Radio communication system

Abstract

To provide a radio communication system that can prevent power consumption from becoming excessive, while guaranteeing communication reliability.SOLUTION: A radio communication system generates, through communication channel control, a channel map showing a plurality of communication channels after excluding a communication channel whose communication quality is reduced from the plurality of communication channels, on the basis of communication quality data indicating the communication quality of each of the plurality of communication channels. The radio communication system determines, through transmission power control, a transmission power value in the plurality of communication channels usable for radio communication shown by the channel map, on the basis of the communication quality data on each of the plurality of communication channels usable for radio communication shown by the channel map.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication system that performs wireless communication between a master node and a slave node via one communication channel that is sequentially selected from a plurality of communication channels. [Background technology]

[0002] For example, Patent Document 1 discloses a battery system that monitors and controls multiple batteries. The battery system includes a master management device and multiple battery modules. Each battery module includes a slave management device and battery cells. The master management device transmits a monitoring control instruction signal to the slave management devices, the monitoring control signal including information on the battery cell measurement details, measurement timing, wireless communication timing for each slave management device, and the frequency channel used for wireless communication. The slave management device transmits a monitoring control result signal, the monitoring control result including information on the battery cell measurement results and the reception status of the monitoring control instruction signal, via the specified frequency channel.

[0003] The master management device manages the communication quality for each slave management device and for each frequency channel. A frequency channel with degraded communication quality is changed to another frequency channel with undegraded communication quality based on the frequency channel information included in the supervisory control instruction signal. In this way, the communication reliability of the supervisory control instruction signal and the supervisory control result signal is maintained at a high level.

[0004] Furthermore, Patent Document 1 also describes that communication reliability can be further improved by increasing the transmission power of the supervisory control instruction signal and the supervisory control result signal, and by changing the hopping pattern of frequency channel hopping. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2015 / 189898A1 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, the system described in Patent Document 1 only considers improving the communication reliability of wireless communication signals (monitoring control instruction signals and monitoring control result signals) transmitted and received between the master management device and the slave management devices. However, if control to improve the communication reliability of a wireless communication system is always performed, as in the system described in Patent Document 1, there is a risk that power consumption will become excessive. For example, when a wireless communication system performs wireless communication by receiving power from a battery, it is also important to suppress power consumption because the power stored in the battery is limited.

[0007] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a wireless communication system that can prevent excessive power consumption while ensuring communication reliability. [Means for solving the problem]

[0008] In order to achieve the above object, a wireless communication system according to the present disclosure is a wireless communication system that performs wireless communication between a master node (20) and slave nodes (30A, 30B, 40A, 40B, 50A) via one communication channel sequentially selected from a plurality of communication channels, a communication channel control unit (S290) that creates a channel map indicating the plurality of communication channels after excluding communication channels whose communication quality has deteriorated from the plurality of communication channels based on communication quality data indicating the communication quality of each of the plurality of communication channels, and selects a communication channel to be used for wireless communication from the plurality of communication channels that can be used for wireless communication indicated by the channel map; a transmission power value determination unit (S310) that determines transmission power values ​​for the plurality of communication channels available for wireless communication indicated by the channel map based on communication quality data of each of the plurality of communication channels available for wireless communication indicated by the channel map; and a transmission power control unit (S320, S470) that controls the transmission power in a plurality of communication channels that can be used for wireless communication and are indicated by the channel map so that the transmission power value determined by the transmission power value determination unit is reached.

[0009] As described above, in the wireless communication system of the present disclosure, the communication channel control unit creates a channel map indicating the plurality of communication channels after excluding communication channels whose communication quality has deteriorated from the plurality of communication channels, based on communication quality data indicating the communication quality of each of the plurality of communication channels. Therefore, the plurality of communication channels available for wireless communication indicated by the channel map can be said to be communication channels that satisfy a certain level of communication quality. The transmission power value determination unit then determines the transmission power values ​​for the plurality of communication channels available for wireless communication indicated by the channel map, based on the communication quality data for each of the plurality of communication channels available for wireless communication indicated by the channel map. Therefore, for example, if it is determined based on the communication quality data that sufficient communication reliability is ensured, the transmission power value determination unit can determine the transmission power value so as to reduce the transmission power value. In this way, by determining the transmission power value based on the communication quality data of communication channels that satisfy a certain level of communication quality, it is possible to prevent unnecessary increases in transmission power. As a result, the wireless communication system of the present disclosure can prevent excessive power consumption while ensuring communication reliability.

[0010] The reference numbers in parentheses above merely indicate an example of a correspondence with specific configurations in the embodiments described below, in order to facilitate understanding of the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

[0011] Furthermore, the technical features of the present disclosure other than those described above will become apparent from the following description of the embodiments and the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a diagram showing an example of the configuration of an in-vehicle system that operates using a wireless communication system and includes a plurality of in-vehicle devices; [Figure 2] FIG. 10 is a diagram illustrating an example of the electric field strength distribution in the communication environment between the master device and the slave device. [Figure 3] FIG. 2 is a diagram illustrating an example of received signal strength of each communication channel. [Figure 4] 10 is a flowchart illustrating an example of a start-up sequence of a master device and a slave device. [Figure 5] 10 is a flowchart illustrating an example of a communication sequence between a master device and a slave device. [Figure 6] 7 is a flowchart showing a first example of the transmission power value determination process in step S310 of the flowchart in FIG. 5. [Figure 7] 10A and 10B are explanatory diagrams for explaining a first example of a transmission power value determination process and a change in received signal strength due to a determined transmission power value. [Figure 8] 7 is a flowchart showing a second example of the transmission power value determination process in step S310 of the flowchart in FIG. [Figure 9] 7 is a flowchart showing a third example of the transmission power value determination process in step S310 of the flowchart in FIG. 5. [Figure 10] 10 is an explanatory diagram for explaining a third example of the transmission power value determination process and a change in received signal strength due to the determined transmission power value. FIG. [Figure 11] 10 is a flowchart showing a fourth example of the transmission power value determination process in step S310 of the flowchart in FIG. [Figure 12] 6 is a flowchart showing a wireless communication mode setting process based on mode setting related information in step S300 of the flowchart in FIG. 5. [Figure 13] 10A to 10C are explanatory diagrams for explaining some specific examples of mode setting related information. [Figure 14]FIG. 10 is a diagram showing a list of settings that combine the state of the in-vehicle device, the wireless communication mode of the wireless communication system, the on / off of communication channel control, and the on / off of transmission power control, as well as expected use cases, operation of the wireless communication system, and advantages for each setting. [Figure 15] FIG. 10 is an explanatory diagram for explaining the relationship between a reliability mode, a reliability-oriented balanced mode, a balanced mode, a power-saving-oriented balanced mode, and a power-saving mode. [Figure 16] 10(a) to 10(d) are explanatory diagrams illustrating the transition of wireless communication modes between the master device and the slave device when a user carrying a digital key approaches a vehicle and attempts to get into the vehicle. [Figure 17] 13 is a flowchart showing processing related to threshold value change and mode transition based on communication quality data in step S670 of the flowchart in FIG. [Figure 18] 18 is an explanatory diagram for explaining a wireless communication mode transition caused by the processing shown in the flowchart of FIG. 17. FIG. [Figure 19] 1 is a diagram illustrating an example of the configuration of a battery pack that is a monitoring target of a battery monitoring device; [Figure 20] FIG. 2 is an explanatory diagram for explaining reactive power of a battery pack. [Figure 21] 10 is a flowchart showing a mode determination process for reducing reactive power. [Figure 22] 10 is a flowchart showing a control process for suppressing unlocking of a vehicle door by a relay attack by utilizing a transition of a wireless communication mode. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present disclosure will be described below with reference to the drawings. Note that identical or similar configurations may be omitted from description by assigning the same reference numerals across multiple drawings. When only a portion of a configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the remaining portions of the configuration. Furthermore, configurations of multiple embodiments may be partially combined, even if not explicitly described, as long as there is no particular problem with the combination.

[0014] (First embodiment) The wireless communication system according to this embodiment includes at least one master device (also referred to as a master node) and at least one slave device (also referred to as a slave node). At least one of the master device and the slave device may be mounted on a vehicle for use. Examples of the vehicle include automobiles, trucks, construction vehicles, motorcycles, and railroad cars.

[0015] 1 shows an example of the configuration of an in-vehicle system 100 according to this embodiment, which includes multiple in-vehicle devices that operate using a wireless communication system 10. As shown in FIG. 1, in the in-vehicle system 100, the wireless communication system 10 can be applied to multiple vehicle devices (vehicle applications). In this case, each of the multiple slave devices 30A, 30B, 40A, and 50A is associated with one of the in-vehicle devices so as to perform wireless communication with the master device 20 for the execution of an application among the multiple vehicle applications (operation of each in-vehicle device).

[0016] For example, the wireless communication system 10 can be applied as one of vehicle applications to a battery monitoring device that monitors the state of a battery mounted as a battery pack (battery assembly) in an electrically powered vehicle such as an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. When the wireless communication system 10 is applied to a battery monitoring device, for example, at least one master device 20 is connected to a first application control device 1 that functions as a monitoring control device, and multiple first application slave devices 30A, 30B are connected to first application devices 35A, 35B that function as detection devices provided in multiple battery stacks that make up the battery pack. In this case, both the master device 20 and the first application slave devices 30A, 30B are mounted in the vehicle.

[0017] The detection devices (first application devices 35A, 35B) provided in each battery stack acquire battery information, such as the voltage and current of each battery cell included in the corresponding battery stack and the temperature of the battery stack, using various sensors. When the first application devices 35A, 35B receive data requesting battery information from the first application control device 1, which is a monitoring control device, via the wireless communication system 10, they transmit the acquired battery information to the first application control device 1 via the wireless communication system 10. Based on the acquired battery information, the first application control device 1 calculates the state of charge (SOC) of the entire battery stack, drives a heating / cooling mechanism to adjust the temperature of the battery pack within an appropriate range, and determines whether to perform so-called equalization processing to equalize the voltages of each battery cell in the battery stack. If the first application control device 1 determines that equalization processing is required for at least one battery stack, it instructs the corresponding first application device 35A, 35B to perform the equalization processing via the wireless communication system 10. In addition, the first application devices 35A and 35B perform processing to determine abnormalities in various sensors and in their own operation, and if an abnormality is determined, they transmit abnormality information to the first application control device 1 via the wireless communication system 10.

[0018] The wireless communication system 10 according to the present embodiment can also be applied to a so-called digital key-compatible smart key (registered trademark, the same applies hereinafter) device or a tire pressure monitoring device as another vehicle application. When the wireless communication system 10 is applied to a digital key-compatible smart key device, for example, the master device 20 is mounted on the vehicle and connected to a second application control device 2 having functions as an in-vehicle unit that locks and unlocks the vehicle doors and controls the on / off of the vehicle's driving source, such as the engine. The second application slave device 40A is mounted on a mobile device (e.g., a smartphone or a smartwatch) used as a digital key or an electronic key, which serves as a second application device 45A. Other second application slave devices 40B are arranged at various locations of the vehicle, such as the front, sides, and rear, to detect the position of the digital key or electronic key relative to the vehicle. The multiple second application slave devices 40B arranged at various locations on the vehicle have a function of, for example, intercepting communication between the master device 20 and the second application slave device 40A mounted on the digital key or electronic key and transmitting the intercepted communication results to the master device 20. As a result, the master device 20 (or the second application control device 2) can detect the position of the digital key or electronic key and the distance from the vehicle using a positioning technique such as multilateration or polygonal surveying based on the position of each second application slave device 40B, the time when each second application slave device 40B intercepted the communication, and / or the angle of arrival of the communication signal at each second application slave device 40B.

[0019] When the wireless communication system 10 is applied to a tire pressure monitoring device, the master device 20 is connected to a third application control device 3 that is mounted on a vehicle and has the function of a monitoring unit that displays tire pressure and issues a warning if the pressure is abnormal. Multiple third application slave devices 50A are connected by wire or wirelessly to air pressure detection devices (third application devices 55A) provided in each tire. The air pressure detected by the third application devices 55A is then transmitted to the third application control device 3 via the wireless communication system 10. The third application control device 3 displays the tire pressure and issues a warning if the air pressure is abnormal based on the received air pressure.

[0020] Note that the configuration shown in FIG. 1 is merely an example of the present disclosure. For example, the in-vehicle system 100 according to the present disclosure does not need to include all of the in-vehicle devices, such as a battery monitoring device, a smart key device, and a tire pressure monitoring device, and may be configured to include at least one in-vehicle device. Furthermore, in the configuration shown in FIG. 1, a wireless communication system 10 including one master device 20 and multiple slave devices 30A, 30B, 40A, and 50A is provided for multiple in-vehicle devices. However, the wireless communication system 10 may include multiple master devices 20. When multiple master devices 20 are provided, the multiple master devices 20 may each communicate with multiple different slave devices 30A, 30B, 40A, and 50A. Alternatively, the multiple master devices 20 may communicate with the same multiple slave devices 30A, 30B, 40A, and 50A. Furthermore, although the configuration shown in FIG. 1 shows that the control devices 1, 2, and 3 of the multiple in-vehicle devices are provided separately, the functions of two or more control devices may be integrated into a single control device.

[0021] In the following embodiment, an in-vehicle system 100 will be described in which the wireless communication system 10 is applied to a battery monitoring device, a smart key device, and a tire pressure monitoring device as multiple in-vehicle devices. In this case, as shown in Fig. 1, the master device 20 and slave devices 30A, 30B, 40A, and 50A of the wireless communication system 10 are all mounted on a vehicle (automobile) (excluding the second application slave device 40A, which is provided on a mobile device or electronic key carried by a user in a smart key device). The master device 20 and each of the slave devices 30A, 30B, 40A, and 50A communicate wirelessly via one communication channel sequentially selected from multiple communication channels, such as Bluetooth Low Energy (Bluetooth is a registered trademark; the same applies hereinafter, and Bluetooth Low Energy will be referred to as Bluetooth LE hereinafter) communication.

[0022] The wireless communication between the master device 20 and each of the slave devices 30A, 30B, 40A, and 50A can use a frequency band used for short-range communication, such as the 2.4 GHz band or the 5 GHz band. Radio waves in such high-frequency bands tend to travel in a more directional manner than radio waves in the LF band, and are more likely to be reflected by metal objects such as vehicle bodies. LF stands for Low Frequency. Standards for short-range communication include the aforementioned Bluetooth and Bluetooth LE. As an example, the master device 20 and each of the slave devices 30A, 30B, 40A, and 50A of this embodiment are configured to be capable of wireless communication compliant with the Bluetooth LE standard (hereinafter referred to as Bluetooth LE communication). Details of the communication method, such as communication connection and encrypted communication, are performed according to a sequence defined in the Bluetooth LE standard.

[0023] 1, the master device 20 includes a control circuit (CNT) 21, a wireless communication circuit (WC) 22, and an antenna 23. In addition to the above elements, the master device 20 may also include an input / output interface and a bus line for wired or wireless communication with devices other than the slave devices 30A, 30B, 40A, and 50A. Note that processes such as communication channel control and transmission power control, which will be described later, may be performed by the control circuit 21, or some or all of these processes may be performed by another control device (for example, the first application control device 1) provided outside the master device 20.

[0024] The control circuit 21 is, for example, a computer including a processor 211 and a memory 212. The memory 212 includes, for example, a RAM and a ROM. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory.

[0025] In the control circuit 21, the processor 211 executes a program stored in the ROM while using the RAM as a temporary storage area, thereby performing predetermined processing (control). The processor 211 executes a plurality of instructions included in the program, thereby establishing a plurality of functional units. There may be multiple processors 211. The storage medium for the program is not limited to the ROM. Various storage media, such as an HDD or SSD, can be used. HDD is an abbreviation for Hard-disk Drive. SSD is an abbreviation for Solid State Drive.

[0026] The processor 211 is, for example, a CPU, an MPU, a GPU, or a DFP. CPU is an abbreviation for Central Processing Unit. MPU is an abbreviation for Micro-Processing Unit. GPU is an abbreviation for Graphics Processing Unit. DFP is an abbreviation for Data Flow Processor. The control circuit 21 may be realized by combining multiple types of arithmetic processing devices such as a CPU, an MPU, and a GPU. Alternatively, the control circuit 21 may be realized as an SoC. SoC is an abbreviation for System on Chip. The control circuit 21 may be realized using an ASIC or FPGA. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field-Programmable Gate Array.

[0027] Control circuit 21 generates commands (e.g., commands requesting data, commands requesting execution of predetermined processing, etc.) requesting processing from each of slave devices 30A, 30B, 40A, and 50A, and transmits transmission data (messages) including the commands in transmission packets to wireless communication circuit 22. Control circuit 21 also receives packets transmitted from each of slave devices 30A, 30B, 40A, and 50A via wireless communication circuit 22, and executes predetermined processing based on the data included in the received packets. In other words, the wireless communication between master device 20 and each of slave devices 30A, 30B, 40A, and 50A is packet communication.

[0028] The wireless communication circuit 22 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. The wireless communication circuit 22 has a transmission function of modulating a transmission signal and oscillating at the frequency of an RF signal. The wireless communication circuit 22 also has a reception function of demodulating a reception signal. RF is an abbreviation for radio frequency.

[0029] The wireless communication circuit 22 modulates packets containing data transmitted from the control circuit 21 and transmits the modulated packets to the slave devices 30A, 30B, 40A, and 50A via the antenna 23. The control circuit 21, for example, encrypts the transmission data using encryption information exchanged in a connection establishment process (described later) and outputs the resulting data to the wireless communication circuit 22. The wireless communication circuit 22 adds data necessary for wireless communication (e.g., communication control information) to the transmission packet and transmits the packet. The data necessary for wireless communication includes, for example, an identifier (ID), a sequence number, a next sequence number, an error detection code, and the like. The wireless communication circuit 22 may also control the data size, communication format, schedule, error detection, and the like of the communication between the master device 20 and the slave devices 30A, 30B, 40A, and 50A. The control circuit 21 may also control these communication-related operations.

[0030] The wireless communication circuit 22 receives packets transmitted from the slave devices 30A, 30B, 40A, and 50A via the antenna 23 and demodulates the packets. The wireless communication circuit 22 then transmits the demodulated packets to the control circuit 21. The antenna 23 converts the electrical signals into radio waves and radiates them into space. The antenna 23 receives the radio waves propagating through space and converts them into electrical signals.

[0031] The multiple slave devices 30A, 30B, 40A, and 50A each have the same configuration. Therefore, the following description will use the first application slave device 30A as a representative example to explain its configuration, operation, and the like. However, the multiple slave devices 30A, 30B, 40A, and 50A may be referred to as necessary.

[0032] 1, the first application slave device 30A includes a control circuit (CNT) 31, a wireless communication circuit (WC) 32, and an antenna 33. In addition to the above elements, the first application slave device 30A also includes an input / output interface and a bus line for wired or wireless communication with devices other than the master device 20. The control circuit 31 has a configuration similar to that of the control circuit 21 of the master device 20. The control circuit 31 includes, for example, a processor 311 and a memory 312. The memory 312 includes, for example, a RAM and a ROM.

[0033] The control circuit 31 executes requested processing (such as a response process of acquiring and returning requested data, or a process of executing the requested processing) based on a request command received via the wireless communication circuit 32. For example, if the request command included in the received data is a request to transmit battery information, the control circuit 31 of the first application slave device 30A transmits the transmission request to a detection device (such as the first application device 35A) of the corresponding battery stack and acquires the battery information from the detection device (such as the first application device 35A). In response to the request, the control circuit 31 transmits data encrypted using encryption information and including the processing result (such as the acquired battery information) to the wireless communication circuit 32. In addition, the control circuit 31 can also change the transmission power of the wireless communication circuit 32 or control devices mounted on the vehicle in accordance with the requested processing, for example.

[0034] The wireless communication circuit 32 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. Similar to the wireless communication circuit 22, the wireless communication circuit 32 has a transmitting function and a receiving function. The wireless communication circuit 32 receives a packet transmitted from the master device 20 via the antenna 33 and demodulates it. Then, it transmits the data contained in the demodulated packet to the control circuit 31. The wireless communication circuit 32 modulates a packet containing the data transmitted from the control circuit 31 and transmits it to the master device 20 via the antenna 33. The wireless communication circuit 32 adds data necessary for wireless communication, such as communication control information, to the transmission packet before transmitting it.

[0035] The wireless communication circuit 32 may control the data size, communication format, schedule, error detection, etc. of communication between the master device 20 and the first application slave device 30A. These communication-related controls may be performed by the control circuit 31. The antenna 33 converts electrical signals into radio waves and radiates them into space. The antenna 33 receives radio waves propagating through space and converts them into electrical signals.

[0036] Fig. 2 is a diagram showing an example of the electric field strength distribution in the communication environment between the master device 20 and the first application slave device 30A. Fig. 2 shows the results of an electromagnetic field simulation at a predetermined timing at a predetermined frequency. Hereinafter, the electric field strength distribution may be referred to as the electric field distribution.

[0037] The master device 20 and the first application slave device 30A are disposed, for example, at predetermined positions in a vehicle. When the master device 20 and the first application slave device 30A, respectively disposed at predetermined positions, transmit radio wave signals of a predetermined frequency, areas of high and low electric field strength are generated in the usage environment due to interference between the transmitted wave and the reflected wave and interference with external noise. The reflected wave is generated by reflection from metal elements of the vehicle present around the master device 20 and the first application slave device 30A, such as reflection from the vehicle body, metal casing, and harness. For this reason, the communication environment between the master device 20 and the first application slave device 30A has multiple so-called NULL points, which are areas of high electric field strength and areas of low electric field strength, as shown in FIG. 2.

[0038] If the first application slave device 30A is located in or near a part of the electric field distribution with the master device 20 where the electric field strength is low, the first application slave device 30A is more likely to be unable to correctly receive the wireless signal from the master device 20, which may result in a communication error. A communication channel where such a communication error is more likely to occur is a communication channel with degraded communication quality.

[0039] When the master device 20 and the first application slave device 30A communicate wirelessly via one communication channel selected sequentially from multiple communication channels, the frequency of each communication channel may differ, and therefore the electric field distribution of each communication channel may vary, resulting in different communication quality among the communication channels.

[0040] For example, as shown in FIG. 3, in wireless communication via communication channel A, the received power (received signal strength), which is one parameter indicating communication quality, is good. Furthermore, in wireless communication via communication channel C, the received power exhibits a very high value. Therefore, when the master device 20 and the first application slave device 30A use communication channels A and C, which have good or very high communication quality, they can perform high-quality wireless communication with sufficiently reduced communication errors. On the other hand, in wireless communication via communication channels B and N, the received power is low. Therefore, when the master device 20 and the first application slave device 30A use communication channels B and N, which have poor communication quality, the likelihood of a communication error occurring in the wireless communication increases. Note that, for ease of understanding, FIG. 3 shows an example of the change in received signal strength with respect to frequency using a solid line. Therefore, it is preferable that the wireless communication between the master device 20 and the first application slave device 30A be performed using a communication channel that can perform high-quality wireless communication, avoiding communication channels with poor communication quality.

[0041] However, the electric field distribution between the master device 20 and the first application slave device 30A changes depending on the external environment (such as external noise) and vibrations of the master device 20 and / or the first application slave device 30A (including vibrations of the metal housing and harness). Therefore, when the master device 20 and the first application slave device 30A are mounted on a vehicle, the electric field distribution in the communication environment between the master device 20 and the first application slave device 30A changes depending on, for example, the state of the vehicle (e.g., whether it is running or stopped) and the state of the vehicle's surrounding environment (e.g., whether there is a lot of external noise or not). As a result, communication channels with good communication quality and communication channels with degraded communication quality are not fixed but may change from moment to moment. Therefore, it is required to continuously monitor the communication quality of each communication channel, and, when the communication quality deteriorates, delete the corresponding communication channel from the multiple communication channels used for wireless communication, and, when the communication quality recovers, restore the corresponding communication channel as one of the multiple communication channels used for wireless communication.

[0042] In the wireless communication system 10 of this embodiment, communication channel control for realizing wireless communication between the master device 20 and the first application slave device 30A using communication channels that ensure a certain communication quality, excluding communication channels with degraded communication quality, as multiple communication channels used for wireless communication, and transmission power control for controlling the transmission power of each communication channel based on the operation or state of an in-vehicle device or communication quality data will be described with reference to the diagram of the communication sequence between the master device 20 and the first application slave device 30A shown in FIG. 5. In FIG. 5, the master device 20 is designated MASTER and the first application slave device 30A is designated SLAVE. The master device 20 individually performs the communication sequence shown in FIG. 5 not only with the first application slave device 30A but also with the other multiple slave devices 30B, 40A, and 50A.

[0043] Here, the master device 20 and the first application slave device 30A execute a connection establishment process before executing the communication sequence shown in Fig. 5. Fig. 4 shows an example of a startup sequence including the connection establishment process that is executed from when the master device 20 and the first application slave device 30A start up until when data communication is performed. Note that the master device 20 also executes this connection establishment process individually with the other multiple slave devices 30B, 40A, and 50A.

[0044] For example, when the wireless communication system 10 is mounted on a vehicle, a startup sequence is initiated when the IG signal is switched from off to on by a user operation. Note that when the master device 20 and the first application slave device 30A are constantly connected, the startup sequence is executed only once at a predetermined timing. However, if an error occurs during communication and the wireless communication connection between the master device 20 and the first application slave device 30A is disconnected, the startup sequence may be executed to reconnect.

[0045] When the startup sequence starts, the master device 20 and the first application slave device 30A perform startup processing in steps S10 and S110, respectively, including initialization processing to initialize various variables, timers, and the like. Then, the master device 20 and the first application slave device 30A perform connection establishment processing in steps S20 and S120, respectively. In the connection establishment processing, for example, the first application slave device 30A performs an advertising operation to transmit an advertising signal via an advertising communication channel, and the master device 20 performs a scanning operation to scan for the advertising signal. The advertising communication channel includes multiple communication channels (for example, three in the case of Bluetooth LE). When the master device 20 receives an advertising signal on any of the communication channels through the scanning operation, it transmits a connection request to the first application slave device 30A that transmitted the advertising signal. When the first application slave device 30A receives this connection request, a communication connection is established between the master device 20 and the first application slave device 30A. If the master device 20 and the first application slave device 30A determine in steps S30 and S130, respectively, that a communication connection has been established, the master device 20 proceeds to step S40, and the first application slave device 30A proceeds to step S140.

[0046] The master device 20 and the first application slave device 30A exchange connection information in steps S40 and S140, respectively. In this connection information exchange, the master device 20 and the first application slave device 30A exchange encryption information used for data communication and share initial information related to frequency channel hopping. The initial information includes, for example, an initial channel map, a hopping pattern, or a function for hopping.

[0047] Next, in steps S60 and S150, the master device 20 and the first application slave device 30A perform data communication via a data communication channel that is sequentially selected by channel hopping from the multiple communication channels available for communication indicated by the channel map for each periodically occurring communication event. The process for performing this data communication is shown in the communication sequence of Figure 5. The master device 20 can communicate with the multiple slave devices 30A, 30B, 40A, and 50A in sequence by allocating communication periods (sub-events) to each of the multiple slave devices 30A, 30B, 40A, and 50A in each communication event.

[0048] When the master device 20 and the first application slave device 30A determine to disconnect the communication connection in steps S70 and S160, respectively, they terminate the startup sequence shown in Fig. 4. For example, when the wireless communication system 10 is mounted on a vehicle, the master device 20 and the first application slave device 30A may determine to disconnect the communication connection when the IG signal is switched from on to off by a user operation. Also, the master device 20 and the first application slave device 30A may determine to disconnect the communication connection when, for example, data communication cannot be performed normally a predetermined number of times in succession.

[0049] Next, a communication sequence for data communication will be described with reference to the flowchart of FIG. 5. As shown in FIG. 5, in step S210, the master device 20 transmits, for example, a data request command, i.e., a data request message, to the first application slave device 30A. However, the master device 20 can also transmit, in addition to the data request message, a request message for executing a predetermined process, for example. Upon receiving the data request message in step S410, the first application slave device 30A performs, for example, a checksum check based on the error detection code included in the packet of the received data request message to confirm whether the data request message was received correctly in step S420. If the first application slave device 30A determines, based on the checksum check result in step S420, that the data request message was not received correctly, the first application slave device 30A transmits, for example, in step S430, a signal indicating that the data request message was not received correctly or a signal requesting retransmission of the data request message. On the other hand, if the first application slave device 30A determines in step S420 that it has correctly received the data request message, then in step S430, it executes a predetermined process required for responding, such as a process of acquiring and transmitting the requested data.

[0050] The master device 20 and the first application slave device 30A switch the data communication channel to be used for each communication event by performing frequency channel hopping to transmit and receive data request messages and requested data. At this time, the master device 20 and the first application slave device 30A determine the communication channel to be switched by frequency channel hopping according to their respective channel maps. For example, in the case of Bluetooth LE communication, 37 communication channels are provided as data communication channels.

[0051] In step S220, the master device 20 receives the requested data. Then, in step S230, the master device 20 performs, for example, a checksum check based on the error detection code included in the received data packet to confirm whether the data was received correctly. In step S240, if the master device 20 determines in step S230 that the data was not received correctly or if it receives a signal from the first application slave device 30A indicating that the data request message was not received correctly, the master device 20 determines whether to perform retransmission within the same communication event. For example, if there is enough time to perform retransmission before the end of the current communication event, the master device 20 may decide to perform retransmission; otherwise, if there is not enough time, the master device 20 may decide not to perform retransmission. If the master device 20 determines to perform retransmission in step S240, it executes the processes from step S210 again. If it determines in step S230 that the data was received correctly or if it determines in step S240 not to perform retransmission, the master device 20 proceeds to step S250.

[0052] In step S250, the master device 20 transmits the received data to the first application control device 1. The first application control device 1 then executes processing based on the information included in the received data. Note that if the processing in step S230 determines that the data was not received correctly, or if the first application control device 1 receives a signal from the first application slave device 30A indicating that the data request message was not received correctly, and if the processing in step S240 determines not to retransmit the data, the processing in step S250 may be omitted, or the processing in step S250 may be executed based on the previously received data.

[0053] In step S260, the master device 20 detects communication quality data such as received signal strength indicator (RSSI) and packet error rate (PER) as characteristic data indicating the communication quality of the signal received from the first application slave device 30A. RSSI is an index indicating the strength of the signal transmitted from the first application slave device 30A and received by the master device 20. PER is a percentage indicating the ratio of the number of error packets to the number of packets received by the master device 20. The master device 20 may detect a signal-to-noise ratio (SNR) / signal-to-interference-to-noise ratio (SINR) instead of RSSI. The SNR / SINR can be detected, for example, by the ratio between the RSSI value when the master device 20 receives a wireless signal from the first application slave device 30A and the RSSI value when the master device 20 does not receive a wireless signal. The master device 20 may also detect a bit error rate (BER) or a packet arrival rate (PAR) instead of PER. The master device 20 saves and accumulates the detected RSSI or SNR / SINR, PER, BER, or PAR for each communication channel. Note that, in addition to or instead of the master device 20 detecting the communication quality data as described above, the first application slave device 30A can also obtain the communication quality data by detecting the RSSI, PER, etc. when receiving a signal from the master device 20 and transmitting them to the master device 20.

[0054] In step S270, the master device 20 determines whether the communication quality of the communication channel used for wireless communication with the first application slave device 30A has deteriorated, based on the communication quality data of the communication channel detected in step S260. The master device 20 then deletes the communication channel whose communication quality has deteriorated from the communication channels used for wireless communication between the master device 20 and the first application slave device 30A. The deleted communication channel is a data communication channel. For example, one condition for determining whether the communication quality has deteriorated is when at least one of the RSSI and the PER does not satisfy the threshold value after comparing the RSSI and the PER with the threshold values. The parameter compared with the threshold value may be a single parameter. The parameter compared with the threshold value may be the parameter detected immediately before in step S260, or may be an average value or a median value of a predetermined number of parameters detected in multiple past wireless communications using the same communication channel.

[0055] In step S280, the master device 20 executes a restoration determination for the communication channel deleted in the deletion determination for the previous communication event. If a predetermined restoration condition is satisfied in this restoration determination, the deleted communication channel is restored as a communication channel to be used for wireless communication. For example, as an example of the predetermined restoration condition, the deleted communication channel may be restored when a predetermined time has elapsed since the communication channel was deleted. Alternatively, as another example of the predetermined restoration condition, the deleted communication channel may be restored as a communication channel to be used for wireless communication when a communication channel adjacent to the deleted communication channel exhibits good communication quality. In this way, a communication channel determined to be restoreable as a communication channel to be used for wireless communication is incorporated into the channel map and is actually used for wireless communication between the master device 20 and the first application slave device 30A. Note that if the communication quality of a communication channel determined to be restored remains degraded when actually used for wireless communication, the communication channel may again be subject to deletion in the deletion determination.

[0056] In step S290, the master device 20 creates a channel map based on the deletion determination result of step S270 and the restoration determination result of step S280. As a result, the channel map includes only multiple communication channels that can be used for wireless communication, i.e., only those communication channels whose communication quality is at least a certain level. Therefore, by performing wireless communication using the multiple communication channels included in the created channel map, the communication reliability of wireless communication can be improved. In other words, creating a channel map that includes at least multiple communication channels after excluding communication channels whose communication quality has deteriorated from the multiple communication channels, and performing communication channel control to select a communication channel to be used for wireless communication from the multiple communication channels included in the channel map means that the wireless communication system 10 performs wireless communication in a reliability mode with improved communication reliability. Note that the processing of step S290 corresponds to the communication channel control unit in this disclosure.

[0057] Here, the channel map may include communication channels that can be used for wireless communication, or may include communication channels that cannot be used. Furthermore, it may include both communication channels that can be used and communication channels that cannot be used. This is because, with either type of channel map, it is possible to grasp multiple communication channels that can be used for wireless communication from the channel map. Furthermore, when the creation of the channel map results in a change in the available / unavailable communication channels, the frequency channel hopping pattern may be updated. If the frequency channel hopping pattern is not updated, for example, if the communication channel to be hopped is unavailable, the next communication channel to be hopped may be used.

[0058] Furthermore, the channel map is updated in the master device 20 and the first application slave device 30A at a predetermined cycle that includes multiple communication events. The deletion determination process and the restoration determination process described above may be performed each time communication is performed between the master device 20 and the first application slave device 30A. Alternatively, the deletion determination process and the restoration determination process may be performed collectively in accordance with the update cycle of the channel map, which is updated at a predetermined cycle, i.e., each time multiple communications are performed between the master device 20 and the first application slave device 30A. In this case, each time communication is performed between the master device 20 and the first application slave device 30A, characteristic data indicating the communication quality of the communication channel used for the communication is detected and accumulated in step S260. Then, based on the accumulated characteristic data, the deletion determination in step S270 and the restoration determination in step S280 may be performed collectively before the start of the channel map update cycle. Similarly, the channel map creation in step S290 may be performed each time communication is performed between the master device 20 and the first application slave device 30A. Alternatively, the channel map may be created before updating to a new channel map in accordance with the channel map update period, and may be transmitted to the first application slave device 30A while the new updated channel map is being used.

[0059] In step S300, the master device 20 acquires mode-setting related information from the in-vehicle device (first application control device 1) and sets the mode of wireless communication with the first application slave device 30A based on the acquired mode-setting related information. The wireless communication modes include a reliability mode that performs at least communication channel control, a power-saving mode that performs at least transmission power control (described later), and a balanced mode that performs both communication channel control and transmission power control. The wireless communication mode setting based on the mode-setting related information will be described in detail later.

[0060] In step S310, the master device 20 determines the transmission power values ​​for the multiple communication channels available for wireless communication indicated by the channel map based on the mode set in step S300 and the communication quality data for each of the multiple communication channels available for wireless communication indicated by the channel map. This determination of the transmission power values ​​will be described in detail later. The process of step S310 corresponds to the transmission power value determination unit of the present disclosure.

[0061] In step S320, the master device 20 sets the transmission power of each communication channel when transmitting a wireless signal from the master device 20 to the first application slave device 30A to the transmission power value set in step S310. However, the transmission power of each communication channel when transmitting a wireless signal from the master device 20 to the first application slave device 30A may always be a constant value regardless of the transmission power value set in step S310. This is because a certain level of power saving effect can be achieved by setting at least the transmission power value of the first application slave device 30A to the transmission power value set in step S310. The processes of steps S310 and S320, and the process of reflecting the transmission power value in the first application slave device 30A in step S470 (described later), correspond to transmission power control and a transmission power control unit.

[0062] Furthermore, the transmission power value of the master device 20 may be set based on communication quality data including the received signal strength received by the first application slave device 30A, rather than on communication quality data including the received signal strength of the signal received by the master device 20. In this case, the transmission power value may be calculated by the first application slave device 30A and transmitted to the master device 20, or may be calculated by the master device 20 based on communication quality data acquired from the first application slave device 30A.

[0063] In step S330, the master device 20 transmits the channel map created in step S290 and the transmission power values ​​for each communication channel determined in step S310 to the first application slave device 30A in the same message. However, the channel map and the transmission power values ​​do not necessarily have to be transmitted in the same message. For example, in the process of step S330, the master device 20 may transmit only the channel map to the first application slave device 30A. The transmission power values ​​may be transmitted, for example, before transmitting the data request message in step S210 or by being included in the data request message.

[0064] The channel map also includes timing information that indicates when to start using the channel map. The timing to start using the channel map occurs every time a channel map update period has elapsed. In other words, the timing to start using the channel map is determined based on the channel map update period. The channel map transmitted to the first application slave device 30A is also updated to a new channel map every time a channel map update period has elapsed. If the master device 20 confirms that the channel map and transmission power values ​​have been successfully received by the first application slave device 30A during the current channel map update period, it does not need to transmit the channel map and transmission power values ​​thereafter until the start of the next channel map update period.

[0065] In step S440, the first application slave device 30A receives the new channel map and transmission power values ​​transmitted from the master device 20. Upon receiving the new channel map and transmission power values ​​in step S440, the first application slave device 30A performs a checksum check based on the error detection code included in the received packet to confirm whether the new channel map and transmission power values ​​were received correctly in step S450. If the first application slave device 30A determines based on the checksum check result in step S450 that the new channel map and transmission power values ​​were not received correctly, for example, the first application slave device 30A does not transmit a reception acknowledgement signal (Ack signal) for the new channel map and transmission power values ​​in step S460. On the other hand, if the first application slave device 30A determines in step S450 that the new channel map and transmission power values ​​were received correctly, the first application slave device 30A returns a reception acknowledgement signal (Ack signal) for the new channel map and transmission power values ​​to the master device 20 in step S460. In step S470, the first application slave device 30A sets the transmission power value of each communication channel in accordance with the received transmission power value. As a result, the transmission power value determined in step S310 is reflected in the transmission power of each communication channel when the first application slave device 30A wirelessly communicates with the master device 20. Note that the transmission power value is reflected in conjunction with switching to the new channel map. However, the transmission power value may be reflected before switching to the new channel map.

[0066] In step S340, the master device 20 receives an Ack signal from the first application slave device 30A. In step S350, the master device 20 performs, for example, a checksum check based on the error detection code included in the received Ack signal to confirm whether the Ack signal was received correctly. If the master device 20 does not receive the Ack signal itself, the checksum check results in NG. In the following step S360, the master device 20 determines whether to retransmit a new channel map and transmission power values ​​within the same communication event, depending on whether the checksum check results in step S350 are OK or NG. More specifically, if the checksum check results in OK, or if the checksum check results in NG but there is not enough time to retransmit in the current communication event, the master device 20 determines not to retransmit within the same communication event and terminates the processing shown in the flowchart of FIG. 5. On the other hand, if the checksum result is NG and there is enough time to retransmit, the master device 20 returns to step S330 and retransmits the new channel map and transmission power value. Note that if the checksum result is OK and the master device 20 and first application slave device 30A have successfully shared the new channel map and transmission power value, the master device 20 does not need to transmit the new channel map and transmission power value in subsequent communication events until the channel map update period expires, as described above.

[0067] Next, before explaining the wireless communication mode setting process based on the mode setting related information in step S300 of the flowchart in FIG. 5, a first example of the transmission power value determination process in step S310 of the flowchart in FIG. 5 will be described in detail with reference to the flowchart in FIG. 6.

[0068] In a first example of the transmission power value determination process, a common channel map is created for all slave devices 30A, 30B, 40A, 40B, and 50A, and common transmission power values ​​are determined for multiple communication channels that can be used for wireless communication and are included in the common channel map. However, instead of creating a common channel map for all slave devices 30A, 30B, 40A, 40B, and 50A, the slave devices 30A, 30B, 40A, 40B, and 50A may be divided into multiple groups, for example, by application, and a common channel map may be created for each group. The common channel map for the multiple slave devices 30A, 30B, 40A, 40B, and 50A is created by extracting communication channels that are included in all of the channel maps corresponding to each slave device 30A, 30B, 40A, 40B, and 50A.

[0069] In step S510, the master device 20 extracts the minimum received signal strength (minimum RSSI) from among multiple communication channels available for wireless communication included in the common channel map created for all slave devices 30A, 30B, 40A, 40B, and 50A. In the following step S520, the master device 20 determines a power control threshold according to the mode set in the wireless communication mode setting process. As will be described in detail later, the wireless communication mode setting process sets one of the reliable mode, balanced mode, and power-saving mode. In the reliable mode, the power control threshold is relatively high; in the power-saving mode, the power control threshold is relatively low; and in the balanced mode, the power control threshold is determined to be an intermediate value between the power control threshold in the reliable mode and the power control threshold in the power-saving mode.

[0070] In step S530, the master device 20 determines whether the minimum received signal strength extracted in step S510 is greater than the power control threshold determined in step S520. If the master device 20 determines that the minimum received signal strength is greater than the power control threshold, the process proceeds to step S540. On the other hand, if the master device 20 determines that the minimum received signal strength is equal to or less than the power control threshold, the process proceeds to step S550.

[0071] In step S540, since the minimum received signal strength is still greater than the power control threshold, the master unit 20 determines that there is room to reduce the transmission power and calculates the amount by which to reduce the transmission power. Meanwhile, in step S550, since the minimum received signal strength is equal to or less than the power control threshold, the master unit 20 calculates the amount by which to increase the transmission power. The method for calculating the amount by which to reduce and increase the transmission power will be described later. However, the process of calculating the amount by which to increase the transmission power in step S550 may be omitted. This is because even if the minimum received signal strength is equal to or less than the power control threshold, it exceeds the deletion threshold shown in FIG. 7 and therefore a certain level of communication quality is ensured.

[0072] In step S560, master device 20 calculates a transmission power value by subtracting the calculated decrease amount from or adding the calculated increase amount to the current transmission power. Then, in step S570, master device 20 determines the calculated transmission power value as a transmission power value that is uniform for all slave devices 30A, 30B, 40A, 40B, and 50A and common to multiple communication channels that are included in the common channel map and can be used for wireless communication.

[0073] For example, as shown on the left side of Figure 7, among the multiple communication channels available for wireless communication included in the common channel map created for all slave devices 30A, 30B, 40A, 40B, and 50A, the received signal strength of communication channel 2 is extracted as the minimum received signal strength for wireless communication at the current transmission power. Note that the received signal strength of communication channel 4 is below the deletion threshold for communication channel control, and therefore is not included in the channel map as a communication channel available for wireless communication, and is therefore excluded from the extraction of the minimum received signal strength. Furthermore, the received signal strength (RSSI) of each communication channel shown on the left side of Figure 7 indicates the minimum received signal strength of each communication channel among all slave devices 30A, 30B, 40A, 40B, and 50A.

[0074] Regardless of the wireless communication mode, the determined power control threshold is greater than the deletion threshold used in the communication channel control process to exclude a communication channel from the communication channels used for wireless communication, as shown on the left side of FIG. 7 . In the communication channel control process, a communication channel is excluded from the communication channels used for wireless communication based on the received signal strength of the corresponding communication channel dropping below the deletion threshold. Therefore, the excluded communication channel is not included in the communication channels available for wireless communication in the channel map. As a result, the received signal strength of the excluded communication channel is not taken into account in the above-mentioned minimum received signal strength extraction process. Therefore, it is possible to prevent an excessively low received signal strength from being extracted as the minimum received signal strength. Furthermore, by determining the transmission power value based on communication quality data of a communication channel that has a received signal strength greater than the deletion threshold and satisfies a certain communication quality, it is possible to prevent unnecessary increases in transmission power. As a result, the wireless communication system 10 of this embodiment can prevent excessive power consumption while ensuring communication reliability.

[0075] As shown on the left side of FIG. 7, when the minimum received signal strength of communication channel 2 exceeds the power control threshold, the amount of reduction in transmission power is calculated by subtracting the power control threshold from the minimum received signal strength. Then, as shown on the right side of FIG. 7, wireless communication of each communication channel is performed at transmission power reduced by the calculated amount of reduction. That is, the transmission power of each communication channel is uniformly reduced by the amount of reduction. As a result, in response to the reduction in transmission power, the received signal strength of each communication channel is reduced so that the minimum received signal strength approaches the power control threshold, as shown on the right side of FIG. 7. Conversely, when the minimum received signal strength of communication channel 2 is equal to or less than the power control threshold, the amount of increase in transmission power is calculated by subtracting the minimum received signal strength from the power control threshold. Then, wireless communication of each communication channel is performed at transmission power increased by the calculated amount of increase. That is, the transmission power of each communication channel is uniformly increased by the amount of increase. As a result, in response to the increase in transmission power, the received signal strength of each communication channel increases so that the minimum received signal strength approaches the power control threshold. In this way, in this embodiment, the transmission power values ​​of the multiple communication channels available for wireless communication included in the channel map are determined based on the difference between the received signal strength included in the communication quality data of each of the multiple communication channels available for wireless communication included in the channel map and the power control threshold.

[0076] As described above, the transmission power when performing wireless communication on each communication channel is increased or decreased so that the minimum received signal strength approaches the power control threshold. In other words, the transmission power when performing wireless communication on each communication channel is increased or decreased based on the power control threshold. As described above, the power control threshold is determined in step S520 to a value corresponding to the set mode. Specifically, the power control threshold is relatively high in the reliability mode, relatively low in the power saving mode, and intermediate between the power control thresholds in the reliability mode and the power saving mode in the balanced mode. As a result, the transmission power of the wireless signal on each communication channel is relatively high in the reliability mode, relatively low in the power saving mode, and intermediate between the transmission power in the reliability mode and the power saving mode in the balanced mode. In this way, the transmission power of each communication channel can be adjusted to an appropriate transmission power for the set mode.

[0077] The power control threshold may be a constant value previously set for each mode. Alternatively, the power control threshold may be adjusted within the adjustment range permitted for each mode based on communication quality data for each of multiple communication channels available for wireless communication included in the channel map, so that the value is smaller when communication reliability is good compared to when communication reliability is poor. For example, if the packet error rate (PER) included in the communication quality data remains below the threshold for a predetermined period of time or the number of consecutive successful packet communications exceeds a predetermined number, communication reliability (almost synonymous with communication quality) can be considered good. In such cases, the power control threshold may be adjusted to a lower value within the adjustment range permitted for each mode. If communication reliability becomes poor as a result of reducing the power control threshold, the power control threshold may be adjusted to a higher value within the adjustment range permitted for each mode.

[0078] Next, a second example of the transmission power value determination process will be described with reference to the flowchart of Fig. 8. In the flowchart of Fig. 8, steps that perform the same processes as those in the flowchart of Fig. 6 are given the same step numbers, and their descriptions may be omitted.

[0079] In a second example of the transmission power value determination process, an individual channel map is created for each of slave devices 30A, 30B, 40A, 40B, and 50A, and a common transmission power value is determined for each of the individual channel maps for multiple communication channels that can be used for wireless communication and that are included in the individual channel map. To this end, in step S512, master device 20 extracts the minimum received signal strength (minimum RSSI) from among the multiple communication channels that can be used for wireless communication and that are included in each individual channel map for each of the individual channel maps created for slave devices 30A, 30B, 40A, 40B, and 50.

[0080] Steps S520 to S560 of the flowchart in Fig. 8 basically perform the same processing as that described in steps S520 to S560 of the flowchart in Fig. 6. However, steps S520 to S560 of the flowchart in Fig. 8 differ in that they are performed for each individual channel map of slave devices 30A, 30B, 40A, 40B, and 50A.

[0081] In step S572, the transmission power value calculated in step S560 is determined as the transmission power value common to multiple communication channels available for wireless communication, which are indicated by the channel maps of the corresponding slave devices 30A, 30B, 40A, 40B, and 50A. This determination of the transmission power value is performed for each individual channel map of slave devices 30A, 30B, 40A, 40B, and 50A.

[0082] In the second example of the transmission power value determination process, for each individual channel map of each slave device 30A, 30B, 40A, 40B, and 50A, if the minimum received signal strength among the multiple communication channels exceeds the power control threshold, as shown on the left side of FIG. 7, the amount of transmission power reduction is calculated by subtracting the power control threshold from the minimum received signal strength. Then, as shown on the right side of FIG. 7, wireless communication on each communication channel is performed at transmission power reduced by the calculated amount of reduction. Conversely, if the minimum received signal strength is equal to or less than the power control threshold, the amount of transmission power increase is calculated by subtracting the minimum received signal strength from the power control threshold. Then, wireless communication on each communication channel is performed at transmission power increased by the calculated amount of increase. In this way, in the second example of the transmission power value determination process, the amount of reduction or increase in transmission power is calculated for each individual channel map of each slave device 30A, 30B, 40A, 40B, and 50A, and the final transmission power value is determined based on the calculated amount of reduction or increase in transmission power.

[0083] In the second example of the transmission power value determination process, the power control threshold may be determined in the same manner as in the first example of the transmission power value determination process. That is, the power control threshold is determined to be relatively high in the reliability mode, relatively low in the power saving mode, and intermediate between the power control threshold in the reliability mode and the power control threshold in the power saving mode in the balanced mode. Also, as in the first example of the transmission power value determination process, the power control value may be a constant value that is set in advance to correspond to each mode, or may be changed within the adjustment range allowed in each mode based on communication quality data for each of a plurality of communication channels that can be used for wireless communication and that are included in the channel map.

[0084] As described above, according to the second example of the transmission power value determination process, a transmission power value is determined for each individual channel map of each of slave devices 30A, 30B, 40A, 40B, and 50A. This makes it possible to determine a more appropriate transmission power value in accordance with the communication state of each of slave devices 30A, 30B, 40A, 40B, and 50A. As a result, the second example of the transmission power value determination process can achieve a more excellent effect in terms of saving power while ensuring communication reliability, compared to the first example of the transmission power value determination process.

[0085] Next, a third example of the transmission power value determination process will be described with reference to the flowchart of Fig. 9. In the flowchart of Fig. 9, steps that perform the same processes as those in the flowchart of Fig. 6 are given the same step numbers, and their descriptions may be omitted.

[0086] In a third example of the transmission power value determination process, a common channel map is created for all slave devices 30A, 30B, 40A, 40B, and 50A, and the transmission power value is determined individually for each of the multiple communication channels included in the common channel map that can be used for wireless communication. However, instead of creating a common channel map for all slave devices 30A, 30B, 40A, 40B, and 50A, the multiple slave devices 30A, 30B, 40A, 40B, and 50A may be divided into several groups, and a common channel map may be created for each group.

[0087] In step S514, the master device 20 extracts the minimum received signal strength (minimum RSSI) of the signal received by each of the slave devices 30A, 30B, 40A, 40B, and 50A on the communication channel used in the immediately preceding communication from among multiple communication channels available for wireless communication included in the common channel map created for all of the slave devices 30A, 30B, 40A, 40B, and 50A.

[0088] Steps S520 to S560 of the flowchart in Fig. 9 basically execute the same processing as that described in steps S520 to S560 of the flowchart in Fig. 6. However, the processing in steps S520 to S560 of the flowchart in Fig. 9 differs in that it is executed for each of multiple communication channels that are included in the common channel map of slave devices 30A, 30B, 40A, 40B, and 50A and that can be used for wireless communication.

[0089] In step S574, the transmission power value calculated in step S560 is determined as the transmission power value for the communication channel used in the most recent communication, which is uniform for all slave devices 30A, 30B, 40A, 40B, and 50A, among the multiple communication channels available for wireless communication included in the common channel map. This determination of the transmission power value is performed for each of the multiple communication channels available for wireless communication included in the common channel map. Note that the flowchart in FIG. 9 illustrates the process of determining the transmission power value for the communication channel used in the most recent communication. However, the transmission power values ​​for each of the multiple communication channels available for wireless communication included in the common channel map may be determined simultaneously based on received signal strength data obtained in past wireless communication.

[0090] For example, as shown on the left side of Fig. 10, assume that a signal having a received signal strength equal to or greater than the deletion threshold (and also equal to or greater than the power control threshold) is received on each communication channel through wireless communication at the current transmission power for multiple communication channels that are included in a common channel map created for all slave devices 30A, 30B, 40A, 40B, and 50A. Note that the received signal strength of each communication channel shown on the left side of Fig. 10 indicates the minimum received signal strength of each communication channel among all slave devices 30A, 30B, 40A, 40B, and 50A.

[0091] As shown on the left side of FIG. 10 , the minimum received signal strength of each communication channel is compared with the power control threshold. If the minimum received signal strength exceeds the power control threshold, the amount of reduction in transmit power for each communication channel is calculated by subtracting the power control threshold from the minimum received signal strength. Then, as shown on the right side of FIG. 10 , wireless communication for each communication channel is performed at a transmit power reduced by the calculated amount of reduction. As a result, in response to the reduction in transmit power, the received signal strength for each communication channel is reduced so that the minimum received signal strength for each communication channel approaches the power control threshold, as shown on the right side of FIG. 10 . Conversely, if the minimum received signal strength for each communication channel is equal to or less than the power control threshold, the amount of increase in transmit power for each communication channel is calculated by subtracting the minimum received signal strength from the power control threshold. Then, wireless communication for each communication channel is performed at a transmit power increased by the calculated amount of increase. As a result, in response to the increase in transmit power, the received signal strength for each communication channel is increased so that the minimum received signal strength for each communication channel approaches the power control threshold.

[0092] In the third example of the transmission power value determination process, the power control threshold may be determined in the same manner as in the first example of the transmission power value determination process. That is, the power control threshold is determined to be relatively high in the reliability mode, relatively low in the power saving mode, and intermediate between the power control threshold in the reliability mode and the power control threshold in the power saving mode in the balanced mode. Also, as in the first example of the transmission power value determination process, the power control value may be a constant value that is set in advance to correspond to each mode, or may be changed within the adjustment range allowed in each mode based on communication quality data for each of the multiple communication channels that can be used for wireless communication and that are included in the channel map.

[0093] As described above, according to the third example of the transmission power value determination process, a transmission power value is determined individually for each of the multiple communication channels available for wireless communication included in the common channel map created for all slave devices 30A, 30B, 40A, 40B, and 50A. Therefore, a more appropriate transmission power value can be determined for each communication channel of each slave device 30A, 30B, 40A, 40B, and 50A, corresponding to the communication state of each communication channel. As a result, the third example of the transmission power value determination process can achieve better power savings while ensuring communication reliability, compared to the first example of the transmission power value determination process.

[0094] Next, a fourth example of the transmission power value determination process will be described with reference to the flowchart of Fig. 11. Note that in the flowchart of Fig. 11, steps that perform the same processes as those in the flowchart of Fig. 6 are given the same step numbers, and descriptions thereof may be omitted.

[0095] In a fourth example of the transmission power value determination process, an individual channel map is created for each of the slave devices 30A, 30B, 40A, 40B, and 50A, and for each individual channel map, a transmission power value is determined individually for each of the multiple communication channels included in the individual channel map that can be used for wireless communication.

[0096] Therefore, in step S516, the master device 20 extracts the received signal strength of the signal received by the corresponding slave device 30A, 30B, 40A, 40B, 50A on the communication channel used in the immediately preceding communication from among multiple communication channels available for wireless communication included in the individual channel map created individually for each of the slave devices 30A, 30B, 40A, 40B, 50A.

[0097] Steps S520 to S560 of the flowchart in Fig. 10 basically execute the same processing as that described in steps S520 to S560 of the flowchart in Fig. 6. However, the processing in steps S520 to S560 of the flowchart in Fig. 10 differs in that it is executed for each of the individual channel maps of slave devices 30A, 30B, 40A, 40B, and 50A, for each of the multiple communication channels that are included in the individual channel maps and that can be used for wireless communication.

[0098] In step S576, the transmission power value calculated in step S560 is determined as the transmission power value for the communication channel used in the previous communication among the multiple communication channels available for wireless communication included in the individual channel map of the corresponding slave device 30A, 30B, 40A, 40B, or 50A. This determination of the transmission power value is performed for each of the multiple communication channels available for wireless communication included in the individual channel map. Note that the flowchart in FIG. 10 illustrates the process of determining the transmission power value for the communication channel used in the previous communication. However, the transmission power value for each of the multiple communication channels available for wireless communication included in one individual channel map may be determined simultaneously based on received signal strength data obtained in a past wireless communication. Furthermore, the transmission power value for each of the multiple communication channels available for wireless communication included in all individual channel maps may be determined simultaneously.

[0099] In the fourth example of the transmission power value determination process, the received signal strength of each communication channel is compared with the power control threshold for each individual channel map of each slave device 30A, 30B, 40A, 40B, and 50A, as shown on the left side of FIG. 10 . If the received signal strength exceeds the power control threshold, the amount of reduction in transmission power for each communication channel is calculated by subtracting the power control threshold from the received signal strength. Then, as shown on the right side of FIG. 10 , wireless communication is performed for each communication channel at a transmission power reduced by the calculated amount of reduction. As a result, in response to the reduction in transmission power, the received signal strength of each communication channel is reduced so that the received signal strength of each communication channel approaches the power control threshold, as shown on the right side of FIG. 10 . Conversely, if the received signal strength of each communication channel is equal to or less than the power control threshold, the amount of increase in transmission power for each communication channel is calculated by subtracting the received signal strength from the power control threshold. Then, wireless communication is performed for each communication channel at a transmission power increased by the calculated amount of increase. As a result, in response to the increase in transmission power, the received signal strength of each communication channel increases so that the received signal strength of each communication channel approaches the power control threshold.

[0100] In the fourth example of the transmission power value determination process, the power control threshold may be determined in the same manner as in the first example of the transmission power value determination process. That is, the power control threshold is determined to be relatively high in the reliability mode, relatively low in the power saving mode, and intermediate between the power control threshold in the reliability mode and the power control threshold in the power saving mode in the balanced mode. Also, as in the first example of the transmission power value determination process, the power control value may be a constant value that is set in advance to correspond to each mode, or may be changed within the adjustment range allowed in each mode based on communication quality data for each of the multiple communication channels that can be used for wireless communication and that are included in the channel map.

[0101] As described above, according to the fourth example of the transmission power value determination process, a transmission power value is determined for each individual channel map created for each slave device 30A, 30B, 40A, 40B, and 50A, and for each of the multiple communication channels available for wireless communication included in the individual channel map. Therefore, for each communication channel available for wireless communication included in the individual channel map for each slave device 30A, 30B, 40A, 40B, and 50A, a more appropriate transmission power value can be determined that corresponds to the communication state of the corresponding communication channel. As a result, the fourth example of the transmission power value determination process is most effective in terms of saving power while ensuring communication reliability, compared to the first, second, and third examples of the transmission power value determination process.

[0102] Next, the wireless communication mode setting process based on the mode setting related information in step S300 of the flowchart in FIG. 5 will be described in detail with reference to the flowchart in FIG.

[0103] In the first step S610, the master device 20 receives mode-setting related information from an in-vehicle device (for example, the first application control device 1) and determines whether the mode-setting related information has been acquired. If it is determined that the mode-setting related information has been acquired, the master device 20 proceeds to step S620. On the other hand, if it is determined that the mode-setting related information has not been acquired, the master device 20 proceeds to step S670. The mode-setting related information is information for setting the mode of wireless communication between the master device 20 and the first application slave device 30A that constitute the wireless communication system 10.

[0104] As will be described in detail later, the communication reliability required for the wireless communication of the wireless communication system 10 varies depending on the operation or state of the in-vehicle device, or the state of the vehicle that affects the operation of the in-vehicle device. When the required communication reliability is not so high, it is possible to reduce the power consumption of the wireless communication of the wireless communication system 10. Therefore, by changing the wireless communication mode of the wireless communication system 10 depending on the operation or state of the in-vehicle device, or the state of the vehicle that affects the operation of the in-vehicle device, it is possible to perform wireless communication in an optimal mode for the in-vehicle system 100 as a whole.

[0105] The mode setting related information is information related to the operation and status of the in-vehicle device, and can also be considered information indicating the required level of communication reliability and whether power saving is possible. Therefore, based on the mode setting related information, the master device 20 can set a reliability mode when the required communication reliability is high, or set a power saving mode when the required communication reliability is not high and operation in a power-saving mode is possible. In this way, the in-vehicle system 100 according to this embodiment can achieve power saving while ensuring communication reliability of the wireless communication system 10 by setting the wireless communication mode of the wireless communication system 10 based on the mode setting related information acquired from the in-vehicle device. The mode setting related information will be described in detail later.

[0106] In step S620, the master unit 20 determines whether to set the wireless communication mode to the reliable mode based on the acquired mode setting related information. If it is determined that the reliable mode should be set, the master unit 20 proceeds to the process of step S630. On the other hand, if it is determined that the reliable mode should not be set, the master unit 20 proceeds to the process of step S640. In step S630, the master unit 20 sets the wireless communication mode with the slave device connected to the application equipment of the in-vehicle device to the reliable mode. This reliability mode may include the reliability-oriented balanced mode. The reliability-oriented balanced mode will be described later.

[0107] In step S640, the master unit 20 determines whether to set the wireless communication mode to the power saving mode based on the acquired mode setting related information. If it is determined that the power saving mode should be set, the master unit 20 proceeds to the processing of step S650. On the other hand, if it is determined that the power saving mode should not be set, the master unit 20 proceeds to the processing of step S660. In step S650, the master unit 20 sets the mode of wireless communication with the slave devices connected to the application device of the in-vehicle device to the power saving mode. This power saving mode may include a power saving balanced mode. The power saving balanced mode will be described later. On the other hand, in step S660, the master unit 20 sets the mode of wireless communication with the slave devices connected to the application device of the in-vehicle device to the balanced mode.

[0108] In step S670, which is executed when the mode setting related information is not acquired, the master device 20 initially sets the balanced mode, and changes the power control threshold and transitions the wireless communication mode based on the communication quality data. The process of threshold change and mode transition based on the communication quality data will be described in detail later.

[0109] Some specific examples of the mode setting related information will be described below with reference to FIGS.

[0110] For example, the master device 20 can acquire, as the mode setting related information, abnormality information indicating that the operating status of the in-vehicle device is abnormal from the in-vehicle device. The abnormality in the operating status of the in-vehicle device includes an abnormality in the application devices 35A, 35B, 45A, and 55A (e.g., a sensor failure or a disconnection in the internal wiring of the application device) and an abnormality in the application control devices 1 to 3 (e.g., an abnormal operation of the control device or a disconnection in the internal wiring). As shown in FIG. 13 , when the master device 20 acquires abnormality information from the in-vehicle device, whether the in-vehicle device is a battery monitoring device, a tire pressure monitoring device, or a smart key device, the master device 20 sets the mode for performing wireless communication in the wireless communication system 10 to the reliable mode in principle to reliably transmit information about the abnormality.

[0111] However, when the in-vehicle device is a tire pressure monitoring device or a smart key device, the application devices 45A and 55A operate by receiving power from an internal battery. When an abnormality occurs in which the remaining power of the internal battery drops below a predetermined threshold, it is preferable to set the mode for wireless communication in the wireless communication system 10 to a power-saving mode in order to minimize power consumption by the application devices 45A and 55A. Therefore, the application control devices 2 and 3 can provide the master device 20 with mode-setting-related information indicating that an abnormality has occurred in which the remaining power of the internal battery of the application device 45A and 55A drops below a predetermined threshold. In this case, the master device 20 sets the wireless communication mode in the wireless communication system 10 to a power-saving mode, as shown in FIG. 13 . Alternatively, the master device 20 may acquire battery-related information, including the remaining power of the internal battery, as the mode-setting-related information, and determine whether the remaining power of the internal battery has dropped below a predetermined threshold, and then change the mode to be set.

[0112] FIG. 14 shows a list of settings that combine the state of the in-vehicle device, the wireless communication mode of the wireless communication system 10, the on / off of communication channel control, and the on / off of transmission power control, as well as assumed use cases, operations of the wireless communication system 10, and advantages for each setting. Note that FIG. 14 only shows settings in which the wireless communication modes of the wireless communication system 10 are the reliable mode and the power saving mode. However, a balanced mode may be added as a wireless communication mode to the various settings in FIG. 14. Alternatively, some of the reliable mode or the power saving mode in the various settings in FIG. 14 may be replaced with the balanced mode. For example, the wireless communication mode in settings No. 1 and No. 11 in FIG. 14 may be replaced with the balanced mode.

[0113] As described above, when abnormality information is acquired from the in-vehicle device, if the reliability mode is set to enhance the reliability of wireless communication in the wireless communication system 10, for example, the setting of No. 5 or No. 6 in FIG. 14 can be adopted. In the setting of No. 5, both communication channel control and transmission power control are executed (ON). In the transmission power control, the power control threshold is set to a relatively high value, as in the reliability-oriented balanced mode described below, and the transmission power is controlled to a value close to the maximum value. This ensures high communication reliability in wireless communication at all times. In addition, in the setting of No. 6, communication channel control is executed (ON), but transmission power control is not executed (OFF). Therefore, the transmission power is set to the maximum value. As a result, wireless communication with the highest communication reliability can be performed at all times.

[0114] On the other hand, when the remaining power of the internal battery drops below a predetermined threshold and the power saving mode is set, for example, settings No. 3 or No. 4, or No. 7 or No. 8 in FIG. 14 can be adopted. In the case of setting No. 3, both communication channel control and transmission power control are executed (ON). In the case of transmission power control, the power control threshold is set to a relatively low value, and the transmission power is controlled to a value slightly lower than the maximum value, as in the power-saving balanced mode described below. This allows for further power saving in wireless communication while ensuring communication reliability. In the case of setting No. 4, communication channel control is not executed (OFF), and transmission power control is executed (ON). In the case of transmission power control, the transmission power is controlled to the minimum value. As a result, wireless communication can be always performed with the most energy saving. In the case of setting No. 7, both communication channel control and transmission power control are executed (ON). In the case of transmission power control, the power control threshold is set to a relatively low value, and the transmission power is controlled to a value close to the minimum value. This allows wireless communication to be performed with as little power consumption as possible while maintaining communication reliability. Also, when setting No. 8, communication channel control is not performed (OFF), but transmission power control is performed (ON). In transmission power control, transmission power is controlled to the minimum value. This allows wireless communication to be performed with the lowest possible power consumption at all times.

[0115] As described above, in this embodiment, in the reliability mode, both communication channel control and transmission power control may be performed, as in the settings of Nos. 1, 5, and 9 in Fig. 14. Also, in the power-saving mode, both communication channel control and transmission power control may be performed, as in the settings of Nos. 3, 7, and 11 in Fig. 14. In other words, the reliability mode includes not only a mode in which communication channel control is performed but transmission power control is not performed (e.g., settings of Nos. 2, 6, and 10 in Fig. 14), but also a reliability-oriented balanced mode in which both communication channel control and transmission power control are performed. Also, the power-saving mode includes not only a mode in which communication channel control is not performed but transmission power control is performed (e.g., settings of Nos. 4, 8, and 12 in Fig. 14), but also a power-saving balanced mode in which both communication channel control and transmission power control are performed.

[0116] Here, the relationship between the reliability mode, reliability-oriented balanced mode, balanced mode, power-saving balanced mode, and power-saving mode will be described in more detail with reference to FIG. 15. As shown in FIG. 15, the reliability mode includes a mode in which communication channel control is performed but transmission power control is not performed. In this mode, transmission power control is not performed, so transmission power is set to the maximum value. Furthermore, the reliability mode includes a reliability-oriented balanced mode in which both communication channel control and transmission power control are performed. In the reliability-oriented balanced mode, the adjustment range of the power control threshold described above is determined so that the transmission power satisfies the relationship: maximum value > transmission power > first threshold TH1.

[0117] The balanced mode is a mode in which both communication channel control and transmission power control are performed. In this balanced mode, the adjustment range of the power control threshold is determined so that the transmission power satisfies the relationship: first threshold TH1 ≥ transmission power ≥ second threshold TH2. As a result, in the balanced mode, the transmission power is controlled within a range in which the amount of reduction from the maximum value is larger than in the reliability-oriented balanced mode. Conversely, in the reliability-oriented balanced mode, the transmission power is controlled within a range in which the amount of reduction from the maximum value is smaller than in the balanced mode.

[0118] As shown in FIG. 15, the power-saving mode includes a mode in which communication channel control is or is not performed and transmission power control is performed. In this mode, transmission power control minimizes transmission power. The minimum transmission power is predetermined as the minimum transmission power within a range that does not interfere with the transmission and reception of wireless communication signals. Whether or not to perform communication channel control can be selected depending on the need to reduce power consumption. That is, as described above, communication channel control requires processes such as creating a channel map, transmitting the channel map, and selecting a communication channel by referring to the channel map. Therefore, performing communication channel control increases the processing load of the master device 20 and each slave device 30A, 30B, 40A, 40B, and 50A, and also increases power consumption. Therefore, when it is necessary to minimize power consumption, a power-saving mode in which communication channel control is not performed may be adopted. However, because not performing communication channel control may reduce communication reliability, a power-saving mode in which both communication channel control and transmission power control are performed is usually adopted.

[0119] The power saving mode also includes a power saving balanced mode in which both communication channel control and transmission power control are performed while the transmission power is set to a value greater than the minimum value, as shown in Fig. 15. That is, in the power saving balanced mode, the adjustment range of the power control threshold value described above is determined so that the transmission power satisfies the relationship of second threshold value TH2 ≥ transmission power > minimum value.

[0120] 15, communication reliability decreases in the following order: reliable mode, reliability-oriented balanced mode, balanced mode, power-saving oriented balanced mode, and power-save mode. Power-saving performance increases in the following order: reliable mode, reliability-oriented balanced mode, balanced mode, power-saving oriented balanced mode, and power-save mode.

[0121] Returning to the explanation of the mode-setting-related information, the master unit 20 can acquire, as the mode-setting-related information, vehicle status information from the in-vehicle devices, relating to whether the vehicle is moving or parked. This is because whether the vehicle is moving or parked affects the operation of each in-vehicle device. Furthermore, as shown in FIG. 13 , if the master unit 20 does not acquire any abnormality information from the in-vehicle devices and the in-vehicle devices are deemed to be operating normally, it is preferable for the master unit 20 to set different wireless communication modes of the wireless communication system depending on whether the vehicle is moving or parked.

[0122] For example, if the in-vehicle device is a battery monitoring device, while the vehicle is running, each battery stack of the battery pack is charged and discharged by supplying power to the drive motor and regenerating power using the regenerative motor. As a result, the voltage, current, temperature, and other parameters of each battery stack change constantly. Therefore, while the vehicle is running, it is preferable for the wireless communication system 10 to perform wireless communication with high communication reliability in order to quickly grasp the measured values ​​of each battery stack. Therefore, when the master device 20 acquires vehicle status information indicating that the vehicle is running as mode setting related information, it sets the wireless communication mode of the wireless communication system 10 for the battery monitoring device to the reliability mode. In this case, for example, settings No. 1 or No. 2 in FIG. 14 can be adopted. In the case of setting No. 1, both communication channel control and transmission power control are executed (ON). In the transmission power control, the power control threshold is set to a relatively high value, and the transmission power is controlled to a value slightly lower than the maximum value, as in the reliability-oriented balanced mode described above. This allows for power saving while maintaining high communication reliability in wireless communication. In addition, in the case of setting No. 2, communication channel control is executed (ON), but transmission power control is not executed (OFF). Therefore, transmission power is set to the maximum value. As a result, wireless communication with the highest communication reliability can be performed at all times.

[0123] On the other hand, if the in-vehicle device is a battery monitoring device, when the vehicle is stopped or parked, there is little change in the state of each battery stack, so wireless communication reliability of the wireless communication system 10 is not required as much as when the vehicle is running. Therefore, in order to ensure a certain level of communication reliability while saving power, the master device 20 sets the wireless communication mode of the wireless communication system 10 for the battery monitoring device to the balanced mode. In this case, for example, setting No. 1 or No. 3 in FIG. 14 can be adopted.

[0124] Furthermore, if the in-vehicle device is a tire pressure monitoring device, the tire pressure affects the running condition of the tires while the vehicle is running. However, even when the vehicle is running, the change in tire pressure is small, so it is sufficient if the tire pressure detected by the tire pressure monitoring device application device 55A is communicated to the master device 20 with a certain level of communication reliability or higher. Therefore, the master device 20 sets the wireless communication mode of the wireless communication system 10 for the tire pressure monitoring device to the balance mode, for example. However, the master device 20 may also set the wireless communication mode of the wireless communication system 10 to the reliability mode instead of the balance mode. In this case, for example, the setting No. 1 in FIG. 14 can be adopted.

[0125] On the other hand, if the in-vehicle device is a tire pressure monitoring device, the tires do not rotate when the vehicle is parked or stopped, so high communication reliability is not required for the wireless communication of the wireless communication system 10. Therefore, the master device 20 sets the wireless communication mode of the wireless communication system 10 for the tire pressure monitoring device to the power saving mode. In this case, for example, setting No. 3 or No. 4 in FIG. 14 can be adopted.

[0126] Furthermore, if the in-vehicle device is a smart entry device, it is preferable that communication with the digital key can be established quickly and reliably when a user carrying the digital key approaches the vehicle while the vehicle is parked. However, because the smart entry device does not know when a user will approach the vehicle, the smart entry device goes into a sleep state while the vehicle is parked, and the master device 20 intermittently performs a scanning operation. During this intermittent scanning operation in the sleep state, it is necessary to reliably receive an advertising signal from the digital key. Therefore, the master device 20 acquires mode setting-related information from the in-vehicle smart entry device, which indicates that the main switch is off (or information indicating that the vehicle is parked) and that the smart entry device is in a sleep state. Then, based on the acquired mode information-related information, the master device 20 sets the wireless communication mode of the wireless communication system 10 for the smart entry device to the reliable mode. In this case, for example, setting No. 9 or No. 10 in FIG. 14 can be adopted. The operation of the wireless communication system 10 when setting No. 9 or No. 10 is the same as the operation of the wireless communication system 10 when setting No. 1 or No. 2, and therefore a description thereof will be omitted. When the master device 20 establishes a communication connection with the slave device provided in the digital key, the smart entry device transitions to an activated state.

[0127] On the other hand, if the in-vehicle device is a smart entry device, the digital key is located inside the vehicle after the vehicle starts moving, so it is sufficient for the master device 20 to periodically confirm that the digital key is located inside the vehicle through wireless communication with the digital key. Therefore, when the vehicle starts moving, the smart entry device transitions to a sleep state, and in this sleep state, the master device 20 intermittently performs a scanning operation. In this case, since the digital key is located inside the vehicle, high communication reliability is not required, and the distance to the digital key is short, so it is possible to reduce the power consumption of the wireless communication of the wireless communication system 10. Therefore, the master device 20 acquires mode setting related information from the smart entry device, which is an in-vehicle device, that indicates that the main switch is on (or information indicating that the vehicle is moving) and that the device is in sleep mode. Then, based on the acquired mode setting related information, the master device 20 sets the wireless communication mode of the wireless communication system 10 for the smart entry device to the power saving mode. In this case, for example, setting No. 11 or No. 12 in FIG. 14 can be adopted. The operation of the wireless communication system 10 in the setting of No. 11 or No. 12 is similar to the operation of the wireless communication system 10 in the setting of No. 3 or No. 4, and therefore a description thereof will be omitted.

[0128] As described above, the wireless communication mode of the wireless communication system 10 for each type of in-vehicle device differs depending on the vehicle's running state, whether the vehicle is running or parked. In particular, for driveline in-vehicle devices involved in driving the vehicle, such as a battery monitoring device or a tire pressure monitoring device, and non-driveline in-vehicle devices not involved in driving the vehicle, such as a smart key device, the wireless communication mode setting of the wireless communication system 10 for the driveline in-vehicle devices differs from the wireless communication mode setting of the wireless communication system 10 for the non-driveline in-vehicle devices, depending on the vehicle's running state.

[0129] Specifically, when the vehicle is traveling, the wireless communication mode of the wireless communication system 10 for the drivetrain in-vehicle devices is set to a mode with higher communication reliability than the wireless communication mode of the wireless communication system 10 for the non-drivetrain in-vehicle devices. This is because the drivetrain in-vehicle devices are involved in driving the vehicle, and therefore it is preferable for the wireless communication system 10 to perform wireless communication with higher communication reliability when the vehicle is traveling. On the other hand, when the vehicle is parked or stopped, the wireless communication mode of the wireless communication system 10 for the drivetrain in-vehicle devices is set to a mode with power consumption equal to or lower than that of the wireless communication mode of the wireless communication system 10 for the non-drivetrain in-vehicle devices. This is because when the vehicle is parked or stopped, the drivetrain in-vehicle devices do not require such high communication reliability in the wireless communication system 10, and therefore power saving is possible. Furthermore, the non-drivetrain in-vehicle devices are not involved in driving the vehicle, and conversely, communicate important data when the vehicle is parked or stopped. Therefore, it is preferable for the wireless communication system 10 to perform wireless communication with higher communication reliability when the vehicle is parked or stopped.

[0130] Furthermore, the master unit 20 can acquire, as mode setting related information, information indicating that the in-vehicle device is in a sleep state where it is inactive, from the in-vehicle device. When the in-vehicle device is in a sleep state, as shown in Fig. 13, the master unit 20 preferably sets a wireless communication mode appropriate for the sleep state of the in-vehicle device.

[0131] For example, if the in-vehicle device is a battery monitoring device, the battery monitoring device may enter a sleep state when the vehicle's main switch (e.g., IG switch) is turned off and the vehicle is parked. In this case, it is sufficient for the battery monitoring device (first application control device 1) to, for example, intermittently wake up from the sleep state and acquire battery-related information from the slave devices connected to each battery stack. Moreover, in this case, since the change in battery capacity of each battery stack is small, high communication reliability is not required. Therefore, when the master device 20 acquires, as mode setting-related information, that the battery monitoring device has entered a sleep state, it can set the mode for performing wireless communication to a power-saving mode. In this case, for example, setting No. 11 or No. 12 in FIG. 14 can be adopted.

[0132] Furthermore, if the in-vehicle device is a tire pressure monitoring device, the tire pressure monitoring device may enter a sleep state when the main switch is turned off and the vehicle is parked. Even in this case, it is sufficient for the tire pressure monitoring device (third application control device 3) to, for example, intermittently wake up from the sleep state and acquire tire pressures from the third application slave devices 50A connected to the respective tire pressure detection devices. Furthermore, in this case, since the tires do not rotate, high communication reliability is not required. Therefore, when the master device 20 acquires, as mode setting related information, information indicating that the tire pressure monitoring device has entered a sleep state, it can set the mode for wireless communication to the power-saving mode. In this case, for example, setting No. 11 or No. 12 in FIG. 14 can be adopted.

[0133] In this way, when the wireless communication system 10 receives, as mode setting related information, sleep information from the in-vehicle device indicating that the in-vehicle device has entered a sleep state in which operation is suspended, the wireless communication mode can be set to the power saving mode. Note that if the in-vehicle device is a smart key device, as described above, the wireless communication mode is set to the power saving mode on the condition that the vehicle is running and in a sleep state.

[0134] Furthermore, if the in-vehicle device is a smart key device, the wireless communication system 10 may acquire, as mode setting related information, distance information from the smart key device, which indicates the distance from the digital key when the user carrying the digital key approaches the vehicle. The wireless communication system 10 may then change the wireless communication mode depending on the acquired distance information. An example of changing the wireless communication mode depending on the acquired distance information will be described below.

[0135] When a user carrying a digital key approaches a vehicle, the smart key device's second application control device 2 intermittently wakes up from a sleep state while the user is outside the wireless communication area. For example, the smart key device's second application control device 2 activates the master device 20 from a reliable mode, setting the transmission power to its maximum value, and causes the master device 20 to perform a scan. In this case, for example, setting No. 2 in FIG. 14 can be adopted. This maximizes the wireless communication area between the master device 20 and the second application slave device 40A provided on the digital key, as shown in FIG. 16(a). This allows the user carrying a digital key approaching the vehicle to be quickly detected.

[0136] As shown in FIG. 16(b), when a user carrying a digital key enters a wireless communication area, a wireless communication connection is established between the master device 20 and the second application slave device 40A provided on the digital key. The wireless communication with the master device 20 is intercepted by second application slave devices 40B provided at various locations in the vehicle. The second application slave device 40B transmits the intercepted communication results to the master device 20. This allows the master device 20 (or the second application control device 2) to detect the location of the digital key and its distance from the vehicle. Immediately after the user carrying the digital key enters the wireless communication area, the distance from the vehicle to the digital key is long. For this reason, it is preferable to set the reliability mode or the reliability-oriented balanced mode to ensure that wireless communication between the master device 20 and the second application slave device 40A can be reliably continued. Therefore, in this case, for example, setting No. 1 or No. 2 in FIG. 14 can be adopted.

[0137] As shown in FIG. 16(c), when the user who has entered the wireless communication area approaches the vehicle, the master device 20 can communicate wirelessly with the second application slave device 40A attached to the digital key carried by the user, even if the wireless communication area is not very large. Therefore, the wireless communication system 10 changes the power control threshold or the wireless communication mode so that the transmission power decreases as the acquired distance information decreases. Then, as shown in FIG. 16(d), when the user gets into the vehicle, the digital key is inside the vehicle, so high communication reliability is not required. Furthermore, because the distance is short, communication is possible even without high transmission power. Therefore, when the master device 20 determines that the digital key is inside the vehicle based on the acquired distance information, it sets the wireless communication mode of the wireless communication system 10 to the power-saving mode.

[0138] In the above example, the mode setting related information relates to the operation or state of the in-vehicle device or the state of the vehicle that affects the operation of the in-vehicle device, and the wireless communication system 10 (master device 20) sets a wireless communication mode suitable for the operation or state of the in-vehicle device based on the acquired mode setting related information. However, the in-vehicle device may determine the wireless communication mode based on its own operation or state, and the wireless communication system 10 may acquire, from the in-vehicle device, information that directly instructs the wireless communication mode of the wireless communication system 10 as the mode setting related information.

[0139] For example, the wireless communication system 10 may acquire, as mode setting related information, mode information indicating the mode of the wireless communication system from the in-vehicle device. In this case, the wireless communication system 10 can set the wireless communication mode to the mode indicated by the acquired mode information. Alternatively, the wireless communication system 10 may acquire, as mode setting related information, communication channel control availability information indicating whether communication channel control is enabled or disabled and / or transmission power control availability information indicating whether transmission power control is enabled or disabled from the in-vehicle device. Furthermore, if transmission power control is enabled, information regarding the setting of a power control threshold may also be acquired. In this case, the wireless communication system 10 can set the wireless communication mode to a mode in which communication channel control is enabled or disabled and / or a mode in which transmission power control is enabled or disabled according to the acquired communication channel control availability information and / or transmission power control availability information.

[0140] Next, the process of threshold change and mode transition based on communication quality data in step S670 of the flowchart in Fig. 12 will be described with reference to the flowchart in Fig. 17. When the master device 20 does not acquire mode setting related information from the in-vehicle device, it initially sets the wireless communication mode of the wireless communication system 10 to the balanced mode. At this time, the power control threshold is determined so that the transmission power value becomes an intermediate value of the transmission power in the balanced mode, for example.

[0141] Here, the wireless communication modes transitioned by the process shown in the flowchart of FIG. 17 will be described with reference to FIG. 18. The example shown in FIG. 18, like the example shown in FIG. 15, has three wireless communication modes: a reliable mode, a balanced mode, and a power-saving mode. However, in the example shown in FIG. 18, the reliability mode does not include a reliability-oriented balanced mode, and the power-saving mode does not include a power-saving balanced mode. In other words, the reliability mode is a mode in which communication channel control is performed but transmission power control is not performed. In this mode, transmission power is set to the maximum value. The power-saving mode is a mode in which communication channel control is performed (or not performed) and transmission power control is performed. In this mode, transmission power is set to the minimum value by transmission power control. In this way, the reliability mode may or may not include the reliability-oriented balanced mode. Furthermore, the power-saving mode may or may not include the power-saving balanced mode. For example, in the example shown in FIG. 18, the reliability mode may include the reliability-oriented balanced mode, and the power-saving mode may include the power-saving balanced mode.

[0142] 17, the master device 20 acquires communication quality data for a certain period of time in the past by reading it from the memory 212. Then, in step S720, the master device 20 determines whether the wireless communication mode transition condition is satisfied based on the communication quality data for the certain period of time. If the master device 20 determines that the wireless communication mode transition condition is satisfied, the master device 20 proceeds to the processing of step S730. On the other hand, if the master device 20 determines that the wireless communication mode transition condition is not satisfied, the master device 20 proceeds to the processing of step S760.

[0143] For example, the condition for transitioning from the reliable mode to the balanced mode may be that the communication reliability is determined to be good based on communication quality data over a certain period of time, whereas the condition for transitioning from the balanced mode to the reliable mode may be that the communication reliability is determined to be poor based on communication quality data over a certain period of time, and the power control threshold is set so that the transmit power is near the upper limit for the balanced mode.

[0144] The condition for transitioning from the power saving mode to the balanced mode may be that communication reliability is determined to be poor based on communication quality data over a certain period of time, whereas the condition for transitioning from the balanced mode to the power saving mode may be that communication reliability is determined to be good based on communication quality data over a certain period of time, and the power control threshold is set so that the transmission power is near the lower limit for the balanced mode.

[0145] In step S730, the master device 20 determines whether communication reliability is good over a certain period of time. If communication reliability is determined to be good, the master device 20 transitions to a mode with higher power saving than the current mode in step S740 (e.g., reliable mode → balanced mode, balanced mode → power saving mode). Conversely, if communication reliability is determined to be poor, the master device 20 transitions to a mode with higher communication reliability than the current mode in step S750 (e.g., balanced mode → reliable mode, power saving mode → balanced mode).

[0146] In step S760, the master device 20 maintains the current mode because the mode transition condition is not satisfied. However, if the current mode is the balanced mode, the power control threshold is changed based on communication quality data for a certain period of time. For example, if communication reliability is poor for a certain period of time, the master device 20 can increase the power control threshold by a predetermined value. Conversely, if communication reliability is good for a certain period of time, the master device 20 can decrease the power control threshold by a predetermined value. The conditions for determining whether communication reliability is poor or good may be the same as or different from the conditions for determining whether communication reliability is poor or good in the mode transition conditions described above.

[0147] Here, the mode transition of wireless communication will be specifically described with reference to Fig. 18. For example, when the master device 20 determines that communication reliability is poor based on communication quality data for a certain period in a state in which the voltage control threshold is set so that the transmission power is near the upper limit of the changeable range in the balance mode, it can transition the wireless communication mode from the balance mode to the reliability mode, as shown in Fig. 18. For example, the master device 20 can determine that communication reliability is poor if the packet error rate (PER) included in the communication quality data becomes a value equal to or greater than a predetermined threshold within the certain period, or if the number of consecutive packet communication failures becomes equal to or greater than a predetermined number Y.

[0148] Furthermore, when the master device 20 determines that communication reliability is good based on communication quality data for a certain period in the reliable mode with the transmission power at its maximum value, it may transition the wireless communication mode from the reliable mode to the balanced mode, as shown in Fig. 18. For example, the master device 20 can determine that communication reliability is good if the packet error rate (PER) included in the communication quality data becomes a value less than a predetermined threshold value for a certain period, or if the number of consecutive successful packet communications exceeds a predetermined number X.

[0149] Furthermore, in the balanced mode, when the master device 20 determines that communication reliability is good based on communication quality data for a certain period in a state in which the voltage control threshold is set so that the transmission power is near the lower limit of the variable range in the balanced mode, the master device 20 may transition the wireless communication mode from the balanced mode to the power saving mode, as shown in Fig. 18. Whether the communication quality is good can be determined in the same manner as above.

[0150] Furthermore, when the master device 20 determines that communication reliability is poor based on communication quality data for a certain period in the power saving mode with the transmission power at the minimum value, it may transition the wireless communication mode from the power saving mode to the balanced mode as shown in Fig. 18. Whether or not the communication quality is poor can be determined in the same manner as above.

[0151] Next, a wireless communication mode setting specific to the case where the in-vehicle device is a battery monitoring device will be described.

[0152] The battery pack monitored by the battery monitoring device is configured by connecting multiple battery stacks in series, as shown in Fig. 19. In a battery pack configured in this manner, the dischargeable power of the battery pack is determined by the battery stack with the lowest remaining battery capacity (SOC). Also, the chargeable power of the battery pack is determined by the battery stack with the highest remaining battery capacity (SOC).

[0153] For example, in the example shown in Figure 20, the No. 3 battery stack has the least remaining battery power, and the No. 24 battery stack has the most remaining battery power. In this case, as described above, the charging and discharging of the assembled battery is determined by the battery stack with the most remaining battery power and the battery stack with the least remaining battery power, respectively. Therefore, the battery capacity equivalent to the difference between the maximum and minimum remaining battery power becomes unusable reactive power. Therefore, if this reactive power can be minimized, the capacity of each battery stack can be utilized to that extent, and charging and discharging performance can be improved.

[0154] Therefore, in the present disclosure, when the in-vehicle device is a battery monitoring device, reactive power is reduced by differentiating the wireless communication mode settings of each first application slave device 30B provided in each battery stack of the battery pack being monitored. Specifically, the master device 20 sets the wireless communication mode with each slave device so that the wireless communication mode with the slave device provided in the battery stack with a relatively low remaining battery power requires less power than the wireless communication mode with the slave device provided in the battery stack with a relatively high remaining battery power. Because each slave device operates by obtaining power from the battery stack, reactive power can be reduced by differentiating the power consumption for wireless communication by the slave device. More specifically, in the present disclosure, reactive power is reduced by saving the power consumption required for wireless communication with the slave device provided in the battery stack with a relatively low remaining battery power. Therefore, reactive power can be reduced without wasting power for wireless communication. Below, the mode determination process for reducing reactive power is described with reference to the flowchart of FIG. 21.

[0155] In step S810, the master unit 20 acquires the remaining battery capacity of each battery stack from the battery monitoring device (first application control device 1) as mode setting related information. Then, in step S820, the master unit 20 calculates the reactive power from the difference between the maximum and minimum remaining battery capacity values ​​among the acquired remaining battery capacity values ​​of each battery stack.

[0156] In step S830, the master unit 20 determines whether the calculated reactive power is greater than a predetermined threshold. If the reactive power is greater than the predetermined threshold, the master unit 20 proceeds to step S840. On the other hand, if the reactive power is equal to or less than the predetermined threshold, the master unit 20 proceeds to step S850.

[0157] In step S840, the master device 20 calculates, for example, the average remaining capacity of all battery stacks, and sets the mode of wireless communication with slave devices of battery stacks whose remaining battery capacity is lower than the average remaining capacity to a mode that consumes less power for wireless communication than the mode of wireless communication with slave devices of battery stacks whose remaining battery capacity is higher than the average remaining capacity. For example, if the mode of wireless communication with slave devices of battery stacks whose remaining battery capacity is higher than the average remaining capacity is set to reliability mode (including reliability-oriented balanced mode) as the desired wireless communication mode, the mode of wireless communication with slave devices of battery stacks whose remaining battery capacity is lower than the average remaining capacity is set to balance mode or power-saving mode (including power-saving balanced mode). Also, if the mode of wireless communication with slave devices of battery stacks whose remaining battery capacity is higher than the average remaining capacity is set to balance mode as the desired wireless communication mode, the mode of wireless communication with slave devices of battery stacks whose remaining battery capacity is lower than the average remaining capacity is set to power-saving mode (including power-saving balanced mode).

[0158] Alternatively, the mode to be set may be changed depending on the difference from the average remaining capacity. For example, if the mode of wireless communication with a slave device of a battery stack whose remaining battery capacity is much higher than the average remaining capacity is set to the reliability mode as the desired wireless communication mode, the mode of wireless communication with a slave device of a battery stack whose remaining battery capacity is relatively higher than the average remaining capacity may be set to the reliability-oriented balanced mode, the mode of wireless communication with a slave device of a battery stack whose remaining battery capacity is close to the average remaining capacity may be set to the balanced mode, the mode of wireless communication with a slave device of a battery stack whose remaining battery capacity is relatively lower than the average remaining capacity may be set to the power-saving balanced mode, and the mode of wireless communication with a slave device of a battery stack whose remaining battery capacity is much lower than the average remaining capacity may be set to the power-saving mode.

[0159] Alternatively, if the mode of wireless communication with the slave device of the battery stack with the highest remaining battery power is set to the reliability mode (including the reliability-oriented balanced mode) as the desired wireless communication mode, the master device 20 may set the mode of wireless communication with the slave device of the battery stack with the lowest remaining battery power to the power-saving mode (including the power-saving balanced mode), and set the mode of wireless communication with the slave devices of the remaining battery stacks to the balanced mode.

[0160] It is desirable that the setting of the wireless communication mode with the slave device of each battery stack according to the remaining battery power of each battery stack is performed when the battery monitoring device is operating normally. In other words, if any abnormality occurs in the battery monitoring device, it is desirable that the wireless communication mode be set to the reliable mode in order to reliably notify information about the abnormality.

[0161] Furthermore, it is preferable to set the wireless communication mode with each slave device so that the difference in power consumption required for wireless communication between the slave device of the battery stack with a relatively high remaining battery power and the slave device of the battery stack with a relatively low remaining battery power is smaller when the vehicle's main switch is on compared to when the vehicle's main switch is off. When the vehicle's main switch is on, it is likely that the vehicle is running or temporarily stopped. When the vehicle is running, for example, if the wireless communication mode with the slave device of the battery stack with the lowest remaining battery power is set to power-saving mode in order to increase the difference in power consumption between the slave devices, there is a risk that the communication reliability required when the vehicle is running cannot be ensured. Therefore, when the vehicle is running, it is preferable to set the wireless communication mode with the slave device of the battery stack with the lowest remaining battery power to a mode with communication reliability equal to or higher than the power-saving balanced mode. On the other hand, when the main switch is off and the vehicle is parked, communication reliability is not required as much, so it is also possible to set the wireless communication mode with the slave device of the battery stack with the lowest remaining battery power to power-saving mode, for example. As a result, the difference in power consumption required for wireless communication between a mode of wireless communication with a slave device of a battery stack with a relatively large remaining battery charge and a mode of wireless communication with a slave device of a battery stack with a relatively small remaining battery charge is smaller when the vehicle's main switch is on than when the vehicle's main switch is off.

[0162] Next, a control for suppressing unlocking of the vehicle door by a so-called relay attack using a transition of wireless communication modes when the in-vehicle device is a smart key device will be described.

[0163] When a user carrying a digital key approaches a vehicle to enter the vehicle, the mode of wireless communication between the digital key and the second application slave device 40A initially transitions from the trusted mode to the balanced mode and then to the power-saving mode, as described with reference to Figures 16(a) to 16(d). On the other hand, when an attempt is made to unlock the vehicle door by a relay attack, wireless communication between the master device 20 and the slave device 40A begins the moment the power of a repeater that relays wireless signals between the second application slave device 40A of the digital key and the master device 20 is turned on. In this case, depending on the location of the repeater, it is highly likely that the wireless communication mode transitions will not necessarily follow the order shown in Figures 16(a) to 16(d).

[0164] Therefore, the smart key device is configured to determine whether the transition sequence of wireless communication modes between the master device 20 and the slave device 40A matches the transition sequence when a user carrying a legitimate digital key approaches the vehicle, and if it does not match, to restrict unlocking of the vehicle doors. This makes it possible to prevent the vehicle doors from being opened by a relay attack. An example of a control process for preventing the unlocking of the vehicle doors by a relay attack using the transition of wireless communication modes will be described below with reference to the flowchart in FIG. 22. The process shown in the flowchart in FIG. 22 can be periodically executed by the smart key device.

[0165] In step S910, the second application control device 2 of the smart key device instructs the master device 20 to perform a scan operation. In step S920, the second application control device 2 determines whether a communication connection has been established between the master device 20 and the second application slave device 40A of the digital key. If it is determined that a communication connection has been established, the second application control device 2 proceeds to step S920. On the other hand, if it is determined that a communication connection has not been established, the second application control device 2 ends the process shown in the flowchart in FIG. 22.

[0166] In step S930, the second application control device 2 extracts ID information of the digital key from the communication signal with the second application slave device 40A. Then, in step S940, the second application slave device 40A determines whether the extracted ID information of the digital key has been registered as ID information authorized to unlock the vehicle doors. If the second application slave device 40A determines that the ID information has not been registered, the second application slave device 40A proceeds to step S950. On the other hand, if the second application slave device 40A determines that the ID information has been registered, the second application slave device 40A proceeds to step S960.

[0167] In step S950, the second application control device 2 disconnects communication with the second application slave device 40A whose digital key ID information is not registered. After that, the second application control device 2 ends the process shown in the flowchart in Fig. 22. Meanwhile, in step S960, the second application control device 2 provides the master device 20 with the distance to the digital key as mode setting related information. As a result, the mode of wireless communication between the master device 20 and the second application slave device 40A transitions as shown in Figs. 16(a) to 16(c) depending on the distance between the vehicle and the digital key.

[0168] In step S970, the second application control device 2 determines whether the vehicle door unlocking condition is met. For example, the second application control device 2 can determine that the vehicle door unlocking condition is met when a user carrying a digital key operates a switch on the vehicle door handle, touches a touch sensor on the door handle, or approaches within a predetermined distance from the vehicle door. If the second application control device 2 determines that the vehicle door unlocking condition is not met, the second application control device 2 proceeds to step S980. On the other hand, if the second application control device 2 determines that the vehicle door unlocking condition is met, the second application control device 2 proceeds to step S990.

[0169] In step S980, the second application control device 2 determines whether the user carrying the digital key has left the vehicle without getting into it, causing the communication connection between the master device 20 and the second application slave device 40A to be disconnected. If the communication connection is disconnected, the second application control device 2 ends the process shown in the flowchart in Fig. 22. On the other hand, if the communication connection is not disconnected, the second application control device 2 returns to the process of step S960.

[0170] In step S990, the second application control device 2 acquires information from the master device 20 regarding mode transitions of wireless communication between the digital key and the second application slave device 40A (or transitions in transmission power values ​​corresponding to wireless communication mode transitions). Then, in step S1000, the second application control device 2 determines whether the acquired wireless communication mode transitions match a pre-stored wireless communication mode transition order when a user carrying a legitimate digital key approaches a vehicle. If it determines that they match, the second application control device 2 proceeds to processing in step S1010. On the other hand, if it determines that they do not match, the second application control device 2 proceeds to processing in step S1020.

[0171] In step S1010, the second application control device 2 unlocks the vehicle doors. On the other hand, in step S1020, the second application control device 2 restricts unlocking of the vehicle doors. In this case, a user carrying a digital key may be able to unlock the vehicle doors by, for example, communicating with a management server that manages the ID information of the digital key and re-authenticating that the user has the authority to unlock the doors, or by using a mechanical key provided on a key fob.

[0172] The above describes preferred embodiments of the present disclosure, but the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms within the scope of the gist of the present disclosure.

[0173] For example, the features described in each of the above-described embodiments can be implemented in combination with the features described in other embodiments, unless it is technically impossible to combine them.

[0174] Furthermore, as a wireless communication mode setting specific to when the in-vehicle device is a tire pressure monitoring device, the wireless communication mode of the slave device connected to the detection device that detects the air pressure of the tires mounted on the vehicle may be different from the wireless communication mode of the slave device connected to the detection device that detects the air pressure of the spare tire. For example, the wireless communication mode with the slave device connected to the detection device that detects the air pressure of the tires mounted on the vehicle may be changed according to the above explanation, while the wireless communication mode with the slave device connected to the detection device that detects the air pressure of the spare tire may always be set to the power saving mode.

[0175] For example, the apparatus, system, and method described herein may be implemented by a special-purpose computer comprising a processor programmed to execute one or more functions embodied in a computer program. The apparatus and method described herein may also be implemented using dedicated hardware logic circuits. The apparatus and method described herein may also be implemented by one or more special-purpose computers configured by combining a processor that executes a computer program with one or more hardware logic circuits. The processor may be any computing core, such as a CPU, MPU, GPU, or DFP (Data Flow Processor). Some or all of the functions of the processor may be implemented by hardware. For example, some or all of the functions of the processor may be implemented using a system-on-chip (SoC), an integrated circuit (IC), or a field-programmable gate array (FPGA). [Explanation of symbols]

[0176] 1: first application control device, 2: second application control device, 3: third application control device, 10: wireless communication system, 20: master device, 21: control circuit, 22: wireless communication circuit, 23: antenna, 30A, 30B: first application slave device, 31: control circuit, 32: wireless communication circuit, 33: antenna, 35A, 35B: first application device, 40A, 40B: second application slave device, 45A: second application device, 50A: third application slave device, 55A: third application device, 100: in-vehicle system

Claims

1. A wireless communication system that performs wireless communication between a master node (20) and slave nodes (30A, 30B, 40A, 40B, 50A) via one communication channel sequentially selected from a plurality of communication channels, a communication channel control unit (S290) that creates a channel map indicating the plurality of communication channels after excluding communication channels whose communication quality has deteriorated from the plurality of communication channels based on communication quality data indicating the communication quality of each of the plurality of communication channels, and selects a communication channel to be used for wireless communication from the plurality of communication channels that are usable for wireless communication and are indicated by the channel map; a transmission power value determination unit (S310) that determines transmission power values ​​for the plurality of communication channels available for wireless communication indicated by the channel map based on the communication quality data of each of the plurality of communication channels available for wireless communication indicated by the channel map; a transmission power control unit (S320, S470) that controls the transmission power in the plurality of communication channels that can be used for wireless communication indicated by the channel map so that the transmission power value is the transmission power value determined by the transmission power value determination unit.

2. 2. The wireless communication system according to claim 1, wherein the transmission power value determination unit determines transmission power values ​​for the plurality of communication channels usable for wireless communication indicated by the channel map based on received signal strength included in the communication quality data for each of the plurality of communication channels usable for wireless communication indicated by the channel map and a predetermined power control threshold.

3. 3. The wireless communication system according to claim 2, wherein the predetermined power control threshold is changed based on the communication quality data of each of the plurality of communication channels available for wireless communication indicated by the channel map, so that the predetermined power control threshold is smaller when communication reliability is good than when communication reliability is poor.

4. the communication channel control unit excludes a corresponding communication channel from communication channels to be used for wireless communication when a received signal strength of the corresponding communication channel drops below a deletion threshold; The wireless communication system according to claim 2 or 3, wherein the predetermined power control threshold is set to a value greater than the deletion threshold.

5. At least two of the slave nodes are provided, the communication channel control unit creates a common channel map for at least two of the slave nodes; 4. The wireless communication system according to claim 2, wherein the transmission power value determiner determines a common transmission power value for the plurality of communication channels usable for wireless communication indicated by the common channel map based on a comparison result between the minimum value of received signal strengths of the plurality of communication channels usable for wireless communication indicated by the common channel map and the predetermined power control threshold.

6. At least two of the slave nodes are provided, the communication channel control unit creates individual channel maps for at least two of the slave nodes; 4. The wireless communication system according to claim 2, wherein the transmission power value determiner determines, for each individual channel map, a common transmission power value for the plurality of communication channels usable for wireless communication indicated by the individual channel map, based on a comparison result between the minimum value of received signal strengths of the plurality of communication channels usable for wireless communication indicated by the individual channel map and the predetermined power control threshold.

7. At least two of the slave nodes are provided, the communication channel control unit creates a common channel map for at least two of the slave nodes; 4. The wireless communication system according to claim 2, wherein the transmission power value determiner determines a transmission power value for each of the plurality of communication channels usable for wireless communication indicated by the common channel map based on a comparison result between a smaller received signal strength in at least two of the slave nodes and the predetermined power control threshold for each of the plurality of communication channels usable for wireless communication indicated by the common channel map.

8. At least two of the slave nodes are provided, the communication channel control unit creates individual channel maps for at least two of the slave nodes; 4. The wireless communication system according to claim 2, wherein the transmission power value determination unit determines, for each of the individual channel maps, a transmission power value for each of the plurality of communication channels usable for wireless communication indicated by the individual channel map, based on a comparison result between the received signal strength of each of the plurality of communication channels usable for wireless communication indicated by the individual channel map and the predetermined power control threshold.

9. the wireless communication system is operable in three modes: a reliability mode in which transmission power is set to a maximum value; a balance mode in which transmission power is set to a value between a maximum value and a minimum value; and a power saving mode in which transmission power is set to a minimum value; The wireless communication system according to claim 1 , wherein a mode of the wireless communication system is transitioned based on the communication quality data of each of the plurality of communication channels available for wireless communication indicated by the channel map.

10. the transmission power value determiner is provided in the master node, The master node transmits the determined transmission power value to the slave node via a message; the transmission power control unit is provided in the slave node, 4. The wireless communication system according to claim 1, wherein the transmission power control unit of the slave node controls transmission power in accordance with a transmission power value transmitted from the master node.

11. the communication channel control unit is provided in the master node, The wireless communication system of claim 10 , wherein the master node transmits the transmission power value and the channel map to the slave node in the same message.

12. 4. The wireless communication system according to claim 1, wherein the wireless communication system is used in a vehicle, and messages communicated between the master node and the slave node include information about a battery.

13. 4. The wireless communication system according to claim 1, wherein the wireless communication system is used in a vehicle, the slave node is connected to a sensor that detects a predetermined physical quantity of an object to be monitored, and the master node is connected to a monitoring device that monitors the object to be monitored based on a detected value of the sensor.

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