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

Abstract

To suppress an increase in power consumption of wireless terminals even in an environment in which available frequency bands are congested in a wireless communication system including the plurality of wireless terminals.SOLUTION: A wireless communication system includes: a plurality of wireless terminals that perform multi-hop communication; and a management device capable of communicating with the plurality of wireless terminals using the multi-hop communication. The management device includes: a collection unit that collects usage status data indicating the usage status of wireless channels around the wireless terminals from the plurality of wireless terminals; a storage unit that stores the usage status data collected from the plurality of wireless terminals in chronological order; and a selection unit that selects a transmission method by which the plurality of wireless terminals transmit data for each period of time based on the usage status data stored in the storage unit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a wireless communication system, a management device, a wireless communication method, and a program. [Background technology]

[0002] In an environment where multiple wireless terminals exist, carrier sensing is performed to check the availability of wireless channels, and if a wireless signal from another wireless terminal is detected, the transmission process is re-executed after a predetermined waiting time has elapsed, or the transmission process is executed on a different wireless channel.

[0003] Also, a technique is known in which a wireless master device and a wireless slave device measure the received radio wave strength of interference waves for all channels, statistically process the measurement data, and select an available wireless channel (see, for example, Patent Document 1).Furthermore, a technique is known in which a channel to be carrier sensed is shared between a local station and surrounding wireless stations, and an available channel is detected using the carrier sense results obtained from surrounding wireless stations and the carrier sense result of the local station (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-187089 [Patent Document 2] Japanese Patent Publication No. 2020-120257 Summary of the Invention [Problem to be solved by the invention]

[0005] The ISM (Industry, Science, and Medical) band is a frequency band allocated for general-purpose use in, for example, the industrial, scientific, and medical fields. The 920 MHz band in the ISM band has traditionally been used in wireless communication systems for remote meter reading using smart meters for electricity, gas, water, and other services. In recent years, there has been a trend toward an increase in measuring instruments, sensors, and other devices connected to wireless communication networks. As a result, it is expected that the frequency band in the ISM band will become congested, and wireless terminals will have to perform carrier sense and retry transmission processing more frequently.

[0006] On the other hand, in wireless communication systems for smart meters for electricity, gas, water, etc., wireless terminals often operate on battery power, so when processes such as carrier sensing and re-execution of transmission processes are repeatedly performed, power consumption increases and usable time is shortened.

[0007] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and in a wireless communication system including multiple wireless terminals, it suppresses an increase in power consumption of the wireless terminals even in an environment where the available frequency band is congested. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, a wireless communication system according to one embodiment of the present invention is a wireless communication system including a plurality of wireless terminals that perform multi-hop communication, and a management device that can communicate with the plurality of wireless terminals using the multi-hop communication, wherein the management device has a collection unit that collects usage status data indicating usage status of a plurality of wireless channels around the wireless terminals from the plurality of wireless terminals at predetermined time intervals, a storage unit that stores the usage status data collected from the plurality of wireless terminals in chronological order, and a selection unit that selects a transmission method by which the plurality of wireless terminals transmit data for each time period based on the usage status data stored in the storage unit in chronological order, and the selection unit is configured to select a transmission method by which the plurality of wireless terminals transmit data for each time period based on the usage status data stored in chronological order, and butIf not, the plurality of wireless terminals select a delay time and a wireless channel for transmission on an available channel. [Effects of the Invention]

[0009] According to one embodiment of the present invention, in a wireless communication system including a plurality of wireless terminals, it is possible to suppress an increase in power consumption of the wireless terminals even in an environment where the available frequency band is congested. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of a system configuration of a wireless communication system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a functional block diagram of a wireless master device according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of a functional block diagram of a wireless slave device according to an embodiment. [Figure 4] FIG. 2 illustrates an example of a hardware configuration of a management apparatus according to an embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of a functional configuration of a management apparatus according to an embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of usage status data according to an embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of a usage status management table according to an embodiment. [Figure 8] FIG. 10 is a sequence diagram illustrating an example of processing in a wireless communication system according to an embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of a data transmission procedure during a usage data acquisition process according to an embodiment. [Figure 10] 10 is a flowchart illustrating an example of a reception monitoring process according to an embodiment. [Figure 11] 10A and 10B are diagrams illustrating a synchronization signal of a wireless transmission frame according to an embodiment. [Figure 12] FIG. 4 is a diagram illustrating a process of selecting a transmission method according to the first embodiment. [Figure 13]FIG. 10 is a diagram (1) for explaining a transmission method selection process according to the second embodiment. [Figure 14] FIG. 10 is a diagram (2) for explaining the transmission method selection process according to the second embodiment. [Figure 15] 11 is a flowchart illustrating an example of a transmission method selection process according to the third embodiment. [Figure 16] FIG. 13 is a diagram illustrating an example of terminal management information according to the fourth embodiment. [Figure 17] FIG. 13 is a diagram illustrating an example of a collection process of usage data according to the fourth embodiment. [Figure 18] FIG. 1 is a diagram illustrating an example of a transmission procedure in a conventional wireless communication system. [Figure 19] FIG. 1 is a diagram illustrating an example of the configuration of a conventional wireless communication network. [Figure 20] FIG. 1 is a diagram illustrating an example of hop count information in a conventional wireless communication network. [Figure 21] FIG. 1 is a diagram illustrating an example of a wireless communication packet in a conventional wireless communication network. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the invention will be described with reference to the drawings.

[0012] <Wireless communication network overview> Before describing the wireless communication system according to this embodiment, an outline of a wireless communication network that is the premise of this embodiment will be described.

[0013] Fig. 19 is a diagram showing an example of the configuration of a conventional wireless communication network. The wireless communication network 1 shown in Fig. 19 is a standard form of multi-hop wireless communication in a conventional wireless communication network, and is an example of a wireless communication network in which multiple wireless terminals A to J communicate data via multi-hop communication.

[0014] 19, A to J indicate wireless terminals that are installed in a distributed manner. Each of the wireless terminals A to J can perform direct wireless communication with other wireless terminals within a predetermined communication range from the wireless terminal itself. Furthermore, each of the wireless terminals A to J can perform wireless communication with all other wireless terminals by performing multi-hop communication via other wireless terminals.

[0015] 19, the dashed lines connecting the wireless terminals A to J indicate wireless communication paths, and indicate that two wireless terminals connected by a dashed line can perform direct wireless communication. Each of the wireless terminals A to J diagnoses the reliability of the communication path by mutually transmitting and receiving, for example, presence notification packets, communication diagnostic packets, etc., and generates hop count information 21a of its own terminal, as shown in FIG. 20, and stores it in a storage unit or the like.

[0016] 20 is an example of hop count information generated and stored by wireless terminal A, and indicates the number of communications (hops) that a packet transmitted by wireless terminal A makes before reaching another wireless terminal. This hop count information 21a indicates, for example, that other wireless terminals to which wireless terminal A can transfer a packet in one communication are wireless terminals B, C, and D. Similarly, it indicates that other wireless terminals to which wireless terminal A can transfer a packet in two communications are wireless terminals E and F, other wireless terminals to which wireless terminal A can transfer a packet in three communications are wireless terminals F, H, and I, and a wireless terminal to which wireless terminal A can transfer a packet in four communications is wireless terminal J.

[0017] However, for example, the hop count information 21a of wireless terminal A does not necessarily mean that wireless terminal A cannot directly communicate with wireless terminals E to H other than wireless terminals B, C, and D. For example, in Fig. 19, wireless terminals E and F may be able to directly communicate with wireless terminal A when the surrounding communication environment is good. However, in this case, the wireless communication from wireless terminal A to wireless terminals E and F is managed as requiring relaying by another wireless terminal due to reasons such as insufficient reliability as a result of the diagnosis of the reliability of the communication path described above.

[0018] Furthermore, each wireless terminal A to J acquires hop count information of other adjacent wireless terminals (other wireless terminals with which direct wireless communication is possible) based on its own hop count information 21a, for example, as shown in FIG. 20, and creates hop count information 22a of the adjacent terminals, for example, as shown in FIG. 20, and stores it in a memory unit or the like.

[0019] The neighboring terminal hop count information 22a in Fig. 20 is an example of neighboring terminal hop count information that wireless terminal A acquires from neighboring wireless terminals B, C, and D and stores. It is not essential that wireless terminal A manages its own hop count information 21a and the neighboring terminal hop count information 22a separately, and they may be managed as a single wireless terminal A hop count information 20a. In the following description, when there is no particular need to distinguish between wireless terminal A's own hop count information 21a and the neighboring terminal hop count information 22a, they will be referred to as wireless terminal A's hop count information 20a.

[0020] Note that the other wireless terminals B to J included in the wireless communication network 1 manage hop count information 20b to 20J of each of the wireless terminals B to J in the same manner as the wireless terminal A. Fig. 20 shows examples of the hop count information 20b of the wireless terminal B, the hop count information 20e of the wireless terminal E, and the hop count information 20g of the wireless terminal G.

[0021] When transmitting a packet to another wireless terminal, each of the wireless terminals A to G refers to its own hop count information 20a to 20j to determine the destination of the packet. The hop count information 20a to 20j is an example of network configuration information.

[0022] As an example, when wireless terminal A transmits a packet addressed to wireless terminal J, wireless terminal A refers to the hop count information 20a of wireless terminal A and transmits the packet to one of wireless terminals B, C, and D that is the shortest hop count from wireless terminal A to wireless terminal J. For example, wireless terminal A transmits a wireless communication packet 30 as shown in FIG. 21 to wireless terminal B, as indicated by the arrow in FIG. 19.

[0023] FIG. 21 is a diagram showing an example of a wireless communication packet in a conventional wireless communication network. In the example of FIG. 21, a wireless communication packet 30 includes a "network ID," a "source RNO," a "destination RNO," a "source RNO," a "destination RNO," and "data." The "network ID" is a network number that identifies the wireless communication network 1. The "source RNO" is the wireless terminal number (hereinafter referred to as RNO) of the wireless terminal that transmitted the wireless communication packet 30. The "destination RNO" is the RNO of the wireless terminal to which the wireless communication packet 30 is to be forwarded. For example, when wireless terminal A transmits a wireless communication packet 30 to wireless terminal J via adjacent wireless terminal B, the RNO of wireless terminal A is set as the "source RNO" and the RNO of wireless terminal B is set as the "destination RNO."

[0024] "Source RNO" is an RNO indicating the wireless terminal that is the source of transmitting "data". "Destination RNO" is an RNO indicating the wireless terminal that is the destination of transmitting "data". For example, when transmitting a wireless communication packet 30 from wireless terminal A to wireless terminal J, the RNO of wireless terminal A is set in "Source RNO" and the RNO of wireless terminal J is set in "Destination RNO". Data to be transmitted to the destination wireless terminal J is stored in "Data".

[0025] A wireless terminal B that receives a wireless communication packet 30 (hereinafter referred to as a packet) from a wireless terminal A determines the destination of the packet by referring to the hop count information 20b of the wireless terminal B, for example, as shown in Fig. 20. For example, the wireless terminal B transfers the packet to a wireless terminal E that is located a few hops away from the wireless terminal B to a wireless terminal J.

[0026] Similarly, wireless terminal E, which has received a packet from wireless terminal B, determines the destination of the packet by referring to hop count information 20e of wireless terminal E, for example, as shown in FIG. 20. For example, wireless terminal E transfers the packet to wireless terminal G, which is the wireless terminal J that is the nearest hop from wireless terminal E. Wireless terminal G, which has received the packet, transfers the packet to adjacent wireless terminal J. This allows wireless terminal A to transmit the packet to wireless terminal J via wireless terminals B, E, and G, as shown by the arrows in FIG. 19.

[0027] In the wireless communication network 1, an RNO (wireless terminal number) is assigned to each wireless terminal as identification information for identifying each wireless terminal A to J. That is, each wireless terminal A to J is originally assigned and registered with identification information for uniquely identifying the wireless terminal, such as a serial number, at the time of manufacture. However, this serial number is long, requiring a size of, for example, about 14 bytes. Therefore, if this serial number is used as identification information for identifying each wireless terminal A to J in the wireless communication network 1, the identification information is basically always transmitted and received in communication between the wireless terminals, which increases the amount of information during communication and increases the communication load.

[0028] Therefore, in the wireless communication network 1, an RNO of, for example, about 1 byte is assigned to each of the wireless terminals A to J, and this RNO is used as identification information for identifying each of the wireless terminals A to J within the wireless communication network 1. Furthermore, the wireless communication network 1 stores and manages, for example, in terminal management information, the correspondence between the RNO of each of the wireless terminals A to J and identification information (hereinafter referred to as ID) unique to each wireless terminal, such as a serial number.

[0029] With the above configuration, in the wireless communication network 1, for example, two-way information exchange is performed between multiple wireless terminals A to J at any timing using short-range wireless communication. Short-range wireless communication systems include low-rate wireless PAN (Personal Area Network) systems, such as those standardized by IEEE802.15, which aim for low-power consumption and low-cost communication. An example of a low-rate wireless PAN system using IEEE802.15 is the internationally standardized ZigBee (registered trademark). In addition, for centralized monitoring systems for gas, water, etc., U-Bus Air is known as a wireless communication method compliant with IEEE802.15.4g / e, which is standardized by the NPO Telemetering Promotion Council.

[0030] Wireless communication networks1 are used to configure networks with wireless nodes equipped with sensors and wireless stations equipped with actuators that control various devices, and are used for home security, safety and security for children and the elderly, health management, home / building facility control, factory control and monitoring, hospital management, automatic meter reading, outdoor monitoring, and more.

[0031] <About the assignment> The ISM (Industry, Science, and Medical) band is a frequency band allocated for general-purpose use in, for example, the industrial, scientific, and medical fields. The 920 MHz band in the ISM band has traditionally been used in wireless communication systems for remote meter reading using smart meters for electricity, gas, water, and other services. In recent years, there has been a trend toward an increase in measuring instruments, sensors, and other devices connected to wireless communication networks. As a result, it is expected that the frequency band in the ISM band will become congested, and wireless terminals will have to perform carrier sense and retry transmission processing more frequently.

[0032] On the other hand, in wireless communication systems for smart meters for electricity, gas, water, etc., wireless terminals often operate on battery power, so when processes such as carrier sensing and re-execution of transmission processes are repeatedly performed, power consumption increases and usable time is shortened.

[0033] This embodiment has been made in consideration of the above-mentioned problems, and suppresses an increase in the power consumption of a wireless terminal in a wireless communication system where there are restrictions on the power consumption of the wireless terminal, even in an environment where the available frequency band is congested.

[0034] The present invention is a technology for suppressing an increase in power consumption of a wireless terminal in a wireless communication network including a plurality of wireless terminals, and the communication method itself is not limited to a specific standard.

[0035] <System configuration> FIG. 1 is a diagram illustrating an example of a system configuration of a wireless communication system according to an embodiment. The wireless communication system 100 includes, for example, a management device 110, a wireless master device 120, and multiple wireless slave devices 130a-130h. The wireless master device 120 and the multiple wireless slave devices 130a-130h are an example of multiple wireless terminals that perform multi-hop communication. In the following description, the wireless master device 120 and the multiple wireless slave devices 130a-130h may be referred to as "multiple wireless terminals." Furthermore, when referring to any wireless slave device among the multiple wireless slave devices 130a-130h, the term "wireless slave device 130" is used. The number of multiple wireless slave devices 130 illustrated in FIG. 1 is an example, and the number of wireless slave devices 130 may be two or more.

[0036] The wireless master device 120 is a wireless terminal having a GW (Gateway) function, and is communicably connected to a higher-level device such as the management device 110 via a communication network 101 such as the Internet or a LAN (Local Area Network). As another example, the wireless master device 120 may be communicably connected to the management device 110 via a wired or wireless connection, or the wireless master device 120 may be included in the management device 110.

[0037] For example, the wireless master device 120 receives data such as sensor data or usage status data from the multiple wireless slave devices 130a to 130h, and transmits the received data to the management device 110. Furthermore, when the wireless master device 120 receives control information or the like addressed to other wireless terminals 130a to 130h from the management device 110, the wireless master device 120 transfers the received control information to the destination wireless terminal.

[0038] The management device 110 is, for example, an information processing device having a computer configuration, or a system including multiple computers. The management device 110 is communicably connected to the wireless master device 120, and can communicate with multiple wireless slave devices 130a to 130h via the wireless master device 120 using multi-hop communication. The management device 110 has a function of collecting sensor data acquired by the multiple wireless slave devices 130a to 130h, storing the data in a database or the like, and managing the data.

[0039] Furthermore, the management device 110 according to this embodiment has a function of collecting, from a plurality of wireless terminals (the wireless master device 120 and a plurality of wireless slave devices 130a-130h), usage status data indicating the usage status of wireless channels around each wireless terminal. Furthermore, the management device 110 has a function of storing the usage status data collected from the plurality of wireless terminals in a memory unit in chronological order, and selecting a transmission method for the plurality of wireless terminals to transmit data for each time period based on the usage status data. Note that the usage status data collected from the plurality of wireless terminals includes, for example, information on the time when each wireless terminal detected interference waves 102 from another wireless system (e.g., other wireless devices 103, 104, etc. in FIG. 1), information on the wireless channel on which the interference waves 102 were received, and the like.

[0040] As one example, the management device 110 selects, for each time period, a transmission timing (one example of a transmission method) that is not affected (or is less affected) by interference waves 102 from other wireless systems, based on the usage status data stored in chronological order in the storage unit. As another example, the management device 110 selects, for each time period, a wireless channel (another example of a transmission method) that is not affected (or is less affected) by interference waves 102 from other wireless systems, based on the usage status data stored in chronological order in the storage unit. In addition, the management device 110 notifies the multiple wireless terminals of the selected transmission method.

[0041] As a result, the multiple wireless terminals transmit data using the communication method notified by the management device 110, i.e., a transmission timing or wireless channel that is less susceptible to interference waves 102 from other wireless systems. Therefore, in the wireless communication system 100 according to this embodiment, even in an environment where the available frequency band is congested, the frequency at which the multiple wireless terminals perform processes such as carrier sense or re-execution of transmission process can be reduced, thereby suppressing an increase in power consumption of the wireless terminals.

[0042] <Configuration of each device> (Wireless base station) 2 is a diagram showing an example of a functional block diagram of a wireless master device according to an embodiment. The wireless master device 120 has functional components such as a wireless communication unit 210, a control unit 220, a storage unit 230, and a communication unit 240. The wireless communication unit 210 is realized by, for example, a wireless communication device for multi-hop communication, and includes a wireless transmission unit 211, a wireless reception unit 212, and a reception level measurement unit 203.

[0043] 21 by multi-hop communication under the control of the control unit 220. The wireless receiving unit 212 outputs the wireless communication packet 30 received by the multi-hop communication to the control unit 220. The reception level measuring unit 203 measures the level of the signal received by the wireless receiving unit 212, such as the reception field strength or RSSI (Received Signal Strength Indicator / Indication), and outputs the measurement result to the control unit 220.

[0044] The control unit 220 is realized by a computer included in the wireless master device 120, a program stored in a storage device, etc., and includes, for example, a communication control unit 221, a reception monitoring unit 222, and an information transmitting unit 223.

[0045] The communication control unit 221 controls the wireless communication unit 210 in accordance with, for example, the setting information 231 stored in the storage unit 230 to perform multi-hop communication with the plurality of wireless slave devices 130. For example, the communication control unit 221 controls the wireless communication unit 210 to transfer data (e.g., sensor data) received from the plurality of wireless slave devices 130 to the management device 110 via the communication unit 240. Furthermore, the communication control unit 221 transmits various control information to the wireless slave devices 130 via the wireless communication unit 210 in accordance with request information received from the management device 110 via the communication unit 240.

[0046] Furthermore, the communication control unit 221 stores and manages the setting information 231 received from the management device 110 via the communication unit 240 in the storage unit 230. Furthermore, the communication control unit 221 stores the communication history of the wireless communication unit 210 as log information 232 in the storage unit 230.

[0047] The reception monitoring unit 222 executes a reception monitoring process to acquire usage status data including, for example, information on the time when the interference wave 102 from another wireless system was detected and information on the wireless channel that received the interference wave 102, in response to a request from the management device 110.

[0048] The information transmitting unit 223 executes an information transmitting process to transmit the usage status data acquired by the reception monitoring unit 222 and the usage status data received by the communication control unit 221 from multiple wireless slave devices 130 to the management device 110 via the communication unit 240.

[0049] The storage unit 230 is realized by, for example, a storage device provided in the wireless master device 120, and stores various information, data, programs, and the like, including the setting information 231 and log information 232 described above.

[0050] The communication unit 240 is realized by, for example, a network interface card (NIC) provided in the wireless master device 120, and executes communication processing for communicating with the management device 110.

[0051] (wireless adapter) 3 is a diagram showing an example of a functional block diagram of a wireless slave device according to an embodiment. The wireless slave device 130 has functional components such as a wireless communication unit 210, a control unit 320, a storage unit 230, a sensor I / F (Interface) 301, and a power supply unit 302. Note that the wireless communication unit 210 and the storage unit 230 are similar to the wireless communication unit 210 and the storage unit 230 of the wireless master device 120 described in FIG. 2, and therefore description thereof will be omitted here.

[0052] The control unit 320 is realized by a computer included in the wireless slave device 130, a program stored in a storage device, etc., and includes, for example, a communication control unit 321, a reception monitoring unit 322, and an information transmitting unit 323.

[0053] The communication control unit 321 controls the wireless communication unit 210 in accordance with, for example, the setting information 231 stored in the storage unit 230, and performs multi-hop communication with the wireless master device 120 and other wireless slave devices 130. For example, when the received wireless communication packet 30 is addressed to the communication control unit 221, the communication control unit 221 acquires data included in the wireless communication packet 30. On the other hand, when the received wireless communication packet 30 is addressed to the wireless master device 120 or other wireless slave devices 130, the communication control unit 221 forwards the wireless communication packet 30 by multi-hop communication.

[0054] In addition, the communication control unit 321 transmits, for example, sensor data measured by the measurement unit 301 using the sensor 310 and usage status data transmitted by the information transmission unit 323 to the wireless base station 120 via multi-hop communication using the wireless communication unit 210.

[0055] Furthermore, the communication control unit 321 stores and manages the setting information 231 received from the management device 110 via the wireless communication unit 210 in the storage unit 230. Furthermore, the communication control unit 321 stores the communication history by the wireless communication unit 210 as log information 232 in the storage unit 230.

[0056] The reception monitoring unit 322 executes a reception monitoring process to acquire usage status data including, for example, information on the time when the interference wave 102 from another wireless system was detected and information on the wireless channel that received the interference wave 102, in response to a request from the management device 110.

[0057] The information transmitting unit 323 executes an information transmitting process for transmitting the usage status data acquired by the reception monitoring unit 322 to the management device 110 via the communication control unit 321 .

[0058] The measurement unit 301 controls the sensor 310 using, for example, a sensor I / F or the like included in the wireless slave device 130 to acquire sensor data and outputs the acquired sensor data to the control unit 320. The power supply unit 302 supplies power output from, for example, a battery included in the wireless slave device 130 to various pieces of hardware included in the wireless slave device 130.

[0059] (Hardware configuration of management device) 4 is a diagram illustrating an example of the hardware configuration of a management device according to an embodiment. The management device 110 has a typical computer configuration, and includes, for example, a processor 401, a memory 402, a storage device 403, a communication device 404, an input device 405, an output device 406, and a bus 407.

[0060] The processor 401 is an arithmetic unit such as a CPU (Central Processing Unit) that executes programs stored in a storage medium such as the memory 402 or the storage device 403 to realize various functions of the management device 110. Note that the processor 401 may include, in addition to (or instead of) the CPU, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array), for example.

[0061] The memory 402 may include various storage devices such as a random access memory (RAM), which is a volatile memory used by the processor 401 as a work area, and a read only memory (ROM) that stores startup programs and the like in advance. The storage device 403 is a large-capacity nonvolatile storage device such as a solid state drive (SSD) or a flash ROM.

[0062] The communication device 404 includes, for example, a NIC for communicating with the wireless master device 120 via the communication network 101. The input device 405 includes various input devices (for example, a keyboard, a touch panel, a pointing device, a microphone, a switch, a button, a sensor, etc.) that accept input from the outside. The output device 406 includes various output devices (for example, a display, a speaker, etc.) that output to the outside. The bus 407 is commonly connected to each of the above components and transmits, for example, address signals, data signals, various control signals, etc.

[0063] (Functional configuration of management device) Fig. 5 is a diagram showing an example of the functional configuration of a management device according to one embodiment. The management device 110 realizes, for example, the functional configuration shown in Fig. 5 by having the processor 401 execute a program stored in a storage medium such as the storage device 403 or the memory 402. In the example of Fig. 5, the management device 110 includes a communication unit 501, a collection unit 502, a selection unit 503, a notification unit 504, a data management unit 505, and a storage unit 510. Note that at least a portion of the above functional configurations may be realized by hardware.

[0064] The communication unit 501 executes communication processing for communicating with the wireless master device 120. For example, the communication unit 501 uses the communication device 404 to connect the management device 110 to a communication network 101 such as a LAN or a WAN (Wide Area Network), and transmits and receives various data to and from the wireless master device 120.

[0065] The collection unit 502 executes a collection process to collect usage status data indicating the usage status of wireless channels around each wireless terminal from multiple wireless terminals (the wireless master device 120 and multiple wireless slave devices 130). For example, the collection unit 502 receives the usage status data acquired by the multiple wireless terminals from the wireless master device 120, and stores the received usage status data 511 in the storage unit 510 or the like.

[0066] Fig. 6 is a diagram showing an example of usage status data according to an embodiment. Fig. 6(A) shows an example of usage status data transmitted by the wireless master device 120 and the wireless slave device 130. Here, an example of usage status data 511a is shown for the case where the number of wireless channels available for multi-hop communication in the wireless communication system 100 is two.

[0067] In the example of Fig. 6(A), the usage status data 511a includes information such as "time," "CH1 (channel 1)," and "CH2 (channel 2)" as items. In Fig. 6(A), for example, the time "10:00" indicates the time period from 10:00 to 11:00, and "CH1" indicates the number of times that interference waves 102 from other wireless systems (e.g., other wireless devices 103, 104, etc. in Fig. 1) were detected on CH1 during each time period. Similarly, "CH2" indicates the number of times that interference waves 102 from other wireless systems were detected on CH2 during each time period. In this way, the usage status data 511a shown in Fig. 6(A) indicates the number of times that interference waves were detected on each wireless channel for each time period.

[0068] 6(B), the usage status data 511b includes information such as "time," "wireless channel," "reception level," and "communication content" as items. This usage status data 511b is log information 232 that indicates the time, wireless channel, and reception level when each "communication content (event)" occurred.

[0069] The usage status data collected by the collection unit 502 may be, for example, usage status data 511b in the form of log information 232 as shown in Fig. 6(B). In this case, the collection unit 502 analyzes the usage status data 511b and counts the number of detected interference waves in each wireless channel, thereby obtaining information similar to, for example, usage status data 511a shown in Fig. 6(A).

[0070] The selection unit 503 executes a selection process to select a transmission method by which a plurality of wireless terminals (the wireless master device 120 and a plurality of wireless slave devices 130) transmit data for each time period, based on the use status data 511 stored in the storage unit 510 by the collection unit 502. For example, the selection unit 503 combines use status data 511a, for example, as shown in FIG. 6(A), stored in the storage unit 510, to create a use status management table 512 as shown in FIG. 7. Furthermore, the selection unit 503 uses the created use status management table 512 to select a transmission method (for example, transmission timing or a wireless channel) by which a plurality of wireless terminals transmit data in a predetermined time period.

[0071] As an example, assume that wireless communication system 100 is a system in which multiple wireless terminals acquire sensor data twice an hour and transmit the acquired sensor data to management device 110. For example, in usage status management table 512 shown in Fig. 7, multiple wireless terminals acquire sensor data at 10:00, 10:30, and 11:00. However, in the example of Fig. 7, a large number of interference waves 102 from other wireless systems are detected during the time period from 10:00 to 20:20.

[0072] In such a case, the selection unit 503 may set the transmission timing (for example, delay time td from a predetermined transmission time) at which the multiple wireless terminals transmit sensor data to 20 minutes, as an example. This allows the multiple wireless terminals to transmit data during the time period from 10:20 to 20:30, when no interference from other wireless systems is detected.

[0073] As another example, when it is desired to transmit data during a time period in which sensor data is acquired (for example, a time period from 10:00 to 10:10), the selection unit 503 may select CH2 as the wireless channel through which multiple wireless terminals transmit sensor data during that time period. This allows the multiple wireless terminals to transmit data using the wireless channel CH2, in which no interference from other wireless systems is detected, during the time period from 10:00 to 10:10, for example.

[0074] The notification unit 504 notifies a plurality of wireless terminals of the transmission method for transmitting data in a predetermined time period selected by the selection unit 503. For example, the notification unit 504 transmits setting information 231 indicating the transmission method for transmitting data in a predetermined time period to a plurality of wireless terminals (the wireless master device 120 and the plurality of wireless slave devices 130).

[0075] The data management unit 505 stores and manages, for example, sensor data 515 received from a plurality of wireless terminals in the storage unit 510. The storage unit 510 stores the above-mentioned usage status data 511, usage status management table 512, sensor data 513, etc. Preferably, the storage unit 510 further stores terminal management information 514, etc., which stores information on a plurality of wireless terminals in advance.

[0076] 5 is an example. For example, at least some of the functional components of the management device 110 may be included in the wireless master device 120. Furthermore, the functional components of the management device 110 may be distributed among multiple computers.

[0077] <Processing flow> Next, the processing flow of the wireless communication method according to this embodiment will be described.

[0078] (Processing of wireless communication systems) 8 shows an example of processing in a wireless communication system according to an embodiment. This processing shows an overview of processing in which the wireless communication system 100 selects a transmission method for transmitting data by a plurality of wireless terminals (a wireless master device 120 and a plurality of wireless slave devices 130) based on usage status data acquired by the plurality of wireless terminals.

[0079] In step S801, the collection unit 502 of the management device 110 transmits an acquisition request for requesting acquisition of usage status data to the wireless master device 120. This acquisition request for usage status data includes information such as the time period for acquiring the usage status data.

[0080] In step S802, the communication control unit 221 of the wireless master device 120 transmits the acquisition request for the usage data received from the management device 110 to the multiple wireless slave devices 130a to 130h using the wireless communication unit 210 through multi-hop communication.

[0081] In step S803, the wireless terminals (the wireless master device 120 and the wireless slave devices 130a to 130h) that have received the request to acquire the utilization status data execute an acquisition process to acquire utilization status data indicating the utilization status of wireless channels around each wireless terminal. Preferably, the wireless terminals acquire the utilization status data while transmitting data by multi-hop communication.

[0082] 9 is a diagram showing an example of a data transmission procedure during a process of acquiring utilization status data according to an embodiment. For example, upon receiving a request to acquire utilization status data, the reception monitoring unit 322 of the wireless slave device 130d performs reception monitoring 900a to detect interference waves from other wireless systems received through multiple wireless channels (e.g., CH1, CH2). The reception monitoring unit 322 also stores the number of times interference waves have been detected through reception monitoring 900a in utilization status data 511a, such as that shown in FIG. 6(A).

[0083] Furthermore, when an event occurs at time t1 in which data is to be transmitted to the wireless master device 120, the communication control unit 321 of the wireless slave device 130d performs carrier sense (CS) to determine whether or not the data can be transmitted. If the data can be transmitted, the communication control unit 321 transmits the data addressed to the wireless master device 120 to the wireless slave device 130a at time t2, for example, and resumes reception monitoring 900a.

[0084] Similarly, when the reception monitoring unit 322 of the wireless slave device 130a receives a request to acquire usage status data, the reception monitoring unit 322 performs reception monitoring 900b to detect interference waves from other wireless systems received through multiple wireless channels. The reception monitoring unit 322 also stores the number of times that interference waves have been detected in reception monitoring 900b in, for example, usage status data 511a as shown in FIG. 6(A).

[0085] Furthermore, at time t2 during reception monitoring 900b, when the reception monitoring unit 322 of the wireless slave device 130a receives data addressed to the wireless master device 120 and transmitted by the wireless slave device 130d, the reception monitoring unit 322 notifies the communication control unit 321 of the reception of the data. In response to this, the communication control unit 321 of the wireless slave device 130a, for example, returns an acknowledgement (ACK) to the wireless slave device 130d that is the sender, and executes a transfer process to transfer the received data to the wireless master device 120. For example, at time t3, the communication control unit 321 of the wireless slave device 130a performs carrier sense (CS) to determine whether data can be transmitted. If data can be transmitted, the communication control unit 321 transmits the data addressed to the wireless master device 120 to the wireless master device 120, for example, at time t4, and resumes reception monitoring 900b.

[0086] Similarly, upon receiving a request to acquire usage status data, the reception monitoring unit 222 of the wireless master device 120 performs reception monitoring 900c to detect interference signals received via multiple wireless channels from other wireless systems. The reception monitoring unit 222 also stores the number of times that interference signals have been detected by reception monitoring 900c in, for example, usage status data 511a as shown in FIG. 6(A).

[0087] Furthermore, at time t4 during reception monitoring 900c, when the reception monitoring unit 222 of the wireless master device 120 receives data addressed to the wireless master device 120 and transmitted by the wireless slave device 130a, the reception monitoring unit 222 notifies the communication control unit 221 of the data reception. In response, for example, at time t5, the communication control unit 221 of the wireless master device 120 returns an ACK to the wireless slave device 130a that is the sender, and starts processing the received data. Furthermore, the reception monitoring unit 222 of the wireless master device 120 resumes reception monitoring 900c at time t5. In this way, in step S803 of FIG. 8, multiple wireless terminals can acquire usage status data while transmitting data via multi-hop communication.

[0088] Fig. 10 is a flowchart showing an example of reception monitoring processing according to an embodiment. This processing shows an example of reception monitoring processing executed by the wireless master device 120 and the wireless slave devices 130a, 130d, etc. in the reception monitoring 900a to 900c in Fig. 9. For ease of explanation, the following description will be given assuming that the wireless slave device 130 executes the reception monitoring processing shown in Fig. 10.

[0089] In step S1001, the reception monitoring unit 322 of the wireless slave device 130 selects a wireless channel. For example, the reception monitoring unit 322 selects one wireless channel (e.g., CH1) from among multiple wireless channels CH1 and CH2 available in the wireless communication system 100.

[0090] In step S1002, the reception monitoring unit 322 sets a monitoring time for performing reception monitoring on the wireless channel selected in step S1001. At this time, the reception monitoring unit 322 sets a monitoring time that is sufficiently shorter than the transmission period of the bit synchronization signal added to the beginning of the wireless transmission frame transmitted by the wireless master device 120 and the other wireless slave devices 130.

[0091] 11 is a diagram illustrating a synchronization signal of a wireless transmission frame according to an embodiment. In a wireless transmission frame 1100 transmitted by the wireless master device 120 and the wireless slave device 130, a synchronization signal 1104 including a bit synchronization signal 1101 and a frame synchronization signal 1102 is added before a data frame 1103. Note that the data frame 1103 stores, for example, a wireless communication packet 30 as shown in FIG. 21.

[0092] The bit synchronization signal 1101 is a repetitive signal of 0s and 1s for the wireless slave device 130 (or wireless master device 120) to synchronize with bit timing in order to receive data by frame synchronization, and is repeatedly transmitted, for example, about 10 to 20 bits. The frame synchronization signal is a signal for the wireless slave device 130 (or wireless master device 120) to detect the start position of a data frame in the received frame configuration, and is repeatedly transmitted, for example, about several bits.

[0093] The reception monitoring unit 322 sets a monitoring time that is sufficiently shorter than the transmission period of the bit synchronization signal 1101 and switches the wireless channel, thereby being able to reliably detect the wireless transmission frame 1100 transmitted on any one of the multiple wireless channels (e.g., CH1, CH2).

[0094] 10, the reception monitoring unit 322 determines whether a carrier has been detected on the selected wireless channel, for example, based on the measurement result of the reception level measurement unit 213. If a carrier has not been detected, the reception monitoring unit 322 shifts the process to step S1004. On the other hand, if a carrier has been detected, the reception monitoring unit 322 shifts the process to step S1006.

[0095] In step S1004, the reception monitoring unit 322 determines whether the set monitoring time has expired. If the monitoring time has not expired, the reception monitoring unit 322 returns the process to step S1003. On the other hand, if the monitoring time has expired, the reception monitoring unit 322 advances the process to S1005.

[0096] In step S1005, the reception monitoring unit 322 changes the wireless channel and returns the process to step S1003. For example, if the wireless channels available in the wireless communication system 100 are CH1 and CH2 and the current wireless channel is CH1, the reception monitoring unit 322 switches the wireless channel to CH2. Also, if the current wireless channel is CH2, the reception monitoring unit 322 switches the wireless channel to CH1.

[0097] By the processes of steps S1003 to S1005, the reception monitoring unit 322 repeatedly executes the process of switching the wireless channel for each monitoring time until a carrier is detected.

[0098] On the other hand, when the process proceeds from step S1003 to step S1006, the communication control unit 321 of the wireless slave device 130 acquires the data frame 1103. Furthermore, in step S1007, the communication control unit 321 determines whether or not the data stored in the received data frame 1103 is data for the wireless communication system 100, which is the wireless communication system of the wireless slave device 130. As described above, the data frame 1103 stores, for example, a wireless communication packet 30 as shown in Fig. 21 , and therefore the communication control unit 321 can determine whether or not the data is data for the wireless communication system 100 based on the "network ID."

[0099] If the data is not from the own system, the communication control unit 321 shifts the process to step S1008. On the other hand, if the data is from the own system, the communication control unit 321 shifts the process to step S1009.

[0100] In step S1008, the reception monitoring unit 322 counts the acquired data frame 1103 as a jamming wave.

[0101] On the other hand, when the process proceeds to step S1009, the communication control unit 321 determines whether or not the acquired data frame 110 is data addressed to the own device. As described above, the data frame 1103 stores, for example, a wireless communication packet 30 as shown in Fig. 21, so the communication control unit 321 can determine whether or not the data is addressed to the own device based on the "destination RNO".

[0102] If the data is not addressed to the own device, the communication control unit 321 shifts the process to step S10101. On the other hand, if the data is addressed to the own device, the communication control unit 321 shifts the process to step S1101.

[0103] In step S1010, the communication control unit 321 uses the wireless communication unit 210 to transfer the data frame 1103 to the destination wireless master device 120 or wireless slave device .

[0104] On the other hand, when the process proceeds to step S1011, the communication control unit 321 acquires data from the data frame 1103 and executes processing corresponding to the acquired data.

[0105] In step S1012, the communication control unit 321 stores the processing content in the log information 232 of the storage unit 230.

[0106] The wireless slave device 130 repeatedly executes the reception monitoring process shown in Fig. 10, thereby being able to acquire the usage status data while transmitting data through multi-hop communication, as explained in Fig. 9. The wireless master device 120 also repeatedly executes the same process, thereby being able to acquire the usage status data while transmitting data through multi-hop communication.

[0107] Returning now to Fig. 8, the description of the sequence diagram illustrating an example of processing in the wireless communication system will be continued. In step S804 in Fig. 8, the information transmitting units 323 of the wireless slave devices 130a to 130h each transmit the usage status data 511 acquired by the reception monitoring units 322 to the wireless master device 120 via multi-hop communication.

[0108] In step S805, the information transmitting unit 223 of the wireless master device 120 transmits the use status data 511 received from the wireless slave devices 130a to 130h and the use status data 511 acquired by the reception monitoring unit 222 of the wireless master device 120 to the management device 110.

[0109] In step S806, the collection unit 502 of the management device 110 stores in the storage unit 510 the usage status data 511 received from the wireless master device 120 and acquired by the multiple wireless terminals (the wireless master device 120 and the multiple wireless slave devices 130).

[0110] In step S807, the selection unit 503 of the management device 110 combines the multiple pieces of usage status data 511 stored in the storage unit 510 by the collection unit 502 to create a usage status management table 512 such as that shown in FIG.

[0111] In step S808, the selection unit 503 executes a transmission method selection process for selecting (determining) a transmission method (for example, transmission timing, a wireless channel to be used, or the like) for multiple wireless terminals to transmit data for each time period, using the created usage status data 511. The transmission method selection process will be described later in the first to third embodiments.

[0112] In step S809, the notification unit 504 of the management device 110 transmits notification information to the wireless master device 120 and the multiple wireless slave devices 130, notifying them of the transmission method by which the multiple wireless terminals will transmit data for each time period selected (determined) by the selection unit 503.

[0113] In step S810, the communication control unit 221 of the wireless master device 120 stores the setting information 231 received from the management device 110 in the storage unit 230. In addition, in step S811, the communication control unit 221 uses the wireless communication unit 210 to transmit the setting information 231 received from the management device 110 to the multiple wireless slave devices 130a to 130h by multi-hop communication.

[0114] In step S812, the communication control units 321 of the wireless slave devices 130a to 130h store the received setting information 231 in the storage units 230, respectively.

[0115] 8 is an example. For example, the wireless slave device 130 may autonomously acquire usage status data in accordance with a predetermined timing for transmitting the log information 232, without receiving a request for acquiring usage status data, and transmit the acquired usage status data to the management device 110. Alternatively, the wireless slave device 130 may acquire usage status data for a predetermined period of time, such as when the wireless slave device 130 is powered on, and transmit the acquired usage status data to the management device 110.

[0116] <Selection of sending method> [First embodiment] In the first embodiment, an example of the transmission method selection process executed by the selection unit 503 of the management device 110 in step S808 in FIG. 8 will be described.

[0117] Fig. 12 is a diagram for explaining a method for selecting a transmission method according to the first embodiment. In the first embodiment, the selection unit 503 of the management device 110 selects (determines) a transmission timing for a plurality of wireless terminals (a wireless master device 120 and a plurality of wireless slave devices 130) to transmit data for each time period, for example, by using a usage status management table 512 as shown in Fig. 7.

[0118] 12(A), the wireless slave device 130 performs measurements at a predetermined measurement period T and transmits the measured sensor data to the wireless master device 120. Here, as an example for the purpose of explanation, it is assumed that the wireless slave device 130 is set to perform measurements every hour, i.e., at 10:00, 11:00, 12:00, and so on.

[0119] 7, it can be seen that multiple wireless slave devices 130 detected interference waves from other wireless systems in the time period from 10:00 to 10:10. Similarly, multiple wireless slave devices 130 also detected interference waves from other wireless systems in the time period from 11:00 to 11:10. In this example, similar to the wireless communication system 100, there is a possibility that there is another wireless system in the vicinity that performs measurement every hour at 10:00, 11:00, 12:00, and so on and transmits data.

[0120] In such a case, the selection unit 503 may select the transmission timings of the multiple wireless terminals so that the sensor data measured at time t0 is transmitted at time t1 after a delay time td, as shown in Fig. 12(A). For example, referring to the usage status management table 512 shown in Fig. 7, in the time period from 10:00 to 11:00, interference waves 102 from other wireless systems are not detected at "time" 10:20, 10:40, and 10:50.

[0121] In this case, the selection unit 503 selects, for example, 20 minutes as the delay time td, which is an example of the transmission timing, in the time slot from 10:00 to 11:00. However, this is not limiting, and in the example of the usage status management table 512 shown in Fig. 7, the selection unit 503 may select 40 minutes or 50 minutes as the delay time td.

[0122] Furthermore, when the selection unit 503 selects 20 minutes as the delay time td, the notification unit 504 of the management device 110 creates, for example, setting information 1200 as shown in FIG. 12(B) and transmits it to multiple wireless terminals (wireless master device 120 and multiple wireless slave devices 130).

[0123] In this way, according to the first embodiment, multiple wireless terminals can transmit sensor data measured at a specified time to the management device 110 at a transmission timing that is less susceptible to interference from other wireless systems.

[0124] [Second embodiment] In the second embodiment, another example of the transmission method selection process executed by the selection unit 503 of the management device 110 in step S808 in FIG. 8 will be described.

[0125] In the second embodiment, the selection unit 503 of the management device 110 selects (determines) a wireless channel for transmitting data from multiple wireless terminals (a wireless master device 120 and multiple wireless slave devices 130) for each time period, for example, using a usage status management table 512 as shown in FIG.

[0126] For example, the selection unit 503 uses the usage status management table 512 shown in Fig. 7 to create a time table 1301 of available wireless channels as shown in Fig. 13(A). In the "Available Wireless Channel" column of the time table 1301 of available wireless channels, "○" indicates that the wireless channel is available, and "×" indicates that the wireless channel is not available (or its use is not desirable).

[0127] For example, in the time period from 10:00 to 10:10, the wireless master device 120 and the multiple wireless slave devices 130 detect interference from other wireless systems on CH1, so the selection unit 503 displays "X" indicating that CH1 is unavailable during that time period. On the other hand, in the time period from 10:00 to 10:10, the wireless master device 120 and the multiple wireless slave devices 130 do not detect interference from other wireless systems on CH2, so the selection unit 503 displays "O" indicating that CH2 is available during that time period.

[0128] Similarly, the selection unit 503 can create a time table 1301 of available wireless channels as shown in Figure 13(A) by determining whether CH1 and CH2 are available in each time period.

[0129] In addition, when the selection unit 503 creates a timetable 1301 of available wireless channels as shown in Figure 13(A), the notification unit 504 of the management device 110 creates, for example, setting information 1302 as shown in Figure 13(B) and transmits it to multiple wireless terminals.

[0130] Thus, according to the second embodiment, multiple wireless terminals can transmit sensor data measured at a predetermined time to the management device 110 via a wireless channel that is less susceptible to interference from other wireless systems.

[0131] (Application example) 13A is an example. For example, depending on the environment in which the wireless communication system 100 is installed, the radio wave environment may change depending on whether it is a weekday, a holiday, or the day of the week. For example, in an office district, interference from other wireless systems may decrease on holidays. In addition, other wireless systems may transmit data collectively on a specific day of the week or a specific date (for example, the end of the month).

[0132] Therefore, the selection unit 503 of the management device 110 may create a timetable 1301 of available wireless channels for one week, as shown in FIG. 14, and select a different transmission method (transmission timing or wireless channel) for each day of the week, for example.

[0133] Furthermore, the selection unit 503 may further create a time table 1301 of available wireless channels corresponding to holidays, etc., and select different transmission methods (transmission timing or wireless channels) depending on whether it is a weekday, a holiday, or a day of the week.

[0134] Furthermore, the management device 110 may create a timetable 1301 of available wireless channels for one month, for example, and create different setting information 1302 for each day, for example, and notify the same to a plurality of wireless terminals.

[0135] [Third embodiment] The first and second embodiments can be applied in combination, for example, as shown in FIG.

[0136] Fig. 15 is a flowchart showing an example of a transmission method selection process according to the third embodiment. This process shows another example of the transmission method selection process executed by the selection unit 503 of the management device 110 in step S808 in Fig. 8, for example. Here, as an example for explanation, it is assumed that the wireless master device 120 and the wireless slave device 130 are set to measure sensor data at 10:00 and transmit the sensor data during a time period from 10:00 to 11:00 (hereinafter referred to as a predetermined time period).

[0137] In step S1501, the selection unit 503 determines whether or not there is an interfering wave from another wireless system during the predetermined transmission time. For example, the selection unit 503 refers to the usage status management table 512 as shown in Fig. 7 to determine whether or not an interfering wave from another wireless system is detected during the time from 10:00 to 10:10 (an example of the predetermined transmission time). In the example of Fig. 7, multiple wireless terminals (wireless master device 120 and multiple wireless slave devices 130) detect an interfering wave on CH1 during the time from 10:00 to 10:10, so the selection unit 503 determines that an interfering wave is present during the predetermined time.

[0138] If there is an interfering wave at the predetermined time, the selection unit 503 shifts the process to step S1503. On the other hand, if there is no interfering wave at the predetermined time, the selection unit 503 ends the process of FIG.

[0139] In step S1502, the selection unit 503 determines whether there is a time period when there is no interference from other wireless systems. For example, the selection unit 503 refers to the usage status management table 512 as shown in Fig. 7 to determine whether there is a time period when multiple wireless terminals are not detecting interference. In the example of Fig. 7, interference is not detected when the "time" is 10:20, 10:40, and 10:50, so the selection unit 503 determines that there is a time period when there is no interference.

[0140] If there is a period of time in which there is no interference wave, the selection unit 503 shifts the process to step S1503. On the other hand, if there is no period of time in which there is no interference wave, the selection unit 503 shifts the process to step S1504.

[0141] In step S1503, the selector 503 selects a delay time td for multiple wireless terminals to transmit data during a time when there is no interference. In the example of Fig. 7, the selector 503 sets the delay time td to, for example, 20 minutes. Alternatively, the selector 503 may set the delay time td to 40 minutes or 50 minutes.

[0142] On the other hand, in step S1504, the selection unit 503 determines whether or not there is an available CH (a wireless channel on which no interference is detected) within the predetermined transmission time. For example, in the example of Fig. 7, at "time" 10:00, multiple wireless terminals do not detect interference on CH2, so the selection unit 503 determines that there is an available CH within the predetermined transmission time.

[0143] If there is an available CH within the predetermined transmission time, the selection unit 503 shifts the process to step S1505. On the other hand, if there is no available CH within the predetermined transmission time, the selection unit 503 shifts the process to step S1506.

[0144] In step 1505, the selection unit 503 selects a wireless channel for transmission on an available CH at a predetermined transmission time. In the example of Fig. 7, the selection unit 503 selects the wireless channel "CH2".

[0145] On the other hand, in step S1506, the selection unit 503 selects a delay time and a wireless channel for transmission on an available channel. For example, the selection unit 503 creates a time table 1301 of available wireless channels as shown in Fig. 13, and selects one time and one wireless channel for which "available wireless channel" is marked with a circle.

[0146] By the process of FIG. 15, the selection unit 503 can determine the transmission method for transmitting data by a plurality of wireless terminals by combining the first embodiment and the second embodiment.

[0147] <Collection and processing of usage data> Next, we will explain another example of a usage data collection process in which the collection unit 502 of the management device 110 collects usage data 511a, for example, as shown in Figure 6, from multiple wireless terminals (wireless master device 120 and multiple wireless slave devices 10).

[0148] For example, in the processing of the wireless communication system described with reference to FIG. 8, the collection unit 502 transmits a request to acquire the usage status data to the wireless master device 120 and all the wireless slave devices 130a to 130h.

[0149] However, there are cases where a plurality of wireless slave devices 130 are installed on the same floor of an apartment building, etc. Therefore, for example, it is advisable to group a plurality of wireless slave devices 130 that are installed nearby and store the grouped wireless slave devices 130 in advance in the terminal management information 514, etc. In this way, the collection unit 502 transmits a request to acquire usage status data to one wireless slave device 130 selected in order (or randomly) from the grouped wireless slave devices 130, thereby making it possible to save power consumption of the other wireless slave devices 130.

[0150] Fig. 16 is a diagram showing an example of terminal management information according to the fourth embodiment. In the example of Fig. 16, the terminal management information 514 stores information such as "RNO," "ID," "installation location," "user," and "group" for each wireless terminal (wireless master device 120 and wireless slave device 130). Note that the terminal management information 514 is an example of information on locations where multiple wireless terminals are installed.

[0151] "RNO" is a wireless terminal number that identifies each wireless terminal within the wireless communication system 100. "ID" is device identification information possessed by each wireless terminal. "Installation location" is information indicating the location where each wireless terminal is installed (for example, an address, or a floor within a building, a department name, a room number, etc.). "User" is information such as the name of a contractor corresponding to each wireless terminal. "Group" is information such as the name or identification information of a group that is registered in advance by grouping multiple wireless terminals installed nearby. The example of FIG. 16 shows that wireless slave devices 130a, 130b, and 130c are installed nearby and are grouped as group "A1."

[0152] (Processing flow) 17 is a flowchart showing an example of a collection process of usage status data according to the fourth embodiment. This process shows an example of a collection process executed by the collection unit 502 when the management device 110 collects, for example, usage status data 511a as shown in FIG. 6(A) from multiple wireless terminals (wireless master device 120 and multiple wireless slave devices 130).

[0153] In step S1701, the collection unit 502 refers to the terminal management information 514 as shown in FIG. 16, for example, and selects one wireless terminal from the grouped wireless terminals in order (or randomly) to perform reception monitoring.

[0154] In step S1702, the collection unit 502 transmits a request to acquire the usage status data to the wireless terminals that will perform reception monitoring (the wireless terminals selected in step S1701 and the wireless terminals that are not grouped).

[0155] In step S1703, the collection unit 502 receives, for example, usage data 511a as shown in FIG. 6(A) from the wireless terminal that transmitted the request to acquire usage data, and stores the received usage data 511a in the memory unit 510.

[0156] In step S1704, the collection unit 502 stores the usage status data 511a received from one wireless terminal selected in step S1701 among the grouped wireless terminals as usage status data 511a of the other wireless terminals in the storage unit 510. This allows the selection unit 503 to create, for example, a usage status management table as shown in FIG.

[0157] By performing the process shown in FIG. 17, the wireless communication system 100 according to the fourth embodiment can effectively reduce the power consumption of a plurality of grouped wireless terminals.

[0158] <Effects> According to each embodiment of the present invention, the wireless communication system 100 measures the radio wave usage status at the wireless master device 120 and the wireless slave device 130, and can transmit data by selecting a transmission timing or wireless channel that is less used by other wireless systems.

[0159] This allows the wireless communication system 100 to avoid communication failures due to interference with other wireless systems and reduce power consumption of the wireless slave device due to retransmission processing. For example, in the conventional technology, as shown in Fig. 18(A), if an ACK cannot be received for data transmitted at time t1 due to interference with other wireless systems, the data is retransmitted at time t2.

[0160] On the other hand, in the wireless communication system 100 according to this embodiment, data is transmitted at a transmission timing or on a wireless channel where there is no (or little) interference from other wireless systems, thereby suppressing interference with other wireless systems and enabling more reliable reception of ACK. Therefore, in the wireless communication system 100 according to this embodiment, it is possible to reduce power consumption required for carrier sense (CS), transmission, etc. in the retransmission process, as shown in Fig. 18(A), for example.

[0161] In addition, in the conventional technology, when data can be transmitted using multiple wireless channels, if a carrier is detected by carrier sensing on wireless channel CH1, carrier sensing is performed on another wireless channel CH2, and data is transmitted only after confirming that no carrier is detected, as shown in Fig. 18(B). Furthermore, if a carrier is detected on wireless channel CH2, carrier sensing must be performed repeatedly.

[0162] On the other hand, in the wireless communication system 100 according to this embodiment, data is transmitted at a transmission timing or on a wireless channel where there is no (or little) interference from other wireless systems, and therefore the number of times carrier sense is performed can be reduced. Therefore, in the wireless communication system 100 according to this embodiment, it is possible to reduce the power consumption required for carrier sense (CS), for example, as shown in Fig. 18(B).

[0163] As described above, according to each embodiment of the present invention, in a wireless communication system including multiple wireless terminals performing multi-hop communication, it is possible to suppress an increase in power consumption of the wireless terminals even in an environment where the available frequency band is congested.

[0164] Although the embodiments of the present invention have been described in detail, the present invention is not limited to the specific embodiments, and various modifications and alterations are possible within the scope of the gist of the present invention described in the claims.

[0165] For example, in each of the above embodiments, the number of wireless channels available in the wireless communication system 100 has been described as two, but the number of wireless channels available in the wireless communication system 100 may be one, or another number such as three or more.

[0166] In each of the above embodiments, the management device 110 selects and notifies a common data transmission timing or wireless channel for multiple wireless terminals (the wireless master device 120 and multiple wireless slave devices 130). However, this is not limiting, and if the influence from other wireless systems differs depending on the location, the management device 110 may select and notify different data transmission timings or wireless channels for each wireless terminal. [Explanation of symbols]

[0167] 100 Wireless Communication System 110 Management device 120 Wireless base station (wireless terminal) 130, 130a~130h Wireless adapter (wireless terminal) 222, 322 Reception monitoring unit 223, 323 Information Transmission Department 502 Collection Department 503 Selection Section 504 Notification Department 510 510 511, 511a, 511b Usage Data 512 Usage Management Table 514 Device management information td delay time

Claims

1. A wireless communication system including a plurality of wireless terminals that perform multi-hop communication and a management device that can communicate with the plurality of wireless terminals using the multi-hop communication, The management device a collection unit that collects, from the plurality of wireless terminals at predetermined time intervals, usage status data indicating usage statuses of a plurality of wireless channels around the wireless terminals; a storage unit that stores the usage status data collected from the plurality of wireless terminals in chronological order; a selection unit that selects a transmission method by which the plurality of wireless terminals transmit data for each time period based on the usage status data stored in the storage unit in chronological order; and A wireless communication system in which the selection unit selects a delay time and a wireless channel for the multiple wireless terminals to transmit on an available channel when there is no time during a predetermined transmission time when there is no time during which there is no interference wave and no available channel during the predetermined transmission time.

2. The wireless communication system according to claim 1 , wherein the selection unit selects a transmission timing for transmitting data from the plurality of wireless terminals for each time period based on the usage status data stored in the storage unit.

3. The wireless communication system according to claim 2 , wherein the transmission timing includes a delay time from a predetermined transmission time of the plurality of wireless terminals.

4. The wireless communication system according to claim 1 , wherein the selection unit selects a wireless channel to be used by the plurality of wireless terminals for each time period based on the usage status data stored in the storage unit.

5. The wireless communication system according to claim 1 , wherein the selection unit selects different transmission methods depending on whether the transmission method is a weekday, a holiday, or a day of the week.

6. The wireless communication system according to claim 1 , wherein the usage status data includes information on the time when the wireless terminal detected interference waves from another wireless system and information on the wireless channel through which the interference waves were received.

7. The wireless terminal a reception monitoring unit that acquires the usage status data in response to a request from the management device; an information transmitting unit that transmits the acquired usage status data to the management device; 7. A wireless communication system according to claim 1, comprising:

8. The collecting unit managing information on locations where the plurality of wireless terminals are installed; The wireless communication system according to claim 7 , wherein the wireless communication system requests one of the plurality of wireless terminals installed in the vicinity to acquire the usage status data.

9. A management device capable of communicating with a plurality of wireless terminals that perform multi-hop communication using the multi-hop communication, a collection unit that collects, from the plurality of wireless terminals at predetermined time intervals, usage status data indicating usage statuses of a plurality of wireless channels around the wireless terminals; a storage unit that stores the usage status data collected from the plurality of wireless terminals in chronological order; a selection unit that selects a transmission method by which the plurality of wireless terminals transmit data for each time period based on the usage status data stored in the storage unit in chronological order; and A management device in which the selection unit selects a delay time and a wireless channel for the multiple wireless terminals to transmit on an available channel when there is no time during the predetermined transmission time when there is no time during which there is no interference wave and there is no available channel during the predetermined transmission time.

10. A plurality of wireless terminals that perform multi-hop communication and a management device that can communicate using the multi-hop communication, collecting, from the plurality of wireless terminals at predetermined time intervals, usage status data indicating usage statuses of a plurality of wireless channels around the wireless terminals; storing the usage status data collected from the plurality of wireless terminals in a storage unit in chronological order; a selection process for selecting a transmission method by which the plurality of wireless terminals transmit data for each time period based on the usage status data stored in the storage unit in chronological order; Run The wireless communication method, wherein the selection process selects a delay time and a wireless channel for the multiple wireless terminals to transmit on an available channel when there is no time during a predetermined transmission time when there is no time free of interference waves and no available channel during the predetermined transmission time.

11. A plurality of wireless terminals that perform multi-hop communication and a management device that can communicate using the multi-hop communication, collecting, from the plurality of wireless terminals at predetermined time intervals, usage status data indicating usage statuses of a plurality of wireless channels around the wireless terminals; storing the usage status data collected from the plurality of wireless terminals in a storage unit in chronological order; a selection process for selecting a transmission method by which the plurality of wireless terminals transmit data for each time period based on the usage status data stored in the storage unit in chronological order; Execute The selection process is a program that selects a delay time and a wireless channel for the multiple wireless terminals to transmit on an available channel when there is no time during a predetermined transmission time when there is no time during which there is no interference wave and no available channel during the predetermined transmission time.

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