Wireless communication system, wireless communication method, and wireless communication program

Abstract

A wireless communication system (10) includes a master device (20) and a slave device (30). When the master device (20) communicates wirelessly with the slave device (30), the communication quality of each communication channel is evaluated, and a communication channel to be used for wireless communication is determined on the basis of the results of the evaluations regarding the communication quality of each communication channel. A channel map indicating the determined communication channel is transmitted from the master device (20) to the slave device (30), and the channel map is shared by the master device (20) and the slave device (30). The channel map shared by the master device (20) and the slave device (30) is periodically updated. The channel map update period is changed in accordance with the communication status of the wireless communication between the master device (20) and the slave device (30), or in accordance with instructions from outside.

Description

Wireless communication system, wireless communication method, and wireless communication program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2023-148805 filed in Japan on September 13, 2023, and the contents of the original application are incorporated by reference in their entirety.

[0002] The present disclosure relates to a wireless communication system, a wireless communication method, and a wireless communication program in which at least one master device performs wireless communication with at least one slave device via one communication channel sequentially selected from a plurality of communication channels.

[0003] A known example of this type of wireless communication system is described in Patent Document 1. In the wireless communication system of Patent Document 1, when a packet error occurs in a signal received by a wireless communication device, if the RSSI value of the wireless signal of the packet is greater than a predetermined threshold Th1, the wireless communication device determines that the reception operation for receiving the packet is a reception error due to interference with other radio waves. The wireless communication device then counts the number of receptions and the number of reception errors and stores the frequency of reception errors due to interference in each frequency channel (number of reception errors / number of receptions). If the reception error frequency exceeds a threshold Th2, the wireless communication device determines that an interference source exists in the frequency channel whose reception error frequency due to interference exceeds the threshold Th2, and stores this frequency channel as an unusable channel.

[0004] Japanese Patent Application Laid-Open No. 2006-128812

[0005] As described above, the wireless communication system of Patent Document 1 designates a frequency channel whose communication quality has deteriorated due to interference with other radio waves as an unavailable channel. Furthermore, the wireless communication system of Patent Document 1 restores the unavailable frequency channel to an available frequency channel after a predetermined set period has elapsed. Hereinafter, this control of designating a frequency channel as an unavailable channel or restoring it to an available channel will be referred to as channel map control in this specification.

[0006] Here, the frequency channels available for wireless communication and the frequency channels to be restored from unavailable channels may change over time. Therefore, a channel map indicating available channels and / or unavailable channels needs to be periodically updated, for example, by channel map control, and the updated channel map needs to be shared between devices performing wireless communication. The channel map can be shared, for example, by transmitting the next channel map from one device to the other device during the period from after the channel map update until before the next channel map update.

[0007] However, if the channel map update period is constant, various problems may arise, as described below. For example, even if the communication environment is relatively good, the number of times the next channel map is transmitted during the period between a channel map update and the next channel map update may be insufficient, resulting in failure to share the next channel map. In this case, if the channel map update period is long and the number of times the next channel map is transmitted is increased, the likelihood of successful sharing of the next channel map can be increased. On the other hand, if a good communication environment deteriorates, due to the influence of noise or the like, even if the number of times the next channel map is transmitted is increased, the likelihood of successful sharing of the next channel map cannot be said to be increased. Furthermore, if an abnormality occurs in a control device that uses information transmitted or received via wireless communication between wireless communication devices, if the channel map is not adapted to the communication environment at the time, in addition to the abnormality that has occurred, a communication abnormality may occur more frequently, and may even exacerbate the abnormality that has occurred.

[0008] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a wireless communication system, a wireless communication method, and a wireless communication program that can solve the various problems described above by changing the update period of the channel map.

[0009] In order to achieve the above object, the wireless communication system according to the present disclosure is a wireless communication system in which at least one master device performs wireless communication with at least one slave device via one communication channel selected sequentially from a plurality of communication channels, and is configured to include: a communication channel determination unit that determines the communication quality of each communication channel when the master device wirelessly communicates with the slave device, and determines the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; a channel map sharing unit that transmits a channel map indicating the communication channel determined by the communication channel determination unit from the master device to the slave device, and shares the channel map between the master device and the slave device; the channel map shared between the master device and the slave device by the channel map sharing unit is periodically updated, and a period change unit that changes the update period of the channel map shared between the master device and the slave device by the channel map sharing unit in accordance with the communication state of the wireless communication between the master device and the slave device or an external instruction.

[0010] Furthermore, a wireless communication method according to the present disclosure is a wireless communication method in which at least one master device performs wireless communication with at least one slave device via one communication channel selected sequentially from a plurality of communication channels, and is configured to include the following steps: when the master device wirelessly communicates with the slave device, determining the communication quality of each communication channel and determining the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; transmitting a channel map indicating the determined communication channel from the master device to the slave device and causing the master device and slave device to share the channel map; the channel map shared by the master device and slave device being periodically updated; and changing the update period of the channel map shared by the master device and slave device in accordance with the communication status of the wireless communication between the master device and slave device or an external instruction.

[0011] Furthermore, a wireless communication program according to the present disclosure is a wireless communication program for at least one master device to perform wireless communication with at least one slave device via one communication channel sequentially selected from a plurality of communication channels, and is configured to cause at least one processor to perform the following: when the master device performs wireless communication with the slave device, determine the communication quality of each communication channel, and determine a communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; transmit a channel map indicating the determined communication channel from the master device to the slave device, and share the channel map between the master device and the slave device; the channel map shared between the master device and the slave device is periodically updated, and change the update period of the channel map shared between the master device and the slave device in accordance with the communication status of the wireless communication between the master device and the slave device or an external instruction.

[0012] As described above, in the wireless communication system, wireless communication method, and wireless communication program disclosed herein, the channel map update period (which can also be referred to as the channel map switching period) is not always constant, but is changed in response to the communication status of the wireless communication between the master device and the slave device or an external instruction. As a result, for example, when the communication status is good, the channel map update period can be made longer than when the communication status is poor, thereby increasing the probability of successful channel map sharing. Conversely, when the communication status is poor, the channel map update period can be made shorter than when the communication status is good, thereby speeding up the sharing of a channel map suitable for the deteriorated communication environment. Alternatively, for example, when an abnormality occurs in a control unit that uses information transmitted or received via wireless communication between the master device and the slave device, an external instruction to shorten the channel map update period can be issued, thereby preventing the abnormality in the wireless communication from becoming worse.

[0013] The reference numbers in parentheses above merely indicate an example of the 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.

[0014] 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.

[0015] 1 is a block diagram showing an overall configuration including a schematic configuration of a wireless communication system according to a first embodiment. FIG. 1 is a diagram showing an example of a field strength distribution in a communication environment between a master device and a slave device. FIG. 2 is a diagram showing an example of received signal strength of each communication channel. FIG. 3 is a flowchart showing an example of a startup sequence between a master device and a slave device. FIG. 4 is a flowchart showing an example of a communication sequence between a master device and a slave device. FIG. 5 is a flowchart showing an example of a channel map update period setting process of the flowchart of FIG. 5. FIG. 6 is a flowchart showing an example of a channel map sharing process of the flowchart of FIG. 5. FIG. 6 is a time chart showing an operation example of a channel map sharing process when the channel map update period is set to X period. FIG. 7 is a time chart showing an operation example of a channel map sharing process when the channel map update period is switched from X period to Y period. FIG. 7 is a flowchart showing an example of a channel map update period setting process in a wireless communication system according to a second embodiment. FIG. 8 is a flowchart showing an example of a channel map update period setting process executed by a master device in a wireless communication system according to a third embodiment. FIG. 9 is a flowchart showing an example of a process executed in a higher-level control device to give an external instruction to the master device to change the channel map update period. FIG. 10 is a flowchart showing an example of a process executed in a higher-level control device to give an external instruction to the master device to change the channel map update period in a fourth embodiment. 13 is a flowchart illustrating an example of processing executed in the upper control device to give an external instruction to the master device to change the update cycle of the channel map in the fifth embodiment.

[0016] 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.

[0017] First Embodiment A wireless communication system according to this embodiment includes at least one master device and at least one slave device. At least one of the master device and the slave device can be mounted on a mobile object. Mobile objects include, for example, vehicles such as automobiles and railroad cars, aircraft such as electric vertical take-off and landing aircraft and drones, ships, construction machinery, agricultural machinery, and the like.

[0018] 1 shows an example of the configuration of a wireless communication system 10 according to the present embodiment when applied to a vehicle. As a specific application in a vehicle, the wireless communication system 10 according to the present embodiment can be applied to a battery management system that manages batteries mounted as a battery pack in an electrically powered vehicle such as an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. When applied to a battery management system, for example, at least one master device 20 is connected to a higher-level control device (battery control device) 1, and at least one slave device 30 is connected to a monitoring device (not shown) provided in at least one battery stack that constitutes the battery pack. In this case, both the master device 20 and the slave device 30 are mounted in the vehicle.

[0019] The monitoring devices provided in the battery stacks 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 monitoring devices receive data requesting battery information from the battery control device 1 via the wireless communication system 10, they transmit the acquired battery information to the battery control device 1 via the wireless communication system 10. Based on the acquired battery information, the battery 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 a so-called equalization process to equalize the voltages of each battery cell. If the battery control device 1 determines that an equalization process is required for at least one battery stack, it instructs the corresponding monitoring device to perform the equalization process via the wireless communication system 10. The monitoring devices also perform processes to determine abnormalities in the various sensors and their own operation, and if an abnormality is detected, transmit abnormality information to the battery control device 1 via the wireless communication system 10.

[0020] Alternatively, the wireless communication system 10 according to the present embodiment may be applied to a so-called smart key system (registered trademark, the same applies hereinafter) or a tire pressure monitoring system in a vehicle. When applied to a smart key system, for example, the master device 20 is mounted on the vehicle and connected to a control device (host control device) 1 that controls locking and unlocking of vehicle doors and on / off of a driving source such as the vehicle engine. At least one slave device 30 is mounted on a portable key or a portable terminal held by at least one user. When applied to a tire pressure monitoring system, the master device 20 is mounted on the vehicle and connected to a control device (host control device) 1 that displays tire pressure and issues a warning when the tire pressure is abnormal. The multiple slave devices 30 are connected by wire or wirelessly to air pressure detection devices provided in each tire.

[0021] Furthermore, the wireless communication system 10 according to the present embodiment may be applied to a vehicle diagnostic system. In this case, for example, a plurality of slave devices 30 are connected to a plurality of on-board devices having a self-diagnosis function, and the master device 20 is connected to a diagnostic control device (host control device) installed in a service shop. In these examples, at least one of the master device 20 and the plurality of slave devices 30 is disposed in a fixed position and / or at least one is mounted on the vehicle.

[0022] However, application examples of the wireless communication system 10 according to the present embodiment are not limited to vehicles, and as described above, the system can also be applied to systems that control and manage various types of equipment, such as mobile objects other than vehicles, for example, aircraft such as drones, ships, construction machinery, agricultural machinery, etc. Furthermore, the wireless communication system 10 according to the present embodiment can also be applied to systems that control and manage various types of equipment in buildings, such as buildings, and production facilities in factories, etc.

[0023] In the following embodiment, an example will be described in which the wireless communication system 10 is applied to a battery management system for managing a battery mounted on a vehicle. In this case, as shown in FIG. 1 , the master device 20 and the slave device 30 of the wireless communication system 10 are both mounted on the vehicle (automobile). In this case, the master device 20 and the slave device 30 may be configured to be disposed in a common housing of a battery pack, or may not be disposed in a common housing. There may be one master device 20 or multiple master devices 20. When multiple master devices 20 are provided, each of the multiple master devices 20 may communicate with at least one slave device 30 belonging to a different group. Alternatively, the multiple master devices 20 may communicate with at least one slave device 30 belonging to the same group. The master device 20 and the slave device 30 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.

[0024] The wireless communication between the master device 20 and the slave device 30 can use frequency bands used in 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 Bluetooth and Bluetooth LE. As an example, the master device 20 and the slave device 30 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 in accordance with the sequence defined in the Bluetooth LE standard.

[0025] 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 device 30. Note that processes such as a channel map control process, a channel map creation process, a channel map update period setting process, and a channel map sharing process, 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 (e.g., the upper control device 1) provided outside the master device 20.

[0026] 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.

[0027] In the control circuit 21, the processor 211 executes a program stored in the ROM while using the RAM as a temporary storage area to perform predetermined processing (control). The processor 211 executes multiple instructions included in the program to establish multiple 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.

[0028] 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.

[0029] The control circuit 21 generates commands requesting processing from the slave device 30 (for example, commands requesting data, commands requesting execution of a predetermined process, etc.), and transmits transmission data including the commands in transmission packets to the wireless communication circuit 22. The control circuit 21 also receives packets transmitted from the slave device 30 via the wireless communication circuit 22, and executes predetermined processing, such as passing data to the upper control device 1, based on the data included in the received packets. In other words, the wireless communication between the master device 20 and the slave device 30 is packet communication.

[0030] 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 has a reception function of demodulating a reception signal. RF is an abbreviation for radio frequency.

[0031] The wireless communication circuit 22 modulates packets containing data transmitted from the control circuit 21 and transmits the modulated packets to the slave device 30 via the antenna 23. The control circuit 21, for example, encrypts transmission data such as battery information request data using encryption information exchanged in the connection establishment process described below, 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 it. The data necessary for wireless communication includes, for example, an identifier (ID), a sequence number, a next sequence number, an error detection code, etc. The wireless communication circuit 22 may control the data size, communication format, schedule, error detection, etc. of the communication between the master device 20 and the slave device 30. The control circuit 21 may also perform these communication-related controls.

[0032] The wireless communication circuit 22 receives the packets transmitted from the slave device 30 via the antenna 23 and demodulates them. Then, it 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.

[0033] 1, the slave device 30 includes a control circuit (CNT) 31, a wireless communication circuit (WC) 32, and an antenna 33. In addition to the elements described above, the slave device 30 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.

[0034] 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 slave device 30 transmits the transmission request to the monitoring device of the corresponding battery stack and acquires the battery information from the monitoring device. Then, in response to the request, the control circuit 31 transmits data encrypted using encryption information, including the processing result (e.g., the acquired battery information), to the wireless communication circuit 32. The control circuit 31 can also execute control of equipment mounted on a vehicle, for example, in accordance with the requested processing.

[0035] 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 packets transmitted from the master device 20 via the antenna 33 and demodulates them. Then, it transmits the data contained in the demodulated packets to the control circuit 31. The wireless communication circuit 32 modulates packets containing the data transmitted from the control circuit 31 and transmits them 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 packets before transmitting them.

[0036] 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 slave device 30. 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.

[0037] The host control device 1 is configured to be able to communicate with other vehicle systems 2, 3, and 4 via an in-vehicle LAN such as a Controller Area Network or a Local Interconnect Network. The other vehicle systems 2, 3, and 4 may be, for example, a navigation system equipped with a communication function with an external management center for updating map data and setting destinations, an ETC system (ETC is a registered trademark; the same applies hereinafter) that automatically collects tolls and the like via wireless communication with the outside, an airbag system that protects occupants in the event of a vehicle collision, a collision mitigation system that avoids or reduces collisions with obstacles, etc. The host control device 1 receives external instructions to change the channel map update period from these other vehicle systems 2, 3, and 4, as will be described in detail later.

[0038] 2 is a diagram showing an example of the electric field strength distribution in the communication environment between the master device 20 and the slave device 30. 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.

[0039] The master unit 20 and the slave unit 30 are disposed, for example, at predetermined positions in a vehicle. When the master unit 20 and the slave unit 30, each disposed at a predetermined position, 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 unit 20 and the slave unit 30, such as reflection from the vehicle body, metal casing, and harness. For this reason, the communication environment between the master unit 20 and the slave unit 30 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.

[0040] If the slave device 30 is located in or near a portion of the electric field distribution with the master device 20 where the electric field strength is low, the slave device 30 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.

[0041] When the master device 20 and the slave device 30 communicate wirelessly via one communication channel selected sequentially from a plurality of communication channels, the frequency of each communication channel may differ, and therefore the electric field distribution of each communication channel may also vary, resulting in different communication qualities for each communication channel.

[0042] 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 slave device 30 use communication channels A and C, which have good or very high communication quality, they can perform high-quality wireless communication in which communication errors are sufficiently suppressed. 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 slave device 30 use communication channels B and N, which have poor communication quality, the likelihood of communication errors occurring in the wireless communication increases. Note that, for ease of understanding, FIG. 3 shows an example of received signal strength versus frequency using a solid line.

[0043] Therefore, it is preferable that wireless communication between the master device 20 and the slave device 30 be performed using a communication channel that can provide high-quality wireless communication, avoiding communication channels with degraded communication quality.

[0044] However, the electric field distribution between the master unit 20 and the slave unit 30 changes depending on the external environment (such as external noise) and vibrations of the master unit 20 and / or the slave unit 30 (including vibrations of the harness). Therefore, when the master unit 20 and the slave unit 30 are mounted on a vehicle, the electric field distribution in the communication environment between the master unit 20 and the slave unit 30 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, when communication quality deteriorates, it is necessary to delete the corresponding communication channel from the multiple communication channels used for wireless communication, and when communication quality recovers, it is necessary to restore the corresponding communication channel as one of the multiple communication channels used for wireless communication.

[0045] In the wireless communication system 10 of this embodiment, a control process for realizing wireless communication between the master device 20 and the slave device 30 using, as multiple communication channels for wireless communication, communication channels that ensure a certain communication quality, excluding communication channels whose communication quality has deteriorated due to channel map control, will be described with reference to the diagram of the communication sequence between the master device 20 and the slave device 30 shown in FIG. 5 . In FIG. 5 , the master device 20 is indicated as MASTER, and the slave device 30 is indicated as SLAVE. Note that FIG. 5 shows a communication sequence executed between the master device 20 and one slave device 30. When multiple slave devices 30 are provided, the master device 20 individually executes the communication sequence shown in FIG. 5 with each of the multiple slave devices 30.

[0046] Here, the master device 20 and the slave device 30 execute a connection establishment process before executing the communication sequence shown in Fig. 5. Fig. 4 shows an example of a startup sequence including a connection establishment process that is executed after the master device 20 and the slave device 30 start up and before data communication is performed. For example, when the wireless communication system 10 is installed in a vehicle, the startup sequence is initiated when the IG signal is switched from off to on by a user operation, for example. Note that if the master device 20 and the slave device 30 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 slave device 30 is disconnected, the startup sequence may be executed to reconnect.

[0047] When the startup sequence begins, the master device 20 and the slave device 30 each execute a startup process in steps S10 and S110, including an initialization process that initializes various variables, timers, and the like. Then, the master device 20 and the slave device 30 each execute a connection establishment process in steps S20 and S120. If multiple slave devices 30 are provided, this connection establishment process is executed between the master device 20 and all of the slave devices 30. In the connection establishment process, for example, the slave device 30 executes an advertising operation to transmit an advertising signal via an advertising communication channel, and the master device 20 executes a scanning operation to scan for the advertising signal. The advertising communication channel includes multiple communication channels (e.g., three in the case of Bluetooth LE). When the master device 20 receives an advertising signal via any of the communication channels through the scanning operation, it transmits a connection request to the slave device 30 that transmitted the advertising signal. This establishes a communication connection between the master device 20 and the slave device 30. When the master device 20 and the slave device 30 determine in steps S30 and S130, respectively, that a communication connection has been established, the master device 20 proceeds to step S40, and the slave device 30 proceeds to step S140.

[0048] The master device 20 and the slave device 30 exchange connection information in steps S40 and S140, respectively. In this connection information exchange, the master device 20 and the slave device 30 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.

[0049] Next, in steps S50 and S150, the master device 20 and the slave device 30 perform data communication via a data communication channel that is sequentially selected from the multiple communication channels to be used for communication indicated by the channel map for each cyclically occurring communication event. The process for performing this data communication is shown in the communication sequence of FIG.

[0050] When the master device 20 and the slave device 30 determine to disconnect the communication connection in steps S60 and S160, respectively, they terminate the startup sequence shown in Fig. 4. For example, when the wireless communication system 10 is installed in a vehicle, the master device 20 and the slave device 30 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 slave device 30 may determine to disconnect the communication connection when data communication cannot be performed normally a predetermined number of times consecutively.

[0051] Next, the communication sequence of data communication will be described with reference to the flowchart of FIG. 5 . As shown in FIG. 5 , the master device 20 transmits, for example, a data request command, i.e., a data request, to the slave device 30 in step S210. However, the master device 20 can also transmit, in addition to a data request, for example, a request to execute a predetermined process. When the slave device 30 receives the data request in step S410, in step S420, it performs, for example, a checksum check based on the error detection code included in the received data request to confirm whether the data request was received correctly. If the slave device 30 determines, based on the checksum check result in step S420, that the data request was not received correctly, it transmits, for example, in step S430, a signal indicating that the data request was not received correctly or a signal requesting a retransmission of the data request. On the other hand, if the slave device 30 determines, in step S420, that the data request was received correctly, it performs, for example, a predetermined process required for responding, such as acquiring and transmitting the requested data.

[0052] The master device 20 and the slave device 30 switch the data communication channel to be used for each communication event by performing frequency channel hopping to transmit and receive data requests and requested data. At this time, the master device 20 and the slave device 30 determine the communication channel to be switched by frequency channel hopping according to their respective channel maps. In the case of Bluetooth LE communication, 37 communication channels are prepared as data communication channels.

[0053] 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 to confirm whether the data was received correctly. In the following 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 slave device 30 indicating that the data request was not received correctly, the master device 20 determines whether to execute a process for retransmission within the same communication event. For example, if there is enough time to perform a retransmission before the end of the current communication event, the master device 20 may decide to perform a retransmission; otherwise, if there is not enough time, the master device 20 may decide not to perform a retransmission. If the master device 20 determines to perform a retransmission in step S240, it executes the process 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 a retransmission, the master device 20 proceeds to step S250.

[0054] In step S250, the master device 20 executes processing based on information contained in the received data. Note that if the processing in step S230 determines that the data was not received correctly, or if a signal indicating that the data request was not received correctly is received from the slave device 30, and if the processing in step S240 determines that retransmission will not be performed, the processing in step S250 may be omitted, or the processing in step S250 may be executed based on the data previously received.

[0055] In step S260, the master device 20 detects communication quality data indicating the communication quality of the signal received from the slave device 30, such as received signal strength indicator (RSSI) and packet error rate (PER). The RSSI is an index indicating the strength of the signal transmitted from the slave device 30 and received by the master device 20. The PER is a percentage of the number of error packets relative to the number of packets received by the master device 20. Instead of the RSSI, the master device 20 may detect a signal-to-noise ratio (SNR) / signal-to-interference-plus-noise ratio (SINR). 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 slave device 30 and the RSSI value when the master device 20 does not receive a wireless signal. Instead of the PER, the master device 20 may detect a bit error rate (BER) or a packet arrival rate (PAR). The master unit 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 unit 20 detecting the communication quality data as described above, the slave unit 30 can also obtain the communication quality data by detecting the RSSI, PER, etc. when receiving a signal from the master unit 20 and transmitting the detected data to the master unit 20.

[0056] In step S270, the master device 20 determines a degradation in the communication quality of the communication channel used for wireless communication with the slave device 30 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 been determined to have degraded from the communication channels used for wireless communication between the master device 20 and the slave device 30. The deleted communication channel is a data communication channel. For example, one condition for determining a degradation in communication quality is that the RSSI is compared with an RSSI threshold and the PER is compared with a PER threshold, and as a result, at least one of the RSSI and the PER does not satisfy the threshold. The parameter compared with the threshold may be a single type. The parameter compared with the threshold 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.

[0057] In step S280, the master device 20 performs a restoration determination for the communication channel deleted in the deletion determination made during the previous communication event. If a predetermined restoration condition is met 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 in wireless communication between the master device 20 and the slave device 30. The deletion determination process in step S270 and the restoration determination process in step S280 correspond to the channel map control process in the present disclosure. Note that a communication channel determined to be restored may again be subject to deletion by a deletion determination if its communication quality remains degraded when actually used for wireless communication.

[0058] In step S290, the master device 20 performs a channel map creation process based on the deletion determination result in step S270 and the restoration determination result in step S280.

[0059] The channel map may indicate communication channels that can be used for wireless communication, or may indicate communication channels that cannot be used. Furthermore, the channel map may indicate both available and unavailable communication channels. Furthermore, when the available / unavailable communication channels are changed by creating a channel map, the frequency channel hopping pattern may be updated. If the frequency channel hopping pattern is not updated, for example, if a communication channel to be hopped to is unavailable, the next communication channel to be hopped to may be used.

[0060] In step S300, the master device 20 executes a channel map update period setting process, which will be described in detail later.

[0061] In step S310, the master device 20 executes a process for sharing the channel map created in the channel map creation process in step S290 with the slave device 30. This channel map sharing process will also be described in detail later.

[0062] 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 slave device 30. Alternatively, the deletion determination process and the restoration determination process may be performed collectively each time multiple communications are performed between the master device 20 and the slave device 30, in accordance with the channel map update period described below. In this case, each time communication is performed between the master device 20 and the slave device 30, characteristic data indicating the communication quality of the communication channel used for the communication is detected and accumulated in step S260. Then, the deletion determination in step S270 and the restoration determination in step S280 are performed collectively based on the accumulated characteristic data. Similarly, the channel map creation process in step S290 may also be performed each time communication is performed between the master device 20 and the slave device 30. Alternatively, the channel map creation process may be performed each time multiple communications are performed between the master device 20 and the slave device 30, in accordance with the channel map update period described below.

[0063] Next, the above-mentioned channel map update period setting process will be described with reference to the flowchart in Fig. 6. The flowchart in Fig. 6 shows an example of the channel map update period setting process. In this embodiment, an example will be described in which the channel map update period is set (changed) in accordance with the communication state of wireless communication between the master device 20 and the slave device 30 in the channel map update period setting process.

[0064] In the first step S510, the master device 20 acquires an overall PER, which indicates a communication error rate, as an index indicating the communication status of wireless communication with the slave device 30. For example, the master device 20 acquires the overall PER by calculating the average or median of the PERs of a predetermined number of recent wireless communications, including the most recent wireless communication with the slave device 30. In this case, the individual PERs used to calculate the average or median are obtained in wireless communications via multiple different communication channels. Note that the master device 20 may also use BER or PAR as an index indicating the communication status of wireless communication with the slave device 30.

[0065] In step S520, the master device 20 compares the acquired overall PER with a first threshold (communication error rate threshold) to determine whether the communication state of the wireless communication between the master device 20 and the slave device 30 is a good, normal communication state or an abnormal communication state in which the communication state has deteriorated. That is, if the acquired overall PER is less than the first threshold, the communication error rate is relatively low and the communication state can be considered a normal communication state. In this case, the process proceeds to step S530, where the master device 20 determines that the communication state of the wireless communication between the master device 20 and the slave device 30 is a normal communication state. On the other hand, if the acquired overall PER is equal to or greater than the first threshold, the communication error rate is relatively high and the communication state can be considered an abnormal communication state. In this case, the process proceeds to step S540, where the master device 20 determines that the communication state of the wireless communication between the master device 20 and the slave device 30 is an abnormal communication state.

[0066] In step S550, the master device 20 determines whether the communication state between the master device 20 and the slave device 30 is normal or abnormal based on the result of identifying the communication state of the wireless communication between the master device 20 and the slave device 30. If the communication state is normal, the master device 20 proceeds to step S560 and sets the channel map update period to X. On the other hand, if the communication state is abnormal, the master device 20 proceeds to step S570 and sets the channel map update period to Y. Here, the relationship of update period X > update period Y holds. That is, the master device 20 sets the channel map update period Y when the overall PER is equal to or greater than the first threshold value to be shorter than the channel map update period X when the overall PER is less than the first threshold value. In this case, to prevent the update period from becoming too short, the master device 20 preferably sets the channel map update period Y to be shorter than the channel map update period X, as long as the shorter period is equal to or greater than a preset minimum period. Conversely, in order to prevent the update period X from becoming too long, it is preferable that the master device 20 make the channel map update period X longer than the channel map update period Y, as long as the update period X is equal to or less than a preset maximum period.

[0067] Next, the above-mentioned channel map sharing process will be described with reference to the flowchart of Fig. 7 and the time charts of Figs. 8 and 9. The flowchart of Fig. 7 shows an example of the channel map sharing process. Fig. 8 is a time chart showing an example of the operation of the channel map sharing process when the channel map update period is set to X period. Fig. 9 is a time chart showing an example of the operation of the channel map sharing process when the channel map update period is switched from X period to Y period.

[0068] 8, the sharing process for a new channel map is initiated during the application period of the current channel map. In other words, the new channel map is created by the channel map creation process based on multiple pieces of communication quality data detected before the application period of the current channel map (when sharing of the new channel map begins), and is determined as the new channel map before the application period of the current channel map. Furthermore, the next new channel map is determined before the application period of the new channel map based on communication quality data detected from communication between the master device 20 and the slave device 30 during the application period of the current channel map.

[0069] The channel map sharing process of the flowchart in FIG. 7 is intended to share a new channel map between the master device 20 and the slave device 30 at each channel map update period X or Y, as shown in the time charts in FIGS. 8 and 9 . In the first step S610, the master device 20 transmits to the slave device 30 a new channel map that was determined before the start of sharing of the new channel map. At this time, the master device 20 transmits, along with the new channel map, information indicating the timing to start using the new channel map. As shown in the examples of the time charts in FIGS. 8 and 9 , the timing to start using the new channel map occurs every time a channel map update period elapses. The timing to start using the new channel map can be calculated based on the channel map update period set in the channel map update period setting process in FIG. 6 . Like the new channel map, the timing to start using the channel map is also determined before the start of sharing of the new channel map. Note that, as shown in the time chart in FIG. 8 , if the new channel map is successfully shared, the new channel map and timing information do not need to be transmitted in subsequent communication events. In FIGS. 8 and 9, an x ​​mark indicates a failure in sharing the channel map, and a ◯ mark indicates a success in sharing the channel map.

[0070] In step S710, the slave device 30 receives the new channel map and timing information transmitted from the master device 20. Upon receiving the new channel map and timing information in step S710, the slave device 30 performs a checksum check based on the error detection code included in the received packet to confirm whether the new channel map and timing information were received correctly in step S720. If the slave device 30 determines based on the checksum check result in step S720 that the new channel map and timing information were not received correctly, for example, the slave device 30 does not transmit an acknowledgment signal (ACK signal) for the new channel map in step S730. On the other hand, if the slave device 30 determines in step S720 that the new channel map and timing information were received correctly, the slave device 30 returns an acknowledgment signal (ACK signal) for the new channel map to the master device 20 in step S730.

[0071] In step S620, the master device 20 receives the Ack signal from the slave device 30. Then, in step S630, 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 S640, the master device 20 determines whether the checksum check results in step S630 were OK or NG. If the checksum check results in OK, the master device 20 proceeds to step S650. On the other hand, if the checksum check results in NG, the master device 20 proceeds to step S660.

[0072] In step S650, the master device 20 determines that the channel map has been successfully shared because it correctly received the Ack signal. Meanwhile, in step S660, the master device 20 determines whether to execute processing for retransmission within the same communication event because it did not correctly receive the Ack signal. If the master device 20 determines to retransmit in step S660, it executes the processing from step S610 again. If the master device 20 determines not to retransmit in step S660, it proceeds to step S670.

[0073] In step S670, the master device 20 determines whether the channel map update period has expired. For example, as shown in the example of the time chart in FIG. 8 , if the update period X is set to a length equivalent to 10 communication events, the channel map update period X is determined to have expired when 10 communication events have been executed since the channel map update period X started. If it is determined in step S670 that the update period has expired, the master device 20 proceeds to step S680. On the other hand, if it is determined that the update period has not expired, the master device 20 ends the channel map sharing process shown in FIG. 7 .

[0074] In step S680, the master device 20 determines the channel map to be transmitted in the next update period based on the channel map created in step S290 in the communication sequence of FIG. 5. At this time, the master device 20 also determines the timing to start using the channel map to be transmitted in the next update period based on the channel map update period set in the channel map update period setting process of FIG. 6. In the next step S690, the master device 20 determines whether the channel map sharing was successful during the expired update period. That is, if the master device 20 determines that the channel map sharing was successful in step S650, it determines that the sharing was successful in step S690. Conversely, if the master device 20 does not determine that the channel map sharing was successful in step S650, it determines that the sharing was unsuccessful in step S690. If it determines that the sharing was successful, the master device 20 proceeds to step S700. If it determines that the sharing was unsuccessful, the master device 20 terminates the channel map sharing process shown in FIG. 7. In step S700, the master device 20 switches the channel map to be used in the next update cycle to the successfully shared channel map. As a result, as shown in the time chart of FIG. 8, in the next update cycle, wireless communication between the master device 20 and the slave device 30 is performed using the successfully shared new channel map.

[0075] As described above, if the master device 20 determines in step S690 that the channel map sharing has failed, it terminates the channel map sharing process shown in FIG. 7 without switching the channel map. Therefore, in this case, the channel map is not switched in the next update cycle, and the channel map used in the previous update cycle continues to be used. If the master device 20 determines that the channel map sharing has failed, this is because it is highly likely that the slave device 30 does not have a new channel map. However, it is also possible that the slave device 30 was able to receive the channel map and timing information to be used in the next update cycle, but the master device 20 was unable to successfully receive the ACK signal used to confirm receipt. Therefore, regardless of whether the channel map sharing has succeeded or failed, the master device 20 may switch the channel map. Regardless of whether the channel map has been switched, the channel map to be used in the next update cycle—in other words, the channel map to be shared—is updated to a new channel map each time the update cycle expires in step S680.

[0076] In addition, even if the master device 20 attempts wireless communication with the slave device 30 while continuing to use the channel map used in the previous update cycle or while switching the channel map used in the previous update cycle, if wireless communication with the slave device 30 is not possible at all, for example, over a predetermined number of update cycles, the master device 20 and the slave device 30 may disconnect their communication connection.

[0077] When the master device 20 and the slave device 30 disconnect their communication connection, the master device 20 and the slave device 30 initiate the startup sequence shown in FIG. 4 described above in order to reestablish the communication connection. This causes an attempt to reconnect the master device 20 and the slave device 30. In the startup sequence, which is the reconnection process, a communication connection is established between the master device 20 and the slave device 30, and further, connection information including a channel map indicating the communication channels to be used for wireless communication is shared between the master device 20 and the slave device 30. At this time, the channel map is initialized to an initial channel map in which all communication channels are used for wireless communication. This enables the master device 20 and the slave device 30 to perform wireless communication again.

[0078] In this embodiment, as shown in the time charts of Figures 8 and 9, the channel map shared by the master device 20 and the slave device 30 is updated, in principle, every multiple communication events (six or ten communication events in the examples shown in the figures). In other words, the channel map used for wireless communication between the master device 20 and the slave device 30 is switched every multiple communication events. Therefore, the period of multiple communication events is both the channel map application period and the channel map update period. By periodically updating the channel map in this way, the master device 20 and the slave device 30 can perform high-quality communication using a channel map that adapts to changes in the communication quality of each communication channel.

[0079] In particular, in the wireless communication system 10 according to the present embodiment, the channel map update period is changed depending on the communication status of the wireless communication between the master device 20 and the slave device 30. This is because if the channel map update period were constant, there would be a possibility that the channel map could not be updated at a period appropriate for the communication environment at any given time. For example, even if the communication environment is relatively good, it is conceivable that the number of channel map transmissions between a channel map update and the next channel map update would be insufficient, resulting in failure to share the channel map. On the other hand, if the communication environment deteriorates from a good state, even if the number of channel map transmissions is large, it cannot be said that this increases the likelihood of successful channel map sharing due to the influence of noise, etc.

[0080] Therefore, in the wireless communication system 10 according to this embodiment, when the communication state is good, the channel map update period X is set longer than when the communication state is deteriorating, as shown in the time chart of Fig. 8. This increases the probability of successful channel map sharing between the master device 20 and the slave device 30. Conversely, when the communication state is deteriorating, the channel map update period Y is set shorter than when the communication state is good, as shown in the time chart of Fig. 9. This allows for the sharing of a channel map suitable for the deteriorated communication environment to be accelerated.

[0081] Second Embodiment Next, a wireless communication system 10 according to a second embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment has the same configuration as the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0082] In the wireless communication system 10 according to the first embodiment, the master device 20 determines whether the communication status of the wireless communication between the master device 20 and the slave device 30 is normal or abnormal based on the overall PER. In contrast, in the wireless communication system 10 according to the present embodiment, the master device 20 determines whether the communication status of the wireless communication between the master device 20 and the slave device 30 is normal or abnormal based on the number of consecutive communication failures in the wireless communication for each communication event. In this manner, the communication status of the wireless communication between the master device 20 and the slave device 30 can also be determined based on the number of consecutive communication failures. Furthermore, the wireless communication system 10 according to the present embodiment is configured to notify the upper control device 1 of the communication status of the wireless communication between the master device 20 and the slave device 30. As a result, the upper control device 1 can determine to use information transmitted or received through the wireless communication between the master device 20 and the slave device 30 when the communication status is normal. On the other hand, if the communication status is abnormal, the upper control device 1 can decide not to use the information transmitted or received by wireless communication between the master device 20 and the slave device 30, and can take measures such as temporarily suspending control based on that information or continuing control based on information transmitted or received in the past.

[0083] The following describes the wireless communication system 10 according to this embodiment, focusing on differences from the wireless communication system 10 according to the first embodiment. The wireless communication system 10 according to this embodiment differs from the wireless communication system 10 according to the first embodiment mainly in the channel map update period setting process.

[0084] 10 is a flowchart showing an example of a channel map update period setting process executed by the master device 20 of the wireless communication system 10 according to this embodiment. In the first step S810, the master device 20 acquires the number of consecutive communication failures in wireless communication with the slave device 30 for each communication event. In step S820, the master device 20 compares the acquired number of consecutive communication failures with a second threshold. If this comparison reveals that the number of consecutive communication failures is less than the second threshold, the master device 20 proceeds to step S830 and determines that the communication status is normal. On the other hand, if the number of consecutive communication failures is equal to or greater than the second threshold, the master device 20 proceeds to step S840 and determines that the communication status is abnormal.

[0085] In step S850, the master device 20 notifies the upper control device 1 of the communication status of the wireless communication between the master device 20 and the slave device 30 determined in step S830 or S840. This allows the upper control device 1 to know whether the communication status is normal or abnormal. The processing of the subsequent steps S860, S870, and S880 is the same as steps S550, S560, and S570 of the channel map update period setting processing in Figure 6 described above, so description thereof will be omitted.

[0086] Third Embodiment Next, a wireless communication system 10 according to a third embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment has the same configuration as the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0087] In the wireless communication system 10 according to the first embodiment described above, the master unit 20 determines whether the communication state of the wireless communication between the master unit 20 and the slave unit 30 is normal or abnormal. In contrast, in the wireless communication system 10 according to the present embodiment, the higher-level control device 1, which uses information transmitted or received through wireless communication between the master unit 20 and the slave unit 30, determines the state of the vehicle system based on the communication state of the wireless communication between the master unit 20 and the slave unit 30, and instructs the master unit 20 about the update period of the channel map according to the determination result. That is, in the present embodiment, the higher-level control device 1 is configured to externally issue an instruction to the master unit 20 to change the update period of the channel map.

[0088] The following describes the wireless communication system 10 according to this embodiment, focusing on differences from the wireless communication system 10 according to the first embodiment. The wireless communication system 10 according to this embodiment differs from the wireless communication system 10 according to the first embodiment mainly in the channel map update period setting process.

[0089] Fig. 11 is a flowchart showing an example of a channel map update period setting process executed in the master device 20 of the wireless communication system 10 according to this embodiment. Fig. 12 is a flowchart showing a process executed in the upper control device 1 to give an external instruction to the master device 20 to change the channel map update period.

[0090] In the first step S910 of Fig. 11, the master device 20 acquires the number of consecutive communication failures in wireless communication with the slave device 30 for each communication event. In step S920, the master device 20 compares the acquired number of consecutive communication failures with a third threshold value (≤ the second threshold value). If this comparison shows that the number of consecutive communication failures is less than the third threshold value, the master device 20 proceeds to step S930 and determines that the communication status is normal. On the other hand, if the number of consecutive communication failures is equal to or greater than the third threshold value, the master device 20 proceeds to step S940 and determines that the communication status is abnormal.

[0091] In step S950, the master unit 20 notifies the higher-level control device 1 of the communication state of the wireless communication between the master unit 20 and the slave unit 30 determined in step S930 or S940. In step S960, the master unit 20 receives the vehicle system state from the higher-level control device 1 as an external instruction to change the channel map update period. Then, in step S970, the master unit 20 determines whether the vehicle system state is normal or abnormal based on the received vehicle system state. If the master unit 20 determines that the vehicle system state is normal, the master unit 20 proceeds to step S980 and sets the channel map update period to X. On the other hand, if the master unit 20 determines that the vehicle system state is abnormal, the master unit 20 proceeds to step S990 and sets the channel map update period to Y.

[0092] Next, the process shown in the flowchart of FIG. 12 , which is executed by the upper control device 1, will be described. In the first step S1010, the upper control device 1 receives the communication status of the wireless communication of the wireless communication system 10 from the master device 20. More specifically, it receives the result of the decision made in step S930 or S940 of the flowchart of FIG. 11 . In step S1020, the upper control device 1 determines the communication status of the wireless communication system 10 based on the received decision result. If the upper control device 1 determines that the communication status of the wireless communication system 10 is normal, the process proceeds to step S1030, where it stops measuring the timer and resets the timer value. On the other hand, if the upper control device 1 determines that the communication status of the wireless communication system 10 is abnormal, the process proceeds to step S1040, where it starts or continues measuring the timer, thereby performing timer measurement. In other words, the timer measures the elapsed time since the communication status of the wireless communication system 10 became abnormal (communication interruption state).

[0093] In step S1050, the upper control device 1 compares the timer value with a fourth threshold. If the timer value is less than the fourth threshold, the upper control device 1 proceeds to step S1060, where it determines that the vehicle system is normal because the information transmitted or received between the master device 20 and the slave device 30 is available. On the other hand, if the timer value is equal to or greater than the fourth threshold, the upper control device 1 proceeds to step S1070, where it determines that the vehicle system is abnormal because the information transmitted or received between the master device 20 and the slave device 30 is unavailable. Note that in the above example, it has been described that the upper control device 1 determines whether the vehicle system is normal or abnormal. However, because this determination is based on the elapsed time since the wireless communication system became abnormal (communication interrupted), it can also be considered that the upper control device 1 determines whether the communication status of the wireless communication system 10 is normal or abnormal on behalf of the master device 20.

[0094] In step S1080, the higher-level control device 1 transmits, as an external instruction to change the update period of the channel map, vehicle system status information to the master device 20 of the wireless communication system 10. The transmitted vehicle system status information is the vehicle system status determined in step S1060 or S1070.

[0095] The master unit 20 sets the channel map update period in accordance with the received vehicle system status information. The setting of the channel map update period in accordance with the vehicle system status information is performed by the processes of steps S970, S980, and S990 in the channel map update period setting process of FIG. 11 described above.

[0096] Fourth Embodiment Next, a wireless communication system 10 according to a fourth embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment has the same configuration as the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0097] In the wireless communication system 10 according to the third embodiment described above, the upper control device 1 issues an external command to the master device 20 of the wireless communication system 10 to change the channel map update period based on the state of wireless communication between the master device 20 and the slave device 30. In contrast, in the wireless communication system 10 according to the present embodiment, when an abnormality (e.g., a CPU abnormality, a sensor abnormality, a voltage abnormality, etc.) occurs in a vehicle system (e.g., a battery management system) controlled by the upper control device 1, the upper control device 1 issues an external command to the master device 20 of the wireless communication system 10 to shorten the channel map update period. This reduces the possibility of a wireless communication abnormality occurring and makes it possible to prevent the wireless communication abnormality from exacerbating an abnormality that has occurred in the vehicle system.

[0098] The following describes the wireless communication system 10 according to this embodiment, focusing on the differences from the wireless communication system 10 according to the third embodiment. In this embodiment, as in the third embodiment, the upper control device 1 issues an external instruction to the master device 20 of the wireless communication system 10 to shorten the update period of the channel map. However, the condition under which the upper control device 1 issues an external instruction to the master device 20 to change the update period of the channel map differs from that in the third embodiment.

[0099] 13 is a flowchart showing an example of a process in which the host control device 1 externally instructs the master device 20 of the wireless communication system 10 to shorten the channel map update period when an abnormality occurs in the vehicle system to be controlled. In the first step S1110, the host control device 1 diagnoses whether an abnormality (e.g., a CPU abnormality, a sensor abnormality, a voltage abnormality, etc.) has occurred in the vehicle system to be controlled. This diagnosis may be performed by a diagnostic device that is capable of communicating with the host control device 1 and is provided separately from the host control device 1.

[0100] In step S1120, the upper control device 1 determines whether the vehicle system is in a normal state or an abnormal state based on the diagnosis result obtained in step S1110. If the upper control device 1 determines that the vehicle system is in a normal state, the process proceeds to step S1130, where it determines that the vehicle system is in a normal state. On the other hand, if the upper control device 1 determines that the vehicle system is in an abnormal state, the process proceeds to step S1140, where it determines that the vehicle system is in an abnormal state. Then, in step S1150, the upper control device 1 transmits vehicle system status information to the master device 20 of the wireless communication system 10 as an external instruction to change the channel map update period. The transmitted vehicle system status information is the vehicle system status determined in step S1130 or S1140.

[0101] The master unit 20 sets the channel map update period in accordance with the received vehicle system status. This setting of the channel map update period in accordance with the vehicle system status can be performed by the same processes as steps S970, S980, and S990 in the channel map update period setting process in FIG. 11 described above.

[0102] Fifth Embodiment Next, a wireless communication system 10 according to a fifth embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment has the same configuration as the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0103] In the wireless communication system 10 according to the fourth embodiment described above, if an abnormality occurs in a vehicle system controlled by the upper control device 1, the upper control device 1 issues an external instruction to the master device 20 of the wireless communication system 10 to shorten the update period of the channel map. In contrast, in the wireless communication system 10 according to the present embodiment, if a communication abnormality occurs in any of the other vehicle systems 2, 3, and 4, or if any of the other vehicle systems 2, 3, and 4 enters an operating state indicating an abnormal vehicle condition (for example, a state in which the possibility of a vehicle collision is increased), the upper control device 1 issues an external instruction to the master device 20 of the wireless communication system 10 to shorten the update period of the channel map.

[0104] For example, if the other vehicle systems are navigation systems or ETC systems that communicate with the outside world, if a communication error occurs in one of these vehicle systems, the vehicle is exposed to a noisy environment, and a communication error is likely to occur in the wireless communication system 10 as well. Therefore, when a communication error occurs in another vehicle system, it is preferable to shorten the channel map update period to reduce the possibility of a wireless communication error occurring in the wireless communication system 10. Furthermore, if the other vehicle systems are, for example, an airbag system that activates when a vehicle collision is imminent or a collision mitigation system that activates when a collision is likely, when these vehicle systems are activated, the vehicle is likely in a critical situation with a high collision probability. In such a situation, particularly when the control target of the host controller 1 is a battery management system, it is important for the host controller 1 to reliably acquire battery status information via the wireless communication system 10. For example, if a vehicle collision actually occurs, the host controller 1 can determine whether the battery is damaged based on the battery status information. If there is a possibility that the battery is damaged, the host controller 1 can take action, such as shutting off a relay. Therefore, when it is considered highly likely that other vehicle systems are operating and the vehicle is in a critical situation where a collision is likely, it is preferable to reduce the possibility of a wireless communication abnormality occurring in the wireless communication system 10 by shortening the channel map update period.

[0105] 14 is a flowchart showing an example of processing in which, when some abnormality occurs in the host control device 1, such as a communication abnormality in the other vehicle systems 2, 3, and 4 or operation of the vehicle in a critical situation, the host control device 1 receives an external instruction from the other vehicle systems 2, 3, and 4 to shorten the update period of the channel map, and provides this instruction to the master device 20 of the wireless communication system 10. In the first step S1210, the host control device 1 receives status information related to the occurrence of the communication abnormality and operation from the other vehicle systems 2, 3, and 4.

[0106] In step S1220, the upper control device 1 determines whether or not the other vehicle systems 2, 3, and 4 are malfunctioning, which indicates a high possibility that a communication abnormality is occurring in the other vehicle systems or that the vehicle is in a critical situation, based on the status information of the other vehicle systems 2, 3, and 4 received in step S1210. If the upper control device 1 determines that the other vehicle systems 2, 3, and 4 are normal, the upper control device 1 proceeds to step S1230 and determines that the other vehicle systems 2, 3, and 4 are normal. On the other hand, if the upper control device 1 determines that the other vehicle systems 2, 3, and 4 are malfunctioning, the upper control device 1 proceeds to step S1240 and determines that the other vehicle systems 2, 3, and 4 are malfunctioning. Then, in step S1250, the upper control device 1 transmits the status information of the other vehicle systems 2, 3, and 4 to the master device 20 of the wireless communication system 10 as an external instruction to change the channel map update period. The status information of the other vehicle systems 2, 3, and 4 that is transmitted is the status of the other vehicle systems 2, 3, and 4 that is the result of the determination in step S1230 or S1240.

[0107] The master unit 20 sets the channel map update period in accordance with the received status of the other vehicle systems 2, 3, and 4. Setting the channel map update period in accordance with the status of the other vehicle systems 2, 3, and 4 can be performed by the same processes as steps S970, S980, and S990 in the channel map update period setting process in FIG.

[0108] 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.

[0109] For example, in each of the above-described embodiments, an example has been described in which one master device 20 communicates wirelessly with one slave device 30. However, a plurality of slave devices 30 may be provided. When a plurality of slave devices 30 is provided, the master device 20 executes the startup sequence of FIG. 4 individually with each of the slave devices 30 and establishes a wireless communication connection with each of the slave devices 30. Then, in the communication sequence, the master device 20 may communicate with the plurality of slave devices 30 in sequence by allocating a communication period (sub-event) to each of the slave devices 30 in each communication event, as shown in the time chart of FIG. 15 .

[0110] In addition, in each of the above-described embodiments, an example has been described in which the channel map update period is changed to two stages in accordance with the communication state of the wireless communication between the master device 20 and the slave device 30 or an external instruction. However, the degree of the communication state of the wireless communication between the master device 20 and the slave device 30 or the type of abnormality may be further subdivided, and the channel map update period may be changed to three or more stages in accordance with an external instruction based on which type applies.

[0111] Finally, this specification discloses the following technical ideas and combinations thereof. The combinations of the following technical ideas apply not only to the wireless communication system 10 but also to a wireless communication method and a wireless communication program.

[0112] (Technical Idea 1) A wireless communication system in which at least one master device (20) performs wireless communication with at least one slave device (30) via one communication channel sequentially selected from a plurality of communication channels, the wireless communication system comprising: a communication channel determination unit (S270, S280, S290) that determines the communication quality of each communication channel when the master device wirelessly communicates with the slave device, and determines the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; a channel map sharing unit (S310) that transmits a channel map indicating the communication channels determined by the communication channel determination unit from the master device to the slave device, and shares the channel map between the master device and the slave device; and a period change unit (S300) that changes the update period of the channel map shared between the master device and the slave device by the channel map sharing unit, in accordance with the communication state of the wireless communication between the master device and the slave device or an external instruction.

[0113] (Technical Idea 2) In the wireless communication system according to Technical Idea 1, the cycle change unit changes the update cycle of the channel map depending on whether the communication state is in a normal communication state where the communication state is good or in an abnormal communication state where the communication state has deteriorated.

[0114] (Technical Idea 3) In the wireless communication system according to Technical Idea 2, the cycle change unit sets the update cycle of the channel map in an abnormal communication state to be shorter than the update cycle of the channel map in a normal communication state.

[0115] (Technical Idea 4) The wireless communication system according to Technical Idea 2 or 3, wherein the period change unit shortens the update period of the channel map in an abnormal communication state to be shorter than the update period of the channel map in a normal communication state, within a range that is equal to or greater than a predetermined minimum period.

[0116] (Technical Idea 5) A wireless communication system according to any one of Technical Ideas 2 to 4, wherein the period change unit makes the update period of the channel map in a normal communication state longer than the update period of the channel map in an abnormal communication state, within a range that is equal to or less than a preset maximum period.

[0117] (Technical Idea 6) The wireless communication system according to any one of Technical Ideas 1 to 5, further comprising: a transmitting unit (S730) that transmits a channel map reception confirmation signal from the slave device to the master device in response to the channel map being received by the slave device; and a channel map switching control unit (S640, S660, S670, S690, S700) that switches the channel map used for wireless communication with the slave device to the transmitted channel map in response to receiving the channel map reception confirmation signal transmitted from the transmitting unit when an update period for the channel map expires, but does not switch the channel map and continues to use the current channel map if the channel map reception confirmation signal cannot be received by the expiration of the update period for the channel map.

[0118] (Technical Idea 7) A wireless communication system described in any one of Technical Ideas 1 to 6, wherein the channel map sharing unit transmits the channel map to be used in the next update cycle from the master device to the slave device during the channel map update cycle in which the current channel map is used, and the channel map sharing unit transmits the channel map a predetermined number of times according to the length of the channel map update cycle in which the current channel map is used.

[0119] (Technical Idea 8) The wireless communication system according to any one of Technical Ideas 1 to 5, further comprising an identification unit (S520, S530, S540, S820, S830, S840) that distinguishes between a normal communication state in which the communication state is good and an abnormal communication state in which the communication state has deteriorated, regarding the communication state of the wireless communication between the master device and the slave device.

[0120] (Technical Idea 9) A wireless communication system according to Technical Idea 8, wherein the identification unit identifies whether the normal state of wireless communication between the master device and the slave device is a normal communication state or an abnormal communication state based on at least one of a communication error rate, which is the ratio of the number of communication errors to the number of communications performed, the number of consecutive wireless communication failures, and the length of time that wireless communication is interrupted.

[0121] (Technical Idea 10) A wireless communication system according to Technical Idea 1, further comprising: a notification unit (S950) that notifies a first control unit (1) of the communication state of the wireless communication between the master device and the slave device, the notification unit using information transmitted or received by the wireless communication between the master device and the slave device; and a determination unit (S1020, S1030, S1040, S1050, S1060, S1070) that is provided in the first control unit and determines whether the communication state is a normal communication state in which the communication state is good, or an abnormal communication state in which the communication state has deteriorated, based on the communication state of the wireless communication between the master device and the slave device, wherein the period change unit uses the determination result of the determination unit as an instruction from the outside and changes the update period of the channel map by the channel map sharing unit in accordance with the determination result of the determination unit.

[0122] (Technical Idea 11) The wireless communication system according to Technical Idea 10, wherein the period change unit shortens the update period of the channel map when the determination unit determines that the communication state is abnormal compared to the update period of the channel map when the determination unit determines that the communication state is normal.

[0123] (Technical Idea 12) A wireless communication system according to Technical Idea 1, further comprising a first control unit (1) that controls a first system and utilizes information transmitted or received by wireless communication between the master device and the slave device, wherein the first control unit has a first abnormality determination unit (S1110) that determines whether an abnormality has occurred in the first system, and wherein the period change unit uses the determination result of the first abnormality determination unit as an instruction from the outside and changes the update period of the channel map shared between the master device and the slave device by the channel map sharing unit in accordance with the determination result of the first abnormality determination unit.

[0124] (Technical Idea 13) The wireless communication system according to Technical Idea 12, wherein the period change unit shortens the update period of the channel map when the first abnormality determination unit determines that an abnormality exists in the first system, compared to the update period of the channel map when the first abnormality determination unit does not determine that an abnormality exists in the first system.

[0125] (Technical Idea 14) A wireless communication system according to Technical Idea 1, further comprising: a first control unit (1) that controls a first system and utilizes information transmitted or received through wireless communication between the master device and the slave device; and a vehicle system (2) that has a second control unit that controls a second system, wherein the first control unit and the second control unit are configured to be able to communicate with each other, the second control unit has a second abnormality determination unit that determines whether an abnormality has occurred in the second system, the second control unit transmits an external instruction to the first control unit to change the update period of the channel map based on the determination result of the second abnormality determination unit, and the period change unit changes the update period of the channel map shared between the master device and the slave device by the channel map sharing unit in response to the external instruction transmitted from the second control unit to the first control unit.

[0126] (Technical Idea 15) The wireless communication system according to Technical Idea 14, wherein the period change unit shortens the update period of the channel map when the second abnormality determination unit determines that an abnormality has occurred in the second system, compared to the update period of the channel map when the second abnormality determination unit does not determine that an abnormality has occurred in the second system.

[0127] (Technical Idea 16) The second control unit controls the second system using a wireless communication other than the wireless communication between the master device and the slave device, and when a communication abnormality occurs in the other wireless communication, the second control unit transmits an external instruction to the first control unit to shorten the update period of the channel map, in the wireless communication system described in Technical Idea 14 or 15.

[0128] (Technical Idea 17) A wireless communication system described in Technical Idea 14 or 15, wherein the first system and the second system are mounted on a vehicle, the second control unit has a function of determining the possibility of a collision of the vehicle, and the second control unit transmits an external instruction to the first control unit to shorten the update period of the channel map in response to determining that the possibility of a collision of the vehicle has increased beyond a predetermined threshold.

Claims

1. A wireless communication system in which at least one master device (20) performs wireless communication with at least one slave device (30) via one communication channel selected sequentially from a plurality of communication channels, comprising: a communication channel determination unit (S270, S280, S290) that determines a communication quality of each communication channel when the master device wirelessly communicates with the slave device, and determines a communication channel to be used for wireless communication based on the determined communication quality of each communication channel; a channel map sharing unit (S310) that transmits a channel map indicating the communication channel determined by the communication channel determination unit from the master device to the slave device, and shares the channel map between the master device and the slave device; and a period change unit (S300) that changes the update period of the channel map shared between the master device and the slave device by the channel map sharing unit in response to a communication state of the wireless communication between the master device and the slave device or an external instruction.

2. The wireless communication system according to claim 1, wherein the cycle change unit changes the update cycle of the channel map depending on whether the communication state is in a normal communication state where the communication state is good or in an abnormal communication state where the communication state has deteriorated.

3. The wireless communication system according to claim 2, wherein the period change unit makes the update period of the channel map in an abnormal communication state shorter than the update period of the channel map in a normal communication state.

4. A wireless communication system as described in claim 2 or 3, wherein the period change unit makes the update period of the channel map during an abnormal communication state shorter than the update period of the channel map during a normal communication state, within a range that is equal to or greater than a predetermined minimum period.

5. A wireless communication system as described in claim 2 or 3, wherein the period change unit makes the update period of the channel map in a normal communication state longer than the update period of the channel map in an abnormal communication state, within a range not exceeding a preset maximum period.

6. A wireless communication system as claimed in any one of claims 1 to 3, further comprising: a transmitting unit (S730) which transmits an acknowledgement signal for the channel map from the slave device to the master device in response to the channel map being received by the slave device; and a channel map switching control unit (S640, S660, S670, S690, S700) which, in response to receiving the acknowledgement signal for the channel map transmitted from the transmitting unit, switches the channel map used for wireless communication with the slave device to the transmitted channel map when an update period for the channel map expires, but if an acknowledgement signal for the channel map cannot be received by the expiration of the update period for the channel map, does not switch the channel map and continues to use the current channel map.

7. A wireless communication system as claimed in any one of claims 1 to 3, wherein the channel map sharing unit transmits the channel map to be used in the next update period from the master device to the slave device during an update period of the channel map in which the current channel map is used, and the channel map sharing unit transmits the channel map a predetermined number of times according to the length of the update period of the channel map in which the current channel map is used.

8. A wireless communication system according to any one of claims 1 to 3, further comprising an identification unit (S520, S530, S540, S820, S830, S840) for identifying a normal communication state in which the communication state of wireless communication between the master device and the slave device is good and an abnormal communication state in which the communication state has deteriorated.

9. The wireless communication system of claim 8, wherein the identification unit identifies whether the normal state of wireless communication between the master device and the slave device is a normal communication state or an abnormal communication state based on at least one of a communication error rate, which is the ratio of the number of communication errors occurring to the number of communications performed, the number of consecutive wireless communication failures, and the length of time that wireless communication is interrupted.

10. A wireless communication system as described in claim 1, further comprising: a notification unit (S950) that notifies a first control unit (1) of the communication state of wireless communication between the master device and the slave device, the notification unit utilizing information transmitted or received by wireless communication between the master device and the slave device; and a judgment unit (S1020, S1030, S1040, S1050, S1060, S1070) provided in the first control unit that judges whether the communication state is a good normal communication state or a deteriorated abnormal communication state based on the communication state of wireless communication between the master device and the slave device, wherein the period change unit uses the judgment result of the judgment unit as an instruction from the outside and changes the update period of the channel map by the channel map sharing unit in accordance with the judgment result of the judgment unit.

11. The wireless communication system described in claim 10, wherein the period change unit makes the channel map update period when the judgment unit judges that the communication state is abnormal shorter than the channel map update period when the judgment unit judges that the communication state is normal.

12. A wireless communication system as described in claim 1, further comprising a first control unit (1) that controls a first system and utilizes information transmitted or received by wireless communication between the master device and the slave device, wherein the first control unit has a first abnormality judgment unit (S1110) that judges whether or not an abnormality has occurred in the first system, and the period change unit uses the judgment result of the first abnormality judgment unit as an instruction from the outside and changes the update period of the channel map shared between the master device and the slave device by the channel map sharing unit in accordance with the judgment result of the first abnormality judgment unit.

13. The wireless communication system described in claim 12, wherein the period change unit shortens the update period of the channel map when the first abnormality determination unit determines that there is an abnormality in the first system, compared to the update period of the channel map when the first abnormality determination unit does not determine that there is an abnormality in the first system.

14. A wireless communication system as described in claim 1, further comprising: a first control unit (1) that controls a first system and utilizes information transmitted or received through wireless communication between the master device and the slave device; and a vehicle system (2) having a second control unit that controls a second system, wherein the first control unit and the second control unit are configured to be able to communicate with each other, the second control unit has a second abnormality judgment unit that judges whether an abnormality has occurred in the second system, the second control unit transmits to the first control unit an instruction from the outside to change the update period of the channel map based on a judgment result by the second abnormality judgment unit, and the period change unit changes the update period of the channel map shared between the master device and the slave device by the channel map sharing unit in response to the instruction from the outside transmitted from the second control unit to the first control unit.

15. The wireless communication system described in claim 14, wherein the period change unit shortens the update period of the channel map when the second abnormality determination unit determines that there is an abnormality in the second system, compared to the update period of the channel map when the second abnormality determination unit does not determine that there is an abnormality in the second system.

16. The wireless communication system described in claim 14 or 15, wherein the second control unit controls the second system using wireless communication other than the wireless communication between the master device and the slave device, and when a communication abnormality occurs in the other wireless communication, the second control unit transmits an instruction from the outside to the first control unit to shorten the update period of the channel map.

17. A wireless communication system as described in claim 14 or 15, wherein the first system and the second system are mounted on a vehicle, the second control unit has a function of determining a possibility of collision of the vehicles, and the second control unit transmits an external instruction to the first control unit to shorten the update period of the channel map in response to determining that the possibility of collision of the vehicles has increased beyond a predetermined threshold.

18. A wireless communication method in which at least one master device (20) performs wireless communication with at least one slave device (30) via one communication channel selected sequentially from a plurality of communication channels, the wireless communication method comprising: determining a communication quality of each communication channel when the master device wirelessly communicates with the slave device, and determining a communication channel to be used for wireless communication based on a result of the determination of the communication quality of each communication channel (S270, S280, S290); transmitting a channel map indicating the determined communication channel from the master device to the slave device, and causing the master device and the slave device to share the channel map (S310); and the channel map shared by the master device and the slave device is periodically updated, and changing an update period of the channel map shared by the master device and the slave device in response to a communication state of the wireless communication between the master device and the slave device or an external instruction (S300).

19. A wireless communication program for at least one master device (20) to perform wireless communication with at least one slave device (30) via one communication channel selected sequentially from a plurality of communication channels, the wireless communication program causing at least one processor to execute the following: when the master device wirelessly communicates with the slave device, determine the communication quality of each communication channel, and determine the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel (S270, S280, S290); transmit a channel map indicating the determined communication channel from the master device to the slave device, and cause the master device and the slave device to share the channel map (S310); and the channel map shared by the master device and the slave device is periodically updated, and change the update period of the channel map shared by the master device and the slave device in response to the communication state of the wireless communication between the master device and the slave device or an external instruction (S300).

Images