Decision device, decision method, and communication device

Abstract

To provide a determination device, a determination method, and a communication device capable of appropriately setting a preamble to be used on communication and capable of stable communication.SOLUTION: The determination device is for selecting and determining a preamble to be used for communication by a communication target device from a predetermined set of preambles in communication using a preamble. The determination device has a controller. The controller collects information on usage state preambles used in ongoing communications around a communication target device, detects the usage state preambles on the basis of the collected information on the usage state preambles, and determines the preamble to be used for the communication of the communication target device on the basis of the detected usage state preambles.SELECTED DRAWING: Figure 3

Description

Technical Field

[0006] , , , ,

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

Background Art

[0002] In recent years, in the field of communication, wireless communication has been increasing due to advantages in installation such as the needlessness of wiring. For example, UWB (Ultra Wide Band) communication using radio waves in the 8 GHz band has less radio wave interference with radio waves used in Wi-Fi (registered trademark) and mobile terminals such as smartphones, and due to its wide bandwidth of 500 MHz, it has good permeability and its applications are expanding. In addition, UWB communication is expected as a communication means for in-vehicle devices because communication is likely to be established even in a narrow space with a lot of wiring inside a vehicle, which is a metal space.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when UWB communication becomes widely popular, in a narrow space such as inside a vehicle, there is a possibility that radio wave interference may occur between devices performing UWB communication and communication may become unstable. This problem of radio wave interference may similarly occur not only in UWB but also when a plurality of devices communicate using radio waves in the same frequency band.

[0005] The present application has been made in view of the above, and an object thereof is to provide a determination device, a determination method, and a communication device capable of performing stable communication.

Means for Solving the Problems

[0006] The decision device according to the present invention is a decision device that, in communication using a preamble, selects and determines from a predetermined set of preambles which a communication target device will use for communication, and comprises a controller. The controller collects information on the usage status preambles used in communication currently running around the communication target device, detects a usage status preamble based on the collected information on the usage status preambles, and determines the preamble to be used for communication by the communication target device based on the detected usage status preamble. [Effects of the Invention]

[0007] According to the present invention, the preamble used for communication can be appropriately set, resulting in the effect of stable communication. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a diagram showing an overview of the communication system according to the embodiment. [Figure 2] Figure 2 shows the main characteristics of the communication method (UWB) used in communication systems. [Figure 3] Figure 3 is a block diagram of a UWB communication device. [Figure 4] Figure 4 shows an example of equipment information. [Figure 5] Figure 5 shows the frame format used in UWB communication. [Figure 6] Figure 6 shows the success rate (experimental results) for each combination of preamble types used by two UWB communications when two UWB communications are performed simultaneously. [Figure 7] Figure 7 shows the results of the analysis of the experimental results shown in Figure 6. [Figure 8] Figure 8 shows the determination processing information for the preamble code determination process, which is used to determine the preamble code of the preamble used for communication. [Figure 9]Figure 9 illustrates an example of how to modify the preamble used for UWB communication based on the slave device's category level. [Figure 10] Figure 10 is a sequence diagram illustrating the operation flow of the master ECU and slave unit when the preamble is changed. [Figure 11] Figure 11 shows the process for determining the preamble code. [Modes for carrying out the invention]

[0009] Below, one embodiment (hereinafter referred to as "Embodiment") for realizing the determination device, determination method, and communication device according to the present application will be described in detail with reference to the drawings. Note that this embodiment does not limit the determination device and determination method according to the present application. Furthermore, the same parts are denoted by the same reference numerals in each of the following embodiments, and redundant descriptions are omitted.

[0010] First, an overview of the communication system according to the embodiment will be described using Figures 1 and 2. Figure 1 is a diagram showing an overview of the communication system according to the embodiment. Figure 2 is a diagram (table) showing the main characteristics of the communication method (UWB) used in the communication system.

[0011] In recent years, UWB communication has become available for use both indoors and outdoors in Japan. Its applications are expanding because it experiences less interference with Wi-Fi (registered trademark) and radio waves used by mobile devices such as smartphones, and because it uses a wide bandwidth with good penetration. UWB communication is particularly promising as a communication method for in-vehicle equipment because it can easily establish communication even in the confined space of a car with many wires.

[0012] In FIG. 1, as an example of a system using UWB communication, a slave device 1a to 1d mounted on a vehicle C and a master ECU 100 perform wireless communication via UWB communication, and an example of a vehicle control system S (hereinafter, communication system S) in which the master ECU 100 controls the slave devices 1a to 1d is shown. Specifically, the slave devices 1a to 1d transmit sensor values and the like detected by sensors provided therein to the master ECU 100 via communication, or control actuators provided therein based on control signals transmitted from the master ECU 100.

[0013] For example, the master ECU 100 is an ECU of a center device that controls each in-vehicle device in an integrated cooperation, the slave device 1a is an air conditioner device that performs air conditioning in the vehicle interior, and the slave device 1b is a navigation device that performs route guidance. Then, the air conditioner device transmits a state signal of the internal / external air circulation to the center device via UWB communication, and the navigation device transmits a running state in a tunnel to the center device via UWB communication.

[0014] Based on the state information of the internal / external air circulation of the air conditioner device received by the center device via UWB communication and the running state information in the tunnel from the navigation device, the center device generates a switching control signal for the internal / external air circulation of the air conditioner device and transmits the switching control signal to the air conditioner device via UWB communication. Thereby, the center device can control the air conditioner device to operate according to various states of the vehicle.

[0015] In such a control state, in the communication system S of FIG. 1, the slave devices 1a to 1d and the master ECU 100 perform data communication via UWB communication.

[0016] Also, in FIG. 1, an example of a scene where a terminal device 200 and a terminal slave device 210 held by a user (brought into the vehicle) perform wireless communication via UWB communication in the communication area of the communication system S in the vehicle C is shown. For example, the terminal device 200 executes an application program that detects the position of the terminal slave device 210 via UWB communication and displays the position of the terminal slave device 210 on the screen of the terminal device 200.

[0017] In the example shown in FIG. 1, in a scenario where a plurality of UWB communications are executed simultaneously, that is, when UWB communication between the master ECU 100 and its communication target device (any one of the slave devices 1a to 1d) and UWB communication between the terminal device 200 and the terminal slave device 210 are performed simultaneously, there is a possibility of radio wave interference due to radio waves in the same frequency band (for example, 8 GHz band) being transmitted from a plurality of devices.

[0018] In this case, with respect to the UWB communication radio waves between the master ECU 100 and its communication target device, interference waves, which are the UWB communication radio waves between the terminal device 200 and the terminal slave device 210, may cause radio wave interference, and there is a possibility that communication between the master ECU 100 and its communication target device may become impossible.

[0019] FIG. 2 is a communication characteristic table showing an overview of UWB communication on channel 9. As shown in FIG. 2, channel 9 is a UWB communication in which the center frequency is 7987.2 MHz, the bandwidth is 499.2 MHz, and preambles of six types of preamble codes (3, 4, 9, 10, 11, 12) can be selectively used.

[0020] Among the preamble codes, the preambles of code 3 and code 4 are low-code preamble groups of 16 PRF (Pulse Repletion Freqency), and the four preambles of code 9, code 10, code 11, and code 12 are high-code preamble groups of 64 PRF. And the communication of each preamble of code 9, code 10, code 11, and code 12 of 64 PRF is less susceptible to radio wave interference in relation to the code length (the longer the code length, the more likely it is to have a part that is out of radio wave interference and it is easier to detect a predetermined data pattern of the preamble) and the PRF value compared to the communication of each preamble of code 3 and code 4 of 16 PRF, and the reception of the radio waves of the preambles of 64 PRF is prioritized (communication is more likely to succeed during radio wave interference).

[0021] In other words, in UWB communication, if communication using a preamble of code 9, code 10, code 11, or code 12 interferes with communication using a preamble of code 3 or code 4, the communication using a preamble of code 9, code 10, code 11, or code 12 is more likely to succeed. In the following, codes 9, 10, 11, and 12 may be referred to as high codes, and codes 3 and 4 as low codes.

[0022] Furthermore, since low-code preambles have a larger data volume (transmission time of the preamble itself) than high-code preambles, communication using low-code preambles is advantageous (faster) in terms of communication speed.

[0023] Furthermore, if multiple communications are occurring simultaneously, radio interference between them can make communication difficult. However, if each communication uses a different preamble in this situation, a slight delay in communication timing may allow the preamble to be partially recognized, enabling subsequent synchronization and other communication establishment processes, and potentially allowing the reception of device data. In contrast, if each communication uses the same preamble in this situation, even if a slight delay in communication timing allows the preamble to be partially recognized, it will be impossible to determine which communication it corresponds to, making subsequent synchronization and other communication establishment processes difficult.

[0024] Furthermore, communications that have recognized the preamble and completed communication establishment processes such as synchronization are resistant to radio interference due to the redundancy function of the data itself. In other words, in communications using a preamble, communications that start earlier have the characteristic of being able to communicate preferentially over communications that start later.

[0025] Therefore, the communication system according to this embodiment incorporates features that enable stable communication by utilizing the characteristics of communication using these preambles.

[0026] Specifically, in the communication system S according to this embodiment, the system selects and sets an appropriate preamble code for communication in the communication system S to suppress communication failures due to radio interference and ensure stable communication.

[0027] The following describes the general operation of the communication system S. It is assumed that the master ECU 100 and slave units 1a to 1d have a built-in determination device that selects and sets the preamble code according to the communication status (thus determining the preamble to be used for UWB communication). However, either the master ECU 100 or any of the slave units 1a to 1d may have this determination device built-in.

[0028] Furthermore, in the example shown in Figure 1, the terminal device 200 and the slave terminal 210 are assumed not to have the decision device built in.The following explanation describes the case where slave unit 1a communicates with the master ECU 100, but the operation is the same when slave units 1b to 1d communicate with the master ECU 100, or when slave units 1a to 1d communicate with each other.

[0029] Specifically, when the slave unit 1a performs UWB communication with the master ECU 100, it receives radio waves transmitted from communication devices (in the case of Figure 1, terminal sub-unit 210) located around the slave unit 1a (in a position where it can receive UWB communication radio waves), that is, radio waves that the slave unit 1a can receive (detect).

[0030] The slave device 1a then analyzes the preamble pattern of the signal in the received radio waves, extracts and stores information about the preamble code being used (resulting in the storage of the preamble type). In other words, the slave device 1a collects information about the status preamble being used in communications currently running in its vicinity. After collecting preamble codes from preambles in the surrounding radio waves for a predetermined period of time, the slave device 1a detects the status preamble based on the collected preamble codes and determines the preamble code to be used when communicating based on the detected status preamble.

[0031] In the example shown in Figure 1, the slave device 1a has collected (detected) the preamble code 9 of the preamble used by the terminal device 210 for UWB communication. Therefore, the slave device 1a decides to use a high-code preamble code other than preamble code 9, for example, preamble code 10, as the preamble code to be used for UWB communication. The slave device 1a then performs UWB communication using this preamble code (for example, preamble code 10) that is not being used by the surrounding communication devices. The determined preamble code is used both when the slave device 1a transmits radio waves to the master ECU 100 and when the master ECU 100 transmits radio waves to the slave device 1a. Details on how to determine the preamble code of the preamble used for UWB communication will be described later in Figure 8.

[0032] Thus, in the communication system S according to this embodiment, by performing UWB communication with the target device while avoiding the use of preambles that are being used for UWB communication by other communication devices in the surrounding area (the range affected by interference), it is possible to suppress instability of UWB communication due to radio wave interference, even when UWB communication overlaps (interference waves are present). In other words, stable UWB communication can be performed according to the communication system S according to this embodiment.

[0033] In Figure 1, an example of operation against radio interference caused by UWB communication between terminal device 200 and terminal slave 210 was explained. However, the same effect can be obtained against radio interference caused by UWB communication between other slave devices 1b to 1d by slave device 1a performing the same operation as described above (using a different preamble than slave devices 1b to 1d). Furthermore, slave devices 1b to 1d can also obtain the same effect by performing the same operation as slave device 1a during their own UWB communication (using a different preamble between other devices (such as between terminal device 200 and terminal slave 210) and between other slave devices 1x).

[0034] Next, an example of the configuration of a UWB communication device (slave units 1a to 1d, master ECU 100) 1 incorporating a decision device according to the embodiment will be described using Figure 3. Figure 3 is a block diagram of the UWB communication device 1. In Figure 3, the example is given where the UWB communication device 1 is a slave unit 1 (1a to 1d) and the communication target device is the master ECU 100, but the UWB communication device 1 or the target device may be the master ECU 100, a terminal device 200, or a terminal slave unit 210. As shown in Figure 3, the UWB communication device 1 according to the embodiment comprises a communication unit 2, a storage unit 3, and a control unit 4.

[0035] The communication unit 2 performs UWB communication with communication target devices such as the master ECU 100, and is implemented by a UWB communication device, such as a NIC (Network Interface Card) equipped with a UWB communication interface (UWB communication circuit).

[0036] The memory unit 3 stores various data used by the program executed by the control unit 4, and is composed of memory devices such as RAM, ROM, non-volatile memory, flash memory, and hard disk drives. In order to determine the preamble code of the preamble used in UWB communication, the memory unit 3 stores device information D31 in the device information storage unit 31. The memory unit 3 also stores decision processing information D32 in the decision processing information storage unit 32.

[0037] Device information D31 is information about communication devices performing UWB communication that are present around UWB communication device 1. Device information D31 is updated each time UWB communication device 1 detects a communication device performing UWB communication (receives UWB communication radio waves). Figure 4 shows an example of device information D31. As shown in Figure 4, device information D31 includes information on "device ID", "preamble code", and "category level".

[0038] "Device ID" is identification information that identifies a communication device. It is the identification information of the source device, extracted by analyzing the radio waves received from the communication device (extracting the source identification information contained in the header signal). "Preamble Code" is preamble code information, which is the identification information of the preamble, extracted by analyzing the radio waves received from the communication device (recognizing the signal pattern of the preamble and comparing it with the signal pattern of each preamble to determine the corresponding preamble code). "Category Level" is information that indicates the importance of the communication performed by the communication device. For example, it is extracted by analyzing the radio waves received from the communication device (extracting the category level information contained in the header signal. In this case, it is necessary to specify that category level information be added to the header signal). In Figure 4, category level "0" is considered to be of higher importance than "1". Category level information can be obtained by adding category level information to the communication data itself, or by determining the category level based on table data (comparison data between device type and category level) from the device type (device type information is included in the header signal or the communication data itself, and the received radio waves are analyzed and recognized).

[0039] Returning to the explanation of Figure 3, let's describe the control unit 4. The control unit 4 is a so-called controller and includes, for example, a computer and various circuits having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), a hard disk drive, input / output ports, etc. The computer's CPU functions, for example, by reading and executing a program stored in ROM.

[0040] The control unit 4 comprises a collection unit 41, a determination unit 42, and a setting unit 43.

[0041] The collection unit 41 collects information on the preamble codes of preambles used by communication devices surrounding the UWB communication device 1. First, the collection unit 41 switches to a UWB radio wave reception mode to receive UWB communications. For example, it switches to a radio wave reception mode that receives radio waves in the 8GHz band, which is the frequency band for UWB communications, and performs data decoding. The switch to the radio wave reception mode occurs, for example, when the UWB communication device 1 is started up, at predetermined intervals after startup, or when a mode change instruction is given by the user.

[0042] In radio wave reception mode, communication with the master ECU 100, etc., is not performed, and only radio waves are received and some data is decoded. After switching to radio wave reception mode, the data acquisition unit 41 monitors UWB communication radio waves and analyzes the received radio waves each time it receives UWB communication radio waves to recognize the preamble code and category level of the preamble.

[0043] Here, we will explain the frame format used in UWB communication using Figure 5. Figure 5 is a diagram showing the frame format used in UWB communication. As shown in Figure 5, the UWB communication frame format F 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 (referred to as the data body to make the difference from the preamble, SFD, and PHR clearer).

[0044] A preamble is a predetermined pattern of bit sequence that is transmitted before the data itself in digital communication to inform the receiver that data is about to be sent. Multiple patterns of preambles exist, and a preamble code is a code used to identify these preambles. The collection unit 41 analyzes the bit sequence of the first preamble in the frame of the received radio wave and extracts the preamble code.

[0045] The Small Format Data (SFD) is a specific pattern of bits used to signal the beginning of data in a frame. The Personal Record (PHR) contains information necessary for decoding the packet. For example, the PHR may include the address of the communication partner and information about the length of the data that follows.

[0046] The data body is the main body of the information to be sent to the communication partner and contains the actual data to be transmitted. For example, the data body may include information such as the ID information of the frame's recipient, the ID information of the sender, sensor values ​​detected by sensors provided by the UWB communication device 1, the operating status of the actuator controlled by the UWB communication device 1, and category level.

[0047] The collection unit 41 then analyzes the data body of the received radio waves and extracts the category level and source identification information. The collection unit 41 associates the extracted source identification information, preamble code, and category level and stores them in the storage unit 3 as device information D31. In other words, it generates a data record of the extracted source identification information in the device information storage unit 31 and stores the preamble code and category level corresponding to that data record. If a record of the same source identification information already exists in the device information storage unit 31, the record will be overwritten with the preamble code and category level of the newly extracted same source identification information.

[0048] Furthermore, since the process of determining the preamble used by the UWB communication device 1 for communication does not require the use of source identification information, when storing the collected information in the device information storage unit 31, the device ID data in the device information storage unit 31 may be appropriately created by the determination device. However, this method has the drawback that if a communication device changes its preamble during a single UWB radio wave reception mode period, an unused preamble will be determined to be in use. However, this is thought to occur infrequently, and the impact can be sufficiently suppressed by setting an appropriate length for the UWB radio wave reception mode period.

[0049] After the data collection unit 41 has entered radio wave reception mode, if a predetermined time has elapsed, it will switch from radio wave reception mode to normal mode (a mode in which it communicates with the master ECU 100, etc., in response to a communication request).

[0050] Furthermore, the collection unit 41 may collect not only information on the UWB radio wave conditions around its own UWB communication device 1, but also information on the UWB radio wave conditions around the UWB communication devices that will be the communication partners (other slave devices 1x, master ECU 100). In this case, information on the UWB radio wave conditions of each communication device is collected through communication with the UWB communication devices that will be the communication partners (using the preamble in use at that time). Each communication device will have its collection unit 41 collect information on the UWB radio wave conditions in the same manner as described above.

[0051] The determination unit 42 determines the preamble code of the preamble that the UWB communication device 1 will use for communication, based on the preamble codes of the preambles in use by the surrounding devices, which were collected by the collection unit 41 during the radio wave reception mode. The method for determining the preamble code will now be explained using Figures 6 to 8.

[0052] Figure 6 shows the success rate (experimental results) of each combination of preamble types used by two UWB communications when two UWB communications are performed simultaneously. Figure 7 is a table showing the analysis of the experimental results shown in Figure 6.

[0053] Based on the experimental results in Figure 6, and as shown in the table of analysis results in Figure 7, there appear to be four patterns in the trend of communication success rates.

[0054] Pattern (1) is when the preamble is the same in each UWB communication, in which case both the first and second communications are likely to fail.

[0055] Furthermore, pattern (2) is when the preamble in each UWB communication is a different low-code preamble, in which case both the first and second communications are likely to succeed.

[0056] Furthermore, pattern (3) is the case where one preamble in each UWB communication is a high-code preamble and the other is a low-code preamble, in which case the communication using the high-code preamble is more likely to succeed.

[0057] Furthermore, pattern (4) is when the preamble in each UWB communication is a different high-code preamble, in which case both the first and second communications are likely to succeed.

[0058] Figure 8 shows the determination processing information D32 for the preamble code determination process, which determines the preamble code of the preamble used for communication. This information is created in advance based on the trend of communication success rates based on the preamble used for UWB communication shown in Figures 6 and 7, and is stored in the storage unit 3. The determination unit 42 then determines the preamble code of the preamble used by the UWB communication device 1 for UWB communication according to this determination processing information D32.

[0059] The decision processing information D32 shown in Figure 8 includes information on the number of communications taking place in the surrounding area, the type of preamble used in those communications (preamble usage status), and the preamble code of a preamble suitable for use in relation to the status of communications taking place in the surrounding area (number of communications and type of preamble used) (preferred preamble code).

[0060] Specifically, the determination unit 42 calculates the status of surrounding communications by aggregating and summarizing the number of preamble types (preamble code types) used in communications taking place in the surrounding area (hereinafter referred to as the number of preamble types used) and the breakdown of the preamble types (preamble code types) being used, based on the data of the device information D31. Then, it refers to the determination processing information D32 based on the calculated communication status and determines the preamble code of a preamble that is suitable for use.

[0061] For example, according to the decision processing information D32 shown in Figure 8, if the number of preamble types used is zero (if there are no preambles in use), the decision unit 42 determines one of the high-code preamble codes, codes 9 to 12, as the preamble code for the preamble that the UWB communication device 1 will use for communication.

[0062] High-code preambles are more resistant to interference than low-code preambles. Therefore, even if other communications using low-code preambles or high-code preambles begin during communication using a high-code preamble, the communication is less likely to be disrupted by radio interference. In this example, there are no other communications in the vicinity, and there is no impediment to using a high-code preamble, so stable communication is achieved by using a high-code preamble.

[0063] Furthermore, if the number of preamble types used is 1 and the number of preamble types used is a low-code preamble, the determination unit 42 determines one of the high-code preamble codes, codes 9 to 12, or another low-code preamble, as the preamble code for the preamble that the UWB communication device 1 will use for communication. In other words, if there is a preamble of a type belonging to the high-code preamble group that is not in use, the determination unit 42 determines that the preamble of a type belonging to the high-code preamble group that is not in use will be the preamble that the UWB communication device 1 will use for communication. As a result, if surrounding communications that affect the UWB communication of the UWB communication device 1 are using low-code preambles, the UWB communication device 1 will perform UWB communication using a low-code preamble that is not in use or a high-code preamble that is less affected by the surrounding communications, and the UWB communication will be less susceptible to communication interference caused by radio waves.

[0064] Furthermore, if the number of preamble types used is 1 and the preamble used is a high-code preamble, the determination unit 42 determines a different high-code preamble as the preamble code for the preamble that the UWB communication device 1 will use for communication. As a result, if surrounding communications that affect the UWB communication of the UWB communication device 1 are using high-code preambles, the UWB communication device 1 will perform UWB communication using a high-code preamble that is not currently in use and is less affected by those surrounding communications, thus making the UWB communication less susceptible to communication interference caused by radio waves.

[0065] Furthermore, if the number of preamble types used is 2 and all preambles used are low-code preambles, the determination unit 42 determines a high-code preamble as the preamble code for the preamble that the UWB communication device 1 will use for communication. As a result, if surrounding communications that affect the UWB communication of the UWB communication device 1 are using low-code preambles, the UWB communication device 1 will perform UWB communication using a high-code preamble that is not currently in use and is less affected by those surrounding communications, thus making the UWB communication less susceptible to communication interference caused by radio waves.

[0066] Furthermore, if the number of preamble types used is 2 and all of the preambles used are high-code preambles, the determination unit 42 determines a different high-code preamble as the preamble code for the preamble that the UWB communication device 1 will use for communication. As a result, if surrounding communications that affect the UWB communication of the UWB communication device 1 are using high-code preambles, the UWB communication device 1 will perform UWB communication using a high-code preamble that is not currently in use and is less affected by those surrounding communications, thus making the UWB communication less susceptible to communication interference caused by radio waves.

[0067] Furthermore, if the number of preamble types used is 3, and the preambles used are a mixture of low-code and high-code preambles, or all are high-code preambles, the determination unit 42 determines a different high-code preamble as the preamble code for the preamble that the UWB communication device 1 will use for communication. As a result, if surrounding communications that affect the UWB communication of the UWB communication device 1 are using high-code preambles (including cases where low-code preambles are used), the UWB communication device 1 will perform UWB communication using a high-code preamble that is not currently in use and is less affected by those surrounding communications, thus making the UWB communication less susceptible to communication interference caused by radio waves.

[0068] Furthermore, if the number of preamble types used is 4 and all of the preambles used are high-code preambles, the determination unit 42 determines a low-code preamble as the preamble code for the preamble that the UWB communication device 1 will use for communication. As a result, if the surrounding communications that affect the UWB communication of the UWB communication device 1 are using all of the high-code preambles, the UWB communication device 1 will perform UWB communication using a low-code preamble that is not in use and is less affected by the surrounding communications, so that UWB communication will be less susceptible to communication interference caused by radio waves.

[0069] Furthermore, if the number of preamble types used is 4, and the preambles used are a mixture of low-code and high-code preambles, the determination unit 42 determines a different high-code preamble as the preamble code for the preamble that the UWB communication device 1 will use for communication. As a result, if surrounding communications that affect the UWB communication of the UWB communication device 1 are using low-code and high-code preambles, the UWB communication device 1 will perform UWB communication using a high-code preamble that is not currently in use and is less affected by those surrounding communications, thus making the UWB communication less susceptible to communication interference caused by radio waves.

[0070] Furthermore, if the number of preamble types used is 5 (in this case, the preamble types used will be a mix of low-code and high-code preambles), the determination unit 42 determines the preamble code of the preamble with the fewest number of communications using that preamble among the high-code preambles to be used as the preamble code for communication by the UWB communication device 1. In other words, if there are no preamble types belonging to the unused high-code preamble group, and there are preamble types belonging to the used low-code preamble group, the determination unit 42 counts the number of communications using each preamble type belonging to the high-code preamble group, and determines the preamble with the fewest counted communications to be used as the preamble for communication by the UWB communication device 1. As a result, the UWB communication device 1 will perform UWB communication using a high-code preamble that is not in use, which is less susceptible to interference from surrounding communications, or a high-code preamble that is relatively unlikely to be in use (because there are fewer communications using it, the possibility of simultaneous communication is low). Therefore, the UWB communication will be less susceptible to communication interference caused by radio waves.

[0071] Furthermore, if all high-code preambles are in use, and all or one low-code preamble is also in use, the likelihood of radio interference increases. Therefore, in such situations, one method is to add a function that changes the preamble used by UWB communication device 1, which performs other communications of lower importance (priority).

[0072] Specifically, in the communication system S shown in Figure 1, an importance level (category level shown in Figure 4) is set for each slave unit 1a to 1d. In communication between the master ECU 100 and these slave units 1a to 1d, if communication overlaps, the preamble used for each communication is arbitrated according to the importance level of the slave units 1a to 1d (and the communication between them) (prioritizing the preamble used for communication with the high-importance slave unit 1x so that communication with the high-importance slave unit is more likely to be established). For example, if all high-code preambles are in use and low-code preambles are also in use, the master ECU 100 sets the preamble used for communication with the high-importance slave unit 1x to a high-code preamble, and sets the preamble used for communication with other slave units 1y to another preamble.

[0073] Figure 9 illustrates an example of changing the preamble used for UWB communication based on the category level (importance) of the slave device 1x. In the example in Figure 9, the preamble with preamble code 11 is set as the preamble used for communication on slave device 1a, which has a category level of 1. The preamble with preamble code 11 is also set as the preamble used for communication on slave device 1b, which has a category level of 0. It is also assumed that preambles with higher codes other than preamble code 11 are used for other UWB communication (slave device 1x, which has a category level of 0). Note that category level 0 indicates a higher importance of communication than category level 1.

[0074] In this situation, the data collection unit 41 of the slave unit 1b monitors (receives) UWB communication radio waves and detects UWB communication taking place in the vicinity (that affects UWB communication). The data collection unit 41 of the slave unit 1b then learns (stores information) the identification information of the slave unit, the importance of the communication, and the preamble code of the preamble being used in the UWB communication taking place in the vicinity. When the slave unit 1b performs UWB communication, the determination unit 42 of the slave unit 1b determines the preamble code of the preamble to be used for UWB communication using the method described above, based on the learned information (in the example in Figure 9, preamble code 11 is determined). In this decision, if there is no suitable preamble that is not being used and the preamble decided to be used is duplicated, the decision unit 42 compares the category level (category level 1) of the other communication (slave device 1a) using the duplicated preamble with the category level (category level 0) of its own communication (slave device 1b). If the category level of the other communication device (slave device 1a) is higher (low importance), it requests a change of the preamble used by the other communication device (slave device 1a) via the master ECU 100 (to change the preamble used by slave device 1a to the preamble code 3: the master ECU 100 sends a command to slave device 1a to change the preamble used based on the request from slave device 1b). Until the preamble used by the other communication device (slave device 1a) is changed, the device's own communication will use a duplicate preamble, which may slightly increase the likelihood of unstable communication. However, once the preamble used by the other communication device (slave device 1a) is changed, the original communication will be less affected by the duplicate preamble, and stable communication can be expected.

[0075] The setting unit 43 performs the process of setting the preamble corresponding to the preamble code determined by the determination unit 42 as the preamble to be used for UWB communication.

[0076] Specifically, the setting unit 43 notifies the communication partner (in the case of slave unit 1x, the master ECU 100) of a request to change the preamble used for communication to the preamble code determined by the determination unit 42. Then, when the setting unit 43 receives a change permission notification (reception confirmation notification) from the communication partner granting permission to change the preamble used for communication (or, in the case of automatic change, confirmation of receipt of the change request), it sets the preamble used for communication with the communication partner to the preamble code determined by the determination unit 42. This preamble setting is performed by instructing the communication unit 2 to use the preamble using the preamble code, and the communication unit 2 performs communication using the preamble of the type (preamble code) based on that instruction.

[0077] Furthermore, while communications regarding changes to the preamble used for these communications will be conducted using the preamble of the previous type, the small data volume means that the impact of radio interference will be minimal.

[0078] Furthermore, the control unit 4 (setting unit 43) of the communication device on the other party's side (in this communication system S, the master ECU 100 or the slave device 1x) sends a change permission notification (reception confirmation notification) to the communication device on the other party's side based on the preamble change request from the other party, and also instructs its own communication unit 2 to use the preamble using the said preamble code.

[0079] Figure 10 is a sequence diagram illustrating the operation flow of the master ECU 100 and slave unit 1a (explained as a representative of slave unit 1x) when the preamble is changed. It shows the operation when slave unit 1a requests a change in the preamble.

[0080] As shown in Figure 10, the slave device 1a first learns the type of preamble (preamble code) used by surrounding communication devices by receiving radio waves from those devices, and then determines the preamble code of the preamble that the slave device 1a will use for communication (step S101).

[0081] Next, the slave unit 1a notifies the master ECU 100, its communication partner, of the request to change to the determined preamble code (step S102).

[0082] Next, the master ECU 100 notifies the slave unit of the change permission notice (step S103). After that, the master ECU 100 changes the preamble used for communication with the slave unit 1a to the preamble code for which the change request was made.

[0083] Next, when slave unit 1a receives a change permission notification from master ECU 100, it sets the preamble used for communication to the preamble for which the change permission was granted (step S104), and starts communication with master ECU 100 using that preamble (step S105).

[0084] Furthermore, when determining the preamble using category levels and requesting a preamble change from another communication device (let's call this communication device slave 1b), the master ECU 100 also transmits the preamble change request information to slave 1b in step S102. Then, along with the operation in step S103 (notification of permission to change to slave 1a), the master ECU 100 transmits a preamble change command to slave 1b, and subsequently changes the preamble used for communication with slave 1b to the preamble specified in the preamble change command.

[0085] Next, the preamble code determination process will be explained using Figure 11. Figure 11 is a diagram showing the preamble code determination process. The process shown in Figure 11 is performed immediately after the UWB communication device 1 is started up, and is also performed repeatedly at regular intervals thereafter. This allows for stable communication with reduced interference from radio waves immediately after the target device is started up. Furthermore, even if the surrounding radio wave environment changes, such as when a communication device is brought in after startup, stable communication can still be performed with reduced interference.

[0086] As shown in Figure 11, the control unit 4 switches to a mode for receiving radio waves in the 8GHz band, which is the UWB communication band for checking the surrounding UWB communication environment (step S201).

[0087] Next, the control unit 4 determines whether or not it has received a UWB communication signal (step S202). If it has received a signal (step S202: Yes), it demodulates and decodes the UWB communication signal to extract the preamble, etc., and analyzes the preamble code, the type of transmitting device of the source, the category (and further the category level based on the category) (step S203).

[0088] Next, the control unit 4 stores the analyzed preamble code and other information as device information D31 in the device information storage unit 31 of the storage unit 3 (step S204).

[0089] Next, the control unit 4 determines whether a predetermined time has elapsed since switching to the 8GHz band radio wave reception mode, which is defined as the UWB communication environment detection period (step S205).

[0090] If a predetermined time has elapsed (step S205: Yes), the control unit 4 determines the preamble code for the preamble to be used for its own UWB communication based on the preamble (preamble code) of the device information D31 used in the surrounding UWB communication (step S206), and terminates processing. Then, the control unit 4 (setting unit 43) sets the preamble to be used for UWB communication based on the determined preamble code, and UWB communication is performed using the set preamble.

[0091] On the other hand, in step S202, if the control unit 4 does not receive radio waves from UWB communication taking place in the surrounding area (meaning no UWB communication is taking place in the surrounding area) (step S202: No), it proceeds to step S205. Also, in step S205, if the predetermined time has not elapsed (step S205: No), the control unit 4 proceeds to step S202.

[0092] As described above, the UWB communication device 1 according to this embodiment determines the preamble to be used when performing UWB communication according to the surrounding UWB communication conditions, and more specifically, the type of preamble used in the surrounding UWB communication. Therefore, the UWB communication device 1 performs UWB communication using a preamble suitable for suppressing the effects of radio interference from surrounding UWB communication, thereby enabling stable communication.

[0093] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0094] 1 UWB communication device 1a~1d Slave Unit 2 Communications Department 3 Storage section 4. Control Unit 31 Device information storage section 32 Decision Processing Information Storage Unit 41 Collection Department 42 Decision Section 43 Settings section 100 Master ECU 200 terminal devices 210 Terminal handset D31 Device information D32 Decision Processing Information C Vehicle F Frame Format

Claims

1. In communication using preambles, a determination device is used to select and determine the preamble to be used by the communication target device from a predetermined set of preambles, including a high-code preamble group and a low-code preamble group with different pulse repetition frequencies, and the device has a controller. The aforementioned controller, The system detects the usage status preamble used for ongoing communications around the target device. The group to which the aforementioned usage status preamble belongs, and the preamble to be used for communication by the communication target device based on the aforementioned usage status preamble, are determined. decision device.

2. The aforementioned controller, If no usage status preamble exists, the preamble to be used for communication by the communication target device will be selected from among the types of preambles belonging to the high-code preamble group. The determination device according to claim 1.

3. The aforementioned controller, If there are preambles of a type belonging to the high-code preamble group that are not in use, the preamble of a type belonging to the high-code preamble group that is not in use is determined to be the preamble used for communication by the communication target device. The determination device according to claim 1.

4. The aforementioned controller, If there are no preambles of the type belonging to the high-code preamble group that are not in use, and there are preambles of the type belonging to the low-code preamble group that are in use, the number of communications in which each preamble of the type belonging to the high-code preamble group is used is counted, and the preamble with the fewest counted communications is determined to be the preamble used for communication by the communication target device. The determination device according to claim 1.

5. A determination device for communication using a preamble, wherein the device to be communicated selects and determines a preamble to be used for communication from a predetermined set of preambles, and the device has a controller, The aforementioned controller, The system collects information on the usage status preamble used in communications currently running around the target device and information indicating the importance of those communications. Based on the collected usage status preamble information and importance, it determines the preamble to be used for communications by the target device. decision device.

6. The aforementioned controller, If no unused preambles exist, a request to change the preamble is made for communication devices whose importance is lower than that of the communication target device. The determination device according to claim 5.

7. A method for determining which preamble to use for communication by a communication target device, by selecting from a predetermined set of pre-defined preambles, including a high-code preamble group and a low-code preamble group with different pulse repetition frequencies. The system detects the usage status preamble used for ongoing communications around the target device. The group to which the aforementioned usage status preamble belongs, and the preamble to be used for communication by the communication target device based on the aforementioned usage status preamble, are determined. How to decide.

8. A communication device that performs communication using a preamble code, comprising a communication unit and a controller, The aforementioned controller, The system detects a status preamble used in communications currently running in the surrounding area, and from a predetermined set of predefined preambles, including high-code preamble groups and low-code preamble groups with different pulse repetition frequencies, it selects and determines a preamble to be used for communication based on the group to which the status preamble belongs and the status preamble itself, and issues a communication instruction to the communication unit to perform communication using the determined preamble. The aforementioned communications unit is Communication is performed using a preamble based on communication instructions from the aforementioned controller. Communication device.

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