the importance of the communication, the higher the priority, and the lower the importance of the communication, the lower the priority. The importance of the communication is determined, for example, by the characteristics or functions of the slave unit itself, or by the environment in which the vehicle C1 equipped with the communication system SYS1 is located. Since the importance of the communication may change depending on the environment in which the vehicle C1 equipped with the communication system SYS1 is located, the priority that has been set may be changed later. This will be explained later.

[0060] In the example shown in Figure 7, priority is classified as either "High" or "Low". "High" indicates a high priority. "Low" indicates a low priority. Note that in this example, priority is classified into two categories, "High" and "Low," but this is merely an example, and priority may be classified into three or more categories.

[0061] In the connection information table T1, "ID" functions as the primary key of the table. That is, a data record is generated for each ID. The data record stores the "preamble code" and "priority," which are information corresponding to each ID. The master unit 10 obtains the ID, preamble code, and priority from information obtained, for example, through UWB communication with the slave unit 20. However, this is merely an example. The master unit 10 may, for example, determine the priority of the slave unit 20 itself based on the characteristics and functions of the slave unit 20.

[0062] In Figure 7, as can be seen from the connection information table T1, three slave devices 20—one with ID "XXX", one with ID "YYY", and one with ID "ZZZ"—are connected to the master device 10. Hereafter, in order to distinguish between slave devices 20 with different IDs, the first letter of the ID may be appended to the name of the slave device 20. For example, the slave device 20 with ID "XXX" will be written as slave device 20X.

[0063] In Figure 7, the high-priority slave units 20X and 20Z are assigned high-code preamble codes, while the low-priority slave unit 20Y is assigned a low-code preamble code. As can be seen from Figure 4 above, UWB communication between slave unit 20X and master unit 10 has a high probability of success even if UWB communication between slave unit 20Z and master unit 10 occurs at the same time, because they use high-code preamble codes with different code values. Similarly, UWB communication between slave unit 20X and master unit 10 has a high probability of success even if UWB communication between slave unit 20Y and master unit 10 occurs at the same time, because there is a difference between high-code and low-code preamble codes. Likewise, UWB communication between slave unit 20Z and master unit 10 has a high probability of success even if the timing of the communication is the same as that of UWB communication between slave unit 20X and master unit 10, and UWB communication between slave unit 20Y and master unit 10.

[0064] On the other hand, UWB communication between the slave unit 20Y and the master unit 10 is more likely to fail if the timing of the communication is the same as that of the slave unit 20X or the slave unit 20Y and the master unit 10, due to the difference between low and high preamble codes. However, since the communication of the slave unit 20Y has a lower priority, a communication failure will not be a major problem.

[0065] The slave unit 20A shown in Figure 7 is a new slave unit that requests a new communication connection from the master unit 10. As shown in Figure 7, the new slave unit 20A has an ID of "AAA", a default preamble code of "10" used for UWB communication with the master unit 10, and a priority of "High". The default preamble code is a preamble code that is assigned to the new slave unit 20A in advance. The new slave unit 20A requests a communication connection from the master unit 10 using the default preamble code.

[0066] Furthermore, the master unit 10 can perform UWB communication in conjunction with any of the preamble codes (there are six types as described above) that can be selected and used on channel "9". This configuration can be achieved, for example, by having the master unit 10 equipped with as many communication devices as there are preamble codes that can be selected and used on channel "9".

[0067] Furthermore, the default preamble code for a new slave unit 20A is predetermined regardless of the connection information of the master unit 10 (information included in the connection information table T1). For this reason, the default preamble code may be the same as the preamble code used by a slave unit 20 already connected to the master unit 10. For this reason, if a new slave unit 20A uses the default preamble code as is, the probability of UWB communication failure may increase. Taking this into consideration, the system is configured so that when a communication connection request is received from a new slave unit 20A, a preamble code determination process is performed.

[0068] In the example shown in Figure 7, at the time a new slave unit 20A requests a communication connection, there is a slave unit 20Z already connected to the master unit 10 (an existing slave unit) that uses the same preamble code as the new slave unit 20A. Specifically, both the default preamble code and the preamble code used by slave unit 20Z have a code value of "10". The control unit 11 of the master unit 10 detects this by referring to the connection information table T1. The control unit 11 determines the preamble code to be used for UWB communication with the new slave unit 20A so that the preamble codes do not have the same value (code value).

[0069] For example, the control unit 11 can select a preamble code that is not used by the already connected slave units 20X, 20Y, or 20Z from among the preamble codes available on channel "9" to be used for UWB communication with the new slave unit 20A. In the example shown in Figure 7, one of the code values ​​"4", "11", or "12" can be selected as the unused (available) preamble code. For example, from the available preamble codes, it is possible to select the one with the largest code value (in this example, "12") or the one with the smallest code value (in this example, "4").

[0070] However, in this embodiment, a preferred configuration is that the control unit 11 determines the preamble code to be used for UWB communication with a new slave unit 20A based on priority information provided to each slave unit 20. By configuring the system to assign a preamble code to a new slave unit 20 while considering priority information in this way, it is possible to suppress situations such as a decrease in the success rate of important UWB communications.

[0071] More specifically, the control unit 11 determines, based on priority information, which of several groups of preamble codes to use for UWB communication with the new slave device 20A. More specifically, the control unit 11 determines, based on priority information, whether to use a high-code or low-code preamble code for UWB communication with the new slave device 20A. For example, if the priority of UWB communication with the new slave device 20A is high, the control unit 11 assigns a high-code preamble code to the UWB communication. Also, for example, if the priority of UWB communication with the new slave device 20A is low, the control unit 11 assigns a low-code preamble code to the UWB communication.

[0072] In the example shown in Figure 7, the priority of the new slave unit 20A is "High," indicating a high communication priority. For this reason, the control unit 11 assigns a high code, which indicates a high success rate of communication, to the preamble code used for UWB communication with the new slave unit 20A. In this case, the control unit 11 selects an available preamble code from among the high-code preamble codes that is not being used by the already connected slave units 20X, 20Y, and 20Z. In the example shown in Figure 7, the code values ​​of the available preamble codes are "11" or "12," so the control unit 11 selects one of these. The selection can be determined based on a predetermined rule. The predetermined rule may be, for example, selecting the smallest of the candidate code values. Once the control unit 11 has determined the preamble code to be assigned to the new slave unit 20A, it updates the connection information table T1.

[0073] Once the preamble code to be assigned to the new slave unit 20A is determined, UWB communication using the default preamble code is performed between the master unit 10 and the new slave unit 20A. Through this UWB communication, the master unit 10 notifies the new slave unit 20A of the determined preamble code. When the new slave unit 20A responds to this notification, the master unit 10 and the new slave unit 20A then perform UWB communication using the determined preamble code.

[0074] Figure 8 shows the connection information table T1 after the preamble code to be assigned to the new slave unit 20A has been determined in the example shown in Figure 7. In the example shown in Figure 8, the control unit 11 assigns the new slave unit 20A the code value "11", which is the smallest code value among the available high-code preamble codes.

[0075] In the example shown in Figure 7, if the priority of the new slave unit 20A is "Low," the preamble code assigned to the new slave unit 20A may be a low code, but if there is a high code available, a high code may be assigned. Also, if the priority of the new slave unit 20A is "Low" and there are no low code preamble codes available, the new slave unit 20A may be assigned a preamble code that overlaps with that of the already connected slave unit 20, which has a low UWB communication priority. In such a configuration, the success rate of communication for the new slave unit 20A may decrease, but this is not a major problem because the communication priority is low.

[0076] Figure 9 illustrates a different example from Figure 7 of the preamble code determination operation in the communication system SYS1. The left side of Figure 9 shows the connection information table T1 at the time a new slave device 20A makes a communication connection request. The right side of Figure 9 shows the connection information table T1 after the preamble code assigned to the new slave device 20A has been determined. In the example shown in Figure 9, the new slave device 20A has an ID of "AAA", a default preamble code of "10" used for UWB communication with the master device 10, and a priority of "High".

[0077] In the example shown in Figure 7, at the time of the communication connection request from the new slave unit 20A, there was an available high-code preamble code among the selectable and available high-code preamble codes that was not being used by the already connected slave unit 20. In contrast, in the example shown in Figure 9, at the time of the communication connection request from the new slave unit 20A, all of the selectable and available high-code preamble codes were being used by the already connected slave unit 20. In other words, there were no available high-code preamble codes that were not being used by the already connected slave unit 20.

[0078] In the example shown in Figure 9, the control unit 11, similar to the example shown in Figure 7, decides to assign a high-code preamble to the preamble code used by the new slave unit 20A based on priority information. However, in the example shown in Figure 9, since there are no available high-code preamble codes, the control unit 11 checks whether there is a low-priority slave unit 20 among the already connected slave units 20 that are using high-code preamble codes. In the example shown in Figure 9, there is a slave unit 20U that is using a high-code preamble code and has low priority. The control unit 11 decides to assign a low-code preamble code to slave unit 20U, and then assign the high-code preamble code (code value "10") that became available to the new slave unit 20A. In this way, the success rate of low-priority communications may decrease, but the decrease in the success rate of communications for high-priority slave units 20 can be suppressed. For low-priority communications, a decrease in the success rate of communications is not a major problem.

[0079] In other words, in this example as well, as explained in Figure 7, the control unit 11 determines the preamble code to be used for UWB communication with the new slave unit 20A based on the connection information and priority information with the slave unit 20 that is already connected. Then, in this example, the control unit 11 determines, based on the priority information, whether to change the preamble code used for UWB communication with the already connected slave unit 20 at the time of the request for a new communication connection. Specifically, the control unit 11 determines, based on the priority information, whether or not to change the preamble code used for UWB communication with the already connected slave unit 20 from a high code to a low code. By configuring the system so that the preamble code of the already connected slave unit 20 is changed based on the priority information, it is possible to suppress the decrease in the success rate of communication for the new slave unit 20A, which has a higher priority.

[0080] Unlike the example shown in Figure 9, there may be cases where there are no low-priority slave units 20 among the already connected slave units 20 using high-code preamble codes, making it impossible to generate an available high-code preamble code. In such cases, for example, a configuration may be used in which a high-code preamble code that is estimated to be used infrequently for UWB communication is assigned to the new slave unit 20A. Alternatively, if there is an available low-code preamble code, a configuration may be used in which a low-code code is assigned even if it has high priority. Furthermore, if the communication standard is IEEE 802.15.4z, an available distance measuring code may be assigned instead of a high-code code. Additionally, when designing the communication system SYS1, the number of slave units 20 performing high-priority communication may be configured so as not to exceed the number of available high-code preamble codes.

[0081] Furthermore, in the example shown in Figure 9, the assigned code value for the slave device 20U, whose preamble code assignment has been changed from a high code to a low code, is "3," but it could also be "4." When multiple slave devices 20 are assigned duplicate preamble codes, the assignment may be performed based on predetermined rules. The predetermined rules may be, for example, a configuration that selects the smallest of the candidate code values. Also, when multiple slave devices 20 are assigned duplicate preamble codes, a configuration may be used in which a code value is estimated to be used infrequently in UWB communication is selected from among the candidate code values.

[0082] Furthermore, in the example shown in Figure 9, if the priority of the new slave unit 20A is "Low," the preamble code assigned to the new slave unit 20A should be a low code. There are two candidate code values ​​for the low code preamble code: "3" and "4." The choice between them can be made in the same way as described above. If either of the code values ​​is unused and available, it should be selected. If there are no available code values, the code value to be selected should be determined based on predetermined rules or the frequency of UWB communication usage.

[0083] Figure 10 is a flowchart illustrating the process of determining the preamble code to be assigned to a new slave device 20, which is executed by the master unit 10. This flowchart shows the technical details of the computer program that causes the computer (control unit 11) in the master unit 10 to perform the process of determining the preamble code to be assigned to the new slave device 20. The process shown in Figure 10 starts when the master unit 10 becomes ready to accept a new communication connection request from the slave device 20.

[0084] In step S1, the control unit 11 monitors for any new communication connection requests from the slave devices 20. The control unit 11 determines that there is a new communication connection request when it receives a UWB signal transmitted by the communication unit 13 from a slave device 20 other than an already connected slave device 20. In other words, the control unit 11 detects a new slave device 20. If there is a new communication connection request (Yes in step S1), the process proceeds to the next step S2. If there is no new communication connection request (No in step S1), the monitoring process in step S1 continues.

[0085] In step S2, the control unit 11 determines whether the new slave unit 20 that has requested a new communication connection has a high priority. Whether or not it has a high priority is included, for example, in the information transmitted from the new slave unit 20 to the master unit 10 via UWB communication. If it is determined that the priority is high (Yes in step S2), the process proceeds to the next step S3. If it is determined that the priority is low (No in step S2), the process proceeds to step S8.

[0086] In step S3, the control unit 11 determines whether there are any unused preamble codes among the selectable high-code preamble codes (9, 10, 11, 12 in this example). This determination can be performed using the connection information table T1 described above. If there are available high-code preamble codes (Yes in step S3), the process proceeds to the next step S4. If there are no available high-code preamble codes (No in step S3), the process proceeds to step S7.

[0087] In step S4, the control unit 11 determines which of the available high-code preamble codes will be assigned to the new slave unit 20. Once the preamble code is determined, the process proceeds to the next step S5.

[0088] In step S5, the control unit 11 notifies the new slave unit 20 of the determined preamble code. Once this notification process is complete, the process proceeds to the next step S6. The new slave unit 20, upon receiving the notification, sends a response to the master unit 10 indicating that it has received the notification. The new slave unit 20 also sets the preamble code used for UWB communication with the master unit 10 to the preamble code notified by the master unit 10.

[0089] In step S6, the control unit 11 receives a response from the new slave unit 20. Based on this, the control unit 11 sets the preamble code used for UWB communication with the new slave unit 20 to the previously determined preamble code. The control unit 11 updates the connection information table T1. Note that, due to some trouble, it may not be possible to receive a response from the new slave unit 20. In this case, the control unit 11 can repeat the notification process to the new slave unit 20 in step S5.

[0090] In step S7, the control unit 11 performs a preamble code assignment adjustment process, taking into account the change of the preamble code of the already connected slave unit 20, because there are no available high-code preamble codes. The preamble code assignment adjustment process includes changing the preamble code of the already connected slave unit 20, which has a low UWB communication priority, from a high code to a low code, and generating an available high-code preamble code. Through the preamble code assignment adjustment process, a high-code preamble code is assigned to the new slave unit 20, which has a high UWB communication priority. The preamble code of the new slave unit 20 is determined by the assignment process. After this, the process proceeds to step S5 described above.

[0091] In step S8, the control unit 11 determines whether there are any unused preamble codes among the selectable and available preamble codes (3, 4, 9, 10, 11, 12 in this example). This determination can be performed using the connection information table T1 described above. If there are available preamble codes (Yes in step S8), the process proceeds to the next step S9. If there are no available preamble codes (No in step S8), the process proceeds to step S10. In the process of step S8 shown here, even if the priority of the new slave unit 20 in UWB communication is low, if there are available high-code preamble codes, a high-code preamble code may be assigned. However, if the priority is low, a low-code preamble code may always be assigned.

[0092] In step S9, the control unit 11 determines which of the available preamble codes will be assigned to the new slave unit 20. Once the preamble code is determined, the process proceeds to step S5.

[0093] In step S10, the control unit 11 determines that the preamble code to be assigned to the new slave unit 20 is one that overlaps with a preamble code already assigned to a low-priority, already connected slave unit 20, because there are no available preamble codes. The method for overlapping assignment of low-priority preamble codes is as described above. Once the preamble code is determined, the process proceeds to step S5 above.

[0094] [3-2. Operation to Change Preamble Code] In the communication system SYS1 of this embodiment, the preamble code assigned to an already connected slave unit 20 that is already connected to the master unit 10 may be changed in a situation other than when a new slave unit 20 is connected. This will be explained below.

[0095] Vehicle information, which is information related to the vehicle C1, is input to the control unit 11. The vehicle information may be provided to the master unit 10 (control unit 11) from an ECU or sensor connected to the master unit 10 via a CAN (Controller Area Network) bus or the like. Alternatively, the vehicle information may be provided to the master unit 10 (control unit 11) from a slave unit 20 that communicates with the master unit 10 via UWB.

[0096] Vehicle information, in more detail, is information that informs the status of the vehicle itself. Here, "vehicle itself" refers to vehicle C1 equipped with the communication system SYS1. Information that informs the status of the vehicle itself may include, for example, information about an accident occurring in the vehicle, information about the vehicle approaching a highway toll booth, information about the vehicle starting to back up, information about the vehicle starting to park, etc. Vehicle information may be information that informs the status of the vehicle directly or indirectly. Vehicle information may be, for example, the information about an accident occurring in the vehicle itself, or information that makes it possible to obtain information about an accident occurring in the vehicle. Examples of information that makes it possible to obtain information about an accident occurring in the vehicle include G-sensor detection information and airbag deployment information.

[0097] The control unit 11 changes the preamble code used for UWB communication with the already connected slave unit 20 based on the vehicle information at the time the vehicle information is acquired. With this configuration, the preamble code used for UWB communication with the slave unit 20 can be flexibly changed according to the situation in which the vehicle is located.

[0098] In detail, the control unit 11 determines the priority of communication with already connected slave units 20 based on the vehicle information at the time of vehicle information acquisition. Then, the control unit 11 changes the preamble code used for UWB communication with already connected slave units at the time of vehicle information acquisition according to the priority determined based on the vehicle information. With this configuration, the communication priority, which changes depending on the situation in which the vehicle is located, can be appropriately determined, and a preamble code with a high success rate can be assigned to UWB communication that handles information with high priority at that time. In other words, the control unit 11 changes the priority information set for each of the multiple slave units 20 based on the acquired vehicle information. Furthermore, the control unit 11 changes the preamble code used for UWB communication with connected slave units 20 based on the changed priority information.

[0099] The following provides a more detailed explanation with specific examples. Figure 11 is a diagram illustrating the operation of changing the preamble code in the communication system SYS1. The table shown in Figure 11 is the connection information table T1 of the master unit 10. Note that the connection information table T1 shown in Figure 7 and other diagrams above did not include "device name" in the data record items generated for each ID, unlike the connection information table T1 shown in Figure 11. This is because the explanation of "device name" was omitted in the explanation of Figure 7 and other diagrams above because it was not particularly necessary.

[0100] The item "Device Name" is the name of the slave unit 20 that is connected to the master unit 10 in communication, corresponding to the type of slave unit 20. "Multimedia ECU" is an ECU that is connected to an antenna for television broadcasting or radio broadcasting and performs signal processing, for example. "Emergency Call ECU" is an ECU that performs the process of making an emergency call to an external party of the vehicle C1 using a telephone line, for example. "GPS Sensor ECU" is an ECU that is connected to a GPS sensor and performs signal processing. "Drive Recorder ECU" is an ECU that performs overall control of the drive recorder.

[0101] Figure 11 shows, in detail, the changes (transitions) in the connection information table T1 that occur when the preamble code is changed in multiple slave units 20 already connected to the master unit 10. The connection information table T1 transitions from the top row to the bottom row.

[0102] The upper connection information table T1 in Figure 11 shows the state before the preamble code change operation begins. As shown in the upper connection information table T1, the master unit 10 is connected to the following slave units: slave unit 20X, which is a multimedia ECU; slave unit 20Y, which is an emergency call ECU; slave unit 20Z, which is a GPS sensor ECU; and slave unit 20A, which is a drive recorder ECU. Each slave unit 20X, 20Y, 20Z, and 20A is assigned a preamble code determined according to its priority. Specifically, the high-priority slave units 20X and 20A are assigned high-code preamble codes that have a high success rate in communication, while the low-priority slave units 20Y and 20Z are assigned low-code preamble codes that tend to have a lower success rate in communication than the high-code codes.

[0103] In the example shown in Figure 11, it is assumed that the control unit 11 of the master unit 10 has acquired accident occurrence information indicating that an accident has occurred in its own vehicle as vehicle information. The control unit 11 may be configured to acquire the accident occurrence information itself from a device that is communicated with the master unit 10, or it may be configured to detect (acquire) the accident occurrence information itself based on information acquired from the device that is communicated with.

[0104] Upon acquiring accident information, the control unit 11 determines the priority level for the already connected slave units 20X, 20Y, 20Z, and 20A at the time of acquisition. In this case, because an accident has occurred in the vehicle itself, the control unit 11 determines that communication with the equipment necessary for dealing with the accident has a high priority. Specifically, as shown in the connection information table T1 in the middle of Figure 11, the control unit 11 determines that communication with slave unit 20X, which is a multimedia ECU, has a low priority. This is because the multimedia ECU is not particularly necessary for dealing with the accident. On the other hand, the control unit 11 determines that communication with slave unit 20Y, which is an emergency call ECU, slave unit 20Z, which is a GPS sensor ECU, and slave unit 20A, which is a drive recorder ECU, has a high priority. This is because these ECUs 20Y, 20Z, and 20A are necessary for dealing with the accident. Such determination processing can be performed, for example, based on table information stored in the storage unit 12 beforehand.

[0105] The control unit 11 updates the information stored in the "Priority" item of the connection information table T1 according to the determination result of whether the priority is high or low. The middle connection information table T1 in Figure 11 is an updated version of the upper connection information table T1 in Figure 11, according to the determination result of whether the priority is high or low.

[0106] The control unit 11 determines the preamble code to be assigned to each slave unit 20X, 20Y, 20Z, and 20A according to the updated priority information. High-priority slave units 20 are assigned high-code preamble codes, and low-priority slave units 20 are assigned low-code preamble codes. The assignment is made so that the code values ​​of the preamble codes do not overlap for each slave unit 20X, 20Y, 20Z, and 20A.

[0107] In detail, the control unit 11 changes the preamble code of the sub-unit 20X, which is a multimedia ECU, from the high-code preamble code "9" to the low-code preamble code "3" because it has a low priority. The control unit 11 changes the preamble code of the sub-unit 20Y, which is an emergency call ECU, from the low-code preamble code "3" to the high-code preamble code "9" because it has a high priority. The control unit 11 changes the preamble code of the sub-unit 20Z, which is a GPS sensor ECU, from the low-code preamble code "4" to the high-code preamble code "10" because it has a high priority. The control unit 11 maintains the preamble code of the sub-unit 20A, which is a drive recorder ECU, at the high-code preamble code "11" because it has a high priority.

[0108] As described above, UWB communication using high-code preamble codes has a high success rate, so in vehicle C1, the functions of high-priority slave units 20Y, 20Z, and 20A can be appropriately utilized to take the necessary actions in the event of an accident.

[0109] Furthermore, when the control unit 11 changes the preamble code, it updates the information stored in the "Preamble Code" item of the connection information table T1. The lower connection information table T1 in Figure 11 is an updated version of the middle connection information table T1 in Figure 11, corresponding to the change in the preamble code.

[0110] Furthermore, the priority assigned at the time of an accident may no longer be appropriate once the accident has been dealt with. For this reason, it is preferable to either revert to the original priority or re-evaluate the priority once the accident has been dealt with. It is also preferable to perform a preamble code modification process in conjunction with the timing of the priority being reverted.

[0111] Furthermore, while the above example assumes that vehicle information is accident occurrence information, this is merely an example. For example, vehicle information could be information about approaching a toll booth on a highway. In this case, the priority of communication with the ETC (Electronic Toll Collection system)-ECU, which normally has a low priority, may be increased, and the preamble code assigned to the ETC-ECU may be changed from a low code to a high code accordingly. Whether or not the vehicle is approaching a toll booth may be determined, for example, using the vehicle's location information obtained using a GPS sensor and map information stored in the memory unit 12.

[0112] Furthermore, for example, the vehicle information may be the vehicle's reverse start information. In this case, the priority of communication with the backup monitor ECU, which normally has a low priority, may be increased, and the preamble code assigned to the backup monitor ECU may be changed from a low code to a high code accordingly. Note that whether or not the vehicle starts to reverse may be determined by whether or not the vehicle's gear setting is in reverse gear.

[0113] Figure 12 is a flowchart illustrating the process of changing the preamble code assigned to an already connected slave unit 20, which is executed according to vehicle information. This flowchart shows the technical details of the computer program that causes the computer (control unit 11) in the master unit 10 to implement the process of changing the preamble code assigned to an already connected slave unit 20. The process shown in Figure 12 is executed, for example, when there are multiple already connected slave units 20 that have established a UWB communication connection with the master unit 10.

[0114] In step S21, the control unit 11 monitors whether or not specific vehicle information has been acquired. Specific vehicle information is vehicle information that affects the priority of UWB communication, and includes, for example, the accident occurrence information, information about approaching a highway toll booth, or information about starting to reverse. If the control unit 11 acquires specific vehicle information (Yes in step S21), it proceeds to the next step S22. If the control unit 11 does not acquire specific vehicle information (No in step S21), it continues the monitoring process in step S21.

[0115] In step S22, the control unit 11 determines the priority of UWB communication for each of the multiple already connected slave units 20 based on the acquired specific vehicle information. The priority may be determined, for example, according to table information that shows the relationship between vehicle information and the priority for each communication type, which is stored in the storage unit 12 beforehand. Once the priority has been determined for each of the already connected slave units 20, the process proceeds to the next step S23.

[0116] In step S23, the control unit 11 updates the information stored in the "Priority" item of the connection information table T1 according to the priority of each of the already connected slave units 20 determined in step S22. Once the priority information update process is complete, the process proceeds to the next step S24.

[0117] In step S24, the control unit 11 performs a preamble code modification process according to the priority information of each connected slave device 20 that was updated in step S23. High-priority slave devices 20 are assigned high-code preamble codes. Low-priority slave devices 20 are assigned low-code preamble codes. If there are available high-code preamble codes, a low-priority slave device 20 may be assigned a high-code preamble code. Once the preamble code modification process is complete, the process proceeds to the next step S25.

[0118] In step S25, the control unit 11 notifies the slave unit 20 whose preamble code has been changed of the changed preamble code. During this notification, the preamble code before the change is used for UWB communication between the master unit 10 and the slave unit 20. If there are multiple slave units 20 whose preamble codes have been changed, the control unit 11 notifies each of the multiple slave units 20 of the change in preamble code. Once this change notification process is completed, the process proceeds to the next step S26.

[0119] Upon receiving notification of a change in the preamble code, the slave unit 20 sends a response to the master unit 10 to acknowledge receipt of the notification. This response is sent using the preamble code before the change. The slave unit 20 also sets the preamble code used for UWB communication with the master unit 10 to the preamble code notified by the master unit 10.

[0120] In step S26, the control unit 11 receives a response from the slave unit 20 that has received notification of a change in the preamble code. As a result, the control unit 11 confirms the preamble code to be used for UWB communication with the slave unit 20 that decided to change the preamble code, and updates the information stored in the "Preamble Code" item of the connection information table T1. From then on, the master unit 10 performs UWB communication using the changed preamble code. However, it is possible that the master unit 10 may not be able to receive a response from the slave unit 20 due to some trouble. In such a case, the control unit 11 may repeat the notification process to the slave unit 20 in step S25 for the slave unit 20 that failed to send a response.

[0121] [3-3. Modifications] In the embodiments described above, the preamble code to be assigned to a new slave unit 20 is determined based on priority information provided to the slave unit 20, but this is merely an example. A configuration in which the preamble code to be assigned to a new slave unit 20 is determined without using priority information is also possible.

[0122] The control unit 11 may determine the preamble code to be used for UWB communication with a new slave unit 20 according to a pre-set arrangement based on the type and number of preamble codes. More specifically, the control unit 11 may determine the preamble code to be used for UWB communication with a new slave unit 20 based on a pre-set arrangement based on the type and number of preamble codes, and the connection information of already connected slave units 20. The type of preamble code is a type of preamble code stratified by pulse repetition frequency, such as the low code and high code mentioned above. Even with a configuration like the modified example, when a new slave unit 20 requests a new communication connection, the preamble code to be used for UWB communication with the new slave unit 20 can be quickly determined in a way that minimizes radio interference with UWB communication with other slave units 20.

[0123] Figure 13 shows an example of an arrangement based on the type and number of preamble codes. In Figure 13, "Preamble Code in Use" refers to the preamble code that the already connected slave unit 20 is using for UWB communication with the master unit 10. In Figure 13, "n" refers to the number of preamble codes in use. In Figure 13, "Code Type" refers to the type of preamble code, which in this modified example is either a low code or a high code. This is because IEEE 802.15.4 is used as the communication standard; if IEEE 802.15.4z is used as the communication standard, "Code Type" will be a low code, a high code, or a distance measuring code. In Figure 13, "Selected Code" indicates the type of preamble code selected by the control unit 11.

[0124] According to the arrangement shown in Figure 13, the control unit 11 will determine the preamble code as follows. The arrangement shown in Figure 13 is stored as table information in the storage unit 12. Here again, the channel used for UWB communication is "9". There are six types of selectable preamble code values: low codes "3" and "4", and high codes "9", "10", "11", and "12".

[0125] If the number of preamble codes currently in use is zero (n=0) (i.e., there are no already connected slave devices 20), the control unit 11 assigns one of the four high-code preamble codes (any of code values ​​9 to 12) to be used as the preamble code for the new slave device 20 to use for UWB communication. By using a high-code preamble code, the success rate of UWB communication for the new slave device 20 can be increased.

[0126] The selection of which of the multiple high-code preamble codes to choose from among the candidates can be performed according to predetermined rules. For example, the system may select the code value with the smallest number among the candidates, or the code value with the largest number. The same method can be used in other cases as well. For this reason, the explanation of this point will be omitted below.

[0127] Furthermore, if n=1 and the code type is a low code, the control unit 11 assigns one of the four high-code preamble codes (one of code values ​​9 to 12) to the preamble code that the new slave unit 20 will use for UWB communication, just as in the case of n=0. In this case as well, using a high-code preamble code can increase the success rate of UWB communication for the new slave unit 20.

[0128] Furthermore, if n=1 and the code type is a high code, the control unit 11 assigns one of three high code preamble codes—one of the high code preamble codes currently in use and another with a different code value—to the new slave unit 20 for UWB communication. UWB communications using high code preamble codes with different code values ​​do not interfere with each other, and all have a high success rate (see Figure 4), thus increasing the success rate of the new slave unit 20's UWB communication.

[0129] Furthermore, if n=2 and all code types are low codes, the control unit 11 assigns one of the four high-code preamble codes to be used by the new slave unit 20 for UWB communication, just as in the case of n=0. UWB communication using a high-code preamble code has a high success rate even when it occurs simultaneously with UWB communication using a low-code preamble code (see Figure 4). Therefore, by determining the preamble code to be assigned to the new slave unit 20 in this way, the success rate of UWB communication for the new slave unit 20 can be increased.

[0130] Furthermore, if n=2 and all code types are high-code, or a mixture of low-code and high-code, the control unit 11 assigns the preamble code to be used by the new slave unit 20 for UWB communication as follows: The control unit 11 assigns one of the high-code preamble codes (two or three types exist) with a code value different from the high-code preamble code currently in use as the preamble code to be used by the new slave unit 20 for UWB communication. UWB communications using high-code preamble codes with different code values ​​always have a high success rate. Also, UWB communications using high-code preamble codes have a high success rate even when they occur simultaneously with UWB communications using low-code codes (see Figure 4 for both). Therefore, by determining the preamble code to be assigned to the new slave unit 20 in this way, the success rate of the new slave unit 20's UWB communication can be increased.

[0131] Furthermore, if n=3 and all code types are high-level codes, or a mixture of low-level and high-level codes, the control unit 11 assigns the preamble code to be used by the new slave unit 20 for UWB communication as follows: The control unit 11 assigns one of the high-level preamble codes (one or two types exist) that are different from the high-level preamble code currently in use to the new slave unit 20 for UWB communication. The effect of this is the same as in the case where n=2 and all code types are high-level codes, or a mixture of low-level and high-level codes.

[0132] Furthermore, if n=4 and all code types are high codes, the control unit 11 assigns one of the two low code preamble codes to be used by the new slave unit 20 for UWB communication. This configuration allows for the assignment of a preamble code that is not currently in use for UWB communication with the new slave unit 20, thereby suppressing a decrease in the communication success rate.

[0133] Furthermore, if n=4 and the code types are a mix of low and high codes, the control unit 11 assigns the preamble code to be used by the new slave unit 20 for UWB communication as follows: The control unit 11 assigns a high-code preamble code (one type exists) with a code value different from the high-code preamble code currently in use to the new slave unit 20 for UWB communication. The effect of this is the same as in the case where n=2 and all code types are high codes, or a mix of low and high codes.

[0134] Furthermore, if n = 5 or more and the code types are a mixture of low and high codes, the control unit 11 assigns the preamble code to be used by the new slave unit 20 for UWB communication as follows: The control unit 11 assigns the preamble code with the lowest usage (or zero usage) among the high-code preamble codes to be used by the new slave unit 20 for UWB communication. In this method, multiple UWB communications may occur using high-code preamble codes with the same code value. However, since the preamble code is determined in such a way that the number of these multiple UWB communications is kept to a minimum, the possibility of these multiple UWB communications occurring simultaneously can be reduced as much as possible. In other words, this configuration can suppress a decrease in the success rate of communication for the new slave unit 20.

[0135] For example, as shown in Figure 7, let's assume that three slave units 20X, 20Y, and 20Z are connected to the master unit 10. The preamble code "9" is used for UWB communication between the master unit 10 and slave unit 20X. The preamble code "3" is used for UWB communication between the master unit 10 and slave unit 20Y. The preamble code "10" is used for UWB communication between the master unit 10 and slave unit 20Z. In other words, slave units 20X and 20Z use high-code preamble codes for UWB communication with the master unit 10. Slave unit 20Y uses a low-code preamble code for UWB communication with the master unit 10. However, in this example, priority information is not assigned to each slave unit 20.

[0136] In this assumed example, the preamble code currently in use is n=3, and the code values ​​are a mix of low and high codes. Therefore, according to the arrangement shown in Figure 13, the code value of the preamble code of the new sub-unit 20A will be a high code value different from the high code value currently in use. The code values ​​of the high code preamble code currently in use are "9" and "10". Therefore, the candidate code values ​​for the preamble code of the new sub-unit 20A are "11" or "12". The method for selecting from the multiple candidate code values ​​may be determined based on the predetermined rules as described above. If the rule is to select the smallest of the multiple candidate code values, then the code value "11" will be selected as the preamble code of the new sub-unit 20A.

[0137] <4. Points to Note, etc.> Various technical features disclosed in the embodiments for carrying out the invention in this specification can be modified in various ways without departing from the spirit of the technical creation. In addition, the multiple embodiments and modifications disclosed in the embodiments for carrying out the invention in this specification may be combined to the extent possible.

[0138] <5. Addendum> The following addendum is disclosed with respect to the multiple embodiments, examples, and modifications shown above.

[0139] This disclosure can take the following configurations (1) to (9).

[0140] (1) A communication device used as a master unit capable of UWB communication with multiple slave units, comprising a control unit, wherein the control unit determines a preamble code to be used for UWB communication with a new slave unit based on connection information including preamble code information of a slave unit that has already been connected.

[0141] (2) The communication device according to (1), wherein the control unit determines the preamble code to be used for UWB communication with the new slave unit based on priority information provided to each of the plurality of slave units.

[0142] (3) The communication device according to (2), wherein the preamble codes are stratified into a plurality of groups having different pulse repetition frequencies, and the control unit determines, based on the priority information, which of the plurality of groups the preamble code to be used for UWB communication with the new slave unit is to be.

[0143] (4) The communication device according to (2) or (3), wherein the control unit determines, based on the priority information, whether to change the preamble code used for UWB communication with the connected slave unit.

[0144] (5) The communication device according to (4), wherein the preamble code includes a high-code preamble code and a low-code preamble code having different pulse repetition frequencies, and the control unit determines, based on the priority information, whether or not to change the preamble code used for UWB communication with the connected slave unit from the high-code to the low-code.

[0145] (6) A communication device mounted on a vehicle, wherein the control unit changes the priority information set for each of the plurality of slave units based on the vehicle information which is acquired information relating to the vehicle, and changes the preamble code used for UWB communication with the slave unit that has already been connected based on the changed priority information, according to any one of (1) to (5).

[0146] (7) The communication device according to (6), wherein the vehicle information includes at least one of the following: information on the occurrence of an accident in the vehicle, information on approaching a highway toll booth, and information on the start of reversing.

[0147] (8) The communication device according to (1), wherein the control unit determines the preamble code to be used for UWB communication with the new slave unit based on a pre-set arrangement of the type and number of preamble codes and the connection information.

[0148] (9) A communication program that causes a computer in a communication device used as a master unit capable of UWB communication with multiple slave units to function as a means for determining a preamble code to be used for UWB communication with a new slave unit, based on connection information including preamble code information of a slave unit that is already connected.

[0149] 10... Master unit (communication device) 11... Control unit 20... Slave unit (communication device) 121... Communication program C1... Vehicle T1... Connection information table

Claims

1. A communication device used as a master unit capable of UWB communication with multiple slave units, comprising a control unit, wherein the control unit determines the preamble code to be used for UWB communication with a new slave unit based on connection information including the preamble code information of a slave unit that is already connected.

2. The communication device according to claim 1, wherein the control unit further determines the preamble code to be used for UWB communication with the new slave unit based on priority information provided to each of the plurality of slave units.

3. The communication device according to claim 2, wherein the preamble code is stratified into a plurality of groups having different pulse repetition frequencies, and the control unit determines, based on the priority information, which of the plurality of groups the preamble code to be used for UWB communication with the new slave unit is to be.

4. The communication device according to claim 2, wherein the control unit determines, based on the priority information, whether to change the preamble code used for UWB communication with the connected slave unit.

5. The communication device according to claim 4, wherein the preamble code includes a high-code preamble code and a low-code preamble code having different pulse repetition frequencies, and the control unit determines, based on the priority information, whether or not to change the preamble code used for the UWB communication with the connected slave device from the high-code to the low-code.

6. A communication device mounted on a vehicle, wherein the control unit changes the priority information set for each of the plurality of slave units based on the vehicle information which is acquired information relating to the vehicle, and changes the preamble code used for the UWB communication with the slave unit that has already been connected based on the changed priority information, according to any one of claims 1 to 5.

7. The communication device according to claim 6, wherein the vehicle information includes at least one of the following: information on the occurrence of an accident in the vehicle, information on approaching a highway toll booth, and information on the start of reversing.

8. The communication device according to claim 1, wherein the control unit determines the preamble code to be used for UWB communication with the new slave unit based on a pre-set arrangement of the type and number of preamble codes and the connection information.

9. A communication program that causes a computer in a communication device used as a master unit capable of UWB communication with multiple slave units to function as a means for determining the preamble code to be used for UWB communication with a new slave unit, based on connection information including the preamble code information of a slave unit that is already connected.

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