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

Abstract

To suppress deterioration of a communication reliability, while executing a channel map control.SOLUTION: In the case where a reception confirmation signal from a slave 30 cannot be normally received even if a channel map is transmitted to a slave device 30 from a master device 20, and it is not determined that a sharing of the channel map can be made, a transmission of the channel map is repeated by the master device 20. However, in the case where it is not determined that the sharing of the channel map has been made even once even if the number of transmissions of the channel map is reached to a first predetermined number, the master device 20 disconnects a communication connection with the slave device 30 at a predetermined timing. Thus, a continuous communication error occurs due to a difference between the master device 20 and the slave device 30 in the channel map, and the generation of an event that a communication reliability is deteriorated can be suppressed.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a wireless communication system, a wireless communication method, and a wireless communication program in which a master device performs wireless communication with a slave device via one communication channel that is 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). If the frequency of reception errors exceeds a threshold Th2, the wireless communication device determines that an interference source exists in the frequency channel where the frequency of reception errors 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, in the wireless communication system of Patent Document 1, a frequency channel whose communication quality has deteriorated due to interference with other radio waves is designated as an unavailable channel. In addition, in the wireless communication system of Patent Document 1, the frequency channel designated as an unavailable channel is returned to an available frequency channel after a set period has elapsed. Such control of setting a frequency channel as an unavailable channel or returning it to an available channel is hereinafter referred to as channel map control in this specification.

[0005] Here, the master device and the slave devices constituting the wireless communication system need to have a common channel map. By having the common channel map, the master device and the slave device can sequentially select the same communication channel. Note that the channel map indicates multiple communication channels that can be used in wireless communication between the master device and the slave device.

[0006] When the communication channel used for wireless communication is changed by the above-mentioned channel map control, the channel map is also updated. Therefore, the updated channel map needs to be shared between the master device and the slave device together with information indicating the timing to start using the channel map. For this reason, for example, it is conceivable that the master device transmits information indicating the updated channel map and the timing to start using the channel map to the slave device in response to the channel map being updated. However, if the transmission from the master device and / or the reception by the slave device of the updated channel map and the timing to start using the channel map are not performed normally, there is a risk that the channel maps of the master device and the slave device will not match. If the channel maps do not match, the communication channels used for communication will differ, which may cause continuous communication errors and reduce communication reliability.

[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 are capable of suppressing a decrease in communication reliability while performing channel map control. [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 a master device (20) performs wireless communication with a slave device (30) via one communication channel sequentially selected from a plurality of communication channels, a quality determination unit (S270, S280) for determining the communication quality of each communication channel when the master device wirelessly communicates with the slave device; a communication channel determination unit (S290) that determines a communication channel to be used for wireless communication based on a result of the communication quality determination unit of each communication channel; a channel map sharing unit (S520) that causes the master device to transmit a channel map indicating the communication channel determined by the communication channel determination unit to the slave device, and causes the master device and the slave device to share the channel map; a sharing determination unit (S540, S550) that determines whether the channel map has been shared between the master device and the slave device based on a reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map; a communication disconnection unit (S620, S246) for disconnecting a communication connection with the slave device in the master device; the channel map sharing unit repeats transmission of the channel map when the sharing determination unit does not determine that the channel map has been shared even though the channel map has been transmitted; The communication disconnection unit is configured to disconnect the communication connection with the slave device at a predetermined timing based on the fact that the sharing determination unit has never determined that the channel map has been shared even though the number of times the channel map sharing unit has transmitted the channel map has reached a first predetermined number of times.

[0009] A wireless communication method according to the present disclosure is a wireless communication method in which a master device (20) performs wireless communication with a slave device (30) via one communication channel sequentially selected from a plurality of communication channels, the method comprising: a quality determination step (S270, S280) of determining the communication quality of each communication channel when the master device wirelessly communicates with the slave device; a communication channel determination step (S290) of determining a communication channel to be used for wireless communication based on a result of the communication quality determination step of each communication channel; a channel map sharing step (S520) of transmitting a channel map indicating the communication channel determined in the communication channel determination step from the master device to the slave device and sharing the channel map between the master device and the slave device; a sharing determination step (S540, S550) of determining whether or not the channel map has been shared between the master device and the slave device based on a reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map; a communication disconnection step (S620, S246) for disconnecting the communication connection between the master device and the slave device, In the channel map sharing step, if it is not determined in the sharing determination step that the channel map has been shared even though the channel map has been transmitted, transmission of the channel map is repeated; The communication disconnection step is configured to disconnect the communication connection with the slave device at a predetermined timing based on the fact that, in the channel map sharing step, the number of times the channel map has been transmitted reaches a first predetermined number of times, but in the sharing determination step, it is not determined that the channel map has ever been shared.

[0010] A wireless communication program according to the present disclosure is a wireless communication program executed by at least one processor, for causing a master device (20) to perform wireless communication with a slave device (30) via one communication channel sequentially selected from a plurality of communication channels, the program comprising: When the wireless communication program is executed, the wireless communication program causes at least one processor to A quality determination function (S270, S280) for determining the communication quality of each communication channel when the master device wirelessly communicates with the slave device; a communication channel determination function (S290) for determining a communication channel to be used for wireless communication based on a result of the communication quality determination function of each communication channel; a channel map sharing function (S520) for causing the master device to transmit a channel map indicating the communication channel determined by the communication channel determination function to the slave device, and for causing the master device and the slave device to share the channel map; a sharing determination function (S540, S550) that determines whether the channel map is shared between the master device and the slave device based on a reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map; A communication disconnection function (S620, S246) for disconnecting the communication connection with the slave device is realized in the master device; If the sharing determination function does not determine that the channel map has been shared even though the channel map has been transmitted by the channel map sharing function, the transmission of the channel map is repeated. The communication disconnection function is configured to disconnect the communication connection with the slave device at a predetermined timing based on the fact that the sharing determination function has never determined that the channel map has been shared even though the number of times the channel map has been transmitted by the channel map sharing function has reached a first predetermined number of times.

[0011] As described above, in the wireless communication system, wireless communication method, and wireless communication program according to the present disclosure, if it is not determined that the channel map has been shared despite the channel map being transmitted, the channel map is repeatedly transmitted. This increases the possibility that the master device and the slave device can share the channel map. However, if it is not determined that the channel map has been shared even once despite the number of times the channel map has been transmitted reaching a first predetermined number of times, the communication connection with the slave device is disconnected at a predetermined timing. This makes it possible to prevent the occurrence of a situation in which communication errors occur continuously due to differences in the channel maps between the master device and the slave device, resulting in a decrease in communication reliability.

[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 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] 5 is a flowchart showing an example of a connection sequence between a master device and a slave device according to the first embodiment. [Diagram 5] 5 is a flowchart showing an example of a communication sequence between a master device and a slave device according to the first embodiment. [Figure 6] 11 is a flowchart showing an example of a channel map sharing process according to the first embodiment. [Figure 7] 5 is a time chart for explaining an example of control by a channel map sharing process according to the first embodiment. [Figure 8] 13 is a flowchart showing an example of a channel map sharing process according to the second embodiment. [Figure 9] 10 is a time chart for explaining an example of control by a channel map sharing process according to the second embodiment. [Figure 10] 10 is a flowchart showing an example of a communication sequence between a master device and a slave device according to the second embodiment. [Figure 11]10 is a flowchart showing an example of a communication sequence between a master device and a slave device according to 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 of 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 can be mounted on a moving object for use. The moving object includes, 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] As a specific application in a vehicle, the wireless communication system 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, a hybrid vehicle, a plug-in hybrid vehicle, or other electric vehicle. When applied to the battery management system, for example, a master device is connected to a battery control device, and multiple slave devices are connected to monitoring devices provided in multiple battery stacks that constitute the battery pack. In this case, both the master device and the multiple slave devices are mounted in the vehicle.

[0018] Each monitoring device provided for each of the battery stacks 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 each monitoring device receives data requesting battery information from the battery control device via the wireless communication system, it transmits the acquired battery information to the battery control device via the wireless communication system. Based on the acquired battery information, the battery control device 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 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. Also, each 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 via the wireless communication system.

[0019] Alternatively, the wireless communication system according to the present embodiment may be applied to a so-called smart key system or tire pressure monitoring system in a vehicle. When applied to a smart key system, for example, the master device is mounted on the vehicle and connected to a control device that controls locking and unlocking of the vehicle doors and turning on and off of a driving source such as the vehicle engine. At least one slave device 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 is mounted on the vehicle and connected to a control device that displays the tire pressure and issues a warning when the tire pressure is abnormal. The multiple slave devices are provided in each tire and connected to an air pressure detection device also provided in each tire.

[0020] Furthermore, the wireless communication system according to the present embodiment may be applied to a vehicle diagnostic system. In this case, for example, a plurality of slave devices are connected to a plurality of vehicle-mounted devices having a self-diagnosis function, and the master device is connected to a diagnostic control device installed in a service factory. In these examples, at least one of the master device and the plurality of slave devices 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 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 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] FIG. 1 is a block diagram showing a schematic configuration of a wireless communication system 10. Both a master device 20 and a slave device 30 of the wireless communication system 10 are mounted on, for example, a vehicle (automobile). In this case, the master device 20 and the slave device 30 may be configured to be arranged in a common housing, 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, or 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 in sequence from multiple communication channels, such as Bluetooth Low Energy (Bluetooth is a registered trademark, hereinafter referred to as Bluetooth LE) communication.

[0023] As an example, the wireless communication system 10 of the present embodiment includes one master device 20 and multiple slave devices 30. Although only one slave device 30 is shown in Fig. 1 for the sake of simplicity, all of the multiple slave devices 30 may be configured in the same manner.

[0024] 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.

[0025] 1, the master device 20 includes a control circuit (CNT) 21, a wireless communication circuit (WC) 22, and an antenna 23. In addition to the above elements, the master device 20 includes 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, 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 provided outside the master device 20.

[0026] The control circuit 21 is, for example, a computer including a processor 211 and a memory 212. The memory 212 includes, for example, a RAM and a ROM. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory.

[0027] In the control circuit 21, the processor 211 executes a 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.

[0028] The processor 211 is, for example, a CPU, an MPU, a GPU, or a DFP. CPU is an abbreviation for Central Processing Unit. MPU is an abbreviation for Micro-Processing Unit. GPU is an abbreviation for Graphics Processing Unit. DFP is an abbreviation for Data Flow Processor. The control circuit 21 may be realized by combining 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.

[0029] 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.

[0030] The wireless communication circuit 22 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. The wireless communication circuit 22 has a transmission function of modulating a transmission signal and oscillating at the frequency of an RF signal. The wireless communication circuit 22 has a reception function of demodulating a reception signal. RF is an abbreviation for radio frequency.

[0031] The wireless communication circuit 22 modulates 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 necessary for wireless communication such as communication control information to the transmission packet and transmits it. The data necessary for wireless communication includes, for example, an identifier (ID), a sequence number, a next sequence number, an error detection code, 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.

[0032] The wireless communication circuit 22 receives the packets transmitted from the slave device 30 via the antenna 23 and demodulates them. Then, it transmits the demodulated packets to the control circuit 21. The antenna 23 converts the electrical signals into radio waves and radiates them into space. The antenna 23 receives the radio waves propagating through space and converts them into electrical signals.

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

[0034] 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, in response to the request, transmits data encrypted using the encryption information including the processing result (for example, the acquired battery information) to the wireless communication circuit 32. The control circuit 31 can also execute control of equipment mounted on a vehicle, for example, in accordance with the requested processing.

[0035] The wireless communication circuit 32 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. 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.

[0036] 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.

[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. Fig. 5 also shows a communication sequence executed between the master device 20 and one slave device 30. 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 a connection sequence including a connection establishment process from when the master device 20 and the slave device 30 are started up to when data communication is performed. For example, when the wireless communication system 10 is mounted on a vehicle, the connection 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 connection 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 connection sequence may be executed to reconnect.

[0046] When the connection sequence is started, the master device 20 and the slave device 30 execute an initialization process to initialize 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 to be connected to the master device 20 in wireless communication, this connection establishment process is executed between the master device 20 and all of the slave devices 30. In the connection establishment process, for example, the slave device 30 executes an advertising operation to transmit an advertising signal via a communication channel for advertising, and the master device 20 executes a scanning operation to scan 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, a 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 execute data communication via a data communication channel selected in sequence from the multiple communication channels for each communication event that occurs periodically. The process for performing this data communication is shown in the communication sequence of Fig. 5. When multiple slave devices 30 are provided, the master device 20 communicates with the multiple slave devices 30 in sequence by allocating communication periods (sub-events) to each of the multiple slave devices 30 in each communication event.

[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 connection 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. In addition, 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 (corresponding to a third predetermined number in the claims) in succession. Furthermore, in this embodiment, as described later, when the master device 20 determines that a new channel map cannot be shared with the slave device 30 during a channel map update period (channel map update cycle), the master device 20 determines to disconnect the communication connection.

[0050] Next, the communication sequence of data communication will be described with reference to the flowchart of FIG. 5. As shown in FIG. 5, the master device 20 transmits, for example, a data request command 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 S310, in step S320, it 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 S320 that the data request has not been correctly received based on the checksum determination result, for example, in step S330, 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 S320 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 S330.

[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 (sub-event), the master device 20 can decide to perform retransmission, and if there is not enough 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 a received signal strength indicator (RSSI) and a packet error rate (PER) as characteristic data indicating the communication quality of the signal received from the slave device 30. The RSSI is an index indicating the strength of the signal transmitted from the slave device 30 and received by the master device 20. The PER 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 the 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 the 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 characteristics data indicating the communication quality as described above, the slave device 30 can also obtain the characteristics data by detecting the RSSI, PER, etc. when receiving a signal from the master device 20 and transmitting them 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 characteristic data indicating the communication quality 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 a threshold value for RSSI and comparing the PER with a 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 regarding 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. In this embodiment, individual channel maps are created for the multiple slave devices 30. However, it is also possible to create a common channel map for the multiple slave devices 30. When creating a common channel map, an AND operation is performed on the communication channels included in the channel maps of the slave devices 30, and multiple communication channels that are common to all of the channel maps are extracted.

[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. 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, 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 be described in detail later.

[0060] Here, the deletion determination process and the return determination process described above may be performed every time communication is performed between the master device 20 and the slave device 30. Alternatively, the deletion determination process and the 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.

[0061] Next, the above-mentioned channel map sharing process will be described with reference to the flowchart of Fig. 6. The flowchart of Fig. 6 shows an example of the channel map sharing process.

[0062] In this embodiment, as shown in the time chart of FIG. 7, the channel map shared by the master device 20 and the slave device 30 is updated every multiple communication events (six communication events in the example shown in the figure). That is, the period of multiple communication events is the application period of the channel map and also the channel map update period. By periodically updating the channel map in this way, the master device 20 and the slave device 30 can perform high-quality communication using a channel map adapted to changes in the communication quality of each communication channel. However, the channel map may be updated irregularly, for example, on the condition that the channel map has been updated. That is, the channel map may be updated on the condition that a change has occurred in the communication channel included in the channel map as a result of the deletion determination process and the return determination process. Note that, as shown in FIG. 7, in each communication event, the master device 20 is configured to perform one communication in the sub-event assigned to each slave device 30.

[0063] As shown in the time chart of Fig. 7, 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 characteristic data indicating communication qualities detected before the application period of the current channel map, and is determined as the new channel map. More specifically, the next new channel map is created based on a plurality of characteristic data indicating communication qualities detected from the communication between the master device 20 and the slave device 30 during the application period of the current channel map, and is determined as the next new channel map before the application period of the new channel map.

[0064] The channel map sharing process in the flowchart of Fig. 6 is for sharing a new channel map between the master device 20 and the slave device 30 for each channel map update period shown in the time chart of Fig. 7. In the first step S510, the master device 20 determines whether the value of the map sharing counter is zero, which indicates that the channel map has been successfully shared between the master device 20 and the slave device 30. Note that the map sharing counter is initially set to a value other than zero when the channel map update period begins.

[0065] If the value of the map sharing counter is zero and the master device 20 and slave device 30 have successfully shared the new channel map, there is no longer any need to transmit the new channel map from the master device 20 to the slave device 30. Therefore, the master device 20 proceeds to step S590. On the other hand, if the value of the map sharing counter is other than zero and the new channel map has not yet been shared between the master device 20 and slave device 30, the master device 20 proceeds to step S520.

[0066] In step S520, the master unit 20 transmits the new channel map to the slave unit 30. At this time, the master unit 20 transmits, together with the new channel map, information indicating the timing to start using the new channel map. The timing to start using the new channel map occurs every time a channel map update period elapses, as shown in the example of the time chart in FIG.

[0067] 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.

[0068] In step S530, the master device 20 receives the Ack signal from the slave device 30. Then, in step S540, 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 S550, the master device 20 determines whether the checksum check results in step S540 are OK or NG. If the checksum check results in OK, the master device 20 proceeds to step S560. On the other hand, if the checksum check results in NG, the master device 20 proceeds to step S570.

[0069] In step S560, the master device 20 resets the above-mentioned map sharing counter to zero. In this way, the map sharing counter is reset to zero when it is determined that the slave device 30 has correctly received the new channel map and timing information, an Ack signal is transmitted from the slave device 30, and the Ack signal is correctly received by the master device 20. Therefore, when the value of the map sharing counter is zero, it can be said that this indicates that the master device 20 and the slave device 30 have successfully shared the new channel map, as described above.

[0070] 7 shows an example in which a slave device 30 indicated as "Slave1" normally receives a new channel map and timing information from the master device 20 in the first communication (i.e., communication event=1) after the channel map update period starts and new channel map sharing starts, and furthermore, an Ack signal transmitted from the slave device 30 is normally received by the master device 20, so that the new channel map is shared between the master device 20 and the slave device 30. In this case, the map sharing counter is reset to zero in step S560. Therefore, in the second and subsequent communications during the channel map update period (i.e., communication events=2 to 6), the determination result in step S510 becomes "Yes", so that it is not necessary to further transmit a new channel map and timing information.

[0071] On the other hand, in step S570, since the master device 20 has not received the Ack signal correctly, the master device 20 determines whether or not to execute processing for retransmission within the same communication event. If the master device 20 determines to retransmit in step S570, it executes the processing from step S520 again. If the master device 20 determines not to retransmit in step S570, the master device 20 proceeds to step S580. In step S580, the master device 20 increments the map sharing counter by 1. In this way, the map sharing counter is incremented when it is not considered that the master device 20 and the slave device 30 have successfully shared the new channel map. Therefore, if the value of the map sharing counter is other than zero, it can be said to indicate that the master device 20 and the slave device 30 have not yet successfully shared the new channel map.

[0072] For example, the time chart in FIG. 7 shows an example in which the slave device 30 indicated as "Slave2" fails to receive the new channel map and timing information from the master device 20 normally in the first communication (i.e., communication event=1) after the channel map update period starts and the new channel map sharing starts, and therefore the Ack signal is not returned, or the slave device 30 transmits an Ack signal, but the master device 20 fails to receive the Ack signal normally, and therefore the sharing of the new channel map between the master device 20 and the slave device 30 is deemed to have failed. In this case, in step S580, the map sharing counter is incremented by 1 and becomes a value other than zero. Therefore, in the second and subsequent communications (i.e., communication events=2 to 6) during the channel map update period, the determination result in step S510 is "No," and the process in and after step S520 is executed. In other words, the transmission of the new channel map and timing information from the master device 20 to the slave device 30 is repeatedly executed for each communication event. This transmission of new channel map and timing information continues for the channel map update period until the master device 20 and slave device 30 have successfully shared the channel map and the map sharing counter has been reset to zero.

[0073] In step S590, the master unit 20 judges whether the waiting time until updating to a new channel map has elapsed, i.e., whether the channel map update period has expired. If it is judged in this judgment process that the waiting time has elapsed, the master unit 20 proceeds to step S600. On the other hand, if it is judged that the waiting time has not elapsed, the master unit 20 ends the process shown in the flowchart of FIG.

[0074] In step S600, the master device 20 determines whether the value of the map sharing counter is zero. If the value of the map sharing counter is zero, the value of the map sharing counter indicates that the master device 20 and the slave device 30 have successfully shared the new channel map. Therefore, in step S610, the master device 20 updates the channel map from the current channel map to the new channel map. This allows the master device 20 and the slave device 30 to communicate via a communication channel selected according to the new channel map.

[0075] On the other hand, if it is determined in step S600 that the value of the map sharing counter is a value other than zero, there is a possibility that sharing of the new channel map between the master device 20 and the slave device 30 has failed despite the new channel map and timing information being transmitted a predetermined number of times (corresponding to the first predetermined number in the claims) (for example, six times in the example shown in FIG. 7). Therefore, the master device 20 disconnects the communication connection with the slave device 30 in step S620. At this time, the communication connection that is disconnected is the wireless communication connection with the slave device 30 that is considered to be unable to share the channel map among the multiple slave devices 30.

[0076] 7, the timing of disconnecting the communication connection with the slave device 30 corresponds to the timing when the application period of the new channel map begins, i.e., the timing when use of the new channel map begins. This makes it possible to prevent successive communication errors caused by differences in the channel maps of the master device 20 and the slave device 30, and suppress the occurrence of situations in which communication reliability decreases.

[0077] When the master device 20 cuts off the communication connection with the slave device 30, the master device 20 starts the connection sequence of FIG. 4 described above in order to reconnect with the slave device 30 whose communication connection has been cut off. On the other hand, when the slave device 30 is unable to perform data communication with the master device 20 and the number of communication errors reaches a predetermined number (a number corresponding to a third predetermined number in the claims), the slave device 30 cuts off the communication connection with the master device 20. After the communication connection is cut off, the slave device 30 also starts the connection sequence of FIG. 4. This causes an attempt to reconnect the master device 20 and the slave device 30. In the connection 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 a communication channel to be used for wireless communication is shared between the master device 20 and the slave device 30. This allows the master device 20 and the slave device 30 to perform wireless communication again.

[0078] 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.

[0079] In the wireless communication system 10 according to the first embodiment described above, if it is determined that the master device 20 and the slave device 30 have not successfully shared the new channel map despite transmitting a new channel map and timing information a predetermined number of times in a channel map update period, the master device 20 disconnects the communication connection with the slave device 30 at the timing of starting to use the new channel map. Here, in the first embodiment described above, the master device 20 determines whether the master device 20 and the slave device 30 have successfully or unsuccessfully shared the new channel map based on the fact that it is unable to receive a channel map reception acknowledgement signal (Ack signal) from the slave device 30.

[0080] However, even if the master device 20 cannot normally receive the Ack signal from the slave device 30, there is a possibility that the slave device 30 can normally receive the new channel map and timing information transmitted from the master device 20. If the slave device 30 can normally receive the new channel map and timing information, the master device 20 and the slave device 30 can communicate using the new channel map. Therefore, if the slave device 30 can receive the new channel map and timing information, it is not necessary to disconnect the communication connection with the slave device 30 based on the fact that the master device 20 cannot normally receive the Ack signal from the slave device 30. Furthermore, if the communication connection with the slave device 30 is disconnected, the master device 20 and the slave device 30 will not be able to communicate data for the period required for reconnection.

[0081] Therefore, in the wireless communication system 10 according to this embodiment, in order to prevent unnecessary disconnection of the communication connection, the master device 20 is configured to disconnect the communication connection with the slave device 30 not simply because an Ack signal cannot be received normally, but after confirming that the master device 20 and the slave device 30 are not able to share the new channel map.

[0082] The wireless communication system 10 according to the present disclosure will be described below, focusing on the differences from the wireless communication system 10 according to the first embodiment.

[0083] Fig. 8 is a flowchart showing a channel map sharing process executed in the wireless communication system 10 according to this embodiment. The channel map sharing process of the second embodiment shown in the flowchart of Fig. 8 is different from the channel map sharing process of the first embodiment shown in the flowchart of Fig. 6 in that steps S600 and S620 are deleted. As for other processes, there is no difference between the channel map sharing process shown in the flowchart of Fig. 8 and the channel map sharing process shown in the flowchart of Fig. 6.

[0084] In the channel map sharing process shown in the flowchart of FIG. 8, steps S600 and S620 have been deleted, so that when master device 20 determines in step S590 that the waiting time until updating to a new channel map has elapsed, it always updates the channel map from the current channel map to the new channel map in step S610 without determining whether sharing of the new channel map has been successful based on successful reception of an Ack signal.

[0085] Then, as shown in the time chart of Fig. 9, the master device 20 attempts data communication with the slave device 30 a predetermined number of times (corresponding to the second predetermined number in the claims) via a communication channel selected according to the updated new channel map. In the example shown in the time chart of Fig. 9, this predetermined number is set to one time, but it is not limited to one time and may be two or more times. However, the predetermined number corresponding to the second predetermined number is set to a number less than the predetermined number corresponding to the third predetermined number used to determine whether to cut off the communication connection when communication errors occur consecutively, rather than when the sharing of the channel map fails.

[0086] If the master device 20 is able to communicate with the slave device 30 in a predetermined number of communication attempts, it can be considered that the master device 20 and the slave device 30 have successfully shared the new channel map. Therefore, the master device 20 continues to communicate with the slave device 30 using the new channel map.

[0087] On the other hand, if the master device 20 is unable to communicate with the slave device 30 in a predetermined number of communication attempts, it may be considered that sharing of the new channel map between the master device 20 and the slave device 30 has failed. In this case, the master device 20 disconnects the communication connection with the slave device 30 at the timing when it is determined that communication with the slave device 30 is not possible even after a predetermined number of communication attempts. In the example shown in the time chart of FIG. 9, the master device 20 attempted to communicate once with the slave device 30 shown as "Slave2" via a communication channel selected according to the new channel map, but was unable to communicate with the slave device 30 of "Slave2", and therefore disconnected the communication connection with the slave device 30 of "Slave2" at the timing when the first communication event ended.

[0088] In order to realize the disconnection of the communication connection at the above-mentioned timing, the wireless communication system 10 according to the second embodiment executes the communication sequence shown in the flowchart of Fig. 10 while using the new channel map. The communication sequence shown in the flowchart of Fig. 10 is obtained by adding the processes of steps S232, S242, S244, and S246 to the communication sequence of the first embodiment shown in the flowchart of Fig. 5.

[0089] 10, in step S232, it is determined whether the checksum judgment is OK or NG based on the checksum judgment result in step S230. If the checksum judgment is OK, it can be considered that the master device 20 and the slave device have successfully transmitted and received a data request and corresponding data in the processes of steps S210 and S310 and steps S220 and S330 using the new channel map. Therefore, if the checksum judgment is OK in step S232, the master device 20 proceeds to step S250 and continues communication with the slave device 30 using the new channel map.

[0090] On the other hand, if the checksum judgment is NG in step S232, the master device 20 proceeds to step S240. In step S240, as in the first embodiment, it is judged whether or not to execute processing for retransmission within the same communication event. If the master device 20 decides to execute retransmission in step S240, it executes the processing from step S210 again. If the master device 20 decides not to execute retransmission in step S240, the master device 20 proceeds to step S242.

[0091] In step S242, the master device 20 judges whether or not the master device 20 and the slave device 30 have succeeded in sharing a new channel map in the previous channel map update period. More specifically, immediately before the start of the channel map update period in which the new channel map is applied, the master device 20 judges whether or not the new channel map has been shared in the previous channel map update period based on the value of the map sharing counter in the flowchart of FIG. 8, and stores the judgment result. Then, in step S242, the master device 20 judges whether or not the new channel map has been shared in the previous channel map update period based on the stored judgment result. If it is determined that the new channel map has been shared in the previous channel map update period, the master device 20 proceeds to the process of step S250 and continues communication with the slave device 30. However, if the master device 20 is unable to perform data communication normally a predetermined number of times (corresponding to a third predetermined number in the claims) in succession, the master device 20 disconnects the communication connection. On the other hand, if it is determined that the new channel map was not successfully shared within the immediately preceding channel map update period, the master device 20 proceeds to step S244. In step S244, it is determined whether communication with the slave device 30 has failed a predetermined number of times (corresponding to a second predetermined number in the claims) after updating the channel map to the new channel map. At this time, if it is determined that communication with the slave device 30 has failed the predetermined number of times, the master device 20 proceeds to step S246. In step S246, the master device 20 disconnects the communication connection with the slave device 30.

[0092] Note that, if communication with the slave device 30 is successful at least once after updating to a new channel map, the processes of steps S242, S244, and S246 may be skipped thereafter. Alternatively, even if the channel maps of the master device 20 and the slave device 30 are different, communication may occasionally be successful, so the processes of steps S242, S244, and S246 may be executed regardless of whether communication is successful at one time.

[0093] 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.

[0094] For example, in each of the above-described embodiments, if sharing of the channel map between the master device 20 and the slave device 30 is not successful, the channel map is transmitted from the master device 20 to the slave device 30 in all communication events (communication events = 1 to 6) in the channel map update period.

[0095] However, the upper limit number of times (corresponding to the first predetermined number in the claims) for transmitting the channel map from the master device 20 to the slave device 30 in a channel map update period may be set to be less than the planned number of communications between the master device 20 and the slave device 30 from the start of sharing the channel map to the start of using the channel map, i.e., the number of communication events included in the channel map update period. If it is not determined that the channel map sharing has been successful even though the number of times the channel map has been transmitted from the master device 20 to the slave device 30 reaches the upper limit number (first predetermined number), the master device 20 may disconnect the communication connection with the slave device 30 at the timing at which it is determined to have been successful (corresponding to the third timing in the claims).

[0096] For example, in the example shown in the time chart of FIG. 11, the master device 20 disconnects the communication connection with the slave device 30 when it is determined that the sharing of the channel map has failed five times, which is fewer than the number of communication events (six) during the channel map update period. If the sharing of the new channel map is not successful, the communication between the master device 20 and the slave device 30 is unlikely to be successful during the application period (next channel map update period) in which the new channel map is applied. Therefore, in this modified example, the communication connection is disconnected at an earlier timing than, for example, waiting for the start of the next channel map update period before disconnecting the communication connection. This allows the master device 20 and the slave device 30 to be reconnected early. As a result, it is possible to shorten the period during which communication between the master device 20 and the slave device 30 is interrupted due to a mismatch in the channel maps. This makes it possible to shorten the period during which important communications cannot be performed in the vehicle, for example, when at least one of the master device 20 and the slave device 30 is mounted on the vehicle, such as communications for notifying that an abnormality has occurred in the on-vehicle device or communications for issuing commands to perform important controls in the on-vehicle device, between the master device 20 and the slave device 30. Note that the above-mentioned upper limit number may be set to a number less than the number of communication errors in data communication (the number corresponding to the third predetermined number in the claims) at which the master device 20 cuts off the communication connection with the slave device 30.

[0097] Furthermore, in the second embodiment described above, the number of times the channel map is retransmitted may be less than the number of communication events included in the channel map update period, and the master device 20 may execute other processing (e.g., creating the next new channel map for the slave device 30 with which the communication connection is maintained) in a communication event in which the channel map is not transmitted. For example, in the example shown in the time chart of Fig. 9, in the sixth communication event, the channel map may not be retransmitted to "Slave2", and the master device 20 may execute other processing in the sixth communication event. This allows the processing resources of the master device 20 to be allocated to other processing.

[0098] 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.

[0099] (Technical thought 1) A wireless communication system in which a master device (20) performs wireless communication with a slave device (30) via one communication channel sequentially selected from a plurality of communication channels, a quality determination unit (S270, S280) that determines the communication quality of each communication channel when the master device wirelessly communicates with the slave device; a communication channel determination unit (S290) for determining a communication channel to be used for wireless communication based on a result of the communication quality determination unit for each communication channel; a channel map sharing unit (S520) that causes the master device to transmit a channel map indicating the communication channel determined by the communication channel determination unit to the slave device, and causes the master device and the slave device to share the channel map; a sharing determination unit (S540, S550) for determining whether or not the channel map has been shared between the master device and the slave device based on a reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map; a communication disconnection unit (S620, S246) in the master device that disconnects the communication connection with the slave device; the channel map sharing unit repeats transmission of the channel map when the sharing determination unit does not determine that the channel map has been shared despite the channel map having been transmitted; A wireless communication system in which, when the number of times that the channel map sharing unit has transmitted the channel map has reached a first predetermined number of times, the communication disconnection unit disconnects the communication connection with the slave device at a predetermined timing based on the fact that the sharing determination unit has never determined that the channel map has been shared.

[0100] (Technical thought 2) the channel map sharing unit transmits, together with the channel map, information indicating a timing for starting use of the channel map; The wireless communication system described in Technical Idea 1, wherein the predetermined timing corresponds to a first timing for starting to use the channel map.

[0101] (Technical Thought 3) the channel map sharing unit transmits, together with the channel map, information indicating a timing for starting use of the channel map; The wireless communication system described in Technical Idea 1, wherein the specified timing corresponds to a second timing at which the master device determines that it is unable to communicate with the slave device even after attempting communication with the slave device a second specified number of times at the timing at which the master device starts using the channel map and communicates with the slave device on a communication channel selected in accordance with the channel map transmitted to the slave device.

[0102] (Technical Thought 4) The wireless communication system described in Technical Idea 3, wherein if the master device is able to communicate with the slave device within the second predetermined number of communication attempts, it continues communication via communication channels selected sequentially according to the channel map transmitted to the slave device.

[0103] (Technical Thought 5) When the sharing determination unit determines that the channel map has been shared, the master device communicates with the slave device via a communication channel that is selected sequentially according to the channel map transmitted to the slave device at the timing when the master device starts using the channel map, and when the master device is never able to communicate with the slave device despite communicating with the slave device a third predetermined number of times that is greater than the second predetermined number of times, the communication disconnection unit disconnects the communication connection with the slave device.

[0104] (Technical Thought 6) the channel map sharing unit transmits, together with the channel map, information indicating a timing for starting use of the channel map; the first predetermined number is set to be less than a planned number of communications between the master device and the slave device before starting to use the channel map; The wireless communication system described in Technical Idea 1, wherein the specified timing corresponds to a third timing at which the sharing determination unit determines that the channel map has never been shared, even though the channel map sharing unit has transmitted the channel map a first specified number of times.

[0105] (Technical Thought 7) A wireless communication system as described in any one of Technical Ideas 1 to 6, wherein when the communication connection with the slave device is disconnected by the communication disconnection unit, the master device attempts to reconnect the wireless communication with the slave device, and during the reconnection process, communication channel information used for wireless communication is shared between the master device and the slave device.

[0106] (Technical Thought 8) the master device communicates with a plurality of the slave devices at the same time, The wireless communication system described in any one of Technical Ideas 1 to 7, wherein the communication disconnection unit disconnects wireless communication with a slave device among the multiple slave devices that is deemed not to be able to share the channel map at the specified timing.

[0107] (Technical Thought 9) the communication channel determination unit periodically updates a communication channel to be used for wireless communication based on a result of the communication quality determination unit determining the communication quality of each communication channel; The channel map sharing unit periodically transmits an updated channel map indicating updated communication channels from the master device to the slave device, and shares the updated channel map between the master device and the slave device. [Explanation of symbols]

[0108] 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 a master device (20) performs wireless communication with a slave device (30) via one communication channel sequentially selected from a plurality of communication channels, a quality determination unit (S270, S280) that determines the communication quality of each communication channel when the master device wirelessly communicates with the slave device; a communication channel determination unit (S290) for determining a communication channel to be used for wireless communication based on a result of the communication quality determination unit for each communication channel; a channel map sharing unit (S520) that causes the master device to transmit a channel map indicating the communication channel determined by the communication channel determination unit to the slave device, and causes the master device and the slave device to share the channel map; a sharing determination unit (S540, S550) that determines whether or not the channel map has been shared between the master device and the slave device based on a reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map; a communication disconnection unit (S620, S246) in the master device that disconnects the communication connection with the slave device; the channel map sharing unit repeats transmission of the channel map when the sharing determination unit does not determine that the channel map has been shared despite the channel map having been transmitted; A wireless communication system in which, when the number of times the channel map is transmitted by the channel map sharing unit reaches a first predetermined number of times, the communication disconnection unit disconnects the communication connection with the slave device at a predetermined timing based on the fact that the sharing determination unit has never determined that the channel map has been shared.

2. the channel map sharing unit transmits, together with the channel map, information indicating a timing for starting use of the channel map; The wireless communication system according to claim 1 , wherein the predetermined timing corresponds to a first timing for starting to use the channel map.

3. the channel map sharing unit transmits, together with the channel map, information indicating a timing for starting use of the channel map; 2. The wireless communication system according to claim 1, wherein the predetermined timing corresponds to a second timing at which the master device determines that it is unable to communicate with the slave device even after attempting communication with the slave device a second predetermined number of times at the timing at which the master device starts using the channel map and executes communication with the slave device on a communication channel selected in accordance with the channel map transmitted to the slave device.

4. 4. The wireless communication system according to claim 3, wherein if the master device is able to communicate with the slave device within the second predetermined number of communication attempts, the master device continues communication via communication channels selected sequentially according to the channel map transmitted to the slave device.

5. 4. The wireless communication system of claim 3, wherein when the sharing determination unit determines that the channel map has been shared, the master device communicates with the slave device via communication channels that are selected in sequence according to the channel map transmitted to the slave device at a timing when the master device starts using the channel map, and when the master device is never able to communicate with the slave device despite communicating with the slave device a third predetermined number of times that is greater than the second predetermined number of times, the communication disconnection unit disconnects the communication connection with the slave device.

6. the channel map sharing unit transmits, together with the channel map, information indicating a timing for starting use of the channel map; the first predetermined number is set to be less than a planned number of communications between the master device and the slave device before starting to use the channel map; 2. The wireless communication system according to claim 1, wherein the predetermined timing corresponds to a third timing at which the sharing determination unit determines that the channel map has never been shared, even though the number of times the channel map sharing unit has transmitted the channel map has reached the first predetermined number of times.

7. 7. The wireless communication system according to claim 1, wherein when the communication connection with the slave device is disconnected by the communication disconnection unit, the master device attempts to reconnect the wireless communication with the slave device, and during the reconnection process, communication channel information used for wireless communication is shared between the master device and the slave device.

8. the master device communicates with a plurality of the slave devices at the same time, 7. The wireless communication system according to claim 1, wherein the communication disconnection unit disconnects wireless communication with a slave device among the plurality of slave devices that is deemed not to be able to share the channel map at the predetermined timing.

9. the communication channel determination unit periodically updates a communication channel to be used for wireless communication based on a result of the communication quality determination unit determining the communication quality of each communication channel; 7. The wireless communication system according to claim 1, wherein the channel map sharing unit periodically transmits an updated channel map indicating updated communication channels from the master device to the slave device, and shares the updated channel map between the master device and the slave device.

10. A wireless communication method in which a master device (20) performs wireless communication with a slave device (30) via one communication channel sequentially selected from a plurality of communication channels, comprising: a quality determination step (S270, S280) of determining a communication quality of each communication channel when the master device wirelessly communicates with the slave device; a communication channel determination step (S290) of determining a communication channel to be used for wireless communication based on a result of the communication quality determination step of each communication channel; a channel map sharing step (S520) of transmitting a channel map indicating the communication channel determined in the communication channel determination step from the master device to the slave device and sharing the channel map between the master device and the slave device; a sharing determination step (S540, S550) of determining whether or not the channel map has been shared between the master device and the slave device based on a reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map; a communication disconnection step (S620, S246) of disconnecting the communication connection between the master device and the slave device, In the channel map sharing step, if it is not determined in the sharing determination step that the channel map has been shared even though the channel map has been transmitted, transmission of the channel map is repeated; A wireless communication method in which, based on the fact that the number of times the channel map has been transmitted in the channel map sharing step has reached a first predetermined number of times, and the fact that the channel map has never been shared in the sharing determination step, the communication connection with the slave device is disconnected at a predetermined timing in the communication disconnection step.

11. A wireless communication program executed by at least one processor for causing a master device (20) to wirelessly communicate with a slave device (30) via one communication channel sequentially selected from a plurality of communication channels, the program comprising: When the wireless communication program is executed, the at least one processor a quality determination function (S270, S280) for determining the communication quality of each communication channel when the master device wirelessly communicates with the slave device; a communication channel determination function (S290) for determining a communication channel to be used for wireless communication based on a result of the communication quality determination function of each communication channel; a channel map sharing function (S520) for causing the master device to transmit a channel map indicating the communication channel determined by the communication channel determination function to the slave device, and for causing the master device and the slave device to share the channel map; a sharing determination function (S540, S550) that determines whether or not the channel map has been shared between the master device and the slave device based on a reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map; A communication disconnection function (S620, S246) for disconnecting the communication connection with the slave device is realized in the master device; If the sharing determination function does not determine that the channel map has been shared even though the channel map has been transmitted by the channel map sharing function, the transmission of the channel map is repeated; A wireless communication program in which, when the number of times the channel map is transmitted by the channel map sharing function reaches a first predetermined number of times, the sharing determination function never determines that the channel map has been shared, the communication disconnection function disconnects the communication connection with the slave device at a predetermined timing.

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