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

Abstract

To prevent costs from being increased in a wireless communication system in which a master device communicates with a plurality of slave devices while ensuring effectiveness of channel map control.SOLUTION: Slave devices 30 that are targets for sharing a channel map are determined according to a communication state of wireless communication between a master device 20 and each of a plurality of slave devices 30. Therefore, a processing load when performing channel map control can be suppressed, and an increase in system costs can be avoided. Furthermore, when the number of slave devices 30 determined as targets for performing channel map control is small, timing for sharing the channel map is configured to be advanced as a whole of the determined slave devices 30 compared to when the number of determined slave devices 30 is large.SELECTED DRAWING: Figure 4

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 sequentially selected from a plurality of communication channels. [Background technology]

[0002] A known example of this type of wireless communication system is described in Patent Document 1. In the wireless communication system of Patent Document 1, when a packet error occurs in a signal received by a wireless communication device, if the RSSI value of the wireless signal of that packet is greater than a preset threshold Th1, the wireless communication device determines that the reception operation for receiving this packet is a reception error due to interference with other radio waves. The wireless communication device then counts the number of receptions and the number of reception errors, and stores the frequency of reception errors due to interference in each frequency channel (number of reception errors / number of receptions). If the reception error frequency exceeds threshold Th2, the wireless communication device determines that an interference source exists in the frequency channel where the reception error frequency due to interference exceeds threshold Th2, and stores this frequency channel as an unusable channel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-128812 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the wireless communication system of Patent Document 1 designates a frequency channel whose communication quality has deteriorated due to interference with other radio waves as an unusable channel. Furthermore, the wireless communication system of Patent Document 1 restores the frequency channel designated as an unusable channel to an available frequency channel after a set period of time has elapsed. Hereinafter, this control of designating a frequency channel as an unusable channel or restoring it to an available channel will be referred to as channel map control in this specification.

[0005] Here, when a wireless communication system includes at least one master device and at least two or more slave devices, and each of the slave devices communicates wirelessly with the master device, it becomes necessary to perform channel map control for each of the slave devices. Channel map control is mainly realized by software processing according to a program by a computer equipped with a processor. Therefore, the greater the number of slave devices, the greater the computer processing load for channel map control. Therefore, if channel map control is to be performed for all slave devices, a high-performance computer will be required, which may increase the cost of the wireless communication system.

[0006] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a wireless communication system, a wireless communication method, and a wireless communication program that can suppress increases in the cost of a wireless communication system while ensuring the effectiveness of channel map control in a wireless communication system in which a master device communicates with multiple slave devices. [Means for solving the problem]

[0007] 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 plurality of slave devices are provided, and the master device performs wireless communication with each of the plurality of slave devices. a communication channel determination unit (S70, S80, S90) that, when a master device wirelessly communicates with a plurality of slave devices, determines the communication quality of each communication channel for each slave device and determines the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; a channel map sharing unit (S120) that transmits a channel map indicating the communication channels determined by the communication channel determination unit from the master device to the corresponding slave device, and causes the master device and the corresponding slave device to share the channel map; a slave device determination unit (S100) that determines a slave device with which a channel map sharing unit will share a channel map according to a communication state of wireless communication between the master device and each of the plurality of slave devices; The device is configured to include a timing change unit (S420, S430, S434, S436) that advances the timing at which the channel map sharing unit shares the channel map for all of the determined slave devices when the number of slave devices determined by the slave device determination unit is small, compared to when the number of determined slave devices is large.

[0008] 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: The master device communicates wirelessly with each of the plurality of slave devices, a communication channel determination step (S70, S80, S90) of determining the communication quality of each communication channel for each slave device when the master device wirelessly communicates with a plurality of slave devices, and determining the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; a channel map sharing step (S120) of transmitting a channel map indicating the communication channels determined in the communication channel determination step from the master device to the corresponding slave device, and causing the master device and the corresponding slave device to share the channel map; a slave device determination step (S100) of determining a slave device to be the target of channel map sharing in the channel map sharing step according to a communication state of wireless communication between the master device and each of the plurality of slave devices; When the number of slave devices determined in the slave device determination step is small, the timing change step (S420, S430, S434, S436) is configured to advance the timing of sharing the channel map in the channel map sharing step for all of the determined slave devices, compared to when the number of determined slave devices is large.

[0009] A wireless communication program according to the present disclosure is a wireless communication program executed by at least one processor, for allowing 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: The master device communicates wirelessly with each of the plurality of slave devices, When the wireless communication program is executed, the program causes at least one processor to a communication channel determination function (S70, S80, S90) for determining the communication quality of each communication channel for each slave device when the master device wirelessly communicates with a plurality of slave devices, and determining the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; a channel map sharing function (S120) that transmits a channel map indicating the communication channels determined by the communication channel determination function from the master device to the corresponding slave device, and allows the master device and the corresponding slave device to share the channel map; a slave device determination function (S100) for determining a slave device with which a channel map will be shared by the channel map sharing function according to the state of wireless communication between the master device and each of the plurality of slave devices; When the number of slave devices determined by the slave device determination function is small, the timing change function (S420, S430, S434, S436) is configured to advance the timing of sharing the channel map by the channel map sharing function for all determined slave devices, compared to when the number of determined slave devices is large.

[0010] As described above, in the wireless communication system, wireless communication method, and wireless communication program according to the present disclosure, a slave device to which a channel map is to be shared is determined based on the communication status of wireless communication between the master device and each of multiple slave devices. In this way, in the present disclosure, channel map control is not always performed on all slave devices, but rather the slave device to which channel map control is to be performed is determined based on the communication status. Therefore, the processing load when performing channel map control can be reduced. As a result, channel map control can be performed without using a high-performance computer, thereby avoiding an increase in system costs.

[0011] Furthermore, the wireless communication system, wireless communication method, and wireless communication program according to the present disclosure are configured to advance the timing of channel map sharing for all of the determined slave devices when the number of slave devices selected as targets for channel map control is small, compared to when the number of determined slave devices is large. Therefore, for example, when a slave device has a deteriorated communication state, the timing of channel map sharing can be advanced by reducing the number of slave devices selected as targets for channel map sharing. As a result, it is possible to quickly improve the communication state of a slave device whose communication state has deteriorated. In this way, the effectiveness of channel map control can be ensured.

[0012] The reference numbers in parentheses above merely indicate an example of the correspondence with specific configurations in the embodiments described below, in order to facilitate understanding of the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

[0013] Furthermore, the technical features of the present disclosure other than those described above will become apparent from the following description of the embodiments and the accompanying drawings. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a schematic configuration of a wireless communication system according to a first embodiment. [Figure 2] FIG. 10 is a diagram illustrating an example of the electric field strength distribution in a communication environment between a master device and a slave device. [Figure 3] FIG. 2 is a diagram illustrating an example of received signal strength of each communication channel. [Figure 4] 10 is a flowchart illustrating an example of a communication sequence between a master device and a slave device. [Figure 5] 5 is a flowchart showing an example of a target slave determination process in the flowchart of FIG. 4. [Figure 6] 5 is a flowchart showing an example of a channel map transmission process in the flowchart of FIG. 4. [Figure 7] 10 is a time chart showing an example of timing for updating the channel map of each slave device when all slave devices are subject to channel map control. [Figure 8] 10 is a time chart showing an example of timing for updating the channel map of each slave device when some slave devices are subject to channel map control. [Figure 9] 10 is a flowchart illustrating an example of a target slave determination process according to the second embodiment. [Figure 10] 10 is a flowchart showing an example of a channel map transmission process according to the second embodiment. [Figure 11]10 is a time chart showing an example of the timing of updating the channel map of each slave device when a slave device in a deteriorated communication state is targeted for channel map control in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present disclosure will be described below with reference to the drawings. Note that identical or similar configurations may be omitted from the description by assigning the same reference numerals across multiple drawings. When only a portion of a configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the remaining portion of the configuration. Furthermore, 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 this embodiment includes at least one master device and at least two slave devices. Each of the at least two slave devices communicates wirelessly with one master device. At least one of the master device and the multiple slave devices may be mounted on a mobile object. Mobile objects include, for example, vehicles such as automobiles and railroad cars, flying objects such as electric vertical take-off and landing aircraft and drones, ships, construction machinery, agricultural machinery, etc.

[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 electrically powered vehicle such as an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. When applied to a battery management system, for example, 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 make up 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 multiple battery stacks acquires battery information, such as the voltage and current of each battery cell included in the corresponding battery stack and the temperature of the battery stack, using various sensors. When 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, activates a heating / cooling mechanism to adjust the temperature of the battery pack within an appropriate range, and determines whether to perform so-called equalization processing to equalize the voltages of each battery cell. If the battery control device determines that equalization processing is necessary for at least one battery stack, it instructs the corresponding monitoring device to perform the equalization processing via the wireless communication system. Each monitoring device also performs processing to determine abnormalities in the various sensors and its own operation, and if an abnormality is detected, 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 locks and unlocks the vehicle doors and controls the on / off of a driving source such as the vehicle engine. Multiple slave devices are mounted on portable keys or portable terminals held by multiple users. 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 pressure is abnormal. 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 this embodiment may be applied to a vehicle diagnostic system. In this case, for example, multiple slave devices are connected to multiple on-board devices having self-diagnosis functions, and the master device is connected to a diagnostic control device installed in a service shop. In these examples, at least one of the master device and the multiple slave devices is located in a fixed position and / or at least one is installed in 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 also be applied to systems that control and manage various types of equipment in moving bodies other than vehicles, such as flying bodies such as drones, ships, construction machinery, agricultural machinery, etc. Furthermore, the wireless communication system according to the present embodiment can also be applied to systems that control and manage various types of equipment in buildings such as buildings, production facilities in 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 arranged in a common housing, or may not be arranged in a common housing. There may be one master device 20 or multiple master devices 20. When multiple master devices 20 are provided, the multiple master devices 20 may communicate with multiple slave devices 30 belonging to different groups, or the multiple master devices 20 may communicate with multiple slave devices 30 belonging to the same group. The master device 20 and the slave devices 30 communicate wirelessly via one communication channel sequentially selected 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 this 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] The wireless communication between the master device 20 and the slave device 30 can use frequency bands used in short-range communication, such as the 2.4 GHz band and the 5 GHz band. Radio waves in such high-frequency bands tend to travel in a more directional manner than radio waves in the LF band, and are more likely to be reflected by metal objects such as vehicle bodies. LF is an abbreviation for Low Frequency. Bluetooth and Bluetooth LE, for example, can be used as standards for short-range communication. As an example, the master device 20 and the slave device 30 of this embodiment are configured to be able to perform wireless communication compliant with the Bluetooth LE standard (hereinafter referred to as Bluetooth LE communication). Details of the communication method, such as communication connection and encrypted communication, are performed in accordance with the sequence defined in the Bluetooth LE standard.

[0025] 1, the master device 20 includes a control circuit (CNT) 21, a wireless communication circuit (WC) 22, and an antenna 23. In addition to the above elements, the master device 20 also 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 some 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 program stored in the ROM while using the RAM as a temporary storage area to perform predetermined processing (control). The processor 211 executes a plurality of instructions included in the program to establish a plurality of functional units. There may be multiple processors 211. The storage medium for the program is not limited to the ROM. Various storage media, such as an HDD or SSD, can be used. HDD is an abbreviation for Hard-disk Drive. SSD is an abbreviation for Solid State Drive.

[0028] The processor 211 is, for example, a CPU, an MPU, a GPU, or a DFP. CPU is an abbreviation for Central Processing Unit. MPU is an abbreviation for Micro-Processing Unit. GPU is an abbreviation for Graphics Processing Unit. DFP is an abbreviation for Data Flow Processor. The control circuit 21 may be realized by combining multiple types of arithmetic processing devices such as a CPU, an MPU, and a GPU. Alternatively, the control circuit 21 may be realized as an SoC. SoC is an abbreviation for System on Chip. The control circuit 21 may be realized using an ASIC or FPGA. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field-Programmable Gate Array.

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

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

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

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

[0033] 1, the slave device 30 includes a control circuit (CNT) 31, a wireless communication circuit (WC) 32, and an antenna 33. In addition to the above 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 configuration similar to that of the control circuit 21 of the master device 20. The control circuit 31 includes, for example, a processor 311 and a memory 312. The memory 312 includes, for example, a RAM and a ROM.

[0034] The control circuit 31 executes requested processing (such as response processing, such as acquiring and returning requested data, or executing the requested processing) based on the request command received via the wireless communication circuit 32. For example, if the request command included in the received data is a request to transmit battery information, the control circuit 31 of the slave device 30 transmits the transmission request to the monitoring device of the corresponding battery stack and acquires the battery information from the monitoring device. Then, in response to the request, the control circuit 31 transmits data encrypted using encryption information, including the processing result (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. Similar to the wireless communication circuit 22, the wireless communication circuit 32 has a transmitting function and a receiving function. The wireless communication circuit 32 receives a packet transmitted from the master device 20 via the antenna 33 and demodulates it. Then, it transmits the data contained in the demodulated packet to the control circuit 31. The wireless communication circuit 32 modulates a packet containing the data transmitted from the control circuit 31 and transmits it to the master device 20 via the antenna 33. The wireless communication circuit 32 adds data necessary for wireless communication, such as communication control information, to the transmission packet before transmitting it.

[0036] The wireless communication circuit 32 may control the data size, communication format, schedule, error detection, etc. of communication between the master device 20 and the slave device 30. These communication-related controls may be performed by the control circuit 31. The antenna 33 converts electrical signals into radio waves and radiates them into space. The antenna 33 receives radio waves propagating through space and converts them into electrical signals.

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

[0038] The master unit 20 and the slave unit 30 are disposed, for example, at predetermined positions in a vehicle. When the master unit 20 and the slave unit 30, each disposed at a predetermined position, transmit radio wave signals of a predetermined frequency, areas of high and low electric field strength are generated in the usage environment due to interference between the transmitted wave and the reflected wave and interference with external noise. The reflected wave is generated by reflection from metal elements of the vehicle present around the master unit 20 and the slave unit 30, such as reflection from the vehicle body, metal casing, and harness. For this reason, the communication environment between the master unit 20 and the slave unit 30 has multiple so-called NULL points, which are areas of high electric field strength and areas of low electric field strength, as shown in FIG. 2.

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

[0040] When the master device 20 and the slave device 30 communicate wirelessly via one communication channel selected sequentially from multiple communication channels, the frequency of each communication channel may differ, and therefore the electric field distribution of each communication channel may also vary, resulting in different communication quality for each communication channel.

[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 communication quality, is good. Furthermore, in wireless communication via communication channel C, the received power exhibits a very high value. Therefore, when the master device 20 and the slave device 30 use communication channels A and C, which have good or very high communication quality, they can perform high-quality wireless communication in which communication errors are sufficiently suppressed. On the other hand, in wireless communication via communication channels B and N, the received power is low. Therefore, when the master device 20 and the slave device 30 use communication channels B and N, which have poor communication quality, there is a high possibility that communication errors will occur in the wireless communication. Note that, for ease of understanding, FIG. 3 shows an example of received signal strength versus frequency using 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 provide 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 / or the slave unit 30 are mounted on a moving body such as a vehicle, the electric field distribution in the communication environment between the master unit 20 and the slave unit 30 changes depending on, for example, the state of the moving body and the state of the environment surrounding the moving body. As a result, communication channels with good communication quality and communication channels with degraded communication quality are not fixed but may change from moment to moment. Therefore, when communication quality deteriorates, it is required to delete the corresponding communication channel from the multiple communication channels used for wireless communication, and when communication quality recovers, to restore the corresponding communication channel as one of the multiple communication channels used for wireless communication.

[0044] In the wireless communication system 10 of this embodiment, a control process for realizing wireless communication between the master device 20 and the slave device 30 using, as multiple communication channels used for wireless communication, communication channels that ensure a certain communication quality, excluding communication channels whose communication quality has deteriorated due to channel map control, will be described with reference to the diagram of the communication sequence between the master device 20 and the slave device 30 shown in FIG. 4. In FIG. 4, the master device 20 is indicated as MASTER and the slave device 30 is indicated as SLAVE. FIG. 4 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. 4 with the multiple slave devices 30.

[0045] First, the master device 20 and the slave device 30 execute a connection establishment process before executing the communication sequence shown in Fig. 4. For example, if the wireless communication system 10 is installed in a vehicle, the connection establishment process is executed when the IG signal is switched from off to on by a user operation, for example. This connection establishment process is executed between the master device 20 and all slave devices 30 that are targets for wireless communication connection with the master device 20. Note that if the master device 20 and the slave devices 30 are constantly connected, the connection establishment process is executed only once at a predetermined timing. However, if an error occurs during communication and the wireless communication connection between the master device 20 and the slave device 30 is disconnected, the connection establishment process may be executed to reconnect.

[0046] In the connection establishment process, for example, the slave device 30 performs an advertising operation to transmit an advertising signal via an advertising communication channel, and the master device 20 performs a scanning operation to scan for advertising signals. The advertising communication channel includes multiple communication channels (for example, three in the case of Bluetooth LE). When the master device 20 receives an advertising signal on any of the communication channels through the scanning operation, it transmits a connection request to the slave device 30 that transmitted the advertising signal. This establishes a communication connection between the master device 20 and the slave device 30. Furthermore, after the communication connection is established, the master device 20 and the slave device 30 exchange encryption information to be 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.

[0047] After the connection establishment process is completed, the master device 20 and the slave devices 30 execute the communication sequence shown in the flowchart of Fig. 4 for each communication event that occurs periodically. In this communication sequence, data communication is performed via a data communication channel that is selected sequentially from multiple communication channels by frequency channel hopping for each communication event. The master device 20 assigns communication periods to the multiple slave devices 30 in order for each communication event, so that sub-communication events in which the master device 20 communicates with each of the multiple slave devices 30 occur in a predetermined order.

[0048] As shown in FIG. 4, in step S10, the master device 20 transmits, for example, a data request command, i.e., a data request, to the slave device 30. However, the master device 20 can also transmit, in addition to a data request, for example, a request to execute a predetermined process. Upon receiving the data request in step S210, the slave device 30 performs, in step S220, a checksum check, for example, based on the error detection code included in the received data request, to confirm whether the data request was received correctly. If, in step S220, the slave device 30 determines based on the checksum check result that the data request was not received correctly, then, for example, in step S230, the slave device 30 transmits a signal indicating that the data request was not received correctly or a signal requesting a retransmission of the data request. On the other hand, if, in step S220, the slave device 30 determines that the data request was received correctly, then, in step S230, the slave device 30 performs a predetermined process required for responding, such as acquiring and transmitting the requested data.

[0049] As described above, the master device 20 and the slave device 30 switch the data communication channel to be used for each communication event by performing frequency channel hopping to transmit and receive data requests and requested data. At this time, the master device 20 and the slave device 30 determine the communication channel to be switched by frequency channel hopping according to their respective channel maps. In the case of Bluetooth LE, 37 communication channels are provided as data communication channels.

[0050] In step S20, the master device 20 receives the requested data. Then, in step S30, the master device 20 performs, for example, a checksum check based on the error detection code included in the received data to confirm whether the data was received correctly. In the following step S40, if the master device 20 determines in step S30 that the data was not received correctly, or if the master device 20 receives from the slave device 30 a signal indicating that the data request was not received correctly or a signal requesting a retransmission of the data request, the master device 20 determines whether to execute a process for retransmission within the same communication event. For example, if there is enough time to perform a retransmission before the end of the current communication event (sub-communication event), the master device 20 may decide to perform a retransmission; otherwise, if there is not enough time, the master device 20 may decide not to perform a retransmission. If the master device 20 determines in step S40 that the data was received correctly, or if it determines in step S40 that a retransmission is not performed, the master device 20 proceeds to step S50.

[0051] In step S50, master device 20 executes processing based on information contained in the received data. Note that if it is determined in step S30 that the data has not been received correctly and it is decided in step S40 that retransmission will not be performed, step S50 may be omitted, or the processing of step S50 may be executed based on previously received data.

[0052] In step S60, 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 is a percentage indicating the ratio of the number of error packets to the number of packets received by the master device 20. The master device 20 may detect a signal-to-noise ratio (SNR) / signal-to-interference-to-noise ratio (SINR) instead of the RSSI. The SNR / SINR can be detected, for example, by the ratio between the RSSI value when the master device 20 receives a wireless communication signal from the slave device 30 and the RSSI value when the master device 20 does not receive a wireless communication 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 and at least one of the PER, BER, or PAR for each communication channel. In addition to or instead of the master device 20 detecting the characteristic data indicating the communication quality as described above, the slave device 30 can also obtain the characteristic data by detecting the RSSI, PER, etc. when receiving a wireless communication signal from the master device 20 and transmitting the detected data to the master device 20.

[0053] In step S70, the master device 20 determines a degradation in the communication quality of the communication channel used for wireless communication with the slave device 30 based on the characteristic data indicating the communication quality of the communication channel detected in step S60. The master device 20 then deletes the communication channel determined to have degraded communication quality from the communication channels used for wireless communication between the master device 20 and the slave device 30. The deleted communication channel is a data communication channel. For example, one condition for determining a degradation in communication quality is that the RSSI is compared with a threshold for RSSI and the PER is compared with a threshold for PER, and as a result, at least one of the RSSI and the PER does not satisfy the threshold. The parameter compared with the threshold may be one type. The parameter compared with the threshold may be the parameter detected immediately before in step S60, or may be an average value or a median value of a predetermined number of parameters detected in multiple past wireless communications related to the same communication channel.

[0054] In step S80, the master device 20 performs a restoration determination for a communication channel that was deleted in a deletion determination during a previous communication event. If a predetermined restoration condition is satisfied in this restoration determination, the deleted communication channel is restored as a communication channel to be used for wireless communication. For example, as an example of the predetermined restoration condition, the deleted communication channel may be restored when a predetermined time has elapsed since the communication channel was deleted. Alternatively, as another example of the predetermined restoration condition, the deleted communication channel may be restored as a communication channel to be used for wireless communication when a communication channel adjacent to the deleted communication channel exhibits good communication quality. In this way, a communication channel determined to be restoreable as a communication channel to be used for wireless communication is incorporated into the channel map and is actually used in wireless communication between the master device 20 and the slave device 30. However, if the communication quality when actually used for wireless communication remains degraded, the communication channel may again be subject to deletion in the deletion determination.

[0055] In step S90, the master device 20 performs a channel map creation process based on the deletion determination result of step S70 and the restoration determination result of step S80. In this embodiment, an individual channel map is created for each of the multiple slave devices 30. However, it is also possible to create a common channel map for 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 each slave device 30, and multiple communication channels common to all of the channel maps are extracted. When creating a common channel map, the common channel map may be created from the channel maps of the slave devices 30 determined as targets for channel map control in the target slave determination process described below.

[0056] The channel map may indicate communication channels that can be used for wireless communication, or may indicate communication channels that cannot be used. Furthermore, the channel map may indicate both communication channels that can be used and communication channels that cannot be used. Furthermore, when the creation of the channel map results in a change in communication channels that can be used / unused, the frequency channel hopping pattern may be updated. When the frequency channel hopping pattern is not updated, for example, when a communication channel that is scheduled to be hopped to is unavailable, the next communication channel that is scheduled to be hopped to may be used.

[0057] In step S100, the master device 20 determines the slave devices 30 to be subjected to channel map control based on the communication status of wireless communication with each slave device 30. In channel map control, as described above, a channel map is created in step S90 so that only communication channels that ensure a certain level of communication quality are included in the channel map based on the result of the communication channel deletion determination in step S70 and the result of the deleted communication channel restoration determination in step S80. The slave devices 30 to be subjected to this channel map control receive a channel map transmitted from the master device 20 in a channel map transmission process in step S120 (described later). Upon receiving a new channel map, the slave devices 30 update their stored channel maps with the received channel map. Conversely, a new channel map is not transmitted from the master device 20 to slave devices 30 that are not subjected to channel map control. In this case, the slave devices 30 continue to use the channel map they retain. The process of determining the slave devices 30 to be subjected to channel map control is periodically performed. Depending on the result, the slave devices 30 to be subjected to channel map control are updated.

[0058] FIG. 5 is a flowchart showing an example of the target slave determination process in step S100 of the flowchart in FIG.

[0059] In step S310, the master device 20 acquires, for example, the PER calculated when wireless communication with each slave device 30 is performed to determine whether the communication status with each slave device 30 is good or bad. In step S320, the master device 20 selects one slave device 30 from among the multiple slave devices 30 for which the communication status will be determined. Then, in step S330, the master device 20 determines whether the PER acquired for the selected slave device 30 is smaller than a threshold. If the PER is smaller than the threshold, the communication status can be considered good. Therefore, in step S340, the master device 20 determines the communication status of the slave device 30 whose communication status is to be determined as "normal." On the other hand, if the PER is equal to or greater than the threshold, the communication status cannot be considered good. Therefore, in step S350, the master device 20 determines the communication status of the slave device 30 whose communication status is to be determined as "abnormal."

[0060] The parameter used to determine whether the communication state of wireless communication with each slave device 30 is good or bad is not limited to PER. For example, the master device 20 may use RSSI, SNR / SINR, and BER or PAR as parameters for determining the communication state of wireless communication with each slave device 30. The master device 20 may also determine the communication state of wireless communication with each slave device 30 by combining multiple parameters. The parameter used to determine the communication state may be a parameter acquired in the immediately preceding wireless communication. Alternatively, the parameter may be an average value of multiple parameters acquired in multiple wireless communications. Furthermore, the master device 20 may use the number of communication channels available for wireless communication corresponding to each slave device 30, i.e., the number of communication channels included in the channel map corresponding to each slave device 30, as a parameter for determining the communication state.

[0061] In step S360, the master device 20 determines whether or not it has completed determining the communication status of all slave devices 30. If it has completed determining the communication status of all slave devices 30, the master device 20 proceeds to step S370. On the other hand, if it has not completed determining the communication status of all slave devices 30, the master device 20 returns to step S320 and selects a slave device 30 whose communication status has not yet been determined.

[0062] In step S370, the master device 20 determines whether the communication status of all the slave devices 30 has been determined to be "normal" through the processing of steps S320 to S360 described above. If the communication status of all the slave devices 30 has been determined to be "normal," the master device 20 proceeds to step S380. On the other hand, if the communication status of all the slave devices 30 has not been determined to be "normal" and the communication status of some of the slave devices 30 has been determined to be "abnormal," the master device 20 proceeds to step S390.

[0063] In step S380, the master device 20 determines all slave devices 30 as slave devices 30 for which channel map control is to be performed. On the other hand, in step S390, the master device 20 determines the slave devices 30 for which the communication state is determined to be "abnormal" as slave devices 30 for which channel map control is to be performed.

[0064] Returning to the flowchart of Fig. 4, the explanation will be continued. In step S110, the master device 20 determines whether the slave device 30 with which wireless communication has been performed in the communication sequence shown in the flowchart of Fig. 4 is a target for channel map control. If the slave device 30 is a target for channel map control, the master device 20 proceeds to the channel map transmission process of step S120. On the other hand, if the slave device 30 is not a target for channel map control, the master device 20 skips the channel map transmission process of step S120. Therefore, the new channel map is not transmitted to slave devices 30 other than the target for channel map control.

[0065] FIG. 6 is a flowchart showing an example of the channel map transmission process in step S120 of the flowchart in FIG.

[0066] In the first step S410, the master device 20 determines whether all slave devices 30 are targets for channel map control. If all slave devices 30 are targets for channel map control, the master device 20 proceeds to step S420. On the other hand, if all slave devices 30 are not targets for channel map control, the master device 20 proceeds to step S430. In step S420, the master device 20 sets the channel map transmission period, in other words, the update period for sharing the channel map, to the longest period. Specifically, the master device 20 sets the channel map transmission period to a period equal to or greater than the number of all slave devices 30. On the other hand, in step S430, the master device 20 sets the channel map transmission period to a period shorter than the transmission period in step S420. Specifically, the master device 20 sets the channel map transmission period to a period shorter than the channel map transmission period when all slave devices 30 are targets for channel map control and equal to or greater than the number of slave devices 30 for which channel map control is to be performed.

[0067] 7 is a time chart showing an example of the timing of updating the channel map of each slave device 30 when channel map control is performed on all slave devices 30. As shown in FIG. 7, in this embodiment, in order to distribute the processing load for sharing the channel map in the master device 20, that is, the processing load for transmitting a new channel map from the master device 20 to each slave device 30, the master device 20 staggers the timing of transmitting the channel map (the timing at which the channel map is shared) for each slave device 30. In the example shown in FIG. 7, the master device 20 performs wireless communication with six slave devices 30. In the first communication cycle (communication event), the master device 20 transmits a channel map to the slave device 30 in "S1." Thereafter, the master device 20 transmits the channel map to the slave device 30 at "S2" in the second communication cycle (communication event), transmits the channel map to the slave device 30 at "S3" in the third communication cycle (communication event), transmits the channel map to the slave device 30 at "S4" in the fourth communication cycle (communication event), transmits the channel map to the slave device 30 at "S5" in the fifth communication cycle (communication event), and transmits the channel map to the slave device 30 at "S6" in the sixth communication cycle (communication event).

[0068] In each communication cycle (communication event), as described above, the master device 20 communicates with each of the slave devices 30 "S1" to "S6" in the divided sub-communication events. Therefore, for example, in the first communication cycle (communication event), during the sub-communication event with the slave device 30 "S1", the master device 20 communicates data with the slave device 30 "S1" and also transmits a channel map.

[0069] However, the master device 20 does not necessarily have to stagger the timing of channel map transmission for each slave device 30. For example, if the control device (processor) has the processing power to perform channel map transmission processing for two or more slave devices 30 in the same communication event, the channel map transmission processing for some (e.g., two) of the slave devices 30 may be performed during the same communication event. In other words, instead of using different communication events for each slave device 30, the timing of the channel map transmission processing may be distributed over multiple timings (multiple communication events), and the channel map transmission processing for two or more grouped slave devices 30 may be performed at the same time (in the same communication event). In this case, for example, when the longest channel map transmission period is set, the channel map transmission period is set to a number of periods equal to or greater than the number of groups of slave devices 30.

[0070] 7, when the channel map transmission timing is staggered for each slave device 30, the master device 20 sets the channel map transmission period to every six communication periods so that the channel map transmission process is not performed simultaneously (in the same communication event) for two or more slave devices 30. However, six communication periods is just an example, and the channel map transmission period may be any number of periods equal to or greater than the number of slave devices 30 that are the targets of channel map control. Alternatively, when the channel map transmission process is performed simultaneously for two or more slave devices 30, the channel map transmission period may be any number of periods equal to or greater than the number of groups of slave devices 30 that perform the channel map transmission process simultaneously.

[0071] 8 is a time chart showing an example of the timing of updating the channel map of each slave device 30 when some slave devices 30 in an abnormal communication state are targeted for channel map control. In the example shown in FIG. 8, four slave devices 30, "S2" to "S5," are targeted for channel map control. In the example shown in FIG. 8, similar to the example shown in FIG. 7, in order to stagger the timing of transmitting the channel map to each slave device 30, the master device 20 transmits the channel map to the slave device 30 "S2" in the first communication cycle (communication event). Thereafter, in the second communication cycle (communication event), the master device 20 transmits the channel map to the slave device 30 "S3," in the third communication cycle (communication event), the master device 20 transmits the channel map to the slave device 30 "S4," and in the fourth communication cycle (communication event), the master device 20 transmits the channel map to the slave device 30 "S5." 8, when the channel map transmission timing is staggered for each slave device 30, the channel map transmission period is set to five communication periods so that the channel map transmission process is not performed simultaneously (in the same communication event) for two or more slave devices 30. Note that five communication periods is just an example, and the channel map transmission period may be shorter than the channel map transmission period when all slave devices 30 are targets for channel map control and may be equal to or greater than the number of slave devices 30 that are targets for channel map control. Alternatively, the channel map transmission period may be shorter than the channel map transmission period when all slave devices 30 are targets for channel map control and may be equal to or greater than the number of groups of slave devices 30 that perform the channel map transmission process at the same time.

[0072] In this embodiment, as shown in the examples of Figures 7 and 8, when the number of slave devices 30 determined as targets for channel map control is small, the channel map transmission period (the period for sharing the channel map) is set shorter than when the number of determined slave devices 30 is large. This makes it possible to advance the timing for sharing the channel map for all slave devices 30 determined as targets for channel map control. As a result, it becomes possible to quickly improve the communication status of a slave device 30 whose communication status has deteriorated. In this way, the effectiveness of channel map control can be improved.

[0073] In the examples shown in the time charts of FIGS. 7 and 8, the channel map transmission timing is scheduled so that a channel map is transmitted to one slave device 30 at each communication event. In step S440 of the flowchart of FIG. 6, the channel map created in step S90 is transmitted to the slave device 30 for which the channel map transmission timing has arrived. The corresponding slave device 30 receives the channel map in step S510. Upon receiving the channel map in step S510, the slave device 30 performs, for example, a checksum check based on the error detection code attached to the received channel map to confirm whether the channel map was correctly received in step S520. If the slave device 30 determines, based on the checksum check result in step S520, that the channel map was not correctly received, it transmits, for example, in step S530, a signal indicating that the channel map was not correctly received or a signal requesting retransmission of the channel map. On the other hand, if the slave device 30 determines, in step S520, that the channel map was correctly received, it updates its stored channel map to the newly received channel map. Then, in step S530, a reception acknowledgement signal (Ack signal) for the channel map is transmitted to master device 20.

[0074] In step S450, the master device 20 receives the Ack signal. Then, in step S460, the master device 20 performs, for example, a checksum check based on the error detection code included in the received Ack signal to confirm whether the Ack signal was received correctly. In step S470, if the master device 20 determines that the Ack signal was not received correctly, or if the master device 20 receives a signal from the slave device 30 indicating that the channel map was not received correctly or a signal requesting retransmission of the channel map, the master device 20 determines whether to execute processing for retransmission within the same communication event. For example, if there is enough time to perform retransmission before the end of the current communication event (sub-communication event), the master device 20 may decide to perform retransmission; otherwise, the master device 20 may decide not to perform retransmission. If there is not enough time, the master device 20 may decide not to perform retransmission. If it determines to perform retransmission in step S470, the master device 20 executes the processing from step S440 again. If it is determined that the Ack signal has been received correctly, or if it is determined in step S470 that retransmission will not be performed, master device 20 ends the channel map transmission process.

[0075] (Second embodiment) Next, a wireless communication system 10 according to a second embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment has the same configuration as the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0076] In the wireless communication system 10 according to the first embodiment, the communication state of wireless communication with each slave device 30 is classified as "normal" or "abnormal" by comparing the PER with a threshold value. When channel map control is performed for a slave device 30 whose communication state is determined to be "abnormal," the channel map transmission period is made shorter than the channel map transmission period when the communication states of all slave devices 30 are determined to be "normal." In contrast, in the wireless communication system 10 according to the second embodiment, the communication state of wireless communication with each slave device 30 is classified into three or more stages, including "normal," "temporary communication disruption," and "continuous communication disruption," depending on the length of the communication disruption period, and the timing of transmitting the channel map is more appropriately controlled according to each classified communication state.

[0077] Hereinafter, the target slave determination process for determining the slave device 30 that is the target of channel map control, and the channel map transmission process for transmitting a channel map to the target slave device 30, which are performed in the wireless communication system 10 according to this embodiment, will be described with reference to the flowcharts of FIGS. 9 and 10.

[0078] In the target slave determination process of the second embodiment shown in the flowchart of Fig. 9, the processes of steps S330, S350, and S390 are deleted from the target slave determination process of the first embodiment shown in the flowchart of Fig. 5, and instead the processes of steps S332, S352, S354, S356, S392, S394, and S396 are added. As for other processes, there are no differences between the target slave determination process shown in the flowchart of Fig. 9 and the target slave determination process shown in the flowchart of Fig. 5. Therefore, the following description will focus on the differences from the first embodiment.

[0079] In the target slave determination process shown in the flowchart of FIG. 9, in step S332, it is determined whether the communication disruption period is less than a first threshold. The communication disruption period is defined, for example, as a period during which packet errors (or bit errors) occur consecutively. Therefore, the communication disruption period can be detected, for example, by a timer that starts timing when the first packet error is detected and is reset when a packet is successfully received. If the communication disruption period is less than the first threshold, the communication state can be considered normal. Therefore, in step S340, the master device 20 determines that the communication state of the slave device 30 to be determined is "normal."

[0080] On the other hand, if the communication interruption duration is equal to or greater than the first threshold, the master device 20 proceeds to step S352. In step S352, the master device 20 further determines whether the communication interruption duration is less than a second threshold. If the communication interruption duration exceeds the first threshold but is less than the second threshold, the communication status of the wireless communication with the slave device 30 has deteriorated, but the degree of deterioration can be considered to be minor. Therefore, if the communication interruption duration is less than the second threshold, the master device 20 determines in step S354 that the communication status of the wireless communication with the slave device 30 is a "temporary communication interruption" state, which indicates a minor deterioration. However, if the communication interruption duration is equal to or greater than the second threshold, the communication status of the wireless communication with the slave device 30 has deteriorated, and the degree of deterioration can be considered to be major. Therefore, if the communication interruption duration is equal to or greater than the second threshold, the master device 20 determines in step S356 that the communication status of the wireless communication with the slave device 30 is a "continuous communication interruption" state, which indicates a major deterioration.

[0081] In addition to comparing the communication outage period with the first and second thresholds as described above, the degree of deterioration of the communication state can also be determined by comparing communication quality data, such as PER, BER, PAR, RSSI, and SNR / SINR, which indicate the communication quality of wireless communication of each slave device 30, with multiple thresholds.

[0082] 9, if the communication status of all slave devices 30 is not determined to be "normal" in step S370, the master device 20 executes step S392. In step S392, the master device 20 determines whether there are any slave devices 30 in a "continuous communication interruption" state, which indicates a severe deterioration in the communication status. If there are no slave devices 30 in a "continuous communication interruption" state, i.e., if there are only slave devices 30 in a "temporary communication interruption" state, which indicates a mild deterioration in the communication status, the master device 20 proceeds to step S394. On the other hand, if there are any slave devices 30 in a "continuous communication interruption" state, the master device 20 proceeds to step S396.

[0083] In step S394, the master device 20 determines the slave device 30 in the "temporary communication interruption" state as the target for channel map control. On the other hand, in step S396, the master device 20 determines the slave device 30 in the "continuous communication interruption" state as the target for channel map control.

[0084] In this embodiment, as in the first embodiment, when the communication status of all slave devices 30 is "normal," the channel map transmission period is set to the longest, as shown in the example of the time chart in FIG. 7. When the communication status of at least one slave device 30 is "temporary communication interruption," the channel map transmission period is set to be shorter than the longest, as shown in the example of the time chart in FIG. 8. In this shorter transmission period, the number of slave devices 30 that can be the targets of channel map control is limited, for example, to prevent channel maps from being simultaneously transmitted to two or more slave devices 30 in the same communication event. When this limited number is set as a first number, if the number of slave devices 30 in the "temporary communication interruption" state is less than the first number, slave devices 30 with relatively poor communication status may be added as targets of channel map control until the first number is reached. Conversely, for example, if the number of slave devices 30 in the "temporary communication interruption" state is greater than the first number, slave devices 30 with relatively good communication conditions may be excluded from targets for channel map control until the number reaches the first number. Note that the communication conditions of each slave device 30 can be ranked based on the above-mentioned communication quality data and / or the number of communication channels available for wireless communication.

[0085] Furthermore, if the communication state of at least one slave device 30 is a "continuous communication interruption" state, the channel map transmission period is set to be shorter than the longest transmission period. Additionally, as will be described in detail later, the channel map transmission time is set so that the channel map is transmitted to the slave devices 30 that are targets of channel map control during the same communication event. Therefore, the number of slave devices 30 that can be targets of channel map control is limited based on the relationship between the processing load required to transmit the channel map during the same communication event and the processing capacity of the control device (processor) required to process it. When this limited number is set as a second number, if the number of slave devices 30 in the "continuous communication interruption" state is less than the second number, slave devices 30 in relatively poor communication states may be added as targets for channel map control until the number reaches the second number. Conversely, for example, if the number of slave devices 30 in the "continuous communication interruption" state is greater than the second number, slave devices 30 in relatively good communication states may be excluded from targets for channel map control until the number reaches the second number.

[0086] The channel map transmission process of the second embodiment shown in the flowchart of Fig. 10 is different from the channel map transmission process of the first embodiment shown in the flowchart of Fig. 6 in that step S430 is deleted and steps S432, S434, and S436 are added instead. As for other processes, there are no differences between the channel map transmission process shown in the flowchart of Fig. 10 and the channel map transmission process shown in the flowchart of Fig. 5. Therefore, the following description will focus on the differences from the first embodiment.

[0087] 10, if it is determined in step S410 that none of the slave devices 30 are targets for channel map control, the master device 20 executes the process of step S432. In step S432, the master device 20 determines whether the slave devices 30 for which channel map control is to be performed include any slave devices 30 in the "continuous communication interruption" state. If it is determined that the slave devices 30 for which channel map control is to be performed do not include any slave devices 30 in the "continuous communication interruption" state, that is, that only slave devices 30 in the "temporary communication interruption" state, the master device 20 proceeds to step S434. On the other hand, if it is determined that the slave devices 30 for which channel map control is to be performed include any slave devices 30 in the "continuous communication interruption" state, the master device 20 proceeds to the process of step S436.

[0088] In step S434, the master device 20 sets the channel map transmission period to be shorter than the transmission period in step S420, while varying the timing of transmitting the channel map for each slave device 30 that is the subject of channel map control. Specific examples of setting the transmission period are the same as those in the first embodiment. Therefore, the timing of transmitting the channel map to each slave device 30 that is the subject of channel map control is the same as that shown in the time chart of FIG. 8.

[0089] Meanwhile, in step S436, the master device 20 synchronizes the transmission timing of the channel map among the individual slave devices 30 that are the targets of channel map control, while setting the transmission period of the channel map to be shorter than the transmission period of step S420. This transmission period may be the same as or shorter than the transmission period of step S434. The timing chart of Figure 11 shows an example of the timing at which the channel map of each slave device 30 is transmitted when the transmission timing and transmission period of the channel map are set in step S436.

[0090] In the example shown in FIG. 11, three slave devices 30, "S3" to "S5," are targets for channel map control. In the example shown in FIG. 11, unlike the examples shown in FIGS. 7 and 8, a channel map is transmitted to the slave devices 30, "S3" to "S5," in the same communication event (communication cycle 1, communication cycle 6, and communication cycle 11). The channel map transmission cycle is five communication cycles, which is the same as the channel map transmission cycle in the example shown in the time chart of FIG. 8. Even if the transmission cycles are the same, the channel map transmission timing is synchronized for the multiple slave devices 30 that are targets for channel map control, thereby making it possible to advance the timing of channel map transmission for the multiple slave devices 30 as a whole.

[0091] The above describes preferred embodiments of the present disclosure, but the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms within the scope of the gist of the present disclosure.

[0092] 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.

[0093] (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 plurality of the slave devices are provided, the master device wirelessly communicates with each of the plurality of slave devices; a communication channel determination unit (S70, S80, S90) that, when the master device wirelessly communicates with the plurality of slave devices, determines the communication quality of each communication channel for each of the slave devices and determines the communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; a channel map sharing unit (S120) that transmits a channel map indicating the communication channel determined by the communication channel determination unit from the master device to the corresponding slave device, and causes the master device and the corresponding slave device to share the channel map; a slave device determination unit (S100) that determines the slave device as a target for sharing the channel map by the channel map sharing unit according to a communication state of wireless communication between the master device and each of the plurality of slave devices; a timing change unit (S420, S430, S434, S436) that advances the timing at which the channel map sharing unit shares the channel map for all of the determined slave devices when the number of slave devices determined by the slave device determination unit is small, compared to when the number of determined slave devices is large.

[0094] (Technical thought 2) The wireless communication system described in Technical Idea 1, wherein when the communication status of wireless communication with at least one of the slave devices deteriorates, the slave device determination unit determines a number of slave devices that is fewer than the number of all of the slave devices as targets for sharing the channel map by the channel map sharing unit, compared to when the communication status of wireless communication with all of the slave devices is good.

[0095] (Technical Thought 3) The wireless communication system according to Technical Concept 2, wherein the slave device determination unit determines the fewer number of slave devices in descending order of the degree of deterioration of communication conditions.

[0096] (Technical Thought 4) The wireless communication system described in any one of Technical Ideas 1 to 3, wherein, when the communication state of wireless communication with at least one of the slave devices is a first communication state indicating a deterioration in the communication state, the slave device determination unit determines a first number of the slave devices, which includes the at least one of the slave devices and is less than the number of all of the slave devices, as targets for sharing the channel map by the channel map sharing unit.

[0097] (Technical Thought 5) The wireless communication system described in Technical Idea 4, wherein, when the communication state of wireless communication with at least one of the slave devices is a second communication state that is worse than the first communication state, the slave device determination unit determines a second number of the slave devices, including that at least one of the slave devices and which is less than the first number, as targets for sharing the channel map by the channel map sharing unit.

[0098] (Technical Thought 6) The wireless communication system according to Technical Idea 4 or 5, wherein the slave device determination unit determines whether the communication state between the master device and the plurality of slave devices has deteriorated based on a period of time during which communication has been interrupted.

[0099] (Technical Thought 7) the channel map sharing unit periodically causes the master device and the corresponding slave device to share the latest channel map; The wireless communication system described in any one of Technical Ideas 1 to 6, wherein the timing change unit shortens the period for sharing the channel map when the number of slave devices determined by the slave device determination unit is small compared to when the number of determined slave devices is large, thereby advancing the timing for sharing the channel map by the channel map sharing unit for all of the determined slave devices.

[0100] (Technical Thought 8) The timing change unit, when the number of slave devices determined by the slave device determination unit is large, shifts the timing at which the channel map sharing unit shares the channel map for the determined multiple slave devices to multiple timings, while when the number of slave devices determined by the slave device determination unit is small, shares the channel map for the determined multiple slave devices at the same time, thereby advancing the timing at which the channel map sharing unit shares the channel map for all of the determined slave devices.

[0101] (Technical Thought 9) The wireless communication system described in any one of Technical Ideas 1 to 8, wherein the slave device determination unit determines all of the slave devices as targets for sharing the channel map by the channel map sharing unit when the master device is in a communication state in which it can communicate wirelessly with each of the multiple slave devices normally.

[0102] (Technical Thought 10) the channel map sharing unit periodically causes the master device and the corresponding slave device to share the latest channel map; The wireless communication system described in Technical Idea 9, wherein when the slave device determination unit determines all of the slave devices as targets for sharing the channel map by the channel map sharing unit, the timing change unit makes the period for sharing the channel map the longest, thereby delaying the timing for sharing the channel map by the channel map sharing unit for all of the determined slave devices.

[0103] (Technical Thought 11) The wireless communication system described in Technical Idea 9 or 10, wherein, when the slave device determination unit determines all of the slave devices as targets for which the channel map sharing unit will share the channel map, the timing change unit shifts the timing at which the channel map sharing unit will share the channel map for all of the determined slave devices to multiple timings, thereby distributing the processing load for sharing the channel map.

[0104] (Technical Thought 12) The wireless communication system described in any one of Technical Ideas 1 to 11, wherein the slave device determination unit determines the slave device to which the channel map sharing unit will share the channel map using at least one of a packet error rate (PER), a bit error rate (BER), a packet arrival rate (PAR), a received signal strength indicator (RSSI), a signal-to-noise ratio (SNR), and a signal-to-interference-to-noise ratio (SINR) when the master device performs wireless communication with each of the multiple slave devices.

[0105] (Technical Thought 13) The wireless communication system described in any one of Technical Ideas 1 to 11, wherein the slave device determination unit determines the slave device to which the channel map sharing unit will share the channel map, using the number of communication channels available for wireless communication for each slave device.

[0106] (Technical Thought 14) The wireless communication system according to any one of Technical Ideas 1 to 13, wherein the slave device determination unit periodically updates the determination of the slave device with which the channel map is to be shared. [Explanation of symbols]

[0107] 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 plurality of the slave devices are provided, the master device wirelessly communicates with each of the plurality of the slave devices; a communication channel determination unit (S70, S80, S90) for determining a communication quality of each communication channel for each of the slave devices when the master device wirelessly communicates with the plurality of slave devices and determining a communication channel to be used for wireless communication based on a result of the determination of the communication quality of each communication channel; a channel map sharing unit (S120) that transmits a channel map indicating the communication channel determined by the communication channel determination unit from the master device to the corresponding slave device, and causes the master device and the corresponding slave device to share the channel map; a slave device determination unit (S100) that determines the slave device as a target for sharing the channel map by the channel map sharing unit according to a communication state of wireless communication between the master device and each of the plurality of slave devices; a timing change unit (S420, S430, S434, S436) that advances the timing at which the channel map sharing unit shares the channel map for all of the determined slave devices when the number of slave devices determined by the slave device determination unit is small, compared to when the number of slave devices determined is large.

2. 2. The wireless communication system according to claim 1, wherein, when the communication state of wireless communication with at least one of the slave devices deteriorates, the slave device determination unit determines a number of the slave devices that is less than the number of all of the slave devices as targets for sharing the channel map by the channel map sharing unit, compared to when the communication state of wireless communication with all of the slave devices is good.

3. 3. The wireless communication system according to claim 2, wherein the slave device determination unit determines the fewer number of slave devices in descending order of the degree of deterioration of communication conditions.

4. 2. The wireless communication system according to claim 1, wherein, when a communication state of wireless communication with at least one of the slave devices is a first communication state indicating a deterioration of the communication state, the slave device determination unit determines a first number of the slave devices, which includes the at least one of the slave devices and is less than the number of all of the slave devices, as targets for sharing the channel map by the channel map sharing unit.

5. 5. The wireless communication system according to claim 4, wherein, when a communication state of wireless communication with at least one of the slave devices is a second communication state that is further deteriorated than the first communication state, the slave device determination unit determines a second number of the slave devices, including the at least one of the slave devices and which is less than the first number, as targets for sharing the channel map by the channel map sharing unit.

6. 6. The wireless communication system according to claim 4, wherein the slave device determination unit determines the deterioration of the communication state between the master device and the plurality of slave devices based on a period during which communication is interrupted.

7. the channel map sharing unit periodically causes the master device and a corresponding slave device to share the latest channel map; 6. The wireless communication system according to claim 1, wherein the timing modification unit shortens the period for sharing the channel map when the number of the slave devices determined by the slave device determination unit is small compared to when the number of the determined slave devices is large, thereby advancing the timing for sharing the channel map by the channel map sharing unit for all of the determined slave devices.

8. 6. The wireless communication system according to claim 1, wherein when the number of slave devices determined by the slave device determination unit is large, the timing change unit shifts the timing at which the channel map sharing unit shares the channel map for the determined plurality of slave devices to a plurality of timings, while when the number of slave devices determined by the slave device determination unit is small, the timing change unit shares the channel map for the determined plurality of slave devices at the same time by the channel map sharing unit, thereby advancing the timing at which the channel map sharing unit shares the channel map for all of the determined slave devices.

9. The wireless communication system according to any one of claims 1 to 5, wherein when the master device is in a communication state in which it can normally communicate wirelessly with each of the plurality of slave devices, the slave device determination unit determines all of the slave devices as targets for which the channel map sharing unit will share the channel map.

10. the channel map sharing unit periodically causes the master device and the corresponding slave device to share the latest channel map; 10. The wireless communication system of claim 9, wherein when the slave device determination unit determines that all of the slave devices are targets for which the channel map sharing unit will share the channel map, the timing modification unit makes the period for sharing the channel map the longest, thereby delaying the timing at which the channel map sharing unit shares the channel map for all of the determined slave devices.

11. 10. The wireless communication system of claim 9, wherein when the slave device determination unit determines all of the slave devices as targets for which the channel map sharing unit will share the channel map, the timing change unit shifts the timing at which the channel map sharing unit will share the channel map for all of the determined slave devices to a plurality of timings, thereby distributing the processing load for sharing the channel map.

12. 6. The wireless communication system according to claim 1, wherein the slave device determination unit determines the slave device as a target for sharing the channel map by the channel map sharing unit, using at least one of a packet error rate (PER), a bit error rate (BER), a packet arrival rate (PAR), a received signal strength indicator (RSSI), a signal to noise ratio (SNR), and a signal to interference plus noise ratio (SINR) when the master device performs wireless communication with each of the plurality of slave devices.

13. 6. The wireless communication system according to claim 1, wherein the slave device determination unit determines the slave device as the target for sharing the channel map by the channel map sharing unit, using the number of communication channels available for wireless communication for each slave device.

14. The wireless communication system according to claim 1 , wherein the slave device determination unit periodically updates the determination of the slave device with which the channel map is to be shared.

15. 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: the master device wirelessly communicates with each of the plurality of slave devices; a communication channel determination step (S70, S80, S90) of determining a communication quality of each communication channel for each of the slave devices when the master device wirelessly communicates with the plurality of slave devices, and determining a communication channel to be used for wireless communication based on a result of the determination of the communication quality of each communication channel; a channel map sharing step (S120) of transmitting a channel map indicating the communication channel determined in the communication channel determination step from the master device to the corresponding slave device and causing the master device and the corresponding slave device to share the channel map; a slave device determination step (S100) of determining a slave device to be a target for sharing the channel map in the channel map sharing step according to a communication state of wireless communication between the master device and each of the plurality of slave devices; a timing change step (S420, S430, S434, S436) of advancing the timing of sharing the channel map in the channel map sharing step for all of the determined slave devices when the number of slave devices determined in the slave device determination step is small, compared to when the number of slave devices determined is large.

16. 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: the master device wirelessly communicates with each of the plurality of slave devices; When the wireless communication program is executed, the at least one processor a communication channel determination function (S70, S80, S90) for determining a communication quality of each communication channel for each of the slave devices when the master device wirelessly communicates with the plurality of slave devices and determining a communication channel to be used for wireless communication based on a result of the determination of the communication quality of each communication channel; a channel map sharing function (S120) for transmitting a channel map indicating the communication channel determined by the communication channel determination function from the master device to the corresponding slave device and for causing the master device and the corresponding slave device to share the channel map; a slave device determination function (S100) for determining a slave device as a target for sharing the channel map by the channel map sharing function in accordance with a communication state of wireless communication between the master device and each of the plurality of slave devices; A wireless communication program that realizes a timing change function (S420, S430, S434, S436) that advances the timing of sharing the channel map by the channel map sharing function for all of the determined slave devices when the number of slave devices determined by the slave device determination function is small, compared to when the number of determined slave devices is large.

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