Wireless communication system, wireless communication control method, and wireless terminal

Abstract

This wireless communication system comprises: a wireless terminal provided with a plurality of wireless modules that carry out wireless communication through mutually different channels; a base station that carries out wireless communication with the wireless modules; and a plurality of relay devices that relay the wireless communication between the base station and each of the wireless modules. The wireless terminal uses one of the wireless modules as a usage module, and stops data transmission from those other than the usage module. The wireless terminal switches the usage module so that the transmission time rate of each of the wireless modules does not exceed a prescribed upper limit.

Description

Technical Field

[0001] The present invention relates to a technique for controlling a wireless terminal that performs wireless communication by switching a plurality of channels.

Background Art

[0002] A wireless communication system including a base station and a wireless terminal is known. A typical example of a wireless communication system is a public-use wireless LAN (Local Area Network). In a public-use wireless LAN, for example, a use case of transmitting data from a base station to a wireless terminal such as a computer terminal or a smartphone terminal is assumed. Further, with the recent spread of IoT (Internet of Things) terminals, the use cases of transmitting data from the wireless terminal side to the base station are increasing.

[0003] In relation to wireless communication for IoT, the use of the unlicensed Sub-1GHz band has been institutionalized in various countries around the world (see Non-Patent Document 1). In Japan, the 920 MHz band is allocated as the frequency band for an electronic tag system. For example, as an active electronic tag system, LPWA (Low Power Wide Area) wireless communication systems such as LoRa (registered trademark) and WiSUN (registered trademark) are known. Also, the use of IEEE 802.11ah, which is one of the wireless LAN standards, is also being considered.

[0004] Since the number of frequency channels in the 920 MHz band is limited, a case of performing wireless communication while changing the channels to be used is also conceivable.

[0005] For example, in Japan, there is a limit on the total transmission time when using the 920MHz band, and the total transmission time per hour must be within 360 seconds. Wireless communication devices restrict data transmission to comply with this total transmission time limit, and therefore throughput is also limited. However, for wireless communication device enclosures that switch between two non-overlapping channels, a total transmission time of up to 360 seconds per channel per hour, for a total of 720 seconds, is permitted. Therefore, to improve throughput, it is conceivable to perform wireless communication while changing the channels used by the wireless communication device enclosure. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] "Standard Specifications for Radio Equipment for Telemetry, Telecontrol, and Data Transmission in the 920MHz Band," Association of Radio Industries and Businesses (ARIB), ARIB STD-T108 Version 1.3, April 12, 2019. [Overview of the project] [Problems that the invention aims to solve]

[0007] Let's consider the case where a wireless terminal transmits data to a base station via a relay device. In situations where there are constraints on the transmission time rate for each channel, throughput can be improved by switching the channel used by the wireless terminal. However, switching the channel used within the wireless module of the wireless terminal requires complex processing.

[0008] One object of the present invention is to provide a technology that can simplify the process of switching channels used by wireless terminals. [Means for solving the problem]

[0009] The first perspective relates to wireless communication systems. The wireless communication system is A wireless terminal equipped with multiple wireless modules that perform wireless communication on different channels, A base station that performs wireless communication with multiple wireless modules, Multiple relay devices that relay wireless communication between each of the multiple wireless modules and the base station It is equipped with. Wireless terminals are, One of several wireless modules is designated as the active module, and data transmission from the other wireless modules is stopped. Switching between multiple wireless modules to ensure that the transmission time rate of each module does not exceed a predetermined upper limit. It is configured in this way.

[0010] The second aspect relates to a wireless communication control method for controlling wireless communication between a wireless terminal and a base station via multiple relay devices. The wireless terminal comprises multiple wireless modules that communicate wirelessly on different channels. Multiple relay devices relay wireless communication between each of the multiple wireless modules and the base station. Wireless communication control method is, This involves using one of several wireless modules as the primary module and stopping data transmission from the other wireless modules. Switching between multiple wireless modules so that the transmission time rate of each module does not exceed a predetermined upper limit. Includes.

[0011] The third aspect relates to base stations that communicate wirelessly with wireless terminals via multiple relay devices. Wireless terminals are, Multiple wireless modules that communicate wirelessly on different channels, Control unit and It is equipped with. Multiple relay devices relay wireless communication between each of the multiple wireless modules and the base station. The control unit is Use one of the plurality of wireless modules as a usage module, stop data transmission from wireless modules other than the usage module, and switch the usage module so that the transmission time ratio of each of the plurality of wireless modules does not exceed a predetermined upper limit. It is configured as follows.

Advantages of the Invention

[0012] According to the present invention, a wireless terminal includes a plurality of wireless modules that perform wireless communication on different channels. By switching the usage module among the plurality of wireless modules, the channel used for wireless communication can be easily switched. Since there is no need to switch channels within a single wireless module, it is possible to simplify the processing required for channel switching.

Brief Description of the Drawings

[0013] [Figure 1] It is a block diagram showing the basic configuration of a wireless communication system according to an embodiment. [Figure 2] It is a timing chart for explaining the outline of data transmission control involving module switching processing according to an embodiment. [Figure 3] It is a block diagram for explaining the outline of a control unit according to an embodiment. [Figure 4] It is a block diagram showing a configuration example of a control unit according to an embodiment. [Figure 5] It is a block diagram showing a configuration example of a wireless communication system according to an embodiment. [Figure 6] It is a conceptual diagram for explaining a first processing example by a first control unit and a second control unit according to an embodiment. [Figure 7] It is a timing chart for explaining a first processing example by a first control unit and a second control unit according to an embodiment. [Figure 8] It is a flowchart showing a first processing example by a base station according to an embodiment. [Figure 9]This is a conceptual diagram illustrating a second processing example by the first control unit and the second control unit according to the embodiment. [Figure 10] This is a timing chart illustrating a second processing example performed by the first control unit and the second control unit according to the embodiment. [Figure 11] This flowchart shows a second example of processing by a base station according to the embodiment. [Figure 12] This is a block diagram showing another configuration example of the wireless communication system according to the embodiment. [Figure 13] This flowchart shows an example of processing by a wireless terminal according to the embodiment. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described with reference to the attached drawings.

[0015] 1. Overview of the Wireless Communication System 1-1.Basic configuration Figure 1 is a block diagram showing the basic configuration of a wireless communication system 1 according to this embodiment. The wireless communication system 1 includes a wireless terminal 10, a base station 20, and a plurality of relay devices 30. The wireless terminal 10 and the base station 20 communicate wirelessly with each other via the relay devices 30. In other words, the relay devices 30 relay wireless communication between the wireless terminal 10 and the base station 20. The relay devices 30 also make it possible to accommodate wireless terminals 10 that are far away from the base station 20. For example, the wireless communication system 1 is a wireless LAN system. For example, the wireless communication system 1 uses the unlicensed Sub-1GHz band for wireless communication. For example, the wireless communication system 1 uses the 920MHz band for wireless communication.

[0016] The wireless terminal 10 according to this embodiment can perform wireless communication by switching between multiple channels (frequency channels). More specifically, the wireless terminal 10 comprises multiple wireless modules 11 that perform wireless communication on different channels that do not overlap with each other. Each wireless module 11 includes, for example, a network interface controller (network interface card). Each of the multiple wireless modules 11 is connected to a multiple relay device 30. In other words, the multiple wireless modules 11 perform wireless communication with a single base station 20 via each of the multiple relay devices 30. To put it another way, the multiple relay devices 30 relay the wireless communication between each of the multiple wireless modules 11 and the single base station 20.

[0017] In the example shown in Figure 1, the wireless terminal 10 includes a first wireless module 11-1 and a second wireless module 11-2. The first wireless module 11-1 is configured to perform wireless communication on the first channel CH-1. The first wireless module 11-1 is connected to the first relay device 30-1 and performs wireless communication with the base station 20 on the first channel CH-1 via the first relay device 30-1. On the other hand, the second wireless module 11-2 is configured to perform wireless communication on the second channel CH-2, which does not overlap with the first channel CH-1. The second wireless module 11-2 is connected to the second relay device 30-2 and performs wireless communication with the base station 20 on the second channel CH-2 via the second relay device 30-2.

[0018] 1-2. Module switching process The channel used for wireless communication can be easily switched by switching the wireless module 11 used by the wireless terminal 10. One of the multiple wireless modules 11 that is selectively used will be referred to below as the "used module 11S". The used module 11S can also be referred to as the "selected module". Furthermore, the process of switching the used module 11S in the wireless terminal 10 will be referred to below as the "module switching process".

[0019] The wireless terminal 10 transmits data by using one of the multiple wireless modules 11 as the user module 11S. More specifically, in addition to the multiple wireless modules 11, the wireless terminal 10 includes a higher layer 12 and a selector 13. The selector 13 receives transmission data from the higher layer 12 and outputs the transmission data to the user module 11S. The selector 13 does not pass the transmission data to any wireless module 11 other than the user module 11S. The user module 11S transmits the transmission data from the higher layer 12, and the wireless modules 11 other than the user module 11S stop transmitting data.

[0020] Next, let's consider a situation where there are constraints (upper limits) on the transmission time rate for each channel used by the wireless terminal 10. For example, in Japan, there is a limit on the total transmission time when using the 920MHz band, and the total transmission time per hour must be within 360 seconds. For a chassis that switches between two non-overlapping channels, a total transmission time of up to 360 seconds per hour for each channel, totaling 720 seconds, is permitted. Therefore, a module switching process that switches the module 11S used by the wireless terminal 10 is effective in improving throughput.

[0021] Figure 2 is a timing chart illustrating the overview of data transmission control involving module switching processing according to this embodiment. Here, we consider the switching between the first wireless module 11-1 (first channel CH-1) and the second wireless module 11-2 (second channel CH-2).

[0022] During the period from time t1 to t2, the first radio module 11-1 is selected as the module 11S to be used. Data transmission from the first radio module 11-1 is permitted, but data transmission from the second radio module 11-2 is prohibited. In other words, the period from time t1 to t2 is the transmission permission period PA for the first radio module 11-1 and the transmission prohibition period PB for the second radio module 11-2. The radio terminal 10 uses the first radio module 11-1 as the module 11S and performs wireless communication with the base station 20 on the first channel CH-1 via the first relay device 30-1. At the same time, the radio terminal 10 stops transmitting data from the second radio module 11-2.

[0023] At time t2, the wireless terminal 10 switches the module 11S being used from the first wireless module 11-1 to the second wireless module 11-2.

[0024] During the period from time t2 to t3, the second radio module 11-2 is selected as the module 11S to be used. Data transmission from the second radio module 11-2 is permitted, but data transmission from the first radio module 11-1 is prohibited. In other words, the period from time t2 to t3 is a transmission prohibition period PB for the first radio module 11-1 and a transmission permission period PA for the second radio module 11-2. The radio terminal 10 uses the second radio module 11-2 as the module 11S to communicate wirelessly with the base station 20 on the second channel CH-2 via the second relay device 30-2. At the same time, the radio terminal 10 stops transmitting data from the first radio module 11-1.

[0025] At time t3, the wireless terminal 10 switches the module 11S being used from the second wireless module 11-2 to the first wireless module 11-1. The period from time t3 to t4 is the same as the period from time t1 to t2.

[0026] The transmission permission period PA does not overlap between the first radio module 11-1 and the second radio module 11-2. Similarly, the transmission prohibition period PB does not overlap between the first radio module 11-1 and the second radio module 11-2.

[0027] Furthermore, the transmission time ratio of each wireless module 11 can be calculated from the transmission time of each wireless module 11 in the measurement cycle PM.

[0028] To realize the module switching process described above, the wireless communication system 1 according to this embodiment includes a "control unit 100" that manages and controls the module switching process.

[0029] Figure 3 is a block diagram illustrating the overview of the control unit 100. The control unit 100 monitors and manages the transmission time and transmission time rate of each of the multiple wireless modules 11 (multiple channels) of the wireless terminal 10. The control unit 100 then determines the usage schedule for each of the multiple wireless modules 11 so that the transmission time rate of each of the multiple wireless modules 11 of the wireless terminal 10 does not exceed a predetermined upper limit. For example, the usage schedule includes a transmission permission period (PA) assigned to each wireless module 11. The usage schedule can also be called the transmission timing. Various examples of triggers for module switching processing are possible, but at a minimum, the usage schedule is determined so that the transmission time rate of each wireless module 11 does not exceed a predetermined upper limit.

[0030] Furthermore, the control unit 100 controls the wireless terminal 10 to perform module switching processing according to the determined usage schedule. In other words, the control unit 100 controls the wireless terminal 10 to switch the usage modules 11S according to the determined usage schedule. The wireless terminal 10 switches the usage modules 11S according to the usage schedule determined by the control unit 100. Each wireless module 11 operates as a usage module 11S according to the usage schedule determined by the control unit 100.

[0031] 1-3. Effects As described above, according to this embodiment, the wireless terminal 10 includes a plurality of wireless modules 11 that perform wireless communication on different channels. By switching the module 11S used among the plurality of wireless modules 11, the channel used for wireless communication can be easily switched. Since it is not necessary to switch channels within a single wireless module 11, the processing required for channel switching can be simplified. In addition, since the wireless terminal 10 does not need to be restarted when switching channels, the communication downtime is reduced and a deterioration in service quality is prevented.

[0032] Furthermore, according to this embodiment, the control unit 100 determines the usage schedule for each wireless module 11 so that the transmission time rate of each wireless module 11 of the wireless terminal 10 does not exceed a predetermined upper limit. Because the control unit 100 accurately manages the transmission time rate of each wireless module 11, it becomes possible to use each channel up to the upper limit of the transmission time rate. In other words, it becomes possible to expand the transmission time rate of the wireless terminal 10 as a whole and effectively improve throughput.

[0033] Furthermore, according to this embodiment, since the wireless terminal 10 is equipped with multiple wireless modules 11, redundancy is ensured and reliability is improved.

[0034] Furthermore, according to this embodiment, the relay device 30 can also accommodate wireless terminals 10 that are far away from the base station 20.

[0035] 2. Example of Control Unit Configuration Figure 4 is a block diagram showing an example configuration of the control unit 100 according to this embodiment. In the example shown in Figure 4, the control unit 100 is a computer equipped with one or more processors 110 (hereinafter simply referred to as "processor 110") and one or more storage devices 120 (hereinafter simply referred to as "storage devices 120"). For example, the processor 110 includes a CPU (Central Processing Unit). The storage devices 120 store various information necessary for processing by the processor 110. Examples of storage devices 120 include volatile memory, non-volatile memory, HDD (Hard Disk Drive), SSD (Solid State Drive), etc.

[0036] The control program 130 is a computer program executed by the processor 110. The processor 110 executes the control program 130, thereby realizing the functions of the control unit 100. The control program 130 is stored in the storage device 120. The control program 130 may also be recorded on a computer-readable recording medium. The control program 130 may also be provided to the control unit 100 via a network.

[0037] The storage device 120 stores module switching management information 200. Module switching management information 200 is information for managing the module switching process. For example, module switching management information 200 includes the transmission time and transmission time rate for each of the multiple wireless modules 11 of the wireless terminal 10. Module switching management information 200 may also include the usage schedule for each of the multiple wireless modules 11. For example, the usage schedule includes the transmission permission period PA (e.g., a combination of start time and duration) assigned to each wireless module 11. The usage schedule can also be called the transmission timing.

[0038] The storage device 120 may also store relay device status information 300. The relay device status information 300 indicates the status of each relay device 30 connected to the base station 20. The relay device status information 300 includes identification information for each relay device 30. It also includes information (number, etc.) of the wireless terminals 10 and wireless modules 11 under each relay device 30. As another example, the relay device status information 300 may include the distance between each relay device 30 and the wireless terminals 10 under it. As yet another example, the relay device status information 300 may include the traffic status and transmission time rate of each relay device 30. As yet another example, the relay device status information 300 may include the channel used and transmission power of each relay device 30. The control unit 100 communicates with each relay device 30 and obtains the relay device status information 300 from each relay device 30.

[0039] 3. Example of processing when the control unit is distributed between the wireless terminal and the base station. Figure 5 is a block diagram showing an example configuration of the wireless communication system 1 according to this embodiment. In the example shown in Figure 5, the control unit 100 is distributed between the wireless terminal 10 and the base station 20. That is, the wireless terminal 10 includes a first control unit 100-1, and the base station 20 includes a second control unit 100-2. The first control unit 100-1 and the second control unit 100-2 each perform a part of the functions of the control unit 100.

[0040] The following describes in detail the processing in the wireless communication system 1 shown in Figure 5.

[0041] 3-1. First Processing Example Figure 6 is a conceptual diagram illustrating a first processing example by the first control unit 100-1 and the second control unit 100-2. Figure 7 is a timing chart illustrating a first processing example by the first control unit 100-1 and the second control unit 100-2.

[0042] The second control unit 100-2 of the base station 20 determines a "priority period" for each of the multiple radio modules 11 of the radio terminal 10, during which it is recommended that the module be used 11S. The priority period can also be described as a period with high priority as a transmission permission period PA (transmission timing). The priority periods are set so as not to overlap among the multiple radio modules 11. For example, the second control unit 100-2 determines the priority period for each radio module 11 so that the module used 11S switches at regular intervals. The priority period is defined, for example, by a combination of start time and duration.

[0043] The second control unit 100-2 may hold module switching management information 200 (see Figure 4). The second control unit 100-2 monitors the transmission time and transmission time rate of each of the multiple wireless modules 11 of the wireless terminal 10 and updates the module switching management information 200. Based on the module switching management information 200, the second control unit 100-2 may determine a priority period for each wireless module 11 so that the transmission time rate of each wireless module 11 does not exceed a predetermined upper limit. The trigger for the module switching process is arbitrary, but it is preferable that the priority period is determined so that the transmission time rate of each wireless module 11 does not exceed a predetermined upper limit.

[0044] When the second control unit 100-2 determines the priority period for each wireless module 11, it generates first control information CON1 indicating the determined priority period. The second control unit 100-2 then notifies (transmits) the first control information CON1 to the wireless terminal 10 via one of the relay devices 30.

[0045] The first control unit 100-1 of the wireless terminal 10 receives the first control information CON1 transmitted from the second control unit 100-2. The first control unit 100-1 refers to the priority period indicated in the first control information CON1 and determines the switching timing of the module 11S being used.

[0046] The first control unit 100-1 may also hold module switching management information 200 (see Figure 4). The first control unit 100-1 monitors the transmission time and transmission time rate of each of the multiple wireless modules 11 of the wireless terminal 10 and updates the module switching management information 200. The first control unit 100-1, while referring to the first control information CON1, determines the switching timing of the modules 11S used based on the module switching management information 200 so that the transmission time rate of each wireless module 11 does not exceed a predetermined upper limit.

[0047] Then, the first control unit 100-1 performs module switching processing according to the determined switching timing. That is, the first control unit 100-1 switches the module 11S to be used according to the determined switching timing.

[0048] The first control unit 100-1 may determine the usage schedule for each wireless module 11. More specifically, the first control unit 100-1 determines the usage schedule for each wireless module 11 based on the module switching management information 200, such that the transmission time rate of each wireless module 11 does not exceed a predetermined upper limit. The usage schedule includes a transmission permission period PA assigned to each wireless module 11, that is, a transmission permission period PA during which each wireless module 11 operates as a module 11S. The transmission permission period PA is defined, for example, by a combination of start time and duration. The transmission permission periods PA are set so as not to overlap among multiple wireless modules 11. The first control unit 100-1 performs module switching processing according to the determined usage schedule.

[0049] The first control unit 100-1 may also take into consideration the timing of downlink traffic from the base station 20 and determine the schedule to be consistent with the timing of downlink traffic from the base station 20.

[0050] During communication, the second control unit 100-2 of the base station 20 may update the priority period for each wireless module 11. For example, the second control unit 100-2 understands the communication quality and traffic status of the base station 20. The traffic status may include the transmission time rate of the base station 20. Based on the communication quality and traffic status of the base station 20, the second control unit 100-2 updates the priority period for each wireless module 11. Then, the second control unit 100-2 notifies the wireless terminal 10 of first control information CON1 indicating the updated priority period.

[0051] Figure 8 is a flowchart showing a first processing example by the base station 20 (second control unit 100-2).

[0052] In step S110, the second control unit 100-2 determines whether or not it has received a connection status update notification from any of the relay devices 30. A connection status update notification is a notification indicating that the connection status between the relay device 30 and the wireless terminal 10 (wireless module 11) has been updated. If a connection status update notification is received (step S110; Yes), the process proceeds to step S111.

[0053] In step S111, the second control unit 100-2 determines the priority period for each wireless module 11 under the control of the relay device 30. The priority period is the period during which it is recommended that the wireless module 11 operate as the module 11S in use, and is a period with high priority as the transmission permission period PA.

[0054] In step S112, the second control unit 100-2 notifies the wireless terminal 10 of the first control information CON1 indicating the priority period via the relay device 30.

[0055] According to the first processing example, the control unit 100 determines the usage schedule for each wireless module 11 so that the transmission time rate of each wireless module 11 of the wireless terminal 10 does not exceed a predetermined upper limit. Because the control unit 100 accurately manages the transmission time rate of each wireless module 11, it becomes possible to use each channel up to the upper limit of the transmission time rate. In other words, it becomes possible to expand the transmission time rate of the wireless terminal 10 as a whole and effectively improve throughput.

[0056] In particular, since the control unit 100 is distributed between the wireless terminal 10 and the base station 20, it is possible to determine the usage schedule for each wireless module 11 while considering the status of both the wireless terminal 10 and the base station 20. This makes it possible to increase the transmission time rate of the wireless terminal 10 as a whole while appropriately ensuring communication quality, and to effectively improve throughput.

[0057] 3-2. Second Processing Example In the second processing example, we will consider the connection process between the wireless module 11 and the relay device 30 in particular. When the wireless module 11 connects to the relay device 30, we assume that there are multiple candidate relay devices 30 as connection destinations. The relay devices 30 that are candidate connection destinations for the wireless module 11 will be referred to below as "candidate relay devices".

[0058] The second control unit 100-2 of the base station 20 holds relay device status information 300 (see Figure 4). The second control unit 100-2 constantly monitors the status of each relay device 30 connected to the base station 20 and updates the relay device status information 300. For example, the relay device status information 300 includes information on the wireless terminals 10 and wireless modules 11 under each relay device 30. As another example, the relay device status information 300 includes the traffic status and transmission time rate as a relay device for each relay device 30.

[0059] The second control unit 100-2 sets the priority of each candidate relay device based on the relay device status information 300. For example, the second control unit 100-2 understands the congestion status of each candidate relay device based on the available bandwidth and the number of connected terminals. Then, the second control unit 100-2 lowers the priority of candidate relay devices with limited wireless resources. As another example, if there are constraints on the transmission time rate for downlink traffic from relay device 30 to wireless terminal 10, the second control unit 100-2 understands the current status of downlink traffic and transmission time rate. Then, the second control unit 100-2 lowers the priority of candidate relay devices with limited transmission time rate.

[0060] Furthermore, the second control unit 100-2 generates second control information CON2 regarding the priority of the candidate relay devices. For example, the second control information CON2 indicates the correspondence between each candidate relay device and its priority. As another example, the second control information CON2 may indicate the "priority relay device," which is the candidate relay device with the highest priority. The second control unit 100-2 then notifies (transmits) the second control information CON2 to the wireless terminal 10 via any of the relay devices 30. The second control unit 100-2 may also notify the wireless terminal 10 of the second control information CON2 via the priority relay device.

[0061] The first control unit 100-1 of the wireless terminal 10 receives the second control information CON2 transmitted from the second control unit 100-2. The first control unit 100-1 refers to the second control information CON2 and selects (determines) the relay device 30 to which the wireless module 11 will connect. For example, the first control unit 100-1 refers to the second control information CON2 and selects the priority relay device with the highest priority as the connection destination for the wireless module 11. Alternatively, the first control unit 100-1 may select the relay device 30 to which the wireless module 11 will connect based on the second control information CON2 and the state of the wireless terminal 10. The first control unit 100-1 then instructs the wireless module 11 to connect to the selected relay device 30.

[0062] A second processing example will be described with reference to Figures 9 and 10. In the example shown in Figures 9 and 10, the base station 20 is connected to the first relay device 30-1, the second relay device 30-2, and the third relay device 30-3.

[0063] The first wireless module 11-1 of the wireless terminal 10 transmits a connection inquiry INQ to a nearby relay device 30. When each relay device 30 receives a connection inquiry INQ, it transmits a connection inquiry notification NTF to the second control unit 100-2 of the base station 20. In response to the connection inquiry notification NTF, the second control unit 100-2 sets the priority of candidate relay devices, which are relay devices 30 that are not connected to other wireless modules 11. Here, for example, the first relay device 30-1 is set to have the highest priority. The second control unit 100-2 generates second control information CON2 regarding the priority of the candidate relay devices. The second control information CON2 may indicate the first relay device 30-1 with the highest priority. The second control unit 100-2 then notifies the wireless terminal 10 of the second control information CON2 via any of the relay devices 30. The second control unit 100-2 may also notify the wireless terminal 10 of the second control information CON2 via the first relay device 30-1 with the highest priority.

[0064] The first control unit 100-1 of the wireless terminal 10 receives the second control information CON2 transmitted from the second control unit 100-2. The first control unit 100-1 refers to the second control information CON2 and selects (determines) the relay device 30 to which the first wireless module 11-1 will connect. For example, the first control unit 100-1 selects the first relay device 30-1 as the connection destination for the first wireless module 11-1. Then, the first control unit 100-1 instructs the first wireless module 11-1 to connect to the selected first relay device 30-1. As a result, a connection process is performed between the first wireless module 11-1 and the first relay device 30-1.

[0065] Subsequently, the second radio module 11-2 of the wireless terminal 10 transmits a connection inquiry INQ to a nearby relay device 30. Upon receiving the connection inquiry INQ, each relay device 30 transmits a connection inquiry notification NTF to the second control unit 100-2 of the base station 20. In response to the connection inquiry notification NTF, the second control unit 100-2 sets the priority of candidate relay devices, which are relay devices 30 that are not connected to other wireless modules 11. Here, for example, the priority of the second relay device 30-2 is set to be the highest. The second control unit 100-2 generates second control information CON2 regarding the priority of the candidate relay devices. The second control information CON2 may indicate the second relay device 30-2 with the highest priority. The second control unit 100-2 then notifies the wireless terminal 10 of the second control information CON2 via any of the relay devices 30. The second control unit 100-2 may also notify the wireless terminal 10 of the second control information CON2 via the second relay device 30-2 with the highest priority.

[0066] The first control unit 100-1 of the wireless terminal 10 receives the second control information CON2 transmitted from the second control unit 100-2. The first control unit 100-1 refers to the second control information CON2 and selects (determines) the relay device 30 to which the second wireless module 11-2 will connect. For example, the first control unit 100-1 selects the second relay device 30-2 as the connection destination for the second wireless module 11-2. The first control unit 100-1 then instructs the second wireless module 11-2 to connect to the selected second relay device 30-2. As a result, a connection process is performed between the second wireless module 11-2 and the second relay device 30-2.

[0067] Figure 11 is a flowchart showing a second processing example by the base station 20 (second control unit 100-2).

[0068] In step S120, the second control unit 100-2 determines whether it has received a destination inquiry notification NTF from at least one relay device 30. The destination inquiry notification NTF is a notification indicating that the relay device 30 has received a destination inquiry INQ from the wireless module 11. If the destination inquiry notification NTF is received (step S120; Yes), the process proceeds to step S121.

[0069] In step S121, the second control unit 100-2 sets the priority of candidate relay devices that are candidates for connection destinations based on the relay device status information 300.

[0070] In step S122, the second control unit 100-2 notifies the wireless terminal 10 of the second control information CON2 regarding the priority of the candidate relay device via the relay device 30.

[0071] As described above, according to the second processing example, it is possible to appropriately select the connection destination of the wireless module 11 according to the state of the relay device 30 (traffic, transmission time rate, etc.). By combining the first and second processing examples described above, it is possible to further improve throughput efficiently.

[0072] 4. Example of processing when a wireless terminal includes a control unit. Figure 12 is a block diagram showing another configuration example of the wireless communication system 1 according to this embodiment. In the example shown in Figure 12, the wireless terminal 10 includes a control unit 100. The control unit 100 included in the wireless terminal 10 performs module switching processing to switch the module 11S to be used without referring to control information from the base station 20.

[0073] More specifically, the control unit 100 monitors the transmission time and transmission time rate of each of the multiple wireless modules 11 and updates the module switching management information 200 (see Figure 4). Based on the module switching management information 200, the control unit 100 switches the module 11S to be used so that the transmission time rate of each of the multiple wireless modules 11 does not exceed a predetermined upper limit.

[0074] There are various possible triggers for the control unit 100 to perform module switching processing. For example, the control unit 100 may perform module switching processing at regular intervals. Another example is that the control unit 100 may perform module switching processing when the communication quality of the module 11S being used deteriorates. In any case, the control unit 100 performs module switching processing so that the transmission time rate of each wireless module 11 does not exceed a predetermined upper limit.

[0075] If the transmission time rate of a particular wireless module 11 exceeds a predetermined upper limit, the control unit 100 stops the use of that wireless module 11. If the transmission time rate of the wireless terminal 10 as a whole exceeds a predetermined upper limit, the control unit 100 stops data transmission from that wireless terminal 10.

[0076] Figure 13 is a flowchart showing an example of processing by the wireless terminal 10 (control unit 100).

[0077] In step S130, the control unit 100 selects one of the multiple wireless modules 11 as the module to be used 11S according to the initial settings. The wireless terminal 10 uses the module to be used to communicate wirelessly with the base station 20.

[0078] In step S131, the control unit 100 determines whether or not there is a trigger for module switching processing. In other words, the control unit 100 determines whether or not the conditions for executing module switching processing (hereinafter referred to as "module switching conditions") are met. For example, a module switching condition is that the transmission time rate of the module 11S in use reaches a predetermined upper limit. Another example of a module switching condition is that a certain amount of time has elapsed since the start of use of the module 11S in use. Yet another example of a module switching condition is that the communication quality of the module 11S in use falls below a threshold. If the module switching conditions are not met (step S131; No), the process returns to step S131. On the other hand, if the module switching conditions are met (step S131; Yes), the process proceeds to step S132.

[0079] In step S132, the control unit 100 performs a module switching process and switches the module 11S to be used.

[0080] In step S133, the wireless terminal 10 performs wireless communication using the module 11S after the switchover. The process returns to step S131. [Explanation of symbols]

[0081] 1…Wireless communication system, 10…Wireless terminal, 11…Wireless module 11, 11-1…First wireless module, 11-2…Second wireless module, 11S…Module in use, 12…Upper layer, 13…Selector, 20…Base station, 30…Relay device, 30-1…First relay device, 30-2…Second relay device, 100…Control unit, 100-1…First control unit, 100-2…Second control unit, 110…Processor, 120…Storage device, 130…Control program, 200…Module switching management information, 300…Relay device status information, CON1…First control information, CON2…Second control information, INQ…Connection destination inquiry, NTF…Connection destination inquiry notification, PA…Transmission permission period, PB…Transmission prohibition period

Claims

1. A wireless terminal equipped with multiple wireless modules that perform wireless communication on different channels, A base station that performs wireless communication with the aforementioned multiple wireless modules, A plurality of relay devices that relay the wireless communication between each of the plurality of wireless modules and the base station. Equipped with, The total transmission time per unit of time is limited for each channel. The aforementioned wireless terminal is One of the aforementioned multiple wireless modules is used as the active module, and data transmission from wireless modules other than the active module is stopped. The modules being used are switched so that the transmission time rate of each of the aforementioned multiple wireless modules does not exceed a predetermined upper limit. It is configured in such a way Wireless communication system.

2. A wireless communication system according to claim 1, The aforementioned base station is For each of the aforementioned plurality of wireless modules, a priority period is determined during which it is recommended to operate as the module in use. The first control information indicating the priority period for each of the plurality of wireless modules is notified to the wireless terminal. It is configured in such a way, The aforementioned wireless terminal is Referencing the priority period indicated in the first control information, the switching timing of the module being used is determined so that the transmission time rate of each of the plurality of wireless modules does not exceed the predetermined upper limit. The module to be used is switched according to the aforementioned switching timing. It is configured in such a way Wireless communication system.

3. A wireless communication system according to claim 2, The base station determines the priority period for each of the plurality of wireless modules so that the module being used switches at regular intervals. Wireless communication system.

4. A wireless communication system according to claim 1, The plurality of wireless modules include a first wireless module, The aforementioned base station further, The system maintains relay device status information indicating the status of each relay device connected to the base station, When a connection destination inquiry is received from the first wireless module, the priority of candidate relay devices that are candidates for connection destination of the first wireless module is set based on the relay device status information. The second control information relating to the priority of the candidate relay device is notified to the wireless terminal. It is configured in such a way, The aforementioned wireless terminal is Referring to the second control information, the first relay device is selected as the connection destination for the first wireless module. The first wireless module is instructed to connect to the selected first relay device. It is configured in such a way Wireless communication system.

5. A wireless communication system according to claim 4, The second control information indicates the priority relay device with the highest priority, The base station notifies the wireless terminal of the second control information via the priority relay device. Wireless communication system.

6. A wireless communication system according to claim 1, The wireless terminal switches the modules being used so that the transmission time rate of each of the multiple wireless modules does not exceed a predetermined upper limit, without referring to control information from the base station. Wireless communication system.

7. A wireless communication control method for controlling wireless communication between a wireless terminal and a base station via multiple relay devices, The wireless terminal comprises multiple wireless modules that perform wireless communication on different channels from each other. The plurality of relay devices relay the wireless communication between each of the plurality of wireless modules and the base station. The total transmission time per unit of time is limited for each channel. The wireless communication control method is, One of the aforementioned multiple wireless modules is used as the active module, and data transmission from wireless modules other than the active module is stopped. Switching the modules used so that the transmission time rate of each of the aforementioned plurality of wireless modules does not exceed a predetermined upper limit. including Wireless communication control method.

8. A wireless terminal that communicates wirelessly with a base station via multiple relay devices, Multiple wireless modules that communicate wirelessly on different channels, Control unit and Equipped with, The plurality of relay devices relay the wireless communication between each of the plurality of wireless modules and the base station. The total transmission time per unit of time is limited for each channel. The control unit, One of the aforementioned multiple wireless modules is used as the active module, and data transmission from wireless modules other than the active module is stopped. The modules being used are switched so that the transmission time rate of each of the aforementioned multiple wireless modules does not exceed a predetermined upper limit. It is configured in such a way Wireless terminal.

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