Wireless communication method, wireless communication system, and control program for causing a computer to execute the wireless communication method

Abstract

A wireless communication method between a base station and a plurality of wireless terminals, the base station being provided with a plurality of first wireless modules that perform wireless communication on mutually different non-overlapping channels, and each of the plurality of wireless terminals being provided with a second wireless module that performs wireless communication on one of the communication channels. The wireless communication method according to the present disclosure includes: executing a channel switching process for switching the use state of the plurality of first wireless modules on a prescribed schedule so as to enable one of the plurality of first wireless modules to carry out transmission, and disable the other of the plurality of first wireless modules from carrying out transmission; and, for each of the plurality of wireless terminals, causing operation of the second wireless module to be halted while a first wireless module performing wireless communication on a communication channel is disabled from carrying out transmission in the schedule.

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication system that performs wireless communication by switching between multiple channels. [Background technology]

[0002] Wireless communication systems consisting of base stations and wireless terminals are known. A typical example of a wireless communication system is a public wireless local area network (LAN). In a public wireless LAN, for example, a use case in which data is transmitted from a base station to a wireless terminal such as a computer terminal or a smartphone terminal is expected. Furthermore, with the recent spread of IoT (Internet of Things) terminals, there has been an increase in use cases in which data is transmitted from a wireless terminal to a base station.

[0003] In relation to wireless communications for IoT, the use of the unlicensed sub-1 GHz band has been institutionalized in various countries around the world (see Non-Patent Documents 1 and 2). In Japan, the 920 MHz band has been allocated as a frequency band for electronic tag systems. For example, low-power wide-area (LPWA) wireless communication systems such as LoRa (registered trademark) and WiSUN (registered trademark) are known as active electronic tag systems. The use of IEEE 802.11ah, a wireless LAN standard, is also being considered.

[0004] Since the number of frequency channels in the 920 MHz band is limited, it is conceivable that wireless communication may be carried out while changing the channel used.

[0005] For example, in Japan, there is a limit on the total transmission time when using the 920 MHz band, requiring that the total transmission time per hour be within 360 seconds. Wireless communication devices limit data transmission to comply with this total transmission time limit, which also limits throughput. However, for wireless communication device housings that switch between two non-overlapping channels, a total transmission time of 360 seconds per channel per hour is allowed, for a total of 720 seconds. Therefore, in order to improve throughput, it is possible for wireless communication devices to change the channel they use while communicating wirelessly. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] "Standard for Radio Equipment for Telemetry, Telecontrol and Data Transmission in the 920 MHz Band," Association of Radio Industries and Businesses, ARIB STD-T108 Version 1.3, April 12, 2019 [Non-patent document 2] “IEEE Standard for Information technology - Telecommunications and information exchange between systems Local and metropolitan area networks - Specific requirements, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Amendment 2: Sub 1 GHz License Exempt Operation,” IEEE Computer Society, IEEE Std 802.11ah TM-2016, 7 December 2016. Summary of the Invention [Problem to be solved by the invention]

[0007] As the number of wireless terminals connected to one base station increases, downlink traffic also increases. Therefore, there is a need to reduce the total transmission time, especially for downlink traffic, by switching between multiple channels for wireless communication. Furthermore, when a large number of wireless terminals communicate wirelessly on one channel, there is a risk that frame collisions between the uplink traffic of each wireless terminal will increase, resulting in a decrease in throughput, especially when access control is performed using CSMA / CA (Carrier-sense Multiple Access with Collision Avoidance).

[0008] On the other hand, when considering the control overhead and feasibility when there are a large number of wireless terminals, it is desirable that the wireless terminals do not require additional control devices or control functions when switching between multiple channels to perform wireless communication.

[0009] One object of the present disclosure is to provide a technique that can reduce the total transmission time for downlink traffic without requiring an additional control device or control function in the wireless terminal. Another object of the present disclosure is to provide a technique that can reduce frame collisions between the uplink traffic of each wireless terminal. [Means for solving the problem]

[0010] The first aspect relates to a wireless communication method between a base station and a plurality of wireless terminals that form a wireless communication network with the base station. The base station includes a plurality of first wireless modules that perform wireless communication on different non-overlapping channels, and each of the plurality of wireless terminals includes a second wireless module that performs wireless communication on one of the channels. A wireless communication method according to a first aspect includes: executing a channel switching process that switches the usage states of the plurality of first wireless modules according to a predetermined schedule so that one of the plurality of first wireless modules is enabled for transmission and the others are prohibited from transmitting; and for each of the plurality of wireless terminals, suspending operation of the second wireless module while the first wireless module that performs wireless communication on the communication channel is prohibited from transmitting according to the schedule.

[0011] The second aspect relates to a method of wireless communication between a base station and a plurality of wireless terminals that form a wireless communication network with the base station. The base station includes a plurality of first wireless modules that perform wireless communication on different non-overlapping channels, and each of the plurality of wireless terminals includes a second wireless module that performs wireless communication on one of the channels. A wireless communication method according to a first aspect includes: executing a channel switching process that switches the usage states of the plurality of first wireless modules according to a predetermined schedule so that one of the plurality of first wireless modules is enabled for transmission and the others are prohibited from transmitting; and not causing each of the plurality of wireless terminals to request a response frame from the base station when transmitting a frame.

[0012] The third aspect relates to a wireless communication system. A wireless communication system according to a third aspect includes a base station, a plurality of wireless terminals that form a wireless communication network with the base station, and a control device that controls the base station. The base station includes a plurality of first wireless modules that perform wireless communication on different non-overlapping channels, and each of the plurality of wireless terminals includes a second wireless module that performs wireless communication on one of the channels. The control device executes a channel switching process for switching the use states of the first wireless modules according to a predetermined schedule so that one of the first wireless modules is enabled for transmission and the others are disabled for transmission, and the base station notifies the plurality of wireless terminals of the schedule. Each of the plurality of wireless terminals is configured to suspend operation of the second wireless module while transmission of the first wireless module that performs wireless communication on the communication channel is prohibited in the schedule.

[0013] A fourth aspect relates to a wireless communication system. A wireless communication system according to a fourth aspect includes a base station, a plurality of wireless terminals that form a wireless communication network with the base station, and a control device that controls the base station. The base station includes a plurality of first wireless modules that perform wireless communication on different non-overlapping channels, and each of the plurality of wireless terminals includes a second wireless module that performs wireless communication on one of the channels. The control device executes a channel switching process for switching the use states of the plurality of first wireless modules according to a predetermined schedule so that any one of the plurality of first wireless modules is enabled for transmission and the others are prohibited from transmission. Each of the plurality of wireless terminals is configured not to request a response frame from the base station when transmitting a frame.

[0014] The fifth aspect relates to a control program executed by a computer. A control program according to a fifth aspect causes a computer to execute the wireless communication control method according to the first or second aspect. [Effects of the Invention]

[0015] According to the present disclosure, transmission from a base station to a wireless terminal can be switched among multiple channels, thereby reducing the total transmission time for downlink traffic, particularly without requiring an additional control device or control function in each of the multiple wireless terminals. Furthermore, according to the present disclosure, multiple wireless terminals are distributed into groups that perform wireless communication using different communication channels, thereby reducing frame collisions between the uplink traffic of each of the multiple wireless terminals. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a block diagram conceptually showing the configuration of a wireless communication system according to a first embodiment. [Figure 2] 1 is a conceptual diagram for explaining an example of wireless communication by a wireless communication method realized by a wireless communication system according to a first embodiment. [Figure 3] FIG. 10 is a diagram conceptually illustrating an example of a frame collision. [Figure 4] FIG. 2 is a block diagram showing the configuration of a base station according to the first embodiment. [Figure 5] 2 is a block diagram showing an example of the configuration of a control device according to the first embodiment. FIG. [Figure 6] 10 is a flowchart showing a process executed in a first example of connection destination control. [Figure 7] 10 is a flowchart showing a process executed in a second example of connection destination control. [Figure 8] 10 is a flowchart showing a process executed in a third example of connection destination control. [Figure 9] 10 is a flowchart showing a process executed in a fourth example of connection destination control. [Figure 10] FIG. 10 is a conceptual diagram showing an example of the operation of a first wireless module in a base station according to a modified example. [Figure 11] FIG. 10 is a conceptual diagram for explaining an example of wireless communication by a wireless communication method realized by a wireless communication system according to a second embodiment. [Figure 12] FIG. 10 is a conceptual diagram for explaining an example of wireless communication by a wireless communication method realized by a wireless communication system according to a second modification of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0018] 1. First embodiment Overview 1 is a block diagram showing a schematic configuration of a wireless communication system 1 according to the first embodiment. The wireless communication system 1 includes a base station (AP) 10 and a plurality of wireless terminals (STAs) 20 that form a wireless communication network with the base station 10. The base station 10 and the plurality of wireless terminals 20 communicate wirelessly with each other.

[0019] For example, the wireless communication system 1 is a wireless LAN system, and the base station 10 is an access point of the wireless LAN. A cell consisting of the access point and a plurality of wireless terminals 20 is called a BSS (Basic Service Set).

[0020] The wireless communication system 1 performs wireless communication using, for example, the unlicensed Sub-1 GHz band. For example, the wireless communication system 1 performs wireless communication using the 920 MHz band.

[0021] In the wireless communication system 1 according to the first embodiment, the base station 10 is configured to be able to perform wireless communication over multiple channels (frequency channels), while each of the multiple wireless terminals 20 is configured to perform wireless communication over any one of the channels.

[0022] According to the first embodiment, wireless communication between the base station 10 and the wireless terminal 20 uses a wireless module. That is, the base station 10 and the wireless terminal 20 are equipped with a wireless module. The wireless module is, for example, a network interface card (NIC). Hereinafter, the wireless module equipped in the base station 10 will be referred to as a "first wireless module," and the wireless module equipped in the wireless terminal 20 will be referred to as a "second wireless module."

[0023] In the example shown in FIG. 1, the base station 10 includes a plurality of NICs as first wireless modules. Here, sub-numbers such as "NIC-i" are used to distinguish the plurality of NICs. Furthermore, N is an integer equal to or greater than 2. For example, N is 2. The plurality of NIC-1 to NIC-N are configured to perform wireless communication on different non-overlapping channels CH-1 to CH-N. Therefore, by switching the usage states of the plurality of NIC-1 to NIC-N, the base station 10 can switch the channel used for wireless communication. For example, by switching the NIC to be used among the plurality of NIC-1 to NIC-N, the base station 10 can switch the channel used for wireless communication. In this way, the process of switching the channel used for wireless communication by the base station 10 is hereinafter referred to as "channel switching process."

[0024] Hereinafter, a NIC that is selectively used among the multiple NIC-1 to NIC-N will be referred to as a "selected NIC." The "selected NIC" can also be referred to as a "used NIC" or an "active NIC," etc. The channel switching process can also be said to be a "NIC switching process" that switches the selected NIC among the multiple NIC-1 to NIC-N.

[0025] 1, each of the multiple wireless terminals 20 includes one NIC as a second wireless module. The NIC included in each of the multiple wireless terminals 20 is configured to perform wireless communication on any one of channels CH-1 to CH-N. However, the channels for performing wireless communication may be set to be different among the multiple wireless terminals 20. For example, in FIG. 1, the NIC included in each of the wireless terminals 20 may be configured so that the wireless terminals 20 shown as STA#1 and STA#2 perform wireless communication on channel CH-1, and the wireless terminal 20 shown as STA#3 performs wireless communication on channel CH-2.

[0026] Hereinafter, the channel through which wireless communication is performed for each of the multiple wireless terminals 20 will be referred to as a "communication channel." In the above example, the communication channel for the wireless terminals 20 designated as STA#1 and STA#2 is channel CH-1, and the communication channel for the wireless terminal 20 designated as STA#3 is channel CH-2.

[0027] The base station 10 and the multiple wireless terminals 20 can be considered to constitute multiple BSSs that perform wireless communication on different non-overlapping channels CH-1 to CH-N. That is, for each of channels CH-1 to CH-N, N BSSs can be considered, each consisting of a base station 10 and a wireless terminal 20 that performs wireless communication on channel CH-i. When considered in this way, the base station 10 can be considered to function as N access points using the multiple NIC-1 to NIC-N.

[0028] Hereinafter, a BSS that performs wireless communication over channel CH-i will be referred to as "BSS-i," and a group of wireless terminals 20 that make up BSS-i will be referred to as "STAs-i." In other words, the communication channel for wireless terminals 20 included in STAs-i is channel CH-i. Furthermore, when the base station 10 is considered to function as N access points, an access point realized by NIC-i will be referred to as "AP-i." In other words, BSS-i is composed of AP-i and STAs-i.

[0029] Each of the multiple wireless terminals 20 may be capable of switching communication channels. In other words, each of the multiple wireless terminals 20 may be capable of switching the AP-i to which it is connected, and may not be fixed to a specific communication channel.

[0030] The wireless communication system 1 according to the first embodiment further includes a control device 100 that controls the base station 10. In particular, the control device 100 manages and controls channel switching processing (NIC switching processing).

[0031] In the example shown in FIG. 1 , a control device 100 is connected to a base station 10. However, the control device 100 does not necessarily need to be connected to an external device of the base station 10. The functions of the control device 100 may be included within the base station 10. For example, the base station 10 executes a control program to realize the functions of the control device 100. In this case, the base station 10 that executes the control program itself functions as the control device 100.

[0032] In the following description, the control device 100 and the control program that manages and controls the channel switching process will be collectively referred to as the "control device 100" or "control function."

[0033] The control device 100 (control function) according to the first embodiment executes a channel switching process for switching the usage states of the plurality of NIC-1 to NIC-N. In particular, in the channel switching process, the control device 100 (control function) switches the usage states of the plurality of NIC-1 to NIC-N according to a predetermined schedule so that any one of the plurality of NIC-1 to NIC-N is enabled for transmission and the others are prohibited from transmission.

[0034] Here, the schedule is information that provides a transmission enabled period and a transmission prohibited period for each of the multiple NIC-1 to NIC-N. However, the transmission enabled periods are provided so that they do not overlap among the multiple NIC-1 to NIC-N. The schedule may also be information that provides one cycle of transmission enabled period and transmission prohibited period for each of the multiple NIC-1 to NIC-N. In this case, the usage status of the multiple NIC-1 to NIC-N due to the channel switching process is periodically repeated according to the schedule.

[0035] The schedule may be provided in advance as a control program, or may be provided as appropriate depending on the communication environment. For example, the control device 100 (control function) may provide a schedule based on the number of connected wireless terminals 20 or traffic information. For example, the schedule may be provided so that the transmittable periods of each of the multiple NIC-1 to NIC-N in one cycle are in proportion to the number of wireless terminals 20 connected to each of the multiple NIC-1 to NIC-N, or in proportion to the traffic volumes of the corresponding channels CH-1 to CH-N.

[0036] Furthermore, the priority of the traffic of the corresponding channels CH-1 to CH-N may be obtained, and a schedule may be given so that the transmittable period of NIC-i corresponding to a channel CH-i with a high priority is extended.

[0037] During the transmission prohibition period, data reception is possible but data transmission is prohibited. As a variant, even during the transmission prohibition period, transmission of only specific wireless frames (e.g., a response frame (ACK) in response to reception of an uplink frame) may be permitted.

[0038] The base station 10 according to the first embodiment acquires a schedule from the control device 100 and notifies the plurality of wireless terminals 20 of the schedule. Here, the notification of the schedule is typically performed as data transmission via wireless communication. In this case, it is desirable that the plurality of NIC-1 to NIC-N are configured so that data transmission related to the notification of the schedule is permitted even during a transmission prohibition period. It is also desirable that the notification of the schedule is performed before starting wireless communication with the plurality of wireless terminals 20. However, if the schedule is changed, the notification of the schedule may be performed each time.

[0039] Each of the wireless terminals 20 according to the first embodiment is configured to suspend the operation of the NIC (second wireless module) while the NIC-i (first wireless module) performing wireless communication over the communication channel CH-i is prohibited from transmitting in the schedule. This can be achieved by each of the wireless terminals 20 supporting a standard technology such as TWT (Target Wake Time).

[0040] Fig. 2 is a conceptual diagram for explaining an example of wireless communication by a wireless communication method realized by the wireless communication system 1 according to the first embodiment. Fig. 2 shows a case where the base station 10 includes, as first wireless modules, NIC-1 that performs wireless communication on channel CH-1 and NIC-2 that performs wireless communication on channel CH-2. Therefore, multiple wireless terminals 20 are classified into a group STAs-1 in which the communication channel of the NIC included as the second wireless module is CH-1, and a group STAs-2 in which the communication channel is CH-2.

[0041] 2 shows the example of data transmission and reception over a two-cycle period when a one-cycle schedule is given. Here, the schedule is given so that the period from the start time T0 of one cycle to time T0+DT1, when time DT1 has elapsed, is the transmission enabled period for NIC-1, and the period from the end time T0+DT1 of the transmission enabled period for NIC-1 to time T0+DT1+DT2, when time DT2 has elapsed, is the transmission enabled period for NIC-2. Note that while NIC-1 is in the transmission enabled period, NIC-2 is in the transmission prohibited period, and while NIC-2 is in the transmission enabled period, NIC-1 is in the transmission prohibited period.

[0042] Therefore, as shown in Figure 2, each of the wireless terminals 20 included in STAs-1 performs wireless communication with the base station 10 (receiving beacons, sending and receiving data, and sending and receiving response frames (ACK)) during the transmission period of NIC-1, while suspending (sleeping) the operation of the NIC during the transmission period of NIC-2 (the transmission prohibited period of NIC-1), from T0+DT1 to T0+DT1+DT2.

[0043] In addition, each of the wireless terminals 20 included in STAs-2 performs wireless communication with the base station 10 during the transmission enabled period of NIC-2, while suspending the operation of its NIC from T0 to T0+DT1, which is the transmission enabled period of NIC-1 (the transmission prohibited period of NIC-2).

[0044] The base station 10 is configured to set the transmission time per unit time of each of the plurality of NIC-1 to NIC-N (first wireless modules) to a first predetermined time or less, and to set the total transmission time per unit time of each of the plurality of NIC-1 to NIC-N (first wireless modules) to a second predetermined time or less. For example, the unit time is one hour, the first predetermined time is 360 seconds, and the second predetermined time is 720 seconds. This may be realized by the control function (control program) of the control device 100 or the base station 10. By configuring the base station 10 in this way, it is possible to comply with the limitation on the total transmission time for the base station 10.

[0045] Similarly, each of the multiple wireless terminals 20 is configured to set the transmission time per unit time of the NIC (second wireless module) to a first predetermined time or less. This may be achieved by a control function (control program) of each of the multiple wireless terminals 20. By configuring each of the multiple wireless terminals 20 in this manner, it is possible to comply with the total transmission time limit for each of the multiple wireless terminals 20.

[0046] As described above, according to the first embodiment, the base station 10 includes a plurality of NIC-1 to NIC-N (first wireless modules) that perform wireless communication on different non-overlapping channels. Each of a plurality of wireless terminals 20 that form a wireless communication network with the base station 10 includes a NIC (second wireless module) that performs wireless communication on one of the channels CH-1 to CH-N. The control device 100 executes a channel switching process that switches the usage state of the plurality of NIC-1 to NIC-N according to a predetermined schedule so that one of the plurality of NIC-1 to NIC-N is enabled for transmission and the others are prohibited from transmission. Each of the plurality of wireless terminals 20 is configured to suspend operation of its NIC (second wireless module) while the NIC-i (first wireless module) that performs wireless communication on the communication channel CH-i is prohibited from transmission according to the schedule.

[0047] This allows transmission from the base station 10 to the wireless terminal 20 to be performed by switching among multiple channels CH-1 to CH-N, thereby alleviating the total transmission time for downlink traffic. Note that if a schedule is set so that switching occurs frequently, it is also possible to sufficiently reduce delays in downlink and uplink traffic due to switching.

[0048] Incidentally, a conventional technique for reducing the total transmission time is to provide a plurality of NICs, each of which is set to perform wireless communication on a plurality of channels CH-1 to CH-N, just like the base station 10, and to configure the base station 10 and the plurality of wireless terminals 20 to switch channels CH-i for wireless communication in synchronization with each other. In other words, this is a method of performing channel switching processing in one BSS consisting of the base station 10 and the plurality of wireless terminals 20.

[0049] With this technology, channel switching is performed at each of the multiple wireless terminals 20, so it is possible to alleviate the total transmission time of not only downlink traffic but also uplink traffic. However, downlink traffic usually increases as the number of wireless terminals 20 connected to the base station 10 increases, while uplink traffic depends on the content of each communication. Therefore, considering that the increase in total transmission time due to the large number of wireless terminals 20 is an issue, there is little need to alleviate the total transmission time of uplink traffic; it is sufficient to be able to alleviate downlink traffic.

[0050] Furthermore, the above technology requires an additional control device or control function to perform channel switching processing in each of the multiple wireless terminals 20. Therefore, there are concerns about the feasibility of this technology due to the control overhead and increased costs when there are a large number of wireless terminals 20.

[0051] Furthermore, in the above technology, since the channel switching process is performed in one BSS, the number of wireless terminals 20 connected to the base station 10 does not change before and after the channel switching. Therefore, when there are many wireless terminals 20, there is a risk that frame collisions between the multiple wireless terminals 20 are more likely to occur in the uplink traffic. As a result, there is a risk that the capacity of the BSS will decrease.

[0052] 3 is a diagram conceptually illustrating an example of frame collision. In the example shown in FIG. 3, a base station (AP) 10 and multiple wireless terminals (STAs) 20 form one BSS, using channel CH-1 from T0 to T1 and CH-2 from T1 to T2. FIG. 3 shows a time series of frames transmitted by the base station 10 and a time series of frames transmitted by two of the multiple wireless terminals 20. As shown in FIG. 3, a frame collision (marked with a cross) occurs when two wireless terminals 20 transmit frames at the same time. Such frame collisions are more likely to occur in wireless communications using CSMA / CA access control when a large number of wireless terminals 20 form one BSS.

[0053] In this way, the above technique can alleviate the total transmission time, but may not be efficient when there are a large number of wireless terminals 20.

[0054] On the other hand, according to the first embodiment, as described above, it is possible to alleviate the total transmission time for downlink traffic, and it is sufficient for each of the multiple wireless terminals 20 to support a standard technology (for example, TWT). As a result, there is no need for an additional control device or control function in each of the multiple wireless terminals 20. Of course, by providing each of the multiple wireless terminals 20 with an additional control device or control function, it is also possible to realize, for example, pausing the operation of the second wireless module according to a schedule.

[0055] Furthermore, according to the first embodiment, the multiple wireless terminals 20 are distributed among multiple groups STAs-i that perform wireless communication using different communication channels CH-i by multiple NIC-1 to NIC-N. This reduces frame collisions between the uplink traffic of each of the multiple wireless terminals 20. This in turn is expected to improve the capacity of the uplink traffic and expand the range of priority setting that controls communication quality (for example, delay and error rate) in a relatively preferential manner.

[0056] Furthermore, according to the first embodiment, since the transmission enabled periods of the plurality of NIC-1 to NIC-N do not overlap, it is possible to take measures against power leakage between the corresponding channels CH-1 to CH-N, which in turn can be expected to have the effect of reducing power consumption.

[0057] 1-2.Configuration 4 is a block diagram showing the configuration of the base station 10 according to the first embodiment. The base station 10 includes one or more processors 11, one or more storage devices 12, a wired NIC, and multiple wireless NICs (NIC-1 to NIC-N).

[0058] The processor 11 performs various types of information processing. For example, the processor 11 includes a CPU (Central Processing Unit). The storage device 12 stores various types of information required for processing by the processor 11. Examples of the storage device 12 include a volatile memory, a non-volatile memory, an HDD (Hard Disk Drive), and an SSD (Solid State Drive).

[0059] The control program 13 is a computer program executed by the processor 11 (computer). The processor 11 executes the control program 13 to realize the functions of the base station 10. The control program 13 is stored in the storage device 12. The control program 13 may be recorded on a computer-readable recording medium. The control program 13 may be provided to the base station 10 via a network. The processor 11 that executes the control program 13 corresponds to the control device 100 that controls the base station 10.

[0060] The management information 14 includes at least information used to manage and control the channel switching process described above. For example, the management information 14 includes a network identifier (BSSID), a channel, a schedule, etc. for each NIC. The management information 14 may also include a total transmission time for each NIC. The management information 14 is stored in the storage device 12.

[0061] Furthermore, the base station 10 may be provided with an interface 15 for external operation. For example, the interface 15 is connected to an external control device 100. The interface 15 may include a user interface.

[0062] Furthermore, the base station 10 may include a timer 16 for managing the timing of switching in the channel switching process (NIC switching process).

[0063] 5 is a block diagram showing an example of the configuration of the control device 100 according to the first embodiment. The control device 100 includes one or more processors 110 and one or more storage devices 120.

[0064] The processor 110 performs various types of information processing. For example, the processor 110 includes a CPU. The storage device 120 stores various types of information required for processing by the processor 110. Examples of the storage device 120 include a volatile memory, a non-volatile memory, an HDD, and an SSD.

[0065] The control program 130 is a computer program executed by the processor 110 (computer). The processor 110 executes the control program 130 to realize the functions of the control device 100. The control program 130 is stored in the storage device 120. The control program 130 may be recorded on a computer-readable recording medium. The control program 130 may be provided to the control device 100 via a network.

[0066] The management information 140 includes information used to manage and control the channel switching process described above. For example, the management information 140 includes a network identifier (BSSID), a channel, a schedule, etc. for each NIC. The management information 140 may also include a total transmission time for each NIC. The management information 140 is stored in the storage device 120.

[0067] Furthermore, the control device 100 may include an interface 150. For example, the interface 150 is connected to the base station 10. The interface 150 may include a user interface.

[0068] Furthermore, the control device 100 may include a timer 160 for managing the timing of switching in the channel switching process (NIC switching process).

[0069] The configuration of the wireless terminal 20 according to the first embodiment may be the same as the configuration of the base station 10 shown in Fig. 4. However, the wireless terminal 20 has one wireless NIC.

[0070] 1-3. Connection control According to the wireless communication system 1 of the first embodiment, a plurality of BSS-1 to BSS-N are formed in which the base station 10 and a plurality of wireless terminals 20 perform wireless communication on different non-overlapping channels CH-1 to CH-N, and the total transmission time for downlink traffic can be reduced by performing channel switching processing in the base station 10. Here, as described above, the plurality of wireless terminals 20 are divided into a plurality of groups STAs-1 to STAs-N that respectively constitute the plurality of BSS-1 to BSS-N.

[0071] Incidentally, it is expected that the grouping of the multiple wireless terminals 20 will have a significant effect on the traffic on each of the multiple channels CH-1 to CH-N. For example, when comparing group STAs-1 and group STAs-2, if the number of wireless terminals 20 included in group STAs-1 is large, if transmission and reception is frequent, or if the amount of data transmitted and received is large, it is expected that the traffic volume on channel CH-1 will be larger than the traffic volume on channel CH-2. In this case, a situation may occur in which BSS-1 quickly reaches its limit on the total transmission time, while BSS-2 has plenty of time left in the total transmission time.

[0072] Therefore, in the wireless communication system 1 according to the first embodiment, connection destination control is performed to control connections between the base station 10 and the wireless terminals 20 so that the wireless terminals 20 are appropriately grouped based on traffic information. This makes it possible to more effectively reduce the total transmission time. The connection destination control is realized by executing processing by the control device 100, the control function (control program) of the base station 10, or the control function (control program) of the wireless terminal 20.

[0073] Various examples of connection destination control performed in the wireless communication system 1 according to the first embodiment will be described below, with overlapping content being omitted where appropriate in each description.

[0074] 1-3-1. First example In a first example of connection destination control, the base station 10 collectively specifies connection destinations. Fig. 6 is a flowchart showing the processing executed in the first example of connection destination control. The flowchart shown in Fig. 6 may be repeatedly executed at predetermined intervals, or may be started under predetermined conditions. For example, it may be started when the total transmission time of a certain BSS-i reaches a limit.

[0075] In step S100, the base station 10 acquires downlink traffic information for each of the connected wireless terminals 20. The acquired traffic information includes, for example, a TIM (Traffic Information Map), traffic type, priority, etc. In step S100, the base station 10 may also acquire uplink traffic information.

[0076] In step S110, the base station 10 determines how to group the wireless terminals 20 based on the traffic information acquired in step S100. For example, the grouping may be determined so that the amount of downlink traffic on the multiple channels CH-1 to CH-N is uniform. Alternatively, the grouping may be determined based on the traffic type, such that STAs-1 connected to AP-1 (NIC-1) is made up of wireless terminals 20 transmitting and receiving sensor-related data, and STAs-2 connected to AP-2 (NIC-2) is made up of wireless terminals 20 transmitting and receiving video-related data. In this case, when it is determined that communication with AP-2 (NIC-2) is congested and communication quality cannot be maintained (for example, when a preset upper limit on the number of connected wireless terminals 20 or an upper limit on traffic volume is exceeded), the grouping may be performed so that the wireless terminals 20 transmitting and receiving sensor-related data are included in STAs-1. Furthermore, the wireless terminals 20 connected to the base station 10 may be grouped so that only wireless terminals 20 transmitting and receiving high-priority data are included. In this case, there may be a wireless terminal 20 that is not included in any of the groups STAs-1 to STAs-N.

[0077] In step S120, the base station 10 notifies each of the plurality of wireless terminals 20 of a connection destination in accordance with the grouping determined in step S110. The notification of the connection destination may be performed by a notification frame (for example, a beacon frame) transmitted by the base station 10, or may be performed individually by transmitting a specific frame, etc. Furthermore, in step S120, the base station 10 may notify the schedule together with the notification of the connection destination.

[0078] In step S130, the base station 10 and the plurality of wireless terminals 20 execute a reconnection process. As a result, a plurality of BSS-1 to BSS-N are realized according to the grouping determined in step S110. The reconnection process may be realized by a function that is normally provided in a known wireless module.

[0079] 1-3-2. Second example In a second example of connection destination control, the base station 10 designates a connection destination for each of the plurality of wireless terminals 20. Fig. 7 is a flowchart showing processing executed in the second example of connection destination control. The flowchart shown in Fig. 7 is executed by designating any one of the plurality of wireless terminals 20. Here, the flowchart shown in Fig. 7 may be executed sequentially for each of the plurality of wireless terminals 20 at predetermined intervals, or may be executed by designating a wireless terminal 20 that satisfies predetermined conditions. For example, it may be executed by designating a wireless terminal 20 for which the type or amount of data to be transmitted or received has changed.

[0080] In step S200, the base station 10 acquires downlink traffic information for the designated wireless terminal 20. The base station 10 may also acquire uplink traffic information.

[0081] In step S210, the base station 10 determines how to group the designated wireless terminals 20 based on the traffic information acquired in step S100.

[0082] In step S220, the base station 10 notifies the designated wireless terminal 20 of the connection destination in accordance with the group determined in step S210. The base station 10 may also notify the designated wireless terminal 20 of the connection destination and the schedule.

[0083] In step S230, the base station 10 and the designated wireless terminal 20 execute a reconnection process, thereby realizing a plurality of BSS-1 to BSS-N according to the grouping determined in step S110.

[0084] 1-3-3. Third example In a third example of connection destination control, each of the multiple wireless terminals 20 specifies a connection destination. Fig. 8 is a flowchart showing processing executed in the third example of connection destination control. The flowchart shown in Fig. 8 may be repeatedly executed at predetermined intervals by each of the multiple wireless terminals 20, or may be started by a wireless terminal 20 that satisfies predetermined conditions. For example, it may be started by a wireless terminal 20 in which the type or amount of data to be transmitted or received has changed.

[0085] In step S300, the wireless terminal 20 receives the congestion status (e.g., the number of connected wireless terminals 20 and the number of packets sent and received) and traffic information (e.g., traffic type and priority) of the multiple BSS-1 to BSS-N through notification frames (e.g., beacon frames, probe response frames, etc.) from each of the multiple AP-1 to AP-N.

[0086] In step S310, the wireless terminal 20 selects a destination AP-i based on the congestion status and traffic information received in step S300. For example, the wireless terminal 20 selects the AP-i of the BSS-i with the least congestion based on the congestion status (for example, the fewest number of connected wireless terminals 20 or the fewest packets sent and received during the transmittable period). Furthermore, the destination AP-i may be selected based on the traffic type. For example, the destination AP-i may be selected so that sensor-related data is sent and received in BSS-1 and video-related data is sent and received in BSS-2. The connectable APs may also be limited based on priority. For example, AP-2 may be configured to allow only wireless terminals 20 with a certain priority or higher to connect.

[0087] In step S320, the wireless terminal 20 executes a connection process to the AP-i selected in step S310. The connection process may be implemented by a function that is standardly provided in a known wireless module. By executing the flowchart shown in Fig. 8 in each of the multiple wireless terminals 20, the multiple wireless terminals 20 are grouped based on congestion status and traffic information.

[0088] 1-3-4. Fourth Example In a fourth example of connection destination control, each of the multiple wireless terminals 20 specifies a connection destination, and then the base station 10 determines whether to permit or deny the connection. Fig. 9 is a flowchart showing the processing executed in the fourth example of connection destination control. The flowchart shown in Fig. 9 may be executed repeatedly at predetermined intervals, or may be started under predetermined conditions.

[0089] In step S400, the wireless terminal 20 receives congestion status and traffic information of the plurality of BSS-1 to BSS-N through the notification frame of each of the plurality of AP-1 to AP-N.

[0090] In step S410, the wireless terminal 20 selects an AP-i to connect to based on the congestion status and traffic information received in step S400.

[0091] In step S420, the wireless terminal 20 executes a connection process to the AP-i selected in step S410.

[0092] In step S430, the wireless terminal 20 determines whether the destination AP-i has rejected the connection in response to the connection process executed in step S420, or whether a connection notification to another AP-i has been received. Here, the destination AP-i is configured to reject the connection to the wireless terminal 20 or to transmit a connection notification to another AP-i when it cannot increase the number of connected wireless terminals 20 (for example, when the number of connected wireless terminals 20 exceeds an expected value).

[0093] The wireless terminal 20 may be configured to receive a connection notification to another AP-i from the AP-i to which it is connected after connecting to the AP-i through the connection process executed in step S420.

[0094] If the destination AP-i rejects the connection process executed in step S420, or if a connection notification to another AP-i is received (step S430; Yes), the wireless terminal 20 executes connection process to the other AP-i (step S440). Here, if a connection notification to another AP-i is received in step S430, the wireless terminal 20 executes connection process to the AP-i specified in the connection notification. After step S440, the process proceeds to step S430 again.

[0095] The flowchart shown in Figure 9 is executed in each of the multiple wireless terminals 20, and when the connection processing executed in step S420 or step S440 is completed successfully (step S430; No), grouping of the multiple wireless terminals 20 based on congestion status and traffic information is realized.

[0096] 1-4. Variations The wireless communication system 1 according to the first embodiment may employ the following modified aspects.

[0097] The base station 10 may be configured to suspend operation of the NIC-i during a transmission prohibition period. Fig. 10 is a conceptual diagram showing an example of operation of the first wireless modules (NIC-1 and NIC-2) in the base station (AP) 10 according to a modified example. Fig. 10 shows a case where the base station 10 includes, as the first wireless modules, NIC-1 that performs wireless communication on channel CH-1 and NIC-2 that performs wireless communication on channel CH-2.

[0098] 10, in the base station 10 according to the modification, the operation of NIC-1 is paused (sleep) during the transmission prohibition period of NIC-2 (transmission enable period of NIC-1) from T0 to T0+DT1, and the operation of NIC-2 is paused (sleep) during the transmission prohibition period of NIC-1 (transmission enable period of NIC-2) from T0+DT1 to T0+DT1+DT2.

[0099] By adopting such a modified embodiment, it is possible to reduce power consumption in the base station 10. Note that the base station 10 according to the modified embodiment is realized by using, for example, Implicit TWT of IEEE 802.11ah.

[0100] 2. Second embodiment The second embodiment will be described below, with the overlapping content with the first embodiment being omitted as appropriate, and differences from the first embodiment being described in particular detail. 2-1. Overview The configuration of the wireless communication system 1 according to the second embodiment may be the same as the configuration of the wireless communication system 1 according to the first embodiment shown in Fig. 1. That is, the wireless communication system 1 includes a base station (AP) 10, a plurality of wireless terminals (STAs) 20 that form a wireless communication network with the base station 10, and a control device 100 that controls the base station 10. The base station 10 also includes a plurality of NIC-1 to NIC-N as first wireless modules, and each of the plurality of wireless terminals 20 includes one NIC as a second wireless module.

[0101] The control device 100 (control function) executes a channel switching process that switches the usage status of the multiple NIC-1 to NIC-N according to a predetermined schedule so that one of the multiple NIC-1 to NIC-N is enabled for transmission and the others are prohibited from transmission.

[0102] Each of the multiple wireless terminals 20 according to the second embodiment does not suspend the operation of its NIC (second wireless module). In other words, the NIC (second wireless module) continues to operate even while the NIC-i, which performs wireless communication over the communication channel CH-i, is prohibited from transmitting in the schedule. On the other hand, each of the multiple wireless terminals 20 according to the second embodiment is configured not to request a response frame from the base station 10 when transmitting a frame (or not to transmit a frame that requires a response frame). For example, the ACK policy is set to "No ACK" for each of the multiple wireless terminals 20. Alternatively, the RTS threshold is set high so that RTS transmission is not actually performed. These can be realized by standard functions of the wireless modules.

[0103] 11 is a conceptual diagram for explaining an example of wireless communication by a wireless communication method realized by the wireless communication system 1 according to the second embodiment. FIG. 11 shows the same situation as FIG.

[0104] 11, in the wireless communication system 1 according to the second embodiment, each of the wireless terminals 20 included in STAs-1 continues the operation of its NIC even during the transmission prohibition period of NIC-1, from T0+DT1 to T0+DT1+DT2. Similarly, each of the wireless terminals 20 included in STAs-2 continues the operation of its NIC even during the transmission prohibition period of NIC-2, from T0 to T0+DT1.

[0105] On the other hand, as shown in Fig. 11, in the wireless communication system 1 according to the second embodiment, the base station (AP) 10 does not transmit a response frame even when it receives data from STAs-1 and STAs-2. In other words, even if STAs-1 and STAs-2 continue to operate the NIC during a transmission prohibition period of NIC-1 or NIC-2, downlink traffic does not increase. Consequently, as in the wireless communication system 1 according to the first embodiment, the total transmission time for downlink frames can be alleviated. Furthermore, wireless communication can be continued during a transmission prohibition period of NIC-1 or NIC-2.

[0106] It should be noted that for data transmitted by the wireless terminal 20, it is possible to detect downstream data packet loss by using a response frame of an upper layer such as TCP-ACK.

[0107] Similarly to the first embodiment, the base station 10 may be configured to set the transmission time per unit time of each of the plurality of NIC-1 to NIC-N (first wireless modules) to a first predetermined time or less, and to set the total transmission time per unit time of each of the plurality of NIC-1 to NIC-N (first wireless modules) to a second predetermined time or less. Each of the plurality of wireless terminals 20 may be configured to set the transmission time per unit time of its NIC (second wireless module) to the first predetermined time or less. This makes it possible to comply with the limit on the total transmission time for the base station 10 and each of the plurality of wireless terminals 20.

[0108] As described above, according to the second embodiment, the base station 10 includes a plurality of NIC-1 to NIC-N (first wireless modules) that perform wireless communication on different non-overlapping channels. Furthermore, each of a plurality of wireless terminals 20 that form a wireless communication network with the base station 10 includes a NIC (second wireless module) that performs wireless communication on one of the communication channels CH-1 to CH-N. The control device 100 executes a channel switching process that switches the usage state of the plurality of NIC-1 to NIC-N according to a predetermined schedule so that one of the plurality of NIC-1 to NIC-N is enabled for transmission and the others are prohibited from transmission. Furthermore, each of the plurality of wireless terminals 20 is configured not to request a response frame from the base station 10 when transmitting a frame (or not to transmit a frame that requires a response frame).

[0109] This allows the total transmission time for downlink traffic to be alleviated, similar to the first embodiment. In particular, there is no need for an additional control device or control function in each of the multiple wireless terminals 20. Furthermore, each of the multiple wireless terminals 20 can continue wireless communication without increasing downlink traffic even when the NIC-i corresponding to the communication channel is in a transmission prohibited period.

[0110] Furthermore, according to the second embodiment, similarly to the first embodiment, it is possible to reduce frame collisions between the uplink traffic of each of the multiple wireless terminals 20. As a result, it is expected that the capacity of the uplink traffic will be improved and the range of priority setting that controls communication quality (for example, delay and error rate) will be expanded.

[0111] Furthermore, according to the second embodiment, as in the first embodiment, the transmission enabled periods do not overlap among a plurality of NIC-1 to NIC-N, so it is possible to take measures against power leakage between the corresponding channels CH-1 to CH-N, and as a result, it is possible to expect the effect of reducing power consumption.

[0112] 2-2.Configuration In the second embodiment, the base station 10, the wireless terminal 20, and the control device 100 may be the same as those in the first embodiment, that is, may have the configurations shown in FIGS.

[0113] 2-3. Connection Control The wireless communication system 1 according to the second embodiment may perform connection destination control in the same manner as in the first embodiment. In this case, the second embodiment can also achieve the same effects as the first embodiment by applying the connection destination control described in the first embodiment.

[0114] 2-4. Variations The wireless communication system 1 according to the second embodiment may employ the following modified aspects.

[0115] 2-4-1. Variation 1 Each of the multiple wireless terminals 20 may be configured to be able to request a response frame from the base station 10 when transmitting a frame while NIC-i (first wireless module) performing wireless communication over communication channel CH-i is in a transmittable period in the schedule. For example, each of the multiple wireless terminals 20 changes the ACK policy to remove "No ACK" while NIC-i performing wireless communication over communication channel CH-i is in a transmittable period in the schedule. Alternatively, each of the multiple wireless terminals 20 changes the RTS threshold to perform RTS transmission.

[0116] By adopting this modified embodiment, it is possible to detect downstream data packet loss without using a response frame of an upper layer such as TCP-ACK during a transmission-enabled period in the NIC-i schedule for wireless communication over the communication channel CH-i, thereby preventing a long delay until retransmission when a data packet loss occurs.

[0117] 2-4-2. Variation 2 The plurality of wireless terminals 20 may include a wireless terminal 20 that is capable of switching communication channels in order to reduce the total transmission time.

[0118] Fig. 12 is a conceptual diagram for explaining an example of wireless communication by a wireless communication method realized by a wireless communication system 1 according to Modification 2. Fig. 12 shows a case where a base station 10 includes, as first wireless modules, NIC-1 that performs wireless communication on channel CH-1 and NIC-2 that performs wireless communication on channel CH-2.

[0119] The wireless communication system 1 according to the second modification is characterized by including a wireless terminal 20 that can switch communication channels. That is, in Fig. 12, the multiple wireless terminals 20 are classified into a group STAs-1 in which the communication channel of the NIC provided as the second wireless module is CH-1, a group STAs-2 in which the communication channel is CH-2, and a group STAs-3 in which the communication channel can be switched between CH-1 and CH-2.

[0120] The operations of STAs-1 and STAs-2 are the same as those shown in FIG. 11. STAs-3 uses CH-1 as the communication channel between T0 and T1, and operates in the same manner as STAs-1. On the other hand, it uses CH-2 as the communication channel between T2 and T3, and operates in the same manner as STAs-2. That is, each of the wireless terminals 20 included in STAs-3 can transmit data by switching between CH-1 and CH-2. Consequently, each of the wireless terminals 20 included in STAs-3 can reduce the total transmission time.

[0121] The switching of the communication channel of STAs-3 may be performed in synchronization with the channel switching process in the base station 10. In this case, each of the wireless terminals 20 included in STAs-3 may be configured to be able to request a response frame from the base station 10 when transmitting a frame.

[0122] By adopting such a modified embodiment, it is possible to reduce the total transmission time even for a plurality of wireless terminals 20. [Explanation of symbols]

[0123] 1. Wireless communication systems 10 Base station (AP) 11 processors 12 Storage device 13 Control Program 14 Management information 15 Interface 16 Timers 20 Wireless Terminal Station (STA) 100 control device 110 processors 120 Storage device 130 Control Program 140 Management information 150 Interface 160 Timer CH-i Channel NIC-i Network Interface Card (1st Wireless Module) NIC Network Interface Card (Second Wireless Module)

Claims

1. A wireless communication method between a base station and a plurality of wireless terminals that form a wireless communication network with the base station, comprising: the base station includes a plurality of first wireless modules that perform wireless communication using different non-overlapping channels; each of the plurality of wireless terminals includes a second wireless module that performs wireless communication through any one of the channels; The wireless communication method includes: executing a channel switching process for switching the use states of the plurality of first wireless modules according to a predetermined schedule so that one of the plurality of first wireless modules is enabled for transmission and the others are disabled for transmission; notifying the plurality of wireless terminals of the schedule before starting wireless communication; When the schedule is changed, notifying the plurality of wireless terminals of the changed schedule; each of the plurality of wireless terminals storing the notified schedule; each of the plurality of wireless terminals suspends operation of the second wireless module while transmission of the first wireless module performing wireless communication on the communication channel is prohibited in the schedule, according to the latest schedule read from storage; Contains A wireless communication method comprising:

2. 2. The wireless communication method according to claim 1, the schedule is information that provides a transmission enabled period and a transmission disabled period for each of the plurality of first wireless modules; The wireless communication method includes: and assigning the transmission enabled period and the transmission prohibited period in the schedule based on the number of the wireless terminals connected to each of the plurality of first wireless modules or traffic information of the channel. A wireless communication method comprising:

3. 3. The wireless communication method according to claim 1 or 2, determining the communication channel for each of the plurality of wireless terminals based on traffic information of the channel, and performing connection destination control for controlling connections between the base station and the plurality of wireless terminals; A wireless communication method comprising:

4. A wireless communication method between a base station and a plurality of wireless terminals that form a wireless communication network with the base station, comprising: the base station includes a plurality of first wireless modules that perform wireless communication using different non-overlapping channels; each of the plurality of wireless terminals includes a second wireless module that performs wireless communication through any one of the channels; The wireless communication method includes: executing a channel switching process for switching the use states of the plurality of first wireless modules according to a predetermined schedule so that one of the plurality of first wireless modules is enabled for transmission and the others are disabled for transmission; and causing each of the plurality of wireless terminals not to request a response frame from the base station when transmitting a frame. Including, The method further includes, for each of the plurality of wireless terminals, enabling the first wireless module that performs wireless communication on the communication channel to request the response frame from the base station when transmitting the frame while the first wireless module is capable of transmitting in the schedule. A wireless communication method comprising:

5. A base station; a plurality of wireless terminals forming a wireless communication network with the base station; a control device that controls the base station; Including, the base station includes a plurality of first wireless modules that perform wireless communication using different non-overlapping channels; each of the plurality of wireless terminals includes a second wireless module that performs wireless communication through any one of the channels; the control device executes a channel switching process for switching the use states of the plurality of first wireless modules according to a predetermined schedule so that one of the plurality of first wireless modules is enabled for transmission and the others are disabled for transmission; the base station notifies the plurality of wireless terminals of the schedule before starting wireless communication, and, when the schedule is changed, notifies the plurality of wireless terminals of the changed schedule; Each of the plurality of wireless terminals is configured to store the notified schedule, and suspend operation of the second wireless module while transmission of the first wireless module performing wireless communication on the communication channel is prohibited in the schedule, according to the latest schedule read from the storage. A wireless communication system comprising:

6. A base station; a plurality of wireless terminals forming a wireless communication network with the base station; a control device that controls the base station; Including, the base station includes a plurality of first wireless modules that perform wireless communication using different non-overlapping channels; each of the plurality of wireless terminals includes a second wireless module that performs wireless communication through any one of the channels; the control device executes a channel switching process for switching the use states of the plurality of first wireless modules according to a predetermined schedule so that one of the plurality of first wireless modules is enabled for transmission and the others are disabled for transmission; Each of the plurality of wireless terminals is configured not to request a response frame from the base station when transmitting a frame, and is further configured to be able to request the response frame from the base station when transmitting the frame while the first wireless module that performs wireless communication on the communication channel is able to transmit in the schedule. A wireless communication system comprising:

7. A control program that is executed by a computer and causes the computer to execute the wireless communication method according to any one of claims 1 to 4.

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