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

Abstract

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

Description

Technical Field

[0001] The present disclosure relates to a wireless communication system, a wireless communication method, and a wireless communication program in which a master device performs wireless communication with a slave device via one communication channel sequentially selected from a plurality of communication channels.

Background Art

[0002] As this type of wireless communication system, for example, the one described in Patent Document 1 is known. In the wireless communication system of Patent Document 1, when a packet error occurs in the received signal of a wireless communication device, if the RSSI value of the wireless signal of this packet is greater than a preset threshold Th1, the wireless communication device determines that the reception operation of receiving this packet is a reception error due to interference with other radio waves. Then, the wireless communication device counts the number of receptions and the number of reception errors, and stores the frequency of reception errors due to interference (number of reception errors / number of receptions) in each frequency channel. When the frequency of reception errors exceeds the threshold Th2, the wireless communication device determines that there is an interference source in the frequency channel where the frequency of reception errors due to interference exceeds the threshold Th2, and stores this frequency channel as a non-usable channel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in the wireless communication system of Patent Document 1, frequency channels whose communication quality has deteriorated due to interference with other radio waves are designated as unusable channels. Furthermore, in the wireless communication system of Patent Document 1, frequency channels designated as unusable channels are restored to usable channels after a set period has elapsed. This control of setting frequency channels as unusable channels and restoring them to usable channels is hereinafter referred to as channel map control in this specification.

[0005] Here, the master and slave devices that constitute the wireless communication system must have a common channel map. Having a common channel map allows the master and slave devices to sequentially select the same communication channel. The channel map indicates the multiple communication channels available for wireless communication between the master and slave devices.

[0006] When the communication channel used for wireless communication is changed by the channel map control described above, the channel map is also updated. Therefore, the updated channel map, along with information indicating the start time of its use, needs to be shared between the master and slave devices. For this reason, for example, the master device could send the updated channel map and information indicating the start time of its use to the slave device in response to the channel map update. However, if the transmission from the master device and / or reception by the slave device of the updated channel map and information indicating the start time of its use does not occur properly, there is a risk that the channel maps of the master and slave devices will not match. If the channel maps do not match, the communication channels used for communication will differ, which may lead to a series of communication errors and a decrease in communication reliability.

[0007] This disclosure has been made in view of the above-mentioned points, and aims to provide a wireless communication system, a wireless communication method, and a wireless communication program that can suppress a decrease in communication reliability while implementing channel map control. [Means for solving the problem]

[0008] To achieve the above objective, the wireless communication system according to this disclosure is a wireless communication system in which a master device (20) performs wireless communication with a slave device (30) via one communication channel that is sequentially selected from a plurality of communication channels, When the master device communicates wirelessly with the slave device, a quality determination unit (S270, S280) determines the communication quality of each communication channel, A communication channel determination unit (S290) determines the communication channel to be used for wireless communication based on the communication quality determination result of each communication channel by the quality determination unit, A channel map sharing unit (S520) causes the master device to transmit a channel map indicating the communication channel determined by the communication channel determination unit to the slave device, and shares the channel map between the master device and the slave device. A sharing determination unit (S540, S550) determines whether the channel map is shared between the master and slave devices based on the reception result of a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map, The master device includes a communication disconnection unit (S620, S246) for disconnecting the communication connection with the slave device, The channel map sharing unit will repeat the transmission of the channel map if the sharing determination unit does not determine that the channel map has been shared despite the channel map having been transmitted. If the number of channel map transmissions by the channel map sharing unit reaches a predetermined number, but the sharing determination unit never determines that the channel map has been shared, the communication disconnection unit is configured to disconnect the communication connection with the slave device at a predetermined timing.

[0009] Furthermore, the wireless communication method according to this disclosure is a wireless communication method in which a master device (20) performs wireless communication with a slave device (30) via one communication channel that is sequentially selected from a plurality of communication channels, When the master device communicates wirelessly with the slave device, there is a quality determination step (S270, S280) that determines the communication quality of each communication channel, A communication channel determination step (S290) determines the communication channel to be used for wireless communication based on the results of the communication quality determination for each communication channel in the quality determination step, In the communication channel determination step, the master device transmits a channel map showing the determined communication channel to the slave device, and the channel map is shared between the master device and the slave device in a channel map sharing step (S520). A sharing determination step (S540, S550) is performed to determine whether the channel map has been shared between the master and slave devices, based on the result of receiving a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map. The master device includes a communication disconnection step (S620, S246) for disconnecting the communication connection with the slave device, In the channel map sharing step, if the channel map has been sent but the sharing determination step does not determine that the channel map has been shared, the channel map sending is repeated. In the channel map sharing step, even though the number of channel map transmissions reaches a first predetermined number, if the sharing determination step does not determine that the channel map has been shared even once, the communication connection with the slave device is disconnected at a predetermined timing in the communication disconnection step.

[0010] Furthermore, the wireless communication program according to this disclosure is a wireless communication program executed by at least one processor for a master device (20) to perform wireless communication with a slave device (30) via one communication channel that is sequentially selected from a plurality of communication channels, When the wireless communication program is executed, at least one processor, When the master device communicates wirelessly with the slave device, it has a quality determination function (S270, S280) that determines the communication quality of each communication channel, A communication channel determination function (S290) determines the communication channel to be used for wireless communication based on the results of the communication quality determination function for each communication channel, The channel map sharing function (S520) causes the master device to send a channel map indicating the communication channel determined by the communication channel determination function to the slave device, and allows the master device and the slave device to share the channel map. A sharing determination function (S540, S550) determines whether the channel map is shared between the master and slave devices based on the reception result of the channel map reception confirmation signal transmitted from the slave device in response to the reception of the channel map, The master device implements a communication disconnection function (S620, S246) to disconnect the communication connection with the slave device. If the channel map is sent using the channel map sharing function, but the sharing detection function does not determine that the channel map has been shared, the channel map will be sent repeatedly. If the number of channel map transmissions via the channel map sharing function reaches a predetermined number, but the sharing determination function does not determine that the channel map has been shared even once, the communication disconnection function is configured to disconnect the communication connection with the slave device at a predetermined timing.

[0011] As described above, in the wireless communication system, wireless communication method, and wireless communication program disclosed herein, if it is not determined that the channel map has been shared despite the channel map being transmitted, the transmission of the channel map is repeated. Therefore, the possibility of the master device and the slave device sharing the channel map can be increased. However, if it is not determined that the channel map has been shared even after the number of channel map transmissions has reached a first predetermined number, the communication connection with the slave device is disconnected at a predetermined timing. This prevents a situation in which communication errors occur continuously due to differences in the channel maps between the master device and the slave device, resulting in a decrease in communication reliability.

[0012] The reference numbers in the above parentheses are only examples of the correspondence with the specific configurations in the embodiments described later for ease of understanding of the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

[0013] Also, regarding the technical features described in each claim of the claims other than the features of the present disclosure described above, they will become clear from the description of the embodiments described later and the accompanying drawings.

Brief Description of the Drawings

[0014] [Figure 1] It is a block diagram showing a schematic configuration of a wireless communication system according to the first embodiment. [Figure 2] It is a diagram showing an example of the electric field strength distribution in the communication environment between the master device and the slave device. [Figure 3] It is a diagram showing an example of the received signal strength of each communication channel. [Figure 4] It is a flowchart showing an example of the connection sequence between the master device and the slave device according to the first embodiment. [Figure 5] It is a flowchart showing an example of the communication sequence between the master device and the slave device according to the first embodiment. [Figure 6] It is a flowchart showing an example of the channel map sharing process according to the first embodiment. [Figure 7] It is a time chart for explaining an example of control by the channel map sharing process according to the first embodiment. [Figure 8] It is a flowchart showing an example of the channel map sharing process according to the second embodiment. [Figure 9] It is a time chart for explaining an example of control by the channel map sharing process according to the second embodiment. [Figure 10] It is a flowchart showing an example of the communication sequence between the master device and the slave device according to the second embodiment. [Figure 11]This flowchart shows an example of a communication sequence between a master device and a slave device, relating to a modified example. [Modes for carrying out the invention]

[0015] Preferred embodiments of this disclosure will be described below with reference to the drawings. Note that identical or similar configurations may be given the same reference numeral across multiple drawings, and their descriptions may be omitted. If only a portion of a configuration is described in each embodiment, the other parts of that configuration can be replaced with configurations from other embodiments described earlier. Furthermore, configurations from multiple embodiments may be partially combined, even if not explicitly stated, as long as there are no particular problems with the combination.

[0016] (First Embodiment) The wireless communication system of this embodiment includes at least one master device and at least one slave device. At least one of the master device and the slave device may be mounted on a mobile device. Mobile devices include, for example, vehicles such as automobiles and railway cars, aircraft such as electric vertical take-off and landing aircraft and drones, ships, construction machinery, agricultural machinery, and the like.

[0017] As a specific application in vehicles, the wireless communication system according to this embodiment can be applied to a battery management system that manages batteries mounted as battery packs in electric vehicles such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles. When applied to a battery management system, for example, the master device is connected to a battery control device, and multiple slave devices are each connected to monitoring devices provided on multiple battery stacks that make up the battery pack. In this case, both the master device and the multiple slave devices are mounted on the vehicle.

[0018] Each monitoring device, provided for each battery stack, acquires battery information such as the voltage and current of each battery cell in the corresponding battery stack, and the temperature of the battery stack, using various sensors. When each monitoring device receives data requesting battery information from the battery control unit via a wireless communication system, it transmits the acquired battery information to the battery control unit via the wireless communication system. Based on the acquired battery information, the battery control unit calculates the state of charge (SOC) of the entire battery stack, drives the heating and cooling mechanism to adjust the temperature of the battery pack to an appropriate range, and determines whether or not to perform a so-called equalization process to equalize the voltage of each battery cell. If the battery control unit determines that equalization processing is necessary for at least one battery stack, it instructs the corresponding monitoring device to perform the equalization process via the wireless communication system. In addition, each monitoring device performs processing to determine abnormalities in various sensors and abnormalities in its own operation, and if an abnormality is detected, it transmits the abnormality information to the battery control unit via the wireless communication system.

[0019] Alternatively, the wireless communication system according to this embodiment may be applied to a vehicle, such as a smart key system or a tire pressure monitoring system. When applied to a smart key system, for example, the master device is mounted on the vehicle and connected to a control device that controls the locking and unlocking of vehicle doors and the on / off switching of power sources such as the vehicle's engine. At least one slave device is mounted on a portable key or mobile terminal owned by at least one user. When applied to a tire pressure monitoring system, the master device is mounted on the vehicle and connected to a control device that displays tire pressure and provides warnings if the tire pressure is abnormal. Multiple slave devices are provided inside each tire and connected to tire pressure detection devices also provided inside each tire.

[0020] Furthermore, the wireless communication system according to this embodiment may also be applied to a vehicle diagnostic system. In this case, for example, multiple slave devices are connected to multiple in-vehicle equipment equipped with self-diagnostic functions, and the master device is connected to a diagnostic control device installed in a service factory. In these examples, at least one of the master device and the multiple slave devices is located in a fixed position and / or at least one is mounted on the vehicle.

[0021] However, the application examples of the wireless communication system according to this embodiment are not limited to vehicles. As mentioned above, it can also be applied to systems that control and manage various types of equipment, such as other mobile objects, like drones, ships, construction machinery, and agricultural machinery. Furthermore, the wireless communication system according to this embodiment can also be applied to systems that control and manage various equipment in buildings and production facilities in factories.

[0022] Figure 1 is a block diagram illustrating the schematic configuration of the wireless communication system 10. The master device 20 and slave device 30 of the wireless communication system 10 are both mounted, for example, in a vehicle (automobile). In this case, the master device 20 and slave device 30 may be configured to be located in a common housing, or they may not be located in a common housing. There may be one master device 20 or there may be multiple master devices 20. If multiple master devices 20 are provided, each of the multiple master devices 20 may communicate with at least one slave device 30 belonging to a different group, or multiple master devices 20 may communicate with at least one slave device 30 belonging to the same group. The master device 20 and slave device 30 communicate wirelessly via a single communication channel that is sequentially selected from multiple communication channels, such as Bluetooth Low Energy (Bluetooth is a registered trademark, hereinafter referred to as Bluetooth LE) communication.

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

[0024] In wireless communication between the master device 20 and the slave device 30, frequency bands used for short-range communication, such as the 2.4 GHz band and the 5 GHz band, can be used. Radio waves in such high-frequency bands have stronger directivity than LF band radio waves and are easily reflected by metal objects such as vehicle bodies. LF is an abbreviation for Low Frequency. As a standard for short-range communication, for example, Bluetooth or Bluetooth LE can be adopted. As an example, the master device 20 and slave device 30 of this embodiment are configured to perform wireless communication compliant with the Bluetooth LE standard (hereinafter referred to as Bluetooth LE communication). Details of the communication method related to communication connection and encrypted communication are carried out according to the sequence specified in the Bluetooth LE standard.

[0025] As shown in Figure 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 elements described above, the master device 20 also includes input / output interfaces and bus lines for wired or wireless communication with devices other than the slave device 30. The channel map control processing, channel map creation processing, and channel map sharing processing described later may be performed by the control circuit 21, or some or all of these processes may be performed by a separate control device located outside the master device 20.

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

[0027] In the control circuit 21, the processor 211 executes a program stored in ROM while using RAM as a temporary storage area to perform predetermined processing (control). The processor 211 constructs multiple functional units by executing multiple instructions included in the program. There may be multiple processors 211. The program storage medium is not limited to ROM. Various storage media such as HDDs and SSDs can be used. HDD is an abbreviation for Hard-disk Drive. SSD is an abbreviation for Solid State Drive.

[0028] The processor 211 can be, for example, a CPU, MPU, GPU, or 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 implemented by combining multiple types of processing units, such as a CPU, MPU, and GPU. Alternatively, the control circuit 21 may be implemented as an SoC. SoC is an abbreviation for System on Chip. The control circuit 21 may also be implemented using an ASIC or FPGA. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field-Programmable Gate Array.

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

[0030] The wireless communication circuit 22 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. The wireless communication circuit 22 has a transmitting function that modulates the transmission signal and oscillates at the frequency of the RF signal. The wireless communication circuit 22 has a receiving function that demodulates the received signal. RF is an abbreviation for radio frequency.

[0031] The wireless communication circuit 22 modulates the packet containing the data transmitted from the control circuit 21 and transmits it to the slave device 30 via the antenna 23. The control circuit 21 outputs encrypted data, such as battery information request data, to the wireless communication circuit 22, using encryption information exchanged in the connection establishment process described later. The wireless communication circuit 22 adds data necessary for wireless communication, such as communication control information, to the transmission packet and transmits it. Data necessary for wireless communication includes, for example, an identifier (ID), a sequence number, the next sequence number, and an error detection code. The wireless communication circuit 22 may also control the data size, communication format, schedule, and error detection of the communication between the master device 20 and the slave device 30. This control related to communication may also be performed by the control circuit 21.

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

[0033] As shown in Figure 1, the slave device 30 includes a control circuit (CNT) 31, a wireless communication circuit (WC) 32, and an antenna 33. In addition to the elements described above, the slave device 30 also includes input / output interfaces and bus lines for wired or wireless communication with devices other than the master device 20. The control circuit 31 has a configuration similar to the control circuit 21 of the master device 20. The control circuit 31 includes, for example, a processor 311 and a memory 312. The memory 312 includes, for example, RAM and ROM.

[0034] The control circuit 31 executes the requested processing (such as response processing, like acquiring and returning the requested data, or execution processing of the requested processing) based on the request command received via the wireless communication circuit 32. For example, if the request command included in the received data is a request to transmit battery information, the control circuit 31 of the slave device 30 transmits the transmission request to the monitoring device of the corresponding battery stack and acquires the battery information from the monitoring device. Then, as a response to the request, the control circuit 31 transmits encrypted data, including the processing result (e.g., acquired battery information), to the wireless communication circuit 32 using encrypted information. The control circuit 31 can also perform, for example, control of equipment mounted on a vehicle, according to the requested processing.

[0035] The wireless communication circuit 32 includes an RF circuit (not shown) for wirelessly transmitting and receiving packets. Similar to the wireless communication circuit 22, the wireless communication circuit 32 has both transmitting and receiving functions. The wireless communication circuit 32 receives packets transmitted from the master device 20 via the antenna 33 and demodulates them. It then transmits the data contained in the demodulated packets to the control circuit 31. The wireless communication circuit 32 modulates the packets containing the data transmitted from the control circuit 31 and transmits them back 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 transmitted packets before transmitting them.

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

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

[0038] The master device 20 and the slave device 30 are, for example, positioned at predetermined locations in a vehicle. When radio signals of a predetermined frequency are transmitted from the master device 20 and the slave device 30, which are positioned at predetermined locations, interference between the transmitted wave and the reflected wave, as well as interference with external noise, results in areas of high and low electric field strength in the operating environment. The reflected wave is caused by reflection from metal elements of the vehicle surrounding the master device 20 and the slave device 30, such as reflection from the vehicle body, reflection from the metal housing, and reflection from the harness. For these reasons, the communication environment between the master device 20 and the slave device 30 has multiple so-called NULL points, which are areas of high electric field strength and areas of low electric field strength, as shown in Figure 2.

[0039] If the slave device 30 is located in or near a low-field-strength area in the electric field distribution with the master device 20, the slave device 30 is highly likely to be unable to properly receive wireless signals from the master device 20, potentially resulting in a communication error. Communication channels that are highly likely to experience such communication errors are those with degraded communication quality.

[0040] In this scenario, when the master device 20 and the slave device 30 perform wireless communication via a single communication channel sequentially selected from multiple communication channels, the frequency of each communication channel differs, and therefore the electric field distribution of each communication channel may also change. As a result, the communication quality may differ across each communication channel.

[0041] For example, as shown in Figure 3, in wireless communication via communication channel A, the received power (received signal strength), which is one of the parameters indicating communication quality, is good. Also, in wireless communication via communication channel C, the received power is very high. Therefore, when the master device 20 and slave device 30 use communication channels A and C, which have good or very high communication quality, they can perform high-quality wireless communication with communication errors 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 slave device 30 use communication channels B and N, which have degraded communication quality, the possibility of communication errors occurring in wireless communication increases. Note that in Figure 3, for ease of understanding, an example of received signal strength against frequency is shown with a solid line.

[0042] Therefore, it is preferable that wireless communication between the master device 20 and the slave device 30 be performed using a communication channel capable of high-quality wireless communication, avoiding communication channels with degraded communication quality.

[0043] However, the electric field distribution between the master device 20 and the slave device 30 changes due to external environmental factors (such as external noise) and vibrations of the master device 20 and / or the slave device 30 (including harness vibrations). Therefore, when the master device 20 and the slave device 30 are mounted on a vehicle, the electric field distribution of the communication environment between the master device 20 and the slave device 30 changes depending on, for example, the state of the vehicle (e.g., driving or stopped) and the state of the surrounding environment of the vehicle (e.g., a lot of external noise or little noise). 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 remove the communication channel in question from the multiple communication channels used for wireless communication when the communication quality deteriorates, and to restore the communication channel in question as one of the multiple communication channels used for wireless communication when the communication quality recovers.

[0044] In the wireless communication system 10 of this embodiment, control processing for realizing wireless communication between the master device 20 and the slave device 30 is explained with reference to the diagram showing the communication sequence between the master device 20 and the slave device 30, which is shown in Figure 5. In Figure 5, the master device 20 is shown as MASTER and the slave device 30 as SLAVE. Figure 5 also shows the communication sequence executed between the master device 20 and one slave device 30. The master device 20 individually executes the communication sequence shown in Figure 5 with multiple slave devices 30.

[0045] Here, the master device 20 and the slave device 30 perform a connection establishment process before executing the communication sequence shown in Figure 5. Figure 4 shows the connection sequence, including the connection establishment process, from the startup of the master device 20 and the slave device 30 until data communication is performed. For example, if the wireless communication system 10 is installed in a vehicle, the connection sequence starts when, for example, the IG signal is switched from off to on by a user operation. Note that if the master device 20 and the slave device 30 are always connected, the connection sequence is performed only once at a predetermined timing. However, if an error occurs during communication and the wireless communication connection between the master device 20 and the slave device 30 is disconnected, the connection sequence may be performed to reconnect.

[0046] When the connection sequence begins, the master device 20 and the slave device 30 perform initialization processes in steps S10 and S110, respectively, to initialize various variables and timers. Subsequently, the master device 20 and the slave device 30 perform connection establishment processes in steps S20 and S120, respectively. This connection establishment process is performed between the master device 20 and all slave devices 30 if there are multiple slave devices 30 that are to be connected to the master device 20 for wireless communication. In the connection establishment process, for example, the slave device 30 performs an advertising operation, sending an advertising signal via an advertising communication channel, and the master device 20 performs a scan operation, scanning for the advertising signal. The advertising communication channel includes multiple communication channels (for example, three in the case of Bluetooth LE). When the master device 20 receives an advertising signal on any of the communication channels through the scan operation, it sends a connection request to the slave device 30 that sent the advertising signal. This establishes a communication connection between the master device 20 and the slave device 30. If the master device 20 and the slave device 30 determine in steps S30 and S130, respectively, that a communication connection has been established, the master device 20 proceeds to step S40 and the slave device 30 proceeds to step S140.

[0047] In steps S40 and S140, the master device 20 and the slave device 30 exchange connection information. In this exchange of connection information, the master device 20 and the slave device 30 exchange encryption information used for data communication and share initial information related to frequency channel hopping. The initial information includes, for example, a channel map, a hopping pattern, or a function for hopping.

[0048] Next, in steps S50 and S150, the master device 20 and the slave device 30, respectively, perform data communication via a data communication channel sequentially selected from multiple communication channels for each periodically occurring communication event. The process for performing this data communication is shown in the communication sequence in Figure 5. If multiple slave devices 30 are provided, the master device 20 communicates with each of the multiple slave devices 30 sequentially by assigning a communication period (sub-event) to each of the multiple slave devices 30 for each communication event.

[0049] If the master device 20 and the slave device 30 determine to disconnect the communication connection in steps S60 and S160, respectively, they terminate the connection sequence shown in Figure 4. For example, if the wireless communication system 10 is installed in a vehicle, the master device 20 and the slave device 30 may determine to disconnect the communication connection if the IG signal is switched from on to off by user operation. In addition, the master device 20 and the slave device 30 may determine to disconnect the communication connection if data communication cannot be performed normally for a predetermined number of consecutive times (corresponding to the third predetermined number in the claims). Furthermore, in this embodiment, as will be described later, if the master device 20 determines that it cannot share a new channel map with the slave device 30 during the channel map update period (channel map update cycle), the master device 20 determines to disconnect the communication connection.

[0050] Next, the data communication sequence will be explained with reference to the flowchart in Figure 5. As shown in Figure 5, in step S210, the master device 20 sends, for example, a data request command, i.e., a data request, to the slave device 30. However, the master device 20 can also send, for example, a request to perform a predetermined process, in addition to a data request. When the slave device 30 receives the data request in step S310, in step S320, it performs, for example, a checksum determination based on the error detection code included in the received data request to confirm whether the data request was received correctly. If the slave device 30 determines in step S320 that the data request was not received correctly based on the checksum determination result, it sends, for example, a signal in step S330 indicating that the data request was not received correctly, or a signal requesting retransmission of the data request. On the other hand, if the slave device 30 determines in step S320 that the data request was received correctly, it performs a predetermined process necessary to respond in step S330, for example, a process to acquire and transmit the requested data.

[0051] The master device 20 and the slave device 30 switch the data communication channel to be used for each communication event by performing frequency channel hopping, and then send and receive data requests and requested data. In this process, the master device 20 and the slave device 30 determine the communication channel to be switched to by frequency channel hopping according to their respective channel maps. In the case of Bluetooth LE communication, 37 communication channels are available for data communication.

[0052] In step S220, the master device 20 receives the requested data. Then, in step S230, the master device 20 performs a checksum determination, for example, based on the error detection code contained in the received data, to confirm whether the data was received correctly. In the following step S240, if the master device 20 determines in step S230 that the data was not received correctly, or if it receives a signal from the slave device 30 indicating that the data request was not received correctly, it decides whether to perform processing for retransmission within the same communication event. For example, if the master device 20 has enough time to retransmit before the end of the current communication event (sub-event), it may decide to retransmit; if there is not enough time, it may decide not to retransmit. In step S240, if the master device 20 decides to retransmit, it repeats the processing from step S210. If the processing in step S230 determines that the data was received correctly, or if the master device 20 decides not to retransmit in step S240, the master device 20 proceeds to the processing in step S250.

[0053] In step S250, the master device 20 performs processing based on the information contained in the received data. However, if it is determined in the processing of step S230 that the data was not received correctly, or if a signal is received from the slave device 30 indicating that the data request was not received correctly, and it is decided in the processing of step S240 that retransmission will not be performed, the processing of step S250 may be omitted, or the processing of step S250 may be performed based on previously received data.

[0054] In step S260, the master device 20 detects the received signal strength (RSSI) and the packet error rate (PER) as characteristic data indicating the communication quality of the signal received from the slave device 30. RSSI is an index indicating the strength of the signal transmitted from the slave device 30 and received by the master device 20. PER is the ratio of the number of error packets to the number of packets received by the master device 20, expressed as a percentage. The master device 20 may also detect the signal-to-noise ratio (SNR) / signal interference-to-noise ratio (SINR) instead of RSSI. SNR / SINR can be detected, for example, by the ratio of the RSSI value when the master device 20 receives a wireless signal from the slave device 30 to the RSSI value when it does not receive a wireless signal. Alternatively, the master device 20 may also detect the bit error rate (BER) or packet arrival rate (PAR) instead of PER. The master device 20 stores and accumulates the detected RSSI or SNR / SINR, along with PER, BER, or PAR for each communication channel. Furthermore, characteristic data indicating communication quality can be obtained not only by detection by the master device 20 as described above, but also by the slave device 30 detecting RSSI, PER, etc., when it receives a signal from the master device 20 and transmitting it to the master device 20.

[0055] In step S270, the master device 20 determines a decrease in the communication quality of the communication channel used for wireless communication with the slave device 30, based on the characteristic data indicating the communication quality of the communication channel detected in step S260. The master device 20 then removes the communication channel that it has determined to have decreased communication quality from the communication channels used for wireless communication between the master device 20 and the slave device 30. The communication channel to be removed is a data communication channel. For example, one example of a condition for determining a decrease in communication quality is that, as a result of comparing the RSSI with a threshold for RSSI and the PER with a threshold for PER, at least one of the RSSI and PER does not meet the threshold. Note that there may be only one type of parameter to compare with the threshold. The parameter to compare with the threshold may be the parameter detected immediately before step S260, or it may be the average value of a predetermined number of parameters detected in multiple past wireless communications on the same communication channel, or their median value.

[0056] In step S280, the master device 20 performs a recovery determination for communication channels that have been deleted based on the deletion determination during previous communication events. In this recovery determination, if predetermined recovery conditions are met, the deleted communication channel is recovered as a communication channel to be used for wireless communication. For example, as an example of predetermined recovery conditions, a deleted communication channel may be recovered in accordance with the elapsed time since the communication channel was deleted. Alternatively, as another example of predetermined recovery conditions, a deleted communication channel may be recovered as a communication channel to be used for wireless communication in accordance with the communication channel adjacent to the deleted communication channel showing good communication quality. In this way, the communication channels determined to be recoverable as communication channels to be used for wireless communication are incorporated into the channel map and are actually used for wireless communication between the master device 20 and the slave device 30. The deletion determination process in step S270 and the recovery determination process in step S280 correspond to the channel map control process in this disclosure. Note that if the communication quality of a communication channel that has been recovered remains poor when actually used for wireless communication, it may be subject to deletion again by the deletion determination.

[0057] In step S290, the master device 20 performs channel map creation processing based on the deletion determination result in step S270 and the recovery determination result in step S280. In this embodiment, individual channel maps are created for multiple slave devices 30. However, it is also possible to create a common channel map for multiple slave devices 30. When creating a common channel map, an AND operation is performed on the communication channels included in the channel map of each slave device 30, and multiple communication channels common to all channel maps are extracted.

[0058] The channel map may show communication channels that are available for wireless communication, or it may show communication channels that are unavailable. Furthermore, it may show both available and unavailable communication channels. In addition, if there are changes to the available / unavailable communication channels as a result of creating the channel map, the frequency channel hopping pattern may be updated. If the frequency channel hopping pattern is not updated, and the communication channel scheduled for hopping is unavailable, then, for example, the next communication channel scheduled for hopping should be used.

[0059] In step S300, the master device 20 performs a process to share the channel map created in the channel map creation process of step S290 with the slave device 30. This channel map sharing process will be described in detail later.

[0060] Here, the deletion determination process and the recovery determination process described above may be performed each time communication occurs between the master device 20 and the slave device 30. Alternatively, the deletion determination process and the recovery determination process may be performed collectively each time multiple communications occur between the master device 20 and the slave device 30, in accordance with the channel map update cycle described later. In this case, each time communication occurs between the master device 20 and the slave device 30, characteristic data indicating the communication quality of the communication channel used for communication is detected and stored in step S260. Then, based on the stored characteristic data, the deletion determination in step S270 and the recovery determination in step S280 are performed collectively. Similarly, the channel map creation process in step S290 may also be performed each time communication occurs between the master device 20 and the slave device 30. Alternatively, the channel map creation process may be performed each time multiple communications occur between the master device 20 and the slave device 30, in accordance with the channel map update cycle described later.

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

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

[0063] As shown in the time chart in Figure 7, the sharing process for the new channel map begins during the application period of the current channel map. In other words, the new channel map is created by the channel map creation process based on multiple characteristic data indicating communication quality detected prior to the application period of the current channel map, and is then finalized as the new channel map. Furthermore, the next new channel map is created based on multiple characteristic data indicating communication quality detected from the communication between the master device 20 and the slave device 30 during the application period of the current channel map, and is finalized as the next new channel map before the application period of the new channel map.

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

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

[0066] In step S520, the master device 20 transmits the new channel map to the slave device 30. At this time, the master device 20 also transmits information indicating when to start using the new channel map. The timing to start using the new channel map arrives each time the channel map update cycle has elapsed, as shown in the example time chart in Figure 7.

[0067] In step S710, the slave device 30 receives the new channel map and timing information transmitted from the master device 20. Upon receiving the new channel map and timing information in step S710, the slave device 30 performs a checksum determination in step S720 based on the error detection code contained in the received packet to confirm whether the new channel map and timing information was received correctly. If the slave device 30 determines in step S720, based on the checksum determination result, that the new channel map and timing information was not received correctly, for example, in step S730, it does not send an acknowledgment signal (Ack signal) for the new channel map. On the other hand, if the slave device 30 determines in step S720 that the new channel map and timing information was received correctly, it sends an acknowledgment signal (Ack signal) for the new channel map back to the master device 20 in step S730.

[0068] In step S530, the master device 20 receives an Ack signal from the slave device 30. Then, in step S540, the master device 20 performs a checksum determination, for example, based on the error detection code contained in the received Ack signal, to confirm whether the Ack signal was received correctly. If the master device 20 was unable to receive the Ack signal itself, the result of the checksum determination will be NG. In the following step S550, the master device 20 determines whether the result of the checksum determination in step S540 was OK or NG. If the result of the checksum determination is OK, the master device 20 proceeds to step S560. On the other hand, if the result of the checksum determination is NG, the master device 20 proceeds to step S570.

[0069] In step S560, the master device 20 resets the map sharing counter to zero. The map sharing counter is reset to zero when the slave device 30 determines that it has successfully received the new channel map and timing information, sends an Ack signal from the slave device 30, and the master device 20 successfully receives that Ack signal. Therefore, when the value of the map sharing counter is zero, it indicates that the master device 20 and the slave device 30 have successfully shared the new channel map, as described above.

[0070] For example, the time chart in Figure 7 shows an example where a slave device 30, labeled "Slave1," successfully receives the new channel map and timing information from the master device 20 during the first communication after the channel map update cycle begins and the new channel map sharing starts (i.e., communication event = 1). Furthermore, the Ack signal transmitted from the slave device 30 is also successfully received by the master device 20, thus demonstrating that the new channel map is shared between the master device 20 and the slave device 30. In this case, the map sharing counter is reset to zero in step S560. Therefore, in subsequent communications during the channel map update cycle (i.e., communication events = 2 to 6), the determination result in step S510 becomes "Yes," and further transmission of the new channel map and timing information is not required.

[0071] On the other hand, in step S570, the master device 20 determines whether to perform processing for retransmission within the same communication event because it has not received the Ack signal correctly. If the master device 20 decides to retransmit in step S570, it repeats the processing from step S520. If it decides not to retransmit in step S570, the master device 20 proceeds to step S580. In step S580, the master device 20 increments the map sharing counter by 1. Thus, the map sharing counter is incremented when the sharing of the new channel map between the master device 20 and the slave device 30 is not considered successful. Therefore, if the value of the map sharing counter is not zero, it indicates that the sharing of the new channel map between the master device 20 and the slave device 30 has not yet been successful.

[0072] For example, the time chart in Figure 7 shows an example where, in the first communication after the channel map update cycle begins and the sharing of the new channel map starts (i.e., communication event = 1), the slave device 30, labeled "Slave2," fails to receive the new channel map and timing information from the master device 20, resulting in either no Ack signal being sent back, or the slave device 30 sending an Ack signal but the master device 20 failing to receive it properly. In this case, in step S580, the map sharing counter is incremented by 1, becoming a non-zero value. Therefore, in subsequent communications during the channel map update cycle (i.e., communication events = 2 to 6), the determination result in step S510 becomes "No," and the processing from step S520 onwards is executed. In other words, the transmission of the new channel map and timing information from the master device 20 to the slave device 30 is repeatedly performed for each communication event. The transmission of this new channel map and timing information continues for the duration of the channel map update cycle, until the channel map is successfully shared between the master device 20 and the slave device 30 and the map sharing counter is reset to zero.

[0073] In step S590, the master device 20 determines whether the waiting time for updating to the new channel map has elapsed, that is, whether the channel map update cycle has expired. If the master device 20 determines that the waiting time has elapsed, it proceeds to step S600. On the other hand, if it determines that the waiting time has not elapsed, the master device 20 terminates the process shown in the flowchart of Figure 6.

[0074] In step S600, the master device 20 determines whether the value of the map sharing counter is zero. If the value of the map sharing counter is zero, it indicates that the sharing of the new channel map between the master device 20 and the slave device 30 has been successful. Therefore, in step S610, the master device 20 updates the channel map from the current channel map to the new channel map. As a result, the master device 20 and the slave device 30 can communicate via the communication channel selected according to the new channel map.

[0075] On the other hand, if in step S600 the value of the map sharing counter is determined to be a value other than zero, it is possible that the sharing of the new channel map between the master device 20 and the slave device 30 has failed, even though the new channel map and timing information have been transmitted a predetermined number of times (corresponding to the first predetermined number in the scope of the claim) (for example, 6 times in the example shown in Figure 7). For this reason, in step S620, the master device 20 disconnects the communication connection with the slave device 30. In this case, the communication connection that is disconnected is the wireless communication connection with the slave device 30 that is deemed not to have been able to share the channel map among the multiple slave devices 30.

[0076] The timing for disconnecting the communication connection with the slave device 30 corresponds to the timing when the application period of the new channel map begins, that is, the timing when the use of the new channel map begins, as shown in the time chart in Figure 7. Therefore, it is possible to prevent continuous communication errors from occurring due to differences in the channel maps between the master device 20 and the slave device 30, thereby suppressing situations in which communication reliability is reduced.

[0077] Furthermore, if the master device 20 disconnects the communication connection with the slave device 30, the master device 20 initiates the connection sequence shown in Figure 4 to reconnect with the slave device 30 that has disconnected the communication connection. On the other hand, if the slave device 30 becomes unable to communicate data with the master device 20 and the number of communication errors reaches a predetermined number (corresponding to the third predetermined number in the claim), it disconnects the communication connection with the master device 20. After the communication connection is disconnected, the slave device 30 also initiates the connection sequence shown in Figure 4. This attempts to reconnect the master device 20 and the slave device 30. In this connection sequence, which is the reconnection process, a communication connection is established between the master device 20 and the slave device 30, and connection information, including a channel map indicating the communication channel used for wireless communication, is shared between the master device 20 and the slave device 30. As a result, the master device 20 and the slave device 30 can once again perform wireless communication.

[0078] (Second Embodiment) Next, a wireless communication system 10 according to the second embodiment of this disclosure will be described with reference to the drawings. Since the wireless communication system 10 according to this embodiment is configured in the same way as the wireless communication system 10 of the first embodiment, a description of the configuration will be omitted.

[0079] In the wireless communication system 10 according to the first embodiment described above, if the master device 20 and the slave device 30 are not determined to have successfully shared the new channel map despite the transmission of a predetermined number of new channel map and timing information during the channel map update cycle, the master device 20 disconnects the communication connection with the slave device 30 at the timing when the new channel map should be used. In this first embodiment described above, the master device 20 determines whether the master device 20 and the slave device 30 have successfully shared the new channel map or not based on the fact that the master device 20 cannot receive a channel map reception acknowledgment signal (Ack signal) from the slave device 30.

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

[0081] Therefore, in the wireless communication system 10 according to this embodiment, in order to prevent unnecessary disconnections of communication connections, the master device 20 is configured to disconnect the communication connection with the slave device 30 not simply because it is unable to receive the Ack signal properly, but after confirming that the master device 20 and the slave device 30 are not able to share the new channel map.

[0082] The following description will focus on the differences between the wireless communication system 10 described herein and the wireless communication system 10 according to the first embodiment.

[0083] Figure 8 is a flowchart showing the channel map sharing process performed in the wireless communication system 10 according to this embodiment. The channel map sharing process of the second embodiment shown in the flowchart of Figure 8 differs from the channel map sharing process of the first embodiment shown in the flowchart of Figure 6 in that steps S600 and S620 are omitted. There are no other differences between the channel map sharing process shown in the flowchart of Figure 8 and the channel map sharing process shown in the flowchart of Figure 6.

[0084] In the channel map sharing process shown in the flowchart of Figure 8, steps S600 and S620 have been removed. As a result, in step S590, if the master device 20 determines that the waiting time for updating to the new channel map has elapsed, it will always update the channel map from the current channel map to the new channel map in step S610, without determining whether the sharing of the new channel map was successful based on the normal reception of the Ack signal.

[0085] Then, as shown in the time chart in Figure 9, the master device 20 attempts to communicate data with the slave device 30 a predetermined number of times (corresponding to the second predetermined number in the claims) via the communication channel selected according to the updated new channel map. In the example shown in the time chart in Figure 9, this predetermined number is set to 1, but it may be 2 or more times, not just 1. However, the predetermined number corresponding to the second predetermined number is set to be fewer than the predetermined number corresponding to the third predetermined number, which is used to determine the disconnection of the communication connection when communication errors occur consecutively, rather than due to a failure to share the channel map.

[0086] If the master device 20 is able to communicate with the slave device 30 after a predetermined number of communication attempts, it can be considered that the sharing of the new channel map between the master device 20 and the slave device 30 has been successful. Therefore, the master device 20 continues to communicate with the slave device 30 using the new channel map.

[0087] On the other hand, if the master device 20 is unable to communicate with the slave device 30 after a predetermined number of attempts, it can be considered that the sharing of the new channel map between the master device 20 and the slave device 30 has failed. In that case, the master device 20 disconnects the communication connection with the slave device 30 when it determines that it is unable to communicate with the slave device 30 even after attempting to communicate a predetermined number of times. In the example shown in the time chart of Figure 9, the master device 20 attempted to communicate with the slave device 30, indicated as "Slave2," once via the communication channel selected according to the new channel map, but was unable to communicate with the slave device 30, "Slave2." Therefore, at the end of the first communication event, the master device 20 disconnects the communication connection with the slave device 30, "Slave2."

[0088] To achieve the disconnection of the communication connection at the timing described above, the wireless communication system 10 according to the second embodiment executes the communication sequence shown in the flowchart of Figure 10 while utilizing the new channel map. The communication sequence shown in the flowchart of Figure 10 has the processing of steps S232, S242, S244, and S246 added to the communication sequence of the first embodiment shown in the flowchart of Figure 5.

[0089] In the flowchart of Figure 10, step S232 determines whether the checksum determination was OK or NG based on the checksum determination result in step S230. If the checksum determination is OK, it can be considered that the master device 20 and the slave device were able to successfully send and receive data requests and corresponding data in the processes of steps S210 and S310 and steps S220 and S330 using the new channel map. Therefore, if the checksum determination is determined to be OK in step S232, the master device 20 proceeds to step S250 and continues communication with the slave device 30 using the new channel map.

[0090] On the other hand, if the checksum determination in step S232 is NG, the master device 20 proceeds to step S240. In step S240, similar to the first embodiment, it is determined whether or not to perform retransmission processing within the same communication event. In step S240, if the master device 20 decides to perform retransmission, it repeats the processing from step S210. If it decides not to perform retransmission in step S240, the master device 20 proceeds to step S242.

[0091] In step S242, the master device 20 determines whether the master device 20 and the slave device 30 successfully shared the new channel map within the previous channel map update cycle. More specifically, immediately before the start of the channel map update cycle to which the new channel map is applied, the master device 20 determines whether the sharing of the new channel map was successful within the previous channel map update cycle based on the value of the map sharing counter in the flowchart of Figure 8, and saves the determination result. Then, in step S242, the master device 20 determines whether the sharing of the new channel map was successful based on the saved determination result. If it determines that the sharing of the new channel map was successful within the previous channel map update cycle, the master device 20 proceeds to the process in step S250 and continues communication with the slave device 30. However, if the master device 20 is unable to perform data communication normally for a predetermined number of consecutive times (corresponding to the third predetermined number in the scope of the claim), it disconnects the communication connection. On the other hand, if it is determined that sharing the new channel map was not successful within the previous channel map update cycle, the master device 20 proceeds to step S244. In step S244, after updating the channel map to the new channel map, it is determined whether communication with the slave device 30 has failed a predetermined number of times (corresponding to the second predetermined number of times in the scope of the claim). If it is determined that communication with the slave device 30 has failed a predetermined number of times, the master device 20 proceeds to step S246. In step S246, the master device 20 disconnects the communication connection with the slave device 30.

[0092] Furthermore, if communication with the slave device 30 is successful even once after updating to the new channel map, the process in steps S242, S244, and S246 may be skipped. Alternatively, since there is a possibility that communication may succeed even if the channel maps of the master device 20 and the slave device 30 are different, the process in steps S242, S244, and S246 may be executed regardless of whether communication has been successful at least once.

[0093] While preferred embodiments of this disclosure have been described above, this disclosure is not limited in any way to the embodiments described above and can be implemented in various modified forms without departing from the spirit of this disclosure.

[0094] For example, in each of the embodiments described above, if the sharing of the channel map between the master device 20 and the slave device 30 is unsuccessful, the master device 20 is configured to send the channel map to the slave device 30 in all communication events (communication events = 1 to 6) of the channel map update cycle.

[0095] However, in the channel map update cycle, the maximum number of times the master device 20 sends the channel map to the slave device 30 (corresponding to the first predetermined number in the scope of the claim) may be set to be less than the number of planned communications between the master device 20 and the slave device 30 from the start of channel map sharing to the start of channel map use, i.e., the number of communication events included in the channel map update cycle. Furthermore, if the number of times the master device 20 sends the channel map to the slave device 30 reaches the maximum number (the first predetermined number), but it is not determined that the channel map has been successfully shared even once, the master device 20 may disconnect the communication connection with the slave device 30 at the time such determination is made (corresponding to the third timing in the scope of the claim).

[0096] For example, in the example shown in the time chart of Figure 11, the master device 20 disconnects the communication connection with the slave device 30 when it determines that there have been five channel map sharing failures, which is fewer than the number of communication events (6) during the channel map update cycle. If the sharing of the new channel map is unsuccessful, the probability of successful communication between the master device 20 and the slave device 30 during the application period (next channel map update cycle) in which the new channel map is applied is low. Therefore, in this modified example, the communication connection is disconnected at an earlier timing than, for example, waiting until the start of the next channel map update cycle to disconnect the communication connection. This makes it possible to reconnect the master device 20 and the slave device 30 earlier. As a result, it becomes possible to shorten the period in which communication between the master device 20 and the slave device 30 is interrupted due to channel map mismatch. This allows for a reduction in the period during which important communications within the vehicle are unavailable, such as communications to notify the master device 20 of an abnormality in the in-vehicle equipment or communications to issue commands for important control operations in the in-vehicle equipment, when at least one of the master device 20 and the slave device 30 is installed in the vehicle. The above-mentioned upper limit may be set to a number less than the number of data communication errors (corresponding to the third predetermined number in the scope of the claim) during which the master device 20 disconnects the communication connection with the slave device 30.

[0097] Furthermore, in the second embodiment described above, the number of channel map retransmissions may be less than the number of communication events included in the channel map update cycle, and in communication events where a channel map is not transmitted, the master device 20 may perform other processing (for example, creating the next new channel map for the slave device 30 whose communication connection is maintained). For example, in the example shown in the time chart of Figure 9, the channel map to "Slave2" may not be retransmitted in the 6th communication event, and the master device 20 may perform other processing in that 6th communication event. This allows the processing resources of the master device 20 to be allocated to other processing.

[0098] Finally, this specification discloses several technical ideas and several combinations thereof, which are listed below. These combinations of technical ideas apply not only to the wireless communication system 10 but also to the wireless communication method and the wireless communication program.

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

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

[0101] (Technical Thought 3) The channel map sharing unit transmits information indicating the timing for starting to use the channel map, along with the channel map itself. The wireless communication system according to Technical Concept 1, wherein the predetermined timing corresponds to a second timing in which the master device, at the timing of starting to use the channel map, performs communication with the slave device on a communication channel selected according to the channel map transmitted to the slave device, and determines that it is not possible to communicate with the slave device even after attempting to communicate a second predetermined number of times.

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

[0103] (Technical Thought 5) If the sharing determination unit determines that the channel map has been shared, the master device, at the timing of starting to use the channel map, performs communication with the slave device via a communication channel sequentially selected according to the channel map transmitted to the slave device, and if, despite performing a third predetermined number of communications with the slave device that is greater than the second predetermined number, it is never able to communicate with the slave device, the communication disconnection unit disconnects the communication connection with the slave device, the wireless communication system according to technical concept 3 or 4.

[0104] (Technical Thought 6) The channel map sharing unit transmits information indicating the timing for starting to use the channel map, along with the channel map itself. The first predetermined number is set to be less than the planned number of communications between the master device and the slave device before the channel map is put into use. The wireless communication system according to Technical Concept 1, wherein the predetermined timing corresponds to a third timing in which the sharing determination unit determines that the channel map has not been shared even once, despite the number of times the channel map has been transmitted by the channel map sharing unit reaching the first predetermined number of times.

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

[0106] (Technical Thought 8) The master device communicates with multiple slave devices simultaneously. The wireless communication system according to any one of Technical Concepts 1 to 7, wherein the communication disconnection unit disconnects wireless communication with a slave device that is deemed not to be sharing the channel map among a plurality of slave devices at a predetermined timing.

[0107] (Technical Thought 9) The communication channel determination unit periodically updates the communication channels used for wireless communication based on the results of the quality determination unit's determination of the communication quality of each communication channel. The wireless communication system according to any one of technical ideas 1 to 8, wherein the channel map sharing unit periodically causes the master device to transmit an updated channel map indicating the updated communication channel to the slave device, and shares it between the master device and the slave device. [Explanation of Symbols]

[0108] 10: Wireless communication system, 20: Master device, 21: Control circuit, 22: Wireless communication circuit, 23: Antenna, 30: Slave device, 31: Control circuit, 32: Wireless communication circuit, 33: Antenna, 211: Processor, 212: Memory, 311: Processor, 312: Memory

Claims

1. A wireless communication system in which a master device (20) performs wireless communication with a slave device (30) via one communication channel that is sequentially selected from multiple communication channels, When the master device communicates wirelessly with the slave device, a quality determination unit (S270, S280) determines the communication quality of each communication channel, A communication channel determination unit (S290) determines the communication channel to be used for wireless communication based on the result of the quality determination unit's determination of the communication quality of each communication channel, A channel map sharing unit (S520) causes the master device to transmit a channel map indicating the communication channel determined by the communication channel determination unit to the slave device, and allows the master device and the slave device to share the channel map. A sharing determination unit (S540, S550) determines whether the channel map is shared between the master device and the slave device based on the result of receiving a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map, The master device includes a communication disconnection unit (S620, S246) for disconnecting the communication connection with the slave device, The channel map sharing unit will repeat the transmission of the channel map if, despite having transmitted the channel map, the sharing determination unit does not determine that the channel map has been shared. A wireless communication system in which, despite the number of times the channel map has been transmitted by the channel map sharing unit reaching a first predetermined number of times, the sharing determination unit has never determined that the channel map has been shared, and the communication disconnection unit disconnects the communication connection with the slave device at a predetermined timing.

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

3. The channel map sharing unit transmits information indicating the timing for starting to use the channel map, along with the channel map itself. The wireless communication system according to claim 1, wherein the predetermined timing corresponds to a second timing in which the master device, at the timing of starting to use the channel map, performs communication with the slave device on a communication channel selected according to the channel map transmitted to the slave device, and determines that it is not possible to communicate with the slave device even after attempting to communicate a second predetermined number of times.

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

5. If the sharing determination unit determines that the channel map has been shared, the master device, at the timing of starting to use the channel map, performs communication with the slave device via a communication channel sequentially selected according to the channel map transmitted to the slave device, and despite performing a third predetermined number of communications with the slave device that is greater than the second predetermined number of times, it is unable to communicate with the slave device even once, the communication disconnection unit disconnects the communication connection with the slave device, as described in claim 3.

6. The channel map sharing unit transmits information indicating the timing for starting to use the channel map, along with the channel map itself. The first predetermined number is set to be less than the planned number of communications between the master device and the slave device before the channel map is put into use. The wireless communication system according to claim 1, wherein the predetermined timing corresponds to a third timing in which the sharing determination unit determines that the channel map has not been shared even once, despite the number of times the channel map has been transmitted by the channel map sharing unit reaching the first predetermined number of times.

7. The wireless communication system according to any one of claims 1 to 6, wherein when the communication connection with the slave device is disconnected by the communication disconnection unit, the master device attempts to reconnect wireless communication with the slave device, and in the process of reconnection, communication channel information used for wireless communication is shared between the master device and the slave device.

8. The master device communicates with multiple slave devices simultaneously. The wireless communication system according to any one of claims 1 to 6, wherein the communication disconnection unit disconnects wireless communication with a slave device that is deemed not to be sharing the channel map among a plurality of slave devices at a predetermined timing.

9. The communication channel determination unit periodically updates the communication channels used for wireless communication based on the results of the quality determination unit's determination of the communication quality of each communication channel. The wireless communication system according to any one of claims 1 to 6, wherein the channel map sharing unit periodically causes the master device to transmit an updated channel map indicating the updated communication channel to the slave device, and shares it between the master device and the slave device.

10. A wireless communication method in which a master device (20) performs wireless communication with a slave device (30) via one communication channel that is sequentially selected from multiple communication channels, When the master device communicates wirelessly with the slave device, a quality determination step (S270, S280) is taken to determine the communication quality of each communication channel. A communication channel determination step (S290) is performed to determine the communication channel to be used for wireless communication based on the results of the communication quality determination for each communication channel in the quality determination step, A channel map sharing step (S520) is performed in which the master device transmits a channel map indicating the communication channel determined in the communication channel determination step to the slave device, and the master device and the slave device share the channel map. A sharing determination step (S540, S550) is performed to determine whether the channel map has been shared between the master device and the slave device, based on the result of receiving a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map, The master device includes a communication disconnection step (S620, S246) for disconnecting the communication connection with the slave device, In the channel map sharing step, if the channel map has been transmitted but the sharing determination step does not determine that the channel map has been shared, the transmission of the channel map is repeated. A wireless communication method in which, despite the number of channel map transmissions reaching a first predetermined number in the channel map sharing step, the channel map is never determined to have been shared in the sharing determination step, and the communication connection with the slave device is disconnected at a predetermined timing in the communication disconnection step.

11. A wireless communication program for a master device (20) to perform wireless communication with a slave device (30) via one communication channel sequentially selected from multiple communication channels, which is executed by at least one processor, When the wireless communication program is executed, at least one of the processors, When the master device communicates wirelessly with the slave device, it has a quality determination function (S270, S280) that determines the communication quality of each communication channel, A communication channel determination function (S290) determines the communication channel to be used for wireless communication based on the results of the communication quality determination of each communication channel by the quality determination function, A channel map sharing function (S520) that causes the master device to transmit a channel map indicating the communication channel determined by the communication channel determination function to the slave device, and to share the channel map between the master device and the slave device, A sharing determination function (S540, S550) determines whether the channel map has been shared between the master device and the slave device, based on the result of receiving a channel map reception confirmation signal transmitted from the slave device in response to receiving the channel map, The master device implements a communication disconnection function (S620, S246) for disconnecting the communication connection with the slave device. If, despite the channel map being transmitted using the channel map sharing function, the sharing determination function does not determine that the channel map has been shared, the transmission of the channel map will be repeated. A wireless communication program in which, despite the number of times the channel map has been transmitted by the channel map sharing function reaching a first predetermined number of times, the sharing determination function has never determined that the channel map has been shared, and the communication disconnection function disconnects the communication connection with the slave device at a predetermined timing.

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