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

Abstract

In the present invention, a plurality of slave devices (30A, 30B, 40A, 40B) are grouped into two or more groups. In addition, a communication channel to be used for wireless communication is determined for each of the slave devices belonging to at least one grouped group, and a shared channel map is created by extracting shared communication channels from the determined communication channels. A master device (20) and the slave devices grouped into the at least one group execute wireless communication via a communication channel selected from the shared communication channels indicated by the shared channel map.

Description

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

[0001] This application is based on Patent Application No. 2023-166448 filed in Japan on September 27, 2023, and the contents of the original application are incorporated by reference in their entirety.

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

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

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

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

[0006] Here, when a master device performs wireless communication with multiple slave devices, it is conceivable to extract common communication channels from the frequency channels (communication channels) available to each slave device and create a common channel map for each slave device. Creating such a common channel map simplifies various processes related to the channel map, such as updating, saving, and transmitting the channel map, which are required for wireless communication with each of the multiple slave devices. However, if a master device simply creates a common channel map for multiple slave devices with which it performs wireless communication, it may be difficult to ensure a sufficient number of communication channels available for wireless communication, for example, when the number of communication channels common to each slave device is small.

[0007] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a wireless communication system, a wireless communication method, and a wireless communication program that are capable of using a common channel map for multiple slave devices while suppressing the occurrence of a situation in which a sufficient number of communication channels cannot be secured.

[0008] In order to achieve the above object, the wireless communication system according to the present disclosure is a wireless communication system in which at least one master device and multiple slave devices perform wireless communication via one communication channel selected sequentially from multiple communication channels, and includes: a grouping unit that groups the multiple slave devices into two or more groups; a communication channel determination unit that, when the master device performs wireless communication with each of the multiple slave devices, determines the communication quality of each communication channel for the slave devices belonging to at least one group grouped by the grouping unit, and determines the communication channel to be used for wireless communication based on the determination results of the communication quality of each communication channel; and a creation unit that, for the slave devices belonging to at least one group grouped by the grouping unit, extracts a common communication channel that is a communication channel common to the slave devices belonging to at least one group based on the communication channel to be used for wireless communication determined by the communication channel determination unit, and creates a common channel map; and the master device and the slave devices grouped into at least one group are configured to perform wireless communication via a communication channel selected from the common communication channels indicated in the common channel map created by the creation unit.

[0009] Further, a wireless communication method according to the present disclosure is a wireless communication method for at least one master device and multiple slave devices to perform wireless communication via one communication channel selected sequentially from multiple communication channels, the method comprising: grouping the multiple slave devices into two or more groups; determining the communication quality of each communication channel for the slave devices belonging to at least one of the grouped groups when the master device performs wireless communication with each of the multiple 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; extracting a common communication channel that is a communication channel common to the slave devices belonging to at least one group based on the communication channel to be used for wireless communication determined for the slave devices belonging to at least one of the grouped groups, and creating a common channel map; and the master device and the slave devices grouped into at least one group are configured to perform wireless communication via a communication channel selected from the common communication channels indicated by the created common channel map.

[0010] Furthermore, a wireless communication program according to the present disclosure is a wireless communication program for at least one master device and multiple slave devices to perform wireless communication via one communication channel selected sequentially from multiple communication channels, and causes at least one processor to perform the following: grouping the multiple slave devices into two or more groups; determining the communication quality of each communication channel for the slave devices belonging to at least one of the grouped groups when the master device performs wireless communication with each of the multiple slave devices, and determining a communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; and extracting a common communication channel that is a communication channel common to the slave devices belonging to at least one group based on the communication channel to be used for wireless communication determined for the slave devices belonging to at least one of the grouped groups, and creating a common channel map; and the master device and the slave devices grouped into at least one group are configured to perform wireless communication via a communication channel selected from the common communication channels indicated by the created common channel map.

[0011] As described above, in the wireless communication system, wireless communication method, and wireless communication program disclosed herein, multiple slave devices are grouped into two or more groups. Then, communication channels to be used for wireless communication are determined for slave devices belonging to at least one of the grouped groups, and a common communication channel is extracted from the determined communication channels to create a common channel map. Thus, according to the wireless communication system, wireless communication method, and wireless communication program disclosed herein, rather than simply creating a common channel map for all slave devices, multiple slave devices are grouped into two or more groups, and a common channel map is created for slave devices belonging to at least one of the grouped groups. Therefore, it is possible to prevent a situation in which a sufficient number of communication channels cannot be secured for multiple slave devices while using a common channel map.

[0012] The reference numbers in parentheses in the claims 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.

[0014] 1 is a block diagram showing an overall configuration including a schematic configuration of a wireless communication system according to a first embodiment. FIG. 2 is a diagram showing an example of a field strength distribution in a communication environment between a master device and a slave device. FIG. 3 is a diagram showing an example of received signal strength of each communication channel. FIG. 4 is a flowchart showing an example of a startup sequence between a master device and a slave device. FIG. 5 is a flowchart showing an example of a communication sequence between a master device and a slave device. FIG. 6 is a diagram showing an example of a list held by a master device (or a control device) that associates identification information of multiple slave devices with information on the groups to which each slave device belongs. FIG. 7 is a diagram showing an example of the relationship between communication events and sub-events when there are two slave devices. FIG. 8 is a flowchart showing an example of the channel map creation process of the flowchart of FIG. 5. FIG. 9 is a table showing an example of creating a common channel map for all slave devices when a master device communicates with a total of nine slave devices. FIG. 10 is a table showing an example of grouping a total of nine slave devices into three groups and creating a common channel map for each group. FIG. 11 is a flowchart showing an example of a communication sequence in a wireless communication system according to a second embodiment. FIG. 12 is an explanatory diagram for explaining a grouping technique used in a wireless communication system according to a third embodiment. FIG. 13 is a diagram showing an example of grouping multiple slave devices according to the grouping technique used in a wireless communication system according to the third embodiment. FIG. 10 is a diagram showing another example in which a plurality of slave devices are grouped in accordance with the grouping method used in the wireless communication system according to the third embodiment. FIG. 11 is a diagram showing an example in which a plurality of slave devices are grouped in accordance with the grouping method used in the wireless communication system according to the fourth embodiment. FIG. 12 is a diagram showing an example in which a plurality of slave devices are grouped in accordance with the grouping method used in the wireless communication system according to the fifth embodiment. FIG. 13 is a diagram showing a modified example of the wireless communication system according to the fifth embodiment. FIG. 14 is a diagram showing another modified example of the wireless communication system according to the fifth embodiment. FIG. 15 is a diagram showing yet another modified example of the wireless communication system according to the fifth embodiment.10 is a flowchart showing a grouping method in a wireless communication system according to a fourth embodiment.

[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 description by assigning the same reference numerals across multiple drawings. When only a portion of a configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the remaining portions of the configuration. Furthermore, configurations of multiple embodiments may be partially combined, even if not explicitly described, as long as there is no particular problem with the combination.

[0016] First Embodiment A wireless communication system according to this embodiment includes at least one master device and multiple slave devices. At least one of the master device and the slave devices can be mounted on a mobile object. Mobile objects include, for example, vehicles such as automobiles and railroad cars, aircraft such as electric vertical take-off and landing aircraft and drones, ships, construction machinery, agricultural machinery, and the like.

[0017] 1 shows an example of the configuration when a wireless communication system 10 according to this embodiment is applied to a vehicle 100. As a specific application of the vehicle 100, the wireless communication system 10 according to this embodiment can be applied to a variety of vehicle systems (vehicle applications). In this case, each of the plurality of slave devices 30A, 30B, 40A, and 50A is associated with one of the plurality of vehicle applications so as to perform wireless communication with the master device 20 to execute one of the applications.

[0018] For example, the wireless communication system 10 can be applied as one of vehicle applications to a battery management system that manages batteries installed as a battery pack in an electrically powered vehicle such as an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. When the wireless communication system 10 is applied to a battery management system, for example, at least one master device 20 is connected to a control device 1 that functions as a battery control device, and multiple slave devices 30A, 30B are connected to first application devices 35A, 35B that function as monitoring devices and are provided for multiple battery stacks that make up the battery pack. In this case, both the master device 20 and the slave devices 30A, 30B are installed in the vehicle.

[0019] The monitoring devices (first application devices 35A, 35B) provided in each battery stack acquire battery information, such as the voltage and current of each battery cell included in the corresponding battery stack and the temperature of the battery stack, using various sensors. When the monitoring devices (first application devices 35A, 35B) receive data requesting battery information from the battery control device (control device 1) via the wireless communication system 10, they transmit the acquired battery information to the battery control device (control device 1) via the wireless communication system 10. Based on the acquired battery information, the battery control device (control device 1) calculates the state of charge (SOC) of the entire battery stack, drives a heating / cooling mechanism to adjust the temperature of the battery pack within an appropriate range, and determines whether to perform a so-called equalization process to equalize the voltages of the battery cells in the battery stack. If the battery control device (control device 1) determines that an equalization process is required for at least one battery stack, it instructs the corresponding monitoring device (first application devices 35A, 35B) to perform the equalization process via the wireless communication system 10. In addition, the monitoring device (first application equipment 35A, 35B) performs processing to determine abnormalities in various sensors and abnormalities in its own operation, and if an abnormality is determined, transmits abnormality information to the battery control device (control device 1) via the wireless communication system 10.

[0020] The wireless communication system 10 according to the present embodiment can also be applied as another vehicle application to a so-called smart key system (registered trademark, the same applies hereinafter) compatible with a digital key or a tire pressure monitoring system. When the wireless communication system 10 is applied to a smart key system compatible with a digital key, for example, the master unit 20 is mounted on the vehicle and connected to a control device 1 having a function as a vehicle control device that controls locking and unlocking of vehicle doors and turning on and off of a driving source such as the vehicle engine. The multiple slave units are mounted on mobile devices (not shown) used as digital keys (e.g., smartphones or smartwatches) or electronic keys, and are also disposed at various locations on the vehicle, such as the front, sides, and rear, to detect the position of the digital key or electronic key relative to the vehicle 100. The multiple slave units 40A disposed at various locations on the vehicle have a function of, for example, intercepting communication between the master unit 20 and the slave units mounted on the digital key or electronic key and transmitting the intercepted communication results to the master unit 20. This allows the master device 20 (or the control device 1) to detect the position of the digital key or electronic key using location identification techniques such as multilateration or polygonal surveying based on the position of each slave device 40A, the time when each slave device 40A intercepted the communication, and / or the angle of arrival of the communication signal at each slave device 40A.

[0021] When the wireless communication system 10 is applied to a tire pressure monitoring system, the master unit 20 is mounted on a vehicle and connected to a control unit 1 having functions as an air pressure monitoring control device that displays tire pressure and issues warnings when the air pressure is abnormal. The multiple slave units 50A are connected by wire or wirelessly to air pressure detection devices (third application devices 55A) provided in each tire. The air pressures detected by the air pressure detection devices (third application devices 55A) are then transmitted via the wireless communication system 10 to the air pressure monitoring control device (control unit 1). The air pressure monitoring control device (control unit 1) displays the tire pressure and issues warnings when the air pressure is abnormal based on the received air pressure.

[0022] Furthermore, the wireless communication system 10 according to the present embodiment may be applied to a vehicle diagnostic system in place of or in addition to one of the vehicle applications described above. In this case, for example, a plurality of slave devices are connected to a plurality of in-vehicle devices (application devices) having self-diagnosis functions, and the master device is connected to a diagnostic control device installed in a service shop. In this example, a plurality of slave devices are installed in the vehicle 100.

[0023] However, application examples of the wireless communication system 10 according to the present embodiment are not limited to vehicle applications, and as described above, the system can also be applied to systems (applications) that control and manage various equipment of moving objects other than vehicles, such as aircraft such as drones, ships, construction machinery, agricultural machinery, etc. Furthermore, the wireless communication system 10 according to the present embodiment can also be applied to systems that control and manage various equipment in buildings such as buildings, production facilities in factories, etc.

[0024] In the following embodiment, an example will be described in which the wireless communication system 10 is applied to a battery management system, a smart key system, and a tire pressure monitoring system as multiple vehicle applications. In this case, as shown in FIG. 1 , the master device 20 and slave devices 30A, 30B, 40A, and 50A of the wireless communication system 10 are all mounted on a vehicle (automobile) 100. 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 30A, 30B, 40A, and 50A that belong to different groups. Alternatively, the multiple master devices 20 may communicate with multiple slave devices 30A, 30B, 40A, and 50A that belong to the same group. The master device 20 and the slave devices 30A, 30B, 40A, and 50A communicate wirelessly via one communication channel that is sequentially selected from a plurality of communication channels, such as Bluetooth Low Energy (Bluetooth is a registered trademark; the same applies hereinafter, and Bluetooth Low Energy will be referred to as Bluetooth LE hereinafter) communication.

[0025] The wireless communication between the master device 20 and the slave devices 30A, 30B, 40A, and 50A can use frequency bands used in short-range communication, such as the 2.4 GHz band and the 5 GHz band. Radio waves in these high-frequency bands tend to travel in a more directional manner than radio waves in the LF band and are more likely to be reflected by metal objects such as vehicle bodies. LF stands for Low Frequency. Standards for short-range communication include Bluetooth and Bluetooth LE. As an example, the master device 20 and slave devices 30A, 30B, 40A, and 50A of this embodiment are configured to be capable of wireless communication compliant with the Bluetooth LE standard (hereinafter referred to as Bluetooth LE communication). Details of the communication method, such as communication connection and encrypted communication, are performed in accordance with the sequence defined in the Bluetooth LE standard.

[0026] 1, the master device 20 includes a control circuit (CNT) 21, a wireless communication circuit (WC) 22, and an antenna 23. In addition to the above elements, the master device 20 may also include an input / output interface and a bus line for wired or wireless communication with devices other than the slave devices 30A, 30B, 40A, and 50A. Note that processes such as 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 (e.g., the control device 1) provided outside the master device 20.

[0027] 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.

[0028] In the control circuit 21, the processor 211 executes a program stored in the ROM while using the RAM as a temporary storage area to perform predetermined processing (control). The processor 211 executes multiple instructions included in the program to establish multiple functional units. There may be multiple processors 211. The storage medium for the program is not limited to the ROM. Various storage media, such as an HDD or SSD, can be used. HDD is an abbreviation for Hard-disk Drive. SSD is an abbreviation for Solid State Drive.

[0029] 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.

[0030] Control circuit 21 generates commands (e.g., commands requesting data, commands requesting execution of predetermined processing, etc.) requesting processing from slave devices 30A, 30B, 40A, and 50A, and transmits transmission data including the commands in transmission packets to wireless communication circuit 22. Control circuit 21 also receives packets transmitted from slave devices 30A, 30B, 40A, and 50A via wireless communication circuit 22, and executes predetermined processing based on the data included in the received packets. In other words, wireless communication between master device 20 and slave devices 30A, 30B, 40A, and 50A is packet communication.

[0031] The wireless communication circuit 22 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. The wireless communication circuit 22 has a transmission function of modulating a transmission signal and oscillating at the frequency of an RF signal. The wireless communication circuit 22 also has a reception function of demodulating a received signal. RF is an abbreviation for radio frequency.

[0032] The wireless communication circuit 22 modulates packets containing data transmitted from the control circuit 21 and transmits them to the slave devices 30A, 30B, 40A, and 50A via the antenna 23. The control circuit 21, for example, encrypts the transmission data using encryption information exchanged in the connection establishment process described below, and outputs the resulting data to the wireless communication circuit 22. The wireless communication circuit 22 adds data necessary for wireless communication (e.g., communication control information) to the transmission packet and transmits it. The data necessary for wireless communication includes, for example, an identifier (ID), a sequence number, a next sequence number, an error detection code, and the like. The wireless communication circuit 22 may control the data size, communication format, schedule, error detection, and the like of the communication between the master device 20 and the slave devices 30A, 30B, 40A, and 50A. The control circuit 21 may also perform these communication-related controls.

[0033] The wireless communication circuit 22 receives packets transmitted from the slave devices 30A, 30B, 40A, and 50A via the antenna 23 and demodulates them. The wireless communication circuit 22 then transmits the demodulated packets to the control circuit 21. The antenna 23 converts the electrical signals into radio waves and radiates them into space. The antenna 23 receives the radio waves propagating through space and converts them into electrical signals.

[0034] The slave devices 30A, 30B, 40A, and 50A each have the same configuration. The following describes the configuration and operation of the slave device 30A as a representative example. However, multiple slave devices 30A, 30B, 40A, and 50A may be referred to as necessary.

[0035] 1, the slave device 30A includes a control circuit (CNT) 31, a wireless communication circuit (WC) 32, and an antenna 33. In addition to the elements described above, the slave device 30A also includes an input / output interface and a bus line for wired or wireless communication with devices other than the master device 20. The control circuit 31 has a configuration similar to that of the control circuit 21 of the master device 20. The control circuit 31 includes, for example, a processor 311 and a memory 312. The memory 312 includes, for example, a RAM and a ROM.

[0036] The control circuit 31 executes requested processing (e.g., response processing such as acquiring and returning requested data, execution processing of the requested processing, etc.) 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 30A transmits the transmission request to a monitoring device (e.g., the first application device 35A) of the corresponding battery stack and acquires the battery information from the monitoring device (e.g., the first application device 35A). Then, in response to the request, the control circuit 31 transmits data encrypted using encryption information, including the processing result (e.g., the acquired battery information), to the wireless communication circuit 32. The control circuit 31 can also execute control of, for example, a device mounted on a vehicle, in accordance with the requested processing.

[0037] The wireless communication circuit 32 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. Similar to the wireless communication circuit 22, the wireless communication circuit 32 has a transmitting function and a receiving function. The wireless communication circuit 32 receives packets transmitted from the master device 20 via the antenna 33 and demodulates them. Then, it transmits the data contained in the demodulated packets to the control circuit 31. The wireless communication circuit 32 modulates packets containing the data transmitted from the control circuit 31 and transmits them to the master device 20 via the antenna 33. The wireless communication circuit 32 adds data necessary for wireless communication, such as communication control information, to the transmission packets before transmitting them.

[0038] 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 30A. These communication-related controls may be performed by the control circuit 31. The antenna 33 converts electrical signals into radio waves and radiates them into space. The antenna 33 receives radio waves propagating through space and converts them into electrical signals.

[0039] 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 30A. This figure shows the results of an electromagnetic field simulation at a specific frequency and a specific timing. Hereinafter, the electric field strength distribution may be referred to as the electric field distribution.

[0040] The master unit 20 and the slave unit 30A are disposed, for example, at predetermined positions in a vehicle. When the master unit 20 and the slave unit 30A, 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 30A, 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 30A has multiple so-called NULL points, which are areas of high electric field strength and areas of low electric field strength, as shown in FIG. 2.

[0041] If the slave device 30A 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 30A is more likely to be unable to correctly receive the wireless signal from the master device 20, which may result in a communication error. A communication channel where such a communication error is more likely to occur is a communication channel with degraded communication quality.

[0042] When the master device 20 and the slave device 30A communicate wirelessly via one communication channel selected sequentially from multiple communication channels, the frequency of each communication channel may differ, and therefore the electric field distribution of each communication channel may also vary, resulting in different communication quality for each communication channel.

[0043] For example, as shown in FIG. 3 , in wireless communication via communication channel A, the received power (received signal strength), which is one parameter indicating communication quality, is good. Furthermore, in wireless communication via communication channel C, the received power exhibits a very high value. Therefore, when the master device 20 and the slave device 30A 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 30A use communication channels B and N, which have poor communication quality, the likelihood of communication errors occurring in the wireless communication increases. Note that, for ease of understanding, FIG. 3 shows an example of received signal strength versus frequency using a solid line.

[0044] Therefore, it is preferable that wireless communication between the master device 20 and the slave device 30A be performed using a communication channel that can provide high-quality wireless communication, avoiding communication channels with degraded communication quality.

[0045] However, the electric field distribution between the master unit 20 and the slave unit 30A changes depending on the external environment (such as external noise) and vibrations of the master unit 20 and / or the slave unit 30A (including vibrations of the metal housing and harness). Therefore, when the master unit 20 and the slave unit 30A are mounted on a vehicle, the electric field distribution in the communication environment between the master unit 20 and the slave unit 30A changes depending on, for example, the state of the vehicle (e.g., whether it is running or stopped) and the state of the vehicle's surrounding environment (e.g., whether there is a lot of external noise or not). As a result, communication channels with good communication quality and communication channels with degraded communication quality are not fixed but may change from moment to moment. Therefore, it is necessary to continuously monitor the communication quality of each communication channel, and, if the communication quality deteriorates, delete the corresponding communication channel from the multiple communication channels used for wireless communication, and, if the communication quality recovers, restore the corresponding communication channel to the multiple communication channels used for wireless communication.

[0046] 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 30A using multiple communication channels for wireless communication, with a certain communication quality ensured, 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 30A shown in FIG. 5 . In FIG. 5 , the master device 20 is designated MASTER and the slave device 30A is designated SLAVE. Note that FIG. 5 shows the communication sequence executed between the master device 20 and the slave device 30A. The master device 20 individually executes the communication sequence shown in FIG. 5 with the multiple slave devices 30A, 30B, 40A, and 50A. However, the master device 20 can also simultaneously transmit data to the multiple slave devices 30A, 30B, 40A, and 50A by group. Groups will be described in more detail later.

[0047] Here, the master device 20 and the slave device 30A execute a connection establishment process before executing the communication sequence shown in Fig. 5. Fig. 4 shows an example of a startup sequence including the connection establishment process that is executed from when the master device 20 and the slave device 30A start up until when data communication is performed. Note that the master device 20 also executes this connection establishment process individually with the multiple slave devices 30A, 30B, 40A, and 50A.

[0048] For example, when the wireless communication system 10 is installed in a vehicle, a startup sequence is initiated when the IG signal is switched from off to on by a user operation. If the master device 20 and the slave device 30A are constantly connected, the startup sequence is executed only once at a predetermined timing. However, if an error occurs during communication and the wireless communication connection between the master device 20 and the slave device 30A is disconnected, the startup sequence may be executed to reconnect the devices.

[0049] When the startup sequence begins, the master device 20 and the slave device 30A each perform a startup process in steps S10 and S110, including an initialization process that initializes various variables, timers, and the like. Then, the master device 20 and the slave device 30A each perform a connection establishment process in steps S20 and S120. In the connection establishment process, for example, the slave device 30A performs an advertising operation to transmit an advertising signal via an advertising communication channel, and the master device 20 performs a scanning operation to scan for the advertising signal. The advertising communication channel includes multiple communication channels (e.g., 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 30A that transmitted the advertising signal. This establishes a communication connection between the master device 20 and the slave device 30A. When the master device 20 and the slave device 30A determine in steps S30 and S130, respectively, that a communication connection has been established, the master device 20 proceeds to step S40, and the slave device 30A proceeds to step S140.

[0050] The master device 20 and the slave device 30A exchange connection information in steps S40 and S140, respectively. In this connection information exchange, the master device 20 and the slave device 30A exchange encryption information used for data communication and share initial information related to frequency channel hopping. The initial information includes, for example, an initial channel map, a hopping pattern, or a function for hopping. Furthermore, in the connection information exchange, the master device 20 acquires identification information from the slave device 30A for identifying each of the slave devices 30A, 30B, 40A, and 50A. This identification information may be an identifier included in the communication control information, or may be identification information separate from the identifier included in the communication control information.

[0051] The master device 20 (or the control device 1) maintains a list associating the identification information of each of the multiple slave devices 30A, 30B, 40A, and 50A with information about the groups to which each of the multiple slave devices 30A, 30B, 40A, and 50A belongs. Fig. 6 shows an example of a list maintained by the master device 20 (or the control device 1) that associates the identification information of the multiple slave devices 30A, 30B, 40A, and 50A with information about the groups to which each of the slave devices 30A, 30B, 40A, and 50A belongs. As shown in Fig. 6, the list lists, for each group, the identification information of the slave devices 30A, 30B, 40A, and 50A belonging to each group.

[0052] In this embodiment, each group corresponds to a vehicle application. As described above, each of the multiple slave devices 30A, 30B, 40A, and 50A is associated with one of the multiple vehicle applications so as to perform wireless communication with the master device 20 to execute one of the applications. Therefore, in this embodiment, a list is defined so that each of the multiple slave devices 30A, 30B, 40A, and 50A belongs to a group defined for the corresponding application. In step S50, the master device 20 (or the control device 1) refers to the list and groups the slave devices 30A based on the identification information wirelessly transmitted from the slave device 30A to the master device 20.

[0053] Alternatively, each of the multiple slave devices 30A, 30B, 40A, and 50A may be configured to hold identification information for identifying the respective slave devices 30A, 30B, 40A, and 50A and group information indicating the group to which each slave device belongs. In this case, each of the multiple slave devices 30A, 30B, 40A, and 50A transmits its identification information and group information to the master device 20 when exchanging connection information for the startup sequence with the master device 20. The master device 20 can obtain information similar to the list described above from the identification information and group information transmitted from each of the multiple slave devices 30A, 30B, 40A, and 50A. Therefore, the master device 20 (or the control device 1) can group the slave devices 30A, 30B, 40A, and 50A based on the received identification information and group information.

[0054] Next, in steps S60 and S150, the master device 20 and the slave device 30A, respectively, perform data communication via a data communication channel selected sequentially by channel hopping from the multiple communication channels available for communication indicated by the channel map for each periodically occurring communication event. The process for performing this data communication is shown in the communication sequence of FIG. 5. The master device 20 communicates with the multiple slave devices 30A, 30B, 40A, and 50A in sequence by assigning communication periods (sub-events) to each of the multiple slave devices 30A, 30B, 40A, and 50A in each communication event. The time chart of FIG. 7 shows an example of the relationship between communication events and sub-events when there are two slave devices. For example, in the example shown in the time chart of FIG. 7, the master transmits and receives data to and from Slave 1 during sub-event 1 of each communication event, and transmits and receives data to and from Slave 2 during sub-event 2. Alternatively, the Master can transmit data to all Slaves 1 and 2 simultaneously during subevent 1 of each communication event, and data transmission from each Slave 1 and Slave 2 can be performed during subevent 1 and subevent 2, respectively.

[0055] When the master device 20 and the slave device 30A determine to terminate the communication connection in steps S70 and S160, respectively, they terminate the startup sequence shown in Fig. 4. For example, when the wireless communication system 10 is installed in a vehicle, the master device 20 and the slave device 30A may determine to terminate the communication connection when the IG signal is switched from on to off by a user operation. The master device 20 and the slave device 30A may also determine to terminate the communication connection when data communication cannot be performed normally a predetermined number of times in succession.

[0056] Next, a communication sequence for data communication will be described with reference to the flowchart of FIG. 5. As shown in FIG. 5, the master device 20 transmits, for example, a data request command, i.e., a data request, to the slave device 30A in step S210. However, the master device 20 can also transmit, in addition to a data request, a request to execute a predetermined process, for example. When the slave device 30A receives the data request in step S410, it performs, for example, a checksum check based on the error detection code included in the received data request in step S420 to confirm whether the data request was received correctly. If the slave device 30A determines, based on the checksum check result in step S420, that the data request was not received correctly, it transmits, for example, in step S430, a signal indicating that the data request was not received correctly or a signal requesting a retransmission of the data request. On the other hand, if the slave device 30A determines, in step S420, that the data request was received correctly, it performs, for example, a predetermined process required for responding, such as acquiring and transmitting the requested data, in step S430.

[0057] The master device 20 and the slave device 30A switch the data communication channel to be used for each communication event by performing frequency channel hopping to transmit and receive data requests and requested data. At this time, the master device 20 and the slave device 30A determine the communication channel to be switched by frequency channel hopping according to their respective channel maps. For example, in the case of Bluetooth LE communication, 37 communication channels are prepared as data communication channels.

[0058] In step S220, the master device 20 receives the requested data. Then, in step S230, the master device 20 performs, for example, a checksum check based on the error detection code included in the received data to confirm whether the data was received correctly. In the following step S240, if the master device 20 determines in step S230 that the data was not received correctly or if it receives a signal from the slave device 30A indicating that the data request was not received correctly, the master device 20 determines whether to execute a process for retransmission within the same communication event. For example, if there is enough time to perform a retransmission before the end of the current communication event, the master device 20 may decide to perform a retransmission; otherwise, if there is not enough time, the master device 20 may decide not to perform a retransmission. If the master device 20 determines to perform a retransmission in step S240, it executes the process from step S210 again. If it determines in step S230 that the data was received correctly or if it determines in step S240 not to perform a retransmission, the master device 20 proceeds to step S250.

[0059] In step S250, the master device 20 transmits the received data to the control device 1, and the control device 1 executes processing based on the information contained in the received data. Note that if the processing in step S230 determines that the data was not received correctly, or if a signal indicating that the data request was not received correctly is received from the slave device 30A, and if the processing in step S240 determines that retransmission will not be performed, the processing in step S250 may be omitted, or the processing in step S250 may be executed based on the previously received data.

[0060] In step S260, the master device 20 detects communication quality data indicating the communication quality of the signal received from the slave device 30A, such as received signal strength indicator (RSSI) and packet error rate (PER). The RSSI is an index indicating the strength of the signal transmitted from the slave device 30A and received by the master device 20. The PER is a percentage of the number of error packets relative to the number of packets received by the master device 20. Instead of RSSI, the master device 20 may detect a signal-to-noise ratio (SNR) / signal-to-interference-plus-noise ratio (SINR). The SNR / SINR can be detected, for example, by the ratio between the RSSI value when the master device 20 receives a wireless signal from the slave device 30A and the RSSI value when the master device 20 does not receive a wireless signal. Instead of PER, the master device 20 may detect a bit error rate (BER) or a packet arrival rate (PAR). The master unit 20 saves and accumulates the detected RSSI or SNR / SINR, PER, BER, or PAR for each communication channel. Note that, in addition to or instead of the master unit 20 detecting the communication quality data as described above, the slave unit 30A can also obtain the communication quality data by detecting the RSSI, PER, etc. when receiving a signal from the master unit 20 and transmitting the detected data to the master unit 20.

[0061] In step S270, the master device 20 determines a degradation in the communication quality of the communication channel used for wireless communication with the slave device 30A based on the communication quality data of the communication channel detected in step S260. The master device 20 then deletes the communication channel whose communication quality has been determined to have degraded from the communication channels used for wireless communication between the master device 20 and the slave device 30A. The deleted communication channel is a data communication channel. For example, one condition for determining a degradation in communication quality is that the RSSI is compared with an RSSI threshold and the PER is compared with a PER threshold, and as a result, at least one of the RSSI and the PER does not satisfy the threshold. Note that only one type of parameter may be compared with the threshold. The parameter compared with the threshold may be the most recent parameter detected in step S260, or may be an average value or a median value of a predetermined number of parameters detected in multiple past wireless communications using the same communication channel.

[0062] In step S280, the master device 20 executes a restoration determination for the communication channel deleted in the deletion determination performed during the previous communication event. If a predetermined restoration condition is satisfied in this restoration determination, the deleted communication channel is restored as a communication channel to be used for wireless communication. For example, as an example of the predetermined restoration condition, the deleted communication channel may be restored when a predetermined time has elapsed since the communication channel was deleted. Alternatively, as another example of the predetermined restoration condition, the deleted communication channel may be restored as a communication channel to be used for wireless communication when a communication channel adjacent to the deleted communication channel exhibits good communication quality. In this way, a communication channel determined to be restoreable as a communication channel to be used for wireless communication is incorporated into the channel map and is actually used in wireless communication between the master device 20 and the slave device 30A. The deletion determination process in step S270 and the restoration determination process in step S280 correspond to the channel map control process in the present disclosure. Note that a communication channel determined to be restored may again be subject to deletion by a deletion determination if its communication quality remains degraded when actually used for wireless communication.

[0063] In step S290, the master device 20 performs a channel map creation process based on the deletion determination result in step S270 and the restoration determination result in step S280. This channel map creation process will be described in detail later.

[0064] Here, 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 the available / unavailable communication channels, the frequency channel hopping pattern may be updated. If the frequency channel hopping pattern is not updated, for example, if the communication channel to be hopped is unavailable, the next communication channel to be hopped may be used.

[0065] The deletion determination process and the return determination process described above may be performed each time communication is performed between the master device 20 and the slave device 30A. Alternatively, the deletion determination process and the return determination process may be performed all at once in accordance with the channel map update period, which is updated at a predetermined interval, i.e., each time multiple communications are performed between the master device 20 and the slave device 30A. In this case, each time communication is performed between the master device 20 and the slave device 30A, characteristic data indicating the communication quality of the communication channel used for the communication is detected and accumulated in step S260. Then, based on the accumulated characteristic data, the deletion determination in step S270 and the return determination in step S280 are performed all at once, for example, before the start of the channel map update period shown in the time chart of FIG. 7. Similarly, the channel map creation process in step S290 may also be performed each time communication is performed between the master device 20 and the slave device 30A. Alternatively, the channel map creation process may be performed in accordance with the channel map update period, before the start of a new channel map update period, so that the channel map creation process can be transmitted to the slave device 30A during the new channel map update period.

[0066] In step S300, the master unit 20 transmits the channel map created by the channel map creation process in step S290 to the slave unit 30A. At this time, the master unit 20 also transmits information indicating the timing to start using the channel map along with the channel map. The timing to start using the channel map occurs every time a channel map update period has elapsed. In other words, the timing to start using the channel map is determined based on the channel map update period. Furthermore, as will be described later, the channel map created by the channel map creation process is also updated every time a channel map update period has elapsed.

[0067] In step S440, the slave device 30A receives the new channel map and timing information transmitted from the master device 20. Upon receiving the new channel map and timing information in step S440, the slave device 30A performs a checksum check based on the error detection code included in the received packet to confirm whether the new channel map and timing information were received correctly in step S450. If the slave device 30A determines based on the checksum check result in step S450 that the new channel map and timing information were not received correctly, for example, the slave device 30A does not transmit an acknowledgment signal (ACK signal) for the new channel map in step S460. On the other hand, if the slave device 30A determines in step S450 that the new channel map and timing information were received correctly, the slave device 30A returns an acknowledgment signal (ACK signal) for the new channel map to the master device 20 in step S460.

[0068] In step S310, the master device 20 receives an ACK signal from the slave device 30A. In step S320, the master device 20 performs, for example, a checksum check based on the error detection code included in the received ACK signal to confirm whether the ACK signal was received correctly. If the master device 20 fails to receive the ACK signal, the checksum check results in NG. In the following step S330, the master device 20 determines whether to retransmit the new channel map and timing information within the same communication event, depending on whether the checksum check results in step S320 were OK or NG. More specifically, if the checksum check results in OK, or if the checksum check results in NG but there is not enough time to retransmit in the current communication event, the master device 20 determines not to retransmit within the same communication event and terminates the processing shown in the flowchart of FIG. 5. On the other hand, if the checksum result is NG and there is enough time to retransmit, the master device 20 returns to step S300 and retransmits the new channel map and timing information. Note that if the checksum result is OK and the master device 20 and slave device 30A have successfully shared the new channel map and timing information, the master device 20 does not need to transmit the new channel map and timing information in subsequent communication events until the channel map update period expires.

[0069] Next, the channel map creation process will be described with reference to the flowchart of Fig. 8. Fig. 8 is a flowchart showing an example of the channel map creation process executed by the master device 20 (or the control device 1).

[0070] Here, when the master device 20 performs wireless communication with multiple slave devices 30A, 30B, 40A, and 50A, it is conceivable to extract common communication channels from the communication channels available to each of the slave devices 30A, 30B, 40A, and 50A and create a common channel map for each of the slave devices 30A, 30B, 40A, and 50A. Creating such a common channel map simplifies various channel map-related processes, such as updating, saving, and transmitting the channel map, that are required for wireless communication with each of the multiple slave devices 30A, 30B, 40A, and 50A. However, if the master device 20 simply creates a common channel map for the multiple slave devices 30A, 30B, 40A, and 50A with which the master device 20 performs wireless communication, it may be difficult to ensure a sufficient number of communication channels available for wireless communication, for example, when the number of communication channels common to each of the slave devices 30A, 30B, 40A, and 50A is small.

[0071] 9 shows an example in which three slave devices S_A1 to S_A3, S_B1 to S_B3, and S_C1 to S_C3 are associated with vehicle application A, vehicle application B, and vehicle application C, respectively, and the master device 20 communicates with a total of nine slave devices S_A1 to S_A3, S_B1 to S_B3, and S_C1 to S_C3. In the table of FIG. 9, communication channels available for wireless communication by each of the slave devices S_A1 to S_A3, S_B1 to S_B3, and S_C1 to S_C3 are indicated by "1," and unusable communication channels are indicated by "0." Furthermore, the common channel map shows the result of an AND operation between "1" indicating an available communication channel for each of the slave devices S_A1 to S_A3, S_B1 to S_B3, and S_C1 to S_C3 and "0" indicating an unusable communication channel. In other words, the common channel map indicates communication channels that can be used by all slave devices S_A1 to S_A3, S_B1 to S_B3, and S_C1 to S_C3. As shown in the example of Figure 9, if master device 20 simply created a common channel map for all slave devices S_A1 to S_A3, S_B1 to S_B3, and S_C1 to S_C3, there is a possibility that the number of common communication channels that can be used for communication will be zero.

[0072] Therefore, in this embodiment, as described above, the multiple slave devices 30A, 30B, 40A, and 50A are grouped by vehicle application, and a common channel map is created for each group. As a result, for example, when three slave devices S_A1 to S_A3, S_B1 to S_B3, and S_C1 to S_C3 are associated with vehicle application A, vehicle application B, and vehicle application C, respectively, as shown in the table of FIG. 10 , a common channel map for vehicle application A, a common channel map for vehicle application B, and a common channel map for vehicle application C are created. Because a common channel map is created for each group in this way, each common channel map can ensure a sufficient number of communication channels available for communication.

[0073] Therefore, according to this embodiment, it is possible to prevent a situation in which a sufficient number of communication channels cannot be secured for multiple slave devices 30A, 30B, 40A, and 50A while using a common channel map.

[0074] In the first step S510 of the flowchart in Figure 8, the master device 20 determines whether it is time to create a common channel map for the slave device 30A with which it has communicated. For example, the timing for creating the common channel map is set to the timing immediately before the start of a new channel map update period in the time chart of Figure 7. This allows the created common channel map to be transmitted from the master device 20 to the slave device 30A during the new channel map update period, making it possible for the common channel map to be shared between the master device 20 and the slave device 30A.

[0075] The length and / or phase of the channel map update period may be different for at least two groups. When the length and / or phase of the channel map update period are different for at least two groups, the timing of creating the common channel map may also be different for each group.

[0076] In step S520, the master device 20 identifies a group for which a common channel map is to be created. For example, the master device 20 can identify the group to which the slave device 30A belongs based on the identification information and / or group information received from the slave device 30A with which it has wireless communication, thereby identifying the group for which a common channel map is to be created. In step S530, the master device 20 selects each of the slave devices 30A, 30B, 40A, and 50A that belong to the identified group, for example, by referring to a list, and reads out channels available for communication for each of the selected slave devices 30A, 30B, 40A, and 50A. In step S540, the master device 20 extracts common communication channels, which are common communication channels, from the read communication channels available for each of the slave devices 30A, 30B, 40A, and 50A. Then, in step S550, the master device 20 creates a common channel map from the extracted common communication channels.

[0077] In this way, a new common channel map is created for each group every time a channel map update period elapses. The created common channel map is transmitted to the slave device 30A in step S300 of the flowchart of FIG. 5 described above, at least until the common channel map is successfully shared, during the channel map update period during which the current common channel map is applied, as shown in the time chart of FIG. 7 . Then, upon the start of a new channel map update period, the master device 20 and the slave device 30A switch the common channel map to be used in the next update period to the successfully shared common channel map. As a result, as shown in the time chart of FIG. 7 , wireless communication between the master device 20 and the slave device 30A is performed using the successfully shared new common channel map in the next update period. By periodically updating the common channel map in this way, the master device 20 and the slave device 30A can perform high-quality communication using a common channel map that adapts to changes in the communication quality of each communication channel.

[0078] Second Embodiment Next, a wireless communication system 10 according to a second embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to 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.

[0079] In the wireless communication system 10 according to the first embodiment, multiple slave devices 30A, 30B, 40A, and 50A are grouped for each vehicle application, and a common channel map is created for each group. However, the required communication quality may vary depending on the vehicle application. For example, in a tire pressure monitoring system, the tire pressure monitored changes only slightly over time, so even if several communication errors occur in a short period of time during wireless communication by the wireless communication system 10, this does not pose a significant problem. Furthermore, even if a vehicle application is implemented as an entertainment system that connects a mobile device brought by a vehicle occupant to an in-vehicle system to play music, videos, and the like stored on the mobile device, the communication quality of the wireless communication does not need to be high because this does not directly affect vehicle control.

[0080] On the other hand, for example, the changes in the state of a battery (such as voltage or temperature) over time that are the target of a battery management system are greater than the changes in tire pressure over time, etc. Therefore, when the wireless communication system 10 is applied to a battery management system, it is desirable to minimize the occurrence of communication errors.

[0081] Therefore, in this embodiment, the wireless communication system 10 is configured to exclude slave devices from being subject to channel map updates at each update period to ensure communication quality, or to use different criteria for determining communication channels to be used for wireless communication, depending on the group corresponding to the vehicle application. For example, by excluding slave devices belonging to one group from being subject to channel map updates, the processing load for executing channel map control in the master unit 20 or the control unit 1 can be reduced. Furthermore, for example, by relaxing the criteria for deleting communication channels for vehicle applications that do not require strict communication quality, wireless communication can be performed using more communication channels.

[0082] The following describes the wireless communication system 10 according to this embodiment, focusing on differences from the wireless communication system 10 according to the first embodiment. The wireless communication system 10 according to this embodiment and the wireless communication system 10 according to the first embodiment differ mainly in the processing in the communication sequence.

[0083] Fig. 11 is a flowchart showing an example of a communication sequence of the wireless communication system 10 according to this embodiment. The flowchart of Fig. 11 includes step S255 in addition to the flowchart of Fig. 5. Furthermore, the flowchart of Fig. 11 includes step S275 instead of step S270 of the flowchart of Fig. 5.

[0084] In step S255, the master device 20 determines whether the slave devices 30A, 30B, 40A, and 50A that have communicated belong to a non-target group that is excluded from the channel map update targets. If the slave device belongs to a non-target group, the master device 20 does not perform the processes from step S260 onward and ends the communication sequence shown in the flowchart of FIG. 11. Therefore, for slave devices that belong to a non-target group, the determination of a communication channel to be used for wireless communication by deleting and restoring a communication channel and the creation of a common channel map in steps S275 and S280 are not performed. Slave devices that belong to a non-target group can continue to communicate with the master device 20 using the initial common channel map exchanged as part of the connection information in the startup sequence.

[0085] Whether or not to exclude each slave device belonging to a predetermined group from the channel map update target may be determined based on the communication quality of each slave device belonging to the predetermined group. For example, if the communication quality data of each slave device belonging to the predetermined group all exceeds a predetermined standard, it can be determined that the quality of wireless communication between the master device 20 and each slave device belonging to the predetermined group is maintained at a good level. In such a case, each slave device belonging to the predetermined group may be excluded from the channel map update target. However, in this case, since it is necessary to acquire communication quality data for each slave device, it is necessary to execute at least step S260 of the flowchart in FIG. 11 and processes for determining communication quality, such as steps S275 and S280. Then, if any of the communication quality data of each slave device belonging to the predetermined group deteriorates, that slave device may be restored to the channel map update target. Alternatively, at least one predetermined slave device belonging to the predetermined group may be excluded from the channel map update target. In this case, a common channel map for the predetermined group is created from the communication-available channels of the remaining slave devices excluding the at least one predetermined slave device. In other words, the communication-available channels of the at least one predetermined slave device are excluded from the calculation target for creating the common channel map. In this case, when a common channel map for a specified group is created and updated, at least one specified slave device also belongs to the specified group, and therefore may use the updated common channel map to perform wireless communication with the master device 20.

[0086] In step S275, the master device 20 determines a degradation in the communication quality of the communication channel used for wireless communication with the slave device 30A based on the communication channel communication quality data detected in step S260, similar to step S270 in the flowchart of FIG. 5 . The master device 20 then deletes the communication channel for which the communication quality is determined to have degraded from the communication channels used for wireless communication between the master device 20 and the slave device 30A. However, in step S275, the master device 20 determines a degradation in communication quality based on a determination criterion corresponding to the group to which the communicating slave device 30A belongs. When high communication quality is required, the determination criterion is set strict. For example, when determining communication quality based on RSSI, the threshold as the determination criterion is set relatively high, and when determining communication quality based on PER, the threshold as the determination criterion is set relatively low. Conversely, when high communication quality is not required, the determination criterion is relaxed. For example, when determining communication quality based on RSSI, the threshold as the determination criterion is set relatively low, and when determining communication quality based on PER, the threshold as the determination criterion is set relatively high. This makes it possible to determine whether or not a communication channel needs to be deleted depending on the required level of communication quality.

[0087] 11 only shows that the criteria for determining whether to delete a communication channel are determined according to the group to which the corresponding slave device belongs. However, the criteria for determining whether to restore a communication channel in step S280 may also be determined according to the group to which the corresponding slave device belongs. For example, if high communication quality is required, a longer wait time before restoring a deleted communication channel may be set as the restoration determination criterion. Alternatively, if the determination of whether to restore a deleted communication channel is based on the communication quality of an adjacent channel, restoration may be permitted when the communication quality of the adjacent channel meets a higher determination criterion.

[0088] Third Embodiment Next, a wireless communication system 10 according to a third embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment has the same configuration as the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0089] In the wireless communication system 10 according to the first embodiment described above, the slave devices 30A, 30B, 40A, and 50A are grouped according to vehicle applications. FIG. 12 shows an example of the arrangement of the slave devices S_A1 to S_A5, S_B1 to S_B4, and S_C1 in the vehicle 100, which are grouped according to vehicle applications. In FIG. 12, the slave devices S_A1 to S_A5 are associated with a smart key system. The slave devices S_B1 to S_B4 are associated with a tire pressure monitoring system. In the example shown in FIG. 12, the slave device S_C1 of the mobile device carried by the occupant is grouped into one group.

[0090] When a group is formed for each vehicle application, the corresponding slave devices S_A1 to S_A5, S_B1 to S_B4, and S_C1 may be arranged over a wide area, as shown in Fig. 12. In this case, it is possible that the communication environments (e.g., the effects of vibration and noise) of the individual slave devices S_A1 to S_A5 and S_B1 to S_B4 belonging to the same group may differ. For this reason, when a group is formed for each vehicle application, if a slave device with a poor communication environment is included, this may result in a decrease in the number of communication channels included in the common channel map.

[0091] In contrast, in this embodiment, as shown in Fig. 13, multiple slave devices S_A1 to S_A2, S_B1 to S_B2, S_C1 to S_C2, S_D1 to S_D2, S_E1, and S_F1 are grouped into multiple areas defined so that any one of the areas includes the locations of multiple slave devices S_A1 to S_A2, S_B1 to S_B2, S_C1 to S_C2, S_D1 to S_D2, S_E1, and S_F1 that communicate wirelessly with master device 20, based on the installation location of master device 20. In the example shown in Fig. 13, six areas are defined so that slave devices S_A1 to S_A2, slave devices S_B1 to S_B2, slave devices S_C1 to S_C2, slave devices S_D1 to S_D2, slave device S_E1, and slave device S_F1 each form a group.

[0092] In this way, by setting multiple areas based on the position of master device 20 and grouping the slave devices S_A1 to S_A2, S_B1 to S_B2, S_C1 to S_C2, S_D1 to S_D2, S_E1, and S_F1 included in those areas, it is possible to group the slave devices S_A1 to S_A2, S_B1 to S_B2, S_C1 to S_C2, S_D1 to S_D2, S_E1, and S_F1 that have similar communication environments.

[0093] In this embodiment, slave devices belonging to at least one of the multiple groups may be excluded from targets for updating the channel map to ensure communication quality. For example, if the communication quality data of the slave devices belonging to at least one of the multiple groups exceeds a predetermined standard, it can be determined that the quality of wireless communication between the master device 20 and the slave devices belonging to that group is maintained at a good level. In such a case, the slave devices belonging to that group may be excluded from targets for updating the channel map. However, in this case, since communication quality data of each slave device must be obtained, it is necessary to execute at least step S260 of the flowchart in FIG. 11 and processes for determining communication quality, such as steps S275 and S280.

[0094] 13 shows an example in which a plurality of relatively small areas are defined around the master unit 20 based on the installation position of the master unit 20. However, the way in which the areas are defined is not limited to the example shown in Fig. 13. For example, as shown in Fig. 14, an in-vehicle area, an in-vehicle area, and an out-vehicle area may be defined based on the installation position of the master unit 20, and the slave units S_A1, S_B1 to S_B8, and S_C1 included in each area may be grouped.

[0095] Fourth Embodiment Next, a wireless communication system 10 according to a fourth embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment 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.

[0096] In the wireless communication system 10 according to the third embodiment described above, a plurality of areas are defined and the slave devices belonging to each area are grouped based on the installation position of the master device 20. In contrast, in the wireless communication system 10 according to the present embodiment, the master device 20 is provided with a plurality of antennas, a plurality of areas are defined based on the installation positions of the plurality of antennas, and the slave devices belonging to each area are grouped.

[0097] 15 , the master unit 20 has a plurality of antennas 23A-23E for wireless communication with a plurality of slave units S_A1-S_A2, S_B1-S_B2, S_C1, S_D1-S_D2, and S_E1-S_E3. The plurality of antennas 23A-23E are installed at different positions on the vehicle 100. The plurality of slave units S_A1-S_A2, S_B1-S_B2, S_C1, S_D1-S_D2, and S_E1-S_E3 are grouped into a plurality of areas defined based on the installation positions of the plurality of antennas 23A-23E, so as to include in any one of the areas the positions of the plurality of slave units S_A1-S_A2, S_B1-S_B2, S_C1, S_D1-S_D2, and S_E1-S_E3 that communicate wirelessly with the master unit 20.

[0098] Therefore, in the wireless communication system 10 according to this embodiment, as in the third embodiment, it is possible to group the slave devices S_A1 to S_A2, S_B1 to S_B2, S_C1, S_D1 to S_D2, and S_E1 to S_E3 that have similar communication environments.

[0099] Fifth Embodiment Next, a wireless communication system 10 according to a fifth embodiment of the present disclosure will be described with reference to the drawings. The wireless communication system 10 according to this embodiment has the same configuration as the wireless communication system 10 according to the first embodiment, and therefore a description of the configuration will be omitted.

[0100] In the first embodiment described above, the slave devices associated with each vehicle application are grouped. Furthermore, in the third and fourth embodiments, a plurality of areas are defined based on the installation positions of the master device 20 or the plurality of antennas 23A to 23E, and the slave devices belonging to each area are grouped. However, the grouping method is not limited to the above-described method. For example, fixed slave devices installed in fixed locations and mobile slave devices that can be moved may be grouped in different groups.

[0101] Hereinafter, as the fifth embodiment, several examples will be described in which fixed slave devices and mobile slave devices are grouped into different groups.

[0102] FIG. 16 shows a wireless communication system 10 related to a smart key system as an example of this embodiment. In the example shown in FIG. 16, a master unit 20 and four slave units S_A1 to S_A4 are installed at predetermined fixed positions in a vehicle 100. That is, the four slave units S_A1 to S_A4 are fixed slave units. One slave unit S_B1 is mounted on an electronic key held by an occupant of the vehicle 100. That is, the single slave unit S_B1 is a mobile slave unit. Note that when multiple electronic keys are present within a range capable of communicating with the master unit 20, the multiple slave units mounted on the multiple electronic keys may be grouped together. Alternatively, the multiple slave units mounted on the multiple electronic keys may be grouped together as separate groups.

[0103] The communication environment of a fixed slave device is considered to change less over time than the communication environment of a mobile slave device. Therefore, as described above, by grouping the fixed slave devices and the mobile slave devices into different groups, it is possible to create and update a channel map appropriate for each group.

[0104] FIG. 17 shows a wireless communication system 10 related to a battery management system as another example of this embodiment. In the example shown in FIG. 17, a vehicle 100 is equipped with three battery stacks A to C that constitute a battery pack. The three battery stacks A to C are housed in separate housings. Slave devices S_A1 to S_A3 are installed in the housings of the three battery stacks A to C, respectively. In other words, the slave devices S_A1 to S_A3 are fixed slave devices. A master device 20 is installed in the housing of battery stack A. The master device 20 has multiple antennas. The multiple antennas are installed inside the housing of battery stack A, outside the housing of battery stack A, inside the housing of battery stack B, and inside the housing of battery stack C. This allows the master device 20 to perform wireless communication with the slave devices S_A1 to S_A3 arranged in each housing under approximately the same conditions.

[0105] The battery management system uses a wireless device of a mobile device (e.g., a smartphone) carried by an occupant of the vehicle 100 as a slave device S_B1. The mobile device has a function of receiving and displaying information about the battery status (e.g., charge level and temperature) through wireless communication between the master device 20 and the slave device S_B1. The slave device S_B1 of the mobile device corresponds to a mobile slave device.

[0106] As shown in Fig. 17, the slave devices S_A1 to S_A3, which are fixed slave devices, and the slave device S_B1, which is a mobile slave device, are grouped into different groups. As a result, a channel map suitable for each group can be created and updated, just like the example shown in Fig. 16.

[0107] 16 and 17, slave device S_B1, which is a mobile slave device, may be excluded from the targets for periodically updating the channel map. Furthermore, when mobile slave device S_B1 performs wireless communication with master device 20, mobile slave device S_B1 may function as the master device, and master device 20 may function as the slave device.

[0108] The configuration of the wireless communication system 10 for the battery management system shown in FIG. 17 can be implemented in various modifications. For example, as shown in FIG. 18, the battery stacks A to C constituting the battery pack may be housed in a common housing rather than in individual housings. Furthermore, a wireless device 25 functioning as a master device and disposed in the housing may also be configured to function as a slave device. In this case, the wireless device 25 functions as a master device when communicating wirelessly with the slave devices S_A1 to S_A3 disposed in the housing of the battery pack, and as a slave device when communicating wirelessly with the master device 20 separately provided in the vehicle 100. That is, in this case, the wireless device 25 functions as a relay device in communication between the master device 20 and each of the slave devices S_A1 to S_A3 connected to the monitoring device of each battery stack housed in the housing.

[0109] 18, the master device 20 does not need to communicate individually with each of the slave devices S_A1 to S_A3 connected to the monitoring device of each battery pack, and can obtain information about the battery stack included in each battery pack and control the state of the battery stack by communicating only with the wireless device 25 that acts as a relay device. Furthermore, if the battery performance of a battery pack deteriorates due to aging, the battery pack can be easily replaced.

[0110] Note that communication between the wireless device 25 and each of the slave devices S_A1 to S_A3 in the battery pack may be wired communication instead of wireless communication, as shown in Fig. 19. In this case, the wireless device 25 only needs to have the function of a slave device that communicates wirelessly with the master device 20.

[0111] Alternatively, as shown in Fig. 20, the wireless device of the mobile device may function as the master device, and wireless device 25 disposed inside the battery pack housing may function as the slave device. Furthermore, as described above, the wireless device of the mobile device, which is a mobile slave device, may function as the master device, and master device 20 may function as the slave device, and the wireless device of the mobile device may communicate wirelessly with master device 20.

[0112] Sixth Embodiment Next, a wireless communication system 10 according to a sixth 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.

[0113] In this embodiment, a method for grouping multiple slave devices 30A, 30B, 40A, and 50A into multiple groups using a method different from the above-described embodiments will be described. The grouping method according to this embodiment does not pre-group the slave devices 30A, 30B, 40A, and 50A into multiple groups based on the application, area, whether the devices are fixed or mobile, etc. Instead, the grouping method dynamically groups the multiple slave devices 30A, 30B, 40A, and 50A based on the communication channels used for wireless communication determined for each slave device 30A, 30B, 40A, and 50A so that the number of common communication channels is equal to or greater than a predetermined threshold. Therefore, in this embodiment, it can be said that slave devices with similar communication environments are grouped together based on the number of common communication channels available. Note that the slave devices belonging to each group may or may not change over time. FIG. 21 is a flowchart illustrating the grouping method according to this embodiment.

[0114] In the first step S610, the master device 20 selects any one slave device (e.g., slave device 30A) to be grouped. In step S620, the master device 20 determines whether one or more groups have already been formed. If no groups have been formed in this determination process, the master device 20 proceeds to step S630. On the other hand, if one or more groups have been formed, the master device 20 proceeds to step S640.

[0115] In step S630, the master device 20 selects any slave device (e.g., slave device 30B) other than the one slave device (e.g., slave device 30A) to be grouped, and sets up one group including the selected slave device (e.g., slave device 30B).

[0116] In step S640, the master device 20 determines the common communication channels that will be used when the selected slave device to be grouped (e.g., slave device 30A) is grouped into an existing group based on the communication channels of the selected slave device to be grouped (e.g., slave device 30A) and the common communication channels of the existing groups, and calculates the number of common communication channels. The common communication channels of a group refer to communication channels that are common to all of the slave devices belonging to that group. Furthermore, if there are multiple existing groups, in step S640, the master device 20 determines the common communication channels that will be used when the selected slave device to be grouped (e.g., slave device 30A) is grouped into the existing groups, and calculates the number of common communication channels. Furthermore, if one group is set in step S630, in step S640, the master device 20 sets the communication channels of the slave device (e.g., slave device 30B) included in the set group as the common communication channels of the group.

[0117] In step S650, the master device 20 determines whether or not there is a group for which the number of available common communication channels calculated in step S640 is equal to or greater than a threshold. If there is no group for which the number of available common communication channels is equal to or greater than the threshold, the master device 20 proceeds to step S660. On the other hand, if there is a group for which the number of available common communication channels is equal to or greater than the threshold, the master device 20 proceeds to step S670.

[0118] In step S660, if the slave device to be grouped (e.g., slave device 30A) is grouped into an existing group, the number of available common communication channels will fall below the threshold. Therefore, the master device 20 sets a new group and groups the slave device to be grouped (e.g., slave device 30A) into the new group. Meanwhile, in step S670, the master device 20 determines whether there are multiple groups whose number of available common communication channels is equal to or greater than the threshold. If there is not multiple groups whose number of available common communication channels is equal to or greater than the threshold, i.e., if there is only one group whose number of available common communication channels is equal to or greater than the threshold, the master device 20 proceeds to step S680. On the other hand, if there are multiple groups whose number of available common communication channels is equal to or greater than the threshold, the master device 20 proceeds to step S690.

[0119] In step S680, the master device 20 groups the slave devices (e.g., slave device 30A) to be grouped into groups whose number of available common communication channels is equal to or greater than the threshold. Meanwhile, in step S690, the master device 20 determines whether the number of available common communication channels is the same for multiple groups whose number of available common communication channels is equal to or greater than the threshold. If the numbers of available common communication channels are different, the master device 20 proceeds to step S700. On the other hand, if the numbers of available common communication channels are the same, the master device 20 proceeds to step S710.

[0120] In step S700, the master device 20 selects the group with the larger number of common communication channels and groups the slave device to be grouped (e.g., slave device 30A) into the selected group. On the other hand, in step S710, the master device 20 selects the group with the smallest number of slave devices from among multiple groups with the same number of common communication channels. If the numbers of slave devices are also the same, either group may be selected. In step S720, the master device 20 groups the slave device to be grouped (e.g., slave device 30A) into the selected group.

[0121] In step S730, the master device 20 determines whether grouping of all slave devices has been completed. If grouping of all slave devices has not been completed, the master device 20 repeats the process from step S610. If grouping of all slave devices has been completed, the master device 20 ends the grouping process shown in FIG. 21.

[0122] In this sixth embodiment, slave devices belonging to at least one of the groups may be excluded from the channel map update. For example, if the number of common communication channels is equal to or greater than the exclusion threshold, the number of channels available for communication is large, and the communication quality of each slave device belonging to that group can be considered to be at a high level. In other words, the communication quality level of each slave device can be determined from the number of channels available for communication. In such a case, slave devices belonging to that group may be excluded from the channel map update.

[0123] 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.

[0124] For example, the features described in each of the above-described embodiments can be implemented in combination with the features described in other embodiments, unless it is technically impossible to combine them.

[0125] 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.

[0126] (Technical Idea 1) A wireless communication system in which at least one master device (20) and multiple slave devices (30) perform wireless communication via one communication channel sequentially selected from multiple communication channels, comprising: a grouping unit (S50) that groups the multiple slave devices into two or more groups; a communication channel determination unit (S270, S280) that, when the master device communicates wirelessly with each of the multiple slave devices, determines the communication quality of each communication channel for the slave devices belonging to at least one group grouped by the grouping unit and determines a communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; and a creation unit (S290) that creates a common channel map by extracting a common communication channel that is a communication channel common to the slave devices belonging to the at least one group based on the communication channel to be used for wireless communication determined by the communication channel determination unit for the slave devices belonging to the at least one group grouped by the grouping unit, A wireless communication system in which the master device and the slave devices grouped into at least one group perform wireless communication via a communication channel selected from common communication channels indicated by the common channel map created by the creation unit.

[0127] (Technical Idea 2) The creation unit periodically updates the common channel map by repeatedly creating the common channel map over time, and the slave devices that belong to at least one other group other than the at least one group grouped by the grouping unit are excluded from the periodic updating of the common channel map, in the wireless communication system described in Technical Idea 1.

[0128] (Technical Idea 3) The slave devices each belonging to two or more groups grouped by the grouping unit are the targets for determining a communication channel to be used for wireless communication by the communication channel determination unit, and the communication channel determination unit determines a communication channel to be used for wireless communication for the slave devices each belonging to the two or more groups using a different judgment criterion for each group. This is a wireless communication system described in Technical Idea 1.

[0129] (Technical Idea 4) A wireless communication system according to any one of Technical Ideas 1 to 3, wherein each of the plurality of slave devices is associated with one of the plurality of applications so as to perform wireless communication with the master device for executing one of the applications, and the grouping unit groups the slave devices associated with each of the plurality of applications for each of the plurality of applications.

[0130] (Technical Idea 5) The wireless communication system according to Technical Idea 1 or 2, wherein the grouping unit groups the plurality of slave devices into a plurality of areas defined based on the installation position of the master device, such that any one of the areas includes the placement positions of the plurality of slave devices that perform wireless communication with the master device.

[0131] (Technical Concept 6) The wireless communication system according to Technical Concept 5, wherein the master device is mounted in a vehicle, and the plurality of areas are divided into a vehicle interior area, a vehicle interior area, and an exterior area of ​​the vehicle.

[0132] (Technical Idea 7) A wireless communication system according to Technical Idea 1 or 2, wherein the master device has a plurality of antennas for wireless communication with the plurality of slave devices, the plurality of antennas being installed at different positions, and the grouping unit groups the plurality of slave devices into a plurality of areas defined based on the installation positions of the plurality of antennas, the areas being defined so that any one of the areas includes the placement positions of the plurality of slave devices that perform wireless communication with the master device.

[0133] (Technical Idea 8) The wireless communication system according to any one of Technical Ideas 1 to 7, wherein the plurality of slave devices include fixed slave devices that are installed at fixed positions and mobile slave devices that are movable, and the grouping unit groups the plurality of slave devices such that the fixed slave devices and the mobile slave devices are in different groups.

[0134] (Technical Idea 9) The wireless communication system according to Technical Idea 8, wherein the mobile slave devices grouped in a different group from the fixed slave devices are excluded from the targets of periodic updating of the common channel map.

[0135] (Technical Idea 10) The wireless communication system according to Technical Idea 8 or 9, wherein the mobile slave device is an electronic device carried by a user, and when the mobile slave device and the master device perform wireless communication, the mobile slave device functions as the master device, and the master device functions as the slave device.

[0136] (Technical Idea 11) A wireless communication system described in any one of Technical Ideas 1 to 10, wherein the multiple slave devices have identification information for identifying each of the slave devices and transmit the identification information in wireless communication with the master device, the master device has a list that associates the identification information with information on the group to which the slave device belongs, and the grouping unit groups the multiple slave devices in accordance with the list based on the identification information wirelessly transmitted from each of the multiple slave devices to the master device.

[0137] (Technical Idea 12) A wireless communication system described in any one of Technical Ideas 1 to 10, wherein the multiple slave devices have identification information for identifying each of the slave devices and group information indicating the group to which they belong, and transmit the identification information and the group information in wireless communication with the master device, and the grouping unit groups the multiple slave devices based on the identification information and the group information wirelessly transmitted from each of the multiple slave devices to the master device.

[0138] (Technical Idea 13) The wireless communication system according to Technical Idea 1 or 2, wherein the grouping unit groups the plurality of slave devices based on the communication channels to be used for wireless communication determined for each slave device by the communication channel determination unit so that the number of common communication channels is equal to or greater than a predetermined threshold.

[0139] (Technical Idea 14) A wireless communication system according to Technical Idea 13, wherein the grouping unit determines a common communication channel when the slave devices to be grouped are grouped into at least one existing group based on the communication channel used for wireless communication of the slave devices to be grouped and a common communication channel in at least one existing group, and if the number of determined common communication channels is equal to or greater than the predetermined threshold, groups the slave devices to be grouped into the existing group, and if the number is less than the predetermined threshold, groups the slave devices to be grouped into a new group.

[0140] (Technical Idea 15) A wireless communication system according to Technical Idea 13 or 14, wherein the grouping unit determines a common communication channel when the slave devices to be grouped are grouped into at least one existing group based on the communication channel used for wireless communication of the slave devices to be grouped and the common communication channel in at least one existing group, and when there are multiple existing groups in which the number of determined common communication channels is equal to or greater than the predetermined threshold, groups the slave devices to be grouped into the existing group in which the number of determined common communication channels is the largest.

[0141] (Technical Idea 16) A wireless communication system according to any one of Technical Ideas 13 to 15, wherein the grouping unit determines a common communication channel when the slave devices to be grouped are grouped into at least one existing group based on a communication channel used for wireless communication of the slave devices to be grouped and a common communication channel in at least one existing group, and if there are multiple existing groups in which the number of determined common communication channels is equal to or greater than the predetermined threshold and the numbers of determined common communication channels are the same for the multiple existing groups, the grouping unit groups the slave devices to be grouped into the existing group containing the fewer slave devices.

Claims

1. A wireless communication system in which at least one master device (20) and multiple slave devices (30) perform wireless communication via one communication channel selected sequentially from multiple communication channels, comprising: a grouping unit (S50) that groups the multiple slave devices into two or more groups; a communication channel determination unit (S270, S280) that, when the master device wirelessly communicates with each of the multiple slave devices, determines the communication quality of each communication channel for the slave devices belonging to at least one of the groups grouped by the grouping unit and determines a communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel; and a creation unit (S290) that extracts a common communication channel that is a communication channel common to the slave devices belonging to the at least one group grouped by the grouping unit based on the communication channel to be used for wireless communication determined by the communication channel determination unit for the slave devices belonging to the at least one group grouped by the grouping unit, and creates a common channel map; A wireless communication system in which the master device and the slave devices grouped into at least one group perform wireless communication via a communication channel selected from common communication channels indicated by a common channel map created by the creation unit.

2. The wireless communication system described in claim 1, wherein the creation unit periodically updates the common channel map by repeatedly creating the common channel map over time, and the slave devices belonging to at least one other group other than the at least one group grouped by the grouping unit are excluded from the periodic updating of the common channel map.

3. The wireless communication system according to claim 1, wherein the slave devices each belonging to two or more groups grouped by the grouping unit are used to determine a communication channel to be used for wireless communication by the communication channel determination unit, and the communication channel determination unit determines a communication channel to be used for wireless communication for the slave devices each belonging to the two or more groups using different judgment criteria for each group.

4. A wireless communication system as described in any one of claims 1 to 3, wherein each of the plurality of slave devices is associated with one of the plurality of applications so as to perform wireless communication with the master device for executing one of the plurality of applications, and the grouping unit groups the slave devices associated with each of the plurality of applications for each of the plurality of applications.

5. A wireless communication system as described in claim 1 or 2, wherein the grouping unit groups the slave devices into a number of areas defined based on the installation position of the master device so that any one of the areas includes the placement positions of the slave devices that perform wireless communication with the master device.

6. The wireless communication system according to claim 5, wherein the master device is mounted in a vehicle, and the plurality of areas are divided into an in-vehicle area, an in-vehicle area, and an outside-vehicle area.

7. A wireless communication system as described in claim 1 or 2, wherein the master device has a plurality of antennas for wireless communication with the plurality of slave devices, the plurality of antennas being installed at different positions, and the grouping unit groups the plurality of slave devices into a plurality of areas defined based on the installation positions of the plurality of antennas, the areas including the positions of the plurality of slave devices that perform wireless communication with the master device.

8. A wireless communication system as described in claim 1 or 2, wherein the plurality of slave devices include fixed slave devices that are installed at fixed positions and mobile slave devices that are movable, and the grouping unit groups the plurality of slave devices such that the fixed slave devices and the mobile slave devices are in different groups.

9. The wireless communication system according to claim 8, wherein the mobile slave units grouped in a different group from the fixed slave units are excluded from being targets for periodically updating a common channel map.

10. The wireless communication system according to claim 8, wherein the mobile slave device is an electronic device carried by a user, and when the mobile slave device and the master device perform wireless communication, the mobile slave device functions as the master device and the master device functions as the slave device.

11. The wireless communication system described in claim 1, wherein each of the multiple slave devices has identification information for identifying the slave device and transmits the identification information in wireless communication with the master device, the master device has a list that associates the identification information with information on the group to which the slave device belongs, and the grouping unit groups the multiple slave devices in accordance with the list based on the identification information wirelessly transmitted from each of the multiple slave devices to the master device.

12. The wireless communication system described in claim 1, wherein the multiple slave devices have identification information for identifying each of the slave devices and group information indicating the group to which they belong, and transmit the identification information and the group information in wireless communication with the master device, and the grouping unit groups the multiple slave devices based on the identification information and the group information wirelessly transmitted from each of the multiple slave devices to the master device.

13. A wireless communication system as described in claim 1 or 2, wherein the grouping unit groups a plurality of the slave devices based on the communication channel to be used for wireless communication determined for each slave device by the communication channel determination unit so that the number of common communication channels is equal to or greater than a predetermined threshold value.

14. The wireless communication system described in claim 13, wherein the grouping unit determines a common communication channel when the slave devices to be grouped are grouped into at least one of the existing groups based on the communication channel used for wireless communication of the slave devices to be grouped and a common communication channel in at least one of the existing groups, and if the number of common communication channels determined is equal to or greater than the predetermined threshold, groups the slave devices to be grouped into the existing group, and if the number is less than the predetermined threshold, groups the slave devices to be grouped into a new group.

15. The wireless communication system described in claim 13, wherein the grouping unit determines a common communication channel when the slave devices to be grouped are grouped into at least one of the existing groups based on the communication channel used for wireless communication of the slave devices to be grouped and a common communication channel in at least one of the existing groups, and when there are multiple existing groups in which the number of determined common communication channels is equal to or greater than the predetermined threshold, the grouping unit groups the slave devices to be grouped into the existing group in which the number of determined common communication channels is the largest.

16. The wireless communication system described in claim 13, wherein the grouping unit determines a common communication channel when the slave devices to be grouped are grouped into at least one of the existing groups based on the communication channel used for wireless communication of the slave devices to be grouped and a common communication channel in at least one of the existing groups, and if there are multiple existing groups in which the number of determined common communication channels is equal to or greater than the predetermined threshold and the numbers of determined common communication channels are the same for the multiple existing groups, the grouping unit groups the slave devices to be grouped into the existing group containing the fewer slave devices.

17. A wireless communication method for at least one master device (20) and a plurality of slave devices (30) to perform wireless communication via one communication channel selected sequentially from a plurality of communication channels, comprising: grouping a plurality of the slave devices into two or more groups (S50); determining a communication quality of each communication channel for the slave devices belonging to at least one of the grouped groups when the master device wirelessly communicates with each of the plurality of slave devices, and determining a communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel (S270, S280); and extracting a common communication channel that is a communication channel common to the slave devices belonging to the at least one group based on the communication channel to be used for wireless communication determined for the slave devices belonging to the at least one group, and creating a common channel map (S290), wherein the master device and the slave devices grouped into the at least one group perform wireless communication via a communication channel selected from the common communication channels indicated by the created common channel map.

18. A wireless communication program for at least one master device (20) and multiple slave devices (30) to perform wireless communication via one communication channel selected sequentially from multiple communication channels, the program causing at least one processor to execute the following steps: grouping the multiple slave devices into two or more groups (S50); determining the communication quality of each communication channel for the slave devices belonging to at least one of the grouped groups when the master device wirelessly communicates with each of the multiple slave devices, and determining a communication channel to be used for wireless communication based on the determination result of the communication quality of each communication channel (S270, S280); and extracting a common communication channel that is a communication channel common to the slave devices belonging to the at least one group based on the communication channel to be used for wireless communication determined for the slave devices belonging to the at least one group, and creating a common channel map (S290), wherein the master device and the slave devices grouped into the at least one group perform wireless communication via a communication channel selected from the common communication channels indicated by the created common channel map.

Images