Radio communication system, radio communication method, and radio communication program

Abstract

To solve problems in the case of an update period of a channel map being constant by changing an update period of a channel map.SOLUTION: A radio communications system 10 includes a master device 20 and a slave device 30. When performing radio communication with the slave device 30, the master device 20 determines the communication quality of respective communication channels and decides a communication channel to be used for the radio communication on the basis of communication quality determination results of the respective communication channels. A channel map indicating the decided communication channel is transmitted from the master device 20 to the slave device 30 so that 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. An update period of the channel map is changed depending on a communication state between the master device 20 and the slave device 30 or an instruction from the outside.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] 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. [Background technology]

[0002] As this type of wireless communication system, for example, the one described in Patent Document 1 is known. 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 preset threshold Th1, the wireless communication device determines that the reception operation of receiving this packet is a reception error caused by interference with other radio waves. Then, the wireless communication device counts the number of receptions and the number of reception errors, and stores the frequency of reception errors caused by interference in each frequency channel (number of reception errors / number of receptions). When the reception error frequency exceeds a threshold Th2, the wireless communication device determines that an interference source exists in the frequency channel where the reception error frequency caused by interference exceeds the threshold Th2, and stores this frequency channel as an unavailable channel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-128812 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the wireless communication system of Patent Document 1 sets a frequency channel whose communication quality has deteriorated due to interference with other radio waves as an unavailable channel. In addition, the wireless communication system of Patent Document 1 restores the frequency channel that has been set as an unavailable channel to an available frequency channel after a predetermined set period has elapsed. Such control of setting a frequency channel as an unavailable channel or restoring it to an available channel is hereinafter referred to as channel map control in this specification.

[0005] Here, the frequency channels available for wireless communication and the frequency channels to be restored from unavailable channels may change over time. For this reason, the channel map indicating the available channels and / or unavailable channels needs to be periodically updated by, for example, 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 is updated until before the next channel map is updated.

[0006] However, if the update period of the channel map is constant, various problems such as those described below may occur. For example, even if the communication environment is relatively good, the number of times the next channel map is transmitted during the period from after the channel map is updated until the next channel map is updated may not be sufficient, and therefore sharing of the next channel map may fail. In this case, if the update period of the channel map is long and the number of times the next channel map is transmitted is large, the possibility of successful sharing of the next channel map can be increased. On the other hand, if the communication environment, which was good, deteriorates, it cannot be said that the possibility of successful sharing of the next channel map can be increased even if the number of times the next channel map is transmitted is large due to the influence of noise, etc. In addition, if some abnormality occurs in a control device that uses information transmitted or received by 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, the possibility of a communication abnormality occurring increases, and the abnormality that has occurred may be aggravated.

[0007] 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. [Means for solving the problem]

[0008] In order to achieve the above object, a wireless communication system according to the present disclosure is a wireless communication system 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, 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 the 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; the channel map shared by the master device and the slave device by the channel map sharing unit is periodically updated; The device is configured to include a period change unit (S300) that changes the update period of the channel map shared by the master device and the slave device by the channel map sharing unit in response to the communication state of wireless communication between the master device and the slave device or an external instruction.

[0009] A wireless communication method according to the present disclosure is 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 sequentially selected from a plurality of communication channels, the method comprising: When the master device wirelessly communicates with the slave device, the master device judges the communication quality of each communication channel, and determines the communication channel to be used for the wireless communication based on the judgment result of the communication quality of each communication channel (S270, S280, S290); A channel map indicating the determined communication channel is transmitted from the master device to the slave device, and the channel map is shared between the master device and the slave device (S310); The channel map shared between the master and slave devices is periodically updated; and changing an update period of a channel map shared by the master device and the slave device in response to a communication state of wireless communication between the master device and the slave device or an external instruction (S300).

[0010] A wireless communication program according to the present disclosure is a wireless communication program for at least one master device (20) performing wireless communication with at least one slave device (30) via one communication channel sequentially selected from a plurality of communication channels, the program comprising: At least one processor has When the master device wirelessly communicates with the slave device, the master device judges the communication quality of each communication channel, and determines the communication channel to be used for the wireless communication based on the judgment result of the communication quality of each communication channel (S270, S280, S290); A channel map indicating the determined communication channel is transmitted from the master device to the slave device, and the channel map is shared between the master device and the slave device (S310); The channel map shared between the master and slave devices is periodically updated; and changing (S300) the update period of the channel map shared by the master device and the slave device in response to the communication state of wireless communication between the master device and the slave device or an external instruction.

[0011] As described above, in the wireless communication system, wireless communication method, and wireless communication program according to the present disclosure, the channel map update period (which can also be called the channel map switching period) is not always constant, but is changed according to the communication state of wireless communication between the master device and the slave device or an instruction from the outside. As a result, for example, when the communication state is good, the channel map update period can be made longer than when the communication state is deteriorated, thereby increasing the probability of successful channel map sharing. Conversely, when the communication state is deteriorated, the channel map update period can be made shorter than when the communication state is good, thereby speeding up the sharing of a channel map suitable for the deteriorated communication environment. Alternatively, for example, when some abnormality occurs in a control unit that uses information transmitted or received by wireless communication between the master device and the slave device, an external instruction to shorten the channel map update period can be generated, thereby making it possible to prevent the abnormality in wireless communication from being aggravated.

[0012] The reference numbers in parentheses above are merely an example of a correspondence with a specific configuration in an embodiment 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.

[0013] In addition, technical features described in each claim in addition to the features of the present disclosure described above will become apparent from the description of the embodiments described below and the accompanying drawings. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing an overall configuration, including a schematic configuration, of a wireless communication system according to a first embodiment. [Diagram 2] FIG. 4 is a diagram illustrating an example of the electric field strength distribution in a communication environment between a master device and a slave device. [Diagram 3] FIG. 4 is a diagram showing an example of received signal strength of each communication channel. [Figure 4] 10 is a flowchart showing an example of a start-up sequence of a master device and a slave device. [Diagram 5] 6 is a flowchart showing an example of a communication sequence between a master device and a slave device. [Figure 6] 6 is a flowchart showing an example of a channel map update period setting process in the flowchart of FIG. 5. [Figure 7] 6 is a flowchart showing an example of a channel map sharing process in the flowchart of FIG. 5. [Figure 8] 13 is a time chart showing an example of the operation of a channel map sharing process when the update period of the channel map is set to X periods. [Figure 9] 13 is a time chart showing an example of the operation of a channel map sharing process when the update cycle of the channel map is switched from an X cycle to a Y cycle. [Figure 10] 13 is a flowchart showing an example of a channel map update period setting process in the wireless communication system according to the second embodiment. [Figure 11]13 is a flowchart showing an example of a channel map update period setting process executed by a master device in the wireless communication system according to the third embodiment. [Figure 12] 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 for changing the update period of the channel map. [Figure 13] 13 is a flowchart showing an example of processing executed in a higher-level control device to give an external instruction to the master device for changing the update period of the channel map in the fourth embodiment. [Figure 14] 13 is a flowchart showing an example of processing executed in a higher-level control device to give an external instruction to the master device for changing the update period of the channel map in the fifth embodiment. [Figure 15] 10 is a time chart for explaining a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. Note that the same or similar configurations may be omitted from description by assigning the same reference number across multiple drawings. When only a portion of a configuration is described in each embodiment, the configuration of another embodiment described above may be applied to the other portion of the configuration. In addition to the combination of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

[0016] (First embodiment) The wireless communication system according to the present embodiment includes at least one master device and at least one slave device. At least one of the master device and the slave device may be mounted on a moving object for use. The moving object may include, for example, a vehicle such as an automobile or a railroad car, an aircraft such as an electric vertical take-off and landing aircraft or a drone, a ship, a construction machine, an agricultural machine, and the like.

[0017] FIG. 1 shows an example of a configuration in which a wireless communication system 10 according to the present embodiment is 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 electric 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 constituting a battery pack. In this case, both the master device 20 and the slave device 30 are mounted in the vehicle.

[0018] The monitoring device provided in the battery stack acquires battery information such as the voltage and current of each battery cell included in the corresponding battery stack, the temperature of the battery stack, etc., using various sensors. Then, when the monitoring device receives data requesting the battery information from the battery control device 1 via the wireless communication system 10, it transmits 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 to an appropriate range, and determines whether or not it is necessary to perform a so-called equalization process to equalize the voltages of each battery cell. When the battery control device 1 determines that it is necessary to perform an equalization process in at least one battery stack, it instructs the corresponding monitoring device to perform the equalization process via the wireless communication system 10. In addition, the monitoring device performs a process to determine abnormalities in various sensors and in its own operation, and when an abnormality is determined, it transmits abnormality information to the battery control device 1 via the wireless communication system 10.

[0019] 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 below) 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 (upper control device) 1 that controls locking and unlocking of the vehicle doors and on / off of a driving source such as an engine of the vehicle. 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 (upper control device) 1 that displays the tire pressure and issues a warning when the tire pressure is abnormal. The multiple slave devices 30 are connected by wire or wirelessly to an air pressure detection device provided in each tire.

[0020] 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 vehicle-mounted devices having a self-diagnosis function, and the master device 20 is connected to a diagnostic control device (higher-level control device) installed in a service factory. In these examples, at least one of the master device 20 and the plurality of slave devices 30 is disposed at a fixed position and / or at least one is mounted on the vehicle.

[0021] 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 be applied to systems that control and manage various equipment of moving objects other than vehicles, such as aircraft such as drones, ships, construction machinery, agricultural machinery, etc. Furthermore, the wireless communication system 10 according to the present embodiment can be applied to systems that control and manage various equipment of buildings such as buildings, production facilities such as factories, etc.

[0022] In the following embodiment, an example in which the wireless communication system 10 is applied to a battery management system for managing a battery mounted on a vehicle will be described. In this case, as shown in FIG. 1, both the master device 20 and the slave device 30 of the wireless communication system 10 are mounted on the vehicle (automobile). In this case, the master device 20 may be configured to be arranged in a common housing of a battery pack together with the slave device 30, or may not be arranged in a common housing. There may be one master device 20 or more. 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 perform wireless communication via one communication channel selected sequentially from multiple communication channels, such as Bluetooth Low Energy (Bluetooth is a registered trademark, and the same applies below, and Bluetooth Low Energy will be referred to as Bluetooth LE hereinafter) communication.

[0023] In the wireless communication between the master device 20 and the slave device 30, a frequency band used in short-distance communication, such as the 2.4 GHz band or the 5 GHz band, can be used. Radio waves in such high-frequency bands tend to travel in a more directional manner than radio waves in the LF band, and tend to be reflected by metal objects such as the body of a vehicle. LF is an abbreviation for Low Frequency. For example, Bluetooth and Bluetooth LE can be adopted as standards for short-distance communication. As an example, the master device 20 and the slave device 30 of this embodiment are configured to be able to carry out wireless communication conforming to the Bluetooth LE standard (hereinafter, Bluetooth LE communication). Details of the communication method related to the communication connection and encrypted communication are carried out according to a sequence defined in the Bluetooth LE standard.

[0024] 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 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 a part or all of these processes may be performed by another control device (e.g., a higher-level control device 1) provided outside the master device 20.

[0025] 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.

[0026] In the control circuit 21, the processor 211 executes a predetermined process (control) by executing a program stored in the ROM while using the RAM as a temporary storage area. The processor 211 executes a plurality of instructions included in the program to construct a plurality of functional units. There may be a plurality of processors 211. The storage medium for the program is not limited to the ROM. For example, various storage media such as an HDD or SSD can be adopted. HDD is an abbreviation for Hard-disk Drive. SSD is an abbreviation for Solid State Drive.

[0027] 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 a plurality of 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 an FPGA. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field-Programmable Gate Array.

[0028] The control circuit 21 generates a command requesting processing from the slave device 30 (e.g., a command requesting data, a command requesting execution of a predetermined process, etc.), and transmits transmission data including the command in a transmission packet to the wireless communication circuit 22. The control circuit 21 also receives a packet transmitted from the slave device 30 via the wireless communication circuit 22, and executes a predetermined process based on the data included in the received packet. That is, the wireless communication between the master device 20 and the slave device 30 is packet communication.

[0029] 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.

[0030] The wireless communication circuit 22 modulates a packet including the data transmitted from the control circuit 21 and transmits it to the slave device 30 via the antenna 23. The control circuit 21 outputs to the wireless communication circuit 22 data obtained by encrypting transmission data such as battery information request data using encryption information exchanged in a connection establishment process described later. The wireless communication circuit 22 adds data required for wireless communication (e.g., communication control information) to the transmission packet and transmits it. The data required for wireless communication includes, for example, an identifier (ID), a sequence number, a next sequence number, an error detection code, and the like. The wireless communication circuit 22 may control the data size, communication format, schedule, error detection, and the like of the communication between the master device 20 and the slave device 30. The control circuit 21 may perform control related to these communications.

[0031] 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.

[0032] 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 above-mentioned elements, 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 similar configuration to the control circuit 21 of the master device 20. The control circuit 31 includes, for example, a processor 311 and a memory 312. The memory 312 includes, for example, a RAM and a ROM.

[0033] The control circuit 31 executes requested processing (such as a response process of acquiring and returning requested data, or an execution process of the requested processing) based on a request command acquired 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 a monitoring device of the corresponding battery stack and acquires the battery information from the monitoring device, and then transmits data encrypted using the encryption information including the processing result (for example, the acquired battery information) to the wireless communication circuit 32 in response to the request. The control circuit 31 can also execute control of, for example, equipment mounted on a vehicle in accordance with the requested processing.

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

[0035] The wireless communication circuit 32 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 31 may perform control related to these communications. The antenna 33 converts an electric signal into a radio wave and radiates it into space. The antenna 33 receives the radio wave propagating through space and converts it into an electric signal.

[0036] The upper 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 are, 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 below) 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, and a collision mitigation system that avoids and reduces collisions with obstacles. The upper control device 1 receives external instructions to change the update period of the channel map from these other vehicle systems 2, 3, and 4, which will be described in detail later.

[0037] Fig. 2 is a diagram showing an example of an electric field strength distribution in a communication environment between the master unit 20 and the slave unit 30. Fig. 2 shows the results of an electromagnetic field simulation at a specific timing at a specific frequency. Hereinafter, the electric field strength distribution may be referred to as the electric field distribution.

[0038] The master unit 20 and the slave unit 30 are disposed, for example, at predetermined positions in a vehicle. When a radio wave signal of a predetermined frequency is transmitted from the master unit 20 and the slave unit 30 disposed at the respective predetermined positions, parts 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, reflection from a metal casing, and reflection from a harness. For this reason, the communication environment of the master unit 20 and the slave unit 30 has a plurality of so-called NULL points, which are parts of high electric field strength and parts of low electric field strength, as shown in FIG. 2.

[0039] If the slave unit 30 is located in or near a portion of low electric field strength in the electric field distribution with the master unit 20, the slave unit 30 is more likely to be unable to correctly receive the wireless signal from the master unit 20, which may result in a communication error. A communication channel with a high probability of causing such a communication error is a communication channel with degraded communication quality.

[0040] When the master device 20 and the slave device 30 perform wireless communication via one communication channel selected in sequence from a plurality of communication channels, the frequency of each communication channel is different, and therefore the electric field distribution of each communication channel may also change. As a result, the communication quality of each communication channel may differ.

[0041] For example, as shown in FIG. 3, in wireless communication via communication channel A, the received power (received signal strength), which is one of the parameters indicating the communication quality, is good. In addition, in wireless communication via communication channel C, the received power indicates 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, there is a high possibility that a communication error will occur in the wireless communication. Note that in FIG. 3, for ease of understanding, an example of the received signal strength versus frequency is shown by a solid line.

[0042] 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 perform high-quality wireless communication, avoiding communication channels with degraded communication quality.

[0043] 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 of the communication environment between the master unit 20 and the slave unit 30 changes depending on, for example, the state of the vehicle (for example, whether it is running or stopped) and the state of the surrounding environment of the vehicle (for example, whether there is a lot of external noise or not). As a result, the communication channels with good communication quality and the communication channels with deteriorated communication quality are not fixed but may change from moment to moment. Therefore, it is required that when the communication quality deteriorates, the corresponding communication channel is deleted from the multiple communication channels used for wireless communication, and when the communication quality recovers, the corresponding communication channel is restored as one of the multiple communication channels used for wireless communication.

[0044] In the wireless communication system 10 of the present embodiment, a control process for realizing wireless communication between the master device 20 and the slave device 30 using a communication channel with a certain communication quality, excluding a communication channel whose communication quality has been degraded by channel map control, as a plurality of communication channels used for wireless communication will be described with reference to a diagram showing a communication sequence between the master device 20 and the slave device 30 shown in Fig. 5. In Fig. 5, the master device 20 is shown as MASTER, and the slave device 30 is shown as SLAVE. Note that Fig. 5 shows a communication sequence executed between the master device 20 and one slave device 30. When a plurality of slave devices 30 are provided, the master device 20 individually executes the communication sequence shown in Fig. 5 with the plurality of slave devices 30.

[0045] 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 from when the master device 20 and the slave device 30 start up until data communication is performed. For example, when the wireless communication system 10 is mounted on a vehicle, the startup sequence is started when the IG signal is switched from off to on by a user operation, for example. Note that when the master device 20 and the slave device 30 are constantly connected, the startup sequence is executed only once at a predetermined timing. However, when 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.

[0046] When the start-up sequence is started, the master device 20 and the slave device 30 execute a start-up process including an initialization process for initializing various variables, timers, etc., in steps S10 and S110, respectively. After that, the master device 20 and the slave device 30 execute a connection establishment process in steps S20 and S120, respectively. When a plurality of 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 for transmitting an advertising signal via a communication channel for advertising, and the master device 20 executes a scanning operation for scanning the advertising signal. The communication channel for advertising includes a plurality of communication channels (for example, three in the case of Bluetooth LE). When the master device 20 receives an advertising signal on any of the communication channels by the scanning operation, it transmits a connection request to the slave device 30 that transmitted the advertising signal. As a result, a communication connection is established 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.

[0047] 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.

[0048] 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 selected in sequence from the multiple communication channels to be used for communication indicated by the channel map for each communication event that occurs periodically. The process for performing this data communication is shown in the communication sequence of FIG.

[0049] When the master device 20 and the slave device 30 determine to disconnect the communication connection in steps S60 and S160, respectively, they end the start-up sequence shown in Fig. 4. For example, when the wireless communication system 10 is mounted on 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 in succession.

[0050] Next, a 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 to the slave device 30 in step S210. However, the master device 20 can also transmit, for example, a request to execute a predetermined process in addition to the data request. When the slave device 30 receives the data request in step S410, in step S420, the slave device 30 performs, for example, a checksum determination based on the error detection code included in the received data request to confirm whether the data request has been correctly received. If the slave device 30 determines in the process of step S420 that the data request has not been correctly received based on the checksum determination result, for example, in step S430, it transmits a signal indicating that the data request has not been correctly received or a signal requesting retransmission of the data request. On the other hand, if the slave device 30 determines in the process of step S420 that the data request has been correctly received, it performs, for example, a predetermined process required for responding, such as a process of acquiring and transmitting the requested data, in step S430.

[0051] The master device 20 and the slave device 30 switch the data communication channel to be used for each communication event by frequency channel hopping to transmit and receive a data request or 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 the channel map that each device has. In the case of Bluetooth LE communication, 37 communication channels are prepared as data communication channels.

[0052] In step S220, the master device 20 receives the requested data. 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 has been received correctly. In the following step S240, if the master device 20 determines in the process of step S230 that the data has not been received correctly, or if the master device 20 receives a signal from the slave device 30 indicating that the data request has not been 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 retransmission before the end time of the current communication event, the master device 20 can decide to perform retransmission, and if there is no time, the master device 20 can decide not to perform retransmission. In step S240, if the master device 20 determines to perform retransmission, it executes the process from step S210 again. If it is determined in the process of step S230 that the data has been received correctly, or if it is determined in step S240 that retransmission is not to be performed, the master device 20 proceeds to the process of step S250.

[0053] In step S250, the master device 20 executes processing based on information included in the received data. If the processing in step S230 determines that the data has not been received correctly, or if a signal indicating that the data request has not been 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 previously received data.

[0054] In step S260, the master device 20 detects communication quality data indicating communication quality, such as received signal strength indicator (RSSI) and packet error rate (PER), as characteristic data indicating communication quality of the signal received from the slave device 30. RSSI is an index indicating the strength of the signal transmitted from the slave device 30 and received by the master device 20. PER indicates the ratio of the number of error packets to the number of packets received by the master device 20, expressed as a percentage. The master device 20 may detect a signal-to-noise ratio (SNR) / signal-to-interference-to-noise ratio (SINR) instead of RSSI. For example, the SNR / SINR can be detected 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. The master device 20 may also detect a bit error rate (BER) or a packet arrival rate (PAR) instead of PER. The master device 20 saves and accumulates the detected RSSI or SNR / SINR, PER, BER, or PAR for each communication channel. In addition to or instead of the master device 20 detecting the communication quality data as described above, the slave device 30 can also obtain the communication quality data by detecting the RSSI, PER, etc. when receiving a signal from the master device 20 and transmitting the same to the master device 20.

[0055] In step S270, the master device 20 determines the degradation of 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. Then, the master device 20 deletes the communication channel whose communication quality is determined to be 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 communication channel for data. For example, an example of a condition for determining the degradation of communication quality is that at least one of the RSSI and the PER does not satisfy the threshold value as a result of comparing the RSSI with the threshold value for RSSI and comparing the PER with the threshold value for PER. The parameter to be compared with the threshold value may be one type. The parameter to be compared with the threshold value may be the parameter detected immediately before in step S260, or may be an average value of a predetermined number of parameters detected in multiple past wireless communications related to the same communication channel, or a median value thereof.

[0056] In step S280, the master device 20 executes a restoration determination of the communication channel deleted by the deletion determination at the time of the previous communication event. In this restoration determination, if a predetermined restoration condition is satisfied, 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 in response to a predetermined time having 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 in response to a communication channel adjacent to the deleted communication channel exhibiting good communication quality. In this way, the communication channel determined to be capable of restoration as a communication channel to be used for wireless communication is incorporated into the channel map and is actually used for wireless communication between the master device 20 and the 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 the communication channel determined to be restored may again be subject to deletion by the deletion determination if the communication quality remains deteriorated when actually used for wireless communication.

[0057] In step S290, the master device 20 performs a channel map creation process based on the deletion determination result in step S270 and the return determination result in step S280.

[0058] The channel map may indicate communication channels available 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 the channel map, the frequency channel hopping pattern may be updated. When the frequency channel hopping pattern is not updated, for example, when the communication channel to be hopped is unavailable, the communication channel to be hopped next may be used.

[0059] In step S300, master device 20 executes a channel map update period setting process, which will be described in detail later.

[0060] 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.

[0061] The above-mentioned deletion determination process and return determination process may be performed every time communication is performed between the master device 20 and the slave device 30. Alternatively, the deletion determination process and return determination process may be performed collectively every time communication is performed between the master device 20 and the slave device 30 in accordance with a channel map update period described later. In this case, every 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 in the communication is detected and accumulated in step S260. Then, based on the accumulated characteristic data, the deletion determination in step S270 and the return determination in step S280 are performed collectively. Similarly, the channel map creation process in step S290 may also be performed every time communication is performed between the master device 20 and the slave device 30. Alternatively, the channel map creation process may be performed every time communication is performed between the master device 20 and the slave device 30 in accordance with a channel map update period described later.

[0062] 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 setting process is set (changed) depending on the communication state of wireless communication between the master device 20 and the slave device 30.

[0063] 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 state of wireless communication with the slave device 30. For example, the master device 20 acquires the overall PER by calculating an average or median value of the PERs of a predetermined number of recent wireless communications, including the latest wireless communication with the slave device 30. At this time, the individual PERs used to calculate the average or median value are obtained in wireless communication via multiple different communication channels. The master device 20 may use a BER or a PAR as an index indicating the communication state of wireless communication with the slave device 30.

[0064] In step S520, the master device 20 compares the acquired total PER with a first threshold (communication error rate threshold) to identify 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. In other words, if the acquired total PER is less than the first threshold, the communication error rate is relatively low, so the communication state can be considered to be 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 total PER is equal to or greater than the first threshold, the communication error rate is relatively high, so the communication state can be considered to be 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.

[0065] In step S550, the master device 20 judges whether the communication state is a normal communication state or an abnormal communication state based on the identification result of the communication state of the wireless communication between the master device 20 and the slave device 30. If it is judged to be a normal communication state, the master device 20 proceeds to step S560 and sets the channel map update period to X. On the other hand, if it is judged to be an abnormal communication state, 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 is established. That is, the master device 20 makes the channel map update period Y when the total PER is equal to or greater than the first threshold shorter than the channel map update period X when the total PER is less than the first threshold. At this time, in order to prevent the update period from becoming too short, it is preferable that the master device 20 makes the channel map update period Y shorter than the channel map update period X within a range 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 for master device 20 to set channel map update period X to be longer than channel map update period Y, provided that the update period X is equal to or less than a preset maximum period.

[0066] Next, the above-mentioned channel map sharing process will be described with reference to the flowchart in Fig. 7 and the time charts in Figs. 8 and 9. The flowchart in Fig. 7 shows an example of the channel map sharing process. Fig. 8 is a time chart showing an operation example of the channel map sharing process when the channel map update cycle is set to X cycles. Fig. 9 is a time chart showing an operation example of the channel map sharing process when the channel map update cycle is switched from X cycles to Y cycles.

[0067] For example, as shown in the time chart of Fig. 8, a sharing process of a new channel map is started during the application period of the current channel map. That is, the new channel map is created by a channel map creation process based on a plurality of communication quality data detected before the application period of the current channel map (start of sharing of the new channel map), and is determined as the new channel map before the application period of the current channel map. More specifically, the next new channel map is determined before the application period of the new channel map based on communication quality data detected from the communication between the master device 20 and the slave device 30 during the application period of the current channel map.

[0068] The channel map sharing process in the flow chart of FIG. 7 is for sharing a new channel map between the master device 20 and the slave device 30 at each channel map update period X or update period Y, as shown in the time charts of FIGS. 8 and 9. In the first step S610, the master device 20 transmits to the slave device 30 a new channel map that has been determined before the sharing of the new channel map starts. At this time, the master device 20 transmits information indicating the timing to start using the new channel map together with the new channel map. The timing to start using the new channel map comes every time a channel map update period elapses, as shown in the example of the time charts of FIGS. 8 and 9. 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 of FIG. 6. The timing to start using the channel map is also determined before the sharing of the new channel map starts, like the new channel map. Note that, as shown in the time chart of FIG. 8, if the sharing of the new channel map is successful, the new channel map and timing information do not need to be transmitted in the subsequent communication event. 8 and 9, a cross mark indicates a failure in sharing the channel map, and a circle mark indicates a success in sharing the channel map.

[0069] In step S710, the slave device 30 receives the new channel map and timing information transmitted from the master device 20. When the slave device 30 receives the new channel map and timing information in step S710, in step S720, 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 have been correctly received. If the slave device 30 determines in step S720 based on the checksum check result that the new channel map and timing information have not been correctly received, for example, in step S730, it does not transmit an acknowledgement signal (Ack signal) for the new channel map. On the other hand, if the slave device 30 determines in step S720 that the new channel map and timing information have been correctly received, it returns an acknowledgement signal (Ack signal) for the new channel map to the master device 20 in step S730.

[0070] In step S620, the master device 20 receives an 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 check whether the Ack signal has been 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 are 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.

[0071] In step S650, the master device 20 has correctly received the Ack signal and therefore determines that the sharing of the channel map has been successful. Meanwhile, in step S660, the master device 20 determines whether or not to execute processing for retransmission within the same communication event since the Ack signal was not correctly received. If the master device 20 determines to perform retransmission in step S660, it executes the processing from step S610 again. If it determines not to perform retransmission in step S660, the master device 20 proceeds to step S670.

[0072] 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 corresponding 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.

[0073] 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 judges whether the sharing of the channel map was successful during the expired update period. That is, if it is determined in step S650 that the sharing of the channel map was successful, the master device 20 judges in step S690 that the sharing was successful. Conversely, if it is determined in step S650 that the sharing of the channel map was not successful, the master device 20 judges in step S690 that the sharing was unsuccessful. If it is determined that the sharing was successful, the master device 20 proceeds to step S700. If it is determined that the sharing was unsuccessful, the master device 20 ends 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.

[0074] As described above, when it is determined in step S690 that the sharing of the channel map has failed, the master device 20 ends the channel map sharing process shown in FIG. 7 without switching the channel map. Therefore, in this case, in the next update period, the channel map is not switched, and the channel map used in the previous update period continues to be used. When it is determined that the sharing of the channel map has failed, it is because there is a high possibility 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 period, but the master device 20 was not able to normally receive the Ack signal for confirming the reception. Therefore, regardless of whether the sharing of the channel map has succeeded or failed, the master device 20 may switch the channel map. Then, regardless of whether the channel map has been switched, the channel map to be used in the next update period, in other words, the channel map to be shared, is updated to a new channel map in step S680 each time the update period expires.

[0075] Note that 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, but is unable to establish any wireless communication with the slave device 30 over, for example, a predetermined number of update cycles, the master device 20 and the slave device 30 may disconnect their communication connection.

[0076] When the master device 20 and the slave device 30 disconnect the communication connection, the master device 20 and the slave device 30 start the above-mentioned startup sequence of Fig. 4 in order to reconnect 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.

[0077] In this embodiment, as shown in the time charts of Figures 8 and 9, in principle, the channel map shared by the master device 20 and the slave device 30 is updated 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 the application period of the channel map and also the channel map update period. In this way, by periodically updating the channel map, the master device 20 and the slave device 30 can perform high-quality communication using a channel map adapted to changes in the communication quality of each communication channel.

[0078] In particular, in the wireless communication system 10 according to the present embodiment, the channel map update period is changed according to the communication state of wireless communication between the master device 20 and the slave device 30. If the channel map update period is constant, there is a possibility that the channel map cannot be updated at a period suitable for the communication environment at that time. For example, even if the communication environment is relatively good, the number of times the channel map is transmitted during the period from after the channel map is updated until before the next channel map is updated may not be sufficient, and therefore sharing of the channel map may fail. On the other hand, when the communication environment that was good deteriorates, it cannot be said that the possibility of successful sharing of the channel map can be increased even if the number of times the channel map is transmitted is large due to the influence of noise, etc.

[0079] Therefore, in the wireless communication system 10 according to the present embodiment, when the communication state is good, the channel map update period X is made longer than when the communication state is deteriorated, 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 deteriorates, the channel map update period Y is made shorter than when the communication state is good, as shown in the time chart of Fig. 9. This allows the sharing of a channel map suitable for the deteriorated communication environment to be accelerated.

[0080] 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 the present embodiment is configured similarly to the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0081] In the wireless communication system 10 according to the first embodiment described above, the master device 20 judges whether the communication state 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 judges whether the communication state 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 way, the communication state of the wireless communication between the master device 20 and the slave device 30 can also be judged 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 state of the wireless communication between the master device 20 and the slave device 30. As a result, the upper control device 1 can decide to use information transmitted or received by the wireless communication between the master device 20 and the slave device 30 when the communication state is normal. On the other hand, if the communication state 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.

[0082] The following describes the wireless communication system 10 according to the present embodiment, focusing on differences from the wireless communication system 10 according to the first embodiment. The wireless communication system 10 according to the present embodiment and the wireless communication system 10 according to the first embodiment differ mainly in the channel map update period setting process.

[0083] 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 for each communication event with the slave device 30. In step S820, the master device 20 compares the acquired number of consecutive communication failures with a second threshold. In this comparison, if 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 state 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 state is abnormal.

[0084] In step S850, the master device 20 notifies the upper control device 1 of the communication state 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 state is normal or abnormal. The subsequent processing of 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 a description thereof will be omitted.

[0085] 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 the present embodiment is configured similarly to the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0086] In the wireless communication system 10 according to the first embodiment described above, the master unit 20 judges 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 by wireless communication between the master unit 20 and the slave unit 30, judges 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 of the update period of the channel map according to the judgment result. That is, in the present embodiment, the higher-level control device 1 is configured to give an external instruction to the master unit 20 to change the update period of the channel map.

[0087] The following describes the wireless communication system 10 according to the present embodiment, focusing on differences from the wireless communication system 10 according to the first embodiment. The wireless communication system 10 according to the present embodiment and the wireless communication system 10 according to the first embodiment differ mainly in the channel map update period setting process.

[0088] 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.

[0089] In the first step S910 of Fig. 11, the master device 20 acquires the number of consecutive communication failures in wireless communication for each communication event with the slave device 30. In step S920, the master device 20 compares the acquired number of consecutive communication failures with a third threshold (≦second threshold). In this comparison, if the number of consecutive communication failures is less than the third threshold, the master device 20 proceeds to step S930 and determines that the communication state is normal. On the other hand, if the number of consecutive communication failures is equal to or greater than the third threshold, the master device 20 proceeds to step S940 and determines that the communication state is abnormal.

[0090] 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 update period of the channel map. 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 update period of the channel map 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 update period of the channel map to Y.

[0091] Next, the process shown in the flowchart of FIG. 12 executed by the upper control device 1 will be described. In the first step S1010, the upper control device 1 receives the communication state 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 judges the communication state of the wireless communication system 10 based on the received result of the decision. In this judgment, if the communication state of the wireless communication system 10 is judged to be normal, the upper control device 1 proceeds to step S1030, stops the measurement of the timer, and resets the timer value. On the other hand, if the communication state of the wireless communication system 10 is judged to be abnormal, the upper control device 1 proceeds to step S1040, and starts or continues the measurement of the timer, thereby performing the timer measurement. That is, the timer measures the elapsed time since the communication state of the wireless communication system 10 became abnormal (communication interruption state).

[0092] In step S1050, the upper control device 1 compares the timer value with a fourth threshold value. In this comparison, if the timer value is less than the fourth threshold value, 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 value, 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. In the above example, it has been described that the upper control device 1 determines whether the vehicle system is normal or abnormal. However, such determination is based on the elapsed time since the wireless communication system became abnormal (communication interruption state), so it can also be considered that the upper control device 1 determines whether the communication state of the wireless communication system 10 is normal or abnormal on behalf of the master device 20.

[0093] In step S1080, the higher level control device 1 transmits, as an external instruction to change the update period of the channel map, status information of the vehicle system to the master device 20 of the wireless communication system 10. The transmitted status information of the vehicle system is the status of the vehicle system as a result determined in step S1060 or S1070.

[0094] 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.

[0095] (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 is configured similarly to the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0096] In the wireless communication system 10 according to the third embodiment described above, the upper control device 1 provides an external command to the master device 20 of the wireless communication system 10 to change the update period of the channel map based on the communication 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 some abnormality (e.g., CPU abnormality, sensor abnormality, 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 provides an external command to the master device 20 of the wireless communication system 10 to shorten the update period of the channel map. This makes it possible to reduce the possibility of an abnormality occurring in wireless communication and to prevent the abnormality in wireless communication from worsening the abnormality occurring in the vehicle system.

[0097] The wireless communication system 10 according to this embodiment will be described below, focusing on the differences from the wireless communication system 10 according to the third embodiment. In this embodiment, similar to the third embodiment, the upper control device 1 gives 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 gives an external instruction to the master device 20 to change the update period of the channel map is different from that of the third embodiment.

[0098] 13 is a flow chart showing an example of a process in which the higher-level 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 when some abnormality occurs in the vehicle system to be controlled. In the first step S1110, the higher-level control device 1 diagnoses whether or not some abnormality (e.g., CPU abnormality, sensor abnormality, 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 higher-level control device 1 and is provided separately from the higher-level control device 1.

[0099] In step S1120, the upper control device 1 judges whether the state of the vehicle system is normal or abnormal based on the diagnosis result performed in step S1110. If the upper control device 1 judges that the vehicle system is normal, the process proceeds to step S1130 and determines that the vehicle system is normal. On the other hand, if the upper control device 1 judges that the vehicle system is abnormal, the process proceeds to step S1140 and determines that the vehicle system is abnormal. Then, in step S1150, the upper control device 1 transmits status information of the vehicle system to the master device 20 of the wireless communication system 10 as an external instruction to change the update period of the channel map. The transmitted status information of the vehicle system is the status of the vehicle system as a result determined in step S1130 or S1140.

[0100] The master unit 20 sets the channel map update period in accordance with the received vehicle system status. 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.

[0101] 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 is configured similarly to the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0102] In the wireless communication system 10 according to the fourth embodiment described above, when some abnormality occurs in the vehicle system controlled by the upper control device 1, the upper control device 1 gives 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, when a communication abnormality occurs in the other vehicle systems 2, 3, 4 or when the other vehicle systems 2, 3, 4 enter an operating state indicating an abnormal state of the vehicle (for example, a state in which the possibility of a vehicle collision is increased), the upper control device 1 gives an external instruction to the master device 20 of the wireless communication system 10 to shorten the update period of the channel map.

[0103] For example, when the other vehicle systems are navigation systems or ETC systems that communicate with the outside, if a communication abnormality occurs in the vehicle systems, the vehicle is exposed to a noisy environment, and it is considered that a communication error is likely to occur in the wireless communication system 10 as well. Therefore, when a communication abnormality occurs in the other vehicle systems, it is preferable to shorten the update period of the channel map to reduce the possibility of a wireless communication abnormality occurring in the wireless communication system 10. Also, for example, when the other vehicle systems are airbag systems that are activated when a vehicle collision accident is about to occur, or collision mitigation systems that are activated when a collision possibility occurs, when the vehicle systems are activated, the vehicle is likely to be in a critical situation with a high probability of collision. In such a situation, particularly when the control target of the upper control device 1 is a battery management system, it is important for the upper control device 1 to reliably obtain battery status information via the wireless communication system 10. For example, when a vehicle collision actually occurs, the upper control device 1 can determine whether the battery is damaged or not from the battery status information. If there is a possibility that the battery is damaged, the upper control device 1 can take measures such as cutting off the relay. Therefore, when it is 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 wireless communication abnormalities occurring in the wireless communication system 10 by shortening the channel map update period.

[0104] 14 is a flowchart showing an example of a process in which, when some abnormality occurs in the host control device 1, such as a communication abnormality in the other vehicle systems 2, 3, 4 or operation in a critical vehicle situation, the host control device 1 receives an external instruction from the other vehicle systems 2, 3, 4 to shorten the update period of the channel map, and provides the 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 or operation from the other vehicle systems 2, 3, 4.

[0105] In step S1220, the higher-level control device 1 judges whether or not the other vehicle systems 2, 3, and 4 have an abnormality, which may indicate that there is a high possibility that the other vehicle systems have a communication abnormality 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 other vehicle systems 2, 3, and 4 are determined to be normal in this judgment, the higher-level 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 other vehicle systems 2, 3, and 4 are determined to be abnormal, the higher-level control device 1 proceeds to step S1240 and determines that the other vehicle systems 2, 3, and 4 are abnormal. Then, in step S1250, the higher-level 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 update period of the channel map. The status information of the other vehicle systems 2, 3, 4 that is transmitted is the status of the other vehicle systems 2, 3, 4 that is the result of the determination in step S1230 or S1240.

[0106] The master device 20 sets the channel map update period in accordance with the received states of the other vehicle systems 2, 3, 4. Setting of the channel map update period in accordance with the states of the other vehicle systems 2, 3, 4 can be performed by the same processes as steps S970, S980, and S990 in the channel map update period setting process in FIG.

[0107] Although the above describes preferred embodiments of the present disclosure, the present disclosure is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure.

[0108] For example, in each of the above-described embodiments, an example has been described in which one master device 20 wirelessly communicates with one slave device 30. However, a plurality of slave devices 30 may be provided. When a plurality of slave devices 30 are 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 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.

[0109] 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 response to the state of wireless communication between the master device 20 and the slave device 30 or an external instruction. However, the degree of the wireless communication state 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 response to an external instruction based on which type is present.

[0110] 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.

[0111] (Technical thought 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, 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 a result of the determination of the 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; the channel map shared by the master device and the slave device by the channel map sharing unit is periodically updated; a period change unit (S300) that changes the update period of the channel map shared by the master device and the slave device by the channel map sharing unit in response to a communication state of wireless communication between the master device and the slave device or an external instruction.

[0112] (Technical thought 2) The wireless communication system according to Technical Idea 1, wherein the period change unit changes the update period of the channel map depending on 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.

[0113] (Technical Thought 3) The wireless communication system according to Technical Idea 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.

[0114] (Technical Thought 4) The wireless communication system described in Technical Idea 2 or 3, 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, within a range that is equal to or greater than a predetermined minimum period.

[0115] (Technical Thought 5) A wireless communication system described in 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 not exceeding a predetermined maximum period.

[0116] (Technical Thought 6) a transmission unit (S730) for transmitting a reception confirmation 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; The wireless communication system described in any one of Technical Ideas 1 to 5 further includes 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 upon expiration of an update period of the channel map in response to receiving an acknowledgement signal for the channel map transmitted from the transmitting unit, and does not switch the channel map and continues to use the current channel map if an acknowledgement signal for the channel map cannot be received by the expiration of the update period of the channel map.

[0117] (Technical Thought 7) the channel map sharing unit transmits the channel map to be used in a next update cycle from the master device to the slave device during an update cycle of the channel map in which a current channel map is being used, A wireless communication system described in any one of technical ideas 1 to 6, wherein the channel map sharing unit transmits the channel map a predetermined number of times corresponding to the length of the update period of the channel map in which the current channel map is used.

[0118] (Technical Thought 8) The wireless communication system according to any one of technical ideas 1 to 5 further comprises 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.

[0119] (Technical Thought 9) The wireless communication system described in 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 occurring to the number of communications performed, the number of consecutive wireless communication failures, and the length of time that wireless communication is interrupted.

[0120] (Technical Thought 10) a notification unit (S950) that notifies a first control unit (1) of a communication state of wireless communication between the master device and the slave device, the first control unit (1) utilizing information transmitted or received through wireless communication between the master device and the slave device; a determination unit (S1020, S1030, S1040, S1050, S1060, S1070) provided in the first control unit for determining whether a communication state is a good normal communication state or a deteriorated abnormal communication state based on a communication state of wireless communication between the master device and the slave device, The wireless communication system described in technical idea 1, wherein the period change unit changes the update period of the channel map by the channel map sharing unit in accordance with the judgment result of the judgment unit, using the judgment result of the judgment unit as an instruction from the outside.

[0121] (Technical Thought 11) The wireless communication system described in Technical Idea 10, wherein the period change unit makes the update period of the channel map when the judgment unit judges that the communication state is abnormal shorter than the update period of the channel map when the judgment unit judges that the communication state is normal.

[0122] (Technical Thought 12) 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; The first control unit has a first abnormality determination unit (S1110) that determines whether or not an abnormality has occurred in the first system, The wireless communication system described in Technical Idea 1, wherein 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 accordance with the judgment result of the first abnormality judgment unit, using the judgment result of the first abnormality judgment unit as an instruction from the outside.

[0123] (Technical Thought 13) The wireless communication system described in Technical Idea 12, wherein the period change unit makes the update period of the channel map when the first abnormality judgment unit judges that an abnormality in the first system is present shorter than the update period of the channel map when the first abnormality judgment unit does not judge that an abnormality is present in the first system.

[0124] (Technical Thought 14) 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; The vehicle system (2) further includes a second control unit that controls the second system. 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 or not 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 an update period of the channel map based on a determination result by the second abnormality determination unit; The wireless communication system described in technical idea 1, wherein 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.

[0125] (Technical Thought 15) The wireless communication system described in Technical Idea 14, wherein the period change unit makes the update period of the channel map when the second abnormality judgment unit judges that an abnormality in the second system is present shorter than the update period of the channel map when the second abnormality judgment unit does not judge that an abnormality is present in the second system.

[0126] (Technical Thought 16) the second control unit controls the second system by using wireless communication different from wireless communication between the master device and the slave device, The wireless communication system described in Technical Idea 14 or 15, wherein the second control unit transmits an external instruction to the first control unit to shorten the update period of the channel map when a communication abnormality occurs in the other wireless communication.

[0127] (Technical Thought 17) the first system and the second system are mounted on a vehicle; The second control unit has a function of determining a possibility of a collision of the vehicle, The wireless communication system described in Technical Idea 14 or 15, wherein 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. [Explanation of symbols]

[0128] 10: wireless communication system, 20: master device, 21: control circuit, 22: wireless communication circuit, 23: antenna, 30: slave device, 31: control circuit, 32: wireless communication circuit, 33: antenna, 211: processor, 212: memory, 311: processor, 312: memory

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 sequentially selected from a plurality of communication channels, 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 a result of the determination of the 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; the channel map shared by the master device and the slave device by the channel map sharing unit is periodically updated; A wireless communication system comprising: a period change unit (S300) that changes the update period of the channel map shared by the master device and the slave device by the channel map sharing unit in response to the communication state of 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 is 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. 4. 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, within a range equal to or greater than a predetermined minimum period.

5. 4. The wireless communication system according to claim 2, 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 transmitting unit (S730) for transmitting a reception confirmation 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) that switches the channel map used for wireless communication with the slave device to the transmitted channel map upon expiration of an update period of the channel map in response to receiving an acknowledgement signal for the channel map transmitted from the transmission unit, and that does not switch the channel map and continues to use the current channel map if an acknowledgement signal for the channel map cannot be received by the expiration of the update period of the channel map.

7. the channel map sharing unit transmits the channel map to be used in a next update cycle from the master device to the slave device during an update cycle of the channel map in which the current channel map is being used, The wireless communication system according to claim 1 , wherein the channel map sharing unit transmits the channel map a predetermined number of times according to a length of an update period of the channel map in which the current channel map is used.

8. 4. The wireless communication system according to claim 1, further comprising an identification unit (S520, S530, S540, S820, S830, S840) that identifies, with respect to the communication state of wireless communication between the master device and the slave device, a normal communication state in which the communication state is good and an abnormal communication state in which the communication state has deteriorated.

9. 9. The wireless communication system according to claim 8, wherein the identification unit identifies whether a 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 a 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 notification unit (S950) that notifies a first control unit (1) that uses information transmitted or received through wireless communication between the master device and the slave device of a communication state of wireless communication between the master device and the slave device; a determination unit (S1020, S1030, S1040, S1050, S1060, S1070) provided in the first control unit and configured to determine whether a communication state is a good normal communication state or a deteriorated abnormal communication state based on a communication state of wireless communication between the master device and the slave device, The wireless communication system according to claim 1 , wherein the period changing unit changes the update period of the channel map by the channel map sharing unit in accordance with the determination result of the determination unit, using the determination result of the determination unit as the instruction from the outside.

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

12. 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, The first control unit has a first abnormality determination unit (S1110) that determines whether or not an abnormality has occurred in the first system, 2. The wireless communication system according to claim 1, wherein 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 accordance with the judgment result of the first abnormality judgment unit, using the judgment result of the first abnormality judgment unit as an instruction from the outside.

13. 13. The wireless communication system according to claim 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.

14. 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; and a vehicle system (2) having a second control unit that controls the second system. 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 or not 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 an update period of the channel map based on a determination result by the second abnormality determination unit; 2. The wireless communication system according to claim 1, wherein 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.

15. The wireless communication system according to claim 14, wherein the period change unit makes the channel map update period when the second abnormality determination unit determines that an abnormality has occurred in the second system shorter than the channel map update period when the second abnormality determination unit does not determine that an abnormality has occurred in the second system.

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

17. the first system and the second system are mounted on a vehicle; The second control unit has a function of determining a possibility of a collision of the vehicle, 16. The wireless communication system according to claim 14, wherein 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.

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 sequentially selected from a plurality of communication channels, comprising: When the master device wirelessly communicates with the slave device, a communication quality of each communication channel is determined, and a communication channel to be used for the wireless communication is determined based on a result of the determination of the communication quality of each communication channel (S270, S280, S290); A channel map indicating the determined communication channel is transmitted from the master device to the slave device, and the channel map is shared between the master device and the slave device (S310); the channel map shared by the master device and the slave device is periodically updated; changing an update period of the channel map shared by the master device and the slave device in response to a communication state of wireless communication between the master device and the slave device or an external instruction (S300).

19. A wireless communication program for performing wireless communication between at least one master device (20) and at least one slave device (30) via one communication channel sequentially selected from a plurality of communication channels, the program comprising: At least one processor, When the master device wirelessly communicates with the slave device, a communication quality of each communication channel is determined, and a communication channel to be used for the wireless communication is determined based on a result of the determination of the communication quality of each communication channel (S270, S280, S290); A channel map indicating the determined communication channel is transmitted from the master device to the slave device, and the channel map is shared between the master device and the slave device (S310); the channel map shared by the master device and the slave device is periodically updated; A wireless communication program that executes a wireless communication program, the wireless communication program executing the program, and changing (S300) the update period of the channel map shared by the master device and the slave device in response to a communication state of wireless communication between the master device and the slave device or an external instruction.

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